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Biomedical subjects

M Broyer

Publications and source records attributed to M Broyer.

At least 37 records · Page 2Linked to original sources
PubMed2000

Size-dependent electron-electron interactions in metal nanoparticles

The internal thermalization dynamics of the conduction electrons is investigated in silver nanoparticles with radius ranging from 13 to 1.6 nm using a femtosecond IR pump-UV probe absorption saturation technique. A sharp increase of the electron energy exchange rate is demonstrated for nanoparticles smaller than 5 nm. The results are consistent with electron-electron scattering acceleration due to surface induced reduction of the Coulomb interaction screening by the conduction and core electrons.

Journal Article↗
PubMed2000

Polarizability of KC60: evidence for potassium skating on the C60 surface

We present the first measurement of the polarizability and the permanent dipole moment of isolated KC60 molecules by molecular beam deflection technique. We have obtained a value of 2506+/-250 A(3) for the polarizability at room temperature. The addition of a potassium atom enhances by more than a factor of 20 the polarizability of a pure C60 molecule. This very high polarizability and the lack of observed permanent dipole show that the apparent polarizability of KC60 is induced by the free skating of the potassium atom on the C60 surface, resulting in a statistical orientation of the dipole. The results are interpreted with a simple model similar to the Langevin theory for paramagnetic systems.

Journal Article↗
PubMed2000

Pretransplant blood transfusions with cyclosporine in pediatric renal transplantation.

Pretransplant transfusions were repeatedly shown to be associated with improved graft survival in the "pre-cyclosporine era," and have recently been shown to be beneficial in patients on modern immuno-suppressive regimes. In an attempt to improve this transfusion effect and minimize the potential development of cytotoxic antibodies, we have given these transfusions, with concomitant cyclosporine cover, prior to transplantation. Ninety-two renal transplantations were performed in 91 children in the study group (group 1) and all received pretransplant transfusions with cyclosporine cover. Results were compared with a preceding group of 102 children (104 transplantations) who had received pretransplant transfusions without cyclosporine cover (group 2). There were 70 cadaver and 22 living-related donor (LRD) transplants in group 1, and 88 cadaver and 16 LRD transplants in group 2. Graft survival rates (1- and 5-year) for cadaver transplantation were 96% and 90% in group 1 compared with 78% and 64% in group 2 (P = 0.001). For LRD transplantation, these figures were 95% and 87% in group 1 and 81% and 69% in group 2. There was no difference between the two groups in terms of age at transplantation, sex, donor age, HLA-A, -B, -DR mismatches, or cold and warm ischemia times. All cadaver graft recipients received quadruple, sequential immunosuppression post transplant. However, 9 patients in group 1 were changed to tacrolimus for recurrent rejection episodes. No patient developed persistent lymphocytotoxic antibodies post transfusion or side effects of cyclosporine. Cyclosporine can be safely given with whole blood prior to transplantation with no adverse effect and no sensitization. Graft survival was significantly improved in this group of patients and graft loss due to rejection was exceptional. This effect should be further evaluated in prospective studies.

Anticoagulants↗
PubMed2000

Alterations of protein metabolism by metabolic acidosis in children with chronic renal failure.

BACKGROUND: Several reports suggest that metabolic acidosis may induce significant alterations in protein metabolism and that its outbreak may even result in growth retardation in children with chronic renal failure (CRF). However, the effects of metabolic acidosis on protein metabolism kinetics have never been investigated in these settings. METHODS: Postabsorptive leucine metabolism, a marker of whole-body protein metabolism, was measured by using a primed, continuous intravenous infusion of L-[1-13C]leucine in 10 CRF children who were one to four years old. RESULTS: Interindividual values of whole-body protein turnover exhibited a very large range, which was mainly accounted for by acidotic status (plasma HCO3-) and body composition [fat-free mass (FFM)]. After correction for differences in FFM, plasma HCO3- was highly correlated with protein breakdown (R2 = 0.65, P < 0.001), so that CRF children were divided in two groups according to their acid-base status: Group A had a mean plasma HCO3- level of 15.8 +/- 1.5 mmol. L-1 (mean +/- SD, N = 5), whereas group B had near-normal values (HCO3-, 22.6 +/- 3.0 mmol. L-1, N = 5). The leucine rate of appearance from protein breakdown was markedly higher in group A than in group B (4.15 +/- 1.43 vs. 2.46 +/- 0.47 micromol. kg-1. min-1, respectively, P < 0.05), and the net leucine balance tended to be more negative in group A (-0.73 +/- 0.34 vs. -0.44 +/- 0.26 micromol. kg-1. min-1, respectively). CONCLUSIONS: Metabolic acidosis in children with CRF results in an excessive catabolic state, suggesting that acidosis-related protein wasting could contribute to growth retardation.

Acidosis↗
PubMed2000

[Cystinosis from childhood to adulthood].

Nephropathic cystinosis is a metabolic disease related to lysosomal cystine accumulation in almost all tissues of the body. The first symptoms set up from 5 or 6 months of age including anorexia vomiting polyurodipsia and failure to thrive associated with a proximal tubulopathy (glycosuria, tubular proteinuria, loss of bicarbonate, potassium, phosphorus, etc.) Treatment by cysteamine dramatically changed the prognostic. If started early this treatment allows to delay and possibly to prevent the spontaneous evolution towards end stage renal disease between 6 and 12 years of age and to avoid the growth failure. On the long term the disease involves other organs: eyes, thyroid endocrine pancreas, muscle and central nervous system. The diagnosis of cystinosis is based on the cystine leukocyte assay allowing also the follow up and the adjustment of the treatment. Prenatal diagnosis is possible on chorionic sample. The gene of this recessive disease, mapping on chromosome 17 was recently identified. This gene encodes a protein of the lysosomal membrane involved in the transport of cystine out of the lysosome. There is a juvenile, late onset, form of cystinosis its main symptom is proteinuria with variable tubular alterations. The so called adult form is asymptomatic its only symptom is corneal deposits most often found by chance examination.

Adult↗
PubMed2000

Role of the bladder in delayed failure of kidney transplants in boys with posterior urethral valves.

PURPOSE: There is a tendency toward less favorable long-term graft function in patients with posterior urethral valves than in controls. We studied the role of the bladder in boys who underwent transplantation by simultaneously evaluating renal graft and voiding function. MATERIALS AND METHODS: Between 1972 and 1994, 66 boys with posterior urethral valves underwent kidney transplantation. Of these boys 44 with a mean age of 9.7 years who retained a functional renal graft did not undergo any surgery on the lower urinary tract except for the initial treatment of posterior urethral valves. Long-term evaluation included a voiding questionnaire, radiological assessment and serum creatinine measurement. RESULTS: Average followup was 9.01 years (range 2.4 to 19.6). There was no voiding dysfunction symptomatology in 23 boys, while 3 (14.2%) and 8 (38.1%) of the remaining 21 had daytime and nighttime frequency, respectively. Dysuria and incontinence were present in 11 (52.4%) and 12 (57.1%) patients, respectively. Urodynamics in 11 cases revealed a mean bladder compliance plus or minus standard deviation of 11.3+/-2.8 ml./cm. water. In boys with a voiding disorder mean serum creatinine increased after 5 years of followup. At 10 years after kidney transplantation mean serum creatinine was 140.3+/-36.0 and 285.7+/-36.2 micromol./l. in asymptomatic boys and those with a voiding disorder, respectively (p<0.01). CONCLUSIONS: Valve bladder has a role in the deterioration of renal transplants in boys with posterior urethral valves. In those with a voiding disorder closer followup is needed, including urodynamic and radiological studies. Bladder dysfunction, such as hypocompliance and/or hyperreflexia, requires medical or surgical treatment.

Child↗
PubMed1999

Diabetes mellitus in patients with infantile cystinosis after renal transplantation.

Diabetes mellitus is a frequent long-term complication of infantile nephropathic cystinosis. We studied 44 cystinotic patients, aged 22.1+/-5.4 years, transplanted at a mean age of 11.3+/-2.5 years; 25% were treated with insulin at 20 years of age or 10 years after transplantation, and over half required insulin at latest follow-up. In comparison, diabetes mellitus occurred in only 1% of non-cystinotic transplanted patients. Sequential oral glucose tolerance tests (OGTTs) in these patients showed the progressive deterioration of glucose metabolism. All but 2 patients had an abnormal response at latest follow-up. The high doses of corticosteroid given after transplantation or during rejection episodes were responsible for transient insulin dependency. However, the development of impaired glucose tolerance and diabetes mellitus depended mainly on the cystinotic process, which developed slowly with time. The deterioration of glucose tolerance was correlated with a decreased early phase of insulin secretion, estimated from the plasma insulin level at 30 min of the OGTT, while there was no evidence of insulin resistance. The occurrence of diabetes mellitus correlated with a worsening of the vital prognosis.

Adolescent↗
PubMed1999

Chronic renal failure after Puumala virus infection.

Chronic renal failure has never been described after Puumala hantavirus infection, which usually causes acute renal failure with spontaneous full recovery. We report a 15-year-old boy who presented with Puumala hantavirus infection and initial severe acute renal failure. His renal function gradually improved, but more than 2 years after the acute episode it was still moderately impaired, with a creatinine clearance of about 60 ml/min per 1.73 m(2)

Adolescent↗
PubMed1999

[Passage from sandimmun to neoral in kidney transplantation in children].

BACKGROUND: The cyclosporine microemulsion formulation Neoral, which allows a better absorption and a more regular pharmacokinetic profile, is proposed for replacing the original formulation, Sandimmun. The present study reports the results of conversion from Sandimmun to Neoral in children with a kidney graft, a population for which information remains limited. METHODS AND PATIENTS: Twenty children, 2.5 to 10.5 years of age, who had a kidney graft with a stable renal function for between six months to five years (m = 2.6) were the subjects of this study. The patients were switched from Sandimmun to Neoral at the same dose, adjusted afterwards on a cyclosporine trough level. RESULTS: After six months, the mean dose decreased from 9.1 mg/kg/d to 8.4 mg/kg/d, i.e., 12.5%. After one year, the mean dose was 7 mg mg/kg/d, i.e., 28%. Of the 65% of patients who had a decreased dose, most of them had the highest dose of Sandimmun at the start. Mean serum creatininemia levels slightly increased from 85.6 to 89.5 mumol/L after six months (P = 0.03). None of the patients had a rejection crisis during the first six months under Neoral. Blood pressure did not change significantly, hirsutism improved in two cases but increased or appeared in two cases as well. Gingival hypertrophy increased or appeared in four cases. DISCUSSION: A decrease in the dose was decided on either to maintain the trough CsA blood level in the desired range or because of the appearance of a symptom suggesting a side effect of cyclosporine, especially the increase of creatinemia. The trough level did not appear to be the best index for adapting the dose. CONCLUSION: In stable pediatric kidney transplant recipients, the switch from Sandimmun to Neoral provided a reduction in drug dosage in 65% of cases without an increase in adverse events.

Age Factors↗
PubMed1999

Molecular characterization of CTNS deletions in nephropathic cystinosis: development of a PCR-based detection assay.

Nephropathic cystinosis is an autosomal recessive disorder that is characterized by accumulation of intralysosomal cystine and is caused by a defect in the transport of cystine across the lysosomal membrane. Using a positional cloning strategy, we recently cloned the causative gene, CTNS, and identified pathogenic mutations, including deletions, that span the cystinosis locus. Two types of deletions were detected-one of 9.5-16 kb, which was seen in a single family, and one of approximately 65 kb, which is the most frequent mutation found in the homozygous state in nearly one-third of cystinotic individuals. We present here characterization of the deletion breakpoints and demonstrate that, although both deletions occur in regions of repetitive sequences, they are the result of nonhomologous recombination. This type of mechanism suggests that the approximately 65-kb deletion is not a recurrent mutation, and our results confirm that it is identical in all patients. Haplotype analysis shows that this large deletion is due to a founder effect that occurred in a white individual and that probably arose in the middle of the first millenium. We also describe a rapid PCR-based assay that will accurately detect both homozygous and heterozygous deletions, and we use it to show that the approximately 65-kb deletion is present in either the homozygous or the heterozygous state in 76% of cystinotic patients of European origin.

Alleles↗
PubMed1999

Severity of phenotype in cystinosis varies with mutations in the CTNS gene: predicted effect on the model of cystinosin.

Infantile nephropathic cystinosis is a rare, autosomal recessive disease caused by a defect in the transport of cystine across the lysosomal membrane and characterized by early onset of renal proximal tubular dysfunction. Late-onset cystinosis, a rarer form of the disorder, is characterized by onset of symptoms between 12 and 15 years of age. We previously characterized the cystinosis gene, CTNS, and identified pathogenic mutations in patients with infantile nephropathic cystinosis, including a common, approximately 65 kb deletion which encompasses exons 1-10. Structure predictions suggested that the gene product, cystinosin, is a novel integral lysosomal membrane protein. We now examine the predicted effect of mutations on this model of cystinosin. In this study, we screened patients with infantile nephropathic cystinosis, those with late-onset cystinosis and patients whose phenotype does not fit the classical definitions. We found 23 different mutations in CTNS; 14 are novel mutations. Out of 25 patients with infantile nephropathic cystinosis, 12 have two severely truncating mutations, which is consistent with a loss of functional protein, and 13 have missense or in-frame deletions, which would result in disruption of transmembrane domains and loss of protein function. Mutations found in two late-onset patients affect functionally unimportant regions of cystinosin, which accounts for their milder phenotype. For three patients, the age of onset of cystinosis was <7 years but the course of the disease was milder than the infantile nephropathic form. This suggests that the missense mutations found in these individuals allow production of functional protein and may also indicate regions of cystinosin which are not functionally important.

Age of Onset↗
PubMed1998

Biological parameters in major depression: effects of paroxetine, viloxazine, moclobemide, and electroconvulsive therapy. Relation to early clinical outcome.

BACKGROUND: Clinical and pharmacologic studies report a relative or absolute serotonergic deficiency in major depression; however, the variability of clinical characteristics of illness has led to controversial results. In the present work, we looked for a possible relationship between i) biochemical values that indirectly reflect aminergic neurons activity and clinical characteristics and ii) their evolution and the early clinical outcome under antidepressive therapies (ATs). METHODS: Platelet serotonin content, platelet monoamine oxydase activity, and urinary biopterins were measured in 27 depressed patients before and during four different ATs (paroxetine, viloxazine, moclobemide, or electroconvulsive therapy). Depressive symptomatology and its evolution under ATs were quantified using three clinical rating scales. RESULTS: A severe symptomatology, high serotonin (5-HT) platelet content, and high or low urinary B could represent risk factors leading to a smaller or delayed response to an AT. Furthermore, the early improvement under ATs was negatively correlated to pretreatment 5-HT platelet content. CONCLUSIONS: Determination of 5-HT level could be useful in the choice of an AT.

Adrenergic Uptake Inhibitors↗
PubMed1998

Familial juvenile nephronophthisis.

Familial juvenile nephronophthisis (NPH) is an autosomal recessive interstitial nephritis leading to terminal renal failure around puberty. Associations with extrarenal symptoms have been reported, mainly with Leber amaurosis (termed Senior-Løken syndrome). By means of linkage analysis a gene NPH1 for the purely renal form of NPH has been localized to chromosome 2. Genetic heterogeneity has been shown between NPH and Senior-Løken syndrome and also within the group of isolated NPH cases. Further characterization of the NPH1 region led to the isolation of large homozygous deletions in approximately 70% of patients with NPH. The detection of these deletions by PCR represents a simple noninvasive method for precise diagnosis in the majority of patients suspected of having NPH.

Chromosome Mapping↗
PubMed1998

Recombinant human growth hormone treatment of children on hemodialysis. French Society of Pediatric Nephrology.

Forty-two children, aged 2-21.5 years on hemodialysis with a height below -2.0 standard deviation score (SDS) for age, were selected to receive recombinant human growth hormone (rhGH) therapy at 17 French centers. Of the 42 children, 36 were prepubertal and 8 were in early puberty (testicular volume between 4 and 8 ml for boys, breast development B2 or B3 in girls). All received 1 IU/kg per week by daily subcutaneous injection for 1-5 years. The year before rhGH therapy served as a control period. During the 1st year of treatment, mean growth velocity increased from 3.5 to 7.0 cm/year (P < 0.0001) and was always over 2.5 cm/year. This velocity allowed a catch-up growth of +0.5 height SDS. Neither weight nor the body mass index varied compared with the pretreatment year. No change was observed in urea, creatinine, or glucose tolerance. The mean increment in bone age was 0.9 years. The mean growth velocity decreased over subsequent years (P < 0.0001), but remained higher than the prestudy velocity. A significant negative correlation was observed during the 1st year between the increase in growth velocity and the prestudy velocity (P < 0.0001), with the least gain in patients who had the best spontaneous velocity. Pubertal status had no influence on response to rhGH. No significant side effects were observed during the 103 treatment-years. Five patients developed secondary hyperparathyroidism and 1 suffered from acute pancreatitis, but the relationship with rhGH therapy remains uncertain. rhGH therapy appears indicated for children on hemodialysis, even though the potential benefits appear somewhat lower for those with a spontaneous growth velocity over 6 cm/year.

Adolescent↗