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Biomedical subjects

B T Chen

Publications and source records attributed to B T Chen.

At least 37 records · Page 2Linked to original sources
PubMed1995

Regional differences in the effects of mainstream cigarette smoke on stored mucosubstances and DNA synthesis in F344 rat nasal respiratory epithelium.

This study was designed to determine the effects of mainstream cigarette smoke (MCS) on stored intraepithelial mucosubstances (IM) and DNA synthesis within the nasal respiratory epithelium of F344 rats and whether such effects persist after cessation of exposure. Rats were exposed to filtered air or diluted MCS for 9 days over a 2-week period. Two hours prior to termination rats were injected with bromodeoxyuridine (BrdU) to label cells synthesizing DNA 1 or 14 days after the last exposure. Sections of nasal tissue blocks taken from a region immediately posterior to the incisor teeth were processed for light microscopy and histochemically stained to detect acidic and neutral IM and immunochemically stained to detect BrdU-labeled cells. The nasal septum was divided into three measurement zones (dorsal, mid-, and ventral) for morphometric quantitation of the volume density of IM and the unit length labeling index (ULLI). MCS-exposed rats terminated 1 day after the last exposure had 270% more IM in the dorsal septum, 58% less IM in the midseptum (due to regions of squamous metaplasia), and amounts of IM in the ventral septum similar to controls. MCS-exposed rats sacrificed 14 days after exposure still had increased amounts of IM in the dorsal septal region, but no regions of squamous metaplasia or amounts of IM in the mid- and ventral septal regions that were different from air-exposed controls. MCS exposure resulted in a significant increase in the ULLI 1 day but not 14 days after exposure in the ventral and midseptal regions only. The results of this study indicate that MCS exposure induces transient alterations in the mucous-producing apparatus in the rat anterior nasal cavity that are resolved following 2 weeks of recovery. However, the type and magnitude of the initial epithelial responses are dependent on the intranasal location of the airway epithelium examined.

Animals↗
PubMed1995

[Study on ultrastructure of platelets in migraine patients with blood stasis type].

To study the relationship between ultrastructure of platelets and migraine patients with blood stasis type (MBS). The morphologic appearance and aggregation of platelets in MBS patients were examined before and after treatment with Tongbike oral liquor (20 cases in treated group and.10 in control). The results showed that the MBS patients' platelets appeared irregular, easy to aggregate and adhere to red cells, which was more severe when ADP was added, but improved after treated with Chinese medicinal herbs. According to the results it was assumed that platelets from MBS patients were in an abnormal activated state, the abnormal morphology and functional disturbance might be the pathologic basis of MBS. Tongbike oral liquor could markedly improve the morphologic and functional state of platelets, which was relevant to the inhibition of platelet aggregation and the inducing of platelet depolymerization.

Adolescent↗
PubMed1994

[Double valve replacement in 400 cases].

From 1985 to 1992, 400 patients received mitral and aortic double valve replacement. Of the patients, 218 were male and 187 female. In early operative days, 6.25% of the patients died. Follow-up study showed that 91.3% of the patients are alive. Perioperative management and improvement of operative technics are detailed.

Adolescent↗
PubMed1993

[Mitral valve replacement with preservation of mitral valve device].

40 patients underwent mitral valve replacement with preservation of the posterior leaflet, chordae tendineae and papillary muscles. Twelve of the patients had double valve replacement and 10 tricuspid annuloplasty in combination with valve replacement. The incidence of postoperative low cardiac output syndrome was low. LADD was significantly decreased and EF was slightly lowered postoperatively. A new surgical technique and its indications were concisely described.

Adolescent↗
PubMed1991

[Valve replacement in patients with huge heart].

In general, valve replacement for patients with big heart (cardiac-thoracic rate greater than 0.80) has been considered a contraindication. Mitral valve replacement was done in 11 patients with a C/T rate of 0.81 to 0.97. In addition, aortic valve replacement was performed in 2 patients and tricuspid valvuloplasty in 5. One patient died from low cardiac output after operation. The heart function of the survivor was improved from III or IV to II degree after operation. We consider that active pre- and postoperative management for preserving myocardial function and preoperative technique are important for the successful treatment of patients with huge heart.

Adolescent↗
PubMed1989

Inhaled cigarette smoke induces the formation of DNA adducts in lungs of rats.

Cigarette smoking causes a variety of adverse human health effects, including lung cancer. The molecular events associated with smoke-induced carcinogenesis are thought to be related in part to the genotoxic activities of the chemicals associated with smoke. The purpose of this investigation was to determine the molecular dosimetry of compounds in cigarette smoke in lungs of rats exposed by inhalation. These studies investigated the effects of exposure mode, sex, and time (adduct persistence) on the level of DNA adducts. Male and female F344/N rats were exposed 6 hr/day, 5 days/week for 22 days to cigarette smoke by nose-only intermittent (NOI), nose-only continuous (NOC), or whole-body continuous (WBC) exposures. Separate groups of rats were sham-exposed nose-only (NOS) or whole-body (WBS) to filtered air. All smoke exposure modes yielded daily smoke exposure concentration X time products of 600 mg particulate.hr/m3 for the first week and 1200 mg particulate.hour/m3 thereafter. Groups of rats were killed at 18 hr and 3 weeks after the 22-day exposure period and DNA adducts in lung tissues were quantified by the 32P-postlabeling method. There were significant (p less than 0.05) increases in levels of clearly resolved lung DNA adducts in male and female rats exposed to smoke compared to sham-exposed rats. There were no significant effects of exposure mode or sex on lung DNA adducts. Mean levels (+/- SE) of clearly resolved lung DNA adducts for both sexes combined in NOI, NOC, WBC, NOS, and WBS groups were 50 +/- 4, 52 +/- 6, 52 +/- 7, 21 +/- 6, and 22 +/- 4 adducts per 10(9) bases, respectively. Levels of clearly resolved DNA adducts were significantly less in lungs of rats killed 3 weeks after exposure and had declined to near control levels, suggesting that smoke-induced adducts are repaired by lung DNA repair enzymes. A single unidentified adduct accounted for about 20% of the total clearly resolved lung DNA adducts quantified in smoke-exposed rats and was increased 9- to 14-fold over control levels. Levels of this adduct in NOI, NOC, WBC, NOS, and WBS were 14 +/- 0.9, 9 +/- 0.7, 11 +/- 0.9, 1.4 +/- 0.2, and 1.1 +/- 0.2 adducts per 10(9) bases, respectively. The results from these experiments indicate that inhaled cigarette smoke induces lung DNA adducts which may play an important role in cigarette smoke-induced lung carcinogenesis.

Adenosine Triphosphate↗
PubMed1989

Cytogenetic effects of cigarette smoke on pulmonary alveolar macrophages of the rat.

To determine accurately the potential genetic damage induced by toxic inhaled agents, the cells that receive a high concentration of such agents should be analyzed. Pulmonary alveolar macrophages (PAMs) represent such cells. We compared the cytogenetic effects of cigarette smoke on PAMs of rats exposed repeatedly by different methods. This study was part of a larger investigation of the health effects resulting from different methods of exposing rats to cigarette smoke. Fischer 344/N male rats (4/group) were randomly selected from five different exposure groups: 1) nose-only sham-exposed (air) control, 2) whole-body sham-exposed control, 3) nose-only intermittent, 4) nose-only continuous, and 5) whole-body continuous. The rats were exposed 6 hr/day, 5 days/week for 22-24 days. All smoke-exposed rats received the same daily concentration x time product (600 mg.hr.m-3 for the first week, 1200 mg.hr.m-3 thereafter) of cigarette smoke. Rats were injected intraperitoneally with colchicine at the end of exposure. PAMs were obtained by lung lavage and chromosomal damage was measured. Highly significant smoke-induced differences in both structural and numerical aberrations were observed in continuously exposed rats vs. sham controls, regardless route of exposure. The structural aberrations observed were chromatid-type deletions. Both hypoploid and hyperploid cells were detected. Our data suggest that cigarette smoke is clastogenic and may disrupt spindle-fiber formation. These activities may play a role in the induction of human carcinogenesis caused by cigarette smoke exposure.

Animals↗
PubMed1989

Deposition of cigarette smoke particles in the rat.

The fractional deposition of cigarette smoke particles in the respiratory tracts of rats was studied. Male and female rats were conditioned in nose-only exposure tubes 25 min/day for 2 days, exposed to cigarette smoke at mass concentrations of 95 or 341 mg/m3, 25 min/day for 3 days, and then exposed to smoke at mass concentrations of 212 and 657 mg/m3, 25 min/day for 5 days. Mainstream cigarette smoke was generated by a modified Walton smoking machine from two 1R3 research cigarettes burned sequentially for each exposure. Deposition studies were conducted by placing the rats in plethysmograph tubes to allow respiratory minute volume measurements during exposure, then exposing them to [14C]dotriacontane-labeled cigarette smoke at mass concentrations of 202 or 624 mg/m3 for 25 min, using the same smoking machine. Size distribution, real-time concentration, and 14C activity of the smoke particles were determined using a multijet Mercer impactor, a real-time aerosol monitor, and filter samples, respectively. Immediately after the exposure, the rats were terminated to determine the distribution of the 14C. Individual lung lobes, trachea and lobar bronchi, head, larynx, kidneys, liver, gastrointestinal (GI) tract, blood, and depleted carcass of each rat were analyzed for 14C content. Results showed that the GI tract contained 16-31% of the total activity, indicating significant clearance from the large airways and nose to the GI tract during the exposure and during the 10-15 min between the cessation of the exposure and the removal of the organs. Total deposition of the inhaled 14C activity was 20.1 +/- 1.6% for both exposure concentrations. The intrapulmonary deposition fractions (lung lobes plus airways below the lobar bronchi) were 12.4 +/- 0.9 and 15.9 +/- 1.4% for concentrations of 202 and 624 mg/m3, respectively, suggesting a slight enhancement in upper airway deposition for animals exposed to the higher smoke concentration.

Alkanes↗
PubMed1989

Inhaled cigarette smoke induces preneoplastic changes in rat tracheal epithelial cells.

Rats were exposed 6 h/day, 5 days/week for 5 weeks to levels of cigarette smoke designed to deposit amounts of particulate per gram of lung similar to those experienced by a heavy smoker. Tracheal epithelial cells were isolated and examined in culture for the presence of preneoplastic variants. Two- to three-fold increases in the frequency of variants were observed in cells isolated from smoke-exposed animals compared to those from air-exposed controls. These results provide an estimate of the frequency of cigarette smoke-induced initiation events in respiratory epithelium that will be useful in further defining the role of cigarette smoke in the development of lung cancer.

Animals↗
PubMed1989

[Brain energy metabolism of cerebral ischemic mice and the effects of some drugs].

Two simple cerebral ischemic models of mice were used for studying brain energy metabolism and the effects of drugs. Model one is partial occlusion of the left carotid artery and total occlusion of the right one including the vagus. The behavior of the animals appeared splaying of the contralateral extremities, circling around counterclockwise and in a comatose motionless state. Following the designated ischemic time, the animals were put into liquid N2. Model two is decapitation induced ischemia of mouse brain. The whole animal (control) and the severed head were rapidly frozen in liquid nitrogen 0, 10, 30, 60 s after decapitation. Brain samples were powdered at liquid N2 temperature, extracted and determined for ATP, phosphocreatine (Pcr) and lactic acid (LA). The data from model one indicate that after an ischemic period of 10 min, brain LA level increased significantly compared with values from the sham operated group, while no significant alteration was observed in brain ATP, and Pcr level. At 180 min of ischemia, levels of ATP and Pcr were considerably reduced while LA level increased significantly. The degree of symptoms induced by brain ischemia showed good correlation with brain energy metabolism. In model 2 brain LA level was found to be increased, while ATP and Pcr levels decreased after whole brain ischemia. However, brain ATP and Pcr levels were increased and LA level was decreased significantly in the normal and ischemic animal after administration of phenobarbital (225 mg/kg ip). LA level decreased significantly in the unischemic mice treated with Rb1 (100 mg/kg ip). It is indicated that both models of cerebral ischemia were simple and sensitive methods for studying brain ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1987

Effect of dose on the absorption and excretion of [14C]benzene administered orally or by inhalation in rats and mice.

The effect of dose on the absorption and excretion of [14C]benzene was studied using 13-week old male F344/N rats, Sprague-Dawley rats, and B6C3F1 mice. Gastrointestinal absorption of benzene administered by gavage was greater than 97% in these species for doses between 0.5 and 150 mg benzene/kg body wt. At oral doses below 15 mg/kg, greater than 90% of the 14C excreted was in the urine as nonethylacetate extractable material. Above 15 mg/kg, in both rats and mice, an increasing percentage of the administered benzene was exhaled unmetabolized, suggesting saturation of metabolic pathways. Above 50 mg/kg, total metabolites (as determined by 14C in the urine, feces, and carcass after 2 days) were not linearly related to administered dose. Total metabolites per unit body weight was equal in F344/N rats and B6C3F1 mice at gavage doses up to 50 mg/kg; however, total metabolites in mice did not increase at higher doses. For inhalation exposures, the percentage of inhaled benzene that was absorbed and retained during a 6-hr exposure decreased from 33 +/- 6% (mean +/- standard deviation) to 15 +/- 9% in rats, and from 50 +/- 15 to 10 +/- 2% in mice as the exposure concentration was increased from approximately 26 to 2600 micrograms/liter (10 to 1000 ppm at 615 Torr, 23 degrees C). Total metabolite formation was exponentially related to the benzene exposure concentration with one-half the maximal amount of metabolite formation occurring at 220 micrograms/liter (84 ppm) for B6C3F1 mice and 650 micrograms/liter (250 ppm) for F344/N rats. Total metabolites were higher in mice than in rats at any of the vapor concentrations used due mainly to the higher amount inhaled by mice. Saturation of overall metabolism in mice but not in rats at high doses by both routes of administration indicates species differences in metabolism of benzene.

Administration, Inhalation↗
PubMed1986

Significance of residual tumor at the esophageal stump after resection for carcinoma.

Residual tumor at the esophageal stump was found in 103, or 14.3%, of a series of 719 resected esophageal specimens for carcinoma. The residual tumor pathologically presented as basal epithelial-cell carcinomatous change in 16 (15.5%), carcinoma in situ in 26 (25.5%), invasive carcinoma in 51 (49.5%), and cancerous emboli in 6 (5.8%) cases. A follow-up study of the 719 patients showed that the long-term survival rate of those with residual tumor was significantly lower than that of those without. Factors of occurrence besides inadequate resection were analyzed, and indications of surgical treatment were recommended. The presence of residual tumor is not an important factor in the development of anastomotic leakage.

Anastomosis, Surgical↗