Biomedical subjects
S Sepsenwol
Publications and source records attributed to S Sepsenwol.
In vitro induction of crawling in the amoeboid sperm of the nematode parasite, Ascaris suum.
In a highly synchronous process, the immotile spermatids of Ascaris suum extend pseudopods and become rapidly crawling sperm when treated with an extract from the glandular vas deferens of the male under strict anaerobic conditions. Within 9-12 min, a pseudopod develops, elongates rapidly, and exhibits a continuous flow of membrane specializations, the villipodia, from tip toward base. When attached to acid-washed glass, the pseudopod pulls the cell body along at speeds exceeding 70 microns/min. The pseudopod length remains constant while retrograde flow of villipodia proceeds at the same rate as the sperm's forward movement. Cohorts of about 15 villipodia form at the leading edge, move rearward together, and disappear at the junction of pseudopod and cell body. These are the terminations of branched, refringent fibers, which extend the length of the pseudopod. The latter are the fiber complexes that form its cytoskeleton (Sepsenwol et al.: Journal of Cell Biology 108:55-66, 1989). Locomoting cells sometimes change direction when another crawls by and follow each other. When cells are exposed to air, forward movement ceases in a predictable pattern: the forward extension of the leading edge ceases, the pseudopod shortens from the base, and the cell body continues to be pulled forward. These data contribute to a model for Ascaris sperm amoeboid motility in which independent processes of continuous extension at the leading edge and continuous shortening at the base of the pseudopod act to propel the cell forward.
A unique cytoskeleton associated with crawling in the amoeboid sperm of the nematode, Ascaris suum.
Nematode sperm extend pseudopods and pull themselves over substrates. They lack an axoneme or the actin and myosins of other types of motile cells, but their pseudopods contain abundant major sperm protein (MSP), a family of 14-kD polypeptides found exclusively in male gametes. Using high voltage electron microscopy, a unique cytoskeleton was discovered in the pseudopod of in vitro-activated, crawling sperm of the pig intestinal nematode Ascaris suum. It consists of 5-10-nm fuzzy fibers organized into 150-250-nm-thick fiber complexes, which connect to each of the moving pseudopodial membrane projections, villipodia, which in turn make contact with the substrate. Individual fibers in a complex splay out radially from its axis in all directions. The centripetal ends intercalate with fibers from other complexes or terminate in a thickened layer just beneath the pseudopod membrane. Monoclonal antibodies directed against MSP heavily label the fiber complexes as well as individual pseudopodial filaments throughout their length. This represents the first evidence that MSP may be the major filament protein in the Ascaris sperm cytoskeleton. The large fiber complexes can be seen clearly in the pseudopods of live, crawling sperm by computer-enhanced video, differential-interference contrast microscopy, forming with the villipodia at the leading edge of the sperm pseudopod. Even before the pseudopod attaches, the entire cytoskeleton and villipodia move continuously rearwards in unison toward the cell body. During crawling, complexes and villipodia in the pseudopod recede at the same speed as the spermatozoon moves forward, both disappearing at the pseudopod-cell body junction. Sections at this region of high membrane turnover reveal a band of densely packed smooth vesicles with round and tubular profiles, some of which are associated with the pseudopod plasma membrane. The exceptional anatomy, biochemistry, and phenomenology of Ascaris sperm locomotion permit direct study of the involvement of the cytoskeleton in amoeboid motility.
Four-dimensional microscopy of Ascaris sperm motility.
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Adenylate cyclase activity is absent in inactive and motile sperm in the nematode parasite, Ascaris suum.
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FSH and testosterone effects in seminiferous tubules of immature hypophysectomized rats.
The effects of follicle-stimulating hormone (FSH) and testosterone on the development of the cytosolic germ cell adenylate cyclase and germ cell morphology in rats hypophysectomized at 29 days of age were studied. Following hypophysectomy, the adenylate cyclase content fell to marginal levels and germ cell development ceased at the late pachytene stage. Testosterone treatment led to a moderate increase in the cytosolic enzyme content and to progression of spermatid cell development to stages 8-12. FSH treatment with doses of 80-100 micrograms/day restored enzyme content to levels seen in control rats, as well as progression of germ cell development up to stages 15-16, i.e., to the same stages present in age-matched control (sham-operated) rats. The results indicate that in immature rats FSH is essential for spermatid cell maturation as is evidenced by its ability to stimulate the formation of cytosolic germ cell adenylate cyclase to quantitatively normal levels, as well as to stimulate the development of spermatid cells.
Sperm tail axoneme alterations in the Wobbler mouse.
In Wobbler mice (neurological mutants affected with progressive motor neurone degenerative disease) a defect in sperm tail mobility and axonemal geometry was observed. Similar but less extensive abnormalities were seen in the ciliary axonemes of the ductuli efferentes.
Mn2+-sensitive, soluble adenylate cyclase in rat testis. Differentiation from other testicular nucleotide cyclases.
In subcellular fractions prepared from homogenate of adult rat testis adenylate cyclase (ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1) activity was found in the particulate, primarily 600 X g for 10 min, fractions, as well as in the cytosol. The properties of the adenylate cyclase in the cytosol differs substantially from the adenylate cyclase system associated with the 600 X g for 10 min particulate fraction. The cytosol enzyme, in contrast to the particulate adenylate cyclase, was found to be fluoride- and gonadotropin hormone-insensitive. The cytosol adenylate cyclase appears to be located in the germ cell while the particulate enzyme system in the non-germ cell component of the seminiferous tubules, The cytosol adenylate cyclase was found to be distinct also from the guanylate cyclase present in the rat testis cytosol. The adenylate cyclase appears to be located in the germ cell component while the guanylate cyclase, in the non-germ cell tubular component. Furthermore, it was found that the cytosol guanylate cyclase develops at an earlier stage of spermatogenesis, and precedes the development of the cytosol adenylate cyclase.
Failure to observe testosterone-induced nucleus-lysosome interaction in rat ventral prostate.
The possibility that sex steroids act to promote the association of lysosomes with nuclei was studied by 2 methods in the secretory epithelium of ventral prostate of castrated rats treated with androgens: (a) electron microscopic (EM) examination of intact tissue and (b) study of fresh nuclear suspensions isolated from prostate homogenates using the fluorescing dye acridine orange (AO) and EM. AO-stained particles in nuclear suspensions were found to correspond to either (i) section granules, (ii) primary lysosomes or (iii) heterogenous dense bodies (HDB), considered to be lysosomes. Intact prostate tissue and crude nuclear suspensions were studied in adult rats 3-21 days after castration and in normal rats. Changes in nuclear architecture are evident 8 days or more after castration; the number of HDB increase while secretion granules and primary lysosomes decrease. Whether from prostate of castrated, normal or hormone-treated animals, a small number of the lysosomal HDB or primary lysosomes are seen closely apposed to epithelial cell nuclei. In response to short-term testosterone administration (15 or 60 min) in 10- and 21-day castrate rats, chromatin distribution appears to become more condensed; yet the number of associations of nuclei with lysosomal elements does not change. These studies of androgen action in rat ventral prostate (a classical target organ for the study of androgen action) provide no evidence to support the idea that lysosomal association with, or invasion of, nuclei in target cells is a general feature of sex steroid hormone action.
LH- and FSH-stimulating of adenylate cyclase in seminiferous tubules from young rats: functional FSH and LH receptors unmasked by homogenization.
LH- and FSH-sensitive adenylate cyclase activity was present in homogenates of whole testis tissue as well as in microdissected seminiferous tubules derived from young rats. In homogenates of seminiferous tubules a single adenylate cyclase appears to interact with both LH and FSH through separate hormone-specific receptors. Disruption of testis tissue by homogenization exposes functional FSH and LH receptors which are inaccessible to the hormones in intact cell preparations. These results indicate that in certain seminiferous tubule cell types only a fraction of the total functional receptors present is accessible to the cell surface for interaction with hormone.
Stimulation of 14C-cyclic AMP accumulation by FSH and LH in testis from mature and immature rats.
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Leucoplast of the cryptomonad Chilomonas paramecium. Evidence for presence of a true plastid in a colorless flagellate.
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