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Biomedical subjects

R Vincent

Publications and source records attributed to R Vincent.

At least 91 records · Page 5Linked to original sources

Ossiculoplasty with J.B. Causse composite prostheses: our experience with 500 cases.

In ossicular pathology, many options are available when the restoration of the columellar effect is required. Autoplasty, heteroplasty and homoplasty have advantages and disadvantages, but considerable recent progress in development of the prosthesis has changed the state of the situation. 500 partial and total prostheses (Porp and Torp) of composite material (Flex HA and Teflon HA) designed by Jean-Bernard Causse and developed by Microtek, were used from January 1992 until December 1993. The authors present results at short and middle term involving all aspects of otologic surgery, as well as surgical techniques that were used.

Biocompatible Materials↗

Cellular kinetics in the lungs of aging Fischer 344 rats after acute exposure to ozone.

Lung repair in aging Fischer 344 male rats was investigated after an acute inhalation exposure to ozone. Adult (9-month-old) and senescent (24-month-old) rats were exposed to 0.8 ppm ozone for a single period of 6 hours, and thereafter studied over 5 days of recovery in clean air. The animals were given intraperitoneal injections of colchicine and [3H]thymidine, 4 hours and 1.5 hours before termination, respectively. The lungs were inflated with glutaraldehyde, and tissue samples were embedded in epoxy resin for electron microscopy, or in glycol methacrylate for light-microscopic autoradiography. Exposure to ozone produced epithelial injury in alveolar ducts and terminal bronchioles, later reflected by the transient increase in mitotic activity of nonciliated bronchiolar cells and alveolar type 2 cells. The increase in metaphase-arrested cells and [3H]thymidine-labeled cells in bronchioles followed similar time courses, ie, maximal at days 1.5 to 2, and subsiding by day 3. In the alveoli, type 1 cell necrosis was observed early after exposure (6 hours recovery), without notable structural changes in the interstitial and endothelial compartments. The increased mitotic activity in the alveolar septa was mostly due to proliferation of epithelial type 2 cells, which was maximal at day 1.5, and of interstitial cells, maximal at day 2.5. The magnitude of the mitotic responses of nonciliated bronchiolar cells, alveolar type 2 cells and interstitial cells was highest (+50%) in the lungs of senescent rats. Although the cellular events during repair are essentially similar in both age groups, the results indicate that senescent rats have a significantly higher level of initial injury from inhalation of ozone than adult animals.

Administration, Inhalation↗

Poor vibration of inner ear fluids as a cause of low tone tinnitus.

Tinnitus due to otosclerosis may be caused by poor vibration of the inner ear fluids. The goal of this article is to suggest some explanations, to enhance future research work carried out by other authors on this important issue, and to show what are the results of surgery to relieve tinnitus in the author's experience. Only complete resolution of the tinnitus 1 year after surgery was taken into account in the assessment of the results.

Adult↗

Differential transcriptional activities of HLA-DR genes in the various haplotypes.

The regulation of HLA class II genes is of particular interest with regard to the modulation of the immune response. The polymorphism of their coding regions is directly involved in the specificity of the Ag presentation, and their level of expression affects the extent of T cell activation. Previously, we have described an allelic polymorphism in the proximal promoter regions of HLA-DRB genes. The aim of this study was to compare the transcriptional activities of the promoters of the DRB genes and DRB1 alleles in a transient expression system. We have demonstrated a marked difference in their promoter strengths, as determined by their relative abilities to initiate transcription of the chloramphenicol acetyltransferase reporter gene in human B cell lines. The polymorphism of the promoter regions has been mapped to the regulatory boxes, and, by using gel retardation experiments, we found a differential ability of the nuclear proteins to bind to the partially conserved X box regions. Taken together, our results demonstrate the functional consequences of the allelic polymorphism of the proximal promoter regions of the DRB genes. These findings strongly suggest the existence, for the HLA-DR genes, of an interdependence between the polymorphism of the coding regions, which directly affects the capacity of peptide binding, and the polymorphism of the regulatory regions, which influences the transcriptional activities of the promoters.

Base Sequence↗

Occupational exposure to organic solvents during paint stripping and painting operations in the aeronautical industry.

The exposure of workers to methylene chloride and phenol in an aeronautical workshop was measured during stripping of paint from a Boeing B 747. Methylene chloride exposure was measured during two work days by personal air sampling, while area sampling was used for phenol. During paint stripping operations, methylene chloride air concentrations ranged from 299.2 mg/m3 (83.1 ppm) to 1888.9 mg/m3 (524.7 ppm). The exposures to methylene chloride calculated for an 8-h work day ranged from 86 mg/m3 (23.9 ppm) to 1239.5 mg/m3 (344.3 ppm). In another aeronautical workshop, exposure to organic solvents, especially ethylene glycol monoethylether acetate (EGEEA), was controlled during the painting of an Airbus A 320. The external exposure to solvents and EGEEA was measured by means of individual air sampling. The estimation of internal exposure to EGEEA was made by measuring its urinary metabolite, ethoxyacetic acid (EAA). Both measurements were made during the course of 3 days. The biological samples were taken pre- and post-shift. During painting operations, methyl ethyl ketone, ethyl acetate, n-butyl alcohol, methyl isobutyl ketone, toluene, n-butyl acetate, ethylbenzene, xylenes and EGEEA were detected in working atmospheres. For these solvents, air concentrations ranged from 0.1 ppm to 69.1 ppm. EGEEA concentrations ranged from 29.2 mg/m3 (5.4 ppm) to 150.1 mg/m3 (27.8 ppm). For biological samples, the average concentrations of EAA were 108.4 mg/g creatinine in pre-shift and 139.4 mg/g creatinine in post-shift samples. Despite the fact that workers wore protective respiratory equipment during paint spraying operations, EEA urinary concentrations are high and suggest that percutaneous uptake is the main route of exposure for EGEEA.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollutants, Occupational↗

Adrenaline-responsive electromechanical dissociation.

Electromechanical dissociation (EMD) occurs when there is no detectable blood pressure in the presence of organised electrocardiographic activity. This condition excludes pulseless ventricular tachycardia, and traditionally was thought to result from a failure of electrical depolarisation in the myocardium to elicit mechanical contraction. It is now understood from echocardiographic evidence that 'pseudo-EMD' is more common-where electrical activity is associated with myocardial contractions too weak to sustain a detectable blood pressure [1]. Three cases of EMD in association with subarachnoid haemorrhage (SAH) are described. This form of cardiovascular collapse appears to respond readily to the use of adrenaline. To our knowledge, this has not been reported previously. We suggest that this form of EMD occurs despite adequate myocardial function and results from sympathetic failure with loss of peripheral vascular resistance.

Adult↗

Quantitative immunocytochemical analysis of Mn SOD in alveolar type II cells of the hyperoxic rat.

We have analyzed the magnitude and uniformity of the expression of manganese superoxide dismutase (Mn SOD) protein in alveolar type II cells of rats exposed to hyperoxia using quantitative colloidal gold immunocytochemistry and morphometric techniques. Sprague-Dawley rats were exposed continuously to normal air or to 85% oxygen for 7 and 14 days. The lungs were fixed by intratracheal instillation of a paraformaldehyde-glutaraldehyde fixative. Lung samples were dehydrated in ethanol and embedded in LR-White. Thin sections for electron microscopy were labeled with anti-rat Mn SOD rabbit antiserum followed by protein-A gold. The labeling density (gold particles/micron 2) over subcellular compartments was determined, and relative organelle volumes were measured using a random point overlay. The results confirm that alveolar type II cells are a locus of Mn SOD response in the lungs of hyperoxic rats and contribute to this response through a combination of changes: an increase of Mn SOD concentration in the mitochondrial matrix, an increase of mitochondrial volume per cell, and type II cell hyperplasia.

Animals↗

Ossiculoplasty with composite prostheses. Overview and analysis.

Aeration of a mucosa-lined tympanic cavity is essential for a functioning middle ear. Extrusions of even the best-designed prostheses occur from abnormal middle ear conditions such as atelectasis, middle ear fibrosis, recurrent cholesteatoma, tympanic membrane perforation, and otitis media. Various polymers have been developed in an attempt to maximize prosthetic biocompatibility and ease of use while minimizing the chance of extrusion. One such polymer is a composite of hydroxyapatite and Silastic, known as Flex H/A. This material has been incorporated into two ossicular prostheses, the Universal Plus and the Causse Flex H/A prostheses. Certainly, refinements will continue to be made in the chemical makeup of the bioceramics in order to achieve optimal biocompatibility. In addition to biocompatibility, cost containment issues have influenced the development of ossicular prostheses. A universal prosthesis eliminates the need to stock multiple designs, thereby reducing the cost to institutions. One of the greatest challenges in the future will be to define the appropriate prosthetic design for optimal sound transmission. Consideration of prosthesis weight, head size, and footplate attachment are future research questions that need to be addressed in a scientific biologic model.

Biocompatible Materials↗

Space-group determination of human tooth-enamel crystals.

In the present work, we have determined the space group of human tooth-enamel crystals using--for the first time for a biological crystal--convergent beam electron diffraction (CBED). The symmetries observed in the different patterns we have obtained lead us to the P6(3)/m hydroxyapatite space group. Disorder, most likely situated in the columns formed by the hydroxyl ions of the crystals, is suggested as a cause of weak intensity in the otherwise forbidden 000l (l odd) reflections and low visibility of first-order Laue zone (FOLZ) reflections in the CBED pattern from crystals oriented along the [0001] zone axis. A monoclinic phase was not observed.

Adult↗

Polymorphism in the regulatory region of HLA-DRB genes correlating with haplotype evolution.

Class II genes of the human major histocompatibility complex (MHC) are polymorphic. Allelic variation of the coding region of these genes is involved in the antigen presentation and is associated with susceptibility to certain autoimmune diseases. The DR region is unique among human class II regions in that multiple DRB genes are expressed. Differential expression of the different DRB loci has been demonstrated, and we sequenced the proximal promoter region of the HLA-DRB genes, known to be involved in the regulation of these genes. We found locus-specific and allele-specific nucleotide variations in their regulatory regions and we determined the relationship between the regulatory regions of HLA-DRB genes. This polymorphism found in the regulatory conserved boxes could be involved in the observed differential expression of DRB loci. In addition, we found a polymorphism between the regulatory regions of DRB1 alleles which might be involved in an allele-specific regulation and therefore could be considered as an additional factor in susceptibility to autoimmune diseases.

Base Sequence↗

Sternal fracture: what investigations are indicated?

A retrospective study of 55 patients with sternal fractures is presented in an attempt to determine which investigations are predictive of complications. We conclude that isolated sternal fractures, in the absence of clinical evidence of cardiac or respiratory complications, and with a normal electrocardiogram and postero-anterior chest radiograph, require no further investigation.

Adolescent↗

Out-of-hospital resuscitation in East Sussex: 1981 to 1989.

OBJECTIVE: To assess the impact of extended training in advanced life support on the outcome of resuscitation. DESIGN: Analysis of the successful resuscitations from 1981 to 1989. SETTING: Brighton and East Sussex. RESULTS: 248 patients were resuscitated from cardiac or respiratory arrest in the community and subsequently survived to leave hospital. Their mean age was 64 years and one year survival was 77%. In most cases the cause of collapse was cardiac but 38 (15%) suffered a respiratory arrest. In 140 of the successful resuscitations (56%) collapse occurred before the arrival of the ambulance. Basic life support, with ventilation and chest compression where necessary, was sufficient to revive 35 (14%) of the patients. Defibrillation was also required in 107 patients (43%), and in a further 106 patients (43%) who had prolonged cardiorespiratory arrest requiring endotracheal intubation and the use of several drugs. Review of ambulance forms and case notes showed that in 87 cases (35%) the abilities of the paramedical ambulance staff in advanced resuscitation techniques contributed decisively to the success of resuscitation. These skills are illustrated by eight case reports. CONCLUSIONS: Extended training for ambulance staff increases the likelihood of successful resuscitation from out-of-hospital cardiopulmonary arrest. Though instruction in defibrillation must have the highest priority, full paramedical training can bring appreciable additional benefits.

Adolescent↗

Fast ECG data compression algorithms suitable for microprocessor systems.

ECG data compression techniques have received extensive attention in ECG analysis. Numerous data compression algorithms for ECG signals have been proposed during the last three decades. We describe two algorithms based on the scan-along polygonal approximation algorithm (SAPA) that are suitable for multichannel ECG data reduction on a microprocessor-based system. One represents a modification of SAPA (MSAPA) which adopts the method of integer division table searching to speed up data reduction; the other (CSAPA) combines MSAPA and TP, a turning-point algorithm, to preserve ST segment signals. Results show that our algorithms achieve a compression ratio of more than 5:1 and a percent rms difference (PRD) to the original signal of less than 3.5%. In addition, the maximum execution time of MSAPA for processing one data point is about 50 microseconds. Moreover, the CSAPA algorithm retains all of the details of the ST segment, which are important in ischaemia diagnosis, by employing the TP algorithm.

Algorithms↗

Intracerebral haemorrhage after thrombolytic therapy for acute myocardial infarction.

Seven cases of intracerebral haemorrhage were identified following the use of thrombolytic therapy in a total of 710 patients with acute myocardial infarction. Each case was reviewed in detail with particular attention to the presenting symptoms. A confusional state was the commonest initial feature. Increased age and male sex were associated with increased risk of cerebral bleed. The possible role of intravenous heparin in increasing risk and the management of affected cases is discussed. Early recognition and action is emphasized.

Age Factors↗

Quantitative analysis of signal-averaged P waves in idiopathic paroxysmal atrial fibrillation.

Detailed analysis of the QRS complex can identify patients at risk from ventricular arrhythmias, but similar techniques applied to the atria have been disappointing. This study attempts to quantitate differences in the fine morphology of P waves in a group of 9 patients with paroxysmal atrial fibrillation (AF) versus 15 control subjects. Atrial triggered signal-averaging was combined with a detailed investigation of P-wave duration, high-frequency spatial voltage and spatial velocity. Signal-averaged P-wave duration was significantly increased in patients with paroxysmal AF (135 +/- 8 vs 126 +/- 4 ms, p less than 0.05). The root-mean-square voltage at frequencies greater than 35 Hz in these patients was also significantly greater (16 +/- 3 vs 12 +/- 1 microV, p less than 0.05). Similar observations were made at frequencies greater than 40 Hz (10 +/- 3 vs 7 +/- 1 microV, p less than 0.05). These differences appeared to be confined to the third quarter of the P wave (third quarter root-mean-square voltage at greater than 40 Hz expressed as a ratio of total P-wave root-mean-square voltage, 1.4 +/- 0.1 vs 1.2 +/- 0.1, p = 0.005). Spatial velocity was also increased in the paroxysmal AF group (peak spatial velocity 6.4 +/- 1.8 vs 4.6 +/- 0.5 mV/s, p less than 0.05). These observations support previous intracardiac data that implicate delay and fragmentation of intraatrial conduction in the pathogenesis of paroxysmal AF.

Adult↗

Reduction in hospital time to thrombolytic therapy by audit of policy guidelines.

Despite the importance of early thrombolysis in the treatment of acute myocardial infarction, unacceptable delays in drug administration still occur in hospital. From March 1989 we decided to monitor our performance, and thereby to reduce avoidable in-hospital delay to a minimum. Potential candidates for thrombolytic therapy were identified by paramedic ambulancemen whenever this was feasible. Rapid check-lists were used for inclusion and exclusion criteria in the Accident and Emergency Department. A target of 15 min was set for time to treatment, and reasons for any gross deviation (greater than 30 min) were explored in each instance. As a result of these strategies, we achieved a median time from admission to initiation of thrombolysis in 50 consecutive patients of 17 min. The 39 patients treated with injections of APSAC as opposed to infusions of streptokinase had a median in-hospital delay to treatment of only 13 min.

Aged↗