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Biomedical subjects

G R Gray

Publications and source records attributed to G R Gray.

At least 37 records · Page 2Linked to original sources
PubMed1995

Authentic standards for the reductive-cleavage method. The positional isomers of partially methylated and acetylated or benzoylated 1,5-anhydro-D-glucitol.

Described is an efficient method for the synthesis of the sixteen positional isomers of methylated and acetylated or benzoylated 1,5-anhydro-D-glucitol. The compounds are generated simultaneously by partial methylation of 1,5-anhydro-D-glucitol and subsequent benzoylation, and the individual isomers are obtained in pure form by high-performance liquid chromatography. Debenzoylation of the latter and acetylation yielded the desired acetates. Reported are the 1H NMR spectra of the benzoates and the electron-ionization mass spectra of the acetates and the tetra-O-methyl derivative. Also reported for the acetates and the tetra-O-methyl derivative are their linear temperature programmed gas-liquid chromatography retention indices on three different capillary columns.

Acetates↗
PubMed1995

Synthesis and characterization of authentic standards for the analysis of ribofuranose-containing carbohydrates by the reductive-cleavage method.

Described herein is the synthesis of all positional isomers of partially methylated and acetylated or benzoylated 1,4-anhydro-D-ribitol. The benzoates are generated simultaneously from 1,4-anhydro-D-ribitol by sequential partial methylation and benzoylation or sequential partial benzoylation and methylation. The individual isomers are obtained in pure form by high-performance liquid chromatography. Debenzoylation and acetylation provided the corresponding acetates. Reported herein are the 1H NMR spectra of the benzoates and the electron-ionization mass spectra of the acetates and the tri-O-methyl derivative and also for the acetates and the tri-O-methyl derivative, their linear temperature programmed gas-liquid chromatography retention indices on three different capillary columns.

Acetates↗
PubMed1995

Authentic standards for the reductive-cleavage method. The positional isomers of partially methylated and acetylated or benzoylated 1,5-anhydro-D-galactitol.

Described herein is an efficient method for the synthesis of the sixteen positional isomers of methylated and acetylated or benzoylated 1,5-anhydro-D-galactitol. The compounds are generated simultaneously by partial methylation of 1,5-anhydro-D-galactitol and subsequent benzoylation, and the individual isomers are obtained in pure form by high-performance liquid chromatography. Debenzoylation and acetylation yielded the desired acetates. Reported herein are the 1H NMR spectra of the benzoates and the electron-ionization mass spectra of the acetates and the tetra-O-methyl derivative. Also reported for the acetates and the tetra-O-methyl derivative are their linear temperature-programmed gas-liquid chromatography retention indices on three different capillary columns.

Acetylation↗
PubMed1995

Hb Lulu Island (alpha 2 beta 2 107[G9]Gly-->Asp)-beta zero- thalassemia (codon 15; TGG-->TAG), a form of thalassemia intermedia.

Hb Lulu Island [beta 107(G9)Gly-->Asp] was discovered in an East Indian female who carried a common beta zero-thalassemia allele, i.e., codon 15, TGG-->TAG (is a stop codon) in trans. Both abnormalities were detected through sequencing of the amplified beta-globin genes and were confirmed by hybridization with 32P-labeled probes. Hb Lulu Island is mildly unstable with a borderline decrease in oxygen affinity; its instability is less severe than that of Hb Burke or beta 107(G9)Gly-->Arg. The compound heterozygosity expresses as a thalassemia intermedia with moderate anemia, a variable need for blood transfusions, Heinz body formation, and a red cell morphology which is typical for such a condition. The level of HbA2 was greatly increased (6.5-7.0%) as was the delta chain level (12% of total non-alpha) probably because of the instability of Hb Lulu Island and the decreased ability of the beta x chain to form dimers with the normal alpha chain.

Adult↗
PubMed1994

An improved procedure for the analysis of linkage positions in 2-acetamido-2-deoxy-D-glucopyranosyl residues by the reductive-cleavage method.

The conditions of the reductive-cleavage method were modified to allow simultaneous analysis of 2-acetamido-2-deoxy-D-glucopyranosyl residues and monosaccharides of other classes. Methyl 2-deoxy-3,4,6-tri-O-methyl-2-(N-methylacetamido)-beta-D-glucopyran oside was found to undergo transglycosidation under reductive-cleavage conditions when the reaction was quenched with an alcohol. Transglycosidation proceeded via an oxazolinium-ion intermediate, which then acted as a glycosyl donor to form an anomerically pure product. Time-course studies showed that in the presence of trimethylsilyl trifluoromethanesulfonate (Me3SiOSO2CF3), 4 h were required for complete conversion of the substrate into this intermediate, which was then trapped with methanol-d4. When the reaction was conducted in the presence of a mixture of trimethylsilyl methanesulfonate (Me3SiOSO2Me) and boron trifluoride etherate (BF3.OEt2) or with BF3.OEt2 alone, 24 h and 48 h, respectively, were required for complete conversion. The alpha anomer was unreactive after 24 h under all conditions, confirming earlier results. Reaction with racemic 2-butanol yielded a pair of diastereomers, in a 1:1 ratio, which were distinguishable by their GLC retention times and their 1H NMR spectra. Reaction with (S)-2-butanol gave only one of the diastereomeric products. These experiments demonstrated the feasibility of using the reductive-cleavage method to determine the absolute configuration of 2-acetamido sugars.

Acetylglucosamine↗
PubMed1994

Analysis by the reductive-cleavage method of a polysaccharide containing 2-acetamido-2,6-dideoxy-D- and -L-galactopyranosyl residues.

Modifications of the reductive-cleavage method for the analysis of 2-acetamido sugars were tested using a polysaccharide containing alpha-linked 2-acetamido-2,6-dideoxy-L-galactopyranosyl (Fuc pNAc) residues, beta-linked D-Fuc pNAc residues and 2-linked D-glucopyranosyl residues. Reductive cleavage of the fully methylated O-antigenic polysaccharide of Pseudomonas aeruginosa ATCC 33358 in the presence of triethylsilane and trimethylsilyl trifluoromethanesulfonate, followed by quenching with methanol and subsequent acetylation, unexpectedly resulted in nearly complete cleavage of all glycosidic linkages to yield 2-O-acetyl-1,5-anhydro-3,4,6-tri-O-methyl-D-glucitol (1a) and methyl 3-O-acetyl-2,6-dideoxy-4-O-methyl-2-(N-methylacetamido)-beta-D- and -L- galactopyranosides (3a and 4a) as the major products. When the reductive-cleavage reaction was quenched with (S)-2-butanol, the major FucNAc derivatives were the diastereomeric (S)-2-butyl glycosides 15a and 17a, confirming the presence of enantiomeric FucNAc residues in the repeating unit of the polysaccharide. However, compounds 15a and 17a were not detected in equimolar proportions, presumably as a consequence of diastereoselectivity in the reaction of the chiral alcohol with the respective intermediate oxazolinium ions. Reductive cleavage of the fully methylated polysaccharide in the presence of a mixture of trimethylsilyl methanesulfonate and boron trifluoride etherate, followed by quenching with methanol, resulted in incomplete cleavage, giving rise to three disaccharide derivatives whose sequences overlap that of the trisaccharide repeating unit in the polysaccharide. The lack of selectivity for cleavage at beta-D-FucNAc residues suggests that the alpha-L-FucNAc residues underwent anomerization prior to transglycosidation.

Benzoates↗
PubMed1993

Structural analysis of sialic acid-containing carbohydrates by the reductive-cleavage method.

The applicability of the reductive-cleavage method to the structural analysis of sialic acid-containing carbohydrates was investigated using fully methylated methyl alpha- and beta-N-acetylneuraminic acid (1 and 2, respectively). Both compounds were fully stable to reductive cleavage in the presence of borane dimethylsulfide and boron trifluoride etherate but were slowly degraded in the presence of triethylsilane and promoters such as trimethylsilyl trifluoromethanesulfonate, boron trifluoride etherate, or a mixture of trimethylsilyl methanesulfonate and boron trifluoride etherate. However, after selective reduction of the ester groups of 1 and 2 with sodium borohydride, the products (3 and 4, respectively) underwent rapid reductive cleavage to yield the expected anhydroalditols, which were characterized as their acetates (8 and 11) by GLC-MS. The major product was also characterized as its benzoate (9) by 1H NMR spectroscopy. The usefulness of this analytical method was demonstrated using 3'-sialyllactose, i.e., alpha-Neu5Ac-(2-->3)-beta-D-Galp-(1-->4)-D-Glc. The methylated and ester-reduced trisaccharide (13) was reductively cleaved with Me2S.BH3-BF3.ET2O and the products were acetylated. Analysis by GLC-MS revealed the products expected from terminal (nonreducing) Neu5Ac (8 and 11), 3-linked Galp (16), and 4-linked Glcp (15) residues in relative molar ratios of 1.2:1.0:1.0, respectively. However, direct reductive cleavage of the fully methylated trisaccharide (12) yielded the fully methylated disaccharide-anhydroalditol derivative alpha-Neu5Ac-(2-->3)-1,5An-D-Gal (14) and the product (15) derived from 4-linked Glcp residues. These experiments therefore established both the composition and the sequence of the trisaccharide.

Borohydrides↗
PubMed1993

Authentic standards for the reductive-cleavage method. The positional isomers of partially methylated and acetylated or benzoylated 1,5-anhydro-D-fucitol.

Described herein is an efficient method for the synthesis of the eight positional isomers of methylated and acetylated or benzoylated 1,5-anhydro-D-fucitol. The compounds are generated simultaneously by partial methylation of 1,5-anhydro-D-fucitol and subsequent benzoylation, and the individual isomers are obtained in pure form by high-performance liquid chromatography. Debenzoylation of the latter and acetylation yielded the desired acetates. Reported herein are the 1H NMR spectra of the benzoates and the electron-ionization mass spectra of the acetates and the tri-O-methyl derivative. Also reported for the acetates and the tri-O-methyl derivative are their linear temperature programmed gas-liquid chromatography retention indices on three different capillary columns.

Acetates↗
PubMed1993

Applications of a new fluorimetric enzyme assay for the diagnosis of aspartylglucosaminuria.

L-Aspartic acid-beta-7-amido-4-methylcoumarin is a sensitive and specific fluorogenic substrate for lysosomal glycoasparaginase (aspartylglucosaminidase). Fibroblasts and leukocytes from 8 patients with aspartylglucosaminuria, showed 1-7% of the mean normal glycoasparaginase activity. Heterozygotes showed intermediate activities. Glycoasparaginase activity in chorionic villi, cultured trophoblasts, cultured amniotic fluid cells and amniotic fluid was readily detectable, indicating that prenatal analysis of aspartylglucosaminuria should be possible with this assay. beta-Aspartyl-4-methylumbelliferone was synthesized but this potential substrate can not be used to assay glycoasparaginase since it hydrolyses spontaneously.

Acetylglucosamine↗
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↗