Stronger Neural Modulation by Visual Motion Intensity in Autism Spectrum Disorders

Theories of autism spectrum disorders (ASD) have focused on altered perceptual integration of sensory features as a possible core deficit. Yet, there is little understanding of the neuronal processing of elementary sensory features in ASD. For typically developed individuals, we previously established a direct link between frequency-specific neural activity and the intensity of a specific sensory feature: Gamma-band activity in the visual cortex increased approximately linearly with the strength of visual motion. Using magnetoencephalography (MEG), we investigated whether in individuals with ASD neural activity reflect the coherence, and thus intensity, of visual motion in a similar fashion. Thirteen adult participants with ASD and 14 control participants performed a motion direction discrimination task with increasing levels of motion coherence. A polynomial regression analysis revealed that gamma-band power increased significantly stronger with motion coherence in ASD compared to controls, suggesting excessive visual activation with increasing stimulus intensity originating from motion-responsive visual areas V3, V6 and hMT/V5. Enhanced neural responses with increasing stimulus intensity suggest an enhanced response gain in ASD. Response gain is controlled by excitatory-inhibitory interactions, which also drive high-frequency oscillations in the gamma-band. Thus, our data suggest that a disturbed excitatory-inhibitory balance underlies enhanced neural responses to coherent motion in ASD.     

A rapid method for the isolation of L-cell surface membranes using an aqueous two-phase polymer system

Summary A dextran-polythylene glycol aqueous two-phase system has been used to separate cell surface membranes from other cellular organelles. The surface membranes have been identified on the basis of morphology, content of Na⁺, K⁺-ATPase, and presence of surface antigen as detected by a⁵¹Cr release method. Contamination of the surface membrane preparations by smooth endoplasmic reticulum, mitochondria, and nuclei has been found to be minimal. An average of 6.5% of the total protein was found in the membrane fraction. Less than two hours is required to isolate the membrane fraction after preparation of a Dounce homogenate. Fractionation by aqueous two-phase polymer systems appears to be a rapid and effective method for the isolation of surface membranes.     

A Simple Method for Testing Monthly Statistical Rates for Normalization

The spectral analysis of birth statistics, expressed in monthly rates, shows a strong periodic component even if a single child is born every day of the year. This is, of course, due to the different number of days per month. Most human or animal statistics as well as agricultural and biometeorological variables are only available as monthly, and not daily rates or values. If spectral components of time series are of interest, it is necessary to normalize monthly rates. This necessity has been a pre-analytical routine for quite some time, and various methods of normalization are described in the literature (1,3,7): the rates are either expressed as the daily mean within a month or as rates of normalized months with 31, 30 or 30.4 days (the latter results in a 365-day year). Each of the different methods leads to the same result, if the analysis can be based on relative deviations from the mean.

In the majority of the statistical material, the chosen method of normalization is clearly stated. But if a study tries to cover many different statistical populations and as many years as possible, the statistical material is often based on several (partly secondary) sources and photocopied extracts from large volumes. This can lead to confusion whether the used statistics contain normalized or crude original monthly rates.     

Inhibition of platelet activation by 2-mercaptopropionylglycin in vitro and in vivo

2-mercaptopropionylglycin (2-MPG), a cell membrane penetrating thiol, was evaluated for its antithrombotic potential using in vitro and in vivo tests. 2-MPG was found to inhibit agonist-induced platelet aggregation and serotonin release as well as prostaglandin/thromboxane synthesis in platelet-rich plasma. Administration of 2-MPG to rats resulted in an inhibition of laser-induced thrombus formation in mesenteric vessels. When plasma was incubated with 2-MPG and then used for determination of various standard coagulation parameters, significant prolongation of the clotting times were observed.     

Effect of diamide (azodicarboxylic acid-bis-dimethylamide) on arachidonic acid release from human blood platelet phospholipids

It was found that the thiol-oxidizing agent diamide inhibits the formation of arachidonic acid metabolites in thrombin-stimulated platelets. An inhibition of arachidonic acid release from membrane phospholipids in diamide-treated platelets is concluded since diamide does not diminish the formation of stable metabolites from exogenous arachidonic acid. The role of the cellular thiol-disulfide status for the activities of phospholipases involved in arachidonic acid release is discussed.