Biomedical subjects
Publications and source records attributed to M Contreras.
The first case of AIDS associated with blood transfusion was described in 1982. Over the following two years great advances were made in the understanding and prevention of this new hazard associated with blood transfusion, culminating in 1985 with the introduction of a screening test for blood donation.
Twelve patients receiving long-term oxygen therapy were assessed for possible detrimental neuropsychological effects of short-term withdrawal of oxygen. Patients served as their own controls and received either their usual oxygen prescriptions or room air, through nasal prongs, over four-hour periods on two successive days. A battery of neuropsychological tests assessing memory and learning, sustained concentration, and motor and visuomotor speed were administered. In the room-air condition, the mean arterial oxygen partial pressure fell from 86.1 +/- 25.7 to 59.1 +/- 11.7 mm Hg, and the mean oxygen saturation fell from 94.7% +/- 3.2% to 89.9% +/- 5.3%, but the mean carbon dioxide partial pressure did not change significantly. No significant differences in neuropsychological test scores were found between the two conditions, suggesting that four hours of mild hypoxemia causes no significant deficits in cognition in patients receiving long-term oxygen therapy. Paradoxically, low-order inverse correlations were found between arterial oxygen partial pressures and results of visuomotor speed and memory tests, suggesting that an improvement in performance may have taken place during oxygen withdrawal.
The synthesis of new 3,5-diamino-1,2,6-thiadiazine 1,1-dioxide derivatives is described and their structures discussed on the basis of 1H and 13C-N.M.R. data. The antiparasitic activity of these and related compounds was evaluated. The bacterial mutagenicity of the parent compound (I) was studied.
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Pooling of screening red cells used in pre-transfusion testing has been discouraged by many workers since it might lead to the failure to detect alloantibodies. However, there is minimal scientific data to support this view and in the UK a high proportion of blood transfusion laboratories were still using pooled red blood cells for antibody screening in 1982-1983. In order to solve the dilemma of sensitivity of serological tests when using pooled versus individual screening cells, a comparative evaluation of both approaches was carried out. One hundred and five sera known to contain weak, warm-reacting clinically significant alloantibodies were tested by the three same standard sensitive techniques using samples of individual screening cells and a pool of the same cells in parallel. Our results show that when pooled cells were used, 12% of the selected alloantibodies were undetectable and a further 23% were only detectable microscopically. All antibodies examined were easily detectable macroscopically when individual screening cells were used. It is concluded that the sensitivity of pre-transfusion screening tests is reduced when pooled red cells are employed as opposed to individual samples of screening cells and that the use of pooled cells should be discouraged in routine pre-transfusion and antenatal antibody screening.
Rh-negative women, immunized to Rh by previous pregnancies, with only low concentrations of IgG anti-Rh(D) in their plasma were assigned at random to test and control groups (7 subjects in each group). Both groups were challenged with an intravenous injection of 0.28 ml of Rh-positive red cells; in addition, the test group received 500 micrograms anti-Rh intramuscularly. 2 weeks after the injections, all subjects showed an increase in plasma anti-Rh concentration; levels in test and control groups were similar. It is concluded that in Rh-immunized subjects with low levels of IgG anti-Rh a secondary response to Rh cannot be prevented by giving passively administered anti-Rh with the red cells.
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The N-terminal structures of the Miltenberger (Mi-) blood group class I and II specific human MN erythrocyte membrane sialoglycoproteins were determined by manual sequencing of tryptic glycopeptides and various secondary fragments. The Mi-I and Mi-II active glycoproteins were found to exhibit a threonine leads to methionine and threonine leads to lysine exchange, respectively, at position 28 which prevents N-glycosylation of asparagine 26. Due to the absence of the N-glycosidic oligosaccharide chain, the monomeric form of the Mi-I and Mi-II specific glycoproteins possesses a slightly increased sodium dodecyl sulfate/polyacrylamide gel electrophoretic mobility, in comparison to its normal counterpart. Serological studies suggest that antibodies, specific for Mi-I or Mi-II red cells, react with the structurally altered region of the MN glycoprotein.
After more than 20 years the extended pedigree of the only known kindred carrying the low frequency antigen Ria (Ridley) was reinvestigated. It is established that Ria is governed by a gene which is part of or very closely linked to the MNSs locus. Further serological and frequency studies are reported.
Dantu, a previously undescribed low-incidence red cell antigen, is inherited as a Mendelian dominant character. The Dantu antigen is associated with very weak s antigen, protease resistant N antigen and either very weak or no U antigen. Two of the propositi had previously been shown to have an unusual hybrid MNSs sialoglycoprotein, and it is probably this which carries these unusual N, s and U antigens as well as the Dantu antigen. A study of the family of one propositus suggests, by conventional genetics, that Dantu is not controlled by the MNSs locus; a possible explanation is given. Several examples of anti-Dantu are known, one was found to cause a positive direct antiglobulin reaction on neonatal red cells.
37 subjects have been immunized with A or B human blood group substances. All subjects showed at least a threefold increase in potency of their ABO antibodies. Use of the resulting plasma has considerably improved the quality of our ABO grouping reagents. The IgG component of these antibodies increased in all subjects and an IgA component was seen in the majority of post-immunization samples. All group O subjects developed cross-reacting anti-A,B antibodies.
The response to 0.8 ml of D-positive (ccDEE) red cells injected i.v., together with 1 microgram anti-D i.m., was studied in 13 D-negative male volunteers (test subjects); the red cells were labelled with 51Cr and were found to have a mean survival time of 24 d, after correction for Cr elution. Within the following 5 months, nine of the 13 subjects made anti-D, compared with four out of 12 control subjects in a previous series who received 1 ml of red cells from the same donor but without passively-administered antibody. The time at which anti-D was first detected and the maximum concentration of anti-D attained were similar in test and control subjects. After a second injection of D-positive red cells, given 5 months after the first, the total number of subjects making anti-D became 11 out of 13 in the test series, compared with six out of 12 in the previous control series. Antibody concentrations were similar in test and control subjects. Evidently, Rh immunization was not augmented if this term implies accelerated formation of antibody or an obvious increase in antibody concentration. On the other hand, the suggestive increase in the proportion of responders, though not statistically significant, is consistent with the earlier observations of others and suggests that the effect of a small dose of passively administered antibody is to facilitate primary immunization.
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