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Biomedical subjects

C M King

Publications and source records attributed to C M King.

At least 109 records · Page 6Linked to original sources
PubMed1988

The endothelium partially obscures enhanced microvessel reactivity in DOCA hypertensive rats.

This study examined the contribution of the endothelium to pressor and depressor responses in the isolated, perfused mesentery of mineralocorticoid hypertensive rats. Following uninephrectomy, adult male rats were made hypertensive by subcutaneous implantation of deoxycorticosterone acetate (DOCA; 200 mg/kg); control rats were sham-treated. All rats received drinking water that contained 1.0% NaCl and 0.2% KCl. Following 4 to 6 weeks of treatment, the rats were anesthetized and the mesenteric vasculature was isolated and pump-perfused (constant flow with buffer) to evaluate changes in perfusion pressure. Vascular responses were determined before and after disruption of endothelial function by perfusion with oxygen free radicals generated in the buffer by electrical stimulation. Vasodilator responsiveness to acetylcholine and nitroprusside in the intact mesentery of hypertensive rats did not differ from that in the intact mesentery of normotensive rats, whereas pressor responses to norepinephrine in the intact mesentery of hypertensive rats were greater than normotensive values. Following disruption of endothelial function, depressor responses to acetylcholine were greatly attenuated whereas those to nitroprusside were unaltered or increased. Pressor responses to norepinephrine were potentiated in mesentery that had undergone endothelial disruption, and this potentiation was greater in hypertensive rats than in control rats. The slopes of pressure-flow curves in the presence of norepinephrine were less steep in mesentery with intact endothelium. The flow-modified component of these pressure-flow curves that was related to the endothelium was greater in mesenteric vascular beds of hypertensive rats. These results indicate that a factor released from the endothelium partially masks the enhanced vascular reactivity characteristic of this animal model of mineralocorticoid hypertension.

Acetylcholine↗
PubMed1988

Metabolism and biological effects of nitropyrene and related compounds.

The aim of this project was to compare the carcinogenicities of 1,3-, 1,6-, and 1,8-dinitropyrene, 1-nitropyrene, and the metabolic phenolic derivatives of 1-nitropyrene. The biochemical goal was to establish how these inert compounds are converted metabolically, by target tissues, to reactive species that can alter the DNA of the susceptible cell. The comparative tumorigenicities were assessed by the use of female CD rats. Control groups consisted of animals that had been given only the solvent, dimethylsulfoxide, which has a low toxicity, to maximize solubility. Equimolar doses (1.7 mumole/ml; 10 mumole/kg body weight) of the compounds were administered to weanling rats by intraperitoneal injection, or by intragastric intubation, three times each week for four weeks, for a total dose of 16 mumoles. Newborn animals were treated by subcutaneous injection of the 1,3-, 1,6-, or 1,8-dinitropyrene or 1-nitropyrene within 24 hours of birth, and at seven weekly intervals, for a total dose of 6.3 mumoles. The possible carcinogenicities of phenolic metabolites of 1-nitropyrene were examined by subcutaneous treatment of newborn animals, and at seven weekly intervals, with 1-nitropyrene, 3-hydroxy-1-nitropyrene, or a mixture of 6-hydroxy-1-nitropyrene and 8-hydroxy-1-nitropyrene (70 mumoles/ml; 100 mumoles/kg body weight; total dose, 63 mumoles). The relative carcinogenicity of 1-nitropyrene in the female Fischer 344 rats was established by the concurrent treatment of appropriate animals. The smaller, inbred Fischer rats received a total dose of 40 mumoles. Subcutaneous and intraperitoneal treatments of weanling female CD rats (70 mumoles/ml; 100 mumoles/kg body weight; 5 weekly injections) with 1-nitropyrene were carried out to explore possible differences because of the different routes of administration in animals of the same age. Dinitropyrenes are much more carcinogenic than 1-nitropyrene (1,6- greater than 1,8- greater than 1,3-dinitropyrene greater than 1-nitropyrene). Phenolic derivatives of 1-nitropyrene are no more carcinogenic than the parent compound. The most likely tumors to be induced in this animal model are malignant fibrous histiocytomas (MFHs), mammary gland tumors, and leukemias. Animals treated with 1,6- or 1,8-dinitropyrene by subcutaneous injection yielded MFHs at the site within 15 weeks of the first injection (i.e., at 15 weeks of age), and this did not permit them to survive more than 20 to 25 weeks. Leukemia developed in these animals within this brief period, but mammary gland tumors were observed only when survival of the animal was not limited by the formation of the more aggressive MFHs.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Evidence for in vitro translesion DNA synthesis past a site-specific aminofluorene adduct.

The ability of Escherichia coli DNA polymerase I and T7 DNA polymerase to bypass bulky C-8 guanyl-2-aminofluorene adducts in DNA was studied by in vitro DNA synthesis reactions on a site-specific aminofluorene-modified M13mp9 template. This site-specifically modified DNA was prepared by ligating an oligonucleotide containing a single aminofluorene adduct into a gapped heteroduplex of M13mp9 DNA (Johnson, D. L., Reid, T. M., Lee, M.-S., King, C. M., and Romano, L. J. (1986) Biochemistry 25, 449-456). The resulting covalently closed duplex DNA molecule was then cleaved with a restriction endonuclease, denatured, and annealed to a primer on the 3' side of the adduct to form a template specifically designed to study bypass. In this system, any synthesis that was not blocked by the bulky aminofluorene adduct would proceed to the 5' terminus of the single-stranded template, while synthesis interrupted by the adduct would terminate at or near the adduct location. We have measured DNA synthesis on this template and find that the amount of radiolabeled nucleotide incorporated by either E. coli DNA polymerase I (large fragment) or T7 DNA polymerase was much greater than would be predicted if the aminofluorene adduct were an absolute block to DNA synthesis. Furthermore, the products of similar reactions electrophoresed on polyacrylamide gels showed conclusively that the majority of the DNA synthesized by either the T7 DNA polymerase or E. coli DNA polymerase I bypassed the aminofluorene lesion. Substitution of Mn2+ for Mg2+ as the divalent cation resulted in even higher levels of translesion synthesis.

2-Acetylaminofluorene↗
PubMed1987

Calcium influx and vascular reactivity in systemic hypertension.

Numerous studies have focused on functional vascular changes that characterize the hypertensive state. Recent evidence that suggests that increased vascular reactivity in hypertension is due to changes in the delivery of activator Ca++ through channels in the cell membrane will be reviewed. The primary evidence supporting this hypothesis comes from studies that characterize the effects of Ca++-free solution and calcium channel blockers on contractile properties of isolated vascular smooth muscle. In the present study, experiments were performed to investigate the role of Ca++ influx in vascular contractions produced by interventions that cause membrane depolarization. Isometric tension development in helical strips of carotid arteries from stroke-prone spontaneously hypertensive rats in response to elevated K+ and tetraethylammonium chloride was greater than that in carotid arteries from Wistar-Kyoto normotensive rats. The rate of tension development to K+-free solution in carotid arteries from stroke-prone spontaneously hypertensive rats was faster than in Wistar-Kyoto normotensive rat arteries. Contractile responses to all 3 depolarizing interventions were reduced in arterial strips incubated in Ca++-free solution containing the chelator ethylene glycol bis-(beta-aminoethyl ether) N,N,N',N'-tetraacetic acid and in arterial strips treated with the Ca++ channel blocker verapamil. These results are consistent with the hypothesis that constrictor stimuli that produce membrane depolarization cause an opening of Ca++ channels in the plasma membrane that are sensitive to the organic channel blockers. Further, a change in Ca++ permeability or membrane depolarizing mechanisms contributes to increased contractile responsiveness in carotid arteries of stroke-prone spontaneously hypertensive rats.

Animals↗
PubMed1987

Chemical stability of oligonucleotides containing the acetylated and deacetylated adducts of the carcinogen N-2-acetylaminofluorene.

We have prepared and characterized the single-stranded oligonucleotide heptamer 5'-ATCCGTC-3' in which the lone guanine of the oligonucleotide is modified at the C8 position with either the acetylated or deacetylated form of the carcinogenic adduct 2-aminofluorene. These two lesions represent the two major adducts formed upon the in vivo administration of the potent experimental carcinogen N-2-acetylaminofluorene. The stability of the adducts was compared by analyzing the oligonucleotide for strand scission or depurination by polyacrylamide gel electrophoresis following treatment under either neutral, acidic or basic conditions or incubation in the presence of piperidine. The results show that both adducts are stable near neutral pH but that the deacetylated adduct is less stable than the acetylated adduct to either basic or acidic conditions. Both adducts are equally susceptible to piperidine. The method of analysis described here could prove useful for characterizing other adduct structures, thus providing a general procedure to determine the stability of a variety of lesions in DNA.

2-Acetylaminofluorene↗
PubMed1987

Free radical-mediated endothelial damage in blood vessels after electrical stimulation.

The endothelium plays an important role in mediating vasodilator effects of several agents (acetylcholine, thrombin, A23187, etc.). The goal of this study was to determine the ability of oxygen free radicals generated by electrical field stimulation to alter endothelial function in isolated tissue systems. Tail artery strips and the mesenteric microvasculature isolated from Sprague-Dawley rats were used. Following smooth muscle contraction induced by norepinephrine, these preparations relaxed in response to acetylcholine chloride or ionophore A23187. All vessels were then subjected to electrical stimulation (9 V, 1-2 ms, 4 Hz) of the physiological buffer in which they were bathed or perfused. In some of these preparations, an antioxidant, (10(-4) M sodium ascorbate, 3.6 X 10(-5) M glutathione, 1.3 X 10(-2) M dimethyl sulfoxide) was included in the buffer. Relaxation responses persisted in vessels where an antioxidant had been included in the electrically stimulated buffer. Tissues stimulated without this protection did not relax on subsequent exposures to endothelium-dependent vasodilators. Scanning-electron microscopy of the tissues revealed significant endothelial damage (cell membrane pitting) in tissues exposed to electrical stimulation without antioxidant protection. These results suggest that electrical stimulation causes endothelial damage in isolated vascular preparations. This seemingly adverse effect proves to be a useful tool for removing the endothelium in studies of isolated vascular tissues.

Acetylcholine↗
PubMed1986

Preparation and characterization of a viral DNA molecule containing a site-specific 2-aminofluorene adduct: a new probe for mutagenesis by carcinogens.

The synthetic oligonucleotide heptamer 5'-ATCCGTC-3' was reacted in vitro with N-acetoxy-N-(trifluoroacetyl)-2-aminofluorene and the resulting product isolated by reverse-phase high-performance liquid chromatography (HPLC). This purified oligonucleotide, which was shown by chemical and enzymatic analysis to be a heptamer containing a single N-(deoxyguanin-8-yl)-2-aminofluorene adduct, was then used to situate the putatively mutagenic aminofluorene lesion within the genome of M13 mp9 by ligating it into a complementary single-stranded region located at a specific site in the negative strand of the duplex M13 mp9 DNA molecule. The presence of the adduct at the anticipated location was confirmed by taking advantage of the facts that AF adducts inhibit many restriction enzymes when located in or near their restriction sites and that the AF moiety should be contained within the HincII recognition sequence on M13 mp9 DNA. Upon attempted cleavage of the M13 DNA containing the site-specific AF adduct with HincII, we find that the large majority of the DNA remained circular, demonstrating the incorporation of the AF adduct in high yield into the DNA molecule at this location. This system should prove useful in vivo for the study of mutagenesis by chemical carcinogens and in vitro to study the interaction of purified DNA metabolizing proteins with a template containing a site-specific lesion.

Base Sequence↗
PubMed1986

Compound allergy to medicaments.

7 patients who reacted on patch testing to medicaments, but who had negative reactions to the individual ingredients are described. The possible mechanisms of this phenomenon are discussed.

Adult↗
PubMed1986

Vasopressin and oxytocin responses to acute and chronic osmotic stimuli in man.

The regulation of both arginine vasopressin (AVP) and oxytocin secretion was studied during rapid and prolonged osmotic stimuli in normal adult volunteers. In five subjects given an intravenous infusion of 0.85 mol NaCl at 0.05 ml/kg per min over 2 h there was a significant (P less than 0.05) rise only in plasma AVP, with no significant change in plasma levels of oxytocin. In six further subjects 5 days of restriction to 500 ml fluid daily resulted in significant increases of both plasma and 24-h urinary AVP, whereas there was no change in corresponding oxytocin levels. During another 5-day period in which the same subjects were given an additional 200 mmol sodium as well as having their fluid intake restricted to 1000 ml daily, there were again significant rises in plasma and 24 h urinary AVP with no change in corresponding oxytocin levels. We conclude that, in man, AVP is selectively secreted in response to both dehydration and high sodium intake, whilst even after the stimulus of rapidly increasing plasma osmolality during intravenous infusion of hypertonic saline the rise in oxytocin is not statistically significant. It therefore appears unlikely that oxytocin has a significant role in the physiological control of fluid balance in man.

Adult↗
PubMed1986

Contact sensitivity to the amide anesthetics lidocaine, prilocaine, and mepivacaine. Case report and review of the literature.

Multiple sensitivities to amide local anesthetics occurred in a 70-year-old woman following dental treatment. Soft-tissue swelling of the cheek was the clinical presentation. Patch testing confirmed type IV hypersensitivity to lidocaine, prilocaine, mepivacaine, and dibucaine. We review the classification of local anesthetics and the literature relating to contact sensitivity to the amide group.

Aged↗
PubMed1985

Metabolism of N-hydroxy-2-acetylaminofluorene and N-hydroxy-phenacetin by guinea pig liver microsomal enzymes.

Deacylation has been proposed as a mechanism of activation of arylhydroxamic acids. In the present studies solubilized preparations from guinea pig liver microsomes, a source of high deacylase activity, were subjected to gel filtration on Sephacryl S-200. A single peak (peak I) of activity was found when column fractions were assayed colorimetrically for deacylation of N-hydroxy-2-acetylaminofluorene (N-OH-AAF). Corresponding to this peak were the following activities: binding of [3H-ring]-N-hydroxy-phenacetin (N-OH-P) to tRNA and deacylation of N-OH-P and N-OH-AAF, measured by the formation of nitrosophenetole (N = O-P) and nitrosofluorene (N = O-F), respectively. The binding of [3H-ring]-N-OH-AAF to tRNA was catalyzed by peak I, but to a greater extent by a second peak (II). The binding of both N-OH-P and N-OH-AAF to tRNA was inhibited by paraoxon, an esterase inhibitor. H.p.l.c. analysis revealed that for peak I, the major ether-extractable metabolites of N-OH-P and N-OH-AAF were the corresponding nitroso derivatives. In the presence of peak II, little metabolism to organic-extractable metabolites occurred. These data indicate that more than one mechanism is involved in the activation of N-OH-P and N-OH-AAF in this system, and that the difference in the activation of these arylhydroxamic acids cannot be explained by differences in the formation of deacylated metabolites.

2-Acetylaminofluorene↗
PubMed1985

Different responses to phenobarbital promotion in the development of gamma-glutamyltranspeptidase-positive foci in the liver of rats initiated with diethylnitrosamine, N-hydroxy-2-acetyl-aminofluorene and aflatoxin B1.

The promoting activities of phenobarbital (PB) on the development of gamma-glutamyl-transpeptidase-positive (gamma-GT+) foci in rat liver with three different initiating agents were compared in a short-term system (8 weeks). Male F344 rats were initiated by a single application of 200 mg/kg of diethylnitrosamine (DEN), 30 mg/kg of N-hydroxy-2-acetylaminofluorene (N-OH-AAF), 1.0 or 0.5 mg/kg of aflatoxin B1 (AFB1) or the vehicles alone. Two weeks after the initiation, animals were placed on a 0.05% PB diet for 6 weeks. Partial hepatectomy was performed at the end of the third week of the experiment. As a positive control, some animals were fed diet containing 0.06% 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) after the initiation. The number and area of gamma-GT+ foci in the liver were quantified. All three initiators showed a summation effect with 3'-Me-DAB on the appearance of gamma-GT+ foci. Promotion by PB, however, was observed only in DEN-initiated rats and not in N-OH-AAF- or AFB1-initiated rats. It is apparent from the present experimental data that the promoting potential of PB on liver carcinogenesis depends on the initiating agent.

Aflatoxin B1↗
PubMed1985

Lichen sclerosus et atrophicus following radiation therapy.

Several years after postmastectomy radiation therapy, lichen sclerosus et atrophicus (LSA) developed in two patients within the radiation fields. This sequence, to our knowledge, has not previously been described. The etiology of LSA is largely unknown, but trauma has been implicated as a provoking factor in some cases, and LSA might be an isomorphic response to the trauma of radiation therapy.

Atrophy↗
PubMed1984

The purification of rat liver arylhydroxamic acid N,O-acyltransferase.

Rat liver arylhydroxamic acid N,O-acyltransferase, a noninducible soluble enzyme that can transform N-hydroxy-N-2-aminofluorenes and N-hydroxy-N-acyl-4-aminobiphenyls into reactive derivatives capable of binding protein and oligonucleotides, has been purified greater than 3000-fold by sequential use of the following methods: homogenization and fractional centrifugation, ammonium sulfate precipitation, chromatography on DEAE-cellulose followed by Sephacryl S-200 filtration, preparative polyacrylamide electrophoresis, and preparative isoelectric focusing. These procedures allowed a 14% recovery of enzyme activity. The molecular weight of the enzyme, as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, is 38,500. The isoelectric point, as determined by preparative and analytical flat-bed isoelectrofocusing, is 4.5; the pH optimum is 7.0. N,O-Acyltransferase showed a Km for N-hydroxy-N-acetyl-2-aminofluorene of 6.3 X 10(-6) M with a Vmax of 10.4 nmol of aminofluorene bound to tRNA/min/mg of protein. Activity was not inhibited by the esterase inhibitor paraoxon. Rat liver N,O-acyltransferase is an enzyme that is very unstable, due in part to labile sulfhydryl groups which easily oxidize in air. The enzyme cannot, however, be fully stabilized with the addition of dithiothreitol.

Acetyltransferases↗
PubMed1984

Mutagenicity of some benzidine congeners and their N-acetylated and N,N'-diacetylated derivatives in different strains of Salmonella typhimurium.

The Ames Salmonella/microsome test was used to compare the mutagenic response of Salmonella typhimurium TA100, TA98, TA1538, and TA1535 to 12 benzidine derivatives, ie, benzidine, 3,3'-dimethoxybenzidine, 3,3'-dimethylbenzidine, 3,3'-dichlorobenzidine, and the corresponding N- and N,N'-diacetylated derivatives. With a few exceptions, the mutagenic response to this series of compounds varied in the order TA98 greater than TA1538 greater than TA100 greater than TA1535 = 0, and the N-monoacetylated derivatives were more mutagenic than either the parent diamines or the N,N'-diacetyl derivatives. The relative mutagenicities of the parent amines for TA98 were 3,3'-dichlorobenzidine much greater than 3,3'-dimethoxybenzidine greater than benzidine greater than 3,3'-dimethylbenzidine.

Benzidines↗