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Biomedical subjects

R Chang

Publications and source records attributed to R Chang.

At least 181 records · Page 10Linked to original sources
PubMed1982

Generation of cytotoxic lymphocytes by SV40-induced antigens.

In order to study the correlation of in vivo tumor transplantation immunity and in vitro immunologic assays, cell-mediated cytotoxicity against SV40-transformed cells was studied in AL/N strain mice by using 51Cr-release assay. Killing of SV40-transformed AL/N fibroblast cells was observed by spleen cells of AL/N mice immunized with syngeneic SV40-transformed cells. Immunization with the solubilized SV40 tumor-specific transplantation antigen (TSTA) that induced transplantation immunity in vivo did not elicit cytotoxic spleen cells in vitro. However, the spleen cells from mice immunized with solubilized TSTA and then sensitized in vitro with SV40-transformed cells became cytotoxic against SV40-transformed fibroblasts. Similarly, SV40 TSTA (T antigen) purified by immunoprecipitation was able to prime the lymphocytes in AL/N mice: the primed lymphocytes could differentiate into cytotoxic lymphocytes upon in vitro stimulation by SV40-transformed cells. These data indicate that SV40 TSTA (T antigen) plays a role in the induction of cytotoxic lymphocytes.

Animals↗
PubMed1981

Endothelial mosaic in Fuchs' dystrophy. A qualitative evaluation with the specular microscope.

The progressive morphological changes of cornea guttata in Fuchs' endothelial dystrophy have been characterized by clinical specular photomicroscopy. Five specific stages in the development of excrescences can be discerned using this in vivo technique. Several stages can be observed in the same cornea at a given time, although in most cases the majority of guttate changes seemed to have progressed to the same stage of development. All five stages of cornea guttata discerned in this study can occur in a cornea clinically free of edema. Two types of cornea guttata can be identified in vivo. One has a smooth, regular posterior surface, whereas the posterior contour of the second is irregular.

Cornea↗
PubMed1981

Corneal edema secondary to vitreocorneal contact.

Aphakic eyes, some with edematous corneas, and others with corneas free of edema, but all with formed vitreous humor in contact with the corneal endothelium, were studied. Removal of vitreous humor from the anterior chamber by closed vitrectomy resulted in substantial improvement in the state of corneal hydration and, in some cases, in the elimination of clinically notable corneal edema. Specular microscopy showed endothelial abnormalities in the edematous corneas that were not present in corneas with vitreous contact that remained free of edema. However, those endothelial changes seen in edematous corneas before vitrectomy seemed to persist after vitrectomy and corneal deturgescence. Thus, elimination of vitreous contact may result in clinical reversal of corneal edema despite a prolonged period of vitreous contact and in the face of seemingly irreversible endothelial changes.

Aged↗
PubMed1980

Evidence for genetic control of nondisjunction in man.

Data on factors associated with the occurrence of Down syndrome in a highly inbred population were evaluated to investigate the presence of a genetic control of nondisjunction in man. In Kuwait, close consanguinity occurs in 40% of marriages. In its main obstetric hospital, 20 trisomic Down babies out of 11,614 singleton births were delivered over a 12-month period. Chi-square analyses indicate the occurrence of Down syndrome to be linked to two independent factors: consanquinity of parents and maternal age. The relative risk is approximately four times greater for closely related than for nonrelated parents (P less than .005); a possible explanation for this is the existence of a gene that induces mitotic nondisjunction in the homozygous fertilized ovum. An alternative explanation is the existence of an autosomal recessive gene which results in meiotic nondisjunction in the homozygous parents. Consanguinity is usually perpetuated in certain families, or sections of the population, and parents in highly inbred families have a higher probability to be homozygotes for that gene.

Adult↗
PubMed1978

Effect of charcoal-broiled beef on antipyrine and theophylline metabolism.

Eight healthy volunteers were sequentially fed a control diet, a charcoal-broiled beef--containing diet, and the control diet a second time. The mean plasma half-lives (t1/2) of antipyrine and theophylline were each decreased by 22% after the subjects were fed the charcoal-broiled beed--containing diet. The main plasma t1/2s for these drugs returned to control values when the subjects were fed the control diet for a second time. Considerable individuality occurred in the responsiveness of the subjects to the charcoal-broiled beef--containing diet. The decreases in antipyrine plasma t1/2s among the 8 subjects ranged from 5% to 39%, and the decreases in theophylling t1/2s ranged from 0% to 42%.

Adult↗
PubMed1977

Angiotensinase activity in red blood cell membranes and intact adrenal cells.

The present study was undertaken to characterize angiotensinase activity in human red blood cells (RBCs), RBC ghosts and rabbit adrenal cells. It was found, by the use of paper chromatography, that each of these preparations possess enzymes capable of converting angiotensin II to its heptapeptide derivative, [des=Asp1] angiotensin II (angiotensin III). Further characterization of these enzymes by the use of a chromogenic assay indicates that although intact RBCs do not split sarcosine-beta-naphthylamide, RBC ghosts do. Intact rabbit adrenal cells from the zona glomerulosa, however, do show activity against sarcosine-beta-naphthylamide. This is interpreted to indicate the presence of non-specific angiotensinases on the inside of the RBC membrane and the outside of the adrenal cell membrane.

Adrenal Cortex↗
PubMed1976

A simple restraining device for use with neonatal and small nonhuman primates.

A simple and inexpensive restraining device was designed for use with neonatal and small nonhuman primates weighing less than 2 kg. With this device a technician working alone can collect blood samples, fecal or vaginal smears, nasal or oral swabs, or perform a variety of routine procedures including physical examination and administration of medication.

Animals↗
PubMed1975

On the location of the sulfhydryl group in bovine plasma albumin.

A series of spin labels has been empolyed to explore the environment of the sulfhydryl group in bovine plasma albumin. The spin labels consist of the nitroxide-free radical and a maleimide (or iodoacetamide)-attaching group separated by varying chain lenghths. Both sets of spin labels preferentially bind to the sulfhydryl group under appropriate conditions. From the change in the electron spin resonance spectra of these nitroxides as a function of chain length, we conclude that the sulfhydryl group is located in a crevice approx. 9.5 A in depth.

Animals↗
PubMed1972

A mutant of Escherichia coli that requires high concentrations of biotin.

A recessive mutation (bir) of E. coli, at 77 min on the standard map, destroys ability of the bacteria to take up biotin or to grow except at high concentrations of biotin. In a biotin prototroph, the bir mutation causes overproduction and excretion of biotin, and derepression of at least one biosynthetic gene (bioD). Growth of the bir mutant is inhibited by avidin or high concentrations of dethiobiotin. Both effects are reversed by biotin.

Biotin↗
PubMed1972

Location of promoter and operator sites in the biotin gene cluster of Escherichia coli.

Biotin independence in E. coli requires five closely linked genes, bioA, bioB, bioF, bioC, and bioD. The residual gene activity of deletion mutants has been studied by complementation and enzyme assays. Deletion of the left end of the bioA gene does not impair expression of the remaining genes, but deletions from the left extending into bioB abolish all gene expression. Nonsense mutations in bioB reduce expression of bioC, bioF, and bioD. Therefore, the four genes, bioB, bioF, bioC, and bioD, are transcribed as a unit from left to right, from a promotor located between bioA and bioB. Expression of the bio genes is repressible by added biotin. Deletions removing the left end of bioA do not affect repressibility of bioD. Therefore the operator, as well as the promoter, lie to the right of bioA. One deletion that removes bioA, bioB, and bioF renders the bioD gene constitutive, presumably by fusion to an unknown operon. Therefore, the operator lies to the left of bioC.

Biotin↗