Effects of activin A and somatostatin on intact FSH secretion and intracellular Ca2+ concentration in human FSH-secreting pituitary adenoma cells.

Activin A stimulated synthesis and secretion of intact FSH in dispersed human FSH-secreting adenoma cells. Significant stimulation was observed after 24 hr. Activin A caused an increase in Ca2+ concentration ([Ca2+]i). This response occurred soon after the activin A action. These effects were blocked in Ca(2+)-deficient medium and by nitrendipine (5 microM). Somatostatin inhibited the activin A-induced intact FSH secretion and the [Ca2+]i response. These findings indicated that Ca2+ influx through voltage-gated Ca2+ channel was involved in the activin A induced synthesis and secretion of intact FSH.     

Tumor necrosis factor and interleukin-1 induce activin A gene expression in a human bone marrow stromal cell line.

Activin A, a homodimer of the beta A chain, regulates hematopoiesis. In a human bone marrow-derived stromal cell line, KM-102, phorbol myristate acetate, tumor necrosis factor-alpha and interleukin-1 beta induced great increases in beta A chain mRNA levels and production of activin A activities. The phorbol ester-induced beta A chain gene expression was inhibited by cycloheximide and down regulation of protein kinase C, whereas the cytokine-induced expression was little affected by these treatments. These results indicate that the inflammatory cytokines directly stimulate beta A chain gene expression via protein kinase C-independent pathways.     

Biphasic effects of alcohols on the phase transition of poly(L-lysine) between alpha-helix and beta-sheet conformations.

Poly(L-lysine) exists as a random-coil at neutral pH, an alpha-helix at alkaline pH, and a beta-sheet when the alpha-helix poly(L-lysine) is heated. The present Fourier-transform infrared (FTIR) study showed that short-chain alcohols (methanol, ethanol, and 2-propanol) partially transformed alpha-helix poly(L-lysine) to beta-sheet when their concentrations were low. At higher concentrations, however, these alcohols reversed the reaction, and the alcohol-induced beta-sheet was transformed back to alpha-helix structure. The reversal occurred at 1.40 M methanol, 0.96 M ethanol, and 0.55 M 2-propanol. The alcohol effects on the secondary structure were further investigated by circular dichroism (CD) on the thermally induced beta-sheet poly(L-lysine). Methanol, ethanol, and 1-propanol, but not 1-butanol, shifted the negative mean-residue ellipticity at 217 nm of the beta-sheet poly(L-lysine) to the positive side at low concentrations of the alcohols and to the negative side at high concentrations. With 1-butanol, only the positive-side shift was observed. The positive-side shift at low concentrations of alcohols indicates enhancement of the hydrophobic interactions among the side chains of the polypeptide in the beta-sheet conformation. The negative-side shift indicates a partial transformation to alpha-helix. The shift from the positive to negative side occurred at 7.1 M methanol, 4.6 M ethanol, and 3.1 M 1-propanol. The alcohol concentrations for the beta-to-alpha transition were higher in the CD study than in the IR study.(ABSTRACT TRUNCATED AT 250 WORDS)     

Purification and partial characterization of two types of growth-inhibitory protein latently present in rabbit serum.

Normal rabbit serum contained two kinds of growth-inhibitory protein, GI-I and GI-II, in latent forms. These latent inhibitors were activated by incubation at 37 degrees C for 12 h, and their activation was lowered by inhibitors for serine, cysteine and metalloproteinases. Both growth inhibitors were highly purified in active forms by successive column chromatographies. GI-I showed a major protein band with an Mr of 18,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, while GI-II showed a major protein band with an Mr of 36,000. GI-I and GI-II half-inhibited the growth of rat tumorigenic cell line (RSV-BRL) at concentrations of 0.5 ng/ml and 10 ng/ml, excess concentrations. Of the 15 cell lines tested, GI-I specifically inhibited the growth of rodent and lagomorph cells, whereas GI-II nonspecifically inhibited the growth of all cell lines tested. Specificities for cell type and malignancy were not observed with either inhibitor. These growth inhibitors were stable to a reducing reagent and proteinase inhibitors, but labile to urea, acid, organic solvents, trypsin, plasmin and heating at 95 degrees C for 5 min. These properties suggested that both growth inhibitors might be distinct from known growth-inhibitory factors.     

Distinct effects of different low temperatures on the induction of NAD-sorbitol dehydrogenase activity in diapause eggs of the silkworm,Bombyx mori

Summary Diapause eggs of the silkworm, Bombyx mori, exposed to 5°C and 0.5°C from 2 or 30 days after oviposition, were examined for changes in contents of glycogen, sorbitol and glycerol. Cold acclimation did not alter the profile of accumulation of sorbitol from that in eggs kept continuously at 25°C. However, acclimation at 5°C resulted in conversion of sorbitol to glycogen, while acclimation at 0.5°C was not accompanied by the utilization of sorbitol. NAD-sorbitol dehydrogenase (NAD-SDH; EC 1.1.1.14) activity was examined in the cold-acclimated eggs. The activity was induced by acclimation at 5°C but not at 0.5°C. Incubation at 0.5°C suppressed any further increase in the activity that had been induced. Temperature-directed changes in NAD-SDH activity paralleled those in sorbitol content. Hatching of the diapause eggs was monitored after cold acclimation for various periods of time and subsequent transfer to 25°C. Incubation at 0.5°C was less effective than 5°C at breaking diapause. The time required for the eggs to hatch in synchrony after acclimation at 5°C coincided with that required for the induction of NAD-SDH activity. These results show that different effects result from acclimation at 5°C and near 0°C with respect to the control of NAD-SDH activity, that utilization of sorbitol is controlled by NAD-SDH activity, and that induction of this activity is temperature-dependent. Furthermore, induction of NAD-SDH activity is involved in the termination of diapause in B. mori.Abbreviations DH diapause hormone - NAD nicotinamide-adenine-dinucleotide - NAD-SDH NAD-sorbitol-dehydrogenase     

An ultrastructural and immunohistochemical study of extracellular matrix in meningiomas

Extracellular matrix of meningiomas was studied by light and electron microscopy with the aid of immunohistochemical techniques. Special attention was paid to the distribution of type I, III, IV, V collagens and laminin with a comparison between meningothelial and fibroblastic types. Connective tissue fibers and basement membrane were not found among the tumor cells in the meningothelial type, but were found in the fibroblastic type. The immunolocalizations were consistently demonstrated extracellularly, but were not within the cytoplasm. Type I, III and V collagens were usually demonstrated in the fibrous septum in the meningothelial type, while they were localized among the tumor cells in the fibroblastic type. Furthermore, type IV collagen and laminin were demonstrated within the vascular walls or around the syncytium in the meningothelial type, while they were localized among the tumor cells in the fibroblastic type. In both types the expression of type IV collagen and laminin was closely related to the distribution of basement membrane. Although meningothelial and fibroblastic meningiomas showed quite different distribution of extracellular matrices, the profile of collagen types expressed by these two basic types was essentially the same. The cellular derivation of meningiomas was discussed with particular attention to the structure of human arachnoid villi and meninges.     

Hormonal induction of all stages of spermatogenesis in germ-somatic cell coculture from immature Japanese eel testis

In cultivated male eel, spermatogonia are the only germ cells present in testis. Our previous studies using an organ culture system have shown that gonadotropin and 11-ketotestosterone (11-KT, a potent androgen in teleost fishes) can induce all stages of spermatogenesis in vitro. for detailed investigation of the control mechanisms of spermatogenesis, especially of the interaction between germ cells and testicular somatic cells during 11-KT-induced spermatogenesis in vitro, we have established a new culture system in which germ cells and somatic cells are cocultured after they are aggregated into pellets by centrifugation. Germ cells (spermatogonia) and somatic cells (mainly Sertoli cells) were isolated from immature eel testis. Coculture of the isolated germ cells and somatic cells without forming aggregation did not induce spermatogenesis, even in the presence of 11-KT. In contrast, when isolated germ cells and somatic cells were formed into pellets by centrifugation and were then cultured with 11-KT for 30 days, the entire process of spermatogenesis from premitotic spermatogonia to spermatozoa was induced. However, in the absence of 11-KT in the culture medium spermatogenesis was not induced, even when germ cell and somatic cells were aggregated. These results demonstrate that physical contact of germ cells to Sertoli cells is required for inducing spermatogenesis in response to 11-KT.     

Induction of Light Dependent Pyruvate Transport into Chloroplasts of Mesembryanthemum crystallinum by Salt Stress

Mode of photosynthesis in Mesembryanthemum crystallinum changesfrom C₃ to Crassulacean acid metabolism (CAM) when the plantswere stressed with high salinity. [¹⁴C]Pyruvate uptake for 30s into intact chloroplasts isolated from leaves of the CAM modeof M. crystallinum was enhanced more than 5-fold in the lightcompared with that in the dark. The stromal concentration ofpyruvate in the light reached to more than 2.5 times of themedium. In contrast, little or no pyruvate uptake occurred inchloroplasts from C₃ leaves in either light or dark condition.The initial uptake rate (10 s incubation at 4°C) into theCAM chloroplasts in the light was about 3-fold higher than therate in the dark. K_m and V_max of the initial uptake in the lightwere 0.54 mM and 8.5 µmol (mg Chl)^–1 h^–1 respectively.These suggest that pyruvate was actively incorporated into theCAM chloroplasts against its concentration gradient across theenvelope in the light. When hydroponically grown M. crystallinumwere stressed by 350 mM NaCl, the capacity of chloroplasts forpyruvate uptake was induced in 6 d corresponding to the inductionof the activities of PEP-carboxylase and NAD(P)⁺-malic enzymesin response to salt stress. (Received October 12, 1995; Accepted January 19, 1996)