Molecular mechanisms involved in mammalian gamete fusion.

Fusion between gametes is a key event in the fertilization process involving the interaction of specific domains of the sperm and egg plasma membranes. During recent years, efforts have been made toward the identification of the specific molecular components involved in this event. The present work will focus on the best characterized candidates for mediating gamete membrane fusion in mammals. These molecules include members of the ADAM (a disintegrin and a metalloprotease domain) family, i.e., testicular proteins fertilin alpha, fertilin beta, and cyritestin, which are thought to interact with integrins in the egg plasma membrane through their disintegrin domains, and a member of the cysteine-rich secretory proteins (CRISP) family, i.e., epididymal protein DE, which participates in an event subsequent to sperm-egg binding and leading to fusion through specific complementary sites localized on the fusogenic area of the egg surface. The identification and characterization of these molecules will contribute not only to a better understanding of the molecular mechanisms underlying mammalian sperm-egg fusion but also to the development of new methods for both fertility regulation and diagnosis and treatment of human infertility.

Evidence that human epididymal protein ARP plays a role in gamete fusion through complementary sites on the surface of the human egg.

Human epididymal sperm protein ARP, a member of the cysteine-rich secretory proteins (CRISP) family, exhibits significant homology with rat epididymal protein DE, a candidate molecule for mediating sperm-egg fusion in rodents. The aim of this study was to investigate the involvement of ARP in human gamete fusion. Sequential extraction of proteins from ejaculated human sperm revealed the existence of a population of ARP that is tightly associated with the sperm surface and thus, potentially capable of participating in gamete interaction. Exposure of capacitated human sperm to a polyclonal antibody against recombinant ARP (anti-ARP) produced a significant and concentration-dependent inhibition in the ability of human sperm to penetrate zona-free hamster eggs. This inhibition was not due to a deleterious effect on the gametes because anti-ARP affected neither sperm viability or motility, nor egg penetrability. The antibody did not inhibit the occurrence of spontaneous or Ca(2+) ionophore-induced acrosome reaction, nor did it inhibit the ability of sperm to bind to the oolema, supporting a specific inhibition of the antibody at the sperm-egg fusion level. As a relevant evidence for a role of ARP in gamete fusion, the existence of complementary sites for this protein on the surface of human eggs was investigated. Experiments in which zona-free human oocytes discarded from in vitro fertilization programs were exposed to ARP, fixed, and subjected to indirect immunofluorescence revealed the presence of specific ARP-binding sites on the entire surface of the human egg, in agreement with the fusogenic properties of the human oolema. Together, these results strongly support the participation of ARP in the sperm-egg fusion process, suggesting that this protein would be the functional homologue of DE in humans.

Relationship between the association of rat epididymal protein "DE" with spermatozoa and the behavior and function of the protein.

Rat epididymal glycoprotein DE associates with the dorsal region of the sperm head during sperm maturation, migrates to the equatorial segment (ES) with the acrosome reaction (AR), and is involved in gamete membrane fusion. In the present study we examined the association of DE with the sperm surface and the relationship of this interaction with the behavior and function of the protein. Cloning and sequencing of DE revealed a lack of hydrophobic domains and the presence of 16 cysteine residues in the molecule. Experiments in which cauda epididymal sperm were subjected to different extraction procedures indicated that while most of the protein is removable from sperm by mild ionic strength, a low amount of DE, resistant to even 2 M NaCl, can be completely extracted by agents that remove integral proteins. However, the lack of hydrophobic domains in the molecule and the failure of DE to interact with liposomes, does not support a direct insertion of the protein into the lipid bilayer. These results, and the complete extraction of the tightly bound protein by dithiothreitol, suggest that this population would correspond to a peripheral protein bound to a membrane component by strong noncovalent interactions that involve disulfide bonds. While ELISA experiments showed that no protein could be extracted by NaCl from capacitated sperm, indirect immunofluorescence studies revealed the ability of the NaCl-resistant protein to migrate to the ES. Together, these results support the existence of two populations of DE: a major, loosely bound population that is released during capacitation, and a minor strongly bound population that remains after capacitation, migrates to the ES with the AR, and thus would correspond to the one with a role in gamete fusion.

La reticulohistiocitosis multicentrica y el cancer interno / Multicenter reticulohistiocytosis and internal cancer

Se comunica un caso de reticulohistiocitosis multicéntrica asociado a un linfoma nodular. Se revisan las observaciones de reticulohistiocitosis multicéntrica asociadas a malignidades internas: carcinoma de estómago, colon, árbol bronquial, cuello del útero, ovario, mama, sarcoma axiliar, carcinomatosis sin individualización del primitivo, leucosis y linfoma. La reticulohistiocitosis multicéntrica puede integrarse a las paraneoplasias dermatológicas

La reticulohistiocitosis multicentrica y el cancer interno / Multicenter reticulohistiocytosis and internal cancer

Se comunica un caso de reticulohistiocitosis multicéntrica asociado a un linfoma nodular. Se revisan las observaciones de reticulohistiocitosis multicéntrica asociadas a malignidades internas: carcinoma de estómago, colon, árbol bronquial, cuello del útero, ovario, mama, sarcoma axiliar, carcinomatosis sin individualización del primitivo, leucosis y linfoma. La reticulohistiocitosis multicéntrica puede integrarse a las paraneoplasias dermatológicas (AU)

Hodgkin's disease in childhood: therapy results in Argentina.

From 1940 to 1977, a total of 152 children aged 15 years or less with the histologic diagnosis of Hodgkin's disease were treated in Argentina. For analysis, these patients were placed into three periods which displayed the most outstanding changes in diagnostic workup and therapy. The periods are as follows: (1) 1940 to 1966 (43 children), (2) 1967 to 1972 (35 children), and (3) 1973 to 1977 (74 children). The patients were treated with extended field radiation therapy and followed by courses of cyclophosphamide-vinblastine-procarbazine-prednisone, with CCNU added (CCVPP) or not added (CVPP) in a randomized trial. The mean age of the whole group was 7.5 years (range 2 to 15 years) and there was a predominance of males (79%). Crude 6-year survival for the three periods were as follows: 1940 to 1966, 34%; 1967 to 1972, 50%; and 1973 to 1977, 79%. We conclude that (1) survival of Hodgkin's disease of childhood has shown a rather marked improvement during the last decade and this progress is probably due to the use of combined multidrug chemotherapy administered under collaborative controlled clinical trials; (2) preliminary evaluation of the results of CVPP and CCVPP therapy shows that the latter combination (CCVPP) neither increases the percent of patients achieving complete remission nor prolongs relapse-survival in Hodgkin's disease of childhood: and (3) all stages of childhood Hodgkin's disease can be successfully managed with multidrug chemotherapy alone.