Biomedical subjects

P C do Nascimento

Publications and source records attributed to P C do Nascimento.

9 recordsLinked to original sources

PubMed2004

Interaction of aluminium ions with some amino acids present in human blood.

The interaction of aluminium with some amino acids present in human blood was studied combining ion-chromatography (IC), atomic absorption spectrometry (AAS) and ultrafiltration (UF) techniques. An IC system for simultaneous determination of ornithine, lysine, glutamic acid, aspartic acid and tyrosine was developed. By adding aluminium to standard solutions of the amino acids and keeping the pH at 6 and 7 it was possible to verify that aluminium caused a reduction on the amino acid chromatographic signals. Similar experiment, carried out for copper showed the same behaviour (with different percentage of signal reductions) and validated the results for aluminium, considering that the interaction Cu-amino acid is well-established. The AAS analysis of sample fractions (500 microl) after the IC separation showed that aluminium (as copper as well) is not present in the fractions in which the amino acid peaks appear in the chromatogram. These approaches carried out with serum samples after UF showed that part of the "free" fraction of serum aluminium is distributed, besides other ligands, among these amino acids. It was found that in serum the affinity for aluminium followed the sequence Lys>Orn>Tyr>Glu approximately Asp.

Aluminum↗

PubMed2001

HPLC-based method using sample pre-column clean-up for the determination of methanethiol and ethanethiol in parenteral amino acid solutions.

A method has been developed for the chromatographic determination of methanethiol (MT) and ethanethiol (ET) as contaminants in amino acid parenteral nutrition (PN) solutions. The clean-up of the samples before chromatographic analysis was investigated by solid-phase extraction (SPE) on pre-columns filled with polyethylene powder (PE), aluminium oxide (AlOx), silica (SiOx), or polyurethane foam (PUF) as adsorbents. The thiols were more efficiently separated from the matrices by SPE on PUF pre-columns. Simultaneous derivatization and elution with DTNB (5,5'-dithiobis(2-nitrobenzoic acid)) enabled further discrimination between MT and ET by reversed-phase HPLC with spectrophotometric detection. The retention times for the derivatized MT and ET species were 12.5 and 23.0 min, respectively. Recoveries from spiked PN samples were calculated to be approximately 90%, and the MT and ET content of commercial PN solutions was determined using the methodology described. Detection limits of 15 and 10 microg L(-1) were calculated for MT and ET, respectively.

Aluminum Oxide↗

PubMed2001

Interference in the Limulus amebocyte lysate assay for endotoxin determination in peritoneal dialysis fluids and concentrates for hemodialysis.

The interference of the saline concentration of fluids for peritoneal dialysis and concentrates for hemodialysis on the Limulus amebocyte lysate (LAL) assay for endotoxins was investigated. The experiments were carried out individually with each substance that compose fluids for hemodialysis, to determine the possible inhibition or enhancement effects that they could cause on the LAL assay. The compositions were also assayed to investigate the possibility of synergistic effect. They were assayed by the gel-clot method from two different suppliers, and the samples that showed inhibition effect were also assayed by the chromogenic method. The samples were analysed at successive dilutions, with different LAL sensitivities, to satisfy the endotoxin limits of 5 EU/ml for the concentrate and 0.25 EU/ml for the fluid for dialysis peritoneal. The results showed that the major interference on the gel-clot assay occurs in presence of acetic acid and in concentrates containing acid acetic, even the pH being adjusted between 6.5 and 7.5. However, the test, after an adequate dilution, could be validating for all samples. Chromogenic test can be used for peritoneal dialysis fluids considering a limit of 0.25 EU/ml and sample dilution of eight times, but it cannot be used for concentrates for hemodialysis without further dilution. Considering the results and that the chromogenic is a more time-consuming method, endotoxins in fluids for hemodialysis can be satisfactorily assayed by the gel-clot method.

Dialysis Solutions↗

PubMed2001

Influence of the glass packing on the contamination of pharmaceutical products by aluminium. Part I: salts, glucose, heparin and albumin.

The presence of aluminium (Al) in pharmaceutical products used parenterally as sodium and potassium chlorides, glucose, heparin and albumin were investigated with respect to their storage in glass containers. As glasses can have aluminium in their composition, the aluminium may be released from the glass into the solution. The action of the substances above mentioned were investigated storing their solutions in glass and plastic containers, and measuring the aluminium in solution at determined time intervals. The aluminium present in the commercial pharmaceutical products, stored in both plastic and glass containers were also measured. All glass containers were analysed to determine their aluminium content. The aluminium determinations were done by atomic absorption spectrometry. The resuLts showed that aluminium is present in all analysed glasses in a percentage of 0.6 to 3%. Although all substances already have a residual aluminium contamination, the major contribution comes from the glass containers in which their solutions were stored. The contamination arising from glass depends too much on the nature of the substance. While the salts extracted about 400 microg Al/l in 60 days, glucose extracted 150 microg Al/l, and albumin and heparin about 500 microg Al/l in the same time interval. Commercial solutions of glucose contain about 10 microg Al/l when stored in polyethylene and from 350 to 1,000 microg Al/l when in glass ampules. Considering all commercial products, solutions stored in plastic containers contained no more than 20 microg Al/l whereas in glass the aluminium contamination reached 1,000 microg/l, and in all of them the aluminium increases with the age of the product.

Albumins↗

PubMed2001

Influence of the glass packing on the contamination of pharmaceutical products by aluminium. Part II: amino acids for parenteral nutrition.

The presence of aluminium in amino acids parenteral nutrition solutions can be related to the affinity of the amino acids for aluminium present in glass containers used for storage. For this study solutions of 19 amino acids used in parenteral nutrition were stored individually in glass flasks and the aluminium measured at determined time intervals. Solutions of complexing agents for aluminium, as ethylene-diaminetetraacetic acid, nitrilotriacetic acid, citrate, oxalate and fluoride ions were also stored in the same flasks and the aluminium measured during the same time interval. The measurements were made by electrothermal atomic absorption spectrometry. The aluminium content of the glass containers was also measured. The results showed that the glasses have from 0.6% to 0.8% Al. Only solutions of cysteine, cystine, aspartic acid and glutamic acid became contaminated by aluminium. As the same occurred with the complexing agents, aluminum can be released from glass due to an affinity of the substances for aluminium. Comparing the action of complexing agents and amino acids for which the stability constants of aluminium complex are known, it is possible to relate the magnitude of the stability constant with the aluminium leached from glass, the higher the stability constant, the higher the aluminium released. The analysis of commercial formulations with and without cysteine, cystine, glutamic acid or aspartic acid stored in glass containers confirms that the presence of these amino acids combined with the age of the soLution are, at least partially, responsible for the aluminium contamination. The resuLts demonstrated that the contamination is an ongoing process due to the presence of aluminium in glass combined with the affinity of some amino acids for this element.

Aluminum↗

PubMed2000

Effect of aluminum on delta-aminolevulinic acid dehydratase from mouse blood.

The objective of this study was to investigate aluminum deposition in whole blood and plasma of mice and the activity of blood delta-aminolevulinic acid dehydratase (ALA-D) after in vitro and in vivo exposure to this element. In vitro experiments showed activation and inhibition of the enzyme activity when 0.01-5.0 mM of aluminum sulphate were used (IC(50): 1.31 mM). Treatment with citrate and aluminum plus citrate increased ALA-D activity in vivo and the increase in enzyme activity was parallel to the increase in aluminum content in blood and plasma. These results show that aluminum has a distinct effect on ALA-D activity: first, at relatively lower concentrations it activated, and at high concentration it inhibited, blood ALA-D in vitro; second, it activated the enzyme when administered to drinking water. One important toxicological finding of the present report is that the apparent irrelevant addition of citrate to the drinking water significantly increased the level of aluminum in blood and plasma. Thus, in order to predict more accurately the extent of human exposure to aluminum it would be advantageous to consider the level of citrate ingestion and not exclusively the aluminum level in water or food.

Administration, Oral↗

PubMed1998

Cyanide determination in biological fluids using a microdiffusion method with a flow system and polarographic detection.

The report describes a method for the automated polarographic determination of cyanide as tetracyanonickelate (II) anion complex in a gas-diffusion flow system. The volatile cyanide, existing in whole blood, plasma and urine samples, was measured after gas-diffusion using 8 x 10-5 mol l-1 hexaaminenickel solution as acceptor. The linear range of calibration, for measurements at the hanging mercury-drop electrode (HMDE), was from 0.1 to 2.0 micrograms cyanide with r = 0.998. The RSD was, respectively, 3.4 and 1.2% (n = 5) for 0.4 microgram cyanide measured with and without the flow-system configuration. Detection limits of 7.4 microgram l-1 were calculated using the flow system and the method was compared with the classical method using Cavet flasks. Parameters that affect the cyanide determination in the proposed method, such as acceptor solution, pH, flow rate and temperature, were investigated.

Cyanides↗

PubMed1997

Automated polarographic determination of sulfide as contaminant in parenteral amino acid solutions.

A method for the automated polarographic determination of sulfide in a gas-diffusion flow system was developed. The volatile sulfide, existing as a contaminant in parenteral amino acid solutions, was measured after gas diffusion using 0.1 mol l-1 NaOH solution as acceptor. The linear range of calibration, for measurements at a dropping-mercury electrode (DME), was from 5 to 100 micrograms of sulfide with r = 0.999 and RSD = 7.5% (n = 5) for 10 micrograms of sulfide. For measurements at the hanging mercury-drop electrode (HMDE), with a preconcentration time of 30 s, the linear range of calibration was from 0.9 to 20 micrograms of sulfide with r = 0.998 and RSD = 5.8% (n = 5) for 2 micrograms of sulfide. Detection limits of 59 and 11 micrograms l-1 at the DME and HMDE, respectively, were calculated and the recoveries of sulfide from spiked samples were 91.5-104.5%. Parameters that affect the sulfide determination using this method, such as the organic content of the matrix, pH, flow rate and sample size, were investigated.

Amino Acids↗

PubMed1997

Liquid chromatography with ultraviolet absorbance detection of ethylenethiourea in blood serum after microwave irradiation as an auxiliary cleanup step.

The report describes a method of deproteinizing serum that combines the action of acids with microwave irradiation. The acid concentration is ten times smaller than in the usual acid deproteinization method and the results are similar. The main advantages of the proposed method are the maintenance of the pH of the supernatant at around 5, and the reduction of the concentration of the deproteinizing agent. The procedure was applied to the determination of ethylenethiourea in serum samples by HPLC with spectrophotometric detection. Using 0.5 ml of serum, 0.04 microgram of ethylenethiourea were determined with recoveries between 89 and 109%.

Carcinogens↗