Physiological role of neuropeptide Y in the regulation of the ascending phase of the peristaltic reflex

The physiological role of neuropeptide Y (NPY) and of specific NPY receptors in regulating the intestinal peristaltic reflex was examined in three-compartment flat-sheet preparations of rat colon. Graded muscle stretch or mucosal stimulation applied to the central compartment inhibited NPY release in the orad compartment where ascending contraction was measured. NPY and the Y1-receptor agonist [Leu31, Pro34]NPY inhibited, whereas the selective Y1-receptor antagonist BIBP 3226 augmented ascending contraction and substance P (SP) release in the orad compartment induced by muscle stretch or mucosal stimulation. Neither agonist nor antagonist had any effect on descending relaxation or VIP release in the caudad compartment. The Y2-receptor agonist NPY13-36 and antagonist BIIE 0246 had no effect on peptide release or mechanical response. The results indicate that suppression of a tonic inhibitory influence of NPY neurons on excitatory neurotransmitter release contributes substantially to the orad contractile phase of the peristaltic reflex. The effect of NPY on neurotransmitter release is mediated by Y1 receptors.     

Modulation of habit formation by levodopa in Parkinson's disease

Dopamine promotes the execution of positively reinforced actions, but its role for the formation of behaviour when feedback is unavailable remains open. To study this issue, the performance of treated/untreated patients with Parkinson's disease and controls was analysed in an implicit learning task, hypothesising dopamine-dependent adherence to hidden task rules. Sixteen patients on/off levodopa and fourteen healthy subjects engaged in a Go/NoGo paradigm comprising four equiprobable stimuli. One of the stimuli was defined as target which was first consistently preceded by one of the three non-target stimuli (conditioning), whereas this coupling was dissolved thereafter (deconditioning). Two task versions were presented: in a 'Go version', only the target cue required the execution of a button press, whereas non-target stimuli were not instructive of a response; in a 'NoGo version', only the target cue demanded the inhibition of the button press which was demanded upon any non-target stimulus. Levodopa influenced in which task version errors grew from conditioning to deconditioning: in unmedicated patients just as controls errors only rose in the NoGo version with an increase of incorrect responses to target cues. Contrarily, in medicated patients errors went up only in the Go version with an increase of response omissions to target cues. The error increases during deconditioning can be understood as a perpetuation of reaction tendencies acquired during conditioning. The levodopa-mediated modulation of this carry-over effect suggests that dopamine supports habit conditioning under the task demand of response execution, but dampens it when inhibition is required. However, other than in reinforcement learning, supporting dopaminergic actions referred to the most frequent, i. e., non-target behaviour. Since this is passive whenever selective actions are executed against an inactive background, dopaminergic treatment could in according scenarios contribute to passive behaviour in patients with Parkinson's disease.     

Sleep fragmentation in mentally retarded people decreases with increasing daylength in spring

We studied the sleep-wake behavior of mentally retarded people from late winter to early summer at 60 degrees N. During this time the daylength increased 8 h 51 min. The data were collected by observing the sleep-wake status of 293 subjects at 20-min intervals for five randomized 24h periods (= recording days). The intervals during which the individual recording days of the same order (1st, 2nd, etc.) were carried out, were called recording periods. Consequently, there were five recording periods, each containing 293 individual recording days. Even though there was overlap among the recording periods, the median daylength from one period to another increased approximately by 100 min. In the initial statistical analysis, the number of wake-sleep transitions was found to differ significantly among the five recording periods (Friedman test, p < 0.001). The mean ranks in the Friedman test suggested that the number of wake-sleep transitions was highest during the 1st and lowest during the 5th recording period. In further statistical analyses using a program for mixed effects regression analysis (MIXOR 2.0) it was found that the increase in daylength during the study period was associated with a simultaneous decrease of approximately 0.5 wake-sleep transitions in the whole study population (p < 0.001). The decrease in the number of wake-sleep transitions was significant only in the subgroups of subjects with a daylength change of more than 350 min between the 1st and 5th recording days (Wilcoxon tests, p < 0.005). This suggests that after a marked prolongation of the natural photoperiod, the reduction in sleep episodes was more probable than after smaller changes in daylength. It is concluded that the sleep of mentally retarded people living in a rehabilitation center at a northern latitude is more fragmented in winter than in early summer and that the change is related probably to the simultaneous increase in the length of the natural photoperiod. The sleep quality of persons living in institutional settings might be improved by increasing the intensity and/or duration of daily artificial light exposure during the darker seasons.     

Horizontal transmission of epizootic ulcerative syndrome (EUS)-associated virus in the snakehead Ophicephalus striatus under simulated natural conditions

Natural transmission of the epizootic ulcerative syndrome (EUS) was conducted on na?ve snakeheads Ophicephalus striatus (also known as Channa striata) kept (A) in aquifer water, (B) in lakewater, (C) cohabiting with EUS snakeheads in lakewater, and (D) cohabiting with apparently healthy snakeheads in lakewater during the 1994 to 1995 EUS season. The results showed that EUS-like lesions developed in 6 to 14 d among na?ve snakeheads cohabiting with EUS snakeheads and with apparently healthy snakeheads in lakewater (Treatments C and D). Among na?ve fish exposed to lakewater (Treatment B), similar lesions developed in 16 to 21 d, while na?ve fish in aquifer water (Treatment A) did not develop EUS-like lesions. EUS signs began as Grade I (slight) lesions that gradually progressed to Grades III-IV (severe) 3 to 5 d from lesion onset, similar to the naturally affected EUS fish. The virus was recovered from some but not all naturally EUS-affected snakeheads, snakeheads with healing lesions and apparently healthy snakeheads, but not from na?ve snakeheads. The results provide evidence of a waterborne horizontal transmission of the EUS-associated virus. This is the first report of a successful horizontal transmission of the EUS-associated virus from apparently healthy snakeheads to na?ve fish under natural conditions and of virus recovery in tissue culture from naturally exposed experimental fish.     

Coupling optical and electrical measurements in artificial membranes: Lateral diffusion of lipids and channel forming peptides in planar bilayers

Planar lipid bilayers (PLB) were prepared by the Montal-Mueller technique in a FRAP system designed to simultaneously measure conductivity across, and lateral diffusion of, the bilayer. In the first stage of the project the FRAP system was used to characterise the lateral dynamics of bilayer lipids with regards to phospholipid composition (headgroup, chain unsaturation etc.), presence of cholesterol and the effect of divalent cations on negatively-charged bilayers. In the second stage of the project, lateral diffusion of two fluorescently-labelled voltage-dependent pore-forming peptides (alamethicin and S4s from Shaker K⁺ channel) was determined at rest and in the conducting state. This study demonstrates the feasibility of such experiments with PLBs, amenable to physical constraints, and thus offers new opportunities for systematic studies of structure-function relationships in membrane-associating molecules.     

Inhibitory effects of orotate on precursor incorporation into nucleic acids.

The influence of orotic acid on the incorporation of precursors into nucleic acids was studied in mice and rats and in isolated cells. In vivo, orotate levels were modified by two diets which are known to increase the rate of pyrimidine nucleotide synthesis in rat liver. Of these diets, a 1% orotate diet had greater inhibitory effects than an arginine-deficient diet on the incorporation of [3H]orotate into RNA of mouse kidney than mouse liver. This contrasted with the situation in the rat where there was a greater effect in the liver than the kidney. The situation in the rat was more readily interpreted than in the mouse in terms of previously established effects of these diets on ribonucleotide pool sizes. However, studies using [3H]adenosine as a precursor for incorporation into RNA suggested that even in the mouse the effects of orotate were on pool sizes rather than an inhibitory effect on RNA synthesis. The incorporation of [3H]thymidine into DNA was inhibited by orotate to a similar degree in cultured HTC hepatoma cells and a line of rat liver epithelial cells. An effect on DNA synthesis rather than solely on pool sizes was suggested by the observation that the pool size of dTTP was not increased by 5 mM orotate under conditions in which there was a four-fold increase in the level of UTP in HTC cells. An inhibitory effect of orotate on DNA synthesis was further supported by an observation of decreased incorporation of [3H]deoxyadenosine into DNA and a lower rate of cellular proliferation.     

1-Thiazol-2-yl-N-3-methyl-1H-pyrozole-5-carboxylic acid derivatives as antitumor agents

A class of substituted 1-thiazol-2-yl-N-3-methyl-1H-pyrozole-5-carboxylic acid derivatives was found to have potent anti-proliferative activity against a broad range of tumor cell lines. A compound from this class (14) was profiled across a broad panel of hematologic and solid tumor cancer cell lines demonstrating cell cycle arrest at the G0/G1 interphase and has potent anti-proliferative activity against a distinct and select set of cancer cell types with no observed effects on normal human cells. An example is the selective inhibition of human B-cell lymphoma cell line (BJAB). Compound 14 was orally bioavailable and tolerated well in mice. Synthesis and structure activity relationships (SAR) in this series of compounds are discussed.     

Reliability of maternal-reports regarding the use of household pesticides: experience from a case-control study of childhood leukemia

Introduction: Self-reported household pesticide use has been associated with higher risk of childhood leukemia in a number of case–control studies. The aim of this study is to assess the reliability of self-reported household use of pesticides and potential differences in reliability by case–control status, and by socio-demographic characteristics. Methods: Analyses are based on a subset of the Northern California Childhood Leukemia Study population. Eligible households included those with children less than 8 years old who lived in the same residence since diagnosis (reference date for controls). The reliability was based on two repeated in-person interviews. Kappa, percent positive and negative agreements were used to assess reliability of responses to ever/never use of six pesticides categories. Results: Kappa statistics ranged from 0.31 to 0.61 (fair to substantial agreement), with 9 out of the 12 tests indicating moderate agreement. The percent positive agreement ranged from 46 to 80% and the percent negative agreement from 54 to 95%. Reliability for all pesticide types as assessed by the three reliability measures did not differ significantly for cases and controls as confirmed by bootstrap analysis. For most pesticide types, Kappa and percent positive agreement were higher for non-Hispanics than Hispanics and for households with higher income vs. lower income. Conclusions: Reproducibility of maternal-reported pesticide use was moderate to high and was similar among cases and controls suggesting that differential recall is not likely to be a major source of bias.     

Investigation of the terminal P4 domain in a series of D-phenylglycinamide-based factor Xa inhibitors

Several P4 domain derivatives of the general d-phenylglycinamide-based scaffold (2) were synthesized and evaluated for their ability to bind to the serine protease factor Xa. Some of the more potent compounds were evaluated for their anticoagulant effects in vitro. A select subset containing various P1 indole constructs was further evaluated for their pharmacokinetic properties after oral administration to rats.     

Multiclonal asymptomatic Plasmodium falciparum infections predict a reduced risk of malaria disease in a Tanzanian population

Protective immunity to malaria is acquired after repeated exposure to the polymorphic Plasmodium falciparum parasite. Whether the number of concurrent antigenically diverse clones in asymptomatic infections predicts the risk of subsequent clinical malaria needs further understanding. We assessed the diversity of P. falciparum infections by merozoite surface protein 2 genotyping in a longitudinal population based study in Tanzania. The number of clones was highest in children 6-10 years and in individuals with long time to previous anti-malarial treatment. Individual exposure, analysed by circumsporozoite protein antibody levels, was associated with parasite prevalence but not with the number of clones. The risk of subsequent clinical malaria in children free of acute disease or recent treatment was, compared to one clone, reduced in individuals with multiclonal infections or without detectable parasites, with the lowest hazard ratio 0.28 (95% confidence interval 0.10-0.78 Cox regression) for 2-3 clones. The number of clones was not associated with haemoglobin levels. A reduced risk of malaria in asymptomatic individuals with multiclonal persistent P. falciparum infections suggests that controlled maintenance of diverse infections is important for clinical protection in continuously exposed individuals, and needs to be considered in the design and evaluation of new malaria control strategies.