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J S Chen

Publications and source records attributed to J S Chen.

At least 19 recordsLinked to original sources
PubMed1992

Bipartite structure of the downstream element of the mouse beta globin (major) poly(A) signal.

The downstream region of the mouse beta (major) globin poly(A) signal was mutated and analyzed for function in transfected COS cells. From analysis of unidirectional Bal31 deletions, the 3' boundary of the downstream element was defined as +22 (22 nucleotides downstream from the cleavage site). Analysis of cluster mutations, in which 5 or 6 adjacent bases were replaced with a random CA-containing sequence in a manner that did not alter spacing, confirmed +22 as the 3' boundary of the downstream element. The analysis also revealed two short UG-rich sequences, located from +5 to +10 and from +17 to +22, as major functional components. In contrast, a more refined series of mutations, in which clusters of 3 bases were replaced, failed to cause loss of function. We conclude that the downstream element of the mouse beta globin poly(A) signal is bipartite in structure, and that portions of its sequence are functionally redundant.

Animals↗
PubMed1992

Molecular dosimetry of urinary aflatoxin-DNA adducts in people living in Guangxi Autonomous Region, People's Republic of China.

Hepatocellular carcinoma is one of the five leading human cancers causing at least 250,000 deaths each year. One of the major risk factors for this disease is exposure to dietary aflatoxins, and the development of appropriate molecular dosimetry biomarkers would facilitate the identification of individuals at risk. This study was undertaken to explore the relationship between dietary intake of aflatoxins and the excretion of the major aflatoxin-DNA adduct and other metabolites into the urine of chronically exposed people. The following protocol was developed for this investigation in Guangxi Autonomous Region, People's Republic of China, where the diets of 30 males and 12 females (ages, 25-64 years) were monitored for 1 week and aflatoxin intake levels determined each day. Starting on the fourth day, total urine volumes were obtained in consecutive 12-h fractions for 3 or 4 days. High performance liquid chromatography and competitive radioimmunoassay analyses were done on each of the urine samples, and the relationships between excretion of total aflatoxin metabolites, aflatoxin-N7-guanine, aflatoxin M1, aflatoxin P1, and aflatoxin B1, and aflatoxin B1 intake values were determined. The average intake of aflatoxin B1 by men was 48.4 micrograms/day, giving a total mean exposure during the study period of 276.8 micrograms. The average daily intake by women was 77.4 micrograms/day, resulting in a total average exposure during the 7-day period of 542.6 micrograms aflatoxin B1. Initial efforts to characterize aflatoxin metabolites in urine samples were with an analysis by competitive radioimmunoassay. The analysis by linear regression of the association between aflatoxin B1 intake/day and total aflatoxin metabolite excretion/day showed a correlation coefficient of only 0.26. These findings stimulated the immunoaffinity/analytical high performance liquid chromatography analysis for individual metabolites. When the data were analyzed by linear regression analysis, the aflatoxin N7-guanine excretion and aflatoxin B1 intake from the previous day showed a correlation coefficient of 0.65 and P less than 0.000001. Similar analysis for aflatoxin M1 resulted in a correlation coefficient of 0.55 and P less than 0.00001, whereas there was no positive statistical association between exposure in the diet and aflatoxin P1 excretion, despite aflatoxin P1 being quantitatively a major metabolite. Analysis of the total aflatoxin-N7-guanine excretion in the urine during the complete collection period plotted against the total aflatoxin B1 exposure in the diet for each of the individuals, smoothing the day to day variations, revealed a correlation coefficient of 0.80 and P less than 0.0000001.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Spontaneous loss of HBsAg in children with chronic hepatitis B virus infection.

Spontaneous loss of HBsAg is infrequent in adult HBV carriers. Little is known about this serological change in children. In a prospective study of 420 hepatitis B virus-carrier children who were observed for 1 to 12 yr (mean = 4.3 yr), spontaneous loss of HBsAg occurred in 10 patients, with an average incidence of 0.6%/yr. The HBsAg clearance rate was significantly higher in children who had anti-HBe; children who were at an older age on entry; children whose mothers were HBsAg-; or children with severe liver histological changes detected while they were HBeAg+. Children who seroconverted from HBeAg to anti-HBe before the age of 6 or who had a peak serum ALT level above 100 IU/L were more likely to clear HBsAg. In all 10 patients who became HBsAg-, serum hepatitis B virus DNA became undetectable by both spot hybridization and the polymerase chain reaction, suggesting a complete clearance of the virus from serum. After the loss of HBsAg, the anti-HBs levels were higher in the children born to carrier mothers than in those born to noncarrier mothers. These findings suggest that chronic hepatitis B virus-carrier children rarely lose HBsAg, especially if they have been infected during the perinatal period and have mild histological changes. The poor humoral immune response to HBsAg may be a contributing factor in the establishment of carrier status during horizontal infection but may not be primarily involved in the establishment of carrier status during perinatal infection.

Adolescent↗
PubMed1992

Peripheral blood hematopoietic progenitor cells in beta-thalassemia major.

Colony assays in methylcellulose (semisolid medium) of erythroid precursors and granulocyte-macrophage precursors from the peripheral blood of 34 patients with beta-thalassemia major and 31 age-matched normal controls were studied. In patients homozygous for beta-thalassemia, a significant increase of circulating erythroid progenitor cells to 3-5 times of normal controls was observed. Furthermore, the number of circulating colony forming units-granulocyte-macrophage (CFU-GM) and colony forming units-mixed (CFU-Mixed) also increased significantly. In these subjects, there was a linear relationship between the number of burst forming units-erythroid (BFU-E) and CFU-GM. The serum level of erythropoietin (EPO) was also significantly higher than that of normal controls (p < 0.05). The increased hematopoiesis, indicated by an increased number of circulating hematopoietic progenitor cells and an elevated serum level of EPO, suggests that the physiologic regulation of erythropoiesis still operated in patients with beta-thalassemia major.

Adolescent↗
PubMed1992

Pelvic peritoneal reconstruction to prevent radiation enteritis in rectal carcinoma.

Some patients with rectal cancer who undergo exenterative surgery may require radiation therapy as an adjuvant treatment for recurrent or residual disease. A common devastating side effect of this treatment modality is radiation enteritis, a radiation-induced small bowel injury. Hence, the prevention of such a complication is essential for both the surgeon and the radiation oncologist. A new surgical method using the posterior rectus sheath and peritoneum to partition the abdominal cavity at the level of the umbilicus to the sacral promontory seems to accomplish this purpose, keeping the small bowel away from the pelvic cavity. After removal of the rectal lesion [eight abdominoperineal resections (APRs), nine Hartmann's procedures, and one low anterior resection (LAR)] in 18 patients with rectal cancer, this new surgical procedure was performed. One of the patients had an early postoperative intestinal obstruction, and all but one of the patients received postoperative adjuvant radiation therapy. In addition, a small bowel series was performed before the radiation therapy and six months and one year after surgery. Upon examination, most of these patients still had their small bowel kept intact in the abdominal cavity. During the follow-up period of 10 months to 2 years with an average of 18 months, two late complications of intestinal obstruction were noted. Exploratory laparotomy of these two patients revealed radiation enteritis of the small bowel. Therefore, the failure rate of the following procedure is 12 percent, since 2 of the 17 patients received small bowel injury. Although the follow-up period for this surgical method is short, the results have encouraged us to continue the use of this procedure on advanced rectal cancer patients who require postoperative radiation therapy.

Abdominal Muscles↗
PubMed1992

Postoperative adjuvant radiotherapy in Astler-Coller stages B2 and C rectal cancer.

Between 1979 and 1983, 127 patients with Stages B2 or C rectal cancer treated with surgery plus postoperative adjuvant radiotherapy (RT group) and 122 patients treated with surgery alone (S group) were compared to evaluate the effect of postoperative radiotherapy on survival and disease recurrence. Each group was stratified into subgroups according to stage and tumor differentiation as follows: Subgroups BW (Stage B2 and well-differentiated tumor), BM (Stage B2 and moderately differentiated tumor), CW (Stage C and well-differentiated tumor), CM (Stage C and moderately differentiated tumor), and P (poorly differentiated tumor). Ninety-five percent of the patients were followed until death or, if alive, to five years after surgery. Postoperative radiotherapy was associated with a reduced five-year survival rate in Subgroup BW (67 vs. 87 percent; P = 0.02). In the remaining subgroups of the RT group, there was a statistically insignificant trend toward a worse survival rate (56 vs. 65 percent, 47 vs. 64 percent, 41 vs. 46 percent, and 50 vs. 36 percent for Subgroups BM, CW, CM, and P, respectively). The local failure rates for the S group and RT group were 10 vs. 23 percent (P = 0.15) in Subgroup BW, 32 vs. 21 percent (P = 0.4) in Subgroup BM, 24 vs. 25 percent (P = 0.6) in Subgroup CW, and 18 vs. 18 percent (P = 0.6) in Subgroup CM, respectively. Eight percent (9/127) had severe or life-threatening radiation-related complications. Postoperative adjuvant radiotherapy alone did not improve the survival of patients with Stages B2 or C rectal cancers. It may have led to worsened survival in the subgroup of patients with well-differentiated Stage B2 rectal cancer.

Adenocarcinoma↗
PubMed1992

Transesophageal echocardiography in adults with a continuous precordial murmur.

In order to assess the ability of echocardiography in the detection of intracardiac and extracardiac shunts, we studied 11 patients (aged 22-64 yr) with a continuous precordial murmur using transthoracic and transesophageal echocardiography, and correlated the results with the subsequent angiographic and surgical findings. We found that only in 5 of 6 patients with a patent arterial duct could the continuous flow pattern be detected in pulmonary artery using transthoracic echocardiography, whereas it could be readily and accurately identified by transesophageal echocardiography in all patients. The diameters of the patent arterial duct were also measured and found to be in good correlation with subsequent surgical findings (r = 0.98, p less than 0.05). In 2 patients with a ruptured aneurysm of sinus of Valsalva which originated from the right coronary sinus and perforated into the right ventricle, transesophageal echocardiography gave a better image than transthoracic echocardiography. In 2 patients with coronary artery fistula, the origin and site of drainage of the coronary artery could be imaged using transesophageal echocardiography, but the course of coronary artery fistula was more easily detected by transthoracic echocardiography. In one patient with aortopulmonary window, the defect between ascending aorta and main pulmonary artery could readily be imaged by transesophageal echocardiography. We therefore recommend transesophageal echocardiography when evaluating patients with precordial continuous murmur in whom intracardiac and extracardiac shunts or defects are suspected.

Adult↗
PubMed1992

Cutaneous angiocentric T-cell lymphoma associated with Epstein-Barr virus.

BACKGROUND: Two unusual cases of cutaneous angiocentric T-cell lymphoma were found to be associated with Epstein-Barr virus infection. OBJECTIVE: The objective was to study the clinical course and the response of the disease to conventional chemotherapy. METHODS: Histologic specimens from both patients were studied. Clonal proliferation was assessed by Southern blot hybridization. RESULTS: The disease in both patients was rapidly progressive and responded poorly to aggressive treatment. Biopsy specimens showed infiltration of atypical lymphoid cells with angiocentricity and angiodestruction, which probably resulted in the observed tissue necrosis. Clonal proliferation of Epstein-Barr virus DNA was detected in tissue from primary skin lesions and disseminated nasal lesions. CONCLUSION: Epstein-Barr virus-associated angiocentric T-cell lymphoma in our patients was characterized by an aggressive course and resistance to conventional chemotherapy. A search for Epstein-Barr virus and the human T-lymphotropic virus should be performed in patients with atypical features of cutaneous T-cell lymphoma.

Adult↗
PubMed1992

Intracoronary PGE2 and veratrine inhibits renin release in conscious dogs via chemosensitive ventricular afferents.

1. Prostaglandins (PG) and veratrum alkaloids stimulate ventricular sensory receptors with non-myelinated vagal afferents and mediate inhibitory circulatory responses. 2. The present study in conscious instrumented dogs was carried out to determine the effects of intracoronary artery infusions of veratrine (Ver-IC) and PGE2 (PGE2-IC) on plasma renin activity (PRA). 3. A 15-20 mmHg decrease in arterial pressure was produced during Ver-IC (0.2-0.8 micrograms/kg per min) and PGE2-IC (10-50 ng/kg per min), but there was no change in PRA or heart rate. 4. In contrast, significant increases in PRA (+3.51 +/- 0.37 ng angiotensin I/mL per h; P less than 0.01) and heart rate (+38.5 +/- 6.2 beats/min; P less than 0.001) were elicited in response to a 15-20 mmHg decrease in arterial pressure produced by intravenous infusions of nitroprusside. 5. Pharmacological blockade of afferent fibres in the pericoronary region of the left main coronary artery during Ver-IC resulted in significant hypotension-induced increases in PRA (P less than 0.001) and heart rate (P less than 0.001), thus removing the inhibitory influence of chemosensitive ventricular afferents. 6. Therefore, intracoronary veratrum alkaloids and prostaglandins inhibit hypotension-induced increases in PRA and heart rate in the conscious dog. This is mediated by chemosensitive receptors located in the left ventricular myocardium along with afferent nerves in the pericoronary region and cervical vagi.

Animals↗
PubMed1992

Purification and properties of 3-hydroxybutyryl-coenzyme A dehydrogenase from Clostridium beijerinckii ("Clostridium butylicum") NRRL B593.

The enzyme 3-hydroxybutyryl-coenzyme A (CoA) dehydrogenase has been purified 45-fold to apparent homogeneity from the solvent-producing anaerobe Clostridium beijerinckii NRRL B593. The identities of 34 of the N-terminal 35 amino acid residues have been determined. The enzyme exhibited a native M(r) of 213,000 and a subunit M(r) of 30,800. It is specific for the (S)-enantiomer of 3-hydroxybutyryl-CoA. Michaelis constants for NADH and acetoacetyl-CoA were 8.6 and 14 microM, respectively. The maximum velocity of the enzyme was 540 mumol min-1 mg-1 for the reduction of acetoacetyl-CoA with NADH. The enzyme could use either NAD(H) or NADP(H) as a cosubstrate; however, kcat/Km for the NADH-linked reaction was much higher than the apparent value for the NADPH-linked reaction. Also, NAD(H)-linked activity was less sensitive to changes in pH than NADP(H)-linked activity was. In the presence of 9.5 microM NADH, the enzyme was inhibited by acetoacetyl-CoA at concentrations as low as 20 microM, but the inhibition was relieved as the concentration of NADH was increased, suggesting a possible mechanism for modulating the energy efficiency during growth.

Amino Acid Sequence↗
PubMed1992

Acute volume expansion enhances baroreceptor discharge in dogs.

By recording single-unit discharge from the carotid sinus nerve of normal dogs in the control and in the volume-expanded state, both with the sinus open to the circulation and with it isolated, the effects of acute volume expansion on baroreceptor discharge sensitivity were investigated. The carotid sinus was vascularly isolated except for the common carotid and external carotid arteries. Inflation of hydraulic occluders on these vessels completely isolated the sinus from the systemic circulation. Flow and diameter changes of the carotid sinus were measured. Plasma volume was expanded with isotonic, isoncotic dextran in normal saline until the left ventricular end-diastolic pressure reached a value of 20-25 mmHg. In the group with the sinus open to the circulation, volume expansion did not depress baroreceptor discharge sensitivity; in fact, it augmented baroreceptor activity (peak discharge = 39.2 +/- 1.6 vs. 49.9 +/- 3.3 spikes/s, P less than 0.05). There was no such effect in the group with the sinus isolated from the circulation during volume expansion. In the group with the sinus open to the circulation, volume expansion significantly increased flow through the common carotid artery and shifted the carotid sinus pressure-diameter curves upward without a change in compliance. These data suggest that acute volume expansion augments baroreceptor discharge, and this phenomenon may be mediated either by some circulating substance(s) or by an increase in flow through the carotid sinus during volume expansion.

Animals↗
PubMed1992

Baro- and ventricular reflexes in conscious dogs subjected to chronic tachycardia.

It has been well documented that the arterial baroreflex is depressed in chronic congestive heart failure. Furthermore, cardiopulmonary reflexes have also been shown to be depressed in heart failure. Because cardiac reflexes can be mediated by both mechanical and chemical stimuli, we undertook the current study to determine whether chemically activated cardiac reflexes (Bezold-Jarisch) are abnormally depressed in dogs with chronic heart failure at a point in time when arterial baroreflexes were clearly depressed. We studied heart rate and arterial pressure responses in 13 conscious instrumented dogs before and after chronic ventricular pacing at 250 beats/min for 4-5 wk. At the time the study was done each dog showed both hemodynamic and clinical signs of congestive heart failure. The arterial baroreflex was evaluated by analyzing the heart rate response to acute injections of phenylephrine and nitroglycerin. The Bezold-Jarisch reflex was assessed in nine dogs by determining the heart rate and blood pressure responses to intracoronary injections of various doses of veratridine. Arterial baroreflex responses were uniformly depressed following ventricular pacing. The phenylephrine slope was reduced by 55.8 +/- 6.9% (P < 0.001), and the nitroglycerin slope was reduced by 67.9 +/- 5.0% (P < 0.0001) in the heart failure state. Significant bradycardia and hypotension were seen at each dose of veratridine given (0.01, 0.1, and 0.4 microgram/kg). When compared with the prepaced control state, the magnitude of the hypotension was no different in the heart failure state in response to any dose of veratridine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

[Clinical study of 76 cases of counterattack induced by acute organic phosphorus pesticides intoxication].

76 cases of counterattack induced by acute organic phosphorus pesticides intoxication were analysed. The activity of cholinesterase did not show a significant difference before the counterattack as compared to that after the counterattack (P > 0.05). The average dosage of atropine for pre-atropinization was 58.6 +/- 2.7 mg/h and it was 203.9 +/- 17.7 mg/h between the post-counterattack and the second atropinization (P < 0.01). Compared the mortality in reaching and non-reaching the second atropinization was 22.8% VS 100% (P < 0.01). The survival rate was 37.5% in collaborating blood transfusion cases and 20.6% in noncollaborating ones (P > 0.05). We also studied on the treatment, mechanism, precursory symptoms, causes of death, degrees of intoxication and pesticide types etc.

Adolescent↗
PubMed1992

Operative laparoscopy in benign cystic teratoma of ovary.

Eighteen women of reproductive age underwent laparoscopic management of unilateral ovarian benign cystic teratoma from 3 to 7 cm in diameter. Nine patients received pelviscopic enucleation of ovarian cysts and nine patients received unilateral oophorectomy or salpingo-oophorectomy. No major surgical complication was encountered and the hospital stay was short. Our series suggest that operative laparoscopy is a safe and effective method in the management of benign cystic teratoma.

Adult↗
PubMed1992

Pericardiocentesis: a 20 patients study.

Emergency pericardiocentesis, guided by a two-dimensional echocardiography, was performed on twenty patients with symptomatic pericardial effusion of various types and causes. There were fourteen men and six women. The underlying causes were: primary lung cancer (6 cases), metastatic cardiac tumors (3 cases), tuberculosis (4 cases), complicated interventional procedures with cardiac chamber or vessel perforations (2 cases), dissecting aortic aneurysm (1 case), systemic lupus erythematous (1 case), idiopathic pericarditis (1 case), bacterial pericarditis (1 case), and myxedema heart disease (1 case). Seventeen cases were performed through the left xipho-sternal approach and 3 cases through the apical approach. None of the patients died as a result of these procedures. A two-dimensional echocardiogram is useful in diagnosing cardiac tamponade as well as in guiding pericardiocentesis, and obtaines highly positive results (20/20). The positive rate of pericardial fluid cytology for malignant cells was 89% (8/9), however, pericardial fluid cultures or direct smear for tuberculosis were negative (0/4). In cancer patients, the mean survival time following pericardiocentesis was 4.2 months (range, 1-7.8 months). We concluded that neoplastic involvement of the pericardium is the most frequent cause of symptomatic pericardial effusion. Pericardiocentesis assisted by a two-dimensional echocardiogram is safe and easy. In addition, pericarditis caused by TB is still significant and must be considered in every case in our nation.

Adult↗