Delayed ureterectomy after incomplete nephroureterectomy for upper tract urothelial carcinoma: pathologic findings and outcomes

OBJECTIVES

To evaluate the pathologic findings and outcomes after distal ureterectomy for a retained ureteral segment following incomplete nephroureterectomy for urothelial carcinoma of the renal pelvis or ureter.

MATERIALS AND METHODS

After IRB approval, an institutional database identified patients who underwent distal ureterectomy for a retained ureteral segment after assumed complete nephroureterectomy for urothelial carcinoma of the upper ureter or renal pelvis. Clinical and pathologic variables were analyzed.

RESULTS

From January 1993 to July 2007, 12 patients were identified with median age at the time of ureterectomy of 60.5 years (41-85 years). Initial approach to surgery was open in 9 patients and laparoscopic in 3 patients. The median time from nephroureterectomy to distal ureterectomy was 23.5 months (range 2-66). At the time of initial surgery, pathologic stage was Ta, T1, T2, and T3 in 3,4,1, and 4 patients respectively. Initial pathology was urothelial carcinoma; grade 2 in 6 patients and grade 3 in six patients. Pathology from the subsequent surgery demonstrated urothelial carcinoma in the retained ureteral segment in 8 patients, dysplasia or atypia in 3 patients, and 1 patient with chronic inflammation. Local recurrence in 2 patients was present in a segment of ureter discontinuous with the bladder after laparoscopic nephroureterectomy. Three patients (25%), all with initial grade 3 renal pelvis lesions, developed metastatic disease.

CONCLUSIONS

Tumor recurrence in a retained ureteral segment after incomplete nephroureterectomy is a significant problem and may contribute to intravesical recurrence or metastatic disease. Complete, en bloc resection is imperative to minimize these risks.

Phase I trial of intravesical recombinant adenovirus mediated interferon-α2b formulated in Syn3 for Bacillus Calmette-Guérin failures in nonmuscle invasive bladder cancer

PURPOSE

A phase I trial of intravesical recombinant adenovirus mediated interferon-α2b gene therapy (rAd-IFNα) formulated with the excipient SCH Syn3 was conducted in patients with nonmuscle invasive bladder cancer who had disease recurrence after treatment with bacillus Calmette-Guérin. The primary objective was to determine the safety of rAd-IFNα/Syn3. Secondary end points were demonstrated effective rAd-IFNα gene expression and preliminary evidence of clinical activity at 3 months.

MATERIALS AND METHODS

A total of 17 patients with recurrent nonmuscle invasive bladder cancer after bacillus Calmette-Guérin treatment were enrolled in the study. A single treatment of rAd-IFNα (3 × 10(9) to 3 × 10(11) particles per ml) formulated with the excipient Syn3 was administered. Patient safety was evaluated for 12 or more weeks. Efficacy of gene transfer was determined by urine IFNα protein concentrations. Preliminary drug efficacy was determined at 3 months.

RESULTS

Intravesical rAd-IFNα/Syn3 was well tolerated as no dose limiting toxicity was encountered. Urgency was the most common adverse event and all cases were grade 1 or 2. rAd-IFNα DNA was not detected in the blood. However, transient low serum IFNα and Syn3 levels were measured. High and prolonged dose related urine IFNα levels were achieved with the initial treatment. Of the 14 patients treated at doses of 10(10) or more particles per ml with detectable urine IFNα, 6 (43%) experienced a complete response at 3 months and 2 remained disease-free at 29.0 and 39.2 months, respectively.

CONCLUSIONS

Intravesical rAd-IFNα/Syn3 was well tolerated with no dose limiting toxicity encountered. Dose dependent urinary IFNα concentrations confirmed efficient gene transfer and expression. Intravesical rAd-IFNα/Syn3 demonstrated clinical activity in nonmuscle invasive bladder cancer recurring after bacillus Calmette-Guérin.

Cardiac history and risk of post-cystectomy cardiac complications

OBJECTIVES

To evaluate risk factors for postoperative cardiac complications (POCC). Patients undergoing cystectomy often have significant baseline cardiac disease. Despite preoperative medical optimization, postoperative cardiac complications remain a significant source of morbidity.

METHODS

A retrospective review of all radical cystectomies for bladder cancer between January 2004 and September 2006 was performed. Twelve preoperative risk factors were evaluated, including age, Charlson Comorbidity Index, type of urinary diversion, and previous cardiac history. All complications, including myocardial infarction (MI) and new onset arrhythmia, were recorded for 90 days postoperatively. Univariate and multivariate analysis were performed.

RESULTS

A total of 283 patients underwent cystectomy for bladder cancer between January/2004 and September 2006. The median age of the cohort was 70 (35-90) years. Of 283 patients, 64 (23%) had a significant preoperative cardiac history, including 18 (6%) with prior coronary artery bypass and 30 (11%) with a history of MIs. Thirty-one (11%) patients had either new onset arrhythmia (22, 8%) or MI (10, 4%) and 1 had both. On univariate analysis, cardiac history, age, type of urinary diversion, and the Charlson Comorbidity Index demonstrated significance. The risk of POCC was associated with ileal conduit urinary diversion (P = .026, OR 5.58 [1.23-25.36]) and the Charlson Index score (P = .030, OR 1.28 [1.024-1.60]) on multivariate analysis.

CONCLUSIONS

Multiple, inter-related factors may predict cardiac complications in the early postoperative period. Despite perioperative optimization, patients with a prior cardiac history should be counseled, regarding the increased risk of postoperative cardiac complications. The association between cardiac complications and ileal conduit diversion highlights the selection bias toward patients with preexisting comorbid disease.

Lift-assisted offset lithotomy: positioning for transurethral operations in morbidly obese

The incidence of morbid obesity is rapidly increasing in the United States. This presents a unique challenge in the diagnosis, management, and surgical treatment of urologic disease. The use of the lithotomy position for transurethral procedures is often not possible because of the body habitus and equipment-specific weight limitations. During positioning, it becomes imperative to maintain the safety of both the patient and the operating room personnel. We present a new, bariatric lift-assisted positioning technique used in the management of a 311-kg morbidly obese man with high-grade, superficial, papillary urothelial carcinoma.

Extraction of UroLume endoprosthesis with one-stage urethral reconstruction using buccal mucosa

Long-term analyses of the UroLume Endoprosthesis have shown conflicting results with regard to efficacy and restricture rates. The best management of recurrent urethra stricture disease at the site of a previous UroLume stent is unknown. We describe a previously unreported technique for transperineal excision of the UroLume for recurrent bulbar urethral stricture disease with one-stage reconstruction using buccal mucosa. At 9 months of follow-up, the patient was voiding well with no evidence of stricture recurrence.

Patient opinion of urologists’ reimbursement

OBJECTIVES

To determine patient assumptions and opinions of the billing and reimbursement process in an urban urologic practice. Healthcare policy and physician reimbursement has been discussed in political and economic forums; however, few studies exist that reflect a patient's perspective of reimbursement issues.

METHODS

An anonymous, voluntary 11-question survey was given to 825 patients during a 10-week interval. The instrument measured patient perceptions on the amounts (in percentages) that would, and should, be covered by insurance carriers and collected by their urologist. It also measured the time frames perceived for these events to occur. Our aim was to evaluate their knowledge of office urologic reimbursement.

RESULTS

Overall, 532 patients (75%) surveyed believed their insurance would cover 80% to 100% of their bill. A total of 309 patients (49%) thought their urologist would receive 80% to 100% of the bill, and 383 (60%) thought they should receive that level of compensation (P < 0.0001). Respondents with prior surgical contact thought their urologist would (P = 0.004) and should (P = 0.01) be reimbursed at a greater level than those without prior surgical contact. When asked about the time to reimbursement, 340 (73%) thought their doctor would be paid within 6 weeks compared with 453 (95%) who thought their urologist should be paid within that time (P < 0.0001).

CONCLUSIONS

The survey responses demonstrated patients' convictions that their urologists should be reimbursed in a timely manner. Additional studies examining both patient and healthcare provider perspectives are needed to better educate both of these groups on the medical billing and reimbursement process.

Continent urinary diversion with a urachal remnant

The Mitrofanoff procedure, first described in 1980, has been widely adopted for pediatric continent urinary diversion to increase patient independence and continence, decrease morbidity and infections, and preserve renal function. Although this principle employs the appendix primarily, numerous other tissue conduits have been described. We report a unique use of a urachal remnant as a continent conduit resulting in less morbidity by maintaining the integrity of the native urinary bladder, while maintaining patient continence and allowing easy and successful catheterization.

The Literature Increasingly Supports Expectant (Conservative) Management of Renal Trauma — A Systematic Review

BACKGROUND

The perfect degree of operative intervention in renal trauma is unknown. However, expectant management for most blunt renal trauma is the standard of care, and nonoperative management is increasingly accepted for stab wounds. The best treatment of gunshot wounds and vascular injuries is still unclear; however, recent data indicates that a trial of nonoperative therapy may be warranted in those not exsanguinating from the kidney. Conservative management has many benefits, the greatest of which is decreasing the rate of iatrogenic nephrectomy. We have reviewed the world's literature to determine the level of support for expectant management of renal injury.

METHODS

The English language literature concerning renal trauma was identified with the assistance of Medline, and additional cited works not picked up in the initial search were obtained. One hundred and ten citations were ultimately reviewed dating back to 1947.

RESULTS

Most modern citations support at least a trial of expectant management for renal trauma patients not exsanguinating from the kidney, and without ureteral or renal pelvis injuries. The treatment of renovascular injuries has less consensus, but it appears that 'conservative' management by the application of nephrectomy is often the best approach, although renovascular repair may be attempted in rare cases.

CONCLUSION

Dozens of papers going back as far as 50 years seem to support the wider use of nonoperative therapy of renal injuries, although for unclear reasons, this approach is not yet universally accepted.

Breast Carcinoma Metastatic to the Bladder and Renal Pelvis Requiring Fulguration

Breast cancer metastatic to the bladder has rarely been reported in the literature. A patient presented to our institution with pathologically confirmed breast cancer metastatic to the bladder with renal pelvis involvement as seen on retrograde pyelography. We believe cystoscopy with biopsy and fulguration to be the treatment of choice for breast cancer that has metastasized to the bladder because of the low rate of survival in patients with hematuria related to metastatic breast cancer.

The role of hepatic and extrahepatic UDP-glucuronosyltransferases in human drug metabolism

At present, the methods and enzymology of the UDP-glucuronosyltransferases (UGTs) lag behind that of the cytochromes P450 (CYPs). About 15 human UGTs have been identified, and knowledge about their regulation, substrate selectivity, and tissue distribution has progressed recently. Alamethicin has been characterized as a treatment to remove the latency of microsomal glucuronidations. Most UGT isoforms appear to have a distinct hepatic and/or extrahepatic expression, resulting in significant expression in kidney, intestine, and steroid target tissues. The gastrointestinal tract possesses a complex expression pattern largely containing members of the UGT1A subfamily. Thus, these forms are poised to participate in the first pass metabolism of oral drugs. The authors and others have identified a significant expression of UGT1A1 in human small intestine, an enzyme possessing considerable allelic variability and a polymorphic expression pattern in intestine. Intestinal glucuronidation therefore plays a major role not only in first pass metabolism, but also in the degree of interindividual variation in overall oral bioavailability. Due to issues such as significant genetic variability and tissue localization in first-pass organs, clearance due to UGT1A1 should be minimized for new drugs.

Active site characteristics of CYP4B1 probed with aromatic ligands

The active site topography of rabbit CYP4B1 has been studied relative to CYP2B1 and CYP102 using a variety of aromatic probe substrates. Oxidation of the prochiral substrate cumene by CYP4B1, but not CYP2B1 or CYP102, resulted in the formation of the thermodynamically disfavored omega-hydroxy metabolite, 2-phenyl-1-propanol, with product stereoselectivity for the (S)-enantiomer. Reaction of CYP4B1, CYP2B1, and CYP102 with phenyldiazene produced spectroscopically observable sigma-complexes for each enzyme. Subsequent oxidation of the CYP2B1 and CYP102 complexes followed by LC/ESI--MS analysis yielded heme pyrrole migration patterns similar to those in previous literature reports. Upon identical treatment, no migration products were detected for CYP4B1. Intramolecular deuterium isotope effects for the benzylic hydroxylation of o-xylene-alpha-(2)H(3), p-xylene-alpha-(2)H(3), 2-(2)H(3),6-dimethylnaphthalene, and 4-(2)H(3),4'-dimethylbiphenyl were determined for CYP4B1 and CYP2B1 to further map their active site dimensions. These probes permit assessment of the ease of equilibration, within P450 active sites, of oxidizable methyl groups located between 3 and 10 A apart [Iyer et al. (1997) Biochemistry 36, 7136--7143]. Isotope effects for the CYP4B1-mediated benzylic hydroxylation of o- and p-xylenes were fully expressed (k(H)/k(D) = 9.7 and 6.8, respectively), whereas deuterium isotope effects for the naphthyl and biphenyl derivatives were both substantially masked (k(H)/k(D) approximately equal to 1). In contrast, significant suppression of the deuterium isotope effects for CYP2B1 occurred only with the biphenyl substrate. Therefore, rapid equilibration between two methyl groups more than 6 A apart is impeded within the active site of CYP4B1, whereas for CYP2B1, equilibration is facile for methyl groups distanced by more than 8 A. Collectively, all data are consistent with the conclusion that the active site of CYP4B1 is considerably restricted relative to CYP2B1.

Tissue distribution and interindividual variation in human UDP-glucuronosyltransferase activity: relationship between UGT1A1 promoter genotype and variability in a liver bank

The variability in a liver bank and tissue distribution of three probe UDP-glucuronosyltransferase (UGT) activities were determined as a means to predict interindividual differences in expression and the contribution of extrahepatic metabolism to presystemic and systemic clearance. Formation rates of acetaminophen-O-glucuronide (APAPG), morphine-3-glucuronide (M3G), and oestradiol-3-glucuronide (E3G) as probes for UGT1A6, 2B7, and 1A1, respectively, were determined in human kidney, liver, and lung microsomes, and in microsomes from intestinal mucosa corresponding to duodenum, jejunum and ileum. While formation of E3G and APAPG were detectable in human kidney microsomes, M3G formation rates from kidney microsomes approached the levels seen in liver, indicating significant expression of UGT2B7. Interestingly, rates of E3G formation in human intestine exceeded the hepatic rates by several fold, while APAPG and M3G formation rates were low. The intestinal apparent Km value for E3G formation was essentially identical to that seen in liver, consistent with intestinal UGT1A1 expression. No UGT activities were observed in lung. Variability in APAPG and M3G activity across a bank of 20 human livers was modest (< or = 7-fold), compared to E3G formation, which varied approximately 30-fold. The E3G formation rates were found to segregate by UGT1A1 promoter genotype, with wild-type (TA)6 rates significantly greater than homozygous mutant (TA)7 individuals. Kinetic analyses were performed to demonstrate that the promoter mutation altered apparent Vmax without significantly affecting apparent Km. These results suggest that glucuronidation, and specifically UGT1A1 activity, can profoundly contribute to intestinal first pass metabolism and interindividual variability due to the expression of common allelic variants.

Immunochemical identification of UGT isoforms in human small bowel and in caco-2 cell monolayers

Previous work had suggested the presence of significant levels of UDP-glucuronosyltransferase 1A1 (UGT1A1) catalytic activity in human small intestinal microsomes, with undetectable to low UGT1A6 and 2B7 activities. To confirm the presence of UGT1A1 isoform in human small bowel, to explore the possible absence of UGT1A6 and 2B7 in the organ, and to examine induced Caco-2 cells as a potential model for human intestinal metabolism, Western blot analysis was performed using specific antibodies to the relevant UGT isoforms. Significant expression of UGT1A1 protein was observed in all samples of human small intestinal microsomes, while UGT1A6 expression was undetectable to faint and UGT2B7 immunoreactivity was faint to detectable. Caco-2 cells treated with typical enzyme-inducing agents resulted in low UGT2B7 expression but failed to mimic the UGT1A1 levels found in human small bowel. Further work needs to be performed to develop a comprehensive in vitro model for human small intestinal first-pass metabolism.

In vitro glucuronidation using human liver microsomes and the pore-forming peptide alamethicin

The UDP-glucuronosyltransferases (UGTs) are a superfamily of membrane-bound enzymes whose active site is localized inside the endoplasmic reticulum. Glucuronidation using human liver microsomes has traditionally involved disruption of the membrane barrier, usually by detergent treatment, to attain maximal enzyme activity. The goals of the current work were to develop a universal method to glucuronidate xenobiotic substrates using microsomes, and to apply this method to sequential oxidation-glucuronidation reactions. Three assays of UGT catalytic activity estradiol-3-glucuronidation, acetaminophen-O-glucuronidation, and morphine-3-glucuronidation, which are relatively selective probes for human UGT1A1, 1A6, and 2B7 isoforms, respectively, were developed. Treatment of microsomes with the pore-forming peptide alamethicin (50 microg/mg protein) resulted in conjugation rates 2 to 3 times the rates observed with untreated microsomes. Addition of physiological concentrations of Mg(2+) to the alamethicin-treated microsomes yielded rates that were 4 to 7 times the rates with untreated microsomes. Optimized assay conditions were found not to detrimentally affect cytochrome P450 activity as determined by effects on testosterone 6beta-hydroxylation and 7-ethoxycoumarin deethylation. Formation of estradiol-3-glucuronide displayed atypical kinetics, and data best fit the Hill equation, yielding apparent kinetic parameters of K(m)(app) = 0.017 mM, V(max)(app) = 0.4 nmol/mg/min, and n = 1.8. Formation of acetaminophen-O-glucuronide also best fit the Hill equation, with K(m)(app) = 4 mM, V(max)(app) = 1.5 nmol/mg/min, and n = 1.4. Alternatively, morphine-3-glucuronide formation displayed Michaelis-Menten kinetics, with K(m)(app) = 2 mM and V(max)(app) = 2. 5 nmol/mg/min. Finally, alamethicin treatment of microsomes was found to be effective in facilitating the sequential oxidation-glucuronidation of 7-ethoxycoumarin.

Enzymatic determinants of the substrate specificity of CYP2C9: role of B'-C loop residues in providing the pi-stacking anchor site for warfarin binding

Previous modeling efforts have suggested that coumarin ligand binding to CYP2C9 is dictated by electrostatic and pi-stacking interactions with complementary amino acids of the protein. In this study, analysis of a combined CoMFA-homology model for the enzyme identified F110 and F114 as potential hydrophobic, aromatic active-site residues which could pi-stack with the nonmetabolized C-9 phenyl ring of the warfarin enantiomers. To test this hypothesis, we introduced mutations at key residues located in the putative loop region between the B' and C helices of CYP2C9. The F110L, F110Y, V113L, and F114L mutants, but not the F114Y mutant, expressed readily, and the purified proteins were each active in the metabolism of lauric acid. The V113L mutant metabolized neither (R)- nor (S)-warfarin, and the F114L mutant alone displayed altered metabolite profiles for the warfarin enantiomers. Therefore, the effect of the F110L and F114L mutants on the interaction of CYP2C9 with several of its substrates as well as the potent inhibitor sulfaphenazole was chosen for examination in further detail. For each substrate examined, the F110L mutant exhibited modest changes in its kinetic parameters and product profiles. However, the F114L mutant altered the metabolite ratios for the warfarin enantiomers such that significant metabolism occurred for the first time on the putative C-9 phenyl anchor, at the 4'-position of (R)- and (S)-warfarin. In addition, the Vmax for (S)-warfarin 7-hydroxylation decreased 4-fold and the Km was increased 13-fold by the F114L mutation, whereas kinetic parameters for lauric acid metabolism, a substrate which cannot interact with the enzyme by a pi-stacking mechanism, were not markedly affected by this mutation. Finally, the F114L mutant effected a greater than 100-fold increase in the Ki for inhibition of CYP2C9 activity by sulfaphenazole. These data support a role for B'-C helix loop residues F114 and V113 in the hydrophobic binding of warfarin to CYP2C9, and are consistent with pi-stacking to F114 for certain aromatic ligands.

Identification of a meander region proline residue critical for heme binding to cytochrome P450: implications for the catalytic function of human CYP4B1

Alignment of xenobiotic-metabolizing P450 protein sequences highlights an invariant proline residue in the meander region two amino acids N-terminal to the distal arginine of the putative ERR triad thought to be important for heme binding. This occurs as a serine in the sequences derived from human CYP4B1 gDNA and both human lung and placental CYP4B1 cDNAs. Reversion of this serine to the conserved proline residue (Ser427 --> Pro) by site-directed mutagenesis conferred the ability to incorporate heme on the human placental enzyme. Mutation of the corresponding proline in rabbit CYP4B1 (Pro422 --> Ser) abolished heme incorporation. Membrane preparations of human CYP4B1(Pro) and rabbit CYP4B1(Pro), but not the corresponding CYP4B1(Ser) variants, supported lauric acid hydroxylation preferentially at the omega-position. Purified, reconstituted human CYP4B1(Pro) and rabbit CYP4B1(Pro) formed 12-hydroxylauric acid at rates of 17-21 min-1, and both enzymes were also C-8 to C-10 fatty acid omega-hydroxylases preferentially, with total rates of hydroxylation decreasing in the order C-12 > C-10 > C-9 > C-8. Finally, neither human nor rabbit CYP4B1(Pro) formed detectable levels of any hydroxylated testosterone metabolites. Therefore, the presence of a consensus Pro-X-Arg motif is critical for incorporation of the heme prosthetic group in human and rabbit CYP4B1 proteins expressed in insect cells. Native human CYP4B1, expressed in vivo, is likely to be functionally impaired if Pro427 is required for holoenzyme expression in mammalian cells.

P450-catalyzed in-chain desaturation of valproic acid: isoform selectivity and mechanism of formation of Delta 3-valproic acid generated by baculovirus-expressed CYP3A1

The mechanism of formation of the in-chain, unsaturated fatty acid metabolite, Delta3-valproic acid (Delta3-VPA) by rat liver microsomes was examined. Microsomal rates of formation of Delta3-VPA were below quantifiable limits in reactions catalyzed by control female rat liver microsomes, but were induced more than 20-fold following pretreatment with triacetyloleandomycin and pregnenolone-16alpha-carbonitrile. Microsomal incubations conducted with 3-hydroxy-VPA or [2-2H1]VPA demonstrated that Delta3-VPA did not arise by dehydration of preformed alcohol nor was it reversibly isomerized to Delta2-VPA. CYP3A1 expression was optimized in the baculovirus expression vector system, and infected insect cell membranes which were supplemented with P450 reductase catalyzed formation of 3-OH-, 4-OH-, 5-OH-, Delta3-, and Delta4-VPA in ratios of 160:35:6:3:1. Intramolecular deuterium isotope effects on metabolite formation, determined with cDNA-expressed CYP3A1 and either [3,3-2H2]VPA or [4,4-2H2]VPA, yielded kH/kD values for Delta3-VPA of 2.00 +/- 0.06 and 2.36 +/- 0.08, respectively. These values were significantly lower than the isotope effects observed in the same incubations for 3-OH-VPA formation from 3,3-D2-VPA (kH/kD = 6.04 +/- 0.08), or for 4-OH- and Delta4-VPA formation from 4, 4-D2-VPA (kH/kD > 5). Collectively, these data demonstrate the existence of a microsomal P450-dependent in-chain fatty acid desaturase system distinct from the well-documented cytochrome b5-linked CoA desaturases and suggest further that CYP3A1-dependent formation of Delta3-VPA arises via nonselective, initial hydrogen atom abstraction from either the C-3 or the C-4 position.

Positional specificity of rabbit CYP4B1 for omega-hydroxylation1 of short-medium chain fatty acids and hydrocarbons

Rabbit CYP4B1 was incubated with a series of fatty acid and hydrocarbon substrates and metabolites were identified by gas chromatography and gas chromatography/mass spectrometry. C-7 to C-10 n-alkyl fatty acids were preferentially hydroxylated at the terminal carbon (omega/omega-1 = 1.1-7.4) with turnover numbers of 1-11 min-1. The C-7 to C-10 n-alkyl hydrocarbons exhibited turnover numbers of 11-33 min-1 for the corresponding reactions and even higher regioselectivities for hydroxylation at the thermodynamically disfavored site (omega/omega-1 = 1.6-23). These results demonstrate a functional link between CYP4B1 and other CYP4 fatty acid hydroxylases, and show further that CYP4B1's unusual positional specificity is not dictated by the presence of a carboxylate (or polar) anchor on the substrate. This suggests the presence of a dominant hydrocarbon binding site which effectively restricts the access of short-medium chain n-alkyl substrates to the perferryl species in the active site of rabbit CYP4B1.

Cytochrome P450-dependent desaturation of lauric acid: isoform selectivity and mechanism of formation of 11-dodecenoic acid

Cytochrome P450-catalyzed desaturation reactions have been reported infrequently in the literature. Previously, we documented the formation of the terminal olefinic metabolite of valproic acid by various members of the CYP2B and CYP4B sub-families. However, despite the extensive use of fatty acid substrates in drug metabolism studies, other examples of terminal desaturation at non-activated carbon centers are lacking. The goals of the present studies were to determine whether the archetypal P450 substrate, lauric acid (dodecanoic acid; DDA), also undergoes desaturation reactions, identify specific rabbit P450 isoforms which catalyze this reaction and examine its mechanism. A highly sensitive, capillary GC/MS assay was developed to separate and quantitate the trimethylsilyl derivatives of 11-ene-DDA, cis- and trans-10-ene-DDA and cis- and trans-9-ene-DDA. Among all of these potential olefinic metabolites, only 11-ene-DDA was formed at a significant rate by rabbit liver microsomes. The formation of 11-ene-DDA was NADPH-dependent, and was induced markedly by acetone pre-treatment, but not by phenobarbital, rifampin or Arochlor 1254. Studies with seven purified, reconstituted rabbit P450 isoforms showed that the most rapid rates of desaturation were obtained with CYP2E1, CYP4A5/7 and CYP4B1. Non-competitive, intermolecular isotope effect experiments, conducted with [12,12,12-2H3]DDA and [11,11-2H2]DDA, demonstrated further that CYP4B1-mediated terminal desaturation of DDA is initiated by removal of a hydrogen atom from the omega-1 rather than the omega position.

Human CYP2C9 and CYP2A6 mediate formation of the hepatotoxin 4-ene-valproic acid

Cytochrome P450-dependent desaturation of the anticonvulsant drug valproic acid (VPA) results in formation of the hepatotoxin, 4-ene-VPA. Polytherapy with other anticonvulsants which are known P450 inducers increases the flux through this bioactivation pathway. The aim of the present study was to identify specific, inducible forms of human liver P450 which catalyze terminal desaturation of VPA. Oxidized VPA metabolites formed in an NADPH-dependent manner by human liver microsomes were quantified by gas-chromatography/mass spectrometry. In vitro reaction conditions were established which reflected the product profile found in vivo. Production of 4-ene-VPA by microsomal P450s could be inhibited significantly by coumarin, sulfaphenazole and diethyldithiocarbamate, but not by triacetyloleandomycin, quinidine or furafylline. Recombinant human CYP3A4 did not form detectable levels of 4-ene-VPA and, of nine additional isoforms expressed in either HepG2 or lymphoblastoid cells which were screened for VPA desaturase activity, only CYP2C9 and CYP2A6 formed detectable levels of metabolite. Consequently, CYP3A4, the isoform usually associated with induction by anticonvulsants cannot be responsible for the enhanced 4-ene-VPA formation that occurs during polytherapy. Instead, enhanced activity in vivo likely results from induction of CYP2A6 and/or CYP2C9.

Lisinopril versus placebo in the treatment of heart failure: the Lisinopril Heart Failure Study Group

Lisinopril, a long-acting, angiotensin-converting enzyme inhibitor, was compared with placebo in a randomized, parallel, double-blind, 12-week study of 193 patients with heart failure. All patients were New York Heart Association Functional Class II, III, or IV and had remained symptomatic despite optimal dosing with digoxin and diuretics. After 12 weeks of therapy, the improvement in treadmill exercise duration was greater in the lisinopril group (113 seconds) compared with the placebo group (86 seconds). This improvement in exercise duration was particularly evident in patients with left ventricular ejection fractions less than 35% (lisinopril = 130 seconds; placebo = 94 seconds). In patients receiving lisinopril, the increase in exercise duration was accompanied by an improvement in quality of life as measured by the Yale Scale Dyspnea/Fatigue Index and in signs and symptoms of heart failure. In addition, the lisinopril group had a larger mean increase (3.7%) in left ventricular ejection fraction when compared with the placebo group (1.3%). Thus, lisinopril, administered once daily for 12 weeks, was well tolerated and efficacious in the treatment of heart failure when used concomitantly with diuretics and digoxin.

Formation, characterization, and immunoreactivity of lysine thioamide adducts from fluorinated nephrotoxic cysteine conjugates in vitro and in vivo

Fluorinated nephrotoxic cysteine conjugates undergo bioactivation via the beta-lyase pathway to thionoacetyl fluorides (TAF), the putative reactive intermediates. The TAF derived from S-(1,1,2,2,-tetrafluoroethyl)-L-cysteine (TFEC) difluorothionoacetylates amine nucleophiles found in proteins and lipids. A specific antisera, raised against (trifluoroacetamido)lysine adducts formed in vivo after halothane treatment, has previously been used to localize TFEC-derived protein adducts immunohistochemically, and a good correlation between adduction and toxicity was demonstrated. Interestingly, thioamide formation is facilitated by acyl-transfer catalysts such as imidazoles and phenols. However, although putative lysine adducts have been reported to be formed from the related TAF derived from S-(2-chloro-1,1,2-trifluoroethyl)-L-cysteine (CTFC), protein adducts derived from CTFC metabolism have not been completely characterized. In the present investigation we characterize (chlorofluorothionacetamido)lysine (CFTAL) adduct formation during S-(2-chloro-1,1,2-trifluoroethyl)-L-cysteine (CTFC) metabolism, both in vitro and in vivo. Our data indicate that formation of CTFC-derived lysine thioamides was not as dependent on nucleophilic catalysis as observed for TFEC, and this appears to be due to an apparent greater reactivity of the TAF resulting in a higher trapping efficiency in the absence of catalyst. Also, qualitative and quantitative differences in the structures and time course of CTFC versus TFEC adduct breakdown were observed. Antibodies raised against the halothane metabolite protein adduct (trifluoroacetamido)lysine cross-react with specific mitochondrial proteins from the kidneys of TFEC-treated rats. Using this antibody, we have found that the pattern of adducted proteins from TFEC- and CTFC-treated Fischer rats was similar, but the intensity was considerably lower after treatment with equimolar concentrations of CTFC in vivo.

Changes in dyspnea-fatigue ratings as indicators of quality of life in the treatment of congestive heart failure

A new clinical index of dyspnea and fatigue has been applied to rate the condition of patients with congestive heart failure. The index has 3 components, each rated on a scale from 0 to 4, for the magnitude of the task that evokes dyspnea or fatigue, the magnitude of the pace (or effort) with which the task is performed and the associated functional impairment in general activities. The ratings for each component are added to form an aggregated score, which can range from 0, for the worst condition, to 12, for the best. Because dyspnea and fatigue are prime symptoms and sources of clinical distress, the index helps reflect the quality of life in patients with congestive heart failure. In double-blind trials of therapy, changes in the index showed good correlations with patients' self-selected ratings of improvement. The posttherapeutic changes in the index ratings were significantly higher with a new active agent (lisinopril) than with placebo or another active agent (captopril).

Lisinopril and captopril in the treatment of heart failure in older patients. Comparison of a long- and short-acting angiotensin-converting enzyme inhibitor

Heart failure is a common cardiovascular disorder that increases in prevalence with age. Older patients may respond differently than younger patients to the various classes of drugs used in the treatment of congestive heart failure (CHF). The responses of older patients (at least 65 years of age) were evaluated as part of a large multicenter trial utilizing angiotensin-converting enzyme (ACE) inhibitors in the treatment of CHF. A prospectively planned subgroup analysis of older CHF patients' therapeutic response to the long-acting (approximately 24-hour) ACE inhibitor lisinopril was compared with their response to captopril, a short-acting (less than eight-hour) ACE inhibitor. Symptomatic improvement occurred in both the lisinopril and captopril groups. Exercise duration also improved for patients treated with both agents. However, there was a tendency for lisinopril to be more effective than captopril (p = 0.08). Thus, the low level of renin activity often found in the plasma of older patients did not decrease the ability of the ACE inhibitors to improve effort tolerance. Left ventricular ejection fraction increased in patients treated with lisinopril but not in those treated with captopril. The improvement in left ventricular ejection fraction with lisinopril may be indicative of a more favorable prognosis in patients with CHF, since another long-acting ACE inhibitor, enalapril, reduces the rate of mortality associated with CHF. ACE inhibitors were generally well-tolerated by the older patients in the study. Therefore, ACE inhibitors appear to offer a useful therapeutic approach to the management of CHF in the older age group.

Immunological characterization of maize starch branching enzymes

Highly purified fractions of three starch branching enzymes from developing maize (Zea mays L.) endosperm were used to prepare antisera in rabbits. In double diffusion experiments, no immunoprecipitate was observed when branching enzyme IIa or IIb was tested against branching enzyme I antiserum. No immunoprecipitate was formed when branching enzyme I was tested against branching enzyme IIa or IIb antiserum. Increasing amounts of antisera in the above combinations also failed to inhibit enzyme activity. Branching enzyme IIa antiserum cross-reacted and formed spurs with branching enzyme IIb when compared with branching enzyme IIa antigen. Comparison of branching enzyme IIb antiserum with branching enzyme IIa also resulted in an immunoprecipitate. Increasing levels of branching enzyme IIa antiserum inhibited branching enzyme IIb as did the reciprocal combination. The data indicated that branching enzymes IIa and IIb are immunologically similar while branching enzyme I is distinct. The data supports the classification of starch branching enzymes based on genetic, kinetic, and chromatographic properties.

Myocardial revascularization in patients with chronic renal failure

Symptomatic coronary artery disease in patients with chronic renal failure can complicate their management in a dialysis program. Hypotension associated with hemodialysis and the anemia of chronic renal disease can produce anginal episodes refractory to medical management. Untreated coronary artery disease may be a contraindication to renal transplantation in an otherwise acceptable candidate. We have encountered three cases of coronary artery disease severe enough to necessitate coronary bypass in patients from our long-term hemodialysis program. All three patients had uncomplicated postoperative courses, none had perioperative infarction, and in all three patients postoperative angiography demonstrated patency of all grafts. One patient subsequently underwent successful renal transplantation; the other two patients have continued in hemodialyses since bypass. We believe our experience and the reported experience of others confirm the feasibility of coronary bypass grafting in patients with chronic renal failure.

Effect of protein intake and dialysis on the abnormal growth hormone, glucose, and insulin homeostasis in uremia

To evaluate the role of protein intake in the altered growth hormone (GH) secretion of chronic renal failure, GH responses to mild exercise and to an oral glucose tolerance test were measured in ten uremic patients ingesting both low and normal protein diets. To delineate the effect of uremia on any interaction between GH and protein intake, tests were performed before dialysis, after daily dialyses for 3-4 days and after withholding dialysis for 3-4 days. Results were as follows: (1) exercise-stimulated GH release was increased compared to controls; (2) protein intake did not alter GH secretion, (3) basal GH concentrations were significantly correlated with creatinine levels and were significantly lower after dialysis, (4) dialysis did not improve the oral glucose tolerance test, (5) there was no correlation between glucose tolerance and exercise-stimulated GH levels, basal GH concentrations, or the sum of GH values after glucose, and (6) dialysis significantly increased the insulin response to glucose.

CONCLUSIONS

In chronic renal failure enhanced GH secretion is not affected by protein intake, does not cause glucose intolerance, and may be related to the degree of uremia. Dialysis does not improve glucose tolerance, but does increase glucose-stimulated insulin release suggesting that insulin antagonism is not ameliorated.