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Biomedical subjects

D Horton

Publications and source records attributed to D Horton.

At least 19 recordsLinked to original sources
PubMed2005

Impact of operational maintenance on the asset life of storm reed beds.

This paper reviews the operation of storm reed beds to determine whether the current system of operational maintenance is contributing to premature process failures and if not, to identify other factors of importance. Twelve storm reed beds of the horizontal subsurface flow type, at seven locations in the South Warwickshire area of the United Kingdom, were surveyed. Each survey consisted of a site visit, an interview with the operators in charge and an assessment of the treatment performance based on routine monitoring data. Although some sites suffered from varying degrees of sludge accumulation, surface blinding and/or weed growth, all effluent concentrations remained far below the consent levels. Thorough operational maintenance on a reed bed is proven to be important for the asset life. However, there are other factors or features of a reed bed that play a more pivotal role in premature process failure such as the lack of pretreatment and a premature operation of the storm overflow.

Biodegradation, Environmental↗
PubMed2001

Synthetic explorations towards 3-deoxy-3-fluoro derivatives of D-perosamine.

Based on a literature precedent, preparation of methyl 4-azido-3,4,6-trideoxy-3-fluoro-alpha-D-mannopyranoside (18) was attempted via fluorination of methyl 4-azido-2-O-benzyl-4,6-dideoxy-alpha-D-altropyranoside with diethylaminosulfur trifluoride (DAST). Contrary to expectations, the reaction took place with retention of configuration at the site of the fluorination yielding methyl 4-azido-2-O-benzyl-3,4,6-trideoxy-3-fluoro-alpha-D-altropyranoside. Treatment with DAST of methyl 4-azido-2-O-benzyl-4,6-dideoxy-alpha-D-allopyranoside (8), or its 2-(p-methoxybenzyl) analog 9 resulted in fluorination with inversion of configuration at position 3, to give the corresponding 3-deoxy-3-fluoro glucopyranosides 10 and 11, respectively. Accordingly, compound 18 was prepared from 11, by de-p-methoxybenzylation at O-2, followed by inversion of configuration at C-2 in the resulting methyl 4-azido-3,4,6-trideoxy-3-fluoro-alpha-D-glucopyranoside. The 2-O-methyl analog of 18 (19) was prepared by methylation of 18. Compounds 18 and 19 were converted, conventionally, into the 3-fluoro analogs of the terminal determinants of the O-PS of Vibrio cholerae O:1, serotype Inaba and Ogawa, respectively.

Diethylamines↗
PubMed2001

Sumio Umezawa.

Explore the source record for details and available documents.

Aminoglycosides↗
PubMed2000

Cu, Pt, and Pd complexes of the 3-deoxy-1,2-bis(thiosemicarbazone) derived from D-glucose.

3-Deoxy-D-erythro-hexos-2-ulose bis(thiosemicarbazone) (1) acts as a tetradentate ligand of the N2S2 type which forms stable coordination complexes with metal(II) cations. The Cu(II), Pt(II), and Pd(II) chelates (2, 4, and 6, respectively) of 1 were synthesized and characterized by elemental analysis and NMR spectroscopy. The NMR spectra of the Pt complex (4) showed the coupling of H-1 and C-1, C-2 of the bis(thiosemicarbazone) with 195Pt (33.7% naturally occurring), which supports the structure proposed for the chelate. The complexes 2, 4, and 6 were acetylated to give the corresponding tri-O-acetyl derivatives 3, 5, and 7. Elimination of Cu(II) from 3 with hydrogen sulfide afforded 8, the tri-O-acetyl derivative of 1. Preliminary studies have shown antiviral activity of chelates 2, 4, and 6 against poliovirus type 1.

Animals↗
PubMed2000

Analysis of anthocyanins in foods by liquid chromatography, liquid chromatography-mass spectrometry and capillary electrophoresis.

This article reviews recent developments in the methodology for the measurement of anthocyanins that offer several advantages over classical methods of analysis. The use of UV-diode array and mass spectrometric (MS) detectors, with improved methods of liquid chromatography analysis has facilitated identification of these analytes. The use of capillary electrophoresis (CE) analysis of the anthocyanins under acid conditions has significantly increased peak resolution and improved the detection limits by several orders of magnitude. CE offers the advantage of economies of very small sample size, very small solvent consumption, and short analysis times along with the future possibility of being combined with MS detection.

Anthocyanins↗
PubMed2000

Characterization of prenylated xanthones and flavanones by liquid chromatography/atmospheric pressure chemical ionization mass spectrometry.

Reversed-phase liquid chromatography with atmospheric pressure chemical ionization mass spectrometry (LC/APCI-MS) in the positive-ion mode was utilized to analyze crude ether extracts from the root bark of Maclura pomifera, a tree known to have a high content of prenylated xanthones and flavanones. Identification of three xanthones and two flavanones was based on their unique mass spectra. Under optimum conditions peaks corresponding to the [MH](+) ion and characteristic fragments for each compound were observed. (1)H NMR data were used to confirm the identities of two xanthones that had the same molecular mass and similar fragmentation patterns. Fragmentation of the analytes was achieved by application of an electrostatic potential at the entrance of the single quadrupole mass spectrometer. The optimum voltage for fragmentation was found to be related to the class of compounds analyzed and, within each class, to be dependent on the structure of the prenyl moiety. Collision-induced pathways consistent with precedent literature describing the MS characterization of similar compounds and with the observed fragmentation patterns are tentatively proposed.

Chromatography, Liquid↗
PubMed1999

Synthesis of the 3-methyl ether and 4-deoxy derivatives of 4-cyanophenyl 1,5-dithio-beta-D-xylopyranoside (Beciparcil).

Treatment of the 2,3-isopropylidene acetal of the title dithioxyloside with 2,4,5-triiodoimidazole-PPh3 caused replacement of the 4-hydroxyl group by iodine to afford 82% of the 4-axial iodide 6, converted by base into 4-cyanophenyl 2,3-O-isopropylidene-1,5-dithio-beta-D-glycero-pent-3-enopyranoside++ + (8). Acid treatment of 8 gave 87% of the deacetonated glycos-3-ulose, borohydride reduction of which afforded 63% of 4-cyanophenyl 4-deoxy-1,5-dithio-alpha-L-threo-pentopyranoside (3), together with 27% of the 3-axial epimer. The 3-methyl ether of the title dithioxyloside was satisfactorily prepared via 2,4-protection as the cyclic phenylboronate, methylation, and deprotection; alternative strategy via the 2,4-bis(triisopropylsilyl) ether was complicated because of silyl-group migration under methylation conditions.

Chromatography, Thin Layer↗
PubMed1998

Reoperation for recurrent coronary artery disease: results of 200 consecutive cases.

BACKGROUND: It is well known that reoperation for recurrent coronary artery disease is more difficult than primary coronary artery bypass grafting. However, it is possible to reduce the morbidity and mortality of reoperation to the same level as the initial procedure with careful surgical technique. METHODS: A retrospective study of the first 200 patients who underwent redo coronary bypass grafting was undertaken. RESULTS: In the first 200 cases of redo coronary bypass grafting at St George Hospital, Sydney (August 1986-January 1995), there were five in-hospital deaths (2.5%). There was one case of sternal infection (0.5%), which required surgical debridement, three cases of stroke (1.5%), one case of postoperative bleeding (0.5%), which required a return to theatre and six cases (3%) required mechanical ventilation for more than 24 h. The need for major postoperative support (such as intra-aortic balloon pumping/adrenaline infusion) was significantly affected by the degree of urgency and the degree of pre-operative ventricular impairment. CONCLUSIONS: The mortality rate of redo coronary artery bypass grafting in this series is similar to that of primary surgery described in other reports.

Adult↗
PubMed1997

5-Deoxy-5-C-(5-ethoxycarbonyl-1,2,3,- triazol-1-yl)-1,2-O-isopropylidene-alpha-D-xylofuranose.

Two unrelated molecules of the title compound, ethyl 1-(5-deoxy-1,2-O-isopropylidene-alpha-D-xylofuranos-5-C- yl)-1,2,3-triazole-5-carboxylate, C13H19N3O6, that are not linked by hydrogen bonding, comprise the asymmetric unit. There are no unusual bond lengths or angles. The two molecules differ in the degree of rotation around the methylene C atom that joins the triazole ring to the sugar part of the molecule. Molecules of the same conformation form infinite chains joined by hydrogen bonding between a H atom on the hydroxyl group of one molecule and an N atom in the triazole ring of another molecule generated by the 2(1) screw axis. Relevant intermolecular N...O distances are 3.013 (3) and 2.806 (3) A.

Crystallization↗
PubMed1997

Early antenatal ultrasound diagnosis of fetal intracranial teratoma.

The commonest fetal intracranial tumour is a teratoma. The prognosis is poor with death usually occurring shortly after birth. Modern high resolution ultrasound scanners facilitate examination of the cranial contents, allowing earlier diagnosis. We report a case where an intracranial teratoma was identified at 21 weeks gestation, the earliest gestational age that this has been reported. The ultrasound appearances are discussed.

Adult↗
PubMed1996

Characterization and interconversions of 2-S-ethyl-2-thio-D-mannose diethyl dithioacetal and the facile epimerization of 2-thio-D-mannopyranose derivatives.

3,4,5,6-Tetra-O-benzoyl-D-glucose diethyl dithioacetal (2) reacts with ethanethiol under acidic conditions to afford 3,4,5,6-tetra-O-benzoyl-2-S-ethyl-2-thio-D-mannose (3), the stereochemistry at C-2 of which has been assigned by chemical conversions on its debenzoylated derivative, the crystalline 2-S-ethyl-2-thio-D-mannose diethyl dithioacetal (4). In the presence of mercuric chloride (1.1 molar equiv), 4 is converted into crystalline ethyl 2-S-ethyl-1,2-dithio-alpha-D-mannofuranoside (5). Complete demercaptalation of 4 affords syrup 2-S-ethyl-2-thio-D-mannopyranose (6), which was characterized as its phenylhydrazone 7 and the crystalline alpha-pyranose tetraacetate 9. Extended treatment of 4 with mercuric chloride and aqueous sodium hydrogencarbonate resulted in isolation of 6, along with its crystalline 2-epimer, 2-S-ethyl-2-thio-beta-D-glucopyranose (10). Remercaptalation of 6 affords the manno diethyl dithioacetal 4 as the major product, whereas similar treatment of 10 yields ethyl 2-S-ethyl-1,2-dithio-alpha-D-glucopyranoside (13). The mechanism of conversion of 2 into 3, as well as the unusually facile interconversion of 2-S-ethyl-2-thio-D-mannose (6) and its D-gluco epimer 10, has been investigated.

Acetals↗
PubMed1996

Potential allergens stimulate the release of mediators of the allergic response from cells of mast cell lineage in the absence of sensitization with antigen-specific IgE.

A number of structurally diverse antigens preferentially stimulate the synthesis of IgE antibodies, but no unifying principle has been proposed that explains the nature of isotype selection. In the present study, we show that common allergens present in bee venom, house dust mite emanations and parasite proteins induce mast cell and basophil degranulation and stimulate interleukin-4 synthesis, and secretion in the absence of antigen-specific IgE. These data point to a linkage between the initial activation of cells of the innate immune system and subsequent adaptive immune responses. They suggest that IgE-independent mast cell and basophil degranulation is predictive of potential allergenicity and can be evaluated by means of a cellular assay. Our study indicates that non-immunological degranulation by prototypic allergens, such as bee venom phospholipase A2 or proteases associated with house dust mite emanations, is critically dependent on enzymatic activity. These findings have potentially important implications for vaccine design in allergic and parasitic disease.

Allergens↗
PubMed1996

Hypericin: a new laser phototargeting agent for human cancer cells.

Laser activation of anthracycline-related drugs combines chemotherapy with photoablation for improved treatment. Hypericin, a structurally related anthraquinone, was tested for laser activation and cytotoxicity in human cancer cells. Viability of P3 squamous cell carcinoma cells incubated with 1 to 20 microgram/mL hypericin was reduced by more than 95% after 1 minute exposure at 4 degrees C to an argon laser (514 nm, 5 W), a KTP-532 laser (532 nm, 5 W), or a 20-A xenon lamp. Viability was reduced over 90% in six human carcinoma, sarcoma, and melanoma cell lines by this combined treatment, but only trace toxicity was seen after separate exposure to hypericin or light alone. These results show that hypericin is a sensitive agent for phototherapy of human cancer cells in vitro and indicate that this drug may be useful for tumor targeting via minimally invasive imaging-guided laser fiber optics.

Anthracenes↗
PubMed1995

Acute renal failure following cardiac surgery: incidence, outcomes and risk factors.

BACKGROUND: Acute renal failure (ARF) is a recognised complication following cardiac surgery, but the incidence varies widely in the published literature and there are no Australian data available to help predict the risks of ARF in patients with pre-existing renal disease. AIM: To determine the incidence, outcome and risk factors for ARF following cardiac surgery. METHODS: A retrospective case control analysis of 903 consecutive patients who had cardiac surgery (795 CABG, 68 valve/septal surgery, 40 combined valve/CABG) in 1992-93. ARF was defined as doubling of serum creatinine concentration (Cr) to > 0.13 mmol/L if serum Cr was < or = 0.13 mmol/L pre-operatively, or else a rise in serum Cr of > or = 0.10 mmol/L after cardiac surgery. For each subject with ARF, two case control subjects were matched for date of surgery, surgeon, age, sex, type of surgery and pre-operative serum Cr to permit analysis of the influence of pre-operative factors (hypertension, diabetes mellitus, left ventricular systolic dysfunction) and for the comparison of cardiopulmonary bypass time upon the development of ARF. Subsidiary endpoints were mortality, need for dialysis and length of hospital stay. RESULTS: ARF developed in only 1.1% of patients with 'normal' pre-operative renal function (creatinine < or = 0.13 mmol/L) and none required dialysis. ARF developed in 16% of those with impaired pre-operative renal function, 20% of whom required dialysis. Mortality from ARF was 13%. The risk of ARF rose from 10.4% in those with pre-operative serum Cr 0.14-0.20 mmol/L to 36.8% if the serum Cr was > 0.20 mmol/L (p < 0.01). Mortality was higher (4.2% vs 0.7%, p < 0.01) and length of hospital stay longer (14.5 vs nine days [median], p < 0.001) in those with impaired pre-operative renal function. ARF was more likely in those over 65 years, if valve surgery was included and where there was prolonged cardiopulmonary bypass time. CONCLUSIONS: These data confirm that ARF following cardiac surgery is uncommon without pre-operative impairment of renal function but currently carries a mortality rate of 13%. Impaired renal function alone is associated with higher mortality and prolonged hospital stay. Studies to prevent ARF in this setting should focus on the high risk subsets described in this study.

Acute Kidney Injury↗