Associative memory impairment in acute stress disorder: Characteristics and time course

Stress and episodic memory impairment have previously been associated. Acute stress disorder (ASD) is a maladaptive stress response, which develops in some individuals following traumatic life events. Recently, the authors demonstrated a specific deficit in associative memory for emotionally neutral stimuli in ASD and posttraumatic stress disorder (PTSD). This study further tested the relationship between this memory impairment and the course of ASD. We assessed new learning and memory for item and associative information in patients diagnosed with ASD (n=14) and matched trauma naïve controls (n=14). Memory performance and posttraumatic symptoms were examined for approximately 1 and 10 week periods following the traumatic experience. In the two experiments, participants studied a list of stimuli pairs (verbal or visual) and were then tested for their memory of the items (item recognition test), or for the association between items in each pair (associative recognition test). In both experiments, ASD patients showed a marked associative memory deficit compared to the control group. After 10 weeks, ASD symptoms were resolved in most patients. Interestingly, their performance on associative recognition for verbal stimuli improved, while the associative deficit for visual stimuli remained unchanged. Potential mechanisms underlying such an associative memory deficit in post-trauma patients are discussed.     

Hydrogen Peroxide in Exhaled Breath Condensate (EBC) vs Eosinophil Count in Induced Sputum (IS) in Parenchymal vs Airways Lung Diseases"

We compared exhaled breath condensate (EBC) and induced sputum (IS) for assessing inflammation in pulmonary diseases in patients with obstructive lung disease (n = 20), persistent cough >6 months (n = 20), interstitial lung disease (n = 25) and controls (n = 10). EBC was collected by suspending a Teflon perfluoroalkoxy tube installed in an ice-filled container and connected to a polypropylene test tube. IS was recovered after 20’ inhalation of 3% saline with an ultrasonic nebulizer, and 300 cells were differentially counted in cytospin Giemsa-stained slides. H₂0₂ was measured by a method based on oxidation of phenolsulfonphthalein (phenol red) mediated by horseradish peroxidases and H₂0₂. Pulmonary function tests were performed by conventional methods. H₂0₂ levels in EBC and % eosinophils in IS were significantly different between groups. A positive and significant correlation was found between % eosinophils in IS and the levels of H₂0₂ in EBC for each group and for all patients combined.     

Eye position compensation improves estimates of response magnitude and receptive field geometry in alert monkeys

Studies of visual function in behaving subjects require that stimuli be positioned reliably on the retina in the presence of eye movements. Fixational eye movements scatter stimuli about the retina, inflating estimates of receptive field dimensions, reducing estimates of peak responses, and blurring maps of receptive field subregions. Scleral search coils are frequently used to measure eye position, but their utility for correcting the effects of fixational eye movements on receptive field maps has been questioned. Using eye coils sutured to the sclera and preamplifiers configured to minimize cable artifacts, we reexamined this issue in two rhesus monkeys. During repeated fixation trials, the eye position signal was used to adjust the stimulus position, compensating for eye movements and correcting the stimulus position to place it at the desired location on the retina. Estimates of response magnitudes and receptive field characteristics in V1 and in LGN were obtained in both compensated and uncompensated conditions. Receptive fields were narrower, with steeper borders, and response amplitudes were higher when eye movement compensation was used. In sum, compensating for eye movements facilitated more precise definition of the receptive field. We also monitored horizontal vergence over long sequences of fixation trials and found the variability to be low, as expected for this precise behavior. Our results imply that eye coil signals can be highly accurate and useful for optimizing visual physiology when rigorous precautions are observed.     

Erythropoietin enhances immune responses in mice

Erythropoietin (Epo) is the main erythropoietic hormone. Recombinant human Epo (rHuEpo) is thus used in clinical practice for the treatment of anemia. Accumulating data reveals that Epo exerts pleiotropic activities. We have previously shown an anti-neoplastic activity of Epo in murine multiple myeloma (MM) models, and in MM patients. Our findings that this anti-neoplastic effect operates via CD8+ T lymphocytes led us to hypothesize that Epo possesses a wider range of immunomodulatory functions. Here we demonstrate the effect of Epo on B lymphocyte responses, focusing on three experimental models: (i) tumor-bearing mice, (5T2 MM mouse); (ii) antigen-injected healthy mice; and (iii) antigen-injected transgenic mice (tg6), overexpressing human Epo. In the MM model, despite bone marrow dysfunction, Epo-treated mice retained higher levels of endogenous polyclonal immunoglobulins, compared to their untreated controls. In both Epo-treated wild type and tg6 mice, Epo effect was manifested in the higher levels of splenocyte proliferative response induced in vitro by lipopolysaccharide. Furthermore, these mice had increased in vivo production of anti-dinitrophenyl (DNP) antibodies following immunization with DNP-keyhole limpet hemocyanin. Epo-treated mice showed an enhanced immune response also to the clinically relevant hepatitis B surface antigen. These findings suggest a potential novel use of rHuEpo as an immunomodulator.     

Neuromuscular disorder in response to anterior cruciate ligament creep

OBJECTIVE: To determine the effect of creep developed in the anterior cruciate ligament and other viscoelastic knee structures on the function of the flexor and extensor muscles of males and females. DESIGN: Static load applied to the proximal tibia of young healthy male and female subjects in a laboratory setting with maximal voluntary knee flexion and extension performed before and after the load application. BACKGROUND: Static loads applied to various joints during occupational and sports activities are epidemiologically linked to higher than normal rates of disability reports. The physiological and biomechanical processes active in the development of such a neuromuscular disorder are not known. We hypothesize that creep developed in the anterior cruciate ligament due to prolonged static load will have pronounced impact on the reflexive activation of the associated musculature in a manner that may increase the risk of injury. Females are expected to be exposed to higher risk than males. METHODS: Male and female groups performed maximal voluntary knee flexion and extension before and after applying 200 and 150 N, respectively, to the proximal tibia for a 10 min period. Flexion and extension forces as well as electromyograph from agonist and antagonist muscles were measured at 35 degrees and 90 degrees knee flexion. Data was analyzed through repeated measures of analysis of variance. RESULTS: It was found that in extension, quadriceps electromyographic activity increased significantly after anterior cruciate ligament creep while hamstrings co-activation did not change. There was also a trend towards increased extension force after creep was developed, with significant effect of gender (larger increase in females). Similarly, significant increase in hamstrings electromyographic activity and a trend towards increased force during knee flexion was observed but with no effect of gender. Electromyographic spasms from the flexors and extensors were recorded in 30% of the subjects during the 10 min static loading period at 90 degrees angle and from the flexors only at 35 degrees. Creep in the ligament was marginally greater in females than in males with a significant effect of angle, being greater at 35 degrees than in 90 degrees knee flexion. CONCLUSIONS: The results suggest that ligament creep may develop a neuromuscular disorder consisting of spasms, increased electromyography and force in the agonist muscles without compensation from the antagonist. Static loading of a joint, therefore, may develop a neuromuscular disorder compounded with laxity of the ligaments and subject the individual to increased risk of injury. RELEVANCE: The data provides evidence that prolonged static loads applied to the anterior cruciate ligament and associated viscoelastic structures results in unbalanced muscular activation which puts individuals at increased exposure to injury. Work and sports activities should be scheduled while minimizing periods of static joint loading and emphasizing sufficient rest periods to allow recovery of creep and return to balanced muscular activation and co-activation.