Explore the vast range of titles available.

Animal models point towards a key role of brain-derived neurotrophic factor (BDNF), insulin-like growth factor-I (IGF-I) and vascular endothelial growth factor (VEGF) in mediating exercise-induced structural and functional changes in the hippocampus. Recently, also platelet derived growth factor-C (PDGF-C) has been shown to promote blood vessel growth and neuronal survival. Moreover, reductions of these neurotrophic and angiogenic factors in old age have been related to hippocampal atrophy, decreased vascularization and cognitive decline. In a 3-month aerobic exercise study, forty healthy older humans (60 to 77years) were pseudo-randomly assigned to either an aerobic exercise group (indoor treadmill, n=21) or to a control group (indoor progressive-muscle relaxation/stretching, n=19). As reported recently, we found evidence for fitness-related perfusion changes of the aged human hippocampus that were closely linked to changes in episodic memory function. Here, we test whether peripheral levels of BDNF, IGF-I, VEGF or PDGF-C are related to changes in hippocampal blood flow, volume and memory performance. Growth factor levels were not significantly affected by exercise, and their changes were not related to changes in fitness or perfusion. However, changes in IGF-I levels were positively correlated with hippocampal volume changes (derived by manual volumetry and voxel-based morphometry) and late verbal recall performance, a relationship that seemed to be independent of fitness, perfusion or their changes over time. These preliminary findings link IGF-I levels to hippocampal volume changes and putatively hippocampus-dependent memory changes that seem to occur over time independently of exercise. We discuss methodological shortcomings of our study and potential differences in the temporal dynamics of how IGF-1, VEGF and BDNF may be affected by exercise and to what extent these differences may have led to the negative findings reported here. •Exercise-related changes in BDNF, IGF, VEGF and PDGF were measured in older adults•Changes in hippocampal perfusion, volume (via 7T MRI) and memory were assessed•Fitness-related vascular hippocampal plasticity was not linked to growth factors•Changes in IGF-I, hippocampal volume and memory were linked independent of exercise•Potential reasons for negative findings and methodological shortcomings are discussed

The hippocampus has been shown to demonstrate a remarkable degree of plasticity in response to a variety of tasks and experiences. For example, the size of the human hippocampus has been shown to increase in response to aerobic exercise. However, it is currently unknown what underlies these changes. Here we scanned sedentary, young to middle-aged human adults before and after a six-week exercise intervention using nine different neuroimaging measures of brain structure, vasculature, and diffusion. We then tested two different hypotheses regarding the nature of the underlying changes in the tissue. Surprisingly, we found no evidence of a vascular change as has been previously reported. Rather, the pattern of changes is better explained by an increase in myelination. Finally, we show that hippocampal volume increase is temporary, returning to baseline after an additional six weeks without aerobic exercise. This is the first demonstration of a change in hippocampal volume in early to middle adulthood suggesting that hippocampal volume is modulated by aerobic exercise throughout the lifespan rather than only in the presence of age related atrophy. It is also the first demonstration of hippocampal volume change over a period of only six weeks, suggesting that gross morphometric hippocampal plasticity occurs faster than previously thought. •Human anterior hippocampal volume can be increased by only six weeks of regular aerobic exercise.•This increase in anterior hippocampal volume returns to baseline in the absence of continued aerobic exercise.•These changes can occur in middle adulthood, not only in the presence of age related atrophy.•Multimodal neuroimaging techniques support a change in myelination but not a change in vasculature within anterior hippocampus.

Diurnal rhythms have been observed in human behaviors as diverse as sleep, olfaction, and learning. Despite its potential impact, time of day is rarely considered when brain responses are studied by neuroimaging techniques. To address this issue, we explicitly examined the effects of circadian and homeostatic regulation on functional connectivity (FC) and regional cerebral blood flow (rCBF) in healthy human volunteers, using whole-brain resting-state functional magnetic resonance imaging (rs-fMRI) and arterial spin labeling (ASL). In common with many circadian studies, we collected salivary cortisol to represent the normal circadian activity and functioning of the hypothalamic–pituitary–adrenal (HPA) axis. Intriguingly, the changes in FC and rCBF we observed indicated fundamental decreases in the functional integration of the default mode network (DMN) moving from morning to afternoon. Within the anterior cingulate cortex (ACC), our results indicate that morning cortisol levels are negatively correlated with rCBF. We hypothesize that the homeostatic mechanisms of the HPA axis has a role in modulating the functional integrity of the DMN (specifically, the ACC), and for the purposes of using fMRI as a tool to measure changes in disease processes or in response to treatment, we demonstrate that time of the day is important when interpreting resting-state data.

This research examined the impact of aerobic exercise intensity and dose on acute post‐exercise cerebral shear stress and blood flow. Fourteen young adults (27 ± 5 years of age, eight females) completed a maximal oxygen uptake (V̇O2max ${{\\dot{V}}_{{{\\mathrm{O}}}_2}\\max }}$ ) treadmill test followed by three randomized study visits: treadmill exercise at 30% of V̇O2max ${{\\dot{V}}_{{{\\mathrm{O}}}_2}\\max }}$for 30 min, 70% of V̇O2max ${{\\dot{V}}_{{{\\mathrm{O}}}_2}\\max }}$for 30 min and 70% of V̇O2max ${{\\dot{V}}_{{{\\mathrm{O}}}_2}\\max }}$for a duration that resulted in caloric expenditure equal to that in the 30% V̇O2max ${{\\dot{V}}_{{{\\mathrm{O}}}_2}\\max }}$visit (EqEE). A venous blood draw and internal carotid artery (ICA) ultrasound were collected before and immediately following exercise. ICA diameter and blood velocity were determined using automated edge detection software, and blood flow was calculated. Using measures of blood viscosity, shear stress was calculated. Aerobic exercise increased ICA shear stress (time: P = 0.005, condition: P = 0.012) and the increase was greater following exercise at 70% V̇O2max ${{\\dot{V}}_{{{\\mathrm{O}}}_2}\\max }}$(∆4.1 ± 3.5 dyn/cm2) compared with 30% V̇O2max ${{\\dot{V}}_{{{\\mathrm{O}}}_2}\\max }}$(∆1.1 ± 1.9 dyn/cm2; P = 0.041). ICA blood flow remained elevated following exercise (time: P = 0.002, condition: P = 0.010) with greater increases after 70% V̇O2max ${{\\dot{V}}_{{{\\mathrm{O}}}_2}\\max }}$(Δ268 ± 150 mL/min) compared with 30% V̇O2max ${{\\dot{V}}_{{{\\mathrm{O}}}_2}\\max }}$(∆125 ± 149 mL/min; P = 0.041) or 70% V̇O2max ${{\\dot{V}}_{{{\\mathrm{O}}}_2}\\max }}$EqEE (∆127 ± 177 mL/min; P = 0.004). Therefore, aerobic exercise resulted in both intensity‐ and dose‐dependent effects on acute post‐exercise ICA blood flow whereby vigorous intensity exercise provoked a larger increase in ICA blood flow compared to light intensity exercise when performed at a higher dose. What is the central question of this study? What are the independent and combined effects of exercise intensity and dose on post‐exercise internal carotid artery (ICA) haemodynamics? What is the main finding and its importance? The combined effects of exercise intensity and dose evoked the greatest haemodynamic response whereby vigorous intensity exercise for a longer duration resulted in the greatest increase in post‐exercise ICA blood flow. Therefore, exercise intensity and dose are important considerations for utilizing exercise to improve cerebrovascular function.

Purpose The aim of this study is to assess the incidence of sublingual microcirculatory flow alterations, according to a predefined arbitrary cutoff value, in patients with “clinical signs of impaired organ perfusion”. Secondary endpoints were the changes in microvascular flow index (MFI), “clinical signs of impaired organ perfusion”, and stroke volume (SV) after fluid administration, and the differences between groups. Methods Prospective, single-center, observational study in a 22-bed mixed intensive care unit (ICU). Patients ≥18 years with invasive hemodynamic monitoring and “clinical signs of impaired organ perfusion” as the principal reason for fluid administration were included. Before and after fluid challenge, systemic hemodynamics and direct in vivo observation of the sublingual microcirculation with sidestream dark-field imaging were obtained. Microvascular flow index (MFI) <2.6 was predefined as abnormal. Results N  = 50. At baseline, MFI <2.6 was present in 66 % of the patients. In these patients, MFI increased from 2.3 (2–2.5) at baseline to 2.5 (2.1–2.8) after fluid challenge ( p  = 0.003). This was accompanied by a reduction in the number of “clinical signs of impaired organ perfusion” from 2 (1–2) to 1 (0–2) ( p  < 0.001). However, in patients with MFI >2.6 at baseline, MFI and clinical signs changed insignificantly [2.8 (2.8–2.9) versus 2.8 (2.7–3), p  = 0.45, respectively, 1 (1–2) versus 1 (1–2), p  < 0.32]. These changes were not restricted to patients with a rise in SV ≥10 %. Conclusions These data add to the understanding that noninvasive assessment of microvascular blood flow may help to identify patients eligible for fluid therapy, and to evaluate its effect.

The use of acute carbon monoxide inhalation (COi) and hot water immersion (HWI) are of growing interest as interventions to stimulate erythropoietin (EPO) production. However, whether EPO production is further augmented when combining these stressors and whether there are sex differences in this response are poorly understood. Therefore, we measured circulating EPO concentration in response to acute COi and HWI independently and in combination and determined whether the responses were altered by sex. Participants completed three study visits—COi, HWI, and combined COi and HWI—separated by 1 week in a randomized, balanced, crossover design. Renal blood velocity was measured during all interventions, and carboxyhaemoglobin was measured during and after COi. Serum samples were analysed every hour for 6 h post‐intervention for EPO concentration. HWI decreased renal blood velocity (46.2 cm/s to 36.2 cm/s) (P < 0.0001), and COi increased carboxyhaemoglobin (1.5%–12.8%) (P < 0.0001) without changing renal blood velocity (46.4–45.2 cm/s) (P = 0.4456). All three interventions increased peak EPO concentration from baseline (COi: 6.02–9.74 mIU/mL; HWI: 6.80–11.10 mIU/mL; COi + HWI: 6.71–10.91 mIU/mL) (P = 0.0048) and to the same extent (P = 0.3505). On average, females increased EPO while males did not in response to COi (females: 6.17 mIU/mL; males: 1.27 mIU/mL) (P = 0.0010), HWI (females: 6.47 mIU/mL; males: 2.14 mIU/mL) (P = 0.0104), and COi and HWI (females: 6.65 mIU/mL; males: 1.76 mIU/mL) (P = 0.0256). These data emphasize that combining these interventions does not augment EPO secretion and that these interventions may work better in females. What is the central question of the study? Do acute heat stress and carbon monoxide inhalation alone and in combination increase erythropoietin, and are there sex differences in erythropoietin? What is the main finding and its importance? All interventions increased erythropoietin, but combining the two interventions did not further augment erythropoietin. While erythropoietin increased in females in response to all interventions, there was greater erythropoietin variability in males and therefore, on average, males did not increase erythropoietin. This suggests that combining heat and hypoxic stressors does not further augment erythropoietin concentrations but these interventions may have greater efficacy in females.

PurposeThe purpose of the present study was to examine the effect of repeated, single leg heating on lower limb endothelial function.MethodsMacrovascular function was assessed with superficial femoral artery (SFA) reactive hyperemia flow-mediated dilation (RH-FMD) and sustained stimulus FMD (SS-FMD). Calf microvascular function was assessed as the peak and area under the curve of SFA reactive hyperemia (RH). Participants (n = 13 females, 23 ± 2 yrs) had one leg randomized to the single leg heating intervention (EXP; other leg: control (CON)). The EXP leg underwent 8 weeks of single leg heating via immersion in 42.5 ℃ water for five 35-min sessions/week. At weeks 0, 2, 4, 6, and 8, SFA RH-FMD, SS-FMD (shear stress increased via plantar flexion exercise), and SFA RH flow were measured.ResultsNone of the variables changed with repeated, single leg heating (interaction week*limb RH-FMD: p = 0.076; SS-FMD: p = 0.958; RH flow p = 0.955). Covariation for the shear stress stimulus did not alter the FMD results.ConclusionEight weeks of single leg heating did not change SFA endothelial or calf microvascular function. These results are in contrast with previous findings that limb heating improves upper limb endothelial function.

Introduction Isometric resistance training has repeatedly shown to be an effective exercise modality in lowering resting blood pressure (BP), yet associated mechanisms and sex differences in the response to training remain unclear. Exploration into potential sex differences in the response to isometric resistance training is necessary, as it may allow for more optimal and sex-based exercise prescription, thereby maximizing the efficacy of the training intervention. Purpose Therefore, we investigated, in normotensives, whether sex differences exist in the response to isometric handgrip (IHG) training. Methods Resting BP and endothelium-dependent vasodilation (brachial artery flow-mediated dilation; FMD) were assessed in 11 women (23 ± 4 years) and 9 men (21 ± 2 years) prior to and following 8 weeks of IHG training (four, 2-min unilateral contractions at 30 % of maximal voluntary contraction; 3 days per week). Results Main effects of time were observed (all P  < 0.05), whereby IHG training reduced systolic BP (Δ 8 ± 6 mmHg), diastolic BP (Δ 2 ± 3 mmHg), mean arterial pressure (Δ 4 ± 3 mmHg), and pulse pressure (Δ 5 ± 7 mmHg), accompanied by increases in absolute (Δ 0.09 ± 0.15 mm) and relative (Δ 2.4 ± 4.1 %) brachial artery FMD; however, no significant sex differences were observed in the magnitude of post-training change in any variable assessed (all P  > 0.05). Conclusion IHG training effectively lowers resting BP and improves endothelium-dependent vasodilation in men and women, without significant sex differences in the magnitude of response.

Cognitive paradigms induce changes in cerebral blood flow (CBF) associated with increased metabolic demand, namely neurovascular coupling (NVC). We tested the hypothesis that the effect of complexity and duration of cognitive paradigms will either enhance or inhibit the NVC response. Bilateral CBF velocity (CBFV) in the middle cerebral arteries (MCAs) via transcranial Doppler ultrasound (TCD), blood pressure (BP), electrocardiogram (ECG) and end-tidal CO 2 (EtCO 2 ) of 16 healthy participants (aged 21–71 years) were simultaneously recorded at rest and during randomized paradigms of different complexities (naming words beginning with P-,R-,V- words and serial subtractions of 100–2,100–7,1000–17), and durations (5s, 30s and 60s). CBFV responses were population mean normalized from a 30-s baseline period prior to task initiation. A significant increase in bilateral CBFV response was observed at the start of all paradigms and provided a similar pattern in most responses, irrespective of complexity or duration. Although significant inter-hemispherical differences were found during performance of R-word and all serial subtraction paradigms, no lateralisation was observed in more complex naming word tasks. Also, the effect of duration was manifested at late stages of 100–7, but not for other paradigms. CBFV responses could not distinguish different levels of complexity or duration with a single presentation of the cognitive paradigm. Further studies of the ordinal scalability of the NVC response are needed with more advanced modelling techniques, or different types of neural stimulation.

BACKGROUND Large artery stiffness is a major risk factor for the development of hypertension and cardiovascular disease. Persistent prehypertension accelerates the progression of arterial stiffness. METHODS Forty-three unmedicated prehypertensive (systolic blood pressure (SBP) = 120-139mm Hg or diastolic blood pressure (DBP) = 80-89mm Hg) men and women and 15 normotensive time-matched control subjects (NMTCs; n = 15) aged 18-35 years of age met screening requirements and participated in the study. Prehypertensive subjects were randomly assigned to a resistance exercise training (PHRT; n = 15), endurance exercise training (PHET; n = 13) or time-control group (PHTC; n = 15). Treatment groups performed exercise training 3 days per week for 8 weeks. Pulse wave analysis, pulse wave velocity (PWV), and central and peripheral blood pressures were evaluated before and after exercise intervention or time-matched control. RESULTS PHRT and PHET reduced resting SBP by 9.6±3.6mm Hg and 11.9±3.4mm Hg, respectively, and DBP by 8.0±5.1mm Hg and 7.2±3.4mm Hg, respectively (P < 0.05). PHRT and PHET decreased augmentation index (AIx) by 7.5% ± 2.8% and 8.1% ± 3.2% (P < 0.05), AIx@75 by 8.0% ± 3.2% and 9.2% ± 3.8% (P < 0.05), and left ventricular wasted pressure energy, an index of extra left ventricular myocardial oxygen requirement due to early systolic wave reflection, by 573±161 dynes s/cm2 and 612±167 dynes s/cm2 (P < 0.05), respectively. PHRT and PHET reduced carotid-radial PWV by 1.02±0.32 m/sec and 0.92±0.36 m/sec (P < 0.05) and femoral-distal PWV by 1.04±0.31 m/sec and 1.34±0.33 m/sec (P < 0.05), respectively. No significant changes were observed in the time-control groups. CONCLUSIONS This study suggests that both resistance and endurance exercise alone effectively reduce peripheral arterial stiffness, central blood pressures, augmentation index, and myocardial oxygen demand in young prehypertensive subjects.