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Biomedical subjects

D Tang

Publications and source records attributed to D Tang.

At least 163 records · Page 9Linked to original sources
PubMed1991

Biologic markers in ethylene oxide-exposed workers and controls.

Ethylene oxide (EtO) is an alkylating agent and a model direct-acting mutagen and carcinogen. This study has evaluated a panel of biologic markers including EtO-hemoglobin adducts (EtO-Hb), sister-chromatid exchanges (SCEs), micronuclei, chromosomal aberrations (CAs), DNA single-strand breaks (SSB) and an index of DNA repair (ratio of UDS to NA-AAF-DNA binding) in the peripheral blood cells of 34 workers at a sterilization unit of a large university hospital and 23 controls working in the university library. Comprehensive environmental histories were obtained on each subject including detailed occupational and smoking histories. Industrial hygiene data obtained prior to the study and personal monitoring during the 8 years preceding the study showed that workers were subject to low-level exposure near or below the current Occupational Safety and Health Administration (OSHA) standard of 1 ppm (TWA). Personal monitoring data obtained during 2 weeks prior to blood sampling were uniformly less than 0.3 ppm (TWA). After adjusting for smoking, EtO workplace exposure was significantly (p less than 0.001) associated with EtO-Hb (a carcinogen-protein adduct) and 2 measures of SCEs [the average number of SCEs/cell (SCE50) and the number of high frequency cells (SCEHFC)]. There was an apparent suppression of DNA repair capacity in EtO-exposed individuals as measured by the DNA repair index; i.e., the ratio of unscheduled DNA synthesis (UDS) and NA-AAF-DNA binding (p less than 0.01). No association of DNA repair index with smoking was found. Another important finding of this study is the highly significant correlation between EtO-Hb adduct levels and SCEHFC (p less than 0.01) and SCEs (p less than 0.02) which provides evidence of a direct link between a marker of biologically effective dose and markers of genotoxic response. In contrast, micronuclei, CAs and SSBs were not significantly elevated in the workers. The activity of the u-isoenzyme of glutathione-S-transferase (GT) was measured as a possible genetic marker of susceptibility and a modulator of biomarker formation. However, possibly because of confounding by age, no significant relationships were found between GT and any of the exposure-related markers by ANOVA or among other independent variables by regression. This study demonstrates significant effects of low-level EtO exposure, independent of smoking history, near or below 1 ppm on multiple biomarkers and suggests that the current OSHA standard may not be adequately protective. Previously described effects of smoking on EtO-Hb adducts, SCEs and SCEHFC were also seen in this study.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1991

[Experimental acupuncturology and its role in acupuncture education--suggestion offering the course of experimental acupuncture in acupuncture education].

Experimental Acupuncturology is a new subject which probes the channel and principle of acupuncture with the help of modern scientific technique and experimental method. In channel research, the basic responsibility of Experimental Acupuncturology is to expand the essence of the channel. For nearly half a century, the research has been concentrated mainly on the channel detection, the phenomena of channels and the relationship between channel-point and viscera, etc. In the research on the principle of acupuncture, Experimental Acupuncturology has accumulated a lot of information to prove that therapeutic effect of acupuncture is credible. The effect of acupuncture is influenced by many factors. Thus, it is also one of the basic tasks for Experimental Acupuncturology to programme the experimental procedure according to the principles of diagnosis and treatment based on an overall analysis of symptoms and signs, so that the best wiring scheme can be chosen out. Summarily, Experimental Acupuncturology has, at beast, three important significances in training modern specialists of acupuncture medicine. Firstly, it can make it possible for students to get deeper understanding on the thought of traditional acupuncture and realize the advantage of acupuncture, thus, encourage their faith on this medical means. Secondly, it can enrich the contents of acupuncture medicine and broaden the outlook of students, because it introduces modern science, technology and experimental method into traditional theory. Finally, it can train students' ability in scientific researches through strengthening the practicability of acupuncture. Therefore, its active significance in acupuncture education has been granted by acupuncture specialists in our country. Nowadays, more and more colleges of TCM has offered this subject which were welcome widely.(ABSTRACT TRUNCATED AT 250 WORDS)

Acupuncture Therapy↗
PubMed1990

Regulation and molecular characterization of dopamine D2 receptors in a prolactin-secreting 7315a anterior pituitary tumor.

The regulation and molecular properties of the dopamine (DA) D2 receptors were compared in the prolactin-secreting 7315a anterior pituitary tumor with those in the striatum of rats. Chronic treatment with haloperidol increases the maximal binding for [3H]spiroperidol in tumor and striatum, but the percent increase is much higher in tumor than in striatum. Photoaffinity labelling of DA D2 receptors with N-(p-azido-m-[125I]iodophenethyl)spiperone ([125I]N3-NAPS) yielded a major specifically labeled peptide with the Mr of 32-34 kDa in tumor, and two specifically labeled peptides with Mr of 32-34 and 92-94 kDa in striatum. The analysis of DA D2 receptor mRNA shows that the size is similar in tumor and striatum. The DA D2 receptor mRNA in tumor is very low and chronic treatment with haloperidol produces a considerable increase of the specific mRNA. It is postulated that the reported defect in regulation of prolactin release by DA agonists might be due to posttranslational changes in the tumor DA D2 receptor.

Animals↗
PubMed1989

Antibodies to a synthetic peptide corresponding to a Ser-40-containing segment of tyrosine hydroxylase: activation and immunohistochemical localization of tyrosine hydroxylase.

A peptide corresponding to position 32-47 in tyrosine hydroxylase was synthesized (TH-16) and polyclonal antibodies against this peptide were raised in rabbits (anti-TH-16). The effects of anti-TH-16 on modulation of tyrosine hydroxylase activity were investigated. Anti-TH-16 enhanced the enzymatic activity in a concentration-dependent manner, and the antigen TH-16 inhibited the stimulatory activity of the antiserum in a concentration-dependent manner. The activated enzyme had a lower Km app for the cofactor 2-amino-4-hydroxy-6-methyl-5,6,7,8-tetrahydropterin and a higher Vmax app than the nonactivated enzyme. Anti-TH-16 was characterized further by its ability to immunoprecipitate the enzyme activity by labeling tyrosine hydroxylase after Western blotting and by immunohistochemical labeling of catecholaminergic neurons. Anti-TH-16 did not block activation of tyrosine hydroxylase by phosphorylation catalyzed by cyclic AMP-dependent protein kinase. Exposure of the enzyme to anti-TH-16 and subsequent phosphorylation of the enzyme resulted in a greater activation of the enzyme than the sum of activation produced by these two treatments separately. However, the activation was less than additive when the enzyme was first phosphorylated and subsequently exposed to anti-TH-16. The present study demonstrates the utility of anti-TH-16 in investigating the molecular aspects of the enzyme activation.

Adrenal Gland Neoplasms↗
PubMed1989

Plasminogen activator and plasminogen activator inhibitor activities in men with coronary artery disease.

Although elevated levels of plasminogen activator inhibitor-1 (PAI-1) have been associated with the development of myocardial infarction, the correlation between the presence of coronary artery disease and increased levels of PAI-1 is controversial. The present study evaluated the association between angiographically-documented coronary artery disease and plasma levels of PAI-1 and tissue-type plasminogen activator (t-PA) in 65 men (ages 35 to 65 years) who had no previous history of myocardial infarction, angioplasty, or other medical illnesses. PAI-1 activity in these 65 patients was inversely correlated with t-PA activity, which was measured before and after venous occlusion. PAI-1 activity correlated positively with levels of triglycerides. There was a significant negative correlation between PAI-1 activity and levels of high-density lipoprotein. Each patient was placed in one of five groups according to the severity of coronary atherosclerosis, which ranged from normal vessels (group I) to greater than 50% occlusion of three vessels (group V). There were no significant differences among the five groups with respect to mean activity of PAI-1 (p = 0.98) or t-PA activity measured before venous occlusion (p = 0.22) or after occlusion (p = 0.70). T-PA and PAI-1 activities in these five groups were not different from those in 35 healthy men. These data indicate that there is no association between activities of PAI-1 or t-PA and coronary artery disease in this well-characterized male population.

Adult↗
PubMed1981

Measurement of excretion characteristics of theophylline and its major metabolites.

Analysis of urinary excretion after administration of 320 mg of theophylline to six normal volunteers appears to indicate the occurrence of capacity limited formation of most of the theophylline metabolites and non-linear renal excretion of theophylline. The renal clearance is elevated at high concentrations where the metabolic clearance is reduced. Even though the individual process of elimination is non-linear, the compensating relationship appears to yield a constant total elimination clearance. The implication of these results in chronic therapy and dose adjustment is discussed.

Humans↗
PubMed1979

Projections of lamprey spinal neurons determined by the retrograde axonal transport of horseradish peroxidase.

The spinal cords of larval sea lampreys (Petromyzon marinus) and adult river lampreys (Ichthyomyzon unicuspis) were injected with horseradish peroxidase through a transection 1 cm caudal to the last gill. Some animals also had a spinal hemisection 1 cm caudal to the injection. After recovery periods of 1 to 52 days, the spinal cords were treated with diaminobenzidene and hydrogen peroxide, and the projections of various cell types determined in wholemount slides. From these observations the following conclusions were drawn. Most dorsal cells (primary sensory cells) are bipolar with a long rostral projection and a short caudal projection of no more than 5-10 mm. Both processes travel in the ipsilateral dorsal column. Their peripheral processes enter the dorsal roots as branches of their central axons. Some dorsal cells send processes out three or more dorsal roots both rostral and caudal to the cell body. Myotomal motoneurons have characteristic locations in the medial gray column and send prominent transversely oriented dendrites into the lateral columns. A few motoneurons are unusually large. In addition to giant interneurons the majority of smaller rostrally projecting interneurons also have decussating axons. A recently described cell type, the oblique bipolar cell, appears to have an exclusively crossed rostral projection. Although most edge cells project rostrally, as many as 20% may have a caudal projection or both rostral and caudal projections. Edge cells project equally to the ipsilateral and contralateral spinal hemicord, but their processes do not extend more than about 18 mm in sea lamprey larvae and 37 mm in adult river lampreys. Lateral cells project exclusively to the ipsilateral caudal hemicord. A few cells which resemble lateral cells in location and in possessing large lateral dendrites, project rostrally. However, these have atypical morphologic features which probably distinguish them from true lateral cells. Thus far, regardless of cell type, all decussating axons seem to pass ventral to the central canal, while decussating medial dendrites pass dorsally.

Animals↗
PubMed1979

Mechanical problems in the use of the intra-aortic balloon.

Although there are many complications in the use of the intraortic balloon (IAB) support device, they are relatively benign compared to the benefits of the device. The purpose of this paper is, firstly, to review a protocol in the safe use of this device, and secondly to remind enthusiastic users of the IAB that the use of this method is not always as benign as we would like it to be. Rarely reported findings at postmortem examination in two patients who died in cardiogenic shock are described. The aorta of one of the two cases in this report had a longitudinal tear which involved only the intima and extended from the common femoral artery to well above the renal arteries. In the second case, the balloon tip had entered at the bifurcation of the aorta in a subintimal manner and had re-entered well below the renal arteries, to be relocated in the proper site in the descending aorta.

Aortic Dissection↗
PubMed1978

Purification of a DNA nicking-closing enzyme from mouse L cells.

A DNA nicking-closing enzyme has been purified from the nuclei of mouse L cells to 90% homogeneity. The denatured and reduced form of the enzyme has a molecular weight of 68,000 which is in agreement with the molecular weight of the native enzyme as determined by gel filtration and by sucrose sedimentation velocity assuming the protein is globular. Therefore, the active form of the enzyme is a monopolypeptide. Its isoelectric point is pH 4.2 +/- 0.2. The nicking-closing activity does not require a cofactor and does not involve any sulfhydryl group. The enzyme requires 0.2 M NaCl and pH in the range of 6.5-7.5 for optimal activity.

Cell Nucleus↗
PubMed1975

Action of nicking-closing enzyme on supercoiled and nonsupercoiled closed circular DNA: formation of a Boltzmann distribution of topological isomers.

Highly purified nicking-closing enzyme from mouse cells in 20-fold enzyme/substrate excess converts closed circular native PM2, ColE1, and Minicol DNA into limit product sets of DNAs. Each set has a mean degree of supercoiling of approximately zero. The individual species in the sets differ by deltatau = +/-1, +/-2, etc., and the relative masses fit a Boltzmann distribution. It was also demonstrated that "nonsupercoiled" closed circular duplex molecules serve as substrates for the nicking-closing enzyme, and that a distribution of topological isomers is generated. Polynucleotide ligase, acting on nicked circular DNA, forms under the same conditions, the same set of closed DNAs. The latter enzyme freezes the population into sets of molecules otherwise in configurational equilibrium in solution.

Animals↗