An automatic liquid-nitrogen filling system for multiple Ge detectors.

In order to reduce the time and effort of the daily task of refilling Dewar vessels of Ge detectors with liquid nitrogen (LN(2)), we have developed an automatic LN(2) filling system equipped with a LN(2) plant. With this system, we were freed from the work of LN(2) filling. Such an LN(2) filling system is useful for moderate-scale Ge detector arrays consisting of fewer than 20 Ge detectors.

Clearance of bacterial lipopolysaccharides and lipid A by the liver and the role of argininosuccinate synthase.

The liver is thought to be involved in the systemic clearance and detoxification of lipopolysaccharide (LPS). Argininosuccinate synthase (AS), a liver cytosolic urea cycle enzyme, has been found to bind to and inactivate LPS and lipid A. To elucidate the participation of AS in the clearance of LPS by liver and hepatocytes, we investigated the correlation between AS content and the removal of lipid A and LPS in vivo and in vitro, tracing levels of biological activity. A hepatotoxic model in which mice were injected with CCl(4) revealed a significant reduction in lipid A clearance along with liver failure on day 1; total body clearance was changed to 0.534 ml/min from 1.42 ml/min. AS content in liver concomitantly decreased to about half and AS leaked to blood at about 6 microg/ml. Total body clearance of i.v. injected AS was estimated at 0.083 ml/min, which predicted about 24-h leakage of AS after CCl(4) injection. The treatment also reduced the clearance of R-type LPSs to a lesser degree the larger its polysaccharide portion. S-type LPS, which has a large O-antigen polysaccharide, exhibited enhancement of clearance on CCl(4) treatment. When pretreated in vitro with AS and injected into normal mice, lipid A and R-type LPS showed a similar pattern of clearance of residual activities to the untreated forms, but S-type LPS exhibited enhancement of clearance. Comparison between different strains of mice revealed a correlation of AS content in liver and lipid A clearance, where the higher AS strain C3H/He mice showed a more rapid clearance than the lower AS strains C57BL/6 and BALB/c. Primary spheroid cultures of hepatocytes treated with 0.1 microM dexamethasone and 1 microM glucagon showed about a 2-fold increase in AS amount and a more rapid clearance of LPS from culture medium than untreated cells. These results suggest that AS in hepatocytes may be involved in the process of lipid A and LPS clearance and the extracellular leakage of AS may also participate in the systemic detoxification.

Induction of multicellular 3-D spheroids of MCF-7 breast carcinoma cells by neutrophil-derived cathepsin G and elastase.

In tumor metastasis, multicellular aggregates of tumor cells form and disseminate into the blood or lymph vessels from the tumor mass, following the formation of tumor cell emboli in distant vessels. However, the mechanism by which aggregates form in the tumor mass is unknown. Neutrophils often exist in tumors and are considered to affect tumor development. We observed that neutrophils had the capacity to induce the aggregation of MCF-7 human breast carcinoma cells adhering to culture substrates. When MCF-7 cells were cultured with rat inflammatory neutrophils, the soluble fraction of their lysate, and the conditioned medium of neutrophils stimulated with N-formyl-Met-Leu-Phe plus cytochalasin B, multicellular aggregates formed within 16 h, and tightly aggregated 3-D spheroids formed when the cultures were prolonged. The spheroid-inducing reaction was reversible and energy-dependent. The MCF-7 cells induced to aggregate by the neutrophil extract showed growth potential, although the growth rate of the cells was slightly reduced. The aggregation was dependent on E-cadherin, because the spheroids dispersed into isolated cells on incubation with EGTA or anti-E-cadherin antibody following pipetting. The aggregation-inducing activity in neutrophils was completely inhibited by soybean trypsin-chymotrypsin inhibitor. Moreover, the commercially available human neutrophil elastase and cathepsin G induced the aggregation of MCF-7 cells and formation of spheroids. The proteases secreted by infiltrated neutrophils in tumors are implicated in the dissemination of tumor aggregates from primary tumor sites.

Characterization of synthetic adsorbents with fine particle sizes for preparative-scale chromatographic separation.

Synthetic adsorbents with fine particle sizes (15-30 microm) were manufactured. These adsorbents are made of poly(styrenedivinylbenzene) and polymethacrylate, and have the same chemical structure as analytical- (5-10 microm) or industrial- (200-600 microm) grade synthetic adsorbents. Both of them have very similar porous structure to those of analytical or industrial sizes, so that they can adsorb compounds of various molecular masses. Chromatographic separation characteristics of newly manufactured fine-particle grades of synthetic adsorbents were evaluated and compared to those of analytical or industrial adsorbents. Reasonable dependency of separation performance on particle size of synthetic adsorbents was obtained. Hydraulic properties of fine-grade adsorbents had also been measured in view of column operations. Furthermore, scalability and applicability of these adsorbents for preparative-scale chromatographic separation of bioactive compounds was evaluated. Separation of soybean isoflavones and tea catechin derivatives had revealed that fine-grade synthetic adsorbents could be well applied with scalability under the same elution conditions used for analytical use. Scalability up to a 22400-fold loading amount was achieved from a small column packed with analytical-grade adsorbent used for method development to a scale-up preparative column packed with fine-grade adsorbent used for preparative purification. These results showed the usefulness of the fine-grade synthetic adsorbents for more precise purification of bioactive compounds, including pharmaceuticals and functional food additives with higher recovery.