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  • Ultrastructure  (67)
  • healthy volunteers  (54)
  • Springer  (121)
  • 1985-1989  (61)
  • 1980-1984  (60)
  • 1955-1959
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  • 1
    Electronic Resource
    Electronic Resource
    Ultrastructure of the sperms ofPlumbago zeylanica (1981)
    Springer
    Protoplasma 107 (1981), S. 85-107 
    Details
    ISSN: 1615-6102
    Keywords: Male cytoplasmic inheritance ; Plumbago ; Pollen grain ; Pollen tube ; Sperm ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Male gametes ofPlumbago zeylanica were examined in pollen grains and tubes using light and electron microscopy of chemically and physically fixed tissues, and Nomarski interference microscopy of isolated, living sperm cells. Male gametes are elongate, spindleshaped cells containing a nucleus, mitochondria, ER, ribosomes, vesicles, dictyosomes, probable microfilaments, and a variable number of plastids. In mature pollen grains ofP. zeylanica, the two sperm cells are directly linked; they share a transverse cell wall with plasmodesmata and are enclosed together by the inner vegetative cell plasma membrane. One of these two sperms is also associated with the vegetative nucleus as a consistent feature of pollen grain organization. The basis of this association appears to be a long, narrow projection of the sperm cell (averaging 〈 1 μm wide and about 30 μm long) which wraps around the periphery of the vegetative nucleus and occupies embayments of that nucleus. This association is maintained throughout pollen tube growth but becomes less extensive near the completion of tube growth and is severed following tube discharge. The consistent occurrence of the sperm-vegetative nucleus association in pollen grains, tubes and isolated pollen cytoplasm suggests that the two structures may be directly connected, but attempts to visualize this type of connection were unsuccessful. Possibly, the entwining nature and extent of complementary interfaces between vegetative nucleus and sperm may have a role in stabilizing their association. Functionally, the two sperms and vegetative nucleus appear to travel as a linked unit within the pollen tube, possibly increasing the effectiveness of gamete delivery and helping to ensure nearly simultaneous transmission of sperms into the receptive megagametophyte.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01275610
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  • 2
    Electronic Resource
    Electronic Resource
    The pharmacokinetics and haemodynamics of BTS 49465 and its major metabolite in healthy volunteers (1985)
    Springer
    European journal of clinical pharmacology 28 (1985), S. 659-664 
    Details
    ISSN: 1432-1041
    Keywords: BTS 49465 ; hypertension ; pharmacokinetics ; blood pressure effect ; heart rate effect ; side-effects ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetic and haemodynamic effects of a 200 mg oral dose of BTS 49465 (7-fluoro-1-methyl-3-methylsulphinyl-4-quinolone) were investigated in a double-blind placebo controlled study. BTS 49465 was rapidly absorbed and cleared from the systemic circulation with a half-life of 1.6 h by oxidation to the sulphone metabolite. The metabolite was cleared with a half-life of 37.6 h. Saliva concentrations of both BTS 49465 and its metabolite correlated well with the plasma concentrations. Compared to placebo, BTS 49465 produced statistically significant reductions in blood pressure and increases in heart rate both supine and after a 60° head up tilt. The time course of the haemodynamic changes suggested that the sulphone metabolite contributed to the overall hypotensive response. Plasma Renin Activity was only marginally elevated and there was no evidence of acute fluid retention. BTS 49465 was well tolerated in terms of haematological and biochemical parameters and subjective side-effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00607911
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of alaproclate on antipyrine metabolite formation in man (1984)
    Springer
    European journal of clinical pharmacology 27 (1984), S. 447-452 
    Details
    ISSN: 1432-1041
    Keywords: alaproclate ; antipyrine clearance ; serotonin reuptake inhibitor ; healthy volunteers ; antipyrine metabolism ; metabolite clearance ; alaproclate kinetics ; inhibition of drug metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Alaproclate, a selective serotonin reuptake inhibitor, presently undergoing clinical trial for the treatment of major depressive disorders, has been shown to inhibit hexobarbital metabolism in mice. In the present study the influence of oral alaproclate on the total plasma clearance of antipyrine and on the formation of its metabolites was investigated in 10 healthy volunteers. The peak level of alaproclate was reached after about 1.5 h, and after a distribution phase, its plasma elimination half-life was between 3.0 and 3.5 h. Antipyrine tests were performed before treatment, during the first four doses and after the seventh dose of alaproclate 200 mg/day. During treatment, total plasma antipyrine clearance and the clearance for production of all antipyrine metabolites were reduced by 30%, indicating non-selective inhibition of oxidative drug-metabolizing enzyme activity in man by alaproclate. After the last dose of alaproclate, antipyrine plasma clearance and the clearance to its metabolites returned to control values. In order to allow more detailed evaluation of the results, the time course of the clearances for production of metabolites was investigated. This revealed that the extent of inhibition of metabolite formation by alaproclate was dependent on the plasma alaproclate level, indicating a rapidly reversible inhibition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00549593
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of atrial natriuretic peptide on plasma renin activity, plasma aldosterone, and urinary dopamine in man (1986)
    Springer
    European journal of clinical pharmacology 31 (1986), S. 223-226 
    Details
    ISSN: 1432-1041
    Keywords: renin ; aldosterone ; dopamine ; natriuretic hormone ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The acute natriuretic effect of human atrial natriuretic peptide (ANP) has been well described in man. We have now studied possible hormonal mediators of this effect. We studied six healthy volunteers on two occasions when they received either an infusion of ANP of 1.5 pmol·kg−1·min−1 for 30 min followed by 15 pmol·kg−1·min−1 for a further 30 min, or matching vehicle infusions in a randomized single-blind fashion. On the placebo day, plasma renin activity (PRA) rose from 1.26±0.08 to 1.57±0.14 ng A1·ml−1·h−1, while on the ANP study day PRA fell from 1.45±0.15 to 1.28±0.05 ng A1·ml−1·h−1 (p〈0.01). No significant changes were found in plasma aldosterone concentrations or in urinary dopamine excretion. These results provide evidence that ANP suppresses renin release in man.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00606663
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  • 5
    Electronic Resource
    Electronic Resource
    Studies of the different metabolic pathways of antipyrine in man (1982)
    Springer
    European journal of clinical pharmacology 21 (1982), S. 433-441 
    Details
    ISSN: 1432-1041
    Keywords: antipyrine ; antipyrine metabolites ; drug metabolism ; route of administration ; healthy volunteers ; urinary excretion ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of antipyrine in plasma and saliva, and urinary excretion of its major metabolites, were studied following i.v. and oral administration of antipyrine 500 mg to 6 healthy volunteers. Data from both plasma and saliva showed that the oral bioavailability of antipyrine given as an aqueous solution was complete. The saliva/plasma concentration ratio was constant with time from about 3 h onwards, with a mean value of 0.87 after oral and 0.91 after i.v. administration. It is concluded that the pharmacokinetic parameters of antipyrine can be satisfactorily established on the basis of salivary data, although the volume of distribution and clearance values are then slightly too high. After i.v. administration, 3.8±1.9% of the dose was excreted in urine as unchanged antipyrine in 48h, 24.9±6.3% as 4-hydroxyantipyrine, 16.5±3.2% as norantipyrine, 13.0±2.2% as 3-hydroxymethyl-antipyrine and 5.8±1.0% as 3-carboxy-antipyrine. No significant differences were observed following oral administration. The half-lives calculated from the linear part of the urinary excretion rate curves of the metabolites were about the same for oral and i.v. administration, and were of the same order of magnitude as the elimination half-life of parent drug in plasma and saliva. It is important for determination of the ultimate metabolite ratio that urine is collected for at least 36h, because there is a delay in the excretion of 3-hydroxymethyl-antipyrine in urine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00542332
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  • 6
    Electronic Resource
    Electronic Resource
    Ultrastructure of the cyanobacterium,Mastigocladus laminosus (1982)
    Springer
    Archives of microbiology 133 (1982), S. 11-19 
    Details
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Ultrastructure ; Mastigocladus laminosus ; Fischerella ; True branching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The morphology and ultrastructure of the thermophilic cyanobacteriumMastigocladus laminosus were examined by scanning and transmission electron microscopy. Mature cultures consisted of relatively old, wide filaments that branched frequently to form younger, thinner filaments. The cells of the younger filaments had a consistently cylindrical morphology, while those of older filaments were rounded and pleomorphic. The internal ultrastructure of the cells depended somewhat on their age. As young cells became larger and wider, their thylakoids underwent slight rearrangement and spread out toward the center of the cytoplasm. Polyphosphate bodies, carboxysomes (polyhedral bodies), and lipid-body-like structures increased in number as the cells aged, but ribosomes and cyanophycin granules were depleted. Cell division involved septum formation followed by ingrowth of the outer membrane and sheath. Cells in older filaments were separated from each other by a complete layer of sheath material. Septum formation in older cells was also seen to occur parallel to the long axis of the filament, thereby confirming that true branching took place.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00943762
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  • 7
    Electronic Resource
    Electronic Resource
    The effects of nitrogen limitation on the ultrastructure of the cyanobacterium Agmenellum quadruplicatum (1981)
    Springer
    Archives of microbiology 130 (1981), S. 204-212 
    Details
    ISSN: 1432-072X
    Keywords: Agmenellum quadruplicatum ; Nitrogen starvation ; Ultrastructure ; PATO poststain ; Cyanobacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of nitrogen limitation on the ultrastructure of the unicellular cyanobacterium, Agmenellum quadruplicatum, were studied by thin sectioning transmission electron microscopy. Nitrogen became limiting for growth 14–15 h after transfer to nitrogen-limiting medium, but cultures retained full viability for at least 45 h. The c-phycocyanin: chlorophyll a ratio and cellular nitrogen content of the culture dropped rapidly after 14–15 h, as a progressive deterioration of major cell structures took place. Phycobilisomes were degraded first, followed by ribosomes and, then, thylakoid membranes. These structures were virtually depleted from the cells within 26 h. Intracellular polysaccharide accumulated in place of the normal cell structures throughout this period. Nitrogen limitation did not affect polyphosphate bodies, carboxysomes, lipid granules, the cell envelope, or the extra-cellular glycocalyx. All of the ultrastructural changes resulting from nitrogen limitation were reversed upon addition of nitrate to a starved culture. Most cell structures were restored within 3 h, and restoration was complete within 9 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00459520
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  • 8
    Electronic Resource
    Electronic Resource
    Immunogold localization of coenzyme F420-reducing formate dehydrogenase and coenzyme F420-reducing hydrogenase in Methanobacterium formicicum (1989)
    Springer
    Archives of microbiology 151 (1989), S. 307-313 
    Details
    ISSN: 1432-072X
    Keywords: Methanobacterium formicicum ; Formate dehydrogenase ; F420-hydrogenase ; Immunogold ; Ultrastructure ; Methanogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ultrastructural locations of the coenzyme F420-reducing formate dehydrogenase and coenzyme F420-reducing hydrogenase of Methanobacterium formicicum were determined using immunogold labeling of thin-sectioned, Lowicryl-embedded cells. Both enzymes were located predominantly at the cell membrane. Whole cells displayed minimal F420-dependent formate dehydrogenase activity or F420-dependent hydrogenase activity, and little activity was released upon osmotic shock treatment, suggesting that these enzymes are not soluble periplasmic proteins. Analysis of the deduced amino acid sequences of the formate dehydrogenase subunits revealed no hydrophobic regions that could qualify as putative membrane-spanning domains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00406556
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  • 9
    Electronic Resource
    Electronic Resource
    Microscopic examination and fatty acid characterization of filamentous bacteria colonizing substrata around subtidal hydrothermal vents (1989)
    Springer
    Archives of microbiology 152 (1989), S. 64-71 
    Details
    ISSN: 1432-072X
    Keywords: Thiothrix sp. ; Beggiatoa sp. ; Sulfideoxidizing ; Polyunsaturated ; Fatty acids ; Inclusions ; Sheath ; Southern California ; Ultrastructure ; Sulfur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microscopic examination of the whitish mat that covered the substrata around subtidal hydrothermal vents at White Point in southern California revealed a “Thiothrix-like” bacterium containing sulfur inclusions as the dominant filamentous form in this microbial community. The matlike appearance developed as a result of the closely-packed manner inwhich the basal ends of the filaments were anchored to the substrate. The dominant phospholipid fatty acids of these filaments (16:0, 16:1w7c, 18:0, 18:1w7c) were similar to those recovered from a sample of Beggiatoa isolated from a spring in Florida. Filaments from both sources contained small quantities of C18 and C20 polyunsaturated fatty acids, as well. A larger but less abundant sheathless, filamentous form, which also contained sulfur inclusions and displayed a cell wall structure similar to a previously described Thioploca strain, also colonized the substrata around the subtidal mat. The preservation methods used in the preparation of thin-sections of the subtidal mat material were found to be inadequate for defining some key cellular structures of the large filaments. Nevertheless, the results demonstrate that the filamentous bacteria comprising the microbial mat in the vicinity of the subtidal vents exhibit some of the features of the free-living filamentous microorganisms found in deep-water hydrothermal areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00447013
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  • 10
    Electronic Resource
    Electronic Resource
    Structural features of the epididymis in a dasyurid marsupial (Antechinus stuartii) (1989)
    Springer
    Cell & tissue research 258 (1989), S. 203-210 
    Details
    ISSN: 1432-0878
    Keywords: Epididymis ; Histology ; Ultrastructure ; Antechinus stuartii (Marsupialia)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ductus epididymidis of the marsupial mouse Antechinus stuartii was divided into caput, corpus, and caudal regions using several constant morphological landmarks. Tubule diameter and epithelial height increased gradually from caput to cauda. In contrast, the surface area of the lumen of the ductus epididymidis increased to a maximum in the distal caput region, but decreased markedly in the distal cauda in association with characteristic changes in lumen shape (from circular to slit-shaped) and epithelial height. Epithelial cells of the ductus epididymidis were generally similar in structure to those described in other mammalian species. Principal and basal cells were common throughout the epithelium. Clear and mitochondria-rich cells were also identified, but occurred less frequently. Regional variations in cell ultrastructure were observed only in principal cells. Numerous vesicular inclusions occurred in the apical cytoplasm of cells in caput segments, membrane-bounded, electron-dense bodies were common in distal corpus regions, and a brush border of microvilli characterized the luminal surface of principal cells in caudal segments. Sperm index increased in the proximal caput, declined to basal levels in the distal caput and proximal corpus, and then increased to a maximum in segment 9 of the distal corpus and remained at about this level throughout the cauda epididymidis. Nuclear rotation, loss of cytoplasmic droplets, and other sperm maturational changes were observed along the epididymis. Discarded cytoplasmic droplets collected in large masses interspersed between aggregates of spermatozoa throughout the distal regions of the duct. There was no evidence of phagocytosis by principal cells of cytoplasmic droplets. The epididymis of A. stuartii differs from that of other mammals. The unusual caudal region, which has little storage capacity for sperm, is an unusual adaptation in a species in which the male is known to be polygamous.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223158
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