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Biomedical subjects

N Vincent

Publications and source records attributed to N Vincent.

31 records · Page 2Linked to original sources
PubMed1992

Glycine, a new regulator of glutamine metabolism in isolated rat-liver cells.

Glycine (0.1-10 mM) caused a dose-dependent increase in the removal of 5 mM [1-14C]glutamine by isolated rat-liver cells; at low concentrations of glycine, an increase in the formation of 14CO2, urea and glucose from glutamine occurred. At 2-10 mM, glycine also caused an accumulation of ammonia, a well-established activator of glutaminase (E.C. 3.5.1.2) and, at concentrations found in the presence of glutamine plus glycine, ammonia stimulated glutamine removal. The inhibition of urea synthesis from glutamine observed with 10 mM glycine was relieved by the addition of ornithine, suggesting that this inhibition occurred by reducing the availability of ornithine for the ornithine transcarbamoylase reaction. The metabolism of glycine as sole substrate led to a small increase in the accumulation of ammonia. Glycine did not alter hepatic glutaminase activity but swelling of rat hepatocytes, a factor considered to stimulate glutamine metabolism, was observed in the presence of glycine (1 mM). It is concluded that stimulation by glycine of hepatic utilization of glutamine is mediated by the accumulation of ammonia arising from both glycine and glutamine metabolism and by hepatocyte osmotic swelling secondary to glycine transport.

Ammonia↗
PubMed1992

Distal transcript of the dystrophin gene initiated from an alternative first exon and encoding a 75-kDa protein widely distributed in nonmuscle tissues.

A transcript generated by the distal part of the Duchenne Muscular Dystrophy (DMD) gene was initially detected in cells where the full size 14-kilobase (kb) messenger RNA is not found at a significant level. This transcript, approximately 4.5 kb long, corresponds to the cysteine-rich and carboxyl-terminal domains of dystrophin. It begins with a novel 80- to 100-nucleotide exon containing an ATG start site for a new coding sequence of 17 nucleotides in-frame with the consecutive dystrophin cDNA sequence from exon 63. This result suggests the existence of a third promoter that would be localized about 8 kilobases upstream from exon 63 of the DMD gene. The distal transcript is widely distributed but is absent in adult skeletal and myometrial muscle. It is much more abundant in fetal tissues. With an antibody directed against the dystrophin carboxyl terminus, the protein corresponding to this transcript was detected as a 70- to 75-kDa entity on Western blots. It was found in all tissues analyzed except in skeletal muscle. It was not found in lymphoblastoid cells from a Duchenne patient with a complete deletion of the dystrophin gene. The role and subcellular localization of this protein is not known. It may explain extramuscular symptoms exhibited by some Duchenne patients.

Animals↗
PubMed1992

Release and fixation of CO2 by guinea-pig kidney tubules metabolizing aspartate.

1. The metabolism of L-[U-14C]aspartate, L-[1-14C]aspartate and L-[4-14C]aspartate was studied in isolated guinea-pig kidney tubules. 2. Oxidation of C-1 plus that of C-4 of aspartate accounted for 90-92% of the CO2 released from aspartate, whereas oxidation of the inner carbon atoms of aspartate (which occurs beyond the 2-oxoglutarate dehydrogenase step) represented only 8-10% of aspartate carbon oxidation. 3. The formation of [1-14C]glutamine and [1-14C]glutamate from [1-14C]aspartate and [4-14C]aspartate indicated that about one-third of the oxaloacetate synthesized from aspartate underwent randomization at the level of fumarate. 4. With [U-14C]aspartate as substrate, the percentage of the C-1 of glutamate and glutamine found radiolabelled after 60 min of incubation was 92.7% and 47.5% in the absence and the presence of bicarbonate respectively. 5. That CO2 fixation occurred at high rates in the presence of bicarbonate was demonstrated by incubating tubules with aspartate plus [14C]bicarbonate; under this condition, the label fixed was found in C-1 of glutamate, glutamine and aspartate, as well as in C-4 of aspartate, demonstrating not only randomization of aspartate carbon but also aspartate resynthesis secondary to oxaloacetate cycling via phosphoenolpyruvate carboxykinase, pyruvate kinase and pyruvate carboxylase. 6. The importance of CO2 fixation in glutamine synthesis from aspartate is discussed in relation to the possible role of the guinea-pig kidney in systemic acid-base regulation in vivo.

Acetazolamide↗
PubMed1992

Are cysteine-rich and COOH-terminal domains of dystrophin critical for sarcolemmal localization?

It has been hypothesized that the tight localization of dystrophin at the muscle membrane is carried out by its cysteine-rich and/or carboxyl domains. We report the results of biochemical and immunocytochemical investigations of dystrophin in muscle from a 1-yr-old patient with a large deletion that removes the distal part of the dystrophin gene, thus spanning the exons coding for the cysteine-rich and the carboxy-terminal domains, and extends beyond the glycerol kinase and congenital adrenal hypoplasia genes. Immunological analysis of muscle dystrophin shows that the deletion results in the production of a truncated, but stable, polypeptide correctly localized at the sarcolemma. These data indicate that neither the cysteine-rich domain, nor the carboxyl domain, are necessary for the appearance of normal dystrophin sarcolemmal localization.

Cysteine↗
PubMed1992

[Neonatal digestive implantation of streptococcus group B. Influence of antibiotic therapy].

Group B streptococcus (GBS) is an important cause of neonatal infection. Early-onset diseases are due to perinatal contamination. The epidemiology of late-onset infections is poorly known. Maternal colonization may be responsible for some of them. The relationships between neonatal colonization and late disease could be a colonization of the gut. The purpose of this 3 year-prospective study was to analyse the kinetics of gut colonization in neonates and the influence of antibiotherapy. One hundred and nineteen infants less than one month of age were included because of the presence of GBS in their gastric aspirates or GBS infection. Depending on the therapeutic strategy, the infants were separated into 3 groups: 1) amoxicillin plus aminoside greater than or equal to 10 days because of neonatal infection (28 infants), 2) same combination less than or equal to 5 days because a GBS infection was suspected but not confirmed (17 infants), 3) no antibiotics (77 infants). Fecal flora was regularly analysed by differential count. Antibiotics caused rapid disappearance of GBS from the gut. However, the same strain reappeared after stopping the antibiotics at a rate of 13.5%. Without antibiotics, GBS was implanted in 33% of cases. This difference of implantation rate is statistically significant (p less than 0.05). No GBS infection was observed in any infant after a follow-up examination of 6 months to 2 years. Among the clinical and bacteriological factors studied, adhesion only was correlated with the GBS implantation. These results allow to discuss therapeutic abstention in colonized infants without any signs of infection.

Ampicillin↗
PubMed1991

Orientation based on nursing diagnoses. Old concepts in today's practice.

Although many operating room orientation programs contain content necessary to meet accrediting guidelines, very few tie the nursing process to the content. Our orientation is structured within a nursing framework (ie, Dr Gordon's "Eleven Functional Health Patterns") and emphasizes nursing diagnoses, theory, and clinical competencies. Although the new orientation program has been in effect for only two years, we feel the following list reflects the positive outcomes so far: decreased staff turnover (ie, one nurse out of 26 full-time equivalents in 18 months), increased success in recruiting nurses into the operating room (ie, multiple applicants as positions open), new nurses demonstrate comfort with basic perioperative nursing practice with-in six months, and nurses who did not complete new orientation program are requesting all or portions of the content. By using this plan, essential aspects of perioperative practice are consistent with hospital-wide nursing practice, practice standards for the operating room, and accrediting standards.

Curriculum↗
PubMed1989

Simultaneous synthesis and degradation of glutamine in isolated rat liver cells. Effect of vasopressin.

When hepatocytes suspensions obtained from whole livers of 48-h-fasted rats were incubated in Krebs-Henseleit buffer with a near-physiological concentration (1 mM) of L-[1-14C]glutamine as substrate, the apparent removal of glutamine was low, but the release of 14CO2 was much larger than the enzymatically measured removal of glutamine. This indicates that glutamine was metabolized at rates much higher than those accounted for by the apparent removal of glutamine. This also suggests that glutamine utilization was, at least in part, masked by concomitant synthesis of glutamine from endogenous substrates via glutamine synthetase. Evidence that such synthesis occurred was obtained by: (i) addition of methionine sulfoximine, an inhibitor of glutamine synthetase, which caused a large increase in the apparent removal of glutamine; and (ii) measurement of the specific radioactivity of L-[1-14C]glutamine which was shown to decrease during incubation. Addition of vasopressin (10(-7) M) led to a marked increase in glutamine removal by a dual mechanism: it accelerated flux through glutaminase, the enzyme which initiates the hepatic degradation of glutamine, and inhibited flux through glutamine synthetase.

Animals↗
PubMed1989

[Recent advances in the clinical study of the renin system. Reference values and conditions of validity].

Plasma renin activity, angiotensinogen, active renin and aldosterone concentrations and, 1 hour after addition of trypsin 1 mg per ml of plasma at -4 degrees C, prorenin and total renin concentrations were measured in 49 normotensive volunteers. Renin activity and active renin concentration were correlated (n = 98, r = 0.902, p less than 0.01) and their ratio was not dependent on the angiotensinogen concentration. Prorenin accounted for 90 per cent of total renin and was 40 per cent higher in males than in females in both supine and upright positions (p = 0.02 and p = 0.01). The change in position markedly increased plasma renin activity as well as active renin and aldosterone concentrations and, to a lesser degree, prorenin concentration, thereby raising the active/total renin ratio. Plasma renin activity, active renin concentration and plasma aldosterone concentration were significantly and negatively correlated with age, but not with urinary sodium excretion. Plasma renin activity and active renin and angiotensinogen concentrations were also measured in 14 patients with high angiotensinogen concentration (pregnant women and oestrogen users) and in 14 patients with cirrhosis and subnormal angiotensinogen concentration. In these patients the ratio of plasma renin activity to active renin concentration was correlated with the angiotensinogen concentration (n = 28, r = 0.643, p less than 0.01). The slope of the regression line between renin activity and active renin concentration was significantly different in patients with cirrhosis and in healthy volunteers, the measurement of renin activity leading to a ten-fold underestimation of active renin concentration. In clinical investigations of the renin system, plasma samples should be handled at room temperature to avoid cryoactivation of prorenin. The determination of active renin concentration should be preferred to that of plasma renin activity because it is not influenced by physiological or pathological variations in angiotensinogen.

Adolescent↗
PubMed1986

The "floating knee" in children.

The term "floating knee" describes the flail joint resulting from fractures of the shaft or adjacent metaphyseal region of the ipsilateral femur and tibia; we have reviewed 15 children with this combined injury seen at the Winnipeg Children's Hospital. All had been involved in motor vehicle accidents, eight having been struck while cycling; the biomechanics of such an injury have also been studied. Treatment is difficult and the regimes varied. Results were poor when both fractures were treated nonoperatively and we recommend that at least one of the fractures should be rigidly fixed.

Adolescent↗
PubMedDate not supplied

Optimised helper virus-free production of high-quality adeno-associated virus vectors.

BACKGROUND: Clinical development of adeno-associated virus (AAV) requires standardised, safe, efficient and scalable procedures for the manufacture of the rAAV vector, including production, purification and testing. Several strategies have been reported for the approach to the manufacturing problem. We report a helper virus-free process that produces high quality rAAV stocks. METHODS: rAAV were produced by triple transfection, a helper virus-free process. After lysis of the cells in the presence of nuclease, the rAAV produced were purified by HPLC through two ion-exchange columns in tandem followed by dialysis. rAAV stocks were thoroughly characterised for biological activity and for the presence of residual contaminants. The titer of infectious particles and of rep + particles was determined by dRA assay. Contaminating DNA and RNA were determined by fluorescent dye binding and real-time PCR. The protein content of the rAAV stocks was characterised by SDS-PAGE, ELISA test, Western blot and specific enzymatic assays for putative residual contaminating protein. The in vivo biological activity of the stocks was evaluated in mouse muscle. RESULTS: rAAV stocks obtained following this procedure elicit: 2-5 x 10(12) pp/ml; 3-6 x 10(10) ip/ml; < 10(3) rep + particles/ml; <0.3 mUeq/ml of residual benzonase activity; non-detectable Ad or beta-galactosidase proteins; <35 pg/ml of cellular genomic DNA; in vivo expression in mouse muscle without any immune reaction detected. CONCLUSIONS: This work demonstrates the possibility of producing purified high-quality rAAV free of helper virus. The procedure described in this paper is easily adaptable for large-scale production of clinical rAAV vectors.

Animals↗