Morphological and histochemical obervations on the ovarian balls of Centrorhynchus corvi (Acanthocephala)

Unlike in other acanthocephalans, the overian balls of Centrorhynchus corvi are complex and are composed of 24–30 ovarian ball units. Each ovarian ball unit consists of three structural and functional units – the oogonial syncytium, developing oogenetic cells and the supporting syncytium – complementary to the ovarian balls of other acanthocephalans. Three metamorphic stages of the nuclei in the oogonial syncytium are described, depending on the nuclear morphology, chromatin structure and appearance of the nucleolus. Third-stage nuclei bulge out at the periphery of the oogonial syncytium and are surrounded by its cytoplasm and a thin membrane. Ultimately these are separated from the oogonial syncytium to from oogonia containing small amounts of cytoplasmic components derived from the oogonial syncytium. Nuclei of the young oogonia, oognia at the budding stage, and 3rd-stage nuclei of the oogonial syncytium all possess nucleoli and are similar also in their nuclear dimensions and cytochemical affinities. Nuclear resemblances, and cytoplasmic similarities of the oogonia and oogonial syncytium with regard to the presence of lipids, RNA and proteins support the concept of the origin of oogonia from the oogonial syncytium.The free oogonia divide mitotically in the cellular zone where they undergo a single mitotic division and the resulting oocytes enter the prophase of meiosis. I. The meiotic primary oocytes in contrast to the permeiotic primary oocytes of other acanthoscephalans enter the growth phase which is closely accompanied by the accumulation of various ooplasmic components such as basophilic yolk nucleus which is composed of RNA, proteins, lipoproteins and phospholipids. Histochemical features of the oogonial and supporting syncytium are described.

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Mps1 promotes poleward chromosome movements in meiotic pro-metaphase

10.1101/2020.06.28.176370 ◽

2020 ◽

Author(s):

Régis E Meyer ◽

Aaron R Tipton ◽

Gary J Gorbsky ◽

Dean S Dawson

Keyword(s):

Chromosome Pair ◽

Single Unit ◽

Spindle Pole ◽

Microtubule Depolymerization ◽

Data Support ◽

Chromosome Movements ◽

Meiosis I ◽

Prophase Of Meiosis

ABSTRACTIn prophase of meiosis I, homologous partner chromosomes pair and become connected by crossovers. Chiasmata, the connections formed between the partners enable the chromosome pair, called a bivalent, to attach as a single unit to the spindle. When the meiosis I spindle forms in prometaphase, most bivalents are associated with a single spindle pole and go through a series of oscillations on the spindle, attaching to and detaching from microtubules until the partners of the bivalent are bi-oriented, that is, attached to microtubules from opposite sides of the spindle, and prepared to be segregated at anaphase I. The conserved, kinetochore-associated kinase, Mps1, is essential for the bivalents to be pulled by microtubules across the spindle in prometaphase. Here we show that MPS1 is not required for kinetochores to attach microtubules but instead is necessary to trigger the migration of microtubule-attached kinetochores towards the poles. Our data support the model that Mps1 triggers depolymerization of microtubule ends once they attach to kinetochores in prometaphase. Thus, Mps1 acts at the kinetochore to co-ordinate the successful attachment of a microtubule and the triggering of microtubule depolymerization to move the chromosome.

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The requirements for protein synthesis and degradation, and the control of destruction of cyclins A and B in the meiotic and mitotic cell cycles of the clam embryo.

The Journal of Cell Biology ◽

10.1083/jcb.116.3.707 ◽

1992 ◽

Vol 116 (3) ◽

pp. 707-724 ◽

Cited By ~ 122

Author(s):

T Hunt ◽

F C Luca ◽

J V Ruderman

Keyword(s):

Protein Synthesis ◽

Cyclin A ◽

Mitotic Cell ◽

Mitotic Division ◽

Cyclin B ◽

Cell Cycles ◽

Activated State ◽

Inhibition Of Protein Synthesis ◽

M Phase ◽

Meiosis I

Fertilization of clam oocytes initiates a series of cell divisions, of which the first three--meiosis I, meiosis II, and the first mitotic division--are highly synchronous. After fertilization, protein synthesis is required for the successful completion of every division except meiosis I. When protein synthesis is inhibited, entry into meiosis I and the maintenance of M phase for the normal duration of meiosis occur normally, but the chromosomes fail to interact correctly with the spindle in meiosis II metaphase. By contrast, inhibition of protein synthesis immediately after completion of meiosis or mitosis stops cells entering the next mitosis. We describe the behavior of cyclins A and B in relation to these "points of no return." The cyclins are synthesized continuously and are rapidly destroyed shortly before the metaphase-anaphase transition of the mitotic cell cycles, with cyclin A being degraded in advance of cyclin B. Cyclin destruction normally occurs during a 5-min window in mitosis, but in the monopolar mitosis that occurs after parthenogenetic activation of clam oocytes, or when colchicine is added to fertilized eggs about to enter first mitosis, the destruction of cyclin B is strongly delayed, whereas proteolysis of cyclin A is maintained in an activated state for the duration of metaphase arrest. Under either of these abnormal conditions, inhibition of protein synthesis causes a premature return to interphase that correlates with the time when cyclin B disappears.

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The external mechanics of the chromosomes III-Meiosis in triploids

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1936.0066 ◽

1936 ◽

Vol 121 (823) ◽

pp. 290-300 ◽

Cited By ~ 2

Keyword(s):

Sexual Reproduction ◽

Chromosome Pairing ◽

Natural Experiment ◽

Diploid Species ◽

Homologous Chromosomes ◽

Normal Series ◽

Mitosis And Meiosis ◽

Meiosis I ◽

Prophase Of Meiosis ◽

The Way

Triploid organisms have three homologous chromosomes of each kind instead of the two of diploids. The regular mechanism of heredity fails in these circumstances. The triploid is incapable of breeding true by sexual reproduction. But the way in which it carries out the process of chromosome pairing and segregation is of great significance. The processes take place in normal series, but the relationships they establish are abnormal. A triploid thus provides a natural experiment, with the diploid of its own species as a control for one variable, and with triploids of different species as controls for others. In Tulipa and Hyacinthus I have made use of this experiment for inducing the principles of the external mechanics of chromosomes during the prophase of meiosis. I have inferred from them the relationships between the forces working in mitosis and meiosis. The triploid forms of various Fritillaria species make it possible to test the principles of metaphase mechanics induced from observations on structural hybrids and other polyploids (Darlington, 1932, b , and 1933, c ) as well as from the exceptional behaviour in the diploid species of Fritillaria already discussed.

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The essential roles of Mps1 in spermatogenesis and fertility in mice

Cell Death and Disease ◽

10.1038/s41419-021-03815-4 ◽

2021 ◽

Vol 12 (6) ◽

Author(s):

Qiang Fang ◽

Xue-Lin Chen ◽

Lei Zhang ◽

Ya-Bin Li ◽

Tian-Zeng Sun ◽

...

Keyword(s):

Critical Role ◽

Cell Loss ◽

Conditional Knockout ◽

Male Mice ◽

Fertility Reduction ◽

Monopolar Spindle ◽

Apoptotic Genes ◽

Mitosis And Meiosis ◽

Meiosis I ◽

Prophase Of Meiosis

AbstractMonopolar spindle 1 (MPS1), which plays a critical role in somatic mitosis, has also been revealed to be essential for meiosis I in oocytes. Spermatogenesis is an important process involving successive mitosis and meiosis, but the function of MPS1 in spermatogenesis remains unclear. Here, we generated Mps1 conditional knockout mice and found that Ddx4-cre-driven loss of Mps1 in male mice resulted in depletion of undifferentiated spermatogonial cells and subsequently of differentiated spermatogonia and spermatocytes. In addition, Stra8-cre-driven ablation of Mps1 in male mice led to germ cell loss and fertility reduction. Spermatocytes lacking Mps1 have blocked at the zygotene-to-pachytene transition in the prophase of meiosis I, which may be due to decreased H2B ubiquitination level mediated by MDM2. And the expression of many meiotic genes was decreased, while that of apoptotic genes was increased. Moreover, we also detected increased apoptosis in spermatocytes with Mps1 knockout, which may have been the reason why germ cells were lost. Taken together, our findings indicate that MPS1 is required for mitosis of gonocytes and spermatogonia, differentiation of undifferentiated spermatogonia, and progression of meiosis I in spermatocytes.

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Commitment to meiosis in Saccharomyces cerevisiae: involvement of the SPO14 gene.

Genetics ◽

10.1093/genetics/130.4.703 ◽

1992 ◽

Vol 130 (4) ◽

pp. 703-716 ◽

Cited By ~ 5

Author(s):

S M Honigberg ◽

C Conicella ◽

R E Espositio

Keyword(s):

Saccharomyces Cerevisiae ◽

Gene Product ◽

Mitotic Division ◽

Temperature Sensitive ◽

Unusual Property ◽

Phenotypic Analysis ◽

New Gene ◽

Late Stages ◽

Reductional Division ◽

Meiosis I

Abstract This paper describes the identification, cloning and phenotypic analysis of SPO14, a new gene required for meiosis and spore formation. Studies of strains carrying a temperature-sensitive mutation or a disruption/duplication allele indicate that spo14 mutants have the unusual property of being able to return to mitotic division, even from the late stages of meiotic development. Early meiotic events, such as DNA replication and intragenic and intergenic recombination, occur normally. In contrast, later meiotic processes are defective in spo14 mutants: the meiosis I division appears to be executed at slightly depressed levels, the meiosis II division is reduced more severely, and no spores are formed. Epistasis tests using mutants defective in recombination or reductional division support these findings. Based on these data, we suggest that the SPO14 gene product is involved in the coordinate induction of late meiotic events and that this induction is responsible for the phenomenon of commitment.

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Egg production in Brugia pahangi(Nematoda: Filarioidea)

Parasitology ◽

10.1017/s0031182000059746 ◽

1989 ◽

Vol 98 (1) ◽

pp. 105-113 ◽

Cited By ~ 7

Author(s):

C. J. Delves ◽

H. H. Rees ◽

R. E. Howells

Keyword(s):

Germ Cells ◽

Meiotic Prophase ◽

Egg Production ◽

Polar Body ◽

Chromosome Complement ◽

Mitotic Division ◽

Synthetic Activity ◽

Brugia Pahangi ◽

Meiosis I

SummaryOogenesis in Brugia pahangi has been studied by means of the aceto-orcein chromosomal squash technique and light-microscope autoradiography. The use of colchicine has demonstrated a 2–3 mm terminal germinative zone within the ovary, in which continuous and rapid mitotic division of germ cells occurs. In 80% of the gonads, oocytes within a 1–2 mm length of the ovary proximal to the germinative zone were at the prophase of meiosis I. Primary oocytes with markedly less condensed chromatin, apparently interphase cells, were observed in the corresponding region of the ovary in the remaining 20% of material examined. A cyclical or phased development of primary oocytes is suggested. Autoradiographic studies, concerned with the incorporation of [5-3H]uridine into germ cells of B. pahangi in vitro, further suggest that the onset of meiotic prophase is associated with the initiation of high RNA synthetic activity. Following meiotic prophase, oocytes complete meiosis I before entering a period of growth during which the chromatin material is decondensed. Recondensation of chromosomes prior to meiosis II is only observed after fertilization within the seminal receptacle. On completion of meiosis II, with the extrusion of a polar body, the haploid chromosome complement of the female unites with that of the male, re-establishing the diploid number of the zygote (2n = 10).

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