Koeveringe, G.A. van

Urodynamic follow-up of experimental urethral obstruction in individual guinea pigs (Article)

2001-12-18T00:00:00Z

It is unknown whether changes in bladder function due to urethral obstruction follow a specific sequence. To answer this, we adapted a small animal model to allow repeated complete pressure-flow studies, enabling individual follow-up of changes in bladder function on urethral obstruction. Obstruction was induced in guinea pigs by placing a silver ring around the urethra. Urodynamic studies were repeated under anesthesia with ketamine/xylazine. Bladders were filled and bladder pressure measured through a single suprapubic catheter. Urine flow rate was measured using an ultrasound probe around the penis. Accurate measurements of bladder pressure and urine flow rates were obtained at 1-week intervals for 11 weeks in individual guinea pigs. In the control animals, the urodynamic parameters did not show significant changes. In the obstructed group, urethral resistance (P(low,ave)) increased from 20 to 35 cm H(2)O after 4 weeks and remained at that level. The maximum flow rate (Q(max)) increased from 0.17 to 0.24 mL/s after 2 to 3 weeks. After this peak, it gradually decreased to lower than the starting value after 10 to 11 weeks. The pressure at maximum flow rate (p(Qmax)) increased from 24 to 47 cm H(2)O after 6 to 7 weeks and thereafter declined. During weeks 1 through 4 of obstruction, unstable contractions were seen. All animals followed a similar sequence of patterns but at variable rates. Our animal model allows complete urodynamic follow-up of individual animals with urethral obstruction. We observed a specific sequence of changes in urodynamic patterns and parameters of bladder function

Photolysis of caged calcium using a low-cost flash unit: efficacy analysis with a calcium selective electrode (Article)

1994-01-01T00:00:00Z

Photolysis of caged calcium (Nitr5, Calbiochem) can be used to study calcium dependent processes such as excitation-contraction coupling and muscular mechanics. Expensive high energy light sources are routinely used for UV light exposure, but this study describes an alternative low cost xenon flash unit constructed in our laboratory. A 300 J short arc xenon flash lamp (Heimann) was mounted in an elliptical reflector and driven by a modified Metz 60 CT 4 photoflash unit up to 240 J input energy and 4 ms flash duration. A 20 microliters cuvette containing a test solution was placed in a complementary elliptical reflector. An ion selective calcium electrode was used to measure the free calcium concentration [Ca2+] before and after flash in test solutions containing 1.00 mM Nitr5 in combination with different added [Ca2+]s. Using this technique we estimated that 1 flash on 1.00 mM Nitr5 increased the free [Ca2+] from 10(-7) to 1.1 x 10(-5) M. When the added [Ca2+] was less than 2.3 x 10(-4) M, the used Nitr5 behaved as a strong calcium chelator because 23% of it was unloaded with calcium. It is concluded that a physiologically relevant change in free [Ca2+] can be evoked by photolysis of Nitr5 using a low cost (approximately $1500) xenon flash unit, and that ion selective Ca electrodes can be adequately used to monitor the resulting changes in [Ca2+].

Effect of partial urethral obstruction on force development of the guinea pig bladder (Article)

1993-01-01T00:00:00Z

We created gradual partial urethral obstruction in 20 guinea pigs using silver jeweler's jump rings. After 4 or 8 weeks obstruction all animals underwent cystometry and were assigned to one of five urodynamic categories: normal, high pressure voiding, unstable, low compliance, or decompensated. After sacrifice, the contractile responses of bladder strips to electrical field stimulation of intramural nerves, direct electrical muscle stimulation, 0.1 mM carbachol, and high K+ solution were sampled by computer for phase plot analysis. Following 8 weeks obstruction, the value of the phase plot parameter Fiso, indicative of the number of contractile muscle units, was reduced to 60% of the control response to nerve stimulation (P < 0.05) and to 77% of the control response to carbachol stimulation (P < 0.05). Parameter C, the slope of the phase plot (indicative of unit recruitment during force development), was unchanged for all forms of stimulation. Although in the latter case not statistically significant, obstruction affected responses to nerve and muscle stimulation similarly suggesting that muscle change may possibly be a common denominator of dysfunction. In view of the reduction in Fiso and the increase in bladder weight, instability may represent a more advanced form of dysfunction due to obstruction than high pressure voiding.