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Biomedical subjects

A C Richardson

Publications and source records attributed to A C Richardson.

18 recordsLinked to original sources
PubMed1992

The detection of lipase activity in bacteria using novel chromogenic substrates.

The propionate (Pro), decanoate (Dec) and laurate (Lau) esters of 5-(4-hydroxy-3,5-dimethoxyphenylmethylene)-2-thioxothiazoline++ +-3-acetic acid were assessed as substrates for lipase and esterase. On hydrolysis these substrates yield an intensely red coloured phenol which could be assayed at 505 nm. The Pro ester was an effective substrate for porcine esterase and was hydrolysed at a rate 20 times greater than the Lau and Dec esters. Conversely, Pseudomonas lipase had a high activity towards the Lau and Dec esters, especially in the presence of bovine serum albumin, but little activity towards the Pro ester. The Dec and Lau were used to detect lipolytic activity in Pseudomonas strains associated with milk spoilage. For this purpose, the substrates were absorbed onto filter paper disks, which were placed over bacterial colonies growing on agar plates; activity was indicated by bright red colouration of discs within 2 h. Escherichia coli colonies hydrolysed the Pro but not the Lau or Dec esters.

Benzoates↗
PubMed1991

Thio and epidithio derivatives of methyl beta-lactoside.

Treatment of methyl beta-lactoside with triphenylphosphine-carbon tetrabromide in pyridine gave the 3',6'-anhydro-6-bromo-6-deoxy derivative, from which 6-thio derivatives were prepared, and methyl 3',4'-O-isopropylidene-beta-lactoside gave the 6,6'-dibromo-6,6'-dideoxy derivative. A dibromide was prepared also from methyl 4',6'-O-benzylidene-beta-lactoside by bromination with Ph3P-CBr4, acetylation, and then treatment with N-bromosuccinimide. Various 6,6'-dithio derivatives were prepared from the 6,6'-dibromide by nucleophilic substitution reactions. Reaction of the 6,6'-dibromide with thiourea led to the 6,6'-epidithio derivative and, with potassium tricarbonate, the bridged 6,6'-trithiocarbonate was formed. The 6,6'-dibromo derivative underwent selective nucleophilic substitution to give a variety of 6'-bromo-6-thio derivatives. Likewise, with azide, the 6-azide was formed first, followed by the 6,6'-diazide and the product of elimination, the 6-azido-5%-ene. Raney nickel-mediated desulphuration of the various 6,6'-dithio derivatives afforded methyl 6,6'-dideoxy-beta-lactoside and desulphuration of the 6'-bromo-6-thio derivatives could be accomplished without reductive dehalogenation to give methyl 6'-bromo-6,6'-dideoxylactoside.

Carbohydrate Sequence↗
PubMed1991

Improved methods for the detection of beta-galactosidase activity in colonies of Escherichia coli using a new chromogenic substrate: VBzTM-gal (2-(2-(4-(beta-D-galactopyranosyloxy)-3-methoxyphenyl)-vinyl)-3- methylbenzothiazolium toluene-4-sulphonate).

The use of a new substrate 2-(2-(4-(beta-D-galactopyranosyloxy)-3- methoxyphenyl)-vinyl)-3-methylbenzothiazolium toluene-4-sulphonate (VB-zTM-gal) is described for the detection of beta-galactosidase activity in colonies of wild type and mutant strains of Escherichia coli. On enzymic hydrolysis this substrate, which is soluble in water, released a chromophore which is red at pH 7 and bound to cellulose and nitrocellulose. The best procedure for the detection of activity was to grow colonies on standard nitrocellulose membranes (pore size 0.45 microns) laid onto an agar plate and to float the membranes over a solution of the substrate. Coloured colonies developed within 3 min, which were stable at 4 degrees C for several days, and this identified the expression of beta-galactosidase activity. This was found to be more specific than methods using triphenyltetrazolium or Eosin Methylene Blue media, and more economical than methods using X-gal (5-bromo-4-chloro-3-indolyl beta-D-galactopyranoside). VBzTM-gal should have applications in gene cloning technology and in the detection of coliform organisms in polluted water.

Chromogenic Compounds↗
PubMed1990

Synthesis of 1-deoxy-6-epicastanospermine and 1-deoxy-6,8a-diepicastanospermine.

Extension of the carbon spine of 2,3;4,5-di-O-isopropylidene-beta-D-fructopyranoside by oxidation at C-1 followed by a Wittig reaction using the phosphorane Ph3P = CHCO2Et gave an oct-4-ulose derivative, which was then transformed into the key intermediate 1-azido-1,2,3-trideoxy-D-arabino-oct-4-ulose. Catalytic hydrogenolysis of this azide, followed by reductive amination between the resulting 1-amino substituent and the 4-keto-group then gave a mixture of pyrrolidines. After sulphonylation at the terminal 8-position, the pyrrolidines were then cyclised further between the nitrogen and C-8 to give 1-deoxy-6-epicastanospermine and 1-deoxy-6,8a-diepicastanospermine.

Alkaloids↗
PubMed1990

The structural basis of the inhibition of human glycosidases by castanospermine analogues.

A series of epimers and deoxy derivatives of castanospermine has been synthesized to investigate the contribution of the different chiral centres to the specificity and potency of inhibition of human liver glycosidases. Castanospermine inhibits all forms of alpha- and beta-D-glucosidases, but alteration to any of the five chiral centres in castanospermine markedly decreases the inhibition. 6-Epicastanospermine, which is related to D-pyranomannose in the same way as castanospermine is to D-pyranoglucose, does not inhibit lysosomal (acidic) alpha-mannosidase, but is a good inhibitor of the cytosolic or neutral alpha-mannosidase. Conversely, 1-deoxy-6-epicastanospermine inhibits acidic alpha-mannosidase strongly, but not the neutral alpha-mannosidase. An explanation of this different inhibition based on preferential recognition of different configurations of mannose by the different forms of alpha-mannosidase is postulated. All derivatives of 6-epicastanospermine also have the minimum structural feature for the inhibition of alpha-L-fucosidase, but those with a beta-anomeric substituent do not inhibit the enzyme, or do so very weakly. 1-Deoxy-6,8a-diepicastanospermine, which has four chiral centres identical with alpha-L-fucose, is, however, a potent inhibitor of alpha-L-fucosidase (Ki 1.3 microM).

Alkaloids↗
PubMed1990

The apical location of calculus within the intrabony defect.

Although several studies have concluded that calculus removal becomes more difficult as pocket depth increases, few have examined the clinical location of calculus within the intrabony defect. This study evaluated the relationship between apical calculus position and the depth and morphology of the intrabony defect. As part of an on-going study of new attachment procedures in humans, 260 intrabony defects were surgically entered in 39 patients. Using magnifying loops and fiber optics in all defects, the most apical level of calculus was grooved to serve as both a clinical and histologic reference point. Clinical measurements made prior to root debridement included the alveolar crest to base of calculus, and the base of calculus to base of defect. The type of defect was classified by the number of remaining osseous walls. Calculus has not been found apical to the groove in any histologic section. The mean distance measured clinically between the base of the calculus and the base of the defect was found to increase with the depth of the defect. This relationship did not vary with either tooth type or number of remaining osseous walls in the defect. Data analysis of this group of patients (N = 39) showed a positive correlation (r = .83) between increasing depth of intrabony defect and the distance of the most apical calculus from the defect base.

Alveolar Process↗
PubMed1990

"VRA-GlcNAc": novel substrate for N-acetyl-beta-D-glucosaminidase applied to assay of this enzyme in urine.

We describe a new chromogenic substrate and assay for determining N-acetyl-beta-D-glucosaminidase (EC 3.2.1.30; NAG) activity in normal and pathological human urine. The novel substrate, ammonium 5-[4-(2-acetamido-2-deoxy-beta-D-glucopyranosyloxy)-3- methoxyphenylmethylene]-2-thioxothiazolidin-4-one-3-ethan oate (VRA-GlcNAc), is prepared by condensation of vanillyl N-acetyl-beta-D-glucosaminide and rhodanine-3-ethanoic acid. The phenol released by enzyme action has an intense absorption peak at 492 nm (epsilon = 37,000 L.mol-1.cm-1). The Km for NAG in urine was 0.5 mmol/L at pH 4.5. The substrate solution may be stored at 4-7 degrees C for one week without any increase in the substrate blank. For optimal assay conditions, we used a substrate concentration of 3 mmol/L and a 15-fold sample dilution at pH 4.5-5.0, with measurement at 505 nm, not significantly different from that at 492 nm. The sensitivity of the assay with VRA-GlcNAc as substrate is twice that of the MNP-GlcNAc [2-methoxy-4-(2'-nitrovinyl)-phenyl GlcNAc] procedure (Clin Chim Acta 1982;124:195-204) and can detect low amounts of minor NAG isoenzymes. This assay is an improvement on previously available colorimetric methods and could be easily incorporated into kits based on either an enzyme calibrant or the molar absorptivity of the phenol.

Acetylglucosamine↗
PubMed1987

Careful surgical technique can reduce infectious morbidity after cesarean section.

A total of 635 consecutive cesarean sections performed in private practices during the past 20 years are reviewed. In the course of this 20 year period, we have tried to alter gradually our surgical technique used for this procedure to conform to the principles of surgery developed by Halsted. The study is divided into three periods of time to examine the results of changes in technique. With the use of the standard definition of febrile morbidity (temperature of greater than or equal to 100.4 degrees F during any two 24-hour periods after the first postoperative 24 hours) the postoperative morbidity rate was 15% during 1967 to 1973, 5.4% during 1974 to 1979, and 0.7% during the period 1980 through 1986. Prophylactic antibiotics were used with decreasing frequency. It was clear that the reduction in morbidity was the result of the modifications in surgical technique.

Anti-Bacterial Agents↗
PubMed1977

Transformations of cellobiose derivatives into analogues of lactose.

The preparation of benzyl beta-cellobioside 2,3,6,2',3'-pentabenzoate (2b) via a 4',6'-benzylidene acetal in 27% overall yield from cellobiose is described. This pentabenzoate has been utilised for conventional syntheses of the 6'-amino-, 4'-amino-, and 4',6'-diamino-analogues of lactose, via the 4',6'-dimesylate. In addition, reaction of the pentabenzoate 2b with sulphuryl chloride initially afforded the 6'-chloro derivative, which was then slowly transformed into a mixture of the 4',6'-dichloro-lactoside and an isomer in which the non-reducing ring of the disaccharide had been transformed into a 3',6'-dideoxy-3',6'-dichloro-gulopyranoside. The latter probably arose by neighbouring-group participation by the 3'-benzoloxy group prior to the introduction of the secondary 3'-chloro substituent. The former dichlorocompound was subsequently converted into 4',6'-dideoxy-4',6'-dichloro-lactose. It was found that the rate of nucleophilic displacement at C-4' of a cellobioside was much lower than that for the corresponding alpha-linked disaccharide, maltose. Furthermore, nucleophilic displacement at C-4' of a lactoside was accompanied by substantial elimination, to give the 4'-ene, together with some cleavage of the interglycosidic bond. tthe origins of these effects are discussed.

Cellulose↗
PubMed1976

A new look at pelvic relaxation.

The concept is presented that most cystoceles and/or urethroceles result from insolated defects in the connective tissue supports of the anterior quadrant of the pelvis. Four areas in which defects have been found to occur are identified. Sixty patients are presented who were found to have isolated defects in the endopelvic fascia at the lateral sidewall of the pelvis with significant cystourethroceles and stress urinary incontinence. The surgical treatment consisted only of a direct approach to and closure of the isolated defect. The operative results at 3 to 48 months were excellent in 91.7 per cent, improved in 5 per cent, and failed in 3.3 per cent. Discussion is offered of the possibility of the study of the pelvic floor from the viewpoint of a mechanical engineer.

Female↗
PubMed1976

Decreasing postpartum sexual abstinence time.

Postpartum sexual abstinence time can be safely shortened for most patients when episiotomy repair is done meticulously with fine PGA suture on small needles. The time preferred by patients for resumption of intercourse seems to be between the second and third postpartum week. We have seen no ill effects from this, and we feel that sexual intercourse at these early dates does not influence the healing of the episiotomy in any way.

Episiotomy↗
PubMed1976

Synthesis of the allo-analogue of trehalose.

Selective benzoylation of HO-2 and HO-2' of 4,6-O-benzylidene-alpha-D-glucopyranosyl 4,6-O-benzylidene-alpha-D-glucopyranoside with N-benzoylimidazole led to the exclusive formation of 2-O-benzoyl-4,6-O-benzylidene-alpha-D-glucopyranosyl 2-O-benzoyl-4,6-O-benzylidene-alpha-D-glucopyranoside. Oxidation of either the dibenzoate or the corresponding ditosylate with methyl sulphoxide--phosphorus pentaoxide gave the 3,3'-diulose, and subsequent reduction with borohydride gave the 3,3'diepimers having the allo-allo configuration. De-esterification and hydrolysis of the benzylidene substituents gave alpha-D-allopyranosyl alpha-D-allopyranoside.

Disaccharides↗
PubMed1975

Some benzylidene acetal derivatives of theophylline nucleosides.

The reaction of some hexopyranosyltheophylline nucleosides with benzaldehyde in the presence of zinc chloride gave the expected benzylidene acetals. Thus, 7-alpha-D-mannopyranosyltheophylline gave the 2',3':4',6'-diacetal as a mixture of diastereoisomers, one of which was isolated. The beta-D-galacto- and beta-D-gluco-pyranosyltheophyllines gave the 4',6'-acetals, which were characterised as 2',3'-diesters. Mild, acidic hydrolysis of 7-(4,6-O-benzylidene-2,3-di-O-mesyl-beta-D-glucopyranosyl)theophylline gave 7-(2,3-di-O-mesyl-beta-D-glucopyranosyl)theophylline, and strongly basic hydrolysis gave 7-(2,3-anhydro-4,6-O-benzylidene-beta-D-allopyranosyl)theophylline. Ring-opening of this 2',3'-epoxide with iodide anion afforded mainly 7-(4,6-O-benzylidene-2-deozy-2-iodo-beta-D-altropyranosyl)theophylline, which was characterised as the 6'-acetate.

Benzylidene Compounds↗