9 research outputs found
Hydroxylated sterols : matabolism and effects on steroid production and steroid uptake
The isolated rat adrenal cell was used as a model system. The
isolation technique for rat adrenal cells has been extensively studied : in
our laboratory (Falke et al., 1975a,b, 1976a,b) . Starting with these cells
we looked at the properties of hydroxylated sterols as a precursor for
steroid production. In :intact cells exogenous substrates have to pass
through several membranes to reach the mitochondrion, where the side-chain
cleavage occurs. In order to eliminate possible effects on transport
through membranes, we also used damaged bovine adrenal mitochondria to
investigate the conversion of hydroxylated sterols. We also studied the
effects of hydroxylated sterols on short-term stimuli of steroid production. Either the total cell suspension (Chapters 4 and 5) or
suspensions containing largely glomerulosa cells or fasciculata/reticularis
cells (Chapter 6) were used in these studies. Before exerting their action, steroid hormones have to be taken up by
target cells and bound to receptors. It is commonly assumed that steroid
hormones diffuse passively through the cell membrane, although there is
some evidence for a mediated uptake rnechanism (Rao, 1981). In the rat,
corticosterone is the main glucocorticoid and the liver is an important
target organ. To study possible effects of hydroxylated sterols on steroid
uptake we used the uptake of corticosterone in isolated rat liver cells as
a model system (Chapter 7). In addition the effects of several sterols on
the uptake and conversion of pregnenolone in isolated rat adrenal cells
were investigated (Chapter 8) . As will be discussed in Cllapter 3, the method of cell isolation used
for the rat adrenal can be applied to the human fetal adrenal, yielding
viable cells. Also the method of separating cells of the fetal zone from
those of the definitive zone by means of density gradient centrifugation
can be used. With these cells the properties of hydroxylated sterols as
steroid precursors were studied ( Chapter 9)
Differential diagnosis of (inherited) amino acid metabolism or transport disorders
__Abstract__
Disorders of amino acid metabolism or transport are most clearly expressed in urine. Nevertheless the interpretation of abnormalities in urinary amino acid excretion remains difficult. An increase or decrease of almost every amino acid in urine can be due to various etiology. To differentiate between primary and secondary aminoacido-pathies systematic laboratory investigation is necessary. Early diagnosis of disorders of amino acid metabolism or transport is very important, because most of them can be treated, leading to the prevention of (further) clinical abnormalities. In those disorders, which cannot be treated, early diagnosis in an index-patient may prevent the birth of other siblings by means of genetic counseling and prenatal diagnosis. Primary aminoacidopathies can be due to genetically determined transport disorders and enzyme deficiencies in amino acid metabolism or degradation. Secondary aminoacidopathies are the result of abnormal or deficient nutrition, intestinal dysfunction, organ pathology or other metabolic diseases like organic acidurias. A survey of amino acid metabolism and transport abnormalities will be given, illustrated with metabolic pathways and characteristic abnormal amino acid chromatograms
Functional hyperactivity of hepatic glutamate dehydrogenase as a cause of the hyperinsulinism/hyperammonemia syndrome: effect of treatment
OBJECTIVE: The combination of persistent hyperammonemia and hypoketotic
hypoglycemia in infancy presents a diagnostic challenge. Investigation of
the possible causes and regulators of the ammonia and glucose disposal may
result in a true diagnosis and predict an optimum treatment. PATIENT:
Since the neonatal period, a white girl had been treated for
hyperammonemia and postprandial hypoglycemia with intermittent
hyperinsulinism. Her blood level of ammonia varied from 100 to 300
micromol/L and was independent of the protein intake. METHODS: Enzymes of
the urea cycle as well as glutamine synthetase and glutamate dehydrogenase
(GDH) were assayed in liver tissue and/or lymphocytes. RESULTS: The
activity of hepatic GDH was 874 nmol/(min.mg protein) (controls: 472-938).
Half-maximum inhibition by guanosine triphosphate was reached at a
concentration of 3.9 micromol/L (mean control values:.32). The ratio of
plasma glutamine/blood ammonia was unusually low. Oral supplements with
N-carbamylglutamate resulted in a moderate decrease of the blood level of
ammonia. The hyperinsulinism was successfully treated with diazoxide.
CONCLUSION: A continuous conversion of glutamate to 2-oxoglutarate causes
a depletion of glutamate needed for the synthesis of N-acetylglutamate,
the catalyst of the urea synthesis starting with ammonia. In addition, the
shortage of glutamate may lead to an insufficient formation of glutamine
by glutamine synthetase. As GDH stimulates the release of insulin, the
concomitant hyperinsulinism can be explained. This disorder should be
considered in every patient with postprandial hypoglycemia and
diet-independent hyperammonemia
Prenatal diagnosis of morquio disease type A using a simple fluorometric enzyme assay
A new fluorogenic substrate, 4 methylumbelliferyl B-D-6-sulphogalactoside, was used for the
assay of galactose-6-sulphate sulphatase activity in chorionic villi, cultured villus cells, and
amniocytes. The fluorometric assay is much more convenient than the conventional assay
using radiolabelled, sulphated oligosaccharides. Both types of substrate were used in the
prenatal diagnosis of three pregnancies at risk for Morquio type A disease using amniocytes.
These enzyme tests, as well as electrophoresis of glycosaminoglycans in the amniotic fluid,
indicated affected fetuses in two pregnancies and a non-affected fetus in one
Prenatal diagnosis of isovaleric acidaemia by enzyme and metabolite assay in the first and second trimesters
Isovaleric acidaemia (IVA) is caused by a deficiency of isovaleryl CoA dehydrogenase. The diagnosis can be established biochemically by the demonstration of increased levels of isovalerylglycine (IVG) and 3-hydroxyisovaleric acid in urine and by the deficiency of incorporation of radiolabel from [14C]isovaleric acid in macromolecules in cultured fibroblasts. This paper reports a consecutive series of 24 prenatal diagnoses in pregnancies at high risk, using both methods-metabolite and indirect enzyme assay. Affected fetuses were diagnosed in four pregnancies: three in the second trimester and one recent case in the first trimester. The latter represents the first reported case of a first-trimester diagnosis of IVA by direct analysis of chorionic villi. We also report the first demonstration of strongly accumulated IVG in the amniotic fluid in the 12th week of an affected pregnancy
Glutamine supplementation of parenteral nutrition does not improve intestinal permeability, nitrogen balance, or outcome in newborns and infants undergoing digestive-tract surgery: results from a double-blind, randomized, controlled trial
OBJECTIVE: To assess the effect of isocaloric isonitrogenous parenteral
glutamine supplementation on intestinal permeability and nitrogen loss in
newborns and infants after major digestive-tract surgery. SUMMARY
BACKGROUND DATA: Glutamine supplementation in critically ill and surgical
adults may normalize intestinal permeability, attenuate nitrogen loss,
improve survival, and lower the incidence of nosocomial infections.
Previous studies in critically ill children were limited to
very-low-birthweight infants and had equivocal results. METHODS: Eighty
newborns and infants were included in a double-blind, randomized trial
comparing standard parenteral nutrition (sPN; n = 39) to
glutamine-supplemented parenteral nutrition (GlnPN; glutamine target
intake, 0.4 g kg day; n = 41), starting on day 2 after major
digestive-tract surgery. Primary endpoints were intestinal permeability,
as assessed by the urinary excretion ratio of lactulose and rhamnose
(weeks 1 through 4); nitrogen balance (days 4 through 6), and urinary
3-methylhistidine excretion (day 5). Secondary endpoints were mortality,
length of stay in the ICU and the hospital, number of septic episodes, and
usage of antibiotics and ICU resources. RESULTS: Glutamine intake
plateaued at 90% of the target on day 4. No differences were found between
patients assigned sPN and patients assigned GlnPN regarding any of the
endpoints. Glutamine supplementation was not associated with adverse
effects. CONCLUSIONS: In newborns and infants after major digestive-tract
surgery, we did not identify beneficial effects of isonitrogenous,
isocaloric glutamine supplementation of parenteral nutrition. Glutamine
supplementation in these patients therefore is not warranted until further
research proves otherwise
β-Mannosidase deficiency: Heterogeneous manifestation in the first female patient and her brother
Summary
β-Mannosidase deficiency was demonstrated in fibroblasts of a girl who showed severe psychomotor retardation, bone deformities and gargoylism and recurrent skin and r
Rapid ultraperformance liquid chromatography-tandem mass spectrometry assay for a characteristic glycogen-derived tetrasaccharide in pompe disease and other glycogen storage diseases
BACKGROUND: Urinary excretion of the tetrasaccharide 6-α-D- glucopyranosyl-maltotriose (Glc4) is increased in various clinical conditions associated with increased turnover or storage of glycogen, making Glc4 a potential biomarker for glycogen storage diseases (GSD). We developed an ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) assay to detect Glc4 in urine without interference of the Glc4 isomer maltotetraose (M4). METHODS: Urine samples, diluted in 0.1% ammonium hydroxide containing the internal standard acarbose, were filtered, and the filtrate was analyzed by UPLC-MS/MS. RESULTS: We separated and quantified acarbose, M4, and Glc4 using the ion pairs m/z 644/161, 665/161, and 665/179, respectively. Response of Glc4 was linear up to 1500 μmol/L and the limit of quantification was 2.8 μmol/L. In