16 results on '"Kan YM"'
Search Results
2. Effect of texture on dielectric properties and thermal depoling of Bi4Ti3O12 ferroelectric ceramics
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Yan, HX, Reece, MJ, Liu, J, Shen, ZJ, Kan, YM, Wang, PL, Yan, HX, Reece, MJ, Liu, J, Shen, ZJ, Kan, YM, and Wang, PL
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- 2006
3. SPS processing of bismuth-layer structured ferroelectric ceramics yielding highly textured microstructures
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Liu, J, Shen, ZJ, Nygren, M, Kan, YM, Wang, PL, Liu, J, Shen, ZJ, Nygren, M, Kan, YM, and Wang, PL
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- 2006
4. Distributed boundary representation and Boolean operations on a massively parallel computer
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Hui, KC, primary and Kan, YM, additional
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- 1996
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5. Postpartum thromboprophylaxis with enoxaparin: a prospective cohort study on patients' adherence, injection experience, and information retention after counselling by pharmacists.
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Kho BP, Ho HT, Tan SY, Chee FS, Kow FT, Ooi S, and Kan YM
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- Humans, Female, Prospective Studies, Adult, Health Knowledge, Attitudes, Practice, Young Adult, Malaysia, Cohort Studies, Patient Education as Topic, Enoxaparin administration & dosage, Enoxaparin adverse effects, Pharmacists, Postpartum Period, Medication Adherence statistics & numerical data, Anticoagulants administration & dosage, Anticoagulants adverse effects, Counseling methods
- Abstract
Objectives: This research aimed to determine postpartum females' self-reported adherence to and experience with short-term thromboprophylaxis using enoxaparin injection, after counselling by pharmacists. It also sought to assess their knowledge of thromboprophylaxis, injection techniques, and confidence in self-injecting., Methods: This prospective cohort study was conducted at a public tertiary hospital in Malaysia from March to June 2023. Self-injection-naïve postpartum females who were initiated on thromboprophylaxis and counselled by a pharmacist were conveniently sampled. Knowledge regarding thromboprophylaxis, injection readiness, and technique were assessed one day after the counselling session. A telephonic interview was conducted at the end of the 10-day therapy to determine adherence and adverse effects experienced., Key Findings: A total of 259 subjects were successfully followed up, with 87.6% (n = 227) adherent to the therapy. Nonadherence was predominantly due to forgetfulness; four had their treatment withheld due to bleeding. One-third of subjects experienced localised pain and bruising. Subjects answered a median of 5/7 knowledge questions and recalled a median of 8/10 injection steps correctly, with those who read the information leaflet provided after counselling scoring significantly higher (P = .02). The majority declared moderate confidence in their ability to self-inject. Subjects who intended to self-inject (P < .01) and were more confident (P = .02) demonstrated better injection technique., Conclusions: Postpartum females counselled by pharmacists largely adhered to short-term enoxaparin for thromboprophylaxis. The impact of the counselling session may be enhanced by addressing their psychological readiness to self-inject, awareness of adverse effects identification, mitigation, and management, as well as setting reminders to prevent forgetfulness to inject., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Royal Pharmaceutical Society. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)
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- 2024
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6. Antiviral activity of Vigna radiata extract against feline coronavirus in vitro .
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Chou AA, Lin CH, Chang YC, Chang HW, Lin YC, Pi CC, Kan YM, Chuang HF, and Chen HW
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- Animals, Cats, Virus Replication drug effects, Cell Line, Coronavirus, Feline drug effects, Antiviral Agents pharmacology, Plant Extracts pharmacology, Feline Infectious Peritonitis drug therapy, Feline Infectious Peritonitis virology, Vigna chemistry, Lactams, Leucine analogs & derivatives, Sulfonic Acids
- Abstract
Feline infectious peritonitis (FIP) is a fatal illness caused by a mutated feline coronavirus (FCoV). This disease is characterized by its complexity, resulting from systemic infection, antibody-dependent enhancement (ADE), and challenges in accessing effective therapeutics. Extract derived from Vigna radiata (L.) R. Wilczek (VRE) exhibits various pharmacological effects, including antiviral activity. This study aimed to investigate the antiviral potential of VRE against FCoV, addressing the urgent need to advance the treatment of FIP. We explored the anti-FCoV activity, antiviral mechanism, and combinational application of VRE by means of in vitro antiviral assays. Our findings reveal that VRE effectively inhibited the cytopathic effect induced by FCoV, reduced viral proliferation, and downregulated spike protein expression. Moreover, VRE blocked FCoV in the early and late infection stages and was effective under in vitro ADE infection. Notably, when combined with VRE, the polymerase inhibitor GS-441524 or protease inhibitor GC376 suppressed FCoV more effectively than monotherapy. In conclusion, this study characterizes the antiviral property of VRE against FCoV in vitro , and VRE possesses therapeutic potential for FCoV treatment.
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- 2024
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7. Translation, cross-cultural adaptation, and psychometric validation of the Malay version of the Assessment of Quality of Life-6 Dimensions (Malay-AQoL-6D) instrument among Malaysians living with chronic heart failure.
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Tan YJ, Ong SC, Goh SP, Chen G, Yong VS, Khor WW, Kan YM, Choong YY, Zameram AM, Tan LY, Voo JYH, Lam KK, Yen CH, Wahab MJA, and Abdulla ZB
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- Humans, Malaysia, Male, Female, Reproducibility of Results, Middle Aged, Aged, Chronic Disease, Surveys and Questionnaires, Translations, Adult, Southeast Asian People, Quality of Life psychology, Psychometrics instrumentation, Psychometrics methods, Psychometrics standards, Heart Failure psychology, Heart Failure ethnology, Cross-Cultural Comparison
- Abstract
Background: This study aimed to translate and culturally adapt the Assessment of Quality of Life (AQoL)-6D into Malay (Malay-AQoL-6D), and assesses the instrument's acceptability, reliability, and validity among Malaysians living with chronic heart failure (HF)., Methods: The translation and cross-cultural adaptation process adhered to international guidelines. The Malay-AQoL-6D underwent content and face validity assessments via expert review, and pretesting among healthy individuals and patients with chronic conditions. Subsequent psychometric validation utilised clinico-sociodemographic data and paired AQoL-6D and EQ-5D-5L data from a health-related quality-of-life (HRQoL) survey involving Malay-speaking patients with HF, which encompassed assessments of Malay-AQoL-6D acceptability, internal consistency and test-retest reliability, as well as its construct, concurrent, convergent and divergent, and known-group validity., Results: The Malay-AQoL-6D was deemed acceptable among clinicians and local patients, achieving a 90.8% completion rate among 314 patients surveyed. The instrument demonstrated strong content validity (item-level content validity index [CVI]: 0.83-1.00, average CVI: 0.98), internal consistency (Cronbach's alpha: 0.72-0.89; MacDonald's omega: 0.82-0.90, excluding the Senses dimension), and test-retest reliability (average intraclass correlation coefficients: 0.79-0.95). Confirmatory factor analysis confirmed the instrument's two-level, six-factor structure (Satorra-Bentler [SB]-scaled χ2(df: 164): 283.67, p-value < 0.001; root mean square error of approximation [RMSEA]: 0.051; comparative fix index [CFI]: 0.945, Tucker-Lewis index [TLI]: 0.937; standardised root mean-squared error [SRMR]: 0.058). The Malay-AQoL-6D's concurrent validity was evident through its good agreement with EQ-5D-5L. Multiple hypothesis tests further affirmed its construct and known-group validity. The Malay-AQoL-6D's psychometric properties remained consistent across different missing data techniques., Conclusion: The findings suggest that Malay-AQoL-6D could be a culturally acceptable, reliable, and valid HRQoL measure for quantifying HRQoL among the local HF population. Future studies are necessary to further validate the instrument against other measures and confirm the instrument's test-retest reliability and responsiveness, which are possible with the availability of the Malay-AQoL-6D., (© 2024. The Author(s).)
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- 2024
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8. Is Using Sodium-Glucose Cotransporter-2 Inhibitors to Treat Adults with Chronic Heart Failure Cost-Effective? A Systematic Review of Cost-Effectiveness Studies.
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Tan YJ, Ong SC, and Kan YM
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- Humans, Adult, Cost-Benefit Analysis, State Medicine, Stroke Volume, Ventricular Function, Left, Systematic Reviews as Topic, Chronic Disease, Glucose, Sodium, Sodium-Glucose Transporter 2 Inhibitors therapeutic use, Heart Failure drug therapy
- Abstract
Objective: This systematic review aimed to summarise the outcomes of economic evaluations that evaluated sodium-glucose cotransporter-2 inhibitors (SGLT2i) in combination with standard of care compared to standard of care alone for patients with chronic heart failure., Methods: This systematic review searched MEDLINE, CINAHL+, Econlit, Scopus, the Cochrane Library, the National Health Service Economic Evaluation Database and the Cost-Effectiveness Analysis Registry from inception to 31 December, 2022, for relevant economic evaluations, which were critically appraised using the Consolidated Health Economic Evaluation Reporting Standards (CHEERS) and Bias in Economic Evaluation (ECOBIAS) criteria. The costs, quality-adjusted life-years, incremental cost-effectiveness ratios and cost-effectiveness thresholds were qualitatively analysed. Net monetary benefits at different decision thresholds were also computed. Subgroup analyses addressing the heterogeneity of economic outcomes were conducted. All costs were adjusted to 2023 international dollar (US$) values using the CCEMG-EPPI-Centre cost converter., Results: Thirty-nine economic evaluations that evaluated dapagliflozin and empagliflozin in patients with heart failure were found: 32 for the left ventricular ejection fraction (LVEF) ≤ 40% and seven for LVEF > 40%. Sodium-glucose cotransporter-2 inhibitors were cost-effective in all but two economic evaluations for LVEF > 40%. Economic outcomes varied widely, but favoured SGLT2i use in LVEF ≤ 40% over LVEF > 40% and upper-middle income over high-income countries. At a threshold of US$30,000/quality-adjusted life-year, ~ 90% of high to upper-middle income countries would consider SGLT2i cost-effective for heart failure treatment. The generalisability of study findings to low- and low-middle income countries is limited because of insufficient evidence., Conclusions: Using SGLT2i to treat heart failure is cost-effective, with more certainty in LVEF ≤ 40% compared to LVEF > 40%. Policymakers in jurisdictions where economic evaluations are not available could potentially use this study's findings to make informed decisions about treatment adoption., Systematic Review Protocol Registration: This study protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO; CRD42023388701)., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)
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- 2023
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9. Eye drop instillation technique among patients with glaucoma and evaluation of pharmacists' roles in improving their technique: an exploratory study.
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Kan YM, Kho BP, Kong L, Chong QX, Tiong MNJ, and Wong LMJ
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- Humans, Ophthalmic Solutions, Cross-Sectional Studies, Antihypertensive Agents, Pharmacists, Glaucoma
- Abstract
Objectives: This study aimed to explore the eye drop instillation technique of patients with glaucoma and whether a pharmacist-led counselling session can improve their technique. Patients' perceptions of pharmacists' role in providing the counselling were also explored., Methods: This cross-sectional study was conducted between December 2020 and March 2021 at Sarawak General Hospital, Malaysia. Convenience sampling was used to recruit patients with glaucoma who self-administered their eye drops. Participants' background information were obtained using an investigator-administered questionnaire before their eye drop instillation technique was assessed. Those with imperfect techniques were counselled by a pharmacist before being reassessed. Differences in eye drop instillation competency were determined using paired T-test., Key Findings: A total of 138 participants were recruited. Participants were on a median of two eye drops (IQR 2-4) for a median of five years (IQR 2-8). Prior to being counselled, they demonstrated a mean total of 8.4/13 steps (SD 2.33) correctly. A statistically significant improvement in eye drop instillation technique was observed post-pharmacists' counselling, with a mean increase of 4.3 steps demonstrated correctly (95% CI, 4.0 to 4.7, P < 0.001). The majority of participants agreed that pharmacists are knowledgeable in providing counselling on eye drop administration techniques., Conclusions: Patients with glaucoma treated at Sarawak General Hospital had imperfect eye drop instillation techniques, despite most having used their eye drops for several years. Interventions by pharmacists to improve eye drop instillation are crucial to optimise the medical treatment of patients with glaucoma., (© The Author(s) 2022. Published by Oxford University Press on behalf of the Royal Pharmaceutical Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)
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- 2022
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10. Diagnostic accuracy of fecal calprotectin in predicting significant gastrointestinal diseases.
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Kan YM, Chu SY, and Loo CK
- Abstract
Background and Aim: It is often unreliable to triage patients for timely endoscopic investigations based on symptoms alone. We need an objective assessment to differentiate between organic gastrointestinal diseases and functional bowel symptoms. We evaluated the diagnostic accuracy of fecal calprotectin (FC) in predicting organic gastrointestinal diseases., Methods: In a prospective observational study, consecutive patients referred for colonoscopy to the Department of Medicine and Geriatrics at the Kwong Wah Hospital in Hong Kong were recruited. Stool samples were collected within 24 h before colonoscopy. FC was measured by a commercial kit. Upper endoscopy investigations were then proceeded if normal colonoscopy but elevated FC., Results: Two hundred and seventy out of 429 patients had FC above 50 μg/g. Eighty-six out of 270 with elevated FC had significant colonoscopy pathological findings. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of FC test for diagnosing a significant organic colonoscopy or upper endoscopy disease were 91.7, 55.6, 57.0, and 91.2%, respectively. The NPV of FC for colorectal cancer, high risk polyp, and colon inflammation were 98.7, 96.2, and 98.1%, respectively. The NPV of FC in the condition of altered bowel habit or abdominal pain in predicting colorectal cancer and inflammation were 93.8 and 100%, respectively., Conclusions: FC is a reliable marker of ruling out organic bowel diseases. A single negative FC test could be used as a triage tool to prioritize the need and urgency of further investigation, particularly in the setting of altered bowel habits and abdominal pain., (© 2021 The Authors. JGH Open published by Journal of Gastroenterology and Hepatology Foundation and John Wiley & Sons Australia, Ltd.)
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- 2021
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11. Use of glecaprevir/pibrentasvir in patients with chronic hepatitis C virus infection and severe renal impairment.
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Yap DYH, Liu KSH, Hsu YC, Wong GLH, Tsai MC, Chen CH, Hsu CS, Hui YT, Li MKK, Liu CH, Kan YM, Yu ML, and Yuen MF
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- Aminoisobutyric Acids, Antiviral Agents therapeutic use, Benzimidazoles, Child, Cyclopropanes, Female, Hepacivirus, Humans, Lactams, Macrocyclic, Leucine analogs & derivatives, Male, Proline analogs & derivatives, Pyrrolidines, Quinoxalines, Sulfonamides, Hepatitis C, Chronic drug therapy, Renal Insufficiency drug therapy
- Abstract
Background/aims: Data on treatment efficacy and safety of glecaprevir/pibrentasvir (GLE/PIB) for chronic hepatitis C virus (HCV) infection in Asian patients with severe renal impairment are limited. This study aimed to study the treatment and side effects of GLE/PIB in these patients infected with non-1 genotype (GT) HCV., Methods: We prospectively recruited patients with Child's A cirrhosis and eGFR <30 mL/min/1.73 m2 in Hong Kong and Taiwan during 2017-2018 to receive GLE/PIB treatment., Results: Twenty-one patients (GT2, n=7; GT3, n=6; and GT6, n=8) received GLE/PIB for 11.2±1.8 weeks. All except one were treatment-naïve. GLE/PIB was initiated in 16 patients while on dialysis (seven on peritoneal dialysis [PD] and nine on hemodialysis) and in five patients before dialysis. One patient died of PD-related peritonitis during treatment and two were lost to follow up. The SVR12 rate in the remaining 18 patients was 100%. All patients achieved undetectable levels at 4-, 12-, 24- and 48-week after treatment. Patients with deranged alanine aminotransferase showed normalization after 4 weeks and the response was sustained for 48 weeks. No significant adverse event was observed., Conclusion: GLE/PIB treatment was associated with high efficacy and tolerability in HCV-infected patients with severe renal impairment.
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- 2020
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12. An outbreak of refrigerant-induced acute hepatitis in Hong Kong.
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Kan YM, Lau CF, Chan WC, Chan WS, Tung YM, and Loo CK
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- Adult, Diagnosis, Differential, Disease Outbreaks, Hong Kong, Humans, Inhalation Exposure, Male, Occupational Diseases chemically induced, Occupational Exposure, Chlorofluorocarbons, Ethane adverse effects, Hepatitis diagnosis, Liver pathology, Occupational Diseases diagnosis
- Abstract
We report a cluster of acute hepatitis in five air-conditioning maintenance workers following accidental exposure to 2,2-dichloro-1,1,1-trifluoroethane (HCFC-123). They presented to us with complaints of feverishness, generalised malaise, and epigastric discomfort. Their blood biochemistry tests were compatible with acute hepatitis. Viral hepatitis serology, tests for autoimmune hepatitis, and analyses for drugs and alcohol consumption were all negative. No focal hepatic lesion was detected by ultrasound imaging. Percutaneous liver biopsy samples were taken from two of them. The patients were managed with supportive treatment. All had spontaneous, but slow, recovery. Their liver function tests returned to normal after 4 months and their outcomes were favourable. Physicians should be aware of this occupational disease entity.
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- 2014
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13. Chronic hepatitis C genotype 6 responds better to pegylated interferon and ribavirin combination therapy than genotype 1.
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Tsang OT, Zee JS, Chan JM, Li RS, Kan YM, Li FT, Lo FH, Chow DA, Cheung KW, Chan KH, Yeung YW, Ng FH, Li MK, Kwan WK, and Lai TS
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- Adolescent, Adult, Age Factors, Aged, Antiviral Agents adverse effects, Biopsy, Chi-Square Distribution, Drug Therapy, Combination, Female, Genotype, Hepatitis C, Chronic diagnosis, Hong Kong, Humans, Interferon alpha-2, Interferon-alpha adverse effects, Logistic Models, Male, Middle Aged, Phenotype, Polyethylene Glycols adverse effects, RNA, Viral blood, Recombinant Proteins, Retrospective Studies, Ribavirin adverse effects, Risk Assessment, Risk Factors, Time Factors, Treatment Outcome, Viral Load, Young Adult, Antiviral Agents therapeutic use, Hepatitis B virus genetics, Hepatitis C, Chronic drug therapy, Interferon-alpha therapeutic use, Polyethylene Glycols therapeutic use, Ribavirin therapeutic use
- Abstract
Background and Aims: Chronic hepatitis C genotype 6 is common in Hong Kong, especially among i.v. drug abusers. Responses of these patients to combination of pegylated interferon and ribavirin treatment were inconsistent and the numbers of patients involved in previous studies were small. We performed a retrospective study to compare the therapeutic responses of this regimen in patients infected with genotype 6 and genotype 1., Methods: Seventy patients with either genotype 6 or genotype 1 were recruited. Both groups received 800-1200 mg of ribavirin daily plus either 180 mg of pegylated alpha-interferon-2a or 1.5 mg/kg pegylated alpha-interferon-2b weekly for 48 weeks. Their responses to treatments were compared., Results: The early virological response to combination therapy of patients with genotype 6 was significantly better than that of genotype 1 (88.6% vs 74.3%, P = 0.03). Significant difference was also identified in the end of treatment response of the two genotypes (60% vs 81.4% for genotype 1 and 6, respectively; P = 0.005). The sustained virological response (SVR) to treatment in patients with genotype 6 was also significantly superior to that of patients with genotype 1 (75.7% vs 57.1%, P = 0.02). Multiple logistic regression analysis demonstrated that age of 55 years or less, genotypes of hepatitis C virus, liver biopsy staging and baseline hepatitis C virus RNA of 200,000 IU/mL or less were independent predictors for better SVR in this cohort., Conclusion: Patients with chronic hepatitis C genotype 6 respond better to pegylated interferon and ribavirin combination treatment than patients with genotype 1.
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- 2010
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14. Prospective multicentre study of the natural history of atherosclerotic renal artery stenosis in patients with peripheral vascular disease.
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Pillay WR, Kan YM, Crinnion JN, and Wolfe JH
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- Aged, Aged, 80 and over, Arteriosclerosis pathology, Arteriosclerosis physiopathology, Blood Pressure physiology, Disease Progression, Follow-Up Studies, Humans, Male, Middle Aged, Peripheral Vascular Diseases pathology, Peripheral Vascular Diseases physiopathology, Prognosis, Prospective Studies, Renal Artery Obstruction pathology, Renal Artery Obstruction physiopathology, Survival Analysis, Arteriosclerosis etiology, Peripheral Vascular Diseases etiology, Renal Artery Obstruction etiology
- Abstract
Background: Many patients with peripheral vascular disease have coincident renal artery stenosis. The present study characterized the natural history of the condition., Methods: Some 98 patients (71 men) with more than 50 per cent atherosclerotic renal artery stenosis (unilateral 64, bilateral 34) were recruited prospectively. Measurements of serum creatinine, blood pressure and renal size were recorded at baseline and every 6 months, for a minimum of 2 years., Results: Data were available for 85 patients with a minimum follow-up of 2 years. The mean age was 71 (range 51-87) years. All 52 patients with unilateral renal artery stenosis were managed conservatively (group 1); 21 of the 33 patients with bilateral disease had no intervention (group 2) and the remaining 12 had angioplasty or reconstruction (group 3). The overall mortality rate was 32 per cent at 2 years (27 patients) and this was similar in all three groups. In only three patients was death related directly to renovascular disease; coronary disease accounted for the majority of deaths. All three patients who needed dialysis died within 1 year. In survivors from groups 1 and 3 there was a significant increase in serum creatinine concentration at follow-up. Blood pressure did not increase significantly., Conclusion: Patients with renal artery stenosis and peripheral vascular disease had a poor prognosis, but this was not directly attributable to renal failure.
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- 2002
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15. Hemodynamic effects of supervised calf muscle exercise in patients with venous leg ulceration: a prospective controlled study.
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Kan YM and Delis KT
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- Aged, Case-Control Studies, Exercise Tolerance, Female, Hemodynamics physiology, Humans, Male, Prospective Studies, Exercise, Isotonic Contraction, Leg blood supply, Leg Ulcer physiopathology, Muscle, Skeletal physiopathology
- Abstract
Hypothesis: Because more than two thirds of patients with venous ulcer have an impaired calf muscle pump, enhancement of its ejecting ability with physical training may generate an improved hemodynamic milieu sufficient to promoting ulcer healing. This study evaluated the effects of short-term supervised calf exercise on calf muscle pump function and venous hemodynamics in limbs with venous ulceration., Design: Prospective controlled study., Settings: University-associated tertiary care hospital., Patients: The study consisted of 2 groups. An exercise group comprised 10 patients (median age, 72 years) receiving supervised isotonic calf muscle exercise for 7 consecutive days. A control group comprised 11 patients matched with those in the exercise group for age, sex, ulcer size, and ulcer duration (all, P>.09). Patients in both groups had perimalleolar venous leg ulcers, impaired calf muscle function (ejection fraction, <60%), and full ankle joint movement., Interventions: After providing a complete clinical history, both groups underwent a physical examination, venous duplex scanning, and air plethysmography. The venous filling index, venous volume, residual venous volume, and residual volume fraction of the calf on standing were measured plethysmographically at baseline and on day 8, in addition to calf muscle endurance as determined by the maximal number of plantar flexions performed against a fixed 4-kg resistance during 6 minutes (1 flexion/s). Operators were blinded to the subject's group. Exercise in the first group entailed consecutive active plantar flexions using a standardized 4-kg resistance pedal ergometer. Subjects daily completed 3 sets of flexions of 6 minutes each. All patients had short-stretched compression bandaging., Main Outcome Measures: The ejected venous volume and ejection fraction were evaluated in both groups at baseline and on day 8., Results: Both groups had a similar hemodynamic performance at baseline for all the variables evaluated (P>.10). After 7 days of exercise, patients in the exercise group improved their ejected venous volume by 67.5%, ejection fraction by 62.5%, residual venous volume by 25% (all 3, P =.006), and their residual volume fraction by 28.6% (P =.008). Changes in the control group within the same period were small (all, P>.10). By day 8, the exercise group had a significantly better ejected venous volume (P<.001) and ejection fraction (P<.001) than the control group. The venous filling index and the venous volume did not change (P>.50) in either study group. Calf muscular endurance in the exercise group increased 135%, from a median 153 plantar flexions at baseline to 360 on day 7 (P<.001)., Conclusions: By increasing the muscular endurance, efficacy, and power of the calf muscle, isotonic exercise improves its ejecting ability and the global hemodynamic status in limbs with venous ulceration. Prospective evaluations of the clinical effects of calf muscle pump strengthening for the treatment of venous leg ulceration are indicated by the results of this study.
- Published
- 2001
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16. Ligustrazine-induced endothelium-dependent relaxation in pulmonary arteries via an NO-mediated and exogenous L-arginine-dependent mechanism.
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Peng W, Hucks D, Priest RM, Kan YM, and Ward JP
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- Animals, Arginine blood, Endothelium, Vascular physiology, Male, Muscle Relaxation drug effects, Pulmonary Artery physiology, Rats, Rats, Wistar, Vasodilator Agents pharmacology, Arginine physiology, Endothelium, Vascular drug effects, Nitric Oxide physiology, Pulmonary Artery drug effects, Pyrazines pharmacology
- Abstract
1. Ligustrazine (tetramethylpyrazine, TMP) is a vasodilator that has been reported to have pulmonary selective properties in vivo, but not in vitro. Although TMP is generally described as being endothelium-independent, we provide evidence here that TMP may have an endothelium-dependent and nitric oxide (NO)-mediated mechanism in pulmonary arteries that could predominate at concentrations used therapeutically in China. 2. The study was performed on isolated pulmonary (1-2 mm i.d.), intrapulmonary (200-850 microns) and mesenteric (200-400 microns) arteries of the rat using a Mulvaney-Halpen small vessel myograph, following preconstriction with phenylephrine (PE, 10 microM), prostaglandin F2 alpha (PGF2 alpha, 100 microM), or 75 mM K+ (KPSS, equimolar substitution for Na+). Values are shown as mean +/- s.e.mean, or for EC50S as mean [+/-95% confidence limits]. 3. TMP caused a concentration-dependent relaxation against all three agonists in both large (1.56 +/- 0.04 mm) and small (399 +/- 20 microM) pulmonary arteries; it was more potent in small compared to large arteries constricted with PE or PGF2 alpha (P < 0.05), but not those constricted with KPSS. The NO synthase (NOS) inhibitor, NG-monomethyl-L-arginine (L-NMMA, 100 microM) caused a significant shift to the right of these relationships, such that the EC50 for TMP in large pulmonary arteries constricted with PE increased from 522 [+130, -104] microM (n = 12) to 1828 [+395, -325] microM (n = 6, P < 0.01). Both removal of the endothelium and methylene blue (10 microM) had similar effects. 4. L-Arginine substantially reduced the EC50 for TMP in pulmonary arteries; in the presence of 400 microM L-arginine the EC50 for TMP in large arteries constricted with PE was 14.7 [+21.0, -8.6] microM, (n = 6, P < 0.001), and with 10 microM L-arginine 96.7 [+45.1, -30.7] microM, (n = 6, P < 0.001). Similar effects were seen in small arteries. L-Arginine had no effect in the absence of an endothelium. D-Arginine was ineffective, and inhibition of L-arginine uptake with L-lysine blocked the action of L-arginine. L-Arginine (400 microM) had no significant effect on TMP-induced relaxation in mesenteric arteries (n = 5). 5. L-Arginine itself caused a concentration-dependent relaxation in intrapulmonary arteries (639 +/- 34 microM) constricted with PE, reaching a maximum relaxation around 100-400 microM (42.4 +/- 3.0%, n = 16), but this was independent of the endothelium. TMP (10 and 100 microM) significantly enhanced the relaxation to L-arginine, with a maximum relaxation in the presence of 100 microM TMP of 81.7 +/- 6.2% (n = 5, P < 0.01), but the effect of TMP was entirely dependent on the endothelium. A similar effect was observed in PGF2 alpha-constricted pulmonary arteries. 6. These results show that TMP stimulates NO production at low concentrations in pulmonary arteries, via an apparently novel endothelium-resident mechanism that is dependent on exogenous L-arginine. Normal plasma L-arginine levels of around 150 microM would allow this mechanism to be maximally activated. As mesenteric arteries do not seem to express the mechanism to any significant extent, at low concentrations TMP would be effectively selective to the pulmonary vasculature, and may thus have potential as a therapeutic agent in pulmonary vascular disease.
- Published
- 1996
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