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  • Ultrastructure  (103)
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  • 1980-1984  (84)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 9 (1990), S. 101-109 
    ISSN: 1432-0789
    Schlagwort(e): Phryganella acropodia ; Testate amoeba ; Growth rate ; Rhizopoda ; Feeding ; Fungal species ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Clones of Phryganella acropodia were cultivated under different trophic conditions with bacteria as the food source. The doubling time was estimated to be 3 days. The edibility of four species of fungi, Aspergillus niger, Cunninghamella echinulata, Penicillium echinulatum and Stilbella bulbicola, was tested, but only Penicillium enchinulatum and Stilbella bulbicola were eaten and digested by the amoeba. An ultrastructure examination showed that there are two contractile vacuoles, many dictyosomes, a single nucleus with several nucleoli, and peroxisomes. The pseudopodia are filiform when attached to the substrate but change to lobose when the animal is floating. A thin organic membrane covers the aperture of resting forms.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 192 (1983), S. 42-44 
    ISSN: 1432-041X
    Schlagwort(e): Chick embryo ; Gastrulation ; Adenylate cyclase ; cAMP phosphodiesterase ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The ultrastructural localization of adenylate cyclase (E.C. 4.6.1.1.) and cAMP phosphodiesterase (PDE) (E.C. 3.1.4.17.) in the ectoderm of the developmental stage 4 chick embryo was studied. Adenylate cyclase was localized in the lateral surfaces of the ectodermal cells. In the primitive streak cells the enzymatic activity was observed on all the lateral surfaces, whereas in the periphery of the blastoderm the reaction product was localized in the apical parts of the lateral plasma membranes only. cAMP PDE localized in the apical cytoplasm of the ectodermal cells, with highest activity in the globular projections.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 192 (1983), S. 171-178 
    ISSN: 1432-041X
    Schlagwort(e): Differentiation ; Digestive tract ; Endoderm ; Organ culture ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The self-differentiation potency of the endoderm of the chick embryo was investigated mainly by transmission electron microscopy. Endodermal fragments isolated from 4- to 6-day stomach or small intestine were cultured in the absence of mesenchyme and were able to differentiate in vitro into organ-specific epithelia. Endodermal fragments isolated from the stomach region differentiated into a pseudo-stratified epithelium with periodic acid Schiff-positive mucous granules in the apical cytoplasm, while those from the small intestinal region differentiated into a simple columnar epithelium with a striated border which was positive in alkaline phosphatase activity. These features are comparable with those of the mucous secretory epithelium of the normal embryonic stomach and the absorptive epithelium of normal embryonic small intestine, respectively. Next, the self-differentiation potencies were investigated of the upper and lower layers of the blastoderms, at stages 1–5 of Hamburger and Hamilton (H. and H.). Both stomach-type and small-intestine-type epithelia developed only when fragments of the lower layer isolated from the blastoderms older than stage 3 of H. and H. were cultured, suggesting that cells possessing the potency to differentiate into the stomach- and small-intestine-type epithelia exist in the definitive endoderm at the beginning of its formation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    ISSN: 1432-072X
    Schlagwort(e): Intercellular junctions ; Multicellularity in prokaryotes ; Bacterial magnetotaxis ; Ultrastructure ; Bacterial co-ordination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A many-called magnetotactic prokaryote obtained from brackish water was observed to possess intercellular connections at points of contact between the outer membranes of constituent cells. Each aggregate organism consisted of 10 to 30 individual Gram-negative cells containing material with the appearance of poly-β-hydroxybutyrate and magnetosomes of unusual arrangement, structure and composition. The aggregate, which possessed prokaryotic-type flagella arranged at the outwards surfaces of each cell, showed motility indicative of co-ordination between individual component cells. These results suggest that this organism could be a multicellular prokaryote.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 134 (1983), S. 295-298 
    ISSN: 1432-072X
    Schlagwort(e): Actinomycetes ; Streptomyces thermoviolaceus ; Sporogenesis ; Spore ornamentation ; Cupular knobs ; Sheath ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The sporogenesis of aerial spores in Streptomyces thermoviolaceus corresponded to a common sporulation type in the genus. The sporulation septum was composed of an outer ring-shaped constriction wall and an inner interspace septum arising by the inwards growth of a double annulus. In mature spores the wall was composed of two layers, the outer one was part of the parent hyphal wall and septum material, the inner one was formed de novo. The spore chains were enclosed by the thin breakable sheath containing small rod-like elements. The ornamentation in the form of knobs, which were a characteristic feature of the species originated from the sheath. The knobs were hemispherical particles with an inner electron dense core and an outer electron transparent shell. The term “cupular knobs” was suggested for this type of tuberculate ornamentation. Frequently, the knobs became detached from the surface in which case the inner core separated easily from the shell.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    ISSN: 1432-072X
    Schlagwort(e): Cyanobacteria ; Ultrastructure ; Nitrogen fixation ; Water stress ; Taxonomy ; DNA ; Plasmids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Two strains of desiccation-tolerant coccoid cyanobacteria, Chroococcus S24, a marine form, and Chroococcus N41, a cryptoendolith isolated from a hot-desert rock, have been characterized. The mol % DNA base compositions of the strains are 47.1 and 48.9% respectively. Plasmid DNA was not detected in either strain. The pigment contents and nutritional characteristics of the strains are identical. Both lack phycoerythrinoid pigments and, in culture, behave as slow-growing halotolerant marine forms with elevated requirements for Na+, Cl−, Mg2+ and Ca2+. Sucrose was the only carbon source of those tested that supported photoheterotrophic growth. Each strain synthesizes nitrogenase under anaerobic conditions but not in air. Morphologically the two strains are indistinguishable. They are considered to be independent isolates of the same cyanobacterial species. Chroococcus N41 was studied in detail with the electron microscope. When brought to equilibrium at matric water potentials of-168 MPa and lower (to-673 MPa=c0.12a w) the protoplast shrinks, but the cells maintain the same size and diameter as those at-2,156 kPa (MN medium; control); the sheath expands and remains attached to the cell wall outer membrane by fibrils. The cell wall, cell membrane, thylakoid membranes, cyanophycin granules and carboxysomes appeared intact in desiccated cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    ISSN: 1432-0878
    Schlagwort(e): Adrenal cortex ; Tissue culture ; Corticosterone ; Ultrastructure ; Lipoproteins ; Mevinolin ; Rat (Sprague-Dawley)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The present study was undertaken to define the effects of lipoprotein-derived cholesterol and endogenous, de novo synthesized cholesterol on the ultrastructure and function of undifferentiated rat adrenocortical cells [lipoprotein (HDL3 and LDL) receptor-negative, zona glomerulosa-like adrenocortical cells] in primary culture. For this purpose human plasma high density lipoprotein (HDL3) or low density lipoprotein (LDL) was added to culture medium devoid of cholesterol. Steroid secretion remained at the low basal level even after addition of lipoproteins, and the amount of intracellular lipid droplets did not increase. When mevinolin (0.96 µg/ml), an inhibitor of cholesterol synthesis, was added to the culture medium, a low secretion of corticosterone was measured both in serum-free and serum-containing media. Ultrastructurally, lipid droplets disappeared after treatment with mevinolin in both media used. At this concentration of mevinolin cell proliferation was similar to that in the controls, but at higher concentrations (4.8 or 9.6 µg/ml) proliferation was inhibited to 42% and 26% in serum-free medium, and 20% and 12% in serum-supplemented medium, respectively. This study demonstrates that cell proliferation and synthesis of corticosterone by undifferentiated rat adrenocortical cells is identical in the absence or presence of exogenous lipoprotein cholesterol. Inhibition of de novo cholesterol synthesis by mevinolin over a period of 7 days does not inhibit corticosterone secretion or proliferation of cells but decreases the amount of intracellular lipid droplets, thus suggesting utilization of intracellular cholesterol esters. However, higher concentrations of mevinolin inhibit proliferation of cells both in serum-free and serum-containing media.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 260 (1990), S. 495-505 
    ISSN: 1432-0878
    Schlagwort(e): Cuticle ; Epithelium, branchial ; Gills ; Hemocoel ; Histology ; Ultrastructure ; Carcinus maenas (Crustacea)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The phyllobranchiate gills of the green shore crab Carcinus maenas have been examined histologically and ultrastructurally. Each gill lamella is bounded by a chitinous cuticle. The apical surface of the branchial epithelium contacts this cuticle, and a basal lamina segregates the epithelium from an intralamellar hemocoel. In animals acclimated to normal sea water, five epithelial cell types can be identified in the lamellae of the posterior gills: chief cells, striated cells, pillar cells, nephrocytes, and glycocytes. Chief cells are the predominant cells in the branchial epithelium. They are squamous or low cuboidal and likely play a role in respiration. Striated cells, which are probably involved in ionoregulation, are also squamous or low cuboidal. Basal folds of the striated cells contain mitochondria and interdigitate with the bodies and processes of adjacent cells. Pillar cells span the hemocoel to link the proximal and distal sides of a lamella. Nephrocytes are large, spherical cells with voluminous vacuoles. They are rimmed by foot processes or pedicels and frequently associate with the pillar cells. Glycocytes are pleomorphic cells packed with glycogen granules and multigranular rosettes. The glycocytes often mingle with the nephrocytes. Inclusion of the nephrocytes and glycocytes as members of the branchial epithelium is justified by their participation in intercellular junctions and their position internal to the epithelial basal lamina.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 260 (1990), S. 601-616 
    ISSN: 1432-0878
    Schlagwort(e): Autonomic ganglia ; Catecholamines ; Intestines ; Innervation ; Ultrastructure ; Domestic fowl (Aves)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary An ultrastructural study was made of the neurons, satellite cells and vesiculated axons of the intestinal nerve of the domestic fowl. Broad membrane-to-membrane contacts between adjacent nerve cell bodies were sometimes observed. The cell bodies and processes were not always separated from the extracellular space by a capsule of satellite cells. Following fixation using potassium permanganate, catecholamine (CA)-containing neurons in the intestinal nerve, unlike those in the lumbar parasympathetic ganglia, did not possess any small granular vesicles (SGV). Following exposure to noradrenaline, SGV could be demonstrated in the cell bodies of the juxta-ileal ganglia but not the juxta-rectal ganglia of the intestinal nerve. Non-CA axons were examined in tissue from birds that had been pretreated with 6-hydroxydopamine. Approximately one half of the non-CA axons formed axo-somatic contacts. Most of the non-CA axons contained varying proportions of small clear vesicles, large clear vesicles and large granular vescles. Statistical analysis showed that the non-CA axons could not be subdivided according to their vesicle content. CA-axons contained many SGV and were found in close apposition to neuronal somata and processes, and in the neuropil.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    ISSN: 1432-0878
    Schlagwort(e): Stomach ; Enteroendocrine cells ; Enterochromaffin-like (ECL) cell ; Enterochromaffin cell (EC) ; Histamine ; Ultrastructure ; Secretory granules ; Didelphis albiventris (Marsupialia)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary An ultrastructural study of enterochromaffin-like (ECL) cells in the gastric mucosa of the white-belly opossum Didelphis albiventris (Marsupialia) was carried out. In parallel, histochemical methods were used at the light-microscopical level to demonstrate argentaffin cells, argyrophilic cells, and serotonin- and histamine-immunoreactive elements. Argentaffin and serotonin-immunoreactive cells were scattered, and argyrophilic cells were numerous, within the full thickness of the mucosa. Argyrophilic cell distribution was similar to that of histamine-immunoreactive elements. At the electron-microscopical level, the oxyntic mucosa of D. albiventris presented endocrine cells with secretory granules morphologically similar to those of the ECL cell of eutherian mammals. However, in this marsupial, the ECL cell exhibited a variable mixture of two distinct types of secretory granules: (1) granules with the morphological appearance of the eutherian ECL cell, and (2) granules morphologically similar to those of the eutherian enterochromaffin (EC) cells. Based on this morphological pattern of the ECL cell granules, it is proposed that in the oxyntic mucosa of the opossum D. albiventris, the EC and ECL cells represent distinct steps in the same line of cell differentiation; the ECL cell should also be a site of histamine storage.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 234 (1983), S. 411-425 
    ISSN: 1432-0878
    Schlagwort(e): Intestines (chicken) ; Innervation ; Catecholamines ; Adrenergic fibres ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Axons in the duodenum, ileum and rectum of the domestic fowl were identified as catecholamine-containing (CA) on the basis of positive reactivity following chromaffin fixation for electron microscopy. CA-axons in association with blood vessels in all regions of the intestine and in non-vascular sites in the small intestine had a ‘ typical’ adrenergic appearance, in that they contained many small granular vesicles (SGV) and variable numbers of large granular vesicles (LGV). In the rectum the non-vascular CA-axon profiles were atypical, in that there were many elongated LGV and few SGV, and the chromaffin reactivity was weak. The nerve profiles in the rectum were dramatically reduced following 6-hydroxydopamine and reserpine treatment and were absent in rectum cultured in the absence of extrinsic ganglia. It was concluded that the profiles, in spite of their low chromaffin reactivity, truely represent CA-axons. The possibility was raised that the atypical morphology and reduced chromaffin reactivity is due to the presence of adrenaline.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 234 (1983), S. 427-437 
    ISSN: 1432-0878
    Schlagwort(e): Corticotropes ; Rat fetus ; Ultrastructure ; Immunocytochemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Corticotropes of rat fetuses aged 16, 18 and 21 days were localized by the indirect antibody-enzyme method on semithin sections of the pituitary. The development of the ultrastructure of these cells was observed on consecutive ultrathin sections. In comparison with previous data our present results show that identification of a fetal cell type cannot be based entirely on morphological criteria. The structural peculiarities of corticotropes obtained from studies in vivo are compared with those observed in cells maintained in vitro.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 234 (1983), S. 679-689 
    ISSN: 1432-0878
    Schlagwort(e): Odontogenesis ; Rats ; Cyclophosphamide ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Cyclophosphamide-induced changes in rodent odontogenesis were investigated by light and electron microscopy in four-day-old Sprague Dawley rats given one injection of 40 mg/kg of body weight of cyclophosphamide and killed at intervals of one hour, one day, one week and two weeks. Incisor and molar teeth were dissected from the animals, fixed in 2.0% glutaraldehyde in 0.1 M sodium cacodylate with 3.4% sucrose, and subsequently some were incubated for alkaline phosphatase reaction, and embedded in Spurr's medium for sectioning at light- and electron-microscopic levels. From three days a cell-sparse zone was created in the pulp in the growing end of the tooth and progressive cellular changes were observed which became more severe in the one-week and two-week specimens. Subodontoblast and adjacent pulpal cells were the most affected showing nuclear changes, damage to, or loss of, organelles, and inclusion bodies. Odontogenic epithelium was less affected and odontoblasts appeared to be unaffected by the drug. A new irregular matrix was laid down in the defect area and seemed to be the product of depolarized odontoblasts. This new matrix showed alkaline phosphatase activity, as did the cells embedded in it, and later it became mineralized. It is speculated that the polarity of odontoblasts might be maintained by an intact subodontoblastic layer; when this is lost the odontoblasts become depolarized and capable of secreting matrix from both ends.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 14
    ISSN: 1432-0878
    Schlagwort(e): Adrenal cortex ; Differentiation ; Tissue culture ; Mevinolin ; Steroids ; Ultrastructure ; Rat (Sprague-Dawley)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Mevinolin, an inhibitor of cholesterol synthesis, was used to study the effect of endogenous cholesterol synthesis on the morphology and function of differentiating and differentiated fetal rat adrenocortical cells grown in primary culture. Upon adrenocorticotrophic hormone (ACTH) stimulation under conditions in which endogenous cholesterol synthesis was inhibited but exogenous (lipoprotein) cholesterol was available, the cells differentiated normally from glomerulosa-like to fasciculata-like cells; the steroid hormone secretion was maximally induced. Under conditions in which cholesterol synthesis was maximally inhibited by mevinolin and the cells had no access to exogenous cholesterol, the cells did not differentiate into fasciculata-like cells; the ACTH-induced steroid response was highly suppressed under these conditions. The addition of either human low-density lipoprotein (LDL) or high-density lipoprotein (HDL3) to the culture medium restored the ACTH-induced differentiation and steroid secretion. Thus, in the absence of exogenous cholesterol, endogenous cholesterol synthesis was a prerequisite for differentiation. In cultures grown in the presence of exogenous cholesterol and ACTH with mevinolin-inhibited cholesterol synthesis and high steroid output, an increase in cytoplasmic lipids was evident, suggesting upregulation of LDL and HDL receptors. The results also demonstrated that induction of phenotypic differentiation from glomerulosalike into fasciculata-like cells can proceed in the presence of a cholesterol synthesis inhibitor like mevinolin; this differentiation in the absence of endogenous cholesterol synthesis is accompanied by the appearance of cytoplasmic cholesterol ester droplets, typical of fasciculata cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 15
    ISSN: 1432-0878
    Schlagwort(e): Atrial appendage ; Atrial-specific granules ; Atrial natriuretic polypeptides ; Exocytosis ; Ultrastructure ; Rat (Sprague-Dawley)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Atrial appendage cardiocytes of mammals, including man, contain multiple cytoplasmic granules that vary in number in different physiological states. Using morphologic and comprehensive morphometric techniques, these granules were assessed in Sprague-Dawley rats following dehydration for 5 days, volume-loading by substituting 1% NaCl as drinking water for 7 days, unilateral nephrectomy plus volume-loading for 7 days, and in late term pregnant animals (18–20 days; term ≈21 days). Although principally located in the paranuclear region, granules were observed throughout the sarcoplasm. Cytological features indicative of synthetic activity and granule formation were readily apparent in all groups with the exception of pregnant rats where they were infrequently observed. Granule contents were released by exocytosis and observed in the right appendage of control, dehydrated and nephrectomy/volume-loaded groups and left appendage of volumeloaded animals. Exocytosis was not observed in pregnant animals. By point counting, the proportional volume of cardiocytes occupied by granules (V v ) in controls was significantly greater for right than for left appendage (2.12±0.22% vs 1.29±0.16%; mean±SEM;p〈0.05). A significantly similar difference was found for nephrectomy/volume-loaded animals. There was no significant difference inV v for right appendage between the control and experimental groups; for left appendage there was a significant increase inV v to 2.42±0.09% (p〈0.05) for volume-loaded animals only. Estimation of the maximum diameter of granule profiles in control animals was 238±9 nm and 230±6 nm for right and left appendages, respectively. The profile diameters in the left appendages of dehydrated (202±9 nm) and pregnant (200±7 nm) animals were significantly (p〈0.05) less than those of the control animals. The morphometric findings did not correlate with predictions based upon published biochemical data. In the course of this study, a previously unreported bimembranous, circular to ovoid structure was observed in the cardiocyte sarcoplasm of all animals; the nature and function of this structure is unknown.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 259 (1990), S. 33-41 
    ISSN: 1432-0878
    Schlagwort(e): Photoreceptor cells ; Ultrastructure ; Volumetric change ; Light/dark cycle ; Lampetra japonica (Cyclostomata)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Short photoreceptor cells of the lamprey retina exhibited a 30% increase in the width of the myoid process and a 20% increase in that of the axonal process during a 12-h light period, compared to the measurements obtained during a 12-h dark period. An increase in the amount of cytoplasm, dilation of ER cisterns, and swelling of the nucleus appeared to cause the enlargement of the myoid parts. Accumulation of synaptic vesicles occurred concurrently with a thickening of the axonal process. These morphological changes presumably represent a phase of the diurnal cycle and current synaptic activity of the short cell. By contrast, the long photorecpetor cell showed neither measurable changes nor any indication of “retinomotor movement”.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 17
    ISSN: 1432-0878
    Schlagwort(e): Cerebrospinal fluid-contacting neurons ; Paraventricular organ ; Posterior recess organ ; Somatostatin ; Serotonin ; Ultrastructure ; Immunocytochemistry ; Dogfish,Squalus acanthias skate,Raja radiata (Elasmobranchii)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The paraventricular organ (PVO) and the posterior recess organ (PRO) of two elasmobranch species, the spiny dogfish,Squalus acanthias, and the skate,Raja radiata, were investigated by use of scanning and transmission electron microscopy and immunocytochemistry employing a series of primary antisera. The PVO and PRO contained four types of cerebrospinal fluid (CSF)-contacting neurons. One type was free of secretory granules and projected a dendrite-like process into the ventricle. The other three types were distinguished according to the size of their secretory granules. The ventricular extensions of these cells were filled with secretory granules. By means of immunocytochemistry three types of CSF-contacting neurons were observed in the PVO and PRO. Type I contained only serotonin; type 2 displayed only somatostatin; type 3 was endowed with both serotonin and somatostatin. Type I dominated in the PRO, whereas type 3 was the most frequent in the PVO. The latter cells appear to be the site of origin of a loose tract formed by serotonin- and somatostatinimmunoreactive fibers projecting from the PVO into the neuropil of the PRO. Compact bundles formed exclusively by serotonin fibers were also shown to extend between the PVO and PRO. The basal processes of the CSF-contacting neurons of the PRO penetrated into the underlying neuropil. This neuropil is rich in synapses and can be regarded as an integrative area to which the basal processes of the local CSF-contacting neurons, serotonin and somatostatin fibers from the PVO, and fibers containing immunoreactive thyrotropin-releasing hormone of unknown origin, support a conspicuous input. The present findings indicate that the PVO and PRO of elasmobranchs are functionally integrated structures.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 232 (1983), S. 579-591 
    ISSN: 1432-0878
    Schlagwort(e): Cavernous bodies ; Endothelial cells ; Respiratory activity ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Work on endothelial cells has been limited by the availability of procedures for obtaining such cells in quantities adequate for direct in vitro analysis. The present paper describes a method for the isolation of endothelial cells from bovine cavernous bodies. A number of cells ranging from 2.5 to 4 × 108 per animal has been obtained. The cells were identified as follows 1) presence of the “Weibel and Palade” bodies in the isolated cells, 2) “cobblestone” appearance of cell cultures, and 3) presence of factor VIII, as demonstrated by immunofluorescence assays. The cell viability at the end of the purification procedure was tested 1) by dye-exclusion tests and 2) by metabolic assays. Features of this preparation are 1) the very high yield of viable endothelial cells, 2) the absence of contamination by fibroblasts and smooth muscle cells and a very low contamination by erythrocytes and 3) the fine dispersion of the isolated cells. These properties allow functional and subcellular fractionation studies on freshly isolated endothelial cells of microvascular origin.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 233 (1983), S. 427-438 
    ISSN: 1432-0878
    Schlagwort(e): Myocardium ; Thunnus alalunga ; Ultrastructure ; Mitochondria ; Myofibrils
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The common ventricle in the heart of the Thunnus alalunga was studied. The ventricular myocardium consists of an outer compact layer and a thick inner spongy layer. The compact layer has slightly larger cells (4–6 μm diameter) than the spongy layer (2.5–5 μm diameter). Ultrastructurally the myocardium displays normal arrangements of myofibrils and mitochondria. The sarcoplasmic reticulum is poorly developed. The intercalated discs are simple with the fascia adherens being the most frequent junctional type observed; occasionally a desmosome was seen. Nexus type junctions are present but are unassociated with the intercalated discs. There are no t-tubules evident but the plasmalemma exhibits numerous caveolae which rarely form couplings with the sarcoplasmic reticulum. A morphometric analysis of the volume percent of mitochondria and myofibrils showed that the myocardial cells in the spongy layer of the heart have a significantly greater volume percentage of mitochondria than the compact layer. No significant differences were found between myocardial regions when the volume percentages of myofibrils were compared. The physiological studies revealed that the albacore tuna has heart rates (120 bpm) and ventricular blood pressures (100 mmHg) that are among the highest reported for fish.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 233 (1983), S. 523-537 
    ISSN: 1432-0878
    Schlagwort(e): Epididymis (rat) ; Myosin ; Actin ; Fibronectin ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The anatomical distribution of smooth muscle actin, myosin, fibronectin and basement membrane has been investigated immunohistochemically, using the indirect immunofluorescence technique, in the rat epididymis. The findings were correlated with the ultrastructural organization of the organ. Actin was found to be distributed in the stereociliary region of the epithelial principal cells and in the terminal web region. Actin was also visible along the base of the epithelium. Myosin was detected in the terminal web and in the terminal bar regions of the epithelium. The contractile cells showed a strong stain for both proteins. Basement membrane immunoreactivity was distributed along the epithelial basement membrane and around the contractile cells of the wall. In the cauda, between the epithelium and the contractile cell layers, the lamina propria, containing blood vessels and a thin layer of cells, was negative for all antigens investigated. Fibronectin showed a granular distribution around the contractile cells, mainly in the cauda. The ultrastructural study showed only thin (5–6 nm in diameter) filaments in the stereocilia and terminal web region. Thin filaments were also visible in the cytoplasm of the basal cells, thus suggesting a contractile function of this cell type. The heterogeneous appearance of the contractile cells of the wall seemed to support the different contractile pattern of the epididymal regions: caput, corpus and cauda. The cells present in the lamina propria showed cytoplasmic vesicles with dark granules resembling the “A” cell granules of the endocrine pancreas and gut mucosa cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 233 (1983), S. 563-577 
    ISSN: 1432-0878
    Schlagwort(e): Nematocysts ; Structure ; Ultrastructure ; Function ; Cubozoa
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Microbasic p-mastigophores, euryteles of two size groups, holotrichous isorhizas and atrichous isorhizas, comprise the cnidom of Chironex fleckeri, a cubozoan that has been responsible for several human fatalities. In its undischarged state each microbasic mastigophore of C. fleckeri consists of a capsule containing matrix and an inverted tube possessing a smooth-walled butt which is loosely coiled helically and which narrows to form a thread that is tightly coiled helically and markedly pleated. Both butt and thread carry three helices of spines and contain a granular matrix. During discharge, the proximal butt spines form initially a piercing stylet. Granular material from the butt and thread is released prior to the release of capsular material. Each eurytele possesses a tube with a butt composed of three bulbs, the middle bulb bearing long spines. Each holotrichous isorhiza possesses a coiled tube bearing small spines along its length. Each atrichous isorhiza exhibits a tube that is devoid of spines and loosely folded in the undischarged condition. The probable role of each type of nematocyst is inferred from its structure and features that enable the ready separation of the nematocysts of C. fleckeri from those of scyphozoan jellyfish are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 233 (1983), S. 629-638 
    ISSN: 1432-0878
    Schlagwort(e): Ciliary process ; Cultured explant ; Epithelial cells ; Ultrastructure ; Bovine and rabbit eyes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The ultrastructural characteristics of ciliary epithelium from bovine, pigmented rabbit, and fetal albino rabbit were studied in cultured explants. The tips of ciliary processes were cultured in plastic dishes with Dulbecco Modified Eagle Medium (DMEM) containing 5% fetal bovine serum. More than half of the expiants adhered to the plastic culture dish, and epithelial cells spread as monolayers within a few days. Initially the explant contains two layers, the outer (nonpigmented cells) and the inner (pigmented cells). Later the explant exhibits three layers: 1) outermost lightly pigmented flattened cells, 2) an outer layer of nonpigmented cells, and 3) an inner layer of densely pigmented cuboidal cells. The cells of the outermost layer are continuous with the cells of the inner layer. A narrow space lies between the outermost layer and the outer layer. The columnar cells in the outer layer contain well developed organelles but no pigment granules; they possess a basement membrane, lateral interdigitations, and junctional complexes near their apices. Numerous focal junctions and some ciliary channel-like structures were detected between the columnar cells of the outer layer and the cuboidal cells of the inner layer. The cuboidal cells of the inner layer are filled with pigment granules. These observations suggest that the columnar cells of the outer layer are nonpigmented epithelium, the cuboidal cells of the inner layer are pigmented epithelium, and the flatened cells in the outermost layer are derived from pigmented epithelium.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 233 (1983), S. 693-698 
    ISSN: 1432-0878
    Schlagwort(e): Thyroid gland ; Human fetus ; Follicles ; Ultrastructure ; Differentiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Thyroid glands from 40 human fetuses ranging from 30 to 175 mm in length were examined by electron microscopy. At the 30 mm stage, the cells are arranged in cords or clusters and contain numerous free ribosomes. The rough-surfaced endoplasmic reticulum (RER) is poorly developed and the Golgi complex consists of saccules, smooth and coated vesicles. Mitochondria, microfilaments, glycogen particles, occasional lysosome-like structures, and single cilia are observed. At sites of incipient follicle formation, intercellular clefts containing interdigitating microvilli, delimited by junctional complexes, are evident. In addition, the apical region of some cells contains vacuoles. At the 50-mm stage, intercellular clefts are more apparent, some of them organized into small follicles through the enlargement of the lumen, the incorporation of additional cells, and the formation of a basal lamina. With increasing gestational age, more follicles are established. The lumina vary from round to clover-leaf shaped and have an electron-dense content. Cisternae of RER are dilated and contain flocculent material. The Golgi complex is more extensive, and lysosome-like structures are more numerous. By the 100-mm stage, the follicular cells appear morphologically well differentiated. The results demonstrate an extracellular origin of the follicular lumen in the human fetal thyroid.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 24
    ISSN: 1432-0878
    Schlagwort(e): Fibronectin ; Lung ; Development ; Ultrastructure ; Immunocytochemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary In a previous study changes in the macrodistribution of fibronectin during rat-lung development were examined. Using the peroxidase-antiperoxidase immunocytochemical technique, we have demonstrated the presence of fibronectin in embryonic, neonatal, and adult rat lung at the ultrastructural level. In the embryo, fibronectin is found both in an intra-and extracellular association with isolated pneumoblasts, and in a periodic distribution along the basal lamina. The neonate displays fibronectin in an intracellular association with early type-I cells and on their basal and luminal surfaces, but not in association with type-II cells. Neonatal basal lamina is diffusely labeled by anti-fibronectin antiserum. Fibronectin in adult tissue is found both intracellularly and on the basal and luminal surfaces of type-I cells but not in type-II cells. The basal lamina and interstitial connective tissue are slightly or non-reactive. These observations confirm and extend our initial suggestion that fibronectin is involved in rat-lung development.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 25
    ISSN: 1432-0878
    Schlagwort(e): Sea star ; Development ; Cuticle ; Extracellular materials ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The fine structure of conspicuous extracellular materials during the life history of a sea star (Patiria miniata) is described. The outer surface of the developing sea star is covered by two morphologically different cuticles that appear sequentially during ontogeny. The primary cuticle, which is about 120 nm thick and two-layered, is present from mid-blastula through the end of the larval stage. The secondary cuticle, which is about 1 μm thick and three-layered, first appears on the epidermis of the rudiment region of the larva and, after metamorphosis, covers the entire epidermis of the juvenile and adult stages. During ontogeny, there are only two conspicuous gut cuticles: the first lines the newly invaginated archenteron at the start of the gastrula stage, and the second lines the esophagus during the larval stage. A blastocoelic basal lamina first appears at mid-blastula and persists as subectodermal and subendodermal basal laminae. Ruthenium red-positive granules are detectable between the lateral surfaces of adjacent ectodermal cells during part of the gastrula stage; this transient intercellular material may possibly aid in lateral adhesion between cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 26
    ISSN: 1432-0878
    Schlagwort(e): Median eminence ; Catecholamines ; Neuropeptides ; Immunocytochemistry ; Double labeling ; Ultrastructure ; Triturus alpestris (Urodela)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Dopaminergic and peptidergic nerve fibers were simultaneously demonstrated with a double-labeling technique at the ultrastructural level. The first antibody, raised against tyrosine hydroxylase, was applied during the preembedding phase and visualized with the peroxidase method. The second antibody, raised against one of the peptides met-enkephalin, somatostatin or gonadotropin-releasing hormone (GnRH), was applied to the ultrathin sections and visualized with gold-labeled goat anti-rabbit IgG. The fibers of both categories were present in the zona externa of the median eminence, frequently contacting the basal lamina of the portal vessels. In addition, topographical relationships between different types of nerve fibers were observed in the perivascular areas, although there were no morphological signs of synaptic specializations. Using serial sections, it could be established that one GnRH-fiber contacted both a dopaminergic fiber and a fiber immunoreactive for met-enkephalin. The observations support earlier physiological data concerning the regulation of the hypothalamo-hypophyseal axis, with special emphasis on the release of neurohormones in the median eminence of the newt.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 259 (1990), S. 599-602 
    ISSN: 1432-0878
    Schlagwort(e): Crystalloids ; Filaments ; Sertoli cells ; Testis ; Ultrastructure ; Three-toed sloth,Bradypus tridactylus (Edentata)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Crystalloids were found in Sertoli cells of the testis of the three-toed sloth by examination at the lightand electron-microscopic levels. Needle-, or spindle-shaped crystalloids, varying in length, were located in the basal part of the Sertoli cells. They consisted of bundles of filaments each measuring ~ 11 nm in diameter. Several filaments were packed hexagonally to form a bundle. The center-to-center distance between individual filaments of a bundle was ~ 17 nm. Periodical lateral projections emanated from the filaments. Cross sections of crystalloids showed that the projections radiated from each filament in three directions, forming an equilateral triangle with a side length of ~ 15 nm. Scattered polyribosomes were found between and around the bundles.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 260 (1990), S. 469-477 
    ISSN: 1432-0878
    Schlagwort(e): Testis ; Interstitial tissue ; Leydig cells ; Lymphatics ; Ultrastructure ; Spinifex hopping mouse ; Notomys alexis (Rodentia)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The organization of testicular interstitial tissue of the spinifex hopping mouse, Notomys alexis differs from that of other rodents. It comprises between 10.3% and 17.3% (average 15.0%) of the total testicular volume, and is variable in its organization both at different locations within the testis of the one animal and among different individuals. Abundant, closely packed Leydig cells are usually present; however, in some regions large, thick-walled blood vessels and extensive peritubular lymphatic spaces, often lacking an endothelium adjacent to the Leydig cells, are also prominent. The Leydig cells in contact with the large blood vessels and lymphatics, unlike those in regions where lymph is sparse, are not densely packed and sometimes contain numerous lipid droplets. Ultrastructure of Leydig cells is typical of steroid-producing cells; however, mitochondria are often extremely large, unusual in shape or bizarely arranged in relation to one another. Also electrondense bodies displaying a paracrystalline-like internal structure of parallel, electron-dense filaments arranged in a lattice pattern occur in the cytoplasm of many cells. The significance of these unusual ultrastructural features and the organization of the interstitial tissue remain to be determined conclusively, but may relate to steroid synthesis, secretion and uptake.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 29
    ISSN: 1432-0878
    Schlagwort(e): Atrial natriuretic peptide ; Heart ; Freshwater fish ; Seawater fish ; Immunohistochemistry ; Ultrastructure ; Radioimmunoassay ; Cyprinus carpio (Teleostei) ; Narke japonica (Elasmobranchii) ; Eptatretus burgeri (Cyclostomata)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The immunoreactivity of atrial natriuretic peptide and ultrastructure of cardiocytes were examined in 5 species each of freshwater and seawater teleosts, as well as in 2 species each of elasmobranchs and cyclostomes. Immunoreactivity was strong in the atria of Cyprinus carpio, Anguilla japonica and Conger myriaster, rather weak in atria of Channa maculata, Lepomis macrochirus, Salmo gairdneri, Oplegnathus fasciatus and Eptatretus burgeri, very weak in atria of Pagrus major, Trachurus japonicus and Triakis scyllia, and not detectable in atria of Hexagrammos otakii, Narke japonica and Lampetra japonica. The immunoreactivity of the atrial cardiocytes was generally stronger in freshwater than seawater fish. Ventricular immunoreactivity was detected only in 7 species, always being weaker than that observed in the atrium. Ultrastructurally, however, secretory granules were found in atria and ventricles of all species examined, being more frequent in the former than the latter. By radioimmunoassay, immunoreactive ANP was detected in the extracts of blood plasma and both atrial and ventricular tissues of all species examined. There were no statistically significant differences in the values between freshwater and seawater species.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 30
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 261 (1990), S. 423-430 
    ISSN: 1432-0878
    Schlagwort(e): Hepatocytes ; Liver ; Ultrastructure ; Digitonin perfusion ; Metabolic zonation ; Rat (Wistar)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary It has been shown that pulse perfusion of rat liver with a digitonin-containing medium results in a highly zonated hepatocyte permeabilization, allowing selective sampling of cytosolic constituents from periportal and perivenous (centrolobular) hepatocytes “in situ”. In the present paper we provide an ultrastructural evaluation of the perfusion method. Identical changes in hepatocytes from affected periportal and perivenous zones are found. Affected hepatocytes appear light (electron-lucent) in electron micrographs with a sharp transition to normal hepatocytes. The most conspicuous ultrastructural findings are: (1) transformation of the sinusoidal part of the light hepatocytes, the lipocyte processes and the endothelium of affected zones apparently unifying into a continuous layer dominated by disrupted plasma membranes and 7-nm filaments; (2) deposition of osmiophilic digitonin-cholesterol complexes along the sinusoidal plasma membranes of affected zones; and (3) reduction of the cytoplasmic matrix (cytosol) in the light hepatocytes, a dilation of the mitochondrial intermembrane space with a preserved mitochondrial matrix, and a dilation of cisternae of the granular endoplasmic reticulum. The ultrastructural findings are consistent with marker-enzyme activity measured in eluates from digitonin-perfused livers, except that lysosomes appear intact, apparently contrasting with the observed eluation of amyloglucosidase (Quistorff et al. 1985).
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 31
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 261 (1990), S. 451-459 
    ISSN: 1432-0878
    Schlagwort(e): Harderian gland ; Ultrastructure ; Morphometry ; Carbamylcholine ; Secretion ; Rat (Slc: SD)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary To determine the effect of cholinergic secretagogue on the Harderian gland of rats, several light- and electron-microscopic parameters were morphometrically assessed at different time intervals after carbamylcholine injection. In controls, two types of glandular cells (type A cells having 40–55 large vacuoles per cell profile and type B cells containing 30–38 smaller vacuoles per cell profile) and myoepithelial cells were recognized. At 5 min after injection of carbamylcholine, when rats secreted “bloody tears”, many alveoli showing narrower lumina and exocytotic figures in both types of cells were observed. Some vacuoles, which were covered by thin cytoplasmic sheets, protruded into the alveolar lumina. However, there was no evidence of apocrine or holocrine secretion. At 30 min and 120 min after injection, most of the alveolar lumina were dilated, and a pronounced decrease in the number of vacuoles in the glandular cells was observed. At 300 min after injection, the secretory vacuoles in both cell types reaccumulated. Transitional forms between the two cell types were not observed. The two types of Harderian gland cells can therefore be considered independent populations rather than different secretory stages of the same cell. It appears that the secretory process of the Harderian gland of rat is affected by cholinergic stimulation of the two types of glandular cells and of myoepithelial cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 261 (1990), S. 501-508 
    ISSN: 1432-0878
    Schlagwort(e): Photoadaptation ; Stereology ; Ultrastructure ; Accumulation bodies ; Zooxanthellae ; Symbiodinium sp. ; Protozoa ; Dinoflagellata
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Quantitative ultrastructural studies on the effects of visible and ultraviolet radiation on zooxanthellae in culture and in situ showed an inverse relationship between the volume fraction of chloroplast and irridiance. An independent effect of ultraviolet radiation was detected in cultured zooxanthellae only. The volume fraction of chloroplasts in cultured zooxanthellae and zooxanthellae in situ were the same, while the surface density of thylakoid lamellae relative to chloroplast volume in cultured zooxanthellae was less than in zooxanthellae in situ for all irradiances. Additionally, zooxanthellae in situ showed an effect of ultraviolet radiation on surface density of thylakoid lamellae. The response to different irradiances suggests a limit to photoadaptation by means of changing chloroplast volume, and that changes in thylakoid density are responsible for the continued photoadaptive plasticity observed. Flow cytometry and stereological studies show that the volume fraction of accumulation bodies within zooxanthellae increases with irradiance and ultraviolet radiation. Ultrastructurally, accumulation bodies do not resemble plant peroxisomes or glyoxysomes, while other inclusions observed in this stydy are suggestive of peroxisomes. This evidence suggests that accumulation bodies are not peroxisomes, but does support the previous assumptions concerning their role in autophagic processes.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 33
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 262 (1990), S. 67-79 
    ISSN: 1432-0878
    Schlagwort(e): Urinary bladder ; Smooth muscle ; Hypertrophy ; Ultrastructure ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The fine structure of the muscle of the urinary bladder in female rats is similar to that of other visceral muscles, although it is arranged in bundles of variable length, cross-section and orientation, forming a meshwork. When distended, the musculature is 100–120 μm thick, with some variation and occasional discontinuity. Extended areas of cell-to-cell apposition with uniform intercellular space occur between muscle cells, whereas attachment plaques for mechanical coupling are less common than in other visceral muscles. There are no gap junctions between muscle cells. Many bundles of microfilaments and small elastic fibres run between the muscle cells. After chronic partial obstruction of the urethra, the bladder enlarges and is about 15 times heavier, but has the same shape as in controls; the growth is mainly accounted for by muscle hypertrophy. The outer surface of the hypertrophic bladder is increased 6-fold over the controls; the muscle is increased 3-fold in thickness, and is more compact. Mitoses are not found, but there is a massive increase in muscle cell size. There is a modest decrease in percentage volume of mitochondria, an increase in sarcoplasmic reticulum, and no appreciable change in the pattern of myofilaments. Gap junctions between hypertrophic muscle cells are virtually absent. Intramuscular nerve fibres and vesicle-containing varicosities appear as common in the hypertrophic muscle as in controls. There is no infiltration of the muscle by connective tissue and no significant occurrence of muscle cell death.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 34
    ISSN: 1432-0878
    Schlagwort(e): Hibernation ; Ultrastructure ; Plasma renin activity ; Renal changes ; Spermophilus lateralis (Rodentia)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Chronological changes in renal glomerular morphology and plasma renin activity were investigated during active and hibernating periods in the golden-mantled ground squirrel Spermophilus lateralis. The objective of this study was to determine whether the glomerular endothelium, visceral epithelium (podocytes), basement membrane, mesangial cells, proximal convoluted tubule cells and plasma renin activity exhibit measurable sequential differences between as well as within active and hibernating states at various time points. Limitations in the size of the experimental population prevented an evaluation of changes in these parameters during other important periods such as periodic arousal between hibernation bouts. In this study, glomerular endothelial pore number and epithelial filtration slit number significantly decreased by early hibernation when compared to those during summer activity, and then they increased back toward summer levels by late hibernation. In contrast, podocytic pedicel width along the glomerular basement membrane increased from summer activity to early hibernation, before significantly decreasing again by late hibernation. Mesangial cell and proximal convoluted tubule cell activity appeared increased during hibernation as compared to summer activity, whereas the width of the glomerular basement membrane showed no significant alterations throughout. Plasma renin activity significantly increased during early hibernation and mid-hibernation when compared to summer levels but had decreased by late hibernation toward summer values. The glomerular and plasma renin activity changes observed in this study clearly illustrate the drastic structural and functional adjustments which hibernating species make during torpor and also correlate well with the reported decrease in renal perfusion pressure and urine formation during hibernation. The observed morphological changes during hibernation do not appear to be temperature-dependent, because significant alterations in most of the parameters studied occurred during this period despite the fact that cold-room temperatures were kept constant throughout. The chronological approach to this study and its morphometric evaluation represent a pilot attempt at accurately documenting these changes during two critical states in the hibernator's cycle and may eventually lead to the characterization of these changes during the entire circannual cycle.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 35
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 114 (1983), S. 85-92 
    ISSN: 1615-6102
    Schlagwort(e): Chloroplasts ; Iron stress ; Sugar beet ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary When grown in iron-free media, the youngest leaves of healthy green sugar beet plants became completely yellow after 6 to 8 days. This chlorosis was quickly reversed by resupplying iron. A study of the ultrastructure of the iron -stressed leaves revealed apparently normal subcellular organization except for the plastids which were small and undeveloped, contained a rudimentary, disorganized grana-fretwork and clusters of vesicles in the periphery. Twelve to 16 hours after resupply of iron, aggregates of phytoferritin were observed in the stroma, and the granal fretwork underwent further development. There was an increased orientation of the membranes along the long axis of the plastids and an increase in the length of the individual grana stacks. By 48 hours, leaf chlorophyll content was about 40% of the control. At the ultrastructural level, parallel alignment of membrane orientation was complete and the grana stacks began to increase in the number of thylakoids per stack.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 115 (1983), S. 1-10 
    ISSN: 1615-6102
    Schlagwort(e): Brassica napus ; Nucleolus ; Pisum sativum ; Ultrastructure ; Zea mays
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The karyosome is a spherical body up to 1 μm in diameter that lies on the nucleolus of certain plant species, particularly those with a relatively low nuclear DNA content and an areticulate nuclear structure. It can be seen in the light microscope after impregnation with silver; in the electron microscope its structure consists of fibrillo-granular material. Nucleoli of cells in root apices may bear 0, 1, or 2 karyosomes. The frequency with which these numbers of karyosomes are observed depends on the location of the cells within the apex. In roots ofPisum sativum andZea mays the nucleoli of both slowly-dividing and young differentiating cells bear karyosomes more frequently than the nucleoli of rapidly-dividing cells. The karyosome seems to adopt a preferred location on the nucleolus, lying most frequently on the nucleolar surfaces directed towards the apex or base of the root. The origin and functional significance of the karyosome are discussed. Morphological evidence suggests that it may be material that formerly was part of a fibrillar centre.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 116 (1983), S. 1-13 
    ISSN: 1615-6102
    Schlagwort(e): Cuticle ; Peristomatal transpiration ; Stomata ; Ultrastructure ; Funaria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Cuticle and pore development in the guard cells ofFunaria were investigated with the electron microscope. Pore cuticle formation is simultaneous with the creation of the pore itself. The morphology of the pore cuticle is unlike that of any cuticle described in the literature. It has many lamellae which are penetrated by electron dense fibrils. Three different cuticular morphologies exist from the pore to the subsidiary cell walls. The cuticles on the pore and outer walls contain fibrils that sometimes reach to the surface. The subsidiary cell cuticle lacks fibrils altogether. It is hypothesized that (1) cuticularization of the middle lamella contributes to ventral wall separation and (2) differences in extent of cuticular fibrils are related to greater water loss from stomata than from subsidiary cells (peristomatal transpiration).
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 116 (1983), S. 115-124 
    ISSN: 1615-6102
    Schlagwort(e): Microtubules ; Moss ; MTOC ; Sporogenesis ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Microtubule systems appear sequentially at the distal and proximal poles of tetrad members during mid-sporogenesis in the mossTetraphis pellucida Hedw. The distal microtubule system emanates from a microtubule organizing center (MTOC) located between the single plastid and the nucleus. The distal MTOC and associated microtubules, which appear immediately after cytokinesis, are ephemeral and do not appear to be associated with the deposition of exine occuring at the same time. The proximal microtubule system, which appears slightly later than the distal system, is a more stable component of mid-sporogenesis. The proximal MTOC is an irregularly lobed, patelliform aggregation of electron-dense granules located beneath the plasma membrane at the proximal spore pole. Several bundles of microtubules radiate from the proximal MTOC and traverse the cell, enclosing the nucleus in an cone of microtubules. The proximal microtubule system is thought to function in aperture development and organelle migration. The relatively large nucleus migrates a short distance in the small spore early in the tetrad stage and maintains its acentric position at the proximal pole throughout later stages of sporogenesis. The plastid migrates later in the tetrad stage from its meiotic position parallel to the distal surface to a position perpendicular to the distal surface with one tip in close proximity to the proximal MTOC. The proximal microtubule system reaches its maximum development by the end of the tetrad stage and all micrographic evidence of it is lost in the maturation stages of late sporogenesis.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 116 (1983), S. 99-114 
    ISSN: 1615-6102
    Schlagwort(e): Sphaerostilbe repens ; Ultrastructure ; Differentiation ; Coremia ; Rhizomorphs
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The differentiating stages of coremia and rhizomorphs inSphaerostilbe repens were studied by transmission electron microscopy. Vegetative mycelium is characterized by highly cytoplasmic cells rich in ribosomes and mitochondria and with few vacuoles as well as endoplasmic reticulum. Cell walls are thin attaining a maximum thickness of 0.10 μm. During the aggregating phase a prosenchymatous mass of randomly oriented cells is produced by localized elongation and branching of the filaments. The hyphae in this region have the appearance of actively metabolising cells. In the course of the differentiating phase, numerous hyphae of the median zone of the aggregate grow upward and downward to give rise to coremium and rhizomorph primordia respectively. The individual hyphal tips lay parallel to each other and cells of the growing apices retain their meristematic characteristics. At the periphery of the aggregate and to a lesser extent in the subapical rhizomorphic zone, cells reduce their cytoplasmic density as a consequence of a decrease in the number of ribosomes. These cells also increase in size and become isodiametric and vacuolated. During cellular differentiation walls increase steadily in thickness and at the elongating phase they reach 0.30 μm in the rhizomorphic cortex. Mucilaginous material is progressively deposited around hyphae and in the most differentiated zones, coalesce to fill interhyphal spaces. This extracellular matrix seems to play a role in maintaining cohesiveness of the aggregated organs. The tissue in the process of differentiation is scattered with cells highly enriched in mitochondria and with cells virtually undifferentiated. Accumulation of microfilaments takes place in the differentiating zone localized behind the immersed meristematic apex. These structures might be involved in wall synthesis. Glycogen rosettes accumulate in the vegetative mycelium surrounding the aggregating centers, suggesting the possibility of supplying energy during the differentiating processes. The vacuolar system, represented by autophagic vacuoles which are present until the differentiation phase, presumably may also participate in the biochemical changes that occur during aggregation. Coremial cells are characterized by an increase in wall thickness, a highly sinuous plasma-membrane as well as large amounts of mucilaginous compounds accumulated between hyphae, but in all other respects they resemble the cells of actively growing vegetative hyphae.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 40
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 116 (1983), S. 125-135 
    ISSN: 1615-6102
    Schlagwort(e): Ciliated protozoan ; Sorogenesis ; Extracellular matrix ; Secretion ; Extrusive organelles ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Sorogena stoianovitchae Bradbury andOlive is an unusual kinetophragminophoran ciliate characterized by the aggregation of individual trophic cells to form a multicellular sorogen that rises aerially from the medium surface to produce a sorocarp. A light and electron microscope study of sorogenesis revealed how the sorogenic cells produce the stalk. The feeding ciliates contain numerous subpellicular expansions of rough endoplasmic reticulum cisternae that are only one element of the secretory system necessary for stalk formation. Upon aggregation, the stalk secretory system develops further, initially with the proliferation of the subpellicular expansions. Then, during later aggregation and early sorogenesis, other secretory elements appear: stalk material vesicles, dense granule vesicles, and electron lucent vacuoles. These are all derived from the rough endoplasmic reticulum. Only the subpellicular expansions and stalk material vesicles appear to add to the stalk matrix. The dense granule vesicles could be precursors of the stalk material vesicles; the electron lucent vacuoles, which can be demonstrated to contain fibrillar material, are perhaps by-products of the secretory process. Sorogenesis inSorogena occurs by a mechanism unique among the stalk-producing protists that have been studied.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 116 (1983), S. 136-144 
    ISSN: 1615-6102
    Schlagwort(e): Stalk ; Ciliated protozoan ; Sorogenesis ; Extracellularmatrix ; Ultrastructure ; Secretion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The sorogenic cells of the haptorid ciliateSorogena stoianovitchae Bradbury andOlive secrete a hydrated, fibrillar matrix that becomes organized to form a stalk. This light and electron microscope study examines the role of the secreted stalk matrix in the development of the sorocarp. The stalk material is secreted as a compact clump or clumps of material that expands as it hydrates. The expanded stalk material is initially viscous, but soon, through dehydration or cross-linking, solidifies to form a sheath. The sheath is the outside layer of the stalk, provides structural support, and controls the expansion of the newly secreted stalk material. The sorogenic cells continue to secrete stalk material that expands once it is outside of the cell. The resulting expansion force is directed upward by the sheath, thereby moving the cells further above the surface. The continued dehydration of the sheath material provides an inwardly directed force that also contributes to the upward movement of the sorogen.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 42
    ISSN: 1615-6102
    Schlagwort(e): Cytochrome oxidase ; Cytochemistry ; Ultrastructure ; Neurospora ; Heat treatment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Cytochrome oxidase (EC 1.9.3.1) activity of conidia of wild-typeNeurospora crassa was detected cytochemically at the ultrastructural level by 3,′-diaminobenzidine (DAB) reaction during heat treatment at 46 °C and after shift down to 25 °C. At 46 °C the decrease in the enzyme activity was shown to be time-dependent (0–10 hours) in the progressively overswelling conidia. Gradual recovery of the DAB reaction occurred in mitochondria of conidia outgrowing conidiogenous germ tubes (microcycle conidiation) when shifted down to 25 °C. Inactivation of cytochrome oxidase was efficiently prevented during heat treatment in the presence of Tween 20. Such conidia no longer overswelled but still required shift down to 25 °C to produce germ tubes with delayed conidiogenous ability.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 43
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 117 (1983), S. 7-16 
    ISSN: 1615-6102
    Schlagwort(e): Beta vulgaris ; Chloroplast ; Ultrastructure ; Ultraviolet radiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The effect of UV-C (254 nm) and UV-B (290–320 nm) radiation on leaves ofBeta vulgaris L. at the ultrastructural level was investigated. Although the damage caused by UV-C radiation was more striking than that resulting from UV-B radiation, several structural changes were seen in the UV-B treated material. Generally the effects of UV-B and UV-C radiation were different, suggesting different mechanisms of action, discernible even at the ultrastructural level.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 44
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 117 (1983), S. 116-129 
    ISSN: 1615-6102
    Schlagwort(e): Pollen ; Amoeboid tapetum ; Arum italicum ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A tapetum is found around all higher plant meiocytes and is thought to nourish them. It may, in turn, be influenced by their development. The mature tapetal membrane in amoeboid (or periplasmodial) tapeta, of whichArum italicum is an example, fits closely around the developing meiocyte. This description of tapetal ultrastructure starts from the meiotic prophase when the tapetum is still cellular and comprises two rows of cells on the inside of the tetrasporangiate anther. The radial walls of the still cellular tapetum start to dissolve during leptotene of the first meiosis. The lysis begins in the middle lamella in those areas penetrated by the most plasmodesmata. The walls in contact with the meiocytes on the other hand do not disappear until after the first meiosis. At telophase the now fused cytoplasmic tapetal mass begins to extend its joint plasmamembrane, amoeboid fashion, into the loculus. A cluster of microtubules can be seen at the apex of this intrusion apparently initiating or maintaining the shape of the invading plasmamembrane front. The tapetum now adheres closely to the microspores. The tapetal zone closest to the spores has a prominent population of microtubules and just a little ER, whereas the outer zone away from the spores contains all the other organelles. The inner zone, in a squash preparation, is not readily separated from the spores. The microtubules, at the middle microspore stage, are no longer to be seen in a circle around the microspores, but spread out with some lying orthogonal to the now-forming exine surface. In places the tapetal plasmamembrane begins to retract from the exine leaving roughly cone-shaped zones (spines) which become filled with fibrillar material. This material begins to be deposited on the exine surface. These “spines” are both PAS. and Coomassie-blue positive and susceptible to acetolysis.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 45
    ISSN: 1615-6102
    Schlagwort(e): Histochemistry ; Sclerotia ; Sclerotial germination ; Sclerotinia ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Cytoplasmic reserves and extracellular substances were progressively broken down and utilized during carpogenic germination of sclerotia ofSclerotinia minor. Glycogen, wall polysaccharides and polyphosphate granules were removed first from regions of the sclerotium distant from developing apothecia, while protein bodies near the base of apothecial stipes were hydrolysed before those further away. The number of profiles of mitochondria and endoplasmic reticulum in cortical and medullary hyphae increased at the onset of germination, indicating increased metabolism in the hyphae. In contrast to developing sclerotia, simple pores with Woronin bodies were frequent in walls and septa during germination. Hyphae that appeared to converge towards the base of apothecial initials retained their cytoplasm and organelles until late in germination and hydrolysis of their reserves was delayed; these are interpreted as translocatory hyphae, although further work is required to determine their role unequivocally. When apothecia were fully developed, hyphae throughout the sclerotium were empty and the walls and extracellular matrix of cortical and medullary hyphae had almost completely broken down.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 46
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 118 (1983), S. 56-70 
    ISSN: 1615-6102
    Schlagwort(e): Carposporophyte ; Cell division ; Mitosis ; Rhodophyta ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Mitotic ultrastructure was observed in meristematic cells of carposporophyte generations of the freshwater red algaBatrachospermum ectocarpum. Prior to nuclear division, cell elongation occurs resulting in the nucleus being located at the proximal end of the cell and separated by a large central vacuole from a distal “empty region” which the daughter nucleus eventually occupies. In late prophase, nuclear envelope-attached polar rings are situated adjacent to shallow nuclear invaginations. At prometaphase the nuclear invaginations extend deeply into the nucleus forming continuous cytoplasmic channels containing microtubules. Perinuclear ER and a typical equatorial chromosomal plate are formed by metaphase at which time the nuclear envelope lining the cytoplasmic channels has dispersed. Chromosomal and non-chromosomal microtubules converge at the poles where a single, large gap is seen in the otherwise intact nuclear envelope. Polar rings were not detected in the few mitotic cells observed beyond prometaphase but are thought to be present. During anaphase an interzonal midpiece is formed and the distal-most incipient daughter nucleus moves laterally past the central vacuole into the apical “empty region”. Features of mitosis inBatrachospermum are believed to be intermediate between those exhibited by the lower and higher orders of red algae, this being consistent with the taxonomic placement of the genus in theNemaliales, the least advanced order of the classFlorideophyceae.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 47
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 118 (1983), S. 95-103 
    ISSN: 1615-6102
    Schlagwort(e): Nuclear bodies ; Nucleolus ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Nuclear bodies are found in interphase nuclei of root apices of a number of plant species. They often show differences in structure and position relative to the nucleolus and this has led to an attempt to define two classes of body. However, in some species their separation into two classes on structural grounds alone breaks down, indicating that although they may occupy different positions within the nucleus they may in these particular cases be only different forms of the same body. The two extremes of the range of bodies examined represent what have been called “nucleolus-associated body” (karyosome) and “dense body”. The nucleolus-associated body is typically attached to, or adjacent to, the nucleolus. It is composed of fibrils 4–8 nm wide and often has an open structure showing compound threads or fibrils separated from each other by electron-lucent spaces. The dense body is more compact in structure and typically lies free in the nucleoplasm. Both types of body have an affinity for silver ions which, together with their staining reaction following treatment with EDTA, indicates that they consist of ribonucleoprotein. The characteristics of nuclear bodies found in different plant species have some relationship with the structure and DNA content of the interphase nucleus. Nucleolus-associated bodies are characteristic of species with an areticulate nuclear structure (2 C DNA content 〈6 pg), while dense bodies are common in species with a reticulate nuclear structure (2 C DNA content 〉6 pg). The possible functions of the two forms of nuclear body are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 48
    ISSN: 1615-6102
    Schlagwort(e): Calcification ; Coccolithophorids ; Polysaccharide localization ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Emiliania huxleyi is a marine coccolithophorid which produces coccoliths,i.e., particles consisting of calcite and macromolecular organic material. The coccoliths are formed intracellulary in specialized organelles which comprise a coccolith vesicle (CV) and a reticular body (RB), together forming the CV/RB system or calcifying system. After termination of calcification, the coccolith is extruded and incorporated into the coccosphere,i.e., one or several layers of extracellular coccoliths surrounding the cell. Apart from the coccolith-producing cells (C cells) ofE. huxleyi, there are naked cells (N cells) which seem to have lost the capacity to produce coccoliths but are very similar to the C cells in other morphological respects. Biochemical studies have revealed that polysaccharides may play a regulatory role in calcification. The aim of the present study was to determine the localization of polysaccharides in both C and N cells electron microscopically. For this purpose, a cytochemical staining technique according toThiéry (1967) was applied. The CV/RB system of C cells was conspicuously stained. Due to the excellent stainability of this system, a putative succession of morphological stages during coccolithogenesis could be described. The staining pattern of the N cells closely resembled that of the C cells. It was found, however, that the “calcifying” system of N and C cells differed in both morphology and position. It is suggested that the divergent morphology of the “calcifying” system of N cells accounts for its failure to produce coccoliths.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 153 (1990), S. 178-185 
    ISSN: 1615-6102
    Schlagwort(e): Cryptophyceae ; Dinoflagellate ; Dinophyceae ; Endosymbiosis ; Gymnodinium ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The freshwater dinoflagellateGymnodinium acidotum is known to harbor a cryptomonad endosymbiont whose chloroplasts give the organism its blue-green coloration. Every cell examined from a wild population possessed chloroplasts, mitochondria, and other organelles which are of endosymbiotic origin. Transmission electron microscopy and fluorescence microscopy revealed that only 33% of these cells possessed the nucleus of the endosymbiont. The lack of a cryptomonad nucleus in some cells did not appear to affect the cells' ability to photosynthesize or move in response to varying levels of illumination. This represents the first report of a host/endosymbiont relationship in which a significant number of individuals from a given population lack a major endosymbiont organelle.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 50
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 154 (1990), S. 122-131 
    ISSN: 1615-6102
    Schlagwort(e): Cellulose degradation ; Ultrastructure ; Rumen ciliate ; Polyplastron multivesiculatum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The feeding behaviour of the rumen ciliatePolyplastron multivesiculatum has been studied with scanning and transmission electron microscopy. In contrast to other large entodiniomorphs,Polyplastron scarcely attaches to plant substrata such as straw or alfalfa; however, it readily phagocytes cellulose fibres (like epidermal bristles of alfalfa) suspended in the rumen fluid. The different stages of ingestion and intracellular degradation of this particular substrate are described at the ultrastructural level. Engulfment involves active movements of the vestibular lips. The digestion follows a peculiar pattern (“permeative” way): the cellulose substrate is gradually decomposed in situ inside the primary digestive vacuole without large fragmentation or pinching off of small vesicles. Thus degradation products are not stored in secondary vesicular systems as they are for other plant substrates (“cytotic” way). Thus, there is no single or general pattern of cellulosic structures lysis in entodiniomorph rumen ciliates. Rather, several pathways can be observed, probably according to the nature of the ingested plant material.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 51
    ISSN: 1615-6102
    Schlagwort(e): Basidiomycetes ; Cytoplasmic connections ; Host-parasite interaction ; Tetragoniomyces uliginosus ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The cellular interaction ofTetragoniomyces uliginosus andRhizoctonia sp. was restudied by transmission electron microscopy. During the first stages of interaction a body of medium electron density is visible at the center of the haustorial apex in close association with the plasmalemma. A single micropore is produced between the haustorial filament and the host cell. Cytoplasmic connection via the pore always occurred. The pore membrane is continuous with the plasmalemma of both cells. The protoplasts of both the haustorium and the host cell fuse via the micropore. An electron transparent to dense body occlude the pore. Among basidiomycetes, direct connection between the parasite and host protoplasts represents a hitherto unknown type of parasitic interaction.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 52
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 154 (1990), S. 25-33 
    ISSN: 1615-6102
    Schlagwort(e): Selenium deficiency ; Culture medium ; Crustacea ; Daphnia magna ; Ultrastructure ; Cytopathology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The effect of selenium deprivation onDaphnia magna was examined under controlled rearing conditions in a synthetic culture medium. After three generations, fertility was significantly reduced in deprived (Se−) animals. Growth and mortality of parent daphnids and development of parthenogenetic eggs were not affected during this period. In the fourth generation Se− daphnids rejected parts of their second antennae. At the ultrastructural level antennal muscle tissue was severely affected. Animals deprived of selenium had mitochondria and sarcoplasmic reticulum with myelin-like alterations. Giant lysosomes were present and complete lysis of muscle fibrils was observed in antennal muscle cells. These alterations are characteristic features of peroxidic damage in tissues. This interpretation is consistent with the function of selenium as a constituent of the enzyme glutathione peroxidase which protects cells from peroxidation. Selenium should be included in synthetic culture media for daphnids.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 53
    ISSN: 1615-6102
    Schlagwort(e): Ascodesmis nigricans ; Ascosporogenesis ; Freeze substitution fixation ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Freeze substitution proved to be a valuable technique for studying the early stages of ascosporogenesis inAscodesmis nigricans. Our observations indicate that the ascus vesicle originated from the ascus plasma membrane. Invaginations of the plasma membrane produced ascus vesicle initials consisting of two closely spaced unit membranes. The appearance of the outer leaflet of each of these membranes was identical to that of the inner leaflet of the ascus plasma membrane. Apparent points of continuity between ascus vesicle initials and the plasma membrane were observed. Ascus vesicle initials accumulated in the ascus cytoplasm near the plasma membrane and then coalesced to form the ascus vesicle, a peripheral, cylinder-like structure consisting of two closely spaced unit membranes that extended from the ascus apex to the ascus base. The ascus vesicle then became invaginated in a number of regions and subsequently gave rise to eight sheet-like segments, or ascosporedelimiting membranes, that encircled uninucleate segments of cytoplasm forming ascospore initials. Like the ascus vesicle, each ascospore-delimiting membrane consisted of two closely spaced unit membranes, the inner of which became the ascospore plasma membrane. The ascospore wall then developed between the spore plasma membrane and the outer membrane. Many details of ascospore maturation were clearly visible in freeze substituted samples.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 54
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 157 (1990), S. 3-18 
    ISSN: 1615-6102
    Schlagwort(e): Chilling ; Cytomorphogenesis ; Heat ; “Heat shock granules” ; Micrasterias ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Exposure of growingMicrasterias cells to high (32°–36°C) and low (3°–10°C) temperatures produces changes in morphology that are accompanied by several ultrastructural alterations. Whereas low temperatures essentially cause simplification of cell ornamentation, a variety of cell malformations result from high temperature treatment. These are the loss of cell symmetry leading to markedly aberrant cell shapes and an increase of “main lobes” with reduced degree of differentiation. Preliminary studies indicate that a shift in the distribution of membrane-associated Ca2+ by elevated temperatures probably underlies these abnormal cytomorphogenetic events. Both, low and high temperature cause a reduction in size of the young half cell and affect cytoplasmic streaming. Moreover, nuclear migration is retarded and chloroplast arrangement is influenced by temperature treatment at both ranges. Growth velocity of primary wall responsible for cell shaping is increased at high and slowed down at low temperatures compared to cells grown at 20°C. The main ultrastructural alterations induced by high temperatures are an increase in amount and length of ER cisternae, the appearance of “heat shock granule” aggregations localized in the cytoplasm, a reduced number of ribosomes and polysomes, the presence of oil bodies in growing cells and a varying thickness of the primary wall. Influences of low temperatures on ultrastructure are less pronounced. They are manifested in the formation of large aggregations of ER cisternae slightly differing from those found in untreated cells, a disturbed arrangement of the microtubule system surrounding the nucleus and a decrease of the number of cell wall forming cytoplasmic vesicles. It is thought that most of the temperature effects are due to an influence on membranes probably an alteration of ionic currents and, in addition, a modulation of normal protein synthesis.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 55
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 156 (1990), S. 9-18 
    ISSN: 1615-6102
    Schlagwort(e): Esophageal glands ; Plant-parasitic nematodes ; Secretory granules ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The dorsal and subventral esophageal glands and their secretory granules in the root-knot nematodeMeloidogyne incognita changed during parasitism of plants. The subventral esophageal glands shrank and the dorsal gland enlarged with the onset of parasitism. While secretory granules formed by both types of glands were spherical, membrane-bound, and Golgi derived, the granules differed in morphology and size between the two types of glands. Subventral gland extensions in preparasitic second-stage juveniles were packed with secretory granules which varied in diameter from 700–1,100 nm and had a finely granular matrix. Within the matrix of each subventral gland granule was an electron-transparent core that contained minute spherical vesicles. The size and position of the core varied within different granules. Few granules were present in the dorsal gland extension in preparasitic juveniles. The matrix of dorsal gland secretory granules formed during parasitism was homogeneous and more electron-dense than the matrix of subventral gland granules. Subventral gland secretory granules of parasitic juveniles and adult females appeared degenerate.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 56
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 156 (1990), S. 45-56 
    ISSN: 1615-6102
    Schlagwort(e): Cytochemistry ; Grasses ; Microhairs ; Partitioning membranes ; Polysaccharides ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Secretory activities of bicellular microhairs from grasses belonging to the subfamilies Chloridoideae, Arundinoideae, Panicoideae, and Bambusoideae, and including the “chloridoid”, “panicoid” and “Enneapogon” microhair morphological types, have been investigated. Light microscopic histochemistry indicated that all microhairs studied secrete polysaccharide and protein (or glycoprotein), including those which also secrete salt. Localization of polysaccharide at ultrastructural level using periodic acid-thiocarbohydrazidesilver proteinate staining revealed that in “panicoid type” microhairs dictyosomes are involved in polysaccharide secretion, whereas in the “chloridoid” and “Enneapogon” types “partitioning membranes” seem to be involved instead.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 57
    ISSN: 1615-6102
    Schlagwort(e): Tetraselmis striata ; Prasinophyceae ; Flagellar scales ; Isolation ; Purification ; Ultrastructure ; Biochemical composition ; 2-keto-sugar acids ; Polypeptide composition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Flagellar scales from the green flagellateTetraselmis striata (Prasinophyceae) were isolated, purified by isopycnic cesium chloride-gradient and zonal sucrose gradient centrifugation and their structure and biochemical composition investigated. Three types of flagellar scales were purified to more than 90% purity, a fourth type up to 75% purity. In addition to the previously known types of flagellar scales (pentagonal scales, rod-shaped scales, hair-scales), a novel scale type (i.e., the knotted scales) was discovered. New information about the asymmetric structure of the rod-shaped scales is presented and consequently they are renamed “man scales”. Flagellar scales consist mainly of carbohydrate (50–70%), significant amounts of protein (11% of dry weight) were found only in pentagonal scales. The main sugars (90%) of the pentagonal and man scales are the unusual 2-keto-sugar acids 3-deoxy-5-O-methyl-2-octulosonic acid (5 OMeKDO), 3-deoxy-2-heptulosaric acid (DHA), and 3-deoxy-2-octulosonic acid (KDO), the knotted scales contain as major sugars galactose and arabinose in addition to KDO and 5 OMeKDO but lack DHA. 13 major polypeptides were identified in flagellar scales by one-dimensional SDS-PAGE, 11 of these are of high molecular mass (〉116 kDa). While the majority of polypeptides was found associated with pentagonal scales, at least 4 polypeptides were tentatively assigned to the hair-scales and knotted scales.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 58
    Digitale Medien
    Digitale Medien
    Springer
    Journal of applied phycology 2 (1990), S. 293-296 
    ISSN: 1573-5176
    Schlagwort(e): heavy metal ; photosynthesis ; periphyton ; tolerance ; Cyanophyceae ; genetic adaptation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A study was made of the tolerance to Cu of 11 strains of Cyanophyceae and 7 strains of eukaryotes. These had all been tested within 6 months after isolation for their photosynthetic activity when exposed to Cu (Takamuraet al., 1989) and had repeatedly been subcultured in the medium without Cu for 2 years. Photosynthetic measurements were made in two ways: precultured in medium without Cu or precultured (for one subculture) in medium containing Cu (645 μg 1−1). The results were compared with those obtained within 6 months of isolation. The tolerance of the eukaryotes did not change significantly in any case, but most strains of Cyanophyceae lost their tolerance to Cu within a few subcultures in medium without Cu; however tolerance recovered following one subculture in medium containing an intermediate level of Cu. This rapid adaptation cannot be explained by a constitutive mutation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 59
    ISSN: 1573-5176
    Schlagwort(e): Cystoseira barbata ; photosynthesis ; light ; temperature ; salinity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The net photosynthesis of the Mediterranean brown seaweedCystoseira barbata f.repens is measured according to irradiance, temperature and salinity. There is not only, a good utilization of low light intensities (light-shade adaptation), but also a specific ability to use a broad range of irradiance, which corresponds in the photosynthesis-irradiance curves to a high initial slope and an extended light saturation level from 300 to 1500 μmol photon m−2 s−1; only very high irradiances induce photoinhibition. Maximum net photosynthesis occurred at temperatures ranging from 20 °C to 30 °C. The alga tolerates not only a low level of salinity, but also a slight increase in salinity; however, at more than 47.5 g 1−1 NaCl, oxygen exchange is significantly reduced. Light, temperature and salinity requirements are discussed, taking into account ecological considerations. Yields and quality of alginic acid are presented according to the irradiance and yearly evolutionin situ in order to aid future cultivation of this species.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 60
    Digitale Medien
    Digitale Medien
    Springer
    Journal of applied phycology 2 (1990), S. 163-171 
    ISSN: 1573-5176
    Schlagwort(e): Gracilaria ; strain selection ; growth ; photosynthesis ; rubisco ; agar
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A strain selection procedure using Gracilaria verrucosa gametophytic sporelings was found to be an efficient tool for the improvement of Gracilaria strains. Two strains, C-2 and A-18, which were isolated and grown clonally, showed higher growth rates under high and low temperature conditions, respectively, than the local Gracilaria conferta. Growth rate, photosynthesis and chlorophyll, which were measured under different temperature and photon flux densities, demonstrated an overall advantage of the selected strains over the wild type strains of both G. verrucosa and G. conferta. Growth rates were also generally in positive correlation with the carboxylase activity of Rubisco. The G. verrucosa wild type also had a 40% higher agar content than G. conferta. The selected strains thus showed higher potential for outdoor cultivation than local wild type populations.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 61
    ISSN: 1573-8469
    Schlagwort(e): Canopy enclosure ; stomatal conductance ; light response curve ; light use efficiency ; photosynthesis ; Solanum tuberosum L. ; transpiration ; water use efficiency
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Beschreibung / Inhaltsverzeichnis: Samenvatting Aardappelplanten (Solanum tuberosum L.) cv.Saturna werden onderworpen aan stress als gevolg vanVerticillium dahliae en droogte. In vroege stadia van de groei werden stomataire geleiding, transpiratie en netto fotosynthese bij lichtverzadiging (PAR〉300 W m−2) gemeten aan individuele bladeren en met een mobiel instrumentarium met behulp van gewaskappen. Er werden geen significante verschillen gevonden in de waarden van de stomataire geleiding en de gasuitwisslingskarakteristieken als gevolg vanV. dahliae-besmetting tot een maand na opkomst. Daarna leidde infectie metV. dahliae tot een afname van de stomataire geleiding, transpiratie en netto fotosynthese, speciaal bij oudere bladeren en bij planten die meer aan zonlicht waren blootgesteld. Soms vertoondeV. dahliae interactie met droogte en bleken beide effecten minder dan optelbaar. De hoge waarden van de variatiecoëfficiënten maakten een groot aantal metingen per behandeling noodzakelijk; dit was vooral het geval bij metV. dahliae geïnfecteerde planten hetgeen aantoont datV. dahliae vooral in het begin van de groei niet alle bladeren in gelijke mate aantast. Door de matigende invloed van de integratie van alle bladlagen en mogelijk doordat de bovenste bladeren werden gestimuleerd, werd de totale gewasfotosynthese in mindere mate beïnvloed doorV. dahliae dan de individuele bladfotosynthese. De bovenste niet geïnfecteerde bladeren bleken verantwoordelijk voor het grootste gedeelte van de gewas-fotosynthese. De resultaten tonen aan, dat volgend op een infectie metV. dahliae, de fotosynthese reeds in een vroeg stadium van de groei wordt verminderd als een gevolg van droogtestress in de bladeren.
    Notizen: Abstract Potato (Solanum tuberosum L.) plants cv.Saturna were subjected to infection withVerticillium dahliae and drought stress. At the early stages of growth, stomatal conductance, transpiration and net photosynthesis were measured at light saturation (PAR〉300 m−2) on individual leaves and with mobile field equipment with the aid of field enclosures. No significant changes in stomatal conductance and gas exchange characteristics occurred as a result ofV. dahliae instomatal conductance, transpiration and and photosynthetic rates, especially on older leaves and on plants exposed to direct sunlight for a longer period of time. In combination with drought,V. dahliae only occasionally showed interaction; their effects being less than additive. High values of coefficients of variatoon necessitated a high number of measurements per treatment; the more so in the inoculated plants which shows thatV. dahliae seems to affect certain leaves while not affecting others early in growth. Crop photosynthesis was less reduced byV. dahliae than individual leaf photosynthesis due to the levelling effect of integration over the whole canopy and possibly through a stimulation of the top leaves. The upper non-affected leaves are responsible for the bulk of photosynthetic crop activity. The results indicate that following an infection withV. dahliae photosynthesis is reduced early in growth as a result of drought stress in the leaves.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 62
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 71 (1983), S. 147-153 
    ISSN: 1573-5036
    Schlagwort(e): Cortex ; Endodermis ; Picea sitchensis ; Tilia cordata ; Transfer cells ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The endodermis of bothTilia cordata andPicae citchensis progressess through 3 characteristic phases of development. These developments are delayed somewhat in the xylem pole endodermis ofT. cordata, while inP. sitchensis 3–5 passage cells are found. The cortex ofT. cordata is characterised by very thick walls, while that ofP. sitchensis is characterised by a thick walled layer just outside the endodermis and by 2–3 outer layers of transfer cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 63
    ISSN: 1573-5079
    Schlagwort(e): cytochrome c ; photosynthesis ; photosynthetic bacteria ; electron transport ; Chloroflexus aurantiacus ; green bacteria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The membrane-bound photooxidizable cytochrome c-554 from Chloroflexus aurantiacus has been purified. The purified protein runs as a single heme staining band on SDS-PAGE with an apparent molecular mass of 43 000 daltons. An extinction coefficient of 28 ± 1 mM−1 cm−1 per heme at 554 nm was found for the dithionite-reduced protein. The potentiometric titration of the hemes takes place over an extended range, showing clearly that the protein does not contain a single heme in a well-defined site. The titration can be fit to a Nernst curve with midpoint potentials at 0, +120, +220 and +300 mV vs the standard hydrogen electrode. Pyridine hemochrome analysis combined with a Lowry protein assay and the SDS-PAGE molecular weight indicates that there are a minimum of three, and probably four hemes per peptide. Amino acid analysis shows 5 histidine residues and 29% hydrophobic residues in the protein. This cytochrome appears to be functionally similar to the bound cytochrome from Rhodopseudomonas viridis. Both cytochrome c-554 from C. aurantiacus and the four-heme cytochrome c-558-553 from R. viridis appear to act as direct electron donors to the special bacteriochlorophyll pair of the photosynthetic reaction center. They have a similar content of hydrophobic amino acids, but differ in isoelectric point, thermodynamic characteristics, spectral properties, and in their ability to be photooxidized at low temperature.
    Materialart: Digitale Medien
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  • 64
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 23 (1990), S. 67-72 
    ISSN: 1573-5079
    Schlagwort(e): leaf size ; light ; photosynthesis ; shading ; soybeans ; specific leaf weight
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract This study investigated the basis of the negative relationship between leaf size and photosynthetic rate per unit of area among five cultivars of soybeans. Exposure of developing mainstem leaves to light, and sizes and light saturated photosynthesis rates of those leaves at maturity were compared in cultivars grown in field plots for two years at Beltsville, Maryland, USA. Plants were grown both in stands at 2.5 cm by 1 m spacing and as isolated plants. While cultivar differences in leaf size were large and consistent in both planting arrangements, significant cultivar differences in light saturated photosynthetic rates were found only in plants grown in stands. Similarly, leaf size was significantly correlated with specific leaf weight only for plants grown in stands. The mainstem apex and developing mainstem leaves experienced more severe shading in large-leaved cultivars than in small-leaved cultivars when plants were grown in stands. Thus, cultivar differences in photosynthetic capacity were probably a consequence of differences in the exposure of developing leaves to light.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 65
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 23 (1990), S. 313-318 
    ISSN: 1573-5079
    Schlagwort(e): thylakoid membranes ; electron transfer ; photoacoustic spectroscopy ; energy storage ; photosynthesis ; plastoquinone
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The photosynthetic energy storage yield of uncoupled thylakoid membranes was monitored by photoacoustic spectroscopy at various measuring beam intensities. The energy storage rate as evaluated by the half-saturation measuring beam intensity (i50) was inhibited by 3-(3,4-dichlorophenyl)-1,1 dimethylurea, by heat inactivation or by artificial electron acceptors specific for photosystem I or photosystem II; and was activated by electron donors to photosystem I. The reactions involving both photosystems were all characterized by a similar maximal energy storage yield of 16±2 percent. The data could be interpreted if we assumed that the energy storage elicited by the photosystems at 35 Hz is detected at the level of the plastoquinone pool.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 66
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 25 (1990), S. 77-82 
    ISSN: 1573-5079
    Schlagwort(e): autobiography ; chloroplast structure ; chloroplast proteins ; chloroplast lipids ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract An autobiographic report of studies on the elucidation of the structure of the chloroplast is presented here. It deals with the discovery of the lamellar structure of chloroplasts by polarization-microscopy, the representation of their layer-like structure with the ultraviolet microscope and the results obtained by the electron-microscope leading to the discovery of the structural elements of the lamellar system. These lamellar structures were in the form of vesicles, and were named thylakoids. Isolation of the chloroplasts made it possible to determine their chemical composition. Amphiphilic lipids, together with water, create bimolecular layers and, therefore, are responsible for the structure of the thylakoid-membranes. The role of membrane proteins was emphasized. The isolation of the individual polypeptides was possible after dissociation in sodium-dodecyl-sulfate. Antisera to these polypeptides were used to localize them in the membrane. These antisera are able to inhibit special steps in the electron transport. Our results of the spectroscopic examination of photosynthetic membrane components are also discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 24 (1990), S. 109-113 
    ISSN: 1573-5079
    Schlagwort(e): atrazine ; diuron ; photosystem II ; photosynthesis ; thylakoids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The binding of the herbicide atrazine to thylakoid membranes is often used to quantify Photosystem II reaction centres. Two atrazine binding sites, with high and low affinities, have been observed on the D1 and D2 polypeptides of Photosystem II, respectively (McCarthy S., Jursinic P. and Stemler A. (1988) Plant Physiol. 86S:46). We have observed that the accessibility of the low-affinity binding sites is variable, being limited in freshly isolated thylakoids or in fresh frozen-thawed thylakoids, but increasing during storage of the membranes on ice. In contrast, the accessibility of the high-affinity binding sites, which are titratable at low concentrations (〈 500 nM) of herbicide, is much less variable, although the dissociation constant is greatly influenced by ethanol. We conclude that to quantify Photosystem II reaction centres by atrazine binding, it is sufficient and more reliable to assay only the high-affinity binding sites.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 68
    ISSN: 1573-5079
    Schlagwort(e): cyanobacteria ; photosynthesis ; psbC gene ; psbD gene ; translational start codon ; overlapping genes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The unicellular photoheterotrophic cyanobacterium Synechococcus sp. PCC 7002 was shown to encode two genes for the Photosystem II reaction center core protein D2 and one gene for the reaction center chlorophyhll-binding protein CP43. These three genes were cloned and their DNA sequences determined along with their flanking DNA sequences. Northern hybridization experiments show that both genes which encode D2, psbD1 and psbD2, are expressed at roughly equivalent levels. For each of the two psbD genes, there are 18 nucleotide differences among the 1059 nucleotides which are translated. The DNA sequences surrounding the coding sequences are nearly 70% divergent. Despite the DNA sequence differences in the genes, the proteins encoded by the two genes are predicted to be identical. The proteins encoded by psbD1 and psbD2 are ∼92% homologous to other sequenced cyanobacterial psbD genes and ∼86% homologous to sequenced chloroplast-encoded psbD genes. The single gene for CP43, psbC, overlaps the 3′ end of psbD1 and is co-transcribed with it. Results from previous sequencing of psbC genes encoded by chloroplasts suggest that the 5′ end of the psbC gene overlaps the 3′ end of the coding sequence of psbD by ∼50 nucleotides. In Synechococcus sp. PCC 7002, the methionine codon previously proposed to be the start codon for psbC is replaced by an ACG (threonine) codon. We propose an alternative start for the psbC gene at a GTG codon 36 nucleotides downstream from the threonine codon. This GTG codon is preceded by a consensus E. coli-like ribosome binding sequence. Both the GTG start codon and its preceding ribosome binding sequence are conserved in all psbC genes sequenced from cyanobacteria and chloroplasts. This suggests that all psbC genes start at this alternative GTG codon. Based on this alternative start codon, the gene product is ∼85% identical to other cyanobacterial psbC gene products and ∼77% identical to eucaryotic chloroplast-encoded psbC gene products.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 69
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 24 (1990), S. 245-252 
    ISSN: 1573-5079
    Schlagwort(e): inorganic carbon transport ; light ; Chlamydomonas ; CO2 exchange ; photorespiration ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effect of photon flux density on inorganic carbon accumulation and photosynthetic CO2 assimilation was determined by CO2 exchange studies at three, limiting CO2 concentrations with a ca-1 mutant of Chlamydomonas reinhardiii. This mutant accumulates a large internal inorganic carbon pool in the light which apparently is unavailable for photosynthetic assimilation. Although steady-state photosynthetic CO2 assimilation did not respond to the varying photon flux densities because of CO2 limitation, components of inorganic-carbon accumulation were not clearly light saturated even at 1100 μmol photons m-2 s-1, indicating a substantial energy requirement for inorganic carbon transport and accumulation. Steady-state photosynthetic CO2 assimilation responded to external CO2 concentrations but not to changing internal inorganic carbon concentrations, confirming that diffusion of CO2 into the cells supplies most of the CO2 for photosynthetic assimilation and that the internal inorganic carbon pool is essentially unavailable for photosynthetic assimilation. The estimated concentration of the internal inorganic carbon pool was found to be relatively insensitive to the external CO2 concentration over the small range tested, as would be expected if the concentration of this pool is limited by the internal to external inorganic carbon gradient. An attempt to use this CO2 exchange method to determine whether inorganic carbon accumulation and photosynthetic CO2 assimilation compete for energy at low photon flux densities proved inconclusive.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 70
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 25 (1990), S. 17-24 
    ISSN: 1573-5079
    Schlagwort(e): delayed light ; oxygen evolution ; photosynthesis ; thermoluminescence (money plant, pothos aurea leaf)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effect of ultraviolet light on thermoluminescence, oxygen evolution and the slow component of delayed light has been investigated in chloroplasts and Pothos leaves. All peaks including peak V (48°C) were inhibited by UV. However, the peak at 48°C which was induced by DCMU was enhanced following UV irradiation of chloroplasts at ambient temperature (23°C) whereas peak II (-12°C) and peak III (10°C) which were also induced by DCMU were inhibited. Chloroplasts treated with DCMU and dark incubated for several minutes at ambient temperature prior to recording of glow curves have also shown enhancement of peak at 48°C. A slow component of delayed light and photosystem II activity of chloroplasts were inhibited by UV whereas photosystem I activity was marginally affected. These results corroborate involvement of photosystem II in generating thermoluminescence and slow components of delayed light in photosynthetic materials.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 71
    ISSN: 1573-5079
    Schlagwort(e): carbon dioxide ; Glycine max ; photosynthesis ; stomatal conductances ; water potential ; water stress
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Soybean [Glycine max (L.) Merr. cv. Williams 82 and A3127] plants were grown in the field under long-term soil moisture deficit and irrigation to determine the effects of severe drought stress on the photosynthetic capacity of soybean leaves. Afternoon leaf water potentials, stomatal conductances, intercellular CO2 concentrations and CO2-assimilation rates for the two soil moisture treatments were compared during the pod elongation and seed enlargement stages of crop development. Leaf CO2-assimilation rates were measured with either ambient (340 μl CO2 l−1) or CO2-enriched (1800 μl CO2 l−1) air. Although seed yield and leaf area per plant were decreased an average of 48 and 31%, respectively, as a result of drought stress, leaf water potentials were reduced only an average of 0.27 MPa during the sampling period. Afternoon leaf CO2-assimilation rates measured with ambient air were decreased an average of 56 and 49% by soil moisture deficit for Williams 82 and A3127, respectively. The reductions in leaf photosynthesis of both cultivars were associated with similar decreases in leaf stomatal conductance and with small increases in leaf intercellular CO2 concentration. When the CO2-enriched air was used, similar afternoon leaf CO2-assimilation rates were found between the soil moisture treatments at each stage of crop development. These results suggest that photosynthetic capacity of soybean leaves is not reduced by severe soil moisture deficit when a stress develops gradually under field conditions.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 72
    ISSN: 1573-5079
    Schlagwort(e): chloroplast coupling factor ; induction ; thioredoxin ; regulation ; ATP synthase ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Simultaneous, non-invasive measurements were made of the rate of photosynthetic CO2 fixation and the state of activation of the chloroplast CF1CF0-ATP synthase (CF) in field-grown sunflower (Helianthus annuus L.) during the dark-to-light transition at sunrise. CO2 fixation showed a linear response with light intensity from zero to about 500–700 μE m-2 s-1. However, at light intensities of only 5–22 μE m-2 s-1, the energetic threshold for activation of the CF was found to be significantly lowered (as compared to the pre-dawn state), presumably through reduction of the regulatory sulfhdryl groups of the γ-subunit of the CF. When these studies were extended to chamber-grown plants, it was found that as little as 5 seconds of illumination at 4 μE m-2 s-1 caused apparently full CF reduction. It is clear, therefore, that the catalytic activation of CF is not rate limiting to the induction of carbon assimilation under field conditions during a natural dark-to-light transition at sunrise. A model, based on the redox properties of the regulatory sulfhydryls, was developed to examine the significance of sulfhydryl midpoint potential in explaining the differences in light sensitivity and oxidation and reduction kinetics, between the CF and other thioredoxin-modulated chloroplast enzymes. Computer simulations of the light-induced regulation of three representative thioredoxin-modulated enzymes are presented.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 73
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 4 (1983), S. 87-97 
    ISSN: 1573-5079
    Schlagwort(e): acclimation ; irradiance ; photosynthesis ; temperature
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Photosynthetic characteristics at high measurement irradiance were analyzed for single leaves of two C3 and one C4 species grown under twenty one combinations of irradiance level, irradiance duration, and air temperature in order to test the idea that photosynthetic characteristics developed by leaves in different environments are controlled by the daily amount of photosynthesis. Photosynthetic rates per unit area and mesophyll conductances at 25°C and air levels of CO2 and O2, and parameters for two photosynthesis models were used to characterize the photosynthetic properties of the leaves. Leaves with highest values of the photosynthetic parameters for each species were often developed in environments with irradiance levels below saturation for photosynthesis, and with only 12 hours of iradiance per day. Lower air temperature during growth increased the photosynthetic characteristics for a given irradiance regime. Photosynthetic characteristics had higher correlation coefficients with daily photosynthesis of mature leaves divided by 24-hour leaf elongation rates of young leaves, than with daily photosynthesis alone, indicating that photosynthetic characteristics may be related to a balance between photosynthesis and leaf expansion.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 74
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 4 (1983), S. 171-178 
    ISSN: 1573-5079
    Schlagwort(e): Amaranthus tricolor ; intercellular CO2 ; concentration ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The gas exchange characteristics are reported for Amaranthus tricolor, a C4 vegetable amaranth of southeastern Asia. Maximum photosynthetic capacity was 48.3±1.0μmol CO2 m−2s−1 and the temperature optimum was 35°C. The calculated intercellular CO2 concentration at this leaf temperature and an incident photon flux (400–700 mm) of 2 mmol m−2s−1 averaged 208±14 μl l−1, abnormally high for a C4 species. The photosynthetic rate, intercellular CO2 concentration, and leaf conductance all decreased with an increase in water vapor pressure deficit. However, the decrease in leaf conductance which resulted in a decrease in intercellular CO2 concentration accounted for only one fourth of the observed decrease in photosynthetic rate as water vapor pressure deficit was increased. Subsequent measurements indicated that the depence of net photosynthesis on intercellular CO2 concetration changed with water vapor pressure deficit.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 75
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 4 (1983), S. 245-256 
    ISSN: 1573-5079
    Schlagwort(e): State I-state II transitions ; blue-green alga ; cyanobacterium ; photosynthesis ; energy transfer ; cyclic electron flow ; phase transitions ; Synechococcus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effects of electron acceptors, inhibitors of electron flow and uncouplers and inhibitors of photophosphorylation on a state II to I transition were studied. 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) did not inhibit the state II to I transition. By contrast, 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB), methyl viologen and antimycin A inhibited the transition indicating that the cyclic electron flow around photosystem I, but not the oxidation of electron carriers (such as plastoquinone), induced the state II to I transition. Uncouplers, but not inhibitors of photophosphorylation, inhibited the state transition suggesting that the proton transport through the cyclic electron flow was related to the transition.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 76
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 123 (1990), S. 217-222 
    ISSN: 1573-5036
    Schlagwort(e): growth chamber ; nutrient solution ; 15NO3 assimilation ; photosynthesis ; relative growth rate ; seedlings ; short-term NaCl stress
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Short-term studies for comparing some primary metabolic and growth-responses to salt stress in seedlings of two maize genotypes differing in drought resistance were carried out under controlled conditions. Both genotypes revealed high yielding ability in favourable environments. Treatments: Control (Hoagland-Arnon No 1 solution) and salt stress (Hoagland-Arnon solution plus NaCl, Ψs = −0.84MPa). It was found that in both genotypes the activity of the principal metabolic pathway supplying reduced nitrogen (15N) for the synthesis of amino acids and proteins as well as the assimulatory number (14CO2—assimilation relation rate per chlorophyll unit) were decreased under the effect of the stress. These effects were more marked in the resistant genotype. In this genotype the stress induced metabolic activity decline was accompanied by a corresonding reduction of the relative growth rate. Conversely, continuing growth, resulting probably from accumulation of solutes, was observed in the susceptible genotype. On the basis of these and other observations it is assumed that the resistant genotype manifests short-term energy saving stress reactions.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 77
    Digitale Medien
    Digitale Medien
    Springer
    Euphytica 51 (1990), S. 33-39 
    ISSN: 1573-5060
    Schlagwort(e): Triticum aestivum ; wheat ; photosynthesis ; chlorophyll fluorescence ; harvest index ; biological yield ; economic yield ; short straw ; dwarfism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Improvements in bread wheat productivity have been related to changes in plant morphology and function associated with a large increase in the harvest index for a more or less constant biological yield. The appearance of short genotypes possessing dwarfism genes may modify markedly the objectives of breeding as the upper limits of the harvest index are approached. The aim of the investigations presented here was to identify some contrasts between short and tall genotypes in terms of the physiological characteristics associated with grain yield, so as to orientate more efficiently the selection of genotypes, with or without dwarfism genes, for productivity. Various parameters of flag leaf functioning (photosynthesis rate, chlorophyll fluorescence index, leaf area duration) were related to the biological and economic yields and the harvest index for two groups of genotypes that were differentiated by their height. For all genotypes, the relationships between the various traits and the grain yield were difficult to ascertain. For the tall genotypes without dwarfism genes, the classical relationships between grain yield, harvest index, flag leaf area duration and net photosynthesis rate were confirmed. Moreover, the rate of chlorophyll fluorescence decrease (Rfd) during the slow Kautsky kinetics phase, which is representative of the leaf photosynthesis at low light, was found to be an excellent marker of economic yield. Chlorophyll fluorescence decrease was closely related to grain yield and also with other factors that are known to be important in its expression (harvest index, flag leaf area duration). In very short genotypes, the biological yield and directly related factors (leaf area, plant height) were the main parameters associated with economic yield, since the harvest index had approached its upper limit. The selection of short genotypes must therefore maintain the biological yield through an increase in the size of the aerial organs to counterbalance the decrease in height.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 78
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 23 (1990), S. 131-162 
    ISSN: 1573-5079
    Schlagwort(e): photosynthesis ; Photosystem II ; review ; structure/function aspects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In the last few years our knowledge of the structure and function of Photosystem II in oxygen-evolving organisms has increased significantly. The biochemical isolation and characterization of essential protein components and the comparative analysis from purple photosynthetic bacteria (Deisenhofer, Epp, Miki, Huber and Michel (1984) J Mol Biol 180: 385–398) have led to a more concise picture of Photosystem II organization. Thus, it is now generally accepted that the so-called D1 and D2 intrinsic proteins bind the primary reactants and the reducing-side components. Simultaneously, the nature and reaction kinetics of the major electron transfer components have been further clarified. For example, the radicals giving rise to the different forms of EPR Signal II have recently been assigned to oxidized tyrosine residues on the D1 and D2 proteins, while the so-called Q400 component has been assigned to the ferric form of the acceptor-side iron. The primary charge-separation has been meaured to take place in about 3 ps. However, despite all recent major efforts, the location of the manganese ions and the water-oxidation mechanism still remain largely unknown. Other topics which lately have received much attention include the organization of Photosystem II in the thylakoid membrane and the role of lipids and ionic cofactors like bicarbonate, calcium and chloride. This article attempts to give an overall update in this rapidly expanding field.
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  • 79
    ISSN: 1573-5079
    Schlagwort(e): photosynthesis ; thermal emission ; P700 ; quantum yield ; energy conversion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Thermal emission and photochemical energy storage were examined in photosystem I reaction center/core antenna complexes (about 40 Chl a/P700) using photoacoustic spectroscopy. Satisfactory signals could only be obtained from samples bound to hydroxyapatite and all samples had a low signal-to-noise ratio compared to either PS I or PS II in thylakoid membranes. The energy storage signal was saturated at low intensity (half saturation at 1.5 W m-2) and predicted a photochemical quantum yield of 〉90%. Exogenous donors and acceptors had no effect on the signal amplitudes indicating that energy storage is the result of charge separation between endogenous components. Fe(CN)6 -3 oxidation of P700 and dithionite-induced reduction of acceptors FA-FB inhibited energy storage. These data are compatible with the hypothesis that energy storage in PS I arises from charge separation between P700 and Fe-S centers FA-FB that is stable on the time scale of the photoacoustic modulation. High intensity background light (160 W m-2) caused an irreversible loss of energy storage and correlated with a decrease in oxidizable P700; both are probably the result of high light-induced photoinhibition. By analogy to the low fluorescence yield of PS I, the low signal-to-noise ratio in these preparations is attributed to the short lifetime of Chl singlet excited states in PS I-40 and its indirect effect on the yield of thermal emission.
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  • 80
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 25 (1990), S. 225-232 
    ISSN: 1573-5079
    Schlagwort(e): state 1-state 2 transitions ; Mutant nicotiana (tobacco aurea mutant Su/su) ; photoacoustics ; photosynthesis ; energy distribution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Photoacoustic detection of oxygen evolution and Emerson enhancement in state 1 and state 2 were compared in a tobacco wild type and mutant (Su/su) deficient in chlorophyll. The mutant shows smaller changes in the distribution of excitation energy between the two photosystems than the wild type. Analysis of Emerson enhancement saturation curves indicates that in the mutant which is deficient in grana partitions and shows less stacking, state 1-state 2 transitions reflect changes in the yield of energy transfer from PS II to PS I (spillover). On the other hand, the wild type containing large grana shows changes in absorption cross-sections of the two photosystems upon state transitions. NaF, a specific phosphatase inhibitor, blocks the transition to state 1, indicating that LHC II phosphorylation has a role in excitation energy regulation in both the mutant as well as the wild type. It is demonstrated that N-ethylmaleimide, a specific sulfhydryl reagent, blocks the transition to state 2, suggesting that a disulfide-sulfhydryl redox couple activates the LHC II kinase in vivo.
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  • 81
    ISSN: 1573-5079
    Schlagwort(e): LED-Array Spectrophotometer ; difference spectroscopy ; time resolved spectra ; photosynthesis ; cytochrome b/f complex ; cytochrome b 559 ; heat-stress
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A new type of computer controlled spectrophotometer is described which is based on an array of independent, monochromatic pulsed light sources consisting of light emitting diodes (LED) equipped with narrow band interference filters. The LEDs are sequentially pulsed at a high repetition rate. The absorbance information at specific wavelengths is sampled in the μs-time range, using a computer-controlled, highly selective technique of synchronous amplification. A first prototype of this LED Array Spectrophotometer allows simultaneous recording of kinetic changes at 16 different wavelengths in the range from 530 to 600 nm, with a time resolution of 1 ms/point. Special features of the new type of spectrophotometer are: Weak integrated measuring light intensity, high signal/noise ratio even with scattering samples like intact leaves, active baseline adjustment by LED current regulation, computer control of system operation and data analysis. To deconvolute the complex absorbance changes in the cytochrome α-band region, ‘standard spectra’ of the major components are stored in computer memory and used for curve fitting of difference spectra and kinetic changes. As an example of application, the light-induced absorbance changes in a heat-pretreated spinach leaf are analysed. The system effectively separates specific absorbance changes of C550, cyt f, cyt b 559 and cyt b 563 from a large background of non-specific changes.
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  • 82
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 26 (1990), S. 59-66 
    ISSN: 1573-5079
    Schlagwort(e): Video imaging ; fluorescence induction kinetics ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A fluorescence video imaging system utilizing relatively inexpensive commercial components is described. The instrument utilizes a black and white CCD video camera detector, a commercial video imaging board and a IBM-AT compatible computer. The color output of the imaging board greatly aids in the users ability to visually discriminate areas of interest in the video field. Software development that enables the user to capture kinetic traces in real time from the video images is also described. The system is used to monitor fluorescence from photosynthetic systems. The usefulness of the system in screening for photosynthetic mutants is also demonstrated. The cost of the system can be kept below $12,000.
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  • 83
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 25 (1990), S. 119-128 
    ISSN: 1573-5079
    Schlagwort(e): adaptation ; genetic variation ; photosynthesis ; wild emmer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Wild emmer wheat (Triticum dicoccoides Korn) has shown wide genetic diversity for disease resistance and morpho-physiological traits of economic importance. Our objectives were to test for genetic variation (VG) in photosynthetic characteristics residing within and between native populations sampled from three ecogeographical regions of Israel, and to identify potential sources of high photosynthetic efficiency for future wheat improvement. Accessions sampled in the center of wild emmer distribution (upper Jordan Valley) in a relatively narrow geographical range showed the greatest diversity in CO2-assimilation rate per unit leaf area (A) or per unit chlorophyll (A/Chl). Genetic variation was absent for internal CO2 concentration (Ci) and water-use efficiency (WUE) and generally lacking for stomatal conductance (gs). Leaf area, although quite variable, was not a significant cofactor in assessing genetic potential for photosynthesis. Accessions within a given population showed 10-times more variation in A and A/Chl than populations sampled from different locations in a region. Accessions with the highest photosynthetic efficiency were derived from upland steppic populations located in marginal habitats extending southward into Israel. Some accessions having high photosynthetic capacity (A=32 μmol m-2 s-1) with no significant reduction in leaf size constitute a potentially valuable genetic resource yet untapped for genetic improvement of hexaploid (T. aestivum L.) wheat.
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  • 84
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 25 (1990), S. 309-316 
    ISSN: 1573-5079
    Schlagwort(e): photoacoustics ; photosynthesis ; O2-evolution ; gas-exchange ; heat evolution ; chlorophyll fluorescence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A newly developed photoacoustic system for measurement of photosynthetic reactions in intact leaves is described. The system is based on pulsed light-emitting diodes, the pulse program and pulse response analysis being computer controlled. Separation of various components in the overall photoacoustic signal is achieved by curve fitting analysis of the responses following individual measuring light pulses in the millisecond time domain. This procedure is in distinction to the conventionally used analysis in the frequency domain, with the advantage that various signal components are obtained by on-line deconvolution, yielding simultaneous recordings of photothermal (complement of energy storage) and photobaric (evolution and uptake) signals. The basic components of the new system are described by block diagrams and the principal steps for deconvolution of the overall photoacoustic response are outlined. An example of application with simultaneous recording of chlorophyll fluorescence is given. It is apparent that the photobaric uptake component represents a significant part of the overall signal, particularly during induction of photosynthesis after dark-adaptation. This component probably contains not only O2-uptake but uptake of CO2 as well.
    Materialart: Digitale Medien
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  • 85
    ISSN: 1573-5079
    Schlagwort(e): Chloroplasts ; Kranz anatomy ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Several leaf anatomical and ultrastructural characteristics usually related with photosynthetic capacity were examined in two Flaveria species with strong differences in anatomy and their F1 hybrid. Flaveria trinervia (Spreng.) Mohr (C4) was the female parent and F. brownii A.M. Powell (C4-like) was the male parent. Quantitative anatomical analysis was made on transverse sections of leaves at both the light and electron microscope level. Four kinds of photosynthetic tissues were considered: bundle sheath (BS), mesophyll adjacent to the BS, mesophyll not adjacent to the BS, and larger spongy mesophyll cells. Flaveria trinvervia partitioned a larger proportion of its photosynthetic cells to BS and the mesophyll layer adjacent to BS and also possessed larger chloroplasts, especially in BS, than did F. brownii. These results suggest that although F. brownii is very C4-like, its anatomy is not as completely C4 as is the case for F. trinervia. In the F1 hybrid the relative contribution of the different tissues to the total photosynthetic tissue volume and area per unit leaf area was quite similar to that of F. trinervia. On the other hand, the chloroplast density and size of the F1 hybrid were fairly similar to those of F. brownii, especially in BS. Thus, there was no evidence of maternal inheritance in the chloroplast characteristics studied. A negative correlation (P〈0.05) between chloroplast size and density was observed among species and relicates within each kind of tissue. This correlation was highest (r=−0.94, P〈0.001) for the BS and when values were plotted on a logarithmic scale. Thus, higher chloroplast numbers for F. brownii and the F1 hybrid were offset by larger chloroplasts in F. trinervia. Less complete C4 photosynthesis in F. brownii may be partially due to incomplete development of Kranz anatomy usually associated with C4 photosynthesis.
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  • 86
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 4 (1983), S. 87-97 
    ISSN: 1573-5079
    Schlagwort(e): acclimation ; irradiance ; photosynthesis ; temperature
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Photosynthetic characteristics at high measurement irradiance were analyzed for single leaves of two C3 and one C4 species grown under twenty one combinations of irradiance level, irradiance duration, and air temperature in order to test the idea that photosynthetic characteristies developed by leaves in different environments are controlled by the daily amount of photosynthesis. Photosynthetic rates per unit area and mesophyll conductances at 25°C and air levels of CO2 and O2, and parameters for two photosynthesis models were used to characterize the photosynthetic properties of the leaves. Leaves with highest values of the photosynthetic parameters for each species were often developed in environments with irradiance levels below saturation for photosynthesis, and with only 12 hours of irradiance per day. Lower air temperature during growth increased the photosynthetic characteristics for a given irradiance regime. Photosynthetic characteristics had higher correlation coefficients with daily photosynthesis of mature leaves divided by 24-hour leaf elongation rates of young leaves, than with daily photosynthesis alone, indicating that photosynthetic characteristics may be related to a balance between photosynthesis and leaf expansion.
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  • 87
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 4 (1983), S. 171-178 
    ISSN: 1573-5079
    Schlagwort(e): Amaranthus tricolor ; intercellular CO2 concentration ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The gas exchange characteristics are reported for Amaranthus tricolor, a C4 vegetable amaranth of southeastern Asia. Maximum photosynthetic capacity was 48.3±1.0 μmol CO2 m-2 s-1 and the temperature optimum was 35°C. The calculated intercellular CO2 concentration at this leaf temperature and an incident photon flux (400–700 mm) of 2 mmol m-2 s-1 averaged 208±14 μl l-1, abnormally high for a C4 species. The photosynthetic rate, intercellular CO2 concentration, and leaf conductance all decreased with an increase in water vapor pressure deficit. However, the decrease in leaf conductance which resulted in a decrease in intercellular CO2 concentration accounted for only one fourth of the observed decrease in photosynthetic rate as water vapor pressure deficit was increased. Subsequent measurements indicated that the dependence of net photosynthesis on intercellular CO2 concentration changed with water vapor pressure deficit.
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  • 88
    ISSN: 1573-5117
    Schlagwort(e): hydrography ; nutrients ; photosynthesis ; subsurface chlorophyll maxima ; southeastern Brazil
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The physical and chemical environment, and the phytoplankton primary production of southeastern Brazil were studied in relation to the general oceanographic structure during two research cruises (winter and summer). In each cruise, a total of 91 stations were occupied. Data were collected on the spatial distribution of nutrients, phytoplankton biomass and photosynthetic capacity over the coastal, shelf and oceanic areas off São Paulo, Paraná and Santa Catarina States. During wintertime, the mixing processes between tropical warm waters of the Brazil Current and subantarctic waters of the Malvinas Current formed strong environmental gradients. The drainings of Rio de La Plata and Lagoa dos Patos are transported northwards by coastal currents, enriching the shelf waters off Santa Catarina State with inorganic nutrients and consequently increasing the chlorophyll ‘a’ to the highest concentrations (〉 3.5 mg m −3) measured during the two cruises. In slope waters chlorophyll values were always low (0.05–0.45 mg m −3). The chlorophyll within the euphotic layer varied from 8.8–36.7 and 1.2–18.5 mg m−2 during winter and summer, respectively. The surface photosynthetic rates during winter and summer cruises ranged respectively from 0.21–9.17 and 0.66–19.60 mgC/mgChl.a/h. The mean rates were higher in nearshore waters and decreased seaward. The thermal structure of the water column affected the vertical distribution of chlorophyll a and photosynthesis within the euphotic zone; During unstratified periods (winter) they were uniformly distributed but the occurrence of subsurface peaks of chlorophyll and strong photosynthetic inhibition of low light adapted cells in deeper layers are associated to the seasonal thermocline. Occasionally, upwelling of deep waters from shelf break enriched the deeper euphotic layers in offshore areas. Intensive upwelling was observed off Paranagua Bay (Parana State) and the mechanisms of its formation are discussed.
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  • 89
    ISSN: 1573-5117
    Schlagwort(e): Ecklonia cava ; Phaeophyta ; photosynthesis ; respiration ; seaweed ; zoosporangial sori
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Photosynthetic rates were compared between Ecklonia cava bladelets with and without zoosporangial sori sampled from the subtidal zone (about 5 m deep) in Nabeta Bay, Shimoda, Japan. Photosynthetic rates of bladelets were lower in the sorus portion than in the non-sorus portion on the basis of area, dry weight and chlorophyll a. Respiration rates were higher in the sorus portion than in the non-sorus portion on the basis of area and chlorophyll a, whereas they were almost the same on a dry weight basis. The differences were mainly due to a large difference in dry weight per unit bladelet area between the sorus and the non-sorus portion. Light compensation points were higher in the sorus portion than in the non-sorus portion.
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  • 90
    Digitale Medien
    Digitale Medien
    Springer
    Hydrobiologia 203 (1990), S. 93-97 
    ISSN: 1573-5117
    Schlagwort(e): sediments ; nitrogen ; phosphorus ; nutrient limitation ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A diffusion enrichment technique is presented which allows for chemical enrichment of soft surficial and shallow subsurface sediments and subsequent measurement of O2 production. The sediment is enriched by inserting a perforated tube containing dialysis tubing filled with a nutrient/agar mixture. O2 production by surficial sediment is measured using an inverted, translucent, polyethylene chamber over the sediment. The inside of the chamber contains a collapsible bag connected to the water outside the chamber. When water overlying the sediment is withdrawn from a sampling port, it is displaced with water from outside the chamber, thus preventing contamination of water samples with pore water from below. The technique was tested by enriching near-shore sediments in a large oligotrophic lake with inorganic N and P. NHinf4/p+ additions significantly stimulated benthic primary production as measured by 02 production, whereas enrichment with POinf4/3- had no effect.
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  • 91
    ISSN: 1573-5117
    Schlagwort(e): Gracilaria ; growth ; light ; photosynthesis ; RuBPcase ; temperature
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The local species Gracilaria conferta and the foreign G. verrucosa were grown together under a wide range of photon flux density and temperature conditions. Gracilaria verrucosa showed a higher growth rate, especially under low temperatures, and higher photosynthetic performances as well as higher ribulose-1,5-bisphosphate carboxylase activity as compared with G. conferta. Gracilaria verrucosa also showed a better quality and yield of agar, suggesting that this species could be more suitable than G. conferta for outdoor cultivation in Israel and may improve winter growth in ponds. Growth rate and agar quality (gel strength) were rated as the most suitable characteristics influencing the preference of strains for outdoor cultivation.
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  • 92
    ISSN: 1573-5117
    Schlagwort(e): Gelidium ; photosynthesis ; physiological responses ; Pterocladia ; Rhodophyta
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Manometric studies were conducted on Pterocladia capillacea, Gelidium latifolium and Gelidium spinulosum from the Azores, Portugal to determine optimal values of temperature, light and salinity for growth. Physiological responses were considered in relation to vertical distribution patterns of these species commonly observed throughout the Azores. Optimal parameters for the growth of Pterocladia capillacea, Gelidium latifolium and G. spinulosum were 17 to 25 °C, a photon flux density between 200 and 300 µmol m−2 s−1 and salinities of 25 to 35‰.
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  • 93
    Digitale Medien
    Digitale Medien
    Springer
    Plant cell, tissue and organ culture 22 (1990), S. 205-211 
    ISSN: 1573-5044
    Schlagwort(e): CO2 enrichment ; Cymbidium ; in vitro ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The photosynthetic characteristics of the Cymbidium plantlet in vitro cultured on Hyponex-agar medium with 2% sucrose were determined based on the measurements of CO2 concentration inside and outside of the culture vessels. The CO2 measurements were made with a gas chromatograph at a PPF (photosynthetic photon flux) of 35, 102 and 226 μmol m-2 s-1, a chamber air temperature of 15, 25 and 35°C and a CO2 concentration outside the vessel of approximately 350, 1100 and 3000 ppm. The net photosynthetic rates were determined on individual plantlets and were expressed on a dry weight basis. The steady-state CO2 concentration during the photoperiod was lower inside the vessel than outside the vessel at any PPF greater than 35 μmol m-2s-1 and at any chamber air temperature. The photosynthetic response curves relating the net photosynthetic rate, PPF, and CO2 concentration in the vessel and chamber air temperature were similar to those for Cymbidium plants grown outside and other C3 plants grown outside under shade. The results indicate that CO2 enrichment for the plantlets in vitro at a relatively high PPF would promote photosynthesis and hence the growth of chlorophyllous shoots/plantlets in vitro and that the plantlets in vitro would make photoautotrophic growth under environmental conditions favorable for photosynthesis.
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  • 94
    ISSN: 1573-5079
    Schlagwort(e): Glycine max L. ; photosynthesis ; ribulose 1,5-bisphosphate carboxylase/oxygenase ; ribulose 5-phosphate kinase ; senescence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The abundances of ribulose-1,5-bisphosphate carboxylate/oxygenase (Rubisco) and ribulose-5-phosphate (Ru5P) kinase in field-grown soybean (Glycine max L. Merr.) leaves were quantified by a Western blot technique and related to changes in chlorophyll and photosynthetic capacity during senescence. Even though the leaf content of Rubisco was approximately 80-fold greater than that of Ru5P kinase, the decline in the levels of these two Calvin cycle enzymes occurred in parallel during the senescence of the leaves. Moreover, the decrease in the content of Rubisco was accompanied by parallel decreases of both the large and small subunits of this enzyme but not by an accumulation of altered large or small subunit isoforms. With increasing senescence, decreases in abundances of Rubisco, Ru5P kinase and chlorophyll were closely correlated with the decline in photosynthetic capacity; thus, the specific photosynthetic capacity when expressed per abundance of any of these parameters was rather constant despite an 8-fold decrease in photosynthetic capacity. These results suggest that during senescence of soybean leaves the chloroplast is subject to autolysis by mechanisms causing an approximately 80-fold greater rate of loss of Rubisco than Ru5P kinase.
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  • 95
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 25 (1990), S. 187-197 
    ISSN: 1573-5079
    Schlagwort(e): excessive light ; photoprotection ; photosynthesis ; photosystem II regulation ; xanthophyll cycle
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The possibility that zeaxanthin mediates the dissipation of an excess of excitation energy in the antenna chlorophyll of the photochemical apparatus has been tested through the use of an inhibitor of violaxanthin de-epoxidation, dithiothreitol (DTT), as well as through the comparison of two closely related organisms (green and blue-green algal lichens), one of which (blue-green algal lichen) naturally lacks the xanthophyll cycle. In spinach leaves, DTT inhibited a major component of the rapidly relaxing high-energy-state quenching' of chlorophyll fluorescence, which was associated with a quenching of the level of initial fluorescence (F′0) and exhibited a close correlation with the zeaxanthin content of leaves when fluorescence quenching was expressed as the rate constant for radiationless energy dissipation in the antenna chlorophyll. Green algal lichens, which possess the xanthophyll cycle, exhibited the same type of fluorescence quenching as that observed in leaves. Two groups of blue-green algal lichens were used for a comparison with these green algal lichens. A group of zeaxanthin-free blue-green algal lichens did not exhibit the type of chlorophyll fluorescence quenching indicative of energy dissipation in the pigment bed. In contrast, a group of blue-green algal lichens which had formed zeaxanthin slowly through reactions other than the xanthophyll cycle, did show a very similar response to that of leaves and green algal lichens. Fluorescence quenching indicative of radiationless energy dissipation in the antenna chlorophyll was the predominant component of ‘high-energy-state quenching’ in spinach leaves under conditions allowing for high rates of steady-state photosynthesis. A second, but distinctly different type of ‘high-energy-state quenching’ of chlorophyll fluorescence, which was not inhibited by DTT (i.e., it was zeaxanthin independent) and which is possibly associated with the photosystem II reaction center, occurred in addition to that associated with zeaxanthin in leaves under a range of conditions which were less favorable for linear photosynthetic electron flow. In intact chloroplasts isolated from (zeaxanthin-free) spinach leaves a combination of these two types of rapidly reversible fluorescence quenching occurred under all conditions examined.
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  • 96
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 4 (1983), S. 271-279 
    ISSN: 1573-5079
    Schlagwort(e): electron transport ; inside-out thylakoids ; oxygen evolution ; photosynthesis ; thykoid polypeptides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A 23 kDa protein has recently been demonstrated to participate in photosynthetic oxygen evolution by reconstitution experiments on inside-out thylakoid vesicles (Åkerlund H-E, Jansson C and Andersson B (1982) Biochim Biophys Acta 681:1–10). Here we describe the isolation of the 23 kDa protein from a spinach chloroplast extract using ion-exchange chromatography. The protein was obtained in a yield of 25% and with less than 1% of contaminating proteins. The ability of the protein to stimulate oxygen evolution in inside-out thylakoids was preserved throughout the various fractionation steps. The isolated protein was highly water soluble and appeared as a monomer. Its isoelectric point was at pH=7.3. The amino acid composition showed a high content of polar amino acids, resulting in a polarity index of 49%. The isolated protein lacked metals and other prosthetic groups. Its function as a catalytic or regulating subunit in the oxygen evolving complex is discussed.
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  • 97
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 4 (1983), S. 375-383 
    ISSN: 1573-5079
    Schlagwort(e): absorption spectra ; chlorophyll-proteins ; curve resolution ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The three major chlorophyll-proteins of spinach chloroplasts were solubilized with digitonin and isolated by electrophoresis with deoxycholate. The gel bands were identified from their absorption and fluorescence spectra measured at 77 K. The slowest moving band was a Photosystem I complex (CPI); the second, a Photosystem II complex (Cpa); and the third, a chlorophyll a-b, antenna complex (LHCP). When absorption spectra (630–730 nm) of the bands were added in the proportions found in the gel, the sum closely matched the absorption of the chloroplasts both before and after solubilization. Thus these spectra represent the native absorption of the major antenna chlorophyll-proteins of green plants. Each of these spectra was resolved with a computer assisted, curve-fitting program into 8 mixed Gaussian-Lorentzian shaped components. The major, Chl a components in the 3 fractions were different both in peak positions and bandwidths. This result suggests that each chlorophyll-protein has its own unique set of chlorophyll a spectral forms or components.
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  • 98
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 4 (1983), S. 271-279 
    ISSN: 1573-5079
    Schlagwort(e): electron transport ; inside-out thylakoids ; oxygen evolution ; photosynthesis ; thykoid polypeptides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A 23 kDa protein has recently been demonstrated to participate in photosynthetic oxygen evolution by reconstitution experiments on inside-out thylakoid vesicles (Åkerlund H-E, Jansson C and Andersson B (1982) Biochim Biophys Acta 681:1–10). Here we describe the isolation of the 23 kDa protein from a spinach chloroplast extract using ion-exchange chromatography. The protein was obtained in a yield of 25% and with less than 1% of contaminating proteins. The ability of the protein to stimulate oxygen evolution in inside-out thylakoids was preserved throughout the various fractionation steps. The isolated protein was highly water soluble and appeared as a monomer. Its isoelectric point was at pH=7.3. The amino acid composition showed a high content of polar amino acids, resulting in a polarity index of 49%. The isolated protein lacked metals and other prosthetic groups. Its function as a catalytic or regulating subunit in the oxygen evolving complex is discussed.
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  • 99
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 4 (1983), S. 245-256 
    ISSN: 1573-5079
    Schlagwort(e): State I-state II transitions ; blue-green alga ; cyanobacterium ; photosynthesis ; energy transfer ; cyclie electron flow ; phase transitions ; Synechococcus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effects of electron acceptors, inhibitors of electron flow and uncouplers and inhibitors of photophosphorylation on a state II to I transition were studied. 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) did not inhibit the state II to I transition. By contrast, 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB), methyl viologen and antimycin A inhibited the transition indicating that the cyclic electron flow around photosystem I, but not the oxidation of electron carriers (such as plastoquinone), induced the state II to I transition. Uncouplers, but not inhibitors of photophosphorylation, inhibited the state transition suggesting that the proton transport through the cyclic electron flow was related to the transition.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 4 (1983), S. 375-383 
    ISSN: 1573-5079
    Schlagwort(e): absorption spectra ; chlorophyll-proteins ; curve resolution ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The three major chlorophyll-proteins of spinach chloroplasts were solubilized with digitonin and isolated by electrophoresis with deoxycholate. The gel bands were identified from their absorption and fluorescence spectra measured at 77 K. The slowest moving band was a Photosystem I complex (CPI); the second, a Photosystem II complex (Cpa); and the third, a chlorophyll a-b, antenna complex (LHCP). When absorption spectra (630–730 nm) of the bands were added in the proportions found in the gel, the sum closely matched the absorption of the chloroplasts both before and after solubilization. Thus these spectra represent the native absorption of the major antenna chlorophyll-proteins of green plants. Each of these spectra was resolved with a computer assisted, curve-fitting program into 8 mixed Gaussian-Lorentzian shaped components. The major, Chl a components in the 3 fractions were different both in peak positions and bandwidths. This result suggests that each chlorophyll-protein has its own unique set of chlorophyll a spectral forms or components.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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