Immunochemical analysis of respiratory-chain components of micrococcus luteus (lysodeikticus).

Membrane-bound antigens of the respiratory chain of Micrococcus luteus were analyzed by crossed immunoelectrophoresis after growth of the organism in the presence of 59Fe, the flavin adenine dinucleotide-flavin mononucleotide precursor D-[2-14C]riboflavin, or the heme precursor 5-amino-[4-(14)C]levulinic acid. Using zymograms and procedures of selective extraction in conjunction with autoradiography, it was possible to resolve and partially characterize a number of antigens. Succinate dehydrogenase (EC 1.3.99.1) was shown to possess covalently bound flavin and nonheme iron and was possibly present as a complex with cytochrome. Three other dehydrogenases, namely, NADH dehydrogenase, NAD(P)H dehydrogenase (EC 1.6.99.3), and malate dehydrogenase (EC 1.1.1.37), contained flavin in noncovalent linkage, the NAD(P)H dehydrogenase also possessing nonheme iron. Four other discrete antigens (or antigen complexes) containing both iron and heme centers also resolved, as were two minor immunogens possessing iron as the sole detectable prosthetic group.     

Stimulus-secretion coupling of glucose-induced insulin release. LI. Divalent cations and ATPase activity in pancreatic islets

Pancreatic islets can be viewed as a fuel-sensor organ. The amount of ATP used by the islet cells for the maintenance of adequate Ca2+ gradients across membranes is not known. An indirect approach to this issue consists in the measurement of Ca-ATPase activity. The kinetics of Ca-ATPase in islet homogenates yielded a Km for ATP close to 0.1 mM and two Km values for Ca2+ close to 0.13 and 4-6 microM, respectively. Within limits, the Ca-ATPase appeared as a distinct entity from Mg-ATPase. Several divalent cations, including Mg2+, inhibited the Ca-ATPase activity. Calmodulin also inhibited, significantly albeit modestly Ca-ATPase. The activity of the enzyme was increased at high pH or in the presence of bicarbonate. The reaction velocity at close-to-physiological concentrations of ATP, Ca2+ and H+ suggests that the consumption of ATP by the Ca-ATPase may account for a major fraction of the overall rate of ATP breakdown in intact islets.     

The exchange hypothesis for the formation of chromatid aberrations: an experimental test using bleomycin

The association between bleomycin-induced chromatid aberrations and BUdR-label exchange between sister chromatids was investigated in order to evaluate Revell's exchange hypothesis for the formation of chromatid aberrations. The results of this study indicate that a larger than expected proportion of chromatid breaks can be accounted for by the exchange hypothesis though not all breaks are the result of incomplete exchange.     

Human class I histocompatibility antigens (HLA-A,B,C). A small proportion only is phosphorylated

Human Class I HLA antigens (HLA-A,B,C) were isolated by immune precipitation from cells labelled with 32P, [35S]methionine or 125I (by lactoperoxidase-catalysed cell-surface iodination) and were analysed using both one- and two-dimensional electrophoretic systems. In several B-lymphoblastoid cell lines and in human peripheral blood lymphocytes the electrophoretic mobility of the 32P-labelled HLA-A,B,C heavy chains consistently differed from that of molecules labelled by other means. Thus the 32P-labelled heavy chains appeared to be larger and to possess a more acidic pI than did heavy chains labelled with [35S]methionine or 125I, or identified by Coomassie Blue staining. Phosphatase treatment of immunoprecipitates, under conditions where 32P-labelled antigens were shown to be dephosphorylated, did not affect the mobilities of the [35S]methionine-labelled heavy chains. On glycosidase treatment, the positions of the 32P-labelled heavy chains were affected by neuraminidase but not by endo-beta-N-acetylglucosaminidase H. These results imply that phosphorylated HLA-A,B,C antigens comprise only a small proportion (relative to the total cellular HLA-A,B,C antigens) of the biosynthetically mature molecules. The possible significance of such heterogeneity is discussed.     

Interactions of lens proteins. Self-association and mixed-association studies of bovine alpha-crystallin and gamma-crystallin

Concentrated solutions of calf alpha-crystallin (up to 45 g/l) and gamma-crystallin (up to 67 g/l) were subjected to frontal exclusion chromatography at pH 7.3, ionic strength 0.17 and 20 degrees C. The experimental concentration dependence of the weight-average partition coefficient was compared with theoretical expressions, which include considerations of thermodynamic non-ideality effects, for the concentration dependence of a single solute and of a solute undergoing reversible self-association. Two types of association pattern were examined, discrete dimerization and indefinite self-association. The partition chromatography results are consistent with an indefinite self-association of gamma-crystallin, governed by an isodesmic association constant of 6.7 X 10(-3) l/g. alpha-Crystallin appears to self-associate either very weakly, with a maximal association constant of 0.9 X 10(-3) l/g, or not at all; the distinction depends on the assessment of the non-ideality coefficients. The consequences of excluded volume effects on these self-association equilibria at high total protein concentration are discussed. Mixtures of alpha-crystallin and gamma-crystallin were analyzed by frontal exclusion chromatography (up to 14 g/l) and sedimentation velocity (up to 115 g/l): no interaction was observed.     

Leg chaetotaxy and the classification of the Uropodina (Acari: Mesostigmata)

Details of the segmental chaetotaxy of the legs of 47 species of Uropodina are given. On the basis of the ontogenetic development of the chaetotaxy, the Uropodina may be divided into two groups which coincide with the concepts of the Lower (Polyaspidoidea) and Higher (Uropodoidea) Uropodina of certain authors. Chaetotactic criteria do not support the classification of the Polyaspidini and Trachyuropodini sensu Hirschmann and Z-Nicol within the Oplitinae Hirschmann & Z-Nicol, the Diarthrophallini within the Uroactiniinae Hirschmann & Z-Nicol or the genus Trachytes within the Uropodini.
A critical appraisal is given of the classification of the Uropodidae (based on "Gangmerk-male") by Hirschmann and Z-Nicol.     

Isolation and Characterization of Temperature-Sensitive Mutants of Vesicular Stomatitis Virus, New Jersey Serotype

Forty-eight temperature-sensitive (ts) mutants have been isolated from a wild-type strain of the New Jersey serotype of vesicular stomatitis virus (VSV) after exposure to the base analogue mutagen 5-fluorouracil. Of these mutants, 47 have been classified into 6 nonoverlapping complementation groups containing 21, 17, 4, 3, 2, and 1 mutant, respectively (1 mutant remaining unallocated). The ribonucleic acid (RNA) phenotype of 23 of these mutants has been established. Four of the six groups contain one or more mutants unable to synthesize detectable amounts of viral RNA under restrictive conditions (39 C). No complementation was observed in mixed infection with ts mutants from the five established complementation groups of the Indiana serotype of VSV.