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A Pyörnilä

Publications and source records attributed to A Pyörnilä.

18 recordsLinked to original sources
PubMed2001

Expression of L-type calcium channels associated with postnatal development of skeletal muscle function in mouse.

Several factors have an influence on the improvement of muscle activity and motor co-ordination of mammals during post-natal development. One of them is voltage sensitive L-type calcium channel function. In striated muscles of adult mammals these channels are located in T-tubule membranes thus linking the on-coming action potential to the molecular process of muscle contraction. The postnatal development of L-type calcium channels is therefore critical not only for contraction but also for all subsequent motor learning. We used high affinity enantiomer of dihydropyridine labelled with a fluorophore in order to show the relative amount of L-type calcium channels by histofluorescence in tissue. We found by qualitative microscopical analysis that the amount of L-type calcium channels increased during the postnatal development in the mouse skeletal muscle (m. rectus femoris and m. gastrocnemius). We also noted variation between different fibre types in the increase of the amount of L-type calcium channels, as judged by the intensity of histofluorescence. We showed by histochemical staining and statistical analysis that the high density of L-type calcium channels in adult muscles is correlated with fast oxidative glycolytic fibre type of striated muscles rather than slow oxidative or fast glycolytic fibres. Based on this finding we propose that the development of L-type calcium channels can be considered as one of the factors determining the different physiological properties of fibre types.

Aging↗
PubMed2000

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.

Acclimatization↗
PubMed1999

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.

Angiotensin II↗
PubMed1991

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.

Animals↗
PubMed1980

The influence of 6-OHDA on hypothermia produced by intrahypothalamically-injected carbachol in the pigeon.

The involvement of the noradrenergic system in hypothermia induced by intrahypothalamically-injected carbachol (CCh) was studied by depleting hypothalamic noradrenaline (NA) with the catecholamine neurotoxin 6-hydroxydopamine (6-OHDA) and repeating the CCh injections after 6-OHDA treatment. The results suggest that noradrenergic neurons may be involved in hypothermia produced by CCh in the pigeon.

Animals↗
PubMed1980

Apomorphine and oxotremorine hypothermia in the pigeon: dopaminergic-cholinergic interaction and the effect of paleostriatal lesions.

The role of central dopaminergic and cholinergic systems and their interaction in avian temperature regulation was studied. Pigeons were injected with apomorphine intrahypothalamically and apomorphine and oxotremorine intramuscularly (i.m.) at 20 degrees C. The injections caused suppression of shivering, a decline in body temperature, and with the i.m. injections most frequently a transient increase in foot temperature. Pretreatment with atropine (i.m.) did not affect hypothermia induced by i.m. apomorphine. Bilateral electrolytic lesions placed in the dopamine and acetylcholinesterase-rich brain region (paleostriatum augmentatum) did not attenuate the responses to i.m. apomorphine and oxotremorine. These results suggest that medial aspects of paleostriatum augmentatum in the pigeon do not contribute to hypothermia induced by dopaminergic and cholinergic stimulation of the brain. They also indicate that no cholinergic link is involved in mechanisms mediating the hypothermic effects of i.m. apomorphine.

Animals↗
PubMed1978

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

1. Pigeons with chronically implanted injection cannula in the hypothalamus were injected with noradrenaline (NA, 10 micrograms/microliter) and 5-hydroxytryptamine (5-HT, 10 micrograms/microliter) at the ambient temperature (Ta) of 38 degrees or 42 degrees C. 2. Initial tests at cold (6 degrees C) indicated that birds responded hypothermically to NA and in most instances also to 5-HT. 3. Intrahypothalamic injection of NA (10 micrograms/microliter) had no appreciable effect on oxygen consumption (VO2), body temperature (Tb), foot temperature (Tf), or heart and respiratory rates at Ta 38 degrees C. The increase of VO2, Tb and Tf noted after similar injection at 42 degrees C was in all probability due to observed excitement and bursts of struggling rather than effects on thermoregulatory mechanisms. 4. 5-HT (10 micrograms/microliter) injected at Ta 38 degrees 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 degrees 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.

Animals↗
PubMed1977

Effect of intrahypothalamic phentolamine on hypothermia produced by peripheral noradrenaline in the pigeon.

1 The effect of intrahypothalamic phentolamine (1 and 1 microliter of a 10 microgram/microliter solution) on hypothermia induced by intramuscular injection of noradrenaline (NA, 2 mg/kg) at different times (2, 10, 20 min) after phentolamine was investigated in pigeons. 2 Administration of phentolamine shortly before NA was shown to attenuate hypothermic responses to NA. 3 It is suggested that the attenuation is due to blockade of central hypothermic effects of intramuscular NA. 4 The mapping of injection sites in the brains was carried out.

Animals↗
PubMed1976

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

1. The hyperthermic effect of intramuscular NA at 32 degrees 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 in heart rate. 3. After NA the respiratory rate was gradually increased in birds preinjected either with propranolol or with phentolamine.

Animals↗