Keratinocyte growth-promoting activity from human placenta

Extracts of term human placenta were tested for enhancement of proliferative growth of primary cultures of human keratinocytes. Saline extracts or supernatants from homogenates were dialyzed extensively, lyophilized, and tested in subcultures of keratinocytes in MCDB 153 medium with 0.1 mM Ca++ containing only defined supplements (insulin, hydrocortisone, transferrin, ethanolamine, phosphoethanolamine). Cells plated in the absence of EGF at moderately high densities (1000-3000 cells per cm2) formed colonies and grew in the presence of placental extract at 25-500 micrograms/ml. Extracts of cord serum or maternal serum were inactive, suggesting that the activity is derived from placental tissue. The activity is not EGF, since the activity in the placental extract, unlike EGF, did not promote growth at low cell density, was synergistic with EGF under some conditions, and did not produce changes in colonial morphology which occurred in the presence of EGF. Unlike keratinocyte growth-promoting activity in bovine hypothalamic extract, the activity is non-dialyzable and is destroyed at 100 degrees C. Placental extract could not replace any of the defined components of the medium and is therefore distinct from them. The presence of activity in the placenta with distinctive properties suggests that this is a previously undescribed material with growth-promoting properties for epithelium.     

Schistosoma mansoni: killing of transformed schistosomula by the alternative pathway of human complement

The interaction of mechanically transformed schistosomula of Schistosoma mansoni with the alternative pathway of human complement was studied in vitro. To detect early changes in transformation, the schistosomula were prepared at a low temperature and used immediately. As shown previously, freshly transformed schistosomula were highly susceptible to killing by normal human serum and by C4-depleted normal human serum. This serum activity was concentration dependent and was markedly reduced on a twofold serum dilution. Upon incubation at 37 C in defined synthetic medium, schistosomula rapidly became refractory to killing by the alternative pathway of complement. After 1 hr of incubation at 37 C, the percentage of schistosomula which were resistant to killing increased from 16 to 85. This conversion was accompanied by a fivefold decrease in deposition of C3b on schistosomula which had been exposed to 37 C for 1 hr and then further incubated with C4-depleted normal human serum. The following events occurred concomitantly during incubation of freshly transformed schistosomula at 37 C with a half-life of 30-60 min: (1) Decrease in activation and consumption of the alternative pathway of complement by schistosomula; (2) appearance of a strong complement consuming activity in the supernatant of incubating schistosomula; and (3) shedding of protein- and carbohydrate-containing substances from the surface of schistosomula into the supernatant. Isolated external membranes of freshly transformed schistosomula consumed the alternative pathway of complement to a greater extent than membranes of schistosomula preincubated in medium at 37 C. The results demonstrate that transformed schistosomula acquire resistance to complement killing via the alternative pathway by shedding complement-activating substances.(ABSTRACT TRUNCATED AT 250 WORDS)     

Complementarity of regulation for the two glutamine synthetases from Bacillus caldolyticus, an extreme thermophile

Chromatophores from Rhodopseudomonas capsulata cells grown semiaerobically in the dark oxidize NADH, succinate, and dichlorophenolindophenol. In the presence of N₃^? these activities are inhibited, but light induces oxidation of dichlorophenolindophenol with O₂ as a terminal electron acceptor. Cyanide also inhibits electron transport but much higher concentrations are required to inhibit the photooxidation than the dark oxidation. The photooxidation was studied in a mutant strain of Rhodopseudomonas capsulata (YIV) which cannot grow anaerobically in the light, but similarly to the wild type, grows in the presence of oxygen. Chromatophores from YIV mutant catalyze photophosphorylation and dark oxidation activities with the same properties as those of the wild type. However, the rate of photooxidation in the mutant is only one-third that of the wild type. Based on the differential inhibitor sensitivity and on the mutation it is suggested that the photooxidase is different from the two respiratory oxidases and that this photooxidation activity might be essential for growth of the cells under anaerobic conditions in the light.     

Modulation of the expression of interleukin 2 receptors of human thymocytes by recombinant interleukin 2

The effect of purified recombinant interleukin 2 on the expression of the receptors for interleukin 2 by human thymocytes was examined. Interleukin 2 augmented the expression of interleukin 2 receptors and interferon-gamma synthesis by thymocytes activated with concanavalin A, and it was required to maintain the growth of thymocytes in vitro and the expression of interleukin 2 receptors. The increase observed in the number of receptor bearing thymocytes and in the density of receptors due to interleukin 2 occurred within the first 2 days of culture. Dexamethasone inhibited the expression of interleukin 2 receptors, the synthesis of interferon-gamma, and the early proliferation and protein synthesis of lectin-activated thymocytes during the first 2 days of culture. The inhibitory effect of dexamethasone on the expression of interleukin 2 receptors and on the synthesis of interferon-gamma was reversed by interleukin 2, whereas its effect on proliferation and on protein synthesis during the first two days of culture was not reversed by interleukin 2. Interleukin 2 induced the proliferation of thymocytes in vitro, even in the absence of activation by lectin; however, the number of cells displaying receptors which could be detected with anti-Tac remained low throughout the first week of culture and interferon-gamma synthesis was not observed. Nonetheless, interleukin 2-induced proliferation was inhibited by anti-Tac on a dose dependent manner. The results of the study document that recombinant interleukin 2, like purified natural interleukin 2, is required for the expression of interleukin 2 receptors, for interferon-gamma synthesis, and for the growth of thymocytes in vitro.     

Absent aldosterone response to metoclopramide in patients with high spinal cord transection: evidence that metoclopramide stimulates aldosterone secretion through central pathways

This study evaluates dopaminergic regulation of aldosterone secretion in 6 patients with high spinal cord transections. Administration of the dopamine antagonist metoclopramide resulted in a marked rise in plasma aldosterone and 18-hydroxycorticosterone levels in 12 normal individuals, but no change in plasma levels of these zona glomerulosa corticosteroid products in spinal cord patients. Spinal cord transected patients also did not have the rise in plasma renin activity that was observed in normals following metoclopramide administration. Basal levels of aldosterone, 18 hydroxycorticosterone, corticosterone and renin activity as well as the aldosterone responses to graded dose infusion of adrenocorticotropin were similar in the spinal cord patients and the normals. These data suggest that dopaminergic regulation of adrenal zona glomerulosa corticosteroid and renal renin secretion is absent in patients with high spinal cord transections, suggesting that intact neural pathways from the central nervous system are necessary for metoclopramide stimulation of aldosterone and renin secretion in men. Since basal plasma aldosterone levels were normal in spinal cord transected patients, it appears that the absence of dopaminergic control does not result in elevated secretion.     

Effect of 5,7-unsaturated sterols on ethanol tolerance in Saccharomyces cerevisiae.

Structural membrane lipids are known to contribute to the high ethanol resistance of Saccharomyces cerevisiae (2, 4, 17). By manipulating the yeast cellular sterol level by changing the carbon-to-nitrogen source ratio in the chemostat growth medium, high delta 5,7-sterol levels were found to increase the resistance of yeast populations to ethanol-induced death. The resistance of the erg2 (delta 8----delta 7-sterol isomerase) mutant to ethanol-induced death was generally comparable with that of the delta 5,7-sterol-synthesizing strain. In contrast, the sensitivity of anaerobic growth to inhibition by ethanol was higher in the erg2 mutant in comparison with the delta 5,7-sterol-synthesizing strains but a high level of those sterols increased the vulnerability of anaerobic growth to ethanol inhibition.