Relaxant effect of dopamine on isolated rabbit pulmonary artery

In rabbit pulmonary artery, dopamine (10(-11)-10(-5) M) produced a concentration-dependent relaxation of the arterial strips contracted with prostaglandin F2 alpha (PGF2 alpha) in the presence of prazosin (10(-6) M), yohimbine (10(-6) M), propranolol (10(-6) M), and methysergide (10(-6) M). SKF38393, an agonist for D1 or DA1 dopamine receptor, mimicked partially the concentration-response curve for dopamine, whereas LY171555 and apomorphine did not. The order of potency of dopamine antagonists on the inhibitory effect was: cis-flupenthixol greater than bulbo-capnine greater than metoclopramide greater than haloperidol. Sulpiride was inactive. Cis-flupenthixol did not block the relaxation induced by acetylcholine, adenosine, and papaverine. In the arterial strips of the rabbits pretreated with 6-hydroxydopamine, the concentration-response curve for dopamine was similar to that in non-treated rabbits. Thus it is concluded that a specific dopamine receptor is located on the postsynaptic muscle membrane of the rabbit pulmonary artery.     

Expression of human atrial natriuretic polypeptide gene in Cos 7 cells

Cos 7 cells transfected with human atrial natriuretic polypeptide (hANP) gene with SV40 enhancer and replication origin sequences expressed hANP gene. The expressed RNA was indistinguishable from native hANP mRNA and the transcribed protein seemed to be properly processed to alpha-hANP and beta-hANP. This system provides a useful approach to investigate the processing of hANPs and the structure-function relationship of amino acid sequences of hANPs.     

Regulation of the expression of the rat angiotensin II receptor mRNA.

Regulation of the expression levels of the rat angiotensin II receptor mRNA in the adrenal, aorta, kidney, and brain was assessed by the competitive polymerase chain reaction method. The bilateral nephrectomy or the administration of Dup753 markedly reduced the expression levels of this receptor mRNA in the adrenal and brain stem, but not in the kidney nor aorta. A continuous infusion of angiotensin II increased the expression level of this receptor mRNA in the adrenal but not in the other tissues. It is suggested that the expression level of this receptor mRNA in the adrenal is dependent on the renin angiotensin aldosterone system.     

Virtual issue: cell wall functions in plant growth and environmental responses

Journal of Plant Research - Plant cell walls have multiple functions, including determining cell shape and size, cell–cell adhesion, controlling cell differentiation and growth, and promoting...     

Molecular dynamics simulation of diffusion of hydrogen in binary hydrogen–tetrahydrofuran hydrate

The binary structure II hydrogen–tetrahydrofuran (THF) hydrate was studied with molecular dynamics simulation. The simulations were carried out at 300, 310 K and 10.1 MPa, and with various contents of hydrogen and THF. The migrations of hydrogen molecules from cage to cage were observed. The migration process of hydrogen was also analysed, and the diffusion coefficients of hydrogen in the hydrate were calculated. The calculated diffusion coefficients qualitatively agreed with the experimental data. Double and quintet occupancies of hydrogen molecules were observed in the small and large cages, respectively, without changing the hydrate structure.     

Molecular dynamics simulation of fluorination effect for solvation of trifluoromethylbenzoic acid isomers in supercritical carbon dioxide

A molecular dynamics (MD) simulation was applied to carbon dioxide+trifluoromethylbenzoic acid isomer and carbon dioxide+methylbenzoic acid isomer systems to investigate the interactions between carbon dioxide and the solutes. The pair correlation functions between the carbon dioxide and trifluoromethyl group or methyl group in the solutes were calculated to study the fluorination effect of solvation. As a result, it was found that the interactions between carbon dioxide and trifluoromethyl group in trifluoromethylbenzoic acid isomers were stronger than those between carbon dioxide and the methyl group in methylbenzoic acid isomers. The simulation results had the same tendency as the experimental solubility enhancements and coincided with the trend of the interaction parameters of the Peng-Robinson equation of state that were determined from the solubility data.     

Enzymatic Synthesis of the Crithidia Factors in Cell-free Extracts of Serratia indica

The concomitant production of formic acid and pterin compounds from guanosine-5′-triphosphate (GTP) has been found in cell-free extracts of Serratia indica. Among the pterin compounds, l-threo-neopterin–the major Crithidia factor in S. indica–, a cyclic phosphate of neopterin (cNP), d-erythro-neopterin and 6-hydroxymethyl pterin were detected and isolated. Formate-¹⁴C elimination from GTP-8-¹⁴C was quantitatively distributed in the ethyl acetate layer in the ehyl acetate-hydrochloric acid partition system. Carbon 8 of GTP was released as formic acid. Enzymatic production of formate and cNP was linear for 2 hr at 37°C. Formate production was proportional to the enzyme concentration. The optimum pH for formate elimination was observed around pH 8.6. Optimum temperature for the production of formate and cNP was 50°C. The apparent Km value of GTP for formate production was 6.2×10^?bm. Formate eliminating activity was activated by disodium phosphate but was inhibited by Mg²⁺ or AMP. Incorporation of GTP-U-¹⁴C into pterin compounds was also regulated with disodium phosphate. Effective incorporation into cNP and d-erythro-neopterin occurred in the presence of phosphate. When phosphate was omitted from the system, however, effective incorporation into 6-hydroxymethyl pterin was observed. The biosynthetic process of the Crithidia factors, i.e. l-threo-neopterin and cNP, from GTP in S. indica is also discussed.