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Biomedical subjects

T Chung

Publications and source records attributed to T Chung.

At least 73 records · Page 4Linked to original sources
PubMed1996

Interpreting the results of pediatric central venous catheter studies.

Radiographic evaluation of central venous catheters (CVCs) with contrast material is a commonly performed procedure in pediatric radiology, but the criteria for interpreting the results of such studies are not well described in the literature. Careful evaluation of the images from a contrast material-enhanced CVC study frequently demonstrates a cause of CVC malfunction. In a series of 166 contrast-enhanced CVC studies performed in children, 112 studies (67%) demonstrated abnormal results. The most common abnormalities were mural thrombus, catheter tip thrombus, catheter tip against the vessel wall, and sleeve thrombus. Other causes of catheter malfunction include reservoir thrombus, catheter break, and catheter malposition. When catheter malfunction is due to catheter thrombus formation, the patient is usually treated with urokinase (bolus injection or infusion). Short catheters that ended in the innominate or subclavian vein had a much higher frequency of abnormalities than longer catheters that ended in the superior vena cava or right atrium.

Catheterization, Central Venous↗
PubMed1996

Percutaneous biopsy for prognostic testing of neuroblastoma.

PURPOSE: To determine whether percutaneous biopsy can provide the diagnostic and prognostic information necessary to treat children with advanced neuroblastoma. MATERIALS AND METHODS: From 1991 through 1995, 21 percutaneous biopsies were performed in 20 children with advanced neuroblastoma by using 15- or 16-gauge core biopsy needles. An average of six samples were obtained. Since September 1994, fresh tissue was sent to the reference laboratory, where touch preparations were prepared for N-myc evaluation. RESULTS: Histologic confirmation and prognostic information (Shimada classification) were obtained in all cases. Genetic prognostic information was obtained in 19 patients (95%), DNA index (ploidy) in 18 (90%), N-myc gene expression in 14 (70%), and cytogenetic analysis in 10 (50%). N-myc and ploidy determinations were successful in all five biopsy specimens obtained since September 1994. CONCLUSION: Percutaneous biopsy of advanced neuroblastoma is a feasible alternative to open biopsy.

Adolescent↗
PubMed1996

Staging in the onset of DSM-IV alcohol symptoms in adolescents: survival/ hazard analyses.

OBJECTIVE: This research examined staging in the time to onset of DSM-IV alcohol symptoms in adolescents. Consistent staging in the onset of symptoms provides important tests of the construct validity of diagnostic systems, and aids the development of early case identification strategies. METHOD: The Structured Clinical Interview for the DSM (SCID), adapted to assess DSM-IV alcohol abuse and dependence symptoms, was used to determine time to symptom onset in 102 male and 97 female adolescent drinkers with and without alcohol use disorders. The sample provided a broad range of drinking practices and alcohol-related problems. Symptom onset patterns were examined using survival-hazard analyses. RESULTS: Survival and hazard data suggested three stages of alcohol problems distinguished by time to onset: heavy and heedless drinking with associated social and role obligation problems, psychological dependence, and withdrawal. This three-stage model fit both the male and female data, and described staging patterns in 70% of the subjects. CONCLUSIONS: The symptom onset model suggested a first stage of adolescent alcohol symptoms characterized by heavy and heedless drinking with associated interpersonal and role obligation problems. The data did not support the construct validity of DSM-IV alcohol abuse when applied to adolescents, and suggested staging among DSM-IV alcohol dependence symptoms. Implications for the diagnosis and early identification of adolescent alcohol problems are discussed.

Adolescent↗
PubMed1996

A randomized, double blind, controlled trial of tocolysis to assist external cephalic version in late pregnancy.

BACKGROUND: External cephalic version at term is not always successful. This trial was done to ascertain whether tocolysis has any effect on the success rate. METHODS: A randomized, double blind, controlled trial, with continuous paired sequential analysis. Fifty-one consecutive patients with a singleton fetus in a breech presentation between 36 and 38 weeks gestation, external version being attempted on each. Ritodrine infusion or placebo was infused before attempt at external cephalic version. SETTING: A university teaching hospital with 8000 confinements annually. RESULTS: Version was successful in 17 of the 25 patients given tocolysis, but in only eight of the 25 given placebo (p < 0.01). A positive benefit for tocolysis was shown after version had been completed in 10 pairs of patients. However the trial was continued until 25 pairs had been analyzed. The benefit deteriorated during analysis of the last 15 pairs suggesting that the initial benefit may reflect a learning curve for the procedure. CONCLUSION: Tocolysis is likely to improve the success rate of external cephalic version in late pregnancy, especially in nulliparous mothers or where doctors are learning the technique.

Adult↗
PubMed1995

Comparison of direct vision and electronic two- and three-dimensional display systems on surgical task efficiency in endoscopic surgery.

Task efficiency and knot strength was evaluated under standardized conditions using direct vision and electronic imaging with two-dimensional (2-D) and three-dimensional (3-D) systems. Three operators with different endoscopic surgical experience tied a surgeon's knot with standard endoscopic instruments using the three different visual systems in random order. Each operator tied 20 knots with each visual system. Median task efficiency (defined as the time to complete the knot) was 35.0 (interquartile range (i.q.r.) 30.3-43.8) s for direct vision and 53.0 (i.q.r. 45.3-62.8) s and 53.5 (i.q.r. 45.0-64.8) s for 2-D and 3-D imaging respectively (P < 0.05). With respect to direct vision, this represented an overall degradation of task efficiency with the use of electronic imaging of 52 per cent, with no detectable difference between 2-D and 3-D imaging. The knot strength, representing the degree of tightening, was weaker with electronic imaging but the difference was not significant due largely to variation between the three operators.

Clinical Competence↗
PubMed1995

Onset and staging of DSM-IV alcohol dependence using mean age and survival-hazard methods.

Orderly onset of psychiatric symptoms has implications for both case detection and the construct validity of the underlying illness. Mean age and survival-hazard techniques were used to study the onset of alcohol abuse and dependence (as defined in the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders; American Psychiatric Association, 1994) in 369 clinical cases drawn from a heterogeneous regional sample. The methods provided a similar general pattern of symptom sequencing, though only survival-hazard analysis described a punctuated onset of alcoholism in 3 discrete stages: alcohol abuse, dependence, and accommodation to the illness. This model survived a rigorous program of tests for goodness of fit and described the majority of the sample, supporting the construct validity of both alcohol abuse as a discrete first illness phase and of dependence as a set of core constructs distinct from and succeeding abuse. The specific strengths of survival-hazard analysis as a research tool in illness staging research are discussed.

Adult↗
PubMed1995

Normal maturing distal tibia and fibula: changes with age at MR imaging.

PURPOSE: To describe the normal appearance of the maturing distal tibia and fibula at magnetic resonance (MR) imaging. MATERIALS AND METHODS: The authors retrospectively studied 50 MR examinations of patients aged 2 months to 21 years, dividing them into six developmental groups according to the appearance of the distal tibia and fibula. Epiphyseal ossification, physeal closure, and the signal characteristics of physeal cartilage were evaluated. RESULTS: Distal tibial epiphyseal ossification and physeal closure both began anteromedially and usually occurred earlier than in the fibula. The tibial physis developed an anteromedial undulation (Kump hump) before closure; volume averaging at the Kump hump simulated premature closure. The cartilaginous epiphysis had a lower signal intensity than the physis on T2-weighted images. The physis was most conspicuous on gradient-recalled-echo and fat-suppressed spin-echo proton-density-weighted images. CONCLUSION: Developmental cartilaginous and bone changes in the distal tibia and fibula follow a definite pattern and are well seen at MR imaging.

Adolescent↗
PubMed1995

Pulmonary edema in association with an intravenous infusion of sulprostone.

We encountered a patient with pre-eclampsia who developed pulmonary edema whilst receiving an infusion of sulprostone. Recent evidence suggests that pulmonary hypertension following the administration of prostaglandins may result from stimulation of an EP3 or thromboxane receptor in the pulmonary artery. This has implications for therapeutic use of prostaglandins.

Abortifacient Agents, Nonsteroidal↗
PubMed1994

Classification of impulse radar waveforms using neural networks.

In this paper, it is demonstrated that multilayer neural networks, trained with the backpropagation algorithm and radial basis functions, can classify impulse radar waveforms from three different asphalt-covered bridge decks, each with its own structure. It might be thought that the thickness of asphalt and the depth of concrete over the reinforcing bars would be nearly constant for any one bridge deck; however in practice this is not the case. There are often significant changes in the thickness of the asphalt and the cover over reinforcement. Furthermore, a certain amount of damage to the concrete caused by severe winter climate often produces a random variation in the reflected waveforms obtained from different locations. These factors lead to a significant number of combinations of waveforms that can be obtained from any given structural type of deck. The classification accuracies achieved ranged between 89.9% and 100%. The accuracies achieved after using principal components analysis to reduce the dimensionality of the input data ranged between 95.6% and 100%.

Algorithms↗
PubMed1994

Transvaginal sonography and the conservative management of spontaneous abortion.

Once a diagnosis of early pregnancy failure has been made, it is normal gynaecological practice to proceed to evacuation of any retained products of conception. In many cases, however, there may be little residual tissue within the uterus, and the patient may be exposed to an unnecessary operative procedure. The purpose of this study was to use sonographically derived measurements of the uterine cavity to select cases suitable for conservative management. Of 50 women presenting with a diagnosis of spontaneous abortion, 32 were chosen for non-operative treatment based upon their uterine cavity measurements. In all of these cases, bleeding had ceased within 2 weeks of selection and the pregnancy test had become negative. There were no subsequent complications. In our opinion, sonographic examination of the uterus allows the selection of those cases which can safely be managed conservatively.

Abortion, Spontaneous↗
PubMed1993

Randomized, double blind, placebo controlled comparison of ritodrine and hexoprenaline for tocolysis prior to external cephalic version at term.

External cephalic versions in the study period were performed in a double blind design by 2 experienced practitioners. Sixty-three patients were allocated to treatment with either placebo, ritodrine or hexoprenaline. The main outcome measure studied was successful completion of external cephalic version. Hexoprenaline, but not ritodrine, was statistically more likely to be associated with successful version than placebo (p = 0.04 versus p = 0.22).

Adult↗
PubMed1993

Relative expression of the products of glyoxylate bypass operon: contributions of transcription and translation.

Although the genes of the aceBAK operon are expressed from the same promoter, the relative cellular levels of their products are approximately 0.3:1:0.003. Gene and operon fusions with lacZ were constructed to characterize this differential expression. The upshift in expression between aceB and aceA resulted from differences in translational efficiency. In contrast, inefficient translation and premature transcriptional termination contributed to the downshift in expression between aceA and aceK. Premature transcriptional termination occurred within aceK and appears to result from inefficient translation. Deletion of repetitive extragenic palindromic elements between aceA and aceK had little effect on the relative expression of these genes. Rather, the sequences responsible for inefficient expression of aceK lie within the aceK ribosome binding site.

Base Sequence↗
PubMed1993

Insulin-like growth factor-binding protein-1, glucose tolerance and fetal growth in human pregnancy.

Two hundred Chinese primigravidae had 50 g 3-h oral glucose tolerance tests (OGTTs) twice in pregnancy; between 20 and 24 weeks and between 30 and 34 weeks of gestation. In 149 women, a single sample was taken for insulin-like growth factor-binding protein-1 (IGFBP-1) measurement 0, 1, 2 or 3 h after the glucose load at both visits; in 55 women IGFBP-1 levels were estimated in all four OGTT samples. Fetal growth was assessed by ultrasound performed at the first and second visit and, if possible, at term, and by anthropometry of the neonate. Cord serum IGFBP-1 was measured in 144 of the babies. Mothers who developed gestational diabetes were excluded. Maternal levels of IGFBP-1 were inversely related to glucose levels at 0, 1 and 2 h in the third trimester of pregnancy. IGFBP-1 measured at 1 h in an OGTT increased between the second and third trimester. There was an inverse correlation between maternal IGFBP-1 measured in the second trimester and all fetal measurements at that time, and with most neonatal measurements and birthweight. Levels of IGFBP-1 in the third trimester were inversely correlated to neonatal abdominal circumference, skinfold thickness and birthweight. Cord blood IGFBP-1 was inversely related to growth of abdominal circumference. The strongest inverse relationship was between IGFBP-1 and maternal weight. Fasting glucose in the second trimester was positively correlated to fetal subcutaneous fat and growth of abdominal circumference. In the third trimester it was related to fetal abdominal circumference, the growth of abdominal circumference, birthweight and neonatal skinfold thickness.(ABSTRACT TRUNCATED AT 250 WORDS)

Birth Weight↗
PubMed1992

Prelabour rupture of the membranes at term and unfavourable cervix; a randomized placebo-controlled trial on early intervention with intravaginal prostaglandin E2 gel.

Fifty nine women with prelabour rupture of membranes, unfavourable cervix and no evidence of infection or fetal distress were randomized formally to receive prostaglandin E2 (3mg) gel or sterile K-Y Jelly intravaginally. Conservative expectant management was followed for the next 24 hours. The subsequent management of the labour followed departmental protocol. The women who received prostaglandin went into labour sooner and were delivered earlier but the duration of labour was not significantly different. There were no significant differences in other clinical outcomes. There was 1 case of uterine rupture in the prostaglandin group. We conclude that early intervention with prostaglandin E2 gel intravaginally confers no advantage compared with conservative management except for earlier confinement in this group of patients.

Administration, Intravaginal↗
PubMed1992

Answering MCQs: a study of confidence amongst medical students.

Medical students at the beginning of their obstetrics and gynaecology module were asked to complete a multiple choice question paper from an earlier module. Half the students were asked to answer only those questions where they were certain of the answers. The other half were asked to answer all questions. The mean mark in the second group was 86% higher than that in the first group. A computer programme was written where multiple choice questions were asked in a standard true/false format but instead of a don't know alternative the students were asked to rate their degree of certainty in having answered correctly on a scale of 0 to 100. Five students completed a total of 45 multiple choice question papers (each with 20, 5-part questions) both before and towards the end of their obstetrics and gynaecology module. The mean mark increased by 68.5% over the course of the module reflecting the students' increased knowledge. Their mean certainty level only increased by 50%, suggesting that the students underestimated their newly acquired knowledge.

Educational Measurement↗
PubMed1990

Regulation of the glyoxylate bypass operon: cloning and characterization of iclR.

In Escherichia coli, expression of the glyoxylate bypass operon appears to be controlled, in part, by the product of iclR+. Mutations in iclR have been found to yield constitutive expression of this operon, suggesting that iclR+ encodes a repressor protein. We have cloned iclR+ by taking advantage of its tight genetic linkage with the glyoxylate bypass operon. The clone complemented a mutant allele of iclR in trans, restoring an inducible phenotype for this operon. Deletion analysis identified a region of ca. 900 base pairs that was necessary and sufficient for complementation. The nucleotide sequence of the insert was then determined. Translation of this sequence revealed an open reading frame capable of encoding a protein with Mr 29,741 preceded by a potential Shine-Dalgarno ribosome-binding site. The deduced amino acid sequence includes a region at the amino terminus that may form a helix-turn-helix motif, a structure found in many DNA-binding domains.

Amino Acid Sequence↗
PubMed1988

Two distinct cytolytic mechanisms of macrophages and monocytes activated by phorbol myristate acetate.

Pulmonary alveolar macrophages (PAM) and peripheral blood monocytes (PBMO) of the miniature swine can be converted to cytolytically active effector cells by treating with phorbol myristate acetate (PMA) as determined by enhancement of cytotoxicity to various target cells. Kinetics of the PMA-activated PAM and PBMO in cytotoxicity show that the effective PMA concentration ranges from 10 to 1,000 ng/ml. Induction of cytotoxic macrophages and monocytes occurred as early as 30 min and to their maximum cytotoxicity after 1 hr exposure to PMA and the enhanced cytotoxic activity persisted up to 24 to 40 hr when PMA was removed by washing after 1 hr exposure, but prolonged exposure to PMA for more than 6 hr resulted in a drastic decrease of cytolytic activities suggesting the prolonged exposure to PMA causes macrophages and monocytes to become refractory to PMA stimulation. Target cells displayed varying degrees of cytotoxic sensitivity to the PMA-activated PAM and PBMO; PRBC, SRBC, and K562 were sensitive, WEHI-164 and U937 were relatively sensitive, and SB was very resistant to these activated effector cells. The mechanisms of PMA-induced cytotoxicity could largely be divided into two categories. One was the H2O2 mediated killing as shown by complete reduction of cytotoxicity after adding catalase in the assay. The other was the proteases mediated cytolysis, which could be blocked by protease inhibitors, Phenyl methyl sulfonyl fluoride (PMSF), and N- alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK). H2O2 was the only mediator produced in large enough quantities from PBMO to kill target cells, whereas PAM could produce both mediators (H2O2 and proteases). PRBC, SRBC, and K562 appeared to be killed by H2O2 produced by PAM and PBMO. In contrast, U937 and WEHI-164 appeared to be killed by proteases in PAM mediated cytolysis but by H2O2 in PBMO-mediated cytolysis. These results suggest that the observed cytolytic mechanisms can be differed by type of target cells as well as the source of mononuclear phagocytes within the individual animal.

Animals↗