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Biomedical subjects

Y Tsong

Publications and source records attributed to Y Tsong.

At least 19 recordsLinked to original sources
PubMed1997

Multiple-time-point dissolution specifications for a sampling acceptance plan.

In dissolution testing, multiple dissolution measurements at specific time points are used to obtain the dissolution characteristics for most extended-release and some immediate-release drug products. This paper presents a general procedure for defining specifications by a multivariate confidence region or by simultaneous confidence limits on the dissolution values of individual time points. The confidence regions and simultaneous confidence limits were estimated using two approaches: the first approach assumed a multivariate normal distribution on the multiple dissolution values and the second approach used the bootstrap resampling method. The multivariate confidence region was constructed using the Hotelling's T2 statistic (equivalently, Mahalanobis distance D2), and the simultaneous confidence limits were based on the Mahalanobis statistic as well as on the Bonterroni adjustment. The Mahalanobis simultaneous confidence limits specification criteria have the overall false out-of-specification rate too low in both parametric and bootstrap approaches.

Chemistry, Pharmaceutical↗
PubMed1996

In-vitro dissolution profile comparison: statistics and analysis, model dependent approach.

PURPOSE: To develop and propose a "model dependent' approach for the in-vitro dissolution profiles comparison. METHODS: Diltiazem hydrochloride tablet dissolution profiles were compared using a statistical approach based on a mathematical model. A similarity region (SR) was defined based on the intra- and inter-lot parameter variances of the final production size standard lots. Statistical distances between the test and reference lot parameter means were computed and normalized. A 90% confidence region (CR) was developed around the statistical distance. The confidence region was compared with the similarity region to assess the similarity or dis-similarity of the test and reference (REF) lot dissolution profiles. Two test lots, one with a "minor' modification (mm) the other with a "major' modification (MM), were evaluated. RESULTS: "Weibull' was selected as the "model' function. A comparison of the confidence regions around the statistical distance of "mm-REF' and "MM-REF' with the similarity region, suggested that the dissolution profiles of the "minor' modification lot were similar and that of "major' modification lot were dis-similar to the reference lot. CONCLUSIONS: A "model dependent' approach was shown to be useful for the inter-lot in-vitro dissolution profiles comparison.

Cardiovascular Agents↗
PubMed1995

Comparing reporting rates of adverse events between drugs with adjustment for year of marketing and secular trends in total reporting.

The Food and Drug Administration has collected spontaneous reports on adverse events (AE) from manufacturers and individuals. These data provide useful information on the safety of marketed drugs. Due to many unique characteristics of this reporting system, the information is difficult to evaluate. Incidence rates for specific adverse events and drug combinations cannot be estimated. However, reporting rates (number of reports per market share) based on prescriptions can be computed. These reporting rates provide signals of serious adverse experience that may deserve attention. When the ratio of reporting rates is used for the comparison of two drugs of the same drug class, adjustments are needed for the marketing year and secular trends of all-drug-all-AE reporting. The Mantel-Haenszel procedure is used to combine the multiyear data into one summary statistic. Application of this analysis is illustrated on reports of upper gastrointestinal bleeding, perforation, and ulcer associated with nonsteroidal anti-inflammatory drugs, as given in Rossi et al. (12).

Adverse Drug Reaction Reporting Systems↗
PubMed1995

Estimation of the shelf-life of drugs with mixed effects models.

This paper proposes a normal mixed effects model for stability analysis. An EM algorithm is developed to compute the maximum likelihood estimates of regression coefficients of the fixed effects and random effects, and variance components. The likelihood ratio test is used for the preliminary testing of batch-to-batch variation. An example from a marketing stability study is given to illustrate the proposed procedure.

Algorithms↗
PubMed1995

Dissolution test acceptance sampling plans.

The U.S. Pharmacopeia (USP) general monograph provides a standard for dissolution compliance with the requirements as stated in the individual USP monograph for a tablet or capsule dosage form. The acceptance rules recommended by USP have important roles in the quality control process. The USP rules and their modifications are often used as an industrial lot release sampling plan, where a lot is accepted when the tablets or capsules sampled are accepted as proof of compliance with the requirement. In this paper, the operating characteristics of the USP acceptance rules are reviewed and compared to a selected modification. The operating characteristics curves show that the USP acceptance rules are sensitive to the true mean dissolution and do not reject a lot or batch that has a large percentage of tablets that dissolve with less than the dissolution specification.

Capsules↗
PubMed1992

False alarm rates of statistical methods used in determining increased frequency of reports on adverse drug reaction.

Several statistical methods have been proposed or used in the determination of an increase in frequency of reports of adverse drug reactions. Some of the methods are based on large sample approximation or equal sample sizes assumption. The actual type I error may differ significantly from the predetermined nominal level of 5% when the methods are applied to rare adverse events. Simulated false alarm rates of the methods were compared under the assumption of 10 or less expected reports in the reference period.

Drug-Related Side Effects and Adverse Reactions↗
PubMed1990

Mortality resulting from blood dyscrasias in the United States, 1984.

Blood dyscrasias are rare but serious diseases. We used national death certificate data for the year 1984 to estimate the number and rate of deaths caused by four blood dyscrasias. These diseases contributed to 4,490 deaths, corresponding to a mortality rate of 18.9 per million United States population. Aplastic anemia was the most frequent cause of death, followed by thrombocytopenia, agranulocytosis, and hemolytic anemia. Mortality rates varied by age, with a small peak in young children, lower rates for ages five through 34 years, and exponentially increasing rates beyond 35 years of age. Although drug relatedness could not be reliably ascertained from our data, other surveys have estimated that approximately 30% of fatal blood dyscrasias are caused by therapeutic drugs. Assuming that 30% drug attribution also applies to the U.S. population as a whole, approximately 1,350 blood dyscrasia deaths in the U.S. in 1984 may have been caused by drugs.

Adolescent↗
PubMed1990

Competing risk analysis of life table data: application to lifetime risk computation.

In this pedagogic note we propose to assess the safety of treatment in a clinical trial, or the effect of risk exposure in a chronic animal study, in terms of two lifetime risks. These risks are computable from life table type data and take into account the effects of competing risks. We first describe their computational procedures in detail to demonstrate the need for their implementation in a computer program. We then illustrate their practical application through use of the data obtained from an actual clinical study.

Health Status Indicators↗
PubMed1990

Scaling of response scale adverbs among black-American adults.

Although some attention has been given to the scale characteristics of modifying adverbs in Likert scales, the existing work has been concerned primarily with majority group members. Toward the goal of identifying valid labels for use on Likert scales with black-American respondents, 105 black-American adults scaled each of 27 adverbs (e.g., very, most) on four different adjectives (e.g., important). Four criteria for a set of ideal adverbs were identified for univalent scales. No set of four adverbs, however, met the criteria. Differences in the mean ratings of eight of the adverbs were found by sex group and across the four adjectives modified. The adverbs were not scored at the extremes of the continuum, despite our asking the respondents to rate the adverbs used to define the end points of the continuum. High variances were found across all adverbs. Further research must address the respondents' perceptual frame in the use of such scales.

Adult↗
PubMed1989

Beta-endorphin levels in the human menstrual cycle.

To examine the fluctuation in plasma beta-Endorphin (beta-EP) concentration throughout the menstrual cycle, 8 healthy females with normal cycles were studied. After an overnight fast, the subject's blood samples were drawn between 8 and 10 a.m. They gave blood at 2 or 4 day intervals through three menstrual cycles. Using the LH surge as day 0, the mean beta-EP concentrations were higher on days -10, -9, -8 (6.5 +/- 2.6, 6.9 +/- 3.8 and 6.7 +/- 2.7 pmol/l, follicular phase), on days -1, 0, +1 (9.2 +/- 3.3, 9.1 +/- 5.2 and 8.8 +/- 3.3 pmol/l, periovulatory phase), and on days +9 and +12 (8.6 +/- 2.5 and 8.8 +/- 3.8 pmol/l, luteal phase). Most beta-EP levels were low during menstruation. The rise and fall in beta-EP and its relation to temporal LH and FSH secretion are discussed. The findings show that three beta-EP rises take place during the menstrual cycle and that beta-EP may be involved in the regulation of ovulation.

Adult↗
PubMed1988

Role of interferon in leukocyte histamine release caused by common respiratory viruses.

Asthmatic attacks are often precipitated by viral respiratory infections. The mechanism of virus-induced asthma is still unclear. Interferon could be an important mediator in virus-induced hypersensitivity reactions, because interferon is induced by some respiratory viruses, and it can enhance IgE-mediated histamine release in vitro. We studied the effect of common respiratory viruses, including both interferon inducers and non-interferon inducers, on IgE-mediated leukocyte histamine release. Leukocytes from healthy, nonallergic donors were exposed to different strains of respiratory viruses, and basophils were challenged with antibody to IgE to release histamine. We found that the viruses are capable of enhancing IgE-mediated histamine release in the presence or absence of interferon. Our results suggest that although interferon may play a role in virus-induced hypersensivity reactions, other mechanisms probably also play a significant role.

Basophils↗
PubMed1988

Ethnic variation in blood pressure among preadolescent children.

As part of a study on methods for assessing diet and exercise among 163 3rd to 6th grade students, data were collected on blood pressure, diet, urinary electrolytes, aerobic activity, resting pulse, and body composition. Data were collected on a stratified sample, with almost equal numbers of children of both sexes from 3rd or 4th and 5th or 6th grades; from three ethnicities: Anglo-, Black- and Mexican-American. Three resting blood pressures were obtained using a Hawksley random zero sphygmomanometer. Data analytic procedures relied on analyses of variance and covariance to assess differences across design factors in blood pressure, with dietary sodium, resting pulse, body surface area, and energy expended as covariates. No differences were detected across ethnic groups in systolic pressures, but Mexican-American children were shown to have significantly higher diastolic fourth phase pressures than Anglo- or Black-American children. Only the dietary variables differed across ethnic groups, but not in the same pattern. Differences in the covariates did not account for the difference across ethnic groups in diastolic pressures.

Analysis of Variance↗
PubMed1987

Inhibitory action of peptide YY on gastric acid secretion.

The purpose of this study is to investigate the effect of peptide YY (PYY) on pentagastrin-, histamine-, and bethanechol-stimulated gastric acid secretion and the possible mechanisms by which PYY inhibits gastric acid secretion. Six mongrel dogs with chronic gastric and duodenal fistulas were given an intravenous infusion of pentagastrin (0.5 microgram . kg-1 . h-1), histamine (18 micrograms . kg-1 . h-1), or bethanechol (80 micrograms . kg-1 . h-1) either alone or simultaneously with intravenous PYY (100, 200, 400, pmol . kg-1 . h-1). PYY (100, 200, 400 pmol . kg-1 . h-1) inhibited pentagastrin-stimulated gastric acid secretion in a dose-dependent manner. PYY (400 pmol . kg-1 . h-1) did not depress bethanechol-stimulated gastric acid secretion. PYY (400 pmol . kg-1 . h-1) also failed to inhibit histamine-stimulated gastric acid secretion. Furthermore, PYY inhibit pentagastrin-stimulated gastric acid secretion in the face of atropine, vagotomy, or indomethacin treatment. These findings indicate that the inhibitory action of PYY on gastric acid secretion is in part independent of long and short cholinergic pathways. These findings also indicate that the inhibitory mechanism of PYY is independent of prostaglandin synthesis. Our findings are discussed in relation to previous reports regarding the effects of PYY on gastric acid secretion.

Animals↗
PubMed1987

Aerobic physical activity among third- to sixth-grade children.

We observed the level of activity, and determined which of 24 third- to sixth-grade children were present during that activity, for two weekdays per child. No events of aerobic activity, as defined by nationally accepted criteria, were detected in that 48 days of observation. By a less stringent criterion, only half the children engaged in aerobic activity on any one day. With regard to who was active, there was no evidence for day-to-day consistency. Fathers were virtually absent during periods of activity. Issues relating to promoting aerobic activity are discussed.

Child↗
PubMed1986

Classification of primate spinothalamic and somatosensory thalamic neurons based on cluster analysis.

Data analyzed in this study were derived from the responses of 128 spinothalamic tract (STT) cells and 110 thalamic neurons recorded in 75 anesthetized monkeys. A k-means cluster analysis, a nonhierarchical clustering technique, was performed using the relative magnitudes of responses to a graded series of innocuous and noxious mechanical stimuli applied to the receptive field. For comparison, a parallel analysis was performed based on definitions of low-threshold (LT), wide dynamic range (WDR), and high-threshold (HT) cells used by our laboratory. For 128 STT cells, a classification scheme with three clusters was found statistically to be the best. This yielded groups of 22, 57, and 49 cells in clusters 1, 2, and 3, respectively. Cluster 1 cells were activated best by low-intensity mechanical stimuli, whereas cluster 3 cells were activated primarily by nociceptive stimuli. Cluster 2 cells had intermediate characteristics. When the classification scheme based on the cluster analysis was compared with the classification of the same neurons as LT, WDR, and HT cells, cluster 1 cells were divided into LT and WDR cells, whereas cluster 2 and 3 cells included WDR and HT cells. For 110 thalamic neurons, a classification scheme with five clusters was found statistically to be the best. Clusters 1-5 contained 25, 34, 17, 10, and 24 cells, respectively. Response characteristics of cells in each group indicated a gradual change in sensitivity to higher intensities of peripheral input from cluster 1 to 5. When this classification scheme was compared with the classification scheme previously used by our laboratory, cluster 1 cells belonged to the LT group, clusters 2 and 3 split into LT and WDR cells, and clusters 4 and 5 included WDR and HT cells. It is concluded that a classification scheme based on a cluster analysis of the responses of neurons to standardized stimuli may provide an objective and functionally meaningful way to categorize somatosensory neurons.

Animals↗
PubMed1983

Nervous tension and serum cholesterol: findings from the Chicago Coronary Prevention Evaluation Program.

Of 519 coronary-prone middle-aged men participating in the Chicago Coronary Prevention Evaluation Program, 416 reported their self-perceived state as one of no tension or tension at various periodic visits over years in the Program. Group mean serum cholesterol was significantly higher by about 4 mg/dl with tension vs. no tension (slight, moderate, or marked). This relationship was independent of weight change, intercurrent infection, use of medication, and month of year.

Adult↗
PubMed1982

The selective lipid-lowering effect of vegetarianism on low density lipoproteins in a cross-over experiment.

In a cross-over experiment the effect of short-term vegetarianism on serum lipids, lipoproteins and apoproteins was studied. The experimental diet was free of animal products, with the exception of skim milk, and consequently low in saturated fat and cholesterol. Fifteen free-living individuals were randomly assigned to 3-week periods on either the experimental diet or a control diet which closely approximated the usual intake in the U.S.A. Significant reductions in total cholesterol (12.5%), low density lipoprotein cholesterol (14.7%), and apo B (13.2%) were observed, accompanied by a non-significant decrease in high density lipoprotein cholesterol (10%), apo A-I (3%) and a non-significant increase in apo-II (4%). These data suggest that a fat-modified diet low in total fat, saturated fat and cholesterol, and moderate (not high) in polyunsaturated fat may not lower HDL-C or its apoproteins as much as a diet high in polyunsaturated fat, while having similar effects on LDL-C, and would therefore be preferable as the basis for primary prevention of atherosclerosis.

Adult↗