Alteration of the erythrocyte membrane skeletal ultrastructure in hereditary spherocytosis, hereditary elliptocytosis, and pyropoikilocytosis

The membrane skeleton of normal erythrocytes is largely organized into a hexagonal lattice of junctional complexes (JC) crosslinked by spectrin tetramers, and occasional double tetramers and hexamers. To explore possible skeletal alterations in hereditary spherocytosis (HS), elliptocytosis (HE), and pyropoikilocytosis (HPP), we have studied the ultrastructure of the spread membrane skeletons from a subpopulation of HS patients with a partial spectrin deficiency ranging from 43% to 86% of normal levels, and in patients with HPP who, in addition to a mild spectrin deficiency, also carried a mutant spectrin that was dysfunctional, thus reducing the ability of spectrin dimers to assemble into tetramers. Membrane skeletons derived from Triton-treated erythrocyte ghosts were examined by negative staining electron microscopy. HS membrane skeletons contained structural elements, consisting of JC and spectrin filaments similar to the normal skeleton. However, less spectrin filaments interconnected the JC, and the decrease of spectrin filaments attached to JC appeared to correlate with the severity of spectrin deficiency. Only in severe HS associated with severe spectrin deficiency was the loss of spectrin sufficient enough to disrupt the overall skeletal architecture. In contrast, membrane skeletons prepared from red blood cells (RBCs) of subjects with HPP were strikingly different from HS RBCs with a comparable degree of spectrin deficiency. Although HPP RBCs were only mildly deficient in spectrin, their skeletal lattice was grossly disrupted, in contrast to only mild ultrastructural abnormalities of HS membrane skeletons with a nearly identical degree of spectrin deficiency. Skeletons from patients with common mild HE or asymptomatic carriers, carrying the mutant spectrin but having normal spectrin content, exhibited a moderate disruption of the skeletal lattice. We propose that the above differences in skeletal ultrastructure may underlie differences in the biomechanical properties and morphology of HS, HE, and HPP RBCs.     

Ultrastructural studies of the interaction of spectrin with phosphatidylserine liposomes

Spectrin was shown previously to interact with phosphatidylserine and phosphatidylethanolamine, which are preferentially localized in the inner half of the membrane lipid bilayer, but this interaction is not well characterized. In the present study we used electron microscopy of rotary-shadowed platinum replicas of spectrin dimer-phosphatidylserine complexes to study the interaction of spectrin with phosphatidylserine vesicles. At a spectrin concentration of 0.6 mg/mL, 60% of spectrin dimers were associated with phosphatidylserine vesicles and at a spectrin concentration of 1.2 mg/mL, some vesicles were crosslinked by spectrin dimers. The length of the protruding segment of spectrin dimer from the liposome edge ranged from 400 to 960A degrees and the contact region to phosphatidylserine extended 272 +/- 144A degrees from either end of the molecule. Therefore, these data are consistent with multiple binding sites to phosphatidylserine throughout the spectrin dimer molecule. Spectrin tetramers, when bound to phosphatidylserine liposomes, extended 1804 +/- 79A degrees from the liposome edge and crosslinked liposomes, suggesting that some of the binding sites to phosphatidylserine vesicles is in the proximity of the tail end of spectrin. The association between spectrin dimers to phosphatidylserine was demonstrated by nondenaturing gel electrophoresis. The complexes were separated into multiple bands with molecular weight of 1.4 X 10(6), 1.8 X 10(6), and 2.3 X 10(6). These bands did not represent self- associated spectrin oligomers, since postincubation treatment with Triton-X-100 dissociated them into spectrin dimers. Furthermore, these spectrin high molecular weight bands, as visualized by Coomassie blue absorbance, closely corresponded to the 14C-phosphatidylserine distribution. These data provide ultrastructural and biochemical evidence that spectrin binds to phosphatidylserine at multiple sites including the tail end region.     

Reliability and validity of two new instruments for measuring aspects of mental slowness in the daily lives of stroke patients

The objective of the study was to examine psychometric characteristics of two measures related to mental slowness experienced after stroke: One measure is aimed at performance on tasks, the other is a questionnaire evaluating perceived consequences of mental slowness. A group of 37 stroke patients and 33 matched controls were studied. A subgroup of 10 patients and 22 controls was observed by two independent raters to determine inter-rater reliability, a subgroup of 18 patients completed the questionnaire twice over a two-week interval to determine test-retest stability. Results showed that internal consistency was acceptable for the Mental Slowness Observation Test (Cronbach's α = .61 and .73) and good for the Mental Slowness Questionnaire (α = .91). For the Observation Test, correlations between the results of the two raters ranged between .77 and .99 and intra-class correlation coefficients were between .86 and .99. For the Questionnaire, correlations between two test occasions ranged between .85 and .90 and intra-class correlation coefficients were between .91 and .95. Correlations of between .52 and .67 were found between the Observation Test and neuropsychological tasks for speed of information processing. The Questionnaire correlated most strongly with scores on tests for activities of daily living (ADL) functioning, and fatigue and depression (correlations ranged between .37 and .63). It was concluded that the two new instruments offer reliable and valid methods for measuring limitations in daily activities related to mental slowness and some of the consequences of mental slowness in terms of sense of time pressure, fatigue, depressive complaints and independent ADL functioning.     

A multicenter randomized controlled trial to compare subacute 'treatment as usual' with and without mental practice among persons with stroke in Dutch nursing homes

ObjectiveSystematic reviews suggest that mental practice as an additional therapy for people with stroke might be effective and suggest that more trials with better defined interventions are needed. This study investigated whether imagining the skilled movement systematically can contribute to a quicker and/or better recovery of stroke patients in long term care.DesignA multicenter randomized controlled trial.SettingDutch nursing homes.ParticipantsStroke patients in the subacute phase of recovery.InterventionsStudy participants were randomly assigned to the control or experimental group. Over a 6-week intervention period, both groups received multi professional therapy as usual. Additionally, patients in the experimental group had instruction on mental practice with a 4-step framework embedded in regular therapy time.Main OutcomeOutcomes were assessed at 6 weeks and 6 months with the patient-perceived effect on performance of daily activities (10-point Numeric Rating Scale). Six secondary outcomes on impairment and activity level were also assessed. Primary analyses were performed according to the intention-to-treat principle. Generalized estimating equations (GEE) were used to analyze effects.ResultsThirty-six adult stroke patients (average age 77.8, ±7.2 years) participated in the trial. No effect in favor of the mental practice intervention on any outcome measure could be detected at either measuring points.ConclusionsThis study could not show differences between embedded mental practice and current standard of care. However, stroke pathways in Dutch nursing homes select specific and frail patients, which might have reduced the effects of training.     

Gait adaptations to simultaneous cognitive and mechanical constraints

Previous studies have shown that walking is not a purely automatic motor task but places demands on sensory and cognitive systems. We set out to investigate whether complex walking tasks, as when walking down a steeper gradient while performing a concurrent cognitive task, would demand gait adaptation beyond those required for walking under low-challenge conditions. Thirteen healthy young individuals walked at their self-selected speed on a treadmill at different inclinations (0, −5 and −10%). Gait spatio-temporal measures, pelvis angular excursion, and sacral centre of mass (CoM) motion were acquired while walking or while walking and performing a mental tracking task. Repeated-measures ANOVAs revealed that decreasing treadmill inclination from 0 to −10% resulted in significant decreased walking speed (P < 0.001), decreased stride length (P < 0.001), increased pelvis tilt (P = 0.006) and obliquity variability (P = 0.05), decreased pelvis rotation (P = 0.02), and increased anterio-posterior (A-P) CoM displacement (P = 0.015). Compared to walking alone, walking under dual-task condition resulted in increased step width (P < 0.001), and increased medio-lateral (M-L) CoM displacement (P = 0.039) regardless of inclination grade, while sagittal plane dynamics did not change. Findings suggest that gait adapts differently to cognitive and mechanical constraints; the cognitive system is more actively involved in controlling frontal than sagittal plane gait dynamics, while the reverse is true for the mechanical system. Finally, these findings suggest that gait adaptations maintain the ability to perform concurrent tasks while treadmill walking in healthy young adults.     

In-hospital mortality among women undergoing contemporary elective percutaneous coronary intervention: a reexamination of the gender gap

BACKGROUND: Previous studies have indicated that, compared with men, women are at increased risk for in-hospital mortality following percutaneous coronary intervention (PCI); however, angioplasty techniques and mortality rates have improved since earlier reports. HYPOTHESIS: We sought to reevaluate and explore further the relationship between gender and angioplasty outcomes in contemporary "real world" practice. METHODS: The influence of gender and other covariates on in-hospital mortality and other adverse events among all patients who underwent elective coronary angioplasty in New York State from 1999 to 2001 (n = 106,262) was examined. RESULTS: In-hospital mortality rates for elective angioplasty were low; however, women demonstrated a two-fold mortality excess compared with men (0.6 vs. 0.3%, p < 0.0001). Women were older and more likely than men to demonstrate certain higher-risk features (heart failure, class III-IV angina, renal failure, vascular disease); however, men were more likely to have depressed ejection fraction, prior myocardial infarction, and prior coronary revascularization. Using multivariate analysis adjusting for clinical risk factors, gender remained an independent predictor of in-hospital mortality at all ages. Women were also more likely to experience nonfatal adverse events following PCI, including more frequent need for emergency bypass surgery. CONCLUSIONS: Despite improvements in angioplasty outcomes with time, women remain at significantly higher risk of in-hospital death than men after elective PCI. This increased mortality is observed in every age group, even after adjusting for other significant comorbidities.