Season of the year, vitamin D and COVID-19.

Vitamin D supplementation reduced the risk of acute respiratory tract infection in two meta-analyses. Mendelian randomization shows a causal effect of low vitamin D on bacterial pneumonias risk. These studies involved patients before COVID-19 pandemic. Several association studies found higher incidence of SARS-CoV-2 positivity, greater COVID-19 severity and higher risk of mortality in vitamin D deficient subjects compared to vitamin D non-deficient controls. We draw attention to the trend of inverse relative COVID-19 mortality in Europe versus the states of the Southern Hemisphere (Australia, Brazil, South Africa) in dependence on season, which may be associated with intensity of ultraviolet radiation and consequent seasonal fluctuation of serum vitamin D levels. Although we cannot yet confirm causal role of vitamin D in SARS-CoV-2 positivity or COVID-19, we recommend consumption of vitamin D rich food or vitamin D supplementation in the non-sunny season to prevent vitamin D deficiency.

Latent toxoplasmosis reduces gray matter density in schizophrenia but not in controls: voxel-based-morphometry (VBM) study.

OBJECTIVES: To address the role of latent T. gondii infection in schizophrenia we studied the influence of latent toxoplasmosis on brain morphology. METHODS: An optimized voxel-based morphometry of magnetic resonance imaging was analyzed by analysis of variance with diagnosis and seropositivity as factors in 44 schizophrenic patients (12 T. gondii positive) and 56 controls (13 T. gondii positive). RESULTS: Grey matter (GM) volume was reduced in schizophrenia patients compared with controls in the cortical regions, hippocampus and in the caudate. In the schizophrenia sample we found a significant reduction of GM volume in T. gondii positive comparing with T. gondii-negative patients bilaterally in the caudate, median cingulate, thalamus and occipital cortex and in the left cerebellar hemispheres. T. gondii-positive and -negative controls did not differ in any cluster. Among participants seropositive to T. gondii the reduction of GM in the schizophrenia subjects was located in the same regions when comparing the entire sample (11,660 over-threshold voxels (P ≤ 0.05, FWR corrected). The differences between T. gondii-negative patients and controls consisted only of 289 voxels in temporal regions. CONCLUSIONS: Our study is the first to document that latent toxoplasmosis reduces GM in schizophrenia but not in controls.

Electroencephalographic spectral and coherence analysis of ketamine in rats: correlation with behavioral effects and pharmacokinetics.

AIMS: This study was designed to evaluate the changes in EEG power spectra and EEG coherence in a ketamine model of psychosis in rats. Analyses of behavioral measurements--locomotion and sensorimotor gating--and the pharmacokinetics of ketamine and norketamine were also conducted. METHODS: Ketamine and norketamine levels in rat sera and brains were analyzed by gas chromatography-mass spectrometry after ketamine 30 mg/kg (i.p.). Ketamine 9 and 30 mg/kg (i.p.) were used in the behavioral and EEG experiments. Locomotor effects in an open field test and deficits in prepulse inhibition of acoustic startle reaction (PPI ASR) were evaluated in the behavioral experiments. EEG signals were simultaneously recorded from 12 implanted active electrodes; subsequently, an EEG power spectral and coherence analysis was performed. RESULTS: Ketamine had a rapid penetration into the brain; the peak concentrations of the drug were reached within 15 min after administration. Ketamine induced marked hyperlocomotion and deficits in the PPI ASR. EEG spectral analysis mainly showed increases in EEG power as well as coherence. These were most robust at 10-15 min after the administration and influenced all parts of the spectrum with ketamine 30 mg/kg. CONCLUSIONS: Ketamine at behaviorally active doses induces a robust increase in EEG power spectra and coherence. The maximum levels of change correlated with the kinetics of ketamine.