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Biomedical subjects

H J Tang

Publications and source records attributed to H J Tang.

8 recordsLinked to original sources
PubMed2005

Analysis of cyclic dynamics for networks of linear threshold neurons.

The network of neurons with linear threshold (LT) transfer functions is a prominent model to emulate the behavior of cortical neurons. The analysis of dynamic properties for LT networks has attracted growing interest, such as multistability and boundedness. However, not much is known about how the connection strength and external inputs are related to oscillatory behaviors. Periodic oscillation is an important characteristic that relates to nondivergence, which shows that the network is still bounded although unstable modes exist. By concentrating on a general parameterized two-cell network, theoretical results for geometrical properties and existence of periodic orbits are presented. Although it is restricted to two-dimensional systems, the analysis can provide a useful contribution to analyze cyclic dynamics of some specific LT networks of high dimension. As an application, it is extended to an important class of biologically motivated networks of large scale: the winner-take-all model using local excitation and global inhibition.

Action Potentials↗
PubMed2003

Enhancement of dissolved phosphorus release from sediment to lake water by Microcystis blooms--an enclosure experiment in a hyper-eutrophic, subtropical Chinese lake.

To clarify the possible influence of Microcystis blooms on the exchange of phosphorus (P) between sediment and lake water, an enclosure experiment was conducted in the hypereutrophic subtropical Lake Donghu during July-September 2000. Eight enclosures were used: six received sediment while two were sediment-free. In mid-August, Microcystis blooms developed in all the enclosures. There was a persistent coincidence between the occurrence of Microcystis blooms and the increase of both total P (TP) and soluble reactive P (SRP) concentrations in the water of the enclosures with sediments. In sediment-free enclosures, TP and SRP concentrations remained rather stable throughout the experiment, in spite of the appearance of Microcystis blooms. The results indicate that Microcystis blooms induced massive release of P from the sediment, perhaps mediated by high pH caused by intense algal photosynthesis, and/or depressed concentrations of nitrate nitrogen (NO3-N).

China↗
PubMed2003

Expression of COX-2 in stomach cancers and its relation to their biological features.

BACKGROUND/AIM: Cyclooxygenase-2 (COX-2) is one of the key isoenzymes in the production of prostaglandins, and is believed to be involved in carcinogenesis. This study was conducted to examine the role of COX-2 in the development and biological behavior of stomach cancer. METHODS: Expression of COX-2 at the mRNA and protein levels was analyzed using RT-PCR and immunoblotting assay in 50 cancerous and corresponding non-cancerous tissue specimens. Also, COX-2 expression was detected by an immunohistochemical method in 55 paraffin-embedded gastric adenocarcinoma tissues. RESULTS: Of the 50 carcinoma tissue samples analyzed, 38 (76.0%) had overexpression of COX-2 as compared to the paired non-cancerous specimens. The overexpression of COX-2 (91.7%) was more prevalent in tumors with sizes of >5 cm than those (61.5%) of </=5 cm (p < 0.05). COX-2 overexpression was higher in tumors with >6 metastatic nodes compared to those with </=6 metastatic nodes (100.0 vs. 61.3%, p < 0.01). The rate of COX-2 overexpression in non-signet ring cell carcinoma was significantly higher compared with signet ring cell carcinoma (84.1 vs. 16.7%, p < 0.05). The rate of COX-2 overexpression (86.8 or 90.9%) in patients with a cancer invasion depth of pT3 + pT4 or with stage III + IV was significantly higher than that (41.7 or 47.1%) in patients with pT1 + pT2 or with stage I + II (both p < 0.01). Furthermore, consistent with the results at the protein and mRNA levels, immunohistochemical stain indicated that COX-2 protein was overexpressed in 39 of 55 (70.9%) carcinomas, and the 5-year survival rate (25.6%) for patients with COX-2 overexpression seemed better than that (50.0%) of patients without overexpression, though the difference was not significant (p < 0.05). CONCLUSION: Our results indicate that COX-2 may play a role in the development of gastric cancer and its overexpression is associated with lymphatic metastasis, tumor invasion and differentiation of gastric carcinoma.

Adenocarcinoma↗
PubMed2001

Clinical characteristics of emphysematous pyelonephritis.

A total of 21 patients (20 women and one man) with emphysematous pyelonephritis (EPN), treated in the Kaohsiung Veterans General Hospital during the period from 1991 through 1999 were included in this study. All of the patients were diabetic. The most common symptoms or signs were fever/chills (80%) and costovertebral angle knocking pain (71%). Diagnosis was confirmed by the presence of gas in the parenchyma or paranephric space on plain X-ray of the abdomen or computed tomography. The left kidney (11 cases, 52%) was more frequently affected than the right one (nine cases, 43%), and both kidneys were involved in one case. Obstruction of the corresponding renoureteral unit was found in 19% of the patients, and renal or ureteral stone was found in 23% of the patients. One third of the patients had type I EPN, and two-thirds had type II EPN. Escherichia coli was the most commonly isolated organism, accounting for 61%, 76%, and 47% of isolates from blood, urine, and aspirated pus culture respectively. Prompt control of blood sugar was begun and intravenous antibiotics were given. Drainage was performed in 71% of the patients, and two persons required nephrectomy because of poor control of the infection or complications. Overall survival was 72%. Emphysematous pyelonephritis is a rare, life-threatening, suppurative infection of the renal parenchyma and perirenaL tissues. For successful management of EPN, appropriate medical treatment should be initiated, and immediate nephrectomy or drainage should not be delayed.

Adult↗
PubMed2000

Impact of genetic polymorphisms in cytochrome P450 2E1 and glutathione S-transferases M1, T1, and P1 on susceptibility to esophageal cancer among high-risk individuals in China.

Esophageal cancer, which is prevalent in China, is believed to be induced by environmental carcinogens such as nitrosamines and other agents. The disproportionate geographical distribution of this cancer among individuals suggests a role for gene-environment interactions in developing the disease. We have shown in our preliminary study that a genetic polymorphism in cytochrome P450 2E1 (CYP2E1) that is known to activate nitrosamines may be a susceptibility factor involved in the early events leading to the development of esophageal cancer (Lin et al., Cancer Epidemiol. Biomark. Prev., 7: 1013-1018, 1998). This relatively larger study was conducted to compare the results with our previous findings. One hundred and fifty cases with esophageal cancer, 146 cases with esophageal dysplasia, and 150 normal controls were residents of Linxian, China, a high-risk area. Genomic DNA samples were assayed for restriction fragment length polymorphisms in the CYP2E1 and GSTP1 loci by PCR amplification followed by digestion with RsaI and Alw26I, respectively. Deletion of the GSTM1 and GSTT1 genes was detected by multiplex PCR. The distribution of CYP2E1 c1/c1 allele frequency was found to be significantly different between controls (44.0%) and cases with cancer (71.3%) or cases with dysplasia (70.6%; P < 0.0001). Individuals having the c1/c1 genotype were at a 3.1-fold [95% confidence interval (CI), 2.4-3.9] increased risk of developing dysplasia and a 3.2-fold (95% CI, 2.5-4.1) increased risk of developing squamous cell carcinoma of the esophagus. Although polymorphisms in the GSTT1 and GSTP1 were not significantly different between cases with cancer or cases with dysplasia and controls, the frequency of the GSTM1 non-null (+/+ and +/0) genotypes appeared to be overrepresented in cases with cancer compared with controls (odds ratio, 2.3; 95% CI, 1.8-3.0). Furthermore, a joint effect of the CYP2E1 c1/c1 genotype and GSTM1 non-null genotype on the cancer risk was observed, showing an odds ratio of 8.5 (95% CI, 3.7-19.9). These results demonstrate that CYP2E1 and perhaps GSTM1 are genetic determinants in the development of squamous cell carcinoma of the esophagus.

Carcinoma, Squamous Cell↗
PubMed1989

413 cases of abnormal fetal position corrected by auricular plaster therapy.

The authors corrected the abnormal fetal position in 413 cases of pregnant women by the auricular plaster therapy (APT) with a success rate of 83.3%--remarkably higher than treatment by knee-chest positioning. Further analysis showed that APT was also superior to the knee-chest positioning for primiparae, breech fetal position, and pregnancies over 33 weeks. The authors also noted the clinical signs of successful cases and failures.

Acupuncture Points↗