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Biomedical subjects

O A Mamer

Publications and source records attributed to O A Mamer.

At least 19 recordsLinked to original sources
PubMed1998

Measurement of sulfate concentrations and tracer/tracee ratios in biological fluids by electrospray tandem mass spectrometry.

A reproducible and very sensitive method is described for the quantitation of inorganic sulfate in biological fluids by negative electrospray ionization tandem mass spectrometry. After addition to the sample of (34)S-labeled sodium sulfate internal standard and deproteinization with methanol, interfering bicarbonate anions are removed by acidification and chloride and phosphate by means of a single filtration step. The tandem mass spectrometer is used in neutral loss mode to detect HSO(4)(-) ions free of interference from residual isobaric H(2)PO(4)(-) ions. Organic sulfates do not interfere with the measurement. Serum and urinary inorganic sulfate concentrations measured with this technique agree closely with determinations by ion-exchange chromatography with conductivity detection. Unlike the latter method, this technique does not require dedicated equipment. The method is also suitable for measuring the ratio of (34)S-labeled sulfate to unlabeled sulfate in serum and hence represents an attractive alternative for the use of the radioactive (35)S isotope in human studies of body composition and oxidation of sulfur-containing substrates to sulfate.

Chemistry Techniques, Analytical↗
PubMed1997

Effects of leucine on whole body leucine, valine, and threonine metabolism in humans.

We tested whether expansion of the plasma leucine pool distorts leucine or valine tracer kinetics, causing errors in the derived values of whole body proteolysis. Seven normal adults received a 10-h primed-continuous tracer infusion of L-[5,5,5-2H3]leucine, L-[(1-13)C]valine, and L-[(1-13)C]threonine, during the final 7 h of which L-leucine was infused at a rate that more than tripled the plasma leucine concentration. Leucine, valine, and threonine rates of appearance were converted to a common value of whole body proteolysis on the basis of their concentrations in body proteins. The conversion of labeled leucine and valine to their corresponding branched-chain alpha-keto and alpha-hydroxy acids was also monitored. Before the unlabeled leucine infusion, postabsorptive whole body proteolysis was estimated similarly by the three tracers (approximately 180 mg protein.kg-1.h-1. The leucine infusion reduced proteolysis by an average of 21% (P < 0.006), as estimated by use of valine or threonine kinetics, and by 10% by use of leucine kinetics (P < 0.02). No delay in the conversion of valine to alpha-ketoisovalerate occurred during the leucine infusion. Thus all three tracers indicated similar postabsorptive rates of whole body proteolysis and a reduction of proteolysis during leucine administration, although the magnitude of the effect was underestimated with use of the leucine tracer.

Adult↗
PubMed1996

Acute-phase response in rat to carbon tetrachloride-azathioprine induced cirrhosis and partial hepatectomy of cirrhotic liver.

Irreversible liver cirrhosis was induced in rats by supplementing their diet with 0.02% azathioprine and intubating them twice a week with carbon tetrachloride in corn oil. Over period of 3 mo, intoxicated rats showed an atypical acute-phase reaction (APR). The relative concentrations of haptoglobin, beta-lipoprotein, alpha-1-antitrypsin, an unknown peak "X, " and transferrin increased exponentially following a mild initial drop, while albumin, C3c + C3, alpha-1-acid glycoprotein, alpha-1-lipoprotein, and macroglobulin declined continually during the experiment. The accumulated peritoneal fluid was found to contain a similar spectrum of APR proteins. On the other hand, histological examination revealed gradual liver damage manifested as a gradual increase in the areas of collagen separating liver cells, and at the end of the experiment, severe liver damage was evident with isolated hepatocytes in a matrix of collagen. The available data point to the disparity that exists between the physical status of hepatocytes and their biochemical function, which suggests that the remaining metabolically fatigued hepatocytes of the cirrhotic liver continue to biosynthesize and release elevated concentrations of some secretable APR proteins and less of others. Changes in the spectrum of APR plasma components during the progression of inflammatory or physical lesion remain a valid biochemical measure of the pathological function of the acutely intoxicated liver. Partial hepatectomy (PH) of cirrhotic liver displayed a mute APR and no regenerative activity of the remnant hepatic tissue, most likely due to the substantial depletion of hepatic DNA and possible chemical damage to DNA of the remaining viable hepatocytes. A possible cause for the depressed APR to the surgical insult of PH is that the initial azathioprine-CCl4 intoxication had maximally affected APR gene expression and a second injury would then elicit minimal further changes in mRNA levels. Thus, in a compounded pathological condition, the initial inflammatory stimulus on various pre-rRNAs, rRNAs, and mRNAs is rate-limiting to the hepatic biosynthesis and secretion of APR proteins and may not respond linearly, if at all, to a second stimulus.

Acute-Phase Reaction↗
PubMed1996

15N conservation in the metabolic conversion of isoleucine to alloisoleucine in the rat.

15N,13C6-L-Isoleucine was given by stomach tube to a pair of rats and the urine excreted over the following 6 h period was collected. The urinary amino acid fraction showed that the majority of the L-alloisoleucine produced from the labeled isoleucine was formed with the 15N label intact. This fails to support the commonly held supposition that L-isoleucine and L-alloisoleucine interconversion occurs through the reversible enolization of the 2-keto-3-methylvaleric acids formed by their transamination. In contrast to 15N label conservation in L-alloisoleucine, the majority of the 15N in the administered L-isoleucine underwent exchange with 14N.

Acetamides↗
PubMed1996

Artificial liver support: the pipe dream of today should be the reality of the near future.

The title of this article is taken from an interesting Letter to the Editor entitled 'Artificial liver support-Pipe dream or reality' by Cattral and Levy of the Toronto Hospital, Canada, published in the New England Journal of Medicine 1994, in which the authors persuasively propose possibilities of artificial liver support and suggest its advantages. We find that their suggestions agree with the core of our thoughts on this subject. The present article deals with the concept of implanting livers taken from humans, primates or non-primates (e.g. hog) into patients in parallel with their own metabolically fatigued or cirrhotic livers, with minimal surgical manipulation, as a prelude to total artificial liver support via a liver dialysis device. While the possibility exists that the host liver may recover function, a donor liver, whether implanted into the patient's abdomen or connected in vitro to the patient's circulatory system extracorporeally, may provide the host liver respite and a period for recovery and proliferation, if possible. Once recovery is under way, the donor liver may be removed and the patient will not experience the usual risks of rejection and the necessary side-effects of immunosuppression associated with conventional full hepatectomy and donor transplantation. The viability of a liver implantation model in rats is correlated in this article with hepatic acute phase response.

Animals↗
PubMed1996

Biogenesis of hepatic acute-phase response to trauma.

The bioorganic pathway(s) of hepatic acute-phase response in rat to single and compounded traumata triggered either by chemical or physical injury has been re-evaluated for the purpose of advancing a better understanding of mechanisms of hepatic regeneration. These insights would be useful in cases of liver cirrhosis and end-stage liver diseases and may allow avenues of surgical management other than liver transplantation. Mechanisms of acute-phase response in rat to a single inflammatory stimulus, e.g. intoxication with phalloidin, alpha-amanitin, subcutaneous administration of carageenan, subcutaneous implantation of Yoshida sarcoma or i.p. administration of Zajdela ascites are discussed and compared with (a) acute-phase response to intoxication by various factors leading to the development of liver cirrhosis, and (b) acute-phase response of nascent hepatocytes where hepatic regenerative activities were induced by chemical intoxication or surgical partial hepatectomy. Interestingly, hepatic acute-phase response was not limited only to these injuries outlined above but also to psychological conditions.

Acute-Phase Proteins↗
PubMed1995

Comparison of thermally oxidized lipids and acetaminophen with concurrent consumption of ethanol as inducers of liver cirrhosis.

The mechanism(s) of liver damage initiated by ingestion of toxic components of thermally oxidized lipids was compared in a rat model with the documented mechanisms of hepatic failure and necrosis initiated by acetaminophen. Acetaminophen (50 mg/kg body weight) or oxidized lipids (0.15 ml oxidized trilinolein or 1.05 ml oxidized butter oil per rat) were intubated at 12-h intervals to rats. Treated rats were allowed free access to food and water containing 3% ethanol. Changes in relative concentration of acute-phase plasma proteins, determined by two-dimensional (2D) immunoelectrophoresis, were taken as a marker of liver damage. In contrast to simple inflammation, acute-phase plasma proteins in this study disproportionately increased or decreased as histological damage of the liver due to intubation oxidized lipids or acetaminophen. Histological examination of liver of rats intoxicated with oxidized lipids revealed severe liver cirrhosis at the end of the trial, where the remaining viable hepatocytes were separated in a matrix of collagen. [3H1]Thymidine incorporation in hepatic DNA of acetaminophen or oxidized lipid intoxication increased in the early stages of intoxication, indicative of regenerative activity of the liver. Further progression of the cirrhosis inhibited continued liver regeneration and [3H1]thymidine incorporation into hepatic DNA. The cirrhotic liver at this stage failed to regenerate to the original mass upon 75% partial hepatectomy. Therefore, it may be concluded that hepatic necrosis produced by oxidized lipids or by acetaminophen may have similar mechanisms.

Acetaminophen↗
PubMed1993

Determination of amphetamine, methamphetamine and desmethyldeprenyl in human plasma by gas chromatography/negative ion chemical ionization mass spectrometry.

A sensitive and specific assay for the quantitative determination of amphetamine, methamphetamine and desmethyldeprenyl in human plasma specimens is described. Electron capture/negative ion chemical ionization gas chromatography/mass spectrometry is used to determine the extracted plasma concentrations of the three target compounds as their N-heptafluorobutyryl derivatives. Quantitation is performed by stable isotope dilution using d6-amphetamine and d6-methamphetamine as internal standards. Selected ion monitoring of the [M-HF]- ions of both the analytes and internal standards results in minimum quantifiable limits of 0.10 ng ml-1 for both amphetamine and methamphetamine and 0.25 ng ml-1 for desmethyldeprenyl. Excellent linearity (r = 0.998) up to at least 5.00 ng ml-1 is demonstrated.

Amphetamine↗
PubMed1993

Clones of T cells discriminate between native and deglycosylated forms of MHC class II antigen in allostimulation.

The aim of this study was to clarify the role of the oligosaccharide side chains of MHC Class II antigens in allostimulation. The approach was to cleave the oligosaccharides from protein by subjecting plasma membranes (PM) of the Daudi cell line to chemical deglycosylation yielding deglycosylated (dgl) proteins and a supernatant fraction containing plasma membrane oligosaccharides (dgl sup). MHC Class II antigens affinity purified from the native and the dgl PM were inserted into the plasma membrane of peripheral blood leukocytes (PBL) used as stimulators in a mixed leukocyte reaction (MLR). Cells used as stimulators and as responders were from the same donor. Both native and to a lesser extent the dgl antigen could elicit a proliferative as well as a cytolytic (CML) response. A comparable reduction in the CML reaction was also obtained when native antigen was used to elicit effector cells, but the target was stripped of N-linked oligosaccharides by pretreatment with tunicamycin (TM). Five clones of responding cells raised against the native antigen were studied. Two gave proliferative reactions of equal magnitude to native and to dgl antigen alike, while three responded only to the native form. These three clones did not lyse TM-treated target cells. Inhibition experiments of CML were performed with either the dgl sup containing Daudi PM oligosaccharides or with an anti MHC-Class II MoAb. CML reactivity of the three clones which responded to native antigen was blocked by the dgl sup but not by the anti-MHC antibody. Conversely, the reaction of the two clones reactive to both forms of antigen was only inhibited by the anti-MHC antibody using intact or TM-treated targets. Accordingly, in terms of the latter set of clones oligosaccharide side chains of MHC may not be required for allostimulation. Data obtained with the set of three clones suggest that oligosaccharides could act as target of cytotoxic T cells.

Cell Line↗
PubMed1993

Methylmalonic acidemia with a severe chemical but benign clinical phenotype.

A 5-year-old boy of West African origin had methylmalonic acidemia with a mut- enzyme phenotype, no clinical response to hydroxycobalamin, and metabolite measurements indicative of the severe form of mutase deficiency. His development, both mental and physical, was satisfactory and he had no episodes of metabolic decompensation. The explanation for the neurotoxic effects and metabolic decompensation in typical methylmalonic acidemia and the (allelic) genotype that explains this patient's phenotype are uncertain.

Amino Acid Metabolism, Inborn Errors↗
PubMed1993

Alpha-keto and alpha-hydroxy branched-chain acid interrelationships in normal humans.

Plasma concentrations of the branched-chain amino acids leucine, isoleucine and valine, and those of leucine's and isoleucine's transamination products alpha-ketoisocaproic acid (KICA) and alpha-keto-beta-methylvaleric acid (KMVA), respectively, are known to increase after a protein meal or during extended fasting, but little or no increase in the concentration of valine's transamination product, alpha-ketoisovaleric acid (KIVA), has been observed under these conditions. To determine whether this could be explained by the conversion of KIVA to its alpha-hydroxy analogue, we measured the plasma concentrations of KICA, KMVA and KIVA, as well as their alpha-hydroxy analogues [alpha-hydroxyisocaproic acid (HICA), alpha-hydroxy-beta-methylvaleric acid (HMVA) and alpha-hydroxyisovaleric acid (HIVA)], in normal volunteers immediately after a protein meal or during a 60-h fast. We also determined the oxidoreduction equilibrium constants for HIVA/KIVA and HICA/KICA and their extent of plasma protein binding. In subjects in the postabsorptive state, the plasma concentrations of KICA and KMVA were 100 times those of HICA and HMVA, whereas that of KIVA was only twice that of HIVA. Shortly after a protein meal, KICA and KMVA concentrations increased significantly by 30 and 60%, respectively, whereas that of KIVA decreased by 25% (P < 0.05). HICA, HMVA and HIVA concentrations did not change. During prolonged fasting the plasma concentrations of all six metabolites increased gradually. The high plasma keto/hydroxy acid ratios were not related to their K(eq), which favored alpha-hydroxy analogue formation. The reduction of the branched-chain alpha-keto acids to their alpha-hydroxy analogues seems to take place too slowly to attain thermodynamic equilibrium.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

On the mechanisms of the formation of L-alloisoleucine and the 2-hydroxy-3-methylvaleric acid stereoisomers from L-isoleucine in maple syrup urine disease patients and in normal humans.

2-Keto-3-methylvaleric acid (KMVA) has been found not to undergo spontaneous keto-enol tautomerization in neutral aqueous solution, alone or in the presence of large concentrations of pyridoxamine or pyridoxamine-5-phosphate. This finding denies the commonly held suppositions that 3R-KMVA is derived spontaneously from 3S-KMVA in vivo, and that L-alloisoleucine is the product of the reamination of this 3R-KMVA. Evidence presented here suggests that racemization of the 3-carbon of L-isoleucine occurs during transamination, that L-alloisoleucine is an inherently unavoidable by-product of L-isoleucine transamination (and vice versa), and that a KMVA enol is not obligate in this racemization. The four stereoisomers of 2-hydroxy-3-methylvaleric acid have been synthesized and the mass spectra of their trimethylsilyl derivatives recorded. An achiral methylsilicone column was used to separate the diastereomeric pairs and to determine their relative ratios in plasma and urine from normal controls and two maple syrup urine disease (MSUD) patients. The urinary ratio of the two diastereomers is different from that for plasma, both in normals and in MSUD patients. The plasma ratios may provide a rapid and simple measure of residual branched chain 2-keto acid dehydrogenase activity in MSUD patients.

Chromatography, Gas↗
PubMed1992

Hereditary tyrosinaemia type II in a consanguineous Ashkenazi Jewish family: intrafamilial variation in phenotype; absence of parental phenotype effects on the fetus.

We describe an Ashkenazi Jewish family in which two adults, offspring of consanguineous parents, have persistent hypertyrosinaemia (770-1110 mumol/L; normal less than 110 mumol/L). The metabolic disorder in this family is apparently due to hepatic cytosolic tyrosine aminotransferase deficiency (hereditary tyrosinaemia, type II; McKusick, 276600), because it is associated with the oculocutaneous manifestations of Richner-Hanhart syndrome. The association of this syndrome with hereditary tyrosinaemia type II is presumed to be constant. It is not in this family. The affected female sib (age 41 years) has hypertyrosinaemia and oculocutaneous signs; the brother (age 39 years) has hypertyrosinemia but no oculocutaneous disease. Both sibs have two children; none has signs of a metabolic fetopathy. Maternal hypertyrosinaemia and maternal hyperphenylalaninaemia evidently constitute different risk factors for the fetus. Paternal hypertyrosinaemia is apparently not a risk to male infertility.

Adult↗
PubMed1992

3-Methylglutaconic aciduria: a marker for as yet unspecified disorders and the relevance of prenatal diagnosis in a 'new' type ('type 4').

The Mendelian disorder known as 3-methylgutaconic aciduria (McKusick 250950) gives evidence of allelic and locus heterogeneity. Type 1 has a mild clinical phenotype and confirmed 3-methylgutaconyl-CoA hydratase deficiency; inheritance is autosomal recessive. Other forms have major clinical manifestations and subdivide into X-linked (type 2), a form in Iraqi Jews with optic atrophy (so-called type 3); and untyped (putative autosomal recessive) forms without identified enzyme defects. In the latter, 3-methylglutaconic aciduria may simply be a marker for another metabolic disorder. We describe a male proband with 3-methylglutaconic aciduria designated here as 'type 4' (autosomal recessive, with severe psychomotor phenotype and cerebellar dysgenesis). He is the offspring of Italian consanguineous parents. Born with congenital malformations, he has been followed for 18 years, showing profound developmental delay and cerebellar dysgenesis. Measures of hydratase activity in cultured fibroblasts from the proband and 11 additional patients (two with type 1 disease, 9 with either type 2 or an unspecified form) revealed deficient enzyme activity in type 1 cases and normal activity in the proband and the other 11 cases. Two of the untyped cases probably have 3-methylglutaconic aciduria of the type described here. Prenatal diagnosis in the form described here may be feasible by analysis of amniotic fluid metabolites in pregnancies at risk if the mother does not entirely remove elevated concentrations. A female sibling of the proband had normal metabolite values in amniotic fluid. Postnatal follow-up confirmed absence of the disease. We give the normal values for amniotic fluid and results on these additional fetuses at risk (none affected).

Amniotic Fluid↗
PubMed1992

Maple syrup urine disease: interrelations between branched-chain amino-, oxo- and hydroxyacids; implications for treatment; associations with CNS dysmyelination.

Four patients with classical maple syrup urine disease were treated for up to 5885 days per patient with a relaxed protocol allowing branched-chain amino acid levels in plasma to rise about 5 times the normal mean value. The patients have had satisfactory development and lifestyle. They spent 318 days in hospital during 19,937 aggregate treatment days. Plasma levels of leucine and the corresponding 2-oxo acid were shown to be elevated disproportionately relative to the other branched-chain metabolites. Levels of isoleucine and valine were lower than those of leucine apparently because of runout into alternative metabolite pools, namely the R metabolites for isoleucine and the hydroxyacid for valine. The chronic accumulation of branched-chain 2-oxo acid(s) in our patients was associated with chronic dysmyelinating changes in CNS visible by imaging. Another patient with a thiamine-responsive variant of maple syrup urine disease had five acute crises incurring 29 days in hospital in a total of 6910 treatment days. However, she did not have chronic metabolic dyshomeostasis (her average plasma amino acid values were normal) and she had no evidence of dysmyelination. A relaxed treatment protocol for patients with maple syrup urine disease may benefit them in quality of life, but it apparently exacts a cost in metabolic control and CNS pathology.

Adolescent↗
PubMed1992

Brain dysgenesis and congenital intracerebral calcification associated with 3-hydroxyisobutyric aciduria.

Monozygotic male twins born to nonconsanguineous parents had dysmorphic facial features, microcephaly, migrational brain disorder, and congenital intracerebral calcification. They excreted excessive amounts of 3-hydroxyisobutyric acid, a metabolite of valine, and had evidence of impaired oxidative metabolism and metabolic acidosis. The level of 3-hydroxyisobutyrate in stored samples of midtrimester amniotic fluid was found to be high. The association of 3-hydroxyisobutyric aciduria with brain dysgenesis is a newly recognized mendelian disorder; its recurrence in a family at risk is potentially avoidable by prenatal diagnosis.

Amniotic Fluid↗
PubMed1991

Metabolism of deuterium-labeled nonanoic acids in the riboflavin-deficient rat model of multiple acyl-CoA dehydrogenase deficiency.

Riboflavin-deficient rats are used to study the metabolism of deuterium-labeled nonanoic acids under conditions mimicking the human disorder of multiple acyl-CoA dehydrogenase deficiency in which large amounts of ethyl-malonic, glutaric, adipic, suberic, 4-octenedioic, sebacic and 4-decenedioic acids are excreted. Both control and deficient rats convert the nonanoic acids to labeled azelaic and pimelic acids. The labeling pattern in pimelic acid is consistent with the omega-oxidation of nonanoic acids to azelaic acid followed by beta-oxidation to pimelic acid.

Acyl-CoA Dehydrogenases↗