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C Desjardins

Publications and source records attributed to C Desjardins.

At least 19 recordsLinked to original sources
PubMed1992

Distribution of somatostatin immunoreactivity in the forebrain of the squirrel monkey: basal ganglia and amygdala.

The distribution of somatostatin immunoreactivity in the basal ganglia and amygdala of the squirrel monkey (Saimiri sciureus) was studied with specific polyclonal antibodies directed against somatostatin-28 and somatostatin-28(1-12). Both antibodies gave similar results with regard to the distribution of somatostatin-immunoreactive neuronal profiles. A moderately dense and highly heterogeneous network of somatostatin-positive fibers was observed throughout the striatum. A dorsoventral gradient of increasing immunoreactivity was noted in the striatum and the caudate nucleus was found to strain generally less intensely than the putamen. The immunoreactive fibers within the striatum were mostly thin and varicose and formed patches corresponding to the striosomes, as visualized on adjacent sections immunostained for calbindin. Although some somatostatin cell bodies rimmed the striosomes, most of the positive cells were rather uniformly scattered in the striatum. These medium-sized cells were significantly smaller in the caudate nucleus (93 microns2, S.D. = 26 microns2) than in the putamen (122 microns2, S.D. = 39 microns2), but their density was significantly higher in the caudate nucleus (29.7 cells/mm2, S.D. = 8.8 cells/mm2) than in the putamen (20.5 cells/mm2, S.D. = 7.0 cells/mm2). The nucleus accumbens stained moderately and positive cell bodies were evenly dispersed throughout this structure. In contrast, the olfactory tubercle displayed a heavily stained neuropil but positive neurons were encountered only in its polymorph layer. In the sublenticular region, dense fiber plexuses appeared in register with nonreactive cell clusters of the nucleus basalis of Meynert and of the nucleus of the anterior commissure. More caudally, a dense bundle of positive fibers was observed at the level of the ansa lenticularis, the inferior thalamic peduncle, and the adjoining bed nucleus of the stria terminalis. Several fibers contributing to this bundle were of the woolly type. Woolly fibers also coursed in the substantia innominata between the ventral aspect of the globus pallidus and the optic tract, and ascended in the internal medullary lamina separating the internal and external segments of the globus pallidus. Somatostatin-immunoreactive cell bodies were uniformly scattered throughout the substantia innominata. The various nuclei of the amygdala showed a wide range of immunoreactivity. The central nucleus was lightly reactive, whereas the intercalated masses displayed a moderate staining. A dorsoventral gradient of immunostaining was noted in the ventrolateral portion of the amygdala, the lateral nucleus being moderately to densely stained and the basal nucleus very lightly to lightly immunoreactive.(ABSTRACT TRUNCATED AT 400 WORDS)

Amygdala↗
PubMed1991

Microvascular pressure distribution in the hamster testis.

Convective transport is a critical element in the regulation of steroidogenesis and spermatogenesis in the testis. Steroid hormones are distributed to their target cells within seminiferous tubules via interstitial fluid. The movement of interstitial fluid and lymph, which transports protein hormones and many of the substrates required for spermatogenesis and steroidogenesis, is driven by capillary filtration. Despite the importance of convective transport in testicular function, however, the mechanisms regulating transvascular exchange in the testis are unknown. As a first step in understanding this process, we measured directly the microvascular hydrostatic pressure distribution in the hamster testis (pentobarbital sodium, 70 mg/kg ip). Using a servo-null transducer, intravascular pressure was measured in all vessel types accessible beneath the surface of the testis of 19 animals. Systemic arterial pressure averaged 89 +/- 2 (SE) mmHg. The most significant observations were that mean capillary pressure was extremely low (10.1 +/- 0.8 mmHg) and remarkably constant (range 8.2-13.3 mmHg), despite a 45 mmHg range in systemic mean arterial pressure among the animals observed. The maintenance of a low hydrostatic pressure in testicular capillaries may serve to sustain fluid filtration at a rate that prevents washout of essential solutes while preserving convective transport. Unfortunately, the anatomical and functional characteristics that determine this unique microvascular environment may also expose the testis to significant pathological risks. For example, the large pre- to postcapillary resistance ratio observed suggests that testicular capillaries must be highly susceptible to increases in venous pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Heparinase treatment suggests a role for the endothelial cell glycocalyx in regulation of capillary hematocrit.

Physiological stimuli induce rapid and unexplained increases in the number of red blood cells within capillaries of skeletal muscle. We hypothesized that such alterations in intracapillary red cell numbers might be due to an undefined interaction between one or more components of blood and the luminal surface of the capillary. This proposition was tested by in situ microperfusion of capillaries with enzymes directed against macromolecules likely to be expressed on the surface of endothelial cells. The instantaneous fractional volume of red blood cells within a capillary (tube hematocrit) was used as an index of a capillary's response to enzyme microperfusion. Five to 8 min of perfusion with enzyme vehicle (0.25% albumin-Ringer solution) produced no significant alteration in capillary tube hematocrit. Perfusion with solutions containing heparinase raised the tube hematocrit at least twofold (P less than 0.05) without a significant change in red cell velocity. Heat-denatured heparinase and other enzymes such as neuraminidase, hyaluronidase, papain, pronase E, and clostripain had no detectable effect on the tube hematocrit (P greater than 0.05). After enzyme treatment, application of adenosine (10(-4) M) or oxygen caused brisk vasomotor responses in arterioles feeding perfused capillary units, but the usual changes in the tube hematocrit were not observed. Thus heparinase treatment results in a sustained elevation in the capillary tube hematocrit and a dissociation of the typical relationship between vasomotor changes and red cell distribution in capillaries. These findings suggest that physiological stimuli which alter the number of red blood cells within capillaries may operate by modifying interactions between plasma and one or more components on the luminal surface of capillaries.

Animals↗
PubMed1979

Rabbit lutropin: preparation, characterization of the hormone, its subunits and radioimmunoassay.

The purification of rabbit lutropin is described. A product with a potency of 1.53 X NIH-LH-Sl was obtained as assayed by the ovarian ascorbic acid depletion assay. In a homologous radioimmunoassay, which is described, rabbit lutropin has a potency 4.83 X NIH-LH-Sl. In a radioligand assay, utilizing labeled ovine lutropin as the trace, the relative potency was 0.47 X NIH-LH-Sl measured by 50% inhibition comparison since rabbit lutropin response in this system did not parallel ovine lutropin. A counter-current distribution procedure for separation of rabbit lutropin subunits is described. Amino acid composition of the isolated subunits and intact rabbit lutropin was determined. The carbohydrate composition of the latter is presented; only amino sugar determinations are available for the subunits. The NH2-terminal amino acids are phenylalanine (alpha subunit) and alanine (beta subunit). Preliminary data on COOH-terminal amino acids are provided.

Amino Acid Sequence↗
PubMed1979

Follicle-stimulating hormone-induced, adenosine 3',5'-monophosphate-mediated movement of immature rat sertoli cells in primary culture.

Sertoli cells dissociated from 10-day-old rat testes form colonies in primary culture in response to FSH. FSH and dibutyryl cAMP stimulated the attachment of Sertoli cells to an equal extent; however, FSH-treated cultures contained a small number of large colonies while dibutyryl cAMP-treated cultures contained a large number of small colonies. This relationship was not altered by the addition of a number of other peptide or steroid hormones. Extracellular cAMP levels and colony density were negatively correlated. Colony size at 24 h of culture was diminished in FSH-treated cultures by the addition of a cAMP antibody at 6 or 12 h of incubation. The addition of cAMP at 24 h to FSH-treated cultures caused a dose-dependent stimulation of colony size but not colony density at 48 h of culture. A point source of cAMP (4 x 10(-3) M in agar) inhibited migration of cells toward the agar spot. An agar spot on the dish substratum containing Sepharose-bound FSH exhibited a halo of cells next to the spot, with a zone lacking cells distal to it. Radioautographs of [125I]iodo-FSH-treated cultures exhibited a nonhomogeneous distribution of silver grains; colony size increased faster than the number of labeled cells. Taken together, the results suggest that 1) FSH is stimulating the attachment of Sertoli cells through an increase in intracellular cAMP, 2) FSH is promoting active aggregation of Sertoli cells in culture through a modulation of extracellular cAMP, and 3) cells with a large amount of bound FSH are acting as centers for aggregation.

Animals↗
PubMed1979

Development of Leydig cell tumors and onset of changes in the reproductive and endocrine systems of aging F344 rats.

The age-dependent onset of spontaneous testicular interstitial cell tumors was examined in F344 male rats. Light microscopy of testes established that nodular interstitial cell hyperplasia was evident in 3 of 5 12-month-old rats and in 5 of 5 rats at 15, 18, 21, and 24 months of age. Involution of the seminiferous epithelium was evident in all testes exhibiting extensive interstitial cell proliferation. Striking increments in serum prolactin and estradiol levels were noted with advancing age, whereas serum levels of follicle-stimulating hormone were unequivocally lower at 21 and 24 months than at 6 months of age. No measurable changes were detected in serum testosterone concentrations between 6 and 18 months of age, but marked increments in this androgen, without any measurable change in circulating luteinizing hormone titers, were apparent in 21- and 24-month-old rats. These findings point to a dynamic relationship between testicular interstitial cell tumorigenesis and age-related changes in the synthesis and/or secretion of gonadal and adenohypophyseal hormones.

Aging↗
PubMed1978

Endocrine regulation of reproductive development and function in the male.

Sexual development is an ordered process that begins at the moment of fertilization and terminates with the production and transfer of viable gametes. The formation of the male gonad depends upon genes located on both sex chromosomes and autosomes. Differentiation and growth of the male reproductive system is directed by the fetal testis through the production of a putative peptide which causes the regression of the Mullerian ducts and the secretion of testosterone which virilizes the Wolffian duct and thereby directs the differentiation of the internal accessory structures of reproduction. A third hormone, dihydrotestosterone, is synthesized intracellularly from testosterone within the urogenital sinus and tubercle. The action of this hormone controls the formation of the prostate and the external genitalia characteristic of the male phenotype. The postnatal growth of the testis and accessory sex tissues follows a characteristic curvilinear pattern with the most prominent increments coincident with the onset in testosterone production. Spermatogonial differentiation may proceed in the absence of hypophyseal or gonadal hormones but the respective maturation divisions of primary and secondary spermatocytes and the completion of spermiogenesis are clearly dependent upon testicular steroids produced under the influence of LH. Germ cells differentiate in a unique environment created, in part, by the blood testis barrier which arises as a result of tight-junctional complexes formed between adjacent Sertoli cells. Sertoli cells actively secrete fluids and export an androgen binding protein under the influence of androgens and FSH. Maintenance of spermatogenesis depends on high intratubular concentrations of testosterone, provided in part by the steroidogenic actions of LH on the Leydig cell and, in part, by the production of androgen binding protein by the Sertoli cell. Thus, both gonadotropins act in concert to maintain germ cell production. Selective removal of either LH or FSH curtails sperm production but testosterone supplementation, in adequate amounts, allows spermatogenesis to proceed in the absence of the pituitary gland.

Androgens↗
PubMed1977

Dominant-subordinate relationships in castrated male mice bearing testosterone implants.

This study tested the hypothesis that subordination in male mice is directly related to reduced levels of circulating testosterone. Several measures of aggressiveness and submissiveness were quantified during or after daily encounters between pairs of intact males, castrated males, or castrated males bearing testosterone implants that were designed to maintain plasma testosterone titers at levels slightly above those of intact males. Behavioral measures included the total amount of fighting that resulted from daily pairing, the tendency for subordinates to fight back, and the relative frequency of urine marking. In all these regards, pairs of testosterone-implanted, castrated males formed dominant-subordinate relationships that involved apparently normal submissive behavior (compared to intact control pairs). Thus we found no evidence that submissive behavior was directly related to a reduction in circulating testosterone titers.

Animals↗
PubMed1977

Reproductive failure in aged CBF1 male mice: interrelationships between pituitary gonadotropic hormones, testicular function, and mating success.

Circulating pituitary gonadotropins and testicular function were examined in aged CBF1 male mice using two experimental designs: a) a longitudinal analysis of 2 to 30-month-old males, and b) a direct comparison of weight-matched, sexually-active vs. sexually-inactive 24-month-old males, all of whom were relatively robust. Measurements included serum concentrations of testosterone, follicle stimulating hormone, and luteinizing hormone, gonadotropic responsiveness to castration, success in a 4-day mating test, testicular sperm content, and reproductive organ weights. The longitudinal analysis showed progressive losses in mating success and sperm production between 18 and 30 months, changes which were correlated with decreased levels of serum LH and testosterone but not with FSH. The direct comparison of robust, sexually-active vs.-inactive males provided a better design for identifying reproductive-specific effects of aging, as opposed to debilitative changes that are general to several supporting systems. Such comparisons in 24-month-old CBF1 males suggest the existence of a subpopulation of mice in which reproductive failure is specifically correlated with a loss in the episodic release of LH.

Aging↗
PubMed1977

Response of plasma corticosteroids and circulating leukocytes in cattle following intravenous injection of different doses of adrenocorticotropin.

The relationships among exogenous adrenocorticotropin (ACTH), plasma corticosteroids, and circulating leukocytes were studied in 7 lactating cows. Blood samples were obtained from jugular cannulas at -2, -1, and 0 hours before ACTH was injected (base line) and 0.25, 0.50, 1, 2, 3, 6, and 24 hours after injection. Plasma corticosteroids were increased progressively by injecting doses of ACTH between 1 and 200 IU. Plasma corticosteroids reached peak concentrations between 15 and 30 minutes and returned to base line within 1 to 3 hours after 1, 5, and 10 IU doses of ACTH were injected, but required as long as 6 hours after injection of 100 and 200 IU. Base line counts of circulating leukocytes averaged 7.3 X 10(3) cells/mm3 and remained unchanged after injecting 0 and 1 IU of ACTH (P less than 0.05). Significant dose-dependent increases in circulating leukocytes were detected within 2 hours after administering 5, 10, and 100 IU of ACTH. Responses to 100 and 200 IU were similar. The average concentration of leukocytes increased up to 6 hours after ACTH administration and returned to base line values within 12 to 24 hours in cows injected with 5 and 10 IU, but not until 48 hours in cows injected with 100 and 200 IU of ACTH. In contrast to the delayed and sustained responses observed for leukocytes, corticosteroid responses were rapid and transient. Moreover, the administration of 200 IU of ACTH was considered to increase circulating corticosteroids and leukocytes beyond that found in dairy cattle exposed to stress associated with overmilking, acute coliform mastitis, or parturition.

Adrenal Cortex Hormones↗