Effect of specific antibodies onNeisseria catarrhalis (lys−) transformation frequency

Zusammenfassung Antikörper mit einer gegen kompetenteN. catarrhalis gerichteten Spezifität vermindern deren Transformationshäufigkeit bedeutend. Diese Beobachtung könnte auf die Existenz von Membranrezeptoren für transformierende Wildtyp-DNS hinweisen.

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This investigation was supported by the Research Corporation of Chicago No. 40-84 and Eastern Kentucky University Research Grant No. 05-03-422-41.     

Inositol trisphosphate receptor localization in brain: variable stoichiometry with protein kinase C

Many neurotransmitters, hormones and growth factors act at membrane receptors to stimulate the phosphodiesteratic hydrolysis of phosphatidyl-inositol 4,5-bisphosphate generating the comessengers inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) and diacylglycerol. Diacylglycerol stimulates protein kinase C3 while Ins(1,4,5)P3 is postulated to activate specific receptors leading to release of intracellular calcium, probably from the endoplasmic reticulum. In recent preliminary reports, Rubin and associates detected 32P-Ins(1,4,5)P3 binding to liver and adrenal microsomes and to permeabilized neutrophils and liver cells. We now report the biochemical and autoradiographic demonstration in brain of high affinity, selective binding sites for 3H- and 32P-labelled Ins(1,4,5)P3 at levels 100-300 times higher than those observed in peripheral tissues. The potencies of various myoinositol analogues at the Ins(1,4,5)P3 binding site correspond to their potencies in releasing calcium from microsomes, supporting the physiological relevance of this receptor. Brain autoradiograms demonstrate discrete, heterogeneous localization of Ins(1,4,5)P3 receptors. In some regions localizations of Ins(1,4,5)P3 receptors resemble those of protein kinase C14, while in others they differ markedly, suggesting a novel mechanism whereby the relative activity of the two limbs of the PI cycle can be differently regulated.     

Cloned and expressed nitric oxide synthase structurally resembles cytochrome P-450 reductase.

Nitric oxide is a messenger molecule, mediating the effect of endothelium-derived relaxing factor in blood vessels and the cytotoxic actions of macrophages, and playing a part in neuronal communication in the brain. Cloning of a complementary DNA for brain nitric oxide synthase reveals recognition sites for NADPH, FAD, flavin mononucleotide and calmodulin as well as phosphorylation sites, indicating that the synthase is regulated by many different factors. The only known mammalian enzyme with close homology is cytochrome P-450 reductase.     

Differential removal of insulin-like growth factor binding proteins in rat serum by solvent extraction procedures

Solvent extraction of serum and other biological fluids at an acidic pH is a convenient method to remove the insulin-like growth factor binding proteins (IGFBPs); however, an incomplete removal of IGFBPs can occur and this can potentially interfere with the radioimmunoassay of insulin-like growth factors (IGFs). This study compared the removal of IGFBPs from normal adult rat serum and 5-day old neonatal rat serum by acid-gel filtration, and three solvent extraction methods, i.e., acid-ethanol (AE), acid-cryo-ethanol (ACE) and formic acid-acetone (FAA) treatments by western ligand blotting and slot-blotting analysis. In adult rat serum all three extraction methods removed nearly 75% of total IGFBPs present. For the neonatal serum, AE and FAA were very inefficient in eliminating the IGFBPs, while ACE was somewhat better, as it removed nearly 30% of IGFBPs. Ligand blots of extracted samples showed that IGFBPs of lower size range, 24 to 32 kDa (IGFBP-4, IGFBPs-1 and-2), were resistant to solvent extraction. Acid-gel filtration, in contrast, eliminated >95% of IGF-binding components in both sera. Determination of IGF-I concentrations in samples after gel filtration and extraction methods revealed lower IGF-I values in neonatal serum in acid extracted samples. These data caution against using solvent extractions for IGFBP removal in fetal/neonatal serum.