Direct impact analysis of multi-leaf collimator leaf position errors on dose distributions in volumetric modulated arc therapy: a pass rate calculation between measured planar doses with and without the position errors.

We propose a new method for analyzing the direct impact of multi-leaf collimator (MLC) leaf position errors on dose distributions in volumetric modulated arc therapy (VMAT). The technique makes use of the following processes. Systematic leaf position errors are generated by directly changing a leaf offset in a linac controller; dose distributions are measured by a two-dimensional diode array; pass rates of the dose difference between measured planar doses with and without the position errors are calculated as a function of the leaf position error. Three different treatment planning systems (TPSs) were employed to create VMAT plans for five prostate cancer cases and the pass rates were compared between the TPSs under various leaf position errors. The impact of the leaf position errors on dose distributions depended upon the final optimization result from each TPS, which was explained by the correlation between the dose error and the average leaf gap width. The presented method determines leaf position tolerances for VMAT delivery for each TPS, which may facilitate establishing a VMAT quality assurance program in a radiotherapy facility.

Release of spirosin associated with potassium phosphate-induced autolysis in Lactobacillus reuteri DSM 20016.

We have studied the effect of medium components on spirosin production in Lactobacillus reuteri DSM 20016 to get some insight into the function of spirosome in Lactobacillus. Among those investigated, only potassium phosphate was found to influence the production of spirosin. Though it was not effective at concentrations lower than 0.6%, it promoted the spirosin production and its accumulation into culture medium in particular, at higher concentrations. The accumulation has been demonstrated to originate inthe release of spirosin due to the bacterial autolysis induced by the higher concentrations of potassium phosphate, The autolytic effect of potassium phosphate was assumed to be a concerted action by phosphate and potassium ions at the concentrations higher than 0.1 and 0.4 M, respectively. A possible role of spirosin as a sensor protein of bacterial two-component regulatory system was discussed.

Characterization of a newly established cell line (JR-St) derived from human gastric signet ring cell cancer, producing tumor markers.

Despite the importance of in vitro study of gastric cancer, there are very few established cell lines derived from human gastric carcinoma. We have recently established a new cell line derived from human gastric cancer which has the ability to produce tumor markers. This cell line has been designated JR-St. This cell line was derived from the cerebrospinal fluid of a 37-yr-old female patient who had metastatic brain tumor of signet ring cell gastric adenocarcinoma. This cell line has been maintained for more than 24 months through 80 passages with stable growth. PAS staining showed intracellular mucin granules. Transmission and scanning electron microscopy revealed cells with numerous microvilli and fine projections as well as intracellular granules, indicating mucin. This cell line had the ability to produce high concentrations of tumor markers such as carcinoembryonic antigen (CEA) and carbohydrate antigen (CA) 19-9. Thus Thus this cell line should provide a very useful tool for the investigation of gastric cancer such as analysis of tumor markers as well as effects of anti-cancer drugs or growth factors.

Endothelin-1 secretion from cultured rabbit gastric epithelial cells.

It has been shown that endothelin-1 (ET-1) is synthesized in various extraendothelial tissues. Although ET-1 has been reported to have potent ulcerogenic action in the stomach, the synthesis and physiological roles of ET-1 in the gastric mucosa are poorly understood. The aim of the present study was to investigate whether or not cultured gastric epithelial cells secrete ET-1 and possess autocrine functions. Gastric epithelial cells from rabbits were cultured in medium supplemented with 10% FBS after isolation. ET-1 was extracted by C18 columns from serum-free culture media and measured by radioimmunoassay (RIA). Effects of ET-1 on the intracellular concentration of calcium of the cultured cells were examined with Indo-1. Prostaglandin E2 (PGE2) was measured by RIA. Primary cultures of gastric epithelial cells were mainly composed of mucous cells. ET-1 was detected in the culture medium by RIA, and 70 pg/10(6) cells/24 h of ET-1 was secreted by cultured cells. Tumor growth factor-beta (4 ng/ml) and thrombin (8 U/ml) significantly increased ET-1 secretion. Exogenously administered ET-1 up to 10(-6) M neither modulated the intracellular calcium concentration nor affected PGE2 release by these cells. These results suggest that gastric mucous cells in culture secrete ET-1. Further studies are needed to explore the possible involvement of such paracrine function in the reported ulcerogenic action of ET-1.

A monolayer culture of gastric mucous cells from adult rabbits.

A new method for the primary monolayer cultures of adult rabbit gastric mucous cells has been developed. Rabbit gastric mucosal cells were isolated with etylenediaminetetraacetic acid and collagenase. Cells were cultured in Coon's modified Ham's F-12 medium supplemented with 10% fetal bovine serum, 15mM HEPES buffer, antibiotics, and antimycotic. The cells reached confluency on days 3-4. Histochemically 92% of the cells contained PAS positive gramules (mucous cells), 3% of cells showed a strong reaction for succinic dehydrogenase activity (parietal cells), 2% of the cells showed positive granules by Bowie staining (chief cells), and G6PDH staining was positive in 5% of the cells (surface mucous cells). Fibroblasts were rarely seen until day 7 (less than 1%). Thus rabbit cultured gastric cells were considered to be mainly comosed of mucous neck cells. These cells produced prostaglandin (PG) E2 and PGI2. Quantitatively cultured cells synthesized 1.475 +/- 0.039 ng/mg protein/hour of PGE2 and 0.244 +/- 0.042 pg/mg protein/hour of PGI2. This relatively simple and convenient technique provides a useful model for the study of cellular functions of gastric mucosa.

[Establishment and characterization of a tumor marker producing cell line (JR-1) derived from a gastric scirrhous cancer].

Despite the importance of in vitro study of gastric cancer, the established cell lines derived from human gastric carcinoma are very few. We have recently established a new cell line derived from human gastric cancer which has the ability to produce several tumor markers. This cell line has been designated JR-1. The cancer cells were obtained from the cerebrospinal fluid of a 37 year-old female patient who had metastatic brain tumor of the poorly differentiated gastric adenocarcinoma. The cells were inoculated into the tissue culture flask containing Ham's F-12 medium supplemented with 10% fetal bovine serum, antibiotics. Within 24 hours, the cells attached to the surface of the flask and started to grow. The first subcultures were performed at 1 week, and subsequent subcultures have been done once a week. This cell line has been maintained for more than 15 months through 60 passages with a stable growth. Chromosome analysis of the cells was performed. The doubling time of the 20th passage was 72 hours. Under phase contrast microscopy, monolayered pavement-like cell arrangement was observed. PAS staining showed intracellular mucin granules. Transmission and scanning electron microscopy revealed spindle-shaped cells with numerous microvilli and fine projections as well as intracellular granules, indicating mucin. Tumor markers produced by this cell line were CEA, CA19-9, TPA and Procollagen III.

An evaluation of broad-spectrum sunscreens against topical PUVA-induced erythema.

Protection against topical PUVA with broad-spectrum sunscreens was investigated. A protection factor against topical PUVA was established for broad-spectrum sunscreens against topical PUVA-induced erythema.