Thermoreceptor distribution in different skin layers and its significance for thermoregulation

• 1.1.|The activity pattern of 50 cold receptors of the rabbit nose back skin was investigated.
• 2.2.|The latency of the response of individual cold receptors to identical cold stimuli varied between 0.8 ± 0.3 to 29.4 ± 4.5 s; maximal firing rates are attended after 5.5 ± 0.5 to 72.2 ± 6.2 s. Characteristic phasic responses are only demonstrated by short latency receptors.
• 3.3.|The results suggest that cold receptors are distributed throughout the skin of the rabbit's nose.
• 4.4.|Changes of temperature gradients between different skin layers were measured at different ambient temperatures.
• 5.5.|It is suggested that cold receptors might indicate heat flow through the skin.

     

The effects of ATP and cAMP on the thermal tolerance of the mudpuppy,Necturus maculosus

• 1.1.|Data from previous studies suggest that cellular thermal tolerance depends in part on the availability of high-energy metabolites. To determine if a similar phenomenon is involved in the regulation of thermal tolerance in whole organisms, we treated the mudpuppy, Necturus maculosus, with drugs presumed to elevate or depress hypothalamic levels of either adenosine triphosphate (ATP) or cyclic adenosine monophosphate (cAMP).
• 2.2.|Injections, into the third ventricle, of ATP, cAMP, and theophylline (which elevates endogenous levels of cAMP) elicited dose-related increases in the critical thermal maximum (CTM).
• 3.3.|A dose-related decrease in the CTM resulted when animals were treated with 2-deoxy-D-glucose, a nonmetabolizable glucose analogue.

     

Significance of scrotal afferents within the general thermoafferent system

• 1.1.|Switching neurons, in the past referred to as a special scrotal afferent system, intergrate information not only from the scrotum, but from various body areas.
• 2.2.|They are present in male and female rats, as well as in guinea-pigs.
• 3.3.|They are present in midbrain, thalamus, hypothalamus and cortical areas.
• 4.4.|Information processing from the scrotum, is not a special system, but part of the general thermo-and noci-afferent system.
• 5.5.|Switching neurons seem to interact with behavioral, perhaps with autonomic thermoregulatory mechanisms, too.

     

Populational analysis of thermal responses—I. Changes in the heat resistance of muscle tissue and contractile muscle models of Salamandra salamandra larvae

• 1.1.|Study has been made of the heat resistance of m. rectus superficialis and their contractile models of larvae of 12 families of Salamandra salamandra kept at three different temperatures: 14, 21 (optimal) and 27°C. The heat resistance of the organism has been studied only in larvae kept at 21°C.
• 2.2.|An inverse linear relation has been found between the level of the average heat resistance of muscles for offspring, of the same family, under optimal conditions and its increase caused by a change in environmental temperature. A similar relationship was observed in contractile muscle models. This implies that a population responds to a change in environmental temperature as a function al system.
• 3.3.|The analysis of individual differences in the pattern of response of muscles, and their contractile models, to changes in environmental temperature allows the systemal and individual components to be isolated. The extent of co-ordination in responses of different individuals of the population can be evaluated from the proportion of the systemal component. The value of this component varies from 0.60 to 0.90.
• 4.4.|Selective advantage during thermal selection belongs to individuals with lower heat resistance of muscles.

     

Short-term thermoregulatory adjustments involving opposite regional temperature changes

• 1.1. Experimental evidence is presented that short-term thermoregulatory adjustments occurring not far from thermoneutrality, involve temperature changes that are opposite in sign in different body regions. In man, exposure to hot ambient temperature (T_a), induced a decrease in esophageal and rectal temperatures. In rabbit, exposure to cold T_a induced an increase in hypothalamic temperature.
• 2.2.|Similar results could be obtained by simulation on a mathematical model of man's thermoregulatory system.
• 3.3.|The above results, as well as analogues results described in the literature, can be accounted for by a scheme of interpretation standing on current concepts of thermoregulation. If the gain of the thermoregulatory system is high, thermal stimulation of a region of the body will induce opposite temperature changes in other regions of the body.

     

Phosphorylation in crayfish (Procambarus clarkii) eggs during hatching

• 1.1.|The high-energy phosphorylation metabolism in crayfish, Procambarus clarkii eggs during brooding and juvenile crayfish after hatching was studied by in vivo³¹P nuclear magnetic resonance (³¹P NMR) spectroscopy.
• 2.2.|Inorganic phosphoric acid (Pi) and adenosine-5′-triphosphate ATP(γ-,α-,β-) were detected in the dark brownish red eggs after oviposition.
• 3.3.|In orange unhatched eggs, only sugar phosphate (SP), Pi and resolved phosphometabolite from ATP were observed.
• 4.4.|Peaks of SP, Pi, arginine phosphate (Arg-P), and ATP (γ,α,β) appeared in larvae of crayfish after hatching (nauplius, zoea and juvenile crayfish).
• 5.5.|The high-energy phosphorylation metabolism changed to an anaerobic condition along with a decrease in the concentration of dissolved oxygen in fresh water.

     

Comparison of U-small nuclear RNA levels in tissues of the silkmoth,Bombyx mori

• 1.1. Tissue-specific abundance of the capped small RNAs in the silkmoth Bombyx mori was compared using preparative immunoprecipitation with anti-trimethylguanosine antibody.
• 2.2. The yields of total capped small RNAs from larval posterior silk gland, 1. early, 2. late in the fifth-instar, and 3. immortal ovarian-derived cells in culture, were determined to be 187, 50 and 218 ng, respectively, per mg of total cellular RNA.
• 3.3. Separation of immunoprecipitated RNAs by polycrylamide gel electrophoresis, followed by densitometric analysis of the bands, allowed the quantitation of individual capped molecules.
• 4.4. This analysis revealed tissue-specific patterns.
• 5.5.|The data indicate that the total abundance of capped small RNAs in Bombyx is highest in rapidly-dividing cells.

     

Electromyographic activity during shivering of muscles acting at the human elbow

• 1.1.|Surface electromyograms have been recorded from biceps and triceps brachii during cold induced shivering in normal human subjects.
• 2.2.|Biceps was commonly found to be co-contracting with triceps when the shivering subject was voluntarily producing an extension force at the elbow; when the subject was warm only triceps contracted.
• 3.3.|During shivering the EMG spectra of both biceps and triceps normally showed a pronounced peak in the range 7–12 Hz. The cross-spectrum of the EMGs for the two muscles showed a similar peak, with their linked activity organised reciprocally (i.e. approximately 180 out of phase).

     

Ascaris suum: Influence of embryonation temperature on the viability of the infective larva

• 1.1.|The infective larvae of Ascaris suum develop in the egg between the temperatures 16 ± 1°C and 34 ± 1°C. Within this temperature range, increases in temperature increase the rate of development. The maximum rate of egg development is attained at 31 ± 1°C.
• 2.2.|Eggs embryonated at 28 ± 1°C and above give rise to infective larvae which have less ability to hatch in vitro, shorter longevity when aged in phosphate buffered saline (pH 7.2) at 37°C, and more limited ability to penetrate tissue membranes in vitro, when compared with those larvae from eggs embryonated at lower temperatures.
• 3.3.|Maximum larval viability and ability to penetrate tissues in vitro was achieved when eggs were embryonated at 22 ± 1°C. These results suggest that the optimal temperature for rate of development and larval viability, or survivability are not the same, a point which has not previously been emphasised.
• 4.4.|The practical significance of these results are discussed in relation to the epidemiology of Ascarias and the known biology of the parasite.

     

Diurnal temperature sensitivity of dairy cattle in a naturally cycling environment

• 1.1.|Vaginal temperatures of 15 Bos taurus cattle were monitored for 17 days in daily pens exposed to normal environmental fluctuations.
• 2.2.|Regressions of vaginal temperature on ambient temperature were made for each collection time in the 24 h cycle. Slopes of regressions provided an index of animal sensitivity to environmental temperature.
• 3.3.|Fluctuations in sensitivity occurred throughout the day with positive slopes excepts at 0630 h.

     

A simple technique for estimating operative environmental temperature

• 1.1.|Operative environmental temperature (T_c) is commonly measured using a taxidermic mount consisting of a hollow copper cast of an animal's body covered by the animal's integument. We compare estimates of T_c made using such mounts with those derived from use of painted metal sphere thermometers, which are easier to construct and more rugged than taxidermic mounts.
• 2.2.|Comparison of data for 4 bird species indicates that metal spheres may be acceptable T_c-thermometers for analyses involving multiple measurements over moderately long time-scales (e.g. several hours).
• 3.3.|In this case, positive and negative differences between operative temperature estimated from use of taxidermic mounts and painted spheres tend to compensate and the average difference is usually less than 2°C. This difference is similar to that resulting from postural variation of taxidermic mounts or variation among individual mounts in identical postures.
• 4.4.|Sensitivity analysis indicates that use of painted spheres is unlikely to be an important source of error in estimates of total daily energy expenditure.
• 5.5.|In contrast, use of painted sphere thermometers in analyses involving fewer measurements over shorter-time scales can produce unacceptable discrepancies from values obtained from taxidermic mounts (i.e. up to 6.3°C).

     

Dehydration does not influence the summer versus winter thermal adaptation changes in rabbits (oryctolagus cuniculus), living in natural photoperiod

• 1.1.|Resting metabolic rate of laboratory rabbits kept indoors is susceptible to seasonal fluctuations and is higher in winter than in summer.
• 2.2.|Thermoneutral zone of rabbits under these conditions may shift downwards in winter and upwards in summer.
• 3.3.|Both of these adjustments in thermoregulation seem to be related to the seasonally changing photoperiod.
• 4.4.|Dehydration does not influence these thermoregulatory adaptive changes.

     

Influence of repeated hyperthermia on the early development of carcinogen-induced rat mammary cancers; Refinement of a technique for hyperthermia research

• 1.1.|Hyperthermia (c. 41°C) occurs in mammals (e.g. humans) during normal life-history events such as fever and vigorous exercise. The effects of such episodic hyperthermia on early developmental stages of cancer are of potential importance, yet have been investigated hardly at all.
• 2.2.|We injected female Sprague-Dawley rats with the mammary-gland carcinogen 7,12-dimethylbenzathracene and, over a 4-week period before cancer onset, subjected them to 20 1-h episodes of whole-body hyperthermia (41.2°C colonic) to determine effects on subsequent appearance of carcinomas.
• 3.3.|Hyperthermia did not have significant effects on the development of clinical disease in this system, indicating that precancerous or incipient cancerous cells are not susceptible to damage by the levels of hyperthermia associated with normal life-history events.
• 4.4.|For repeated induction of hyperthermia with minimal confounding effects of stress, we refined a technique in which hyperthermia-treated animals, as well as controls, were anesthetized with sodium pentabarbital during thermal treatments, thus suppressing thermoregulation and higher brain functions.

     

Thermotolerance and thermal sensitization in a differentiating murine erythroleukemia cell line

• 1.1.|Friend erythroleukemia cells (FELC, a differentiating cell line) were heated at various temperatures and heating sequences. Heat treatments which ranged from 41.0 to 45.0°C and did not cause differentiation in FELC and inhibited the differentiation response to DMSO in FELC.
• 2.2.|Heating resulted in cell killing which increased with temperature and heating time. Protracted low temperature heating (40.0–42.0°C) or incubation at 37°C between two heat treatments at 45.0°C resulted in thermotolerance for both the endpoints of cell killing and differentiation.
• 3.3.|High temperature heating (45.0°C) before heating at 41.0–42.0°C resulted in increased thermal sensitivity to the latter heat treatments. This was observed for both the survival and differentiation endpoints.
• 4.4.|A comparison was made of the thermal sensitivity for the two endpoints of cell killing and differentiation.

     

Alteration of 5-hydroxytryptophan-induced hypothermia by serotonergic agents in the adult domestic fowl (Gallus domesticus)

• 1.1.|5-Hydroxytryptophan (5-HTP) induced a dose-dependent hypothermia in adult fowls.
• 2.2.|The hypothermic effect of 5-HTP was potentiated by carbidopa, citalopram, additive with (±), (−) and (+) propanolol and antagonised by methysergide and metitepine.
• 3.3.|Cyproheptadine, xylamidine and ketanserin did not antagonised 5-HTP-induced hypothermia.
• 4.4.|The results suggest that the hypothermic effect of 5-HTP in fowls may be mediated mainly via activation of central 5-HT receptors, probably 5-HT₁ receptors.

     

A two-peak circadian system in body temperature and activity in the domestic cat,Felis catus L.

• 1.1.|The body temperature and activity of cats exhibit two-peak patterns during the 24 hr period.
• 2.2.|The two peaks are retained when the temperature and activity are permitted to freerun.
• 3.3.|A third prominent peak appears in the actograms in cats in the main colony, induced by the presence of humans.

     

Thermal acclimation of metabolism and preferred body temperature in lizards

• 1.1.|The standard metabolic rates (SMRs) and preferred body temperatures (PBTs) of the tropical cordylid Cordylus jonesi and temperature lacertid Lacerta lilfordi were determined following acclimation to constant environmental temperatures of 20 and 30°C.
• 2.2.|Although after 5 weeks the SMRs of Cordylus jonesi and Lacerta lilfordi displayed partial compensations of 20.9 and 10.5%, respectively, their PBTs did not alter over this period. Therefore, acclimation does not maintain complete metabolic homeostasis during either the active or inactive phase of the lizard.
• 3.3.|Cordylus jonesi allowed to thermoregulate behaviourally at their PBT during activity possessed similar SMRs to control animals maintained continually at the same background temperatures, indicating that acclimation state in lizards is determined by the body temperatures experienced while at rest.
• 4.4.|The particular acclimatory problems of animals exhibiting behavioural homeothermy are discussed.

     

Variation in thermally induced melanism in monarch butterflies (Lepidoptera: Nymphalidae) from three North American populations

• 1.As ectotherms, insects often experience varying temperatures throughout their life cycle, and some respond by becoming more or less melanistic (dark coloring) during development to increase or decrease thermal energy absorption as larvae or adults.
• 2.Monarch butterflies (Danaus plexippus) breed in temperate and tropical environments worldwide and are exposed to different average and extreme temperatures in different parts of their geographic range. In this study, we compared variation in thermally induced melanism among monarch butterflies from eastern and western North America and from South Florida.
• 3.We raised the progeny of wild-captured adult butterflies from these populations in a common garden experiment, rearing individuals in cold (19 °C), moderate (26 °C), and hot (32 °C) temperatures to examine population variation in larval and adult pigmentation.
• 4.Across all populations, monarch larvae developed the darkest coloration in the cold treatment and were lightest when reared in hot temperatures. Similar results were observed for measures of adult wing melanism, with the exception of adult females, which developed darker colored wings in warmer temperatures.
• 5.Significant population-level differences in average measures of melanism among larvae and adult butterflies were observed. Larvae from the eastern population became substantially darker in colder temperatures than S. Florida or western larvae. Western larvae were lightest overall, which might be adaptive to high temperatures experienced throughout portions of their summer breeding range. S. Florida larvae showed a lower response to cold temperatures relative to monarchs from either migratory population.
• 6.Population level differences were also observed for thermal responses in wing melanism, particularly among adult females. Moreover, we found significant family level effects for each measure of larval and adult melanism, pointing to a genetic basis or strong maternal effects influencing these traits in monarch butterflies.

     

A model of sensible heat transfer across the boundary layer of animal hair coat

• 1.1.|A mechanistic model that predicts the sensible heat loss through the boundary layer of animal hair coat in relation to the climatic environment and hair coat properties is presented.
• 2.2.|The predicted sensible heat loss is positively related with hair density but is negatively related with depth of hair coat.
• 3.3.|Wind speed is a major determinant of the rate of heat loss across the boundary layer especially at low air temperatures.

     

The temperature of the air within the external auditory meatus compared with esophageal temperature during anaesthesia and surgery

• 1.1.|Air temperature within the external auditory meatus, sensed by a thermistor insulated from the walls of the aural canal, was compared with the temperature recorded from a probe in the esophagus in patients under general anaesthesia.
• 2.2.|In the first study of 14 patients, aural temperatures at the time of induction of anaesthesia were more than 3°C lower, and the changes during surgery were more variable, than those recorded from the esophagus.
• 3.3.|In a second study of 35 patients in which heat loss from the external ear was reduced by ear protectors, there was also a poor correlation between temperatures of the ear and esophagus. Aural temperature was initially lower and rose over time in most cases whereas esophageal temperature generally decreased.
• 4.4.|These results suggest that air temperature within the aural canal is not a useful estimate of deep body temperature since it reflects mainly skin temperature.