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Biomedical subjects

H Tsang

Publications and source records attributed to H Tsang.

13 recordsLinked to original sources
PubMed2000

Molecular analyses of a repetitive DNA sequence in wheat (Triticum aestivum L.).

A repetitive sequence designated WE35 was isolated from wheat genomic DNA. This sequence consists of a 320-bp repeat unit and represents approximately 0.002% of the total wheat DNA. It is unidirectionally distributed either continuously or discretely in the genome. Ladder-like banding patterns were observed in Southern blots when the wheat genomic DNA was restricted with endonuclease enzymes EcoRI, HincII, NciI, and NdeI, which is characteristic for tandemly organized sequences. Two DNA fragments in p451 were frequently associated with the WE35 repetitive unit in a majority of lambda wheat genomic clones. A 475-bp fragment homologous to the 5'-end long terminal repeat (LTR) of cereal retroelements was also found in some lambda wheat genomic clones containing the repetitive unit. Physical mapping by fluorescence in situ hybridization (FISH) indicated that one pair of wheat chromosomes could be specifically detected with the WE35 positive probe p551. WE35 can be considered a chromosome-specific repetitive sequence. This repetitive unit could be used as a molecular marker for genetic, phylogenetic, and evolutionary studies in the tribe Triticeae.

Amino Acid Sequence↗
PubMed2000

Reliability and validity of a simple measure for assessing the social skills of people with schizophrenia necessary for seeking and securing a job.

The literature shows that social and vocational impairments are common problems among people with schizophrenia. However, assessment instruments available for measuring social competence of people with schizophrenia in the workplace are limited. This article describes a two-part measure developed and validated based on a model (Tsang & Pearson, 1996) for assessing social skills necessary for seeking and maintaining a job for people with schizophrenia. The measure consists of a 10 item self-administered checklist and a role-play exercise. The self-administered checklist measures clients' perceived competence in handling work-related social situations. The role-play exercise assesses the social skills necessary for job acquisition and maintenance in two simulated situations (participating in a simulated job interview and requesting urgent leave from work). Cronbach alpha coefficients (self-administered checklist: .80 (n = 140); role-play test: .96 (n = 60)) show that both parts had good internal consistency. In addition, correlation coefficients show that the self-administered checklist has acceptable test-retest reliability (.35 to .78), and the role-play exercise has good interrater reliability (.77 to .90). The concurrent validity is also shown to be good for both parts of the measure using the method of contrasted groups. It is suggested that this measure is suitable for use by clinicians, rehabilitation administrators and researchers. Application of the instrument in other countries is discussed. Finally, further research is suggested.

Adult↗
PubMed2000

Development and validation of the workshop behavior checklist: a scale for assessing work performance of people with severe mental illness.

The Workshop Behavior Checklist is a standardized assessment instrument to assess the work performance of people with severe mental illness using the situational assessment approach. It is modified from the Behavior Identification Form developed by the Material Development Center. The modification process was conducted by enlisting input from mental health professionals (n = 150) and potential employers of discharged patients with mental illness (n = 31) by questionnaires specially designed for this purpose. The results of these questionnaires were then analyzed by an expert panel consisting of 10 therapists and one psychiatrist working in relevant fields. Altogether 14 items in general behaviors, vocational behaviors, and social behaviors were selected. In addition, a new version of the checklist together with its rating guidelines were designed. Exploratory factor analysis (n = 112) shows that all 14 items fit well into a four-factor model explaining 67.2% of total variance, which is in line with the original design of the revised checklist. Cronbach alpha analysis shows that the revised checklist has acceptable to very good internal consistency (.51 to .84) and intraclass correlation coefficients indicate that it has good to excellent inter-rater (.57 to .81) and test-retest (.86 to .94) reliability. Clinical implications and further research are discussed.

Adolescent↗
PubMed2000

Predictors of post-hospital employment status for psychiatric patients in Hong Kong: from perceptions of rehabilitation professionals to empirical evidence.

Fifty participants with mental illness and a concrete discharge plan were selected from two mental hospitals in Hong Kong and assessed on their Psychosocial support by the Chinese Version of the Significant Others Scale, social vocational competence using the Workshop Behavior Checklist and the Vocational Social Skills Scale, medical history, work history, and demographic variables. At three months after discharge, the employed participants (n = 12) were shown to have better psychosocial support and social vocational competence than the unemployed participants (n = 24) by univariate comparison. The employed and unemployed participants did not differ in their medical and work history, and demographic variables. Implications of the results for rehabilitation programming are discussed.

Adolescent↗
PubMed1999

Biodegradation of commercial dental composites by cholesterol esterase.

The research literature suggests that current dental polymeric composites are not chemically inert at the material/biological interface. Several studies have investigated the process of "biodegradation" on dental composites in the presence of enzymes, by monitoring changes in weight loss and surface hardness properties. However, it is hypothesized that these methods can provide an erroneous measure of biochemically induced degradation, since they are less sensitive to molecular events and lack the ability to provide chemical information. Knowledge of the latter is important because it relates to the biological significance of biodegradation, i.e., the identification and quantification of released compounds that may be capable of influencing cell, bacteria, or enzyme function. It was the objective of this study to compare three methods (weight loss, surface micro-hardness, and liquid chromatography combined with mass spectrometry) for their ability to measure the effect of enzyme-induced biodegradation on three commercial composite resin materials. The enzyme was cholesterol esterase, and the composites were Silux Plus XL, Z100 A2 (3M), and TPH XL (L.D. Caulk). Biodegradation was readily detected by liquid chromatography, and its sensitivity was shown to be substantially greater than that of weight loss or surface hardness measurements, although surface hardness measurements did show some agreement with liquid chromatography data. The data also indicated that the levels and distribution of released degradation products can vary substantially from one product to the next, and that this merits further investigation if the potential impact of different commercial restorative materials on cell and bacteria function is to be assessed.

Bacteria↗
PubMed1998

Digital dynamic telepathology--the Virtual Microscope.

The Virtual Microscope is being designed as an integrated computer hardware and software system that generates a highly realistic digital simulation of analog, mechanical light microscopy. We present our work over the past year in meeting the challenges in building such a system. The enhancements we made are discussed, as well as the planned future improvements. Performance results are provided showing the system scales well, so that many users can be adequately serviced by an appropriately configured data server.

Computers↗
PubMed1988

Cloning of a gamma 2b gene encoding anti-Pseudomonas aeruginosa H chains and its introduction into the germ line of mice.

A complete, functional gamma 2b gene (pVCM) was cloned from a mouse hybridoma (VD93) with antibody activity to Pseudomonas aeruginosa. DNA sequencing of the VDJ region of pVCM determined that the VH gene was a member of the J558 family rearranged to JH2. Upon transfection into myeloma cells the gamma 2b gene gave rise to high levels of gamma 2b mRNA and gamma 2b protein. The gamma 2b protein had the same IEF pattern as the parent hybridoma protein VD93 and the antibodies formed from a combination of the pVCM gamma 2b chains and the myeloma lambda-chains bound weakly to P. aeruginosa. However, the hybrid antibodies did not discriminate between the serotypes 2 and 3, whereas the parent protein was specific for serotype 3. Transgenic mice were produced with the pVCM gamma 2b gene which expressed the gamma 2b mRNA (both membrane and secreted forms) only in lymphoid organs. However, contrary to expectations, the gamma 2b mRNA levels were higher in T cells than in B cells in three different transgenic lines. The serum of the transgenic mice had no activity to P. aeruginosa indicating the importance of L chains for the conformation of the Ag binding site. These gamma 2b transgenic mice provide a convenient tool for the study of feedback inhibition of Ig gene rearrangement.

Animals↗
PubMed1987

Regulation of pantothenic acid transport in the heart. Involvement of a Na+-cotransport system.

Pantothenic acid transport was studied in the isolated perfused rat heart and isolated sheep cardiac sarcolemmal vesicles. In the perfused heart, pantothenic acid transport was significantly greater if hearts were perfused as working hearts rather than Langendorff hearts, but was unaffected by the perfusion substrates used (11 mM glucose or 1.2 mM palmitate). Uptake rates of pantothenic acid in working hearts are dependent on perfusate concentrations of pantothenic acid (a Vmax of 418 nmol/g dry weight/30 min and a Km for pantothenic acid of 10.7 mircoM were obtained). Reduction in perfusate Na+ concentration from 145 to 105 mM (the Na+ was replaced with 40 mM choline) resulted in a small but significant decrease in pantothenic acid uptake. At 145 mM Na+, addition of a mixture of amino acids, whose uptake is Na+-dependent, resulted in a significant decrease in pantothenic acid uptake by the heart (173 +/- 5 to 132 +/- 12 nmol/g dry weight). If an inward Na+ gradient in isolated, purified sarcolemmal vesicles, was imposed, a rapid uptake of pantothenic acid was observed. Uptake rates are markedly reduced if Na+ was replaced by equimolar concentrations of K+ or if external Na+ was reduced below 40 mM. In the presence of Na+, increasing pantothenic acid concentrations resulted in an increase in pantothenic acid uptake by the vesicles. Combined, these data demonstrate that pantothenic acid is transported across the myocardial sarcolemmal membrane by a Na+-dependent mechanism, which may be common to a number of small molecules.

Animals↗
PubMed1987

Inhibition of the human flexion reflex by low intensity, high frequency transcutaneous electrical nerve stimulation (TENS) has a gradual onset and offset.

The present study examines the inhibitory effect of segmentally applied TENS on the nociceptive component of the flexion reflex elicited in various lower limb muscles, in an attempt to gain some insight into the underlying mechanism. The flexion reflex from 11 normal subjects was recorded electromyographically from the biceps femoris (BF), the tibialis anterior (TA), and in 2 subjects, the hip flexor (HF), in the manner described in a previous paper [9]. Amplitude and area values of the flexion reflex of each muscle were computerized prior to, during, and 50 min after the application of placebo or low intensity TENS at 100 Hz, for 30 min to the low back, at levels of segmental innervation (L4-S1) similar to those of the muscles under study. In the majority of subjects, we found that: Low intensity TENS caused a significant inhibition of the flexion reflex in proximal limb flexors. Thus, the BF measured 64% and 52%, and the HF 45% and 51%, of their respective mean control amplitude and area values at the time of maximum inhibition during TENS. Moreover, less reduction of the mean values of the flexion reflex was observed in the TA, a distal limb (ankle) flexor. It is noteworthy that in both the BF and HF, the time to peak maximum inhibitory effect took 30 and 20 min respectively after the onset of TENS, and the flexion reflex often did not return to control values even at 40-50 min after TENS. In contrast, placebo TENS application resulted in no significant change of the flexion reflex in all the muscles examined. These findings showed that prolonged stimulation of large diameter fibers by conventional TENS application to the lumbosacral level, exerts a progressive and long latency inhibitory influence on a number of lower limb flexor motoneurons. In keeping with functional demand, this effect was found to be more prominent on the proximal than distal limb muscles. Furthermore, a gradual onset and offset of this inhibitory action is consistent with the results of some investigators demonstrating the possible involvement of endogenous opioids.

Electric Stimulation Therapy↗
PubMed1987

Metabolism of palmitate in isolated working hearts from spontaneously diabetic "BB" Wistar rats.

Myocardial fatty acid metabolism was studied in spontaneously-diabetic "BB" Wistar rats. The study involved 4 groups: control Wistar rats, nondiabetic littermates of "BB" Wistar rats, insulin-treated diabetic "BB" rats, and diabetic "BB" rats in which insulin treatment was removed 24 hours prior to study (uncontrolled diabetes). Hearts were perfused for 30 minutes as isolated working hearts in perfusate containing 1.2 mM (1-14C)-palmitate bound to 3% albumin, and 11 mM glucose. Palmitate oxidative rates, calculated as micromoles palmitate oxidized per gram dry weight per minute, were significantly decreased in both diabetic groups (0.447 +/- 0.043 and 0.528 +/- 0.038 in uncontrolled diabetic and treated diabetic versus 0.584 +/- 0.032 and 0.629 +/- 0.033 in nondiabetic littermate and control rats, respectively). This decrease was accompanied, however, by a significant decrease in the heart rate of these 2 groups when compared with control or nondiabetic animals. If the decreased heart function in the diabetic animals was accounted for, no decrease in palmitate oxidative rates occurred, suggesting that fatty acid oxidative metabolism is not impaired in the diabetic myocardium. In the uncontrolled diabetic rats, an increased rate of palmitate incorporation into myocardial triglycerides was seen compared with treated diabetic, nondiabetic littermates, and control rats (8.5 +/- 0.3 mumol/g dry wt/30 min versus 4.8 +/- 0.3, 5.9 +/- 0.7, and 5.7 +/- 0.3, respectively). Myocardial levels of coenzyme A were elevated in the uncontrolled diabetic rats compared with all other groups (647 +/- 25 nmol/g dry wt versus 484 +/- 27, 508 +/- 56, and 534 +/- 9, in treated diabetic, nondiabetic, and control rats, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Left ventricular size, output, and structure during guinea pig pregnancy.

We investigated left ventricular (LV) hemodynamics, pressure-volume relations, and morphometry to determine what cardiac changes characterize pregnancy in the guinea pig. Time-bred virgin guinea pigs were paired by weight with unbred controls. Hemodynamic studies and LV pressure-volume relations were obtained on days 59-68 of the 68-day gestation. Weight of control sows increased from 817 to 902 g (P less than 0.01) and pregnant sows from 810 to 1,251 g (P less than 0.01). LV weights were not different. When indexed for maternal weight minus uterus and contents, pregnancy produced increases in O2 consumption, +48% (P less than 0.01); cardiac output, +32% (P less than 0.05); and stroke volume, +46% (P less than 0.025). Passive LV pressure-volume curves (dP/dV) were shifted to the right (P less than 0.025), but dP/dV at constant pressure was unchanged. Using a thin-walled spherical model, elastic modulus at constant stress was not different. The percent LV inter- and intracellular volumes and myocyte myofibril and organelle volumes were unchanged during pregnancy. In the guinea pig, pregnancy increases LV output, stroke volume, and size without changes in LV mass, morphometry, or elastic modulus.

Animals↗