Disease-Free Survival of Patients With Muscle-Invasive Bladder Cancer Treated With Radical Cystectomy Versus Bladder-Preserving Therapy: A Nationwide Study

PURPOSE

Although level I evidence is lacking that radical cystectomy (RC) is superior to bladder-preserving therapy (BPT), RC is still advocated as the recommended treatment in patients with nonmetastatic muscle-invasive bladder cancer (MIBC). This study sought to compare the survival of patients with MIBC treated with BPT versus those treated with RC.

METHODS AND MATERIALS

All patients with nonmetastatic MIBC diagnoses were identified via the population-based Netherlands Cancer Registry. Only patients treated with BPT or RC were included. The primary endpoint was 2-year disease-free survival (DFS), defined as time from start of treatment until locoregional recurrence, distant metastasis, or death. The secondary endpoint was overall survival (OS). Inverse propensity treatment weighting (IPTW) was used based on propensity scores to adjust for baseline differences between treatment groups. Survival was analyzed with Kaplan-Meier and Cox proportional hazards models.

RESULTS

A total of 1432 patients were included, of whom 1101 underwent RC and 331, BPT. Median follow-up was 39 months (range, 27-51 months). The IPTW-adjusted 2-year DFS was 61.5% (95% CI, 53.5%-69.6%) with BPT and 55.3% (95% CI, 51.6%-59.1%) with RC, with an adjusted hazard ratio of 0.84 (95% CI, 0.69-1.05). The adjusted 2-year OS for patients treated with BPT versus RC was 74.0% (95% CI, 67.0%-80.9%) versus 66.0% (95% CI, 62.7%-68.8%), respectively, with an adjusted hazard ratio of 0.80 (95% CI, 0.64-0.98).

CONCLUSIONS

There was no statistically significant difference between the 2-year DFS of patients treated with BPT and RC. We propose that both RC and BPT should be offered as a curative treatment option to eligible patients with nonmetastatic MIBC.

Chemoradiation for muscle-invasive bladder cancer using 5-fluorouracil versus capecitabine: A nationwide cohort study

BACKGROUND AND PURPOSE

Oral capecitabine and intravenous 5-fluorouracil (5-FU) are both used as a radiosensitizer in chemoradiotherapy (CRT). A capecitabine-based regimen is more convenient for both patients and healthcare professionals. Since large comparative studies are lacking, we compared toxicity, overall survival (OS) and disease-free survival (DFS) between both CRT-regimens in patients with muscle-invasive bladder cancer (MIBC).

MATERIALS AND METHODS

All patients diagnosed with non-metastatic MIBC between November 2017-November 2019 were consecutively included in the BlaZIB study. Data on patient, tumor, treatment characteristics and toxicity were prospectively collected from the medical files. From this cohort, all patients with cT2-4aN0-2/xM0/x, treated with capecitabine or 5-FU-based CRT were included in the current study. Toxicity in both groups was compared using Fisher-exact tests. Propensity score-based inverse probability treatment weighting (IPTW) was applied to correct for baseline differences between groups. IPTW-adjusted Kaplan-Meier OS and DFS curves were compared using log-rank tests.

RESULTS

Of the 222 included patients, 111 (50%) were treated with 5-FU and 111 (50%) with capecitabine. Curative CRT was completed according to treatment plan in 77% of patients in the capecitabine-based group and 62% of the 5-FU group (p = 0.06). Adverse events (14 vs 21%, p = 0.29), 2-year OS (73% vs 61%, p = 0.07) and 2-year DFS (56% vs 50%, p = 0.50) did not differ significantly between groups.

CONCLUSIONS

Chemoradiotherapy with capecitabine and MMC is associated with a similar toxicity profile compared to 5-FU plus MMC and no difference in survival was found. Capecitabine-based CRT, as a more patient-friendly schedule, may be considered as an alternative to a 5-FU-based regimen.

International differences in chronic kidney disease prevalence: a key public health and epidemiologic research issue

In this narrative review, we studied the association of risk factors for chronic kidney disease (CKD) and CKD prevalence at an ecological level and describe potential reasons for international differences in estimated CKD prevalence across European countries. We found substantial variation in risk factors for CKD such as in the prevalence of diabetes mellitus, obesity, raised blood pressure, physical inactivity, current smoking and salt intake per day. In general, the countries with a higher CKD prevalence also had a higher average score on CKD risk factors, and vice versa. There was no association between cardiovascular mortality rates and CKD prevalence. In countries with a high CKD prevalence, the prevention of noncommunicable diseases may be considered important, and, therefore, all five national response systems (e.g. an operational national policy, strategy or action plan to reduce physical inactivity and/or promote physical activity) have been implemented. Furthermore, both the heterogeneity in study methods to assess CKD prevalence as well as the international differences in the implementation of lifestyle measures will contribute to the observed variation in CKD prevalence. A robust public health approach to reduce risk factors in order to prevent CKD and reduce CKD progression risk is needed and will have co-benefits for other noncommunicable diseases.

CKD Prevalence Varies across the European General Population

CKD prevalence estimation is central to CKD management and prevention planning at the population level. This study estimated CKD prevalence in the European adult general population and investigated international variation in CKD prevalence by age, sex, and presence of diabetes, hypertension, and obesity. We collected data from 19 general-population studies from 13 European countries. CKD stages 1-5 was defined as eGFR<60 ml/min per 1.73 m(2), as calculated by the CKD-Epidemiology Collaboration equation, or albuminuria >30 mg/g, and CKD stages 3-5 was defined as eGFR<60 ml/min per 1.73 m(2) CKD prevalence was age- and sex-standardized to the population of the 27 Member States of the European Union (EU27). We found considerable differences in both CKD stages 1-5 and CKD stages 3-5 prevalence across European study populations. The adjusted CKD stages 1-5 prevalence varied between 3.31% (95% confidence interval [95% CI], 3.30% to 3.33%) in Norway and 17.3% (95% CI, 16.5% to 18.1%) in northeast Germany. The adjusted CKD stages 3-5 prevalence varied between 1.0% (95% CI, 0.7% to 1.3%) in central Italy and 5.9% (95% CI, 5.2% to 6.6%) in northeast Germany. The variation in CKD prevalence stratified by diabetes, hypertension, and obesity status followed the same pattern as the overall prevalence. In conclusion, this large-scale attempt to carefully characterize CKD prevalence in Europe identified substantial variation in CKD prevalence that appears to be due to factors other than the prevalence of diabetes, hypertension, and obesity.

Quality of Reporting and Study Design of CKD Cohort Studies Assessing Mortality in the Elderly Before and After STROBE: A Systematic Review

BACKGROUND

The STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) statement was published in October 2007 to improve quality of reporting of observational studies. The aim of this review was to assess the impact of the STROBE statement on observational study reporting and study design quality in the nephrology literature.

STUDY DESIGN

Systematic literature review.

SETTING & POPULATION

European and North American, Pre-dialysis Chronic Kidney Disease (CKD) cohort studies.

SELECTION CRITERIA FOR STUDIES

Studies assessing the association between CKD and mortality in the elderly (>65 years) published from 1st January 2002 to 31st December 2013 were included, following systematic searching of MEDLINE & EMBASE.

PREDICTOR

Time period before and after the publication of the STROBE statement.

OUTCOME

Quality of study reporting using the STROBE statement and quality of study design using the Newcastle Ottawa Scale (NOS), Scottish Intercollegiate Guidelines Network (SIGN) and Critical Appraisal Skills Programme (CASP) tools.

RESULTS

37 papers (11 Pre & 26 Post STROBE) were identified from 3621 potential articles. Only four of the 22 STROBE items and their sub-criteria (objectives reporting, choice of quantitative groups and description of and carrying out sensitivity analysis) showed improvements, with the majority of items showing little change between the period before and after publication of the STROBE statement. Pre- and post-period analysis revealed a Manuscript STROBE score increase (median score 77.8% (Inter-quartile range [IQR], 64.7-82.0) vs 83% (IQR, 78.4-84.9, p = 0.05). There was no change in quality of study design with identical median scores in the two periods for NOS (Manuscript NOS score 88.9), SIGN (Manuscript SIGN score 83.3) and CASP (Manuscript CASP score 91.7) tools.

LIMITATIONS

Only 37 Studies from Europe and North America were included from one medical specialty. Assessment of study design largely reliant on good reporting.

CONCLUSIONS

This study highlights continuing deficiencies in the reporting of STROBE items and their sub-criteria in cohort studies in nephrology. There was weak evidence of improvement in the overall reporting quality, with no improvement in methodological quality of CKD cohort studies between the period before and after publication of the STROBE statement.

Methodology used in studies reporting chronic kidney disease prevalence: a systematic literature review

Background

Many publications report the prevalence of chronic kidney disease (CKD) in the general population. Comparisons across studies are hampered as CKD prevalence estimations are influenced by study population characteristics and laboratory methods.

Methods

For this systematic review, two researchers independently searched PubMed, MEDLINE and EMBASE to identify all original research articles that were published between 1 January 2003 and 1 November 2014 reporting the prevalence of CKD in the European adult general population. Data on study methodology and reporting of CKD prevalence results were independently extracted by two researchers.

Results

We identified 82 eligible publications and included 48 publications of individual studies for the data extraction. There was considerable variation in population sample selection. The majority of studies did not report the sampling frame used, and the response ranged from 10 to 87%. With regard to the assessment of kidney function, 67% used a Jaffe assay, whereas 13% used the enzymatic assay for creatinine determination. Isotope dilution mass spectrometry calibration was used in 29%. The CKD-EPI (52%) and MDRD (75%) equations were most often used to estimate glomerular filtration rate (GFR). CKD was defined as estimated GFR (eGFR) <60 mL/min/1.73 m² in 92% of studies. Urinary markers of CKD were assessed in 60% of the studies. CKD prevalence was reported by sex and age strata in 54 and 50% of the studies, respectively. In publications with a primary objective of reporting CKD prevalence, 39% reported a 95% confidence interval.

Conclusions

The findings from this systematic review showed considerable variation in methods for sampling the general population and assessment of kidney function across studies reporting CKD prevalence. These results are utilized to provide recommendations to help optimize both the design and the reporting of future CKD prevalence studies, which will enhance comparability of study results.

Translational research in nephrology: chronic kidney disease prevention and public health

This narrative review evaluates translational research with respect to five important risk factors for chronic kidney disease (CKD): physical inactivity, high salt intake, smoking, diabetes and hypertension. We discuss the translational research around prevention of CKD and its complications both at the level of the general population, and at the level of those at high risk, i.e. people at increased risk for CKD or CKD complications. At the population level, all three lifestyle risk factors (physical inactivity, high salt intake and smoking) have been translated into implemented measures and clear population health improvements have been observed. At the ‘high-risk’ level, the lifestyle studies reviewed have tended to focus on the individual impact of specific interventions, and their wider implementation and impact on CKD practice are more difficult to establish. The treatment of both diabetes and hypertension appears to have improved, however the impact on CKD and CKD complications was not always clear. Future studies need to investigate the most effective translational interventions in low and middle income countries.

Taming the chronic kidney disease epidemic: a global view of surveillance efforts

Chronic kidney disease is now recognized to be a worldwide problem associated with significant morbidity and mortality and there is a steep increase in the number of patients reaching end-stage renal disease. In many parts of the world, the disease affects younger people without diabetes or hypertension. The costs to family and society can be enormous. Early recognition of CKD may help prevent disease progression and the subsequent decline in health and longevity. Surveillance programs for early CKD detection are beginning to be implemented in a few countries. In this article, we will focus on the challenges and successes of these programs with the hope that their eventual and widespread use will reduce the complications, deaths, disabilities, and economic burdens associated with CKD worldwide.

Longitudinal association of body mass index and waist circumference with left ventricular mass in hypertensive predialysis chronic kidney disease patients

Background

This study aimed to investigate the association of both body mass index (BMI) and waist circumference (WC) with left ventricular mass (LVM) in hypertensive predialysis chronic kidney disease (CKD) patients.

Methods

From 2004 to 2005, 206 consecutive incident adult patients from the outpatient CKD clinics of two hospitals in Greece were included. Inclusion criteria were the presence of CKD and hypertension. BMI (kg/m²), WC (cm) and LVM (g) were assessed annually for 3 years.

Results

The mean age was 68.1 years, mean BMI 29.1 kg/m² and mean WC was 103.7 cm. The median LVM was 245.7 g (n = 179). In the cross-sectional data, linear regression models showed that WC {β = 1.2 [95% confidence interval (CI) 0.15; 2.3]}, and not BMI [β = 2.1 (95% CI: −0.70; 4.8)], was significantly associated with LVM. After adjustment for age, sex, primary renal disease, smoking and history of cardiovascular disease, both BMI [β = 4.7 (95% CI: 2.0; 7.4] and WC [β = 1.2 (95% CI: 0.14; 2.3)] were significantly associated with LVM. These associations were pronounced in CKD stage 1–3, but not in CKD stage 4–5. In the longitudinal analysis, linear mixed models adjusting for confounders showed that both an increase in BMI [β = 2.9 (95% CI: 0.74; 5.1)] and an increase in WC [β = 1.1 (95% CI: 0.28; 1.8)] were significantly associated with an increase in LVM.

Conclusions

In hypertensive predialysis CKD patients, both BMI and WC were associated with LVM in CKD stage 1–3, but not in CKD stage 4–5. In the longitudinal analysis, both an increase in BMI and WC were associated with an increase in LVM. Future studies should focus on mechanisms responsible for the associations between anthropometric variables and LVM.

Comparison of thermoregulatory characteristics of patients with intra- and suprasellar pituitary adenomas

Thermoregulatory capabilities under physiologic cold and heat exposure of 37 patients with suprasellar pituitary adenomas (As) and 10 patients with intrasellar adenomas (Ai) were analyzed and compared to each other and to 13 controls (Ctr.) In Ai no shift of the thermoregulatory threshold temperatures was observed. In As the regulation was shifted to a 0.5 degrees C higher mean body temperature in 82% of the patients, indicating a "set-point" elevation. The accuracy of the regulation against thermal loads was maintained, the velocity was reduced. Postoperative examination of As revealed a normalisation of the "set-point". Modifications of the hypothalamic amine systems by the compressive effect of the suprasellar adenomas are discussed to be the most probable cause for the observed thermoregulatory alterations.

Temperature effects on ventilatory rate, heart rate, and preferred pedal rate during cycle ergometry

According to the most customary exercise protocols, core temperature (Tc) rises in parallel with workload (WL) and experimental time. Physiological variables, however, may be related to each of these factors. To investigate effects of WL independent of experimental time and body temperature, we employed four moderate WLs in 4-min steps between 35 and 65% peak O2 uptake (VO2 peak) in randomized order. To investigate independent effects of body temperature, the same work protocol was performed both after resting in comfortable ambient temperature [control test (Cont)] and after a double cold exposure [precooling test (Pret)], where Tc and the temperature set point are decreased by approximately 0.6 and 0.3 degrees C, respectively. Eight male subjects (24 +/- 1.9 yr, VO2 peak 4.9 +/- 0.5 l/min) worked on a cycle ergometer in a climatic chamber. Heart rate (HR) and breathing frequency (BF), but not preferred pedal rate (PR), were positively correlated to Tc, the slopes amounting to 17 and 3.75 min-1/degree C for HR and BF, respectively. The regression appeared linear over the whole temperature range, and the regression lines were not shifted by precooling. PR was increased by time, but Pret-Cont differences of PR and Tc were inversely correlated (r = -0.50, P < 0.01). The effects of WL were highly significant on HR, O2 uptake, and rate of perceived exertion but not on BF, PR, and sweat rate. The relation of rate of perceived exertion to HR was shifted by precooling.(ABSTRACT TRUNCATED AT 250 WORDS)

Modifications of thermoregulation in patients with suprasellar pituitary adenomas

Thermoregulation was investigated pre and postoperatively in 5 and only preoperatively in 7 patients with suprasellar pituitary adenomas by exposing them to external cold and heat in a climatic chamber. Five healthy subjects served as controls. Body core and skin temperatures, oxygen consumption, electromyographic activity, skin blood flow and local sweating rates were continuously measured. Threshold temperatures for activation of heat production and heat loss were calculated from these data. Hormone analysis was performed before and after stimulation with releasing factors. In the patients, core temperatures as well as threshold temperatures for heat production and heat loss were elevated by about 0.5 degrees C as compared with controls. This elevation of core and threshold temperatures was achieved, despite a reduced resting metabolic rate, by a reduction of skin blood flow indicated by a low mean skin temperature. After successful operation the thermoregulatory alterations normalized. Serum levels of growth hormone were reduced preoperatively and stimulation by GHRF did not cause an appropriate increase. Prolactin was elevated in 6 patients with prolactinomas, but there was no correlation with changes in thermoregulatory threshold temperatures. Stimulation of the other hypophyseal hormones by the combined anterior pituitary function test revealed a normal hormonal response. Apart from prolactin there were no significant hormonal changes postoperatively. It is concluded that disturbances of temperature regulation are present in patients with suprasellar adenomas, but that they are not detectable by routine clinical methods. These alterations probably depend on a disturbance of hypothalamic function and are reversible by surgery.

Cardiac responses to the Valsalva manoeuvre in different body positions

A standardized Valsalva manoeuvre (VM) with a 15-s straining period was repeated in each of four postures by six male subjects. The postures were supine (SUP), sitting leaning back (LB), sitting leaning forward (LF) and standing (ST). During straining, the increase in heart rate (fc) was different between LB and LF (+50% and +23%, respectively P less than 0.05). The decrease in stroke volume (SV), which was monitored by means of impedance cardiography, was different (63%, 68%, 39%, and 72%, P less than 0.001) as well as the decrease in cardiac output (CO) (55%, 53%, 26%, and 61%, P less than 0.001) in SUP, LB, LF, and ST, respectively. Accordingly, after pressure release the smallest changes of SV, fc and CO were found in LF. In conclusion, cardiovascular stability during straining was increased during LF. Consequently, this posture would appear to be superior to other postures during unavoidable VM (weight lifting and defaecation). To perform tests on autonomic function LB would appear to be superior to the other postures because of the large autonomic responses, combined with minimum risk for the subject. The impedance method provided simple and reproducible determinations of SV changes during VM.

Comparison of energy expenditure by the doubly labeled water technique with energy intake, heart rate, and activity recording in man

Average daily energy expenditure determined by the doubly labeled water technique (dlwEE) was compared in six subjects (aged 20-30 y) over 2 wk under usual living conditions; average food energy intake and energy expenditure estimated from individual diary records of physical activity. In addition, energy expenditure was estimated from 24-h heart rate recordings carried out on two randomly chosen days of the 2-wk period. The group means of the dlwEE were 1.94 +/- 0.24 (means +/- SD) times larger than resting metabolic rate (= 1.94 met) and nearly identical to the average daily energy intake (1.93 +/- 0.23 met). Energy expenditure estimated from the diaries of activity and from the 24-h heart rate recording varied between 1.67 and 2.24 met depending on the calculation procedure. The dlwEE (1.94 +/- 0.24 met) is much higher than that recently determined for sedentary people (1.25 met) and thus explains that young students may achieve body weight balance with a relatively high daily food energy intake.

Thermoregulatory, cardiovascular, and muscular factors related to exercise after precooling

The effect of slightly lowered body temperature on endurance time and possibly related physiological factors was studied in seven male volunteers exercising on a cycle ergometer at an ambient temperature (Ta) of 18 degrees C. Work load was increased to 40% in a stepwise manner (phase I, min 0-16) followed by a period at 80% of peak oxygen consumption (VO2) sustained to exhaustion. On one day, exercise was preceded by a double cold exposure (precooling test, PRET), resulting in a 204-kJ/m2 negative heat storage and a 4 and 0.2 degrees C lower mean skin and core temperature at the start of exercise compared with the control test (CONT). Core temperature dropped further during exercise in PRET. Endurance time at 80% of peak VO2 was increased by 12% (P less than 0.05) in PRET. Heart rate (HR) was decreased throughout PRET (P less than 0.05); oxygen pulse and arteriovenous O2 difference were significantly increased in phase I of PRET, whereas the PRET-CONT differences in stroke volume and cardiac output were not significant. In phase II of PRET (min 16-28, heavy exercise) sweat rate (SR) and heat conductivity, indicating forearm blood flow, were lower (-39%, P less than 0.001; -37%). Pedal rate (PR) was 9% lower (P less than 0.01) in phase II of PRET. At the termination of exercise, PRET-CONT differences in HR, SR, and PR had disappeared.

Body temperature related factors diminishing the drive to exercise

The effects of slightly below-normal body temperatures (delta Tcore-0.5 to 1 degree C) on exercise performance were examined in four series of studies employing a standardized precooling maneuver. In both the precooling tests and the control tests the subjects exercised on a cycle ergometer at an ambient temperature of 18 degrees C with the following results. In series 1, the subjects were exercising at a heart rate of 120 beats X min-1. Work rate and oxygen pulse were significantly increased, and sweat rate was less elevated in precooling tests than in controls. In series 2, in 12 well-trained rowers subjected to an incremental performance test, maximum work rate, peak VO2, time to exhaustion, and total work were not reduced in precooling tests. Eight well-trained rowers in series 3 were requested to work as hard as possible for 1 h. The mean work rate, VO2, and oxygen pulse were increased in the precooling tests by 6.8, 9.6, and 5.6%, respectively, whereas the sweat rate was 20% lower. In series 4 after a 16-min period of easy exercise (phase 1) the subjects exercised at a work rate corresponding to 80% VO2max up to exhaustion. Endurance time at this work rate was increased in precooling tests by 12% (18.5 vs. 20.8 min, p = 0.035). Heart rate was lower throughout the exercise period in precooling tests.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptive changes in thermoregulation and their neuropharmacological basis

Adaptive changes of the thermoregulatory system include morphological and functional modifications. The morphological modifications such as changes in body shape and insulation need time periods of months to years to develop, unless they are genetically fixed and appear seasonally. In general, they are preceded by functional modifications, including changes in capacity of the effector systems and changes in regulatory characteristics, which need much less time to develop. These early changes in regulatory characteristics, which can be defined as deviations in threshold and gain of the thermoregulatory responses, have been described and subdivided into short-term (minutes) and long-term (weeks) modifications. Evidence for the participation of monoaminergic brain stem systems in these modifications has been reviewed. On the basis of recent insights into the organization of the thermoregulatory system, and of evaluation of experimental evidence from electrophysiological, neuropharmacological, and neuroanatomical studies it can be concluded that these systems are involved in adaptive modifications. Receiving information from several sensory systems they seem to deliver additional modulatory signals, which may interfere with the processing of specific thermal information at several sites. Theoretically, the central monoamines may participate in the control of thermal input, in the central integration of thermal signals, and in modification of output signals to thermoregulatory effectors. Best documented is their modulatory action on thermosensitive and thermointegrative hypothalamic neurons. There, the monoamines 5-hydroxytryptamine and noradrenaline act as antagonists, which enhance or diminish the effects of thermal afferents mediated by other transmitters. Moreover, the antagonistic monoaminergic systems are interconnected and can influence each other at the level of lower brain stem. The activity in central monoaminergic systems can also be modified by neurohumoral feedback mechanisms from the periphery. By means of these interrelations the vegetative responses of the organism can be corrected and optimized. These interrelations can explain also some cross-adaptive changes in the thermoregulatory threshold for shivering evoked by nonthermal factors such as food intake or long-distance running.

Effects of passive heat adaptation and moderate sweatless conditioning on responses to cold and heat

Two series of experiments were performed in physically untrained subjects. In series A (heat adaptation, HA), seven male subjects were adapted to dry heat (five consecutive days at 55 degrees C ambient air temperature (Ta) for 1 h X day-1) under resting conditions. Before and after HA, the subjects' shivering responses were determined in a cold test (Ta + 10 to 0 degrees C). In series B, eight male subjects underwent mild exercise training (five consecutive days at a heart rate, HR, of 120 b X min-1) under Ta conditions individually adjusted (Ta + 15 to +5 degrees C) to prevent both sweating and cold sensations. Before and after "sweatless training", the subjects were subjected to a combined cold and heat test. During HA the thresholds for shivering, cutaneous vasodilatation (thumb and forearm) and sweating were shifted significantly (p less than 0.05) towards lower mean body temperatures (Tb). The mean decrease in threshold Tb was 0.36 degrees C. "Sweatless training" resulted in a mean increase in work rate (at HR 120 b X min-1) and oxygen pulse of 13 and 8%, respectively. However, "sweatless training" did not change the threshold Tb for shivering or sweating. Neither HA nor "sweatless training" changed the slopes of the relationships of shivering and sweating to Tb. It is concluded that the previously reported lowering of shivering and sweating threshold Tb in long-distance runners is not due to an increased fitness level, but is essentially identical with HA. The decreased shivering threshold following HA is interpreted as "cross adaptation" produced by the stressors cold and heat.

Are non-thermal factors important in the cutaneous vascular response to exercise? A proponent's view

Direct forearm blood flow measurements showed that the threshold for vasodilation is shifted to a higher core temperature and that the slope describing the relationship between skin blood flow and core temperature is reduced during submaximum exercise in comparison with supine resting conditions. These changes in skin blood flow characteristics have been shown to be proportionately related to work load in at least one study, but not in others. With heavy exercise, indirect evidence was obtained for the elicitation of vasoconstriction after body core temperature had attained a level of 39 degrees C; this caused a dramatic rise of T core to above 40 degrees C. In other studies, such terminal vasoconstriction was not observed; the subjects stopped exercising (75 percent VO2 max), independently of its duration, when rectal temperature had reached about 39 degrees C. Such inconsistent results in regard to the importance of extrathermal control of skin blood flow may be traced to variations in the motivational and emotional state; moreover, a phenomenon described as "short-term adaptation" may be responsible for some discrepant results. In conclusion, there is evidence for the concept that blood pressure control by peripheral vasoconstriction may have, under certain circumstances, preference over the demands of temperature regulation.

Influence of menstrual cycle on shivering, skin blood flow, and sweating responses measured at night

In 10 women, external cold and heat exposures were performed both in the middle of luteal phase (L) and in the early follicular phase (F) of the menstrual cycle. Serum progesterone concentrations in L and F averaged 46.0 and 0.9 nmol X l-1, respectively. The experiments took place between 3:00 and 4:30 A.M., when the L-F core temperature difference is maximal. At neutral ambient temperature, esophageal (Tes), tympanic (Tty), rectal (Tre), and mean skin (Tsk) temperatures averaged 0.59 degrees C higher in L than in F. The thresholds for shivering, chest sweating, and cutaneous vasodilation (heat clearance technique) at the thumb and forearm were increased in L by an average of 0.47 degrees C, related to mean body temperature [Tb(es) = 0.87Tes + 0.13 Tsk] and to Tes, Tty, Tre, or Tsk. The above-threshold chest sweat rate and cutaneous heat clearances at the thumb and forearm were also enhanced in L, when related to Tb(es) or time. The metabolic rate, arm blood flow, and heart rate at thermoneutral conditions were increased in L by 5.0%, 1.1 ml X 100 ml-1 X min-1, and 4.6 beats X min-1, respectively. The concomitant increase in threshold temperatures for all autonomic thermoregulatory responses in L supports the concept of a resetting of the set point underlying the basal body temperature elevation in L. The effects of the increased threshold temperatures are counteracted by enhanced heat loss responses.

Influence of menstrual cycle on thermoregulatory, metabolic, and heart rate responses to exercise at night

Ten women [mean maximal O2 uptake (VO2max), 2.81 l X min-1] exercised for 15 min on a cycle ergometer in the middle of the luteal phase (L) and in the early follicular phase (F) of the menstrual cycle at the same constant work rates (mean 122 W) and an ambient temperature of 18 degrees C. Serum progesterone averaged 44.7 nmol X l-1 in L and 0.7 nmol X l-1 in F. After a 4-h resting period, exercise was performed between 3 and 4 A.M., when the L-F core temperature difference is maximal. Preexercise esophageal (Tes), tympanic (Tty), and rectal (Tre) temperatures averaged 0.6 degrees C higher in L. During exercise Tes, Tty, and Tre averaged 0.5 degrees C higher. The thresholds for chest sweating and cutaneous vasodilation (heat clearance technique) at the thumb and forearm were elevated in L by an average of 0.47 degrees C, related to mean body temperature (Tb(es) = 0.87Tes + 0.13Tskin), Tes, Tty, or Tre. The above-threshold chest sweat rate and cutaneous heat clearances were also increased in L. The mean exercise heart rate was 170.0 beats X min-1 in L and 163.8 beats X min-1 in F. The mean exercise VO2 in L (2.21 l X min-1) was 5.2% higher than in F (2.10 l X min-1), the metabolic rate was increased in L by 5.6%, but the net efficiency was 5.3% lower. No significant L-F differences in the respiratory exchange ratio and postexercise plasma lactate were demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of a precooling maneuver on body temperature and exercise performance

Twelve subjects exercised to exhaustion at an ambient temperature of 18 degrees C on a bicycle ergometer with the load being stepwise increased. On one day, exercise was preceded by a precooling maneuver. In the precooling tests, deep body temperature attained values of about 1 degree C lower than in the control tests. There was no indication of metabolic cold defense reactions being evoked throughout the exercise period. In the precooling tests, heart rate was significantly lower than in the controls, but the mean maximum work rate, peak oxygen uptake (VO2), time to exhaustion, and total work were not reduced, i.e., work rate and VO2 were increased for a given heart rate. In the three subjects with the lowest maximum work rates, total work and exhaustion time and, in two cases, maximum work rate were increased after precooling. The onset of sweating occurred at higher work rates but at lower core, mean skin, and mean body temperature after precooling. However, the accumulated sweat secretion was considerably smaller after precooling, indicating less thermoregulatory effort.

Thermoregulatory noradrenergic and serotonergic pathways to hypothalamic units

1. In guinea-pigs hypothalamic single units were extracellularly tested for their response to thermal stimulation of the skin and to electrical stimulation of two different pontine areas, the nucleus raphé magnus and the dorsomedial reticular formation. Furthermore, thermoregulatory control actions were measured during the stimulations.2. Electrical stimulation of those reticular formation areas containing noradrenaline cells caused an increase of oxygen uptake, electrical muscle activity and body temperature, while stimulation of the nucleus raphé magnus, known to contain serotonin cells, brought about inhibition or had no effect.3. The recorded units could be subdivided into three groups. Cell type a. Neurones on the boundary of preoptic and anterior hypothalamic regions which increased their firing rate when the skin was cooled and decreased it when the nucleus raphé magnus was stimulated. Cell type b. Neurones in the anterior hypothalamus which did not respond to brain-stem stimulation. Cell type c. More posterior neurones which increased their firing rate when the skin was warmed or when the nucleus raphé magnus was stimulated and decreased their firing rate when the reticular formation was stimulated.4. Cell type a seems to represent interneurones which are connected to the ascending serotonergic thermoregulatory pathway. As for cell type c, it is inferred that it could represent interneurones which control the threshold for shivering and non-shivering thermogenesis.

Effects of electrical stimulation in the lower brainstem on temperature regulation in the unanaesthetized guinea-pig

Electrical stimulation in lower brainstem areas presumed to be parts of the ascending noradrenergic system was carried out in the unanaesthetized guinea-pig. In the same animals noradrenaline (NA) was also injected into the anterior hypothalamus. Certain points in the lower brainstem were found, the stimulation of which resulted in a rise of oxygen uptake (more than 60% over the resting level), of body temperature and of electrical muscle activity at an ambient temperature of 29-30 degrees C. Respiratory rate also rose on stimulation, while heart rate did not show a consistent change. All these changes were found to be very similar to those obtained after an intrahypothalamic injection of NA. When the electrical stimulations at the same sites were repeated several times the extent of rise in oxygen uptake became gradually smaller, amounting to only half of the initial response after four periods of stimulation. An intrahypothalamic injection of NA restored the effectiveness of electrical stimulation in the lower brainstem to the original extent. These results suggest that the thermogenesis evoked by the electrical stimulation of these lower brainstem areas may be ascribed to the activation of ascending noradrenergic pathways terminating in the hypothalamus.

Cold-adaptive modifications in man induced by repeated short-term cold-exposures and during a 10-day and-night cold-exposure

Two types of cold exposures were carried out in humans. A. Fourteen subjects were exposed 4-7 times within 2 weeks to the following conditions: ambient temperature was decreased from 28 degrees C to between plus and minus 5 degrees C; the subjects wore a bathing suit and remained in a resting position during the exposure which lasted for 1h. B. Nine conscripts were studied before and after a 10-day exercise, during which they were exposed to moderately cold conditions during day and night. The exercise did not require increased physical activity. In two thirds of the subjects A, metabolic reactions and shivering threshold were shifted to a lower weighted mean body temperature as well as a lower esophageal temperature ("hypothermic" type of adaptation). This modification in the thermoregulatory system was linked with a reduction in thermal discomfort and cold sensation. No change was found in the resting metabolic rate nor was there any indication of the development of non-shivering thermogenesis. Similar modifications were found in 4 of the 9 soldiers (study B). These 4, however, had particularly high shivering thresholds before the 10-day exercise and the values found thereafter were no lower than those found in the remaining five and in the subjects of group A before the cold-exposure regimen.

Alteration of shivering threshold in cold- and warm-adapted guinea pigs following intrahypothalamic injections of noradrenaline and of an adrenergic alpha-receptor blocking agent

The role of adrenergic receptors in the central thermoregulatory pathways controlling the shivering activity has been studied in groups of cold-adapted (CA), warm-adapted (WA) and newborn (NB) guinea pigs, which show quantitative differences in shivering threshold. In the CA and NB animals, which normally start to shiver at lower mean body temperature levels than the WA controls, microinjection of noradrenaline (1 mug in 1 mul) into the noradrenaline-sensitive area of the anterior hypothalamus elicited shivering at higher body temperatures at which normally only WA animals start to shiver. Similar injections into the hypothalamus of WA animals did not induce any further shift of the shivering threshold. Microinjections of the alpha-receptor blocking agent phentolamine into the same brain area shifted the shivering threshold in all groups of animals to lower body temperatures, the shift being proportional to the injected dose of phentolamine. The CA and NB animals required higher doses of phentolamine to produce a change in shivering threshold. It is concluded that adrenergic alpha receptors are involved in the central thermoregulatory mechanisms which adjust the thresholds for the thermoregulatory reactions.

Adaptive modifications in the thermoregulatory system of long-distance runners

In seven long-distance runners (42 km or more) the thermoregulatory responses to acute external cooling and heating, under resting conditions, were recorded and compared with those in physically untrained controls. Sweating as well as shivering thresholds were significantly decreased in the runners when compared either in terms of mean body temperature (Tb) or esophageal temperature (Tes); Tb and Tes were reduced in the runners at rest under thermoneutral conditions. Moreover, cold sensation in the runners occurred at lower Tb. The runners thus behaved as if the "set point" of their thermoregulatory system had been reset to a lower level. As for the sweating threshold, the shift is quantitatively comparable to that found in heat adaptation. The described modifications in long-distance runners would prolong the time period until a dangerous body temperature-one of the important limiting factors in physical endurance-is reached during heavy exercise.