Biomedical subjects

M D'Almeida

Publications and source records attributed to M D'Almeida.

4 recordsLinked to original sources

PubMed1989

Epidemiological study of neuro-cysticercosis in northern Togo (West Africa).

In april 1987, an epidemiologic study in Northern Togo was carried out in order to evaluate the prevalence of cysticercosis and epilepsy. The survey also aimed to investigate possible connections between these two illnesses. The study encompassed 5264 subjects over 15 years old, selected using random sampling techniques; 125 cases of cysticercosis were diagnosed (2.4% of sample population); 12 by anatomo-pathological examination of cysts 18 (14.4%) based on skull and muscle x-ray calcifications and 104 patients were identified using ELISA tests on 1527 serum samples (optical density greater than or equal to 0.4). Among 88 epileptic patients (prevalence = 16.7 per thousand), 27 also suffered from cysticercosis (38.7% of all epileptic patients, 21.6% of cysticercosis patients and 0.51% of the total population).

Adolescent↗

PubMed1985

Antibodies to spermatozoa and seminal plasma antigens detected by various enzyme-linked immunosorbent (ELISA) assays.

Various ELISA methods have been applied by different research centers to test the efficiency of this approach for the diagnosis of sperm-immune infertility cases. The antigens used were either whole spermatozoa or solubilized spermatozoal membrane preparations and were immobilized on microtiter plates, except in one case where plastic beads were employed. Polyvalent second antibodies or protein-A labelled with enzymes served as tracers. A high frequency of positive sera was found in all groups including fertile controls with tests using whole spermatozoa as antigen. The methods using solubilized antigen preparations showed fewer positives on the whole and correlated better with the various clinical categories of the WHO sera. Whilst there was some agreement in the results between the various laboratories on a few sera, most of the positive sera found by one laboratory were reported as negative by others. More investigative work is needed to improve reproducibility between different laboratories and to reduce non-specific reactions with normal controls. A more precise definition of the proper cut-off levels for positives and negatives is also needed. Despite these short-comings, the development of an ELISA for the diagnosis of sperm-immune infertility cases seems to be justified in the long term.

Antibodies↗

PubMed1979

Resistance of female guinea pig fertility to efficient iso-immunization with spermatozoa autoantigens.

Virgin female guinea pigs received two courses of immunization with S, P or T spermatozoa autoantigens and Freund's complete adjuvant and were mated from 1 up to 18 weeks after the end of each course. The immunizations were efficient as judged by the titers of circulating antibodies to S, P or T, the existence of antibodies to the corresponding immunizing antigen in cervico-vaginal secretions and by cutaneous reactions of delayed hypersensitivity. In spite of this successful immunization, the fertility rate was 100% after the first course and only slightly decreased after the second one. The only significant events were a delay in the time of fertilization and a high rate of intrauterine death (as already observed following anti-S immunization). The absence of fertility impairment was not due to a lack of a relevant antigen in the injected preparations since immunizing female guinea pigs with either epididymal spermatozoa or crude water-soluble extract also did not decrease the fertility. The mechanisms responsible for such a resistance remain to be elucidated; they may involve spermatozoa coating substances, enhancing antibodies or sperm immunosuppressive factors.

Animals↗

PubMed1975

Characterization of spermatozoal auto-, iso- and allo-antigens.

Three approaches are utilized to study and characterize spermatozoal antigens. An immunological approach has demonstrated the presence of spermatozoal auto-, iso- and allo-antigens. Spermatozoal auto-antigens studies by several authors are able to induce the whole spectrum of immune reactions (delayed hypersensitivity, complement-fixing antibodies and anaphylactic antibodies0 as well as of autoimmune aspermatogenic orchiepididymitis (AIAO). Different extraction procedures result in various preparations and even in different independent autoantigens (at least four), one protein, one membrane-linked antigen and at least two glyco-proteins. Spermatozoal iso-antigens stricto sensu are determined by the Y chromosome and present on at least 50% of the spermatozoa. Spermatozoal allo-antigens are also present at the surface of spermatozoa, especially blood group antigens (ABO and MNS systems), transplantation antigens (HL-A, H-2) and also some other unidentified ones. A biochemical approach has mainly been directed towards spermatozoal enzymes that have been directed towards spermatozoal enzymes that have been shown to be antigenic even in the species of origin. This is the case for lactic dehydrogenase LDH-X (a mid-piece enzyme) and for acrosomal enzymes, e.g., hyaluronidase, possibly sorbitol dehydrogenase and trypsin-like acrosomal proteinase (the auto- and allo-antigenicity of the latter having not been established). At least three of these enzymes are known or supposed to play a role in the process of fertilization. A clinical approach has described the presence of spermatozoal-coating antigen(s), such as transferrin or blood group substances from secretors obtained following the admixture of the secretions of the seminal vesicles. Indications were also obtained for the existence of antibodies directed against defined antigens. Several types of localization of antibodies on spermatozoa were described: acrosome (front part), equatorial segment, post-nuclear region, mid-piece and tail. Attempts at fractionation of human psermatozoal antigens are still at a preliminary stage. Whatever the approach, the main interest of these antigens is that they are able to induce, in the species of origin or in a related species antibodies capable of interfering with the normal process of reproduction, especially fertilization..

Alcohol Oxidoreductases↗