Biomedical subjects

M J Yang

Publications and source records attributed to M J Yang.

51 records · Page 3Linked to original sources

PubMed1993

Prevalence and characteristics of areca nut chewers among junior high school students in Changhua county, Taiwan.

Some studies indicate that betel quid and its ingredients chewing can produce cell mutagenicity and tumorigenicity. In Taiwan studies, betel quid chewing is the main cause of submucous fibrosis and oral cancer. Understanding the distribution and characteristics of the areca nut chewing population is one of the first steps in the effort to prevent these oral diseases. A stratified cluster random sample of 2442 junior high school students in Changhua county, Taiwan, were surveyed for the habit of areca nut chewing. Significantly more male students chewed areca nut than female students (9.2% vs 0.9%). The proportion of students who were chewing areca nuts increased with increasing (seventh to ninth) grades. Areca nut was used by junior high school students at a higher rate in village (rural) areas as compared to town (semi-urban) and city (urban) areas (6.4%, 3.7% and 3.0%, respectively). More students in the ordinary achievement classes were chewing areca nuts than those in the high achievement classes (8.4% vs 1.6%). Areca nut chewing students tended to have users in their families. Cigarette smoking and alcohol drinking were positively associated with areca nut chewing. More than half (53.6%) of the areca nut chewing students first experimented with this habit with a family member, most often the father or grandfather.

Adolescent↗

PubMed1992

Detection of human cytomegalovirus antigen and DNA in lymph nodes and peripheral blood mononuclear cells of patients with angioimmunoblastic lymphadenopathy with dysproteinemia.

The cause of angioimmunoblastic lymphadenopathy with dysproteinemia (AILD) remains unknown. It is characterized by acute onset, severe constitutional symptoms, cervical or generalized lymphadenopathy, lymphopenia, and polyclonal hypergammaglobulinemia, all of which are highly suggestive of a viral origin. Using immunohistochemical methods, employing murine monoclonal antibody as the primary antibody, we detected human cytomegalovirus antigen in the lymph nodes of eight of 11 patients with AILD. Cytomegalovirus DNA was also detected in the peripheral blood mononuclear cells by DNA dot hybridization in all five of the patients with AILD who were tested using this technique. None of the lymph nodes from the 11 patients stained positive for the rubella virus antigen. Based on the above evidence and the similarity of the immunologic abnormalities found in both AILD and cytomegalovirus infection, the possible role of cytomegalovirus as one of the causative agents for AILD is proposed.

Adult↗

PubMed1991

The MAS-encoded processing protease of yeast mitochondria. Interaction of the purified enzyme with signal peptides and a purified precursor protein.

The matrix of yeast mitochondria contains a chelator-sensitive protease that removes matrix-targeting signals from most precursor proteins transported into this compartment. The enzyme consists of two nonidentical subunits that are encoded by the nuclear genes MAS1 and MAS2. With the aid of these cloned genes, we have now overexpressed the active holoenzyme in yeast, purified it in milligram amounts, and studied its biochemical and physical properties. Atomic absorption analysis shows that the purified enzyme lacks significant amounts of zinc, manganese, or cobalt; if none of these metal ions is added during the assay, the enzyme is catalytically inactive but can still cleave substoichiometric amounts of substrate. The amino-terminal sequences of the two mature subunits were determined; comparison with the deduced amino acid sequences of the corresponding precursors revealed that the MAS1 and MAS2 subunits are synthesized with prepeptides composed of 19 and 13 residues, respectively, which have similar sequences. The enzyme is inhibited competitively by chemically synthesized matrix-targeting peptides; the degree of inhibition correlates with the peptides' targeting efficacy. Matrix-targeting peptides containing the cleavage site of the corresponding authentic precursor protein are cleaved correctly by the purified enzyme. A purified artificial precursor protein bound to the holoenzyme can be photocross-linked to the MAS2 subunit.

Amino Acid Sequence↗

PubMed1991

Using ultrasonic measurement of cardiac size in predicting congenital heart defect.

A Duplex Color apparatus equipped with real-time imaging and Doppler sector scanner was used to scan fetal hearts, ranging from 17 to 41 weeks gestational age. A total of 323 normal fetuses were studied. The four-chamber view was obtained in a horizontal section just above the level of the fetal diaphragm. Five variables of the Chinese fetal heart in relation to the width of the right ventricle, width of the left ventricle, ratio of right ventricle/left ventricle (RV/LV), length of the fetal heart and the cardiac volume of a four-chamber view were set against gestational age in weeks and expressed in regression equations. The ratio of RV/LV is quite constant in relation to the gestational age. The mean ranges between 0.9916 for 17 weeks gestation and 1.0045 for a term fetus. In 10 abnormal cases with congenital cardiac defects, using the 5th and the 95th percentiles of this normal data as cutoff points, the RV/LV ratio had the highest sensitivity rate of 70% (7/10) in predicting fetal cardiac anomaly. The width of the left ventricle was the second most sensitive parameter with a sensitivity of 4/10 (40%). The RV/LV ratio of a four-chamber view is a simple, time-saving screening parameter for predicting congenital cardiac defects antenatally.

Female↗

PubMed1991

Managements of placenta accreta.

From January 1986 to June 1990 at Veterans General Hospital-Taipei, 12 cases of placenta accreta were reviewed. The incidence were 1 per 1,101 deliveries. Eight cases were confirmed by pathological examination, and the incidence was 0.06% (1/1,652). Placenta previa was found in 7 cases (58.3%); 6 of them had history of cesarean section. All the cases had history of uterine surgery. Seven cases underwent cesarean section, and the other one received myomectomy. Hysterectomy was performed on 6 patients, and conservative treatments were employed on the other 6 cases. No maternal mortality occurred. Besides one case of missed abortion, there was only one perinatal loss due to immaturity. Accurate prenatal diagnosis of placenta accreta by ultrasound was obtained in 4 cases. Although hysterectomy is the definite treatment of placenta accreta, conservative managements should be tried before this intervention.

Adult↗

PubMed1991

Analysis of ras gene mutations in gastrointestinal cancers.

Point mutations of c-Ki-ras genes were analyzed in 33 samples of human gastrointestinal malignancy. DNA extracted from the frozen tissue was amplified by polymerase chain reaction (PCR) and analyzed by direct sequencing and slot-blot hybridization at codons 12, 13 and 61 of c-Ki-ras. In 7 cases out of 19 colorectal cancers, point mutations were found: 3 cases at codon 12, 1 at codon 13, 2 at codon 61 of c-Ki-ras and one case had double mutations at codon 12 and codon 13. In 11 cases of gastric cancer, 4 showed point mutations: 1 at codon 12 and 3 at codon 13 of c-Ki-ras. In 3 pancreatic carcinomas, 2 had point mutations: one at codon 12 and the other at codon 13 of c-Ki-ras. The results indicate that c-Ki-ras gene point mutations are involved in the tumorigenesis of the human gastrointestinal system.

Adult↗

PubMed1990

The MAS-encoded processing protease of yeast mitochondria. Overproduction and characterization of its two nonidentical subunits.

The amino-terminal presequences of proteins imported from the cytoplasm across the mitochondrial inner membrane are cleaved off by a soluble matrix-localized protease composed of two nonidentical homologous subunits. In the yeast Saccharomyces cerevisiae, these are encoded by the nuclear MAS1 and MAS2 genes. We have now constructed yeast strains in which either one or both of the genomic MAS genes are controlled by a galactose-inducible strong promoter. In these strains, the intramitochondrial concentration of each MAS-encoded subunit as well as of the holo-protease can be varied over a wide range. When overproduced, the MAS1 protein precipitates in the matrix whereas the MAS2 protein remains soluble. The MAS2 protein was obtained at a purity of 98% in milligram amounts. The purified MAS2 subunit exists largely as a soluble 52-kDa monomer. Its cleavage activity is very low and might well reflect the 2% contamination by holoprotease. Activity is restored by adding the solubilized purified MAS1 subunit. Yeast cells depleted of one or both MAS subunits continue to import precursor proteins into mitochondria, but fail to cleave them; eventually the deficient cells stop growing. This growth arrest is partly suppressed on minimal medium or under conditions in which the cells are less dependent on mitochondrial metabolism. Depletion of the MAS1 subunit causes overproduction of the MAS2 subunit.

Cell Nucleus↗

PubMed1989

Lateralization in the visual perception of Chinese characters and words.

It has been reported that tachistoscopic perception of single Chinese characters is better with a left-visual-field (LVF) than with a right-visual-field (RVF) presentation and that of Chinese words consisting of characters is better with a RVF presentation (O. J. L. Tzeng, D. L. Hung, B. Cotton, & S.-Y. Wang, 1979, Nature (London), 382, 499-501). In this study, the nature of this character-word difference in lateralization was explored in a task in which stimuli were presented unilaterally to a visual field for recognition test. Four types of stimuli were used: Single character, single pseudo- or noncharacter, two-character word, and two-character pseudoword. Results show (a) no visual-field advantage for illegal characters and words, (b) a LVF-advantage effect for characters associated with a more prominent LVF than RVF character-superiority effect, (c) a RVF-advantage effect for words associated with a more prominent RVF than LVF word-superiority effect, and (d) these two visual-field effects for characters and words being not absolute, they occur only with a low rather than with a high recognition for their respective illegal counterparts. These results suggest that the character-word difference is due to a more efficient lexical interpretation of character stimuli in the right than in the left hemisphere and a more efficient lexical interpretation of word stimuli in the left than in the right hemisphere.

Adult↗

PubMed1988