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Biomedical subjects

A Chung

Publications and source records attributed to A Chung.

At least 19 recordsLinked to original sources
PubMed2006

Sub-Tenon anaesthesia: reduction in subconjunctival haemorrhage with controlled bipolar conjunctival cautery.

PURPOSE: To evaluate the effect of controlled conjunctival cautery on the frequency and extent of subconjunctival haemorrhage (SCH) associated with sub-Tenon anaesthetic (STA) injection in patients with various clotting states. METHODS: One hundred forty-four patients suitable for cataract surgery with STA were prospectively divided into four groups: group A (n=36) were on warfarin (INR 1.8-4.2); group B (n=48) on aspirin (75 mg); group C (n=12) on clopidogrel (75 mg); and group D (n=48) on no anticoagulant or antiplatelet agents. All patients had no other known coagulopathy. Each group was randomly divided into two subgroups, one of which received localised bipolar cautery under microscope control to the STA conjunctival entry site before tissue dissection, whereas the other served as a control. chi(2) and Fisher's exact tests were used to analyse the data with the SPSS package (v11.0). RESULTS: Conjunctival cautery reduced the frequency of SCH from 67 to 6% in group A (P=0.0001); from 37.5 to 4% in group B (P=0.005); from 50 to 0% in group C (P=0.9); and from 17 to 0% in group D (P=0.55). This overall reduction in SCH was highly significant (P<0.0001), especially in groups A and B. No statistically significant reduction in the extent of SCH was found. CONCLUSIONS: Controlled localised bipolar conjunctival cautery before STA injection may significantly reduce the frequency of SCH, especially in patients on warfarin or aspirin.

Aged↗
PubMed2005

Novel molecular basis of an Inab phenotype.

The Cromer blood group system consists of ten high-prevalence and three low-prevalence antigens carried on decay-accelerating factor (DAF). DAF is found in the cell membranes of RBCs, granulocytes, platelets, and lymphocytes and is widely represented in other body tissues. Sequence analyses of DNA were performed on a blood sample from a 91-year-old Japanese woman whose serum contained an alloantibody to a high-prevalence antigen in the Cromer blood group system (anti-IFC). A blood sample from her daughter was also studied. Sequence analysis revealed a substitution of 508C7>T in exon 4 of DAF in the proband. The proband's daughter was heterozygous for 508C/T. This study describes an Inab phenotype in which the 508C>T nonsense mutation is predicted to change arginine at amino acid residue 136 to a stop codon. This change is in SCR 3 of DAF. This study reports on the molecular basis of a new proband with the Inab phenotype who had no history of intestinal disorders.

Aged↗
PubMed2004

Effect of Lepidium meyenii (Maca) on spermatogenesis in male rats acutely exposed to high altitude (4340 m).

Lepidium meyenii (Maca) is a Peruvian hypocotyl that grows exclusively between 4000 and 4500 m in the central Andes. Maca is traditionally employed in the Andean region for its supposed fertility-enhancing properties. The aim of this study was to test the hypothesis that Maca can prevent high altitude-induced testicular disturbances. Adult male rats were exposed for 21 days to an altitude of 4340 m and treated with vehicle or aqueous extract of Maca (666.6 mg/day). The lengths of the stages of the seminiferous epithelium and epididymal sperm counts were obtained at 0, 7, 14 and 21 days of exposure. The stages of the seminiferous tubules were assessed by transillumination. A dose-response study was also performed at sea level to determine the effect of Maca given to male rats at doses of 0, 6.6, 66.6 and 666.6 mg/day for 7 days on body weight, seminiferous tubule stages and epididymal sperm count. The length of stage VIII and the epididymal sperm count were increased in a dose-dependent manner in Maca-treated rats but treatment reduced the length of stage I. At the highest dose, sperm count increased 1.58 times, the length of stage VIII increased 2.4 times and the length of stage I was reduced 0.48 times compared with the value at dose 0. Exposure to high altitude resulted in a reduction in epididymal sperm count after 7 days and lower values were maintained up to 21 days. Altitude reduced spermiation (stage VIII) to half and the onset of spermatogenesis (stages IX-XI) to a quarter on days 7 and 14 but treatment with Maca (666.6 mg/day) prevented these changes. Data on transillumination and epididymal sperm count in the Maca-treated group exposed to high altitude were similar to those obtained at sea level. Maca increased the sperm count on day 21 of exposure to high altitude to values similar (1095.25 +/- 20.41x10(6) sperm, means +/- S.E.M.) to those obtained in the Maca-treated group at sea level (1132.30 +/- 172.95x10(6) sperm). Furthermore, in the Maca-treated group exposed for 21 days to high altitude, epididymal sperm count was higher than in the non-treated group at sea level (690.49 +/- 43.67x10(6) sperm). In conclusion, treatment of rats with Maca at high altitude prevented high altitude-induced spermatogenic disruption.

Altitude↗
PubMed2003

Effect of high altitude exposure on spermatogenesis and epididymal sperm count in male rats.

The present study was designed to determine the effect of exposure to high altitude on spermatogenesis using transillumination technique and sperm count in male rats. In addition, the effect of oral intubation for intragastric administration of vehicle on testicular parameters in adult male rats in a schedule of 42 days was assessed. Male rats were exposed to Cerro de Pasco (Peru) at 4340 m for 3, 7, 14, 21, 28, 35 and 42 days resulting in a modification of the pattern of the seminiferous tubule stages. At day 3, stages I, IV-V, VI, VII and IX-XI were relatively shorter at high altitude than at sea level. At day 7, stages VIII, IX-XI, XII and XIII-XIV were reduced. At day 14, stages VII, VIII and IX-XI were reduced. At day 21 and 28, stages VIII, XII and XIII-XIV were significantly increased at high altitude. At day 35 an increase in stage XIII-XIV was observed. At day 42, stages II-III, IX-XI and XII were significantly increased at high altitude. Epididymal sperm count was significantly reduced at day 7 of exposure to high altitude and maintained low levels with respect to sea level up to 42 days. In conclusion, high altitude exposure affects spermatogenesis, particularly onset of mitosis and spermiation. This in turn affects epididymal sperm count.

Altitude↗
PubMed2003

Effect of Lepidium meyenii (Maca), a root with aphrodisiac and fertility-enhancing properties, on serum reproductive hormone levels in adult healthy men.

Lepidium meyenii (Maca) is a Peruvian hypocotyl that grows exclusively between 4000 and 4500 m in the central Andes. Maca is traditionally employed in the Andean region for its supposed aphrodisiac and/or fertility-enhancing properties. This study was a 12-week double-blind, placebo-controlled, randomized, parallel trial in which active treatment with different doses of Maca Gelatinizada was compared with a placebo. The study aimed to test the hypothesis that Maca has no effect on serum reproductive hormone levels in apparently healthy men when administered in doses used for aphrodisiac and/or fertility-enhancing properties. Men aged between 21 and 56 Years received 1500 mg or 3000 mg Maca. Serum levels of luteinizing hormone, follicle-stimulating hormone, prolactin, 17-alpha hydroxyprogesterone, testosterone and 17-beta estradiol were measured before and at 2, 4, 8 and 12 weeks of treatment with placebo or Maca (1.5 g or 3.0 g per day). Data showed that compared with placebo Maca had no effect on any of the hormones studied nor did the hormones show any changes over time. Multiple regression analysis showed that serum testosterone levels were not affected by treatment with Maca at any of the times studied (P, not significant). In conclusion, treatment with Maca does not affect serum reproductive hormone levels.

17-alpha-Hydroxyprogesterone↗
PubMed2002

Gender gaps, gender traps: sexual identity and vulnerability to sexually transmitted diseases among women in Vietnam.

We conducted a qualitative study to explore the pathways by which traditional gender roles may ultimately affect Vietnamese women's interpretation of sexually transmitted disease (STD) symptoms and health-seeking strategies. Data on gender roles, perceptions of types of sexual relationships, perceptions of persons with STDs, and STD patient experiences were gathered through in-depth interviews and focus groups with 18 men and 18 women in the general population of northern Vietnam. A framework integrating Andersen's behavioral model of health services use and Zurayk's multi-layered model was used to conceptualize women's health-seeking behavior for STD symptoms. Both men and women noted clear gender differences in sexual roles and expectations. According to participants, a woman's primary roles in northern Vietnam are socially constructed as that of a wife and mother-and in these roles, she is expected to behave in a faithful and obedient manner vis à vis her husband. It emerged that men's marital and sexual roles are less clearly defined by traditional norms and are more permissive in their tolerance of premarital and extramarital sex. For women, however, these activities are socially condemned. Finally, since STDs are associated with sexual promiscuity, both men and women expressed anxiety about telling their partners about an STD; women's expressions were characterized more by fear of social and physical consequences, whereas men expressed embarrassment. Community level interventions that work towards disassociating STDs from traditional social norms may enable Vietnamese women to report possible STD symptoms and promote diagnosis and care for STDs.

Adult↗
PubMed2002

Effect of Lepidium meyenii (MACA) on sexual desire and its absent relationship with serum testosterone levels in adult healthy men.

This study was a 12-week double blind placebo-controlled, randomized, parallel trial in which active treatment with different doses of Maca Gelatinizada was compared with placebo. The study aimed to demonstrate if effect of Maca on subjective report of sexual desire was because of effect on mood or serum testosterone levels. Men aged 21-56 years received Maca in one of two doses: 1,500 mg or 3,000 mg or placebo. Self-perception on sexual desire, score for Hamilton test for depression, and Hamilton test for anxiety were measured at 4, 8 and 12 weeks of treatment. An improvement in sexual desire was observed with Maca since 8 weeks of treatment. Serum testosterone and oestradiol levels were not different in men treated with Maca and in those treated with placebo (P:NS). Logistic regression analysis showed that Maca has an independent effect on sexual desire at 8 and 12 weeks of treatment, and this effect is not because of changes in either Hamilton scores for depression or anxiety or serum testosterone and oestradiol levels. In conclusion, treatment with Maca improved sexual desire.

Adult↗
PubMed2001

Detection of alkaline ultrafine atmospheric particles at Bakersfield, California.

Two collected micro-orifice uniform deposit impactors (MOUDIs) and a filter-based sampler were used to measure the size distribution and chemical composition of atmospheric particulate matter at Bakersfield, CA, between January 14 and 23, 1999. The peak number concentration of airborne ultrafine particles measured was 1.45 x 10(11) m-3, which is a factor of approximately 3 higher than the peak airborne ultrafine-particle number concentration measured previously in Pasadena, CA. Chemical analysis revealed that airborne ultrafine particles (Dp < 0.1 micron) at Bakersfield contained significant amounts of water-soluble species, including calcium, sodium, ammonium ion, nitrate, and sulfate. Other chemical species detected in the ultrafine size range included potassium, iron, copper, zinc, and strontium. A balance of aqueous ions showed that ultrafine particles were alkaline in nature with calcium acting as the dominant cation. Bulk samples of airborne particles with diameter less than 2.0 microns (PM2.0) were essentially neutral, but particle acidity was found to be a strong function of particle size. The results of this experiment suggest that areas deep in the human lung that preferentially collect particles in the ultrafine size range could be exposed to locally acidic or alkaline conditions even if the integrated airborne particle complex is essentially neutral.

Air Pollutants↗
PubMed2001

Cost-effectiveness of a trial of labor after previous cesarean.

OBJECTIVE: To determine the cost-effective method of delivery, from society's perspective, in patients who have had a previous cesarean. METHODS: We completed an incremental cost-effectiveness analysis of a trial of labor relative to cesarean using a computerized model for a hypothetical 30-year old parturient. The model incorporated data from peer-reviewed studies, actual hospital costs, and utilities to quantify health-related quality of life. A threshold of $50,000 per quality-adjusted life-years was used to define cost-effective. RESULTS: The model was most sensitive to the probability of successful vaginal delivery. If the probability of successful vaginal birth after cesarean (VBAC) was less than 0.65, elective repeat cesarean was both less costly and more effective than a trial of labor. Between 0.65 and 0.74, elective repeat cesarean was cost-effective (the cost-effectiveness ratio was less than $50,000 per quality-adjusted life-years), because, although it cost more than VBAC, it was offset by improved outcomes. Between 0.74 and 0.76, trial of labor was cost-effective. If the probability of successful vaginal delivery exceeded 0.76, trial of labor became less costly and more effective. Costs associated with a moderately morbid neonatal outcome, as well as the probabilities of infant morbidity occurring, heavily impacted our results. CONCLUSION: The cost-effectiveness of VBAC depends on the likelihood of successful trial of labor. Our modeling suggests that a trial of labor is cost-effective if the probability of successful vaginal delivery is greater than 0.74. Improved algorithms are needed to more precisely estimate the likelihood that a patient with a previous cesarean will have a successful vaginal delivery.

Adult↗
PubMed2001

Variation in practice patterns of anesthesiologists in California for prophylaxis of postoperative nausea and vomiting.

STUDY OBJECTIVE: To assess the responses to a survey asking anesthesiologists to report their clinical practice patterns for postoperative nausea and vomiting (PONV) prophylaxis. These practice patterns data may be useful for understanding how to optimize the decision to provide PONV prophylaxis. DESIGN: A written questionnaire with three detailed clinical scenarios with differing levels of a priori risk of PONV (a low-risk patient, a medium-risk patient, and a high-risk patient) was mailed to 454 anesthesiologists. SETTING: Survey was completed by anesthesiologists (n = 240) in 3 university and 3 community practices in California. MEASUREMENTS: Type and number of pharmacological and nonpharmacological interventions for PONV prophylaxis were recorded. To assess the variability in the responses (by the a priori risk of patient), we counted the number of different regimens that would be necessary to account for 80% of the responses. MAIN RESULTS: For the 240 respondents, we found that 1, 9, and 11 different pharmacological prophylaxis regimens were required to account for 80% of the variability in practice patterns for the low-, medium-, and high-risk patients, respectively. For the low-risk patient, 19% of practitioners would use pharmacological prophylaxis, and 37% would use nonpharmacological prophylaxis. For the medium-risk patient, 61% would use nonpharmacological prophylaxis and 67% of practitioners would use multidrug prophylaxis: 45% of patients would receive a 5HT(3) antagonist, 35% would receive metoclopramide, and 16% would receive droperidol. For the high-risk patient, 94% of practitioners would administer a 5HT(3) antagonist, whereas 84% would use multi-drug prophylaxis. CONCLUSIONS: We found a wide range of PONV prophylaxis management patterns. This variation in clinical practice may reflect uncertainty about the efficacy of available interventions, or differences in practitioners' clinical judgment and beliefs about how to treat PONV. Some therapies with proven benefit for PONV may be underused. Our results may be useful for designing studies aimed at determining the impact on PONV rates when physicians develop and implement guidelines for PONV prophylaxis.

Adult↗
PubMed2001

Comparison of real-time instruments used to monitor airborne particulate matter.

Measurements collected using five real-time continuous airborne particle monitors were compared to measurements made using reference filter-based samplers at Bakersfield, CA, between December 2, 1998, and January 31, 1999. The purpose of this analysis was to evaluate the suitability of each instrument for use in a real-time continuous monitoring network designed to measure the mass of airborne particles with an aerodynamic diam less than 2.5 microns (PM2.5) under wintertime conditions in the southern San Joaquin Valley. Measurements of airborne particulate mass made with a beta attenuation monitor (BAM), an integrating nephelometer, and a continuous aerosol mass monitor (CAMM) were found to correlate well with reference measurements made with a filter-based sampler. A Dusttrak aerosol sampler overestimated airborne particle concentrations by a factor of approximately 3 throughout the study. Measurements of airborne particulate matter made with a tapered element oscillating microbalance (TEOM) were found to be lower than the reference filter-based measurements by an amount approximately equal to the concentration of NH4NO3 observed to be present in the airborne particles. The performance of the Dusttrak sampler and the integrating nephelometer was affected by the size distribution of airborne particulate matter. The performance of the BAM, the integrating nephelometer, the CAMM, the Dusttrak sampler, and the TEOM was not strongly affected by temperature, relative humidity, wind speed, or wind direction within the range of conditions encountered in the current study. Based on instrument performance, the BAM, the integrating nephelometer, and the CAMM appear to be suitable candidates for deployment in a real-time continuous PM2.5 monitoring network in central California for the range of winter conditions and aerosol composition encountered during the study.

Air Pollution↗
PubMed2001

Lepidium meyenii (Maca) improved semen parameters in adult men.

AIM: The present study was designed to determine the effect of a 4-month oral treatment with tablets of Lepidium meyenii (Maca) on seminal analysis in nine adult normal men aged 24-44 years old. METHODS: Nine men received tablets of Maca (1500 or 3000 mg/day) for 4 months. Seminal analysis was performed according to guidelines of the World Health Organization (WHO). Serum luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin (PRL), testosterone (T) and estradiol (E2) were measured before and after treatment. RESULTS: Treatment with Maca resulted in increased seminal volume, sperm count per ejaculum, motile sperm count, and sperm motility. Serum hormone levels were not modified with Maca treatment. Increase of sperm count was not related to dose of Maca. CONCLUSION: Maca improved sperm production and sperm motility by mechanisms not related to LH, FSH, PRL, T and E2.

Adult↗
PubMed2000

HIV in Vietnam: the evolving epidemic and the prevention response, 1996 through 1999.

OBJECTIVES: To describe epidemiologic patterns and trends in HIV infection in Vietnam from 1996 through 1999, and to summarize the national response to the epidemic. METHODS: We reviewed nationwide HIV case reports, and we analyzed annual seroprevalence among different sentinel populations in 21 provinces, using the chi2 test for linear trend to assess trends in HIV prevalence. HIV prevention efforts were also reviewed. RESULTS: Through 1999, 17,046 HIV infections, including 2947 AIDS cases and 1523 deaths had been reported in Vietnam. The cumulative incidence rate for the country was 22.5 per 100,000 population. Injection drug users (IDUs) represented 89.0% of all those for whom risk was reported before 1997 and 88.0% in the period 1997 to 1999. In 1999, HIV prevalence rates among IDUs ranged by province from 0% to 89.4%. Significantly increasing HIV trends among IDUs (p <.05) were found in 14 of the 21 sentinel provinces during 1996 to 1999. HIV prevalence among commercial sex workers (CSWs) ranged from 0% to 13.2%, increased significantly in 6 of 21 provinces. In 1999, prevalence among pregnant women, blood donors, and military recruits were 0.12%, 0. 20% and 0.61%, respectively. Major prevention activities include mass information; peer education and outreach among groups at increased risk; availability of low-cost syringes and condoms through pharmacies; needle exchange pilot projects; widely available treatment for sexually transmitted diseases; antibody screening of blood for transfusion; and free medical treatment at government hospitals. DISCUSSION: The HIV epidemic continues to evolve rapidly, intensifying among IDUs and increasing among CSWs. Serosurveillance indicators of HIV in the population at large continue to indicate the relatively slow extension beyond those at highest risk. Immediate, intensive preventions in high-risk groups may decelerate expansion to the broader population.

Adolescent↗
PubMed1999

cAMP regulates Ca2+-dependent exocytosis of lysosomes and lysosome-mediated cell invasion by trypanosomes.

Ca2+-regulated exocytosis, previously believed to be restricted to specialized cells, was recently recognized as a ubiquitous process. In mammalian fibroblasts and epithelial cells, exocytic vesicles mobilized by Ca2+ were identified as lysosomes. Here we show that elevation in intracellular cAMP potentiates Ca2+-dependent exocytosis of lysosomes in normal rat kidney fibroblasts. The process can be modulated by the heterotrimeric G proteins Gs and Gi, consistent with activation or inhibition of adenylyl cyclase. Normal rat kidney cell stimulation with isoproterenol, a beta-adrenergic agonist that activates adenylyl cyclase, enhances Ca2+-dependent lysosome exocytosis and cell invasion by Trypanosoma cruzi, a process that involves parasite-induced [Ca2+]i transients and fusion of host cell lysosomes with the plasma membrane. Similarly to what is observed for T. cruzi invasion, the actin cytoskeleton acts as a barrier for Ca2+-induced lysosomal exocytosis. In addition, infective stages of T. cruzi trigger elevation in host cell cAMP levels, whereas no effect is observed with noninfective forms of the parasite. These findings demonstrate that cAMP regulates lysosomal exocytosis triggered by Ca2+ and a parasite/host cell interaction known to involve Ca2+-dependent lysosomal fusion.

1-Methyl-3-isobutylxanthine↗
PubMed1999

Functional characterization of monoclonal antibodies to interferon-tau.

Interferon tau (IFNtau) produces an array of biological effects, including antiluteolytic, antiviral, antiproliferative and immunomodulatory activities, without the consequent cytotoxicity associated with other type I IFNs. Four anti-IFNtau monoclonal antibodies (MAbs) have been characterized by determining regional epitopes and observation of their effects on IFNtau binding, antiviral and antiproliferative activity. Using an enzyme-linked immunoadsorbent assay (ELISA) developed against six overlapping synthetic peptides representing the entire linear sequence of IFNtau, three antibodies, HL-98, HL-100 and HL-127, were found to react with the carboxy terminal peptide, while HL-129 bound the penultimate amino terminal peptide. Binding studies indicated that MAbs directed against either region could effectively inhibit the binding of alkaline phosphatase labeled IFNtau to cells expressing type I IFN receptors. While only two of the MAbs significantly reversed IFNtau-induced growth inhibition, the antiviral activity of IFNtau was significantly inhibited by MAbs that bound the amino and carboxy termini, confirming the functional importance of these domains in the binding and subsequent activity of IFNtau.

Animals↗
PubMed1999

Maximum diameter of prostatic carcinoma is a simple, inexpensive, and independent predictor of prostate-specific antigen failure in radical prostatectomy specimens. Validation in a cohort of 434 patients.

The amount of tumor in radical prostatectomy specimens can be determined with several techniques. Maximum tumor diameter correlates well with total tumor volume and can readily be obtained in incompletely submitted specimens. Initial results in a small series suggested that this measure also may predict for prostate-specific antigen (PSA) failure. We studied whether maximum tumor diameter was an independent predictor of PSA failure in a series of 434 men who underwent radical prostatectomy because of prostatic adenocarcinoma; 118 (27.2%) had PSA failure. Preoperative PSA, Gleason score, pathologic stage, margin status, and largest tumor diameter were determined, and multivariate logistic modeling was performed on the outcome of PSA failure. Maximum tumor diameter was an independent risk factor for PSA failure, along with preoperative serum PSA level, and Gleason score > or = 8. Only 15% of men with tumor with maximum diameter < 1 cm had PSA failure, compared with 73% of men with tumor with maximum diameter > 2. Maximum tumor diameter of prostatic carcinoma is a simple, inexpensive, and independent predictor of PSA failure that can be obtained readily from partially submitted radical prostatectomy specimens.

Adenocarcinoma↗
PubMed1999

International reference reagents: antihuman globulin. An ISBT/ICSH joint working party report. International Society of Blood Transfusion. International Committee for Standardization in Haematology.

An international working party has conducted a study designed to select a suitable reference reagent for antihuman globulin, to replace those first made available in 1987. The chosen preparation contains levels of anti-IgG and anti-C3 (anti-C3c and anti-C3d) potency that are considered suitable to serve for reference when evaluating either polyspecific antihuman globulin reagents or those containing their separate monospecific components. The reference material is available in 2-ml freeze-dried aliquots from seven assigned distribution centres.

Coombs Test↗