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M Toropila

Publications and source records attributed to M Toropila.

27 records · Page 2Linked to original sources
PubMed1982

Influence of the seasons on the circadian rhythm of blood glucose and tissue glycogen in male Wistar rats.

Adult, ad libitum fed male Wistar rats were adapted for three weeks to standard laboratory conditions and a 12:12 h light:dark regimen (7 a.m. to 7 p.m., 7 p.m. to 7 a.m.). In January, in April, in July and in October they were decapitated at 3-hour intervals and the glucose level was determined in their blood and the glycogen concentration in their liver, skeletal muscle, heart and white and brown adipose tissue. The influence of the seasons on circadian variation of the given parameters was not the same in all the tissues. Circadian variation of the liver and heart glycogen concentration was the least affected. The liver glycogen curves attained the maximum at the beginning of the light part of the day in all the seasons except the autumn; the rhythm was present everywhere. The rhythm was not demonstrated in the heart in the winter only and except for the summer the curves attained the maximum at the end of the dark part of the day. Pronounced seasonal changes were observed in the blood glucose and skeletal muscle glycogen concentration, whose curves reached the maximum in various parts of the day and where the rhythm was absent in the autumn - and in the case of skeletal muscle in the summer as well. The glycogen concentration in the two adipose tissues displayed the greatest seasonal changes. The shape of the circadian oscillation curves and their maxima in the various seasons were very different, with absence of the rhythm in the autumn. Determination of the influence of the photoperiodic reactions and of changes in hormones and the key enzymes regulating the main metabolic routes might help to explain the basis of circaannual variations in the metabolism of the laboratory rat.

Adipose Tissue↗
PubMed1982

Influence of light regimens on circadian changes in the blood glucose and tissue glycogen concentration in the rat.

Adult male Wistar rats allowed food and drinking water ad libitum were kept 2- 5 weeks under standard conditions, but with a different artificial light regimens. The standard regimen was 12:12 h light and dark (LD) and the other variants were 12:12 h dark and light (DL), continuous darkness (DD) and continuous light (LL). The blood glucose level and the liver, skeletal muscle, heart and brown and white adipose tissue glycogen concentration were tested during the day at 3-hour intervals. The experiments were carried out during the winter and were evaluated by an analysis of variance and the cosinor test. Circadian variation of the blood glucose level and the liver and both the adipose tissue glycogen concentrations was only slightly affected by changes in the light regimen. Conversely, the oscillations of the skeletal muscle and heart glycogen concentration reacted markedly to the variants of the light regimen, their reaction being manifested in the localization of the acrophases in different parts of the day, especially when comparing the DD and LD regimens.

Adipose Tissue↗
PubMed1982

Influence of the season on the circadian rhythm of serum lipids in male Wistar rats.

Young male Wistar rats were adapted to a 12:12 h light: dark regimen (7 a.m. to 7 p.m., 7 p.m. to 7 a.m.), with free access to food and water. In January, April, July and October they were killed at 3-hour intervals and non-esterified fatty acids, tri-glycerides, total cholesterol and phospholipids were determined in their serum. Serum cholesterol was the least influenced by the season; a rhythm was present in all the seasons, the acrophases came in approximately the same part of the day and the mean adjusted oscillation (mesor) values (in the cosinor test) did not differ the whole year round. Serum triglycerides displayed a rhythm except in the summer; their autumn values were lower and their curves attained the maximum in different parts of the photophase. Non-esterified fatty acids and phospholipids were found to be significantly influenced by the season; the shapes of their curves and their maxima varied during the year. For evaluation of the influence of the seasons on the circadian oscillations of lipid metabolism in the rat, information on the ratio of the formation and utilization/degradation of tissue lipids in the various parts of the year is still lacking.

Animals↗
PubMed1982

Influence of the light regimen on the circadian rhythm of serum lipids in the laboratory rat.

Young male rats of a conventional Wistar breed were adapted for several weeks (3-6) to a 12:12 h light:dark (7 a.m. - 7 p.m., 7 p.m. - 7 a.m.) regimen (LD), to inversion of this standard regimen (DL), to continuous darkness (DD) or to continuous light (LL). After adaptation, groups of animals were killed at 3-hour intervals during the day and the basic lipid fractions were determined in their serum. Under the standard light regimen the cosinor test demonstrated a rhythm in all the indicators (triacylglycerols, total cholesterol, phospholipids) except for non-esterified fatty acids. When the regimen was inverted (DL), the peaks of the circadian non-esterified fatty acid and triacylglycerol curves shifted to the antiphase. The acrophases of "free-running" serum lipid rhythm under the DD regimen of the standard regimen rhythms differed in the case of cholesterol and phospholipids. In the case of triacylglycerols and phospholipids there was disagreement between the DD and LL regimen curves. With reference to the localization of the acrophase under the DD and LD regimens it was assumed that the influence of the light regimen on the synchronization of circadian rhythms is small in the case of serum non-esterified fatty acids and triacylglycerols and that it is greater in the case of serum cholesterol and phospholipids.

Animals↗
PubMed1981

Circadian rhythm of the lactate and pyruvate concentration in rat liver and blood.

Diurnal changes in the blood and liver lactate and pyruvate concentration and in the blood glucose, serum insulin and liver glycogen level were studied in the spring, at 3-hour intervals, in adult ad libitum fed male Wistar rats adapted to standard laboratory conditions and a 12:12 h light and dark regimen (7-19 and 19-7 h). The marked liver and blood lactate oscillations attained maximum values during the dark period, together with the serum insulin oscillations. The pyruvate concentration oscillations culminated in the light part of the day in the liver and in the dark part in the blood; they were not very pronounced, probably owing to rapid metabolization. The curve for the liver lactate/pyruvate index resembled the lactate curve and attained the maximum in the dark period; the blood curve for this index was different, because of the different times at which the two substrates pass from the liver and other tissues into the blood stream. The blood glucose circadian oscillations culminated in the second half of the light period, parallel with the first serum insulin maximum. The oscillations of the liver glycogen values were typical, with the maximum at the end of the dark period and the beginning of the light period. The circadian oscillations of the given substances furnish information on the time sequence of period metabolic processes dependent on the illumination or alimentary regimen, on the waking and sleep cycle and on other synchronizers.

Animals↗
PubMedDate not supplied

[Effect of restricted feeding on metabolic changes in lipids following a single lethal irradiation of rats].

A study was made of the influence of adaptation of rats to limited feeding (2 h a day during 3 weeks) and the response of the adapted animals to total-body X-irradiation with a lethal dose of 14.35 Gy. The concentration of unesterified fatty acids in the blood and the total cholesterol content were shown to decrease between the 1st and 24th hours following irradiation: the content of phospholipids decreased 60 min after irradiation. In the bone marrow of rats adapted to limited feeding, a more pronounced accumulation of triacylglycerols was noted as late as 72 h after irradiation.

Adaptation, Physiological↗
PubMedDate not supplied

[Plasma and tissue lipids in rats after a flight on the Kosmos-1129 biosatellite].

Concentrations of triglycerides, total cholesterol, lipid phosphorus and nonesterified fatty acids were measured in blood plasma, liver, thymus, bone marrow and adipose tissues of rats flown for 18.5 days onboard the biosatellite Cosmos-1129. This exposure was accompanied by increases in lipomobilization, content of total cholesterol and lipid phosphorus in plasma, and triglycerides in the thymus and bone marrow. The postflight exposure to repeated stresses demonstrated changes in the lipid content in all animal groups, especially in flight rats.

Adaptation, Physiological↗