Lack of visual evoked potentials amplitude decrement during prolonged reversal and motion stimulation in migraineurs.

OBJECTIVE: We evaluated response decrement during a short time repetitive low and high contrast reversal and low contrast motion stimulation in controls and migraineurs. METHODS: A total of 39 migraine patients (out of which 19 were in the interictal period and without prophylactic treatment) and 36 healthy volunteers were examined using pattern-reversal (PR-VEP) and motion-onset (M-VEP) visual evoked potentials. Binocular stimulation lasted 2.5 min and the decrement assessment was blinded. RESULTS: Evidence of significant decrement was observed in healthy volunteers for high contrast PR-VEP amplitude of P100-N75 ratios between the fifth and first blocks (0.9; p=0.001) with a linear decline (-0.7 µV/min, p=0.001) and in the P100-N145 amplitude with linear decline (-0.5 µV/min, p=0.004). Significant decrement was also observed for the ratio between the fifth and first block P1-N2 amplitudes in M-VEP (0.9, p=0.006). No significant decrement was noted in the low contrast PR-VEP or among migraineurs. CONCLUSIONS: We confirm differences in decrease of VEPs amplitude during short term examination between controls and migraineurs. We showed the decrement deficit also in the extrastriatal regions of the migraineurs' visual cortex. SIGNIFICANCE: Low contrast and motion-onset stimuli in short time decrement assessment did not increase the test sensitivity.

Visual mismatch negativity in the dorsal stream is independent of concurrent visual task difficulty.

The manipulation of attention can produce mismatch negativity-like components that are not necessarily connected to the unintentional sensory registration of the violation of probability-based regularity. For clinical purposes, attentional bias should be quantified because it can vary substantially among subjects and can decrease the specificity of the examination. This experiment targets the role of attention in the generation of visual mismatch negativity (vMMN). The visual regularity was generated by a sequence of two radial motions while subjects focused on visual tasks in the central part of the display. Attentional load was systematically varied and had three levels, no-load, easy, and difficult. Rare, deviant, and frequent standard motions were presented with a 10/60 ratio in oddball sequences. Data from 12 subjects was recorded from 64 channels and processed. vMMN was identified within the interval of 142-198 ms. The mean amplitude was evaluated during the aforementioned interval in the parietal and fronto-central regions. A general linear model for repeated measures was applied to the mean amplitude with a three-factor design and showed a significant difference [F (1, 11) = 17.40, p = 0.002] between standard and deviant stimuli and between regions [F (1, 11) = 8.40, p = 0.01]; however, no significant effect of the task [F (2, 22) = 1.26, p = 0.30] was observed. The unintentional detection of irregularity during the processing of the visual motion was independent of the attentional load associated with handling the central visual task. The experiment did not demonstrate an effect of attentional load manipulation on mismatch negativity (MMN) induced by the motion-sequence, which supports the clinical utility of this examination. However, used stimulation paradigm should be further optimized to generate mismatch negativity that is stable enough to be usable not only for group comparisons but also for a single subject assessment.

In vitro growth-inhibitory effect of plant-derived extracts and compounds against Paenibacillus larvae and their acute oral toxicity to adult honey bees.

In total, 26 natural compounds of various chemical classes (flavonoids, alkaloids, terpenoids) and 19 crude extracts from selected plants were tested in vitro for antibacterial activity against three strains of P. larvae, the causal agent of American Foulbrood Disease of honey bees (AFB) by the broth microdilution method. Among the individual substances, sanguinarine (MIC 4 microg/ml), followed by thymoquinone, capsaicin, trans-2-hexenal and nordihydroguaiaretic acid (MIC 4-32 microg/ml) possessed the strongest antibacterial effect. In case of extracts, common hop (Humulus lupulus L.) and myrtle (Myrtus communis L.) methanolic-dichloromethane extracts exhibited the highest growth-inhibitory effect with MICs ranging from 2 to 8 microg/ml. Acute oral toxicity of the most active natural products was determined on adult honey bees, showing them as non-toxic at concentrations as high as 100 microg peer bee. Our study leads to identification of highly potent natural products effective against AFB in vitro with very low MICs compared to those reported in literature, low toxicity to adult honey bees and commercial availability suggesting them as perspective, low cost and consumer-acceptable agents for control of AFB.

Intracranial pressure and experimental model of diffuse brain injury in rats.

OBJECTIVE: In this study, we present a simple closed head injury model as a two-stage experiment. The height of the weight drop enables gradation of head trauma severity. METHODS: The head injury device consists of three parts and there are three adjustable parameters-weight (100-600 g), height of fall (5-100 cm) and elasticity of the springs. Thirty male Wistar rats underwent monitoring of intracranial pressure with and without induction of the head injury. RESULTS: The weight drop from 45 to 100 cm led to immediate seizure activity and early death of the experimental animals. Severe head injury was induced from 40 cm weight drop. There was 50% mortality and all surviving rats had behavioral deterioration. Intracranial pressure was 9.3 +/- 3.76 mmHg. Moderate head injury was induced from 35 cm, mortality decreased to 20-40%, only half of the animals showed behavioral pathology and intracranial pressure was 7.6 +/- 3.54 mmHg. Weight drop from 30 cm caused mild head injury without mortality and neurological deterioration. Intracranial pressure was slightly higher compared to sham group- 5.5 +/- 0.74 mmHg and 2.9 +/- 0.81 mmHg respectively. CONCLUSION: This model is an eligible tool to create graded brain injury with stepwise intracranial pressure elevation.