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Biomedical subjects

B Berg

Publications and source records attributed to B Berg.

At least 127 records · Page 7Linked to original sources
PubMed1976

Sequence composition of the template-active fraction of rat liver chromatin.

Rat liver chromatin has been separated into nuclease-sensitive and -resistant fractions after mild digestion with DNAase II. The nuclease-sensitive material is further fractionated into Mg2+ -soluble and -insoluble chromatin fractions. The kinetics of production of these chromatin fractions have been investigated. After a brief enzyme treatment (5 min at 10 enzyme units/A260 unit of chromatin at pH 6.6), 11% of the input chromatin DNA is found in the Mg2+ -soluble fraction. This DNA has a weight-average single-strand length of about 400 nucleotides and, as determined by renaturation kinetics, comprises a subset of nonrepetitive DNA sequences and a subset of families of middle repetitive sequences. This demonstrates the nonrandom distribution of repetitive and single copy sequences in the Mg2+ -soluble fraction of chromatin. Previous studies have shown that the Mg2+ -soluble fraction is enriched in nonrepeated sequences which are transcribed in vivo (Gottesfeld, J.M., Garrard, W.T., Bagi, G., Wilson, R.F., and Bonner, J. (1974), Proc. Natl. Acad. Sci. U.S.A. 71, 2193-2197). We now report that the Mg2+ -soluble fraction of liver chromatin contains a low proportion of sequences in common with the Mg2+ -soluble fraction of brain chromatin. Thus, fractionation does not depend on some general property of chromatin but is specific with regard to the template activity of the tissue from which the chromatin was obtained.

Animals↗
PubMed1976

A new pattern of multiple endocrine adenomatosis: chemodectoma, bronchial carcinoid, GH-producing pituitary adenoma, and hyperplasia of the parathyroid glands, and antral and duodenal gastrin cells.

A female patient was found to have a chemodectoma, a GH-producing pituitary tumour and a bronchial carcinoid combined with hyperplasia of the parathyroids and of antral and duodenal gastrin cells. This combination of endocrine tumours and hyperplasias does not fit with the two multiple endocrine adenomatosis syndromes recognized at present. The case stresses the importance of scanning the patient for other endocrine tumours, once one has been diagnosed.

Adenoma↗
PubMed1975

Cellulase location in Cellvibrio fulvus.

The location of cellulase in C. fulvus depends on the carbon source for growth and the age of the culture. When cells were grown on glucose or cellobiose all CMC-hydrolyzing enzyme was cell-bound but only part of the activity was located on the cell surface. Treatment of cells with EDTA, lysozyme, and detergents and subsequent fractionation experiments showed that cellulase was also located in the periplasm and bound to a membrane fraction. Growth on cellulose gave cell-free cellulase active against CMC. The enzyme was repressed by glucose but formed at a constant differential rate on cellobiose and amylose. This rate was 8-10 times lower than on cellulose and possible reasons for this are discussed.

Amylose↗
PubMed1975

The ultrastructure of the cellulolytic bacterium Cellvibrio fulvus.

Thin sections of the cellulolytic bacterium Cellvibrio fulvus were investigated before and after treatment with polymyxin B and Triton X-100. The Gram-negative vibrio appeared to have no separate stained g2 layer between the L and C membranes. Cells lysed after treatment with polymyxin or swelled in the presence of 5% sucrose. Blebs were formed from the L membrane, and the inner structure of the cells changed. Triton X-100 lysed cells even in the presence of 20% sucrose. The flagellum disappeared before lysis; one of the membranes was dissolved; and no organized inner structure could be seen.

Bacteria↗