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Biomedical subjects

S Chen

Publications and source records attributed to S Chen.

At least 1,369 records · Page 76Linked to original sources
PubMed1990

Opposing regulatory functions of positive and negative elements in UASG control transcription of the yeast GAL genes.

The yeast GAL1 and GAL10 genes are transcribed at a remarkably low basal level when galactose is unavailable and are induced by over 4 orders of magnitude when it becomes available. Approximately six negative control elements (designated GAL operators GALO1 to GALO6) are located adjacent to or overlapping four binding sites for the transcription activator GAL4 in the GAL upstream activating sequence UASG. The negative control elements contribute to the broad range of inducibility of GAL1 and GAL10 by inhibiting two GAL4/galactose-independent activating elements (GAE1 and GAE2) in UASG. In turn, multiple GAL4-binding sites in UASG are necessary for GAL4 to overcome repression by the negative control elements under fully inducing conditions. When glucose in addition to galactose is available (repressing conditions), the ability of GAL4 to activate transcription is diminished as a result of its reduced affinity for DNA and the reduced availability of inducer. Under these conditions, the negative control elements inhibit transcriptional activation from the glucose-attenuated GAL4 sites, thus accounting at least in part for glucose repression acting in cis. A normal part of transcriptional regulation of the GAL1 and GAL10 genes, therefore, appears to involve a balance between the opposing functions of positive and negative control elements.

Base Sequence↗
PubMed1990

The role of pneumolysin in ocular infections with Streptococcus pneumoniae.

Pneumolysin, a cytolytic protein produced by Streptococcus pneumoniae, has many properties which suggest it may be an important virulence factor in pneumococcal ocular infections. To directly test this possibility, we have constructed pneumolysin-negative strains of S. pneumoniae and compared their virulence with that of the wild type in a rabbit model of intracorneal infection. A pneumolysin-negative strain produced by chemical mutagenesis (probably a point mutant) was found to be no less virulent than the parent strain. However, a strain bearing a deletion in the pneumolysin gene showed greatly reduced virulence. This strain produced less pathology while showing significantly higher bacterial counts. These results suggest that a property of the pneumolysin molecule other than its cytolytic (hemolytic) activity may be involved in its pathogenic mechanism of action. This property may be the ability to activate complement, known to be a function of pneumolysin, which results in influx of PMNs, reducing the bacterial counts but also producing tissue damage.

Animals↗
PubMed1990

[Study of an MPTP-induced parkinsonian animal model in the rhesus monkey and the mechanism of the action of MPTP].

In this paper are presented the data of the use of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to create a parkinsonian animal model in rhesus monkey. We studied the mechanism of the action of MPTP through testing monoamine oxidase B (MAO-B) inhibitor, deprenyl and L-prolyl-L-leucyl-glycinamide (PLG) against the neurotoxicity of MPTP. The results indicated that: (1) the use of MPTP can establish a useful parkinsonian animal model in rhesus monkey; (2) pretreatment with deprenyl can effectively prevent the neurotoxicity of MPTP; and (3) whether PLG can prevent or alleviate the neurotoxicity of MPTP requires further study.

Animals↗
PubMed1990

Clinical application of microcomputer to visual function examination.

Microcomputer technique is put into use in ophthalmological clinical visual function examination. In visual EOG, ENG, visual tracking, contrast sensitivity and VEP examination, objectifying and standardization of experiment and data analysis are achieved by computer technique. In addition, a lot of manpower and time is saved, test results are obtained faster and more accurately. The basic rational of computerization in clinical visual function examination is presented.

Adult↗
PubMed1990

Influence of EA on the electrical conductance in the marginal area of the acute ischemic myocardium in the rabbit.

AMI was produced by occlusion of LVB for 30 min in the rabbit, lengthening the conductive time of myocardium in the ischemic area and resulting in asynchronous activation state of myocardium. EA could facilitate the conductance of electric activation in the ischemic marginal area and make the activation of myocardial cells in this area synchronous which is of importance in blocking the formation of reentrant circuit. The finding suggests that EA possesses an antiarrhythmic effect.

Action Potentials↗
PubMed1990

Relationship between PO-AH and PHA in the effects of EA at neiguan in the rabbit.

The activity of PHA neurons was extracellularly recorded by using glass microelectrodes and the mutual relationship between PO-AH and PHA during the regulation activity of EA was analysed. The results were as follows: 1. The activity of most PHA neurons could be changed by PO-AH stimulation. 2. The activity of some PHA neurons could be affected by AMI. 3. The AMI-induced PHA neurons activity could be changed by EA at "Neiguan". 4. The effect of EA could be enhanced in some PHA neurons by PO-AH stimulation under EA. The findings suggest that PO-AH and PHA possess some coordination effect in the regulation of EA at "Neiguan" on the functional activity of the heart.

Acupuncture Points↗
PubMed1990

Creating an endoscopy capability in Army community hospitals.

The purchase of gastrointestinal endoscopic services can be a fiscal drain on the Army Community Hospital. We describe a method whereby a quality endoscopic service can be created at the Army Community Hospital level.

Education, Medical, Continuing↗
PubMed1990

[Therapeutic effect of yupingfeng san and shengmai yin on Coxsackie B viral myocarditis].

A "LDH release method" was used to determine NK cell activity in 30 cases of Coxsackie B viral myocarditis and contrasted with 20 normal volunteers. About 80% cases revealed NK cell activity deficiency. Among them, the NK activity of 24 cases (80%) was less than 14%; and 15 cases (50%) less than 10%. After Yupingfeng San and Shengmai Yin treatment for 2-3 months, their NK cell activity was elevated from 12.26 +/- 1.31% to 31.99 +/- 4.23% (P less than 0.001). At the same time, their clinical manifestations and EKG changes were improved or returned to normal.

Adult↗
PubMed1990

[Experimental research on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced parkinsonian animal models in the rhesus monkey and C57 black mouse].

Parkinson's disease (PD) is a common neurodegenerative disease of old age characterized by triad of akinesia, rigidity and tremor, reduction of dopamine (DA) content in the nigrostriatum, and severe degeneration of neuron in the substantia nigra. The significant changes after the use of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to rhesus monkeys and C57 black mice are (a) serotonin-like reactions and Parkinsonian symptoms in monkeys and "stickclimbing" disturbance in mice; (b) marked DA reduction in substantia nigra (72.5%), putamen (93.3%), caudate nucleus (91.2%) of monkeys and striatum (94%) of mice; (c) reduction of Met-enkephalin (75%) and Leu-enkephalin (66%) in mouse striatum; and (d) severe degeneration of neurons in the substantia nigra of monkeys and mice. The results suggest that MPTP-treated monkey and C57 black mouse provides useful Parkinsonian animal models and produces behavioral, biochemical and histopathological changes similar to those of human PD.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1990

[Pest control and yield increase of areca by root-zone application of carbofuran in admixture with fertilizers].

The result of our experiment has shown that by root-zone application of carbofuran in admixture with fertilizers to Areca in spring the serious pest Tirathaba rufivena can be controlled for 4 months during flowering and young fruiting stage and the yield can increase by 50%. The final residual amount of carbofuran in fruits is below 0.1-0.01 ppm or too low to be examined, and there is no decrease in total alkaloid content in fruits.

Alkaloids↗
PubMed1990

[Rapid detection of human cytomegalovirus DNA in urine samples by polymerase chain reaction in vitro gene amplification].

In the detection of human cytomegalovirus (HCMV) DNA in the urine by polymerase chain reaction (PCR). We have designed and synthesized two pairs of oligonucleotide primers (patent pending) corresponding to the specific and conserved DNA sequences of HCMV AD 169 strain. The sequences of the primers were checked that they did not have cross reaction with either normal human genomic DNA or with other herpesviruses. As less as 1fg of HCMV DNA (equal to the amount of DNA from four HCMV virions) in urine can be detected by the method A total of 47 urine specimens from infants suspected of HCMV infection was examined by PCR and conventional virus isolation simultaneously 31 samples were positive in both PCR and virus isolation; 12 samples were negative in either; 4 samples were positive in PCR but negative in virus isolation. So the samples were further examined by serology and the data showed that there was HCMV-specific IgM in all the virus isolation negative sera examined. The result suggests that HCMV in the above samples is possibly underdetected by virus isolation. Therefore the method described in the paper is a specific, sensitive, rapid conventional and non radioisotopic one for detection of HCMV in urine samples.

Cytomegalovirus↗
PubMed1990

Severe withdrawal symptoms after discontinuation of alprazolam in eight patients with combat-induced posttraumatic stress disorder.

Eight patients with combat-induced chronic posttraumatic stress disorder (PTSD) receiving long-term alprazolam therapy for anxiety or depression (maximum dose of 2-9 mg/day for 1-5 years) had alprazolam therapy withdrawn. Most of the patients underwent gradual medication withdrawal. All patients had a prior history of alcohol abuse or benzodiazepine dependence. During withdrawal, all patients had severe reactions including anxiety, sleep disturbance, rage reactions, hyperalertness, increased nightmares, and intrusive thoughts; and 6 of the 8 patients had homicidal ideation. As a result of this report, the authors suggest that the potential for severe withdrawal reactions, even with gradual tapering, should be considered before prescribing alprazolam therapy for this group of patients.

Adult↗