Exaggerated jaundice in Navajo neonates. The role of bilirubin production.

We have explored further the mechanism of exaggerated neonatal hyperbilirubinemia in the Navajo by determining bilirubin production rates with measurements of endogenous carbon monoxide excretion. Navajo newborns had elevated serum bilirubin concentrations and endogenous carbon monoxide excretion measurements at 2 days of age compared with a Caucasian control population. These findings could not be explained by differences in gestational age, postnatal age, or hemoglobin concentration.

5-Azido-2'-deoxyuridine 5'-triphosphate: a photoaffinity-labeling reagent and tool for the enzymatic synthesis of photoactive DNA.

We have synthesized the photoactive deoxyuridine nucleotide 5-azido-2'-deoxyuridine 5'-triphosphate (5-N3dUTP) and used it to synthesize light-sensitive DNA by enzymatic incorporation. In the absence of ultraviolet light, 5-N3dUTP is a substrate for Escherichia coli DNA polymerase I. In in vitro DNA synthesis reactions using bacteriophage M13 single-stranded DNA as the template and 5-N3dUTP in place of dTTP, a photoactive complementary strand was synthesized by DNA polymerase I.

Stimulation of cardiac myofilament force, ATPase activity and troponin C Ca++ binding by bepridil.

We report that bepridil, a Ca++ channel blocker and calmodulin antagonist, which has been shown to enter myocytes, stimulates the mechanical and biochemical activity of cardiac myofilaments. Bepridil increased significantly the level of Ca++-dependent actomyosin Mg++-ATPase activity of myofibrils and the submaximal force developed by chemically skinned trabeculae of pig heart. In the range of concentrations (10-100 microM) in which bepridil showed this stimulatory activity, diltiazem and verapamil were without effect.

Cyanide-induced neurotoxicity: role of neuronal calcium.

The effect of cyanide on whole-brain calcium levels was determined in mice administered KCN and correlated with the neurotoxic signs manifested during acute cyanide poisoning. KCN (10mg/kg, sc) significantly increased whole-brain total calcium levels from 48.1 +/- 1.

The in vitro effects of methotrexate on the phagocytosis and intracellular killing of Staphylococcus aureus by human neutrophils.

The in vitro effect of therapeutic concentrations of methotrexate on the phagocytosis and intracellular killing of Staphylococcus aureus by circulating human neutrophils was assessed. Neutrophils were isolated from whole blood of six healthy human volunteers by density centrifugation and incubated with 10(-3) M methotrexate. Staphylococcus aureus was opsonized in human serum and added to the prepared neutrophils.

Localization of a felodipine (dihydropyridine) binding site on calmodulin.

The fluorescent dihydropyridine calcium antagonist drug felodipine binds to calmodulin (CaM) in a Ca2+-dependent manner. Its binding can be regulated by the interaction of CaM antagonist drugs through allosteric mechanisms [Mills, J.S.

Stereochemistry and function of oxaloacetate keto-enol tautomerase.

Oxaloacetate keto-enol tautomerase, partially purified from porcine kidney, catalyzes the conversion of enol- to keto-oxaloacetate by a mechanism in which solvent protons end up equally distributed between the two prochiral positions at C3 of keto-oxaloacetate. This conclusion is based upon the observation that when enzyme catalyzed ketonization is conducted in 3H2O in the presence of excess malate dehydrogenase and NADH, only 50% of the 3H in the isolated (2S)-[3-3H]malate is labilized to solvent upon treatment with fumarase. From a stereochemical perspective, this enzyme is unlike phenylpyruvate keto-enol tautomerase that is known to catalyze stereospecific proton transfer between solvent and the pro-R position of keto-substrate.

Intracellular free Ca2+ and the hypercontracture of adult rat heart myocytes.

The Ca2+ sensitivity of a population of isolated adult rat heart myocytes has been related to the Na+ content of the cells prior to Ca2+ exposure, and the intracellular free Ca2+ as reported by quin2 fluorescence when the cells are challenged with millimolar external Ca2+. Myocytes exposed to Ca2+ during quin2 loading show a resting intracellular free Ca2+ of 150 +/- 30 nM and retain the rod cell morphology of heart cells in situ. The myocytes take up Na+ and lose K+ when incubated in the cold in the absence of Ca2+.

Metal ions as allosteric regulators of calmodulin.

Previously we have shown that the fluorescence of the dihydropyridine calcium antagonist felodipine provides an accurate means of monitoring the formation of an allosterically potentiated conformer of calmodulin (Mills, J. S., and Johnson, J.

The oxidative disposition of potassium cyanide in mice.

The role of oxidative metabolism in the disposition of potassium cyanide (KCN), was investigated in mice administered KCN, (4.6 mg/kg, s.c.

In vivo modulation of yeast tRNA gene expression by 5'-flanking sequences.

A pentadecanucleotide sequence, TTTCAACAAATAAGT, contiguous with the 5'-end of Saccharomyces cerevisiae tRNA-Leu3 coding sequence acts as a positive modulator of transcription in a homologous in vitro system. To determine whether modulation also takes place in vivo, the amber suppressor forms of tRNA-Leu3 genes with different 5'-flanking sequences were generated by site-specific mutagenesis and cloned into YCp19, a yeast vector maintained at 1-2 copies per cell. These plasmids were transformed into S.

Cooperativity among calmodulin's drug binding sites.

The binding of felodipine, a dihydropyridine Ca2+ antagonist, to calmodulin has been studied by equilibrium dialysis and fluorescence techniques. Analysis using the Hill equation gives a Hill coefficient of 2. A plot of bound [felodipine] vs.

UV inactivation of pathogenic and indicator microorganisms.

Survival was measured as a function of the dose of germicidal UV light for the bacteria Escherichia coli, Salmonella typhi, Shigella sonnei, Streptococcus faecalis, Staphylococcus aureus, and Bacillus subtilis spores, the enteric viruses poliovirus type 1 and simian rotavirus SA11, the cysts of the protozoan Acanthamoeba castellanii, as well as for total coliforms and standard plate count microorganisms from secondary effluent. The doses of UV light necessary for a 99.9% inactivation of the cultured vegetative bacteria, total coliforms, and standard plate count microorganisms were comparable.

Quantification of expired metabolites following potassium cyanide administration: a new method.

A sensitive and specific radiolabel method for measuring expired hydrogen cyanide (HCN) or carbon dioxide (CO2) derived from cyanide was developed. An ethanol collecting solution containing a 10(-2) M of cobalt chloride trapped 88% of the H14CN passed through the solution following acid volatilization of a known amount of K14CN. The range of linearity, r = 0.

A mechanism to inhibit input activation and its dysfunction in schizophrenia.

Schizophrenics appear to be unable to regulate adequately the effects of external stimulation, but the cause of this deficit is unclear. Recent evidence suggests that input activation can normally be inhibited by an appropriate leading or conditioning stimulus; such inhibition has been found to be diminished in schizophrenics. Based on this evidence, a feed-forward regulating mechanism that serves to stabilise reactivity to environmental events is described; it is hypothesised that failure of the mechanism to inhibit adequately surges of activity is an underlying cause of schizophrenic symptoms.