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At least 19 recordsLinked to original sources

PubMed1989

Viability of meiotic prophase spermatocytes of rats is facilitated in primary culture of dispersed testicular cells on collagen gel by supplementing epinephrine or norepinephrine: evidence that meiotic prophase spermatocytes complete meiotic divisions in vitro.

Dispersed testicular cells prepared from 14-d-old rats were cultured on type 1 collagen gels using a medium composed of a 1:1 mixture of Ham's F12 medium and Leibovitz's L15 medium (F12-L15 medium) containing 10% (vol/vol) fetal bovine serum. The viability of the spermatogenic cells was facilitated by supplementing a rat adrenal extract into the medium. The effective substance(s) (the survival factor) was purified from acid extracts of adrenals by molecular sieve high performance liquid chromatography and identified as epinephrine and norepinephrine. Both epinephrine and norepinephrine promoted the survival of the spermatogenic cells with a half saturating dose of 10 ng/ml. The spermatogenic cells, which could be cultured for 2 wk on a collagen gel by supplementing with the survival factor (epinephrine or norepinephrine), were subjected to Giemsa staining and to DNA flow cytometry. The following results were obtained: a) The spermatogenic cells from 14-d-old rats did not contain spermiogenic cells (1c-cells). b) During a culture period of 2 to 7 d the ratio of meiotic prophase spermatocytes (4c-cells) to premeiotic cells (2c-cells) increased. On Day 7, more than 90% of the surviving cells were meiotic prophase spermatocytes. c) On Day 10, spermatids (1c-cells) appeared for the first time. The time of the first appearance of spermatids in the culture was consistent with that in vivo. These results suggest that both epinephrine and norepinephrine facilitated the viability of meiotic prophase spermatocytes and that a part of the meiotic prophase spermatocytes completed the meiotic divisions in the testicular cell culture.

Adrenal Cortex↗

PubMed1991

Pachytene spermatocyte protein(s) stimulate Sertoli cells grown in bicameral chambers: dose-dependent secretion of ceruloplasmin, sulfated glycoprotein-1, sulfated glycoprotein-2, and transferrin.

Interactions between pachytene spermatocytes and Sertoli cells were investigated using the bicameral culture chamber system. Pachytene spermatocytes were isolated from adult rats with a purity in excess of 90% by centrifugal elutriation. The pachytene spermatocytes were cultured in a defined media and pachytene spermatocyte protein prepared from the conditioned media by dialysis and lyophilization. This pachytene spermatocyte protein was reconstituted at various concentrations and incubated with confluent epithelial sheets of immature Sertoli cells cultured in bicameral chambers. Pachytene spermatocyte protein stimulated secretion of total [35S]methionine-labeled protein from Sertoli cells in a dose-dependent manner predominantly in an apical direction. This stimulatory effect of pachytene spermatocyte protein was domain specific from the apical surface of Sertoli cells, and seemed specific for secretion because total intracellular protein did not increase under the influence of pachytene spermatocyte protein. Pachytene spermatocyte protein and follicle-stimulating hormone additively stimulated Sertoli cell secretion. The physicochemical characteristics of the stimulatory pachytene spermatocyte protein are indicative of heat stability, whereas the stimulatory pachytene spermatocyte protein exhibit acid, dithiothreitol and trypsin sensitivity, and partial urea sensitivity. Furthermore, Sertoli cell secretion of ceruloplasmin, sulfated glycoprotein-1, sulfated glycoprotein-2, and transferrin in response to various concentrations of pachytene spermatocyte protein were determined by immunoprecipitate of these [35S]methionine-labeled proteins with polyclonal antibodies. Maximal stimulation of ceruloplasmin and sulfated glycoprotein-1 secretion from Sertoli cells was observed at a dose of 50 micrograms/ml pachytene spermatocyte protein, whereas maximal stimulation of sulfated glycoprotein-2 and transferrin secretion from Sertoli cells was observed at a dose of 100 micrograms/ml of pachytene spermatocyte protein. These results suggest that pachytene spermatocytes modulate Sertoli cell secretory function of at least four proteins in the regulation of spermatogenesis.

Animals↗

PubMed1991

Micronuclei and chromosome aberrations in Xenopus laevis spermatocytes and spermatids exposed to adriamycin and colcemid.

Cultured testes and spermatocytes from the frog Xenopus laevis have been incubated (40-42 h) with adriamycin or colcemid followed by quantitation of chromosome aberrations in secondary spermatocytes and quantitation of micronuclei in secondary spermatocytes, early round spermatids, and round spermatids with acrosomal vacuoles (AV) at 18-162 h of culture. Micronucleus frequencies were consistently higher in secondary spermatocytes relative to round spermatids after exposure to either adriamycin or colcemid due to a higher rate of micronucleus formation during meiosis I compared to meiosis II. Also, some of the micronuclei formed during meiosis I did not survive meiosis II to form micronucleated spermatids. Micronucleus formation occurred in 3-7% of secondary spermatocytes with detectable chromosome aberrations, depending upon drug treatment. Thus, the ratio of micronuclei to total chromosome aberrations in secondary spermatocytes was always higher in colcemid-treated cells compared to adriamycin-treated cells following 18- and 42-h treatment periods. Adriamycin induced significant increases in micronuclei in both secondary spermatocytes and spermatids after 162 h of culture, the time for initial pachytene stages to develop into secondary spermatocytes and spermatids. The data show that cultured testes and spermatocytes from Xenopus may be used to quantify specific meiotic chromosome aberrations induced by both clastogens and spindle poisons using either a rapid secondary spermatocyte micronucleus assay or meiotic chromosome analysis.

Animals↗

PubMed1977

Ribonucleic acid synthesis in vitro in primary spermatocytes isolated from rat testis.

The incorporation of [(3)H]uridine into RNA was studied quantitatively (by incorporation of [(3)H]uridine into acid-precipitable material) and qualitatively (by phenol extraction and electrophoretic separation of RNA in polyacrylamide gels) in preparations enriched in primary spermatocytes, obtained from testes of rats 26 or 32 days old. The rate of incorporation of [(3)H]uridine into RNA of isolated spermatocytes was constant during the first 8h of incubation, after which it decreased, but the decreased rate of incorporation was not reflected in a marked change in electrophoretic profiles of labelled RNA. In isolated spermatocytes, [(3)H]uridine was incorporated mainly into heterogeneous RNA with a low electrophoretic mobility. Most of this RNA was labile, as shown when further RNA synthesis was inhibited with actinomycin D. Spermatocytes in vivo also synthesized heterogeneous RNA with a low electrophoretic mobility. A low rate of incorporation of [(3)H]uridine into rRNA of isolated spermatocytes was observed. The cleavage of 32S precursor rRNA to 28S rRNA was probably retarded in spermatocytes in vitro as well as in vivo. RNA synthesis by preparations enriched in early spermatids or Sertoli cells was qualitatatively different from RNA synthesis by the spermatocyte preparations. It is concluded that isolated primary spermatocytes maintain a specific pattern of RNA synthesis, which resembles RNA synthesis in spermatocytes in vivo. Therefore isolated spermatocytes of the rat can be used for studying the possible regulation of RNA synthesis during the meiotic prophase.

Animals↗

PubMed1992

Validation studies with the micronucleus test for early spermatids of rats. A tool for detecting clastogenicity of chemicals in differentiating spermatogonia and spermatocytes.

Male Wistar rats were given a single i.p. injection with different doses of ethylnitrosourea, mitomycin C, methyl methanesulphonate, cyclophosphamide or vincristine sulphate. Clastogenic damage induced in differentiating spermatogonia and spermatocytes was measured by counting micronuclei in derived early spermatids. At dose levels not resulting in cell death of resting spermatocytes, all chemicals--with the exception of vincristine--induced most of the damage in G1- and S-phase of primary spermatocytes (also called resting, pre-leptotene or pre-meiotic spermatocytes). However, at doses causing death of G1- and S-phase spermatocytes, high frequencies of micronuclei may be observed in early spermatids derived from spermatocytes treated in diplotene, diakinesis and MI and II. This is exemplified by our results with ethylnitrosourea. In our experience, the most sensitive stage of primary spermatocyte development (i.e. G1- and S-phase cells) can best be sampled 20 days after treatment. This is the optimal time interval for demonstrating the clastogenic potential of low or moderate doses of a test chemical in meiotic male germ cells of rats. The optimal sampling time for the detection of typical spindle poisons remains to be established. In general, at low or moderate dose levels, smaller or negligible amounts of chromosomal damage were induced in differentiating spermatogonia, in spermatocytes in meiotic prophase and in dividing primary or secondary spermatocytes. For obvious reasons, the micronucleus test for early spermatids cannot be used to detect clastogens which act exclusively on postmeiotic male germ cells.

Animals↗

PubMed1991

The Golgi apparatus of rat pachytene spermatocytes during spermatogenesis.

A morphological and immunocytochemical study of the Golgi apparatus in pachytene spermatocytes was performed in an effort to correlate the structure and function of this organelle during meiotic prophase. In stages I-III of the cycle, the Golgi complex of pachytene spermatocytes is a flattened discoid, 0.5-1 microns in diameter, composed of vesicles interspersed with classically described Golgi cisternae. During subsequent maturation of pachytene spermatocytes (stages IV-XIII), the size of the Golgi complex increases significantly, attaining a size of 2-3 microns. However, unlike pachytene spermatocytes of stages I-III, the majority of the Golgi complex of more mature spermatocytes is characterized by an abundance of distinct stacks of cisternae interspersed with numerous vesicles and tubules. The composition of the Golgi complex was also studied by using two monoclonal antibodies that recognize either the cis or the trans Golgi cisternae, respectively, and employing biotin-streptavidin-peroxidase immunocytochemistry in 5 micron frozen sections of testes. Immunodetection of the distinct cisternae revealed that the increase in size of the Golgi complex during maturation of pachytene spermatocytes was due predominantly to an accumulation of trans Golgi; the amount of cis Golgi remained unchanged. The morphological data presented in this study are consistent with an heightened secretory activity of pachytene spermatocytes during their maturation. In addition, the increase in size of the Golgi apparatus during the extensive prophase of pachytene spermatocytes may suggest that the mechanism employed by germ cells to partition the Golgi complex during the first division of meiosis varies significantly from that of somatic cells undergoing mitosis.

Animals↗

PubMed1977

Movement of spermatocytes from the basal to the adluminal compartment of the rat testis.

The progressive movement of primary spermatocytes from the basal to the adluminal compartment of the seminiferous tubule was studied after testes were fixed with standard and hypertonic solutions. In stages VI, VII and VIII of the cycle (classification of Leblond and Clermont, '52), preleptotene spermatocytes were observed within the basal compartment of the seminiferous tubule. Resting on the basal lamina, these cells were bound tightly to neighboring Sertoli cells by desmosome-like junctions. In late stage VIII and early stage IX, basal processes of Sertoli cells were observed between the newly formed leptotene cells and the basal lamina, and in stage IX, the Sertoli processes met to form a junction of the zonula adherens type. This junction formed a permeability barrier which restricted the free access of fixative into the spaces around leptotene cells. Evidence for this was found in the absence of the shrinkage artifact produced with hypertonic solutions in earlier stages. In longitudinal sections, the permeability barrier was first observed in an area of the tubule in which sperm release was also taking place. In mid-stage IX and in stage X, sertoli-Sertoli junctional specializations formed de novo below the leptotene spermatocyte, while those from the preceding stages, present above the leptotene spermatocytes, remained intact. Thus, tight junctions were in evidence for a considerable period of the time, both above and below the leptotene spermatocytes. At no time in the process of germ cell movement toward the lumen did these cells exhibit evidence of amoeboid movement or lose desmosome-like contacts with the surrounding Sertoli cells. From this study it is concluded that the Sertoli cells play an active role in the transfer of spermatocytes to the adluminal compartment. A transient intermediate compartment of the seminiferous tubule is described, one which allows for the continual maintenance of the blood-testis barrier during transit of spermatocytes from the basal to the adluminal compartment.

Animals↗

PubMed1978

The lipid composition of isolated rat spermatids and spermatocytes.

The lipids composition of enriched fractions of spermatids and spermatocytes, isolated from rat testicular tissue, has been investigated. More than 20% of the total fatty acids of spermatids but only 10% of those of spermatocytes, isolated from testes of mature rats, was 4,7,10,13,16-docosapentaenoic acid. Spermatocyte-enriched fractions isolated from testes of immature rats had fatty acid compositions similar to those isolated from testes of mature rats. On the other hand, spermatids isolated from immature rats had a level of docosapentaenoic acid which was intermediate between the level found in spermatocytes and that of spermatids from mature rats. Major phospholipid classes and the triacylglycerols of spermatids contained much more of the docosapentaenoic acid than the corresponding lipid types from spermatocytes. Differences in content of total phospholipids, individual classes of phospholipids and triacylglycerols among spermatocytes, spermatids and late spermatids were also observed.

Aging↗

PubMed1977

Delayed formation of chromosome aberrations in mouse pachytene spermatocytes treated with triethylenemelamine (TEM).

Induction of chromosome aberrations in pachytene spermatocytes of mice by 2 mg/kg TEM was compared with induction by 400 R X rays. These doses induced comparably high dominant lethal effects in pachytene spermatocytes of mice. Cytological analysis at diakinesis-metaphase I stage showed that whereas 76.4% of the cells treated with X rays at pachytene stage had aberrations, the frequencies observed in two TEM experiments were only 0.8 and 2.2%. On the other hand, 5% of the progeny from TEM-treated pachytene spermatocytes were found to be translocation heterozygotes. This is the first report on the recovery of heritable translocations from treated spermatocytes of mice. The aberration frequencies observed for TEM in diakinesis-metaphase I were much too low to account for all the lethal mutations and heritable translocations. Thus, the formation of the bulk of aberrations induced by TEM in pachytene spermatocytes was delayed--a marked contrast to the more immediate formation of X-ray-induced aberrations. It is postulated that the formation of the bulk of TEM-induced aberrations in pachytene spermatocytes and in certain postmeiotic stages occurs sometime during spermiogenesis, and not through the operation of postfertilization pronuclear DNA synthesis.

Animals↗

PubMed1989

Quantitative evaluation of the maintenance and development of spermatocytes and round spermatids in cultured tubule fragments from immature rat testis.

Maintenance and development of spermatocytes and round spermatids was studied in an in-vitro incubation system. This system consisted of open tubule fragments from 26-day-old rat testes, obtained after collagenase treatment. The tubule fragments contained Sertoli cells and spermatogenic cells up to and including a small number of early round spermatids. The number of primary spermatocytes and round spermatids in the tubule fragments was estimated using flow-cytometric analysis, immediately after isolation and after 72 h of incubation. In addition, the activity of LDH-C4 in the tubule fragments was measured. After 72 h of incubation, the percentage of spermatocytes was reduced by 70-80%, but the percentage of spermatids was doubled. The total LDH-C4 activity per well was increased 2-3-fold during 72 h of incubation of the fragments. A modest improvement of the culture results was observed when a combination of FSH, insulin, retinol and testosterone was added to the medium. LDH-C4 activity was investigated to see whether it could be used as a quantitative marker of isolated and cultured spermatocytes and spermatids. It was observed that LDH-C4 activity per cell was decreased when spermatocytes and spermatids were isolated and/or incubated at 4 degrees C. However, the cellular enzyme activity returned to control values during subsequent incubation of the cells at 32 degrees C, either in the absence or presence of a protein synthesis inhibitor. Cellular LDH-C4 activity may be influenced not only by temperature, but possibly also by other cell isolation conditions. It is concluded that LDH-C4 activity may not be a reliable quantitative marker for the presence of spermatocytes and spermatids in culture, but should be used in combination with other analytical methods such as DNA estimation and DNA flow cytometry.

Adenosine Triphosphate↗

PubMed1990

Multiple, compensatory regulatory elements specify spermatocyte-specific expression of the Drosophila melanogaster hsp26 gene.

The hsp26 gene of Drosophila melanogaster is expressed in six tissues during development and in a tissue-general response to heat shock. To be able to compare tissue-specific and heat-induced mechanisms of hsp26 expression, we have begun an analysis of the sequences involved in the spermatocyte-specific expression of the hsp26 gene by using germ line transformation. hsp26 mRNA synthesized in the spermatocytes has the same start site as sites previously demonstrated for nurse cell-specific and heat-induced mRNAs. Three regions of the hsp26 gene (nucleotides -351 to -135, -135 to -85, and +11 to +632) were able to stimulate spermatocyte-specific expression when fused with promoter sequences (nucleotides -85 to +11) that alone were insufficient to stimulate expression. These stimulatory regions appear to contain elements that provide redundant functions. While each region was able to stimulate expression independently, the deletion of any one region from a construct was without consequence as long as another compensatory region(s) was still present. There must reside, at a minimum, two independent spermatocyte-specifying elements within the sequences that encompass the three stimulatory regions and the promoter. At least one element is contained within sequences from -351 to -48. This region, in either orientation, can stimulate spermatocyte-specific expression from a heterologous promoter. A second element must reside in sequences from -52 to +632, since these sequences are also sufficient to direct spermatocyte-specific expression.

Animals↗

PubMed1992

Characterisation of secondary spermatocytes in the marbled newt (Triturus marmoratus).

Secondary spermatocytes in the marbled newt (Triturus marmoratus) were identified by means of cytophotometric quantification of nuclear DNA in the testicular lobules containing primary spermatocytes in advanced stages of the first meiotic division (from pachytene onwards) and newly formed spermatids. The nucleus of secondary spermatocytes has an intermediate size between that of primary spermatocytes and round spermatids and was characterised by the presence of abundant masses of dense chromatin and the absence of a nucleolus. At the prophase the chromatin masses were located at the periphery of the nucleus. The ultrastructural study revealed that the nuclear envelope displayed blebs and that the cytoplasm was very similar to that of primary spermatocytes including the presence of smooth endoplasmic reticulum whorls, multiple small dictyosomes, and a proacrosomal-like granule near the nucleus. This granule stained weakly with aqueous PTA and was observed in about 6% of secondary spermatocytes. Many of the mitochondria were grouped beneath the plasma membrane. Approximately 2% of these cells presented an axoneme which was not associated with other flagellar components.

Animals↗

PubMed1992

Partitioning of the Golgi apparatus in rat primary and secondary spermatocytes during meiosis.

We examined the disassembly and reformation of the Golgi apparatus as a function of the cycle of the seminiferous epithelium in adult rats during stages XIII and XIV, i.e., just prior to and during meiosis I and II. Serial section analysis of primary spermatocytes at metaphase I demonstrated the presence of two Golgi complexes. At the ultrastructural level, these Golgi complexes were shown to be composed of stacks of cisternae and vesicles, with each stack having a varying number of saccules. Although Golgi complex intermediates resulting from the process of organelle disassembly were not clearly identified in diplotene spermatocytes immediately prior to nuclear envelope vesiculation, we did observe clusters of vesicles resembling the "nuage," with each cluster varying in size and number of vesicles. Meiosis I results in the formation of secondary spermatocytes that exhibit a well-formed spherical Golgi complex approximately half the size of the diplotene spermatocyte Golgi. Next, secondary spermatocytes enter meiosis II. In contrast to metaphase I, during metaphase II reformation of the Golgi apparatus into stacks was not observed and only small clusters of vesicles at two poles of dividing cells were detected. In addition, "nuage"-like structures were not identified during meiosis II. Our results begin to characterize the process by which Golgi apparatus partitioning is accomplished during meiosis, presumably resulting in the delivery of equal complements of this organelle to four round spermatids. We suggest that partitioning of the Golgi apparatus takes place prior to metaphase I and that the two steps of meiosis may exhibit subtle differences with respect to Golgi partitioning.

Animals↗

PubMed1990

Prophase of meiosis in human spermatocytes analysed by EM microspreading in infertile men and their controls and comparisons with human oocytes.

Observations at the electron microscope (EM) level have been made on 1883 primary spermatocytes from 40 chromosomally normal subfertile men and 566 spermatocytes from 10 fertile controls, using the technique of microspreading. Spermatocytes of infertile men in general showed greater indications of degeneration including higher levels of background silver deposition, nucleolar organising region - XY associations, fragmentation of synaptonemal complexes and overproduction of XY excrescences. A few oligospermic men also showed an immature morphology of the XY pair and/or a reduced extent of XY synapsis. Dissociation of the sex chromosome axes at prophase was found to occur with a much lower frequency than that recorded for separated X and Y chromosomes at metaphase I. In a single spermatocyte, synaptonemal complex formation was observed between Xqter and Yqter, a situation that could enable rare XqYq interchange. A proteinaceous stalked body exists on the Y axis towards its non-pairing end; this structure might have a functional relationship with the gene for spermatogenesis, (AZF), located at the euchromatin/heterochromatin interface. Compared with human oocytes, spermatocytes show fewer anomalies of synapsis, i.e. asynapsed segments or whole axes, non-homologous associations, interchanges, interlocks. These latter data agree well with findings from the mouse.

Adult↗

PubMed1979

A sequential analysis of meiosis in the male mouse using a restricted spermatocyte population obtained by a hydroxyurea/triaziquone treatment.

A method is described to restrict the spermatocyte population in mice and other rodents using hydroxyurea (HU) and triaziquone (T). HU affects cells in S-phase, whereas T is an agent especially active on spermatogonia and not on spermatocytes. An application of three i.p. HU injections with 12 h intervals, followed about nine days later by one i.p. T injection creates two large gaps in the spermatogenic line. The two gaps enclose a small, well-defined group of primary spermatocytes in meiotic interphase. - The development of the restricted spermatocyte population is followed day by day. The analysis of meiosis in male mice has revealed the correct sequence of meiotic, and especially prophase I stages. On account of clearly visible differences in chromosome morphology the diplotene stage could be divided into three periods. It is suggested to use the following nomenclature: pre-diffuse diplotene, diffuse diplotene and post-difuse diplotene. The experiment was also informative about the timing of the stages in spermatocyte development by correlating the days at which the successive stages were observed with the corresponding stage of the epithelial cycle. The calculation of the position and duration of the diffuse diplotene, enables us to put forward a proposal about the significance of the diffuse diplotene. - A combination of the HU/T method with cell separation techniques provides good perspectives for detailed biochemical studies on processes taking place during meiosis.

Animals↗

PubMed1992

Deficiency of X and Y chromosomal pairing at meiotic prophase in spermatocytes of sterile interspecific hybrids between laboratory mice (Mus domesticus) and Mus spretus.

The normal association between the X and Y chromosomes at metaphase I of meiosis, as seen in air-dried light microscope preparations of mouse spermatocytes, is frequently lacking in the spermatocytes of the sterile interspecific hybrid between the laboratory mouse strains C57BL/6 and Mus spretus. The purpose of this work is to determine whether the separate X and Y chromosomes in the hybrid are asynaptic, caused by failure to pair, or desynaptic, caused by precocious dissociation. Unpaired X-Y chromosomes were observed in air-dried preparations at diakinesis, just prior to metaphase I. Furthermore, immunocytology and electron microscopy studies of surface-spread pachytene spermatocytes indicate that the X and Y chromosomes frequently fail to initiate synapsis as judged by the failure to form a synaptonemal complex between the pairing regions of the X and Y chromosomes. Several additional chromosomal abnormalities were observed in the hybrid. These include fold-backs of the unpaired X or Y cores, associations between the autosome and sex chromosome cores, and autosomal univalents. The occurrence of abnormal autosomal and XY-autosomal associations was also correlated with cell degeneration during meiotic prophase. The primary breakdown in hybrid spermatogenesis occurs at metaphase I (MI), with the appearance of degenerated cells at late MI. In those cells, the X and Y are decondensed rather than condensed as they are in normal mouse MI spermatocytes. These results, in combination with the previous genetic analysis of spermatogenesis in hybrids and backcrosses with fertile female hybrids, suggest that the spermatogenic breakdown in the interspecific hybrid is primarily correlated with the failure of XY pairing at meiotic prophase, asynapsis, followed by the degeneration of spermatocytes at metaphase I. Secondarily, the failure of XY pairing can be accompanied by failure of autosomal pairing, which appears to involve an abnormal sex vesicle and degeneration at pachytene or diplotene.

Animals↗

PubMed1992

Basic fibroblast growth factor (bFGF) in rodent testis. Presence of bFGF mRNA and of a 30 kDa bFGF protein in pachytene spermatocytes.

We have previously described a 30 kDa basic fibroblast growth factor (bFGF)-like protein in rodent testicular homogenates and have shown that pachytene spermatocytes are the sites of predominant immunoreactivity for this bFGF-like protein (Mayerhofer, A., Russell, L.D., Grothe, C., Rudolf, M. and Gratzl, M. (1991) Endocrinology 129, 921-924). We have now addressed the question whether this 30 kDa bFGF-like protein is a large bFGF form and whether it is produced by pachytene spermatocytes. We detected bFGF mRNA in homogenates of isolated mouse spermatocytes (which consisted mainly of pachytene spermatocytes) using S1 nuclease protection assays. As shown by Western blot analyses, the bFGF mRNA in mouse spermatocytes is translated into bFGF of an approximate molecular weight of 30 kDa. Neither bFGF mRNA, nor bFGF itself, was observed in isolated mouse Leydig cells. These results indicate that the immunoreactive bFGF-like protein observed previously in germ cells of the murine testis is identical to bFGF. Thus, germ cells of the testis produce bFGF, which may exert regulatory function in the process of spermatogenesis.

Animals↗

PubMed1989

The response of spermatogonia and spermatocytes of the Northern vole Microtus oeconomus to the induction of sex-chromosome nondisjunction, diploidy and chromosome breakage by X-rays and fast fission neutrons.

Microtus males were exposed to different doses of 250 kV X-rays or fast fission neutrons of 1 MeV mean energy. Early (= round) spermatids were analyzed for the presence of extra sex chromosomes, diploidy and micronuclei at different time intervals corresponding with treated differentiating spermatogonia and spermatocytes. Induction of nondisjunction of sex chromosomes could not be detected. In contrast, induction of diploids by both types of radiation was statistically significant at all sampling times. Dose-effect relationships for most of the sampling times were linear and sometimes linear-quadratic concave upward or downward. There were pronounced stage-specific differences in sensitivity as reflected by differences in doubling doses that ranged from 4 to 22 cGy for X-rays and from 0.4 to 4 cGy for neutrons. Spermatocytes at pachytene were the most sensitive cells and proliferating spermatogonia the least sensitive ones. The relative biological effectiveness (RBE) of neutrons depended on the cell stage treated and fluctuated between 1.4 and 9.2. Evidence for radiation-induced chromosomal breakage events was obtained via detection of micronuclei. Induction of micronuclei by X-rays or neutrons was statistically significant at all spermatocyte stages tested. There was no effect in spermatogonia. With a few exceptions dose-effect relationships were linear. Differences in stage sensitivity were clearly present as evidenced by doubling dose which ranged from 5 to 29 cGy for X-rays and from 1 to 3 cGy for neutrons. RBE values varied from 5.2 to 12.7. Maximum sensitivity was detected in spermatocytes at diakinesis, MI and MII. Resting primary spermatocytes (G1 and S phase) were somewhat less sensitive and actively proliferating spermatogonia were the least sensitive cells. The pattern of stage sensitivity for induction of diploids was distinctly different from that for induction of chromosomal breakage.

Aneuploidy↗