Heat Tolerance Tests Research Articles

The Impact of Piriformospora indica on plant heat and drought tolerance

In recent years, the global rise in temperatures has led to drought and heat becoming major environmental stresses that limit plant growth. Previous research has demonstrated the potential of Piriformospora indica in augmenting plant stress resistance. However, specific studies on its effects and underlying mechanisms in cuttings of Rosa chinensis, Jasminum sambac, and Rhododendron simsii Planch are relatively limited. The objective of this study is to explore the effects and mechanisms of P. indica on cuttings and tissue-cultured seedlings of these plants under conditions of drought and high-temperature stress. The experiment involved subjecting P. indica-inoculated and non-inoculated plants to drought (one week without watering) and high-temperature (24-hour exposure to 45°C) stress in a controlled environment chamber. Indicators such as chlorophyll content, chlorophyll fluorescence parameter Fv/Fm, and antioxidant enzyme activity were measured. The results showed that inoculation with P. indica significantly increased the survival rate of the three types of plant cuttings under drought conditions by 13%, 17%, and 16.6% respectively, and resulted in a substantial decrease in malondialdehyde content alongside an increase in chlorophyll content. Under high-temperature stress at 45°C, the chlorophyll fluorescence parameter Fv/Fm values increased by 27.3%, 10.3%, and 51.1% compared to the control group. Furthermore, heat tolerance tests at 42°C showed a 2% higher survival rate in the P. indica inoculated Rhododendron tissue-cultured seedlings than in the control group, with a positive effect observed on the activities of superoxide dismutase and peroxidase. These findings demonstrate that inoculation with P. indica significantly enhances the resistance of Rhododendron, Jasminum sambac, and Rosa to drought and high-temperature stresses, providing insights for sustainable agricultural development and the comprehensive exploitation of the potential value of P. indica.

Sex-Specific Transcriptome Responses in Circulating Immune Cells During Exercise-Heat Stress and Acclimation

Objective: To examine the sex-based differences in heat stress and acclimation we used transcriptomic analysis to test the hypotheses that 1) gene expression varies by biological sex before and after acute heat exposure and 2) circulating immune cell transcriptome responses differ between naïve and acclimated state. Methods: Participants (3F/3M, VO2max >40/45 ml×kg×min−1) completed two heat tolerance tests (HTT), termed HTT1 (120min walking at 1.39 m/s at 2% grade) and HTT2 (~70% vVO2max until rectal temperature (Trec) reached 39.5°C) before and after a 5-day heat acclimation (HA1-5, daily 60min run/jog at Trec 38.5-39.5°C), in a hot environment (40°C, 40%RH). Blood was collected in PAXgene blood RNA tubes PRE and POST HTT1, HTT2, HA1, and HA5 with a recovery (REC) timepoint ~30min after HTT2. Paired end sequencing of ribodepleted total RNA from 84 samples (14 timepoints) was performed on a NovaSeq 6000 (Illumina, Inc., San Diego, CA). All samples passed quality checks with Fastp read trimming retaining 98.2% of reads with a GC content of 49.1%. HISAT2 indexed and mapped an average of 75.9M reads to GrCh38.105. Expression was quantified with htseq-counts, excluding genes with <3 mapped fragments per sample resulting in 26,671 genes. Principal component analysis indicated 36% of variation could be attributed to sex. Differential expression was assessed using DESeq2's generalized linear model, applying a Benjamini-Hochberg correction with an FDR of 0.1 and an adjusted p-value threshold of 0.1. DE genes were analyzed for functional annotation and pathways. Results: In total, we detected 8611 unique DE genes composed of protein coding (6241), lncRNA (1498), and 636 pseudogenes. Males and Females exhibited significant differences in gene expression at baseline, in naïve state (PREHA) with >1555 genes showing sex differences (FDR<0.1). Reactome pathways differing between M and F included cytokine signaling, response, and regulation, cell senescence, cell growth and death, cell cytoskeleton and extracellular structure and innate immunity processes (p<0.05). Interestingly, heat acclimation increased the responsiveness of the transcriptome while reducing the overall magnitude of the response. PREHA HTT2 had 86 DE genes at POST rising to 3170 at REC (vs. PRE, FDR<0.1). While POSTHA HTT2 had 602 DE genes at POST rising to 1236 at REC (vs. PRE, FDR<0.1). GO terms protein serine kinase activity, GTPase binding, and GDP binding were present at PREHA, but absent POSTHA. Conclusion: Acute exercise-heat stress induces marked changes in circulating immune cell transcriptional landscape, while acclimation reduces this response to the same challenge in an adapted state. Sex differences exist and are the subject of ongoing analyses. Funding: DoD BA200299. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Sex Differences In Energy Expenditure, Metabolic Heat, And Substrate Utilization During Exercise-Heat Stress

Purpose: To understand the influence of repeated heat exposures and biological sex on metabolic outcomes surrounding heat acclimation (HA). Based on previous data, we hypothesized that repeated heat exposures would result in higher resting caloric expenditure and exercising metabolic heat production in men (vs. women). Methods: Twenty participants (65% men, 22±3 yrs, 70.1±13.7 kg, VO2max 49.9±6.8 mL·kg −1·min −1) had 8 daily exercise-heat sessions (40°C, 40%rh, at least 60min) including heat tolerance tests (HTT; 120 min, 3.1 mph, 2% grade) on days 1 and 8. Resting energy expenditure (REE) and respiratory exchange ratio (RER) were assessed pre- and post-HTT on days 1 and 8. Metabolic heat production (MHP) and RER were collected during the HTT. Data are presented as mean difference (MD) (95% confidence intervals). For REE and RER, a 2x2 ANOVA compared metrics before HTT vs. after HTT session, pre-HA vs. post HA with sex as a between-subjects factor. For MHP and RER during exercise, a dependent samples t-test compared pre-HA vs. post-HA and independent samples t-test compared sexes pre-HA vs. post-HA. Results: Pre-HA: RER was higher before vs. after the HTT (MD:0.07 (0.05,0.09) A.U., p<0.001) overall with no difference between sexes. REE was not different before vs. after the HTT (p>0.05) overall, but males had higher REE before HTT (MD:564 (291,836) kcal·day −1, p<0.001) and after HTT (MD:666 (395,938) kcal·day −1, p<0.001) than women. Post-HA: RER was higher before vs. after the HTT (MD:0.08 (0.06,0.10) A.U., p<0.001) overall with no difference between sexes. REE was not different before vs. after the HTT (p>0.05), but males had higher REE before (MD:581 (328,834) kcal·day −1, p<0.001) and after HTT (MD:617 (411,823) kcal·day −1, p<0.001) compared to women. Comparing HA Status: RER was not different between HA status before or after the HTT (p>0.05). REE was not different between HA status before the HTT (p>0.05). After HTT, REE was greater pre-HA compared to post-HA (MD:142 (26,259) kcal·day −1, p=0.019). During activity, MHP was greater pre-HA compared to post-HA (MD:14 (-2,31) W/m2, p=0.042); RER was not different (p>0.05). Pre-HA there were no differences in MHP or RER between sexes (p>0.05); post-HA, men had greater MHP than women (MD:36 (3,67) W/m2, p=0.016); there were no sex differences in RER. Conclusion: Men exhibited greater REE than women at each time point under both conditions and men produced more metabolic heat following HA. In response to completing 8 heat exposures as part of a HA protocol, men and women differed in caloric expenditure and MHP, but not in substrate utilization. Thus, our findings provide supporting evidence for sex-specific nutritional recommendations surrounding exercise-heat stress. Funding Source: DoD BA200299. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Anatomical Differences and Physiological Responses of Sunburned Satsuma Mandarin (Citrus unshiu Marc.) Fruits.

Sunburn causes fruit browning and other physiological symptoms, reducing fruit production and quality. Therefore, we aimed to investigate the anatomical differences and abiotic stress responses in ‘Nichinan 1 gou’ satsuma mandarin (Citrus unshiu Marc.) according to the severity of sunburn damage (five grades: control, no sunburn; I to IV, increasing severity of sunburn). Additionally, the quality of sunburned and non-sunburned fruits was compared, and the sunburn-inducing temperature was estimated. Anatomical observations confirmed that with increased severity of symptoms, the damage to fruit rind surface and oil glands was increased. In the analysis of peel pigments, chlorophyll content in the rind gradually decreased compared with IV, whereas the carotenoid content gradually increased up to III. The flavonoid content in the peel and pulp was the highest in III. In the 1,1-diphenyl-2-picrylhydrazyl and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) radical analyses, the IC50 (the concentration of compound at which the percentage of inhibition is 50%) value was the lowest in grade III in peel or IV in pulp, indicating a high free radical scavenging ability. The fruit quality analysis between sunburned and non-sunburned fruits showed differences in total soluble solid content, total acidity, firmness, coloration, and free sugar and organic acid contents, indicating a significant effect on fruit quality. In the heat tolerance tests on fruit rind in the laboratory and field, the damage was confirmed at temperatures above 47 °C.

Effectiveness of skin-heating using a water-perfused suit as passive and post-exercise heat acclimation strategies.

The purpose of the present study was to evaluate the effectiveness of passive and post-exercise heat acclimation strategies through directly heating the skin with a water-perfused suit. Nineteen young males participated in the heat acclimation (HA) protocols for 10 days, which were conducted at an air temperature of 33oC with 60%RH. The exercise-only condition (N=6) conducted 1-h treadmill walking (6km·h-1) followed by 1-h rest. The post-exercise passive-heating condition (N=6) wore the suit (inflow water temperature 44.2oC) for 1-h after 1-h walking. The passive-heating condition (N=7) donned the suit for 2h. Heat tolerance tests (leg immersion in 42oC water for 60min) were conducted before and after the training to evaluate changes due to the 10-day intervention. Reflecting that suit-wearing for 10 days as both passive and post-exercise HA strategies can effectively induce adaptive changes, significant interaction effects appeared in: increase or decrease in mean skin temperature (P<0.05) and elevation in whole-body sweat rate (P<0.05). Reduction in rectal temperature (P<0.05) and blood pressure (P<0.05) were found most prominently in the passive-heating condition. These results indicate that this new method of heat acclimation training, donning a skin-heating water-perfused suit, can generate thermoregulatory benefits. The passive HA intervention could be applied to individuals for whom doing exercise regularly are not feasible.

Exercise Heat Exposure Induced Changes In Genetic Expression Before And After Heat Acclimation In Humans

PURPOSE: To evaluate changes in genetic expression of proteins that are implicated in physiological adaptation to exercise heat exposure (Hypoxia Inducible Factor -1α [HIF-1α], Erythropoietin [EPO], and Vascular Endothelial Growth Factor [VEGF]) during systemic adaptation related to Heat Acclimation (HA) in humans. METHODS: Participants (n=18, 13 males, 5 females: 30 ± 7.34 y; 173.1 ± 7.673 cm; 76.25 ±14.17 kg) underwent two Heat Tolerance Tests (HTT 1 & 2; 120 min walking, 5 km/h, 2.0% grade, 40 °C, 40% rh) with 12-14 days between tests. Participants in experimental group (HA) underwent six heat acclimation days between tests, while the control group (CON) avoided exercise heat exposure between HTT’s. Blood was drawn pre- and post- each HTT and isolated into Peripheral Blood Mononuclear Cells, then further isolated into RNA. Then, cDNA was synthesized for Quantitative Real-Time Polymerase Chain Reaction to quantify gene expression. The data was then analyzed using the ΔΔCT to acquire fold change. RESULTS: No statistical difference in resting rectal temperature was observed before HTT2 in HA (-0.13±0.36 °C) vs. CON (-.08±0.47 °C; P=0.80). No significant changes were observed between HTT1 and HTT2 in the control group for HIF-1α, EPO, or VEGF. However, it was observed that acute EPO fold change increased 10.6x; (P=0.14) from pre- to post- in HTT1 for each group. An increased fold change was also observed in both HIF-1α and EPO between HTT1 and HTT2 (3.24x; P=0.04) & (7.19x; P=0.03) respectively in the HA group. No significant changes in VEGF were found in either group. CONCLUSION: Although the HA protocol utilized in this investigations was not stressful enough to induce observable rectal temperature changes, genetic expression of HIF-1α and EPO was significantly upregulated in response to chronic exercise heat stress. Grant Info: This publication was supported by the Mountain and Plains - Educational Research Center (MAP-ERC) Pilot Grant & the High Plains Intermountain Center for Agricultural Health & Safety (HICAHS) Pilot Grant.

A new occupational heat tolerance test: A feasibility study

Heat tolerance tests identify those susceptible to heat illnesses and monitor heat adaptations. Currently, tolerance tests do not replicate the uncompensable heat strain environments experienced in some occupations. In addition, tests can take up to 2 h to complete, and cannot offer intra and inter individual comparisons, due to the use of a fixed exercise intensity. This study aimed to assess the validity and reliability of a new heat occupational tolerance test (HOTT: 40 min at 6 W kg−1 metabolic heat production, 50 °C 10% RH, in protective clothing) to the standard heat tolerance test (HTT: 2 h walk at 5 km h−1 1% gradient, 40 °C 40% RH, in shorts and t-shirt). Eighteen participants (age: 21 ± 3 yrs, body mass: 81.3 ± 5.9 kg) completed trials to assess the validity and/or reliability of the HOTT. Peak rectal temperature (Tre) displayed strong agreement and low measurement error (0.19 °C) between HTT (38.7 ± 0.4 °C) and HOTT (38.6 ± 0.4 °C). Strong agreement was also displayed for physiological and perceptual measures between the two HOTT trials, including peak Tre (38.5 ± 0.4 °C vs. 38.5 ± 0.4 °C) and peak heart rate (182 ± 20 b min−1 vs. 182 ± 21 b min−1). The HOTT is the first tolerance test that assesses individuals’ responses whilst wearing protective clothing in high temperatures. It can consistently identify individuals’ levels of heat tolerance within a reduced time frame. In addition, it allows for participant monitoring over time and comparisons between individuals to be made. A continuum based approach is recommended when assessing individuals’ responses to the HOTT.

Adaptation strategies of yak to seasonally driven environmental temperatures in its natural habitat.

The gradual increase of ambient temperature (TA) at high altitude can cause heat stress as an effect of climate change and may shift the traditional habitat of yak to further higher altitude. Therefore, an attempt has been made in this study to evaluate the thermo-adaptability of yaks to different seasons at high altitude. The adaptive capabilities of yaks were assessed based on different heat tolerance tests in relation to changes in rectal temperature (RT; °F), respiration rate (RR; breaths/min), pulse rate (PR; beats/min), and plasma heat shock protein (HSP) profile. The experiment was conducted in 24 yaks, divided into three groups based on age as calf (n = 8), adult (n = 8), and lactating cow (n = 8). Thermal adaptability was determined by temperature humidity index (THI), dairy search index (DSI), and Benezra's thermal comfort index (BTCI) along with HSP70 profile. The THI was higher (P < 0.01) in summer than winter which increased from lowest (40.87) to highest (61.03) in summer by 20 points, where yaks were under heat load beyond THI 52. The RT (100.09 ± 0.18°F), RR (21.76 ± 0.18), and PR (59.78 ± 0.32) increased by 23-35%, and this was correlated to the higher values of DSI exceeding 1 in calves (1.35 ± 0.03), lactating cows (1.29 ± 0.04), and adults (1.23 ± 0.32) during summer in comparison to winter (0.98 ± 0.02). The BTCI also showed values greater (P < 0.01) than 2 in calves (3.47 ± 0.27), lactating cows (3.23 ± 0.28), and adults (2.98 ± 0.29) which reflected 49-75% increase in rectal temperature and respiration rate during summer. Further, heat stress was substantiated by threefold higher (P < 0.01) level of plasma HSP70 in calves (189.61 ± 3.90pg/ml) followed by lactating cows (168.62 ± 3.03pg/ml) and adults (155.33 ± 2.30pg/ml) against the winter average of 87.92 ± 3.19pg/ml. Present results revealed that yaks were experiencing heat stress in summer at an altitude of 3000m above sea level and calves were more prone to heat stress followed by lactating cows and adults.

Impact of the Naval Health Research Center's heat tolerance testing within the U.S. Navy

Introduction: The Naval Health Researcher Center (NHRC) has conducted 145 Heat Tolerance Tests (HTTs) on Naval Special Warfare (NSW) personnel consisting of Basic Underwater Demolition/SEAL (Sea, Air Land) students, Special Warfare Combatant-Craft crewmen, SEALs, and non-specific NSW personnel. The purpose of this work is to provide insight into the reproducibility of the HTT and the importance of a plateauing Core Temperature (Tcore) during the test, along with the economic and operational readiness impact of the HTT.

Study on environmental indices and heat tolerance tests in hair sheep.

The ability to predict the effects of climatic factors on animals and their adaptability is important for livestock production. The aim of the present study was to analyze whether existing indices are suitable for evaluating heat stress in Santa Ines and Morada Nova sheep, which are locally adapted hair sheep breeds from northeastern Brazil, and if the limits used to classify thermal stress are suitable for these breeds. Therefore, climatic, physiological, and physical parameters, as well as thermographic images, were collected in 26 sheep, 1 1/2years old, from two genetic groups (Santa Ines 12 males and 4 females; Morada Nov. 7 males and 3 females) for 3days in both morning (4:00 a.m.) and afternoon (2:00 p.m.) with six repetitions, totalizing 156 repetitions. Statistical analysis included correlations and broken-line regressions. Iberia and Benezra indices were the tolerance tests that best correlated with the assessed parameters. High correlations between environmental indices and rectal or skin surface temperatures was observed, which indicates that these indices can be used for Santa Ines and Morada Nova sheep raised in central Brazil. However, some indicative values of thermal discomfort are different from the existing classification. Therefore, in order to classify appropriately, the model used needs to be carefully studied, because these classifying values can vary according to the species and model. Further research is necessary to establish indicators of thermal stress for sheep breeds raised in the region.

Drought affects the heat-hardening capacity of alpine plants as indicated by changes in xanthophyll cycle pigments, singlet oxygen scavenging, α-tocopherol and plant hormones

Alpine environments in Europe are increasingly affected by more erratic precipitation patterns, and more frequent drought and heat waves. Heat-hardening capacity is a key feature for survival of these abiotic stress factors, but it is poorly understood how heat and drought affect plant performance when combined. The main objectives of this study were (1) to determine maximum heat hardening capacity in 14 selected plant species and (2) to study how alpine plants respond to combined heat and drought stress compared to heat alone. (3) For risk assessment maximum leaf temperatures were measured in the field and (4) important methodological aspects of testing heat tolerance were evaluated. Heat hardening capacity was assessed by Tc, the heat threshold of photosystem II (PS II), and by heat tolerance tests based on visual inspection of leaf tissue damage or potential quantum efficiency of PS II (Fv/Fm). A purpose-built Heat Tolerance Testing System (HTTS) was used, which allows for controlled heat exposure of whole plants under nearly natural conditions. Additionally, in two species from contrasting habitats, Senecio incanus and Primula minima, the dynamics of heat hardening was studied during and after 8days exposure to heat (H), or to a combination of heat and severe drought (H+D) within a light-transmissive heat hardening chamber at the alpine field site. In both species, H treatment significantly increased heat tolerance (LT50), determined by the HTTS, to 58.0°C and 54.9°C, respectively, and was accompanied by elevated production of abscisic acid (ABA) and salicylic acid (SA), whereas jasmonic acid (JA) levels decreased. Under H+D the LT50 was only 56.5°C and 51.6°C, respectively, and levels of ABA were higher in S. incanus and SA lower in both species in comparison to H. Changes in xanthophyll cycle pigments, α-tocopherol and carotenoids:chlorophyll ratio were more pronounced in P. minima than in S. incanus. In P. minima both H and H+D significantly increased singlet oxygen (1O2) scavenging capacity, determined by electron paramagnetic resonance spectroscopy (EPR). In the field, the maximum half-hourly mean (HHM) leaf temperature of P. minima (32.2°C) was significantly lower than of S. incanus (46.5°C, a potentially harmful temperature). We conclude that the investigated species are well adapted to the prevailing temperature conditions in the field. They also possess an outstanding heat hardening capacity, but this can be curtailed when heat is combined with drought. As drought further increases leaf temperatures, the risk of suffering lethal heat damage of some species may increase in the future, particularly at south exposed, ruderal alpine sites with uncertain water supply.

Physiological Strain Index (PSI) May be Used to Classify Level of Strain During a Heat Tolerance Test

The physiological strain index (PSI) is a simple 0 to 10 scale that utilizes cardiovascular and thermoregulatory parameters to calculate a PSI score, which can quickly be used to assess levels of physiological strain during exercise in the heat. Heat tolerance tests (HTTs) typically use these same cardiovascular and thermoregulatory parameters to determine heat tolerance of an individual, yet no data has been presented showing expected PSI scores of passed and failed HTTs. PURPOSE: To present PSI scores associated with passed and failed HTTs. METHODS: Eighty-two military personnel (mean ± SD age: 25 ± 3.9 years, height: 178.8 ± 8.1 cm, weight: 85.2 ± 9.9 kg) completed NHRC’s HTT with 63 passed and 19 failed tests. Of these 82 individuals, 50 had a prior documented heat stroke and 32 had no prior heat injury. NHRC’s HTT consists of 120 minutes of treadmill walking at 3.3 mph and 4% grade in 40° C and 40% RH. A failed HTT occurs if rectal temperature (Tre) exceeds 38.6°C or heart rate (HR) exceeds 160 bpm during the 120 minutes. End of test (EOT) PSI scores were calculated for each test and then compared based on passed versus failed HTTs. RESULTS: The mean ± SD EOT PSI scores for those that passed and failed were 4.0 ± 1.2 and 6.5 ± 0.8, respectively. As expected, PSI scores for those that passed were significantly lower than for those that failed (p < 0.001). Of those that passed, 19% were categorized as no/little strain (PSI 0-2), 55% were categorized as low strain (PSI 3-4), 24% were categorized as moderate strain (PSI 5-6), and 2% were categorized as high strain (PSI 7-8). Of the individuals that failed, 56% were categorized as moderate strain, while 44% were categorized as high strain. CONCLUSION: Our results suggest that individuals with the thermoregulatory capacity to pass a HTT will exhibit much lower PSI scores than those that fail a HTT. When assessing heat tolerance, it appears that individuals who pass the HTT would be expected to complete the HTT with a PSI score in the low to moderate range, indicating a moderate level of thermal strain.

The effect of 10 days of heat acclimation on exercise performance in acute hypobaric hypoxia (4350 m)

ABSTRACTTo examine the effect (“cross-tolerance”) of heat acclimation (HA) on exercise performance upon exposure to acute hypobaric hypoxia (4350 m). Eight male cyclists residing at 1600 m performed tests of maximal aerobic capacity (VO2max) at 1600 m and 4350 m, a 16 km time-trial at 4350 m, and a heat tolerance test at 1600 m before and after 10 d HA at 40°C, 20% RH. Resting blood samples were obtained pre-and post- HA to estimate changes in plasma volume (ΔPV). Successful HA was indicated by significantly lower exercise heart rate and rectal temperature on day 10 vs. day 1 of HA and during the heat tolerance tests. Heat acclimation caused a 1.9% ΔPV, however VO2max was not significantly different at 1600 m or 4350 m. Time-trial cycling performance improved 28 sec after HA (p = 0.07), suggesting a possible benefit for exercise performance at acute altitude and that cross-tolerance between these variables may exist in humans. These findings do not clearly support the use of HA to improve exercise capacity and performance upon acute hypobaric hypoxia, however they do indicate that HA is not detrimental to either exercise capacity or performance.

An in vitro study of antifungal drug susceptibility of Candida species isolated from human immunodeficiency virus seropositive and human immunodeficiency virus seronegative individuals in Lucknow population Uttar Pradesh.

Background:Candidiasis is the most common opportunistic infection in human immunodeficiency virus (HIV) seropositive patients, starting from asymptomatic colonization to pathogenic forms and gradual colonization of non-albicans in patients with advanced immunosuppression leads to resistance for azole group of antifungal drugs with high rate of morbidity and mortality.Objectives:To isolate the Candida species and determine of antifungal drug susceptibility against fluconazole, itraconazole, nystatin, amphotericin B, and clotrimazolein HIV seropositive and control individuals, with or without clinical oropharyngeal candidiasis (OPC).Materials and Methods:Includes samples from faucial region of 70 subjects with and without clinical candidiasis in HIV seropositive and controls were aseptically inoculated onto Sabaraud's Dextrose Agar media and yeasts were identified for the specific species by Corn Meal Agar, sugar fermentation and heat tolerance tests. Antifungal drug susceptibility of the isolated species was done against above-mentioned drugs by E-test and disc diffusion method.Results:The commonly isolated species in HIV seropositive and controls were Candida albicans, Candida glabrata and Candida tropicalis Candida guilliermondii and Candida dubliniensis isolated only in HIV seropositive patients. Susceptibility against selected antifungal drugs was observed more in HIV-negative individuals whereas susceptible dose-dependent and resistance were predominant in HIV-positive patients.Conclusion:Resistance is the major problem in the therapy of OPC, especially in HIV seropositive patients due to aggressive and prolonged use of antifungal agents, therefore, our study emphasizes the need for antifungal drug susceptibility testing whenever antifungal treatment is desired, especially in HIV-infected subjects.

Light-stimulated heat tolerance in leaves of two neotropical tree species, Ficus insipida and Calophyllum longifolium

Previous heat tolerance tests of higher plants have been mostly performed with darkened leaves. However, under natural conditions, high leaf temperatures usually occur during periods of high solar radiation. In this study, we demonstrate small but significant increases in the heat tolerance of illuminated leaves. Leaf disks of mature sun leaves from two neotropical tree species, Ficus insipida Willd. and Calophyllum longifolium Willd., were subjected to 15min of heat treatment in the light (500µmol photons m-2s-1) and in the dark. Tissue temperatures were controlled by floating the disks on the surface of a water bath. PSII activity was determined 24h and 48h after heating using chlorophyll a fluorescence. Permanent tissue damage was assessed visually during long-term storage of leaf sections under dim light. In comparison to heat treatments in the dark, the critical temperature (T50) causing a 50% decline of the fluorescence ratio Fv/Fm was increased by ~1°C (from ~52.5°C to ~53.5°C) in the light. Moreover, illumination reduced the decline of Fv/Fm as temperatures approached T50. Visible tissue damage was reduced following heat treatment in the light. Experiments with attached leaves of seedlings exposed to increasing temperatures in a gas exchange cuvette also showed a positive effect of light on heat tolerance.

Heat- and cold-shock responses in Fusarium graminearum 3 acetyl- and 15 acetyl-deoxynivalenol chemotypes

Fusarium graminearum Schwabe is the primary cause of Fusarium head blight (FHB) in North America. Chemically distinct F. graminearum sub-populations can be identified based on the type or composition of deoxynivalenol (DON) mycotoxin derivatives, including 3-acetyl (3-ADON) and 15-acetyl (15-ADON). The evaluation of randomly selected 3-ADON and 15-ADON isolates, collected from spring wheat throughout Canada, was performed using thin layer chromatography (TLC), high-performance liquid chromatography (HPLC), ice-nucleation activity (INA), and heat and cold tolerance tests conducted within a temperature range of -70°C to 65°C. The results indicated that the 3-ADON sub-population, which is responsible for the highest disease severity and has rapidly displaced the 15-ADON sub-population, produces more DON and zearalenone (ZEA) than the 15-ADON sub-population when exposed to heat and cold. Following exposures (1 and 2 h) to extremely high or low temperatures, 3-ADON isolates exhibited faster mycelial growth than 15-ADON isolates. In addition, the warmest temperature at which INA activity occurred was in 3-ADON (-3.6°C) vs. 15-ADON (-5.1°C). Taken together, these features suggest that the newly emerging 3-ADON sub-population is more resilient than the resident 15-ADON sub-population. Overall, the differences between the two sub-populations could provide new insights into FHB epidemiology and if validated under field conditions, may provide important information for predicting future FHB epidemics.

Heat Tolerance in Women—Reconsidering the Criteria

Exertional heat stroke (EHS) is the most dangerous heat-related injury. EHS may be followed by a state of heat intolerance. The Israeli Defense Forces (IDF) performs heat tolerance tests (HTT) to all heat injury victims 6-8 wk following injury as part of the "return to duty" process. The HTT protocol and normal values are based on vast experience with young healthy men. Over the last several years an increasing number of female soldiers have been joining combat units. Heat injuries and, thus, HTT among women have become more frequent. Due to potential gender-related physiological and thermoregulatory differences, we examined the necessity for validating the HTT protocol for women. Retrospective physiological data from our database on heat injuries and HTT between the years 2008-2010 was compared between 9 female subjects and 170 male subjects who had similar background characteristics. Defining heat intolerance as peak rectal temperature > 38.5 degrees C, peak heart rate > 150 bpm, or the inability to reach equilibrium in these values, we diagnosed 67% of the female subjects as heat intolerant. In the male subjects, only 26% were diagnosed as heat intolerant using the same criteria. Using the standard HTT criteria, women are more frequently diagnosed as heat intolerant than men. Further studies should be performed in order to re-evaluate the normal values for a "female HTT" in order to optimize the process of safe return to duty of female heat injury victims and to minimize false positive results among female soldiers.

혈압 관리를 위한 4주간의 착의훈련이 고혈압 전단계자의 내열성에 미치는 영향

This study was performed on 5 prehypertensive male participants to investigate the effects of the clothing program for improving the vascular compliance on heat tolerance. The clothing program means the alternate stimulation of the temperature using clothes. The participants wore two different garments with <TEX>$1.5^{\circ}C$</TEX> difference in the temperature inside clothing in a climatic chamber (<TEX>$18.8{\pm}0.2^{\circ}C$</TEX>, <TEX>$38{\pm}3%RH$</TEX>) alternately for 4 weeks. Heat tolerance tests were conducted in the climatic chamber of <TEX>$35.2{\pm}0.5^{\circ}C$</TEX>, <TEX>$54{\pm}3%RH$</TEX> before and after the clothing program. The results were as follows. The <TEX>$\overline{T}$</TEX>sk, Tr and heart rate were lower in the post test than in the pre test (p<.01). The whole body and local sweat rates as well as systolic and diastolic blood pressures had reduced the tendencies in the post test. Participants felt less wet and more comfortable in the post test than in the pre test(p<.01). These results showed that the clothing program through the alternate stimulation of the temperature positively affected the improvement of heat tolerance.

Comparative evaluation of the analgesic efficacy of ibuprofen, dextropropoxyphene, and their combination in healthy volunteers

Nine healthy male volunteers received ibuprofen 400 mg + dextropropoxyphene 65 mg, ibuprofen 400 mg alone, and dextropropoxyphene 65 mg alone in a three-way crossover study, using a Latin-square, complete-block multiple group design. Pain threshold was measured by using the ischemic pain and radiant heat tolerance tests. The volunteers underwent both tests before drug therapy and periodically for up to 5 hours after drug administration. The ischemic pain tolerance test was administered at baseline, at drug dosing, and at 30, 60, 90, 120, 150, 180, 210, 240, 300, 330, 360 minutes after drug therapy. The radiant heat tolerance test was performed at baseline, at drug dosing, and at 45, 75, 105, 135, 165, 195, 225, 285, 315, 345, 375 minutes after drug therapy. In both tests, the fixed-dose combination of ibuprofen 400 mg + dextropropoxyphene 65 mg showed a significantly ( P < 0.05) larger area under the curve than either ibuprofen 400 mg or dextropropoxyphene 65 mg alone. These results suggest that the two drugs have a synergistic effect and confirm that the combination of ibuprofen 400 mg + dextropropoxyphene 65 mg is superior to the individual drugs used alone.

Screening Soybean Genotypes for Drought and Heat Tolerance

AbstractSeveral soybean [Glycine max (L.) Merr.] germplasms from maturity groups III through VII were evaluated at three osmotic potential levels (‐0.017, 0.3 and ‐0.5 MPa) using polyethylene glycol M.W. 8000 and four temperature regimes (10, 25, 50 and 110°C) for drought and heat tolerance, respectively. Heat injury varied significantly among growth stages with the highest heat injury occurring at the flowering stage. Susceptibility to heat injury decreased toward maturity with the exception of a few genotypes. Genotypic variability was found among the lines in both drought and heat tolerance tests. This study identified the lines PI 408.155, PI 423.827B, PI 423.759 and Pershing as both drought and heat tolerant. In general, the larger‐seeded lines failed to germinate at ‐0.50 MPa. A positive and significant relationship between promptness index and germina‐tion stress index was found. However, no significant correlation was observed between germination stress index and the heat tolerance test. Based on the results from the germination test, lines PI 393.550, PI393.547, PI 86.103, PI 171.437, PI 86.490 and PI 423.852 had high germination stress indices and need further testing for heat stress tolerance.