Evidence that GYKI 52466, a novel non-NMDA antagonist enhances the decay of kainate-induced current in cultured chicken cortical neurons.

The effect of a novel non-competitive non-NMDA glutamate receptor antagonist, GYKI 52466 was studied on the glutamate agonist-induced currents in one month old cultured embryonal chicken brain neurons by a whole cell patch-clamp technique. AMPA, applied in different concentrations (30-1000 microM) did not evoke any current. Kainate evoked an increase of steady-state current (KA-current). NMDA induced a current with 5-10 times higher peak amplitude than KA, but GYKI 52466 failed to affect this current. It reduced the amplitude of KA-current in a concentration-dependent (1-100 microM) manner, and produced a slow decay of it. The IC50 value of GYKI 52466 against 100 microM KA was 20.4 +/- 6.4 microM with a Hill coefficient of 1.12. The inhibition of KA-currents was voltage-dependent with greater inhibition between -110 to -40 mV than between -30 and +60 mV. In order to compare the effect of GYKI 52466 with a well-known competitive non-NMDA antagonist, we also studied the effect of the quinoxalinedione CNQX. When GYKI 52466 and CNQX were applied together there was only a small additive effect. Our results with GYKI 52466 on glutamate agonist-induced currents in embryonic chicken cortical neurons are similar to those observed in rat hippocampal neurons.

Pathological and experimental investigations in a case of gigantism.

A pituitary adenoma was transsphenoidally removed from a 4.5-year-old girl suffering from gigantism. Prior to the operation both the growth hormone (GH) and the prolactin (PRL) levels in the serum were elevated. By light microscopy the tumor appeared to be an acidophilic adenoma. Two distinct cell types, the densely granulated and the sparsely granulated cells, could be distinguished by electron microscopy. Double immunolabeling revealed the presence of GH alone in some densely granulated cells and PRL alone in some sparsely granulated cells, as well as GH and PRL co-localized in both of the morphologically distinguished cell types. Both cell types were identified in the monolayer and the suspension cultures by electron microscopy. GH and PRL concentrations in the culture media were measured by radioimmunoassay. The basal secretion of growth hormone was almost uniform during the 3-week cell culture period. GH and PRL release was significantly inhibited by bromocriptine. Our studies revealed a bimorphous and bihormonal mixed adenoma in childhood.

Influence of oligopeptide aldehydes on intracellular Ca2+ concentration in rat pituitary cells.

We investigated the effects of some synthetic tripeptide aldehydes, earlier shown to influence pituitary hormone secretion and 45Ca2+ uptake, on the intracellular free Ca2+ concentration ([Ca2+]i) of rat anterior pituitary cells in suspension. Boc-D-Phe-Leu-Phenylalaninal or Boc-D-Phe-Leu-Prolinal in the tested range of 1-100 or 200 microM, respectively, were ineffective in influencing basal [Ca2+]i but caused a concentration-dependent inhibition in K+ (25 mM)-induced [Ca2+]i elevation. The IC50 of both effects was about 50 microM. In contrast, they did not interfere with the stimulation caused by the calcium channel agonist BAY K 8644 and were also ineffective in influencing the receptor-mediated stimulus of thyrotropin-releasing hormone on [Ca2+]i. On the basis of the present and foregoing results the possible involvement of calcium channels is discussed, but different mechanisms mediating the tripeptide aldehyde inhibition are also considered. A third tripeptide aldehyde, Boc-Gln-Leu-Lysinal (Boc-GLL), showed ionophore-like properties. This nontoxic substance caused a dose-dependent rise up to 400% (at 100 microM) in [Ca2+]i. Its effect is not mediated by voltage-dependent calcium channels, as it cannot be inhibited either by the classical calcium channel antagonists verapamil and nifedipine, or by the above-mentioned inhibitory tripeptide aldehydes. When we decreased the extracellular Ca2+ concentration by the addition of 4 mM EGTA, the effect was inverted and Boc-GLL caused a large fall in [Ca2+]i. We suggest that Boc-GLL may open cell membrane pores through which Ca2+ moves along the concentration gradient.(ABSTRACT TRUNCATED AT 250 WORDS)

Morphological and functional characterization of cell cultures from adult human adenohypophyses.

Parallel primary cultures have been prepared from dispersed cells of adult human pituitary anterior lobes and can be used as a model system for cell-biological studies. The cultured cells were able to secrete all the known hormones of the adenohypophysis. Bromocriptine administration markedly reduced prolactin release into the medium while slightly enhanced growth hormone release. The adequate response of somatotrophs to GRF and SRIF could not be demonstrated.

Early and late hormonal modulation of cholinergic maturation in culture of embryonic mesencephali.

Dissociated cells from 13- and 17-day-old embryonic rat mesencephali have grown in primary cultures in order to compare the early and late influences of different agents--insulin, dexamethasone and nerve growth factor (NGF)--on the expression of cholinergic maturation process. We have studied cholin acetyltransferase (ChAT) activity, which is regarded as a specific marker for cholinergic function of the brain, and a widely used differentiation marker, the acetyl-cholinesterase (AchE) enzyme. Biochemical maturation of increasing specific activity of ChAT in both younger and older cells was taken into consideration. During cultivation the AchE activity was slightly increased in younger cells, but a dramatic decrease could be noted in older ones. Insulin in concentration from 10 to 27 micrograms mL-1 causes a significant inhibition in ChAT activity in comparison with the enzyme activity measured in control cultures (insulin ranging from 1 to 100 ng), independently of embryos age. This polypeptide hormone is able to enhance AchE activity in the cultured cells, especially in older ones. With continuous treatment of the culture with dexamethasone, a synthetic glucocorticoid, the ChAT activity in younger cells reaches a maximum curve by day 9 (nine). At this time the AchE activity shows a slighter, no significant increase than at any other time during cultivation. In cell cultures taken from 17-day-old embryos however dexamethasone treatment evoked a significant decrease in ChAT activity with a concomitant increase of AchE activity which was compared to insulin treatment. In spite of the fact that the NGF is able to enhance the ChAT activity, no significant alteration in AchE activity can be measured in younger cell cultures. These results suggest an uneven expression of the enzymes in embryonic rat mesencephali in the presence of above agents depending on the age of cells.

The mathematical analysis of spontaneous and induced potentials in neural cultures.

We compare the power spectra of activities of neural cultures from the cortex and spinal cord of embryonic rat. The measurements were made in a microelectrode culture chamber by non-invasive methods. The data suggest that the fundamental frequencies of cortical and spinal cultures significantly differ, while the general patterns of the spectra are rather similar.

Multielectrode culture chamber: a device for long-term recording of bioelectric activities in vitro.

A multi-microelectrode culture chamber system was constructed for monitoring simultaneously morphological and electrophysiological development of neural cells in vitro. The setup consisted of a pattern of gold conductor lines evaporated onto a glass substrate and insulated with polyamide. The width of each electrode was 10 microns, and the distance between the electrodes was 60 microns. The electrode patterns were constructed and the uncovering of the electrode tips were carried out by photo-etching. This system allowed us to record spontaneous activities in both explant- and primary monolayer cultures of either rat or mouse spinal cords and forebrains, during neuronal regeneration and maturation.

Colloidal gold-labeled lipoprotein binding and internalization in adrenocortical cells in vitro.

Human (normal and adenomatous) and rat (normal) adrenocortical cells were incubated in vitro with colloidal gold labeled low-density (LDL-Au) and high-density (HDL-Au) lipoproteins, respectively, in order to visualize lipoprotein binding and internalization at an electron microscopic level. Both normal and adenomatous human adrenocortical cells accumulated LDL-Au by receptor-mediated endocytosis via coated pits, coated vesicles, noncoated vesicles, and lysosomes. HDL-Au was not internalized. In rat adrenocortical cells, both HDL-Au and to a lesser extent LDL-Au were internalized. It is concluded that LDL-Au and HDL-Au conjugates can be used to identify lipoprotein receptors and to follow lipoprotein internalization in adrenocortical cells.

45Ca2+ uptake and peptide hormones secretion in the presence of excess Mg2+ content.

Studies have been performed on the relationship between PRL and GH production and the 45Ca2+ influx in high magnesium content in vitro. The obtained data show that an elevated magnesium concentration in Krebs-Ringer solution is capable of inhibiting some hormonal function of the pituitary gland. It has been found, that PRL and GH released into the media in normal KRB solution revealed nearly two times higher concentration than in the presence of high Mg2+. Instead the cellular iPRL and iGH did not show any significant differences in control and in treated cultures. The incorporation of 4.5-3H-leucine into the prolactin and growth hormone demonstrate a significant decrease in the presence of high Mg2+ indicating that the ion is able to inhibit the secretion of newly synthesized PRL an GH. High concentration of Mg2+ abolished either the stimulation effect of releasing hormones on calcium uptake.

Molecular form of human lymphocyte membrane-bound acetylcholinesterase.

The membrane-bound acetylcholinesterase (AchE) from human peripheral blood lymphocyte gives only one symmetrical peak on sucrose density gradient centrifugation in the presence of Triton X-100 detergent, with the calculated sedimentation coefficient of 6.5 S. However, this dimeric form of AchE was converted to a monomeric 3.8 S form when treated with 2-mercaptoethanol and iodoacetic acid. The results are consistent with studies which have shown by sodium dodecyl sulfate gel electrophoresis that the enzyme is built up of two identical monomers inter-linked by disulfide bond(s). Under reducing conditions, revealed a single species of 70,000 molecular weight, whereas under non-reducing conditions, another species of 140,000 molecular weight of the AchE was found. Polyacrylamide gel electrophoresis indicated a single band with AchE activity in the presence of Triton X-100. In contrast, in the absence of the same detergent multiple band pattern could be observed. These results suggest that membrane-bound AchE enzyme is present in homogenous dimeric form on human lymphocyte membrane.

Proteinase inhibitors while influencing hormone release do not affect cell morphology of hypophyseal cultures.

Cultured cells from adult rat anterior pituitaries and intermediate lobes were treated with proteinase inhibitor substrate analogues (Boc-DPhe-Pro-Arginal [BOC-DPPA], DPhe-Pro-Arginal [DPPA], BOC-DPhe-Leu-Lysinal [BOC-DPLL], BOC-DPhe-Phe-Lysinal [BOC-DPPL]) to elucidate their effect on cell morphology. It was established that BOC-DPPA and DPPA (which in previous studies stimulated alpha-MSH release [6]) caused a slight decrease in the number of immunoreactive secretory granules in melanotrophs. BOC-DPLL, which inhibited growth hormone and prolactin release, did not alter the fine structural features of cultured cells. No difference was observed in the membrane turnover traced by cationic ferritin when cells were treated with BOC-DPPL. We suggest that substrate analogues used are harmless to pituitary cells.

Dissimilar responsiveness of cultured corticotrophs and melanotrophs to tripeptide aldehydes.

Cultured cells from adult rat anterior pituitaries or intermediate lobes were treated with the proteinase inhibitor tripeptide aldehydes BOC-DPhe-Pro-Arg-H (Boc-fPRH) and DPhe-Pro-Arg-H (fPRH), ovine corticotropin-releasing factor (oCRF), and bromocriptine. One millimolar fPRH stimulated basal, and slightly enhanced oCRF-induced ACTH release by melanotrophs in short-term experiments. The basal release of alpha-MSH was also stimulated by the drug. In long-term experiments, fPRH elevated markedly both the release and the intracellular level of ACTH; BOC-fPRH caused an increased alpha-MSH release. Tritiated fPRH had no preference for POMC-producing cells and BOC-fPRH or fPRH were harmless to the cell morphology. In anterior pituitary cell cultures, fPRH diminished slightly basal and oCRF-induced ACTH release. Bromocriptine was ineffective on corticotrophs, however, in melanotrophs it inhibited ACTH release markedly with or without fPRH in the medium. The dissimilar responsiveness of the corticotrophs and melanotrophs to the peptide aldehydes may be interpreted in terms of their differing membrane receptors or intracellular mechanism of stimulus-secretion coupling.

Long-term suspension culture of isolated hypothalamic nuclei of the rat: morphological differentiation and release of substances influencing corticotropin and growth hormone secretion.

Individual hypothalamic nuclei were removed from 17-day-old rat embryos with 300 microns punches and maintained in suspension culture. Suspension culture of isolated nuclei appears to be suitable for studying morphological and functional differentiation of neural tissue and release of bioactivity influencing corticotropin and growth hormone release. During the 4 weeks in culture, neurons and glial cells differentiated well in each nucleus studied. The fine structure of the arcuate, periventricular, ventromedial and dorsomedial nuclei resembled that of the adult nuclei with many mature synapses; in contrast, in the neuropil of cultured preoptic, paraventricular and posterior hypothalamic nuclei mature synapses were very few or absent. The release of substances influencing corticotropin and growth hormone secretion by the cultured nuclei was tested in bioassays using anterior pituitary cell cultures and radioimmunoassay of hormones released into the medium. Corticotropin-releasing bioactivity was tested at weekly intervals. Cultured preoptic and paraventricular nuclei released corticotropin-releasing activity for up to 4 weeks whereas arcuate nuclei released corticotropin-releasing activity at 1 week only. The ventromedial and dorsomedial nuclei did not release corticotropin-releasing activity. The release of substances influencing growth hormone secretion was studied between 3 and 11 days in culture. After 3 days the medium of some hypothalamic nuclei stimulated growth hormone secretion, but after 7 and 11 days all cultured nuclei strongly inhibited it. The present findings demonstrate that hypothalamic nuclei can be cultured separately and suggest that neurons capable of releasing corticotropin-releasing activity(ies) are present in the preoptic and paraventricular nuclei of the rat whereas all hypothalamic nuclei studied contain intrinsic neurons capable of synthesizing and secreting somatostatin-like bioactivity.

Lung maturation and prevention of hyaline membrane disease.

Small pieces of 7 to 12 week old human foetal lung, derived from legal abortions, were maintained in organ culture for 21 days. In the last 5 days of cultivation the explants were treated with dexamethasone (10 ng/ml) or betamethasone (10 ng/ml) or fenoterol (10 ng/ml), or fenoterol + dexamethasone, or bromhexine VIII metabolite (ambroxol: 12 ng/ml) and were then prepared for electronmicroscopic examination. In another experimental group the pregnant were treated before the interruption of 14-17-week old pregnancies with ambroxol (total dose, 1080 mg). The interruption was carried out with PgF2 alpha, and lung pieces were immediately prepared for electron microscopic examination. From the experiments the following conclusions can be drawn: Surfactant production can already be induced in 7-12 week old human fetal pneumocytes; Corticosteroids (dexamethasone, betamethasone) stimulate the formation of osmiophilic lamellar bodies; Fenoterol has probably no effect on the surfactant production. Its administration together with dexamethasone, however, does not inhibit the development of osmiophilic lamellar bodies; Ambroxol has a marked effect on the synthesis of lamellar bodies in vitro: Ambroxol or its active metabolite probably have a reduced placental transport in the first trimester of human pregnancy; Thin-layer chromatography has revealed no qualitative difference between the treated and untreated cultures.

Responsiveness of intermediate lobe cells to neural mediators in culture.

Immunologically and biologically active ACTH, as well as biologically active alpha-MSH were secreted by monolayer cultures of rat pituitary intermediate lobe cells. The release of the immunoreactive ACTH and the bioactive alpha-MSH was inhibited by dopamine and by the dopamine agonist bromocriptine. The inhibition is probably mediated by specific dopaminergic receptors, since simultaneously added haloperidol prevented the dopamine induced hormone release inhibition. Pro-Leu-Gly-NH2, a potent inhibitor of the alpha-MSH secretion, had no effect on the release of ACTH. Synthetic ovine CRF stimulated the release of both immunoreactive ACTH and bioactive alpha-MSH in dose-dependent fashion. Corticosterone was without effect on hormone release in the cultures derived from both adrenalectomized and sham-operated animals.

GnRH secreting cultured fetal rat hypothalamic cells do not degrade GnRH.

The possible degradation of GnRH in the hypothalamus was investigated. Rat fetal hypothalamic cells were kept in culture for two weeks and basal and stimulated GnRH release was measured by highly sensitive RIA. These intact hypothalamic cells did not degrade GnRH during 4 hours of incubation, but a 50% degradation occurred after 24 hours incubation followed by HPLC using specifically tritium labeled GnRH or RIA. The rate of degradation or the kinetic of degradation did not change by increasing GnRH concentration in the medium or by mechanical instead of enzymatic dispersion of the cells. For comparison GnRH degradation in homogenized hypothalamic tissue and in synaptosomal preparation was measured and rapid degradation was found. Our results suggest that intact hypothalamic cells under physiological circumstances do not degrade extracellular GnRH.

Induction of lamellar body synthesis by corticosteroids in first-trimester human fetal lungs.

Small pieces of 7- to 12-week-old human fetal lung, originating from legal abortions, were maintained in organ culture for 21 days. In the last 5 days of cultivation the explants were treated with dexamethasone (10 ng/ml) or betamethasone (10 ng/ml) and were then prepared for electron-microscopic examination. In response to corticosteroid treatment numerous characteristic osmiophilic lamellar bodies had developed in the cytoplasm of alveolar cells. Their fine structure resembled the osmiophilic myelin structure which can be found in type II pneumocytes of the mature lung. No difference could be observed between the effects of dexamethasone and betamethasone. The steroids did not alter the normal fine structure of the lung cells. It was concluded that corticosteroids may have a direct effect on the formation of lamellar bodies and phospholipid synthesis in type II pneumocytes by 7-12 weeks of gestation.