Maturation Division Research Articles

Reproduction, reproductive organs, and meiosis in the bisexual non‐parthenogenetic mite Caloglyphus mycophagus, with reference to oocyte degeneration in virgins (Sarcoptiformes: Acaridae)

AbstractMeiosis is described in virgin females, inseminated females and males of the acarid mite Caloglyphus mycophagus (Megnin). The observed sex determining mechanism is an XO‐type with the male having a diploid chromosome number of 15. Oogenesis in mated females is regular. Pachytene is the earliest meiotic stage which is readily identifiable. At metaphase I eight bivalents are observed. Both products of the first maturation division divide at the second maturation division. After the fusion of the pronuclei either 15 or 16 chromosomes are observed in cleaving eggs.Nurse cells are not observed during the growth period of the oocyte. Such oocytes are attached to a central structure of the ovary by a cone‐shaped organelle. At this stage the nucleus appears as a germinal vesicle; a nucleolus is present and the diffuse chromatin appears to extend from the nucleolus to the nuclear membrane. Nuclear extrusion bodies can be seen adjacent to the nuclear membrane both within and outside of the nucleus.Virgin females do not oviposit. The aberrant morphology and behavior of bivalents in post diakinetic oocytes which have not been penetrated by a sperm are described. Neither chromatin nor a chorion could be demonstrated in aberrant oocytes situated in the oviduct. It is suggested that oocyte degeneration in virgins is an adaptive feature in an animal order in which parthenogenesis is the more common mode of reproduction.

Endocrine control of oocyte maturation and oviducal jelly release in the toad, Bufo bufo (L.).

Abstract An investigation has been carried out into the endocrine control of oocyte maturation and jelly release in the toad. Injection of gravid females with HCG will cause maturation division of the oocytes, ovulation, and release of jelly from the oviducal glands into the oviduct lumen. It has been demonstrated that a progestin released from the ovarian follicles causes both oocyte maturation and jelly release. This conclusion is based on the following results: (a) Jelly release is a response to an ovarian hormone, and oocyte maturation occurs in response to a secretion of the ovarian follicle. (b) Of the different steroids tested, progesterone was the most effective in provoking both oocyte maturation and jelly release. (c) Ovarian influence over both jelly release and oocyte maturation is exerted at least 12 hr before ovulation.

The reproductive cycle of Gorgonocephalus caryi (Echinodermata; Ophiuroidea).

1. Samples of gonads from Gorgonocephalus caryi collected monthly over a 13-month period were examined histologically to determine the course of the reproductive cycle.2. The reproductive cycle of both sexes was divided into 5 stages: Post-spawning, Early Growth, Resting, Late Growth, and Spawning. The Maturity Index (Yoshida, 1952) was calculated separately for males and females for each month.3. The histology of the ovaries in the various stages is described.4. Maturation divisions in females probably occur on the day of spawning and proceed very much as in the crinoid, Comanthus japonica (Dan, 1952).5. Gorgonocephalus has an annual reproductive cycle and spawns for six months of the year, from June through November in the population studied in 1965-1966. In the winter of 1966-1967, animals collected from a different location spawned in the laboratory from November through March.6. Each animal spawns more than once during the spawning season.7. Gonad development is arrested after the initial stages of gametogenesis have commenced rather than immediately after spawning, as occurs in most other echinoderms.8. The curve for growth of the largest oocytes corresponds well with the female Maturity Index, indicating that oocyte size is a good measure of gonadal maturity.9. The male and female Maturity Indices correspond well, and the differences between them can be explained by differences between oogenesis and spermatogenesis.

Studies on the structure and function of the mammalian testis. II. Cytological and histochemical observations on the testis of the rat after a single exposure to heat applied for different lengths of time.

The scrotal regions of five groups of rats were exposed to a temperature of 43 °C for progressively longer periods, ranging from 10 to 30 min in steps of 5 min. The animals were then killed at 3 days, 7 days, 3 weeks and 6 weeks after heat-treatment, and their testes examined by various cytological and histochemical procedures. Appropriate control animals were killed alongside the experimental groups. There was essentially no change seen in the 10 min group. In the 15 min group two critical periods were established where further development of the germ cells failed; the first occurred as cells in the early transitional condition attempted to develop into late transitional forms, while the second operated from late pachytene to the end of the maturation division. This led to what has been termed the pattern of mild heat damage. As the exposure time was increased the pattern of mild heat damage was extended, and after 20 min the two critical periods merged. A third also began to appear, such that while cells in the Golgi phase were able to form cap-phase cells they could not develop into acrosome- phase spermatids. Twenty-five minutes exposure produced a similar result but the third critical period was then firmly established, since neither the Golgi or cap-phase spermatids developed into acrosome-phase spermatids. After 30 min all the previous critical periods were extended and merged and their extreme boundaries marked two new critical periods, one operating at the spermatogonial level and the other at the acrosome-phase. In animals treated for 15, 20 and 25 min there was a variable degree of recovery which occurred between 7 and 21 days after heating, during which time the critical periods disappeared. The damage to the germinal epithelium was accompanied by an increase in the lipid content of the Sertoli cells which progressively gave a red colour with Nile blue (non-acidic) and a positive reaction to Schultz’s test for unsaturated sterols. This effect is interpreted as an indirect one resulting from the damage to the germinal epithelium and the cessation of sperm atogenic activity. The high lipid/sterol content of the Sertoli cells was reduced to normal levels with the recovery of the germinal epithelium, notably during the maturation division of the primary and secondary spermatocytes corresponding to stages IX-XIV of the cycle of the seminiferous epithelium. Injections of follicle-stimulating hormone (FSH) into rats exposed to the heat for 30 min did not reduce the lipid/sterol content of the Sertoli cells to normal levels as found previously when the same gonadotrophin was administered to oestrogen-treated rats. This is attributed to the extensive damage caused to the germ cells in the 30 min group. The work on the heat-treated animals provides further evidence in support of the view that the lipids/sterols of the Sertoli cells represent material normally utilized by the germ cells in the course of their development; it emphasizes that the cells which primarily use this material are the spermatocytes and finally suggests that the last-mentioned cells govern or regulate sterol metabolism by the Sertoli cells. The Leydig cells in all groups appeared to be unaffected by the heat-treatment.

The cytological basis for reproductive variability in the Anoetidae (Sarcoptiformes: Acari).

Meiosis is described in a thelytokous strain of the anoetid mite Histiostoma feroniarum (Dufour) and in both sexes of the arrhenotokous strain of this species. Oogenesis in the thelytokous strain is accomplished by ameiotic mitosis with only one pseudo-maturation division. During this division one or more chromosomes may move to the poles precociously and while in this position can be mistaken for centrioles. Fourteen chromosomes are found at metaphase of the pseudo-maturation division and in cleaving eggs of this strain. In the arrhenotokous strain, male meiosis consists of a single mitotic division. Oogenesis is regular and 7 bivalents are observed at the first maturation division. Metaphases of the first cleavage division in fertilized eggs show 14 chromosomes and 7 chromosomes in unfertilized eggs.

Down's syndrome and maternal age.

THE risk of producing offspring with mongolism (Down's syndrome) increases abruptly with maternal age after the age of 30. German1 argued that a decreasing frequency of coitus with age, and an increase in the average interval between the follicular release and the fertilization of the female germ cell, might account for the observed age dependence. He regards the second maturation division as the vulnerable stage, during which errors in chromosomal segregation could occur. Cannings and Cannings2 criticized this argument on the grounds that it fails to account for the general form of age dependence. James3 disagrees both with German and with Cannings and Cannings. He concludes that German's hypothesis cannot, without auxiliary hypotheses, account for the magnitude of the age dependence3.

Morphological studies of the rat ova with special reference to the maturation division of oocytes

Morphological studies of the rat ova with special reference to the maturation division of oocytes

Maturation of the mouse oocyte in vitro. I. Sequence and timing of nuclear progression.

AbstractLiberation of mouse follicular oocytes into a chemically defined Krebs‐Ringer salt solution with pyruvate is followed by resumption of meiosis and completion of the first maturation division. Examination of fixed whole mount preparations by light microscopy reveals that 90–95% of the germinal vesicles breakdown and proceed at least as far as metaphase I where about 5% arrest; the remainder go on to metaphase II.Three stages of chromatin condensation from the dictyate (germinal vesicle) stage are seen, first with filament shortening forming a chromatin lattice‐work followed by condensation about the nuclear and nucleolar periphery and finally the appearance of discrete bivalents. Just prior to appearance of the spindle, the bivalents are circularly arranged and reach their maximum shortness. Spindle formation is followed by prometaphase I, metaphase I, anaphase I, telophase I with first polar body formation, the chromatin mass stage in which the chromatin assumes a half‐moon shape, prometaphase II and finally metaphase II, the stage at which oocytes arrest both in vitro and in vivo.Examination at one‐two hour intervals reveals first meiotic spindle formation beginning after three hours of culture and metaphase I first appearing at 4 and one‐half hours. After nine hours of culture the majority of the oocytes are in metaphase I and anaphase I first appears at this time. There appears to be a six hour asynchrony in this division, some germinal vesicles requiring six hours to breakdown and the metaphase II stage accumulating between 11 and 17 hours of culture.

Studies of the Action of Leucogenenol on the Myeloid and Lymphoid Tissues of the Sublethally Irradiated Mouse

Studies of the action of leucogenenol on the peripheral leukocytes, the myeloid cells found in bone marrow, and the lymphoid cells found in the spleen of sublethally irradiated mice strongly suggest that leucogenenol stimulates the maturation and/or cellular division of cells of both the myeloid and lymphoid series. Accordingly, as indicated by the increase in the number of peripheral leukocytes, as well as the increase in the number of myeloid and lymphoid cells found in the bone marrow and spleen, mice treated with leucogenenol appear to recover more rapidly than untreated controls.

DNA synthesis is essential for increased haemoglobin synthesis in response to erythropoietin.

MAMMALIAN erythropoietic stem cells differentiate into granulocytes or erythrocytes. In differentiating into erythrocytes they go through several maturation divisions during which the basophilia of the cytoplasm diminishes, protein accumulates and the nucleus changes its structure and is eventually expelled. The most basophilic cells make little or no haemoglobin whereas most of the metabolism of reticulocytes is directed to its synthesis. Maturation of these cells is stimulated by erythropoietin, a glycoprotein produced in the kidney in response to low oxygen tension in the blood. This stimulation can be studied in cultured bone marrow or foetal liver cells. It has been shown that the response involves both haemoglobin and RNA synthesis; RNA synthesis occurs first and the entire process can be eliminated by treatment with actinomycin D1. We report here experiments which show that DNA synthesis is a prerequisite for any increase in haemoglobin synthesis following erythropoietin, although cell division is not.

Post-fertilization effect of incompatibility factors in Mormoniella.

1. Females from the stocks R pe-333, R ti-277, R st-940, and R oy-2 produce few or no female offspring when mated with + males. In each case, the reciprocal cross yields the normal percentage (85%) of female offspring. 2. The females from these incompatible stocks contain active sperm within their spermathecae after mating with + males. 3. In incompatible crosses, almost all eggs laid develop into males with no evidence that female embryos or larvae fail to develop. 4. Egg maturation and fertilization normally follows a pattern similar to Habrobracon. 5. Sperm from + males enter R ti-277 eggs but form a tangled mass of chromatin instead of chromosomes. The maturation divisions of the eggs are normal, and only the chromosomes of the egg pronuclei contribute to the development of the offspring.

Germinal development in Philophthalmus megalurus (Cort, 1914) (Trematoda: Digenea).

The life cycle of Philophthalmus megalurus includes a minimum of five polymorphic generations: the hermaphroditic adult in the conjunctival sacs of birds, a paedogenetic miracidium which develops in the egg, and the sporocyst, mother redia, and daughter redia which parasitize the snail host. Daughter rediae produce a few granddaughter rediae first and then cercariae. The diploid chromosome number is 20 and gametogenesis in the adult is typical with 10 bivalents appearing during the first maturation division of gametocytes. In all generations, an unequal first cleavage produces a smaller propagatory, and a larger somatic cell. Unequal division of the propagatory cell again results in a larger somatic and a smaller daughter propagatory cell from which the sporocyst develops within the miracidium before the egg hatches. In other generations, repeated unequal division of the daughter propagatory cell results in small, dark germinal cells which may multiply by mitosis. They are interpreted as oogonia which transform directly to oocytes in all generations except cercarial embryos. In that process, each undergoes meiotic prophase to diakinesis with the appearance of 10 bivalent chromosomes, then returns to interphase, grows, and becomes the large “germinal cell” typical of sporocysts and rediae of trematodes. Each oocyte cleaves without polar body formation to form an embryo of the next generation. Reproduction in the germinal sacs accordingly is diploid parthenogenesis and polyembryony is not involved. The term “larval trematodes” for generations reproducing in the molluscan host is inaccurate and should be restricted to miracidia and cercariae, the only stages that undergo metamorphosis.

GAMETOGENESIS DURING THE ANNUAL REPRODUCTIVE CYCLE IN A CIDAROID SEA URCHIN (STYLOCIDARIS AFFINIS)

1. Periodic sampling of a Neapolitan population of the cidaroid sea urchin Stylocidaris affinis, revealed an annual reproductive cycle.2. In female urchins, primary oocyte growth begins only in September and continues for almost a year until maximum size is attained the following August.3. In the oocytes of this species, conspicuous components of the yolk granules are protein and neutral mucopolysaccharide. Acid mucopolysaccharides, probably destined to be cortical components of the ripe egg, are synthesized only as the primary oocytes are nearing their maximum size.4. After reaching their maximum size in August, the primary oocytes undergo maturation divisions (probably en masse) to become ripe eggs. The ripe eggs are apparently shed soon after being produced in August or September.5. In male urchins, spermatogonia give rise to spermatocytes, which accumulate in an ever-thickening layer in the testes during the winter, spring and summer. The spermatocytes seem blocked from differentiating into more advanced germinal cell types until late summer, when they abruptly differentiate into spermatids and subsequently spermatozoa. The spermatozoa are apparently shed in late August or early September.6. The lack of an extended period of egg accumulation in the female urchins as well as the presence of an extended period of spermatocyte accumulation in the male urchins, sets gametogenesis in this cidaroid (subclass: Perischoechinoidea) apart from gametogenesis in other echinoids that have been studied (subclass: Euechinoidea).7. The possible control of the annual reproductive cycle by exogenous environmental factors is discussed.

Cytology and Reproduction of Helicotylenchus Dihystera and H. Erythrinae 1)

Several populations of the monosexual species Helscotylenchus dihystera were studied with respect to their chromosomal complement and mode of reproduction to clarify the question of digonic hermaphroditism. No synapsis of homologous chromosomes takes place and maturation consists of a single mitotic division. The somatic chromosome number observed at anaphase or telophase of the maturation division and at prometaphase of the first cleavage division was 2n = 38 in two populations from North Carolina (with possible variation from 38 to 40), 2n = 34 in one population from North Carolina, and 2n = 30 in two populations from Wisconsin. Cleavage proceeded without fertilization. Reproduction in H. dihystera is, therefore, by mitotic parthenogenesis; there is no evidence of hermaphroditism. Cytology and reproduction were also studied in a single population of the bisexual species H. erythrinae from North Carolina. Synapsis of homologous chromosomes takes place, and maturation is normal, consisting of two divisions. The somatic chromosome number observed at prometaphase of oogonial divisions is 2n = 10 and the reduced chromosome number seen at anaphase of the first maturation division and metaphase of the second maturation division of oocytes is n = 5. Re-establishment of the somatic chromosome number takes place through fertilization. No substantial differences in size and shape of the chromosomes of these two species were observed. This is interpreted as indicating the existence of polyploidy in H. dihystera.

OOCYTE DEVELOPMENT AND INCORPORATION OF H3- THYMIDINE AND H3-URIDINE IN PECTINARIA (CISTENIDES) GOULDII

1. The development and growth of the primary oocytes in the coelomic fluid are described. Oocytes progress from a packet stage to a single oocyte stage accompanied by vegetative growth of the germinal vesicle. Evidence presented indicates that the germinal vesicle breaks down and the oocyte reaches the first maturation division prior to shedding under natural conditions.2. Nuclear uptake of H3-thymidine is confined to the ovarian cells following the last oogonial division in the premeiotic phase. There is evidence that free coelomic oocyte packets incorporate H3-thymidine directly into the cytoplasm. The cytoplasmic label is removed by treatment with DNase.3. Short pulses of H3-uridine are taken up diffusely by the ovarian oocytes while small packets and single oocytes incorporate H3-uridine primarily in the nucleus and in the nucleolus. Extended exposure from 4 to 48 hours indicates that some of the nuclear uridine moves into the cytoplasm in the packet oocytes. Individual oocytes show strong nuclear lab...

Development of the gonads in Channa punctatus Bloch (Osteichthyes: Channidae).

AbstractThe history of the germ cells is traced from the time of hatching. The germ cells are larger in size and have faintly staining cytoplasm, clear cell outline and a distinct nucleus. They migrate by ameboid movement to reach the genital ridge and aggregate to lie against the gonadal epithelium prior to the formation of gonads. The germ cells are distributed along the gonad primordia.The period of sex differentiation occurs between the 5.4 mm to 12 mm stage. The testis formation is recognized by the presence of germ cell nests and the sperm duct cord. The formation of the ovary is noted by the enlargement of the germ cells of uniform size and the development of the ovarian cavity.The ovaries are described in four stages ranging from 21 mm to 135 mm fish. At 21 mm stage the ovarian cavity is continuous but is obliterated at 35 mm stage due to the projection of the ovigerous lamellae. The common opening for both the ovaries develops at 35 mm stage. The testes are described in four stages ranging from 23 mm to 135 mm fish. They differentiate more slowly and the first maturation division is seen at 90 mm stage.

Polyploidy and reproductive patterns in the root-knot nematode Meloidogyne hapla.

AbstractA total of 32 populations and egg mass isolates of Meloidogyne hapla obtained from various geographical areas were studied cytologically and with respect to their mode of reproduction. In 29, maturation of oocytes is by regular meiosis. The reduced chromosome number at metaphase I is 17 in 18 populations, 16 in 8, and 15 in 3 populations. Reproduction in all these populations is by cross‐fertilization, although nonfertilized eggs can develop by parthenogenesis. In the latter case, the two groups of telophase chromosomes of the second maturation division become enclosed in the same pronucleus, thus reestablishing the somatic chromosome number. Maturation of spermatocytes in three populations studied is by regular meiosis and the reduced chromosome number appears to be equal to that of the oocytes. In the remaining three populations, no synapsis takes place and the somatic number of 45 chromosomes is observed at metaphase of the single maturation division of both oocytes and spermatocytes. Reproduction is by obligatory mitotic parthenogensis. It is postulated that the basic chromosome number for the genus is nine and that the facultatively parthenogenetic populations are tetraploid, whereas, the obligatorily parthenogenetic populations are pentaploid. A preliminary scheme of the phylogeny in the family Heteroderidae is given.

Gametogenesis and Reproduction in the Wheat Nematode, Anguina Tritici1)

Oogenesis and spermatogenesis in Anguina tritici follow the classical pattern common in diploid amphimictic animals. Gonial cell multiplication occurs in the germinal zone of the gonads through regular mitotic divisions. Following a period of growth oocytes and spermatocytes undergo two regular maturation divisions. Fusion of sperm and egg pronuclei takes place regularly. The somatic chromosome number is 38 in both sexes. No sex chromosomes could be distinguished.

Nuclear origin of the mitotic spindle in the oogenesis of Oligotrophus schmidti (Cecidomyiidae; Diptera).

In the oogenesis of the gall midge Oligotrophus schmidti, a material assumed to be precursor material of the first maturation division spindle appears in the middle area of the early diplotene nucleus in close association with the chromosomes. At the beginning of the growth stage of the oocyte this material together with the chromosomes is transported as a characteristic ring-shaped body toward the nuclear membrane. Having approached the nuclear membrane the ring material spreads all over its inner surface. Next, it differentiates into a continuous cortical layer of a non-chromosomal material and the chromosomal vesicles. The cortical layer, about 1μ, thick, is appressed tightly to the inner surface of the nuclear membrane, being delimited against the nuclear sap by a membrane-like boundary. At the end of diakinesis the chromosomes congregate in the middle area of the nucleus, and at the same time the spindle organizing activity of kinetochores begins. At the early stages of its development the spindle is a compound structure, consisting of a number of individual spindles, each of them being organized by a separate group of chromosomes. Changes in the structure of the cortical layer before and during prometaphase spindle formation are interpreted to indicate that the precursor material of the spindle is dissolved and diffuses into the nuclear sap. The nuclear membrane and the remnants of the cortical layer do not disappear until late prometaphase when the process of spindle formation is nearly completed.

On the antigenic composition of sevruga oocytes, and its changes during maturation

TIME paper presents an attempt to use immunological techniques for the study of maturation processes of vertebrate oocytes. Experiments on anurans showed [1] that oocytes passed two stages during maturation: the properties of the nuclear sap of the germinal vesicle (GV) were the first to undergo changes, while those of the cytoplasm were affected by the changed nuclear sap. At the end of the first stage the GV membrane dissolves, and the oocyte acquires maturation inertia. It seems that similar regularities manifest themselves during oocyte maturation of sturgeons [a]. Oocytes of sevruga (Acipenser sfellufus Pall.) obtained from coelomic operations on females [2] were used in the experiments. Original oocytes at the IVth maturation stage were taken from just caught females or from those kept for 2-3 days. Maturing oocytes were taken several hours after hypophysial injection shortly after dissolution of the GV membrane, at the prometaphase and metaphase of the 1st maturation division. Standard extracts were prepared from purified and washed pieces of ovaries on the cooled physiological solution of 0.85 NaCl. The samples were preserved by means of mertiolate 1: 10,000. Extracts of mature eggs were prepared in the same manner. The supernatant (protein level 12-16 mg/ml) was used as an antigen. Immunization of rabbits was performed by the Freund method [3] employing as adjuvant repeated subcutaneous injection of vitamin B,, at a single dose of 15X!,O pg. The analysis was based on precipitation on agar according to the Ouchterlony method 141. In cross-tests w-ith 3 antisera against oocytes at the IVth maturation stage 3 samples of the original oocytes, maturing oocytes and mature eggs were examined by 2-3 replications in each group. First an attempt was made to characterize the antigenic composition of the oocytes at the IVth maturation stage. To this aim tests were performed in which 2-fold subsequent dilutions of the extract reacted with undiluted antiserum; in reciprocal tests several dilutions of the serum reacted with the most concentrated sample of the extract. The pattern presented in Fig. Id gave the possibility of following the succession of individual precipitates at the transition from one kind of tests to another. In the obtained spectra 11-12 precipitates can be discriminated, each of which is quite distinct yet not on all agar plates and in rather limited concentration range of reagents. Thus, the disconnection of the 2nd and 3rd precipitates becomes evident at considerable dilutions of the extract (Fig. lb), while that of the 11th and 12th ones, on the contrary, is evident only in experiments with diluted serum (Fig. ldj. Taking into consideration mutual arrangement of individual lines, they were conditionally united to groups. The 1st of the groups, internal in respect to the whole pattern, is distinct at antigen dilutions from 16-4 to & mg/ml of protein, the 2nd