Biomedical subjects

D Lin

Publications and source records attributed to D Lin.

At least 109 records · Page 6Linked to original sources

PubMed1998

[Direct detoxification of N-acetoxy-PhIP by tea polyphenols: a possible mechanism for chemoprevention against PhIP-DNA adduct formation in vivo].

OBJECTIVE: We have shown that green tea inhibited food-borne carcinogen 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP)-induced carcinogen-DNA adduct formation in rats, and this protective effect of tea appears not relote to the modifications of metabolic enzymes involved in PhIP metabolism. The aim of this study was to explore the direct reaction of tea and tea polyphenols with N-acetoxy-PhIP, an ultimate carcinogen of PhIP formed via metabolic activation. METHODS: DNA binding assays were conducted to examine the effect of aqueous extract of tea and tea polyphenols on the reaction of [3H]N-acetoxy-PhIP with DNA. The reaction mixtures were analyzed by HPLC for the possible product (s) formed by the reaction of [3H]N-acetoxy-PhIP with tea polyphenols. RESULTS: It was found that agueous extract of tea and tea polyphenols strongly inhibited covalent binding of [3H]N-acetoxy-PhIP to DNA, and the inhibition was concentration-dependent with respect to inhibitors. HPLC analyses of reaction mixture containing [3H]N-acetoxy-PhIP and tea polyphenols revealed the production of the parent amine, PhIP, indicating a redox mechanism. CONCLUSION: In view of the presence of tea polyphenols in rat and human plasma after ingestion of tea, these results suggest that direct reduction of ultimate carcinogen N-acetoxy-PhIP by tea polyphenols is likely to be involved in the mechanism of chemoprevention of tea against PhIP-DNA adduct formation in vivo.

Animals↗

PubMed1998

[Relationship between tumor cell proliferating activity and biological behavior, prognosis in laryngeal carcinoma].

Using PC 10, an antibody to proliferating cell nuclear antigen (PCNA) and a standard immunohistochemical staining the authors examined 11 cases of simple hyperplasia of epithelium (SHE), 32 cases of atypical hyperplasia of epithelium (AHE) and 42 cases of laryngeal squamous cell carcinoma (LSCC) for expression of PCNA, a protein associated with DNA polymerase dalta and DNA replication, a marker for tumor cell proliferation. The results revealed that PCNA indices in SHE, AHE and LSCC were 9.5%, 27.33% and 68.05%, respectively. The PCNA indices were 63.68%, 69.57%, 71.18% in the well, moderately and poorly differentiated LSCC, respectively, there were significant differences. The PCNA indices were 63.88%, 70.82%, 66.20% and 69.04%, respectively in stages I, II, III, and IV of LSCC; no significance was found. There was a strong negative correlation betwee survival time and the tumor cell proliferative activity (r = 0.6243). PCNA might provide a useful tool for studying cell proliferation in situ under normal and pathological condition.

Adult↗

PubMed1998

[Chemoprevention of 2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine-induced carcinogen-DNA adducts by Chinese cabbage in rats].

OBJECTIVES: To examine the preventive effect of Chinese cabbage (Brassica chinensis) against colon carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced PhIP-DNA adduct formation in rats and its possible mechanism. METHODS: Sprague-Dawley rats were maintained for 10 days on lab chow or chow containing 20% (w/w) freeze-dried cabbage powder prior to administration of a single dose of PhIP (10 mg/kg) by oral gavage. Rats were sacrificed at 20 h after PhIP treatment and PhIP-DNA adducts in the colon, heart, lung, and liver were analyzed using 32P-postlabeling technique. Levels of hepatic cytochrome P450 (CYP) 1A1 and 1A2, as indicated by 7-ethoxyresorufin O-deethylase and 7-methoxyresorufin O-demethylase activity, and cytosolic glutathione S-transferases (GST) towards CDNB in the liver, lung and colon mucosa were measured. RESULTS: Rats pre-treated with Chinese cabbage and given a single dose of PhIP had reduced levels of PhIP-DNA adducts in the colon, heart, lung and liver, with an inhibition rate of 82.3, 60.6, 48.4 and 48.9%, respectively (P < 0.01). Enzyme assays revealed that both CYP1A1 and 1A2 were induced by cabbage, but the induction was preferential for CYP1A1 over 1A2 (80.6% vs 50.2%). GST activity towards CDNB in the liver and lung, but not colon, was also significantly induced by the cabbage. CONCLUSION: The results indicate a preventive effect of Chinese cabbage against PhIP-initiated carcinogenesis in rats and the mechanism is likely to involve induction of detoxification enzymes.

Animals↗

PubMed1998

[Genetic polymorphisms of cytochrome P450 2E1 and glutathione S-transferase P1 and susceptibility to esophageal cancer].

OBJECTIVES: To study the association between genetic polymorphisms of cytochrome P4502E1 (CYP2E1) and/or glutathione S-transferase P1 (GSTP1) and susceptibility to esophageal cancer. METHODS: Genotyping of CYP2E1 and GSTP1 was performed using PCR-based RFLP analysis on DNA isolated from surgically removed esophageal tissues or scraped esophageal epithelium from cancer cases (n = 45), severe epithelial hyperplasia cases (n = 45), and normal controls (n = 45). RESULTS: The variant genotypes (c1/c2 and c2/c2) detected by RsaI digestion was found in 17% of epithelial hyperplasia cases, 20.0% of esophageal cancer cases and 55.6% of controls, with the differences being statistically significant (P < 0.001). Subjects carrying wild-type genotype of CYP2E1 had more than 5-fold risk for developing severe epithelial hyperplasia (odds ratio, OR = 5.78; 95% confidence interval, CI = 2.2-15.2) and esophageal cancer (OR = 5.00; 95% CI = 2.0-12.8). No association with the risk of severe epithelial hyperplasia and esophageal cancer was observed for the DraI polymorphism of CYP2E1 or for the Awl26I polymorphism of GSTP1. CONCLUSION: CYP2E1 is a genetic susceptibility factor involved in the early events for esophageal carcinogenesis.

Adult↗

PubMed1998

Quantitative anatomy of the transverse foramen and pedicle of the axis.

Forty dry C2 cervical vertebrae were obtained to evaluate quantitatively the anatomy of the C2 transverse foramen and pedicle. Computed tomography (CT) scans and plain radiographs were also obtained of 20 specimens to evaluate the internal structure of the transverse foramen and pedicle. The results of the measurements showed that differences between male and female specimens were found to be significant for four of seven linear parameters and for one of the two angular parameters. With regard to the sides, differences were found to be significant for two of the seven linear parameters and both of the angular parameters between right and left measurements. The variation of the foramen size between sexes was more significant than that between sides, and a remarkable variation between sides and between sexes was found in the transverse foramen horizontal angle and the pedicle width. The inferior pedicle width was approximately 3 mm less than the superior pedicle width. CT scans revealed that the lateral wall of the pedicle is very thin compared with the medial wall. Considering the greater variation of the C2 foramen orientation, smaller inferior pedicle dimension, and thinner lateral pedicle wall, a screw placement as close as possible to the mediosuperior cortex is recommended to avoid violation of the transverse foramen if transpedicular screw fixation in C2 is intended.

Adult↗

PubMed1997

Use of low-dose oral contraceptives and stroke in young women.

BACKGROUND: Low-dose oral contraceptives are widely used, but there are limited data on the cerebrovascular risks associated with these medications. OBJECTIVE: To determine whether use of low-dose oral contraceptives influences the risk for stroke. DESIGN: Population-based case-control study. SETTING: Women 18-44 years of age who resided in western Washington State between 1991 and 1995. PARTICIPANTS: Patients with ischemic stroke (n = 60), hemorrhagic stroke (n = 102), and other types of stroke (n = 11) and controls identified through random-digit dialing (n = 485). MEASUREMENTS: Details about oral contraceptive use and other risk factors for stroke were obtained through in-person interviews. RESULTS: The estimated incidences of hemorrhagic stroke and ischemic stroke were 6.4 and 4.3 per 100,000 women-years, respectively. Compared with women who had never used oral contraceptives (after adjustment for risk factors for stroke), current users of low-dose oral contraceptives had estimated odds ratios of 0.93 (95% CI, 0.37 to 2.31) for hemorrhagic stroke and 0.89 (CI, 0.27 to 2.94) for ischemic stroke. Compared with past users of oral contraceptives, current users had odds ratios of 1.41 (CI, 0.67 to 2.96) for hemorrhagic stroke and 1.37 (CI, 0.49 to 3.81) for ischemic stroke. For past users compared with never users, the odds ratios were 0.59 (CI, 0.30 to 1.18) for hemorrhagic stroke and 0.57 (CI, 0.25 to 1.32) for ischemic stroke. The odds ratio for hemorrhagic stroke in current users of low-dose oral contraceptives containing norgestrel or levonorgestrel was elevated (3.23 [CI, 1.24 to 8.41]). Among patients with hemorrhagic stroke, the odds ratio for aneurysmal bleeding associated with current use of low-dose oral contraceptives containing norgestrel or levonorgestrel was 4.46 (CI, 1.58 to 12.53). CONCLUSION: The overall risk for stroke and type of stroke was not increased among current users of low-dose oral contraceptives in the study population. Larger studies are needed to clarify both the relation of risk for stroke to past use of oral contraceptives and the possible association between current use of norgestrel-containing oral contraceptives and hemorrhagic stroke.

Adolescent↗

PubMed1997

beta2-adrenergic receptor desensitization, internalization, and phosphorylation in response to full and partial agonists.

Previous studies indicated that partial agonists cause less desensitization of the beta2-adrenergic receptor (betaAR) than full agonists; however, the molecular basis for this in intact cells has not been investigated. In the present work, we have determined the rates of desensitization, internalization, and phosphorylation caused by a series of betaAR agonists displaying a 95-fold range of coupling efficiencies. These studies were performed with HEK-293 cells overexpressing the betaAR with hemagglutinin and 6-histidine epitopes introduced into the N and C termini, respectively. This modified betaAR behaved identically to the wild type receptor with regard to agonist Kd, coupling efficiency, and desensitization. The coupling efficiencies for betaAR agonist activation of adenylyl cyclase relative to epinephrine (100%) were 42% for fenoterol, 4.9% for albuterol, 2.5% for dobutamine, and 1.1% for ephedrine. At concentrations of these agonists yielding >90% receptor occupancy, the rate and extent (0-30 min) of agonist-induced desensitization of betaAR activation of adenylyl cyclase followed the same order as coupling efficiency, i.e. epinephrine >/= fenoterol > albuterol > dobutamine > ephedrine. The rate of internalization of the betaAR with respect to these agonists also followed the same order as the desensitization and exhibited a slight lag. Like internalization and desensitization, betaAR phosphorylation exhibited a dependence on agonist strength. The two strongest agonists, epinephrine and fenoterol, provoked 11-13-fold increases in the level of betaAR phosphorylation after just 1 min, whereas the weak agonists dobutamine and ephedrine caused only 3-4-fold increases, similar to levels induced by cAMP-dependent protein kinase activation with forskolin. With longer treatment times, the level of betaAR phosphorylation declined with strong agonists, but it progressively increased with the weaker partial agonists, such that after 30 min the -fold elevation with epinephrine (6.2 +/- 0.82) was not appreciably different from ephedrine (5.0 +/- 0.96) and significantly less than that caused by albuterol (10.4 +/- 1.7). In summary, our results demonstrate an excellent proportionality between the agonist strength and agonist-induced desensitization, internalization, and the rapid initial phase of phosphorylation. The data support the hypothesis that increasing agonist-coupling efficiency primarily affects desensitization by increasing the rate of betaARK phosphorylation of the betaAR.

Adenylyl Cyclases↗

PubMed1997

Duration of estrogen replacement therapy in relation to the risk of incident myocardial infarction in postmenopausal women.

BACKGROUND: There is little information about whether an increasing duration of estrogen replacement therapy is associated with a declining risk for myocardial infarction in postmenopausal women. OBJECTIVE: To conduct a population-based, case-control study among enrollees of the Group Health Cooperative (GHC) of Puget Sound, Seattle, Wash. SUBJECTS AND METHODS: Case subjects were all post-menopausal women who were enrolled in the GHC with an incident fatal or nonfatal myocardial infarction from July 1986 through December 1993. Control subjects were a stratified random sample of postmenopausal women who were enrolled in the GHC without myocardial infarction and matched to case subjects by age and calendar year. We reviewed the medical records of the 850 case subjects and 1974 control subjects and conducted telephone interviews with consenting survivors. Use of estrogen or estrogen and progestin was assessed using GHC's computerized pharmacy database. RESULTS: Among women who were currently using estrogen, a longer duration of use was inversely associated with a risk for myocardial infarction after adjustment for age, year of identification, diabetes mellitus, angina, and smoking. For categories of increasing duration of estrogen use (never, > 0-< 1.8 years, 1.8-< 4.2 years, 4.2-< 8.2 years, and > or = 8.2 years), the odds ratios for myocardial infarction were 1.00 (reference), 0.91, 0.70, 0.65, and 0.55 (for trend among the current users, P = .05). Among women who had used estrogen in the past, there was no evidence of decreasing risk with increasing duration of estrogen use. CONCLUSION: In this study, a long duration of hormone replacement therapy among women currently using estrogen was associated with a reduced risk for first myocardial infarction.

Adult↗

PubMed1997

The nucleotide sequence of Saccharomyces cerevisiae chromosome V.

Here we report the sequence of 569,202 base pairs of Saccharomyces cerevisiae chromosome V. Analysis of the sequence revealed a centromere, two telomeres and 271 open reading frames (ORFs) plus 13 tRNAs and four small nuclear RNAs. There are two Tyl transposable elements, each of which contains an ORF (included in the count of 271). Of the ORFs, 78 (29%) are new, 81 (30%) have potential homologues in the public databases, and 112 (41%) are previously characterized yeast genes.

Base Sequence↗

PubMed1997

Cyclosporine or cyclosporine plus methylprednisolone for prophylaxis of graft-versus-host disease: a prospective, randomized trial.

Patients with a lymphohematopoietic malignancy considered to be at high risk for posttransplant relapse were enrolled in a study to compare the use of cyclosporine (CSP) as a single agent with a combination of methylprednisolone (MP) and CSP for graft-versus-host disease (GVHD) prophylaxis after marrow transplantation from an HLA-identical sibling donor. Sixty patients were randomized to receive CSP only and 62 were randomized to receive CSP plus MP. Daily CSP was started on day -1 (5 mg/kg/d intravenously) and administered at gradually reduced doses until day 180. MP was started on day 7 at 0.5 mg/kg/d, increased to 1.0 mg/kg/d on day 15, started on a taper schedule on day 29, and discontinued on day 72. All 104 evaluable patients (surviving > or =28 days) had sustained engraftment. The incidence rates of grades II-IV acute GVHD were 73% and 60% for patients receiving CSP and CSP plus MP, respectively (P = .01). No difference was seen for grades III-IV GVHD. However, chronic GVHD occurred somewhat more frequently in patients receiving CSP plus MP (44%) than in patients receiving only CSP (21%; P = .02). The incidence of de novo chronic GVHD was marginally higher in patients receiving CSP plus MP (P = .08). No significant differences in the risk of infections were observed. There was a suggestion that the risk of relapse was lower in patients receiving CSP plus MP (P = .10) and, although the overall survival in the two groups was not different (P = .44), there was a slight advantage in favor of CSP plus MP-treated patients for relapse-free survival (P = .07). These results suggest that prophylactic MP, when combined with CSP, has only limited efficacy in acute GVHD prevention and may increase the probability of chronic GVHD.

Adolescent↗

PubMed1997

Cloning of human 25-hydroxyvitamin D-1 alpha-hydroxylase and mutations causing vitamin D-dependent rickets type 1.

The secosteroid hormone, 1,25-dihydroxyvitamin D [1,25(OH)2D], plays a crucial role in normal bone growth, calcium metabolism, and tissue differentiation. The key step in the biosynthesis of 1,25(OH)2D is its 1 alpha-hydroxylation from 25-hydroxyvitamin D (25-OHD) in the kidney. Because its expression in the kidney is very low, we cloned and sequenced cDNA for 25-OHD-1 alpha-hydroxylase (P450c1 alpha) from human keratinocytes, in which 1 alpha-hydroxylase activity and mRNA expression can be induced to be much greater. P450c1 alpha mRNA was expressed at much lower levels in human kidney, brain, and testis. Mammalian cells transfected with the cloned P450c1 alpha cDNA exhibit robust 1 alpha-hydroxylase activity. The identity of the 1,25(OH)2D3 product synthesized in transfected cells was confirmed by HPLC and gas chromatography-mass spectrometry. The gene encoding P450c1 alpha was localized to chromosome 12, where the 1 alpha-hydroxylase deficiency syndrome, vitamin D-dependent rickets type 1 (VDDR-1), has been localized. Primary cultures of human adult and neonatal keratinocytes exhibit abundant 1 alpha-hydroxylase activity, whereas those from a patient with VDDR-1 lacked detectable activity. Keratinocyte P450c1 alpha cDNA from the patient with VDDR-1 contained deletion/frameshift mutations either at codon 211 or at codon 231, indicating that the patient was a compound heterozygote for two null mutations. These findings establish the molecular genetic basis of VDDR-1, establish a novel means for its study in keratinocytes, and provide the sequence of the key enzyme in the biological activation of vitamin D.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗

PubMed1997

Distributions of the cardiac plexuses and ganglia in the Beijing duck.

Distributions of the cardiac plexuses and cardiac ganglia were gross-anatomically and histologically studied in eight Beijing ducks. The cardiac plexuses consisted of two components, the cardiac nerve arising from the sympathetic trunk and the cranial and caudal cardiac nerves arising from the vagus. Branches of these nerves made the cardiac plexuses on the epicardium. The cardiac plexuses could be divided into the six plexuses, that is, the right and left coronary plexuses, pericardiac transverse sinus plexus, caudal cardiac plexus, and right and left superior cardiac plexuses. There were small ganglia in the caudal cardiac plexus and the right and left coronary plexuses. These ganglia containing multipolar neurons were found like a linking chain in a single nerve.

Animals↗

PubMed1997

[Differentiation-inducing effect of stepholidine and retinoic acid on human head and neck carcinoma].

To observe the differentiation-inducing effect of Stepholidine (ST) and Retinoic Acid (RA) on laryngeal and nasopharyngeal carcinoma, the expression of oncogene (C-myc, bcl-2) protein and tumor suppressor gene (p53) was done by using flow cytometry and ABC immunohistochemical methods combined with image analysis technique. The results indicated that after treated with ST and RA, the cells became well-differentiated, the cell growth was suppressed, contact suppress was partially recovered, colony forming was decreased, protooncogenes (C-myc bcl-2) protein was decreased, tumor suppressor gene (p53) protein was increased. No significant difference was observed between the cells treated with ST and TA. We believed that the Chinese medicine-Stephania might be expected to become a new prospective differentiation inducer in carcinoma of head and neck.

Berberine↗

PubMed1997

[Medium effects on derivative reaction between fluorescamine and primary arlyamine].

The effects of pH, various organic solvents, surfactants, beta-CD and PVA on derivative reaction and fluorescence properties of its product between fluorescamine and p-amino phenyl sulfonic acid have been studied. The results show that the derivative reaction needs the organic solvent, many kind of organic solvents are available, but its amount should not be too large. The rate of derivative reaction was slowed and fluorescence intensity of product was decresed with increase in amount of organic solvent and precision is not good because of the fluorescence intensity is changing with delay time. Only tritonX-100 enhanced the fluorescence of product in all of the surfactants tested. Span20, Tween80 and Brij35 which same as tritonX-100 are non-ionic surfactant, and PVA, beta-CD do not exhibit sensitization. Ionic Surfactant CTAB, SDS quench the fluorescence. The sensitization of tritonX-100 is dependent on the amount of organic solvent. A competitive effect between tritonX-100 micellae and organic solvent is exhibition. In this paper, the derivative reaction between fluorescamine and p-chloroaniline is compared and studied too.

English Abstract↗

PubMed1997

Impact mass chemotherapy with praziquantel on schistosomiasis control in Fanhu village, People's Republic of China.

The paper describes the endemic situation of schistosomiasis japonica in Fanhu village, Poyang Lake region, China and the effect of the strategy of combining annual mass chemotherapy with health education on schistosomiasis control in the community. The results showed that the prevalence of infection with schistosome reduced form 26.0% in 1992 to 10.7% in 1994, the intensity of infection in residents decreased from 1.92 in 1992 to 0.55 in 1994 and the condition of hepatomegaly, splenomegaly and liver fibrosis also improved after chemotherapy in the individuals in the case prospective study. Moreover, the future strategies of schistosomiasis control in this area have been suggested according to the transmission of schistosomiasis in the lake region and the effect of anti-schistosomiasis control indifferent populations.

Adolescent↗

PubMed1997

[The treatment of nasopharyngeal carcinoma by using thermoradiotherapy].

The treatment effect of radiotherapy combined with local hyperthermia for nasopharyngeal carcinoma was studied in 23 patients. In 24 cases of the control group (radiotherapy), conventionally dynamic fractionation of dose was used. At 40 Gy, the regression of tumor was observed 83% in the study group and 54% in the controls group. No severe complications in patients treated by thermotherapy were noted. This paper discusses the role and the mechanism of local hyperthermia as a rediomodifying factor.

Adult↗

PubMed1997

[The effect of composition and structure of radiological equivalent materials on radiological equivalent].

Morphology of inorganic material powders before and after being treated by ultrafine crush was observed by transformite electron microscope. The length and diameter of granules were measured. Polymers inorganic material powders before and after being treated by ultrafine crush were used for preparing radiological equivalent materials. Blending compatibility of inorganic meterials with polymer materials was observed by scanning electron microscope. CT values of tissue equivalent materials were measured by X-ray CT. Distribution of inorganic materials was examined. The compactness of materials was determined by the water absorbed method. The elastic module of materials was measured by laser speckle interferementry method. The results showed that the inorganic material powders treated by the ultrafine crush blent well with polymer and the distribution of these powders in the polymer was homogeneous. The equivalent errors of linear attenuation coefficients and CT values of equivalent materials were small. Their elastic modules increased one order of magnitude from 6.028 x 10(2) kg/cm2 to 9.753 x 10(3) kg/cm2. In addition, the rod inorganic material powders having rod granule blent easily with polymer. The present study provides a theoretical guidance and experimental basis for the design and synthesis of radiological equivalent materials.

Calcium↗

PubMed1996

Altered cardiac troponin T in vitro function in the presence of a mutation implicated in familial hypertrophic cardiomyopathy.

Familial hypertrophic cardiomyopathy (HCM) can be caused by dominant missense mutations in cardiac troponin T (TnT), alpha-tropomyosin, C-protein, or cardiac myosin heavy chain genes. The myosin mutations are known to impair function, but any functional consequences of the TnT mutations are unknown. This report describes the in vitro function of troponin containing an IIe91Asn mutation in rat cardiac TnT, corresponding to the HCM-causing Ile79Asn mutation in man. Mutant and wild-type TnT cDNAs were expressed in bacteria and the proteins purified and reconstituted with the other troponin subunits, the mutation had no effect on troponin's affinity for tropomyosin, troponin-induced binding of tropomyosin to actin, cooperative binding of myosin subfragment 1 to the thin filament, CA(2+)-sensitive regulation of thin filament-myosin subfragment 1 ATPase activity, or the CA2+ concentration dependence of this regulation. However, the mutation resulted in 50% faster thin filament movement over a surface coated with heavy meromyosin in in vitro motility assays. The increased sliding speed suggests an unexpected role for the amino terminal region of TnT in which this mutation occurs. The relationship between this faster motility and altered cardiac contraction in patients with HCM is discussed.

Actins↗