Marginal biotin deficiency can be induced experimentally in humans using a cost-effective outpatient design.

To date, marginal, asymptomatic biotin deficiency has been successfully induced experimentally by the use of labor-intensive inpatient designs requiring rigorous dietary control. We sought to determine if marginal biotin deficiency could be induced in humans in a less expensive outpatient design incorporating a self-selected, mixed general diet. We sought to examine the efficacy of three outpatient study designs: two based on oral avidin dosing and one based on a diet high in undenatured egg white for a period of 28 d. In study design 1, participants (n = 4; 3 women) received avidin in capsules with a biotin binding capacity of 7 times the estimated dietary biotin intake of a typical self-selected diet. In study design 2, participants (n = 2; 2 women) received double the amount of avidin capsules (14 times the estimated dietary biotin intake). In study design 3, participants (n = 5; 3 women) consumed egg-white beverages containing avidin with a biotin binding capacity of 7 times the estimated dietary biotin intake. Established indices of biotin status [lymphocyte propionyl-CoA carboxylase activity; urinary excretion of 3-hydroxyisovaleric acid, 3-hydroxyisovaleryl carnitine (3HIA-carnitine), and biotin; and plasma concentration of 3HIA-carnitine] indicated that study designs 1 and 2 were not effective in inducing marginal biotin deficiency, but study design 3 was as effective as previous inpatient study designs that induced deficiency by egg-white beverage. Marginal biotin deficiency can be induced experimentally by using a cost-effective outpatient design by avidin delivery in egg-white beverages. This design should be useful to the broader nutritional research community.

Urinary excretion of 3-hydroxyisovaleric acid and 3-hydroxyisovaleryl carnitine increases in response to a leucine challenge in marginally biotin-deficient humans.

Experimentally increasing metabolic flux in a pathway in which an essential step is catalyzed by a vitamin-dependent enzyme (a challenge test) has been used in assessing functional vitamin status and elucidating common and alternate metabolic pathways. Conversion of 3-methylcrotonyl CoA to 3-methylglutaconyl CoA in the leucine catabolic pathway is catalyzed by the biotin-dependent enzyme methylcrotonyl-CoA carboxylase (MCC). Marginal biotin deficiency reduces MCC activity and increases urinary excretion of 3-hydroxyisovaleric acid (3HIA) and 3-hydroxyisovaleryl carnitine (3HIA-carnitine) measured in 24-h urine collections. We assessed urinary excretion of 3HIA and 3HIA-carnitine in response to a leucine challenge in humans made progressively biotin deficient by egg white consumption. In 2 cohorts of healthy adults (Study 1: n = 5; Study 2: n = 7) rendered biotin deficient over 28 d, urinary excretion of 3HIA and 3HIA-carnitine in response to a leucine challenge was quantitated weekly for 3 or 4 wk, respectively. In both studies, mean urinary excretion of both 3HIA and 3HIA-carnitine increased >2-fold by d 14 (P < 0.002 for both indicators for both studies). Diagnostically, both indicators were highly sensitive, but diagnostic sensitivities were not superior to those of 24-h excretion of 3HIA and 3HIA-carnitine. These studies provide evidence that urinary excretions of 3HIA and 3HIA-carnitine in response to an oral leucine challenge are early and sensitive indicators of marginal biotin deficiency in humans. The variability of the proportion of leucine catabolites excreted as 3HIA suggests substantial population heterogeneity in the metabolic capacity of the 3HIA-carnitine detoxification pathway.

Long-Term Acute Care Hospitals Extend ICU Capacity for COVID-19 Response and Recovery.

The COVID-19 pandemic has presented novel challenges for the entire health-care continuum, requiring transformative changes to hospital and post-acute care, including clinical, administrative, and physical modifications to current standards of operations. Innovative use and adaptation of long-term acute care hospitals (LTACHs) can safely and effectively care for patients during the ongoing COVID-19 pandemic. A framework for the rapid changes, including increasing collaboration with external health-care organizations, creating new methods for enhanced communication, and modifying processes focused on patient safety and clinical outcomes, is described for a network of 94 LTACHs. When managed and modified correctly, LTACHs can play a vital role in managing the national health-care pandemic crisis.

The posture-based motion planning framework: new findings related to object manipulation, moving around obstacles, moving in three spatial dimensions, and haptic tracking.

We describe the results of recent studies inspired by the posture-based motion planning theory (Rosenbaum et al., 2001). The research concerns analyses of human object manipulation, obstacle avoidance, three-dimensional movement generation, and haptic tracking, the findings of which are discussed in relation to whether they support or fail to support the premises of the theory. Each of the aforementioned topics potentially challenges the theory's claim that, in motion, goal postures are planned before the selection of movements towards those postures. However, even the quasi-continuous phenomena under study show features that comply with prospective, end-state-based motion planning. We conclude that progress in motor control should not be frustrated by the view that no model is, or will ever be, optimal. Instead, it should find promise in the steady growth of insights afforded by challenges to existing theories.

Haptic tracking permits bimanual independence.

This study shows that in a novel task-bimanual haptic tracking-neurologically normal human adults can move their 2 hands independently for extended periods of time with little or no training. Participants lightly touched buttons whose positions were moved either quasi-randomly in the horizontal plane by 1 or 2 human drivers (Experiment 1), in circle and square patterns in the vertical plane by 2 human drivers (Experiment 2), or at different frequencies in the horizontal plane by 2 human drivers (Experiment 3). Bimanual contact was maintained equally well in all conditions even though in Experiment 1 the left- and right-hand motions were uncorrelated (in the 2-driver condition), in Experiment 2 the left- and right-hand motions were spatially incongruous when circles and squares were tracked at the same time, and in Experiment 3 the left- and right-hand motions maintained different frequency ratios. Because haptic tracking has revealed that humans can in fact move their 2 hands independently, it may have potential as a new behavioral tool for revealing other perceptual-motor capabilities.

Use of a Central Catheter Maintenance Bundle in Long-Term Acute Care Hospitals.

OBJECTIVE: Evidence-based guidelines have resulted in decreases in bloodstream infections associated with central catheters (CLABSIs) in hospital intensive care units. However, relatively little is known about CLABSI incidence and prevention in long-term acute care hospitals (LTACHs). METHODS: A central catheter maintenance bundle was implemented in 30 LTACHs, and compliance with the bundle was tracked for 6 months. CLABSI rates were monitored for 14 months before and 14 months after the bundle was implemented. RESULTS: The pooled mean CLABSI rate (No. of infections per 1000 days with a central catheter) was 1.28 before the bundle and 0.96 after the bundle (repeated measures general linear model; F1,58 = 6.973; P = .01; partial η(2) = .11). From 14 months before to 14 months after the bundle was implemented, the mean number of CLABSIs per LTACH decreased by 4.5 (95% CI, 1.85-7.15). Time series modeling showed a significant decrease in the mean hospital CLABSI rate after the bundle was implemented (-0.511 CLABSI/1000 catheter days, SE = 0.050), indicating an immediate effect of the bundle. The mean hospital CLABSI rate was decreasing slightly before the bundle was implemented and continued to decrease at a reduced rate after the bundle was implemented. CONCLUSION: The bundle resulted in a significant and sustained reduction in CLABSI rates in 30 LTACHs for 14 months. These results encourage the development and implementation of similar bundles as effective strategies for infection reduction in LTACHs.

The motor system computes well but remembers poorly.

The psychological approach to human voluntary movements advocated by F. Mechsner (2004) can be aligned with the view that motor commands are generated afresh but are not retrieved from memory. This movement-generation hypothesis gains indirect support in the findings Mechsner reviewed and obtains more direct support from the results of studies of memory for movement and computational modeling of motor planning.

Long-term acute care hospitals have low impact on medicare readmissions to short-term acute care hospitals.

The relative contribution of long-term acute care hospital (LTACH) to short-term acute care hospital (STACH) Medicare patient readmissions is important because of the high acuity of LTACH patients. A retrospective cohort study was conducted to determine the magnitude of LTACH Medicare heart failure (HF) and pneumonia (PN) inpatient readmissions to STACHs within 30 days of LTACH admission and the relative contribution of LTACH patient readmissions to each STACH's total readmissions. Seventy-five for-profit LTACHs and their associated host or primary referral STACHs were studied. An average of 8% HF and 8% PN LTACH Medicare inpatients were readmitted to host or primary referral STACHs within 30 days of admission, representing 0.4% and 0.8% of the total number of HF and PN Medicare patients, respectively, readmitted to the STACHs in fiscal year 2010. The low rates of readmission from LTACHs to STACHs suggest an appropriate level of care for the LTACHs studied.

Reliability and validity of the Virtual Reality Lateralized Attention Test in assessing hemispatial neglect in right-hemisphere stroke.

OBJECTIVE: Many tests of hemispatial neglect are insensitive to subtle (but clinically relevant) forms of the disorder. This study provides additional reliability and validity data on the Virtual Reality Lateralized Attention Test (VRLAT), an easy-to-administer computerized measure of hemispatial neglect that mimics the attentional demands of real-world tasks, and has previously shown strong validity and sensitivity (Dawson, Buxbaum, & Rizzo, 2008). The present study assessed a large sample of patients with the aim of developing a clinically useful version of the test, and established the concurrent criterion validity of the VRLAT as measured by its association with performance in a real-world task. METHOD: Seventy consecutively recruited right-hemisphere stroke patients were assessed with the VRLAT, which requires participants to name objects as they navigate (or are navigated) along a winding virtual path. They also performed a real-world navigation task, tests of sensory and motor function, and paper-and-pencil neglect tests. RESULTS: The VRLAT demonstrated strong sensitivity and specificity, minimal practice effects, and strong validity, and outperformed traditional paper-and-pencil tests in the prediction of real-world collisions. CONCLUSIONS: The VRLAT is a sensitive, valid, and reliable measure of hemispatial neglect that requires no specialized equipment, is easy to administer, and is useful for both clinical and research purposes. Moreover, a shortened version with a 5-min administration time has many of the desirable psychometric properties of the original full-length task.

The impact of left hemisphere stroke on force control with familiar and novel objects: neuroanatomic substrates and relationship to apraxia.

Fingertip force scaling for lifting objects frequently occurs in anticipation of finger contact. An ongoing question concerns the types of memories that are used to inform predictive control. Object-specific information such as weight may be stored and retrieved when previously encountered objects are lifted again. Alternatively, visual size and shape cues may provide estimates of object density each time objects are encountered. We reasoned that differences in performance with familiar versus novel objects would provide support for the former possibility. Anticipatory force production with both familiar and novel objects was assessed in six left hemisphere stroke patients, two of whom exhibited deficient actions with familiar objects (ideomotor apraxia; IMA), along with five control subjects. In contrast to healthy controls and stroke participants without IMA, participants with IMA displayed poor anticipatory scaling with familiar objects. However, like the other groups, IMA participants learned to differentiate fingertip forces with repeated lifts of both familiar and novel objects. Finally, there was a significant correlation between damage to the inferior parietal and superior and middle temporal lobes and impaired anticipatory control for familiar objects. These data support the hypotheses that anticipatory control during lifts of familiar objects in IMA patients are based on object-specific memories and that the ventro-dorsal stream is involved in the long-term storage of internal models used for anticipatory scaling during object manipulation.