Brain cell RNA: sexual differences in the rat

Sexual differences in the total content of ribosomal RNA, established by cytophotometric measurements in neurones from selected brain regions, were studied in rats of the Wistar strain. In females of reproductive age, cyclic changes of RNA were synchronized with their oestrous cycle, the values being higher in the oestrous phase than in dioestrus. These changes were observed in pyramidal cells of the hippocampus and of the frontal cortex, in cells of anterior thalamus, of ventromedial and lateral hypothalamus and of tuberculi olfactorii. However, cycling cells were not disclosed in septum and thalamus posterior. A dependence upon the actual level of ovarial hormones was found in ventromedial hypothalamic cells only. In general, the RNA values in males of the same age corresponded to values of dioestrous females. The differences between newborn and 7-day-old pups were not marked enough and did not allow to define the critical period responsible for initiation of this sexual difference. In senescent rats, this difference persisted. During the stable phase of long-lasting dioestrus, the total RNA content in cells of the frontal cortex, hippocampus and hypothalamus was higher in females than in males of the same age which may suggest a faster reduction of this substance in aged males. The prolonged influence of oestrogens in the oestrous phase of the climacteric period (preceding the permanent dioestrus) decreased the RNA values in hippocampal and hypothalamic neurones even below the level established during the permanent dioestrus (and thus reached male values). On the contrary, in frontal cortical neurones, the female values remained higher in the permanent dioestrus as well as during long-lasting oestrus. A discussion concerns the possible participation of genetic determination and of the actual state of ovarial hormones in the manifestation of sexual differences in brain cells of the rat.

A simple device for sectioning fresh rat brain

This article describes a simple device that enables sectioning of an unfixed unfrozen fresh rat brain corresponding in position with the de Groote's stereotaxic coordinate systems. The construction of this device allows adjustment of the thickness of the individual brain slices and, thus, facilitates quick and precise removal of whole discrete brain particles or nuclei from a minimal number of slices. Adaptation of this device for other stereotaxic brain atlases is easily possible.

[Incidence and treatment of dermatitis digitalis in dairy cows]

In dairy cows of the Black Pied Lowland, Bohemian Pied breeds and their crossbreds loosely in large cow houses VKK 900 on slatted floors, 24% incidence of dermatitis digitalis was recorded during the period of one year. Relations between the occurrence of this disease, age and efficiency of dairy cows, time of parturition and season of the year were studied. Therapeutical effects of several methods of treatment were evaluated and compared. No effect of age and efficiency of dairy cows, nor of the year season on the occurrence of this disease was observed. A significantly higher occurrence was proved in the period before and after parturition, when 80% of the total occurrence of digitalis dermatitis were diagnosed. During this period, however, the cows were housed in a stable with markedly worse environmental circumstance than those in production stable. 91% cases of dermatitis were diagnosed on the digits of pelvic limbs. Relapses were determined only in five dairy cows. There was no case of the disease occurring in calves reared in the prophylactorium of the calf house. Therapeutical results were best after repeated mass treatment of the digits of dairy cows in 5% formaldehyde baths. The results of this study point at a conclusion that probable pathogens of this disease are specific infection agents, or that there are more synergic pathogens. A significant pre-disposition factor are bad environmental circumstances.

Bioelectrical activity of the rat brain after premature weaning and after RNA administration

Male laboratory rats prematurely weaned on the 15th day of life exhibited in adulthood an increase in seizure susceptibility in the septum, hypothalamus and hippocampus. The resting EEG of these animals exhibited characteristic changes demonstrated in the EEG spectrum power density by shifts in the power of individual frequencies. The administration of RNA to adult prematurely weaned animals affected in all structures under study the seizure susceptibility as well as the resting EEG, having caused in septum and hippocampus the return to values found in normally weaned rats. In hypothalamus the administration of RNA also changed the state given by the premature weaning but the return to normalcy was not complete.

Electrophysiological correlates of the reversed postoptokinetic nystagmus in the rabbit: activity of vestibular and floccular neurons

Unit activity changes accompanying the optokinetic nystagmus (OKN) and reversed postoptokinetic nystagmus (RPN) in the rabbit were examined in 180 vestibular and floccular neurons. After initial charging of the RPN generator by 60-min optokinetic stimulation, a sequence of 1-min optokinetic stimulation (OKN) followed by 1-min darkness (RPN) and 1-min illumination of the stationary optokinetic drum (L), was cycled while corresponding unit activity changes were recorded during 3--5 cycles and evaluated with a computer. About 50% of vestibular neurons (type A) increased their activity during OKN and/or decreased it during RPN with respect to the L period, whereas 24% (type B) reached in a reciprocal manner. The remaining neurons were either unaffected or responded in an atypical way. Most floccular neurons (75%) were activated during ipsilateral optokinetic stimulation, but were not significantly affected by RPN. It is suggested that the neural trace of RPN develops in the vestibular complex and vestibulocerebellum as a part of the process compensating for the effect of continued optokinetic stimulation.

Effect of D-tubocurarine immobilization on the resting electroencephalogram in the rat

The EEG curve and the power spectral density curve recorded from the septum, medial hypothalamus, dorsal hippocampus and frontal cortex of adult male rats kept under free activity conditions were compared with analogous curves from the same animals immobilized by D-tubocurarine and subjected to artificial ventilation. Immobilization caused an increase in the proportion of slow activities (up to 2 c/sec) in the hypothalamus, the septum and the hippocampus and the appearance of a second peak in the theta band in the hypothalamus and hippocampus. A simultaneous decrease in fast frequencies (6-15 c/sec) was observed; all these changes took place in subcortical regions only. The differences in EEG patterns are probably brought about by the effect of immobilization which is suggested to induce appreciable alterations in the stimulus field of the animal.