Elevated thymic and serum galactosyltransferase with low-molecular-weight acceptor activity in murine leukemia

Galactosyltransferase activity (UDP-galactose:N-acetyl-D-glucosamine-D-galactosyltransferase) could be measured in thymus and sera from different strains of mice. Total thymic homogenates or thymocyte preparations obtained from thymoma carrying AKR/J mice exhibited higher enzyme activity compared to nonleukemic control mice. A similar difference was also noted in Swiss mouse thymus which develop thymic leukemia upon a single injection of 5-(3,3-dimethyl-1-triazeno)-imidazole-4-carboximide. Galactosidase, which was 25 times less active than galactosyltransferase, was not responsible for this difference. These observations were extended to an evaluation of the serum level of the enzyme as a potential tumor biomarker. A 3- to 4-fold increase in the activity of galactosyltransferase was detected in serum samples obtained from both leukemic mice models (AKR/J and Swiss) compared to the controls, whereas the sera from P388 tumor-bearing DBA/2 mice showed a statistically nonsignificant increase of only 20%. The data indicate that serum galactosyltransferase (that accepts the low-molecular-weight acceptor, N-acetyl-D-glucosamine) levels are elevated in the presence of thymic leukemia, and suggest the possibility of shedding of this enzyme from the tumor cells to the systemic circulation of the host. The implications, including the potential diagnostic significance of the results, are discussed.     

Sonographic features of mesenteric gas.

OBJECTIVE: To describe the sonographic appearance of air in the mesentery of the small bowel. METHODS: Sonography was performed with convex and linear array transducers in 2 patients with acute abdomen. RESULTS: In 1 patient, sonography revealed fluid and air in the peritoneal cavity. A thick-walled small-bowel loop with a thick echogenic mesentery was seen. Air was seen in the mesentery as linear bright echoes with acoustic shadowing. An uncomplicated diverticulum was seen. In the second patient, air was seen in the thick and echogenic mesentery of a thick-walled small bowel. An inflamed diverticulum was also seen. CONCLUSIONS: Sonographic features of mesenteric air due to perforated diverticulitis of the jejunum are described.     

Mechanisms underlying erythrocyte and endothelial nitrite reduction to nitric oxide in hypoxia: role for xanthine oxidoreductase and endothelial nitric oxide synthase

Reduction of nitrite (NO(2)(-)) provides a major source of nitric oxide (NO) in the circulation, especially in hypoxemic conditions. Our previous studies suggest that xanthine oxidoreductase (XOR) is an important nitrite reductase in the heart and kidney. Herein, we have demonstrated that conversion of nitrite to NO by blood vessels and RBCs was enhanced in the presence of the XOR substrate xanthine (10 micromol/L) and attenuated by the XOR inhibitor allopurinol (100 micromol/L) in acidic and hypoxic conditions only. Whereas endothelial nitric oxide synthase (eNOS) inhibition had no effect on vascular nitrite reductase activity, in RBCs L-NAME, L-NMMA, and L-arginine inhibited nitrite-derived NO production by >50% (P<0.01) at pH 7.4 and 6.8 under hypoxic conditions. Western blot and immunohistochemical analysis of RBC membranes confirmed the presence of eNOS and abundant XOR on whole RBCs. Thus, XOR and eNOS are ideally situated on the membranes of RBCs and blood vessels to generate intravascular vasodilator NO from nitrite during ischemic episodes. In addition to the proposed role of deoxyhemoglobin, our findings suggest that the nitrite reductase activity within the circulation, under hypoxic conditions (at physiological pH), is mediated by eNOS; however, as acidosis develops, a substantial role for XOR becomes evident.     

Evaluation of nanostructured composite collagen--chitosan matrices for tissue engineering

The development of suitable three-dimensional matrices for the maintenance of cellular viability and differentiation is critical for applications in tissue engineering and cell biology. The structure and composition of the extracellular matrix (ECM) has been shown to modulate cell behavior with respect to shape, movement, proliferation, and differentiation. Although collagen and chitosan have separately been proposed as in vitro ECM materials, the influence of chitosan--collagen composite matrices on cell morphology, differentiation, and function is not well studied. To this end, gel matrices of different proportions of collagen and chitosan were examined ultrastructurally and characterized for their ability to regulate cellular activity. A three-chamber system with circulating hydraulic fluids was used to evaluate the gel stability under fluid force. Results indicated that overall matrix integrity increased with the proportion of chitosan. Scanning electron microscopy indicated that the addition of chitosan greatly influences ultrastructure and changes collagen fiber cross-linking, reinforcing the structure and increasing pore size. K562 cells cultured in three-dimensional gels were examined for cell proliferation and differentiation. Although cell proliferation was inhibited with an increasing proportion of chitosan, cell function based on cytokine-release was greatly augmented. Results suggest that a hybrid chitosan--collagen matrix may have potential biological and mechanical benefits for use as a cellular scaffold.