Bradykinin and thrombin effects on polyphosphoinositide hydrolysis and prostacyclin production in endothelial cells.

Prostacyclin (PGI2) production by thrombin- and bradykinin-stimulated bovine aortic endothelial cells (BAEC) and human umbilical vein endothelial cells (HUVEC) was related to the receptor-linked activation of inositide hydrolysis. Bradykinin caused a rapid and transient 3-fold increase in the formation of inositol polyphosphates in BAEC. The increase in InsP3 reflected changes mainly in the Ins(1,4,5)P3 isomer. Thrombin was less effective than bradykinin in increasing InsP3 levels and appeared to only minimally stimulate the production of PGI2 in BAEC. In HUVEC, thrombin caused a 5-fold elevation of Ins(1,4,5)P3, closely related to a rise in PGI2 production. However, bradykinin did not affect inositol phosphates and PGI2 production in HUVEC. Other inositol phosphates were also assessed to obtain information on putative metabolism of Ins(1,4,5)P3. The present study supports the notion that formation of Ins(1,4,5)P3 is linked to an increase in PGI2 production in endothelial cells and furthermore provides evidence for a large degree of heterogeneity in the responses of BAEC and HUVEC to thrombin and bradykinin.     

45Ca2+ uptake and peptide hormones secretion in the presence of excess Mg2+ content

Studies have been performed on the relationship between PRL and GH production and the 45Ca2+ influx in high magnesium content in vitro. The obtained data show that an elevated magnesium concentration in Krebs-Ringer solution is capable of inhibiting some hormonal function of the pituitary gland. It has been found, that PRL and GH released into the media in normal KRB solution revealed nearly two times higher concentration than in the presence of high Mg2+. Instead the cellular iPRL and iGH did not show any significant differences in control and in treated cultures. The incorporation of 4.5-3H-leucine into the prolactin and growth hormone demonstrate a significant decrease in the presence of high Mg2+ indicating that the ion is able to inhibit the secretion of newly synthesized PRL an GH. High concentration of Mg2+ abolished either the stimulation effect of releasing hormones on calcium uptake.     

Biotechnology of petroleum pollutant biodegradation

Procedures designed to meet the physiological needs of petroleum hydrocarbon (PHC) degrading microorganisms are useful in mitigating environmental damage caused by marine and terrestrial PHC spills. By similar approaches, soil can be utilized as a cost-effective biological incinerator for hazardous PHC wastes. Physiological ecology needs to complement genetic engineering efforts for an effective attack on environmental pollution problems.     

Hydrocarbon Metabolism by Brevibacterium erythrogenes: Normal and Branched Alkanes

Branched- and straight-chain alkanes are metabolized by Brevibacterium erythrogenes by means of two distinct pathways. Normal alkanes (e.g., n-pentadecane) are degraded, after terminal oxidation, by the beta-oxidation system operational in fatty acid catabolism. Branched alkanes like pristane (2,6,10,14-tetramethylpentadecane) and 2-methylundecane are degraded as dicarboxylic acids, which also undergo beta-oxidation. Pristane-derived intermediates are observed to accumulate, with time, as a series of dicarboxylic acids. This dicarboxylic acid pathway is not observed in the presence of normal alkanes. Release of (14)CO(2) from [1-(14)C]pristane is delayed, or entirely inhibited, in the presence of n-hexadecane, whereas CO(2) release from n-hexadecane remains unaffected. These results suggest an inducible dicarboxylic acid pathway for degradation of branched-chain alkanes.     

Thyrotropin-releasing hormone (TRH) is not thyrotropic but somatotropic in fed and starved adult chickens.

Adult fed and starved Warren chickens, 2 yr of age, and approaching the end of the second laying year, were injected iv with 1 of the following products: 10 micrograms of thyrotropin releasing hormone (TRH); 100 micrograms of bovine thyrotropin (bTSH); 100 micrograms of ovine growth hormone (oGH); saline. The influence on plasma concentrations of thyroxine (T4), triiodothyronine (T3) or chicken GH (cGH) were followed. Prior to injection, it was clear from the control values that starvation for 3 d decreased plasma levels of T3 and increased cGH, whereas 7 d of fasting increased T4 and cGH. The plasma levels of cGH were elevated greater than 10-fold at 15 min following the TRH challenge in food-deprived chickens compared to a less than 4-fold increase in normal fed hens. This increase was followed by a rise in T3 after 1 h, which was also more pronounced in the starved animals, whereas T4 decreased or remained unaffected. Increases in T4 can, however, be obtained with 100 micrograms TSH in normal fed (2-fold) or starved animals (greater than 3-fold). Following injection of 100 micrograms oGH, a significant increase in T3 levels was observed which in fed animals was already present at 30 min, but the higher levels persisted for 1 and 2 h in fed and starved hens. At the same time, a decrease in T4 was observed in both groups of GH-treated chickens. It is concluded that TRH at the dose used is not thyrotropic but has a somatotropic effect and is responsible for the peripheral conversion of T4 into T3.     

Carbon Flow in Mercury Biomethylation by Desulfovibrio desulfuricans

Radiocarbon incorporation from pyruvate and serine into monomethylmercury by Desulfovibrio desulfuricans was consistent with the proposal that the methyl group originates from C-3 of serine. Immunodiagnostic assays measured 4 to 35 μg of tetrahydrofolate and 58 to 161 ng of cobalamin or a closely related cobalt porphyrin per g of cell protein in D. desulfuricans. The light-reversible inhibition of mercury methylation by propyl iodide in D. desulfuricans indicates methyl transfer by a cobalt porphyrin.     

Effects of Jet Fuel Spills on the Microbial Community of Soil

Hydrocarbon residues, microbial numbers, and microbial activity were measured and correlated in loam soil contaminated by jet fuel spills resulting in 50 and 135 mg of hydrocarbon g of soil⁻¹. Contaminated soil was incubated at 27°C either as well-aerated surface soil or as poorly aerated subsurface soil. In the former case, the effects of bioremediation treatment on residues, microbial numbers, and microbial activity were also assessed. Hydrocarbon residues were measured by quantitative gas chromatography. Enumerations included direct counts of metabolically active bacteria, measurement of mycelial length, plate counts of aerobic heterotrophs, and most probable numbers of hydrocarbon degraders. Activity was assessed by fluorescein diacetate (FDA) hydrolysis. Jet fuel disappeared much more rapidly from surface soil than it did from subsurface soil. In surface soil, microbial numbers and mycelial length were increased by 2 to 2.5 orders of magnitude as a result of jet fuel contamination alone and by 3 to 4 orders of magnitude as a result of the combination of jet fuel contamination and bioremediation. FDA hydrolysis was stimulated by jet fuel and bioremediation, but was inhibited by jet fuel alone. The latter was traced to an inhibition of the FDA assay by jet fuel biodegradation products. In subsurface soil, oxygen limitation strongly attenuated microbial responses to jet fuel. An increase in the most probable numbers of hydrocarbon degraders was accompanied by a decline in other aerobic heterotrophs, so that total plate counts changed little. The correlations between hydrocarbon residues, microbial numbers, and microbial activity help in elucidating microbial contributions to jet fuel elimination from soil.     

Apparatus for monitoring the mineralization of volatile C-labeled compounds

Quantitative mineralization studies on radiolabeled compounds having high vapor pressures need to cope with several technical difficulties. An incubation and trapping system is described that was successfully used in mineralization studies on highly volatile trichlorobenzenes and other xenobiotic pollutants.