Prevalence of eosinophilic esophagitis: A multicenter study on a pediatric population evaluated at thirty-six Latin American gastroenterology centers

INTRODUCTION AND OBJECTIVE

Eosinophilic esophagitis is a chronic, immune-mediated disease described in case series and publications worldwide. Over the past twenty years, the authors of different studies have attempted to evaluate its incidence and prevalence. The objetive of the present study was to estimate the prevalence of eosinophilic esophagitis in a group of children seen at 36 pediatric gastroenterology centers in ten Latin American countries.

MATERIALS AND METHODS

A multicenter, observational, and cross-sectional study was conducted that estimated the period prevalence of eosinophilic esophagitis in children seen at outpatient consultation and that underwent diagnostic upper gastrointestinal endoscopy for any indication at 36 centers in 10 Latin American countries, within a 3-month time frame.

RESULTS

Between April and June 2016, 108 cases of eosinophilic esophagitis were evaluated. Likewise, an average of 29,253 outpatient consultations and 4,152 diagnostic upper gastrointestinal endoscopies were carried out at the 36 participating centers. The period prevalence of eosinophilic esophagitis in the population studied (n=29,253) was 3.69 cases×1,000 (95% CI: 3.04 to 4.44), and among the children that underwent routine upper gastrointestinal endoscopy (n=4,152), it was 26x1,000 (95% CI: 22.6 to 29.4).

CONCLUSIONS

The general period prevalence of eosinophilic esophagitis in a group of children evaluated at 36 Latin American pediatric gastroenterology centers was 3.69×1,000, and in the children that underwent endoscopy, it was 26×1,000. There was important prevalence variability between the participating countries and centers. The present analysis is the first study conducted on the prevalence of pediatric eosinophilic esophagitis in Latin America.

Selective CD28 Blockade Results in Superior Inhibition of Donor-Specific T Follicular Helper Cell and Antibody Responses Relative to CTLA4-Ig

Donor-specific antibodies (DSAs) are a barrier to improved long-term outcomes after kidney transplantation. Costimulation blockade with CTLA4-Ig has shown promise as a potential therapeutic strategy to control DSAs. T follicular helper (Tfh) cells, a subset of CD4⁺ T cells required for optimal antibody production, are reliant on the CD28 costimulatory pathway. We have previously shown that selective CD28 blockade leads to superior allograft survival through improved control of CD8⁺ T cells relative to CTLA4-Ig, but the impact of CD28-specific blockade on CD4⁺ Tfh cells is unknown. Thus, we identified and characterized donor-reactive Tfh cells in a murine skin transplant model and then used this model to evaluate the impact of selective CD28 blockade with an anti-CD28 domain antibody (dAb) on the donor-specific Tfh cell-mediated immune response. We observed that the anti-CD28 dAb led to superior inhibition of donor-reactive CXCR5⁺ PD-1^high Tfh cells, CD95⁺ GL7⁺ germinal center B cells and DSA formation compared with CTLA4-Ig. Interestingly, donor-reactive Tfh cells differentially upregulated CTLA4 expression, suggesting an important role for CTLA4 in mediating the superior inhibition observed with the anti-CD28 dAb. Therefore, selective CD28 blockade as a novel approach to control Tfh cell responses and prevent DSA after kidney transplantation warrants further study.

Cytomegalovirus Infection in Patients with Sepsis Due to Bloodstream Infections: Lower Risk and Better Outcomes in New versus Already Hospitalised Intensive Care Unit Admissions

Few studies have examined cytomegalovirus (CMV) reactivation exclusively in immunocompetent patients with sepsis due to bloodstream infections. In a cohort of CMV-seropositive critically ill otherwise non-immunosuppressed patients with sepsis due to bloodstream infection, weekly testing for CMV viraemia was performed. Outcomes were assessed at 30 days or until death/discharge from the intensive care unit (ICU). CMV viraemia developed in 20% (20/100) of the patients. Age ( P=0.044) and blood transfusions ( P=0.022) were significantly associated with CMV viraemia. There was no difference in the primary endpoint (mortality and/or multi-organ failure) between patients with and without CMV viraemia ( P=0.49). However, CMV viraemia was associated with significantly fewer ICU-free days ( P=0.023) and fewer ventilator-free days ( P=0.031). Patients hospitalised in the ICU for more than 48 hours prior to the onset of bloodstream infection were more likely to develop CMV viraemia ( P=0.006), have high-grade viraemia ( P=0.010), and fewer ICU-free days ( P=0.018) and ventilator-free days ( P=0.029) than those admitted within 48 hours of bloodstream infection. Thus, CMV reactivation was associated with fewer ICU- and ventilator-free days, however overall mortality was not affected. Patients already in the ICU at the onset of sepsis had higher risk of CMV reactivation and worse outcomes than new ICU-bound patients suggesting that a targeted approach for interventions for CMV could conceivably be directed towards those with a more protracted course of illness.

Pathogen Stimulation History Impacts Donor-Specific CD8(+) T Cell Susceptibility to Costimulation/Integrin Blockade-Based Therapy

Recent studies have shown that the quantity of donor-reactive memory T cells is an important factor in determining the relative heterologous immunity barrier posed during transplantation. Here, we hypothesized that the quality of T cell memory also potently influences the response to costimulation blockade-based immunosuppression. Using a murine skin graft model of CD8(+) memory T cell-mediated costimulation blockade resistance, we elicited donor-reactive memory T cells using three distinct types of pathogen infections. Strikingly, we observed differential efficacy of a costimulation and integrin blockade regimen based on the type of pathogen used to elicit the donor-reactive memory T cell response. Intriguingly, the most immunosuppression-sensitive memory T cell populations were composed primarily of central memory cells that possessed greater recall potential, exhibited a less differentiated phenotype, and contained more multi-cytokine producers. These data, therefore, demonstrate that the memory T cell barrier is dependent on the specific type of pathogen infection via which the donor-reactive memory T cells are elicited, and suggest that the immune stimulation history of a given transplant patient may profoundly influence the relative barrier posed by heterologous immunity during transplantation.

Osteochondritis dissecans of the humeral capitellum: reliability of four classification systems using radiographs and computed tomography

BACKGROUND

The radiographic appearance of osteochondritis dissecans (OCD) of the humeral capitellum varies according to the stage of the lesion. It is important to evaluate the stage of OCD lesion carefully to guide treatment. We compared the interobserver reliability of currently used classification systems for OCD of the humeral capitellum to identify the most reliable classification system.

METHODS

Thirty-two musculoskeletal radiologists and orthopaedic surgeons specialized in elbow surgery from several countries evaluated anteroposterior and lateral radiographs and corresponding computed tomography (CT) scans of 22 patients to classify the stage of OCD of the humeral capitellum according to the classification systems developed by (1) Minami, (2) Berndt and Harty, (3) Ferkel and Sgaglione, and (4) Anderson on a Web-based study platform including a Digital Imaging and Communications in Medicine viewer. Magnetic resonance imaging was not evaluated as part of this study. We measured agreement among observers using the Siegel and Castellan multirater κ.

RESULTS

All OCD classification systems, except for Berndt and Harty, which had poor agreement among observers (κ = 0.20), had fair interobserver agreement: κ was 0.27 for the Minami, 0.23 for Anderson, and 0.22 for Ferkel and Sgaglione classifications. The Minami Classification was significantly more reliable than the other classifications (P < .001).

CONCLUSIONS

The Minami Classification was the most reliable for classifying different stages of OCD of the humeral capitellum. However, it is unclear whether radiographic evidence of OCD of the humeral capitellum, as categorized by the Minami Classification, guides treatment in clinical practice as a result of this fair agreement.

Rapamycin ameliorates the CTLA4-Ig-mediated defect in CD8(+) T cell immunity during gammaherpesvirus infection

Latent viral infections are a major concern among immunosuppressed transplant patients. During clinical trials with belatacept, a CTLA4-Ig fusion protein, patients showed an increased risk of Epstein-Barr virus-associated posttransplant lymphoproliferative disorder, thought to be due to a deficient primary CD8(+) T cell response to the virus. Using a murine model of latent viral infection, we observed that rapamycin treatment alone led to a significant increase in virus-specific CD8(+) T cells, as well as increased functionality of these cells, including the ability to make multiple cytokines, while CTLA4-Ig treatment alone significantly dampened the response and inhibited the generation of polyfunctional antigen-specific CD8(+) T cells. However, the addition of rapamycin to the CTLA4-Ig regimen was able to quantitatively and qualitatively restore the antigen-specific CD8(+) T cell response to the virus. This improvement was physiologically relevant, in that CTLA4-Ig treated animals exhibited a greater viral burden following infection that was reduced to levels observed in untreated immunocompetent animals by the addition of rapamycin. These results reveal that modulation of T cell differentiation though inhibition of mTOR signaling can restore virus-specific immune competence even in the absence of CD28 costimulation, and have implications for improving protective immunity in transplant recipients.

Cardiac biomarkers for infarct diagnosis and early exclusion of acute coronary syndrome

The acute coronary syndrome (ACS) represents a diagnostic challenge: on the one hand patients need to be quickly identified to initiate treatment and on the other hand early exclusion of patients without ACS is important to relieve patient stress as well as overcrowded emergency departments. A growing number of biomarkers are becoming available to aid physicians with this task. This review gives an overview of the current research concerning early exclusion with an emphasis on the clinically most important biomarker: cardiac troponin.

Darstellung, Kristallstruktur und Schwingungsspektren von Rubidiumperoxoniobat (Rb3NbO8) / Preparation, Crystal Structure, and Vibrational Spectra of Rubidiumperoxoniobate (Rb3NbO8)

The crystal structure of Rb3NbO8 (SG I4̅2m, Nr. 121) has been determined on single crystals to a final R = 0.041. The structure is isotypic to the K3CrO8 type. Vibrational spectra of the title compound have been recorded on powdered samples and are discussed with respect to the internal vibrations of the peroxo-group and the dodecahedral NbO8 3- ion. The stretching vibrations of the O2 2- groups are found at 838 (Raman) and 813 cm- 1(IR). A factor group analysis for the K3CrO8 type is given.

An anti-CD154 domain antibody prolongs graft survival and induces Foxp3(+) iTreg in the absence and presence of CTLA-4 Ig

The use of monoclonal antibodies targeting the CD154 molecule remains one of the most effective means of promoting graft tolerance in animal models, but thromboembolic complications during early clinical trials have precluded their use in humans. Furthermore, the role of Fc-mediated deletion of CD154-expressing cells in the observed efficacy of these reagents remains controversial. Therefore, determining the requirements for anti-CD154-induced tolerance will instruct the development of safer but equally efficacious treatments. To investigate the mechanisms of action of anti-CD154 therapy, two alternative means of targeting the CD40-CD154 pathway were used: a nonagonistic anti-CD40 antibody and an Fc-silent anti-CD154 domain antibody. We compared these therapies to an Fc-intact anti-CD154 antibody in both a fully allogeneic model and a surrogate minor antigen model in which the fate of alloreactive cells could be tracked. Results indicated that anti-CD40 mAbs as well as Fc-silent anti-CD154 domain antibodies were equivalent to Fc-intact anti-CD154 mAbs in their ability to inhibit alloreactive T cell expansion, attenuate cytokine production of antigen-specific T cells and promote the conversion of Foxp3(+) iTreg. Importantly, iTreg conversion observed with Fc-silent anti-CD154 domain antibodies was preserved in the presence of CTLA4-Ig, suggesting that this therapy is a promising candidate for translation to clinical use.

Preparation of Metal Nanosuspensions by High-Pressure DC-Sputtering on Running Liquids

A modified VERL-process (Vacuum evaporation on running liquids) employing high pressure magnetron sputtering has been used for the preparation of suspensions with metal nanoparticles. The method has been tested for Ag- and Fe-suspensions by varying the pressure of the Argon sputtering atmosphere in the range of 1 to 30 Pa. A narrow particle size distribution with a mean particle size ranging from 5–18 nm has been found. The mean particle size increases with increasing Argon pressure in the pressure range under investigation. A descriptive model for the process of particle formation as a function of sputtering gas pressure is given.

Antigenic disparity impacts outcome of agonism but not blockade of costimulatory pathways in experimental transplant models

Treatment regimens consisting of CTLA-4 Ig/anti-CD154 or agonistic anti-CD28/rapamycin have both been shown to prevent GVHD in fully allogeneic murine model systems. Using a transgenic approach to track the fate of host-reactive T cells in a minor antigen disparity model of GVHD, we found that while treatment with CTLA-4 Ig/anti-CD154 retained efficacy, the costimulation agonist anti-CD28 combined with rapamycin failed to prevent GVHD. Analysis of the host-reactive CD4(+) and CD8(+) T-cell responses revealed that in contrast to CTLA-4Ig/anti-CD154-treated recipients, host-reactive T cells in recipients treated with agonistic anti-CD28/rapamycin displayed enhanced and accelerated T-cell proliferation and failed to undergo activation-induced cell death. An increase in systemic levels of inflammatory cytokines was observed in the anti-CD28/rapamycin-treated recipients of the minor but not major antigen disparity bone marrow transplants. Our results demonstrate the intricacies of costimulatory receptor signaling pathways, and reveal how agonism of the CD28 pathway can have opposing outcomes depending on the degree of antigenic disparity.

Outcome of Imported Liver Allografts and Impact on Patient Access to Liver Transplantation

Liver allografts declined by local transplant centers are then offered regionally or nationally as imported grafts. Most of these grafts are declined because of poor donor quality. We retrospectively reviewed the medical records of patients who underwent liver transplantation between January 2004 and December 2005. There were 102 liver transplants in 98 recipients. They were divided into two groups: imported graft recipients (n = 37) and locally procured grafts recipients (n = 61). Eighty-six percent (32 of 37) of imported grafts were obtained from extended criteria donors defined as subjects treated with high doses of ionotropes with elevated liver enzymes, donor age over 70 years, macrosteatosis above 25%, positive hepatitis C or hepatitis B core antibody serology, systemic disease, history of cancer, hypernatremia, or with infection. The remaining grafts were declined due to unavailability of suitable recipients or social history. Recipient age and etiology of liver disease were similar for both groups. The mean MELD score was 22.1 +/- .9 among the imported graft recipients and 26.1 +/- 1 for the locally procured graft recipients (P < .01). There was no difference in blood loss or postoperative complications. Postoperative mean peak total bilirubin was similar in both groups. However, imported graft recipients had significantly higher mean peak AST (2436 +/- 282 vs 1380 +/- 165 U/L, P < .001) and ALT (1098 +/- 114 vs 803 +/- 87 U/L, P < .05). Primary graft nonfunction as well as 30 day and 1-year patient and graft survivals were similar for both groups. In conclusion, imported grafts can be transplanted in selected patients with outcomes comparable to locally procured grafts.

Reasons for non-treatment of hepatitis C in veterans in care

We prospectively studied 354 patients with hepatitis C virus (HCV) infection who were referred to a hepatology specialty clinic to find the reasons for non-treatment of HCV. The median age was 48 years (range 27-77 years), 98.5% were male and 71% were white. Seventy per cent of the patients were not treated. The most common reasons for non-treatment were non-adherence to follow-up visit (24%), normal liver enzymes (14%), concurrent medical problems (11%), alcohol and drug use (9%), psychiatric problems (7%), advanced liver disease (7%), referral for transplant evaluation (6.4%) and patient refusal, transfer of care to another facility and non-detectable HCV RNA levels (5% each). The reason was not recorded for 5% of the patients and was treatment deferred in 2.4% while waiting for pegylated interferon approval. Non-treatment was more likely in patients with less than 12 years of education and a history of incarceration. Patients who were lost to follow-up and refused treatment were more likely to have current alcohol and drug use and a history of incarceration.

[Nanoparticulate silver. A new antimicrobial substance for bone cement]

BACKGROUND

Multiresistant bacteria have become an important problem in prosthetic joint infections. Their frequent resistance against gentamicin, which is commonly used in antibiotic-loaded bone cements, makes a new prophylaxis necessary.

METHODS

PMMA-cement was loaded with 1% nanoparticulate silver and its antibacterial activity tested in vitro against gentamicin-resistant MRSE and MRSA strains as well as being compared to the activity of plain and gentamicin-loaded bone cements. A quantitative elution testing was also done to study the potentially cytotoxic effects of NanoSilver cement.

RESULTS

Unloaded and PMMA-cement loaded with 2% gentamicin did not exhibit any antibacterial activity against MRSE and MRSA. At 1%, NanoSilver cement completely inhibited the proliferation of MRSA and MRSE. NanoSilver bone cement did not show any significant differences compared to the non-toxic control group.

CONCLUSIONS

If these promising in vitro results can be confirmed in vivo, NanoSilver bone cement may be of considerable value in total joint arthroplasty.

Pneumonia in long-term care: a prospective case-control study of risk factors and impact on survival

BACKGROUND

Pneumonia is a major cause of morbidity and mortality in long-term care facilities. Prior studies of pneumonia have failed to identify risk factors potentially amenable to intervention. Our objectives were to (1) identify modifiable risk factors for the occurrence of pneumonia and (2) determine the long-term impact of pneumonia on survival.

METHODS

We performed a case-control study among residents of a Veterans Affairs long-term care facility. Case patients included all patients developing pneumonia from 2 days to 1 year after admission. Control subjects were matched for admission date, level of nursing care, and dependence in activities of daily living. Patients were followed up for 2 years or until death or discharge from the facility.

RESULTS

We identified 104 case-control pairs. Risk factors significantly associated with pneumonia included witnessed aspiration (odds ratio, 13.9; 95% confidence interval, 1.7-111.0; P =.01), sedative medication (odds ratio, 2.6; 95% confidence interval, 1.2-5.4; P =.01), and comorbidity score (odds ratio, 1.2; 95% confidence interval, 1.0-1.4; P =.05). Mortality due to pneumonia was 23% at 14 days. Patients with pneumonia had a significantly higher mortality than did controls at 1 year (75% vs 40%; P<.001); survival curves converged at 2 years. In a Cox proportional hazards regression model, an episode of pneumonia was independently associated with mortality during follow-up (odds ratio, 2.6; 95% confidence interval, 1.7-3.9; P<.001).

CONCLUSIONS

Among long-term care patients closely matched for age, level of dependency, and duration of institutionalization, an episode of pneumonia is associated with significant excess mortality that persists for up to 2 years. Two identified risk factors, large-volume aspiration and receipt of sedating medication, are potentially amenable to intervention.

Failure to induce neonatal tolerance in mice that lack both IL-4 and IL-13 but not in those that lack IL-4 alone

Current evidence suggests that neonatal tolerance to a foreign Ag is the consequence of IL-4-mediated Th2 immunity rather than the thymic deletion of Ag-specific T cells. Here, we addressed the role of IL-4 in neonatal tolerance by testing whether tolerance to a minor histocompatibility Ag can be induced in newborn mice that lack IL-4 (IL-4(-/-)). We found that IL-4 does not play a dominant role in the induction of neonatal tolerance as newborn female IL-4(-/-) mice could be readily tolerized to the H-Y male Ag. In contrast, mice that lack both IL-4 and IL-13 (IL-4(-/-)/IL-13(-/-)) were resistant to the induction of neonatal tolerance, and their splenocytes produced exaggerated amounts of IFN-gamma on rechallenge with the same Ag encountered during the neonatal period. These findings argue against the view that IL-4 alone is critical for the induction of neonatal tolerance and suggest that the combined actions of both IL-4 and IL-13 are essential for this process.

[Serological diagnosis of celiac disease: anti-gliadin peptide antibodies and tissue anti-transglutaminase]

Serological markers currently used for the diagnosis of celiac disease are anti-gliadin (AG) and anti-endomysium (AE) antibodies. Recently tissue transglutaminase (tTG) was identified as the specific autoantigen for endomysial antibodies. The aim of this work was to determine sensitivity and specificity of ELISA tests developed by using defined molecular structures as capture antigen for AG and AE antibodies. Three synthetic peptides, from the amino terminal region of alpha gliadin, were used as immobilized antigens for AG, and the transglutaminase from guinea pig liver for AE. A total of 80 sera from celiac patients, non celiac disease controls and healthy controls were examined. Age range was 7 months to 14 years. A sensitivity of 97% and a specificity of 86% was obtained for IgG determined by using as antigen one of the three synthetic peptides (corresponding to residues 31-55 of alpha gliadin). Therefore, this peptide appears as a highly sensitive antigen and more specific than gliadin. The best result, showing 100% of sensitivity and specificity, was obtained for IgA anti-tTG, thus pointing out the relevance of these antibodies as serological markers for celiac disease.

Alloantigen-driven T cell death mediated by Fas ligand and tumor necrosis factor-alpha is not essential for the induction of allograft acceptance

BACKGROUND

Fas ligand (FasL)-Fas and tumor necrosis factor alpha (TNFalpha)-tumor necrosis factor receptor (TNFR) interactions regulate immune responses and contribute to self-tolerance by mediating antigen-driven T cell apoptosis. It is not known whether FasL and TNFalpha, expressed by the recipient's lymphoid or nonlymphoid cells, are essential for the apoptosis of alloreactive T lymphocytes and the induction of allograft acceptance.

METHODS

We compared the survival of fully allogeneic vascularized cardiac allografts between wild-type (wt) and FasL-mutant (gld) recipient mice. In addition, we studied cardiac allograft survival in gld mice injected with TNFalpha-neutralizing antibody. Allograft acceptance (graft survival >100 days) was induced by treating the recipients with CTLA4Ig, a recombinant fusion protein that blocks B7-CD28 T cell costimulation. In vivo alloantigen-driven apoptosis of mature CD4+ and CD8+ T lymphocytes was analyzed in mice repeatedly stimulated with allogeneic splenocytes.

RESULTS

We found that CTLA4Ig induces 100% long-term acceptance of cardiac allografts in wt and gld mice. Similarly, CTLA4Ig induced 100% allograft acceptance in gld recipients injected with TNFalpha-neutralizing antibody. In vivo alloantigen-driven apoptosis of mature CD4+ and CD8+ T cells was significantly reduced in gld mice and in wt mice treated with anti-TNFalpha antibody. However, neutralizing TNFalpha activity in gld mice failed to abrogate alloantigen-driven T cell apoptosis.

CONCLUSIONS

These data indicate that: (1) FasL and TNFalpha expression are not obligatory for the induction of long-term allograft acceptance by CTLA4Ig and (2) FasL- and TNFalpha-independent death pathways contribute to alloantigen-driven T cell apoptosis.

Emery-Dreifuss muscular dystrophy

Emery-Dreifuss muscular dystrophy (EDMD) is the third most common X-linked muscular dystrophy. This disorder is characterized by childhood onset of early contractures, humeroperoneal muscle atrophy, and cardiac conduction abnormalities. Weakness is slowly progressive, but there is a broad spectrum of clinical severity. Patients and carriers are at risk of sudden death. Regular cardiac evaluation is mandatory to assess the risk of cardiac arrhythmias. Unique atrial pathology is seen at autopsy. The mutated gene in EDMD is localized to the long arm of the X chromosome. Mutations in the gene lead to abolished synthesis of the gene product, emerin. Emerin is localized to the nuclear membrane of skeletal, cardiac, and smooth muscle. The term Emery-Dreifuss syndrome describes patients who have the EDMD phenotype without X-linked inheritance. There is no treatment for the underlying disease, but early placement of pacemakers may be lifesaving.

Fever in liver transplant recipients in the intensive care unit

Whether febrile illnesses in the intensive care unit (ICU) have unique spectrum, etiologies, and outcome has not been determined in liver transplant recipients. We studied 78 consecutive febrile patients over a 4-yr period; 49% (38/78) were in the ICU and 51% (40/78) were in the non-ICU setting. Of febrile patients in the ICU, 87% (33/38) had infection and 13% had non-infectious etiology for fever. Seventy-nine percent (26/33) of the infections associated with fever in the ICU were bacterial, 9% (3/33) were viral, and 9% (3/33) were fungal in etiology. Pneumonia (30%), catheter-related bacteremia (15%), and biliary tree (9%) were the predominant sources of infections associated with fever in the ICU. Bacteremia was documented in 45% of the patients with fever in the ICU. Fifty-three percent (20/38) of the febrile episodes in the ICU occurred during the initial post-transplant stay, and 47% (18/ 38) during a subsequent readmission. Pneumonia accounted for 41% of all febrile infections during the first 7 d of ICU stay, but only 14% of those after 7 d. Febrile patients in the ICU had higher APACHE II scores (p = 0.001), higher APS scores (p = 0.0001), higher bilirubin (p = 0.001), lower cholesterol (p = 0.019), higher prothrombin time (p = 0.001), were more tachycardiac (p = 0.002), and were more likely to have abnormal blood pressure (p = 0.001) than those in the non-ICU setting. Twenty-three percent of all infections in the ICU were unaccompanied by fever and 9% were accompanied by hypothermia. Mortality at 14 d (24 versus 0%, p = 0.001) and at 30 d (34 versus 5%, p = 0.001) was significantly higher in febrile patients in the ICU, as compared to the patients in the non-ICU setting. These data have implications for diagnostic evaluation and management of critically ill febrile liver transplant recipients.

Efficacy and selectivity in flexible database docking

Flexible database docking with DOCK 4.0 has been evaluated for its ability to retrieve biologically active molecules from a database of approximately 1,000 compounds with known activities against thrombin and the progesterone receptor. The retrieval of known actives and chemically similar but inactive molecules was monitored as a function of conformational and orientational sampling. The largest enrichment of actives among the 10% highest ranking molecules is obtained when only five conformations are used to seed the next round of ligand reconstruction and limited sampling is applied to place the base fragment in the binding site. The performance of energy and chemical scoring, as implemented in DOCK 4.0, was found to depend on the protein used for docking. For the progesterone receptor, energy scoring yields the largest enrichments (64%) in terms of actives retrieved among the 10% top scoring molecules, while chemical scoring performs best for thrombin (94%). With the exception of the application of energy scoring to the progesterone receptor, both energy-based scoring schemes applied in this study do not discriminate well between true actives and chemically similar but inactive compounds. In conclusion, flexible docking is able to effectively prioritize high-throughput screening databases, using less conformational sampling than normally required for appropriate reconstruction of protein-ligand complexes. The more subtle discrimination between chemically similar classes of active and inactive compounds remains, however, problematic.

Feedback to nursing staff as an intervention to reduce catheter-associated urinary tract infections

Because of high incidence of catheter-related urinary tract infections (UTIs) in our Veterans Affairs medical center, we began providing nursing staff with unit-specific UTI rates. In our preintervention period, the first quarter of 1995, 38 infections occurred in 1186 catheter-patient-days or 32/1000 catheter-patient-days (95% CI, 22.9-43.7). Thereafter, nursing staff members were provided with a quarterly report with catheter-related UTI rates depicted graphically by unit. In the 18 months after this intervention, the mean UTI rate decreased to 17.4/1000 catheter-patient-days (95% CI, 14.6-20.6, P =.002). We estimated a cost savings of $403,000. We conclude that unit-specific feedback of nosocomial UTI rates to nursing staff is a highly effective method of reducing infection rates and reducing costs associated with nosocomial UTI.

The role of the common cytokine receptor gamma-chain in regulating IL-2-dependent, activation-induced CD8+ T cell death

IL-2-dependent, activation-induced T cell death (AICD) plays an important role in peripheral tolerance. Using CD8+ TCR-transgenic lymphocytes (2C), we investigated the mechanisms by which IL-2 prepares CD8+ T cells for AICD. We found that both Fas and TNFR death pathways mediate the AICD of 2C cells. Neutralizing IL-2, IL-2R alpha, or IL-2R beta inhibited AICD. In contrast, blocking the common cytokine receptor gamma-chain (gamma c) prevented Bcl-2 induction and augmented AICD. IL-2 up-regulated Fas ligand (FasL) and down-regulated gamma c expression on activated 2C cells in vitro and in vivo. Adult IL-2 gene-knockout mice displayed exaggerated gamma c expression on their CD8+, but not on their CD4+, T cells. IL-4, IL-7, and IL-15, which do not promote AICD, did not influence FasL or gamma c expression. These data provide evidence that IL-2 prepares CD8+ T lymphocytes for AICD by at least two mechanisms: 1) by up-regulating a pro-apoptotic molecule, FasL, and 2) by down-regulating a survival molecule, gamma c.

Superposition of three-dimensional chemical structures allowing for conformational flexibility by a hybrid method

The superposition of three-dimensional structures is the first task in the evaluation of the largest common three-dimensional substructure of a set of molecules. This is an important step in the identification of a pharmacophoric pattern for molecules that bind to the same receptor. The superposition method described here combines a genetic algorithm with a numerical optimization method. A major goal is to adequately address the conformational flexibility of ligand molecules. The genetic algorithm optimizes in a nondeterministic process the size and the geometric fit of the substructures. The geometric fit is further improved by changing torsional angles combining the genetic algorithm and the directed tweak method. This directed tweak method is based on a numerical quasi-Newton optimization method. Only one starting conformation per molecule is necessary. Molecules having several rotatable bonds and quite different initial conformations are modified to find large structural similarities. A set of angiotensin II antagonists is investigated to illustrate the performance of the method.

Orthotopic liver transplantation in high-risk patients: risk factors associated with mortality and infectious morbidity

BACKGROUND

One of the most controversial areas in patient selection and donor allocation is the high-risk patient. Risk factors for mortality and major infectious morbidity were prospectively analyzed in consecutive United States veterans undergoing liver transplantation under primary tacrolimus-based immunosuppression.

METHODS

Twenty-eight pre-liver transplant, operative, and posttransplant risk factors were examined univariately and multivariately in 140 consecutive liver transplants in 130 veterans (98% male; mean age, 47.3 years).

RESULTS

Eighty-two percent of the patients had postnecrotic cirrhosis due to viral hepatitis or ethanol (20% ethanol alone), and only 12% had cholestatic liver disease. Ninety-eight percent of the patients were hospitalized at the time of transplantation (66% United Network for Organ Sharing [UNOS] 2, 32% UNOS 1). Major bacterial infection, posttransplant dialysis, additional immunosuppression, readmission to intensive care unit (P=0.0001 for all), major fungal infection, posttransplant abdominal surgery, posttransplant intensive care unit stay length of stay (P<0.005 for all), donor age, pretransplant dialysis, and creatinine (P<0.05 for all) were significantly associated with mortality by univariate analysis. Underlying liver disease, cytomegalovirus infection and disease, portal vein thrombosis, UNOS status, Childs-Pugh score, patient age, pretransplant bilirubin, ischemia time, and operative blood loss were not significant predictors of mortality. Patients with hepatitis C (HCV) and recurrent HCV had a trend towards higher mortality (P=0.18). By multivariate analysis, donor age, any major infection, additional immunosuppression, posttransplant dialysis, and subsequent transplantation were significant independent predictors of mortality (P<0.05). Major infectious morbidity was associated with HCV recurrence (P=0.003), posttransplant dialysis (P=0.0001), pretransplant creatinine, donor age, median blood loss, intensive care unit length of stay, additional immunosuppression, and biopsy-proven rejection (P<0.05 for all). By multivariate analysis, intensive care unit length of stay and additional immunosuppression were significant independent predictors of infectious morbidity (P<0.03). HCV recurrence was of borderline significance (P=0.07).

CONCLUSIONS

Biologic and physiologic parameters appear to be more powerful predictors of mortality and morbidity after liver transplantation. Both donor and recipient variables need to be considered for early and late outcome analysis and risk assessment modeling.

[New developments in asthma therapy: how do individual leukotriene antagonists work?]

Today it is generally acknowledged that bronchial asthma is a chronic inflammatory airway disease which is marked by recurrent bronchial obstructions and hyperreactivity of the airways. The best anti-inflammatory characteristics are shown by corticosteroids. However these can have considerable side-effects in long-term, systemic use. The search for alternative forms of therapy has for some time concentrated on the development and testing of leukotriene antagonists. These can limit the effect of leukotrienes via receptor antagonism or synthesis inhibition. The leukotrienes B4, C4, and D4 count as important key mediators in bronchial asthma. They are released by numerous inflammatory cells, have a bronchoconstricting effect and chemotactic characteristics, promote vessel permeability and increase mucous secretion. In addition, they probably increase bronchial hyperreactivity. Among biosynthesis restrictors, the 5-lipoxygenase restrictors have shown an anti-inflammatory effect in both experimental asthma models and in clinical use. In mild to moderate asthma, lung function improved and the use of a concomitant beta-agonist medication was reduced. While the older leukotriene receptor antagonists were rather disappointing, the newer substances display a significantly improved effect, are generally well tolerated and can also be given orally. In experimental asthma models, receptor antagonists, after antigen provocation, led to a marked reduction in bronchoconstriction and a decrease in the number of inflammatory cells (lymphocytes and eosinophils) in bronchial alveolar fluid. In clinical studies, this new class of drugs showed a reduction in clinical symptoms and an improvement in lung function in mild to moderate asthma. In addition, a bronchodilatatory effect was shown. The option of oral administration and good tolerance should improve compliance. The potential and long-term efficacy in severe asthma remains unclear. Further studies are required to elucidate the scope of their role and define their place in the treatment of asthma.

Hepatitis C virus genotypes in liver transplant recipients: impact on posttransplant recurrence, infections, response to interferon-alpha therapy and outcome

BACKGROUND

End-stage liver disease due to hepatitis C virus (HCV) is the most common indication for liver transplantation in U.S. veterans. We investigated the influence of HCV genotypes on the incidence and timing of recurrent HCV hepatitis, survival, infectious morbidity, and response to interferon-alpha therapy in this unique patient population.

METHODS

HCV genotype was determined by direct sequencing of the NS5 region of HCV with type-specific primers.

RESULTS

Genotype 1a (66%, 32/47) was the predominant genotype. Type 1b was found in 25% (12/47) of patients and type 2b was found in 9% (4/47). Histopathologically recurrent HCV hepatitis developed in 53% (25/47) of the patients after transplantation. This group included 45% (14/31) of the patients with type 1a, 67% (8/12) of the patients with type 1b, and 25% (1/4) of the patients with type 2b (P>0.5). The time to recurrence and the severity of HCV recurrence as defined by aminotransferase levels or Knodell scores were not different among the three genotypes. There was a trend toward a higher incidence of major infections in patients with type 1b (75%) versus type 1a (48%) and type 2b (50%) (P=0.11). The response to interferon-a therapy did not differ significantly among the genotypes. Mortality at 5 years was 16% (5/31) in patients with genotype 1a, 42% (5/12) in patients with genotype 1b, and 50% (2/4) in patients with genotype 2b (P=0.06).

CONCLUSIONS

The incidence, time to recurrence, and response to interferon-alpha therapy did not differ between the various genotypes in our liver transplant recipients. However, there was a trend toward higher infectious morbidity and overall mortality in patients with genotype 1b after transplantation.

Isolation and characterization of the complete mouse emerin gene

Emery-Dreifuss muscular dystrophy (EMD) is an X-linked recessive disorder associated with muscle wasting, contractures, and cardiomyopathy. The responsible emerin gene has recently been identified and found to encode a serine-rich protein similar to lamina-associated protein 2 (LAP2), although the disease mechanism remains obscure. In order to pursue the pathophysiology of this disorder, we report here the isolation and characterization of the complete mouse emerin gene. The emerin cDNA was isolated from murine strain BALB/c, and the emerin gene was isolated from strain 129. The 2.9-kb mouse emerin gene was completely sequenced and found to be composed of 6 exons and encode a protein 73% identical to that of the human protein. Key similarities with LAP2 were found to be conserved, including critical LAP2 phosphorylation sites. Examination of the murine promoter revealed three previously unrecognized cAMP response elements (CRE) conserved between human and mouse. While Northern analysis shows emerin to be widely expressed in the mouse, as it is in humans, these promoter elements may indicate cAMP responsiveness. These data provide the necessary elements to further investigate EMD in a murine system.

The comparison of geometric and electronic properties of molecular surfaces by neural networks: application to the analysis of corticosteroid-binding globulin activity of steroids

It is shown how a self-organizing neural network such as the one introduced by Kohonen can be used to analyze features of molecular surfaces, such as shape and the molecular electrostatic potential. On the one hand, two-dimensional maps of molecular surface properties can be generated and used for the comparison of a set of molecules. On the other hand, the surface geometry of one molecule can be stored in a network and this network can be used as a template for the analysis of the shape of various other molecules. The application of these techniques to a series of steroids exhibiting a range of binding activities to the corticosteroid-binding globulin receptor allows one to pinpoint the essential features necessary for biological activity.

Pneumonia in a long-term care facility. A prospective study of outcome

BACKGROUND

Pneumonia is a major cause of morbidity and mortality among patients in long-term care facilities.

OBJECTIVES

To conduct a prospective study of 108 consecutive patients who acquired pneumonia in a Veterans Affairs facility from January through December 1993, and to identify (1) the short- and long-term outcome of pneumonia, (2) the determinants of outcome, and (3) the frequency of recurrent episodes.

METHODS

Patient characteristics, including scores from the Activities of Daily Living (ADL) Index of Katz et al and the Comorbidity Index of Charlson et al, were recorded End points were survival at 14 days and 12 and 24 months, recurrent episodes of pneumonia, and hospitalization for nonpneumonic illness.

RESULTS

Fourteen-day mortality was 19%; outcome was significantly related to the ADL score. There was no relationship between short-term outcome and age or the Comorbidity Index score. Mortalities at 12 and 24 months were 59% and 75%, respectively. Long-term survival also correlated with the ADL score. For the least debilitated patients (ie, those with an ADL score < or = 10), mortalities were 33% and 48% at 12 and 24 months, respectively; for those with ADL scores of 11 to 15, the corresponding mortalities were 60% and 75%; and for those with ADL scores of 16 or greater, the mortalities were 65% and 77% (P = .02). Within 12 months, 43% of the survivors had additional episodes, and 37% required transfer to an acute care facility for other diagnoses. Functional status did not change among the most dependent patients.

CONCLUSIONS

Functional status is the major determinant of survival following pneumonia. Pneumonia in a debilitated patient in a long-term care facility predicts recurrent pneumonia and death within 1 to 2 years.

Locating biologically active compounds in medium-sized heterogeneous datasets by topological autocorrelation vectors: dopamine and benzodiazepine agonists

Electronic properties located on the atoms of a molecule such as partial atomic charges as well as electronegativity and polarizability values are encoded by an autocorrelation vector accounting for the constitution of a molecule. This encoding procedure is able to distinguish between compounds being dopamine agonists and those being benzodiazepine receptor agonists even after projection into a two-dimensional self-organizing network. The two types of compounds can still be distinguished if they are buried in a dataset of 8323 compounds of a chemical supplier catalog comprising a wide structural variety. The maps obtained by this sequence of events, calculation of empirical physicochemical effects, encoding in a topological autocorrelation vector, and projection by a self-organizing neural network, can thus be used for searching for structural similarity, and, in particular, for finding new lead structures with biological activity.

The peptide-based thrombin inhibitor CRC 220 is a new substrate of the basolateral rat liver organic anion-transporting polypeptide

The peptidomimetic thrombin inhibitor CRC 220, 4-methoxy-2,3,6-trimethylphenylsulfonyl-L-aspartyl-D-4-amidinop henylalanyl- piperidide, is taken up into isolated rat hepatocytes through active, carrier-mediated transport. This uptake is inhibited by bile acids. Functional expression in Xenopus laevis oocytes was performed to identify the transport system responsible for the hepatocellular CRC 220 uptake. Injection of poly(A)+RNA in X. laevis oocytes resulted in a two- to three-times higher uptake of CRC 220, compared with uninjected or water-injected control oocytes. Taurocholate (200 mumol/L) inhibited this uptake completely. No uptake of the peptidomimetic thrombin inhibitor was observed, when X. laevis oocytes were injected with complementary RNA (cRNA) encoding either the cloned rat liver Na(+)-dependent taurocholate transporter Ntcp, the renal oligopeptide carrier rhaPT or the intestinal oligopeptide transporter PepT1. However, after injection of cRNA of the cloned rat liver Na(+)-independent organic anion transporting polypeptide oatp, a specific and saturable CRC 220 uptake was observed (Michaelis-Menten constant 29.5 mumol/L). Cis-inhibition with known oatp-substrates, e.g., 20 mumol/L Bromsulphalein (BSP), 2007 mumol/L taurocholate and 2007 mumol/L cholate, occurred in oatp-expressing X. laevis oocytes, whereas substrates of the two peptide carriers as well as dipeptide- and single-amino acid constituents of the thrombin inhibitor itself lacked any significant inhibitory effects. These data show that the modified dipeptide CRC 220 is a highly selective substrate of the organic anion transporting polypeptide oatp in the basolateral plasma membrane of rat hepatocytes.

Comparison of structurally different allosteric modulators of muscarinic receptors by self-organizing neural networks

Similarities in the molecular structure and surface properties of the allosteric modulators of muscarinic receptors, alcuronium, gallamine, tubocurarine, and the hexamethonium compound W84, a well-known pharmacological tool, are explored. The analysis of the molecular electrostatic potential (MEP) as well as of the shape of the molecular surface is performed by self-organizing neural networks. A distorted sandwich conformation of W84 is suggested to be the active form. The importance of the MEP for binding of these compounds could be established.

Determinants of compliance with antiretroviral therapy in patients with human immunodeficiency virus: prospective assessment with implications for enhancing compliance

Non-compliance with therapy is a significant problem, particularly when the disease process is chronic and therapeutic regimens are employed for prolonged periods. We assessed the prevalence and variables associated with compliance with antiretroviral therapy in patients with human immunodeficiency virus infection, by means of a longitudinal observational study of 46 patients aged 23 to 68 years, with human immunodeficiency virus infection, followed at the Pittsburgh VA Medical Center. Data on demographics, medical status, physical functioning (Karnofsky performance scores), CD4 lymphocyte count, depression (Beck depression inventory), coping (inventory of coping with illness scale scores), and psychological and emotional stress (profile of mood states scale scores), were prospectively assessed on all patients at baseline and every 6 months. Compliance was assessed at 6 and 12 months: patients taking > or = 80% of antiretroviral therapy were considered compliant. Overall, 63% of patients were compliant with antiretroviral therapy. Age, education, employment, religious support, and perceived quality of life did not correlate with compliance. By univariate analysis, lack of prior intravenous drug use was significantly associated with compliance (p = 0.01). Compliant patients had significantly better adaptive coping (p = 0.03), and less depression (p = 0.04). By multivariate analysis, black race was significantly associated with non-compliance independent of intravenous drug use and educational status. History of prior opportunistic infection (which presumably heightens the perceived severity of illness) (p = 0.02), and lesser psychological disturbance scores (p = 0.02) were associated with compliance. Compliance was observed despite the greater number of prescription medications taken by compliant patients (p = 0.04). At 12 months, Karnofsky scores were better in compliant patients (p = 0.02), although mortality was not different. Besides identifying predictors of compliance, our data suggest that symptoms of depression and psychological stress be sought in patients with non-adherence.

Pulmonary infections in liver transplant recipients receiving tacrolimus. Changing pattern of microbial etiologies

Pulmonary infections are a significant cause of morbidity after liver transplantation; Gram-negative bacilli, cytomegalovirus, and Pneumocystis carinii were the usual pulmonary pathogens in the earlier studies in liver transplant recipients receiving cyclosporine. We prospectively assessed the impact of pulmonary infection in 101 consecutive liver transplant recipients receiving the new immunosuppressive agent tacrolimus (FK506). Fifteen percent (15/101) of the patients had 19 episodes of pneumonia; 58% (11/19) of the pneumonias were bacterial, 37% (7/19) were fungal, and 5% (1/19) were protozoal (Toxoplasma gondii). Twenty-seven percent of the bacterial pneumonias were due to Legionella. None of the patients had cytomegalovirus or P carinii pneumonia. Seven percent (7/10) of the study patients had fungal pneumonitis; 4% had invasive aspergillosis and 3% had cryptococcosis. Mortality was significantly higher (53%, 8/15) for patients with pneumonia than for patients without pneumonia (10%, 9/86, P = 0.0004). Only fungal pneumonias were the direct cause of death; 63% (5/8) of the deaths were in patients with fungal pneumonitis. Our data suggest a changing pattern of microbial etiologies of pneumonitis in the era of modern immunosuppressive agents. We show that P carinii pneumonia and cytomegalovirus can be effectively curtailed with appropriate prophylaxis. Fungal infections, on the contrary, not only constituted a major proportion of the pneumonia, but also carried the highest pneumonia-associated mortality. Legionella infections can be overlooked unless specialized laboratory methodology (cultured on selective media, urinary antigen) are applied routinely on all cases of pneumonia. We recommend routine culture on the water supply for Legionella in all transplant centers.

A high incidence of native portal vein thrombosis in veterans undergoing liver transplantation

The incidence of native portal vein thrombosis (PVT) in liver transplant recipients has been reported to range from 2.1 to 13.8%. We have identified an inordinately high incidence of PVT in a consecutive series of U.S. veterans receiving liver transplants. Between October 1989 and February 1994, 88 consecutive U.S. veterans received 99 orthotopic liver transplants under primary Tacrolimus (Prograf, formerly FK506) based immunosuppression. A number of clinical features were examined in an effort to identify risk factors for PVT and outcome was compared to patients without PVT. Native PVT was present in 23/88 (26%) patients. All of these patients were male U.S. veterans with a mean age of 47 years. When compared to the 65 patients without PVT, we found no significant difference with respect to underlying liver disease, age, Childs-Pugh score (mean = 12), UNOS status as defined prior to April 1995 (95% UNOS 3 or 4), previous abdominal surgery, or liver volume. Median blood loss for patients with PVT (21 units of packed red blood cells) was greater than for those without PVT (14 units, P = 0.04). Portal thrombectomy was performed in 11 patients, 11 patients required mesoportal jump grafts, and 1 patient had an interposition graft. Standard veno-venous bypass was used in 10 patients with single bypass utilized for the remainder. Actuarial patient survival for all patients at 1, 2, and 4 years was 88, 85, and 79%, respectively. There was no significant difference in patients with or without PVT. Patients with PVT had poorer graft survival than patients without PVT (86% vs 65%, 1 year; 81% vs 65%, 2 years; 81% vs 61%, 4 years; P = 0.03); however, this was not related to technical problems with the portal venous inflow. PVT occurred in 26% of U.S. veterans undergoing liver transplantation. These patients had significantly higher operative blood loss and poorer graft survival. The high incidence of postnecrotic cirrhosis in a predominantly male group of patients with advanced disease, as is evident by the high mean Childs-Pugh score and UNOS status, perhaps accounts for our observations.

Determinants of nontraditional therapy use in patients with HIV infection. A prospective study

BACKGROUND

The popularity and use of nontraditional therapies among patients with human immunodeficiency virus (HIV) infection has grown enormously.

DESIGN

A prospective, longitudinal cohort study of 56 patients aged 23 through 68 years with HIV infection followed up at the HIV clinic at a university-affiliated Veterans Affairs Medical Center.

OBJECTIVE

To assess the demographic and psychologic characteristics of patients who seek nontraditional remedies, and their impact on disease progression and mortality from HIV.

METHODS

A standardized, self-administered questionnaire to assess the incidence and type of nontraditional therapies used by patients with HIV. Data on demographics, medical status, physical functioning (Karnofsky performance score), CD4 lymphocyte counts, depression (Beck Depression Inventory), coping (inventory of coping with illness scale), psychological and/or emotional stress (Profile of Mood States scores), and compliance with prescribed therapy were prospectively assessed on all patients at baseline and every 6 months.

RESULTS

Thirty percent of patients reported using nontraditional therapies. Nontraditional therapy users were significantly older than patients who did not use such therapies (44 vs 38 years, P = .03); with 94% of patients who used nontraditional therapy being older than 35 years compared with 56% of conventional therapy users (P = .005). Alternative therapy use did not correlate with race, education, HIV-risk group affiliation, duration of HIV seropositivity, stage of HIV disease, CD4 cell count, or Karnofsky performance scores. Nontraditional therapy users reported greater community-based acquired immunodeficiency syndrome group support (P = .06), greater perceived social support (P = .08), and significantly higher recreational or "street drugs" use (P = .02). Depression, adaptive coping, and emotional stress were not different between nontraditional and conventional therapy users; however, nontraditional therapy users were significantly more assertive (P = .04). On follow-up, CD4 cell count, HIV disease progression, physical functioning, or mortality were similar between the two groups.

CONCLUSIONS

Recourse to nontraditional therapy is common among patients with HIV. Because of the possibility of untoward effects and potential adverse drug interactions associated with nontraditional therapy, HIV care givers should be aware of its use in their patients and take a history of nontraditional therapy first. Patients who choose nontraditional remedies do so not because they are depressed or emotionally disturbed, but rather because they seek greater control of the outcome of their disease. However, no beneficial effect on disease progression, CD4 cell count, or mortality was observed in these patients when compared with patients receiving only conventional medical therapy.

Expression cloning and functional characterization of the kidney cortex high-affinity proton-coupled peptide transporter

The presence of a proton-coupled electrogenic high-affinity peptide transporter in the apical membrane of tubular cells has been demonstrated by microperfusion studies and by use of brush border membrane vesicles. The transporter mediates tubular uptake of filtered di- and tripeptides and aminocephalosporin antibiotics. We have used expression cloning in Xenopus laevis oocytes for identification and characterization of the renal high-affinity peptide transporter. Injection of poly(A)+ RNA isolated from rabbit kidney cortex into oocytes resulted in expression of a pH-dependent transport activity for the aminocephalosporin antibiotic cefadroxil. After size fractionation of poly(A)+ RNA the transport activity was identified in the 3.0- to 5.0-kb fractions, which were used for construction of a cDNA library. The library was screened for expression of cefadroxil transport after injection of complementary RNA synthesized in vitro from different pools of clones. A single clone (rPepT2) was isolated that stimulated cefadroxil uptake into oocytes approximately 70-fold at a pH of 6.0. Kinetic analysis of cefadroxil uptake expressed by the transporter's complementary RNA showed a single saturable high-affinity transport system shared by dipeptides, tripeptides, and selected amino-beta-lactam antibiotics. Electrophysiological studies established that the transport activity is electrogenic and affected by membrane potential. Sequencing of the cDNA predicts a protein of 729 amino acids with 12 membrane-spanning domains. Although there is a significant amino acid sequence identity (47%) to the recently cloned peptide transporters from rabbit and human small intestine, the renal transporter shows distinct structural and functional differences.

Variation of the oxime function of bispyridinium-type allosteric modulators of M2-cholinoceptors

The bisbenzylether of the bispyridinium oxime, DUO 3-O (4,4'-Bis-[(2,6-dichlorobenzyloxyimino)-methyl]-1,1'-propane-1,3- diyl-bispyridinium dibromide), has been found to stabilize the antagonist binding to the M2-cholinoceptors which is indicative of an allosteric action. The oxygen of the oxime group was replaced with a nitrogen and a CH2-group leading to DUO 3-N and 3-C, respectively. The allosteric potency of the compounds was characterized by the concentrations which retarded the rate of dissociation of [3H]N-methyl-scopolamine from porcine cardiac cholinoceptors by a factor of 2 (EC50). The hydrazone derivative DUO 3-N was found to be the most active compound (ED50 = 2.7 microM) exceeding in activity DUO 3-O by a factor of 1.6 and DUO 3-C by a factor of 5. No correlation was found between the lipophilicity, determined as octanol/water partition coefficient, and the allosteric potency. The distribution of charges in the molecules was calculated by means of PEOE and displayed as Kohonen maps: The calculations exhibit a shift of the positive charge in the pyridinium ring from the nitrogen to the carbon atom in para-position when going from DUO 3-C to 3-O and 3-N. This shift parallels the rank order of the allosteric potency. From these results the conclusion has been drawn that the between distance the terminal ring-system and the positive charge is pivotal for the interaction of the allosteric modulators with the receptor protein.