Impacts of age, diabetes, and hypertension on serum endothelial monocyte-activating polypeptide-II after prolonged work in the heat

BACKGROUND

With rising temperature extremes, older workers are becoming increasingly vulnerable to heat-related injuries because of age- and disease-associated decrements in thermoregulatory function. Endothelial monocyte-activating polypeptide-II (EMAP-II) is a proinflammatory cytokine that has not yet been well-characterized during heat stress, and which may mediate the inflammatory response to high levels of physiological strain.

METHODS

We evaluated serum EMAP-II concentrations before and after 180 min of moderate-intensity work (200 W/m² ) in temperate (wet-bulb globe temperature [WBGT] 16°C) and hot (WBGT 32°C) environments in heat-unacclimatized, healthy young (n = 13; mean [SD]; 22 [3] years) and older men (n = 12; 59 [4] years), and unacclimatized older men with hypertension (HTN) (n = 10; 60 [4] years) or type 2 diabetes (T2D) (n = 9; 60 [5] years). Core temperature and heart rate were measured continuously.

RESULTS

In the hot environment, work tolerance time was lower in older men with HTN and T2D compared to healthy older men (both p < 0.049). While core temperature and heart rate reserve increased significantly (p < 0.001), they did not differ across groups. End-exercise serum EMAP-II concentrations were higher in young men relative to their older counterparts due to higher baseline levels (both p ≤ 0.02). Elevations in serum EMAP-II concentrations were similar between healthy older men and older men with HTN, while serum EMAP-II concentrations did not change in older men with T2D following prolonged work in the heat.

CONCLUSION

Serum EMAP-II concentrations increased following prolonged moderate-intensity work in the heat and this response is influenced by age and the presence of HTN or T2D.

Comorbidity and functional outcomes after hip fracture: an umbrella review protocol

OBJECTIVE

The objective of the review is to examine the association between comorbidity and functional outcomes after hip fracture.

INTRODUCTION

Patients who have suffered a hip fracture are at risk of poor functional recovery, which may be influenced by factors such as age, functional status at baseline, and comorbid conditions. Patients recovering from a hip fracture seldom present without other comorbid conditions. This proposed review will lead to a better understanding of the association between comorbidity and functional recovery after hip fracture and will assist in the medical support of patients recovering from these injuries.

INCLUSION CRITERIA

Systematic reviews that include cohort studies reporting on comorbidity and functional outcomes after hip fracture in adults (≥ 18 years old) published at any time will be included. Study protocols, papers that are not systematic reviews, papers not reporting on comorbidities or functional outcomes, and papers published in languages other than English will be excluded from the review.

METHODS

The JBI methodology for umbrella reviews will be followed. MEDLINE, Embase, and the Cochrane Database of Systematic Reviews will be searched. Two reviewers will screen the titles and abstracts against the eligibility criteria. Data extraction will be performed by 2 independent reviewers on the reviews selected for inclusion. Extracted study characteristics will include the author, year published, databases searched, number of studies/patients included, comorbidity measures, functional outcomes, presence of meta-analysis, and bias appraisal results. The quality of included studies will be reported using the JBI critical appraisal checklist for systematic reviews and research syntheses. A summary of the extracted data will be presented in tabular format and a narrative synthesis will be performed on the collected systematic reviews that meet the inclusion criteria.

SYSTEMATIC REVIEW REGISTRATION NUMBER

PROSPERO CRD42021272502.

Characteristics and outcomes of COVID-19-Positive Individuals Admitted for Inpatient Rehabilitation in Toronto, Canada

OBJECTIVE

To describe the sociodemographic features, impairments, and functional changes of COVID-19-positive individuals who underwent inpatient rehabilitation at three rehabilitation hospitals in Toronto, Canada.

DESIGN

Retrospective chart review of patients admitted to three COVID-19 rehabilitation units between 20 April 2020 and 3 June 2020. Sociodemographic factors, impairments, length of stay, and Functional Independence Measure data were reported.

RESULTS

A total of 41 patients were included in this study, including 22 males and 19 females. The median age was 75 years. Thirty-six percent of patients were admitted to the intensive care unit during their acute stay. The most commonly affected body functions were: neuromusculoskeletal (73.2%); combined cardiovascular, haematological, immunological, and respiratory (65.9%); and mental functions (29.3%). Median total Functional Independence Measure score was 85 at admission and 108.5 at discharge.

CONCLUSION

This study represents some of the first data on the characteristics and outcomes of COVID-19-positive individuals admitted to inpatient rehabilitation in Toronto, Canada early in the COVID-19 pandemic.

A systematic review of the impact of obesity on stroke inpatient rehabilitation functional outcomes

BACKGROUND

Obesity is a known risk factor for stroke, but its impact on functional recovery is less clear. Understanding the effect of obesity on functional recovery during inpatient rehabilitation will aid clinicians in patient counselling and help administrators with program planning.

OBJECTIVE

To determine if obesity affects the functional outcomes of adults undergoing inpatient stroke rehabilitation.

METHODS

MEDLINE, Embase, CINAHL, and Cochrane databases were searched using the subject headings and text word terms for stroke, rehabilitation, and obesity. Two independent reviewers screened the articles against pre-defined eligibility criteria and extracted the data. Outcomes of interest included FIM, mRS, Fugl-Meyer Assessment of Sensorimotor Recovery after Stroke, and Barthel Index.

RESULTS

Seven studies from five countries with a total of 3070 participants were included. There was significant heterogeneity among the studies in the BMI cut-off points and functional outcome measures used. Two studies found a positive association between obesity and functional outcome, two studies found no association, and three studies reported a negative relationship.

CONCLUSIONS

No conclusions could be drawn regarding whether the functional outcome of adults undergoing inpatient stroke rehabilitation differ between individuals with and without obesity.

Identifying priorities and developing strategies for building capacity in amputation research in Canada

BACKGROUND

Compared to other patient population groups, the field of amputation research in Canada lacks cohesion largely due to limited funding sources, lack of connection among research scientists, and loose ties among geographically dispersed healthcare centres, research institutes and advocacy groups. As a result, advances in clinical care are hampered and ultimately negatively influence outcomes of persons living with limb loss.

OBJECTIVE

To stimulate a national strategy on advancing amputation research in Canada, a consensus-workshop was organized with an expert panel of stakeholders to identify key research priorities and potential strategies to build researcher and funding capacity in the field.

METHODS

A modified Delphi approach was used to gain consensus on identifying and selecting an initial set of priorities for building research capacity in the field of amputation. This included an anonymous pre-meeting survey (N = 31 respondents) followed by an in-person consensus-workshop meeting that hosted 38 stakeholders (researchers, physiatrists, surgeons, prosthetists, occupational and physical therapists, community advocates, and people with limb loss).

RESULTS

The top three identified research priorities were: (1) developing a national dataset; (2) obtaining health economic data to illustrate the burden of amputation to the healthcare system and to patients; and (3) improving strategies related to outcome measurement in patients with limb loss (e.g. identifying, validating, and/or developing outcome measures). Strategies for moving these priorities into action were also developed.

CONCLUSIONS

The consensus-workshop provided an initial roadmap for limb loss research in Canada, and the event served as an important catalyst for stakeholders to initiate collaborations for moving identified priorities into action. Given the increasing number of people undergoing an amputation, there needs to be a stronger Canadian collaborative approach to generate the necessary research to enhance evidence-based clinical care and policy decision-making.IMPLICATIONS FOR REHABILITATIONLimb loss is a growing concern across North America, with lower-extremity amputations occurring due to complications arising from diabetes being a major cause.To advance knowledge about limb loss and to improve clinical care for this population, stronger connections are needed across the continuum of care (acute, rehabilitation, community) and across sectors (clinical, advocacy, industry and research).There are new surgical techniques, technologies, and rehabilitation approaches being explored to improve the health, mobility and community participation of people with limb loss, but further research evidence is needed to demonstrate efficacy and to better integrate them into standard clinical care.

Return to work after occupational and non-occupational lower extremity amputation

Background

Factors impacting on return to work (RTW) after lower extremity amputation are important in occupational rehabilitation.

Aims

Our objective was to compare RTW in patients who had traumatic work-related amputation with amputations from other causes.

Methods

A retrospective cohort study was conducted with participants employed at the time of amputation and at least 1 year post-discharge from amputee rehabilitation. The primary outcome measure was RTW.

Results

One hundred and forty-seven amputees were included with 69% returning to work. Amputation reason did not impact on RTW (odds ratio [OR] 1.83, P = non-significant). Trans-femoral amputees were less likely to RTW (OR 0.22, P < 0.05). Years since amputation (OR 1.20, P = 0.001) and Reintegration to Normal Living Index (OR 1.05, P < 0.001) were predictive of RTW after adjusting for other covariates.

Conclusions

Amputation aetiology did not impact on RTW. Years since amputation, level of amputation and Return to Normal Living Index were associated with RTW which may be important to consider in RTW prognosis and planning.

Occupational handling of nickel nanoparticles: a case report

A 26-year-old female chemist formulated polymers and coatings usually using silver ink particles. When she later began working with nickel nanoparticle powder weighed out and handled on a lab bench with no protective measures, she developed throat irritation, nasal congestion, "post nasal drip," facial flushing, and new skin reactions to her earrings and belt buckle which were temporally related to working with the nanoparticles. Subsequently she was found to have a positive reaction to nickel on the T.R.U.E. patch test, and a normal range FEV1 that increased by 16% post bronchodilator. It was difficult returning her to work even in other parts of the building due to recurrence of symptoms. This incident triggered the company to make plans for better control measures for working with nickel nanoparticles. In conclusion, a worker developed nickel sensitization when working with nanoparticle nickel powder in a setting without any special respiratory protection or control measures.

Human thermoregulation: separating thermal and nonthermal effects on heat loss

Human thermoregulatory control during heat stress has been studied at rest, during exercise and more recently during exercise recovery. Heat balance in the body is maintained by changes in the rate of heat loss via adjustments in skin blood flow and sweating. Independent of thermal control, the actions of nonthermal factors have important consequences in the control of heat loss responses during and following exercise. While the effect of these nonthermal factors is largely considered to be an inhibitory or excitatory stimulus which displaces the set-point about which temperature is regulated, their effects on human thermoregulatory control are far reaching. Many factors can affect the relative contribution of thermal and nonthermal influences to heat balance including exercise intensity, hemodynamic status, and the level of hyperthermia imposed. This review will characterize the physiological responses associated with heat stress and discuss the thermal and nonthermal influences on sweating and skin blood flow in humans. Further, recent calorimetric evidence for the understanding of thermal and nonthermal contributions to human heat balance will also be discussed.

Pandemic influenza: implications for occupational medicine

This article reviews the biological and occupational medicine literature related to H5N1 pandemic influenza and its impact on infection control, cost and business continuity in settings outside the health care community. The literature on H5N1 biology is reviewed including the treatment and infection control mechanisms as they pertain to occupational medicine. Planning activity for the potential arrival of pandemic avian influenza is growing rapidly. Much has been published on the molecular biology of H5N1 but there remains a paucity of literature on the occupational medicine impacts to organizations. This review summarizes some of the basic science surrounding H5N1 influenza and raises some key concerns in pandemic planning for the occupational medicine professional. Workplaces other than health care settings will be impacted greatly by an H5N1 pandemic and the occupational physician will play an essential role in corporate preparation, response, and business continuity strategies.

Macrophage inflammatory response to self-assembling rosette nanotubes

Rosette nanotubes (RNTs) are a new class of nanomaterials with significant therapeutic potential. However, societal concerns related to the potential adverse health effects of engineered nanomaterials drew attention towards the investigation of their interaction with the human U937 macrophage cell line. The cells are treated with medium only (control), lysine (50 microg mL(-1)), lysine-functionalized RNTs (RNT-K; 1, 5, and 50 microg mL(-1)), Min-U-Sil quartz microparticles (80 microg mL(-1)), or lipopolysaccharide (1 microg mL(-1)). The supernatant and cells are assayed for cell viability, cytokine protein, and mRNA expression at 1, 6, and 24 h post-treatment. The results indicate that RNT-K activate transcription of proinflammatory genes (interleukin-8 and tumor necrosis factor-alpha (TNF-alpha)) within 1 h, but this effect is not accompanied by protein secretion into the supernatant. The effect of the length of RNTs on human U937 macrophage viability is also investigated. Although both short and long RNT-K exhibit time-dependent effects on TNF-alpha transcription, only the short RNT-K (5 microg mL(-1)) increase TNF-alpha concentration at 6 h relative to the long RNT-K. Moreover, RNT-K (1 and 5 microg mL(-1)) have no effect on cell viability by 24 h. These data indicate that RNT-K do not induce a robust inflammatory response or cytotoxicity in the U937 human macrophage cell line, and therefore could be used for biomedical applications.

Can supine recovery mitigate the exercise intensity dependent attenuation of post-exercise heat loss responses?

Cutaneous vascular conductance (CVC) and sweat rate are subject to non-thermal baroreflex-mediated attenuation post-exercise. Various recovery modalities have been effective in attenuating these decreases in CVC and sweat rate post-exercise. However, the interaction of recovery posture and preceding exercise intensity on post-exercise thermoregulation remains unresolved. We evaluated the combined effect of supine recovery and exercise intensity on post-exercise cardiovascular and thermal responses relative to an upright seated posture. Seven females performed 15 min of cycling ergometry at low- (LIE, 55% maximal oxygen consumption) or high-(HIE, 85% maximal oxygen consumption) intensity followed by 60 min of recovery in either an upright seated or supine posture. Esophageal temperature, CVC, sweat rate, cardiac output, stroke volume, heart rate, total peripheral resistance, and mean arterial pressure (MAP) were measured at baseline, at end-exercise, and at 2, 5, 12, 20, and every 10 min thereafter until the end of recovery. MAP and stroke volume were maintained during supine recovery to a greater extent relative to an upright seated recovery following HIE (p <or= 0.05) and were paralleled by an elevated CVC and sweat rate response (p <or= 0.05). A significantly lower esophageal temperature was subsequently observed when supine throughout recovery (p <or= 0.05). Although we observed a reflex bradycardia and increased stoke volume with supine recovery following LIE, no differences were observed for MAP, CVC, sweat rate or esophageal temperature. Supine recovery attenuates the post-exercise reductions in MAP, CVC, and sweat rate in a manner dependent directly on exercise intensity. This effect is likely attributable to a non-thermal baroreceptor mechanism.

Menstrual cycle and oral contraceptive use do not modify postexercise heat loss responses

It is unknown whether menstrual cycle or oral contraceptive (OC) use influences nonthermal control of postexercise heat loss responses. We evaluated the effect of menstrual cycle and OC use on the activation of heat loss responses during a passive heating protocol performed pre- and postexercise. Women without OC (n = 8) underwent pre- and postexercise passive heating during the early follicular phase (FP) and midluteal phase (LP). Women with OC (n = 8) underwent testing during the active pill consumption (high exogenous hormone phase, HH) and placebo (low exogenous hormone phase, LH) weeks. After a 60-min habituation at 26 degrees C, subjects donned a liquid conditioned suit. Mean skin temperature was clamped at approximately 32.5 degrees C for approximately 15 min and then gradually increased, and the absolute esophageal temperature at which the onset of forearm vasodilation (Th(vd)) and upper back sweating (Th(sw)) were noted. Subjects then cycled for 30 min at 75% Vo(2 peak) followed by a 15-min seated recovery. A second passive heating was then performed to establish postexercise values for Th(vd) and Th(sw). Between 2 and 15 min postexercise, mean arterial pressure (MAP) remained significantly below baseline (P < 0.05) by 10 +/- 1 and 11 +/- 1 mmHg for the FP/LH and LP/HH, respectively. MAP was not different between cycle phases. During LP/HH, Th(vd) was 0.16 +/- 0.24 degrees C greater than FP/LH preexercise (P = 0.020) and 0.15 +/- 0.23 degrees C greater than FP/LH postexercise (P = 0.017). During LP/HH, Th(sw) was 0.17 +/- 0.23 degrees C greater than FP/LH preexercise (P = 0.016) and 0.18 +/- 0.16 degrees C greater than FP/LH postexercise (P = 0.001). Postexercise thresholds were significantly greater (P < or = 0.001) than preexercise during both FP/LH (Th(vd), 0.22 +/- 0.03 degrees C; Th(sw), 0.13 +/- 0.03 degrees C) and LP/HH (Th(vd), 0.21 +/- 0.03 degrees C; Th(sw), 0.14 +/- 0.03 degrees C); however, the effect of exercise was similar between LP/HH and FP/LH. No effect of OC use was observed. We conclude that neither menstrual cycle nor OC use modifies the magnitude of the postexercise elevation in Th(vd) and Th(sw).

Low inflammatory activation by self-assembling Rosette nanotubes in human Calu-3 pulmonary epithelial cells

Rosette nanotubes (RNT) are a new class of metal-free organic nanotubes synthesized through self-assembly. Because of the wide range of potential biomedical applications associated with these materials, it is necessary to evaluate their potential in vitro toxicity. Here the cytotoxicity of a lysine-functionalized nanotube (RNT-K) in a human Calu-3 pulmonary epithelial cell line is investigated. The cells were treated with media only (control), lysine (50 mg mL(-1)), RNT-K (1, 5, and 50 microg mL(-1)), Min-U-Sil quartz microparticles (QM; 80 microg mL(-1)), and lipopolysaccharide (LPS; 1 microg mL(-1)). The supernatants were analyzed at 1, 6, and 24 h after treatment for the expression of three proinflammatory mediators: IL-8, TNF-alpha and EMAP-II. Cellular viability determined with the Trypan blue assay is significantly reduced in the QM and high-dose RNT-treated groups. TNF-alpha and EMAP-II are undetectable by enzyme-linked-immunosorbent assay (ELISA) in the supernatant of all groups. Although IL-8 concentrations do not differ between treatments, its concentrations increase with time within each of the groups. Quantitative reverse-transcriptase polymerase chain reaction (qRTPCR) of IL-8 mRNA shows increased expression in the high-dose RNT-treated groups at both 1 and 6 h, while an adhesion molecule, ICAM-1 mRNA, shows the greatest increase at 6 h in the QM-treated group. In summary, RNT-K neither reduces cell viability at moderate doses nor does it induce a time-dependent inflammatory response in pulmonary epithelial cells in vitro.

Hyperthermia modifies the nonthermal contribution to postexercise heat loss responses

PURPOSE

This study investigated the nonthermoregulatory control of cutaneous vascular conductance (CVC) and sweating during recovery from exercise-induced hyperthermia as well as possible sex-related differences in these responses. Two hypotheses were tested in this study: 1) active and passive recovery would be more effective in attenuating the fall in mean arterial pressure (MAP) than inactive recovery, but CVC and sweat rate responses would be similar between all recovery modes; and 2) the magnitude of the change in postexercise heat loss and hemodynamic responses between recovery modes would be similar between sexes.

METHODS

Nine males and nine females were rendered hyperthermic (esophageal temperature = 39.5 degrees C) by exercise, followed by 60 min of 1) active, 2) inactive, and 3) passive recovery. CVC, sweat rate, and MAP were recorded at baseline, after 2, 5, 12, and 20 min, and at every 10 min until the end of recovery.

RESULTS

MAP was elevated above inactive recovery by 6 +/- 2 and 4 +/- 1 mm Hg for active and passive recovery, respectively (P < 0.001). No differences were observed between modes during the initial 10 min of recovery for CVC and 50 min of recovery for sweat rate. However, relative to inactive recovery CVC and sweat rate were subsequently greater by 16.2 +/- 5.8% of CVCpeak and 0.28 +/- 0.04 mg.min.cm, respectively, during active recovery, and by 11.6 +/- 2.9% of CVCpeak and 0.23 +/- 0.03 mg.min.cm, respectively, during passive recovery.

CONCLUSION

We conclude that in the presence of a greater thermal drive associated with hyperthermia, the influence of nonthermal input on postexercise heat loss responses is still observed. However, thermal control predominates over nonthermal factors in the first 10 min of recovery for CVC and for up to 50 min postexercise for sweating. Sex did not influence the effect of recovery mode on any variable.

Rosette nanotubes show low acute pulmonary toxicity in vivo

Nanotubes are being developed for a large variety of applications ranging from electronics to drug delivery. Common carbon nanotubes such as single-walled and multi-walled carbon nanotubes have been studied in the greatest detail but require solubilization and removal of catalytic contaminants such as metals prior to being introduced to biological systems for medical application. The present in vivo study characterizes the degree and nature of inflammation caused by a novel class of self-assembling rosette nanotubes, which are biologically inspired, naturally water-soluble and free of metal content upon synthesis. Upon pulmonary administration of this material we examined responses at 24 h and 7d post-exposure. An acute inflammatory response is triggered at 50 and 25 microg doses by 24 h post-exposure but an inflammatory response is not triggered by a 5 microg dose. Lung inflammation observed at a 50 microg dose at 24 h was resolving by 7d. This work suggests that novel nanostructures with biological design may negate toxicity concerns for biomedical applications of nanotubes. This study also demonstrates that water-soluble rosette nanotube structures represent low pulmonary toxicity, likely due to their biologically inspired design, and their self-assembled architecture.

High-aspect ratio nanoparticles in nanotoxicology

In this Learned Discourse, we introduce nanotoxicology and note that little information is available on the role of aspect ratio in nanomaterial toxicity. Aspect ratio has implications for clearance from the lungs and for phagocytic cells such as the macrophage. Whether the role of aspect ratio on the nanoscale presents unique toxicological considerations remains unknown. In the case of rosette nanotubes, other physicochemical factors, such as solubility and the absence of metal content, might outweigh any possible effects incurred by aspect ratio. However, more systematic toxicity studies are required to determine the role of specific nanomaterial properties relative to biological responses.

Postexercise heat loss and hemodynamic responses during head-down tilt are similar between genders

PURPOSE

We evaluated the hypothesis that during recovery from dynamic exercise in the 15 degrees head-down tilt (HDT) position, the attenuation of the fall in mean arterial pressure (MAP), cutaneous vascular conductance (CVC), and sweat rate, and the augmentation of the rate of esophageal temperature (T(es)) decay relative to the upright seated (URS) posture, would be different between males and females.

METHODS

Fourteen subjects (seven males, seven females) performed two experimental protocols: 1) 15 min of cycle ergometry at 75% VO2peak and then 60 min of recovery in the URS posture; or 2) 15 min of cycle ergometry at 75% VO2peak and then 60 min of recovery in the 15 degrees HDT position. Mean skin temperature, Tes, CVC, sweat rate, cardiac output (CO), stroke volume (SV), heart rate (HR), total peripheral resistance (TPR), and MAP were recorded at baseline; end of exercise; 2 min, 5 min, 8 min, 12 min, 15 min, and 20 min after exercise; and every 5 min until the end of recovery (60 min).

RESULTS

During recovery from exercise, we observed significantly greater values for MAP, CVC, and sweat rate with HDT in comparison with the URS recovery posture (P <or= 0.05). The magnitude of these responses to HDT did not differ between genders, and a significantly lower T(es) was subsequently observed with HDT for the duration of recovery (P <or= 0.05) for both males and females. In the URS posture, females showed a greater decrease of postexercise MAP than did males (P <or= 0.05). At the end of 60 min of recovery, T(es) remained significantly elevated above baseline with the URS recovery posture (P <or= 0.05). With HDT, T(es) returned to baseline after 20 min.

CONCLUSION

HDT attenuates the reductions in MAP, CVC, and sweat rate observed after exercise in a gender-independent manner, and this likely is attributable to a nonthermal baroreceptor influence.

Expression and function of endothelial monocyte-activating polypeptide-II in acute lung inflammation

OBJECTIVE AND DESIGN

We tested the hypothesis that total endothelial monocyte-activating polypeptide-II (EMAP-II) expression (proEMAP/p43 and mature EMAP-II) is up-regulated in lipopolysaccharide (LPS)-induced acute lung inflammation (ALI) and that mature EMAP-II induces monocyte/macrophage and granulocyte recruitment in vivo.

MATERIALS

Thirty-five 10 week old, male Sprague-Dawley rats.

TREATMENT

Animals were instilled intratracheally with 250 microg of E. coli LPS (N = 15) or saline (N = 5) or 20 microg of mature EMAP-II (N = 5).

METHODS

Total EMAP-II was quantified using ELISA and the protein was localized with light and electron microscopic immunocytochemistry in lungs of rats at 1, 3 and 12 h (n = 5/group).

RESULTS

ELISA showed increased total EMAP-II concentrations (p < 0.05) in lungs from LPS-treated rats compared to control animals. Compared to the controls, light and electron microscopic imunocytochemistry localized total EMAP-II in monocytes/macrophages and alveolar septa at 1 and 3 h and in vascular smooth muscles at 12 h post-LPS treatment. Instillation of mature EMAP-II increased lung monocytes/macrophages and granulocytes compared with control animals (p < 0.05). However, compared to the LPS treatment, mature EMAP-II instillation did not induce expression of IL-1beta and MIP-2 (p < 0.05) and provoked less vigorous recruitment of monocytes/macrophages.

CONCLUSION

EMAP-II expression is increased in LPS-induced ALI, and that intra-tracheal instillation of mature EMAP-II induces recruitment of monocytes/macrophages and granulocytes into the lungs without stimulating IL-1beta or MIP-2 expression.

Disturbance of thermal homeostasis following dynamic exercise

Recovery from dynamic exercise results in significant perturbations of thermoregulatory control. These perturbations evoke a prolonged elevation in core body temperature and a concomitant decrease in sweating, skin blood flow, and skin temperature to pre-exercise baseline values within the early stages of recovery. Cutaneous vasodilation and sweating are critical responses necessary for effective thermoregulation during heat stress in humans. The ability to modulate the rate of heat loss through adjustments in vasomotor and sudomotor activity is a fundamental mechanism of thermoregulatory homeostasis. There is a growing body of evidence in support of a possible relationship between hemodynamic changes postexercise and heat loss responses. Specifically, nonthermoregulatory factors, such as baroreceptors, associated with hemodynamic changes, influence the regulation of core body temperature during exercise recovery. The following review will examine the etiology of the post-exercise disturbance in thermal homeostasis and evaluate possible thermal and nonthermal factors associated with a prolonged hyperthermic state following exercise.

Thermoregulatory control following dynamic exercise

Post-exercise thermoregulatory control in humans has received limited attention. In the post-exercise period skin blood flow and sweating return to pre-exercise levels despite a persistent elevation in esophageal temperature, suggesting an alteration in thermoregulatory control. The esophageal temperature response post-exercise appears to be correlated to the marked cardiovascular changes that occur after dynamic exercise. Recent work has shown that non-thermoregulatory factors associated with hemodynamic changes and hydration status post-exercise may influence the regulation of core temperature during exercise recovery. This review will characterize the thermal response and describe our current understanding of the physiological influences on thermoregulatory control during recovery from dynamic exercise.

Postexercise hypotension causes a prolonged perturbation in esophageal and active muscle temperature recovery

We examined the effect of two levels of exercise-induced hypotension on esophageal (Tes) and active and nonactive muscle temperatures during and following exercise. Seven males performed an incremental isotonic test on a Kin-Com isokinetic apparatus to determine their peak oxygen consumption during bilateral knee extensions (VO2sp). This was followed on separate days by 15-min of isolated bilateral knee extensions at moderate (60% VO2sp) (MEI) and high (80% VO2sp) (HEI) exercise intensities, followed by 90 min of recovery. Muscle temperature was measured with an intramuscular probe inserted in the left vastus medialis (Tvm) and triceps brachii (Ttb) muscles under ultrasound guidance. The deepest sensor (tip) was located approximately 10 mm from the femur and deep femoral artery and from the superior ulnar collateral artery and humerus for the Tvm and Ttb, respectively. Additional sensors were located 15 and 30 mm from the tip with an additional sensor located at 45 mm for the Tvm measurements only. Following exercise, mean arterial pressure (MAP) remained significantly below preexercise rest for the initial 60 min of recovery after MEI and for the duration of the postexercise recovery period after HEI (P< or =0.05). After HEI, significantly greater elevations from preexercise rest were recorded for Tes and all muscle temperatures paralleled a greater decrease in MAP compared with MEI (P< or =0.05). By the end of 90-min postexercise recovery, MAP, Tes, and all muscle temperatures remained significantly greater after HEI than MEI. Furthermore, a significantly shallower muscle temperature profile across Tvm, relative to preexercise rest, was observed at the end of exercise for both HEI and MEI (P< or=0.05), and for 30 min of recovery for MEI and throughout 90 min of recovery for HEI. No significant differences in muscle temperature profile were observed for Ttb. Thus we conclude that the increase in the postexercise hypotensive response, induced by exercise of increasing intensity, was paralleled by an increase in the magnitude and recovery time of the postexercise esophageal and active muscle temperatures.

15° Head-down tilt attenuates the postexercise reduction in cutaneous vascular conductance and sweating and decreases esophageal temperature recovery time

The following study examined the effect of 15° head-down tilt (HDT) on postexercise heat loss and hemodynamic responses. We tested the hypothesis that recovery from dynamic exercise in the HDT position would attenuate the reduction in the heat loss responses of cutaneous vascular conductance (CVC) and sweating relative to upright seated (URS) recovery in association with an augmented hemodynamic response and an increased rate of core temperature decay. Seven male subjects performed the following three experimental protocols: 1) 60 min in the URS posture followed by 60 min in the 15° HDT position; 2) 15 min of cycle ergometry at 75% of their predetermined V̇o2 peak followed by 60 min of recovery in the URS posture; or 3) 15 min of cycle ergometry at 75% of their predetermined V̇o2 peak followed by 60 min of recovery in the 15° HDT position. Mean skin temperature, esophageal temperature (Tes), skin blood flow, sweat rate, cardiac output (CO), stroke volume (SV), heart rate (HR), total peripheral resistance, and mean arterial pressure (MAP) were recorded at baseline, end exercise, 2, 5, 8, 12, 15, and 20 min, and every 5 min until end of recovery (60 min). Without preceding exercise, HDT decreased HR and increased SV ( P ≤ 0.05). During recovery after exercise, a significantly greater MAP, SV, CVC, and sweat rate and a significantly lower HR were found with HDT compared with URS posture ( P ≤ 0.05). Subsequently, a significantly lower Tes was observed with HDT after 15 min of recovery onward ( P ≤ 0.05). At the end of 60 min of recovery, Tes remained significantly elevated above baseline with URS ( P ≤ 0.05); however, Tes returned to baseline with HDT. In conclusion, extended recovery from dynamic exercise in the 15° HDT position attenuates the reduction in CVC and sweating, thereby significantly increasing the rate of Tes decay compared with recovery in the URS posture.

Differences in the postexercise threshold for cutaneous active vasodilation between men and women

The purpose of this study was to evaluate the possible differences in the postexercise cutaneous vasodilatory response between men and women. Fourteen subjects (7 men and 7 women) of similar age, body composition, and fitness status remained seated resting for 15 min or cycled for 15 min at 70% of peak oxygen consumption followed by 15 min of seated recovery. Subjects then donned a liquid-conditioned suit. Mean skin temperature was clamped at ∼34°C for 15 min. Mean skin temperature was then increased at a rate of 4.3 ± 0.8°C/h while local skin temperature was clamped at 34°C. Skin blood flow was measured continuously at two forearm skin sites, one with (UT) and without (BT) (treated with bretylium tosylate) intact α-adrenergic vasoconstrictor activity. The exercise threshold for cutaneous vasodilation in women (37.51 ± 0.08°C and 37.58 ± 0.04°C for UT and BT, respectively) was greater than that measured in men (37.33 ± 0.06°C and 37.35 ± 0.06°C for UT and BT, respectively) ( P < 0.05). Core temperatures were similar to baseline before the start of whole body warming for all conditions. Postexercise heart rate (HR) for the men (77 ± 4 beats/min) and women (87 ± 6 beats/min) were elevated above baseline (61 ± 3 and 68 ± 4 beats/min for men and women, respectively), whereas mean arterial pressure (MAP) for the men (84 ± 3 mmHg) and women (79 ± 3 mmHg) was reduced from baseline (93 ± 3 and 93 ± 4 mmHg for men and women, respectively) ( P < 0.05). A greater increase in HR and a greater decrease in the MAP postexercise were noted in women ( P < 0.05). No differences in core temperature, HR, and MAP were measured in the no-exercise trial. The postexercise threshold for cutaneous vasodilation measured at the UT and BT sites for men (37.15 ± 0.03°C and 37.16 ± 0.04°C, respectively) and women (37.36 ± 0.05°C and 37.42 ± 0.03°C, respectively) were elevated above no exercise (36.94 ± 0.07°C and 36.97 ± 0.05°C for men and 36.99 ± 0.09°C and 37.03 ± 0.11°C for women for the UT and BT sites, respectively) ( P < 0.05). A difference in the magnitude of the thresholds was measured between women and men ( P < 0.05). We conclude that women have a greater postexercise onset threshold for cutaneous vasodilation than do men and that the primary mechanism influencing the difference between men and women in postexercise skin blood flow is likely the result of an altered active vasodilatory response and not an increase in adrenergic vasoconstrictor tone.

Nonthermoregulatory control of cutaneous vascular conductance and sweating during recovery from dynamic exercise in women

The purpose of the study was to examine the effect of 1) active (loadless pedaling), 2) passive (assisted pedaling), and 3) inactive (motionless) recovery modes on mean arterial pressure (MAP), cutaneous vascular conductance (CVC), and sweat rate during recovery after 15 min of dynamic exercise in women. It was hypothesized that an active recovery mode would be most effective in attenuating the fall in MAP, CVC, and sweating during exercise recovery. Ten female subjects performed 15 min of cycle ergometer exercise at 70% of their predetermined peak oxygen consumption followed by 20 min of 1) active, 2) passive, or 3) inactive recovery. Mean skin temperature (Tsk), esophageal temperature (Tes), skin blood flow, sweating, cardiac output (CO), stroke volume (SV), heart rate (HR), total peripheral resistance (TPR), and MAP were recorded at baseline, end exercise, and 2, 5, 8, 12, 15, and 20 min postexercise. Cutaneous vascular conductance (CVC) was calculated as the ratio of laser-Doppler blood flow to MAP. In the active recovery mode, CVC, sweat rate, MAP, CO, and SV remained elevated over inactive values (P < 0.05). The passive mode was equally as effective as the active mode in maintaining MAP. Sweat rate was different among all modes after 12 min of recovery (P < 0.05). TPR during active recovery remained significantly lower than during recovery in the inactive mode (P < 0.05). No differences in either Tes or Tsk were observed among conditions. The results indicate that CVC can be modulated by central command and possibly cardiopulmonary baroreceptors in women. However, differences in sweat rate may be influenced by factors such as central command, mechanoreceptor stimulation, or cardiopulmonary baroreceptors.

The Postexercise Increase in the Threshold for Cutaneous Vasodilation and Sweating is Not Observed With Extended Recovery

The following study was conducted to evaluate the hypothesis that an increase in the postexercise onset threshold for cutaneous vasodilation (ThVD) and sweating (ThSW) would not be observed upon the restoration of baseline mean arterial pressure (MAP). Subjects remained either seated resting for 15 min or performed 15 min of treadmill running at 70% [Formula: see text]peak followed by either 20- (short) or 60-min (extended) recovery. At the end of each recovery protocol (20 and 60 min) a water perfusion suit was then used to increase mean skin temperature until ThVD and ThSW was noted. Exercise resulted in an increase in ThVD and ThSW of 0.24 ± 0.03 and 0.24 ± 0.02 °C, respectively, above no-exercise for the short recovery (p < 0.05). No increase was measured for the extended recovery. Postexercise MAP was significantly reduced prior to whole-body warming for the short recovery whereas no reduction was measured for the extended recovery. The increase in ThVD and ThSW, measured during the early stages of recovery, is reversed with the reestablishment of baseline MAP. Key words: postexercise hypotension, exercise recovery, baroreceptors, heat stress

Lower body positive and negative pressure alter thermal and hemodynamic responses after exercise

INTRODUCTION

The purpose of this study was to determine the effect of upright lower body positive and negative pressure (LBPP/LBNP) application on the post-exercise thermal response. It was hypothesized that the application of LBPP would decrease core temperature secondary to increases in skin blood flow (SkBF) and sweating, whereas the application of LBNP would maintain core temperature secondary to attenuated SkBF and sweating responses.

METHODS

There were six subjects who randomly underwent each of the following treatments in the upright posture, separated by a minimum of 48 h: 1) +45 mmHg LBPP; 2) -20 mmHg LBNP; or 3) no pressure for 45 min after performing 15 min of cycle ergometry exercise at 70% of their VO2peak. Measurements included mean arterial pressure (MAP), heart rate (HR), cardiac output (Q), stroke volume (SV), total peripheral resistance (TPR), mean skin temperature (Tsk), mean heat flux, esophageal temperature (Tes), SkBF, and sweat rate.

RESULTS

After the application of LBPP, we observed a significantly greater decrease in core temperature relative to the LBNP and control conditions (p < 0.001). This was accompanied by increases in SkBF, sweating, and heat flux (p < 0.05), all of which were higher than the LBNP and control conditions. Core temperature, SkBF, sweating, and heat flux in the LBNP and control conditions were not different from each other. LBPP promoted the restoration of hemodynamics while LBNP and control prolonged the post-exercise hemodynamic state.

CONCLUSION

We conclude that during recovery from exercise in the upright seated posture, core temperature recovery is affected by compromised SkBF and sweating secondary to nonthermal cardiovascular influences.

Control of cutaneous vascular conductance and sweating during recovery from dynamic exercise in humans

The purpose of the study was to examine the effect of 1) passive (assisted pedaling), 2) active (loadless pedaling), and 3) inactive (motionless) recovery modes on mean arterial pressure (MAP), skin blood flow (SkBF), and sweating during recovery after 15 min of dynamic exercise. It was hypothesized that an active recovery mode would be most effective in attenuating the fall in MAP, SkBF, and sweating during exercise recovery. Six male subjects performed 15 min of cycle ergometer exercise at 70% of their predetermined peak oxygen consumption followed by 15 min of 1) active, 2) passive, or 3) inactive recovery. Mean skin temperature (T̄sk), esophageal temperature (Tes), SkBF, sweating, cardiac output (CO), stroke volume (SV), heart rate (HR), total peripheral resistance (TPR), and MAP were recorded at baseline, end exercise, and 2, 5, 8, 12, and 15 min postexercise. Cutaneous vascular conductance (CVC) was calculated as the ratio of laser-Doppler blood flow to MAP. In the active and passive recovery modes, CVC, sweat rate, MAP, CO, and SV remained elevated over inactive values ( P < 0.05). The passive mode was equally as effective as the active mode in maintaining CO, SV, MAP, CVC, and sweat rate above inactive recovery. Sweat rate was different among all modes after 8 min of recovery ( P < 0.05). TPR during active recovery remained significantly lower than during recovery in the passive and inactive modes ( P < 0.05). No differences in either Tesor T̄skwere observed among conditions. Given that MAP was higher during passive and active recovery modes than during inactive recovery suggests differences in CVC may be due to differences in baroreceptor unloading and not factors attributed to central command. However, differences in sweat rate may be influenced by factors such as central command and mechanoreceptor stimulation.

Effect of exercise intensity on the postexercise sweating threshold

The hypothesis that the magnitude of the postexercise onset threshold for sweating is increased by the intensity of exercise was tested in eight subjects. Esophageal temperature was monitored as an index of core temperature while sweat rate was measured by using a ventilated capsule placed on the upper back. Subjects remained seated resting for 15 min (no exercise) or performed 15 min of treadmill running at either 55, 70, or 85% of peak oxygen consumption (V(o2 peak)) followed by a 20-min seated recovery. Subjects then donned a liquid-conditioned suit used to regulate mean skin temperature. The suit was first perfused with 20 degrees C water to control and stabilize skin and core temperature before whole body heating. Subsequently, the skin was heated ( approximately 4.0 degrees C/h) until sweating occurred. Exercise resulted in an increase in the onset threshold for sweating of 0.11 +/- 0.02, 0.23 +/- 0.01, and 0.33 +/- 0.02 degrees C above that measured for the no-exercise resting values (P < 0.05) for the 55, 70, and 85% of V(o2 peak) exercise conditions, respectively. We did note that there was a greater postexercise hypotension as a function of exercise intensity as measured at the end of the 20-min exercise recovery. Thus it is plausible that the increase in postexercise threshold may be related to postexercise hypotension. It is concluded that the sweating response during upright recovery is significantly modified by exercise intensity and may likely be influenced by the nonthermal baroreceptor reflex adjustments postexercise.

Cutaneous active vasodilation in humans during passive heating postexercise

The hypothesis that exercise causes an increase in the postexercise esophageal temperature threshold for onset of cutaneous vasodilation through an alteration of active vasodilator activity was tested in nine subjects. Increases in forearm skin blood flow and arterial blood pressure were measured and used to calculate cutaneous vascular conductance at two superficial forearm sites: one with intact alpha-adrenergic vasoconstrictor activity (untreated) and one infused with bretylium tosylate (bretylium treated). Subjects remained seated resting for 15 min (no-exercise) or performed 15 min of treadmill running at either 55, 70, or 85% of peak oxygen consumption followed by 20 min of seated recovery. A liquid-conditioned suit was used to increase mean skin temperature ( approximately 4.0 degrees C/h), while local forearm temperature was clamped at 34 degrees C, until cutaneous vasodilation. No differences in the postexercise threshold for cutaneous vasodilation between untreated and bretylium-treated sites were observed for either the no-exercise or exercise trials. Exercise resulted in an increase in the postexercise threshold for cutaneous vasodilation of 0.19 +/- 0.01, 0.39 +/- 0.02, and 0.53 +/- 0.02 degrees C above those of the no-exercise resting values for the untreated site (P < 0.05). Similarly, there was an increase of 0.20 +/- 0.01, 0.37 +/- 0.02, and 0.53 +/- 0.02 degrees C for the treated site for the 55, 70, and 85% exercise trials, respectively (P < 0.05). It is concluded that reflex activity associated with the postexercise increase in the onset threshold for cutaneous vasodilation is more likely mediated through an alteration of active vasodilator activity rather than through adrenergic vasoconstrictor activity.

Cardiovascular responses to apneic facial immersion during altered cardiac filling

The hypothesis that reduced cardiac filling, as a result of lower body negative pressure (LBNP) and postexercise hypotension (PEH), would attenuate the reflex changes to heart rate (HR), skin blood flow (SkBF), and mean arterial pressure (MAP) normally induced by facial immersion was tested. The purpose of this study was to investigate the cardiovascular control mechanisms associated with apneic facial immersion during different cardiovascular challenges. Six subjects randomly performed 30-s apneic facial immersions in 6.0 +/- 1.2 degrees C water under the following conditions: 1) -20 mmHg LBNP, 2) +40 mmHg lower body positive pressure (LBPP), 3) during a period of PEH, and 4) normal resting (control). Measurements included SkBF at one acral (distal phalanx of the thumb) and one nonacral region of skin (ventral forearm), HR, and MAP. Facial immersion reduced HR and SkBF at both sites and increased MAP under all conditions (P < 0.05). Reduced cardiac filling during LBNP and PEH significantly attenuated the absolute HR nadir observed during the control immersion (P < 0.05). The LBPP condition did not result in a lower HR nadir than control but did result in a nadir significantly lower than that of the LBNP and PEH conditions (P < 0.05). No differences were observed in either SkBF or MAP between conditions; however, the magnitude of SkBF reduction was greater at the acral site than at the nonacral site for all conditions (P < 0.05). These results suggest that the cardiac parasympathetic response during facial immersion can be attenuated when cardiac filling is compromised.