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Biomedical subjects

A Giuditta

Publications and source records attributed to A Giuditta.

At least 73 records · Page 4Linked to original sources
PubMed1984

[Effect of sleep on cerebral DNA synthesized during learning].

Female Wistar rats weighing 200 g were implanted with cortical electrodes and with an intraventricular cannula. Five days later they were injected with 3H-thymidine and subjected to a two-way active avoidance session lasting four hours. During the following three hours they were left free to sleep while their EEG activity was being recorded. Biochemical analyses carried out in different brain regions and in liver indicated that the concentration of cerebral radioactive DNA was markedly lower in non-learning rats as compared to learning animal and to the control group. An increase in synchronized sleep and in paradoxical sleep was observed in learning animals, whereas non-learning rats exhibited an increment of synchronized sleep only. On the basis of these results and of previous data obtained with rats analyzed soon after the training session, it is concluded that the effect observed in non-learning animals stems from a loss of radioactive DNA synthesized during training. Such a loss takes place in the following resting period and is to be related to the variations of sleep pattern recorded. The process of DNA degradation might reflect the elimination of molecules associated with neural information non longer usable for adaptive aims.

Animals↗
PubMed1983

Origin of axoplasmic RNA in the squid giant fiber.

The origin of axoplasmic RNA in the squid giant fiber was investigated after exposure of the giant axon or of the giant fiber lobe to [3H]uridine. The occurrence of a local process of synthesis was indicated by the accumulation of labeled axoplasmic RNA in isolated axons incubated with the radioactive precursor. Similar results were obtained in vivo after injection of [3H]uridine near the stellate nerve at a sizable distance from the ganglion. Exposure of the giant fiber lobe to [3H]uridine under in vivo and in vitro conditions was followed by the appearance of labeled RNA in the axoplasm and in the axonal sheath. While the latter process is attributed to incorporation of precursor by sheath cells, a sizable fraction of the radioactive RNA accumulating in the axoplasmic is likely to originate from neuronal perikarya by a process of axonal transport.

Animals↗
PubMed1983

Synthesis of brain DNA during acquisition of an active avoidance task.

The possible involvement of cerebral DNA synthesis in the learning process was examined in rats injected intracerebrally with 3H thymidine. During the period of incorporation (4.5 hr) one rat was trained to an active avoidance task while a second animal was kept in the same experimental room. In comparison with control rats paired to learning animals, the concentration of PCA-soluble radioactivity and of radioactive DNA of the cerebral cortex increased in all animal groups, i.e., control rats paired to non-learning animals, learning rats and non-learning rats. No change occurred in liver. In the cerebral cortex the slope of the regression line obtained by plotting the concentration of radioactive DNA versus the concentration of PCA-soluble radioactivity was lower in learning rats than in the group of pooled control animals. A comparable effect was noted in the hippocampus. In non-learning animals a similar decrease was present in the cerebral cortex and in cerebellum. In addition, it was found that in learning animals the percent incorporation was inversely related to the total number of avoidances only in the cerebral cortex. In non-learning rats a similar inverse relationship was present in the cerebral cortex and in cerebellum. In the former region the regression line of learning rats was shifted upwards in comparison with the regression line of non-learning animals. These results are interpreted to indicate that the incorporation of 3H-thymidine into cerebral DNA is directly related to the level of stress and is increased by learning.

Animals↗
PubMed1983

Incorporation of 3H-amino acids into proteins in a partially purified fraction of axoplasm: evidence for transfer RNA-mediated, post-translational protein modification in squid giant axons.

Transfer RNA (tRNA) has been demonstrated to be present in axons of both invertebrates and the higher vertebrates, but nothing is known of its role in the metabolism of the axon. The present experiments were performed to determine whether tRNA functions in axons as a participant in post-translational protein modification of endogenous proteins. RNA was extracted from the axoplasm of squid giant axons and incubated with a variety of 3H-amino acids, aminoacyl-tRNA synthetases (obtained from squid optic lobe), and an appropriate reaction mixture. All of the amino acids tested were bound to an RNA fraction, but this reaction did not occur when samples were incubated in the presence of ribonuclease or in the absence of axoplasmic RNA. When radioactive RNA was chromatographed by polyacrylamide gel electrophoresis, the radioactivity comigrated with known tRNA markers, suggesting the presence of 3H-aminoacylated tRNA. Aminoacylation of RNA could also be demonstrated by incubating fresh axoplasm with labeled amino acids and a reaction mixture, minus exogenous aminoacyl-tRNA synthetases. These findings indicate the presence in axoplasm of a variety of species of aminoacyl-tRNAs as well as their corresponding synthetase enzymes. In the latter experiment no radioactivity was found associated with the protein fraction. This was also the finding when 3H-aminoacylated tRNA was either injected directly into the axon or incubated with extruded axoplasm. Thus, under the conditions described above, there is no evidence of transfer of amino acids from tRNA to proteins. In other experiments, axoplasm was pooled to a volume of 50 to 100 microliters, homogenized gently, and centrifuged at 150,000 X g for 1 hr. Some of the high speed supernatant was incubated with labeled amino acids and an appropriate reaction mixture, and the remainder was passed through an S-200 Sephacryl column before incubation with the same reaction mixture. There was no incorporation of amino acids into protein in the high speed supernatant fraction. However, in the S-200 purified fraction 3H-labeled Arg, Lys, Tyr, Leu, and Asp were all incorporated into proteins in amounts of 44, 30, 7, 5 and 3.5 times heat-inactivated controls. The reaction is not inhibited by Ca2+ or Ca2+-activated proteases, but appears to be dependent on the presence of tRNA. The addition of amino acids to protein is not protein synthesis since the reactions occurred in a partially purified fraction of the 150,000 X g supernatant, a fraction devoid of ribosomes and free amino acids.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acids↗
PubMed1982

DNA turnover in rat cerebral cortex.

After the intracranial injection of [methyl-3H]thymidine the specific activity of rat cortical DNA increases rapidly, reaching a maximum at about 5 h. More than half of the radioactive DNA disappears from the tissue in the following few hours. During the same period of time the concentration of radioactive DNA in liver remains essentially constant. Minor variations occur in both organs after 41 h. An apparent rapid turnover of DNA is also present in a fraction of purified neuronal perikarya prepared from the cerebral cortex.

Animals↗
PubMed1980

Deprivation of paradoxical sleep. Effect on weight and nucleic acid content of liver and brain.

Male Wistar rats weighing between 200 and 350 g were deprived of paradoxical sleep (PS-D) by placing them on small platforms surrounded by water. In comparison with rats kept in similar cages but without water, PS-D animals manifested a marked decrease in body and liver weight, which depended on animal size and o time of exposure to the condition of PS-D. A comparable weight loss occurred in the spleen, while more limited effects were present in brain and cerebellum. Exposure to the condition of PS-D induced a pronounced increase in the concentration of liver DNA and RNA. The latter effect occurred considerably earlier. On the other hand, only limited and uncertain variations were noted in the DNA concentration of brain and cerebellum. Body and liver changes were readily reversed after a period of recovery lasting two days.

Animals↗
PubMed1980

Influence of synchronized sleep on the biosynthesis of RNA in two nuclear classes isolated from rabbit cerebral cortex.

The biosynthesis of RNA during sleep has been studied in two purified nuclear fractions, separated from rabbit cerebral cortex after subarachnoidal injection of radioactive orotate. The biochemical parameters have been referred to the percent EEG synchronization recorded during the period of incorporation (1 hr). The content of radioactive RNA per nucleus increases significantly with percent synchronization in the fraction of large nuclei (of neuronal and astroglial origin). While sedimentation and electrophoretic analyses of this RNA are consistent with the hypothesis of an enhanced turnover of rRNA during wakefulness, the accumulation of labelled RNA which is observed during sleep may be due to a modified turnover of nuclear heterogeneous RNA. On the other hand, in the fraction of small nuclei (mostly of oligodendroglial origin) the content of radioactive RNA per nucleus and the pattern of sedimentation of labelled RNA show no dependence on the electrical state of the cortex. These data indicate that in the cerebral cortex the sleep-wakefulness transition is accompanied by a different cellular response in RNA turnover.

Animals↗
PubMed1980

Influence of synchronized sleep on the biosynthesis of RNA in neuronal and mixed fractions isolated from rabbit cerebral cortex.

Adult male rabbits implanted with dural electrodes were injected intraventricularly with [3H]orotate and killed 1 h later. During the period of incorporation they were left undisturbed while their EEG activity was continuously monitored. In the fraction of neuronal perikarya prepared from cerebral cortex by a method developed by Satake and Abe in 1966, the relative content of radioactive RNA of the nuclear particulate showed a twofold increase in the transition from 0 to 100% synchronization. On the other hand, a slight but significant decline was observed in the corresponding cytoplasmic compartment. A marked increase in the relative content of radioactive RNA was similarly observed in the nuclear particulate prepared from the mixed cellular fraction. The corresponding cytoplasmic compartment showed a nonsignificant increase. These results indicate that during sleep neuronal nuclei accumulate newly synthetised RNA (presumably hnRNA) at a faster rate. Under the same conditions the process of RNA transfer to the cytoplasm (presumably rRNA) may be reduced. These effects may be only partly shared by other cerebral cells.

Animals↗
PubMed1980

Effect of electroconvulsive shock on polysomes of rabbit brain, liver and kidney.

Following electroshock treatment of the rabbit, polysomes have been found to disaggregate in the liver and kidney to an extent comparable with disaggregation in the cerebral cortex. After a single electroconvulsive shock, the process of polysomal disaggregation in the former two organs reaches maximum values at 10 and 60 min, but returns to control values at intermediate times. In the cerebral cortex the shift to control values observed at 20 min is not statistically significant.

Animals↗
PubMed1979

Excess DNA in the nuclei of the subesophageal region of octopus brain.

Cytophotometric analyses of Feulgen-stained nuclei present in homogenates of vertical and subesophageal lobes of octopus brain have shown that the latter region contains larger nuclei with up to several times the amount of DNA present in vertical nuclei. No obvious relationship was found between DNA content and nuclear size. Except for a rather small minority, nuclei of the vertical lobe have a uniform size and the expected diploid amount of DNA. These parameters are not substantially dependent on body weight. In contrast, the DNA content of subesophageal nuclei increases progressively with body weight. The amount of DNA found in subesophageal nuclei does not seem to be a simple multiple of the diploid or haploid value.

Animals↗