Somatostatin-detergent interaction

The effect of cationic, anionic and nonionic detergents on the EPR spectrum of spin-labeled somatostatin has been studied. At detergent concentrations well above the critical micelle concentration, nonionic detergents do not alter the EPR spectrum. Sodium dodecyl sulfate markedly alters both the line height ratio and the hyperfine splitting constant, whilst dodecyltrimethylammonium bromide alters only slightly the hyperfine splitting constant and line height ratio. The somatostatin-sodium dodecyl sulfate complex appeared monodisperse by sedimentation equilibrium with about 17 g bound detergent per g peptide. Circular dichroic and difference spectra of the dodecyl sulfate-somatostatin complex show that the tryptophanyl residue is buried in a nonpolar environment and that the secondary and tertiary structure of the peptide is markedly altered. Sedimentation equilibrium studies suggest that two types of dodecyltrimethylammonium-somatostatin complex exist. One type resembles the dodecyl sulfate-peptide complex, whilst the other appears to include several peptide units with only about one gram bound detergent per gram peptide.     

Plant phosphoglucose isomerase genes lack introns and are expressed in Escherichia coli

Nuclear genes that appear to encode both cytosolic and plastid isozymes of phosphoglucose isomerase (PGI), an essential glycolytic enzyme, have been isolated from three diploid species of the annual wild flower genus Clarkia (Onagraceae). The genes do not contain introns and are expressed to varying degrees in Escherichia coli when cloned in either Charon 35 phage or pUC plasmid vectors. The PGI proteins synthesized in E. coli form dimers, are catalytically active, and their electrophoretic mobilities are similar to those of appropriate Clarkia PGIs. The nucleotide sequence of a gene encoding a plastid isozyme of C. unguiculata is described.     

Denaturation thermodynamics of chicken cardiac metmyoglobin

The unfolding at pH 8 of chicken cardiac aquometmyoglobin was examined as a function of temperature and concentration of guanidinium chloride using the two-state model. The isothermal unfolding data at 25°C were fitted to Tanford's transfer model and the binding model of Aune and Tanford. The estimates obtained for ΔG_D) were virtually identical, viz., 8.3 ±0.3 kcal mol^?1. The chicken metmyoglobin is thus some 5.3 kcal mol^?1 less stable than that of sperm whale metmyoglobin. The unfolding parameters α and Δn were decreased 20% from those of mammalian myoglobins thus far examined, suggesting nonidentity of native conformations. The apparent enthalpy change on unfolding was dependent on both temperature and denaturant concentration. The decreases in the isothermal unfolding parameters from those of sperm whale are principally assigned to three of the 46 sequence changes.     

Calcium uptake by isolated nerve endings: evidence for a rapid component mediated by the breakdown of phosphatidylinositol

Several physiological stimuli, including neuronal depolarization, increase the production of phosphatidate (PA) from phosphatidylinositol (PI) and increase calcium fluxes across cell membranes. To determine if breakdown of PI is required for neuronal calcium uptake, we tested inhibitors of PI-specific phospholipase C on depolarization-dependent uptake of calcium by isolated brain synaptosomes. At a concentration of 0.1 mM these inhibitors reduced calcium uptake produced by depolarization for 1 to 3 sec, but did not affect uptake due to more prolonged depolarization. Exogenous PA also stimulated calcium accumulation by synaptosomes and this uptake was not reduced by the enzyme inhibitors. These results suggest that the rapid calcium influx produced by neuronal depolarization may be mediated by the breakdown of PI.     

Recruitment: the ins and outs of spindle pole formation

Microtubule-organizing centers are a diverse but interrelated set of cellular organelles that appear when needed at specific times in the cell cycle. Diversity is introduced into MTOCs, and thus into microtubule structures, by post-translational modification, by morphological changes, by de novo synthesis, and by recruitment of cytoplasmic proteins. Understanding the mechanisms that lead to such diversity should contribute to a better understanding of the myriad of cellular events which depend on microtubules.     

A phylogenetic analysis and revised classification of the Monocotylidae Taschenberg, 1879 (Monogenea)

The Monocotylidae Taschenberg, 1879 is revised based on a cladistic analysis of relationships between the constituent species and genera. The monophyly of the family is supported by three apomorphic character states: division of the haptor into one central and eight peripheral loculi; the ovary looping the right intestinal caecum; and tetrahedral eggs. The family is divided into six subfamilies: Calicotylinae Monticelli, 1903 (comprising Calicotyle Diesing, 1850, Dictyocotyle Nybelin, 1941); Dasybatotreminae Bychowsky, 1957 (comprising Anoplocotyloides Young, 1967, Dasybatotrema Price, 1938, Timofeevia n. g., Troglocephalus Young, 1967); Decacotylinae n. subfam. (comprising Decacotyle Young, 1967, Papillicotyle Young, 1967); Heterocotylinae n. subfam. (comprising Heterocotyle Scott, 1904, Neoheterocotyle Hargis, 1955, Nonacotyle Ogawa, 1991, Potamotrygonocotyle Mayes, Brooks & Thorson, 1981, Spinuris Doran, 1953); Merizocotylinae Johnston & Tiegs, 1922 (comprising Cathariotrema Johnston & Tiegs, 1922, Empruthotrema Johnston & Tiegs, 1922, Merizocotyle Cerfontaine, 1894, Squalotrema Kearn & Green, 1983, Triloculotrema Kearn, 1993); and Monocotylinae Taschenberg, 1879 (comprising Clemacotyle Young, 1967, Dendromonocotyle Hargis, 1955, Monocotyle Taschenberg, 1878). The Dendromonocotylinae Hargis, 1955 is removed from subfamilial status and the two genera previously assigned to the subfamily are reassigned to the Monocotylinae. Timofeevia is proposed for Timofeevia rajae (Timofeeva, 1983) n. comb. (formerly Dasybatotrema rajae). Mycteronastes Kearn & Beverley-Burton, 1990 and Thaumatocotyle Scott, 1904 are synonymised with Merizocotyle. Gymnocalicotyle Nybelin, 1941 is not considered a distinct taxon. Revised diagnoses and keys for subfamilies and genera of the Monocotylidae are provided.