Initial Experiences with Amyloid-Related Imaging Abnormalities in Patients Receiving Aducanumab Following Accelerated Approval

Aducanumab is the first FDA-approved amyloid-lowering immunotherapy for Alzheimer's disease. There is little real-world data to guide management of amyloid-related imaging abnormalities (ARIA), a potentially serious side-effect which requires surveillance with magnetic resonance imaging. We report our experiences in managing ARIA in patients receiving aducanumab at the Butler Hospital Memory and Aging Program during the year following FDA approval. We followed the Appropriate Use Recommendations for aducanumab to guide patient selection, detection, and management of ARIA (1). ARIA-E occurred in 6 out of 24 participants treated; all APOE-ε4 carriers. Treatment was discontinued in 4 cases of moderate-severe ARIA-E, temporarily held in 1 moderate case, and dosed through in 1 mild case (mean duration = 3 months, range, 1-6 months). No participants required hospitalization or high dose corticosteroids. Participants on anticoagulation were excluded and no macrohemorrhages occurred. These data support the measured approaches to treatment outlined in the Appropriate Use Recommendations.

The Role of Basement Membranes in Cerebral Amyloid Angiopathy

Dementia is a neuropsychiatric syndrome characterized by cognitive decline in multiple domains, often leading to functional impairment in activities of daily living, disability, and death. The most common causes of age-related progressive dementia include Alzheimer's disease (AD) and vascular cognitive impairment (VCI), however, mixed disease pathologies commonly occur, as epitomized by a type of small vessel pathology called cerebral amyloid angiopathy (CAA). In CAA patients, the small vessels of the brain become hardened and vulnerable to rupture, leading to impaired neurovascular coupling, multiple microhemorrhage, microinfarction, neurological emergencies, and cognitive decline across multiple functional domains. While the pathogenesis of CAA is not well understood, it has long been thought to be initiated in thickened basement membrane (BM) segments, which contain abnormal protein deposits and amyloid-β (Aβ). Recent advances in our understanding of CAA pathogenesis link BM remodeling to functional impairment of perivascular transport pathways that are key to removing Aβ from the brain. Dysregulation of this process may drive CAA pathogenesis and provides an important link between vascular risk factors and disease phenotype. The present review summarizes how the structure and composition of the BM allows for perivascular transport pathways to operate in the healthy brain, and then outlines multiple mechanisms by which specific dementia risk factors may promote dysfunction of perivascular transport pathways and increase Aβ deposition during CAA pathogenesis. A better understanding of how BM remodeling alters perivascular transport could lead to novel diagnostic and therapeutic strategies for CAA patients.

The ubiquitin ligase UBE4B regulates amyloid precursor protein ubiquitination, endosomal trafficking, and amyloid β42 generation and secretion

The extracellular accumulation of amyloid β (Aβ) fragments of amyloid precursor protein (APP) in brain parenchyma is a pathological hallmark of Alzheimer's disease (AD). APP can be cleaved into Aβ on late endosomes/multivesicular bodies (MVBs). E3 ubiquitin ligases have been linked to Aβ production, but specific E3 ligases associated with APP ubiquitination that may affect targeting of APP to endosomes have not yet been described. Using cultured cortical neurons isolated from rat pups, we reconstituted APP movement into the internal vesicles (ILVs) of MVBs. Loss of endosomal sorting complexes required for transport (ESCRT) components inhibited APP movement into ILVs and increased endosomal Aβ42 generation, implying a requirement for APP ubiquitination. We identified an ESCRT-binding and APP-interacting endosomal E3 ubiquitin ligase, ubiquitination factor E4B (UBE4B) that regulates APP ubiquitination. Depleting UBE4B in neurons inhibited APP ubiquitination and internalization into MVBs, resulting in increased endosomal Aβ42 levels and increased neuronal secretion of Aβ42. When we examined AD brains, we found levels of the UBE4B-interacting ESCRT component, hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs), were significantly decreased in AD brains. These data suggest that ESCRT components critical for membrane protein sorting in the endocytic pathway are altered in AD. These results indicate that the molecular machinery underlying endosomal trafficking of APP, including the ubiquitin ligase UBE4B, regulates Aβ levels and may play an essential role in AD progression.

Transforming growth factor-β promotes basement membrane fibrosis, alters perivascular cerebrospinal fluid distribution, and worsens neurological recovery in the aged brain after stroke

Aging and stroke alter the composition of the basement membrane and reduce the perivascular distribution of cerebrospinal fluid and solutes, which may contribute to poor functional recovery in elderly patients. Following stroke, TGF-β induces astrocyte activation and subsequent glial scar development. This is dysregulated with aging and could lead to chronic, detrimental changes within the basement membrane. We hypothesized that TGF-β induces basement membrane fibrosis after stroke, leading to impaired perivascular CSF distribution and poor functional recovery in aged animals. We found that CSF entered the aged brain along perivascular tracts; this process was reduced by experimental stroke and was rescued by TGF-β receptor inhibition. Brain fibronectin levels increased with experimental stroke, which was reversed with inhibitor treatment. Exogenous TGF-β stimulation increased fibronectin expression, both in vivo and in primary cultured astrocytes. Oxygen-glucose deprivation of cultured astrocytes induced multiple changes in genes related to astrocyte activation and extracellular matrix production. Finally, in stroke patients, we found that serum TGF-β levels correlated with poorer functional outcomes, suggesting that serum levels may act as a biomarker for functional recovery. These results support a potential new treatment strategy to enhance recovery in elderly stroke patients.

Sex-specific Association of Matrix Metalloproteinases with Secondary Injury and Outcomes after Intracerebral Hemorrhage

OBJECTIVE

Intracerebral hemorrhage affects approximately 2 million individuals per year. While the incidence is roughly equal in men and women, few studies have examined the influence of sex on secondary injury and associated long-term functional outcomes. Matrix metalloproteinases (MMPs) promote vessel rupture and worsen outcomes by potentiating blood-brain barrier breakdown after injury. We hypothesized that different MMP isoform levels would be predictive of injury severity, secondary injury, and long-term functional outcomes in males and females, respectively.

METHODS

We examined the levels of MMP isoforms in serum samples from a prospective patient biobank (n = 55). Baseline clinical, radiographic, and laboratory data were also analyzed.

RESULTS

We found that MMP-1 (P = .036), MMP-2 (P = .014), MMP-3 (P < .001), and MMP-9 (P = .02) levels gradually increased over time in male patients until 10 DPI. In female patients, we found a different pattern of activation: MMP-8 (P = .02) was the only isoform that significantly changed with time, which reached a peak at 3-5 days postinjury. Several MMP isoforms correlated with markers of secondary injury in female patients (all P < .05). Additionally, serum levels of MMP-3 (P = .011) in males and MMP-10 (P = .044) in females were significantly associated with long-term functional outcomes in a sex-specific manner.

CONCLUSIONS

This is the first sex-specific study to examine serum MMP levels and their correlation with clinicoradiologic measures after intracerebral hemorrhage, and identifies potential biomarkers of secondary injury and long-term outcomes in both sexes.

Abstract TMP35: Perivascular Astrocytes Alter the Basement Membrane Through TGF-Beta in an Aged Brain Post-Stroke

Individuals over 65 make up the majority of stroke patients in the United States. Post-stroke recovery within the elderly population maybe impeded through enhanced glial scarring and reduced glymphatic flow. Following stroke, reactive astrocytes remodel the basement membrane through transforming growth factor-beta (B) signaling (TGF-B), altering glymphatic flow. Impaired glymphatic flow leads to a buildup of waste products, such as amyloid-beta, further inhibiting post-stroke recovery.

We hypothesize that post-stroke astrogliosis and basement membrane fibrosis are induced through TGF-B signaling, resulting in chronic glymphatic impairment in aged mice. To test this hypothesis, we used an in vivo model of ischemia to measure TGF-B signaling and reactive astrogliosis. In vivo studies used young (3 month, n=5-8) and aged (20-month, n=5-8) male C57/Bl6 mice that underwent distal middle cerebral artery occlusion (DMCAO). Outcome measurements included TGF-B signaling, reactive astrogliosis within the glymphatic system, and impaired glymphatic flow. As a potential therapy, an implantable subcutaneous osmotic pump was inserted post-stroke with a TGF-B antagonist (GW788388 Hydrate-10mg/kg/day) to determine the impact on astrogliosis, glymphatic flow, and functional outcome. Results for in vivo studies using immunohistochemistry demonstrated a significant increase (p<0.05) in TGF-B expression in aged sham/DMCAO compared to young sham/DMCAO. There was a significant (p<0.01) increase in astrogliosis in aged sham/DMCAO compared to young sham/DMCAO. Glymphatic flow was assessed using an injected dextran dye, results demonstrated a significant (p<0.05) reduction in glymphatic flow for aged DMCAO compared to naïve mice. Functional measurements demonstrated that aged DMCAO had a significant reduction (p<0.05) in Paw Area/Time (Digigait) compared to naïve. Following TGF-B antagonist treatment, there was no difference between aged DMCAO and naïve mice in astrogliosis, glymphatic flow, or Paw Area/Time. This demonstrates that TGF-B impairs post-stroke recovery through astrogliosis, and impaired glymphatic flow. While this study demonstrated positive effects post-stroke, future studies should target downstream pathways of TGF-B.

Inhibition of calcium/calmodulin-dependent protein kinase kinase (CaMKK) exacerbates impairment of endothelial cell and blood-brain barrier after stroke

Brain microvascular endothelial cells play an essential role in maintaining blood-brain barrier (BBB) integrity, and disruption of the BBB aggravates the ischemic injury. CaMKK (α and β) is a major kinase activated by elevated intracellular calcium. Previously, we demonstrated that inhibition of CaMKK exacerbated outcomes, conversely, overexpression reduced brain injury after stroke in mice. Interestingly, CaMKK has been shown to activate a key endothelial protector, sirtuin 1 (SIRT1). We hypothesized that CaMKK protects brain endothelial cells via SIRT1 activation after stroke. In this study, Oxygen-Glucose Deprivation (OGD) was performed in human brain microvascular endothelial cells. Stroke was induced by middle cerebral artery occlusion (MCAO) in male mice. Knockdown of CaMKK β using siRNA increased cell death following OGD. Inhibition of CaMKK β by STO-609 significantly and selectively down-regulated levels of phosphorylated SIRT1 after OGD. Changes in the downstream targets of SIRT1 were observed following STO-609 treatment. The effect of STO-609 on cell viability after OGD was absent, when SIRT1 was concurrently inhibited. We also demonstrated that STO-609 increased endothelial expression of the pro-inflammatory proteins ICAM-1 and VCAM-1 and inhibition of CaMKK exacerbated OGD-induced leukocyte-endothelial adhesion. Finally, intracerebroventricular injection of STO-609 exacerbated endothelial apoptosis and reduced BBB integrity after 24-hr reperfusion following MCAO in vivo. Collectively, these results demonstrated that CaMKK inhibition reduced endothelial cell viability, exacerbated inflammatory responses and aggravated BBB impairment after ischemia. CaMKK activation may attenuate ischemic brain injury via protection of the microvascular system and a reduction in the infiltration of pro-inflammatory factors.

Serum Markers of Blood-Brain Barrier Remodeling and Fibrosis as Predictors of Etiology and Clinicoradiologic Outcome in Intracerebral Hemorrhage

Background: Intracerebral hemorrhage (ICH) is a stroke subtype associated with high disability and mortality. There is a clinical need for blood-based biomarkers that can aid in diagnosis, risk stratification, and prognostication. Given their role in the pathophysiology of ICH, we hypothesized markers of blood-brain barrier disruption and fibrosis would associate with neurologic deterioration and/or long-term functional outcomes. We also hypothesized these markers may be unique in patients with ICH due to cerebral amyloid angiopathy (CAA) vs. other etiologies.

Methods: Seventy-nine patients enrolled in prospective ICH registries at two separate hospitals (the University of Texas Health Science Center at Houston and Hartford Hospital) were included in this study. We assessed initial injury severity and admission variables along with measures of inpatient deterioration (hematoma expansion, perihematomal edema (PHE), and early and delayed neurologic deterioration) and functional outcome [modified Rankin Scale (mRS) score at discharge and 90 days]. Serial biospecimens were obtained at 5 pre-specified timepoints (within 24 h, 1–2, 3–5, 6–8, and 10 days); serum samples were analyzed for fibronectin, all three TGF-β isoforms, and 7 matrix metalloproteinases (MMPs).

Results: In our initial correlation analysis, MMP 10 and 3 were associated with hematoma expansion and early neurologic deterioration, whereas MMP 8 and MMP 1 were associated with PHE and delayed neurologic deterioration (respectively). Subacute levels of MMP 8 (sampled from day 6–10) positively correlated with PHE even after adjusting for multiple comparisons (p = 0.02). Acute levels of MMP 1, TGF-β1, and TGF-β3 were predictive of functional outcome, with TGF-β1 and TGF-β3 associating with 90 day mRS independent of age, hematoma volume, hemorrhage location, GCS, and IVH [p = 0.02; OR 1.03 (95% CI 1.0–1.05); p = 0.03; OR 3.1 (95% CI 1.1–8.8)]. When evaluated together as a panel, the cytokines distinguished patients with ICH due to CAA vs. ICH due to hypertension (AUC 0.81).

Conclusions: Serum levels of fibronectin, TGF-β, and MMPs may be useful in refining ICH etiology and prognosis. Further large-scale studies are needed to confirm these findings, particularly regarding patients with CAA.

Abstract 71: Circulating Inter-alpha Inhibitor Protein Levels Decline After Stroke in Humans: Exogenous Supplementation is Protective in Multiple Animal Models of Ischemic Stroke

Introduction: Inter-alpha Inhibitor Proteins (IAIP) are a family of endogenous plasma and extracellular matrix molecules. IAIPs have been shown to down-regulate inflammation, inhibit destructive serine proteases, and bind extracellular histones to neutralize cytotoxicity. Interestingly, many of these factors also regulate neuroprotection after stroke. In our initial studies, we found that IAIP treatment was neuroprotective in the middle cerebral artery occlusion model. Here, we analyzed if stroke alters IAIP using plasma samples from both mice and human stroke patients, and we investigated whether IAIP could provide neuroprotection using multiple stroke models.

Methods: C57BL/6 mice were subjected to stroke with an autologous thromboembolic clot followed by reperfusion using t-PA. A separate cohort underwent the permanent occlusion model. Mice were randomized to receive IAIP or vehicle at 6h and 18h after stroke onset. Infarct was assessed 48h after reperfusion with t-PA, or 72h after permanent occlusion. Plasma samples from stroke patients and vascular risk factor matched controls were used for changes in IAIP levels using ELISA. Statistics were performed by two-sample t-test or Wilcoxon rank-sum test. P <0.05 considered significant.

Results: IAIP treatment significantly reduced total injury size (t-PA alone 22±2% vs. t-PA+IAIP 13±3%; n=4-5/grp). Protection was also seen after permanent occlusion (vehicle 59.4±3.9% vs IAIP 39.5±5.9%; n=6-8/gp, p<.05), showing efficacy of IAIP in two different models. IAIP treatment improved survival rates (82% with IAIP vs 63% with vehicle) and neurological scores compared to vehicle group (p<0.05). Mean IAIP levels were significantly lower (stroke patients 134.4 ug/ml; n=51 vs controls 157.5 ug/ml; n=40), in parallel, increased IAIP-Histone complexes were seen in these patients. Similar changes were identified in mouse samples.

Conclusions: Our results show that delayed IAIP treatment can significantly reduce cell death in both permanent ischemia and/or in combination with t-PA. IAIP could potentially represent an important, novel treatment for stroke. Our studies in combination with t-PA further strengths this clinical translatability and to design personalized dosing based on IAIP levels.

Abstract 68: Peripheral Markers of Blood-Brain Barrier Remodeling Predict Intracerebral Hemorrhage Etiology and Outcomes

Introduction: Intracerebral hemorrhage (ICH) dramatically remodels the blood-brain barrier (BBB). However, BBB remodeling may differ between ICH cases due to location (lobar or deep hemorrhage) as well as etiology (hypertension, trauma or amyloid-β). This study addresses whether serum levels of BBB remodeling proteins, including matrix metalloproteases (MMPs), transforming growth factor-β (TGF-β) and fibronectin (FN), are biomarkers of ICH etiology and outcomes.

Hypothesis: We hypothesize that serum MMP, TGF-β and FN levels are predictive of ICH etiology, severity and functional outcomes.

Methods: Patient data (n=37 lobar, n=42 deep ICH patients) were abstracted from prospective ICH databases detailing admission data, radiology, hospital course (ICH score, NIH stroke scale [NIHSS], Glasgow Coma Scale [GCS]), and functional outcomes (modified Rankin Scale [mRS], Euroqol). Serum samples were drawn from admission to 10 days post-injury. Levels of TGF-β isoforms, MMPs and FN were measured by multiplex ELISA (11 cytokines total) and divided into early (<24hrs-5 days) and late (6-10 days) groups for analysis. P-values were obtained by Spearman correlation, Wilcoxon rank sum or Kruskal Wallis tests, with false discovery rate controlled at 0.05.

Results: Early FN levels were lower in lobar than deep hemorrhages ( p=0.007 ). Levels of early MMP-8, -9 and -10, as well as levels of TGF-β1, TGF-β2 and TGF–β3 positively correlated with initial neurological deficits (NIHSS, p=0.005-0.039 ). Additionally, late MMP-8 levels negatively correlated with edema ( p=0.018 ). Furthermore, early MMP-1, TGF-β1 and TGF-β3 levels positively correlated with persistent neurologic deficits (mRS) at discharge and 90-days post-injury ( p=0.003-0.041 ). Finally, females had lower early levels of MMP-8, -9 and -10 than males ( p=0.019, 0.019, 0.019 ).

Conclusion: BBB remodeling markers change with ICH location and patient sex, and are predictive of functional deficits and recovery. Specifically, these markers correlate with (1) the type and severity of initial injury, (2) the induction of secondary injury and (3) long-term functional recovery. This research improves our understanding of BBB responses to ICH, and may lead to novel biomarkers for ICH diagnosis and treatment.

Abstract WP412: Fibronectin Increases the Paravascular Deposition of Amyloid-β in Aging and Stroke

Introduction: Ischemic stroke is a major risk factor for cerebral amyloid angiopathy (CAA), which may be driven by alterations in the paravascular transport of cerebrospinal fluid (CSF) amyloid-β 1-40 (Aβ 40 ) through the basement membrane (BM). Post-stroke BM thickening may favor CSF Aβ 40 deposition within brain microvessels. This study identifies BM fibronectin (FN) and its receptor, α5β1 integrin, as novel drivers of paravascular Aβ 40 deposition after stroke in aged animals.

Hypothesis: We hypothesize that stroke-induced FN expression induces paravascular deposition of CSF Aβ 40 within the brain. This may worsen with aging due to increased FN binding to α5β1 integrin.

Methods: Young (3 months-old) and aged (18 months-old) male mice were subjected to experimental stroke, and fluorescent tracers were intracisternally microinjected 30 days later to measure brain uptake of CSF Aβ 40 . BM thickening (lectin staining), as well as endogenous levels of FN and α5β1 integrin, were measured by immunohistochemistry and Western blot. To assess FN-Aβ 40 binding, naïve young and aged mice were intracisternally injected with FN or vehicle, and Aβ 40 uptake from CSF measured. Statistical significance was confirmed by two-way ANOVA with Dunnet’s post-hoc test.

Results: Stroke enhanced paravascular Aβ 40 deposition compared to size-matched dextran in young animals ( p<.05 ), which worsened with aging ( p<.001 ). Interestingly, BM thickening positively correlated with paravascular Aβ 40 deposition after stroke in both age groups (R=.98, p<.001 ). Furthermore, FN levels increased in both young ( p<.05 ) and aged ( p<.05 ) cortex after stroke, with additional increases seen in α5β1 integrin expression in aged cortex at baseline ( p<.05 ) and with stroke ( p<.01 ). Finally, FN exhibited affinity for Aβ 40 in vitro (IC50= 216nM), and FN infusion increased paravascular Aβ 40 deposition in vivo ( p<.05 ), which worsened with aging ( p<.05 ) .

Conclusion: These results indicate that FN induces paravascular Aβ 40 deposition after stroke. Furthermore, increased α5β1 integrin may ‘prime’ the aged vasculature for FN-Aβ binding, worsening Aβ 40 deposition after stroke in aged animals. Targeting FN-Aβ adhesion may provide a novel therapeutic avenue to reduce CAA in stroke survivors.

Abstract WP438: The Role of Transforming Growth Factor-beta in Post-Stroke Glymphatic Impairment

Introduction: The recently discovered glymphatic system may protect the brain from dementia by clearing toxic amyloid-β (Aβ) along the basement membrane (BM) via bulk flow of cerebrospinal fluid (CSF). It is not known whether stroke impairs glymphatic flow, or how this might occur. Previous work has shown that stroke enhances astrocytic transforming growth factor-β (TGF-β) signaling, which could increase the expression of pro-fibrotic BM proteins such as fibronectin. BM fibrosis may obstruct glymphatic flow after stroke, driving Aβ accumulation and neurodegenerative disease in stroke survivors.

Hypothesis: I hypothesize that stroke induces BM fibrosis via enhanced TGFβ-Smad2 signaling in perivascular astrocytes, impairing glymphatic flow.

Methods: To test this hypothesis, the glymphatic influx of CSF tracer in mice following stroke or TGF-β treatment (ICV, 500 ng) was assessed. TGF-β signaling was measured as Smad2 phosphorylation. Brain expression of fibronectin and GFAP (astrocytes) were assessed by western blot and immunohistochemistry.

Results: Stroke impaired the glymphatic distribution of FITC-dextran and FITC-Aβ bilaterally ( Fig. 1 ). TGF-β treatment also inhibited glymphatic distribution, measured by reduced 14 C-Inulin uptake (38 fold-reduction, p < .05). Increased fibronectin (5.5 ± 0.7 fold-increase) and GFAP (2.3 ± .2 fold-increase) expression was found after stroke (p < .05 ), localized to the glial scar and around vessels bilaterally . Finally, Smad2 phosphorylation was increased in cortex contralateral to injury (2.5 ± 0.2 fold, p < .01).

Conclusion: The present study shows that stroke impairs glymphatic flow, which may be mediated through increased TGF-β signaling and global BM fibrosis. This could impair the clearance of Aβ, leading to dementia in stroke survivors. TGF-β inhibition can rescue post-stroke fibrosis, glymphatic flow and Aβ clearance, presenting a novel therapeutic target for post-stroke dementia.

Abstract TP452: Systemic Inflammation Reverses Stroke-induced Changes in Astrocytic Aquaporin-4 Expression

Introduction: Aquaporin-4 (AQP4) is a perivascular water channel that plays a key role in regulating the blood-brain barrier (BBB). Stroke acutely reduces expression and polarization of AQP4 on astrocytic endfeet, and these vascular changes might persist chronically and evolve with systemic inflammation. Reduced polarization of AQP4 after traumatic brain injury (TBI) leads to impaired perivascular clearance of debris and cognitive decline in mice, and if similar changes occur after stroke, then they may also contribute to post-stroke dementia.

Hypothesis: Stroke will cause lasting changes in vascular organization, reducing astrocytic AQP4 expression and polarization in the area of injury.

Methods: Thirty male Balb/cJ mice were subjected to distal middle cerebral artery ligation, allowed to survive for 28 days, and sacrificed 24 hours after injection with lipopolysaccharide (LPS, 0.33 mg/kg i.p.) or saline to model systemic inflammation. Three sequential coronal sections (20 μm) near the site of infarct (0.25 mm from Bregma) were stained with lectin, AQP4, and glial fibrillary acidic protein (GFAP) to evaluate BBB organization. Vessel density was evaluated with AngioTool. AQP4 expression was evaluated by Western blot.

Results: Stroke increased vascular density in the injured hemisphere (11 ± 0.8% vs 7.6 ± 0.8% in sham mice, p < 0.05). Decreased AQP4 expression and polarization near the site of the infarct was observed, which were reversed with LPS (Figure 1). LPS increased AQP4 protein levels in stroke (2.5 ± 0.37 fold-increase, p < 0.05), but not sham mice.

Conclusions: Stroke caused a chronic increase in vascular density, with peri-infarct vessels displaying decreased expression and changed polarity of AQP4. However, with systemic inflammation, this is reversed, potentially contributing to neuroinflammation and worsened cognitive outcomes in stroke patients who encounter infections via increased permeability of these abnormal vessels.

Prevention and management of stroke in women

Stroke is the leading cause of acquired disability and the third leading cause of death in women worldwide. Sex differences in risk factors, treatment response and quality of life after stroke complicate stroke management in women. Women have an increased lifetime incidence of stroke compared to men, largely due to a sharp increase in stroke risk in older postmenopausal women. Women also have an increased lifetime prevalence of stroke risk factors, including hypertension and atrial fibrillation in postmenopausal women, as well as abdominal obesity and metabolic syndrome in middle-aged women. Controversy continues over the risks of oral contraceptives, hormone therapy and surgical intervention for carotid stenosis in women. Pregnancy and the postpartum period represent a time of increased risk, presenting challenges to stroke management. Recognition of these issues is critical to improving acute care and functional recovery after stroke in women.

Hippocampal theta, gamma, and theta-gamma coupling: effects of aging, environmental change, and cholinergic activation

Hippocampal theta and gamma oscillations coordinate the timing of multiple inputs to hippocampal neurons and have been linked to information processing and the dynamics of encoding and retrieval. One major influence on hippocampal rhythmicity is from cholinergic afferents. In both humans and rodents, aging is linked to impairments in hippocampus-dependent function along with degradation of cholinergic function. Cholinomimetics can reverse some age-related memory impairments and modulate oscillations in the hippocampus. Therefore, one would expect corresponding changes in these oscillations and possible rescue with the cholinomimetic physostigmine. Hippocampal activity was recorded while animals explored a familiar or a novel maze configuration. Reexposure to a familiar situation resulted in minimal aging effects or changes in theta or gamma oscillations. In contrast, exploration of a novel maze configuration increased theta power; this was greater in adult than old animals, although the deficit was reversed with physostigmine. In contrast to the theta results, the effects of novelty, age, and/or physostigmine on gamma were relatively weak. Unrelated to the behavioral situation were an age-related decrease in the degree of theta-gamma coupling and the fact that physostigmine lowered the frequency of theta in both adult and old animals. The results indicate that age-related changes in gamma and theta modulation of gamma, while reflecting aging changes in hippocampal circuitry, seem less related to aging changes in information processing. In contrast, the data support a role for theta and the cholinergic system in encoding and that hippocampal aging is related to impaired encoding of new information.

Metabolic patterns and insulin responsiveness of enlarging fat cells

The rate and pattern of glucose metabolism, basal lipolysis, and intracellular concentration of free fatty acids were determined in isolated epididymal fat cell preparations (mean volume 30-800 pl) from rats on the basis of fat cell number and in relation to the cell volume. The effects of increasing glucose concentrations in the medium and of insulin on the cellular metabolic activities were compared. Expanding fat cell volume correlated positively and significantly (P < 0.001) with the synthesis of glyceride glycerol from glucose (correlation coefficient, r = 0.919), with rates of basal lipolysis (r = 0.663), and with intracellular free fatty acid accumulation (r = 0.796); it correlated negatively and significantly with glucose conversion to glyceride fatty acids (r = -0.814, P < 0.01). The differences in patterns of glucose metabolism and basal lipolysis between small (<100 pl) and large (>400 pl) fat cells were not modified by insulin or by increments in glucose concentration. The results indicate that the reduced capacity of the large fat cells to respond to insulin cannot be attributed solely to a limited capacity of the cells to take up and metabolize increasing amounts of glucose. The acquired unresponsiveness of the large cells to insulin may result from an alteration in the mechanism of action of insulin and may be related to an intracellular metabolic derangement with increased basal lipolysis, free fatty acid accumulation, and accelerated glyceride synthesis resulting from the accumulation of triglyceride.