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Biomedical subjects

B Lemieux

Publications and source records attributed to B Lemieux.

At least 91 records · Page 5Linked to original sources
PubMed1983

A new French-Canadian family affected by hyperargininaemia.

A new French-Canadian family from the province of Quebec is reported, in which a male child was diagnosed as hyperargininaemic after showing positive tests for cystinuria on neonatal screening. The child has no residual activity of erythrocyte arginase, and a plasma arginine level of 633 mumol/l. Both parents have 32-38% of arginase activity. A newborn sister has normal enzyme levels. The propositus did not show abnormal plasma ammonia elevation even after a protein tolerance test (1.5 g protein/kg body weight) but excretes high levels of urinary orotate (845 mg/g creatinine). At 3 1/2 years of age the hyperargininaemic child had started showing abnormal gait, ataxia and slowing of intellectual development. It is suggested that all newborn children showing cystinuria-lysinuria pattern of amino acid excretion be tested for arginase deficiency.

Adult↗
PubMed1982

Ultrastructural observations on spinal ganglion biopsy in Friedreich's ataxia: a preliminary report.

We report the preliminary study of a dorsal root ganglion obtained at biopsy during a surgical intervention in a patient with Friedreich's ataxia. There was an apparent decrease in the number of large myelinated fibers without necrosis, but with numerous axonal swellings consisting mainly of dense accumulated neurofilaments. Large amounts of lipofuscin were also found as well as some onion bulb formations suggesting a process of axonal atrophy.

Adult↗
PubMed1982

Pathogenesis of respiratory insufficiency in myotonic dystrophy: the mechanical factors.

We have previously shown that the chemosensitivity of the respiratory centers is well preserved in myotonic dystrophy but that the ventilatory output is reduced. The present study was designed to determine at which degree of ventilatory performance weakness and fatigability of the respiratory muscles are interfering with ventilation and which mechanical factors contribute to the tachypnea of patients with myotonic dystrophy at rest and during low ventilatory output. We studied 10 patients with the disease and 10 normal control subjects. The strength of respiratory muscles was assessed by measurements of maximal pressure-volume diagrams generated against airway occlusion. Performance was evaluated during 1-min maximal voluntary ventilation (1-min MVV) test, during 7-min 7% CO2 breathing and during quiet breathing. Occlusion pressure (P0.1) in patients at rest was slightly higher than in control subjects, and during CO2 breathing, it was similar to that of control subjects. Maximal static pressure was reduced in patients to an average of 35% of that of control subjects. During the 1-min MVV test, there was a 50% reduction in esophageal and transdiaphragmatic pressure output (Pes, Pdi) in patients, resulting in similar reduction in ventilation (VE) and patients had rapid cycles of alternating dominant thoracic and abdominal volume displacements (Vrc/Vabd) suggesting respiratory muscle fatigue. During the 3- to 4-fold increase in breathing drive induced by hypercapnia, pressure output and the Vrc/Vabd were identical in both groups. However, ventilation was reduced in patients who had tachypneic respiration. In patients, tachypnea was also observed during quiet breathing. This tachypnea was associated with higher impedance of the respiratory system (Zrs) in patients and identical impedance of the lung (ZL) in both groups. In addition, Pdi during tidal volume was significantly higher in patients. These data demonstrate that the ventilatory output in out patients was altered predominantly by weakness and fatigability of the respiratory muscles during high ventilatory performance and by increased impedance of the respiratory system at lower degrees of ventilation.

Adolescent↗
PubMed1980

Diet and medications giving positive ninhydrin reactions on TLC in a newborn urinary screening program.

During amino acid analysis of over 520,000 urine samples (provided by a urinary screening program), we often noticed different dietary compounds or medications giving positive ninhydrin reactions which could interfere with the interpretation of the thin layer chromatograms. Consequently, we have done an in vitro study of the chromatographic behaviour of the most frequently encountered artifacts in urine. We believe that the results of this work should make it easier for other laboratories doing similar analyses to recognize the presence of such compounds, thus facilitating the evaluation of their chromatograms.

Amino Acids↗
PubMed1980

An automated method for the determination of orotic acid in the urine of children being screened for metabolic disorders.

Urinary orotic acid is believed to be a valuable probe for early diagnosis of inborn errors of metabolism leading to hyperammonemia and increased pyrimidine synthesis. For the purpose of our urinary mass screening programme, we developed an automated colorimetric method which is reliable in the range of 1 to 50 micrograms/ml orotic acid and allows analyses at a rate of 160 samples per hour. Preliminary results are presented which illustrate that various disorders can be recognized by measuring orotic acid in urine.

Autoanalysis↗
PubMed1980

The cardiomyopathy of Friedreich's ataxia morphological observations in 3 cases.

In the light of the recent finding of deposits of calcium salts and iron in myocardial cells in one case of Friedreich's ataxia, we have made a detailed morphological study of 3 new cases of this cardiomyopathy. Calcium deposits were not found in the muscle fibers but lipofuscin granules and deposits of iron were observed in our 3 cases. In addition to the usual findings of interstitial fibrosis, hypertrophy and degeneration of myocardial fibers, foci of segmental active muscle necrosis were constantly present. There is a possibility that Friedreich's ataxia could be a neurocardiac degenerative disease with a membrane defect which could be related to defective metabolism of vitamin E or other micronutrients.

Adolescent↗
PubMed1980

Glycosylated hemoglobins in Friedreich's ataxia.

In a study of glycosylated hemoglobins in Friedreich's Ataxia patients and in family members, the level was found to be higher in insulin dependent diabetics than in healthy non-diabetic control subjects (p < 0.01), but was similar to non-ataxic diabetic control subjects. Results for non-diabetic Friedreich's Ataxia patients and siblings were similar to those for non-diabetic control subjects while levels were slightly increased in the heterozygotes. It is concluded that in Friedreich's Ataxia patients and family members (apart from the insulin dependent diabetics), there was no hyperglycemia sufficient to be detected as an increase in glycosylated hemoglobins.

Diabetes Complications↗
PubMed1980

Control and modulation of respiration in Steinert's myotonic dystrophy.

Respiratory impairment in patients with Steinert's muscular dystrophy is known to lead to respiratory failure. Both the blunted chemical drive of breathing and the respiratory muscle weakness have been cited in the pathophysiology of premature death in these patients. To further assess the chemical control of breathing in these patients, we measured their respiratory responses to hypoxia (Weil's method), hyperoxia (Dejours' method), and hypercapnia (Read's method). In response to the stimuli from these respiratory centers, minute ventilation (VE), tidal volume (VT), respiratory frequency (F), mean inspiratory flow rate (VT/Ti), and occlusion pressure (P0.1) were measured in 12 patients and in 12 normal persons matched to the patients on the basis of age, sex, and arm span. The patients were similar to the control subjects in occlusion pressure results. However, they differed significantly (P less than 0.01) in ventilatory responses by a lower VE, lower VT, higher F, and lower VT/Ti in response to the hypercapnia and hypoxia tests. The responses of patients and control subjects were similar during the hyperoxia tests. Our study, therefore, established that the chemosensitivity of the respiratory centers, as measured by P0.1, is well preserved in Steinert's myotonic dystrophy, but the output to breathing (VE, VT, F, VT/Ti) is modulated by the impaired respiratory mechanics causing a tachypneic breathing pattern, even in the absence of restricted lung volume.

Adolescent↗
PubMed1979

Rapid thin-layer chromatographic method for the detection of urinary methylmalonic acid.

1. Simple and rapid thin-layer and micro-thin-layer chromatography techniques are described for the detection of methylmalonic acid in urine. 2. The separation of methylmalonic acid from a crude urine sample is performed by thin-layer chromatography with a mixture of silica gel-cellulose and butanol - acetic acid - water solvent system. The methylmalonic acid spot is visualized with tetrazotized o-dianisidine. 3. This system has been successfully developed for a urinary screening programme; it was shown as simple, convenient and rapid, eliminating false-positives and allowing the detection of even traces of methylmalonic acid.

Chromatography, Thin Layer↗
PubMed1979

Single column high pressure liquid chromatographic determination of drugs in blood.

1. Analysis of anticonvulsants (phenobarbital, diphenylhydantoin and carbamazepine), theophylline and an antiarrhythmic agent (disopyramide) in blood using a simple high pressure liquid chromatography apparatus equipped with a reversed -- phase column is described. A simple extraction of plasma or serum with organic solvent is used to isolate the anticonvulsants and theophylline. Disopyramide is extracted with ether and is further purified by a back extraction into acid. 2. Hexanesulfonic acid -- methanol solutions are used for chromatography of the anticonvulsants and disopyramide while the mobile phase for theophylline is a NH4H2PO4 -- methanol mixture. Chromatographic analysis time for the drugs is approximately 15 minutes. The drugs are monitored by a UV detector at 254 nm except for theophylline which is measured at 280 nm. Quantitation is accomplished by comparison of peak heights with those of internal standards. Quantities of serum or plasma routinely used for analysis are: 200 ul for the anticonvulsants, 100 ul for theophylline and 0.5 ml for disopyramide. Detection limits are less than 1 ug/ml for these quantities.

Anticonvulsants↗
PubMed1979

Cardiovascular evaluation of obligate heterozygotes in Friedreich's ataxia.

A study of 17 parents (obligate heterozygotes) of children with Friedreich's ataxia was carried out. In addition to medical histories and physical examinations, a standard 12 lead ECG tracing was obtained. In the age group below 50, there was no significant evidence of ischaemic or primary cardiomyopathy. Older subjects had more frequent risk factors for arteriosclerotic heart disease.

Adult↗
PubMed1979

Evolution of cardio-pulmonary involvement in Friedreich's ataxia.

The evolution of 15 patients initially evaluated during Phase One of the Quebec Cooperative Study of Friedreich's ataxia has been studied approximately three years later. It is concluded that the deterioration of cardio-pulmonary function in Friedreich's ataxia is multifactorial. The neuromyopathy (or the underlying metabolic or cellular defect) appears to be the main contributing factor to the deterioration of cardio-pulmonary function, which is exacerbated by the scoliosis and varying severity of the cardiomyopathy.

Adolescent↗
PubMed1979

Regulation of respiration in Friedreich's ataxia.

Friedreich's Ataxia (F.A.) is a degenerative disease which commonly leads to premature death of cardiorespiratory origin. To explain the early death of these patients, previous investigations have established the existence of 1) a cardiomyopathy in nearly 100% of cases, 2) a restrictive pulmonary syndrome of scoliotic origin and 3) a mild hypoxemia associated with slight respiratory alkalosis and a normal oxyhemoglobin dissociation curve. To further assess the cause of early death in patients with such neuromyopathy, we evaluated, in eleven F.A. patients, the sensitivity of the respiratory centers to hypercapnia, hypoxia, and hyperoxia. Ventilatory (VE, VT, F, VT/Ti) and occlusion pressure (P0.1) responses were taken as indices of the respiratory centers output during progressive hypercapnia (Read's method) and isocarbic hypoxia (Weil's method). We studied 11 Friedreich's Ataxia patients and 11 age, sex, and armspan matched controls. The responses of patients to hypercapnia were significantly greater than controls but their responses to hypoxia were similar to controls. Our study establishes that the respiratory centers are functioning adequately in early Friedreich's Ataxia and do not contribute to cardio-respiratory insufficiency in such neuromyopathy.

Adolescent↗
PubMed1979

Glucose tolerance and erythrocyte insulin receptors in Friedreich's ataxia.

Detailed in vivo and in vitro studies of glucose and insulin metabolism in Friedreich's ataxia patients and unaffected family members have further defined the extent of the abnormalities in carbohydrate metabolism. The high incidence of glucose intolerance and a hyperinsulinemic response to a glucose challenge in a high percentage of Friedreich's ataxia patients has been confirmed. An increased incidence of glucose intolerance among heterozygotes is suggested, while the siblings show a more normal distribution of diabetes and a nearly normal insulin response to the glucose tolerance test. Human growth hormone patterns are normal for all groups. Preliminary studies of insulin binding to erythrocytes suggest a difference in the binding characteristics among diabetic Friedreich's ataxia patients, while the binding in the non-diabetic Friedreich's ataxia group is similar to that of non-diabetic controls. Results from a small group of non-diabetic siblings suggest a normal insulin binding, while a tendency toward increased binding at low insulin concentrations among diabetic family members is noted.

Diabetes Complications↗
PubMed1979

Dicarboxylic amino acid uptake in normal, Friedreich's ataxia, and dicarboxylic aminoaciduria fibroblasts.

Glutamic and aspartic acid uptake was measured in skin fibroblasts from patients with Friedreich's Ataxia, dicarboxylic aminoaciduria, and normal individuals. The results showed no difference in uptake kinetics of either dicarboxylic amino acids between Friedreich's Ataxia and normal cells, but reduced uptake velocities in dicarboxylic aminoaciduria fibroblasts. Friedreich's Ataxia fibroblasts were, however, less calcium-dependent and more magnesium and phosphate-dependent than controls in glucose-free incubation mixture. This difference might be related to some degree of glucose intolerance by Friedreich's Ataxia fibroblasts in culture.

Amino Acids↗