Evoked Potentials and Neuropsychological Tests Validate Positron Emission Topography (PET) Brain Metabolism in Cognitively Impaired Patients

Fluorodeoxyglucose (FDG) Positron Emission Topography (PET) brain hypometabolism (HM) correlates with diminished cognitive capacity and risk of developing dementia. However, because clinical utility of PET is limited by cost, we sought to determine whether a less costly electrophysiological measure, the P300 evoked potential, in combination with neuropsychological test performance, would validate PET HM in neuropsychiatric patients. We found that patients with amnestic and non-amnestic cognitive impairment and HM (n = 43) evidenced significantly reduced P300 amplitudes, delayed latencies, and neuropsychological deficits, compared to patients with normal brain metabolism (NM; n = 187). Data from patients with missing cognitive test scores (n = 57) were removed from the final sample, and logistic regression modeling was performed on the modified sample (n = 173, p = .000004). The logistic regression modeling, based on P300 and neuropsychological measures, was used to validate membership in the HM vs. NM groups. It showed classification validation in 13/25 HM subjects (52.0%) and in 125/148 NM subjects (84.5%), correlating with total classification accuracy of 79.8%. In this paper, abnormal P300 evoked potentials coupled with cognitive test impairment validates brain metabolism and mild/moderate cognitive impairment (MCI). To this end, we cautiously propose incorporating electrophysiological and neuropsychological assessments as cost-effective brain metabolism and MCI indicators in primary care. Final interpretation of these results must await required additional studies confirming these interesting results.     

D-β-hydroxybutyrate is protective in mouse models of Huntington's disease

Abnormalities in mitochondrial function and epigenetic regulation are thought to be instrumental in Huntington's disease (HD), a fatal genetic disorder caused by an expanded polyglutamine track in the protein huntingtin. Given the lack of effective therapies for HD, we sought to assess the neuroprotective properties of the mitochondrial energizing ketone body, D-β-hydroxybutyrate (DβHB), in the 3-nitropropionic acid (3-NP) toxic and the R6/2 genetic model of HD. In mice treated with 3-NP, a complex II inhibitor, infusion of DβHB attenuates motor deficits, striatal lesions, and microgliosis in this model of toxin induced-striatal neurodegeneration. In transgenic R6/2 mice, infusion of DβHB extends life span, attenuates motor deficits, and prevents striatal histone deacetylation. In PC12 cells with inducible expression of mutant huntingtin protein, we further demonstrate that DβHB prevents histone deacetylation via a mechanism independent of its mitochondrial effects and independent of histone deacetylase inhibition. These pre-clinical findings suggest that by simultaneously targeting the mitochondrial and the epigenetic abnormalities associated with mutant huntingtin, DβHB may be a valuable therapeutic agent for HD.     

Primary structure and possible origin of the non-glycosylated basic proline-rich protein of human submandibular/sublingual saliva.

As a first step in determining the molecular mechanism of membrane fusion stimulated by GTP in rough endoplasmic reticulum (RER), we have looked for GTP-binding proteins. Rough microsomes from rat liver were treated for the release of ribosomes, and the membrane proteins were separated by SDS/polyacrylamide-gel electrophoresis. The polypeptides were then blotted on to nitrocellulose sheets and incubated with [alpha-32P]GTP [Bhullar & Haslam (1987) Biochem. J. 245, 617-620]. A doublet of polypeptides (23 and 24 kDa) was detected in the presence of 2 microM-MgCl2. Binding of [alpha-32P]GTP was blocked by 1-5 mM-EDTA, 10-10,000 nM-GTP or 10 microM-GDP. Either guanosine 5'-[gamma-thio]triphosphate or guanosine 5'-[beta gamma-imido]triphosphate at 100 nM completely inhibited binding, but ATP, CTP or UTP at 10 mciroM did not. Pretreatment of microsomes by mild trypsin treatment (0.5-10 micrograms of trypsin/ml, concentrations known not to affect microsomal permeability) led to inhibition of [alpha-32P]GTP binding, suggesting a cytosolic membrane orientation for the GTP-binding proteins. Two-dimensional gel-electrophoretic analysis revealed the 23 and 24 kDa [alpha-32P]GTP-binding proteins to have similar acid isoelectric points. [alpha-32P]GTP binding occurred to similar proteins of rough microsomes from rat liver, rat prostate and dog pancreas, as well as to a 23 kDa protein of rough microsomes from frog liver, but occurred to distinctly different proteins in a rat liver plasma-membrane-enriched fraction. Thus [alpha-32P]GTP binding has been demonstrated to two low-molecular-mass (approx. 21 kDa) proteins in the rough endoplasmic reticulum of several varied cell types.     

IL-4 inhibits vasoactive intestinal peptide production by macrophages

In schistosomiasis, eggs induce granulomas that have a vasoactive intestinal peptide (VIP) immunoregulatory circuit. This study explored the regulation of VIP production at sites of inflammation. Splenocytes from uninfected C57BL/6 mice expressed VIP mRNA and protein, which stopped following egg deposition. Eggs induce a Th2 response, suggesting that Th2 cytokines like interleukin (IL)-4 can regulate VIP. To address this issue, splenocytes from uninfected mice were incubated for 4 h with or without recombinant IL-4. IL-4 inhibited VIP mRNA expression. F4/80+ macrophages were the source of constitutively expressed VIP, subject to IL-4 regulation. In IL-4 knockout mice, splenic VIP production did not downmodulate during schistosome infection, suggesting that IL-4 is a critical cytokine regulating VIP production in wild-type mouse spleen. IL-4-producing granulomas in schistosomiasis made VIP. Experiments showed that granuloma VIP derived from F4/80- (nonmacrophage) cell populations, explaining this paradox. Granuloma F4/80+ cells from IL-4 knockout mice expressed VIP. Thus macrophages can make VIP, which is subject to IL-4 regulation. However, in the Th2 granulomas, other cell types produce VIP, which compensates for loss of macrophages as a source of this molecule.     

Unusual Features of Vaccinia Virus Extracellular Virion Form Neutralization Resistance Revealed in Human Antibody Responses to the Smallpox Vaccine

The extracellular virion form (EV) of vaccinia virus (VACV) is essential for viral pathogenesis and is difficult to neutralize with antibodies. Why this is the case and how the smallpox vaccine overcomes this challenge remain incompletely understood. We previously showed that high concentrations of anti-B5 antibodies are insufficient to directly neutralize EV (M. R. Benhnia, et al., J. Virol. 83:1201–1215, 2009). This allowed for at least two possible interpretations: covering the EV surface is insufficient for neutralization, or there are insufficient copies of B5 to allow anti-B5 IgG to cover the whole surface of EV and another viral receptor protein remains active. We endeavored to test these possibilities, focusing on the antibody responses elicited by immunization against smallpox. We tested whether human monoclonal antibodies (MAbs) against the three major EV antigens, B5, A33, and A56, could individually or together neutralize EV. While anti-B5 or anti-A33 (but not anti-A56) MAbs of appropriate isotypes were capable of neutralizing EV in the presence of complement, a mixture of anti-B5, anti-A33, and anti-A56 MAbs was incapable of directly neutralizing EV, even at high concentrations. This remained true when neutralizing the IHD-J strain, which lacks a functional version of the fourth and final known EV surface protein, A34. These immunological data are consistent with the possibility that viral proteins may not be the active component of the EV surface for target cell binding and infectivity. We conclude that the protection afforded by the smallpox vaccine anti-EV response is predominantly mediated not by direct neutralization but by isotype-dependent effector functions, such as complement recruitment for antibodies targeting B5 and A33.     

NMDA receptor dysfunction contributes to impaired brain‐derived neurotrophic factor‐induced facilitation of hippocampal synaptic transmission in a Tau transgenic model

While the spatiotemporal development of Tau pathology has been correlated with occurrence of cognitive deficits in Alzheimer's patients, mechanisms underlying these deficits remain unclear. Both brain‐derived neurotrophic factor (BDNF) and its tyrosine kinase receptor TrkB play a critical role in hippocampus‐dependent synaptic plasticity and memory. When applied on hippocampal slices, BDNF is able to enhance AMPA receptor‐dependent hippocampal basal synaptic transmission through a mechanism involving TrkB and N‐methyl‐d‐Aspartate receptors (NMDAR). Using THY‐Tau22 transgenic mice, we demonstrated that hippocampal Tau pathology is associated with loss of synaptic enhancement normally induced by exogenous BDNF. This defective response was concomitant to significant memory impairments. We show here that loss of BDNF response was due to impaired NMDAR function. Indeed, we observed a significant reduction of NMDA‐induced field excitatory postsynaptic potential depression in the hippocampus of Tau mice together with a reduced phosphorylation of NR2B at the Y1472, known to be critical for NMDAR function. Interestingly, we found that both NR2B and Src, one of the NR2B main kinases, interact with Tau and are mislocalized to the insoluble protein fraction rich in pathological Tau species. Defective response to BDNF was thus likely related to abnormal interaction of Src and NR2B with Tau in THY‐Tau22 animals. These are the first data demonstrating a relationship between Tau pathology and synaptic effects of BDNF and supporting a contribution of defective BDNF response and impaired NMDAR function to the cognitive deficits associated with Tauopathies.     

Tunicates push the limits of animal evo-devo

The phylum to which humans belong, Chordata, takes its name from one of the major shared derived features of the group, the notochord. All chordates have a notochord, at least during embryogenesis, and there is little doubt about notochord homology at the morphological level. A study in BMC Evolutionary Biology now shows that there is greater variability in the molecular genetics underlying notochord development than previously appreciated.     

STRESS MODIFICATION OF ALLELOPATHY OF HELIANTHUS ANNUUS L. DEBRIS ON SEED GERMINATION

Helianthus annuus L. variety “Russian Mammoth” was grown in pots, in both the greenhouse and the field, under density treatments of 1, 3, 6 or 12 plants per pot and nutrient treatments of full-strength, ½, ¼, ⅛ or 1/16 strength Hoagland's solution. The plants responded in typical fashion to both nutrient and density stress. Within each nutrient treatment, as the density of planting increased, biomass per pot first increased and then leveled off while biomass per plant decreased. Within each density treatment, as the nutrient level decreased, biomass per pot and per plant decreased. Therefore, both nutrient and density treatments imposed a stress (measured as a reduction in biomass) on individual H. annuus plants. Total phenolic compounds from the Helianthus annuus tissue, expressed as chlorogenic acid equivalents and determined by the PVP method, increased with increasing nutrient stress (i.e., lower nutrient availability); however, increasing density stress failed to significantly modify total phenolic compounds. The maximum total phenolic level determined for field-grown plants (69.70 mg g^-1 tissue) was approximately 58% greater than that found for greenhouse-grown plants (44.16 mg g^-1 tissue). When coarsely ground H. annuus plant material from the stress studies was added to soil, there was a significant depressive effect on germination of Amaranthus retroflexus seeds. In these germination was more closely correlated with total phenolic compounds (chlorogenic acid equivalents) added to the soil by the debris than with any other variable measured. Correlations were best for phenolic values of 200 μg g^-1 soil or greater. Chlorogenic acid (an abundant phenolic acid present in H. annuus) did not inhibit A. retroflexus seed germination when added to soil in pure form. The addition of a nutrient solution to soil containing H. annuus debris reduced subsequent inhibition of A. retroflexus seed germination.