Angéla Gyévai

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.

Interrelationship between corticosteroid production and fine structure in the fetal adrenal cortex.

Abstract The cat fetal adrenal is capable of corticosteroid production from an early stage of ontogenesis (crown-rump length: 2–3 cm) and reacts to ACTH by corticosteroid production. Its hormone-producing ability and responsiveness to ACTH operate before the fine structure characterizing the adult zona fasciculata cells is recognizable. In tissue culture of human fetal adrenal, corticosteroids are produced in response to ACTH even if the fine structure of the endoplasmic reticulum and mitochondria, on which corticosteroid production is currently believed to depend, shows marked deviation from the histological picture characterizing the zona fasciculata cells.

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.

Renin production by tissue cultures of renal cortex.

Abstract The renal cortex of the human foetus, the porcine embryo, the newborn cat, and the adult mouse produces and releases renin into the tissue-culture medium for 9 to 15 days following explantation.

Serum-dependent changes in non-specific esterase activity in HeLa cells

SummaryThe activity and the isozyme pattern of nonspecific esterase in HeLa cells (variant 77) were found to depend on the type and concentration of serum present in the culture medium.

Dissimilar responsiveness of cultured corticotrophs and melanotrophs to tripeptide aldehydes.

SummaryCultured cells from adult rat anterior pituitaries or intermediate lobes were treated with the proteinase inhibitor tripeptide aldehydes BOC-DPhe-Pro-Arg-H (Boc-tPRH) 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.

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.

Relation between spontaneous activity and cholinesterase activity of dissociated embryonic and young rat-heart and embryonic chick-heart cells studied in tissue culture

SummaryThe number of spontaneously beating single cells obtained both from rat and chick hearts disaggregated by trypsin, is age-dependent: it is higher in younger than in older hearts. Cholinesterase activity and glycogen content are high in the spontaneously active cells. Being dependent on animal age, many Cholinesterase and PAS-positive cells are present in cultures prepared from early hearts. Succinicacid dehydrogenase-activity is equally feeble in spontaneously active and inactive heart cells. Only in older, already differentiated cells, devoid of spontaneous activity, is it intense.

Histological and histochemical studies of the cells of the human foetal adrenal and hypophysis in tissue culture

SummaryThe histological and histochemical changes taking place in expiants and outgrowing cells of the human foetal adrenals and hypophyses have been studied on the 5th, 10th, 20th, and 28th day of the culture period. In the outgrowth from adrenals, both the epithelial-type and the fibroblast-type cells contain 3β-ol steroid dehydrogenase activity. The cells growing out from hypophyseal expiants appear to be morphologically undifferentiated. Expiants contain differentiated cells in the first 10 to 13 days of the culture period.

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.