Extractions reveal specific argentophilic proteins in rat and bull sperm heads

A new preparation protocol for measurement of testicular sperm production

In studies of male reproductive toxicity, measuring daily sperm production is a quite important criterion. However, the accuracy of the values measured by the basic protocol is still controversial. In order to enhance the homogeneity of countable testicular sperm/spermatid heads, this report introduces a new enzymatic method with a subsequent detergent treatment. The testis of rat was firstly homogenized in phosphate-buffered saline. The homogenate (buffer mix) was then treated with collagenase and trypsin, and then sodium dodecyl sulfate (SDS) was added to produce detergent-resistant sperm/spermatid heads (detergent mix). After examination by hemocytometer, the coefficient of variation (CV) of the number of sperm/spermatid heads was compared with that obtained from the buffer mix. In addition, a MicroCell chamber was applied to the examination, and the CV was compared with other cases. In both examinations, homogeneity was improved by the detergent mix preparation. Counting with the hemocytometer showed an increased number of sperm/spermatid heads compared with that of the buffer mix (P<0.001), and the CV was decreased (P<0.05). In addition, when the MicroCell chamber was applied, the numbers increased about 3-hold compared with that of the buffer mix (P<0.001). The CV of the detergent mix was 23.7%, while that of the buffer mix was 38.9%. These results clearly demonstrate that the new preparation protocol generated in this study can provide more actual and accurate values when measuring daily sperm production.

Acute lymphoblastic leukaemia in rats induces pathomorphological changes in germ cells

Concern about the reproductive potential of long-term survivors of acute lymphoblastic leukaemia (ALL) prompted an investigation into the impact of the disease on spermatogenic cells. Using rats as a model, histological, immunocytochemical and electron microscopic analysis was applied to investigate changes in the seminiferous epithelium. In rats transplanted with leukaemic cells at early puberty, degenerate primary spermatocytes and spermatids were prevalent within stage VIII tubules. Electron microscopically, step 8 spermatids showed acrosomal abnormalities and nuclear contour distortion. In the distorted step 9 spermatids, the microtubules of the manchette were abnormally oriented or deficient. Antitubulin antibody staining was reduced in elongating spermatids in the group transplanted with leukaemic cells at early puberty but was not observed in the older leukaemic group. Step 13 spermatids showed extracted chromatin and degenerate step 19 spermatids were occasionally found. Similar but less severe changes were seen in the group of rats transplanted with leukaemic cells at late puberty. We conclude that germinal cell damage induced by ALL is dependent on the developmental maturity of the seminiferous epithelium. The present findings are of particular importance when interpreting the impact of anticancer chemotherapeutics on germinal cells in patients with ALL.

Actin, alpha-actinin, and spectrin with specific associations with the postacrosomal and acrosomal domains of bovine spermatozoa

BACKGROUND

Characteristic membrane changes in spermatozoa culminating in acrosome reaction and sperm-egg fusion, and suspected involvement of actin-containing cytoskeleton in membrane changes in general, prompted us to investigate subcellular distribution of actin and actin-binding proteins in bovine spermatozoa subjected to various extractions which sequentially denude the sperm investments.

METHODS

Spermatozoa were treated with either 1% SDS, 0.1% Triton X-100, 0.1% Hyamine, or 1 M MgCl2 or were sonicated. Immunostaining of actin, alpha-actinin, spectrin, and acrosin as well as electron microscopic analysis of extracted spermatozoa were carried out.

RESULTS

Extractions caused evagination of the acrosomal lamina which retained focal contacts with the inner acrosomal membrane. Extractions further revealed lateral prongs at the anterior border of the postacrosomal sheath. Labeling for alpha-actinin and spectrin was localized in the acrosin-positive acrosomal lamina, neck, and principal piece, the latter containing also relatively extraction-resistant oligomeric or polymerized actin. In the postacrosomal area, actin was accumulated in the extraction-resistant posterior ring structure and anteriorly at the sites apparently related to the lateral prongs. Notably, spectrin reactivity was enhanced by MgCl2 in head, neck, and principal piece, and sonication abolished cytoskeletal immuno-reactivity in the head.

CONCLUSIONS

Destabilization of membranes with selected extractions induces changes in the acrosomal lamina mimicking acrosomal vesicle formation. The lateral prongs and posterior ring structure, respectively, may serve as anterior and posterior anchors for the extraction-resistant post-acrosomal sheath. The lateral prongs may also be a merger zone for actin, alpha-actinin, and spectrin with important implication on sperm function. The latter two proteins may be involved in acrosomal vesicle formation. It is apparent that extractions have a significant effect on the detectability of sperm cytoskeletal elements.

Immunocytochemical detection of actin and 53 kDa polypeptide in the epididymal spermatozoa of rat and mouse

BACKGROUND

Presence of immunocytochemically detectable actin in the rat and mouse sperm head has been enigmatic for years. In this study, we demonstrate actin in the perinuclear theca and show that the detection of actin epitopes in the rat and mouse epididymal spermatozoa can effectively be enhanced by pre-extraction of sperm cells with SDS.

METHODS

The study with one monoclonal and one polyclonal anti-actin antibody was carried out at conventional and confocal fluorescence and electron microscope level, and by immunoblotting of proteins isolated from the head and tail fractions.

RESULTS

In the head of the control methanol-acetone fixed rat spermatozoa, the polyclonal antibody gave a stronger immunostaining in the postacrosomal area and in the perforatorium than the monoclonal antibody. In the mouse sperm head, the monoclonal antibody labeled the ventral edge of the postacrosomal area and slightly the perforatorium, whereas the polyclonal antibody stained the entire perinuclear space. In the SDS-extracted spermatozoa, an intense postacrosomal and perforatorial labeling was obtained with both antibodies but, in particular in the rat spermatozoa, the middle lateral portion of the postacrosomal segment remained unlabeled. Sonication seemed to cause structural modifications which specifically impeded staining with the monoclonal antibody. Both antibodies detected actin in the basal plate and the monoclonal antibody in the neck. Amorphous matrix of the connecting piece showed immunogold labeling. In the tail, the monoclonal antibody recognized actin and a relatively basic 53 kDa polypeptide, whereas the polyclonal antibody reacted with several protein bands. SDS-soluble actin of the tail was addressed to the midpiece and the SDS-insoluble 53 kDa protein profoundly to the outer dense fibers of the principal piece.

CONCLUSIONS

Intense labeling of actin in the SDS-extracted rat and mouse spermatozoa was presumably due to the generated demasking of actin epitopes embedded in the perinuclear cytoplasm. The results are important in confirming that actin in the rat and mouse sperm head is not lost during spermiogenesis but apparently contributes to the three-dimensional packing of the mature perinuclear cytoplasm. This study further demonstrates the importance of the methods used in sample preparation and advantages of confocal microscopy when attempting to detect cytoskeletal proteins which, as in spermatozoa, may occur in small quantities.