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A western and lectin blot analysis was performed of the major 'maturation-associated' antigen of rat spermatozoa, which is the rat counterpart of human CD52. In the absence of a suitable antibody, direct study of this approximately 26 kDa antigen, named previously SMemG, had been difficult. In the present study, these problems were overcome by raising a polyclonal antibody against a chemosynthetic peptide predicted from the cDNA sequence of the antigen. The antibody bound to a glycoprotein of rat cauda epididymidal tissue and spermatozoa, this glycoprotein was cleaved by phosphatidylinositol-specific phospholipase C and, after deglycosylation, was reduced to approximately 6 kDa. Northern blot analysis confirmed that the CD52 mRNA was transcribed only post-testicularly, and antibody binding to testicular and sperm proteins of different molecular masses was shown to be nonspecific. Flow cytometry also indicated that the antigen was inserted into the sperm membrane during epididymal transit. Moreover, despite the presence of CD52 mRNA in all parts of the rat epididymis, only the 'long' mRNA molecules of the cauda region were efficiently translated and the antigen glycosylated, indicating that expression of rat CD52 is regulated on a post-transcriptional level. Lectin binding and deglycosylation studies supported the contention that there is extensive mucin-type O-glycosylation of rat CD52. In rats, there was no indication of complex N-linked carbohydrates similar to those described for human CD52.

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Through five experiments, we demonstrate and characterize the basic functionality of imaging fiber bundles for optoelectronic chip-level interconnections. We demonstrate the transmission of spot arrays with spot sizes and a spot pitch roughly equal to 2 and 4 times the core pitch, respectively. We show that optoelectronic integrated circuits, including sources and detectors, can be butt coupled directly to fiber bundles without any additional optical elements. We demonstrate a 16-channel interconnect with -23 dB of cross talk, and we characterize the most significant optical loss mechanism. Finally, we show how imaging fiber bundles can be used to implement more complex interconnection structures by an example of a hybrid-bonded structure that implements a low-cost, high-connectivity solution for more advanced system architectures.

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CD52 is an unusually short, bipolar glycopeptide bearing a highly charged N-linked carbohydrate moiety and a glycosylphosphatidylinositol membrane anchor. It is exclusively expressed on lymphocytes and in the male genital tract where it is shed into the seminal plasma and inserts into the sperm membrane. The sperm surface molecule has potential significance as a target for antibodies that inhibit sperm function and gamete interaction. Western blot analyses suggested cell type-specific modifications of the antigen. It was purified from seminal plasma and a detailed structural analysis performed. The majority of anchor structures in male genital tract CD52 showed 2-inositol palmitoylation, rendering molecules insensitive toward phospholipase C, and a sn-1-alkyl-2-lyso-glycerol structure in place of the diacylated anchor described by Treumann et al. (Treumann, A., Lifely, M. R., Schneider, P., and Ferguson, M. A. (1995) J. Biol. Chem. 270, 6088-6099). N-Glycans of the male genital tract product were based on bi-, tri-, and tetraantennary structures of highly charged (up to -7), terminally sialylated complex-type sugars. A substantial proportion carried varying numbers of lactosamine repeats of which nearly 30% were branched. Different from lymphocytes, 10-15% of all N-glycans of the male genital tract antigen also contained peripheral fucose. These data confirm that male genital tract CD52 is distinct from the lymphocyte form by both N-linked glycans and COOH-terminal attached lipid anchor.

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The regional pattern of CD52 expression in the rat epididymis was followed by Northern analyses and carbohydrate-labelling of glycoconjugates on Western blots. CD52 mRNA showed a novel aspect of regionalization, namely region-dependent length differences in its poly(A) tail. 'Short' CD52 mRNA molecules were present in all parts of this organ and also in the seminal vesicles. Additionally, the cauda epididymidis contained mRNA molecules with an extended poly(A) tail. Their appearance coincided with the occurrence of the principal M(r) approximately 26 kDa glycopeptide in the cauda region, representing the CD52 product. CD52 expression seemed to be regulated or modulated synergistically by androgens, temperature, and (an) unknown testicular factor(s), depending on the poly(A) tail length of its mRNA. Androgens alone exerted an effect only on molecules with 'short' poly(A) tails. They were down-regulated in castrated animals, and restored to normal levels upon testosterone supplementation. However, 'long' CD52 mRNA molecules were not affected. Only if combined with the exposure of the epididymis to the elevated temperature of the abdomen, castration of animals resulted in a complete loss of the CD52 mRNA, including the 'long' cauda species. Loss of 'long' CD52 mRNA molecules was also observed when the abdominal location was combined with efferent duct ligation. This combination of treatments, however, did not affect 'short' CD52 mRNA levels. Loss of the 'long' CD52 mRNA molecules by any treatment coincided with a loss of the principal M(r) approximately 26 kDa glycopeptide from caudal protein extracts.

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The membrane of testicular spermatozoa undergoes extensive changes in the epididymis, including rearrangement, modification and loss of pre-existing components, addition of new glycoproteins from epididymal secretions, and exchange of lipid constituents. As a result, the membrane of cauda epididymidal spermatozoa has a different composition and different properties, which collectively contribute to male fertility. Special significance has been attributed to sperm surface structures that only appear post-testicularly in the epididymis, the so-called "maturation antigens". Therefore, human post-testicular proteins have been cloned by substractive screening of epididymal cDNA libraries, employing testis as the primary negative control. To date, there is scanty information on their function and mechanism of deposition on the sperm surface. However, the major maturation antigen CD52 seems to bind firmly to the sperm membrane via its GPI anchor. Its synthesis is carefully regulated by the cells of the epididymal epithelium, with temperature and androgens acting synergistically on CD52 mRNA levels.

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Physicians and other health care workers involved in the delivery of occupational health care can be confronted with difficult questions about fairness, justice and professional ethics. These issues and other ethical considerations are discussed.

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We developed an objective evaluation tool for grading students' performances in the advanced cardiac life support mega code. Specific functions for each student role are delineated. Each function is linked to a point system yielding an actual grade for each role, and pass/fail criteria are based on this grade. Use of the tool can eliminate instructor subjectivity and provide a permanent record of the student's performance.

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KIE: Derr, a philosopher, served as an expert witness in Brophy v. New England Sinai Hospital (decided 21 October 1985), in which a Massachusetts probate court ruled that a gastrostomy tube could not be removed from a patient who had been in a persistent vegetative state for more than two years. Printed here is an edited version of Derr's testimony, during the course of which he presents "six mutually reinforcing biological, social, historical, and ethical considerations" which he believes distinguish withholding or withdrawing food and fluids from withholding or withdrawing medical or surgical therapies. He warns that a social and legal decision to deny food and fluids to patients like Paul Brophy would attack the ethical foundations of law and medicine, and argues that the distinction between sustenance and therapy should be sustained.^ieng

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