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Biomedical subjects

N N Lebedev

Publications and source records attributed to N N Lebedev.

33 records · Page 2Linked to original sources
PubMed1975

[Influence of thyrocalcitonin on the periodic motor activity of the gastro-intestinal tract].

Experiments were conducted on dogs with fistulae of the stomach and various portions of the small intestine in which there was recorded a periodic motor activity. It was shown that intravenous injection of a highly purified bovine thyrocalcitonin (TCT) in doses of 2--10 Units/kg (considerably exceeding the doses used at the clinic in the treatment of patients with bone pathology) caused no changes in a number of indices characterizing the motor periodic activity of the stomach and various portions of the small intestine, despite a distinct reduction (by 10--20%) of the calcium level in the blood serum.

Animals↗
PubMedDate not supplied

Cortico-visceral interrelationships during periodic activity of the stomach.

In chronic experiments on five dogs with stomach fistulas and bipolar electrodes (6-8 pairs) symmetrically implanted in the cranial bones we recorded simultaneously the activity of the stomach balloonographically and the electroencephalogram using the Nikhon Koden encephalograph with automatic analysis of the frequency spectrum within five ranges: 2-4, 4-8, 8-12, 12-20, and 20-30 oscill/sec. The correlation between the frequency spectrum of the EEG and the phases of periodic activity (PA) cycles of the stomach in the form of a regular shift in the predominance of fast (during contraction periods) or slow (during resting periods) components and its changes under the influence of atropine and food stimulants have been described. The EEG complexes typical of periods of contraction or resting are regarded as cortical correlates of the PA under conditions of good adaptation of the animals to the experimental situation. The changes in the correlation under conditions of actions used indicate a firmer association between the PA EEG correlates with other components of the PA rather than with the motor function of the stomach.

Animals↗
PubMedDate not supplied

[Molecular organization of pheophytin a in aqueous solutions of detergents].

Absorption, fluorescence and excitation fluorescence spectra of pheophytin a have been measured in aqueous solutions of nonionic (Triton X-100), anionic (sodium lauryl sulphate) and cationic (Cetyl pyridinium chloride) detergents at different concentrations and pH after system relaxation. By measuring the second derivative and differential spectra, it has been shown, that if detergent concentrations are lower than critical micelles concentration, or if the detergent is completely absent, the pigment forms conglomerates containing both dimeric and monomeric forms with an efficient energy transfer between them. If detergent concentrations are higher than critical micelles concentration, pheophytin a localizes in detergent micelle in monomeric form at neutral and acidic pH, and allomerizes at alkaline pH. The spectral characteristics of pheophytin a dimers in the conglomerate and its monomers in micelles poorly (if at all) depend on the sign of the detergent molecule charge.

Cetylpyridinium↗