Role of protein kinase C in luteinizing hormone-releasing hormone (LHRH)-stimulated progesterone production in rat granulosa cells

Treatment of rat granulosa cells with LHRH or the phorbol ester TPA stimulated progesterone (P) production during a 5-h incubation. The concomitant presence of a potent inhibitor of protein kinase C attenuated the LHRH effect by ca. 60% and completely blocked the stimulatory effect of TPA. Addition of TPA (10(-9), 10(-8) or 10(-7) M) or dioctanylglycerol (100 micrograms/ml) increased P production; these stimulatory effects were not potentiated by the concomitant presence of a calcium ionophore (A23187, 10(-7) or 10(-6)M). These data support the hypothesis that protein kinase C activation have a role in the steroidogenic action of LHRH in the ovary.

Characterization of murine monoclonal antibodies that recognize neutralizing epitopes on human C5a

We generated a panel of 10 murine monoclonal antibodies (MAbs) that recognize human complement fragment C5a. These MAbs were characterized for their ability to immunoprecipitate 125I-labeled C5a, bind C5a in solid-phase enzyme immunoassay, and block 125I-labeled C5a binding to polymorphonuclear leukocytes. Four of these MAbs had affinity constants for C5a in the 1 X 10(9) to 3 X 10(9) M-1 range. These MAbs blocked C5a-induced neutrophil polarization and chemiluminescence. They blocked the ability of passively administered C5a to cause neutropenia in rabbits. These anti-C5a neutralizing MAbs may have potential therapeutic use in states of complement activation.

Environmental effects on photosynthesis, nitrogen-use efficiency, and metabolite pools in leaves of sun and shade plants

Effects of varying light intensity and nitrogen nutrition on photosynthetic physiology and biochemistry were examined in the sun plant Phaseolus vulgaris (common bean) and in the shade plant Alocasia macrorrhiza (Australian rainforest floor species). In both Phaseolus and Alocasia, the differing growth regimes produced large changes in photosynthetic capacity and composition of the photosynthetic apparatus. CO(2)-saturated rates of photosynthesis were linearly related to leaf nitrogen (N) content in both species but photosynthesis per unit leaf N was markedly higher for Phaseolus than for Alocasia. Photosynthetic capacity was also higher in Phaseolus per unit ribulose 1,5-bisphosphate (RuBP) carboxylase (RuBPCase) protein. The leaf content of RuBPCase was linearly dependent on leaf N content in the two species. However, the proportion of leaf N which was RuBPCase was greater in Phaseolus than in Alocasia and was more sensitive to growth conditions, ranging from 6% of leaf N at low light to 20% at high light. In Alocasia, this range was much less, 6 to 11%. However, chlorophyll content was much more sensitive to light intensity in Alocasia. Thus, the RuBPCase/chlorophyll ratio was quite responsive to N availability and light intensity in both species (but for different reasons), ranging from 6 grams per gram for Phaseolus and 2 grams per gram for Alocasia at high leaf N and 1.5 gram per gram for Phaseolus and 0.5 gram per gram for Alocasia at low leaf N. These large changes in the proportions of components of the photosynthetic apparatus had marked effects on the sensitivity of these species to photoinhibition. These environmental effects also caused changes in the absolute levels of metabolites of the photosynthetic carbon reduction cycle. Concentrations of RuBP and P-glycerate were approximately 2-fold higher in high light-grown than low light-grown Phaseolus and Alocasia when expressed on a leaf area basis. However, if metabolite pool sizes are expressed on the basis of the RuBPCase catalytic site concentration, then they were little affected by the marked changes in leaf makeup. There appears to be fundamental differences between these species in the mechanism of sun-shade adaptation and N partitioning in the photosynthetic apparatus that result in significant differences in the N-use efficiency of photosynthesis between Phaseolus and Alocasia but similar RuBPCase:substrate:product ratios despite these differences.

Liver alcohol and aldehyde dehydrogenase isoenzymes in Chinese

Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) isoenzyme phenotypes were determined in 71 autopsy liver specimens by agarose isoelectric focusing and starch gel electrophoresis, respectively. Ninety percent of the livers examined exhibited a pH-optimum for ethanol oxidation at pH 8.5, instead of 10.5 which is usual among Caucasians. The homozygous ADH2 2-2 phenotype was found to be 59%, and the heterozygous ADH2 2-1 phenotype, 31%. The remaining 10% of the livers, exhibiting a pH-optimum at 10.5, were homozygous ADH2 1-1 phenotype. Accordingly, the gene frequencies of the alleles ADH2(2) and ADH2(1) were calculated to be 0.75 and 0.25, respectively. Fifty-eight percent of the 71 livers examined possessed both the activities of ALDH I and ALDH II isoenzymes, whereas 42% lacked the ALDH I activity. The implications of these distributions of liver ADH and ALDH isoenzyme patterns among Orientals for ethanol elimination, alcohol sensitivity and alcoholism are discussed.

Epithelial responses evoked by stimulation of submucosal neurons in guinea pig distal colon

The influence of submucosal neurons on ion transport in the guinea pig distal colon was examined in muscle-stripped sheets of submucosa-mucosa set up in Ussing flux chambers. Spontaneous variations in potential differences (PD) and short-circuit current occurred ranging from positive currents associated with luminal negative PDs to negative currents with luminal positive PDs. Basal current in both groups was reduced by mucosal amiloride. In tissues with positive or negative short-circuit currents, unidirectional mucosal-to-serosal sodium fluxes were greater than serosal-to-mucosal fluxes and small net absorptive fluxes were present. Little or no chloride secretory flux was present. Electrical stimulation of submucosal neurons evoked a tetrodotoxin-sensitive increase in short-circuit current in tissues with positive or negative short-circuit currents. This was due to an increase in net chloride flux and little change in net sodium flux or residual flux. The increase in net chloride flux was due almost entirely to an increase in serosal-to-mucosal chloride flux and was associated with an increase in total tissue conductance. The stimulus-evoked response was reduced by atropine. These results suggest that stimulation of submucosal neurons that innervate the distal colonic epithelium evokes a large chloride secretory response that is due in part to release of acetylcholine at neuro-enterocyte junctions.

Nuclear factors binding to the human immunoglobulin heavy-chain gene enhancer

The human immunoglobulin heavy chain (IgH) gene contains at least two tissue-specific regulatory regions, which are similar to the mouse IgH gene. One is the J-C enhancer and another is located in the 5' promoter region. Using an electrophoretic mobility shift assay and DNase I footprint, we have examined the interaction of factors in B cell nuclear extracts with the two regulatory regions of the human IgH gene. We have identified a nuclear factor in mouse B cell nuclear extracts which bound to specific sequence in the human IgH enhancer. This factor is apparently not present in mouse fibroblast nuclear extracts. We also found factor(s) which bound to the highly conserved octanucleotide sequence within the human IgH enhancer and 5' promoter regions.

Luteinizing hormone-releasing hormone (LHRH)-induced arachidonic acid release in rat granulosa cells. Role of calcium and protein kinase C

In rat granulosa cells prelabeled with [3H]arachidonic acid, addition of LHRH, A23187 or 12-0-tetradecanoyl phorbol-13-acetate (TPA) enhanced the release of [3H]arachidonic acid into the culture medium. The effect of A23187 was significant as early as 5 min and the lowest effective dose was 5 X 10(-8)/M. On the other hand, TPA was effective only at dosages greater than 10(-6)M. These results suggest that the stimulatory effect of LHRH on arachidonic acid release is coupled more tightly to a Ca2+-dependent rather than a protein kinase C-mediated pathway.

Terbium luminescence-lifetime heterogeneity and protein equilibrium conformational dynamics

The fluorescence decay of the rare earth terbium when bound to the protein calmodulin changes from a simple exponential decay to a complex nonexponential decay as the temperature is lowered below 200 K. We have fit the observed decay curves by assuming that the terbium emission is a forced electric dipole transition and proteins have a distribution of continuous conformational states. Quantitative fits to the data indicate that the root-mean-square configurational deviation of the atoms surrounding the terbium ion is 0.2 A, in good agreement with other measurements. We further point out that because the protein seems to undergo a glass transition yet retains configurational order at room temperature, the proper name for the physical state of a protein at room temperature is the rubber-like state.

Obesity and serum lipids: an evaluation of the relative contribution of body fat and fat distribution to lipid levels

The association of obesity and hyperlipidemia does not mean that fatness per se is the primary determinant of the lipid abnormality. To evaluate the contribution of fatness to fasting levels of serum triglycerides (TG), LDL cholesterol (LDL-C), and HDL cholesterol (HDL-C), we analyzed data on 368 caucasian adults (286 women, 82 men) consecutively entering a weight control program. Although most subjects were overweight, the population represented a wide spectrum of body weights and lipid levels. Study variables included body fat mass (by total body water), fat free mass (FFM), body build (chest to height ratio), fat cell size and number (from bilateral buttock biopsy specimens), upper-lower body fat pattern by arm to thigh circumference ratio, central-peripheral fat pattern by subcapsular to triceps skinfold ratio, waist to hip ratio, and the presence or absence of diabetes. Our results concurred with previously noted correlations of body weight with TG (r = 0.29, P less than 0.0001) and with HDL-C (r = -0.28, P less than 0.0001) at least in the larger sample of women, but there was no significant correlation with LDL-C (r = -0.06). In order to evaluate the relative contribution of the various components of body composition and fat distribution to lipid levels, stepwise regression analyses were performed on the subgroups of women and men. Among women: TG level was predicted best by FFM, upper body fat pattern, age, and diabetes (explaining 30 percent of TG variance); LDL-C level was predicted by age only (explaining 12 percent of variance); and HDL-C level was predicted by body build only (8 percent). Among men: TG level was predicted best by central and upper body fat patterns and diabetes (31 percent of variance); LDL-C and HDL-C levels were not significantly predicted by any of the 11 study variables. These results, obtained from cross-sectional analysis of a predominantly obese sample, suggest that lipid levels may be more directly related to body fat pattern, fat free mass and body build than to body fatness itself.

A mechanism by which atrial natriuretic factor mediates its glomerular actions

Differential in vivo glomerular effects of atriopeptin I (AP I) and atriopeptin III (AP III) were studied in parallel with in vitro physiological and biochemical parameters. In anesthetized Sprague-Dawley rats, AP III, but not AP I, significantly increased glomerular filtration rate. Image analysis microscopy was used to assess the effect of AP I and AP III on angiotensin II (ANG II)-induced contraction of cultured rat glomerular mesangial cells. AP III, but not AP I, inhibited ANG II-induced mesangial cell contraction in a concentration-dependent manner. Additional inhibitory agents included exogenous DBcGMP, 8-BrcGMP, Na nitroprusside, and DBcAMP. AP III stimulated mesangial cell cGMP with a lower threshold and greater maximum stimulation than AP I. Neither agent stimulated cAMP accumulation. Since mesangial cell contractility may regulate the glomerular capillary surface area, these results suggest that AP III partially mediates its glomerular effects through inhibition of ANG II-induced mesangial cell contraction. Whereas cGMP is not clearly implicated as the mediator of this effect, it appears that both cGMP and cAMP may regulate the state of mesangial cell contractility.

Regulation of fibronectin receptor distribution by transformation, exogenous fibronectin, and synthetic peptides

Recent studies have shown that fibronectin and its 140K membrane receptor complex are spatially associated with microfilaments to form cell surface linkage complexes which are thought to mediate adhesive interactions between fibroblasts and their substrata. We examined the regulation of the organization of these cell surface structures in transformed and fibronectin-reconstituted cells as well as in cells treated with a competitive synthetic peptide inhibitor of fibronectin binding to its receptor. Correlative localization experiments with interference reflection microscopy and double-label or triple-label immunofluorescence revealed a concomitant loss of fibronectin, 140K receptor, and alpha-actinin colocalization at cell substratum extracellular matrix contact sites after transformation of chick fibroblasts by wild-type or temperature-sensitive Rous sarcoma viruses (RSV). Western and dot immunoblot analyses established that although similar total quantities of intact 140K molecules were present in the transformed cell cultures, significantly more was released into the culture medium of transformed cells. The 140K molecules on transformed cells were available for interaction with exogenously added fibronectin, which could reconstitute fibronectin-140K linkage complexes. In such fibronectin reconstitution experiments, many cells expressed both fibronectin-140K-actin linkage complexes and RSV pp60src, indicating that the morphological reversion could occur even in the continued presence of RSV transformation. The synthetic peptide Gly-Arg-Gly-Asp-Ser derived from the sequence of the cell-binding region of fibronectin could also prevent the organization of fibronectin-140K linkage complexes. Our results suggest that fibronectin interaction with cells regulates the organization of fibronectin receptor complexes and cytoskeletal components at the cell surface.