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Biomedical subjects

G R Gray

Publications and source records attributed to G R Gray.

At least 55 records · Page 3Linked to original sources
PubMed1991

Early endoscopic sphincterotomy for retained bile duct stones after gallbladder surgery.

Endoscopic sphincterotomy (ES) was performed in 36 patients (age range 33-88 years; median 63 years) with retained bile duct stones after cholecystectomy (32 patients) or cholecystostomy (4 patients). The median time interval between surgery and ES was 28 days (range 10-216 days). At the time of ES, 23 patients had a T-tube in situ. Clearance of the bile duct was achieved by T-tube irrigation in 15 patients, and by basket or balloon extraction in seven patients. Spontaneous clearance of the duct after ES occurred in 12 patients, while two patients required widening of the sphincterotomy to allow successful basket extraction. Complications occurred in four patients (11%). Two patients sustained significant haemorrhage from the ES site and subsequently died. One patient developed mild acute pancreatitis while another had persisting cholangitis before and after ES. Both of these patients recovered with conservative management. While ES performed soon after gallbladder surgery allows for early bile duct clearance, the small but significant risk of potentially lethal haemorrhage suggests that its use should be reserved for patients in whom other non-operative methods have failed or are inappropriate.

Adult↗
PubMed1991

Prostaglandins in the treatment of reflux oesophagitis: double-blind placebo controlled clinical trial.

The efficacy of the prostaglandin analogue, rioprostil, in the treatment of reflux oesophagitis has been assessed in a double-blind, randomized, placebo-controlled trial of 25 patients with endoscopic and histological evidence of reflux oesophagitis. At the beginning and end of the study, endoscopic appearances were graded 0-4 (0 = no oesophagitis, 4 = severe oesophagitis) and the symptoms of heartburn, regurgitation, pain and dysphagia were each graded 0-3 (0 = none, 3 = severe). Fourteen patients received rioprostil, 300 micrograms twice daily, and 11 patients received identically marked placebo for a period of 12 weeks. At the end of the study there were no significant differences between the groups in mean (s.d.) endoscopic grading (rioprostil 2.4 (1.3); placebo 1.9 (0.9)) and mean (s.d.) cumulative symptom score (rioprostil 2.5 (3.1); placebo 2.6 (1.5)). Five patients in the rioprostil group reported diarrhoea. Rioprostil had no significant benefit over placebo in the treatment of reflux oesophagitis.

Double-Blind Method↗
PubMed1990

Isolation and analysis by the reductive-cleavage method of linkage positions and ring forms in the Mycobacterium smegmatis cell-wall arabinogalactan.

The Mycobacterium smegmatis arabinogalactan polysaccharide has been isolated from the cell wall by saponification and extraction to remove lipids and subsequent solubilization by treatment with lysozyme. Analysis for neutral sugars demonstrated the presence of D-arabinose and D-galactose in a ratio of 3:1, respectively. Reductive cleavage of the fully methylated polysaccharide in the presence of triethylsilane and trimethylsilyl trifluoromethanesulfonate and subsequent acetylation in situ gave six partially methylated 1,4-anhydroalditol acetates as the major products and three partially methylated 1,5-anhydroalditol acetates as minor products. Partially methylated 1,5-anhydroalditol acetates were not formed when reductive cleavage was accomplished with triethylsilane and a mixture of trimethylsilyl methanesulfonate and boron trifluoride etherate as the catalyst, demonstrating that the polysaccharide is exclusively comprised of furanosyl residues. The partially methylated anhydroalditols so produced were identified by comparison to authentic standards. Their identifies are consistent with the presence in the M. smegmatis arabinogalactan of an octasaccharide repeating unit comprised of a nonreducing terminal D-arabinofuranosyl group, a 2-O-linked D-arabinofuranosyl residue, three 5-O-linked D-arabinofuranosyl residues, a 3,5-di-O-linked D-arabinofuranosyl residue, a 5-O-linked D-galactofuranosyl residue, and a 6-O-linked D-galactofuranosyl residue.

Carbohydrate Conformation↗
PubMed1990

Model studies on the analysis of pyruvic acid acetal-containing polysaccharides by the reductive-cleavage method.

The 4,6-O-(1-methoxycarbonylethylidene), -(hydroxyisopropylidene), and -(methoxyisopropylidene) acetals of methyl 2,3-di-O-methyl-alpha-D-glucopyranoside were subjected to reductive cleavage in the presence of triethylsilane and trimethylsilyl methanesulfonate-boron trifluoride etherate (Me3SiOMs-BF3.Et2O), BF3.Et2O, or trimethylsilyl trifluoromethanesulfonate (Me3SiOSO2CF3) and the mole fractions of products were determined as a function of reaction time. The 4,6-(1-methoxycarbonylethylidene) acetal was quite stable to reductive-cleavage conditions but isomerization of the initial R,S mixture of diastereomers to the more-stable S diastereoisomer was noted. In addition, a slow, regiospecific, reductive ring-opening of the acetal was observed to give 6-O-[1-(methoxycarbonyl)ethyl] derivatives. The 4,6-(hydroxyisopropylidene) acetal was very unstable under reductive-cleavage conditions. Both Me3SiOMs-BF3.Et2O and Me3SiOSO2CF3 catalyzed complete removal of the group, via the intermediate 6-[1-(hydroxymethyl)ethyl] ether, but BF3.Et2O gave a mixture of products. The 4,6-(methoxyisopropylidene) acetal was also very labile under reductive-cleavage conditions; Me3SiOMs-BF3.Et2O catalyzed complete removal of the acetal, via the intermediate 6-[1-(methoxymethyl)ethyl]ether, but the intermediate ether was quite stable in the presence of either BF3.Et2O or Me3SiOSO2CF3. It is concluded from these studies that polysaccharides bearing 4,6-O-(1-carboxyethylidene) substituents can be analyzed directly by sequential permethylation and reductive cleavage. It is proposed that the identity of the substituted monomer and the positions of substitution of the acetal can be determined by sequential permethylation, ester reduction, and reductive cleavage.

Kinetics↗
PubMed1990

Different effects of native Candida albicans mannan and mannan-derived oligosaccharides on antigen-stimulated lymphoproliferation in vitro.

Yeast cell wall mannan polysaccharide has been proposed to contribute to immune dysfunction associated with chronic infections involving Candida albicans. This influence of mannan has been suggested based partially upon studies of the in vitro immunoinhibitory effects of mannans prepared from Saccharomyces cerevisiae or C. albicans by precipitation with Fehling's reagent, which provides a structurally modified product contaminated with copper. We have therefore evaluated the immunoinhibitory influence of a more native C. albicans mannan prepared by complexation with cetyltrimethylammonium bromide (CTAB). CTAB mannan was a potent stimulator of lymphoproliferation when added to human PMBC from donors responsive to Candida; it has no inhibitory influence on lympho-proliferation induced by Candida or other Ag. In contrast, members of a family of mannose oligosaccharides (disaccharide through hexasaccharide) derived from the CTAB mannan by weak alkaline degradation did not stimulate lymphoproliferation, but were potent inhibitors of lymphoproliferation stimulated by Candida and other Ag. Fifty percent inhibitory doses were 260 to 34 microM, respectively. Compositional analyses of these immunoinhibitory oligomers showed them to be composed of mannose and free of contaminating protein. We propose that mannan-derived oligosaccharides produced by catabolism of mannan in vivo are immunoinhibitory and contribute to the deficit in cell-mediated immune function associated with chronic candidiasis.

Antigens, Fungal↗
PubMed1989

Incorporation of bacterial peptidoglycan constituents into macrophage lipids during phagocytosis.

It has previously been established that several glycopeptides of peptidoglycan origin are formed as a result of processing of Bacillus subtilis cell walls by the macrophage-like cell line RAW264. Although the formation of these glycopeptides could account for the humoral immune responses characteristic of bacterial peptidoglycans, their formation does not account for the cellular-mediated immune responses observed for water-in-oil emulsions of peptidoglycan or for lipophilic derivatives of glycopeptide fragments thereof. Therefore, the processing of peptidoglycan by macrophages was reexamined to establish whether the lipophilic derivative of any peptidoglycan-derived glycopeptide was formed. The experiments were performed by incubating B. subtilis cell walls radiolabeled in muramic acid, glucosamine, alanine, glutamic acid, and diaminopimelic acid residues in the presence of the macrophage-like cell line RAW264. The crude lipid fraction derived from the macrophages was further fractionated and analyzed, revealing the presence of two lipophilic glycopeptides that contained glucosamine, muramic acid, and alanine of bacterial origin.

Alanine↗
PubMed1989

Endoscopic sphincterotomy for bile duct stones in patients with intact gallbladders.

Endoscopic sphincterotomy was performed in 121 patients (age ranged 34-92 years; median 80 years) with intact gallbladders and bile duct stones. Clearance of the duct by basket or balloon extraction was attempted in 97 patients (80 per cent) and achieved in 93 of these patients (96 per cent). In 24 patients the duct was left to empty spontaneously and this occurred in 22 patients. Immediate complications due to endoscopic sphincterotomy occurred in five patients (two haemorrhage, two perforation, one haemorrhage and perforation). Of the 101 patients reviewed 12-72 months (median 24 months) after endoscopic sphincterotomy, 76 (75 per cent) have remained asymptomatic throughout the follow-up period. Eighteen patients (18 per cent) required cholecystectomy for recurrent gallbladder symptoms 1-24 months after endoscopic sphincterotomy. One of the asymptomatic patients underwent cholecystectomy on the advice of his consultant. A further seven had recurrent biliary colic or cholangitis necessitating enlargement of the sphincterotomy and further stone retrieval in three of these patients. Endoscopic sphincterotomy is an effective treatment for bile duct stones in high risk patients, but subsequent cholecystectomy is required in a significant number of patients owing to continuing gallbladder symptoms.

Adult↗
PubMed1989

Maintenance cimetidine instead of surgery for duodenal ulcer: the first decade.

Fifty five patients with severe longstanding dyspepsia originally selected as candidates for elective duodenal ulcer surgery were instead entered into a maintenance cimetidine study. Forty six have been reviewed after 10 years. Twenty patients had required surgery, all in the first three years, but six of them had proven or suspected recurrent ulceration during follow up. Twenty six patients avoided surgery, either with continuous cimetidine 400 mg nocte or intermittent full dose cimetidine. Of the 17 on continuous maintenance cimetidine, six had proven or suspected recurrent ulceration responding to full dose cimetidine. All nine patients on intermittent cimetidine experienced symptomatic relapse within eight to 12 weeks of drug withdrawal. By using cimetidine, 64% of patients selected for surgery have avoided operation over this 10 year period, although none has had drug free remission.

Adult↗
PubMed1988

Synthesis and mass spectra of 4-O-acetyl-1,5-anhydro-2,3,6-tri-O-ethyl-D-glucitol and the positional isomers of 4-O-acetyl-1,5-anhydro-di-O-ethyl-O- methyl-D-glucitol and 4-O-acetyl-1,5-anhydro-O-ethyl-di-O-methyl-D-glucitol.

Reductive cleavage of fully methylated, partially O-ethylated cellulose or fully ethylated, partially O-methylated cellulose and subsequent acetylation had previously been shown to produce 4-O-acetyl-1,5-anhydro-2,3,6-tri-O-methyl-, -6- O-ethyl-2,3-di-O-methyl-, -3-O-ethyl-2,6-di-O-methyl-, -2-O-ethyl-3,6-di-O- methyl-, -2,3-di-O-ethyl-6-O-methyl-, -2,6-di-O-ethyl-3-O-methyl-, -3,6-di-O- ethyl-2-O-methyl-, and -2,3,6-tri-O-ethyl-D-glucitol. Described herein is the independent synthesis of these derivatives, except for the first (which had been reported); and their 1H-n.m.r. spectra, chemical-ionization (NH3) mass spectra, and electron-impact mass spectra are tabulated.

Chemical Phenomena↗
PubMed1988

Analysis of positions of substitution of O-methyl or O-ethyl groups in partially methylated or ethylated cellulose by the reductive-cleavage method.

A method is described for the analysis of positions of substitution of O-methyl and O-ethyl groups in commercial samples of O-methylcellulose and O-ethylcellulose, respectively. The method requires perethylation of O-methyl-cellulose and permethylation of O-ethylcellulose. Subsequent reductive cleavage of both polymers gives the same eight products, which are analyzed as their O-acetyl derivatives by gas-liquid chromatography.

Alkylation↗
PubMed1988

Analysis by the reductive-cleavage method of linkage positions in a polysaccharide containing 4-linked D-glucopyranosyluronic residues.

The fate of 4-linked D-glucopyranosyluronic residues under reductive-cleavage conditions was investigated by using the Klebsiella aerogenes type 54 strain A3 capsular polysaccharide. Treatment of the fully methylated polysaccharide with triethylsilane and trimethylsilyl trifluoromethanesulfonate in dichloromethane, followed by in situ acetylation, yielded 1,5-anhydro-2,3,4,6-tetra-O-methyl-D-glucitol, 3,4-di-O-acetyl-1,5-anhydro-2,6-di-O-methyl-D-glucitol, and 3-O-acetyl-1,5-anhydro-2,4-di-O-methyl-L-fucitol, as expected, but the expected product of reductive cleavage of the 4-linked D-glucopyranosyluronic residue, namely, methyl 3-O-acetyl-2,6-anhydro-4,5-di-O-methyl-L-gulonate, was not observed. Instead, methyl 2-O-acetyl-3,6-anhydro-4,5-di-O-methyl-L-gulonate (6) was identified as the sole product of reductive cleavage of the 4-linked D-glucopyranosyluronic residue. That compound 6 arose as a result of rearrangement during reductive cleavage rather than by reductive cleavage of a 5-linked D-glucofuranosyluronic residue, was established by reductive cleavage of the fully methylated polysaccharide following reduction of its ester groups with either lithium aluminum hydride or lithium aluminum deuteride. The products of the latter reductive cleavage were the same as before, except for the absence of 6 and the presence of 4,6-di-O-acetyl-1,5-anhydro-2,3-di-O-methyl-D-glucitol, or its 6,6-dideuterio isomer. Although the reductive-cleavage technique is suitable for the direct analysis of polysaccharides containing 4-linked D-glucopyranosyluronic residues, it does not establish whether the uronic residue is a 4-linked pyranoside or a 5-linked furanoside. The expected product is, however, derived from the 4-linked D-glucopyranosyluronic residue after sequential methylation, reduction of its ester group and reductive cleavage.

Carbohydrate Conformation↗
PubMed1988

Analysis of linkage positions in a polysaccharide containing nonreducing, terminal alpha-D-glucopyranosyluronic groups by the reductive-cleavage method.

The fate of terminal (nonreducing) alpha-D-glucopyranosyluronic groups under reductive cleavage conditions was investigated by using the Klebsiella K2 (strain NCTC-418) capsular polysaccharide. Treatment of the fully methylated polysaccharide (1) with triethylsilane and a mixture of trimethylsilyl methanesulfonate (Me3SiOSO2CH3) and boron trifluoride etherate (BF3.Et2O) as the catalyst, resulted in complete cleavage of all glycosidic linkages to yield the expected products, namely 3-O-acetyl-1,5-anhydro-2,4,6-tri-O-methyl-D-glucitol (2), 3,4-di-O-acetyl-1,5-anhydro-2,6-di-O-methyl-D-mannitol (3), 4-O-acetyl-1,5-anhydro-2,3,6-tri-O-methyl-D-glucitol (4), and methyl 2,6-anhydro-3,4,5-tri-O-methyl-L-gulonate. Treatment of 1 with trimethylsilyl trifluoromethanesulfonate (Me3SiOSO2CF3) as the catalyst resulted in incomplete cleavage of the glycosidic linkage of the methylated D-glucopyranosyluronic group, to yield 4-O-acetyl-1,5-anhydro-2,6-di-O-methyl- 3-O-(methyl2,3,4-tri-O-methyl-alpha-D-glucopyranosyluronate )-D-mannitol (9). Reductive cleavage of 1 in the presence of BF3.Et2O resulted in incomplete cleavage of all glycosidic linkages and gave rise to all four dimers (including 9) that could be formed from a tetrasaccharide repeating unit. The proposed structures of these dimers are based upon their composition, as established by chemical ionization mass spectrometry and by the reported structure of the polysaccharide. A small proportion of 1,5-anhydro-2,4,6-tri-O-methyl-3-O-(methyl 2,3,4-tri-O-methyl-alpha-D-glucopyranosyluronate)-D-mannitol (12) was also detected in the products of the BF3.Et2O-catalyzed reductive cleavage. The presence of 12 is chemical evidence for the phase of the tetrasaccharide repeating unit in the polysaccharide. The reductive cleavage of 1 was also accomplished after reduction of its ester groups with lithium aluminum hydride. Complete cleavage of all glycosidic linkages was observed when either Me3SiOSO2CF3 or Me3SiOSO2CH3-BF3.Et2O was used to catalyze reductive cleavage, and anhydroalditols 2, 3, 4, and 6-O-acetyl-1,5-anhydro-2,3,4-tri-O-methyl-D-glucitol were produced, as expected.

Carbohydrate Conformation↗
PubMed1987

A new catalyst for reductive cleavage of methylated glycans.

Several per-O-methylated D-glucans and D-fructans were used as models in an attempt to identify new catalysts for carrying out reductive cleavage. Included in these model studies were several D-glucans that contained 4-linked D-glucopyranosyl residues as well as one having a 4-linked D-glucitol residue, as both types of residue had previously been found to give rise to substantial proportions of artifactual products. These studies led to the development of a new catalyst for carrying out reductive cleavage, namely, a mixture of 5 equivalents of trimethylsilyl methanesulfonate (Me3SiOSO2Me) and 1 equivalent of boron trifluoride etherate (BF3 . Et2O) per equivalent of acetal. This new catalyst was found to accomplish the reductive cleavage of per-O-methylated, 4-linked D-glucopyranosyl residues and 4-linked D-glucitol residues, to give only the expected derivatives of 1,5-anhydro-D-glucitol and D-glucitol, respectively. The mixture of Me3SiOSO2Me and BF3 . Et2O also catalyzed reductive cleavage of the D-fructofuranosyl residues of per-O-methylated sucrose and inulin, to give only the expected derivatives of 2,5-anhydro-D-mannitol and 2,5-anhydro-D-glucitol. Indeed, when used alone, Me3SiOSO2Me also rapidly catalyzed the reductive cleavage of D-fructofuranosyl residues, but, under the same conditions, D-glucopyranosyl residues were unaffected. The results of these and other model studies demonstrated that catalysis of reductive cleavage by the mixture of Me3SiOSO2Me and BF3 . Et2O occurs in a synergistic manner. Examination of the mixture of Me3SiOSO2Me and BF3 . Et2O by 1H-n.m.r. spectroscopy demonstrated that a reaction occurs to generate trimethylsily fluoride and species of the type F2BOSO2Me, FB(OSO2Me)2, or B(OSO2Me)3 via ligand exchange.

Catalysis↗