Biomedical subjects

M Cimino

Publications and source records attributed to M Cimino.

At least 37 records · Page 2Linked to original sources

PubMed1996

Efflux pump of the proton antiporter family confers low-level fluoroquinolone resistance in Mycobacterium smegmatis.

Due to the resurgence of tuberculosis and the emergence of multidrug-resistant strains, fluoroquinolones (FQ) are being used in selected tuberculosis patients, but FQ-resistant strains of Mycobacterium tuberculosis have rapidly begun to appear. The mechanisms involved in FQ resistance need to be elucidated if the effectiveness of this class of antibiotics is to be improved and prolonged. By using the rapid-growing Mycobacterium smegmatis as a model genetic system, a gene was selected that confers low-level FQ resistance when present on a multicopy plasmid. This gene, lfrA, encodes a putative membrane efflux pump of the major facilitator family, which appears to recognize the hydrophilic FQ, ethidium bromide, acridine, and some quaternary ammonium compounds. It is homologous to qacA from Staphylococcus aureus, tcmA, of Streptomyces glaucescens, and actII and mmr, both from Streptomyces coelicoler. Increased expression of lfrA augments the appearance of subsequent mutations to higher-level FQ resistance.

Amino Acid Sequence↗

PubMed1996

2-(Substituted)amino-2,8-diazaspiro[4,5]decan-1,3-diones as potential muscarinic agonists: synthesis, modeling and binding studies.

A series of 2-(acyl)amino-8-substituted-2,8-diazaspiro[4,5]decan-1,3-diones (5a-j), structurally related to the muscarinic agonist RS-86, was synthesized and compounds tested for their affinity towards muscarinic receptors. Though all compounds proved to be less active than the model in binding studies, only three derivatives (5a, b, c) being able to significantly displace 3H-QNB at mM concentration, their behaviour could be interpreted in terms of theoretical molecular descriptors computed on the basis of the suggestions coming from Molecular Dynamics simulations of ligand-receptor complexes.

Animals↗

PubMed1995

Changes in protein kinase C and its presynaptic substrate B-50/GAP-43 after intrauterine exposure to methylazoxy-methanol, a treatment inducing cortical and hippocampal damage and cognitive deficit in rats.

The involvement of protein kinase C (PKC)-dependent processes in adaptive and plastic changes underlying neuronal plasticity was tested in an in vivo animal model characterized by targeted cellular ablation of cortical and hippocampal neurons, cognitive impairment and lack of induction of long-term potentiation. [3H]Phorbol ester binding performed on brain slices revealed a 67.4 and 35.0% increase in membrane-bound protein kinase C in the cortex and hippocampus respectively of rats treated with methylazoxy-methanol acetate compared with saline-treated control rats, and there was no modification in the expression of mRNAs of different protein kinase C isozymes. In situ phosphorylation experiments performed with 32Pi-labelled synaptosomes from the affected areas demonstrated that the phosphorylation of the nervous tissue-specific presynaptic membrane-associated protein kinase C substrate B-50/GAP-43 was increased by 51.4 and 44.8% in cortex and hippocampus respectively. Western blot analysis of protein kinase C in synaptosomal cytosol and membrane fractions prepared from cortex and hippocampus showed an increased proportion of protein kinase C in the membrane compartment in treated animals, but no change in the total synaptosomal protein kinase C activity. Our data are consistent with increased activity of presynaptic protein kinase C and predict a sustained increase in glutamate release in methylazoxy-methanol-treated rats.

Animals↗

PubMed1995

Expression of neuronal acetylcholine nicotinic receptor alpha 4 and beta 2 subunits during postnatal development of the rat brain.

The expression of the alpha 4 and beta 2 subunits of neuronal nicotinic acetylcholine receptors (nAChRs) was studied in developing rat brain using in situ hybridization. The levels of both transcripts were already high at birth in cerebral cortex, medial habenula, CA1/CA3 regions of the hippocampus and several thalamic nuclei. In general, the beta 2 subunit showed a higher density of hybrids than the alpha 4. Beta 2 expression did not change with age in the medial habenula, medial geniculate nucleus or in the hippocampus whereas it decreased in the cortex. The developmental pattern of the hybridization signal for alpha 4 was different according to the brain area considered. The expression of the two transcripts showed a biphasic pattern in some thalamic nuclei: the lowest levels occurring during the first and second postnatal weeks respectively, and the highest levels during the second and fourth postnatal weeks. The ontogenetic profile of the expression of the alpha 4 subunit in the thalamic nuclei coincided with that of [3H]-L-nicotine binding sites. These findings suggest that the two subunits of nAChRs are independently regulated in most of the brain areas examined, and that in some regions, such as the thalamus, the ontogenetic variations reported for the alpha 4 subunit correlate with those observed for the [3H]-L-nicotine binding sites.

Aging↗

PubMed1995

Respiration in NREM and REM sleep after upper airway surgery for obstructive sleep apnoea.

To verify whether upper airway surgery in obstructive sleep apnoea syndrome affects differently respiration in NREM and REM sleep, 22 patients were studied by polysomnography before and three months after surgical treatment. On the average, treatment improved respiration during both sleep states, but no significant interaction was found between sleep state and effect of surgical treatment. According to the response to treatment, three groups of patients were identified: the first group (N = 6), with an improvement in apnoea-hypopnoea index (AHI), percentage of sleep time spent in apnoea and hypopnoea (time in AH) and mean oxyhaemoglobin saturation (SaO2) in both NREM and REM sleep; the second group (N = 5), with an improvement in AHI only in NREM sleep, associated with improvement in mean SaO2 in both sleep states; the third group (N = 11), without any improvement in AHI and time in AH, either associated (N = 5) or not (N = 6) with an improvement in mean SaO2 in both sleep states. An increase in the percentage of hypopnoeas out of the total AHI after treatment could partly account for the apparent discrepancy between AHI and mean SaO2 behaviour in the subjects of the second group, but not in the patients of the third group who improved their mean SaO2. Mixed apnoeas occurred before surgery in six subjects; they remained numerous after surgery only in two subjects who did not show any SaO2 improvement. In conclusion, the degree of improvement in respiration after upper airway surgery was similar in every patient in NREM and REM sleep.

Journal Article↗

PubMed1995

[Brain stem auditory evoked potentials in obstructive sleep apnea syndrome].

To evaluate a possible brainstem role in pathogenesis of obstructive sleep apnea syndrome, a study on brainstem auditory evoked potentials (BAEP), has been conducted. 15 OSAS patients, medium and severe form, with organic pathologies of the upper respiratory tract have been evaluated. 15 normal subjects were compared as control. All the patients were subjected to audiometry, including total liminal audiometry, timpanometry, acustic reflex, and BAEP study. BAEP evoked with trains of cliks at 11 and 51 periods/sec., showed morphological alterations and a longer central conductance of time interval (I-V interval) in only four patients. BAEP alterations noted in the OSAS-affected patients are neither constant nor specific. Therefore, the observed BAEP alterations might be due to apneas, as a consequence of the chronic hypoxic- hypercapnic status occurring in the brain-stem.

Acoustic Impedance Tests↗

PubMed1995

[Morphologic and ultrastructural changes of soft palate in patients who underwent palatopharyngoplasty].

In order to clarify pathogenesis of Obstructive Sleep Apnea Syndrome (OSAS) in patients with anatomic abnormalities of upper airways, we studied soft palate and uvula of OSAS patients by means of histological and ultrastructural techniques. 38 OSAS patients, severe and moderately severe form, underwent modified Palatopharingoplasty. We evaluated only 16 OSAS patients' soft palate and uvula and observed histological changes in all of them: submucosal edema and minor salivary glandes ipertrophy and iperplasy are present. On the contrary, ultramicroscope showed normal muscle fibers. Strie Z alterations and sarcomeres disorganization, although present, have no statistical value. Very probably, ronflement and apneas determined the observed alterations through trauma on pharingeal wall. Therefore, they are not OSAS primary cause.

Humans↗

PubMed1995

[The surgical treatment of obstructive sleep apnea syndrome].

Studies concerning the anatomical abnormalities of upper airways in patients affected by Obstructive Sleep Apnea Syndrome (OSAS) allowed the corrective surgical treatments in this syndrome. To provide an improvement or a definitive recovery of OSAS, various surgical treatments, i.e. functional nasal surgery, palatal surgery [Partial resection of palate (RPP), Uvulopalatopharingoplasty (UPPP), Palatopharingoplasty (PPP), modified Palatopharingoplasty (modified PPP)], mandibular and base tongue surgery, have been performed in order to obtain an enlargement of upper airways. It has been reported that in RPP, UPPP, PPP and modified PPP partial or total uvula and soft palate resection is conduct; in our research we performed modified PPP. 44 OSAS patients, severe or moderately severe form (polisomnographic diagnosis), underwent surgical treatment: 5 patients underwent functional nasal surgery; 9 patients underwent modified PPP; 29 patients underwent nasal and palatal surgery; only 1 patient underwent base tongue surgery. 32 patients underwent polisomnographic records after surgery (two months later) and we evaluated Apnea Index (I.A.) and a SaO2 low (nadir) with statistic tests. The results have been positive. Therefore, we have now 7 normal, 2 mild form, 7 moderate form, 3 moderately severe form and 13 severe form OSAS patients. If, on the one hand, all these surgical treatments can be considered a good way of therapy, on the other, only tracheostomy represents today the unfailing surgical therapy.

Humans↗

PubMed1994

Localization and age-dependent expression of hexokinase mRNA in the rat brain.

Localization of mRNA encoding for the enzyme hexokinase and its regulation in aged animals was carried out in rat brain using the in situ hybridization technique. The highest levels of the hybridization signal were observed in the olfactory bulb, piriform cortex, tenia tecta, hippocampus and granular cells of the cerebellum. Other brain areas and nuclei including cerebral cortex, thalamus, hypothalamus, substantia nigra, subiculum, choroid plexus and superior colliculus displayed moderate to low density of transcripts. Correlation between relative hexokinase content and levels of its mRNA was found only for some brain regions such as caudate-putamen, geniculate nucleus, ventral and lateral thalamic nuclei, superior colliculus and granular cells of the cerebellum. In the cerebral cortex and hippocampus of old animals the expression of hexokinase was significantly increased at 18 and 24 months of age. From the present data we conclude that although hexokinase is an ubiquitous enzyme, sites of synthesis display a discrete and uneven localization in rat CNS and expression, in the aging brain, might be regulated to compensate for reduced oxidative phosphorylation in the brain tissue.

Aging↗

PubMed1993

Effects of postnatal or adult chronic acetylcholinesterase inhibition on muscarinic receptors, phosphoinositide turnover and m1 mRNA expression.

Muscarinic receptor number, receptor-stimulated phosphoinositide hydrolysis and m1 mRNA expression were examined in the cerebral cortex and hippocampus of rats treated during postnatal development or in adult age with the organophosphate diisopropylfluorophosphate. Developing rats were treated from postnatal days 4-9 or from postnatal days 4-20 and killed on days 10 and 21, respectively, 24 h after the last administration of diisopropylfluorophosphate. Adult animals were treated for 14 days. Acetylcholinesterase activity and muscarinic receptor number were significantly reduced in all groups of treatment. Muscarinic receptor-stimulated phosphoinositide turnover, however, was significantly reduced in postnatal days 4-20 and adult treated rats but not in the postnatal days 4-9 group. No differences were observed in ED50 values. Conversely, m1 mRNA expression was significantly reduced both in the cerebral cortex and hippocampus of postnatal days 4-9 treated rats, but not of postnatal days 4-20 and adult treated rats. These results indicate that chronic inhibition of acetylcholinesterase in developing rats results in significant alterations in muscarinic neurotransmission. These alterations may delay the maturation of the cholinergic system and, therefore, may account for some of the long-lasting neurotoxic effects observed after developmental exposure to organophosphate pesticides.

Acetylcholinesterase↗

PubMed1993

Identification and functional significance of nicotinic cholinergic receptors in the rat pineal gland.

The existence and subunit identification of the nicotinic cholinergic receptors in the rat pineal gland were examined by autoradiography, using [3H]cytisine and [125I]alpha-bungarotoxin as labelled ligands. The experiments performed with radioactive cytisine did not reveal specific binding, while iodinated alpha-bungarotoxin disclosed moderate specific binding density, suggesting that the nicotinic cholinergic receptor in the rat pineal is structurally organized with the alpha 7 or alpha 8 subunits present, the only ones that bind alpha-bungarotoxin with high affinity. In vitro functional experiments using pineal explants demonstrated that the binding site may represent a readily accessible nicotinic cholinergic receptor. Nicotine, though having no effect per se on the synthesis and release of melatonin, significantly diminished, in a dose-dependent manner, the norepinephrine-stimulated melatonin accumulation. This effect could be blocked by coincubation with the cholinergic antagonist d-tubocurarine, suggesting that the nicotinic cholinergic receptor in the rat pineal could be involved in the functional regulation of the gland.

Alkaloids↗

PubMed1993

Selective alteration in B-50/GAP-43 phosphorylation in brain areas of animals characterized by cognitive impairment.

When methylazoxymethanol acetate is administered to pregnant rats at gestational day 19, the offspring are greatly impaired in the learning of a two-way active avoidance task and these behavioral changes are paralleled by a change in the phosphorylation of the protein B-50/GAP-43 in hippocampus but not in cortex. The expression of the protein is not altered, indicating that the phosphorylation of B-50 is a sensitive marker of alterations in synaptic plasticity associated with impairments of learning abilities in rats.

Animals↗

PubMed1992

Cellular expression of somatostatin in MAM-induced microencephaly in the rat.

Methylazoxymethanol acetate (MAM) is a mitotic inhibitor that has been used to selectively destroy neuroblasts at specific times during gestation. The administration of MAM results in a dose-dependent microencephaly. Following MAM treatment at 15 days of gestation, we have noted an increase in the level of SS immunoreactivity in the neocortex, as determined by radioimmunoassay. Northern blot analysis for preproSS mRNA revealed an increase in MAM-treated cortex. The cellular distribution of SS has been determined using in situ hybridization and immunocytochemistry. There was a 30% increase in the density of SS-immunoreactive neurons in the cortex of the MAM-treated animals. These data suggest that SS neurons in the cortex are spared following MAM treatment at GD 15.

Animals↗

PubMed1992

The phosphorylation state of DARPP-32, a third messenger for dopamine, is regulated by in vivo pharmacological treatments.

It has been recently proposed that DARPP-32 participates, as third messenger, in the mediation of effects induced by dopamine at the cellular level. DARPP-32 is indeed localized almost exclusively on dopaminoceptive neurons bearing the D1 receptor subtype and it is phosphorylated by cAMP-dependent protein kinase. In its phospho-form, DARPP-32 acts as an inhibitor of protein phosphatase-1. In vivo pharmacological treatment with selective D1 agonists and antagonists induces changes in the phosphorylation state of DARPP-32 that can be correlated to changes in cAMP, mediated in turn by D1 and D2 receptors. These data demonstrate that the measurement of the phosphorylation state of DARPP-32 with the back-phosphorylation assay can represent a useful biochemical tool to gain further insight into the sequence of events elicited by specific dopaminergic drugs in vivo.

Animals↗

PubMed1992

Distribution of nicotinic receptors in cynomolgus monkey brain and ganglia: localization of alpha 3 subunit mRNA, alpha-bungarotoxin and nicotine binding sites.

The distribution of nicotinic receptors in the brain and ganglia of the Cynomolgus monkey was studied by in situ hybridization and receptor autoradiography. A 35S-labeled antisense riboprobe for the mRNA of the alpha 3 subunit of the human nicotinic receptor, [3H]L-nicotine and [125]alpha-bungarotoxin were used as markers. The highest levels of alpha 3-mRNA were observed in the hippocampus, the medial habenula, the lateral geniculate, the granular layer of the cerebellum, as well as in the pineal gland; moderate levels were found in other nuclei of the thalamus and in the deeper layers of the cerebral cortex. High-affinity binding sites for [3H]L-nicotine were observed mainly in the thalamus. The distribution of [125I]alpha-bungarotoxin binding sites was different from that observed for alpha 3-mRNA and [3H]L-nicotine; they were most abundant in a few specific thalamic nuclei, in the medial habenula and in lamina I of the cerebral cortex. The localization of these three markers was also investigated in the sympathetic, parasympathetic and sensory ganglia of the monkey. Intense labeling was observed for alpha 3-mRNA and for [125I]alpha-bungarotoxin in the sympathetic and parasympathetic ganglia, whereas no positive signal was seen in the ganglion of Gasser. [3H]L-nicotine binding was not detected in any of the ganglia examined. High levels of mRNA for the alpha 3 subunit of the nicotinic receptor were also detected in human sympathetic ganglia. Comparison between alpha 3-mRNA distribution and [3H]L-nicotine binding suggests that in the Cynomolgus monkey brain, the alpha 3 subunit may participate in the formation of more than one nicotinic receptor subtype: a high-affinity binding site for [3H]L-nicotine in the thalamus, and other sites with low affinity for nicotine in the medial habenula and cerebral cortex. Both the alpha 3-mRNA and the [125I]alpha-bungarotoxin are highly expressed in the sympathetic ganglia; however, since no information is presently available on the intraneuronal cellular localization, it cannot be established whether or not they are both present at synaptic sites.

Animals↗

PubMed1991

Differential ontogenetic expression and regulation of proenkephalin and preprosomatostatin mRNAs in rat caudate-putamen as studied by in situ hybridization histochemistry.

Specific oligonucleotide probes and in situ hybridization histochemistry were used to study the ontogeny and regulation of the mRNAs for proenkephalin A and preprosomatostatin in rat brain. In adult brain the most intense hybridization signal for the proenkephalin A mRNA was in caudate putamen, nucleus accumbens and olfactory tubercle. By contrast, the hybridization signal for preprosomatostatin mRNA was more diffusely scattered throughout the brain, with high signals in the neocortex, olfactory bulb and hippocampal formation. Studies of the ontogeny of these mRNAs revealed a different pattern of ontogenetic expression and differential regulation by dopaminergic input. The mRNA for preposomatostatin reached the highest level within the first postnatal week, whereas proenkephalin A mRNA progressively increased throughout the entire period studied. In addition the proenkephalin A mRNA showed a medial to lateral gradient in 2-day-old rat striatum which disappeared with increasing age, whereas preprosomatostatin mRNA increased in most brain areas in fairly uniform fashion with increasing age. Treatment of newborn rats with 6-hydroxydopamine increased the expression of proenkephalin A mRNA by 1.6 fold but had no effect on the expression of preprosomatostatin mRNA. The 6-hydroxydopamine-induced change in proenkephalin A mRNA expression was not observed until postnatal day 32, indicating that enkephalin-containing neurons of the developing striatum are relatively insensitive to dopamine input and that they cannot compensate for the neonatal lesion, despite the fact that the insult was given in a period of high plasticity of the neural tissue.

Aging↗

PubMed1991

Decrease in mRNA levels but not in the density of D2 dopamine receptors in rat striatum after transient forebrain ischemia.

D2 dopamine receptor mRNA was analyzed by in situ hybridization histochemistry in rat striatum 7 days after transient forebrain ischemia. A patchy disappearance of the D2 receptor mRNA was observed in the dorsolateral striatum. In the same area, a disappearance of D1 binding sites occurred in the absence of significant changes in D2 receptor density. These results suggest that, although D2 receptors seem to be apparently unaffected after forebrain ischemia, a long-lasting impairment of their neosynthesis may be present in striatal D2 dopaminoceptive neurons.

Animals↗

PubMed1991

Microencephaly reduces the phosphorylation of the PKC substrate B-50/GAP43 in rat cortex and hippocampus.

The administration of the antimitotic agent methylazoxymethanol (MAM) to rats at day 15 of gestation results in a consistent loss of intrinsic neurons primarily in cortex and hippocampus. These animals when adult, show a cognitive impairment, if tested in specific behavioural tasks. B-50/GAP43 is a neuronal phosphoprotein, specific substrate for protein kinase C (PKC) and involved in the development and plasticity of synaptic connections. Since B-50/GAP43 has been implicated in functional modulation of synapses and in the molecular mechanism underlying cognitive processes, we studied the phosphorylation of B-50 in cortex and hippocampus of control and MAM-treated rats. Here we report that B-50 in MAM-treated rats shows a marked reduction in the phosphate incorporation in the areas affected by the prenatal treatment. In situ hybridization studies demonstrate that the mRNA levels for B-50 are not altered in MAM-treated rats and that the relative amount of the protein, as revealed by Western blot analysis, is also not affected in microencephalic rats. These results suggest that microencephalic animals might represent a useful experimental model to study biochemical correlates of cognitive impairment and synaptic plasticity.

Animals↗