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M Tay

Publications and source records attributed to M Tay.

10 recordsLinked to original sources
PubMed1994

Desulphation of dextran sulphate during kidney ultrafiltration.

The renal clearance of [3H]dextran sulphate by the isolated perfused rat kidney was associated with desulphation of the molecule, as demonstrated by ion-exchange and affinity chromatography of material resident in both glomeruli and urine samples. This process also occurred in vivo. The molecular size distribution of glomerular dextran sulphate in the perfused kidney was indistinguishable from that in the perfusate, and although urinary material was smaller it remained macromolecular. Sulphatase activity was not detected in urine or in the perfusate of perfused kidneys, but was detected in glomerular and non-glomerular cortex fractions isolated by a sieving procedure. The identification of significant biochemical changes to dextran sulphate demonstrates that it does not function as an inert transport probe, and supports the concept of cellular involvement in the process of renal charge selectivity.

Animals↗
PubMed1994

Diagnosis of left atrial myxoma following systemic embolism.

Cardiac myxomas are rare and noted for their varied clinical manifestations. Consequently, the diagnosis is often unsuspected until the symptoms and signs become advanced and obvious, or when the diagnosis is made fortuitously during echocardiography. This report illustrates a case in point in which the diagnosis was made on transthoracic echocardiography and amplified using transesophageal echocardiography.

Echocardiography↗
PubMed1993

Anionic charge concentration of rat kidney glomeruli and glomerular basement membrane.

Estimates of levels of glomerular and glomerular-basement-membrane anion charge should serve as useful quantitative markers for the integrity of the tissues in health and disease. We have developed a simple, rapid, technique to measure this charge through the use of ion exchange with radioisotopes 22Na+ and 36Cl- at low ionic strengths in phosphate buffer. When this technique is used, normal glomeruli isolated from rat have a measured net anion charge concentration of 17.4 +/- 3.7 p-equiv. per glomerulus (n = 20). Perfused rat kidneys that lose approximately half of their glomerular heparan [35S]sulphate content (owing to oxygen-radical damage) exhibited a lower anion charge, of 7.5 +/- 1.6 p-equiv. per glomerulus (n = 5). Glomerular basement membranes prepared from rat glomeruli by a sonication-centrifugation procedure in the presence of enzyme inhibitors had a charge concentration of 6.3 +/- 0.7 mu-equiv./g wet wt. of tissue (n = 4), whereas membranes prepared by sonication, centrifugation, DNAse and detergent treatment had a charge concentration of 7.1 +/- 1.6 mu-equiv./g wet wt. (n = 4). Isotope-dilution experiments with 3H2O on these detergent-prepared glomerular basement membranes demonstrated that they had a water content of approx. 93%, which would then give a net anion charge concentration of 7.6 +/- 1.7 m-equiv./l (n = 4). These values are in good agreement with those obtained by others using titration techniques [Bray and Robinson (1984) Kidney Int. 25, 527-533]. The relatively low magnitude of glomerular anion charge in normal kidneys is consistent with other recent findings that glomerular anion charge is too low to affect the glomerular transport of charged molecules in a direct, passive, biophysical manner through electrostatic interactions.

Animals↗
PubMed1991

Charge selectivity in kidney ultrafiltration is associated with glomerular uptake of transport probes.

The isolated perfused kidney exhibits substantial charge selectivity, as in vivo, in relation to fractional clearance of [3H]dextran sulfate and [3H]dextran. When cycloheximide is present in perfusate, fractional clearance of dextran sulfate is increased and proteinuria becomes significant, but glomerular filtration rate remains essentially unchanged compared with control. The possible role of cells in affecting transglomerular transport was demonstrated when isolated glomeruli from control perfused kidneys showed a very significant resident concentration of [3H]dextran sulfate and [3H]albumin, whereas there was no corresponding accumulation of [3H]dextran or [3H]inulin. Glomerular concentration of dextran sulfate and albumin was significantly reduced by cycloheximide. Kinetics of uptake and release of glomerular dextran sulfate indicated that it had a half-life of glomerular residence of approximately 2-3 min and that this half-life was considerably extended in the presence of cycloheximide. The half-life for glomerular residence of albumin was in the range of 30-40 min. The conclusion from this work is that glomerular charge selectivity for dextran sulfate could be quantitatively rationalized on the basis of transient uptake and release by glomerular cells.

Animals↗
PubMed1990

The inhibitory action of oxygen radical scavengers on proteinuria and glomerular heparan sulphate loss in the isolated perfused kidney.

The perfused isolated kidney is a partial ischemic system that is characterised by glomerular proteinuria and release of glomerular heparan sulfate. Metabolic changes associated with the levels of glutathione, xanthine oxidase and glyceraldehyde 3-dehydrogenase indicated that oxygen radical metabolites were being produced during the perfusion. We have demonstrated that a mixture of oxygen metabolite scavengers containing mannitol, superoxide dismutase and catalase included in the perfusion medium significantly reduced protein excretion. Similar results were obtained with the administration of allopurinol to the rat 24h prior to kidney removal and allopurinol in the perfusion medium. [35S]Heparan sulfate loss from the glomerulus was totally inhibited by the scavenger mixture. These results suggest that reactive oxygen metabolites may be involved in damage to renal capillaries, specifically to heparan sulfate proteoglycan, which leads to proteinuria as a result of partial ischemia produced during perfusion.

Animals↗
PubMed1989

Partial ischemia and proteinuria during isolated kidney perfusion is accompanied by the release of vascular [35S]heparan sulfate.

The isolated kidney perfused with modified Krebs-Henseleit buffer with amino acids yields heavy proteinuria associated with reduced ATP levels characteristic of partial ischemia. These conditions are associated with a similar perfusion time dependent release of degraded vascular [35S]heparan sulfate proteoglycan into the perfusate solution which included a 60% loss of [35S]macromolecular material from the glomerulus after 2h of perfusion. Small amounts of [35S]macromolecular material were found in the urine and lymph. These results demonstrate that partial ischemia promotes a specific response in the overall renal vasculature, probably involving oxygen reactive metabolites, that results in the preferential release of heparan sulphate from the basement membrane and endothelial cells on the luminal side of the capillary wall.

Adenosine Triphosphate↗
PubMedDate not supplied

Doppler-echocardiographic assessment of Carbomedics prosthetic values in the mitral position.

We prospectively studied 37 consecutive patients implanted with the Carbomedics prosthetic heart value in the mitral position (without clinical evidence of prosthetic valve dysfunction) with two-dimensional and Doppler echocardiography. The peak mitral prosthetic gradient ranged from 4.60 to 14.63 (mean 8.97 +/- 2.29) mm Hg; mean mitral prosthetic gradient ranged from 1.67 to 6.18 (mean 3.24 +/- 0.95) mm Hg; pressure half-time derived mitral valve area ranged from 1.67 to 5.30 (mean 2.70 +/- 0.80) cm2. These values compare favorably with that of another bileaflet valve (i.e., the St. Jude Medical valve). There was a wide overlap in peak and mean transmitral gradients, even with the valves of the same size, with a significant but weak inverse relationship between peak mitral gradients and valve size (p = 0.03, r = -0.36). The performance index showed a smaller range of values, again with a significant but weak inverse relationship with valve size (p = 0.001, r = -0.54). The inverse relationship between valve size and peak mitral gradient and performance index should be borne in mind when analyzing Doppler hemodynamic data.

Echocardiography↗