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Biomedical subjects

E Alvarez

Publications and source records attributed to E Alvarez.

At least 253 records · Page 14Linked to original sources
PubMed1984

Antibodies against a tumour-associated antigen in an AKR lymphoma conditioned to grow in BALB/c mice.

An experimental model was used in which AKR lymphoma cells (L15) were conditioned to grow in BALB/c mice leading to tumour-bearing (progressor) and tumour-rejecting (regressor) animals. The behaviour of antibodies present in the sera of these animals was studied using as antigen L15 cells or a soluble tumour-associated antigen TEs. Both sera showed similar IIF and haemagglutinating activity. However differences were observed for the complement cytotoxicity assay. Regressor serum as well as a rabbit anti-tumour-associated antigen serum were strongly cytotoxic for the AKR lymphoma cells while progressor serum showed markedly lower activity. Specific antibodies against the tumour-associated antigen were purified. In both sera they were located mainly in IgG1 but also in IgG2. The purified antibodies agglutinated specifically sensitized sheep erythrocytes and reacted by indirect immunofluorescence with L15 cells but not with AKR thymocytes. It is suggested that two qualitatively different humoral immune responses are involved in the mechanisms leading to tumour enhancement or rejection.

AKR murine leukemia virus↗
PubMed1984

Application of receiver-operator analysis to diagnostic tests of iron deficiency in man.

The objective of the present report is to demonstrate the use of receiver-operator characteristics (ROC) analysis in the selection of diagnostic tests for iron deficiency in a specific population. Conventional ROC curves were prepared with true positive fraction (TPF) and false positive fraction (FPF) determined by the application of different cut-off points for four indicators of iron status. ROC plots were then transformed into normal deviate scales. The advantages of Gaussian transformation of TPF and FPF when underlying decision functions are normally distributed are: the ROC curve is a straight line; and the separation between the two distributions and shape of these distributions can be simply quantitated as intercepts and slopes. In the present study, pretreatment hemoglobin concentration was the most robust diagnostic indicator of iron deficiency as operationally defined by a response of hemoglobin to iron treatment. Free erythrocyte protoporphyrin was a more sensitive and specific predictor than either serum ferritin or transferin saturation when a stringent operational definition of iron deficiency was used. These findings illustrate the utility of ROC analysis in discriminating between diagnostic indicators having different degrees of accuracy.

Anemia, Hypochromic↗
PubMed1984

Body iron reserves of rural and urban Guatemalan women of reproductive age.

Body iron reserves (using serum ferritin as an index), hematological status, and other indicators of iron nutrition were evaluated in three groups of non-pregnant nulliparous women with ages comprised between 14 and 29 years (mean = 19 years). The first group (n = 33) included residents of the rural coastal area (less than 750 m above sea level) (group RCG); the second (n = 32) from the rural highlands (751-1,500 m) (group RHG); and the third group (n = 104) from urban Guatemala City (1,500 m) (group UG). The women in the UG group belonged to the middle or high socioeconomic stratum. Median values in serum ferritin levels (ng/ml) for each group were: RCG = 11.5 (undetectable 50.6); RHG = 17.2 (1.9-83.1) and UG = 20.2 (3.9-56.7). The difference between RCG and UG was statistically significant (P less than 0.05). The percentage of women with serum ferritin levels less than or equal to 9 ng/ml (iron deficiency) was 45 in the RCG, 25 in the RHG and 12 in the UG group. In addition, the prevalence of subnormal hemoglobin levels (below mean - 1 SD) was 46% in the RCG, 12% in the RHG and 8% in the UG. There were no cases of subnormal blood folate levels. As results indicate, the women studied had low iron reserves, the rural coastal group being the most affected. They also evidenced the high prevalence of iron deficiency in the region and the need for public health actions to overcome this nutrition problem.

Adolescent↗
PubMed1977

The inotropic memory of amphibian myocardium.

(1) Experimentally observed changes of contractile force induced by changes in the pattern of stimulation of frog ventricular myocardium were compared with predictions computed on the basis of a model for the contractile conditioning, proposed in a previous paper. (2) For this purpose, two functions (Potentiation and Inhibition) which describe in the model the effect of previous contractions, were determined experimentally. (3) It is shown that the model adequately predicts : force-frequency curve Inotropic Effect Curves at different basal frequencies, effect of the suppression of a contraction in a sequence of definite frequency, frequency-staircases, and strength-interval curves. (4) The formal characteristics of the model are discussed, and it is suggested that the potentiation mechanism results from the recirculation of activator calcium in two types of compartments, from which calcium passes to the myofilaments during the contractions or is lost to the exterior with first order kinetics during the rest period. Possible locations for these compartments are proposed. Various hypothesis on the nature of the inhibitory mechanism are considered.

Animals↗
PubMed1977

Preliminary report of total ankle arthroplasty for osteonecrosis of the talus.

Osteonecrosis of the talus secondary to adrenal corticosteroids is rare. The pathophysiology of the disorder is controversial. This is a report of bilateral talar necrosis secondary to steroid medications in a 23-year-old male. Conservative methods of management of the condition are not altogether satisfactory. Bilateral ankle replacement in this case resulted in alleviation of pain and improvement of function.

Adult↗