Search

The purpose of these studies was to investigate the pattern and timing of preovulatory endocrine events, estrus and ovulation in Brahman X Hereford (F1) heifers synchronized with norgestomet and estradiol valerate. In Exp. 1, 66 nulliparous and 191 primiparous Brahman X Hereford (F1) heifers were used to estimate the interval from norgestomet implant removal to onset of estrus. The mean interval from implant removal to onset of estrus was 29.8 +/- .5 h, with 80.9% exhibiting estrus within 48 h. Endocrine and reproductive characteristics were examined in detail during Exp. 2 with 37 primiparous heifers. Continuous observation for estrus, 6-h or 2-h blood sampling and ovarian palpation per rectum were employed. All animals were artificially inseminated 48 h after implant removal. Mean interval from implant removal to onset of estrus and to onset of the luteinizing hormone (LH) surge were closely related (r = .91; P less than .0001). Mean intervals from implant removal to ovulation, onset of estrus to ovulation and onset of LH surge to ovulation were 59.1 +/- 2.5 h, 23.3 +/- 1.4 h and 23.1 +/- 1.6 h, respectively. Approximately 73% of heifers exhibited estrus within 54 h after implant removal (optimal timing); conception rate was 59.3% in this subgroup. Conception rate of heifers that did not exhibit estrus within 54 h after implant removal or exhibited an LH surge later than 12 h after estrus (delayed timing) was 10%. Assessment of plasma estradiol-17 beta concentrations suggested that retarded selection and(or) maturation of the preovulatory follicle following implant removal delayed estrus and lowered conception in up to 28% of females timed-inseminated at 48 h.

Feeding of C57BL mice with dried thyroid glands (added to their food) for 10 days activates 59Fe incorporation into splenic heme and decreases peripheral granulocyte levels. The importance of the differentiation of haemopoietic stem cells under these conditions was investigated by using the repopulation assays. Transplantation of bone marrow cells into recipients irradiated on day 10 of treatment with thyroid hormones, i.e., in the phase of activation of erythropoiesis, results in an increase in erythropoiesis and a decrease in granulopoiesis. However, following irradiation and transplantation of animals during the phase of rebound, i.e., approximately 5-8 days after cessation of thyroid hormone treatment, erythropoiesis is depressed and granulopoiesis is activated, the values exceeding markedly the control levels. The practical importance of changes in the host inductive milieu favouring granulopoiesis is documented by the results showing that hormonal marrow has an increased capacity to prolong the survival of animals lethally irradiated in the phase of rebound after pretreatment with thyroid hormones.

The relative humaneness of asphyxia and decapitation was objectively evaluated in rats by EEG monitoring. EEG activation (low voltage, fast activity) was considered to indicate discomfort, pain, and affective responses to euthansia. Such activation was present 37.3 plus or minus 7.5 sec after asphyxia and 13.6 plus or minus 4,6 sec after decapitation. Decapitation was also characterized by an immediate large, and relatively long-lasting, ultra-slow voltage, detected by non-polarizable scalp electrodes. Isoelectric activity (death) occurred 69.4 plus or minus 9.9 sec after onset of asphyxia and 27.2 plus or minus 4.4 sec after decapitation.

Peroral application of Isoprinosine for 3, 5 and 10 days increases the number and proliferative activity of haemopoietic stem cells (CFUs) in the bone marrow of mice. Changes in the spleen occur later and are manifested by an increase in CFUs proliferative activity and by a transient decrease in CFUs number.

Total protein (TP), glucose (GL), esterified fatty acids (EFA) and total cholesterol (TC) were determined at 4-hour intervals during the 24-hour cycle in the serum of 270 female Wistar rats, in February, May and July. The results can be summed up under the following points: 1) The differences found between the levels of the given parameters in February, May and July were statistically highly significant. The greatest differences were observed in the TC level, which was lowest in July (0.82 mmol/l) and highest in February (1.87 mmol/l). The highest TP and GL values were found in May (62.5 g/l; 10.69 mmol/l) and the lowest in February (40.1 g/l; 7.8 mmol/l). The smallest differences were observed in the EFA level, which was highest in July (8.09 mEq/l) and lowest in February (6.39 mEq/l). The minimum 24-hour variations in the levels of most of the given parameters during the 24-hour cycle were observed in May (compared with February and July). 2) In a study of TP and GL concentration, the time of day was found to be a very important factor. The maximum TP level during the 24-hour cycle was found most often in the early morning or forenoon, while the blood glucose level was highest at about midday and in some cases in the early morning. The blood cholesterol level was relatively stable during the 24-hour cycle and it is impossible to draw definite conclusions from its fluctuations. Changes in the EFA level during the 24-hour cycle were likewise irregular. 3) Except for cholesterol, interindividual differences in the levels of the given parameters in the various months seem to be statistically non-significant.

Oral administration of dried thyroid gland to C57Bl adult male mice in a dose of 0.6 g per 100 g diet during 10 days increased the metabolic rate and stimulated the erythropoiesis. Three to six days after thyroid pretreatment the radiation resistance of the mice increased, as revealed by their 30-day survival and a higher recovery of peripheral blood cell counts. The period of increased resistance to radiation was correlated with the receding of hypermetabolic effects and with the increase of repopulating abilities of the bone marrow cells.

Male mice of a non-inbred strain "H" were used to verify the effect of a 10-day peroral administration of K and Mg aspartates on haemopoietic functions. The salts were proved to stimulate the proliferation and differentiation processes in the thymus, bone marrow and spleen tissues. Mice exposed to a single whole-body X-irradiation after pretreatment with K, Mg aspartate exhibited a more conspicuous postirradiation regeneration of haemopoietic organs and an increased postirradiation survival. The results suggest the possibility of using K, Mg aspartate for radioprotective purposes.

The basolateral amygdala of rats was stimulated once daily until three successive fully kindled seizures were elicited. Twenty-four hours after the last seizure the rats were sacrificed by focused microwave irradiation to the head. Tissues from homolateral and contralateral amygdala and cerebral cortex were assayed for cAMP and cGMP content. No significant changes in cyclic nucleotides were measured in the kindled animals. These studies indicate that long term changes in the steady-state level of total tissue cyclic nucleotides do not occur concomitant with the persistently altered excitability associated with kindling of the amygdala.

The possibility of radioprotective action of K and Mg aspartate administered in tap water for ten days prior to X-irradiation was investigated in male mice of the strain C 57 Bl/10. In normal animals, thymus weight was found to be increased by 10-day treatment with K and Mg aspartate. The postirradiation regeneration of spleen weight and incorporation of radioactive iron into the spleen and femoral marrow following sublethal irradiation was favorably modified by the treatment used. Pretreatment of mice with K and Mg aspartate delays the onset of early deaths at irradiation with an absolutely lethal X-ray exposure and raises the percentage of surviving animals after nearly lethal exposures.