Maturation Division Research Articles

THE CYTOLOGICAL EFFECTS OF PODOPHYLLIN AND PODOPHYLLOTOXIN ON THE FERTILIZED EGGS OF CHAETOPTERUS

1. Fertilized eggs of the polychaete annelid, Chaetopterus pergamentaceus, were treated with various dilutions of podophyllin and podophyllotoxin, beginning five minutes after insemination. Observations were made on the living eggs and on whole-mount cytological preparations made from samples fixed at various intervals during development. Dosages ranging from 0.1 to 0.00001 mg./ml. were tested.2. Beginning as soon as 60 seconds after the beginning of treatment with moderate to high dosages (0.1 to 0.005 mg./ml.) of podophyllin, the asters of the egg maturation figure began to fade, followed by disappearance of the spindle by about three minutes after the initiation of treatment. The nine egg chromosomes remained in the ring configuration (characteristic of the first maturation division in this form) for approximately two to five minutes longer (depending on the exact dosage), after which they were gradually enclosed in a membrane-surrounded area which appears to have been derived from the spindle substance. By this time they had taken on a somewhat vesicular appearance. The sperm chromosomes were often similarly affected by the podophyllin, although the onset of these effects was usually somewhat slower than for the eggs. Both egg and sperm chromosomes remained contained in this membrane for approximately an hour, after which they were released to lie loose in the egg cytoplasm. No further development occurred at these dosages.3. After treatments with podophyllin concentrations of 0.00005 to 0.00001 mg./ml., a semblance of normal development ensued, although the resulting larvae were usually abnormal. In egg-samples fixed 24 minutes after the beginning of treatment, there was occasional evidence of reduction in size of the asters; by 47-57 minutes after the initiation of treatment, multipolar figures were observed, as well as two entirely separate complex metaphases, often in uncleaved cytoplasm. There was frequently karyokinesis without accompanying cytokinesis. When cleavage continued to occur, it was often retarded and/or abnormal.4. Shape changes ("pear" and polar lobe stages) characteristic of the normal development of Chaetopterus eggs were observed, even after treatment with high dosages which destroyed the achromatic figure. Pseudo-polar bodies, usually without chromatin, were also noted, as well as giant polar bodies.5. The effects of podophyllotoxin were qualitatively much like those of podophyllin, but the dosage required to produce them was very much lower (0.001 mg./ml. for podophyllotoxin vs. 0.01 mg./ml. for podophyllin to completely block division, for example).6. Even short durations of exposure to either podophyllin or podophyllotoxin (10-20 minutes, as compared with the 60-minute duration routinely used in the other experiments) were sufficient to induce marked abnormality with moderate dosages.7. The effects of mitomycin C, N-dichloroacetyl DL serine (sodium) and quercetin were also tested. None of these agents was effective in producing cytological abnormality in Chaetopterus eggs, at the concentrations tested.

STUDIES ON THE PHYSIOLOGY AND GENETICS OF THE ROTIFER, ASPLANCHNA. II. THE GENIC BASIS OF A CASE OF MALE STERILITY.

AbstractTwo mutant clones have been obtained by selfing from closely‐related clones of the rotifer, Asplanchna brightwelli. The females of these male‐sterile clones are fertile but the males are unable to fertilize females of the mutant or of normal clones. Females from the mutant clones were out‐crossed to fertile males of a wildtype clone and F2, F3, and test‐cross generations were obtained. The results of these crosses indicate that the male‐sterile phenotype in both mutant clones is determined by a recessive mutation designated “male‐sterile” (ms). The mutant ms allele also appears to act as a detrimental, for the viability of zygotes (resting eggs) which are heterozygous for this gene is greater than that of homozygous recessives. This gene shows a maternal effects, for the phenotype of the haploid (or homozygous) males is determined by the genotype of their mothers. Test‐crosses of seven individual males born to heterozygous females suggest that each such male carries either the ms or the ms+ allele, but never both. This confirms early cytogenetic studies on oogenesis which indicated that the male rotifer arises by parthenogenetic development from a haploid egg, produced by ordinary meiotic maturation divisions.

Maturation division of bovine oocytes

Maturation division of bovine oocytes

Maturation division of bovine oocytes

13頭のHereford若雌牛の卵巣濾胞から, 34個の卵子を得,細胞学的に牛卵子の成熟分裂の過程を観察した。1) 発情開始前,濾胞は径13mmにも達するが,核はすべてprophaseIにあった。2) 発情初期の10mm以上の濾胞から得た4個の卵子はいずれもmetaphaseIに,発情後期の12mm以上の濾胞から得た7個の卵子は,metaPhaseI(1), telophase I (1)及びmetaphase II (4)の種々のstageにあったほか, 1個は退化卵子であった。3) 10mm以下の小濾胞卵子は,発情開始後もprophase Iに静止したままであった。4) 以上のことから,発情開始前,濾胞はほぼfullsizeに近くまで発育するが,核はprophase Iにある。発情開始と共に10mm以上の濾胞内卵子のみが成熟を開始してmetaphase Iにすすみ,以後のstageは発情の後期において急速にすすむことを知った。

THE RADIOSENSITIVITY OF GERM CELLS

THE RADIOSENSITIVITY OF GERM CELLS

Sporogenesis in Pteris cretica with Special Reference to the Cytoplasmic Inclusions

INTRODUCTION.-Studies dealing with the cytoplasmic inclusions during sporogenesis in polypodiaceous ferns have indicated that in at least three species, Nephrodium molle (Senjaninova 1927), Onoclea sensibilis (Marengo 1949) and Polypodium virginiantum (Marengo 1959), cytokinesis of the spore mother cell results in the formation of a quartet of tetragonally arranged, and upon maturity, monolete, spores. Adiantum hispidulum, a polypodiaceous fern bearing trilete spores was similarly investigated (Marengo 1962). In this species the cytoplasmic inclusions preserved by mitochondrial fixatives were found to be arranged, prior to cytokinesis, in a pattern of six planes marking the sites of the internal walls of the four tetrahedrally arranged spores arising from the spherical spore mother cell. The cytokinetic basis of tetrahedral symmetry in this species was thus found to be identical to that described in Osmunda regalis (Marengo 1954). On the basis of the cytokinetic similarity of the maturation divisions of these two unrelated species, both producing trilete, tetrahedrally symmetrical spores, it was suggested that further studies might show in other species a similar sequence of events in meiosis, and thus possibly reflect a pattern of cytokinesis common to the production of all trilete spores, regardless of the taxonomic position of the species considered. Through the courtesy of Dr. William Steere, material of Pteris cretica was made available at the New York Botanical Garden. This member of the Polypodiaceae produces typically and obviously trilete spores. It is the major object of this paper to describe the cytokinetics of the maturation divisions in this species and to compare them with previously described processes in Osmunda regalis and Adiantumn hispidulum, and to clarify the suggestion that a common process and sequence hold for the production of all trilete spores. 129

THE STRUCTURE AND FUNCTION OF CENTRIOLES AND THEIR SATELLITES IN THE JELLYFISH PHIALIDIUM GREGARIUM.

Testes of jellyfish Phialidium gregarium were fixed in 2 per cent OsO(4) in Veronal-acetate buffer at pH 7.4. Thin sections showed that in young spermatids the spindle fibers of the last maturation division are attached to satellites of the filament-forming centriole. In more mature spermatids this attachment is not observed. During the developmental phase, nine satellites can be observed emanating from the interspaces between the nine tubular triplets of this centriole. A circular region on each of the enlarged distal ends of the satellites attaches them to the cell membrane. The satellites apparently provide a firm anchor for the axial filament. Each of the epithelial cells covering the testis produces a single long flagellum. On the filament-forming centriole often a satellite can be observed to which tubules are attached. These tubules are 180 A in diameter and probably represent remnants of spindle fibers. It is suggested that the distal centriole has the ability to form several satellites or appendages at appropriate times during the cell cycle. These satellites are distinct from the daughter centrioles in that they are supportive structures: in certain phases of cell life, spindle fibers may attach to them, while in other instances the distal centriole and the flagellum it is forming are anchored by them.

Chromosomal development in the Sorex genus: new data

InSorex unguiculatus, a species closely related to the common shrew, 41 chromosomes were observed in the spermatogonia of two male specimens. The meiotic cells show about 21 formations at diakinesis and first maturation division metaphase. The mode of sex determination still remains unsatisfactorily clarified. However, the species investigated is of interest as a further instance of the very complex chromosomal evolution characterizing the genus Sorex. Within this genus, the observed variation in chromosome numbers now ranges from 21 to 41 at the diploid level.

Analysis of the formation of the animal pole plasm in the eggs of Limnaea stagnalis

ABSTRACT The animal pole plasm in the eggs of Limnaea stagnalis becomes visible about 1 hr. before the first cleavage. At this time the male pronucleus is on its way toward the animal pole, while the female pronucleus is being formed by the fusion of karyomeres resulting from the swelling of the egg chromosomes after the completion of the second maturation division.

MATURATION DIVISION OOCYTES IN BOVINE FOLLOWING GONADOTROPIN INJECTIONS.

The maturation division of oocytes has been studied in relation to estrus, and follicle diameter in gonadotropin-treated and untreated beef cattle. Injection of pregnant mare serum (PMS) gonadotropin had no effect on the pattern of maturation division of oocytes. The follicles reached full size shortly before the onset of estrus. During early estrus, all oocytes had nuclei of metaphase I; the maturation division rapidly progressed to metaphase II during late stages of estrus. Human chorionic gonadotropin (HCG) treatment which has been recognized to be effective for stimulating ovulation did not affect the pattern of maturation division of the oocytes. Degeneration of oocytes occurred in all stages of follicular maturation during and following estrus, irrespective of the follicle size.

Studies on the occurrence of polyploidy and its contribution to flower plants breeding. III. On the characteristics and biological significance of a hypotriploid plant obtained from intervarietal crossing in freesias.

In the course of intervarietal crossing in freesias since 1956, a hypotriploid plant (2n=33-1) was obtained unexpectedly from crossing between tetraploid Golden Buttercup (2n=44) and diploid Super Giant Yellow (2n=22). It grows slowly and has a few slender, short, somewhat twisted and palegreen leaves. Each flowerlet born on a curved flower stalk is very small and light-brownish colored, consisting of 5 perigons (3 inner and 2 outer). The maturation division in pollen mother cells is so irregular that almost all pollen grains are degenerate, and thus the plant is completely sterile. Regarding the occurrence of such an abnormal hypotriploid plant, some inferences are described as follows. It is well known, hitherto, that many normally growing aneuploid plants or cultivars have been found in some popular bulbous flowering plants euch as crocus, hyacinth, daffodils etc. These peculiar plants grow vigorously in most cases at present, probably due to their genomic heterognity, namely, partial allopolyploid constitution, transmitted from different kinds of ancestors, and also due to successive natural and artificial selections against long term inferior or lethal characteristics. On the contrary, in some bulbous plants such as canna or freesia, which were derived from ancestors af closely-related or of almost similar genomic constitutions and also were introduced into the horticultural circles in recent centuries, vigorous-growing aneuploid plants would not occur yet, although the normal polyploid levels are present and many tri- or tetraploid strains are used as cultivars already. Furthermore, it is considered that any aneuploid plants will ntver appear in species such as babiana or tritonia which only has single Stable diploid genomes and was newly introduced into Europe in this century from Southern Africa.

Experimental evidence for the humoral stimulation of ripening of the gametes and spawning in the polychaete Arenicola marina (L)

The spawning of the lugworm immediately follows the ripening of the gametes. The gonoducts (nephromixia) automatically accept free spermatozoa and fertilizable eggs, i.e., eggs in metaphase of the first maturation division, so that shedding occurs. Spawning was inhibited by decerebration. Examination of the gametes in decerebrated worms at intervals after the normal breeding season indicated that they had failed to ripen. The spermatozoa were bound together in morulae and the eggs remained in suspended prophase of the first maturation division. Controls spawned normally in the laboratory. Implantation of prostomiums in the body cavities of decerebrated worms failed to restore the capability of spawning. However, both decerebrated males and females were induced to spawn by administration of prostomial homogenates although females only responded to homogenate prepared from female prostomiums. It is suggested, tentatively, that the hormone promoting the maturation of the eggs and spawning of females may be specific to the female brain. An initial analysis of the substance in the prostomium stimulating the spawning of male worms is described.

EFFECT OF OVINE GONADOTROPHINS AND ANTISERUM TO INTERSTITIAL CELL-STIMULATING HORMONE ON THE TESTIS OF THE HYPOPHYSECTOMIZED RAT.

ABSTRACT Rabbit antiserum to ovine ICSH was administered to male Sprague-Dawley rats 2 months after hypophysectomy; further atrophy of the testis ensued. The interstitial tissue, the Sertoli cells, and the germ cells were adversely affected by the treatment. In the absence of gonadotrophins and exogenous androgen, spermatogenesis was nearly arrested. Ovine ICSH repaired the interstitial tissue and stimulated mitotic activity among the spermatogonia. Ovine FSH (NIH-FSH-S-1), containing approximately 1% ICSH activity, stimulated spermatid formation. When antiserum to ICSH was injected together with the FSH, no maturation divisions or spermatids were observed. The combination of FSH and ICSH, 100 μg of each per day injected for a period of 21 days, stimulated extensive and uniform tubular repair and advanced spermiogenesis to the acrosome phase; an enhancement in the secretion of androgen also was effected when FSH was given in combination with ICSH.

The Development of Organ Systems in Nematotaeniid Cestodes. III. Gametogenesis and Embryonic Development in Baerietta diana and Distoichometra kozloffi

The Development of Organ Systems in Nematotaeniid Cestodes. III. Gametogenesis and Embryonic Development in Baerietta diana and Distoichometra kozloffi

SOME CYTOLOGICAL ASPECTS OF FERTILIZATION IN THE CROSS BETWEEN THE FUNA (CARASSIUS CARASSIUS, CYPRINIDAE) AND THE LOACH (MISGURNUS ANGUILLICAUDATUS, COBITIDAE)

1. Insemination and early cleavages were cytologically investigated in the cross between the funa (Carassius carassius) amid the loach (Misgurnus anguillicaudatus), belonging to different families. Eggs of the fumia were artificially insemimiated with bach sperm at water temperatures from 26° C. to 28° C.2. Monospermic insemination was cytologically proved; a simigle spermatozoon of the bach entered the funa egg through the micropyle. Following insemination, the second maturation division of the egg proceeded. About 15 minutes after insemination, the extrusion of the second polocyte occurred. Then the formation of female and male pronuclei followed. About 20 to 25 minutes after insemination, the meeting of the male and female pronuclei took place. In conjugation. both pronuclei came into close contact, side by side, with the nuclear membrane intact, without evidence of actual fusion.3. It was difficult to distinguish clearly groups of chromosomes of paternal and maternal origin or to count the chromosome number in the first cleavage metaphase. During the period from anaphase to telophase, separation of the chromosomes took place symichronously, without evidence of lag or elimination of chromosomes. The first cleavage was completed 35 to 40 minutes after insemination.4. Early cleavages took place at intervals of 15 to 20 minutes after insemination. No abnormality was detected in the cleavage spindle. The second polar body was found lying in its original position at the first cleavage.5. Evidence presented indicates that both insemination ard early cleavage followed normal cytological patterns, and consequently that there is no cytological evidence in this cross to show that the sperm acted as a parthenogenetic agent, in spite of time maternal characters noted in larvae resulting from this cross.

Pre-ovulatory changes in the oocyte of the adult rat

The sequence of nuclear changes in the oocyte of the adult rat has been investigated, with particular emphasis on early pre-ovulatory stages. The condition of the chromosomes during the so-called dictyate phase is discussed, and an attempt made to determine the time at which diakinesis occurs. The relationship between the onset of the successive stages of the maturation division and the diurnal rhythm of light and darkness (‘natural’ and artificial) was determined. The first clear-cut change (condensation of chromatin) occurs at about 5 p. m. under ‘natural’ light conditions, and within the first 1 h of the onset of darkness under artificial illumination (12 h light: 12 h darkness). Ovulation occurs some 9 to 10 h later. An approximate estimate was made of the duration of each stage of the division up to second metaphase. The variability in the onset of the various stages of the division was greater between individual rats kept under ‘natural’ light conditions than between those kept in light-controlled rooms.

Cytology and kinetics of spermatogenesis in the rabbit.

Summary. The cycle of the seminiferous epithelium of the rabbit was divided into eight stages, using as criteria the shape of the spermatid nucleus, the location of the spermatids and spermatozoa in regard to the basement membrane, the presence of meiotic figures and the release of spermatozoa from the lumen. The relative duration (frequency) of Stages 1 to 8 were 27·7, 13·4, 7·3, 11·0, 4·1, 15·7, 12·2 and 8·6%, respectively. Each stem cell (Type A spermatogonium) divided to produce two Type A spermatogonia. One of these was the starting cell for the next generation, while the other gave rise to two intermediate-type spermatogonia. Three more spermatogonial divisions followed, producing sixteen primary spermatocytes from one Type A spermatogonium, as is characteristic for the bull and the ram, but unlike the rat, mouse and hamster. It was estimated that only 3·1 spermatids were generated from one primary spermatocyte, suggesting that in the rabbit there is considerable degeneration of spermatogenic cells during the two maturation divisions.

Ode to an Ootid

Nonfunctional ootid. Hopeless, hapless ootid: product of maturation division; blighted product of unequal fission. Doomed to die without hope or illusion; destined to breakdown and prompt dissolution. Hopeless hapless ootid: punished for something you never did.

Chromosomal differentiations of the lampbrush type formed by the Y chromosome in Drosophila hydei and Drosophila neohydei.

The nuclei of growing spermatocytes in Drosophila hydei and D. neohydei are characterized by the appearance of phase-specific, paired, loop-shaped structures thought to be similar to the loops in lampbrush chromosomes of amphibian oocytes. In X/O-males of D. hydei spermatogenesis is completely blocked before the first maturation division. No spermatozoa are formed in such testes. In the nuclei of X/O-spermatocytes, paired loop formations are absent. This shows the dependence of these chromosomal functional structures upon the Y chromosome. The basis of this dependence could be shown through an investigation of males with two Y chromosomes. All loop pairs are present in duplicate in XYY males. This proves that the intranuclear formations are structural modifications of the Y chromosome itself. These functional structures are species-specific and characteristically different in Drosophila hydei and D. neohydei. Reciprocal species crosses and a backcross showed that the spermatocyte nuclei of all hybrid males possess the functional structures corresponding to the species which donated the Y chromosome. This shows that the morphological character of the functional structures is also determined by the Y chromosome.

Mitotic dynamics of the first cleavage divisions in the eggs of sturgeon (at various temperatures) and of trout

Summary The paper presents data on the dynamics of different mitotic phases at the second cleavage division in the eggs of sturgeon, Acipenser güldenstädti colchicus V. Marti at 11, 16.2 and 23°C, and in those of trout, Salmo trutta morpha lacustris Linné at 1.8±0.3°C. The duration of mitotic phases in all the experiments is expressed in the fractions of one mitotic cycle of the first cleavage divisions τ0. The movement of sister chromosome sets in sturgeon and trout eggs under cleavage proceeds in the following way: the slow process of disjunction of sister chromosomes during metaphase is followed by their fast movement at anaphase. At the transition of ana- to telophase the movement of chromosomes slows down. The separation of telophase nuclei then follows, which exceeds the movement of chromosomes at anaphase in both the velocity of movement and the distance covered. Elongation of the spindle at anaphase proceeds in parallel to the movement of chromosomes and continues up to the beginning of telophase. During telophase the distance between the centers increases. Cytotomy consists of two interrelated phenomena separated under pathological conditions, namely, of the analage of the furrow within the egg and of the ingrowth of the cortical layer. Each mitotic phase in sturgeon and trout eggs is characterised by definite dimensions of the mitotic figure, while ana- and telophase are also characterized by a definite distance between sister chromosomes. Relative duration of the same mitotic phases in three series of sturgeon eggs (at 11, 16.2 and 23°C) and in a series of trout eggs (at 1.8±0.3°C) are characterized by a close similarity. Relative duration of the period of furrow analge within the egg, unlike the phases of nuclear division, undergoes changes with temperature changes. One of the specific disturbances of mitosis at a temperature approaching the upper limit is the untimely separation of centrioles and the appearance of multipolar mitoses. In some eggs repetitive duplication of centrioles takes place under these conditions. Dimensionless characteristics of duration of the primary disjunction of chromosomes and of their rapid movement are very close: at the completion of the second maturation division and at the first cleavage divisions, in different animals (sturgeon, trout) and at different temperature (within the optimal ones). It can be suggested that the ratios found are of a general importance and reflect one of the mechanisms of a strict coordination of the complex of processes leading to the nuclear division.