Effects of Enteral Nutrition on the Barrier Function of the Intestinal Mucosa and Dopamine Receptor Expression in Rats With Traumatic Brain Injury

Background: Impaired intestinal mucosal barrier (IMB) function is common in traumatic brain injury (TBI), but dopamine receptors (DRs) change in intestinal mucosa after TBI, and effects of enteral nutrition (EN) and supplements on IMB function remain unclear. Our purpose was to study the effects of EN and supplements on intestinal mucosal permeability (IMPB) and the expression of DRs DRD1 and DRD2 in the intestinal mucosa of rats with TBI. Methods: Forty‐eight rats were divided into 8 groups; control, animals with TBI, dopamine group, animals with TBI treated with dopamine antagonist, EN alone, or EN combined with glutamine, probiotics, or a combination of probiotics and glutamine daily after TBI. Results: The IMPB was improved in the glutamine, probiotics, and combination groups. Including probiotics improved IMPB more than adding glutamine, and bacterial translocation in the intestines after TBI was reduced in the probiotics and combination groups (all Ps < .01). TBI led to elevated DRD1 and DRD2 mRNA and protein levels, which were reduced in the DA antagonist, glutamine, probiotics, and combination groups. DRD2 mRNA and protein levels in the probiotics and combination groups were decreased more than in the DA antagonist group (all Ps < .01). The increased IMPB after TBI correlated with increased DRD1 and DRD2 levels in the rat intestinal mucosa. Conclusion: EN supplemented with probiotics or combining glutamine and probiotics lowers the increased IMPB, bacterial translocation, and DRD1 and DRD2 mRNA and protein expression in rat intestinal mucosa caused by TBI.     

Impact of Physical Activities on Frailty in Community-Dwelling Older Women

Aims: The aim of the study was to determine whether increased physical activities (PA) affect frailty for old women, 75 years and older (OO), compared to 60–74 years old (YO). Methods: This cross-sectional study measured 19 frailty indicators (muscle strength and endurance, balance, gait characteristics, and function), using 46 community-dwelling women. PA were divided into three levels by caloric expenditure per week (<2,000 kcal/week, 2,000–3,999 kcal/week, >4,000 kcal/week). Results: As PA level increased, a gap (=difference) between OO and YO narrowed for step length and function, but for quadriceps strength and endurance, a gap widened. Conclusions: Frailty progresses with aging but older women who engage in a high level of physical activity (>4,000 kcal/week) can increase mobility and functional capacity, but not for muscle strength and endurance. Starting regular resistance training activities early in the aging process is critical to improve or maintain muscle quality to offset age-related frailty.     

Structural Brain Changes following Long-Term 6° Head-Down Tilt Bed Rest as an Analog for Spaceflight

BACKGROUND AND PURPOSE:Following long-term spaceflight, a subset of the National Aeronautics and Space Administration astronauts present with visual impairment and increased intracranial pressure, known as visual impairment and intracranial pressure syndrome. We investigated structural brain changes following long-term head-down tilt bed rest as a spaceflight analog.MATERIALS AND METHODS:Volumetric analysis was performed on structural pre- and post–bed rest brain MR images.RESULTS:Comparing post–bed rest to pre–bed rest images, we found the following: 1) no significant group differences in GM, WM, CSF, or ventricular volumes; 2) shift of the center of mass of the brain upward and posterior rotation of the brain relative to the skull; 3) a significant correlation between posterior brain rotation and changes in ventricular volume; and 4) significant increases in brain tissue density in regions at the vertex, including the frontoparietal lobes, with contraction of adjacent extra-axial CSF spaces, and significant decreases in tissue density in areas along the base of the brain, including the orbitofrontal cortex.CONCLUSIONS:We observed widespread morphologic changes with brain tissue redistribution in response to gravity changes; possible associated functional changes are unknown. The observation that ventricular change is correlated to posterior brain rotation suggests an alteration in CSF homeostasis. Ultimately, to elucidate any structural changes that may play a role in visual impairment and intracranial pressure syndrome, volumetric analysis of pre- and postflight structural scans of astronauts is needed.

Following long-term missions aboard the International Space Station, increased intracranial pressure and papilledema have been documented in the National Aeronautics and Space Administration (NASA) astronauts. In 1 report¹ investigating 7 astronauts following 6 months of spaceflight, all astronauts demonstrated ophthalmologic findings, with disc edema in 5 astronauts and globe flattening in 5. Lumbar punctures were performed in 4 of these astronauts with opening pressures of 21–28.5 cm H₂O¹. In the 1 astronaut who underwent repeated lumbar punctures, the opening pressure remained elevated 19 months following spaceflight at 22 cm H₂O¹. The etiology of these findings is currently unclear; however, it has been hypothesized that they may result from loss of gravitational hydrostatic pressure gradients and large cephalad fluid shifts. NASA has coined the term “visual impairment and intracranial pressure [VIIP] syndrome” to describe this constellation of signs and symptoms in astronauts and has likened VIIP syndrome to Earth-based idiopathic intracranial hypertension (IIH) or pseudotumor cerebri.A traditional ground-based analog used by NASA and other international space agencies to study physiologic changes associated with long-term spaceflight has been to place healthy subjects in 6° head-down tilt bed rest for varying periods.^2,3 Anecdotally, Russian scientists first devised the head-down-tilt protocol in the early 1970s on the basis of reports by Russian cosmonauts who had the sensation of slipping off the foot of the bed on return to Earth after long-duration missions.³ The foot of the bed was raised until it felt horizontal to help the cosmonauts sleep.³ As an analog for spaceflight, the reduction in Gz gravitational stimuli during bed rest results in an upward shift of body fluids, unloading the upright weight of the body, reduced work against the force of gravity, and lower extremity inactivity.³ As a result, many of the physiologic changes of spaceflight can be reproduced, including decreased cardiac output, orthostatic intolerance, muscle atrophy, and bone loss. This model has been applied extensively to investigate cardiovascular and musculoskeletal deconditioning, immunologic response, and cognitive functioning.^2,3We previously acquired structural MR imaging brain scans of subjects participating in a NASA-sponsored long-term bed rest study.⁴ Given the recent interest in intracranial adaptation to spaceflight, we decided to perform a volumetric analysis of the structural MR imaging dataset to assess any potential alterations in brain structure or CSF distribution that may shed light on the spectrum of findings noted in VIIP syndrome. The results of this analysis are presented here.