Changes In Blood Flow Research Articles

Characteristics of blood flow velocity in the radial artery and finger capillaries using magnetoplethysmogram and photoplethysmogram

The Hall element and optical sensor, which can detect the magnetic field change caused by the minute fluctuations of the permanent magnet according to the periodic movement of the radial artery and the light absorption and reflection intensity according to the change in wrist blood flow, respectively, are used as key elements in digital healthcare devices. The pulse waves of the radial artery inside the wrist were measured and analyzed using a clip-type pulsimeter, magnetoplethysmogram (MPG). The pulse wave, which is the change in blood flow obtained by photoplethysmogram (PPG), was measured on the dorsal side of the wrist or the fingers simultaneously with MPG. The ABFV (artery blood flow velocity) is a few ten cm/s as DH (distance between MPG and PPG) divided by ΔT(a) which is the time difference between the first peaks of MPG and PPG waveforms on the dorsal side of the wrist. The PBFV (peripheral blood flow velocity) is a few mm/s as LH (hand length) divided by ΔT(p), which is the time difference between the first peak of MPG waveform and the third peak PPG waveform on the finger. For four subjects of 20s, SPWV was approximately 0.98∼1.19 m/s, ABFV in the radial artery was approximately 0.40∼0.44 m/s, and finger capillary PBFV was approximately 6.3∼8.6 cm/s. These results show reasonable values similar to the blood velocity of many blood vessels flowing through the human body.

Hybrid dynamic bright and black blood angiography by non-contrast-enhanced vessel selective saturation angiography

The integrity of vessel walls and changes in blood flow are involved in many diseases, and information about these anatomical and physiological conditions is important for a diagnosis. There are several different angiography methods that can be used to generate images for diagnostic purposes, but often using different imaging techniques and MR sequences. The purpose of this study was to develop a method that allows time-resolved, vessel-selective simultaneous bright and black blood imaging by vesselselective blood saturation. Measurements in six volunteers were performed to evaluate the time-resolved bright blood angiography and the significance of the generated black blood contrast. It was shown that this method can be used to generate a black blood contrast with a sufficient signal difference to the surrounding gray matter in addition to the time-resolved and vessel-selective bright blood contrast. Using post-processing methods, whole brain angiograms can be calculated from the acquired data.

Abstract 116: Increased Collagen I/Collagen III Ratio is Associated With Hemorrhage in Brain Arteriovenous Malformations in Human and Mouse

Background and purpose: Brain arteriovenous malformation (bAVM) is an important risk factor for hemorrhagic stroke in young adults, but the underlying mechanisms are unclear. Increase of Col I/Col III ratio enhances vessel wall stiffness and renders vessel less resistant to changes of blood flow and pressure. Hypothesis: Col I/Col III ratio is increased in bAVM vessels, which is associated with bAVM hemorrhage. Method: Human bAVMs were collected from HHT and sporadic bAVM patients. Temporal lobe specimens from epilepsy patients were used as controls. Three mouse models were used: 1) PdgfbicreER; Alk1 f/f ; 2) PdgfbicreER; Eng f/f ; 3) Alk 1 f/f . Mice in models 1 and 2 have Pdgfb promoter driving, tamoxifen (TM) inducible cre expression in endothelial cells (ECs). BAVMs were induced by intra-brain injection of AAV-VEGF to induce angiogenesis and i.p. injection of TM to delete Alk1 or Eng in ECs. In model 3, bAVMs were by intra-brain injection of AAV-VEGF and an adenoviral vector expressing Cre to delete Alk1 gene focally. Colony stimulating factor receptor inhibitor (PLX5622) was given to Alk1 f/f mice 8 week after model induction when bAVMs have fully developed to transiently deplete microglia. Vascular Col I and Col III levels were analyzed by immunostaining using anti- CD31 and anti-Col I or Col II antibodies. Brain AVM bleeding was detected by Prussian blue staining, and RNA-Sequencing used to study gene profiles. Results: Col I and Col III levels and the Col I/Col III ratio were higher in the vessels of human HHT and sporadic bAVM than controls. Col I/Col III ratio was higher in ruptured than unruptured sporadic bAVM. RNA-seq data shown that Col I and Co III mRNA levels were higher in Eng deficient bAVMs than normal brain angiogenic regions. Col I and Col III levels were higher on Alk1 and Eng deficient bAVMs compared to normal vessels. Col I/Col III ratio was also increased in the Alk1 deficient bAVMs. Depletion of microglia by PLX5622 reduced Col I and Col III levels and reduced microhemorrhage of Alk1 deficient bAVMs. Conclusion: Col I, Col III and Col I/Col III ratio are increased on human and mouse bAVM vessels, which is associated with bAVM hemorrhage. Depletion of microglia reduces Col I and Col III and hemorrhage in bAVMs in mice.

Time-Lagged Functional Ultrasound for Multi-Parametric Cerebral Hemodynamic Imaging.

We introduce an ultrasound speckle decorrelation-based time-lagged functional ultrasound technique (tl-fUS) for the quantification of the relative changes in cerebral blood flow speed (rCBF [Formula: see text]), cerebral blood volume (rCBV) and cerebral blood flow (rCBF) during functional stimulations. Numerical simulations, phantom validations, and in vivo mouse brain experiments were performed to test the capability of tl-fUS to parse out and quantify the ratio change of these hemodynamic parameters. The blood volume change was found to be more prominent in arterioles compared to venules and the peak blood flow changes were around 2.5 times the peak blood volume change during brain activation, agreeing with previous observations in the literature. The tl-fUS shows the ability of distinguishing the relative changes of rCBFspeed, rCBV, and rCBF, which can inform specific physiological interpretations of the fUS measurements.

Abstract TP139: Revascularization Improves Vascular Hemodynamics in Pediatric Moyamoya Patients

Introduction: Cerebrovascular reactivity (CVR) reflects the change in cerebral blood flow (CBF) in response to vasodilation. Studies have demonstrated that impaired CVR was associated with a higher risk of acute stroke in patients with intracranial vasculopathy and that bypass surgeries can reduce the risk of strokes. Moyamoya disease is a progress cerebrovascular disorder that begins during childhood. Arterial spin labeling (ASL) is a quantitative MRI technique for non-invasive CBF and CVR measurement; ASL with multiple delays can also measure arterial transit time (ATT). Here, we compare the CBF, CVR, and ATT in pediatric Moyamoya patients before and after bypass using multi-delay ASL. Hypothesis: CVR will increase significantly after bypass surgeries. Methods: Imaging data were acquired from 22 Moyamoya patients (11 months - 18 years, 14 females) using a 3T MRI system. All patients had unilateral or bilateral occlusion at ACA, MCA and/or PCA. Multi-delay ASL data (7 delays) were acquired at baseline and 15 minutes after acetazolamide administration. CBF and ATT were computed using the general kinetic model. CVR was computed as the percentage of CBF change compared with baseline CBF. Flow territories (right and left ACA, MCA, and PCA) were defined using the Harvard-Oxford atlases. Paired t-tests were conducted to compare the mean CVR, CBF, and ATT changes before and after bypass surgeries. Results: The figure shows the hemodynamic maps of an example patients. Overall, CVR and CBF in the affected regions increased after bypass; ATT in these regions decreased after bypass. For this cohort, our analysis showed that CVR of the affected regions increased significantly by 68% and ATT reduced significantly by 10.7% measured by multi-delay ASL, implying improved circulation and lower risk for strokes. Discussion: Multi-delay ASL was effective to detect improved CVR and reduced ATT in pediatric Moyamoya patients after bypass surgeries.

Abstract TP287: Estrous Cycle Stages and Cerebral Blood Flow: Implications for Ischemic Tolerance in Stroke

Introduction: Previous stroke studies in female rodents have demonstrated that the severity of ischemic damage is differentially impacted by the estrous cycle. Estrogen is considered to be neuroprotective, but it is unclear whether this protection is dependent on the vasodilator properties of estrogen. In this study, we investigated the impact of estrus cycle stage on stroke lesion volume and whether that impact was dependent on cerebral blood flow (CBF) changes during stroke. Methods: Ischemia was induced in adult ( 10 weeks) male and female Sprague-Dawley rats by 30 minutes middle cerebral artery occlusion (MCAO) using the suture model. Prior to the stroke procedure, the phases of the estrous cycle (proestrus(P), estrus(E), metestrus(M) and diestrus (D)) were determined by vaginal smear tests in female rats. Cerebral blood flow (CBF) was measured by laser doppler and infarct volume were measured by TTC staining at d2 post-stroke. Results: Females in proestrus and diestrus (P/D) stages of the estrous cycle, which have reportedly high levels of estrogen, had significantly (p<0.05) smaller CBF decreases during ischemia and a trend for smaller infarcts than those in estrous and metestrus stages, which have lower estrogen levels. This suggests that the protective effects of estrogen may be related to effects on blood flow. However, when compared to male rats, females in P/D stages had significantly (p<0.05) smaller brain infarcts despite having similar CBF decreases. This implies that additional mechanisms are responsible for the neuroprotection observed in females when compared to males. Conclusion: Estrous cycle stage affects CBF decrease during ischemia, but this does not account for the difference in infarct size observed between male and female rats. Our study indicates that multiple mechanisms are responsible for ischemic tolerance in specific stages of the estrous cycle. Keywords: stroke, estrous cycle, CBF, estrogen

Individual aerodynamic and physiological data are critical to optimise cycling time trial performance: one size does not fit all

Cycling time trials are characterised by riders adopting positions to lessen the impact of aerodynamic drag. Aerodynamic positions likely impact the power a rider is able to produce due to changes in oxygen consumption, blood flow, muscle activation and economy. Therefore, the gain from optimising aerodynamics must outweigh the potential physiological cost. The aim was to establish the relationship between energy expenditure and aerodynamic drag, with a secondary aim to determine the reliability of a commercially available handlebar mounted aero device for measuring aerodynamic drag. Nine trained male cyclists volunteered for the study. They completed 4 × 3200 m on an outdoor velodrome where stack height was adjusted in 1 cm integers. The drag coefficient (CdA), oxygen consumption and aerodynamic-physiological economy (APE) were determined at each stack height, with data used to model 40 km TT performance. Small to moderate effect sizes (ES) in response to stack height change were found for CdA, APE and energy cost. The change in TT time was correlated to ∆aerodynamic drag and ∆APE. Meaningful impacts of change in stack height on CdA, APE, energy cost and predicted TT performance, are apparent with highly individualised responses to positional changes.

Prospective single-center study on the reliability of ipsilateral cerebral oximetry using near-infrared spectroscopy as a predictor for selective shunting during carotid endarterectomy.

Many techniques are available for the intraoperative assessment of brain perfusion during carotid endarterectomy, such as carotid stump pressure, near-infrared spectroscopy, somatosensory evoked potentials, transcranial Doppler, electroencephalography, and clinical assessment. The decision for selective carotid shunt insertion is dependent on clinical deterioration or the detection of cerebral hypoperfusion after cross-clamping of the internal carotid artery. Monitoring cerebral oximetry using near-infrared spectroscopy is a noninvasive technique for cerebral oxygen saturation measurement, reflecting changes in cerebral blood flow during carotid endarterectomy. The aim of this study was to evaluate the reliability of near-infrared spectroscopy as a predictor of selective shunting during carotid endarterectomy. In total, 47 conventional carotid endarterectomy surgeries were performed at our hospital between March 2016 and December 2021. All surgeries were performed under a regional cervical block supplemented with local infiltration anesthesia. All patients were monitored by cerebral oximetry using bilateral near-infrared spectroscopy probes and clinical assessment through communication with the patient (numerical, visual, and verbal) to indicate a selective shunt. Near-infrared spectroscopy values were recorded before and after internal carotid cross-clamping and after declamping. Any decrease in ipsilateral cerebral oximetry-near-infrared spectroscopy values equal to or more than 20% from the pre-clamping baseline reading associated with deterioration in neurological status (hemiparesis, aphasia, or deterioration in level of consciousness) after internal carotid artery cross-clamping was considered an indication for intraluminal carotid shunting. After internal carotid artery cross-clamping, 5 of 47 patients (10.6%) developed a significant drop in cerebral oxygen saturation associated with obvious clinical assessment deterioration in verbal communication and weakness in contralateral arm power. A Pruitt-Inahara carotid shunt was subsequently inserted, and 42 patients remained stable throughout surgery. The average decline in ipsilateral near-infrared spectroscopy values was 23.8% in patients with clinical deterioration. The average decline was 8.6% in patients who remained stable. Monitoring ipsilateral cerebral oximetry using near-infrared spectroscopy is an easy and reliable method for indicating selective shunting during carotid endarterectomy. A 20% decrease in ipsilateral brain tissue oximetry after internal carotid artery cross-clamping provides a reliable cut-off value for selective intraluminal carotid shunting during carotid endarterectomy.

Spatiotemporal modulation of nitric oxide and Notch signaling by hemodynamic-responsive Trpv4 is essential for ventricle regeneration

Zebrafish have a remarkable ability to regenerate injured hearts. Altered hemodynamic forces after larval ventricle ablation activate the endocardial Klf2a-Notch signaling cascade to direct zebrafish cardiac regeneration. However, how the heart perceives blood flow changes and initiates signaling pathways promoting regeneration is not fully understood. The present study demonstrated that the mechanosensitive channel Trpv4 sensed the altered hemodynamic forces in injured hearts and its expression was regulated by blood flow. In addition to mediating the endocardial Klf2a-Notch signal cascade around the atrioventricular canal (AVC), we discovered that Trpv4 regulated nitric oxide (NO) signaling in the bulbus arteriosus (BA). Further experiments indicated that Notch signaling primarily acted at the early stage of regeneration, and the major role of NO signaling was at the late stage and through TGF-β pathway. Overall, our findings revealed that mechanosensitive channels perceived the changes in hemodynamics after ventricle injury, and provide novel insights into the temporal and spatial coordination of multiple signaling pathways regulating heart regeneration.

Comparing the performance potential of speckle contrast optical spectroscopy and diffuse correlation spectroscopy for cerebral blood flow monitoring using Monte Carlo simulations in realistic head geometries.

The non-invasive measurement of cerebral blood flow based on diffuse optical techniques has seen increased interest as a research tool for cerebral perfusion monitoring in critical care and functional brain imaging. Diffuse correlation spectroscopy (DCS) and speckle contrast optical spectroscopy (SCOS) are two such techniques that measure complementary aspects of the fluctuating intensity signal, with DCS quantifying the temporal fluctuations of the signal and SCOS quantifying the spatial blurring of a speckle pattern. With the increasing interest in the use of these techniques, a thorough comparison would inform new adopters of the benefits of each technique. We systematically evaluate the performance of DCS and SCOS for the measurement of cerebral blood flow. Monte Carlo simulations of dynamic light scattering in an MRI-derived head model were performed. For both DCS and SCOS, estimates of sensitivity to cerebral blood flow changes, coefficient of variation of the measured blood flow, and the contrast-to-noise ratio of the measurement to the cerebral perfusion signal were calculated. By varying complementary aspects of data collection between the two methods, we investigated the performance benefits of different measurement strategies, including altering the number of modes per optical detector, the integration time/fitting time of the speckle measurement, and the laser source delivery strategy. Through comparison across these metrics with simulated detectors having realistic noise properties, we determine several guiding principles for the optimization of these techniques and report the performance comparison between the two over a range of measurement properties and tissue geometries. We find that SCOS outperforms DCS in terms of contrast-to-noise ratio for the cerebral blood flow signal in the ideal case simulated here but note that SCOS requires careful experimental calibrations to ensure accurate measurements of cerebral blood flow. We provide design principles by which to evaluate the development of DCS and SCOS systems for their use in the measurement of cerebral blood flow.

Functional Analysis of TRPA1, TRPM3, and TRPV1 Channels in Human Dermal Arteries and Their Role in Vascular Modulation.

Transient receptor potential (TRP) channels are pivotal in modulating vascular functions. In fact, topical application of cinnamaldehyde or capsaicin (TRPA1 and TRPV1 channel agonists, respectively) induces "local" changes in blood flow by releasing vasodilator neuropeptides. We investigated TRP channels' contributions and the pharmacological mechanisms driving vasodilation in human isolated dermal arteries. Ex vivo studies assessed the vascular function of artery segments and analyzed the effects of different compounds. Concentration-response curves to cinnamaldehyde, pregnenolone sulfate (PregS, TRPM3 agonist), and capsaicin were constructed to evaluate the effect of the antagonists HC030031 (TRPA1); isosakuranetin (TRPM3); and capsazepine (TRPV1). Additionally, the antagonists/inhibitors olcegepant (CGRP receptor); L-NAME (nitric oxide synthase); indomethacin (cyclooxygenase); TRAM-34 plus apamin (K+ channels); and MK-801 (NMDA receptors, only for PregS) were used. Moreover, CGRP release was assessed in the organ bath fluid post-agonist-exposure. In dermal arteries, cinnamaldehyde- and capsaicin-induced relaxation remained unchanged after the aforementioned antagonists, while PregS-induced relaxation was significantly inhibited by isosakuranetin, L-NAME and MK-801. Furthermore, there was a significant increase in CGRP levels post-agonist-exposure. In our experimental model, TRPA1 and TRPV1 channels seem not to be involved in cinnamaldehyde- or capsaicin-induced relaxation, respectively, whereas TRPM3 channels contribute to PregS-induced relaxation, possibly via CGRP-independent mechanisms.

Association between white matter hyperintensities and altered cerebral blood flow in maintenance hemodialysis patients: a longitudinal study

ObjectivesTo explore changes in cerebral blood flow (CBF) and white matter in hemodialysis patients.MethodsThirty-three hemodialysis patients who underwent two brain MRI at an interval of three years and 33 age- and sex-matched healthy controls (HC) underwent structural and arterial spin-labeling MRI examinations. Intergroup differences in CBF in the gray matter, white matter, and whole matter, and regional white matter hyperintensities (WMH) were analyzed. Based on the changes in CBF between the baseline and follow-up groups, the hemodialysis patients were divided into two subgroups: an increased CBF group and a decreased CBF group. Differences in CBF and WMH between the subgroups and HC were analyzed.ResultsPatients undergoing hemodialysis exhibited increased cerebral watershed (CW) WMH, deep WMH, and periventricular WMH (P < 0.01). The CBF of patients with decreased CBF was higher than that of HC at baseline (,P < 0.01) and lower than that of HC at follow-up (P < 0.01). Compared with the increased CBF group, obvious development of deep WMH was found in the decreased CBF group for the gray matter, white matter, and whole matter (P < 0.01).ConclusionsWMH in hemodialysis patients were distributed in the deep white matter, periventricular white matter and CW, and progressed with the extension of hemodialysis duration. CBF in hemodialysis patients could manifest as both increased and decreased, and WMH in patients with decreased CBF developed severely with prolongation of hemodialysis duration.Advances in knowledgeThese findings provide a basis for exploring neuropathological changes of hemodialysis patients.

Heart-brain interaction in cardiogenic dementia: pathophysiology and therapeutic potential.

Diagnosis and treatment of patients with cardiovascular and neurologic diseases primarily focus on the heart and brain, respectively. An increasing number of preclinical and clinical studies have confirmed a causal relationship between heart and brain diseases. Cardiogenic dementia is a cognitive impairment caused by heart dysfunction and has received increasing research attention. The prevention and treatment of cardiogenic dementia are essential to improve the quality of life, particularly in the elderly and aging population. This study describes the changes in cognitive function associated with coronary artery disease, myocardial infarction, heart failure, atrial fibrillation and heart valve disease. An updated understanding of the two known pathogenic mechanisms of cardiogenic dementia is presented and discussed. One is a cascade of events caused by cerebral hypoperfusion due to long-term reduction of cardiac output after heart disease, and the other is cognitive impairment regardless of the changes in cerebral blood flow after cardiac injury. Furthermore, potential medications for the prevention and treatment of cardiogenic dementia are reviewed, with particular attention to multicomponent herbal medicines.

Auditory Cortical Plasticity in Patients with Single-Sided Deafness Before and After Cochlear Implantation

PurposeThis study investigated neuroplastic changes induced by postlingual single-sided deafness (SSD) and the effects of a cochlear implantation for the deaf ear. Neural processing of acoustic signals from the normal hearing ear to the brain was studied before and after implantation using a positron emission tomography (PET)/CT scanner.MethodsEight patients with postlingual SSD received a cochlear implant (CI) in a prospective clinical trial. Dynamic imaging was performed in a PET/CT scanner using radioactively labeled water ([15O]H2O) to localize changes in the regional cerebral blood flow (rCBF) with and without an auditory task of logatomes containing speech-like elements without meaningful context. The normal hearing ear was stimulated before implantation and after the use of the cochlear implant for at least 8 months (mean 13.5, range 8.1–26.6). Eight age- and gender-matched subjects with normal hearing on both sides served as healthy control subjects (HCS).ResultsWhen the normal hearing ear of SSD patients was stimulated before CI implantation, the [15O]H2O-PET showed a more symmetrical rCBF in the auditory regions of both hemispheres in comparison to the HCS. The use of CI increased the asymmetry index (AI) in six of eight patients indicating an increase of activity of the contralateral hemisphere. Non-parametric statistics revealed a significant difference in the AI between patients before CI implantation and HCS (p < .01), which disappeared after CI implantation (p = .195).ConclusionThe functional neuroimaging data showed a tendency towards normalization of neuronal activity after CI implantation, which supports the effectiveness of CI in SSD patients.Trial RegistrationClinicalTrials.gov Identifier: NCT01749592, December 13, 2012.

Pulsatile microvascular cerebral blood flow waveforms change with intracranial compliance and age.

Diffuse correlation spectroscopy (DCS) is an optical method to measure relative changes in cerebral blood flow (rCBF) in the microvasculature. Each heartbeat generates a pulsatile signal with distinct morphological features that we hypothesized to be related to intracranial compliance (ICC). We aim to study how three features of the pulsatile rCBF waveforms: the augmentation index (AIx), the pulsatility index, and the area under the curve, change with respect to ICC. We describe ICC as a combination of vascular compliance and extravascular compliance. Since patients with Chiari malformations (CM) () have been shown to have altered extravascular compliance, we compare the morphology of rCBF waveforms in CM patients with age-matched healthy control (). AIx measured in the supine position was significantly less in patients with CM compared to healthy controls (). Since physiologic aging also leads to changes in vessel stiffness and intravascular compliance, we evaluate how the rCBF waveform changes with respect to age and find that the AIx feature was strongly correlated with age (, , and , ). These results suggest that the AIx measured in the cerebral microvasculature using DCS may be correlated to changes in ICC.

Intraoperative evaluation of local cerebral hemodynamic change by laser speckle contrast imaging for predicting postoperative cerebral hyperperfusion during STA-MCA bypass in adult patients with moyamoya disease

Cerebral hyperperfusion (CHP) occurred frequently after direct superficial temporal artery–middle cerebral artery (STA-MCA) bypass surgery for moyamoya disease (MMD). We analyzed cortical microvascular density (CMD) and the change of cerebral blood flow (LΔCBF) using intraoperative laser speckle contrast imaging (LSCI) on 130 hemispheres of 95 consecutive adult patients with MMD. The demographic characteristics, cortical hemodynamic sources, bypass methods, intraoperative blood flow data, and relative CBF changes on single-photon emission computed tomography (SPECT) examination (SΔrCBF) were compared between the groups with and without CHP. The median values for CMD, LΔCBF, and SΔrCBF were significantly higher in the CHP group than in the non-CHP group (CMD 0.240 vs 0.206, P = 0.004; LΔCBF 2.285 vs 1.870, P < 0.001; SΔCBF 1.535 vs 1.260, P < 0.001). Multivariate analysis revealed that hemodynamic sources of recipient parasylvian cortical arteries from MCA (M-PSCAs), end-to-side (E-S) bypass method, CMD ≥ 0.217, and LΔCBF ≥ 1.985 were the risk factors for CHP. Intraoperative LSCI was useful for evaluating hemodynamics and predicting CHP in patients with MMD.

The impact of the ketogenic diet on the health of patients with Alzheimer’s disease

INTRODUCTION:&#x0D; Diet is an integral element of every individual's health. Its impact on the functioning of the human body has fascinated scientists for years. One of the diets that alters the mechanism of the body's functioning is the ketogenic diet. The impact of the ketogenic diet on various disorders is still under investigation. It is known to have shown numerous benefits in reducing epileptic seizures, but its impact on other neurological disorders is less known. In this literature review, the efficacy of ketogenic therapies was assessed in Alzheimer's disease.&#x0D; &#x0D; AIM OF STUDY:&#x0D; Review of the current literature (since 2018) on the effects of implementing a ketogenic diet in patients with Alzheimer's disease.&#x0D; &#x0D; MATERIALS AND METHODS:&#x0D; The review was based on data gathered from the PubMed database using the keywords: 'ketogenic diet in Alzheimer’s disease,' 'ketogenic therapies Alzheimer disease,' and 'ketogenic diet in neurological disease’.&#x0D; &#x0D; SUMMARY:&#x0D; The ketogenic diet enhances the daily functioning of Alzheimer's patients. It significantly improves their cognitive functions, and changes in brain blood flow are visible in imaging studies. The ketogenic diet also positively modulates the gut microbiome in Alzheimer's patients. It represents a promising option in combating cognitive symptoms of Alzheimer's disease.

Diagnostic Ultrasound-Based Investigation of Central vs. Peripheral Arterial Changes Consequent to Low-Dose Caffeine Ingestion.

Caffeine is present in various foods and medicines and is highly accessible through various routes, regardless of age. However, most studies on caffeine have focused on the effects of high-dose caffeine ingestion based on the recommended daily amount for adults. In this study, we examined the physiological changes in the central and peripheral vessels that may occur when ingesting low-dose caffeine due to its high accessibility, with the aim of creating an environment of safe caffeine ingestion. This study included 26 healthy participants in their 20s. Peak systolic velocity (PSV), heart rate (HR), and pulse wave velocity (PWV) for vascular stiffness assessment were measured at 0, 30, and 60 min after caffeine ingestion using diagnostic ultrasound to determine the physiological changes in the blood vessels, common carotid artery (CCA) and radial artery (RA). In addition, percutaneous oxygen saturation (SpO2), blood pressure (BP), and accelerated photoplethysmography (APG) were measured. In comparison with before ingestion, the HR tended to decrease and showed a significant difference at 30 and 60 min (p = 0.014 and p = 0.031, respectively). PSV significantly decreased in both vessels at 30 and 60 min (p < 0.001 and p < 0.001, respectively). APG showed a decreasing trend until 60 min after ingestion, with a significant difference at 30 and 60 min (p = 0.003 and p = 0.012, respectively). No significant difference was observed in SpO2, BP, or PWV; however, they showed a tendency to increase after ingestion. Decreased HR may occur because of the baroreflex caused by an increase in BP. The RA has many branches and a smaller diameter; therefore, the PSV was lower in the RA than that in the CCA. This effect can occur because of the difficulty in the smooth expansion of blood vessels, which leads to a decrease in blood flow. In addition, an increase in intracellular calcium concentration can prevent vasodilation and increase the propagation velocity of pulse waves. The reflected waves can increase systolic blood pressure but reduce PWV and vascular elasticity. These results suggest that even low-dose caffeine can improve blood vessel health by providing temporary stimulation to the blood vessels; however, it can also cause changes in blood flow and blood vessel elasticity, which can lead to serious diseases such as stroke and high blood pressure. Therefore, caution should be exercised when caffeine consumption is indiscriminate.

Network response of brain microvasculature to neuronal stimulation

Neurovascular coupling (NVC), or the adjustment of blood flow in response to local increases in neuronal activity is a hallmark of healthy brain function, and the physiological foundation for functional magnetic resonance imaging (fMRI). However, it remains only partly understood due to the high complexity of the structure and function of the cerebrovascular network. Here we set out to understand NVC at the network level, i.e. map cerebrovascular network reactivity to activation of neighbouring neurons within a 500×500×500 μm3 cortical volume (∼30 high-resolution 3-nL fMRI voxels). Using 3D two-photon fluorescence microscopy data, we quantified blood volume and flow changes in the brain vessels in response to spatially targeted optogenetic activation of cortical pyramidal neurons. We registered the vessels in a series of image stacks acquired before and after stimulations and applied a deep learning pipeline to segment the microvascular network from each time frame acquired. We then performed image analysis to extract the microvascular graphs, and graph analysis to identify the branch order of each vessel in the network, enabling the stratification of vessels by their branch order, designating branches 1–3 as precapillary arterioles and branches 4+ as capillaries. Forty-five percent of all vessels showed significant calibre changes; with 85 % of responses being dilations. The largest absolute CBV change was in the capillaries; the smallest, in the venules. Capillary CBV change was also the largest fraction of the total CBV change, but normalized to the baseline volume, arterioles and precapillary arterioles showed the biggest relative CBV change. From linescans along arteriole-venule microvascular paths, we measured red blood cell velocities and hematocrit, allowing for estimation of pressure and local resistance along these paths. While diameter changes following neuronal activation gradually declined along the paths; the pressure drops from arterioles to venules increased despite decreasing resistance: blood flow thus increased more than local resistance decreases would predict. By leveraging functional volumetric imaging and high throughput deep learning-based analysis, our study revealed distinct hemodynamic responses across the vessel types comprising the microvascular network. Our findings underscore the need for large, dense sampling of brain vessels for characterization of neurovascular coupling at the network level in health and disease.

Neurological disorders with general overheating of the body (scientific and literary review)

Based on the understanding of the pathophysiology of heat stroke, it has been suggested that heat stroke can be considered as a form of hyperthermia that is associated with a systemic inflammatory response leading to a syndrome of multiple organ dysfunction in which encephalopathy predominates. Mechanisms of neuronal injury in heat stroke include: cellular effects (damage to membranes, mitochondria, and DNA, stimulation of excitotoxic mechanisms, protein denaturation), local effects (ischemia, inflammatory changes, edema, cytokine release, vascular damage), systemic effects (changes in cerebral blood flow, endotoxemia, translocation of bacteria through a dysfunctional gastrointestinal tract). Neurological manifestations of heat stroke develop in 3 stages according to the time of occurrence: acute, convalescent and late. In the acute stage, cerebral dysfunction prevails. Overheating of the body directly caused polyetiological cerebral dysfunction with deep suppression of consciousness in the acute stage; circulatory shock, hypoxia and cerebral ischemia, excessive accumulation of cytotoxic free radicals and oxidant brain damage developed. During the convalescence stage, cerebral dysfunction gradually decreases. This stage is characterized by transient cerebellar dysfunction. For the late stage, long-term neurological and cardiovascular complications with a constant risk of death are typical. When late stage with permanent neurologic deficits develop, cerebellar dysfunction is the most common symptom. The delayed onset of degeneration and deafferentation suggests that the syndrome is not caused by the primary lesion itself but may be a consequence of postsynaptic hypersensitivity or secondary reorganization of the involved pathways.