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Biomedical subjects

L Maggi

Publications and source records attributed to L Maggi.

At least 37 records · Page 2Linked to original sources
PubMed2000

Controlled release of swine semen encapsulated in calcium alginate beads.

A quick and successful encapsulation method of swine spermatozoa is described: hydroxypropylmethylcellulose and calcium chloride were added to the sampled ejaculate swine sperm (sperm-rich fraction: creamy white) and then this suspension was dropped into an aqueous solution of sodium alginate. In order to obtain different capsule thicknesses, different calcium chloride concentrations were used. The influence of different formulations on in vitro spermatozoa release behavior and on the mechanical properties has been studied. In vitro sperm kinetics (motility and average velocity) have been determined. The results obtained from motility and average velocity tests of treated seminal material are promising, especially if the difficulty of preservation of swine spermatozoa compared to bovine sperm is considered. The different membranes obtained from the different calcium concentrations have had an influence on mechanical properties and on the release profile of spermatozoa from the capsules, and therefore, it is possible to modulate the release rate of the cells.

Alginates↗
PubMed2000

Technological and biological evaluation of tablets containing different strains of lactobacilli for vaginal administration.

Ten strains of lactobacilli were evaluated for the administration of viable microorganisms to restore the normal indigenous flora in the treatment of urogenital tract infections (UTI) in women. As the strains considered are facultative anaerobes, optimization of the production process was particularly critical to preserve bacterial viability. The microorganisms were formulated in single- and double-layer vaginal tablets. The two layers were characterized by different release properties: one is an effervescent composition that ensures a rapid and complete distribution of the active ingredient over the whole vaginal surface; while the second is a sustained release composition capable of releasing the lactobacilli over a longer period of time. Three different retarding polymers were tested, and all the formulations and tablets were evaluated in terms of technological processability, bacterial viability and stability, and cell adhesion properties of the microorganisms. From the results obtained, three out of ten strains appear particularly suitable for their application in the treatment of UTI. A larger batch of tablets made with a mixture of the three strains was then evaluated, confirming the feasibility of their industrial production and a good bacterial viability in the final dosage form.

Administration, Intravaginal↗
PubMed2000

SDF-1alpha-mediated modulation of synaptic transmission in rat cerebellum.

The functional expression of the seven-transmembrane domain G protein-coupled chemokine receptor CXCR-4/fusin in rat nerve cell was demonstrated by staining with a polyclonal anti-CXCR-4 Ab, and by evaluating the calcium responses to the physiological agonist stromal-derived cell factor-1alpha (SDF-1alpha) in both cerebellar granule cells in culture and Purkinje neurons (PNs) in cerebellar slices. Cerebellar glial, granule and Purkinje cells showed a pronounced staining for CXCR-4. Furthermore, cultured granule cells exhibited Ca2+ transients elicited by the application of SDF-1alpha, both in cell bodies and in neuronal processes. Whole-cell patch-clamped PNs in cerebellar slices responded to SDF-1alpha application by a slow inward current followed by an increase of both intracellular Ca2+ level and spontaneous synaptic activity. In particular, the SDF-1alpha-induced slow inward current was considerably reduced by ionotropic glutamate receptor blockers, but developed fully in a medium in which synaptic transmission was inhibited, indicating that this current might be, at least in part, mediated by extrasynaptic glutamate, possibly released from the surrounding glial and/or nerve cells. Taken together, these findings indicate a functional involvement of CXCR-4 in the modulation of synaptic transmission, adding another member to the repertoire of the chemokine receptors exerting a neuromodulatory role in the cerebellum.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed2000

Disintegration propensity of tablets evaluated by means of disintegrating force kinetics.

The aim of this work was to measure the disintegrating force concomitantly with tablet disintegration, in order to evaluate the disintegration propensity of tablets. Disintegration and dissolution were measured on tablets containing two poorly soluble drugs (diclofenac sodium or ketoprofen), including different percentages of two disintegrants (Explotab or Ac-Di-Sol). Because of the experimental setup, the disintegrating force measured was the result of the force generated by disintegrant swelling and dissipated by tablet disintegration. The disintegrating force versus time curves had shapes ranging from a skewed distribution curve to a bell-shaped curve, depending on slow or rapid disintegration of tablets, respectively. Interestingly, the shape of the resulting curves was very sensitive to the composition of the tablet. When the disintegrant in the formula was increased, the force-time curve approached the bell-like shape. The disintegration propensity of the tablet can be evaluated by the disintegrating force development during disintegration. The disintegration improvement of the formula can be predicted. The disintegrating force curve allows for the clear identification of the optimal percentage of disintegrant to be used.

Algorithms↗
PubMed1999

Nicotinic acetylcholine receptors assembled from the alpha7 and beta3 subunits.

Intracellular recordings were performed in voltage-clamped Xenopus oocytes upon injection with a mixture of cDNAs encoding the beta3 and mutant alpha7 (L247Talpha7) neuronal nicotinic acetylcholine receptor (nAChR) subunits. The expressed receptors maintained sensitivity to methyllycaconitine and to alpha-bungarotoxin but exhibited a functional profile strikingly different from that of the homomeric L247Talpha7 receptor. The heteromeric L247Talpha7beta3 nAChR had a lower apparent affinity and a faster rate of desensitization than L247Talpha7 nAChR, exhibited nonlinearity in the I-V relationship, and was inhibited by 5-hydroxytryptamine, much like wild type alpha7 (WTalpha7) nAChR. Single channel recordings in cell-attached mode revealed unitary events with a slope conductance of 19 picosiemens and a lifetime of 5 ms, both values being much smaller than those of the homomeric receptor channel. Upon injection with a mixture of WTalpha7 and beta3 cDNAs, clear evidence was obtained for the plasma membrane assembly of heteromeric nAChRs, although ACh could not activate these receptors. It is concluded that beta3, long believed to be an orphan subunit, readily co-assembles with other subunits to form heteromeric receptors, some of which may be negative regulators of cholinergic function.

Aconitine↗
PubMed1999

Influence of the moisture on the performance of a new dry powder inhaler.

An accelerated stability test was carried out on two prototypes of a new dry powder inhaler (DPI) to verify the influence of moisture uptake on the performance of the device. The prototypes were stored at 40 degrees C and 75% relative humidity (RH) for different storage times and their performance was assessed in terms of emitted dose and respirable fraction (Twin Impinger). At the same time intervals, the water content of the powder contained in the drug reservoir was evaluated using Karl Fischer's method. The respirable fraction was strongly influenced by the moisture content of the powder, on the contrary, the dosing precision and reproducibility is independent of this variable. The results show that a suitable protection from the external environment is necessary to prevent moisture uptake in the powder and the consequent loss of efficiency of the delivery device.

Drug Delivery Systems↗
PubMed1999

Procedure for analysis of radium in freshwaters by adsorption on basic lead rhodizonate.

Radium analysis is carried out by batch adsorption from natural waters on basic lead rhodizonate supported on charcoal, LERHO, starting from 2-L samples. 133Ba is added to allow the measurement of the overall chemical yield by gamma counting. Radium is recovered with a few milliliters of 1.5 M HCl, and lead is removed by a chromatographic column filled with Dowex 2 x 8. Finally 50 micrograms of barium carrier is added, and the radium is coprecipitated as sulfate on a preformed bed of barium sulfate, to prepare a sample suitable for alpha and gamma counting. The detection limit of the proposed method is 0.002 Bq/L 226Ra. This value is far beyond the radium activity admissible for drinking waters. Due to lack of appropriate samples, the procedure was tested using mineral waters spiked with 226Ra and two commercially available mineral waters with very low radium contents.

Adsorption↗
PubMed1999

Formulation of biphasic release tablets containing slightly soluble drugs.

A new biphasic release system for slightly soluble drugs has been proposed. To enhance the dissolution rate, the drug was milled with a superdisintegrant. Then, double-layer tablets were prepared. One layer was formulated to release the drug in a very short time (fast-release). The other consisted of an extended-release hydroxypropylmethylcellulose (HPMC) matrix. Different HPMC concentrations (10, 16 and 22%) and viscosity grades (Methocel K4, K15 and K100M) were used to obtain different release rates of the drug from the extended-release layer, ketoprofen and praziquantel were used as slightly soluble model drugs. The in vitro dissolution tests of the prepared double-layer systems, showed the desired biphasic behaviour: the drug contained in the fast releasing layer dissolved within the first 15 min, while the drug contained in the prolonged-release layer was released at different times, depending on the formulation of the hydrophilic matrix. In particular, an increase in the percentage and viscosity grade of HPMC, in the extended release layer, leads to a decrease in the drug delivery rate and produces a wide range of different release rates from only a few hours up to 24 h.

Chemistry, Pharmaceutical↗
PubMed1999

Selective effects of a 4-oxystilbene derivative on wild and mutant neuronal chick alpha7 nicotinic receptor.

1. We assessed the pharmacological activity of triethyl-(beta-4-stilbenoxy-ethyl) ammonium (MG624), a drug that is active on neuronal nicotinic receptors (nicotinic AChR). Experiments on the major nicotinic AChR subtypes present in chick brain, showed that it inhibits the binding of [125I]-alphaBungarotoxin (alphaBgtx) to the alpha7 subtype, and that of [3H]-epibatidine (Epi) to the alpha4beta2 subtype, with Ki values of respectively 106 nM and 84 microM. 2. MG624 also inhibited ACh elicited currents (I(ACh)) in the oocyte-expressed alpha7 and alpha4beta2 chick subtypes with half-inhibitory concentrations (IC50) of respectively 109 nM and 3.2 microM. 3. When tested on muscle-type AChR, it inhibited [125I]-alphaBgtx binding with a Ki of 32 microM and ACh elicited currents (I(ACh)) in the oocyte-expressed alpha1beta1gammadelta chick subtype with an IC50 of 2.9 microM. 4. The interaction of MG624 with the alpha7 subtype was investigated using an alpha7 homomeric mutant receptor with a threonine-for-leucine 247 substitution (L247T alpha7). MG624 did not induce any current in oocytes expressing the wild type alpha7 receptor, but did induce large currents in the oocyte-expressed L247T alpha7 receptor. The MG624 elicited current (I(MG62)) has an EC50 of 0.2 nM and a Hill coefficient nH of 1.9, and is blocked by the nicotinic receptor antagonist methyllycaconitine (MLA). 5. These binding and electrophysiological studies show that MG624 is a potent antagonist of neuronal chick alpha7 nicotinic AChR, and becomes a competitive agonist following the mutation of the highly conserved leucine residue 247 located in the M2 channel domain.

Acetylcholine↗
PubMed1998

Effects of Zn2+ on wild and mutant neuronal alpha7 nicotinic receptors.

Zn2+ is a key structural/functional component of many proteins and is present at high concentrations in the brain and retina, where it modulates ligand-gated receptors. Therefore, a study was made of the effects of zinc on homomeric neuronal nicotinic receptors expressed in Xenopus oocytes after injection of cDNAs encoding the chicken wild or mutant alpha7 subunits. In oocytes expressing wild-type receptors, Zn2+ alone did not elicit appreciable membrane currents. Acetylcholine (AcCho) elicited large currents (IAcCho) that were reduced by Zn2+ in a reversible and dose-dependent manner, with an IC50 of 27 microM and a Hill coefficient of 0.4. The inhibition of IAcCho by Zn2+ was competitive and voltage-independent, a behavior incompatible with a channel blockade mechanism. In sharp contrast, in oocytes expressing a receptor mutant, with a threonine-for-leucine 247 substitution (L247Talpha7), subnanomolar concentrations of Zn2+ elicited membrane currents (IZn) that were reversibly inhibited by the nicotinic receptor blockers methyllycaconitine and alpha-bungarotoxin. Cell-attached single-channel recordings showed that Zn2+ opened channels that had a mean open time of 5 ms and a conductance of 48 pS. At millimolar concentrations Zn2+ reduced IAcCho and the block became stronger with cell hyperpolarization. Thus, Zn2+ is a reversible blocker of wild-type alpha7 receptors, but becomes an agonist, as well as an antagonist, following mutation of the highly conserved leucine residue 247 located in the M2 channel domain. We conclude that Zn2+ is a modulator as well as an activator of homomeric nicotinic alpha7 receptors.

Acetylcholine↗
PubMed1998

4-Oxystilbene compounds are selective ligands for neuronal nicotinic alphaBungarotoxin receptors.

1. Starting from the structure of an old 4-oxystilbene derivate with ganglioplegic activity (MG624), we synthesized two further derivates (F2 and F3) and two stereoisomers of F3 (F3A and F3B), and studied their selective effect on neuronal nicotinic acetylcholine receptor (AChR) subtypes. 2. MG 624, F3, F3A and F3B inhibited of 125I-alphaBungarotoxin (alphaBgtx) binding to neuronal chick optic lobe (COL) membranes, with nM affinity, but inhibited 125I-alphaBgtx binding to TE671 cell-expressed muscle-type AChR only at much higher concentrations. 3. We immobilized the alpha7, beta2 and beta4 containing chick neuronal nicotinic AChR subtypes using anti-subunit specific antibodies. MG 624, F3, F3A and F3B inhibited 125I-alphaBgtx binding to the alpha7-containing receptors with nM affinity, but inhibited 3H-Epi binding to beta2-containing receptors only at very high concentrations (more than 35 microM); their affinity for the beta4-containing receptors was ten times more than for the beta2-containing subtype. 4. Both MG624 and F3 compounds inhibited the ACh evoked currents in homomeric oocyte-expressed chick alpha7 receptors with an IC50 of respectively 94 and 119 nM. 5. High doses of both MG 624 and F3 depressed the contractile response to vagus nerve stimulation in guinea pig nerve-stomach preparations although at different IC50s (49.4 vs 166.2 microM) The effect of MG624 on rat nerve-hemidiaphragm preparations was 33 times less potent than that of F3 (IC50 486 vs 14.5 microM). 6. In conclusion, MG624 and F3 have a high degree of antagonist selectivity for neuronal nicotinic alphaBgtx receptors containing the alpha7 subunit.

Animals↗
PubMed1998

Effects of fluoxetine on wild and mutant neuronal alpha 7 nicotinic receptors.

Fluoxetine is used in the treatment of a variety of clinical disorders including depression and obesity, and of cocaine detoxification or alcoholism. It is generally believed that fluoxetine exerts its clinical effects because it selectively blocks 5-hydroxytryptamine (5HT) reuptake into nerve terminals. In here we describe that fluoxetine antagonized the neuronal homomeric alpha 7 nicotinic acetylcholine receptors (nAChR) expressed in Xenopus oocytes, with an IC50 of 43 microM, when fluoxetine was coapplied with ACh, and of 1.6 microM when the oocytes were pretreated briefly with fluoxetine. A similar block occurred in oocytes expressing L247T alpha 7 mutant nAChR. Furthermore, blockage of mutant alpha 7 receptors appeared non-competitive and was stronger with cell membrane hyperpolarization. Cell-attached single channel recordings in oocytes expressing L247T alpha 7 mutant nAChR showed that the voltage-dependence of the blockage by fluoxetine could be due to a drastic decrease in channel opening frequency accompanied by marked channel flickering and reduced channel conductance. We conclude that fluoxetine behaves as a reversible blocker of both wild and mutant alpha 7 receptors; and that the Leu-247T mutation in the channel domain renders the blockage of alpha 7 nAChR by fluoxetine voltage-dependent. These effects of fluoxetine on alpha 7 receptors may be clinically important.

Acetylcholine↗
PubMed1998

Formulation and characterization of calcium alginate beads containing ampicillin.

The purpose of this work was the preparation and characterization of calcium alginate beads containing ampicillin. Aqueous solutions of drug and sodium alginate (three viscosity grades) were added drop by drop to aqueous solutions of calcium chloride; the droplets instantaneously formed gel beads, which were then dried. Morphological studies and drug contents, in vitro release, and erosion tests were carried out for the characterization of the prepared beads. The dried particles were characterized by irregular shape and a smooth or rough surface, depending on the viscosity grade of the alginate used. The control of the drug for different time intervals depended on the molecular weight of the polymer used; however, the pH-change test showed that this capacity was much lower in the case of acid-treated particles. The results obtained show that the ampicillin beads prepared are suitable for intramammary therapy.

Alginates↗
PubMed1998

Pneumonia due to Leptospira spp.: results of an epidemiological and clinical study.

OBJECTIVE: To evaluate the prevalence of Leptospira spp. infections in a population of in- and out-patients with community acquired pneumonia (CAP) and the incidence of leptospiral pneumonia. DESIGN AND RESULTS: Of 176 patients infected with CAP who were evaluated for the presence of Leptospira spp. as causative agent, 10 were found positive for leptospiral antibodies (prevalence rate: 5.7%), but seroconversion was observed in only one case (incidence rate: 0.6%). The patient had had recent contact with possibly contaminated water. She had pulmonary involvement and signs of mild hepatic damage, but recovered fully. CONCLUSION: The authors highlight the importance of testing for leptospirosis in case of pneumonia in endemic areas where the more common causative pathogens for CAP can not be documented and when initial empiric therapy is ineffective.

Adult↗
PubMed1997

Neuronal nicotinic threonine-for-leucine 247 alpha7 mutant receptors show different gating kinetics when activated by acetylcholine or by the noncompetitive agonist 5-hydroxytryptamine.

Mutation of the highly conserved leucine residue (Leu-247) converts 5-hydroxytryptamine (5HT) from an antagonist into an agonist of neuronal homomeric alpha7 nicotinic acetylcholine receptor expressed in Xenopus oocytes. We show here that acetylcholine (AcCho) activates two classes of single channels with conductances of 44 pS and 58 pS, similar to those activated by 5HT. However, the mean open time of AcCho-gated ion channels (11 ms) is briefer than that of 5HT-gated ion channels (18 ms). Furthermore, whereas the open time of AcCho channels lengthens with hyperpolarization, that of 5HT channels is decreased. In voltage-clamped oocytes, the apparent affinity of the alpha7 mutant receptor for 5HT is not modified by the presence of dihydro-beta-erythroidine, which acts on the AcCho binding site in a competitive manner. This indicates a noncompetitive action of 5HT on nicotinic acetylcholine receptors. Considered together, our findings show that AcCho gates alpha7 mutant channels with similar conductance but with different kinetic profile than the channels gated by 5HT, suggesting that the two agonists act on different docking sites. These results will help to understand the crosstalk between cholinergic and serotonergic systems in the central nervous system.

Acetylcholine↗
PubMed1997

A novel Mn++-dependent ribonuclease that functions in U16 SnoRNA processing in X. laevis.

The intron-encoded U16 small nucleolar RNA (snoRNA) is a component of a new family of molecules which originate by processing of pre-mRNA in which they are contained. The mechanism of U16 snoRNA biosynthesis involves an initial step of endonucleolytic cleavage of the pre-mRNA with the release of a pre-snoRNA molecule; the subsequent step consists of exonucleolytic trimming that produces mature U16 molecules. In order to identify the molecular components involved in this peculiar biosynthetic pathway, we have undertaken the characterization of the endonucleolytic activity by biochemical fractionation of Xenopus laevis oocyte nuclear extract. In this paper we show the production of a protein fraction (BSF) which is highly enriched for a specific endonucleolytic activity that exactly reproduces the cleavage pattern of the U16-containing pre-mRNA identified in vivo in X. laevis oocytes and in unfractionated nuclear extract.

Animals↗
PubMed1997

Evaluation of preservative effectiveness in pharmaceutical products: the use of a wild strain of Pseudomonas cepacia.

A sodium benzoate-sorbic acid preservative system of a pharmaceutical product was proved effective against a wild strain of Pseudomonas cepacia, following the official method of the Italian and British Pharmacopoeias. However, this preservative system was ineffective against a challenge of Ps. cepacia wild strain cells grown in the unpreserved pharmaceutical product and on culture media different from those described by the Pharmacopoeias. The adaptive resistance of the wild strain of Ps. cepacia was not demonstrated with a laboratory strain (ATCC 25609). In contrast, p-hydroxybenzoate-based preservative systems proved to be efficient in protecting the pharmaceutical product against a challenge of wild and laboratory strains of Ps. cepacia grown in the different conditions described above. The results obtained suggest the usefulness, in the official methods for testing pharmaceutical preservatives, of using wild microbial strains isolated from the pharmaceutical environment. Metabolic adaptive responses, capable of affecting the antimicrobial sensitivity of wild micro-organisms used to challenge the preserved product, can be detected by using cells grown in the unpreserved pharmaceutical product.

Benzoates↗