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91.
The duration of the preautomatic pause as a function of sinoatrial node, the type of pacemaker cells, acetylcholine concentration,
the duration of high-frequency stimulation, and the conductivity of gap junctions has been studied. It was found that the
preautomatic pause in peripheral pacemakers occurs at a higher concentration of acetylcholine as compared with central pacemakers.
The dependence of the duration of the preautomatic pause on the gap junction conductivity is a nonlinear one. 相似文献
92.
M Fossi K Ahlsten T Pohjanvirta M Anttila T Kokkonen TK Jensen M Boye A Sukura K Pelkola S Pelkonen 《Acta veterinaria Scandinavica》2005,46(4):257
A hippurate-negative biovariant of Brachyspira pilosicoli (B. pilosicoli
hipp-) is occasionally isolated in diarrhoeic pigs in Finland, often concomitantly with hippurate-positive B. pilosicoli or Lawsonia intracellularis. We studied pathogenicity of B. pilosicoli
hipp- with special attention paid to avoiding co-infection with other enteric pathogens. Pigs were weaned and moved to barrier
facilities at the age of 11 days. At 46 days, 8 pigs were inoculated with B. pilosicoli
hipp- strain Br1622, 8 pigs were inoculated with B. pilosicoli type strain P43/6/78 and 7 pigs were sham-inoculated. No signs of spirochaetal diarrhoea were detected; only one pig, inoculated
with P43/6/78, had soft faeces from day 9 to 10 post inoculation. The pigs were necropsied between days 7 and 23 after inoculation.
Live pigs were culture-negative for Brachyspira spp., but B. pilosicoli
hipp- was reisolated from necropsy samples of two pigs. The lesions on large colons were minor and did not significantly differ
between the three trial groups. In silver-stained sections, invasive spirochaetes were detected in colonic mucosae of several
pigs in all groups. Fluorescent in situ hybridisation for genus Brachyspira, B. pilosicoli and strain Br1622 was negative. However, in situ detection for members of the genus Leptospira was positive for spirochaete-like bacteria in the colonic epithelium of several pigs in both infected groups as well as in
the control group. L. intracellularis, Salmonella spp., Yersinia spp. and intestinal parasites were not detected. The failure of B. pilosicoli strains to cause diarrhoea is discussed with respect to infectivity of the challenge strains, absence of certain intestinal
pathogens and feed and management factors. 相似文献
93.
94.
Aliev RR Rozenshtraukh LV 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2006,92(9):1069-1077
We have simulated electrical and vagal stimulation of a central sino-atrial node cell. Both positive and negative chronotropic effects have been observed. The type of the effect is dependent on the phase of stimulation. Stimulation in early phases resulted in shortening of the cycle, while stimulation in late phases resulted in prolongation of the cycle. 相似文献
95.
R. R. Aliev 《Biophysics》2008,53(6):645-647
The effect of periodic stimulation of the vagus nerve on the activity of the central cell of the sinoatrial node has been simulated. The regions of synchronization and desynchronization have been revealed, and the phase shift at different stimulation frequencies has been estimated. The positive chronotropic effect has been shown to occur at some frequencies of stimulation. 相似文献
96.
D O Levitski? M K Aliev T S Levchenko I Ia Lipitskaia V N Smirnov 《Biokhimii?a (Moscow, Russia)》1976,41(5):854-863
A microsomal preparation with a high ability for Ca2+ uptake has been isolated from pigeon heart. A method of further purification of Ca2+-accumulating system of heart, based on the ability of sarcoplasmic reticulum for the energy-dependent Ca2+ accumulation in the presence of oxalate, has been developed. Upon centrifugation in the gradient of sucrose and KCl concentration the fragments of sarcoplasmic reticulum, rendered "heavy" by calcium oxalate, can be separated from foreign cell membranes. The main component of heart "calcium pump" is Ca2+-dependent ATPase (making up to about 50% of all proteins of the purified reticulum), having a molecular weight of 100.000--105.000. Specific activity of heart Ca2+-ATPase as well as the ability of purified heart sarcoplasmic reticulum for Ca2+ uptake are only slightly less than those of the skeletal muscle reticulum. The data obtained suggest that heart sarcoplasmic reticulum may be efficient for providing heart muscle relaxation. 相似文献
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