Biomedical subjects

D Konkel

Publications and source records attributed to D Konkel.

5 recordsLinked to original sources

PubMed1991

Regulation of diazepam binding inhibitor in rat adrenal gland by adrenocorticotropin.

Diazepam binding inhibitor (DBI) is a 9-kDa polypeptide that was initially isolated from rat brain and subsequently found to be present in several peripheral tissues. DBI is particularly abundant in steroidogenic tissues, such as the adrenal glands and testes, which also contain a high concentration of peripheral/mitochondrial benzodiazepine receptors (MBRs). Because occupancy of adrenal MBRs with DBI results in increased steroidogenesis, we have investigated the relation between ACTH, DBI, and the MBR in the rat adrenal glands. Evidence presented here indicates that both the amount of DBI and its rate of synthesis in the adrenal cortex are under the control of ACTH. Seven and 9 days after hypophysectomy, the amount of DBI-like immunoreactivity (DBI-LI) in rat adrenal glands decreased dramatically from approximately 80 to 15 ng/mg tissue. The administration of single dose of ACTH (ACTH residues 1-39; 200 mU/kg, iv) or repeated doses of ACTH-R (ACTH in saline containing 16% gelatin; 15 U/kg, sc, twice daily) reduced the decrease in adrenal DBI-LI caused by hypophysectomy. In hypophysectomized rats (7 days after hypophysectomy) the increases in both adrenal DBI-LI and plasma corticosterone induced by ACTH 1 h after a single injection (200 mU/kg, iv) were inhibited by injection of cycloheximide (40 mg/kg, ip) 10 min after ACTH. However, cycloheximide at this dose had no effect on the ACTH-induced increase in adrenal cAMP concentration or the number of affinity of MBRs for 4'-[3H]chlorodiazepam.

Adrenal Glands↗

PubMed1984

Isolation, purification and partial sequence of a neuropeptide (diazepam-binding inhibitor) precursor of an anxiogenic putative ligand for benzodiazepine recognition site.

Diazepam binding inhibitor (DBI), a brain neuropeptide putative ligand for benzodiazepine binding sites, has been isolated and purified to homogeneity. This compound, like the anxiogenic beta-carbolines, injected intracerebroventricularly facilitates shock-induced suppression of drinking in thirsty rats. Cyanogen bromide (CNBr) cleavage of DBI produces three peptide fragments: the carboxy terminal fragment (F3 approximately equal to 1800 mol.wt.) and an intermediate fragment (F2 approximately equal to 3200 mol.wt.) are inactive, whereas the fragment that contains the amino terminus (F1 approximately equal to 6500 mol. wt.) facilitates punishment inhibition of operant behavior in rat. These data suggest that the F1 peptide contains the active sequence. The latter might be the natural effector of benzodiazepine recognition sites while DBI could be a polyprotein functioning as the precursor of the putative endogenous ligand of the benzodiazepine recognition site.

Amino Acid Sequence↗

PubMed1983

Isolation, characterization, and purification to homogeneity of an endogenous polypeptide with agonistic action on benzodiazepine receptors.

A brain polypeptide termed diazepam-binding inhibitor (DBI) and thought to be chemically and functionally related to the endogenous effector of the benzodiazepine recognition site was purified to homogeneity. This peptide gives a single band of protein on NaDodSO4 and acidic urea gel electrophoresis. A single UV-absorbing peak was obtained by HPLC using three different columns and solvent systems. DBI has a molecular mass of approximately equal to 11,000 daltons. Carboxyl-terminus analysis shows that tyrosine is the only residue while the amino-terminus was blocked. Cyanogen bromide treatment of DBI yields three polypeptide fragments, and the sequences of two of them have been determined for a total of 45 amino acids. DBI is a competitive inhibitor for the binding of [3H]diazepam, [3H]flunitrazepam, beta-[3H]carboline propyl esters, and 3H-labeled Ro 15-1788. The Ki for [3H]-diazepam and beta-[3H]carboline binding were 4 and 1 microM, respectively. Doses of DBI that inhibited [3H]diazepam binding by greater than 50% fail to change [3H]etorphine, gamma-amino[3H]butyric acid, [3H]-quinuclidinyl benzilate, [3H]dihydroalprenolol, [3H]adenosine, and [3H]imipramine binding tested at their respective Kd values. DBI injected intraventricularly at doses of 5-10 nmol completely reversed the anticonflict action of diazepam on unpunished drinking and, similar to the anxiety-inducing beta-carboline derivative FG 7142 (beta-carboline-3-carboxylic acid methyl ester), facilitated the shock-induced suppression of drinking by lowering the threshold for this response.

Amino Acids↗

PubMed1982

Globin genes: a paradigm of gene structure, function, and evolution.

Access to the detailed structure of the globin (and other) genes has taught us at least three valuable, but not necessarily expected, lessons regarding the structure and evolution of the genes. Foremost, at least in terms of its surprising nature, is the fact that many genes are interrupted, i.e., they contain discontinuous blocks of coding and noncoding information. No less surprising are the accompanying facts that chromosomal DNA changes by the movement and rearrangement of large pieces of DNA and that genetic loci are highly and unexpectedly complex, consisting of arrays of related genes and pseudo (or apparently nonfunctional) genes. Here we review some of the evidence upon which these conclusions rest, and we try to form a coherent picture of gene evolution. The evidence that we shall use is based on studies of the mouse globin. Evidence from various other genetic systems leads us to believe that these genes serve as an instructive general model rather than an idiosyncratic one.

Animals↗

PubMed1980

Mouse globin system: a functional and evolutionary analysis.

Structural and functional analysis of the mouse alpha-globin and beta-globin genes reveals that the globin genes are encoded in discontinous bits of coding information and that each gene locus is much more complex than was originally supposed. Each seems to consist of an array of several authentic genes as well as several apparently inactive pseudogenes. Comparison of the sequences of some of these genes to one another indicates that chromosomal DNA is a dynamic structure. Flanking and intervening sequences change in two ways: quickly, by duplication and extensive insertions and deletions, and slowly, by point mutation. Active coding sequences are usually limited to the slower mode of evolution. In addition to identifying fast and slow modes of evolution, it has also been possible to test the function of several signals that surround these genes and to identify those that appear to play a role in gene expression.

Animals↗