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Biomedical subjects

L Dallaire

Publications and source records attributed to L Dallaire.

At least 91 records · Page 5Linked to original sources
PubMed1979

Reactivity of amniotic fluid alpha-fetoprotein with concanavallin A in diagnosis of neural tube defects.

Alpha-fetoprotein (AFP) concanavallin-A-affinity molecular variant patterns were determined in amniotic fluid samples from 10 pregnancies complicated by anencephaly (6), spina bifida (1), Turner's syndrome (1), osteogenesis imperfecta congenita (1), and fetal death (1) and 20 normal pregnancies between 14.6 and 25.5 weeks of gestation. With the exception of one anencephalic pregnancy, the AFP concentrations in samples from women with a fetal abnormality were more than 5 SD above normal for gestational age. In every case, however, the proportion of total amniotic fluid AFP that was not reactive with concanavallin A was significantly smaller in the presence of a fetal abnormality (mean 2%) than when the fetus was normal (mean 20%). The results suggest that measuring the amount of concanavallin-A-non-reactive amniotic fluid AFP will be a valuable test for diagnosing fetal abnormality, especially when an increase in total amniotic fluid AFP concentration is equivocal or gestational age is uncertain.

Amniotic Fluid↗
PubMed1979

Antenatal diagnosis of neural tube defects in Canada: extension of a collaborative study.

Experience with the diagnosis of neural tube defects from alpha1-fetoprotein (AFP) concentrations in amniotic fluid is reported from a prospective study of five laboratories testing for 13 Canadian genetic centres. The results of the study indicate that antenatal diagnosis of open neural tube defects is being carried out effectively in Canada (in 99.2% of cases the AFP measurements were interpreted correctly). Amniocentesis should be recommended to women at high risk for having a child with a neural tube defect (i.e., those who have a child, a parent or a sibling with a neural tube defect). The rate of neural tube defects in 182 high-risk pregnancies was 2.2% for an open defect and 1.1% for a closed defect, whereas the rate in 673 pregnancies in which amniocentesis was being performed for other reasons was 0.3%. This suggests that the AFP concentration should be measured in any sample of amniotic fluid collected for other reasons (usually fetal karyotyping). There were three instances of false-negative results, for a rate of 0.4%. Two closed neural tube defects were not detected; this limitation of the test has also been found by others. One of the six fetuses with an open neural tube defect, who died in utero, had a large myelocele in the neck that was not recognized. There were also four instances of false-positive results, for a rate of 0.5%. The findings suggest that AFP values that are more than 2 but less than 7 standard deviations (SDs) above the mean may indicate a neural tube defect, and that values 7 or more SDs above the mean very likely indicate such a defect, although other reasons for such high values (e.g., fetal erythrocytes in the amniotic fluid, intrauterine death and mistaken gestational age) must be ruled out by other methods.

Amniocentesis↗
PubMed1979

Purification and some properties of liver and brain beta-N-acetyl-hexosaminidase S.

beta-N-Acetyl-hexosaminidase S (2-acetamido-2-deoxy-beta-hexoside acetamido-deoxyhexohydrolase, EC 3.2.1.52) was purified from liver and brain of a patient deceased of type O GM2 gangliosidosis (Sandhoff's disease). Brain beta-N-acetyl-hexosaminidase S was further purified by preparative polyacrylamide gel electrophoresis. The pH optimum of the purified liver and brain enzyme was 5.0 and Km values were 0.8--0.9 mM and 0.3--0.4 mM with 4-methylumbelliferyl-beta-D-N-acetylglucosamine and beta-D-N-acetylgalactosaminide derivatives, respectively. beta-N-Acetyl-hexosaminidase S was thermolabile losing most of its activity after 50 min at 50 degrees C. The apparent molecular weights of the purified liver and brain enzymes were 154 000 and 152 000, respectively. Hexosamines activated beta-N-acetyl-hexosaminidase S whereas the isoenzyme A and B were inhibited. The glycoprotein nature of beta-N-acetyl-hexosaminidase S was suggested by its affinity towards Concanavalin A-Sepharose.

Binding Sites↗
PubMed1979

Neuraminidase in cultured fibroblasts and leucocytes of homozygotes and heterozygotes for the mucolipidosis II gene (I-cell disease).

The significance of neuraminidase deficiency reported to be the primary defect in mucolipidosis II has been evaluated by determination of this enzyme activity in cultured fibroblasts, culture medium, and leucocytes from homozygote and heterozygous carriers of the disease. A new and sensitive fluorometric assay of neuraminidase was used with sodium (4-methylumbeliferyl-alpha-D-N-acetylneuraminate) as substrate. We report: 1) nearly total deficiency of neuraminidase in mucolipidosis fibroblasts, 2) partial deficiency of this enzyme in leucocytes of one patient, 3) this decreased activity ceases to exist following Triton X-100 treatment, and 4) intermediary mean neuraminidase activity in fibroblasts and leucocytes from obligate heterozygotes. Although these results would be consistent with the suggestion that neuraminidase deficiency is the primary defect in this disease, evidence from the work of other authors suggests that the enzyme deficiency results from a secondary effect of the mucolipidosis II mutation.

Cells, Cultured↗
PubMed1979

Pyruvate dehydrogenase, lipoamide dehydrogenase and citrate synthase activity in fibroblasts from patients with Friedreich's and Charlevoix-Saguenay ataxia.

The activity of lipoamide dehydrogenase and two closely related enzymes was studied simultaneously in early, mild, and late passage fibroblast cultures. Friedreich's ataxia fibroblasts tended to lose pyruvate dehydrogenase and citrate synthase activities, while lipoamide dehydrogenase activity remained constant with aging of the cells. Mean pyruvate dehydrogenase activity was lower over-all in fibroblasts from ataxics. Mean citrate synthase activity was higher in ataxic fibroblasts. Present tissue culture media do not represent the best conditions in which to reproduce cofactor binding defects such as those found in other genetic diseases with structural enzyme mutations.

Ataxia↗
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↗
PubMed1979

Origin and developmental patterns of lactase and other glycosidases in sheep amniotic and allantoic fluid.

Intestinal lactase activity (with its associated cellobiase, 4-methylumbelliferyl-beta-galactosidase and -beta-glucosidase activities) was used as a specific intestinal marker enzyme to study the release of protein and enzymes of intestinal origin in sheep amniotic fluid during gestation. In amniotic fluid, intestinal lactase activity peaked at 66--85 days of gestation and then decreased with gestation. This enzyme activity was very low or absent in allantoic fluid throughout gestation suggesting that there is no important transfer of amniotic fluid lactase towards the allantoic cavity. Maltase and 4-methylumbelliferyl-alpha-glucosidase showed no statistically significant variation with gestation in both amniotic and allantoic fluid whereas alpha-galactosidase and N-acetyl-beta-hexosaminidase which were first higher in allantoic than in amniotic fluid increased in amniotic fluid to reach allantoic fluid levels near term. Such patterns are consistent with the suggestion that the fetal urine is a source of alpha-galactosidase and N-acety-beta-hexosaminidase activities and that sheep urine is first accumulated in the allantoic sac via the urachus up to 86--90 days of gestation and thereafter passes more and more into the amniotic sac.

Allantois↗
PubMed1979

Viability assessment by dye exclusion. A fluorescent method for fungal cells.

A new fluorescent staining technique for fungi utilizes the differential affinity of dead cells for rhodamine B. A mounting medium has been devised that includes the dye. This medium allows direct processing of cells from a broth and provides optimal conditions for fluorescence intensity. Comparison with the standard methylene blue exclusion test as applied to the Candida albicans yeast phase indicates similar specificity. Various pseudohyphae and several fungi also exhibited selective uptake of the dye when killed. This technique should prove useful in studying the effect of both drugs and cells on pathogenic yeasts.

Cell Survival↗
PubMed1978

Confirmation of regional assignment of nucleoside phosphorylase (NP) on chromosome 14 by gene dosage studies.

Gene dosage studies yielded results consistent with assignment of the locus for nucleoside phosphorylase to band 14q13. The red blood cells from a patient with the karyotype 47,XX,+der(14),t(8;14)(8qter leads to 8q24::14q21 leads to 14pter)pat had enzyme activity 50% higher than red cells from 47 normal controls, two trisomies involving chromosomes other than 14, and five balanced translocations involving chromosome 14. On the other hand, the red cells of a case with a karyotype 45,XX,-14,-22+der(22),t(14;22)(14qter leads to 14q11 or 14q12::22p11 leads to 22qter)mat and a case with a a karyotype 47,XX,+der(14),t(14;16)(14pter leads to 14q11::16q24 leads to 16qter)mat had normal activity

Child, Preschool↗
PubMed1978

Lipoamide dehydrogenase in cultured human skin fibroblasts.

Lipoamide dehydrogenase was identified in cultured skin fibroblasts of normal individuals and patients with Friedreich's ataxia. The optimum conditions for its assay were defined. Data disclosed a normal range of 36--122 mumol/min/mg protein in control fibroblasts and 61--112 mumol/min/mg protein in patients fibroblasts. Numerous precautions should be taken in handling fibroblast cultures for lipoamide dehydrogenase determination.

Buffers↗
PubMed1978

Developmental patterns of intestinal disaccharidases in human amniotic fluid.

A close relationship exists between relative disaccharidase activities (maltase, sucrase, trehalase, palatinase, turanase, lactase, and cellobiase) in amniotic fluid and corresponding jejunal mucosa of five human fetuses (16 to 21 weeks of gestation) suggesting that these intestinal enzymes pass into amniotic fluid. Serial determination of disaccharidase activities in amniotic fluid samples collected between 10 and 42 weeks of gestation showed maximum mean activities at 14 to 17 weeks of gestation and a rapid drop to less than 12 per cent maximum values at about 22 weeks. This drop is probably caused by combined effects of decreased extrusion rate of intestinal disaccharidases and increased reabsorption of the enzymes in swallowed amniotic fluid with fetal development.

Amniotic Fluid↗
PubMed1978

Lipoamide dehydrogenase in Friedreich's ataxia fibroblasts.

Lipoamide dehydrogenase was measured in cultivated skin fibroblasts from twelve patients with Friedreich's ataxia and nine normal controls. No difference in specific activity, subcellular distribution and Vmax or Km was observed between patients and controls.

Cells, Cultured↗
PubMed1977

N-Acetyl-beta-hexosaminidase isoenzymes of amniotic fluid and maternal serum. Their relevance to prenatal diagnosis of the GM2 gangliosidoses.

The isoenzymes of N-acetyl-beta-hexosaminidase were quantitated in 30 amniotic fluid and 13 maternal serum samples collected between 11 and 40 weeks of gestation using DEAE-Sephadex A-25 chromatography. Isoenzymes A and B consitituted the major components of most amniotic fluids but seven samples characterized by high N-acetyl-beta-hexosaminidase activities contained high proportion of an isoenzyme apparently identical to isoenzyme P of maternal serum. This passage of maternal serum N-acetyl-beta-hexosaminidase into the amniotic cavity could lead to false negative diagnosis of type B and type O GM2 gangliosidoses if the diagnosis rely solely upon isoenzyme analysis in amniotic fluid. However, the release of maternal enzyme into amniotic fluid seems to be restricted to the third trimester of gestation and should not interfere with prenatal diagnosis of the GM2 gangliosidoses ususally performed at an earlier stage of gestation.

Amniotic Fluid↗
PubMed1977

Dicarboxylic aminoaciduria: an inborn error of amino acid conservation.

A 38-month-old apparently healthy male has been followed for three years because of a massive glutamic and aspartic aminoaciduria detected shortly after birth in a neonatal screening program. Amino acid clearance studies revealed the presence of renal wastage of dicarboxylic amino acids. Intestinal transport and in vitro oxidation of dicarboxylic amino acids were found to be intact. Clinical and metabolic data obtained on a previously described patient and the present case suggest that some patients with dicarboxylic aminoaciduria might have a selective renal conservation defect without clinical abnormalities, whereas others might demonstrate an additional defect in intestinal transport associated with fasting hypoglycemia.

Amino Acids, Dicarboxylic↗