Proton nuclear magnetic resonance spectroscopy of isolated rabbit fundic glands

1H-nuclear magnetic resonance spectroscopy (NMR) was adapted to isolated rabbit fundic glands and identification made of compounds responsible for several observed spectral resonances. A minimum gland concentration of 0.5 mg dry weight or 5 mg wet weight per 0.5 ml was needed for adequate signal-to-noise ratio. At physiological temperature and pH, the glands demonstrated reproducible spectra, stability for accumulation times greater than 30 min and responsiveness to histamine stimulation, as measured by oxygen consumption and aminopyrine uptake. The relatively anaerobic conditions favored use of proton compared to phosphorus NMR, since 1H-NMR allowed significantly shorter spectral accumulation times and therefore did not compromise glandular viability to the same extent as 31P-NMR. The most conspicuous resonance in the gland spectrum was assigned to the -N+(CH3)3 protons of choline and related compounds. In membrane-free lysates, several components of the signal were resolvable and assigned to choline, phosphatidylcholine, phosphocholine and L-alpha-glycerophosphocholine. Thin-layer chromatography verified that phosphatidylcholine and phosphatidylethanolamine were the major phospholipids present in gland lipid. Presumably, they represent the source of the surface-active phospholipids present in gastric juice, which may play a role in gastric cytoprotection.     

Evidence that neutral spingomyelinase of cultured murine neuroblastoma cells is oriented externally on the plasma membrane

The activity of the neutral, Mg²⁺-stimulated sphingomyelinase of cultured neuroblastoma cells (N1E-115) is enriched in the plasma membrane fraction and is reduced following treatment of intact or broken cells with trypsin, α-chymotrypsin, papain, and protease. Two protease-sensitive enzymes of the cell interior (lactate dehydrogenase and NADPH-cytochrome c reductase) are not affected by protease treatment of intact cells. These results indicate that the neutral, Mg²⁺-stimulated sphingomyelinase is oriented externally on the plasma membrane of the cultured neuroblastoma cell.     

Altered sensitivity of carnitine palmitoyltransferase to inhibition by malonyl-CoA in ketotic diabetic rats.

Carnitine palmitoyltransferase of liver mitochondria prepared from ketotic diabetic rats has a diminished sensitivity to inhibition by malonyl-CoA compared with carnitine palmitoyltransferase of mitochondria prepared from normal fed rats.     

The effect of phenylephrine on excretion of fluid and electrolytes by the parotid and mandibular glands of the rat

The effect has been investigated of the alpha-adrenergic agonist, phenylephrine, on excretion of water and electrolytes (Na, K, and HCO3) by the parotid and mandibular glands of the rat. In the mandibular glands the agonist was as effective as acetylcholine (or parasympathetic nerve stimulation) in stimulating secretion, and the electrolyte excretory patterns seen in the two modes of stimulation were similar. In the parotid gland, phenylephrine was only one-fifth as potent as acetylcholine (or parasympathetic nerve stimulation) in evoking a secretory response but, when due allowance for flow rate differences is made, the electrolyte excretion patterns were similar. In both glands the secretory response to phenylephrine was totally different, in magnitude and in electrolyte excretion pattern, to that evoked by the beta-adrenergic agonist, isoprenaline. It is concluded, as has already been established for secretion of exportable protein, that alpha-adrenergic agonists have very similar effects to muscarinic agonists both on endpiece and on duct cells and that these actions are completely different from those evoked by activation of beta-adrenergic receptors.     

Structural studies on the murine Ia alloantigens. VI. Evidence that both subunits of the I-A alloantigen are encoded by the I-A subregion.

The alpha and beta subunits of the murine I-A alloantigens from several H-2 haplotypes were examined by comparative tryptic peptide mapping by using double label (3H and 14C) techniques. Significant structural variation between alleles was detected in both subunits. Tryptic digests of the alpha polypeptides from s, b, and d showed only 65% co-elution with k; beta-chains from s, b, d, and r were about 50% similar to the k beta subunit. Peptide analysis of the Ak subunits from intra-H-2 recombinant strains indicated that both the alpha and beta polypeptides are encoded within the I-A subregion.     

Phosphonate utilization by bacteria.

Bacteria able to use at least one of 13 ionic alkylphosphonates of O-alkyl or O,O-dialkyl alkylphosphonates as phosphorus sources were isolated from sewage and soil. Four of these isolates used 2-aminoethylphosphonic acid (AEP) as a sole carbon, nitrogen, and phosphorus source. None of the other phosphonates served as a carbon source for the organisms. One isolate, identified as Pseudomonas putida, grew with AEP as its sole carbon, nitrogen, and phosphorus source and released nearly all of the organic phosphorus as orthophosphate and 72% of the AEP nitrogen as ammonium. This is the first demonstration of utilization of a phosphonoalkyl moiety as a sole carbon source. Cell-free extracts of P. putida contained an inducible enzyme system that required pyruvate and pyridoxal phosphate to release orthophosphate from AEP; acetaldehyde was tentatively identified as a second product. Phosphite inhibited the enzyme system.     

Quercetin inhibits hexose transport in a human diploid fibroblast

Summary The flavonol quercetin, a phloretin analog, inhibits transport of 2-deoxyglucose and 3-O-methylglucose in a cultured human diploid fibroblast. This inhibition is related to transport itself and not to the reported effects of flavonoids on membrane-bound ATPases. From concentration-inhibition curves at several pH's we conclude that uncharged (acid) quercetin (pK=7.65) is the inhibitory form of the molecule (K _I =10m). Quercetin, unlike phloretin, is rapidly degraded in 0.1n NaOH; the degradation products are weakly inhibitory to hexose transport.     

The effect of precursors, products, and product analogs of prostaglandin cyclooxygenase upon iris sphincter muscle.

Contractions of isolated iris sphincter muscles were measured in response to several free fatty acids, hydroperoxy and hydroxy derivatives of 20:3(n-3), 20:3(n-6) and 20:4, PGH₂, and the epoxymethano methano analogs of PGH₂. The free acids of prostaglandin precursors elicited comparatively strong contractions, hydroperoxy and hydroxy acids gave intermediate and nonspecific response whereas nonprostaglandin precursor acids elicited little response. PGH₂ was 100 to 1000 times more effective than arachidonic acid or the epoxymethano analogs. The latter compounds inhibited the production of contractions by PGH₂. These results allow an interpretation that the iris sphincter muscle contains an active thromboxane synthase and receptors for endoperoxide and thromboxane that initiate contraction.