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Biomedical subjects

A Novelli

Publications and source records attributed to A Novelli.

At least 37 records · Page 2Linked to original sources
PubMed2001

Amoxicillin/clavulanate in chronic rhinosinusitis: tissue and serum distribution.

UNLABELLED: Amoxicillin/clavulanate in chronic rhinosinusitis: tissue and serum distribution. OBJECTIVE: The aim of the present study is to determine the concentrations of coamoxiclav in the sinusal mucosa of patients undergoing surgery for chronic sinusitis in comparison to serum levels after single oral administration. METHODOLOGY: 24 patients affected by chronic sinusitis, undergoing sinus surgery, were divided into three groups receiving an oral dose of 1 g of coamoxiclav (875 mg amoxicillin, 125 g of clavulanic acid, 7:1 ratio) at 2 h (first group), 4 h (second group) and 6 h (third group) before surgery. The mean concentration of amoxicillin and clavulanic acid were determined biologically in serum and in tissues. RESULTS: The highest concentrations of coamoxiclav both in serum and tissues were observed in the group which received the antibiotic 2 hours before surgery. However the tissue levels of both amoxicillin and clavulanic acid in the time period within 2-6 h after administration were higher than the Minimum Inhibitory Concentration (MIC) for the most frequent causative pathogens of sinus bacterial infections. CONCLUSIONS: Since penicillins need to maintain concentrations above the MIC for at least 40 to 60% of the interval time between administrations to be potentially effective, the Authors concluded that since both amoxicillin and clavulanic acid spread well in the ENT tissues, 1 g twice a day of the combination seems to be clinically effective even in patients suffering from acute episodes of chronic rhinosinusitis.

Adolescent↗
PubMed2001

[Role of parenteral cephalosporins for outpatients treatment of infections].

OPAT (Outpatient Parenteral Antibiotic Therapy) arose in the early 1980s in the USA and later in many other countries from the primary consideration that outpatient treatment is more cost-effective than hospitalisation. Currently, several thousand patients undergo OPAT programmes all over the world and several different bacterial infections are included in the list of treatable diseases, especially those requiring long-term parenteral treatment such as osteomyelitis and soft tissue infections. All injectable antibiotics are suitable for OPAT according to their microbiological spectrum, although clearly some pharmacological properties make one antibiotic more preferable than another. Beta-lactams represent more than half of the antibiotic world market and two-thirds of them are cephalosporins. Such a widespread use of cephalosporins is certainly due to their wide antibacterial spectrum and good tolerability. Among third-generation cephalosporins, covering the majority of micro-organisms responsible for community-acquired infections, ceftriaxone is the only one with an 8-hour half-life, thereby permitting a single daily dose, which represents a great advantage when undertaking an OPAT programme. Analysis of antibiotic consumption used for OPAT therapies, based on data collected from the International OPAT Registry project, with the participation of many countries (USA, Canada, Britain, Argentina, etc.) including Italy, shows that ceftriaxone is the most widely used antibiotic for home therapy, clearly due to the above-mentioned properties.

Ambulatory Care↗
PubMed2000

Mutual conformational adaptations in antigen and antibody upon complex formation between an Fab and HIV-1 capsid protein p24.

BACKGROUND: Elucidating the structural basis of antigen-antibody recognition ideally requires a structural comparison of free and complexed components. To this end we have studied a mouse monoclonal antibody, denoted 13B5, raised against p24, the capsid protein of HIV-1. We have previously described the first crystal structure of intact p24 as visualized in the Fab13B5-p24 complex. Here we report the structure of the uncomplexed Fab13B5 at 1.8 A resolution and analyze the Fab-p24 interface and the conformational changes occurring upon complex formation. RESULTS: Fab13B5 recognizes a nearly continuous epitope comprising a helix-turn-helix motif in the C-terminal domain of p24. Only 4 complementarity-determining regions (CDRs) are in contact with p24 with most interactions being by the heavy chain. Comparison of the free and complexed Fab reveals that structural changes upon binding are localized to a few side chains of CDR-H1 and -H2 but involve a larger, concerted displacement of CDR-H3. Antigen binding is also associated with an 8 degrees relative rotation of the heavy and light chain variable regions. In p24, small conformational changes localized to the turn between the two helices comprising the epitope result from Fab binding. CONCLUSIONS: The relatively small area of contact between Fab13B5 and p24 may be related to the fact that the epitope is a continuous peptide rather than a more complex protein surface and correlates with a relatively low affinity of antigen and antibody. Despite this, a significant quaternary structural change occurs in the Fab upon complex formation, with additional smaller adaptations of both antigen and antibody.

Amino Acid Sequence↗
PubMed2000

Antihistamine terfenadine potentiates NMDA receptor-mediated calcium influx, oxygen radical formation, and neuronal death.

We previously reported that the histamine H1 receptor antagonist terfenadine enhances the excitotoxic response to N-methyl-D-aspartate (NMDA) receptor agonists in cerebellar neurons. Here we investigated whether this unexpected action of terfenadine relates to its antihistamine activity, and which specific events in the signal cascade coupled to NMDA receptors are affected by terfenadine. Low concentrations of NMDA (100 microM) or glutamate (15 microM) that were only slightly (<20%) toxic when added alone, caused extensive cell death in cultures pre-exposed to terfenadine (5 microM) for 5 h. Terfenadine potentiation of NMDA receptor response was mimicked by other H1 antagonists, including chlorpheniramine (25 microM), oxatomide (20 microM), and triprolidine (50 microM), was prevented by histamine (1 mM), and did not require RNA synthesis. Terfenadine increased NMDA-mediated intracellular calcium and cGMP synthesis by approximately 2.4 and 4 fold respectively. NMDA receptor-induced cell death in terfenadine-treated neurons was associated with a massive production of hydrogen peroxides, and was significantly inhibited by the application of either (+)-alpha-tocopherol (200 microM) or the endogenous antioxidant melatonin (200 microM) 15 min before or up to 30 min after receptor stimulation. This operational time window suggests that an enduring production of reactive oxygen species is critical for terfenadine-induced NMDA receptor-mediated neurodegeneration, and strengthens the importance of antioxidants for the treatment of excitotoxic injury. Our results also provide direct evidence for antihistamine drugs enhancing the transduction signaling activated by NMDA receptors in cerebellar neurons.

Animals↗
PubMed2000

On excitotoxicity.

Explore the source record for details and available documents.

Gene Expression Regulation↗
PubMed2000

NMDA receptor dependent and independent components of veratridine toxicity in cultured cerebellar neurons are prevented by nanomolar concentrations of terfenadine.

Exposure of cultured neurons to nanomolar concentrations of terfenadine prevented the NMDA receptor-mediated early appearance (30min.) of toxicity signs induced by the voltage sensitive sodium channel activator veratridine. Terfenadine also provided an histamine-insensitive protection against delayed neurotoxicity by veratridine (24h), occurring independently of NMDA receptor activation, while not protecting from excitotoxicity following direct exposure of neurons to glutamate. Terfenadine reduced tetrodotoxin-sensitive inward currents, and reduced intracellular cGMP formation following veratridine exposure. Our data suggest that nanomolar concentrations of TEF may reduce excitatory aminoacid release following neuronal depolarization via a presynaptic mechanism involving voltage sensitive sodium channels, and therefore may be considered as a prototype for therapeutic drugs in the treatment of diseases that involve excitatory aminoacid neurotransmission.

Animals↗
PubMed2000

Postantibiotic leukocyte enhancement of meropenem against gram-positive and gram-negative strains.

The postantibiotic leukocyte enhancement (PALE) of meropenem in vitro in comparison with that of imipenem was evaluated with 24 recently isolated gram-positive and gram-negative strains. In general, pre-exposure to carbapenems (at four times the MIC for 2 h) led to increased polymorphonuclear cell phagocytic killing. The PALE of imipenem was generally significantly less than that observed with meropenem.

Anti-Bacterial Agents↗
PubMed2000

Interactions between triazoles and amphotericin B against Cryptococcus neoformans.

The interaction of amphotericin B (AmB) and azole antifungal agents in the treatment of fungal infections is still a controversial issue. A checkerboard titration broth microdilution-based method that adhered to the recommendations of the National Committee for Clinical Laboratory Standards was applied to study the in vitro interactions of AmB with fluconazole (FLC), itraconazole (ITC), and the new investigational triazole SCH 56592 (SCH) against 15 clinical isolates of Cryptococcus neoformans. Synergy, defined as a fractional inhibitory concentration (FIC) index of < or =0.50, was observed for 7% of the isolates in studies of the interactions of both FLC-AmB and ITC-AmB and for 33% of the isolates in studies of the SCH-AmB interactions; additivism (FICs, >0.50 to 1.0) was observed for 67, 73, and 53% of the isolates in studies of the FLC-AmB, ITC-AmB, and SCH-AmB interactions, respectively; indifference (FICs, >1.0 to < or =2.0) was observed for 26, 20, and 14% of the isolates in studies of the FLC-AmB, ITC-AmB, and SCH-AmB interactions, respectively. Antagonism (FIC >2.0) was not observed. When synergy was not achieved, there was still a decrease, although not as dramatic, in the MIC of one or both drugs when they were used in combination. To investigate the effects of FLC-AmB combination therapy in vivo, we established an experimental model of systemic cryptococcosis in BALB/c mice by intravenous injection of cells of C. neoformans 2337, a clinical isolate belonging to serotype D against which the combination of FLC and AmB yielded an additive interaction in vitro. Both survival and tissue burden studies showed that combination therapy was more effective than FLC alone and that combination therapy was at least as effective as AmB given as a single drug. On the other hand, when cells of C. neoformans 2337 were grown in FLC-containing medium, a pronounced increase in resistance to subsequent exposures to AmB was observed. In particular, killing experiments conducted with nonreplicating cells showed that preexposure to FLC abolished the fungicidal activity of the polyene. However, this apparent antagonism was not observed in vivo. Rather, when the two drugs were used sequentially for the treatment of systemic murine cryptococcosis, a reciprocal potentiation was often observed. Our study shows that (i) the combination of triazoles and AmB is significantly more active than either drug alone against C. neoformans in vitro and (ii) the concomitant or sequential use of FLC and AmB for the treatment of systemic murine cryptococcosis results in a positive interaction.

Amphotericin B↗
PubMed2000

New insight into the clinical pharmacokinetics of cefaclor: tissue penetration.

The serum pharmacokinetic data presented are generally in agreement with those obtained by other authors with both the cefaclor IR (immediate release) and AF (advanced formulation) or MR (modified release) formulations. With the new sustained-release formulation, the time of peak (Tmax) and mean residence time (MRT) values are significantly longer than those observed with the standard cefaclor IR. For the first time the penetration of the MR formulation of cefaclor was determined both in suction blister fluid (SBF) and alveolar epithelial lining fluid (ELF). Cefaclor demonstrated a high tissue distribution, with a high penetration index (PI) into blister fluid, which is at least representative of a relatively large volume of fluid-filled spaces and in part of highly vascularized tissues. SBF and ELF concentrations were higher than blood levels starting at the 4th-6th hour after dose, with longer elimination half-lives from the extravascular compartment than from serum. Cefaclor has a favorable pharmacokinetic profile, especially the new sustained-release formulation, which maintains effective concentrations for a longer time than the IR preparation. The MR formulation improves the kinetic properties of the cefaclor molecule with a prolonged MRT which allows a daily dosage of 750 mg every 12 h.

Aged↗
PubMed2000

Cefodizime in skin suction blister fluid and serum following a single intravenous or intramuscular dose in adult patients.

Cefodizime is a third generation cephalosporin for parenteral use. The pharmacokinetics of this cephem antibiotic were determined in serum and skin suction blister fluid (SBF) after intravenous (i.v.) or intramuscular (i.m.) administration of a single 1 g dose in 8 adult patients with normal renal and hepatic function who volunteered for the study. The concentration versus time curve showed a slower elimination rate from the extravascular compartment: the half-lives were 4.4+/-0.5 and 5.4+/-0.4 hours after i.v. and i.m. route respectively. The relatively long elimination half-life in SBF with a mean residence time of about 8 hours allows the use of cefodizime once-a-day for the treatment of infections due to sensitive pathogens.

Adult↗
PubMed1999

Terfenadine prevents NMDA receptor-dependent and -independent toxicity following sodium channel activation.

Exposure of cultured cerebellar neurons to terfenadine prevented the N-methyl-D-aspartate (NMDA) receptor-mediated early appearance (30 min) of toxicity signs induced by the voltage sensitive sodium channel (VSSC) activator veratridine. Delayed neurotoxicity by veratridine (24 h) occurring independently from NMDA receptor activation was also prevented by terfenadine. Terfenadine did not protect from excitotoxicity following direct exposure of neurons to glutamate. Our results suggest that terfenadine may modulate endogenous glutamate release following activation of VSSCs.

Animals↗
PubMed1999

Aluminum-induced degeneration of astrocytes occurs via apoptosis and results in neuronal death.

The mechanisms by which aluminum interacts with the nervous system are only partly understood. In this study, we used cultured astrocytes and neurons to investigate the effects of long exposures to aluminum (1 mM). We found that aluminum accumulated both in neurons and astrocytes. After 8-12 days exposure, aluminum caused strong changes in the morphology of astrocytes including shrinkage of cell bodies and retraction of processes. Exposures over 15-18 days reduced astrocytes viability by 50%. Aluminum-induced degeneration of astrocytes involved the DNA fragmentation characteristic of apoptosis, and staining of aluminum-treated astrocytes with the DNA-binding fluorochrome Hoeschst 33258 revealed the typical apoptotic condensation and fragmentation of chromatin. Aluminum was also found to be neurotoxic, causing first (4-6 days) abnormal clustering and aggregation, and later (8-12 days) neuronal death. Interestingly, aluminum neurotoxicity occurred in neuroglial cultures containing approximately 10% astrocytes but not in near-pure neuronal cultures containing only 1% astrocytes. Staining of co-cultured cells with Hoeschst 33258 showed apoptotic condensation and fragmentation of chromatin in aluminum-treated astrocytes but not in co-cultured neurons. Our study demonstrates that aluminum can induce the apoptotic degeneration of astrocytes, and that this toxicity is critical in determining neuronal degeneration and death. Aluminum-mediated apoptosis of cultured astrocytes may be also a valuable model system to study the mechanisms underlying apoptosis in glial cells.

Aluminum↗
PubMed1999

Head-to-tail dimers and interdomain flexibility revealed by the crystal structure of HIV-1 capsid protein (p24) complexed with a monoclonal antibody Fab.

The crystal structure of an intact molecule of HIV-1 capsid protein (p24) in complex with a monoclonal antibody fragment recognizing an epitope on the C-terminal domain has been determined at 3 A resolution. The helical N- and C-terminal domains of p24 are linked by an extended peptide forming a flexibly linked dumb-bell-shaped molecule 75 A in overall length. The p24 construct used is a variant with an N-terminal extension that mimics to some extent the Gag context of p24. We observed a novel head-to-tail dimer of p24 molecules which occurs through the formation of a substantial intermolecular interface between the N- and C-terminal domains. Comparison with previously observed p24 dimers shows that the same residues and secondary structural elements can partake in different interfaces revealing a remarkable stickiness and plasticity of the p24 molecule, properties which, combined with the inter-domain flexibility, are presumably important in the assembly and maturation of viral particles. Previous mutagenesis studies designed to test specific N-N and C-C homodimer interfaces do not discriminate fully against the possibility of the observed N-C interface.

Amino Acid Sequence↗
PubMed1999

Diagnosis of DiGeorge and Williams syndromes using FISH analysis of peripheral blood smears.

We describe the use of a FISH protocol for detecting chromosome microdeletions in peripheral blood smear leukocytes. This method has the advantage of a smaller sample requirement than classical metaphase chromosome analysis and the potential for analysis of a larger number of chromosome microdeletions using a routine blood smear. A selected series of 10 DiGeorge syndrome (DGS) and 12 Williams-Beuren syndrome (WBS) patients were correctly diagnosed by this method confirming results obtained by molecular cytogenetic metaphases. These results support effectiveness of interphase FISH analysis on peripheral blood smears as a focused, single-step method for the detection of chromosome microdeletions.

Adolescent↗
PubMed1999

Terfenadine induces toxicity in cultured cerebellar neurons: a role for glutamate receptors.

Exposure of cultured cerebellar neurons to the histamine H1 receptor antagonist terfenadine resulted in neuronal degeneration and death. Terfenadine neurotoxicity was dependent upon concentration and time of exposure. After 2 h exposure, 20 microM terfenadine reduced the number of surviving neurons by 75%, and as low as 10 nM terfenadine induced significant neurotoxicity after 5 days of exposure. Neuronal sensitivity to terfenadine changed with age in culture, and at 25 days in culture neurons appeared to be much less sensitive than at 5 or 9-17 days in culture. Neurotoxicity by terfenadine could not be prevented by high concentrations of histamine (5 mM), but it was significantly delayed by blocking NMDA or non-NMDA glutamate receptors with MK-801 or CNQX respectively, suggesting the involvement of excitatory transmission mediated by glutamate in the neurotoxicity induced by terfenadine in these neurons. We also found that the presence of terfenadine (5 microM) unveiled the potential excitotoxity of the non-NMDA receptor agonist AMPA (100 microM), and reduced the concentration of glutamate necessary to induce excitotoxicity, compared to untreated cultures. These results suggest a role for terfenadine in the modulation of the excitotoxic response mediated in cerebellar neurons through ionotropic glutamate receptors.

Animals↗
PubMed1999

Atypical deletions suggest five 22q11.2 critical regions related to the DiGeorge/velo-cardio-facial syndrome.

Deletions of chromosome 22q11.2 have been associated with distinct phenotypes including DiGeorge syndrome (DGS) and velo-cardio-facial (VCFS) syndrome. These diseases result from a failure to form derivatives of the third and fourth branchial arches during development. DGS/VCFS deletions usually encompass about 3 Mb of genomic DNA in more than 90% of patients. However, deletion mapping studies have failed to demonstrate the existence of a single small region of overlap (SRO) and ruled out any obvious correlation between site or size of deletion and severity of clinical phenotype. We describe three patients carrying 'atypical' deletions presenting the DGS/VCFS phenotype. A comparative analysis of deletions in our patients and those previously published has suggested the existence of five distinct critical regions within the 22q11.2 locus. This observation argues that DGS/VCFS results from haploinsufficiency secondary to a complex and as yet unexplained molecular mechanism, probably involving chromatin effects in mediating gene expression throughout the entire region.

Child, Preschool↗