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Biomedical subjects

B L Baker

Publications and source records attributed to B L Baker.

At least 73 records · Page 4Linked to original sources
PubMed1977

Immunohistochemical localization of gonadotropin-releasing hormone (GnRH) in the fetal and early postnatal mouse brain.

The objectives were to (a) determine the age in development when GnRH is first detectable in the brain and (b) observe the distribution of GnRH throughout the fetal and early postnatal period. GnRH was localized immunohistochemically in fetal (15, 16, 17 and 19 days of gestation) and early postnatal (1- and 7-day-old) mice with the peroxidase-antiperoxidase (PAP) method of Sternberger. In the organum vasculosum of the lamina terminalis (OVLT) and in the median eminence of the fetus, GnRH was first detected at 17 days of gestation. In the OVLT, GnRH was found ventral to the preoptic recess of the third ventricle near the ventral surface of the brain. In addition, GnRH was located adjacent to the superficial portal capillaries near the surface of the median eminence. At 19 days of gestation, the distribution of GnRH was similar to that observed at 17 days and there was a marked increase in amount. In the newborn mouse, GnRH was undetectable in the OVLT and its content in the median eminence was decreased as compared to that observed in the fetus. By the seventh postnatal day, a considerable accumulation of GnRH had occurred in the OVLT and median eminence. In the OVLT, it was associated with capillaries ventral to the preoptic recess, and its distribution in the median eminence was similar to that in the adult mouse. In both the OVLT and median eminence of the fetal and early postnatal mouse GnRH appeared to be stored in axons and axon endings, but was not detectable in nerve cell bodies or ependymal cells. These observations suggest that the potential for neuroendocrine control of gonadotropin secretion exists in the fetal mouse early as 17 days of gestation.

Age Factors↗
PubMed1977

An immunocytochemical study of human pituitary mammotropes from fetal life to old age.

The objectives were to (a) describe the cytology and distribution of mammotropes in the human pituitary gland, (b) determine whether the mammotrope is a distinctive secretory cell type and (c) ascertain when it first appears in the fetal hypophysis. Identification of mammotropes was based primarily on the Sternberger peroxidase-antiperoxidase immunocytochemical method used with an antiserum to human prolactin. Hypophyses from 25 male and 6 female adults, and 21 fetuses ranging in gestational age from 6 to 23 weeks were studied. In the adult two morphological forms of mammotropes were observed. Mammotrope I possessed a small perikaryon that commonly was located centrally in parenchymal cell cords. From the perikaryon long cytoplasmic processes extended toward neighboring capillaries. Mammotrope I reached its highest incidence in the posterolateral zones of the pars distalis. Mammotrope II possessed a larger perikaryon with short processes; cells of this form were fewer and occurred chiefly in the anteromedian zone. Mammotropes with intermediate morphological features that prevented classification into categories I or II were common in some hypophyses. Both forms of mammotropes were present prepuberally (one 6-week and one 9-year-old male) and in adult males and females. Mammotropes were only slightly more prominent in females than males. Regression of mammotropes was evident in old age. Mammotropes were distinctly different from somatotropes, corticotropes, gonadotropes and thyrotropes. In the fetal hypophysis mammotropes appeared first at 14 weeks of gestational age and remaind few through 16.5 weeks. Their number increased greatly at 23 weeks.

Adolescent↗
PubMed1976

Distribution of growth hormone-release-inhibiting hormone (somatostatin) in the rat brain as observed with immunocytochemistry.

The objective was to determine the distribution of growth hormone-release-inhibiting hormone (somatostatin) in the rat brain using the peroxidase-antiperoxidase immunocytochemical method with antisera prepared against unconjugated, synthetic somatostatin. Somatostatin occurred in low quantity in the organum vasculosum of the lamina terminalis. It was present throughout the full length of the median eminence and occupied the entire width between the tuberoinfundibular sulci. Most somatostatin was located in the dorsal portion of the external lamina, and the amount varied according to the mediolateral position. The bodies labeled for somatostatin were most often granules; occasionally they appeared as clusters of granules that seemed to be membrane-enclosed. Some of these bodies appeared to be portions of axons. Many of the larger bodies were arranged alongside tanycytes, but no label was distributed generally in tanycyte cytoplasm. Somatostatin was highly concentrated in the proximal one-quarter of the infundibular stem and appeared in lower concentration throughout the distal portion of the stem. It was absent from the pars nervosa and pars intermedia of the pituitary gland. The distribution of somatostatin in the median eminence differed considerably from that of gonadotropin-releasing hormone. Somatostatin was identified in the ventromedial and/or dorsomedial hypothalamic nuclei of only two animals. Here it was probably located in axons that terminated on neuronal cell bodies but also may have been present in a restricted portion of the perikaryonal cytoplasm.

Animals↗
PubMed1976

Effect of hypophysectomy on immunocytochemically demonstrated gonadotropin-releasing hormone in the rat brain.

The objective was to determine the effect of hypophysectomy on the store of gonadotropin-releasing hormone (GnRH) in certain parts of the brain as revealed by immunocytochemistry. The antiserum used was prepared against synthetic GnRH conjugated with limpet hemocyanin. No change was observed in the store of GnRH in the organum vasculosum of the lamina terminalis or in the cephalic segment of the median eminence GnRH was depleted severely from the central and caudal (junction with the infundibular stem) segments of the median eminence. GnRH was not found in the axons of magnocellular neurons that regenerate during repair of the median eminence-pituitary stalk after hypophysectomy.

Animals↗
PubMed1976

Hypercupremia associated with a monoclonal immunoglobulin.

Although copper is an essential constituent of many physiologic systems, most human diseases effect minimal changes in copper homeostasis. Therefore, the association of marked hypercupremia with copper deposition in the ocular media and with a circulating immunoglobulin G in an apparently healthy woman prompted our interest. Balance and radioisotopic studies suggest a normal gastrointestinal and renal threshold for copper but a specific and tight binding between the serum copper and the anomalous protein, the probable result of a preclinical myeloma. Because the response of the hypercupremia to chelation therapy was limited, the multiple myeloma was treated with cytoxic drugs.

Adult↗
PubMed1975

The genesis of cell types in the adenohypophysis of the human fetus as observed with immunocytochemistry.

Hypophyses of 21 human fetuses, ranging in gestational age from 6 to 23 weeks, were studied by immunocytochemical and histological staining to ascertain (1) the time of origin of specific cell types and (2) the development of parenchymal cell zonation in the pars distalis. No hormones were identified at six weeks. Probable corticotrophin-containing cells appeared at seven weeks. Somatotrophs were observed first at 10.5 weeks; correlation with other reports indicates that they appear at eight to nine weeks. Melanotrophs were detected at 14 weeks; the cells containing melanotrophin were far fewer than corticotrophs. The youngest fetus to possess gonadotrophs was 10.5 weeks old. In all specimens gonadotrophs (LH-cells) stained well with immunocytochemical procedures but poorly with histological methods. Thyrotrophs first occurred at 13 weeks. Zonal distribution of cell types in the pars distalis was evident almost from the time of their appearance. Somatotrophs were most numerous laterally and immediately anterior to the residual cleft. At 10.5 weeks corticotrophs were confined chiefly to the borders of vascularized connective tissue (trabeculae) and to the lateral peripheral region of the pars distalis. Thyrotrophs appeared chiefly in the anteromedian zone, particularly in its superior portion, but were found laterally also. In the older specimens, gonadotrophs generally occurred throughout the pars distalis but were less numerous near the trabeculae and in the anterolateral region. There was good correlation between the time of appearance of various cell types and published data on secretory capacity of the gland.

Adrenocorticotropic Hormone↗
PubMed1975

Immunocytochemical analysis of cells in the pars tuberalis of the rat hypophysis with antisera to hormones of the pars distalis.

The objective was to acquire evidence regarding the secretory capacity of cells in the pars tuberalis of the rat pituitary by the application of immunocytochemical staining. For this purpose the conjugated antibody and immunoglobulin-enzyme bridge techniques were utilized with antisera to the following hormones of the pars distalis: human somatotropin, human thyrotropin, human beta-melanotropin, ovine luteinizing hormone (LH), porcine beta17-39-corticotropin, and beta1-24-corticotropin. Only LH-containing cells were demonstrated. They were exceedingly rare in the cephalic pars tuberalis beneath the median eminence. The frequency of LH-cells was greater in the pars tuberalis associated with the infundibulum and increased distally. LH-cells were most common ventrolateral to the infundibular stem and occurred singly and in clusters. These results indicate that following hypophysectomy the portion of the pars tuberalis that remains in situ has the capacity to secrete only LH of all the pars distalis hormones.

Animals↗
PubMed1975

Distribution of gonadotropin-releasing hormone in the rat brain as observed with immunocytochemistry.

The distribution of gonadotropin-releasing hormone (GnRH) was studied in the brain of adult female rats with three immunocytochemical techniques using antisera to unconjugated synthetic GnRH and to GnRH conjugated with limpet hemocyanin. GnRH was found in nervous tissue surrounding blood vessels of the organum vasculosum of the lamina terminalis. In the median eminence it occurred in nervous tissue associated primarily with the tuberoinfundibular sulci throughout their extent. Cephalic to the pars tuberalis GnRH often spread across the median eminence from sulcus to sulcus. Caudally, with widening of the median eminence, GnRH occurred dorsal to the tuberoinfundibular sulci, and especially in the external lamina medial to the sulci. A broad median zone of the median eminence was rather free of GnRH. GnRH was most concentrated in the region of continuity between the dorsolateral walls of the infundibulum and floor of the third ventricle where the tuberoinfundibular sulci are deep. Caudal to the infundibulum GnRH was disposed in a flat zone through the cephalic portion of the floor of the mammillary recess. In the median eminence GnRH appeared to be located in axons that terminated there. The amount of demonstrable GnRH varied significantly from rat to rat. The distributions of GnRH as revealed by use of antisera to unconjugated and conjugated GnRH were essentially the same. The apparent order of sensitivity of the immunocytochemical methods was: the peroxidase-antiperoxidase (PAP) (Sternberger et al.) procedure greater than the immunoglobulin-enzyme bridge (Mason et al.) procedure smaller than the conjugated antibody (Nakane and Pierce) procedure.

Animals↗