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Resume L'aptitude a l'effort des patients transplantes cardiaques (HTR) a distance de la greffe reste insuffisante. Les facteurs limitants peripheriques musculaires semblent jouer un role preponderant: la lactatemie arterielle, le debit ventilatoire et le rejet de CO2 augmentent plus rapidement chez les HTR que chez les normaux, alors que les pentes de VO2, du debit cardiaque et de la difference arterioveineuse en O2 sont comparables a celles des sujets normaux. Nous avons soumis sept patients HTR et trois sujets temoins (C) a un entrainement court en endurance de 6 semaines selon un protocole en creneaux de 45 minutes (SWEET de Gimenez, 1982 ). L'intensite des bases (B) etait fixee au niveau du seuil ventilatoire, celle des pics (P) a celui de la puissance maxima toleree, prealablement determinee lors d'un effort maximal par increments. Ces niveaux de puissance ont pu etre progressivement augmentes au cours de 6 semaines d'entrainement, avec un gain final d'environ 40% en travail mecanique total. Au terme de cet entrainement une diminution significative des grandeurs mesurees a la fin de chaque 4e minute des B a ete observee dans les deux groupes pour: la frequence cardiaque, le debit ventilatoire, le rejet de CO2, la lactatemie et l'ammoniemie arterielles, les concentrations en catecholamines. Ces resultats confirment le caractere predominant peripherique de la limitation a l'effort des transplantes cardiaques et l'amelioration objective des parametres ventilatoires et metaboliques par ce type d'entrainement en endurance.

Longitudinal (T1) and transverse (T2) nuclear magnetic resonance relaxation times were measured in vitro at 37, 30, 25, 15, and 5 degrees C on serum, brain, liver, kidney, and heart samples from a hibernator, the European hamster, active in summer (SA), active in winter, or in the hibernating state in winter; from a less efficient hibernator, the golden hamster; and from a homeotherm, the rat. T1 and T2 relaxation times varied between species and in the European hamster between the active and hibernating subjects. Despite the major relaxation time differences between the organs, NMR relaxation time measurements showed a general trend to an increase in the viscosity of water for the European hamster in the active state. Although these modifications were not directly related to the process of hibernation itself, the relaxation times observed in the hibernating animals were closer to those seen in the rat. This evidenced that changes of physical properties of water reflect a better adaptation to low temperatures of the hamster, as compared to the nonhibernator, given that the low water viscosity of SA hamster allows the decrease of the viscosity with temperature during the hibernating state. These in vitro studies permit the study the viscosity which is an important physicochemical parameter involved in NMR longitudinal relaxation time of water proton. More detailed studies of other physiological parameters must be undertaken by further in vivo measurements.

The breakdown of blood pressure and body fluid homeostasis observed in heart transplant (Htx) recipients may partly be due, as in heart failure, to a blunted renal response to elevated atrial natriuretic peptide (ANP).This possibility was addressed through determination of the relationship between ANP, the urinary cyclic guanosine monophosphate (cGMP), a biologic marker of ANP renal activity, and the early renal responses to 10 mL/kg isotonic saline infusion over 30 minutes in 8 control subjects and 8 matched Htx recipients.Urine flow, natriuresis, and urinary cGMP excretion increased similarly in both groups, resulting in elimination of, respectively, 1/2 and 2/3 of the sodium and the water load during the experiment that lasted 4 hours and 30 minutes. Plasma renin and aldosterone decreases were similar in both groups. Elevated ANP further increased in Htx after saline infusion (from 19.5 +/- 3.7 to 33.8 +/- 5.6 pmol/L, P.001). Plasma cGMP paralleled ANP in both groups (r = 0.81; P.001). Significant correlations were observed between plasma ANP and urinary cGMP excretion (r = 0.48, P.025 and r = 0.43, P.05 in Htx recipients and control subjects) and between plasma ANP and urinary sodium excretion (r = 0.64, P.001 in Htx recipients).In spite of a relative renal hyporesponsiveness to the cardiac hormone, with higher plasma ANP being not associated with increased renal excretions in Htx recipients, ANP is likely to participate in the appropriate short-term renal response to acute volume expansion in Htx recipients.

Hemodynamic improvement after heart transplantation is expected to normalize the neuroendocrine balance, but circulating atrial natriuretic peptide (ANP) remains elevated. Endothelin stimulates ANP secretion and its concentration increases after heart transplantation, suggesting a role for this peptide in the cardiovascular adaptative response to heart transplantation.To investigate whether endothelin may induce ANP increase in heart transplant recipients, we monitored daily ANP, endothelin, and related hormonal, biologic, and hemodynamic parameters before and during the first week after either heart transplantation (n = 15) or coronary artery bypass grafting (n = 10).Surgery induced a transient secretory peak of arginine vasopressin and endothelin in both groups at day 1. Bypass grafting did not modify normal ANP (11.8 +/- 2.1 pmol/L), endothelin (2.4 +/- 0.3 pmol/L), renin activity (0.11 +/- 0.04 pmol/L/sec), or aldosterone (492 +/- 122 pmol/L) values. Heart transplantation normalized the renin-aldosterone axis, but the early decrease observed for ANP (from 27.2 +/- 4.8 to 21.14 +/- 1.4 pmol/L) was only partial and transient. Endothelin further increased (from 4.4 +/- 0.8 to 9.14 +/- 1.8 pmol/L; p0.01) after transplantation. Positive correlations were observed between endothelin, isoproterenol dose, creatinine, right atrial pressure, and ANP, but multiple correlation analysis showed the important role of endothelin (r = 0.69, p0.001). Cyclic guanosine monophosphate correlated with ANP (r = 0.65, p0.001).Elevated endothelin, suggesting vascular dysfunction, likely contributes to the ANP increase observed early after heart transplantation. Furthermore, ANP, through a cardiac endothelium feedback, may act in the maintenance of circulatory homeostasis in heart transplant recipients.

To investigate whether cardiac innervation modulates atrial natriuretic peptide (ANP) secretion, we performed acute volume expansion on eight normal and eight matched (age, weight, and total blood volume) transplanted denervated heart patients (Htx), while monitoring fluid-regulating hormone, systemic blood pressure, and echocardiographic atrial area changes. At rest, plasma ANP and guanosine 3',5'-cyclic monophosphate (cGMP) were lower in control subjects than in Htx (45 +/- 16 vs. 103 +/- 35 pg/l and 0.9 +/- 0.3 vs. 3.5 +/- 1.4 pM, respectively; P < 0.001). Plasma active renin, aldosterone, and catecholamines did not differ significantly in the two populations, whereas arginine vasopressin and cortisol were higher in controls (P < 0.01 and P < 0.005). Although volume expansion (+15%) and atrial stretch were similar in the two groups, plasma ANP and cGMP increased significantly only in the Htx group (103 +/- 35 to 189 +/- 69 pg/l and 3.5 +/- 1.4 to 5.8 +/- 1.4 pM, respectively; P < 0.001). The decrease observed for the other hormones was not significant except for arginine vasopressin and cortisol (P < 0.05 and P < 0.001) in the control group. These results support the hypothesis of an inhibitory role of cardiac innervation in biologically active ANP secretion in humans, at rest and after acute volume expansion.

Rats with an intracardiac chronic catheter were offered dietary self-selection between glucids, proteins and lipids intakes. They are infused continuously with 0.9% NaCl except on the test day with glucose, amino acids or lipids. Parenteral load is about 25% of the daily total food intake. With glucose infusion a selective decrease in glucids intake is observed of about 80% of the caloric glucose load. Aminoacidemic and lipidic infusions lead not only to decrease respectively in proteins and lipids intakes, but also in glucids intakes. So, in this case, total caloric intake decreased more than caloric load. Results are discussed in the hypothesis of existence of a hepatic chemosensibility.

Cycles of body weight lasting a few weeks occurred in dormice fed ad libitum, throughout the year with the same food. The pattern of the fluctuations suggests an oscillation between an upper and a lower limit. When the lower limit is reached, compensatory mechanisms acting on the food intake are induced which cause an increase in body weight to the upper one; when this upper limit is reached, other mechanisms cause the body weight to decrease to the lower one. Thus, body weight and variations in food intake may well be controlled by the difference between the body weight and the limit it will reach. In a warm environment (23-25 degrees C) these fluctuations are smaller than in the cold (5-6 degrees C). They are also smaller during summer than during winter in animals placed in natural climatic conditions. In summer, the body weight stays near the upper limit; in this season, as in the warm environment, the lower limit approaches the upper one. Thus, the main circannual variation of body weight regulation in dormice may be the elevation during summer of the lower body weight limit.

Fetal blood pH, pCO2, and lactic acid were measured before and after the final period of the second stage of labor in an attempt to better understand th validity fetal heart rate (FHR) monitoring at this time. Following a classification derived from Melchior, six FHR patterns were recognized: 0, 1, 2a, 2b, 3, and 4. In the second stage of labor, until bearing-down efforts began, the fetal acid-base status did not change regardless of the type of tracing. At the time of delivery, as compared with values measured before the beginning of the final stage, the highest shift of lactic acid, coupled with the lowest pH shift, was associated with the type 3 pattern. The most rapid increases of lactic acid and pCO2 and decreases in pH were associated with type 2b patterns. Both type 3 and 2b patterns were ominous, but low Apgar scores were more frequent in type 3 because the duration of the final stage of labor was longer. Working from the mean slopes of the shifts of biologic parameters as a function of time, theoretical limits were derived and discussed for safe duration of the final stage of labor.

The actual effects of glucose infusion on fetal acid-base status were studied during 125 normal deliveries in which plasma glucose and acid-base parameters were determined after maternal infusion of either 10% glucose or Ringer's solution. After 80 minutes, mean (+/- SD) plasma glucose levels were significantly higher in the glucose group (N = 59) than in the Ringer's group (N = 66), both for the mother (183.6 +/- 46.8 versus 95.3 +/- 18.0 mg/dL) and the fetus (108.4 +/- 41.4 versus 64.8 +/- 16.2 mg/dL). Fetal plasma lactate concentrations did not differ between the glucose and the Ringer's groups, but were significantly lower in the fetuses delivered by elective cesarean section in both groups. With glucose administration, fetal pCO2 was higher and pH values were lower than in the Ringer's group. However, the magnitude of acid-base status changes, indicated by both pH and pCO2 shifts (ie, the difference between umbilical artery and scalp values), failed to differ between the two groups. In fetuses with progressing hypoxia, no differences in any of the acid-base parameters were observed between glucose and Ringer's administration. These data indicate that at a glucose infusion rate of 30 g/hour, fetal acidosis, when it occurs, results from hypoxia rather than from maternal glucose administration.

During recovery from a five days' fasting, rats fed with separately presented glucids, proteins and lipids, show a 22 days' increase of the total caloric intake, and thus the fasting caloric lack is exactly compensated. On the contrary, rats fed with choice between proteins or glucids-lipids mixture (with various ratios) do not show such an increase, and thus do not compensate. The conclusion is, that the alimentary conditions are determinant in these kinds of experimentations.