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Biomedical subjects

B Petit

Publications and source records attributed to B Petit.

At least 37 records · Page 2Linked to original sources
PubMed1999

Development and validation of a high-performance liquid chromatographic assay using solid-phase extraction for the novel antitumor agent pancratistatin in human plasma.

The stability of the experimental anti-tumour agent pancratistatin in human plasma has been investigated. A solid-phase extraction technique and an HPLC assay with external standards have been developed and validated. Extraction was performed using C18 cartridges and HPLC, analysis was performed on a 15 cm Hypersil BDS column using isocratic elution with 13% acetonitrile and aqueous solution of 1% (w/v) acetic acid. The lower limit of quantification for pancratistatin in 5% DMF-95% water was found to be 0.58 ng/ml (+/-10.58%) and 2.3 ng/ml (+/-9.2%) following extraction from human plasma. Mean recovery of 89.4% (+/-4.73%) was obtained over the concentration range 0.0023-9.45 microg/ml for a five day validation study. Pancratistatin was stable at room temperature in light or dark for at least 15 days, in the refrigerator at 4 degrees C for at least 16 days and in the freezer at -20 degrees C or -80 degrees C for at least 28 days. Under all conditions monitored, % recovery of pancratistatin from human plasma was greater than 95% and no evidence of degradation had occurred. There also was no loss of pancratistatin after three cycles of freezing and thawing.

Amaryllidaceae Alkaloids↗
PubMed1999

The role of cadence on the VO2 slow component in cycling and running in triathletes.

The purpose of this study was to compare the effect of two different types of cyclic severe exercise (running and cycling) on the VO2 slow component. Moreover we examined the influence of cadence of exercise (freely chosen [FF] vs. low frequency [LF]) on the hypothesis that: 1) a stride frequency lower than optimal and 2) a pedalling frequency lower than FF one could induce a larger and/or lower VO2 slow component. Eight triathletes ran and cycled to exhaustion at a work-rate corresponding to the lactate threshold + 50% of the difference between the work-rate associated with VO2max and the lactate threshold (delta 50) at a freely chosen (FF) and low frequency (LF: - 10 % of FF). The time to exhaustion was not significantly different for both types of exercises and both cadences (13 min 39 s, 15 min 43 s, 13 min 32 s, 15 min 05 s for running at FF and LF and cycling at FF and LF, respectively). The amplitude of the VO2 slow component (i.e. difference between VO2 at the last and the 3rd min of the exercise) was significantly smaller during running compared with cycling, but there was no effect of cadence. Consequently, there was no relationship between the magnitude of the VO2 slow component and the time to fatigue for a severe exercise (r = 0.20, p = 0.27). However, time to fatigue was inversely correlated with the blood lactate concentration for both modes of exercise and both cadences (r = - 0.42, p = 0.01). In summary, these data demonstrate that: 1) in subjects well trained for both cycling and running, the amplitude of the VO2 slow component at fatigue was larger in cycling and that it was not significantly influenced by cadence; 2) the VO2 slow component was not correlated with the time to fatigue. If the nature of the linkage between the VO2 slow component and the fatigue process remains unclear, the type of contraction regimen depending on exercise biomechanic characteristics seems to be determinant in the VO2 slow component phenomenon for a same level of training.

Adult↗
PubMed1999

Oxygen deficit is related to the exercise time to exhaustion at maximal aerobic speed in middle distance runners.

The purpose of this study was to show the relationship between oxygen deficit and the time to exhaustion (tlim) at maximal aerobic speed (MAS). The minimum speed that elicits VO(2max) was assumed to be the maximal aerobic speed (MAS). Fourteen subelite male runners (mean (SD: age = 27 +/- 5 yrs: VO(2max) = 68.9 +/- 4.6 ml kg (-1). min ( -1); MAS = 21.5 +/- 1 km h (-1) ) participated in the study. Each subject performed an incremental test to determine and MAS. The subjects ran to exhaustion at velocities corresponding to 100 and 120 % MAS. Oxygen deficit was measured during the period exercise to exhaustion at 120% of MAS and was calculated from the difference between O(2) demand and the accumulated O 2 uptake. The tlim values at 100% MAS were correlated with the values of tlim at 120% MAS (r = 0.52). The results reveal that the oxygen deficit was related to the time to exhaustion at MAS and indicate that the greater the oxygen deficit, the greater the time to exhaustion at MAS. It was also noted that the adjustment of oxygen consumption is related to the oxygen deficit. In other words, the subjects who have an important anaerobic capacity are the most efficient during an exercise time to exhaustion at MAS. The time limit values can be expressed by a linear regression making intervene MAS and anaerobic capacity. This conclusion could be of great interest in the training of middle distance runners.

Adult↗
PubMed1999

Effect of the laryngeal mask airway on oesophageal pH: influence of the volume and pressure inside the cuff.

We studied gastro-oesophageal reflux (GOR) with a face mask and laryngeal mask airway (LMA), and the effects of inflation pressure and volume of the LMA cuff on oesophageal pH, in 60 patients. Patients were managed with either a face mask (group I) or LMA inflated to obtain a seal in the anaesthesia circuit at 7 cm H2O (group II) or 15 cm H2O (group III). A pH-sensitive probe with two electrodes, 10 cm apart, was placed in the oesophagus during anaesthesia and recordings were made continuously until patients awakened. There was a significant difference in the incidence of GOR between the face mask (group I) and the LMA (groups II-III) (P < 0.05) in the lower oesophagus but there was no difference in the mid-oesophagus. No correlation was found between pressure and volume inside the cuff and variations in oesophageal pH. We conclude that LMA use was associated with increased reflux in the low oesophagus but oesophageal pH was not influenced by variations in pressure or volume inside the LMA cuff.

Adult↗
PubMed1999

Interval training at VO2max: effects on aerobic performance and overtraining markers.

PURPOSE: Between inefficient training and overtraining, an appropriate training stimulus (in terms of intensity and duration) has to be determined in accordance with individual capacities. Interval training at the minimal velocity associated with VO2max (vVO2max) allows an athlete to run for as long as possible at VO2max. Nevertheless, we don't know the influence of a defined increase in training volume at vVO2max on aerobic performance, noradrenaline, and heart rate. METHODS: Eight subjects performed 4 wk of normal training (NT) with one session per week at vVO2max, i.e., five repetitions run at 50% of the time limit at vVO2max, with recovery of the same duration at 60% vVO2max. They then performed 4 wk of overload training (OT) with three interval training sessions at vVO2max. RESULTS: Normal training significantly improved their velocity associated with VO2max (20.5+/-0.7 vs 21.1+/-0.8 km x h(-1), P = 0.02). As a result of improved running economy (50.6+/-3.5 vs 47.5+/-2.4 mL x min(-1) x kg(-1), P = 0.02), VO2max was not significantly different (71.6+/-4.8 vs 72.7+/-4.8 mL x min(-1) x kg(-1)). Time to exhaustion at vVO2max was not significantly different (301+/-56 vs 283+/-41 s) as was performance (i.e., distance limit run at vVO2max: 2052.2+/-331 vs 1986.2+/-252.9 m). Heart rate at 14 km x h(-1) decreased significantly after NT (162+/-16 vs 155+/-18 bpm, P < 0.01). Lactate threshold remained the same after normal training (84.1+/-4.8% vVO2max). Overload training changed neither the performance nor the factors concerning performance. However, the submaximal heart rate measured at 14 km x h(-1) decreased after overload training (155+/-18 vs 150+/-15 bpm). The maximal heart rate was not significantly different after NT and OT (199+/-9.5, 198+/-11, 194+/-10.4, P = 0.1). Resting plasma norepinephrine (veinous blood sample measured by high pressure liquid chromatography), was unchanged (2.6 vs 2.4 nm x L(-1), P = 0.8). However, plasma norepinephrine measured at the end of the vVO2max test increased significantly (11.1 vs 26.0 nm x L(-1), P = 0.002). CONCLUSION: Performance and aerobic factors associated with the performance were not altered by the 4 wk of intensive training at vVO2max despite the increase of plasma noradrenaline.

Adult↗
PubMed1998

High level runners are able to maintain a VO2 steady-state below VO2max in an all-out run over their critical velocity.

During prolonged and intense running exercises beyond the critical power level, a VO2 slow component elevates VO2 above predicted VO2-work rates calculated from exercise performed at intensities below the lactate threshold. In such cases, the actual VO2 value will increase over time until it reaches VO2max. The aims of the present study were to examine whether the VO2 slow component is a major determinant of VO2 over time when running at a speed beyond critical velocity, and whether the exhaustion latency period at such intensity correlates with the magnitude of the VO2 slow component. Fourteen highly trained long-distance runners performed four exhaustive runs, each separated by one week of light training. VO2 and the velocity at VO2max (vVO2max) were determined for each by a graded treadmill exercise. The critical velocity (86.1 +/- 1.5% vVO2max) of each runner was calculated from exhaustive treadmill runs at 90, 100 and 105% of vVO2max. During supra-critical velocity runs at 90% of vVO2max, there was no significant rise in VO2max (20.9 +/- 2.1 ml min-1 kg-1 between the third and last min of tlim 90), such that the runners reached a VO2 steady-state, but did not reach their vVO2max level over time (69.5 +/- 5.0 vs 74.9 +/- 3.0 ml min-1 kg-1). Thus, subjects' time to exhaustion at 90% of vVO2max was not correlated with the VO2max slow component (r = 0.11, P = 0.69), but significantly correlated with the lactate threshold (r = 0.54, P = 0.04) and the critical velocity (% vVO2max; r = 0.65, P = 0.01). In conclusion, the present study demonstrates that for highly trained long-distance runners performing exhaustive, supra-critical velocity runs at 90% of vVO2max, there was not a VO2 slow component tardily completing the rise of VO2. Instead, runners will maintain a VO2 steady-state below VO2max, such that the time to exhaustion at 90% of vVO2max for these runners is positively correlated with the critical velocity expressed as % of vVO2max.

Adult↗
PubMed1998

[Lymphoproliferative syndromes after renal transplantation].

UNLABELLED: Following kidney transplantation, lymphoproliferative disorders (LD) are encountered at a frequency of 1%. The onset of these LD is correlated with the degree of immunosuppression. The mortality is elevated (> 50%) especially in late forms. Since 1984 we have performed two hundred and seventeen kidney transplantations. The patients received sequential quadruple-drug immunosuppressive therapy: antilymphocyte globulin (ALG), azathioprine, corticosteroids and cyclosporine. A diagnosis of LD was established in ten patients, four were of early onset (within twelve months of transplantation) and six late (after five to nine years). Rejection occurred in two patients, one of which was steroid resistant requiring ALG. Three LD arose from the graft hilum, four had a voluminous tumor mass with extranodal sites: the graft (1), stomach (2), gingiva (1), meninges (1), and bone marrow (1). Histologically there were eight cases of large-cell B lymphoma, 1 mononucleosis-like LD, and a MALT lymphoma. A search for EBV was positive seven times. Treatment consisted of decreasing immunosuppressive therapy only (1), combined with antiviral treatment (1), or with surgical removal of the graft (3), and/or chemotherapy (5). Nine patients are still alive, in complete remission, graft loss occurred in four cases. CONCLUSION: In our series, we found a high frequency of LD. Despite 4 LD with a voluminous tumor mass and unfavorable histological prognosis requiring chemotherapy, all the LD in our series had a favorable outcome.

Adult↗
PubMed1997

[Obstructive renal insufficiency caused by amoxicillin crystalluria].

A 76-year-old woman was admitted to the ICU for a meningitis with rhombencephalitis due to Listeria monocytogenes. The treatment included amoxicillin (250 mg.kg-1.day-1) and gentamicin (3 mg.kg-1.day-1 over 6 days). Neurological outcome was favourable. However at the 14th day, an acute renal failure occurred, following macroscopic haematuria and milkiness urine. CT scan and sonography confirmed the diagnosis of obstructive renal failure with bilateral ureteral obstruction. Crystalluria caused by amoxicillin was suspected. Endoscopic ureteral insertion of double-J catheters permitted the recovery of a normal renal function.

Acute Kidney Injury↗
PubMed1997

Automated liquid-chromatographic analyzer used for toxicology screening in a general hospital: 12 months' experience.

We evaluated the clinical utility of an automated HPLC system (Remedi, Bio-Rad) for identification of drugs and metabolites in biological fluids. Serum or urine or both from 354 consecutive cases of poisoning were analyzed by the system and by a set of fluorescence polarization immunoassay (FPIA, Abbott) and thin-layer chromatographic (TLC) procedures. Antidepressants and most phenothiazines were recognized by the new system. Comparison of Remedi results with final clinical diagnoses yielded diagnostic specificity and sensitivity of 80% and 90%, respectively. Remedi detected 26 additional compounds that were neither reactive in the immunoassay screening tests nor detected by TLC procedures. Because the Remedi expands the range of drugs covered by the immunoassays and provides a rapid, preliminary report in emergency situations, we conclude that this system can be a useful complementary technique in the clinical toxicology laboratory. Although urine toxicological screening seemed adequate for a good toxicological report, blood analysis allows extra toxicokinetic data such as blood concentrations and half-life estimations.

Chromatography, High Pressure Liquid↗
PubMed1996

Characterization of crosslinked collagens synthesized by mature articular chondrocytes cultured in alginate beads: comparison of two distinct matrix compartments.

We have characterized immunohistochemically and biochemically the collagens accumulating in two compartments of the matrix formed by mature bovine articular chondrocytes in alginate beads. At all times of the 28-day culture period, more than 90% of the collagen molecules were recovered from the rim of cell-associated matrix (CM) which encapsulates individual chondrocytes and chondrocyte clusters. Both the total amount and concentration of collagens in this matrix compartment rose progressively with time. The ratio of collagen/proteoglycan remained relatively constant with time and was always five to seven times higher in the CM than in the interterritorial matrix compartment further removed from the cells. In the CM, collagen types II, IX and XI were present on Day 28 in relative proportions (95/l/3) similar to those in adult cartilage. A higher proportion of newly synthesized collagen type XI than types II or IX molecules did not become incorporated into the pericellular rim of matrix but accumulated in the further removed matrix. Although collagen type I was synthesized in small amounts by flattened cells at the surface of the beads, it did not become incorporated as heterotrimers or homotrimers in the matrix. Mature pyridinium crosslinks, principally pyridinoline, were detected as early as Day 7 of culture but became much more abundant between Days 15 and 28, especially in the CM which contained at all times more than 90% of the crosslinks formed. The codistribution of collagen types II, IX and XI and mature collagen-specific crosslinks support the contention that mature chondrocytes cultured in alginate matrix surround themselves with a protective shell whose composition is very similar to that which encapsulated the cells in vivo.

Alginates↗
PubMed1996

Effect of protocol on determination of velocity at VO2 max and on its time to exhaustion.

The velocity associated with the achievement of VO2 max during an incremental treadmill test (v VO2 max) has been reported to be an indicator of performance in middle distance running events. Previous study has shown the reproducibility of the time to exhaustion (time limit: tlim) at v VO2 max performed by well-trained males in the same condition at one week of interval (Billat et al., 1994b). It is essential in studies involving tlim at v VO2 max that the v VO2 max be precisely determined, or else the measured tlim will be meaningless. The purpose of this study was to examine the influence of the stage duration and velocity incrementation on the velocity at VO2 max and, consequently, on the two times to exhaustion (tlim) associated with the two v VO2 max generated by the two protocols. v VO2 max was determined in 15 trained male endurance athletes as the lowest speed at which VO2 max was attained in speed-incremented 0%-slope treadmill tests. For one test, increments were 1.0 km.h-1 and stages were 2 min in duration; for the other test, increments were 0.5 km.h-1 and stages were 1 min in duration. Results of paired means t-tests revealed no difference in v VO2 max obtained using the two protocols. v VO2 max was 20.7 +/- 1.0 km.h-1 with the 1.0 km.h-1 x 2 min protocol and 20.8 +/- 0.9 km.h-1 with the 0.5 km.h-1 x 1 min protocol. In addition, VO2, VCO2, VE, VE/VO2 and respiratory exchange ratio at the submaximal intensities that were common to both protocols (e.g., 17.0 km.h-1, 18.0 km.h-1, 19.0 km.h-1, 20.0 km.h-1) did not differ. Times to exhaustion at the two v VO2 max demonstrated a high degree of inter-individual variability (coefficients of variation were 35% and 45%) but did not differ (345 +/- 120 s versus 373 +/- 169 s). These results demonstrated that small changes in protocol have no significant impact on the value of v VO2 max and in consequence on tlim v VO2 max.

Adult↗
PubMed1995

[Hypoxemia and exhaustion time to maximal aerobic speed in long-distance runners].

A recent paper (Billat et al., 1994a) has shown the reproducibility but also the great variability between subelite long-distance runners in their time to exhaustion at the velocity which elicits VO2max, called the maximal aerobic speed (MAS). The present study delved further into the reasons for this large difference between runners having the same VO2max. The question addressed was whether the exercise-induced hypoxemia (EIH) was more important for athletes having the longest time to exhaustion at 90 (Tlim 90), 100 (Tlim 100), or 105% (Tlim 105) of MAS. The study was conducted on 16 elite male runners. EIH was observed, that is, arterial oxyhemoglobin saturation and arterial partial pressure of oxygen dropped significantly after all the Tlim tests. However, EIH was only correlated with Tlim 90 (r = -0.757; -0.531, respectively).

Adult↗
PubMed1995

Times to exhaustion at 90, 100 and 105% of velocity at VO2 max (maximal aerobic speed) and critical speed in elite long-distance runners.

Previous studies had concluded that the treadmill velocity-endurance time hyperbolic relationship for runs could be accuratly approached with a regression at condition that bouts of exercise duration were included between 2 and 12 min. This regression allows to calculate the critical speed (CS) defined as the slope of the regression of work (distance) on time to exhaustion, the anaerobic running capacity (ARC) being the intercept of this line (Monod & Scherrer, 1965). The purpose of this investigation was to give practical indication concerning the choice of the velocities in reference to the maximal aerobic speed (MAS i.e. the minimum speed which elicits VO2max). Subjects were fourteen elite male long-distance runners (27 +/- 3 years old; VO2max = 74.9 +/- 2.9 ml.kg-1.min-1, MAS = 22.4 +/- 0.8 km.h-1, CS = 19.3 +/- 0.7 km.h-1 and 86.2 +/- 1.5% MAS). tlim 100 values (321 +/- 83 s) were negatively correlated with MAS (r = -0.538, p < 0.05) and with CS (km.h-1) (r = -0.644, p < 0.01). tlim 90 (1015 +/- 266 s) was positively correlated with CS when expressed in % MAS (r = 0.645, p < 0.01) and not when expressed in km.h-1 (r = -0.095, P > 0.05). tlim 105 (176 +/- 40 s) only was correlated with ARC (r = 0.526, p < 0.05). These data demonstrate that running time to exhaustion at 100 and 105% of MAS in a homogeneous elite male long-distance runners group is inversely related to MAS. Moreover, tlim 90 is positively correlated with CS (%MAS) but neither with tlim 100 and 105 nor with maximal aerobic speed. So from a practical point of view, the velocities chosen to determine the critical speed, would be closed to the maximal aerobic speed (time to exhaustion around 6 min), taking into account that the tlim 105 is correlated with the anaerobic capacity, whereas tlim 90 is correlated with the critical speed.

Adult↗
PubMed1995

Implementing total quality management in an academic surgery setting: lessons learned.

Total Quality Management, a philosophy developed by W. Edwards Deming, has been used successfully in many countries and in many types of organizations to improve the quality of processes. The system is based upon the scientific method and provides the ability to solve long-standing, recalcitrant problems. The application of the TQM philosophy to health care, although recommended by many medical economists, is still in its infancy. At our medical center, three departments (Surgery, Anesthesiology, and Operating Room Services) joined forces to implement TQM. Critical activities early in implementation included establishing a Steering Committee, training key employees, providing systems for communicating TQM activities, and developing the leadership, facilitator, and other resources needed to support teams. Two of our first teams studied very different processes (one in the Operating Room, the other in outpatient Surgery clinics), providing many useful insights regarding keys to successful application of the TQM philosophy. We have learned strategies for increasing acceptance of and participation in TQM efforts on the part of staff members and, in particular, physicians, and for initiating the cultural change needed for TQM. Although the teams have met with resistance to behavioral changes and a lack of full support from some upper-level administrators in the Medical Center and the Hospital, most of them have been quite successful in improving the processes under study. We conclude that, with the proper leadership and facilitation, the TQM philosophy can be successfully implemented in the health care environment. Total Quality Management (TQM) as a system for improving the quality of processes has been successful in many countries throughout the world for organizations offering a wide variety of products and services. This article will describe specific TQM endeavors, both successful and unsuccessful, undertaken in an academic surgery department in the United States. This description will illustrate the lessons we have learned in our attempt to change a complex organization and will enable readers to determine whether an analogy exists between our organization's response to problem solving and theirs.

Academic Medical Centers↗
PubMed1994

Times to exhaustion at 100% of velocity at VO2max and modelling of the time-limit/velocity relationship in elite long-distance runners.

The aim of this study was to measure running times to exhaustion (Tlim) on a treadmill at 100% of the minimum velocity which elicits VO2max (vVO2max in 38 elite male long-distance runners (VO2max = 71.4 +/- 5.5 ml.kg-1.min-1 and vVO2max = 21.8 +/- 1.2 km.h-1). The lactate threshold (LT) was defined as a starting point of accelerated lactate accumulation around 4 mM and was expressed in %VO2max. Tlim value was negatively correlated with vVO2max (r = -0.362, p < 0.05) and VO2max (r = -0.347, p < 0.05) but positively with LT (% vVO2max) (r = 0.378, p < 0.05). These data demonstrate that running time to exhaustion at vVO2max in a homogeneous group of elite male long-distance runners was inversely related to vVO2max and experimentally illustrates the model of Monod and Scherrer regarding the time limit-velocity relationship adapted from local exercise for running by Hughson et al. (1984).

Adult↗