Learning with probabilistic labeling

A nonsupervised parametric learning model using a randomized labeling procedure is discussed. Our model is an extension of the Agrawala's model and is applicable even in the case where the probability of occurrence of each category is unknown. Furthermore, the method proposed here is computationally feasible to identify a finite mixture. The learning algorithm for multivariate normal distribution is presented in this paper.     

Development of a new estimation method of ingestion time to suspected food in food-poisoning outbreaks

In food-poisoning outbreaks, the ingestion time of suspect foods has been estimated using the Sartwell method (Hirayama method), the graphical method and maximum likelihood estimation. These methods are based upon the assumption that the incubation period is log-normally distributed. However, these methods may not always be valid because the bias and variability of the estimates are large. We constructed a database from 341 food-poisoning cases in the literature. Using this database, we developed a method to estimate the actual ingestion time based on the period from the ingestion time to the first outbreak, using a multiple linear regression equation. Since only 9.09% of cases showed log-normal distribution, the above three methods would not be valid in most cases. The new method was applicable in all cases. In addition, the values estimated by the new method showed higher correspondence and accuracy than the values estimated by the other methods. Therefore, we consider that the new method is superior to those methods.     

Magnetic force-based cell patterning using Arg-Gly-Asp (RGD) peptide-conjugated magnetite cationic liposomes

Micropatterning of target cells is highly desired for tissue engineering and cell biology. Although recent progress in surface chemistry has enabled the spatial control of cell adhesion onto substrates, conventional methods usually require specialized devices and time-consuming processes to fabricate the substrate. In this study, we demonstrate a simple and rapid cell-patterning procedure using magnetite nanoparticles and magnetic force. To label the target cells magnetically, magnetite nanoparticles were encapsulated in cationic liposomes (magnetite cationic liposomes; MCLs). To promote cell attachment, an Arg-Gly-Asp (RGD)-motif-containing peptide was coupled to the phospholipid of MCLs (RGD-MCLs). A human keratinocyte cell line, HaCaT, which has a high anchorage dependency, was used as a model. The RGD-MCLs were added to an ultralow-attachment plate, whose culture surface is modified with a covalently bound hydrogel layer that is hydrophilic and neutrally charged, and then HaCaT cells were seeded to the plates. The RGD-MCLs induced cell adhesion, spreading, cytoskeletal organization, and fibronectin expression. When steel plates with a 200 microm width placed on a magnet were set under a culture surface, magnetically labeled cells aligned on the surface where the steel plate was positioned, resulting in cell patterning. Furthermore, various cell patterns using a computer-aided design were successfully fabricated. These results suggest that cell patterning using RGD-MCLs is a promising approach to tissue engineering and studies in cell biology.     

Preparation of hydrophobic electrocatalyst layer and inorganic porous electrolyte layer for water absorbing porous electrolyte electrolysis cell

A water-absorbing porous electrolyte electrolysis cell is presented consisting of a hydrophobic gas diffusion layer (GDL), a controlled-hydrophobicity electrocatalyst layer, and a hydrophilic porous electrolyte layer. The specific character of this cell is that high-pressure water is injected directly into the porous electrolyte layer and is resisted by the electrocatalyst layer and GDL, which have strong water support force. In this study, the preparation method of the electrocatalyst layer and the porous inorganic electrolyte layer, and the evaluation of water electrolysis using the prepared layers were investigated. The optimized conditions and preparation methods of each layer of the MEA (i.e. the GDL, electrocatalyst layer, electrolyte layer) were determined. The assembly method and conditions of these three layers were also determined for fabricating MEAs for water electrolysis. The evaluation of water electrolysis tests using this MEA showed that the hydrogen evolution rate obeyed Faraday's Law in the low current density region (<10 mA cm^?2).     

Regulation of the biosynthesis of platelet-activating factor in alveolar macrophages

Activities of enzymes which metabolize lysoplatelet-activating factor (lysoPAF) and platelet-activating factor (PAF) were studied in rabbit alveolar macrophage lysates. Substantial acetyltransferase activity was noted in the presence of 100 μM acetyl-coenzyme A (CoA), and this activity was increased in A23187-stimulated cell lysate. On the other hand, in the absence of exogenous acetyl-CoA, lysoPAF was mainly acylated through a transacylation pathway rather than by acetyltransferase in both control and A23187-stimulated cell lysates. We confirmed that the intracellular concentration of acetyl-CoA is relatively low. The observations suggest that the transacylation system may play an equally important role in the regulation of the availability of lysoPAF in intact cells. Intracellular lysoPAF was also maintained at relatively low levels. Interestingly, large amounts of PAF were produced even in unstimulated cells upon addition of an excess of exogenous lysoPAF, suggesting that generation of an adequate amount of lysoPAF within cells may be sufficient to trigger PAF synthesis in this type of cells. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Lipid composition of 30 species of yeast

The detailed composition of cellular lipid of more than 23 species of yeast has been determined quantitatively by thinchrography on quartz rods, a method previously used for estimating cellular lipids of seven species of yeast. That data was fortified by neutral and phospholipid quantitations on 30 species of yeast cells. Most of the test organisms contained 7–15% total lipid and 3–6% total phospholipid per dry cell weight, except for the extremely high accumulation of triglycerides in two species ofLipomyces. Qualitatively, 30 species of yeast cells contained similar neutral lipid constituents (triglyceride, sterol ester, free fatty acid, and free sterol) and polar lipid components (phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl serine, phosphatidyl inositol, cardiolipin, and ceramide monohexoside) without minor constituents. Based on the quantitative composition of neutral lipids, the 30 species of yeast were divided into two groups, the triglyceride predominant group and the sterol derivative group. These groupings were fairly well overlapped from the standpoint of the distribution characteristics of fatty acid. The relative polar lipid compositions also grossly resembled each other. Only one exception of polar lipid composition in yeast cells was found inRhodotorula rubra species which contained phosphatidyl ethanolamine as the most abundant phospholipid. Fatty acid distribution patterns in yeast cells consistently coincided with other reports concerning fatty acid composition of yeast cells. Correlation of lipid composition and classification of yeasts are suggested and discussed. A part of this investigation has been reported at the 14th conference of the Japan Oil Chemists' Society, Nagoya, Japan, October 1975.     

The fungicidal activity of the unsaturated fatty acids and quaternary salts prepared from fish oils

Summary Saturated and unsaturated fatty acids and 10 unsaturated fatty acid fractions and ethyl esters of unsaturated fatty acid fractions prepared from fish oils were tested on their inhibitory activity againstCandida albicans. Oxidation of highly unsaturated fractions from fish oil and ethyl esters of unsaturated fatty acid fractions of menhaden, pilchard, and cod liver oils increases their antifungal activity. Saturated and unsaturated quaternaries were tested for their antifungal activity. Hexadecyltriethylammonium bromide and hexadecylpyridinium bromide showed the highest activity againstCandida albicans, Aspergillus niger, andRhyzopus nigricans. Any lengthening of the carbon chain more than C₁₆ weakened the activity of both saturated triethylammonium bromide and pyridinium bromide. An increase of unsaturation enhanced it. The antifungal activity of quaternaries prepared from fish oils was about 4,000 times stronger than that of oxidized highly unsaturated fatty acid fractions prepared from fish oils. The decisive factor in the highly inhibitory activity of quaternaries against fungi might depend on their positively charged portion since the surface of microorganisms is, as a rule, negatively charged. Aided by a grant from the Collett-Week Company, Ossining, N. Y.