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Biomedical subjects

A Vila

Publications and source records attributed to A Vila.

At least 19 recordsLinked to original sources
PubMed2005

PLA-PEG particles as nasal protein carriers: the influence of the particle size.

Previous studies have shown that PLA-PEG nanoparticles (NP) are able to enhance the transport of the encapsulated model protein, tetanus toxoid (TT), across the rat nasal mucosa. The aim of this work was to study if the size of PLA-PEG particles affects the nasal transport of the encapsulated protein and, also, the potential contribution of blank nanoparticles to the transport of the free protein. To achieve this purpose, 125I-TT was encapsulated into PLA-PEG particles of different sizes (200 nm, 1.5, 5 and 10 microm) prepared by the water-in-oil-in-water solvent evaporation technique. Firstly, in order to investigate the carrier role of the particles, two series of either conscious or anaesthetized rats were nasally treated with 125I-TT-loaded NP, free 125I-TT, and a physical mixture of blank NP and free 125I-TT. Secondly, the influence of the particle size on the nasal transport of TT encapsulated into PLA-PEG particles was evaluated in conscious rats. The amount of radioactivity recovered in the blood compartment, lymph nodes and other relevant tissues was monitored for up to 24h. Finally, the nasal bioavailability of 125I-TT-loaded PLA-PEG NP was calculated. The results indicated that the use of anaesthesia enhances the transport of 125I-TT and that the physical presence of PLA-PEG NP does not affect the transport of the toxoid. In contrast, when TT was encapsulated into the particles its transport across the nasal mucosa of conscious rats was significantly enhanced. Furthermore, the efficacy of this transport was related to the particle size, reaching the most important transport for the smallest particle size. The intensity of this transport was also illustrated by the high nasal bioavailability of TT encapsulated into nanoparticles (200 nm) (F = 70-80%). These results led us to conclude that PLA-PEG NP can be accepted as nasal protein carriers for nasal administration.

Administration, Intranasal↗
PubMed2005

Leaving previously implanted central venous catheters (ports) in place does not increase morbidity in patients undergoing autologous peripheral stem cell transplantation.

We sought to assess if leaving in place a previously inserted noncolonized or infected implantable catheter (IC) is associated with an increase in morbidity in patients undergoing autologous peripheral stem cell transplantation (APSCT). Medical records from all patients between March 1997 and January 2002 undergoing APSCT with an IC in place were reviewed. Case group (IC in place) was compared with a control group (no IC) from 6 days prior to 60 days after APSCT. In all, 43 cases were matched with 43 controls by underlying disease, age and sex. In both groups, duration of neutropenia and use of antimicrobial prophylaxis were comparable. Underlying malignancies were lymphoma (22/24), multiple myeloma (14/12), leukemia (3/3), and others (7/7) in case and control groups. Cases and controls had comparable rates of risk for fever, bloodstream infection, use of vancomycin and amphotericin B, and death, as well as comparable lengths of stay and readmissions. ICs were used in 20 of 43 patients. Using the IC did not significantly increase the risk of fever, bloodstream infection, length of stay, and/or readmissions after APSCT but was associated with increased use of antibacterial and antifungal agents. Leaving in place a previously inserted, noncolonized or infected IC did not increase morbidity in patients undergoing APSCT.

Adult↗
PubMed2004

PEG-PLA nanoparticles as carriers for nasal vaccine delivery.

This report presents an overview of the potential of nanoparticles as nasal carriers for drug/vaccine administration. In addition, this report shows, for the first time, the efficacy of polylactic acid nanoparticles coated with a hydrophilic polyethyleneglycol coating (PEG-PLA nanoparticles) as carriers for the nasal transport of bioactive compounds. For this purpose, tetanus toxoid (TT), a high molecular weight protein (Mw 150,000 Da), was chosen as a model antigen and encapsulated in the PEG-PLA nano- and microparticles (200 nm and 1.5 microm respectively). These nanosystems were first characterized for their stability in the presence of lysozyme and also for their size, electrical charge, loading efficiency, in vitro release of antigenically active toxoid and afterwards, these formulations were administered intranasally to mice and the systemic and mucosal anti-tetanus responses were evaluated for up to 24 weeks. Additionally, PEG-PLA particles labeled with rhodamine 6G were administered intranasally to rats in order to visualize their interaction with the nasal mucosae by fluorescence microscopy. Their behavior was compared with that of the well known PLA nanoparticles (200 nm). The results showed that PLA nanoparticles suffered an immediate aggregation upon incubation with lysozyme, whereas the PEG-coated nanoparticles remained totally stable. The antibody levels elicited following i.n. administration of PEG-coated nanoparticles were significantly higher than those corresponding to PLA nanoparticles. Furthermore, PEG-PLA nanoparticles generated an increasing and a long lasting response. The qualitative fluorescence microscopy studies revealed that PEG-PLA particles are able to cross the rat nasal epithelium. These studies indicate that the PEG coating around the particles has a role in stabilizing PLA particles in mucosal fluids and that it facilitates the transport of the nanoencapsulated antigen, hence eliciting a high and long lasting immune response.

Administration, Intranasal↗
PubMed2002

Design of biodegradable particles for protein delivery.

Major research issues in protein delivery include the stabilization of proteins in delivery devices and the design of appropriate protein carriers in order to overcome mucosal barriers. We have attempted to combine both issues through the conception of new biodegradable polymer nanoparticles: (i) poly(ethylene glycol) (PEG)-coated poly(lactic acid) (PLA) nanoparticles, chitosan (CS)-coated poly(lactic acid-glycolic acid (PLGA) nanoparticles and chitosan (CS) nanoparticles. These nanoparticles have been tested for their ability to load proteins, to deliver them in an active form, and to transport them across the nasal and intestinal mucosae. Additionally, the stability of some of these nanoparticles in simulated physiological fluids has been studied. Results showed that the PEG coating improves the stability of PLA nanoparticles in the gastrointestinal fluids and helps the transport of the encapsulated protein, tetanus toxoid, across the intestinal and nasal mucosae. Furthermore, intranasal administration of these nanoparticles provided high and long-lasting immune responses. On the other hand, the coating of PLGA nanoparticles with the mucoadhesive polymer CS improved the stability of the particles in the presence of lysozyme and enhanced the nasal transport of the encapsulated tetanus toxoid. Finally, nanoparticles made solely of CS were also stable upon incubation with lysozyme. Moreover, these particles were very efficient in improving the nasal absorption of insulin as well as the local and systemic immune responses to tetanus toxoid, following intranasal administration. In summary, these results show that a rational modification in the composition and structure of the nanoparticles, using safe materials, increases the prospects of their usefulness for mucosal protein delivery and transport.

Animals↗
PubMed2001

Spontaneous intermembrane transfer of various cholesterol-derived hydroperoxide species: kinetic studies with model membranes and cells.

Whereas spontaneous and protein-mediated transfer/exchange of cholesterol (Ch) between membranes has been widely studied, relatively little is known about the translocation of Ch oxidation products, particularly hydroperoxide species (ChOOHs), which can act as cytotoxic prooxidants. A major aim of the present study was to examine and compare the intermembrane transfer characteristics of several biologically relevant ChOOH isomers, including singlet oxygen-derived 5alpha-OOH, 6alpha-OOH, and 6beta-OOH and free radical-derived 7alpha-OOH and 7beta-OOH. These species were generated in [(14)C]Ch-labeled donor membranes [erythrocyte ghosts or unilamellar DMPC/Ch (1.0:0.8 mol/mol) liposomes] by means of dye-sensitized photoperoxidation. Spontaneous transfer to nonoxidized acceptor membranes (DMPC liposomes or ghosts, respectively) at 37 degrees C was monitored by thin-layer chromatography with phosphorimaging radiodetection (HPTLC-PI) or liquid chromatography with mercury cathode electrochemical detection [HPLC-EC(Hg)]. The former allowed measurement of total (unresolved) ChOOH along with parent Ch, whereas the latter allowed measurement of individual ChOOHs. Ghost membranes in which approximately 4% of the Ch had been peroxidized, giving mainly 5alpha-OOH, transferred total ChOOH and Ch to liposomes in apparent first-order fashion, the rate constant for ChOOH being approximately 65 times greater. Like Ch desorption, ChOOH desorption from donor membranes was found to be rate limiting, and rate varied inversely with size when liposomal donors were used. For individual ChOOHs, rate constant magnitude (7alpha/7beta-OOH > 5alpha-OOH > 6alpha-OOH > 6beta-OOH) correlated inversely with reverse-phase HPLC retention time, suggesting that faster transfer reflects greater hydrophilicity. Liposome-borne ChOOHs exhibited the same order of toxicity toward COH-BR1 cells, which are deficient in ability to detoxify these peroxides. The prospect of disseminating oxidative cell injury via translocation of ChOOHs and other lipid hydroperoxides is readily apparent from these findings.

Breast Neoplasms↗
PubMed2001

Regulation of the nuclear orphan receptor Nur77 in bone by parathyroid hormone.

Osteoblasts function under the control of several hormones and growth factors. Among them, parathyroid hormone (PTH) and steroid hormones have significant effects on bone metabolism. We show that PTH induced the expression of Nur77, a member of the NGFI-B subfamily of nuclear orphan receptors in bone. PTH rapidly and transiently induced Nur77 mRNA in primary mouse osteoblasts that peaked at 1 h and at 10 nM of hormone. Cycloheximide did not affect the induction of Nur77 mRNA, suggesting that protein synthesis is not required for the PTH effect. PTH also induced Nur77 mRNA in calvariae cultures. Finally Nur77 protein expression was induced in nuclear protein extracts of cells treated with PTH. NGFI-B nuclear receptors have been implicated in retinoic acid, vitamin D, and thyroid hormone signaling. We propose that induction of NGFI-B nuclear orphan receptors represents a potential cross-talk mechanism between PTH and steroid hormone signaling to regulate bone metabolism.

Animals↗
PubMed2001

Clinical ergotism induced by ritonavir.

Ritonavir strongly inhibits cytochrome P450, thus altering the metabolism of other drugs. We report on an HIV-positive man who, on his 13th day of ritonavir therapy, developed severe ergotism after self-administration of low doses of ergotamine. Drug interactions, the degree of responsibility of the patient and the availability of over-the-counter medications must be considered when prescribing antiretroviral therapy.

Adult↗
PubMed2000

The role of PEG on the stability in digestive fluids and in vivo fate of PEG-PLA nanoparticles following oral administration.

The aim of the present work was to evaluate if the presence of a polyethylenglycol (PEG) coating around PLA nanoparticles would affect their interaction with biological surfaces, following oral administration to rats. For this purpose, a model antigen, 125I-radiolabeled tetanus toxoid, was encapsulated in PLA and PLA-PEG nanoparticles by a modified water-in-oil-in-water solvent evaporation technique. Firstly, the stability of the nanoparticles in simulated gastrointestinal fluids was evaluated. Results showed an interaction between the nanoparticles and the enzymes of the digestive fluids, this interaction being considerably reduced by the PEG coating around the particles. On the other hand, the PLA forming the nanoparticles was found to be only slightly degraded (9% converted to lactate for PLA nanoparticles and 3% for PLA-PEG nanoparticles) and that the encapsulated tetanus toxoid remained mostly associated to the nanoparticles upon incubation in the digestive fluids for up to 4 h. Finally, the in vivo experiments showed that, after oral administration to rats, the levels of encapsulated radioactive antigen in the blood stream and lymphatics were higher for PLA-PEG nanoparticles than for PLA nanoparticles. In conclusion, the PLA-PEG nanoparticles have a promising future as protein delivery systems for oral administration.

Journal Article↗
PubMed2000

Dissemination of peroxidative stress via intermembrane transfer of lipid hydroperoxides: model studies with cholesterol hydroperoxides.

Lipid hydroperoxides (LOOHs) can be generated in cells when cholesterol (Ch) and other unsaturated lipids in cell membranes are degraded under conditions of oxidative stress. If LOOHs escape reductive detoxification by glutathione-dependent selenoperoxidases, they may undergo iron-catalyzed one-electron reduction to free radical species, thus triggering peroxidative chain reactions which exacerbate oxidative membrane damage. LOOHs are more polar than parent lipids and much longer-lived than free radical precursors or products. Accordingly, intermembrane transfer of LOOHs (analogous to that of unoxidized precursors) might be possible, and this could jeopardize acceptor membranes. We have investigated this possibility, using photoperoxidized [(14)C]Ch-labeled erythrocyte ghosts as cholesterol hydroperoxide (ChOOH) donors and unilamellar liposomes [e.g., dimyristoyl-phosphatidylcholine/Ch, 9:1 mol/mol] as acceptors. ChOOH material consisted mainly of 5alpha-hydroperoxide, a singlet oxygen adduct. Time-dependent transfer of ChOOH versus Ch at 37 degrees C was determined, using high-performance liquid and thin-layer chromatographic methods to analyze liposomal extracts for these species. A typical experiment in which the starting ChOOH/Ch mol ratio in ghosts was approximately 0.05 showed that the initial transfer rate of ChOOH was approximately 16 times greater than that of parent Ch. Using [(14)C]Ch as a reporter in liposome acceptors, we found that transfer-acquired ChOOHs, when exposed to a lipophilic iron chelate and ascorbate, could trigger strong peroxidative chain reactions, as detected by accumulation of [(14)C]Ch oxidation products. These findings support the hypothesis that intermembrane transfer of ChOOHs can contribute to their prooxidant membrane damaging and cytotoxic potential.

Cell Membrane↗
PubMed1999

Variation in diagnostic strategy of the EMG examination--a multicentre study.

OBJECTIVES: In order to improve the universal quality of the EMG examination, knowledge about the variation among physicians is needed. METHODS: The variation among physicians in diagnostic strategy or criteria for diagnosing was analysed from a multicentre database with 940 EMG examinations sampled by seven physicians from six laboratories in Europe. RESULTS: For the whole group of patients as well as for the subgroup of patients with polyneuropathy, variation among physicians in examination techniques, number of examined structures per patient and number of abnormal structures per patient required for a diagnosis was found. Some of the variation may be explained by use of different techniques, which showed differences in sensitivity, while some of the variation may be due to differences in diagnostic strategy and criteria for diagnosing. CONCLUSIONS: The study indicates a need for development and revision of international guidelines for EMG practice although implementation of standards requires caution.

Decision Making↗
PubMed1999

Long-term effects of cyclosporine A in Alport's syndrome.

BACKGROUND: In 1991, our initial results of cyclosporine A (CsA) administration in eight patients with Alport's syndrome were published. A significant decrease in or disappearance of proteinuria and apparently good tolerance to CsA were observed in all patients. METHODS: CsA administration has been maintained in these eight patients with the aim of obtaining further information about the clinical course of the disease. The ages of these eight patients currently range from 15 to 27 years, and the mean duration of treatment is from 7 to 10 years (x = 8.4 years). RESULTS: Renal function has remained stable, with no evaluable changes in serum creatinine levels compared with pre-CsA treatment values. Proteinuria in all patients has either remained negative or are values far lower than pretreatment levels. A second renal biopsy was performed in all patients after five years of CsA administration. No aggravation of the lesion present at the first biopsy or lesions typical of cyclosporine intoxication was observed. CONCLUSIONS: After a mean duration of 8.4 years and with no deterioration in renal function, we found possible beneficial effects of the continued treatment of CsA in patients with Alport's syndrome who present evidence of progression to renal insufficiency.

Adolescent↗
PubMed1999

Peripheral neuropathy in sleep apnea. A tissue marker of the severity of nocturnal desaturation.

Because chronic obstructive pulmonary disease (COPD) is well known to induce peripheral neuropathy and resistance to ischemic nerve conduction failure (RICF), we performed a case-control study examining peripheral nerve function during ischemia in 17 patients with severe obstructive sleep apnea (OSA) without daytime hypoxemia and 10 control subjects. Median nerve conduction was studied before, during, and after a 30-min period of ischemia. Preischemic sensory and mixed nerve potential amplitudes and sensory conduction velocity were lower in OSA patients than in control subjects despite higher supramaximal stimulation. During ischemia, seven OSA patients manifested RICF (OSA-RICF), whereas both the other 10 patients, who were nonresistant to ischemic conduction failure (OSA-NR), and control subjects did not. OSA-RICF patients had the lowest initial nerve-potential amplitude, whereas OSA-NR patients had a response intermediate between that of control subjects and OSA-RICF patients. OSA-RICF patients had a lower mean nocturnal SaO2 and a higher body mass index (BMI) and duration of SaO2 < 70% than did OSA-NR patients. Seven patients (four OSA-RICF and three OSA-NR) were reevaluated after at least 2 mo of treatment with nasal continuous positive airway pressure (nCPAP). RICF disappeared in all OSA-RICF patients, whereas preischemic nerve conduction parameters were unchanged in both OSA-RICF and OSA-NR patients. Thus OSA patients have peripheral nerve dysfunction whose severity is partly related to the level of nocturnal hypoxemia. Abnormal preischemic nerve conduction suggests axonal lesions, whereas RICF, which appears to be a sensitive but nonspecific tissue marker of the severity of hypoxemia, may result from adaptative mechanisms.

Adult↗