Effects Of Moderate Heat Stress Research Articles

Effect of moderate heat stress on tuberization of potato genotypes: Morphological and physiological changes using in vitro and ex vitro propagation

Potato plants are often subjected to heat stress during growth and development, resulting in loss of yield and quality. However, the possibility exists that commercially important genotypes show tolerance to heat stress. In this study, we aim to investigate the morphological and physiological effects of moderate conditions of heat stress on tuberization in nine potato genotypes, and how it affects propagation using an ex vitro and in vitro system. The plant material came from the In Vitro Germplasm Bank of the International Potato Center (CIP). The incubation temperatures of the cultures in in vitro and ex vitro conditions were the ambient in the laboratory and greenhouse, respectively. In in vitro system a randomized complete block design was employed in nine genotypes, two treatments: multiplication culture medium and the same culture medium supplemented with 8.0% sucrose and 500 mg/L-1 CCC, six flasks and five explants per experimental unit. Among all genotypes evaluated, Leona and Liberteña did not form tubers under ex vitro treatment conditions. Under in vitro conditions, Amarilis, Capiro, Perricholi and Tacna showed no evidence of tuberization, and Canchán was the only genotype where 100% formation of tuberous structures were produced in all evaluations. The findings concluded in this study showed that of all the potatoes evaluated, Canchán best responded to the evaluations under both in ex vitro and in vitro conditions, at maximum temperatures between 22.4 to 26.9 and 27.0 to 28.2 oC, respectively. Therefore, it is vitally important to consider its development potential in different producing locations around the world, which are directly and indirectly affected by climate change.

Study of High-Temperature-Induced Morphological and Physiological Changes in Potato Using Nondestructive Plant Phenotyping.

Potato (Solanum tuberosum L.) is vulnerable to high temperatures, which are expected to increase in frequency and duration due to climate change. Nondestructive phenotyping techniques represent a promising technology for helping the adaptation of agriculture to climate change. In this study, three potato cultivars (Agria, Bellarosa and Desiree) were grown under four temperature treatments: 20/15 °C (T1), 25/20 °C (T2), 30/25 °C (T3), and 35/30 °C (T4). Multispectral and chlorophyll fluorescence imaging, 3D multispectral scanning, and gas exchange analysis were used to study the effect of moderate heat stress on potato morphology and physiology and select phenotypic traits most responsive to increased temperatures. The most responsive morphological traits to increased temperatures are related to decreased leaf area, which were detected already at T2. Increased temperatures (already T2) also changed leaf spectral characteristics, indicated by increased red, green, and blue reflectance and decreased far-red reflectance and anthocyanin index (ARI). Regarding chlorophyll fluorescence, increasing temperatures (T2) caused an increase in minimal fluorescence of both dark-adapted (F0) and light-adapted (F0') plants. Stomatal conductance, transpiration rate, photosynthetic rate, instantaneous water use efficiency (WUE), and intrinsic water use efficiency increased from T1 to T3 and decreased again in T4. Using recursive partitioning analysis, the most responsive potato phenotypic traits to increased temperature were leaf area projected (LAP), ARI, F0, and WUE. These traits could be considered marker traits for further studying potato responses to increased temperatures.

Effect of moderate heat stress on Arabidopsis thaliana with modified BPMs expression

In Arabidopsis thaliana (L.) Heynh., a major part of MATH-BTB protein family (BPM proteins) participate in the ubiquitin‐proteasome pathway as substrate-specific adaptors of Cullin 3 dependent E3 ligase. Through targeting of specific proteins for degradation, BPMs are involved in various developmental processes, as well as in the plant’s ability to adapt to changing environmental conditions. The aim of this research was to investigate the oxidative stress response of Arabidopsis with modified BPMs expression to moderate heat stress. Seedlings of wild type, line overexpressing BPM1 gene (oeBPM1), and line with down-regulation of BPM1, 4, 5, and 6 genes (amiR bpm) were exposed to 37 °C for six hours. Seedlings were sampled immediately after stress and after a recovery period of 24 h. Control seedlings were grown at 24 °C and were collected at the same time points as treated ones. The level of lipid peroxidation, H2O2 and proline content, as well as the activity of antioxidant enzymes (G POD, APX, CAT, and SOD) were evaluated. Control amiR bpm and oeBPM1 seedlings generally had lower H2O2 and proline content, respectively, than wild type. After exposure to 37 °C, oeBPM1 and amiR-bpm lines showed reduced proline content, while no change in lipid peroxidation level and H2O2 content was observed. Further, seedlings with modified BPMs expression showed differences in the activity of G POD, APX, and SOD, while no change was observed in the activity of CAT. The results obtained suggest involvement of BPM proteins in the response of Arabidopsis to moderate heat stress.

Single-Dose Neoadjuvant AKT Pathway Inhibitor Reduces Growth of Hepatocellular Carcinoma after Laser Thermal Ablation in Small-Animal Model.

BackgroundLocal recurrence following thermal ablation of hepatocellular carcinoma (HCC) larger than 2-3 cm remains a challenging clinical problem. Prior studies suggest that phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR)-dependent protein kinase B (AKT) signaling mediates HCC cell survival caused by moderate heat stress in vitro, but these findings need in vivo validation.PurposeTo test the hypothesis that neoadjuvant inhibition of PI3K/mTOR/AKT signaling reduces HCC tumor growth in vivo after laser ablation and to evaluate the effects of moderate heat stress on molecular signaling and cellular function in HCC cells in vitro.Materials and MethodsHCC tumor-bearing mice were randomized to neoadjuvant PI3K/mTOR inhibitor (BEZ235) or control groups followed by an intentional partial laser ablation or sham ablation; there were at least nine mice per group. Postablation tumor growth was monitored up to 7 days. Tumor volumes were compared for drug or ablation groups by using two-way analysis of variance. N1S1 HCC cells pretreated with BEZ235 or control and subjected to moderate heat stress (45°C for 10 minutes) or control (37°C for 10 minutes) were analyzed by using mass spectrometry. Protein interaction networks were derived from protein expression analysis software, and cellular function activation state (Z-score) and fold-change in AKT phosphorylation were calculated.ResultsThere was a 37%-75% reduction in HCC tumor volume by day 7 after ablation in the BEZ235 plus ablation group (713 mm3 ± 417) compared with vehicle plus sham (1559 mm3 ± 552), vehicle plus ablation (1041 mm3 ± 591), and BEZ235 plus sham (1108 mm3 ± 523) groups (P < .001, P = .04, and P = .005, respectively). PI3K/mTOR inhibition prevented moderate heat stress-induced AKT signaling (Z-score, -0.2; P < .001) and isoform-specific AKT phosphorylation compared with the vehicle plus heat stress group. PI3K/mTOR inhibition prevented moderate heat stress-induced global effects on HCC molecular signaling and cellular function, including decreased cell survival, growth, and proliferation (Z-score, -0.3 to -3.2; P < .001) and increased apoptosis and cell death (Z-score, 0.4-1.1; P < .001).ConclusionModerate heat stress induces PI3K/mTOR/AKT-dependent global effects on hepatocellular carcinoma (HCC) cell survival, function, and death. Neoadjuvant PI3K/mTOR/AKT inhibition reduces postablation HCC tumor growth.© RSNA, 2019Online supplemental material is available for this article.See also the editorial by White in this issue.

Heat Stress and Agonists of Muscarinic Cholinergic Receptors Modulate Sensitivity of Nicotinic Cholinergic Receptors in Soil Nematode Caenorhabditis elegans.

We studied the effect of moderate heat stress (30oC) and muscarinic cholinergic receptor agonists arecoline and pilocarpine on sensitivity of the behavior of the nematode Caenorhabditis elegans of N2 line to the action of the agonist of nicotinic cholinergic receptor agonist levamisole. Heat stress and muscarinic cholinergic receptor agonists increased the sensitivity of swimming induced by mechanical stimulation to levamisole (32-64 μM), which manifested in dyscoordination of locomotor muscles during swimming and complete loss of ability to swim. Combined exposure to heat stress and muscarinic cholinergic receptor agonists revealed their synergism in the influence on sensitivity of swimming behavior to levamisole: heating to 30oC potentiated the effect of arecoline and arecoline potentiated the effect of heat stress. It is assumed, that the effect of heat stress on the sensitivity of nicotinic receptors is mediated by its effect on muscarinic receptors.

Opposite effects of moderate heat stress and hyperthermia on cholinergic system of soil nematodes Caenorhabditis elegans and Caenorhabditis briggsae

Cholinergic system plays important role in all functions of organisms of free-living soil nematodes C. elegans and C. briggsae. Using pharmacological analysis we showed the existence of two opposite responses of nematodes cholinergic system to moderate and extreme heat stress. Short-term (15min) noxious heat (31–32°C) caused activation of cholinergic synaptic transmission in C. elegans and C. briggsae organisms by sensitization of nicotinic ACh receptors. In contrast, hyperthermia blocked cholinergic synaptic transmission by inhibition of ACh secretion by neurons. The resistance of behavior to extreme high temperature (36–37°C) was significantly higher in C. briggsae than in C. elegans, and thermostability of cholinergic transmission correlated with resistance of behavior to hyperthermia. Activation of cholinergic transmission by moderate heat stress can be the reason of movement speed increase in such adaptive behavior as noxious heat escape. Inhibition of ACh release is one of reasons for behavior failure caused by extreme high temperature since partial inhibition of ACh-esterase by aldicarb protected C. elegans and C. briggsae behavior against hyperthermia. Antagonist of mAChRs atropine almost completely prevented the rise in behavior thermotolerance caused by aldicarb. Pilocarpine, agonist of mAChRs, protected nematodes behavior against hyperthermia similarly with aldicarb. Therefore it is evident that it is the deficiency of mAChRs activity that is the reason for nematodes' behavior failure by hyperthermia.

Effect of exercise, heat stress and dehydration on myocardial performance.

Myocardial dysfunction is a well-documented outcome of extended periods of high cardiac output. Whether similar effects occur during firefighting, an occupation characterized by repeated periods of work compounded by dehydration and heat stress, is uncertain. To investigate the independent and combined effects of moderate heat stress and dehydration on indicators of myocardial performance following intermittent, submaximal treadmill exercise while wearing personal protective equipment (PPE). Twelve aerobically fit young men (age 21.5±2.6 years; maximal oxygen uptake [VO2max] 60.3±4.4ml kg(-1) min(-1)) performed intermittent treadmill walking exercise consisting of three 20min bouts at an intensity of ~40% VO2max separated by two periods of rest in four different conditions in random order: (i) no heat stress-euhydrated, (ii) heat stress-euhydrated (heat stress created by wearing PPE, (iii) no heat stress-dehydrated and (iv) heat stress-dehydrated. We measured core temperature by a telemetric gastrointestinal pill. We determined cardiac variables by standard echocardiographic techniques immediately before and ~30min after exercise. We recorded no significant changes in markers of systolic (ejection fraction, shortening fraction, tissue Doppler-S) or diastolic (mitral peak E velocity, tissue Doppler-E' and E/E') function following exercise in any of the four conditions. In this model of exercise designed to mimic the work, heat stress and dehydration associated with firefighting activities, we observed no negative effects on myocardial inotropic or lusitropic function.

Determination of NABE in urine of high-yield dairy cows in early lactation in conditions of moderate heat stress

The work presents the results of investigations of the effect of moderate heat stress on the acidobasal status in high-yield dairy cows in early lactation. Improving performance in high-yield dairy cows increases their inclination toward metabolic disorders. The most likely to be affected is the acid-base balance, in particular when cows are exposed to heat stress. Investigations so far have shown that the taking of urine samples and their analysis is the best and fastest way to diagnose disorders in the acid-base balance. Investigations were carried out on 7 clinically healthy cows of the Holstein- Friesian breed in the phase of early lactation, 30 to 40 days (on days 30, 33 and 40 ) following calving during the summer period, during the month of July, when there were significant variations in daily and nightly temperatures. The cows were in the second and fourth lactation, the annual milk yield was 8000 L milk per cow. The average daily milk production in the early phase of lactation ranged from 35 to 40 L. The cows were fed mixed rations (TMR) twice daily. Lucerne hay in limited quantities was given to the cows prior to the mixed feed ration. The ration for this animal category was optimized on the grounds of the daily milk production. The balance of cations and anions in the feed ration stood at 95 mEq/kg DM. The results clearly demonstrate the cows' response to moderate heat stress through the defense parameters in urine (urine pH, NABE (net-acid-base-excretion), acids, bases, ammonium ion (NH4). The determination of the kidney NABE yields more correct data than the urine pH on acidotic conditions. The results of examinations of the urine pH do not show any digressions from physiological values and are approximately the same in all cows during the investigated periods. Normal NABE values are from 100-200 mmol/L. Burdening with acid products results in a NABE range from 0-100mmol/L, and metabolic acidosis results in NAB&lt;0 mmol/L. NABE in the cows in this experiment revealed that the organism is burdened by acid metabolic products and it stood at 58.28?27.96 mmol/L on day 30, 69.28?29.89 mmol/L on day 33, and 60.60?26.88mmol/L on day 40. Consequently, it seems that NABE values are decreased in cases of acidosis due to stepped up H+ excretion and stepped up bicarbonate reabsorption.

Glycinebetaine alleviates the inhibitory effect of moderate heat stress on the repair of photosystem II during photoinhibition

Transformation with the bacterial gene codA for choline oxidase allows Synechococcus sp. PCC 7942 cells to accumulate glycinebetaine when choline is supplemented exogenously. First, we observed two types of protective effect of glycinebetaine against heat-induced inactivation of photosystem II (PSII) in darkness; the codA transgene shifted the temperature range of inactivation of the oxygen-evolving complex from 40–52 °C (with half inactivation at 46 °C) to 46–60 °C (with half inactivation at 54 °C) and that of the photochemical reaction center from 44–55 °C (with half inactivation at 51 °C) to 52–63 °C (with half inactivation at 58 °C). However, in light, PSII was more sensitive to heat stress; when moderate heat stress, such as 40 °C, was combined with light stress, PSII was rapidly inactivated, although these stresses, when applied separately, did not inactivate either the oxygen-evolving complex or the photochemical reaction center. Further our studies demonstrated that the moderate heat stress inhibited the repair of PSII during photoinhibition at the site of synthesis de novo of the D1 protein but did not accelerate the photodamage directly. The codA transgene and, thus, the accumulation of glycinebetaine alleviated such an inhibitory effect of moderate heat stress on the repair of PSII by accelerating the synthesis of the D1 protein. We propose a hypothetical scheme for the cyanobacterial photosynthesis that moderate heat stress inhibits the translation machinery and glycinebetaine protects it against the heat-induced inactivation.

Modulation of Rubisco activase gene expression during heat stress in cotton ( Gossypium hirsutum L.) involves post-transcriptional mechanisms

Inhibition of photosynthesis by heat stress involves deactivation of Rubisco and is exacerbated by the low thermal stability of Rubisco's chaperone, activase. Activase structure, activity and protein expression have been the focus of previous work examining the effect of heat stress on this enzyme. Relatively little is known about the response of activase gene expression to moderate heat stress or the extent to which transcriptional mechanisms control acclimation of photosynthesis to heat stress. In the current study, the effect of moderate heat stress on the diurnal expression of three activase genes in cotton ( Gossypium hirsutum L.), including a newly identified member of the gene family, was examined. All three activase genes displayed a diurnal pattern of expression under optimal growth conditions, as determined by real-time RT-PCR. Although steady-state mRNA levels were reduced in the short-term by heat stress, transcript levels appeared to recover by the next diurnal cycle. Nuclear run-on assays utilizing real-time RT-PCR suggested mRNA stability, not synthesis, was responsible for the observed acclimatization. Identification of activase transcripts with alternative 3′-untranslated regions suggests a possible means for increasing transcript stability and hastening recovery of steady-state mRNA levels during heat stress. Together the results indicate activase gene expression is influenced by post-transcriptional mechanisms that may contribute to acclimation of photosynthesis during extended periods of heat stress.

Effects of moderate heat stress on photosynthesis: importance of thylakoid reactions, rubisco deactivation, reactive oxygen species, and thermotolerance provided by isoprene

ABSTRACTPhotosynthesis is particularly sensitive to heat stress and recent results provide important new insights into the mechanisms by which moderate heat stress reduces photosynthetic capacity. Perhaps most surprising is that there is little or no damage to photosystem II as a result of moderate heat stress even though moderate heat stress can reduce the photosynthetic rate to near zero. Moderate heat stress can stimulate dark reduction of plastoquinone and cyclic electron flow in the light. In addition, moderate heat stress may increase thylakoid leakiness. At the same time, rubisco deactivates at moderately high temperature. Relationships between effects of moderate heat on rubisco activation and thylakoid reactions are not yet clear. Reactive oxygen species such as H2O2 may also be important during moderate heat stress. Rubisco can make hydrogen peroxide as a result of oxygenase side reactions and H2O2 production by rubisco was recently shown to increase substantially with temperature. The ability to withstand moderately high temperature can be improved by altering thylakoid lipid composition or by supplying isoprene. In my opinion this indicates that thylakoid reactions are important during moderate heat stress. The deactivation of rubisco at moderately high temperature could be a parallel deleterious effect or a regulatory response to limit damage to thylakoid reactions.

The effects of moderate heat stress and open-plan office noise distraction on SBS symptoms and on the performance of office work

Three air temperatures (22/26/30 degrees C) and two acoustic conditions-quiet (35 dBA) or open-plan office noise (55 dBA)-were established in an office. Thirty subjects aged 18-29 years (16 male), clothed for thermal neutrality at 22 degrees C, performed simulated office work for 3 h under all six conditions. Many more (68% vs. 4%) were dissatisfied with noise in the noise condition (P < 0.01). Warmth decreased thermal acceptability (P < 0.001) and perceived air quality (P < 0.01) and increased odour intensity (P < 0.05) and stuffiness (P < 0.01). After 2 h, some forehead sweating was observed on 4, 36 and 76% of subjects (P < 0.001) at 22, 26 and 30 degrees C, while 0, 21 and 65% felt "warm" (P < 0.001). Raised temperature increased eye, nose and throat irritation (P < 0.05), headache intensity (P < 0.05), difficulty in thinking clearly (P < 0.01) and concentrating (P < 0.01), and decreased self-estimated performance (P < 0.001). Noise increased fatigue (P < 0.05) and difficulty in concentrating (P < 0.05) but did not interact with thermal effects on subjective perception. In an addition task, noise decreased workrate by 3% (P < 0.05), subjects who felt warm made 56% more errors (P < 0.05) and there was a noise-temperature interaction (P < 0.01): the effect of warmth on errors was less in the noise condition. Typing speed (P < 0.05) and reading speed (P < 0.05) were higher in noise. This paper demonstrates that open office noise distraction, even at the realistic level of 55 dBA, increases fatigue and has many negative effects on the performance of office work, as does a moderately warm air temperature. These findings may be used to provide economic justification for the provision of private offices and air temperature control in hot weather. The additional finding that noise distraction and heat stress can sometimes counteract each other in the short term is of academic interest only, as they both increase subjective distress and fatigue. In practice, neither should be deliberately introduced to counteract the other.

Cardiac response to combined moderate heat and exercise in men with coronary artery disease

The effect of moderate heat stress on cardiac performance during sustained moderate physical work was evaluated in men ≥6 weeks after a cardiac event. Subjects (n = 10) performed upright leg cycle ergometer exercise at approximately 50% of peak oxygen uptake for up to 60 minutes in warm (30.0 ± 0.9 °C) and thermoneutral (21.5 ± 0.3 °C) environments. Cardiac output (carbon dioxide rebreathing method), left ventricular ejection fraction and relative left ventricular end-diastolic volume (portable nuclear VEST monitor) were periodically determined. In both environments, heart rate increased (p < 0.05), stroke volume decreased (p < 0.05), and cardiac output remained unchanged with exercise time. In the warmer environment, heart rate was increased (p < 0.05) and stroke volume tended to be decreased (p < 0.08), with no difference in cardiac output. In both environments, left ventricular ejection fraction did not change from minute 6 to 60 of exercise, whereas relative left ventricular end-diastolic volume decreased (p < 0.05) with exercise time. Arterial blood pressure was unchanged from minute 6 to 60 in the warm environment. Arrhythmias were not altered by exercise time or environment, and no subjects had evidence of myocardial ischemia. The data indicate that although heart rate increased and stroke volume and relative left ventricular end-diastolic volume decreased with exercise time, cardiac output and left ventricular ejection fraction remained unchanged in both thermoneutral and warm environments. The results suggest that there is preserved cardiac function in men with uncomplicated coronary artery disease when performing sustained moderate work in combination with moderate heat stress.

The effect of moderate heat stress on auditory brain stem evoked response in man

1. 1.|The effect of moderate heat load on the auditory brain stem response (ABR) was studied in 13 healthy normal subjects. Heat stress was induced by a combined exposure to heat and physical exercise performed in a climatic room. 2. 2.|Significant latency decreases were observed in the ABR waves III and V as well as in the interpeak latency differences (IPLD), indicative of changes at the midbrain area. Latency of waves V and III as well as IPLD V-I and V-III were highly correlated ( r = 0.73, r = 0.79 and r = 0.54, respectively) with temperature elevation. 3. 3.|The best fitted curve to latency changes induced by moderate heat stress was found to be quadratic. ABR may serve as an objective neurological measure with clinical applications to the study of heat stress.

The effects of moderate heat stress on mental performance : Wyon, D.P., Andersen, I., and Lundqvist, G.R.Scandinavian Journal of Work, Environment and Health, Dec 1979, 5.4, 352–361

The effects of moderate heat stress on mental performance : Wyon, D.P., Andersen, I., and Lundqvist, G.R.Scandinavian Journal of Work, Environment and Health, Dec 1979, 5.4, 352–361

The effects of moderate heat stress on mental performance.

Moderate heat stress is believed to affect mental performance by lowering levels of arousal. Conscious effort can counteract this effect. In most experiments, raised temperatures are perceived at the start by subjects and can act as a stimulus to exert conscious effort. In practice, temperatures usually rise slowly and may therefore have a more marked effect. Thirty-six male and 36 female 17-year-old subjects in standard cotton uniforms (0.7 clo) were exposed in groups of four in a climate chamber to rising air-temperature conditions typical of occupied classrooms, in the range 20--29 degrees C. The maximum rate of rise was 4 degrees C/h. Each group performed mental work during three successive periods of 50 min with 10-min breaks between. During each break the air temperature was reduced by 3 degrees C. Sentence comprehension was significantly reduced by intermediate levels of heat stress in the third hour. A multiplication task was performed significantly more slowly in the heat by male subjects, showing a minimum at 28 degrees C. Recognition memory showed a maximum at 26 degrees C, decreasing significantly at temperatures below and above, and an independent measure of degree of certainty in recall showed a maximum at 27 degrees C. These findings are in accordance with the hypothesis of reduced arousal in moderate heat stress in the absence of conscious effort.

The effects of moderate heat stress on typewriting performance : Wyon, D.P.Ergonomics May 1974, 17.3, 309–318

A re-analysis is given of data from the Report of the New York State Commission on Ventilation (1923). Four climate chamber experiments are examined, in which typewriting performance was studied at air temperatures of 20 and 24°C. Sixteen male subjects worked for five days, seven hours a day, in a balanced design with different temperatures in morning and afternoon. Eight female subjects worked for 10 days under similar conditions. A further 16 male subjects worked for six days in a balanced design with three full days at each temperature, and seven female subjects worked for 10 days with five full days at each temperature. In every half-day of these experiments, during which subjects otherwise were obliged to work very hard, there was a period during which subjects could work at a typewriter if they chose, but were unsupervised and free to converse or rest- Tables of raw data from the typewriting task were published. By using non-parametric statistical methods that were not available at the time of origi...

The retention of cold acclimatization in sheep

SUMMARYShorn Blackface sheep were acclimatized to cold by acute or chronic exposures. Acclimatization caused increased resistance to body cooling (IRC) during acute exposure and elevated heart rates at thermoneutrality (28°C). The length of time these effects were retained during subsequent periods at thermoneutrality was monitored.The effect of moderate heat stress (36°C) on previous cold acclimatization was also measured in Blackface and Merino sheep.Conclusions were:1. IRC resulted from previous exposure to chronic cold or acute cold. IRC induced by chronic cold began to decay after 2 weeks at thermoneutrality. IRC induced by one acute exposure was maximal 2 weeks after exposure and had disappeared by 8 weeks. IRC induced by two acute exposures combined with chronic cold showed little decrease even after 8 weeks at thermoneutrality.2. Merino sheep showed 50% lower initial cold resistance and smaller IRC following acclimatization than equivalent Blackfaces.3. Heat stress for 10 days after cold acclimatization had no effect on IRC in Blackfaces or Merinos.4. Heart rates measured at 28°C were increased by 20 to 50% following acute and chronic cold exposure. After 3 days at thermoneutrality about 70% of the increase remained; but after 8 days almost all the increase had disappeared.5. Two components of cold acclimatization were distinguished:(i) Increased resistance to body cooling probably caused by an enhanced peak metabolic rate capability.(ii) Increased resting metabolic rate evidenced by high heart rates. After the cessation of cold treatment the rates of decay of these two components were different.

The effects of moderate heat stress on typewriting performance.

A re-analysis is given of data from the Report of the New York State Commission on Ventilation (1923). Four climate chamber experiments are examined, in which typewriting performance was studied at air temperatures of 20 and 24°C. Sixteen male subjects worked for five days, seven hours a day, in a balanced design with different temperatures in morning and afternoon. Eight female subjects worked for 10 days under similar conditions. A further 16 male subjects worked for six days in a balanced design with three full days at each temperature, and seven female subjects worked for 10 days with five full days at each temperature. In every half-day of these experiments, during which subjects otherwise were obliged to work very hard, there was a period during which subjects could work at a typewriter if they chose, but were unsupervised and free to converse or rest- Tables of raw data from the typewriting task were published. By using non-parametric statistical methods that were not available at the time of original publication, it is shown that subjects performed considerably and significantly more work at 20° than at 24°C on the typewriting task