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Biomedical subjects

J Tang

Publications and source records attributed to J Tang.

At least 325 records · Page 18Linked to original sources
PubMed1996

An opioidergic cortical antinociception triggering site in the agranular insular cortex of the rat that contributes to morphine antinociception.

We report an anatomically defined opioid-responsive site in the rostral agranular insular cortex (RAIC) of the rat and characterize the antinociception produced by morphine acting within this region. Immunohistochemistry for the mu-opioid receptor identified a discretely localized cluster of densely labeled dendrite-like processes in the agranular insular cortex. The antinociceptive effect of morphine microinjected unilaterally into this area was evaluated using the formalin test. Antinociception was observed in both ipsilateral and contralateral hindpaws. Local pretreatment with naltrexone in the RAIC blocked the antinociception of local morphine injection, confirming that morphine was acting at an opioid receptor. Unilateral injection of naloxone methiodide into the RAIC reversed the behavioral antinociception of systemic morphine bilaterally in the formalin test. Evidence for a descending inhibitory mechanism acting on spinal nociceptive neurons was obtained by monitoring noxious stimulus-induced c-fos expression in rats having undergone formalin testing and by electrophysiological recording of single units in the lumbar dorsal horn after localized application of morphine into the RAIC. A significant reduction in the number of Fos-like immunoreactive neurons was found ipsilateral to the formalin stimulus in nociresponsive areas of the dorsal horn after on-site injections of morphine into the RAIC. Electrophysiological recording of nociresponsive dorsal horn neurons demonstrated a naloxone-reversible reduction in noxious thermal stimulus-evoked firing after morphine injection into this same area. These results suggest that the RAIC contributes to opioid-receptor-mediated antinociception after either local or systemic morphine administration and that these effects may be associated with an increased descending inhibition of dorsal horn neurons.

Animals↗
PubMed1996

Crystal structures of complexes of a peptidic inhibitor with wild-type and two mutant HIV-1 proteases.

Crystal structures of the protease of human immunodeficiency virus type 1 (HIV-1) and two mutant proteases, V82D and V82N, have been determined. In all three cases the enzyme forms a complex with the peptidic inhibitor U-89360E. All structures have been determined to 2.3 A resolution and have satisfactory agreement factors: 0.173 for wild type, 0.175 for V82D, and 0.182 for V82N. Comparison of the three crystal structures provides explanations which are consistent with the known kinetic properties of these mutant enzymes with the U-89360E inhibitor [Lin, Y., Lin, X., Hong, L., Foundling, S., Heinrikson, R. L., Thaisrivongs, S., Leelamanit, W., Raterman, D., Shah, M., Dunn, B.M., & Tang, J. (1995) Biochemistry 34, 1143-1152]. Unfavorable van der Waals interactions between the inhibitor and the mutated side chains at position 82 are consistent with diminished affinity for the inhibitor by the mutant enzymes. If a mutation is potentially resistant to an inhibitor, the mutant enzyme should not only have an increased Ki for the inhibitor but should also preserve considerable catalytic capability. The V82D mutant possesses these qualities. In the V82D crystal structure, a water molecule, which connects the protease flap to the inhibitor, is missing or of low occupancy. Absence of this bridge may be important in determining catalytic capability. Moreover, mutation at position 82 induces change in two polypeptide backbone regions, 35-41 and 67-68, which may be related to protease flap mobility.

Crystallography, X-Ray↗
PubMed1996

Nck inhibits NGF and basic FGF induced PC12 cell differentiation via mitogen-activated protein kinase-independent pathway.

Proto-oncogene Nck, an adapter molecule containing three SH3 and one SH2 domains, binds to cell surface receptors and mediates mitogenic effects in the cells. Overexpression of Nck caused cell transformation in vitro and tumor formation in the nude mice. The mechanism of this action by Nck, however, remained unclear. Rat adrenal pheochromocytoma cell line PC12 provides a useful system for studying growth factor-regulated cell proliferation and differentiation. Serum and epidermal growth factor (EGF) stimulate proliferation, whereas nerve growth factor (NGF) and basic fibroblast growth factor (bFGF) cause growth arrest and sympathetic neurite outgrowth in these cells. To study the function of Nck, we generated stable clones of PC12 cells overexpressing the human Nck. We report here that the overexpressed Nck caused continued proliferation of PC12 cells even in the presence of NGF and blocked both the NGF- and bFGF-induced neurite outgrowth. Anti-sense but not sense oligonucleotides to the human Nck resumed the NGF-induced differentiation, indicating the specific inhibitory effect of Nck. Interestingly, Nck did not interfere with the kinetics of NGF- and EGF-stimulated protein tyrosine phosphorylation and the mitogen-activated protein kinase (MAPK) activation, suggesting that Nck inhibited the induced PC12 cell differentiation via a MAPK-independent mechanism. This study has provided a useful system for further understanding the function of Nck.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Quantification of volumetric coronary blood flow with dual-energy digital subtraction angiography.

BACKGROUND: As a solution to the well-documented problems associated with visual interpretation of coronary arteriograms, more physiological methods of assessing coronary artery stenosis are being investigated. Volumetric coronary blood flow (BF) can be a valuable aid in the analysis of functional significance of arterial obstruction. METHODS AND RESULTS: The left anterior descending coronary artery (LAD) of 15 anesthetized pigs (40 to 50 kg) was dissected free from the epicardium in its proximal portion, and a transmit-time ultrasound flow probe of the appropriate size was applied. A vascular occluder was positioned distal to the flow probe for flow adjustments. Contrast injections (2 to 4 mL/s for 3 seconds) were made into the left main coronary artery during image acquisition with a motion-immune dual-energy digital subtraction angiography (DE DSA) system. Tissue-suppressed energy-subtracted images were used to generate time-density curves. BF measurements were made in the LAD vascular bed with use of the time-density curve, with consideration that blood was momentarily replaced with contrast during the injection. In 19 comparisons, the mean BF, measured with the use of DE DSA, correlated extremely well with the mean ultrasound flow (DE DSA=0.90 ultrasound+3.10 mL/min, r=.96). Also, contrast injection increased the BF by an average of only 15% during the image-acquisition time interval. CONCLUSIONS: Accurate BF measurements can be made with motion-immune DE DSA. The BF measurements can be completed before the onset of significant changes in BF due to contrast injection. Furthermore, it is possible to make the BF measurements during routine coronary arteriography.

Angiography, Digital Subtraction↗
PubMed1996

Purification, characterization and partial amino acid sequencing of two new aspartic proteinases from fresh flowers of Cynara cardunculus L.

Two new aspartic proteinases have been isolated from stigmas of the cardoon Cynara cardunculus L. by a two-step purification procedure including extraction at low pH, gel filtration on Superdex 200, and ion-exchange chromatography on Mono Q. To follow the conventional nomenclature for aspartic proteinases, we have named these proteinases cardosin A and cardosin B. On SDS/PAGE, cardosin A migrated as two bands with apparent molecular masses of 31 000 Da and 15 000 Da whereas the chains of cardosin B migrated as bands of 34 000 Da and 14 000 Da. The partial amino acid sequences of the two cardosin revealed that they are similar but not identical, and that they differ from the previously reported cardoon proteinases named cynarases, which were assumed to be derived from a common precursor. Although the cardosins show some degree of similarity to each other, we could detect no immunological crossreactivity between them. Both cardosins were active at low pH and were inhibited by pepstatin, with Ki values of 3 nM for cardosin A and 1 nM for cardosin B, indicating that they belong to the class of aspartic proteinases. Significant differences between the two enzymes were also found for the Kcat/km values for the hydrolysis of two chromophoric synthetic peptides. The active-site ionization constants, pKe1 and pKe2, for cardosin A are 2.5 +/- 0.2 and 5.3+/- 0.2, whereas for cardosin B they are 3.73 +/- 0.09 and 6.7 +/- 0.1. The results herein described on the structural and kinetic properties of the cardosins indicate that they are the products of distinct genes which have probably arisen by gene duplication. A scheme for the proteolytic processing of the two enzymes is also proposed.

Amino Acid Sequence↗
PubMed1996

Interstitial diode laser hyperthermia in the treatment of subcutaneous tumor.

BACKGROUND AND OBJECTIVE: Interstitial Laser Hyperthermia (ILH) has been investigated since the early 80s in the treatment of deep seated tumors. The purpose of this study was to evaluate the efficiency of diode ILH (830 nm) in a subcutaneous tumor model. STUDY DESIGN/MATERIALS AND METHOD: The antitumoral effect of diode ILH was assessed in a randomized study performed on 80 Swiss nu/nu mice. The tumor model was a subcutaneously implanted HT29 colonic carcinoma. The animals were assigned to four groups of 20 mice: Groups 1 and 3 were treated by ILH, groups 2 and 4 were not treated (control groups). Tumors were removed on day 3 in groups 1 and 2, and on day 30 in groups 3 and 4. The treatment was performed on tumors of 8 mm in diameter and a volume of 140 mm3. A laser irradiation of 360 J (power: 0.2 W; irradiation time: 1800 s) was delivered through a 300 microns optical fiber implanted in the tumor. The laser parameters insured temperatures of 46 degrees C in the central part of the tumor and 42 degrees C at the periphery. Tumor features were evaluated on day 3 and day 30. RESULTS: Untreated tumors grew rapidly up to a mean volume of 241 mm3 on day 3 (group 2) and 2,000 mm3 on day 30 (group 4). Treated tumors regressed to a mean volume of 32 mm3 on day 3 (group 1). On day 30, 40% of the tumors had totally disappeared and 60% showed partial response with small and peripheral residual tumor of 172 mm3 on an average, as to say 11.2 times smaller than in group 4. CONCLUSION: ILH with a low power 830 nm diode laser is an efficient treatment of subcutaneous tumor model. Partial responses are attributed to an insufficient heating at the tumor periphery. More precise control of the peripheral tumor temperature will improve the ILH results.

Animals↗
PubMed1996

Study of heat shock protein HSP90 alpha, HSP70, HSP27 mRNA expression in human acute leukemia cells.

The expression of three heat shock proteins (HSPs)-HSP90 alpha, HSP70, HSP27 in cells obtained from 22 patients with leukemia, K562 erythroleukemia cell line, and normal blood cells was observed by means of RNA dot blot analysis. The results showed that the expression of the HSP27 gene was enhanced in 4 cases of acute lymphoid leukemia (ALL), 7 cases of acute nonlymphoid leukemia (ANLL) and 2 cases of myelodysplastic syndrome (MDS) as compared with that of the normal blood cells, yet there was no significant difference in the HSP27 expression between the ALL and ANLL cells. The expression of HSP70 in all the 5 ALL and ANLL patients was much lower than that of the normal subjects, except 1 case of ALL and 1 case of MDS, in which the expression was obviously enhanced. All the cases including 11 ANLL, 5 ALL and 1 MDS had higher HSP90 alpha expression than the normal subjects. The enhanced expression of HSP90 alpha in leukemia cells may be associated with the active and indefinite proliferation of leukemia cells. Our results also suggest that the high expression of the HSP27 gene may not be confined to a specific type of acute leukemia.

HSP70 Heat-Shock Proteins↗
PubMed1996

Interleukin-5 messenger RNA expression in peripheral blood CD4+ cells in asthma.

BACKGROUND: IL-5 has been implicated in the pathogenesis of asthma through its regulatory role on eosinophil survival, proliferation, and effector function. OBJECTIVE: The study was designed to investigate the relationships between IL-5 messenger RNA expression in circulating CD4+ cells and serum concentrations of eosinophil cationic protein (ECP), a marker of eosinophil activation, and disease activity in asthma. METHODS: IL-5 gene expression was assessed semiquantitatively in ex vivo stimulated CD4+ cells by reverse transcription-polymerase chain reaction and serum ECP concentration measured from venous blood samples collected from patients with acute severe asthma before the commencement of systemic steroid therapy (day 1) and on day 7 and from patients with stable asthma and healthy volunteers. RESULTS: IL-5 gene expression was significantly higher in patients with acute asthma before steroid treatment than in those with stable disease and healthy subjects (p < 0.0001). Similar results were obtained with serum ECP levels: levels in patients with acute asthma were highest (20.30 +/- 5.31 micrograms/L), followed by levels in patients with stable asthma (2.76 +/- 0.65 micrograms/L) and levels in normal control subjects (1.37 +/- 0.06 micrograms/L; p < 0.01 for all comparisons). Significant falls in both IL-5 expression and serum ECP level were seen on day 7 (p < 0.001) and coincided with a significant improvement in peak expiratory flow (p < 0.0001). Significant correlations were observed between IL-5 expression and ECP level (rho = 0.39, p < 0.01), IL-5 expression and peak expiratory flow (rho = -0.55, p < 0.0002), and peak expiratory flow and ECP level (rho = -0.32, p < 0.04). CONCLUSION: Our data therefore support an important regulatory role of IL-5 on eosinophil function in human asthma in vivo.

Acute Disease↗
PubMed1996

Implementation of a breast and cervical cancer screening program in a public hospital emergency department. Cancer Control Center of Harlem.

STUDY OBJECTIVE: To assess the feasibility and yields of screening for breast and cervical cancer in an urban public hospital emergency department. METHODS: Women who presented to the ED of a large, urban public hospital during the study period with nonurgent conditions were eligible for a Papanicolaou test (Pap smear) and a clinical breast examination (CBE) if they were 18 years of age or older and for a mammogram if they were 40 years of age or older, provided they had not had the screening examination within the past year. The Pap smear and CBE were performed by a nurse, and mammography was scheduled for a later date. Women with gynecologic complaints were excluded. RESULTS: On the basis of screening history, medical status, and age, 1,850 (32%) of the 5,830 women seen in the ER during the 23-month study period were eligible for both mammography and CBE, and 2,361 (41%) were eligible for Pap smears. Of these women, 116 (6%) completed mammography and CBE, and 644 (27%) received Pap smears. Among screened women, 10 (9%) and 20 (3%), respectively, had results that were suspicious or positive for breast or cervical cancer. Follow-up rates were low: 20% for breast screening and 50% for Pap smears. Among those receiving follow-up, 1 woman was found to have breast cancer and 8 were found to have cervical neoplasia. CONCLUSION: ED cancer screening was feasible and yielded a high rate of cancer detection. Program efficiency was hampered by low volume and high numbers of patients lost to follow-up after abnormal screening results. Greater integration into the acute care setting and more intensive recruitment and follow-up strategies are needed to maximize the potential yield and cost effectiveness of such programs.

Adolescent↗
PubMed1996

F-actin sequesters elongation factor 1alpha from interaction with aminoacyl-tRNA in a pH-dependent reaction.

The machinery of eukaryotic protein synthesis is found in association with the actin cytoskeleton. A major component of this translational apparatus, which is involved in the shuttling of aa-tRNA, is the actin-binding protein elongation factor 1alpha (EF-1alpha). To investigate the consequences for translation of the interaction of EF-1alpha with F-actin, we have studied the effect of F-actin on the ability of EF-1alpha to bind to aa-tRNA. We demonstrate that binding of EF-1alpha:GTP to aa-tRNA is not pH sensitive with a constant binding affinity of approximately 0.2 microM over the physiological range of pH. However, the sharp pH dependence of binding of EF-1alpha to F-actin is sufficient to shift the binding of EF-1alpha from F-actin to aa-tRNA as pH increases. The ability of EF-1alpha to bind either F-actin or aa-tRNA in competition binding experiments is also consistent with the observation that EF-1alpha's binding to F-actin and aa-tRNA is mutually exclusive. Two pH-sensitive actin-binding sequences in EF-1alpha are identified and are predicted to overlap with the aa-tRNA-binding sites. Our results suggest that pH-regulated recruitment and release of EF-1alpha from actin filaments in vivo will supply a high local concentration of EF-1alpha to facilitate polypeptide elongation by the F-actin-associated translational apparatus.

Actins↗
PubMed1996

Intra-specific heterogeneity of the rDNA internal transcribed spacer in the Simulium damnosum (Diptera: Simuliidae) complex.

The internal transcribed spacer (ITS) of the rRNA gene cluster has been used as a model for the study of the action of concerted evolution and molecular drive on repeated sequence families. In contrast to this general finding, preliminary DNA sequence analysis of cloned representatives of the ITS from the West African black fly species complex Simulium damnosum s.1. demonstrated extensive intra-individual and intra-specific polymorphisms. Variability in the ITS was primarily confined to the ITS1 domain. The degree and type of intra-individual and intra-specific variability within the ITS was further characterized using gel electrophoresis, DNA hybridization, and heteroduplex analysis of the PCR products generated from the ITS1 domain. ITS1 copies from individual S. damnosum s.1. differed in length and sequence composition. These results, when taken together, demonstrate that a large degree of intra-individual and intra-specific heterogeneity exists in the ITS of S. damnosum s.1. The intra-individual heterogeneity was greater in the savanna-dwelling than forest-dwelling sibling species of S. damnosum s.1. This heterogeneity may be due in part to inter-breeding among sympatric sibling species, coupled with disturbance of S. damnosum s.1. populations resulting from intensive vector control efforts.

Animals↗
PubMed1996

Comparison of rocuronium and mivacurium to succinylcholine during outpatient laparoscopic surgery.

Tracheal intubating conditions and neuromuscular effects of succinylcholine, rocuronium, and mivacurium were studied in 100 healthy women undergoing outpatient laparoscopic surgery. After a standardized fentanyl-thiopental induction, tracheal intubation was facilitated with succinylcholine 1 mg/kg in Groups I (n = 23) and II (n = 25), rocuronium 0.6 mg/kg in Group III (n = 27), or mivacurium 0.2 mg/kg in Group IV (n = 25). If clinically indicated, bolus doses of rocuronium 5-10 mg (Groups I and III) or mivacurium 2-4 mg (Groups II and IV) were administered during the maintenance period. Anesthesia was maintained with desflurane and nitrous oxide 60% in oxygen. At the end of the surgery, residual neuromuscular block was reversed with edrophonium 0.5 mg/kg and atropine 10 micrograms/kg, if needed. The neuromuscular function was assessed using electromyography with a train-of-four mode of stimulation every 10 s at the wrist. Intubating conditions 90 s after succinylcholine and rocuronium were significantly better than after mivacurium. The onset time (from the end of injection until 95% suppression of the first twitch [T1]) for succinylcholine (63 +/- 21 s and 62 +/- 17 s in Groups I and II, respectively) were significantly shorter than for rocuronium (158 +/- 76 s) or mivacurium (210 +/- 93 s). Moreover, the onset times for rocuronium were significantly shorter than mivacurium. The recovery times (of T1 to 25% of the control value) were significantly shorter with succinylcholine and mivacurium than rocuronium. Significantly fewer patients needed reversal of residual neuromuscular blockade after mivacurium compared to rocuronium. One patient in Group I and six patients in Group IV displayed erythema on the upper body. Postoperative myalgia were experienced by 16% of the patients in Groups I and II compared to none in Groups III and IV. There was on difference in the incidence of postoperative nausea and vomiting among the four groups. In conclusion, rocuronium appears to be an acceptable alternative to succinylcholine for tracheal intubation. However, rocuronium's longer duration of action increases the need for reversal drugs. When rapid tracheal intubation is unnecessary, mivacurium is also an acceptable alternative to succinylcholine and is associated with a more rapid spontaneous recovery than rocuronium.

Adult↗
PubMed1996

A comparison of costs and efficacy of ondansetron and droperidol as prophylactic antiemetic therapy for elective outpatient gynecologic procedures.

Ondansetron and droperidol are both effective prophylactic antiemetics for gynecologic outpatient procedures. However, increased drowsiness, delayed discharge, and postdischarge restlessness may occur with droperidol, and ondansetron is costly. In this prospective, randomized, double-blind, placebo-controlled study involving 161 women, we compared the efficacy, safety, and cost-effectiveness of ondansetron (4 mg intravenously [i.v.] with droperidol (0.65 mg or 1.25 mg i.v.) in the prevention of postoperative nausea and vomiting (PONV) after outpatient gynecologic surgery. The incidence of PONV, times to achieving preset recovery criteria, and patient-evaluated visual analog scales for sedation, anxiety, pain, and nausea were recorded, along with postdischarge emetic episodes, medications, quality of sleep, and time to resumption of food intake, normal activity, and return to work. A decision analysis tree was used to divide each data set into nine mutually exclusive subgroups, and costs and probabilities were assigned to each subgroup. The cost-effectiveness ratio was determined by summing these weighted costs and dividing by the number of patients free from both PONV and side effects of antiemetic therapy. The incidence of PONV in the hospital and after discharge, the need for rescue antiemetic therapy, and recovery and discharge times were similar for the ondansetron and both droperidol groups but differed significantly from those for the placebo group. The cost-effectiveness ratios for both droperidol 0.65 mg and 1.25 mg groups were significantly lower than those for the ondansetron and placebo groups. We conclude that droperidol 0.625 mg i.v. provides antiemetic prophylaxis comparable to that of ondansetron 4 mg i.v. without increasing side effects or delaying discharge and is most cost-effective.

Activities of Daily Living↗
PubMed1996

Molecular phylogeny and typing of blackflies (Diptera: Simuliidae) that serve as vectors of human or bovine onchocerciasis.

A subregion of the mitochondrial large subunit (16s) rRNA gene was amplified by polymerase chain reaction (PCR) from nine species of blackflies (Diptera: Simuliidae) which serve as natural or experimental vectors of human or bovine Onchocerca parasites. PCR products from each species of blackfly were tested by directed heteroduplex analysis (DHDA), and their genotypes established according to diagnostic banding patterns of the heteroduplex products. Three alleles of mitochondrial 16s rRNA were found to exist in members of the Simulium (Ewardsellum) damnosum sensu lato complex from West Africa, and two alleles were found in the Neotropical Simulium (Psilopelmia) ochraceum Walker complex and the Simulium (Simulium) metallicum Bellardi complex. Different single alleles were detected in Austrosimulium bancrofti, in English S.(S)noelleri and in two North American laboratory vectors: Simulium (Psilozia) vittatum Zetterstedt and S.(S.)decorum Walker. Phylogenetic analysis of 16s sequences indicated that blackflies from West Africa and the Americas formed distinct clades. Neotropical onchocerciasis vectors were found to be more closely related to Nearctic and Palaearctic non-vector Simulium species than to the African vectors of onchocerciasis.

Animals↗
PubMed1996

Simple in vitro translation assay to analyze inhibitors of rhinovirus proteases.

We have developed a simple in vitro translation method to analyze compounds that inhibit the rhinovirus 3C protease in peptide substrate assays but demonstrate no antiviral activity. This complementary assay, which provides both qualitative and quantitative results, detects the inhibition of the 3CD protease in the native polyprotein form.

3C Viral Proteases↗
PubMed1996

Identification and characterization of a yeast gene encoding the U2 small nuclear ribonucleoprotein particle B" protein.

The inessential yeast gene MUD2 encodes a protein factor that contributes to U1 small nuclear ribonucleoprotein particle (snRNP)-pre-mRNA complex (commitment complex) formation. To identify other genes that contribute to this early splicing step, we performed a synthetic lethal screen with a MUD2 deletion strain. The first characterized gene from this screen, MSL1 (MUD synthetic lethal 1), encodes the yeast homolog of the well studied mammalian snRNP protein U2B". The yeast protein (YU2B") is a component of yeast U2 snRNP, and it is related to other members of the UIA-U2B" family, the human U2B" protein, the human U1A protein, and the yeast U1A protein. It binds in vitro to its RNA target, U2 snRNA stem-loop IV, without a protein cofactor, and the target resembles more closely the U1 snRNA binding site of the human U1A protein than it does the U2 snRNA binding site of human U2B". Surprisingly, the YU2B" protein lacks a C-terminal RNA binding domain, which is conserved in all other family members. Possible functional and evolutionary relationships among these proteins are discussed.

Amino Acid Sequence↗