Effect of the epiphysis and hypophysis on the circadian organization of the wakefulness-primary sleep cycle in the frog Rana temporaria

Using continuous non-contact registration of the heart rate and motor activity in unrestrained frogs, studies have been made of the effects of hypophysectomy and epiphysectomy on functional state of the organism. It was shown that removal of the epiphysis alleviates the circadian physiological rhythm of natural changes of functional states in wakefulness-primary sleep cycle, whereas removal of the hypophysis results in additional cyclic rhythm of two functional states in the diurnal periodicity of the behaviour. The latter effect is considered to be the ultradian rhythm, which in the intact animals is masked by the circadian one modulated by natural diurnal illumination. It is suggested that removal of the epiphysis reveals endogenous rhythm of the activity typical of periodic regimes of the spontaneous excitation at early stages of ontogenesis.     

Effect of photostimulation on the wakefulness-sleep cycle in the common frog Rana temporaria

Effect of daily 30-min photostimulation in the 10 s light: 10 s pause (the total of 5 days) on the time structure of the wakefulness--protosleep cycle (WPC) was studied in the common frog Rana temporaria. Changes were analyzed of EEG wave components in three immobility forms of the type of catalepsy (P-1), catatonia (P-2), and cataplexy (P-3) that form protosleep. The first three photostimulations promoted a gradual increase of the P-1 state to 84.16 +/- 11.6% [the initial value (IV) 22.9 +/- 9.1%] and a decrease of representation of wakefulness to 4.86 +/- 2/1% (IV 13.8 +/- 7.8%), of P-2 to 11.1 +/- 5.3 (IV 53.3 +/- 13.3%), and of P-3 to 2.21 +/- 1.0% (IV 11.1 +/- 5.6%). After 4-5 photostimulations and especially after their complete cessation the percentage of P-1 in the WPC was restored to initial values, whereas the percentage of the frog WPC P-3 considered to be a precursor of the homoiothermal sleep rose to 20 +/- 8.3% after 5 photostimulations and to 38.5 +/- 6.7% the next day. Changes in the frog EEG spectra appeared only after one photostimulation and were characterized by a brief increase of power of alpha-like waves and by inhibition of slow 6-waves. In P-2 the power of the slow delta-waves gradually rose. In P-3 the EEG parameters did not change. In all experimental animals a decrease of the relative thymus and adrenal masses was revealed, which indicates the photostimulation regime used in the work induces stress. The obtained data allow thinking that a certain neurohormonal response to stress has already been formed at the amphibian level and that an important role in this response realization is played by a coordinated interaction of the hypothalamic sleep-regulating system providing protosleep manifestations and of the hypothalamic neurosecretory system triggering the stress-reaction hormonal cascade.     

Effect of photostimulation on the wakefulness-sleep cycle in the common frog Rana temporaria

Effect of daily 30-min photostimulation in the 10 s light: 10 s pause regime (the total of 5 days) on the time structure of the wakefulness-protosleep cycle (WPC) was studied in the common frog Rana temporaria. Changes of EEG wave components were analyzed in three immobility forms of the types of catalepsy (P-1), catatonia (P-2), and cataplexy (P-3) that form protosleep. The first three photostimulations promoted a gradual increase of the P-1 state to 84.16 ± 11.6% (the initial value (IV) 22.9 ± 9.1%) and a decrease of representation of wakefulness to 4.86 ± 2.1% (IV 13.8 ± 7.8 %), of P-2 to 11.1 ± 5.3 (IV 53.3 ± 13.3 %), and of P-3 to 2.21 ± 1.0% (IV 11.1 ± 5.6%). After 4–5 photostimulations and especially after their complete cessation the percentage of P1 in the WPC was restored to initial values, whereas the percentage of the frog WPC P-3 considered to be a precursor of the homoiothermal sleep rose to 20 ± 8.3% after 5 photostimulations and to 38.5 ± 6.7% the next day. Changes in the frog EEG spectra appeared only after one photostimulation and were characterized by a brief increase of power of α-like waves and by inhibition of slow δ-waves. In P-2 the power of the slow δ-waves gradually rose. In P-3 the EEG parameters did not change. In all experimental animals a decrease of the relative thymus and adrenal masses was revealed, which indicates the stress nature of the photostimulation regime used in the work. The obtained data allow thinking that a certain neurohormonal response to stress has already been formed at the amphibian level and that an important role in this response realization is played by a coordinated interaction of the hypothalamic sleep-regulating system providing protosleep manifestations and of the hypothalamic neurosecretory system triggering hormonal cascade of the stress-reaction.     

Effect of apomorphine on the wakefulness--sleep cycle of the common frog Rana temporaria

This work considers effects of introduction into spinal lymphatic sac of dopamine agonist--apomorphine-(APO) at doses of 0.1, 1.0, 2.0 and 4.0 mg/kg body weight on the common frog wakefulness-sleep cycle (WSC). Usually the frog WSC is represented by wakefulness and three types of passive-protective behavior: by immobility states of the type of catalepsy, catatonia, and cataplexy that are characterized by high thresholds of arousal and by different (corresponding to the name) skeletal musculature tones. These immoboloty forms are considered as homologues of mammalian stress-reaction, hibernation, and sleep. Low apomorphine doses produced in WSC a marked decrease of portion of wakefulness and an increase of the immoboloty state of the catalepsy; high doses, on the contrary, initially promoted in CNS an increase of wakefulness and the state of catalepsy by demonstrating thereby its stressogenic action; after this, in WSC these increased the portion of the sleep-like immobility state of the catalepsy type that is considered as a functional homologue of sleep of homoiotherms. In spectra of electrograms of the flog telencephalon the representation of waves of the delta diapason rose. Taking into account that the states of catalepsy and cataplexy in frogs are under control of the anterior hypothalamus, it can be suggested that manifestations of cataplexy (sleep) in frog are due to the low level of dopaminergic activity, whereas manifestations of catalepsy (the homologue of stress reaction) are due to the high dopamine content in the anterioi hypothalamic structures. Comparative analysis of changes in WSC of amphibians and mammals in response to administration of dopamine and its agonists allows thinking that the role of the dopaminergic neurotransmitter system in regulation of the vertebrate WSC is unanimous: the low level of activity of this system facilitates development of sleep (catalepsy), whereas the high level provides reaction of arousal and is actively included in the system providing stress-reaction.     

MHC zygosity in the frog,Rana temporaria

The major histocompatibility complex (MHC) zygosity of the field-collected frogs, Rana temporaria, was detected by progeny testing. Groups of sibling tadpoles were grafted with intrafamilial tail-tip allografts and the ratio of rapidly rejected allografts to slowly rejected ones was estimated. Twenty-five percent of parental frogs appeared to be MHC homozygotes. Thus, MHC homozygosity in natural frog populations seems to be considerably higher than in wild mouse populations.     

The hypothalamo-hypophysial system of the frog Rana temporaria

Summary The median eminence (ME) of the adult frog, Rana temporaria, was studied by means of electron microscopy including quantitative electron-microscopic autoradiography. In frogs captured in May and June numerous peptidergic neurosecretory fibres extending via the internal zone to the pars nervosa display large swellings containing few granules, mitochondria, neurotubules and cisternae of the smooth endoplasmic reticulum. In addition, few secretory globules up to 1.5 m in diameter occur in these varicosities. In animals collected during the autumn period many of these neurosecretory swellings filled with neurosecretory granules and polymorphic inclusions resemble Herring bodies. Three types of granule-containing neurosecretory fibres were observed in the external zone (EZ) of the ME of adult R. temporaria. Peptidergic A₁- and A₂-type fibres are characterized by granules 150–220 nm and 100–160 nm in diameter, respectively. Monoaminergic fibres of type B with granules approximately 100 nm in diameter represent 50% of all neurosecretory elements in the EZ of the frog ME; 12% of the total number of granule-bearing axons in the EZ actively taking up radiolabelled 5-hydroxytryptophan are thought to be serotoninergic terminals. Neurosecretory terminals of all types and glial vascular endfeet establish direct contacts with the perivascular space of the primary portal capillaries. Some neurosecretory terminals are separated from the lumen of the third ventricle by a thin cytoplasmic lamella of tanycytes. The possible physiological significance of this structural pattern is discussed.     

Stretch receptors of the lungs in the frog Rana temporaria

In experiments on isolated lungs, studies have been made on the activity of single afferent fibers during simulated expiration and inspiration. Both slowly adapting and rapidly adapting voluminous stretch receptors were found in the frog lungs. The latter type exhibits the activity also during fast simulated expiration. Using acetylcholine and histamine, it was shown that the level of excitability of the receptors investigated depends on functional condition of the plain muscles in the pulmonary wall.     

Genome size variation in the common frog Rana temporaria

Genome size variation in the common frog (Rana temporaria) was investigated with flow cytometry in three latitudinally separated populations in Sweden to see whether it could provide a useful tool for sex-identification in this species. Depending on the sex and population, per cell DNA content (2C value) varied from 8.823 to 11.266 pg with a mean (+/- SE) 2C value of 9.961+/-0.083 pg. Analysis of variance revealed significant differences in genome size among populations and between sexes. Females had ca 3% larger genomes (x=10.133+/-0.068 pg) than males (x=9.832+/-0.068 pg) in all of the populations (sex x population interaction: P>0.10). Individuals from the southern-most population had significantly (x=9.330+/-0.081 pg) smaller genomes than those from the more northern populations (x=10.032+/-0.085 and x=10.584+/-0.085 pg, respectively). These results are in line with the interpretation that males in the common frog are the heterogametic sex, and that there exists large (up to 12%) geographic variation in genome size in this species. However, the sex differences in the genome size are too small to be useful in individual sex identification.     

Role of the pulmonary mechanoreceptor apparatus in molding the natural respiration of the frog Rana temporaria

In acute experiments on the frog Rana temporaria, studies have been made of the effect of afferent impulsation in pulmonary mechanoreceptors on respiration pattern. Simultaneous recordings were made of total afferent activity in the pulmonary branch of the vagal nerve and of the activity of motor respiratory nerves as an index of respiration pattern. It was shown that to the end of ventilation period, the level of afferentation decreases up to a threshold value which favours the onset of inspiration. Artificial decrease of afferentation level by the increase in CO2 content in the lung or by novocain application to the latter always resulted in extra-inspiration. On vagotomized frogs, it was found that maximum level of afferent influences is necessary for the onset of expiration.     

Effect of an inhibitor of serotonin synthesis--para-chlorophenylalanine on the structure of primary sleep in the frog Rana temporaria

On the basis of statistical analysis of the EEG of the forebrain in frogs, new data have been obtained concerning neurophysiological nature of the resting forms of the primary sleep. It was found that natural rest occurring with the increase in the rigid muscle tonue (P-2) is identical to the condition which results from injections of parachlorphenylalanine, an inhibitor of serotonin synthesis. New data were obtained showing participation of the posterior hypothalamus in regulation of one of the resting forms of the primary sleep (P-2). Possible homology of the rest of catatonic type (P-2) and anabiosis of frogs is discussed.     

Possible apical respiration in the olfactory epithelium of the frog Rana temporaria

Bioluminescent analysis has been made of the effect of oxygen supply on the content of ATP in the isolated olfactory epithelium of the frog. It was shown that storage of epithelium preparations in the air increases their ATP content. When preparations are kept in the atmosphere of an inert gas, ATP level in the epithelium rapidly decreases, being recovered after transition of preparations to the air medium. The data obtained indicate the existence of apical type of respiration in the olfactory epithelium of the frog.     

GABA immunoreactivity in the main olfactory bulb of the frog Rana temporaria

Immunoreactivity for gamma-aminobutyric acid (GABA) was localized at the light microscopic level in the main olfactory bulb (MOB) of the frog, Rana temporaria. By means of free-floating peroxidase-antiperoxidase immunocytochemical technique, GABA was found in a large number of neurons in the granular cell layer, in a few small somata in the mitral cell layer and in two different types of cell somata in the glomerular layer. Individual GABA-immunopositive cells were found in the olfactory nerve layer. GABA immunostaining was also localized in cell processes and fiber fragments. There were many immunoreactive puncta in all layers of the MOB. GABA-positive punctate structures often outlined immunonegative cells in the mitral cell and glomerular layers. Rounded tightly packed groups of immunoreactive puncta were found only along ventral border of the glomerular layer. The results are discussed in comparison with data obtained on mammalian MOB in terms of MOB functional organization.     

Ultrastructure of the joint receptors in the frog (Rana temporaria).

The ultrastructure of sensory nerve endings was examined in joint capsules of large limb joints in three adult frogs (Rana temporaria). The joint receptors are represented by the only one kind of sensory nerve endings--by free nerve endings. The unmyelinized preterminal desintegrates into single terminals. This branching is bound on the most peripheral cell of the Schwann cell by means of mesaxons, they pass from the pericaryum of the Schwann cell peripherally. The branches of the nerve terminal are surrounded by a cover of 1...3 cytoplasmatic processes of the Schwann cell. The surface lamella is covered by a distinct basal membrane. Bundles of collagenous fibrils pass along the branches of the nerve terminal. Quite naked nerve endings were not observed. The axoplasma of the nerve terminal contains strikingly few cell organels. Besides axially passing neurofilaments and neurotubules only sporadic mitochondria and clear vesicles were observed. The accumulation of mitochondria, characteristic for the axoplasma of nerve terminals, was observed in no case. Free nerve endings which were found in the joint capsules of the frog belong among so called "free penicillate nerve endings".