Endogenous peroxidatic activity in astrocytes after spinal cord injury

After spinal cord injury, endogenous peroxidatic-like activity develops along the axis of the cord. At 2 weeks postinjury, this activity appears in cells whose processes are intimately associated with microvessels. The objectives of this study were to further characterize this response and to identify the cellular localization of endogenous peroxidatic-like activity. After traumatic injury to the rat spinal cord, adjacent sections of spinal cord were processed in medium to visualize antiglial fibrillary acidic protein, endogenous peroxidatic activity, or cytochrome oxidase activity. In addition, certain sections, stained for endogenous peroxidatic-like activity, were prepared for electron microscopy. To identify the nature of the activity, some sections were exposed to an incubation medium that included inhibitors of either catalase or heme protein activity. The distribution of prominent glial fibrillary acidic protein immunoreactivity in the dorsal columns corresponded to that of marked staining for endogenous peroxidatic-like activity and cytochrome oxidase. At the ultrastructural level, endogenous peroxidatic-like activity was identified in the cytoplasmic compartment of the astrocyte. This activity was abolished when potassium cyanide (an inhibitor of heme protein) was added to the incubation medium. Spinal cord injury elicited a pronounced cellular response along the axis of the cord that was characterized by enhanced staining for antiglial fibrillary acidic protein, cytochrome oxidase activity, and endogenous peroxidatic-like activity. It is not clear whether pronounced cytochrome oxidase activity corresponded to astrocytes that also expressed prominent endogenous peroxidatic-like activity. However, according to both light and ultrastructural findings, endogenous peroxidatic-like activity was prominently associated with the astrocytic cytoplasm. The biochemical nature of the peroxidatic activity is unknown, but these results suggest that it is related to a heme-containing protein.     

Spontaneous appetence for wheel-running: a model of dependency on physical activity in rat

According to human observations of a syndrome of physical activity dependence and its consequences, we tried to examine if running activity in a free activity paradigm, where rats had a free access to activity wheel, may present a valuable animal model for physical activity dependence and most generally to behavioral dependence. The pertinence of reactivity to novelty, a well-known pharmacological dependence predictor was also tested. Given the close linkage observed in human between physical activity and drugs use and abuse, the influence of free activity in activity wheels on reactivity to amphetamine injection and reactivity to novelty were also assessed. It appeared that (1) free access to wheel may be used as a valuable model for physical activity addiction, (2) two populations differing in activity amount also differed in dependence to wheel-running. (3) Reactivity to novelty did not appeared as a predictive factor for physical activity dependence (4) activity modified novelty reactivity and (5) subjects who exhibited a high appetence to wheel-running, presented a strong reactivity to amphetamine. These results propose a model of dependency on physical activity without any pharmacological intervention, and demonstrate the existence of individual differences in the development of this addiction. In addition, these data highlight the development of a likely vulnerability to pharmacological addiction after intense and sustained physical activity, as also described in man. This model could therefore prove pertinent for studying behavioral dependencies and the underlying neurobiological mechanisms. These results may influence the way psychiatrists view behavioral dependencies and phenomena such as doping in sport or addiction to sport itself.     

Seizure-like events in brain slices: suppression by interictal activity

A major concern in epilepsy research is the relationship between ictal (seizure) electrophysiological activity and interictal (between seizure) activity. Much research is carried out in vitro using brain slice models. Although they allow detailed electrophysiology, the events recorded are generally more similar to interictal than ictal activity. We have described an in vitro model of epileptiform activity in the hippocampal slice (exposure to artificial cerebrospinal fluid containing no added magnesium) in which the events closely resemble those seen in vivo during seizures. However, this model is limited by the brief period during which this ictaform activity occurs before it is replaced by interictal-like activity. We now report that as the frequency of the interictal activity is suppressed by the GABA_B agonist baclofen, the ictal activity returns. Moreover, when frequent interictal activity is reinduced, the ictal activity again is suppressed. These results suggest that interictal activity may decrease the probability of a seizure. Furthermore, they suggest that substances which may be shown to inhibit interictal activity in various models of epilepsy may not necessarily inhibit ictal activity.     

Gender and acculturation influences on physical activity in latino adults

Background: Studies examining physical activity levels have used samples primarily composed of non-Latino Whites and have focused on leisure time physical activity (LTPA). Additionally, few studies have investigated differences in physical activity between Latino men and Latina women, or the relationship between acculturation and activity.Purpose: To examine the subjective and objective physical activity of Latinos and gender differences in physical activity and the extent to which LTPA and non-LTPA were predictive of overall accelerometer physical activity. An additional objective was to examine the relationship between acculturation and different types of physical activity.Methods: Data were obtained from 155 Latinos (n = 86 female, n = 69 male). Comparisons were made between Latino men and women.Results: Latino men participated in significantly greater occupational and overall objective and subjective physical activity than Latina women; however, women participated in greater household activity. Regression analyses demonstrated that recreational, occupational, and household activity were significant predictors of overall accelerometer physical activity for the complete sample. Among women, recreational and household activity were significant predictors; however, overall accelerometer physical activity was not significantly predicted in men. Additionally, it was demonstrated that acculturation was related to occupational activity, but not to recreational activity.Conclusions: These results suggest that gender differences in physical activity are present among Latinos and that acculturation may be a correlate of various types of physical activity. Funding for this study was provided by a National Institutes of Health Minority Predoctoral Fellowship (No. AG05921), Graduate College Dissertation Research Grant, and the Paul D. Doolen Scholarship. Special thanks are extended to Sarah Nieves, Carmen Nevarez, and Raquel Gonzales for their assistance with the study.     

Influence of moderate and strenuous daily physical activity on fibrinolytic activity of blood: possibility of plasminogen activator stores depletion.

Fibrinolysis was studied in 10 alpinists during regular physical activity of different intensity. Blood was sampled at rest and after exposure to submaximal workload on the treadmill on three occasions: before and after 6 months physical conditioning (moderate physical activity), and after 6 weeks of an alpinistic expedition (strenuous physical activity). Measurements included submaximal working capacity, fibrinogen, euglobulin clot lysis time (ELT), whole plasma clot lysis time, and estimations derived from ELT--percent increase in fibrinolytic activity after exercise (RFS), and absolute increase in fibrinolytic activity after exercise (PAR). Regular moderate activity increased the resting level of ELT, but strenuous activity decreased is. After each treadmill testing, a marked increase in fibrinolytic activity was observed. RFS was unaltered at all three testings. PAR increased after moderate activity, but decreased after strenuous activity. The results indicate that regular physical activity can lead from enhanced to decreased resting activity of plasminogen activator in blood. It is presumed that increased release of activator during prolonged stress causes partial depletion of endothelial stores with the consequence of decreased activator activity in the blood.     

Reconceptualizing poststroke activity level using the Frenchay Activities Index

Modifications of the Frenchay Activities Index were implemented in a study of postacute stroke rehabilitation outcomes. These modifications incorporated the prestroke activity levels and postrehabilitation goals and assessments of activity importance of 136 persons with stroke who received services in either a single modality or comprehensive outpatient rehabilitation setting. Prestroke activity levels were assessed retrospectively at admission to postacute rehabilitation, and current activity levels were assessed at discharge and 3 months post discharge. Prestroke activity levels were used to determine postrehabilitation goal attainment. Results showed that activities for which goals were less likely to be attained were more strenuous in nature, and activities for which goals were more likely to be attained were more sedentary in nature. The importance persons placed on specific activities was used to tailor the estimates of overall activity levels to reflect their importance to each person. Results showed that adjusting for importance decreased the estimate of prestroke activity level but had little effect on poststroke activity level. Incorporation of these modifications represents a reconceptualization of poststroke activity levels that clinicians can use to guide their selection of postacute rehabilitation therapy goals.     

Reward-period activity in primate dorsolateral prefrontal and orbitofrontal neurons is affected by reward schedules

Reward-period activity observed in the dorsolateral prefrontal cortex (DLPFC) and the orbitofrontal cortex (OFC) is thought to represent the detection of reward delivery. To investigate whether this activity plays the same role in these areas, we examined this activity under different reward schedules and whether the reward schedule has similar effects on this activity in each of these areas. A monkey performed an oculomotor delayed-response (ODR) task under two reward schedules. In the ODR-1 schedule, the monkey received a large amount of reward only after four successful trials, whereas in the ODR-2 schedule, it received a small amount of reward after every successful trial. Although reward-period activity was observed in both areas, more neurons exhibited this activity in the OFC. Reward-period activity was modulated by the proximity to reward delivery in both areas and this feature was observed more frequently in the OFC. The onset time of this activity also gradually advanced depending on the proximity to reward delivery. Moreover, many OFC neurons with this activity responded to free reward delivery. These results indicate that reward-period activity in the OFC represents the detection of reward delivery and that the gradual change in the magnitude and the onset time of this activity represents the expectation of reward delivery. Similar features of reward-period activity were observed in DLPFC neurons, although a significant number of DLPFC neurons did not respond to free reward delivery and no advance was observed in the onset time of this activity. These results suggest that reward-period activity in the DLPFC participates in whether or not correct performance was achieved. Thus, although similar reward-period activity was observed in both areas, the activity in the OFC represents the detection of reward delivery and is affected by the monkey's motivational state, whereas that in the DLPFC seems to participate in monitoring whether or not the necessary performance is achieved.     

Care staff intentions to support adults with an intellectual disability to engage in physical activity: an application of the Theory of Planned Behaviour

Researchers suggest that people with an intellectual disability (ID) undertake less physical activity than the general population and many rely, to some extent, on others to help them to access activities. The Theory of Planned Behaviour (TPB) model was previously found to significantly predict the intention of care staff to facilitate a healthy diet in those they supported. The present study examined whether the TPB was useful in predicting the intentions of 78 Scottish care staff to support people with ID to engage in physical activity. Regression analyses indicated that perceived behavioural control was the most significant predictor of both care staff intention to facilitate physical activity and reported physical activity levels of the people they supported. Attitudes significantly predicted care staff intention to support physical activity, but this intention was not itself significantly predictive of reported activity levels. Increasing carers’ sense of control over their ability to support clients’ physical activity may be more effective in increasing physical activity than changing their attitudes towards promoting activity.     

The effect of hypertonic solutions on the electrical activity of isolated frog muscle spindles]

Electrical activity of an isolated frog muscle spindle was investigated in hypertonic solutions obtained by adding 400 mM of sucrose, glucose or glycerine to the Ringer solution. In sucrose and glucose hypermedia the frequency of background impulse activity first increased and then decreased up to zero; receptor potentials and evoked impulse activity simultaneously decreased and disappeared. In the glycerine hypermedia impulse activity after some increase returned to normal and then a second rise of frequency to a constant supernormal level was observed. After returning to the Ringer solution from sucrose or glucose the background and evoked impulse activity progressively returned to normal. But after glycerine hypermedia a significant growth in the background impulse activity and a small change in frequency of evoked impulse activity were observed. The observed changes of electrical activity of the muscle spindle in hypermedia are discussed in terms of deformation of sensory endings and intrafusal muscles fibres leading to depolarization of the receptor membrane.     

Phospholipase C mediated inhibition of factor VII requires triglyceride-rich lipoproteins

The reduction of plasma factor VII (FVII) activity by phospholipase C (PLC), in vitro, has been proposed as a possible indication of a risk of cardiovascular disease. The ability of PLC to reduce FVII activity was found to require calcium ions and the presence of triglyceride-rich lipoproteins (e.g. chylomicra and very-low density lipoproteins) rather than high or low density lipoproteins. The PLC-mediated reduction of FVII activity was prevented by pre-incubation of PLC with chylomicra, before adding FVII, and this suggests that PLC may act on triglyceride-rich lipoproteins already bound to FVII in order to reduce FVII activity. At optimal PLC concentration, the extent of the reduction in FVII activity was proportional to the concentration of chylomicra. The detergent, Tween, prevented any loss of FVII activity, in both plasma and purified systems, if it was present at the beginning of the incubation with PLC. Addition of Tween, but not EDTA, after inhibition of FVII activity had occurred, caused a partial restoration of FVII activity. It is concluded that PLC reduces FVII activity by modifying triglyceride-rich lipoproteins to a form which binds to FVII, independently of calcium ions, and which inhibits procoagulant activity. The detection of PLC-sensitive procoagulant activity. The detection of PLC-sensitive FVII activity may therefore have no greater significance than the measurement of plasma triglyceride levels in predicting a risk of cardiovascular disease.     

Low natural killer cell cytotoxic activity in autism: the role of glutathione, IL-2 and IL-15

Although many articles have reported immune abnormalities in autism, NK cell activity has only been examined in one study of 31 patients, of whom 12 were found to have reduced NK activity. The mechanism behind this low NK cell activity was not explored. For this reason, we explored the measurement of NK cell activity in 1027 blood samples from autistic children obtained from ten clinics and compared the results to 113 healthy controls. This counting of NK cells and the measurement of their lytic activity enabled us to express the NK cell activity/100 cells. At the cutoff of 15-50 LU we found that NK cell activity was low in 41-81% of the patients from the different clinics. This NK cell activity below 15 LU was found in only 8% of healthy subjects (p<0.001). Low NK cell activity in both groups did not correlate with percentage and absolute number of CD16(+)/CD56(+) cells. When the NK cytotoxic activity was expressed based on activity/100 CD16(+)/CD56(+) cells, several patients who had displayed NK cell activity below 15 LU exhibited normal NK cell activity. Overall, after this correction factor, 45% of the children with autism still exhibited low NK cell activity, correlating with the intracellular level of glutathione. Finally, we cultured lymphocytes of patients with low or high NK cell activity/cell with or without glutathione, IL-2 and IL-15. The induction of NK cell activity by IL-2, IL-15 and glutathione was more pronounced in a subgroup with very low NK cell activity. We conclude that that 45% of a subgroup of children with autism suffers from low NK cell activity, and that low intracellular levels of glutathione, IL-2 and IL-15 may be responsible.     

Relationship between prefrontal task-related activity and information flow during spatial working memory performance

While monkeys performed spatial working memory tasks, cue- (C), delay- (D), and response-period (R) activities or their combinations (CD, CR, DR, CDR) were observed in prefrontal neurons. In the present study, we tried to understand information flow during spatial working memory performances and how each task-related neuron contributed to this process. We first characterized each neuron based on which task-related activity was exhibited and which information (cue location or saccade direction) each task-related activity represented, then classified these neurons into 9 groups (C, Dcue, Dsac, CDcue, DcueRcue, DsacRsac, DcueRsac, CDcueRcue and CDcueRsac). Preferred directions were similar between cue- and delay-period activities in CDcue, CDcueRcue, and CDcueRsac, indicating that the directional selectivity of delay-period activity is affected by the directional selectivity of cue-period activity, all of which represented visual information. Preferred directions were also similar between delay- and response-period activities in DcueRcue, CDcueRcue, and DsacRsac, indicating that the directional selectivity of delay-period activity affects the directional selectivity of response-period activity in these neurons. By the comparison of temporal profiles of delay-period activity among these groups, we found (1) cue-period activity could affect directional selectivity of delay-period activity of CDcue and CDcueRcue, (2) cue-period activity of C, CDcue, and CDcueRcue might contribute to the initiation and the maintenance of delay-period activity of CDcue, CDcueRcue, Dcue, and DcueRcue, and (3) saccade-related activity of DsacRsac could be affected by delay-period activity of Dsac and DsacRsac. These results suggest that the combination of task-related activities, the information represented by each activity, and the temporal profile of delay-period activity are important factors to consider information flow and processing and integration of the information in the prefrontal cortex during spatial working memory processes.     

A lifestyle physical activity intervention for caregivers of persons with Alzheimer's disease

BACKGROUND: The purpose of this pilot study was to examine the effects of lifestyle physical activity in caregivers (CGs) of persons with Alzheimer's disease. METHODS: Fifteen CGs engaged in lifestyle physical activity during a 6-month, home-based health promotion program. Mean changes in self-reported physical activity were compared using repeated-measures analysis of variance. RESULTS: Fifty percent of CGs increased total self-reported minutes and 42% increased total moderate minutes of physical activity from preintervention to postintervention; however, no CG engaged in vigorous physical activity and there were no significant improvements in self-reported physical activity for the total group. Hot summer weather, heavy non-caregiving responsibilities, heavy caregiving responsibilities, and feelings of anxiety, depressive symptoms, and fatigue were the most frequently identified physical activity barriers. CONCLUSION: Incorporating an individualized, home-based program of lifestyle physical activity appears feasible; however, attention needs to be given in the future to physical activity barriers identified by this select group of CGs.     

ACTIGRAPHIC EVIDENCE FOR NIGHT-TIME HYPERKINESIA IN PARKINSON’S DISEASE

Parkinson's disease is a common motor disorder that not only leads to motor symptoms but also autonomic dysregulation, mental changes, sensory disturbances, and sleep disorders such as increased daytime sleepiness and sleep fragmentation. The aim of this study was to find out how the daytime and night-time motor activity levels in individuals without motor disorders differ from patients with Parkinson's disease. Daytime and night-time motor activity levels in 17 PD patients and 69 controls were measured for three consecutive days and nights via actigraphy, a method of continuous long-term assessment of activity levels. A ratio between night-time and daytime motor activity was calculated. PD patients had a 1.5–2-fold lower daytime motor activity but also showed 1.5–2-fold higher motor activity at night time. Older controls showed a lower daytime but similar night-time motor activity when compared to younger controls. A ratio of night-time to daytime motor activity could clearly distinguish controls and patients. The possibility to distinguish patients and controls by the ratio of night-time to daytime motor activity is worth further investigation.     

Are parental health habits transmitted to their children? An eight year longitudinal study of physical activity in adolescents and their parents

Parents are believed to play a role in influencing their children's health behaviours. This longitudinal study of two generations (parents and their children) examined associations between parents' self-reported leisure-time physical activity changes and the self-reported physical activity changes of their offspring in a sample of 557 adolescents over an 8 year period (from 13 to 21 years of age). The results revealed only weak and non-existent associations between changes in parents' physical activity and changes in adolescent physical activity from 13 to 21 years of age. The findings did not support the hypothesis that adolescents' leisure-time physical activity covaried with their parents' leisure-time physical activity over time. This may mean that parental physical activity is not transmitted to their children to the degree that is often believed.     

Induction of synchronous oscillatory activity in the rat lateral amygdala in vitro is dependent on gap junction activity

Synchronized and rhythmic activity within the amygdala is thought to play a pivotal role in the generation of fear- and anxiety-related behaviour. The aim here was to determine the validity of the in vitro amygdala slice preparation to investigate the generation of rhythmic activity similar to that observed in vivo. Extracellular population activity recorded from the lateral nucleus of the amygdala in vitro showed significant enhancement of activity within the theta-band frequency (3-9 Hz) in the presence of kainic acid (100 nm; n=18). Alterations in the patterns of oscillatory activity within the gamma frequency band (20-40 Hz) were observed in the presence of (RS)-3,5-dihydroxyphenylglycine (10 microm; n=7) or carbachol (50 microm; n=5). Theta frequency oscillatory activity was blocked in the presence of the gap junction blocker carbenoxolone (100 mm), whereas gamma frequency oscillatory activity showed increased variability in the dominant frequency of rhythmic activity. The results suggest that the neuronal circuitry of the amygdala in vitro is capable of generating and sustaining rhythmic activity and that intercellular communication via gap junctions may play a role in the synchronization of population activity underlying this oscillatory activity.     

Dynamics of telomerase activity in response to acute psychological stress

Telomerase activity plays an essential role in cell survival, by lengthening telomeres and promoting cell growth and longevity. It is now possible to quantify the low levels of telomerase activity in human leukocytes. Low basal telomerase activity has been related to chronic stress in people and to chronic glucocorticoid exposure in vitro. Here we test whether leukocyte telomerase activity changes under acute psychological stress. We exposed 44 elderly women, including 22 high stress dementia caregivers and 22 matched low stress controls, to a brief laboratory psychological stressor, while examining changes in telomerase activity of peripheral blood mononuclear cells (PBMCs). At baseline, caregivers had lower telomerase activity levels than controls, but during stress telomerase activity increased similarly in both groups. Across the entire sample, subsequent telomerase activity increased by 18% one hour after the end of the stressor (p < 0.01). The increase in telomerase activity was independent of changes in numbers or percentages of monocytes, lymphocytes, and specific T cell types, although we cannot fully rule out some potential contribution from immune cell redistribution in the change in telomerase activity. Telomerase activity increases were associated with greater cortisol increases in response to the stressor. Lastly, psychological response to the tasks (greater threat perception) was also related to greater telomerase activity increases in controls. These findings uncover novel relationships of dynamic telomerase activity with exposure to an acute stressor, and with two classic aspects of the stress response – perceived psychological stress and neuroendocrine (cortisol) responses to the stressor.     

Regulation of cytochrome oxidase protein levels by functional activity in the macaque monkey visual system

The activity of cytochrome oxidase (CO), a mitochondrial enzyme of oxidative energy metabolism, is regulated by nerve cell functional activity. The mechanism of CO activity regulation was studied using histochemical and immunohistochemical methods to show the distributions of CO activity and protein, respectively, in the macaque monkey visual system under normal and experimental conditions. In normal animals, patterns of CO activity were found to reflect underlying patterns of CO protein distribution; for example, puffs of high CO activity in cortical area 17 contained high levels of CO protein. Experimental animals were injected monocularly with TTX for 3-4 weeks; this treatment blocks retinal impulses in the injected eye and results in decreased CO activity in lateral geniculate laminae and striate cortical columns normally driven by the treated eye. The experimentally induced decreases in CO activity were also found to reflect underlying parallel decreases in CO protein levels. These results suggest that CO activity is regulated mainly at the level of the local amount rather than the turnover number of the enzyme and imply that the rates of CO synthesis and/or degradation are regulated by neural functional activity.     

Timecourse of object-related neural activity in the primate prefrontal cortex during a short-term memory task

We studied the timecourse of neural activity in the primate (Macacca mulatta) prefrontal (PF) cortex during an object delayed-matching-to-sample (DMS) task. To assess the effects of experience on this timecourse, we conducted the task using both novel and highly familiar objects. In addition, noise patterns containing no task-relevant information were used as samples on some trials. Comparison of average PF ensemble activity relative to baseline activity generated by objects and noise patterns revealed three distinct activity periods. (i) Sample onset elicited a transient sensory visual response. In this sensory period, novel objects elicited stronger average ensemble activity than both familiar objects and noise patterns. (ii) An intermediate period of elevated activity followed, which began before sample offset, and continued well into the delay period. In the intermediate period, activity was elevated for noise patterns and novel objects, but near baseline for familiar objects. (iii) Finally, after average ensemble activity reached baseline activity at the end of the intermediate period, a reactivation period occurred late in the delay. Experience had little effect during reactivation, where activity was elevated for both novel and familiar objects compared to noise patterns. We show that the ensemble average resembles the activity timecourse of many single prefrontal neurons. These results suggest that PF delay activity does not merely maintain recent sensory input, but is subject to more complex experience-dependent dynamics. This has implications for how delay activity is generated and maintained.     

Cl-inactivator-resistant fibrinolytic activity in plasma euglobulin fractions: Its relation to vascular activator in blood and its role in euglobulin fibrinolysis

Addition of Cl-inactivator to plasma euglobulin fractions revealed that part of their fibrinolytic activity is resistant to this inhibitor, while another part is inactivated. The resistant part of the activity fluctuates in parallel with changes in blood fibrinolytic activity caused by diurnal fluctuations, stress or venous occlusion. Purified plasminogen activators of extrinsic origin (human tissue activator and vascular perfusion activator) were found to be resistant to Cl-inactivator. The resistant part of the euglobulin activity therefore seems to indicate the presence of fluctuating amounts of a plasminogen activator of extrinsic origin in plasma. Optimal recovery of the resistant activity from plasma was achieved in euglobulin fractions prepared at pH 5.9 with a plasma dilution 1:10, in which resistant activity could be quantitatively assayed. Samples of morning plasma with baseline levels of fibrinolytic activity have levels of resistant activity amounting to only a few blood activator units (BAU)/ml. Samples of afternoon plasma showed a moderate increase in the resistant activity, while plasma collected after venous occlusion of the arm showed an enormous increase to 138 ± 29 (SD) BAU/ml (n=7). The Cl-inactivator susceptible activity can be optimally recovered by isoelectric precipitation in the presence of dextran sulphate. It seems to originate from intrinsic proactivator systems. It was demonstrated that extrinsic activator has the capacity to enhance the generation of activator activity in these intrinsic systems in vitro.