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Biomedical subjects

F Chu

Publications and source records attributed to F Chu.

10 recordsLinked to original sources
PubMed1979

Effect of deglycosylation of yeast invertase on its uptake and digestion in rat yolk sacs.

The uptake by rat yolk sacs of native invertase and invertase which was deglycosylated by treatment with endo-beta-N-acetylglucosaminidase was compared. The initial rate of uptake of the deglycosylated enzyme was severalfold greater and its accumulation leveled off much earlier than that of the native enzyme. Uptake rates of the deglycosylated and native forms of the enzyme were proportional to their concentration in the medium in the range employed and were inhibited about 85% by 10(-6) M glucagon in both cases. After preloading of yolk sacs with native invertase, the tissue level of activity remained relatively constant over a subsequent 6-h time period, while with the deglycosylated form, activity declined substantially. Since this difference appears not to be attributable to differences in thermal stability, it is suggested that the deglycosylated form of the protein is more susceptible to intracellular proteolytic digestion. In vitro studies on the digestion of these two forms of invertase by trypsin are consistent with this suggestion.

Animals↗
PubMed1978

The relationship between the spoT gene, the synthesis of stable RNA, ribosomal proteins, and the beta beta' subunits of RNA polymerase following a nutritional shiftup of Escherichia coli.

The level of ppGpp and rates of synthesis of stable RNA, ribosomal protein, and the beta and beta' subunits of RNA polymerase were measured following a nutritional shiftup in Escherichia coli strains, NF 929 (spoT+) and NF 930 (spoT-). In the spoT+ strain, ppGpp levels decreased 50% within 2 min following shiftup, and the rates of synthesis of stable RNA, ribosomal proteins, and the beta and beta' subunits of RNA polymerase increased with little or no lag. In contrast, in the spoT- strain, ppGpp levels transiently increased 40% during the first 6 min following shiftup. An inhibition in the rate of stable RNA synthesis and a delay in the increased synthesis of ribosomal proteins and beta and beta' subunits occurred concurrently with the transient increase in ppGpp. In addition, the DNA-dependent synthesis in vitro of the beta and beta' subunits of RNA polymerase was inhibited by physiological levels of ppGpp. Because of the timing and magnitude of the changes in ppGpp levels in the spoT- strain versus the timing when the new rates of stable RNA, ribosomal protein, and beta and beta' subunits synthesis are reached, it is concluded that ppGpp is not the sole element regulating the expression of these genes.

DNA-Directed RNA Polymerases↗
PubMed1977

Radiation treatment planning.

Radiation treatment planning has developed into a substantial and effective component of the entire radiation treatment approach. Over the last 2 decades, with the development of high energy electron and x-ray sources, and also with the availability of new radionuclides and techniques for internally applied radiation, all of which permit a high degree of concentration of radiation, treatment planning has been developed to make best use of these modalities. The use of automatic computation has proved necessary in order to handle the large amounts of radiation data involved in treatment dose calculation. Tumor and anatomical localization has been carried out with increasing precision. Several cases are described which illustrate planning and in particular the use of computerized transverse tomography. The use of moving shadow-shields is also described. For internally applied radiation, the features of iodine-125 are illustrated.

Adult↗
PubMed1977

A comparative study of two preoperative radiation regimens with cystectomy for bladder cancer.

This report surveys the results of two programs of preoperative irradiation with radical cystectomy for bladder cancer in 205 patients. Irradiating the true pelvis to 4000 rads in 4 weeks with radical cystectomy after 6 weeks was implemented in 119 patients (Group 1) from 1959 to 1965; 2000 rads given in 1 week to the true pelvis and radical cystectomy within the following week was implemented in 86 patients (Group 2) from 1966 to 1970. Determinate survival without evidence of recurrence at 5 years was 43% in Group 1 and 42% in Group 2. Mortality with recurrence of bladder cancer in 5 or more years was 44% in group 1 and 42% in group 2. Pelvic complications occurred in 13% of group 1 and 9% of group 2.

Adenocarcinoma↗
PubMed1977

mRNA-dependent in vitro synthesis of ribosomal proteins L12 and L10 and elongation factor Tu.

RNA extracted from growing Escherichia coli can direct the in vitro synthesis of ribosomal proteins L12 and L10 and elongation factor Tu when an E. coli system is used. The synthesized L12 can be bound to L12-depleted ribosomes and the synthesized elongation factor Tu can form complexes with both elongation factor Ts and GDP. Guanosine 5'-diphosphate 3'-diphosphate has no effect on the synthesis of these proteins from an RNA template but inhibits their synthesis when a DNA template is used.

Cell-Free System↗
PubMed1976

DNA dependent synthesis of protein L12 from escherichia coli ribosomes, in vitro.

The in vitro synthesis of ribosomal protein L12 has been obtained in a coupled system with DNA extracted from the transducing phage lambdarifd18 as template. In addition, a second protein (molecular weight of 16,000) with immunological, chemical, and ribosome-binding characteristics similar to L12 is formed in this in vitro system. The synthesis of both proteins is depressed by one-half when guanosine-5'-diphosphate-3'-diphosphate is added to the reaction mixture.

Bacterial Proteins↗