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Biomedical subjects

K Liu

Publications and source records attributed to K Liu.

At least 73 records · Page 4Linked to original sources
PubMed2001

Gait alterations associated with walking impairment in people with peripheral arterial disease with and without intermittent claudication.

OBJECTIVES: To describe gait alterations associated with impaired walking endurance in patients with and without lower-extremity peripheral arterial disease (PAD) and determine whether the Caltrac accelerometer provides a valid measure of physical activity in PAD. DESIGN: Cross-sectional. SETTING: Academic medical center. PARTICIPANTS: PAD (n = 40) and non-PAD patients (n = 22) from two Chicago hospitals. MEASUREMENTS: Participants underwent measurement of the ankle brachial index (ABI), leg length, and 6-minute walk. Steps per minute and step length were measured during the first and last 100 feet of the 6-minute walk. Participants wore a Caltrac accelerometer, sensitive to vertical acceleration, during the 6-minute walk and for 7 continuous days. RESULTS: Five PAD participants (13%) and one non-PAD participant (5%) ceased walking before the end of 6 minutes. Among the remaining participants, distance walked in 6 minutes was more highly related to walking velocity during the last 100 feet of the walk than walking velocity during the first 100 feet. ABI was associated significantly with cadence (20.77 steps/minute per unit ABI, P <.001) but not step length (10.12 centimeters/unit ABI, P =.08). ABI was associated significantly with 6-minute walk distance (493 feet/unit ABI, P =.018), but this association disappeared completely after adjustment for step length and cadence. We found no difference in accelerometer scores between PAD and non-PAD participants over a fixed distance of 800 feet (7.34 vs 7.17 activity units, P =.789). However, scores were significantly different after 7 days (730.8 vs 1,485.0 activity units, P =.003). CONCLUSION: Walking performance in PAD patients who completed 6 minutes of walking was largely determined by a decline in walking velocity rather than slower initial walking velocity. ABI was more closely associated with cadence than step length. Future studies should assess the effect of exercise programs and revascularization on cadence and step length in PAD.

Aged↗
PubMed2001

Prostaglandin E2 is involved in the increase of cytochrome P-450 2B1 expression by alpha-tocopheryl succinate in primary rat hepatocytes in the presence of phenobarbital.

The modulation of cytochrome P-450 2B1 expression by alpha-tocopheryl succinate and whether prostaglandin E2 is involved in this modulation in primary rat hepatocytes in the presence of phenobarbital were investigated. A primary rat hepatocyte culture model that faithfully reproduces the phenobarbital response observed in vivo was used. Intracellular alpha-tocopherol content was dose dependently increased by alpha-tocopheryl succinate incubation. Hepatocytes were demonstrated to have prostaglandin E2-synthesizing capability. alpha-Tocopheryl succinate inhibited prostaglandin E2 synthesis by hepatocytes and increased cytochrome P-450 2B1 expression in the presence of phenobarbital; however, it had little effect on intracellular cAMP level. To mimic the exogenous source of prostaglandin E2 from nonparenchymal cells, various concentrations of prostaglandin E2 were added to the cell culture. High doses of exogenous prostaglandin E2 (100 and 1,000 nM) inhibited the cytochrome P-450 2B1 expression in the presence of phenobarbital compared with low doses (1 and 10 nM); however, the presence of high doses of prostaglandin E2 had no effect on intracellular cAMP level. Forskolin significantly increased intracellular cAMP level and inhibited cytochrome P-450 2B1 expression in the presence of phenobarbital. The results of this study indicate that alpha-tocopheryl succinate increases cytochrome P-450 2B1 expression via its inhibition of prostaglandin E2 synthesis in the presence of phenobarbital; however, changes in intracellular cAMP level are not related to cytochrome P-450 2B1 expression.

Animals↗
PubMed2001

Synthesis and binding affinity of a chiral PNA analogue.

The synthesis of a chiral peptide nucleic acid (PNA), which is composed of N-aminoethyl-cis-4-nucleobase-L-proline units, was described. The chiral PNA monomers containing all four nucleobases (A. T, C and G) were steroselectively prepared. The x-ray diffraction data from a single crystal confirmed the configuration of a key intermediate. Binding activity of the oligomers with their complementary DNA targets was also investigated.

DNA↗
PubMed2001

The effect of dexamethasone on postoperative pain and emesis after intrathecal neostigmine.

UNLABELLED: We evaluated the effect of a single dose of dexamethasone on the incidence and severity of postoperative nausea and vomiting (PONV) after intrathecal injection of tetracaine plus neostigmine. Sixty ASA physical status I patients scheduled for inguinal herniorrhaphy were studied with a randomized, double-blinded, placebo-controlled protocol. The dexamethasone group (Group D) received 10 mg of dexamethasone IV before performance of spinal anesthesia, whereas the placebo group (Group P) received saline. Spinal anesthesia was performed with intrathecal injection of 15 mg tetracaine plus neostigmine 100 microg in both groups. Pain, PONV, and other side effects were evaluated 24 h after surgery. The duration and severity of analgesia and the incidence of PONV were not significantly different between the two groups. Our results demonstrate that a single dose of dexamethasone (10 mg) did not potentiate the analgesic effect or reduce the incidence of PONV after intrathecal injection of tetracaine and neostigmine. IMPLICATIONS: The results of our evaluation of the effect of IV dexamethasone versus saline control on analgesia and nausea and vomiting after intrathecal neostigmine and tetracaine suggest that IV dexamethasone did not enhance the analgesic effect of neostigmine or reduce the incidence of emesis after intrathecal administration.

Adult↗
PubMed2001

Internal aluminum block of plant inward K(+) channels.

Aluminum (Al) inhibits inward K(+) channels (K(in)) in both root hair and guard cells, which accounts for at least part of the Al toxicity in plants. To understand the mechanism of Al-induced K(in) inhibition, we performed patch clamp analyses on K(in) in guard cells and on KAT1 channels expressed in Xenopus oocytes. Our results show that Al inhibits plant K(in) by blocking the channels at the cytoplasmic side of the plasma membrane. In guard cells, single-channel recording revealed that Al inhibition of K(in) occurred only upon internal exposure. Using both "giant patch" recording and single-channel analyses, we found that Al reduced KAT1 open probability and changed its activation kinetics through an internal membrane-delimited mechanism. We also provide evidence that a Ca(2)+ channel-like pathway that is sensitive to antagonists verapamil and La(3)+ mediates Al entry across the plasma membrane. We conclude that Al enters plant cells through a Ca(2)+ channel-like pathway and inhibits K(+) uptake by internally blocking K(in).

Aluminum↗
PubMed2001

A novel large-memory neural network as an aid in medical diagnosis applications.

This paper describes the application of a large memory storage and retrieval (LAMSTAR) neural network to medical diagnosis and medical information retrieval problems. The network is based on Minsky's knowledge-lines (k-lines) theory of memory storage and retrieval in the central nervous system. It employs arrays of self-organized map modules, such that the k-lines are implemented via link weights (address correlation) that are being updated by learning. The network also employs features of forgetting and of interpolation and extrapolation, thus being able to handle incomplete data sets. It can deal equally well with exact and fuzzy information, thus being specifically applicable to medical diagnosis where the diagnosis is based on exact data, fuzzy patient interview information, patient history, observed images, and test records. Furthermore, the network can be operated in closed loop with Internet search engines to intelligently use data from the Internet in a higher hierarchy of learning. All of the above features are shown to make the LAMSTAR network suitable for medical diagnosis problems that concern large data sets of many categories that are often incomplete and fuzzy. Applications of the network to three specific medical diagnosis problems are described: two from nephrology and one related to an emergency-room drug identification problem. It is shown that the LAMSTAR network is hundreds and thousands times faster in its training than back-propagation-based networks when used for the same problem and with exactly the same information.

Computational Biology↗
PubMed2001

Crossed-beam studies of neutral reactions: state-specific differential cross sections.

Crossed-molecular-beam and laser techniques have enabled experimentalists to measure the state-resolved differential cross sections of elementary chemical reactions. This article reviews recent progress in this area. Particular emphasis is placed on some intriguing physical phenomena associated with a few benchmark reactions and how these measurements help in answering fundamental questions about reaction dynamics. We examine specifically the geometric phase effects in the reaction H + D2, the dynamical resonance phenomenon in F + HD, the unusually large spin-orbit reactivity in Cl((2)P) + H2, the insertion reaction O((1)D) + H2, and the mode-specific reactivity in Cl + CH4(nu). The give-and-take between experiment and theory in unraveling the physical picture of the dynamics is illustrated throughout this review.

Journal Article↗
PubMed2001

Pulse pressure compared with other blood pressure indexes in the prediction of 25-year cardiovascular and all-cause mortality rates: The Chicago Heart Association Detection Project in Industry Study.

We compared the relations of 4 blood pressure (BP) indexes (pulse pressure [PP], systolic BP [SBP], diastolic BP [DBP], and mean arterial pressure [MAP]) with 25-year mortality rates for coronary heart disease (CHD), cardiovascular disease (CVD), and all causes in younger, middle-aged, and older men and women by using data from a long-term prospective epidemiological study of employed persons who were screened between 1967 and 1973. A single supine BP measurement was obtained at baseline. Vital status was determined through 1995. We report on 5 groups (total, 28 360 participants) consisting of men age 18 to 39, 40 to 59, and 60 to 74 years and of women age 40 to 59 and 60 to 74 years who were not receiving antihypertensive treatment, had no history of CHD, and did not have diabetes. Cox proportional hazards analyses were used to determine multivariate-adjusted hazard ratios with a 1-SD higher value for each BP index; Wald chi(2) tests were used to compare the strength of relations. Relations of PP were less strong than were those of SBP for all end points in all age/gender groups. SBP or MAP showed the strongest relations to all end points in all age/gender groups (hazard ratio, 1.17 to 1.36). The relations of SBP to death were stronger than were those of DBP, except for middle-aged men and for CVD in women. DBP showed significant positive associations with death, after control for SBP, in middle-aged participants. In conclusion, these data indicate that the long-term risk of high BP should be assessed mainly on the basis of SBP or of SBP and DBP together, not on the basis of PP, in apparently healthy adults.

Adolescent↗
PubMed2001

Peripheral arterial disease and depressed mood in older men and women.

The objective of this study was to determine whether lower extremity peripheral arterial disease (PAD) is associated with depressive symptoms and whether PAD-related disability mediates the association between PAD and depressive symptoms. The study used a cross-sectional design set in an academic medical center. A cohort of men and women aged 55 years and older with (n = 93) or without (n = 74) PAD was recruited. PAD subjects were identified from a blood flow laboratory and a general medicine practice. Non-PAD subjects were identified from the same general medicine practice. PAD was diagnosed and quantified using the ankle-brachial index (ABI). Depressive symptoms were assessed by the 15-item short version of the Geriatric Depression Scale (GDS-S; score range 0-15, 0 = no depressive symptoms). The six-minute walk test and the Walking Impairment Questionnaire (WIQ) distance score (score range 0-100, 100 = better walking ability) were measures of walking impairment. PAD subjects had depressive mood (DM) (defined by GDS-S score >5) twice as often as controls (24% vs 12%, p = 0.06). After adjustment for age, education, and number of comorbidities, the prevalence of depressive mood among PAD subjects was increased, but this association was not significant (OR = 1.8, 95% CI 0.7-4.4). The WIQ distance score weakened the association between PAD and DM, and higher distance scores were associated with a lower likelihood of DM (OR = 0.98 per one unit of the WIQ, 95% CI 0.96-0.99). Among PAD subjects, severe PAD (ABI <0.5) was not significantly associated with DM (OR = 1.4, 95% CI 0.5-4.1), but a greater 6-min walk distance was associated with a lower likelihood of DM (OR = 0.8 per 100 feet, 95% CI 0.70-0.97). Substituting the WIQ scores for six-min walk distance in the model showed that higher WIQ scores were associated with lower likelihood of DM among PAD subjects (OR= 0.98 per one unit of the WIQ, 95% CI 0.95-1.0), though the association did not achieve statistical significance. In conclusion, these data suggest that PAD may be associated with an increased risk of DM and that this relationship may be related to PAD-associated disability. An evaluation for depression may be appropriate in men and women with PAD. Findings should be evaluated in a larger study cohort.

Aged↗
PubMed2001

Interactions between Medicare and Medicaid home care in Connecticut: responses to the 1997 BBA.

Although overlaps exist in the provision of home care services financed by Medicare and Medicaid, interactions of the two funding sources at the beneficiary and home care provider levels have not been widely studied. The recent dramatic declines in Medicare home health spending present a rare opportunity to examine how changes in Medicare spending can affect the provision of Medicaid home care services. We conducted a study of Medicare-Medicaid dynamics in the state of Connecticut to shed light on the inter-relationships of the two funding sources.

Aged↗
PubMed2001

How do they manage? Disabled elderly persons in the community who are not receiving Medicaid long-term care services.

OBJECTIVE: To expand our understanding of how low-income functionally impaired elderly persons are able to remain in the community. DATA SOURCES AND STUDY SETTING: In-person and telephone interviews with 25 elderly individuals who applied for but did not enroll in Connecticut's Home Care Program for Elders (CHCPE). All met the state's nursing home level-of-care criteria. STUDY, DESIGN: In-depth discussions with a small, purposefully selected sample of functionally impaired elderly persons in the community. PRINCIPLE FINDINGS: Many sample members with very high levels of impairment and multiple chronic health conditions remained in the community without CHCPE services because of Medicare home health services combined with extensive levels of informal care. Some sample members, particularly those with more limited informal care networks, did not receive the level of care that they needed. Virtually all were at high risk for medical complications, hospitalizations for acute illnesses, falls, and further loss of functioning. Further, in many cases, informal care networks were overextended, stressed and vulnerable to break down. All but a few of those we interviewed were not receiving services through the waiver program for financial reasons. Most met Medicaid's income criteria but had assets that exceeded Medicaid's $2,000 limit. Several were not participating due to concerns about estate recovery. CONCLUSIONS: Additional formal help is needed to avoid eventual nursing home placement for many sample members. This could be achieved by expanding the availability of case management services and/or relaxing program financial requirements. Further, efforts to reduce Medicare home health expenditures must recognize the heightened vulnerability of many beneficiaries for potentially costly adverse outcomes.

Activities of Daily Living↗
PubMed2001

Promoter polymorphisms of hepatic lipase gene influence HDL(2) but not HDL(3) in African American men: CARDIA study.

Hepatic lipase encoded by the hepatic lipase gene (LIPC) is involved in the metabolism of several lipoproteins. Four promoter polymorphisms in LIPC have been found to be in complete disequilibrium and associated with high density lipoprotein cholesterol (HDL-C) and apolipoprotein (apo)A-I levels in both white and black populations. We investigated the association between the promoter polymorphism and lipid profiles as well as anthropometric phenotypes in African American men in the Coronary Artery Risk Development in Young Adults study. We performed serial cross-sectional analyses and longitudinal analyses of lipids from 578 subjects in five examinations over 10 years of follow-up. Results showed that the allele frequency (0.52) in our black population was consistent with that reported in black subjects but much higher than that reported (approximately 0.2) in white populations. Analysis of covariance tests of the three genotypic means in each examination showed that the P values ranged from 0.01 to 0.08 for HDL-C (except P = 0.54 in the fourth examination), from 0.006 to 0.01 for HDL(2)-C, and from 0.06 to 0.07 for apoA-I. Mean HDL(3)-C levels were essentially identical among the three genotypes. Total cholesterol, low density lipoprotein cholesterol (LDL-C), triglycerides, and apoB, which are mainly involved in the very low density lipoprotein-LDL pathway, were not significantly different according to the promoter polymorphism, except for triglycerides in the third examination (P = 0.01). No significant association was found between anthropometric phenotypes and the LIPC polymorphism in any of five examinations. The change of the anthropometric variables was not significantly associated with genotypes. In conclusion, our results indicated that the LIPC promoter polymorphism has exclusive effects on HDL(2)-C but not HDL(3)-C levels.

Adolescent↗
PubMed2001

[Influence of scatter factor/hepatocyte growth factor on the growth and transmission of hepatocarcinoma SMMC 7721 cells].

OBJECTIVE: To explore the influence of scatter factor/hepatocyte growth factor (SF/HGF) on the growth and transmission of hepatocarcinoma SMMC 7721 cells by SF/HGF cDNA transfection. METHODS: Gene transfection was operated by lipofectin method. In vitro, SF/HGF and c-met expression was tested by ELISA and Western blot. Cell proliferation and motility were compared by growth curves and wound healing assays. In vivo, cells before and after transfection were implanted subcutaneously into nude mice respectively to observe tumor growth and metastasis. RESULTS: After transfection, the expression of SF/HGF reached 694 pg/ml, compared with 0.26 pg/ml before transfection; however the expression of c-met protein did not change obviously. Growth curves showed that cells after transfection proliferated more rapidly than those before transfection and had an increased capability of motility together with enlarged morphological changes. In vivo experiment, tumors originated from SF/HGF(+) cells grew faster than those from SF/HGF(-) cells and had embolism formed inside and metastasis in the corresponding lung tissues, whereas no such findings in SF/HGF(-) cell originated tumors. CONCLUSIONS: High expression of SF/HGF can stimulate tumor cell proliferation and metastasis in hepatocellular carcinoma

Animals↗
PubMed2001

Prolonged interference of patent blue on pulse oximetry readings.

BACKGROUND: We evaluated the effect of intra-arterial injection of Patent Blue (PB) on pulse oximetry. METHODS: Ten consecutive female patients who underwent intra-arterial insertion of catheter for chemotherapy were enrolled in this study. All patients received general anesthesia and ECG, pulse oximetry, and direct arterial blood pressure were monitored throughout the perioperative period. Baseline arterial blood saturation (SpO2), haemoglobin concentration (Hgb), estimated arterial saturation (SaO2), arterial oxygen partial pressure (PaO2) were obtained through arterial blood gas analysis, and true arterial saturation (ScoO2) through CO-Oximetry analysis. The subsequent values obtained at various points of time following the intra-arterial administration of PB were compared with the baseline data. RESULTS: The SpO2 readings taken after intra-arterial injection of PB were significantly lower than the baseline reading. The extent of the reduction of SpO2 readings two hours after the administration of PB was relevant to the total accumulative dosage of PB (rs = -0.846, P < 0.05). However, the reduction of SpO2 bore no significant relation with Hgb concentration or with the ratio of PB dosage to Hgb concentration. CONCLUSIONS: Intra-arterial administration of PB interferes with pulse oximetry readings and the effect lasts for a variable duration. The extent of desaturation may be related to the total accumulative dosage of intra-arterial PB injected.

Adult↗
PubMed2001

[Effect of ATXII on opening modes of myocyte sodium channel, action potential and QT intervals of ECG].

Single sodium channel currents were recorded by patch clamp technique in isolated guinea-pig ventricular myocytes, and action potentials of papillary muscle and ECG were conventionally measured. Sea anemone toxin (ATXII), a high affinity toxin to sodium channel, was used to change the sodium channel dynamics. Changes in the duration of action potentials and the QT interval of ECG depending on the channel modes were studied in order to provide hints to an understanding of pathogenesis of the long QT syndrome (a genetic disease). With the binding of ATXII to the sodium channel, the occurrence frequency and the open time constant of the "long opening" mode of single Na channels increased significantly, whereas the action potential durations, APD50 and APD90, were prolonged by 23% and 27% respectively. Following application of ATXII, on the other hand, the QT interval and the QTc, a rectified QT interval, increased by 18.6% and 18.9% respectively. The results suggest that the dynamics or modes of Na channel play an important role in determining the action potential duration and the QT interval of ECG. The dynamical changes in Na channels induced by genetic mutation may be partially responsible for the long QT syndrome.

Action Potentials↗
PubMed2001

On the mechanism of Cr (VI)-induced carcinogenesis: dose dependence of uptake and cellular responses.

Cr (VI) compounds are widely used industrial chemicals and are recognized human carcinogens. The mechanisms of carcinogenesis associated with these compounds remain to be investigated. The present study focused on dose-dependence of Cr (VI)-induced uptake and cellular responses. The results show that Cr (VI) is able to enter the cells (human lung epithelial cell line A549) at low concentration (< 10 microM) and that the Cr (VI) uptake appears to be a combination of saturable transport and passive diffusion. Electron spin resonance (ESR) trapping measurements showed that upon stimulation with Cr (VI), A549 cells were able to generate reactive oxygen species (ROS). The amount of ROS generated depended on the Cr (VI) concentration. ROS generation involved NADPH-dependent flavoenzymes. Cr (VI) affected the following cellular parameters in a dose-dependent manner, (a) activation of nuclear transcription factors NF-kappaB, and p53, (b) DNA damage, (c) induction of cell apoptosis, and (d) inhibition of cell proliferation. The activation of transcription factors was assessed by electrophoretic mobility shift assay and western blot analysis, DNA damage by single cell gel electrophoresis assay, cell apoptosis by DNA fragmentation assay, and cell proliferation by a non-radioactive ELISA kit. At the concentration range used in the present study, no thresholds were found in all of these cell responses to Cr (VI). The results may guide further research to better understand and evaluate the risk of Cr (VI)-induced carcinogenesis at low levels of exposure.

Antioxidants↗
PubMed2001

Epstein-Barr virus infection of sinonasal lymphoepithelial carcinoma in Guangzhou.

OBJECTIVES: To investigate the prevalence of sinonasal lymphoepithelial carcinoma (SNLEC) in Guangzhou, a high incidence area of nasopharyngeal carcinoma (NPC), and to detect whether it is associated with Epstein-Barr virus (EBV) infection. METHODS: Twenty confirmed SNLEC specimens were collected from all of the sinonasal carcinoma biopsies performed in the 8 years 1989-1996 at the Sun Yat-sen University of Medical Sciences. EBV encoded early RNAs were detected by use of in-situ hybridization. A variety of antigens, including the EBV nuclear antigen 1, latent membrane protein 1, BZLF1 protein, diffuse early antigen, viral capsid antigen and membrane antigen, were detected using immunohistochemistry. Additionally, 36 NPC specimens were used for comparison. RESULTS: Twenty SNLECs were identified. Seventeen SNLECs were developed in the nasal cavity, and 3 in the maxillary sinus. The mean age (46.25 y), male to female ratio (3:1), histopathology and lymphoinfiltration of the 20 SNLECs were identical with those of the 36 NPCs. Thirteen (65.0%) of the 20 SNLECs showed an expansive growth pattern, while 27 (75.0%) of the 36 NPCs showed an infiltrating or mixed growth pattern. The majority of cancer cells in all of the 20 SNLECs showed EBV encoded early RNAs. The EBV nuclear antigen 1 expression of SNLEC was less intensive than that of NPC. The expression rate of latent membrane protein 1 for SNLEC (3/20, 15%) was lower than that for NPC (19/36, 52.8%). The expression rates of BZLF1 protein (2/20, 10.0%), diffuse early antigen (19/20, 95.0%), viral capsid antigen (15/20, 75.0%), and membrane antigen (13/20, 65.0%) for SNLEC were higher than those (0/36, 0.0%; 31/36, 86.0%; 18/36, 50%; and 14/36, 38.9%) for NPC. CONCLUSIONS: SNLEC is not uncommon in Guangzhou. This tumour is also consistently associated with EBV infection like NPC. As compared to NPC, the EBV harbored in SNLECs seems to express the EBV nuclear antigen 1 weakly and has a lower expression rate of latent membrane protein 1 as well as higher expression rates of EBV lytic products.

Adult↗