An ethical dilemma: malignant melanoma in a 51-year-old patient awaiting simultaneous kidney and pancreas transplantation for type 1 diabetes.

Malignant melanoma is a high-risk skin cancer that, in potential transplant recipients, is considered a substantial contraindication to solid organ transplantation due to significant risk of recurrence with immunosuppression. Current guidelines stipulate waiting between 3 and 10 years after melanoma diagnosis. However, in young patients with end-stage organ failure and malignant melanoma, complex ethical and moral issues arise. Assessment of the true risk associated with transplantation in these patients is difficult due to lack of prospective data, but an autonomous patient can make a decision that clinicians may perceive to be high risk. The national and worldwide shortage of available organs also has to be incorporated into the decision to maximize the net benefit and minimize the risk of graft failure and mortality. The incidence of malignant melanoma worldwide is increasing faster than that of any other cancer and continues to pose ethically challenging decisions for transplant specialists evaluating recipients for solid organ transplantation.

Subacute meningoencephalitis in a subset of patients with AD after Abeta42 immunization.

BACKGROUND: AD is characterized by cerebral deposition of beta-amyloid plaques with amyloid beta-peptide (Abeta) 42 as the major peptide constituent, along with neurofibrillary tangles and neuronal loss. In transgenic mice, active immunization against Abeta42 removes these plaques and improves cognitive function. A Phase I study in AD patients demonstrated good safety and tolerability of multiple injections of aggregated Abeta42 (AN1792) with QS-21 as adjuvant. METHODS: Three hundred seventy-two patients with mild to moderate AD were randomized to receive IM injections of AN1792 or placebo (4:1) at baseline and at months 1, 3, 6, 9, and 12 in a multicenter Phase II safety, tolerability, and pilot efficacy study. Dosing was terminated after four early reports of meningoencephalitis, but follow-up continued. The study remains blinded, and further results will be reported after its termination. RESULTS: Symptoms and laboratory findings consistent with meningoencephalitis occurred in 18 of 298 (6%) patients treated with AN1792 compared with 0 of 74 on placebo (p = 0.020). Sixteen of the 18 had received two doses, one had received one dose, and one had received three doses of the study drug before symptoms occurred. The median latency from the first and last injections to symptoms was 75 and 40 days. No case occurred later than 6 months after the first immunization. Anti-Abeta42 antibody titers were not correlated with the occurrence or severity of symptoms or relapses. Twelve patients recovered to or close to baseline within weeks, whereas six remain with disabling cognitive or neurologic sequelae. All 18 patients remain alive to date (December 31, 2002), 6 months to >1 year after symptom onset. CONCLUSIONS: Postvaccination meningoencephalitis occurred without clear relation to serum anti-Abeta42 antibody titers. Potential mechanisms such as T-cell and microglial activation may be responsible and are under consideration to develop a safer anti-Abeta immunotherapy for AD.

Metabolic fate and hepatocyte toxicity of reverse amide analogs of conjugated ursodeoxycholate in the rat.

Reverse amide analogs of conjugated bile acids were tested for their effects on the viability of cultured primary rat hepatocytes, for their transport and metabolism in the intact rat, and for their susceptibility to hydrolysis by intestinal bacteria. Succinylnorursodeoxycholanylamide (SNUDCN) and its parent C23 amine showed the same general lack of toxicity toward hepatocytes as the normal conjugates of ursodeoxycholic acid, at concentrations up to 500 microM. The 3alpha,7alpha,12alpha-trihydroxy analog and its parent amine were more toxic than the corresponding dihydroxy compounds, although their effects were similar to those observed for the normal conjugates of cholic acid. Following intraduodenal infusion, greater than 80% of administered SNUDCN appeared in the bile of bile fistula rats. Analysis of bile fractions indicated the presence of SNUDCN (81.5 mol% of original amount) and two metabolites, the taurine conjugate of SNUDCN (9.4 mol%) and SNUDCN containing an additional hydroxy group (9.1 mol%). Although SNUDCN underwent an efficient first pass enterohepatic circulation, it displayed a shorter biological half life than taurocholate (T1/2: 8.9 h vs 39.6 h, respectively). The reverse amide analogs were not hydrolyzed by any of a variety of intestinal bacteria known to hydrolyze normal conjugated bile acids. Despite the shorter half-life, the reverse amide analogs may be of potential use in the targeting of therapeutic bile acids to the colon.

Expression and transport properties of the human ileal and renal sodium-dependent bile acid transporter.

The enterohepatic circulation of bile acids is maintained by Na(+)-dependent transport mechanisms. To better understand these processes, a full-length human ileal Na(+)-bile acid cotransporter cDNA was identified using rapid amplification of cDNA ends and genomic cloning techniques. Using Northern blot analysis to determine its tissue expression, we readily detected the ileal Na(+)-bile acid cotransporter mRNA in terminal ileum and kidney. Direct cloning and mapping of the transcriptional start sites confirmed that the kidney cDNA was identical to the ileal Na(+)-bile acid cotransporter. In transiently transfected COS cells, ileal Na(+)-bile acid cotransporter-mediated taurocholate uptake was strictly Na+ dependent and chloride independent. Analysis of the substrate specificity in transfected COS or CHO cells showed that both conjugated and unconjugated bile acids are efficiently transported. When the inhibition constants for other potential substrates such as estrone-3-sulfate were determined, the ileal Na(+)-bile acid cotransporter exhibited a narrower substrate specificity than the related liver Na(+)-bile acid cotransporter. Whereas the multispecific liver Na(+)-bile acid cotransporter may participate in hepatic clearance of organic anion metabolites and xenobiotics, the ileal and renal Na(+)-bile acid cotransporter retains a narrow specificity for reclamation of bile acids.

A multicenter clinical trial of Gadolite Oral Suspension as a contrast agent for MRI.

The purpose of this study was to assess the effectiveness and safety of Gadolite Oral Suspension as a gastrointestinal (GI) contrast agent for MRI in a phase II and two phase III multicenter clinical trials. Gadolite was administered to 306 patients with known or suspected abdominal and/or pelvic disease. MRI with T1- and T2-weighted sequences was performed before and after ingestion. Efficacy was evaluated by having two masked readers rate the certainty of their MR diagnosis (0 = uncertain, 1 = probable, 2 = definite) on randomly presented pre- and post-Gadolite Oral Suspension enhanced images. Principal investigators also evaluated the images and established the final diagnosis. Vital signs, clinical chemistries, and adverse events were documented. Blood and urine samples were analyzed for gadolinium content to determine whether Gadolite Oral Suspension was absorbed systemically. Certainty in MR diagnosis increased significantly (P < .001) for both blinded readers between pre- and post-Gadolite images (.49-1.18 for reader 1: .46-1.53 for reader 2). Sensitivity, specificity, and accuracy also increased for both masked readers. No gadolinium was detected in blood or urine samples. There were no serious adverse events and no apparent drug-related trends in mean vital signs or laboratory values. Gadolite is a highly effective, safe, and well tolerated contrast agent for clinical use with MRI.

Primary bile acid malabsorption caused by mutations in the ileal sodium-dependent bile acid transporter gene (SLC10A2).

Primary bile acid malabsorption (PBAM) is an idiopathic intestinal disorder associated with congenital diarrhea, steatorrhea, interruption of the enterohepatic circulation of bile acids, and reduced plasma cholesterol levels. The molecular basis of PBAM is unknown, and several conflicting mechanisms have been postulated. In this study, we cloned the human ileal Na+/bile acid cotransporter gene (SLC10A2) and employed single-stranded conformation polymorphism analysis to screen for PBAM-associated mutations. Four polymorphisms were identified and sequenced in a family with congenital PBAM. One allele encoded an A171S missense mutation and a mutated donor splice site for exon 3. The other allele encoded two missense mutations at conserved amino acid positions, L243P and T262M. In transfected COS cells, the L243P, T262M, and double mutant (L243P/T262M) did not affect transporter protein expression or trafficking to the plasma membrane; however, transport of taurocholate and other bile acids was abolished. In contrast, the A171S mutation had no effect on taurocholate uptake. The dysfunctional mutations were not detected in 104 unaffected control subjects, whereas the A171S was present in 28% of that population. These findings establish that SLC10A2 mutations can cause PBAM and underscore the ileal Na+/bile acid cotransporter's role in intestinal reclamation of bile acids.

Continuous spectrophotometric assay of conjugated bile acid hydrolase.

Conjugated bile acid hydrolase (CBAH) refers to a class of enzymes which catalyze the cleavage of the amino acid moieties from conjugated bile acids. These enzymes are significant because of their role in providing substrates for further microbial metabolism in the gastrointestinal tract. They also are used in research laboratories for the deconjugation of bile acids prior to structural analyses. A continuous spectrophotometric assay for CBAH activity was developed using a conjugate of cholic acid and the chromophore, 5-amino-2-nitro-benzoic acid. The free chromophore is detected by virtue of its absorbance at 410 nm. The CBAH from Clostridium perfringens displayed a Km for this substrate of 120 microM. These results demonstrate that this new compound functions as an effective substrate of the enzyme and forms the basis for a convenient and rapid method to monitor CBAH activity.

Synthesis and characterization of novel analogs of conjugated bile acids containing reversed amide bonds.

New analogs of amino acid-conjugated bile acids were synthesized in which the amide bond was reversed from its normal configuration. These structural isomers of the beta-alanyl conjugates of cholic acid and ursodeoxycholic acid were synthesized by reaction of succinic anhydride with the 24-nor-23-amine derivatives of cholic acid and ursodeoxycholic acid. The chemical and physical properties of these reverse amide conjugated bile acid analogs were compared with those of the normal glycine and beta-alanine conjugates. The reverse amide analogs comigrated with their isomeric beta-alanine conjugates during thin-layer chromatography using a variety of solvent systems. However, the isomeric pairs could be resolved by reversed-phase high performance liquid chromatography, with the reverse amides having greater retention times compared to the beta-alanine conjugates. Critical micelle concentrations, solubility of undissociated forms, and acid dissociation constants were similar for the isomeric pairs. Significant differences in melting points were observed, however, While the isomeric pairs showed no significant differences in sensitivity to base hydrolysis, the reverse amides were not hydrolyzed by the cholylglycine hydrolase from Clostridium perfringens, even after long incubation periods.

Lower extremity muscle thickness during 30-day 6 degrees head-down bed rest with isotonic and isokinetic exercise training.

Muscle thickness was measured in 19 bed-rested (BR) men (32-42 year) subjected to isotonic (ITE, cycle ergometer) and isokinetic (IKE, torque ergometer) lower extremity exercise training, and no exercise (NOE) training. Thickness was measured with ultrasonography in anterior thigh--rectus femoris (RF) and vastus intermedius (VI), and combined posterior leg--soleus, flexor hallucis longus, and tibialis posterior (S + FHL + TP)--muscles. Compared with ambulatory control values, thickness of the (S + FHL + TP) decreased by 9%-12% (p < 0.05) in all three test groups. The (RF) thickness was unchanged in the two exercise groups, but decreased by 10% (p < 0.05) in the NOE. The (VI) thickness was unchanged in the ITE group, but decreased by 12%-16% (p < 0.05) in the IKE and NOE groups. Thus, intensive, alternating, isotonic cycle ergometer exercise training is as effective as intensive, intermittent, isokinetic exercise training for maintaining thicknesses of rectus femoris and vastus intermedius anterior thigh muscles, but not posterior leg muscles, during prolonged BR deconditioning.

Clinical trial of indomethacin in Alzheimer's disease.

In a 6-month, double-blind, placebo-controlled study, 100 to 150 mg/d indomethacin appeared to protect mild to moderately impaired Alzheimer's disease patients from the degree of cognitive decline exhibited by a well-matched, placebo-treated group. Over a battery of cognitive tests, indomethacin patients improved 1.3% (+/- 1.8%), whereas placebo patients declined 8.4% (+/- 2.3%)--a significant difference (p < 0.003). Caveats include adverse reactions to indomethacin and the limited scale of the trial.