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Biomedical subjects

R G Price

Publications and source records attributed to R G Price.

At least 37 records · Page 2Linked to original sources
PubMed1994

[Age-dependent urinary N-acetyl-beta-D-glucosaminidase activity in healthy children].

Urinary N-acetyl-beta-D-glucosaminidase activity was measured in 123 healthy children aged between 1-14 years by two newly developed colorimetric procedures using MNP-GlcNAc and VRA-GlcNAc substrates and was compared to the well established PNP-GlcNAc assay. The enzyme activity was factored with the urinary creatinine concentration and expressed as NAG index. The applicability and the advantages of the new methods are discussed. The NAG values obtained with each substrate decreased with age as a result of a concomitant rise in the urinary creatinine concentration.

Acetylglucosaminidase↗
PubMed1994

Modulating influence of barley on the altered metabolism of glucose and of basement membranes in the diabetic rat.

A study was conducted to explore the effects of different sources of dietary carbohydrate on the altered metabolism of basement membrane proteins (type IV collagen and laminin) that occurs in the streptozotocin-diabetic rat. The substitution of barley for sucrose reduced the elevated plasma concentration of 7-S collagen and of laminin P2, peptide fragments that retain antigenicity of the parent proteins. Similar effects were noted in the liver and kidney content of these peptides. It is suggested that the beneficial property of barley is due to its high content of chromium, as has been demonstrated in the study of glucose metabolism.

Animals↗
PubMed1994

Early urinary markers of target nephron segments as studied in cadmium toxicity.

A number of chemicals may adversely affect one or more of the anatomical structures of the kidney, such as the glomerulus, the tubular apparatus, the medullary, or interstitial cells. To recognize subclinical renal dysfunction, a battery of new, non-invasive tests was applied in comparison to established ones. The study on cadmium exposed subjects, performed within the framework of a collaborative European research project, exemplifies the concept of target selectivity within a nephron. One hundred seventy-two subjects were classified according to urinary cadmium excretion as controls (< 1.5 micrograms/g creatinine), or subjects with moderate or high cadmium body burden (1.5 to 5 micrograms/g creatinine, > 5 micrograms/g creatinine). Twenty-six urinary analytes (such as serum derived proteins, tubular enzymes, eicosanoids) and four plasma markers, related to the function or integrity of specific nephron segments, were investigated in a cross-sectional study. The group with the moderate cadmium body burden showed alterations of proximal tubular integrity, that is, increased excretion of tubular brush-border antigens. The group with higher cadmium body burden revealed an involvement of the whole nephron. The most prominent quantitative changes were found for the glomerular markers high molecular weight proteins, and thromboxane B2 and for the proximal tubular markers retinol binding protein, alpha 1-microglobulin, N-acetyl-beta-D-glucosaminidase, and the intestinal alkaline phosphatase. A diagnostic approach to screen for nephrotoxicity due to environmental hazards like cadmium should include proximal tubular markers (alpha 1-microglobulin and tubular enzymes, that is, intestinal alkaline phosphatase) but the measurement of glomerular markers is also advisable.

Adult↗
PubMed1993

Comparison of several new chromogenic galactosides as substrates for various beta-D-galactosidases.

The kinetic characteristics of beta-galactosidases from bovine liver and testes, Escherichia coli, Aspergillus niger and Jack bean were studied using five newly-developed colorimetric substrates. All the chromophores released by enzyme hydrolysis had high extinction coefficients in the visible region of the spectrum. Varying amounts of substrate inhibition were found with each of these substrates (VBzTM-Gal, VLM-Gal, VLPr-Gal, VQM-Gal and VQPr-Gal), but this was not a significant problem if the correct assay conditions were used. The substrates attached particularly tightly to the active centre of E. coli beta-D-galactosidase resulting in low Km values. The data suggest that the chemical properties of the heterocyclic portion of the aglycone distant from the glycosidic oxygen do not affect the substrate specificity and the substrate inhibition can be attributed to interactions not involving the catalytic site. When the product of the maximum observed velocity (Vm) and the molar absorption coefficient is calculated for each substrate, the relative merits of the substrates for the assay of each enzyme can be assessed. The beta-D-galactosidases from fungal and bacterial sources hydrolysed the substrates most efficiently, indicating that they may be of particular value in areas of molecular biology and biotechnology.

Animals↗
PubMed1992

High resolution proton magnetic resonance spectroscopy of cyst fluids from patients with polycystic kidney disease.

High field 1H-NMR spectra of fluid collected from the cysts of six renal transplant recipients with autosomal dominant polycystic kidney disease (ADPKD) have been measured and the major metabolite signals assigned. Quantitative NMR measurements have revealed a combination of unusual biochemical features of the cystic fluids that shows them to be distinct from both blood plasma and urine. Isoleucine, lysine, threonine and valine were present at mM concentrations, in cyst fluid and in some cases levels up to 2 orders of magnitude higher than normal plasma or urine were recorded. Mean glucose concentrations in the cyst fluids ranged from 3.4-9.6 mM and a number of organic acids and bases, including acetate, lactate, succinate, creatinine and dimethylamine were also present at high concentration and in different ratios to those found in either plasma or urine. The majority of cyst fluids examined also contained significant quantities of glycoproteins with characteristic 1H-NMR signals from N-acetyl groups of amino-sugar and sialic acid side chains which had a high degree of molecular mobility (as indicated by their relatively long T2 relaxation times, greater than 120 ms). High levels of ethanol (0.5-12.6 mM/l) were found in all fluid samples from the six transplanted patients (confirmed by conventional analysis). In general there was little variation in the 1H-NMR spectral patterns of either the intra- or interpatient cyst fluids, although the contribution of the protein macromolecules to individual spectra was lower in a few cysts. This constancy of biochemical composition probably reflects the chronic nature of the accumulation of cyst fluid and a long turnover of the cystic fluid components which has the effect of averaging composition. These findings suggest that the dynamic composition of cyst fluid from ADPKD patients is unique among the other body fluids and that the unusual composition may be related to epithelial polarity reversal of the cystic epithelium which could also contribute to the growth of the cysts.

Amino Acids↗
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↗
PubMed1992

AMC-anti-FITC conjugates: novel reagents for amplified immunochemical techniques. Immunofluorescent staining of human fibroblasts.

Fluorescein antibodies were labelled with 7-aminocoumarin (AMC) derivatives, the 3-acetic acid and the 3-propionic acid N-hydroxysuccinimide esters. The labelled antibodies were used in conjunction with fluorescein isothiocyanate (FITC) and carboxyfluorescein-conjugated primary and secondary antibodies to develop novel immunofluorescent staining procedures. These methods combine the advantages of the fluorescence properties of AMC and the ready availability of FITC-labelled antisera to provide an amplified fluorescence signal as well as overcoming the photobleaching problems in FITC staining. The method is easy to perform and is expected to make an important contribution to the improvement of the quality of staining achieved with immunofluorescence. Details of the procedure used to stain human fibroblasts with antifibronectin antibodies are reported in order to illustrate the method.

Animals↗
PubMed1992

Reduction of the rate of fluorescence decay of FITC- and carboxyfluorescein-stained cells by anti-FITC antibodies.

Anti-fluorescein antibodies were found to prevent the fading of emitted fluorescence from fibroblasts stained with fluorescein-labelled fibronectin antibodies. The prevention of fading is the result of specific binding of the fluorochromes present on the stained cells by the anti-fluorescein antibodies. The sheep anti-FITC antibody used in this study was equally effective in preventing the fading of both FITC- and carboxyfluorescein-labelled fibronectin antibodies. The method is simple, effective, does not interfere with the primary immune reaction, and in addition to preventing the fading of fluorescence it reduced the background fluorescence of the specimens. The procedure is expected to make an important contribution to improving the quality of fluorescence immunohistochemical techniques used in diagnosis.

Fibroblasts↗
PubMed1992

Assay of N-acetyl-beta-D-glucosaminidase in urine from neonates: comparison of two new colorimetric methods using MNP-GlcNAc and VRA-GlcNAc as substrates.

The NAG activity present in urine from newborn babies was assayed using two colorimetric procedures with either MNP-GlcNAc or VRA-GlcNAc as substrate and compared with data obtained with the well established PNP-GlcNAc procedure. Both new assays were easy to perform and reproducible. The MNP-GlcNAc method has the advantage that it is now available as a kit; however, the VRA-GlcNAc procedure is more sensitive. NAG activity, creatinine concentration and NAG-index values were determined in normal neonates and within-run imprecision calculated. Excellent correlations were found between MNP-GlcNAc-ase and VRA-GlcNAc-ase indices (r = 0.984) and between PNP-GlcNAc-ase and VRA-GlcNAc-ase indices (r = 0.952). When low molecular weight urinary components were removed by gel filtration no significant change in VRA-GlcNAc-ase activity was observed.

Acetylglucosamine↗
PubMed1992

The role of NAG (N-acetyl-beta-D-glucosaminidase) in the diagnosis of kidney disease including the monitoring of nephrotoxicity.

The assay of urinary N-acetyl-beta-D-glucosaminidase (NAG) provides an early indication of tubular dysfunction resulting from renal disease or nephrotoxic damage. False positives are rare and its activity remains high during active disease or a sustained toxic insult but falls to normal levels on recovery or removal of the toxin. Urinary NAG activity can be used in conjunction with other tests to assess disease activity and prognosis. The assay of NAG isoenzymes increases the diagnostic potential of this test while the availability of dipsticks and simple assay kits will allow its use outside the laboratory.

Acetylglucosaminidase↗
PubMed1992

Measurement of N-acetyl-beta-glucosaminidase and its isoenzymes in urine methods and clinical applications.

1. N-Acetyl-beta-glucosaminidase is the most widely used urinary enzyme assay for the assessment of renal disease and the detection of nephrotoxicity. 2. An increase in N-acetyl-beta-glucosaminidase activity in urine is a sensitive test for renal tubular damage, since its relative molecular mass (M(r) > 130,000) precludes its filtration by the glomerulus and it is the most active of the glycosidases found in the lysosomes in the proximal tubule. 3. The analytical methods available for the determination of urinary N-acetyl-beta-glucosaminidase include fluorometric, colorimetric, spectrophotometric and a dipstick test. 4. The isoenzyme profile of N-acetyl-beta-glucosaminidase in urine varies at different stages of renal disease and damage. In particular there are increases in the B and I2 forms which may reflect perturbation of the cellular biosynthetic processes. 5. The value of N-acetyl-beta-glucosaminidase assays in various areas of medicine is briefly discussed and attention paid to its future role.

Acetylglucosaminidase↗
PubMed1992

Subacute cor pulmonale due to tumor embolization.

Pulmonary tumor embolism is a rare but well-documented cause of respiratory failure in patients with cancer. This entity is probably clinically underrecognized and may represent an important cause of mortality and morbidity in patients with cancer. Pulmonary tumor embolization may present at any stage of the patient's illness and indeed may be the first presentation of an occult carcinoma. In a review of 1069 nonmedicolegal autopsy protocols, we recently encountered three cases in which death had occurred from subacute cor pulmonale due to tumor embolization from breast, lung, and ovarian carcinoma. Recent advances in cytologic examination of blood samples obtained from Swan-Ganz catheters may prove useful in the diagnosis of this entity.

Aged↗
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↗
PubMed1991

Comparison of proteoglycans synthesized by porcine normal and polycystic renal tubular epithelial cells in vitro.

Newly synthesized porcine tubular epithelial cell proteoglycans were labeled in vitro with Na2[35S]SO4. At the beginning of the labeling period (24 h) [35S] sulfate incorporated into macromolecules was measured following PD-10 chromatography. There was a significant reduction in the amount of 35S-labeled macromolecules isolated from polycystic cells compared to that from normal cells. The distribution of recovered radiolabeled material among the medium, cell surface, and intracellular fractions was similar for both normal and polycystic cells. Analysis of the proteoglycans in polycystic cells demonstrated that 86 and 73% of 35S-labeled macromolecules were of the heparan sulfate type in polycystic and normal cells, respectively. The remainder was chondroitin sulfate. Proteoglycans were characterized using DEAE-Sephacel ion-exchange chromatography, chondroitinase ABC, heparitinase, and nitrous acid digestion followed by Sepharose CL-4B gel permeation chromatography. The majority of radiolabeled material in the medium, cell surface, and intracellular fractions eluted between 0.35 and 0.39 M NaCl. However, a second peak (peak II) that eluted at 0.25 M NaCl was found in the medium from polycystic cells. This peak accounted for 27% of the total macromolecules secreted into the medium. Proteoglycans in the major peak were susceptible to nitrous acid and chondroitinase ABC digestion. A similar proportion of peak II was degraded by chondroitinase ABC. However, the remainder was only slightly susceptible to treatment with nitrous acid or heparitase. In normal cells a small amount of material eluted at a similar low charge; the proteoglycans were the same as those found in the major peak and appeared as a shoulder on this peak.

Animals↗
PubMed1991

Variation in the isoenzymes of N-acetyl-beta-D-glucosaminidase and protein excretion in aminoglycoside nephrotoxicity in the rat.

Three aminoglycosidic antibiotics: tobramycin, amikacin and sisomicin were administered to rats. There was an increase in the activity of N-acetyl-beta-D-glucosaminidase (NAG) excreted in the urine and this was characterized by a change in the isoenzyme profiles eluted from DEAE--cellulose. The largest increase in NAG activity was observed following sisomicin administration due mainly to an increase in the B-form of NAG with a concomitant fall in the intermediate (I-form). Separation of urinary proteins by SDS-polyacrylamide gel electrophoresis demonstrated a mixed tubular and glomerular proteinuria following administration of sisomicin. It is concluded that the separation of NAG isoenzymes and urinary proteins provides valuable additional information on the nature and severity of antibiotic nephrotoxicity.

Acetylglucosaminidase↗