Unravelling developmental disregard in children with unilateral cerebral palsy by measuring event-related potentials during a simple and complex task

Background

In a subset of children with unilateral Cerebral Palsy (CP) a discrepancy between capacity and performance of the affected upper limb can be observed. This discrepancy is known as Developmental Disregard (DD). Though the phenomenon of DD has been well documented, its underlying cause is still under debate. DD has originally been explained based on principles of operant conditioning. Alternatively, it has been proposed that DD results from a diminished automaticity of movements, resulting in an increased cognitive load when using the affected hand. To investigate the amount of involved cognitive load we studied Event-Related Potentials (ERPs) preceding task-related motor responses during a single-hand capacity and a dual-hand performance task. It was hypothesised that children with DD show alterations related to long-latency ERP components when selecting a response with the affected upper limb, reflecting increased cognitive load in order to generate an adequate response and especially so within the dual-hand task.

Methods

Fifteen children with unilateral CP participated in the study. One of the participants was excluded due to major visual impairments. Seven of the remaining participants displayed DD. The other seven children served as a control group. All participants performed two versions of a cue-target paradigm, a single-hand capacity and a dual-hand performance task. The ERP components linked to target presentation were inspected: the mid-latency P2 component and the consecutive long-latency N2b component.

Results

In the dual-hand performance task children with DD showed an enhancement in mean amplitude of the long-latency N2b component when selecting a response with their affected hand. No differences were found regarding the amplitude of the mid-latency P2 component. No differences were observed regarding the single-hand capacity task. The control group did not display any differences in ERPs linked to target evaluation processes between both hands.

Conclusion

These electrophysiological findings show that DD is associated with increased cognitive load when movements are prepared with the affected hand during a dual-hand performance task. These findings confirm behavioural observations, advance our insights on the neural substrate of DD and have implications for therapy.     

The substrate radical of Escherichia coli oxygen-independent coproporphyrinogen III oxidase HemN

During porphyrin biosynthesis the oxygen-independent coproporphyrinogen III oxidase (HemN) catalyzes the oxidative decarboxylation of the propionate side chains of rings A and B of coproporphyrinogen III to form protoporphyrinogen IX. The enzyme utilizes a 5'-deoxyadenosyl radical to initiate the decarboxylation reaction, and it has been proposed that this occurs by stereo-specific abstraction of the pro-S-hydrogen atom at the beta-position of the propionate side chains leading to a substrate radical. Here we provide EPR-spectroscopic evidence for intermediacy of the latter radical by observation of an organic radical EPR signal in reduced HemN upon addition of S-adenosyl-L-methionine and the substrate coproporphyrinogen III. This signal (g(av) = 2.0029) shows a complex pattern of well resolved hyperfine splittings from at least five different hydrogen atoms. The radical was characterized using regiospecifically labeled (deuterium or 15N) coproporphyrinogen III molecules. They had been generated from a multienzyme mixture and served as efficient substrates. Reaction of HemN with coproporphyrinogen III, perdeuterated except for the methyl groups, led to the complete loss of resolved proton hyperfine splittings. Substrates in which the hydrogens at both alpha- and beta-positions, or only at the beta-positions of the propionate side chains, or those of the methylene bridges, were deuterated showed that there is coupling with hydrogens at the alpha-, beta-, and methylene bridge positions. Deuterium or 15N labeling of the pyrrole nitrogens without labeling the side chains only led to a slight sharpening of the radical signal. Together, these observations clearly identified the radical signal as substrate-derived and indicated that, upon abstraction of the pro-S-hydrogen atom at the beta-position of the propionate side chain by the 5'-deoxyadenosyl radical, a comparatively stable delocalized substrate radical intermediate is formed in the absence of electron acceptors. The observed hyperfine constants and g values show that this coproporphyrinogenyl radical is allylic and encompasses carbon atoms 3', 3, and 4.     

A new combination of methods for the localization,identification, and three-dimensional reconstruction of the sensory endings of articular afferents characterized by electrophysiology

A combination of methods is described to identify and reconstruct corpuscular and non-corpuscular sensory endings of group II and group III nerve fibers following functional examination by electrophysiology. Afferent units activated by electrical stimulation of the medial articular nerve of the cat's knee were analyzed by single fiber recordings and characterized by their responsiveness to mechanical stimuli. The receptive fields of the units were closely demarcated by fine needles when the responses elicited by insertion of the needles were being recorded. After fixation, the tissue around the demarcated field was dissected and histologically processed. Series of semithin sections were cut from the embedded tissue blocks containing the receptive fields. Corpuscular endings of group II fibers and peripheral myelinated group III nerve fibers, presumably corresponding to the characterized units, were identified by light microscopy of semithin sections and localized within the demarcated area. Non-corpuscular endings were identified by electron microscopy of ultrathin sections cut in alternation with, or after re-embedding of, semithin sections. Morphometric analysis of ultrathin section series allowed the measurement of parameters such as the mean axon diameter and the organelle content of the sensory endings. The methods described are appropriate for collecting data that correlate the structural and functional characteristics of sensory endings in deep tissues.     

The stress responsive and morphologically regulated <Emphasis Type="Italic">hsp90</Emphasis> gene from <Emphasis Type="Italic">Paracoccidioides brasiliensis</Emphasis> is essential to cell viability

Background  

Paracoccidioides brasiliensis is a dimorphic fungus that causes the most prevalent systemic mycosis in Latin America. The response to heat shock is involved in pathogenesis, as this pathogen switches from mycelium to yeast forms in a temperature dependent fashion that is essential to establish infection. HSP90 is a molecular chaperone that helps in the folding and stabilization of selected polypeptides. HSP90 family members have been shown to present important roles in fungi, especially in the pathogenic species, as an immunodominant antigen and also as a potential antifungal therapeutic target.     

Effects of four different single exercise sessions on lipids, lipoproteins, and lipoprotein lipase

The purpose ofthis study was to determine the threshold of exercise energyexpenditure necessary to change blood lipid and lipoproteinconcentrations and lipoprotein lipase activity (LPLA) in healthy,trained men. On different days, 11 men (age, 26.7 ± 6.1 yr; bodyfat, 11.0 ± 1.5%) completed four separate, randomly assigned,submaximal treadmill sessions at 70% maximalO₂ consumption. During eachsession 800, 1,100, 1,300, or 1,500 kcal were expended. Compared withimmediately before exercise, high-density lipoprotein cholesterol(HDL-C) concentration was significantly elevated 24 h after exercise(P < 0.05) in the 1,100-, 1,300-, and 1,500-kcal sessions. HDL-C concentration was also elevated(P < 0.05) immediately after and 48 h after exercise in the 1,500-kcal session. Compared with values 24 hbefore exercise, LPLA wassignificantly greater (P < 0.05) 24 h after exercise in the 1,100-, 1,300-, and 1,500-kcal sessions andremained elevated 48 h after exercise in the 1,500-kcal session. Thesedata indicate that, in healthy, trained men, 1,100 kcal of energyexpenditure are necessary to elicit increased HDL-C concentrations.These HDL-C changes coincided with increased LPLA.

     

Calcium oscillation linked to pacemaking of interstitial cells of Cajal: requirement of calcium influx and localization of TRP4 in caveolae

Interstitial cells of Cajal (ICC) are considered to be pacemaker cells in gastrointestinal tracts. ICC generate electrical rhythmicity (dihydropyridine-insensitive) as slow waves and drive spontaneous contraction of smooth muscles. Although cytosolic Ca(2+) has been assumed to play a key role in pacemaking, Ca(2+) movements in ICC have not yet been examined in detail. In the present study, using cultured cell clusters isolated from mouse small intestine, we demonstrated Ca(2+) oscillations in ICC. Fluo-4 was loaded to the cell cluster, the relative amount of cytosolic Ca(2+) was recorded, and ICC were identified by c-Kit immunoreactivity. We specifically detected Ca(2+) oscillation in ICC in the presence of dihydropyridine, which abolishes Ca(2+) oscillation in smooth muscles. The oscillation was coupled to the electrical activity corresponding to slow waves, and it depended on Ca(2+) influx through a non-selective cation channel, which was SK&F 96365-sensitive and store-operated. We further demonstrated the presence of transient receptor potential-like channel 4 (TRP4) in caveolae of ICC. Taken together, the results infer that the Ca(2+) oscillation in ICC is intimately linked to the pacemaker function and depends on Ca(2+) influx mediated by TRP4.