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Biomedical subjects

C Chang

Publications and source records attributed to C Chang.

At least 415 records · Page 23Linked to original sources
PubMed1981

Copper(I) . bleomycin. A structurally unique oxidation-reduction active complex.

Cu(I) and Cu(II) form stable 1:1 complexes with bleomycin (BLM). The affinity of both metals for the drug is greater than that of Fe(II). Cu(I) . BLM A2 binds to calf thymus DNA with about the same affinity as Fe(II) . BLM, as judged by DNA-induced fluorescence quenching of the bithiazole moiety of BLM. Based on 1H NMR and potentiometric titration data, the Cu(I) complexes of BLM are shown to have geometries very different than those of other BLM . metal(II) complexes studied thus far. As Cu(I) . BLM is oxidation-reduction active, its geometry is of importance in defining the structural requirements for BLM activity.

Animals↗
PubMed1981

Correlates of intelligence test results in treated phenylketonuric children.

The Collaborative Study of Children Treated for Phenylketonuria was initiated in 1967. The data presented are based on findings in 132 children treated from near birth to 6 years of age. Two treatment groups were randomly formed. The target for blood phenylalanine was 1.0 to 5.4 mg/100 ml for group 1 and 5.5 to 9.9 mg/100 ml for group 2. Although mean blood phenylalanine levels for both groups initially fell within the prescribed ranges, a steady increase over time resulted in mean six year levels of 11.4 mg/100 ml and 13.0 mg/100 ml for the two groups, respectively. Because it was not possible to maintain the prescribed differences in blood phenylalanine levels between the two groups, they were combined for further analyses. The mean IQ of the total sample at age 6 years was 98 on the Stanford-Binet Intelligence Scale. Multiple regression analysis showed that, among selected treatment and psychosocial factors, the most important predictors of IQ for 6-year-old children were: (1) mothers' intellectual ability (as measured on the Wechsler Adult Intelligence Scale); (2) age at which the subjects were first treated; and (3) how well the subjects adhered to the phenylalanine-restricted diet. It was concluded that optimal early treatment will result in normal levels of intelligence at 6 years of age.

Age Factors↗
PubMed1981

LIver abnormalities in patients with Gaucher's disease.

Clinical and liver histopathological observations are described in 25 patients with Gaucher's disease. Although 24 patients had hepatomegaly, and the majority had abnormalities of serum transaminases, alkaline phosphatase, and BSP clearance, only 3 had evidence of portal hypertension and complications of advanced liver disease. Liver biopsies showed scattered foci of Gaucher cells in 5 patients and prominent centrilobular accumulation of Gaucher cells in 14 patients. Three patients had cirrhosis, which was associated with extensive replacement of the liver by storage cells. The severity of liver abnormalities correlated with the occurrence of other severe complications of Gaucher's disease. The wide spectrum of liver abnormalities in Gaucher's disease should be considered in evaluating trials of therapeutic enzyme replacement.

Adolescent↗
PubMed1980

Placental beta-endorphin-like peptides.

Acid extract of human placental tissue contain, by both radioimmunoassay and radioreceptor assay, beta-endrophin-like material. Half of this material will not go through a 5000-dalton filter and on Sephadex G-200 has a molecular size between 25,00 and 50,000 daltons. Of the material going through a 5000-dalton ultrafilter, 80 percent is excluded on Sephadex G-25 and held back, very slightly, on Bio-Rad P6, indicating a molecular size of approximately 4500 to 4800 daltons. Thus, placenta appears to have macromolecular precursors from which a beta-endorphin-like material is released, with a size approximately 12 amino acids longer than half of the pituitary hormone.

Endorphins↗
PubMed1980

Perinatal study in Tientsin: 1978.

Clinical records of a total of 3320 singleton births, representing the year 1978, at the two Tientsin Medical College Hospitals, Tientsin, People's Republic of China, were studied to ascertain (a) reproductive parameters such as the average age of the mothers at first and successive births and (b) the relationships between perinatal deaths, prematurity and birth weight and the mothers's age, number of previous pregnancies, parity, maternal conditions in the prenatal and delivery period and operative procedures of delivery.

Adult↗
PubMed1980

Relationship among Tau antigens isolated from various lines of simian virus 40-transformed cells.

In addition to the virus-specified tumor antigens, simian virus 40-transformed cells contain at least one other protein which can be immunoprecipitated with serum from animals bearing simian virus 40-induced tumors. This protein, which is designated Tau antigen, has an apparent molecular weight of 56,000 as determined by electrophoresis on acrylamide gels. The relationship among Tau antigens isolated from different lines of simian virus 40-transformed cells was examined by comparing the methionine-labeled tryptic peptides of these proteins by two-dimensional fingerprinting on thin-layer cellulose plates. In this fashion, we initially determined that the Tau antigens isolated from three different lines of transformed mouse cells were very similar. Second, we found that Tau antigen isolated from a line of rat transformants was closely related, but not identical, to the mouse cell Tau antigens. Approximately 70% of their methionine peptides comigrated in two dimensions. Finally, we showed that Tau antigen isolated from a line of transformed human cells was only partially related to the mouse and rat proteins. About 40% of the methionine peptides of the human protein were also contained in the Tau antigens from the other two species. These results strongly indicate that the Tau antigens isolated from these various simian virus 40-transformed cell lines contain common amino acid sequences.

Animals↗
PubMed1980

Formation and reactions of negative ions relevant to chemical ionization mass spectrometry. I. CL mass spectra of organic compounds produced by F- reactions.

A systematic study of the negative-ion chemical ionization mass spectra produced by the reaction of F(-) with a wide variety of organic compounds has been accomplished. A time-of-flight mass spectrometer fitted with a modified high pressure ion source was employed for these experiments. The F(-) reagent ion was generated from CF(3)H or NF(3), typically at an ion source pressure of 100 mum. In pure NF(3), F(-) is the major ion formed and constitutes more than 90% of the total ion intensity. While F(-) is also the major primary ion formed in pure CF(3)H, it undergoes rapid ion-molecule reactions at elevated source pressures, yielding (HF)(n)F(-) (n = 1-3) ions, which makes CF(3)H less suitable as a chemical ionization reagent gas. Among the organic compounds investigated were carboxylic acids, ketones, aldehydes, esters, alcohols, phenols, halides, nitriles, nitrobenzene, ethers, amines and hydrocarbons. An intense (M - 1)(-) ion was observed in the F(-) chemical ionization mass spectra of carboxylic acids, ketones, aldehydes and phenols. Alcohols yield only (M + F)(-) ions upon reaction with F(-). A weaker (M + F)(-) ion was also detected in the F(-) chemical ionization spectra of carboxylic acids, aldehydes, ketones and nitriles. The F(-) chemical ionization mass spectra of esters, halides, nitriles, nitrobenzene and ethers are characterized primarily by the ions, RCOO(-), X(-), CN(-), NO(2) (-), and OR(-), respectively. In addition, esters show a very weak (M - 1)(-) ion (except formates). In the F(-) chemical ionization spectra of some aliphatic alkanes and o-xylene, a very weak (M + F)(-) ion was observed. Amines and aliphatic alkenes exhibit only insignificant fragment ions under similar conditions, while aromatic hydrocarbons, such as benzene and toluene are not reactive at all with the F(-) ion. The mechanisms of the various reactions mentioned are discussed, and several experimental complications are noted. In still other studies, the effects of varying several experimental parameters, including source pressure, relative proportions of the reagent and analyte, and other ion source parameters, on the observed chemical ionization mass spectra were also investigated. In a mixture of NF(3) and n-butanol, for example, the ratio of the intensities of the ions characteristic of the alcohol to that of the (HF)(n)F(-) ion was found to decrease with increasing sample pressure, with increasing NF(3) pressure, and with increasing electron energy. No significant effects on the spectra were observed to result from variation of the source repeller field or the source temperature. The addition of argon to the source as a potential moderator did not alter the F(-) chemical ionization spectrum significantly, but the use of oxygen appears to inhibit formation of the (HF)(n)F(-) cluster ion. The advantages of using F(-) as a chemical ionization reagent are discussed, and comparisons are made with other reagent ions.

Anions↗
PubMed1980

Radiation therapy of nasopharyngeal carcinoma.

Carcinoma of the nasopharynx is one of the most frequent malignant tumors in the southern parts of China. A total of 3 263 cases treated with irradiation in the course of the thirty years since the Liberation have been analysed retrospectively. The 5-year survival rate has risen from 27.7 per cent for cases treated during 1955 to 1960 to 54 per cent for those treated in 1973. The technique of irradiation is described, emphasizing the importance of suitable techniques for the treatment of the cervical lymph nodes. The value of elective irradiation of cervical regions not involved clinically is elucidated. Finally, the causes of failure of treatment are discussed.

Cobalt Radioisotopes↗
PubMed1979

Induction of simian virus 40-specific tumour rejection by the Ad2+ND2 hybrid virus.

Immunization of BALB/c mice with Ad2+ND2, a non-defective hybrid virus containing about half of the early region of simian virus 40 (SV40) DNA covalently integrated into the human adenovirus 2 (Ad2) genome, can confer protection against subsequent challenge by syngeneic SV40 tumour cells. Analysis of subcellular fractions from Ad2+ND2-infected cells shows a close correlation between the tumour rejection activity and the presence of the two SV40-specific proteins induced by this hybrid virus. These two proteins, with mol. wt. of 56 000 (56K) and 42 000 (42K), can be specifically immunoprecipitated using sera obtained from hamsters bearing SV40-induced tumours. Such immunoprecipitates, which contain no detectable contaminating components as determined by polyacrylamide gel electrophoresis, can efficiently immunize mice against SV40 tumour challenge, suggesting that the 56K and 42K proteins are directly responsible for the induction of tumour rejection. Moreover, we have found, by immunoprecipitation, a novel antigen in SV40-transformed BALB/c cells, also of 56 000 mol. wt.; possibly, this 56K protein is responsible for induction of transplantation immunity in SV40-transformed cells.

Adenoviruses, Human↗
PubMed1979

Relationship between T-antigen and tumor-specific transplantation antigen in simian virus 40-transformed cells.

The simian virus 40 (sv40) tumor antigen (T-antigen) and tumor-specific transplantation antigen (TSTA) have been partially purified and studied to clarify their relationship. The T-antigen and the TSTA were partially purified from nuclei of SV AL/N cells, and SV40-transformed mouse embryo fibroblast line, by precipitation with ammonium sulfate and chromatography on DEAE- and DNA-cellulose. The T-antigen was assayed by complement fixation, and the TSTA was assayed by its ability to immunize mice against SV40-containing ascites tumor cells. When T-antigen- and TSTA-containing preparations were sedimented through sucrose gradients, each antigen had a major peak of activity at a sedimentation coefficient of 6.7 and minor peaks in other regions. Antiserum against T-antigen (from tumor-bearing hamsters) immunoprecipitated the TSTA activity. A preparation of T-antigen from human SV80 cells, which exhibited only one protein band after sodium dodecylsulfate-polyacrylamide gel electrophoresis, had TSTA activity when as little as 0.6 microgram of protein per mouse was used for immunization. These experiments demonstrate that the T-antigen, the product of the SV40 early A gene is capable of inducing specific immunity against transplantation of SV40-transformed tumor cells in mice.

Antigens, Neoplasm↗
PubMed1979

Multiple forms of polyoma virus tumor antigens from infected and transformed cells.

At least three distinct forms of polyoma virus tumor antigens were isolated from productively infected and transformed hamster cells by immunoprecipitation with anti-T serum. These proteins had approximate molecular weights of 105,000 (large T antigen), 63,000 (middle T antigen), and 20,000 (small T antigen) as estimated by acrylamide gel electrophoresis. An examination of the appearance of these antigens in polyoma-infected mouse cells showed that all three polypeptides were synthesized maximally at approximately the same time after infection. Analysis of the methionine-containing tryptic peptides of these proteins indicated that the large, middle, and small forms of polyoma T antigens contained five similar or identical peptides. In addition, the 63,000- and 20,000-dalton antigens contained two other methionine peptides absent from the large T-antigen species. Other methionine peptides were found only in the large or middle T-antigen forms. These results and results obtained previously suggested that the three T-antigen species have the same NH2-terminal end regions but different COOH termini. A model is presented describing the synthesis of these polypeptides from different regions of the polyoma virus genome.

Animals↗
PubMed1979

Identification and partial characterization of new antigens from simian virus 40-transformed mouse cells.

Two new species of antigens were detected in simian virus 40-transformed mouse cells, in addition to the large (94,000 daltons) and small (20,000 daltons) tumor antigens. These antigens were immunoprecipitated from cell extracts by using anti-T serum and not normal, nonimmune serum. One of these was a protein with a molecular weight of approximately 130,000 and was present in some but not all SV40-transformed mouse cells. The other, which we have named Tau antigen, has a molecular weight of 56,000 as estimated by electrophoresis through acrylamide gels and was found in all virus-transformed cells examined. The 13,000-daltons antigen contained about 15 methionine-tryptic peptides which were also present in the large SV40 tumor antigen as determined by ion-exchange chromatography. This strongly suggested that the protein was virus coded. The 56,000-dalton Tau antigen appeared to share only two methionine-tryptic peptides with the large species of SV40 tumor antigen, as determined by ion-exchange and paper chromatographies. Our results are compatible with a cellular origin for Tau antigen. However, our data do not exclude the possibility that this protein contains sequences specified by the virus DNA.

Animals↗
PubMed1979

Experimentally induced autoantibody to heat-stable alkaline phosphatase in the baboon.

Experimental evidence has been collected which signifies that autoantibody has been induced against lung heat-stable alkaline phosphatase which represented 60% of the total alkaline phosphatase of that tissue. Immunization of a male baboon with highly purified human placental alkaline phosphatase (heat-stable and cross-reactive with the baboon heat-stable enzyme) resulted in production of a precipitating factor in the immune serum which reacted with the heat-stable enzyme of both the human and baboon but not the heat-labile form of alkaline phosphatase of either species. This precipitating factor is a baboon autoantibody because 1) it had a gamma mobility on immunoelectrophoresis and retarded the electrophoretic mobility of the heat-stable enzyme from both normal and immunized baboons; 2) its titer increased as more booster injections were administered; 3) it formed a well-defined precipitin rocket with the baboon heat-stable enzyme in the Lurell's antigen-antibody crossed electrophoresis; 4) in immunodiffusion it formed a discrete precipitin line with the baboon heat-stable enzyme, which fused partially with the precipitin line of human placental alkaline phosphatase (immunogen).

Alkaline Phosphatase↗