Organochlorine pesticides in commercial Pacific salmon in the Russian Far Eastern seas: Food safety and human health risk assessment.

Concentration of organochlorine pesticides (OCPs) (α-, ß-, γ- hexachlorocyclohexane (HCH), dichlorodiphenyltrichloroethane (DDT), dichlorodiphenyldichloroethane (DDD), dichlorodiphenyldichloroethylene (DDE)) in four species of Pacific salmon (pink, chum, chinook, and sockeye) are presented. OCPs in salmon organs increased in the following order: muscle < liver < eggs < male gonads. Concentrations of the OCP in salmon organs increased in following order: DDE < γ-HCH < α-HCH. The level of pollutants in salmon is compared with the sanitary and epidemiological norms of Russia and other countries. Cancer and noncancer hazard ratios through consumption of salmon in Russian Far East for both men and women also were summarized. Noncancer and cancer hazard ratio values were far below threshold values (<1.0).

[Dependence of the rate of myofibril contraction on MgATP concentration. A theoretical examination]. / Zavisimost' skorosti sokrashcheniia miofibrill ot kontsentratsii MgATF. Teoreticheskoe rassmotrenie.

We propose simple model for the mechano-biochemical cycle of the myosin cross-bridges, taking into account the contribution of "slow binding" bridges in the negative strength. Mathematical analysis of this model allows us to obtain an analytical expression for the dependence of the contraction velocity on the MgATP concentration. Parameters of this equation are rate constants of dissociation of "slow binding" bridges from thin filament, liberation of inorganic phosphate and binding of MgATP. The model leads to the bell-shaped dependence of myofibrillar contraction velocity on the substrate concentration similar to the experimental one. The values of above mentioned constants for the isolated myofibrils are estimated to be close to values obtained in unstructured contractile models.

[Aggregation of isolated myofibrils stimulated by their contraction. II. Aggregation mechanism]. / Agregatsiia izolirovannykh miofibrill, stimuliruemaia ikh sokrashcheniem. II. Mekhanizm agregatsii.

Aggregation of contracted myofibrils was studied as a function of experimental conditions at myofibril contraction. The aggregation rate increased at higher concentrations of suspensions and at increased ionic strength of the medium to achieve the maximum at 0.1 M KCL in the last case. The aggregate sizes grow with an increase of ionic strength and concentration of MgATP and reduce with addition of F-actin. Aggregation of myofibrils develops only in the case of their complete or significant contraction. It was suggested that aggregation is stimulated by dehydration of myofibril at contraction.

[Changes in the mechano-chemical properties of actomyosin during desensitization]. / Izmenenie mekhanokhimicheskikh svoistv aktomiozina pri desensibilizatsii.

The loss of Ca2+-sensitivity by natural actomyosin (desensitisation) after treatment with low ionic strength solutions results in marked deceleration of protein superprecipitation. This phenomenon is not due to the removal of minor proteins, since a similar effect was observed during "desensitisation" of synthetic actomyosin containing only myosin and actin. However, addition to desensitised actomyosin of tropomyosin, especially in combination with alpha-actinin markedly restores the initial parameters of superprecipitation and ATPase activity. It was assumed that desensitisation has a direct modifying influence on actomyosin, whose effect is weakened in the presence of tropomyosin and alpha-actinin.

[Oligomerization of integral membrane proteins under lipid peroxidation]. / Oligomerizatsiia integral'nykh membrannykh belkov pri perekisnom okislenii lipidov.

Using polyacrylamide gel electrophoresis in the presence of Na-SDS, the oligomerization of membrane proteins of the retinal rod outer segments of the frog and the wall-eyed pollock and of rabbit skeletal muscle sarcoplasmic reticulum was studied. It was shown that under storage of the retinal rod outer segments the rhodopsin oligomerization is inhibited by the lipid peroxidation inhibitor--ionol. Similar oligomerization was observed under induction of lipid peroxidation in the membranes; the accumulation of the lipid peroxidation product--malonic dialdehyde--was accompanied by disappearance of the rhodopsin monomeric form in the outer segments. The cross-linking agent--glutaric dialdehyde--also causes oligomerization of the rhodopsins. Similar aggregation is also characteristic of the major protein of the sarcoplasmic reticulum fragments, i. e. Ca2+-dependent ATP-ase. Thus, one of the main changes in the protein content of biomembranes under lipid peroxidation is the oligomerization of integral proteins due to their interaction with bifunctional reagents, i. e. lipid peroxidation products.

[Accessibility of sulfhydryl groups to 5,5'-dithiobis-2-nitrobenzoic acid and acid-base properties of bovine and walleye pollock rhodopsin preparations]. / Izuchenie dostupnosti sh-grupp 5,5-ditiobis-2-nitrobenzoínoí kislote i kislotno-oshovnykh svoístv razlichnykh preparatov podopsina.

Both the number of exposed SH-groups and the rate of reaction with 5,5'dithiobis-2-nitrobenzoic acid (DTNB) in walleye pollock and bovine rhodopsin depend on a degree of native structure of the preparation to be investigated. The preparations studied can be arranged in the order of increase of these parameters as follows: ROS less than rhodopsin extracted by digitonin less than triton X-100 less than cetyltrimethylammonium bromide (CTAB) less than sodium dodecylsulphate (SDS). After illumination of ROS and digitonin, triton X-100 and CTAB-solubilized rhodopsin, and increase was observed in the number of modified SH-groups. Dark and bleached samples of walleye pollock rhodopsin exhibited a faster rate reaction and a more number of modified SH-groups as compared to bovine preparation. The differences between bovine and walleye pollock preparation disappeared after complete opsin unfolding as a result ROS solubilization in SDS. Six SH-groups per molecule of rhodopsin were modified in both preparation under these conditions. No differences in the number of cysteine residues (10--11), disulfide groups (2), acid (35--40) and base (25--30) titratable groups per rhodopsin molecule were found between bovine and walleye pollock ROS membranes. The isoelectric point of both rhodopsin preparations was within the pH range 5.2--5.6. After proteolysis of ROS with papain, a fragment with molecular weight 24500 +/- 1000 was detected, which contained the same number of SH-groups and cysteine residues as in the case of intact rhodopsin. The results obtained suggest that, in spite of a similar primary structure, the walleye pollock visual pigment has more "loose" and "fluid" space packing in the ROS membrane than the bovine pigment.