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At least 325 records · Page 18Linked to original sources
PubMed1987

Identification of a meiotic prophase-specific nuclear matrix protein in the rat.

We have identified a 110-kDa pI 5.6 phosphoprotein with DNA binding properties in the rat pachytene spermatocyte nuclear matrix. By immunoblotting and indirect immunofluorescence assays using polyclonal antibodies against the 110-kDa protein, we observed that it was germ cell nuclear matrix specific, more prominent in pachytene spermatocytes compared to premeiotic spermatogonia or postmeiotic round spermatids, and present in rat oocytes and in germ cells of mouse and monkey. We propose that this protein could play an important role in the meiotic process.

Animals↗
PubMed1986

Nuclear lamins during prophasing and telophasing in heterophasic HeLa and Chinese hamster homokaryons.

We have perturbed the dynamics of the nuclear lamins by means of cell fusion between mitotic and interphase cells and have studied redistribution of lamins in fused cells as a function of extracellular pH levels. We show here that in heterophasic M-1 HeLa homokaryons disassembly of interphase lamins predominates at low pH levels between 7.0 to 7.3, whereas deposition of cytoplasmic lamins around condensed metaphase chromosomes was observed at pH 8.0. In HeLa homokaryons lamina disassembly and lamina deposition around chromosomes are mutually exclusive. Using heterophasic M-1 homokaryons of the Chinese hamster cell line DON we observed that disassembly of interphase lamins and deposition of lamins around condensed chromosomes coexisted in the same homokaryon kept at pH 7.0. Disassembly of lamins developed synchronously with premature chromosome condensation (PCC) whereas lamina deposition around the condensed M-chromosomes was followed by telophasing. In fusions kept at pH 8.0 cytoplasmic lamins were exclusively deposited around mitotic chromosomes. The results are interpreted as showing that pH regulates the lamina dynamics in homokaryons of mitotic and interphase cells.

Animals↗
PubMed1984

Lampbrush chromosomes and gene utilization in meiotic prophase.

The main features of lampbrush chromosome organization are reviewed and the significance of RNA transcription on lampbrush loops is questioned. Special consideration is given to evidence for the transcription on lampbrush loops of satellite DNA, low copy number genes with defined functions, the histone genes, the 5S genes and the genes for ribosomal RNA. It is concluded that there is widespread but somewhat indiscriminate transcription on lampbrush loops of a range of repetitive DNA sequences, transcription of a wide range of mRNAs, continuous transcription of histone and 5S RNA, and low or aberrant transcription of ribosomal RNA. The 'read-through' hypothesis of lampbrush loop transcription is explained and evaluated, and some of the assumptions underlying it and the problems it raises are examined and discussed. The hypothesis requires that transcription starts at a normal promoter site for a functional gene situated at the thin end of a lampbrush loop, and that once started the transcribing polymerase cannot stop until it reaches another promoter that is already initiated or some condensed and untranscribable chromatin. The following questions are considered. Why should polymerase on a lampbrush loop disregard normal termination signals? Why should polymerase stop when it encounters another initiated promoter sequence? Why is the number of loops or transcription units related to genome size signifying, according to the read-through hypothesis, that oocytes from animals with large genomes have more active 'functional gene promoters' than those from animals with small genomes? Finally, some special situations where there is enhanced or reduced lampbrush activity are considered and their significance in relation to ideas about the function of lampbrush chromosomes is discussed. Specific examples include the frog, Ascaphus truei, whose oocytes have eight germinal vesicles each with a full complement of lampbrush chromosomes, another frog, Flectonotus pygmaeus, in which each oocyte starts with several thousand meiotic nuclei only some of which go into a lampbrush phase, and certain species of reptile in whose germinal vesicles the chromosomes never acquire a lampbrush form.

Animals↗
PubMed1993

[The variability of the pattern of human G-band chromosomes in the late prophase-early metaphase].

Original modification of the harvest procedure, hypotonic treatment and slide-making techniques were used to obtain prometaphase spreads of good quality fitted to G-banding or to FISH. Human blood cultures were synchronized with a methotrexate block during synthesis, and following this with a thymidine release. Cells were then proceeded into prometaphase and early metaphase and were quickly harvested without exposure to colcemid. Following incubation in a mixture of 0.56% KCl and 1% sodium citrate (1:1) for 20-23 min at room temperature, cells were fixed in 4 changes of fixative made of 3 parts of absolute methanol and 1 part of glacial acetic acid. Three or four 100-105 microliters volume of a suspension of fixed cells were blew with a strength through pasteur pipette tip from a distance 5-6 cm onto chilled superclean slides wetted by water. These slides were then quickly flame dried. Prior to staining, prometaphase bearing spreads were held in thermostat overnight at 37 degrees C. Prometaphases were G-banded with the aid of a modified technique elaborated in the Department of Clinical Genetics, Lund University Hospital (Sweden). The slides were incubated for 1-4 min at room temperature in 0.01 versene solution, containing 0.011% w/v trypsin (Difco), 0.4 mg/ml D-glucose, 0.17 mg/ml KCl, 1.7 mg/ml NaCl. Following a 15 sec incubation in a solution containing 1 mg/ml D-glucose, 0.4 mg/ml KCl, 8 mg/ml NaCl, G-banding was completed by staining the slides with 2% Giemsa (Merck) in pH 6.8 phosphate buffer for 4-5 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1996

[Localization of RecA-like proteins in preparations of spread nuclei of mouse spermatocytes at meiotic prophase I].

Earlier, polyclonal antibodies to Escherichia coli RecA protein were used to identify immunologically related proteins in meiotic spermatocytes of different eukaryotes. At least one such protein proved to be a component of the synaptonemal complex (SC) [1]. Subsequent experiments on localization of RecA-like antigens in SCs of spermatocytes were performed by indirect immunocytochemical methods and electron microscopy, which showed that RecA-like protein(s) at early leptotene are largely associated with chromatin. During SC formation (at leptotene and zygotene), they are found in both lateral elements and the central space of SC. In some cases, RecA-like proteins are associated with SC substructures that resemble recombination nodules. When spermatocytes enter late diplotene, Rec-A-like proteins cease to be detected in SC structures.

Animals↗
PubMed1984

Enzyme studies on TPPase-reactive cytoplasmic structures observed in early meiotic prophase I of the hamster oocyte.

Ovaries of immature and adult hamsters were incubated in medium containing thiamine pyrophosphate (TPP) to determine the age at which TPPase-reactive cytoplasmic structures first appear in the germ cells, and at what age the structures cease to be present. The structures were found only in oocytes from animals 8-15 days of age. They occur in predictyate germ cells in polyovular follicles and in very early dictyate oocytes in unilaminar follicles. The TPPase-reactive structures were never observed in atretic oocytes, in unilaminar follicles of adult animals, nor in multilaminar follicles of animals at any age. Ovaries of 8-12-day-old animals and adults were then incubated in media in which one of the following substrates was substituted for TPP: uridine diphosphate (UDP), inosine diphosphate (IDP), and adenosine monophosphate (AMP). Half of the samples in each experiment were incubated in medium containing the inhibitor L-p-bromotetramisole. beta-Glycerophosphate was used in control incubations, or the substrate was omitted entirely. The cytoplasmic structures were found to be reactive after incubation in UDP-containing media, but not after incubation in media containing AMP. With IDP as substrate, reactions were atypical and confined to peripheral regions of the cytoplasm. Other sites of enzyme activity after incubation with the various substrates (cell membranes, zona pellucida, endoplasmic reticulum and Golgi apparatus) are also described and discussed.

Aging↗
PubMed1979

Silver-stained structures in mammalian meiotic prophase.

Silver staining of mammalian spermatocytes revealed, in light microscopy, synaptonemal complex and structures within the sex vesicle. It is feasible to follow the chromosome pairing phenomenon from zygotene to pachytene by examining the behavior of synaptonemal complexes. Nucleolus organizer regions take heavy silver stain in pachytene but are no longer detectable in later stages of meiosis.

Animals↗
PubMed1979

Association of the extra chromosome of tertiary trisomic male mice with the sex chromosomes during first meiotic prophase, and its significance for impairment of spermatogenesis.

Pachytene nuclei were studied in five tertiary trisomic male mice of Ts(1(13))70H and two of Ts(5(12))31H, with special attention given to the sex vesicles. Silver stained air dried cells analysed by light microscopy were used mainly, but in addition one sample of surface spread, ethanolic phosphotungstic acid stained nuclei was analysed by electron microscopy. With both techniques and both karyotypes, the extra chromosome (or the greater part of it) almost consistently aggregated with the sex chromosomes. Thereby, the chromatin structure of the extra chromosome as judged by a fine granular appearance resembled that of the sex chromosomes. The animals used ranged from almost azospermic to fertile oligospermic. This variation was not reflected in the position and morphology of the chromosomes 1(13) and 5(12). -Using the whole mount spreading EM technique within a Ts(1(13))70H tertiary trisomic, both 13;13;1(13) trivalents and 1(13) univalents were observed. The 13;13;1(13) trivalents showed a variety of morphologies, ranging from a situation showing classical partner exchange to complete synapsis between the two 13 homologues with the 1(13) telomeric region adhering. The latter configuration is thought not to lead to chiasma formation.

Animals↗
PubMed1986

Prophase pairing in a mosaic 18p-;iso 18q human female foetus studied by surface spreading.

The pachytene configurations formed in the ovary of a mosaic 18p-;iso 18q human foetus (22 weeks gestation) are analysed using a surface spreading technique. Three features of interest are the apparent meiotic delay of oocyte development, oocyte degeneration, and the triple pairing which occurs in one cell line when the iso 18q both pairs with itself and with the normal chromosome 18.

Cell Line↗