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Biomedical subjects

P Liu

Publications and source records attributed to P Liu.

At least 217 records · Page 12Linked to original sources
PubMed1997

Current source density analysis of the potential evoked in hippocampus by perirhinal cortex stimulation.

Previous anatomical research has demonstrated that the perirhinal cortex (PRC) projects to the dorsal hippocampal CA1 field. We have recently presented data (Liu and Bilkey, Hippocampus 1996; 6:125-135) which suggests that this pathway courses via the lateral perforant path (LPP). In the present study, laminar profiles of the average evoked potentials and current source density (CSD) analysis were used to study the input from the perirhinal cortex to the dorsal hippocampus in the urethane-anaesthetized rat. Stimulation of the lateral perforant path activated a current sink in the stratum lacunosum-moleculare of CA1 and the outer molecular layer of the dentate gyrus with an onset latency of 3.5 ms. Stimulation of the perirhinal cortex produced a very similar sink-source pattern with an onset latency of 4.0 ms. Higher-intensity stimulation of lateral entorhinal cortex also produced a similar pattern with an onset latency of 4.5 ms. Electrolytic lesions of PRC conducted 4-5 days prior to testing resulted in a major decrease (58%) in the amplitude of the LPP-elicited potentials and a corresponding reduction across the whole source-sink pattern. A similar result was observed following ibotenic acid lesions of PRC. In contrast, similar-sized electrolytic lesions of lateral entorhinal cortex produced a much smaller (16%) decrease in potential amplitude and little change in the source-sink pattern. These data provide further support for the hypothesis that perirhinal cortex projects to both the dentate gyrus and CA1 regions of the hippocampus via the lateral perforant path.

Afferent Pathways↗
PubMed1997

Hepatocarcinogenesis in woodchuck hepatitis virus/c-myc mice: sustained cell proliferation and biphasic activation of insulin-like growth factor II.

Transgenic mice carrying the c-myc oncogene under control of woodchuck hepatitis virus (WHV) DNA sequences invariably develop hepatocellular carcinoma (HCC), despite a temporally limited expression of the transgene in the neonatal liver. To better characterize the different steps of the tumorigenic process, we analyzed the liver expression of the c-myc transgene and several growth-related genes by in situ hybridization and Northern blotting. In parallel studies, proliferated changes were investigated by detection of bromodeoxy-uridine-positive S-phase nuclei and apoptosis was evaluated by in situ nick end-labeling of DNA. During the neonatal period, high levels of c-myc messenger RNAs (mRNAs) were detected in all hepatocytes, and the expression of insulin-like growth factor II (IGF II) was frequently enhanced, correlating with increased cell proliferation. Despite elevated expression of the p53 gene, no change in liver cell apoptosis was observed. After weaning, c-myc transgene expression decreased to undetectable levels in all hepatocytes, whereas proliferation decreased but remained notably higher than in age-matched controls. The expression of c-fos, c-jun, and c-H-ras was highly variable during the preneoplastic period and in the tumors, with no consistent increase compared with controls. Resurgence of c-myc transgene expression was evidenced in all cells from hyperplastic lesions and carcinomas, accompanied with frequent focal reactivation of IGF II. Thus the strong proliferative stimulus induced by the combined effects of c-myc and IGF II in the neonatal liver might initiate a process characterized by persistent, dysregulated hepatocyte proliferation, in turn greatly increasing the risk of hepatocellular transformation.

Animals↗
PubMed1997

A prospective study of a serum-pooling strategy in screening blood donors for antibody to hepatitis C virus.

BACKGROUND: To examine the feasibility and to perform a cost-benefit analysis of a pooling protocol of enzyme immunoassay (EIA) screening for antibody to hepatitis C virus (anti-HCV) under real conditions, a prospective study was carried out using sera from 1875 local blood donors. STUDY DESIGN AND METHODS: In the absence of knowledge of the anti-HCV reactions, the donor's sera were pooled into groups of five consecutive samples for testing by EIA. The dilution and final volume of the serum pool were adjusted to equal those recommended for single-serum EIA by the manufacturer of the test kit. The results obtained were compared with those of single-serum EIA to assess the feasibility of the pooling protocol. By applying probability theory, the percentage of reduction in the number of tests performed (L value) when the serum-pooling strategy was used was calculated for several anti-HCV seroprevalences and for varied sizes of pool. The calculations were performed on a computer using a program compiled by the authors. RESULTS: The results showed that seroprevalence was 2.24 percent (95% CI, 1.57-2.91%); the rate of false negativity was 0 (95% CI, 0-8.4%), the sensitivity of the pooling protocol was 100 percent (95% CI, 91.6-100.0%), the rate of false positivity was 0.8 percent (95% CI, 0-1.8%), and the specificity of the pooling protocol was 99.2 percent (95% CI, 98.2-100.0%). Cost-benefit analysis showed that the pooling protocol could save 69.3 percent of the cost. A table of L values can be used conveniently by serologists to determine the optimum pool size if estimates of seroprevalence are available. CONCLUSION: The pool EIA did not perform worse than individual EIAs, and the pooling strategy was markedly less expansive. The pooling protocol was recommended for screening of anti-HCV-positive subjects from large populations with low seroprevalence.

Adolescent↗
PubMed1997

The mechanism of the initial natriuresis after transjugular intrahepatic portosystemic shunt.

BACKGROUND & AIMS: The pathogenesis of the delayed natriuresis after transjugular intrahepatic portosystemic shunt (TIPS) insertion is unknown. This was studied to elucidate the mechanism involved. METHODS: In 12 patients with cirrhosis and refractory ascites after TIPS, systemic and renal hemodynamics, renal sodium handling, central blood volume, neurohumoral factors, and hepatic function were studied weekly after the shunt with the patients receiving a diet of 20 mmol sodium/day. RESULTS: Two weeks after TIPS, the initial natriuresis (4 +/- 1 to 18 +/- 3 mmol/day; P < 0.05) was associated with significant reductions in corrected sinusoidal pressure (24.4 +/- 1.8 to 7.5 +/- 0.4 mm Hg; P < 0.001), proximal renal tubular reabsorption of sodium (P = 0.05), and renin-angiotensin-aldosterone activity (P < 0.05), but with significant systemic vasodilatation (P < 0.05). At 4 weeks, negative sodium balance was achieved (52 +/- 21 mmol/day; P < 0.01), despite continued systemic arterial vasodilatation, associated with significant increases in total central and cardiac volumes (P < 0.05) and normalization of serum aldosterone levels (P < 0.01). Four late responders were significantly older (P = 0.01) and had significantly lower baseline glomerular filtration rates (P = 0.02). CONCLUSIONS: In cirrhosis, sinusoidal portal hypertension and an activated renin-angiotensin-aldosterone system seem to be important in the pathogenesis of sodium retention. Systemic vasodilatation without arterial underfilling does not prevent natriuresis. Delayed natriuresis after TIPS is associated with increasing age and pre-TIPS renal impairment.

Adult↗
PubMed1997

Cellular and molecular mechanisms of murine autoimmune myocarditis.

Dilated cardiomyopathy is a prevalent cause of progressive heart disease and sudden death, and most patients with cardiomyopathy have a history of viral myocarditis. Coxsackie B3 (CB3) picornaviruses can be detected in as many as 50% of these patients and CB3 infections have been epidemiologically linked to chronic heart disease. Several clinical and experimental studies suggest that chronic stages of disease are mediated by an autoimmune response against heart muscle myosin. Human heart disease can be mimicked in mice using cardiac myosin as autoantigen. Murine cardiac myosin-induced myocarditis is an organ-specific autoimmune disease and mediated by CD4+ T cells that recognize a myosin-specific peptide in association with MHC class II molecules. Here, the recent discovery of autoimmune epitopes derived from the alpha isoform of cardiac myosin, the functional roles of surface receptor and signal transduction molecules, and the molecular mechanisms of target organ susceptibility will be discussed.

Amino Acid Sequence↗
PubMed1997

The Epstein-Barr virus-induced Ca2+/calmodulin-dependent kinase type IV/Gr promotes a Ca(2+)-dependent switch from latency to viral replication.

The switch from latency to viral replication in Epstein-Barr virus (EBV)-transformed human B cells is mediated by Zta, the protein product of immediate-early EBV gene BZLF1. BZLF1 transcription is normally suppressed in EBV-transformed B cells but can be induced in some cell lines upon ligation of surface immunoglobulin by mechanisms that include the activation of Ca(2+)-dependent signaling pathways. The multifunctional Ca2+/calmodulin-dependent kinase type IV/Gr (CaMKIV/Gr) is normally absent in primary human B cells, but its expression is induced by the EBV oncoprotein LMP1 in the course of B-cell growth transformation by EBV. In this study, we demonstrate that activated CaMKIV/Gr induces transcription from the BZLF1 promoter and upregulates the expression of Zta in permissive cells. Transcriptional activation of the BZLF1 promoter by CaMKIV/Gr is dependent on the CREB/AP1 binding element ZII and is greatly augmented by the Ca2+/calmodulin-dependent phosphatase calcineurin. These results outline a virus-regulated mechanism involving CaMKIV/Gr which promotes transition from latency to productive viral replication in response to Ca(2+)-mobilizing extracellular signals.

Binding Sites↗
PubMed1997

Formation of nitric oxide, superoxide, and peroxynitrite in myocardial ischemia-reperfusion injury in rats.

In the present study, the contribution of nitric oxide (NO), superoxide, and peroxynitrite to the inflammatory response induced by myocardial ischemia-reperfusion (MI/R) was investigated. Male Sprague-Dawley rats were anesthetized, and the left main coronary artery was ligated for 20 min and reperfused for 5 h. MI/R induced severe arrhythmias, indicated by a significantly elevated arrhythmia score in the MI/R group compared with that in the sham control group. Creatine kinase activity in the left ventricular free wall of the MI/R group was significantly reduced by 38%. In contrast, myeloperoxidase activity in the left ventricular free wall of the MI/R group was increased by 140%. Similarly, superoxide and tissue NO levels in the ischemic region of the heurt were increased by 140 and 90%, respectively. Superoxide and NO values in the nonischemic regions were similar to the sham control group. Total NO synthase (NOS) activity was elevated by 212%; moreover, inducible NOS (iNOS) activity increased 6.7-fold in the ischemic vs. nonischemic regions. MI/R also induced both systemic and remote organ (lung) inflammatory responses. Circulating neutrophils and plasma NO levels were increased by 163 and 138%, respectively, in MI/R rats compared with sham control animals. NO levels and superoxide generation were increased by 90 and 176%, respectively, in the lung tissues. The expression of iNOS and peroxynitrite generation were demonstrated by immunohistochemical staining with polyclonal anti-iNOS and monoclonal anti-nitrotyrosine antibodies, respectively. Sections of both the ischemic area of the ventricular wall and the lung tissue of MI/R animals exhibited a marked immunoreactivity with anti-iNOS and anti-nitrotyrosine antibodies, indicating the presence of iNOS and nitrotyrosine. Our data indicate that NO, superoxide, and peroxynitrite formation are elevated after reperfusion of the ischemic heart, suggesting that these inflammatory mediators may be involved in MI/R injury.

Animals↗
PubMed1997

Students' stress in China, Japan and Korea: a transcultural study.

In this transcultural comparison of stress among Chinese, Japanese and Korean students, the authors examined stressors with the Stress Questionnaire Form for College Students, strategies for coping with Ways of Coping-Revised, and physical reactions to the stressors with the Physical Symptom Scale of Stress. Compared to the Japanese and Korean students, Chinese students had a multitude of stressors and experienced the highest level of stress. In coping with stressful events, Koreans were the most active, Chinese the least active and Japanese were intermediately active. Physical symptoms were found to be most serious in Koreans and less serious in Chinese and Japanese. Coping techniques seemed unrelated to alleviating physical symptoms in Koreans but mildly related in Chinese and Japanese.

Adaptation, Psychological↗
PubMed1997

Impact of psychosocial factors on health outcomes in the elderly. A prospective study.

One hundred and thirty-five initially healthy men and women older than 65 years of age were studied prospectively to identify factors associated with health outcomes. At study onset, measures of personality, social interaction, and health locus of control were obtained while participants were still healthy. A reliable health outcome measure was developed, based on the annual objective coding of morbidity. Correlations between variables showed significant associations between age, a less independent personality trait, and poor health outcomes. Anxiety and low levels of social interaction were associated with poor health after 8 years. Gender and health locus of control were not significantly related to health outcomes. A path analysis showed significant direct paths between age and trait anxiety and 8-year health outcomes, and indirect paths between anxiety and extroversion and 8-year health, by way of social interaction. There was no evidence that social interaction mediated the effects of either anxiety or extroversion on health. The structure of psychosocial characteristics of the healthy elderly sample was revealed in the pattern of correlations between personality, social interaction, and locus of control.

Aged↗
PubMed1997

[Actions of salvianolic acid A on CCl4-poisoned liver injury and fibrosis in rats].

AIM: To study the actions of salvianolic acid A (SA-A) on liver injury and liver fibrosis. METHODS: The liver fibrotic rat was made by i.p. injection of CCl4. The model rats were divided into 3 groups treated with SA-A, colchicine (Col), and Salvia miltiorrhiza Bunge (SMB), respectively. Six wk later the rat liver pathology was examined, type I and III collagen in the liver were examined by immunohistochemistical method. Also hydroxyproline (Hyd) and malondialdehyde (MDA) in the liver, alanine aminotransferase (AlaAT), aspartate aminotransferase (AspAT), and albumin (Alb) levels in the serum were measured. RESULTS: SA-A inhibited serum AlaAT and AspAT activities, decreased MDA and Hyd contents, alleviated liver fibrogenesis, protected deposition of type I and III collagen in liver matrix. The actions of SA-A on liver fibrosis were similar to those of Col and SMB, action of SA-A decreasing MDA was better than that of Col. CONCLUSION: SA-A has marked effects against liver injury and fibrosis, associated with its anti-lipid peroxidation actions.

Alanine Transaminase↗
PubMed1997

116 cases of coronary angina pectoris treated with powder composed of radix ginseng, radix notoginseng and succinum.

116 cases of coronary angina pectoris were treated with a powder composed of Radix Ginseng, Radix Notoginseng and Succinum, which was an empirical prescription of Dr. Yue Meizhong ([symbol: see text]), and compared with patients treated Fufang Danshen Tablet (a compound prescription of Radix Salviae Miltiorrhizae) as the control group. Results indicated that the curative effects and ECG in the treated group were better than that in the control group (P < 0.01), so were improvement of general symptoms, physical strength as well as changes of lipid metabolism and microcirculation of nail fold.

Adult↗
PubMed1997

[Changes of corneal topography and refraction after radial keratotomy and its combination with transverse incision].

OBJECTIVE: In order to understand the changes of morphology and refractive power of cornea after radial keratotomy (RK) and its combination with transverse incision (T-incision), and the wound healing of the T-incision. METHODS: Corneal topography aided with a computer was used to analyze the changes of patients having undergone RK and RK combined with T-incision. The wound healing was analyzed, and the refractive powers of strong axis and weak axis of corneas were measured. RESULTS: Corneal surface regularity index (SRI) and surface asymmetry index (SAI) became greater and greater along with the increase of myopia-astigmatism. The refractive powers of corneal visual area 3, 5, 7 mm decreased when getting closer to the center of the cornea. The refractive power of the strong axis in cornea with RK combined with T-incision obviously decreased more than that of RK. There was no such difference at weak axis between RK and RK combined with T-incision. CONCLUSIONS: Corneal SAI and SRI will increase when myopia-astigmatism increases. The morphologic changes are from positive non-spherical lens before surgery to negative non-spherical lens after surgery. The increase of radius of curvature and the decrease of refractive power are due to incisions. These phenomena become clearer when the incision getting closer to the visual area or more incisions are performed. A T-incision less than 2 mm long along the strong axis of astigmatism not only can lessen refractive power of strong axis, but also can not affect RK results. This kind of T-incision does not delay the wound healing either.

Adolescent↗
PubMed1997

[Giant-cell tumor of bone: a review of diagnosis and treatment of 105 cases].

OBJECTIVE: To summarize the experience in the diagnosis and treatment of giant-cell tumor of bone, the selection of various operation methods and their effects were evaluated and discussed. METHODS: From 105 cases of giant-cell tumor of bone data were collected and reviewed. The clinical features were analyzed in association with radiological and histological characteristics. Prognosis was assessed by long-term follow-up. RESULTS: Among 105 cases, one had multiple giant-cell tumors and two had distant metastases. In some cases, the radiological and histological appearances didn't accord with the clinical findings. The recurrence rate was 36% in patients treated with curettage. Although no recurrence was seen in patients treated by local excision, the joint function could not be fully retained. CONCLUSION: Diagnosis should be made on the basis of integrated clinical, radiological and pathological manifestations. Early diagnosis and operation are important. The function of joint must be retained as much as possible. Pre-operative embolization of tumor of sacrum and pelvis is very helpful to ensure operative success and to minimize recurrence.

Adolescent↗
PubMed1997

[Direct protection of injured primary cultured hepatocytes of rats treated with carbon tetrachloride by salvianic acid B].

The incorporation of [3H]thymidine obviously tends to decrease in the primary cultured hepatocytes of rats when the cells are treated with carbon tetrachloride. Meanwhile the activity of ALT markedly increases in the medium. But these pathologic alterations are inhibited by Salvianic acid B(SA-B) and the effect of 10(-6) mol/L SA-B is the best.

Alanine Transaminase↗
PubMed1997

[Separation and determination of metsulfuron, bensulfuron, acetochlor by high performance liquid chromatography].

In this paper a high performance liquid chromatographic method for the separation and determination of metsulfuron, bensulfuron and acetochlor in the composite herbicide "Nongjiayi" is described. The concentration of methanol in the mobile phase and the temperature of the column affected the k' factor and the separation of the three active ingredients. Impurities in the "Nongjiayi" did not interfere with the determination. Chromatographic conditions were Shim-Pack CLC-C8 (150 mm x 6 mm i.d., 5 microm), mobile phase of methanol-water (60:40, V/V) and UV detector at 240 nm. Quantification was carried out with the three external standards. The average recovery was 98.81% with RSD=0.80% for metsulfuron, 99.10% with RSD=0.78% for bensulfuron and 99.72% with RSD=0.69% for acetochlor. The linear range of this method was 0.10-0.40 microg (r=0.9994) for metsulfuron, 0.40-1.60 microg (r=0.9995) for bensulfuron and 10-40 microg (r=0.9987) for acetochlor. The method is accurate, rapid and reproducible and can be applied to quality control for the "Nongjiayi".

Chromatography, High Pressure Liquid↗
PubMed1997

Angiotensin-converting enzyme inhibition in myocardial infarction--Part 1: Clinical data.

There is an increasing body of clinical trial evidence to support the use of angiotensin-converting enzyme (ACE) inhibitors in the management of patients following myocardial infarction (MI). Enthusiasm for the use of ACE inhibitors in the acute phase of MI had previously been tempered by the adverse results of an early trial. However, exciting new information is available from several large, randomized studies that has not only quelled those initial concerns but also attests to the efficacy of using this class of medication in the first 24 h after an acute MI. A Canadian National Opinion Leader Symposium was held in November 1995 to review the results of the major ACE inhibitor clinical trials and to discuss key issues and controversies surrounding their use in acute MI. The focus of this paper, the first of two parts, is on the results of the major ACE inhibitor clinical trials.

Angiotensin-Converting Enzyme Inhibitors↗