PubMed Health⌕ Search

Biomedical subjects

I Reisert

Publications and source records attributed to I Reisert.

At least 55 records · Page 3Linked to original sources
PubMed1989

Early sexual differentiation of diencephalic dopaminergic neurons of the rat in vitro.

Development of dopaminergic neurons was investigated in dissociated cell cultures raised from the diencephalon of male and female rat fetuses from days 14 and 17 of gestation. Striking differences in morphology and function of male and female dopaminergic neurons were observed. Outgrowth of tyrosine hydroxylase-immunoreactive processes initially proceeded at a faster rate in female than in male cultures. Morphological differences disappeared in cultures of gestational day 17. Irrespective of the age of the cultures and of the length of cultivation, the uptake capacity for (3H)dopamine per immunoreactive neuron was twice as high in female than in male cultures. Treatment of the cultures with sex steroids did not influence morphology, numbers or transmitter uptake of tyrosine hydroxylase-immunoreactive neurons. The results suggest that diencephalic dopaminergic systems exhibit a sexual dimorphism that develops unexpectedly early in ontogeny and is independent of the action of gonadal hormones.

Animals↗
PubMed1989

Rapid maturation of synaptic functions of prenatal serotoninergic neurons in short-term cultures: absence of sex differences and hormone effects.

Serotonin is believed to modulate neuronal differentiation during early stages of brain development. In order to assess basic functional requirements for such a role, it was investigated how early serotoninergic neurons mature with respect to transmitter storage and stimulus-secretion coupling. Dissociated cell cultures were raised from embryonic rat rhombencephalon obtained at gestational day 14 and cultured for 3-8 days, which may roughly correspond to the prenatal period in vivo. Because of a possible involvement of serotonin in processes leading to sexual differentiation of the brain, gender-specific cultures were raised in addition and treated with sex steroids. Sensitivity of [3H]serotonin uptake to fluoxetine could already be observed at 3 days in vitro. Vesicular storage as probed with reserpine and nigericin, and the capability of releasing preaccumulated serotonin in a Ca2+-dependent manner were also present as early as 3 days in vitro. Seven per cent of the pre-accumulated transmitter could be released per minute upon stimulation with 54 mM K+. Immunocytochemical and autoradiographic preparations demonstrated that, after the same short culture period, the neurons had formed large fiber networks. No differences could be detected regarding any of the above parameters between female and male serotonin neurons and between cultures treated with and without estradiol, testosterone and dihydrotestosterone. It is concluded that, in contrast to other neuronal phenotypes, serotoninergic neurons are functionally mature when or shortly after they are taken into culture, i.e. around gestational day 14. The functional competence of prenatal serotonin systems should be a prerequisite for their suspected role in modulating neural development at pre and postsynaptic sites. The present results provide no evidence for the occurrence of a sexual dimorphism of serotonin neurons at this early developmental stage.

Animals↗
PubMed1989

Sexual differentiation of mesencephalic neurons in vitro: effects of sex and gonadal hormones.

In order to study the influence of gender on the development of transmitter uptake by dopaminergic neurons, dissociated cell cultures were raised separately from male and female midbrains of gestational day 14 rats. It was ascertained by use of specific inhibitors and by autoradiography that the uptake of [3H]dopamine was restricted to neurons immunoreactive for tyrosine hydroxylase and that these neurons have dopaminergic properties. The uptake capacity was higher in male than in female dopaminergic neurons by a factor of 1.5. This sexual dimorphism in dopamine uptake was present in cultures of tissue removed before the perinatal rise of testosterone occurs in males, and was present even in the absence of hormonal additives to the culture medium. It therefore appears to be independent of the presence of gonadal steroids. It occurred likewise in cultures raised with serum-supplemented and serum-free medium, which may indicate that glia are not decisive in generating these differences. In addition, sexual differences were found regarding hormone responsiveness. Whereas testosterone and dihydrotestosterone were ineffective, estradiol was seen to promote dopamine uptake in female but not in male neurons. The results would suggest that mesostriatal and/or mesolimbic dopaminergic systems assume an early role in the development of some sexual dimorphisms of the brain.

Animals↗
PubMed1988

Abundant GABAergic innervation of rat posterior pituitary revealed by inhibition of GABA-transaminase.

An antibody against gamma-aminobutyric acid (GABA) was used to identify GABAergic elements immunocytochemically in the rat posterior pituitary. In order to increase the intracellular concentration of GABA, rats were treated with the GABA-transaminase inhibitor gamma-vinyl-GABA (GVG). Light-microscopic observations of Vibratome and semithin sections revealed the presence of numerous immunoreactive nerve fibers throughout the neural lobe; the mean number and length of these fibers increased by 90% after GVG treatment. Electron microscopy demonstrated the immunostained axons to be of small diameter. The reaction product was confined to small vesicles. No immunostaining occurred in pituicytes. The richness of the GABAergic innervation of the neural lobe contrasts with previous reports using antibodies against glutamate decarboxylase and supports the idea that GABA participates in the presynaptic control of neurosecretion.

4-Aminobutyrate Transaminase↗
PubMed1987

Sex steroids promote neurite growth in mesencephalic tyrosine hydroxylase immunoreactive neurons in vitro.

The influence of steroid hormones on the differentiation of catecholaminergic and serotonergic (5-HT) neurons was studied in dissociated cell cultures from embryonic day 14 (E14) rat diencephalon, mesencephalon and metencephalon treated for 6 days with 17 beta-estradiol (E), testosterone (T), 5 alpha-dihydrostestosterone (DHT), progesterone (P), dexamethasone (DEX), or E + T. The effects of these hormones on morphologic differentiation were determined by morphometric measurements of total length of neurites of immunocytochemically identified neurons in culture, which were stained with antisera against tyrosine hydroxylase (TH) or 5-HT. A significant increase in neurite length was observed in cultures of TH-immunoreactive (TH-IR) neurons from the mesencephalon treated with E, T, E + T, but not with P, DHT or DEX. Based on labeling with [3H]dopamine (DA) uptake and competition with specific inhibitors, these mesencephalic TH-IR cells appear to represent DA neurons of the A8-A10 groups (which includes the substantia nigra). No statistically significant effects of these steroids were observed on TH-IR neurons from the diencephalon (assumed to be precursors of the tuberoinfundibular and incertohypothalamic dopaminergic groups). The 5-HT neurons of the raphe nuclei (metencephalon) showed no statistically significant response to steroids. We conclude that during the early fetal period, sex steroids can affect the morphologic differentiation of mesencephalic DA neurons in vitro, indicating that these hormones are capable of selectively influencing the development of a specific population of monoamine neurons during this critical period.

Animals↗
PubMed1986

Different developmental schedules of dopaminergic and noradrenergic neurons in dissociation culture of fetal rat midbrain and hindbrain.

The development of dopaminergic and noradrenergic neurons in dissociation cultures of mesencephalon and rhombencephalon obtained from 18-day-old rat fetuses was characterized by their capacity to take up and release catecholamines. In both types of cultures, uptake of [3H]dopamine and [3H]noradrenaline was obtained which could be inhibited by reserpine. Autoradiographic studies demonstrated an almost exclusive neuronal localization of the labeled catecholamines. The transmitters could be released by depolarization with K+ in a Ca2+-dependent manner during the entire cultivation period. In contrast, catecholamine uptake by cultures of neocortex was minimal, could not be inhibited by reserpine, and the accumulated radioactivity could not be released upon depolarization. These points provide evidence for an active accumulation of the exogenous transmitters and for the presence of stimulus-secretion coupling in a distinct population of neurons of both brain stem cultures. Striking differences between the two brain stem cultures concerned their sensitivity to desmethylimipramine and benztropine as well as the time course of the development of the uptake capacity. Desmethylimipramine inhibited the uptake of both catecholamines in rhombencephalic, but not in mesencephalic cultures. The reverse was true for benztropine. It is concluded that cultures of rhombencephalon contain predominantly noradrenergic, and those of mesencephalon dopaminergic cells. Comparison of the uptake behaviour suggested that noradrenergic neurons mature considerably later than dopaminergic neurons. The results show that dissociation cultures of mid- and hindbrain, inspite of their heterogeneous composition, can serve as valuable models for the study of development and function of dopaminergic and noradrenergic neurons, respectively.

Adrenergic Fibers↗
PubMed1985

Quantitative assessment of GABA-uptake sites in the neural lobe by electron-microscopic autoradiography.

Distribution of (3H)GABA in the rat neural lobe was investigated 5 min after intracarotid administration using quantitative electron-microscopic autoradiography. Specificity of (3H)GABA-uptake was tested by pretreatment of control animals with nipecotic acid. It was concluded that, apart from a small fraction in the perivascular spaces, radioactivity was present exclusively in pituicytes. The results confirm and quantify earlier in-vitro observations; they are compared with recent immunocytochemical findings that reveal the presence of glutamate-decarboxylase-containing axons in the neural lobe. It is concluded that there may be GABAergic terminals that lack an uptake mechanism for exogenous transmitter. Nevertheless, (3H)GABA autoradiography is useful in demonstrating other functional components of GABAergic systems, i.e., glial cells.

Animals↗
PubMed1984

The glial reaction in the course of axon regeneration: a stereological study of the rat hypoglossal nucleus.

Both hypoglossal nuclei were examined by electron microscope stereology after unilateral axotomy. The principal aim of this study was a quantitative assessment of the accompanying glial reaction. Volume densities (%) of neuronal and glial perikarya, as well as their processes, were evaluated in terms of volume plus surface densities (mm-1). In addition, specific surfaces (surface to volume ratio) of these neuronal and glial processes were assessed. First, a temporary decrease of dendritic volume density was detected on the ipsilateral side only. Further, the astrocytic reaction displayed differences between stem and lamellar processes. One day after axotomy, a bilateral decrease of volume density, as well as surface density of stem processes, was observed, yet their normal dimensions soon were reestablished. However, a more severe lamellar process reaction was evident. During the first 4 days, a significant increase of volume density and surface density was apparent. In the contralateral hypoglossal nucleus, this glial reaction also occurred but disappeared by day 14, whereas the ipsilateral nucleus continued to display a severe reaction of lamellar processes, only returning to normal status at day 77. In addition, a transient, severe reaction of presumptive microglia was established by employing the volume density and surface density quantitation procedure. Nevertheless, in comparison with the volume and surface contribution of astrocytic processes, the presumed microglial component was minimal. This study indicates a two-step involvement of astrocytes in regenerative repair. Namely, the first phase seems to result in an increase of lamellar processes through reshaping of the stem process.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Coexistence of glutamate decarboxylase and somatostatin immunoreactivity in cultured hippocampal neurons of the rat.

The immunoperoxidase-antiperoxidase method (PAP) was combined with immunofluorescence for simultaneous localization of glutamate decarboxylase (GAD)-and somatostatin-like immunoreactivity in rat hippocampal neurons growing in dissociated cell culture. A subpopulation of GAD-immunoreactive neurons additionally exhibited somatostatin-like immunostaining. GAD-negative somatostatin-positive cells could not be observed. It is discussed whether the cultured somatostatin-containing GAD neurons correspond to a certain subclass of basket cells as they occur in situ.

Animals↗
PubMed1984

Pathways of lymphocyte migration within the periarterial lymphoid sheath of rat spleen.

Male Wistar rats were injected intravenously with 5-(3H)uridine-labeled lymphocytes isolated from lymph nodes of syngeneic donors and enriched in T cells. After short periods of time (3 to 120 min after injection), labeled lymphocytes were localized in spleen compartments using autoradiography to identify routes of lymphocyte movement from blood into splenic parenchyma and to follow migration pathways of recirculating lymphocytes within the periarterial lymphoid sheath (PALS). Topographical analysis of labeled lymphocytes was performed in specific planes of PALS characterized by the diameter of the arterial vessel and termed PALS large, PALS medium, and PALS small (PALS L, PALS M, PALS S, respectively). Attention was also paid to accumulations of labeled lymphocytes close to the arterial vessel wall. Initially, labeled lymphocytes were localized in PALS S and PALS M near the terminal branching of arterial vessels and in the marginal zone (MZ). We conclude that lymphocytes emigrate from blood into splenic parenchyma within two white pulp compartments: in MZ, and directly within PALS through the wall of capillary vessels. The sequential accumulation of labeled cells near arterial vessels of increasing diameter suggests that the recirculating pool of lymphocytes migrates into the central part of PALS L by two routes: from MZ, and along arterial vessels from PALS S and PALS M.

Animals↗
PubMed1984

Angiotensin II promotes development of neurophysin neurons in dissociated culture.

Dissociated cultures of retrochiasmatic hypothalamus of 18-day-old rat embryos were continuously treated with 2 X 10(-9) M angiotensin II (ang II) from the third day in vitro on. Cultivation was terminated at days 9 and 16 in vitro, respectively. Neurons immunoreactive for neurophysin, arg-vasopressin and oxytocin were visualized by immunocytochemistry, using the unlabeled antibody technique, and counted. Large, well-differentiated magnocellular neurons and small, probably immature cells could be distinguished. A certain number of large neurons were, in addition, immunoreactive for either vasopressin or oxytocin whereas the small cells were devoid of such staining. Ang II treatment brought about a modest increase in neurophysin-immunoreactive (NEU-IR) cell numbers at day 9 and a drastic augmentation of both large and small NEU-IR cells at day 16 in vitro, without appreciably affecting the total counts of neurons per culture.

Angiotensin II↗
PubMed1983

GABAergic neurons in dissociated cultures of rat hypothalamus, septum, and midbrain.

Cultures of dissociated tissue blocks from 18 day-old rat embryos containing either septum plus anterior hypothalamus, retrochiasmatic hypothalamus, or midbrain, were maintained for 8-29 days in vitro. GABAergic neurons were visualized by incubation with (3H) gamma-aminobutyric acid followed by autoradiography and by immunocytochemistry using an antiserum against glutamic acid decarboxylase. Positive neurons were of variable shapes and sizes. Labeled neurons in the three cultured regions represented 3.4, 1.1 and 1.7%, respectively, of all neurons. Apart from a few exceptions, autoradiographic labeling and immunocytochemical staining coincided. Glial cells did not stain and showed very low grain densities. Radioactivity could be released from preloaded cultures upon depolarization by 50 mM potassium and 100 microM Veratridine. The demonstration of GABAergic neurons in cultures that are known to contain a variety of peptidergic neurons opens up the possibility of studying the interaction between the two classes of neurons in vitro.

Animals↗
PubMed1982

Volume densities and specific surfaces of neuronal and glial tissue elements in the rat supraoptic nucleus.

The present study was undertaken to provide an explanation for previous autoradiographic results suggesting a several times higher rate of synthesis of glycoconjugates per unit volume of hypothalamic glia than of neurons. Volume densities, specific surfaces (surface-volume ratios), and relative surfaces (contribution of the surface of a tissue element to the total surface of the tissue) were assessed. Neuronal elements occupy about 74% and glial elements about 8% of the total volume. The specific surface, i.e., the amount of plasma membrane per unit volume of structure, is more than 30 times higher in the neuropil than in the neuronal perikaryal fraction. The largest specific surface is found with (unmyelinated) axons and astroglial processes. The specific surface of the average astrocyte is about twice that of the average neuron. If the surface of the entire cell is considered in relation to the perikaryal volume only, this ratio is about seven times as large for glial cells as for neurons. It follows that an astrocyte perikaryon has to renew a several times larger plasma membrane than a neuron, which can account for the above differences in perikaryal synthesis rates of glycoconjugates.

Animals↗
PubMed1982

Nerve cells immunoreactive for vasoactive intestinal polypeptide in dissociation cultures of rat hypothalamus and midbrain.

Immunocytochemistry using the unlabeled antibody (PAP) technique reveals the presence of 0.01-0.3% neurons reacting with an antiserum against vasoactive intestinal polypeptide (VIP) in dissociation cultures of hypothalamus and midbrain. The cultures are obtained from 18-day-old rat fetuses and maintained for 22 and 29 days in vitro. Most of the neurons appear well differentiated giving off branched processes with pronounced varicosities. These can often be seen to contact perikarya as well as processes of unstained neurons.

Animals↗
PubMed1982

Extraction of label during processing of brain tissue for electron microscopic autoradiographic investigation of glycoprotein metabolism.

Rats were injected intracerebrally with (3H) fucose and survived for 30 min and 24 h. Following perfusion fixation with aldehydes, Vibratome sections of the brains were processed for embedding in resin and the radioactivity in the various solutions measured by scintillation counting. The decline of radioactivity was monitored in up to 18 successive buffer washes. Whereas 85% of the initial radioactivity could be eluted after 30 min, only 7% were extractable after 24 h survival time. Addition of unlabelled L-fucose to the fixative and buffers caused a small insignificant increase of the total radioactivity extracted. Only small amounts of radioactivity could be removed by treatment with trichloroacetic acid after extensive rinsing in buffer. It is concluded that thorough rinsing in buffer (which is more important with short-time experiments) is effective in removing the acid-soluble radioactivity. An additional safe-guard lies in dehydration by ethanol. The ethanol series also removes acid-soluble radioactivity in addition to small amounts of what is probably higher molecular weight material.

Animals↗