Genetic analysis of the S-mephenytoin polymorphism in a Chinese population

The 4'-hydroxylation of S-mephenytoin exhibits a polymorphism in humans, with the poor metabolizer phenotype exhibiting a lower frequency in white (3% to 5%) than in Oriental populations (13% to 23%). Two mutations in CYP2C19 (CYP2C19m1 and CYP2C19m2) have recently been described that account for approximately 85% of white and 100% of Japanese poor metabolizers. This study examines whether these mutations account for the poor metabolizer phenotype in the Chinese population. The metabolism of S-mephenytoin exhibited a bimodal distribution in 244 unrelated Chinese subjects, although the distribution of the two phenotypes overlapped. In 75 selected Chinese subjects, CYP2C19 genotype analysis predicted the phenotype with 100% accuracy. The frequency of the poor metabolizer phenotype was approximately 11% (95% confidence interval 7% to 15%). The frequency of the CYP2C19m1 allele was 0.289, whereas that of CYP2C19m2 was 0.044. Homozygous extensive metabolizers had slightly lower ratios of S/R-mephenytoin compared with heterozygous extensive metabolizers, showing a gene-dosage effect. These data show the advantages of genotype analysis in investigations of the mephenytoin phenotype in Oriental subjects.

Nitric oxide synthase complexed with dystrophin and absent from skeletal muscle sarcolemma in Duchenne muscular dystrophy

Nitric oxide (NO) is synthesized in skeletal muscle by neuronal-type NO synthase (nNOS), which is localized to sarcolemma of fast-twitch fibers. Synthesis of NO in active muscle opposes contractile force. We show that nNOS partitions with skeletal muscle membranes owing to association of nNOS with dystrophin, the protein mutated in Duchenne muscular dystrophy (DMD). The dystrophin complex interacts with an N-terminal domain of nNOS that contains a GLGF motif. mdx mice and humans with DMD evince a selective loss of nNOS protein and catalytic activity from muscle membranes, demonstrating a novel role for dystrophin in localizing a signaling enzyme to the myocyte sarcolemma. Aberrant regulation of nNOS may contribute to preferential degeneration of fast-twitch muscle fibers in DMD.

Effect of eradication of Helicobacter pylori infection on gastric epithelial cell proliferation

Helicobacter pylori infection has been linked with gastric carcinoma. Epithelial cell proliferation is an indicator of cancer risk. The aim of this study was to assess gastric epithelial cell proliferation before and after eradication therapy and to assess the efficacy of treatment of H. pylori infection using lanzoprazole and clarithromycin. Twenty-three patients with H. pylori-associated gastritis were treated with lanzoprazole 30 mg daily for four weeks and clarithromycin 500 mg three times a day for two weeks. Antral mucosal biopsies were taken for gastric epithelial cell proliferation analysis using the in vitro bromodeoxyuridine (BrdU) immunohistochemical technique before and four weeks after eradication therapy. Labeling index percent (LI%) was calculated as the percent ratio of proliferating cells to the total number of cells in the gastric pit. Efficacy of treatment was assessed in 16 subjects. Eight were negative for H. pylori infection 28 days after therapy and in eight patients H. pylori infection was not eradicated. The eradication rate for the regime was 50%. Cell kinetics were assessed in 19 subjects who completed treatment. Patients with H. pylori infection had a significantly higher LI% compared to normal (N = 19, LI%: 5.01 +/- 0.3 vs 3.2 +/- 0.2, N = 29). Eradication of H. pylori infection significantly reduced epithelial cell proliferation (N = 9, LI%: 5.2 +/- 0.4 to 3.2 +/- 0.8, P < 0.001), whereas it was unaltered in those whose infection was not eradicated (N = 10, LI%: 4.8 +/- 0.4 to 5.5 +/- 0.5, P = 0.18).(ABSTRACT TRUNCATED AT 250 WORDS)

Standardization of disk diffusion test and its clinical significance for susceptibility testing of metronidazole against Helicobacter pylori

Susceptibilities of 121 clinical Helicobacter pylori strains to metronidazole were determined by both a 5-micrograms metronidazole disk diffusion test and a plate dilution method in duplicate and after different periods of incubation. The distribution of MICs of metronidazole against H. pylori among the strains was found to be bimodal. The diameters of inhibitory zones obtained by the disk diffusion test and the MICs obtained by the plate dilution method correlated well, especially after 4 days of incubation (r = 0.77). An inhibitory zone diameter of 20 mm was found to correspond to a MIC of 8 micrograms/ml and is recommended as a suitable zone for differentiating susceptibility and resistance with a 5-micrograms metronidazole disk. Three interpretive categories of susceptibility results were defined; strains with inhibitory zone diameters of more than 26 mm were defined as susceptible (MIC, < 4 micrograms/ml), strains with zone diameters of 20 to 26 mm were deemed intermediate (MIC, 4 to 8 micrograms/ml), and those with zone diameters of less than 20 mm were deemed resistant (MIC, > 8 micrograms/ml). Furthermore, 76 H. pylori-positive patients with duodenal ulcers or nonulcer dyspepsia were treated with a 1 week of triple therapy (colloidal bismuth subcitrate, metronidazole, and tetracycline). H. pylori strains were isolated before treatment from antral biopsies from those patients, and the metronidazole susceptibilities of the strains were determined by the disk diffusion test. H. pylori status was evaluated again 4 weeks after completion of treatment. The eradication rates for susceptible, intermediate, and resistant strains were 95.9% (47 of 49), 62.5% (5 of 8), and 52.6% (10 of 19), respectively. It is included that the 5-micrograms disk diffusion test is easy to perform and gives final results similar to those of the plate dilution method. The three interpretive categories of susceptibility may be of benefit for clinical choice of chemotherapy in eradicating H. pylori.

Identification of conserved amino acid residues in the beta subunit of human choriogonadotropin important in holoprotein formation

The beta subunits of mammalian glycoprotein hormones contain 20 invariant amino acid residues, including 12 Cys residues that form six disulfide bonds, as well as other highly conserved residues. Such stringent conservation suggests an important role for those residues in chain folding, holoprotein formation, or receptor binding/activation, but not receptor specificity. Using site-directed mutagenesis, we have prepared and characterized replacements of 14 conserved non-Cys residues in human choriogonadotropin beta for which there is little, if any, information available: Pro7, Thr32, Tyr37, Thr40, Val56, Tyr59, Phe64, Pro70, Gly71, Ser81, Tyr82, Val84, Ala85, and Ser87. The cDNAs were subcloned into a pRSV mammalian expression vector and transiently transfected into Chinese hamster ovary cells containing a stably integrated gene for bovine alpha. Holoprotein formation was assessed by radioimmunoassays, and in vitro competitive binding and steroidogenic assays were used to determine potencies. Our results demonstrated that Tyr37, Thr40, Tyr59, and Ala85 participate directly or indirectly in holoprotein formation, as may Ser81. Replacements of the other conserved amino acid residues resulted in no significant change in subunit assembly or receptor binding/activation as measured, although an Arg at position 81 or 82 reduced secretion. This study has identified several amino acid residues of the beta subunit that are important in alpha binding and has raised interesting questions on the constraints that maintain conservation of amino acid residues during evolution.

A region in the human glycoprotein hormone alpha-subunit important in holoprotein formation and receptor binding

Using site-directed mutagenesis of the human glycoprotein hormone alpha-subunit, we have shown that single replacements of Ala36 and Pro38 with Glu and Asp, respectively, result in mutant subunits that do not bind significantly to hCG beta. In contrast, the replacement of Lys44 with Ala did not interfere with hCG beta binding, but the resulting holoprotein failed to exhibit high affinity binding to the LH/CG receptor. These results in conjunction with other data suggest that the region of human alpha between positions 33-45 contains several amino acid residues that participate in subunit binding and others that function in receptor binding.

Lysine residues 2 and 104 of the human chorionic gonadotrophin beta subunit influence receptor binding

Human chorionic gonadotrophin (hCG), like other members of the glycoprotein hormone family, contains a common alpha subunit and a hormone-specific beta subunit. The latter is a 145 amino acid residue polypeptide with six sites of glycosylation. Positions 2 and 104 are occupied by basic amino acid residues in the 12 known amino acid sequences of mammalian beta subunits from CG and LH, a related gonadotrophin that acts through the same receptor. Lysine residues are found in both these positions in hCG-beta. Using site-directed mutagenesis, each of these two lysines in hCG-beta was replaced with glutamic acid. The mutant and wild-type cDNAs were subcloned into a eukaryotic expression vector, which was then transiently transfected into Chinese hamster ovary cells containing a stably integrated gene for the bovine alpha subunit. Holoprotein formation occurred with each of the two heterologous gonadotrophin mutants, i.e. the bovine alpha subunit bound to hCG-beta (Glu2) and to hCG-beta (Glu104), as well as with the control, i.e. the bovine alpha subunit bound to the hCG-beta wild-type subunit. In two in-vitro assays, one a competitive binding assay with 125I-labelled hCG as bound ligand and the other based on stimulation of progesterone production in a transformed murine Leydig cell line, MA-10, both the heterodimers containing a mutant beta subunit exhibited bioactivity, but their potencies were lower than that of the bovine alpha subunit bound to the hCG-beta wild-type subunit. These results suggest that the basic amino acid residues at positions 2 and 104 in hCG-beta participate, either directly or indirectly, in receptor binding.

Replacement of the invariant tyrosine in the CAGY region of the human chorionic gonadotropin beta subunit

The mammalian glycoprotein hormone beta subunits contain a highly conserved amino acid sequence, Cys-Ala-Gly-Tyr-Cys (residues 34-38 of human chorionic gonadotropin beta), that is denoted as the 'CAGY region'. Using site-directed mutagenesis we have replaced Tyr-37 in hCG beta, i.e., the invariant Tyr in all known mammalian CG, LH, FSH, and TSH beta subunits, with two hydrophobic amino acid residues, Phe and Leu. The resultant mutant forms were characterized for alpha subunit binding and the resulting heterodimers were analyzed for biological activity using two in vitro assays with transformed murine Leydig cells (MA-10). Chinese hamster ovary cells containing a stably integrated gene for bovine alpha were transiently transfected with a eukaryotic expression vector containing a Rous sarcoma viral promoter and the wild-type and mutant cDNAs. The hCG beta(Phe-37) mutant bound to alpha essentially to the same extent as hCG beta wild-type, while the hCG beta(Leu-37) mutant formed somewhat less heterodimer. The heterologous heterodimeric mutant and wild-type gonadotropins were equipotent in a competitive binding assay with [125I]hCG. In a steroidogenic assay, the mutant hormones were active, but they appeared slightly less potent than the wild-type form. Thus, this invariant Tyr can be replaced with another aromatic amino acid residue or with a hydrophobic, but not aromatic amino acid residue in hCG beta without any dramatic effect on function. These results indicate that Tyr-37 in hCG beta, while not obligatory, may participate, either directly or indirectly, in subunit assembly and that the hydroxyl group may function in a modulatory role in signaling.

Mutagenesis of the 'determinant loop' region of human choriogonadotropin beta

The hormone-specific beta subunits of the four human glycoprotein hormones are homologous, and mapping studies are underway in many laboratories to delineate the amino acid residues responsible for receptor binding and activation. Results on the human choriogonadotropin beta (hCG beta) subunit, obtained using synthetic peptides, chemically modified derivatives, and mutant forms prepared via site-directed mutagenesis, have suggested that amino acid residues enclosed by the purported disulfide loop between Cys-93 and Cys-100 may contribute to receptor binding and perhaps specificity. Indeed, the 93-100 amino acid sequence is referred to as a determinant loop. We have used site-directed mutagenesis to prepare single amino acid residue replacements at positions not previously investigated in full length beta subunits; these include Arg-95, Ser-96, Thr-97, and Thr-98. In addition, Leu-92 was studied in an effort to determine whether changes immediately adjacent to the determinant loop alter receptor binding. The wild-type and mutant cDNAs for hCG beta were subcloned into a Prsv expression vector and transiently transfected into Chinese hamster ovary cells containing a stably integrated gene for bovine alpha. The concentrations of total expressed hCG beta in heterodimer form with the bovine alpha subunit were determined by radioimmunoassays. The mutant gonadotropins were assayed in vitro using a competitive binding assay with [125I]hCG and progesterone production, both in the transformed murine Leydig cell line, MA-10. Mutant beta subunits containing the replacements Lys-92, Ser-95, Asp-96, and Tyr-97 exhibited normal alpha subunit binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Extraction of pesticide residues in tea by water during the infusion process

The extraction rate of pesticide residues in water during the infusion process is dependent on the water solubility. The extraction of pesticide residues by boiling water can be regarded as a reversible equilibrium between adsorption and dissolution. The influence of chemical degradation is not important. When the water solubility is lower than 5 mg/kg, the extraction rate is 1-4%. Within the water solubility range of 10-150 mg/kg the extraction rate (Ri) is very sensitive to the water solubility (S); the relationship can be described as Ri = 59.8log S-42.5. When water solubility is higher than 170 mg/kg, the extraction rate is 90-100%.

[The augmenting effect of selenium(Se) on cell-mediated immunity. III. Se enhances delayed-type hypersensitivity reaction by promoting antigen presentation]

Delayed-type hypersensitivity reaction (DTH) to TNCB in TNCB-primed mice was increased when mice was treated with sodium selenite. In vitro studies showed that primed T cells proliferated more vigorously when TNP-conjugated spleen adherent cells (SAC) from Se-treated mice were the stimulators as compared with SAC of untreated controls. TNP-conjugated SAC treated in vitro with sodium selenite were even stronger stimulators than SAC treated in vitro. The results indicate that Se enhances DTH by promoting antigen presentation.

Developmental aspects of the sinus valves and the sinus venosus septum of the right atrium in human embryos

In 32 human embryos from 5 to 27 mm of length, stages 13 to 23 (according to the Carnegie system of stages), the contributions of the sinus venosus septum and the right sinus valve of the right atrium to the formation of the Eustachian and Thebesian valve were examined by scanning electron microscopy. The sinus septum takes part in the subdivision of the right sinus valve into the Eustachian and the Thebesian valves. From its first origin the sinus septum forms a septal structure between the orifices of the right hepatic vein (hepatic portion of the inferior caval vein), the precursor of the inferior caval vein, and the left horn of the sinus venosus, the precursor of the coronary sinus. Before the incorporation of the sinus venosus into the right atrium, it has an intra-sinusal position, and extends between the bases of the left and the right sinus valve. During the incorporation of the sinus venosus into the right atrium the sinus septum receives an intra-atrial position, and its positional relationships to the sinus valves and the orifices of the corresponding veins remain unchanged in principle. Due to the connection between the sinus septum and the right sinus valve, after completion of the incorporation of the sinus, the superior portion of the right sinus valve branches y-like into a lateral limb, (i.e. its original inferior portion) and into a medial limb, (i.e. the sinus septum).(ABSTRACT TRUNCATED AT 250 WORDS)