Induction of cerebellar hsp72 in rats learning a two-way active avoidance task.

The involvement of brain heat shock proteins in learning was examined by Western analyses in rats trained for an active avoidance task, and in passive and active controls. Expression of the constitutive hsp73 was intense in brain, liver, and kidney of all rats. Conversely, expression of the inducible hsp72 occurred in the cerebellum of most trained rats, but not in passive or active controls. Significant correlations were present between avoidances and cerebellar scores determined 8 h after training. Induction of hsp72 may therefore be attributed to learning in the cerebellum, while in other brain regions, liver and kidney stress-related stimuli may play a prevalent role.

Post-trial sleep in old rats trained for a two-way active avoidance task.

Nine male Wistar rats aged 27 months were trained for a two-way active avoidance task and tested for retention the following day. At variance with young adult rats, most of which succeed in mastering the task, all old rats displayed a large majority of freezing responses throughout the training and the retention sessions, thereby confirming the condition of learning impairment of aged rats. Comparison of baseline and post-trial sleep indicated the presence of a transient, but marked, increment in the average duration and total amount of post-trial slow-wave sleep followed by waking, and of a decrease in total amount of quiet waking. On the other hand, variables of paradoxical sleep and of slow-wave sleep followed by paradoxical sleep or by transition sleep did not show significant variations. Because these sleep variables are known to undergo significant variations in learning in young adult rats, the present data confirm that the latter effects are related to memory-processing events rather than to nonspecific effects of training. An additional outcome of training consisted in a marked post-trial decrement in the number of spike-wave discharges, which are known to occur in old rats during periods of quiet waking.

Response variability to ischemic injury in the Mongolian gerbil: an electroencephalographic and behavioral study.

The early effects of 5 or 10 min global cerebral ischemia, sham operation and halothane anesthesia were evaluated in Mongolian gerbils by means of electroencephalography (EEG), neurological examination and passive avoidance training. The "ischemia-sensitive" gerbils (33% and 64% of the 5 and 10 min ischemic groups, respectively) died during carotid ligation or within 24 h; the "ischemia-resistant" gerbils showed variable behavioral responses. Six hours after ischemia, all of the animals presented EEG activity characterized by increased delta (1-4 Hz) activity and a decreased theta 2 (6-9 Hz) band, with a tendency to recovery at 24 h. Learning impairment was observed in 5 of the 5 min ischemic animals (83%) and in 1 sham (17%) and 1 halothane (17%) control. Fourteen days after ischemia, histologic damage was observed in 4 ischemic gerbils and 1 sham control. On the whole, this study confirms the widely variable susceptibility of gerbils to cerebral ischemia. Moreover, although the variable effects of carotid occlusion have been attributed to multiple factors involving the cerebrovascular system, our data suggest that endogenous cellular mechanisms might protect against ischemia. In view of this consideration, it would be useful to investigate the molecular causes of the variable cerebral ischemic tolerance shown by Mongolian gerbils.

Sequential hypothesis of sleep function. V. Lengthening of post-trial SS episodes in reminiscent rats.

Rats failing to learn a two-way active avoidance task during the training session were tested for performance the following day. One group of rats maintained its low level of avoidances (non improving or NI rats), while the remaining rats dramatically improved their avoidance score (improving or I rats). EEG recording during the posttrial period demonstrated significant variations in the sleep structure of I rats, in comparison with NI rats. The main change consisted in an increase in the average duration of the episodes of slow wave sleep followed by wakefulness or by paradoxical sleep. These variations occurred in the third hour of the posttrial period, while an increment in the amount of PS was observed in the sixth hour. In I rats, but not in NI rats, comparable variations emerged from the comparison of baseline sleep (determined the day before training) with posttrial sleep. The data are in agreement with the main postulate of the sequential hypothesis of sleep function which attributes a primary role to slow wave sleep in the processing of newly acquired memories.

Sleep-wake variables and EEG power spectra in Mongolian gerbils and Wistar rats.

Using electroencephalographic methods (EEG), we have analyzed the basal sleep structure and the EEG power spectra of gerbils and rats during periods of wakefulness (W), synchronized sleep (SS) and paradoxical sleep (PS). During the 6 hr light period examined, duration of sleep was similar for rats and gerbils, but gerbils showed fewer PS episodes and a longer amount of SS episodes followed by wakefulness. In addition, SS episodes preceding PS were of longer duration in gerbils than in rats. EEG power spectral analysis indicated a higher relative output in the 1-4 Hz range in gerbils in comparison with rats. On the whole, the data indicate the existence of significant differences in the basal sleep structure and EEG power spectra of gerbils and rats. This background information might be useful in the comparison of the effects of a given experimental treatment, such as cerebral ischemia, on the EEG activity of these two animal species.

The structure of sleep is related to the learning ability of rats.

Using electroencephalographic methods, rats learning or not learning a two-way active avoidance task were found to differ significantly in the structure of sleep determined the day before training. The main differences concerned (i) synchronized sleep episodes followed by wakefulness, which were longer and fewer in learning rats; (ii) paradoxical sleep episodes, which were longer in learning rats. Significant correlations were present between the number and/or the average duration of synchronized sleep episodes followed by wakefulness or by paradoxical sleep and the number of avoidances or escapes scored in the training session. Power spectral analysis indicated that the relative output in the 6-7-Hz region was higher in learning rats, notably during short episodes of synchronized sleep followed by paradoxical sleep. As two-way active avoidance training induces comparable modifications in postacquisition sleep (Ambrosini et al., Physiol. Behav., 51, 217-226, 1992), the features of preacquisition sleep which prevail in learning rats might directly determine their capacity to learn. Alternatively, they might reflect the existence of a genetic determinant independently conditioning the ability to learn.

Differential changes in Cu, Zn and Mn superoxide dismutase activity in developing rat brain and liver.

The aim of our study was to assess the pattern of copper and zinc-containing superoxide dismutase (Cu, ZnSOD) and manganese-containing superoxide dismutase (MnSOD) activity from embryonic life to senescence in rat brain and liver. The two isoenzymes showed different profiles in the two organs examined. In particular, the cerebral MnSOD activity profile suggests a primary role during differentiation of this enzymatic form.

The role of antioxidant enzymes in benzo(a)pyrene-induced carcinogenesis.

Chick embryo hepatocytes were cultured in the presence of benzo(a)pyrene in order to study the effects of this carcinogen on catalase, glutathione peroxidase and superoxide dismutase activity. The results demonstrate that benzo(a)pyrene is incapable of modifying the activity of these enzymes, even though it is taken up by cultured cells to form benzo(a)pyrene-DNA adducts. The effect of culturing, however, caused a marked reduction in the activity of these enzymes. The significance of these activity variations in benzo(a)pyrene in vitro carcinogenesis is discussed.

Possible role of certain antioxidant enzymes in dimethylnitrosamine-induced liver carcinogenesis.

An investigation was carried out to establish whether the reduction in catalase, glutathione peroxidase and superoxide dismutase activity, normally observed in liver tumours, is an early event and therefore of pathogenetic importance, or whether it is a late occurrence. Experiments performed on dimethylnitrosamine-treated hepatectomized and non-hepatectomized rats show that the decrease in activity of these enzymes is entirely due to hepatectomy, since the tumour-inducing doses of dimethylnitrosamine failed to provoke variations in the activity of these enzymes, in either normal or regenerating liver.

Different behaviour of normal and neoplastic cells cultured in vitro in the presence of catalase and superoxide dismutase.

Chicken embryo fibroblasts and hepatocytes were studied in the presence of catalase and superoxide dismutase in order to establish whether these enzymes had the capacity to favour cell multiplication as previously shown for in vitro tumour ascites cells (ATP C+). The results indicate that, unlike ATP C+ cells, both fibroblasts and hepatocytes are inhibited in their multiplication by superoxide dismutase. Similar effects are exerted on hepatocytes by catalase, whereas the multiplication of fibroblasts is favoured by high doses of this enzyme. Enzyme determinations revealed high levels of catalase and superoxide dismutase in hepatocytes, whereas both enzymes were poor in fibroblasts and ATP C+.

[Karyotype 46,XY,22p+ in a male patient (author's transl)]. / Etude d'un sujet avec caryotype 46,XY,22p+.

The authors report the case of a 2-month-old infant with psychomotor retardation and several physical stigmata. Cytogenetic studies of the patient using the normal technique show in all the cells a karyotype 46,XY with a G group chromosome substituted by an F-like mediocentric element with satellites. The R, G and C-banding methods reveal that it is the 22 with too developed short arms (22p+). This element was found in the mother's and maternal grandfather's karyotypes although they both present normal phenotypes. The authors advance two hypotheses concerning the origin of the alteration but cannot exclude a possible connection between this particular chromosome and the proband's anomalies. The difficulties of genetic counselling in this case are evident.

A case of true hermaphroditism with 45X/46XY mosaicism.

The authors describe a case of true hermaphroditism of mainly female phenotype, ambiguous genitalia, and ovotestis. The cytogenetic revealed 45X/46XY mosaicism and an absence of Barr bodies.