Biomedical subjects

M M Becker

Publications and source records attributed to M M Becker.

25 records · Page 2Linked to original sources

PubMed1988

Selective visualization of gene structure with ultraviolet light.

The ability of the ultraviolet (UV) "footprinting" technique to detect chromatin has been investigated in vitro. Two basic types of chromatin, a phased nucleosome and a phased nucleosome containing a phased H1 protein, have been reconstituted onto a cloned 5S ribosomal RNA gene from sea urchin. The histone-DNA interactions in each complex have been probed with exonuclease III, DNase I, dimethyl sulfate, and UV light. Whereas DNase I and exonuclease III readily detect interactions between histones and DNA, UV light and dimethyl sulfate do not. In contrast to histone-DNA interactions, we demonstrate that intimate sequence-specific contacts between the same sea urchin 5S DNA and the Xenopus laevis transcription factor IIIA (TFIIIA) are readily detected with UV light. Since the sensitivity of UV light for TFIIIA contacts is similar to its sensitivity for other regulatory protein-DNA contacts, these studies demonstrate the feasibility of using UV light to selectively visualize regulatory protein-DNA interactions in vivo with little or no interference from histone-DNA interactions.

Animals↗

PubMed1988

Selenium increases hydrogenase expression in autotrophically cultured Bradyrhizobium japonicum and is a constituent of the purified enzyme.

We have investigated the effect of added selenite on autotrophic growth and the time course of hydrogen oxidation derepression in Bradyrhizobium japonicum 122DES cultured in a medium purified to remove selenium compounds. In addition, hydrogenase was purified to near homogeneity and examined for the specific incorporation of Se into the enzyme. The addition of Se at 0.1 microM significantly increased total cell protein and hydrogenase specific activity of harvested cells. Also, the addition of SeO3(2-) enhanced the time course of hydrogenase derepression by 133%, whereas VO3, AsO2(2-), SO2(2-), and TeO3(2-) failed to substantially affect hydrogenase derepression. During the final chromatographic purification of hydrogenase, a striking coincidence in peaks of protein content, Se radioactivity, and hydrogenase activity of fractions was obtained. The total Se content expressed per milligram of protein increased manyfold during the purification procedure. The mean Se content of the purified hydrogenase was 0.56 +/- 0.13 mol of Se per mol of enzyme. These results indicate that Se is an important element in the H2 metabolism of B. japonicum and that hydrogenase from B. japonicum is a seleno protein.

Culture Media↗

PubMed1986

Alterations in the synthesis of proteins in hepatocytes of rainbow trout fed cyclopropenoid fatty acids.

Hepatocytes from rainbow trout reared on a diet containing cyclopropenoid fatty acids were analyzed for alterations in protein composition and synthesis by double label experiments. Both cytosolic and microsomal hepatocyte fractions were investigated. In the cytosolic fraction, the synthesis of proteins in the range of 68,000 to 74,000 daltons were significantly decreased. The identity of these proteins remains uncertain. A pronounced depression in both the mass and apparent synthesis of a 200,000 to 240,000 dalton microsomal protein was also observed. Immunoblotting with antibodies raised against goose acetyl-CoA carboxylase and avidin-peroxidase staining suggest that this protein is acetyl-CoA carboxylase. Moreover, synthesis of this protein as well as mass of the protein in cyclopropenoid fatty acid-fed fish were less than 20% of that found in control fish.

Acetyl-CoA Carboxylase↗

PubMed1984

2,4,5,2',4',5'-Hexachlorobiphenyl-lipoprotein (LDL, HDL, VLDL) interaction and induced lipidosis in cultured skin fibroblasts.

2,4,5,2',4',5'-Hexachlorobiphenyl (HCB) induced cytoplasmic inclusions and lipidosis in normal ( AG1437 ) and hypercholesterolemic ( GM488 ) human skin fibroblasts. Quantitative and qualitative microsocopic fluorescence analysis showed that the cytoplasmic inclusions are formed as early as 3 hr after treatment with HCB. The inclusions contain lipids but no detectable nonesterified cholesterol or cholesteryl ester. High density lipoproteins (HDL), low density lipoproteins (LDL), and very low density lipoproteins (VLDL) facilitate the apparent uptake of HCB by skin fibroblasts. HDL and LDL appeared to reverse the induction of cytoplasmic inclusions and lipidosis when cells were pretreated with HCB, the HCB was removed from media, and the cells were incubated with LDL or HDL. The results suggest that lipoproteins participate in the uptake and egress of HCB from skin fibroblasts.

Cells, Cultured↗

PubMed1984

Phospholipid and glyceride biosynthesis in 2,4,5,2',4',5'-hexachlorobiphenyl-treated human skin fibroblasts.

2,4,5,2',4',5'-Hexachlorobiphenyl (HCB) was taken up by cultured human skin fibroblasts ( A61437 ; GM488 ). HCB caused enhanced incorporation of [2-14C]acetate into phospholipids and glycerides at low concentration and reduced incorporation at high concentrations. sn-[U-14C]Glycerol-3-phosphate incorporation into phospholipids was inhibited. No significant change in total cellular phospholipids was observed. Triglyceride cellular content was increased 29%. The observed stimulation and inhibition of phosphoglyceride synthesis are similar to results obtained with rat liver microsomes.

Cells, Cultured↗

PubMed1982

Determination of the binding of 2,4,5,2',4',5'-hexachlorobiphenyl by low density lipoprotein and bovine serum albumin.

The mechanism of transport of polychlorinated biphenyls (PCBs) to and from peripheral cells is not known. Plasma proteins, which bind a variety of compounds including hydrophobic molecules, are most likely to be involved in PCB transport. In order to study the role of lipoproteins in the transport and distribution of PCBs to cells, an assessment of the nature and extent of the interaction and binding of PCBs to plasma proteins is necessary. In this report a simple filter assay procedure for the analysis of binding of 2,4,5,2',4',5'-hexachlorobiphenyl (HCB) by low density lipoproteins and serum albumin is described. The method allowed compete recovery of the PCBs, and reduced errors due to nonspecific binding to the apparatus to insignificant values. Low density lipoprotein bound HCB at several noninteractive sites (number of binding sites n = 30; binding constant K = 2.7 x 10(5); dissociation constant Kd = 7.2 x 10(-6) M). Bovine serum albumin bound HCB at one noninteractive site (n = 0.53; K = 5.1 x 10(5); Kd = 1.9 x 10(-6) M). The results indicate that albumin and low density lipoprotein bind HCB effectively and suggest that plasma proteins may play a role in its distribution to peripheral cells.

Humans↗

PubMedDate not supplied

Use of light for footprinting DNA in vivo.

A new ' photofootprinting ' technique, which uses light to detect protein-DNA contacts as well as changes in the structure of DNA at the base pair level, has been developed and used to detect contacts between lac repressor and the lac operator in Escherichia coli cells.

Base Sequence↗