Blockade of alpha-adrenergic receptors by analogues of phosphatidylcholine

The experimental evidence reviewed in this article suggests that the kidneys may have an additional function in regulating blood pressure besides their role in controlling both blood volume by urine formation and the relative state of vasoconstriction by the renin-angiotensin system. That is, the kidneys may have an additional influence upon the vasculature of a hormonal vasodilating system. The interstitial cells of the renal medulla appear to be mediating this activity and lipid compounds have been extracted from the renal medulla which display depressor activity. One such compound, the antihypertensive polar renomedullary lipid (APRL), has been demonstrated to consist of specific alkyl ether analogues of phosphatidylcholine. The vascular responses to these compounds include vasodilation of both arterioles and venules, rapid lowering of arterial blood pressure with little or no tachycardia, increased depressor activity in hypertensive animals, and blockade of vascular smooth muscle alpha 1-adrenergic receptors. Most recently, APRL and a synthetic analogue, 1-0-octadecyl-2-acetyl-sn-glycero-3-phosphorylcholine, have been used to demonstrate alpha-adrenergic receptor blockade on a smooth muscle cell line (DDT1) by radioligand assays. This action may be due to the insertion of these compounds into cell membranes causing subsequent steric interactions and blockade of the alpha-adrenergic receptor.     

Abnormal functional development of sympathetic nerve terminal-smooth muscle complex in neonatal spontaneously hypertensive rats

In neonatal and young adult SH and WK rats, maturation of a functional unit consisting of sympathetic nerve terminals and smooth muscle (levator palpebrae) was assessed $\text{in vivo}$ by measuring the contractile response to tyramine, an agent which releases endogenous norepinephrine from sympathetic nerve terminals. Responses in SH are comparable to WK at 5–6 days postnatally, smaller from the 8th through 19th day and larger in young adults (41–46 days old). Results indicate that functional maturation of the nerve terminal-smooth muscle complex is retarded in SH relative to WK during the 2nd and 3rd postnatal weeks. It is suggested that retardation in the neonatal SH rat is an expression of a genetic defect in the growth of the complex and that the enhanced response in young adult SH is a consequence of the neonatal abnormality.     

Energy deprivation and guanosine 5''-diphosphate 3''-diphosphate synthesis in cyanobacteria

A reduction in the incident light intensity has been used to elicit guanosine 5'-diphosphate 3'-diphosphate accumulation in cyanobacteria. Inhibitors of photophosphorylation, 2,4-dinitrophenol, and carbonyl cyanide-m-chlorophenyl hydrazone elicited accumulation in three species of cyanobacteria when they were grown on dinitrogen or nitrate, but not in cultures grown on ammonium or glutamine. Accumulation of guanosine 5'-diphosphate 3'-diphosphate also preceded a substantial reduction of the purine nucleoside triphosphate pools. This accumulation of guanosine 5'-diphosphate 3'-diphosphate is therefore not primarily dependent upon reduced ATP concentration or proton gradient potential, but rather upon the source of combined nitrogen. In this respect, incident light step down is not comparable with nutritional step-down procedures in heterotrophic bacteria.     

Studies of the induction of anti-DNA in normal mice

Injection of PBA has previously been demonstrated to induce anti-DNA. In the present study, we found that the combination of neonatal thymectomy and chronic administration of PBA (LPS + poly rI . rC) led to significantly higher anti-DNA levels than either PBA or thymectomy separately. These results suggested that a thymic regulatory process normally serves to suppress anti-DNA after chronic PBA exposure. Indeed, antigen-nonspecific suppressor function was found to be deficient in such thymectomy + PBA-treated mice. In addition, the cells of such mice in vitro interfered with the development of normal suppressor function by control cells.     

Reaction of uric acid and 3-N-ribosyluric acid with 1,1-diphenyl-2-picrylhydrazyl

Antioxidants can be assayed by their reaction with 1,1-diphenyl-2-picrylhydrazyl (DPPH), which results in a decrease in absorbance at 517 nm of the DPPH. Both uric acid and 3-ribosyluric acid reacted with DPPH to produce about the same change in absorbance at 517 nm as an equal concentration of ascorbic acid. Fourteen related purines, pyrimidines, and their nucleosides, including xanthine and xanthosine, failed to give a reaction with DPPH at the same concentration as the urates or at 10 times this concentration. When DPPH interacted with [2-¹⁴C]uric acid, it was converted to allantoin. Cold trichloroacetic acid extracts of bovine blood contained two major compounds that reacted with DPPH, ribosyluric acid and glutathione. These compounds were found only in the red cells and not in the plasma.     

6,9-deepoxy-6,9,-(phenylimino)-delta 6,8-prostaglandin I1, (U-60,257), a new inhibitor of leukotriene C and D synthesis: in vitro studies

Addition of the calcium inophore, A 23187, and cysteine to isolated mononuclear cells from rat peritoneal washings causes a marked increase in the formation of thromboxane B2 (TxB2) along with the formation of leukotrienes C and D (LT's). The formation of LT's in this system was inhibited by 6,9-deepoxy-6,9-(phenylimino)-delta 6,8-prostaglandin I1, U-60,257, or its methyl ester, U-56,467, (ID50 4.6 and 0.31 microM, respectively). There was no inhibition of TxB2 formation. By contrast, two structurally-related compounds, PGI2 and its stable analog, 6-beta-PGI1, did not affect the formation of either LT's or TxB2. The inhibition of LT formation by U-60,257 was rapidly reversed after removal of this compound from the cells. U-60,257 did not inhibit the cyclooxygenase of human polymorphonuclear leukocytes. Nor did it inhibit formation of 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) in human platelets. On the other hand, U-60,257 inhibited glutathione S-transferase activity of rat basophil leukemia cells (ID50, 37 microM), suggesting that this compound may inhibit the last step in LTC biosynthesis. In addition to inhibiting LT synthesis, U-60,257 also appears to be a competitive inhibitor of the action of LT on the guinea pig ileum, although this inhibition requires a higher drug concentration than those ordinarily encountered during assay for LT's in U-60,257-treated incubations.     

Reduced cell proliferation in fetal lung after maternal administration of pilocarpine: a scintillation autoradiographic study.

Fetuses were obtained on the 28th gestational day from pregnant New Zealand white rabbits treated daily, on the 24th through the 27th gestational day, with pilocarpine HCl, 5 mg/kg in saline, or saline alone. Lung fragments from these fetuses were incubated for two hours in medium containing 3H-thymidine. Scintillation autoradiography of 1-micrometer-thick sections of these fetal lungs revealed that the lung tissue from pilocarpine-treated fetuses had significantly lower labelled cell indices for both alveolar epithelial cells and interstitial cells. These results indicate that pilocarpine treatment promotes differentiation of immature cells in the fetal lung at the expense of cell proliferation.     

A simple assembly for anaerobic spectrophotometric reaction kinetics studies.

Details are given for the construction and use of a simple spectrophotometer cuvetteclosure that makes possible the study of reaction rates and enzyme assays under anaerobic conditions. The preparation of solutions and assembly of the cuvette unit is carried out in a N2 atmosphere in a glove box, but the spectrophotometric studies are conducted in a spectrophotometer with no modification except for the cell compartment cover.     

N-demethylation of lergotrile by Streptomyces platensis.

Thirty-eight microorganisms were screened for their ability to produce metabolites of the semisynthetic alkaloid, lergotrile. A total of five microorganisms were found to biotransform lergotrile, and N-desmethyl lergotrile was detected as the principal metabolite with most organisms. Streptomyces platensis (NRRL 2364) appeared to form the metabolite in highest yield, and a preparative-scale conversion was accomplished with a recovered yield of 50%. Structure proof was accomplished with comparative thin-layer chromatography, mixed melting point, mass spectrometry, and remethylation to lergotrile.     

Specificity and site of action of a mammary gland thioesterase which releases acyl moieties from thioester linkage to the fatty acid synthetase

The lactone (I) of 2-hydroxy-1-naphthaleneacetic acid was developed as a reagent for novel, highly efficient, covalent attachment of an excited-state proton transfer fluorescence probe (i.e. 2-naphthol) to protein amino groups. The lactone (I) was shown to react with amines faster than it was hydrolyzed. Reaction of the lactone (I) with bovine serum albumin (BSA) was faster than its reaction with corresponding concentrations of small organic amines, which suggested that the lactone (I) first adsorbed to BSA and subsequently reacted covalently; data are presented which suggest that this covalent binding occurs at a unique, single site on BSA (i.e., affinity labeling). Equilibrium studies involving instantaneous and time-dependent fluorescence changes were interpreted in terms of a 1:1 lactone:BSA labeling ratio at neutral pH. Steady-state fluorescence spectroscopy of the 1:1 lactone:BSA conjugate and of the conjugate of the lactone with glycine ethyl ester were recorded, compared and interpreted in terms of the microenvironment of the protein-bound fluorescence probe. Applications are suggested for use of this new and powerful procedure for study of the conformational changes and molecular interactions in other proteins.