In vitro metabolism and toxicity assessment of N-methylcarbazole in primary cultured rat hepatocytes

N-Methycarbazole (NMC), a carcinogen and mutagen in tobacco smoke, was converted to two major metabolites by primary cultured rat hepatocytes as measured by high performance liquid chromatography (HPLC): N-hydroxymethylcarbazole (NHMC) and carbazole. These two metabolites had comparable retention times and identical ultraviolet spectra as those of reference standards. Identical retention times and mass spectra were also observed as detected by gas chromatography-mass spectroscopy (GC-MS) for NHMC and its reference standard. The toxicities of NMC and its two metabolites were assessed by lactate dehydrogenase (LDH) leakage and neutral red (NR) uptake. The rank order of cytotoxicity of NMC and its metabolites was found to be: NHMC greater than NMC greater than carbazole. Thus, we conclude that the hydroxylation of NMC to NHMC may represent a toxification step, while the further dealkylation to carbazole is most likely a detoxication process.

Structure of ribonuclease H phased at 2 A resolution by MAD analysis of the selenomethionyl protein

Ribonuclease H digests the RNA strand of duplex RNA.DNA hybrids into oligonucleotides. This activity is indispensable for retroviral infection and is involved in bacterial replication. The ribonuclease H from Escherichia coli is homologous with the retroviral proteins. The crystal structure of the E. coli enzyme reveals a distinctive alpha-beta tertiary fold. Analysis of the molecular model implicates a carboxyl triad in the catalytic mechanism and suggests a likely mode for the binding of RNA.DNA substrates. The structure was determined by the method of multiwavelength anomalous diffraction (MAD) with the use of synchrotron data from a crystal of the recombinant selenomethionyl protein.

Expression, purification, and crystallization of natural and selenomethionyl recombinant ribonuclease H from Escherichia coli

Ribonuclease H (RNase H) from Escherichia coli is an endonuclease that specifically degrades the RNAs of RNA:DNA hybrids. The enzyme is a single polypeptide chain of 155 amino acid residues, of which 4 are methionines. To solve the crystallographic three-dimensional structure of E. coli RNase H by the multi-wavelength anomalous diffraction technique, we have constructed methionine auxotrophic strains of E. coli that overexpress selenomethionyl RNase H. MIC88 yields about 10 mg of selenomethionyl RNase H per liter of culture, which is comparable to the overexpression of the natural recombinant protein. We have purified both proteins to homogeneity and crystallized them isomorphously in the presence of sulfate. These are Type I crystals of space group P2(1)2(1)2(1) with the cell parameters a = 41.8 A, b = 86.4 A, c = 36.4 A, one monomer per asymmetric unit, and approximately 36% (v/v) solvent. Crystals of both proteins diffract to beyond 2-A Bragg spacings and are relatively durable in an x-ray beam. On replacement of sulfate with NaCl, crystals of natural RNase H grow as Type I' (very similar to Type I) at pH between 7.0 and 8.0; at pH 8.8, crystals of Type II are obtained in space group P2(1)2(1)2(1) with a = 44.3 A, b = 87.3 A, and c = 35.7 A. Type II crystals can be converted to Type I by soaking in phosphate buffer. RNase H crystals of Type II have also been reported by Kanaya et al. (Kanaya, S., Kohara, A., Miyakawa, M., Matsuzaki, T., Morikawa, K., and Ikehara, M. (1989) J. Biol. Chem. 264, 11546-11549).

Neodymium: YAG laser therapy in aphakic pupillary block glaucoma and aphakic malignant (ciliovitreal block) glaucoma

Aphakic pupillary block glaucoma and malignant glaucoma (ciliovitreal block) are severe complications of the intracapsular cataract extraction, presenting clinically as elevated intraocular pressure, persistent shallow anterior chamber and severe vitreal hernia. Six eyes (four women and two men) with aphakic pupillary block glaucoma and aphakic malignant glaucoma were resolved by Neodymium: YAG laser iridotomy and hyaloidotomy. The laser therapy resulted in immediate deepening of the anterior chamber and reducing of intraocular pressure. No side effect was observed. Neodymium: YAG laser iridotomy and hyaloidotomy may be more effective and simple than penetrating surgery in such cases.

[Analgesic and anti-inflammatory effects and toxicity of houjianxi]

It is effective for acute and chronic laryngopharyngitis clinically. Houjianxi can raise the pain thresholds during hot-plate test in mice, tail flick test in rats, and writhing test in mice with single dose ig 0.125 to 2.0 g/kg. Houjianxi can also inhibit the swelling of hind paw induced by sc 1% carrageenin 0.1 ml in rats as well as the increased vascular permeability induced by ip 0.7% HAC in mice. Toxic side effects were not observed for Houjianxi ig 48 g/kg x 3 within a day in mice and 1.8 g/kg daily for 90 d in rats.

[Short-term curative effect of cultured Cordyceps sinensis (Berk.) Sacc. Mycelia in chronic hepatitis B]

33 cases of chronic hepatitis B. patients treated with cultured Cordyceps sinensis mycelia have shown that the drug improves the liver function, promotes negative transfer HBsAg, and markedly helps to raise plasma albumin, resist high gamma globulin and to adjust body immunocompetence. It is therefore suggested that cultured Cordyceps sinensis mycelia may be used as a medicine for chronic hepatitis B. patients in adjusting protein metabolism and correcting inversion of albumin and globulin.

Crystallization and characterization of human chorionic gonadotropin in chemically deglycosylated and enzymatically desialylated states

Crystals suitable for X-ray diffraction studies at moderate resolution have been grown from two forms of human chorionic gonadotropin (hCG): HF-treated hCG and neuraminidase-treated hCG. The enzymatically desialylated form of hCG produced crystals that diffract to 2.8 A as compared to the HF-treated hCG crystals that diffract to 3.0 A. Although it was assumed that the high and heterogeneous carbohydrate content of the glycoprotein hormones inhibited their crystallization, this report suggests that it is the negatively charged surface sugars and neither the total carbohydrate content nor its heterogeneity which interferes with crystal formation. Chemical deglycosylation resulted in significantly increased protein degradation during crystal growth. Such peptide bond cleavages were observed to a much lesser extent in the crystals grown from neuraminidase-digested hCG. Sequence analysis of the HF-treated hCG crystals suggested that up to 45% of the molecules within the crystal had an acid-labile peptide bond cleaved. In contrast, the neuraminidase-treated hCG exhibited less than 9% of this type of cleavage. The increase in heterogeneity of the polypeptide chains within both crystals over that existent in the starting proteins was apparently due to changes occurring during crystal growth. The manner in which hCG was treated prior to crystallization was found to be a very important factor in the extent of peptide bond cleavages occurring during crystal growth. HF treatment of glycoproteins may render glycoproteins more susceptible to peptide bond cleavages during crystal growth.

Identification of 5-hydroxytryptamine1A receptor proteins in bovine frontal cortex

5-Hydroxytryptamine1A (5-HT1A) receptor proteins were identified by a novel approach in which photoaffinity labeling technique was used in conjunction with affinity column chromatography. 5-HT1A receptors were solubilized from bovine frontal cortical membranes with 0.3% digitonin and 0.1% Nonidet P-40, and bound effectively to 1-[2-(4-aminophenyl)ethyl]-4-(3-trifluoromethylphenyl)piperazine (PAPP)-coupled Affi-Gel 10 in a time-dependent manner. PAPP was shown previously to be a selective ligand for the 5-HT1A receptor. Two protein bands with molecular masses of approximately 55,000 and 38,000 daltons revealed on sodium dodecyl sulfate-polyacrylamide gel electrophoresis were eluted from the affinity column with either 1 mM 5-HT or 1 microM [3H]1-[2-(4-azidophenyl)ethyl]-4-(3-trifluoromethyl-phenyl)piperazine ([3H]p-azido-PAPP). [3H]p-Azido-PAPP is a selective photoaffinity labeling probe for the 5-HT1A receptor. The intensity of these two protein bands and the incorporation of [3H]p-azido-PAPP into these two proteins decreased significantly when the solubilized fraction was preincubated with excess 5-HT or PAPP (saturating all 5-HT1A receptors) prior to affinity column chromatography. These results suggest strongly that these two proteins are related to the 5-HT1A receptor protein. The isoelectric points of the photolabeled 5-HT1A receptor proteins were 6.0 and 6.5.

Reliability and validity of a Chinese computerized diagnostic instrument

This paper reports on the development and testing of a new Chinese diagnostic instrument--the Adult Diagnostic Interview Schedule-Present (ADIS-P). This instrument uses a selection of items adapted from DIS and SADS. It is administered within approximately 25 min by a trained clinician using a small portable computer that provides an immediate diagnosis. The instrument was tested on 1,331 patients from six large mental hospitals across the country. The concurrent validity was good: compared to the concensus diagnosis of two senior clinicians (who were blinded to the ADIS-P result), the overall diagnostic accuracy was 83% and the weighted Kappa value was 0.60. The 1 month test-retest reliability was satisfactory (weighted Kappa = 0.55). We conclude that ADIS-P is a convenient, reliable and valid diagnostic instrument.

Hardness, softness, and the fukui function in the electronic theory of metals and catalysis

The concepts of hardness eta = (2E/N2)nu and fukui function f(r) = [rho (r)/N]nu, which have recently been associated with the theory of chemical reactivity in molecules, are extended to the theory of metals. It is shown that at T = 0, 1/eta = g(epsilon F) and f(r) = g(epsilon F, r)/g(epsilon F), where g(epsilon F), and g(epsilon F, r) are the density of states and the local density of states, at the Fermi energy epsilon F. Softness S and local softness s(r) are defined as 1/eta and Sf(r), respectively, and it is shown that (formula; see text) where the averages are over a grand canonical ensemble. It is pointed out that the postulate that f(r) or g(epsilon F, r) determines site selectivity for metals in chemisorption and catalysis is synonymous with the recent argument by Falicov and Somorjai [Falicov, L. M. & Somorjai, G. A. (1985) Proc. Natl. Acad. Sci. USA 82, 2207-2211] that such selectivity is determined by low-energy density fluctuations.

Defect in alpha-ketobutyrate metabolism: a new inborn error

A pair of siblings with clinical symptoms of cyclic vomiting and ketoacidosis were found to have a biochemical triad of normoglycemia, ketoacidosis and elevated levels of alpha-hydroxy- and alpha-aminobutyrate in plasma and urine. Methionine loading studies in both sibs produced prompt rises in plasma methionine and alpha-aminobutyrate levels, with a subsequent increase in urinary alpha-hydroxybutyrate, as well. Leukocytes from both siblings showed normal oxidation of [3-14C]propionate. Increased inorganic sulfate excretion after methionine loading implied an intact transsulfuration pathway in both siblings. On the basis of the studies detailed in this report, we conclude that these siblings suffer from a defect in alpha-ketobutyrate oxidation, a newly described defect of organic acid metabolism.

Medium-chain acyl-CoA dehydrogenase deficiency in children with non-ketotic hypoglycemia and low carnitine levels

Three children in two families presented in early childhood with episodes of illness associated with fasting which resembled Reye's syndrome: coma, hypoglycemia, hyperammonemia, and fatty liver. One child died with cerebral edema during an episode. Clinical studies revealed an absence of ketosis on fasting (plasma beta-hydroxybutyrate less than 0.4 mmole/liter) despite elevated levels of free fatty acids (2.6-4.2 mmole/liter) which suggested that hepatic fatty acid oxidation was impaired. Urinary dicarboxylic acids were elevated during illness or fasting. Total carnitine levels were low in plasma (18-25 mumole/liter), liver (200-500 nmole/g), and muscle (500-800 nmole/g); however, treatment with L-carnitine failed to correct the defect in ketogenesis. Studies on ketone production from fatty acid substrates by liver tissue in vitro showed normal rates from short-chain fatty acids, but very low rates from all medium and long-chain fatty acid substrates. These results suggested that the defect was in the mid-portion of the intramitochondrial beta-oxidation pathway at the medium-chain acyl-CoA dehydrogenase step. A new assay for the electron transfer flavoprotein-linked acyl-CoA dehydrogenases was used to test this hypothesis. This assay follows the decrease in electron transfer flavoprotein fluorescence as it is reduced by acyl-CoA-acyl-CoA dehydrogenase complex. Results with octanoyl-CoA as substrate indicated that patients had less than 2.5% normal activity of medium-chain acyl-CoA dehydrogenase. The activities of short-chain and isovaleryl acyl-CoA dehydrogenases were normal; the activity of long-chain acyl-CoA dehydrogenase was one-third normal. These results define a previously unrecognized inherited metabolic disorder of fatty acid oxidation due to deficiency of medium-chain acyl-CoA dehydrogenase.

Prenatal administration of biotin in biotin responsive multiple carboxylase deficiency

Biotin responsive multiple carboxylase deficiency was suspected in a third trimester conceptus on the basis of enzymatic confirmation in fibroblasts cultured from an earlier sibling who suffered a demise in the immediate neonatal period. Maternal urinary organic acid profile was normal throughout the final 4 wk of pregnancy. Oral administration of biotin, 10 mg/day to the mother resulted in a 100-fold increase in urinary biotin excretion within 7 days. Urinary biotin excretion over the subsequent 2 wk decreased steadily, suggesting either decreased maternal absorption or increased fetal sequestration. After the birth of nonidentical twins, cord blood and urinary organic acid profiles of the infants were normal. However, cord blood biotin concentration was 4 to 7-fold that of normal newborns. Subsequent enzymatic and genetic complementation studies utilizing cultured skin fibroblasts from the infants demonstrated one of them to be affected by the multiple carboxylase defect, although he was clinically and biochemically normal throughout the neonatal period. Thus, prenatal therapy of this inborn enzymatic defect can be safely and effectively accomplished by administration of pharmacologic biotin doses in the last month of pregnancy.

Diet and vitamin nutrition of the high esophageal cancer risk population in Linxian, China

In order to examine the nutritional status of the population of Linxian (in Henan, China) known to be at high risk for esophageal cancer (EC), we analyzed blood samples and conducted 3-day dietary surveys on 3 groups of normal adults, age 40-50, from Henan province. Two groups were from Linxian, where the EC mortality rate is about 138/100,000 (Group C, consisting of volunteers with a family history of EC, and Group NC, consisting of those who did not have a family history of EC). The third group, Group F, was from Fanxian, where the EC mortality rate is about 24/100,000. The average plasma retinol level was found to be about 0.27 micrograms/ml in all 3 groups; about 13%-20% of the individuals had a level less than 0.2 micrograms/ml. The average plasma carotene level of all 3 groups appeared to be adequate, ranging from 0.5-1.0 micrograms/ml. About 23% of the subjects in both Groups C and NC had low (less than 2 micrograms/ml) plasma ascorbate levels; in Group F, 16% had low ascorbate levels. Less than 12% of the individuals in each of the 3 groups had erythrocyte glutathione reductase activation coefficients less than 1.2, indicating a widely occurring riboflavin deficiency. Consumption of alcoholic beverages was not found to be a contributing factor to EC. The results of the present study reveal a deficiency of vitamins in the study populations, but do not indicate that the average nutritional status of the volunteers in Group C was worse than that of Groups NC and F with regard to vitamin A, ascorbate, and riboflavin.

Serum and urinary biotin levels during treatment of holocarboxylase synthetase deficiency

Measurements of blood and urine biotin levels have been performed during treatment of a patient with holocarboxylase synthetase deficiency. During the first 24 hours of therapy, the infant progressed from a moribund, shock-like state to a clinically normal baby. Urinary biotin concentration increased more that 100-fold after 12 hours of treatment. Within 48 hours of treatment, blood biotin levels were greater than 10 times control levels. On the basis of the data presented, it is suggested that therapeutic blood levels of biotin can be achieved by enteral administration of 10 mg of biotin per day.

Rapid gas chromatographic-mass spectrometric analysis of [15N]urea: application to human metabolic studies

A rapid gas chromatographic-mass spectrometric method for [15N]urea analysis is described which is based on the formation of a TFA-urea derivative. The method is extremely sensitive, being capable of detecting less than 0.2 atom % excess [15N]urea in as little as 50 microliter of plasma and 10 microliter of urine with a coefficient of variation of 11%. The method was used to measure in vivo the disappearance of [15N]urea from plasma and the incorporation of [15N]ammonium acetate into [15N]urea. The values obtained for urea pool size and flux are 4.5 +/- 0.30 g nitrogen/total body weight and 16.2 +/- 1.34 g nitrogen per 24 h per 1.73 m2. Following the ingestion of [15N]ammonium acetate nearly 90% of the 15N label was incorporated into [15N]urea by 30 min.

Holocarboxylase synthetase deficiency: a biotin-responsive organic acidemia

The clinical and biochemical features of an infant affected by holocarboxylase synthetase deficiency are presented. The patient was the sibling of the deceased child in whose cultured skin fibroblasts the precise enzymatic disorder was first determined. This fact permitted administration of specific therapy in the form of oral biotin, resulting in immediate improvement from impending respiratory failure and shock. The clinical response to biotin was accompanied by recovery of the biochemical mechanisms known to be biotin-dependent, as manifested by disappearance of intermediates in urine and blood. The variability of biotin responsiveness and the diversity of clinical presentation in the patients originally thought to have a deficiency of beta methylcrotonylCoA carboxylase, a biotin-dependent enzyme, raises the question of a separate, specific apocarboxylase defect.

Heteropolypeptides from poly-alpha-cyanoglycine and hydrogen cyanide: a model for the origin of proteins

Poly-alpha-cyanoglycine, a homopolymer synthesized from the N-carboxyanhydride of alpha-cyanoglycine, is converted by cumulative reaction of hydrogen cyanide to heteropolypeptides that can be hydrolyzed to protein amino acids, including glycine, alanine, valine, aspartic acid, and glutamic acid. These results are consistent with the hypothesis that the original heteropolypeptides on the earth arose spontaneously from hydrogen cyanide and water without the intervening formation of alpha-amino acids.

Reciprocal inhibition of mouse leukemia virus infection by Fv-1 allele cell extracts

Soluble extracts of mouse cells with Fv-1(n) or Fv-1(b) gene alleles specifically and reciprocally inhibit infection of B- or N-tropic mouse leukemia viruses in permissive cell cultures. NB-tropic virus infection was not inhibited by either cell extract. Extracts from Fv-1(-) cells did not inhibit infection by the three virus host-range types, but N- or B-tropic virus infection of Fv-1(-) cells was inhibited by extracts of the nonpermissive cells, and Fv-1(nb) cell extracts inhibited both viruses. The maximum degree of inhibition was 50-80% as determined by immunofluorescent or plaque assays, with extracts containing up to 500 mug/ml of nonpermissive cell protein. The inhibitor(s) is relatively unstable since activity is lost after 2 hr at 37 degrees or 30 min at 56 degrees . The inhibitor(s) was most effective if added 2 hr before or within 2 hr after infection, did not react with the virus directly, inhibit virus attachment, or inhibit the normal cell functions tested. These results indicate that nonpermissive mouse cells contain a product, possibly determined by the Fv-1 gene, which inhibits some early postpenetration event(s) in leukemia virus infection.

The redox potentials of the two-iron plant and algal ferredoxins. An electrostatic model

The two-iron-sulphur co-ordination centre in plant and algal ferredoxins is considered as a collection of charged ions whose net negative charge is twice that of the one-iron-sulphur protein rubredoxin. Calculation of the electrostatic free-energy changes for reduction of the two types of proteins indicates that the redox potential of the two-iron-sulphur proteins should be more negative than that of the one-iron-sulphur protein and that in biological systems the ferredoxins should function as one-electron transfer proteins.