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Biomedical subjects

M V Martin

Publications and source records attributed to M V Martin.

At least 91 records · Page 5Linked to original sources
PubMed1992

The role of oral microorganisms in cancer therapy.

It has been assumed that the principal changes that occur in the oral flora during cancer therapy are yeast and gram-positive coccal proliferation. Recent studies have shown that treatment with topical antifungals or disinfectants has failed to relieve such complications as irradiation mucositis that occur during anticancer therapy. Thus, many of the oral lesions observed during treatment are not due to candidiasis or streptococcal infection. It has been shown that anticancer therapy impairs or reduces the carriage defense of the oropharynx and is accompanied by colonization and proliferation of gram-negative bacilli. It is argued that if oral infectious complications are to be prevented during anticancer therapy, then the selective elimination of gram-negative bacilli may be indicated.

Antineoplastic Agents↗
PubMed1991

The use of antibiotics in the prevention of post-operative infection: a re-appraisal.

The use of antibiotics to prevent infection is a contentious issue in all surgical specialties. Ideally, antibiotic administration should reduce morbidity and mortality. In reality, they may cause drug interactions, allergic and other untoward reactions, and reduce colonisation resistance; this can result in infections with resistant microorganisms. Therefore, when used injudiciously, the patient may suffer more than if antibiotics had not been prescribed. The most effective use of prophylactic antibiotics has been shown to be in short term, high dosage regimens that are active against the common pathogens. To achieve any protective effect, antibiotics must be administered pre-operatively to provide adequate tissue concentrations at the time of surgery.

Anti-Bacterial Agents↗
PubMed1991

Prophylactic antibiotics for patients with artificial joints undergoing oral and dental surgery: necessary or not?

Prophylactic antibiotic cover for certain oral and dental procedures for patients with artificial joints is a controversial issue. This paper examines the evidence supporting the use of antibiotic cover and concludes that routinely, for the majority of patients with artificial joints, it is not justified. Certain medically compromised patients with artificial joints have a slightly increased risk of infection and, under these circumstances, antibiotic prophylaxis may be justified. The antibiotic recommended for this group is cephradine or in the case of penicillin allergy, clindamycin. Preoperative dental fitness is mandatory for all patients who are to receive artificial joints. This information will be of interest to the oral and maxillofacial surgeon in his own clinical practice, and when giving advice to local general dental practitioners.

Anti-Bacterial Agents↗
PubMed1991

Antibiotic-resistant oral streptococci in dental patients susceptible to infective endocarditis.

The aim of this study was to determine the incidence of amoxycillin and erythromycin resistance in oral streptococci in patients at risk from infective endocarditis. Samples of gingival crevicular flora were taken from 65 patients at the site of dental treatment, prior to the prophylactic administration of amoxycillin (54 patients) or erythromycin (11 patients). Samples were also taken from 65 dental patients who were not considered to be at risk from infective endocarditis. No isolate had a minimum inhibitory concentration (MIC) of amoxycillin greater than 24 mg/L. However, erythromycin-resistant oral streptococci with MIC values greater than 3.5 mg/L were isolated from 22% of patients receiving amoxycillin prophylaxis, 9% of patients receiving amoxycillin prophylaxis, 9% of patients given erythromycin prophylaxis and 9% of patients not at risk from infective endocarditis. The antibiotic-resistant streptococci comprised mainly Streptococcus sanguis biotype II, although S. sanguis biotype I, S. mitis and S. salivarius were also frequently recovered.

Amoxicillin↗
PubMed1990

Cytochrome P-450 enzyme-specific control of the regio- and enantiofacial selectivity of the microsomal arachidonic acid epoxygenase.

Chiral analysis of the rat liver microsomal arachidonic acid epoxygenase metabolites shows enantioselective formation of 8,9-, 11,12-, and 14,15-cis-epoxyeicosatrienoic acids in an approximately 2:1, 4:1, and 2:1 ratio of antipodes, respectively. Animal treatment with the cytochrome P-450 inducer phenobarbital increased the overall enantiofacial selectivity of the microsomal epoxygenase and caused a concomitant inversion in the absolute configurations of its metabolites. These effects of phenobarbital were time-dependent and temporally linked to increases in the concentration of microsomal cytochrome P-450 enzymes. Reconstitution of the epoxygenase reaction utilizing several purified cytochrome P-450 demonstrated that the asymmetry of epoxidation is under cytochrome P-450 enzyme control. These results established that the chirality of the hepatic arachidonic acid epoxygenase is under regulatory control and confirm cytochromes P-450 IIB1 and IIB2 as two of the endogenous epoxygenases induced in vivo by phenobarbital.

8,11,14-Eicosatrienoic Acid↗
PubMed1990

Cytochrome P-450-dependent oxidation of arachidonic acid to 16-, 17-, and 18-hydroxyeicosatetraenoic acids.

Incubation of rat liver microsomal fractions with arachidonic acid in the presence of NADPH results in the formation of three novel monohydroxylated fatty acid metabolites. Utilizing chromatographic and mass spectral techniques, these metabolites have been identified as 16-, 17-, and 18-hydroxyeicosatetraenoic acids. The NADPH-dependent microsomal metabolism of arachidonic acid to 16-, 17-, 18-, and 19-hydroxyeicosatetraenoic acids is induced after animal treatment with beta-naphthoflavone. Reconstitution of the arachidonic acid oxygenase utilizing individual purified cytochrome P-450 enzymes demonstrates regioselectivity, controlled by the protein catalyst, for the hydroxylation of the sp3 carbon atoms adjacent to the methyl end of the fatty acid.

Animals↗
PubMed1990

In situ localization and distribution of xenobiotic-activating enzymes and aryl hydrocarbon hydroxylase activity in lungs of untreated rats.

The present investigation was undertaken to more precisely establish where xenobiotics can be oxidatively metabolized and bioactivated within the lung. To accomplish this, antibodies raised against NADPH-cytochrome P-450 reductase (EC 1.6.2.4) and cytochromes P-450 BNF-B, PB-B, and PCN-E (the major forms of cytochrome P-450 induced by beta-naphthoflavone, phenobarbital, and pregnenolone-16 alpha-carbonitrile, respectively) that had been purified to apparent homogeneity from rat liver microsomes were used to determine the localizations and distributions of these enzymes immunohistochemically at the light microscopic level within lungs of untreated rats. Additionally, the intrapulmonary sites at which benzo(alpha)pyrene undergoes hydroxylation were identified in situ by means of fluorescence histochemistry. Immunohistochemical staining for NADPH-cytochrome P-450 reductase and cytochromes P-450 BNF-B, PB-B, and PCN-E was detected in bronchial epithelial cells, both ciliated and nonciliated (Clara) bronchiolar epithelial cells, and type II pneumocytes as well as other cells in the alveolar wall. Results of microfluorometric analyses of the immunofluorescence staining intensities of bronchial epithelial cells, Clara cells, and type II pneumocytes demonstrated further that Clara cells bound the antibodies raised to NADPH-cytochrome P-450 reductase and cytochrome P-450 PB-B to significantly greater extents than did bronchial epithelial cells and type II pneumocytes. Thus, in lungs of untreated rats, Clara cells contain the greatest amounts of these two enzymes. In marked contrast, the antibodies directed against cytochromes P-450 BNF-B and PCN-E were each bound to similar extents by bronchial epithelial cells, Clara cells, and type II pneumocytes. In agreement with immunohistochemical observations on the intrapulmonary localizations of NADPH-cytochrome P-450 reductase and cytochromes P-450 BNF-B, PB-B, and PCN-E in untreated rats, benzo(alpha)pyrene was hydroxylated in situ by bronchial and bronchiolar epithelial cells and alveolar wall cells, especially type II pneumocytes. These immunohistochemical and histochemical findings, thus, demonstrate that bronchial epithelial cells, Clara and ciliated bronchiolar epithelial cells, and type II pneumocytes as well as other alveolar wall cells represent sites for the in vivo oxidative metabolism and bioactivation of xenobiotics in lungs of untreated rats.

Animals↗
PubMed1989

Roles of individual human cytochrome P-450 enzymes in the bioactivation of benzo(a)pyrene, 7,8-dihydroxy-7,8-dihydrobenzo(a)pyrene, and other dihydrodiol derivatives of polycyclic aromatic hydrocarbons.

Human liver microsomes oxidized 7,8-dihydroxy-7,8-dihydrobenzo(a)pyrene [B(a)P-7,8-diol] to products that yield DNA adduct formation and umu gene expression in the tester system Salmonella typhimurium TA1535/pSK1002. The umu response is correlated to levels of microsomal cytochrome P-450NF (P-450NF) and nifedipine oxidation in different human liver samples used for activation, and both the (+)- and (-)-enantiomers of B(a)P-7,8-diol gave similar results in these and other assays. The microsomal umu response was inhibited by antibodies raised against P-450NF. 7,8-Benzoflavone stimulated the B(a)P-7,8-diol-dependent umu response observed with purified P-450NF and human liver and lung microsomes. Thus, P-450NF appears to be the major enzyme involved in the activation of B(a)P-7,8-diol in human liver and possibly lung. Similar results were obtained for the activation of trans-9,10-dihydroxy-9,10-dihydrobenzo(b)fluoranthene and trans-3,4-dihydroxy-3,4-dihydro-7,12-dimethylbenz(a)anthracene, compounds that are known to form highly tumorigenic diol-epoxides. The major product of the oxidation of (+)-B(a)P-7,8-diol was the cis-syn isomer of benzo(a)pyrene-7,8,9,10-tetraol[7 beta, 8 alpha, 9 beta, 10 beta-tetrahydroxy-7,8,9,10-tetrahydrobenzo(a)pyrene]. Studies on the nature of the human liver enzymes involved in the formation of B(a)P-7,8-diol [from benzo(a)pyrene] indicate that neither P-450NF, P-450PA, P-450j, P-450DB, nor P-450MP is involved. The correlation of 7,8-diol formation with phenacetin O-deethylation in a set of liver samples and the partial inhibition of the reaction by 7,8-benzoflavone and anti-rat P-450 beta NF-B suggest that the enzyme involved may be P1-450, the human ortholog of rat P-450 beta NF-B, which catalyzes both the formation of B(a)P-7,8-diol and its subsequent oxidation in tissues of polycyclic hydrocarbon-treated rats. The differential effects of inhibitors indicate that benzo(a)pyrene 3-hydroxylation, 4,5-epoxidation, and 9,10-epoxidation are catalyzed by an enzyme(s) distinct from that which forms the 7,8-epoxide. The roles of the human P-450 enzymes differ from the rodent orthologs in the paradigm for bioactivation of polycyclic hydrocarbons; further, flavones appear to have opposing effects on diol formation and further epoxidation in both human liver and lung.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1989

Human liver microsomal cytochrome P-450 enzymes involved in the bioactivation of procarcinogens detected by umu gene response in Salmonella typhimurium TA 1535/pSK1002.

A total of 57 procarcinogens was examined for induction of umu gene response in the chimeric plasmid pSK1002, carried in Salmonella typhimurium TA 1535, after incubation with a series of human liver microsomal preparations which had been selected on the basis of characteristic levels of individual cytochrome P-450 (P-450) enzymes. The 18 most active compounds were selected and further analyzed using the umu gene response and correlative studies with a larger number of microsomal preparations, enzyme reconstitution studies involving purified enzymes, immunochemical inhibition, and patterns of stimulation and inhibition of catalytic activity by 7,8-benzoflavone. The results collectively indicate that 16 of these 18 most potent genotoxins examined are activated primarily either by P-450NF (the nifedipine oxidase) or P-450PA (the phenacetin O-deethylase). P-450NF appears to be the major enzyme involved in the bioactivation of aflatoxin B1, aflatoxin G1, sterigmatocystin, trans-7,8-dihydroxy-7,8-dihydrobenzo(a)pyrene, 6-aminochrysene, and tris-(2,3-dibromopropyl)phosphate in human liver. P-450PA appears to be the major enzyme involved in the bioactivation of 2-amino-3-methylimidazo[4,5-f]quinoline, 2-amino-3,5-dimethylimidazo[4, 5-f]quinoline, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, 2-aminoanthracene, 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole, 2-aminofluorene, 2-acetylaminofluorene, 4-aminobiphenyl, 3-amino-1-methyl-5H-pyrido[4,3-b] indole, and 2-aminodipyrido[1,2-a:3',2'-d]imidazole. More than one enzyme appears to contribute significantly to the bioactivation of the other two compounds examined, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b] indole and 6-nitrochrysene. The literature suggests that the two human liver P-450s involved in activation of these 16 procarcinogens are highly inducible by barbiturates, macrolide antibodies, and certain steroids (P-450NF) and by smoking and ingestion of charcoal-containing food (P-450PA); noninvasive assays are available to monitor the function of both P-450NF and P-450PA.

Animals↗
PubMed1989

A study of the use of autoclave bags in non-vacuum autoclaves.

Two types of autoclave bags have been tested in five commonly used dental, non-vacuum autoclaves. The bags did not prevent the sterilization of instruments provided that most of the air was removed and the bags of instruments were not stacked. The use of a sterilization indicator in the bag is mandatory.

Dental Instruments↗
PubMed1989

A comparison of fluconazole and ketoconazole in the treatment of rat palatal candidosis.

The efficacy of fluconazole and ketoconazole in the treatment of rat palatal candidosis has been investigated. To induce oral candidosis, the palatal tissues of Wistar rats were inoculated with Candida albicans NCPF 3091 and covered with acrylic plates. The rats were treated with either fluconazole or ketoconazole by intragastric gavage for 14 days. Palatal epithelial thickness, the number of yeasts present and the histopathological appearance of the tissue were assessed to compare treatment with the two azoles. A fluconazole dose of 0.75 mg kg-1 body weight once daily for 14 days was required to cure the palatal candidosis and prevent recrudescence, whereas with ketoconazole a dose of 7.0 mg kg-1 body weight was necessary to achieve the same effect. From these results it is concluded that fluconazole is effective at a dose nine times lower than ketoconazole in resolving rat palatal candidosis.

Animals↗
PubMed1989

Does Candida have a role in oral epithelial neoplasia?

Candida species are responsible for a wide variety of superficial infections of man [59] and the pathogenic role of these yeasts in many conditions has now been defined. There is, however, a great deal of controversy concerning the role of Candida species in the development of epithelial neoplasia. Vaginal and cutaneous candidosis are relatively common but there is little firm clinical or epidemiological evidence to link them to cervical neoplasia or skin carcinoma [59]. The converse is true however for oral candidosis where chronic Candida infection and neoplasia have been strongly linked. The aim of this review is to explore and evaluate the experimental and epidemiological evidence supporting an association between Candida species and oral neoplasia.

Animals↗