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Biomedical subjects

M A Soto

Publications and source records attributed to M A Soto.

At least 19 recordsLinked to original sources
PubMed2005

Structural effects of titanium citrate on the human erythrocyte membrane.

The structural effects of titanium citrate on the human erythrocyte membrane were studied through its interaction with intact erythrocytes and isolated unsealed human erythrocyte membranes (IUM). The studies were carried out by scanning electron microscopy and fluorescence spectroscopy, respectively. Titanium citrate induced shape changes in erythrocytes, which were damaged and ruptured leaving empty and retracted membranes. Fluorescence spectroscopy measurements in IUM indicated a disordering effect at both the polar head group and the acyl chain packing arrangements of the membrane phospholipid bilayer. Titanium citrate also interacted with molecular models of the erythrocyte membrane consisting in bilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), representing classes of phospholipids located in the outer and inner monolayers of the erythrocyte membrane, respectively. X-ray diffraction indicated that titanium citrate induced structural perturbation of the polar head group and of the hydrophobic acyl regions of DMPC, while the effects on DMPE bilayers were negligible. This conclusion is supported by fluorescence spectroscopy measurements on DMPC large unilamellar vesicles. All these findings indicate that the structural perturbations induced by titanium to human erythrocytes can be extended to other cells, thereby affecting their functions.

Acylation↗
PubMed2005

[Hydro-colloidal dressings which release hydro-active silver].

The study presented is a multicentric, prospective, open and comparative study designed with the objective of evaluating the performance of an antibacterial hydrocolloid dressing with hydroactivated silver (Comfeel Plata), when used to activate the healing process in wounds with high bacterial load, clinical signs of infection or malodour. Additionally, once the wound bed was appropriately prepared, a comparison in terms of efficacy was made between, on the one hand, continued treatment with the antibacterial hydrocolloid dressing, and, on the other hand, continued treatment with other dressings specifically designed for the proliferative phase of healing. Included into this study were 43 patients with chronic ulcers who were divided into two parallel treatment groups: In one group, Comfeel Plata (Coloplast AIS) was used until complete wound healing or for a maximum of 10-12 weeks, and in the second group Comfeel Plata (Coloplast A/S) was used until a clean wound bed was obtained and until the wound showed signs of positive evolution, at which moment the treatment was continued until complete healing or for a maximum of 10-12 weeks with dressings without silver designed especially for the proliferative phase of healing [Alione, Comfeel or Biatain (Coloplast AIS)]. The results obtained from the various study parameters indicate that the use of Comfeel Plata in the treatment of infected or colonized wounds prepares the wound bed and facilitates more rapid healing, and that the use of Comfeel Plata effectively reduces pain and malodour. The results indicate that once a clean wound bed is obtained, the use of a dressing without silver specifically for the proliferative phase will facilitate healing.

Bandages, Hydrocolloid↗
PubMed2003

Peroxyl radicals promoted changes in water permeability through gramicidin channels in DPPC and lecithin-PC vesicles.

Gramicidin incorporation to DPPC or lecithin-PC large unilamellar vesicles (LUVs) leads to pore formation that, under hyper-osmotic conditions, produces a noticeable increase in the rate of trans-membrane water flow. This pore formation is more efficient in the more fluid lecithin-PC LUVs. Exposure of these vesicles to peroxyl radicals generated in the aerobic thermolysis of 2,2'-azo-bis(2-amidinopropane) (AAPH), changes the physical properties of the bilayer (as sensed employing fluorescent probes), modifies gramicidin molecules (as sensed by the decrease in Trp fluorescence) and notably reduces the transbilayer rate of water outflow. In order to evaluate if this reduced water-transport capacity is due to changes in the membrane due to lipid-peroxidation and/or direct damage to gramicidin channels, results obtained in the oxidable vesicles (lecithin-PC) were compared to those obtained in DPPC vesicles. The data obtained show that most of the water transport efficiency loss can be ascribed to a direct disruption of gramicidin channels by AAPH derived peroxyl radicals.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2003

A pentapeptide-based method for protein secondary structure prediction.

We present a new method for protein secondary structure prediction, based on the recognition of well-defined pentapeptides, in a large databank. Using a databank of 635 protein chains, we obtained a success rate of 68.6%. We show that progress is achieved when the databank is enlarged, when the 20 amino acids are adequately grouped in 10 sets and when more pentapeptides are attributed one of the defined conformations, alpha-helices or beta-strands. The analysis of the model indicates that the essential variable is the number of pentapeptides of well-defined structure in the database. Our model is simple, does not rely on arbitrary parameters and allows the analysis in detail of the results of each chosen hypothesis.

Databases, Protein↗
PubMed2001

Transmission of white spot syndrome virus (WSSV) to Litopenaeus vannamei from infected cephalothorax, abdomen, or whole shrimp cadaver.

Shrimp viruses can remain infectious in frozen shrimp tissue and have been found in frozen commodity shrimp. Therefore, the threat of viral outbreaks in wild and cultured shrimp via frozen commodity shrimp exists. Because frozen shrimp are imported with and without the cephalothorax, more knowledge is needed concerning the infectivity of a cephalothorax relative to that of an abdomen. We compared the mortality rates from shrimp exposed to a WSSV-infected cephalothorax, abdomen, or whole shrimp cadaver. Estimates of transmission coefficients from the exposures to the infected cephalothorax, abdomen, or whole shrimp were also calculated because the transmission coefficients account for differences in the initial doses. In addition, we compared the variability in infectivity of pieces of shrimp by feeding 24 equal-sized pieces of cephalothorax and abdomen to 24 individually isolated shrimp. In Expt 1, susceptible shrimp did not completely consume the infected abdomen, and a significant difference was detected among shrimp exposed to the abdomen (mortality rate = 0.40), cephalothorax (mortality rate = 0.75), and whole shrimp cadaver (mortality rate = 0.67). The calculated transmission coefficients were 0.95 from an infected cephalothorax, 0.59 from an infected abdomen, and 0.69 from an infected whole shrimp cadaver. In Expt 2, susceptible shrimp were starved to ensure complete ingestion of each dose. No significant difference was observed in the estimated mortality rates from an infected cephalothorax (0.58), abdomen (0.63), or whole shrimp (0.67). The calculated transmission coefficients were 0.84 from an infected cephalothorax, 0.83 from an infected abdomen, and 0.60 from an infected whole shrimp cadaver. In Expt 3, no difference was observed in the mortality rates resulting from exposures to pieces of infected cephalothorax (0.57) or abdomen (0.58). Our results suggested that there was no difference in the viral loads of a WSSV-infected cephalothorax or abdomen, but that the cephalothorax was more infectious, probably because it was more palatable. In addition, our results are inconsistent with some assumptions of pathogen transmission used in epidemiological models. Some shrimp may be less aggressive feeders; therefore, susceptible shrimp are differentially contacting the dead infected shrimp in the exposure tanks, violating the random mixing assumption. Moreover, virus is probably not homogeneously distributed throughout an infected shrimp, suggesting that contacts between susceptible and infected shrimp are not equally likely to result in transmission.

Animals↗
PubMed2001

Epidemiological parameters of White Spot Syndrome Virus infections in Litopenaeus vannamei and L. setiferus.

An experimental protocol based on a mathematical epidemiology model was developed to study the transmission, virulence, and recovery rates of White Spot Syndrome Virus (WSSV). Two modes of transmission were compared for WSSV in Litopenaeus vannamei. We compared transmission by ingestion of infected cadavers to transmission by cohabitation with infected animals. In addition, we compared the ingestion transmission of WSSV in L. vannamei and in L. setiferus. Finally, we compared the virulence and recovery rates of WSSV in L. vannamei and L. setiferus. The transmission rate of WSSV to L. vannamei by cohabitation was 0.01. The transmission rate by ingestion of infected cadavers was over an order of magnitude larger at 0.46, suggesting that cohabitation is a much less important mode of transmission for WSSV. A statistically significant difference was detected between the estimates of ingestion transmission of L. vannamei (0.46) and those of L. setiferus (0.84), yet no differences in the virulence or recovery rates were detected between hosts. The overall estimated virulence rate was 0.34, and the overall estimated recovery rate from a WSSV infection was 0.007 for both species. According to epidemiological theory the threshold density of hosts necessary for an epidemic to occur is directly related to the virulence and recovery rates and inversely related to the transmission rate. Therefore, the epidemic threshold density may be lower for ingestion transmission than cohabitation transmission and lower for L. setiferus than for L. vannamei.

Animals↗
PubMed2000

Biocryptography.

A new cryptology that uses biomolecules as carriers of hidden information is described here. The huge dimension of biopolymers permits the insertion there of private messages and the rapidity and specificity of biomolecular interactions facilitate the identification of classified communications. Otherwise, this process can be implemented in a virtual context.

Base Sequence↗
PubMed2000

Fast DNA sequencing.

A method for fast nucleotide sequencing is described. It is based in the selection of well-known small oligomers able to be hybridized with the unknown target. The selected oligomers are afterwards ordered following a simple statistical approach. The use of capillary electrophoresis for the analysis is emphasized.

Base Sequence↗
PubMed1997

Effect of polyunsaturated fatty acid deficiency on dipole relaxation in the membrane interface of rat liver microsomes.

The influence of a fat-free diet on the lipid dynamics of rat liver microsomes and liposomes of microsomal lipids was studied by using different fluorescence methods. Lifetime distribution and rotational diffusion of probes with different localization in the lipid bilayer were measured using multifrequency fluorometry. Lateral mobility was studied by measuring excimer formation of pyrenedodecanoic acid. Dipolar relaxation in the interfacial region was studied using 2-dimethyl-amino-6-lauroylnaphthalene (Laurdan). In spite of large changes in the fatty acid composition of microsomal lipids, polyunsaturated fatty acid deficiency showed no effect on the lifetime distribution and rotational mobility of 1,6-diphenyl-1,3,5-hexatriene (DPH). l-(4-(trimethylamino)phenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH), 2- 7- and 12-(9-anthroiloxy)stearic acids. The treatment did not change the lateral diffusion of pyrenedodecanoic acid, either. However, generalized polarization of Laurdan fluorescence was higher in polyunsaturated fatty acid deficient microsomes as compared to the polyunsaturated fatty acid sufficient ones. This effect was also observed in liposomes of the total microsomal lipids, indicating that the changes in fatty acid composition resulting from polyunsaturated fatty acid deficiency produced a small but significant decrease in the rate of dipolar relaxation in the region of the lipid polar groups of the bilayer. The absence of lipid gel phase domains in rat liver microsomes was also indicated by Laurdan fluorescence features.

Animals↗
PubMed1996

Physical state of bulk and protein-associated lipid in nicotinic acetylcholine receptor-rich membrane studied by laurdan generalized polarization and fluorescence energy transfer.

The spectral properties of the fluorescent probe laurdan (6-dodecanoyl-2-dimethylaminonaphthalene) were exploited to learn about the physical state of the lipids in the nicotinic acetylcholine receptor (AChR)-rich membrane and compare them with those in reconstituted liposomes prepared from lipids extracted from the native membrane and those formed with synthetic phosphatidylcholines. In all cases redshifts of 50 to 60 nm were observed as a function of temperature in the spectral emission maximum of laurdan embedded in these membranes. The so-called generalized polarization of laurdan exhibited high values (0.6 at 5 degrees C) in AChR-rich membranes, diminishing by approximately 85% as temperature increased, but no phase transitions with a clear Tm were observed. A still unexploited property of laurdan, namely its ability to act as a fluorescence energy transfer acceptor from tryptophan emission, has been used to measure properties of the protein-vicinal lipid. Energy transfer from the protein in the AChR-rich membrane to laurdan molecules could be observed upon excitation at 290 nm. The efficiency of this process was approximately 55% for 1 microM laurdan. A minimum donor-acceptor distance r of 14 +/- 1 A could be calculated considering a distance 0 < H < 10 A for the separation of the planes containing donor and acceptor molecules, respectively. This value of r corresponds closely to the diameter of the first-shell protein-associated lipid. A value of approximately 1 was calculated for Kr, the apparent dissociation constant of laurdan, indicating no preferential affinity for the protein-associated probe, i.e., random distribution in the membrane. From the spectral characteristics of laurdan in the native AChR-rich membrane, differences in the structural and dynamic properties of water penetration in the protein-vicinal and bulk bilayer lipid regions can be deduced. We conclude that 1) the physical state of the bulk lipid in the native AChR-rich membrane is similar to that of the total lipids reconstituted in liposomes, exhibiting a decreasing polarity and an increased solvent dipolar relaxation at the hydrophilic/hydrophobic interface upon increasing the temperature; 2) the wavelength dependence of laurdan generalized polarization spectra indicates the presence of a single, ordered (from the point of view of molecular axis rotation)-liquid (from the point of view of lateral diffusion) lipid phase in the native AChR membrane; 3) laurdan molecules within energy transfer distance of the protein sense protein-associated lipid, which differs structurally and dynamically from the bulk bilayer lipid in terms of polarity and molecular motion and is associated with a lower degree of water penetration.

2-Naphthylamine↗
PubMed1996

Neural system states and networks.

A neural circuit at the human cerebellar cortex and nuclei is interpreted in terms of an optimized code and a reliable network.

Cell Communication↗
PubMed1996

Body position effects on EMG activity of sternocleidomastoid and masseter muscles in patients with myogenic cranio-cervical-mandibular dysfunction.

This study was conducted in order to determine the effects of body position on integrated electromyographic (IEMG) activity of sternocleidomastoid and masseter muscles in 17 patients with myogenic cranio-cervical-mandibular dysfunction. EMG recordings at rest and during swallowing of saliva and maximal voluntary clenching were performed by placing surface electrodes on the sternocleidomastoid and masseter muscles (contralateral to the habitual side of sleeping of each patient), in the following body positions: standing, seated, supine, and lateral decubitus position. Significant higher EMG activities were recorded in the sternocleidomastoid muscle in the lateral decubitus position and in the supine position (except during swallowing), whereas a significant higher EMG activity was recorded in the masseter muscle during maximal voluntary clenching in standing and seated positions. The EMG pattern observed suggests that the presence of parafunctional habits and body position could be closely correlated with the clinical symptomatology in the sternocleidomastoid and masseter muscles at wakening and during waking hours, respectively, in patients with myogenic cranio-cervical-mandibular dysfunction.

Adult↗
PubMed1995

On the nature of mutations in molecular evolution.

In this work it is proposed tht in evolution amino acid substitutions implying strong physico chemical and structural differences are more revelant and more frequent that substitutions between similar amino acids. This analysis is made over a group of protein families representing about 10000 substitutions and as examples the evolutionary trees of fibrinopeptides A and calcitonins were constructed and compared.

Amino Acid Sequence↗
PubMed1995

Neural network in the transcription-translation process in eukaryotic cells and viruses, a comparison.

The transcription-translation process in the virus-host cell system is analyzed in terms of a virtual neural network. In contrast to findings in the transcription-translation process in eukaryotic cells, an inverse correlation between the frequency of protein amino acids and code degeneracy and between code degeneracy and the rate of amino acid substitutions was not found. Misuse of the virtual host cell network by virus protein synthesis could be attributed to the different amino acid composition of the virus proteins (input unit) studied here.

Amino Acids↗
PubMed1994

Neural network in the transcription-translation process.

The transcription-translation process is represented by a virtual neural network. The input unit corresponds to the transcription process, the hidden unit to the mRNA-ribosome-tRNA interaction and the output unit to the final state of the protein. A correlation was found between the natural amino acid frequency and the degree of codon degeneracy and an inverse correlation between the code degeneracy and the number of amino acid substitutions in the protein.

Amino Acids↗