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Biomedical subjects

A M Marini

Publications and source records attributed to A M Marini.

At least 37 records · Page 2Linked to original sources
PubMed1998

N'-Phenylindol-3-ylglyoxylohydrazide derivatives: synthesis, structure-activity relationships, molecular modeling studies, and pharmacological action on brain benzodiazepine receptors.

A series of N'-phenylindol-3-ylglyoxylohydrazides, isosters of the N-benzylindol-3-ylglyoxylamide derivatives previously described by us, were synthesized and tested for their ability to displace [3H]Ro 15-1788 from bovine brain membranes. These compounds were designed with the aim of obtaining products which could exert an in vivo activity, thanks to a higher hydrosolubility and consequently a better bioavailability. Affinity was restricted to the derivatives unsubstituted in the 5 position of the indole nucleus (1, 6, 9, 12, 15, 18, 23, and 26), with Ki values ranging from 510 to 11 nM. The most active compounds (6, 9, 23, and 29) proved to be effective in antagonizing pentylenetetrazole-induced seizures. Molecular modeling studies were performed to rationalize the lack of affinity of hydrazides with a chloro or a nitro group in the 5 position of the indole nucleus. It was hypothesized that the conformational preference of the hydrazide side chain, characterized by a gauche disposition of lone pairs and substituents about the N-N bond, prevents all hydrazides from binding to the receptor similarly to other classes of indole analogues previously investigated. The potency of 5-H hydrazides was attributed to a binding mode which is not feasible for 5-Cl and 5-NO2 counterparts. This theoretical model of ligand-receptor interaction permitted a more stringent interpretation of structure-affinity relationships of hydrazides and of recently described benzylamide derivatives (Da Settimo et al. J. Med. Chem. 1996, 39, 5083-5091).

Animals↗
PubMed1998

Infarction in the territory of the anterior cerebral artery.

Infarction in the anterior cerebral artery (ACA) territory is an uncommon cause of stroke. The clinical findings of ACA infarctions are not fully characterized but include contralateral hemiparesis, urinary incontinence, transcortical aphasia, agraphia, apraxia, and executive dysfunction. We report a patient with a large right ACA infarction, who in addition to previously reported findings also had a complete hemiplegia, profound sensory neglect, and micrographia.

Aged↗
PubMed1998

[A diagnostic protocol in cherubism].

Cherubism is a rare hereditary maxillo-facial pathology with unknown pathogenesis. The purpose of the present study is to describe a correct diagnostic approach to cherubism, especially for the differential diagnosis with other maxillo-mandibular cystic diseases. Therefore, the typical clinical, radiological, genetical and histopathological aspects of this pathology are examined. Moreover, an adequate therapy for the cases examined in this study is suggested.

Adolescent↗
PubMed1997

Toward the development of strategies to prevent ischemic neuronal injury. In vitro studies.

Cerebellar granule cells in culture, which are extremely vulnerable to excitotoxin glutamate or N-methyl-D-aspartate (NMDA), were used to study mechanisms of neuronal cell death and protection. Paradoxically, pretreatment of these cells with subtoxic concentrations of NMDA markedly blocked the neurotoxicity resulting from subsequent exposure to glutamate or NMDA. The NMDA-mediated neuroprotection can be antagonized by pretreatment of these cells with protein synthesis inhibitors, suggesting an involvement of protein(s) with neuroprotectant properties, most likely neurotrophic factors. Because basic fibroblast growth factor (BFGF) is well known to prevent neuronal cell death following mechanical or chemical injury, we have tested whether NMDA increases the synthesis of bFGF in cerebellar granule cells. NMDA elicited a rapid and time-dependent increase in bFGF mRNA, suggesting that availability of this trophic factor may play a role in the NMDA-mediated neuroprotection.

Animals↗
PubMed1997

Calretinin-containing neurons in rat cerebellar granule cell cultures.

Using an antiserum against calretinin, a calcium-binding protein, we discovered two distinct neuronal cell types that stain intensely in enriched cerebellar granule cells. One neuronal cell type resembles unipolar brush cells, whereas the other resembles Lugaro cells. During early culture times, these calretinin-positive neurons are most numerous but represent less than one percent of the total neuronal population. In cultured cells, calretinin mRNA levels peak at day three in vitro, followed by a rapid decline to undetectable levels by day six in vitro. However, calretinin-immunoreactive neurons are observed up to 29 days in vitro. Excitotoxic concentrations of glutamate receptor agonists failed to elicit an excitotoxic response on the intensely staining calretinin-positive neurons, whereas greater than 95% of the cerebellar granule cells were susceptible to the excitotoxic actions of the glutamate receptor agonists. To distinguish between the two possibilities that calretinin-positive neurons either do not express glutamate receptors or they are not susceptible to the excitotoxic effects of glutamate receptor agonists, we performed immunocytochemistry using glutamate receptor antibodies to detect the presence of receptor protein. We found that the AMPA/kainate glutamate receptor (GluR2R3) colocalized with calretinin, suggesting that calretinin-immunoreactive neurons express the AMPA/kainate receptor; cerebellar granule cells, which are known to express this receptor, were also immunoreactive for the GluR2R3 receptor.

Animals↗
PubMed1997

A family of ammonium transporters in Saccharomyces cerevisiae.

Ammonium is a nitrogen source supporting growth of yeast cells at an optimal rate. We recently reported the first characterization of an NH4+ transport protein (Mep1p) in Saccharomyces cerevisiae. Here we describe the characterization of two additional NH4+ transporters, Mep2p and Mep3p, both of which are highly similar to Mep1p. The Mep2 protein displays the highest affinity for NH4+ (Km, 1 to 2 microM), followed closely by Mep1p (Km, 5 to 10 microM) and finally by Mep3p, whose affinity is much lower (Km, approximately 1.4 to 2.1 mM). A strain lacking all three MEP genes cannot grow on media containing less than 5 mM NH4+ as the sole nitrogen source, while the presence of individual NH4+ transporters enables growth on these media. Yet, the three Mep proteins are not essential for growth on NH4+ at high concentrations (>20 mM). Feeding experiments further indicate that the Mep transporters are also required to retain NH4+ inside cells during growth on at least some nitrogen sources other than NH4+. The MEP genes are subject to nitrogen control. In the presence of a good nitrogen source, all three MEP genes are repressed. On a poor nitrogen source, MEP2 expression is much higher than MEP1 and MEP3 expression. High-level MEP2 transcription requires at least one of the two GATA family factors Gln3p and Nil1p, which are involved in transcriptional activation of many other nitrogen-regulated genes. In contrast, expression of either MEP1 or MEP3 requires only Gln3p and is unexpectedly down-regulated in a Nil1p-dependent manner. Analysis of databases suggests that families of NH4+ transporters exist in other organisms as well.

Amino Acid Sequence↗
PubMed1996

Synthesis, structure-activity relationships, and molecular modeling studies of N-(indol-3-ylglyoxylyl)benzylamine derivatives acting at the benzodiazepine receptor.

A number of N-(indol-3-ylglyoxylyl)benzylamine derivatives were synthesized and tested for [3H]flunitrazepam displacing activity in bovine brain membranes. Some of these derivatives (9, 12, 14, 15, 17, 27, 34, 35, 38, 41, and 45) exhibited high affinity for the benzodiazepine receptor (BzR) with Ki values ranging from 67 to 11 nM. The GABA ratio and [35S]-tert-butylbicyclophosphorothionate binding data, determined for the most active compounds, showed that they elicit an efficacy profile at the BzR which depends on the kind of substituent present on the phenyl ring of the benzylamine moiety. Moreover, lengthening (propylamine derivatives 1-3) and shortening (aniline derivatives 46-54) of the distance between the phenyl ring and the amide group of the side chain gave compounds with a drastically lower binding potency. The biological results are discussed in the light of a recently proposed pharmacophore model and compared, by molecular modeling studies, with those obtained from effective BzR ligands.

Animals↗
PubMed1995

Synthesis of 3-(2'-furoyl)indole derivatives as potential new ligands at the benzodiazepine receptor, structurally more restrained analogues of indoleglyoxylylamides.

A number of furoylindoles were synthesized with the aim of obtaining structurally more restrained analogues of the previously described indoleglyoxylylamides, which are high affinity ligands at the benzodiazepine receptor. In these new compounds, the oxygen atom of the oxalyl CO(2) is inserted into the rigid furan ring. However, unlike the glyoxylylamides, they proved to be incapable of interacting with the benzodiazepine receptor. To rationalize these results, molecular electrostatic potentials were calculated; these indicated a positive electrostatic potential region for the furan oxygen, which thus prevents the formation of a hydrogen bond necessary for interaction with the receptor. Nevertheless, these findings confirmed that the CO(2) of the indoleglyoxylylamide derivatives represents one of the principal points of interaction with the receptor site for these kinds of ligands, as previously hypothesized by us.

Animals↗
PubMed1994

1-Methyl-4-phenylpyridinum kills differentiated PC12 cells with a concomitant change in protein phosphorylation.

1-Methyl-4-phenylpyridinum (MPP+), a selective neurotoxin, destroys the dopaminergic nigrostriatal pathway and results in a parkinsonian syndrome. Exposure of differentiated PC12 cells with nerve growth factor for 5 days to MPP+ (100 microM) for 4 h induced DNA fragmentation which is typical for the programmed cell death. MPP+ treatment (100 microM) concomitantly stimulates S6 kinase activity and resultant phosphorylation of S6 protein of 40S ribosomal subunits in the cells. Cycloheximide treatment prevents the MPP(+)-induced DNA fragmentation and enhancement of the phosphorylation of S6 protein. The present data demonstrate that neurotoxin, MPP+, kills differentiated PC12 cells by the apparent involvement of apoptotic process. Furthermore, the data strongly suggest that a change in protein phosphorylation might be involved in the signal transduction of MPP+ neurotoxicity and/or the protection from its toxicity.

1-Methyl-4-phenylpyridinium↗
PubMed1994

Cloning and expression of the MEP1 gene encoding an ammonium transporter in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, the transport of ammonium across the plasma membrane for use as a nitrogen source is mediated by at least two functionally distinct transport systems whose respective encoding genes are called MEP1 and MEP2. Mutations in the MEP2 gene affect high affinity, low capacity ammonium transport while mutations in the MEP1 gene disrupt a lower affinity, higher capacity system. In this work, the MEP1 gene has been cloned and sequenced and its expression analyzed. The predicted amino acid sequence reveals a highly hydrophobic, 54 kDa protein with 10 or 11 putative membrane-spanning regions. The predicted Mep1p protein shares high sequence similarity with several bacterial proteins of unknown function, notably the product of the nitrogen-regulated nrgA gene of Bacillus subtilis, and with that of a partial cDNA sequence derived from Caenorhabditis elegans. The Mep1p and related proteins appear to define a new family of transmembrane proteins evolutionarily conserved in at least bacteria, fungi and animals. The MEP1 gene is most highly expressed when the cells are grown on low concentrations of ammonium or on 'poor' nitrogen sources like urea or proline. It is down-regulated, on the other hand, when the concentration of ammonium is high or when other 'good' nitrogen sources like glutamine or asparagine are supplied in the culture medium. The overall properties of Mep1p indicate that it is a transporter of ammonium. Its main function appears to be to enable cells grown under nitrogen-limiting conditions to incorporate ammonium present at relatively low concentrations in the growth medium.

Amino Acid Sequence↗
PubMed1994

The reduced unsubstituted pteroate moiety is required for folate toxicity of cultured cerebellar granule neurons.

The proconvulsive and putative excitotoxic properties of folates led us to study folate toxicity in cultured rat cerebellar granule neurons. Exposure of these neurons to tetrahydrofolate (THF) (EC50 = 263 +/- 12 microM) and dihydrofolate (EC50 = 709 +/- 29 microM), but not to folate, formyl-THF, methyl-THF or methotrexate, resulted in a concentration-dependent neurotoxicity. THF and dihydrofolate toxicity were characterized by prominent neuronal swelling and early loss of neurite networking and could not be blocked by glutamate receptor antagonists, L-channel calcium blockers or anticonvulsants. Cleavage of THF into glutamate and tetrahydropteroate by glutamate carboxypeptidase in the presence of 1 microM MK-801 and 5 microM 6-cyano-7-nitroquinoxaline-2,3,dione shifted the concentration-toxicity curve to the left (EC50 = 47 +/- 4 microM). These results suggest (1) that the glutamate moiety is not necessary for folate toxicity, (2) that the unsubstituted reduced pteroate moiety is required for folate toxicity and (3) that unsubstituted reduced pteroates are previously unrecognized neurotoxins. Because there is no endogenous glutamate carboxypeptidase activity in cerebellar granule neuron cultures and no increase of glutamate levels in the medium of cultures exposed to THF or dihydrofolate, pteroate metabolites are unlikely to mediate the THF or dihydrofolate toxicity of cultured cerebellar granule neurons.

Animals↗
PubMed1993

MK-801 and memantine protect cultured neurons from glutamate toxicity induced by glutamate carboxypeptidase-mediated cleavage of methotrexate.

Cleavage of methotrexate into glutamate and diaminomethylpteroate by intrathecal glutamate carboxypeptidase is a new approach to the treatment of acute methotrexate neurotoxicity. The simulation of glutamate carboxypeptidase rescue from high-dose methotrexate in neuron astrocyte cocultures of rat cerebellum or cerebral cortex resulted in a selective, concentration-dependent neurotoxicity. The neurotoxicity was caused by the enzymatic release of glutamate from methotrexate at lower concentrations of methotrexate, and by both glutamate and diaminomethylpteroate at concentrations of methotrexate exceeding 200 microM. The good neuroprotection afforded by MK-801 and memantine suggested that glutamate toxicity was mediated by N-methyl-D-aspartate receptors. Methotrexate alone was not toxic to astrocytes, neurons, or the neurite networking. [3H]thymidine and [3H]deoxyuridine incorporation studies showed that astrocyte proliferation in the presence of methotrexate was maintained by the reutilization of pyrimidine bases for DNA synthesis. N-methyl-D-asparate receptor antagonists should be coadministered in future experimental and clinical trials examining intrathecal glutamate carboxypeptidase rescue of methotrexate toxicity.

Animals↗