Catalytic properties of a human cytomegalovirus-induced protein kinase

Human cytomegalovirus, a DNA virus whose genome contains a fragment of transforming DNA, induces a threonine-serine protein kinase having a molecular mass of 68 kDa (p68). p68 was extracted from cells 96-144 h after infection, and immunoprecipitated with a monoclonal antibody (F6b). Antibody-enzyme complexes were immobilized on heat/formaldehyde-inactivated Staphylococcus aureus. The best substrates for p68 were acidic proteins, phosvitin and casein. Glycogen synthase, phosphorylase alpha and histones were phosphorylated at rates not higher than 1-4% that obtained with phosvitin as substrate. ATP and GTP were equally good substrates of p68. p68 is able to autophosphorylate at the same residues (i.e. threonine and serine) as the protein substrates. Autophosphorylation does not seem to represent an intermediate in substrate phosphorylation. The protein kinase activity of p68 was not enhanced by cAMP, calcium ions, or polyamines like spermine or spermidine. Only at low Mg2+ concentration spermine enhanced by 68% the rate of casein phosphorylation. Heparin, a potent inhibitor of casein kinase II, inhibits p68 activity too, but ten-times higher concentrations were required for the same degree of inhibition. Quercetin, a bioflavonoid, acts as a strong inhibitor of p68 protein kinase activity. The inhibitory effect of quercetin was competitive towards the nucleotide substrate (Ki = 2.8 microM), and non-competitive towards the protein substrate (Ki = 15 microM).     

Intra-individual length heterogeneity of Rana esculenta mitochondrial DNA

Mitochondrial DNA extracted from Rana esculenta oocytes appears heterogeneous in size. The length of these molecules varies continuously from 18,700 bp to 19,700 bp. Each animal is heteroplasmic and can be characterized by the range of the variation (400-700 bp) and the extreme sizes of the various molecules it carries. The variable region of the genome has been localized between the coding region and the replication origin area.     

Further results on the survival of a gene represented in a founder population

This paper is concerned with gene survival in a population which may increase without density dependence according to a generalization of the Moran model for haploid individuals. A selective advantage to one allele and the possibility of differential reproductive rates are allowed. Simple conditions are given for ultimate homozygosity to be certain and for the possibility of ultimate polymorphism. The results complement and extend those of Heyde (1981, 1982).     

Fluorescence technique for comparative studies of substrate-binding subsites in serine proteinases. Application to subtilisins.

A fluorescence technique for comparative studies of substrate-binding subsites in serine proteinases is described. It consists of: selective labelling of the corresponding subsites with a fluorescent group by using N alpha-dansyl(5-dimethylaminonaphthalene-1-sulphonyl)ated peptide chloromethanes containing different numbers of amino acid residues, and probing the immediate environment of the subsites by quenching experiments using ionic and neutral quenchers. Intramolecular distances between the subsites and particular chromophores can be also determined. The technique is of general applicability to all serine proteinases. The above mentioned approach was applied to two proteinases: subtilisin Novo and mesentericopeptidase. It was concluded that the substrate-binding site of mesentericopeptidase is considerably more polar than that of subtilisin Novo. Intramolecular distances between the labelled subsites and tryptophan residues in the two proteinases were determined.     

Dissociation of inductive from differentiative signals transmitted by C8-substituted guanine ribonucleosides to B cells from SJL mice

A hitherto unknown defect in the immune responsiveness of B lymphocytes from SJL mice has enabled us to distinguish two qualitatively distinct classes of signal delivered to B cells by C8-substituted guanine ribonucleosides. This defect renders B cells from SJL mice unresponsive to the inductive (early acting) signal of 8-mercaptoguanosine (8MGuo) that culminates in mitogenesis and nonspecific secretion of immunoglobulin. Unresponsiveness is not attributable to a shift in either the dose-response or kinetic profiles, nor can the presence of suppressor cells be demonstrated. In striking contrast, however, SJL B cells exhibit normal responsiveness to the differentiative (T cell-like, or late acting) signal provided by the substituted nucleoside. This signal enables SJL B cells, depleted of T cells, to respond to T cell-dependent antigens, and synergizes with T cell-derived lymphokines. These data suggest 1) that nonspecific secretion of immunoglobulin is dependent on both inductive and differentiative signals, 2) that antigen alone can supply an effective inductive signal for antigen-specific responses, and 3) that the SJL mouse will provide a useful model for selective study of inductive vs differentiative events.     

Anti-My-26: a monoclonal antibody inhibiting human phagocyte chemiluminescence

Anti-My-26, a mouse monoclonal IgG1 antibody, was raised against human granulocytes and has been shown to inhibit luminol-enhanced, glucose-independent chemiluminescence (CL) of human granulocytes (or monocytes) responding to the soluble secretagogues A23187 or ionomycin (calcium ionophores) and phorbol myristate acetate (PMA). Anti-My-26 inhibition of CL was reversible and was dependent on both secretatogue and monoclonal antibody concentration. This inhibition appeared to be directed at the component of granulocyte CL that is independent of NAD(P)H-oxidase-catalyzed formation of superoxide anion, because neither opsonized zymosan-stimulated CL nor the PMA-induced decrease in NAD (P)H-associated autofluorescence was affected by anti-My-26. In addition, ionomycin, over a wide concentration range, failed to generate any decrease in granulocyte autofluorescence. The A23187-induced CL inhibited by anti-My-26 was correlated with its depression of oxygen consumption. Furthermore, anti-My-26 was not cytotoxic and did not itself induce oxidative metabolism when used as a stimulant. Binding of anti-My-26 to phagocytic cells was not decreased by pre-exposure of cells to either A23187 or PMA. Evidence is presented to suggest that the binding of anti-My-26 to the granulocyte surface inhibits the oxidative response to calcium ionophore and PMA by blocking a common pathway(s) stimulated by these different secretagogues.     

Clinico-epidemiological characteristics of Q fever in the Carpathian region

The study of the specific epidemiological and clinical features of Q fever revealed the existence of an active focus of infection among humans due to their contacts with agricultural animals in one of the districts of the region. The focus was manifested by group morbidity among the cattle-tending personnel of a dairy farm. The source of this infection was cattle. The infection was transferred mainly through the air. The disease took a moderately severe course. The study of the rickettsial contamination of humans, animals and ticks suggested the presence of the active epidemic process and made it possible to work out concrete antiepidemic measures.     

Haematological correlates of burrowing in Ctenomys

Haematological parameters related to O2 transport and regulation of acid-base equilibrium were determined for two species of Ctenomys. The oxygen capacity values of Ctenomys blood are similar to those of other fossorial mammals. Ctenomys blood has almost half the number of red blood cells of Rattus blood but the amount of Hb in each blood cell is 2-2.5 times higher. Blood pH is within typical mammalian values. Concentration of inorganic phosphate is higher in Ctenomys than in rats while bicarbonate and protein values are within typical mammalian range.