Cerebellar output controls generalized spike-and-wave discharge occurrence

Objective

Disrupting thalamocortical activity patterns has proven to be a promising approach to stop generalized spike‐and‐wave discharges (GSWDs) characteristic of absence seizures. Here, we investigated to what extent modulation of neuronal firing in cerebellar nuclei (CN), which are anatomically in an advantageous position to disrupt cortical oscillations through their innervation of a wide variety of thalamic nuclei, is effective in controlling absence seizures.

Methods

Two unrelated mouse models of generalized absence seizures were used: the natural mutant tottering, which is characterized by a missense mutation in Cacna1a, and inbred C3H/HeOuJ. While simultaneously recording single CN neuron activity and electrocorticogram in awake animals, we investigated to what extent pharmacologically increased or decreased CN neuron activity could modulate GSWD occurrence as well as short‐lasting, on‐demand CN stimulation could disrupt epileptic seizures.

Results

We found that a subset of CN neurons show phase‐locked oscillatory firing during GSWDs and that manipulating this activity modulates GSWD occurrence. Inhibiting CN neuron action potential firing by local application of the γ‐aminobutyric acid type A (GABA‐A) agonist muscimol increased GSWD occurrence up to 37‐fold, whereas increasing the frequency and regularity of CN neuron firing with the use of GABA‐A antagonist gabazine decimated its occurrence. A single short‐lasting (30–300 milliseconds) optogenetic stimulation of CN neuron activity abruptly stopped GSWDs, even when applied unilaterally. Using a closed‐loop system, GSWDs were detected and stopped within 500 milliseconds.

Interpretation

CN neurons are potent modulators of pathological oscillations in thalamocortical network activity during absence seizures, and their potential therapeutic benefit for controlling other types of generalized epilepsies should be evaluated. Ann Neurol 2015;77:1027–1049

Paragonimosis in the Cajabamba and Condebamba districts, Cajamarca, Peru

Stool samples from 409 pre-school and school students, living in six villages of the Cajabamba and Condebamba districts, Cajamarca, Perú, were examined using wet preparations and Lumbreras' method, looking for Paragonimus eggs. Fecal and sputum samples from two children (0. 5%) of 6 and 8 year-old showed eggs of Paragonimus. One hundred and twenty freshwater crabs, Hypolobocera chilensis eigenmanni, were collected from the Condebamba valley and 21 (17.5%) of them were infected with P. mexicanus (syn. P. peruvianus) metacercariae. Our results show the persistence of Paragonimus in human beings and in the main source of infection, the crabs.

Stress analysis of a flexible one-piece type first metatarsophalangeal joint implant

Two-dimensional finite element analysis was used to obtain the magnitude and distribution of the stresses in models of two different designs of a flexible one-piece double-stemmed first metatarsophalangeal joint implant. The loading and constraint conditions have been reported by previous researchers to occur in vivo at the joint during the push-off phase of the normal walking cycle. Based on the results obtained, the authors recommend the direction that future studies in this area should take.

Hepatitis B in a highly active prostitute population: evidence for a low risk of chronic antigenemia

The epidemiology of hepatitis B in female prostitutes was studied in a cross-sectional survey of 467 prostitutes and 510 control prenatal clinic patients from Lima and Iquitos, Peru. Prostitutes reported a mean of 8.8 +/- 6.7 years of active prostitution and a mean of 205 +/- 137 sexual contacts in the month prior to the study. Hepatitis B surface antigen (HBsAg) was found in comparable percentages of prostitutes (1.7%) and controls (0.8%; P = .305). In contrast, seropositivity for both antigen and antibody markers (HBsAg, anti-HBs, or anti-hepatitis B core) was found in a significantly higher percentage of prostitutes than controls (67.0% vs. 10.0%; P less than .0001). By multivariate analysis, both prostitution (odds ratio [OR] 14.6) and the number of years of exposure as a prostitute (OR 3.2 for 10 years of exposure at age 35 years) were significantly associated with seropositivity for hepatitis B markers when adjusted for age. In this study, the prevalence of HBsAg was not substantially increased in highly active female prostitutes compared with the general population, even though hepatitis B transmission was greatly increased. These data suggest that in adult women with a high level of hepatitis B infection, hepatitis B antigenemia may not persist as frequently as previously indicated in studies of other populations.