Encapsulation of p-THPP into nanoparticles: cellular uptake, subcellular localization and effect of serum on photodynamic activity

The cellular uptake, localization and efflux of meso-tetra-(4-hydroxyphenyl)porphyrin (p-THPP)-loaded nanoparticles have been studied in EMT-6 tumor cells. The effect of blood serum on photocytotoxicity has also been evaluated. Sub-130 nm nanoparticles based on poly(D,L-lactide-co-glycolide) (PLGA) (50:50 PLGA and 75:25 PLGA) and poly(D,L-lactide) (PLA) have been examined in comparison with free p-THPP. For all formulations tested, uptake of photosensitizer into cells was dependent on concentration, time and temperature. All nanoparticulate formulations accumulated within the cells to a greater extent relative to free drug. Indeed, the fluorescence intensities measured on EMT-6 cells treated with p-THPP-loaded nanoparticulate formulations were at least two-fold higher than those obtained with free dye. Furthermore, the highest accumulation level was found with PLGA nanoparticles. Fluorescence microscopy revealed that endocytosis is a major intracellular sequestration mechanism of these p-THPP formulations and that these were localized into early and late endosomes. The efflux study performed on both nonirradiated and irradiated cells indicated that free and p-THPP-loaded nanoparticles gradually escaped from EMT-6 cells as a function of time. This was more pronounced when cells were treated with nanoparticles and irradiated, reflecting important photodamage. It was also found that regardless of the nanoparticulate formulations tested, p-THPP photocytotoxicity was influenced by the concentration of the serum.

[Localizing and prognosis value of 99Tcm-ECD spect in patients with refractory temporal lobe epilepsies]

Interictal and ictal 99Tcm ECD-SPECT were retrospectively studied in 46 patients with refractory temporal lobe epilepsy. Forty two of these patients underwent an anterior temporal lobectomy with amygdalo-hippocampectomy or a cortical resection. SPECT findings as indicator of localization for the epileptogenic zone (EZ) and surgical prognosis were validated by comparison with other investigations including video-EEG monitoring with surface electrodes in all the patients, intracranial electrodes in 18 patients and the results of post-surgery outcome. Reliability of SPECT for localizing the epileptogenic zone (EZ) was found for mesial temporal epilepsy (28 patients) and the presumed bilateral temporal epilepsies (7 patients). In these latter cases, ECD-SPECT findings may serve to replace invasive methods with use of intracranial electrodes. SPECTs were unreliable when EZ was undetermined whether mesial or lateral by other non invasive investigations. Unilateral mesial temporal hyperperfusion associated with hypoperfusion of contralateral mesial structures evidenced by ictal SPECTs appear to be preoperative criteria for a successful outcome after surgery.

[A case of external human ophthalmomyiasis by Oestrus ovis in Toulouse (France)]

We report a case of external human ophthalmomyiasis by OEstrus ovis was observed in a child living in southwestern France. The patient was contaminated on the playground of a school in a suburban village near Toulouse. Eleven first stage larvae were extracted from the eye. This case illustrates that contamination can occur in suburban areas of a large city remote from any cattle breeding zone.

Rapid access to synthetic lysobisphosphatidic acids using P(III) chemistry

An expeditious route to synthetic lysobisphosphatidic acid S,S-1, its enantiomer, and regioisomers is reported. Synthetic difficulties concerning lipid stability and stereochemistry are bypassed using a phosphite triester approach in combination with multiple silyl protection. Spectroscopic studies evidence that acyl group migration in S,S-1 is accelerated by nonpolar solvents and inhibited by pyridine.

Evidence for a dynamic role for proline376 in the purine-cytosine permease of Saccharomyces cerevisiae

The purine-cytosine permease (PCP), a carrier located in the plasma membrane of Saccharomyces cerevisiae, mediates the active transport of purine (adenine, guanine and hypoxanthine) and cytosine into the cell. Previous studies [Ferreira, T, Brèthes, D., Pinson, B., Napias, C. & Chevallier, J. et al. (1997) J. Biol. Chem. 272, 9697-9702] suggest that the hydrophilic segment 371-377 (-I-A-N-N-I-P-N-) of the polypeptide chain may play a key role in the correct three-dimensional structure of the active carrier. This paper describes the effects of mutations in this particular segment: a four-residue deletion, Delta374-377, and two substitutions, P376G and P376R. The Delta374-377 PCP was expressed in tiny amounts and was totally inactive. When compared with the wild-type, the P376G PCP showed slightly decreased amounts and was able to transport the bases with significantly increased affinity and decreased turnover. The P376R PCP was normally expressed and targeted to the plasma membrane; however, despite a normal number of base-binding sites [1000-1200 pmol.(mg protein)-1], this mutated carrier was completely unable to transport any of its ligands. In addition, the Kd(app) for hypoxanthine binding was completely independent of the pH (within the range 3.5-6.0), showing that the conformational change induced by ligand binding was no longer present. Our results show that the 374-377 segment is essential for the expression and activity of this carrier. They also show that the P376 residue is part of an unusual secondary structure, probably a beta-turn motif, which must play a crucial dynamic role in the translocation process.

Only one of the charged amino acids located in membrane-spanning regions is important for the function of the Saccharomyces cerevisiae uracil permease

The transport of uracil into the yeast Saccharomyces cerevisiae is mediated by uracil permease, a specific co-transporter encoded by the FUR4 gene. Uracil permease is a multispan membrane protein that is delivered to the plasma membrane via the secretory pathway. Experimental results led to the proposal of a two-dimensional model of the protein's topology. According to this model, the membrane domain of Fur4p contains three charged amino acid residues (Glu-243, Lys-272 and Glu-539) that are conserved in the members of the FUR family of yeast transporters. We have previously shown that a mis-sense mutation leading to the replacement of Lys-272 by Glu severely impairs the function of uracil permease. In the present paper, the role of the three charged residues present in the membrane-spanning regions of Fur4p was further investigated by using site-directed mutagenesis. The variant permeases were correctly targeted to the plasma membrane and their stabilities were similar to that of the wild-type permease. The effect of the mutations was studied by measuring the uptake constants for uracil on whole cells and equilibrium binding parameters on plasma membrane-enriched fractions. We found no evidence for ionic interaction between either of the glutamic residues in transmembrane segments 3 and 9 and the lysine residue in transmembrane segment 4. Of the three charged residues, only Lys-272 was important for the transport activity of the transporter. Its replacement by Ala, Glu or even Arg strongly impaired both the binding and the translocation of uracil.

Screening of an intragenic second-site suppressor of purine-cytosine permease from Saccharomyces cerevisiae. Possible role of Ser272 in the base translocation process

The purine-cytosine permease from Saccharomyces cerevisiae mediates the active transport through the plasma membrane of adenine, hypoxanthine, guanine and cytosine using the proton electrochemical potential difference as an energy source. Analysis of the activity of strains mutated in a hydrophilic segment (371-377) of the polypeptidic chain has shown the involvement of this segment in the maintenance of the active three-dimensional structure of the carrier. In an attempt to identify permease domains that could interact functionally and/or physically with this segment, we looked for second-site mutations that could suppress the effects of amino acid changes in this region. This paper describes a positive screen that has allowed the isolation of one suppressor from a permease mutant displaying the N374I change (fcy2-20 allele), a substitution that induces a dramatic decrease in the affinity of the carrier for adenine, cytosine and hypoxanthine. The second-site mutation corresponds to the replacement of the Ser272 residue by Leu. Its suppressive effect is shown to be a partial restoration of the binding of cytosine and hypoxanthine to the permease. To test whether this second-site mutation is specific for the fcy2-20 allele, two double mutants were constructed (Fcy2pT213I, S272L and Fcy2pS272L, N377G). Results obtained with these two double mutants showed that the suppressive effect of S272 L replacement was not specific for the original N374I change. To understand the general effect of this amino acid replacement for the three distinct double mutants, a strain overexpressing Fcy2pS272I, was constructed. Kinetic analysis of this strain showed that, by itself, the S272 L change induced an improvement in the base-binding step that could account for its global suppressive effect. Moreover, S272 L induced a decrease in the turnover of the permease, thus showing the involvement of S272 in the translocation process. Taking into account the topological model of the permease proposed here, this Ser residue is probably located in a transmembrane amphipathic alpha-helix (TM5). The location and the observed decrease in the turnover of the carrier observed with the S272 L change lead us to propose that S272 could be part of a hydrophilic pore involved in the translocation of the base and/or the proton.

[Cowden disease: treatment with acitretine]

INTRODUCTION

Cowden's disease is a rare hereditary skin disease which is important to recognize due to the risk of cancer.

CASE REPORT

A 40-year-old man was hospitalized for psoriasis. He presented florid papillomatous lesions involving the lip and the buccal cavity, a thyroid adenoma and polyposis of the gut. The diagnosis of Cowden's disease was retained. Treatment with acitretin, 0.75 mg/kg/d was initiated for the psoriatic lesions. Hypertrophic lesions of the lip and mouth regressed during treatment but reappeared when the drug dose was tapered of then withdrawn. The course of the polyposis was not verified.

DISCUSSION

This case demonstrates the frequency of digestive tract involvement in Cowden's disease and the favorable, though transient, effect of oral retinoids on mucosal lesions in Cowden's disease.

Characterization of the Saccharomyces cerevisiae cytosine transporter using energizable plasma membrane vesicles

The purine-cytosine permease is a carrier localized in the plasma membrane of the yeast Saccharomyces cerevisiae. The energetics of cytosine transport catalyzed by this permease has been studied in an artificial system obtained by fusion between proteoliposomes containing beef heart cytochrome c oxidase and plasma membrane-enriched fractions of a S. cerevisiae strain overexpressing the permease. Upon addition of an energy donor, a proton-motive force (inside alkaline and negative) is created in this system and promotes cytosine accumulation. By using different phospholipids, it is shown that cytosine uptake is dependent on the phospholipids surrounding the carrier. It was demonstrated that the purine-cytosine permease is able to catalyze a secondary active transport of cytosine. By using nigericin and valinomycin, the DeltapH component of the proton-motive force is shown to be the only force driving nucleobase accumulation. Moreover, transport measurements done at two pH values have shown that alkalinization of intravesicular pH leads to a significant increase in cytosine uptake rate. Finally, no specific role of K+ ions on cytosine transport could be demonstrated in this system.

Functional analysis of mutated purine-cytosine permease from Saccharomyces cerevisiae. A possible role of the hydrophilic segment 371-377 in the active carrier conformation

The purine-cytosine permease (PCP) is an active transporter located in the plasma membrane of the yeast Saccharomyces cerevisiae. This protein mediates purine (adenine, guanine, and hypoxanthine) and cytosine accumulation in the cell by using an electrochemical potential difference in proton as the energy source. Various mutant strains, with altered Kt(app) (apparent Michaelis constant of transport) of uptake for one or several bases, have already been selected. Their cloning and sequencing revealed that three of them presented substitutions in the same region of the putative sequence of the PCP: this region might correspond to the hydrophilic segment 371-377 (I-A-N-N-I-P-N). Two mutants displayed single mutations, resulting in only one amino acid residue change (N377I and N374I, respectively), and the other displayed three amino acid substitutions (I371V, I375V, and N377G). Therefore, to analyze the contribution of individual amino acid changes to the phenotype of the complex mutant, single (N377G) and double (I371V,I375V) mutants were constructed by site-directed mutagenesis. The influence of single mutations in this region was studied by measuring, for adenine, hypoxanthine, and cytosine, the uptake constants on cells and equilibrium binding parameters on plasma membrane-enriched fractions. Uptake and binding constant determinations showed that all the variations observed for the Kt(app) of uptake were correlated with variations of the binding Kd(app) for the corresponding solutes. Thus, our results emphasize the role of the two asparagine residues, located at positions 374 and 377, respectively, in the binding of the bases. In addition, the sole substitution of the 377 asparagine residue by glycine is responsible for the phenotype of the triple mutant. The effect of pH on the apparent hypoxanthine binding dissociation constant showed that the effects of N377G and N377I changes were, at least partially, due to a shift of the pKa of an ionizable amino acid residue of the unliganded permease. These two amino acid residue changes induced a shift of the pKa of this group in the unliganded, deprotonated permease about two units toward acidic pH. This result suggests that the 371-377 segment might play a key role in the proper three-dimensional structure of the active purine-cytosine permease.

In vivo phosphorylation of the purine/cytosine permease from the plasma membrane of the yeast Saccharomyces cerevisiae

The purine/cytosine permease, encoded by the FCY2 gene, is a carrier located in the plasma membrane of the yeast Saccharomyces cerevisiae. Polyclonal antibodies were raised against two peptides that corresponded to the sub-N-terminal and C-terminal sequences of the putative protein deduced from the FCY2 gene. Immunoprecipitation experiments performed with protein extracts labelled in vivo with 35S showed that purine/cytosine permease is specifically detected as a broad and diffuse band. The apparent molecular mass of this protein was 45-50 kDa. By means of in vivo pulse/chase 35S-labelling experiments, we observed a slight increase in the apparent molecular mass of purine/cytosine permease during the chase. This shift in electrophoretic mobility of the protein suggested a post-translational modification. This molecular mass increase was eliminated by alkaline phosphatase treatment of the immunoprecipitate, which strongly suggested phosphorylation of the carrier. This proposal was confirmed by in vivo [32P]P(i) labelling and immunoprecipitation of purine/cytosine permease with purified anti-(sub-N-terminal peptide) IgG or anti-(C-terminal peptide) IgG. Phosphoamino acid analysis indicated that phosphorylation occurred on seryl residues of purine/cytosine permease. By means of thermosensitive secretory-pathway-mutant strains, we demonstrated that purine/cytosine permease phosphorylation occurred either between the Golgi apparatus and the plasma membrane or in the plasma membrane itself.

Replacement of Lys by Glu in a transmembrane segment strongly impairs the function of the uracil permease from Saccharomyces cerevisiae

The co-transport of uracil and protons through the plasma membrane of the yeast Saccharomyces cerevisiae is mediated by a specific permease encoded by the FUR4 gene. The uracil permease is a multi-spanning membrane protein that follows the secretory pathway to the plasma membrane. Recent experimental data led to the proposal of a two-dimensional model of its topology. A spontaneous mutant corresponding to the substitution of Lys-272 by glutamic acid was obtained. The influence of this mutation was studied by comparing the wild-type and mutant permeases produced in a strain carrying a chromosomal deletion of the FUR4 gene. The mutant permease is correctly targeted to the plasma membrane and its stability is similar to that of the wild-type permease. The uptake parameters for the mutant permease were impaired and showed an approximately 65-fold increase of apparent K(m) and a decrease in apparent Vmax. Equilibrium binding measurements with enriched plasma membrane preparations showed an approximately 70-fold increase in apparent Kd in the mutant, whereas its Bmax. was similar to that of the wild type. Lys-272 is fully conserved in the uracil permease family and is predicted to lie in the fourth transmembrane segment of the protein. It seems to be essential for both efficient uracil binding and translocation.

[Tropical sprue: diagnostic difficulties. Apropos of 2 cases in Guadeloupe]

The authors report two cases of tropical sprue occurring in Guadeloupe, in the French Lesser Antilles, a region in which this disease had previously been reported only once. One of the patients was treated with quinolone (ofloxacin).

[Recurrent metabolic encephalopathy, self-administered gastric lavage and Munchausen syndrome]

A case report of recurrent metabolic encephalopathy with disorders of hydro-electrolytic balance, predominantly severe hypochloremic alkalosis, resulting from self-induced vomiting and self-administered gastric tubage and lavage. Munchausen syndrome was diagnosed. Some established characteristics of this syndrome as well as some atypical features concerning patient-doctor relationship and natural history are discussed.