The cartilage endplates (CEPs) on the superior and inferior surfaces of the intervertebral disc (IVD), are the primary nutrient transport pathways between the disc and the vertebral body. Passive diffusion is responsible for transporting small nutrient and metabolite molecules through the avascular CEPs. The baseline solute diffusivities in healthy CEPs have been previously studied, however alterations in CEP diffusion associated with IVD degeneration remain unclear. This study aimed to quantitatively compare the solute diffusion in healthy and degenerated human CEPs using a fluorescence recovery after photobleaching (FRAP) approach. Seven healthy CEPs and twenty-two degenerated CEPs were collected from five fresh-frozen human cadaveric spines and seventeen patients undergoing spine fusion surgery, respectively. The sodium fluorescein diffusivities in CEP radial and vertical directions were measured using the FRAP method. The CEP calcification level was evaluated by measuring the average X-ray attenuation. No difference was found in solute diffusivities between radial and axial directions in healthy and degenerated CEPs. Compared to healthy CEPs, the average solute diffusivity was 44% lower in degenerated CEPs [Healthy: 29.07(23.96-33.62) µm²/s; Degenerated: 16.32(13.84-18.84) µm²/s, p<0.001]. The average solute diffusivity had an inverse relationship with the degree of CEP calcification as determined by the normalized X-ray attenuation values. This study suggests that solute diffusion through the disc and vertebral body interface is significantly hindered by CEP calcification, providing clues to help further understand the IVD degeneration mechanism.

Background: Abnormal alterations in cerebral blood flow (CBF) have been implicated in cognitive decline and neurodegeneration. Maintaining adequate CBF in astronauts during long-duration microgravity is therefore crucial for the success of manned spaceflight. However, the quantitative assessment of CBF during space missions remains challenging. Methods: Thirty-six participants underwent a 90-d −6° head-down tilt bed rest (HDTBR) protocol, a well-established ground-based analog of microgravity. Multimodal imaging data, including internal carotid artery Doppler ultrasound and brain magnetic resonance imaging, were collected during HDTBR. Multiple machine learning (ML) algorithms were developed to investigate carotid–CBF mapping relationship and establish CBF change prediction models. Results: After 90-d HDTBR, significant regional CBF decreases were observed, primarily in the right Heschl’s gyrus, right middle cingulate gyrus, and right superior frontal gyrus. The optimal ML model CatBoost showed robust predictive performance for CBF in these regions (right Heschl’s gyrus: AUC = 0.88, accuracy = 0.84; right middle cingulate gyrus: AUC = 0.92, accuracy = 0.83; right superior frontal gyrus: AUC = 0.82, accuracy = 0.72). To enhance accessibility and practical utility, the prediction model was implemented as an interactive web application for in-orbit deployment. Conclusion: This study demonstrates the feasibility of constructing ML-driven CBF prediction models under microgravity based on multimodal imaging. The developed prediction models show promise as early warning tools for brain health of astronauts in spaceflight.

Background: It is unclear whether dobutamine, commonly used clinically in echocardiography and short-term congestive heart failure treatment for promoting increased myocardial contractility, affects brain microcirculatory behavior. Cerebral microcirculation plays an important role in ensuring adequate oxygen transport. Therefore, we investigated the effects of dobutamine on cerebral hemodynamics. Methods: Forty-eight healthy volunteers without cardiovascular or cerebrovascular disease underwent MRI to obtain cerebral blood flow (CBF) maps using 3D pseudocontinuous arterial spin labeling before and during the dobutamine stress test. Additionally, cerebrovascular morphology was obtained based on 3D-time-off-light (3D-TOF) magnetic resonance angiography (MRA). Electrocardiogram, heart rate (HR), respiration rate (RR), blood pressure, and blood oxygen were simultaneously recorded before and during dobutamine injection and during recovery (not during MRI). The anatomic features of the circle of Willis and the basilar artery (BA) diameter were assessed on MRA images by two radiologists with extensive neuroimaging experience. Binary logistic regression was used to test for the independent determinants of CBF changes. Results: HR, RR, systolic (SBP), and diastolic blood pressure (DBP) significantly increased after dobutamine infusion. Blood oxygen levels remained similar. Compared to the CBF in the resting state, the CBF values exhibited significantly lower CBF levels in both grey matter and white matter. Furthermore, compared with the CBF in the resting state, that in the stress state was decreased in the anterior circulation, mainly in the frontal lobe (voxel level P < 0.001, pixel level P < 0.05). Logistic regression showed that body mass index (BMI; odds ratio [OR] 5.80, 95% confidence interval [CI] 1.60–21.01, P = 0.008], resting SBP (OR 0.64, 95% CI 0.45–0.92, P = 0.014), and BA diameter (OR 11.04, 95% CI 1.05–116.53, P = 0.046) were significantly associated with frontal lobe CBF changes. Conclusions: Dobutamine-induced stress significantly decreased CBF in the frontal lobe anterior circulation. Individuals with a high BMI and low SBP during the dobutamine stress test are more likely to have a stress-induced CBF decrease. Thus, attention should be paid to blood pressure, BMI, and cerebrovascular morphology of patients undergoing dobutamine stress echocardiography or those receiving intensive care or anesthesia.

Dobutamine, a sympathomimetic agent, is widely used clinically, influencing cardiac output, heart rate (HR), and blood pressure (BP), which may impact cerebral blood flow (CBF), critical for brain metabolism. However, the effects of dobutamine on CBF and internal carotid artery (ICA) blood flow remain unclear, with contradictory reported in both clinical and animal studies. It is necessary to investigate the effects of dobutamine on cervical and cerebral hemodynamics. This study aimed to evaluate the effects of dobutamine infusion on ICA blood flow and CBF, explore their relationship, and identify factors influencing CBF to facilitate timely monitoring in clinical practice. Forty-eight healthy volunteers underwent physiological assessment, ICA ultrasound, and brain magnetic resonance imaging (MRI) data before and after the administration of dobutamine. Paired t and Wilcoxon signed-rank tests were used to analyze changes, while logistic regression explored associations between hemodynamic factors and CBF. Dobutamine infusion significantly increased HR, respiration rate, systolic BP (SBP), diastolic BP (DBP), and mean arterial pressure, while blood oxygen remained stable. Compared with those in the resting state, the peak systolic velocity (Vs), resistance index, pulsatility index, and systolic/diastolic ratio increased, whereas end-diastolic velocity (Vd) decreased. ICA diameter and mean velocity showed no changes. CBF significantly decreased in the anterior and middle cerebral arteries. Logistic regression identified SBP, DBP, and S/D difference as key factors associated with CBF reduction. Dobutamine altered ICA hemodynamics and reduced CBF in anterior and middle cerebral arteries. Real-time ICA ultrasound monitoring provides valuable guidance during clinical use.

This study aimed to investigate cervical vessel hemodynamics during 7 days of −6° head-down tilt (HDT) bed rest (BR) and 5 days of recovery in 40 healthy males, focusing on bilateral analysis and dynamic temporal monitoring. Diameter, flow velocity, and blood flow volume (BFV) of bilateral common (CCAs), internal (ICAs), external carotid arteries and vertebral arteries (VAs) were measured at eight time points using ultrasound. Cervical vessels exhibited heterogeneous and lateralized responses. Left VA exhibited the most pronounced BFV and velocity fluctuations, with significant reductions during HDT and recovery to baseline post-HDT, while right VA remained stable. CCAs and ICAs had dynamic diameter and velocity changes, but stable BFVs. Left VA BFV reduction was significantly associated with right VA dominance, elevated heart rate, and increased mean arterial pressure at HDT 3 d. Despite stable total BFV, left VA BFV declined during BR, warranting further monitoring.