Acute renal failure: unusual complication of Epstein-Barr virus-induced infectious mononucleosis.

A 17-year-old boy with juvenile rheumatoid arthritis presented with jaundice, confusion, hemolytic anemia, thrombocytopenia, and acute renal failure secondary to titer-confirmed acute Epstein-Barr virus (EBV). Renal biopsy specimen revealed interstitial nephritis with an inflammatory infiltrate composed of cytotoxic/suppressor T cells, and interstitial mononuclear cell nuclei expressed EBV encoded RNA-1 (EBER-1) mRNA. Methylprednisolone treatment resulted in rapid improvement.

Frizzled-4 expression during chick kidney development.

Wnts have been implicated in metanephric kidney development. To determine whether Frizzleds, the genes that encode Wnt receptors, are present at early stages of nephrogenesis, we examined the expression of several recently identified Frizzled genes in the chick by in situ hybridization. Here we report the cloning and characterization of chick Frizzled-4 (cFz-4), which we found to be expressed in the developing chick kidney. cFz-4 was first expressed in the pronephros caudal to the third somite at Hamburger and Hamilton stage 10. Its expression increased with maturation, becoming restricted to the newly induced glomeruli and tubules in the mesonephros and metanephros. Within the metanephros, cFz-4 and Wnt-4 expression patterns were similar, whereas Wnt-11 was expressed solely in the tips of the branching ureteric bud. cFz-4 expression was compared with that of known kidney markers. It preceded that of Lmx-1, but was similarly restricted to developing glomeruli and tubules. In contrast, Pax-2 expression and Lim 1/2 antibody labeling occurred in intermediate mesoderm caudal to the fifth somite in the early pronephros, and each persisted in both the tubules and nephric ducts throughout further development.

Signals from trunk paraxial mesoderm induce pronephros formation in chick intermediate mesoderm.

We used Pax-2 mRNA expression and Lim 1/2 antibody staining as markers for the conversion of chick intermediate mesoderm (IM) to pronephric tissue and Lmx-1 mRNA expression as a marker for mesonephros. Pronephric markers were strongly expressed caudal to the fifth somite by stage 9. To determine whether the pronephros was induced by adjacent tissues and, if so, to identify the inducing tissues and the timing of induction, we microsurgically dissected one side of chick embryos developing in culture and then incubated them for up to 3 days. The undisturbed contralateral side served as a control. Most embryos cut parallel to the rostrocaudal axis between the trunk paraxial mesoderm and IM before stage 8 developed a pronephros on the control side only. Embryos manipulated after stage 9 developed pronephric structures on both sides, but the caudal pronephric extension was attenuated on the cut side. These results suggest that a medial signal is required for pronephric development and show that the signal is propagated in a rostral to caudal sequence. In manipulated embryos cultured for 3 days in ovo, the mesonephros as well as the pronephros failed to develop on the experimental side. In contrast, embryos cut between the notochord and the trunk paraxial mesoderm formed pronephric structures on both sides, regardless of the stage at which the operation was performed, indicating that the signal arises from the paraxial mesoderm (PM) and not from axial mesoderm. This cut also served as a control for cuts between the PM and the IM and showed that signaling itself was blocked in the former experiments, not the migration of pronephric or mesonephric precursor cells from the primitive streak. Additional control experiments ruled out the need for signals from lateral plate mesoderm, ectoderm, or endoderm. To determine whether the trunk paraxial mesoderm caudal to the fifth somite maintains its inductive capacity in the absence of contact with more rostral tissue, embryos were transected. Those transected below the prospective level of the fifth somite expressed Pax-2 in both the rostral and the caudal isolates, whereas embryos transected rostral to this level expressed Pax-2 in the caudal isolate only. Thus, a rostral signal is not required to establish the normal pattern of Pax-2 expression and pronephros formation. To determine whether paraxial mesoderm is sufficient for pronephros induction, stage 7 or earlier chick lateral plate mesoderm was cocultured with caudal stage 8 or 9 quail somites in collagen gels. Pax-2 was expressed in chick tissues in 21 of 25 embryos. Isochronic transplantation of stage 4 or 5 quail node into caudal chick primitive streak resulted in the generation of ectopic somites. These somites induced ectopic pronephroi in lateral plate mesoderm, and the IM that received signals from both native and ectopic somites formed enlarged pronephroi with increased Pax-2 expression. We conclude that signals from a localized region of the trunk paraxial mesoderm are both required and sufficient for the induction of the pronephros from the chick IM. Studies to identify the molecular nature of the induction are in progress.

Antibody response of pediatric solid organ transplant recipients to immunization against influenza virus.

We studied the immunogenicity of the 1992-1993 trivalent split-virus influenza vaccine in pediatric solid organ transplant recipients (PSOTRs) and their healthy siblings. One month after immunization, 41 (82%) of 50 subjects achieved protective titers of antibodies to influenza A, and 30 (60%) to influenza B, rates similar to those in healthy siblings. Achievement and persistence of protective titers occurred significantly more often in children with preexisting antibody. We recommend annual immunization of PSOTRs, their household contacts, and health care workers; immunologically naive PSOTRs may benefit from immunization before transplantation.

Influenza B virus infection in pediatric solid organ transplant recipients.

OBJECTIVE: Influenza B virus causes epidemic infection in normal children, but only one case of infection in an immunocompromised solid organ transplant (SOT) recipient has been reported. Characterization of the clinical course of influenza B virus infection in pediatric SOT recipients may increase the utilization of preventive and therapeutic interventions by pediatricians caring for these immunocompromised children. DESIGN: Retrospective chart review of patients whose respiratory viral cultures yielded influenza B from January 1989 through March 1992. PATIENTS: Twelve pediatric SOT recipients with influenza B virus infection were identified. These included five renal, four hepatic, and three cardiac allograft recipients, ranging from 19 months to 17 years 9 months of age (median 6 years 2 months). The posttransplant interval ranged from 6 weeks to 4 years 6 months (average 26.7 months). No patient had been immunized against influenza. Exposure histories were documented for eight children; five of these occurred in the hospital. RESULTS: Clinical symptoms included fever (12/12), respiratory (11/12), or gastrointestinal complaints (8/12). Five patients had neurologic involvement; one died of uncal herniation. Ten children were hospitalized (median duration, 3 days; range, 2 to 79 days). Two patients (post-transplant interval, 3 to 8 months) required mechanical ventilation, and one of these received aerosolized ribavirin. Three children had concurrent allograft rejection. CONCLUSIONS: Influenza B infection is potentially life-threatening in pediatric SOT recipients. We recommend annual immunization of pediatric SOT recipients, their household contacts, and health care workers. Prospective studies are needed to evaluate the efficacy of influenza vaccination in pediatric SOT recipients.

The binding of acetaldehyde to the active site of ribonuclease: alterations in catalytic activity and effects of phosphate.

Ribonuclease A was reacted with [1-13C,1,2-14C]acetaldehyde and sodium cyanoborohydride in the presence or absence of 0.2 M phosphate. After several hours of incubation at 4 degrees C (pH 7.4) stable acetaldehyde-RNase adducts were formed, and the extent of their formation was similar regardless of the presence of phosphate. Although the total amount of covalent binding was comparable in the absence or presence of phosphate, this active site ligand prevented the inhibition of enzymatic activity seen in its absence. This protective action of phosphate diminished with progressive ethylation of RNase, indicating that the reversible association of phosphate with the active site lysyl residue was overcome by the irreversible process of reductive ethylation. Modified RNase was analysed using 13C proton decoupled NMR spectroscopy. Peaks arising from the covalent binding of enriched acetaldehyde to free amino groups in the absence of phosphate were as follows: NH2-terminal alpha amino group, 47.3 ppm; bulk ethylation at epsilon amino groups of nonessential lysyl residues, 43.0 ppm; and the epsilon amino group of lysine-41 at the active site, 47.4 ppm. In the spectrum of RNase ethylated in the presence of phosphate, the peak at 47.4 ppm was absent. When RNase was selectively premethylated in the presence of phosphate, to block all but the active site lysyl residues and then ethylated in its absence, the signal at 43.0 ppm was greatly diminished, and that arising from the active site lysyl residue at 47.4 ppm was enhanced. These results indicate that phosphate specifically protected the active site lysine from reaction with acetaldehyde, and that modification of this lysine by acetaldehyde adduct formation resulted in inhibition of catalytic activity.

Covalent binding of acetaldehyde selectively inhibits the catalytic activity of lysine-dependent enzymes.

Hepatic ethanol metabolism generates the reactive intermediate, acetaldehyde, which binds to proteins. The binding of acetaldehyde to purified enzymes was determined in order to ascertain whether such binding altered their catalytic functions. [14C]Acetaldehyde was incubated with alcohol dehydrogenase, glucose-6-phosphate dehydrogenase, lactate dehydrogenase and RNase A, each at 37 degrees C (pH 7.4). In some reactions, sodium cyanoborohydride was included for stabilization of Schiff bases, formed as a result of the reaction between acetaldehyde and the amino groups of the enzymes. Portions of each reaction mixture were removed for determination of stable and total (stable plus borohydride-reducible) adducts. Alcohol dehydrogenase and lactate dehydrogenase were not inhibited by adduct formation. Glucose-6-phosphate dehydrogenase and RNase, the activities of which depend on a lysine residue at their catalytic sites, were inhibited in a dose- and time-dependent manner. The degree of inhibition directly correlated with total adduct formation. Phosphate, known to inhibit binding to the active site lysine of RNase, prevented the inhibition of catalytic activity caused by adduct formation. These findings indicate that the binding of acetaldehyde to lysine at the catalytic site can inhibit enzyme activity.

Actions of glucagon on flux rates in perfused rat liver. 1. Kinetics of the inhibitory effect on glycolysis and the stimulatory effect on glycogenolysis.

Changes in the rates of glucose, lactate and pyruvate production following infusion of glucagon were studied in isolated livers from fed or fasted rats perfused with non-recirculating Krebs-Henseleit bicarbonate buffer. Evidence was presented that under these experimental conditions, the release of lactate plus pyruvate into the perfusate represents 80-90% of the total glycolytic flux; oxidation of pyruvate derived from glucose and/or glycogen accounts for the remaining 10-20%, whereas recycling of pyruvate to glucose is negligible. In the presence of glucagon, rates of lactate plus pyruvate production were diminished to less than 30% in the fed state (glycogen as substrate) and to less than 10% in the fasted state (glucose as substrate). Rates of pyruvate oxidation were unchanged. Although recycling of pyruvate to glucose was enhanced, it could account for not more than 20% of the decrease in lactate plus pyruvate production. The data indicate a strong inhibition of the substrate flux through glycolysis. The glucagon concentration for half-maximal inhibition of glycolysis was 0.2 nM, independent of the substrate (glucose or glycogen) and the nutritional state. The effective concentrations were within the physiological range of glucagon concentrations reported for portal venous blood. Transient state analyses indicated that the inhibition of glycolysis precedes the stimulation of glycogenolysis. When after a delay glycogenolysis was accelerated, it was followed by a transient stimulation of glycolysis. The stimulatory component in the glucagon effect on glycolysis was diminished in glycogen-depleted livers and when glucose was the main substrate. The coordinated control of glycolysis and glycogenolysis by glucagon and the interaction of the two processes in the transient state are discussed.

Actions of glucagon on flux rates in perfused rat liver. 2. Relationship between inhibition of glycolysis and stimulation of respiration by glucagon.

The relationship between inhibition of glycolysis and stimulation of oxygen consumption by glucagon was studied in perfused rat livers. The two effects exhibit similar kinetics and dose-response curves; they are slower and less sensitive to the glucagon concentration than the stimulatory effect on glycogenolysis. A stoichiometry of 1 mol extra oxygen consumed/1.8 mol of diminished lactate plus pyruvate production was found. Under conditions where glucagon did not cause a marked inhibition of glycolysis (i.e. low glycolytic flux rates in the fasted state or in the presence of ethanol), oxygen consumption was also not markedly increased. These findings provide evidence that the major portion of glucagon-induced stimulation of hepatic respiration in the fed state is due to an enhanced demand for mitochondrial oxidative phosphorylation to compensate for the diminished extramitochondrial ATP production following inhibition of glycolysis by glucagon.