Embryonic heart mesenchymal cell migration in laminin

Laminin, a large glycoprotein and major component of basement membranes, influences cell adhesion, migration, morphology, and differentiation. A peptide sequence, YIGSR, from the B1 chain of laminin has been found to correspond to an active site for cell adhesion. We report here that cardiac mesenchymal cells migrate vigorously within three-dimensional gels of laminin and that the YIGSR peptide will completely abolish this migratory activity. In contrast, migration of the mesenchymal cells into three-dimensional gels composed of collagen or collagen + laminin is not effected by YIGSR or other peptides (GRGDS, GRGDTP) reported to mediate cellular adhesion.     

15N-labeled 5S RNA. Identification of uridine base pairs in Escherichia coli 5S RNA by 1H-15N multiple quantum NMR

Escherichia coli 5S RNA labeled with 15N at N3 of the uridines was isolated from the S phi-187 uracil auxotroph grown on a minimal medium supplemented with [3-15N]uracil. 1H-15N multiple quantum filtered and 2D chemical shift correlated spectra gave resonances for the uridine imino 1H-15N units whose protons were exchanging slowly with solvent. Peaks with 1H/15N shifts at 11.6/154.8, 11.7/155.0, 11.8/155.5, 12.1/155.0, and 12.2/155.0 ppm were assigned to GU interactions. Two labile high-field AU resonances at 12.6/156.8 and 12.8/157.3 ppm typical of AU pairs in a shielded environment at the end of a helix were seen. Intense AU signals were also found at 13.4/158.5 and 13.6/159.2 ppm where 1H-15N units in normal Watson-Crick pairs resonate. 1H resonances at 10.6 and 13.8 ppm were too weak, presumably because of exchange with water, to give peaks in chemical shift correlated spectra. 1H chemical shifts suggest that the resonance at 13.8 ppm represents a labile AU pair, while the resonance at 10.6 ppm is typical of a tertiary interaction between U and a tightly bound water or a phosphate residue. The NMR data are consistent with proposed secondary structures for 5S RNA.     

The immunocytochemical localization of superoxide dismutase in the enterocytes of the avian intestine: The effect of vitamin D3

Summary Both light microscopical and electron microscopical immunocytochemical techniques were utilized to localize CuZnsuperoxide dismutase (SOD) in the duodenum of normal, rachitic and vitamin-D₃-replete chicks. This enzyme catalyses the dismutation of the superoxide anion, a toxic free radical generated during the normal aerobic metabolism of most respiring cells. Light microscopy showed no SOD activity associated with the duodenal enterocytes of normal and rachitic chicks. However, in rachitic animals subsequently treated with vitamin D, i.e. vitamin-D-replete chicks, intense immunoreactivity for the enzyme was seen in association with the apical border of the duodenal absorptive cells. Immunostaining for SOD was not seen in goblet cells. With electron microscopy, immunostaining for SOD activity was identified in association with the apical microvilli and, to a lesser degree, with the terminal web, a well as in association with both lysosomes and peroxisomes. From this report it appears that there is a physiological relationship between vitamin D, SOD and the intestinal absorptive cell. However, the precise relationship must await further clarification.     

Comparison of LDH-B4 allozymes of macrourids (Teleostei: Gadiformes) by electrophoresis and peptide mapping

The heart-type lactate dehydrogenase (LDH-_B4) homologs of two species of Nezumia and eight species of Coryphaenoides are isomobile on two commonly used electrophoretic buffer systems. To test the hypothesis that the homologs possess the same primary structures, the allozymes from N. bairdii and four species of Coryphaenoides were purified by affinity chromatography on an oxamate aminohexyl Sepharose column and digested with trypsin. The resulting peptide mixtures were then mapped using reversed-phase high-performance liquid chromatography. The peptide maps of the enzyme homologs indicate that the overall similarity of the homologs is high, but unique peptides in each species indicate that the allozymes are not identical in primary structure.     

The reaction mechanism of Na, K-ATPase

To help characterize the Na,K-ATPase active site with enzyme incorporated into phospholipid vesicles, the activities with alternative substrates were compared, 22Na/Na-transport was equivalent with ATP, CTP, carbamylphosphate and acetylphosphate, but slower with CTP, 3-O-methylfluoresceinphosphate (3-O-MFP), nitrophenylphosphate and umbelliferonephosphate. It indicates a slower rate of formation of phosphorylating enzyme complex in conformation position of E1 (E1P) when the second group of substrates is bound with enzyme active center. 22Na/K-transport was half as effective with CTP as with ATP and was far slower with the other substrates. It indicates a more stringent selectivity at the low-affinity site of enzyme in conformation E2 that accelerates the slow step of this transport mode. Although enzyme modification with fluoresceinisothiocyanate blocks the high-affinity site to ATP, the K-phosphatase reaction catalyzed by E2 is retained, even with a substrate, 3-O-MFP, that binds to the adenine pocket. Dimethylsulfoxide inhibits hydrolysis of the nucleotides and of the carboxylic phosphate substrates of the K-phosphatase reaction, but stimulates hydrolysis of the phenolic phosphate substrates (nitrophenylphosphate and umbelliferone phosphate) which normally are hydrolyzed more slowly than the other substrates. On the basis of these data the authors propose the model of Na,K-ATPase active center.