[Analysis of occupational morbidity and ways of further improving occupational therapy in Leningrad region].

Retrospective clinical and epidemiologic analysis covered occupational diseases in Leningrad region. Findings are that over recent years a tendency to lower number of primarily diagnosed occupational diseases continues. The authors justify necessity to work out the programs on prevention of occupational diseases in the region.

[Role of arginine and histidine residues in the biological activity of botulinic neurotoxin A]. / Rol' ostatkov arginina i gistidina v biologicheskoi aktivnosti botulinicheskogo neirotoksina tipa A.

Treatment of botulinic neurotoxin A with cyclohexanedione demonstrated that modification of 5 to 10 arginine residues does not change the neurotoxin toxicity, while after modification of 15-20 arginine residues the toxicity is decreased by 40-50% of the original value. Butanedione exerts a stronger detoxicating effect on neurotoxin than cyclohexanedione. The molecular conformation of the modified toxin derivatives and their precipitability upon interaction with antisera against toxin and toxin fragments does not change thereby. The non-toxic derivatives of toxin containing 40 modified arginine residues possess a partial serological affinity for the original toxin in a reaction with antiserum against toxin but do not interact with the antifragment sera. The molecular conformation of these preparations is changed considerably. It is assumed that one or two arginine residues are located near the toxic site of the neurotoxin molecule and are also components of its antigenic determinants. Modification of histidine residues in the neurotoxin molecule by diethylpyrocarbonate is accompanied by a decrease of its toxicity. An additional 10% toxicity is revealed upon modification of 11-13 histidine residues. The molecular conformation of the modified derivatives of neurotoxin and their precipitability do not change thereby. It is probable that 1 or 2 histidine residues are located at or near the toxic site. The data obtained suggest that histidine residues are not localized in antigenic determinants of the neurotoxin molecule.

[Molecular structure and immunochemical properties of highly purified hemagglutinin from Clostridium botulinum type A]. / Issledovanie molekuliarnoi struktury i immunokhimicheskikh svoistv vysokoochishchennogo gemaggliutinina Clostridium botulinum tipa A.

A procedure for isolation of highly purified hemagglutinin from a toxic complex of culture filtrates of Cl. botulinum type A is described. This procedure includes precipitation with (NH4)2SO4, chromatography on Sephadex G-100, G-200 and DEAE-cellulose, specific adsorption on human erythrocytes and affinity chromatography. Using polyacrylamide gel electrophoresis, it was shown that hemagglutinin is a heteropolymeric protein consisting of a monomer (Mr 53 000) and a trimer (Mr 160 000). The monomer is made up of two subunits with Mr 13 000 and one subunit with Mr 27 000 covalently linked by SS-crosslinks. The number and nature of the SS-crosslinks and SH-groups in the protein molecule were determined and a hypothetical structural model of hemagglutinin was proposed. Using immunochemical analysis, it was shown that some (but not all) serological properties of the highly purified protein from Cl. botulinum type A and of its partially purified counterpart are similar to those of hemagglutinin from Cl. botulinum type B.

[Effect of photooxidation on biological properties of botulinum neurotoxin A]. / Vliianie fotookisleniia na biologicheskie svoistva botulinicheskogo neirotoksina tipa A.

Photooxidation of botulinic neurotoxin A in the presence of methylene blue is associated with a decrease in toxicity down to complete detoxication. During neurotoxin photooxidation, when the toxicity makes up to 1 to 3% of the original one, the conformation of the neurotoxin molecule and its antigenic properties remain unchanged. Under these conditions, using diethylpyrocarbonate, a specific reagent for histidine, the photooxidized neurotoxin was found to contain 5-6 oxidized histidine residues per molecule of neurotoxin; this was accompanied by changes in the UV absorbance spectrum around 280 nm. It was assumed that the main decrease in neurotoxin toxicity during photooxidation is probably due to oxidation of tryptophane, since the differential UV spectra suggest that the higher the extremum around 280 nm, the greater the decrease of toxicity; chemical modification of histidine residues alone causes no noticeable detoxication.

[Changes in biological properties of botulinum neurotoxin a induced by chemical modification of its molecule by tryptophan and tyrosine]. / Izmenenie biologicheskikh svoistv botulinicheskogo neirotoksina tipa A pri khimicheskoi modifikatsii ostatkov triptofana i tirozina v ego molekule.

Using spectrophotometric titration of botulinic neurotoxin A by N-bromosuccinimide, the oxidation of one tryptophane residue was shown to induce an almost complete detoxication of the toxic protein. The conformation of the toxin molecule remained thereby unchanged, as well as the precipitation capacity of the modified toxin after oxidation of two tryptophane residues. The toxin with three or more modified tryptophane residues did not produce precipitation bands with antiserum against original toxin. Nitration of the tyrosine residues in the neurotoxin molecule with tetranitromethane gradually decreased its toxicity. All nitrous derivatives of toxin (both toxic and non-toxic ones) containing 2-18 modified tyrosine residues revealed a precipitating capacity in a reaction with antiserum against original toxin and anfragment sera. The non-toxic toxin nitrous derivatives with 15-18 modified tyrosine residues possessed partial serological affinity for original toxin in a reaction with antiserum against toxin and did not interact with antisera against toxin fragments. The conformation of molecules of toxin nitrous derivatives with 4-5 modified tyrosine residues was not changed irrespective of a 80% loss of the enzyme toxicity.

[Isolation and characterization of the polypeptide fragments obtained by limited proteolysis of botulinic toxin type A]. / Vydelenie i kharakteristika polipeptidnykh fragmentov, poluchennykh pri orgranichennom proteolize botulinicheskogo toksina tipa A.

A limited proteolysis of the botulinic toxin of A type by subtylopeptidase A resulted in two high molecular weight non-toxic fragments. The peptide with mol. weight of 100,000 is made up of two subunits with mol. weights of 52,000 and 48,000. The second peptide whose mol. weight is 40,000 is a single-chained one. The high molecular weight peptide has one S--S bond and two SH-groups, whereas the one with a lower molecular weight--no S--S bond and 1.3--1.5 SH-groups. Dansylation of the first fragment revealed two N-terminal amino acids (histidine, arginine) in toxin, which suggests the localization of the first fragment at the N-end of the toxin molecule. Using immunochemical analysis with monospecific antiserum against original toxin and antifragment sera, the antigenic determinants from the fragments were shown to be serologically different. A structural model of botulinic toxin of A type is proposed.