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D F Hill

Publications and source records attributed to D F Hill.

83 records · Page 5Linked to original sources
PubMed1977

Automated sequencing of insoluble peptides using detergent. Bacteriophage fl coat protein.

Peptides which are highly nonpolar and insoluble under moderate conditions of pH and ionic strength cannot be subjected to automated sequence analysis. We report a method for solubilization of one such peptide, bacteriophage fl coat protein, by chemical modification in the presence of sodium dodecyl sulfate. Following this treatment the 50-residue peptide was degraded stepwise in an automated sequenator using a single cleavage Quadrol program with high repetitive yield through residue 47. We also report a modified program using detergent incorporated into dimethylallylamine buffer which permitted sequencing with high repetitive yields for at least the first 18 residues of the unmodified and otherwise highly insoluble coat protein. The presence of detergent caused no observable difficulties in detection of residues by gas chromatography, thin layer chromatography, or amino acid analysis.

Amino Acid Sequence↗
PubMed1975

Interactions between lysergic acid diethylamide and dopamine-sensitive adenylate cyclase systems in rat brain.

Investigations were carried out on the interactions of the hallucinogenic drug, D-lysergic acid diethylamide (D-LSD), and other serotonin antagonists with catecholamine-sensitive adenylate cyclase systems in cell-free preparations from different regions of rat brain. In equimolar concentration, D-LSD, 2-brono-D-lysergic acid diethylamide (BOL), or methysergide (UML) strongly blocked maximal stimulation of adenylate cyclase activity by either norepinephrine or dopamine in particulate preparations from cerebral cortices of young adult rats. D-LSD also eliminated the stimulation of adenylate cyclase activity of equimolar concentrations of norepinephrine or dopamine in particulate preparations from rat hippocampus. The effects of this hallucinogenic agent on adenylate cyclase activity were most striking in particulate preparations from corpus striatum. Thus, in 10 muM concentration, D-LSD not only completely eradicated the response to 10 muM dopamine in these preparations but also consistently stimulated adenylate cyclase activity. L-LSD (80 muM) was without effect. Significant activation of striatal adenylate cyclase was produced by 0.1 muM D-LSD. Activation of striatal adenylate cyclase of either D-LSD or dopamine was strongly blocked by the dopamine-blocking agents trifluoperazine, thioridazine, chlorpromazine, and haloperidol. The stimulatory effects of D-LSD and dopamine were also inhibited by the serotonin-blocking agents, BOL, 1-methyl-D-lysergic acid diethylamide (MLD), and cyproheptadine, but not by the beta-adrenergic-blocking agent, propranolol. However, these serotonin antagonists by themselves were incapable of stimulating adenylate cyclase activity in the striatal preparations. Several other hallucinogens, which were structurally related to serotonin, were also inactive in this regard, e.g., mescaline, N,N-dimethyltryptamine, psilocin and bufotenine. Serotonin itself produced a small stimulation of adenylate cyclase activity in striatal preparations and, in relatively high concentration (100 muM), partially blocked the activation by 10 muM dopamine, but was without effect on the stimulation by 10 muM D-LSD. The present results indicate that serotonin antagonists, in general, are potent inhibitors of catecholamine-induced stimulation of adenylate cyclase systems in brain cell-free preparations. In addition, these results, coupled with earlier findings on the capacity of D-LSD to interact with serotonin-sensitive adenylate cyclase systems from rat brain23,24 and other neural systems16, strongly suggest that this hallucinogenic agent is capable of acting as an agonist at central dopamine and serotonin receptors, as well as functioning as an antagonist at dopamine, norepinephrine, and serotonin receptors in the brain.

Adenylyl Cyclases↗
PubMed1975

Serotonin-sensitive adenylate cyclase activity of immature rat brain.

Cell-free preparations from superior and inferior colliculi of very young rats (1-3 days old) contained adenylate cyclase systems which were highly responsive to serotonin. The response to serotonin declined markedly during early development and was very low at maturity. Adenylate cyclase activity in the 10,000 times g particulate fraction from colliculi of newborn rats was significantly stimulated by 0.05 muM serotonin. Half-maximal activation was produced with less than 1 muM serotonin. Maximal stimulation of collicular adenylate cyclase was about 80% above basal enzyme activity and occurred with approximately 50 muM serotonin. Tryptamine and several derivatives of serotonin produced responses which were comparable to that obtained with serotonin; 5-methoxytryptamine was uniformly the most active compound tested. Norepinephrine or dopamine produced much smaller increases in adenylate cyclase activity. Stimulation of collicular adenylate cyclase by serotonin was significantly but incompletely blocked by serotonin antagonists, including d-lysergic acid diethylamide (d-LSD), 2-bromo-d-lysergic acid diethylamide, methysergide, 1-methyl-8 beta-carbobenzyloxy-aminomethyl-10 alpha-ergoline and cyproheptadine. Chlorpromazine also produced partial blockade. In contrast, l-lysergic acid diethylamide, haloperidol, propranolol, phenoxybenzamine and morphine were ineffective as serotonin blocking agents. Of the compounds which produced a partial blockage of serotonin action, d-LSD, cyproheptadine and chlorpromazine were themselves capable of stimulating adenylate cyclase activity. These results are consisent with the existence of multiple receptors in rat brain which are capable of interacting with indoleamines.

5-Hydroxytryptophan↗
PubMed1971

The lysosomal membrane complex. Focal point of primary steroid hormone action.

At short intervals after the intravenous administration of oestradiol-17beta, diethylstilboestrol, testosterone or saline control solution to ovariectomized rats, highly purified lysosome samples were prepared in substantial yield from preputial glands, sex accessory organs rich in these organelles. The preparations were essentially devoid of mitochondrial contamination. Exposure in vivo to doses of these hormones varying from 0.1 to 5mug/100g body wt. provoked dose-dependent labilization of the lysosomal membrane surface, as evidenced by significantly diminished structural latency of several characteristic acid hydrolases, including acid phosphatase, beta-glucuronidase and acid ribonuclease II, when such preparations were subsequently challenged in vitro with autolytic conditions, detergent or mechanical stress. Enhanced lytic susceptibility induced by hormone pretreatment was occasionally detectable in the initial preparation without further provocative stimuli in vitro. Comparable results were obtained with the corresponding fractions of uterus, despite the more limited concentration of lysosomes in this steroidal target organ. By the present criteria oestradiol-17alpha was essentially inert, even in a dose 25 times that effective for its active beta-epimer (<0.1mug/100g body wt.). Pretreatment with diethylstilboestrol exerted substantial membrane-destabilizing influence in preputial-gland lysosome samples from orchidectomized rats. Moreover, administration of testosterone to gonadectomized animals resulted in essentially equivalent dose-dependent augmentation of lysosomal enzyme release in preputial-gland preparations of either sex. The membrane stability of lysosome-enriched preparations from uterus, on the other hand, was unaffected by testosterone pretreatment. The sensitivity, specificity and selectivity of the lysosomal response to sex steroids provide evidence for the physiological significance of this phenomenon as a general mechanism for mediation of secondary biochemical transformations in the hormone-stimulated target cell.

Acid Phosphatase↗
PubMedDate not supplied

Mapping the sheep genome: practice, progress and promise.

Over 100 loci have now been mapped on the sheep genome, double that of 3 years ago. Achieved through converging developments in DNA technologies and genetics, this rate of gene mapping is increasing. Its goal is to identify genes for important traits. This will elucidate the biological basis of these traits, paving the way for their manipulation, and accelerate the genetic improvement of sheep and quality of their products by marker-assisted selection. The aim of this review is to provide an introduction to the strategies and methods of gene mapping, highlighting the value of comparative genome analysis. These themes are then elaborated in the description of the ongoing project to map the sheep genome. Opportunities are discussed for the application of the fruits of this research to the understanding and treatment of diseases, and to the development of tools for the genetic improvement of sheep by marker-assisted selection.

Animals↗
PubMedDate not supplied

EPA's GLP compliance review of chemistry laboratories.

The Good Laboratory Practice (GLP) Standards regulations do not provide specific requirements for the operation of a specimen analysis laboratory, such as a testing facility that performs pesticide residue analysis in support of a tolerance study. Thus, some judgment must be applied by a regulated analytical laboratory to assure compliance with GLP Standards regulations that were designed primarily for testing facilities that apply test substances to test systems. This presentation will provide some insight as to EPA's compliance approach, as well as identifying problem areas encountered in past inspections of analytical laboratories.

Chemistry Techniques, Analytical↗