Biomedical subjects
Publications and source records attributed to J J Hoo.
Two further cases of variant Philadelphia chromosome are presented. The possible presence of a specific oncogene on the long arm of chromosome #22 is discussed.
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A relatively simple method of obtaining high resolution chromosomes from amniotic fluid cells is described. The elongated chromosomes are achieved by adding ethidium bromide (5 micrograms/ml) to the culture 4 1/2 hours before harvesting and the high resolution banding can be produced by usual banding procedures.
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By means of the immunoprecipitation method significantly higher activities of creatine kinase BB isoenzyme were measured in the sera of neonates with CNS symptoms than in the sera of healthy or sick neonates without CNS symptoms. The activity of CK-BB inversely correlated with the one-minute Apgar score. These results suggest a leakage of CK-BB from the damaged CNS tissue into the blood circulation. Determination of CK-BB might be helpful in the assessment of perinatal brain damage.
The activity of phosphatidylethanolamine methyltransferase (PMT) in disrupted human erythrocytes and ghost cells was inhibited by lithium (Li+), imipramine and chlorpromazine. There was no inhibitory effect of the drugs in concentrations similar to the average therapeutic blood levels. Li+ exerted an inhibition on PMT activity in hemolysates at concentrations 8 times the average therapeutic level whereas chlorpromazine and imipramine showed an inhibitory effect on PMT in hemolysates at 10(3) fold their respective therapeutic serum level.
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Paracentric inversion of chromosome 7 was found in a female infant with multiple malformations and in her phenotypically normal mother. Examination of prometaphase chromosomes revealed an additional small dark band on the inverted chromosome 7 of the girl. It was assumed that an unequal crossing over at the base of a meiotic loop of chromosome 7 had occurred in the mother and resulted in a tiny interstitial duplication in the girl.
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The presence of a chromosomal translocation was suggested in a large kindred with several cases of mental retardation. Chromosome analysis by means of a high resolution technique revealed a translocation of a tiny terminal portion of 9p onto 20p in the presumptive balanced translocation carriers. Five of the affected family members demonstrated monosomy of the terminal portion of 9p. Their clinical features fitted well to the known 9p- syndrome. The breakpoint on 9p is in the distal part of band 9p23. This family confirmed the assumption that the critical segment for monosomy 9p syndrome is located within the terminal band 9p24.
Haloperidol, chlorpromazine, imipramine and lithium in concentrations similar to the average therapeutic plasma levels did not exert any in vitro inhibition on the erythrocyte catechol-O-methyltransferase (COMT). The inhibitory effects of haloperidol, chlorpromazine and imipramine were noted first at concentrations 1000-10 000 times their respective average therapeutic plasma levels. Unlike the former three psychotropic drugs, lithium exerted an in vitro inhibition already at a concentration 40 times the average therapeutic plasma level and that in a competitive way. The inhibitory effect of lithium could be neutralized by increasing the magnesium concentration, likewise in a competitive way.
A sensitive radioenzymatic assay of catechol-O-methyltransferase (COMT) in hair root cells is presented. Only five hair roots with intact bulb and sheath are needed for one assay. By pulling 15-20 hairs, 3-4 parallel assays can be performed. As in erythrocytes the COMT activity in hair root cells is constant for each individual. Nevertheless, there is no high correlation between the enzyme activities in erythrocyte and in hair root cells (r = 0.26, 0.1 greater than P greater than 0.05, N = 46). The determination of COMT in hair root cells offers a further application of this source in genetic research, as in the study of a correlation between COMT activity and various endogenous psychiatric disorders.
Incubation of CK-BB in serum (1:3, v/v) at 37 degrees C for 3 h caused a change of its electrophoretic mobility and decay of its catalytic activity. Similar effects were observed following incubation in water. Incubation in saline somehow preserved the electrophoretic mobility but not the catalytic activity. No effect was noted when incubated at 4 degrees C for 3 h. Further study on the rate of decay revealed that the decay in albumin solution (1:50, v/v) is quite similar to that in serum. More dramatic decay was noted when incubated in water and less when incubated in saline. It was further shown that the higher the incubation temperature (4 degrees C, 25 degrees C or 37 degrees C) the faster the decay. The rate of decay of CK-MM was much slower in all conditions of incubation. Determination of isoenzyme activities by means of an immunoprecipitation method again demonstrated that CK-BB lost a great deal of its catalytic activity following incubation at 37 degrees C for 1 h, and hence falsification of the isoenzyme pattern.
A significant decrease in catechol-O-methyltransferase (COMT) activity of erythrocytes was found in both male and female schizophrenic patients, as well as in male patients with schizophreniform psychosis. Among control subjects, a sex difference in COMT activity of erythrocytes was found, with males showing significantly higher activity than females. It is suggested that a genetically determined deficiency of catecholamine degradative enzymes in the central nervous system or, alternatively, influences of nongenetic hormonal factors could be implicated in the findings of altered erythrocyte COMT activity reported.
A patient with partial trisomy 9q due to material 9/17 translocation was studied and compared with four previously reported cases. The similarity of their clinical features allowed us to delineate a distinct clinical syndrome, which is characterized by psychomotor retardation, dolichocephaly, beaked nose, deep-seated eyes, and long fingers and toes. There is an overlap between some of the features of this syndrome and those of trisomy 9.
We report a 5 1/2-year-old girl with a tiny supernumerary chromosome fragment found in mosaic. The ring nature of the tiny fragment was demonstrated by the detection of the characteristic products of a ring chromosome. The clinical consequence of a ring chromosome and the impact of finding a supernumerary chromosome fragment, especially in the practice of prenatal chromosome diagnosis, are discussed.