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Biomedical subjects

J P Colombo

Publications and source records attributed to J P Colombo.

At least 19 recordsLinked to original sources
PubMed2001

Urine analysis performed by flow cytometry: reference range determination and comparison to morphological findings, dipstick chemistry and bacterial culture results--a multicenter study.

AIM: To validate whether quantitative flow-cytometric analysis of particulate matter in urine would allow for accurate and rapid enumeration of red blood cells (RBC), leukocytes (WBC), squamous epithelial cells (EC), casts, and bacteria, a Sysmex UF-100 analyzer was tested in a multicenter study. MATERIAL AND METHODS: At first, reference values were established and found to be < 14 for RBC, < 16 for WBC, < 9 for EC, < 2 for casts and < 173 for bacteria, respectively (counts per microl; 97.5 percentile). Due to the wide use of dipstick and microscopic sediment analysis in routine urine diagnostics, comparative studies on 950 random urine samples were performed. Bacterial counting combined with WBC enumeration was further compared in 266 routine urinary microbiologic cultures. RESULTS: Good correlations were found comparing UF-100 results of RBC (r = 0.89), WBC (r = 0.94), and EC (r = 0.74) with Fuchs-Rosenthal Chamber (FRC) counts. However, some misclassification of casts (r = 0.32) could be observed. Correlations of UF-100 with dipstick and sediment testing was significant (p < 0.001), but the scatter of the latter two methods is too wide to consider them as quantitative methods. Promising results further revealed that the analyzer has a good negative predictive value (NPV) for microbiologically negative cultures, especially for cultures with bacterial counts of 10(5)/l (NPV = 95%). CONCLUSION: The analyzer is capable of providing rapid and reliable urine analysis of cellular particles avoiding the known imprecision of dipstick and sediment methodology. Thus, when used in an algorithm, combined with dipstick or quantitative urine chemistry analysis (for hemoglobin, esterase, protein, glucose, etc.), this analyzer might serve as a rapid and accurate screening tool in routine urine analysis, thereby reducing manual reviewing rate as well as the number of missed samples, compared to screening with dipstick alone.

Adolescent↗
PubMed1999

Glutaric aciduria type I: ultrasonographic demonstration of early signs.

BACKGROUND: Glutaric aciduria type I (GA-I) is a rare inherited metabolic disease with increased excretion of glutaric acid and its metabolites. Diagnosis is often delayed until the onset of irreversible neurological deficits. MATERIAL AND METHODS: We reviewed the clinical and imaging (US, CT and MRI) findings in six patients with proven GA-I and with emphasis on the early US findings. Coronal and sagittal US images of the brain were obtained through the anterior fontanelle in all patients. CT was obtained in three patients and MRI was obtained in two. RESULTS: Macrocephaly was found in all patients, being present in three children at birth or developing rapidly within the first weeks of life. US showed, in all patients, bilateral symmetrical cyst-like dilatation of the sylvian fissures. Progressive fronto-temporal atrophy developed within the first months. CT and MRI demonstrated fronto-temporal atrophy with lack of opercularisation in all cases and basal ganglia or periventricular hypodensities in three patients. CONCLUSIONS: In patients with macrocephaly at birth or rapidly developing within the first weeks of life, US should be performed as the primary imaging modality. Cyst-like bilateral widening of the sylvian fissures is the first sign of GA-I, followed by progressive fronto-temporal and ventricular enlargement. These patients should be screened for GA-I in order to initiate treatment in the asymptomatic stage.

Abnormalities, Multiple↗
PubMed1998

Prenatal diagnosis of carbamoyl phosphate synthetase I deficiency by identification of a missense mutation in CPS1.

Carbamoyl phosphate synthetase I (CPS1) deficiency is an autosomal recessive metabolic disorder affecting the first enzymatic step of urea cycle. We report a consanguineous family in which the index patient died at 11 days of age from a severe form of CPS1 deficiency. Initial diagnosis was based on clinical histopathological, and enzymatic investigations. Direct sequencing of the complete CPS1 coding region revealed a disease-associated homozygous Thr544Met mutation in CPS1. On the basis of the molecular data, prenatal diagnosis was established for genomic DNA and performed at gestational week 12, after chorionic villus sampling. The fetus was homozygous for the Thr544Met mutation, and termination of pregnancy was elected. Histopathological signs of the hepatocellular metabolic disorder similar to that of the index patient were found in fetal liver thus giving morphological evidence for this hereditary error of urea cycle function as early as gestational week 12.

Base Sequence↗
PubMed1998

Assessment of troponin-T for detection of clinical cardiac rejection.

Non-invasive detection of cardiac rejection still remains a challenge after heart transplantation. We assessed troponin-T as a new serum marker to diagnose cardiac rejection. Twenty-five heart transplant patients (Berne) were monitored prospectively for up to 2 years, and compared to 89 retrospectively assessed patients (Stanford). Blood samples (392 Berne and 320 Stanford) were analyzed (creatine kinase, isoenzymes MB activity and MB mass, troponin-T and troponin-I). Regression analysis between the results of these blood samples and cardiac rejection grading from simultaneously performed endomyocardial biopsies was carried out. Troponin-T tests done in two different laboratories showed a good correlation (r = 0.91; P < 0.0001), whereas troponin-T versus troponin-I showed a lower correlation (r = 0.53; P < 0.0001). Troponin-T and -I in contrast to other enzymes were elevated for a longer period (up to 4 weeks before returning to baseline) after transplantation than during conventional cardiac surgery. Beyond 3 months the following correlations were found between troponin-T (new or old test) and the other enzymes (creatine kinase: r = 0.26, MB activity: r = 0.4, and MB mass: r = 0.68). The correlation between the degree of rejection and the enzyme release is poor, however, the best results were obtained for troponin-T (r = 0.22; P < 0.001). We found a low correlation between troponin-T and the degree of rejection beyond 3 months after heart transplantation. Despite a troponin-T elevation in some patients with rejection, the new test is not sensitive enough to be used alone for the non-invasive diagnosis of cardiac rejection.

Biomarkers↗
PubMed1998

Free circulating magnesium and renal magnesium handling during acute metabolic acidosis in humans.

Ion-selective electrodes have been designed for determining the ionized concentration of magnesium in blood, the biologically active form of this ion. The effect of acute acidosis induced by ammonium loading on circulating and urinary magnesium was investigated in 11 volunteers. No changes in plasma total and ionized magnesium were noted following administration of ammonium chloride. On the contrary, administration of ammonium chloride increased the plasma free magnesium fraction and the urinary magnesium excretion. The study demonstrates that the hypermagnesiuria induced by acute acidosis is not caused by ionized hypermagnesemia and supports the theory that acidosis decreases the circulating magnesium fraction that is bound to proteins.

Acidosis↗
PubMed1998

Effect of increasing dietary threonine intakes on amino acid metabolism of the central nervous system and peripheral tissues in growing rats.

The threonine content of most of the infant formulas currently on the market is approximately 20% higher than the threonine concentration in human milk. Due to this high threonine content the plasma threonine concentrations are up to twice as high in premature infants fed these formulas than in infants fed human milk. To study the effect of different threonine intakes on plasma and tissue amino acid concentrations, 24 young male Wistar rats were fed three experimental diets based on a mixture of bovine proteins with a whey protein/casein ratio of 60/40 with different threonine contents [group A, 0.86 g of threonine/100 g (n = 8); group B, 1.03 g of threonine/100 g (n = 8); group C, 2.21 g of threonine/100 g (n = 8)]. Eight animals were fed a typical rat diet based on bovine casein as controls. After a feeding period of 15 d, amino acids were measured in plasma and in homogenates of the cerebral cortex, brain stem, liver, and muscle. There was a significant correlation between threonine intake and plasma threonine levels (r = 0.687, p < 0.001). The plasma threonine concentration correlated significantly with the threonine concentration in the cortex (r = 0.821, p < 0.01) and the brain stem (r = 0.882, p < 0.01). There was a positive significant correlation between threonine and glycine concentrations in the cortex (r = 0.673, p < 0.01), and the brain stem (r = 0.575, p < 0.01), whereas the glycine concentration decreased with increasing threonine intakes in the liver and muscle. The presented data indicate that increasing the threonine in plasma leads to increasing brain glycine and thereby affects the neurotransmitter balance in the brain. This may have consequences for brain development during early postnatal life. Therefore, excessive threonine intake during infant feeding should be avoided.

Amino Acids↗
PubMed1996

Ornithine transcarbamylase deficiency: characterization of gene mutations and polymorphisms.

We identified three new and three known mutations in male patients with OTC deficiency using PCR amplification of all the individual exons, including the adjacent intron sequences, followed by direct sequencing of the amplimers. Two mutations were found in males presenting with neonatal fatal hyperammonemia and no detectable enzyme activity in their livers. The H302Y mutation found in one patient affects the putative binding site for ornithine. The second patient had an R141X mutation, which is one of the few recurrent mutations in the OTC gene. Four different missense mutations were identified in male patients with late onset of the disease and residual OTC activities between 14% and 35%. The mutations are Y176C and P220A and the known mutations K88N and T343K, respectively. Four of the patients' mothers were identified as carriers. In two cases, the mutations had occurred spontaneously. In addition, the frequency of four polymorphisms of the OTC gene was studied. The K46R polymorphism in exon 2 and the Q27OR polymorphism in exon 8 were found in 36% and 4% of screened alleles, respectively. Two questionable polymorphisms in exon 4, F101L and L111P, were not present in any of the screened alleles.

Ammonia↗
PubMed1996

Identification of four novel splice site mutations in the ornithine transcarbamylase gene.

Ornithine transcarbamylase (OTC) deficiency, the most common inborn error of the urea cycle, shows X-linked inheritance with frequent new mutations. Using polymerase chain reaction (PCR) amplification of the individual exons including adjacent intron sequences followed by direct sequencing of the amplimers we identified four new mutations affecting donor splice sites of introns 2, 5, 6, and 8. The mutation at the first position of intron 2 was a G to A exchange associated with acute neonatal hyperammonemia in a male patient at the age of 5 months. A G to C substitution in intron 5 was detected in a boy who developed 2 days after birth hypotonia, and respiratory distress, followed by severe hyperammonemia and terminal coma. The intron 6 mutation, a G to T substitution, was detected in a girl presenting with first episodes of vomiting and agitation at the age of 2 months. The mutation in intron 8, also a G to T transition, caused fatal hyperammonemia and early death at the age of 15 days in a male patient. We present four donor splice site mutations resulting in severe neonatal or very early onset of the disease in three boys and in one female patient. As the GT dinucleotide of the 5' donor splice site is invariant and required for correct splicing the described mutations may lead to improperly spliced mRNAs and aberrant gene products.

Amino Acid Metabolism, Inborn Errors↗
PubMed1996

Effect of L-dopa on visual evoked potentials and neuropsychological tests in adult phenylketonuria patients.

Eight adult, untreated patients with classical phenylketonuria received L-dopa and a decarboxylase inhibitor for 2 weeks. No effect of L-dopa therapy on choice reaction time tasks, sustained attention, frontal lobal function as well as latencies of visual evoked potentials was found. The results raise the question if adult patients with phenylketonuria really suffer from functional dopamine deficiency.

Adult↗
PubMed1996

Tyrosine uptake and regional brain monoamine metabolites in a rat model resembling congenital hyperammonemia.

Hyperammonemia found in congenital disorders has a toxic effect on the central nervous system. Disturbances of brain neurotransmitter metabolism have been proposed, such as an increased transport of tryptophan into the brain and an increased flux through the serotonin pathway. Results concerning the catecholamine pathway are, however, contradictory. We therefore studied whether hyperammonermia increases brain uptake of the neurotransmitter precursor amino acid tyrosine and whether these changes affect the concentration of neurotransmitters and their metabolites in different brain areas (frontal cortex, caudatus-putamen, thalamus, hypothalamus, hippocampus/substantia nigra, brainstem) of rats made hyperammonemic with urease. The brain uptake of tyrosine was measured in the forebrain, brainstem, and cerebellum. The brain areas were analyzed for dopamine, 3,4-hydroxyphenylacetic acid; homovanillic acid, norepinephrine, and vanillylmandelic acid. The brain uptake index of tyrosine was increased in the forebrain and brainstem of the hyperammonemic rats with concomitantly elevated concentrations in the forebrain of tyrosine, phenylalanine, and tryptophan. The homovanillic acid content was significantly increased in the hypothalamus, hippocampus/substantia nigra and brainstem. The concentrations of norepinephrine, dopamine, and 3, 4-hydroxyphenylacetic acid were not significantly changed. Vanillylmandellic acid was decreased in the caudatus-putamen, thalamus, and hypothalamus. The data indicate an undisturbed neurotransmitter synthesis and, taken with the augmented tyrosine uptake at the blood-brain barrier, an increased flux through the dopamine pathway. These changes observed in the hyperammonemic animal model could contribute to the understanding of the pathogenic mechanisms and offer an explanation for the neuropsychiatric disturbances observed in children with congenital hyperammonemia.

Amino Acids↗
PubMed1995

Survival after early treatment for carbamyl phosphate synthetase (CPS) I deficiency associated with increase of intramitochondrial CPS I.

The basis for the benefit of early treatment in urea-cycle defects might be an increase in intramitochondrial mutant enzyme in hepatocytes in the postnatal period. In two siblings with carbamyl phosphate synthetase I (CPS I) deficiency, immunoreactive CPS I was greatly reduced in the liver and no residual enzyme activity was detectable. The elder child died at age 4 days, before the diagnosis of CPS I deficiency was established, but in the younger child, age 9 months, treatment was initiated on the 2nd day of life when ammonia concentration was moderately increased, and she has survived. Intramitochondrial CPS I was substantially higher in this sibling than in the elder sister. The different outcome in the younger patient was probably attributable to prompt treatment after early diagnosis.

Amino Acid Metabolism, Inborn Errors↗
PubMed1995

Prenatal diagnosis of the urea cycle diseases: a survey of the European cases.

A European survey of prenatal diagnosis cases involving urea cycle diseases was performed. Citrullinemia was the most frequently investigated disease (108 cases). Other diseases are, in order of frequency, argininosuccinic aciduria (75 cases), ornithine transcarbamylase defect (52 cases), carbamoylphosphate synthetase defect (8 cases), triple H (3 cases), and arginase deficiency (1 case). Only one disease (ornithine transcarbamylase defect) is presently diagnosed using molecular biology methods.

Argininosuccinic Acid↗
PubMed1995

Ornithine transcarbamylase deficiency: new sites with increased probability of mutation.

Ornithine transcarbamylase (OTC) deficiency, the most common inborn error of the urea cycle, shows an X-linked inheritance with frequent new mutations. Investigations of patients with OTC deficiency have indicated an overproportionate share of mutations at CpG dinucleotides. These statistics may, however, be biased because of the easy detection of CpG mutations by screening for TaqI and MspI restriction sites. In the present study, we investigated 30 patients, with diagnosed OTC deficiency, for new sites with an increased probability of mutation by complete DNA sequence analysis of all ten exons of the OTC gene. In six patients, two codons in exons 2 and 5, respectively, contained novel recurrent mutations, all of them affecting CpG dinucleotides. They included C to T and G to A transitions in codon 40, changing an arginine to cysteine and histidine, respectively, and a C to T transition in codon 178 causing the substitution of threonine by methionine. The first two mutations were characterized by a mild clinical course with high risk of sudden death in late childhood or early adulthood, whereas the third mutation showed a more severe phenotypic expression. In addition to these novel mutations, we identified four patients with the known R277W mutation, making it the most common point mutation of the OTC gene.

Adolescent↗