115 research outputs found
Developing a Model for Slow Hypoxic Injury and Vascular Degeneration in Amyloid Burdened Brains
The breakdown of neurovascular systems may play a crucial role in the pathogenesis of Alzheimerâs
disease. However whether this breakdown initiates a degenerative mechanism or is the consequence of
some other deleterious process remains unknown. We examined hippocampal pathology in double
transgenic mice overexpressing a human mutant gene encoding the amyloid precursor protein
(APPSwe/Ind) using a combination of histochemistry and stereologic techniques. Expression of
APPSwe/Ind in these mice is driven by a tetracycline-sensitive promoter. Tetracycline transcriptional
activator (tTA), the second transgene, is driven in turn by a CAM KIIa promoter that is only active in
neurons. Thus this double transgenic construct allows us to control expression of APPSwe/Ind with
doxycycline. Utilizing this characteristic, we created three distinct experimental groups: A, display abeta
plaque pathology and express APPSwe/Ind at time of sacrifice; B, display abeta plaque pathology but do
not express APPSwe/Ind at time of sacrifice; and C, do not display abeta plaque pathology but do
express APPSwe/Ind at time of sacrifice. Stereologic investigation revealed decreased hippocampal
volume in groups A(n=5) and B(n=5) when compared to group C(n=5) and age-matched wildtype (n=9)
Decoupling the effect of mutant amyloid precursor protein (APP) from the effect of plaque on axonal transport dynamics in the living mouse brain: A correlation MRI-microscopy study
The parent protein for amyloid plaques, amyloid precursor protein (APP), mediates cargoâmotor attachments for intracellular transport. Axonal transport is decreased and the distal location of accumulation is altered in transgenic mice expressing human APP with the Swedish and Indiana mutations (APPSwInd) linked to Familial Alzheimerâs Disease, as detected by timeâlapse magnetic resonance imaging (MRI) of transport in living mouse brains (Bearer et al. 2017). Transport is also altered in brains of Down syndrome mice with 3 copies of APP gene. Questions now become whether expression of mutated APP effects transport dynamics independent of plaque, and do plaques alone contribute to transport defects? To address these we used the TetâOff system to decouple expression of APPSwInd from presence of plaques, and then studied transport using our MRI technique in three experimental groups of transgenic mice in which the timing and duration of APPSwInd expression, and thereby plaque formation, was altered with doxycycline: Group A (+ plaques, + APPSwInd)Íž Group B (+ plaques, no APPSwInd), and group C (no plaques, + APPSwInd). Manganeseâenhanced MRI (MEMRI) allows us to perform cell biological experiments in live animals with T1âweighted MRI in a Bruker 11.7T scanner (Medina et al 2016). Timeâlapse MR images were captured before and after stereotactic injection of Mn2+ (3â5nL) into CA3 of the hippocampus at successive timeâpoints. Images of multiple individuals were aligned and processed with our automated computational pipeline (Medina et al. 2017) and statistical parametric mapping (SPM) performed. After MRI brains were harvested for
histopathology or biochemistry. Results show that within group between timeâpoint have altered
transport locations as well as diminished transport in all groups compared to wildtype (p<0.05 FDR n=
36). Preliminary ANOVA betweenâgroup comparisons both by SPM and by region of interest
measurements of images support the visual impression that APPSwInd expression alone may
compromise transport. Groups A and B displayed plaques, but not C, and Western blots showed
APPSwInd expressed 3.2âfold over normal at sacrifice in Groups A and C but not B, with Aβ detected only
in Groups A and B, where phosphoâtau was also present in dystrophic neurites surrounding plaques.
Cholinergic neurons that project to hippocampus from the medial septal nucleus were decreased in
Group C (p=0.0006 by ANOVA, n=15). Isolated hippocampal vesicles contained Mn2+, as well as Trk (NGF
receptor), Rab 5 and 7 (associated with transport vesicles), suggesting a distinct vesicle population is
affected by these APP mutations. These surprising results implicate mutated APPSwInd in transport
defects, separable from the effect of plaque
Witnessing microtubule-based transport in the living brain: Impact of the cargomotor receptor, amyloid precursor protein, and Alzheimerâs plaques
Most amyloid precursor protein (APP)-based Alzheimerâs models overexpress mutant human APP
resulting in Abeta plaques. Yet the relative contribution of this elevated APP and the presence of
plaques to neurodegeneration remains a big question. APPâs role as a cargo-motor receptor for axonal
transport suggests that overexpression might lead to increased transport. Indeed we showed that
transport is increased in Downâs syndrome and decreased in APP knockout mice. Hence transport may
be elevated in APP overexpressors and lead to either beneficial or deleterious consequences. Here we
use high field microMRI with Mn2+, an MR contrast agent useful as a track-tracer, to pose this cell
biological quest
ion within the whole living brains of wildtype and Alzheimerâs model mice. Injection of
Mn2+ into the CA3 region of the hippocampus results in measurable transport over time. Application of
3D unbiased whole brain image analysis detects all circuitry emanating from the hippocampus. By
driving APP Swe/Ind transgene expression with a tetracycline-sensitive promoter, APPSwe/Ind
expression can be decoupled from the presence of plaques with doxycycline (doxy). Three groups of
mice were studied: group âAâ (no doxy, +plaques, +APP); group âBâ (doxy at 8 days before sacrifice,
+plaques, no APP), and group âCâ (doxy prior to conception, and stopped 8 days before sacrifice, no
plaques, +APP). Images were captured before and sequentionally after Mn2+ injection into CA
3 (1, 7, 25
hr). Images were aligned and analyzed by statistical parametric mapping to identify differential
accumulation within the hippocampal projections. Histopathology revealed well-developed plaques in A
and B, and Western blots showed human APP expressed five-fold over WT in in A and C. Our preliminary
results show increased transport in A and C, with APP Swe/Ind expression when compared with B,
where expression is suppressed. Cholinergic neurons in the medial septal nucleus were decreased as
determined by anti-ChAT staining in Group C (p=0.0006 by one-way ANOVA, n=15). In conclusion, the
effects of elevated APP expression are separable from consequences of plaque, and each may
Decoupling the effect of mutant amyloid precursor protein (APP) from the effect of plaque on axonal transport dynamics in the living mouse brain: A correlation MRI-microscopy study
The parent protein for amyloid plaques, amyloid precursor protein (APP), mediates cargoâmotor attachments for intracellular transport. Axonal transport is decreased and the distal location of accumulation is altered in transgenic mice expressing human APP with the Swedish and Indiana mutations (APPSwInd) linked to Familial Alzheimerâs Disease, as detected by timeâlapse magnetic resonance imaging (MRI) of transport in living mouse brains (Bearer et al. 2017). Transport is also altered in brains of Down syndrome mice with 3 copies of APP gene. Questions now become whether expression of mutated APP effects transport dynamics independent of plaque, and do plaques alone contribute to transport defects? To address these we used the TetâOff system to decouple expression of APPSwInd from presence of plaques, and then studied transport using our MRI technique in three experimental groups of transgenic mice in which the timing and duration of APPSwInd expression, and thereby plaque formation, was altered with doxycycline: Group A (+ plaques, + APPSwInd)Íž Group B (+ plaques, no APPSwInd), and group C (no plaques, + APPSwInd). Manganeseâenhanced MRI (MEMRI) allows us to perform cell biological experiments in live animals with T1âweighted MRI in a Bruker 11.7T scanner (Medina et al 2016). Timeâlapse MR images were captured before and after stereotactic injection of Mn2+ (3â5nL) into CA3 of the hippocampus at successive timeâpoints. Images of multiple individuals were aligned and processed with our automated computational pipeline (Medina et al. 2017) and statistical parametric mapping (SPM) performed. After MRI brains were harvested for
histopathology or biochemistry. Results show that within group between timeâpoint have altered
transport locations as well as diminished transport in all groups compared to wildtype (p<0.05 FDR n=
36). Preliminary ANOVA betweenâgroup comparisons both by SPM and by region of interest
measurements of images support the visual impression that APPSwInd expression alone may
compromise transport. Groups A and B displayed plaques, but not C, and Western blots showed
APPSwInd expressed 3.2âfold over normal at sacrifice in Groups A and C but not B, with Aβ detected only
in Groups A and B, where phosphoâtau was also present in dystrophic neurites surrounding plaques.
Cholinergic neurons that project to hippocampus from the medial septal nucleus were decreased in
Group C (p=0.0006 by ANOVA, n=15). Isolated hippocampal vesicles contained Mn2+, as well as Trk (NGF
receptor), Rab 5 and 7 (associated with transport vesicles), suggesting a distinct vesicle population is
affected by these APP mutations. These surprising results implicate mutated APPSwInd in transport
defects, separable from the effect of plaque
Altered Neurocircuitry in the Dopamine Transporter Knockout Mouse Brain
The plasma membrane transporters for the monoamine neurotransmitters dopamine, serotonin, and norepinephrine modulate the dynamics of these monoamine neurotransmitters. Thus, activity of these transporters has significant consequences for monoamine activity throughout the brain and for a number of neurological and psychiatric disorders. Gene knockout (KO) mice that reduce or eliminate expression of each of these monoamine transporters have provided a wealth of new information about the function of these proteins at molecular, physiological and behavioral levels. In the present work we use the unique properties of magnetic resonance imaging (MRI) to probe the effects of altered dopaminergic dynamics on meso-scale neuronal circuitry and overall brain morphology, since changes at these levels of organization might help to account for some of the extensive pharmacological and behavioral differences observed in dopamine transporter (DAT) KO mice. Despite the smaller size of these animals, voxel-wise statistical comparison of high resolution structural MR images indicated little morphological change as a consequence of DAT KO. Likewise, proton magnetic resonance spectra recorded in the striatum indicated no significant changes in detectable metabolite concentrations between DAT KO and wild-type (WT) mice. In contrast, alterations in the circuitry from the prefrontal cortex to the mesocortical limbic system, an important brain component intimately tied to function of mesolimbic/mesocortical dopamine reward pathways, were revealed by manganese-enhanced MRI (MEMRI). Analysis of co-registered MEMRI images taken over the 26 hours after introduction of Mn^(2+) into the prefrontal cortex indicated that DAT KO mice have a truncated Mn^(2+) distribution within this circuitry with little accumulation beyond the thalamus or contralateral to the injection site. By contrast, WT littermates exhibit Mn^(2+) transport into more posterior midbrain nuclei and contralateral mesolimbic structures at 26 hr post-injection. Thus, DAT KO mice appear, at this level of anatomic resolution, to have preserved cortico-striatal-thalamic connectivity but diminished robustness of reward-modulating circuitry distal to the thalamus. This is in contradistinction to the state of this circuitry in serotonin transporter KO mice where we observed more robust connectivity in more posterior brain regions using methods identical to those employed here
Neuroprotective therapies in the NICU in term infants: present and future
Outcomes of neonatal encephalopathy (NE) have improved since the widespread implementation of therapeutic hypothermia (TH) in high-resource settings. While TH for NE in term and near-term infants has proven beneficial, 30â50% of infants with moderate-to-severe NE treated with TH still suffer death or significant impairments. There is therefore a critical need to find additional pharmacological and non-pharmacological interventions that improve the outcomes for these children. There are many potential candidates; however, it is unclear whether these interventions have additional benefits when used with TH. Although primary and delayed (secondary) brain injury starting in the latent phase after HI are major contributors to neurodisability, the very late evolving effects of tertiary brain injury likely require different interventions targeting neurorestoration. Clinical trials of seizure management and neuroprotection bundles are needed, in addition to current trials combining erythropoietin, stem cells, and melatonin with TH
A prospective cohort study of biomarkers of prenatal tobacco smoke exposure: the correlation between serum and meconium and their association with infant birth weight
<p>Abstract</p> <p>Background</p> <p>The evaluation of infant meconium as a cumulative matrix of prenatal toxicant exposure requires comparison to established biomarkers of prenatal exposure.</p> <p>Methods</p> <p>We calculated the frequency of detection and concentration of tobacco smoke metabolites measured in meconium (nicotine, cotinine, and trans-3'-hydroxycotinine concentrations) and three serial serum cotinine concentrations taken during the latter two-thirds of pregnancy among 337 mother-infant dyads. We estimated the duration and intensity of prenatal tobacco smoke exposure using serial serum cotinine concentrations and calculated geometric mean meconium tobacco smoke metabolite concentrations according to prenatal exposure. We also compared the estimated associations between these prenatal biomarkers and infant birth weight using linear regression.</p> <p>Results</p> <p>We detected nicotine (80%), cotinine (69%), and trans-3'-hydroxycotinine (57%) in most meconium samples. Meconium tobacco smoke metabolite concentrations were positively associated with serum cotinine concentrations and increased with the number of serum cotinine measurements consistent with secondhand or active tobacco smoke exposure. Like serum cotinine, meconium tobacco smoke metabolites were inversely associated with birth weight.</p> <p>Conclusions</p> <p>Meconium is a useful biological matrix for measuring prenatal tobacco smoke exposure and could be used in epidemiological studies that enroll women and infants at birth. Meconium holds promise as a biological matrix for measuring the intensity and duration of environmental toxicant exposure and future studies should validate the utility of meconium using other environmental toxicants.</p
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