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M George

Publications and source records attributed to M George.

At least 73 records · Page 4Linked to original sources
PubMed1998

Metabolic activation of racemic and enantiomeric trans-8, 9-dihydroxy-8,9-dihydrodibenzo[a,l]pyrene (dibenzo[def,p]chrysene) to dibenzo[a,l]pyrene-bis-dihydrodiols by induced rat liver microsomes and a recombinant human P450 1A1 system: the role of the K-region-derived metabolic intermediates in the formation of dibenzo[a,l]pyrene-DNA adducts.

Metabolic activation studies of dibenzo[a,l]pyrene (DB[a,l]P) (dibenzo[def,p]chrysene), an extremely potent environmental carcinogen, have been focused on metabolism at the fjord region, a region associated with high mutagenic and carcinogenic activities of the corresponding fjord-region DB[a,l]P-11,12-diol-13,14-epoxides. DB[a,l]P is metabolized by beta-naphthoflavone (BNF)- and 3-methylcholanthrene-induced rat liver microsomes and a recombinant human P450 1A1 system to two major dihydrodiols, the K-region dihydrodiol, DB[a,l]P-8,9-dihydrodiol (DB[a,l]P-8,9-diol), and the fjord-region dihydrodiol, DB[a,l]P-11,12-dihydrodiol. We have investigated the further metabolic activation of DB[a,l]P-8,9-diol by BNF-induced rat liver microsomes and a recombinant human P450 1A1 system with epoxide hydrolase to DB[a,l]P-bis-diols and to DNA adducts. (+/-)-trans-DB[a,l]P-8,9-diol was synthesized and resolved into its enantiomers. Racemic trans-DB[a,l]P-8,9-diol was metabolized by BNF-induced rat liver microsomes to six metabolites: two diastereomers of trans,trans-DB[a,l]P-8,9:11,12-bis-diol, two diastereomers of trans,cis-DB[a,l]P-8,9:11,12-bis-diol, and two diastereomers of trans-DB[a,l]P-8,9:13,14-bis-diol as characterized by NMR, MS, and UV spectroscopy. Metabolic studies using both enantiomeric (-)- and (+)-trans-DB[a,l]P-8,9-diol further demonstrated that each diastereomer of trans,trans-DB[a,l]P-8,9:11, 12-bis-diol and trans-DB[a,l]P-8,9:13,14-bis-diol was comprised of two enantiomers. Similarly, incubations of enantiomeric or racemic trans-DB[a,l]P-8,9-diol with a recombinant human P450 1A1 system and epoxide hydrolase also gave the same two enantiomeric mixtures of diastereomers of trans,trans-DB[a,l]P-8,9:11,12-bis-diol and the same two enantiomeric mixtures of diastereomers of trans-DB[a,l]P-8, 9:13,14-bis-diol. This suggested that the microsomal oxidations of (-)- and (+)-trans-DB[a,l]P-8,9-diol were stereospecific. The stereospecific formation of enantiomers of trans-DB[a,l]P-8,9-diol from DB[a,l]P was examined using both BNF-induced rat liver microsomes and a recombinant human P450 1A1 system with epoxide hydrolase. Stereospecificity was observed as both metabolic systems favored the formation of (-)-trans-DB[a,l]P-8,9-diol by 8-9-fold. DNA adduct studies were undertaken using TLC/HPLC 32P-postlabeling techniques. In the presence of a recombinant human P450 1A1 system with epoxide hydrolase, DB[a,l]P gave two groups of calf thymus DNA adducts. The group of later-eluting adducts were identified as arising from syn- and anti-DB[a,l]P-11,12-diol-13,14-epoxides, while the more polar early-eluting adducts were derived, in part, from the further activation of trans-DB[a,l]P-8,9-diol. Our data indicate that, in P450 1A1-mediated microsomal incubations, DB[a,l]P is metabolized to trans-DB[a,l]P-8,9-diol which is further metabolized to DB[a,l]P-bis-diols. trans-DB[a,l]P-8,9-diol is metabolically activated to intermediates that can bind to DNA and give DNA adducts similar to those observed with DB[a,l]P. These results indicate that DB[a,l]P can be metabolically activated by both fjord-region and K-region pathways.

Animals↗
PubMed1998

Sudden infant death syndrome and nitrogen metabolism: further development of a hypothesis.

BACKGROUND: A hypothesis suggesting an inducible inability of the enteric bacteria to metabolize urea in infants, resulting in metabolic alkalosis and subsequent respiratory insufficiency, has been proposed as the cause of sudden infant death syndrome (SIDS). METHODS: Microbiological cultivation and determination of faecal urease activity and faecal urea content were carried out in 30 cases of unexpected infant deaths out of which 22 were considered to be due to SIDS and eight from other causes. The concentration of nitric oxide (NO) in sealed test tubes was determined after incubation of faeces in normal saline. RESULTS: The SIDS subjects differed significantly from the control cases in two respects: they had low or no sigmoid faecal urease activity and an unmetabolized sigmoid faecal urea content, whereas the control subjects had normal faecal urease activity and none, or very little, remaining faecal urea. The NO concentration in faeces was correlated with the faecal content of urea in the SIDS cases. CONCLUSION: The present findings lend support to the hypothesis of an insufficient metabolism of enteric urea in infants with SIDS.

Case-Control Studies↗
PubMed1998

The conjunctival provocation test model of ocular allergy: utility for assessment of an ocular corticosteroid, loteprednol etabonate.

Two studies were conducted using the conjunctival provocation test (CPT) model of ocular allergy. The objective of the first study was to evaluate the sensitivity of the CPT model to a topical corticosteroid. Selected was loteprednol etabonate 0.5%, previously found effective in the treatment of ocular allergy and inflammation. The study was a randomized double-masked, placebo-controlled, paired-comparison of loteprednol etabonate 0.5% (LE), b.i.d. or q.i.d. Sixty subjects who had a minimum pre-determined allergic response received LE in one eye and placebo in the fellow eye for 28 days from Day 7 to Day 35. Antigen challenges were carried out on Days 0, 7 (baseline), 21 and 35. The primary endpoints were interocular differences in itching and mean redness (the average of ciliary, conjunctival and episcleral vessel beds). LE (either b.i.d. or q.i.d.) was significantly more effective than placebo for reducing mean redness and itching. No clinical or statistically significant changes in intraocular pressure were observed. Based upon the results of Study 1, we used the CPT model to aid in the selection of a concentration of loteprednol etabonate for subsequent studies in environmental seasonal allergic conjunctivitis. This was a randomized double-masked, placebo-controlled, paired-comparison of loteprednol etabonate 0.1%, 0.2% and 0.3%, q.i.d. in 88 subjects. The dosing and testing regimen was similar to the first portion of the study. Loteprednol etabonate, 0.1%, 0.2% and 0.3%, was numerically superior to the placebo in reducing mean redness and itching. At the 20-minute post allergen challenge, the 0.1% concentration was significantly superior (p < 0.05) to the placebo on Visit 4 (2 and 4 hour challenge) in reducing the mean redness; however, LE was only numerically superior in relieving itching. The 0.2% concentration was significantly superior (p < 0.05) to the placebo in the reduction of mean redness and itching on Visit 3 (Day 21) and in reduction of mean redness on Visit 4 (4 hour challenge). The 0.3% concentration was significantly superior (p < 0.05) to the placebo in the reduction of mean redness on all visits, and statistically significant in the reduction of itching on Visit 4 (4 hour challenge). While there were some elevations of IOP with LE 0.2%, they were not clinically significant. In conclusion, the CPT model of ocular allergy is useful in the evaluation of corticosteroids. Furthermore, based upon a dose-response study in this model, 0.2% loteprednol etabonate was selected for further evaluation in environmental seasonal allergic conjunctivitis studies.

Adult↗
PubMed1998

Human follicle fluid vascular endothelial growth factor concentrations are correlated with luteinization in spontaneously developing follicles.

Vascular endothelial growth factor (VEGF) is a cytokine that induces angiogenesis. Angiogenesis is a prominent histologic component of the luteinization process. Luteinization is also characterized by granulosa cell progesterone secretion in response to the luteinizing hormone (LH) surge. Local VEGF production in human pre-ovulatory follicles, induced by LH, was postulated to be a luteinization mediator in women. To investigate this hypothesis, serum and fluid from the dominant follicle of 31 healthy regularly cycling multiparous women undergoing laparoscopic sterilization were obtained. VEGF was measured by enzyme-linked immunosorbent assay, and LH and progesterone were measured by radioimmunoassay. Follicle aspiration was performed at a median of 13 days from the last menstrual period (range 11-17 days). The median pre-ovulatory follicle diameter was 16 mm (range 11-23 mm). Follicle fluid VEGF concentrations (mean 6900 pg/ml, range 1200-17 100 pg/ml) were correlated positively with follicle fluid progesterone concentrations (mean 10 176 nmol/l, range 636-66780 nmol/l, r=0.62, P=0.002). This correlation was even tighter (r=0.87, P < 0.0001) when only samples from the 22 women in the earliest stages of follicle luteinization were considered. In these women serum LH concentrations were also correlated with follicle fluid VEGF concentrations (r=0.51, P=0.02). Our findings demonstrate the close dynamic relationship between VEGF production and early luteinization in human follicles during normal non-stimulated cycles.

Adult↗
PubMed1998

Genetic analysis of multiple vancomycin-resistant Enterococcus isolates obtained serially from two long-term-care patients.

Fifty-eight vancomycin-resistant enterococcal isolates were obtained from two patients over 9 weeks. Numerous pulsed-field gel electrophoresis fingerprinting types were isolated from each patient. By PCR, all isolates were vanA+. However, many isolates from patient B were found to lack vanA by hybridization. Our results demonstrate the importance of examining multiple isolates, especially from patients who are at high risk of infection.

Aged↗
PubMed1998

Alteration of mucin in human conjunctival epithelia in dry eye.

PURPOSE: The objective of this study was to determine whether alteration in mucins could be detected in patients with dry eye symptoms by using the monoclonal antibody H185, which recognizes carbohydrate epitopes on mucin molecules. METHODS: Immunohistochemistry and immunoelectron microscopy was used to examine binding of H185 antibody to conjunctival cells obtained by nitrocellulose filter paper stripping (impression cytology). Two study populations were examined. Study I included 22 patients with dry eye symptoms and 13 normal volunteers. Study II included 16 aqueous-deficient dry eye patients and 14 age-matched control subjects. RESULTS: Results of the studies demonstrated significant differences in binding patterns of H185 to conjunctival cells in normal eyes compared with those of patients with dry eye symptoms. In normal eyes, the antibody bound to apical cells in a mosaic pattern, with cells exhibiting either light, medium, or intense binding. A predominant pattern in patients with dry eye symptoms was loss of the mosaic pattern with replacement by a "starry sky" pattern in which there was a lack of apical cell binding (hence, dark sky) but increased binding to goblet cells (hence, stars in the sky). The starry sky pattern correlated with rose bengal staining. CONCLUSIONS: From these studies it is concluded that there is an alteration either in mucin distribution or mucin glycosylation on the surfaces of apical conjunctival cells in dry eye and that glycosylation of goblet cell mucins changes with the disease.

Adult↗
PubMed1997

Education deficit.

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Clinical Competence↗
PubMed1997

Investigation of group migration in the fragmentation of bis(trimethylsilyl) ethers of diols separated by rigid groups.

Two fragmentations of (CH3)3SiO-CR2-X-CR2-OSi(CH3)3, where X is a rigid group such as a triple bond or an aromatic ring, are losses of a methyl or R group (where R is H or alkyl). The metastable-ion dissociations of [M-R]+ and [M-CH3]+ ions include the rearrangement of a trimethylsilyl (TMS) cation and a (CH3)2Si = O neutral species through an ion-neutral complex. On the basis of tandem mass spectrometry (MS/MS), exact mass measurement and isotopic labeling experiments, it has been established that the two trimethylsilyloxy groups in the TMS ethers interact across a wide range of distances via an ion-neutral complex. The migration of a TMS cation occurs when the group that is bound to carbon is expelled as a radical by an oxygen-directed cleavage to give a trimethylsilylated oxonium ion. If, on the other hand, a methyl radical is lost from the silicon atom, then (CH3)2Si = O migrates. The mobilities of the TMS cation and the neutral (CH3)2Si = O are governed by the capability of the rigid group to delocalize charge.

Ethers↗
PubMed1997

Vancomycin-resistant enterococci in stool specimens submitted for Clostridium difficile cytotoxin assay.

The prevalence of, and clinical risk factors associated with, vancomycin-resistant enterococcal colonization were investigated in patients suspected of having Clostridium difficile infection. Stools submitted for C difficile cytotoxin testing were screened for vancomycin-resistant enterococci (VRE). Isolates were speciated and characterized further by antibiotic susceptibility testing, DNA fingerprinting, and DNA:DNA hybridization for detection of specific vancomycin resistance genes. Of the 79 evaluable patients identified during a 3-month period, 16.5% were VRE-positive. The VRE isolates were genetically heterogeneous, although all carried the vanA gene. DNA fingerprinting data suggest that patient-to-patient transmission occurred, implicating colonized patients as potential reservoirs for VRE transmission. A positive C difficile cytotoxin assay and diabetes mellitus were the only identifiable risk factors associated with VRE colonization. Patients at risk for C difficile infection therefore may serve as reservoirs for VRE.

Anti-Bacterial Agents↗
PubMed1997

Vaginal electrostimulation for the treatment of genuine stress incontinence.

The value of vaginal electrostimulation for genuine stress incontinence was evaluated in 30 women with this condition. Subjective and objective measurements were made before and after 3 and 15 months of treatment using urinary diaries, perineometry and pad tests. After 3 months use, 21 women (70%) reported a subjective improvement, but this had fallen to 9 (30%) by 15 months. There were significant reductions in the numbers of daily incontinent episodes and pad/pant changes and significant increases in the perineometry readings at both 3 and 15 months. There were no side-effects observed with electrostimulator use, but 1 patient withdrew due to a dislike of the method of treatment. Vaginal electrostimulation would seem to be a simple and well tolerated means of managing genuine stress incontinence in a selected group of women.

Adult↗
PubMed1997

A neuropsychological perspective on three schizophrenic patients with midline structural defects.

BACKGROUND: The relationship between midline structural defects and schizophrenia remains unclear, although a number of neuroradiological studies have reported an association between schizophrenia and a range of anomalies. METHOD: Three patients are reported, each diagnosed with schizophrenia and neuroradiological evidence of midline structural anomalies. MRI scans are reported in conjunction with performance over a range of neuropsychological tests designed to assess frontal and lateralised cognitive functions. RESULTS: Evidence of anterior dysfunction was present in all three cases, while on an individual basis patients displayed varying patterns of preserved and dysfunctional cognitive processing. CONCLUSION: The reported findings raise a number of interesting issues regarding the nature of hemispheric involvement in schizophrenia.

Adult↗
PubMed1997

Dimethylarsinic acid treatment alters six different rat biochemical parameters: relevance to arsenic carcinogenesis.

In a previous study, we found that sodium arsenite increased hepatic ornithine decarboxylase (ODC) activity and hepatic heme oxygenase (HO) activity, but did not cause any DNA damage in adult female rat liver or lung, suggesting that arsenite may be a promoter of carcinogenesis. In this study sodium arsenate, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) were administered orally in equitoxic doses to adult female rats at 21 and 4 h prior to sacrifice. DNA damage (DD), cytochrome P450 content (P450), glutathione content (GSH), ODC, serum alanine aminotransferase (ALT) and HO were measured in liver and/or lung tissue. At 60 mg/kg in rat liver, sodium arsenate increased hepatic HO fivefold. MMA decreased ALT at 226 mg/kg, decreased ALT and GSH at 679 mg/kg and also increased P450 at 679 mg/kg in rat liver. DMA decreased ALT and hepatic GSH and increased hepatic HO at 387 mg/kg. In the lung, DMA decreased ODC at both 129 and 387 mg/kg. DD in lung tissue was significantly higher at 387 mg/kg DMA, demonstrating organ specific DNA damage. The biochemical effects and the inferred oncologic potential of the four major forms of arsenic (arsenate, arsenite, MMA and DMA) differ dramatically. The inorganic forms (arsenate and arsenite) are similar to each other (both good HO inducers); the methylated organic forms of arsenic (MMA and DMA) also share a similar pattern of biochemical effects (decreased GSH and ALT, increased P450). All six of the biochemical parameters studied were altered by DMA in either rat liver or lung.

Administration, Oral↗
PubMed1997

Candesartan cilexetil, a new generation angiotensin II antagonist, provides dose dependent antihypertensive effect.

Candesartan is a new generation angiotensin II type 1 receptor blocker, characterised by tight binding to and slow dissociation from the receptor. In order to delineate the dose-response curve for candesartan cilexetil (the orally administered prodrug), results from six European placebo-controlled, dose-response studies were pooled. These were of a double-blind, randomised, parallel group design, with a treatment duration of 4-12 weeks. A total of 1482 patients with mild to moderate primary hypertension were treated with candesartan cilexetil 2 mg (n = 80), 4 mg (n = 216), 8 mg (n = 455) or 16 mg (n = 294), or with placebo (n = 437). Blood pressure (BP) measurements were performed 24 h after dose. The differences in BP change (baseline vs end of the studies) between the placebo group and the groups treated with candesartan cilexetil were assessed using analysis of covariance and dose response curves were estimated by fitting the data to an Emax model. The placebo-corrected mean reductions in sitting diastolic BP were approximately 2.5 mm Hg with 2 mg, 4.5 mm Hg with 4 mg, 6 mm Hg with 8 mg, and 8 mm Hg with 16 mg of candesartan cilexetil. For sitting systolic BP, the placebo-corrected mean reductions were in the order of 5, 7, 10 and 12 mmHg, respectively, with 2, 4, 8 and 16 mg of candesartan cilexetil. The BP reductions were similar in the standing position with no indication of postural hypotension. Age or gender did not influence the BP response to candesartan cilexetil. In conclusion, candesartan cilexetil provides a clinically significant, dose-dependent antihypertensive effect in doses ranging from 4-16 mg once daily.

Adolescent↗