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Biomedical subjects

J Tang

Publications and source records attributed to J Tang.

At least 415 records · Page 23Linked to original sources
PubMed1994

Alterations in pulsatile insulin secretion in the Zucker diabetic fatty rat.

Insulin secretion from the isolated perfused pancreas is characterized by pulses occurring every 5-15 min. The present experiments were performed to explore the role of glucose in regulating these pulses. The pancreata from 12 Wistar (W), 12 Zucker diabetic fatty (ZDF), and 6 nondiabetic lean Zucker control (ZC) male rats were isolated and perfused at 37 degrees C with an oxygenated Krebs Ringer solution containing bovine serum albumin and glucose. In W and ZDF, insulin secretion was pulsatile during constant glucose, as assessed by pulse analysis (ULTRA). The pulse period in W was significantly shorter than in ZDF (7.1 +/- 0.6 vs. 14.7 +/- 1.0 min; P < 0.001), whereas the median relative pulse amplitude was not different. When glucose was administered as a series of 10-min sine waves, spectral analysis showed that the normalized spectral power at 10 min was greater in W and ZC compared with ZDF (34.2 +/- 5.9 and 32.9 +/- 2.9 vs. 3.2 +/- 0.9; P < 0.0001), demonstrating entrainment of the insulin pulses to the exogenous glucose oscillations in W and ZC but not in ZDF. Furthermore, in ZDF, the insulin secretory rates were not higher when 28 mM rather than 7 mM glucose were used. In additional studies, islets of Langerhans from one W, three ZDF, and three ZC rats were isolated and perifused using an oscillatory glucose concentration. Single and groups of islets were studied. Islets from diabetic rats demonstrated the same lack of entrainment by glucose seen in the perfused pancreas, suggesting that the defect is at the cellular level.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Separate pathways for synapse-specific and electrical activity-dependent gene expression in skeletal muscle.

Signaling between nerve and muscle is mediated by multiple mechanisms, including two transcriptional pathways. Signals provided by the nerve terminal activate transcription of acetylcholine receptor (AChR) genes in myofiber nuclei near the synaptic site, and signals associated with myofiber electrical activity inactivate AChR gene expression throughout the myofiber. These opposing effects of innervation are conferred by 1.8 kb of 5' flanking DNA from the AChR delta subunit gene. These results raise the possibility that synapse-specific and electrical activity-dependent gene expression are mediated by the same DNA sequence and that activation and repression are determined by differential regulation of the same DNA binding protein. We produced transgenic mice carrying AChR delta subunit-hGH gene fusions, and we show here that a binding site (E-box) for myogenic basic helix-loop-helix proteins is required for electrical activity-dependent but not for synapse-specific gene expression of the delta subunit gene. These results indicate that a change in the expression or activity of an E-box binding protein(s) mediates electrical activity-dependent gene regulation and that synapse-specific and electrical activity-dependent gene expression require different DNA sequences. Moreover, we show here that the cis-acting elements for both aspects of innervation-dependent gene regulation are contained in 181 bp of 5' flanking DNA from the AChR delta subunit gene.

Animals↗
PubMed1994

[Semiquantitative detection and application about the expression of nitric oxide synthase gene].

Using the Reverse Transcription (RT)-Polymerase Chain Reaction (PCR) method of Martin (1993) for semiquantitation determinating of NOS gene, it was found that NOS mRNA is not only existed in brain, but also distributed extensively in heart, kidney, lung and liver. Among of them, NOS mRNA levels were highest in the brain, followed in descending order by kidney, heart. In addition to endothelial cell, NOS gene was also highly expressed in smooth muscle cells, suggesting that they may be an important site of NOS in organism. Furthermore, NOS mRNA levels were found to decrease significantly in brain, kidney, liver and smooth muscle cell in spontaneous hypertensive rat. These data suggest that pathogeny of hypertension may be related to low expression of NOS gene in these tissues.

Amino Acid Oxidoreductases↗
PubMed1994

["Moist burn ointment" brought about multiple systemic complications in children with burns].

From January 1990 to December 1992, twenty-one burned children, who were treated with "Moist burn ointment", were transferred to our hospital after the occurrence of invasive infection, multiple systemic complications or electrolyte disorder. The age ranged from 1 to 5 years. The total burn area ranged 5-30 per cent (mean 16.0 +/- 5.8 per cent) of the body surface area. All patients exhibited complications of two or more systems and electrolytic disorder when they were admitted. Of the 21 patients, 4 died. We believed that the severe infection of burn wounds, resulted from the application of "Moist burn ointment" was the main factor of causing multiple organ damage. Therefore, it is suggested that the "Moist burn ointment" should be used with great caution.

Administration, Topical↗
PubMed1994

Involvement of nitric oxide in the vasodilator and depressor effect of calcitonin gene-related peptide.

In present study, we examined the effects of NG-nitro-L-arginine (LNNA), an inhibitor of nitric oxide synthase (NOS), and/or methylene blue (MB), a blocker of guanylate cyclase on the vasodilator response of isolated rat arteries including aorta and mesenteric artery to calcitonin gene-related peptide (CGRP) by in vitro vasoconstriction experiment, and the effect of LNNA on the depressor action of CGRP by in vivo hemodynamic experiment. Furthermore, the effect of CGRP on NOS activity and cyclic guanylate monophosphate (cGMP) content were also examined by NOS activity assay and radioimmunoassay (RIA), respectively. The results showed that LNNA and/or MB significantly decreased, but not abolished, the vasodilator response of isolated rat aorta and mesenteric artery to CGRP. The depressor effect of CGRP on LNNA-induced hypertensive rats (LHR) was obviously weaker than that on spontaneously hypertensive rats (SHR), renal hypertensive rats (RHR) and normotensive rats (NWR). In addition, CGRP (0.5 nmol/kg) increased the NOS activity of rat aorta tissue by 1.3 times (P < 0.05) and resulted in an increase of cGMP content of aorta (1.27 times, P < 0.05) and myocardium (1.38 times, P < 0.05). The results suggested that NO is involved in the action of CGRP.

Animals↗
PubMed1994

[Relation of HSP70 gene and spontaneously hypertension in rats].

The level of heat shock protein 70 messenger RNA was examined in aortic smooth muscle cells (ASMC) and hepatic tissue of Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). The restriction fragment length polymorphism (RFLP) was also analysed in hepatic DNA. It was demonstrated that the basic level of heat shock protein 70 messenger RNA in ASMC and hepatic tissue of SHR were lower than that of the WKY rats. The extent of heat shock protein 70 messenger RNA accumulated in ASMC was higher in SHR than in WKY rats when the cells were heated by immersing the culture bottles in 42 degrees C water bath for 15 min and allowed to recover at 37 degrees C for 2 h. In contrast with WKY rats, the Bam HI restricted bepatic DNA showed that a fragment about 5.6 kb was lost in heat shock protein 70 gene from hepatic DNA of SHR. The results suggest that the ASMC of SHR is more sensitive to heat stress than that of WKY rats and the changes of heat shock protein gene sequence may be related to genetic hypertension.

Animals↗
PubMed1994

[Transcription of HSP 70 gene induced by pressure overload in left ventricule of rats].

The changes of heat shock protein 70 (HSP70) messenger RNA was examined in rats after abdominal aortic partial ligation. Four hours after ligation, the systemic arterial pressure was increased and thereafter maintained at a high level. The ratio of left ventricule weight to body weight began to increase at the third day and increased by 59%, comparing with that of the sham-operated rats at 4 w. Accumulation of HSP 70 mRNA was observed at 4 h and maintained at high level at 1 d, 2 d, 1 w and then gradually disappeared there after. The above experimental results suggest that transcription of HSP 70 gene was induced at an early stage of cardiac hypertrophy caused by pressure overload.

Animals↗
PubMed1994

Role of regulatory peptide in pathogenesis of shock.

The present study evaluated the pathogenetic roles of three kinds of regulatory peptide. The results showed that (i) plasma endothelin (ET) level elevated significantly in septic shock rats, persistent intravenous drip of low doses ET caused development of shock state in normal rats and the irreversible outcome of light hemorrhagic shock. Furthermore, i. v. administration of specific ET-antiserum was significantly effective to septic shock rats. (ii) Plasma calcitonin gene-related peptide (CGRP) increased by 260% in septic shock rats, i. v. drip of low doses CGRP both in early and late sepsis were effective to shock rats. (iii) Angiotensin-II (ANG-II) contents of heart and aorta increased dramatically both in early and late septic shock, and inhibiting its increase with Captopril in late sepsis significantly improved the shock state, but results were inverse in early sepsis. It could be concluded that ET was one of the most important factors participating in the pathogenesis of shock, CGRP had a compensatory regulatory role in shock and the role of tissue ANG-II was different during different periods of shock.

Angiotensin II↗
PubMed1993

Subpopulations of bone marrow fibroblasts support VLA-4-mediated migration of B-cell precursors.

Proliferation of normal human lymphoid progenitors in culture is dependent on interaction with bone marrow-derived fibroblast-like cells (BM-FB). To investigate possible heterogeneity in this lymphoid-supportive microenvironment, we studied the interaction of a human B-precursor cell line (NALM-6) with BM-FB. NALM-6 cells associate with BM-FB by either adhesion or migration underneath the fibroblast. Individual fibroblasts in the BM-FB layer showed significant variation in the number of migrating NALM-6 cells. Migration of NALM-6 cells was primarily VLA-4-dependent, although residual migration observable after blocking with anti-VLA-alpha 4 antibody was inhibited by anti-VLA-alpha 5 antibody. Migration was not inhibited by blocking either of the known VLA-4 counterreceptors (VCAM-1 or fibronectin), although slight inhibition was observed using a combination of blocking antibodies to VCAM-1 and fibronectin. In contrast, NALM-6 adhesion without migration was significantly inhibitable by anti-VCAM-1 antibody. VCAM-1 or fibronectin expression on individual BM-FB did not correlate with NALM-6 migration. These results indicate that the adhesion and migration of human B-lymphoid precursors in the bone marrow microenvironment are mechanistically separable events and suggest the possibility of novel VLA-4 ligand(s), which may be important in human lymphopoiesis. Subpopulations of cells in the bone marrow microenvironment may preferentially support important aspects of lymphoid progenitor development.

Adult↗
PubMed1993

Recombinant canditropsin, an extracellular aspartic protease from yeast Candida tropicalis. Escherichia coli expression, purification, zymogen activation, and enzymic properties.

A cDNA fragment which encodes the zymogen of canditropsin, the extracellular aspartic protease from the yeast Candida tropicalis (Togni,G., Sanglard, D., Falchetto, R., and Monod, M. (1991) FEBS Lett. 286, 181-185) was cloned into a T7 expression vector for the synthesis of the recombinant zymogen in Escherichia coli. Recombinant canditropsinogen (Ctg), which was expressed as inclusion bodies in the cytosol of E. coli, was refolded by dialysis from an 8 M urea solution and purified to homogeneity using chromatographies on Sephacryl S-300 and on MonoQ columns. The purified Ctg was converted into canditropsin by either acid activation or trypsin conversion. The specificity of the resulting recombinant canditropsin toward polypeptide substrates is significantly different from other aspartic proteases. Canditropsin hydrolyzes oxidized insulin B chain between Ala-Leu and many other minor cleavage sites. Canditropsin also hydrolyzes keratin and collagen, which are components of connective tissues known to be hydrolyzed by canditropsin during Candida infections. Canditropsin was strongly inhibited by the universal aspartic protease inhibitor pepstatin (Ki = 1.75 x 10(-8) M) and inactivated by two aspartic protease inactivators, DAN and EPNP. Canditropsin is weakly inhibited by leupeptin and antipain, with an apparent Ki of 1.74 x 10(-4)M and 1.5 x 10(-5) M, respectively.

Amino Acid Sequence↗
PubMed1993

Correlation of cilofungin in vivo efficacy with its activity against Aspergillus fumigatus (1,3)-beta-D-glucan synthase.

(1,3)-beta-D-Glucan synthase is a cell wall synthesis enzyme that is the target of cilofungin, an antifungal agent of the lipopeptide class. Cilofungin's glucan synthase inhibitory activity, MIC, and effective dose 50% in a systemic infection mouse model tend to correlate for Candida albicans. This correlation is not seen in Aspergillus fumigatus. MICs for cilofungin against A. fumigatus were consistently > 125 micrograms/ml while the effective dose 50% in a systemic aspergillosis model was determined to be 20.6 mg/kg. To begin to understand this discrepancy, we examined the A. fumigatus glucan synthase. This cell wall enzyme was prepared and its activity was measured by [14C]-glucose incorporation from UDP-[U-14C]glucose into an acid insoluble polymer formed in the presence of alpha-amylase. Enzyme activity in crude membrane preparations was measured in the presence of several antifungal agents. Enzyme inhibition results showed that 1 microgram/ml of papulacandin B, echinochandin B, aculeacin A and cilofungin all inhibited A. fumigatus glucan synthase activity (40-71%) while 1 microgram/ml of amphotericin B, fluconazole, ketoconazole and nikkomycin did not affect enzyme activity. A correlation was therefore established between the inhibitory effect of cilofungin on the A. fumigatus glucan synthase and the effective dose 50% obtained in a systemic aspergillosis mouse model.

Amphotericin B↗