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Biomedical subjects

D E Ryan

Publications and source records attributed to D E Ryan.

At least 109 records · Page 6Linked to original sources
PubMed1982

Purification, characterization and regulation of five rat hepatic microsomal cytochrome P-450 isozymes.

1. Five hepatic microsomal cytochrome P-450 isozymes (cytochromes P-450a, P-450b, P-450c, P-450d, P-450e) have been purified to apparent homogeneity from immature male rats treated with various xenobiotics. 2. The unique electrophoretic properties, substrate specificities and spectral characteristics of these haemoproteins have been compared and contrasted. 3. Structural studies of these cytochrome P-450 isozymes have included NH2-terminal amino acid sequence analyses, as well as electrophoretic profiles of limited proteolytic digests and cyanogen bromide fragments of the haemoproteins. 4. Specific antibodies have been prepared against four of the isozymes and used to evaluate immunochemical relationships among these cytochrome P-450s by Ouchterlony double-diffusion analyses. 5. The levels of some of these cytochrome P-450 isozymes have been quantified immunologically in hepatic microsomal preparations from untreated rats and following induction by phenobarbital, 3-methylcholanthrene or Aroclor 1254. 6. Antibodies directed against cytochromes P-450a and P-450b have been used to establish the presence of more than one 7 alpha- and 16 alpha-testosterone hydroxylase in rat hepatic microsomes. The relative contributions of cytochromes P-450c and P-450d to the overall microsomal metabolism of benzo[a]pyrene have been evaluated using antibodies to these haemoproteins.

Amino Acid Sequence↗
PubMed1982

Human liver microsomal epoxide hydrolase. Correlation of immunochemical quantitation with catalytic activity.

Human liver microsomal epoxide hydrolase was purified to apparent homogeneity as judged by a single protein-staining band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Sheep antibody to human liver epoxide hydrolase reacted with the enzyme in detergent-solubilized human liver microsomes, giving a single immunoprecipitin band which formed a line of identity with the pure human enzyme. Antibody against the human enzyme reacted well with epoxide hydrolase in detergent-solubilized monkey liver microsomes by the Ouchterlony test but less strongly cross-reacted with the enzyme from rat liver and several other species. The antibody produced against purified human liver epoxide hydrolase precipitated the enzyme but did not inhibit catalytic activity, reminiscent of the relationship of rat liver epoxide hydrolase to its antibody. The absolute level of epoxide hydrolase in liver microsomal samples from 11 human subjects, as measured by a radial immunodiffusion assay, varied 3.4-fold whereas the rate of hydration of octene oxide varied 2.9-fold. The excellent correlation of the amounts of epoxide hydrolase determined catalytically or immunochemically (r = 0.99) indicated that interindividual variation in octene oxide hydration rates by human liver microsomes is a consequence of differences in amount of epoxide hydrolase protein which is present, and not the result of differences in levels of endogenous modulators of catalytic activity.

Epoxide Hydrolases↗
PubMed1981

Regulation of three forms of cytochrome P-450 and epoxide hydrolase in rat liver microsomes. Effects of age, sex, and induction.

A procedure for the preparation of monospecific antibody directed against rat liver microsomal cytochrome P-45-a is described. This antibody, together with monospecific antibodies to cytochromes P-450b and P-450c, has been used to show that these three forms of cytochrome P-450 are distinct and share no common antigenic determinants. These antibodies (a) give single immunoprecipitin bands with detergent-solubilized microsomes; (b) do not cross-react with the purified heterologous antigens in Ouchterlony double diffusion analyses; (c) have no effect on catalytic activity of the heterologous antigens but completely inhibit the enzymatic activity of the homologous antigens; and (d) remove only the homologous antigen from detergent-solubilized microsomes when covalently bound to a solid support. With radial immunodiffusion assay, we have quantitated these three forms of cytochrome P-450 in liver microsomes after treatment of rats with seven different inducers of cytochrome P-450. The levels of these cytochrome P-450 isozymes vary independently and are also regulated by the age and sex of the animal. The antibodies have also been used to assess the contribution of cytochromes P-450a, P-450b, and P-450c in the metabolism of xenobiotics by rat liver microsomes. A large proportion of benzo(a)pyrene metabolism and testosterone 16 alpha-hydroxylation in microsomes from untreated rats is not catalyzed by cytochromes P-450a, P-450b, and P-450c. Epoxide hydrolase, another microsomal enzyme involved in the metabolism of xenobiotics, was also quantitated by radial immunodiffusion after prior treatment of rats with microsomal enzyme inducers. The inductions of epoxide hydrolase varies independently of the induction of cytochromes P-450a, P-450b, and P-450c.

Aging↗
PubMed1981

Administration of 3-methylcholanthrene to rats increases the specific hybridizable mRNA coding for cytochrome P-450c.

Poly(A)+-RNA obtained from the livers of 3-methylcholanthrene (3MC)-treated rats was translated into cytochrome P-450c in a cell-free reticulocyte system. In this translational system, no precursor cytochrome P-450c was observed. The mRNA responsible for the synthesis of this cytochrome was isolated by immunoprecipitation of liver polyribosomes obtained at 15 hr after 3MC treatment, and a cDNA was constructed by the reverse transcriptase reaction. The cDNA was further purified by hybridizing at a high R0t (product of RNA concentration and incubation time) to poly(A)+-RNA isolated from control rat liver, and the nonhybridized, single-stranded cDNA was isolated by hydroxylapatite chromatography. This cDNAp-450c was employed in hybridization reactions with poly(A)+-RNA isolated from the livers of rats treated with 3MC for various times. These studies indicated a maximal induction of mRNAp-450c at about 15 hr after 3MC injection, although levels of this mRNA were significantly increased by 7 hr. The mRNAp-450c concentration had diminished by 24 hr but remained higher than control levels for at least 48 hr. These studies establish an effect of 3MC upon the accumulation of mRNAp-450c in rat liver.

Animals↗
PubMed1981

Internal derangements of the temporomandibular joint: correlation of arthrography with surgical findings.

The diagnosis of dysfunctional temporomandibular joint (TMJ) disorders unresponsive to nonsurgical treatments heretofore has often been empirical. With the development of TMJ arthrography, diagnosis has been greatly improved; an accurate picture of the condition of the joint now provides a substantial base on which to build a rational and reasonable treatment plan. Clinical symptoms can be accurately correlated with the radiographic picture, a valid surgical procedure can be performed because the joint condition is known, and a meaningful prognosis can be determined. Successful management, however, very often requires multifaceted treatment consisting not only of surgery but also of bite-plate, occlusal, restorative, and physical therapy, both preoperatively and postoperatively.

Cartilage, Articular↗
PubMed1981

Mutagenicity of the bay-region diol-epoxides and other benzo-ring derivatives of dibenzo(a,h)pyrene and dibenzo(a,i)pyrene.

The mutagenic activities of dibenzo(a,h)(pyrene, dibenzo(a,i)pyrene, and a total of 11 of their benzo-ring derivatives were evaluated in bacterial and mammalian cells in the absence or presence of a mammalian metabolic activation system. trans-1,2-Dihydroxy-1,2-dihydrodibenzo(a,h)pyrene and trans-3,4-dihydroxy-3,4-dihydrodibenzo(a,i)pyrene, the expected dihydrodiol precursors of bay-region diol-epoxides, were metabolized to products which were more mutagenic to strains TA98 and TA100 of Salmonella typhimurium than were the metabolic products formed from their respective parent hydrocarbons. For each dihydrodiol, replacement of the benzo-ring double bond adjacent to the diol moiety with a single bond resulted in tetrahydrodiol derivatives which could not be metabolically activated, suggesting that one or both diastereomeric bay-region diol-epoxides were the bioactivated metabolites. The authentic bay-region diol-epoxide diastereomers of dibenzo(a,h)pyrene and dibenzo(a,i)pyrene in which the benzylic hydroxyl group and the epoxide oxygen are trans (diol-epoxide 2 series) were highly mutagenic in strains TA98 and TA100 of S. typhimurium and in cultured Chinese hamster V79 cells. Neither diol-epoxide was significantly, if at all, metabolized by epoxide hydrolase. The bay-region diol-epoxide of dibenzo(a,i)pyrene was from 1.5 to 5 times more active as a mutagen than the diol-epoxide of dibenzo(a,h)pyrene, and in strain TA98 of S. typhimurium as well as Chinese hamster V79 cells, it had activity comparable to that of the highly carcinogenic bay-region diol-epoxide of benzo(a)pyrene.

Animals↗
PubMed1980

The rapid determination of total bromine and iodine in biological fluids by neutron activation.

Total bromine and iodine are instrumentally determined in 1 mL samples of body fluids by neutron activation under a boron shield at normal concentration levels. No sample treatment is necessary. Bromine is determined by its 80Br nuclide (617.0 keV; T1/2 = 18.0 min) and iodine by its 128I nuclide (442.7 keV;T1/2 = 25.0 min). The method is rapid; four bromine and two iodine determinations can be done in one hour. Bromine and iodine can be detected down to 14 micrograms/dL (1.75 mumol/L) and 2.9 micrograms/dL (0.23 mumol/L), respectively.

Boron↗
PubMed1980

Cardiopulmonary resuscitation: a teaching aid.

Laboratory dogs are used to demonstrate and practice cardiopulmonary resuscitation (CPR) procedures. Cardiovascular collapse, cardiac arrest, and ventricular fibrillation are produced in anesthesized dogs and then managed by the student. The laboratory exercise focuses and emphasizes CPR material taught in the classroom and on mannequins. With the current emphasis on CPR training and certification, we recommend the concept to the dental profession as an added dimension in teaching CPR.

Animals↗
PubMed1980

Mutagenicity and tumor-initiating activity of cyclopenta(c,d)pyrene and structurally related compounds.

The biological activities of benzo(a)pyrene, cyclopenta(c,d)pyrene, and 12 other structurally related compounds were assessed by mutagenicity studies with bacterial and mammalian cells and/or skin tumorigenicity studies with mice. The ability of the parent hydrocarbons to be metabolically activated to mutagenic products was examined in strains TA98 and TA100 of Salmonella typhimurium, using 3 experimental protocols. In each case, cyclopenta(c,d)pyrene was metabolically activated to products mutagenic to the bacteria to a greater extent than was benzo(a)pyrene. However, 7,8-dihydrobenzo(a)pyrene and 0,10-dihydrobenzo(e)pyrene were the best substrates for metabolic activation to bacterial mutagens. Highly purified epoxide hydrase added to a purified and reconstituted monooxygenase system readily abolished the mutagenic activity observed in strain TA100 of S. typhimurium when cyclopenta(c,d)pyrene was the substrate, but not when benzo(a)pyrene was the substrate. Inherent mutagenicity of several epoxides of the hydrocarbons generally paralleled the ability of their potential metabolic precursors to be activated to mutagens. 1-Pyrenyloxirane and 10,11-dihydrocycloheptapyrene 8,9-oxide were highly mutagenic in strains TA98 and TA100 of S. typhimurium, and in the former strain these activities were comparable to that observed with 9,10-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene, 4-Pyrenyloxirane was significantly less mutagenic than was 1-pyrenyloxirane in both strains of bacteria and in mammalian cells. Benzo(a)pyrene was over 20 times more tumorigenic than was cyclopenta-(c,d)pyrene, and it was the most potent of the 11 compounds tested for tumor-initiating activity in 2-stage initiation-promotion experiments on the skin of mice. Cyclopenta(c,d)pyrene had tumor-initiating activity comparable to that of benzo-(a)anthracene, but it was significantly less active than chrysene. Thus, contrary to inferences made from its high mutagenic activity, cyclopenta(c,d)pyrene is a weak tumor initiator on mouse skin.

Animals↗