Biomedical subjects

D C Merrill

Publications and source records attributed to D C Merrill.

At least 19 recordsLinked to original sources

PubMed2001

Genetic susceptibility to preeclampsia: roles of cytosineto-thymine substitution at nucleotide 677 of the gene for methylenetetrahydrofolate reductase, 68-base pair insertion at nucleotide 844 of the gene for cystathionine beta-synthase, and factor V Leiden mutation.

OBJECTIVE: The purpose of this study was to evaluate the association between preeclampsia and 3 relatively common mutations that are important in the development of vascular disease and thrombosis; these are similar to conditions observed in pregnancies complicated by preeclampsia. STUDY DESIGN: Deoxyribonucleic acid was extracted from whole blood or cheek swabs of 281 patients with preeclampsia and 360 control subjects (all white). Control subjects consisted of women who had undergone at least 2 term pregnancies unaffected by preeclampsia. Mutation frequencies among patients with preeclampsia and control subjects were compared by standard chi2 analysis, with P <.05 considered significant. RESULTS: Thirty-three of 281 women with preeclampsia (11.7%) and 22 of 193 women with severe preeclampsia (11.4%) were homozygous for cytosine-to-thymine substitution at nucleotide 677 in the gene for methyltetrahydrofolate reductase (MTHFR), versus 41 of 360 control subjects (11.4%; difference not significant). Forty of 258 women with preeclampsia (15.5%) and 22 of 175 women with severe preeclampsia (12.6%) were heterozygous for the insertion of 68 bases at position 844 in the gene for cystathionine beta-synthase (CBS), versus 58 of 332 control subjects (17.5%). Fifteen of 250 women with preeclampsia (6.0%) and 11 of 169 with severe preeclampsia (6.5%) were heterozygous for the Leiden mutation (glycine-to-alanine substitution at nucleotide 1691) in the gene for factor V (F5), versus 12 of 253 control subjects (4.7%; difference not significant). CONCLUSION: In this white population a missense mutation of MTHFR, an insertion mutation of CBS, and a missense mutation of F5 were not found to be associated with an increased risk for preeclampsia, either independently or in combination.

Amino Acid Substitution↗

PubMed2001

Lipoprotein lipase gene mutations and the genetic susceptibility of preeclampsia.

In the pathogenesis of preeclampsia, endothelial cell activation or dysfunction is a central theme, and marked dyslipidemia may contribute to endothelial cell dysfunction. The objective of this study was to evaluate the association between preeclampsia and mutations within the lipoprotein lipase (LPL) gene. DNA was extracted from whole blood or cheek swabs of 250 preeclamptic patients, 265 control subjects, and 106 offspring of preeclamptic patients (all white). Control subjects were women who had undergone >/=2 term pregnancies unaffected by preeclampsia. All samples were genotyped for 3 LPL polymorphisms with the use of polymerase chain reaction of known allelic variants. The 3 mutations studied were the following: (1) Asp9Asn substitution in exon 2, (2) T-to-G substitution at position -93 of the proximal promotor region (-93T/G), and (3) Asn291Ser substitution in exon 6. Results were analyzed with an chi(2) contingency table. The prevalences of the Asp9Asn mutation, -93T/G promotor mutation, and Asn291Ser mutation were not significantly different among the preeclamptic patients and control subjects (Asp9Asn: patients, 2.8%; control subjects, 4.0%; -93T/G: patients, 4.5%; control subjects, 5.5%; Asn291Ser: patients, 4.0%; control subject, 3.0%). In addition, there was no difference in the frequency of any of the mutations in the offspring of preeclamptic women compared with that observed in the control population. Between a small group of patients with nulliparous HELLP syndrome (a variant of severe preeclampsia: hemolysis, elevated liver enzyme, low platelets) patients (n=12) and control subjects, there was a significant difference in the prevalence of the Asn291Ser mutation (16.7% versus 3.0%, P=0.01). In this large white population, the Asp9Asn mutation, -93T/G promotor mutation, and Asn291Ser mutation were not associated with an increased risk for preeclampsia. In a small subgroup of patients, the Asn291Ser mutation was associated with an increased risk for nulliparous HELLP syndrome.

Female↗

PubMed1999

Randomized, double-masked comparison of oxytocin dosage in induction and augmentation of labor.

OBJECTIVE: To test the hypothesis that high-dose oxytocin, when used in a masked fashion, would result in shorter labors and less need for cesarean delivery. METHODS: We conducted randomized, double-masked trials of high-dose compared with low-dose oxytocin for augmentation and induction of labor. Patients were randomly assigned to receive oxytocin by either a low-dose protocol (1.5 mU/minute initially, increased by 1.5 mU/minute every 30 minutes) or a high-dose protocol (4.5 mU/minute initially, increased by 4.5 mU/minute every 30 minutes). Oxytocin solutions were prepared by a central pharmacy and infusion volumes (mL/hour) were identical, thus ensuring double masking. RESULTS: A total of 1307 patients were randomized (induction, 816; augmentation, 491). In the group receiving oxytocin for induction, high-dose oxytocin was associated with a significant shortening of labor (oxytocin to complete dilatation: 9.7+/-0.3 compared with 7.8+/-0.2 hours, P<.001; oxytocin to delivery: 10.5+/-0.3 compared with 8.5+/-0.3 hours, P<.001). The cesarean delivery rate with low-dose oxytocin was 15.0%, compared with 11.3% with high-dose oxytocin (P = .17). For nulliparous women undergoing induction, cesarean delivery rates were as follows: Total 17.3% (low dose) compared with 11.7% (high dose), P = .15; cephalopelvic disproportion 11.9% (low dose) compared with 5.9% (high dose), P = .06. When used for augmentation, high-dose oxytocin again was associated with a significant shortening of labor without a significant difference in cesarean birth rates. No differences in neonatal outcomes were noted between the groups for either augmentation or induction. CONCLUSION: When used in a double-masked fashion, high-dose oxytocin is associated with significantly shorter labors without any demonstrable adverse fetal or neonatal effects.

Adult↗

PubMed1999

Sympathetic responses to cardiopulmonary vagal afferent stimulation during development.

Previous work in our laboratory has demonstrated impairment of cardiopulmonary reflex control of renal sympathetic nerve activity (RSNA) during the newborn period. The present study was designed to test the hypothesis that this delayed maturation is secondary to incomplete central integration of vagal afferent input. Term fetal (135-140 days; n = 6), newborn (3-7 days of age; n = 8), and young adult (6-8 wk old; n = 8) sheep anesthetized with alpha-chloralose underwent vagal afferent nerve stimulation. All animals had undergone prior sinoaortic denervation to eliminate influences from the arterial baroreceptors. After determination of optimal stimulation parameters, RSNA responses to gradual increases in stimulation frequency (1.0-16 Hz) were recorded and compared by one-way ANOVA. RSNA decreased progressively with increased frequency of stimulation in all three groups of animals. When comparing the three groups at any given frequency of stimulation, reflex withdrawal of RSNA tended to be more pronounced in newborn lambs (P < 0.05 for 1 and 4 Hz). Heart rate (HR) was also noted to decrease significantly with vagal afferent stimulation in each of the groups, but no significant differences in the reflex decreases in HR were noted among the three groups of animals. These results demonstrate that central integration of vagal afferent input is intact in fetal and newborn sheep. These results suggest that the delayed maturation of cardiopulmonary reflex-mediated changes in RSNA seen early in development appears to depend on intrinsic alterations in baroreceptor function rather than incomplete central integration.

Afferent Pathways↗

PubMed1998

The optimal route of delivery for fetal meningomyelocele.

OBJECTIVE: It has been proposed that cesarean section improves the long-term neurologic outcome of children with meningomyelocele. On the basis of this belief, a trial of labor is not offered in many centers. We hypothesized that there is no difference in immediate or long-term outcome by route of delivery for the fetus with meningomyelocele delivered in a tertiary care center. STUDY DESIGN: All fetuses (n = 60) with meningomyelocele delivered at the University of Iowa Hospitals and Clinics between 1971 and 1995 were analyzed. Thirty-six cases were available for long-term follow-up. Motor, sensory, and anatomic levels were converted to a numeric scale. Variables were compared by one-way analysis of variance, chi2 analysis, and Fisher's exact test with significance at P < .05. RESULTS: There were no significant differences by route of delivery for gestational age of delivery, birth weight, meningomyelocele size, or neonatal mortality (vaginal: 1/22 = 4.5%, cesarean section: 2/17 = 11.8%, P = .82). An antenatal diagnosis was made with similar frequency in the two groups (vaginal: 15/21 = 71.4%, cesarean section: 13/15 = 86.7%). In addition, the length of long-term follow-up was similar (vaginal: 54.7 +/- 11.1 months, cesarean section: 33.7 +/- 8.6 months). There was no difference in long-term neurologic outcome as determined by the change in motor level, the change in sensory level, or when comparing the final motor level with the anatomic level. CONCLUSIONS: This study was unable to detect differences between either immediate or long-term outcome for the infant with isolated meningomyelocele when stratified by route of delivery. A multicenter randomized trial should be required before the acceptance of cesarean section as the optimal route of delivery for the fetus with meningomyelocele.

Adult↗

PubMed1997

The kidney androgen-regulated protein promoter confers renal proximal tubule cell-specific and highly androgen-responsive expression on the human angiotensinogen gene in transgenic mice.

Transgenic mice were generated containing a 1542-base pair fragment of the kidney androgen-regulated protein (KAP) promoter fused to the human angiotensinogen (HAGT) gene with the goal of specifically targeting inducible expression of renin-angiotensin system components to the kidney. High level expression of both KAP-HAGT and endogenous KAP mRNA was evident in the kidney of male mice from two independent transgenic lines. Renal expression of the transgene in female mice was undetectable under basal conditions but could be strongly induced by administration of testosterone. Testosterone treatment did not cause a transcriptional induction in any other tissues examined. However, an analysis of six androgen target tissues in males revealed that the transgene was expressed in epididymis. No other extra-renal expression of the transgene was detected. In situ hybridization demonstrated that expression of HAGT (and KAP) mRNA in males and testosterone-treated females was restricted to proximal tubule epithelial cells in the renal cortex. Although there was no detectable human angiotensinogen protein in plasma, it was evident in the urine, consistent with a pathway of synthesis in proximal tubule cells and release into the tubular lumen. These results demonstrate that 1542 base pairs of the KAP promoter is sufficient to drive expression of a heterologous reporter gene in a tissue-specific, cell-specific, and androgen-regulated fashion in transgenic mice.

Angiotensinogen↗

PubMed1997

Use of transgenic and gene-targeted mice to model the genetic basis of hypertensive disorders.

As both essential hypertension and hypertension associated with pregnancy (pre-eclampsia) have been determined to have strong genetic components, considerable recent research has focused on identifying genes that may predispose to the development of these disorders. Recent advances in molecular genetics and the work of the Human Genome Project have facilitated the identification of genes that may be linked to these hypertensive disorders. Although molecular genetic studies performed in humans and animals can be used to link genes or mutations in genes to hypertension (once identified), studies are needed to assess their biochemical and physiologic importance. In this review, we discuss the ever-increasing importance and use of transgenic and gene-targeted mice in modeling the genetic basis of hypertensive disorders.

Animals↗

PubMed1996

Chronic hypertension and altered baroreflex responses in transgenic mice containing the human renin and human angiotensinogen genes.

We have generated a transgenic model consisting of both the human renin and human angiotensinogen genes to study further the role played by the renin-angiotensin system in regulating arterial pressure. Transgenic mice containing either gene alone were normotensive, whereas mice containing both genes were chronically hypertensive. Plasma renin activity and plasma angiotensin II levels were both markedly elevated in the double transgenic mice compared with either single transgenic or nontransgenic controls. The elevation in blood pressure caused by the human transgenes was independent of the genotype at the endogenous renin locus and was equal in mice homozygous for the Ren-1c allele or in mice containing one copy each of Ren-1c, Ren-1d, or Ren-2. Chronic overproduction of angiotensin II in the double transgenic mice resulted in a resetting of the baroreflex control of heart rate to a higher pressure without significantly changing the gain or sensitivity of the reflex. Moreover, this change was not due to the effects of elevated pressure itself since angiotensin-converting enzyme inhibition had minimal effects on the baroreflex in spontaneously hypertensive BPH-2 control mice, which exhibit non-renin-dependent hypertension. This double transgenic model should provide an excellent tool for further studies on the mechanisms of hypertension initiated by the renin-angiotensin system.

Angiotensinogen↗

PubMed1995

Transgenic animals in the study of blood pressure regulation and hypertension.

It is generally accepted that the etiology of essential hypertension is due to a complex interplay of genetic and environmental factors. A great deal of research effort over the past ten years has been focused on the identification of genes the variants of which predispose individuals to high blood pressure. Consequently, transgenic and knockout animals have become important research tools, providing experimental systems in which defined genetic manipulations can be introduced on uniform genetic backgrounds while minimizing environmental variation. These animal models have provided the means by which candidate genes thought to be involved in blood pressure regulation have been studied. Furthermore, these models can be used to test the significance of genes and gene variants identified via genome-wide searches as potential causes of hypertension. The purpose of this review is to provide a brief discussion of transgenic and knockout methodology and its application to study the genetic basis of hypertension.

Angiotensinogen↗

PubMed1995

Impairment of cardiopulmonary baroreflexes during the newborn period.

The present study was designed to characterize the maturation of cardiopulmonary reflex control of renal sympathetic nerve activity (RSNA) independent of influences from the arterial baroreflex. Studies were conducted in conscious newborn lambs (3- to 7-days-old) (n = 16) and older lambs (6- to 8-wk-old) (n = 18). All animals underwent either sinoaortic denervation (SAD) or a sham procedure. Hemodynamic, humoral, neural, and renal responses to volume expansion (6% Dextran 70, 0.7 ml.kg-1.min-1 x 60 min) were recorded. Volume expansion resulted in a significant decrease (P < 0.05) in RSNA in intact newborn (-28.1 +/- 5.3% change from control) and older lambs (-19.4 +/- 10.1%). SAD totally abolished the sympathetic inhibition seen with volume expansion in newborn lambs (-3.6 +/- 5.7%) but not in older lambs (-25.6 +/- 8.4%). Right atrial pressure increased in a similar fashion in both newborn (intact: 5.6 +/- 0.5 mmHg; SAD: 6.1 +/- 0.8 mmHg) and older lambs (intact: 5.2 +/- 0.9 mmHg; SAD: 5.3 +/- 0.9 mmHg) and was not altered by SAD. The reflex bradycardia seen with volume expansion in newborn lambs was blocked by SAD. The present study demonstrates that, during the newborn period, the RSNA and heart rate responses to volume expansion are dependent mainly on the integrity of the arterial baroreflex. Furthermore, these studies suggest that cardiopulmonary reflex control of RSNA in response to volume expansion is impaired early in life and increases with maturation.

Animals↗

PubMed1994

Functional expression of the human angiotensinogen gene in transgenic mice.

The renin-angiotensin system is a major determinant of arterial pressure and volume homeostasis in mammals through the actions of angiotensin II, the proteolytic digestion product of angiotensinogen. Molecular genetic studies in several human populations have revealed genetic linkage between the angiotensinogen gene and both hypertension and increased plasma angiotensinogen. Transgenic mice were generated with a human angiotensinogen genomic clone to develop an animal model to examine tissue- and cell-specific expression of the gene and to determine if overexpression of angiotensinogen results in hypertension. Human angiotensinogen mRNA was expressed in transgenic mouse liver, kidney, heart, adrenal gland, ovary, brain, and white and brown adipose tissue and, in kidney, was exclusively localized to epithelial cells of the proximal convoluted tubules. Plasma levels of human angiotensinogen were approximately 150-fold higher in transgenic mice than that found normally in human plasma. The blood pressure of mice bearing the human angiotensinogen gene was normal but infusion of a single bolus dose of purified human renin resulted in a transient increase in blood pressure of approximately 30 mm Hg within 2 min. These results suggest that abnormalities in the angiotensinogen gene resulting in increased circulating levels of angiotensinogen could potentially contribute in part to the pathogenesis of essential hypertension.

Angiotensinogen↗

PubMed1994

Role of endogenous ANG II on resetting arterial baroreflex during development.

Angiotensin II (ANG II) has been shown in adults to modulate baroreflex responses in heart rate (HR) and sympathetic outflow. To test the hypothesis that high circulating levels of ANG II in the newborn period contribute to the resetting of the arterial baroreflex observed postnatally, we studied baroreflex-mediated changes in HR and renal sympathetic nerve activity (RSNA) before and after angiotensin-converting enzyme (ACE) inhibition in fetal and newborn sheep. In the newborn, administration of the ACE inhibitor enalaprilat produced significant (P < 0.05) decreases in baseline RSNA (69 +/- 5 vs. 47 +/- 7% maximum) and HR (81 +/- 3 vs. 59 +/- 4% max), as well as in the baroreflex curve midpoints for RSNA (93 +/- 4 vs. 87 +/- 3 mmHg) and HR (95 +/- 4 vs. 81 +/- 5 mmHg); no change in the sensitivities (gains) of the baroreflex responses were seen. In contrast, no significant changes in baseline RSNA, HR, baroreflex curve midpoint, or sensitivity were demonstrated in the fetus. Infusion of ANG II in newborn lambs reversed the effects of ACE inhibition on the baroreflex responses. Additional experiments evaluating the effects of ACE inhibition in vagotomized newborns again showed resetting of the baroreflex, demonstrating that vagally mediated mechanisms are not involved in regulating the changes in sympathetic outflow during the neonatal period. These results suggest that endogenous ANG II contributes to the resetting of the baroreflex observed postnatally.

Angiotensin II↗

PubMed1994

Cardiopulmonary and arterial baroreflex responses to acute volume expansion during fetal and postnatal development.

Recent studies demonstrated that renal denervation had no effect on the natriuretic response to volume expansion (VE) in fetal sheep, suggesting that the sensitivity of the cardiopulmonary reflex in response to VE is impaired in the fetus. To test this hypothesis, we investigated the renal sympathetic nerve activity (RSNA) and heart rate (HR) responses to 20 and 50% intravascular VE in fetal (130-135 days gestation; term 145 days) (n = 7), newborn (n = 8), and 6- to 8-wk-old sheep (n = 9). Despite similar increases in right atrial pressure (RAP) in the three groups, 20% VE had no significant effect on RSNA and HR in fetal sheep but significantly decreased RSNA in newborn (-22.8 +/- 7.3%) and 6- to 8-wk-old sheep (-32.1 +/- 11.7%). Bradycardic responses to VE were also observed in both newborn (from 237 +/- 6 to 200 +/- 12 beats/min) and 6- to 8-wk-old sheep (from 170 +/- 9 to 140 +/- 9 beats/min). A 50% VE had no significant effect on fetal RSNA and HR, whereas it increased RAP by 6.8 +/- 0.9 mmHg. In addition, we tested the hypothesis that interactions between cardiopulmonary and arterial baroreflexes in response to VE change during development. We found that 20 and 50% VE shifted the RSNA and HR arterial baroreflex response curves to the right in the fetus but had no significant effects on the gain of the arterial baroreflex curves in either fetal, newborn, or 6- to 8-wk-old sheep.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1994

Ontogenic changes in renal response to alpha 1-adrenoceptor stimulation in sheep.

The present study was designed to examine the effect of direct intrarenal infusion of the alpha 1-adrenoceptor agonist, phenylephrine, on urinary flow rate (UFR) and on renal Na and Cl excretion in conscious and chronically instrumented fetal (128-133 days gestation, term 145 days), newborn (6-12 days), and adult sheep. Five different renal concentrations of phenylephrine, varying from 5 +/- 1 to 72 +/- 2 ng/ml, were studied. Low renal phenylephrine concentration (< or = 12 +/- 1 ng/ml) induced a significant renal vasoconstrictor response in fetuses but not in newborn and adult sheep. The effects of intrarenal phenylephrine infusion on UFR and fractional excretion of Na (FENa) was greater (P < 0.05) in newborn lambs than in fetal and adult sheep. At a renal concentration of phenylephrine between 9 +/- 1 and 12 +/- 1 ng/ml, the percent decrease in UFR was greater (P < 0.05) in newborn lambs (-19.1 +/- 4.7%) than in fetal (9.8 +/- 8.9%) and adult sheep (-3.3 +/- 3.9). The percent decrease in FENa at renal concentration of phenylephrine between 18 +/- 1 and 24 +/- 1 ng/ml was also significantly (P < 0.05) larger in newborn lambs (-20.2 +/- 2.8%) than in fetal (-8.0 +/- 3.1%) and adult sheep (-11.2 +/- 2.6%). In summary, the present results indicate that the fetal kidney has a limited ability to increase sodium reabsorption in response to stimulation of alpha-adrenoceptors and that the effect of renal alpha-adrenoceptor stimulation on urinary volume and urinary sodium excretion increases during the newborn period.

Aging↗

PubMed1994

Role of sympathetic activity in the generation of heart rate and arterial pressure variability in fetal sheep.

Significant fluctuation in heart rate (HR) and arterial pressure occur during fetal life. However, the mechanisms regulating this normal variability are not completely understood. To test the hypothesis that the normal variability in fetal HR and blood pressure are produced by intrinsic fluctuations in sympathetic outflow, we recorded HR, mean arterial blood pressure (MABP), and renal sympathetic nerve activity (RSNA) in conscious, chronically instrumented, near-term fetal sheep (n = 5; 132-137 d of gestation, term being 145 d) and correlated the relationships between RSNA and MABP, and RSNA and HR. RSNA, HR, and MABP were sampled at a frequency of 4 Hz and the values averaged by 5-min blocks over a 4-h period. Linear regression analysis demonstrated a positive correlation between RSNA and both HR and MABP in all five fetuses (p < 0.02). In a second group of fetuses (n = 5), ganglionic blockade with trimethaphan (150-250 mg/kg/min) significantly attenuated (p < 0.05) the coefficients of variation of HR (12.3 +/- 1.9% versus 1.7 +/- 0.6%) and MABP (5.8 +/- 0.6% versus 3.6 +/- 0.5%). These results demonstrate that, in the fetus, fluctuations in HR and MABP are mediated by changes in sympathetic outflow and suggest an important role for the autonomic nervous system in fetal cardiovascular regulation.

Animals↗

PubMed1993

Influence of renal nerves on renal function during development.

The present review summarizes recent studies describing the role of renal sympathetic innervation in the regulation of renal function during development. The afferent renal innervation appears early during fetal life and probably precedes the development of efferent renal nerves. There is suggestive evidence that renal nerves are required for the proper development of the kidney and that neurotrophic growth factors play an important role in renal embryogenesis and in renal tubular differentiation. Renal sympathetic innervation modulates renal hemodynamics early during development. Renal nerve stimulation during alpha-adrenoceptor blockade produces renal vasodilation in fetal and newborn animals but not in adults. Unlike the effect of renal nerves on fetal renal hemodynamics which is observed in the young fetus, the role of renal sympathetic nerves in modulating fluid and electrolyte homeostasis seems to develop during late gestation. Recent studies have also shown that renal nerves play an important role in regulating renin secretion during the transition from fetal to newborn life. For example, renal denervation during fetal life suppressed the physiological rise in plasma renin activity associated with delivery and decreased renal renin mRNA levels after birth. Taken together, these studies suggest that renal nerves influence fetal renal development and that the influence of renal sympathetic innervation on renal hemodynamics and function changes with maturation.

Animals↗

PubMed1993

A case of giant prostatic hyperplasia.

Giant prostatic hyperplasia (GPH) is an uncommon pathologic entity with only 10 reported cases of prostate glands exceeding 500 g. We report the uncomplicated removal of a 526-g prostatic adenoma by simple retropubic prostatectomy.

Aged↗

PubMed1993

The titanium intraprostatic stent: the United States experience.

This multicenter, cooperative study represents the initial United States experience using an expandable, titanium intraprostatic stent in 68 patients (60 to 93 years old). The stents were inserted under direct vision and expanded to 33F using a balloon catheter. All patients had a symptom score analysis, and underwent measurement of peak urine flow and rate and post-void residual urine volume as part of the initial evaluation. Patients were seen at approximately 1, 3, 6 and 18 months after stent insertion (mean followup 16 months). Of the 68 patients 38 presented in urinary retention. The type of anesthesia used included general anesthesia in 6 patients, spinal or epidural anesthesia in 24, intravenous sedation in 20 and intraurethral lidocaine only in 18. All patients were able to void spontaneously within 36 hours after stent insertion. Symptom scores decreased from 16.8 to 3.9, 6.3, 5.0, 5.7 and 3.2 at approximately 1, 3, 6, 12 and 18 months, respectively. Peak urine flow rate increased from 3.9 to 13.8, 11.5, 11.2, 12.4 and 14.4 ml. per second at approximately 1, 3, 6, 12 and 18 months, respectively. Post-void residual urine volume decreased from 74.4 to 30.1, 29.2, 19.8 and 40.2 ml. at approximately 1, 3, 6 and 12 months, respectively. Of the initial 68 patients 5 died of the underlying disorder (all voiding satisfactorily with the stent in place) and 17 underwent uneventful stent removal (10 for technical failure and 7 for treatment failure). Technical failures were secondary to either inaccurate positioning or improper stent sizing. Of the 58 patients with proper placement of the stent and no technical failures 46 (79%) had improvement in symptom scores and urine flow rate. Transient hematuria was noted in 43 patients (63%) and usually resolved within 48 hours. None of the 6 urinary tract infections (9%) was recurrent. In conclusion, the titanium intraprostatic stent, when properly placed, is a promising therapeutic alternative to prostatectomy or long-term catheterization in high risk obstructed patients or those in urinary retention. Studies are currently in progress to determine the long-term efficacy of this therapeutic modality.

Aged↗