Superoxide dismutase activity as an index of the toxic action of pesticides

A biochemical method for evaluation of the pesticide effect on the living organisms has been proposed. The key enzyme of antioxidant protection, superoxide dismutase (SOD) serves as an index of toxic influence. In the experiments with mollusks Physa, the inhibition of enzyme under the action of pesticides has been revealed. A reverse dependence between the activity of SOD and the number of perished mollusks has been revealed on the background of increased concentration of toxicant. The proposed method is delicate, simple, sufficiently informative, with the help of it the determination of permissible concentration of adverse substances considerably accelerates.     

Latent persistence of specific antigens of the causative agent in the composition of circulating immune complexes in typhoid fever

This study revealed the presence of O-antigen of group D salmonellae and Vi-antigen in circulating immune complexes in patients with typhoid fever, bacteriologically confirmed (56 +/- 5.6% and 65 +/- 5.4% of cases, respectively) and not confirmed (15.5 +/- 5% and 39 +/- 7% of cases, respectively), in patients with diarrhea of nontyphoid etiology in the presence of negative results of the coagglutination test and in healthy persons. The level and dynamics of circulating immune complexes were established with respect to the antigens contained in these complexes. Altogether O- and Vi-antigens were detected in circulating immune complexes, respectively, in 92%, 96% and 94% of cases on weeks 1, 2 and 3 from the beginning of the disease, and in all cases on weeks 4 and 5, the antigens being determined together and separately. Thus, the latent persistence of S. typhi antigens as part of circulating immune complexes in the blood serum was established. The determination of such persistence is of great pathogenetic and diagnostic importance, which also applies to the early period of the disease. The use of such specific and sensitive method as the coagglutination test for this purpose accelerates and facilitates the diagnosis of typhoid fever.     

Patchy fur,a Mouse Coat Mutation Associated with X–Y Nondisjunction, Maps to the Pseudoautosomal Boundary Region

Patchy furis a semidominant X-linked mutation in the mouse, resulting in a sparse coat. ThePafmutation also alters the normal segregation of the X and the Y chromosomes during male meiosis by causing nondisjunction at anaphase I. Analysis of 1139 female meioses from an intersubspecific backcross using 15 PCR-based markers localizesPafto an 0.2-cM interval that includes the pseudoautosomal boundary. The meiotic nondisjunction phenotype may result from a chromosomal rearrangement that includes pseudoautosomal sequences and affects XY pairing.     

Distribution of molluscs in Layari River (Sindh), Pakistan

Between January 1982 and December 1985, 65 species of Mollusca were collected from the Layari River, an ephemeral stream that bisects Karachi. Gastropods were dominant followed by bivalves. The upstream region is hypersaline and devoid of molluscs; the stretch within Karachi is heavily polluted and almost no living molluscs occur here.     

Chloroplastic glutamine synthetase from tobacco leaves: a glycosylated protein

The amino acid and carbohydrate content of chloroplastic glutamine synthetase from tobacco leaves has been analysed. The enzyme subunit contanins 5% carbohydrate, mainly represented by glucosamine, galactosamine, glucose, galactose and mannose residues. The enzyme subunit displayed a single band of molecular mass 44000 Da after sodium dodecyl sulphate (SDS) electrophoresis. However, when isoelectrofocussing electrophoresis was performed, four subunits were evident differing by their charge. Furthermore, the four different subunits stained positively when tested with periodic acid Shiff reagent, showing that sugars and amino sugars were present within all the subunits.     

Restriction-modification systems and bacteriophage invasion: Who wins?

The success of a phage that infects a bacterial cell possessing a restriction-modification (R-M) system depends on the activities of the host methyltransferase and restriction endonuclease, and the number of susceptible sites in the phage genome. However, there is no model describing this dependency and linking it to observable parameters such as the fraction of surviving cells under excess phage, or probability of plating at low amount of phages. We model the phage infection of a cell with a R-M system as a pure birth process with a killing state. We calculate the transitional probabilities and the stationary distribution for this process. We generalize the model developed for a single cell to the case of multiple identical cells invaded by a Poisson-distributed number of phages. The R-M enzyme activities are assumed to be constant, time-dependent, or random. The obtained results are used to estimate the ratio of the methyltransferase and endonuclease activities from the observed fraction of surviving cells.