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Biomedical subjects

M Ramos

Publications and source records attributed to M Ramos.

At least 55 records · Page 3Linked to original sources
PubMed2001

[Prevalence of sub-clinical vitamin A deficiency and malnutrition in slum children in Maraicabo - Venezuela].

The present cross sectional study was carried out to estimate the prevalence of vitamin A deficiency among children by means of clinics and conjunctival impression cytology (CIC), and nutritional status by anthropometric indicators H//A, W//A, W//H. The study population included 157 children 2-6 y old, from urban and rural slums of Maracaibo, Venezuela, Conjunctival impression cytology was performed by ICEPO standard procedure. Z-score was applied to anthropometric data with reference values of NCHS-WHO. No evidence of clinical or ophthalmologic signs of vitamin A deficiency were detected. The prevalence of subclinical vitamin A deficiency, as detected by abnormal CIC, was 35.4%, being higher in rural children (48.3%). These prevalence values are higher than the criteria laid down by WHO/UNICEF to indicate a public health problem (> 20%). Mild or moderate protein-energy global malnutrition and stunting were detected in 36.1% and 44.6% of children, respectively. Abnormal CIC was indistinctly observed (approximately equal to 35%) as much in children with adequate nutrition as in malnourished ones. There was no significant difference in the distribution of the CIC results in relation to nutritional status. The findings indicate that CIC and Z-score of nutritional anthropometric data are useful to characterize the risk of vitamin A deficiency and of malnutrition in communities. Beside the implementation of an integral nutritional program which includes supplementation, food fortification and dietary diversification, improvement of socio-economic and sanitation conditions and also the educational level, with emphasis on nutritional and health education, are highly recommended.

Anthropometry↗
PubMed2000

Cyclosporin A targets involved in protection against glutamate excitotoxicity.

The toxicity of glutamate in neuronal cultures has been attributed in part to a mitochondrial dysfunction involving the permeability transition pore. The participation of the permeability transition pore in this process has been pharmacologically demonstrated by the use of cyclosporin A, which inhibits pore opening by interaction with mitochondrial cyclophilin and, thus, prevents cell death and upstream events. Since cyclosporin A also acts on calcineurin, we have investigated which of the targets of cyclosporin A was responsible for the inhibition of glutamate-excitotoxicity in cerebrocortical primary neuronal cultures. Reactive oxygen species production and early (30 min to 2 h) drop in ATP levels are initial events in glutamate excitotoxicity taking place before neuronal death. Cyclosporin A did not inhibit reactive oxygen species production, but reduced the drop in ATP levels and subsequent neuronal death. However, cyclosporin derivatives that do not bind to calcineurin had smaller effect on survival than cyclosporin A, (regardless of whether they were able to bind cyclophilin), indicating that cyclosporin A protects against glutamate toxicity also through calcineurin-related mechanisms. Consistent with this view, ATP loss appears to result from nitric oxide synthase (NOS) activation (including calcineurin-dependent dephosphorylation) and nitric oxide (NO)/peroxinitrite-dependent increase in poly (ADP-ribose) polymerase activity, since it was reduced by inhibitors of these activities. Collectively, these results suggest that cyclosporin A exerts its protective effects through calcineurin-dependent and independent mechanisms.

Adenine Nucleotides↗
PubMed2000

An N-acetylated natural ligand of human histocompatibility leukocyte antigen (HLA)-B39. Classical major histocompatibility complex class I proteins bind peptides with a blocked NH(2) terminus in vivo.

Sequence-independent interactions involving the free peptidic NH(2) terminus are thought to be an essential feature of peptide binding to classical major histocompatibility complex (MHC) class I proteins. Challenging this paradigm, a natural Nalpha-acetylated ligand of human histocompatibility leukocyte antigen (HLA)-B39 was identified in this study. It matched the NH(2)-terminal sequence of two human helicases, was resistant to aminopeptidase M, and was produced with high yield from a synthetic 30 mer with the sequence of the putative parental protein by the 20S proteasome. This is the first reported natural ligand of classical MHC class I antigens that has a blocked NH(2) terminus.

Acetylation↗
PubMed2000

Limited diversity of peptides related to an alloreactive T cell epitope in the HLA-B27-bound peptide repertoire results from restrictions at multiple steps along the processing-loading pathway.

The influence of various factors along the processing-loading pathway in limiting the diversity of HLA-B27-bound peptides around a core protein sequence was analyzed. The C5 proteasome subunit-derived RRFFPYYV and RRFFPYYVY peptides are natural B*2705 ligands. The octamer is an allospecific CTL epitope. Digestion of a 27-mer fragment of C5 revealed that both ligands are generated from this precursor substrate with the 20S proteasome in vitro in a ratio comparable to that in the B*2705-bound peptide pool. The C5 sequence allowed to derive a nested set of six additional peptides with 8-11 residues containing the core octamer sequence and the Arg2 motif of HLA-B27, none of which was found in the B27-bound pool. Together, low proteasomal yield, disfavored TAP-binding motifs, and low affinity for B*2705 accounted for the absence of four of the six peptides. The two remaining differed from the natural octamer or nonamer ligands only by an additional N-terminal Ser residue. Their stability in complex with B*2705 was lower than the respective natural ligands, raising the possibility that N-terminal trimming might have favored a shift toward the more stable peptides. The results suggest that the B*2705-bound peptide repertoire has a highly restricted diversity around a core alloantigenic sequence. This is not explained by a single bottleneck feature, but by multiple factors, including proteasomal generation, TAP-binding motifs, MHC-binding efficiency, and perhaps optimized stability through N-terminal trimming. Tapasin-dependent restrictions, although not excluded, were not required to explain the absence in vivo of the particular peptide set in this study.

Amino Acid Sequence↗
PubMed2000

[Hemodynamic benefits of left ventricular pacing in two pacemakers syndromes with refractory heart failure].

We describe two cases in which right ventricular pacing produced severe hemodynamic deterioration and in which changing the pacing from the right to the left ventricle sharply corrected these alterations, while simultaneous biventricular pacing did not. Chronic left ventricular pacing can solve hemodynamic alterations in severe pacemaker syndromes, thereby avoiding the need for mitral prosthesis implantation in some cases. The use of this procedure today should be individualized, including acute hemodynamic and echocardiographic studies, because the width of the QRS complex during pacing is not a significant predictor of hemodynamic efficiency.

Aged↗
PubMed2000

Capillary electrophoresis characterization of the casein fraction of cheeses made from cows', ewes' and goats' milks.

Casein fractions and their breakdown products in Iberico-type cheeses made from the milk of cows, ewes or goats were analysed by capillary electrophoresis in order to characterize them. The actions of plasmin and chymosin on caseins were evaluated by comparing the electropherograms of caseins from milk and from cheese, both with and without treatment with plasmin. Characteristic capillary electrophoresis patterns were obtained for cheeses made from the milk of each of the three species, and the main components were identified. Caprine para-kappa-casein and bovine beta-caseins, eluting at the first and at the last part of the electropherogram respectively, were found to be indicative of the presence of the milks of these species.

Animals↗
PubMed2000

Application of capillary electrophoresis to the characterization of processed cheeses.

Capillary electrophoresis using a hydrophilically coated capillary and a low pH buffer containing urea has been used to characterize processed cheeses. Different electrophoretic patterns were obtained depending on the ingredients used in the blend such as acid casein, rennet casein, sodium and calcium caseinates and skim milk powder. Isoelectric casein, and sodium and calcium caseinates were shown to contain intact non-glycosylated kappa-casein (kappa-CN), while rennet casein contained only trace amounts of kappa-CN and mainly para-kappa-CN. Therefore, the addition of casein or caseinate to processed cheeses has been detected by analysing the intact non-glycosylated kappa-CN. Quantitation of intact non-glycosylated kappa-CN in processed cheeses of known and unknown composition was carried out using a regression curve from standard mixtures of 150-550 g isoelectric casein/kg total rennet casein. This capillary electrophoresis method successfully confirmed the addition of isoelectric casein or caseinate to processed cheeses of known composition. The quantitative determination range was 0.605-3.688 mg kappa-CN/ml. This method cannot be used for measuring additions of rennet casein or any caseinates that have been exposed to chymosin.

Calcium↗
PubMed2000

Peptide specificity of the Amerindian B*3905 allotype: molecular insight into selection mechanisms driving HLA class I evolution in indigenous populations of the Americas.

HLA-B*3905 is apparently restricted to Amerindian populations and presents a wide geographical distribution, from Mexico to Argentina. It differs from B*3901, one of the founder HLA class I alleles of Central and South Amerindians, by a single nucleotide substitution leading to an Asp74Tyr change in the gene product. The peptide specificity of the B*3905 protein was characterized by pool sequence analysis of B*3905-bound peptides and by sequencing of a set of individual ligands, using electrospray ion trap mass spectrometry. The results indicate a double effect of the B*3905 mutation. First, pocket B specificity was shifted towards an increased preference for His at peptide position 2, which is the main anchor for B39-bound peptides, relative to B*3901. Second, at peptide position 3 acidic residues were favored, and aromatic residues disfavored, relative to B*3901. These features approach the peptide specificity of B*3905 to B*3801 and B*1509, allotypes absent from Central and South Amerindians. Together with B*3909, B*3905 is the second HLA-B39 subtype whose polymorphism results in a shift of peptide specificity towards that of HLA-B allotypes absent from these populations. This suggests that HLA-B39 evolution in Central and South America may be an antigen-driven adaptive response, leading to generate antigen-presenting properties absent from the HLA class I repertoire of the ancestral population.

Amino Acid Motifs↗
PubMed2000

[Development children's eating behavior]

OBJECTIVES: Review the literature, exploring factors that contribute to the development of children's eating behavior such as the role of learning and social context. METHODS: The review of the literature was done using Medline, Psyclit, and Lilacs as resources for assessing international and national research articles on child nutrition, with an emphasis on children's eating behavior. These articles were revised and grouped together according to the topic. RESULTS: Family is responsible for the development of children's eating behavior through social learning. Parents are children's first nutritional educators. Children's eating experiences are influenced by cultural and psychosocial factors. Social context plays a relevant role in this process, especially through the strategies used by parents to encourage children to have a balanced diet and to eat specific foods. These strategies may contain adequate and inadequate stimuli as to the development of children's food preference and food intake self-control. CONCLUSION: The learning process is a determining factor for children's eating behavior, and is associated with three factors: food flavor conditioning, food postingestional consequences, and social context. Parents are deeply concerned with the amount of food their children eat and not with the development of more adequate habits and attitudes related to dietary quality.

Journal Article↗
PubMed2000

Micellar changes induced by high pressure. influence in the proteolytic activity and organoleptic properties of milk.

We investigated the effects of high-pressure treat-of 25 to 60 degrees C, on micelle structure, proteolytic activity, and sensory properties of milk. Pressure treatments at 25 degrees C considerably reduced micelle size, while pressurization at higher temperatures progressively increased micelle dimensions. Pressure-induced denaturation of beta-lactoglobulin (beta-LG) amounted 76% at 25 degrees C and was almost 100% in milks treated at 40 to 60 degrees C. alpha -Lactalbumin (alpha-LA) was resistant to pressure at temperatures up to 40 degrees C, but its denaturation reached 56% at 60 degrees C. Plasmin resisted pressurization at room temperature; however, pressure treatments at higher temperatures increased plasmin inactivation, which reached 86.5% at 60 degrees C. Pressurization at temperatures from 40 to 60 degrees C reduced the proteolytic activity and improved the organoleptical properties of milk, compared with the same treatments at 25 degrees C, which suggested that these combined treatments could be used to produce milk of good sensory properties with an increased shelf life. These results are discussed in the light of the changes found in micellar structure.

Animals↗
PubMed2000

Comparison of three methods to determine the whey protein to total protein ratio in milk.

Three methods for quantification of the ratio of whey protein in total protein [capillary electrophoresis (CE), sodium dodecyl sulfate capillary electrophoresis (SDS-CE), and UV fourth derivative absorption spectroscopy (UV-4th Der.)] were applied to raw (n = 21), pasteurized (n = 5) and UHT (n = 18) milk samples. All methods effectively measured the whey protein to total protein ratio independently of the heat treatment applied to the milk. Mean values obtained by CE, SDS-CE and UV-4th Der. were respectively, 17.1, 18.5, and 17.2% for raw milks, 16.6, 17.7, and 18.8% for pasteurized milks, and 16.8, 17.0, and 17.2% for UHT milks. (Key words: whey protein to total milk protein ratio, capillary electrophoresis, sodium dodecyl sulfate capillary electrophoresis, fourth derivative ultraviolet spectroscopy)

Animals↗
PubMed2000

Reduction of endogenous bacteria associated with catfish fillets using the Grovac process.

Fresh catfish (Ictalurus punctatus) fillets are known to be contaminated with a large number of spoilage and pathogenic bacteria. The Grovac method, a new patented (U.S. 5,543,163) process, was evaluated for its efficacy in reducing the number of pathogens and spoilage microorganisms associated with food. This process involves using a processing solution containing ascorbic acid (AA) and sodium chloride (NaCl), vacuum, and tumbling. A total of 51 bacterial isolates were isolated and identified from whole catfish and catfish fillets using both selective and nonselective media, phenotypic tests, and the Vitek identification system. Psychrotrophic foodborne pathogens included: Aeromonas hydrophila, Escherichia coli, Listeria sp., Plesiomonas shigelloides, Proteus sp., Staphylococcus aureus, and Vibrio parahaemolyticus. High aerobic plate counts (2.6 x 10(7) CFU/g) for catfish fillets indicated that fillets were heavily contaminated during processing of catfish. The Grovac process showed that various treatment combinations of AA and NaCl resulted in a 1.2 to 2.3 CFU/g log reduction of microbial counts associated with catfish fillets. The effectiveness of the process may be related to the synergistic effect of tumbling, AA, NaCl, and vacuum. These results suggested that the Grovac process could be used as an alternative processing procedure to reduce microbial populations associated with catfish fillets and may be useful to improve the shelf-life and food safety of the product. Microbiological data from this study will be used for the development of a hazard analysis for the implementation of the hazard analysis critical control point program for processed catfish fillets.

Animals↗