Biomedical subjects

T L Yang

Publications and source records attributed to T L Yang.

At least 37 records · Page 2Linked to original sources

PubMed1998

The structure and function of murine factor V and its inactivation by protein C.

Factor V (FV) is a central regulator of hemostasis, serving both as a critical cofactor for the prothrombinase activity of factor Xa and the target for proteolytic inactivation by the anticoagulant, activated protein C (APC). To examine the evolutionary conservation of FV procoagulant activity and functional inactivation by APC, we cloned and sequenced the coding region of murine FV cDNA and generated recombinant wild-type and mutant murine FV proteins. The murine FV cDNA encodes a 2,183-amino acid protein. Sequence comparison shows that the A1-A3 and C1-C2 domains of FV are highly conserved, demonstrating greater than 84% sequence identity between murine and human, and 60% overall amino acid identity among human, bovine, and murine FV sequences. In contrast, only 35% identity among all three species is observed for the poorly conserved B domain. The arginines at all thrombin cleavage sites and the R305 and R504 APC cleavage sites (corresponding to amino acid residues R306 and R506 in human FV) are invariant in all three species. Point mutants were generated to substitute glutamine at R305, R504, or both (R305/R504). Wild-type and all three mutant FV recombinant proteins show equivalent FV procoagulant activity. Single mutations at R305 or R504 result in partial resistance of FV to APC inactivation, whereas recombinant murine FV carrying both mutations (R305Q/R504Q) is nearly completely APC resistant. Thus, the structure and function of FV and its interaction with APC are highly conserved across mammalian species.

Amino Acid Sequence↗

PubMed1998

Relative size perception at a distance is best at eye level.

Relative size judgments were collected for two objects at 30.5 m and 23.8 from the observer in order to assess how performance depends on the relationship between the size of the objects and the eye level of the observer. In three experiments in an indoor hallway and in one experiment outdoors, accuracy was higher for objects in the neighborhood of eye level. We consider these results in the light of two hypotheses. One proposes that observers localize the horizon as a reference for judging relative size, and the other proposes that observers perceive the general neighborhood of the horizon and then employ a height-in-visual-field heuristic. The finding that relative size judgments are best around the horizon implies that information that is independent of distance perception is used in perceiving size.

Analysis of Variance↗

PubMed1998

Differential expression of cytokine genes and apoptosis in glioma cell lines upon exposure to bacteria and lipopolysaccharides.

The influences of Escherichia coli, Streptococcus pyogenes and lipopolysaccharides (LPSs) on the expression of cytokines and apoptosis were investigated in two glioma cell lines. IL-1beta and TNF-alpha genes were modulated by bacteria in a time dependent fashion and their expression levels varied from sources of bacteria and cell lines used. E. coli and LPSs induced apoptosis in a very limited cell population as judged by cell counts, membrane alternation and DNA break in situ. The expression of fas and IL-6 genes was not affected by bacterial components. In conclusion, aberrant expression of cytokines but not apoptosis may be the major responses of the cells of glial origin upon exposure to bacteria and their components.

Apoptosis↗

PubMed1998

Orbital lymphoma: results of radiation therapy.

Orbital lymphoma is a rare presentation of non-Hodgkin's lymphoma. Treatment with radiotherapy is well-established. Twenty cases of orbital lymphoma treated at the Singapore General Hospital with radiation therapy were reviewed. All patients had improvement of their initial presenting symptoms and complete remission after radiation. Long-term local control was achieved in 17 of 20 (85%) of the treated orbits.

Adult↗

PubMed1998

The current status of intraoperative radiotherapy in colorectal surgery.

Colorectal cancer is the second most common malignancy in Singapore and its incidence is increasing. Results of surgery have been augmented in selected cases by the addition of radiotherapy and chemotherapy. This standard approach only offers palliation in locally advanced and locally recurrent cancers. Newer modalities and combinations are currently being investigated to improve the results in this particular group of patients. One such modality is the use of intraoperative radiotherapy (IORT). This paper discusses the rationale for using IORT, the patient selection, method of delivery and treatment, tolerance and results in centers which have been using IORT as part of a multi-modality therapy for colorectal cancer.

Colorectal Neoplasms↗

PubMed1997

A case-control study of breast cancer in Taiwan--a low-incidence area.

To investigate risk factors for breast cancer in Taiwan, a low-incidence area, a case-control study was conducted. This comprised 244 subjects with diagnosed and pathologically confirmed breast cancer (age range 20-80 years) and 450 female ophthalmology outpatients as controls. Univariate and multiple logistic regression analysis suggests that breast cancer in Taiwan is aetiologically similar to breast cancer in high to moderate-incidence areas. A family history of breast cancer appears to be the most important factor contributing to the risk of breast cancer (odds ratio = 4.69). The effect of reproductive hormones (represented by the years of history of menses in premenopausal women, odds ratio = 3.35; or the age at menarche in post-menopausal women, odds ratio = 2.67) plays a significant role in tumorigenesis. Breast feeding appears to be a particularly important protective factor in Taiwanese women (odds ratio = 0.57).

Adult↗

PubMed1996

Phylogenetic footprinting of the human cytochrome c oxidase subunit VB promoter.

The human COX5B gene encodes subunit Vb of cytochrome c oxidase (COX). COX Vb is 1 of the 10 subunits of the mitochondrial COX complex encoded by a nuclear gene. We have defined a region in the human COX5B promoter essential for gene expression and shown by phylogenetic footprinting of 11 primate COX5B promoters that many cis-regulatory elements in this region are evolutionarily conserved. The transcription start site of human COX5B was mapped 58 bp upstream of the initiation Met codon by primer extension using a thermostable reverse transcriptase. A 475-bp region (-456 to +20) of the human COX5B gene was shown to function as a promoter for the chloramphenicol acetyl transferase (CAT) gene in expression vectors when transfected into HeLa cells. The human COX5B gene is located in a CpG island and contains several potential binding sites for the transcription factor Sp1, but no consensus TATA box element. Several sequence elements associated with the transcriptional regulation of respiratory genes were also found in the promoter and 5' flanking region, including a single NRF-1 site and two 9-bp direct repeats containing binding sites for ets-domain proteins, such as NRF-2/GABP. Many features of the human COX5B promoter are conserved in the COX5B promoters of primates, in particular, the presence of a single binding site for NRF-1 and multiple sites for Sp1 and NRF-2/GABP. Electrophoretic mobility shift assays demonstrate that the conserved NRF-1 site in primate COX5B promoters is specifically recognized by a factor present in HeLa nuclear extracts. Phylogenetic footprinting has identified additional conserved elements that may also function as binding sites for regulatory factors.

Animals↗

PubMed1996

Patient profile and survival in 270 computer tomography-staged patients with nasopharyngeal cancer treated at the Singapore General Hospital.

This is a report analysing the patient profile and survival results in 270 patients with nasopharyngeal carcinoma treated with radiation therapy between July 1987 and December 1988. The patients had a median age of 52.6 months, and a male-female ratio of 2.5:1. Ninety-four percent of patients were Chinese. The commonest presentation was that of a neck mass (found in approximately 65% of patients). Approximately two-thirds presented with disease more advanced than Ho's stage II. At a median follow-up of 52.6 months, the 5-year actuarial survival rate was 53% and the freedom from relapse rate was 57%. One hundred and seven patients died within the observation period. Of these, 46 patients had disease in the post nasal space, 41 in the neck and 60 in sites outside the head and neck.

Actuarial Analysis↗

PubMed1995

Enhanced sympathetic reactivity to glutamate stimulation in medulla oblongata of spontaneously hypertensive rats.

The distribution and reactivity of vasomotor sites in the ventrolateral (VLM) and dorsomedial medulla (DMM) of stroke-prone spontaneously hypertensive rats (SHRSP), spontaneously hypertensive rats (SHR), and Wistar-Kyoto rats (WKY) were compared. Rats were anesthetized with alpha-chloralose and urethan. Baroreceptor denervation and vagotomy were performed. L-Glutamate (Glu, 10 mM, 30 nl) was microinjected into the DMM or VLM to identify vasoactive sites. The extent and the patterns of distribution of these sites in the three strains of rats were similar. The dose-response curve of the vasoactive site was studied with 1-500 pmol of Glu. The maximum responses of blood pressure and renal sympathetic activity were larger and threshold doses of Glu were lower in hypertensive rats. The significance of the differences among the strains was analyzed before and after adjustment for baseline pressure or activity. Most of the differences were statistically significant before baseline adjustment. After baseline adjustment, many differences between the SHRSP and the WKY remained significant. However, the only significant difference detected between the SHR and the WKY was the threshold dose for eliciting renal sympathetic change in the caudal VLM. These results suggest that there may be a general increase in excitability of the vasomotor neurons in the medulla of the hypertensive rats.

Animals↗

PubMed1995

Hepatic actinomycosis: a case report.

A 64-year-old man with hepatic actinomycosis presented with several months of weight loss and poor appetite. However, no fever was noted before admission. Findings on abdominal sonography and computed tomography scan were suggestive of hepatocellular carcinoma. A sono-guided percutaneous liver biopsy specimen demonstrated only chronic fibrosing inflammation. Therefore, laparotomy was performed and the diagnosis of hepatic actinomycosis was established after surgical resection. The patient was then successfully treated. The fact that hepatic actinomycosis may be very similar to hepatocellular carcinoma should be highly suspected. The hospital course of this patient concerning this condition and a brief review of the literature are presented to illustrate the diagnostic difficulties which may be encountered in such cases.

Actinomycosis↗

PubMed1995

Carcinosarcoma of the urinary bladder--case report and literature review.

We describe a patient who presented with gross haematuria and dysuria. Investigations confirmed a bladder tumour, for which transurethral resection was done. The histology showed a carcinosarcoma, which was muscle invasive but organ-confined. The patient refused radical surgery and underwent a course of radical radiotherapy. He died 14 months later. Carcinosarcoma of the urinary bladder is a rare, mixed malignant tumour, composed of mesenchymal and epithelial elements. It is commoner in elderly men. It is an aggressive tumour with a short clinical course, and must be distinguished from collision tumours and spindle cell tumours. Immunohistochemical stains are useful in its diagnosis. It is probably best managed by radical surgery with or without adjuvant therapy, but because of the small number of incidences reported, there is no universal agreement on its therapy.

Aged↗

PubMed1994

Nasopharyngeal cancer treated in Singapore.

With effect from July 1987 CT-scans of the nasopharynx became routinely available in the staging of nasopharyngeal cancer (NPC) in our department. Eighty-four evaluable cases during these first six months were studied and the results at a median follow-up period of 34 months revealed that 74% were alive at 2 years. The local relapse rate were 4% for T1; 10% for T2 and 35% for T3 tumours.

Adult↗

PubMed1993

Study of the hemodynamic contributing factors of spontaneously hypertensive rats in the early stage of established hypertension.

The neural and nonneural factors contributing to maintain the hemodynamic status in 14 to 16 weeks old stroke prone spontaneously hypertensive rats (SHRSP) and spontaneously hypertensive rats (SHR) were compared with those of the age matched normotensive Wistar Kyoto (WKY) rats under chloralose-urethane anesthesia. The ascending aortic blood flow, arterial blood pressure and heart rate were measured under resting condition, ganglionic blockade by hexamethonium, 5 mg/kg i.v. and maximum vasodilation by hexamethonium and 0.07 mg/kg nitroprusside. The neural component (hexamethonium blockable component) was the major factor in the maintenance of resting blood pressure and total peripheral resistance index (TPRI) in the above three strains of rats. In contrast, the residual component after hexamethonium and nitroprusside administrations was the most important controlling factor for cardiac index (CI). In SHRSPs, the neural component of TPRI and residual component of CI were both significantly higher than those of WKYs by 75% and 47%, respectively. In SHRs, the residual component of CI was 52% higher than that of WKYs. These results suggest that both the increased neural component of TPRI and nonneural component of CI are important contributing factors for the blood pressure increase in the early stage of established hypertension in SHRSPs. On the other hand, in the age matched SHRs, the most important contributing factor for hypertension is the increased nonneural component of CI. Considering the differences between these two strains of hypertensive rats, the neural component of TPRI is the major factor responsible for the different levels of hypertension in SHRSPs and SHRs.

Animals↗

PubMed1993

Malignant duodenocolic fistula: a case report.

A 65 year-old female presented with diarrhea, body weight loss, malnutrition, elevated serum carcinoembryonic antigen (CEA) and electrolyte disturbances. A series of examinations showed colon cancer with a malignant duodenocolic fistula. Patient received extended right hemicolectomy with wide local excision of the duodenum (en bloc resection of the tumor). Recovery was smooth without local recurrence or metastasis after a six-month follow-up. Wide en bloc resection provides the only hope of cure in such cases. Treatment with extended right hemicolectomy with Whipple's procedure, or extended right hemicolectomy with extended local wide excision of duodenum, should be chosen, depending upon the extent of tumor invasion.

Aged↗

PubMed1993

[Malignant transformation of multiple gastric adenomatous polyps in a teenage girl: a case report].

A 14-year-old female was found to have gastric polyposis by gastroscopy and barium meal study. During operation, multiple polyps in different sizes were noted over the whole stomach, the largest one measured 6 x 6 x 4 cm. The pathological report was adenomatous polyps. After 4 years, the polyps finally transformed to multifocal gastric adenocarcinoma. The relationship between gastric polyps and gastric adenocarcinoma, and the management of gastric polyposis were discussed.

Adenocarcinoma↗

PubMed1993

Adenomyoma of the papilla of Vater: a case report.

Adenomyoma of the papilla of Vater is exceedingly rare. Histologically, the adenomyoma is characterized by locules of ducts with interlacing bundles of smooth muscle. A 63-year-old male patient is presented who had developed abdominal pain, progressively darker urine and light color stool, jaundice and dyspepsia over the past two-month period. Impression from radiologic study was neoplasm of the papilla of Vater, pathologic findings proved adenomyoma. This case, and review of the literature, suggest that local excision is the treatment-of-choice.

Ampulla of Vater↗

PubMed1993

Acute acalculous cholecystitis.

To demonstrate the importance of early detection and diagnosis of acute acalculous cholecystitis, 34 patients with this disease, were studied retrospectively. Twenty patients had a delay between the onset of symptoms and operative intervention, exceeding 48 hours; five of them were found to have a perforated gallbladder during operation; however, no such complication was encountered in the 14 patients who underwent surgical treatment within 48 hours of onset. Sixteen patients had post-operative complications, and four patients who died produced in a mortality rate 11% (4/34). Three mortality cases had coexisting cardiovascular disease and the operation was also delayed for more than 48 hours.

Acute Disease↗

PubMed1993

Primary malignant lymphoma of the breast: report of two cases with literature review.

We report two cases of malignant lymphoma of the breast. Extensive investigation on both, demonstrated only a neoplastic lesion confined within the breast. One was managed by local excision, systemic chemotherapy and adjuvant radiotherapy; the other was managed by a modified radical mastectomy, adjuvant radiotherapy and therapeutic chemotherapy. Both of them achieved complete remission 3 years and 1.5 years respectively after management.

Adult↗