Biomedical subjects

J Sterc

Publications and source records attributed to J Sterc.

At least 19 recordsLinked to original sources

PubMed1998

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.

Aging↗

PubMed1995

Oestrous cycle in septal rat females.

Bilateral lesions of the dorsal part of the septal area were produced in the brain of female rats of Wistar and Long-Evans stocks. The cytogram of their vaginal smears was evaluated repeatedly from the 30th day after surgery and permanent impairment of their oestrous cycle was found. In comparison with intact control females, oestrous phases were detected more frequently whereas dioestrous phases were observed less frequently. The proportions between the individual periods of the oestrous phase (i.e. pro-oestrus, oestrus and metoestrus) were equal in both septal and intact animals. No difference was found between the rat stocks used. Similarly, the previous life history of the rats which had been housed either in a socially impoverished environment (i.e. single cages) or in large communities (colonies) exerted no influence upon the postoperative impairment of the oestrous cycle.

Animals↗

PubMed1994

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.

Animals↗

PubMed1993

Maternal behaviour in septal rat females.

Dorsal lesions of the septum influenced the maternal behaviour of Wistar and Long-Evans females, as well as of their hybrids, in a different way. The phenomenon of infanticide appeared in Wistar females only, whereas mothering was not impaired in others. However, the mouse-killing activity was not enhanced in Wistar females displaying infanticide. On the contrary, they exhibited xenoparental behaviour. If these females had grown up in a species-typical environment, characterized by enriched social stimulation during their critical developmental period, no impairment of maternal behaviour following dorsal septal lesions occurred. The ablation of the whole septum caused a break-down of maternal behaviour with the appearance of infanticide in all females regardless of their stock origin and their individual life history. The specific role of the septum in the control of maternal behaviour is discussed.

Aggression↗

PubMed1985

Interstrain differences in the total RNA content in brain cells of the laboratory rat.

Total content of the ribosomal RNA in the cells of the frontal cerebral cortex (FCC), the septum (S), the dorsal hippocampus (DHI) and the lateral and medial hypothalamus (LHY, MHY) in adult males of the laboratory rat was determined cytophotometrically in two albino strains (i.e. in the Wistar strain (W) and in a strain with spontaneous hypertension (SHR) derived from the former) and in two pigmented strains (i.e. in the Long Evans strain (LE) and in the Brattleboro strain with spontaneous diabetes insipidus (DI) derived from the latter). The used quantitative histochemical method turned out to be very sensitive and demonstrated considerable differences in all brain structures examined. The LE strain showed higher values than the W strain in the FCC, S, DHI and LHY cells and lower ones in the MHY cells. The SHR strain was identical with the W strain from which it originated only in the FCC cells; in the S, DHI, and LHY cells it exhibited higher values, in the MHY cells lower ones. In the DI strain all values agreed with those of its original LE strain in all the areas evaluated except in the S and MHY cells where the values were lower. The data evaluated by stepwise discriminant analysis were found to be exceptional in the W strain. The data for the SHR strain were closer to the LE and DI strains, the data for the LE and DI strains intermingled.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

[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.

Animals↗

PubMed1983

The active avoidance reaction of laboratory rats: differences between experiments carried out in the phase of motor activity and inactivity.

The influence of two phases of the circadian cycle (motor activity and motor inactivity) on the rate of acquisition and extinction of an active avoidance reaction was studied in 35-day-old male laboratory rats reared in cages (with limited social contacts), in young reared from the age of 15 days in communities (with the broad social contacts typical of this species) and in adult males reared in cages. A difference was found between the results of experiments carried out in the morning (during the motor inactivity period) and in the early evening (at the outset of the motor activity period) in both young and adult animals. The factor deciding whether acquisition or extinction was influenced depended on the mode of life. In animals reared in cages, inhibition was influenced; extinction was elaborated faster in the evening in adult animals and juvenile young were capable of 100% extinction only in the evening (in the morning only 50%). Community young achieved 100% extinction in both cases. In young rats which lived in a community from the 15th day, acquisition was influenced (it was achieved faster in the evening). The correlation between the rate of acquisition and extinction in cage-bred adult and young rats was negative if the experiments were carried out in the morning and was positive in evening experiments on young animals. In community-bred young it was positive in both cases.

Animals↗

PubMed1983

Strain differences in avoidance reactions of septal laboratory rats.

The effect of a lesion of the dorsal septum on active and passive type of avoidance reactions of adult male Wistar (W) and Long-Evans (LE) rats was studied. The rate of acquisition and extinction of the reaction was studied by 3 different testing methods. The animals were operated on when juvenile (30 days) or adult (90 days). The experiments were always started 50 days after the operation, when the "rage syndrome" was no longer present. In the three different tests we found a single common variable--the strain factor. It was this that determined whether the operation was effective, as well as the direction of deviations and the operation age which led to manifest changes. In W males the lesion did not impair either the acquisition or the extinction of an active avoidance reaction (AAR); the passive avoidance reaction (PAR) was acquired and extinguished more slowly after a lesion in adulthood. The spontaneous passive avoidance reaction (i.e. preference of a small, dark space) was likewise negatively affected by the operation. In intact LE animals the AAR was extinguished more slowly than in intact W males; after a lesion produced in juvenile or adult age extinction was speeded up, so that there were no differences compared either with intact or with septal W animals. Intact LE rats also acquired a PAR more slowly than W rats; a septal lesion led to faster acquisition, irrespective of the age at which the operation was performed, so that the rate for septal LE rats were the same as for intact W animals. The extinction of this reaction took longer after an operation at juvenile age and the rate for these septal LE rats were the same as for those of septal W individuals operated on at 90 days. The spontaneous PAR was qualitatively poorer in intact LE animals than in intact W rats, since only 40% of them preferred the small, dark space. A lesion was followed by improvement, which was especially marked after operation on the 30th day, when all the animals preferred this space, and in a very short time, so that they were equal to intact W males. Correlation of the acquisition and the extinction rate showed that there was imbalance of excitation and inhibition processes in the AAR of the W controls, that they were balanced in the PAR and that the lesion reversed these relationships. Both processes were balanced in the LE control and a septal lesion did not alter the situation.

Animals↗

PubMed1983

Sex-dependent effect of a dorsal septal lesion on the blood pressure of laboratory rats.

The role of the septum in the regulation of blood pressure was studied in adult female and male laboratory (Alderley Park strain of Wistar) rats allowed a free choice between water and a 0.9% or 3% NaCl solution or simply given water. A lesion was formed in the dorsal septum and 30-66 days afterwards the mean arterial pressure was measured in the unanaesthetized animals' tail. In females the blood pressure was not affected either by the lesion itself, or by the lesion combined with a raised NaCl intake. In males, combination of the lesion with a raised salt intake was accompanied by elevation of the blood pressure, which attained values considered to be hypertensive (over 20 kPa). The increase occurred after 9 days' free choice between water and 3% NaCl solution preceded by 14 days' free choice between water and saline. At the same time, the computed NaCl concentration in the total fluids intake was higher in the control and septal females than in the control and septal males for both the salt regimens. Three days after changing from a free choice regimen to plain water intake, the blood pressure of septal males had fallen to normal values. After a protracted water regimen (43 days after discontinuing free choice), these animals had a lower blood pressure than sham-operated males after the same interval. The determinant variable in the effect of a dorsal septal lesion on the blood pressure in the presence of a hypertensogenic stimulus (NaCl) was the sex of the experimental animals.

Animals↗

PubMed1980

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.

Animals↗

PubMed1980

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.

Animals↗

PubMed1980

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.

Animals↗

PubMed1980