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911.
Nucleate and anucleate fragments of parthenogenetically activated mouse oocytes, as well as cybrids obtained by fusion of anucleate fragments (cytoplasts) of maturing and activated matured oocytes were fertilized at different time after activation. Remodelling of the sperm nucleus was studied by electron microscopy at 1.5 and 3 h after fertilization and, in addition, at 14 h in cybrids. Results show that (1) the nuclear envelope of the sperm nucleus can break down when the insemination takes place after the end of M-phase, but the capacity of the parthenote cytoplasm to remodel the sperm nucleus is restricted in time. (2) Male chromatin can decondense within the old, unbroken nuclear envelope, but in such cases formation of a male pronucleus, one of the two nuclei of zygote possessing inactive nucleoli, is never observed. © 1994 Wiley-Liss, Inc. 相似文献
912.
B. R. Niederlehner John Cairns Jr. 《Journal of Aquatic Ecosystem Stress and Recovery (Formerly Journal of Aquatic Ecosystem Health)》1994,3(2):93-99
We review microcosm toxicity tests with 12 chemical stresses and find that the relative sensitivity of certain endpoints is consistent over toxicant type. Changes in species composition occur at very low levels of chronic stress. Endpoints responding at increasing levels of stress are declines in species numbers relative to expected numbers, followed by decreased oxygen production and decreased total production. Other endpoints are quite sensitive in response to some toxicants but insensitive to others (e.g., autotrophic biomass). In addition, other endpoints respond unpredictably to stress, showing stimulation under some conditions and impairment under others. We compare our observations to the progressions of impact suggested from published whole ecosystem experiments and speculate about a general ecosystem distress syndrome and the implications for choosing endpoints in both toxicity testing and monitoring. 相似文献
913.
Zusammenfassung Sekretgranula und andere subzelluläre Strukturen in den Zellen des Hypophysen-Vorderlappens und neurosekretorische Granula in Nervenfasern des Hypophysen-Hinterlappens wurden hinsichtlich ihres Schwefelgehaltes einer Röntgenstrahl-Mikroanalyse unterworfen. Den höchsten Schwefelgehalt weisen die Sekretgranula der TSH- und STH-Zellen sowie die Neurosekretgranula des Hinterlappens auf.
Stipendiat der Alexander von Humboldt-Stiftung
Sonderdruckanforderungen an: Dr. Ewa Stach-Chif, Abteilung für Klinische Morphologie der Universität Ulm, Oberer Eselsberg, D-7900 Ulm a.d. Donau, Federal Republic of Germany 相似文献
Demonstration of sulphur in secretory granules of anterior and posterior pituitary by X-ray microanalysis
Summary The sulphur content of secretory granules and other subcellular structures in the cells of the anterior pituitary and of neurosecrotory granules in the nerve fibers of the neural lobe have been studied by energy dispersive microanalysis. The highes level has been found in the secretory granules of the neural lobe.
Stipendiat der Alexander von Humboldt-Stiftung
Sonderdruckanforderungen an: Dr. Ewa Stach-Chif, Abteilung für Klinische Morphologie der Universität Ulm, Oberer Eselsberg, D-7900 Ulm a.d. Donau, Federal Republic of Germany 相似文献
914.
Carol E Cass Norbert Kolassa Yoshimasa Uehara Ewa Dahlig-Harley Eric R Harley Alan R.P Paterson 《生物化学与生物物理学报:生物膜》1981,649(3):769-777
Cells of an adenosine-resistant clone (AE1) of S49 mouse lymphoma cells were compared with cells of the parental line with respect to (a) characteristics of nucleoside transport, (b) high affinity binding of the inhibitor of nucleoside transport, nitrobenzylthionisine (NBMPR), and (c) the antiproliferative effects of the nucleoside antibiotics, tubercidin, arabinosyladenine and showdomycin. Rates of inward transport of uridine, thymidine, adenosine, 2′-deoxyadenosine, tubercidin, showdomycin, and arabinosyladenine in AE1 cells were less than 1% of those in cells of the parental S49 line. The inhibitor of nucleoside transport, NBMPR, reduced rates of inward nucleoside transport in S49 cells to levels comparable to those seen in the transport-defective mutant. S49 cells possessed high affinity sites that bound NBMPR (6.6 · 104 sites/cell, Kd 0.2 nM), whereas site-specific binding of NBMPR to AE1 cells was not demonstrable, indicating that loss of nucleoside transport activity in AE1 cells was accompanied by loss of the high affinity NBMPR binding sites. Relative to S49 cells, AE1 cells were resistant to the antiproliferative effects of tubercidin and showdomycin, but differences between the two cell lines in sensitivity toward arabinosyladenine were minor, suggesting that nucleoside transport activity was required for cytotoxicity of tubercidin and showdomycin, but not for that of arabinosyladenine. 相似文献
915.
Summary Calreticulin was identified in a variety of rabbit tissues by Western blot analysis. Indirect immunofluorescence studies on cultured cells or frozen sections from the corresponding tissues revealed that the protein was distributed to the endoplasmic reticulum or sarcoplasmic reticulum. Calreticulin was found to be an abundant calcium-binding protein in non-muscle and smooth muscle cells and a constitutent calcium-binding protein in cardiac and skeletal muscle. From the immunoblot data, calreticulin may exist as an isoform in rabbit neural retina. The present study establishes the ubiquity of calreticulin in intracellular calcium binding. 相似文献
916.
Svetlana Bajalica Susanne V. Allander Ewa Ehrenborg Karen Brøndum-Nielsen Holger Luthman Catharina Larsson 《Human genetics》1992,89(2):234-236
Summary Insulin-like growth-factor-binding proteins (IGFBPs) constitute a family of structurally related proteins that specifically bind insulin-like growth factors and modulate their functions. In this study, the chromosomal localization was determined for the gene encoding IGFBP4, i.e. inhibitory-IGFBP. A polymerase chain reaction (PCR) fragment corresponding to the previously published cDNA sequence was used to isolate overlapping cosmid clones. By fluorescent in situ hybridization to metaphase chromosomes, the IGFBP4 gene was then localized to chromosomal region 17q21–21.1. This result was in agreement with PCR analysis of a panel of somatic cell hybrids. 相似文献
917.
Summary Non-histone proteins of normal, non-immunized rats and rats immunized with mouse spleen cells were labelled with three different amino acids: [3H]tryptophan, [3H]methionine and [3H]leucine. Chromatin was fractionated at increasing salt concentrations into three fractions: 0.35 M NaCl-soluble, 2 M NaCl-soluble and residual. Non-histone protein fractions F (Mr 12 000) and H (Mr 3 000) highly labelled with [3H]tryptophan, lower with [3H]methionine but not with [3H]leucine, were present mainly in the residual fraction. After DNAse II treatment non-histone protein fractions F and H disappeared in chromatin fractions and were present in Mg2– soluble fractions which suggests that, similar to the fractions I (Mr below 3 000) and B (Mr 120 000) described previously (5), these fractions may be associated with active transcribed genes. 相似文献
918.
A spatiotemporal pattern of cell death occurred in the chick wing and leg bud mesoderm after removal of apical ectodermal ridge at stages 18–20. Cells died in a region extending from the limb bud distal surface to 150–200 μm into the mesoderm. Limb buds from which ridge was removed at later stages in development did not exhibit a spatiotemporal pattern of cell death. In control experiments in which dorsal ectoderm was removed, a pattern of cell death did not occur. Removal of the ridge and part of the 150- to 200-μm zone of prospective cell death resulted in cell death in an area approximately equal to the amount of the zone remaining. After removal of all of the prospective zone of cell death plus the apical ridge, cell death was observed in the remaining limb bud mesoderm. In these limb buds, cell death occurred in a region in which it had not been seen in limb bud with apical ridge alone removed. We conclude that at stages 18–20 the mesodermal cells 150–200 μm beneath the ridge require the apical ridge to survive. More proximal mesodermal cells do not die after ridge removal alone, but apparently require the presence of the more distal mesoderm to survive. Whether this is a requirement for something intrinsic to the distal mesoderm or something it possesses by way of the ridge is unknown. After stage 23, the limb mesoderm cells do not die when the apical ridge is removed. Nevertheless, at the later stages, ridge continues to be required for limb bud proximal-distal elongation and the differentiation of distal limb elements. 相似文献
919.
Anna Zubrzycka Monika Migdalska-Sk Sawomir Jdrzejczyk Ewa Brzeziaska-Lasota 《Current issues in molecular biology》2021,43(2):900
Endometriosis is a chronic gynecological disease defined by the presence of endometrial-like tissue found outside the uterus, most commonly in the peritoneal cavity. Endometriosis lesions are heterogenous but usually contain endometrial stromal cells and epithelial glands, immune cell infiltrates and are vascularized and innervated by nerves. The complex etiopathogenesis and heterogenity of the clinical symptoms, as well as the lack of a specific non-invasive diagnostic biomarkers, underline the need for more advanced diagnostic tools. Unfortunately, the contribution of environmental, hormonal and immunological factors in the disease etiology is insufficient, and the contribution of genetic/epigenetic factors is still fragmentary. Therefore, there is a need for more focused study on the molecular mechanisms of endometriosis and non-invasive diagnostic monitoring systems. MicroRNAs (miRNAs) demonstrate high stability and tissue specificity and play a significant role in modulating a range of molecular pathways, and hence may be suitable diagnostic biomarkers for the origin and development of endometriosis. Of these, the most frequently studied are those related to endometriosis, including those involved in epithelial–mesenchymal transition (EMT), whose expression is altered in plasma or endometriotic lesion biopsies; however, the results are ambiguous. Specific miRNAs expressed in endometriosis may serve as diagnostics markers with prognostic value, and they have been proposed as molecular targets for treatment. The aim of this review is to present selected miRNAs associated with EMT known to have experimentally confirmed significance, and discuss their utility as biomarkers in endometriosis. 相似文献
920.
Zbigniew Kaniuga Violetta Sączyńska Ewa Miśkiewicz Maciej Garstka 《Acta Physiologiae Plantarum》1999,21(1):45-56
Degradation of leaf polar lipids [monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol
(SQDG) and phosphatidylglycerol (PG)] and chlorophyll (Chl) were studied in four Zea mays genotypes differing in chilling susceptibility following dark chilling and post-chilling rewarming at original growth conditions.
Assessment of visual chilling injury symptoms during post-chilling rewarming differentiated maize inbred lines into chiling-sensitive
(CS) CM7 and Co151 lines and chillingtolerant (CT) S215 and EP1 lines. Severity of chilling injury in CS and CT inbreeds were
correlated with the extent of Chl and polar lipids degradation.
Chilling for either 4 or 6 days followed by 4 days of rewarming caused more extensive degradation of total polar lipids content
in CS than in CT lines. MGDG decreased mostly during chilling whereas DGDG dropped during rewarming only. Chl content was
not affected during chilling but its large decrease, greater in CS than in CT lines, was observed upon rewarming. Extent of
polar lipids breakdown in CS and CT inbreeds during chilling and post-chilling rewarming is correlated with galactolipase
activity in chloroplasts (Kaniuga et al., 1998) and visual assessment of chilling injury.
In view of the data it is likely that contribution of galactolipase activity induced during low-temperature stress of CS plants
is an important factor responsible for thylakoid lipid degradation and development of chilling injury as postulated previously
(Kaniuga 1997). It is suggested that genetically engineered reduction of galactolipase activity or elimination of the factors(s)
involved in induction/stimulation of its activity during chilling might increase tolerance of CS species to chilling stress. 相似文献