Biomedical subjects

R Tang

Publications and source records attributed to R Tang.

At least 91 records · Page 5Linked to original sources

PubMed1998

Possible role of telomerase activation in the cancer predisposition of patients with hereditary nonpolyposis colorectal cancers.

BACKGROUND: Hereditary nonpolyposis colorectal cancer syndrome (HNPCC syndrome; also called Lynch syndrome) is one of the most common cancer predisposition syndromes. Most cases of cancer associated with this syndrome are due to the inheritance of germline mutations in genes that encode proteins required for DNA mismatch repair; defects in these proteins allow mutations to accumulate more rapidly in the DNA and influence the rate of cancer development. Recent studies indicate that the reactivation of the activity of telomerase, an enzyme involved in the synthesis of chromosomal ends, in somatic cells may play a role in carcinogenesis. In this study, we evaluated the expression of telomerase in normal and cancerous colorectal tissue specimens from HNPCC and non-HNPCC patients. METHODS: The polymerase chain reaction-based telomeric repeat amplification protocol was used to assay telomerase activity in colorectal tissue specimens from 33 non-HNPCC patients (23 normal, 26 polyps, and 37 cancer specimens) and from 24 HNPCC patients (24 normal, 0 polyps, and 28 cancer specimens). RESULTS: Thirty-one of 37 carcinoma samples from 18 non-HNPCC patients and 27 of 28 carcinoma samples from 24 HNPCC patients were found to be positive for telomerase activity. Whereas only one of 23 normal mucosa samples from 23 non-HNPCC patients was found to have (weak) telomerase activity, eight of 24 normal mucosa samples from 24 HNPCC patients were positive for telomerase; the difference between the two groups was statistically significant (two-sided P = .0226). IMPLICATION: This study generates the hypothesis that genetic defects in individuals with HNPCC syndrome facilitate the reactivation of telomerase activity, a process which may be associated with their predisposition to develop cancer.

Adult↗

PubMed1998

Increased expression of adenylylcyclase type VI proportionately increases beta-adrenergic receptor-stimulated production of cAMP in neonatal rat cardiac myocytes.

Cellular content of cAMP generated by activation of adenylylcyclase (AC; EC 4.6.1.1) is a key determinant of functional responsiveness in the heart and other tissues. We have tested two hypotheses regarding the relationship between AC content and beta-adrenergic receptor (betaAR)-mediated signal transduction in cardiac myocytes. First, that AC content limits adrenergic signal transduction, and, second, that increased AC, independent of (betaAR) number and G-protein content, yields a proportional increase in betaAR-mediated transmembrane signaling. We used recombinant adenovirus to increase AC isoform VI (ACVI) expression in neonatal cardiac myocytes. Cells that overexpressed ACVI responded to agonist stimulation with marked increases in cAMP production in proportion to protein expressed. In parallel experiments performed on cells transfected with lacZ (control) or ACVI, [3H]forskolin binding, used to assess AC protein expression, was amplified 6-fold, while betaAR-stimulated cAMP production from these cells was increased 7-fold. No changes in betaAR number, or in the heterotrimeric GTP-binding proteins, Galphas or Galphai2, were observed. Previous studies indicate that increased cardiac expression of betaAR or Galphas does not yield proportional increases in transmembrane adrenergic signaling. In contrast, the current data demonstrate that increased ACVI expression provides a proportional increase in beta-adrenergic signal transduction. Our results show that the amount of AC sets a limit on transmembrane beta-adrenergic signaling. We speculate that similar functional responses are possible in other cell types in which AC plays an important physiological role.

Adenylyl Cyclases↗

PubMed1998

Foley catheter-assisted endoscopic treatment of severe anastomotic stenosis following anterior resection of the rectum.

Rectal stenosis following low anterior resection is common. Several methods of treatment have been described. We introduce a simple method for the treatment of anastomotic stenosis using a conventional proctoscope and an electric knife with a Foley catheter as an anvil. Under direct vision, this technique can afford accurate and safe incision of stenosis.

Catheterization↗

PubMed1998

Different prognostic effect of postoperative chemoradiation therapy on diploid and nondiploid high-risk rectal cancers.

PURPOSE: DNA ploidy has been shown to play a role in the response to cytotoxic therapy in a variety of malignancies, including breast cancer and melanoma. However, the importance of DNA ploidy in rectal cancer is unknown. The aim of the present study was to determine whether ploidy status might be associated with response to postoperative chemoradiation in TNM Stages II to III rectal cancer. METHODS: This retrospective study analyzed data from 229 patients with TNM Stages II to III rectal cancer who underwent resection between 1979 and 1984. The ploidy status and treatment modalities in relation to outcome were assessed. RESULTS: The recurrence-free ten-year survival rate was 52.2 percent for patients with diploidy and 50.5 percent for patients with nondiploidy (P = 0.99). The ten-year survival rates for patients with diploidy and patients with nondiploidy were 55 and 19 percent (P = 0.016) in the chemoradiation group, and 51 and 60 percent (P = 0.15) in the nonchemoradiation group, respectively. In the chemoradiation group, DNA nondiploidy was associated with an increased recurrence rate (83.3 vs. 50.0 percent; P = 0.001). The interaction between DNA nondiploidy and chemoradiation remained important in predicting outcome in the Cox regression model. Factors independently correlated with a worse outcome included Stage IIIb (relative risk, 2.9; 95 percent confidence interval, 1.7-5; P = 0.0001), perineural invasion (relative risk, 2.5; 95 percent confidence interval, 1.6-4, P = 0.0001), distal tumor (relative risk, 1.7; 95 percent confidence interval, 1.1-2.7, P = 0.014), and nondiploidy with chemoradiation (relative risk, 2.9; 95 percent confidence interval, 1.2-7.2, P = 0.0213). CONCLUSIONS: These findings suggest that DNA nondiploidy is inversely correlated with long-term outcome among patients with high-risk rectal cancer receiving chemoradiation.

Adult↗

PubMed1998

Light and electron microscopic study of changes in the organization of the cortical actin cytoskeleton during chromaffin cell secretion.

Chromaffin cells cultured for 2 days were incubated in the absence or presence of 10 microM nicotine for 40 sec. Resting and stimulated cells were fixed and either prepared for fluorescence microscopy or treated with Triton X-100 to obtain cytoskeletons for ultrastructural studies. Electron microscopy of cytoskeletons revealed the presence of polygonal areas devoid of actin filaments only in nicotinic receptor-stimulated cells. Staining of these cytoskeleton preparations with rhodamine-phalloidin, a probe for filamentous actin, produced fluorescent patterns and three-dimensional images similar to those obtained from resting or stimulated intact cells prepared directly for fluorescence microscopy. Moreover, the percentage of stimulated cells showing disrupted cytoskeleton at the electron microscopic level was similar to the percentage of stimulated cells showing patched rhodamine fluorescence at the fluorescence microscopic level. In addition, cells stimulated with nicotine for 40 sec showed a fivefold increase in amine output and a significant decrease in F-actin levels. These results provide the first ultrastructural evidence for nicotinic receptor-evoked chromaffin cell F-actin disassembly and show that the rhodamine-phalloidin-unstained areas observed in fluorescence microscopy represent the areas devoid of filamentous actin observed at the electron microscopic level.

Actins↗

PubMed1998

[Constituents in petroleum ether and ethyl acetate extract fractions of Dracaena cochinensis (Lour.) S.C. Chen].

OBJECTIVE: To study the chemical constituents of Dracaena cochinensis. METHODS: Compounds were separated by solvent extraction, column chromatography, TLC and HPLC, and their structures were determined by spectral analysis. RESULTS: Ten compounds were isolated from the petroleum ether and ethyl acetate fractions of D. cochinensis and identified as n-heptacosane, lophenol, docosanyl ferulate, tetracosanyl ferulate, hexacosanyl ferulate, octacosanyl ferulate, pterostilbene, dioctyl phthalate, butyl isobutyl phthalate and 4'-methoxy-3',7-dihydroxy-flavone. CONCLUSION: All the compounds were isolated from this plant for the first time.

Coumaric Acids↗

PubMed1998

[Studies on chemical constituents from the root of Coriaria nepalensis wall (Coriaria sinica Maxim)].

The root of Coriaria nepalensis Wall (Coriaria sinica Maxim) is a Chinese herbal medicine and has been used to treat numbness, toothache due to wind and heat, phlegm-retention syndrome, traumatic injury and acute conjunctivitis. Nine compounds were isolated from the root of Coriaria nepalensis Wall and they were identified as braylin (I), norbraylin (II), dihydrocoriamyrtin (III), coriamyrtin (IV), tutin (V), coriatin (VI), apotutin (VII), hydroxycoriatin (VIII) and gallic acid (IX) on the basis of their physicochemical properties and IR, UV, MS, 1HNMR, 13CNMR data. I, II were isolated from the title plant for the first time; III was obtained from plant origin for the first time, and VII, VIII were new compounds.

Lactones↗

PubMed1998

Bilateral anterior ischemic optic neuropathy following influenza vaccination.

Optic neuritis is an occasional complication of vaccination. Visual loss can be unilateral or bilateral, and most patients recover substantially without treatment. The presumptive mechanism is an immune-mediated demyelinating injury of the optic nerve. We report two patients who had permanent visual loss following influenza vaccination. Their pattern of visual loss, segmental optic disc changes, and failure of visual recovery were atypical for demyelinating optic neuritis and reminiscent of a primary ischemic injury to the optic nerve. We speculate that an immune complex-mediated vasculopathy following vaccination can cause anterior ischemic optic neuropathy. Clinicians should be aware of this entity because of the less favorable prognosis for visual recovery in these cases.

Blindness↗

PubMed1998

Segmental colectomy in the management of colonic inertia.

Subtotal colectomy with ileorectostomy has been proposed for the management of colon inertia-type constipation. However, many patients experience frequent bowel movements, watery diarrhea, or both after such a treatment. The purpose of this study is to determine the proper colectomy with which to treat colon dysmotility constipation without the negative side effects of frequent bowel movements, watery diarrhea, or both. Forty idiopathic constipation patients were studied. All of the patients showed a prolonged right or left colon transit time and normal transit time of the sigmoid and rectum. They received different types of colectomies (left, right, and subtotal) according to the distribution or accumulation of markers in the colon. Within 3 months of surgery, all of the patients experienced a dramatic improvement of their symptoms without frequent bowel movements or watery diarrhea. No significant complications developed after surgery. All the patients were followed up for at least 2 years. Most of them (37 cases) still had satisfactory bowel movements and no other constipation symptoms. However, 3 of the 40 cases developed symptoms of constipation 1 1/2 to 2 years after surgery. They all received subtotal colectomy with ileorectal anastomosis subsequently. They reobtained satisfactory bowel movements and experienced a subsidence of other constipation symptoms 3 months later. These results suggest that directed segmental colectomy can improve colonic inertia constipation without the consequence of frequent bowel movements and diarrhea.

Adult↗

PubMed1998

Butyrate inhibits colon carcinoma cell growth through two distinct pathways.

BACKGROUND: Dietary fiber and the resultant increase in colonic butyrate levels protect against colon carcinogenesis. Previous studies have shown that p21 and histone hyperacetylation are important in basal growth inhibition by butyrate. This study was designed to elucidate other mechanism underlying the butyrate effects on cell growth. METHODS: HT-29 colon carcinoma cells (standard medium or medium lacking serum) were treated with sodium butyrate (NaBu), epidermal growth factor (EGF), or both. Northern blot analyses were performed with cDNA probes specific for c-fos, c-jun, and actin. Cell growth was measured by 3H-thymidine incorporation. Enzyme-linked immunosorbent assay (ELISA) was used to quantify EGF receptor levels. RESULTS: Butyrate and serum starvation (SS) both induced a cell cycle withdrawal by 24 hours. In response to EGF treatment, SS cells exhibited a growth spurt and induced c-fos and c-jun proto-oncogene expression, whereas butyrate-treated cells exhibited minimal growth response to EGF. This relative unresponsiveness to EGF in butyrate-treated cells corresponded to a dramatic decline in EGF receptor levels when compared to untreated controls. CONCLUSIONS: Butyrate appears to inhibit colon cancer cell growth by two mechanisms, one involving histone hyperacetylation and p21 induction and the other related to impaired EGF-responsiveness.

Actins↗

PubMed1997

Morphometric analysis of pediatric and nonhyperplastic prostate glands: evidence that BPH is not a unique stromal process.

BACKGROUND: Although quantitative morphometry of benign prostatic hyperplasia (BPH) has been described, there is a paucity of information on the morphometry of the nonhyperplastic prostate. This study determines the histologic composition of prostates obtained from males, ages 2 days to 40 years, in order to provide insights into the morphometry of the "normal" gland. METHODS: The histologic composition of 45 prostates was obtained from autopsies of males with age groups stratified to reflect the neonatal, childhood, peripubertal, adolescent, and young adult periods. Double immunoenzymatic staining and computer image analysis were used to determine the mean area densities of the smooth muscle (SM), connective tissue (CT), glandular epithelium (E), and lumen (L). RESULTS: A progressive decrease in SM area density throughout childhood, prepuberty, and puberty was seen. The density of SM significantly increased following puberty and throughout adolescence and early adulthood. There was a concomitant increase in CT from the neonatal period throughout childhood, prepuberty, and puberty, and a decrease after puberty and throughout adolescence and early adulthood. Since the changes in SM and CT were inversely related, the percent contribution of the stromal compartment to the total gland remained constant. CONCLUSIONS: The stromal to epithelial ratio remains constant from birth to age 40 in nonhyperplastic glands and is similar to the ratios in asymptomatic and symptomatic BPH tissues.

Adolescent↗

PubMed1997

Pathogenetic implications of DNA nondiploidy in colorectal cancers.

PURPOSE: Several studies propose that proximal and distal colorectal cancers have a different pathogenesis. We tested the hypothesis using flow cytometric DNA analysis. METHODS: DNA analysis was performed in 719 patients with colorectal cancer. In addition, histopathologic data were re-evaluated in a blinded fashion by a single pathologist. RESULTS: Distal tumors were more often nondiploid than were proximal tumors (61 vs. 49 percent; P = 0.015). Compared with the proximal tumor, distal tumors were smaller (P = 0.0001) and had less desmoplastic reaction (39 vs. 53 percent; P = 0.0001). Tumor location had no significant associations with the remaining parameters, including mucin production, perineural invasion, blood/lymphatic vessel invasion, lymphocytic infiltration, histologic grade, tumor stage, gross appearance, age, and gender. CONCLUSIONS: The unequal distribution of ploidy suggests distinct pathogenetic mechanisms at proximal and distal sites.

Colorectal Neoplasms↗

PubMed1997

Stapled colonic J-pouch-anal anastomosis without a diverting colostomy for rectal carcinoma.

PURPOSE: Colonic J-pouch reconstruction is designed to improve functional outcome of coloanal anastomosis. Most surgeons use a diverting colostomy to avoid severe pelvic sepsis caused by anastomotic breakdown. METHODS: We report the outcome of 30 consecutive patients with colonic J-pouch-anal anastomosis without a diverting colostomy performed between November 1992 and October 1993. All patients had carcinoma of the lower two-thirds of the rectum. Patients were seen every three months. Functional results were compared with those of 21 rectal cancer patients with straight coloanal anastomosis who underwent surgery in the same period and 20 normal patients. RESULTS: There were two anastomotic leakages and one postoperative death. After one year, patients with pouch anastomosis had significantly less frequency of defecation and rectal urgency compared with those with straight anastomosis (P < 0.01); 48 percent of patients with straight anastomosis had more than five bowel movements per day, whereas all patients with pouch anastomosis had five or less bowel movements per day. Manometric studies showed maximum tolerable volume was significantly higher in patients with pouch anastomosis (81 vs. 152 ml; P < 0.01). CONCLUSIONS: Stapled colonic J-pouch-anal anastomosis without a diverting colostomy is a reliable procedure that provides good, long-term functional results.

Adult↗

PubMed1997

Retinal changes associated with tamoxifen treatment for breast cancer.

PURPOSE: This study was undertaken to estimate the incidence of retinal changes and determine the prevalence of ocular toxicity associated with tamoxifen treatment in a breast cancer population. METHODS: The study was based on a population cross-sectional survey, including 290 patients taking tamoxifen from 6 months to 12 years; 274 patients were analysed. The main outcome measures were the incidence of retinal changes and visual impairment. RESULTS: The incidence of retinal changes was 0.9% (3 of 274 patients). All 3 patients were asymptomatic. The length of tamoxifen treatment ranged from 39 months to 120 months in the affected patients, with cumulative tamoxifen doses ranging from 23.7 g to 73 g. CONCLUSIONS: Retinopathy in patients receiving low doses of tamoxifen is rare and, in our study, did not result in changes in visual acuity. We found no retinopathy in patients receiving tamoxifen within the first 3 years of treatment or in patients receiving a total tamoxifen dosage of less than 23.7 g. Although retinopathy can occur in a tamoxifen-treated population, its low incidence and an associated good prognosis for vision does not merit special screening for this problem.

Aged↗

PubMed1997

The significance of white-centered retinal hemorrhages in the shaken baby syndrome.

Retinal hemorrhages in healthy children with or without a history of associated trauma are a strong indicator of child abuse. This report describes six cases of battered infants who presented with white-centered retinal hemorrhages. We discuss potential mechanisms for the presence of white-centered retinal hemorrhages in battered children.

Battered Child Syndrome↗

PubMed1997

Effects of advanced glycosylation end products on proliferation and cytosolic free calcium in cultured rat aortic smooth muscle cells.

AIM: To study the effects of advanced glycosylation end products (AGEP) on aortic smooth muscle cell (ASMC) proliferation and its relationship with cytosolic free calcium ([Ca2+]i). METHODS: The effects of AGEP modified bovine serum albumin (AGEP-BSA) on the incorporation of [3H]TdR and [3H]Leu into cultured ASMC were observed. The [Ca2+]i of cultured ASMC was determined with Fura 2-AM. RESULTS: AGEP-BSA stimulated the incorporation of [3H]TdR and [3H]Leu into ASMC in concentration and time-dependent manners (P < 0.01), especially [3H]TdR. In AGEP 200 mg.L-1 group, after 12-h exposure, the incorporation of [3H]TdR obviously increased, but DNA synthesis was concentration-dependently decreased in AGEP 300-400 mg.L-1 groups. The peak incorporation of [3H]TdR was 10 times vs control (P < 0.01). The [Ca2+]i of ASMC incubated with AGEP-BSA for 40 min was increased from control groups 121 +/- 4 to 492 +/- 20 nmol.L-1 (P < 0.01). [Ca2+]i induced by AGEP was elevated with the concentration and incubating time of glucose with BSA. [Ca2+]i in BSA incubated with glucose 80 mmol.L-1 for 12 wk was 580 +/- 37 nmol.L-1 (P < 0.01). CONCLUSION: AGEP stimulated proliferation of ASMC associated with the elevation of [Ca2+]i.

Animals↗

PubMed1997

Endothelins in canine genitourinary tissues.

PURPOSE: To characterize the functional effect of endothelin-1 (ET1) and endothelin-3 (ET3), immunohistochemically localize ET1-like immunoreactivity, and measure the tissue levels of immunoreactive endothelin (irET) in canine genitourinary (GU) tissues. MATERIALS AND METHODS: Canine GU tissues were characterized by measuring ET1 levels using a RIA, immunohistochemical staining of ET1 and isometric tension studies. RESULTS: Immunoreactive endothelin was present, to varying degrees, in the vas deferens, ureter, prostate, bladder and urethra. Functionally, ET1 demonstrated the typical concentration response characteristics in the canine bladder base, bladder body, and prostate. The maximal tension (Emax) measured following ET1 challenge was approximately 20-fold greater in the bladder body (0.67 +/- 0.21 g/mm.2) and bladder base (0.48 +/- 0.18 g/mm.2) as compared to the prostate 0.04 +/- 0.001 g/mm.2 The Emax of ET3 in the bladder body (0.31 +/- 0.12 g/mm.2) and bladder base (0.19 +/- 0.08 g/mm.2) was significantly lower than the corresponding Emax of ET1. No measurable contractile response was elicited by ET3 in the canine prostate. Immunohistochemical staining localized the ET-like immunoreactivity to the glandular epithelium of the prostate and the transitional epithelium of the bladder. CONCLUSIONS: Endothelins are ubiquitous in the canine lower GU tract with predominant localization to the epithelial elements. Endothelins are also functionally active in canine GU tissues, but the specific role of endothelins in the physiology and pathophysiology of GU tissues requires further investigation.

Animals↗

PubMed1997

Primary diffusely infiltrative adenocarcinoma of the colon and rectum.

BACKGROUND: Primary diffusely infiltrative colorectal adenocarcinoma is rare. About 100 cases have been reported in the literature. The mucosal alterations in this type of tumor and their clinicopathological characteristics in relation to survival are not clear. METHODS: We retrospectively reviewed 30 cases of primary diffusely infiltrative colorectal adenocarcinoma operated upon in a single institution. RESULTS: Eighteen (60%) of these 30 patients were women. The average age at diagnosis was 47.4 (SD, 19.3) years. Eighteen tumors (60%) were located in the rectum. The tumors could be classified into two major types. A type 1 tumor had minimal mucosal alteration and no discrete ulcer. A type 2 tumor was associated with a discrete ulcer. The type 1 tumor was more frequently associated with intracellular or extracellular mucin production and stage IV disease. Hematogenous spread (including peritoneal carcinomatosis) was more frequently seen in type 1 than in the type 2 tumors (61% vs. 18%, p = 0.013). The overall median cancer-specific survival time was 15 (SE, 3; 95% confidence interval, 10-21) months. TNM stage is the only significant factor in predicting outcome (p = 0.016). When compared with stages II and III, the odds of death for stage IV was 2.9 (95% confidence interval: 1.1-7.4). CONCLUSION: Diffusely infiltrative colorectal cancer can be separated into two subtypes according to the presence of a discrete ulcer. The type 1 tumor (without a discrete ulcer) was associated with a higher frequency of hematogenous spread. TNM Stage was the only important clinicopathological factor in determining outcome.

Adenocarcinoma↗