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W B Neaves

Publications and source records attributed to W B Neaves.

At least 19 recordsLinked to original sources
PubMed1979

The annual testicular cycle in an equatorial colony of lesser rock hyrax, Heterohyrax brucei.

Adult males from a colony of lesser rock hyrax found near the equator in Kenya exhibited an annual cycle of testicular activity characterized by intense spermatogenesis and elevated androgen status from May to July. Average masses of testes and seminal vesicles taken in these months were almost fourfold greater than those from September to January. During the months of peak testicular activity average diameters of Leydig cells and seminiferous tubules were increased by approximately one half and total tubule length was doubled, compared with values for the quiescent months. Variable testicular development occurred during transitional intervals preceding and following peak testicular activity. From February to Aril thickening of the seminiferous epithelium and appearance of spermatozoa in the caput epididymidis signalled re-establishment of sperm production. In August shedding of germinal cells from the epithelium heralded impending failure of spermatogenesis. Evidence of an annual testicular cycle contradicted the prevalent belief that equatorial hyrax breed all year and suggested that the testicular cycle is a conservative element of hyracoid reproductive strategy.

Animals↗
PubMed1979

The lymphatic drainage of the rat prostate and its status as an immunologically privileged site.

Recent suggestions that the rat prostate is an alymphatic, immunologically privileged site stimulated further investigation of its status using a variety of techniques. Fixation of certain organs by vascular perfusion of glutaraldehyde followed by plastic embedding avoids the distortion and stromal reorganization that often obscures evidence of lymphatic vessels in conventional histological preparations. When applied to the rat prostate, this technique revealed small lymphatic vessels at irregular intervals throughout the sparse stroma. Ink injected into the prostate drained from the organ into iliac lymph nodes within 3 to 4 hr. Enlargement of iliac lymph nodes within 1 week after injection of parental strain lymphoid cells into the prostate of F1 rats confirmed the drainage pattern. Ink and lymphoid cell injections into the bladder wall yielded comparable results, although ink reached iliac nodes sooner than it did in prostate injections. Immunological privilege was investigated by determining survival of skin allografts implanted in the prostate. Skin-into-prostate grafts bearing either major or minor histocompatibility antigens were rejected within a few days of similar orthotopic grafts. The inability of the rat prostate to allow significantly prolonged allograft survival as well as its demonstrated lymphatic drainage argues against an immunologically privileged status.

Animals↗
PubMed1978

Attrition of the human Leydig cell population with advancing age.

Existing evidence suggests that the aging human male experiences a gradual decline in testosterone production, a phenomenon that should be reflected in the Leydig cell population of the testis. It has been proposed that Leydig cells diminish in number with increasing age, but conflicting claims characterize reports of this topic. We have reinvestigated this possibility by histometric analysis of perfused testes from 25 men ranging from 18 to 87 years of age. Average single Leydig cell volume (2,943 +/- 623 micrometer 3, X +/- S.D.) did not change significantly with increasing age (r = 0.24, P greater than 0.2), suggesting that surviving cells remain active. Total testis weight (43.5 +/- 13.9 g) also did not change with age (r = 0.04, P greater than 0.5). However, both total Leydig cell volume and the absolute number of Leydig cells per individual decreased significantly as functions of age (r = -0.71, P less than 0.002, and r = -0.61, P less than 0.005, respectively). Analysis of relationship between these two parameters indicates that the total volume of Leydig cell cytoplasm contained within the human testis is determined by the number of cells present. Our results show that a pair of young adult testes endowed with more than 700 million Leydig cells at 20 years of age may be expected to undergo an attrition rate of approximately 80 million cells per subsequent decade of life. Thus, Leydig cell attrition is an important correlate of declining androgen status in aging men.

Adolescent↗
PubMed1978

Clinical and endocrinological evaluation of patients with congenital microphallus.

Eight patients with congenital microphallus were investigated. Plasma luteinizing hormone, follicle-stimulating hormone, testosterone and androstenedione levels were obtained in all cases. In addition, the response to the administration of human chorionic gonadotropin, luteinizing horomone-releasing hormone and adrenocorticotropic hormone, the assessment of testicular histology by electron microscopy and the measurement of dihydrotestosterone formation by preputial skin were determined in some patients. The results of these studies were compared to similar studies in 6 normal prepubertal boys, 4 boys with bilateral cryptorchidism, 1 male infant with anorchia and 1 adult with hypogonadotropic hypogonadism. The clinical and endocrinological findings in the 8 patients with microphallus can be divided into 2 distinct categories. In 5 patients the disorder is familial, gonadotropin levels are low and there is a normal response to stimulation with chorionic gonadotropin. The data are compatible with the possibility that 3 (possibly 5) of the 8 patients with microphallus have hypogonadotropic hypogonadism. In the other group the cases are sporadic, serum luteinizing hormone and follicle-stimulating hormone levels are elevated and plasma testosterone failed to increase after short-term treatment with chorionic gonadotropin. In these patients a primary testicular disorder appears to be responsible. Experimental and clinical evidence suggests that microphallus results from defective testicular function during the second and third trimesters of pregnancy, either as the result of defective gonadotropin secretion or defective androgen synthesis.

Adolescent↗
PubMed1978

Studies on the subsynaptosomal localization of luteinizing hormone-releasing hormone and thyrotropin-releasing hormone in the rat hypothalamus.

In the current investigation, subcellular particles (synaptosomes) of hypothalamic homogenates were isolated by differential centrifugation and discontinuous sucrose density gradient fractionation and found to be rich in LHRH, TRH, and the neuronal marker, norepinephrine (NE). Of the total quantity of LHRH, TRH, or NE in the nuclei-free homogenate, 52-65% was recovered in synaptosomes, whereas the cytosol, myelin/microsomes, and mitochondria contained only 1-12%. To determine the subsynaptosomal localization of LHRH and TRH, purified synaptosomes were lysed and the resulting suspensions were fractionated on discontinuous sucrose density gradients. LHRH (30-40%) was found to be localized primarily in subsynaptosomal particles which banded at sucrose densities between 0.6-1.0 M. Electron micorscopic analysis of these particles revealed the presence of dense-cored granules (70-80 nm diameter) and synaptosomal membrane remnants. Norepinephrine was found in two pools within the isolated nerve endings: 15-25% of synaptosomal NE was associated with the synaptic vesicles (45-55-nm diameter); about 40% was in the cytosol. TRH was present primarily as a soluble component of the nerve ending. No apparent association of TRH with dense-cored granules was demonstrable in this study; however, there may be some TRH in synaptic vesicles.

Animals↗
PubMed1978

The effect of vasectomy on the testes of inbred Lewis rats.

By 3 months after surgery, testicular weights were 12-14% below control values in a large series of vasectomized rats of the inbred Lewis strain. Testicular sperm concentrations in the vasectomized rats were 25-29% below those in the sham-operated animals. Although modest in magnitude, these differences were highly significant (P less than 0.001). Histometric analysis of testes from a smaller series of vasectomized Lewis rats revealed various proportions of abnormal seminiferous tubules. The degenerative changes included reduction in tubule diameter, fusion of spermatids, and depletion of advanced germinal elements. In the most severely affected tubules, leakiness of the blood-testis barrier was indicated by penetration of lanthanum through Sertoli-cell tight junctions.

Animals↗
PubMed1977

Ontogeny of the subcellular compartmentalization of thyrotropin releasing hormone and luteinizing hormone releasing hormone in the rat hypothalamus.

The 900 x g supernatant fluid prepared from hypothalamic homogenates from male and female rats (ranging in age from -1 to 120 days) was fractionated by means of continuous sucrose density gradient centrifugation. Thyrotropin releasing hormone (TRH) and LH releasing hormone (LHRH) in the gradient fractions were quantified by radioimmunoassay. In adult hypothalamic homogenates, TRH and LHRH were associated with two populations of particles distinguishable by their sedimentation properties. Each peptide was in turn distributed in two subpopulations of parties differing in size but similar in density. The distribution of each peptide within its subpopulations of particles was found to be a function of age. In hypothalami of 22-day-old fetuses, TRH was associated almost entirely with the subpopulation of small particles. However, in the neonates, an age-dependent increase in the fractional amount of the TRH confined to the subpopulation of large particles was observed. By the 7th day of age, the peptide was equally distributed in the two subpopulations. The buoyant density of the 1-day-old neonatal particles and that of the adult small and large particles containing TRH was similar. The ontogeny of the subcellular compartmentalization of LHRH differed appreciably from that of TRH. LHRH was barely detectable in hypothalami of 22-day-old neonates. Nevertheless, at this age, the peptide was confined primarily to the subpopulation of large particles, and a similar compartmentalization was noted in hypothalami of 5- and 7-day-old neonates. However, in hypothalami of 14-day-old males and 21-day-old females, association of LHRH with the subpopulation of small particles was evident. It is concluded that 1) the nature of the hypothalamic subcellular compartmentalization of TRH and LHRH is age dependent, 2) the compartmentalization of each peptide in neonatal hypothalami differs from that in the adults, and 3) the development of the mature profile of subcellular compartmentalization of TRH and LHRH proceeds asynchronously.

Aging↗
PubMed1976

Structural characterization and rapid manual isolation of a reptilian testicular tunic rich in Leydig cells.

During the annual breeding season, the testes of the lizard Cnemidophorus gularis are yellow-orange, oviod organs measuring almost 1 cm in greatest diameter. The pigment is confined to the testicular tunic, which contains a zone of Leydig cells and vascular channels more than 50 mu thick. Leydig cells constitute approximately 60% of the zone, with remaining space occupied by capillaries, sinusoids, and lymphatic vessels. Lymphatics are concentrated at the interface between tunic and seminiferous tubules. Interstitial space is poorly developed among the tubules, accounting for less than 3% of tissue volume. Capillaries, lymphatics, and few widely scattering Leydig cells occur in the sparse interstitial space. Leydig cells in the tunic and elsewhere in the testis show ultrastructural features commonly found in mammalian Leydig cells. Separation of the tunic from the seminiferous tubules is achieved in a few seconds by manual decapsulation of the testis and yields an enriched preparation of Leydig cells that is essentially uncontaminated by tubular elements.

Animals↗
PubMed1975

Leydig cells.

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Animals↗