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Biomedical subjects

G R Gray

Publications and source records attributed to G R Gray.

At least 19 recordsLinked to original sources
PubMed1992

Studies of model compounds for the analysis of ester-containing polysaccharides by the reductive-cleavage method.

The four O-propionyl regioisomers of methyl tri-O-methyl-alpha-D-glucopyranoside and the 2- and 3-O-propionyl regioisomers of methyl tri-O-methyl-beta-D-glucopyranoside were subjected to reductive cleavage in the presence of Et3SiH and Me3SiOSO2CF3, BF3.Et2O, or Me3SiOSO2Me-BF3.Et2O. The O-propionyl group was stable when either Me3SiOSO2CF3 or BF3.Et2O was the catalyst, but was slowly reduced to the (1-propyl) ether when Me3SiOSO2Me-BF3.Et2O was the catalyst. Reductive cleavages catalyzed by Me3SiOSO2CF3 were complete in 6 h, those catalyzed by BF3.Et2O required at least 24 h, and those catalyzed by Me3SiOSO2Me-BF3.Et2O required 30 min or less. In the alpha-series, the rate of reductive cleavage decreased in the order 6-O-propionyl greater than 4-O-propionyl greater than 3-O-propionyl much greater than 2-O-propionyl. The reductive cleavage of beta anomers was faster than that of the corresponding alpha anomers. This effect was particularly striking for the alpha and beta anomers of the 2-O-propionyl regioisomer, as would be expected on the basis of a participation reaction.

Carbohydrate Conformation↗
PubMed1992

Analysis of Macrocystis pyrifera and Pseudomonas aeruginosa alginic acids by the reductive-cleavage method.

Permethylated alginic acids comprised of 4-linked D-mannopyranosyluronic acid and 4-linked L-gulopyranosyluronic acid residues undergo reductive cleavage to yield, after acetylation, methyl 3-O-acetyl-2,6-anhydro-4,5-di-O-methyl-D-mannonate (2b) and methyl 3-O-acetyl-2,6-anhydro-4,5-di-O-methyl-D-gluconate (3b) as major products. Small amounts (ca. 13%) of ring-contracted products, namely methyl 2-O-acetyl-3,6-anhydro-4,5-di-O-methyl-D-mannonate (9) and methyl 2-O-acetyl-3,6-anhydro-4,5-di-O-methyl-D-gluconate (10), were also observed in these experiments. These results are in marked contrast to previous results on the reductive cleavage of 4-linked D-glucopyranosyluronic acid residues, wherein the ring-contracted product was formed exclusively. Formation of the ring-contracted products could be completely eliminated by reduction (LiAlH4) of ester groups in the permethylated alginic acid prior to reductive cleavage. In the latter experiments, 4,6-di-O-acetyl-1,5-anhydro-2,3-di-O-methyl-D-mannitol (5b) and 4,6-di-O-acetyl-1,5-anhydro-2,3-di-O-methyl-L-gulitol (6b) were the sole products of reductive cleavage of the 4-linked ManA and 4-linked GulA residues, respectively. However, in the previous experiments it was noted that low yields of permethylated alginic acids were obtained and that extensive depolymerization occurred under methylation conditions. Depolymerization could be avoided and higher yields of permethylated polysaccharides could be obtained, by reduction of the carboxyl groups of the alginic acids prior to methylation. Reductive cleavage of the latter polysaccharides yielded the products expected from 4-linked D-mannopyranosyl and 4-linked L-gulopyranosyl residues, namely 4-O-acetyl-1,5-anhydro-2,3,6-tri-O-methyl-D-mannitol (13b) and 4-O-acetyl-1,5-anhydro-2,3,6-tri-O-methyl-L-gulitol (14b), respectively. Using the latter analytical strategy, it was established that the Macrocystis pyrifera alginate was comprised of 60% 4-linked ManA and 40% 4-linked GulA residues, whereas the Pseudomonas aeruginosa alginate was comprised of 80% 4-linked ManA and 20% 4-linked GulA residues.

Alginates↗
PubMed1992

Spontaneous remission of multilobated non-Hodgkin lymphoma.

A 67-year-old previously well man was admitted with hypercalcemia after a 7-day history of fever, night sweats, and back pain. The blood showed 5% multilobated lymphoid cells. A multilobated non-Hodgkin lymphoma associated with marked reticulin fibrosis was diagnosed on a bone marrow biopsy. During the next 7 days, in the absence of specific therapy, his symptoms disappeared. Three weeks after admission his biochemical abnormalities had resolved and after 9 weeks his bone marrow examination was normal. He remains in clinical and laboratory remission 16 months after presentation.

Aged↗
PubMed1992

Socio-cognitive skills as a determinant of life satisfaction in aged persons.

The purpose of this study was to explore the viability of a revised model of elderly life satisfaction, specifically evaluating the contribution of socio-cognitive skills. The role of such skills in relation to life satisfaction among aged persons has not been explored in research to date. Pilot data gathered from 60 community-living aged individuals indicated that numerous variables (e.g., subjective/objective health, education, financial satisfaction, role participation, subjective integration) significantly correlated with life satisfaction. However, the combined effects of two variables, persons' feelings of loneliness and isolation from their families and a measure of socio-cognitive skill, accounted for 49 percent of the variability in elderly life satisfaction. The effects of each on life satisfaction were unique however. Implications of these data and possible interventions for increasing elderly persons' life satisfaction are discussed.

Aged↗
PubMed1991

In vitro stimulation of immune functions by lipids derived from macrophages exposed to bacterial peptidoglycan.

It has previously been established that the processing of Bacillus subtilis cell walls by the macrophage-like cell line RAW264 leads to the formation of peptidoglycolipids containing glycopeptides of bacterial origin. In view of the immunologic activities associated with lipophilic muramyl peptide derivatives, lipid extracts derived from macrophages exposed to bacterial cell walls were assayed for mitogenicity. The crude lipid extract derived from RAW264 cells exposed to bacterial cell walls gave a strong mitogenic response when delivered as liposomes to murine splenocytes, whereas lipids derived from macrophages not exposed to bacterial cell walls did not give a mitogenic response. Fractionation of the RAW264 lipids into neutral lipids, glycolipids, and phospholipids demonstrated that mitogenicity was associated primarily with the phospholipid fraction and thus correlated with the presence of the aforementioned peptidoglycolipids. Mitogenicity was specific to the lipids derived from macrophages exposed to bacterial cell walls and was not observed in lipids derived from macrophages that had either been nonspecifically activated by exposure to Con A or had been allowed to phagocytize latex beads. The mitogenic response was found to be dependent on the presence of macrophages in the splenocyte population and to, at least in part, involve macrophage activation.

Animals↗
PubMed1991

Analysis of a pyruvic acid acetal-containing polysaccharide by the reductive-cleavage method.

The applicability of the reductive-cleavage method to the analysis of polysaccharides bearing pyruvic acid acetals has been demonstrated. Direct reductive cleavage of fully methylated gum xanthan yielded the expected products, including 1,5-anhydro-4,6-O-[(S)-1-methoxycarbonylethylidene]-2,3-di-O-methy l-D- mannitol. The latter product was not observed when reductive cleavage was performed subsequent to reduction of ester groups in the fully methylated polysaccharide and mild hydrolysis to remove pyruvic acid acetal substituents. Instead, the latter experiment yielded 1,5-anhydro-2,3-di-O-methyl-D-mannitol, establishing the presence in the polysaccharide of terminal (nonreducing) D-mannopyranosyl groups bearing 4,6-O-(1-carboxyethylidene) substituents. The products of reductive cleavage were characterized, where appropriate, by comparison of the gas chromatographic retention times and chemical ionization- and electron ionization-mass spectra of their acetates to those of authentic standards. Alternatively, the products of reductive cleavage could be characterized without resort to comparison with authentic standards by analysis of the 1H-n.m.r. spectra of their benzoates, which were obtained in pure form by high-performance liquid chromatography. By either method of product characterization, this two-step procedure of analysis reveals the presence of pyruvic-acetal residues in polysaccharides and establishes both the identity of the sugar residue to which they are attached and their positions of attachment.

Carbohydrate Sequence↗
PubMed1991

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

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

Isomerism↗
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↗