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  • 1
    ISSN: 1573-5117
    Keywords: Turbellaria ; karyology ; mixoploidy ; electrophoresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Various kinds of chromosomal polymorphisms or karyotypic variations are found in the Japanese freshwater planarian Polycelis auriculata. Within this species, there are found worms whose chromosome numbers are 2n = 6, 10, 11, 12 and others, and 3x = 6 and 9. There are some which have cells with triploidy and tetraploidy complements (3x = 6 & 4x = 8), and others which have cells with triploidy and hexaploidy complements (3x = 6 & 6x = 12). These worms with such varied karyotypes are usually found in separate habitats, though occasionally they occur together. Electrophoretic analysis of the proteins extracted from the karyotipically different worms which belong to three different local populations shows some dissimilarity in the constitutive proteins according to their karyotypic differences. The results obtained suggest that this species is still in the process of speciation or chromosomal evolution.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 132 (1986), S. 127-135 
    ISSN: 1573-5117
    Keywords: Turbellaria ; polyclads ; eggshell ; shell formation ; sclerotin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Eggshell formation in polyclads was studied by means of transmission electron microscopy and histochemistry. Shell-forming granules (SFG) in the egg, as well as secretions of shell glands (SGS), play roles in eggshell formation. As the oocytes pass through the portion of the female tract where the shell glands open, they are surronded by a two-layered envelope of SGS. This envelope prevents the dispersion of SFGs discharged after oviposition, and its inner layer participates in eggshell formation with the SFGs. In Pseudostylochus sp., most SFGs consist of five parts. Similarities in staining between the parts of the SFGs and the parts of the eggshell indicate that discrete parts of the shell are derived from specific SFG components. Hardening of the eggshell and egg-plate matrix takes place through primary tanning of a sclerotin-like protein.
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  • 3
    ISSN: 1573-5117
    Keywords: spermatozoa ; ultrastructure ; movement ; Turbellaria ; acrosomal proteolytic activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The spermatozoa in the testis of three species of triclad turbellarians showed slightly different morphologies from spermatozoa in the seminiferous tubule and ovovitelline duct, and we suggest these differences relate to maturation of the spermatozoa. Glycogen granules could be found in the flagella between the central core and the peripheral doublets of spermatozoa in the seminiferous tubule and ovovitelline duct but only rarely in spermatozoa in the testis, and connections between a third arm of the doublets and the flagellar membrane were detectable only in those spermatozoa in the ovovitelline duct and seminiferous tubule. The movement of spermatozoa also appeared to change with capacitation: spermatozoa isolated from the spermiducal vesicle swam with either the anterior process or the head leading; those within the ovovitelline duct appeared to move with the anterior process leading. The flagellum, with the so-called ‘9 + 1’ axonemal pattern, was observed to divide into nine branches toward its distal end; the central cylinder of the axoneme did not continue into the branches. An acrosome has not been observed in planarian spermatozoa. Rod-like structures and a dense mass lying in the anterior process and suspected of containing an acrosomal substance, could not be shown to produce acrosome-like proteolytic activity.
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  • 4
    ISSN: 1573-5117
    Keywords: Turbellaria ; chromosomal polymorphism ; mixoploidy ; differentiation of karyotype
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Although the chromosomal number of Polycelis (Seidlia) auriculata Ijima et Kaburaki is basically 2n = 6, this species shows remarkable chromosomal polymorphisms in different populations. Among worms collected at 30 stations in the central part of Japan's Main Island and in Hokkaido, we found five new karyotypes, considered to be variations of tetraploidy and diploidy: 4n?fis1. + 1 = 3SM + 2A + 3T1 + 2T2 + 4M = 14, 4n?fis2.(B) = 2SM + 2A + 4T1 + 2T2 + 4M + (0−2B) = 14 –16, 4n?fis2. + 1 = 2SM + 2A + 4T1 + 2T2+5M= 15, 4n?fis2.−2 = 2SM + 2A + 4T1 + 4M = 12, and 2nM- = 2SM + 2A = 4 (where SM = submetacentric; A = acrocentric; T1 and T2 = telocentric; M = metacentric; B = B-chromosome; fis1. and fis2. = occurrence of one or two centric fissions, respectively; and M- = deletion of a metacentric chromosome). These karyotypes exist singly in one individual or as various mixoploids within the same individual. No individual having only karyotype 2nM- has yet been found. This brings the total number of known karyotypes in P. auriculata to 17; these can be arranged in an order that we believe reflects their evolution.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Molecular and cellular biochemistry 189 (1998), S. 107-111 
    ISSN: 1573-4919
    Keywords: gene expression ; electromagnetic fields ; superinduction ; anisomycin ; immediate early gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Rat pheochromocytoma PC12 cells have been treated with nerve growth factor (NGF) at final concentrations of 2, 4, 8, and 16 ng/ml, and then were exposed to 60-Hz, sinusoidal magnetic fields (MF) of 12.5, 25, 50, and 100 μT (rms) for 30 min. Transcript levels for both c-fos and glyceraldehyde-3 -phosphate dehydrogenase were determined by Northern blot analysis using 32P-labeled cDNA probes. No change in c-fos expression was measured at any condition employed. Treatment of PC12 cells with a combination of agents (NGF, forskolin, and tetradecanoylphorbol acetate [TPA]) increased c-fos expression over that detected with NGF alone. MF exposure of cells treated with the three-agent regimen produced two outcomes, either no change or a doubling of c-fos expression. In subsequent experiments, cells were treated with NGF, NGF + forskolin + TPA, or pre-treated with anisomycin and then treated with NGF + forskolin + TPA. It was determined that MF exposure, like superinduction with anisomycin, increased c-fos expression only in cultures which were not yet exhibiting maximal c-fos expression. It is hypothesized that MF exposure, like anisomycin, may alter the activity of key intracellular protein kinases.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 32 (1996), S. 745-749 
    ISSN: 1573-5028
    Keywords: circadian rhythm ; CO2 fixation ; gene expression ; green alga
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have investigated whether the expression of carbonic anhydrase genes (Cah1 and Cah2) is regulated by a circadian clock in Chlamydomonas. When cells were grown in ordinary air under 12 h light/12 h dark (LD) cycles, the levels of the Cah2 mRNA hardly altered during the cycles, while the Cah1 mRNA showed a strong diurnal rhythm. The rhythm of about 24 h continued at least 3 days even under continuous light. Temperature compensation of the rhythm was demonstrated, using cultures maintained at 16, 22, and 28°C. These results indicate that the abundance of the Cah1 transcript is controlled by a circadian clock.
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  • 7
    ISSN: 1573-5028
    Keywords: C4 photosynthesis ; maize ; phosphoenolpyruvate carboxylase ; transgenic plant ; transcription ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract C4-type phosphenolpyruvate carboxylase (C4PEPC) acts as a primary carbon assimilatory enzyme in the C4 photosynthetic pathway. The maize C4PEPC gene (C4Ppc1) is specifically expressed in mesophyll cells (MC) of light-grown leaves, but the molecular mechanism responsible for its cell type-specific expression has not been characterized. In this study, we introduced a chimeric maize C4Ppc1 5′-flanking region/β-glucuronidase (GUS) gene into maize plants by Agrobacterium-mediated transformation. Activity assay and histochemical staining showed that GUS is almost exclusively localized in leaf MC of transgenic maize plants. This observation suggests that the introduced 5′ region of maize C4Ppc1 contains the necessary cis element(s) for its specific expression in MC. Next, we investigated whether the 5′ region of the maize gene interacts with nuclear proteins in a cell type-specific manner. By gel shift assays with nuclear extracts prepared from MC or bundle sheath cells (BSC), cell type-specific DNA-protein interactions were detected: nuclear factors PEPIb and PEPIc are specific to MC whereas PEPIa and PEPIIa are specific to BSC. Light alters the binding activity of these factors. These interactions were not detected in the assay with nuclear extract prepared from root, or competed out by oligonucleotides corresponding to the binding sites for the maize nuclear protein, PEP-I, which is known to bind specifically to the promoter region of C4Ppc1. The results suggest that novel cell type-specific positive and negative nuclear factors bind to the maize C4Ppc1 5′-flanking region and regulate its differential transcription in MC in a light-dependent manner.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 36 (1998), S. 733-739 
    ISSN: 1573-5028
    Keywords: AGAMOUS ; tomato ; ripening ; calyx ; gene expression ; sepals ; in vitro
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In vitro culture of VFNT Cherry tomato sepals (calyx) at 16–21 °C results in developmental changes that are similar to those that occur in fruit tissue [10]. Sepals become swollen, red, and succulent, produce ethylene, and have increased levels of polygalacturonase RNA. They also produce many flavor volatiles characteristic of ripe tomato fruit and undergo similar changes in sugar content [11]. We examined the expression of the tomato AGAMOUS gene, TAG1, in ripening, in vitro sepal cultures and other tissues from the plant and found that TAG1 RNA accumulates to higher levels than expected from data from other plants. Contrary to reports on the absence of AGAMOUS in sepals, TAG1 RNA levels in green sepals from greenhouse-grown plants is detectable, its concentration increasing with in vitro ripening to levels that were even higher than in red, ripe fruit. Sepals of fruit on transgenic tomato plants that expressed TAG1 ectopically were induced by low temperature to ripen in vivo, producing lycopene and undergoing cell wall softening as is characteristic of pericarpic tissue. We therefore propose that the induction of elevated TAG1 gene expression plays a key role in developmental changes that result in sepal ripening.
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  • 9
    ISSN: 0197-8462
    Keywords: electromagnetic fields ; gene expression ; transcription factors ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Rat PC12 pheochromocytoma cells have been treated with nerve growth factor and then exposed to athermal levels of a packet-modulated radiofrequency field at 836.55 MHz. This signal was produced by a prototype time-domain multiple-access (TDMA) transmitter that conforms to the North American digital cellular telephone standard. Three slot average power densities were used: 0.09, 0.9, and 9 mW/cm2. Exposures were for 20, 40, and 60 min and included an intermittent exposure regimen (20 min on/20 min off), resulting in total incubation times of 20, 60, and 100 min, respectively. Concurrent controls were sham exposed. After extracting total cellular RNA, Northern blot analysis was used to assess the expression of the immediate early genes, c-fos and c-jun, in all cell populations. No change in c-fos transcript levels were detected after 20 min exposure at each field intensity (20 min was the only time period at which c-fos message could be detected consistently). Transcript levels for c-jun were altered only after 20 min exposure to 9 mW/cm2 (average 38% decrease). Bioelectromagnetics 18:223-229, 1997. © 1997 Wiley-Liss, Inc. This article is a US Government work and, as such, is in the public domain in the United States of America.
    Additional Material: 2 Tab.
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