Biomedical subjects
Publications and source records attributed to K W Kang.
Tracheo-oesophageal (TE) fistulas caused by Mycobacterium tuberculosis are rare and usually require both surgical treatment and medical treatment with antituberculosis drugs. A patient with a tuberculous TE fistula and mediastinal lymphadenitis was successfully treated by medical management alone.
Benzo(a)pyrene metabolism in human placental microsomes from smokers was studied. Benzo(a)pyrene metabolites were separated using high pressure liquid chromatographic technique. Reaction of benzo(a)pyrene with a microsomal fraction of placenta from individuals who smoke cigarettes during pregnancy yields 7,8 dihydroxy benzo(a)pyrene as a major metabolite, while 3'-hydroxy benzo(a)pyrene, 4,5 dihydroxy benzo(a)pyrene and quinones constitute minor metabolites. The activities of arylhydrocarbon hydroxylase and 7-ethoxycoumarin deethylase exhibited much higher activities in smokers than in nonsmokers. Examination of specific binding of monoclonal antibodies to cytochrome P-450 isozymes in placental microsomes revealed that cigarette smoking specifically enhanced the level of cytochrome P-450 c and d isozymes in human placental microsomes. Coincubation of 3H-benzo(a)pyrene and calf thymus DNA with placental microsomes yielded acid insoluble 3H-B(a)P from smokers, suggesting that cigarette smoking may induce placental enzymes which convert benzo(a)pyrene into ultimate metabolites to form carcinogen-DNA adducts.
The root extract of Panax ginseng was investigated for its inhibitory effects on DNA synthesis, mutagenicity, and cellular transformation using V79 and NIH 3T3 cells. DNA synthesis measured by the [3H]thymidine incorporation into V79 Chinese hamster lung cells was significantly decreased by the addition of ginseng extract (0-1 microgram/ml) to the medium. However, ginseng extract was found to increase the rate of DNA excision repair synthesis in V79 cells in response to treatment with UV radiation or methyl methanesulfonate. The extract also showed decreased mutation frequency when mutagenicity was examined using V79 cells at the hypoxanthine-guanine phosphoribosyl transferase locus as resistance to 6-thioguanine after exposure to methyl methanesulfonate. We also found that the components of ginseng extract continue to exert an inhibitory effect on the transformation of NIH 3T3 cells initiated by 3-methylchloanthrene, methyl methanesulfonate, and 1-methyl-3-nitro-1-nitrosoguanidine.
HeLa cells treated with 10 J/m2 of ultraviolet (UV) radiation were examined for inhibition of DNA excision by inhibitors of DNA polymerase-alpha and -beta. DNA repair synthesis and excision were inhibited by aphidicolin, a specific inhibitor of DNA polymerase-alpha. Decreased release of radioactive nucleotides from UV-damaged DNA by the inhibitor indicates that the action of DNA polymerase-alpha activity is closely associated with DNA excision. Dideoxythymidine also inhibited DNA repair synthesis but failed to block the excision, suggesting that polymerization by DNA polymerase-beta might precede removal of damaged DNA.
Birthweight was measured on 188 monochorionic monozygotic, 54 dichorionic monozygotic, 102 like-sexed dizygotic, and 94 unlike-sexed dizygotic liveborn twin pairs. Overall, males were found to be significantly heavier than females. These differences were not significant, however, when birthweights were compared within zygosity/chorion-type categories. Males were also characterized by a slightly greater overall total variance. Comparisons of intrapair variation of monochorionic and dichorionic monozygotic twins revealed significant differences between monochorionic pairs and dichorionic separate pairs and no significant differences between monochorionic pairs and dichorionic fused pairs. The results of this study suggest that placental proximity may have as important an influence on variation in birthweight as does the presence or absence of vascular anastomoses.
Nine oral morphologic characters were investigated. Their frequencies are compared with those published for other populations. The possibility of using such characters to estimate genetic distance between populations is discussed and the conclusion is reached that, although previous studies have suggested this to be a valid approach, further studies testing this subject are needed.
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This case demonstrated a mass seen on an ultrasound scan performed prior to amniocentesis to determine fetal maturity. It emphasizes the importance of scanning the entire contents of the amniotic sac rather than simply looking at the portion for which the examination was ordered. It is important to recognize such lesions to prepare for adequate management of the airway in the neonate, to prepare for surgical excision as soon as feasible, and to prepare the family for the birth of a baby with a congenital abnormality.
Over the past 50 years a large number of methods have been proposed for estimating heritability from twin studies. The present paper describes the most commonly cited of these estimates as a first step in evaluating their usefulness. A critical review will then follow.
A computer system for simulation of quantitative twin data is being developed. The capability is being built in a simulate distributions with known means, standard deviations, skewness and kurtosis.
Erythrocyte count, hematocrit, mean corpuscular volume and reticulocyte counts were measured in 59 pairs of monozygotic (MZ) and 69 pairs of dizygotic (DZ) adult, Caucasian male twins. The means of MZ and DZ twins were not significantly different for any of the traits measured. Erythrocyte count and mean corpuscular volume had significant estimates of genetic variance (P less than 0.05).
A method for partitioning genetic variance estimated from twin data into additive and dominance variances was presented using Falconer's variance component model. The effects of dominance and environmental variances on a number of heritability estimates were also reviewed. A heritability estimate, based on the analysis of variance and the genetic variance estimates presented by HASEMAN and ELSTON and CHRISTIAN et al. which utilizes all available information from twin data, was proposed and discussed. This estimate seems to be the least affected by fluctuations in the magnitudes of dominance and environmental variances.
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Previous studies demonstrated a protective effect of hypoxia on subsequent death breathing oxygen. Four groups of rats were exposed to air for 120 hours plus 99% O2 for 52 hours (A + O2); 120 hours of hypoxia plus 52 hours 99% O2 (H + O2); 172 hours of only air (A); and 120 hours of only hypoxia (H). Rats were sacrificed and lung lavage protein (gm/ 100 ml) was 0.57 +/-0.18 in A + O2 and 0.26 +/- 0.12 in H + O2. Hematocrits were increased at sacrifice. Rats with induced hematocrits of 61% did not have a protective effect breathing oxygen. Mean total phospholipid in lung lavage was: A + O2 O.94; H + O2 1.10; A 1.08; and H 1.76 (micronM/ml). Phosphatidyl choline (lecithin) was: A + O2 0.49; H + O2 0.61; A 0.59; and H 1.15 micronM/ml. Differences among the groups were significant for total phospholipids and phosphatidyl choline except between air (A) and hypoxia + O2 (H + O2). Palmitic acid was decreased in A + O2 compared to the other groups. Oxygen breathing results in decreased total phospholipids and phosphatidyl choline in lung lavage. Pretreatment with hypoxia and subsequent oxygen breathing results in amounts similar to rats breathing air only.
Evidence for maternal effects on plasma cholesterol was found by comparing the variance between maternal and paternal half siblings obtained from 83 families of monozygotic twin pairs (424 children). Maternal effects accounted for about one-fifth of the total variance.
Variation in the fatty acid composition of fasting plasma lipids and of cholesteryl esters was studied in 69 sets of adult male twins and 25 of their brothers. Genetic variances were estimated using the twin model. In general, monozygotic (MZ) twins were characterized by the smallest within-pair variance, and brothers of twins by the largest. Variation within dizygotic pairs fell imtermediate to that of MZ twins and brothers. The present study did not reveal consistent significant (P greater than 0.05) genetic variation in plasma fatty acids from total plasma lipids or cholesteryl esters.