Cognitive flexibility training for chronic pain: a randomized clinical study

Introduction

Previous studies suggest an association between cognitive flexibility and development of chronic pain after surgery. It is not known whether cognitive flexibility can be improved in patients with chronic pain.

Objectives

This study tested whether a neurocognitive training program results in improved cognitive flexibility and pain in patients with chronic pain.

Methods

We conducted a single-center, prospective, randomized study investigating 5-week daily neurocognitive training in patients with chronic pain. Participants (n = 145) were randomized into neurocognitive training or care as usual, and they completed assessments at baseline, posttreatment, and 3 months. The treatment group was asked to spend 35 minutes daily completing a program with tasks on cognitive flexibility, memory, attention, and speed. The primary outcome was performance on the neurocognitive performance test (NCPT). Secondary outcomes included levels of pain interference and severity.

Results

At 5 weeks, the treatment group showed greater improvements on NCPT compared with the control group (d = 0.37); effect size was smaller at 3 months (d = 0.18). The treatment group reported lower pain severity at 5 weeks (d = 0.16) and 3 months (d = 0.39) than the control group, but pain interference was only lower at 3 months (d = 0.20).

Conclusions

Outcomes suggest that using neurocognitive training to modify cognitive flexibility in patients with chronic pain may improve pain severity. This study provided effect size estimates to inform sample size calculations for randomized controlled trials to test the effectiveness of neurocognitive interventions for the prevention and treatment of chronic pain.

OXIDATIVE study: A pilot prospective observational cohort study protocol examining the influence of peri-reperfusion hyperoxemia and immune dysregulation on early allograft dysfunction after orthotopic liver transplantation

Early allograft dysfunction (EAD) is a functional hepatic insufficiency within a week of orthotopic liver transplantation (OLT) and is associated with morbidity and mortality. The etiology of EAD is multifactorial and largely driven by ischemia reperfusion injury (IRI), a phenomenon characterized by oxygen scarcity followed by paradoxical oxidative stress and inflammation. With the expanded use of marginal allografts more susceptible to IRI, the incidence of EAD may be increasing. This necessitates an in-depth understanding of the innate molecular mechanisms underlying EAD and interventions to mitigate its impact. Our central hypothesis is peri-reperfusion hyperoxemia and immune dysregulation exacerbate IRI and increase the risk of EAD. We will perform a pilot prospective single-center observational cohort study of 40 patients. The aims are to determine (1) the association between peri-reperfusion hyperoxemia and EAD and (2) whether peri-reperfusion perturbed cytokine, protein, and hypoxia inducible factor-1 alpha (HIF-1α) levels correlate with EAD after OLT. Inclusion criteria include age ≥ 18 years, liver failure, and donation after brain or circulatory death. Exclusion criteria include living donor donation, repeat OLT within a week of transplantation, multiple organ transplantation, and pregnancy. Partial pressure of arterial oxygen (PaO2) as the study measure allows for the examination of oxygen exposure within the confines of existing variability in anesthesiologist-administered fraction of inspired oxygen (FiO2) and the inclusion of patients with intrapulmonary shunting. The Olthoff et al. definition of EAD is the primary outcome. Secondary outcomes include postoperative acute kidney injury, pulmonary and biliary complications, surgical wound dehiscence and infection, and mortality. The goal of this study protocol is to identify EAD contributors that could be targeted to attenuate its impact and improve OLT outcomes. If validated, peri-reperfusion hyperoxemia and immune perturbations could be targeted via FiO2 titration to a goal PaO2 and/or administration of an immunomodulatory agent by the anesthesiologist intraoperatively.

Intraoperative Anesthetic Strategies to Mitigate Early Allograft Dysfunction After Orthotopic Liver Transplantation: A Narrative Review

Orthotopic liver transplantation (OLT) is the most effective treatment for patients with end-stage liver disease (ESLD). Hepatic insufficiency within a week of OLT, termed early allograft dysfunction (EAD), occurs in 20% to 25% of deceased donor OLT recipients and is associated with morbidity and mortality. Primary nonfunction (PNF), the most severe form of EAD, leads to death or retransplantation within 7 days. The etiology of EAD is multifactorial, including donor, recipient, and surgery-related factors, and largely driven by ischemia-reperfusion injury (IRI). IRI is an immunologic phenomenon characterized by dysregulation of cellular oxygen homeostasis and innate immune defenses in the allograft after temporary cessation (ischemia) and later restoration (reperfusion) of oxygen-rich blood flow. The rising global demand for OLT may lead to the use of marginal allografts, which are more susceptible to IRI, and thus lead to an increased incidence of EAD. It is thus imperative the anesthesiologist is knowledgeable about EAD, namely its pathophysiology and intraoperative strategies to mitigate its impact. Intraoperative strategies can be classified by 3 phases, specifically donor allograft procurement, storage, and recipient reperfusion. During procurement, the anesthesiologist can use pharmacologic preconditioning with volatile anesthetics, consider preharvest hyperoxemia, and attenuate the use of norepinephrine as able. The anesthesiologist can advocate for normothermic regional perfusion (NRP) and machine perfusion during allograft storage at their institution. During recipient reperfusion, the anesthesiologist can optimize oxygen exposure, consider adjunct anesthetics with antioxidant-like properties, and administer supplemental magnesium. Unfortunately, there is either mixed, little, or no data to support the routine use of many free radical scavengers. Given the sparse, limited, or at times conflicting evidence supporting some of these strategies, there are ample opportunities for more research to find intraoperative anesthetic strategies to mitigate the impact of EAD and improve postoperative outcomes in OLT recipients.

Establishing the Reliability, Validity, and Prognostic Utility of the Momentary Pain Catastrophizing Scale for Use in Ecological Momentary Assessment Research

Despite the marked increase in ecological momentary assessment research, few reliable and valid measures of momentary experiences have been established. The goal of this preregistered study was to establish the reliability, validity, and prognostic utility of the momentary Pain Catastrophizing Scale (mPCS), a 3-item measure developed to assess situational pain catastrophizing. Participants in 2 studies of postsurgical pain outcomes completed the mPCS 3 to 5 times per day prior to surgery (N = 494, T = 20,271 total assessments). The mPCS showed good psychometric properties, including multilevel reliability and factor invariance across time. Participant-level average mPCS was strongly positively correlated with dispositional pain catastrophizing as assessed by the Pain Catastrophizing Scale (r = .55 and .69 in study 1 and study 2, respectively). To establish prognostic utility, we then examined whether the mPCS improved prediction of postsurgical pain outcomes above and beyond one-time assessment of dispositional pain catastrophizing. Indeed, greater variability in momentary pain catastrophizing prior to surgery was uniquely associated with increased pain immediately after surgery (b = .58, P = .005), after controlling for preoperative pain levels and dispositional pain catastrophizing. Greater average mPCS score prior to surgery was also uniquely associated with lesser day-to-day improvement in postsurgical pain (b = .01, P = .003), whereas dispositional pain catastrophizing was not (b = -.007, P = .099). These results show that the mPCS is a reliable and valid tool for ecological momentary assessment research and highlight its potential utility over and above retrospective measures of pain catastrophizing. PERSPECTIVE: This article presents the psychometric properties and prognostic utility of a new measure to assess momentary pain catastrophizing. This brief, 3-item measure will allow researchers and clinicians to assess fluctuations in pain catastrophizing during individuals' daily lives, as well as dynamic relationships between catastrophizing, pain, and related factors.

Use of Intramuscular Ephedrine Sulfate During Kidney Transplantation

Hypotension during kidney transplantation can be common. Vasopressor use during these procedures is often avoided, with a fear of decreasing renal perfusion in the transplanted kidney. However, adequate perfusion for the rest of the body is also necessary, and given that these patients often have underlying hypertension or other comorbid conditions, an appropriate mean arterial pressure (MAP) has to be maintained. Intramuscular injections of ephedrine have been studied in the anesthesiology literature in a variety of case types, and it is seen as a safe and effective method to boost MAP. We present a case series of three patients who underwent renal transplantation and who received an intramuscular injection of ephedrine for hypotension control. The medication worked well for increasing blood pressures without apparent side effects. All three patients were followed for more than one year, and all patients had good graft function at the end of that time period. This series shows that while further research is necessary in this arena, intramuscular ephedrine may have a place in the management of persistent hypotension in the operating room during kidney transplantation.

Ascertaining Design and Implementation Requirements for a Perioperative Neurocognitive Training Intervention for the Prevention of Persistent Pain After Surgery

BACKGROUND

Persistent postsurgical pain (PPSP) is a common complication that impacts quality of life, often necessitating long-term opioid treatment. Certain neurocognitive factors, including reduced performance on cognitive flexibility tasks, are associated with increased risk of PPSP. We examine the perceptions of surgical patients and clinicians with regard to perioperative pain management activities and needs; patient acceptance and use of a perioperative neurocognitive training intervention; and implementation feasibility.

METHODS

We conducted both individual and focus group interviews with patients undergoing thoracic surgery and clinicians in an academic medical center. The Consolidated Framework for Intervention Research guided the development of interview questions related to the adoption and implementation of a neurocognitive intervention to mitigate PPSP. A thematic analysis was used to analyze the responses.

RESULTS

Forty patients and 15 clinicians participated. Interviews revealed that there is minimal discussion between clinicians and patients about PPSP. Most participants were receptive to a neurocognitive intervention to prevent PPSP, if evidence demonstrating its effectiveness were available. Potential barriers to neurocognitive training program adoption included fatigue, cognitive overload, lack of familiarity with the technology used for delivering the intervention, and immediate postoperative pain and stress. Implementation facilitators would include patient education about the intervention, incentives for its use, and daily reminders.

CONCLUSION

The study identified several guiding principles for addressing patients' and clinicians' barriers to effectively implementing a neurocognitive training intervention to mitigate PPSP after surgery. To ensure the sustainability of neurocognitive interventions for preventing PPSP, such interventions would need to be adapted to meet patients' and clinicians' needs within the perioperative context.

Abstract 1240: RRM2 and mutant p53 as therapeutic targets in TNBC

Triple negative breast cancer (TNBC) is a highly aggressive type of cancer associated with poor prognosis and characterized by the absence of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor type 2 (HER2). TNBC accounts for 10 - 15% of all new cases of breast cancer. TNBC is heterogenous in nature (70% basal-like) and currently doesn't have effective targeted therapy. As such, dose-dense chemotherapeutic agents used in combination, such as doxorubicin (DOXO) with cyclophosphamide, is the regimen of choice for TNBC. However, DOXO has limited efficacy as a therapeutic agent owing to acquired drug resistance and its cardiotoxic effects. Ribonucleotide reductase (RR) is the rate limiting enzyme required for the conversion of ribonucleotide to deoxyribonucleotide in DNA synthesis during cell proliferation. Didox (3,4 dihydroxybenzohydroxamic acid) is a unique RR inhibitor with iron chelating and free radical scavenging properties. We have previously identified that ribonucleotide reductase M2 (RRM2) is upregulated in TNBC cells and is a key contributor to acquired drug resistance. We found that Didox not only inhibits RRM2, but it also reduces mutant p53 protein levels and inhibits the activation of the NF-κB pathway. Through this inhibition, we found that Didox works synergistically with DOXO to inhibit TNBC tumor growth while also minimizing DOXO-induced cardiac damage in mice. In our present study, we have observed that RRM2 expression is upregulated in TNBC patients from three independent data sets and that high RRM2 levels are associated with lower recurrence free survival (RFS) and overall survival (OS). Interestingly, high levels of RRM2 were only predictive of lower RFS and OS in patients with wild-type p53 but not mutant p53. Additionally, we have found that Didox downregulates mutant p53 protein levels in TNBC cell lines but does not alter total p53 in cells with functioning p53. Our data confirms that Didox induced downregulation of mutant p53 is not a transcriptional effect. Finally, we have identified that RRM2 protein levels increase in TNBC with progression of stage as measured in patient tissue microarray analysis. Our data presents a novel and promising approach for the treatment of TNBC that involves inhibition of RRM2, NF-kB activation, and mutant p53 that merits further clinical investigation in human models.

Citation Format: Nahid Sultana, Elizabeth A. Wilson, Howard L. Elford, Jesika S. Faridi. RRM2 and mutant p53 as therapeutic targets in TNBC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1240.

Molecular Targeting of RRM2, NF-κB, and Mutant TP53 for the Treatment of Triple-Negative Breast Cancer

Doxorubicin and other anthracycline derivatives are frequently used as part of the adjuvant chemotherapy regimen for triple-negative breast cancer (TNBC). Although effective, doxorubicin is known for its off-target and toxic side effect profile, particularly with respect to the myocardium, often resulting in left ventricular (LV) dysfunction and congestive heart failure when used at cumulative doses exceeding 400 mg/m² Previously, we have observed that the ribonucleotide reductase subunit M2 (RRM2) is significantly overexpressed in estrogen receptor (ER)-negative cells as compared with ER-positive breast cancer cells. Here, we inhibited RRM2 in ER-negative breast cancer cells as a target for therapy in this difficult-to-treat population. We observed that through the use of didox, a ribonucleotide reductase inhibitor, the reduction in RRM2 was accompanied by reduced NF-κB activity in vitro When didox was used in combination with doxorubicin, we observed significant downregulation of NF-κB proteins accompanied by reduced TNBC cell proliferation. As well, we observed that protein levels of mutant p53 were significantly reduced by didox or combination therapy in vitro Xenograft studies showed that combination therapy was found to be synergistic in vivo, resulting in a significantly reduced tumor volume as compared with doxorubicin monotherapy. In addition, the use of didox was also found to ameliorate the toxic myocardial effects of doxorubicin in vivo as measured by heart mass, LV diameter, and serum troponin T levels. The data present a novel and promising approach for the treatment of TNBC that merits further clinical evaluation in humans.

Abstract 5212: The benefits of Didox in triple negative breast cancer treatment targeting mutant p53

Triple-negative breast cancer (TNBC) is an aggressive histological subtype of malignancy with limited treatment options. Frequently, doxorubicin (DOXO)- based chemotherapy is utilized in this patient population due to the lack of molecular targets available. While DOXO is an effective chemotherapeutic agent, its efficacy is limited due to acquired drug resistance and cardiotoxicity. Therefore the identification of other treatment options for TNBC is needed. TNBC is a heterogeneous malignancy, with 70% of cases classified as a basal subtype, which further complicates the search for an effective molecular target. However, it has been identified that 80% of TNBC samples carry TP53 (tumor protein p53) mutations, which leads to a mutant p53 protein no longer able to act as a tumor suppressor and thus failing to halt cell growth. Mutant p53, when present in malignant cells, is far less susceptible to degradation than its wild-type counterpart, and thus accumulates within the cell. As such, the TP53 is an attractive therapeutic target for TNBC. We have previously identified that ribonucleotide reductase M2 (RRM2) is upregulated in TNBC cells and is a key contributor to acquired drug resistance. The ribonucleotide reductase inhibitor Didox has been shown to be a powerful free radical scavenger and iron chelator. Through these mechanisms, Didox alleviates the non-selective cytotoxic effects of DOXO on non-cancerous tissue, including cardiotoxicity and potentiates DOXO's efficacy against malignant cells. We have previously reported that Didox in combination with DOXO effectively treats TNBC by enhancing tumor inhibition and minimizing DOXO-induced heart damage. Our current study shows that Didox alone or in combination with DOXO downregulates mutant p53 protein levels in the mutant p53 TNBC cell lines MDA-MB 468, MDA-MB 231 and BT-20. This effect is notably absent in breast cancer cell lines with wild-type p53, including MCF7, A3B5 and ZR751, where p53 successfully acts as a tumor suppressor allowing for cell cycle arrest or apoptosis after DNA damage. We hypothesize that mutant p53 is a valid therapeutic target in TNBC. As shown here, the addition of Didox downregulates mutant p53 levels and thus enhances tumor inhibition while alleviating DOXO-associated cardiotoxicity.

Citation Format: Nahid Sultana, Elizabeth A. Wilson, Khyati N. Shah, Howard L. Elford, Jesika S. Faridi. The benefits of Didox in triple negative breast cancer treatment targeting mutant p53 [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5212.

Plasma and Urinary FGF-2 and VEGF-A Levels Identify Children at Risk for Severe Bleeding after Pediatric Cardiopulmonary Bypass: A Pilot Study

Severe bleeding after cardiothoracic surgery with cardiopulmonary bypass (CPB) is associated with increased morbidity and mortality in adults and children. Fibroblast Growth Factor-2 (FGF-2) and Vascular Endothelial Growth Factor-A (VEGF-A) induce hemorrhage in murine models with heparin exposure. We aim to determine if plasma and urine levels of FGF-2 and VEGF-A in the immediate perioperative period can identify children with severe bleeding after CPB. We performed a prospective, observational biomarker study in 64 children undergoing CPB for congenital heart disease repair from June 2015 - January 2017 in a tertiary pediatric referral center. Primary outcome was severe bleeding defined as ≥ 20% estimated blood volume loss within 24-hours. Independent variables included perioperative plasma and urinary FGF-2 and VEGF-A levels. Analyses included comparative (Wilcoxon rank sum, Fisher's exact, and Student's t tests) and discriminative (receiver operator characteristic [ROC] curve) analyses. Forty-eight (75%) children developed severe bleeding. Median plasma and urinary FGF-2 and VEGF-A levels were elevated in children with severe bleeding compared to without bleeding (preoperative: plasma FGF-2 = 16[10-35] vs. 9[2-13] pg/ml; urine FGF-2= 28[15-76] vs. 14.5[1.5-22] pg/mg; postoperative: plasma VEGF-A = 146[34-379] vs. 53 [0-134] pg/ml; urine VEGF-A = 132 [52-257] vs. 45[0.1-144] pg/mg; all p < 0.05). ROC curve analyses of combined plasma and urinary FGF-2 and VEGF-A levels discriminated severe postoperative bleeding (AUC: 0.73-0.77) with mean sensitivity and specificity above 80%. We conclude that the perioperative plasma and urinary levels of FGF-2 and VEGF-A discriminate risk of severe bleeding after pediatric CPB.

A11 Evaluation of phylogenetic inference methods to determine direction of HIV transmission

It has been postulated that the direction of HIV transmission between two individuals can be determined by phylogenetic analysis of HIV sequences. This approach may be problematic, since HIV sequences from newly infected individuals are often more similar to index sequences from samples collected years before transmission, compared to those from samples collected at the time of transmission. We evaluated the accuracy of phylogenetic methods for determining the direction of HIV transmission by analyzing next-generation sequencing (NGS) data from index–partner pairs enrolled in the HIV Prevention Trials Network (HPTN) 052 trial. HIV-infected index and HIV-uninfected partner participants were enrolled as serodiscordant couples; samples were analyzed from couples with index-to-partner HIV transmission that was confirmed by genetic linkage studies. NGS for HIV gp41 (HXB2 coordinates: 7691–8374) was performed using plasma samples from thirty-nine index–partner pairs (seventy-eight samples collected within 3 months of partner seroconversion). Maximum likelihood trees were generated using the entire dataset using FastTree v.2. Topological patterns of HIV from each index–partner pair were analyzed. The analysis included 9,368 consensus sequences and 521,145 total sequence reads for the seventy-eight samples analyzed. In 10 per cent (four out of thirty-nine) of couples, the phylogeny was inconsistent with the known direction of transmission. In 26 per cent (ten out of thirty-nine) of couples, the phylogeny results could not discern directionality. In 64 per cent (twenty-five out of thirty-nine) of couples, the results correctly indicated index-to-partner transmission; in two of these twenty-five cases, only one index sequence was closest to the most recent common ancestor. Phylogenetic analysis of NGS data obtained from samples collected within 3 months of transmission correctly determined the direction of transmission in 64 per cent of the cases analyzed. In 36 per cent of the cases, the phylogenetic topology did not support the known direction of infection, and in one-third of these cases the observed topology was opposite to the known direction of transmission. This demonstrates that phylogenetic topology alone may not be sufficient to accurately determine the direction of HIV transmission.

Hydrophilic Small Molecules That Harness Transthyretin To Enhance the Safety and Efficacy of Targeted Chemotherapeutic Agents

The hydrophobicity of many chemotherapeutic agents usually results in their nonselective passive distribution into healthy cells and organs causing collateral toxicity. Ligand-targeted drugs (LTDs) are a promising class of targeted anticancer agents. The hydrophilicity of the targeting ligands in LTDs limits its nonselective passive tissue distribution and toxicity to healthy cells. In addition, the small size of LTDs allows for better tumor penetration, especially in the case of solid tumors. However, the short circulation half-life of LTDs, due to their hydrophilicity and small size, remains a significant challenge for achieving their full therapeutic potential. Therefore, extending the circulation half-life of targeted chemotherapeutic agents while maintaining their hydrophilicity and small size will represent a significant advance toward effective and safe cancer treatment. Here, we present a new approach for enhancing the safety and efficacy of targeted chemotherapeutic agents. By endowing hydrophobic chemotherapeutic agents with a targeting moiety and a hydrophilic small molecule that binds reversibly to the serum protein transthyretin, we generated small hydrophilic drug conjugates that displayed enhanced circulation half-life in rodents and selectivity to cancer cells. To the best of our knowledge, this is the first demonstration of a successful approach that maintains the small size and hydrophilicity of targeted anticancer agents containing hydrophobic payloads while at the same time extending their circulation half-life. This was demonstrated by the superior in vivo efficacy and lower toxicity of our conjugates in xenograft mouse models of metastatic prostate cancer.

Clarifying dairy calf mortality phenotypes through postmortem analysis

Health problems can be thought of as phenotypic expressions of the complex relationships between genes, environments, and phenomes as a whole. Detailed evaluations of phenotypic expressions of illness are required to characterize important biological outcomes. We hypothesized that classifying dairy calf mortality phenotypes via a systematic postmortem analysis would identify different cause-of-death diagnoses than those derived from treatments alone. This cross-sectional study was carried out on a dairy calf ranch in the northwestern United States from June to September 2017 and focused on calves ≤90 d of age. Comparisons were made between causes of death based on 3 levels of information: on-farm treatment records alone, necropsy-based postmortem analyses in addition to treatment records, and Washington Animal Disease Diagnostic Laboratory (WADDL) results in addition to all other information. A total of 210 dairy calves were necropsied during this study, of which 122 cases were submitted to WADDL. Necropsy- and WADDL-derived mortality phenotypes were in almost perfect agreement (Cohen's κ = 0.86) when broadly categorized as diarrhea, respiratory, diarrhea and respiratory combined, or other causes. The level of agreement between on-farm treatment records and postmortem-derived results was low and varied by the level of diagnostic detail provided. There was just fair agreement (κ = 0.22) between treatment-based and necropsy-based phenotypes without WADDL input and only slight agreement (κ = 0.13) between treatment-based and corresponding necropsy-based phenotypes with WADDL input. Even for those cases in which causes of death aligned along a comparable pathologic spectrum, the lack of detail inherent to standard treatment-based causes of death failed to identify meaningful target areas for intervention. This was especially apparent for numerous cases of necrotizing enteritis and typhlitis (cecal inflammation) that were variously categorized as diarrhea and pneumonia by treatment-based diagnoses. The specificity of these lesions stood in stark contrast to the otherwise generic cause of death diagnoses derived from treatments. The findings from this study supported the hypothesis and highlighted the value of on-farm necropsies and laboratory-based diagnostics to (1) detect antemortem disease misclassifications, (2) provide detail regarding disease processes and mortality phenotypes, and (3) direct disease mitigation strategies.

CDC14A phosphatase is essential for hearing and male fertility in mouse and human

The Cell Division-Cycle-14 gene encodes a dual-specificity phosphatase necessary in yeast for exit from mitosis. Numerous disparate roles of vertebrate Cell Division-Cycle-14 (CDC14A) have been proposed largely based on studies of cultured cancer cells in vitro. The in vivo functions of vertebrate CDC14A are largely unknown. We generated and analyzed mutations of zebrafish and mouse CDC14A, developed a computational structural model of human CDC14A protein and report four novel truncating and three missense alleles of CDC14A in human families segregating progressive, moderate-to-profound deafness. In five of these families segregating pathogenic variants of CDC14A, deaf males are infertile, while deaf females are fertile. Several recessive mutations of mouse Cdc14a, including a CRISPR/Cas9-edited phosphatase-dead p.C278S substitution, result in substantial perinatal lethality, but survivors recapitulate the human phenotype of deafness and male infertility. CDC14A protein localizes to inner ear hair cell kinocilia, basal bodies and sound-transducing stereocilia. Auditory hair cells of postnatal Cdc14a mutants develop normally, but subsequently degenerate causing deafness. Kinocilia of germ-line mutants of mouse and zebrafish have normal lengths, which does not recapitulate the published cdc14aa knockdown morphant phenotype of short kinocilia. In mutant male mice, degeneration of seminiferous tubules and spermiation defects result in low sperm count, and abnormal sperm motility and morphology. These findings for the first time define a new monogenic syndrome of deafness and male infertility revealing an absolute requirement in vivo of vertebrate CDC14A phosphatase activity for hearing and male fertility.

Preliminary in vitro and in vivo investigation of a potent platelet derived growth factor receptor (PDGFR) family kinase inhibitor

Aberrant expression of wild-type and mutant forms of the platelet-derived growth factor receptor (PDGFR) family of receptor tyrosine kinases has been implicated in various oncologic indications such as leukemias, gliomas, and soft tissue sarcomas. Clinically used kinase inhibitors imatinib and sunitinib are potent inhibitors of wild-type PDGFR family members, but show reduced binding to mutant forms. Here we describe compound 5 which binds to both wild-type and oncogenic mutant forms of PDGFR family members, and demonstrates both cellular and in vivo activity.

Harnessing molecular motors for nanoscale pulldown in live cells

Nanoscale pulldown (NanoSPD) miniaturizes the concept of affinity pulldown to detect protein–protein interactions in live cells. NanoSPD hijacks the myosin-based intracellular trafficking machinery to assess interactions under physiological buffer conditions and is microscopy-based, allowing for sensitive detection and quantification.

Protein–protein interactions (PPIs) regulate assembly of macromolecular complexes, yet remain challenging to study within the native cytoplasm where they normally exert their biological effect. Here we miniaturize the concept of affinity pulldown, a gold-standard in vitro PPI interrogation technique, to perform nanoscale pulldowns (NanoSPDs) within living cells. NanoSPD hijacks the normal process of intracellular trafficking by myosin motors to forcibly pull fluorescently tagged protein complexes along filopodial actin filaments. Using dual-color total internal reflection fluorescence microscopy, we demonstrate complex formation by showing that bait and prey molecules are simultaneously trafficked and actively concentrated into a nanoscopic volume at the tips of filopodia. The resulting molecular traffic jams at filopodial tips amplify fluorescence intensities and allow PPIs to be interrogated using standard epifluorescence microscopy. A rigorous quantification framework and software tool are provided to statistically evaluate NanoSPD data sets. We demonstrate the capabilities of NanoSPD for a range of nuclear and cytoplasmic PPIs implicated in human deafness, in addition to dissecting these interactions using domain mapping and mutagenesis experiments. The NanoSPD methodology is extensible for use with other fluorescent molecules, in addition to proteins, and the platform can be easily scaled for high-throughput applications.

`Loving the Computer'

Cognitive psychology has been founded on a model of the mind as an information-processing machine. This paper is not concerned with the arguments for or against modelling the mind on computers, as these arguments are already well rehearsed in the literature. Instead I am interested in what the relation between computer, cognition and the thinking man promises or guarantees. Specifically, I am concerned with how cognition comes to be constituted through certain dominant fantasies of embodiment that the computer metaphor promotes. To what extent does psychology's computational machinery prescribe a disembodied cognition? And in what ways is such a prescription of cognition indebted to the logic of a masculine morphology? The paper draws on Turing's classic essay `Computing Machinery and Intelligence', Atkinson and Shiffrin's early model of human memory, Irigaray's formulation of sexed morphology and Tausk's analysis of the influencing machine in paranoid delusions to argue that at the heart of cognitive theories we find the body of the thinking man.

Targeting Ribonucleotide Reductase M2 and NF-κB Activation with Didox to Circumvent Tamoxifen Resistance in Breast Cancer

Tamoxifen is widely used as an adjuvant therapy for patients with estrogen receptor (ERα)-positive tumors. However, the clinical benefit is often limited because of the emergence of drug resistance. In this study, overexpression of ribonucleotide reductase M2 (RRM2) in MCF-7 breast cancer cells resulted in a reduction in the effectiveness of tamoxifen, through downregulation of ERα66 and upregulation of the 36-kDa variant of ER (ERα36). We identified that NF-κB, HIF1α, and MAPK/JNK are the major pathways that are affected by RRM2 overexpression and result in increased NF-κB activity and increased protein levels of EGFR, HER2, IKKs, Bcl-2, RelB, and p50. RRM2-overexpressing cells also exhibited higher migratory and invasive properties. Through time-lapse microscopy and protein profiling studies of tamoxifen-treated MCF-7 and T-47D cells, we have identified that RRM2, along with other key proteins, is altered during the emergence of acquired tamoxifen resistance. Inhibition of RRM2 using siRRM2 or the ribonucleotide reductase (RR) inhibitor didox not only eradicated and effectively prevented the emergence of tamoxifen-resistant populations but also led to the reversal of many of the proteins altered during the process of acquired tamoxifen resistance. Because didox also appears to be a potent inhibitor of NF-κB activation, combining didox with tamoxifen treatment cooperatively reverses ER-α alterations and inhibits NF-κB activation. Finally, inhibition of RRM2 by didox reversed tamoxifen-resistant in vivo tumor growth and decreased in vitro migratory and invasive properties, revealing a beneficial effect of combination therapy that includes RRM2 inhibition to delay or abrogate tamoxifen resistance.

Detection of Multiple Respiratory Viruses Associated With Mortality and Severity of Illness in Children

OBJECTIVE

Respiratory viral infection is a common source of morbidity and mortality in children. Coinfection with multiple viruses occurs frequently; however, the clinical significance of concomitant viral pathogens is unclear. We hypothesized that presence of more than one respiratory virus is associated with increased morbidity and mortality when compared with children with a single respiratory virus.

DESIGN

Retrospective cohort study.

SETTING

A tertiary care hospital.

PATIENTS

All children at Duke Children's Hospital over a 2-year period with isolation of a virus on an extended viral respiratory panel result. Demographic data, comorbidities, and details of hospital encounter were recorded.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Two hundred thirty-five hospital encounters demonstrated positive extended viral respiratory panels. Immunocompromised status (37%) and respiratory comorbidities (23%) were common. Twenty-eight patients (12%) tested positive for multiple viruses, with adenovirus (23/28) and respiratory syncytial virus (15/28) most prevalent in patients with multiple viruses. Viral codetection was associated with increased use of noninvasive ventilation (p = 0.02), extracorporeal membrane oxygenation (p = 0.02), increased likelihood of moderate or severe illness (p = 0.005), and increased mortality (p = 0.01). Subgroup analysis demonstrated that this mortality association persisted for children with normal immune function (p = 0.003) and children with no comorbidities (p = 0.007).

CONCLUSIONS

Children with multiple respiratory viruses may be at increased risk of moderate or severe illness and mortality, with previously healthy children potentially being at greatest risk. Further studies are indicated to determine the significance and generalizability of this finding and to better understand the pathophysiology of viral coinfection.

Poor Positive Predictive Value of Lyme Disease Serologic Testing in an Area of Low Disease Incidence

BACKGROUND

Lyme disease is diagnosed by 2-tiered serologic testing in patients with a compatible clinical illness, but the significance of positive test results in low-prevalence regions has not been investigated.

METHODS

We reviewed the medical records of patients who tested positive for Lyme disease with standardized 2-tiered serologic testing between 2005 and 2010 at a single hospital system in a region with little endemic Lyme disease. Based on clinical findings, we calculated the positive predictive value of Lyme disease serology. Next, we reviewed the outcome of serologic testing in patients with select clinical syndromes compatible with disseminated Lyme disease (arthritis, cranial neuropathy, or meningitis).

RESULTS

During the 6-year study period 4723 patients were tested for Lyme disease, but only 76 (1.6%) had positive results by established laboratory criteria. Among 70 seropositive patients whose medical records were available for review, 12 (17%; 95% confidence interval, 9%-28%) were found to have Lyme disease (6 with documented travel to endemic regions). During the same time period, 297 patients with a clinical illness compatible with disseminated Lyme disease underwent 2-tiered serologic testing. Six of them (2%; 95% confidence interval, 0.7%-4.3%) were seropositive, 3 with documented travel and 1 who had an alternative diagnosis that explained the clinical findings.

CONCLUSIONS

In this low-prevalence cohort, fewer than 20% of positive Lyme disease tests are obtained from patients with clinically likely Lyme disease. Positive Lyme disease test results may have little diagnostic value in this setting.

Rate constants for formation of bisulfite addition compounds: an examination in terms of No Barrier Theory

We report a study of the rates of sulfite addition to carbonyl compounds. This reaction is useful in separating compounds (aldehydes react more extensively than ketones, thus becoming water soluble) because the reaction is readily reversible. Although the reaction is mainly by addition of sulfite dianion, the equilibrium is much more favorable for the addition of bisulfite to give a monoanionic adduct. It is also of interest because bisulfite addition is very favorable; thus, we are dealing with a very strong nucleophile. This work demonstrates that No Barrier Theory can calculate rates for good nucleophiles (cyanide and now sulfite) as well as poor nucleophiles such as water. It has been necessary to develop good ways to handle the anionic tetrahedral adducts (in the case of sulfite as nucleophile, dianionic), which tend to break down in the gas phase unless explicitly solvated, and modified procedures for crowded transition states to allow for some relief of steric congestion while maintaining the essential definition of the distorted species resulting from bond formation without geometry change.

Adjunctive pregabalin for uncontrolled partial-onset seizures: findings from a prospective audit

AIMS

Pregabalin (PGB) was licensed in Europe as an add-on antiepileptic drug (AED) for the treatment of partial-onset seizures in 2004. This audit assessed the response to adjunctive PGB in patients with uncontrolled seizures.

METHODS

PGB was titrated in 135 patients [73 men; 62 women, aged 18-76 (median 44 years) until one of the following occurred: ≥ 6 months' seizure freedom, ≥ 50% or < 50% seizure reduction over 6 months; PGB withdrawal because of adverse effects, lack of efficacy or both.

RESULTS

Of the 135 patients, 14 (10.4%) became seizure-free for ≥ 6 months (median PGB dose 300 mg/day; range 75-600 mg). A ≥ 50% seizure reduction occurred in 33 (24.4%) patients; 20 (14.8%) had < 50% reduction. PGB was withdrawn in 68 (50.4%) (40 adverse effects, seven lack of efficacy and 21 both). Commonest problems resulting in withdrawal were sedation (n = 18), weight gain (n = 14) and ataxia (n = 9). There was a positive correlation between increasing dose and weight gain (r = 0.42, P = 0.045).

CONCLUSIONS

Add-on PGB benefited 50% of patients, but only 10% achieved 6 months' seizure freedom. Adverse effects, most commonly sedation, dose-related weight gain and ataxia, led to drug discontinuation by 45%. Prospective audits of novel AEDs are a useful adjunct to randomized, controlled trials in managing epilepsy.

"Would I had him with me always": Affects of longing in early artificial intelligence

The science of artificial intelligence (AI) is not as unemotional as it might first appear. Not only are researchers in the field now taking an interest in how to program affective capacities into artificial agents; there is also plenty of historical evidence that concerns about affect have been present in AI from the earliest years. Examination of archival materials from the 1940s and 1950s shows that affects (particularly as they circulate between men) have been a significant part of innovation in AI from the beginning. This essay looks at one fragment of that history: the currents of affective and sexual interests in and around Walter Pitts, one of the important, eccentric, and little-written-about founders of AI.

Feline systemic reactive angioendotheliomatosis: eight cases and literature review

A rare, multisystemic intravascular proliferative disorder was identified postmortem in eight cats. The majority of these cats died or were euthanized following episodes of dyspnea, lethargy, and anorexia. Microscopic examination revealed occlusive, intraluminal proliferations of spindle cells within small vessels. The heart was consistently involved, and myocardial dysfunction was the probable cause of illness in all cats. Immunohistochemically, the majority of intravascular cells expressed von Willebrand factor, and a smaller number expressed smooth muscle actin, compatible with a dual population of endothelial cells and pericytes, suggesting a reactive rather than a neoplastic process. Four cases of a similar feline vascular disorder from the veterinary literature are reviewed. The histopathology resembles reactive angioendotheliomatosis in humans, a benign cutaneous intravascular endothelial and pericytic proliferative condition. However, in contrast, this feline disease is multisystemic and fatal. We propose the name "feline systemic reactive angioendotheliomatosis" for this unique, idiopathic disorder of domestic cats.

Severe retinal degeneration associated with disruption of semaphorin 4A

PURPOSE

Semaphorin 4A (Sema4A) is a member of the transmembrane class 4 family of semaphorins. It has recently been shown to participate in cell-cell communication in the immune system. High levels of sema4A are also present in brain and eye, but its function in the central nervous system has not been studied. To investigate the function of Sema4A, we generated mice deficient in this transmembrane signaling molecule.

METHODS

An embryonic stem (ES) cell clone with a retroviral gene-trap insertion in the sema4A gene was used to generate mice lacking this transmembrane semaphorin. Fundus photography, fluorescein angiography, and electroretinography were used to evaluate retinal anatomy and physiology in mice lacking Sema4A. Electron microscopy and immunohistochemistry with cell-type-specific markers were used to characterize retinal development. In situ hybridization with sema4A-specific riboprobes was used to localize expression of this gene in the developing and adult eye.

RESULTS

Fundus photography performed at 14 weeks of age revealed severe retinal degeneration, attenuated retinal vessels, and depigmentation in mice lacking Sema4A. At this age, the outer nuclear layer was reduced to a single row of photoreceptor cells, and the outer plexiform layer was thin and disorganized. Disruption of Sema4A also compromised the physiological function of both rod and cone photoreceptors. Developmental studies in Sema4A-deficient mice revealed abnormal morphology of photoreceptor outer segments during the time at which they establish contacts with apical microvilli of the retinal pigment epithelium (RPE). Sema4A is expressed in the inner retina and RPE during the time at which photoreceptor outer segments elongate.

CONCLUSIONS

These findings identify a previously unknown function of Sema4A in the developing visual system and provide a useful model for understanding cell-cell interactions that occur between photoreceptors and the RPE.

Widespread regional myocardial transfection by plasmid encoding Del-1 following retrograde coronary venous delivery

This study quantifies myocardial transfection following percutaneous retrograde coronary venous delivery (RCVD) of a plasmid encoding human Del-1. RCVD of Del-1, GFP plasmid, or marker dye was conducted in 14 pigs. After selective cannulation of a coronary vein, a delivery site was confirmed by contrast injection and myocardial blush. Ten milliliters of plasmid hDel-1 or GFP was administered. Animals were euthanized 3 and 7 days post-RCVD. hDel-1 gene expression was evaluated by quantitative RT-PCR. An average myocardial expression of 4.5 x 10(5) copies hDel-1/microg total RNA was observed within the approximately 5 x 5 cm(2) target tissue of the left ventricle. GFP expression was detected by fluorescent microscopy. hDel-1 protein expression was confirmed by immunohistochemistry. Regionalized myocardial expression was found in all pigs. hDel-1 RNA was not found in distant tissues except in the three pigs with prominent venovenous washout (PVW). These levels were 3 to 4 log unites lower than those found in myocardium. Single retrograde coronary venous administration resulted in efficient regional myocyte transfection of hDel-1 and GFP. This method may be useful and clinically feasible for myocardial angiogenesis therapy.

Stewardship or clinical freedom? variations in dialysis decision making

BACKGROUND

It is generally agreed that acceptance criteria for dialysis have varied and changed over time and that implicit rationing, to some extent forced on clinicians by limited capacity, has been widely practised. Our objective was to study the basis and extent of variation in dialysis decision making among nephrologists in one NHS region.

DESIGN AND METHODS

In a clinical judgement analysis, linear regression models were employed to reflect the impact of clinical and non-clinical cues on nephrologists' decisions to offer dialysis to 60 'paper patients' under current capacity constraints and under an assumption of no capacity limit. A short questionnaire was also completed by eight nephrologists to elicit their expressed decision drivers, which were subsequently compared with those tacitly derived from the appraisal of the 60 clinical vignettes.

RESULTS

Doctors showed substantial variation in their propensity to offer dialysis and in their perceptions of the benefits of dialysis. Even for the five patients where the discordance in propensity to offer dialysis was least, the range in perceived gain in life expectancy was from 24 to 264 months (mean 91 months). The decision models had relatively good explanatory power with an average r(2) of 0.67 (0.39-0.90) and 0.70 (0.47-0.95) for decisions made under current capacity constraints and under an assumption of no limit capacity respectively. Surprisingly, for most doctors, the patient's age had very little impact on dialysis decisions but the magnitude of the beta-coefficients for the patient's mental state (mean -30.7) was of a similar order of magnitude to the coefficient for the principal 'renal' drivers (e.g. the mean coefficient for uraemic symptomatology under current capacity constraints was 47.7). The influence of other non-renal factors on the doctor's likelihood to offer dialysis was largely independent of the capacity assumption. A comparison of the doctor's stated decision drivers with those tacitly derived from their decision models showed only modest correlation.

CONCLUSIONS

The extent to which doctors vary in their propensity to offer dialysis is substantial. Very few non-clinical cues appear to influence the decision to offer dialysis. The most important non-renal factor in determining dialysis decisions was the patient's mental state.

Revising appointment, promotion, and tenure procedures to incorporate an expanded definition of scholarship: the University of Kentucky College of Medicine experience

Scholarly activity and scholarly productivity are key features of the academic health center (AHC) and the work of college of medicine faculty. Recent changes in the academic environment of the University of Kentucky (UK) College of Medicine led to an examination of its appointment, promotion, and tenure procedures. This, in turn, led to a re-examination of the college's definition of scholarship. This article describes three of UK's scholarship-related challenges, particularly those related to clinical departments. The authors describe some of the new procedures being implemented to address these challenges; these include new faculty designations, clearer articulation of promotion procedures, explicit recognition of multiple forms of scholarship, expectations for investment in junior faculty, and mandatory discussion of faculty success in chairs' annual reviews. Faculty reactions, positive and negative, to these changes in procedures are also presented.

High dose gabapentin in refractory partial epilepsy: clinical observations in 50 patients

Fifty patients with refractory partial seizures took part in a prospective, observational study of adjuvant gabapentin (GBP) in increasing doses. Thirty-three were started on 400 mg GBP daily with further weekly increments of 400 mg until seizures came under control for at least 6 months or to the limit of tolerability. A further 17 patients, not fully controlled on low dose GBP, followed the same regimen. All patients took the drug three times daily. Comparisons were made with seizure numbers during a 3-month baseline during which antiepileptic medication remained unchanged. Overall, 24 of the 50 patients documented a seizure reduction of 50% or more. Fifteen did so at or below 2400 mg GBP daily. Three of these patients became seizure-free. The remaining nine appeared to respond to higher daily doses of GBP (1:2800 mg; 3:3600 mg; 1:4000 mg; 1:4800 mg; 3:6000 mg), with two becoming seizure-free. Side-effects most commonly reported included tiredness, dizziness, headache and diplopia. On GBP doses exceeding 3600 mg daily, three patients developed flatulence and diarrhoea and two more had myoclonic jerks. Mean circulating GBP concentrations (mg/l) at each 1200 mg dose level were as follows: 1200 mg-4.1; 2400 mg-8.6; 3600 mg 13.2; 4800 mg 15.5; 6000 mg-17.2. In six patients, including three taking 6000 mg daily, GBP concentrations continued to rise linearly at each dosage increment. Although limited, our results do not support the suggestion that GBP absorption is saturable. High dose GBP may be effective in controlling seizures in patients with refractory partial epilepsy.

Multiple options and unique pathways: a new direction for EMS?

The same forces transforming the health care delivery system also are reshaping EMS. The changing economic and organizational structures of the health services delivery system may predict how EMS systems will redesign themselves. We discuss one template for future EMS systems.

The Kentucky medical curriculum. A response to the call for educational reform: a GPEP report card

The resources of an important educational grant provided by the Robert Wood Johnson Foundation, as well as designated local college and medical center funds, provided support for the renewal of the undergraduate medical education program at the University of Kentucky College of Medicine. The fully revised medical curriculum, adapted to changing professional and societal needs and completely in place by the 1994-95 academic year, was influenced by the recommendations of the General Professional Education of the Physician (GPEP) Report, issued by the Association of American Medical Colleges in 1984. This paper details each of the student-centered curricular changes in the context of the GPEP recommendation that it particularly addresses.

New antiepileptic drugs

No fewer than eight new antiepileptic drugs (AEDs) with diverse mechanisms of action have been introduced into clinical practice in the 1990s. Short monographs on lamotrigine, vigabatrin, gabapentin, oxcarbazepine, felbamate, topiramate and vigabatrin have been prepared for this review. Details are provided of mechanisms of action, clinical pharmacokinetics and adverse drug interactions. Each section concentrates on the efficacy, tolerability and practical use of these drugs. The areas where they have potential for superiority over the established AEDs have been highlighted. Specific indications and dosage schedules have been provided. As many of these AEDs have, as yet, limited licences, an attempt has been made to identify ongoing studies and important omissions. Where possible, the eventual place of the new agent in the pharmacological management of epilepsy has been assessed. A more limited summary has been included of zonisamide which, although licensed in Japan, is still regarded as an investigational drug elsewhere. Short discussions of three of the most promising investigational compounds, namely remacemide, losigamone and levetiracetam, complete the picture.

Nursing futures: a process to promote change in the delivery of care

In this era of healthcare reform, performing care using resources in an efficient manner is essential. "Nursing Futures," a process used by a 24-bed general rehabilitation unit in a 530-bed facility, helped the unit to identify key components of care, determine opportunities for improvement, and create a new system for the delivery of care that maximized resources and improved customer satisfaction. A Nursing Futures Committee, composed of nursing staff from all levels and from all shifts, used a continuous quality improvement process to focus on the problems in care delivery and developed ways to solve these problems using the time and talents of registered nurses in the most effective way. The committee also identified expectations of staff by various customer groups; analyzed the delivery system and defined its shortcomings; developed the ideal patient care unit within financial and institutional constraints; and executed the plan, considering cost and evaluation of patient and staff satisfaction before and after the system was implemented. The new system provided consistency in patient care assignments by reorganizing the unit into two nursing teams and by creating a new nursing position, the patient care manager.

Does technique or material used affect bladder tissue reactions when injecting teflon or silicone paste?

OBJECTIVES

Submucosal injections of polytetrafluoroethylene (PTFE) and polydimethylsiloxane (PDMS) paste continue to be used for the correction of vesicoureteral reflux and urinary incontinence. Potential distant particle migration and foreign body tissue reactions are thought to be significantly affected by the technique of injection and the paste material used. A study to determine if injection technique, paste material, or pretreatment of the injection site significantly affects local tissue reaction was performed on 44 New Zealand white rabbits.

METHODS

Animals were randomly assigned to undergo four distinct injection treatments into the submucosa or bladder muscularis. Prior to injecting 0.1 cc of the PTFE or PDMS paste, some sites were pretreated with 0.1 cc saline to separate tissue planes, epinephrine to cause vasoconstriction, or doxycycline to provide sclerosis. Pretreatment controls were also performed without injecting PTFE or PDMS paste. Animals were killed, and quadrant bladder biopsies were performed at 1 hour (9), 1 day (9), 7 days (10), 1 month (8), and 6 months (8). A single pathologist, blinded to the injection treatments, performed a histologic evaluation to determine bleb location and the degree of inflammation, fibrosis, and epithelial necrosis.

RESULTS

Seven of the 12 submucosal PTFE injection treatments were found on biopsy to be primarily within the muscularis, compared to 1 of 9 with PDMS paste. Three of the 24 PTFE injections could not be found at autopsy. Of these, two were injected into the muscularis, and all were discovered at least 1 month following injection. Particles were present in all 22 PDMS injection sites that were retrieved. Pretreatments, especially with doxycycline, resulted in significant epithelial necrosis at 1 and 7 days. At 1 and 6 months there were no differences in inflammation or fibrosis between PTFE and PDMS or any pretreatment combinations with saline or epinephrine.

CONCLUSIONS

Correctly injected, silicone (PDMS) paste appears most likely to remain in the submucosal space. Pretreatment injections may cause early epithelial necrosis. PTFE and PDMS elicit similar foreign body reactions over time.

Physicians for the 21st century: implications for medical practice, undergraduate preparation, and medical education

Changes in medical education and the practice of medicine have resulted from the push for both education and health care reforms. Undergraduates planning application to medical school should broaden their preparation to include communications, computers, economics, and multicultural educational experiences. To prepare graduates for medical practice in the new millennium, the University of Kentucky College of Medicine has implemented a new curriculum focusing on integration of basic and clinical sciences, primary care in ambulatory sites, health promotion and disease prevention, and attention to the ethical, social, psychologic, and financial impact of disease upon the patient, family, and society.

Synaptic organization of serotonin-like immunoreactive amacrine cells in the larval tiger salamander retina

Immunoelectron microscopy was used to investigate the ultrastructural features and synaptic relationships of serotonin-like immunoreactive amacrine cells in the larval tiger salamander retina. Serotonin-positive somas exhibited an evenly distributed peroxidase reaction product throughout their cytoplasm. Their nuclei were unstained and possessed indented nuclear membranes. Serotonin-immunoreactive processes were generally stained throughout with the exception of their mitochondria, whose morphology was often disrupted by the staining reaction. They were further characterized by an occasional dense-cored vesicle/s in addition to a generally homogeneous population of small, round, clear synaptic vesicles. Serotonin-immunoreactive amacrine cell processes formed conventional synapses that were characterized by symmetrical synaptic membrane densities. A total of 222 synaptic arrangements were observed that involved the immunostained processes of serotonin-amacrine cells. As presynaptic elements, they primarily contacted amacrine cells processes (37.8%). They also provided substantial synaptic input to processes that lacked synaptic vesicles (16.2%) and whose origin was unidentified. Serotonin-processes provided a far fewer number of synaptic contacts onto the processes of bipolar cells (1.4%) and the somas of cells in the amacrine cell layer (0.5%). As postsynaptic elements, they received synaptic inputs from amacrine cells (27.9%) and bipolar cells (16.2%). With the exception of their synapses onto bipolar cells and the somas of cells in the amacrine cell layer, each of the synaptic relationships of serotonin-amacrine cells was observed in each of sublayers 1-5 of the inner plexiform layer.