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Biomedical subjects

B Li

Publications and source records attributed to B Li.

At least 595 records · Page 33Linked to original sources
PubMed1996

[Automatic image analysis of argentophil protein granule quantitative measurement on nucleolus area of limbus epithelial neoplasms].

OBJECTIVE: To study the pathological diagnostic significance of argentophil protein (AgNOR) quantitative analysis at nucleolus area of limbus epithelial neoplasms. METHODS: Automatic image analysis system was used for argentophil protein granule measurement in the pathologic diagnosis of 45 cases with limbus epithelial neoplasms, including benign hyperplasia, atypical hyperplasia, carcinoma in situ and squamous cell carcinoma. RESULTS: In various lesions, there were the differences in the distributive pattern, size and area of AgNOR granules, which were closely related to the nature of the neoplasms (benign or malignant) and its cell differentiation. CONCLUSION: Automatic image analysis of AgNOR quantitative measurement on limbus epithelial neoplasms may indicate the proliferative activity and cell differentiation in various lesions, help to differentiate benign or malignant neoplasms and effectively enhance the level of pathologic diagnosis.

Carcinoma in Situ↗
PubMed1996

[Treatment of central retinal artery occlusion with thrombolysis via superselective ophthalmic artery catheterization].

OBJECTIVE: To investigate the therapeutic effect of thrombolysis via superselective ophthalmic artery catheterization for treatment of central retinal artery occlusion (CRAO). METHOD: Urokinase was directly infused via ophthalmic artery (OA) or common carotid artery by catheterization after angiography into 4 eyes of 4 patients with CRAO, The times of onset ranging from 7 to 14 days. RESULTS: The visual acuity was significantly improved in 2 eyes. No visual change was found in 2 eyes in which the beginning part of internal carotid artery (ICA) or OA was occluded. There was no complications. CONCLUSIONS: Good results were obtained in the eyes in which thrombolysis was launched early in the course of the disease and urokinase was successfully infused into the OA. It seems that there is no effect for the eyes complicated with occlusion in ICA and OA.

Adult↗
PubMed1996

The repair of eyelid defect with free hard palate mucosal autograft.

OBJECTIVE: To investigate the free hard palate mucosal autograft as a new replacement in eyelid reconstruction. METHODS: (1) Animal experiment, 12 eyelid defects from 3 dogs were repaired with hard palate mucosal autograft, and after operation they had excellent eyelid appearance. The findings of pathological examination, the morphology and thickness of epithelium are the same as its original. The cells and vascularization in the connective tissue are normal. The arrangement of collagen fiber bundles is regular. (2) Clinical practice, 15 eyelid defects from 13 eyes included 3 upper eyelids, 8 lower eyelids and 2 of both upper and lower eyelids. 5 cases were of malignant tumor and 8 cases of trauma. 6 eyelids were of total defect, 4 eyelids of two-third defect and 5 eyelids of a half to one-third defect. The ages ranged from 22 to 79 years old. We used the intermediate split thickness of hard palate mucosal autograft to do the eyelid reconstruction. All the cases were followed for an average of 11.3 months after the reconstruction. RESULTS: 8 eyelid defects were cured, 3 were improved significantly and 4 improved. No severe complications were found. CONCLUSION: The hard palate mucosal autograft acts not only as a palpebral supporting tissue but also forms palpebral conjunctiva.

Adult↗
PubMed1996

[The detection of the antibodies of human cytomegalovirus in the sera of patients with coronary heart disease].

To explore the relationship between human cytomegalovirus infection and atherosclerosis, we assayed the antibodies of human cytomegalovirus in the sera of 106 patients with coronary heart disease and 80 healthy people by indirect ELISA technique. The results showed that the positive rate of antibodies of HCMV IgG, HCMV IgM and HCMV IgA (95.3%, 12.3%, 13.2% respectively) is significantly higher than that in healthy people (85.0%, 2.5%, 3.8% respectively). Our findings indicated that HCMV infection is related to coronary heart disease. We consider that HCMV may be an etiological factor for human atherosclerosis. The periodical activation of latent HCMV may play a role in atherogenesis.

Adult↗
PubMed1995

Minimization of a polypeptide hormone.

A stepwise approach for reducing the size of a polypeptide hormone, atrial natriuretic peptide (ANP), from 28 residues to 15 while retaining high biopotency is described. Systematic structural and functional analysis identified a discontinuous functional epitope for receptor binding and activation, most of which was placed onto a smaller ring (Cys6 to Cys17) that was created by repositioning the ANP native disulfide bond (Cys7 to Cys23). High affinity was subsequently restored by optimizing the remaining noncritical residues by means of phage display. Residues that flanked the mini-ring structure were then deleted in stages, and affinity losses were rectified by additional phage-sorting experiments. Thus, structural and functional data on hormones, coupled with phage display methods, can be used to shrink the hormones to moieties more amendable to small-molecule design.

Amino Acid Sequence↗
PubMed1995

How is direction selectivity organized in the extrastriate visual area PMLS of the cat?

Although most neurones in the PMLS of the cat are selective for direction of motion, whether the preferred directions are organized into cortical columns, as they are in the MT area of the monkey, is not certain. We have quantitatively investigated the organization of direction selectivity of PMLS neurones. The results showed that adjacent neurones have similar direction selectivity. The preferred direction of neurones sampled successively in a tangential penetration changed continually, occasionally with an approximately 180 degrees reversal, and neurones with bidirectional selectivity tended to be located in the reversal region. It is spectulated that direction selectivity in the PMLS is organized on the basis of preferred axis of motion in such a way that one column with bidirectional preference lies between two columns with opposite unidirectional preferences, a unidirectional column is always adjacent to a bidirectional column and these adjacent columns share a common preferred axis-of-motion.

Animals↗
PubMed1995

Animal model for maturity-onset diabetes of the young generated by disruption of the mouse glucokinase gene.

Glucokinase catalyzes a rate-limiting step in glucose metabolism in hepatocytes and pancreatic beta cells and is considered the "glucose sensor" for regulation of insulin secretion. Patients with maturity-onset diabetes of the young (MODY) have heterozygous point mutations in the glucokinase gene that result in reduced enzymatic activity and decreased insulin secretion. However, it remains unclear whether abnormal liver glucose metabolism contributes to the MODY disease. Here we show that disruption of the glucokinase gene results in a phenotype similar to MODY in heterozygous mice. Reduced islet glucokinase activity causes mildly elevated fasting blood glucose levels. Hyperglycemic clamp studies reveal decreased glucose tolerance and abnormal liver glucose metabolism. These findings demonstrate a key role for glucokinase in glucose homeostasis and implicate both islets and liver in the MODY disease.

Animals↗
PubMed1995

Stereochemistry-dependent bending in oligonucleotide duplexes induced by site-specific covalent benzo[a]pyrene diol epoxide-guanine lesions.

The apparent persistence length of enzymatically linearized pIBI30 plasmid DNA molecules approximately 2300 bp long, as measured by a hydrodynamic linear flow dichroism method, is markedly decreased after covalent binding of the highly tumorigenic benzo[a]pyrene metabolite 7R,8S-dihydroxy-9S,10R-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(+)-anti-BPDE]. In striking contrast, the binding of the non-tumorigenic, mirror-image 7S,8R,9R,10S enantiomer [(-)-anti-BPDE] to DNA has no measurable effect on its alignment in hydrodynamic flow gradients (< or = 2.2% of the DNA bases modified). In order to relate this effect to BPDE-nucleotide lesions of defined stereochemistry, the bending induced by site-specifically placed and stereochemically defined (+)- and (-)-anti-BPDE-N2-dG lesions in an 11mer deoxyoligonucleotide duplex was studied by ligation and gel electrophoresis methods. Out of the four stereochemically isomeric anti-BPDE-N2-deoxyguanosyl (dG) adducts with either (+)-trans, (-)-trans, (+)-cis, and (-)-cis adduct stereochemistry, only the (+)-trans adduct gives rise to prominent bends or flexible hinge joints in the modified oligonucleotide duplexes. Since both anti-BPDE enantiomers are known to bind preferentially to dG (> or = 85%), these observations can account for the differences in persistence lengths of DNA modified with either (+)-anti-BPDE or the chiral (-)-anti-BPDE isomer.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1995

Inhibition of serine/threonine protein phosphatases enhances agonist-stimulated cAMP accumulation in UMR 106 osteoblast-like cells.

Protein phosphatases regulate the activity of signal transduction mechanisms by dephosphorylating activated components. By utilizing selective inhibitors of these phosphatases, we investigated their role in regulating cAMP accumulation in the UMR 106 osteoblast-like tumor cell line. PTHrP, PTH and PGE2 stimulated cAMP accumulation up to 100-fold. Calyculin A, a potent inhibitor of protein phosphatase type 1 (PP1) and type 2A (PP2A), did not affect basal levels of cAMP, but concentrations of 10(-11) M to 10(-8) M increased PTHrP-, PTH-, and PGE2-stimulated cAMP accumulation up to 1.7-fold, and this increase was concentration-dependent. Similar results were obtained with tautomycin, another potent inhibitor of PP1 and PP2A. In contrast, okadaic acid, a potent inhibitor of PP2A which inhibited PP1 less potently, did not enhance PTHrP-, PTH-, or PGE2-stimulated cAMP accumulation. The effect of calyculin A on agonist-stimulated cAMP accumulation persisted in cells treated with isobutyl methylxanthine, a phosphodiesterase inhibitor. When the effect of calyculin A was compared with that of 4 beta-phorbol 12-myristate 13-acetate (PMA), it was found that while PMA enhanced both the receptor and forskolin-stimulated cAMP accumulation, calyculin A had no effect on the forskolin-stimulated cAMP accumulation. The effect of calyculin A on PTHrP- and PTH-stimulated cAMP accumulation persisted in cells treated with PMA. These results suggest that protein phosphatases play an important role in agonist-stimulated cAMP accumulation in osteoblast-like cells, and that PP1 but not PP2A may be the major phosphatase involved. In contrast to activation by protein kinase C, the site of action for the phosphatase appears to be predominantly at a step prior to the activation of adenylyl cyclase in the cAMP signal transduction pathway.

1-Methyl-3-isobutylxanthine↗
PubMed1995

Secretion of the eosinophil-active cytokines interleukin-5, granulocyte/macrophage colony-stimulating factor and interleukin-3 by bronchoalveolar lavage CD4+ and CD8+ T cell lines in atopic asthmatics, and atopic and non-atopic controls.

Specific eosinophil accumulation and activation within the asthmatic bronchial mucosa are thought to occur at least partly through the actions of cytokines, including interleukin (IL)-5, IL-3 and granulocyte/macrophage colony-stimulating factor (GM-CSF). Although mRNA encoding some of these cytokines has been demonstrated in bronchoalveolar lavage (BAL) fluid cells and bronchial biopsies from asthmatics, it has yet to be established whether these cells produce the translated products and whether expression is associated with CD4+ T helper or CD8+ cytotoxic T cells. We addressed this problem by raising polyclonal CD4+ and CD8+ T cell lines from the BAL fluid of six atopic asthmatics, five atopic non-asthmatics and seven non-atopic non-asthmatic controls. BAL fluid cells obtained at fiberoptic bronchoscopy were depleted of adherent cells, and then T lymphocytes expanded by stimulation with monoclonal anti-CD3 antibody and recombinant human IL-2. When lymphocytes had expanded to sufficient numbers, CD4+ and CD8+ cells were separated by positive selection with magnetic beads coated with anti-CD4 or anti-CD8 monoclonal antibodies and further expanded. Cytokine secretion by standardized cell numbers was measured by enzyme-linked immunosorbent assays. BAL CD4+ T cell lines from the asthmatics secreted significantly elevated quantities of both IL-5 and GM-CSF as compared with lines from the atopic and non-atopic controls (p = 0.023-0.003). In contrast, IL-3 secretion did not significantly differ between the groups. In some subjects, CD8+ T cell lines also secreted significant quantities of these cytokines and there was a trend for IL-5 secretion by these cells to be higher in asthmatics than non-atopic controls (p = 0.035). These data are consistent with the hypothesis that activated T lymphocytes from asthmatics, particularly of the CD4+ subset, are predisposed to release elevated quantities of cytokines relevant to the accumulation and activation of eosinophils.

Adult↗
PubMed1995

Delay of dimethylbenz[a]anthracene-induced mammary tumorigenesis in transgenic mice by apoptosis induced by an unusual mutant p53 protein.

Murine p53 containing an Arg-->Leu substitution at amino acid 172 possesses many properties characteristic of wild-type p53, including the ability to induce p21/WAF/Cip1 and apoptosis. To determine if p53-dependent apoptosis plays a critical role in mammary tumorigenesis, transgenic mice were generated in which the expression of this mutant p53 protein was targeted to the mammary gland by using the rat whey acidic protein gene promoter. Mice bearing pituitary isografts were treated with 7,12-dimethylbenz[a]anthracene (DMBA) and examined for mammary tumor development. Mice overexpressing the p53 transgene exhibited a statistically significant increase in apoptosis in the mammary gland and a statistically significant decrease in the incidence of DMBA-induced mammary tumors. No difference in tumor incidence was observed in mice without pituitary isografts who were treated with DMBA, because the transgene is not overexpressed in the absence of hormone stimulation provided by the pituitary isograft. The unexpected wild-type properties of the 172Arg-->Leu mutant p53, including its ability to stimulate apoptosis, make it a possible candidate for use in gene therapy protocols.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1995

Cloning and characterization of differentially expressed genes in imbibed dormant and afterripened Avena fatua embryos.

To analyze the patterns of gene expression associated with seed dormancy in wild oat (Avena fatua), we have isolated cDNA clones corresponding to genes that are differentially expressed in dormant and afterripened line M73 embryos. Gene transcripts of these clones were maintained in embryos of imbibed dormant caryopses, but declined rapidly in afterripened embryos after imbibition. GA3 treatment of dormant caryopses, which breaks dormancy, could lower the transcript levels in dormant embryos. When the germination of afterripened caryopses was inhibited by high temperature (35 degrees C), the decline in abundance of the transcripts in afterripened embryos was arrested. These genes were expressed to various degrees in water-stressed, but not in unstressed, 7-day-old seedlings. The expression of the genes was also ABA-inducible in afterripened embryos. The expression patterns in non-dormant line SH430 wild oat were similar to those of afterripened M73. DNA sequence analyses indicated that some of the cDNA clones encode LEA (late embryogenesis-abundant) proteins and aldose reductase. The significance of the expression of these genes in maintaining seed dormancy or longevity is discussed.

Aldehyde Reductase↗
PubMed1995

Effects of long-term acclimatization in lowlanders migrating to high altitude: comparison with high altitude residents.

The physiological response to submaximal and maximal exercise was assessed in lowlanders and Tibetans at low (500 m above sea level) and high altitude (HA, 3,680 m). The times spent at HA by the lowland migrators was 8 days (n = 60), 7 months (n = 60, same group), 15 months (n = 29) and 27 months (n = 29). After the 15-month stay at HA, the maximal oxygen uptake (VO2max) and maximal heart rate of the lowland migrators almost reached those of the HA native residents (Tibetans, n = 57), but their total work capacity and the gross efficiency (eta) of mechanical work remained lower than those of the Tibetans. The rate of VO2max achieved at 90 W by the Tibetans was lower than that of the lowland migrators. It was concluded that, at HA, the lowlanders regained much of the aerobic capacity which they had lost initially. However, they did not attain the same gross mechanical efficiency as the Tibetans, who seemed to be at an advantage in respect of work at HA.

Acclimatization↗
PubMed1995

Botulinum versus tetanus neurotoxins: why is botulinum neurotoxin but not tetanus neurotoxin a food poison?

Botulinum and tetanus neurotoxins, produced by Clostridium botulinum and Clostridium tetani, respectively, are the most poisonous poisons known to mankind. Although botulinum and tetanus neurotoxins share several characteristics, such as similar mol. wts, similar macrostructure, virtually identical mode of action, and a strong amino acid sequence homology, the two neurotoxins differ in one very significant way; only botulinum neurotoxin is a food poison. Factors responsible for the food poisoning potential of botulinum neurotoxins seem to be a group of complexing proteins that are also produced by C. botulinum, and are known to associate with the neurotoxin. Translation products of nucleotide sequences upstream to the neurotoxin genes of serotypes A, B, C, D, E and F botulinum neurotoxin reveal the location of genes for one of the complexing proteins that could be transcribed as polycistronic mRNA to include neurotoxin sequences. No such protein seems to be present in C. tetani, suggesting that the lack of complexing proteins might be responsible for tetanus not being a food poison.

Amino Acid Sequence↗
PubMed1995

Identification of Mycobacterium tuberculosis complex, Mycobacterium avium and Mycobacterium intracellulare by selective nested polymerase chain reaction.

A nested polymerase chain reaction (PCR) procedure was devised for identification of mycobacteria. The outer reaction exploiting genus-specific sequences on the 16S rRNA gene was able to amplify specifically strains of the genus Mycobacterium. The identification of Mycobacterium tuberculosis complex, Mycobacterium avium and Mycobacterium intracellulare was accomplished by selective reamplification of the outer PCR product in three distinct inner amplifications exploiting species-specific primers mapping to a hypervariable region of mycobacterial 16S rRNA. Detection of mycobacteria, other than those for which species-specific primers were used, was accomplished by adding a supplementary genus-specific upper primer to one of the inner reactions. Specificity of amplification was confirmed for clinical isolates and reference strains of different mycobacterial species with the exception of a M. intracellulare type 7 strain which was recognized as M. avium. The amplification protocol presented thus provides a reliable and cost-effective way for identification of clinically relevant mycobacteria.

Base Sequence↗
PubMed1995

Codon 249 mutation of the p53 gene is a rare event in hepatocellular carcinomas from ethnic Chinese in Singapore.

The present study characterised p53 mutations in 44 hepatocellular carcinomas (HCCs) from Chinese patients residing in a high-incidence area. Twelve point mutations (27%) were detected in tumour tissues using single-strand conformation polymorphism analysis followed by direct DNA sequencing. Remarkably, no mutations were observed at codon 249. This is in contrast to HCCs from other high HCC incidence areas with endemic aflatoxin exposures, in which codon 249 is a mutational hot spot. It is therefore suggested that risk factors other than dietary exposure to aflatoxin may contribute to the high HCC incidence in Singapore.

Adult↗