The Influence of Glove Type on Simulated Wheelchair Racing Propulsion: A Pilot Study.

Our purpose was to examine the influence of glove type on kinetic and spatiotemporal parameters at the handrim in elite wheelchair racers. Elite wheelchair racers (n=9) propelled on a dynamometer in their own racing chairs with a force and moment sensing wheel attached. Racers propelled at 3 steady state speeds (5.36, 6.26 & 7.60 m/s) and performed one maximal effort sprint with 2 different glove types (soft & solid). Peak resultant force, peak torque, impulse, contact angle, braking torque, push time, velocity, and stroke frequency were recorded for steady state and sprint conditions. Multiple nonparametric Wilcoxon matched pair's tests were used to detect differences between glove types, while effect sizes were calculated based on Cohen's d. During steady state trials, racers propelled faster, using more strokes and larger contact angle, while applying less impulse with solid gloves compared to soft gloves. During the sprint condition, racers achieved greater top end velocities, applying larger peak force, with less braking torque with solid gloves compared to soft gloves. Use of solid gloves may provide some performance benefits to wheelchair racers during steady state and top end velocity conditions.

Clinical impact of FDG PET-CT on the management of patients with locally advanced cervical carcinoma.

AIM: To evaluate the impact of staging FDG PET-CT on the initial management of patients with locally advanced cervical carcinoma (LACC) and any prognostic variables predicting survival. MATERIALS AND METHODS: Retrospective analysis of consecutive patients undergoing FDG PET-CT for staging of LACC in a single tertiary referral centre, between April 2008 and August 2011. Comparison was made between MRI and PET-CT findings and any subsequent impact on treatment intent or radiotherapy planning was evaluated. RESULTS: Sixty-three patients underwent FDG PET-CT for initial staging of LACC. Major impact on management was found in 20 patients (32%), a minor impact in five (8%), and no impact in 38 (60%). In those patients where PET-CT had a major impact, 12 had more extensive local nodal involvement, five had occult metastatic disease, two had synchronous tumours, and one patient had equivocal lymph nodes on MRI characterized as negative. PET-positive nodal status at diagnosis was found to be a statistically significant predictor of relapse-free survival (p < 0.05). CONCLUSION: Staging FDG PET-CT has a major impact on the initial management of approximately one-third of patients with LACC by altering treatment intent and/or radiotherapy planning. PET-defined nodal status is a poor prognostic indicator.

Effect of low-compression balls on wheelchair tennis match-play.

The purpose of this study was to compare court-movement variables and physiological responses to wheelchair tennis match-play when using low vs. standard compression tennis balls. Eleven wheelchair basketball players were monitored during repeated bouts of tennis (20 min) using both ball types. Graded and peak exercise tests were completed. For match-play, a data logger was used to record distance and speed. Individual linear heart rate oxygen consumption relationships were used to estimate match-play oxygen uptake. Significant main effects for ball type revealed that total distance (P<0.05), forward distance (P<0.05), and average speed (P<0.05) were higher for play using a low-compression ball. A lower percentage of total time was spent stationary (P<0.001), with significantly more time spent at speeds of 1-1.49 (P<0.05), 1.5-1.99 (P<0.05) and 2.0-2.49 (P<0.05) m ∙ sec(-1) when using the low-compression ball. Main effects for physiological variables were not significant. Greater total and forward distance, and higher average speeds are achieved using a low-compression ball. The absence of any difference in measured HR and estimated physiological responses would indicate that players move further and faster at no additional mean physiological cost. This type of ball will be useful for novice players in the early phases of skill development.

Biofilms in wounds: a review of present knowledge.

Following confirmation of the presence of biofilms in chronic wounds, the term biofilm became a buzzword within the wound healing community. For more than a century pathogens have been successfully isolated and identified from wound specimens using techniques that were devised in the nineteenth century by Louis Pasteur and Robert Koch. Although this approach still provides valuable information with which to help diagnose acute infections and to select appropriate antibiotic therapies, it is evident that those organisms isolated from clinical specimens with the conditions normally used in diagnostic laboratories are mainly in a planktonic form that is unrepresentative of the way in which most microbial species exist naturally. Usually microbial species adhere to each other, as well as to living and non-living surfaces, where they form complex communities surrounded by collectively secreted extracellular polymeric substances (EPS). Cells within such aggregations (or biofilms) display varying physiological and metabolic properties that are distinct from those of planktonic cells, and which contribute to their persistence. There are many factors that influence healing in wounds and the discovery of biofilms in chronic wounds has provided new insight into the reasons why. Increased tolerance of biofilms to antimicrobial agents explains the limited efficacy of antimicrobial agents in chronic wounds and illustrates the need to develop new management strategies. This review aims to explain the nature of biofilms, with a view to explaining their impact on wounds.

Manuka honey inhibits siderophore production in Pseudomonas aeruginosa.

AIMS: The aim of this study was to determine whether manuka honey affected siderophore production by three strains of Pseudomonas aeruginosa. METHODS AND RESULTS: The minimum inhibitory concentration (MIC) of manuka honey against each of the test bacteria was determined. The effect of manuka honey on siderophore production by three strains of Ps. aeruginosa was investigated using the Chrome azurol S assay (CAS) and CAS-agar plates. Manuka honey at ½ and » of the MIC for each strain led to reduced production of siderophores (1·3-2·2-fold less) which was found to be statistically significant when compared to the untreated control. CONCLUSIONS: Manuka honey effectively inhibited siderophore production by all three strains of Ps. aeruginosa used in this study. This suggests that manuka honey may impact on bacterial iron homoeostasis and identified a new target for manuka honey in Ps. aeruginosa. SIGNIFICANCE AND IMPACT OF STUDY: Pseudomonas aeruginosa is an opportunistic human pathogen that can cause acute, life-threatening or persistent wound infections. Part of the virulence repertoire of this micro-organism includes the ability to sequester iron from the host during infection by the synthesis and secretion of siderophores. Manuka honey may limit wound infection by Ps. aeruginosa by limiting its ability to capture iron. This is the first time this mechanism has been investigated.

Physical activity classification utilizing SenseWear activity monitor in manual wheelchair users with spinal cord injury.

STUDY DESIGN: Validation. OBJECTIVES: The primary aim of this study was to develop and evaluate activity classification algorithms for a multisensor-based SenseWear (SW) activity monitor that can recognize wheelchair-related activities performed by manual wheelchair users (MWUs) with spinal cord injury (SCI). The secondary aim was to evaluate how the accuracy in activity classification affects the estimation of energy expenditure (EE) in MWUs with SCI. SETTING: University-based laboratory. METHODS: Forty-five MWUs with SCI wore a SW on their upper arm and participated in resting, wheelchair propulsion, arm-ergometery and deskwork activities. The investigators annotated the start and end of each activity trial while the SW collected multisensor data and a portable metabolic cart collected criterion EE. Three methods including linear discriminant analysis, quadratic discriminant analysis (QDA), and Naïve Bayes (NB) were used to develop classification algorithms for four activities based on the training data set from 36 subjects. RESULTS: The classification accuracy was 96.3% for QDA and 94.8% for NB when the classification algorithms were tested on the validation data set from nine subjects. The average EE estimation errors using the activity-specific EE prediction model were 5.3±21.5% and 4.6±22.8% when the QDA and NB classification algorithms were applied, respectively, as opposed to 4.9±20.7% when 100% classification accuracy was assumed. CONCLUSION: The high classification accuracy and low EE estimation errors suggest that the SW can be used by researchers and clinicians to classify and estimate the EE for the four activities tested in this study among MWUs with SCI.

Effects of cross slopes and varying surface characteristics on the mobility of manual wheelchair users.

Surface characteristics of a cross slope can impact the ease with which a manual wheelchair (MWC) user propels across a surface. The purpose of this research was two-fold. Phase I of this research surveyed MWC users to identify cross slope scenarios that they reported to be more difficult to traverse compared to other common driving obstacles. Our survey results showed that, overall, cross slopes were harder to propel across than narrow and manual doors, and cross-slopes in inclement weather conditions were equal or more difficult than gravel and rough-surfaces. Cross slopes with severe angles and those with compound angles (slope with cross-slope) were the most difficult to traverse. Phase II focused on identifying the responses (e.g., avoid, explore alternative, experience a sense of insecurity, no effect) people had when viewing pictures of various cross-slopes scenarios (e.g., narrow space, compound angles, extreme weather) that wheelchair users encounter. These results showed that people reported that they would avoid or feel insecure on some cross-sloped surfaces, like the weather, that are not within our control, others, like compound angle and curb-cuts on slopes, that can be addressed in the construction of pathways or sidewalks.

The effect of manuka honey on the structure of Pseudomonas aeruginosa.

The purpose of this study was to investigate the effects of manuka honey on the structural integrity of Pseudomonas aeruginosa ATCC 27853. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of manuka honey for P. aeruginosa were determined by a microtitre plate method, and the survival of bacteria exposed to a bactericidal concentration of manuka honey was monitored. The effect of manuka honey on the structure of the bacteria was investigated using scanning and transmission electron microscopy (SEM and TEM, respectively). The MIC and MBC values of manuka honey against P. aeruginosa were 9.5% (w/v) and 12% (w/v) respectively; a time-kill curve demonstrated a bactericidal rather than a bacteriostatic effect, with a 5 log reduction estimated within 257 min. Using SEM, loss of structural integrity and marked changes in cell shape and surface were observed in honey-treated cultures. With TEM, these changes were confirmed, and evidence of extensive cell disruption and lysis was found. Manuka honey does not induce the same structural changes in P. aeruginosa as those observed in staphylococci. Our results indicate that manuka honey has the potential to be an effective inhibitor of P. aeruginosa.

Concanavalin A-mediated binding and sphering of human red blood cells by homologous monocytes.

Human red blood cells sensitized with concanavalin A became bound to homologous peripheral blood monocytes. Binding occured at a concentration of 10(5) molecules of tetrameric Con A per red blood cell (RBC) and increased with additional Con A. RBC binding began within 5 min and was maximal at 90 min. Phagocytosis of sensitized RBCs was minimal. RBC attachment was prevented by 0.01 M alpha-methyl-D-mannopyranoside, and, once the RBC-monocyte rosette was established, bound RBCs were largely removed with this specific saccharide inhibitor of Con A. RBCs attached to monocytes became spherocytic and osmotically fragile. The recognition of concanavalin A (Con A)-coated RBCs was not mediated through the monocyte IgG-Fc receptor. These studies demonstrate that, like IgG and C3b, Con A is capable of mediating the binding of human RBCs to human monocytes. Red cells so bound are damaged at the monocyte surface.

The intracellular effects of manuka honey on Staphylococcus aureus.

The purpose of this study was to investigate the effect of manuka honey on Staphylococcus aureus in order to identify the intracellular target site. The mode of inhibition of manuka honey against S. aureus NCTC 10017 was investigated by determining the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and the effect of time on viability. Structural changes were observed by scanning (SEM) and transmission electron microscopy (TEM) of cells suspended for 4 h at 37 degrees C in 0.05 mM Tris buffer containing 10% (w/v) manuka honey and were compared to cells in buffer alone or buffer containing 10% (w/v) artificial honey (to assess osmotic damage). A bactericidal mode of inhibition for manuka honey on S. aureus was established. Marked structural changes in honey-treated cells were seen only with TEM, where a statistically significant increase in the number of whole cells with completed septa compared to untreated cells were observed (P < 0.05). Structural changes found with TEM suggest that honey-treated cells had failed to progress normally through the cell cycle and accumulated with fully formed septa at the point of cell division without separating. Sugars were not implicated in this effect. The staphylococcal target site of manuka honey involves the cell division machinery.

Absence of bacterial resistance to medical-grade manuka honey.

Clinical use of honey in the topical treatment of wounds has increased in Europe and North America since licensed wound care products became available in 2004 and 2007, respectively. Honey-resistant bacteria have not been isolated from wounds, but there is a need to investigate whether honey has the potential to select for honey resistance. Two cultures of bacteria from reference collections (Staphylococcus aureus NCTC 10017 and Pseudomonas aeruginosa ATCC 27853) and four cultures isolated from wounds (Escherichia coli, methicillin-resistant S. aureus (MRSA), Pseudomonas aeruginosa and S. epidermidis) were exposed to sub-lethal concentrations of manuka honey in continuous and stepwise training experiments to determine whether the susceptibility to honey diminished. Reduced susceptibilities to manuka honey in the test organisms during long-term stepwise resistance training were found, but these changes were not permanent and honey-resistant mutants were not detected. The risk of bacteria acquiring resistance to honey will be low if high concentrations are maintained clinically.

Barriers and facilitators to students with physical disabilities' participation in academic laboratory spaces.

Purpose: To provide empirical evidence on learning barriers and facilitators in instructional science and engineering laboratory settings from a national survey on students with physical disabilities (SwD-P).Methods: A nationwide self-report survey, the Full Participation Science and Engineering Accessibility (FPSEA), was disseminated online via Qualtrics. Approximately 1200 organizations and universities across the United States were contacted through purposive sampling. Descriptive statistics were primarily used for the analysis of the results.Results: Survey findings reveal that students experience a wide range of limitations to full participation in the laboratory, from entering the laboratory (25%) to being given passive roles (50%). Additionally, while 66% of respondents indicated that instructors were willing to help SwD-P participate in science and engineering (S&E) laboratories, 16.8% were not willing to do so, and 47% SwD-P felt that practices were not in place to provide accommodations. The survey also reveals a range of facilitators such as elevators, ramps, accessible course materials and peer assistance. Most respondents (74%) also indicated that peers were helpful in completing laboratory tasks.Conclusion: This survey provides empirical evidence that was previously voiced through non-empirical information in the literature. Participants cited barriers such as inappropriate accommodations and instructors' negative viewpoints, as well as gaining access to facilities even after the enactment of the Americans with Disabilities Act (ADA). These findings suggest that while ADA has lessened some barriers to SwD-P, barriers remain in using the laboratory space. The FPSEA survey fills the gap in finding barriers and facilitators to using S&E laboratories from the SwD-P's perspective.Implications for RehabiliationBarriers students with disabilities encounter in science and engineering (S&E) laboratory environments remain unclear.The FPSEA survey fills the gap in finding barriers and facilitators to using S&E laboratories from the SwD-P's perspective.The FPSEA survey allows former and current SwD-P to share their experiences using a postsecondary S&E instructional laboratory.

High-resolution lymphoscintigraphy is essential for recognition of the significance of internal mammary nodes in breast cancer.

BACKGROUND: Sentinel node biopsy (SNB) of internal mammary nodes (IMNs) in breast cancer is controversial. Most centers rarely identify IMN on lymphoscintigraphy but others report up to 45% of cases. Controversy relates to the technique of lymphatic mapping, safety of IMN SNB, the significance of positive IMN, and potential to impact survival. METHODS: Assessment of drainage rates from two unrelated nuclear medicine departments' databases. Review of related literature. RESULTS: High-resolution lymphoscintigraphy results in IMN drainage in one-third of breast cancers. There is a learning curve for the technique. In 1754 consecutive cases, internal mammary drainage occurred in 53% of medial tumors, 37% midline tumors and 24% of lateral tumors (overall 34%). Extended radical mastectomy series also demonstrate the (approximately) 1/3 ratio when comparing IMN positivity rates to axillary node positivity rates (18.8% : 48.3%) and in node-positive patients (31% : 100%). The management altering potential of IMN assessment and potential survival impact are discussed. CONCLUSIONS: IMN mapping gives information that alters management in up to one-third of cases. These rates of IMN drainage are reproducible and reflect lymphatic density and anatomy of the breast. A priority need exists to establish a collaborative clinical trial to clarify the value of IMN assessment.

Migrations and growth of deep-sea lobsters, Homarus americanus.

In distinct contrast to the restricted movements of coastal stocks of lobsters (Homarus americanus), those inhabiting the outer continental shelf undertake extensive seasonal migrations. Of 5710 tagged lobsters released on the outer continental shelf off New England from April 1968 to June 1969, 400 had been recaptured by April 1970. The distribution of the recoveries demonstrated shoalward migration in spring and summer and a return to the edge of the shelf in fall and winter. Deep-sea lobsters have a faster rate of growth than coastal lobsters; growth increments at molting and the frequency of molting are greater.

Participation in science and engineering laboratories for students with physical disabilities: survey development and psychometrics.

Purpose: The purpose of this study is to address the development of the Full Participation Science and Engineering Accessibility (FPSEA) self-report survey that gathers experiences from students with physical disabilities (SwD-P) using a postsecondary laboratory and to evaluate the survey's stability. Methods: Survey items were generated from an extensive literature review and recommendations articulated by experts. Think-aloud sessions and content validity index (CVI) were used to determine survey content validity and help finalize survey items. Individuals with physical disabilities (n = 20) who have taken a postsecondary science or engineering laboratory course completed the survey and took it again 10-14 days apart. The test-retest reliability was assessed using Spearman Rho coefficients for Likert-scale items, Chi-square and Fisher's exact test for the dichotomous items. Missing data completely at random (MCAR) test was computed before reliability data analysis. Results: Each sub-item passed the MCAR test, indicating that the data are missing completely at random and can be imputed to perform the analysis. Reliability analysis was completed on 20 individuals. The FPSEA had good content reliability: the item-level CVI of items kept ranged from 0.86 to 1. The scale-level CVI was 0.94. Stability was demonstrated with adequate Spearman correlation ranged from 0.56 to 0.86. Conclusions: No previous survey had been developed linking SwD-P and the postsecondary science and engineering (S&E) laboratory setting prior to this work. Overall, FPSEA is reliable and stable for reporting the barriers and facilitators to use S&E laboratories from the SwD-P's perspective. Implications for rehabilitation The barriers students with disabilities encounter in S&E laboratory environments are largely unknown. The FPSEA survey may help identify barriers and facilitators to using S&E laboratories for SwD-P. The FPSEA Survey allows former and current SwD-P to share their experiences using a postsecondary S&E instructional laboratory.

Anemia with spur cells: a red cell defect acquired in serum and modified in the circulation.

The sera and red cells of three patients with severe liver disease and "spur cells" were studied. In each case the per cent of serum cholesterol which was free (unesterified) was elevated, and the serum lecithin: cholesterol acyltransferase activity was depressed. Lipoproteins with beta mobility were increased, but exhibited immune reactivity with antisera to both alpha- and beta-lipoproteins. Serum bile salt concentrations were markedly elevated and consisted primarily of chenodeoxycholic acid, with small amounts of lithocholic acid present as well.SPUR CELLS MANIFESTED A STRIKING INCREASE IN CHOLESTEROL CONTENT AND IN THE CHOLESTEROL: phospholipid ratio, but a normal osmotic fragility. When incubated in heated normal serum, spur cells lost their excess cholesterol and became spherocytic and osmotically fragile. Conversely, sera from patients with spur cells readily transferred up to one-third of their free cholesterol to normal red cells, causing normal cells to become resistant to osmotic lysis. In addition, these sera caused normal red cells to acquire thorny membrane projections. Cholesterol transfer to normal cells also occurred from normal serum which had previously been incubated with spur cells. Changes in cell cholesterol were induced by all of the lipoprotein fractions of spur serum. When transfused into a patient with spur cells, normal red cells became more resistant to osmotic lysis over the course of 24 hr. However, over the subsequent 7 days they underwent a progressive increase in osmotic fragility. These normal cells, as well as the patient's own cells, had a shortened survival. Correlating with the moderate decrease in the filterability of red cells spurred in vitro, red cell destruction occurred predominently in the spleen. Red cells in this disorder appear to serve as repositories for free cholesterol loosely bound to serum lipoproteins. Cholesterol acquisition by the red cell membrane increases its surface area and causes the red cell to be resistant to osmotic lysis. The associated alteration in red cell shape leads to further changes in the cell membrane during circulation in vivo resulting in the loss of membrane surface area and culminating in the cell's premature destruction in the spleen.

Loss of membrane components in the pathogenesis of antibody-induced spherocytosis.

The infusion of hyperimmune agglutinating antibodies into man or animals causes spherocytosis and hemolysis. The mechanism of spherocytosis was studied in rats given rabbit anti-rat red cell antiserum intravenously. During the 18 hr after antibody infusion, a time before the onset of reticulocytosis, hematocrits fell from 40.6 to 27.6%. However, no change occurred in mean cell volume, mean cell hemoglobin content, or the red cell concentrations of potassium or adenosine triphosphate (ATP). There was a progressive loss of membrane constituents and membrane surface area which followed first order kinetics. At 18 hr membrane cholesterol had decreased 23.5%, phospholipid 26.3%, protein 4.7%, and surface area (calculated from a measure of osmotic fragility) 14.2%. There was no change in the per cent composition of the various phospholipids. Similar changes occurred in animals splenectomized before receiving antibody.These studies demonstrate that spherocytosis induced by heterologous agglutinating antibodies in vivo results from a loss of surface area with no accompanying change in cell volume or in the concentration of the major intracellular constituents. It is caused by a process acting at the cell surface leading to the loss of lipid-rich, protein-poor components of the red cell membrane.

Bile salts and cholesterol in the pathogenesis of target cells in obstructive jaundice.

Free cholesterol is in rapid equilibrium between serum lipoproteins and red cells. The level of red cell cholesterol is influenced by bile salts, which shift the serum/cell partition of free cholesterol to the cell phase and which inhibit the cholesterol-esterifying mechanism. During incubation in normal serum possessing an active cholesterol-esterifying mechanism, red cells lose cholesterol and surface area and thereby become more spheroidal and less resistant to osmotic lysis. When exposed to serum from patients with obstructive jaundice or to normal serum with added bile salts, red cells accumulate cholesterol and increase their surface area, thereby acquiring a flattened shape and an increased resistance to osmotic lysis. The described gains and losses of red cell cholesterol and surface area do not involve metabolic injury and occur with no significant change in phospholipid content. The red cells of patients with obstructive jaundice are flat and osmotically resistant and have an increased cholesterol:phospholipid ratio. When transfused into normal subjects these "target cells" rapidly lose their osmotic resistance. Similarly, normal cells acquire osmotic resistance in the circulation of patients with obstructive jaundice. These reversible changes in shape occur with half-times of about 9 and 24 hr, respectively, and occur without impairing cell viability. These studies indicate that the red cell membrane accumulates cholesterol in obstructive jaundice as a consequence of the elevated levels of bile salts. The resulting increment in red cell surface area is responsible for the physical properties and appearance of target cells. These observations substantiate Murphy's findings in vitro indicating that cholesterol is an important determinant of red cell shape and that its content in the cell membrane may vary independently from the phospholipids. Presumably any process or disorder affecting cholesterol exchange in vivo is capable of critically modifying the shape and behavior of red cells.

A furosemide-sensitive cotransport of sodium plus potassium in the human red cell.

The influxes of Na(+) and K(+) into the human red cell appear to be interrelated. This relationship was investigated under conditions in which either Na(+) or K(+) concentration outside the cell was varied or one cation was replaced by Mg(2+), choline(+), or Li(+). The effects of furosemide on Na(+) and K(+) movements were studied in the presence of ouabain. When ouabain was present, Na(+) influx was higher with K(+) ions externally than with other cations externally. Furosemide inhibited this K(+)-stimulated Na(+) influx, but it had little effect when K(+) was absent. Ouabain-insensitive K(+) influx was stimulated two-fold by external Na(+) compared with other cations. Furosemide also inhibited this stimulation, but it had little effect when Mg(2+) or choline(+) replaced external Na(+). Thus it was confirmed that synergism exists between the ouabain-insensitive influxes of Na(+) and K(+) and it was demostrated that furosemide inhibits this cooperative effect. The ouabain-insensitive influx of both K(+) and Na(+) showed a hyperbolic "saturating" dependence on the external concentration of the transported cation. Furosemide therefore eliminates a saturable component of influx of each cation. The net uptake of Na(+) in the presence of ouabain was stimulated by K(+) ions. A similar effect was observed with red cells, in which Li(+) replaced nearly all the internal Na(+) plus K(+) ions. In these cells, net Na(+) uptake was stimulated by external K(+), and net K(+) uptake was stimulated by external Na(+). Furosemide inhibited this mutual stimulation of net cation entries. The inhibitory action of furosemide was not limited to inward flux and net movement of Na(+) and K(+). Furosemide also inhibited the efflux of Na(+) into Na(+)-free media and the efflux of K(+) into K(+)-free media. It appeared, therefore, that the action of furosemide was not explained by inhibition of exchange diffusion. These data are consistent with an ouabain-insensitive transport process that facilitates the inward cotransport of Na(+) plus K(+)-ions, and that can produce a net movement of both ions. Although this process under some conditions mediates an equal bidirectional flux of both Na(+) and K(+), it cannot be defined as exchange diffusion. The contransport process is inhibited by furosemide.

The selective and conjoint loss of red cell lipids.

The pattern of lipid loss from the membrane of red cells incubated in serum is influenced by the availability of glucose. Under homeostatic conditions with respect to glucose, cholesterol alone is lost. This results from esterification of free cholesterol in serum by the serum enzyme, lecithin:cholesterol acyltransferase, and is associated with a proportional decrease in membrane surface area, reflected by an increased osmotic fragility. This selective loss of membrane cholesterol also occurs in hereditary spherocytosis (HS) red cells, even after incubation for 65 hr in the presence of glucose. The loss of free cholesterol from red cells relative to its loss from serum, under these conditions, is greatest at higher hematocrits, similar to those found in the spleen. Although the selective loss of membrane cholesterol increases the spherodicity of normal red cells, it does not lead to a change in their rate of glucose consumption, and both the loss of cholesterol and the increase in osmotic fragility are reversible in vitro. Moreover, normal red cells made osmotically fragile by cholesterol depletion in vitro rapidly become osmotically normal and survive normally after their reinfusion in vivo.In contrast to this selective loss of membrane cholesterol, red cells incubated in the absence of glucose lose both cholesterol and phospholipid. This occurs more rapidly in HS than normal red cells and is followed by a disruption of cation gradients and then by hemolysis. Cholesterol and phospholipid lost under these conditions is not restored during subsequent incubations in vitro. Selective loss of membrane cholesterol is a physiologic event secondary to an altered state of serum lipids. It is reversible both in vitro and in vivo and neither influences cellular metabolism nor impairs viability. Conjoint loss of phospholipid and cholesterol, however, results from intrinsic injury to the red cell membrane which results from prolonged metabolic depletion.