A. Pyörnilä

Nocturnal hypothermia in fasting Japanese quail: The effect of ambient temperature

Japanese quail were equipped with intraperitoneal transmitters for telemetric measurement of body temperature (Tb) and activity. Food deprivation at + 24 degrees C for four days induced a well-defined nocturnal hypothermic response. The normal day-night difference (about 1 degrees C) in Tb increased 1 degrees C per day, reaching 5 degrees C on the fourth night of fast. Nocturnal motor activity decreased during the fast, while daytime activity first increased and then returned to the original level by the end of the fasting period. A strong correlation between Tb and motor activity was found during scotophase (r = .91) but not during photophase (r = .02). At + 4 degrees C, where food was deprived for two days, the level of hypothermia was not different from that at + 24 degrees C, but birds fasting in the cold reached the hypothermic level more rapidly. In control birds, the decrease in Tb at the beginning of scotophase was independent of ambient temperature. In the combined data, the level of hypothermia correlated strongly with body mass loss (r = .90), which shows that quail can directly or indirectly sense the amount of body energy reserves. This is the first report of hypothermia in a fasting gallinaceous bird. The consistent level of hypothermia at varying ambient temperatures suggests that either nonenergetic costs or phylogenetic constraints prevent deeper hypothermia in cold. Accordingly, the regulation of hypothermia cannot be explained by using only energetic arguments.

The influence of high ambient temperature on thermoregulatory response to intrahypothalamic injections of noradrenaline and serotonin in the pigeon

Abstract1.Pigeons with chronically implanted injection cannula in the hypothalamus were injected with noradrenaline (NA, 10 μg/μl) and 5-hydroxytryptamine (5-HT, 10 μg/μl) at the ambient temperature (Ta) of 38° or 42°C.2.Initial tests at cold (6°C) indicated that birds responded hypothermically to NA and in most instances also to 5-HT.3.Intrahypothalamic injection of NA (10μ/μl) had no appreciable effect on oxygen consumption (VO2), body temperature (Tb), foot temperature (Tf), or heart and respiratory rates at Ta 38°C. The increase of VO2, Tb and Tf noted after similar injection at 42°C was in all probability due to observed excitement and bursts of struggling rather than effects on thermoregulatory mechanisms.4.5-HT (10 μg/μl) injected at Ta 38°C depressed respiratory frequency from panting (600 breaths·min−1) to normal rate (ca. 50·min−1) within 2–4 min. The absence of panting lasted about 10 min, but only a slight increase of VO2, Tb and Tf followed. At Ta 42°C, no notable changes of VO2, Tb and Tf were recorded after 5-HT injection.5.It is concluded that 5-HT has an inhibitory action on neuronal pathway controlling panting activity in the pigeon, but NA seems to be ineffective.

Thermoregulatory effects of peripheral injections of monoamines on the pigeon.

Abstract 1. The effects of peripheral injections of different doses of monoamines were tested in pigeons at different ambient temperatures. 2. It was observed that noradrenaline produced a dose-dependent hypothermia at +6°C and a dose-dependent hyperthermia at +32°C. At the thermoneutral zone of +26°C a slight hyperthermic effect was also seen. 3. Adrenaline also inhibited shivering, lowered oxygen consumption and decreased body temperature at +6°C. 4. Like noradrenaline serotonin also produced either hypothermia at +6°C or hyperthermia at +32°C. 5. The hypothermic effect of norarenaline was totally blocked by phentolamine but not by propranolol. 6. It is suggested that the thermoregulatory effects of peripherally injected monoamines act at thermoregulatory centers in the nervous system.

Do birds possess brown adipose tissue

Abstract 1. 1. Fluorescence and electron microscopy were used to visualize differences between avian adipose tissue (AAT) collected from clavicular and abdominal regions of the great tit, the willow tit, the house sparrow and the Japanese quail, and interscapular brown adipose tissue (BAT) obtained from the Djungarian dwarf hamster. 2. 2. Multilocular fat cells were found in AAT. The prerequisite for multilocularity, however, was not simply winter acclimatization [short photophase 4L:20D and low ambient temperature ( 3. 3. Catecholamine fluorescence was seen only around arteries in the AAT. Signs of sympathetic parenchymal innervation were found neither in winter- nor in cold-acclimated birds, but typically, sympathetic nerve fibers forming a basket-like network around every cell were seen in the brown fat of the hamster. 4. 4. Our results show that AAT in the adult birds resembles white adipose tissue more than brown. Multilocularity of adipocytes may improve lipolysis to deliver fatty acids for muscle fuel of shivering or NST.

Effect of peripheral noradrenaline on thermoregulation in temperature-acclimated pigeon

Abstract 1. Pigeons of either sex were acclimated either to 30°C or to 2°C for 3–4 weeks. 2. It was shown that in a cold environment (+6°C) intramuscularly injected noradrenaline (NA) produced hypothermia, which was significantly more effective in the warm-acclimated than in the cold-acclimated pigeon. 3. In contrast to the above results at the ambient temperature of +32°C NA produced hyperthermia, and it was found that the cold-acclimated pigeon was more sensitive to NA than the warm-acclimated pigeon at this ambient temperature. 4. The reason for this discrepancy in the results is discussed.

Effect of acute temperature stress on the plasma catecholamine, corticosterone and metabolite levels in the pigeon.

Abstract 1. Adult pigeons of both sexes were exposed to either +2°C or +32°C for 5, 15, 30 or 60 min. Furthermore, 2 groups of pigeons were housed at these temperatures for 3 weeks. 2. Acute cold or heat stress produced biphasic changes in the blood NA, A and corticosterone concentrations. Both at cold and heat an immediate rise in A level was seen, but corticosterone level increased only at cold, which was followed by a fall at 30 min. Thereafter the corticosterone levels were recovered and at 60 min even exceeded the initial values. In NA level an immediate and controversial fall both at cold and heat was seen. However, at cold, an unexpected and significant elevation above the pre-exposure level was seen at 30 min. 3. In FFA, glycerol and glucose levels an immediate fall at heat but a controversial elevation at cold was observed. 4. Our findings show that there are increased plasma glycerol, FFA, A and NA levels in cold-acclimated pigeon compared with heat-acclimated pigeon.

Local cutaneous water barrier in cold- and heat-acclimated pigeons (Columba livia) in relation to cutaneous water evaporation

The thermoregulatory function of the skin differs in adult cold‐acclimated and heat‐acclimated rock pigeons (Columba livia). In general, the cutaneous evaporative cooling mechanism is not activated by appropriate stimuli in cold‐acclimated pigeons in contrast to heat‐acclimated pigeons. We studied with electron microscopy whether the differences in the function of the skin are reflected in the structure of the epidermal water barrier of these two extreme acclimation states. The epidermis of cold‐acclimated pigeons is attenuated, and the underlying dermis lacks any intimate vascularization. Both the extracellular and the intracellular domains in the stratum corneum contain organized lamellar lipids. At the stratum transitivum–stratum corneum interface, multigranular body secretion is indicated by the highly convoluted cell membranes and membraneous sacculae enclosing the multigranular bodies. Alternatively, multigranular bodies retain in the corneocytes, and the lipoid material originated from them is reprocessed to broad lamellae. The keratohyalin (KH) granules are spotlike and oriented as cortical bands beneath the plasma membrane. In heat‐acclimated pigeons, the epidermis displays modified patches side by side with basic structural type of epidermis. The modified areas are characterized by hypertrophy and abundance of dermal capillaries adjacent to the hypertrophied patch. No lamellar lipids are discerned in the dilated extracellular space. The structure of multigranular bodies is abnormal, and the numbers of lipid droplets in the outer viable epidermis and stratum corneum are decreased. The transitional cells contain stellate KH granules, which form a network throughout the cell. It is concluded that cold‐acclimated pigeons have a lamellar, extracellular water barrier, the cutaneous water evaporation is minimized, and heat is stored in the body core. Acclimation to heat leads to formation of structurally heterogeneous skin. The structurally modified skin patches show disruption of the barrier‐forming machinery in the multigranular bodies and marked reorganization of fibrillar proteins and electron‐dense KH masses in the transitional layer. Thus water barrier adjustments in cold‐ and heat‐acclimated pigeons manifest the dynamic function of avian skin as a thermoregulatory organ. J. Morphol. 246:118–130, 2000

Effect of adrenergic blocking agents on peripheral noradrenaline induced thermoregulatory responses in the pigeon at heat

Summary1.The hyperthermic effect of intramuscular NA at 32°C was abolished by propranolol but not by phentolamine preinjection.2.The lack of hyperthermic response was at least partly due to the blocking effect of propranolol on beta-receptor mediated increase in heart rate.3.After NA the respiratory rate was gradually increased in birds preinjected either with propranolol or with phentolamine.

Cardiovascular and thermoregulatory responses to vasotocin and angiotensin II in the pigeon.

The cardiovascular and thermoregulatory effects of intrahypothalamically (preoptic/anterior hypothalamus) and intravenously injected arginine vasotocin (AVT) and [Val5]angiotensin II (ANG II) were measured at 2 degrees C in the pigeon (Columba livia). In addition, the effects of intrahypothalamic and intravenous injections of AVT on respiratory rates were measured at 10-15 degrees C. Intrahypothalamic and intravenous AVT (500 ng and 20 micrograms/kg, respectively) reduced shivering and body temperature but had no effects on blood pressure, heart rate or respiratory rate. Intrahypothalamic (500 ng and 1 microgram) and intravenous (3 micrograms/kg) ANG II elevated blood pressure. If the blood pressure increased slowly, the shivering and body temperature also increased, whereas a rapid rise in blood pressure inhibited shivering and lowered body temperature. Intravenous ANG II produced tachycardia but intrahypothalamic ANG II did not affect the heart rate.

Vasotocin and angiotensin II affect thermoregulation in the pigeon, Columba livia

Abstract The effects of intrahypothalamic and intravenous arginine vasotocin (AVT) and [Val 5 ]-angiotensin II (ANG II) on thermoregulation were studied in the pigeon (Columba livia). Peptides were injected into the preoptic/anterior hypothalamus of normally hydrated and dehydrated pigeons at 2 and 32°C, and intravenously in normally hydrated pigeons at 2°C. Intrahypothalamic and intravenous AVT reduced shivering, cloacal body temperature and oxygen consumption at 2°C. At 32°C intrahypothalamic AVT had no effect. Shivering, body temperature, foot skin temperature and oxygen consumption were increased by intrahypothalamic and intravenous injections of ANG II. Dehydration had no effect on the responses to intrahypothalamic AVT and ANG II.