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Biomedical subjects

S Han

Publications and source records attributed to S Han.

At least 253 records · Page 14Linked to original sources
PubMed1995

Decay studies of DMPO-spin adducts of free radicals produced by reactions of metmyoglobin and methemoglobin with hydrogen peroxide.

The 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) spin adduct of myoglobin (Mb) or hemoglobin (Hb) was formed when metmyoglobin (MetMb) or methemoglobin (MetHb) reacted with H2O2 in the presence of DMPO, and both decayed with half-life of a few minutes. The DMPO spin adduct of Mb decayed with biphasic kinetics with k1 = 0.645 min-1 and k2 = 0.012 min-1, indicating that the spin adduct consisted of two kinetically heterogeneous species, stable and unstable ones. The DPMO spin adduct of Hb, however, was homogeneous. Decay of both spin adducts was accelerated in the presence of tyrosine, tryptophan or cysteine, but not phenylalanine, methionine or histidine. The decay obeyed the first order kinetics at varying concentrations of the spin adducts. The decay was accelerated by denaturation and proteolysis of protein moiety. The decay rate was not affected by the extra addition of MetMb or MetHb to each spin adduct. The decay rate of the spin adduct of Mb was increased by hematin in the presence of H2O2 and decreased by catalase. Decay of stable spin adduct of Mb, however, was not significantly changed under any experimental conditions used. These results led us to conclude that instability of the DMPO-spin adducts of Mb and Hb is due to intramolecular redox reactions between the spin adducts and amino acid residues and/or products of the reaction between heme and H2O2.

Animals↗
PubMed1995

Anti-liver cytosolic antigen type 1 (LC1) antibodies in childhood autoimmune liver disease.

Antibodies to liver cytosol antigen type 1 (anti-LC1), which recognize a 60-kd peptide contained in the liver cytosolic fraction, have been reported to define a subset of autoimmune hepatitis (AIH) either negative for other autoantibodies or positive for anti-liver kidney microsomal antibody type 1 (LKM-1) and to be best detected in immunodiffusion. To analyze the prevalence of anti-LC1 in childhood liver disease, we have tested the sera of 95 patients using immunoblot, indirect immunofluorescence, and immunodiffusion. Fifteen children had smooth muscle antibody (SMA) and/or anti-nuclear antibody (ANA)-positive AIH, 13 had anti-LKM-1-positive AIH, 14 had autoimmune sclerosing cholangitis (ASC) (all SMA and/or ANA positive), and 53 had non-autoimmune liver disease (10 had alpha 1-anti-trypsin deficiency [alpha 1-ATD], 11 had Wilson's disease [WD], 14 had Alagille's syndrome, and 18 had chronic hepatitis B virus [HBV] infection). Twenty healthy children were studied as controls. Anti-LC1 positivity in immunodiffusion and strong reactivity in immunoblot were found in 4 LKM-1- and 2 SMA/ANA-positive patients with AIH and in 1 patient with ASC, but in none of the patients with other liver diseases nor in controls. A weak 60-kd band was detected by immunoblot in 6 more patients with AIH (2 were LKM-1- and 4 were SMA/ANA-positive) and 6 patients with ASC, all anti-LC1-negative by immunofluorescence and immunodiffusion. No distinct clinical features characterized the anti-LC1-positive patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

[The establishment of ADBS data bank system for autopsy records].

The ADBS data bank system consists of PC 286 microcomputer, (or 386 and other more advanced machine) VGA color monitor, printer and ADBS V. 2.0 software. According to the international classification of diseases (ICD-9 or ICD-10, SNOMED), pathological diagnoses are coded and put into computer. This system has five functions: search, statistics, edition, print and system restore. For facilitating the operation of this system, all orders are listed as window menu. The statistic results can be shown as tables or figures and put out as disk files or prints. The system is currently an advanced computerized system of histopathological and autopsied records in Chinese.

Autopsy↗
PubMed1994

Ca2+ load of guinea-pig ventricular myocytes determines efficacy of brief Ca2+ currents as trigger for Ca2+ release.

1. In guinea-pig ventricular cells, the concentration of ionized cytosolic calcium ([Ca2+]o) was estimated from the fluorescence of 100 microM K5-indo-1. At 36 degrees C and 2 mM [Ca2+]o, the Ca2+ load of the cells was varied by 1 Hz trains of conditioning clamp pulses to -30 mV (low Ca2+ load), 0 mV (intermediate Ca2+ load) and paired pulses (high Ca2+ load). After seven pulses potentiation was steady and short test pulses to 0 mV were tested for their efficacy in triggering [Ca2+]c transients. The influx of trigger Ca2+ was graded by varying the test-pulse duration between 1 and 180 ms. 2. After a 3 min rest period, [Ca2+]c was 100 +/- 20 nM (mean +/- S.E.M.) and 2 ms test pulses were unable to induce [Ca2+]c transients. Test pulses of 2 ms duration, however, induced [Ca2+]c transients after potentiation with single or paired pulses. 3. At high cellular Ca2+ load, the amplitude of the [Ca2+]c transients (delta[Ca2+]c) gradually increased with pulse durations up to 8 ms. Pulse durations between 8 and 160 ms, however, did not further increase delta[Ca2+]c as if the largest part of the [Ca2+]c transient was due to regenerative contribution of Ca(2+)-induced Ca2+ release. 4. Pulses of 160 ms duration induced 'saturating' responses whose amplitudes delta[Ca2+]c, t = infinity decreased from 938 +/- 120 nM at high Ca2+ load, to 610 +/- 90 and 350 +/- 120 nM at intermediate and low Ca2+ loads, respectively. 5. Delta[Ca2+]c was more sensitive to the duration of Ca2+ influx at low or intermediate Ca2+ loads than at high Ca2+ load. When delta[Ca2+]c was plotted against the test-pulse duration, 50% of delta[Ca2+]c, t = infinity was found to be at 9 +/- 2 ms (low), 4.6 +/- 1 ms (intermediate) or 1.8 +/- 0.5 ms pulses (high Ca2+ load). Correspondingly, the efficacy of 2 ms test pulses in triggering [Ca2+]c transients increased with the Ca2+ load. 6. At high Ca2+ load, [Ca2+]c peaked nearly independently of pulse duration at 19 +/- 3 ms. At intermediate or low Ca2+ load, time to peak increased with pulse duration. 7. The results confirm the theory that sarcoplasmic reticulum (SR) Ca2+ release contributes an amount to the [Ca2+]c transient that increases with the cellular Ca2+ load. The results are compatible with the hypothesis that SR Ca2+ release can be activated by both Ca2+ influx and by SR Ca2+ release and that the latter mechanism constitutes a positive feedback, the amplification of which increases with the amount of releasable Ca2+.

Animals↗
PubMed1994

Gradation of Ca(2+)-induced Ca2+ release by voltage-clamp pulse duration in potentiated guinea-pig ventricular myocytes.

1. This study tests the hypothesis that whole-cell cardiac SR Ca2+ release is graded by recruitment of independent 'release units'. Structurally, an individual release unit may comprise ca four sarcolemmal L-type Ca2+ channels, adjacent ryanodine-sensitive sarcoplasmic reticulum (SR) Ca2+ release channels and the junctional gap between them. After depolarization, the first opening of a single L-type Ca2+ channel of the unit provides sufficient Ca2+ influx to increase local [Ca2+] beyond the threshold activating Ca(2+)-induced Ca2+ release (CICR), which amplifies local [Ca2+] until all release channels of the unit are active. This all-or-none activation does not spread to other release units. Gradation of whole-cell Ca2+ release is predicted to correlate with the cumulative probability density distribution of first latency of L-type Ca2+ channels or the activation time course of the calcium current, ICa. 2. Guinea-pig ventricular myocytes were potentiated by paired voltage-clamp pulses (1 Hz, 2 mM [Ca2+]o, 40 microM K5-indo-1, 36 degrees C). When the cellular Ca2+ load was at a steady high level, cytosolic calcium concentration ([Ca2+]c) transients were measured in response to test pulses of varied pulse duration (PD, 1-180 ms) and amplitude (-20, 0, 20 and 50 mV). The maximal rate of rise (RRmax) of the [Ca2+]c transient was used as an indicator for SR Ca2+ release. 3. Fast [Ca2+]c transients due to 4 ms pulses to 0 or 50 mV were blocked by 1 mM cadmium suggesting that these Ca2+ release signals are triggered by Ca2+ influx through L-type Ca2+ channels and not by Ca2+ influx through Na(+)-Ca2+ exchange. 4. RRmax increased with longer PD along the sigmoidal curve [1-exp(-PD/tau)]kappa(exponent k: 2 < k < 3). The time constant, tau, resembled the activation time constant of whole-cell ICa (Cs(+)-dialysed cells). A PD longer than a limiting duration did not modify RRmax. That is, inactivation of ICa was not reflected in the duration dependence. 5. Single L-type Ca2+ channels (cell-attached patches, 36 degrees C, -20 mV, 3.6 mM CaCl2 and 1 microM Bay K 8644 in patch pipette) opened with a waiting time the cumulative probability distribution of which resembled the duration dependence of RRmax, suggesting that the first opening of L-type Ca2+ channels determines whether the corresponding release unit contributes to the [Ca2+]c transient activated during a short voltage-clamp pulse. 6. The time constant, tau, of the duration dependence was shorter at positive than at negative potentials.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

DNA alkylation repair limits spontaneous base substitution mutations in Escherichia coli.

The Escherichia coli Ada and Ogt DNA methyltransferases (MTases) are known to transfer simple alkyl groups from O6-alkylguanine and O4-alkylthymine, directly restoring these alkylated DNA lesions to guanine and thymine. In addition to being exquisitely sensitive to the mutagenic effects of methylating agents, E. coli ada ogt null mutants display a higher spontaneous mutation rate than the wild type. Here, we determined which base substitution mutations are elevated in the MTase-deficient cells by monitoring the reversion of six mutated lacZ alleles that revert via each of the six possible base substitution mutations. During exponential growth, the spontaneous rate of G:C to A:T transitions and G:C to C:G transversions was elevated about fourfold in ada ogt double mutant versus wild-type E. coli. Furthermore, compared with the wild type, stationary populations of the MTase-deficient E. coli (under lactose selection) displayed increased G:C to A:T and A:T to G:C transitions (10- and 3-fold, respectively) and increased G:C to C:G, A:T to C:G, and A:T to T:A transversions (10-, 2.5-, and 1.7-fold, respectively). ada and ogt single mutants did not suffer elevated spontaneous mutation rates for any base substitution event, and the cloned ada and ogt genes each restored wild-type spontaneous mutation rates to the ada ogt MTase-deficient strains. We infer that both the Ada MTase and the Ogt MTase can repair the endogenously produced DNA lesions responsible for each of the five base substitution events that are elevated in MTase-deficient cells. Simple methylating and ethylating agents induced G:C to A:T and A:T to G:C transitions in these strains but did not significantly induce G:C to C:G, A:T to C:G, and A:T to T:A transversions. We deduce that S-adenosylmethionine (known to e a weak methylating agent) is not the only metabolite responsible for endogenous DNA alkylation and that at least some of the endogenous metabolites that cause O-alkyl DNA damage in E. coli are not simple methylating or ethylating agents.

Alkylating Agents↗
PubMed1994

[Detection of anti-BB antibodies in human sera by VIDAS system].

Lyme disease is an infectious disease just known in the latest decade. The sera of people from various origins were detected for Anti-BB antibodies (IgM+IgG) by VIDAS system. The results are as follows: Of 83 sera from the health-cared people, 8 were positive (9.6%); of 20 sera from the patients clinical diagnosed as tuberculosis, none was positive; of 46 sera from the patients clinical diagnosed or suspected as node diseases, 4 were positive (8.7%); of 57 sera from the patients with various ophthalmologic diseases, 13 were positive (22.8%); of 15 sera from the patients with stomatologic diseases, 4 were positive (26.7%); of 17 sera from the patients with various diseases including dermomyositis, liver and spleen swelling, undefined febrile diseases; lung cancer, lung shadow, etc.), 2 were positive (11.8%); of 16 sera from the people highly suspected with lyme disease living in the epidemic areas of Xin Jiang and Hei Long Jiang provinces, 12 were positive (75%). The same 165 sera samples were detected at the same time by VIDAS System and IFA, 24 were positive by VIDAS System (14.5%), and 131 positive by IFA (79%), the accordance rate was only 32.7%.

Antibodies, Bacterial↗
PubMed1993

Translational repression of brlA expression prevents premature development in Aspergillus.

The Aspergillus nidulans brlA developmental regulatory locus consists of two overlapping transcription units, brlA alpha and brlA beta, which encode functionally related polypeptides. We used translational fusions between each of the predicted brlA reading frames and the Escherichia coli lacZ gene to test the hypothesis that developmental regulation of brlA alpha and brlA beta expression occurs through different mechanisms. brlA alpha is transcriptionally controlled and a large portion of brlA alpha-directed beta-galactosidase activity is regulated in a brlA-dependent manner. In contrast, brlA beta mRNA is constitutively transcribed but translation of the brlA polypeptide is prevented by the presence of a short open reading frame (microORF) present in the 5' end of brlA beta mRNA. Removing the microORF initiation codon leads to deregulated brlA expression, resulting in an inappropriate activation of development. We propose that one mechanism for developmental induction in A.nidulans involves translational control.

Aspergillus nidulans↗
PubMed1993

Effects of fire ant venom alkaloids on platelet and neutrophil function.

About 95% of venom of the imported fire ant Solenopsis invicta is composed of dialkyl piperidines. These alkaloids produce a distinct pustule at the site of injection. The formation of this pustule may involve the activation of platelets and neutrophils. The purpose of this paper was to characterize the effects of fire ant venom alkaloids (FAVA) on certain physiological and biochemical functions of human platelets and neutrophils. In platelets, FAVA caused a rise in intracellular [Ca2+], secretion of dense granules as measured by ATP release, and aggregation as measured by light transmission through a suspension of platelets. Aggregation response was less complete with FAVA than with thrombin or PAF. However, secretion response was greater with FAVA than thrombin. One of our most significant findings was that pretreatment of platelets with subthreshold concentrations of FAVA produced enhanced PAF-induced increase in [Ca2+]cyt, suggesting that synergism between the two agonists might play an important role in the physiological response to FAVA. In neutrophils, FAVA produced a rise in intracellular [Ca2+] and aggregation, although the responses were more moderate than those observed in platelets. These results suggest that FAVA activation of platelets and neutrophils may occur in vivo as a response to stings by red fire ants.

Adenosine Triphosphate↗
PubMed1993

Nickel-titanium spring properties in a simulated oral environment.

A study of nickel-titanium springs was undertaken to determine whether their mechanical properties are affected by prolonged exposure to a static, simulated oral environment. Stainless steel springs and polyurethane elastic chains were also studied for comparison. The springs were elongated to twice their rest length and held at that length while immersed in artificial saliva at body temperature for 0, 2, 4 or 6 weeks. Plots of force vs. deformation were made as the springs were stretched from rest length to three times that length and then relaxed back to rest. Nickel-titanium springs suffered no degradation of their spring properties in the simulated oral environment. In contrast, stainless steel springs became slightly more compliant to stretching, and polyurethane elastics lost a large portion of their force-generating capacity. These findings confirm and extend earlier reports which indicate that nickel-titanium is a preferred material for many orthodontic applications.

Dental Alloys↗
PubMed1993

Changes in mitochondrial calcium concentration during the cardiac contraction cycle.

OBJECTIVE: The aim was to examine whether mitochondrial Ca2+ fluxes are high enough to change mitochondrial and cytosolic calcium concentration during the contraction cycle. METHODS: Isolated guinea pig ventricular myocytes were stimulated with paired voltage clamp pulses until contractions were maximal (2 mM [Ca2+]o, 36 degrees C). At defined times of diastole or systole, the cells were shock frozen. Electron-probe microanalysis measured the concentration of total calcium in mitochondria (sigma Ca(mito)) and surrounding cytosol (sigma Cac). Other experiments were performed to evaluate DNP sensitive mitochondrial Ca2+ uptake from depolarisation induced [Ca2+]c transients (K5indo-1 fluorescence). RESULTS: At end of diastole, sigma Ca(mito) was 446 mumol.litre-1. During systole, sigma Ca(mito) increased with a 20 ms delay. A peak sigma Ca(mito) of 1050 mumol.litre-1 was measured 40 ms after start of systole, while 95 ms after start of systole sigma Ca(mito) had fallen to 530 mumol.litre-1. From the changes in sigma Ca(mito) the rates of net mitochondrial Ca2+ flux were estimated at 100 nmol.s-1 x mg-1 protein for Ca2+ influx and 36 nmol.s-1 x mg-1 protein for Ca2+ egress. Decay of sigma Ca(mito) was coupled to a rise in sigma Na(mito). sigma Cl(mito) and sigma K(mito) rose and fell in parallel with sigma Ca(mito), suggesting Ca2+ activation of mitochondrial anion and cation channels. Activation of the non-specific permeability can be excluded. Block of mitochondrial Ca2+ uptake with DNP (100 microM) or FCCP (10 microM) increased the amplitude of the [Ca2+]c transients for 1-3 min by about 50%; evaluation of mitochondrial Ca2+ uptake from DNP sensitive difference signals, however, was hampered by sequestration of mitochondrial Ca2+ into the sarcoplasmic reticulum. CONCLUSIONS: Mitochondrial calcium content changes during each individual contraction cycle; a substantial amount of calcium is taken up during the systole and released during later systole and diastole.

Animals↗
PubMed1993

The rates of cleavage of insoluble and soluble collagens by tissue collagenases.

The cleavage rates of insoluble and acid-soluble bovine collagens by tissue collagenases from the cultures of C3H mouse mammary adenocarcinoma and from human rheumatoid synovial fibroblasts at 37 degrees C were compared by measuring dansyl (Dns)-IIe and Dns-Leu, amino-terminal residues at the cleaved sites after dansylation. The kinetic parameters, Kcat and Km, defined functionally, were as follows: for insoluble Achilles tendon collagen, Km values were 0.89 and 0.83 microM; Kcat/Km 39.2 and 317 microM-1 h-1. For acid-soluble skin collagen the values were 0.83 and 0.82 microM; 44.6 and 354 microM, respectively. The supernatants from the insoluble and acid-soluble collagens contained 28% and 92% of total Dns-IIe and 1.3% and 43% of total Hyp, respectively. Results showed that both tissue collagenases cleaved insoluble collagen almost as rapidly as they did reconstituted collagen fibrils. The cleavage of collagen was proportional to enzyme concentration. The presence of Dns-IIe and Dns-Leu in the supernatant arises from a second cleavage of the collagen molecule.

Adenocarcinoma↗
PubMed1993

High level expression of human prourokinase cDNA in Chinese hamster ovary cells.

We have used Chinese hamster ovary (CHO) cells to express high levels of human prourokinase gene cDNA with recourse to construction of good expression vector, the improvement of transfection technique and gene coamplification. First, we constructed expression plasmid pMG10102 by placing pro-UK cDNA under the control of SR alpha promoter/SV40 polyadenylation signals and expressed it transiently in COS-7 cells. Expression level was about 5 times higher than with SV40 early promoter. Linear plasmids pMG10102 and pSV2-dhfr were then cotransfected into CHO-dhfr cells by calcium phosphorate coprecipitation and cells were cultured in selective medium. Twenty transformants expressing pro-UK were picked, the range of expression levels was 12.5-100IU/10(6) cells/day. When subjected to stepwise selection of methotrexate (MTX), the stable cell lines were obtained that secreted up to 400-500IU/10(6) cells/day. Western blot analysis showed that molecular weight of secreted recombinant pro-UK was the same as that of natural pro-UK, which is 52 kDa, and more than 60% of expression production was single chain urokinase (rscUK) without protease inhibitor in medium.

Animals↗