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Biomedical subjects

R Lazaro

Publications and source records attributed to R Lazaro.

At least 19 recordsLinked to original sources
PubMed2003

Characterization of soluble polymer supported organic compounds by LC/electrospray ionization MS toward a complete automation of the liquid-phase process in combinatorial chemistry.

In the case of a soluble polymer supported synthesis, the tuning of the support solubility depending on the solvent offers new opportunities for combinatorial chemistry for two reasons. First, organic syntheses in solution are generally easily translated on a soluble polymer supported substrate. Second, complete automation of the three successive steps of combinatorial chemistry (synthesis, analytical control, biological test) is approached without releasing the synthesized compound from the support. We report in this paper the preliminary results toward automation of both soluble polymer supported syntheses and their subsequent monitoring by ESI mass spectrometry.

Automation↗
PubMed2000

Red-legged partridges (Alectoris rufa) as bioindicators for persistent chlorinated chemicals in Spain.

Persistent organochlorine residues such as hexachlorobenzene (HCB), hexachlorocyclohexane isomers (HCHs), chlorocyclodienes, and the DDT group (DDTs) were determined in fat and muscle samples of resident red-legged partridges (Alectoris rufa) hunted in Spain. Chlorinated contamination pattern varied largely depending on geographical distribution. Birds collected from the northern part of Spain contained greater concentrations of lindane (34.4 ng/g fat basis) than those from central or southern Spain. In contrast, red-legged partridges collected in southern locations exhibited elevated levels of p,p-DDE (62.3 ng/g fat basis) as compared with central (31.2 ng/g fat basis) and northern areas (5.6 ng/g fat basis). The only cyclodiene detected, dieldrin, showed higher amounts (3.4 ng/g fat basis) in partridges collected in central Spain. The sex differences in pollutant occurrence and concentrations were negligible. One-year-old birds accumulated greater concentrations of beta-HCH, and dieldrin than older birds. Global comparison of organochlorine concentrations indicated that northern partridges are more contaminated by compounds of industrial origin, whereas southern birds contained greater amounts of agricultural chemicals. Estimates of hazards associated with organochlorine levels in resident red-legged partridges in Spain suggested that southern birds may be at risk from exposure to DDTs, and northern birds may be affected by excessive concentrations of lindane. The use of red-legged partridge as bioindicator for OCP contamination is discussed.

Adipose Tissue↗
PubMed1999

Chemical reactivity in matrix-assisted laser desorption/ionization mass spectrometry

During the control of a multistep organic synthesis on a soluble polymer (PEG) by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, a chemical reactivity was encountered when the matrix was acidic, for the samples where the amino moiety of the anchored compounds was protected as a Schiff base. Such imine hydrolysis was proven to be solely mediated by the acidic matrix during analyses since the expected protected structures were detected when the experiments were duplicated with a non-acidic matrix. Even if MALDI mass spectrometry was found to be more convenient than electrospray ionization mass spectrometry for the monitoring of liquid phase organic syntheses, the chemical reactivity imparted by the use of a matrix must be taken into account to avoid erroneous spectra interpretations. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗
PubMed1999

Production of polyclonal antibodies towards the immunodetection of insecticide phosalone.

Hapten synthesis for the production of specific insecticide phosalone polyclonal antibodies was carried out starting from an intermediate of the phosalone synthesis, 6-chloro-2-benzoxazolone 1. Two haptens containing different spacers have been prepared: N-5-carboxypentyl-6-chloro-2-benzoxazolone 7 and N-(2-oxo-3-aza-5-carboxypentyl)-6-chloro-2-benzoxazolone 12. Each of these two haptens conjugated to bovine serum albumine (BSA) was used to immunize four rabbits. Immunoassays of phosalone were performed with ELISA using solid-phase bound hapten thyroglobulin conjugate and horseradish peroxidase labelled goat antirabbit IgG. The more sensitive response was observed when the antiserum obtained from the rabbit immunized with the hapten-BSA conjugate containing the N-2-oxo-3-aza-5-carboxypentyl spacer was in competition with the same hapten coupled to thyroglobulin. An identical response was obtained under the same conditions when using benzoxazolone instead of phosalone as competitor, showing a good recognition of the specific aromatic part of the organophosphate insecticide phosalone. Reduction of coating conjugate concentration (from 2 to 0.05 micrograms/well) and also the use of heterologous coating protein instead of homologous did improve the sensitivity, resulting in a concentration of phosalone required to inhibit binding by 50% of 2 mg/l and a detection limit of 0.02 mg/l.

Animals↗
PubMed1999

Some of the amino acid chemistry going on in the Laboratory of Amino Acids, Peptides and Proteins.

Some of the chemistry of amino acids going on in our laboratory (Laboratoire des Amino acides Peptides et Protéines) is described as well as some mass spectrometry methodology for their characterization particularly on solid supports. Several aspects are presented including: (i) the stereoselective synthesis of natural and unnatural amino acids using 2-hydroxypinan-3-one as chiral auxiliary; (ii) the stereoselective synthesis of natural and unnatural amino acids by deracemization of alpha-amino acids via their ketene derivatives; (iii) the synthesis of alpha-aryl-alpha-amino acids via reaction of organometallics with a glycine cation; (iv) the diastereoselective synthesis of glycosyl-alpha-amino acids; (v) the synthesis of beta-amino acids using alpha-aminopyrrolidinopiperazinediones as chiral templates; (vi) the reactivity of urethane-N-protected N-carboxyanhydrides. To characterize natural and non natural amino acids through their immonium ions by mass spectrometry, some methodology is also described.

Amino Acids↗
PubMed1999

Levels of selected polychlorinated biphenyl congeners in total diet samples from Aragón, Spain.

Six congeners of polychlorinated biphenyls (PCB 28, 52, 101, 138, 153, and 180) were investigated in 281 samples of different meals of the average diet consumed in Aragon, northeast Spain. PCB residues were extracted with organic solvents according to the techniques recommended by the U.S. Food and Drug Administration and the Netherlands' Ministry of Welfare, Health, and Cultural Affairs; the residues were cleaned up by gel permeation chromatography. Quantitation of analytes was carried out by capillary gas-liquid chromatography using electron capture detector. The identity of the peaks was confirmed by mass spectrometry. PCB residues were found only in fish meals (50% positive samples) with a mean level of 96.3 ng/g on a lipid basis. Congeners detected in fish meals were 138, 153, and 180, with mean values of 117.0, 122.3, and 36.2 ng/g on a lipid basis, respectively.

Chromatography, Gas↗
PubMed1998

Synthesis and characterization of a new biotinylated gramicidin.

A new linear gramicidin analog bearing a biotinyl group grafted on C-terminal part was designed to study ligand-receptor interactions. The C-terminal alcohol in the native peptide was first replaced by an amino group. Then the peptide was synthesized on a polystyrene resin functionalized by the 2-chlorotrityl chloride following a biotinylation performed in solution. This new N'-biotinyl-(EDA)15-Gramicidin A was reconstituted in planar lipid bilayers and exhibited channel activities similar to those of natural gramicidin, with unitary conductance value about 30 ps in 1 M KCl. Furthermore this ionophore activity was quenched by addition of streptavidin in the surrounding medium. Our system is an outstanding tool for monitoring ligand-receptor interactions and could be used for designing a new biosensor.

Amino Acid Sequence↗
PubMed1998

Solitary fibrous tumour of the orbit. Report of a new case.

PURPOSE: Solitary fibrous tumour (SFT) of the orbit is a very rare lesion that may be misdiagnosed as fibrous histiocytoma, haemangiopericytoma, or other orbital tumour. We studied a case of SFT of the orbit in a 35-year-old woman. METHODS: The patient, with a 1-year history, reported a 'pressure' sensation behind her right eye, but no pain, vision changes, or other associated symptoms. Ocular examination was normal. Magnetic resonance imaging (MRI) showed a well-circumscribed medial mass in the right orbit. The tumour was excised. RESULTS: The tumour was a cellular spindle-cell neoplasm with a storiform pattern. The tumour cells were spindle-shaped with bland nuclei and rare mitoses. Immunostaining was positive for vimentin and CD34, but negative for cytokeratin (AE1-AE3), EMA, desmin, smooth muscle actin, S-100, CD31, CD45 and bcl-2. CONCLUSION: SFT can infrequently involve the orbit. The tumour must be removed entirely to avoid recurrences. Careful and continued follow-up is important because orbital recurrence may occur several years after the excision of the primary tumour.

Adult↗
PubMed1996

Estimates of mean daily intakes of persistent organochlorine pesticides from Spanish fatty foodstuffs.

In many countries pesticide residues in foods are monitored to ensure that public health is not endangered by residue daily intakes in excess of the recommended tolerance levels (van Dokkum and de Vos 1987). In Spain, there is only a total diet study carried out during 1971-72 by Carrasco et al. (1976). In that study, mean daily intakes of 11.5 mu g alpha-HCH, 13.8 mu g lindane and 78.4 mu g DDTs were calculated. Livestock meat and dairy products were the prime sources of human dietary exposure to organochlorines, since between 60-85% of the mean daily intakes arose from these particular food classes. These percentages are in accordance with the well documented fact that organochlorines predominantly accumulate in the lipid fractions of the human food chain, by which animal fatty foods have become a major route of exposure for humans (Kannan et al. 1992). Since the current daily intakes of organochlorines in Spain are not known, it was considered necessary to carry out a pesticide survey in several foods that compose an average Spanish diet. To accomplish that, we have determined residues of a list of priority organochlorine compounds in several fatty foodstuffs collected between 1987 to 1990, and prepared in the way in which they would normally be eaten. This study is merely an attempt to estimate the actual intakes, since only a selected number of food classes were investigated and no age-sex group, or seasonal differences were taken into account. In spite of these disadvantages, there are merits to such an approach. Approximate intake figures are available for comparison with toxicologically acceptable intakes and with retrospective studies in Spain and other countries around the world, and they serve to outline the temporal trends in organochlorine contamination that have occurred during the last decades. Also, it may contribute to diminish the consumer's concern about possible health risks involved in the consumption of food products and help to restore confidence in the quality of our food supply.

Animals↗
PubMed1994

Nerve entrapment and calf atrophy caused by a Baker's cyst: case report.

An unusual case of leg pain and atrophy in a patient with gastrocnemius due to tibial nerve branch compression by a Baker's cyst is presented. The clinical findings and electrodiagnostic studies were supportive of isolated medial gastrocnemius denervation. Treatment by synovectomy along with decompression of the branch of the posterior tibial nerve to the medial head of the gastrocnemius muscle resulted in clinical improvement. No other cases of such selective branch compression have been previously reported.

Follow-Up Studies↗
PubMed1993

In vivo antidiabetic actions of naglivan, an organic vanadyl compound in streptozotocin-induced diabetes.

The vanadyl (+IV) form of vanadium has been demonstrated to have insulin-mimetic activity in vivo. In an effort to improve the poor gastrointestinal absorption of the ion, an organic complex of vanadyl (naglivan) was synthesized. We tested the antidiabetic effects of naglivan in rats made diabetic with streptozotocin (55 mg/kg, i.v.). Four days after the streptozotocin injection, one diabetic group (DVI) and a control group (CV) were treated with naglivan (50 mg/kg/day, equivalent to 0.06 mmol vanadium/kg/day) by oral gavage. Treatment in the DVI group was supplemented with daily insulin while a second diabetic group (DI) was administered daily titrated doses of insulin alone (Protamine Zinc, s.c.) to achieve stable euglycemia. The dose of exogenous insulin required to maintain normal glucose was significantly lower in the DVI group compared to the DI throughout the treatment period. At the end of week 3, exogenous insulin was withdrawn from both the DVI and DI groups, while naglivan treatment was continued in the CV and DVI groups for an additional 5 weeks. At termination, hearts were isolated and cardiac function (+dP/dt, -dP/dt and left ventricular developed pressure) was assessed in all the animals. After insulin was withdrawn, 4/8 DVI animals which continued to receive naglivan had consistent normoglycemia (as determined by % glycosylated hemoglobin) and an improved cardiac function. All the DI animals and 4/8 DVI rats were hyperglycemic and had depressed heart function despite having similar plasma insulin levels to the euglycemic DVI animals. As with vanadyl sulfate, there were no signs of long-term toxicity with regards to renal or liver function after 8 weeks of treatment. Thus, naglivan is an orally effective form of vanadyl with an oral potency 7.6 times greater than that of vanadyl sulfate (minimum effective dose: 0.06 mmol vanadium.kg-1.day-1) as compared to vanadyl sulfate (0.46 mmol vanadium.kg-1.day-1). The lack of incidence of diarrhea in either control or diabetic animals demonstrates that naglivan could be a more therapeutically desirable form of vanadyl.

Animals↗
PubMed1992

Gramicidin channels that have no tryptophan residues.

In order to understand how aromatic residues modulate the function of membrane-spanning proteins, we examined the role of the four tryptophans in gramicidin A (gA) in determining the average duration and permeability characteristics of membrane-spanning gramicidin channels; the tryptophan residues were replaced by tyrosine (gramicidin T, gT), tyrosine O-benzyl ether [gramicidin T(Bzl), gT(Bzl)], naphthylalanine (gramicidin N, gN), and phenylalanine (gramicidin M enantiomer, gM-). These analogues form channels with durations and conductances that differ some 10- and 16-fold, respectively. The single-channel conductance was invariably decreased by the Trp----Yyy replacement, and the relative conductance alterations were similar in phosphatidylcholine (DPhPC) and monoglyceride (GMO) bilayers. The duration variations exhibited a more complex pattern, which was quite different in the two membrane environments: in DPhPC bilayers, gN channels have an average duration that is approximately 2-fold longer than that of gA channels; in GMO bilayers, the average duration of gN channels is about one-tenth that of gA channels. The sequence-dependent alterations in channel function do not result from alterations in the channels' peptide backbone structure, because heterodimers can form between the different analogues and gramicidine A, and there is no energetic cost associated with heterodimer formation [cf. Durkin, J. T., Koeppe, R. E., II, & Andersen, O. S. (1990) J. Mol. Biol. 211, 221]. The alterations in permeability properties are consistent with the notion that Trp residues alter the energy profile for ion permeation through long-range electrostatic interactions.

Amino Acid Sequence↗
PubMed1991

How can the aromatic side-chains modulate the conductance of the gramicidin channel? A new approach using non-coded amino acids.

In order to elucidate the role of the aromatic side-chains in the mechanism of transduction of monovalent cations through the channel of linear gramicidin, two series of analogues containing non-coded aromatic amino acids were synthesized. In the first series, the four tryptophans were replaced by either four L-3-(8-quinolyl)alanyl or four L-3-(4-quinolyl)alanyl residues and single channel conductance measurements showed that these substitutions led to a strong lowering of the channel conductance, which is attributed to a modification of the orientation of the aromatic side-chains due to an increase of their hydrophobicity. In the second series, the analogues contained both tryptophyl and naphthylalanyl residues in various amounts and positions. The single channel conductance data indicated that the conductance was mainly governed by the number of polar residues (Trp) and not by their positions. The conformational consequences of these results are discussed together with their influence on the energy profile of the gramicidin channel.

Alanine↗
PubMed1991

Enzymatic peptide synthesis in organic solvent mediated by gels of copolymerized acrylic derivatives of alpha-chymotrypsin and polyoxyethylene.

Copolymers of acrylated derivatives of alpha-chymotrypsin and polyethylene glycol (PEG) have been prepared and used as biocatalysts for the synthesis of model peptides in organic solvent containing a low quantity of water. Other peptide couplings have been tried to point out the chemico- and stereoselectivity and examples of segment couplings are given.

Acrylates↗
PubMed1991

Sono-enzymatic peptide synthesis in organic solvent.

Copolymerized compounds of acrylated derivatives of alpha-chymotrypsin and polyethylene glycol (P.E.G.) have been prepared and used as biocatalysts for peptide synthesis in organic solvent containing low quantity of water. In order to increase the velocity of the coupling reactions, without loss of enzyme activity, we have used the principle of sonication. Some results and future projects are presented.

Amino Acid Sequence↗