Effects of age on balance control during walking

OBJECTIVE: To determine the effects of aging on balance control during walking. DESIGN: Two-group repeated-measures design. SETTING: Gait laboratory in Australia. PARTICIPANTS: Convenience sample of 20 healthy older subjects (mean age, 72y) and 20 healthy young subjects (mean age, 24y). INTERVENTIONS: Changes in locomotor performance in response to perturbations to balance were quantified for healthy older adults compared with healthy young adults for (1) straight line walking at preferred speed, (2) straight line walking at fast speed, (3) figure-of-eight walking at preferred speed, and (4) figure-of-eight walking while performing a secondary motor task. MAIN OUTCOME MEASURES: Gait speed, stride length, cadence, and double-limb support duration, using a footswitch system. RESULTS: Healthy older people screened for pathology had gait patterns comparable to young adults for straight line walking at preferred speed. However, multivariate analysis of variance (MANOVA) showed a significant interaction between age and speed when balance was perturbed by requiring subjects to change from walking at preferred to fast speeds (Pillai-Bartlett trace=.259, F(4,35)=3.06, P<.029, partial eta(2)=.259). This occurred because older people did not increase their speed (F(1,38)=7.65, P<.01, partial eta(2)=.168) or stride length (F(1,38)=12.23, P<.01, partial eta(2)=.243) as much as did the young adults. MANOVAs did not show statistically significant interactions between age and turning conditions or age and dual task conditions, although older people walked more slowly and with shorter steps when turning or performing a secondary task. CONCLUSIONS: Balance strategies during gait are task specific and vary according to age. In response to challenges to balance imposed by the requirement to change from preferred to fast walking, older people did not increase their speed and stride length to the same extent as did younger adults. This was possibly a strategy to maintain their stability.     

RPE cells internalize low-density lipoprotein (LDL) and oxidized LDL (oxLDL) in large quantities in vitro and in vivo

PURPOSE: To determine whether plasma low-density lipoprotein (LDL) could be internalized by the RPE and which receptors may be involved. A secondary objective was to determine whether ARPE19 cells could be used as a model to investigate cholesterol processing in the RPE. METHODS: Commercially available human LDL was labeled with rhodamine or AlexaFluor 568. Immunofluorescence was performed using commercially available antibodies to LDL-R, CD36, and LOX-1. Cells and tissues were imaged using epifluorescence and confocal fluorescence microscopy. Immunoblot analysis and RT-PCR were performed using published techniques. RESULTS: Intravenously injected rhodamine-labeled LDL (rhoLDL) was detected in the rat RPE by fluorescence confocal microscopy 24 hours after injection. The rhoLDL was present in some areas and absent in others. Cultured ARPE19 cells were also found to internalize LDL and oxidized LDL (oxLDL) readily. Using AlexaFluor 568-labeled LDL we determined that the average cultured RPE cell could internalize approximately 12 to 16 pg of LDL and oxLDL in 24 hours. Immunoblots readily detected the presence of CD36 and LDL-R in the cultured RPE cells but not LOX-1, whereas RT-PCR detected mRNA for all three receptors. Dual-labeling experiments using AlexaFluor 568-labeled LDL and AlexaFluor 488 for the immunolocalization of the receptors showed colocalization of LDL-R with the internalized LDL and CD36 with oxLDL particles. CONCLUSIONS: Plasma LDL readily enters the RPE through the choriocapillaris but is not found homogeneously throughout the retina. This may suggest some form of regulation to the permeability of the fenestrated choroidal endothelial cell junctions. ARPE19 cells are a good model for studying the internalization mechanisms of LDL and oxLDL in vitro. LDL may be used as a vector to carry hydrophobic molecules into the RPE.     

Russian electrical stimulation: the early experiments

Russian forms of electrical stimulation became popular to a large extent as a result of the activities of Kots, who claimed force gains of up to 40% in elite athletes as a result of what was then a new form of stimulation. He did not provide details of his published work, nor did he give references. Russian electrical stimulation became popular despite the lack of research in the English-language literature. No studies published in English examined whether the "10/50/10" treatment regimen (10 seconds of stimulation followed by 50 seconds rest, repeated for 10 minutes) advocated by Kots is optimal, and only one study addressed whether maximum muscle torque was produced at an alternating current frequency of 2.5 kHz. The few studies that compared low-frequency monophasic pulsed current and Russian electrical stimulation are inconclusive. This article reviews and provides details of the original studies by Kots and co-workers. The authors contend that these studies laid the foundations for the use of Russian forms of electrical stimulation in physical therapy. The authors conclude that there are data in the Russian-language literature that support the use of Russian electrical stimulation but that some questions remain unanswered.     

Respiratory viruses detected in hospitalised paediatric patients with respiratory infections

Over 200 strains of respiratory viruses cause a variety of human infections ranging from common cold to life-threatening pneumonia. Respiratory viruses implicated in this study are respiratory syncytial viruses (RSV), adenovirus, influenza viruses and parainfluenza viruses. The objective of this study is to determine the epidemiology of respiratory viruses in paediatric patients with lower respiratory tract infection. The methods used were direct antigen detection method, shell vial culture method and conventional tube culture method. The samples included in this study are paediatric patients seen in Universiti Kebangsaan Malaysia Hospital, Kuala Lumpur with suspected acute viral respiratory infection, presenting with acute laryngotracheobronchitis (croup), bronchiolitis and pneumonia. Nasopharyngeal aspirates were collected and processed almost immediately. A total of 222 specimens were received during February 1999 to January 2000 showing a dual peak pattern in the months of April and December. The mean age of the patients was 13 months. Pneumonia (77.9%) was the most common clinical diagnosis in children with lower respiratory tract infection. This was followed by bronchiolitis (19.4%) and croup (27%). Viral aetiologies were confirmed in 23.4% of the patients. The most common respiratory virus isolated or detected was RSV, followed by parainfluenza viruses, influenza viruses and adenovirus.     

Predicting Adaptive Behavior in the Environment from Central Nervous System Dynamics

To generate adaptive behavior, the nervous system is coupled to the environment. The coupling constrains the dynamical properties that the nervous system and the environment must have relative to each other if adaptive behavior is to be produced. In previous computational studies, such constraints have been used to evolve controllers or artificial agents to perform a behavioral task in a given environment. Often, however, we already know the controller, the real nervous system, and its dynamics. Here we propose that the constraints can also be used to solve the inverse problem—to predict from the dynamics of the nervous system the environment to which they are adapted, and so reconstruct the production of the adaptive behavior by the entire coupled system. We illustrate how this can be done in the feeding system of the sea slug Aplysia. At the core of this system is a central pattern generator (CPG) that, with dynamics on both fast and slow time scales, integrates incoming sensory stimuli to produce ingestive and egestive motor programs. We run models embodying these CPG dynamics—in effect, autonomous Aplysia agents—in various feeding environments and analyze the performance of the entire system in a realistic feeding task. We find that the dynamics of the system are tuned for optimal performance in a narrow range of environments that correspond well to those that Aplysia encounter in the wild. In these environments, the slow CPG dynamics implement efficient ingestion of edible seaweed strips with minimal sensory information about them. The fast dynamics then implement a switch to a different behavioral mode in which the system ignores the sensory information completely and follows an internal “goal,” emergent from the dynamics, to egest again a strip that proves to be inedible. Key predictions of this reconstruction are confirmed in real feeding animals.     

Protein C zymogen in severe sepsis: a double-blinded,placebo-controlled,randomized study

Purpose

To determine whether protein C zymogen (protein C concentrates or human protein C) improves clinically relevant outcomes in adult patients with severe sepsis and septic shock.

Methods

This is a randomized, double-blind, placebo-controlled, parallel-group trial that from September 2012 to June 2014 enrolled adult patients with severe sepsis or septic shock and high risk of death and of bleeding (e.g., APACHE II greater than 25, extracorporeal membrane oxygenation or disseminated intravascular coagulopathy). All patients completed their follow-up 90 days after randomization and data were analyzed according to the intention-to-treat principle. Follow-up was performed at 30 and 90 days after randomization. The primary endpoint was a composite outcome of prolonged intensive care unit (ICU) stay and/or 30-day mortality. Secondary endpoints included mortality.

Results

The study was stopped early in a situation of futility for the composite outcome of prolonged ICU stay and/or 30-day mortality that was 79 % (15 patients) in the protein C zymogen group and 67 % (12 patients) in the placebo group (p = 0.40) and for a concomitant safety issue: ICU mortality was 79 % (15 patients) in the protein C zymogen group vs 39 % (7 patients) in the placebo group (p = 0.020), and 30-day mortality was 68 vs 39 % (p = 0.072).

Conclusion

Protein C zymogen did not improve clinically relevant outcomes in severe sepsis and septic shock adult patients. Given its high cost and the potential increase in mortality, the use of this drug in adult patients should be discouraged.

     

Giving birth: the voices of Russian women

PURPOSE: To gain an understanding of the meaning of childbirth to women living in St. Petersburg, the Russian Federation. STUDY DESIGN AND METHOD: Twenty-four Russian women who had given birth in the past 6 months participated in this phenomenological study and were interviewed and audio-taped about the meaning of childbirth. Data collection and analysis occurred concurrently. RESULTS: The Russian sociocultural context of childbirth was identified in specific themes: (1) adhering to cultural traditions, (2) accessing information, (3) maintaining a healthy lifestyle, (4) articulating the spiritual and emotional meaning of giving birth, and (5) transforming as a mother and a person. Study participants reported reading extensively during pregnancy as well as accessing Web-based information about childbirth. Women chose to give their newborns traditional Slavic names and have their infants christened. CLINICAL IMPLICATIONS: The findings of qualitative studies can be used to guide clinical practice, because they provide rich data about essential life events and reactions associated with them. Women from Russia are emigrating to countries all over the world, and thus, their cultural views of childbirth are essential knowledge for the provision of appropriate nursing care. With dramatic socioeconomic and political changes occurring over the past 15 years, along with major changes in healthcare delivery systems, listening to the voices of Russian childbearing women giving birth is vital information for nurses working in maternal-child health settings.