Reduction In Flow Research Articles

Loss of glymphatic homeostasis in heart failure.

Heart failure (HF) is associated with progressive reduction in cerebral blood flow (CBF) and neurodegenerative changes leading to cognitive decline. The glymphatic system is crucial for the brain's waste removal, and its dysfunction is linked to neurodegeneration. In this study, we used a mouse model of HF, induced by myocardial infarction (MI), to investigate the effects of HF with reduced ejection fraction on the brain's glymphatic function. Using dynamic contrast-enhanced MRI and high-resolution fluorescence microscopy, we found increased solute influx from the CSF spaces to the brain, i.e. glymphatic influx, at 12 weeks post MI. Two-photon microscopy revealed that cerebral arterial pulsatility, a major driver of the glymphatic system, was potentiated at this timepoint, and could explain this increase in glymphatic influx. However, clearance of proteins from the brain parenchyma did not increase proportionately with influx, while a relative increase in brain parenchyma volume was found at 12 weeks post MI, suggesting dysregulation of brain fluid dynamics. Additionally, our results showed a correlation between brain clearance and CBF. These findings highlight the role of CBF as a key regulator of the glymphatic system, suggesting its involvement in the development of brain disorders associated with reduced CBF. This study paves the way for future investigations into the effects of cardiovascular diseases on the brain's clearance mechanisms, which may provide novel insights into the prevention and treatment of cognitive decline.

Aeromedical evacuation-relevant hypobaria following traumatic brain injury in rats contributes to cerebral blood flow depression, altered neurochemistry, and increased neuroinflammation.

Aircraft cabins are routinely pressurized to the equivalent of 8000 ft altitude. Exposure of lab animals to aeromedical evacuation relevant hypobaria after traumatic brain injury worsens neurological outcomes, which is paradoxically exacerbated by hyperoxia. This study tested the hypothesis that exposure of rats to hypobaria following cortical impact reduces cerebral blood flow, increases neuroinflammation, and alters brain neurochemistry. Rats were exposed to simulated ground (normobaric) or air (hypobaric 8000 ft) transport, under normoxia or hyperoxia, 24 hr after trauma. Hypobaria exposure resulted in lower cerebral blood flow to the contralateral cortex and bilateral thalamus during flight and increased delayed cortical inflammation (ED1 immunoreactivity) at 14 days post injury. Impacted rats exposed to hypobaria had higher cortical creatine levels compared rats maintained at sea level. Exposure to the combination of hyperoxia and hypobaria resulted in the greatest reduction in cortical blood flow and total creatine during flight which persisted up to two weeks. In conclusion, hypoperfusion during hypobaria exposure could contribute to worsening of neuroinflammation and neurochemical imbalances. The presence of excessive O2 during hypobaria results in long-term suppression of cerebral blood flow, indicating that supplemental O2 should be titrated during hypobaria to maintain normoxia.

Evaluation of the Hydrological Response of Nature-Based Solutions (NBS) in Socio-Economically Vulnerable Tropical Urban Settlements: A Case Study in La Guapil, Costa Rica, Under Climate Change Scenarios

Urbanization increases the number of impervious surfaces in watersheds, reducing infiltration and evapotranspiration, which increases runoff volumes and the risks of flooding and the pollution of water resources. Nature-based solutions (NBS) mitigate these effects by managing water volume and quality, restoring the hydrological cycle, and creating sustainable livelihoods that can promote socioeconomic equity by providing green space. In light of the aforementioned information, this study analyzes the hydrological response of NBS in La Guapil, a densely populated and socioeconomically vulnerable area of Costa Rica with approximately 80% impervious surfaces, focusing on their effectiveness in stormwater management and improving hydrological conditions. Field data from the study area’s storm drainage system, as well as hydrological analyses, were collected and processed to evaluate RCP8.5 climate change scenarios using the Clausius–Clapeyron (CC) relationship. Three scenarios were proposed: (1) the “status quo”, reflecting current conditions, (2) green roofs and green improvements, and (3) detention ponds and green improvements, evaluated using the SWMM, with the latter scenario also using the Iber model. Simulations showed that Scenario 2 achieved the greatest reduction in peak flow (53.74%) and runoff volume (57.60%) compared to Scenario 3 (peak: 28.37%; volume: 56.42%). Both scenarios demonstrate resilience to climate change projections. The results of this study provide a foundation for further research into NBS in Costa Rica and other comparable regions.

Computational analysis of flow and transport suggests reduced oxygen levels within intracranial aneurysms, especially in individuals with sickle-cell disease.

Sickle cell disease (SCD) is a genetic condition characterized by an abundance of sickle hemoglobin in red blood cells. SCD patients are more prone to intracranial aneurysms (ICA) compared to the general population, with distinctive features such as multiple intracranial aneurysms: 66% of SCD patients with ICAs have multiples ICAs, compared to 20% in non-sickle patients. The exact mechanism behind these associations is not fully understood, but there is a hypothesized link between hypoxia and impaired synthesis of extracellular matrix, which may weaken the vessel walls, favoring aneurysm formation and rupture. SCD patients experience reduced blood oxygen levels, potentially exacerbating hypoxia in ICAs, and potentially contributing to aneurysm development and early onset in these patients. In this work, we performed a series of computational studies (Fluent) using idealized geometries to investigate the key differences in the oxygen transport and blood flow dynamics inside an aneurysm formation for sickle and non-sickle cases. We found that using SCD parameters resulted in a 14% to 68% reduction in blood flow and a 37% to 70% reduction in oxygen availability within the aneurysm, depending on the vessel curvature and the aneurysm throat diameter, due to factors including oxygen-dependent viscosity and alteration in the oxygen transport. The results indicate that depending on geometry and flow characteristics, some degree of hypoxia maybe present in aneurysm bulb and would be more severe in SCD patients. This study hopes to bring into attention the potential presence of hypoxic environment in the aneurysm bulb.

Regional cerebral blood flow reflects both neurodegeneration and microvascular integrity across the Alzheimer's continuum.

Alzheimer's disease (AD) typically involves both neurodegenerative and vascular pathologies, each associated with reductions in cerebral blood flow (CBF). However, it remains unclear whether vascular and neural contributions to regional CBF can be differentiated. Using 3D background-suppressed arterial spin labeled perfusion magnetic resonance imaging, we evaluated regional CBF in a cohort of 257 participants across the AD continuum and assessed the impact of risk factors for both AD and small vessel disease (SVD) on regional CBF. Vascular risk factors (VRFs) were associated with reduced CBF in normal-appearing periventricular white matter, while amyloid positivity was associated with reduced CBF in the posterior cingulate cortex and precuneus. Putative SVD-sensitive regions in white matter exhibited diagnosis-related CBF changes comparable to those in typical AD cortical regions. Spatial patterns of hypoperfusion may differentiate AD and VRF-related effects on regional CBF. Our findings also support the contribution of SVD in AD pathogenesis. We used 3D background-suppressed pCASL MRI to evaluate CBF across the AD continuum. Putative SVD-sensitive regions in white matter exhibited diagnosis-related CBF changes. AD and/or SVD risk correlated with reduced CBF in AD and/or SVD-related regions. VRFs were associated with more widespread CBF reductions than amyloid positivity. Spatial patterns of hypoperfusion may differentiate AD and VRF-related effects.

Use of the SWAT Model to Simulate the Hydrological Response to LULC in a Binational Basin between Ecuador and Peru

Land use change has played a crucial role in altering the hydrological behavior, making detailed assessments essential to ensure sustainable water resource management and the conservation of natural ecosystems. This study focuses on simulating the impact of different Land Use and Land Cover (LULC) scenarios for the years 1985, 1995, 2005, and 2015 on the water balance in the Puyango-Tumbes River basin, which spans across Ecuador and Peru, during the period 1981-2015. The results indicated an 18.3% increase in the grassland areas and a significant 38.2% reduction in the savanna zones, contributing to an annual 2.1% increase in the Evapotranspiration (PET) rates. These land use changes led to a 29.2% decrease in the Percolation (PERC), a 20.7% decrease in the Surface Runoff (SURQ), a 33% reduction in the Groundwater Flow (GW_Q), and a 26.6% decrease in the Annual Water Yield (WYLD), as well as a slight reduction of 0.9% in the Lateral flow (LAT_Q). These findings highlight the importance of considering land use changes to ascertain the sustainable management of natural resources, particularly in a transboundary basin.

Comparative Evaluation of Salivary Flow Rate in Oral Submucous Fibrosis Patients before and after Transcutaneous Electric Nerve Stimulation: A Research Protocol

Introduction: A persistent, precancerous, and frequently debilitating condition-Oral Submucous Fibrosis (OSMF) is characterised by a slowly progressing fibrosis of the oropharynx and oral cavity. A reduction in salivary flow is one of the common symptoms experienced by sufferers. Using electric current to stimulate nerves, Transcutaneous Electric Nerve Stimulation (TENS) can be an effective method for improving salivation. TENS serves as a simple, affordable, and non invasive approach that can decrease the discomfort associated with long-lasting hyposalivation. Need of the Study: Although the effectiveness of TENS on salivary flow rate has been studied in various conditions, there is a lack of evidence or studies describing the effect of TENS on salivary flow rate in patients with OSMF. This has led to the intention of the present study. Aim: To evaluate and compare the salivary flow rate in OSMF patients before and after TENS. Materials and Methods: This prospective research investigation will be conducted in the Department of Radiology and Oral Medicine, Sharad Pawar Dental College and Hospital, Sawangi, wardha, Maharashtra, India, from February 2024 to January 2025. Patients aged between 18 and 45 years suffering from OSMF will be included in the study, evaluated based on the Inventory of Xerostomia (XI) questionnaire to confirm reduced salivation. Each patient will receive TENS treatment at 40 Hz for 15 minutes. The Modified Schirmer Test (MST) will be used to evaluate the salivary flow rate before and after TENS therapy. All findings will be recorded in a tabular format and subjected to appropriate statistical tests to evaluate the statistical significance regarding the improvement in salivary flow rate.

Investigations to reduce rarefied gap flows within positive displacement vacuum pumps by utilising surface structures

Abstract The ultimate pressure and efficiency of positive displacement vacuum pumps is limited by the backflow through the gaps within the machines. These gap flows are typically reduced by decreasing the gap height, which is limited for reasons of operational safety. Therefore, this study concentrates on the reduction of rarefied gap flows by means of suitable surface structures whose dimensions are small compared to the gap height without simultaneously reducing the minimum gap height. For this purpose, a method is presented to efficiently calculate the impact of the surface structure on these gap flows. Based on this method, design parameters for the choice of a suitable surface structure are discussed. Furthermore, a possible transfer for the application on the rotors is shown including a proposal for the machining process.

The Effect of Using Ureolytic Bacteria as Self-Healing Agent in Concrete on Workability, Density and Absorption

Abstract Concrete is one of the fastest growing construction materials in Indonesia. Concrete has a low tensile strength that causes concrete to crack easily. One way to overcome this is by using self-healing concrete. This concrete is able to repair small cracks. Ureolytic bacteria can be used as a medium in self-healing concrete. These bacteria undergo a CaCO3 precipitation process to produce calcite which later fills the cracks in the concrete. This research aims to determine the effect of the application of ureolytic bacteria on the workability, density, and absorption of high-strength concrete. Additionally, the study investigates the elemental composition of self-healing concrete using Bacillus sp., Solibacillus sp., and Staphylococcus sp. as the healing medium. In the study, the test specimens used were cubes measuring 5 cm × 5 cm × 5 cm. The tests carried out in this study were testing the workability, density, and absorption of concrete. In this study, ureolytic bacteria Bacillus sp., Solibacillus sp., and Staphylococcus sp. were used with variations of 0%, 0.5%, 0.6% and 0.7% by weight of fine aggregate. The lowest flow reduction value is found in the addition of Bacillus sp. 0.5% bacteria with a value of 2%. The decrease in density value in self-healing concrete is not too significant. The lowest decrease was found in concrete with the addition of Staphylococcus sp. 0.5% bacteria with a value of 0.3%. The lowest absorption value is found in the specimen without the addition of bacterial capsules, which is 2.44%. Energy dispersive X-ray spectroscopy (EDS) test results on ureolytic bacterial self-healing concrete show that there are elements of C, O, Mg, Al, Si, S, and Ca in this concrete.

Assessing flow diverter porosity: a comparative analysis of quantification techniques based on imaging and simulation

ABSTRACT Background/Purpose Flow diverter porosity directly influences the blood flow reduction at the aneurysm neck level and the anatomical result of the treatment. In this research, we present and compare three methodologies to determine the local porosity of deployed flow diverters. Method Three-dimensional rotational angiography was used to obtain computational vessel models of three patients. Different flow diverters were virtually deployed in the computational models and implanted in 3D-printed models of the vasculatures by interventional neuroradiologists. Experimental porosity determinations were conducted using 2D microscope photographs and 3D Dyna-CT images (i.e. cone-beam Computed Tomography angiographic images), while simulated porosity was computed using ANKYRAS software. Results No statistically significant differences were observed between the porosity distributions from the three methods (p > 0.01). When computing the differences point-by-point, narrow distributions centered on zero were obtained, revealing a good agreement in the determinations. Orthogonal regression analysis affirmed this equivalence. The lowest agreement between porosity measurement methods was observed to occur at curve segments with relatively low porosity. Conclusions The local porosity of deployed flow diverters can be accurately determined by the three methods presented in this work. Assessing FD porosity with 3D Dyna-CT images would allow the evaluation of real patient data, whereas simulations could determine local porosity before the treatment.

Assessment of cerebral perfusion alterations in dementia with Lewy bodies and Alzheimer's disease.

Dementia with Lewy bodies (DLB) and Alzheimer's disease (AD) are common forms of dementia, characterized by overlapping clinical symptoms. Functional neuroimaging can provide valuable information for precise diagnosis. Our objective was to explore cerebral perfusion alterations in DLB and AD, and to determine which perfusion parameters are helpful in distinguishing DLB and AD. A total of 25 DLB patients, 34 AD patients, and 40 normal controls (NC) underwent neuropsychological testing and pseudo-continuous arterial spin labeling (pcASL) for assessing cerebral perfusion [mean cerebral flow (mCBF); arterial transit time (ATT)] indexes. Differences in perfusion indexes among the three groups were analyzed and the family-wise error (FWE) was used for multiple comparisons. Spearman analysis assessed the relationships between the mCBF and neuropsychological scores [mini-mental state examination (MMSE); Montreal Cognitive Assessment (MoCA)]. A receiver operating characteristic (ROC) analysis was conducted to evaluate the performance and discriminant value of different perfusion indices in distinguishing between the two diseases. Compared with NC, the mCBF of patients with DLB was reduced mainly in the bilateral frontal lobe, bilateral parietal lobes, bilateral temporal lobes, and the right occipital lobe. AD patients showed lower mCBF mainly in the bilateral frontal lobes, the right temporal lobe, and the left parietal lobe. Compared with AD, DLB patients showed decreased mCBF in the bilateral frontal and parietal lobes. ATT in almost all major arterial regions was prolonged in DLB and AD when compared to NC. Compared with AD, ATT was significantly prolonged in DLB (P<0.05). Furthermore, the DLB demonstrated a significant positive correlation between mCBF and MMSE scores, particularly in regions such as the left superior parietal lobule (r=0.596, P=0.002) and the right precuneus (r=0.498, P=0.01). Similarly, AD exhibits a positive correlation between mCBF and MMSE scores within regions, such as the right middle temporal gyrus (r=0.550, P=0.001) and the left inferior parietal lobule (r=0.571, P<0.001). The perfusion indexes could help distinguish DLB from AD. DLB demonstrates a different pattern of regional blood flow reduction and prolonged ATT, which is different from that in AD. ASL-derived parameters provide critical discriminative information for differentiating DLB and AD.

Transaxillary access for PDA Stenting in Neonates with Duct-Dependent Cyanotic Congenital Heart: A Retrospective Study

Background: Duct-dependent cyanotic congenital heart is a critical heart disease in infants. In neonates, patients with obstructing native ductus arteriosus may need palliative stenting to maintain adequate blood flow during the transition period. These babies are similar to ductal-dependent lesions but require patent ductus arteriosus (PDA) flow for their transition from fetal to neonatal circulation. PDA stenting is a well-recognized palliative for duct-dependent cyanotic congenital heart in neonates. Objectives: The study highlights the clinical utilities of transaxillary access for PDA stenting in neonates with duct-dependent cyanotic congenital heart Methods: The study aimed to evaluate the effectiveness of transaxillary access for direct stenting and stent placement in neonates with stable duct-dependent congenital heart disease and cyanosis due to non-obstructive arterial duct. The study involved a retrospective approach, using existing data and focusing on acute interventional procedure success with transaxillary access. Secondary endpoints included successful weaning from access to surgical conduit, cannula removal, antegrade flow reduction if connected to BDG, need and success rate of transaxillary plug insertion, and major and minor complications associated with AXA. The study design allowed for a comprehensive evaluation of the feasibility of this technique and its potential benefits and drawbacks. Data was collected from electronic medical records, Picture Archiving and Communication System, and the electronic database of the Intensive Care Unit of a hospital between 2016 and 2021. The study aimed to evaluate the risk-benefit of performing DDC in neonates through the AS in a new cohort of patients in the future. Results: This retrospective study examined the management of cyanotic congenital heart disease in 36 neonates, with eight cases involving elbow neoaortic utilization and 28 having a PDA diameter less than 1 mm. In seven cases, a 4-Fr angiographic pigtail was inserted retrograde to image the PDA, which was then accessed by navigating a 4-Fr JB1 catheter from the cannulation site. A portable X-ray unit was used exclusively to position these catheters and wires during the procedures under C-arm guidance. Diagnostic catheter removals were managed differently in this study, following the same principles used for sheath extractions in 29 retrospective and prospective presentations. The study reported on the procedural outcomes for transaxillary access and PDA stenting in neonates with duct-dependent cyanotic congenital heart disease. The study found no specific demographic or additional pre-procedural risk factors that would affect the results of the study. Conclusion: Transaxillary PDA stenting is a safe method for treating duct-dependent hypoxic congenital hearts in neonates, but has limitations like limited use, long transcatheter treatment periods, and anesthesia risks. It's recommended for developing countries with limited access to advanced care. The study improved palliative PDA stenting standard in CCTGA patients with complex congenital heart disease. Recommendations include insertion of a transaxillary sheath, support, and arterial access under ultrasound guidance.

Negative hemodynamic response in the visual cortex: Evidence supporting neuronal origin via hemodynamic observation and two-photon imaging

The positive hemodynamic response (PHR) during stimulation often co-occurs with a strong, sustained negative hemodynamic response (NHR). However, the characteristics and neurophysiological mechanisms of the NHR, especially in regions distal to the PHR, remain incompletely understood. Using intrinsic optical imaging (OI) and two-photon imaging, we observed that forelimb electrical stimulation evoked strong PHR signals in the forelimb region of the primary somatosensory cortex (S1FL). Meanwhile, NHR signals primarily appeared in the primary visual cortex (V1), with a delayed onset and lower amplitude relative to the PHR signals. Additionally, stimulation led to a reduction in cerebral blood flow (CBF) in the NHR region. Notably, there was an overall suppression of the calcium response in the NHR region, although a small proportion (14 %) of neurons exhibited concurrent activation. Axon tracing revealed cortico-cortical projections from S1FL to V1. These findings suggest that neuronal deactivation significantly contributes to the origin of the NHR, offering additional insights into the specific inhibitory mechanisms underlying the NHR.

Sympathetic Nerves, Salivary Secretion, and the Parched Mouth of Fear: Unraveling Historical Perspectives on Persistent Contradiction in Physiology Textbooks.

We have observed two starkly contradictory notions regarding the sympathetic influence on the salivary outflow in discussions with our students. Most of them believe that sympathetic nerves decrease salivation and are antagonistic to parasympathetic nerves. Some students, however, show awareness of the cooperative stimulatory action of both types of autonomic fibers. We have found a similar dichotomy in the descriptions of the sympathetic effect on secretion of the main salivary glands and their inconsistent illustrations in Anatomy/Physiology textbooks. We have investigated the historical roots of this discrepancy. Ludwig discovered excitatory actions of both parasympathetic and sympathetic nerves on salivary flow by 1856. The next year, Czermak proposed the hypothesis of an inhibitory effect of sympathetic nerves, observing their interference with salivation induced by the chorda tympani (i.e., parasympathetic) stimulation. Bernard and Eckhard soon confirmed Ludwig's findings, but Czermak's notion persisted because sympathetically evoked salivation was unstable and potentially abatable by glandular vasoconstriction. The salivary secretory response to moderate sympathetic nerve electrostimulation was reaffirmed by Langley who also discovered salivation in response to adrenaline injection at the beginning of the 20th century. A few years later, Cannon, on a purely theoretical basis, attributed the sensation of dry mouth occasionally associated with fear to hyposalivation induced by elevated sympathetic discharge. Despite subsequent researchers' inability to find unequivocal evidence of salivary flow reduction by sympathetic activation, Cannon's assumption gained acceptance in some textbooks. Most Anatomy/Physiology textbook authors, however, recognized the excitatory action of sympathetic nerves on salivary glands established by Ludwig and Bernard.

Coronary Microvascular Dysfunction Is Associated With Augmented Lysosomal Signaling in Hypercholesterolemic Mice.

Accumulating evidence indicates that coronary microvascular dysfunction (CMD) caused by hypercholesterolemia can lead to myocardial ischemia, with or without obstructive atherosclerotic coronary artery disease. However, the molecular pathways associated with compromised coronary microvascular function before the development of myocardial ischemic injury remain poorly defined. In this study, we investigated the effects of hypercholesterolemia on the function and integrity of the coronary microcirculation in mice and the underlying mechanisms. Mice were fed a hypercholesterolemic Paigen's diet for 8 weeks. Echocardiography data showed that Paigen's diet caused CMD, characterized by significant reductions in coronary blood flow and coronary flow reserve, but did not affect cardiac remodeling or dysfunction. Immunofluorescence studies revealed that Paigen's diet-induced CMD was associated with activation of coronary arterioles inflammation and increased myocardial inflammatory cell infiltration. These pathological changes occurred in parallel with the upregulation of lysosomal signaling pathways in endothelial cells (ECs). Treating hypercholesterolemic mice with the cholesterol-lowering drug ezetimibe significantly ameliorated Paigen's diet-induced adverse effects, including hypercholesterolemia, steatohepatitis, reduced coronary flow reserve, coronary endothelial cell inflammation, and myocardial inflammatory cell infiltration. In cultured mouse cardiac ECs, 7-ketocholesterol increased mitochondrial reactive oxygen species and inflammatory responses. Meanwhile, 7-ketocholesterol induced the activation of transcriptional factor EB and lysosomal signaling in mouse cardiac ECs, whereas the lysosome inhibitor bafilomycin A1 blocked 7-ketocholesterol-induced transcriptional factor EB activation and exacerbated 7-ketocholesterol-induced inflammation and cell death. Interestingly, ezetimibe synergistically enhanced 7-ketocholesterol-induced transcriptional factor EB activation and attenuated 7-ketocholesterol-induced mitochondrial reactive oxygen species and inflammatory responses in mouse cardiac ECs. These results suggest that CMD can develop and precede detectable cardiac functional or structural changes in the setting of hypercholesterolemia and that upregulation of transcriptional factor EB-mediated lysosomal signaling in endothelial cells plays a protective role against CMD.

CFD investigations of a shape-memory polymer foam-based endovascular embolization device for the treatment of intracranial aneurysms.

The hemodynamic and convective heat transfer effects of a patient-specific endovascular therapeutic agent based on shape-memory polymer foam (SMPf) are evaluated using computational fluid dynamics studies for six patient-specific aneurysm geometries. The SMPf device is modeled as a continuous porous medium with full expansion for the flow studies and with various degrees of expansion for the heat transfer studies. The flow simulation parameters were qualitatively validated based on the existing literature. Further, a mesh independence study was conducted to verify an optimal cell size and reduce the computational costs. For convective heat transfer, a worst-case scenario is evaluated where the minimum volumetric flow rate is applied alongside the zero-flux boundary conditions. In the flow simulations, we found a reduction of the average intra-aneurysmal flow of > 85% and a reduction of the maximum intra-aneurysmal flow of > 45% for all presented geometries. These findings were compared with the literature on numerical simulations of hemodynamic and heat transfer of SMPf devices. The results obtained from this study provide a novel and practical framework for optimizing the design of patient-specific SMPf devices, integrating advanced computational models of hemodynamics and heat transfer. This framework could guide the future development of personalized endovascular embolization solutions for intracranial aneurysms with improved therapeutic outcome.

A Mouse Model for Vascular Cognitive Impairment and Dementia Based on Needle-guided Asymmetric Bilateral Common Carotid Artery Stenosis.

Vascular cognitive impairment and dementia (VCID) results from vascular brain injury. Given VCID's high incidence, which is expected to continue rising as the population ages, it is critical to establish a robust animal model for the disease. This paper presents a novel method of creating a mouse model of VCID that is based on asymmetric bilateral common carotid artery stenosis, which mimics human chronic cerebral hypoperfusion caused by carotid atherosclerosis. Briefly, common carotid arteries (CCAs) are ligated to different gauge needles (32 G for the right CCA and 34 G for the left CCA) using 7-0 silk sutures followed by immediate needle removal. The remaining suture rings cause persistent blood flow reduction and long-term cognitive impairment associated with white matter injury, microinfarcts, and reactive gliosis, thus closely mimicking the pathogenesis of VCID. Importantly, in this needle model, the clinical representations do not revert with time, providing reliable long-term cognitive impairment. Moreover, the survival rate 24 weeks post surgery was 81.6%, which is higher compared to the other established models of VCID with a similar level of blood flow reduction. Additional advantages include low material cost and compatibility with MRI to monitor brain injury in live animals since no metal is implanted. The main challenge in employing the needle model of VCID is the requirement for developing advanced surgical skills since mouse CCAs are less than 0.6 mm in diameter and are very fragile. High-quality visual representation of the surgery will thus help researchers to master this technique and advance our understanding of VCID, potentially leading to the development of novel therapeutic modalities to decrease the devastating cognitive decline associated with VCID.

Exercise-induced reductions in central command network cerebral blood flow assessed with arterial spin labeling MRI

Abstract Habitual aerobic exercise positively impacts brain health. However, less is known about the acute effects of exercise on regional cerebral blood flow (CBF). Most studies have used exercise methods that required a 10-minute or longer delay before acquiring CBF data or methods that assessed global, rather than regional, CBF. In the current feasibility study, an aerobic exercise stimulus was administered using an MRI-compatible cardio step module connected to the MRI table. This allowed participants (N = 12, mean age = 20 years) to exercise at light-to-moderate intensity while in the bore of the MRI scanner. Pseudo-continuous arterial spin labeling MRI with multiple delays was collected on a 3T Siemens MRI scanner immediately pre- and post-exercise. CBF and arterial transit time changes were examined within the central command network, which impacts motor and cardiovascular systems during exercise. Associations with perceived exertion and cardiorespiratory fitness were assessed. CBF in central command regions decreased following exercise, with greater decreases in regions associated with cardiovascular control. For example, CBF in the left insula decreased by -9.03 ± 8.69 mL/100g/min (-11.45%, p &amp;lt; 0.01); CBF in the left and right rostral anterior cingulate decreased by -4.91 ± 6.08 mL/100g/min (-6.17%, p = 0.02) and by -5.04 ± 6.34 mL/100g/min (-7.43%, p = 0.02); and CBF in the left lateral orbitofrontal cortex decreased by -7.30 ± 8.11 mL/100g/min (-9.50%, p = 0.01). Decreased CBF was also associated with greater ratings of perceived exertion in cardiovascular command regions including right insula (r = -0.67, p = 0.03), medial orbitofrontal cortex (r = -0.64, p = 0.04), and lateral orbitofrontal cortex (r = -0.75, p = 0.01). The current study further demonstrates the feasibility of assessing CBF immediately following exercise using an exercise stimulus in the bore of the MRI scanner. These results contribute to a small but growing body of literature describing cerebral hemodynamics immediately following exercise.

Prolonged intracranial catheter dwell time exacerbates penumbral stress and worsens stroke thrombectomy outcomes

BackgroundThe duration of mechanical thrombectomy (MT) is a negative predictor of outcomes in acute ischemic stroke (AIS), yet the precise mechanisms are unclear. We investigated whether the placement of large-bore...

Effects of reduced flow gradient on benthic biofilm communities' ecological network and community assembly.

The intensification of human activities has led to flow reduction and cut-off in most global rivers, seriously affecting riverine organisms and the biogeochemical processes. As key indicators of river ecosystems' structure and function, benthic biofilms play a critical role in driving primary production and material cycling in rivers. This research aimed to investigate the characteristics of microbial communities' complexity and stability during river flow reduction. Benthic biofilms were grown in artificial channels and subjected to eight gradients of flow reduction (represented by flow velocity from 0.4 to 110 cm/s). Biofilms' biodiversity, ecological networks and community assembly of bacteria, fungi and algae were investigated by high-throughput sequencing. Results showed significant differences in community composition and structure under different flow conditions. The eight flow gradients' microbial communities were divided into three groups: low, medium and high flows. The flow reduction led to significant decreases in bacterial and fungal communities' Chao1 index. Low flow conditions enriched the bacterial phyla Oxyphotobacteria, Alphaproteobacteria and Mollicutes, but significantly decreased the fungal phylum Chytridiomycota. Lowering flow reduced the fungal network's number of nodes and increased the algal network's number of edges. Cross-domain interactions network analysis showed a gradual increase in node and edge numbers with decreasing flow, while decreasing average path length. The neutral model predicted stochastic processes primarily drove biofilm community assembly, and that model's explanations decreased as the flow gradient decreased. The null model analysis revealed diffusion limitation as the most common stochastic ecological process for bacterial and algal communities, with reduced flow reducing heterogeneous selection and increasing diffusion-limited processes. This study provides an in-depth analysis of flow reduction's effects on biofilm communities' ecological networks and community assembly.