Neuraminidase I and neuraminidase II from Arthrobacter ureafaciens were characterized. As determined by gel filtration on Ultrogel AcA 44, the molecular weights of neuraminidases I and II were 51,000 and 39,000, respectively. Neuraminidases I and II were similar to each other in their enzymatic properties except for the substrate specificities towards gangliosides and erythrocyte stroma. Their optimal pHs were between 5.0 and 5.5 with N-acetylneuraminosyl-lactose or bovine submaxillary mucin as substrates, but with colominic acid as a substrate, the pH optimum was between 4.3 and 4.5. They were most active around 53 degrees C, were stable between pH 6.0 and 9.0, and were thermostable up to 50 degrees C. They did not require Ca2+ for activity and were not inhibited by EDTA. They were inhibited only slightly or not at all by p-chloromercuribenzoic acid of Hg2+. Both neuraminidases I and II were able to hydrolyze the alpha-ketosidic linkage of N-glycolylneuraminic acid as well as that of N-acetylneuraminic acid, and were able to liberate substantially all of the sialic acid from various kinds of substrates. However, they cleaved only about 50% of the sialic acid from bovine submaxillary mucin. The saponification of bovine submaxillary mucin by mild alkali treatment, on the other hand, resulted in an increased susceptibility to the neuraminidases and brought about the complete liberation of sialic acid. Remarkable differences were observed between neuraminidases I and II as regards substrate specificities on gangliosides; the initial rate of hydrolysis by neuraminidase I was 74 times, and its maximum velocity constant was 91 times those of neuraminidase II. The addition of sodium cholate markedly stimulated the enzymatic hydrolysis of gangliosides, and increased the maximum velocity constant of neuraminidase I twofold and that of neuraminidase II 143-fold. Although neuraminidases I and II were able to hydrolyze (alpha,2-3), (alpha,2-6), and (alpha,2-8) linkages, the initial rate of hydrolysis of N-acetylneuraminosyl-alpha,2-6-lactose was greater than that of the alpha,2-3-isomer.

N-Acetylneuraminate lyase [N-acetylneuraminic acid aldolase EC 4.1.3.3] from Escherichia coli was purified by protamine sulfate treatment, fractionation with ammonium sulfate, column chromatography on DEAE-Sephacel, gel filtration on Ultrogel AcA 44, and preparative polyacrylamide gel electrophoresis. The purified enzyme preparation was homogeneous on analytical polyacrylamide gel electrophoresis, and was free from contaminating enzymes including NADH oxidase and NADH dehydrogenase. The enzyme catalyzed the cleavage of N-acetylneuraminic acid to N-acetylmannosamine and pyruvate in a reversible reaction. Both cleavage and synthesis of N-acetylneuraminic acid had the same pH optimum around 7.7. The enzyme was stable between pH 6.0 to 9.0, and was thermostable up to 60 degrees C. The thermal stability increased up to 75 degrees C in the presence of pyruvate. No metal ion was required for the enzyme activity, but heavy metal ions such as Ag+ and Hg2+ were potent inhibitors. Oxidizing agents such as N-bromosuccinimide, iodine, and hydrogen peroxide, and SH-inhibitors such as p-chloromercuribenzoic acid and mercuric chloride were also potent inhibitors. The Km values for N-acetylneuraminic acid and N-glycolylneuraminic acid were 3.6 mM and 4.3 mM, respectively. Pyruvate inhibited the cleavage reaction competitively; Ki was calculated to be 1.0 mM. In the condensation reaction, N-acetylglucosamine, N-acetylgalactosamine, glucosamine, and galactosamine could not replace N-acetylmannosamine as substrate, and phosphoenolpyruvate, lactate, beta-hydroxypyruvate, and other pyruvate derivatives could not replace pyruvate as substrate. The molecular weight of the native enzyme was estimated to be 98,000 by gel filtration methods. After denaturation in sodium dodecyl sulfate or in 6 M guanidine-HCl, the molecular weight was reduced to 33,000, indicating the existence of 3 identical subunits. The enzyme could be used for the enzymatic determination of sialic acid; reaction conditions were devised for determining the bound form of sialic acid by coupling neuraminidase from Arthrobacter ureafaciens, lactate dehydrogenase, and NADH.

MR imaging was the most accurate breast imaging modality for the tumor exten of breast cancer, although MR imaging had a substantial of risk of overestimation. MR imaging, MDCT and US can complement MMG for the preoperative evaluation of patients who are candidates for breast-conserving surgery.

In order to clarify genetic changes in flat adenomas, K‐ras codon 12 point mutations were examined in 56 flat adenomas, 81 polypoid adenomas and 42 cancers of colon and rectum. The mutation frequency in flat adenomas was 23% (13/56), significantly lower than that in polypoid adenomas (67%: 54/81) and cancers (76%: 32/42). Even mildly dysplastic adenomas or small (less than 5 mm) adenomas showed higher mutation incidence in polypoid type (62%, 57%) than in flat type (23%, 19%). Among flat adenomas, flat elevated lesions exhibited relatively higher mutation frequency than completely flat or depressed ones. As for cancers, 14 tumors (33%) contained mutations only in a minor tumor cell population, indicating that these mutations occur at a late stage of tumorigenesis. These results suggest that the adenoma‐carcinoma sequence through flat adenomas may he different from that through polypoid adenomas, and genetic changes may be heterogeneous in colorectal carcinogenesis.

We have performed a retrospective study to evaluate whether surgical treatment is beneficial in patients with hepatic metastases from breast cancer. Between September 1985 and September 1998, 25 patients with hepatic metastases (14 solitary and 11 multiple), eight of whom had extrahepatic metastases, underwent hepatectomy. All of the detectable liver metastasis were resected in all of the cases. There were no severe postoperative complications. All but one of the patients received adjunctive polychemotherapy after the hepatectomy. After the hepatectomy, recurrent tumors were detected in 18 of the patients, being located in the liver in 12 (67%) of them. Overall, however, hepatectomy ensured that the liver was clinically recurrence-free for a median of 24 months (range 2-132 months). Eleven patients died of recurrent tumors, two died of other causes and the remaining 12 are currently alive. The 2- and 5-year cumulative survival rates after hepatectomy were 71% and 27%, respectively, and the median survival duration was 34.3 +/- 3.2 months, much better than the period of 8.5 months for another series of patients treated with standard or non-surgical therapies at our institution. The number and the size of hepatic metastases, the interval between treatment of the primary lesion and hepatectomy, and the existence of extrahepatic metastasis were not adverse prognostic factors. In conclusion, our data, although limited and highly selective, suggest that surgical treatment of hepatic metastases from breast cancer may prolong survival in certain subgroups of patients to a greater extent than standard or non-surgical therapies.