On the specificity of the acetylcholinesterase defect in dystrophic mice

The tetrameric form of acetylcholinesterase (AChE) in ReJ/129 dystrophic mice was demonstrated to be absent from endplate-poor regions of skeletal muscle but present in endplate-rich regions. Skeletal muscle secreted normal amounts of this form of AChE. Visceral organs had normal amounts and distribution of the AChE molecular forms. These results suggest that the AChE defect in dystrophic mice is limited to skeletal muscle, and the defect does not reflect an abnormality of AChE synthesis but probably reflects an inability to incorporate the enzyme into skeletal muscle membranes.     

Ethanol‐Induced Increase of Agouti‐Related Protein (AgRP) Immunoreactivity in the Arcuate Nucleus of the Hypothalamus of C57BL/6J,but not 129/SvJ,Inbred Mice

Background: The melanocortin (MC) system is composed of peptides that are cleaved from the polypeptide precursor, pro‐opiomelanocortin (POMC). Previous research has shown that MC receptor (MCR) agonists reduce, and MCR antagonists increase, ethanol consumption in rats and mice. Consistently, genetic deletion of the endogenous MCR antagonist, agouti‐related protein (AgRP), causes reductions of ethanol‐reinforced lever pressing and binge‐like ethanol drinking in C57BL/6J mice. Ethanol also has direct effects on the central MC system, as chronic exposure to an ethanol‐containing diet causes significant reductions of α‐melanocyte stimulating hormone (α‐MSH) immunoreactivity in specific brain regions of Sprague‐Dawley rats. Together, these observations suggest that the central MC system modulates neurobiological responses to ethanol. To further characterize the role of the MC system in responses to ethanol, here we compared AgRP and α‐MSH immunoreactivity in response to an acute injection of saline or ethanol between high ethanol drinking C57BL/6J mice and moderate ethanol drinking 129/SvJ mice. Methods: Mice received an intraperitoneal (i.p.) injection of ethanol (1.5 g/kg or 3.5 g/kg; mixed in 0.9% saline) or an equivolume of 0.9% saline. Two hours after injection, animals were sacrificed and their brains were processed for AgRP and α‐MSH immunoreactivity. Results: Results indicated that acute ethanol administration triggered a dose‐dependent increase in AgRP immunoreactivity in the arcuate (ARC) of C57BL/6J mice, an effect that was not evident in the 129/SvJ strain. Although acute administration of ethanol did not influence α‐MSH immunoreactivity, C57BL/6J mice had significantly greater overall α‐MSH immunoreactivity in the ARC, dorsomedial, and lateral regions of the hypothalamus relative to the 129/SvJ strain. In contrast, C57BL/6J mice displayed significantly lower α‐MSH immunoreactivity in the medial amygdala. Conclusions: The results show that acute ethanol exposure has direct effects on endogenous AgRP activity in ethanol preferring C57BL/6J mice. It is suggested that ethanol‐induced increases in AgRP may be part of a positive feedback system that stimulates excessive binge‐like ethanol drinking in C57BL/6J mice. Inherent differences in α‐MSH immunoreactivity may contribute to differences in neurobiological responses to ethanol that are characteristically observed between the C57BL/6J and 129/SvJ inbred strains of mice.     

Defining sporadic Creutzfeldt-Jakob disease strains and their transmission properties

The biological determinants of the phenotypic variation in sporadic Creutzfeldt-Jakob disease (sCJD) are unknown. To categorize sCJD cases, the prion protein (PrP) codon 129 genotype and the biochemical characteristics of the disease-associated form of PrP (PrP^Sc) can be combined to form six subgroups (MM1, MM2, MV1, MV2, VV1, and VV2). This classification largely correlates with the known variation in the clinical and pathological features of sCJD, with the MM1 and MV1 cases representing the “classic” phenotype of sCJD. To address how this classification relates to different strains of sCJD we have inoculated each subgroup of sCJD to a panel of mice expressing different forms of the human PRNP gene (129MM, 129VV, and 129MV). We have established that all subtypes are transmissible to at least one genotype of mouse, and both agent and host factors determine transmission efficiency and the form of PrP^Sc deposited in the brain. Moreover, we have identified four distinct strains of sCJD using our in vivo strain typing panel.     

Local prolactin is a target to prevent expansion of basal/stem cells in prostate tumors

Androgen-independent recurrence is the major limit of androgen ablation therapy for prostate cancer. Identification of alternative pathways promoting prostate tumor growth is thus needed. Stat5 has been recently shown to promote human prostate cancer cell survival/proliferation and to be associated with early prostate cancer recurrence. Stat5 is the main signaling pathway triggered by prolactin (PRL), a growth factor whose local production is also increased in high-grade prostate cancers. The first aim of this study was to use prostate-specific PRL transgenic mice to address the mechanisms by which local PRL induces prostate tumorogenesis. We report that (i) Stat5 is the major signaling cascade triggered by local PRL in the mouse dorsal prostate, (ii) this model recapitulates prostate tumorogenesis from precancer lesions to invasive carcinoma, and (iii) tumorogenesis involves dramatic accumulation and abnormal spreading of p63-positive basal cells, and of stem cell antigen-1–positive cells identified as a stem/progenitor-like subpopulation. Because basal epithelial stem cells are proposed to serve as tumor-initiating cells, we challenged the relevance of local PRL as a previously unexplored therapeutic target. Using a double-transgenic approach, we show that Δ1–9-G129R-hPRL, a competitive PRL-receptor antagonist, prevented early stages of prostate tumorogenesis by reducing or inhibiting Stat5 activation, cell proliferation, abnormal basal-cell pattern, and frequency or grade of intraepithelial neoplasia. This study identifies PRL receptor/Stat5 as a unique pathway, initiating prostate tumorogenesis by altering basal-/stem-like cell subpopulations, and strongly supports the importance of further developing strategies to target locally overexpressed PRL in human prostate cancer.     

Measurement of 129Xe gas apparent diffusion coefficient anisotropy in an elastase‐instilled rat model of emphysema

Hyperpolarized noble gas (³He and ¹²⁹Xe) apparent diffusion coefficient (ADC) measurements have shown remarkable sensitivity to microstructural (i.e., alveolar) changes in the lung, particularly emphysema. The ADC of hyperpolarized noble gases depends strongly on the diffusion time (Δ), and ³He ADC has been shown to be anisotropic for Δ ranging from a few milliseconds down to a few hundred microseconds. In this study, the anisotropic nature of ¹²⁹Xe diffusion and its dependence on Δ were investigated both numerically, in a budded cylinder model, and in vivo, in an elastase‐instilled rat model of emphysema. Whole lung longitudinal ADC (D_L) and transverse ADC (D_T) were measured for Δ = 6, 50, and 100 ms at 73.5 mT, and correlated with measurements of the mean linear intercept (L_m) obtained from lung histology. A significant increase (P = 0.0021) in D_T was measured for Δ = 6 ms between the sham (0.0021 ± 0.0005 cm²/s) and elastase‐instilled (0.005 ± 0.001 cm²/s) cohorts, and a strong correlation was measured between D_T (Δ = 6 ms) and L_m, with a Pearson's correlation coefficient of 0.90. This study confirms that ¹²⁹Xe D_T increases correlate with alveolar space enlargement due to elastase instillation in rats. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.     

MRI of the lungs using hyperpolarized noble gases.

The nuclear spin polarization of the noble gas isotopes (3)He and (129)Xe can be increased using optical pumping methods by four to five orders of magnitude. This extraordinary gain in polarization translates directly into a gain in signal strength for MRI. The new technology of hyperpolarized (HP) gas MRI holds enormous potential for enhancing sensitivity and contrast in pulmonary imaging. This review outlines the physics underlying the optical pumping process, imaging strategies coping with the nonequilibrium polarization, and effects of the alveolar microstructure on relaxation and diffusion of the noble gases. It presents recent progress in HP gas MRI and applications ranging from MR microscopy of airspaces to imaging pulmonary function in patients and suggests potential directions for future developments.     

Cross-protective immunity against o'nyong-nyong virus afforded by a novel recombinant chikungunya vaccine

Emerging mosquito-borne alphavirus infections caused by chikungunya virus (CHIKV) or o'nyong-nyong virus (ONNV) are responsible for sporadic and sometimes explosive urban outbreaks. Currently, there is no licensed vaccine against either virus. We have developed a highly attenuated recombinant CHIKV candidate vaccine (CHIKV/IRES) that in preclinical studies was demonstrated to be safe, immunogenic and efficacious. In this study we investigated the potential of this vaccine to induce cross-protective immunity against the antigenically related ONNV. Our studies demonstrated that a single dose of CHIKV/IRES elicited a strong cross-neutralizing antibody response and conferred protection against ONNV challenge in the A129 mouse model. Moreover, CHIKV/IRES immune A129 dams transferred antibodies to their offspring that were protective, and passively transferred anti-CHIKV/IRES immune serum protected AG129 mice, independently of a functional IFN response. These findings highlight the potential of the CHIKV/IRES vaccine to protect humans against not only CHIKV but also against ONNV-induced disease.     

A small animal peripheral challenge model of yellow fever using interferon-receptor deficient mice and the 17D-204 vaccine strain

Yellow fever virus (YFV), a member of the genus Flavivirus, is a mosquito-borne pathogen that requires wild-type (wt), virulent strains to be handled at biosafety level (BSL) 3, with HEPA-filtration of room air exhaust (BSL3+). YFV is found in tropical regions of Africa and South America and causes severe hepatic disease and death in humans. Despite the availability of effective vaccines (17D-204 or 17DD), YFV is still responsible for an estimated 200,000 cases of illness and 30,000 deaths annually. Besides vaccination, there are no other prophylactic or therapeutic strategies approved for use in human YF. Current small animal models of YF require either intra-cranial inoculation of YF vaccine to establish infection, or use of wt strains (e.g., Asibi) in order to achieve pathology. We have developed and characterized a BSL2, adult mouse peripheral challenge model for YFV infection in mice lacking receptors for interferons α, β, and γ (strain AG129). Intraperitoneal challenge of AG129 mice with 17D-204 is a uniformly lethal in a dose-dependent manner, and 17D-204-infected AG129 mice exhibit high viral titers in both brain and liver suggesting this infection is both neurotropic and viscerotropic. Furthermore the use of a mouse model permitted the construction of a 59-biomarker multi-analyte profile (MAP) using samples of brain, liver, and serum taken at multiple time points over the course of infection. This MAP serves as a baseline for evaluating novel therapeutics and their effect on disease progression. Changes (4-fold or greater) in serum and tissue levels of pro- and anti-inflammatory mediators as well as other factors associated with tissue damage were noted in AG129 mice infected with 17D-204 as compared to mock-infected control animals.     

Programmed electrical stimulation of the heart in coronary artery disease

The induction of ventricular arrhythmia in patients with a history of malignant ventricular arrhythmia by programmed electrical stimulation (PES) is associated with a poor prognosis. However, the incidence and significance of inducible arrhythmia in patients with stable coronary artery disease (CAD) who do not have a history of serious arrhythmia are unknown. We studied 32 such patients (31 men, mean age 55 years) with PES at the time of cardiac catheterization. Fourteen patients (Group I) manifested greater than or equal to 3 extraventricular responses when challenged with 1 to 3 propagated right ventricular extrastimuli during ventricular pacing. Twelve (86%) of these 14 had evidence of left ventricular dysfunction (LVD), defined by a global ejection fraction of less than 50% or regional wall motion abnormalities. The remaining 18 patients (Group II) manifested less than or equal to 2 responses to extrastimulation. Only 4 (22%) of these 18 had LVD. Proximal 3-vessel CAD was more frequent in Group I patients (10 of 14, 71%) than in Group II (7 of 18, 39%). Only 5 patients (4 from Group I and 1 from Group II) demonstrated complex arrhythmia during exercise testing or ambulatory monitoring. The induction of extraventricular responses during PES may serve as an independent marker of electrical instability in the coronary population and is a much more common finding in those with LVD.     

Influence of intracoronary platelet aggregation on ventricular electrical properties during partial coronary artery stenosis

Several clinical studies suggest that drugs which interfere with platelet function may protect persons at risk for sudden death. However, there is no direct evidence that intracoronary platelet aggregation produces cardiac arrhythmias. Induction of fixed partial coronary stenoses in dogs resulted in spontaneous cyclical reductions in coronary blood flow of 21 to 81% (p less than 0.01). These changes are known to be associated with the formation and distal embolization of platelet aggregates. These reductions in coronary blood flow were accompanied by significant decreases in the repetitive extrasystole (-40%) and ventricular fibrillation (-38%) thresholds. Prostacyclin (PGI2), a potent vasodilator and inhibitor of platelet activation, in increasing doses of from 25 to 100 ng/kg/min caused a stepwise decrease in the frequency and magnitude of coronary blood flow fluctuations and restored the vulnerable period thresholds to control levels. Indomethacin (5 mg/kg), an inhibitor of cyclo-oxygenase activation and platelet thromboxane A2 production, produced similar results. The mechanism of coronary blood flow reduction appears to be mechanical blockade of the vessel lumen by platelet thrombi and production of myocardial ischemia. These results suggest that intracoronary platelet aggregation contributes to electrical destabilization of the myocardium and may predispose to ventricular fibrillation. A model is thus available for further investigating the role of platelets and antiplatelet drugs in modulating ventricular electrical stability.