Biological variations of hematologic and biochemical parameters in cows during early lactation.

The aim of the study was to determine biologic variations of the main parameters in cows in early lactation and to compare intra-individual variations of parameters in cows and other species. 50 cows were included in the experiment. Blood samples were taken at the moment of calving, then on 1st, 7th, 14th and 28th day after calving. CVi had the following values: 1.9-5% for MCV, MCH, MCHC, GLU, TProt, ALB, UREA, Ca, P and Mg; 5.1-10% for RBC, Hgb, Hct, WBC, NEU, LYM, BHB, ALT, CHOL, TGC and >10% for PLT, NEFA, TBil, AST and GGT. For RBC, Hgb, Hct, MCV, MCH subject-based reference values or the reference change value should be used. For all other parameters except AST, population-based reference intervals should be used with caution. For LYM, NEU, PLT, GLU, TProt, ALB, CHOL and TGC index of individuality was close to 0.6 which means that subject-based reference values can be much more adequate to use then population-based reference intervals. For AST population-based intervals should be used. There is little effect of parity (increase CVi with parity) and no effect of milk production. CVi values obtained in cows in early lactation are specific because they deviate from the CVi values of other animal species and human. Calculated RCVs varied from 5.5% for MCHC to 41% for AST. High individuality index for many metabolic parameters opens possibility for development of model for longitudinal monitoring of metabolic status of individual animals during lactation. That requires further research.

Distinct vasopressin content in the hypothalamic supraoptic and paraventricular nucleus of rats exposed to low and high ambient temperature.

Both high and low ambient temperature represent thermal stressors that, among other physiological responses, induce activation of the hypothalamic-pituitary-adrenal (HPA) axis and secretion of arginine-vasopressin (AVP). The exposure to heat also leads to disturbance of osmotic homeostasis. Since AVP, in addition to its well-known peripheral effects, has long been recognized as a hormone involved in the modulation of HPA axis activity, the aim of the present study was to elucidate the hypothalamic AVP amount in the acutely heat/cold exposed rats. Rats were exposed to high (+38°C) or low (+4°C) ambient temperature for 60min. Western blot was employed for determining hypothalamic AVP levels, and the difference in its content between supraoptic (SON) and paraventricular nucleus (PVN) was detected using immunohistochemical analysis. The results showed that exposure to both high and low ambient temperature increased hypothalamic AVP levels, although the increment was higher under heat conditions. On the other hand, patterns of AVP level changes in PVN and SON were stressor-specific, given that exposure to cold increased the AVP level in both nuclei, while heat exposure affected the PVN AVP content alone. In conclusion, our results revealed that cold and heat stress influence hypothalamic AVP amount with different intensity. Moreover, different pattern of AVP amount changes in the PVN and SON indicates a role of this hormone not only in response to heat as an osmotic/physical threat, but to the non-osmotic stressors as well.

Distinct and combined effects of acute immobilization and chronic isolation stress on MAO activity and antioxidative protection in the heart of normotensive and spontaneously hypertensive rats.

The heart is an organ especially sensitive to the sympathetic overstimulation and therefore to the influence of stressors and hypertension. The aim of the present study was to investigate the effect of two distinct types of stressors, acute immobilization (2 h) and chronic isolation stress (21 days), as well as their combined effect on the activity of monoamine oxidase (MAO), superoxide dismutase, catalase (CAT) and the ascorbic acid (AA) content in the heart of normotensive and spontaneously hypertensive rats (SHR). The results obtained show that in basal conditions heart MAO and CAT activity (p < 0.05), as well as AA concentration (p < 0.01) were higher in SHR than in normotensive ones. The acute immobilization significantly decreased heart MAO activity in both examined strains (p < 0.01). On the other hand, chronic isolation, separately or in combination with immobilization, did not affect this enzyme, in the heart of either hypertensive or normotensive rats, which was associated with the reduced antioxidative protection (p < 0.01, p < 0.05).

Time-dependent effects of starvation on serum, pituitary and hypothalamic leptin levels in rats.

Leptin is produced by white adipose tissue and other cell types and is involved in both short- and long-term appetite control. Here we studied effects of starvation on serum, pituitary and hypothalamic levels of leptin during 72 h period. Each of the starved groups was sacrificed simultaneously with the group of ad libitum fed animals. The progression of the discrete starvation response phases was monitored by testing the blood glucose, free fatty acid, urea and corticosterone levels. Starvation caused biphasic increase in corticosterone and free fatty acid levels, and significant but transient decrease in urea and glucose levels. Starvation also abolished diurnal rhythm of changes in leptin concentrations in serum and hypothalamic and pituitary tissues. Only 6 h starving period was sufficient to lock serum leptin at low levels, whereas 12 h were needed to silence leptin production/secretion in hypothalamus for the whole examined period. In contrast, leptin production by pituitary tissues of starved animals required 24 h to reach minimum, followed by full recovery by the end of starvation period. These results indicate the tissue specific pattern of leptin release and suggest that the locally produced leptin could activate its receptor in pituitary cells independently of serum levels of this hormone.