Effect of biotin on ribonucleic acid synthesis.

A single injection of biotin to biotin-deficient rats produces a two-fold increase in the incorporation, both in vivo and in vitro of precursors into nucleic acids as early as 2 h after the biotin treatment. The specific activity of the precursor pool is not affected by biotin. Analysis of the polysome profile at various times following biotin treatment and a kinetic study of the effect of excess poly(U) on the incorporation of phenylalanine by cell-free amino acid incorporation experiments indicate a marked decrease in messenger-free ribosomes in rat liver after biotin administration.

A prospective study of infant zinc nutrition during intensive care.

Zinc nutritional status was evaluated during intensive care for 55 infants. Plasma zinc, serum albumin, alkaline phosphatase, growth, nutrient intake, and clinical data were examined. The more premature infants (less than 32 wk gestational age) had higher zinc levels on admission, but their levels declined more rapidly than in more mature infants. Zinc level did not correlate with albumin or alkaline phosphatase. Low zinc levels (45 microgram/dl or less) occurred at about 6 wk in 14 of 39 premature infants. True zinc deficiency occurred in two premature infants; it was manifest by increased gastric residuals, poor suck, and decreased growth, but neither infant had the skin or gastrointestinal signs generally expected with zinc deficiency. There was evidence that sick premature infants may need more zinc than is currently recommended to supplement parenteral nutrition and more than the amount supplied in premature infant formulas currently available.

Gasoline sniffing and tetraethyl lead poisoning in children.

Two cases of acute organic lead poisoning following gasoline sniffing, with one death, are reported. Signs of lead encephalopathy with elevated blood lead levels and markedly decreased levels of erythrocytic delta-amino levulinic dehydratase (ALAD) were demonstrated. Erythrocytic ALAD activity was used as a screening test for the detection of tetraethyl lead (TEL) poisoning in a group of 43 children who were presumed gasoline sniffers. Their mean ALAD activity was 190 units compared to a mean of 538 units for a control group. A survey of schoolchildren in another isolated community revealed that 59% had decreased ALAD activity, which correlated well with a history of gasoline sniffing. Only 5% of the children had blood lead levels over 40 microgram/dl. The two surveys herein reported suggest that there may be large numbers of children living in isolated communities who are suffering from TEL poisoning as a result of gasoline sniffing. This constitutes a major medical, public health, and social problem heretofore virtually unrecognized.

Chemiluminescence: applications for the clinical laboratory.

The chemical features and applications of chemiluminescence are reviewed, with special attention to bacterial and firefly bioluminescence and to uses of chemiluminescence in direct substrate assays, enzyme assays, solid-phase reactions, and immunoassays.

Cyclosporine monitoring by fluorescence polarization immunoassay.

The monitoring of cyclosporine levels in whole blood and serum has become a routine procedure for the post-transplant management of immunosuppression. We have developed fluorescence polarization immunoassays for cyclosporine in whole blood and in serum using a monoclonal antibody. These assays are fast (20 determinations in less than 22 min), sensitive (25 micrograms/L for whole blood samples and 10 micrograms/L for serum samples), and precise (CV less than 7% in both assays). Cross-reactivities with AM1 (Metabolite 17) and AM4N (Metabolite 21) are less than 8.5 and 2.5%, respectively, for both assays.

Urine drug screening by gas chromatography-mass spectrometry. Application to a pediatric environment.

A GC-MS urine drug screening procedure is described. Its application to drug ingestion in the pediatric age group is illustrated by two case histories. The advantages and limitations of GC-MS urine drug screening are discussed.

The potential toxicity to neonates of multivitamin preparations used in parenteral nutrition.

This study compares two groups of infants weighing less than 1500 g at birth. In the propylene glycol (PG) group, 30 infants received MVI-Concentrate containing 300 mg of PG daily with their intravenous nutrition (ivn), and vitamin E, 50 mg/week by intramuscular injection. In the mannitol group, 30 infants received MVI-Pediatric (containing 245 mg mannitol), 65% of a vial/day. Serum and urine osmolality, serum PG, blood-urea-nitrogen, creatinine, sodium, and glucose were measured on days 0, 2, 5, 12, 19, 26, 33 and 40 of ivn. Weight, urine output, and fluid intake were measured daily. Vitamin E levels were measured on days 5, 26, and 33 of ivn. There were no significant differences between the groups in birth weight, gestational age, sex, age, or weight at start of ivn. Our results indicated that neither MVI-Concentrate nor MVI-Pediatric was associated with a clinically significant diuresis. MVI-Pediatric, 65% of a vial/day, may produce higher than desirable blood levels of vitamin E, and use of drugs containing PG can produce significant blood levels of PG, in very low birth weight infants.

Evaluation of the Du Pont Theophylline Assay adapted to a centrifugal analyzer.

We evaluated the Du Pont Theophylline Assay, a particle-enhanced turbidimetric inhibition immunoassay (PETINIA) for the measurement of theophylline in human serum. The procedure was applied to the Cobas-Bio centrifugal analyzer, and was compared to an enzyme immunoassay (EMIT) method and a high performance liquid chromatographic (HPLC) procedure. Day-to-day precision was 3.7% (1 SD coefficient of variation) at 7.1 mg/L, 3.3% at 17.7 mg/L, and 3.9% at 27.8 mg/L. The assay was linear up to 40 mg/L, and the correlation between the PETINIA, EMIT, and HPLC methods was good [PETINIA/EMIT: y = 0.94x + 0.63, r = 0.98, Syx = 1.13; PETINIA/HPLC: y = 1.00x - 0.89, r = 0.99, Syx = 0.66, where Syx is the standard deviation of the residual error of regression], when evaluated using specimens from 135 patients receiving theophylline. No interference from hemolysis, lipemia, icterus, or other methylxanthines was observed. Of the major metabolites of theophylline, only 1,3-dimethyluric acid showed any significant cross-reactivity (2.1 mg/L apparent theophylline at 20 mg/L 1,3-dimethyluric acid). The method is reliable and cost-effective for the measurement of theophylline in serum.

Biotin-mediated protein biosynthesis.

The effect of administration of biotin to biotin-deficient rats on protein biosynthesis was studied. Biotin treatment resulted in stimulation by more than twofold of amino acid incorporation into protein, both in vivo and in vitro in rat liver, pancreas, intestinal mucosa and skin. Analysis of the products of amino acid incorporation into liver proteins in vivo and in vitro indicated that the synthesis of some proteins was stimulated more than twofold, but others were not stimulated at all. This indicates a specificity in the stimulation of protein synthesis mediated by biotin.

Methylmalonic acidemia with the unusual complication of severe hyperglycemia.

We describe a case of neonatal methylmalonic acidemia with the unusual complication of severe, insulin-resistant hyperglycemia. Methylmalonic acidemia, an inherited metabolic disease affecting the catabolism of propionic acid, is manifested by persistent metabolic acidosis, urinary excretion of large amounts of methylmalonic acid, and occasionally by hypoglycemia. Severe and persistent metabolic acidosis and hyperglycemia, despite large doses of insulin, were observed in this infant, who excreted large amounts of methylmalonic acid. The diagnosis of methylmalonic acidemia was confirmed by gas chromatography-mass spectroscopy, but the patient died before the defect in glucose tolerance could be delineated. We hypothesize that, in addition to the methylmalonic acidemia, the patient may have had an insulin-receptor defect, which was manifested as an inappropriate response to endogenous and exogenous insulin.

A bioluminescence micromethod for measuring chloramphenicol in serum.

Bioluminescence provides a sensitive analytical approach for the measurement of low concentrations of ATP and can be used to monitor any reaction in which ATP is consumed or synthesized. We describe a quick, sensitive method involving bioluminescence for the quantitation of chloramphenicol in serum. Chloramphenicol acetyl transferase catalyzes the acetylation of chloramphenicol in the presence of acetyl coenzyme A. ATP is consumed when the acetylation reaction is coupled to the acetyl coenzyme A synthetase reaction. Residual ATP is then assayed with the firefly luciferin-luciferase reaction. The procedure can be completed in less than 1 h and requires as little as 20 microliter of serum. The response of the assay is linear with concentration through a range of 2 to 20 mg/L and shows good correlation with a gas-chromatographic method (r = 0.978) and a radioenzymic method (r = 0.985). No significant interference was found from five other antibiotics tested. The small sample requirement makes the assay especially applicable to infant and pediatric monitoring, where the effects of toxicity are greatest.

Comparison of a high performance liquid chromatographic and an enzyme immunoassay technique for quantitation of theophylline in serum.

High performance liquid chromatograhic (HPLC) and enzyme immunoassay (EMIT) methods for quantitating theophylline concentrations in serum were evaluated. For both methods, standard curves were linear over the therapeutic range of serum concentrations. Precision was acceptable, with coefficients of variation being less than 9%. The HPLC assay was slightly, but not significantly, more precise. No interference was noted in either method by caffeine, theobromine, diphylline, 8-chlorotheophylline, or by metabolites such as 1-methylxanthine, and 3-methylxanthine, or by potentially interfering compounds such as urea and uric acid. The two methods correlated well, with a correlation coefficient of 0.98%. The enzyme immunoassay was superior in terms of lower costs, greater ease of performance, and potential for automation.

Adaptation of the EMIT gentamicin and tobramycin procedure to the IL microcentrifugal analyzer.

We have adapted the Syva Emit gentamicin and tobramycin procedure to the IL microcentrifugal analyzer, MCA III. With this instrument the recommended instructions for reagent preparation and reaction sequence did not produce a useable standard curve. We modified the dilutions and volumes for the working reagents and reversed the sequence of addition of the working reagents. WE assessed the linearity and precision of the analysis and compared the Syva gentamicin and tobramycin Emit procedure on the IL MCA III with the semiautomated procedure on a Gilford Stasar III spectrophotometer. With the IL MCA III only 3 to 5 microliter of serum is used, 17 analyses can be obtained in 8 min, and the reagent costs are reduced considerably.

Reference values for cerebrospinal fluid glutamine concentration in infants.

We measured cerebrospinal fluid glutamine concentration in a reference group of 85 newborn to 30-month-old infants. All of the spinal taps were performed for the diagnosis of illnesses unrelated to hyperammonemia or hepatic encephalopathy. We also analyzed samples from patients with meningitis or cerebral hemorrhage, or who were receiving total parenteral nutrition. The mean glutamine concentration in cerebrospinal fluid in the reference group was somewhat lower than values reported for older children and adults. Values were significantly higher in patients with meningitis or cerebral hemorrhage and in those infants receiving total parenteral nutrition.

Determination of theophylline concentrations by AccuLevel.

Determination of theophylline concentrations in 29 paired venous samples by AccuLevel and EMIT disclosed excellent correlation. Evaluation of precision of AccuLevel by 20 replicate analyses disclosed a coefficient of variation of 3.5%. AccuLevel is an accurate, precise, rapid method of determination of theophylline concentrations in whole blood.

The neurological manifestations of chronic inhalation of leaded gasoline.

Abnormal neurological signs were found in 46 of 50 children and adolescents chronically sniffing leaded gasoline. These abnormalities resolved within eight weeks in all but one case. Exaggerated deep reflexes, postural tremor and evidence of cerebellar dysfunction occurred in a highly significnat number of patients. Forty-nine had blood lead levels greater than or equal to 40ug/dl. The mean blood lead levels were significantly higher in those with (a) abnormally brisk deep reflexes and (b) with evidence of cerebellar dysfunction, than in those without these findings. Five optional treatment regimes were employed and a classification was used, based on clinical findings, initial blood lead levels and the response to the calcium disodium edatate mobilization test. 39 patients received chelation therapy. These data suggest that neurological manifestations occur frequently in those abusing leaded gasoline and that chelation therapy has an important place in their management.

Adolescent pregnancy testing: which test to use.

In order to study the sensitivity and efficiency of five pregnancy tests, we evaluated four types of urine tests in 162 adolescent girls in whom pregnancy was suspected; a serum test was performed in 46 of them. We found that (1) an increase in sensitivity occurred at the expense of specificity, (2) the quantitation of the beta-subunit of human chorionic gonadotropin in serum proved to be the most reliable test for pregnancy, and (3) the latex agglutination inhibition tube test (Placentex) was the most accurate of the four types of urine tests evaluated. We concluded that for adolescents, the serum pregnancy test is the preferred test, but when it is not available, the urine latex agglutination inhibition tube test offers the most reliable alternative.