Differences between Han Chinese and Caucasians in transcranial magnetic stimulation parameters.

The study was conducted to investigate the difference between Han Chinese and Caucasians on various parameters measured from responses to transcranial magnetic brain stimulation (TMS). Sixteen subjects were studied in each group. A circular coil at the vertex was used for stimulation, whilst recording surface electromyograms from right first dorsal interosseous. In the passive state, motor-evoked potential (MEP) threshold, MEP recruitment, short-interval intracortical inhibition (SICI) and intracortical facilitation were measured. The MEP threshold, recruitment and silent period were also measured in the active state. Chinese subjects showed significantly higher passive thresholds (P < 0.005), less inhibition of the motor response (SICI, P < 0.0005) and a shorter silent period (P < 0.05). Differences in SICI appeared to be a consequence of the differences in passive threshold and were not seen when active threshold was used to determine the conditioning stimulus intensity. Differences in silent period may also reflect differences in cortical excitability rather than inhibitory processes, as they were not seen when the silent-period duration was expressed as a function of MEP size, rather than TMS intensity. There appears to be a significant difference in some TMS parameters between Han Chinese and Caucasian subjects. This may reflect an underlying difference in cortical excitability.

Structural changes in freshwater fish and chironomids exposed to bacterial exotoxins.

Mass fish mortalities have been reported in the past decade from British waters, often coinciding with blooms of filamentous actinobacteria, particularly strains of Streptomyces griseus. The present study has shown that some fractions of the exudate of S. griseus, prepared after a series of high pressure liquid chromatography (HPLC) separations, and analysed with liquid chromatography mass spectrometry (LC-MS), induced pathological changes to the gills of carp and/or tench fry following exposure under laboratory conditions up to 96 h Similar changes were induced by streptomycin, a secondary metabolite of S. griseus, and these included loss of microridging and fusion of secondary lamellae, with carp fry in the case of the exudate of S. griseus being more sensitive than tench fry, especially with exposure to fraction 9 and selected sub-fractions of 9. Some deformities using a severity index were also observed in the head capsule of larvae of the non-biting midge Chironomus riparius, including loss and splitting of teeth on the mentum. The results are discussed in relation to further identification of metabolites derived from samples of the organic filtrate of S. griseus and implications for the functioning of freshwater ecosystems.