Relationships between calf birth weight, prepartum concentrations of plasma energy metabolites and resumption of ovulation postpartum in Limousine suckled beef cows.

The aim of this study was to determine the relationship between energy status before calving and calf birth weight and their potential effects on interval between calving and first ovulation. Sixty-nine Limousine, suckled beef cows were sampled weekly over a 3-yr period during the last 2 m.o. of pregnancy to determine the concentrations of nonesterified fatty acids (NEFA), beta-3-hydroxybutyrate (beta-OHB), glucose and glycerol. After parturition, progesterone concentrations were measured weekly to determine time of resumption of ovulation. Cows were allotted to 3 groups according to calf birth weight (Heavy: > 44 kg, n = 37; Medium: 39 to 43 kg, n = 56; and Light: < 38 kg, n = 45) and to postpartum ovarian resumption of cyclicity (Late: > 11 wk, n = 41; Mid: 7 to 10 wk, n = 57; and Early: < 6 wk, n = 40). Puerperium glycaemia of the dams was steady state (0.66 +/- 0.03 g/L) and was not related to calf birth weight. Plasma NEFA, beta-OHB and glycerol values were higher (P < 0.05) in Heavy than in Medium and Light group dams during the last 4 wk of pregnancy. Interval between calving and first ovulation was significantly longer for primiparous than for multiparous cows (respectively, 9.9 +/- 2.0 and 7.7 +/- 1.4 wk; P < 0.05). Calf birth weight was not related to time of first ovulation. Late primiparous cows had higher NEFA plasma concentrations than Mid and Early group primiparous cows during the last 4 wk of pregnancy, whereas NEFA plasma concentrations were not related to interval between calving and first ovulation in multiparous cows. Thus, lipomobilization increased with calf birth weight during the last 4 wk of pregnancy. High level of body reserves mobilization was associated with delayed first ovulation in primiparous but not in multiparous cows.

Serum cholesterol and triglycerides in postpartum beef cows and their relationship to the resumption of ovulation.

The variations in lipid metabolism according to the physiological stage and their relationship to the resumption of postpartum ovarian cyclicity were assessed in Limousine beef cows fed a grass diet over 3 yr. Weekly blood samples were collected from 59 cows beginning 10 wk before to 20 wk after calving to evaluate serum cholesterol and triglyceride concentrations and electrophoretic lipoprotein fractions. After parturition, progesterone concentrations were also measured at weekly intervals to determine time of resumption of ovulation. Cows were categorized by resumption of postpartum ovarian cyclicity into 3 groups: early (4 to 6 wk post partum, n = 36); mid (7 to 10 wk post partum, n = 46) and late (after 11 wk post partum, n = 38). Higher serum triglyceride values (P<0.05) were observed during the last 10 wk of pregnancy (0.36+/-0.15 g/L) than during the first 20 wk of suckling (0.29+/-0.09 g/L). Cholesterol values decreased significantly (P<0.05) at the end of pregnancy, were minimal (1.01+/-0.03 g/L) at parturition, and increased again up to 9 wk post calving. Increased cholesterolemia and low serum triglyceride values after calving could be linked to the increased bovine alpha-lipoprotein fraction and decreased beta fraction. Serum triglyceride concentrations were not related to the resumption of postpartum ovarian cyclicity. Higher serum cholesterol values were observed from 2 wk before to 4 wk after calving in cows with early rather than mid and late resumption of ovarian cyclicity. Therefore, modifications in lipid metabolism during the puerperium seem to be related to resumption of cyclicity during the early postpartum period.

Circadian rhythms of food intake, plasma glucose and insulin levels in fed and fasted rabbits.

The rhythm of circadian variations of plasma insulin level was similar in 48 h fasted and in fed rabbits; however, the amplitude of variations was less important in fasted animals. Plasma glucose level did not change during circadian cycle. In conclusion, we showed in rabbit a circadian rhythm of insulin with two maxima: one diurnal and the other nocturnal.

Circadian variations and extraadrenal effect of ACTH on insulinemia in rabbit.

The present experiment was designed to study the action of ACTH1-24 on insulin secretion during the circadian cycle in normal rabbits and to provide evidence that ACTH1-24 has an extra-adrenal effect on this secretion. In normal rabbits intravenous administration of three doses of ACTH1-24 (1, 10, 100 micrograms/kg) at 10 a. m. increased plasma insulin levels. Hyperglycemia only occurred with doses of 10 and 100 micrograms/kg. A maximum insulin response was already obtained at 1 micrograms/kg. The same experiment performed at 12 p. m. also induced hyperinsulinemia which was only noted at 10 and 100 micrograms/kg; hyperglycemia was only observed after stimulation by the highest dose (100 micrograms/kg). ACTH was therefore more effective during the day; however, at 12 p. m. plasma insulin levels were the highest, but only with the maximum dose of ACTH (100 micrograms/kg). The effect of ACTH1-24 was evaluated throughout the day on normal and adrenalectomized rabbits. In normal animals injection of ACTH1-24 increased plasma glucose and insulin levels both together. In the contrary, in rabbits deprived of adrenal glands, ACTH1-24 induced high insulinemia along with hypoglycemia. We could, therefore, reasonably conclude that ACTH stimulates directly the pancreatic secretion of insulin.

[Seasonal cycles of adipocyte lipogenesis and blood insulin in the young rabbit]. / Cycles saisonniers de la lipogenèse de l'adipocyte et de l'insulinémie chez le jeune lapin.

The young domestic rabbit (2.5 months old) shows seasonal variation in metabolism similar to wild mammal. During the annual seasonal cycle we observed variations in the intensity of lipogenesis in isolated perirenal adipocytes; fatty acid synthesis, which uses acetate as a precursor rather than glucose, reaches a maximum in winter and a minimum in spring. The magnitude of the glucose induced pancreatic insulin response varies during the annual seasonal cycle and it follows the variations in the lipogenesis cycle; thus, the plasma IRI increase is highest in winter when maximum lipogenesis occurs.

[Radioimmunologic determination of ACTH in the rabbit: stress-ACTH-corticosteroid relationship and diarrhea]. / Dosage radioimmunologique de l'ACTH chez le lapin: relations stress ACTH-corticostéroïdes et diarrhées.

Plasma ACTH was measured in young and adult rabbits with a CEA-SORIN kit. The reliability of the analysis was controlled by liquid chromatography, several biochemical tests such as parallelism and reproducibility and several physiological tests such as plasma ACTH response to ethylic ether stress, to adrenalectomy, to dexamethasone and metopyrone. In young diarrhoeic rabbit plasma, ACTH (293 +/- 45 pg/ml) and corticosteroid (111 +/- 13 ng/ml) levels were significantly much higher than in young healthy rabbits (ACTH: 130 +/- 35 pg/ml; corticosteroids: 66 +/- 7 ng/ml). Furthermore, transporting young rabbits by car caused such violent stress that plasma ACTH levels increased from 52 +/- 11 to 130 +/- 35 pg/ml. A causal relationship between stress - ACTH and diarrhoea is discussed.

Glycoprotein-protein associated effects on the permeability of a model membrane.

1. The osmotic effects on phospholipid vesicles in the presence and absence of bound glycoprotein and protein were used to determine the permeability to some ions and neutral molecules. 2. The permeation times were registered as a function of membrane surface charge and glycoprotein protein molar ratio in the vesicles. 3. The permeation times for ions varied considerably with the change of glycoprotein protein molar ratio. 4. When neutral molecules passed through the membrane, the permeation times did not change varying glycoprotein-protein molar ratio. 5. In all cases the permeation times did not depend on the surface charge. 6. Our results suggest that topographical distribution of hydrophobic and hydrophilic regions of glycoprotein molecule would play a substantial role and influence the permeability in this case.

[Influence of age, season and hypophysectomy on lipogenesis of adipocyte from rabbit. Insulin effects]. / Influences de l'âge, de la saison et de l'hypophysectomie sur la lipogenèse de l'adipocyte chez le lapin; effects de l'insuline.

We studied lipogenesis, either from glucose or from acetate, spontaneous or stimulated by insulin, at the level of the isolated adipocyte of the rabbit's perirenal adipose tissue related to growth, season and hormonal troubles induced by hypophysectomy. 1. For the adipocyte, acetate instead of glucose is the major precursor for fatty acid synthesis. 2. Adipocyte lipogenesis of the immature rabbit of two months is higher than that which is observed in the mature rabbit of six months. 3. Adipocyte lipogenesis is strikingly more important in autumn than in spring, both in the young rabbit and the mature one. 4. After hypophysectomy, fatty acid synthesis from acetate is greatly increased at the level of the adipocyte and, in this case, insulin stimulates efficiently lipogenesis from acetate as well as from glucose.

[Season variations in lipolysis activity of adipocytes from fox, badger and hedgehog]. / Variations saisonnières de la lipolyse des adipocytes de Renard, de Blaireau et de Hérisson. Relation avec les cycles annuels des activités testiculaire et thyroïdienne.

1. We have studied the seasonal variations of the lipolytic response to a beta agonist, isoproterenol, and to theophylline of the isolated adipocyte from fox, badger and hedgehog, related to the circannual variations of testes and thyroid activities. 2. With the fox, we find a coincidence, in spring, between the maximum lipolytic sensitivity of the adipocyte, the thyroid function and the return to sexual rest. 3. With the badger, in winter, the maximum reaction of the adipocyte is contemporary with testes activity and with thyroid rest. 4. With the hedgehog, we observe two maximums in the sensitivity of the adipocyte to the lipolytic agents, one in spring, which coincides with the maximal testes and thyroid activities, the other in autumn, before the deep hibernation state. 5. In conclusion, there is, with these wild mammals, a seasonal variation in the lipolytic reaction of adipocyte which coincides with that of energy needs.

[Measurement of the reactivity of various types of white adipose tissue of rabbits to synacthene and isoproterenol]. / Mesure de la réactivité de différents tissus adipeux blancs du lapin au synacthène et à l'isoprotérénol.

The quantitative evaluation of lipolysis from different adipose deposits in the young rabbit shows that if the response to synacthen is equal to 1 (peristomachal tissue) that of the perirenal and periepididymal tissues would be 0.80 and that of the subcutaneous tissue would be 0.50. Comparatively isoproterenol (beta-adrenergic agonist) induces a lipolytic response which is equal to 0.19 for peristomachal and perirenal adipose tissues, 0.12 for the periepididymal tissue, and 0 for the subcutaneous tissue. Lipolytic efficiency is 600 times more important for synacthen than for isoproterenol whatever the anatomical origin of the adipose tissues is. Subcutaneous tissue, as a permanent mass, would have a thermic protection, while the other tissues, as transient reserves, are involved in the energetic disponibilities.

[The effects of adrenalectomy and of hydrocortisone administration on adenylate cyclase activity in rabbit adipose cells (author's transl)]. / Effets de la surrénalectomie et de l'administration d'hydrocortisone sur l'activité de l'adénylate cyclase de cellules adipeuses du lapin

Adenylate cyclase activity in rabbit adipocyte plasma membranes was studied with special reference to the effects of adrenalectomy and administration of cortisol in vivo. Adrenalectomy was accompanied by an increase in adenylate cyclase activity during basal conditions; cortisol (5 mg/kg body wt., intramuscularly) partly prevents this effect of adrenalectomy. The response of adenylate cyclase to corticotropin, epinephrine and norepinephrine stimulation was higher in the adrenalectomized rabbit than in the sham operated animal. Our in vitro results were in agreement with the striking fat mobilization observed in rabbit plasma after adrenalectomy and with the hypolipemic effects of cortisol we had previously observed in both normal and adrenalectomized rabbit.

[Fat and glucose mobilization in the hypophysectomized rabbit (author's transl)]. / Effets de l'hypophysectomie sur la circulation des lipides et des glucides chez le lapin

1. The metabolic behaviour of the fed hypophysectomized rabbit is quite different from that of the fed normal rabbit, i.e. in the hypophysectomized rabbit we found lasting hypoglycemia and a persistent high lipid plasma level. 2. Fasting induced a large and fast decrease in plasma glucose level which led to a coma; simultaneously it appeared that the hypophysectomized rabbit could not mobilize its adipose stores and that it quickly used up its plasma lipids, among them the essential fatty acids. In contrast, fasting in the normal rabbit induced a large fat mobilization from fat stores and the saturated fatty acids were essentially used, but at the same time plasma glucose remained near the level of control value. 3. Our in vitro results showed the important effect of synacthen in the lipolytic process of isolated fat cells.

[Hormonal control of the adenyl cyclase activity of adipose cell membranes prepared from badger, rabbit, fox and rat adipose tissues]. / Contrôle hormonal de l'activité adénylate cyclase de membranes de cellules adipeuses préparées à partir du tissus adipeux de blaireau, lapin, renard et rat

1. We have shown differences in hormonal regulation of adenylate cyclase activity in fat cell ghosts prepared from rat, rabbit, fox and badger adipose tissue, under the influence of catecholamines, ACTH and insulin. a) In the rat, catecholamines induced a large stimulation (+315%) of adenylate cyclase. b) In the rabbit, ACTH was the most effective hormone. c) In the fox and the badger, only catecholamines could stimulate adenylate cyclase. d) In both rat and rabbit, insulin did not reduce spontaneous enzymatic activity. Moreover, the activation of adenylate cyclase by ACTH in the rabbit was not altered by insulin, while in the rat, this hormone slightly decreased epinephrine stimulation. 2. Hormonal regulation of adenylate cyclase correlated with the lipolytic response.