Biomedical subjects

D A Moon

Publications and source records attributed to D A Moon.

5 recordsLinked to original sources

PubMed2001

Congenital posterior urethral membrane: variable morphological expression.

PURPOSE: We assessed the variable morphological expression of posterior urethral membrane by reviewing video recorded cystoscopy. MATERIALS AND METHODS: Between December 1990 and July 2000, 86 males newborn to 15 years old undergoing cystoscopy for urethral anomalies were identified with a posterior urethral membrane. Recorded cystoscopy was reviewed and membrane degree was graded as minimal, moderate or severe. RESULTS: Of the 86 boys with a membranous lesion in the posterior urethra the condition was considered severe in 40, moderate in 21 and minimal in 21. Four patients on whom data were too inadequately recorded to be properly classified were excluded from study. CONCLUSIONS: This study demonstrates that congenital posterior urethral membrane represents a spectrum of lesions and may vary in the degree of obstruction.

Adolescent↗

PubMed1997

Molecular characterization of two large DNA plasmids in the red alga Porphyra pulchra.

Five plasmids occur in the red alga Porphyra pulchra. The two larger ones (6859 and 6427 bp) differ in their sequences. The three smaller (1896, 2100, and 2102 bp) have sequences that are similar to one another. These plasmids are circular, double-stranded DNA, present in high copy number, and maintained in this organism through successive generations of laboratory culture. Sequence analysis of the two larger plasmids reveals few prominent structural features, but several potential open reading frames (ORFs) occur, some of which are transcriptionally active. Sequence database comparisons find significant sequence similarity between ORF3 or PP6427 and a 411 amino-acid polypeptide previously characterized in plasmid GC2 from the red alga Gracilaria chilensis. These data support the presence of at least one conserved plasmid coding region in distant orders of red algae. Southern blots of total genomic DNA from other red algae probed with plasmids from P. pulchra demonstrate no hybridization to previously studied Gracilariales species but notable hybridization to several species within the genus Porphyra, although the sizes of detected bands vary.

Amino Acid Sequence↗

PubMed1992

High-affinity phlorizin binding in Mytilus gill.

The gill of the marine mussel, Mytilus, contains a high affinity, Na-dependent D-glucose transporter capable of accumulating glucose directly from sea water. We examined the ability of the beta-glucoside, phlorizin, to act as a high-affinity ligand of this process in intact gills and isolated brush border membrane vesicles (BBMV). The time course of association of nanomolar [3H]phlorizin to gills and BBMV was slow, with t50 values between 10 and 30 min, and a half-time for dissociation of approx. 30 min. 1 mM D-glucose reduced equilibrium binding of 1 nM phlorizin by 90-95%, indicating that there was little non-specific binding of this ligand to the gill. In addition, there was little, if any, hydrolysis by the gill of phlorizin to its constituents, glucose and phloretin. Phlorizin binding to gills and BBMV was significantly inhibited by the addition of 50 microM concentrations of D-glucose and alpha-methyl-D-glucose, and unaffected by the addition of L-glucose and fructose. Binding to gills and BBMV was reduced by greater than 90% when Na+ was replaced by K+. Replacement of Na+ by Li+ effectively blocked binding to the intact gill, although Li+ did support a limited amount of glucose-specific phlorizin binding in BBMV. The Kd values for glucose-specific phlorizin binding in intact gills and BBMV were 0.5 nM and 6 nM, respectively. We conclude that phlorizin binds with extremely high affinity to the Na-dependent glucose transporter of Mytilus gill, which may be useful in future efforts to isolate and purify the protein(s) involved in integumental glucose transport.

Animals↗

PubMed1989

Sodium D-glucose cotransport in the gill of marine mussels: studies with intact tissue and brush-border membrane vesicles.

Glucose transport was studied in marine mussels of the genus Mytilus. Initial observations, with intact animals and isolated gills, indicated that net uptake of glucose occurred in mussels by a carrier-mediated, Na+-sensitive process. Subsequent studies included use of brush-border membrane vesicles (BBMV) in order to characterize this transport in greater detail. The highest activity of Na+-dependent glucose transport was found in the brush-border membrane fractions used in this study, while basal-lateral membrane fractions contained the highest specific binding of ouabain. Glucose uptake into BBMV showed specificity for Na+, and concentrative glucose transport was observed in the presence of an inwardly directed Na+ gradient. There was a single saturable pathway for glucose uptake, with an apparent Kt of 3 microM in BBMV and 9 microM in intact gills. The kinetics of Na+ activation of glucose uptake were sigmoidal, with apparent Hill coefficients of 1.5 in BBMV and 1.2 in isolated gills, indicating that more than one Na+ may be involved in the transport of each glucose. Harmaline inhibited glucose transport in mussel BBMV with a Ki of 44 microM. The uptake of glucose was electrogenic and stimulated by an inside-negative membrane potential. The substrate specificity in intact gills and BBMV resembled that of Na+-glucose cotransporters in other systems; D-glucose and alpha-methyl glucopyranoside were the most effective inhibitors of Na+-glucose transport, D-galactose was intermediate in its inhibition, and there was little or no effect of L-glucose, D-fructose, 2-deoxy-glucose, or 3-O-methyl glucose. Phlorizin was an effective inhibitor of Na+-glucose uptake, with an apparent Ki of 154 nM in BBMV and 21 nM in intact gills. While the qualitative characteristics of glucose transport in the mussel gill were similar to those in other epithelia, the quantitative characteristics of this process reflect adaptation to the seawater environment of this animal.

Animals↗

PubMed1989

Intracellular Na+ and the control of amino acid fluxes in the integumental epithelium of a marine bivalve.

The accumulation of amino acids from sea water into the integumental epithelium of the bivalve gill can occur against chemical gradients in excess of 10(6) to 1. The energy to drive this transport has been proposed to come from the inwardly directed Na+ electrochemical gradient. The present study examined the influence of intracellular and extracellular [Na+] on influx and efflux of amino acids in gill tissue from the mussel, Mytilus californianus. Influx of alanine was inhibited by more than 90% when external [Na+] was reduced from 425 to 2 mmol l-1, and by 85% when intracellular [Na+] was increased from approximately 11 to approximately 100 mmol l-1 (by means of a 30-min exposure to the ionophore, nigericin). Efflux of taurine and alanine from gill tissue into normal-Na+ sea water was very low (less than 5% of the Jmax of the carrier-mediated influx pathways). Reducing the external Na+ from 425 to 2 mmol l-1 increased taurine efflux by only 20%. Raising cell [Na+] to approximately 100 mmol l-1 increased taurine efflux 2.7-fold; further increases in cell [Na+] increased taurine efflux another 7.5-fold. These data, in conjunction with results from earlier studies, suggest that activation of integumental amino acid transporters requires an interaction of multiple sodium ions with binding sites of low affinity for this ion. This set of characteristics results in transport systems that are well-adapted for the net accumulation of amino acids from sea water.

Alanine↗