No abstract

Serum total sialic acid (TSA) and lipid-associated sialic acid (LASA) levels have drawn considerable interest because of carbohydrate aberrations in malignant cells. The current investigation determined the TSA, LASA, total protein (TP), and TSA/TP values for 171 cancer patients with various primary sites and differing degrees of metastatic disease, 102 patients with nonmalignant diseases (pathologic controls), and 42 normal individuals. Data analysis indicated significant (p less than 0.01) increases in the mean (+/- SD) TSA and TSA/TP values in the cancer patients (78.1 +/- 19.2 mg/dl and 12.4 +/- 3.8 mg/g, respectively) and in the pathologic controls (76.0 +/- 7.5 mg/dl and 11.6 +/- 2.5 mg/g) when compared to the normal controls (67.3 +/- 7.1 mg/dl and 9.0 +/- 1.1 mg/g), and a significant decrease in the mean TP values in the cancer patients (6.4 +/- 1.1 g/dl) and pathologic controls (6.6 +/- 1.1 g/dl) when compared to normal controls (7.5 +/- 0.5 g/dl). No significant difference was observed between groups in LASA values. Further analysis of the data in patient subgroups based on the tissue involved, specific disease, or severity of the malignancy indicated that the lack of specificity of the markers was due primarily to restricted subgroups and that the sensitivity of TSA and TSA/TP increased as the malignancy became more severe. The results show that TSA/TP was the most useful of the markers tested for detecting malignancies. This marker should prove useful for monitoring malignant disease recurrence and/or progression and for evaluating the effectiveness of various therapeutic approaches.

Human semen contains a large amount of alpha-L-fucosidase activity, the great majority of which is found in the seminal fluid. Immunocytochemical studies indicate that a small amount of semen fucosidase activity is present on the sperm plasma membrane, primarily in the posterior head region. Subcellular fractionation studies also indicate that sperm alpha-L-fucosidase is present in the plasma membrane-enriched fraction. Comparative characterization of human seminal fluid and sperm alpha-L-fucosidases indicates that seminal fluid alpha-L-fucosidase has a broad pH optimum curve with a number of near-equal maxima between pH 4.8 and 7.0 while sperm fucosidase has a major optimum between pH 3.4 and 4.0. Isoelectric focusing indicates that seminal fluid alpha-L-fucosidase contains three to six isoforms with isoelectric points (pI) of 5-7 while sperm fucosidase contains two distinct isoforms with pI values of 5. 2 +/- 0.2 and 7.0 +/- 0.2. Western blotting indicates that seminal fluid fucosidase contains a major protein band with a molecular mass ratio (M(r)) of approximately 56 kDa while sperm fucosidase contains a major protein band of approximately 51 kDa. The overall results indicate the presence of a low-abundance, plasma membrane-associated human sperm alpha-L-fucosidase, which is different in its properties from human seminal fluid alpha-L-fucosidase(s), and whose function is not yet known.

1. Immunocytochemical and biochemical techniques have been used to localize and characterize a novel plasma membrane-associated, neutral-pH-optimum alpha-L-fucosidase from rat spermatozoa. Light and electron microscopy specifically localized the fucosidase on the plasma membrane of the convex region of the principal segment of testicular and cauda epididymal sperm heads. Immunoreactivity for alpha-L-fucosidase was also detected in the Golgi apparatus of spermatocytes and spermatids but no immunoreactivity was observed in the acrosome. 2. Fractionation of epididymal sperm homogenates indicated that over 90% of the alpha-L-fucosidase activity was associated with the 48,000 g pellet. This pellet-associated activity could be solubilized with 0.5 M NaCl but not with 0.5% Triton X-100, suggesting that fucosidase is peripherally associated with membranes. Sucrose-density-gradient centrifugation of sperm homogenates indicated that fucosidase was enriched in the plasma membrane-enriched fraction. Analysis of alpha-L-fucosidase on intact epididymal sperm indicated that the enzyme was active, displayed linear kinetics and had a pH-activity curve (with an optimum near 7) which was comparable to that of fucosidase from epididymal sperm extracts. These results further suggest that fucosidase is associated with plasma membranes, and that its active site is accessible to fucoconjugates. Evidence that most of the fucosidase is associated with the exterior of the plasma membrane came from studies in which intact sperm had fucosidase activity comparable to that of sperm sonicates, and from studies in which approx. 90% of the fucosidase activity on intact sperm could be released from the sperm by gentle shaking with 0.5 M NaCl. Isoelectric focusing indicated that the NaCl-solubilized epididymal sperm fucosidase appears to have one major and one minor isoform with pIs near 7.2 and 5.2, respectively. SDS/PAGE and Western blotting indicated that the NaCl-solubilized extract of epididymal sperm contains two protein bands of 54 and 50 kDa which were highly immunoreactive with the IgG fraction of anti-fucosidase antibodies. Although the function of the novel sperm fucosidase is not known, its specific localization to the plasma membrane of the region of the rat sperm head involved in sperm-egg binding and its high enzymic activity at neutral pH on intact sperm suggest that this enzyme may have a role in sperm-egg interactions.