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Biomedical subjects

J Hong

Publications and source records attributed to J Hong.

At least 19 recordsLinked to original sources
PubMed1997

Metal-catalyzed oxidation of histidine in human growth hormone. Mechanism, isotope effects, and inhibition by a mild denaturing alcohol.

Metal-catalyzed oxidation of proteins represents an important pathway of post-translational modification. We utilized human growth hormone (hGH), a protein with a well defined metal-binding site, to study the detailed mechanism of metal-catalyzed oxidation by ascorbate/Cu(II)/O2. Particularly His18 and His21 within the metal-binding site were oxidized, predominantly to 2-oxo-His with the incorporated oxygen originating from molecular oxygen, based on amino acid analysis, tryptic mapping, mass spectrometry, isotopic labeling, and 1H NMR. The anaerobic reduction of a hGH/Cu(II) mixture by ascorbate generated a hGH-Cu(I) complex with NMR spectral features different from those of native hGH and hGH/Cu(II). The anaerobic reaction of this hGH-Cu(I) complex with hydrogen peroxide resulted in the oxidation of His18 and His21, suggesting that a fraction of Cu(I) was bound at the metal-binding site of hGH. Site-specific oxidation of hGH required an intact metal-binding site and could largely (about 80%) be inhibited by the presence of >/=28% (v/v) 1-propanol which appears (i) to perturb the metal-binding site and (ii) to interact with a reactive oxygen species formed at the perturbed metal-binding site. The inhibition by 1-propanol-d7 (CD3CD2CD2OH) was significantly lower than that by 1-propanol-h7 with [residual hGH]1-propanol-h7/[residual hGH]1-propanol-d7 = 1.95 at 30% (v/v) 1-propanol, reflecting a kinetic isotope effect close to that for the reaction of a hydroxyl radical with Calpha-H/D bonds of methanol, suggesting the involvement of a hydroxyl radical-like species in the oxidation of His.

1-Propanol↗
PubMed1996

A capacitative calcium current in cultured skeletal muscle cells is mediated by the calcium-specific leak channel and inhibited by dihydropyridine compounds.

Calcium stores from cultured skeletal muscle cells were depleted using cyclopiazonic acid (CPA), a reversible inhibitor of Ca2+-ATPases at the sarcoplasmic reticulum. Store depletion led to activation of the calcium-specific leak channel, as assayed using single-channel patch clamp analysis and rates of manganese influx and quenching of fura-2 fluorescence. Two novel dihydropyridine compounds inhibited this single-channel leak channel activity, the resting and depletion-induced manganese influx, and refilling of the CPA-depleted intracellular calcium store. These compounds represent the first antagonists for a calcium leak channel and for a channel that mediates a capacitative current. The development of the skeletal muscle capacitative current was inhibited by genistein, a tyrosine kinase inhibitor, but was not affected by okadaic acid, a phosphatase inhibitor, or econazole. Thus, the capacitative current in cultured skeletal muscle cells was mediated by the calcium leak channel and was inhibited by pharmacological antagonists and may provide a model system for uncovering the complete set of signals leading from store depletion to channel activation.

Animals↗
PubMed1996

Complete 1H, 15N and 13C assignments, secondary structure, and topology of recombinant human interleukin-6.

Essentially complete backbone and side-chain 1H, 15N and 13C resonance assignments for the 185-amino-acid cytokine interleukin-6 (IL-6) are presented. NMR experiments were performed on uniformly [15N]- and [15N,13C]-labeled recombinant human IL-6 (rIL-6) using a variety of heteronuclear NMR experiments. A combination of 13C-chemical shift, amide hydrogen-bond exchange, and 15N-edited NOESY data allowed for analysis of the secondary structure of IL-6. The observed secondary structure of IL-6 is composed of loop regions connecting five alpha-helices, four of which are consistent in their length and disposition with the four-helix bundle motif present in other related cytokines and previously postulated for IL-6. In addition, the topology of the overall fold was found to be consistent with a left-handed up-up-down-down four-helix bundle based on a number of long-range interhelical NOEs. The results presented here provide deeper insight into structure-function relationships among members of the four-helix bundle family of proteins.

Amino Acid Sequence↗
PubMed1996

The promoter region of the carbamoyl-phosphate synthetase III gene of Squalus acanthias.

Carbamoyl-phosphate synthetase III (CPSase III) of Squalus acanthias (spiny dogfish) is a nuclear-encoded mitochondrial enzyme that catalyzes glutamine-dependent formation of carbamoyl phosphate for urea synthesis. In this paper we report the results of cloning a 10-kb segment of genomic DNA which includes the region flanking the 5' end of the spiny dogfish CPSase III gene. A total of 1,295 base pairs of sequence straddling the start codon was obtained. Primer extension experiments revealed that the transcription start site is the G located 114 residues upstream of the translation start codon ATG. The first exon has 240 base pairs, including the 5' untranslated region, the coding sequence for the signal peptide (38 amino acids), and the four N-terminal amino acids of the mature enzyme. The boundary of the first exon and the first intron of the CPSase III gene is concordant with that of rat and frog (Rana catesbeiana) CPSase I, which have been suggested to have evolved from CPSase III. The putative TATA box sequence, TACAAA, is located at position -31 with an uncommonly found C at the third position. Two C/EBP binding site sequences, ATTCTGCAAG (-405 to -397) and GTGCAGTAAG (-168 to -160), were identified in the promoter region, which suggests that spiny dogfish CPSase III might be subjected to transactivation of transcription by C/EBP-related proteins, as has been reported for rat CPSase I. The preparation and binding of a recombinant RcC/EBP-1 protein (the R. catesbeiana homolog of the mammalian C/EBP alpha) to the two spiny dogfish C/EBP binding sequences are described. Two putative heat-shock binding elements were also identified in the promoter region.

Amino Acid Sequence↗
PubMed1996

Arachidonic acid release: an in vitro alternative for dermal irritancy testing.

Validated in vitro alternatives are being utilized extensively for mutagenicity and ocular irritancy testing. However, validation of alternative assays for dermal irritancy is progressing more slowly. As the irritant response in human skin is mediated, at least in part, by eicosanoids derived from arachidonic acid, the effect of relatively pure anionic surfactants (AS, n=8) and surfactant-containing finished products (FP, n=25) on the release of [3H]arachidonic acid from a prelabelled murine fibroblast cell line (C3H-10T1/2 cells) in vitro was examined. Test substances were administered at various non-lethal concentrations, in triplicate, to 12- and 24-well plates containing preconfluent monolayers (80-90% confluence) of C3H-10T1/2 cells. Because it is impossible to test all concentrations of each test substance in a single assay, statistical techniques were developed to 'standardize' in vitro assay results. In each assay, radiolabel release due to a positive control was also measured, using 0.04, 0.05 and 0.06 mM concentrations of sodium dodecyl sulfate (SDS). Test substance releases were then transformed into 'SDS equivalent' responses, significantly reducing both inter- and intra-assay variability. A straight line was fitted to the test substance responses and compared with that for SDS to calculate the relative potency in vitro for individual AS and FP. Relative potencies correlated with in vivo responses, that is primary dermal irritation indices obtained in rabbits, with Spearman p=0.408 (P<0.03) for 32 tested agents, and p=0.976 (P<0.001) for the eight AS. Exclusion of extremely alkaline or acidic FP (pH>11 or <2, n=4) and those which were insoluble in the aqueous cell culture media at the 1% stock dilution (n=5), improved the overall in vivo-in vitro correlation significantly (p=0.683, P<0.001, n=23) and produced a significant correlation for FP alone (p=0.539, P<0.05, n=15). These results suggest that release of [3H]arachidonic acid from cultured skin cells represents a novel, mechanistically based in vitro screen for dermal irritancy testing.

Animal Testing Alternatives↗
PubMed1996

Automated analytical systems for drug development studies. V. A system for enzyme kinetic studies.

Two similar automated analytical systems using liquid chromatography (LC) and microdialysis as an on-line sampling technique were applied to studies of enzyme kinetics. 2',3',5'-Triacetyl-6-azauridine (azaribine) with porcine liver esterase (PLE) and N-acetylphenylalanyl-3,5-diiodotyrosine (AcFY') with pepsin were used as model compounds. The microdialysis sampling technique permitted the rapid separation of low molecular weight analytes from macromolecules, thus simultaneously achieving clean-up of the samples and quenching of the reaction. The combination of rapid LC analysis and microdialysis sampling provided selectivity and automation. The systems are rugged and give reproducible results in agreement with those from manual sampling methods.

Animals↗
PubMed1996

Nosocomial infections and nosocomial pneumonia.

Nosocomial infections are a major source of revenue loss, morbidity, and even mortality to surgical patients. This review presents current issues regarding nosocomial infections and nosocomial pneumonias. This study is a literature review that presents material on nosocomial infections in general and details regarding Clostridium difficile and vancomycin-resistant enterococcus infections. Nosocomial infections, including pneumonias, are serious medical complications, and prevention by strict adherence to barrier precaution is the most important means of protecting the patient from hospital-acquired bacterial flora.

Anti-Bacterial Agents↗
PubMed1996

Giant infantile hemangioendothelioma of the liver. Scintigraphic diagnosis.

Infantile hemangioendothelioma of the liver is benign mesenchymal tumor composed of anastomosing vascular channels lined with plump endothelial cells. It is a congenital lesion noted at birth or during the first 6 months of life. The authors report a large infantile hemangioendothelioma that was imaged with anatomical modalities and Tc-99m RBC scintigraphy. An early "blush" on Tc-99m RBC hepatic scintigraphy is a diagnostic feature of infantile hemangioendothelioma.

Erythrocytes↗
PubMed1995

Estimation of kinetics of mercury detoxification from low-inoculum batch cultures of Pseudomonas aeruginosa PU21 (Rip64).

The growth rate of Pseudomonas aeruginosa PU21 (Rip64) and the mercury detoxification rate were determined by using low-inoculum batch cultures. In order to attain invariant culture conditions for the determination of growth kinetics in mercury-containing Pseudomonas minimal media (PMM), the initial cell concentrations were adjusted to approx. 100 cells per ml, and the initial mercury concentrations used were less than 2 micrograms Hg2+ per ml. It was found that the specific growth rate decreased as mercury concentration increased. The relationship between specific growth rate and glucose concentration was found to follow Monod kinetics. The mercury detoxification rate was determined for the viable cells and the dying (non-growing) cells.

Biotransformation↗
PubMed1995

Nucleotide sequence and tissue-specific expression of the multifunctional protein carbamoyl-phosphate synthetase-aspartate transcarbamoylase-dihydroorotase (CAD) mRNA in Squalus acanthias.

Carbamoyl-phosphate synthetase II (CPSase II), aspartate transcarbamoylase (ATCase), and dihydroorotase (DHOase) catalyze the first three steps of de novo pyrimidine nucleotide biosynthesis, respectively. In mammalian species, these three enzyme activities exist in the cytosol in liver and other tissues as a multifunctional complex on a single polypeptide called carbamoyl-phosphate synthetase-aspartate transcarbamoylase-dihydroorotase (CAD) in the order of NH2-CPSase II-DHOase-ATCase-COOH. Previous studies provided evidence that in Squalus acanthias (spiny dogfish) these enzymes are not expressed in liver and that they exist as separate entities in the cytosol of extra-hepatic tissues such as testes and spleen (Anderson, P. M. (1989) Biochem. J. 261, 523-529). Here we report that the genes for these three enzymes are expressed in testes as a single transcript analogous to CAD in mammalian species and that these genes are not expressed in liver at levels that can be detected by Northern blots or by the polymerase chain reaction. The absence of the pyrimidine pathway in the liver may be related to the exclusive localization of glutamine synthetase in the mitochondrial matrix which provides for efficient assimilation of ammonia as glutamine for urea synthesis in these ureoosmotic species; thus glutamine may not be available for CPSase II or other amidotransferase activities in the cytosol. The amino acid sequence deduced from the nucleotide sequence of the shark CAD cDNA reported here is very similar to CAD from other species; alignment with the hamster CAD sequence shows 77% identical residues.

Amino Acid Sequence↗
PubMed1995

Cross-national comparisons of ageing mothers of adults with intellectual disabilities.

Ageing (55+ years) mothers of adults with intellectual disabilities in the Republic of Ireland, Northern Ireland and the United States were compared with respect to three general issues. Firstly, to what extent do the adults in these three countries differ in their level of reliance on their mothers? Secondly, do the mothers differ in the extent to which they have made plans for the future care of their son or daughter with intellectual disabilities? Thirdly, do the mothers differ in physical, social and psychological well-being? These cross-national comparisons were undertaken to examine the extent to which lifelong caregiving has either a common influence on mothers across national boundaries, or, alternatively, whether the cultural context exerts a unique influence on mothers in each country. Findings supported the latter explanation, even when background characteristics were statistically controlled.

Adult↗
PubMed1995

Salmonella typhimurium pgtB mutants conferring constitutive expression of phosphoglycerate transporter pgtP independent of pgtC.

PgtC is one of the three components of the atypical "two-component" pgt regulatory system. To investigate whether functional PgtC required for the induction of pgtP expression could be bypassed in the signal transduction process, we sought, and succeeded in isolating, intergenic suppressors arising in the low-copy mini-F plasmid, pSJ11, bearing the entire pgt system except for a 168-bp deletion near the end of the pgtC gene. By transport assays, these suppressors were found to confer constitutive pgtP expression. Intriguingly, all five mutations reside near the 5' end of the pgtB gene, at codons 19 and 21. One mutation alters Arg-19 to Gln, two alter Ala-21 to Thr, one alters Ala-21 to Val, and one alters Ala-21 to Ile. Appropriate strains in which the pgtP promoter was fused to lacZ and which bore the pgtB mutations with and without mutations in pgtC and pgtA genes were constructed, and the epistatic relationships of the wild-type pgtC allele, a mutant pgtA allele, and an essentially total deletion of pgtC to the constitutive pgtB mutations were determined. In the mutant strains bearing the Ala-21 --> Ile and Ala-21 --> Val substitutions, the level of constitutive pgtP-lacZ reporter expression was not affected by the presence of the wild-type pgtC allele, nor was it affected by the total absence of PgtC in the case of the Ala-21 --> Val alteration examined; however, in the mutant strains bearing the Ala-21 --> Thr and the Arg-19 --> Gln substitutions, the extent of constitutive pgtP-lacZ reporter expression was markedly enhanced by the presence of wild-type pgtC allele and, in the case of the Arg-19 -->Gln change examined, by the total absence of PgtC as well. These results indicate that PgtC contains no domain necessary for the kinase activity; that PgtB can be activated in the absence of PgtC mutational alterations of the protein itself; and that PgtB and PgtC interact in the signaling process, with PgtC functioning to activate and modulate the kinase activity of Pgtb. In all strains, the replacement of the wild type pgtA allele with a mutant pgtA allele completely abolished expression of the pgtP-lacZ reporter, indicating that functional pgtA is essential for the constitutivity. His-457 of PgtB, a potential site of autophosphorylation, is also required for the constitutivity because its change to Val drastically reduced pgtP-lacZ reporter expression. The structural basis for the activation of the altered PgtB is discussed in terms of putative structure of PgtB in the membrane.

Amino Acid Sequence↗
PubMed1995

Breastfeeding practices in Chengdu, Sichuan, China.

Barriers to increased breastfeeding rates in Chengdu, Sichuan were investigated in 1992 and 1993. Responses of focus groups showed that ignorance about breastfeeding and belief that the mother's milk was inadequate, and lack of support from their families, places of employment, and the health system acted as barriers to the women's breastfeeding their infants up to the age of four to six months. Subsequently, 363 mothers of 4- to 12-month-old Chengdu infants were surveyed. Although most mothers in both studies said breastmilk was the best food for their infant up to age of four to six months, only about half of the mothers breastfed for longer than one month. Both studies showed that infants who roomed with their mothers after birth were more likely to have been put to their mother's breast earlier, fed colostrum, breastfed somewhat longer, and exclusively breastfed for a somewhat longer period, although their mothers' infant feeding knowledge did not differ. The researchers conclude that Chengdu health workers should teach parents and parents-to-be more about breastfeeding, and that rooming-in be expanded in Chengdu hospitals.

Breast Feeding↗
PubMed1995

Four outbreaks of human trichinellosis in Henan Province.

Four outbreaks of human trichinellosis caused by eating pork together had occurred successively in two rural areas and two cities of Henan Province, where the disease is endemic. Of the 110 persons involved, 54 had the onset. All of them had the history of eating pork. In the outbreak of Dengzhou, in those persons who dined together, men were all uninfected and 13 women were infected. The difference found between sexes was suggested to be related with spirit drinking. In these 54 patients, the latent period ranged from 3 to 28 days. The relevant clinical symptoms and signs were fever, edema, myalgia, rash, headache, nausea, abdominal pain and diarrhea. Vomiting was uncommon. Most patients were hospitalized and all cases recovered in two weeks after proper treatment with albendazole.

Animals↗
PubMed1995

The psychological consequences of multiple roles: the nonnormative case.

Occupying multiple roles has been shown to be a major predictor of psychological well-being. We investigated the effects of multiple roles in the nonnormative case: a sample of aging mothers of adult children with mental retardation. These women have been in the role of caregiver for up to five decades, in addition to occupying the range of roles normatively held in adulthood and old age. We found, using longitudinal analyses, that holding multiple roles in significantly and negatively related to depression in this sample, as in the general population. The effect of multiple roles remains significant even after the previous level of depression is controlled. These results support the role accumulation hypothesis predicting positive consequences of multiple roles on psychological well-being, even in this sample of older women who have had lifelong caregiving responsibilities.

Adaptation, Psychological↗
PubMed1994

Carbamyl phosphate synthetase III, an evolutionary intermediate in the transition between glutamine-dependent and ammonia-dependent carbamyl phosphate synthetases.

The amino acid sequence of carbamyl phosphate synthetase (CPS) III from liver of spiny dogfish shark Squalus acanthias was deduced from the nucleotide sequence of its cDNA. Alignment of the derived amino acid sequence of CPS III with sequences of rat and frog CPS I and hamster CPS II reveals a high degree of amino acid identity, indicating that CPS III shares the same common ancestral genes as CPSs I and II. All of the CPSs examined show a high conservation of sequences in the adenine nucleotide binding domains and in residues that have been implicated in catalysis. The active-site cysteine residue required for glutamine-dependent activity by CPS II is preserved in the sequence of CPS III. Nevertheless, analysis of the protein sequences indicates that CPS III is more closely related to CPS I than to CPS II. The structure of CPS III, which is composed of a single polypeptide, is consistent with the view that CPS III evolved by fusion of separate genes coding for the glutaminase and synthetase domains of the enzyme and, like other CPSs, the synthetase domain evolved by duplication and fusion of an ancestral kinase gene. These results, together with the recent finding that frog CPS I retains the active site cysteine residue in the glutaminase domain required for glutamine-dependent activity, indicate that other amino acid substitutions critical for glutamine-dependent activity preceded loss of this catalytic cysteine residue. The results described here together with earlier biochemical evidence support the view that acetylglutamate and glutamine-dependent CPS III found in invertebrates and fish species represents an intermediate in the evolution of ancestral glutamine-dependent CPS II toward the acetylglutamate and ammonia-dependent CPS I of ureotelic terrestrial vertebrates.

Amino Acid Sequence↗
PubMed1994

cAMP, ethanol, and CO2 production with the addition of D-glucose anomer to starved yeast cells.

cAMP, ethanol, and CO2 production in starved yeast cells after the addition of D-glucose anomer was measured and compared over a wide range of anomer concentrations. At 1.0 g/l or higher concentrations, the addition of beta-D-glucose resulted in a higher cAMP peak. beta-D-glucose was more rapidly metabolized to ethanol and CO2 than alpha-D-glucose, although there was no notable difference in the uptake rates of the two anomers. At 0.4 g/l D-glucose anomer, the differences in cAMP and ethanol production rates for the two anomers were not significant. At 0.2 g/l D-glucose anomer or lower concentrations, ethanol production with alpha-D-glucose was higher than that with beta-D-glucose. The uptake rate of alpha-D-glucose was higher than that of beta-D-glucose at this low concentration.

Carbon Dioxide↗