Protein kinase C levels and protein phosphorylation associated with inhibition of proliferation in a murine macrophage tumor

Treatment of M5076 tumor cells with the phorbol estes 12-O-tetradecanoylphorbol 13-acetate (TPA) and phorbol 12,13 dibutyrate (PdBu) inhibited cellular proliferation, whereas 1,2-dioctanoyl-glycerol (DiC8) and 1-oleoyl2-acetyl-glycerol (OAG) did not affect cell growth. Inhibition of cellular proliferation in this cell line appears to be a consequence of protein kinase C (PKC) down-regulation since phorbol esters, but not a single application of diacylglycerols (DGs) down-regulated cellular PKC levels. By repeated application of DGs, PKC down-regulation was achieved and correlated with inhibition of proliferation. Phorbol ester-induced PKC down-regulation was reversible, upon removal of the phorbol ester, and the reappearance of PKC was associated with resumption of proliferation. The mitogenic responsiveness of these cells to added serum depended upon cellular PKC levels. Phorbol esters also caused the phosphorylation of two proteins which were not phosphorylated in response to DG treatment. Inhibition of growth of M5076 cells appears to be associated with phosphorylation of two novel proteins and/or PKC down-regulation.     

Studies on the Effect of Insulin-Like Growth Factor-I on Catecholamine Secretion from Chromaffin Cells

Chromaffin cells cultured in serum-free medium secreted a smaller percentage of their catecholamine stores in response to stimulation by high K+ (55 mM) than did cells cultured in serum-containing medium. Addition of insulin-like growth factor-I (IGF-I) to serum-free medium restored high K(+)-stimulated catecholamine secretion to the levels seen in serum-treated cultures. In contrast, addition of IGF-I to serum-containing medium had little effect on catecholamine secretion. These results suggest that serum contains IGF-I or another factor that maintains the secretory responsiveness of chromaffin cells. IGF-I not only enhanced high K(+)-stimulated catecholamine secretion, but also augmented secretion elicited by the nicotinic agonist dimethyl-phenylpiperazinium, the dihydropyridine agonist Bay K 8644, and Ba2+. IGF-I did not affect the dependence of catecholamine secretion on extracellular Ca2+ concentration nor did it affect the time course of secretion. Experiments using 45Ca2+ demonstrated that IGF-I treatment enhanced Ca2+ uptake into the cells. When cells were permeabilized by treatment with digitonin, Ca2(+)-dependent catecholamine secretion was slightly, but consistently, greater from IGF-I-treated cells than from untreated cells. Our results suggest that IGF-I may enhance catecholamine secretion partly by increasing Ca2+ entry into the cells and partly by affecting a step distal to Ca2+ entry.     

Diffusion effects in calcium-regulated strain fields

The Goodwin-Trainor equations for cellular morphogenesis, based on calcium ion regulation of the visco-elastic properties of the cellular cortex, are generalized to the situation where the concentration of calcium ions (free plus bound) is allowed to change locally. A stability analysis is presented which shows that the generalized equations are also stable against perturbations at low and high wave lengths and may, for certain parameter values, develop instabilities at intermediate wave lengths.     

Quantitative spectrophotometric assay for staphylococcal lipase.

We report the development of a specific spectrophotometric assay for the quantitative determination of lipase activity in Staphylococcus aureus. The assay is based on the rate of clearance of a tributyrin emulsion, and it can detect as little as 1.0 micrograms of purified Pseudomonas lipase per ml. By comparison with the reaction rates obtained with Pseudomonas lipase, we calculated that S. aureus PS54C and S6C produce approximately 15 and 60 micrograms of extracellular lipase per ml, respectively. Neither PS54, which is lysogenized with the converting bacteriophage L54a and is consequently lipase negative (Lip-), nor KS1905, a Lip- transpositional mutant of strain S6C, was positive in our spectrophotometric assay. The specificity of the spectrophotometric tributyrin assay was confirmed with a triolein plate assay; supernatants from S6C and PS54C hydrolyzed triolein, while supernatants from PS54 and KSI905 did not. In contrast to the results of the spectrophotometric tributyrin assay, all enzyme preparations tested (including commercially purified esterase) were positive when examined by a tributyrin plate assay. The lack of specificity in the tributyrin plate assay emphasizes the need to interpret the results of tributyrin lipolysis kinetically for assessing lipase activity in S. aureus.     

Spontaneous hypercholesterolemia in cynomolgus monkeys: evidence for defective low-density lipoprotein catabolism.

Spontaneously hypercholesterolemic (SH) cynomolgus monkeys were identified that have average plasma cholesterol of 202 mg/dl, while that in normal monkeys is 119 mg/dl. The LDL from these SH monkeys have lower affinity for fibroblast LDL receptors in vitro. The amount of LDL2 (1.030 mean value of d 1.063 g/ml) required to displace 50% of [125I]LDL was 3.8 micrograms/ml for normal LDL2 and 6.6 micrograms/ml for SH-LDL2. The binding affinity of LDL1 (1.019 mean value of d 1.030 g/ml) was the same in normal and SH animals. LDL turnover experiments showed that the SH monkeys were comprised of two populations. Normal LDL2 was cleared much slower in two of the SH monkeys than in normocholesterolemic animals, suggesting that these two animals have an LDL receptor defect. However, LDL2 isolated from these two SH monkeys was cleared normally in normal monkeys. LDL2 isolated from two other SH monkeys is cleared slower than is normal LDL2 in normal animals, suggesting that these animals have an LDL defect. Thus, the hypercholesterolemia of these SH monkeys is associated with defective LDL catabolism; two animals appear to have functionally defective LDL receptors, and two animals appear to have functionally defective LDL.     

Differentiation of mite species by using cellulose acetate and equilibrium polyacrylamide gel electrophoresis of isoenzymes

The isoenzymes of various species of medically and economically important mites were studied using cellulose acetate and equilibrium polyacrylamide gel electrophoresis. Interspecific differences in isoenzymes were found, which were species-specific. Intraspecific differences in isoenzymes were also found when individual mites were examined. The efficiency of each technique, and their use in various fields of acarology, are discussed. In addition, possible phylogenetic relationships as revealed by these techniques are suggested.     

Nicotine Effects on Dopamine Clearance in Rat Nucleus Accumbens

Abstract: In vivo voltammetry was used to measure the clearance of exogenously applied dopamine (DA) in the nucleus accumbens following acute systemic nicotine administration in urethane-anesthetized rats. The IVEC-5 system was used for continuous in vivo electrochemical measurements. A finite amount of DA was pressure-ejected (25–100 nl, 200 µ M barrel concentration) at 5-min intervals from micropipettes (tip diameter, 10–15 µm) positioned 250 ± 50 µm from the recording electrode. The peak DA concentration after each DA ejection was significantly decreased in rats following nicotine, but not in rats given saline. In addition, when mecamylamine was administered 20 min before nicotine it clearly antagonized nicotine effects. These results suggest that nicotine may actually facilitate DA transporter systems within the nucleus accumbens.     

EVOLUTIONARY LOSS OF LARVAL FEEDING: DEVELOPMENT,FORM AND FUNCTION IN A FACULTATIVELY FEEDING LARVA,BRISASTER LATIFRONS

Species with large eggs and nonfeeding larvae have evolved many times from ancestors with smaller eggs and feeding larvae in numerous groups of aquatic invertebrates and amphibians. This change in reproductive allocation and larval form is often accompanied by dramatic changes in development. Little is known of this transformation because the intermediate form (a facultatively feeding larva) is rare. Knowledge of facultatively feeding larvae may help explain the conditions under which nonfeeding larvae evolve. Two hypotheses concerning the evolutionary loss of larval feeding are as follows: (1) large eggs evolve before modifications in larval development, and (2) the intermediate form (facultatively feeding larva) is evolutionarily short-lived. I show that larvae of a heart urchin, Brisaster latifrons, are capable of feeding but do not require food to complete larval development. Food for larvae appears to have little effect on larval growth and development. The development, form, and suspension feeding mechanism of these larvae are similar to those of obligate-feeding larvae of other echinoids. Feeding rates of Brisaster larvae are similar to cooccurring, obligate-feeding echinoid larvae but are low relative to the large size of Brisaster larvae. The comparison shows that in Brisaster large egg size, independence from larval food, and relatively low feeding rate have evolved before the heterochronies and modified developmental mechanisms common in nonfeeding echinoid larvae. If it is general, the result suggests that hypotheses concerning the origin of nonfeeding larval development should be based on ecological factors that affect natural selection for large eggs, rather than on the evolution of heterochronies and developmental novelties in particular clades. I also discuss alternative hypotheses concerning the evolutionary persistence of facultative larval feeding as a reproductive strategy. These hypotheses could be tested against a phylogenetic hypothesis.