Kari O. Raivio

Liver Adenine Nuldeotides: Fructose-Induced Depletion and Its Effect on Protein Synthesis

Intravenous administration of D-fructose to rats rapidly depletes liver adenosine triphosphate and inorganic phosphate; marked elevations of uric acid and allantoin in plasma follow. Concomitantly the incorporation of DL-leucine-1-14C into liver protein is almost completely inhibited.

Reperfusion injury as the mechanism of brain damage after perinatal asphyxia

Upon reperfusion of ischemic tissues, reactive oxygen metabolites are generated and are responsible for much of the organ damage. Experimental studies have revealed two main sources of these metabolites: 1) the oxidation of hypoxanthine to xanthine and on to uric acid by the oxidase form of xanthine oxidoreductase and 2) neutrophils accumulating in ischemic and reperfused tissue. Blocking either source will reduce reperfusion damage in a number of experimental situations. Although xanthine oxidoreductase activity may be unmeasurably low in organs other than liver and intestine, it may be involved in reperfusion injury elsewhere because of its localization in capillary endothelial cells. Time course considerations suggest that substrate accumulation and NADH inhibition of dehydrogenase activity may be more important in the pathogenesis than conversion of xanthine dehydrogenase into the oxidase form. Neutrophil accumulation may be partly due to oxidants in the first place, suggesting a link between the two sources of reactive oxygen metabolites. In the clinical context, many of the sequelae of perinatal asphyxia may be accounted for by reperfusion damage to organs such as brain, kidney, heart, liver, and lungs. During asphyxia, substrates of xanthine oxidase accumulate, upon resuscitation the cosubstrate oxygen is introduced, and evidence for oxidant production and effects has been obtained. In the pathogenesis of brain damage after asphyxia, both microvascular injury and parenchymal cell damage are important. Oxygen metabolites are involved in the former, but in the latter process their role is less clear because ischemia-reperfusion triggers not only oxidant production but many other phenomena, including gene activation, ATP depletion, glutamate accumulation, and increase of intracellular calcium. A severe insult results in cell necrosis, but more moderate asphyxia may cause delayed neuronal death through apoptosis. The time course of the changes in high energy phosphates as well as of selective neuronal death suggest that in the first hours of life there is a“therapeutic window,” with future possibilities for prevention of permanent damage.

Depletion of liver adenine nucleotides induced by d-fructose: Dose-dependence and specificity of the fructose effect

Abstract The effect of d -fructose on adenine nucleotide metabolism was studied in rats in vivo by analyzing liver metabolite levels after intravenous fructose injections, and in vitro by measuring allantoin production by the isolated perfused liver after the addition of fructose to the perfusion medium. Significant depression of liver ATP and inorganic phosphate levels was demonstrated after fructose administration. Minimum effective dose was 0.25 m-mole, and maximum depression was observed after 5 min. Analogous, but quantitatively less impressive alterations were produced by l -sorbose and d -sorbitol, whereas d -glucose, d -galactose, d -mannose, d -ribose and 2-deoxy- d -glucose were without effect. In the perfusion studies, marked increase in allantoin production was observed after the addition of d -fructose to the perfusion medium. The minimum effective dose was 0.25 m-mole, corresponding to a mean initial concentration of 4.5 mM in the medium. Allopurinol prevented both the basal allantoin production and the fructose-induced increase. d -galactose, d -ribose, d -sorbitol, sodium- dl -lactate or ethanol did not influence the basal rate of allantoin release. The loss of liver adenine nucleotides in the in vivo experiments was of a similar order of magnitude as the amount of allantoin produced in the perfusion experiments, when calculated per total liver after equal doses of fructose. Therefore, accelerated degradation of preformed purines, rather than increased de novo synthesis, appears to be the main mechanism of fructose-induced increase in uric acid and allantoin production.

Human cystathionine gamma-lyase: developmental and in vitro expression of two isoforms.

Cystathionine gamma-lyase (CGL) is the last enzyme of the trans-sulphuration pathway, which converts methionine into cysteine. To study the possible differences in enzymic activity of the two human cystathionine gamma-lyase isoforms characterized earlier, these were separately expressed in human kidney embryonic 293T cells. Furthermore, developmental changes in the expression of the two mRNA forms as well as the enzymic activity in human liver were studied, as it has been postulated that a change in the relative expression of CGL isoforms causes the postnatal increase in CGL activity. Transfection with the longer isoform increased the CGL activity 1.5-fold, while the activity of the cells transfected with the shorter form did not differ from the basal activity. In human liver samples, CGL activity was only detected in adult tissue (68+/-9 nmol of cysteine/h per mg of protein), whereas activity in fetal, premature and full-term neonatal liver tissue was undetectable. In contrast, strong mRNA expression of both mRNA isoforms was detected from the 19th gestational week onwards and the longer form of CGL appeared to be predominant. The expression of the two mRNA forms varied in parallel. In conclusion, we have shown that only cells overexpressing the longer form of CGL have increased activity, and CGL appears to be regulated at the post-transcriptional level during development.

Iron-overload disease in infants involving fetal growth retardation, lactic acidosis, liver haemosiderosis, and aminoaciduria

BACKGROUND Several cases of a distinctive lethal neonatal disorder have been found in the Childrens Hospital, Helsinki, Finland. However, the combination of presenting features is not typical of any known metabolic disease. We have analysed all known cases of this disorder in the hospital since 1965 and in Finland since 1990 to define clinical features of the disease. METHODS We studied 17 newborn infants with severe growth retardation from 12 Finnish families and traced their genealogy. In addition to routine clinical studies, diagnostic workup included analysis of respiratory-chain function in isolated muscle mitochondria and necropsy specimens, pyruvate dehydrogenase complex activities in fibroblasts, analysis of aminoacids and organic acids in urine, staining of tissue samples for iron, and assay of liver iron content. FINDINGS The infants were born near term (mean 37.8 [SD 3] gestational weeks) but were severely growth retarded (birthweight 1690 [460] g--ie, -3.8 [SD 0.6] SD score for gestational age). By age 24 h, mean pH was 7.00 (0.12), lactate 12.2 (7.5) mmol/L, and pyruvate 121 (57) micromol/L. All had aminoaciduria and failed to thrive; nine died neonatally (age 2-12 days), and eight died in infancy (1-4 months). The liver of four infants showed microscopic haemosiderosis and increased iron content (2.8-5.5 mg iron/g dry weight). In those four infants serum ferritin concentration (1260-2700 microg/L) and transferrin saturation (61-100%) were high, transferrin concentration (0.54-0.76 g/L) was low. INTERPRETATION We describe a previously unrecognised clinical picture of a genetic disease, which presents with fetal growth retardation and lactic acidosis after birth. Genealogical studies indicate an autosomal-recessive mode of inheritance for this disease, which is distinct from other lactic acidoses, neonatal haemochromatosis, and hepatitis. The diagnostic criteria are: fetal growth retardation; severe lactic acidosis; aminoaciduria; iron overload with haemosiderosis of the liver, increased serum ferritin concentration, hypotransferrinaemia, and increased transferrin iron saturation. Organ dysfunction may be partly due to the toxic effects of free iron.

Salla disease: A new lysosomal storage disorder with disturbed sialic acid metabolism

Salla disease is a lysosomal storage disorder associated with increased urinary excretion of free sialic acid. The main clinical features in 34 patients were severe psychomotor retardation of early onset, ataxia, athetosis, rigidity, spasticity, and impaired speech. Growth retardation, thick calvarium, and exotropia were present in about half the patients. The amplitude of EEG decreased progressively with increasing age. Life span appears to be normal; the age range of the patients was 3 to 63 years. Genealogic studies suggest an autosomal mode of inheritance. A thin-layer method is described for the detection of increased urinary free sialic acid excretion. The basic defect is so far unknown.

Plasma 8-isoprostane is increased in preterm infants who develop bronchopulmonary dysplasia or periventricular leukomalacia

Our aim was to assess the plasma free 8-epi–prostaglandin F2α (8-isoprostane) and ascorbyl radical as risk indicators for oxidative damage in extremely low birth weight infants (ELB-WIs) and the effect of N-acetylcysteine (NAC) on these markers. Plasma samples were collected on days 3 and 7 of life from infants who were enrolled in a randomized, controlled trial in which i.v. NAC or placebo was administered to ELBWIs during the first week of life, with the aim of preventing bronchopulmonary dysplasia (BPD). Plasma 8-isoprostane was analyzed in 83 infants using an enzyme immunoassay kit. Ascorbyl radical concentration was measured in 61 infants with electron spin resonance spectroscopy. The 8-isoprostane concentrations were similar in the NAC and placebo groups. In infants who later developed BPD or died (n = 29), the median (range) 8-isoprostane concentration was significantly higher (p = 0.001) on day 3 and day 7 [50.0 pg/mL (19–360) and 57.0 pg/mL (14–460), respectively] than in survivors without BPD [n = 54; 34.5 pg/mL (5–240) and 39.5 pg/mL (7–400), respectively]. The 8-isoprostane levels increased significantly more (p < 0.05) in infants who later developed periventricular leukomalacia. NAC treatment or the later development of BPD was not related to the ascorbyl radical levels. The ascorbyl radical level decreased significantly in all groups from day 3 to day 7, but the difference between the groups was not significant. The mean (SD) ascorbyl radical level on day 3 was significantly higher (p < 0.01) in infants who later developed periventricular leukomalacia [287 (124) versus 194 (90)]. These data suggest that plasma 8-isoprostane could serve as a marker in assessing the risk for BPD development in ELBWIs.

Outcome of children after maternal primary Toxoplasma infection during pregnancy with emphasis on avidity of specific IgG

Congenital toxoplasmosis results from maternal primary infection during pregnancy. In our serologic screening study 42 of 16 733 pregnant women had findings suggestive of primary infection. Here we document the outcome of their offspring, 37 of 39 liveborn children. After 12 months postntally, serologically verified congenital toxoplamosis appeared in 4 children.

Circulating xanthine oxidase and neutrophil activation during human liver transplantation.

BACKGROUND & AIMS Oxygen free radicals, generated by xanthine oxidase (XO) and activated leukocytes, are involved in reperfusion injury in experimental liver transplantation. The roles of XO and neutrophil activation during reperfusion in clinical liver transplantation were studied. METHODS In 10 patients undergoing liver transplantation, we assessed plasma concentrations of circulating XO by enzyme-linked immunosorbent assay (ELISA), the purine metabolites hypoxanthine, xanthine, and urate by high-performance liquid chromatography, lactoferrin by ELISA, and malondialdehyde fluorometrically up to 48 hours postoperatively. RESULTS During reperfusion after portal vein declamping, elevated plasma concentrations of XO (52.1 ng/mL [range, 8.0-440.1]), hypoxanthine (81.62 micromol/L [48.2-108.7]), xanthine (21.01 micromol/L [8.7-22.3]), and lactoferrin (532.6 ng/mL [370.4-1326.6]) were observed compared with the preoperative levels (0 ng/mL [0-12], 1.88 micromol/L [0.62-3.15], 0.95 micromol/L [0-0.41], and 164.3 ng/mL [73.7-334.1], respectively; all P < 0.05). No changes occurred in urate or malondialdehyde. After portal vein declamping, XO, hypoxanthine, and xanthine levels were substantially greater in the hepatic than portal vein (all P < 0.05). Marginal transhepatic differences occurred in lactoferrin. CONCLUSIONS Reperfusion during liver transplantation is associated with liberation of xanthine oxidase, hypoxanthine, and xanthine from the liver into the circulation. During reperfusion, intravascular neutrophil activation takes place in the hepatic circulation.

Cord Plasma Vasopressin, Erythropoietin, and Hypoxanthine as Indices of Asphyxia at Birth

ABSTRACT: To assess the value of cord plasma arginine vasopressin (AVP), erythropoietin (EP), and hypoxanthine (HX) as indices of asphyxia, we studied 62 infants of mothers with preeclampsia, 34 acutely asphyxiated infants, with 5-min Apgar score ≤6 and/or umbilical arterial pH ≤7.05, and 38 control infants. Umbilical arterial AVP in the asphyxia group (geometric mean; 95% confidence interval: 180; 92–350 pg/ml) was higher than in the control group (23; 8–466, p = 0.002) and correlated with umbilical arterial pH (r = −0.447, p = 0.028). AVP levels in the preeclampsia group did not differ from controls. Cord venous EP was higher in infants delivered by elective cesarean section from women with severe preeclampsia (115; 75–177 mU/ml, p < 0.001) than in control infants (23; 18–27); in the whole group EP correlated with pH (r = −0.493, p < 0.001). EP in the asphyxia group was similar (46; 35–65) to controls (40; 33–47) and did not correlate with pH. Cord arterial HX in the preeclampsia group was similar to controls (12.3; 9.5–16.0 μmol/liter), but elevated in the asphyxia group (23.7; 17.6–31.8, p = 0.001), in which HX correlated with pH (r = 0.558, p = 0.008) and AVP (r = 0.588, p = 0.005). EP did not correlate with AVP or HX in any group, nor did any of the variables correlate with the Apgar score. We conclude that cord plasma AVP and HX reflect acute asphyxia, whereas EP is elevated after more prolonged hypoxia.