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Biomedical subjects

J F Chiu

Publications and source records attributed to J F Chiu.

At least 127 records · Page 7Linked to original sources
PubMed1978

Cellular binding proteins for vitamin A in colorectal adenocarcinoma of rat.

Rat colorectal mucosa was examined during the course of carcinogenesis, induced by chronic administration of 1,2-dimethylhydrazine (DMH), for the presence and amount of cellular retinol-binding protein (CRBP) and cellular retinoic acid-binding protein. These two binding proteins are implicated in the action of vitamin A in normal and neoplastic tissue. Induced adenocarcinomas were found to contain low levels of cellular retinoic acid-binding protein (10 pmol/g), similar to the levels found in adjacent mucosa of the same animal and also in colorectal mucosa from normal rats or rats chronically treated with DMH. However, the adenocarcinomas had high levels of CRBP (300 to 500 pmol/g), and these levels were dramatically higher than levels of CRBP in adjacent mucosa of the same animal (40 to 100 pmol/g), colorectal mucosa from normal rats (20 pmol/g), or colorectal mucosa from rats chronically treated with DMH (22 to 25 pmol/g). Consequently, the increase in CRBP occurred only with tumor appearance and not with the general hyperplasia of the crypts caused by DMH administration. The CRBP of the tumor was associated with endogenous retinol (77 to 100% saturation) and was similar to, if not identical with, CRBP of normal tissue, as judged by fluorescence spectra, sedimentation behavior, and elution position on Sephadex G-75.

Adenocarcinoma↗
PubMed1977

Tissue-specific antibodies against human lung and breast carcinoma dehistonized chromatins.

Tissue-specific antisera against human lung and breast carcinoma dehistonized chromatins were obtained. The specificity of these antisera was determined by complement fixation. In the presence of antiserum against human lung carcinoma, only chromatins from lung carcinoma fixed complement significantly, whereas chromatins isolated from human breast carcinoma, HeLa cells, normal lung tissue, breast tissue, or term placenta were negative (i.e., inactive). In a similar assay with the use of antiserum against dehistonized breast carcinoma chromatins, only breast carcinoma chromatins fixed complement. Immunohistochemical localization of the antigens by the horseradish peroxidase bridge method demonstrated their presence in the nuclei.

Animals↗
PubMed1977

Nuclear protein phosphokinases in normal and neoplastic tissues.

Protein phosphokinases were isolated from the nuclei of normal and fetal liver and neoplastic tissues. Chromatography on phosphocellulose columns resolved the normal and fetal liver kinases into five reproducible fractions. Each of the fractions differed in optimal divalent cation and substrate requirements. Hepatic proliferation was accompanied by quantitative changes in the kinase activity profiles (with endogenous phosphoprotein as natural substrate). An additional phosphoprotein kinase activity stimulated by Mn2+ was found in the nuclei of malignant cells. This tumor-specific kinase could not be detected either in tumor cytoplasm or in fetal or regenerating liver nuclei. Mn2+-dependent phosphoprotein kinase from Novikoff hepatoma phosphorylated only one major protein band detectable by polyacrylamide gel electrophoresis. This substrate could not be detected in chromatin of normal tissues.

Adenosine Triphosphate↗
PubMed1976

Testicular chromatin activation in hypophysectomized rats.

Incorporation of labeled thymidine into testicular DNA of hypophysectomized rats began to increase after the administration of testosterone propionate and choriogenic gonadotrophin. While the thymidine incorporation reached maximum in 4 days, the DNA polymerase activity did not culminate until 8 days after the initiation of hormone treatment. The high molecular weight (6--8 S), presumably cytoplasmic DNA polymerase accounted almost entirely for this increase. Administration of testosterone propionate and chorionic gonadotrophin to hypophysectomized rats results in an increase of testicular RNA polymerase and chromatin templating activity. Chain elongation and initiation studies revealed that the increased templating capacity of androgen-stimulated testicular chromatin was almost entirely caused by the increase in the number of initiation sites. While the nuclear polymerase I responded relatively rapidly to hormone stimulation and reached a prominent maximum in about three days, the activity of polymerase II was more sluggish and not as prominent. The in vivo incorporation of ortho[32P]phosphate into chromosomal phosphoproteins occurred early during the androgen treatment and reached a maximum in about 20 h. The protein phosphokinase activity peaked later, approx. 72 h after the first administration of hormones.

Animals↗
PubMed1976

Tissue-specific chromosomal non-histone protein interactions with DNA.

A group of chromosomal non-histone proteins with affinity for DNA (NP) was isolated from rat liver and Novikoff hepatoma. This fraction, which represents less than 5% of the total chromatin protein content, binds preferentially to unique, double-stranded sequences of fractionated homologous DNA. The interactions are strong at low ionic strength (Km = 6.7 X 10(-9) M) and decrease with rising salt concentration. Complexes of the NP protein fraction with homologous DNA are immunologically tissue-specific. As determined by microcomplement fixation, the NP proteins in Novikoff hepatoma are associated with the transcriptionally active, diffuse fraction of chromatin.

Animals↗
PubMed1976

Acceptor proteins in rat androgenic tissue chromatin.

Fractionation of chromatin into urea-soluble chromosomal nonhistone proteins (UP), histones (HP), and DNA-associated nonhistone proteins (NP) revealed that the NP fraction from testicular and prostatic chromatin contains organ-specific acceptors for complexes of 5alpha-dihydrotestosterone (17beta-hydroxy-5alpha-androstan-3-one) and its receptor. This acceptor capacity of androgenic tissue chromatin could be transferred to chromatins from non-target tissues with the NP fraction of DNA-associated proteins. Phosphorylation of chromatin enhanced its hormone-receptor binding capacity.

Animals↗
PubMed1976

In vivo and in vitro phosphoarylation of nuclear proteins in rat liver.

The incorporation of 32P into nuclear nonhistone proteins was compared in rat liver in vivo, in liver slices incubated in vitro, and in isolated nuclei incubated with gamma-[32P]ATP. The highest specific activities of nuclear phosphorproteins were obtained by incubating isolated nuclei. However, the Radioactivity profiles of polyacrylamide gel electrophoretograms of these proteins differed from those obtained in vivo or in liver slice experiments. A group of low molecular weight nonhistone proteins exhibited a very high incporation of labelled phosphate. These proteins could be obtained from the interface when the phosphoproteins were isolated by the buffered phenol extraction procedure. Phosphorylated proteins were also obtained from three cytoplasmic fractions (mitochondria, microsomes, and cytosol). The specific activities of these proteins were much lower than of the nuclear phosphoproteins.

Animals↗
PubMed1975

Regulation of in vitro mRNA transcription by a fraction of chromosomal proteins.

A fractionation scheme was developed which permits the isolation of chromosomal non-histone protein fraction associated with DNA in chromatin. This fraction which represents less than 10% of the total protein content of reticulocyte chromatin was found to be essential for the in vitro transcription of globin mRNA by chromatin preparations reconstituted from DNA and isolated chromosomal protein components.

Animals↗
PubMed1975

DNA-binding chromosomal non-histone proteins. Isolation, characterization, and tissue specifity.

A fractionation schedule is described which allows the isolation of a group of chromosomal non-histone proteins (NP) with affinity for DNA. In polyacrylamide gel electrophoresis these proteins isolated from rat liver are represented principally by a group of low molecular weight polypeptides. The NP fraction comprises about 2-4% of the total chromatin protein content in rat liver or Novikoff hepatoma. Experiments in vivo and in vitro revealed that the NP proteins do not incorporate significant amounts of 32P. Complexes of the chromosomal proteins NP with homologous DNA are immunologically tissue specific and the specificity can be transferred by reconstituting the NP proteins from one tissue to the residual chromatin from another.

Amino Acids↗
PubMed1975

Nuclear phosphoprotein kinase activities in normal and neoplastic tissues.

Nuclear phosphoprotein kinases from normal rat liver and transplantable neoplasms were fractionated and compared. A phosphoprotein kinase fraction activated by Mn2+ was found to be present only in the neoplasms. This nuclear protein kinase phosphorylated nuclear proteins represented by one major and several minor bands as determined by polyacrylamide gel electrophoresis (M approximately 50,000).

Animals↗
PubMed1975

Tissue-specific DNA-protein complexes during azo dye hepatocarcinogenesis.

The immunological tissue specificity could be transferred from one chromatin preparation to another by reconstituting this protein fraction to the DNA and the remaining chromatin components."The immunological tissue specificity could be transferred from one chromatin preparation to another by reconstituting this protein fraction this protein fraction to the DNA and the remaining chromatin components.

Alpha-Globulins↗