Biomedical subjects

M V Ambrosini

Publications and source records attributed to M V Ambrosini.

At least 19 recordsLinked to original sources

PubMed2005

Effects of light physical exercise on sleep in middle-aged rats.

The effects of physical activity on sleep were evaluated in 12-month-old rats. The animals (n = 18) were induced to walk or run for 45 min in a rota-rod treadmill while control mates remained in their home cages. Immediately after the trial, they were left free to sleep for four hours, during which their electroencephalographic activity was recorded. Baseline electroencephalogram showed no differences among groups in sleep parameters and spike wave discharges during wakefulness in all rats. Sleep variables and spike wave discharges remained constant in the controls over times. On the contrary, Student's t-test for paired data indicated a decrease in spike wave discharges in both walking and running rats while paradoxical sleep rose parallel with slow wave sleep in walking animals but declined in running rats, in spite of an increment in slow wave sleep. The results seem to indicate that: i) light exercise improves sleep quality in middle aged rats, provided it is not stressful and ii) physical activity supplies important benefits to waking brain by reducing spike wave discharges.

Age Factors↗

PubMed2005

Ultrastructural investigations on protective effects of NCX 4016 (nitroaspirin) on macrovascular endothelium in diabetic Wistar rats.

The effect of a nitric oxide-donating aspirin derivative, 2-acetoxy-benzoate 3-(nitroxy-methyl)phenyl ester (NCX 4016), and aspirin on the aortic endothelium of diabetic rats was investigated by using scanning and transmission electron microscopy. Control and streptozotocin-treated rats were used. Metabolic control was assessed by measuring blood and urine metabolites, and 24-h urine volume. The ultrastructural study was performed after 7 weeks of diabetes and 6 weeks of therapy. Streptozotocin treatment induced a persistent hyperglycemia which was not influenced by the pharmacological treatments. Values of blood metabolites were in line with the diabetic status. Both scanning and transmission electron microscopy revealed that aortic endothelium was severely damaged in all diabetic rats except for the NCX 4016 treated ones. Our data document the protective effects of NCX 4016 on the vascular endothelium of diabetic rats. Since aspirin had no protective action, NCX 4016 may have exerted its beneficial action by releasing nitric oxide.

Animals↗

PubMed2001

Nitro-aspirin (NCX4016) reduces brain damage induced by focal cerebral ischemia in the rat.

The potential neuroprotective effects of the novel nitro-derivate of aspirin (NCX4016) on permanent focal cerebral ischemia in spontaneously hypertensive rats (SHRs) was investigated. Reference compounds were acetylsalicilic acid (ASA) and FK506 (tacrolimus). Ten minutes after surgery, SHRs were randomly divided into four groups of ten, pharmacologically treated and sacrificed 24 h after treatment. Brains were removed and processed to measure infarct volume, 70 kDa heat shock protein (hsp70), glial fibrillary acidic protein (GFAP) and vimentin (Vim) immunoreactivity (IR), and apoptosis using terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-digoxigenin nick end-labeling (TUNEL) assay. NCX-4016 significantly reduced total infarct volume compared to ASA (-20%, P < 0.05), FK506 (-18%, P < 0.05) and vehicle treatment (-20%, P < 0.05). Experimental groups did not differ in hsp70-IR and GFAP-IR. Conversely, hyperplastic astrocytes, measured by Vim-IR, were significantly lower in NCX-4016 than in the vehicle group (-36%, P<0.01). TUNEL assay indicated a significantly lower degree of apoptosis in NCX-4016 group than vehicle in both the homolateral (-27%, P < 0.01) and contralateral hemisphere (-29%, P < 0.05). These findings indicate that NO release associated with aspirin confers neuroprotective effects against ischemic injury.

Animals↗

PubMed2001

Generalized induction of 72-kDa heat-shock protein after transient focal ischemia in rat brain.

The time course of 72-kDa heat-shock protein (hsp72) induction was evaluated by immunoblotting in cerebral cortex, striatum, hippocampus, cerebellum, liver, and kidney of rats subjected to 60-min focal cerebral ischemia following proximal unilateral occlusion of the right middle cerebral artery (MCA). Neurological examinations indicated that maximum deficits in reflex and sensorimotor functions occurred 24-48 h after reperfusion (40% lower than baseline), while significant recovery occurred at 72 h (33% higher than 48 h). hsp72 was present in all tissues at 6 h. The regions perfused by the occluded MCA showed a higher induction than the corresponding contralateral ones. hsp72 reached its maximum level in ipsilateral cerebral cortex and striatum at 24 h, whereas in the contralateral cortex and cerebellum the protein reached its maximum expression at 48 h, that is 24 h before functional recovery. This delay suggests a role of the protein in plastic events sustaining neurological recovery.

Animals↗

PubMed2001

Effects of light physical exercise on sleep regulation in rats.

PURPOSE: Acute physical exercise is known to enhance slow-wave sleep (SWS) and reduce paradoxical sleep (PS) in humans. In this study, we examined the effects of moderate physical exercise on sleep in rats. METHOD: Young adult Wistar rats underwent a 4-h baseline electroencephalographic (EEG) recording session. The following day, they were induced to walk (0.8 m x min(-1)) or run (4 m x min(-1)) for 45 min in a rota-rod treadmill. Active control rats (ACR) were placed on the locked rota-rod for 45 min, whereas passive control rats (PCR) remained in their home cages. They were then left free to sleep for 4 h during which EEG activity was recorded. Rectal temperature (Tre) was monitored before and after exercise in ACR, walking and running rats (WR and RR, respectively) and at 45 min intervals in PCR. RESULTS: WR were able to walk for 45 min consecutively whereas in RR performances differed. Posttraining Tre was unchanged in ACR, PCR, and WR and resulted about 1.8 degrees C above baseline in RR. In both WR and RR after exercise i) length of SWS and PS, ii) intensity of SWS (spectral power density in 1-4 Hz range), and iii) propensity for falling asleep were enhanced. Interestingly, there was a more conspicuous increment in PS than SWS. In ACR and PCR there were no changes in sleep. CONCLUSIONS: Due to the complexity of sleep regulation, the interaction of several factors might underlie the observed increment in SWS and PS. Nevertheless, it is interesting that light physical exercise favors sleep and above all a harmonic enhancement of both sleep phases.

Animals↗

PubMed1999

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.

Animals↗

PubMed1997

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.

Aging↗

PubMed1996

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.

Anesthesia, Inhalation↗

PubMed1995

Variable response of the Mongolian gerbil to unilateral carotid occlusion: magnetic resonance imaging and neuropathological characterization.

In the present investigation, we estimated both the evolution and the severity of ischemic damage following unilateral carotid occlusion (UCO) in Mongolian gerbils by using conventional magnetic resonance imaging (MRI, i.e. T2 weighted imaging) and histological techniques. Immediately after UCO, the animals showed different clinical effects. The mortality (46%) detected within the first 48h was considered an "stroke-sensitivity", the "stroke-resistant" animals showed wide variability in terms of both temporal evolution and the extent of ischemic damage. The signal hyperintensity and negative MRI observed during the first 30h after UCO did not always correlate with the cerebral damage presented after 14 days, although a close correlation was established between the T2 weighted images taken more than 30h after UCO and neuropathology: the gerbils negative to imaging showed no morphological changes, whereas an enhanced signal was always prognostic of ischemic injury. Moreover, late MRI documented ventricular dilatation. Histopathology showed that the ischemic damage differed among the stroke-resistant gerbils and was often bilateral. The present study confirms the differences in gerbil susceptibility to hemispheric infarction after permanent UCO and suggests that conventional MRI may be a useful non-invasive method for i) identifying the stroke-resistant animals prone to mature ischemic injury and ii) monitoring the evolution of therapeutic efficacy without sacrificing animals.

Animals↗

PubMed1995

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.

Animals↗

PubMed1995

Sleep fragmentation, and changes in locomotor activity and body temperature in trypanosome-infected rats.

The rest-activity and body temperature 24 h cycles, as well as the structure of spontaneous sleep, were studied in rats 3 weeks after infection with monomorphic Trypanosoma brucei brucei. This parasite belongs to the species of trypanosomes that causes in humans African sleeping sickness, a neuropsychiatric syndrome that involves alterations of endogenous biological rhythms. In the infected rats, entrained to a 12 h:12 h photoperiod, a considerable hypokinesia was detected during the hours of darkness. A significant oscillation of the body temperature during 24 h was lost in some infected animals. In the other infected animals, the body temperature cycle displayed a lower amplitude and a phase advance. The mean temperature was slightly higher in the infected than in control rats during the period of light. A detailed analysis of the structure of spontaneous sleep, based on daytime electroencephalographic recordings, revealed during trypanosome infection an increased relative proportion of wake, and a decreased percent value of synchronized sleep. A marked reduction of the mean REM latency and a fragmented pattern of synchronized sleep, resulting in a considerable alteration of the REM-non-REM sleep sequences, were also observed in the infected animals. These findings indicate that trypanosomiasis in the rat results in a striking sleep fragmentation, as well as in changes of locomotor activity and body temperature rhythm. Thus, trypanosome infection in the rat provides an experimental model of sleep dysregulation in a structurally intact brain, and may provide an animal model of endogenous rhythm changes documented in African sleeping sickness.

Analysis of Variance↗

PubMed1994

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.

Action Potentials↗

PubMed1993

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.

Animals↗

PubMed1992

The sequential hypothesis of sleep function. III. The structure of postacquisition sleep in learning and nonlearning rats.

EEG methods were used to examine the structure of postacquisition sleep in learning (L) and nonlearning (NL) rats previously exposed to a session of two-way active avoidance training, and in control rats (C) left in their home cages. In agreement with literature data, the number and total amount of paradoxical sleep (PS) episodes were higher in L rats than in NL rats. In addition, significant differences between L and NL rats concerned the episodes of synchronized sleep followed by wakefulness or by PS (SS-W and SS-PS, respectively). The average duration and related parameters of SS-W episodes, and the average duration, number, amount and related parameters of SS-PS episodes increased in NL and L rats in comparison with C rats. Longer SS-W episodes occurred early in NL and L rats, but the effect lasted longer in NL rats. On the other hand, the increments concerning SS-PS episodes occurred earlier, were more pronounced and laster longer in L rats. The results support a role of SS in brain information processing, as envisaged by the sequential hypothesis on the role of sleep. They suggest, furthermore, that memory traces lacking adaptive value may be destabilized and cleared away during SS-W and SS-PS episodes, while the remaining memory traces may be retained and eventually stored again in more integrated form during SS-PS and PS episodes, respectively.

Animals↗

PubMed1992

The sequential hypothesis of sleep function. IV. A correlative analysis of sleep variables in learning and nonlearning rats.

Female adult rats were trained for a two-way active avoidance task (4 h), and allowed free sleep (3 h). Control rats (C) were left in their home cages during the acquisition period. Dural electrodes and an intraventricular cannula, implanted one week in advance, were used for EEG recording during the period of sleep and for the injection of [3H]thymidine at the beginning of the training session, respectively. Rats were killed at the end of the sleep period, and the DNA-specific activity was determined in the main brain regions and in liver. Correlations among sleep, behavioral and biochemical variables were assessed using Spearman's nonparametric method. In learning rats (L), the number of avoidances was negatively correlated with SS-W variables, and positively correlated with SS-PS variables (episodes of synchronized sleep followed by wakefulness or paradoxical sleep, respectively) and with PS variables. An inverse pattern of correlations was shown by the number of escapes or freezings. No correlations occurred in rats unable to achieve the learning criterion (NL). In L rats, the specific activity of brain DNA was negatively correlated with SS-W variables and positively correlated with SS-PS variables, while essentially no correlation concerned PS variables. On the other hand, in NL rats, comparable correlations were positive with SS-W variables and negative with SS-PS and PS variables. Few and weak correlations occurred in C rats. The data support a role of SS in brain information processing, as postulated by the sequential hypothesis on the function of sleep. In addition, they suggest that the elimination of nonadaptive memory traces may require several SS-W episodes and a terminal SS-PS episode. During PS episodes, adaptive memory traces cleared of nonadaptive components may be copied in more suitable brain sites.

Animals↗

PubMed1991

A simple method for the DNA content assay of culture maintained pancreatic islets of Langerhans.

A simple method for assaying DNA content of in vitro culture maintained pancreatic islets is described. By employing lyophilization of the islets and subsequent fluorometric analysis, we have been able to measure DNA from relatively small cell samples. The method may result advantageous, over others, previously reported, since it is less subject to experiment-related interfering conditions. This procedure, which is easy and reliable, even for very low DNA concentrations, seems to be very useful for culture maintained pancreatic islets, since in vitro work conducted with this endocrine tissue is usually associated with small size cell samples. The method may help for a simple assessment of the viable islet cell mass in in vitro studies.

Ammonium Hydroxide↗

PubMed1990

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.

Age Factors↗

PubMed1988

The sequential hypothesis on sleep function. I. Evidence that the structure of sleep depends on the nature of the previous waking experience.

The sequential hypothesis on sleep function assumes that the information gathered by brain during the waking period is processed during sleep in two main steps occurring during synchronized sleep (SS) and, eventually, during paradoxical sleep (PS). To verify the main consequences of the hypothesis, i.e., (1) that SS is involved in brain information processing; and (2) that the structure of sleep is dependent on the nature of the previous waking experience, an experiment was designed involving rats exposed to a training session (two-way active avoidance) but failing to learn (NL), and rats left in their home cages in the same training room (C). The structure of sleep, determined by EEG techniques in the postacquisition period (3 hr), was different in NL rats in comparison to C rats, chiefly because SS episodes were markedly longer in the former group. A more detailed analysis indicated that, in NL rats, SS episodes not followed by PS increased their duration first, while those followed by PS became longer in the second half of the sleep period. Comparable results were obtained in the comparison of NL and C subgroups deprived of PS at the end of the acquisition period by chlomipramine treatment. The data support the sequential hypothesis and provide evidence for a primary role of SS in brain information processing.

Animals↗