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Biomedical subjects

T Chen

Publications and source records attributed to T Chen.

At least 235 records · Page 13Linked to original sources
PubMed1997

Saccharomyces cerevisiae Mpt5p interacts with Sst2p and plays roles in pheromone sensitivity and recovery from pheromone arrest.

SST2 plays an important role in the sensitivity of yeast cells to pheromone and in recovery from pheromone-induced G1 arrest. Recently, a family of Sst2p homologs that act as GTPase-activating proteins (GAPs) for G alpha subunits has been identified. We have identified an interaction between Sst2p and the previously identified Mpt5p by using the two-hybrid system. Loss of Mpt5p function resulted in a temperature-sensitive growth phenotype, an increase in pheromone sensitivity, and a defect in recovery from pheromone-induced G1 arrest, although the effects on pheromone response and recovery were mild in comparison to those of sst2 mutants. Overexpression of either Sst2p or Mpt5p promoted recovery from G1 arrest. Promotion of recovery by overexpression of Mpt5p required Sst2p, but the effect of overexpression of Sst2p was only partially dependent on Mpt5p. Mpt5p was also found to interact with the mitogen-activated protein kinase homologs Fus3p and Kss1p, and an mpt5 mutation was able to suppress the pheromone arrest and mating defects of a fus3 mutant. Because either mpt5 or cln3 mutations suppressed the fus3 phenotypes, interactions of Mpt5p with the G1 cyclins and Cdc28p were tested. An interaction between Mpt5p and Cdc28p was detected. We discuss these results with respect to a model in which Sst2p plays a role in pheromone sensitivity and recovery that acts through Mpt5p in addition to a role as a G alpha GAP suggested by the analysis of the Sst2p homologs.

CDC28 Protein Kinase, S cerevisiae↗
PubMed1997

Computerized quantification analysis of left ventricular wall motion from echocardiograms.

Two-dimensional echocardiography (2-D echo) imaging is a more attractive clinical tool than other modalities that either involve radiation exposure or are too slow to image heart motion in real-time. Computer-aided analysis of left ventricular(LV) wall motion provides quantitative parameters for diagnosis. This study presents a computerized model for quantitative analysis of left ventricular wall motion from two-dimensional echocardiography by the application of image processing algorithms, including automatic threshold estimation, contrast stretching, boundary detection and border smoothing. The wall motion measurements rely primarily on sequential changes from end-diastolic to end-systolic frames in the left ventricular contours of apical four-chamber view echocardiograms. Left ventricular wall motion was analyzed on the 30 segments of 5 patients with acute myocardial infarction. The results from the computerized model were compared to those obtained from qualitative analysis of echocardiograms by an experienced clinical cardiologist who was unaware of the results of quantitative data.

Algorithms↗
PubMed1997

[Improvement of operating method of repairing fistula of maxillary sinus].

5 cases of fistula of the maxillary sinus have been repaired by improved Teruo method, which uses flaps derived from submucous connective tissue of the palate and buccal mucous to repair the fistula. It has been satisfied after 4-13 years of follow-up observation. This article also discussed the difficulty of fistula repair and the advantage of the method. The authors thought that the method would be an ideal way to repair fistula of the maxillary sinus.

Adult↗
PubMed1997

[Somatostatin and its secretory cells in tumor surrounding mucosa in colorectal cancer patients and its significance].

The somatostatin (SS) levels in tumor surrounding mucosae were determined by RIA, and the SS secretory cells in these tissues were observed by immunocytochemistry in colorectal cancer patients. The mean SS level was higher in cancer-adjacent mucosa (CAM, 0-2 cm from the tumor) than in cancer-distant mucosa (CDM, about 5 cm from the tumor), and in CAM without atypical hyperplasia than in such mucosa with different grades of atypical hyperplasia (P < 0.01). In CAMs, there was a very significant negative correlation between the SS level and cell dysplasia (P < 0.01). The form and location of SS cells in all tumor surrounding mucosae were similar to the normal. Both the mean SS cell number and total positive degree were very significantly higher in CAM than CDM (P < 0.01). SS levels in CAMs were correlated positively with the SS cell numbers and the total positive degrees in CAM (P < 0.01). It is concluded that the elevation of SS level in CAM is mainly caused by the increase of SS cells, which secrete more SS. The change of SS in colorectal cancer surrounding mucosa may play an important role in inhibiting the development of CAM atypical hyperplasia or the tumor, and is a local defensive reaction in the body.

Cell Count↗
PubMed1997

[Application of electronystagmography glycerine test for diagnosing Ménière's disease].

To evaluate electronystagmography (ENG) glycerine test (GT) for diagnosing Ménière's disease (MD), ENG GT were performed in 44 patients (48 ears) with MD and 20 normal subjects (40 ears). In normal subjects, the increase or decrease in percentage of maximum velocity of caloric nystagmus were calculated before and 1, 2, 3 hours after administration of glycerin (1.5 g/kg). According to the statistical analysis, 95% of normal subjects fell below +15% at 44 degrees C and +10% at 30 degrees C, therefore the value of +15% at 44 degrees C and +10% at 30 degrees C were taken as the upper limit of normal range. Increase in maximum velocity of caloric nystagmus beyond the normal range was referred to as positive. In the patients with MD, positive reaction were observed in 86.7% of typical MD, 77.8% of vestibular type MD. The rate of positive response was much higher in stage of attack of hydrolabyrinth than that of remission. The results indicated that this test is another diagnostic method for patient with MD and is particularly suited for diagnosing vestibular type of atypical MD.

Adolescent↗
PubMed1997

[Penetrating gluteal injuries management--the need for management protocols].

Gunshot wounds are the most common cause of penetrating injuries in the gluteal region (PIGR), while only 17.5% result from stabbing. Complications and even death have been described as resulting from stab injury in this area, which is thus a hazard that demands an algorithm for proper management. Recently, DiGiacomo et al. recommended that transpelvic bullet trajectory warrants surgery. Mercer et al., in a study of 81 patients with PIGR, recommended an algorithm based on anatomical gluteal zones and concluded that angiography is not mandatory in such injuries. We describe 9 cases of PIGR, 4 of which were from stab wound and 1 a gunshot wound, which bled from rami of the gluteal arteries. In 2 there was no apparent bleeding, and they were hemodynamically stable. Thus in this type of injury significant damage may be obscured. Our results suggest that angiography is important in the evaluation of such injuries an should be part of the protocol for management of PIGR.

Algorithms↗
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

Effects of losartan and PD123319 on antigensin II-induced proto-oncogene expression and protein synthesis in cultured neonatal rat cardiac myocytes.

To study the effects of specific angiotension II (Ang II) receptor, type-1 (AT1) antagonist (Losartan) and type-2 (AT2) antagonist (PD123319), on Ang II-induced proto-oncogene expression and synthesis of RNA and protein in neonatal rat cardiac myocytes, we used respectively [3H]-uridine and [3H]-leucine incorporation to measure the rate of RNA and protein synthesis, and analyzed the c-myc mRNA level by Northern blot. We found that an acceleration in the rate of RNA and protein synthesis was observed when exposed to 2.5 x 10(-6) mol.L-1 [Sar1] Ang II for 24 h (P < 0.01). Losartan inhibited the action in a dose-dependent manner. The level of c-myc mRNA was up-regulated to 340% of control by 2.5 x 10(-6) mol.L-1 Ang II, and Losartan (10(-5) mol.L-1) suppressed the increase of c-myc mRNA stimulated by Ang II. PD123319 showed similar inhibition on Ang II-induced RNA and protein synthesis, but did not inhibit c-myc expression. Thus, Ang II-stimulated expression of c-myc is mainly mediated by AT1 receptors, and contributes to cardiac myocyte hypertrophy while AT2 receptors are involved in mediation of cellular growth without altering of c-myc expression.

Angiotensin Receptor Antagonists↗
PubMed1996

Deletion map of chromosome 16q in ductal carcinoma in situ of the breast: refining a putative tumor suppressor gene region.

Allelic losses or imbalances affecting chromosome arm 16q appear to be early genomic abnormalities in breast carcinogenesis, because they were observed in a significant number of breast ductal carcinoma in situ lesions in our previous study (Aldaz et al., Cancer Res., 55: 3976-3981, 1995). To define the minimum region of loss of heterozygosity (LOH), we generated a high-resolution allelotype of 35 ductal carcinoma in situ cases and completed a deletion map of chromosome 16q by means of paraffin-embedded tissue microdissection and PCR microsatellite analysis of 22 markers. We observed a strikingly high frequency of LOH in 16q, with 31 of 35 tumors (89%) affected. We identified three distinctive areas with high LOH. Two areas were described previously and correspond to 16q21 and 16q24.2-qter. The third and most commonly affected area spanned the region from marker D16S515 to marker D16S504. The most affected locus was at D16S518, in which LOH was observed in 20 of 26 informative cases (77%), and we estimate that it lies in subregion q23.3-q24.1. The region of highest LOH spanned approximately 2-3 Mb, as determined by a yeast artificial chromosome contig reported to cover this region. Such a high frequency of LOH at a preinvasive stage of breast cancer suggests that a candidate tumor suppressor gene or genes at this location may play an important role in breast carcinogenesis.

Autoradiography↗
PubMed1996

CGM1a antigen of neutrophils, a receptor of gonococcal opacity proteins.

Neisseria gonorrhoeae (GC) or Escherichia coli expressing phase-variable opacity (Opa) protein (Opa+ GC or Opa+ E. coli) adhere to human neutrophils and stimulate phagocytosis, whereas their counterparts not expressing Opa protein (Opa- GC or Opa- E. coli) do not. Opa+ GC or E. coli do not adhere to human lymphocytes and promyelocytic cell lines such as HL-60 cells. The adherence of Opa+ GC to the neutrophils can be enhanced dramatically if the neutrophils are preactivated. These data suggest that the components binding the Opa+ bacteria might exist in the granules. CGM1a antigen, a transmembrane protein of the carcinoembryonic antigen family, is exclusively expressed in the granulocytic lineage. The predicted molecular weight of CGM1a is approximately 30 kDa. We observed specific binding of OpaI+ E. coli to a 30-kDa band of polymorphonuclear leukocytes lysates. To prove the hypothesis that the 30-kDa CGM1a antigen from neutrophils was the receptor of Opa+ bacteria, we showed that a HeLa cell line expressing human CGM1a antigen (HeLa-CGM1a) bound Opa+ E. coli and subsequently engulfed the bacteria. Monoclonal antibodies (COL-1) against CGM1 blocked the interaction between Opa+ E. coli and HeLa-CGM1a. These results demonstrate that HeLa cells when expressing the CGM1a antigens bind and internalize OpaI+ bacteria.

Antigens, Bacterial↗
PubMed1996

Interaction of phosphorylated FcepsilonRIgamma immunoglobulin receptor tyrosine activation motif-based peptides with dual and single SH2 domains of p72syk. Assessment of binding parameters and real time binding kinetics.

To examine the characteristics of the interaction of the FcepsilonRIgamma ITAM with the SH2 domains of p72(syk), the binding of an 125I-labeled dual phosphorylated FcepsilonRIgamma ITAM-based peptide to the p72(syk) SH2 domains was monitored utilizing a novel scintillation proximity based assay. The Kd for this interaction, determined from the saturation binding isotherm, was 1.4 nM. This high affinity binding was reflected in the rapid rate of association for the peptide binding to the SH2 domains. Competition studies utilizing a soluble C-terminal SH2 domain knockout and N-terminal SH2 domain knockouts revealed that both domains contribute cooperatively to the high affinity binding. Unlabeled dual phosphorylated peptide competed with the 125I-labeled peptide for binding to the dual p72(syk) SH2 domains with an IC50 value of 4.8 nM. Monophosphorylated 24-mer FcepsilonRIgamma ITAM peptides, and phosphotyrosine also competed for binding, but with substantially higher IC50 values. This, and other data discussed, suggest that high affinity binding requires both tyrosine residues to be phosphorylated and that the preferred binding orientation of the ITAM is such that the N-terminal phosphotyrosine occupies the C-terminal SH2 domain and the C-terminal phosphotyrosine occupies the N-terminal SH2 domain.

Amino Acid Sequence↗
PubMed1996

Affinity chromatography of trypsin using chitosan as ligand support.

Chitosan beads were prepared for use as affinity adsorbent carrier. The affinity ligand, chicken ovomucoid, was immobilized on the chitosan via a cross-linker, glutaraldehyde. The results showed that 60 mg chicken ovomucoid could be immobilized on l g chitosan, and the maximum binding capacity for trypsin was about 8.10(4) U/g dry adsorbent. The procedure for preparing the chitosan-based affinity adsorbents was much safer and simpler than when a Sepharose-based matrix was the support. Columns packed with the affinity adsorbents were employed for trypsin chromatography. The experimental results revealed that the affinity adsorbents possessed good mechanical strength and storage stability and could be also operated repeatedly. Chitosan was suitable for use as an affinity adsorbent support for laboratory-scale and large-scale purification.

Adsorption↗
PubMed1996

A novel angiogenic molecule produced at the time of chondrocyte hypertrophy during endochondral bone formation.

Angiogenesis is a pivotal event in endochondral ossification. Vessels grow into the hypertrophic cartilage and erode it to produce a scaffold on which osteoblasts settle to produce woven bone. A new culture system was used to determine whether growth-plate chondrocytes produce an angiogenic molecule. Chondrocytes from primary growth plates of bovine fetuses were separated into maturationally distinct subpopulations. When cultured these cells produce an extensive extracellular matrix and the prehypertrophic cells mature to express the hypertrophic phenotype defined by the synthesis of type X collagen and matrix calcification. The culture medium collected from the hypertrophic cells contains a chemoattractant, nonmitogenic molecule for bovine endothelial cells which can induce angiogenesis in vivo in the rabbit cornea model. This molecule has a Mr of approximately 120 x 10(3). The production of this molecule by hypertrophic cells is enhanced by both 1,25-(OH)2 vitamin D3 and 24,25-(OH)2 vitamin D3 at 10(-8)-10(-12) M, but only in pre- and early hypertrophic cells. In contrast, these metabolites have either no effect or an inhibitory effect on the more mature hypertrophic cells. These results describe for the first time the production of an angiogenic molecule by hypertrophic chondrocytes. They demonstrate an important role for vitamin-D3 metabolites in regulating hypertrophy and angiogenesis during normal skeletal growth and differentiation. Thus, a defective regulation of these processes, due to the lack of vitamin-D metabolites, may explain the observed enlargement of the hypertrophic zone and impairment of skeletal growth in rickets which is induced clinically and experimentally by a deficiency of vitamin D.

24,25-Dihydroxyvitamin D 3↗
PubMed1996

Molecular characterization of the 71E late puff in Drosophila melanogaster reveals a family of novel genes.

Early metamorphic development in Drosophila melanogaster is initiated by pulses of the steroid hormone ecdysone, which are transduced into tissue-specific transcriptional cascades. This process begins with the hormone-dependent activation of a set of transcription factors (early genes) that, in turn, activate set of tissue-specific effector genes (late genes). The 71E cytogenetic region of the salivary gland polytene genome contains several ecdysone-regulated transcription units. Molecular techniques were used to analyze these genes, their transcriptional program and their evolutionary relatedness. We find that this region contains a cluster of ten coordinately regulated late genes (L71 genes) that are organized as five divergently transcribed gene pairs. Maximum parsimony analysis suggests that an ancestral L71 gene duplicated to form the first gene pair which was, in turn, duplicated to form the set of gene pairs. The L71 gene products form a family of small, chemically basic proteins with a conserved backbone of cysteine residues. In addition, the 71E region contains another gene (I71-1) with the regulatory and biochemical characteristics of the salivary gland intermolt glue proteins.

Amino Acid Sequence↗
PubMed1996

Imaging of fluorescent molecule and small ion transport through human stratum corneum during high voltage pulsing: localized transport regions are involved.

During the application of high-voltage pulses across the skin, transport of two negatively charged fluorescent molecules through the stratum corneum is highly localized. The apparent size of these localized transport regions (LTR's) is initially 10 microns in diameter for both calcein and sulforhodamine. Appearance of LTR's occurred at or above transdermal voltages of 75 V. In the range of 75 to 160 V, the number of LTR's increases with voltage, but their initial size is the same at all voltages; with additional pulses LTR's increase in size, reaching diameters of approximately 40-80 microns. Small ion currents across the skin are also localized and include the LTR's; however, the areas of current flux appeared to be larger. There was no visible damage to the structure of the skin seen at 100 x magnification for any of the voltages used (< 170 V across the skin). Significantly, LTR's are not sweat ducts or hair follicles.

Adult↗
PubMed1996

Technical approach for the study of the genetic evolution of breast cancer from paraffin-embedded tissue sections.

We have optimized a technique that allows the study of numerous chromosomal loci (n = 20-50) from single paraffin-embedded tissue sections by microsatellite length polymorphism analysis. DNA samples from normal and breast cancerous tissue can be obtained from the same section by means of microdissection. This technique was further improved by subjecting DNA to several cycles of amplification with a degenerate (universal) primer and then with specific microsatellite primers. This amplified DNA was also used to screen for mutations in the p53 gene by means of PCR-SSCP. In addition adjacent tissue sections were used to assess specific chromosome copy number by interphase cytogenetic analyses (chromosome in situ hybridization) and to analyze expression of specific genes such as p53 and ERBB2. As an example of the use of our approach we performed a detailed chromosome 17 allelotypic analysis in 22 breast tumors (5 ductal carcinomas in situ, 13 invasive ductal carcinomas, and 4 invasive lobular carcinomas). We detected mutations in the p53 gene by PCR-SSCP in 36% of the samples. Samples with significant levels of p53 protein accumulation detected by immunohistochemistry were also positive for mobility shifts in the SSCP analysis. We observed that chromosome 17 allelic losses and imbalance occurred at as early a stage as ductal carcinoma in situ (DCIS). Although in some cases we observed allelic losses or imbalance affecting the 17p13 region, close to the p53 locus, several of the tumors showed dissociation between such loss or imbalance and p53 mutation. Lobular carcinomas were predominantly disomic for chromosome 17 in contrast with ductal tumors, which often showed polysomy for chromosome 17. This comprehensive approach correlating the tumor subtype, its allelotype, with specific chromosome copy number and specific gene mutations and expression in preinvasive or early invasive breast cancer lesions will potentially provide information of relevance for a better understanding of the multistep mechanisms of breast carcinogenesis.

Alleles↗
PubMed1996

A constipation scoring system to simplify evaluation and management of constipated patients.

PURPOSE: Constipation is a common complaint; however, clinical presentation varies with each individual. The aim of this study was to assess a standard scoring system for evaluation of constipated patients. MATERIALS AND METHODS: All consecutive patients with idiopathic constipation who were referred for anorectal physiologic testing were assessed. A subjective constipation score was calculated based on a detailed questionnaire that included over 100 constipation-related symptoms. Based on the questionnaire, scores ranged from 0 to 30, with 0 indicating normal and 30 indicating severe constipation. The constipation score was then compared with the objective findings of the physiology tests, which include colonic transit time (CTT), anal manometry (AM), cinedefecography (CD), and electromyography (EMG). Colonic inertia was defined as diffuse marker delay on CTT without evidence of paradoxical contraction on AM, CD, or EMG. Pelvic outlet obstruction was defined as paradoxical puborectalis contraction, rectal prolapse or rectoanal intussusception, rectocele, or sigmoidocele. RESULTS: A total of 232 patients (185 females and 47 males) of a mean age of 64.9 (range, 14-92) years were evaluated. All patients had a score of more than 15; on evaluation of the significance of different symptoms in the constipation score with the Pearson's linear correlation test, 8 of 18 factors were identified as significant (P < 0.05). These factors included frequency of bowel movements, painful evacuation, incomplete evacuation, abdominal pain, length of time per attempt, assistance for evacuation, unsuccessful attempts for evacuation per 24 hours, and duration of constipation. All 232 patients had objective obstruction attributable to one or more of the following causes: paradoxical puborectalis contraction (81), significant rectocele or sigmoidocele (48), rectoanal intussusception (64), and rectal prolapse (9). CONCLUSION: The proposed constipation scoring system correlated well with objective physiologic findings in constipated patients to allow uniformity in assessment of the severity of constipation.

Adolescent↗