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Biomedical subjects

C Jiang

Publications and source records attributed to C Jiang.

At least 217 records · Page 12Linked to original sources
PubMed1994

Two long QT syndrome loci map to chromosomes 3 and 7 with evidence for further heterogeneity.

Cardiac arrhythmias cause sudden death in 300,000 United States citizens every year. In this study, we describe two new loci for an inherited cardiac arrhythmia, long QT syndrome (LQT). In 1991 we reported linkage of LQT to chromosome 11p15.5. In this study we demonstrate further linkage to D7S483 in nine families with a combined lod score of 19.41 and to D3S1100 in three families with a combined score of 6.72. These findings localize major LQT genes to chromosomes 7q35-36 and 3p21-24, respectively. Linkage to any known locus was excluded in three families indicating that additional heterogeneity exists. Proteins encoded by different LQT genes may interact to modulate cardiac repolarization and arrhythmia risk.

Base Sequence↗
PubMed1994

Comparison of the effects of an organic and an inorganic form of selenium on a mammary carcinoma cell line.

The development of new compounds with greater cancer inhibitory activity and that are well tolerated continues to be a priority in chemoprevention research involving selenium. One compound, 1,-4-phenylene-bis(methylene)selenocyanate (p-XSC), is representative of a series of organoselenium compounds with these characteristics. In this study, the effects of p-XSC on a mouse mammary carcinoma cell line were compared to those of sodium selenite, which has been shown to be growth inhibitory. Treatment with p-XSC caused a 3- to 6-fold greater accumulation of selenium within cells than did treatment with equivalent amounts of selenite and cells were able to better tolerate higher cellular levels of selenium derived from p-XSC. Both compounds resulted in a dose-dependent reduction in cell number after 24 h of exposure. Selenite and p-XSC also caused a dose-dependent increase in cell death by apoptosis. This effect was observed within 5 h of treatment. The effect of p-XSC on apoptosis was more pronounced than that of selenite, especially at the 20 microM level of exposure. The induction of apoptosis by selenium compounds may partially account for their chemopreventive activity.

Animals↗
PubMed1994

Effect of lemakalim on action potentials, intracellular calcium, and contraction in guinea pig and human cardiac myocytes.

OBJECTIVE: The aim was to investigate the effects of lemakalim on action potential duration, intracellular free calcium ([free Ca2+]i), and cell contraction in human and guinea pig cardiac myocytes. In addition, the possible modulation by pH of lemakalim induced activation of ATP sensitive potassium (KATP) channels was assessed. METHODS: Single ventricular myocytes were enzymatically dissociated from adult male guinea pigs (300-600 g). Single myocytes were isolated from human ventricular tissues. Cells were loaded with the acetoxymethyl ester form of fura-2 to monitor changes in [free Ca2+]i and subjected to conventional electrophysiological techniques. RESULTS: In guinea pig cells, lemakalim (3, 10, 30 microM) reduced action potential duration in a concentration dependent manner. This decrease was accompanied by hyperpolarisation of the resting membrane potential. Lemakalim (3, 10, 30 microM) reduced the systolic fura-2 fluorescence ratio without having a significant effect on diastolic fluorescence and also reduced the cell contraction in concentration dependent manner. Glibenclamide (1 microM), a specific inhibitor of KATP channels, did not affect action potential duration, fura-2 fluorescence ratio, or cell contraction in the absence of lemakalim. However, the same dose of glibenclamide markedly inhibited the lemakalim induced decrease in action potential duration, fura-2 fluorescence ratio, and cell contraction. Reducing extracellular pH enhanced the decrease in action potential duration induced by lemakalim. In human ventricular myocytes, lemakalim (3, 10 and 30 microM) caused a decrease in action potential duration and systolic fura-2 fluorescence ratio. The reduction in action potential duration and fura-2 fluorescence ratio was also reversed by glibenclamide (1 microM). CONCLUSIONS: These results suggest that lemakalim reduces systolic [free Ca2+]i by activating ATP sensitive potassium channels which results in a decrease of action potential duration in guinea pig and human ventricular myocytes. The reduction in [free Ca2+]i mediates the negative inotropic effect induced by lemakalim. In addition, pH may modulate the KATP channel activation by the channel opener.

Action Potentials↗
PubMed1994

The use of mixture models to detect effects of major genes on quantitative characters in a plant breeding experiment.

An analysis based on Elston's model of mixed major locus and polygenic inheritance is extended to include populations of progeny testing such as F3, B1s and B2s families derived from F2 and backcrosses in a cross between two inbred lines. Genetic hypotheses that can be validly tested by the likelihood ratio method in the analysis of a breeding experiment include homogeneity of variances due to environment and/or polygenes with transformable scale effect by Box-Cox power function, random and independent segregation of major genes, invariance of the effects of major genes with population types and additive and dominant models for polygenes. Testing hypotheses in the order suggested here can lead to a gradual simplification of the models and increases the feasibility of the subsequent analysis, but caution must be paid to the possible bias in parameter estimation and hypotheses tests. The procedure is applied to a set of data on plant height of rice with the effects of dwarf genes in crosses among three varieties. Two recessive dwarf genes are shown to be nonallelic and unlinked. One dwarf gene is shown to reduce plant height about 36-56 cm, and another 52-61 cm. The effect of polygenes, estimated as the standard deviation among possible inbred lines derived from these crosses, is about 11.7 cm. Interactions between the dwarf genes and the polygenic background are found, especially for one of the two genes. Both the polygenic effects and the interactions are much smaller than the effects of the major dwarf genes.

Crosses, Genetic↗
PubMed1994

Inhibition of hypoxia-induced relaxation of rabbit isolated coronary arteries by NG-monomethyl-L-arginine but not glibenclamide.

1. The effects of NG-monomethyl-L-arginine, tetrodotoxin and glibenclamide on hypoxia-induced coronary artery relaxation, induced by bubbling Krebs solution with 95% N2 and 5% CO2 instead of 95% O2 and 5% CO2, were assessed by measuring the changes in isometric tension in isolated epicardial coronary artery rings of the rabbit. In addition, the effects of glibenclamide on the relaxation induced by adenosine were investigated. 2. Hypoxia caused a transient relaxation of 38 +/- 3% (P < 0.01) and 17 +/- 2% (P < 0.01) in endothelium-intact or -denuded arteries respectively. NG-monomethyl-L-arginine (30 and 100 microM) inhibited the relaxation in endothelium-intact rings to 31 +/- 2% (P < 0.05) and 16 +/- 2% (P < 0.01) respectively and slightly but significantly attenuated the relaxation in endothelium-denuded rings to 15 +/- 1% and 13 +/- 1% (P < 0.05) respectively. 3. Glibenclamide, a potassium channel inhibitor, did not significantly after the hypoxia-induced relaxation. 4. Incubation with tetrodotoxin (3 and 10 microM) for 30 min reduced the relaxation to 31 +/- 3% (P < 0.05) and 14 +/- 2% (P < 0.01), and 14 +/- 2% (P < 0.05) and 11 +/- 1% (P < 0.05) in endothelium-intact and -denuded rings respectively. However, indomethacin (10 microM), atropine (1 microM), propranolol (10 microM) and phentolamine (10 microM) did not significantly affect the relaxation. 5. Adenosine (1, 10 and 100 MicroM) caused relaxation of 6 +/- 1%, 52 +/-3% and 97 +/-2% respectively in endothelium-denuded rings precontracted with prostaglandin F2alpha (PGF2 alpha, 3 MicroM) and the relaxation was markedly inhibited by 8-phenyltheophylline. Furthermore, glibenclamide (1 and 10 MicroM) reduced the relaxation induced by adenosine (1, 10 and 100 MicroM) to 2 +/-1% (P<0.05), 38 =/-3% (P<0.05) and 85 +/-2%(P<0.05), and 0.6 +/- 0.4% (P<0.05), 27 +/- 4% (P<0.05) and 72 +/- 4% (P<0.01) respectively, in these endothelium-denuded preparations.6. These data suggest that hypoxia-induced relaxation is mediated by the release of nitric oxide rather than by the activation of glibenclamide-sensitive potassium channels in rabbit isolated coronary arteries. A neurogenic mechanism partially modulates the relaxation, possibly by activating non-adrenergic and noncholinergic nerve endings. The inhibition by glibenclamide on adenosine-induced relaxation in isolated coronary arteries may help to explain the fact that glibenclamide inhibits hypoxic coronary relaxation in perfused hearts but not in isolated coronary preparations.

Adenosine↗
PubMed1994

Mechanisms of neuronal survival during hypoxia: ATP-sensitive K+ channels.

There has been an explosion in our understanding of how nerve cells in mammals respond to O2 deprivation and what are the mechanisms involved in nerve cell injury or survival. This is due to the development of new approaches, techniques and the clinical importance of brain ischemia and hypoxia. Recently, we have focussed on some issues pertaining to brain hypoxia in the newborn and adult. We have demonstrated that during anoxia intracellular K+ decreases significantly in nerve cells and that this K+ efflux is mediated by K+ channels that are sensitive to ATP. We have preliminary evidence that the activation of these channels attenuates the anoxia-induced depolarization in medullary neurons and can play a role in cell survival during anoxia. Further, we have characterized the distribution of these receptors/channels complexes in the CNS of the rat and in an anoxia-resistant animal: the turtle. These channels are present mainly in the cortex, substantia nigra and the cerebellum. Whole cell recordings (dissociated cells) established that these channels are postsynaptic in nature in medullary neurons. Single-channel recordings from our laboratory and those of others have started to reveal the intricacies of the regulation of these channels in excitable cells in general and in nerve cells in particular.

Adenosine Triphosphate↗
PubMed1994

Nitric oxide accounts for dose-dependent estrogen-mediated coronary relaxation after acute estrogen withdrawal.

BACKGROUND: Estrogen replacement therapy reduces the risk of coronary heart disease in postmenopausal women, and estrogen treatment modulates endothelium-dependent vasodilation in ovariectomized, atherosclerotic monkeys. Estradiol-17 beta also induces relaxation in isolated rabbit coronary arteries as well as cerebral basilar arteries. The estrogen concentrations required to induce such relaxation are in the pharmacological range (10(-6) to 10(-5) mol/L). METHODS AND RESULTS: The present study was designed to test whether the sensitivity and specificity of the relaxing response of coronary vascular smooth muscle to exogenous estradiol-17 beta is dependent on the sex hormone status of the animal. In coronary artery rings contracted with PGF2 alpha (3 x 10(-5) mol/L), estradiol-17 beta caused significant relaxation at a physiological estrogen concentration (10(-9) mol/L), in coronary artery rings from oophorectomized, estrogen-treated and acutely estrogen-withdrawn rabbits only. Relaxation induced by estradiol-17 beta at lower concentrations (10(-9) to 10(-6) mol/L) in these rings was 20 +/- 6%, 42 +/- 8%, 54 +/- 9%, and 75 +/- 8%, respectively, compared with 4 +/- 2%, 12 +/- 5%, 16 +/- 7%, and 25 +/- 12% and 5 +/- 2%, 12 +/- 5%, 18 +/- 8%, and 23 +/- 10% in rings from estrogen-maintained and oophorectomized rabbits, respectively (P < .01). The relaxation in coronary artery rings from estrogen-treated and acutely estrogen-withdrawn rabbits was endothelium and nitric oxide dependent since it was abolished by endothelium removal and the nitric oxide synthase inhibitor N omega-nitro-L-arginine. CONCLUSIONS: This study demonstrates that estrogen-induced, endothelium-dependent relaxation of coronary arteries may, in some species, depend on the sex hormone status of the animal. These findings may help to better understand the effects of ovarian steroids in the coronary circulation of females.

Animals↗
PubMed1994

Studies on atrophic change of soleus muscle and its countermeasures in suspended rat.

In the environment of microgravity, the disused atrophy of skeletal muscle, especially leg's muscle, would occur. The three purposes of this study were: 1. To observe the dynamic changes of disused atrophy of skeletal muscle under simulated weightlessness; 2. To approach the mechanism of disused atrophy of muscle; 3. To approach the countermeasures for reducing the degree of atrophy of muscle.

Animals↗
PubMed1994

[Application of the thoraco-umbilical flap in emergent repair of large defect of limbs].

We have repaired larger detect of limbs after emergent debridement using the thoraco-umbilical flap on 13 cases, 6 of which were vascular island flaps, 7 were free flaps. The size of the flaps was 10 cm x 26 cm to 12 cm x 42 cm. All the flaps survived completely. The advantages of the flap are: (1) the pedicle of the flap is long and has a large diameter, (2) the flap can be made quite long so as to cover the whole ulna or tibia, (3) the flap can be used to repair bony defect by carrying a rib as an osteocutaneous flap.

Accidents, Traffic↗
PubMed1994

[Induction of apoptosis by harringtonine and homoharringtonine in HL-60 cells].

Harringtonine (HT) and homoharringtonine (HHT) are two alkaloids isolated from the bark of the evergreen tree Cephalotaxus hainanensis Li in the 1970s. They were found to have activity against murine leukemia, Lewis lung carcinoma and B16 melanoma, and used as anti-leukemia drugs clinically. Apoptosis is an active process of programmed cell suicide and now is believed to be an important target for tumor chemotherapy. In this report, the apoptosis inducing effect of HT and HHT in HL-60 cells were observed. The experiments demonstrated that 2 x 10(-7) mol.L-1 of HT and 10(-7) mol.L-1 of HHT could induce apoptosis in HL-60 cells when the cells were exposed to HT and HHT for 4 h. In agarose gel electrophoresis, DNA extracted from HL-60 cells treated with HT and HHT showed a typical internucleosomal DNA degradation, i.e., DNA ladder and parallel morphological changes as nuclear chromosome segmentation and condensation as well as cytoplasma vacuolation. This effect of HT and HHT was shown to appear in a concentration- and time-dependent manner. The efficacy of HT and HHT in inducing apoptosis of HL-60 cells was found to parallel with their cytotoxic activity in HL-60 cells. These results suggest that the mechanism of antitumor action of HT and HHT is related to their apoptosis inducing activity.

Antineoplastic Agents, Phytogenic↗
PubMed1994

[Morphological observations of effects on mouse brain exposed to subteratogenic--dose of methylmercury].

Short-term and long-term changes in mouse brain caused by in utero exposure to subteratogenic-dose of methylmercury were studied with electronic computer digitalized graphic system, electron microscopy and other methods. Results revealed degeneration and loss of mouse brain cells occurred both in short-term and long-term groups, but the lesions were more severe in the latter than in the former groups. The fact that exposed young mice exhibited no obvious abnormality in their outward appearance and behavior indicated subteratogenic-dose of methylmercury had a long-term and latent toxic effects on mouse brain.

Animals↗
PubMed1994

Oxygen deprivation activates an ATP-inhibitable K+ channel in substantia nigra neurons.

Depending on its severity and duration, O2 deprivation activates mechanisms that can lead to profound deleterious changes in neuronal structure and function. Hypoxia also evokes inherent adaptive mechanisms that can possibly delay injury and increase neuronal survival. One of these neuronal adaptive mechanisms is believed to be the activation of K+ channels, but direct evidence for their activation is lacking. We performed experiments to test the hypothesis that hypoxia induces activation of K+ channels via changes in cytosolic and membrane factors such as ATP, Ca2+, and membrane potential. The effect of hypoxia on single-channel currents was studied in rat substantia nigra neurons, since these have a high density of glibenclamide binding sites. In cell-attached patches, hypoxia or cyanide reversibly activated an outward current. This hypoxia-activated current in excised inside-out patches was K+ selective and voltage dependent, and had a high sensitivity to internal ATP, ADP, and AMP-PNP, a nonhydrolyzable ATP analog. Activation of this channel required the presence of free Ca2+ on the cytosolic side, but charybdotoxin or apamin did not have any effect on this channel. The effect of ATP on channel activity was not a result of Ca2+ chelation because Mg.ATP in high Mg2+ background and K2.ATP in high Ca2+ environment inhibited the channel. These results suggest that although this hypoxia-activated K+ channel shares properties with ATP-sensitive K+ (KATP) channels in other tissues, substantia nigra neurons seem to have a different subtype or isoform of KATP channels. Gating this channel by multiple factors simultaneously would allow this channel to be particularly suitable for activation during metabolic stress.

Adenosine Triphosphate↗
PubMed1994

[Study on clinical application of expanded skin tubes].

Skin transplantation is an operative method generally used in reparative and reconstructive surgery. How to minimize the cicatrices of the donor site, how to repair larger recipient site, and how to reconstruct organs with restoration of their functions and shapes are important problems in plastic surgery. Since September 1990, we have designed a technique of expanding skin tubes for the repair of wounds and for the reconstruction of organs when larger area of skin is required while the skin of the donor site is deficient, or when the cicatrices of the donor site are to be minimized. This technique had been applied clinically in 10 cases. Clinical practice has proved that this new operative method is superior to skin grafts, transplantation of skin flaps, and the conventional technique of expanding skin and soft tissue. This paper describes the five characteristics and the theoretical basis of the technique of expansion of skin tubes.

Adolescent↗
PubMed1993

Mechanisms of anoxia-induced depolarization in brainstem neurons: in vitro current and voltage clamp studies in the adult rat.

To determine the mechanisms underlying the depolarization induced by anoxia in brainstem neurons, we studied single neurons in brainstem slices using conventional micro-electrodes and freshly dissociated hypoglossal and vagal cells using patch clamp techniques (whole-cell configuration). Since glutamate concentration increases in the extracellular space during O2 deprivation, we first tested whether N-methyl-D-aspartate (NMDA) and non-NMDA receptors are involved in this anoxia-induced depolarization. APV, MK-801, CNQX and KYN (NMDA and non-NMDA blockers), which bathed slices after control anoxia runs, did not affect the depolarization trajectory. Decreasing extracellular Na+ (Nao+) from 150 mM to 5 mM attenuated markedly and significantly the depolarization observed during anoxia (15-20% of control). The relation between intracellular adenosine triphosphate (ATP) and the anoxia-induced depolarization was also investigated in the slice and in dissociated single brainstem neurons. In the slice, iontophoresis of ATP did not give consistent results. Since we could not ascertain that ATP was actually iontophoresed through high resistance (50-80 M omega) microelectrodes, we patched single neurons and studied the effect of clamping intracellular ATP levels on the hyperpolarizing holding current (IH) in the voltage clamp mode. The increase in IH with anoxia (or cyanide) was markedly attenuated in cells patched with pipettes containing ATP. We conclude that in brainstem neurons, the anoxia-induced depolarization: (a) is not a function of an increase in extracellular glutamate concentration; and (b) depends on Na+ and ATP-mediated processes.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1993

Inhibition kinetics of chloramphenicol acetyltransferase by selected detergents.

Kinetic analyses indicate that the inhibitory effects of the nonionic detergents Triton X-100 and Nonidet P-40 on chloramphenicol acetyltransferase are exerted by a competitive and a non-competitive mechanism with respect to the substrates chloramphenicol and acetyl-CoA, respectively. Comparison with nonionic detergents without an aromatic moiety like that present in Triton X-100 and Nonidet P-40 suggests that the aromatic groups in these two detergents may compete with chloramphenicol for binding to the hydrophobic, active site in the chloramphenicol acetyltransferase.

Acetyl Coenzyme A↗
PubMed1993

Altered fluid transport across airway epithelium in cystic fibrosis.

In cystic fibrosis (CF), absence or dysfunction of a phosphorylation-regulated chloride channel [CF transmembrane conductance regulator (CFTR)] leads to the loss or reduction of chloride secretion into the airways. Active sodium absorption is also increased in CF, and both of these ion transport changes could alter fluid transport across the airways. Under baseline conditions, cultured human airway epithelia from normal individuals absorbed fluid, and this absorption was increased in epithelia from patients with CF. In normal and CF epithelial cultures fluid absorption was inhibited by amiloride. Adenosine 3',5'-monophosphate stimulated fluid secretion in normal epithelial cultures but not in cultures from individuals with CF. In contrast, fluid secretion induced by nucleotide triphosphates (uridine triphosphate or adenosine triphosphate) was unaltered in cultures of epithelia from patients with CF, suggesting an approach to the treatment of CF.

Absorption↗
PubMed1993

Acute anoxia-induced alterations in MAP2 immunoreactivity and neuronal morphology in rat hippocampus.

Cerebral ischemia induces major neuronal morphological alterations. It is not clear, however, whether this is directly caused by O2 deprivation. To determine the effect of hypoxia on cytoskeletal structures and neuronal morphology, we performed experiments and examined anoxia-induced changes in microtubule-associated protein 2 (MAP2) and cell morphology in hippocampal slices in vitro. Anoxia (measured PO2 = 0 Torr) induced a marked loss in dendritic MAP2 immunoreactivity and cell swelling of hippocampal neurons by 2 h after O2 reinstitution. These changes were severe in CA1 and CA3 neurons and comparatively mild in dentate gyrus neurons. Quantitative analysis showed that 10 min of anoxia induced a 30% loss of MAP2-positive dendrites but this increased to 70% after 30 min of anoxia. A concurrent major increase in somata area of about 100% and 200% was observed in CA1 and CA3 neurons respectively. Somata area in the lower dentate gyrus, however, increased either insignificantly or by only 30% for the respective periods of anoxia. These results suggest that deprivation of O2 can by itself induce a major loss in dendritic MAP2 immunoreactivity and changes in cell morphology in hippocampal neurons. These alterations occur rapidly after hypoxia, and the severity of these changes is directly related to the duration of anoxia and brain region in the hippocampus.

Animals↗