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Biomedical subjects

T I Hwang

Publications and source records attributed to T I Hwang.

24 records · Page 2Linked to original sources
PubMed1989

Functional evaluation of penile arteries with duplex ultrasound in vasodilator-induced erection.

In 657 impotent patients in whom erection was induced by intracavernous injection of papaverine, we evaluated changes in the pulsation, diameter, and blood flow velocity of the penile arteries by duplex sonography and pulsed Doppler spectrum analysis. An additional 18 patients who were proved to have good erection by nocturnal tumescence testing were used as controls. All patients were studied before achieving full erection after papaverine injection. In the flaccid state, the inner diameter of the deep penile arteries averaged 0.51 mm, and blood flow velocity was rarely measurable. The normal arterial reaction to papaverine was an initial increase in the inner diameter of the scanned segment of the cavernous artery with good concentric pulsations and a mean peak blood flow velocity of 34.8 cm per second and a mean diameter of 0.89 mm. With this technique, we assessed the functional capability of each deep and dorsal artery. Arterial and erectile response allowed indirect evaluation of the venous system. Of the 657 patients, 48 had neurogenic or psychogenic impotence or both. In 97, impotence could be ascribed to venogenic causes, in 210 to arteriogenic causes, and to mixed arteriogenic and venogenic causes in 282 patients. The exact cause of impotence in the remaining 20 patients could not be determined. Statistically, patients who were older or had diabetes mellitus or coronary artery disease tended to have smaller penile arteries and lower peak blood flow velocity after papaverine injection.

Adult↗
PubMed1988

Urinary glycosaminoglycans in normal subjects and patients with stones.

Urinary glycosaminoglycans are thought to be macromolecular inhibitors of calcium stone formation. The 24-hour excretion of urinary glycosaminoglycans was measured quantitatively in 24 normal subjects and 206 patients with different etiologies of stone disease. In both groups a positive correlation was found between urinary glycosaminoglycans and total urinary volume and urinary sulfate. In normal subjects total urinary volume was r equals 0.716, p less than 0.001 and urinary sulfate was r equals 0.813, p less than 0.001, while in patients with stones these values were r equals 0.338, p less than 0.001 and r equals 0.326, p less than 0.001, respectively. The only significant difference in excretion of urinary glycosaminoglycans between the groups was found in the subgroup of patients with type I absorptive hypercalciuria. The type I absorptive hypercalciuria value of 33.4 +/- 14.9 mg. per day in patients with stones was significantly higher than the 25.8 +/- 8.3 mg. per day detected in normal subjects (p less than 0.05). Urinary glycosaminoglycan excretion in all other subgroups of nephrolithiasis as well as in a combined group of all patients with stones showed no significant difference when compared to that of normal subjects. Thus, no major quantitative relationship could be demonstrated between urinary glycosaminoglycan excretion and calcium stone formation in this study.

Adult↗
PubMed1988

Modulation by calcium of the inhibitor activity of naturally occurring urinary inhibitors.

The possibility that hypercalciuria could cause calcium stone formation through a mechanism other than by increasing urinary saturation of stone-forming calcium salts was explored. The effect of increasing calcium concentration on the inhibitor activity against the spontaneous precipitation of calcium oxalate was examined in whole urine (in the presence of naturally occurring inhibitors) and in synthetic media (with added inhibitors). In 11 patients with calcium nephrolithiasis, the induced hypercalciuria from calcium supplementation (600 mg/day) caused a significant fall in the urinary inhibitory activity against calcium oxalate precipitation, as shown by a decline in the formation product ratio from 12.6 +/- 1.1 SEM to 9.6 +/- 1.4 (P less than 0.005). In order to more fully explore this observation, the effect of increasing calcium concentration on the inhibitory activities of citrate (2 mM), chondroitin sulfate (0.05 mg/liter) and a heterogeneous group of naturally-occurring urinary inhibitors (1.0 mg/liter) against calcium oxalate precipitation was examined in vitro in synthetic solutions. The inhibitory actions of both citrate and chondroitin sulfate were significantly attenuated by increasing calcium concentration from 0.25 mM to 6.0 mM (P less than 0.01). However, raising the calcium concentration in synthetic media containing a mixture of partially purified urinary inhibitors produced a significant rise in the urinary inhibitory activity of this macromolecular mixture (P less than 0.01). We conclude that hypercalciuria can attenuate the inhibitory activities of citrate and chondroitin sulfate against calcium oxalate precipitation while at the same time accentuating the inhibitory activity of naturally-occurring urinary inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium↗
PubMed1988

Effect of prolonged bedrest on the propensity for renal stone formation.

The effect of prolonged bedrest immobilization on urinary risk factors for stone formation and on the propensity for the crystallization of calcium salts was examined in eight normal subjects. During 5 weeks of bedrest, the mean urinary calcium excretion rose during the first week and remained elevated (from 5.68 to approximately 7.50 mmol/day). Mean urinary phosphorus excretion increased by the second week of bedrest and remained elevated (from 2.70 to approximately 30.6 mmol/day). Urinary sodium and uric acid excretion rose slightly, as did urinary magnesium. Urinary pH, oxalate, and citrate changed slightly or not at all. Owing to these biochemical alterations, urinary saturation of calcium phosphate, calcium oxalate, and monosodium urate increased significantly during bedrest, but that of uric acid did not change. The inhibitor activity against the spontaneous nucleation of brushite (CaHPO4.2H2O) and calcium oxalate was not altered significantly by bedrest. Thus, the propensity for the crystallization of stone-forming calcium salts was enhanced by bedrest, suggesting that immobilization may confer increased risk for the formation of calcium-containing renal stones.

Adult↗