PubMed Health⌕ Search

Biomedical subjects

J A Kappers

Publications and source records attributed to J A Kappers.

18 recordsLinked to original sources
PubMed1978

Localization of indoleamine and protein synthesis in the mammalian pineal gland.

In a table, conditions and compounds have been listed either known or suggested to influence pineal function. In the same model, systems and organs and their products are indicated the function or, respectively, the quantity of which are known or suggested to be influenced by pineal secretory substances. Of the latter, indoleamines and polypeptides are mentioned only although it is now known that also other low molecular weight biologically active compounds are produced by the gland. Problems relating to the localization of indoleamine and protein synthesis in the pinealocyte are discussed. The synthesis of indoleamines, at least of serotonin, may occur freely in the cytosol although, especially in non-mammals, the presence of serotonin seems to be preferentially, but perhaps secondarily, related to the secretory dense-core vesicles. Questions concerning the exact function of pineal melatonin are shortly dealt with. The granules of the secretory vesicles probably also contain a proteinaceous substance which, notwithstanding its unknown chemical nature, has been considered the antigonadotropic principle by some authors. Recent investigations on the production of active proteinaceous compounds in cisterns of the endoplasmic reticulum and between the layers of the nuclear envelope are reviewed. These substances are not concentrated in secretory granular vesicles, so scarce in the pinealocyte which proteinaceous active principle is produced in still largely unsolved as is their exact chemical composition.

Animals↗
PubMed1977

The pineal gland of nocturnal mammals. I. The pinealocytes of the bat (Nyctalus noctula, Schreber).

The ultrastructure of the pinealocytes of noctule bats, mammals which live most of the time in darkness or very low light intensities, was examined and compared with the pinealocytes of other mammals. Two different populations of pinealocytes (I and II) were observed. They differ in general aspect, in location and especially in their content of cell organelles involved in synthetic processes. Mitochondria, ribosomes, lysosomes and lipid inclusions were present in the perikaryon of pinealocytes of both populations. In the pinealocytes of population I some granular vesicles, of presumed Golgi origin, and some other structures were observed. Pinealocytes of population II are characterized by many glycogen granules, more or less associated with a large vacuolar system. Moreover, some small vacuoles originating from cisterns of the granular endoplasmic reticulum and containing flocculent material of a moderate electron density are described. The possibility is discussed that these small vacuoles are involved in one of the secretory processes of the pineal gland while the granular vesicles of the pinealocyte of the population I are the products of another.

Animals↗
PubMed1976

The pineal gland of the mole-rat (Spalax ehrenbergi, Nehring). I. The fine structure of pinealocytes.

The ultrastructure of pinealocytes of the mole-rat (Spalax ehrenbergi), a blind subterranean mammal living in complete darkness, was examined and compared with pinealocytes of other mammals. Two different populations of pinealocytes (I and II) were observed. They differed in general aspect. In location and especially in their content of cell organelles involved in synthetic processes. Mitochondria, ribosomes, granular endoplasmic reticulum, lysosomes, lipid inclusions and glycogen granules were present in the perikarya of pinealocytes of both populations. In the pinealocyte of population I some granular vesicles were occasionally observed in the cell body. Their presumed origin from the Golgi apparatus could not be clearly demonstrated. In the perikaryon of this pinealocyte, concentrations of ribosomes and of cisternae of the granular endoplasmic reticulum were constantly observed. These concentrations may indicate an intensive synthetic activity. Pinealocytes of population II were characterized by accumulations of proteinaceous material in some cisternae of the granular endoplasmic reticulum and between the two layers of the nuclear membrane. The origin of these peculiar elements is discussed.

Animals↗
PubMed1976

The pineal gland of the mole (Talpa europaea L.) III. A fluorescence histochemical study.

The pineal gland of the mole, a mammal which lives in permanent darkness, has been studied using fluorescence histochemistry. An extensive catecholaminergic innervation is demonstrated. A yellow formaldehyde-induced fluorescence, characteristic of indoleamines, was not observed. If formaldehyde vapour treatment was omitted in the procedure, numerous cells containing yellow-orange autofluorescent material could be shown. The nature and possible function of this material is discussed.

Animals↗
PubMed1975

Effect of pinealectomy, gonadectomy, pCPA and pineal extracts on the rat parvocellular neurosecretory hypothalamic system; a fluorescence histochemical investigation.

Using the fluorescence histochemical technique, yellow autofluorescent granules were observed in neurones of the arcuate and ventromedial hypothalamic nuclei of the rat (type I cells). In the same nuclei, neurones could be demonstrated showing a formaldehyde-induced yellow fluorescence (type II cells). Microelectrophoresis and special staining methods applied to the pineal gland revealed the autofluorescent compound to be a protein containing a relatively high content of tryptophan. It is probable that the formaldehyde-induced yellow fluorescence is due to the presence of serotonin. In view of investigating a possible functional relationship between the pineal gland and the parvocellular hypothalamic nuclei mentioned, hypothalamic type I and type II cells, as well as autofluorescent and serotonin-containing pinealocytes, if present, were quantified under the following experimental conditions: (1) p-chlorophenylalanine (pCPA) administration, (2) castration, (3) pinealectomy, and (4) pinealectomy followed by substitution using rat and sheep pineal extract. Administration of pCPA caused a decrease in the number of type II and an increase in the number of type I cells, both in the pineal gland and the hypothalamic nuclei. Castration, in contrast, was followed by an increase in the number of autofluorescent pinealocytes, but a decrease of autofluorescent neurones in the hypothalamic nuclei (type I cells) while the number of serotonin-containing pinealocytes increased; decreasing in both hypothalamic nuclei. After pinealectomy the hypothalamic nuclei showed an increase of type I neurones, but a decrease of type II nerve cells. Pinealectomy followed by substitution using pineal extracts restored the number of type I and type II neurones to that normally found in the arcuate and ventromedial hypothalamic nuclei of control animals. The present investigation brings histological evidence of an influence exerted by the rat pineal gland on nuclei forming part of the hypothalamic hypophyseotropic area. The data obtained and some of the literature strongly suggest that the type II neurones, which probably contain serotonin, inhibit, in the same hypothalamic nuclei, the production of luteinizing hormone-releasing factor (LH-RF). As yet, the function of the autofluorescent compound present in the type I neurones is not known.

Animals↗