Executive functions in agenesis of the corpus callosum: Working memory and sustained attention in the BTBR inbred mouse strain

INTRODUCTION

Agenesis of the corpus callosum (AgCC) is characterized by the congenital partial or complete absence of the corpus callosum. Several strains of mice have been reported to carry AgCC, with the BTBR T⁺ Itpr3^tf /J (BTBR) inbred mouse strain consistently showing a complete absence of the corpus callosum, as well as a variable reduction in the size of the hippocampal commissure. While much research has focused on the social deficits of the BTBR strain, little research on its cognitive behavior has been conducted. The goal of our study was to compare two facets of executive functioning, spatial working memory, and sustained attention between the BTBR and C57BL/6J (B6) strains.

METHODS

Spatial working memory was measured utilizing a delayed matching-to-position (DMTP) task and sustained attention was measured utilizing an operant task in which mice were trained to distinguish signal and nonsignal events.

RESULTS

Both the BTBR and B6 mice demonstrated a predictable decline in performance on the DMTP task as the delay interval increased and predictable increase in performance on the sustained attention task as the duration of the signal event increased. Although no significant differences were found between strains on the performance of these tasks, there was a significant difference in learning the association between lever pressing and food reward. Histological investigation confirmed the complete absence of commissural fibers from the corpus callosum, but also the hippocampal commissure, counter to a previous study.

CONCLUSION

The results suggest spatial working memory and sustained attention are unaffected by the absence of these commissural fibers alone.

Consistent hypersocial behavior in mice carrying a deletion of Gtf2i but no evidence of hyposocial behavior with Gtf2i duplication: Implications for Williams-Beuren syndrome and autism spectrum disorder

Introduction

Williams-Beuren syndrome (WBS) is a developmental disorder caused by hemizygous deletion of human chromosome 7q11.23. Hypersocial behavior is one symptom of WBS and contrasts with hyposociality observed in autism spectrum disorder (ASD). Interestingly, duplications of 7q11.23 have been associated with ASD. The social phenotype of WBS has been linked to GTF2I or general transcription factor IIi (TFII-I). Duplication of GTF2I has also been associated with ASD.

Methods

We compared mice having either a deletion (Gtf2i+/- ) or duplication (Gtf2i+/dup ) of Gtf2i to wild-type (Gtf2i+/+ ) littermate controls in a series of behavioral tasks including open-field activity monitoring, olfactory probes, a social choice task, social transmission of food preference, habituation-dishabituation, and operant social motivation paradigms.

Results

In open-field observations, Gtf2i+/- and Gtf2i+/dup mice demonstrated normal activity and thigmotaxis, and surprisingly, each strain showed a significant preference for a stimulus mouse that was not observed in Gtf2i+/+ siblings. Both Gtf2i+/- and Gtf2i+/dup mice demonstrated normal olfaction in buried food probes, but the Gtf2i+/- mice spent significantly more time investigating urine scent versus water, which was not observed in the other strains. Gtf2i+/- mice also spent significantly more time in nose-to-nose contact compared to Gtf2i+/+ siblings during the open-field encounter of the social transmission of food preference task. In operant tasks of social motivation, Gtf2i+/- mice made significantly more presses for social rewards than Gtf2i+/+ siblings, while there was no difference in presses for the Gtf2i+/dup mice.

Discussion

Results were remarkably consistent across testing paradigms supporting a role for GTF2i in the hypersocial phenotype of WBS and more broadly in the regulation of social behavior. Support was not observed for the role of GTF2i in ASD.

Abstract P3-10-10: Planning and implementation of two regional one-stop breast health centres within a large geographic health authority: Outcomes and quality improvements in health service delivery

Interrogative examination of wait times for the pathway steps leading to diagnosis, surgical treatment, and oncology consultation for breast cancer within a geographically dispersed publically funded health authority led to advocacy for and establishment of two large one-stop Breast Health Centres (BHCs) within the largest urban cities. One year after publication of the 2000 EUSOMA guidelines for breast cancer diagnosis and treatment, regional breast cancer pathways and wait times did not meet guidelines. Population median wait time from date of first investigation to tissue diagnosis was 2.7 or 5.9 weeks (for clinical presentation or screen presentation respectively), 6.0/7.0 weeks to definitive surgical intervention, and 14.3/11.7 weeks to oncology consultation. Only 39 % of patients were diagnosed initially via core needle biopsy. 5 % of patients underwent immediate reconstructive surgery. Due to wait times for initial imaging (mammogram, ultrasound) at hospital facilities, baseline imaging was often performed at private imaging labs without needle diagnostic capability, and repeated again with a series of wait times at the hospitals - as the initial community images were not accessible to the hospital interventional radiologists. Smaller communities and their hospitals maintained shorter wait times in comparison to the large urban centres. Repeat population based measurement in 2009 indicated wait times were unchanged, and MRI guided biopsy was still not available within the region. Nursing support and patient education re breast cancer prognosis and treatment was not available until the time of oncology consultation.

BHCs were planned, funded by the Ministry of Health, established in physical conjunction with the breast screening programs, and became operational as of early 2012. During the first year of BHC operation, population median wait time from date of first investigation was 2.0 weeks for tissue diagnosis, 6.4 weeks for final definitive surgical intervention, and 9.4 weeks for oncology consultation. 90 % of patients were initially diagnosed via initial core needle biopsy with IHC staining for ER, PR, and HER2. Patients served by the BHCs had nurse navigator support and education from time of presentation. The surgical team overcame regional surgical wait time barriers such as available admission beds by establishing the first comprehensive population-based outpatient mastectomy and reconstruction program in Canada with over 1200 performed to date. These wait times have been maintained in spite of increase in the HA population from 1.2 million to 1.6 million during the project timeline.

Citation Format: Martin LA, Janzen R, Wong F, Doris P. Planning and implementation of two regional one-stop breast health centres within a large geographic health authority: Outcomes and quality improvements in health service delivery [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-10-10.

Slowing Down Time: An Exploration of Personal Life Extension Desirability as it Relates to Religiosity and Specific Religious Beliefs

As medical technology continues increasing the possibility of living a longer life, the public's valuing of these developments must be considered. This study examines attitudes toward extending the human life span within a student population at a Christian university. Religious factors were hypothesized to affect life extension desirability. Scores on measures of willingness to defer to God's will, meaning derived from religion, positive afterlife beliefs, and intrinsic religiosity were significantly and inversely related to life extension desirability. Implications of these findings are discussed, including encouraging medical practitioners to respect decision-making processes of religious persons who may find life extension interventions undesirable.

Ecological Genetics and Host Range Expansion by Busseola fusca (Lepidoptera: Noctuidae)

The host plant range of pests can have important consequences for its evolution, and plays a critical role in the emergence and spread of a new pest outbreak. This study addresses the ecological genetics of the indigenous African maize stem borer, Busseola fusca (Fuller) (Lepidoptera: Noctuidae), in an attempt to investigate the evolutionary forces that may be involved in the recent host range expansion and establishment of this species in Ethiopian and southern African sugarcane. We used populations from Ethiopia, Zimbabwe, and South Africa to examine whether the host range expansion patterns shared by the Ethiopian and the southern African populations of B. fusca have evolved independently. Base-pair differences in the cytochrome oxidase I (COI) gene were used to characterize haplotype diversity and phylogenetic relationships. There were seven haplotypes among the 30 sequenced individuals collected on four host plant species from 17 localities in the four countries. Of the seven COI haplotypes identified, the two major ones occurred in both sugarcane and maize. Genetic analyses revealed no detectable genetic differentiation between southern African B. fusca populations from maize and sugarcane (FST = 0.019; P = 0.24). However, there was strong evidence of variation in genetic composition between populations of the pest from different geographic regions (FST = 0.948; P < 0.001). The main implication of these findings is that the B. fusca populations in maize in southern Africa are more likely to shift to sugarcane, suggesting that ecological opportunity is an important factor in host plant range expansion by a pest.

A rapid and visual loop-mediated isothermal amplification assay to detect Leifsonia xyli subsp. xyli targeting a transposase gene

Leifsonia xyli subsp. xyli (Lxx), causal organism of ratoon stunt (RSD), does not produce any reliable internal or external symptoms on sugarcane. Its detection on a large scale is solely based on microscopic and serological methods. These methods require well-equipped laboratories, are time consuming and are not feasible for near-field detection of Lxx. In this study, we developed a loop-mediated isothermal amplification (LAMP) assay for rapid and sensitive detection of Lxx without the use of sophisticated equipment. To the best of our knowledge, this is the first report on the detection of Lxx in 30 min via an isothermal amplification method at 65°C. A transposase gene, ISLxx5, was used to design a set of six primers specifically targeting eight genomic sequences. The xylem sap was used as template, thus circumventing the need to isolate pure genomic DNA. The positive reactions were visually detected through a colour change of hydroxynaphthol blue (HNB) from violet to light blue, thus, eliminating the need for gel electrophoresis. The LAMP method was 10 times more sensitive than serological detection and as sensitive as immunofluorescence microscopy (IFM). The simplicity and sensitivity of the ISLxx5 LAMP assay makes it suitable for near-field diagnosis of RSD.

SIGNIFICANCE AND IMPACT OF THE STUDY

Detection of Leifsonia xyli subsp. xyli (Lxx) on a large scale is based on serological assays such as evaporative-binding enzyme-linked immunoassay (EB-EIA). These methods are time consuming and require well-equipped laboratories. This study presents the development of a loop-mediated isothermal amplification (LAMP) assay which allows detection of Lxx in 30 min at 65°C, using xylem sap as the template. The assay requires minimal laboratory equipment and could be used at near farm conditions, thus saving time and money required to transfer samples from remote areas to diagnostic laboratories. The LAMP method shows potential as an alternative detection method for RSD.

The effects of birth order and birth interval on the phenotypic expression of autism spectrum disorder

A rise in the prevalence of diagnosed cases of autism spectrum disorder (ASD) has been reported in several studies in recent years. While this rise in ASD prevalence is at least partially related to increased awareness and broadened diagnostic criteria, the role of environmental factors cannot be ruled out, especially considering that the cause of most cases of ASD remains unknown. The study of families with multiple affected children can provide clues about ASD etiology. While the majority of research on ASD multiplex families has focused on identifying genetic anomalies that may underlie the disorder, the study of symptom severity across ASD birth order may provide evidence for environmental factors in ASD. We compared social and cognitive measures of behavior between over 300 first and second affected siblings within multiplex autism families obtained from the Autism Genetic Resource Exchange dataset. Measures included nonverbal IQ assessed with the Ravens Colored Progressive Matrices, verbal IQ assessed with the Peabody Picture Vocabulary Test, and autism severity assessed with the Social Responsiveness Scale (SRS), an instrument established as a quantitative measure of autism. The results indicated that females were more severely impacted by ASD than males, especially first affected siblings. When first and second affected siblings were compared, significant declines in nonverbal and verbal IQ scores were observed. In addition, SRS results demonstrated a significant increase in autism severity between first and second affected siblings consistent with an overall decline in function as indicated by the IQ data. These results remained significant after controlling for the age and sex of the siblings. Surprisingly, the SRS scores were found to only be significant when the age difference between siblings was less than 2 years. These results suggest that some cases of ASD are influenced by a dosage effect involving unknown epigenetic, environmental, and/or immunological factors.

Consensus paper: pathological role of the cerebellum in autism

There has been significant advancement in various aspects of scientific knowledge concerning the role of cerebellum in the etiopathogenesis of autism. In the current consensus paper, we will observe the diversity of opinions regarding the involvement of this important site in the pathology of autism. Recent emergent findings in literature related to cerebellar involvement in autism are discussed, including: cerebellar pathology, cerebellar imaging and symptom expression in autism, cerebellar genetics, cerebellar immune function, oxidative stress and mitochondrial dysfunction, GABAergic and glutamatergic systems, cholinergic, dopaminergic, serotonergic, and oxytocin-related changes in autism, motor control and cognitive deficits, cerebellar coordination of movements and cognition, gene-environment interactions, therapeutics in autism, and relevant animal models of autism. Points of consensus include presence of abnormal cerebellar anatomy, abnormal neurotransmitter systems, oxidative stress, cerebellar motor and cognitive deficits, and neuroinflammation in subjects with autism. Undefined areas or areas requiring further investigation include lack of treatment options for core symptoms of autism, vermal hypoplasia, and other vermal abnormalities as a consistent feature of autism, mechanisms underlying cerebellar contributions to cognition, and unknown mechanisms underlying neuroinflammation.

Enhanced expression of the PDGFR/Abl signaling pathway in aromatase inhibitor-resistant breast cancer

BACKGROUND

We have found that the platelet-derived growth factor receptor (PDGFR)/Abl signaling pathway is up-regulated as a determinant of the acquisition of resistance to estrogen deprivation in vitro. We aimed to determine its clinical relevance in aromatase inhibitor (AI)-resistant breast cancer.

PATIENTS AND METHODS

We identified a cohort of 45 patients with estrogen receptor-positive breast cancer who had been treated with an AI, subsequently relapsed and had biopsy material available from both the presentation and post-AI recurrent lesion. PDGFRα, PDGFRβ and Abl expression was assessed in formalin-fixed paraffin-embedded sections.

RESULTS

Tumor protein expression of PDGFRα (1.39-fold, P=0.0065), PDGFRβ (4.32-fold, P=0.006) and Abl (1.8-fold, P=0.001) was increased at the point of relapse. Tumor and stromal expression of PDGFRα as well as PDGFRβ was significantly correlated in pre-treatment and relapse samples. High post-treatment tumor and stromal PDGFRβ levels were associated with a short time to treatment failure (TTF). Expression of PDGFRα in relapsing tumor specimens was correlated with Abl expression and Ki67 levels. Furthermore, changes in Abl correlated significantly with changes in ER expression.

CONCLUSIONS

These clinical data support a role for enhanced PDGF/Abl signaling in AI-resistant disease and provide a rationale for targeting the pathway in endocrine-resistant breast cancer.

Polychlorinated biphenyl congeners that increase the glucuronidation and biliary excretion of thyroxine are distinct from the congeners that enhance the serum disappearance of thyroxine

Polychlorinated biphenyl (PCB) congeners differentially reduce serum thyroxine (T(4)) in rats, but little is known about their ability to affect biliary excretion of T(4). Thus, male Sprague-Dawley rats were orally administered Aroclor-1254, Aroclor-1242 (32 mg/kg per day), PCB-95, PCB-99, PCB-118 (16 mg/kg per day), PCB-126 (40 μg/kg per day), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (3.9 μg/kg per day), or corn oil for 7 days. Twenty-four hours after the last dose, [(125)I]T(4) was administered intravenously, and blood, bile, and urine samples were collected for quantifying [(125)I]T(4) and in bile [(125)I]T(4) metabolites. Serum T(4) concentrations were reduced by all treatments, but dramatic reductions occurred in response to Aroclor-1254, PCB-99 [phenobarbital (PB)-type congener], and PCB-118 (mixed-type congener). None of the treatments increased urinary excretion of [(125)I]T(4). Aroclor-1254, PCB-118, TCDD, and PCB-126 (TCDD-type congener) increased biliary excretion of T(4)-glucuronide by 850, 756, 710, and 573%, respectively, corresponding to marked induction of hepatic UDP-glucuronosyltransferase (UGT) activity toward T(4). PCB-95 and PCB-99 did not induce UGT activity; therefore, the increased biliary excretion of T(4)-glucuronide was related to the affinity of congeners for the aryl hydrocarbon receptor. The disappearance of [(125)I]T(4) from serum was rapid (within 15-min) and was increased by Aroclor-1254, PCB-99 and PCB-118. Thus, reductions in serum T(4) in response to PCBs did not always correspond with UGT activity toward T(4) or with increased biliary excretion of T(4)-glucuronide. The rapid disappearance of [(125)I]T(4) from the serum of rats treated with PB-like PCBs suggests that increased tissue uptake of T(4) is an additional mechanism by which PCBs may reduce serum T(4).

Behavioral flexibility in a mouse model of developmental cerebellar Purkinje cell loss

Although behavioral inflexibility and Purkinje cell loss are both well established in autism, it is unknown if these phenomena are causally related. Using a mouse model, we tested the hypothesis that developmental abnormalities of the cerebellum, including Purkinje cell loss, result in behavioral inflexibility. Specifically, we made aggregation chimeras (Lc/+<-->+/+) between lurcher (Lc/+) mutant embryos and wildtype (+/+) control embryos. Lurcher mice lose 100% of their Purkinje cells postnatally, while chimeric mice lose varying numbers of Purkinje cells. We tested these mice on the acquisition and serial reversals of an operant conditional visual discrimination, a test of behavioral flexibility in rodents. During reversals 1 and 2, all groups of mice committed similar numbers of "perseverative" errors (those committed while session performance was <= 40% correct). Lurchers, however, committed a significantly greater number of "learning" errors (those committed while session performance was between 41% and 85% correct) than both controls and chimeras, and most were unable to advance past reversal 3. During reversals 3 and 4, chimeras, as a group, committed more "perseverative", but not "learning" errors than controls, although a comparison of Purkinje cell number and performance in individual mice revealed that chimeras with fewer Purkinje cells made more "learning" errors and had shorter response latencies than chimeras with more Purkinje cells. These data suggest that developmental cerebellar Purkinje cell loss may affect higher level cognitive processes which have previously been shown to be mediated by the prefrontal cortex, and are commonly deficient in autism spectrum disorders.

Repetitive behavior and increased activity in mice with Purkinje cell loss: a model for understanding the role of cerebellar pathology in autism

Repetitive behaviors and hyperactivity are common features of developmental disorders, including autism. Neuropathology of the cerebellum is also a frequent occurrence in autism and other developmental disorders. Recent studies have indicated that cerebellar pathology may play a causal role in the generation of repetitive and hyperactive behaviors. In this study, we examined the relationship between cerebellar pathology and these behaviors in a mouse model of Purkinje cell loss. Specifically, we made aggregation chimeras between Lc/+ mutant embryos and +/+ embryos. Lc/+ mice lose 100% of their Purkinje cells postnatally due to a cell-intrinsic gain-of-function mutation. Through our histological examination, we demonstrated that Lc/+<-->+/+ chimeric mice have Purkinje cells ranging from zero to normal numbers. Our analysis of these chimeric cerebella confirmed previous studies on Purkinje cell lineage. The results of both open-field activity and hole-board exploration testing indicated negative relationships between Purkinje cell number and measures of activity and investigatory nose-poking. Additionally, in a progressive-ratio operant paradigm, we found that Lc/+ mice lever-pressed significantly less than +/+ controls, which led to significantly lower breakpoints in this group. In contrast, chimeric mice lever-pressed significantly more than controls and this repetitive lever-pressing behavior was significantly and negatively correlated with total Purkinje cell numbers. Although the performance of Lc/+ mice is probably related to their motor deficits, the significant relationships between Purkinje cell number and repetitive lever-pressing behavior as well as open-field activity measures provide support for a role of cerebellar pathology in generating repetitive behavior and increased activity in chimeric mice.

Stereotypies and hyperactivity in rhesus monkeys exposed to IgG from mothers of children with autism

Autism together with Asperger syndrome and pervasive developmental disorder not otherwise specified form a spectrum of conditions (autism spectrum disorders or ASD) that is characterized by disturbances in social behavior, impaired communication and the presence of stereotyped behaviors or circumscribed interests. Recent estimates indicate a prevalence of ASD of 1 per 150 (Kuehn, 2007). The cause(s) of most cases of ASD are unknown but there is an emerging consensus that ASD have multiple etiologies. One proposed cause of ASD is exposure of the fetal brain to maternal autoantibodies during pregnancy [Dalton, P., Deacon, R., Blamire, A., Pike, M., McKinlay, I., Stein, J., Styles, P., Vincent, A., 2003. Maternal neuronal antibodies associated with autism and a language disorder. Ann. Neurol. 53, 533-537]. To provide evidence for this hypothesis, four rhesus monkeys were exposed prenatally to human IgG collected from mothers of multiple children diagnosed with ASD. Four control rhesus monkeys were exposed to human IgG collected from mothers of multiple typically developing children. Five additional monkeys were untreated controls. Monkeys were observed in a variety of behavioral paradigms involving unique social situations. Behaviors were scored by trained observers and overall activity was monitored with actimeters. Rhesus monkeys gestationally exposed to IgG class antibodies from mothers of children with ASD consistently demonstrated increased whole-body stereotypies across multiple testing paradigms. These monkeys were also hyperactive compared to controls. Treatment with IgG purified from mothers of typically developing children did not induce stereotypical or hyperactive behaviors. These findings support the potential for an autoimmune etiology in a subgroup of patients with neurodevelopmental disorders. This research raises the prospect of prenatal evaluation for neurodevelopmental risk factors and the potential for preventative therapeutics.

Sustained attention in the mouse: A study of the relationship with the cerebellum

To explore the role of the cerebellum in sustained attention, the authors tested lurcher, wildtype, and lurcher chimeric mice with zero, normal, and variable numbers of Purkinje cells, respectively, in a previously validated task of sustained attention. Results indicate that lurcher mice had a deficit in performance likely related to their motor disability, whereas lurcher chimeras performed similarly to wildtype controls. Presentation of auditory or visual distracters caused deficits in the performance of all mice that were specific to either signal (auditory) or non-signal (visual) events. The authors' results do not support a role of the cerebellum in sustained attention, instead indicating that behavioral changes are an indirect result of motor deficits.

Enhanced Purkinje cell survival but compromised cerebellar function in targeted anti-apoptotic protein transgenic mice

Regulation of Purkinje cell (PC) number is critical for proper assembly and function of the cerebellum. Murine cerebellar neurogenesis yields supernumerary populations of cells that are subject to programmed cell death during development and aging. This study focuses on the control of mouse PC number during development and the consequences of interrupting normal cell death. Purkinje cell-specific regulatory elements from the pcp2 gene were employed to target expression of two anti-apoptotic proteins, human BCL-2 and adenovirus E1B 19k to the PCs of transgenic mice. Comparative morphometric analyses indicated no significant difference in PC numbers in the strongest BCL-2 expressing line, while a 14.2% increase was noted in the pcp2/E1B 19k transgenic line. The temporal transgene expression patterns of several mouse lines indicated that PC numbers are normally adjusted during the first postnatal week. Crossbreeding studies demonstrated that both Bcl-2 and E1B 19k transgenes provided Purkinje cell protection from SV40 Tag-induced cell death. Interestingly, RotaRod behavioral analysis demonstrated that 'rescued' Purkinje cells degrade cerebellar function. Furthermore, aged E1B 19k and Bcl-2 mice exhibited decreased RotaRod performance despite increased PC numbers. These findings have implications regarding neuronal death during development and aging as well as cellular and genetic strategies to circumvent neuronal degeneration.

A relationship between cerebellar Purkinje cells and spatial working memory demonstrated in a lurcher/chimera mouse model system

New emphasis has been placed upon cerebellar research because of recent reports demonstrating involvement of the cerebellum in non-motor cognitive behaviors. Included in the growing list of cognitive functions associated with cerebellar activation is working memory. In this study, we explore the potential role of the cerebellum in spatial working memory using a mouse model of Purkinje cell loss. Specifically, we make aggregation chimeras between heterozygous lurcher (Lc/+) mutant embryos and +/+ (wildtype) embryos and tested them in the delayed matching-to-position (DMTP) task. Lc/+ mice lose 100% of their Purkinje cells postnatally due to a cell-intrinsic gain-of-function mutation. Lc/+<->+/+ chimeras therefore have Purkinje cells ranging from 0 to normal numbers. Through histological examination of chimeric mice and observations of motor ability, we showed that ataxia is dependent upon both the number and distribution of Purkinje cells in the cerebellum. In addition, we found that Lc/+ mice, with a complete loss of Purkinje cells, have a generalized deficit in DMTP performance that is probably associated with their motor impairment. Finally, we found that Lc/+<->+/+ chimeric mice, as a group, did not differ from control mice in this task. Rather, surprisingly, analysis of their total Purkinje cells and performance in the DMTP task revealed a significant negative relationship between these two variables. Together, these findings indicate that the cerebellum plays a minor or indirect role in spatial working memory.

The cerebellum and spatial ability: dissection of motor and cognitive components with a mouse model system

The cerebellum has recently been linked to spatial navigation, as indicated by the inferior performance of cerebellar mutant or cerebellar lesioned animals in the water maze. The inability to dissociate motor from cognitive deficits in the impaired water maze performance has been a confounding variable in previous studies, however. In this study, we sought to define clearly the role of the cerebellar system in spatial navigation outside of motor control by creating a mouse model of Purkinje cell loss with intact motor ability, and testing these mice in the water maze. To this end, we made aggregation chimeras between Lc/+ mice, which lose all Purkinje cells postnatally, and +/+ control mice. Lc/+ mice are ataxic and show impaired rotor-rod performance. By contrast, we show that Lc/+ left arrow over right arrow +/+ chimeras above a threshold of Purkinje cell loss show no outward signs of motor impairment and demonstrated normal rotor-rod ability. In the water maze, we found that Lc/+ mice showed impaired performance in the place, cue and platform removal tasks, whereas Lc/+ left arrow over right arrow +/+ chimeras performed similarly to controls in all tasks. We found that the impaired performance in the water maze of Lc/+ mice resulted from both motor as well as cognitive impairment that could be separated from one another by statistical means. In addition, through the analysis of individual chimeric mice, the relationships between these deficits and the total number of Purkinje cells were determined and a specific role for Purkinje cells in search strategy was identified.

Cyclooxygenase-2 (COX-2), aromatase and breast cancer: a possible role for COX-2 inhibitors in breast cancer chemoprevention

Interest in chemoprevention in oncology using suppressants of prostaglandin (PG) synthesis has been stimulated by epidemiological observations that the use of aspirin and other non-steroidal inflammatory drugs (NSAIDs) is associated with reduced incidence of some cancers, including cancer of the breast. The main target of NSAID activity is the cyclooxygenase (COX) enzyme. Two isoforms of COX have been identified: COX-1, the constitutive isoform; and COX-2. the inducible form of the enzyme. COX-2 can undergo rapid induction in response to many factors such as bacterial lipopolysaccharides, growth factors, cytokines and phorbol esters. COX-2 is overexpressed in some malignancies including carcinoma of the breast. It has been suggested that such enhanced expression may lead to increased angiogenesis such that the inhibition of COX-2 might have a general anticancer effect via decreased blood vessel formation. In addition, an association between COX-2, its main product PGE2 and aromatase activity in human breast cancer suggests that such inhibitors might have an additional, specific prophylactic mechanism for this tumour. New COX-2 inhibitors are already licensed for use in the treatment of arthritis and are well tolerated. Their potential role in chemoprevention of mammary carcinogenesis in rats has already been investigated. What remains to be seen is if these findings can be extrapolated to human studies.

Dioxygen-dependent metabolism of nitric oxide in mammalian cells

Steady-state gradients of NO within tissues and cells are controlled by rates of NO synthesis, diffusion, and decomposition. Mammalian cells and tissues actively decompose NO. Of several cell lines examined, the human colon CaCo-2 cell produces the most robust NO consumption activity. Cellular NO metabolism is mostly O2-dependent, produces near stoichiometric NO3-, and is inhibited by the heme poisons CN-, CO (K(I) approximately 3 microM), phenylhydrazine, and NO and the flavoenzyme inhibitor diphenylene iodonium. NO consumption is saturable by O2 and NO and shows apparent K(M) values for O2 and NO of 17 and 0.2 microM, respectively. Mitochondrial respiration, O2*-, and H2O2 are neither sufficient nor necessary for O2-dependent NO metabolism by cells. The existence of an efficient mammalian heme and flavin-dependent NO dioxygenase is suggested. NO dioxygenation protects the NO-sensitive aconitases, cytochrome c oxidase, and cellular respiration from inhibition, and may serve a dual function in cells by limiting NO toxicity and by spatially coupling NO and O2 gradients.

Heterogeneous susceptibility of GABA(A) receptor-mediated IPSCs to depolarization-induced suppression of inhibition in rat hippocampus

Depolarization-induced suppression of inhibition (DSI) in central neurons is mediated by a transient reduction of [gamma]-aminobutyric acid (GABA) release from interneurons. DSI is induced by a retrograde signal emitted from principal cells. We used electrophysiological recordings from CA1 neurons of the rat hippocampal slice to test the hypothesis that only certain classes of interneurons are susceptible to DSI. DSI of action potential-dependent, spontaneous, inhibitory postsynaptic currents (sIPSCs) in hippocampus is facilitated by carbachol (3 microM), which increases the occurrence of large sIPSCs. Besides carbachol, noradrenaline (norepinephrine; 10 microM), or elevated extracellular potassium (8 mM), could abruptly increase the occurrence of large sIPSCs and DSI in many cases. DSI appeared and disappeared concomitantly with the onset and offset of these large sIPSCs. In contrast, application of AP-5 and CNQX often markedly increased baseline sIPSC activity without enhancing DSI. A brief train of extracellular electrical stimulation could trigger the onset of prolonged, repetitive IPSC activity that was susceptible to DSI. The magnitude of DSI of single evoked IPSCs (eIPSCs) in a given pyramidal cell could be altered by changes in stimulus strength, but there was no simple relationship between stimulus strength and DSI. Baclofen (0.5-5 microM) eliminated the increase in sIPSC activity and DSI induced by carbachol. A GABA(B)receptor antagonist, CGP 35348, reversed the effects of baclofen. Carbachol-induced sIPSCs had relatively rapid rise and decay phases. There was no marked distinction between DSI-susceptible and non-susceptible sIPSCs. Nevertheless, two kinetically distinct components of the eIPSC could be distinguished by their decay times. DSI reduced GABA(A),(fast) without affecting GABA(A),(slow). Furosemide (frusemide), which blocks only GABA(A),(fast), reduced the eIPSC and occluded DSI. The data suggest that, with respect to DSI, there are at least three functionally distinct types of IPSCs. Two types (one susceptible to DSI and one not) have relatively rapid kinetics are probably made by perisomatic synapses. A third, slow IPSC, which is insensitive to DSI, may be produced by distal dendritic synapses.

Molecular identification of a TTX-sensitive Ca(2+) current

The TTX-sensitive Ca(2+) current [I(Ca(TTX))] observed in cardiac myocytes under Na(+)-free conditions was investigated using patch-clamp and Ca(2+)-imaging methods. Cs(+) and Ca(2+) were found to contribute to I(Ca(TTX)), but TEA(+) and N-methyl-D-glucamine (NMDG(+)) did not. HEK-293 cells transfected with cardiac Na(+) channels exhibited a current that resembled I(Ca(TTX)) in cardiac myocytes with regard to voltage dependence, inactivation kinetics, and ion selectivity, suggesting that the cardiac Na(+) channel itself gives rise to I(Ca(TTX)). Furthermore, repeated activation of I(Ca(TTX)) led to a 60% increase in intracellular Ca(2+) concentration, confirming Ca(2+) entry through this current. Ba(2+) permeation of I(Ca(TTX)), reported by others, did not occur in rat myocytes or in HEK-293 cells expressing cardiac Na(+) channels under our experimental conditions. The report of block of I(Ca(TTX)) in guinea pig heart by mibefradil (10 microM) was supported in transfected HEK-293 cells, but Na(+) current was also blocked (half-block at 0.45 microM). We conclude that I(Ca(TTX)) reflects current through cardiac Na(+) channels in Na(+)-free (or "null") conditions. We suggest that the current be renamed I(Na(null)) to more accurately reflect the molecular identity of the channel and the conditions needed for its activation. The relationship between I(Na(null)) and Ca(2+) flux through slip-mode conductance of cardiac Na(+) channels is discussed in the context of ion channel biophysics and "permeation plasticity."

Demonstration of scrotal disease on bone scintigraphy

The identification of scrotal disease on a bone scan is reportedly rare. Most previous reports involve abnormally increased accumulation of radioisotope in the scrotal region. This article includes a compilation of three cases of incidental scrotal photopenic defects on bone scintigraphy and a brief review of the literature.

Nitric-oxide dioxygenase activity and function of flavohemoglobins. sensitivity to nitric oxide and carbon monoxide inhibition

Widely distributed flavohemoglobins (flavoHbs) function as NO dioxygenases and confer upon cells a resistance to NO toxicity. FlavoHbs from Saccharomyces cerevisiae, Alcaligenes eutrophus, and Escherichia coli share similar spectra, O(2), NO, and CO binding kinetics, and steady-state NO dioxygenation kinetics. Turnover numbers (V(max)) for S. cerevisiae, A. eutrophus, and E. coli flavoHbs are 112, 290, and 365 NO heme(-1) s(-1), respectively, at 37 degrees C with 200 microm O(2). The K(M) values for NO are low and range from 0.1 to 0.25 microm. V(max)/K(M)(NO) ratios of 900-2900 microm(-1) s(-1) indicate an extremely efficient dioxygenation mechanism. Approximate K(M) values for O(2) range from 60 to 90 microm. NO inhibits the dioxygenases at NO:O(2) ratios of > or =1:100 and makes true K(M)(O(2)) values difficult to determine. High and roughly equal second order rate constants for O(2) and NO association with the reduced flavoHbs (17-50 microm(-1) s(-1)) and small NO dissociation rate constants suggest that NO inhibits the dioxygenase reaction by forming inactive flavoHbNO complexes. Carbon monoxide also binds reduced flavoHbs with high affinity and competitively inhibits NO dioxygenases with respect to O(2) (K(I)(CO) = approximately 1 microm). These results suggest that flavoHbs and related hemoglobins evolved as NO detoxifying components of nitrogen metabolism capable of discriminating O(2) from inhibitory NO and CO.

Oncological applications of gene therapy

Despite the rapid technological advances that continue to sustain the field of cancer gene therapy, few individual patients have benefited from the revolution so far. The plethora of clinical trials described confirms that each malignancy will have its own ideal strategy based on the associated molecular defects, and there has been rapid progress from this viewpoint. At the same time, there has been a renewed appreciation for the limitations to gene therapy, which include low efficiency of gene transfer, poor specificity of response and methods to accurately evaluate responses, and lack of truly tumor-specific targets at which to aim. As with all new therapies, we are climbing a steep learning curve in terms encountering treatment-related toxicities, as well as profound ethical and regulatory issues.

Gene therapy: recent progress in the clinical oncology arena

Despite the rapid technological advances that continue to sustain the field of cancer gene therapy, few individual patients have benefited from the revolution so far. The plethora of clinical trials described confirms that each malignancy will have its own ideal strategy based on the associated molecular defects, and there has been rapid progress from this viewpoint. At the same time, there has been a renewed appreciation for the limitations to gene therapy, which include low efficiency of gene transfer, poor specificity of response and methods to accurately evaluate responses, and lack of truly tumor-specific targets at which to aim. As with all new therapies, we are climbing a steep learning curve in terms encountering treatment-related toxicities, as well as profound ethical and regulatory issues.

Steady-state and transient kinetics of Escherichia coli nitric-oxide dioxygenase (flavohemoglobin). The B10 tyrosine hydroxyl is essential for dioxygen binding and catalysis

Escherichia coli expresses an inducible flavohemoglobin possessing robust NO dioxygenase activity. At 37 degrees C, the enzyme shows a maximal turnover number (V(max)) of 670 s(-1) and K(m) values for NADH, NO, and O(2) equal to 4.8, 0.28, and approximately 100 microM, respectively. Individual reduction, ligand binding, and NO dioxygenation reactions were examined at 20 degrees C, where V(max) is approximately 94 s(-1). Reduction by NADH occurs in two steps. NADH reduces bound FAD with a rate constant of approximately 15 microM(-1) s(-1), and heme iron is reduced by FADH(2) with a rate constant of 150 s(-1). Dioxygen binds tightly to reduced flavohemoglobin, with association and dissociation rate constants equal to 38 microM(-1) s(-1) and 0.44 s(-1), respectively, and the oxygenated flavohemoglobin dioxygenates NO to form nitrate. NO also binds reversibly to reduced flavohemoglobin in competition with O(2), dissociates slowly, and inhibits NO dioxygenase activity at [NO]/[O(2)] ratios of 1:100. Replacement of the heme pocket B10 tyrosine with phenylalanine increases the O(2) dissociation rate constant approximately 80-fold and reduces NO dioxygenase activity approximately 30-fold, demonstrating the importance of the tyrosine hydroxyl for O(2) affinity and NO scavenging activity. At 37 degrees C, V(max)/K(m)(NO) is 2,400 microM(-1) s(-1), demonstrating that the enzyme is extremely efficient at converting toxic NO into nitrate under physiological conditions.

Effectiveness of the Quick Medical Reference as a diagnostic tool

A number of computer-based systems with diagnostic capabilities have been developed for internal medicine. Quick Medical Reference (QMR) is one such program. The authors describe key features of QMR and report on their study of its effectiveness as a diagnostic tool. They investigated how frequently the correct diagnosis would appear among the 5 highest ranked diagnoses generated by QMR. The charts of 1144 consecutive patients admitted to a teaching unit were retrospectively screened. Eligible cases included those referred for investigation of an undiagnosed illness with an objectively proven final diagnosis (n = 154). Two physicians familiar with, but not experts in, the use of QMR entered clinical information abstracted from the patients' charts into the program. Physician A obtained the correct diagnosis in 62 (40%) of the 154 cases, and physician B was successful in 56 (36%) of the cases. The authors use study cases to illustrate QMR's strengths and weaknesses.

Muscarinic facilitation of the occurrence of depolarization-induced suppression of inhibition in rat hippocampus

Depolarization-induced suppression of inhibition is a transient decrease in GABAergic input to a hippocampal pyramidal cell following a brief depolarization of that cell. When recorded under whole-cell voltage clamp, monosynaptic, bicuculline-sensitive, GABA(A)-mediated currents are suppressed for a period lasting up to 1 min in response to a retrograde signal released by the pyramidal cell. The depolarization-induced suppression of inhibition process affects spontaneous, action-potential-dependent inhibitory postsynaptic currents, but suppression of these currents is seldom observed in the absence of carbachol, a cholinergic agonist. Because of the central roles played by cholinergic and GABAergic transmission in the regulation of hippocampal rhythmic activity, it will be important to understand the mechanism by which carbachol facilitates the appearance of depolarization-induced suppression of inhibition. As preliminary steps in the investigation of cholinergic actions on depolarization-induced suppression of inhibition, it is necessary to determine which cholinergic receptors are involved and the degree to which activation of these receptors is required for depolarization-induced suppression of inhibition. Nicotine did not mimic the effects of carbachol, and mecamylamine, a nicotinic receptor antagonist, did not block them. In contrast, the actions of carbachol were abolished by atropine and other muscarinic receptor antagonists. The actions of antagonists with relative selectivities for various subtypes of muscarinic receptors [4-diphenylacetoxy-N-methylpiperidine methiodide, pirenzepine, 11-([2-1-piperidinyl]acetyl)-5,11-dihydro-6H-pyrido[2,3-b][1,4]benzod iaz epine-6-one] suggested that cholinergic facilitation of the occurrence of depolarization-induced suppression of inhibition is likely to be mediated through muscarinic receptors of the M1 or M3 rather than M2 subtype. Despite its potent facilitation of the occurrence of depolarization-induced suppression of inhibition, muscarinic stimulation was not required for expression of depolarization-induced suppression of inhibition. Occasionally, depolarization-induced suppression of inhibition of spontaneous inhibitory postsynaptic currents occurred in the absence of carbachol and could not be blocked by atropine, and hence was not likely to be mediated by endogenous acetylcholine. Also, depolarization-induced suppression of inhibition of monosynaptically evoked inhibitory postsynaptic currents occurred without carbachol perfusion, and this was also insensitive to atropine. Therefore, the mechanism of depolarization-induced suppression of inhibition is not dependent on muscarinic receptor activation. Nevertheless, in vivo, septal cholinergic input to the hippocampus may provide the necessary activation of interneurons to allow depolarization-induced suppression of inhibition to occur.

Genetic prodrug activation therapy for breast cancer: A phase I clinical trial of erbB-2-directed suicide gene expression

PURPOSE

This trial was designed to test the safety and efficacy of a tumor-specific genetic prodrug activation therapy targeted by use of the human erbB-2 gene promoter. The erbB-2 oncogene is overexpressed in approximately 20% of cases of breast cancer and is associated with poor prognosis.

PATIENTS AND METHODS

Twelve breast cancer patients received transcriptionally targeted gene therapy in a phase I clinical trial using direct intratumoral injection of plasmid construct combined with systemic administration of prodrug. The genetic prodrug activation therapy is specifically targeted to erbB-2-overexpressing breast cancer cells by use of a therapeutic cassette that contains the Escherichia coli cytosine deaminase gene driven by the tumor-specific erbB-2 promoter, thus allowing activation of fluorocytosine to the active cytotoxic fluorouracil only within tumor cells that express the oncogene.

RESULTS

The approach was shown to be safe and to result in targeted gene expression in up to 90% of cases. Using a number of different assays, we demonstrated that significant levels of expression of the suicide gene were specifically restricted to erbB-2-positive tumor cells, confirming the selectivity of the approach.

CONCLUSION

The results of this study, the first targeted gene therapy for breast cancer and the first to use the cytosine deaminase system in human subjects, are encouraging for the development of genetic prodrug activation therapies that exploit the transcriptional profile of cancer cells.

Essentials of radiation oncology chart design

Medical Dosimetrists are commonly called upon to participate in the design of radiation oncology treatment records. The Medical Dosimetrist is uniquely qualified to provide input in the areas of treatment planning, simulation and delivery documentation. An idealized chart can facilitate the planning and delivery of quality patient care and lead the user to document such care. This publication outlines the essential minimum requirements for inclusion in a radiation oncology treatment chart. Conventional treatment record keeping has been by hard-copy documentation. Paperless treatment record models are presently being tested for efficacy. Either approach should seek to: maintain quality of patient care, enhance communication, and provide integrity in documentation.

Intravenous pharmacokinetics and absolute oral bioavailability of dolasetron in healthy volunteers: part 1

In this first part of a two-part investigation, the intravenous dose proportionality of dolasetron mesylate, a 5-HT3 receptor antagonist, and the absolute bioavailability of oral dolasetron mesylate were investigated. In an open-label, randomized, four-way crossover design, 24 healthy men between the ages of 19 and 45 years received the following doses: 50, 100, or 200 mg dolasetron mesylate administered by 10-min intravenous infusion or 200 mg dolasetron mesylate solution administered orally. Serial blood and urine samples were collected for 48 h after dosing. Following intravenous administration, dolasetron was rapidly eliminated from plasma, with a mean elimination half-life (t1/2) of less than 10 min. Dolasetron was rarely detected in plasma after oral administration of the 200 mg dose. Hydrodolasetron, the active primary metabolite of dolasetron, appeared rapidly in plasma following both oral and intravenous administration of dolasetron mesylate, with a mean time to maximum concentration (t(max)) of less than 1 h. The mean t1/2 of hydrodolasetron ranged from 6.6-8.8 h. The plasma area under the concentration-time curve (AUC0-infinity)) for both dolasetron and hydrodolasetron increased proportionally with dose over the intravenous dose range of 50-200 mg dolasetron mesylate. Approximately 29-33%) and 22% of the dose was excreted in urine as hydrodolasetron following intravenous and oral administration of dolasetron, respectively. For dolasetron as well as hydrodolasetron, mean systemic clearance (C1), volume of distribution (Vd), and t1/2 were similar at each dolasetron dose. The mean 'apparent' bioavailability of dolasetron calculated using plasma concentrations of hydrodolasetron was 76%. The R(+) enantiomer of hydrodolasetron represented the majority of drug in plasma (> 75%) and urine (> 86%). Dolasetron was well tolerated following both oral and intravenous administration.

Single- and multiple-dose pharmacokinetics of oral dolasetron and its active metabolites in healthy volunteers: part 2

The single- and multiple-dose pharmacokinetics and dose-proportionality of oral dolasetron and its active metabolites over the therapeutic dose range was investigated in 18 healthy men. In an open-label, randomized, complete three-way crossover design, each subject received three separate doses: 50, 100, and 200 mg doses of dolasetron mesylate solution given orally. Each dose was administered on the morning of Days 1 and 3-7 during each of the three treatment periods. Serial blood and urine samples were collected for 48 h after the first and last doses. Blood was analysed for dolasetron and hydrodolasetron concentrations; urine was analysed for dolasetron, the R(+) and S(-)-enantiomers of hydrodolasetron, and the 5'-hydroxy and 6'-hydroxy metabolites of hydrodolasetron. Dolasetron was rarely detected in plasma. Hydrodolasetron was formed rapidly, with a time to maximum concentration (t(max)) of less than 1 h. Steady-state conditions for hydrodolasetron were reached 2-3 days after starting once-daily dosing. Although statistical significance was found for hydrodolasetron AUC(0->infinity) and C(max) between dose groups after both single and multiple doses of dolasetron, the differences were small and unlikely to be of clinical significance. About 17-22% of the dose was excreted in urine as hydrodolasetron, with the majority (> 83%) as the R(+) enantiomer.

Development of a mouse model system, coding assignments and identification of the genome segments controlling virulence of African horse sickness virus serotypes 3 and 8

Attenuated (att) and wild type (wt) strains of the nine AHSV serotypes were evaluated for virulence in adult Balb C mice. Although most were avirulent in this system, isolates of AHSV 1att, 3wt, 3att, 4wt, 5att, 7att and 8att caused some mortality when administered via an intranasal route. After plaque cloning, only the attenuated vaccine strain of AHSV 7att caused any mortality via an intravenous route. AHSV 3att and AHSV 8wt were virulent (V) and avirulent (AV) (respectively) in the mouse model and were selected as parental strains for production of genome segment reassortants. These progeny virus strains were plaque cloned, then characterised to identify the genome segments that influence virulence of AHSV in the mouse model. Three virulence phenotypes were observed: fully virulent (V); fully avirulent (A); and a novel intermediate virulence (N) not expressed by either parental strain. Genome segment 2 (encoding outer capsid protein VP2) from the avirulent parent appeared to have a controlling influence in production of the A phenotype. Reassortants with the V phenotype all contained segment 2 from the virulent parent, however in each case they also contained genome segments 5 and 10, also from AHSV 3 (V). Genome segments 5 and 10 encode the smaller outer capsid protein VP5 and the non structural proteins NS3/NS3a, respectively. A combination of genome segments 2, 5 and 6 from the avirulent parent and segment 10 from the virulent parent were found in each of the virus strains with the N phenotype. However, comparison of two reassortants (A79 and A790), which differ only in a single segment, showed that replacement of genome segment 10 from the avirulent parent with that from the virulent parent, conferred the N phenotype on A790.

Phylogenetic analysis of African horse sickness virus segment 10: sequence variation, virulence characteristics and cell exit

African horse sickness virus (AHSV) genome segment 10 encodes the non-structural proteins NS3/NS3a, which is involved in release of virus from cells. Full length segment 10 cDNAs were amplified by reverse transcription-polymerase chain reaction, from isolates of AHSV serotypes 2, 3, 4, 5, 7, 8 and 9. These cDNAs were cloned, sequenced and their phylogenetic relationships analysed. High levels of sequence homology were detected in segment 10 from some isolates of different serotypes, confirming that they could be grouped on this basis (serotypes 4, 5, 6 and 9 (group alpha); serotypes 3 and 7 (group beta); serotypes 1, 2, and 8 (group gamma). However, data from bluetongue virus (the prototype orbivirus) indicate that the AHSV serotype is determined exclusively by the structural outer coat proteins VP2 and VP5, encoded by genome segments 2 and 5 respectively. Therefore, as a direct consequence of genome segment reassortment between AHSV strains from different serotypes, the differences observed in segment 10 do not give a reliable indication of virus serotype. Segment 10 of AHSV 3 (virulent) and AHSV 3att (attenuated) were also analysed. These strains, together with AHSV 8, have been used to study of the genetic basis of virulence using reassortment (O'Hara et al., this publication). Virus release studies, using Culicoides cell cultures, indicate that differences in segment 10 of AHSV 3att and 8 can influence the timing of virus release from the infected cell.

Nitric oxide dioxygenase: an enzymic function for flavohemoglobin

Nitric oxide (NO*) is a toxin, and various life forms appear to have evolved strategies for its detoxification. NO*-resistant mutants of Escherichia coli were isolated that rapidly consumed NO*. An NO*-converting activity was reconstituted in extracts that required NADPH, FAD, and O2, was cyanide-sensitive, and produced NO3-. This nitric oxide dioxygenase (NOD) contained 19 of 20 N-terminal amino acids identical to those of the E. coli flavohemoglobin. Furthermore, NOD activity was produced by the flavohemoglobin gene and was inducible by NO*. Flavohemoglobin/NOD-deficient mutants were also sensitive to growth inhibition by gaseous NO*. The results identify a function for the evolutionarily conserved flavohemoglobins and, moreover, suggest that NO* detoxification may be a more ancient function for the widely distributed hemoglobins, and associated methemoglobin reductases, than dioxygen transport and storage.

Use of transcriptional regulatory elements of the MUC1 and ERBB2 genes to drive tumour-selective expression of a prodrug activating enzyme

In order to exploit differences in gene expression between normal and malignant cells for genetic prodrug-activation therapy, we have generated recombinant retroviruses containing the herpes simplex virus thymidine kinase coding region cloned downstream of sequences derived from the 5'-flanking regions of the MUC1 and ERBB2 genes. Transduction with retroviruses containing MUC1 promoters resulted in an increase in GCV sensitivity in MUC1 positive cells. A further increase in GCV sensitivity was achieved when MUC1-positive cells were transduced with retroviruses containing chimeric-MUC1/ERBB2 promoters. No significant sensitization to GCV was observed when MUC1-negative cells were transduced with these recombinant retroviruses. These results suggest that one may be able to develop a tumour-selective therapy by utilizing the transcriptional regulatory regions of the MUC1 and ERBB2 genes to drive the expression of suicide genes.

Pharmacokinetics of dolasetron after oral and intravenous administration of dolasetron mesylate in healthy volunteers and patients with hepatic dysfunction

In previous studies, dolasetron was shown to have both renal and hepatic elimination mechanisms. This study was conducted to determine the impact of varying degrees of hepatic dysfunction on the pharmacokinetics and safety of dolasetron and its reduced metabolites. Seventeen adults were studied: six healthy volunteers (group I), seven patients with mild hepatic impairment (Child-Pugh class A; group II), and four patients with moderate to severe hepatic impairment (Child-Pugh class B or C1; group III). Single 150-mg doses of dolasetron mesylate were administered intravenously and orally, with a 7-day washout period separating treatments. After intravenous administration, no differences were observed between healthy volunteers and patients with hepatic impairment in maximum plasma concentration (Cmax), areas under the plasma concentration-time curve (AUC), or elimination half-life (t1/2) of intact dolasetron. No significant differences were found in Cmax, AUC, or apparent clearance (C(lapp)) of hydrodolasetron, the primary metabolite of dolasetron. The mean t1/2 increased from 6.87 hours in group I to 11.69 hours in group III. After oral administration, C(lapp) of hydrodolasetron decreased by 42%, and Cmax increased by 18% in patients with moderate to severe hepatic impairment. There were less changes in patients with mildly hepatic impairment. Total percentage of dose excreted as metabolites was similar for healthy volunteers and patients with hepatic impairment, although urinary metabolite profiles differed slightly. Dolasetron was well tolerated and there were no apparent differences in adverse effects between groups or treatments. Because hepatic impairment did not influence Cl(app) of hydrodolasetron after intravenous administration, and the range of plasma concentrations of hydrodolasetron after oral administration was not different from those observed in healthy volunteers, dosage adjustments are not recommended for patients with hepatic disease and normal renal function.

Neuropathic pain in cancer patients: mechanisms, syndromes, and clinical controversies

The identification of a neuropathic pain syndrome in a cancer patient requires a focused clinical evaluation based on knowledge of common neuropathic pain syndromes. If a tumor is directly involved in the etiology of the pain, oncologic treatment is an initial consideration and may include surgery, radiation, or chemotherapy. There is no single accepted algorithm for the analgesic treatment of neuropathic pain and a systematic approach utilizing therapeutic trials of specific agents at gradually increasing doses is warranted. A trial of opioids, perhaps in combination with an NSAID, is warranted. If the pain is relatively unresponsive to an opioid, a trial with an adjuvant analgesic is reasonable. For example, a tricyclic antidepressant might be selected early for patients with continuous dysesthesia, and early treatment with an anticonvulsant might be used if the pain is predominantly lancinating or paroxysmal. Other adjuvant analgesics can be selected if there is insufficient response to these agents. A trial of sympathetic blockade, pharmacologic, anesthetic or surgical, should be considered in patients with evidence of causalgia or reflex sympathetic dystrophy. Physiatric modalities such as massage, heat, or cold; counterstimulation or transcutaneous electrical nerve stimulation (TENS), and orthopedic interventions, such as braces and splints may be useful. Epidural injections or neurostimulation of the spinal cord or brain can be considered in selected cases where appropriate expertise is available. Treatment of neuropathic pain remains a challenge for both clinicians and patients. The complexity of syndromes and underlying etiologic mechanisms warrants further clinical trials to determine the best treatment modalities for individual pain syndromes.

N-ethylmaleimide blocks depolarization-induced suppression of inhibition and enhances GABA release in the rat hippocampal slice in vitro

Regulation of synaptic, GABAA receptor-mediated inhibition is a process of critical importance to normal brain function. Recently, we have described a phenomenon in hippocampus of a transient, yet marked, decrease in spontaneous, GABAA receptor-mediated IPSCs after depolarization activated Ca2+ influx into a pyramidal cell. This process, depolarization-induced suppression of inhibition (DSI), is absent in hippocampal cells that previously had been exposed to pertussis toxin in vivo, implicating a G-protein in the DSI process. To circumvent the problem that a single cell cannot be studied before and after G-protein block using the pertussis toxin pretreatment method, we have used the sulfhydryl alkylating agent N-ethylmaleimide (NEM), which blocks pertussis toxin-sensitive G-proteins, to determine whether acute inhibition of G-proteins can eliminate DSI of spontaneous IPSCs (sIPSCs). In whole-cell recordings from CA1 pyramidal cells that were first determined to express DSI, we have found that NEM does block DSI of sIPSCs. We also report that DSI of monosynaptic, evoked IPSCs is blocked by NEM, suggesting that a similar mechanism underlies both forms of DSI. It was of interest that DSI was abolished at a time when NEM had increased, not decreased, GABA transmission. Indeed, NEM greatly increased quantal GABA release by a Ca(2+)-independent mechanism, an observation with potentially important implications for understanding synaptic GABA release.

Retrograde signalling in depolarization-induced suppression of inhibition in rat hippocampal CA1 cells

1. We have investigated the phenomenon of 'depolarization-induced suppression of inhibition' (DSI) using whole-cell voltage-clamp techniques in Ca1 pyramidal cells of rat hippocampal slices. DSI was induced by eliciting voltage-dependent calcium (Ca2+) currents with 1 s voltage steps of +60 to +90 mV from the holding potential. DSI was apparent as a reduction in synaptic GABAA responses for a period of about 1 min following the voltage step. 2. TTX-sensitive spontaneous IPSCs (sIPSCs) were susceptible to DSI, while TTX-resistant miniature inhibitory postsynaptic current (mIPSCs) were not. Miniature IPSCs are ordinarily infrequent and independent of external Ca2+ in the CA1 region. To increase the frequency of mIPSCs and to induce a population of Ca(2+)-sensitive mIPSCs, we increased the bath K+ concentration to 15 mM. The increased mIPSCs were also insensitive to DSI, however. 3. T whole-cell pipette-filling solution contained 5 mM 2(triethylamino-N-(2,6-dimethyl-phenyl)acetamide (QX-314) to block voltage-dependent Na+ currents and caesium to block K+ currents. Nevertheless, bath application of 50 microM 4-aminopyridine (4-AP) or 250 nM veratridine both clearly reduced DSI, evidently by acting at presynaptic sites. 4. The amplitudes of monosynaptically evoked IPSCs (elicited in the presence of 10 microM 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 50 microM 2-amino-5-phosphonovaleric acid (APV)) were dramatically reduced during the DSI period. Weak stimulation produced small IPSCs and occasional 'failures' of transmission during the control period. The percentage of failures increased markedly during the DSI period. Moderate-intensity stimulation produced larger IPSCs that were often composed of distinguishable multiquantal components. All-or-none failures of multiquantal IPSC components also occurred during DSI. 5. The degree of paired-pulse IPSC depression did not change during DSI, whereas it was decreased, as expected, by baclofen. 6. We conclude that the data represent novel evidence that DSI is mediated by a retrograde signalling process possibly involving presynaptic axonal conduction block.

Direct cell killing by suicide genes

Cell death can be induced by genetic intervention in a variety of ways. We review genetic prodrug activation therapies using both mammalian and non-mammalian enzyme systems as well as the expression of toxin genes and apoptotic triggers. Targeting of the genetic intervention using both transductional restriction and transcriptional control elements is examined in both in vitro and in vivo systems, and the present state of clinical trials is reviewed.

NIRCA: a rapid robust method for screening for unknown point mutations

We describe a method for screening for dispersed point mutations, based on the observation that RNase frequently cleaves both strands of base pair mismatches in duplex RNA targets. The mismatched substrates are generated by in vitro transcription of wild-type and mutant templates amplified by the PCR or reverse transcription (RT)-PCR; bacteriophage promoters are incorporated into the PCR primers to permit both strands of the products to be transcribed into RNA. Complementary wild-type and mutant transcripts are hybridized and treated with RNase, and the cleavage products are separated on agarose gels and detected by visualization of the ethidium-stained sample under UV light. The method is thus non-isotopic, and since the cleavage products remain double-stranded during analysis, the labor-intensive RNase inactivation steps required in the original procedure can be eliminated. Also, nonspecific background cleavage is reduced so that longer target regions (1 kb) can be screened in a single step. The Non-Isotopic RNase Cleavage Assay (NIRCA) achieved a detection rate of 88%-90% in blind studies in a Factor IX model system, and it was also used to detect unknown p53 mutations in breast tumor samples. NIRCA provides a rapid method for sensitive, non-isotopic, high-throughput genetic screening.

MDL 201,307: a novel benzothiazepine modulator of multiple drug resistance

A series of novel benzothiazepine derivatives were evaluated for their relative potential to reverse multiple drug resistance (MDR) phenotype in vitro as well as for their relative cardiovascular activity and neurotoxicity. Compounds were evaluated for antiMDR activity using Chinese hamster ovary cells with derived resistance to either vincristine or doxorubicin, or a human lymphoblastic leukemia line with resistance to vinblastine. Lead compounds with good antiMDR activity were further evaluated for their relative potential to exhibit cardiovascular and neurological pharmacodynamic activity. A single compound, MDL 201,307 with good antiMDR activity and low cardiovascular and neurologic activity was chosen for further study. In contrast to (R)-verapamil, MDL 201,307 showed only a weak potential to block calcium channels. Using a series of related murine fibrosarcoma cell lines (UV-2237M) with varying levels of resistance to doxorubicin, it was shown that MDL 201,307 augmented inhibition of growth due to doxorubicin. The antiMDR compound was also effective in enhancing the cytotoxicity of actinomycin-D and vinblastine although it was ineffective in increasing cytotoxicity of the nonMDR compound, 5FU. MDL 201,307 increased uptake and decreased efflux of doxorubicin suggesting that MDL 201,307 blocks the GP170-mediated efflux pump mechanism. MDL 201,307 represents a novel antiMDR agent with diminished potential for cardiovascular activity and neurologic interactions which presently limit many of the currently available first and second generations of antiMDR compounds.

Dose-ranging evaluation of the antiemetic efficacy of intravenous dolasetron in patients receiving chemotherapy with doxorubicin or cyclophosphamide

Selective 5-HT3 antagonists have proven to be safe and effective for the prevention of chemotherapy-induced nausea and vomiting. Dolasetron is a new highly selective addition to this class of antiemetics that has been shown to have significant antiemetic activity in patients receiving cisplatin-containing regimens. This pilot study was designed to evaluate the antiemetic efficacy of dolasetron in cancer patients receiving doxorubicin and/or cyclophosphamide. This study used an open-label, non-randomized design to evaluate the efficacy and safety of intravenous dolasetron in the prevention of emesis in patients receiving doxorubicin (25-75 mg/m2) and/or cyclophosphamide (400-1200 mg/m2). Sixty-nine patients received a single, intravenous dose of dolasetron over 15-20 min beginning 30 min prior to the start of chemotherapy. Dose levels of dolasetron studied were: 0.3, 0.6, 1.2, 1.8 and 2.4 mg/kg. Patients were monitored for emesis, nausea and adverse events for 24h after the start of chemotherapy. Overall, 61% of patients experienced complete control of emesis. No significant trend towards increased antiemetic efficacy (P = 0.076) or nausea control with increasing dolasetron dose was noted, although the power to detect significant differences was limited by the small number of patients on the 0.3-mg/kg and 2.4-mg/kg dose levels. Age, gender, and type of chemotherapy were significant predictors of complete antiemetic control. Adverse events were generally mild and included headache, chills, lightheadedness, fever, diarrhea, dizziness, and asymptomatic prolongation of ECG intervals. Intravenous dolasetron is safe and effective in the prevention of emesis induced by doxorubicin and/or cyclophosphamide.

Your PC can enhance staff and patient education

Obtaining education materials for both staff and patients can be expensive. Tracking staff certification requirements and available references for individual units can be time consuming and awkward. Using a regular home personal computer and inexpensive software applications, the staff nurse, educator, and manager can produce quality education products, maintain records, and graph representation of administrative trends.

Influence of a sampling review process for radiation oncology quality assurance in cooperative group clinical trials--results of the Radiation Therapy Oncology Group (RTOG) analysis

The Radiation Therapy Oncology Group (RTOG) designed a random sampling process and observed its influence upon radiotherapy review mechanisms in cooperative group clinical trials. The method of sampling cases for review was modeled from sampling techniques commonly used in pharmaceutical quality assurance programs, and applied to the initial (on-study) review of protocol cases. 'In control' (IC) status is defined for a given facility as the ability to meet minimum compliance standards. Upon achieving IC status, activation of the sampling process was linked to the rate of continued patient accrual for each participating institution in a given protocol. The sampling design specified that > or = 30% cases not in compliance would be detected with 80% power. A total of 458 cases was analyzed for initial review findings in four RTOG Phase III protocols. Initial review findings were compared with retrospective (final) review results. Of the 458 cases analyzed, 370 underwent initial review at on-study, while 88 did not require review as they were enrolled from institutions that had demonstrated protocol compliance. In the group that had both initial and final review, 345/370 (93%) were found to have followed the protocol or had a minor variation. Of the exempted cases, 79/88 (90%) were found to be per protocol or a minor variant. The sampling process proved itself to be cost-effective and resulted in a noticeable reduction in the workload, thus providing an improved approach to resource allocation for the group. Continued evaluation of the sampling mechanism is appropriate as study designs and participants vary over time, and as more data become available to study.(ABSTRACT TRUNCATED AT 250 WORDS)