Biomedical subjects

G Atlan

Publications and source records attributed to G Atlan.

At least 19 recordsLinked to original sources

PubMed1999

Interface between bone and nacre implants in sheep.

We have investigated the interface between bone and chronic implants of nacre in sheep. There was no foreign body reaction over the period of 10 months and the implants were not broken down. Light microscopy indicated activity within an osteoprogenitor cellular layer lining the implant, resulting in a complete sequence of new bone formation. Nacre appeared to bind directly to newly formed bone without any intervening fibrous tissue. Scanning electron microscopy and energy dispersive photon X-microanalysis showed calcium and phosphate ions lining the nacre within the osteoprogenitor tissue. These studies show a dynamic activity of the bone/nacre interface, leading to continuity between the nacre and the bone.

Animals↗

PubMed1998

Pharmacological and molecular characterisation of beta-adrenoceptors in adult rat diaphragm muscle.

Using pharmacological and molecular approaches to investigate beta-adrenoceptor (beta-AR) subtype expression in adult rat diaphragm, we found that adenylyl cyclase (AC) was potently stimulated by the beta2-AR-selective agonist fenoterol, weakly stimulated by the beta1-AR-selective agonist prenalterol and unaffected by the beta3-AR agonist CGP12177. AC activity in response to a submaximal isoproterenol concentration was potently inhibited by the beta2-AR-selective antagonist ICI118551, whereas the beta1-AR-selective antagonist CGP20712A was effective only in very high concentrations. (-)-[125I]-cyanopindolol ([125I]-CYP) saturation binding experiments indicated a single affinity component (dissociation constant (Kd) = 22 +/- 2 pM) for beta-AR sites (maximal beta -AR density (Bmax) = 14 +/- 2 fmol/ mg). Eadie-Hofstee analysis of [125I]-CYP displacement curves by beta1-, beta2- or beta3-AR-selective ligands allowed to characterise a homogeneous population of beta2-AR sites. Finally, reverse transcriptase-polymerase chain reaction analysis of beta-AR subtype mRNAs identified beta2-AR transcripts but no beta1- and beta3-AR mRNAs. Our results demonstrate that beta2-AR is the only beta-AR subtype expressed in the diaphragm.

Adenylyl Cyclases↗

PubMed1998

Pulmonary function in sickle cell disease with or without acute chest syndrome.

Recurrent acute chest syndrome (ACS) has been suggested as a risk factor for chronic lung dysfunction in sickle cell disease. To investigate this hypothesis, lung function tests were performed in 49 sickle cell disease outpatients whose condition was stable, including 23 patients with a history of two to four episodes of ACS (ACS+) and 26 with no history of ACS (ACS-). The two groups were comparable regarding the sex ratio, body mass index, smoking history, physical characteristics, clinical history and usual lung function tests. Respiratory resistance (Rrs), measured using the forced oscillation technique, increased with the number of ACS episodes (r=0.55, p<0.0001) and a significant relationship was observed between Rrs as an independent variable and the expiratory flow rates at 25, 50 and 25-75% of the forced vital capacity as explanatory variables (r= 0.36, p<0.02; r=0.35, p<0.02; and r=0.4, p<0.006, respectively), with higher Rrs being associated with lower expiratory flow rates. The transfer factor (TL,CO) and transfer coefficient (KCO) for CO were significantly higher in the ACS+ group than in the ACS-group (TL,CO=84+/-4 versus 71+/-3%, p<0.004 and KCO=102+/-5 versus 90+/-3%, p<0.05, respectively). The data demonstrate that obstructive lung dysfunction is fairly common in sickle cell disease and suggest that recurrent acute chest syndrome may contribute specific obstructive defects. The increase in respiratory resistance associated with acute chest syndrome was accompanied by an increase in diffusion capacity, suggesting that it may have been related to an increase in lung blood volume.

Acute Disease↗

PubMed1997

Reconstruction of human maxillary defects with nacre powder: histological evidence for bone regeneration.

The defective areas in the premolar-molar region of maxillary alveolar bone of eight patients were reconstructed using powdered nacre from the giant oyster Pinctada maxima. Histological, microradiographic and polarized light studies of drill biopsies taken 6 months postoperatively showed that nacre was tightly bound to newly-formed bone. The nacre was gradually and centripetally biodissolved and replaced with immature and then mature lamellar bone. These results are in agreement with our previous experimental in vitro data indicating that nacre has good osteogenic properties.

Animals↗

PubMed1997

Correction of valvular obstruction through a dorsonasal approach.

Since 1975, 210 patients have been operated for nasal valvular obstruction. A dorsonasal approach was chosen, allowing direct control of the correction with peroperative patient cooperation. The analysis of the results shows a complete relief of the airflow impairment and a very acceptable scar in nearly three-quarters of the patients.

Cicatrix↗

PubMed1997

Cervical chrondrocutaneous branchial remnants.

Similar in appearance to preauricular tags but located in the lateral neck, cervical chondrocutaneous branchial remnants are a rather less common and less well known congenital lesion. A retrospective review of admissions at Sainte-Justine Hospital between 1980 and 1993 produced 20 cases of cervical tags, of which 17 were true cervical chrondrocutaneous branchial remnants and 3 were skin tags associated with a thyroglossal duct. Of the 17 true cervical chrondrocutaneous branchial remnants, 15 were operated on in our institution. The clinical characteristics, results of investigations, surgical data, pathologic findings, and associated anomalies were documented. Several interesting facts emerged, including a male predominance (11 of 17), a scarcity of bilateral lesions (1 of 17), the presence of an elastic cartilage core in all operated specimens (15 of 15), and a high incidence of associated anomalies (13 of 17). We suggest that the second branchial arch is the most likely origin for the lesion. We propose a clear, widely acceptable name for this anomaly in order to prevent further diagnostic confusion. Most important, although simple surgical excision is all that is required for treatment, a complete physical examination of the patient and possibly an ultrasound examination of the genitourinary tract are recommended because a cervical chrondrocutaneous branchial remnant has proven in many cases to be a visible "marker" for more serious associated anomalies.

Abnormalities, Multiple↗

PubMed1996

Rat diaphragm during postnatal development. I. Changes in distribution of muscle fibre type and in oxidative potential.

The changes occurring in the histochemical characteristics of the rat diaphragm during the postnatal period were examined. Fibre-type distribution, fibre oxidative capacity, i.e. succinate-dehydrogenase (SDH) activity, and cross-sectional area were compared in the costal (COS) and crural (CRU) regions, and across their abdominal and thoracic surfaces. The proportions of type I and IIb fibres in both COS and CRU increased with age, while the proportion of type IIa fibres progressively decreased. For COS, fibre distribution was homogeneous over the entire muscle and did not change after 4 weeks. For CRU, it was heterogeneous with a higher proportion of type I fibres on the thoracic surface as from the first week. All fibre types significantly increased in cross-sectional area between 1 and 8 weeks, with no significant differences in COS and CRU. Mean SDH activity did not differ between COS and CRU or across the muscles. Mean SDH activitiĕs-were low and identical in all fibre types at birth, and then increased, peaking at the 6th week in type I and IIa fibres. When total muscle fibre oxidative capacity was calculated from an index including fibre-type proportion, cross-sectional area and mean SDH activity, it was significantly higher at 1 than at 8 weeks after birth; this might have functional implications for the newborn.

Animals↗

PubMed1996

Rat diaphragm during postnatal development. II. Resistance to low- and high-frequency fatigue.

The effects on the rat diaphragm of fatigue induced by low- and high-frequency stimulation (at 5 Hz for 1.5 min and 75 Hz for 1 min) were examined during postnatal development. Experiments were performed on isolated costal diaphragm strips. Before stimulation, twitch contraction time and half relaxation time were longest in the neonate and decreased significantly between weeks 1 and 6. Correspondingly, the specific twitch tension (corrected for cross-sectional area) increased progressively with age. After either low- or high-frequency fatigue, the force recovery was complete in 1- and 2-week-old rats, whereas the force production progressively decreased in older rats. In addition, the neonate diaphragm further enhanced its force selectively after high-frequency fatigue. It is concluded that the rat diaphragm is comparably resistant to fatigue during the early postnatal period, whether fatigue is induced by low- or by high-frequency stimulation. This suggests that postnatal changes in diaphragm contractile and fatigue properties may be related to changes in the process of force production. The possibility is discussed that a higher total muscle oxidative potential and the mechanisms leading to force potentiation in the neonate might explain the fatigue resistance.

Animals↗

PubMed1996

Pulmonary clearance and lung function: influence of acute tobacco intoxication and of vitamin E.

Cigarette smoking increases the alveolar epithelial permeability to small solutes, as assessed by the pulmonary clearance of aerosolized 99mTc-labeled diethylenetriaminepentaacetate. The involvement of lipid peroxidation in this increased clearance was tested in eight asymptomatic young smokers by investigating the effects of a 3-wk supplementation with oral vitamin E (1,000 IU/day) on pulmonary clearance according to a protocol designed as a single-blind crossover study. Indexes of acute tobacco intoxication (exhaled CO, carboxyhemoglobin, and urinary cotinine) and lung function parameters [including Krogh factor (KCO)] were also studied. Under control conditions, pulmonary clearance was abnormally increased (2.93 +/- 0.78%/min), whereas KCO was in the normal range. Pulmonary clearance correlated strongly with expired CO (P < 0.04), HbCO (P < 0.005), urinary cotinine (P < 0.003), and KCO (P < 0.004). Supplementation with vitamin E, a highly efficient antioxidant, neither decreased the pulmonary clearance nor altered the above correlations. However, the strong correlations observed between pulmonary clearance and indexes of acute tobacco intoxication, which reflect the amount of inhaled smoke and the resultant oxidant stress, do not allow exclusion of the involvement of lipid peroxidation in the pulmonary clearance increase observed in smokers.

Adult↗

PubMed1995

Laparoscopic cholecystectomy minimally impairs postoperative cardiorespiratory and muscle performance.

Surgery elicits a subjective feeling of postoperative fatigue, at least partly related to an impairment in cardiorespiratory function and muscle performance. Laparoscopic surgery is reported to impair the patient's condition minimally. The aim of this study was to assess exercise performance in patients scheduled for elective laparoscopic cholecystectomy. Nine patients assessed as having American Society of Anesthesiologists (ASA) grade I were enrolled in the study. Subjective feelings of fatigue (measured on a visual analogue scale), and heart rate, systemic arterial pressure oxygen consumption and carbon dioxide production responses to graded exercise testing, were assessed before operation and on days 3 and 10 after operation. There were no significant differences in any of these measurements, at rest or during exercise, between the preoperative and postoperative values. Uncomplicated laparoscopic cholecystectomy does not impair postoperative cardiorespiratory and muscle performance or induce significant postoperative fatigue in patients with ASA I, allowing rapid recovery.

Blood Pressure↗

PubMed1995

Inhibition of nitric oxide synthesis in the forearm arterial bed of patients with advanced cirrhosis.

Increased vascular production of nitric oxide (NO) may contribute to the peripheral vasodilation and hyperdynamic state complicating advanced liver cirrhosis. In this study, we examined the effect on forearm blood flow of local brachial artery infusion of noradrenaline (NA) and NG-monomethyl-L-arginine (L-NMMA), an inhibitor of NO-synthase, in 10 alcoholic ascitic cirrhotic patients (patients with decompensated alcohol-induced liver disease: DALD group) and 10 patients with well-compensated alcohol-induced liver disease (CALD group). Forearm blood flow was measured by venous occlusion plethysmography. As compared with the CALD group, the DALD group had higher cardiac index and forearm blood flow as well as lower systemic blood pressure and vascular resistance. Infusions of NA and L-NMMA produced similar reduction in resting blood flow in the CALD group. However, in the DALD group, NA was significantly less effective than L-NMMA. The forearm vasoconstrictor response to NA was also significantly reduced in the DALD group when compared with the CALD group. In the DALD group, NA decreased forearm blood flow by 21.0 +/- 6.2% and increased vascular resistance by 37.2 +/- 12.3%, whereas respective changes in the CALD group were 41.8 +/- 6.2% (P < .01) and 77.8 +/- 9.9% (P < .02). In contrast, L-NMMA induced greater forearm vasoconstriction in the DALD group than in the CALD group. In decompensated patients, L-NMMA decreased forearm blood flow by 50.4 +/- 2.7% and increased vascular resistance by 115.9 +/- 14.4%, whereas changes in compensated patients were 38.2 +/- 4.9% (P < .05) and 77.4 +/- 16.2% (NS), respectively. These results are consistent with the hypothesis that increased vascular synthesis of NO contributes to the high dynamic state of patients with advanced cirrhosis.

Arginine↗

PubMed1994

Bicoronal incision for nasal bone grafting.

The use of bicoronal incisions has been sufficiently described in neurosurgery and craniofacial surgery including osteotomies and injuries. This approach provides excellent surgical access for nasal reconstruction with a very low rate of morbidity. A series of 11 patients, together with three case reports, illustrates the advantages and possible complications of this type of incision.

Adolescent↗

PubMed1994

Vitamin E does not prevent exercise-induced increase in pulmonary clearance.

It has been observed that sustained exercise results in a prolonged increase in alveolar epithelial permeability, as assessed by the pulmonary clearance rate of aerosolized 99mTc-labeled diethylenetriaminepentaacetate (Lorino et al. J. Appl. Physiol. 67: 2055-2059, 1989). The involvement of lipid peroxidation in this increased permeability was tested in seven nonsmoking volunteers by comparing the exercise-induced increases in pulmonary 99mTc-diethylenetriaminepentaacetate clearance before and after a 3-wk supplementation with oral vitamin E (1,000 IU/day), according to a protocol designed as a single-blind crossover study. The 60-min exercise was performed on a treadmill at a constant load corresponding to 80% of maximal O2 uptake. Administration of vitamin E, a very important antioxidant, did not reduce the exercise-induced increase in lung clearance, suggesting that the exercise-induced increase in lung epithelial permeability does not primarily result from the occurrence of lipid peroxidation in the alveolar membrane. This result thus corroborates the hypothesis of an alteration of the intercellular tight junctions due to the mechanical effects of hyperventilation.

Administration, Oral↗

PubMed1993

[Necrosis of the columella after prolonged intranasal intubation].

A case is reported of necrosis of the columella nasi due to prolonged intubation in a 21-year-old road traffic accident patient. He was intubated by the nasal route because of combined head and facial injuries. The necrosis was discovered during surgery for repair of the bony facial injuries. As the patient was in a poor condition, the lesion was not immediately repaired, and the necrotic area was only removed. Definitive repair was carried out four and a half months later, with closure of the oronasal communication with an intravelar veloplasty. Such maxillofacial complications of prolonged endotracheal intubation are rare. They are related to prolonged vascular compression by the tube. Such accidents must be recognized without any delay by carefully examining patients.

Adult↗

PubMed1993

Effects of obesity on respiratory resistance.

To assess the effects of obesity on pulmonary function, 46 healthy subjects exhibiting various degrees of obesity underwent lung function tests. Subjects were divided into three groups according to body mass index (BMI): 13 had minimal obesity (BMI, 25 to 29 kg/m2, group 1); 24 had a BMI in the 30 to 40 range (group 2); and 9 displayed to morbid obesity (BMI > 40, group 3). Respiratory resistance was estimated by the forced random noise oscillation technique and airway resistance was determined by body plethysmography. Lung volumes and expiratory flows were also determined and significant negative correlations with BMI were found. Expiratory flows diminished in proportion to lung volumes, and the ratio of forced expiratory volume in 1 s to forced vital capacity was within normal limits. Although expiratory flows did not suggest bronchial obstruction, both respiratory resistance and airway resistance rose significantly with the level of obesity (p < 0.005 and p < 0.025, respectively), from 3.2 (+/- 0.02) and 3.2 (+/- 0.02) cm H2O.s.L-1, respectively, in group 1, to 5.5 (+/- 0.06) and 5.0 (+/- 0.05), respectively, in group 3. Evaluation of the factors responsible for this increased resistance disclosed a significant linear correlation between airway conductance and functional residual capacity (r = 0.70, p < 10(-4)), but specific airway conductance was found to be independent of the degree of obesity. The difference between respiratory resistance and airway resistance did not widen significantly according to the level of obesity, suggesting that chest wall resistance was not a factor enhancing these resistances. Taken together, these findings suggest that in addition to the elastic load, obese subjects have to overcome increased respiratory resistance resulting from the reduction in lung volumes related to being overweight.

Adolescent↗

PubMed1993

[The contribution of modern medical imaging in post-traumatic carotid-cavernous fistula. Apropos of a case].

Carotid-cavernous fistulas are unusual complications of facial traumas but this life-threatening complication requires a rapid diagnosis. Noninvasive procedures as ultrasounds will confirm the diagnosis and are helpful to demonstrate hemodynamic conditions of the fistula. Angiography remains the main radiologic examination and embolization is now the preferred method of treatment. Surgical treatment will only be required after failure of the interventional radiology.

Adult↗

PubMed1993

Assessment of the respiratory compliance in awake subjects using pressure support.

Pressure support (PS), a new mode of ventilatory assistance, is known to induce respiratory muscle relaxation. It was used to obtain reliable measurements of the compliance of the respiratory system (Crs) in awake subjects. PS was applied, through a mouthpiece, at four successive levels (0, 0.75, 1 and 1.25 kPa) to 30 healthy subjects. At the highest PS level, the subject's relaxation was obtained as assessed by a decrease in the occlusion pressure from 0.10 +/- 0.06 to 0.05 +/- 0.04 kPa, whereas the minute ventilation increased (from 7.5 +/- 1.5 to 13.8 +/- 3.3 l.min-1), and the end-tidal carbon dioxide tension (PCO2) decreased (from 5.0 +/- 0.4 to 3.2 +/- 0.5 kPa) below its apnoea threshold. In three subjects, respiratory muscle relaxation was confirmed by a fall in diaphragmatic electromyographic activity. Crs was calculated as the ratio of the tidal volume to the corresponding end-inspiratory airway pressure (i.e. PS level) since, at end inspiration, a zero-flow period was obtained. Crs was highly correlated (r = 0.77) to the height (Ht) of the subjects: Crs (l.kPa-1) = 3.56 x Ht (m) -4.86 (+/- 0.23), allowing normal values to be determined. In order to evaluate the applicability of the method to patients, Crs was measured in four patients with scoliosis, and was found to range from 45-82% of the predicted values. It is suggested that this simple method of Crs determination may be used to characterize various chest wall or pulmonary diseases.

Adult↗

PubMed1992

Myoelectrical and metabolic changes in muscle fatigue.

In isometric contraction-induced fatigue force loss has been related to mostly myoelectrical or intramuscular events. However, some factors potentially involved may interfere at more than one site in these events and it has proven difficult to distinguish between those influences. The study of the relationships between force generating capacity, the metabolic state of a muscle and its myoelectrical properties may therefore help broaden our understanding of the fatigue process. In order to investigate these relationships, we have evaluated changes in force-generating capacity, NMR-determined metabolic variables, and myoelectrical activity, as measured from surface EMG, simultaneously in brachial biceps muscle of healthy subjects, during different types of fatiguing isometric exercise and during recovery. Factors studied include intramuscular pH, inorganic phosphate and its diprotonated form concentrations, root-mean square and mean power frequency of the EMG power spectrum, and neuromuscular efficiency index. Results show that different mechanisms are likely to contribute to force loss in fatiguing muscle and during different phases of recovery from fatigue. Indeed, relationships between variables from the three groups differed according to exercise protocol as well as in fatiguing and recovering muscle.

Electromyography↗