Diplotene Stage Research Articles

Cytological evidence for the association of the short arms of the X and Y chromosomes in the human male.

EVIDENCE for the association of the X and Y chromosomes during the first meiotic division in man has been documented1,2. Until the centromere positions of the meiotic chromosomes were located with certainty, no information about the arm relationship between the two sex chromosomes could be obtained. The identification of the positions of the centromere in human male meiotic chromosomes at the late diplotene stage has been reported3. This observation revealed that the short arm of the Y chromosome was in association with the short arm of the X chromosome. Partial support for this finding was presented by Pearson and Bobrow4, who interpreted fluorescent staining of the distal end of the long arm of the Y chromosome of the XY bivalent in man as evidence that the short arm of the Y chromosome was associated with the X chromosome. Because the centromere position of the X chromosome could not be demonstrated in their material, it was not possible to determine which arm of the X chromosome was associated with the short arm of the Y chromosome. The purpose of this communication is to provide additional cytological evidence for the association of the X and Y chromosomes at their short arms.

Synthesis of ribonucleic acid in oocytes of the house cricket (Acheta domesticus).

A large DNA containing body is found in oocytes of the house cricket, Acheta domesticus. Little or no RNA synthesis is associated with the DNA body during the leptotene, zygotene, and pachytene stages of meiotic prophase I. During the early diplotene stage of development, large masses of nucleolar material begin to accumulate at the periphery of the DNA body. The onset of RNA synthesis correlates with a change in the histochemically detectable histone proteins associated with the DNA body. In ovaries of animals injected with uridine-H3, most of the label accumulates in ribosomal RNA. Autoradiographic studies show that the cytoplasm of late diplotene stage cells accumulates uridine label to a greater extent than does the cytoplasm of early diplotene stage cells. Increased transport of nucleolar material through the nuclear envelope of late diplotene stage cells accounts for the increased cytoplasmic labeling.

Comparative aspects of the effects of radiation during oogenesis

Primordial germ cells, which are relatively resistant to radiation administered prior or during migration, become sensitive during sex differentiation of the gonad. Sensitivity increases to a maximum during the peak “wave” of mitosis in oogonia, and especially during the final premeiotic division. The oocyte subsequently becomes increasingly resistant to radiation as it progresses from leptotene to pachytene, after which sensitivity increases with the onset of the period of arrested development (diplotene or dictyate stage). Oocytes vary considerably in radiosensitivity with: ( i) age, ( ii) species, ( iii) inbred or outbred strain, ( iv) stage of growth of the follicle which surrounds the oocyte, and ( v) chromosomal configuration. Those in primordial follicles are highly sensitive in mice, rats and rabbits; moderately sensitive in dogs, cows and pigs; and highly resistant in the guinea pig, monkey and human. The response of oocytes in multi-layered follicles is less variable (2000–4000 R). Reproductive capacity in the irradiated mammal closely parallels the size of the surviving population of oocytes, but the latter appear to be used more efficiently than in controls. The marked species differences in the response of oocytes cannot be fully explained at present. The most important factors are now known to be chromosomal configuration and metabolic activity. A hypothesis to explain differential radio-sensitivity is described.

Partial Desynapsis in <i>Pennisetum ramosum</i> (Hochst.) Schweinf

Meiotic behaviour of two partially desynaptic plants of Pennisetum ramosum (Hochst.) Schweinf., a diploid grass with 2n=10 chromosomes, is described. The normally paired chromosomes tended to fall apart at diplotene and post-diplotene stages, so that at metaphase I of several cells (Table 1) the chromosomes looked somewhat disorganized. The disjunctional stages were quite irregular. Different factors-extrinsic as well as intrinsic-which may have led to these meiotic abormalities are discussed.

A timing study of DNA amplification in Xenopus laevis oocytes.

The time course of meiotic amplification of nucleolar DNA in Xenopus laevis oocytes has been studied autoradiographically. We find that the process is first detectable in zygotene nuclei less than 7 days after the end of premeiotic S-phase. It is completed 3 1/2 weeks later, towards the end of pachytene. Premeiotic S-phase lasts for 1–2 weeks. We are not certain whether it is followed by a short G2 or whether leptotene commences immediately. Leptotene lasts for 5±2 days, zygotene for 7±2 days and pachytene for about 20 days before the oocyte gradually enters the extended diplotene stage. Various molecular mechanisms for amplification are discussed in the light of a 24±3 day amplification time. All are found to be potentially capable of amplifying sufficient nucleolar DNA in the time available.

Cytodifferentiation in theRana pipiens oocyte

This communication is concerned with an analysis of details in the morphogenesis of intramitochondrial yolk in oocytes of immatureRana pipiens, at different times during the prolonged diplotene stage of meiotic prophase in adult females, in fully-grown oocytes, and in those eggs artifically activated during early cleavage. The fine structure of the germinal cytoplasm of cleaving eggs is also characterized. The observations reported are discussed in relation to results obtained by others and in terms of current views regarding mitochondrial function.

Oogenesis in an Adult Prosimian

IN most Eutherian mammals oogenesis, that is, mitotic proliferation of oogonia followed by the formation of oocytes in the arrested diplotene stage of meiosis, occurs only during embryonic life or the first weeks of postnatal life1. Certain prosimians seem to be exceptions to this general rule. Some fifty years ago Gerard2 described germinal cords, containing oogonia and oocytes in the prophase of meiosis, in the ovarian cortex of an adult greater galago (Galago crassicaudatus). Similar histological appearances have been described since then in several other species3. Electron microscopic preparations from the ovarian cortex of an adult Senegal galago (Galago senegalensis senegalensis) show that the germinal cords contain large round cells which have all the ultra-structural features of oogonia seen in mammalian embryos during the period of oogenesis. Some of the cells have synaptinemal cores in their nuclei indicating that they are oocytes in the zygotene/pachytene stage of meiosis4. Metaphase figures are rarely seen in the germinal cords, and it is difficult to be certain whether they are in the oogonia or the pre-granulosa cells. It is maintained that the only acceptable histological evidence of neoformation of germ cells in the adult mammalian ovary would be the observation of mitotic divisions in oogonia1. But if such newly formed oogonia add to the total stock of oocytes it is also necessary to show that some enter the prophase of meiosis and form primordial follicles containing oocytes in arrested diplotene. The only reported attempt to investigate DNA synthesis in the cells of the germinal cords in an adult prosimian is that of Ioannu5. Twenty-four hours after the injection of 3H-thymidine into adult specimens of Demidoff's galago (Galagoides demidoffi) labelled cells were found in the germinal cords. They were considered to be either oogonia in mitotic prophase or oocytes in pre-leptotene or leptotene stages of meiosis. This scanty evidence was interpreted as indicating the occurrence of active oogenesis.

Reinvestigation of meiosis in the male goat, Capra hircus, Linn., with special reference to chiasma formation in the sex and autosomal bivalents.

The chromosome behavior during spermatogenesis of the goat, Capra hircus Linn., has been reinvestigated following hypotonic Earle's treatment technique. The regular process of meiosis in this species has already been reported by Makino (1943) following squash technique, with very little information about chiasmata during division. In this study, a detail account of chiasma formation in each and every autosomal bivalent at diplotene stage and their movement towards terminalisation in different stages of first meiosis have been represented with the remark of average number of chiasmata per cell and per bivalent. Also, this observation differs from previous author, who noticed a spindle fibre attachment between the X and Y during first meiotic division, whereas it has been found here the distinct formation of a chiasma between the X and Y and the homologous part is the minute short arm of X and one of the arms of small metacentric Y.

Meiosis in Coprinus. II. Chromosome pairing and the lampbrush diplotene stage of meiotic prophase.

Chromosome pairing takes two steps: members of the homologous pair become aligned first and then “zip up” throughout their length. Initial contact may begin from one end or from both ends of the chromosomes. Prom late paehytene to diplotene, the chromosomes are somewhat elongated and exhibit lampbrush characteristics. This is followed by a diffuse stage in which the chromosomes are most indistinct. The centrosome divides at this time. The chromosome numbers are as follows: Coprinus lagopus, n=12; C. micaceus, n=12, C. comatus, n=14; and C. atramentarius, n=16.

Synthesis of nucleic acids associated with a DNA-containing body in oocytes of Acheta

A large DNA containing body is found in gonial and in oocyte nuclei of the house cricket, Acheta domesticus. The DNA body is present in addition to chromosomal DNA and accounts for approx. 25% of the DNA in early prophase nuclei. Synthesis of this extra DNA continues into early prophase of meiosis long after DNA synthesis is completed by the chromosomes. While it is being formed, the DNA body is intimately associated with one or more chromosome pairs. Large quantities of nucleolar material accumulate at the periphery of the body during the diplotene stage of development. The DNA body of diplotene cells is composed of an inner core of Feulgen-positive material surrounded by a mass of RNA. As the cells proceed through the diplotene stage, it is proposed that DNA from the central core of the body acts as a template for synthesis of nucleolar RNA and in so doing is incorporated into the nucleolar mass.

Centromeres in human meiotic chromosomes.

Two heterochromnatic spots were observed in most bivalents of human spermnatocytes at the late diplotene stage from six individuals. It is our belief that these dark staining bodies are the centromeres of the meiotic chromosomes.

The uptake of tritiated uridine and phenylalanine by the ovaries of rats and monkeys.

ABSTRACT Rats and monkeys (Macaca mulatto, M. irus) were injected with tritiated uridine or phenylalanine and ovarian tissue was recovered at intervals from 15 min to 24 h later. Autoradiographs were prepared and studied by light microscopy; in addition some specimens which received uridine were examined using the electron microscope. The two isotopes are taken up by the ovaries of both species. The trace obtained with phenylalanine shows a very general distribution, whereas uridine seems to be more selectively in corporated by the various components of the ovary. The nuclei of primordial and growing oocytes are labelled with uridine, and so are the granulosa cells in follicles at all stages of development. The theca surrounding multilayered and vesicular follicles also shows a trace which appears heavier than that over the ovarian stroma. In the neonatal rat, the nuclei of oocytes at the pachytene and diplotene stages take up uridine. Autoradiographs prepared from ovaries fixed from 30 min to 4 h after injection and examined under the electron microscope show silver grains associated with the nucleoli and electron-dense chromosomal cores which are characteristic of these stages in meiotic prophase. Oocytes in primordial follicles, in immature and mature rats, are also labelled, showing that nuclear uptake continues as oocytes enter the ‘resting’ or dictyate stage. Since the chromosomes lose their morphological identity at this time, however, silver grains appear to be randomly distributed over the nuclear matrix. Primordial oocytes in the monkey also have a heavy nuclear label, seen under the light microscope to be associated with chromosomes and nucleoli. At the ultra structural level, most of the extra-nucleolar silver grains are associated with condensed fibrillar material thought to represent part of the lateral component of chromosomes which are of the ‘lampbrush’ type. The synthetic activity of germinal and somatic elements in the ovary is discussed, and possible differences in the structure and metabolic activity, of oocyte chromosomes are considered in relation to intra- and inter-specific variations in radiosensitivity.

Extra-chromosomal DNA in early stages of oogenesis in Acheta domesticus.

ABSTRACT A large extra-chromosomal DNA body is found in gonial and oocyte nuclei of Acheta domesticus. Somatic cells within the ovary do not contain the DNA body which is limited to the nuclei of gametogenic cells. During early prophase of meiosis this bodyisspherically shaped and intensely Feulgen positive. Electron microscopy shows it to be composed of tightly packed fibrogranular material. The body is formed in the nuclei of premeiotic interphase cells where it first appears as a mass of dense chromatin material located within the nucleolus. In nuclei of early prophase cells the body is closely associated with the nuclear membrane. It increases in size, reaching a maximum in mid-pachytene nuclei. During late pachytene-early diplotene stage of meiosis the tight fibrillar material within the body loosens and takes on a less compact appearance. At the same time large fascicles of RNA-containing material accumulate within and around the DNA body. The amount of RNA material surrounding the body increases as the oocytes proceed into an arrested diplotene stage of development.

Nuclear activity during oogenesis in sea urchins

Early meiotic stages of Arbacia punctulata oocytes have revealed the presence of synaptinemal complexes in the chromosomes, which persist through zygotene-pachytene. The synaptinemal complexes conform broadly to the usual tripartite structures found in other higher forms. In addition, nuclei at these stages consist of a small nucleolus and dense bodies of varying sizes. The nucleolus is fibrillar in texture throughout and does not seem to incorporate Uridine-5-3H after pulse labeling, whereas the chromosomes are labeled. The nucleolar label is visualized at diplotene stages and onwards. The nuclear envelope differentiates by the appearance of numerous nuclear pore complexes with dense material in the annuli, and the chromosomes become markedly diffused. At vitellogenesis stage the nucleolus and chromatin become highly labeled after pulse incorporation of Uridine, indicating synthesis of ribosomal and chromosomal RNAs.

The course of the first meiotic prophase in Beta procumbens and in the F1 between B. vulgaris and B. procumbens

The succession of the stages of the first meiotic prophase in Beta procumbens has been ascertained by measurements of the nuclear volume and by other criteria. By this method it has been possible to relate the appearance of pairing gaps to the beginning separation of the chromosomes after pachytene. A zygotene-like stage of early diplotene has been found. Asynchronous condensation of the bivalents and reduction of the chiasma frequency have been observed in diplotene and diakinesis. - The lengths and arm ratios of the pachytene chromosomes of Beta procumbens were determined.Stages similar to those in B. procumbens have been recognized in the F 1 hybrid between Beta vulgaris and Beta procumbens. The pachytene chromosomes appeared to be paired to a great extent. However, only some of the cells showed bivalents in diakinesis, in the majority desynapsis occurred during diplotene or early diakinesis. In metaphase I, bivalents, univalents, cases of secondary association due to stickiness and cases of fragmentation have been observed.

Desynapsis and Intragenomic Differentiation in Cultivated Species of <i>Oryza</i>

Two hybrids between Oryza sativa and O. glaberrima were studied for chromosome pairing at meiosis. In both the hybrids pairing was normal at pachytene. In one of them, desynapsis results in low bivalent formation in diplotene and metaphase stages: The significance of these observations is discussed in relation to the nomenclature of genomes and phylesis.

Cytochemical and ultrastructural studies of ribonucleoprotein containing structures in oocytes of Acheta domesticus

Two distinct types of ribonucleoprotein containing structures are found in oocytes of the house cricket, Acheta domesticus, a large secondary or accessory nucleolus and many small primary nucleoli. The secondary nucleolus increases in size during oocyte development and is similar in appearance to the nucleolus of somatic cells. The primary nucleoli are intimately associated with a large, extrachromosomal DNA containing body. The DNA body is no longer visible in nuclei of late diplotene stage cells when the primary nucleoli are dispersed within the nucleoplasm. Both types of nucleoli contain cytochemically detectable RNA and acid protein, little or no DNA and basic protein, and particulate structures similar to but smaller than cytoplasmic ribosomes.

The diffuse diplotene stage of meiotic prophase in Neurospora.

The prophase stages of meiosis in Neurospora crassa are re-examined following McClintock (1945) and Singleton (1953). A diffuse chromosome stage occurring between pachynema and diakinesis is described. It is proposed that the diffuse stage does not necessarily represent a condition of intense gene activity in the sense of directing the metabolic activity of the ascus.

3H]Uridine incorporation during previtellogenesis and early vitellogenesis in the oocytes of the chick (Gallus gallus)

ABSTRACT During the weeks following hatching of poultry, oocyte differentiation is most advanced in the central part of the ovarian cortex. For instance, in the 5-day-old chicken, oocytes surrounded by a ring of cuboidal cells (constituting early follicles) are appearing in the central part of the cortex. At the extreme periphery of the same cortex one occasionally can find a few germ cells which are still in the late preleptotene, and often all the intermediate stages can be seen at inter-mediate localizations. D’Hollander (1904) has described the different types of oocytes that can be found during the days following hatching. His investigations indicate that during the so-called extrafollicular phase the nucleus probably passes out of pachytene and into a stage when the chromatin is found in heavy filaments split longitudinally in places. Later the cells go through a pseudo-reticular stage in which the nucleoli and the nuclear membrane have reappeared. Between the fifth and the twentieth day after hatching, the intrafollicular phase sets in and the chromatin may also be found in the form of chains (chiasmata), clearly indicating the diplotene stage. From this stage it passes through a granular stage and becomes progressively retracted from the nuclear wall, finally giving ‘barbed’ or lampbrush chromosomes. In the 20-day-old chick, numerous oocyte nuclei with a lampbrush configuration and a large nucleolus can be seen.

Formation, transport, and storage of ribonucleic acid containing structures in oocytes of Acheta domesticus (Orthoptera).

Oocyte development of Acheta domesticus was investigated morphologically and cytochemically. The studies demonstrated a size decrease and final disappearance of a large extrachromosomal DNA body in the nuclei as the cells proceeded through the diplotene stage of meiosis. The body was surrounded by fascicles of RNA containing material. This material remained within the nuclei in individual packets after the DNA body was no longer detectable. An active nucleo-cytoplasmic migration of RNA was seen prior to the disappearance of the DNA body. After the disappearance of the body very little migration was detected. Evidence was presented to demonstrate the ribosomal nature of this migratory RNA. The RNA packets remaining in nuclei of cells arrested in the diplotene stage of oogenesis functioned as storage depots for ribosomal RNA.