scholarly journals Primary Oocyte

2020 ◽  
Author(s):  
Keyword(s):  
Primary Oocyte

CYCLIC CHANGES IN THE GONAD OF THE AMERICAN OYSTER, CRASSOSTREA VIRGINICA (GMELIN)

1964 ◽  
Vol 42 (2) ◽  
pp. 305-321 ◽  
Author(s):  
Austina V. Kennedy ◽  
Helen I. Battle
Keyword(s):  
Crassostrea Virginica ◽  
Gonadal Development ◽  
Germinal Epithelium ◽  
Nuclear Area ◽  
Seasonal Growth ◽  
Body Width ◽  
Visceral Mass ◽  
Current Season ◽  
Primary Oocyte ◽  
Cyclic Changes

Cyclic changes in the gonad of Crassostrea virginica (Gmelin), a dioecious, oviparous lamellibranch, are described as they occurred toward the most northerly limit of the range, Malpeque Bay, P.E.I., Canada, during 1961 and 1962. The gonad, composed of right and left gonadal lobes lying immediately beneath the mantle, consists of extensively branched follicles comprising the outer margin of the visceral mass. The follicles open into peripherally located ducts which lead into paired gonoducts terminating in the suprabranchial chamber. During the fall and winter the germinal epithelium is in an indifferent or inactive state. The sex for the current season is distinguishable when proliferation commences in May. Maximum gonadal development occurs in late June or early July as determined by comparison of gonadal width to body width in mid-transverse sections. Primary oocytes are initially distinguishable from oogonia by the presence of a distinct nucleolus, and later by an amphinucleolus consisting of a plasmosome and a karyosome. Seasonal growth of the primary oocyte was followed by a planimetry method using measurements of total area and nuclear area from prepared sections. The spindle for the first meiotic division is established immediately on rupture of the oocyte from the follicular wall. Spermatogenesis and spermiogenesis are completed within the follicle. Following spawning, amoebocytes infiltrate the follicles and interfollicular connective tissue to phagocytize unspawned gametes. By late October the follicles of both male and female consist of a low germinal epithelium and a few unresorbed gametes, and remain inactive until proliferation the following spring.

Fine structural observations on oocyte development in monogeneans

Parasitology ◽  
1976 ◽  
Vol 73 (1) ◽  
pp. 13-23 ◽  
Author(s):  
D. W. Halton ◽  
S. D. Stranock ◽  
Anne Hardcastle
Keyword(s):  
Meiotic Prophase ◽  
Species Differences ◽  
Ultrastructural Changes ◽  
Cell Periphery ◽  
Annulate Lamellae ◽  
Cellular Activity ◽  
Cortical Granules ◽  
Primary Oocyte ◽  
Nucleolar Volume ◽  
Oocyte Differentiation

SummaryThe ultrastructural changes accompanying oocyte differentiation in the ovaries of the monogeneans, Diclidophora merlangi, Diplozoon paradoxum and Calicotyle kröyeri have been described. In each case, oogenesis in the ovary proceeds as far as meiotic prophase in the primary oocyte. A three-stage sequence of development based on oocyte morphology is proposed: (1) Oogonia and early, immature primary oocytes are typically undifferentiated, with chromatin-laden nuclei occupying most of the cell volume. The cytoplasm contains small clumps of mitochrondria and unattached ribosomal aggregates. There is evidence of mitosis and, in later stages, meiotic prophase is indicated by the appearance of nuclear synaptonemal complexes. (2) Maturing primary oocytes are characterized by increased nucleolar volume associated with the production of RNA for export to the cytoplasm. An organized GER and Golgi apparatus are established and involved in the synthesis and packaging of membrane-limited cortical granules. Annulate lamellae and nucleolus-like bodies appear in the cytoplasm and, with development, the cells increase in size and, peripherally, become interdigitated. (3) Mature primary oocytes represent a resting phase when cellular activity is minimal. Golgi disappear and the ER fragments or becomes reduced in dimensions. Mitochondria and free ribo-somes are numerous and cortical granules move to the cell periphery. The cells separate and, when mature, are released from the ovary. There are minor species differences in oocyte ultrastructure and development.

Oocyte maturation: aberrant post-fusion responses of the rabbit primary oocyte to penetrating spermatozoa

1979 ◽  
Vol 39 (1) ◽  
pp. 1-12
Author(s):  
M. Berrios ◽  
J.M. Bedford
Keyword(s):  
Anterior Part ◽  
Light And Electron Microscopy ◽  
Germinal Vesicle ◽  
Sperm Chromatin ◽  
Fallopian Tubes ◽  
Cortical Granules ◽  
Germinal Vesicle Breakdown ◽  
Acrosomal Membrane ◽  
Primary Oocyte ◽  
Inner Acrosomal Membrane

Primary oocytes cannot be fertilized normally; they begin to develop this capacity as meiosis resumes. To elucidate the changes involved in acquisition of their fertilizability, rabbit primary oocytes displaying a germinal vesicle (GV oocytes) were placed in Fallopian tubes inseminated previously with spermatozoa, recovered 2–5 h later and examined by light and electron microscopy. At least 4 aspects of GV oocyte/sperm interaction were abnormal. Although the vestments and oolemma seem normally receptive to spermatozoa, fusion with the oolemma of the primary oocyte did not elicit exocytosis of cortical granules, and consequently multiple entry of spermatozoa into the ooplasm was common. Secondly, the GV oocyte cortex failed to achieve a normal englufment of the anterior part of the sperm head. It sank into the ooplasm capped by only a small rostral vesicle or left the stable inner acrosomal membrane as a patch in the oolemma. Only rarely then was there significant dispersion of the sperm chromatin, and this remained surrounded by nuclear envelope. The persistence of this envelope constitutes a further aberrant feature, for it disappears immediately in secondary oocytes and was absent in primary oocytes in which germinal vesicle breakdown had occurred. The results are discussed with particular reference to current ideas about male pronucleus formation.

scholarly journals Inheritance of a meiotic abnormality that causes the ovulation of primary oocytes and the production of digynic triploid mice

1993 ◽  
Vol 62 (3) ◽  
pp. 183-193 ◽  
Author(s):  
John D. West ◽  
Sheila Webb ◽  
Matthew H. Kaufman
Keyword(s):  
Inbred Strains ◽  
Meiotic Metaphase ◽  
Major Influence ◽  
Autosomal Gene ◽  
Chromosome 4 ◽  
Normal Allele ◽  
Mammalian Oocyte ◽  
Glucose Phosphate ◽  
Primary Oocyte ◽  
Meiotic Abnormality

SummaryPrevious studies have demonstrated that the LT/SvKau strain of mice ovulates a high proportion of oocytes as diploid primary oocytes rather than secondary oocytes. These ovulated primary oocytes are arrested at meiotic metaphase I but may be fertilized to produce digynic triploid embryos. In the present study, 40·4% of eggs analysed from LT/SvKau females were ovulated as primary oocytes, compared to 1·2% from control C57BL/Ws strain mothers. These two inbred strains were intercrossed to produce eight sets of Fl, F2 and backcross females and the frequency of triploidy was investigated. The results are compatible with segregation of a co-dominant, autosomal gene that has a major influence on the incidence of triploidy. We suggest that the provisional gene symbol Poo (primary oocyte ovulation) be assigned to this gene, with alleles Pool (the ‘mutant’ allele present in the LT/SvKau strain) and Poob (the normal allele present in C57BL/Ws mice). Poo is incompletely penetrant and has variable expressivity because the proportion of oocytes ovulated as primary oocytes by LT/SvKau mice was variable and, in some cases, nil. In putative Pool/Poob heterozygotes the frequency of ovulated primary oocytes was increased only marginally (from 1·2% to 66%) by the presence of one copy of the Pool allele, but this increase was found consistently (in two reciprocal Fl crosses) and was statistically significant. No evidence was found for tight genetic linkage between Poo and two Mendelian loci (brown on chromosome 4 and glucose phosphate isomerase on chromosome 7), that were segregating in the crosses. The Pool mutant in the LT/SvKau strain of mice provides a valuable resource to study the cell and molecular biology of mammalian oocyte maturation and the control of meiosis.

Cumulus expansion initiates physical and developmental autonomy of the oocyte

Zygote ◽  
1996 ◽  
Vol 4 (04) ◽  
pp. 335-341 ◽  
Author(s):  
William J. Larsen ◽  
Lin Chen ◽  
Robert Powers ◽  
Hong Zhang ◽  
Paul T. Russell ◽  
...  
Keyword(s):  
Gap Junctions ◽  
Germ Cell ◽  
Cell Population ◽  
Follicle Cell ◽  
Ovarian Cycle ◽  
Follicle Cells ◽  
Cumulus Expansion ◽  
Primary Oocyte ◽  
Female Germ Cell

As meiosis is initiated and the oogonium is transformed into a primary oocyte, the female germ cell becomes intimately invested by a single squamous layer of sex cord epithelium. As the follicle cell population expands during the initial stages of the ovarian cycle, oocyte and follicle cells become increasingly connected to one another by one of the most extensive populations of gap junctions documented in any epithelium (reviewed in Larsen & Wert, 1988).

scholarly journals New insights in oocyte dynamics shed light on the complexities associated with fish reproductive strategies

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Alba Serrat ◽  
Fran Saborido-Rey ◽  
Cristina Garcia-Fernandez ◽  
Marta Muñoz ◽  
Josep Lloret ◽  
...  
Keyword(s):  
Reproductive Strategies ◽  
Egg Production ◽  
Binary Classification ◽  
Low Cost ◽  
Reproductive Potential ◽  
Major Change ◽  
Temporal Variations ◽  
Conceptual Approach ◽  
Potential Fecundity ◽  
Primary Oocyte

AbstractInformation on temporal variations in stock reproductive potential (SRP) is essential in fisheries management. Despite this relevance, fundamental understanding of egg production variability remains largely unclear due to difficulties in tracking the underlying complex fluctuations in early oocyte recruitment that determines fecundity. We applied advanced oocyte packing density theory to get in-depth, quantitative insights across oocyte stages and seasons, selecting the commercially valuable European hake (Merluccius merluccius) as a case study. Our work evidenced sophisticated seasonal oocyte recruitment dynamics and patterns, mostly driven by a low-cost predefinition of fecundity as a function of fish body size, likely influenced also by environmental cues. Fecundity seems to be defined at a much earlier stage of oocyte development than previously thought, implying a quasi-determinate – rather than indeterminate – fecundity type in hake. These results imply a major change in the conceptual approach to reproductive strategies in teleosts. These findings not only question the current binary classification of fecundity as either determinate or indeterminate, but also suggest that current practices regarding potential fecundity estimation in fishes should be complemented with studies on primary oocyte dynamics. Accordingly, the methodology and approach adopted in this study may be profitably applied for unravelling some of the complexities associated with oocyte recruitment and thereby SRP variability.

Oogenesis in Culicoides Brevitarsis Kieffer (Diptera: Ceratopogonidae) and the Development of a Plastron-Like Layer on the Egg.

1975 ◽  
Vol 23 (2) ◽  
pp. 203 ◽  
Author(s):  
MM Campbell ◽  
DS Kettle
Keyword(s):  
Blood Meal ◽  
Late Stage ◽  
Convex Surface ◽  
Stage Iv ◽  
Stage Iii ◽  
Concave Surface ◽  
Primary Oocyte ◽  
Average Fecundity ◽  
Pore Canals

In C. brevitarsis the mature egg was 290 �m long, average fecundity was 31.3, and duration of oogenesis 30-50 h at 24-26�C. When the first blood meal was consumed oocytes ranged from stage No to I, and 95.8% of females were mated; after a partial blood meal fewer oocytes were initiated and even fewer matured. It is highly likely that C. brevitarsis is anautogenous. Oocytes develop through the same stages as other Culicoides. Chorion developed well below the sheath in late stage IV, causing a reduction in width of oocytes at maturation. Ansulae develop in the space between the sheath and chorion by outward sclerotization, possibly along pore canals; they vary from tall (8-9 �m) and broad on the concave surface to short (5-6 �m) and narrow on the convex surface; those on the concave surface probably act as a plastron. The sheath surrounding the stage IV oocyte is destroyed during maturation. The secondary oocyte commences development when the primary is at stage III, and its development is arrested at either stage N or I almost simultaneously with the primary oocyte completing development. Development of the secondary oocyte is initiated but not controlled by development of the primary in the same ovariole.

scholarly journals Electron Microscopy of the Ovary of Fasciola Hepatica

1964 ◽  
Vol s3-105 (70) ◽  
pp. 213-218
Author(s):  
R. A. R. GRESSON
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Nuclear Envelope ◽  
Fasciola Hepatica ◽  
Amorphous Material ◽  
Primary Oocyte ◽  
Intercellular Region ◽  
Narrow Bridge ◽  
Peripheral Cytoplasm

The external wall of the ovary of Fasciola hepatica is a membrane-like structure in contact with a non-cellular material in the ovary. An intercellular region containing an amorphous material of moderate electron density is present in the ovary. The primary oocytes are provided with peripheral processes that extend into the intercellular region. The oocytes do not proceed beyond the prophase of the first meiotic division until after they leave the ovary. The nucleolus of the primary oocyte contains vacuole-like areas and emits granular material to the nucleoplasm; some of this material may move to the cytoplasm. Pores are present in the nuclear envelope. In older oocytes narrow bridge-like structures connect the nucleolus and the nuclear envelope. The nuclear envelope of the primary oocyte undergoes replication. It is continuous with the endoplasmic reticulum and the plasma membrane. The location of the mitochondria is correlated with the phases of growth of oogonia and oocytes. The mitochondria possess irregularly arranged cristae. Small, round or oval nutritive bodies are present in the peripheral cytoplasm of older oocytes. It is suggested that areas of relatively high density containing vacuole-like structures represent the Golgi complex.

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