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D T Erwin

Publications and source records attributed to D T Erwin.

10 recordsLinked to original sources
PubMed1998

Agglomeration inhibition reflected stone-forming activity during long-term potassium citrate therapy in calcium stone formers.

OBJECTIVES: The agglomeration of preformed crystals of calcium oxalate has been hypothesized to be the rate-limiting step in renal stone-forming activity (SFA). The effect of urine on the in vitro inhibition of agglomeration of seed crystals of calcium oxalate monohydrate, designated [tm], has been used to monitor SFA in calcium oxalate stone formers (CaOxSF). The objective of the present study was to determine whether [tm] could be used to help monitor the long-term effectiveness of oral potassium citrate therapy (K-Cit-Rx) in CaOxSF. METHODS: Clinic and radiographic (or ultrasound) reports were evaluated for 80 patients, aged 20 to 72 years, 55 men and 25 women, who were treated with oral K-Cit for recurrent calcium oxalate urolithiasis at the Ochsner Stone Clinic between January 1992 and July 1996. Seventy-five of these patients had at least one 24-hour citrate excretion rate of less than 3.0 mm/day before or after K-Cit-Rx. SFA graded on a scale of -2 to +2 by radiographic criteria was combined with information on stone passage to evaluate clinical stone status, and 24-hour urine collections were evaluated for volume, pH, calcium, citrate, uric acid, oxalate, creatinine, and [tm] on free diet before and after 6 to 53 months of K-Cit-Rx. Historical information on procedures performed for urolithiasis before and on K-Cit-Rx was also reviewed. RESULTS: K-Cit-Rx resulted in increased urine pH (P <0.0001) and decreased calcium (P=0.0475), [tm] (P=0.0045), number of stones passed per year (P=0.0016), and remedial procedures per year (P <0.0001). Patients taking allopurinol in addition to K-Cit required higher doses (P <0.0001) of K-Cit to control their disease, had lower pretreatment urine pH (P=0.0493), and showed greater increase in urine citrate (P=0.0092) than those on K-Cit alone. Those taking high-dose K-Cit were younger (P=0.0363) and showed greater decrease in SFA (P=0.0005) than those taking lower doses. A small group of 10 medication refractory patients, who retained (n=9) or increased (n=1) their stone burden during K-Cit-Rx, was identified. Compared with the medication-responsive group, the refractory patients were older (P=0.0124), and had greatly increased SFA (P <0.0001) and higher (P=0.0347) urine pH before and during (P=0.0173) treatment (data not shown). CONCLUSIONS: The data confirm that [tm] can be used not only to verify previously documented stone formation rate but also to help evaluate the long-term effectiveness of therapy. In this report, changes in [tm] after K-Cit-Rx reflected decreased stone formation rate and decreased remedial procedures.

Adult↗
PubMed1994

Calcium oxalate stone agglomeration reflects stone-forming activity: citrate inhibition depends on macromolecules larger than 30 kilodalton.

To evaluate the clinical utility of in vitro calcium oxalate monohydrate (COM) crystallization kinetics measurements and to determine the effect of quantitative removal of urinary Tamm-Horsfall glycoprotein on such measurements, we examined 24-hour, room temperature urine collections of patients from our Stone Clinic and of normal subjects from our research laboratories at Ochsner Medical Institutions in New Orleans, LA, and compared their COM kinetic parameters in vitro before and after urine ultrafiltration (30 kd). Data from 53 calcium oxalate stone-forming patients (26% women; mean age, 47 years) who demonstrated radiographic or other evidence of forming at least one stone were compared with data from 22 healthy volunteers (25% women; mean age, 40 years). Hypercalciuria (> 7.5 mm/24 hr), hyperoxaluria (> 0.5 mm/24 hr), and hypocitraturia (< 2.0 mm/24 hr) were present in 38%, 26%, and 26% of the patient population, respectively. Urinary creatinine, urate, calcium, citrate, phosphate, oxalate, pH, volume, total immunoreactive-disaggregated Tamm-Horsfall glycoprotein, and the urine's effects on COM solubility, percent crystal growth inhibition, and crystal agglomeration inhibition [tm] were determined. Calcium oxalate monohydrate agglomeration inhibition, [tm], was reduced in stone-forming patients. It decreased with increasing stone frequency, making [tm] a useful tool for measuring the risk of stone recurrence. Urinary Tamm-Horsfall glycoprotein and citrate concentrations were linearly related to COM agglomeration inhibition. Their effects were synergistic. Tamm-Horsfall glycoprotein removal from urine reduced COM agglomeration inhibition dramatically. Alkali therapy increased urinary citrate concentration and increased [tm].(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Graduate education in the multispecialty group.

Graduate education traditionally has had different reasons for being in the multispecialty clinic. Practitioners in the multispecialty clinics have learned that the best way to ensure high quality patient care is with a graduate education program. This article reviews the components of graduate education in a multispecialty setting.

Academic Medical Centers↗
PubMed1984

Human plasma oxalate concentration re-examined.

In an attempt to reconcile estimates of plasma oxalate concentration by in vitro and in vivo assays, the in vitro radioenzymatic isotope dilution assay (REIDA) for plasma oxalate concentration was modified by initiating precipitation of calcium oxalate from plasma ultrafiltrates within one hour of phlebotomy. Plasma oxalate concentration form normal males was 4.0 mumol/1, consistent with reported values of 3.0 mumol/1 and 2.3 mumol/1 by enzymatic methods, and 2.8 mumol/1 by a gas chromatographic technique, and lower than 10.0 mumol/1 reported previously by chemical/enzymatic methods. This lower estimate of oxalate results, at least in part, from avoiding in vitro conversion of ultrafilterable substances to oxalate, and from the use of 'fire-cleaned' glassware. No difference in plasma oxalate was observed between age-matched, apparently healthy black and white males or with blood collected in the presence and absence of inhibitors of the conversion of glyoxalate to oxalate.

Adult↗
PubMed1976

Nephrolithiasis: recent advances in therapy.

The stone-forming process includes crystal formation, crystal aggregation, and retention time to allow growth. The crystal-forming process, in turn, is influenced by the pH of the urine, the solute load, and inhibitors of crystallization. Idiopathic stone disease is characterized by recurrent formation of calcium oxalate, calcium phosphate, and hydroxyapatite stones without an apparent underlying cause. Treatment of idiopathic stone disease has been aimed at decreasing the solute concentration, increasing the solubility of calcium phosphate, or interfering with extension of the crystal lattice.

Allopurinol↗