Physical training and +Gz tolerance reevaluated

The effect of physical training on +Gz tolerance is of vital interest in the aerospace community. The data on the effect of physical training on orthostatic tolerance or simulated air combat maneuvers is equivocal. The effects of aerobic and strength training programs is briefly reviewed. The data suggest a need for careful reinterpretation of research results in light of conflicting reports and methodological shortcomings. Aerobic training cannot be assumed to always be detrimental nor can strength training be assumed to be universally effective in improving +Gz tolerance. In selecting appropriate screening criteria and training regimens for aircraft personnel, it seems prudent to reinvestigate strength and endurance training effects on +Gz tolerance using multivariate research paradigms. Special attention should be directed to commonly accepted physiological principles which may vary under conditions of altered gravitation.     

Microarray analysis of aberrant gene expression in actinic keratosis: effect of the Toll-like receptor-7 agonist imiquimod

BACKGROUND: The molecular events leading to actinic keratosis (AK) are not well understood. OBJECTIVE: To identify and compare gene expression changes in AK lesions and in sun-exposed nonlesional skin and to determine the effect of imiquimod 5% cream on these changes. METHOD: A double-blind, vehicle-controlled, randomized study was conducted to evaluate the molecular changes in AK treated with imiquimod. Seventeen male subjects with >/= 5 AK lesions on the scalp applied vehicle or imiquimod three times a week for 4 weeks. Gene expression analysis using Affymetrix oligonucleotide arrays was performed on shave biopsies of lesions taken before and after treatment. Confocal microscopy was performed on the study area as an adjunctive diagnostic procedure. RESULTS: We identified gene expression changes which occur in sun-exposed, nonlesional skin as well as in AK lesions. These changes include, but are not limited to, the overexpression of oncogenic and proliferative genes and diminished expression of tumour suppressor genes. The gene expression changes observed in AK lesions and in sun-exposed, nonlesional skin were consistent with the confocal microscopy observations, which showed abnormalities in the sun-exposed, nonlesional skin, similar in nature but less pronounced than abnormalities seen in AK. Imiquimod partially or totally reversed the aberrant expression of some of the genes observed in AK, consistent with clearing of lesions and normalization of confocal cellular images. CONCLUSIONS: The data show that profound gene expression changes occur in sun-exposed, nonlesional skin which progress further in AK lesions. The data also suggest that imiquimod may play a role in normalizing gene expression and cellular morphology in sun-damaged skin.     

Modulation of the tibial nerve H-reflex by mechanical stimulation of afferents in the lumbar spine

The purpose of this study was to describe the convergence of afferent discharges from the ligament-muscular system of the lumbar spine to the segmentally-related gastrocnemius muscle. The subjects were 32 healthy, young volunteers recruited from a college student population. Afferent discharges from the ligament-muscular system of the lumbar spine were evoked by manually moving the trunk into either flexion (n = 16) or left lateral bending (n = 16) using a multi-directional adjustable treatment table (Zenith Cox Flexion Table). Using linear potentiometers affixed to the treatment table and interfaced with a computer data acquisition system, manual movements of the table were visually guided to generate passive trunk movements at velocities of 10 degrees, 20 degrees, and 40 degrees per second. Tibial nerve H-reflex responses were recorded from the right gastrocnemius muscle as the trunk approached its end range of motion. Regardless of velocity for the flexion movement, the H/M(Max) ratio significantly decreased from 28.0% to 20.9% (p < .05). During lateral bending, the H/M(Max) ratio significantly decreased from 27.4% to 24.0% at velocities of 10 degrees and 20 degrees per second (p < .05) with a subsequent decrease to 20.5% at a velocity of 40 degrees per second (p < .05). The nature of these decreases in the H/M(Max) ratios across the different velocities during lateral bending significantly departed from linearity (p < .05). These data provide sufficient evidence to suggest that heteronymous conditioning effects from the ligament-muscular system of the lumbar spine during passive trunk movements attenuate alpha motoneuronal activity of the segmentally-related gastrocnemius muscle.     

Spinal reflex excitability changes after lumbar spine passive flexion mobilization

BACKGROUND: Flexion distraction has gained increased credibility as a therapeutic modality for treatment of low back pain. Although important work in the area has elucidated the intradiskal pressure profiles during flexion distraction, the accompanying neural responses have yet to be described. OBJECTIVE: The purpose of this pilot study was to assess neural reflex responses to motion with 3 degrees of freedom applied to the lumbar spine and to evaluate H-reflex responses of the soleus. METHODS: Subjects (n = 12) were measured for H-maximum reflexes determined from stimulus response recruitment curves measured in neutral prone position. The mean of 10 evoked H-waves (at H-maximum stimulus intensity) were measured in neutral position, flexion, left and right lateral flexion, and axial rotation of the trunk on an adjusting table. H-reflexes were expressed as a percentage of maximal M-wave for the criterion measure. Spinal range of motion was quantified by digitization. RESULTS: The data showed variation in some movement ranges, notwithstanding identical table positioning for all subjects. Mean H-reflex amplitude was decreased (15.2 +/- 5.8 mV to 13.8 +/- 5.8 mV), and the H/M ratio was also decreased in flexion compared with neutral (55.0% +/- 19.1% to 50.3% +/- 19.4%; P <.05). CONCLUSIONS: Trunk flexion is accompanied by inhibition of the motor neuron pool. Slight perturbations in numerous afferent receptors are known to significantly alter the H-reflex. The absence of measurable changes in lateral flexion and trunk rotation may indicate that both slow- and fast-adapting receptors could be involved in lumbar motion. These preliminary findings suggest the need for further dynamic motion studies of the flexion distraction neurophysiologic condition.     

Congenital Muscular Torticollis (Wryneck)

Bacterial infection of the urinary tract in infancy and childhood may be etiologic in the development of chronic pyelonephritis with renal insufficiency. Demonstration of asymptomatic bacteriuria in women who have had urinary tract infection and of unsuspected pyelonephritis in postmortem material has given rise to the speculation that pyelonephritis is a lifelong process. Diagnostic and therapeutic implications are obvious. If bacteria are visualized on smears of centrifuged urine, usually the culture is significantly positive.     

Immune-mediated changes in actinic keratosis following topical treatment with imiquimod 5% cream

Background  

The objective of this study was to identify the molecular processes responsible for the anti-lesional activity of imiquimod in subjects with actinic keratosis using global gene expression profiling.     

Motor neuron excitability: the Hoffmann reflex following exercise of low and high intensity

The current exercise literature lacks physiological evidence for a stress reduction induced by high intensity aerobic work. The purpose of this study was to investigate the effectiveness of high intensity aerobic work on stress reduction and to evaluate the currently tenable hypotheses in view of the data on the response to high intensity work. The subjects participated in a control trial and two 20-min treadmill exercise trials at low and high (40% and 75% VO2max) intensity. The H- and M-wave responses to artificial stimulation of the tibial nerve (Angel and Hofmann, 1963) were used to assess spinal cord activation level which constituted the major dependent variable in the study. Low intensity exercise showed a 12.8% reduction in the H max/M max ratio (P less than 0.05) while high intensity exercise reduced the H max/M max ratio by 21.5% (P less than 0.0002). The two exercise treatment levels were also significantly different from each other (P less than 0.02). These data provide objective evidence for the efficacy of high intensity exercise in stress reduction as measured by the Hoffmann reflex and provide indirect evidence for a possible thermal hypothesis for exercise-induced stress reduction.     

Inhalation of ultrafine and fine particulate matter disrupts systemic vascular function

This study investigated the effects of particulate matter (PM) with aerodynamic diameter 0.02-1 microm (noted as PM1) inhalation during exercise on conduit artery and microvascular function. Inhalation of internal combustion-derived PM is associated with cardiovascular mortality and morbidity. Direct action of PM on the vascular endothelium is likely, as a substantial fraction of ultrafine PM translocates from the alveoli to the circulatory system. Sixteen intercollegiate athletes performed 30 min of exercise while inhaling low or high PM1. Flow-mediated brachial artery dilation (FMD) using high-resolution ultrasonography with simultaneous measurements of forearm oxygen kinetics using near infrared spectrophotometry (NIRS) was done before and after exercise. Basal brachial artery vasoconstriction was found after high PM1 exercise (4.0%, 4.66 +/- 0.609 to 4.47 +/- 0.625 mm diameter; p = .0002), but not after low PM1 exercise (-0.3%, 4.66 +/- 0.626 to 4.68 +/- 0.613 mm diameter). FMD was impaired after high PM1 exercise (6.8 +/- 3.58% for preexercise FMD and 0.30 +/- 2.74% for postexercise FMD, p = .0001), but not after low PM1 exercise (6.6 +/- 4.04% for preexercise FMD and 4.89 +/- 4.42% for postexercise FMD). Reduction in forearm muscle reperfusion estimated by reoxygenation slope-to-baseline after 4 min cuff ischemia was observed for high PM1 exercise (55% vs. 3%, p = .0006); no difference was noted for low PM1 exercise. Brachial artery FMD was significantly correlated to muscle reoxygenation slope-to-baseline (r = .50, p = .005). Acute inhalation of high [PM1] typical of urban environments impairs both systemic conduit artery function and microcirculation. The observed decrease reoxygenation slope-to-baseline after cuff release is consistent with reduced blood flow in the muscle microvasculature.     

Immobilization of cobalt in collapsed non-irradiated and gamma-irradiated X zeolites.

Cobalt exchanged X zeolites were gamma irradiated and heated until the zeolite structure collapsed. Heating destroys the zeolite network as found by X-ray-diffraction and 29Si, 27Al MAS NMR spectroscopy. Gamma irradiation treatment diminished the collapsing temperature of zeolite. Cobalt leaching from crystalline and amorphized zeolites was verified by ion exchange with NaCl solution. Results show that cobalt is not released from the amorphous materials. Furthermore adsorption of xenon and 129Xe NMR spectroscopy reveal that cobalt ions are heterogeneously distributed in the non irradiated amorphous materials. Gamma irradiation causes the mobility of cobalt in the amorphous materials resulting then in a more homogeneous distribution. Cobalt is, thus, retained safely in the amorphous materials.