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Biomedical subjects

K Chen

Publications and source records attributed to K Chen.

At least 145 records · Page 8Linked to original sources
PubMed2000

Yang-Gan-Wan protects mice against experimental liver damage.

The hepatoprotective effect of Yang-Gan-Wan (YGW, Pro-Liver pill), a Chinese herbal remedy, was investigated in mice that were treated with allyl alcohol (AlOH), acetaminophen (AA) or carbon tetrachloride (CCl4). Mice were pretreated daily with 200 mg/kg YGW for 10, 14 and 18 days before treatment with 85 mg/kg AlOH, 475 mg/kg AA or 20 microl/kg CCl4, respectively. YGW dramatically abolished the elevated activities of alanine aminotransferase (ALT) and sorbitol dehydrogenase (SDH) and reduced the necrosis induced by AlOH. YGW also decreased the elevated activities of ALT and SDH and reduced the necrosis induced by AA and CCl4. This study demonstrates that YGW has protective effects against liver damage induced by AlOH, AA, and CCl4.

Acetaminophen↗
PubMed2000

Yang-gan-wan protects mice against apoptosis induced by anti-Fas antibody (Jo2).

We investigated the protective effect of yang-gan-wan (YGW, Pro-Liver pill), a Chinese herbal remedy, against liver apoptosis (programmed cell death) induced by anti-Fas antibody (Jo2). Mice were pretreated daily with 200 mg/kg YGW for 14 days before treatment with 10 microg/20 kg body weight Jo2. YGW significantly reduced the elevated activity of alanine aminotransferase (ALT) and also reduced the elevated activity of sorbitol dehydrogenase (SDH) produced 4 hrs after treatment with Jo2. YGW also increased the survival of mice treated with Jo2 by about 1 hr in 11 out of 16 mice (69%). Most of the mice died 9 hrs after Jo2 injection. This study demonstrates that YGW has protective effects against liver apoptosis induced by Jo2.

Alanine Transaminase↗
PubMed2000

Vitamin C suppresses oxidative lipid damage in vivo, even in the presence of iron overload.

Ascorbate is a strong antioxidant; however, it can also act as a prooxidant in vitro by reducing transition metals. To investigate the in vivo relevance of this prooxidant activity, we performed a study using guinea pigs fed high or low ascorbate doses with or without prior loading with iron dextran. Iron-loaded animals gained less weight and exhibited increased plasma beta-N-acetyl-D-glucosaminidase activity, a marker of tissue lysosomal membrane damage, compared with control animals. The iron-loaded animals fed the low ascorbate dose had decreased plasma alpha-tocopherol levels and increased plasma levels of triglycerides and F(2)-isoprostanes, specific and sensitive markers of in vivo lipid peroxidation. In contrast, the two groups of animals fed the high ascorbate dose had significantly lower hepatic F(2)-isoprostane levels than the groups fed the low ascorbate dose, irrespective of iron load. These data indicate that 1) ascorbate acts as an antioxidant toward lipids in vivo, even in the presence of iron overload; 2) iron loading per se does not cause oxidative lipid damage but is associated with growth retardation and tissue damage, both of which are not affected by vitamin C; and 3) the combination of iron loading with a low ascorbate status causes additional pathophysiological changes, in particular, increased plasma triglycerides.

Animals↗
PubMed2000

Types of marijuana users by longitudinal course.

OBJECTIVE: Taxonomies of alcoholism and antisocial behaviors based on developmental course converge on two-group classifications that emphasize early and late onset. Typologies for users of illicit drugs remain to be developed. This article proposes a developmental taxonomy of marijuana users. METHOD: Cluster analysis was applied to a representative community sample of 708 (364 male, 344 female) marijuana users followed from adolescence to age 34-35. The Ward method, followed by relocation, was used to classify marijuana users into different types based on age of onset, chronicity of heavy use and persistence of use. ANOVA and logit analyses were utilized to describe the cluster solution and examine the correlates of cluster membership. RESULTS: Four marijuana use clusters were identified: early onset-heavy use, early onset-light use, mid onset-heavy use and late onset-light use. The groups differed from each other in degree of involvement in marijuana and other drugs, sociodemographic and lifestyle characteristics. The majority of those with early onset did not become heavily involved in marijuana. Unique factors were associated with membership in each group. Factors differentiating early from mid-onset heavy use included association with marijuana-using peers and having had a mental disorder. Peer delinquency was an additional factor differentiating early initiators who became heavy users from those who did not. CONCLUSIONS: A simple two-type classification fails to take into account the heterogeneity of early and late onset groups. By itself, early onset into marijuana will not lead to problematic use or rapid progression into the use of other drugs. Motivation underlying use and dysfunctional behaviors are associated with the development of problematic drug use and dependence.

Adolescent↗
PubMed2000

Differential brain responses to satiation in obese and lean men.

Knowledge of how the brain contributes to the regulation of food intake in humans is limited. We used positron emission tomography and measures of regional cerebral blood flow (rCBF) (a marker of neuronal activity) to describe the functional anatomy of satiation (i.e., the response to a liquid meal) in the context of extreme hunger (36-h fast) in 11 obese (BMI > or =35 kg/m2, age 27+/-5 years, weight 115+/-11 kg, 38+/-7% body fat; mean +/- SD) and 11 lean (BMI < or =25 kg/m2, age 35+/-8 years, weight 73+/-9 kg, 19+/-6% body fat) men. As in lean men, satiation in obese men produced significant increases in rCBF in the vicinity of the ventromedial and dorsolateral prefrontal cortex and significant decreases in rCBF in the vicinity of the limbic/paralimbic areas (i.e., hippocampal formation, temporal pole), striatum (i.e., caudate, putamen), precuneus, and cerebellum. However, rCBF increases in the prefrontal cortex were significantly greater in obese men than in lean men (P < 0.005). rCBF decreases in limbic/paralimbic areas, temporal and occipital cortex, and cerebellum were also significantly greater in obese men than in lean men (P < 0.005), whereas rCBF decreases in the hypothalamus and thalamus were attenuated in obese men compared with lean men (P < 0.05). This study raises the possibility that the brain responses to a meal in the prefrontal areas (which may be involved in the inhibition of inappropriate response tendencies) and limbic/paralimbic areas (commonly associated with the regulation of emotion) may be different in obese and lean men. Additional studies are required to investigate how these differential responses are related to the pathophysiology of obesity.

Adult↗
PubMed2000

Prolonged febrile seizures in the immature rat model enhance hippocampal excitability long term.

Febrile seizures (FSs) constitute the most prevalent seizure type during childhood. Whether prolonged FSs alter limbic excitability, leading to spontaneous seizures (temporal lobe epilepsy) during adulthood, has been controversial. Recent data indicate that, in the immature rat model, prolonged FSs induce transient structural changes of some hippocampal pyramidal neurons and long-term functional changes of hippocampal circuitry. However, whether these neuroanatomical and electrophysiological changes promote hippocampal excitability and lead to epilepsy has remained unknown. By using in vivo and in vitro approaches, we determined that prolonged hyperthermia-induced seizures in immature rats caused long-term enhanced susceptibility to limbic convulsants that lasted to adulthood. Thus, extensive hippocampal electroencephalographic and behavioral monitoring failed to demonstrate spontaneous seizures in adult rats that had experienced hyperthermic seizures during infancy. However, 100% of animals developed hippocampal seizures after systemic administration of a low dose of kainate, and most progressed to status epilepticus. Conversely, a minority of normothermic and hyperthermic controls had (brief) seizures, none developing status epilepticus. In vitro, spontaneous epileptiform discharges were not observed in hippocampal-entorhinal cortex slices derived from either control or experimental groups. However, Schaeffer collateral stimulation induced prolonged, self-sustaining, status epilepticus-like discharges exclusively in slices from experimental rats. These data indicate that hyperthermic seizures in the immature rat model of FSs do not cause spontaneous limbic seizures during adulthood. However, they reduce thresholds to chemical convulsants in vivo and electrical stimulation in vitro, indicating persistent enhancement of limbic excitability that may facilitate the development of epilepsy.

Animals↗
PubMed2000

Nitric oxide induces heme oxygenase-1 via mitogen-activated protein kinases ERK and p38.

Heme oxygenase-1 (HO), the heat shock/stress cognate of the heat shock protein 32 (HSP32) family of proteins, is postulated to be a component of cellular defense mechanisms against oxidative stress-mediated injury. Nitric oxide (NO) is among the extensive array of stimuli that induce HO-1. The cellular signaling mechanisms that regulate the induction of HO-1 by NO are not understood. In the present study, we have demonstrated that exposure of HeLa cells to the NO donor, sodium nitroprusside (SNP), results in concentration and time-dependent increase in HO-1 mRNA and activation of MAPKs: ERK (ERK1 and ERK2) and p38 pathways, but not SAPK/JNK pathway. Pre-treatment of the cells with PD98059, a selective ERK pathway inhibitor, and SB203580, a p38 MAPK inhibitor, blocked the induction of HO-1 by the NO donor in a dose-dependent manner. In addition, an increase in HO-1 mRNA level that was detected as early as 2 hrs.following SNP treatment preceded c-jun and c-fos induction. These transcription factors are downstream of SAPK/JNK pathway, and their increased expression was detected at 3hr. and 6hr. after SNP treatment. Similarly, AP-1 DNA binding activity was not increased when measured 6 hrs. after SNP treatment. ERK and p38 inhibitors also suppressed induction of HO-1 by SNAP and GSNO. The increase in HO-1 mRNA was inhibited by actinomycin D and cycloheximide, but not by NAC, and was not mimicked by the lipophilic cGMP analogue, 8-bromo-cGMP, suggesting that NO-mediated induction required de novo RNA and protein synthesis and was unrelated to cGMP and redox signaling. Collectively, the findings suggest that MAP kinase ERK and p38 pathways are involved in the NO-mediated induction of HO-1 and that SAPK/JNK pathway and increased DNA binding of AP-1 transcription factor are not involved in HO-1 gene activation by NO. A plausible mechanism by which the NO donors cause HO-1 induction may involve HO-1 gene regulation by its substrate, heme.

Enzyme Activation↗
PubMed2000

Mechanism of protein import across the chloroplast envelope.

The development and maintenance of chloroplasts relies on the contribution of protein subunits from both plastid and nuclear genomes. Most chloroplast proteins are encoded by nuclear genes and are post-translationally imported into the organelle across the double membrane of the chloroplast envelope. Protein import into the chloroplast consists of two essential elements: the specific recognition of the targeting signals (transit sequences) of cytoplasmic preproteins by receptors at the outer envelope membrane and the subsequent translocation of preproteins simultaneously across the double membrane of the envelope. These processes are mediated via the co-ordinate action of protein translocon complexes in the outer (Toc apparatus) and inner (Tic apparatus) envelope membranes.

Amino Acid Sequence↗
PubMed2000

Two hundred and seventeen cases of winter diseases treated with acupoint stimulation in summer.

217 cases of chronic bronchitis and asthma were clinically treated and analyzed for the effects of combining electric stimulation with topical application of drug on acupoints. The results suggested that the combined therapy was superior to unitary therapy (P < 0.05). It is indicated that the combined therapy has a good curative effect in both short- and long-terms.

Acupuncture Points↗
PubMed2000

A study of hemorheological behaviour for patients with Alzheimer's disease at the early stages.

To evaluate the change of hemorheological indexes for patients with Alzheimer's disease (AD) at the early stages and to discuss effects of these changes on AD, high shear value of whole blood viscosity (etabh), reduced high shear value of whole blood viscosity (retabh), low shear value of whole blood viscosity (etabl), reduced low shear, value of whole blood viscosity (retabl), KT value of whole blood viscosity, hematocrit (HCT) and blood plasma viscosity (etaP) were measured in 31 patients with probable AD at the early stages and 33 age-matched healthy subjects. There were significant differences of all hemorheological indexes between AD group and control group except HCT. Step discriminant analysis revealed 81.25% of overall group-classified accuracy in a hemorheological discriminant function consisting of etabl, retabl, retabh and HCT. Significant difference of hemorheological indexes existed between AD and age-matched healthy control subjects. The results showed that measurement of hemorheological indexes could be used as one of reference standards of diagnosis in AD.

Aged↗
PubMed2000

Characterization of thyroid fibrosis in a murine model of granulomatous experimental autoimmune thyroiditis.

This study was initiated to identify and characterize thyroid fibrosis in a murine model of granulomatous experimental autoimmune thyroiditis (G-EAT) and determine if TGF-beta1 might be involved in fibrosis. G-EAT was induced by transfer of mouse thyroglobulin-sensitized spleen cells activated in vitro with thyroglobulin, anti-IL-2R, and IL-12. There was almost complete destruction of thyroid follicles, leading to fibrosis of the gland and reduced serum T4 levels. Fibrosis was confirmed by staining for collagen and alpha smooth-muscle actin, a marker of myofibroblasts. Kinetic studies characterized the onset and development of thyroid fibrosis. TGF-1beta was increased at mRNA and protein levels, and expression of TGF-beta1 protein paralleled G-EAT severity. Comparison of staining patterns showed that TGF-beta1 was expressed in areas of myofibroblast and collagen accumulation, implying that TGF-beta1 may play a role in fibrosis in G-EAT. Further studies demonstrated that myofibroblasts, macrophages, and thyrocytes contributed to TGF-beta1 production. This provides an excellent model to study the mechanisms of fibrosis associated with autoimmune damage.

Actins↗
PubMed2000

Influence of neuraminidase on the characteristics of microrheology of red blood cells.

Surface charge was removed from RBC (erythrocyte) membrane to different degrees with biochemical methods, i.e., treatment of RBCs with neuraminidase, either using different doses for the same incubation time (1 hour) or using the same dose (75 milli-unit) for different incubation time. Several rheological properties of the RBCs with surface charge removal were observed, including the deformation index DI (using traditional ektacytometry) orientation index (DI)or and small deformation index (Dl)d (using new ektacytometry), the viscosity at low and high shear rates (using a cone-plate rotating viscosimeter). In addition, photographs of RBCs aggregation under a microscope and the histograms of RBC aggregate size after treatment with neuraminidase were obtained. It is found from these experiments that the decrease of the surface charge of RBCs leads to the decrease in the deformation and orientation indices as well as the increase in blood viscosity.

Animals↗
PubMed2000

[Clinical effect of Xiongshao capsule on preventing restenosis post-PTCA or/and stenting].

OBJECTIVE: To evaluate the effect of Xiongshao capsule (XSC) in preventing clinical and angiographic restenosis after coronary angioplasty or/and stenting. METHODS: Sixty-five coronary heart disease (CHD) patients with successful angioplasty or and stenting were randomly divided into the control group (37 cases, routine treatment) and the XSC group (28 cases, routine treatment plus XSC). The recurrent of angina, changing of blood stasis syndrome score (BSSS) and coronary angiography within 6 months after coronary angioplasty or/and stenting were observed. RESULTS: Recurrent angina occurred in 6 out of 28 patients in the XSC group, which was much better than that in the control group, 18 out of 37 patients (P < 0.05). Follow-up angiography was performed in 26 including 10 patients in the XSC group (restenosis was observed in 4 cases), and 16 cases in the control group (restenosis in 13 cases), there was significant difference between the XSC group and the control group (P < 0.05). For BSSS at follow-up, XSC group was much lower than that of the control group (P < 0.01). Logistic regress analysis showed the combination with XSC and the base-line BSSS were important affecting factors on the occurrence of restenosis (P < 0.05). The odds ratio of the occurrence of angiographic restenosis (BSSS > 25 to BSSS < or = 25) was 6.5. CONCLUSIONS: XSC could markedly reduce the occurrence of restenosis, recurrence of angina and improve the condition of blood stasis after coronary angioplasty or/and stenting. The severity of blood stasis syndrome was an important affecting factor on the occurrence of restenosis. BSSS > 25 can be served as one of the predicting factors of the occurrence of restenosis after coronary angioplasty or/and stenting.

Adult↗