Cryptosporidium parvum biliary tract infection in adult immunocompetent and immunosuppressed mice.

Biliary tract infection by Cryptosporidium parvum is a frequent complication of intestinal cryptosporidiosis in immunosuppressed patients. Although biliary tract infection can be produced in immunosuppressed models as a late complication of intestinal infection, there is no infection model in immunocompetent animals. A murine model of biliary tract cryptosporidiosis was developed by direct intra-gall bladder injection of C. parvum oocysts. In adult immunocompetent mice, intracellular parasitic stages were detected in the epithelium of the common bile duct in all animals on day 7 post-inoculation (p.i.). These findings were associated with a strong inflammatory reaction. Infection was cleared between days 14 and 21 p.i. All animals developed significant levels of specific serum and bile IgG, IgA and IgM. Dexamethasone treatment resulted in the inability of animals to eradicate the parasite and the establishment of ileal parasitism. This model can be used to study the immunological mechanisms involved in the control of biliary cryptosporidiosis.

[Study of myocardial metabolism of NADH by laser fluorimetry during cardiac catheterization]. / Exploration du métabolisme myocardique par fluorimétrie laser du NADH au cours du cathétérisme cardiaque.

Laser fluorimetry of reduced nicotinamide-adenine-dinucleotide (NADH) p6 a new technique used for in situ and real-time study of myocardial metabolism. We have evaluated its applicability to clinical situations in 5 patients undergoing haemodynamic exploration. An optic fibre was inserted in a catheter the end of which was positioned in the postero-diaphragmatic part of the left ventricle. The optic fibre was connected to a Cilas-Alcatel fluorimeter. Variations in fluorescence were studied during variations in left ventricular end-diastolic pressure (LVEDP) and during coronary arteriography. An increase in LVEDP resulted in a slight increase in NADH, but when the LVEDP was reduced by a nitroglycerin infusion, NADH fell significantly below baseline values in patients with coronary disease. This effect was most probably due to redistribution of the coronary blood flow from healthy territories to ischaemic territories. In patients without significant coronary stenosis, NADH was not modified by an injection of 10 ml of contrast medium into the right coronary artery. In contrast, in patients with severe stenosis NADH fluorescence significantly increased during the injection, reflecting the ischaemia or myocardial anoxia induced by the contrast medium. NADH laser fluorimetry therefore seems to be promising as a means of exploring myocardial metabolism during cardiac catheterization.

[In situ evaluation of tissue metabolism by laser fluorimetry]. / Evaluation in situ du métabolisme tissulaire par fluorimétrie laser.

Laser fluorimetry is a new technique which provides continuous information on tissue metabolism in situ and without destruction. For the moment, it is mainly applied to the study of changes in redox gradients in various organs, including the heart, brain, liver, kidney and skeletal muscle, in cases with imbalance between oxygen supply and oxygen consumption. Other metabolisms, such as that of the crystalline lens with incipient cataract, can also be investigated by this technique.

Attempts at in vitro cultivation of Pneumocystis carinii from human bronchoalveolar lavage fluids without feeder cells.

We attempted to cultivate Pneumocystis carinii obtained from two bronchoalveolar lavage fluids of AIDS patients with P. carinii pneumonia, in a system wherein cysteine and 2-mercaptoethanol were substituted for the feeder cells. The presence of P. carinii cysts was monitored for 11 days under conditions of continuous culture. Moderate increase in cyst forms was observed until day 11. Further study with this system would be required to determine if the observed increase in cyst numbers is reproducible and whether the cyst form is a response to adverse in vitro conditions or is a manifestation of growth.

Evaluation of curative anticryptosporidial activity of paromomycin in a dexamethasone-treated rat model.

A dexamethasone-treated rat model of cryptosporidiosis was used to evaluate the curative activity of paromomycin. Although eradication of the parasite could not be demonstrated, statistically significant decreases in oocyst excretion and in the intensity of ileal parasitism were observed in animals receiving 100 mg of paromomycin per kg of body weight per day.

[Gamma function extrapolation of dilution curves for pulmonary blood volume determination in chronic bronchitis (author's transl)]. / Extrapolation par la fonction gamma des courbes de dilution. Application au calcul du volume sanguin pulmonaire dans la bronchite chronique.

The risk of incorporating inapparent recirculation under the extrapolated downslope of dye dilution curves is greater with exponential than gamma function extrapolation since the latter makes use of ascending and early descending limbs of the curve. Extrapolation of a true gamma function is not affected by the level at which extrapolation begins. With curves obtained in eight normal subjects, cardiac output (phi) was comparable by exponential and gamma extrapolation if the latter began between 75 and 55% of the peak concentration (Cmax.). phi was underestimated or overestimated according to whether extrapolation began higher or lower than the above limits. Therefore, experimental curves were not true gamma functions. However, the level at which extrapolation began had little effect on pulmonary mean transit time and pulmonary blood volume (PBV) calculated by use of the double injection-single sampling method. Similar effects on phi of the level at which extrapolation by a gamma function begins were found with 24 chronic bronchitics. PBV calculated with a gamma function extrapolated from 0.75 X Cmax. downwards and with an exponential function averaged approximately 340 ml and did not differ from one another. The data suggest that the low values of PBV in chronic bronchitis are not an artifact due to the method of extrapolation.

Ventilatory adaptation to metabolic alkalosis in adult awake potassium restricted rats.

The resting ventilation of awake rats, developing metabolic alkalosis as a result of sustained dietary potassium (K) restriction, was compared to that of age-matched controls. Extending the measurements over 17 weeks and using adult rats indicated, as soon as the third week, a significant progressive fall in the minute ventilation of low K rats, which previous studies limited to a single time determination did not consistently ascertain. The ventilatory adaptation observed in all groups, as well as the superimposed respiratory compensation to metabolic alkalosis in low K rats, resulted only from frequency changes. In both groups, the duration of inspiration was inversely correlated with the age of the animals. The duration of expiration was stable in controls but increased significantly with time in low K rats. According to these data, the respiratory compensation to K-depletion alkalosis in the rat is achieved only through an adjustment in the timing component of the control of breathing.

Measurement of pulsatile flows and variable volumes by bolus injection of indicator in a model of the pulmonary circulation.

The reliability and accuracy of the bolus injection-dye dilution technique were assessed for a physiological range of frequencies (13-49 min-1) and stroke volumes (60-160 ml) on a glass model where flows and volumes varied as a preset function of time (n = 320). We found that the technique overestimates flow by about 8% with a 95% confidence interval of +/- 10% for one measurement. Mean transit times are accurate within a +/- 7% confidence interval for one measurement. In a time-dependent flow and volume system this technique measures the mean volume as related to time with fluctuations up to +/- 30% around the mean. Results are independent of time and site of injection. The double injection-single sampling technique gives results that are equivalent to those obtained by single injection and sampling of dye.

Ventilation in awake rats with permanent arterial catheters.

Respiratory frequency (f), tidal volume (VT) and minute ventilation (VE) were measured in restrained awake rats using a volumetric body plethysmograph excluding the head. An arterial catheter was then implanted and ventilatory measurements performed again two or three days later. Arterial blood gases and acid-base status were measured before entry in the plethysmograph (control values) and after, accompanying each ventilatory measurement. The pattern of ventilation (VT and VE) was significantly correlated with the respiratory status, particularly with PaCO2 (P less than 0.001). A ventilatory (VE, VT, f) and respiratory (PaO2, PaCO2, pH) steady state was obtained from the fifteenth minute to the end of the observation period. The present preparation is a stable experimental model providing respiratory and ventilatory data in the awake rat.

Evaluation of high-dose regimen of paromomycin against cryptosporidiosis in the dexamethasone-treated rat model.

In the dexamethasone-treated rat model of cryptosporidiosis, paromomycin was effective at a dosage of 50 mg/kg/day or more for ileal infection and 200 mg/kg/day or more for cecal infection. At 1 and 3 weeks after treatment, a persistent infection was demonstrated in all rats. These results confirm the anticryptosporidial activity of paromomycin and underscore the limitations of this compound because of its potential toxicity at such high dosages and its inability to eradicate the infection.

Pulmonary and systemic effects of increased negative inspiratory intrathoracic pressure in dogs.

Croup and epiglottitis, which cause greater than normal negative inspiratory intrathoracic pressure (NIIP), have been associated with pulmonary edema. To examine the effects of increased NIIP per se on blood gases, hemodynamics, and lung water content, we carried out 2 types of experiments in 18 anesthetized dogs. Short-term, low-pressure experiments (6 control dogs and 6 dogs that generated intratracheal pressures of -12 cm H2O during inspiration for 3 h) and long-term, high-pressure experiments (6 dogs that generated -20 cm H2O during inspiration for 6 h). In the short-term, low-pressure experiments, animals made to generate negative inspiratory pressure differed from control dogs by demonstrating decreased pleural pressure (p less than 0.01), increased arterial PCO2 (p less than 0.05), and decreased minute volume (p less than 0.05); no differences occurred in hemodynamic data (pulmonary arterial, left atrial, and aortic pressures and cardiac index) and in extravascular lung water (indicator dilution and gravimetric analyses). Similarly, in the long-term, high-pressure dogs, arterial PCO2 increased (p less than 0.05) and lung water was normal by gravimetric analysis. We conclude that both 3 and 6 h of increased NIIP cause CO2 retention but have minimal effects on hemodynamics and lung fluid exchange.

Splanchnic blood flow, O2 consumption, removal of lactate, and output of glucose in highlanders.

An impairment of gluconeogenesis has been proposed to explain the low arterial blood glucose of highlanders. Therefore, we studied splanchnic blood flow, splanchnic uptake of oxygen and lactate, and output of glucose in nine normal and six anemic highlanders at an altitude of 3,750 m. Splanchnic blood flow, arteriovenous difference for oxygen, and oxygen consumption were comparable at rest in both groups and in lowlanders from the literature, whereas splanchnic output of glucose, and uptake of lactate were approximately twice those in lowlanders. After 10 min of mild exercise in 12 subjects (7 normals, 5 anemic), no significant changes in splanchnic hemodynamics and metabolism were found. During 29% oxygen breathing in 8 subjects (5 normals, 3 anemics), arterial lactate, splanchnic uptake of lactate and output of glucose fell to normal sea-level values. We concluded that splanchnic hemodynamics are similar in adapted highlanders and in lowlanders, and that there is no evidence of an impaired gluconeogenesis at the altitude of the present study.

Effects of rebreathing conditions and body size on normal human lung tissue volume.

To evaluate the consequences of breathing pattern variations inherent to lung disease on the rebreathing measurement of lung tissue volume (Vt), we carried out a study of ten normal human subjects in whom we assessed the effects of changes in rebreathing volume (Vreb), additional deadspace volume (AVD), respiratory rate (RR), and body height. Vt and alveolar volume (VA) were determined from the end-tidal concentrations of acetylene and helium. We performed Vt measurements using different combinations of Vreb (20, 30 and 50% of predicted vital capacity), of AVD (0, 100, and 200 ml) and of RR (10, 25, and 40 br.min-1). Only slow RR (10 br.min-1) resulted in a higher Vt (p less than 0.001). An increase in Vreb induced an increase in VA but not in Vt. VA and Vt were positively correlated with the height of the subjects. We conclude that, in normal subjects, Vt increases: 1) with the height of subjects; and 2) when the respiratory rate is low. Interpretation of Vt results must take into account these two variables.

[Diagnosis of cellular respiratory arrest by NADH laser fluorimetry. Applications in heart surgery and in experimental pharmacology]. / Diagnostic de l'arrêt de la respiration cellulaire par fluorimétrie laser du NADH. Applications en chirurgie cardiaque et en pharmacologie expérimentale.

The continuous measurement of intratissular NADH concentration allows early detection of cellular respiration arrest during clinical situations, i.e. allows a non-destructive, in situ, continuous measurement of ATP formation. This detection enables the physician or surgeon to intervene during a phase of cellular respiration arrest, before structural cellular alterations occur, thereby preventing potential tissular necrosis. The method has now been validated in experimental cardiac surgery for the monitoring of myocardial preservation techniques during cardiopulmonary by-pass, and in cardiac pharmacology, for analysis of drugs' effects on myocardial energetic metabolism. Its industrial development is currently under way. Preliminary investigation strongly suggests the vast potential of this diagnostic method in both clinical and experimental fields.

NADH in situ laser fluorimetry: effect of pentobarbital on continuously monitored myocardial redox state.

NADH laser fluorimetry was applied to in situ monitoring of pentobarbital overload effect on myocardial redox state in rats. Experiments were carried out on open-chest rats anesthetized with pentobarbital. Use of very thin optical probes allowed measurements of NADH fluorescence directly within the myocardial wall. Quantitative analysis of fluorescent and backscattered light signals was made possible on-line. In 8 animals, a slow IV infusion of 6% pentobarbital (2 mg.min-1 for 10 min) induced an average twofold increase in NADH fluorescence, with constant return to baseline level prior to injection after a maximum period of 50 min. Thus, pentobarbital overload strongly affects the myocardial energetic state, and this effect was precisely evaluated with NADH fluorescence monitoring. In situ-monitored myocardial redox state variations during pentobarbital infusion can constitute a reference for similar studies on pharmacological agents aimed at protecting tissues against ischemic biochemical damages.