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J M Gimble

Publications and source records attributed to J M Gimble.

64 records · Page 4Linked to original sources
PubMed1987

Human immunoglobulin kappa gene enhancer: chromatin structure analysis at high resolution.

The murine immunoglobulin kappa gene enhancer has previously been found to coincide with a region of altered chromatin structure reflected in a DNase I hypersensitivity site detectable on Southern blots of B-cell DNA. We examined the chromatin structure of the homologous region of human DNA using the high-resolution electroblotting method originally developed for genomic sequence analysis by G. Church and W. Gilbert (Proc. Natl. Acad. Sci. USA 81:1991-1995, 1984). Analysis of DNA isolated from cells treated in vivo with dimethyl sulfate revealed two B-cell-specific sites of enhanced guanine methylation. Both sites are located within perfect inverted repeats theoretically capable of forming cruciform structures; one of these repeats overlaps an enhancer core sequence. No enhancement or protection of guanine methylation was observed within sequences similar to sites of altered methylation previously described in the immunoglobulin heavy-chain enhancer. Treatment of isolated nuclei with DNase I or a variety of restriction endonucleases defined a B-cell-specific approximately 0.25-kilobase region of enhanced nuclease susceptibility similar to that observed in the murine kappa enhancer. The 130-base-pair DNA segment that shows high sequence conservation between human, mouse, and rabbit DNAs lies at the 5' end of the nuclease-susceptible region.

B-Lymphocytes↗
PubMed1987

B-cell nuclear proteins binding in vitro to the human immunoglobulin kappa enhancer: localization by exonuclease protection.

Proteins capable of interacting with the enhancer of the immunoglobulin kappa gene in vitro have been detected in extracts of nuclei from human B cells and from human, mouse, and rabbit spleens. The experiments, based on an exonuclease protection technique, demonstrate nuclear protein factors binding to a 30- to 35-base-pair domain containing both the simian virus 40 enhancer core element (TTTCCA) and the octamer CAGGTGGC that was previously identified as the consensus sequence for protein-binding sites in the murine immunoglobulin heavy-chain enhancer. This 30- to 35-base-pair domain in the human kappa enhancer is homologous to a site of protein binding detected in the murine kappa enhancer by other investigators using a gel retardation assay. Our results complement in vivo dimethyl sulfate footprinting studies of the human immunoglobulin kappa enhancer which demonstrated B cell-specific changes in guanine reactivity immediately 5' to the consensus octamer. Together, these findings suggest that DNA-binding proteins in B-cell nuclei interact with the 5' portion of the human kappa-gene enhancer. Such proteins could play a role in the B cell-specific transcription of the human immunoglobulin kappa gene.

B-Lymphocytes↗
PubMed1982

Studies of the Ca2+ transport mechanism of human erythrocyte inside-out membrane vesicles. Evidence for the development of a positive interior membrane potential.

Previous observations on the effects of permeant anions on ATP-dependent calcium transport in inside-out vesicles prepared from human erythrocytes suggested that the calcium pump is electrogenic, generating a positive interior membrane potential. The present work demonstrates the development of a positive interior membrane potential across inside-out vesicle membranes during calcium transport in the absence of permeant anions. Several membrane potential probes, 1-anilino-8-naphthalenesulfonate, 3,3'-dipropylthiodicarbocyanine iodide, and an electron paramagnetic resonant triphenylphosphonium derivative, provide qualitative evidence for the development of a membrane potential. Moreover, a number of parallels are observed between the changes in the membrane potential measured by the probes and calcium transport. These include enhancement by calmodulin, time course of change, similar kinetic properties, and the requirement for intact vesicle membranes. Quantitative measurements of the membrane potential shows a positive interior membrane potential of 26-37 mV using radiolabeled permeant anion distribution and 38-57 mV using 3,3'-dipropylthiodicarbocyanine iodide fluorescence changes. These membrane potentials are of a similar magnitude to those reported for the sarcoplasmic reticulum calcium pump (Zimniak, P., and Racker, E. (1978). J. Biol. Chem. 253, 4631-4637).

Anilino Naphthalenesulfonates↗
PubMed1982

Studies on the Ca2+ transport mechanism of human erythrocyte inside-out plasma membrane vesicles. V. Chlortetracycline fluorescence.

The measurement of chlortetracycline fluorescence was employed as a probe for measuring the process to calcium transport by human erythrocyte inside-out vesicles. Chlortetracycline is a divalent metal chelator which increases its fluorescence when bound to calcium in the presence of a membrane. Addition of calcium and ATP to inside out vesicles in the presence of chlortetracycline increased the chlortetracycline fluorescence as a function of time following an initial delay. Only after a threshold level of calcium had been accumulated did the fluorescence increase. The presence of both ATP and calcium were required. The addition of calmodulin increased the rate and absolute magnitude of the chlortetracycline fluorescence change. Similarly, calmodulin stimulated the rate and extent of 45Ca transport by inside-out vesicles. Moreover, the presence of saponin abolished both chlortetracycline fluorescence change and 45Ca uptake; a non-hydrolyzable ATP analog would not substitute for ATP in either 45Ca transport or chlortetracycline fluorescence experiments. Comparison between the slopes of the linear portions of chlortetracycline fluorescence change and calcium transport time courses at varied free calcium concentrations showed a consistent ratio between the slopes. This suggests that calcium transport change can be calibrated by employing chlortetracycline fluorescence. Based on this data, it is concluded that chlortetracycline fluorescence is a rapid and accurate method for monitoring calcium transport by human erythrocyte inside-out vesicles.

Biological Transport, Active↗
PubMed1981

Studies of the Ca2+ transport mechanism of human erythrocyte inside-out plasma membrane vesicles. I. Regulation of the Ca2+ pump by calmodulin.

Calcium accumulation by human erythrocyte inside-out vesicles was linear for at least 30 min in the presence of ATP. In untreated inside-out vesicles, 3.76 +/- 1.44 nmol of calcium/min/unit of acetylcholinesterase were transported, compared with 10.57 +/- 2.05 (+/- S.D.; n = 11) in those treated with calmodulin. The amount of calmodulin necessary for 50% activation of Ca2+ accumulation was 60 +/- 22 ng/ml (+/- S.D.; n = 4). The Km (Ca2+) for calmodulin-stimulated accumulation was 0.8 +/- 0.05 microM (+/- S.D.; n = 5) using Ca2+ /ethylene glycol bis(beta-aminoethyl ether)N,N,N',N'-tetraacetic acid (EGTA) buffers, or 25 microM with direct addition of unbuffered calcium. In the absence of calmodulin, these values were 0.4 and 60 microM, respectively, Km (ATP) values of 90 and 60 microM in the presence and absence of calmodulin, respectively, were measured at constant magnesium concentration (3 mM). In the presence of calmodulin, a broad pH profile is exhibited from pH 6.6 to 8.2. Maximal calcium accumulation occurs at pH 7.8. In the absence of calmodulin, the pH profile exhibits a linear upward increase from pH 7.0 to 8.2. The (Ca2+-Mg2+)-ATPase activity, measured under identical conditions, was 2.40 +/- 0.72 nmol of Pi/min/unit of acetylcholinesterase in the untreated vesicles and 11.29 +/- 2.87 nmol of Pi/min/unit of acetylcholinesterase (+/- S.D.; n = 4) in calmodulin-treated vesicles. A stoichiometry of 1.6 Ca2+/ATP hydrolyzed was determined in the absence of calmodulin; in the presence of calmodulin, this ratio was decreased to 0.94 Ca2+/ATP hydrolyzed.

Adenosine Triphosphatases↗
PubMed1980

Inhibition of dopamine-beta-hydroxylase by alternative electron donors.

The alternative electron donors ferrocyanide and hydroquinone have been shown to also act as inhibitors of dopamine-beta-hydroxylase (3,4-dihydroxyphenylethylamine, ascorbate:oxygen oxidoreductase (beta-hydroxylating), EC 1.14.17.1). Hydroquine shows uncompetitive inhibition with respect to ascorbate and competitive inhibition with respect to tyramine. Ferrocyanide shows uncompetitive inhibition with respect to ascorbate and mixed type inhibition with respect to tyramine. Inhibition by ferrocyanide at concentrations at or above 2.5 . 10(-5) M was prevented by 2.5 . 10(-6) M cupric ion. These results indicate that the inhibitory action of these alternative electron donors is due to their interaction with a reduced enzyme species. The potency of inhibition of dopamine-beta-hydroxylase by both ferrocyanide and hydroquinone is dependent on the degree of protonation of a group in the enzyme having a pKa of 5.3.

Ascorbic Acid↗
PubMedDate not supplied

Therapeutic treatment of DMBA-induced mammary tumors with PPAR ligands.

The objective of this study was to evaluate the ability of troglitazone (a thiazolidinedione) and Wy-14,643 (a clofibrate) to inhibit progression of non-detectable and detectable mammary tumors in rats induced by 7,12 dimethylbenz(a)anthracene (DMBA) when compared to those receiving no treatment or tamoxifen. Although not as effective as tamoxifen in decreasing overall tumor incidence, Wy-14,643 reduced the percentage and number of malignant tumors that developed when compared to both troglitazone and control. Treatment of detectable tumors with either Wy-14,643 or troglitazone induced regression or stasis of total tumor volume in 40-50% of the animals, compared to only 10% in control and 65% in tamoxifen treated animals. Moreover, each PPAR ligand was as effective as tamoxifen in preventing additional tumor development. In summary, both PPAR ligands were more effective than no treatment in preventing tumor progression once detected. However, only the PPAR-alpha activator, Wy-14,643 was able to reduce the development of malignant tumors when administered prior to detection.

9,10-Dimethyl-1,2-benzanthracene↗