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Biomedical subjects

P Petit

Publications and source records attributed to P Petit.

At least 127 records · Page 7Linked to original sources
PubMed1996

[Electric burns: epidemiological and therapeutic aspects].

OBJECTIVES: A retrospective study of patients with electrical burns was conducted to choose criteria for initial dispatching and establish a treatment protocol for out patient management. METHODS: The study included 67 patients injured by electrical current and admitted at Edouard Herriot Hospital Burns Unit between January 1st 1990 and January 1st 1993. RESULTS: Low-voltage currents (< 1000 Volts) responsible for serious and immediate cardio-vascular diseases occurred in domestic accidents, mostly with children. High-voltage current (> 1000 Volts) responsible for deep burn injuries occurred in accidents at work and mostly with adults. Twenty-two were outpatients and 45 were admitted at once. Two died on admission, 24 were hospitalized less than five days, 11 required repeated surgical treatments and a long stay at hospital, and 8 were severely burned and were admitted to the intensive-care unit. Two required continuous venovenous hemodialysis for three weeks. Morbidity of the last three groups was nil, morbidity remained high in term of functional and aesthetic after-effects. CONCLUSION: Information on prevention of electrical burns should be intensified.

Accidents, Occupational↗
PubMed1996

Crystalline Ropes of Metallic Carbon Nanotubes

Fullerene single-wall nanotubes (SWNTs) were produced in yields of more than 70 percent by condensation of a laser-vaporized carbon-nickel-cobalt mixture at 1200degreesC. X-ray diffraction and electron microscopy showed that these SWNTs are nearly uniform in diameter and that they self-organize into "ropes," which consist of 100 to 500 SWNTs in a two-dimensional triangular lattice with a lattice constant of 17 angstroms. The x-ray form factor is consistent with that of uniformly charged cylinders 13.8 +/- 0.2 angstroms in diameter. The ropes were metallic, with a single-rope resistivity of <10(-4) ohm-centimeters at 300 kelvin. The uniformity of SWNT diameter is attributed to the efficient annealing of an initial fullerene tubelet kept open by a few metal atoms; the optimum diameter is determined by competition between the strain energy of curvature of the graphene sheet and the dangling-bond energy of the open edge, where growth occurs. These factors strongly favor the metallic (10,10) tube with C5v symmetry and an open edge stabilized by triple bonds.

Journal Article↗
PubMed1996

[Hemodynamic profile and serum cytokines in crush syndrome. Analogy with severe burns].

A 71-year-old woman remained under the rubble of her house for 4 hours after an accidental gas explosion. She suffered from a crush syndrome associating fractures, minor skin burns (< 10% body surface area), inhalation lung injury and moderate hypothermia (34 degrees C). In addition to local signs of compression of the lower limbs, the patient presented with hypovolemic shock and developed acute renal failure on day 3. We describe here the variations in hemodynamic and oxymetric parameters and cytokine response during the first post-injury week. A vasoplegic state resulting from low systemic vascular resistances with progressively increasing cardiac index, oxygen delivery and oxygen consumption closely followed the brief hypovolemic shock. Tumor necrosis factor-alpha remained below normal levels while interleukin-6 increased markedly with a major peak on day 2, in parallel with the drop in systemic vascular resistances. Interleukin-6 is a mediator of impairment in cell membrane function and a vasoconstriction inhibitor. Isolated increased interleukin-6 has been previously reported in severely burned patients suggesting a pathophysiological and hemodynamic similarity between crush syndrome and burn injury.

Aged↗
PubMed1996

Discrimination of respiratory dysfunction in yeast mutants by confocal microscopy, image, and flow cytometry.

Living yeast cells can be selectively stained with the lipophilic cationic cyanine dye DiOC6(3) in a mitochondrial membrane potential-dependent manner. Our study extends the use of flow cytometric analysis and sorting to DiOC6(3)-stained yeast cells. Experimental conditions were developed that prevented the toxic side effect of the probe and gave a quantitative correlation between fluorescence and mitochondrial membrane potential, without any staining of other membranes. The localization of the fluorochrome was checked by confocal microscopy and image cytometry. The mitochondrial membrane alterations were also tested through cardiolipin staining with nonyl acridine orange. Differences in light scattering and in fluorescence were detected in mutants (rho-, rho degrees, mit-, or pet-) and wild-type (rho+mit+) populations of yeast. The dye uptake of respiratory-deficient yeast strains was significantly reduced as compared to that of the wild-type. Application of an uncoupler (mCICCP), which collapsed the mitochondrial membrane potential (alphapsi(m)), led to a drastic reduction of the dye uptake. It was observed that a decrease in deltapsi(m), was usually correlated with a decrease in cardiolipin stainability by nonyl acridine orange (NAO). Quantitative flow cytometry is a fast and reproducible technique for rapid screening of yeast strains that might be suspected of respiratory dysfunction and/or mitochondrial structural changes. We give evidence that it is an adequate method to characterize and isolate respiratory mutants through sorting procedure, with selective enrichment of the population studied in respiring or non-respiring yeast cells. Confocal microscopy and image cytometry corroborate the flow cytometry results.

Acridine Orange↗
PubMed1996

[Severe burnt patients: hemodynamic state, oxygen transport and consumption, plasma cytokines].

OBJECTIVE: To assess the haemodynamic and oxymetric variations measured by a pulmonary artery catheter and to correlate them with the variations of the circulating cytokines during the initial intensive care phase of severely burned patients. STUDY DESIGN: Prospective study covering an 18-month period. PATIENTS: Thirteen successive patients, aged over 12 years, without significant medical history, with a thermal burn affecting more than 50 percent of their total body surface area and admitted to our centre during the first six postburn hours. METHODS: The haemodynamic and oxymetric profile was investigated by inserting a blood flow-directed balloon-tipped pulmonary artery fiberoptical catheter. All patients were treated according to the protocol previously used in our centre. Blood samples were drawn on admission, every 12 hours post-injury until the 2nd day, then on the 3rd and 5th days. Cytokines were analyzed by Elisa method. Haemodynamic and oxymetric measurements were achieved simultaneously with the biological samples during the first 5 postburn days. The analysis of variance (ANOVA) with the Duncan test was utilized for multiple comparisons between continuous variables. RESULTS: (mean +/- SEM): The patients were 32 +/- 3 years-old and had a burn surface of 72 +/- 4%. After a short hypovolemic shock period lasting a 12 hours, a hyperdynamic shock occured which increased until the 5th day, with an increased cardiac index (6.9 +/- 0.4 at h120 vs 2.9 +/- 0.3 L.min-1.m-2 at h6, P < 0.05), increased oxygen transport and consumption (respectively 880 +/- 77 at h72 vs 543 +/- 58 mL.min-1 at h12, P < 0.05 and, 203 +/- 15 at h72 vs 129 +/- 25 mL.min-1 at h6, P < 0.05) and markedly decreased systemic vascular resistances (1,002 +/- 118 at h36 vs 2,330 +/- 328 dyn.s.cm-5.m2 at h6, P < 0.05). Circulating cytokines were not clearly modified except for interleukine-6 which reached early striking peaks (16,858 +/- 10,330 at h24 and 15,406 +/- 6,509 pg.mL-1 at h36) simultaneously with the decrease in systemic vascular resistances. CONCLUSIONS: During the first post-injury week, critically burned patients develop a specific hyperdynamic circulatory status during which interleukine-6 could be a mainfactor decreasing systemic arterial resistances.

Adult↗
PubMed1996

Clonidine for major vascular surgery in hypertensive patients: a double-blind, controlled, randomized study.

The utility of clonidine for hypertensive patients presenting for major vascular procedures remains debatable. Twenty-one hypertensive patients presenting for aortic surgery were given clonidine (n = 11) or placebo (n = 10) in a double-blind, randomized manner. Clonidine was administered 6 micrograms/kg per os 120 min before induction of anesthesia and 3 micrograms/kg intravenously (i.v.) over 60 min from aortic declamping to skin closure. Anesthesia was induced with alfentanil 20 micrograms/kg, midazolam, and atracurium and maintained with nitrous oxide 70%, an alfentanil infusion (0.25 microgram.kg-1. min-1), and isoflurane. Anesthetic requirements, circulatory variables, interventions, and isoproterenol dose-response curves (pre- and postoperatively) were determined. Plasma concentrations of clonidine, alfentanil, and vasoactive hormones were measured. When the clonidine group was compared with the placebo group, (a) isoflurane, alfentanil, and midazolam requirements were reduced by 38%, 42%, and 41%, respectively (P = 0.04, 0.03, 0.0002, respectively); (b) supplemental circulatory and anesthetic adjustments were reduced by 51% (P = 0.0006); (c) interventions with vasopressors were not significantly increased (placebo: two; clonidine: five); (d) systolic and mean arterial pressures and heart rate were reduced; (e) increases in norepinephrine, epinephrine, and plasma renin activity were suppressed, whereas vasopressin surge was attenuated; and (f) chronotropic response to isoproterenol was unaffected. Clonidine was effective in reducing anesthetic requirements and in improving circulatory stability in hypertensive patients presenting for major vascular procedures.

Administration, Oral↗
PubMed1996

On two patients with and without the classical Wolf-Hirschhorn syndrome (WHS) sharing the same chromosome 4p16.3 specific probe deletion: evidence of a contiguous gene deletion syndrome.

We report here on phenotype-karyotype correlations in two patients with and without complete features of the WHS but sharing the lack of a specific cosmic probe (D4S96/D4Z1) from 4p16.3. These findings indicate that WHS is true a contiguous gene deletion syndrome in nature and expression.

Abnormalities, Multiple↗
PubMed1996

Study of the mechanisms involved in adenosine-5'-O-(2-thiodiphosphate) induced relaxation of rat thoracic aorta and pancreatic vascular bed.

1. The endothelium-dependent relaxation of blood vessels induced by P2Y-purinoceptor activation has often been shown to involve prostacyclin and/or nitric oxide (NO) release. In this work, we have investigated the mechanisms involved in the relaxant effect of the P2Y agonist, adenosine -5'-O-(2-thiodiphosphate) (ADP beta S) using two complementary preparations: rat pancreatic vascular bed and aortic ring. 2. On the pancreatic vascular bed, ADP beta S (1.5 and 15 microM) infused for 30 min induced a concentration-dependent vasodilatation; it was progressive during the first 10 min (first period) and sustained from 10 to 30 min (second period). Indomethacin (10 microM) delayed ADP beta S-induced vasodilatation (1.5 and 15 microM) by about 6 min. N omega-nitro-L-arginine methyl ester (L-NAME) (200 microM) suppressed the relaxation for about 5 min but thereafter ADP beta S at the two concentrations progressively induced an increase in the flow rate. Even the co-administration of L-NAME and indomethacin did not abolish the ADP beta S-induced vasorelaxation. 3. On 5-hydroxy tryptamine (5-HT) precontracted rings mounted in isometric conditions in organ baths, we observed that ADP beta S induced a concentration-dependent relaxation of rings with a functional endothelium; this effect was stable for 25 min. The ADP beta S relaxant effect was strongly inhibited by Reactive Blue 2 (30 microM) and was suppressed by pretreatment of rings with saponin (0.05 mg ml-1 for 30 min), which also abolished the acetylcholine-induced relaxation. 4. ADP beta S-induced relaxation of 5-HT precontracted rings is largely inhibited by indomethacin (100 or 10 microM) or L-NAME (100 microM). 5. We conclude that: the ADP beta S-induced relaxation is endothelium-dependent, mediated by P2Y-purinoceptors, and at least in part linked to NO and prostacyclin release, depending on the preparation used. Furthermore, on the pancreatic vascular bed, (an)other mechanism(s) than prostacyclin and NO releases may be involved in ADP beta S-induced vasodilatation.

Adenosine Diphosphate↗
PubMed1996

Differences in the distribution and nature of the interstitial telomeric (TTAGGG)n sequences in the chromosomes of the Giraffidae, okapai (Okapia johnstoni), and giraffe (Giraffa camelopardalis): evidence for ancestral telomeres at the okapi polymorphic rob(5;26) fusion site.

Intrachromosomal telomeric sequences (TTAGGG)n were analyzed in the two members of the family Giraffidae, the giraffe and the okapi. The giraffe has a diploid chromosome number of 2n = 30, whereas the okapi chromosome number varies from 2n = 46 to 2n = 45 and 2n = 44 due to a "recent" Robertsonian fusion event. The interstitial telomeres that we detected in these species are of two types: (1) In the okapi, a long interstitial telomeric element is present at the fusion site of the rob(4;26). The nature of this interstitial telomeric element suggests that it is a remnant of the telomeres of the ancestral chromosomes that participated in the fusion event. (2) In the giraffe, short stretches or degenerate telomeric sequences which are part of the satellite DNA are present at intrachromosomal sites. The results of this study provide insights into the origin of interstitial telomeric sequences in the Giraffidae.

Animals↗
PubMed1996

Acute fracture of the distal tibial physis: role of gradient-echo MR imaging versus plain film examination.

OBJECTIVE: Recent reports indicate that, compared with MR imaging, plain film radiography often underestimates the extent of injury in children with physeal fracture-separation. Such underestimation may have significant therapeutic and prognostic outcomes. We performed this study to assess the benefit of MR imaging compared with plain film radiography in the diagnosis and immediate treatment of acute fractures of the distal tibial physis. SUBJECTS AND METHODS: Twenty-nine patients with acute fractures, including 15 Salter-Harris II, four Salter-Harris III, four Salter-Harris IV, and six triplane fractures, were prospectively examined by MR imaging with gradient-echo sequences. The MR images were compared with plain film radiographs. All cases were reviewed in a blind fashion by two experienced radiologists to determine the Salter-Harris classification on the basis of first plain film radiographs and then MR images. Two experienced pediatric surgeons were asked to propose treatment on the basis of first plain film radiographs and then MR images. Both the radiologists and the surgeons were asked to rate the two techniques in terms of degree of confidence and overall diagnostic effectiveness. RESULTS: Only 1 or 29 fractures (3%) was misclassified by plain film radiography. MR imaging never caused the treatment plan to be modified. However, the position of fracture fragments in Salter-Harris IV and triplane fractures was always better appreciated on MR images, facilitating more accurate surgical treatment. Except for those in the misclassified fracture, all other fracture lines were seen on both plain film radiographs and MR images but were more easily seen on MR images. CONCLUSION: Gradient-echo MR imaging allowed easier assessment of fracture lines than did plain film radiography, but the latter technique remains the primary means of evaluating epiphyseal injuries. For acute fractures of the lower extremity of the tibia, gradient-echo MR imaging should be limited to complex fractures and to cases in which the classification of a fracture on the basis of plain film evaluation is uncertain.

Acute Disease↗
PubMed1995

Clonazepam in acute mania: time-blind evaluation of clinical response and concentrations in plasma.

This study was performed to evaluate the optimal doses and clinical efficacy of clonazepam as a first-line drug in acute mania, as well as to determine its effective plasma concentrations. Clonazepam was administered orally to 11 newly admitted inpatients. On day 0, the loading dose was titrated upward according to the clinical global impression; the maintenance dose was calculated with intent to maintain the plasma level that had been achieved after initial dose escalation. Clinically based dose adjustments were allowed on days 4 and 7. Manic symptoms were scored on days 0, 4 and 14 according to a time-blind procedure; clonazepam plasma levels were measured by HPLC. On day 14, there was a significant decrease in manic symptoms and 66.7% of the patients who completed the trial were markedly improved. Steady-state plasma levels of clonazepam were significantly correlated with daily doses (rs = 0.795, P < 0.005) and therapeutic concentrations ranged between 6.5-83.9 micrograms/l. At the onset of therapy, the clinically titrated loading dose resulted in plasma concentrations within the narrow range of 18.9-34.0 micrograms/l. These results support the potential value of clonazepam in the short-term management of acute mania; the initial control of agitation was achieved with plasma drug levels in a remarkably narrow range as compared with the further control of mania.

Acute Disease↗
PubMed1995

Non-invasive continuous haemodynamic and PETCO2 monitoring during peroperative cardiac arrest.

We describe a cardiac arrest which occurred during general anaesthesia in the prone position for surgical correction of lumbar kyphosis in a patient with Marfan's syndrome. Peroperative monitoring was routine with ECG, non-invasive arterial pressure, oximetry, PETCO2 and central venous pressure, plus aortic blood flow and and systolic time intervals via an oesophageal echo-Doppler device. Forty-five minutes after the start of surgery, a sudden decrease in aortic blood flow followed by a decrease in PETCO2 suggested acute cardiac failure despite continuation of the ECG signal. Initial CPR in the prone position produced a slight increase in PETCO2. When the patient was turned to the supine position and the legs elevated, chest compression was more efficient and spontaneous circulation was rapidly restored. Circulatory arrest could be explained by incompletely treated hypovolaemia, or by myocardial depression (decrease in aortic blood flow and lengthened pre-ejection period) combined with excessive hypotension in a patient with Marfan's syndrome, thus compromising coronary blood flow producing ST segment depression. Continuous non-invasive aortic blood flow and PETCO2 monitoring proved valuable in the early detection and treatment of circulatory arrest and in the evaluation of the efficiency of peroperative CPR.

Adolescent↗