Cellular localization of the Mn2+-dependent adenylyl cyclase (AC) in rat testis

In the present study we have examined the exact cellular localization of the Mn2+-dependent adenylyl cyclase (AC) in the rat testis. Several pieces of evidence indicate that this testis specific enzyme is exclusively localized to haploid cells in the testis: firstly, the appearance of Mn2+-dependent adenylyl cyclase coincides in time with the occurrence of haploid cells (IC) in the rat testis. Secondly, tests of tfm rats and mice, in which little or no haploid cells are found, exhibit negligible Mn2+-dependent AC activity. Finally, separation of various testicular cells by BSA gradient sedimentation (Staput fractionation), revealed that this enzyme activity follows the location of haploid cells; the highest specific AC activities being found in the fractions containing elongated spermatids. Some activity found in the primary spermatocyte fraction (4C cells) can to a large extent be explained by the contamination of haploid cells in this fraction.

Regulation of the synthesis of lactate dehydrogenase-X during spermatogenesis in the mouse

Total mouse testis RNA directs the synthesis of the sperm-specific C subunit of lactate dehydrogenase-X (LDH-X) when translated in a cell-free system derived from rabbit reticulocytes. The newly synthesized C subunits were isolated by immunoprecipitation with antibody specific for this isozyme, and quantitated by electrophoresis on SDS polyacrylamide gels. The amount of radioactivity incorporated into the enzyme subunit was directly proportional to the amount of testis RNA added to the translational system, thereby providing a sensitive and reliable method for assessing relative LDH-X mRNA activity. A combination of sucrose gradient centrifugation and oligo(dT)-cellulose chromatography resulted in a 23-fold purification of LDH-X mRNA over total cytoplasmic testis RNA. Analysis of LDH-X mRNA activity in the developing testis indicated that the appearance of functional LDH-X mRNA activity coincides with the appearance of LDH-X catalytic activity at 14 d postpartum. Measurement of LDH-X mRNA levels in separated testis cell populations prepared by centrifugal elutriation demonstrated that LDH-X mRNA represents 0.17-0.18% of the total functional mRNA activity in fractions enriched in pachytene spermatocytes and round spermatids, but only 0.09-0.10% of the translation products of elongated spermatids.

Evidence against gene expression after meiosis in the male mouse

Isozyme patterns in homogenates from various testicular cell types from mice were examined in an effort to ascertain whether the haploid genome is expressed during spermiogenesis. Male mice heterozygous for electrophoretic variants of several glycolytic enzymes were analyzed by starch gel electrophoresis. The enzymes examined were isocitrate dehydrogenase, glucose-6-phosphate dehydrogenase, and glucosephosphate isomerase. The isozyme patterns produced by these dimeric enzymes reflect the relative activity of genes in each cell type. These patterns reveal the presence or absence of the transcription of specific genes during spermiogenesis. We found that the genes encoding these enzymes continue to increase during spermiogenesis. Synthesis of these enzymes most likely continues in spermatids, but this synthesis must depend upon premeiotically produced mRNA. These data provide biochemical evidence for the hypothesis that the phenotype of the haploid mammalian gamete depends upon the preceding diploid genome and that a mechanism must exist for the long term post-transcriptional regulation of gene expression during spermiogenesis.

Enzymic activity of 3-beta-hydroxysteroid dehydrogenase and of some glycolytic enzymes occurring in the testicle of Graphosoma italicum Mull. and of Eurydema ventralis Kol. (Heteroptera--Pentatomidae)

In the testicle of Graphosoma italicum and Eurydema ventralis the histochemical localization of 3-beta-HSD, SDH, MDH and LDH was followed up. The enzymic activity was detected in various stages of the sexual cells; the strongest activity was found in the evoluted spermatids and spermatozoa. As far as the nutritive cells of the testicle are concerned, the reaction of these different enzymes appeared very weak or absent.

Leucyl naphthylamidase activity in pigeon and toad testes under various experimental conditions

The activity pattern and functional significance of leucyl naphthylamidase (LNase) in the pigeon testis under different hormonal and photoperiod conditions as well as in the testes of short- and long-term HCG-treated toads have been studied histochemically. In both the species, the enzyme activity was present in the maturing spermatids and those embedded in the Sertoli cell components, the mature spermatozoa released in the lumen being devoid of any LNase activity. In pigeon, the stimulation of spermatogenic process was associated with enhanced activity of the enzyme, whereas arrest of spermatogenesis showed little or no activity. In toad, short-term HCG treatment caused mild stimulation of spermiation resulting in sperm release from the Sertoli cells and this was accompanied by moderate decrease in LNase activity. The long-term HCG treatment produced an enhanced stimulation of spermiogenesis and spermiation processes resulting in almost total disappearance of LNase activity. The above observations suggest that the enzyme in the testes of both species is related to spermiogenesis and/or spermiation events of spermatogenesis.

Alteration of cytochrome c oxidase activity during spermatogenesis in Carcinus maenas

During spermatogenesis in the crab, Carcinus maenas, mitochondria in the developing spermatids degenerate. In close association with mitochondrial fragments in late spermatids, an elaborate lattice-like complex of fused membranes is formed and lies in a position adjacent to the acrosome. Mature sperm possess no mitochondria, but a whorl of membranes is present alongside the acrosome in the diffuse nucleus. To ascertain whether or not cytochrome c oxidase activity is lost as the mitochondria disintegrate, differentiating Carcinus maenas spermatids and mature sperm have been studied cytochemically. Cytochfome c oxidase activity was localised by means of the osmophilic compound 3,3'-diaminobenzidine (DAB). Cytochrome c oxidase activity is confined to the cristae of mitochondria in the testis. As spermatids mature most mitochondria are lost. A few mitochondrial fragments may be caught up within the lamellar complex. While they are recognisalbe as mitochondria they retain cytochrome c oxidase activity. The lamellar complex does not show this enzyme activity. These results therefore suggest that the mature sperm of Carcinus maenas do not contain the enzymes normally incorporated in the mitochondrial membrane, capable of oxidative phosphorylation.

Gene activation during spermatogenesis

Cell differentiation during spermatogenesis in the rat has been analyzed in terms of the formation of specific "marker" enzymes. Hyaluronidase and other acrosomal enzymes are formed in spermatids according to a highly predictable time schedule which may be termed a "molecular biological clock". The acrosomal enzymes beta-galactosidase and N-acetyl-beta-glucosaminidase exist as isoenzyme forms distinct from enzymes with similar substrate specificities in the lysosomes of precursor cells. Differentiation of spermatids thus involves the loss of gene expression for lysosomal enzymes and the activation of genes for acrosomal isoenzymes. Spermatogenesis is characterized by the sequential loss of expression of many genes, as evidenced by the loss of beta-glucuronidase in the differentiation of spermatogonia to spermatocytes, and the loss of uridine diphosphatase activity in the differentiation of spermatocytes to spermatids. The apparent absence of ornithine decarboxylase activity from spermatids suggests a dependence of these cells upon Sertoli cells for the provision of putrescine and/or spermidine. Such biochemical cooperativity among germinal cells may be necessary as the genes of spermatids are repressed and late spermatids become metabolically inactive. Spermatogenesis is also characterized by changes in the cellular content and rates of synthesis and phosphorylation of specific acidic chromatin proteins. It is hypothesized that these proteins may participate in the activation or repression of genes during spermatogenesis.