Junji Sagawa

Tumor‐promoting Phorbol Ester Induces Alterations of Sialidase and Sialyltransferase Activities of JB6 Cells

Sialidase and sialyltransferase activities were studied in JB6 mouse epidermal cells before and after exposure to phorbol ester, 12‐O‐tetradecanoyl phorbol‐13‐acetate (TPA), which irreversibly induces anchorage‐independent growth and tumorigenicity. JB6 cells exhibited sialidase activities toward 4‐methylumbelliferyl‐α‐d‐N‐acetylneuraminic acid (4MU‐NeuAc) and gangliosides at pH 4.5 in the particulate fraction but apparently not in the cytosol at pH 4.5 or 6.0. In JB6 cells exposed to TPA and in the anchorage‐independent transformants, the sialidase activity toward 4MU‐NeuAc was decreased and the activity toward gangliosides was increased compared with those in untreated JB6 cells. Immunological analysis with antisera against membrane‐associated sialidases I and II revealed that plasma membrane‐associated sialidase I was increased and lysosomal membrane‐associated sialidase II was decreased under these conditions. TPA treatment also affected the sialyltransferase activities of JB6 cells: an elevation of the transfer activities toward asialo‐orosomucoid and asialo‐porcine submaxillary mucin but a reduction of GM3 and GD3 synthase activities were observed on exposure to TPA and in cells transformed by TPA to retain anchorage‐independency. These results suggest that an increase in sialic acid bound to glycoproteins and a decrease in that bound to glycolipids may occur in JB6 cells exposed to TPA and in the anchorage‐independent transformants.

Lymph Flow and Lymph Node Metastasis in Esophageal Cancer

This paper delineates which lymph nodes should be dissected due to the high frequency of metastasis associated with different types of primary lesions of the thoracic esophagus. In cancer involving the upper third of the esophagus (Iu), lymph flow was found to be primarily from the superior mediastinal area to the cervical area; in that involving the middle third (Im), it was broadly distributed from the superior, middle, and inferior mediastinal region to the cervical and abdominal regions; and in that involving the lower third (Ei), it tended to extend from the inferior mediastinal region to the abdominal region, with single primary metastatic nodes also being noted in this area. The significance of the “top” nodes, namely, the nodes located along the right recurrent laryngeal nerve in the upper portion of the thorax, was also investigated, and it was confirmed that the prognosis for patients with metastases to both the top nodes and other nodes was unfavorable. An immunohistochemical study on mediastinal lymph flow using the anti-Su-Ps antibody demonstrated interactions between top nodes and cervical and/or thoracic nodes.

Neoplastic Alteration of a Membrane‐associated Sialidase of Rat Liver

Rat liver participate fraction contains two types of membrane‐associated and gangliosides‐hydrolyzing sialidase, which have been shown to be identical to two membrane‐associated sialidases of rat brain (I and II) chromatographically, immunologically and in substrate specificity. Chromatography on AH‐Sepharose 4B of the membrane sialidases of rat primary hepatoma induced by 3′‐methyl‐4‐dimethylaminoazobenzene (MeDAB) further revealed that hepatocarcinogenesis induces a marked decrease in sialidase II but no decrease in sialidase I. Using antisera against sialidases I and II of rat brain, immunoprecipitation studies of the solubilized particulate fractions of rat liver and MeDAB‐hepatoma gave results similar to those obtained chromatographically. Using the same immunological technique, sialidase II but not sialidase I was found to be decreased in AH109 A hepatoma and in regenerating and fetal liver.

Prevention of fatty liver and maintenance of systemic valine depletion using a newly developed dual infusion system.

BACKGROUND Valine-depleted amino acid imbalance, while having a suppressive effect on tumor growth, may induce fatty liver. METHODS We administered a valine-depleted total parenteral nutrition (TPN) solution by the central venous route to non-tumor-bearing rats and examined the time course of the development of fatty liver. In an attempt to prevent this condition, we administered a continuous infusion of low concentrations of valine via the portal vein simultaneously with administration of central venous valine-depleted nutrition for 4 days. RESULTS A marked accumulation of triglyceride was observed in the liver on day 4 of the administration of valine-depleted nutrition. It is speculated that such accumulation is the cause of fatty liver. The level of valine in the peripheral blood began to decrease soon after administration was begun and resulted in a state of systemic valine deficiency. Rats given 25% or more of the valine concentration in the standard TPN solution via the portal vein simultaneously with the administration of central venous valine-depleted nutrition, had a triglyceride level similar to that of the control group. The group given 50% or less of the valine concentration had a level of valine in the peripheral blood as low as that of the valine-depleted group, indicating the maintenance of a valine-deficient state. CONCLUSION Administration of low concentrations of valine via the portal vein simultaneous with central venous administration of valine-depleted TPN solution may prevent fatty liver.

Membrane-associated Sialidase of Rat Liver and Its Decrease in Hepatomas

Using the participate fraction of tissue homogenate, plasma membrane‐associated sialidase was assayed at pH 4.5 with bovine brain mixed gangliosides as the substrate. The activity was lower in rat hepatoma induced by 3′‐methyl‐4‐dimethylaminoazobenzene (MeDAB) and transplantable AH‐109A rat hepatoma than in normal rat liver. The enzyme was almost quantitatively solubilized from liver particulate fraction by using 0.5% (w/v) sodium deoxycholate plus 0.2% (w/v) Triton X‐100, When chromatographed on DEAE‐cellulose, the solubilized activity emerged as a single peak. The enzyme thus obtained was maximally active at pH 4.5, and readily hydrolyzed mixed gangliosides but was less active toward 4‐methylumbelliferyl‐α‐N‐acetylneuraminic acid, 3′‐sialyllactose and fetuin. The corresponding enzyme from MeDAB‐induced hepatoma was indistinguishable from the liver enzyme in terms of ease of solubilization, pH‐activity relationship, chromatographic behavior and substrate preference. It therefore appears that the plasma membrane‐associated sialidase of hepatomas differs from that of liver only in the tissue level of activity.