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PubMed1989

Free fatty acid availability and temperature regulation in cold water.

The purpose of this study was to investigate whether a reduced availability of plasma free fatty acids (FFA) would impair human temperature regulation during cold exposure. Seven seminude male subjects were immersed on two occasions in 18 degrees C water for 90 min or until their rectal temperature (Tre) decreased to 35.5 degrees C. The immersion occurred after 2 h of intermittent oral ingestion of either nicotinic acid (NIC) or a placebo (PLAC). Plasma FFA levels immediately before the immersion were significantly lower in NIC (87 +/- 15 mumol/l) than in PLAC (655 +/- 116 mumol/l, P less than 0.05). Although FFA levels increased by 73% in NIC during the immersion (P less than 0.05), they remained significantly lower than in PLAC (151 +/- 19 vs. 716 +/- 74 mumol/l, P less than 0.05) throughout the immersion. Muscle glycogen concentrations in the vastus lateralis decreased after cold water immersion in both trials (P less than 0.05), but the rate of glycogen utilization was similar, averaging 1.00 +/- 0.27 mmol glucose unit.kg dry muscle-1.min-1). Plasma glucose levels were significantly reduced after immersion in both trials (P less than 0.05), this decrease being greater in NIC (1.3 +/- 0.2 mmol/l) than in PLAC (0.7 +/- 0.1 mmol/l, P less than 0.05). O2 uptake increased to 3.8 +/- 0.3 times preimmersion values in both trials (P less than 0.05). Mean respiratory exchange ratio (RER) immediately before the immersion was greater in NIC (0.87 +/- 0.02) than in PLAC (0.77 +/- 0.01, P less than 0.05). Cold exposure increased RER in PLAC but not in NIC.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1987

Effect of dermorphin on body temperature in rats.

The effect of dermorphin on regulation of body temperature was studied in the rat under extreme and thermoneutral environmental temperatures and in different nutritional states. Intracerebroventricular (icv) injections of dermorphin at dose levels of 10, 50, 100 ng/rat produced hypothermia in animals placed in cold temperatures (-10 degrees C and +4 degrees C) and hyperthermia at ambient (+22 degrees C) and higher temperatures (+34 degrees C). These data emphasize the importance of using a wide range of environmental temperatures in studying drug effects on thermoregulation. To determine whether the effect of dermorphin on body temperature was related to the nutritional state of the animal, as observed with other neuropeptides (i.e., bombesin, litorin), the thermoregulatory response was followed in fed and fasted rats. The same results were obtained in both experimental groups. In all cases, dermorphin change in body temperature was mediated via an action on typical opioid receptors since it was completely prevented by pretreatment with naloxone.

Analgesics, Opioid↗

PubMed2001

Hypothermia-related deaths--Suffolk County, New York, January 1999-March 2000, and United States, 1979-1998.

Hypothermia is the unintentional lowering of core body temperature to <95 F (<35 C). Core body temperature normally is maintained at 97.7 F (36.5 C). Most hypothermia-related deaths occur during the winter in states that have moderate to severe cold temperatures (e.g., Alaska, Illinois, New York, and Pennsylvania). During 1979-1998, New York had the second highest number of hypothermia-related deaths in the United States. This report presents case reports of four hypothermia-related deaths during January 1999-March 2000 in Suffolk County (1999 population: 1,383,847), the largest county in New York excluding New York City, and summarizes hypothermia-related deaths in the United States during 1979-1998. Such deaths can be prevented by educating health-care providers and the public to identify persons at risk for hypothermia.

Aged↗

PubMed2004

Temperature and the cold pressor test.

UNLABELLED: As a method of experimental pain induction, the cold pressor test is thought to mimic the effects of chronic conditions effectively. A survey of previous studies using the cold pressor, however, revealed a lack of standardization and control of water temperature, questioning comparability and reliability. This study reports the influence of temperature on pain tolerance and intensity by using a commercially available circulating water bath. Twenty-six participants (12 men, 14 women) underwent 4 cold pressor trials with temperature order counterbalanced across 1 degrees C, 3 degrees C, 5 degrees C, and 7 degrees C, temperatures representative of the range used in previous literature. After each cold immersion participants rated pain intensity on a visual analogue scale and the McGill Pain Questionnaire. Tolerance times were recorded for each trial. Significant main effects of temperature were found for tolerance time, with higher temperatures resulting in longer times, and pain intensity, with lower temperatures resulting in higher intensities. Gender differences were found, with men tolerating the stimulus for significantly longer than women. It was concluded that small differences in water temperature have a significant effect on pain intensity and tolerance time. The use of cold pressor equipment that ensures a precise constant temperature of circulating water is necessary to ensure comparable and reliable results. PERSPECTIVE: The cold pressor method of experimental pain induction has been widely used in the evaluation of psychological and physiological pain treatments. This article highlights the need for clear methodologic guidelines for the technique and demonstrates that very minor changes in experimental protocol can produce significant differences.

Adult↗

PubMed1977

Uptake and Growth-promoting Activity of Indoleacetic Acid in Segments of Cold-hardened Wheat Coleoptiles.

Seedings of winter wheat (Triticum aestivum L. cv. Kharkov MC 22) were grown at 24 C (unhardened) and 4 C (hardened). Indoleacetic acid (IAA) was added to excised coleoptile segments after lengthy incubation and their responses were determined by photometric auxanometry at both 25 C and 5 C. The segments' rates of uptake of (14)CIAA were also compared at both temperatures. Cold hardening had no significant effect on the rates of elongation and uptake in a saturating concentration of IAA (2 to 10 muM) at either temperature. Elongation was more sensitive to temperature of measurement than was uptake. At suboptimal concentrations of IAA and 25 C, hardened coleoptiles took up [2-(14)C]-IAA twice as fast but elongated half as fast as unhardened coleoptiles. This and the lack of effect of cold hardening on apparent uptake of [1-(14)C]-IAA raised the possibility that a higher rate of IAA-decarboxylation was coupled with the higher rate of uptake of IAA by hardened coleoptiles. Homeostatic hormonal regulation was also evident in the same endogenous rates of elongation of segments of cold-hardened and unhardened coleoptiles.

Journal Article↗

PubMed2004

Differences of soluble CD40L in sera and plasma: implications on CD40L assay as a marker of thrombotic risk.

INTRODUCTION: Soluble CD40L (sCD40L) ELISA has emerged as a promising predictor of poor outcomes in acute coronary syndrome. Yet many blood processing techniques have been used with little consideration of their effect on the results. METHODS: We measured sCD40L by ELISA in 10 patients with thrombocytopenia and 12 with normal or high platelet counts and 8 healthy controls using three sampling techniques: serum clotted on ice (serum-I) or at room temperature (serum-RT) and platelet poor plasma (PPP). RESULTS: Serum-RT samples, compared to serum-I, gave significantly higher CD40L values (p=0.003), demonstrating that ex vivo sCD40L release by activated platelets is inhibited by cold temperature. Although serum-I and PPP were comparable in patients with normal platelet counts, serum-I gave significantly higher values than PPP in the thrombocytosis group (p=0.01), suggesting that cold inhibition is insufficient in the latter group. To estimate the fraction of sCD40L that was microparticle-bound CD40L (mp-CD40L), 16 samples underwent 0.1-microm filtration. 50.6% of sCD40L was mp-CD40L in serum-RT, whereas 21.3% and 29.9% were observed in serum-I and PPP, respectively. Lastly, plasma sCD40L was assayed in 46 patients with and 35 without thrombosis. Plasma sCD40L did not correlate with platelet count in non-thrombotic, non-inflammatory patients but did (p<0.01) in those with thrombosis. CONCLUSIONS: Sample processing and temperature profoundly affect sCD40L assay. Serum-I and PPP minimize the release of sCD40L ex vivo and better represent sCD40L in vivo. However, PPP may be preferable particularly in patients with thrombocytosis. The existence of mp-CD40L highlights the importance of centrifuge conditions.

Adult↗

PubMed1998

Thermoregulatory responses of the newborn pig during experimentally induced hypothermia and rewarming.

Exposure to a temperature of 14 degrees C was used to induce a progressive hypothermia in fourteen conscious newborn piglets. Heat production, body (rectal) and skin (between the shoulders) temperatures and shivering intensity assessed as the electromyographic activity (EMG) of longissimus thoracis muscle were measured until body temperature reached 30 degrees C and during a recovery period of 2 h at an ambient temperature of 24 degrees C (n = 7) or 34 degrees C (n = 7). During body cooling, heat production increased up to 9.67 +/- 1.28 W (kg BW)-1, but started to decrease below a body temperature threshold of 34.4 +/- 0.7 degrees C. EMG activity increased (P < 0.023) curvilinearly during body cooling; the main increase occurred between body temperatures of 38 and 33 degrees C (+142%, P < 0.001), and changes in EMG activity between 33 and 30 degrees C were not significant (+18%, P > 0.1). A marked increase in circulating levels of glucose (+312%, P < 0.001), glucagon (+76%, P < 0.05), adrenaline (+172%, P < 0.05) and noradrenaline (+113%, P < 0.05) occurred during body cooling. Insulin levels were not detectable at 2 h of life and increased during body cooling. During 2 h of rewarming at 24 degrees C, heat production and EMG activity remained elevated, changes in carbohydrate metabolism were not completely reversed and the final body temperature was only 35.6 +/- 0.9 degrees C. Rewarming of the piglets was faster at 34 degrees C. There was a net influx of heat into the animals and heat production and shivering activity decreased when body temperature reached 33.9 +/- 0.5 degrees C; the final body temperature was 37.5 +/- 0.2 degrees C. Circulating levels of lactate, glucagon and catecholamines returned to control levels. These results show that in conscious piglets exposed to a constant cold temperature there is an inverse relationship between EMG activity and body temperature during moderate hypothermia and that the thermoregulatory response and carbohydrate metabolism of the piglet are seriously impaired below a body temperature of 34 degrees C.

Animals↗

PubMed1987

Thermographic assessment of skin temperature during a cold provocation test.

A description was made of the development and application of infrared thermography and fingertip thermometry for the assessment of finger skin temperature during a cold provocation test. Three hundred and seventeen lumberjacks, grinders, metalworkers, stone cutters, and students were examined in laboratory and field investigations. Under laboratory conditions, the influence of water temperature and exposure duration was studied, and skin temperature measurements were made on the volar and dorsal side of the fingers. In the field occupational health examination, infrared thermography and fingertip thermometry were simultaneously applied during a cold provocation test. The following three types of temperature reaction could be recognized: normal rewarming and moderate delay and strong delay of rewarming. The temperature distribution along the finger length was analyzed. The following conclusions were drawn for practical application of the thermometric methods. Skin temperature must be measured on all 10 fingertips, either on the volar or on the dorsal surface. Fingertip thermometry may be used in occupational health examinations. Infrared thermography may yield more information on the development of disturbances in peripheral circulation along the finger length and may be used in special clinical work.

Adult↗

PubMed2006

Effects of storage temperature on viability, germination and antioxidant metabolism in Ginkgo biloba L. seeds.

The behaviour of the Ginkgo biloba L. seeds was studied during storage at 4 and 25 degrees C. When stored at 25 degrees C, all the seeds died in 6 months. Cold temperatures preserved seed tissue viability for 1 year but did not preserve their capability to germinate, since such capability decreased after 6 months. A significant increase in lipid peroxidation occurred in the seed both in the embryo and in the endosperm. During storage a progressive deterioration of the endosperm tissues was evident. The two major water soluble antioxidants, ascorbate (ASC) and glutathione (GSH), showed different behaviour in the two conditions of storage and in the two main structures of the seed, the embryo and the endosperm. The ASC content of embryos and endosperms remained quite unchanged in the first 9 months at 4 degrees C, then increased. At 25 degrees C a significant decrease in the ASC content in the embryos was evident, whereas it remained more stable in the endosperm. The GSH pool decreased at both storage temperatures in the embryos. As far as the ASC-GSH redox enzymes are concerned, their activities decreased with storage, but changes appeared to be time-dependent more than temperature-dependent, with the exception of the endosperm ascorbate free radical (AFR) reductase (EC 1.6.5.4), the activity of which rapidly decreased at 25 degrees C. Therefore overall the antioxidant enzymes were scarcely regulated and unable to counteract oxidative stress occurring during the long-term storage.

Antioxidants↗

PubMed2000

Remarkably low temperature optima for extracellular enzyme activity from Arctic bacteria and sea ice.

Extracellular degradative enzymes released by psychrophilic marine bacteria (growing optimally at or below 15 degrees C and maximally at 20 degrees C) typically express activity optima at temperatures well above the upper growth limit of the producing strain. In the present study, we investigated whether or not near-zero Arctic environments contain extracellular enzymes with activity optimized to temperatures lower than previously reported. By applying fluorescently tagged substrate analogues to measure leucine-aminopeptidase and chitobiase activity, the occurrence of extracellular enzymatic activity (EEA) with remarkably low temperature optima (15 degrees C) was documented in sea-ice samples. An extremely psychrophilic bacterial isolate, strain 34H, yielded an extract of cell-free protease with activity optimized at 20 degrees C, the lowest optimum yet reported for cell-free EEA from a pure culture. The use of zymogram gels revealed the presence of three proteolytic bands (between 37 and 45 kDa) in the extract and the release of the greatest quantities of the proteases when the strain was grown at -1 degrees C, suggesting a bacterial strategy for counteracting the effects of very cold temperatures on the catalytic efficiency of released enzymes. The detection of unusually cold-adapted EEA in environmental samples has ramifications not only to polar ecosystems and carbon cycling but also to protein evolution, biotechnology and bioremediation.

Acetylglucosaminidase↗

PubMed1994

Interactive effects of temperature and photoperiod on the daily activity and energy metabolism of pouched mice (Saccostomus campestris: Cricetidae) from southern Africa.

The daily activity and energy metabolism of pouched mice (Saccostomus compestris) from two localities in southern Africa was examined following warm (25 degrees C) and cold (10 degrees C) acclimation under long (LD 14:10) and short (LD 10:14) photoperiod. There was no differential effect of photoperiod on the daily activity or metabolism of pouched mice from the two localities examined, which suggests that reported differences in photoresponsivity between these two populations were not the result of differences in daily organisation. Nevertheless, there was a significant increase in metabolism at 10 degrees C, irrespective of photoperiod, even though seven cold-acclimatized animals displayed bouts of spontaneous torpor and saved 16.4-36.2% of their daily energy expenditure. All but one of these bouts occurred under short photoperiod, which suggests that short photoperiod facilitated the expression of torpor and influenced the daily energy metabolism of these individuals. As expected for a nocturnal species, the amount of time spent active increased following acclimation to short photoperiod at 25 degrees C. However, there was a reduction in mean activity levels under short photoperiod at 10 degrees C, possibly because the stimulation of activity by short photoperiod was masked by a reduction in activity during bouts of spontaneous torpor. Cold temperature clearly had an overriding effect on the daily activity and metabolism of this species by necessitating an increase in metabolic heat production and eliciting spontaneous torpor which over-rode the effect of short photoperiod on activity at an ambient temperature of 10 degrees C.

Activity Cycles↗

PubMed2002

Temperature- and surfactant-induced membrane modifications that alter Listeria monocytogenes nisin sensitivity by different mechanisms.

Nisin interacts with target membranes in four sequential steps: binding, insertion, aggregation, and pore formation. Alterations in membrane composition might influence any of these steps. We hypothesized that cold temperatures (10 degrees C) and surfactant (0.1% Tween 20) in the growth medium would influence Listeria monocytogenes membrane lipid composition, membrane fluidity, and, as a result, sensitivity to nisin. Compared to the membranes of cells grown at 30 degrees C, those of L. monocytogenes grown at 10 degrees C had increased amounts of shorter, branched-chain fatty acids, increased fluidity (as measured by fluorescence anisotropy), and increased nisin sensitivity. When 0.1% Tween 20 was included in the medium and the cells were cultured at 30 degrees C, there were complex changes in lipid composition. They did not influence membrane fluidity but nonetheless increased nisin sensitivity. Further investigation found that these cells had an increased ability to bind radioactively labeled nisin. This suggests that the modification of the surfactant-adapted cell membrane increased nisin sensitivity at the binding step and demonstrates that each of the four steps can contribute to nisin sensitivity.

Anti-Bacterial Agents↗

PubMedDate not supplied

Epidemiological studies of acute ozone exposures and mortality.

Many, but not all, observational epidemiological studies of ozone (O(3)) air pollution have yielded significant associations between variations in daily ambient concentrations of this pollutant and a wide range of adverse health outcomes. We evaluate some past epidemiological studies that have assessed the short-term association of O(3) with mortality, and investigate one possible reason for variations in their O(3) effect estimate, i.e., differences in their approaches to the modeling of weather influences on mortality. For all of the total mortality-air pollution time-series studies considered, the combined analysis yielded a relative risk, RR=1.036 per 100-ppb increase in daily 1-h maximum O(3) (95% CI: 1.023-1.050). However, the subset of studies that specified the nonlinear nature of the temperature-mortality association yielded a combined estimate of RR=1.056 per 100 ppb (95% CI: 1.032-1.081). This indicates that past time-series studies using linear temperature-mortality specifications have underpredicted the premature mortality effects of O(3) air pollution. For Detroit, MI, an illustrative analysis of daily total mortality during 1985-1990 also indicated that the model weather specification choice can influence the O(3) health effects estimate. Results were intercompared for alternative weather specifications. Nonlinear specifications of temperature and relative humidity (RH) yielded lower intercorrelations with the O(3) coefficient, and larger O(3) RR estimates, than a base model employing a simple linear spline of hot and cold temperature. We conclude that, unlike for particulate matter (PM) mass, the mortality effect estimates derived by time-series analyses for O(3) can be sensitive to the way that weather is addressed in the model. The same may well also be true for other pollutants with largely temperature-dependent formation mechanisms, such as secondary aerosols. Generally, we find that the O(3)-mortality effect estimate increases in size and statistical significance when the nonlinearity and the humidity interaction of the temperature-health effect association are incorporated into the model weather specification. We recommend that a minimization of the intercorrelations of model coefficients be considered (along with other critical factors such as goodness of fit, autocorrelation, and overdispersion) when specifying such a model, especially when individual coefficients are to be interpreted for risk estimation.

Air Pollutants↗

PubMed2006

A R2R3 type MYB transcription factor is involved in the cold regulation of CBF genes and in acquired freezing tolerance.

Cold temperatures trigger the expression of the CBF family of transcription factors, which in turn activate many downstream genes that confer freezing tolerance to plants. It has been shown previously that the cold regulation of CBF3 involves an upstream bHLH-type transcription factor, ICE1. ICE1 binds to the Myc recognition sequences in the CBF3 promoter. Apart from Myc recognition sequences, CBF promoters also have Myb recognition sequences. We report here that the Arabidopsis MYB15 is involved in cold-regulation of CBF genes and in the development of freezing tolerance. The MYB15 gene transcript is up-regulated by cold stress. The MYB15 protein interacts with ICE1 and binds to Myb recognition sequences in the promoters of CBF genes. Overexpression of MYB15 results in reduced expression of CBF genes whereas its loss-of-function leads to increased expression of CBF genes in the cold. The myb15 mutant plants show increased tolerance to freezing stress whereas its overexpression reduces freezing tolerance. Our results suggest that MYB15 is part of a complex network of transcription factors controlling the expression of CBFs and other genes in response to cold stress.

Acclimatization↗

PubMed1999

Temperature modulation reveals three distinct stages of Wallerian degeneration.

After peripheral nerve transection, axons distal to the cut site rapidly degenerate, a process termed Wallerian degeneration. In wild-type mice the compound action potential (CAP) disappears by 3 d. Previous studies have demonstrated that cold temperatures and lower extracellular calcium ion (Ca2+) concentrations can slow the rate of Wallerian degeneration. We have incubated isolated sciatic nerve segments from wild-type and C57BL/Wld mice (which carry a gene slowing Wallerian degeneration) in vitro at 25 and 37 degrees C. At 25 degrees C we found that the degeneration rate of wild-type axons was slowed dramatically, with the CAP preserved up to 7 d post-transection. In contrast, at 37 degrees C the CAPs were minimal at 2 d. When the temperature of wild-type nerves was raised to 37 degrees C after 24-72 hr at 25 degrees C, degeneration occurred within the subsequent 24 hr. Wld nerves, too, were preserved longer at 25 degrees C but, on return to 37 degrees C, degenerated promptly. Cooling the nerve within 12 hr after axotomy enhanced axonal preservation. Neither wild-type nor Wld nerves showed different degeneration rates when they were incubated with 250 microM or 5 or 10 mM extracellular Ca2+ for 1-2 d, suggesting that an abrupt increase in intracellular Ca2+ occurs at the time of axonal destruction. Wallerian degeneration, thus, appears to progress through three distinct stages. Initiation occurs at the time of injury with subsequent temperature-dependent and -independent phases. Nerves appear to remain intact and are able to exclude Ca2+ from entering until an as yet unknown process finally increases axolemmal permeability.

Animals↗

PubMed2003

Molecular characterization of Brassica napus NAC domain transcriptional activators induced in response to biotic and abiotic stress.

Subtractive expressed sequence tag analysis and screening of cDNA libraries derived from Brassica napus leaves subjected to mechanical wounding, flea beetle feeding or cold temperatures revealed eight genes encoding NAC-domain transcription factors. The genes were found to be differentially regulated in response to biotic and abiotic stresses including wounding, insect feeding, Sclerotinia sclerotiorum infection, cold shock and dehydration. Five BnNAC proteins were orthologous to Arabidopsis thaliana ATAF1 or ATAF2 and gave rise to developmental abnormalities similar to the A. thaliana nam and cuc mutants when expressed ectopically in A. thaliana. Transgenic lines expressing BnNAC14, exhibited large leaves, thickened stems and hyper-developed lateral root systems similar to that observed with A. thaliana NAC1, but also were delayed in bolting and lacked an apical dominant tap root. Several of the BnNAC proteins were capable of activating gene expression in yeast and recognized an element within the CaMV35S promoter. A yeast two-hybrid screen revealed that BnNAC14 interacted with other select BnNAC proteins in vitro and identified an additional BnNAC gene, BnNAC485. The protein interaction and transcriptional activation domains were mapped by deletion analysis.

Amino Acid Sequence↗

PubMed1975

Coding of steady and transient temperatures by cutaneous "cold" fibers serving the hand of monkeys.

Much of the neurophysiological data obtained from rapidly cooled skin surfaces can be related to the mean frequency of discharge in single cold fibers; mean frequency data obtained during steady skin temperatures are less informative. The deterioration of the frequency code during steady temperatures parallels the deterioration in psychophysical measurements of sensations of cold. However, small differences of steady skin temperature alter thermoregulatory responses demonstrating the central availability of detailed information about steady temperatures, even though the mean frequency of the individual cold fiber's adapted discharge lacks this information. Another parameter of the single fiber's response, the temporal arrangement of impulses, provides sufficient information during steady temperatures to account for published data on thermoregulatory responses. Thus the organization of the impulse pattern in cold fibers may constitute an additional code capable of conveying information about steady skin temperature centrally.

Adaptation, Physiological↗

PubMed2006

Ecology of the free-living stages of major trichostrongylid parasites of sheep.

Significant developments over recent decades make it timely to review the ecology of the major gastrointestinal nematode (GIN) species of sheep. These include the relentless development and spread of anthelmintic resistance in all of the major sheep production regions of the world, and the consequent drive towards integrated parasite management (IPM) systems incorporating non-chemotherapeutic strategies such as grazing management. The success of such programs is dependent on a detailed understanding of the environmental influences on the free-living stages of the nematode lifecycle. Major reviews of the subject were conducted prior to 1980, however considerable work has been completed since, including the development of mathematical models describing the epidemiology of GIN infection. Knowledge of the temperature thresholds for free-living development has also improved, while investigations of moisture influences and interactions with temperature have allowed more effective exploitation of environmental effects for IPM. This review re-evaluates our understanding of the factors that determine the success or failure of the free-living phases of the lifecycle in light of these developments. Temperature and moisture are the dominant influences on the free-living stages of Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus colubriformis, with the effects of pasture conditions playing a significant modulating role. Early in the free-living phase, the developmental success of the three GIN species is limited by susceptibility to cold temperatures. In general, H. contortus is most susceptible, followed by T. colubriformis and then T. circumcincta. The length of the development cycle is dependent largely on temperature, with development rate increasing at warmer temperatures. However, in order for development to proceed to the infective larval stage, addition of moisture is generally required. There has been considerably less work quantifying the effects of moisture on free-living development, although it is clear that H. contortus is most susceptible to desiccation during the pre-infective stages. Once the infective stage is reached, the influences of temperature and moisture on survival are less important, resulting in considerable survival times under conditions lethal to pre-infective stages. However, hot, dry conditions can be lethal for infective larvae of all three species, while extreme cold is also lethal with significant species variation. While the existing body of knowledge is substantial, the interpretation of many studies and comparison between them is complicated by inadequate description of, or variation in, the environmental measurements used. Confounding the effects of environmental variables on development to infective stage is the migration of larvae from the faeces and subsequent survival on pasture. There is a need to build on recent efforts to explore interaction between the effects of temperature and moisture, and also the trend to more closely simulate field conditions in laboratory studies. We propose a logical framework for future ecological investigations to overcome some of these problems, facilitate the development of a more integrated dataset on the subject and improve prediction of free-living development.

Animals↗