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PubMed2000

Participation of testicular spermatids in development upon intracytoplasmic injection into eggs of the sawfly, Athalia rosae (Insecta, hymenoptera).

Fertilization by intracytoplasmic injection of mature sperm into mature eggs has previously been achieved in the sawfly, Athalia rosae (Insecta, Hymenoptera). In the present study, we examined the potential of spermatids, premature male gametes, for participating in development. When round spermatids and elongating spermatids from pupal testes were injected into the anterior end of mature eggs, about 5% of the total injected eggs developed into chimeric embryos (independent participation in development of the egg and spermatid nuclei). Some of them developed further, hatched, and pupated, with 1-2% of the total injected eggs becoming haploid chimeric male adults in which both the egg-derived and injected spermatid-derived nuclei contributed to the germline. No fertilized embryos were obtained by these injections. Elongated spermatids (immature sperm) from newly eclosed adult male testes upon injection did produce fertilized embryos that developed into normal diploid females (about 7% of the total injected). These results indicate that insect spermatids (round and elongating) have the potential to participate in development, but only independently of the egg nucleus. J. Exp. Zool. 286:181-192, 2000.

Animals↗
PubMed1996

Sak57, an acidic keratin initially present in the spermatid manchette before becoming a component of paraaxonemal structures of the developing tail.

We have previously reported that Sak57 (for Spermatogenic cell/Sperm-associated keratin of molecular mass 57 kDa) is an acidic keratin found in rat spermatocytes, spermatids, and sperm. Sak57 displays conserved amino acid sequences found in the 1A and 2A regions of the alpha-helical rod domain of keratins in human, rat, and mouse. We now report indirect immunofluorescence, confocal laser scanning microscopy and immunogold electron microscopy data showing that Sak57 is associated with the microtubular mantie of the manchette, a transient microtubular structure largely regarded as formed by tubulin and microtubule-associated proteins. The immunocytochemical localization of Sak57 was detected with a polyclonal antiserum to a multiple antigenic peptide (MAP) containing an amino acid sequence known to be present in the 2A region of the alpha-helical rod domain. During spermiogenic steps 8-12, Sak57 immunoreactive sites were restricted to microtubular mantie of the manchette which encircles the spermatid nucleus during shaping and chromatin condensation. At later stages (spermiogenic steps 12-14), Sak57 immunoreactive sites in the spermatid head region disappeared gradually as specific immunoreactivity appeared along the already assembled axoneme of the developing spermatid tail. Immunogold electron microscopy confirmed the presence of Sak57 immunoreactivity among microtubules of the manchette and on outer dense fibers and the longitudinal columns linking the ribs of the fibrous sheath. Mature spermatids (spermiogenic step 19) displayed tails with an immunofluorescent banding pattern contrasting with the lack of Sak57 immunoreactivity in the head region. Results from this study suggest that, during early spermiogenesis, a microtubular-Sak57 scaffolding is associated with the spermatid nucleus during shaping and chromatin condensation. During late spermiogenesis, the dispersion of the manchette coincides with the progressive visualization of Sak57 in the paraaxonemal outer dense fibers and longitudinal columns of the fibrous sheath in the developing spermatid tail.

Animals↗
PubMed1982

Evolution of Sertoli cell processes invading the cytoplasm of rat spermatids.

Sertoli cell processes invaginating the cytoplasm of rat spermatids were investigated in thin or thick sections stained respectively with ferrocyanide-reduced osmium (Karnovsky, 1971) and the Ur-Pb-Cu metallic impregnation method (Thiéry and Rambourg, 1976). Two types of Sertoli cell processes were observed: Some, seen in steps 11-15 of spermiogenesis, were associated with a tight network of ER cisternae located within the spermatid cytoplasm subjacent to the plasma membrane facing the Seertoli cell process; others, seen from step 11 until the end of spermiogenesis, were not associated with such a spermatid subsurface ER network. Following their formation, the ER-associated Sertoli cell processes were cleaved into double-walled vesicles. Concomitantly, the enclosed Sertoli cell cytoplasm underwent autolysis followed by the dissolution of the Sertoli cell plasma membrane leaving within the spermatid cytoplasm many empty-looking vacuoles delimited only by the plasma membrane of the spermatid. Thereafter, i.e., in steps 15 and 16 of spermiogenesis, these vacuoles clustered, and with the collapse of the vacuoles they gave rise to a single compact mass of interlaced ER cisternae and small vacuoles. With the dissolution of ER cisternae, in step 18, this mass was finally dispersed. These observations suggested that the ER-associated Sertoli cell processes may constitute a pathway for the delivery of material from the Sertoli cells into spermatids. In contrast, the Sertoli cell processes not associated with a network of ER cisternae did not show cleavage or autolysis and appear to be involved mainly in holding the cytoplasm of the spermatid in place.

Acrosome↗
PubMed1989

Mechanism for the removal of residual cytoplasm from spermatids during mouse spermiogenesis.

During spermiogenesis, cytoplasmic processes of Sertoli cells invade spermatid cytoplasm to form a canal complex (Sakai et al., 1988). Thin tubules are formed from the canal complex and intertwine with each other to give rise to the "mixed body." In the present study, analysis of the changes undergone by the intertwining thin tubules indicated that they contribute to the removal of cell organelles from spermatid cytoplasm. Intertwining thin tubules were first detected at step 13. By step 15, their number had greatly increased. In the present study, the membranes of the intertwining thin tubules were clearly observed to be continuous with the spermatid plasma membranes. Thus, the mixed body possibly may be formed as a long pit of the spermatid plasma membrane situated close to the invading Sertoli cell process. With the progress of spermiogenesis, the lumens of the intertwining thin tubules gradually became swollen, and the intertwining swollen tubules fused with each other so that the spermatid cytoplasm enclosed by the intertwining swollen tubules isolated into fragments. This fragmented cytoplasm, which contained a large amount of endoplasmic reticulum, became spherical. Small branches of the invading Sertoli cell processes entered into the lumens of the intertwining swollen tubules and occupied their interior to the point that, finally, they completely engulfed the fragmented spermatid cytoplasm. Because the invading Sertoli cell processes were continuous with Sertoli cell bodies surrounding a spermatid at this step, it is possible for the fragmented cytoplasm to be transported into the latter by way of the invading Sertoli cell processes.

Adenosine Triphosphatases↗
PubMedDate not supplied

Intracytoplasmic spermatid injection can result in the delivery of normal offspring.

Almost one-third of all patients with nonobstructive azoospermia undergoing testicular sperm extraction (TESE) and intracytoplasmic sperm injection (ICSI) have cancelled cycles due to failure to find spermatozoa. For these patients, every attempt should be made to rescue the cycles by searching for spermatids. In this retrospective study, we report our experience in using elongating (stage Sb2) and elongated (stage Sc and Sd1) spermatids for ICSI. The study included 488 consecutive ICSI and TESE cycles performed for 452 patients with nonobstructive azoospermia. In 179 (36.7%) cycles, neither spermatozoa nor mature spermatids (stage Sd2) suitable for injection were found. After an extensive search only Sb2, Sc, and Sd1 spermatids were found in 22 of these 179 cycles (12.3%). These spermatids were used for injection of retrieved oocytes. The fertilization rate was 33.2%, and 19 patients (86.4%) reached the embryo transfer stage. In 6 cycles a chemical pregnancy occurred, and 3 clinical pregnancies were established, resulting in the delivery of 3 healthy boys with normal karyotypes. When normal living spermatozoa or mature spermatids (stage Sd2) cannot be found during TESE, late spermatids (stage Sb2, Sc, and Sd1) can be used successfully and result in the delivery of healthy offspring.

Biopsy↗
PubMed1992

Localization of DNase I-hypersensitive regions during rat spermatogenesis: stage-dependent patterns and unique sensitivity of elongating spermatids.

DNase I-hypersensitivity of rat spermatogenic cells was analyzed 1) to establish overall patterns of hypersensitivity in individual cell types, 2) to correlate these patterns with known changes in chromatin organization and function, and 3) to provide a foundation for further analyses examining DNase I-hypersensitivity and the localization of specific genes during spermatogenesis. Parameters for in situ nick translation, using radioactive and fluorescent probes to visualize DNase I-hypersensitive regions (DHR), were established for fixed and sectioned testicular preparations, permeabilized cells, and isolated germ cell nuclei. As anticipated, the pattern of DHR changed in a cell-type specific manner during the course of spermatogenesis, reflective of known stage-dependent alterations in the composition and structure of both the chromatin and the nuclear lamina/matrix as well as changes in gene expression. DHR in preleptotene spermatocytes were primarily peripheral, while in pachytene spermatocytes they were localized along the condensed chromosomes. The pattern of DHR changed from "checkerboard" in steps 7-8 round spermatid nuclei to "lamellar" in steps 10-11 elongating spermatids. In steps 12-13 elongating spermatids. DHR were localized throughout the nuclei or in a graded manner--increasing from anterior to posterior and mirroring the pattern of chromatin condensation. However, unlike the case in other stages, DNA of steps 12-13 elongating spermatids was exquisitely sensitive to nick translation even in the absence of exogenous DNase I. In contrast to the labeling of earlier stages, steps 16-19 spermatids and mature spermatozoa did not demonstrate DNase I-hypersensitivity under any conditions employed. A variety of agents that interact with topoisomerase II and DNA (teniposide, novobiocin, ethidium bromide, and adenosine triphosphate) were tested to determine the basis for the unique sensitivity to nick translation of steps 12-13 elongating spermatids. None of the agents tested, however, affected this unique labeling. The sensitivity of steps 12-13 elongating spermatids to nick translation in the absence of exogenous nuclease indicators the presence of endogenous nicks, which may relieve torsional stress and aid rearrangement as the chromatin is packaged into a form characteristic of the mature spermatozoon.

Animals↗
PubMed1992

Migration of centromere proteins in rabbit spermatids.

Human autoantibodies were used to localize centromere proteins by immunoelectron microscopy, immunofluorescence, and confocal microscopy in isolated cells and in cryosections of rabbit testis. A computer-assisted three-dimensional reconstruction of the positions and sizes of fluorescent spots allowed us to follow their movements during the different phases of spermiogenesis. In very young spermatids, the centromeres were distributed within a space separated from both the external nuclear limits and the nuclear core. They moved towards the nuclear center in cap phase spermatids, where they clustered into a few large centromeric masses. In preelongating spermatids, the immunolabeled proteins were dispersed within an equatorial area, where they formed one large mass. In late spermatids, the mass moved towards the posterior part of the nucleus, and, in the spermatozoon, the two basal knobs located at the base of the nuclei were the only strongly immunolabeled structures, while no labeling of the main part of the nucleus was observed. Since the number of centromeres remained close to the number of chromosomes until the cap phase of spermatid differentiation, we hypothesize that the labeling of young spermatids corresponds to centrometric proteins associated with their specific DNA counterparts, while the centromere proteins, possibly detached from their DNA loci, were released from nuclei of old spermatids in the same way as are histones and transition proteins.

Animals↗
PubMed1992

Stage-specific expression of rat transition protein 2 mRNA and possible localization to the chromatoid body of step 7 spermatids by in situ hybridization using a nonradioactive riboprobe.

The present study has used methoxyacetic acid (MAA)-induced depletion of specific germ cell types in the rat and in situ hybridization with nonradioactive riboprobes to determine the stages of the spermatogenic cycle at which there is expression of the mRNA for the basic chromosomal protein transition protein 2 (TP2). On Northern blots, an abundant mRNA was detectable in samples from control adult rats, but the amount of message was markedly reduced when RNA was extracted from the testes of rats treated 14 and 21 days previously with methoxyacetic acid. These testes were depleted specifically of step 7-12 spermatids, suggesting that these cells contain TP2 mRNA. When tissue sections were subjected to in situ hybridization, the TP2 mRNA was localized at the cellular and subcellular levels. Messenger RNA for TP2 was first detectable in spermatids at step 7. In these spermatids, at high magnification, in addition to some positive reaction in the cytoplasm, intense staining was located to a perinuclear structure consistent with localization of mRNA within the chromatoid body. The amount of TP2 mRNA in the cytoplasm increased as remodelling of the early spermatid nucleus progressed and was highest in step 10 and 11 spermatids at stages X and XI. Thereafter, the mRNA decreased until it was undetectable in step 14 spermatids at stage XIV. The localization of TP2 mRNA to the chromatoid body of step 7 spermatids would be consistent with this organelle being a storage site for long-lived mRNAs utilized later in spermiogenesis.

Animals↗
PubMed1988

Nuclear protein transitions in cuttle-fish spermiogenesis: immunocytochemical localization of a protein specific for the spermatid stage.

The changes in basic nuclear proteins throughout cuttle-fish spermiogenesis were investigated both by immunocytochemical procedures and by isolation of late spermatid nuclei (by virtue of their resistance to sonication). Antibodies were raised in rabbits to a protein, named protein T, isolated from testis chromatin. The anti-protein T immune serum was found to recognize protein T and not histones from the testis. Immunoperoxidase staining of sections or of smears of testis with anti-protein T antibodies showed that protein T appears in the nuclei of round spermatids, is abundant in elongating spermatid nuclei, but cannot be detected in elongated spermatids. Nuclei from these elongated spermatids were isolated by sonication treatment of testis cells. A protein, named protein Sp, with the characteristic mobility of a protamine, was isolated from elongated spermatid nuclei. This protein has the same mobility as the protamine present in mature spermatozoa. Taken together, the results indicate that in cuttle-fish, nuclear protein transitions involve the replacement of histones by a spermatid-specific protein (protein T), which is replaced at the end of elongation of the nucleus by a protamine (protein Sp). Thus, spermiogenesis of the cuttle-fish (and perhaps of other cephalopods), shows two basic nuclear protein transitions, which are similar to the transitions observed in higher vertebrates such as mammals.

Animals↗
PubMed2005

Differential RNA expression and polyribosome loading of alternative transcripts of the Akap4 gene in murine spermatids.

An X chromosome-linked gene, Akap4, is expressed only during spermiogenesis and encodes the major fibrous sheath protein of the mouse sperm flagellum. All sperm contain the AKAP4 protein even though only X chromosome-bearing spermatids express the gene, indicating that the Akap4 mRNA and/or protein must be shared among the conjoined spermatids via the intercellular bridges. There are two mouse Akap4 cDNA clones, Akap82 and Fsc1, which represent mRNAs that arise by alternative processing of a single gene. Although Akap82 and Fsc1 encode identical mature proteins, they differ in their 5' UTRs. We hypothesized that the expression pattern of these two mRNAs might be relevant to the issue of mRNA and/or protein transport into adjacent spermatids. Expression of both transcripts began in round spermatids, but the amount of the Akap82 transcript in condensing spermatids increased twofold relative to Fsc1. Significantly, only the Akap82 transcript was found on polyribosomes and translated in spermatids. These results indicate that the Akap82 transcript and/or its protein must be shared among the conjoined X and Y chromosome-bearing spermatids. Although Fsc1 was not polysomal, both the Akap82 and Fsc1 transcripts were deadenylated during spermiogenesis, suggesting that deadenylation is not always correlated with loading of mRNAs onto polyribosomes in germ cells. The distinct 5' UTR sequences in Akap82 and Fsc1 did not differ in their ability to regulate translation of reporter constructs either in vivo or in vitro. Antisense RNA transcripts complementary to both the Akap82 and Fsc1 mRNAs were present, suggesting that translatability may be regulated by these RNAs.

5' Untranslated Regions↗
PubMed1993

Nicking of rat spermatid and spermatozoa DNA: possible involvement of DNA topoisomerase II.

Chromatin of rat elongating spermatids, steps 12-13, is distinguished by the replacement of histones with transition proteins and the presence of nicks within its DNA which are formed by an endogenous nuclease, possibly DNA topoisomerase II (topo II). Using an affinity-purified anti-topo II antibody, protein bands of approximately 161 and approximately 137 kDa were detected on immunoblots of pachytene spermatocytes and elongating spermatids, respectively. In cryosections, topo II was localized to meiotic chromosomes of pachytene spermatocytes and to nuclei of elongating spermatids. Extracts of isolated testicular nuclei and sonication-resistant spermatid nuclei (steps 12-19) demonstrated topo II activity as determined by the decatenation of kinetoplast DNA. The potential relationship between nucleoprotein changes during spermatogenesis and the formation of nicks was also examined. Heterogeneous testicular and sonication-resistant spermatid nuclei were treated with 0.8 mM protamine, followed by nick translation in the absence of DNase I. In both cases, there was a dramatic decrease in DNA polymerase I-dependent label incorporation. To determine whether or not endogenous nicks were present in mature sperm, but were inaccessible due to protamine-DNA interactions, epididymal sperm were extracted with high salt-dithiothreitol, followed by nick translation in the absence or presence of DNase I. Extracted sperm nuclei did not nick translate in the absence of DNase I; however, incorporation increased with increasing concentrations of DNase I, indicating that endogenous nicks were repaired prior to the completion of spermatogenesis. These and previously published results suggest that topo II in elongating spermatids may be involved in the DNA alterations that take place during spermatogenesis, including changes in DNA topography, repair, and loop formation, and may serve as a component of the nuclear matrix. The temporal appearance and disappearance of endogenous nicks may reflect the changes that elongating spermatid DNA undergoes as a consequence of alterations in nucleoprotein composition to establish the condensed state of the mature spermatozoon.

Animals↗
PubMed1975

[Morphological studies on abnormal human spermatids and spermatozoa (author's transl)].

Malformed spermatids and spermatozoa in the testes, epididymes, and ejaculates of 29 apparently healthy men and in 171 patients suffering from different andrological diseases were investigated with the electron microscope. The following types of malformations are described: 1) Malformations of the acrosome in contact with the nucleus of the spermatid: Vesicular inclusions in the acrosome vesicle, asymmetric thickenings of the acrosome cap, enfolding of the acrosomal lamina into the spermatid's nucleus, partial separation of the acrosome from the nucleus, apical knob-like thickenings of the acrosome. 2) Malformations of the acrosome independent from the spermatid's nucleus: the acrosomal material is contained in small vesicles, large vacuoles, in ring-like structures, in globular or shell-like laminar structures. The nucleus of such spermatids lacks an acrosome. 3) Malformations of the nucleus: inclusions of vesicles or membranes, excessive packages of membranes, gigantic nuclear vacuoles, lack of condensation of the caryoplasm. 4) Multinucleate spermatids: two or more nuclei within the pericaryon of one spermatid are joined by an acrosome. 5) Duplicate acrosome anlagen. 6) Malformations of the tail: disorganization of the axonema, a lack or excessive numbers of tubules and fibres, doublets of the axial filaments, destruction of the neck region, a lack of the mitochondrial sheath, and enlargement of the fibrous sheath. Malformed germ cells were observed to occur in varying amounts both in apparently healthy men and in those who were apparently infertile. This indicates that germ cell malformations are no absolute indicator of male infertility. However, certain distinct types of malformations (such as round-headed spermatozoa) are definitely associated with infertility, but only if all spermatozoa in the ejaculate of a patient have the same defect.

Acrosome↗
PubMed1993

Synaptonemal polycomplexes in spermatids: a characteristic trait of Orthoptera?

Spermatogenesis was analysed in a cricket, Eneoptera surinamensis (Gryllidae, Orthoptera), using ultrathin serial sections and transmission electron microscopy. Special attention was placed on documentation of the development and structure of synaptonemal polycomplexes (PCs) within spermatid nuclei. Pachytene spermatocytes showed the usual tripartite synaptonemal complexes in the nuclear lumen. PCs were situated close to chromosomes at the periphery of spindles in prometaphase I spermatocytes, where microtubule density was low. The PCs are probably incorporated into the daughter nuclei of both meiotic divisions by adhesion to chromosomes. Finally, PCs end up within spermatid nuclei. Analysis of serial sections through three nuclei of young spermatids revealed at least one PC within each. The PCs were intimately attached to an electron-dense spherical nuclear body. This topographical correlation was confirmed through inspection of random sections. The PCs may have an affinity to the spherical bodies. In more developed spermatids, PCs and nuclear bodies were missing. Disassembly products of the PCs may play a role in spermatid maturation. In a series of other Orthoptera species, PCs have been reported to occur in the cytoplasm or the nuclei of spermatids. In most other systematic groups, PCs do not form at all or disassemble earlier. The presence of PCs in young spermatids, therefore, seems to be typical of Orthoptera.

Animals↗
PubMed1999

Transcriptional and translational regulation of gene expression in haploid spermatids.

During spermiogenesis, round spermatids undergo complex morphological, biochemical, and physiological modifications resulting in the formation of mature spermatozoa. While in round spermatids histones and non-histone proteins are replaced by transition proteins, in elongating spermatids, transition proteins are removed from the condensing chromatin and are replaced by protamines, which are the principal basic nuclear proteins of mature spermatozoa. The tightly packed DNA-protamine complexes cease transcription several days before the completion of spermiogenesis. Thus, major modifications in both nuclear and cytoplasmic structures continue throughout spermiogenesis, stringent temporal and stage-specific gene expression is a prerequisite for the correct differentiation of round spermatids into mature spermatozoa. The genes for transition proteins and protamines are transcribed in round and elongating spermatids. Transcription is regulated via methylation and trans-acting factors that bind to the TATA-box, the CRE-box, or other specific DNA sequences in the promoter region. The transcripts are stored as ribonucleoprotein particles in a translationally repressed state for several days and are translated in elongating and elongated spermatids. It has been demonstrated that, in haploid spermatids, essentially every mRNA exhibits evidence of translational repression. Translational regulation involves protein repressors that bind to the poly-A tail or specific RNA sequences located in the 3'-UTR.

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↗
PubMed1989

Synacrosomal formation after cell fusion of round spermatids of Xenopus laevis.

Cell fusion was induced by hypotonic medium in pairs of spermatids which were derived from single secondary spermatocytes. In a pair of fused spermatids, a single acrosome (synacrosome) eventually formed whenever the cell fusion was induced during the course of acrosomal formation. Direct observation of the process of synacrosomal formation was made on pairs of fused spermatids which had completed acrosomal formation. Two patterns occurred, namely, fusion of two acrosomes or enlargement of one with diminution of the other. The total volume of the two acrosomes before synacrosomal formation almost equaled the volume of the coalesced synacrosomes in fused spermatids. Neither colchicine nor cytochalasin B prevented synacrosomal formation in spermatids which were fused after each had completed acrosomal formation. These results indicate that neither microtubules nor microfilaments seem to play a role in the formation of a synacrosome in pairs of fused spermatids. However, cycloheximide did inhibit acrosomal formation when present during the early stage of acrosome differentiation in pairs of spermatids which had been fused just after second meiotic division. This fact indicates that acrosomal formation is mediated by some protein(s) which are synthesized during the initial period of acrosomal formation.

Acrosome↗
PubMed1980

A study of Sertoli-spermatid tubulobulbar complexes in selected mammals.

Tubulobulbar complexes (TBCs) were found in nine mammalian species (opossum, vole, guinea-pig, mouse, hamster, rabbit, dog, monkey and human) primarily originating from the plasma membrane overlying the acrosome of late spermatids. Fewer complexes (4--10) were noted in these species than has been previously reported for the rat (up to 24). TBCs were not seen emanating from round spermatids or those elongated spermatids located within the deep recesses of the Sertoli cell, but they appeared as the spermatids came to reside much closer to the tubular lumen in preparation for release. TBCs developed in areas deficient or lacking in Sertoli filaments and endoplasmic reticulum (ectoplasmic specialization). In general their structural configuration was similar to that shown in the rat, although minor differences were noted. Fine fibrils were observed connecting the distal portion of the spermatid tube with the Sertoli plasma membrane forming a bristle-coated pit. The length of TBCs from most species studied was 1--2 micrometers, whereas those of the opossum extended 6--8 micrometers into an apical Sertoli process. TBCs were degraded within the Sertoli cell by its lysosomes prior to sperm release, and for most species there was evidence indicating that formation of more than one generation of TBCs occurred. As sperm release approached, TBCs formed preferentially from the leading edge of spermatids with spatulate heads. The Sertoli cell gradually withdrew from around the spermatid head until only the tip of the head was embedded within the Sertoli cell. This region of contact frequently demonstrated TBCs. The proposed functions of TBCs are reviewed and discussed in light of these findings from other species.

Animals↗
PubMed1983

Proteolysis of somatic type histones in transforming rat spermatid chromatin.

Elongated rat spermatid nuclei have been isolated on the basis of their resistance to sonication in 0.32 M sucrose containing 1.5 mM CaCl2. Chemical analyses indicate that approx. 35% of the DNA in these nuclei is associated with somatic type histones, while the remainder represents sperm histone-DNA complex. In contrast to nuclei of somatic cells, when elongated spermatid nuclei are incubated under appropriate conditions, somatic type histones but not sperm histone are rapidly degraded. Differential extraction of elongated spermatid nuclei with 5 mM HCl and then with various concentrations of NaCl followed by 0.2 M HCl has revealed that they contain two kinds of proteases. The protease in the 5 mM HCl extract is acrosin (EC 4.3.21.10). Rapid degradation of somatic type histones is, however, observable upon incubation of elongated spermatid nuclei which have been treated with 5 mM HCl and are therefore free of acrosin or upon incubation of elongated spermatid chromatin where the majority of acrosin is removed, suggesting that the observed proteolysis of somatic type histones is not due to acrosin. Proteases which may represent the enzymes responsible for the histone degradation are extractable from acrosin-free spermatid nuclei with NaCl (0.9 M) and by subsequent treatment of the salt-extracted nuclei with 0.2 M HCl. The proteases in the NaCl and the 0.2 M HCl extract possess identical properties and appear to be the same enzyme which may exist in spermatid chromatin in two different forms.

Animals↗