Biomedical subjects
Publications and source records attributed to M Giorgi.
The title compound, (1S,3R,8R)-2,2-dichloro-3,7,7,10-tetramethyltricyclo[6.4.0.0(1,3)]dodecan-11-one thiosemicarbazone, C17H25Cl2N3S, has two disordered conformations of the cycloheptane moiety and a screw-boat conformation for the cyclohexene ring. The absolute configuration was established.
First measurements of the Collins and Sivers asymmetries of charged hadrons produced in deep-inelastic scattering of muons on a transversely polarized 6LiD target are presented. The data were taken in 2002 with the COMPASS spectrometer using the muon beam of the CERN SPS at 160 GeV/c. The Collins asymmetry turns out to be compatible with zero, as does the measured Sivers asymmetry within the present statistical errors.
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A high-performance liquid chromatography method to determine iohexol (IOX) and p-aminohippuric acid (PAH) in the plasma of dogs is evaluated according to recovery, reproducibility, and linearity utilizing a gradient pump. The mobile phase consists of 50mM sodium dihydrogen phosphate with 0.5mM tetrabutylammonium chloride, the pH is adjusted to 4.1, methanol is added to the final ratio of 90:10 (v/v), the flow rate is set at 1 mL/min, and separation is achieved with an ODS2 Luna column. The UV detector is set at 254 nm. IOX and PAH are used for evaluation of the effective renal plasma flow (ERPF) and glomerular filtration rate (GFR). The present method tested in three dogs demonstrates the accuracy in the evaluation of ERPF and GFR. Because of its precision and simplicity and low cost, it can be considered a good tool for ERPF and GFR in small animal practice.
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Currently, there are no reports on the effects of enrofloxacin (EF), a fluoroquinolone antibiotic, on the cytochrome p450 enzymes in fish, although its use as antimicrobial agent in aquaculture has been put forward. Therefore, the in vivo and in vitro effects of EF on hepatic p450 enzymes of sea bass, a widespread food-producing fish, have been evaluated. Sea bass pretreated with a single dose of EF (3 mg/kg i.p.) or with three daily doses of EF (1 mg/kg i.p.) markedly depressed the microsomal N-demethylation of aminopyrine, erythromycin, the O-deethylation of 7-ethoxycoumarin, ethoxyresorufin and the 6beta-testosterone hydroxylase. In vitro experiments showed that EF at 10 microM inhibited the above-mentioned activities and, in particular, the erythromycin N-demethylase (ERND) and 6beta-testosterone-hydroxylase, likely dependant on a p450 3A isoform. When the nature of ERND inhibition by EF was specifically studied with sea bass liver microsomes, it was found that EF is a potent mechanism-based inhibitor, with K(i) of 3.7 microM and a K(inact) of 0.045 min(-1). An immunoblot analysis with anti p450 3A27 of trout showed that the p450 3A isoform, constitutively expressed in sea bass, is particularly susceptible to inactivation by EF. In vitro experiments with sea bass microsomes have also demonstrated that EF is oxidative deethylated by the p450 system to ciprofloxacin (CF) and that this compound maintains the ability to inactivate the p450 enzymes. The mechanism by which EF or CF inactivate the p450 enzymes has not been studied but an attack of p450 on the cyclopropan ring, present, both in EF and CF structure, with the formation of electrophilic intermediates (i.e. radicals) has been postulated. In conclusion, the EF seems to be a powerful inhibitor of p450s in the sea bass. Therefore, the clinical use of this antibiotic in aquaculture has to be considered with caution.
Grapefruit juice changes the pharmacokinetic parameters of a variety of drugs metabolized primarily by cytochrome P450 3A. In a three-phase crossover study, six male beagle dogs were administered 100 ml of water (control), 100 ml of commercial liquid grapefruit juice, or 10 g of freeze-dried grapefruit juice (equivalent to 100 ml of liquid grapefruit juice) with 100 ml of water, followed after 2 h by single oral dose of praziquantel (30 mg kg(-1)). After treatment, the dogs were sampled at different times. Determination of praziquantel and its metabolite 4'-hydroxy praziquantel (identified by GC/MS) was performed by HPLC. Liquid and freeze-dried grapefruit juice preadministration increased the C(max) of praziquantel about three-fold and the AUC 2.5- and 2.3-fold, respectively. The T(max) (0.75 h) was unaffected by liquid or freeze-dried grapefruit juice, while T(1/2) was 2.3- and 1.7-fold higher compared with controls. The amount of 4'-hydroxy praziquantel was also affected by both liquid and freeze-dried grapefruit juice administration: the AUC and C(max) increased four- and three-fold, respectively and the T(max) was significantly enhanced. These findings demonstrate that both freeze-dried grapefruit juice and commercial liquid grapefruit juice significantly increase plasma concentrations and T(1/2) of praziquantel in dogs.
The title compounds, C(13)H(15)N(3)O(5)S and C(11)H(10)N(2)O(4)S(2), respectively, both contain a phenylsulfonyl group connected, through a methylene bridge, to either a substituted nitroimidazole or nitro-1,3-thiazole ring. In the imidazole-containing molecule, the nitro and sulfonyl groups are trans relative to the sulfonyl-methyl bond, while in the thiazole-containing molecule, these substituents are cis. The stabilizing interactions within the crystals are also different between the two compounds.
Eight healthy Holstein-Friesian calves and 8 Massese lambs of either sex (10-15-days old) were used to evaluate the pharmacokinetics of thiamphenicol after intravenous (i.v.) and oral (p.o.) administration (30 mg/kg). Plasma concentrations of thiamphenicol were determined by high-performance liquid chromatography on blood samples collected over 24h following treatment. Pharmacokinetic variables of the drug were calculated for both species and after both administration routes. After intravenous administration of thiamphenicol, a rapid distribution phase was followed by a slower elimination phase and, when thiamphenicol was administered p.o., the bioavailability was about 60% in both species. The higher volume of distribution and the longer biological elimination half-lives in pre-ruminant compared with adult animals indicate that thiamphenicol distributes widely into the extravascular compartment of pre-ruminants. Interspecies differences were observed in the kinetic behaviour of thiamphenicol with respect to peak plasma concentration (C(max)), time of peak plasma concentration (T(max)), elimination half-life (T(1/2)) and total clearance (Cl(B)). In conclusion intravenous or oral administration of 30 mg/kg of thiamphenicol provides plasma concentrations higher than minimum effective concentrations inhibiting bacterial growth (MICs) against most pathogens in pre-ruminant lambs and calves.
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We have produced a polyclonal antibody that specifically recognizes cGMP-binding cGMP-specific phosphodiesterase (PDE5). The antibody was raised in rabbit using as immunogen a fusion protein, in which glutathione S-transferase was coupled to a 171 amino acid polypeptide of the N-terminal region of bovine PDE5. The antibody is able to immunoprecipitate PDE5 activity from mouse tissues and neuroblastoma extracts while it has no effect on all other PDE isoforms present in the extracts. PDE5 activity recovered in the immunoprecipitates retains its sensitivity to specific inhibitors such as zaprinast (IC(50)=0.6 microM) and sildenafil (IC(50)=3.5 nM). Bands of the expected molecular mass were revealed when solubilized immunoprecipitates were analysed in Western blots. The antibody selectively stained cerebellar Purkinje neurones, which are known to express high levels of PDE5 mRNA. Western blot analysis of mouse tissues revealed the highest expression signal in mouse lung, followed by heart and cerebellum, while a lower signal was evident in brain, kidney and a very low signal was present in the liver. In the hybrid neuroblastoma-glioma NG108-15 cells the antibody revealed a high PDE5 induction after dibutyryl-cAMP treatment.
In the erythrocyte, ankyrin is the major adapter protein linking tetramers of band 3 to the spectrin-actin cytoskeleton. This linkage involves a direct interaction between ankyrin and the 14th-15th repeat unit of beta-spectrin. The spectrin cytoskeleton itself is stabilized by the self-association of spectrin heterodimers into tetramers and larger oligomers, a process mediated by the 17th repeat unit of beta-spectrin and a short NH(2) -terminal sequence in alpha-spectrin. The self-association of spectrin and its ankyrin-mediated membrane binding have generally been considered independent events. We now demonstrate that spectrin self-association, the binding of spectrin to ankyrin, and the binding of ankyrin to the 43-kDa cytoplasmic domain of band 3 (cdb3) are coupled in a positively cooperative way. In solution, [(125)I]-labeled ankyrin was found by ND-PAGE3 to enhance the affinity of spectrin self-association by 10-fold. The reciprocal process was also true, in that spectrin tetramers and oligomers bound ankyrin with enhanced affinity relative to dimer spectrin. Saturation of the beta-spectrin self-association site by an NH(2) -terminal 80-kDa alpha-spectrin peptide enhanced the affinity of spectrin dimer for ankyrin, indicating a direct relationship between ankyrin binding and the occupancy of the beta-spectrin self-association site. cdb3 accentuated these cooperative interactions. Several inherited spectrin mutations that cause hemolytic disease but that do not directly destabilize the self-association or ankyrin-binding sites can be explained by these results. Three classes of mutations appear to disrupt cooperative coupling between self-association and ankyrin binding: (i) mutation of the linker sequences that join helices C and A in repeat units that intervene between the two functional sites, mutations that presumably block repeat-to-repeat transfer of conformational information; (ii) mutations in alpha-spectrin repeats 4 to 6 that disrupt the ability of this region to trans-regulate ankyrin binding by the adjacent beta-spectrin repeats 14-15; and (iii) exon-skipping mutations that shorten alpha-spectrin and force repeats 4 to 6 to fall out-of-register with the ankyrin-binding motif in beta-spectrin. Collectively, these results demonstrate a molecular mechanism whereby a membrane receptor can directly promote cytoskeletal assembly.
The effect of beta-naphthoflavone (beta-NF) on several catalytic activities of cytochrome P450 (CYP) and phase II enzymes putatively controlled by [Ah]-receptor activation in the liver, heart and kidney of gilthead seabream, was investigated. In the liver, beta-NF treatment [intraperitoneal injection (i.p.) 50 mg/kg] resulted in an increase of CYP content, immunoreactive CYP 1A and methoxyresorufin-O-demethylase (MEROD), pentoxyresorufin O-depentylase (PROD) and ethoxyresorufin-O-deethylase (EROD) activities. However, beta-NF had no effect on any of the hepatic phase II enzymes examined (benzaldehyde dehydrogenase, propionaldehyde dehydrogenase, glutathione S-transferase, UDP-glucuronyl-transferase, DT-diaphorase). Single i.p. injection of 10 mg/kg beta-NF showed a maximal induction of CYP 1A-like protein and EROD activity after 3-7 days. CYP 1A and EROD returned to control levels 18-days post-treatment. beta-NF injection also caused a rapid increase of a single band size of mRNA recognized by a CYP 1A1 cDNA fragment from sea bass (Dicentrarchus labrax). Expression of mRNA preceded the increase of EROD activity and declined rapidly by 96 h. Dose-response experiments demonstrated that EROD was significantly enhanced in liver by a single injection of 0.3 mg/kg beta-NF and was the most sensitive measurement for CYP 1A-like induction. beta-NF treatments also increased the expression of CYP 1A-like protein, mRNA and EROD, but not MEROD and PROD activities in heart and kidney.
The effect of cyclic nucleotide phosphodiesterase (PDE) inhibitors Zaprinast and DC-TA-46 has been tested on SK-N-MC neuroblastoma growth. Antiproliferative activity of the tested drugs was assayed both in vitro and in the xenograft model of nude mice. In clonal density experiments, the IC50 value was 3.3 microM for Zaprinast and 1.9 microM for DC-TA-46, while 7.5 microM BCNU alkylating agent was required to obtain the same effect. SK-N-MC cells xenografted in the nude mouse showed that the administration of Zaprinast and DC-TA-46 caused a significant 50% decrease of the tumour weight. These data demonstrate that PDE inhibitors may be useful for at least reducing tumour growth; they may be of interest for further evaluation as alternative molecules in the design of multiple agent protocols for neuroblastoma treatment.
Praziquantel (PZQ) is a broadly effective trematocide and cestocide, widely employed in veterinary and human medicine. In view of several differences in both its pharmacokinetic profile in different animal species and in the cytochrome P450-dependent system between ruminant and nonruminant species, the present study was undertaken to determine the pharmacokinetics of this drug, its effects on the P450 system and the involvement of cytochrome P450 in its metabolism in 3-month-old lambs infested by Fasciola hepatica. Following both oral and i.m. administration, PZQ disposition was best described by a linear one-compartment open model with a rapid absorption and elimination. Although the PZQ dose used by the i.m. route was only half of that used by the oral route, the mean PZQ plasma concentration was higher after i.m. than after oral treatment. Oral treatment with 30 mg/kg/day of PZQ did not modify the mono-oxygenase activities tested, whilst the administration of PZQ at a dose of 60 mg/kg/day for 2 days caused a significant decrease in the P450 3A-dependent erythromycin N-demethylase and 6beta testosterone hydroxylase activities. From the incubation of microsomes from lambs not treated with PZQ, a single metabolite (PZQ 11b-OH or PZQ 1-OH) was identified by GC/MS analysis. By selective inhibition of the 3A subfamily performed with triacetyloleandromycin, the production of this metabolite declined by about 90% suggesting a prominent role of P450 3A isoforms in this oxidation. These features indicate that agents or drugs which are able to modulate P450 3A-dependent catalysis may interfere with the metabolism, bioavailability and therapeutic effects of PZQ.
In this study, several P450-dependent monoxygenase activities in the liver, kidney, and nasal mucosa of ring-necked pheasants were examined. In addition, the presence and inducibility of P450 isoenzymes in the hepatic and renal tissues of pheasants were examined by using typical substrates and inducers of P450s along with polyclonal antibodies raised against mammalian isoforms. Anti-rat P450 1A1 recognized in microsomes of both pheasant liver and kidney a protein that was markedly induced by beta-naphthoflavone and accompanied by an increase of various monooxygenases, in particular, methoxyresorufin-O-demethylase (MROD) activity. Anti-rat P450 2E1 revealed in microsomes of the pheasant liver but not in kidney an immunoreactive protein that was slightly induced by acetone but not accompanied by an increase of para-nitrophenol hydroxylase activity. On the other hand, acetone treatment caused an induction of other hepatic monoxygenases including MROD, erythromycin N-demethylase, and 6beta-testosterone hydroxylase. These two latter activities, known to be markers for 3A isoenzymes in rodents, were also enhanced in pheasant liver by phenobarbital but not by dexamethasone. The treatment with these two inducers also lacked to point out hepatic and renal proteins immunorelated to P450 3A or 2B subfamily, suggesting that these isoforms may be not expressed in pheasant. On the other hand, anti-rat P450 2C11 recognized two immunorelated proteins in the liver of both control and treated pheasants. The treatment with clofibrate, a mammalian inducer of 4A subfamily, induced both in liver and kidney of pheasant: i) a protein that cross-reacted with anti rat P450 4A1 and ii) the (omega) and (omega-1) lauric acid hydroxylase activities, known to be associated in mammals to this P450 subfamily. In the nasal mucosa of pheasant, a protein immunorelated to P450 2A and some monooxygenase activities (i.e., 7-ethoxycoumarin O-deethylase) linked, in mammals, to this isoform have been found; by contrast a protein immunoreactive with anti P450 2G1 was not found. In conclusion, the immunochemical properties and monooxygenase activities of constitutive and inducible P450s in pheasants were different not only from those of mammals but also from those of chickens. The findings of the present work also suggest that the P450 induction profiles might provide a potential biomarker of pheasant exposure to chemicals or environmental pollutants in the wild-field or in the stock-farm.