Continuous monitoring of lactate during exercise in humans using subcutaneous and transcutaneous microdialysis

We have evaluated the possibility of monitoring the plasma lactate concentration in human volunteers during cycle ergometer exercise using subcutaneous and transcutaneous microdialysis. In transcutaneous microdialysis, the relative increase in dialysate lactate concentration exceeded that of plasma lactate concentration by a factor of 6 during exercise due to exercise-induced lactate secretion in sweat. During exercise the subcutaneous microdialysis dialysate lactate concentration underestimated the plasma lactate concentration possibly due to diffusion limitation or adipose tissue lactate production. While it was demonstrated that microdialysis can be used for on-line lactate monitoring, neither subcutaneous nor transcutaneous dialysate lactate concentration were linearly related to the plasma lactate concentration during exercise, and it was found therefore that it was not possible to monitor directly plasma lactate concentration during exercise.     

Histoplasma capsulatum peritonitis associated with continuous ambulatory peritoneal dialysis

This paper reports a case of infection byHistoplasma capsulatum apparently restricted to the peritoneum in a woman submitted to continuous ambulatory peritoneal dialysis. Diagnosis was established by culture of dialysis fluid and peritoneal nodule and by histopathologic examination.     

Serotonergic Regulation of Acetylcholine Release in Rat Frontal Cortex

Abstract: The extent to which serotonin regulates the activity of cortically projecting cholinergic neurons was studied using in vivo microdialysis to monitor interstitial concentrations of acetylcholine in the frontal cortex of freely moving rats. Systemic administration of the serotonin release-inducing agent fenfluramine (3 or 10 mg/kg, i.p.) increased acetylcholine release by 110–130%. The fenfluramine-induced increase in acetylcholine release was significantly attenuated by pretreatment with the selective serotonin uptake inhibitor fluoxetine (10 mg/kg, i.p.). Pretreatment with the selective dopamine D₁ receptor antagonist SCH-23390 (0.3 mg/kg, s.c.) failed to prevent the fenfluramine-induced increase in acetylcholine release. In contrast, the serotonin 5-HT_2A receptor antagonist ketanserin (5 mg/kg, i.p.) blocked fenfluramine-induced increases in acetylcholine release. In contrast to previous studies that have concluded that serotonin has inhibitory actions on cortical acetylcholine release, the present results indicate that fenfluramine increases cortical acetylcholine release in vivo by its ability to enhance serotonin transmission and that serotonin produces these effects at least in part via actions at serotonin 5-HT_2A receptors.     

脑内微透析采样技术及其在神经科学中的应用

作为一种新的在体化学采样技术,脑内微透析引起了神经科学家的关注。它与迅速发展起来的高灵敏度的微量分析技术相结合,实现了对体内细胞外环境中化学物质变化的动态监测,从而在神经科学领域获得应用。本系统地介绍了这一新技术的原理和方法,并扼要地介绍了一这一技术在神经科学中的应用及其取得的新进展,并结合本实验室的工作经验,对该技术存在的一些问题进行了讨论。     

Differences in the In Vitro and In Vivo 5-Hydroxytryptamine Extraction Performance Among Three Common Microdialysis Membranes

The present study summarizes the results of an in vitro and in vivo comparison of the apparent 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid, and 3,4-dihydroxyphenylacetic acid dialysis performance of three types of membrane frequently used in intracerebral microdialysis experiments. The dialysis fiber types examined were a regenerated cellulose Cuprophan (GF), a proprietary polycarbonate ether (CMA), and a polyacrylonitrile/sodium methallylsulfonate copolymer (HOSPAL). The experiments unexpectedly revealed that the HOSPAL membrane-equipped probes displayed clearly aberrant 5-HT diffusion dynamics compared with GF and CMA probes, demonstrable not only in vitro, but also in in vivo experiments. In vitro, the GF and CMA membrane-equipped probes exhibited maximum relative recovery for 5-HT already in the first 20-min sample, whereas the 5-HT recovery of HOSPAL probes increased in a very slow and protracted manner over a period of a little less than 2 h. The GF and CMA probes further displayed an immediate washout of 5-HT when the probes were subsequently transferred to artificial CSF only-containing medium (no 5-HT), whereas approximately 2 h was required to yield near-total extinction of dialysate 5-HT with the standard HOSPAL probes. In vivo, the rat ventral hippocampal dialysate 5-HT output responses to K+ (100 mM) infusion, to Ca2+ omission, and to systemic 8-hydroxy-2-(di-n-propylamino)tetralin injection were all markedly retarded and blunted when HOSPAL instead of GF membrane-equipped probes were used. However, the 5-hydroxyindoleacetic acid and 3,4-dihydroxyphenylacetic acid extraction in vitro and in vivo were comparable using either of the membrane types.(ABSTRACT TRUNCATED AT 250 WORDS)     

Factor scoring models of the Pittsburgh Sleep Quality Index: a comparative confirmatory factor analysis

The Pittsburgh Sleep Quality Index (PSQI) is a rigorously validated questionnaire with extensive use in sleep assessment. Findings from numerous factor analytic studies of the PSQI have been interpreted to support a heterogeneous factor structure model for the test. Nevertheless, the literature continues to lack a focused evaluation of whether this heterogeneous factor structure is justified. A consideration of this issue led to a conclusion that a closer analysis of the PSQI’s factor structure was merited. To address this need a comparative confirmatory factor analysis for assessing the performance of the accepted factors models of the PSQI was conducted. A sample of university students (n = 418), age = 20.92 ± 1.81 years, BMI = 23.30 ± 2.57 kg/m² completed the multi-structured sleep survey at Jamia Millia Islamia, New Delhi, India. Seventeen putative factor structures (three 1-Factor, eight 2-Factor, and six 3-Factor) of the PSQI from the existing literature were selected for analysis. Fourteen models (82.35%) had almost similar values for model fit indices. Two models were misfits, and one model was a poor fit. The two misfit models incorporated gender and age as covariates. The third poor fit model was used to produce a unique path diagram, which made it distinct from the remaining 16 models. The overlapping values in the fit range of the model fit indices did not support the often projected heterogeneous factor structures of the PSQI for the vast majority of the models.     

The impact of rate heterogeneity on inference of phylogenetic models of trait evolution

Rates of trait evolution are known to vary across phylogenies; however, standard evolutionary models assume a homogeneous process of trait change. These simple methods are widely applied in small‐scale phylogenetic studies, whereas models of rate heterogeneity are not, so the prevalence and patterns of potential rate variation in groups up to hundreds of species remain unclear. The extent to which trait evolution is modelled accurately on a given phylogeny is also largely unknown because studies typically lack absolute model fit tests. We investigated these issues by applying both rate‐static and variable‐rates methods on (i) body mass data for 88 avian clades of 10–318 species, and (ii) data simulated under a range of rate‐heterogeneity scenarios. Our results show that rate heterogeneity is present across small‐scaled avian clades, and consequently applying only standard single‐process models prompts inaccurate inferences about the generating evolutionary process. Specifically, these approaches underestimate rate variation, and systematically mislabel temporal trends in trait evolution. Conversely, variable‐rates approaches have superior relative fit (they are the best model) and absolute fit (they describe the data well). We show that rate changes such as single internal branch variations, rate decreases and early bursts are hard to detect, even by variable‐rates models. We also use recently developed absolute adequacy tests to highlight misleading conclusions based on relative fit alone (e.g. a consistent preference for constrained evolution when isolated terminal branch rate increases are present). This work highlights the potential for robust inferences about trait evolution when fitting flexible models in conjunction with tests for absolute model fit.     

腹膜透析病人的预后影响因素

在我国,终末期肾脏病的发病率逐年增加,相应地,腹膜透析病人的数量也在不断增长。明确腹膜透析病人预后的影响因素是临床医师亟待解决的重要课题。尿毒症毒素的积蓄可对腹膜透析病人的心血管系统产生不良作用,影响病人的生活质量。腹膜透析充分性的相关指标对于预测病人的生存率也有一定的指导意义。此外,腹膜炎的发生可使超滤量明显下降,增加病人的死亡率。合并症可能通过加重病人的营养不良状态、促进炎症水平,影响病人的预后。因此,重视病人的尿毒症毒素水平、透析充分性指标与合并症情况,积极防治腹膜炎,将有助于改善腹膜透析病人的预后。     

DNA aqueous solution used for dialytical removal and enrichment of dioxin derivatives

In the present study, a dialytic method that uses a DNA aqueous solution to remove and enrich dioxins from polluted water was proposed. Circular dichroism (CD) and fluorescent spectra indicated that dibenzo-p-dioxin (DD), dibenzofuran (DF) and biphenyl (BP), which are dioxin derivatives, form complexes with DNA. Their experimental dialytic sorption coefficients were measured by quantifying the concentrations of DD, DF, and BP in aqueous solutions before and after dialysis of the DNA solution, and the values were 2.1×10⁵, 1.3×10⁵, and 1.5×10⁷, respectively. As a simulated water treatment model, DNA solution was dialyzed in an aqueous mixture of DD, DF, and BP for 96 h, the HPLC studies showed that the dioxin derivatives have been concentrated in the DNA solution about 200 times. The dialyzed DNA solution was reusable by an extraction with hexane.     

A dialysis system with phytoplankton for monitoring chemical pollution in freshwater ecosystems by alkaline phosphatase assay

The effects of three groups of chemicals, heavy metals, pesticides and phenolics, on alkaline phosphatase activity of intact Chlorella vulgaris cells were investigated. There was a marked inhibitory effect of heavy metals and a slight one due to phenolics, but the pesticides tested showed no effect. In order to detect heavy metals in freshwater ecosystems, we propose a dialysis system, which can be placed in the field and then provide early warning signals of toxicity. This phosphatase inhibition test is recommended the first stage of an enzymatic screening system for chemical pollution in water.