Effect of long-term anemia and retransfusion on central circulation during exercise

The bulk modulus and the shear modulus describe the capacity of material to resist a change in volume and a change of shape, respectively. The values of these elastic coefficients for air-filled lung parenchyma suggest that there is a qualitative difference between the mechanisms by which the parenchyma resists expansion and shear deformation; the bulk modulus changes roughly exponentially with the transpulmonary pressure, whereas the shear modulus is nearly a constant fraction of the transpulmonary pressure for a wide range of volumes. The bulk modulus is approximately 6.5 times as large as the shear modulus. In recent microstructural modeling of lung parenchyma, these mechanisms have been pictured as being similar to the mechanisms by which an open cell liquid foam resists deformations. In this paper, we report values for the bulk moduli and the shear moduli of normal air-filled rabbit lungs and of air-filled lungs in which alveolar surface tension is maintained constant at 16 dyn/cm. Elevating surface tension above normal physiological values causes the bulk modulus to decrease and the shear modulus to increase. Furthermore, the bulk modulus is found to be sensitive to a dependence of surface tension on surface area, but the shear modulus is not. These results agree qualitatively with the predictions of the model, but there are quantitative differences between the data and the model.     

The effect of erythropoietin on the mature burst forming unit erythroid in mice

The aim of the study was to further delineate the erythropoietin (Ep) dependence of the mature Burst Forming Unit-Erythroid - BFU-E(d4). Experiments were performed in normal and polycythemic CBA mice. BFU-E(d4) were determined by means of the methylcellulose culture technique. It was demonstrated that in plethoric mice the number of BFU-E(d4) is reduced from 9 000/femur and 30 000/spleen found in normal mice to less than 1 000/femur and 2 000/spleen on day 6 post-hypoxia. The number of BFU-E(d4) remained low both in the bone marrow and spleen in mice with posthypoxic polycythemia between days 6 and 11 post-hypoxia. When exogenous Ep was injected into the plethoric mice the number of BFU-E(d4) increased after 24 h both in the bone marrow and spleen. In Ep stimulated polycythemic mice the CFU-E:BFU-E(d4) ratio did not achieve normal values, indicating that although Ep stimulation increased the number of BFU(d4), the number of CFU-E produced per BFU-E(d4) was lower than in normal nonpolycythemic mice. The results obtained indicate that BFU-E(d4) population size depends on the effect of Ep on differentiation and proliferation of erythroid committed precursors.     

Ammonium repression of cephalosporin production by Streptomyces clavuligerus

Production of beta-lactam antibiotics took place during growth of Streptomyces clavulgerus in chemically defined medium. The specific activities of isopenicillin N synthetase ("cyclase"), isopenicillin N epimerase, and deacetoxycephalosporin C synthetase ("expandase") increased during the exponential phase of growth. Specific cephalosporin productivity during fermentation followed a similar pattern, reaching a maximum near the end of the growth phase and decaying rapidly in the stationary phase. Ammonium chloride depressed cephalosporin production, presumably as a result of repression of cyclase and expandase formation, but not of epimerase. No inhibitory effects on enzyme activity by ammonium were found. Addition of tribasic magnesium phosphate [Mg3(PO4)2 X 8H2O] prevented the repression of cyclase and markedly stimulated cephalosporin production. Cephamycin C and, in smaller amounts, O-carbamoyldeacetylcephalosporin C were the only cephalosporins detected. Growth with ammonium resulted in lower titers of both compounds, and did not change the relative proportion of each. The correlation found between cephalosporin productivity and cyclase specific activity in different media suggests that formation of this enzyme may be the rate-limiting step in the pathway.     

An early role of maternal mRNA in establishing the dorsoventral pattern in pelle mutant Drosophila embryos

Mutations of the maternal effect locus pelle (pll) cause dorsalized Drosophila embryos. In extreme mutants, the embryo develops into a long hollow tube of dorsal cuticular structures with no sign of ventral pattern elements. Injection of wild-type cytoplasm or poly(A)+RNA into mutant pll embryos partially restores the normal pattern. Rescuing activity is present in the wild-type cytoplasm until the late blastoderm stage, but is already absent from the poly(A)+RNA fraction by the time of pole cell formation. At the same time, pll embryos fail to respond to injected biologically active poly(A)+RNA. This indicates that pll+ mRNA is lost early from the pool of maternal RNA and that there is a non-RNA component of rescue. This component, most likely the pll+ protein, appears to be unequally distributed in wild-type embryos.     

Lipid peroxidation in liver, plasma, and erythrocytes of rats chronically treated with ethanol

The effect of ingestion of water containing 20% ethanol for 1-2 months on lipid peroxide levels of liver, plasma, and erythrocyte was investigated in rats. Our results show that elevated plasma lipid peroxide levels and erythrocyte susceptibility to lipid peroxidation may reflect stimulated lipid peroxidation in rat liver following chronic ethanol ingestion.     

Head-group contributions to bilayer stability: monolayer and calorimetric studies on synthetic, stereochemically uniform glucolipids

Monolayer and differential scanning calorimetry studies have been performed on synthetic, stereochemically uniform glyceroglucolipids having saturated, ether-linked alkyl chains. The limiting area, A0 = 40 A2 X molecule-1, resulting from the monolayer measurements of the glucolipids is comparable to the A0 value found for phosphatidylethanolamine lipids. The area corresponds to twice the value observed with saturated straight chain fatty acids, which indicates that at high surface pressure the space requirement of the glucose head group does not exceed that of the two alkyl chains. The apparent specific heat capacities of the glucolipid dispersions have been found to be higher than those of corresponding phospholipids. They can be approximated from group parameters with the additional assumption that the experimental partial molar heat capacity of glucose is valid for the glucose head groups of the lipids. The transition enthalpies of the C16 and C18 glyceroglucolipids are clearly larger than the delta H values of corresponding phospholipids, while the C14 glyceroglucolipid has the same transition enthalpy as dimyristoylphosphatidylethanolamine or ditetradecylphosphatidylethanolamine. Glucolipids exhibit gel to liquid-crystalline phase transition temperatures which are only slightly lower than those of their phosphatidylethanolamine analogues, although they are uncharged molecules. Like phosphatidylethanolamine the glucolipids do not show a pretransition; however, with the C14 glucolipid a highly cooperative posttransition, approximately 5 deg above the main transition, has been found. Calorimetric experiments with a C14 glucolipid, in which the hydroxyl protons of the glucose moiety have been exchanged by deuterium, suggest that the posttransition might reflect structural changes of the head group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ribosomal protein S6 phosphorylation and morphological changes in response to the tumour promoter 12-O-tetradecanoylphorbol 13-acetate in primary human tumour cells, established and transformed cell lines

The phosphorylation of ribosomal protein S6 in fibroblasts, primary human tumour cells, established and SV40-transformed human cell lines was compared after the addition of 12-O-tetradecanoylphorbol 13-acetate (TPA). In fibroblasts and primary tumour cell cultures, stimulation of S6 phosphorylation was about 4-6-fold. Established and transformed cell lines showed enhanced S6 phosphorylation which was not further stimulated by the addition of TPA. These findings indicated that the influence of TPA on the metabolic pathway, that finally leads to the phosphorylation of protein S6 in cells with a limited lifespan (fibroblasts, primary human tumour cells) can be mimicked by unknown steps also associated with immortalization (establishment function) and the transformed state of the tumour cells. Another interesting observation were morphological changes of the established and SV40-transformed cells which were visible as early as 20 min after the addition of TPA. In fibroblasts and primary tumour cells no changes in morphology were observed, even after 8h incubation.     

Tryptophan residues of creatine kinase: a fluorescence study

Spectroscopic studies of rabbit skeletal muscle creatine kinase (CPK) and its complexes with adenosine phosphates have long suggested the occurrence of a tryptophan residue at or near the coenzyme binding sites [K?gi, J. H. R., Li, T.-K., & Vallee, B. L. (1971) Biochemistry 10, 1007-1015; Price, N. C. (1972) FEBS Lett. 24, 21-23]. This conjecture was further supported by nuclear Overhauser effect (NOE) 1H NMR studies indicating through-space interactions between protons of the adenine ring of bound ADP and one or more aromatic side chains of the proteins [Vasák, M., Nagayama, K., Wüthrich, K., Mertens, M. L., & K?gi, J. H. R. (1979) Biochemistry 18, 5050-5055]. Further evidence for a tryptophan residue in the environment of the active site has now been obtained by fluorescence-quenching studies using iodide and acrylamide as external quenchers. Thus, while by the addition of iodide the tryptophan fluorescence of unliganded CPK is reduced to about 75% of the unquenched control, no such effect is manifested upon addition of this quencher to the CPK.ADP and CPK.ATP complexes. Similarly, the relative effectiveness of quenching of the CPK-coenzyme complexes by acrylamide is only about 60% of that measured in the unliganded enzyme. Both these data and the spectral characteristics of the quenched fluorescence suggest that coenzyme binding perturbs a tryptophan residue that is close to the active site and that is partially exposed to the solvent. The differential effectiveness of external quenchers on unliganded and liganded CPK allows the determination of the ligand binding equilibria by fluorescence-quenchability titration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synthesis and secretion of the human vitamin B12-binding protein, transcobalamin II, by cultured skin fibroblasts and by bone marrow cells

Human skin fibroblasts and bone marrow cells were tested for their ability to synthesize the cobalamin-binding protein transcobalamin II. Cobalamin binders secreted in the media of cultured fibroblasts and of dextran-sedimented bone marrow cells in liquid culture could be identified as transcobalamin II on the basis of immunological, electrophoretical and chromatographical identity with serum transcobalamin II. The net secretion of transcobalamin II increased linearly with time of culture, up to 30 days after confluence. The reversible inhibition of transcobalamin II secretion by cycloheximide demonstrated that human fibroblasts are capable of de novo transcobalamin II synthesis. Addition of cyanocobalamin to the fibroblast culture medium induced a reduction of transcobalamin II net secretion, most likely due to preferred uptake of transcobalamin II saturated with cobalamin, as opposed to unsaturated protein. Addition of lysozymal enzyme inhibitors, ammonium chloride and chloroquine, resulted in a markedly increased secretion of transcobalamin II. In the culture medium of fibroblasts, obtained from two transcobalamin II-deficient patients, functionally deficient transcobalamin II was demonstrated on the basis of strongly reduced secretion of immunoreactive transcobalamin II, and the absence of apotranscobalamin II. Individual phenotypes in the culture media of the fibroblasts and bone marrow cells were identical to the corresponding serum transcobalamin II types.     

Leukotriene A4-hydrolase activity in guinea pig and human liver

Guinea pig and human liver homogenates transformed leukotriene A4 into leukotriene B4. In both species, the enzymatic activity was recovered in the 105000 X g supernatant, and it was found to be susceptible to heat treatment (56 degrees C, 1 h). Digestion with a proteolytic enzyme also resulted in loss of enzymatic activity. The formation of leukotriene B4 was pH-dependent, with an optimum between pH 7 and pH 8.5. In addition, two other organs from the guinea-pig, lungs and kidneys, contained leukotriene A4-hydrolase activity. The identity of leukotriene B4 was ascertained by high-performance liquid chromatography, ultraviolet spectrometry, gas chromatography-mass spectrometry and bioassay. We have recently demonstrated the presence of leukotriene A4-hydrolase activity in mammalian plasma (Fitzpatrick et al. (1983) Proc. Natl. Acad. Sci. USA 80, 5425-5429). The results of the present study suggest several possible origins of this plasma leukotriene A4 hydrolase.