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Biomedical subjects

D Li

Publications and source records attributed to D Li.

At least 559 records · Page 31Linked to original sources
PubMed1997

Full thickness eosinophilia in oesophageal leiomyomatosis and idiopathic eosinophilic oesophagitis. A common allergic inflammatory profile?

Oesophageal leiomyomatosis and idiopathic eosinophilic oesophagitis are both extremely rare. The former is a diffuse proliferation of smooth muscle in the muscularis propria, whilst the latter is an idiopathic inflammatory condition, thought to be associated with background atopy and characterized by an infiltrate of eosinophils throughout the full thickness of the oesophagus. However, two recent cases of oesophageal leiomyomatosis showed similar full thickness infiltration of the oesophageal wall by eosinophils and this inflammatory cell infiltrate was investigated in conjunction with one case of idiopathic eosinophilic oesophagitis. All three had a similar allergic profile characterized by CD45RO-positive primed T-lymphocytes, EG2-positive (i.e., activated) eosinophils, and tryptasepositive mast cells, together with gene expression for interleukin 4. Previous descriptions of leiomyomatosis describe an association with systemic mastocytosis and urticaria and the possibility that there is a common underlying allergic component to both disorders is raised.

Adult↗
PubMed1997

Distribution, splicing and glucocorticoid-induced expression of cardiac alpha 1C and alpha 1D voltage-gated Ca2+ channel mRNAs.

Dihydropyridine-sensitive voltage-gated (l-type) Ca2+ channels play an essential role in cardiac and smooth muscle excitation-contraction coupling. Transcripts for the two pore-forming subunits of l-type Ca2+ channels, alpha 1C and alpha 1D have been detected in heart and lung; however, distribution, structure and regulated expression of these channel subunit mRNAs have not been examined in detail. Here we use RNase protection and RT-PCR assays to identify cardiac-specific features of expression of the two channel mRNAs. First, expression of alpha 1D mRNA is found in lung, aorta and atrium, but is not detected in ventricle. Limited expression of alpha 1D mRNA is also seen in enriched preparations of cardiac myocytes: it is significant in atrial myocytes, but not in ventricular myocytes. Second, RT-PCR analyses indicate that atrial alpha 1D channels exclusively contains the 15-amino acid insertion between third and fourth segments in repeat IV. Finally, expression of alpha 1C mRNA, but not alpha 1D mRNA, is up-regulated by glucocorticoids in atrium and ventricle: adrenalectomy and subsequent injection of the glucocorticoid agonist dexamethasone decreased and increased the channel message, respectively. Dexamethasone also significantly increased the number of dihydropyridine-binding sites in ventricle. In contrast, alpha 1C mRNA levels were glucocorticoid-insensitive in lung and aorta. Thus, basal and glucocorticoid-induced expression, and splicing of the two l-type Ca2+ channel alpha 1 subunit transcripts are tissue specifically controlled in atria and ventricles of rat heart.

Amino Acid Sequence↗
PubMed1997

Denaturing gradient gel electrophoresis (DGGE) increases resolution and informativity of Alu-directed inter-repeat PCR.

By inter-repeat PCR, multiple polymorphic loci can be targeted in parallel. To improve resolution and extend the number of detectable polymorphisms, Alu-directed inter-repeat PCR products from two large pedigrees of the Centre d'Etude du Polymorphisme Humain (CEPH) were electrophoretically resolved in non-denaturing polyacrylamide gels and, separately, on the basis of sequence content by denaturing gradient gel electrophoresis (DGGE). The resolution in DGGE gels was found to be superior to that in non-denaturing gels and a higher number of fragments was detected separately. The number of polymorphic bands detected by DGGE alone, however, was lower than that after size separation. This is ascribed to the fact that because of complete melting, small polymorphic fragments can run off the gel. With three Alu-specific primers, 18 and 16 polymorphic bands per individual were detected by size separation in pedigrees 1200 and 6600, respectively. In the same two pedigrees, seven and 15 polymorphic bands, respectively, were detected by DGGE. Segregation analysis of polymorphisms in the CEPH pedigrees indicated that most polymorphisms detected by DGGE were different from those detected by size separation.

DNA↗
PubMed1997

Babesiasis in Nanjing area, China.

This article discusses the tick-borne babesiases which harm dairy cattle, buffaloes and dogs. In addition, the pathogen, vector, seasonal occurrence, hosts, symptoms, pathological changes and treatment are summarized and analysed. The pathogens in this area were identified as Babesia bigemina, B. bovis and B. gibsoni; the vectors as Boophilus microplus, Rhipicephalus haemaphysaloides, Haemaphysalis longicornis. Affected buffaloes were found from April to September, peak numbers occurred between May and July. Affected dairy cattle were most numerous in July and August. Hunting dogs were the most affected dogs. Infected dogs were found from February until the beginning of December; peak numbers occurred from September to November. Affected animals were acute cases. Symptoms and pathological changes were obvious, but jaundice was rare in dogs. Acaprin, acriflavine, imidocarb and berenil were used early and late. Their effect was ideal but resistance has developed to these drugs.

Acriflavine↗
PubMed1997

Comparative study on the inhibitory effect of recombinant FN polypeptide CH50 and CH56 on the metastasis of melanoma cells.

On the basis of preparation of anti-metastatic recombinant FN polypeptides, CH50 and CH56, we further studied the function of these polypeptides. The capacity of CH50 binding with melanoma cells (ED50 30 mM) was higher than that of CH56 (ED50 45 mM). Both of the polypeptides could significantly suppress the binding of melanoma B16 cells to laminin. There was no significant difference in the inhibitory effect between two polypeptides. In the experimental metastasis of melanoma cells, both of CH50 and CH56 could significantly inhibit the metastasis of the tumor cells, and reduce the number of lung metastasis by about 80%. Our results suggest that III-11 and ED-A repeats influenced, to some extent, the binding capacity of bifunctional-domain polypeptide to cells, but did not affect the inhibition of the polypeptide on the metastasis of melanoma cells. The presence and connection of cell I and Hep II domains are the elements which determine the ability of recombinant FN polypeptides to inhibit the metastasis of tumor cells.

Animals↗
PubMed1997

Truncated-gene reporter system for studying the regulation of manganese peroxidase expression.

The expression of manganese peroxidase (MnP) in nitrogen-limited cultures of Phanerochaete chrysosporium is regulated by Mn, heat shock (HS), and H2O2 at the level of gene transcription. We have constructed a homologous gene reporter system to further examine the regulation of two mnp genes, mnp1 and mnp2, encoding individual MnP isozymes. Internal deletions of 234 and 359 bp were made within the coding regions of the mnp1 and mnp2 genes, respectively. The truncated mnp genes were subcloned into the shuttle vector pOGI18, which includes the Schizophylum commune ade5 gene as a selectable marker, and transformed into a P. chrysosporium Ade1 auxotrophic mutant. Northern-blot analysis of purified Ade+ transformants demonstrated that both of the truncated mnp genes were regulated in a manner similar to the endogenous mnp genes with respect to nitrogen limitation and induction by Mn, HS, and H2O2.

Basidiomycota↗
PubMed1997

A more valid measurement of low-density lipoprotein cholesterol in diabetic patients.

PURPOSE: This study was conducted to determine if the direct low-density lipoprotein (LDL) cholesterol assay would provide a more valid measure of LDL cholesterol in diabetic patients compared with the Friedewald equation. PATIENTS AND METHODS: Fasting plasma from 148 diabetic patients, 40 with insulin-dependent diabetes (IDDM) and 108 with non-insulin dependent diabetes (NIDDM) with triglyceride levels < 400 mg/dL, were analyzed for LDL cholesterol using the Friedewald equation, the direct LDL assay, and beta-quantification. Forty-six diabetic patients with triglyceride levels > or = 400 mg/dL were also studied to determine the validity of the direct LDL cholesterol assay with hypertriglyceridemia. RESULTS: The friedewald equation and the direct LDL cholesterol assay correlated well with beta-quantification (r = 0.969 and r = 0.971, respectively) for LDL cholesterol determination in diabetic patients. Although the Friedewald equation in comparison with beta-quantification underestimated (8%) LDL cholesterol values in diabetic patients, the direct LDL cholesterol assay had a mean bias of < 1%. Also, the underestimation by the Friedewald equation exceeded 10% for the triglyceride subgroup of 200 to 400 mg/dL. Furthermore, the accuracy of the direct LDL cholesterol assay was superior to the Friedewald equation since LDL cholesterol levels determined by the two methods coincided within +/- 10% of beta-quantification in 85% and 68% of diabetic patients, respectively (P = 0.0005). Similar results for both the Friedewald equation and the direct LDL cholesterol assay in comparison with beta-quantification were seen when diabetic patients were subgrouped into IDDM and NIDDM. Also, the direct LDL cholesterol assay appeared to provide a reliable estimate in patients with triglycerides > or = 400 mg/dL. CONCLUSION: The results of our studies indicate that the direct LDL cholesterol assay is a more reliable and accurate method than the Friedewald formula for LDL cholesterol determination in diabetic patients and is more rapid and cost effective than the reference method.

Cholesterol, LDL↗
PubMed1997

Neuronal peptide release is limited by secretory granule mobility.

Neuropeptides are slowly released from a limited pool of secretory granules. To visualize this process, GFP-tagged preproatrial natriuretic factor (ANF) was expressed in nerve growth factor-treated PC12 cells. Biochemical and microfluorimetric experiments demonstrate that proANF-EGFP is packaged in granules that accumulate at neurite endings and is released in a Ca2+-dependent manner by secretagogs. Confocal microscopy shows that secretion is associated with depletion of granules distributed throughout the terminal. Fluorescence recovery after photobleaching and time-lapse particle tracking reveal that only a subpopulation of cytoplasmic secretory granules, similar in size to the releasable pool, can move quickly enough (D = 6 x 10(-11) cm2/s) to support release. Therefore, sustained secretory responses are limited by the number of mobile granules and their slow rate of diffusion.

Animals↗
PubMed1997

Respiratory oxygen cost for dead space challenge is characteristically increased during exercise in patients with chronic heart failure: does it further decrease exercise capacity?

BACKGROUND: Although the work of the respiratory muscles is markedly increased during exercise in patients with chronic heart failure, the role of this abnormality in exercise intolerance is still controversial. This issue may be clarified directly by dead space challenge, as this technique increases minute ventilation. Therefore, in this study, the effects of an external dead space on exercise ventilation, gas exchange data, and exercise capacity in patients with chronic heart failure were examined. METHODS AND RESULTS: Dead space challenge was performed by adding an external dead space to the airway in 20 patients with chronic heart failure and 10 normal subjects. Two hours after completion of the control maximal bicycle exercise, the second exercise was performed under application of an external dead space equivalent to 10% of peak tidal volume. Respiratory gas exchange data were collected during exercise. Aerobic exercise capacity was assessed from the exercise time and the time to anaerobic threshold. The sensation of exertional dyspnea was assessed using Borg's rating scale. As compared with data during the control exercise, minute ventilation was increased by approximately 25% with the external dead space throughout exercise in both groups. A parallel 20% increase in systemic oxygen uptake was observed in the heart failure group, likely reflecting an increase in respiratory muscle work. This response was not observed in the normal group. Despite an additional increase in respiratory muscle work, neither aerobic exercise capacity nor exertional dyspnea was exacerbated in the heart failure group by the external dead space. CONCLUSIONS: Dead space challenge appears to be a unique technique that characteristically increases the work of respiratory muscles during exercise in patients with chronic heart failure. By use of this technique, it was demonstrated that an increase in respiratory muscle work is not important in reducing exercise capacity of patients with chronic heart failure.

Adult↗
PubMed1997

Regional HmPAO SPECT and CT measurements in the diagnosis of Alzheimer's disease.

BACKGROUND: This study investigated the hypothesis that the combination of regional CT brain atrophy measurements and semiquantitative SPECT regional blood flow ratios could produce a diagnostic test for Alzheimer's disease (AD) with an accuracy comparable to that achieved with the present clinical gold standard of the NINCDS-ADRDA criteria. METHODS: Single proton emission computed tomography (SPECT) and CT head scans were performed on 122 subjects referred an UBC Alzheimer clinic and diagnosed as either 'not demented' (ND-37) or 'possible/probable AD' (AD-85) by the NINCDS-ADRDA criteria. Stepwise discriminant analysis (SDA) was performed on the bilateral SPECT regions of interest and compared to bilateral CT qualitative/quantitative assessment in the frontal, parietal and temporal lobes to determine which were most accurate at ND/AD distinction. Receiver operating curves (ROC) were then constructed for these variables individually and for their combined discriminant function. RESULTS: The left temporal qualitative cortical atrophy score (CT) and left temporal perfusion ratio (SPECT) were selected in the SDA. The combined discriminant function was more specific at AD/ND distinction than either of CT or SPECT alone. The accuracy of AD/ND distinction with the combined discriminant function was below that achieved by clinical diagnosis according to the NINCDS-ADRDA criteria and was not significantly different from that achieved with SPECT or CT alone as defined by ROC curve analysis. CONCLUSION: The measurements of left temporal cortical atrophy and regional cerebral blood flow were most indicative of AD; however they lacked the sensitivity and specificity to recommend their use as a diagnostic test for AD.

Aged↗
PubMed1997

Ineffectiveness of the presence of H-ras/p53 combination of mutations in squamous cell carcinoma cells to induce a conversion of a nontumorigenic to a tumorigenic phenotype.

Human tumor cells have properties in vitro or in surrogate hosts that are distinct from those of normal cells, such as immortality, anchorage independence, and tumor formation in nude mice. However, different cells from individual tumors may exhibit some, but not all of these features. In previous years, human tumor cell lines derived from different tumor and tissue types have been studied to determine those molecular changes that are associated with the in vitro properties listed above and with tumorigenicity in nude mice. In the present study, seven cell lines derived from human tumors were characterized for p53 and ras mutations that may occur in SCC tumor phenotypes and for tumor formation in nude mice. This investigation was designed to examine whether co-occurrence of mutated ras and p53 lead to a malignant stage in the progression process. None of the seven cell lines contained mutations in the recognized "hot spots" of the p53 tumor suppressor gene, but four had a nonsense/splice mutation in codon 126 and a mutation in codon 12 of the H-ras gene. The remaining three cell lines had p53 mutations in intron 5, in codon 193, and a missense mutation in codon 126, respectively. Four of seven cell lines were nontumorigenic; two of these cell lines contained a nonsense p53-126 mutation and mutated ras; one had a missense mutation at codon 126 but no mutated ras; the the fourth had only a p53 mutation at codon 193. Two of the nontumorigenic cell lines were converted to tumorigenicity after treatment with methyl methanesulfonate or N-methyl-N'-nitro-N-nitrosoguanidine with no apparent additional mutations in either gene. Our analysis revealed that there was a high frequency of genetic diversity and mutations in both p53 and H-ras. There was also a lack of a causal relationship in the presence of mutations in p53 and the cells' ability to exhibit a malignant potential in nude mice.

Animals↗
PubMed1997

Relation between academic achievement and social adjustment: evidence from Chinese children.

A sample of children in Shanghai, P.R. China, initially aged 10 and 12 years, participated in this 2-year longitudinal project. Information on academic achievement and indexes of social adjustment, including social competence, aggression, social inhibition, leadership, and peer acceptance, was collected from multiple sources. It was found that academic achievement predicted children's social competence and peer acceptance. In turn, children's social functioning and adjustment, including social competence, aggression-disruption, leadership, and peer acceptance, uniquely contributed to academic achievement. These results generally supported the "reciprocal effects" model concerning the relations between academic achievement and social adjustment (S. P. Hinshaw, 1992).

Achievement↗
PubMed1997

Optimizing suicide gene therapy for head and neck cancer.

An effective "suicide gene" therapy strategy in experimental studies has been the use of the herpes simplex virus thymidine kinase gene (HSV-tk) to sensitize tumors to the cytotoxic effects of ganciclovir administration. Previous studies using this model have focused on utilizing maximal viral titers and high levels of ganciclovir that are not compatible with human dosing. Because of the high ganciclovir doses and the maximal viral titers, this strategy has limited application to actual clinical scenarios. In the following studies the authors investigate tumor regression in an oral squamous cell carcinoma animal model as a function of variable adenoviral titers and more physiologic ganciclovir dosing. Using adenoviral titers ranging from 1 x 10(8) to 2 x 10(9) plaque forming units (pfu) to treat oral tumors, they found no statistical difference in tumor regression among the different viral doses, despite differences in mitotic activity. Each treatment group, however, demonstrated a significant effect on tumor regression when compared with controls. Furthermore, the authors were able to reduce the level of ganciclovir administration to 10 mg/kg twice daily from established levels of 100 to 150 mg/kg twice daily while maintaining significant tumor responses to the HSV-tk therapy. Mean survival of animals treated with this lower ganciclovir dose was significantly higher than in controls and was equal to established means based on previous studies using higher ganciclovir doses. The optimization of this suicide gene therapy strategy is imperative in order to minimize theoretical and known viral and ganciclovir toxicities while establishing a foundation upon which to design appropriate and effective clinical trials.

Animals↗
PubMed1997

An interfacial tension model of the interaction of water-soluble polymers with phospholipid composite monolayers.

The axi-symmetric drop-shape analysis-pendant drop technique has been used to measure interfacial tension at the chlorobenzene-water interface in the presence of adsorbed films of dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC), DMPC-cholesterol, DPPC-cholesterol, DMPC-cholesterol-dicetyl phosphate (DCP) and DPPC-cholesterol-DCP. A surface-pressure function, pi * = pi lipid-polymer -pi lipid (where pi lipid is the surface pressure of the mono-layer without polymer and pi lipid-polymer is the surface pressure of the lipid mono-layer and adsorbed polymer at equilibrium at the chlorobenzene-water interface) was used to characterize the interaction of eight water-soluble polymers with the lipid films. The equation, delta pi * = pi II*-pi I* (where the subscripts II and I denote the higher and lower lipid composites, respectively) was used to determine the differential effect of cholesterol and DCP on mono-layer characteristics in the presence of 1% w/v polymer. Cholesterol or polymer individually condensed DMPC films and expanded DPPC films. However, composite films of DMPC-cholesterol-DCP and carboxymethylchitin (CM-chitin), poly(acrylic acid) (PAA) or poly(vinyl alcohol) (PVA) were more expanded than DMPC films whereas composite films of DPPC were neither more condensed nor expanded than DPPC films. A polymer impact ratio, P* = pi lipid-polymer/pi lpolymer was calculated and the polymers were ranked in order of their impact on the lipid film. PVA and polysaccharides gave low and high P* values, respectively, corresponding to high and low levels of film interaction, whereas PAA and hydrophobized polysaccharides gave intermediate values, indicating their affinity for and penetration of interfacial films with little disruption of the mono-layer. The results show that measurement of interfacial pressures at the chlorobenzene-water interface might be advantageous for evaluating the action of polymers on biological membranes.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1997

Purification and sequence analysis of a novel NADP(H)-dependent type III alcohol dehydrogenase from Thermococcus strain AN1.

An NADP(H)-dependent alcohol dehydrogenase was isolated from the hyperthermophilic archaeon Thermococcus strain AN1. This enzyme is a homotetramer with a subunit molecular weight of 46,700. The enzyme oxidizes a series of primary linear alcohols but not methanol. The pH and temperature optima with ethanol as the substrate are 6.8 to 7.0 and 85 degrees C, respectively. The enzyme readily reduced acetaldehyde with NADPH as the cofactor. The gene encoding this enzyme has been cloned and sequenced. An open reading frame of 1,218 bp, starting with ATG and ending with TGA, was identified and corresponded to 406 amino acids. Sequence comparisons show that this Thermococcus strain AN1 enzyme has significant homologies with enzymes from the newly defined type III alcohol dehydrogenase family. Thermococcus strain AN1 alcohol dehydrogenase is the first archaeal enzyme belonging to this family.

Alcohol Oxidoreductases↗
PubMed1997

Naked DNA vaccines expressing the prM and E genes of Russian spring summer encephalitis virus and Central European encephalitis virus protect mice from homologous and heterologous challenge.

Naked DNA vaccines expressing the prM and E genes of two tick-borne flaviviruses, Russian spring summer encephalitis (RSSE) virus and Central European encephalitis (CEE) virus were evaluated in mice. The vaccines were administered by particle bombardment of DNA-coated gold beads by Accell gene gun inoculation. Two immunizations of 0.5 to 1 microg of RSSE or CEE constructs/dose, delivered at 4-week intervals, elicited cross-reactive antibodies detectable by enzyme-linked immunosorbent assay and high-titer neutralizing antibodies to CEE virus. Cross-challenge experiments demonstrated that either vaccine induced protective immunity to homologous or heterologous RSSE or CEE virus challenge. The absence of antibody titer increases after challenge and the presence of antibodies to E and prM, but not NS1, both before and after challenge suggest that the vaccines prevented productive replication of the challenge virus. One vaccination with 0.5 microg of CEE virus DNA provided protective immunity for at least 2 months, and two vaccinations protected mice from challenge with CEE virus for at least 6 months.

Animals↗
PubMed1997

The casein kinase II beta subunit binds to Mos and inhibits Mos activity.

Mos is a germ cell-specific serine/threonine kinase and is required for Xenopus oocyte maturation. Active Mos stimulates a mitogen-activated protein kinase (MAPK) by directly phosphorylating and activating MAPK kinase (MKK). We report here that the Xenopus homolog of the beta subunit of casein kinase II (CKII beta) binds to and regulates Mos. The Mos-interacting region of CKII beta was mapped to the C terminus. Mos bound to CKII beta in somatic cells ectopically expressing Mos and CKII beta as well as in unfertilized Xenopus eggs. CKII beta inhibited Mos-mediated MAPK activation in rabbit reticulocyte lysates and repressed MKK activation by v-Mos in a coupled kinase assay. In addition, microinjection of CKII beta mRNA into Xenopus oocytes inhibited progesterone-induced meiotic maturation and MAPK activation, presumably by binding of CKII beta to Mos and thereby inhibiting MAPK activation. Moreover, this inhibitory phenotype could be rescued by another protein that binds to CKII beta, CKII alpha. The ability of ectopic CKII beta to inhibit meiotic maturation and the detection of a complex between endogenous Mos and CKII beta suggest that CKII beta may act as an inhibitor of Mos during oocyte maturation, perhaps setting a threshold beyond which Mos protein must accumulate before it can activate the MAPK pathway.

Amino Acid Sequence↗