Diel variations in plasma glucose concentrations of Malachite Sunbirds Nectarinia famosa

Plasma glucose concentrations in birds are much higher than those in mammals of similar body mass, and they are thought to be kept more or less constant. We investigated plasma glucose concentrations of Malachite Sunbirds (Nectarinia famosa) to determine whether there was a circadian rhythm in plasma glucose and whether plasma glucose concentrations rose at lower temperatures. We explored the possibility that glycogenolysis and gluconeogenesis might be used by birds before daylight to generate body heat during arousal from torpor or from overnight adaptive heterothermy. Plasma glucose concentration of Malachite Sunbirds were relatively high, between 13.6 and 21.4 mmol/L. Plasma glucose concentrations were higher at 5°C than at 25°C, and generally lower during the scotophase, particularly in the early hours of the morning. Therefore, it appears that Malachite Sunbirds are not increasing plasma glucose concentrations during arousal from torpor or to increase scotophase body temperature levels to photophase levels. It is apparent that these nectarivorous birds have a circadian variation in plasma glucose concentrations that is affected by ambient temperature and feeding patterns.     

Diurnal variations of food consumption, plasma glucose and plasma insulin concentrations in lean and obese hyperglycaemic mice.

Diurnal variations in food consumption and plasma concentrations of glucose and insulin were determined at 3-hourly intervals in obese hyperglycaemic mice (C57BL/6J ob/ob) and lean mice (C57BL/6J+/+). In lean mice, food consumption and plasma insulin concentrations increased during the light period and were reduced during the dark period, whereas plasma glucose concentrations were maximal at the beginning of the light period and declined to a minimum during the early dark period. In ob/ob mice, the plasma glucose concentration declined temporarily at the beginning of both the light and the dark period and became elevated towards the ends of these periods, but there were no significant diurnal variations of food consumption or plasma insulin concentrations. These observations indicate differences in the diurnal regulation of glucose homeostasis in lean and ob/ob mice.     

Seasonal variations in plasma glucose and insulin concentrations after glucose loading in the edible dormouse (Glis glis L.).

Glucose tolerance tests made in the Edible dormouse showed annual variations in B cell secretory capacity, associated with glucose tolerance changes. 1. During autumn and winter, the B cell is sensitive to glucose, and insulin regulates the high peripheral consumption of this hexose. 2. At the beginning of spring, insulin secretion decreases and glucose tolerance is impaired. In June, the B cell response si low or absent and a poor tolerance to glucose still persists. 3. The variations in B cell activity can be related to changing energy requirements during the year.     

Diurnal variations of plasma testosterone in men

Plasma testosterone (T) levels were assayed by a Competitive Protein Binding (CPB) technique in a group of 31 healthy males. In 22 subjects a single blood sample was taken between 8:00 and 9:00 A.M. and the mean T concentration was 6.84 ± 2.11 ng/ml. In the other 9 normal men, blood samples were taken every 4 hours. The existence of temporal variations for testosterone was confirmed by finding the highest mean plasma levels at 4:00 A.M. (9.28 ± 1.17 ng/ml) and lowest mean levels at 8:00 P.M. (2.66 ± 0.52 ng/ml).     

A mathematical model of postradiation autoimmunity

A mathematical model of cellular autoimmune process in exposed mammals was developed. In terms of this model a study was made of the dependence of the autoimmunity kinetics on radiation dose and radiosensitivity of autologous tissues. The model simulates the experimentally observed dynamics of autoimmune diseases.     

Skeletal muscle plasma membrane glucose transport and glucose transporters after exercise

Recent reports have shown that immediately after an acute bout of exercise the glucose transport system of rat skeletal muscle plasma membranes is characterized by an increase in both glucose transporter number and intrinsic activity. To determine the duration of the exercise response we examined the time course of these changes after completion of a single bout of exercise. Male rats were exercised on a treadmill for 1 h (20 m/min, 10% grade) or allowed to remain sedentary. Rats were killed either immediately or 0.5 or 2 h after exercise, and red gastrocnemius muscle was used for the preparation of plasma membranes. Plasma membrane glucose transporter number was elevated 1.8- and 1.6-fold immediately and 30 min after exercise, although facilitated D-glucose transport in plasma membrane vesicles was elevated 4- and 1.8-fold immediately and 30 min after exercise, respectively. By 2 h after exercise both glucose transporter number and transport activity had returned to nonexercised control values. Additional experiments measuring glucose uptake in perfused hindquarter muscle produced similar results. We conclude that the reversal of the increase in glucose uptake by hindquarter skeletal muscle after exercise is correlated with a reversal of the increase in the glucose transporter number and activity in the plasma membrane. The time course of the transport-to-transporter ratio suggests that the intrinsic activity response reverses more rapidly than that involving transporter number.     

Enhancement of radiation sensitivity by postradiation hypoxia

We demonstrate that postradiation hypoxia during colony formation in vitro enhances radiation sensitivity when cells are irradiated in severely hypoxic states. The presence and magnitude of this phenomenon, if it occurs in vivo, raise questions about the importance of the oxygen effect in the radiation response of tumor cells in vivo and suggest that hypoxia may not be an important factor in the probability of tumor control following radiation therapy.     

Immunogenic peptide neogen stimulates postradiation recovery thrombopoiesis

In experiments on mice F1 total exposed to gamma-irradiation at the 5.0 Gy, showed that a intraperitoneal injection neogen at the dose 10 micrograms/kg oue time at the day and night during the 8 days after irradiation results in recovery of the number blood platelets and time issue of blood from standard wound to normal level on the week by compare with irradiated control animals.     

Physiological and pharmacological variations in rabbit prolactin plasma levels

By using a specific homologous double-antibody RIA, physiological and pharmacological variation in prolactin plasma levels were studied in the rabbit. The study of plasma levels during 24 h period demonstrated the presence of a rhythmic secretion of prolactin with higher values between 15.00 and 19.00 h. Prolactin plasma levels were low in neonatal rabbits and increased gradually with the age of the animals. In adult rabbits a significant higher prolactin plasma concentration was found in female animals. Blood levels fluctuate during the first half of pregnancy but the mean levels were higher than those found during the second half of gestation. A remarkable increase of plasma levels was observed 24 h before parturition and during lactation. Plasma prolactin concentrations increased after injection of both chlorpromazine and sulpiride. The hyperprolactinaemic effect of sulpiride was abolished by bromocriptine.     

Pregnancy alters diurnal variation of plasma glucose concentration

Human pregnancy introduces a diurnal variation of fasting plasma glucose concentrations, with significantly lower values found after a daytime fast of eight hours compared with a night-time fast of the same duration. The diurnal variation of plasma glucose clearance, found in nonpregnant subjects, is not demonstrable during pregnancy. Insulin tolerance does not exhibit a circadian valuation but is substantially decreased during pregnancy.