Biomedical subjects

C Tang

Publications and source records attributed to C Tang.

At least 145 records · Page 8Linked to original sources

PubMed1997

Expression of receptors for gut peptides in human pancreatic adenocarcinoma and tumour-free pancreas.

Gut hormones that modulate the growth of normal pancreas may also modulate the growth of cancers originating from pancreas. This study visualized and compared the receptors for cholecystokinin (CCK), bombesin (BBS), secretin and vasoactive intestinal peptide (VIP) in tumour-free tissue sections of human pancreas (n = 10) and pancreatic ductal adenocarcinomas (n = 12) with storage phosphor autoradiography using radioligands. CCK-B receptors, present in control pancreata, were not detected in any of the pancreatic cancers. BBS receptors were visualized in control pancreata, but they were absent in 10 of 12 pancreatic cancers. In 5 of 12 pancreatic cancers, receptors for secretin were visualized, while binding for secretin was present in all tumour-free pancreata. Conversely, no specific binding of VIP was detected in control pancreata but was identified in 3 of 12 pancreatic cancer specimens. It is concluded that the expression of gut peptide receptors in pancreatic cancer differs from that in tumour-free pancreas. Receptors for these peptides are present in only a minority of pancreatic cancer specimens.

Adenocarcinoma↗

PubMed1997

Co-expression of several molecular mechanisms of multidrug resistance and their significance for paclitaxel cytotoxicity in human AML HL-60 cells.

Overexpression of P-glycoprotein (PGP), MRP or LRP has been characterized as the 'proximal', while overexpression of the anti-apoptosis Bcl-2 or Bcl-xL relative to the pro-apoptosis Bax protein has been recognized as the 'distal' mechanism of multidrug resistance in human AML cells. In the present studies, we examined whether these mechanisms can co-exist in human AML HL-60 cells. We also determined how these mechanisms would affect the accumulation and cytotoxicity of a PGP substrate, such as Taxol (paclitaxel). For this, immunoblot analyses were performed to determine the expression of PGP, MRP, Myc, Bcl-2, Bcl-xL and Bax on either the multidrug-resistant HL-60 sublines created under the selection pressure of doxorubicin (HL-60/AR), paclitaxel (HL-60/TAX1000) or vincristine (HL-60/VCR), or sublines created by transfection and overexpression of the bcl-2 (HL-60/Bcl-2) or bcl-xL gene (HL-60/Bcl-xL). As compared to the control HL-60, HL-60/AR cells possess high MRP while HL-60/TAX1000 and HL-60/VCR cells express high levels of the mdr-1 encoded PGP. In addition, these multidrug-resistant cells possess 1.5- to 2.5-fold higher Bcl-2, while their Bax and Myc levels are similar to those in the control HL-60 cells. HL-60/TAX1000 and HL-60/VCR cells also express three- and 2.5-fold higher Bcl-xL levels. PGP, but not MRP, overexpression significantly impaired paclitaxel accumulation and paclitaxel-induced apoptosis, as well as reduced its cytotoxic effects as determined by the MTT assay. In contrast, enforced and much higher expression of Bcl-2 in HL-60/Bcl-2 (five-fold) or Bcl-xL in HL-60/Bcl-xL cells (10-fold) significantly reduced paclitaxel-induced apoptosis and the loss of cell viability, without affecting its intracellular accumulation. These results confirm the possibility of co-expression of multiple mechanisms of multidrug resistance in human leukemic cells which had been selected by exposure to a single drug. The results also indicate that MRP overexpression does not confer resistance against paclitaxel. In addition, these findings suggest that, for Bcl-2 and Bcl-xL, enforced overexpression to high levels is necessary to induce paclitaxel resistance in HL-60 cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1997

Hyper- and hypocardiodynamic states are associated with externalization and internalization, respectively, of alpha-adrenergic receptors in rat heart during sepsis.

Alterations in the distribution of alpha-adrenergic receptors (alpha ARs) in two subcellular organelles, the sarcolemmal membrane and the light vesicle, of rat heart during the progression of sepsis were studied. Sepsis was induced by cecal ligation and puncture (CLP). alpha ARs were assayed by using [3H]prazosin binding and photoaffinity labeling with [125I]arylazidoprazosin in combination with polyacrylamide gel electrophoresis. Septic rat hearts exhibit two distinct phases: an initial hypercardiodynamic (9 h after CLP; early sepsis) followed by a hypocardiodynamic (18 h after CLP; late sepsis) phase. [3H]prazosin binding studies show that during early sepsis, the Bmax (maximal binding capacity) was increased by 21.4% in sarcolemma but was decreased by 22.5% in light vesicles, while during late sepsis, the Bmax was decreased by 25.4% in sarcolemma but was increased by 60.8% in light vesicles. The photoaffinity labeling studies revealed three binding peptides with M(r) of 77, 68, and 39 kDa. The total binding for the three label peptides during early sepsis was increased by 25.5% in sarcolemma but was decreased by 40% in light vesicles, while during late sepsis, the total binding was decreased by 32.1% in sarcolemma but was increased by 35.8% in light vesicles. These data indicate that alpha ARs in the rat heart were externalized from light vesicles to sarcolemma during early hypercardiodynamic phase while they were internalized from surface membranes to intracellular compartment during late hypocardiodynamic phase of sepsis. Because alpha ARs play an important role in regulating myocardial contractility, an initial externalization followed by internalization of alpha ARs may contribute to the development of the initial hypercardiodynamic and the subsequent hypocardiodynamic states during sepsis.

Animals↗

PubMed1997

Allergen-induced airway reactions in atopic asthmatics correlate with allergen-specific IL-5 response by BAL cells.

Allergen-specific cytokine responses in the airways are thought to play a critical role in the pathogenesis of atopic asthma. This study examined whether there is a quantitative difference in bronchoalveolar lavage (BAL) cell allergen-induced IL-5 production between atopic subjects with and without asthma which may relate to a difference in airway response induced by allergen exposure. Twelve atopic asthmatics (AA), nine atopic non-asthmatics (AN) and 10 normal controls (N) underwent inhalation challenge with house dust mite allergen (HDM) extract. AA differed from AN in having late airway reactions (LAR) after HDM inhalation (P < 0.01), which correlated with an increased percentage of BAL eosinophils and increased BAL cell IL-5 production after in vivo or in vitro HDM challenge for the AA group (P < 0.01). IL-5 production by PBMC from both atopic groups was elevated with HDM stimulation in vitro, but AA again had a higher level under baseline conditions than AN (P < 0.02). Furthermore, there was a greater effect of BAL fluid from AA on ECP release by eosinophils compared to that for AN (P < 0.01). These findings suggest that increased IL-5 production in atopic asthmatic airways contributes to the increased physiological response to allergen inhalation, by modulating local eosinophil recruitment and activation.

Adult↗

PubMed1997

Initial experience with a co-radial bipolar pacing lead.

A new type of endocardial bipolar pacing lead has been designed to overcome the potential drawbacks of the conventional coaxial bipolar pacing lead. We prospectively evaluated the new co-radial bipolar pacing leads (Intermedics Thin-Line), which are thinner (5 Fr vs 6-8 Fr) than standard coaxial bipolar leads. X-ray visibility and lead handling were subjectively assessed (excellent, good, adequate, or poor) at implant; lead impedance, sensitivity threshold, and pacing threshold were measured at implant, then at 1, 3, 6, 12, and 18 months. The results were as follows: 103 patients (51 M; age 63.8 +/- 17.4 years) received 71 atrial (A) and 89 ventricular (V) leads. X-ray visibility was excellent in 59/103; good in 23/103; adequate in 11/103; and poor in 10/103. Overall handling was excellent in 56/71 A and 69/89 V; good in 11/71 A and 18/89 V; adequate in 3/71 A and 1/89 V; poor in 1/71 A and 1/89 V. There were two perioperative complications. At implant: impedance in A and V were 370.1 +/- 74.7 and 501.5 +/- 124.4 omega, sensing thresholds in A and V were 3.0 +/- 1.5 and 9.9 +/- 5.0 mV, pacing thresholds at 0.45 ms in A and V were 0.59 +/- 0.21 and 0.41 +/- 0.15 volt, respectively. At 1, 3, 6, 12, and 18 months of follow-up: no pacing lead related complications were reported; pacing lead characteristics remained outstanding and stable. This new lead appears to have significant clinical advantages over the conventional coaxial bipolar pacing lead. Long-term follow-up is required to confirm its reliability and chronic performance characteristics.

Adolescent↗

PubMed1997

Right atrial appendage to right ventricle accessory atrioventricular connection: a case report.

Atrial and ventricular attachments of accessory atrioventricular connections have classically been localized to adjacent atrial and ventricular tissues, and this principle is responsible for the widespread success of radiofrequency catheter ablation. We present anatomical evidence of an unusually located accessory atrioventricular connection, which bridged the atrioventricular ring epicardially, directly from the base of the right atrial appendage to the right ventricle. This observation might offer a new insight into unusual accessory atrioventricular connection locations and may explain why some endocardial radiofrequency catheter ablation procedures might fail.

Adult↗

PubMed1997

Expression of peptide receptors in human endocrine tumours of the pancreas.

BACKGROUND: Gut peptides are known to influence hormone release and growth of endocrine tumours of the pancreas. Although information on somatostatin receptors has been provided recently, little is known on the receptor status of other gastrointestinal hormones in such tumours. AIMS: To analyse the spectrum of gut hormone receptors on endocrine tumours of pancreas. SUBJECTS: Four types of endocrine tumours from eight patientS. METHODS: The receptors for bombesin, secretin, vasoactive intestinal peptide, cholecystokinin, and somatostatin have been visualised and quantified with storage phosphor autoradiography. RESULTS: Bombesin receptors were present in all five gastrinomas and two primary VIPomas. Secretin receptors were expressed in four primary gastrinomas and one primary VIPoma from pancreas. Vasoactive intestinal peptide receptors were identified in four primary gastrinomas and all VIPomas. Furthermore, all VIPomas expressed cholecystokinin-B (gastrin) receptors, whereas, gastrinomas did not contain cholecystokinin-B receptors. The receptors for somatostatin were detected in all gastrinomas and VIPomas. Both somatostatinoma and glucagonoma were negative for all five types of peptide receptors studied. CONCLUSIONS: Besides somatostatin receptors, most of gastrinomas and VIPomas also express receptors for bombesin, secretin, and vasoactive intestinal peptide.

Adenoma, Islet Cell↗

PubMed1997

Characteristics of restitution kinetics in repolarization of rabbit atrium.

The study was designed to characterize restitution kinetics in atrial repolarization of rabbits and to examine effects of K+ or Ca2+ channel blockers on restitution. Action potentials were recorded from rabbit atrial tissue. Restitution curves of phase I amplitude and action potential duration at 50 and 90% repolarization (APD50, APD90) were defined at a basic cycle length of 0.5 s during control and with interventions. Restitution of phase I amplitude had a monoexponential function with a time constant of 2.8 +/- 0.2 s. The curves of APD50 frequently had a monoexponential function and time constants were 1.8 +/- 0.1 s. Restitution curves of APD90 were biphasic: a descending phase followed by an ascending phase. The blocker of Ito1 (a 4-aminopyridine-sensitive component of the transient outward current), 4-aminopyridine, flattened the restitution curves of phase I amplitude, and APD50 and APD90 curves became monophasic. Sotalol, a selective IKr (a rapid component of the delayed rectifier K+ current) blocker, did not alter curves of phase I amplitude and APD50 but shifted APD90 curves upward. Cadmium, a Ca2+ blocker shifted curves of phase I amplitude and APD50 downward and abolished the ascending phase of APD90 curves. We conclude that kinetics of Ito1 and ICa (calcium current) may account for characteristics of restitution of atrial repolarization in rabbit.

Action Potentials↗

PubMed1997

Hypothalamic galanin gene expression and peptide levels in relation to circulating insulin: possible role in energy balance.

The peptide galanin (GAL) exists in dense concentrations within the medial hypothalamus and is synthesized in a population of neurons within the paraventricular nucleus (PVN). This peptide has been linked to energy homeostasis through its behavioral, metabolic and endocrine actions, including pancreatic insulin secretion. This investigation examined whether circulating insulin, in turn, has impact on hypothalamic GAL production, GAL mRNA and peptide concentrations in the hypothalamus. Streptozotocin (STZ)-induced diabetic rats, compared to control subjects, were tested with or without insulin replacement. After STZ treatment, the rats exhibited hyperglycemia, increased food and water intake, and decreased weight gain compared to controls. These changes were reversed by daily, subcutaneous injections of insulin. Measurements of GAL mRNA, via solution hybridization/nuclease protection assay, revealed a 6-fold elevation after STZ treatment compared to controls, accompanied by a similar rise in GAL peptide levels. This increase in GAL message and peptide was reversible by insulin and was detected in a mediodorsal hypothalamic (MDH) dissection which contains the PVN. It was not seen in a dissection of the mediobasal hypothalamus that includes the GAL-synthesizing neurons of the arcuate nucleus. Measurements of GAL in discrete hypothalamic nuclei of STZ diabetic rats showed a 100% increase in peptide concentrations (p < 0.05) in the PVN that was insulin responsive. Other hypothalamic areas examined failed to exhibit any change in peptide. These findings are consistent with other evidence indicating an inverse association, between circulating insulin and GAL message or peptide in the PVN, that may have physiological relevance in the control of energy balance.

Animals↗

PubMed1997

[Protein kinase C involved in the protecttve effect of anoxic preconditioning on vascular smooth muscle cells].

It has been known that anoxic preconditioning (APC) has protective effects not only on cardiomyocyte, but also on vasculature. However, the effects of APC on vascular smooth muscle cells (VSMC) is unknown. On the model of anoxia/reoxygenation (A/R) injury of rabbit VSMC, the effect of APC was observed. It was found that APC could increase the survival rate of VSMC after A/R injury, lower the leakage of lactate dehydrogenase (LDH) and protein from cells, and attenuate peroxidation injury and calcium overload of VSMC. The results also showed that PMA, an activator of protein kinase C (PKC), could mimic, but H7 or polymyxin B (inhibitors of PKC) could abolish the above protective effect of APC. It is suggested that the protective effect of APC on VSMC during A/R injury might be due to the activation of PKC.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1997

[The effect of NO-like relaxing factor on vascular reactivity in tourniquet shock rat].

This work was done on rat tourniquet shock (ToS) model. It was found that reactivity of isolated perfused aortic ring to noradrenaline decreased, while cGMP content of the aortic tissue increased. These changes could be potentiated by perfusion with L-arginine (NO-precursor). On the other side, when the aortic ring was perfused with L-NNA (NO-synthesis inhibitor) or methylene blue (soluble cGMPase inhibitor), the changes could be attenuated. The effect of these drugs are independent of the presence of vascular endothelium. The results suggest that non-endothelium-derived NO-like relaxing factor may be one of the factors causing low vascular reactivity of the ToS animals.

Animals↗

PubMed1997

[The effect of endurance training and exhaustive exercise on metallothionein in rats].

To understand physiological role of metallothionein (MT) during exercise, MT levels in liver, brain, heart, lung, blood vessel, skeletal muscle and serum were observed in rats. The results showed that the levels of MT were decreased by 13-34% in lung, liver, heart and skeletal muscle of rats trained by swimming for 10 weeks and were increased by 21%-75% in skeletal muscle, heart, brain, lung and liver of rats after exhaustive swimming respectively, compared with normal control rats. (P < 0.05 and P < 0.01). But the levels of MT in blood vessel and serum were not changed in two groups of rats by swimming for 10 weeks and acute exhaustive swimming (P > 0.05). It is suggested that the different changes of MT levels under physical training and acute exhaustive exercise may be of importance in protection against oxygen free radicals.

Animals↗

PubMed1997

[Effect of L-arg and LNNA on contractile-relaxant response and cGMP level of thoracic aorta with endothelial injury in rat].

In this study, we have observed the effect of L-arginine(L-arg) and omega N-nitro-L-arginine (LNNA) on the contractile-relaxation response and the cGMP level in arterial strip using the model of rat thoracic aorta with endothelial injury and neointimal formation. Organ chamber experiment and radioimmunoassay showed that, the 3rd day after endothelial injury of the rat thoracic aorta, their endothelium-dependent relaxtion response caused by L-arg, as well as endothelium dependent contractile response caused by LNNA were impaired seriously, basic cGMP reduced obviously, and the change of cGMP caused by L-Arg and LNNA was impaired markedly. On the 10th day after injury a pronounced recovery was noticed, and 21st day, the situation was further improved, but could not restore completely. The results indicate that the production of EDRF in the rat thoracic aorta after endothelial injury may be impaired seriously, and could not recover completely for a longer time.

Animals↗

PubMed1997

Changes of plasma tPA and PAI activities in patients with diabetic retinopathy.

PURPOSE: To investigate the relationship between the diabetic retinopathy (DR) and the activity of plasma tissue plasminogen activator (tPA) and plasminogen activator inhibitor (PAI). METHODS: tPA and PAI activities were measured by chromatogenous substrate assay in plasma samples obtained from patients with and without diabetic retinopathy (n = 42). Retinopathy was determined by stereoscopic color fundus photographs graded according to a modification of Chinese National Fundus Disease Academic Meeting. And 21 sex-age matched normal people were as controls. This study was in a masked fashion. RESULTS: 1. tPA activity was lower and PAI activity was higher in all of diabetic patients than those in controls (P < 0.001); 2. tPA activity was lower and PAI activity was higher in proliferative DR (PDR) subgroup than those in non-DR (NDR) and background-DR (BDR) subgroups (P < 0.01, respectively); 3. there was no significant difference between BDR and NDR subgroups (P > 0.05); and 4. the results also suggested that the severity of DR and duration of diabetes were correlated negatively with the activity of tPA but positively with that of PAI (r = -0.564, -0.416, 0.671, 0.442; P < 0.01, respectively). CONCLUSIONS: Reduced plasma tPA activity and enhanced PAI activity in diabetic patients, probably is one of the causes for thromboembolic diseases and are related to the severity of DR and duration of diabetes. Therefore, the change and imbalance between activities of plasma tPA and PAI might play a role in developing and progression of DR.

Adolescent↗

PubMed1997

[Pharmacological study of cholagogic capsule].

Cholagogic capsule is mainly composed of Fiuctus Cardui, Mariae, Oleum Menthae Piperilae, Radix Currmae, olia taraxaci, Oleum Hyperici. It is shown that Cholagogic Capsule increase the rat's bile secretion significantly, but bile component is not influenced effectively, the retention jaundice models of which are created by ANIT isn't influenced effectively. It can reduce the mouse pinna swelling caused by dimethythenzene and depress the metatarsal swelling induced by carragenin, the antiinflammatory effect keeps for more than 4 h. It inhibits the contraction of gallbladder smooth musele of Guinea Pig caused by Ach. The results show that cholagogic Capsule increase bile secretion, antispasmodic and antiinflammatory effect. It is suggested the therapeutic effects of Cholagogic Capsule in sand-like calcul and acute chronic cholecystitis are related to the above pharmaological effects.

Animals↗

PubMed1997

[Cloning and sequencing of nucleoprotein gene of Chinese rabies virus vaccine strain (5aG)].

Rabies virus 5aG strain (5aGRV) is used to produce primary hamster kidney tissue culture vaccine against Rabies in China. Nucleoprotein (NP), an important constituent of rabies virus, can intrigue Th cell and induce B cell to produce antibody. In order to study the molecular and biological characteristics of 5aG NP, we have cloned and sequenced the nucleoprotein gene. First, total RNA was extracted from infected mouse brain by Guanidine Isothiocyanate one-step method, then the first strand cDNA was synthesized by reverse transcription with oligo (dT) 18 as primer. After RACE (Rapid Amplification of cDNA Ends), one pair of oligonucleotide primers designed referring to the nucleoprotein gene of other strains, were used in PCR to amplify the fragments of nucleoprotein gene (1.4kb). When these fragments were inserted into vector pUC18, sequences of the nucleoprotein gene were obtained by double-stranded sequencing. Comparing the nucleic acid and deduced amino acid sequence of 5aGRV nucleoprotein gene with available NP sequences of other RV strains, we found that the nucleoprotein has less variation than glycoprotein, so nucleoprotein is more suitable to be used as a diagnostic reagent and a subunit vaccine.

Animals↗

PubMed1997

IL-5 production by bronchoalveolar lavage and peripheral blood mononuclear cells in asthma and atopy.

There is increasing evidence to suggest a key role for interleukin-5 (IL-5) in the regulation of airway eosinophilia in asthma. We compared the capacity for IL-5 production in atopic asthmatic, nonatopic asthmatic, atopic nonasthmatic and normal subjects, and evaluated the usefulness of peripheral blood cells for reflecting airway cell reactivity. Bronchoalveolar lavage (BAL) cells and peripheral blood mononuclear cells (PBMC) from 12 atopic and 10 nonatopic asthmatics (without inhaled steroid therapy), 9 atopic nonasthmatics, and 10 normal controls were cultured with or without house dust mite (HDM, 10 microg x mL-1) stimulation. CD4+ T-cell activation, IL-5 and interferon-gamma (IFN-gamma) production in the cultures were assessed. Both for BAL and PBMC samples, atopic and nonatopic asthmatic subjects showed comparable spontaneous production of IL-5, which was significantly higher than that either for atopic nonasthmatics or normal controls (p<0.05 or p<0.01). There was a significant correlation between the percentage of eosinophils in BAL and spontaneous production of IL-5 by BAL cells in both asthmatic groups (p<0.05 or p<0.01). Both these parameters were also associated with asthmatic airway narrowing as denoted by a negative relationship with baseline forced expiratory volume in one second (FEV1) as percentage predicted (p<0.05 and p<0.01, respectively). In contrast, IFN-gamma production by unstimulated BAL cells from normal controls was higher than that for BAL cell cultures of nonatopic asthmatic subjects (p<0.05). Following HDM stimulation, both atopic groups had comparable positive responses in terms of CD4+ T-cell activation, but there was relatively greater IL-5 production in asthmatic PBMC (p<0.05) and, in particular, BAL cell cultures (p<0.01). These findings suggest that elevated IL-5 production is a common feature of BAL cells and PBMC in atopic and nonatopic asthma. In addition, atopic asthmatics show greater IL-5 production in response to specific allergen compared with atopic nonasthmatics, an effect most marked in BAL cells compared to PBMC. Hence, peripheral blood mononuclear cells can reflect cytokine immunoreactivity of airway cells, but lack local cellular interactions, which limits their usage in asthma research.

Adult↗

PubMed1997

Atrial diagnostics in a tiered therapy implantable defibrillator.

Dual chamber sensing has been proposed in implantable defibrillators as an additional diagnostic modality for enhanced differentiation of ventricular and supraventricular tachycardias. A patient with different rates of wide QRS complex tachycardias is described in whom a tiered therapy implantable defibrillator with atrial sensing capability was implanted. Atrial diagnostic data in this patient enabled definitive diagnosis of his ventricular tachycardias and guided management decisions of his arrhythmia.

Defibrillators, Implantable↗