Changes in Leydig cell activity during the annual testicular cycle of the bat Myotis lucifugus lucifugus: histology and lipid histochemistry

Changes in Leydig cell histology and testicular sudanophilic lipids were examined in relation to spermatogenic activity in the bat Myotis lucifugus lucifugus (Chiroptera: Vespertilionidae) throughout the annual cycle in the northeastern United States. These changes were correlated with annual variations in plasma testosterone concentrations which have recently been described for this species. Gametogenic activity occurred during the months of May-August when bats were metabolically most active. During hibernation (October-April), when sperm are stored in the epididymides, and accessory glands are hypertrophic, the seminiferous tubules were at rest, and the germinal epithelium was reduced to reserve spermatogonia and Sertoli cells. Based on their structure and cyclic pattern of sudanophilic lipids, Leydig cells exhibited a pattern of activity that closely paralleled that of the seminiferous epithelium. On renewal of spermatogenesis in spring, Leydig cells became hypertrophied and accumulated lipid inclusions. These inclusions, seen as vacuoles in plastic sections and sudanophilic droplets in frozen sections, reached maximal accumulations in late June. In late July and during August, when peak testosterone levels occur in blood, lipid droplets were dramatically depleted, and Leydig cells were weakly sudanophilic. In September, when testosterone titers return to low baseline levels, Leydig cells had regressed but exhibited a marked increase in sudanophilic inclusions which appeared to be mostly lipofuscins. During the ensuing mating and hibernation periods, Leydig cells were involuted and filled with lipofuscins. During the periarousal period, however, Leydig cells became weakly Sudan-positive while many large, intensely sudanophilic cells were scattered throughout the interstitium. In electron micrographs these cells were identified as macrophages. They appear to play an important role in the annual testicular cycle by phagocytizing the residues of Leydig cell involution in preparation for a new steroidogenic cycle. Seasonal changes in lipid inclusions were also observed in the seminiferous tubules. In addition, the relationship of the Leydig cell cycle to androgen action and the accessory organs in this bat is discussed.     

Inhibition of bone resorption in vitro by serine-esterase inhibitors

The effect of two synthetic serine esterase inhibitors, N-alpha-dansyl(p-guanidino)phenylalaninepiperidine hydrochloride (I 2581) and D-phenylalanyl-L-prolyl-L-arginine chloromethyl ketone (D-Phe-Pro-Arg-CH2Cl), on bone resorption in organ cultured mouse calvaria from neonatal mice has been examined. Mineral mobilization was assessed by analyzing the release of 45Ca, stable calcium (Ca2+) and inorganic phosphate (Pi). Organic matrix degradation was studied by analyzing the release of 3H from [3H]proline-labelled bones, and by quantifying the amounts of hydroxyproline in bone after culture. It was found that I 2581, at and above 30 mumol/l, dose-dependently inhibited 45Ca release induced by thrombin, parathyroid hormone (PTH), prostaglandin E2 and 1-alpha-hydroxyvitamin D-3. I 2581 (50 mumol/l) inhibited PTH-stimulated release of 3H from [3H]proline-labelled bones, and this effect was reversible after withdrawal of I 2581. I 2581 (50 mumol/l) inhibited the release of Ca2+, Pi, beta-glucuronidase and beta-N-acetylglucosaminidase in bones stimulated by PTH and 1-alpha-hydroxyvitamin D-3, without affecting the release of lactate dehydrogenase. In parallel, I 2581 decreased PTH and 1-alpha-hydroxyvitamin D-3 induced reduction of hydroxyproline levels in bones after culture. I 2581 (50 mumol/l) did not affect the basal release of 45Ca, Ca2+, beta-glucuronidase and beta-N-acetylglucosaminidase, nor the basal amounts of hydroxyproline in bones after culture. D-Phe-Pro-Arg-CH2Cl (100 mumol/l) significantly inhibited PTH- and PGE2-induced release of 45Ca without affecting basal release of radioactive calcium. These data indicate that activation of serine proteinase(s) may be a necessary step in the mechanism of action of several stimulators of bone resorption.     

Sequential Expression of Nucleoproteins during Rat Spermiogenesis

Transition proteins and protamines are highly basic sperm-specific nuclear proteins that serve to compact the DNA during late spermiogenesis. To understand their sequential role in this function, transition protein 1 (TP1), transition protein 2 (TP2), and protamine 1 (P1) were assayed by polyacrylamide gel electrophoresis in pools of microdissected, staged seminiferous tubule segments in the rat. The results were compared with immunocytochemical analyses of squash preparations from accurately identified stages of the epithelial cycle. TP2 was the first to appear as a faint band at stages IX–XI, followed by high levels at stages XII–XIV of the cycle. TP1 showed a low expression at stage XII of the cycle and peaked at stages XIII–I, whereas protamine 1 first appeared at stage I of the cycle and remained high throughout the rest of spermiogenesis. Immunocytochemical analyses and Western blots largely confirmed these results: TP2 in steps 9–14, TP1 in steps 12–15, and P1 from late step 11 to step 19 of spermiogenesis. We propose that TP2 is the first nucleoprotein that replaces histones from the spermatid nucleus, and its appearance is associated with the onset of nuclear elongation. TP1 shows up along with the compaction of the chromatin. The two transition proteins seem to have distinct roles during transformation of the nuclei and compaction of spermatid DNA.     

Perinatal Steroid Treatments Alter Alloparental and Affiliative Behavior in Prairie Voles

This experiment was designed to examine the hypothesis that perinatal manipulation of gonadal or adrenal steroids can alter the subsequent expression of juvenile parental (alloparenting) and affiliative behavior in prairie voles (Microtus ochrogaster). Corticosterone (PRECORT), testosterone (PRE-TP), or oil injections (PRESES) were given on Prenatal Days 12–20 or on Postnatal Days 1–6 (CORT6, TP6, or SES6, respectively). Alloparenting was reduced significantly in females in the CORT6 group and in males in the TP6 group. Sibling affiliative preferences were increased significantly in PRE-TP females and stranger preferences were increased in TP6 and CORT6 females. The results suggest timing is a critical factor determining whether hormones have a facilitative or inhibitory effect on alloparental and affiliative behavior in prairie voles. In this species, corticosterone and testosterone have similar organizational effects on affiliative behavior in females. Alloparental behavior is inhibited by postnatal corticosterone administration in females and by postnatal testosterone administration in males, whereas prenatal steroid administration had no significant effect on alloparenting in either gender.     

Molecular evidence for Triticum speltoides as a B-genome progenitor of wheat (Triticum aestivum).

In polyploid wheat, the origin of the B-genome donor has remained relatively unknown in spite of a number of investigations attempting to identify the parental species. A project was designed to isolate and clone a genome-specific DNA sequence from Triticum speltoides L. to determine if that species could be the B-genome donor. A cloning scheme involving the prescreening of 1-kb fragments followed by colony, dot blot, and Southern blot hybridization screenings was used to isolate a speltoides-specific sequence (pSp89.XI). The methods used allowed for rapid isolation of a genome-specific sequence when screened against total DNA from closely related species. Subsequent analyses showed that the sequence was barely detected in any of the other genomes of the annual Sitopsis section. The results of dot blot and Southern blot analyses established that (i) the sequence pSP89.XI, specific to T. speltoides relative to the other species of the Sitopsis section, was present in the genomes of tetraploid and hexaploid wheat, (ii) the relative abundance of pSp89.XI seemed to decrease from the diploid to the polyploid wheats, and (iii) the existence of a related, but modified B genome in polyploid wheat compared with that in modern T. speltoides was probable. Key words : genome-specific, DNA.     

ANTIVIRAL ACTIVITY OF CULTURED BLUE-GREEN ALGAE (CYANOPHYTA)1

Lipophilic and hydrophilic extracts from approximately 600 strains of cultured cyanophytes, representing some 300 species, were examined for antiviral activity against three pathogenic viruses. Approximately 10% of the cultures produced substances that caused significant reduction in cytopathic effect normally associated with viral infection. The screening program identified the order Chroococcales as commonly producing antiviral agents.     

Seasonal variations in pituitary LH-gonadotropes of the hibernating bat Myotis lucifugus lucifugus: an immunohistochemical study

Pituitary gonadotropes were identified throughout the year in the seasonally breeding, hibernating bat Myotis lucifugus lucifugus by means of light microscopic immunohistochemistry. In both male and female bats, these cells were immunoreactive with an antiserum directed to the beta subunit of luteinizing hormone. Some gonadotropes were aggregated near a portion of the infundibular stalk which crosses the anterior lobe, while most were scattered singly in a uniform manner throughout the rest of the pars distalis. This cell population exhibited seasonal variations in both sexes. In males, the proportional volume of the pars distalis occupied by immunoreactive gonadotropes (volume fraction) was significantly reduced in late July, when plasma testosterone levels were approaching their seasonal peak. In females, the volume fraction declined in April, following ovulation, and remained low during pregnancy and lactation. The size and shape of gonadotropes appeared relatively constant throughout the annual reproductive cycle in male bats; the immunoreactive cells were irregular in shape, with cytoplasmic extensions insinuating between and often "cupping" other secretory cell types. In females, the gonadotropes resembled those of males throughout most of the year, except during pregnancy, when these cells became enlarged and ovoid. No evidence of involution was observed in these anterior pituitary cells in either males or females during hibernation.