From patterns to processes: phase and density dependencies in the Canadian lynx cycle

Across the boreal forest of North America, lynx populations undergo 10-year cycles. Analysis of 21 time series from 1821 to the present demonstrates that these fluctuations are generated by nonlinear processes with regulatory delays. Trophic interactions between lynx and hares cause delayed density-dependent regulation of lynx population growth. The nonlinearity, in contrast, appears to arise from phase dependencies in hunting success by lynx through the cycle. Using a combined approach of empirical, statistical, and mathematical modeling, we highlight how shifts in trophic interactions between the lynx and the hare generate the nonlinear process primarily by shifting functional response curves during the increase and the decrease phases.     

Anthracycline antibiotics non-covalently incorporated into the block copolymer micelles: in vivo evaluation of anti-cancer activity

The chemosensitising effects of poly(ethylene oxide)-poly(propylene oxide)-poly-(ethylene oxide) (PEO-PPO-PEO) block copolymers (Pluronic) in multidrug-resistant cancer cells has been described recently (Alakhov VY, Moskaleva EY, Batrakova EV, Kabanov AV 1996, Biocon. Chem., 7, 209). This paper presents initial studies on in vivo evaluation of Pluronic copolymers in the treatment of cancer. The anti-tumour activity of epirubicin (EPI) and doxorubicin (DOX), solubilised in micelles of Pluronic L61, P85 and F108, was investigated using murine leukaemia P388 and daunorubicin-sensitive Sp2/0 and -resistant Sp2/0(DNR) myeloma cells grown subcutaneously (s.c.). The study revealed that the lifespan of the animals and inhibition of tumour growth were considerably increased in mice treated with drug/copolymer compositions compared with animals treated with the free drugs. The anti-tumour activity of the drug/copolymer compositions depends on the concentration of the copolymer and its hydrophobicity, as determined by the ratio of the lengths of hydrophilic PEO and hydrophobic PPO segments. The data suggest that higher activity is associated with more hydrophobic copolymers. In particular, a significant increase in lifespan (T/C> 150%) and tumour growth inhibition (> 90%) was observed in animals with Sp2/0 tumours with EPI/P85 and DOX/L61 compositions. The effective doses of these compositions caused inhibition of Sp2/0 tumour growth and complete disappearance of tumour in 33-50% of animals. Future studies will focus on the evaluation of the activity of Pluronic-based compositions against human drug-resistant tumours.     

Early signs of renal pathology in small intensity chemical exposure

Occupational exposure to vapours, gases and aerosols promotes increase of renal diseases incidence. Wider use of anamnestic data is recommended during preliminary and regular check-ups of this population.     

Microsomal protein changes in the brain of hens in ontogeny

Studies have been made on the peripheral (extracted by 1 M KCl, pH 9.0) and integral (successively extracted by a 1% solution of Triton X-100 and 0.3% solution of sodium dodecyl sulfate) microsomal proteins from the brain of chick embryos beginning from the 8th day of incubation, chicks and adult hens up to 1 year 4 months. Investigation was made of the quantity, fractional composition (by means of polyacrylamide gel electrophoresis) and the rate of incorporation of 14C-lysine. It was found that the content of these membrane proteins and their composition depend on the age of animals. Integral proteins as compared with peripheral ones exhibit higher rate of incorporation of the labeled amino acid, this rate increasing with the age of animals.     

Current state and implications of research on biological effects of millimeter waves: a review of the literature

In recent years, research into biological and medical effects of millimeter waves (MMW) has expanded greatly. This paper analyzes general trends in the area and briefly reviews the most significant publications, proceeding from cell-free systems, dosimetry, and spectroscopy issues through cultured cells and isolated organs to animals and humans. The studies reviewed demonstrate effects of low-intensity MMW (10 mW/cm2 and less) on cell growth and proliferation, activity of enzymes, state of cell genetic apparatus, function of excitable membranes, peripheral receptors, and other biological systems. In animals and humans, local MMW exposure stimulated tissue repair and regeneration, alleviated stress reactions, and facilitated recovery in a wide range of diseases (MMW therapy). Many reported MMW effects could not be readily explained by temperature changes during irradiation. The paper outlines some problems and uncertainties in the MMW research area, identifies tasks for future studies, and discusses possible implications for development of exposure safety criteria and guidelines.     

The use of contact YAG-laser in surgeries on pleura and lungs

The paper presents an epidemiological monitoring of tuberculosis infection with personal computers. The procedure may standardize different epidemiological characteristics, objectively evaluate the level of antituberculosis work in various areas, promptly process a great deal of data. The tuberculosis epidemiological situation in Omsk is analyzed in comparison with the indices of epidemiological well-being.     

METACHROMATIC EFFECT IN HOMOLOGOUS GROUPS OF WHEAT, BARLEY AND RYE PROLAMINS

The metachromatic behavior of wheat, barley and rye prolamins, separated by polyacrylamide gel electrophoresis (PAGE) and staining with Coomassie Brilliant Blue R-250, is described. Metachromasia was detected both visually and by double beam densitometric analysis of sodium dodecyl sulfate-PAGE and acidic-PAGE (A-PAGE) at pH 3.1. Differential readings were recorded at 525 nm, with reference at 625 nm. Metachromatic components were found in the homologous groups, (a) S-poor prolamins: ω-gliadins, C-hordeins, ω-secalins and (b) high molecular weight (HMW)-prolamins: HMW-glutenins, D-hordeins and HMW-secalins, in wheat, barley and rye, respectively. In contrast, proteins having this characteistic have not been found in oat.     

Correlation between the intensity of tropospheric fall-out and the introduction of radionuclides into the human body with bread products and milk

The effect of physical exercises was studied with reference to the content of non-esterified fatty acids (NEFA), cholesterol and beta-lipoproteins, as well as catecholamines and lactic acid in 130 patients with essential and renal hypertension. The control group included 12 normal individuals. The physical exercises were conducted on a bicycle ergometer with a step-wise growth of the load by 150-300 kgm per each 4 min. The value of the maximal tolerated physical load was determined. It was decreasing parallel the progress of the disease. The conducted investigations demonstrated the presence of an inverse relationship between the initial blood level of beta-lipoproteins and cholesterol, on the one hand, and the value of physical load and capacity for work, on the other. The changes in the lipid metabolism parameters are distinctly connected with the activity of catecholamines and lactate concentration.     

Thermal Denaturation of Hake (Merluccius hubbsi) Myofibrillar Proteins. A Differential Scanning Calorimetric and Electrophoretic Study

Denaturation of hake (Merluccius hubbsi) proteins was studied with DSC by monitoring T_max of transitions and denaturation enthalpies. Whole muscle free of connective tissue showed two transitions (T_max 46.5°C and 75.3°C), and ΔH of 4.27 cal/g. The exudative sarcoplasmic fraction showed three transitions (T_max 45.2°C, 59.0°C and 75.5°C) and ΔH of 3.92 cal/g. The sarcoplasmic proteins from whole hake muscle contributed to both denaturation peaks. Muscle depleted of sarcoplasmic proteins by chloride extraction showed a higher thermal sensitivity and a diminished denaturation enthalpy on the second transition. This suggested an additional effect of chloride upon actin in addition to sarcoplasmic protein extraction. pH had an effect upon the native conformation of thick filament proteins, specifically myosin.     

Droppers for pharmaceutical use

122 patients, suspicious for silicoses, with a history of silicogen dust exposure, radiological changes and restricted lung function values were examined by mediastinal biopsy for securing the diagnosis. In 82 patients (67,2%) a silicosis could be confirmed by histological examinations of the mediastinal lymph nodes. A close association between silicosis in the lungs and in the lymph nodes is empirically suggested. If the histological findings were in compliance with suspicious radiological changes and patients history, silicosis was acknowledged as an occupational disease. In patients with beginning silicotic changes in the peripheral two upper lung fields associated with an hilar hyperplasia, a higher proportion of positive results could be found. The most positive alterations were found in the lymph nodes of the right hilus. The mediastinoscopical findings in other parts proved not to be so yielding. Therefore, in cases with anatomical difficulties the surgical examination should not be extended to other parts.