Biomedical subjects

Margarida Bastos

Publications and source records attributed to Margarida Bastos.

15 recordsLinked to original sources

PubMed2006

Efficacy of plant extracts against stored-products fungi.

The fungistatic activity of six aqueous extracts of plants were tested against Aspergillus candidus, Aspergillus niger, Penicillium sp. and Fusarium culmorum. The plants were, chamomile (Anthemis nobilis L.), cinnamon (Cinnamomum verum J. Presl.), French lavender (Lavandula stoechas L.), garlic (Allium sativum L.), malva (Malva sylvestris L.) and peppermint (Mentha piperita L.). The more concentrated extracts of chamomile and malva inhibited totally the growth of the tested fungi with malva the most effective one.

Aspergillus↗

PubMed2006

PROP1 gene analysis in Portuguese patients with combined pituitary hormone deficiency.

OBJECTIVE: Mutations of the PROP1 gene lead to combined pituitary hormone deficiency (CPHD), which is characterized by a deficiency of GH, TSH, LH/FSH, PRL and, less frequently, ACTH. This study was undertaken to investigate the molecular defect in a cohort of patients with CPHD. DESIGN, PATIENTS AND MEASUREMENTS: A multicentric study involving 46 cases of CPHD (17 familial cases belonging to seven kindreds and 29 sporadic cases) selected on the basis of clinical and hormonal evidence of GH deficiency, central hypothyroidism and hypogonadotrophic hypogonadism, in the absence of an identified cause of hypopituitarism. Mutations of PROP1 were investigated by DNA sequencing. Clinical, hormonal and neuroradiological data were collected at each centre. RESULTS: PROP1 mutations were identified in all familial cases: five kindreds presented a c. 301-302delAG mutation, one kindred presented a c. 358C --> T (R120C) mutation and one presented a previously unreported initiation codon mutation, c. 2T --> C. Of the 29 sporadic cases, only two (6.9%) presented PROP1 germline mutations (c. 301-302delAG, in both). Phenotypic variability was observed among patients with the same mutations, particularly the presence and age of onset of hypocortisolism, the levels of PRL and the results of pituitary imaging. One patient presented a sellar mass that persisted into adulthood. CONCLUSIONS: This is the first report of a mutation in the initiation codon of the PROP1 gene and this further expands the spectrum of known mutations responsible for CPHD. The low mutation frequency observed in sporadic cases may be due to the involvement of other unidentified acquired or genetic causes.

Adolescent↗

PubMed2006

Noninvasive analysis of hepatic glycogen kinetics before and after breakfast with deuterated water and acetaminophen.

The contributions of hepatic glycogenolysis to fasting glucose production and direct pathway to hepatic glycogen synthesis were quantified in eight type 1 diabetic patients and nine healthy control subjects by ingestion of (2)H(2)O and acetaminophen before breakfast followed by analysis of urinary water and acetaminophen glucuronide. After overnight fasting, enrichment of glucuronide position 5 relative to body water (G5/body water) was significantly higher in type 1 diabetic patients compared with control subjects, indicating a reduced contribution of glycogenolysis to glucose production (38 +/- 3 vs. 46 +/- 2%). Following breakfast, G5/body water was significantly higher in type 1 diabetic patients, indicating a smaller direct pathway contribution to glycogen synthesis (47 +/- 2 vs. 59 +/- 2%). Glucuronide hydrogen 2 enrichment (G2) was equivalent to body water during fasting (G2/body water 0.94 +/- 0.03 and 1.02 +/- 0.06 for control and type 1 diabetic subjects, respectively) but was significantly lower after breakfast (G2/body water 0.78 +/- 0.03 and 0.82 +/- 0.05 for control and type 1 diabetic subjects, respectively). The reduced postprandial G2 levels reflect incomplete glucose-6-phosphate-fructose-6-phosphate exchange or glycogen synthesis from dietary galactose. Unlike current measurements of human hepatic glycogen metabolism, the (2)H(2)O/acetaminophen assay does not require specialized on-site clinical equipment or personnel.

Acetaminophen↗

PubMed2005

Thermodynamics of self-assembling of hydrophobically modified cationic polysaccharides and their mixtures with oppositely charged surfactants in aqueous solution.

Microcalorimetric techniques, combined with turbidity measurements, were used to study the thermodynamics of self-assembling of hydrophobically modified cationic polysaccharides and their mixtures with oppositely charged surfactants in aqueous solution. The studied polyelectrolytes were a series of polymers based on dextran having pendant N-(2-hydroxypropyl)-N,N-dimethyl-N-alkylammonium chloride groups randomly distributed along the polymer backbone. The parameters for their micellization process are evaluated from the results of the observed dilution enthalpy curves and compared with those of the related cationic surfactants (DTAC and CTAC). The microcalorimetric results for the mixed systems (polyelectrolytes with oppositely charged surfactants) are used along with turbidity measurements to characterize systematically the thermodynamics of their interaction. The phase behavior is described and the interaction enthalpies are derived from the differences between the observed enthalpy curves with and without polyelectrolyte. Therefore, we discuss in detail the effect of changing the alkyl chain length of polyelectrolyte pendant groups, the molecular weight of the dextran backbone, and the temperature of the measurements on the interactions between polyelectrolyte and surfactant.

Cations↗

PubMed2005

Interaction and lipid-induced conformation of two cecropin-melittin hybrid peptides depend on peptide and membrane composition.

The interaction of two hybrid peptides of cecropin A and melittin [CA(1-8)M(1-18) and CA(1-7)M(2-9)] with liposomes was studied by differential scanning calorimetry (DSC), circular dichroism (CD), and quasi-elastic light scattering (QELS). The study was carried out with large unilamellar vesicles (LUVs) of three different lipid compositions: 1,2-dimyristoil-sn-glycero-3-phosphocholine (DMPC), 1,2-dimyristoyl-sn-glycero-3-phospho-rac-(1-glycerol) (DMPG) and a binary mixture of DMPC/DMPG, in a wide range of peptide-to-lipid (P:L) molar ratios (0 to 1:7). DSC results indicate that, for both peptides, the interaction depends on membrane composition, with very different behavior for zwitterionic and anionic membranes. CD data show that, although the two peptides have different secondary structures in buffer (random coil for CA(1-7)M(2-9) and predominantly beta-sheet for CA(1-8)M(1-18)), they both adopt an alpha-helical structure in the presence of the membranes. Overall, results are compatible with a model involving a strong electrostatic surface interaction between the peptides and the negatively charged liposomes, which gives place to aggregation in the gel phase and precipitation after a threshold peptide concentration. In the case of zwitterionic membranes, a progressive surface coverage with peptide molecules destabilizes the membrane, eventually leading to membrane disruption. Moreover, delicate modulations in behavior were observed depending on the peptide.

Amino Acid Sequence↗

PubMed2005

Porphyrin-substrate binding to murine ferrochelatase: effect on the thermal stability of the enzyme.

Ferrochelatase (EC 4.99.1.1), the terminal enzyme of the haem biosynthetic pathway, catalyses the chelation of Fe(II) into the protoporphyrin IX ring. The energetics of the binding between murine ferrochelatase and mesoporphyrin were determined using isothermal titration calorimetry, which revealed a stoichiometry of one molecule of mesoporphyrin bound per protein monomer. The binding is strongly exothermic, with a large intrinsic enthalpy (DeltaH=-97.1 kJ x mol(-1)), and is associated with the uptake of two protons from the buffer. This proton transfer suggests that hydrogen bonding between ferrochelatase and mesoporphyrin is a key factor in the thermodynamics of the binding reaction. Differential scanning calorimetry thermograms indicated a co-operative two-state denaturation process with a single transition temperature of 56 degrees C for wild-type murine ferrochelatase. An increase in the thermal stability of ferrochelatase is dependent upon mesoporphyrin binding. Similarly, murine ferrochelatase variants, in which the active site Glu-289 was replaced by either glutamine or alanine and, when purified, contained specifically-bound protoporphyrin, exhibited enhanced protein stability when compared with wild-type ferrochelatase. However, in contrast with the wild-type enzyme, the thermal denaturation of ferrochelatase variants was best described as a non-co-operative denaturation process.

Animals↗

PubMed2005

Thermodynamic characterization of the interaction behavior of a hydrophobically modified polyelectrolyte and oppositely charged surfactants in aqueous solution: effect of surfactant alkyl chain length.

We have used a precision isothermal titration microcalorimeter (ITC) to measure the enthalpy curves for the interaction of a hydrophobically modified polyelectrolyte (D40OCT30) with oppositely charged surfactants (SC(n)S) in aqueous solution. D40OCT30 is a newly synthesized polymer based on dextran having pendant N-(2-hydroxypropyl)-N,N-dimethyl-N-octylammonium chloride groups randomly distributed along the polymer backbone with degree of substitution of 28.1%. The employed anionic surfactants are sodium octyl sulfate (SC(8)S) and sodium tetradecyl sulfate (SC(14)S). Microcalorimetric results along with turbidity and kinematic viscosity measurements demonstrate systematically the thermodynamic characterization of the interaction of D40OCT30/SC(n)S. A three-dimensional diagram with the derived phase boundaries is drawn to describe the effect of the alkyl chain length of surfactant and of the ratio between surfactant and pendant groups on the interaction. A more complete picture of the interaction mechanism for D40OCT30/SC(n)S systems is proposed here.

Journal Article↗

PubMed2005

Simple measurement of gluconeogenesis by direct 2H NMR analysis of menthol glucuronide enrichment from 2H2O.

The contribution of gluconeogenesis to fasting glucose production was determined by a simple measurement of urinary menthol glucuronide (MG) 2H enrichment from 2H2O. Following ingestion of 2H2O (0.5% body water) during an overnight fast and a pharmacological dose (400 mg) of a commercial peppermint oil preparation the next morning, 364 micromol MG was quantitatively recovered from a 2-h urine collection by ether extraction and a 125 micromol portion was directly analyzed by 2H NMR. The glucuronide 2H-signals were fully resolved and their relative intensities matched those of the monoacetone glucose derivative. The pharmacokinetics and yields of urinary MG after ingestion of 400 mg peppermint oil as either gelatin or enteric-coated capsules 1 h before breakfast were quantified in five healthy subjects. Gelatin capsules yielded 197 +/- 81 micromol of MG from the initial 2-h urine collection while enteric-coated capsules gave 238 +/- 84 micromol MG from the 2- to 4-h urine collection.

Adult↗

PubMed2004

Platelet hyperactivation in maintained growth hormone-deficient childhood patients after therapy withdrawal as a putative earlier marker of increased cardiovascular risk.

GH deficiency (GHD) is associated with a higher risk of vascular disease, whose pathophysiological mechanisms remains not yet fully elucidated. This study aimed to assess the main cardiovascular risk indexes, plasma catecholamines content, and the platelet function in childhood-onset GHD patients. Some of the main clinical examinations related with cardiovascular risk, plasma catecholamines content, as well as platelet intracellular free calcium concentration ([Ca(2+)](i)), whole-blood aggregation, and morphology were evaluated in childhood-onset GHD patients treated with GH for a variable period and off GH therapy for at least 2 yr before entry into study and in sex-, age-, and body mass index-matched control groups. Among the patients, group 1 (GHD-1) has recovered GH levels after withdrawal, whereas group 2 (GHD-2) has remained GH deficient. Minor differences on the cardiovascular risk indexes were observed between the groups. Plasma catecholamine concentrations in the GHD groups did not statistically differ from the control group, but higher adrenaline content was observed in the GHD-2 group when compared with the GHD-1 one. Basal and thrombin-evoked [Ca(2+)](i) and platelet aggregation were identical between the GHD-1 group and the matched control. However, the GHD-2 group has increased thrombin-evoked [Ca(2+)](i) (297.0 +/- 15.7 Deltanmol/liter; P < 0.01), collagen, and ADP-induced platelet aggregation (33.3 +/- 4.3 and 12.5 +/- 2.1 Omega, respectively; P < 0.05) vs. the control-2 group (Delta[Ca(2+)](i): 102.1 +/- 13.6 Deltanmol/liter; aggregation: 19.6 +/- 2.9 and 6.2 +/- 0.8 Omega). The platelet hyperreactivity state in the GHD-2 was reinforced by morphologic studies of electron microscopy. In conclusion, there were minor differences between the GHD-1 group and the controls, which might be due to the recovery of GH levels after therapy withdrawal. However, the maintained GHD group, despite minor cardiovascular risk index differences, has increased [Ca(2+)](i) and aggregation, which could indicate a hyperactivation state that might be viewed as an earlier marker of cardiovascular disturbances.

Adult↗

PubMed2004

Protein stabilization by osmolytes from hyperthermophiles: effect of mannosylglycerate on the thermal unfolding of recombinant nuclease a from Staphylococcus aureus studied by picosecond time-resolved fluorescence and calorimetry.

2-O-alpha-Mannosylglycerate, a negatively charged osmolyte widely distributed among (hyper)thermophilic microorganisms, is known to provide notable protection to proteins against thermal denaturation. To study the mechanism responsible for protein stabilization, pico-second time-resolved fluorescence spectroscopy was used to characterize the thermal unfolding of a model protein, Staphylococcus aureus recombinant nuclease A (SNase), in the presence or absence of mannosylglycerate. The fluorescence decay times are signatures of the protein state, and the pre-exponential coefficients are used to evaluate the molar fractions of the folded and unfolded states. Hence, direct determination of equilibrium constants of unfolding from molar fractions was carried out. Van't Hoff plots of the equilibrium constants provided reliable thermodynamic data for SNase unfolding. Differential scanning calorimetry was used to validate this thermodynamic analysis. The presence of 0.5 m potassium mannosylglycerate caused an increase of 7 degrees C in the SNase melting temperature and a 2-fold increase in the unfolding heat capacity. Despite the considerable degree of stabilization rendered by this solute, the nature and population of protein states along unfolding were not altered in the presence of mannosylglycerate, denoting that the unfolding pathway of SNase was unaffected. The stabilization of SNase by mannosylglycerate arises from decreased unfolding entropy up to 65 degrees C and from an enthalpy increase above this temperature. In molecular terms, stabilization is interpreted as resulting from destabilization of the denatured state caused by preferential exclusion of the solute from the protein hydration shell upon unfolding, and stabilization of the native state by specific interactions. The physiological significance of charged solutes in hyperthermophiles is discussed.

Calorimetry↗

PubMed2004

[Pancreas transplantation].

A clinic case of simultaneous pancreas/kidney transplantation on a type 1 diabetic patient is described. A six years follow-up was made with both organs functionating and a good quality of live. Then the authors make a review of the available surgical techniques, indications and complications of this form of treatment. A comparison between the Portuguese and the International experience was discussed.

Adult↗

PubMed2004

Interaction of antiinflammatory drugs with EPC liposomes: calorimetric study in a broad concentration range.

Isothermal titration calorimetry was used to characterize and quantify the partition of indomethacin and acemetacin between the bulk aqueous phase and the membrane of egg phosphatidylcholine vesicles. Significant electrostatic effects were observed due to binding of the charged drugs to the membrane, which implied the use of the Gouy-Chapman theory to calculate the interfacial concentrations. The binding/partition phenomenon was quantified in terms of the partition coefficient (K(p)), and/or the equilibrium constant (K(b)). Mathematical expressions were developed, either to encompass the electrostatic effects in the partition model, or to numerically relate partition coefficients and binding constants. Calorimetric titrations conducted under a lipid/drug ratio >100:1 lead to a constant heat release and were used to directly calculate the enthalpy of the process, DeltaH, and indirectly, DeltaG and DeltaS. As the lipid/drug ratio decreased, the constancy of reaction enthalpy was tested in the fitting process. Under low lipid/drug ratio conditions simple partition was no longer valid and the interaction phenomenon was interpreted in terms of binding isotherms. A mathematical expression was deduced for quantification of the binding constants and the number of lipid molecules associated with one drug molecule. The broad range of concentrations used stressed the biphasic nature of the interaction under study. As the lipid/drug ratio was varied, the results showed that the interaction of both drugs does not present a unique behavior in all studied regimes: the extent of the interaction, as well as the binding stoichiometry, is affected by the lipid/drug ratio. The change in these parameters reflects the biphasic behavior of the interaction-possibly the consequence of a modification of the membrane's physical properties as it becomes saturated with the drug.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2004

Unfolding of ubiquitin studied by picosecond time-resolved fluorescence of the tyrosine residue.

The photophysics of the single tyrosine in bovine ubiquitin (UBQ) was studied by picosecond time-resolved fluorescence spectroscopy, as a function of pH and along thermal and chemical unfolding, with the following results: First, at room temperature (25 degrees C) and below pH 1.5, native UBQ shows single-exponential decays. From pH 2 to 7, triple-exponential decays were observed and the three decay times were attributed to the presence of tyrosine, a tyrosine-carboxylate hydrogen-bonded complex, and excited-state tyrosinate. Second, at pH 1.5, the water-exposed tyrosine of either thermally or chemically unfolded UBQ decays as a sum of two exponentials. The double-exponential decays were interpreted and analyzed in terms of excited-state intramolecular electron transfer from the phenol to the amide moiety, occurring in one of the three rotamers of tyrosine in UBQ. The values of the rate constants indicate the presence of different unfolded states and an increase in the mobility of the tyrosine residue during unfolding. Finally, from the pre-exponential coefficients of the fluorescence decays, the unfolding equilibrium constants (KU) were calculated, as a function of temperature or denaturant concentration. Despite the presence of different unfolded states, both thermal and chemical unfolding data of UBQ could be fitted to a two-state model. The thermodynamic parameters Tm = 54.6 degrees C, DeltaHTm = 56.5 kcal/mol, and DeltaCp = 890 cal/mol//K, were determined from the unfolding equilibrium constants calculated accordingly, and compared to values obtained by differential scanning calorimetry also under the assumption of a two-state transition, Tm = 57.0 degrees C, DeltaHm= 51.4 kcal/mol, and DeltaCp = 730 cal/mol//K.

Animals↗

PubMedDate not supplied

[Diabetic nephropathy. Study protocol for pre-kidney transplantation].

Between May 1990 and October 1998, 67 diabetic patients with end-stage renal disease, on dialysis, were submitted to a standardized protocol in order to assess the coexistence and degree of other diabetic and nondiabetic complications that could affect transplantation. Some of the results were analysed. Type 2 diabetic patients had more abnormal results on the lower limbs doppler ultrasound and on the lower limbs arteriography than type 1 (p < 0.05). Type 2 diabetic patients had more cardiovascular complications so the decision to transplant should be taken on a case by case basis.

Adult↗

PubMedDate not supplied

[Diabetic hyperosmolality. Retrospective study of 60 cases].

AIMS AND METHODS: Our aims were to determine the frequency of diabetic hyperosmolality (DH) in our Department, its causes, therapeutic implications and evolution. A five-years retrospective study was performed in 60 patients regarding age, sex, type and duration of diabetes mellitus (DM), previous antidiabetic therapy, underlying diseases, biochemical data, precipitating factors, therapeutic management and outcome. RESULTS: The hyperosmolar coma was responsible for 90% of the metabolic comas and for 3% of the diabetic patients. The median age of the cohort was 54.6 +/- 9.4 years, being females 61.7% and males 38.3% In 40% no prior diagnosis of DM was made and in the remaining patients the previous antidiabetic therapy was unknown in 61%. Altered consciousness was found in 90%, being 28% in coma. The metabolic acidosis was detectable in 22.2%, the average glycaemia was 956 +/- 267 mg/dl and the osmolality was 349.4 +/- 34.3 mosm/l. The precipitating factors were: poor metabolic control in all patients (HbA1C 12.5 +/- 2.75%), infections in 76.6%, suspension of antidiabetic therapy in 10% and concomitant hyperglycaemic drugs in 6.6% of patients. The global mortality was 20%. CONCLUSIONS: The majority of the situations could be preventable if an attempted screening and diagnosis of DM was made and precipitating factors avoid or promptly treated.

Diabetes Complications↗