Effect of desialylation on low density lipoproteins: comparative study before and after oxidative stress

Aim of our study was to investigate the effect of the desialylation induced by neuraminidase treatment on low density lipoprotein susceptibility to peroxidative stress induced by incubation with copper ions. Our results show that peroxidative stress induces the formation of aggregates that was not observed in desialylated low density lipoproteins. An increase in thiobarbituric reactive substances and a decrease in polyunsaturated fatty acids content have been shown in oxidized LDL. These modifications were less pronounced in oxidized low density lipoproteins previously treated by neuraminidase. The present data suggest a lower susceptibility to peroxidative stress in previously desialylated low density lipoproteins.

Standardisation of 31phosphorus-nuclear magnetic resonance spectroscopy determinations of high energy phosphates in humans

A procedure is described for standardising the determination of adenosine 5'-triphosphate and phosphocreatine concentration ([ATP] and [PC], respectively, in absolute arbitrary units) in human muscle by nuclear magnetic resonance (NMR) spectroscopy. The individual 31phosphorus (31P)-NMR spectra obtained on equal hemispherical tissue volumes (muscle plus skin and fat) were corrected for the thickness of the skin and of the subcutaneous fat. The volumes investigated were standardised using an external reference. The procedure described made possible the comparison of high energy phosphate concentrations among different subjects. It was applied to the assessment of [ATP] and [PC] in four groups of sedentary subjects (children, and adults aged 20-35, 35-50 and over 50 years), and in a group of athletes (volleyball players). The [ATP] and [PC] were not statistically different in the groups investigated.

Determinants of peak muscle power: effects of age and physical conditioning

The relationships between absolute peak muscle power (Wpeak), muscle cross sectional area (CSAtot, i.e. the sum of both thigh and calf CSA) and muscle high energy phosphate concentration (adenosine 5'-triphosphate [ATP] and phosphocreatine concentrations [PC]) were studied in 47 subjects classified into five groups: A, 10 sedentary (S) subjects aged 20-35 years; B, 9 S aged 35-50 years; C, 9 S aged more than 50 years; D, 13 children aged 8-13 years; and E, 6 athletes (top level volleyball players) aged 24 (SD 3) years. The Wpeak was measured during a maximal vertical high jump off both feet on a force platform. The CSAtot was measured anthropometrically. The [ATP] and [PC] were determined by 31Phosphorus nuclear magnetic resonance spectroscopy. The Wpeak decreased with age, was 65% lower in D than in A, and 43% higher in E than in A. The CSAtot did not vary with age, was 45% smaller in D than in A, and 15% greater in E than in A. The [ATP] and [PC] were essentially the same in all groups. The changes observed in Wpeak were only partially accounted for by changes in CSAtot. Therefore, in addition to the variables investigated, other factors appear to have been involved in the determination of Wpeak with increasing age and training. An important role may be played by hormonal, particularly at puberty, and neural factors.

Plasma membrane order parameter in periportal and perivenular hepatocytes isolated from ethanol-treated rats

Hepatic ethanol (EtOH) metabolism has been assumed to involve hepatocytes differently, according to their location in the hepatic acinus. This study's aim was to gain information on plasma membrane (PM) order parameter in periportal (PP) and perivenular (PV) hepatocyte-enriched fractions isolated by a digitonin-collagenase perfusion technique from rats pair-fed for 6-8 wk liquid diets containing either EtOH or isocaloric carbohydrates. Fluorescence polarization (P) studies have been performed to measure PM order parameter of PP and PV hepatocytes cultured for 2-6 h on glass cover slips and labeled with 1-[4-(trimethylamino)phenyl]-6-phenylhexa-1,3,5-triene (TMA-DPH), a specific probe for PM of living cells. Fluorescence polarization and microscopy indicated that TMA-DPH is a suitable probe to study PM order parameter in subconfluent rat hepatocyte monolayers where it labeled, after a rapid incorporation, PM of cells. In pair-fed control rats, PM order parameter was lower in PP hepatocytes than in PV cells (P = 0.366 +/- 0.013 vs. 0.381 +/- 0.021, respectively, P < 0.02; n = 7). In EtOH-treated rats, these zonal differences tended to disappear (P = 0.419 +/- 0.012 in PP cells vs. 0.417 +/- 0.007 in PV cells; n = 7). In addition, the order parameter was significantly higher either in PP or PV hepatocytes compared with pair-fed control animals (P < 0.002 and 0.003, respectively). A 30-min culture of cells in the presence of 40-200 mM EtOH significantly decreased the PM order parameter of hepatocytes isolated from pair-fed control rats with respect to EtOH-treated animals both in PP and PV cells (P < 0.01 and 0.02, respectively; n = 4).(ABSTRACT TRUNCATED AT 250 WORDS)

Immunoscintigraphy using 111in-labelled F(ab')2 fragments of anti-carcinoembryonic antigen (CEA) monoclonal antibody for staging of non-small cell lung carcinoma

28 patients with primitive lung cancers were imaged by immunoscintigraphy (IS) with 111indium-labelled F(ab')2 anti-carcinoembryonic antigen (CEA), to assess this technique for mediastinal staging. IS revealed primitive tumours in 21 cases in whom mediastinal extension was assessed. There was concordance between clinical staging and IS confirmed by surgery in 17 cases, and discordance in 4. After surgery, discordance was in favour of IS in 2 cases (1 true positive and 1 true negative) and in favour of clinical staging in 2 (false positive of immunoscintigraphy). Anti-CEA IS could be useful for improving mediastinal staging of lung cancer.

Pygmy locomotion

The hypothesis that Pygmies may differ from Caucasians in some aspects of the mechanics of locomotion was tested. A total of 13 Pygmies and 7 Caucasians were asked to walk and run on a treadmill at 4-12 km.h-1. Simultaneous metabolic measurements and three-dimensional motion analysis were performed allowing the energy expenditure and the mechanical external and internal work to be calculated. In Pygmies the metabolic energy cost was higher during walking at all speeds (P < 0.05), but tended to be lower during running (NS). The stride frequency and the internal mechanical work were higher for Pygmies at all walking (P < 0.05) and running (NS) speeds although the external mechanical work was similar. The total mechanical work for Pygmies was higher during walking (P < 0.05), but not during running and the efficiency of locomotion was similar in all subjects and speeds. The higher cost of walking in Pygmies is consistent with the allometric prediction for smaller subjects. The major determinants of the higher cost of walking was the difference in stride frequency (+9.45, SD 0.44% for Pygmies), which affected the mechanical internal work. This explains the observed higher total mechanical work of walking in Pygmies, even when the external component was the same. Most of the differences between Pygmies and Caucasians, observed during walking, tended to disappear when the speed was normalized as the Froude number. However, this was not the case for running. Thus, whereas the tested hypothesis must be rejected for walking, the data from running, do indeed suggest that Pygmies may differ in some aspects of the mechanics of locomotion.

[Intrathoracic hydatid cyst. Contribution of tomodensitometry. Apropos of 25 cases]

Twenty-five cases of thoracic hydatic disease, studied by CT since 1982, are reviewed. Fifteen patients were Maghrebin, 10 were native. The lungs were interested 22 times, the mediastinum 3 times and the heart only once. Complications of hydatic disease were present 8 times. We compare contribution of CT to the other diagnosis criterious. Our results show the accuracy of CT for the diagnosis of non complicated cyst and the lack of specificity for complicated cysts.

Maximal lactic capacity at altitude: effect of bicarbonate loading

The aim of the present study was to test the hypothesis that the net maximal blood lactate accumulation ([La]max) during heavy exercise in lowlanders acclimatized to chronic hypoxia may be limited by the reduced bicarbonate stores. Six men [age 32 +/- 4 (SD) yr] performed supramaximal exercise until voluntary exhaustion at sea level (204 +/- 54 W) and after sojourning for 1 mo at 5,050 m (175 +/- 23 W), without (C) and with (B) oral sodium-bicarbonate loading (0.3 g/kg body wt). Exhaustion time, arterial blood lactate concentration, arterial pH (pHa), arterial PCO2, and intramuscular pH were measured at rest and after exercise. At sea level, exhaustion time increased from 6.5 +/- 2.8 min in C to 7.5 +/- 2.7 min in B (P < 0.05). At altitude, exhaustion times were similar to the sea level C values and the same in C and B. At sea level, resting pHa increased from 7.41 +/- 0.02 in C to 7.46 +/- 0.03 in B (P < 0.001); the corresponding values at altitude were 7.46 +/- 0.04 and 7.55 +/- 0.03 (P < 0.001). Postexercise pHa at sea level was 7.22 +/- 0.02 in C and 7.25 +/- 0.08 in B (NS). After exercise at altitude, pHa was 7.32 +/- 0.04 and 7.44 +/- 0.03 in C and B, respectively (P < 0.001). [La]max increased from 12.86 +/- 1.45 mM in C to 16.63 +/- 1.76 mM in B (P < 0.01) at sea level and from 6.85 +/- 1.40 mM in C to 7.95 +/- 1.74 mM in B (NS) at altitude.(ABSTRACT TRUNCATED AT 250 WORDS)

Energy cost and efficiency of riding aerodynamic bicycles

Traction resistance (Rt) was determined by towing two cyclists in fully dropped posture on bicycles with an aerodynamic frame with lenticular wheels (AL), an aerodynamic frame with traditional wheels (AT), or a traditional frame with lenticular wheels (TL) in calm air on a flat wooden track at constant speed (8.6-14.6 m.s-1). Under all experimental conditions, Rt increased linearly with the square of air velocity (v2a); r2 equal to greater than 0.89. The constant k = delta Rt/delta v2a was about 15% lower for AL and AT (0.157 and 0.155 N.s2 x m-2) than for TL bicycles (0.184 N.s2 x m-2). These data show firstly, that in terms of mechanical energy savings, the role of lenticular wheels is negligible and, secondly, that for TL bicycles, the value of k was essentially equal to that found by others for bicycles with a traditional frame and traditional wheels (TT). The energy cost of cycling per unit distance (Cc, J.m-1) was also measured for AT and TT bicycles from the ratio of the O2 consumption above resting to speed, in the speed range from 4.7 to 11.1 m.s-1. The Cc also increased linearly with v2a, as described by: Cc = 30.8 + 0.558 v2a and Cc = 29.6 + 0.606 v2a for AT and TT bicycles. Thus from our study it would seem that AT bicycles are only about 5% more economical than TT at 12.5 m.s-1 the economy tending to increase slightly with the speed.(ABSTRACT TRUNCATED AT 250 WORDS)

Physico-chemical properties of copper-oxidized high density lipoprotein: a fluorescence study

The modifications of the physico-chemical properties of the high density lipoprotein (HDL) before and after in vitro induced oxidation by copper ions have been studied using the fluorescence polarization (Pf) of the phosphatidylcholine derivative of 1,6-diphenyl-1,3,5-hexatriene (DPH-PC) and of the cationic derivative (TMA-DPH). We have observed that HDL oxidation is associated with a decrease of the molecular order at the lipoprotein surface as demonstrated by the increase in Pf with respect to untreated HDL. Moreover in oxidized HDL the polarity-sensitive probe laurdan has shown a decrease of the polarity in its microenvironment. It has been suggested that a decrease in HDL fluidity would inhibit cholesterol reverse transport from peripheral tissues in form of HDL core cholesteryl esters. Peroxidation of HDL, if occurring in vivo, could contribute to the progress of atherogenesis by decreasing cholesterol efflux from peripheral tissues.

Ventilatory response to exercise after heart and lung denervation in humans

This study, aimed at investigating some aspects of breathing control at work, was conducted on 8 heart and lung transplant recipients (HLTR) (age 33 +/- 13 years, mean +/- SD; 10 +/- 6 months post-transplantation) and on two control groups, i.e. 11 heart transplant recipients (HTR) and 11 healthy untrained subjects (C). The patients performed a series of 2 to 6 1-min exercise bouts (at 25 or 50 W, corresponding to about 50% of their VO2max) on a bicycle ergometer, followed by a 5 min 25 or 50 W constant load. C exercised both at 50 W (C1) and at 50% of their VO2max (C2). Inspiratory (VI) and expiratory (VE) ventilation, tidal volume (VT), respiratory frequency (fR), end-tidal O2 and CO2 partial pressures (PETO2 and PETCO2 and gas exchange (VO2 and VCO) were measured breath-by-breath. "Phase I" ventilatory response (ph I) was determined as the mean changes of VI, VE, VT, fR, PETO2 and PETCO2, compared to rest, during the first two respiratory cycles following exercise onset. In HLTR ph I did not significantly differ from that of C1 and C2, whereas the response was lower in HTR. VE, VO2 and VCO2 responses during "phase II" (t 1/2 on-) and "phase III" (steady state exercise) were similar in HLTR and in HTR. t 1/2 on- were longer in HLTR and in HTR compared to C1. In 3 HLTR the ventilatory pattern during the 5 min constant loads was similar to that of HTR and C, whereas 4 HLTR presented higher VT and lower fR values. It is concluded that: 1) The ventilatory response to exercise, in all its phases, is substantially preserved despite lung denervation. When slight alterations are found (i.e. the slower phase II), they are presumably of peripheral origin. 2) The normal ph I in HLTR indicates that cardiac and/or pulmonary inputs to the respiratory centers are not involved in its regulation, or that their role can be subserved by other ventilatory control mechanisms.

Limitations to VO2max in humans after blood retransfusion

Seven young, healthy male subjects performed maximal exercise on a cycloergometer with central venous and arterial catheters, before and after autologous retransfusion of red blood cells. Maximal oxygen consumption (VO2max), blood gas composition and haemodynamic variables were measured, in order to test the hypothesis of monofactorial vs. polyfactorial VO2max limitation. Autologous blood retransfusion led to significant increases in haemoglobin concentration and consequently arterial oxygen concentration during maximal exercise, while maximal cardiac output, heart rate and stroke volume were not significantly changed. The relationship between maximal oxygen delivery (cardiac output.arterial oxygen concentration; (Q.CaO2)max and maximal oxygen consumption in this study was VO2max (L.min-1) = 0.02 + 0.64.(Q.CaO2)max (L.min-1), the slope being significantly less than unity. These results suggest that (Q.CaO2)max plays but a fractional role in limiting VO2max, in agreement with recent models concerning the resistance to oxygen flow in the respiratory system (di Prampero and Ferretti, Respir. Physiol. 80: 113-128, 1990). The relative increase in VO2max after blood retransfusion matched the relative increase in 'aerobic performance', measured as the maximal power output that could be maintained aerobically for 30 min. Furthermore, the increase in maximal power output (15 +/- 3 watts) could account for almost all of the extra oxygen consumption. This match suggests that there is an inability to fully utilize muscle oxidative capacity in the normocythaemic state.

Changes of plasma lipids and erythrocyte membrane fluidity in psoriatic children

Psoriasis has been associated with an abnormal plasma lipid metabolism, and changes of erythrocyte membrane lipid composition and fluidity have been shown in adult patients. To investigate whether the alterations of plasma lipids appear also in pediatric patients, we have studied plasma lipids and lipoproteins in 15 prepubertal children affected by mild-to-moderate psoriasis with respect to healthy controls. The patients showed higher levels of plasma total cholesterol (4.44 +/- 0.78 versus 4.03 +/- 0.58 mmol/L), a significant increase of cholesterol associated with HDL (1.39 +/- 0.26 versus 1.13 +/- 0.28 mmol/L, p = 0.02), and a significant decrease of the ratio LDL cholesterol to HDL cholesterol (1.73 +/- 0.6 versus 2.46 +/- 0.8, p = 0.02). By using fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene, we have shown a significant increase in fluidity in erythrocyte membrane of psoriatic children that was associated with a slight, but not significant, decrease in the cholesterol to protein ratio (422 +/- 127 versus 503 +/- 117 nmol/mg). No significant changes of phospholipid fatty acid composition have been shown, in disagreement with previous studies in adult patients. Our results support the relation between childhood psoriasis and plasma lipid changes, which are likely related to the slight compositional changes in erythrocytes. However, the observed abnormalities are expressed differently in children than in adults.

Membrane heterogeneity in isolated rat hepatocytes and liver plasma membrane subfractions: a comparative study using DPH and its cationic derivative TMA-DPH

The fluorescence decay of 1,6-diphenyl-1,3,5-hexatriene (DPH) and of 1-(4-trimethylammonium-phenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) has been studied in hepatocytes isolated from rat liver and in isolated plasma membrane subfractions (cLPM, canalicular membranes and bLPM, basolateral membranes) using frequency domain fluorometry. The decay has been analyzed either by using a model of discrete exponential components or a model that assumes a continuous distribution of lifetime values in order to study different aspects of membrane heterogeneity. The results obtained by the two analyses are practically superimposable but the distributional approach allows an evaluation of membrane heterogeneity through the width of the distribution that has shown particularly significant differences when freshly hepatocytes are compared with in vitro aged hepatocytes. Moreover, the comparison of the distributional analysis of the two probes has shown in cLPM a tendency to higher values of the main lifetime component and a narrower distribution width with respect to bLPM. These results indicate changes of membrane domain organization that have been discussed in relation with the specific lipid composition that characterizes the two membrane subfractions. Our results indicate that frequency domain fluorometry may be used to study membrane heterogeneity in intact cells and isolated membranes.

Central sleep apnoea syndrome with upper airway collapse

We report on an 83 yr old man with hypersomnia and central sleep apnoea (CSA). He had several possible causes for CSA, including a central nervous system lesion, hypocapnia and anatomical narrowing of the airway at the hypopharyngeal level. We postulate that reduced central respiratory drive occurring in conjunction with upper airway narrowing may have led to central apnoeas. These in turn could have facilitated a complete passive hypopharyngeal collapse at the end of each apnoea, as visualized by somnofluoroscopy. The CSA could also have been favoured by respiratory instability due to chronic hypocapnia.

Central sleep apnoea syndrome with upper airway collapse

We report on an 83 yr old man with hypersomnia and central sleep apnoea (CSA). He had several possible causes for CSA, including a central nervous system lesion, hypocapnia and anatomical narrowing of the airway at the hypopharyngeal level. We postulate that reduced central respiratory drive occurring in conjunction with upper airway narrowing may have led to central apnoeas. These in turn could have facilitated a complete passive hypopharyngeal collapse at the end of each apnoea, as visualized by somnofluoroscopy. The CSA could also have been favoured by respiratory instability due to chronic hypocapnia.

Properties of a phosphatidylcholine derivative of diphenyl hexatriene (DPH-PC) in lymphocyte membranes. A comparison with DPH and the cationic derivative TMA-DPH using static and dynamic fluorescence

Using static and dynamic fluorescence we studied the fluorescence properties of a phosphatidylcholine analog of 1,6-diphenyl-1,3,5-hexatriene (DPH-PC) incorporated in lymphocyte plasma membranes with respect to DPH and its cationic derivative 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH), in order to study if phospholipid derivatives of DPH may be used to investigate structural and physicochemical properties of specific membrane lipid domains. DPH-PC and TMA-DPH showed similar fluorescence polarization values that were significantly higher with respect to DPH, suggesting a localization of the fluorescent portion of DPH-PC in a more ordered region of the membrane which was probably due to the elecrostatic interactions between phospholipid head-groups. The localization of the fluorescent moiety of DPH-PC near the membrane surface was also supported by the study of the fluorescence decay of the three probes using frequency-domain fluorometry. The main lifetime component of DPH-PC was rather similar to that of TMA-DPH (6.74 versus 6.24, ns) but considerably lower with respect to DPH (10.52 ns), in agreement with data obtained from exponential analysis. In lymphocyte membranes obtained from concanavalin A treated cells, a significant decrease of fluorescence polarization has been shown with DPH and its phosphatidylcholine derivative, but not with TMA-DPH. In liposomes obtained from total lipids extracted from lymphocyte membranes, a decrease of fluorescence polarization has been observed only with DPH. Our results suggest that DPH-PC localizes the fluorescent portion of its molecule in membrane microenvironments of different properties with respect to those probed by DPH and TMA-DPH. The use of DPH-phospholipid derivatives and other DPH-probes may represent an useful tool to study plasma membrane heterogeneity in biological membranes.

Evaluation of the upper airway in sleep apnea syndrome

The upper airway is the final common site for abnormalities in respiratory control and neuromuscular function leading to sleep apnea. This review summarizes the information that pharyngeal assessment provides for understanding upper airway pathophysiology and selecting treatment. The applications and limitations of both static and dynamic techniques are examined in awake and sleeping patients. The effects of posture on the upper airway and the usefulness for predicting treatment efficiency are examined.

Lower susceptibility of low density lipoprotein to in vitro oxidation in diabetic patients

The susceptibility to peroxidative stress of low density lipoprotein (LDL), induced by incubation with CuSO4, has been studied in eleven diabetic patients and eleven control subjects. Our results suggest that oxidized LDL (OX-LDL) of diabetic patients have a significant higher reactivity to 2,4,6-trinitrobenzene sulfonic acid (TNBS) than controls, that indicates a lower susceptibility of LDL to oxidative stress. Furthermore using the fluorescence polarization (Pf) of 1,6-diphenyl-1,3,5-hexatriene (DPH) and its phosphatidylcholine derivative (DPH-PC) we have shown that peroxidation induces a decrease of fluidity in OX-LDL of controls and diabetic patients, both at the lipoprotein surface, where is localized DPH-PC and at the interface between lipoprotein surface and core which is probed by DPH.