Changes In Total Activity Research Articles

Sex- and strain-dependent effects of ageing on sleep and activity patterns in Drosophila.

The fruit fly Drosophila is a major discovery platform in the biology of ageing due to its balance of relatively short lifespan and relatively complex physiology and behaviour. Previous studies have suggested that some important phenotypes of ageing, for instance increasingly fragmented sleep, are shared from humans to Drosophila and can be useful measures of behavioural change with age: these phenotypes therefore hold potential as readouts of healthy ageing for genetic or pharmacological interventions aimed at the underpinning biology of ageing. However, some age-related phenotypes in Drosophila show differing results among studies, leading to questions regarding the source of discrepancies among experiments. In this study, I have tested females and males from three common laboratory strains of Drosophila to determine the extent to which sex and background strain influence age-related behavioural changes in sleep and activity patterns. Surprisingly, I find that some phenotypes-including age-related changes in total activity, total sleep, and sleep fragmentation-depend strongly on sex and strain, to the extent that some phenotypes show opposing age-related changes in different sexes or strains. Conversely, I identify other phenotypes, including age-related decreases in morning and evening anticipation, that are more uniform across sexes and strains. These results reinforce the importance of controlling for background strain in both behavioural and ageing experiments, and they imply that caution should be used when drawing conclusions from studies on a single sex or strain of Drosophila. At the same time, these findings also offer suggestions for behavioural measures that merit further investigation as potentially more consistent phenotypes of ageing.

Older rats show slow modulation of hippocampal theta rhythm during voluntary running

Aging causes brain function degeneration and slows many motor and behavioural responses. The hippocampal theta rhythm (4–12 Hz) is related to cognition and locomotion. However, the findings on aging-related changes in the frequency and amplitude of hippocampal theta oscillations have been inconsistent. We hypothesized that older rats have slower responses in terms of hippocampal theta rhythm during voluntary wheel running than do young adult rats. By simultaneously recording electroencephalography and physical activity (PA), we evaluated theta oscillations in 8-week-old (young adult) and 60-week-old (middle-aged) rats before and during wheel running, which was conducted only during the rats' 12-h dark period. To test the alterations of hippocampal theta rhythm in voluntary wheel running, we analyzed the signals without (8-s) or with (2-s) chronological order. No significant difference was observed in total frequency (TP, 4–12 Hz), low-frequency (LT, 4–6.5 Hz), or high-frequency (9.5–12 Hz) theta activity between active waking and overall running in either group. The theta oscillations were slower in the middle-aged rats than in the young adult rats during wheel running but increased during running for both age groups. During wheel running, the middle-aged rats exhibited an increased LT, which was related to PA. On the basis of the chronological order of running, the young adult rats exhibited increased TP, and the middle-aged rats exhibited significant increases in middle-frequency (MT, 6.5–9.5 Hz) theta activity. The dominant modulations of MT in the middle-aged rats may have caused nonsignificant changes in total activity. These between-group differences in theta rhythm characteristics during voluntary running provide insights into age-related brain function decline.

Less Medication Use in Inpatients With Severe Mental Illness Receiving a Multidisciplinary Lifestyle Enhancing Treatment. The MULTI Study III.

Besides having an unhealthy lifestyle contributing to premature mortality, inpatients with severe mental illness (SMI) use high dosages of medication. Previous research has shown improved health after lifestyle improvements in SMI. In addition, we aimed to retrospectively study whether a multidisciplinary lifestyle enhancing treatment (MULTI) was associated with changes in medication use after 18 months, as compared with patients that continued treatment as usual (TAU) and explored mediation by a change in physical activity. We conducted an observational study within a cohort of inpatients with SMI, who received MULTI (N = 65) or continued TAU (N = 49). Data on their somatic and psychotropic medications were collected, converted into defined daily dose (DDD), and analyzed using linear multilevel regression, correcting for baseline value and differences between groups in age, diagnosis, and illness severity. Compared with TAU, the DDD for psychotropic medication significantly decreased with MULTI (B = −0.55, P = 0.02). Changes in total activity did not mediate this association, suggesting that multiple components of MULTI contributed. Corrected between-group analyses for subgroups of medication were not possible due to lack of power and skewed distributions. Within-group data showed a decreased proportion of users as well as median DDD in both groups for almost all medications. In addition to previously reported health improvements after 18 months of MULTI, we observed a significant decrease in dose of psychotropic medication in MULTI compared to TAU. This first study evaluating a wide range of medications indicates a possible effect of lifestyle improvements on medication use in inpatients with SMI. Findings need to be confirmed in future controlled studies, however.

Improved psychosocial functioning and quality of life in inpatients with severe mental illness receiving a multidisciplinary lifestyle enhancing treatment. The MULTI study II

Patients hospitalised with severe mental illness (SMI) have poor physical health. Recently, a multidisciplinary lifestyle enhancing treatment for inpatients with SMI (MULTI) was implemented after which improvements of physical health were observed in the longer term. As part of a comprehensive evaluation of MULTI, we aimed to additionally analyse changes in perceived psychosocial functioning and quality of life after 18 months of MULTI compared to treatment as usual (TAU). Furthermore, we explored whether increased physical activity mediated significant changes. In this observational study, we collected data on psychosocial functioning (HoNOS) and quality of life (EQ-5D and WHOQoL-Bref) within our cohort of inpatients with SMI. This was supplemented by repeated physical activity measurement (ActiGraph GT3X+). Data were analysed using linear multilevel regression, adjusting for baseline values of outcome and differences between groups. Patients receiving MULTI (n = 65) showed significantly improved functioning on sum score and subscales for impairment and social functioning compared to TAU (n = 47). Quality of life improved within MULTI but did not differ significantly from TAU. Changes in total activity did not mediate improvements in psychosocial functioning, suggesting that multiple components of MULTI contribute to these improvements. In addition to previously observed improvement of physical health, MULTI showed to be a feasible treatment to sustainably improve psychosocial functioning compared to TAU and increase the quality of life in inpatients with SMI.

Changes in physical and psychiatric health after a multidisciplinary lifestyle enhancing treatment for inpatients with severe mental illness: The MULTI study I

Patients hospitalized with severe mental illness (SMI) often have an unhealthy lifestyle. Changing their sedentary behavior and deficiency in physical activity is challenging and effective interventions are lacking. We evaluated changes in sedentary behavior, physical activity, metabolic health and psychotic symptoms after 18 months of Multidisciplinary Lifestyle enhancing Treatment for Inpatients with SMI (MULTI) compared to treatment as usual (TAU) and explored mediation by change in total activity. We measured sedentary behavior and physical activity using accelerometry (ActiGraph GT3X+), reflected in total activity counts. Data on metabolic health and psychotic symptoms were retrieved from routine screening data within our cohort of inpatients with SMI. Of 65 patients receiving MULTI versus 43 receiving TAU, data were analyzed using linear and logistic multilevel regression, adjusting for baseline values of outcome and differences between groups. Compared to TAU, in which no improvements were observed, we found significantly (p < 0.05) improved total activity (B = 0.5 standardized total activity counts per hour), moderate-to-vigorous physical activity (B = 1.8%), weight (B = −4.2 kg), abdominal girth (B = −3.5 cm), systolic blood pressure (B = −8.0 mmHg) and HDL cholesterol (B = 0.1 mmol/l). No changes in psychotic symptoms were observed. Changes in total activity did not mediate metabolic improvements, suggesting that multiple components of MULTI contribute to these improvements. In contrast to previously unsuccessful attempts to change lifestyle behavior in inpatients with SMI in the longer term, MULTI showed to be a feasible treatment to sustainably improve PA and metabolic health.

Pilot study evaluating the effect of feeding method on overall activity of neutered indoor pet cats

Abstract Indoor housing of cats is associated with a higher incidence of multiple diseases, including obesity. Increased exercise is often recommended as a method of creating or increasing the negative energy balance required for weight loss. Food-dispensing toys have been suggested as a method of increasing cat activity and providing environmental enrichment but have not been systematically evaluated in client-owned cats. To compare the effect of meal feeding from a bowl versus a food-dispensing toy on overall activity, 19 client-owned cats were enrolled in a 2-way, 2-period, and randomized repeated-measures mixed-effects crossover study. All cats were acclimated to wearing an accelerometer attached to a collar during week 1. Cats randomized to the bowl-first condition were acclimated to bowl feeding during week 2, and activity counts were collected during week 3. Cats randomized to the toy-first condition were acclimated to toy feeding during week 2, and activity counts were collected during week 3. During week 4, feeding methods were crossed. Cats randomized to the bowl-first condition were acclimated to toy feeding during week 4, and activity counts were collected during week 5. Cats randomized to the toy-first condition were acclimated to bowl feeding during week 4, and activity counts were collected during week 5. The outcome measure of interest was the change in total activity during weeks 3 and 5 for both groups. No significant difference was found in average weekly ( P = 0.30) or daily activity counts ( P = 0.17) when cats were fed from a toy compared with a bowl. A treatment effect by day was observed with activity decreasing in the toy-first group and increasing in the bowl-first group between days 3 and 4 ( P = 0.028). In addition, we found that overall activity of cats decreased 6%-7% with each 1-year increase in age ( P = 0.041). Although the type of feeding method in this pilot study did not affect overall activity, providing meals to cats using food toys may provide other benefits related to satiety, stress reduction, and overall well-being. More research is needed to explore the benefits of alternative feeding practices for indoor cats.

Nesfatin-1-like peptide is a novel metabolic factor that suppresses feeding, and regulates whole-body energy homeostasis in male Wistar rats.

Nucleobindin-1 has high sequence similarity to nucleobindin-2, which encodes the anorectic and metabolic peptide, nesfatin-1. We previously reported a nesfatin-1-like peptide (NLP), anorectic in fish and insulinotropic in mice islet beta-like cells. The main objective of this research was to determine whether NLP is a metabolic regulator in male Wistar rats. A single intraperitoneal (IP) injection of NLP (100 μg/kg BW) decreased food intake and increased ambulatory movement, without causing any change in total activity or energy expenditure when compared to saline-treated rats. Continuous subcutaneous infusion of NLP (100 μg/kg BW) using osmotic mini-pumps for 7 days caused a reduction in food intake on days 3 and 4. Similarly, water intake was also reduced for two days (days 3 and 4) with the effect being observed during the dark phase. This was accompanied by an increased RER and energy expenditure. However, decreased whole-body fat oxidation, and total activity were observed during the long-term treatment (7 days). Body weight gain was not significantly different between control and NLP infused rats. The expression of mRNAs encoding adiponectin, resistin, ghrelin, cholecystokinin and uncoupling protein 1 (UCP1) were significantly upregulated, while leptin and peptide YY mRNA expression was downregulated in NLP-treated rats. These findings indicate that administration of NLP at 100 μg/kg BW reduces food intake and modulates whole body energy balance. In summary, NLP is a novel metabolic peptide in rats.

Berberine-induced changes in protein expression and antioxidant enzymes in melanoma cells

Proteomic identification of differentially expressed proteins after treatment with berberine, a natural alkaloid, was investigated in this study. The 23 differentially expressed proteins, 3 of which were enhanced and 20 were reduced, were associated with diverse biological functions including cell death and molecular chaperone. The proteomic result was also validated by western blot analysis of ezrin, septin, UQCRC1 and elongation factor Tu. Moreover, changes in total activity and isozyme pattern of antioxidant enzymes were examined via activity assay and in-situ activity staining, respectively. Total activities of catalase and superoxide dismutase were enhanced, while those of glutathione peroxidase and glutathione reductase were unchanged by berberine. Taken together, the results showed that berberine elicited alteration of protein expression patterns and signaled the induction of isozyme of catalase and superoxide dismutase in melanoma cells.

Dissociation between the Processivity and Total Activity of γ-Secretase: Implications for the Mechanism of Alzheimer's Disease-Causing Presenilin Mutations

The amyloid β-peptide (Aβ), strongly implicated in the pathogenesis of Alzheimer's disease (AD), is produced from the amyloid β-protein precursor (APP) through consecutive proteolysis by β- and γ-secretases. The latter protease contains presenilin as the catalytic component of a membrane-embedded aspartyl protease complex. Missense mutations in presenilin are associated with early-onset familial AD, and these mutations generally both decrease Aβ production and increase the ratio of the aggregation-prone 42-residue form (Aβ42) to the 40-residue form (Aβ40). The connection between these two effects is not understood. Besides Aβ40 and Aβ42, γ-secretase produces a range of Aβ peptides, the result of initial cutting at the ε site to form Aβ48 or Aβ49 and subsequent trimming every three or four residues. Thus, γ-secretase displays both overall proteolytic activity (ε cutting) and processivity (trimming) toward its substrate APP. Here we tested whether a decrease in total activity correlates with decreased processivity using wild-type and AD-mutant presenilin-containing protease complexes. Changes in pH, temperature, and salt concentration that reduced the overall activity of the wild-type enzyme did not consistently result in increased proportions of longer Aβ peptides. Low salt concentrations and acidic pH were notable exceptions that subtly alter the proportion of individual Aβ peptides, suggesting that the charged state of certain residues may influence processivity. Five different AD mutant complexes, representing a broad range of effects on overall activity, Aβ42:Aβ40 ratios, and ages of disease onset, were also tested, revealing again that changes in total activity and processivity can be dissociated. Factors that control initial proteolysis of APP at the ε site apparently differ significantly from factors affecting subsequent trimming and the distribution of Aβ peptides.

SU-E-T-769: An Evaluation of Post-Implant Dosimetrics in Simulated Mixed Activity LDR Prostate Brachytherapy Implants

Purpose: To investigate the post‐operative dosimetric impact of mixed activity I‐125 LDR prostate brachytherapy using clinically realistic post‐implant source distributions. Methods: The plans and post‐implant source distributions of 20 recent LDR prostate brachytherapy patients were randomly selected from the institutional database. Blinded to the outcome of the implant, two new mixed‐activity plan variations were created to deliver a minimum peripheral dose of 144 Gy using sources of 0.6U and 0.9U, in addition to the standard activity of 0.424U. The specific aim was to attempt to improve coverage of the anterior superior quadrant (ASQ) of the prostate. In the first variation (V1), this was accomplished by substituting high activity seeds in this quadrant. In addition to this, the second variation (V2) reduced needle redundancy where appropriate to minimize trauma. Importantly, the needle depths and source positions used were subsets of those actually implanted. Consequently, after identifying the positions of the planned sources in the post‐implant CT, the impact of the mixed‐activity variations on post‐operative dose metrics could be simulated by reassigning the activity of the appropriate seeds. Results: The mean change in total activity due to the attempted boost was +5% (V1) and +2% (V2) over what was implanted clinically. Mean V100 increased by 3.5% and 1.7% respectively, while the mean V100 in the ASQ boost region rose by 14.4% and 12.0%. Mean D90 rose by 11.4 (V1) and 4.8 Gy (V2), but urethral V150 and rectal V100 were not impacted, varying less than <0.02cc on average, with negligible maximum increases of 0.35cc (V1) and 0.41cc (V2). Eliminating inefficient needles in V2 resulted in a mean reduction of 4.6 needles per case, and implants of 20% fewer seeds. Conclusions: A mixed activity methodology may improve implant efficiency, reduce the impact of misplacement, and faciliate focal boosts without additional needles. This research is supported by grants from Varian Medical Systems and the Prostate Cancer Foundation of BC.

Does a terminal drought tolerance QTL contribute to differences in ROS scavenging enzymes and photosynthetic pigments in pearl millet exposed to drought?

The control of reactive oxygen species (ROS) and the stability of photosynthetic pigments under stress conditions are hypothesized to contribute to drought tolerance. Here we studied how ascorbic peroxidase (APX), superoxide dismutase (SOD), catalase (CAT) isozyme activities and chlorophyll a, b (Chl a, b) and carotenoids (Car) contents responded to water stress and whether they related to presence of a terminal drought tolerance QTL in pearl millet. We used PRLT2/89-33 (QTL donor), H77/833-2 (sensitive), and near-isogenic lines (QTL-NILs) introgressed with the QTL in H77/833-2 background. Under water stress there was no significant change in the total APX activity; only the proportional APX5 activity increased, with higher band intensity in tolerant genotypes. There were no significant changes in total activities of CAT and SOD under water stress, with similar band intensities in all genotypes, and a new CAT isozyme was induced in all genotypes. The photosynthetic pigment content decreased under water stress, although not differently in any genotype. Under water stress, the activities of most APX, CAT and SOD isozymes were closely related to the total chlorophyll/carotenoids ratio. Overall, besides APX5, water stress did not lead to major changes in the profile of isoenzymes involved in ROS scavenging. Similarly, the pigment content under stress did not discriminate genotypes according to the presence/absence of the QTL. This absence of discrimination for the ROS scavenging enzymes and for the pigment content under stress suggests that these traits may not play a key role in terminal drought tolerance in pearl millet.

Effect of an exercise consultation on maintenance of physical activity after completion of phase III exercise-based cardiac rehabilitation

Many patients do not maintain physical activity levels after completion of phase III exercise-based cardiac rehabilitation. This study determined the effect of an exercise consultation on maintenance of physical activity and cardiorespiratory fitness 12 months after completion of a phase III exercise programme. Seventy cardiac patients were randomized to the experimental (exercise consultation and exercise information) or control groups (exercise information only). Outcomes recorded at baseline, 6 and 12 months were: physical activity (stage of change, 7-day recall, accelerometer), cardiorespiratory fitness, lipids, quality of life, anxiety and depression. Both groups were regularly active at baseline. The between-group difference for the change in total activity (min/week) assessed by the 7-day recall was significant from baseline to 12 months [98% confidence interval (CI) -295, -20]. Total activity was maintained in the experimental group (98% CI -63, 154) and significantly decreased in the control group (115 min/week; 98% CI -228, -28) from baseline to 12 months. The between-group difference for the change in accelerometer counts/week was not significant from baseline to 6 (98% CI -1 143 720, 607 430) or 12 months (98% CI -1 131 128, 366 473). A comparable, significant decrease in peak oxygen uptake occurred from baseline to 12 months in experimental (1.8 ml/kg per min; 98% CI -3.2, -0.3) and control participants (2.3 ml/kg per min; -3.8, -0.8). Lipids, quality of life, anxiety and depression were normal at baseline and did not significantly change in either group over time. Exercise consultation was effective in maintaining self-reported physical activity, but not peak oxygen uptake, for 12 months after completion of phase III.

Aluminum stress in the roots of naked barley

Phytotoxicity of aluminum (Al) is the major limiting factor for the crops grown in acid soils rapidly inhibiting root elongation. In this study, changes in root growth, total activity and isozyme patterns of antioxidant enzymes such as peroxidase, ascorbate peroxidase, catalase and glutathione reductase by Al stress were investigated in the roots of naked barley (Hordeum vulgare L. cv. Kwangwhalssalbori). As Al concentration increased up to 500 M, the rooting rate and root elongation substantially decreased. Growth results suggested that this cultivar is an Al-sensitive species. Total activities of antioxidant enzymes generally increased at lower Al concentrations and then gradually decreased at higher Al concentrations. They also increased when the exposure time to Al was extended up to 48 hr. Changes in the isozyme patterns of antioxidant enzymes were investigated byin situ enzyme activity staining on a non-denaturing PAGE gel. They generally coincided with the changes in the total activity in parallel. Changes in the total activity of antioxidant enzymes also coincided with the changes of the root growth. Since growth reduction in the roots by Al stress could be related with the changes in the activities of antioxidant enzymes, these results suggested that Al might cause the oxidative stress in the roots of this cultivar of naked barley.

Tyrosine Kinases and Phosphatases in the Estivating Spadefoot Toad

To endure seasonally arid conditions, spadefoot toads (Scaphiopus couchii) spend 9-10 months underground each year in a hypometabolic state, termed estivation. Protein tyrosine kinases (PTKs) and phosphatases (PTPs) were evaluated in organs of control and estivating toads to assess their possible role in signal transduction during estivation. Total PTK activity decreased by 27-52 % in liver, lung and skeletal muscle during estivation but rose by 66% in heart. Total PTP activity changed only in liver (55 % decrease) and heart (74 %increase). Analysis of the distribution of PTKs between cytoplasmic and membrane-associated forms showed that estivation-linked changes in both fractions occurred in heart (increase) and liver (decrease) whereas in lung and skeletal muscle only the soluble fraction was affected. PTPs were assessed using both a general substrate (ENDpYINASL) and a substrate (DADEpYLIPQQG) specific for PTPs containing the SH2 binding site; both revealed estivation-associated changes in activities and subcellular distribution of PTPs in all tissues. DEAE-Sephadex chromatography showed multiple forms of skeletal muscle PTKs and PTPs in both soluble and insoluble fractions. Each fraction showed three major peaks of PTK activity, two of which shifted in elution position during estivation. The data show that PTKs and PTPs are modified in an organ-specific fashion during estivation by three mechanisms: changes in total activity, changes in subcellular distribution and possible protein covalent modification.

Age, period, and cohort effects on physical activity among elderly men during 10 years of follow-up: the Zutphen Elderly Study.

Data regarding the nature of change in physical activity as elderly people become progressively older are scarce. The present study describes changes in the physical activity pattern of a cohort of elderly Dutch men between 1985 and 1995. Self-reported physical activity was assessed with a reliable and valid questionnaire designed for retired men. In 1985, 863 men (aged 65-84 years) were examined, in 1990, 520 surviving men, and in 1995, 343 men. Three analytical perspectives (cross-sectional, longitudinal, and time-series) were used concurrently to untangle effects of aging, period, and birth cohort on the 10-year change in physical activity. Mean total time spent on physical activity decreased by 33% (28 min/day) during 10 years of follow-up. Time spent on bicycling, gardening, and total activity decreased with aging. A period effect was observed for time spent on bicycling and total activity in 1990 (increase) and gardening in 1995 (decrease). No differences in physical activity between birth cohorts were observed. Time spent on walking remained stable during follow-up, but its relative contribution to total time spent on physical activity increased with aging. The pattern of change in total activity was not affected by functional status. Mean total time spent on physical activity by elderly men clearly decreased during follow-up. This could not be fully explained by declining functional status, but was partly explained by aging. In contrast to other physical activity parameters, time spent on walking was not affected by aging. These results suggest an increasingly restrictive physical activity pattern with aging.

CHANGES IN HUMAN SERUM ALCOHOL DEHYDROGENASE ACTIVITY DURING RETINOIC ACID TREATMENT OF CANCER PATIENTS

Retinoids can inhibit cell growth and induce cell differentiation in experimental tumour models. Human alcohol dehydrogenase (ADH) exists as a group of enzymes that can be placed into five classes based upon structural and functional distinctions. Human class I ADH catalyses the oxidation of a wide variety of alcohols including ethanol and retinol, whereas human class II ADH does not catalyse the oxidation of retinol. Using specific fluorescent substrates, class I and class II ADH activity in human sera was determined. No significant changes in class I or II activity were observed after 4 weeks of treatment with cis-retinoic acid (cRA). While total ADH activity was increased from 84 +/- 78 mU/1 to 206 +/- 70 mU/1 (mean +/- SD, P < 0.02) after 1 week of treatment, there were no further significant changes after 4 weeks of treatment with cRA. Sex-related differences were observed on total ADH activity after 1 week of treatment with cRA. Although total ADH activity of patients with cancer of the cervix increased significantly after 1 week of treatment, there were no significant changes in total activity in head and neck cancer patients. This sex-related difference might be dependent on the stage of the menstrual cycle. The elimination of ethanol in women can be either faster or slower than in men depending on the stage of menstrual cycle. This study therefore suggests that the main ADH activity observed in serum belongs to class II, and not to class I ADH. The data from this study also suggest that retinoic acid has a positive feedback effect on total ADH activity after 1 week of treatment.

Augmentation of exercise-induced muscle sympathetic nerve activity during muscle heating

The muscle metabo- and mechanoreflexes have been shown to increase muscle sympathetic nerve activity (MSNA) during exercise. Group III and IV muscle afferents, which are believed to mediate this response, have been shown to be thermosensitive in animals. The purpose of the present study was to evaluate the effect of muscle temperature on MSNA responses during exercise. Eleven subjects performed ischemic isometric handgrip at 30% of maximal voluntary contraction to fatigue, followed by 2 min of postexercise muscle ischemia (PEMI), with and without local heating of the forearm. Local heating of the forearm increased forearm muscle temperature from 34.4 +/- 0.2 to 38.9 +/- 0.3 degree C (P = 0.001). Diastolic and mean arterial pressures were augmented during exercise in the heat. MSNA responses were greater during ischemic handgrip with local heating compared with control (no heating) after the first 30 s. MSNA responses at fatigue were greater during local heating. MSNA increased by 16 +/- 2 and 20 +/- 2 bursts per 30 s for control and heating, respectively (P = 0.03). When expressed as a percent change in total activity (total burst amplitude), MSNA increased 531 +/- 159 and 941 +/- 237% for control and heating, respectively (P = 0.001). However, MSNA was not different during PEMI between trials. This finding suggests that the augmentation of MSNA during exercise with heat was due to the stimulation of mechanically sensitive muscle afferents. These results suggest that heat sensitizes skeletal muscle afferents during muscle contraction in humans and may play a role in the regulation of MSNA during exercise.

Sympathetic and vascular responses to head-down neck flexion in humans.

Animal studies have demonstrated increases in sympathetic nerve outflow with vestibular stimulation. The purpose of the present study was to determine whether vestibulosympathetic reflexes are engaged in humans. Muscle sympathetic nerve activity (MSNA), heart rate, arterial pressure, calf blood flow (CBF), and calculated calf vascular resistance (CVR; mean arterial pressure/CBF) were determined during 10 min of baseline (laying prone with chin supported) and 10 min of head-down neck flexion (HDNF). MSNA responses were measured in nine subjects, and calf vascular responses were determined in seven of these subjects. Heart rate increased during the first minute of HDNF (71 +/- 2 to 76 +/- 3 beats/min; P < 0.05) and remained slightly elevated (71 +/- 2 to 74 +/- 3 beats/min; P < 0.05) for the duration of HDNF. Diastolic and mean arterial pressures also increased slightly with HDNF (80 +/- 3 to 82 +/- 3 and 96 +/- 3 to 98 +/- 3 mmHg, respectively; P < 0.05). Systolic arterial pressure did not change significantly during HDNF. CBF decreased 14% (4.63 +/- 0.78 to 3.97 +/- 0.60 ml x min(-1) x 100 ml(-1); P < 0.05), and CVR increased 12% (24.0 +/- 4.3 to 27.4 +/- 4.7 units; P < 0.05) during HDNF. These changes corresponded with significant increases in MSNA during HDNF. MSNA, expressed as burst frequency, increased from 14 +/- 2 to 20 +/- 2 bursts/min (P < 0.05) and increased 63 +/- 23% (P < 0.05) when expressed as the percent change in total activity. All variables returned to baseline during recovery. Thoracic impedance measured in five subjects did not change during HDNF (19.6 +/- 1.2 to 19.7 +/- 1.5 omega), suggesting no major change in central blood volume. The results indicate that HDNF elicits increases in CVR that are mediated by the augmentation of MSNA. Arterial pressure responses and thoracic impedance data suggest that high and low pressure baroreflexes were not the mechanism for sympathetic activation. The immediate increase in MSNA with HDNF suggests a role for vestibulosympathetic reflexes.

Bioelectronic monitoring of parasite‐induced stress in brown trout and roach

A non‐contact bioelectronic monitoring system was used to record changes in heart rate, ventilation rate and swimming activity in brown trout Salmo trutta and roach Rutilus rutilus, following exposure to two species of cercariae of digenean trematodes: Diplostomum pseudospathaceum which is a common parasite in the lens of fishes and xiphidiocercariae of Plagiorchis elegans, a parasite of anatid birds, both of which have the snail Lymnaea stagnalis as their first intermediate host. Swimming activity increased significantly in roach exposed to Diplostomum cercariae at densities as low as 3.8l−1 and remained elevated for 24–36 h post exposure. Brown trout showed no response when exposed to low densities of Diplostomum (2.9 and 5.7 cercariae 1−1) but there was a significant response at higher cercarial exposure densities (&gt;501−1). Total activity of brown trout increased immediately, peaking after 2 h and returning to pre‐exposure levels within 5–6 h. There was a simultaneous increase in heart and ventilation rates which both declined following the reduction in activity of the fish. Heart rate then increased for a second time to a maximum level at 14–16 h and thereafter declined to reach a steady state at 3 days post‐exposure. During this period there was no significant change in total activity. The qualitative nature of the heart response was identical in five infected brown trout although the magnitude of the response varied widely among fish. Exposure to cercariae of P. elegans elicited no response in either fish species. (c) 1996 The Fisheries Society of the British Isles

Infusions of Diazepam and Allopregnanolone into the Midbrain Central Gray Facilitate Open-Field Behavior and Sexual Receptivity in Female Rats

We have previously shown that blocking GABAA receptors with bicuculline in the dorsal and lateral quadrants of the rostral two-thirds of the midbrain central gray (MCG) in rats reduces the lordosis quotient (LQ) and proceptive behaviors without increasing the defensive index (McCarthy, Pfaff, and Schwartz-Giblin, 1991b), indicating that tonic release of endogenous GABA in the MCG has a primary facilitatory effect on reproductive behaviors. The present study tests whether two modulators of the GABAA-benzodiazepine-receptor complex, diazepam and the progesterone metabolite, allopregnanolone, facilitate female receptivity as well as open-field behavior. Ovariectomized estradiol benzoate (EB)-treated rats were bilaterally infused in the MCG with vehicle, diazepam, or allopregnanolone and tested 20 min after diazepam and 12 min after allopregnanolone. Animals were tested once each for both receptive or open-field behavior with testing sessions being at least 1 week apart in a crossover design between vehicle and one of the two drugs. Both diazepam and allopregnanolone significantly increased the lordosis quotient in a dose-dependent manner, the lowest effective dose tested being 100 and 250 ng, respectively. In the open-field test, infusion of diazepam (100 ng) in EB-treated rats significantly increased the ratio of central squares entered to total squares entered (C/T) without a change in total activity. Rats without EB elicited comparable C/T ratios when tested with five times as much diazepam. Diazepam infusions at more dorsal sites in the midbrain and in overlying cortex were without effect on C/T ratios in EB-treated rats. Allopregnanolone (500 ng) infusions in MCG of EB-treated rats did not alter C/T ratios compared to animals without EB. Our results are consistent with diazepam and allopregnanolone acting through the GABAA receptors of the MCG to enhance female sexual receptivity and with estradiol potentiating the effect of diazepam in the MCG to increase openfield behavior.