| Name | Michele |
| Surname | Papa |
| Institution | Università degli Studi della Campania Luigi Vanvitelli |
| michele.papa@unicampania.it | |
| Address | II Division of Neurology & Center fo Rare Diseases Department of Medical Surgical, Neurological, Metabolic Sciences, and Aging, University of Campania Luigi Vanvitelli, Edificio 10 Via Sergio Pansini, 580131 Naples, Italy |
The apomyoglobin mutant W7FW14F forms amyloid-like fibrils at physiological pH. We examined the kinetics of fibrillogenesis using three techniques: the time dependence of the fluorescence emission of thioflavin T and 1-anilino-8-naphthalenesulfonate, circular dichroism measurements, and electron microscopy. We found that in the early stage of fibril formation, non-native apomyoglobin molecules containing beta-structure elements aggregate to form a nucleus. Subsequently, more molecules aggregate around the nucleus, thereby resulting in fibril elongation. We evaluated by MTT assay (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) the cytotoxicity of these aggregates at the early stage of fibril elongation versus mature fibrils and the wild-type protein. Similar to other amyloid-forming proteins, cell toxicity was not due to insoluble mature fibrils but rather to early pre-fibrillar aggregates. Propidium iodide uptake showed that cell toxicity is the result of altered membrane permeability. Phalloidin staining showed that membrane damage is not associated to an altered cell shape caused by changes in the cytoskeleton.
The aim of this study was to trace by molecular imaging techniques the neural substrates of attention deficit hyperactivity disorder (ADHD) using the spontaneously hypertensive rat (SHR) as animal model. Adult SHR and Wistar-Kyoto (WKY) controls were used throughout this study. In experiment 1, naive male SHR and WKY were used, whereas in experiment 2 SHR and WKY rats of both genders were trained on a multiple fixed interval (FI (120 s for water, 5-min extinction)) paradigm and sacrificed 6 months later. In both experiments coronal sections of the anterior forebrain were processed for quantitative cytochrome oxidase (COase) histochemistry by the method of Gonzalez-Lima. Optical density values were transformed into actual enzyme activity units by using tissue-calibrated standards. In experiment 1, non-trained male rats of the SHR line showed lower COase activity in the medial and lateral prefrontal cortices, compared with WKY controls. In experiment 2, there was a line x treatment interaction effect in the pole of the nucleus accumbens (ACB). Regional correlative analyses revealed that: (i) under basal conditions, SHR are more synchronized than WKY rats in the COase level of different brain regions; and (ii) the training desynchronizes COase activity in the WKY, further synchronizes it and increases the cross-talk between hemispheres in male SHR only. Neurobehavioral covariations between behavioural scores and metabolic capacity in the medial and lateral prefrontal/frontal cortices, the caudate-putamen complex (CPU), the pole, core, and shell of the accumbal complex (ACB), and the ventral pallidum (VP), indicated that, in the WKY rats, the frequency of lever pressing covaried positively with the COase activity in the CPU, whereas in the SHR covaried with both medial and lateral prefrontal/frontal cortices. The bursts of activity during the 1-1.33-s segment was positively correlated, in the WKY rats only, with the core and shell of the ACB, and with the VP. Finally, the correlative profiles showed significant gender differences with effects in male SHR only. Thus, the results lend support to the involvement of the cortico-striato-pallidal system in ADHD.
The aim of this study was to map the neural substrates of attention-deficit hyperactivity disorder (ADHD) in the spontaneously hypertensive rat (SHR), which is thought to be a model for ADHD. To this aim, the Ca2+/calmodulin-dependent protein kinase II (CaMKII) and transcription factors (TF) were used as markers. The focus of interest was the nucleus accumbens complex (ACB) which is thought to be an interface between limbic and motor systems. Juvenile, male rats of the SHR line and Wistar-Kyoto (WKY) controls were perfused and the brains processed for immunocytochemistry for CaMKII and the TF peptides of the FOS, JUN-B and ZIF-268 families. The results revealed that: (i) in both groups there were more CaMKII-positive neurones in the shell than in the core of the ACB; (ii) SHR had a reduced number of CaMKII-positive elements in anterior portions of the shell; and (iii) SHR had a lower expression of peptide products of the FOS family (c-FOS, in particular) and ZIF-268. In addition, there was a lower expression of c-FOS and zif-268 in the core of the ACB in the SHR. In contrast, there was an increased basal level of JUN-B in the core of the ACB of SHR. The reduced number of CaMKII and TF-positive elements in the most rostral portions of the accumbal complex of SHR, associated to the higher number of binding sites for the DA D-1/D-5 subtype, appears as a discrete alteration in the prosomeric development of the anterior basal forebrain and could be the key to the understanding of ADHD.
Transcription factors have been used as neuronal markers in the nucleus accumbens (ACB) of male juvenile spontaneously hypertensive rats (SHR), an animal model of attention-deficit hyperactivity disorder (ADHD), to trace putative neural substrates. In SHR, immunocytochemistry and PC-assisted image analysis showed lower expression of pan-fos, c-fos, zif/268 in the shell, and the c-fos and zif/268 in the core, with an increased level of Jun-B in the core. The differential lower basal expression of transcription factors in the ACB of an animal model of ADHD implies a reduced number of modules and might represent a neural substrate of the attention deficits seen in SHR and children with ADHD at low motivational levels.
THIS study aimed at investigating putative neural substrates of attention-deficit hyperactivity disorder in children using the spontaneously hypertensive rat (SHR) as animal model and the Ca2+/calmodulin-dependent protein kinase II (CaMKII) as a marker in the nucleus accumbens, an interface between limbic and motor systems. In prehypertensive male SHR and Wistar-Kyoto rats image analysis of CaMKII immunocytochemistry showed more positive elements in the shell than in the core, and in the former a lower level in SHR. The data indicate a reduced number of nucleus accumbens modules available for limbic-motor integration revealing putative substrates of the altered attentional and reinforcement mechanisms demonstrated in the SHR and in children with attention-deficit hyperactivity disorder.
The aim of these studies was to map the neural consequences of exposure to a spatial novelty on the expression of immediate gene (IEG) and on unscheduled brain DNA synthesis (UBDS) in two genetic models of altered activity and hippocampal functions, i.e., the Naples High- (NHE) and Low-excitability (NLE) rats. Adult male rats of NLE and NHE lines, and of a random-bred stock (NRB) were tested in a Làt-maze, and corner crossings, rearings, and fecal boli were counted during two 10-min tests 24 h apart. For IEG expression, rats were exposed to a Làt-maze with nonexposed or repeatedly exposed rats used as controls, and were sacrificed at different time intervals thereafter. For UBDS, rats were sacrificed immediately after the first or the second exposure o a Làt-maze. IEG expression was measured by immunocytochemistry for the FOS and JUN proteins. NRB rats exposed for the first time to the maze showed extensive FOS and JUN positive cells in the reticular formation, the granular and pyramidal neurons of hippocampus, the amygdaloid nuclei, all layers of somatosensory cortex, and the granule cells of the cerebellar cortex. The positivity, stronger in rats exposed for the first time, was present between 2 and 6 h and was prevented by the NMDA receptor antagonist CPP (5 mg/kg). The positivity was very low in NHE rats, and it was stronger in NLE compared to NRB rats. UBDS was measured in ex vivo homogenates of brain areas by the incorporation into DNA of 3H-[methyl]-thymidine given intraventricularly 15 min before test trial 1 or 2 (pulse of 0.5 h).(ABSTRACT TRUNCATED AT 250 WORDS)
The role of nitric oxide in learning and memory processes has been tested in the albino rat by a histochemical and a behavioral study, following behavioral habituation to spatial novelty. Histochemically, the neural consequences of behavioral testing were mapped in the brain by staining for NADPH-d, known to be a NOS, whereas behaviorally the formation of LTH has been interfered with by posttrial NOS-inhibition. In the histochemical study, adult male Sprague-Dawley rats were tested in a Làt-maze and sacrificed at different time intervals thereafter. Handled unexposed rats served as controls. The brains were perfused with aldheide and processed for NADPH-d staining. In unexposed control rats the basal expression of NADPH-d was low and scattered. It pertained to few cells in the neostriatum, cerebral cortex, and CA1 hippocampal regions. In contrast, rats that had been exposed for the first time to the maze (spatial novelty) showed NADPH-d activity in the dorsal hippocampus (granule cells, few hilar neurons, and some CA1 pyramidal cells), the caudate-putamen complex, the cerebellum, and in all layers of somatosensory cortex. The positivity was not due to activity per se, since immediately after exposure it was not different from baseline. In contrast, it was present by 2 h and decreased significantly 24 h later. In addition, a strong neuronal discharge induced by the convulsant pentylentetrazol did not induce NADPH-d 2 h afterwards. The staining was prevented by pretreatment with the NMDA receptor antagonist CPP (5 mg/kg) or with the NOS inhibitor L-NOARG (10 mg/kg). In the behavioral study, rats were given an intraperitoneal injection of 1-10 mg/kg (L-NOARG) or vehicle immediately following exposure to a Làt-maze. The highest dose used (10 mg/kg) disrupted habituation of the vertical component only, known to be mainly of emotional meaning. Conversely, both doses disrupted emotional habituation based on defecation scores. The data indicate that the formation of LTH to novelty triggers a cascade of neurochemical events also involving NOS neurons. Further, the widespread induction of NADPH-d by exposure to novelty suggests that spatial and emotional information processing activate neural networks across different organizational levels of the CNS.