Biomedical science最新文献

The effect of native alcohol dehydrogenase (ADH) and ADH modified by polyethylene glycol on alcohol consumption and certain other behavioural parameters in rats were studied. Intravenous injection of native heterologous ADH significantly suppressed alcohol consumption between the 10th and 15th days after injection with a duration of the effect of 40 days or more. During this period, a low but reliable production of anti-ADH antibodies occurred. ADH modified by covalent attachment of polyethylene glycol did not give these results. Native ADH and ADH modified by polyethylene glycol caused enhanced nociception and active avoidance formation.

A mathematical model for the generation of free radicals by mitochondria in ischemia-reperfusion is proposed. Computations show that normally two stable equilibrium states exist: the intact state, and the state characterized by damage to mitochondrial structures and a high rate of radical formation. Transition from one state to another occurs after hypoxia of a certain degree of severity and duration. The model also describes a number of phenomena observed during development of reperfusion injuries and drug therapy.

Identification of the target cells for the immunomodulatory action of muramyl dipeptide (MDP) was addressed by investigation of various B-cell and T-cell lines. The lines used were: IM-9, a human lymphoblastoid B-cell line that spontaneously produces IgG; EL-4, a murine T-cell line that produces interleukin-2 (IL-2) on stimulation with phorbol myristate acetate; and CTLL-2, an IL-2-dependent murine T-cell line. MDP was shown to modulate such T-cell and B-cell functions as cell proliferation and secretion of IL-2 and IgG, respectively, in vitro. The effect of MDP in vitro was determined by both MDP dose and the control level of cell activity. The evidence obtained supports the possibility of the direct action of MDP on T and B lymphocytes.

Ca2+ ATPase was isolated from rabbit skeletal muscle sarcoplasmic reticulum and used to form structures resembling potential-dependent calcium channels within the membrane lipid bilayer of liposomes. The orientation of these structures in the bilayer was dependent on the conditions used for enzyme incorporation. The results obtained indicate that Ca2+ ATPase may be involved in the passive transport of calcium ions from the sarcoplasmic reticulum which may be regulated by the membrane potential. The membrane potential within the reticulum is probably positive at the moment of calcium ion release.

Parameters of cellular and humoral immunity, and the levels of neurotransmitters and hormones both before and after the administration of various stimulators and blocking agents that affect the immune and neuroendocrine systems were investigated in 100 patients suffering from chronic alcoholism. The results direct attention to the significance of the impairment of interactions between these biological systems during chronic alcoholism.

The composition of the collagen and proteoglycan components of the extracellular matrix in human rib cartilage under normal conditions at different stages of ontogenesis (from 7 weeks of intrauterine development to 60 years of age) has been analysed. Polyacrylamide gel electrophoresis of collagen CNBr-peptides has shown the presence of type I collagen in embryonal cartilage and a gradual decrease in the quantity of this component relative to type II collagen with increasing age. Analysis of reducible and mature collagen cross-links revealed traces of lysylpyridinoline in addition to hydroxylysylpyridinoline in human rib cartilage. The increase in the content of mature cross-links during ontogenesis was accompanied by a decrease in the content of dihydroxylysinonorleucine. Electrophoretic analysis of proteoglycan monomers revealed four fractions of different mobility and the ratio of these fractions altered in the course of ontogenesis. An increase in the glucosamine/galactosamine ratio in the core proteins was observed with increase in age of the donors. During electrophoretic analysis of the link protein fraction a protein of molecular mass 200 kDa was found. This protein first appeared after 9 weeks of intrauterine development and was present in the rib cartilage at all subsequent stages of embryogenesis. This protein has been identified as tenascin by immunoblotting.

It was postulated that similar genetic elements that are 'hot spots' for genetic variation might exist in both the HIV-1 and the human genome. To test this possibility a short repeated sequence from a region of variability in the HIV-1 glycoprotein (env) gene was amplified and used as a probe for blot hybridization with human genome DNA. Human genomic regions were hybridized and characterized by a set of polymorphic restriction DNA fragments. The pattern of the restriction fragments was individual specific. Thus a DNA probe from the HIV-1 env gene can serve as a genetic marker for hybridization with human genome regions and for the identification of individuals.

The combination of two epileptogenic factors--rhythmic photostimulation at frequencies of 5-6 Hz, and local injury to the visual cortex by freezing--were used to induce paroxysmal spike-and-wave type activity in rabbits. This activity (5-6 discharges per second) was observed near the injured site, as well as in the mirror foci, but it never extended to the frontal cortex. Spike-and-wave discharges were also observed in the lateral geniculate body and the superior colliculus. Diazepam completely inhibited this epileptic activity, but pentylenetetrazol and caffeine potentiated its manifestation. The dominant theta-rhythm frequency coincides with the main electroencephalogram synchronization frequency, and with the frequency of rhythmical photostimulation which was able to induce the seizures. These findings are discussed with respect to the theory of synchronization of biorhythms in the brain.

The functional state of internalized epidermal growth factor (EGF) receptors is reviewed. It is shown that in A431 cells internalized EGF-receptor complexes remain in an undissociated and nondegraded state for a long time. The internalized EGF-receptor complexes retain activated tyrosine kinase activity capable of autophosphorylation and phosphorylation of exogenous substrates. It is concluded that the activated tyrosine kinase of growth factor receptors is translocated from the plasma membrane into the cytoplasm and that the activated state is maintained for long enough to allow phosphorylation of intracellular substrates which may be inaccessible to the kinase while the latter is associated with the membrane.

The responses of sensorimotor cortical neurons in hungry and in fed rabbits to stimulation of the lateral hypothalamic (LH) hunger centre were studied in the presence and absence of food. It was found that in the absence of food the response of the sensorimotor cortical neurons to LH stimulation differed between hungry and fed animals. No changes in firing rate were observed in 50% of neurons in hungry rabbits, and firing was inhibited in 45% of neurons in fed animals. Feeding reinforcement changed the nature of neuronal responses to LH stimulation. Qualitative changes in the responses to LH stimulation were observed in 77% of neurons in hungry rabbits, and in 61% of neurons in fed rabbits. Most neurons increased their rate of firing both in hungry and in fed animals.