Formation of spray-dried powder of S-adenosyl-L-methionine

S-Adenosyl-L -methionine (SAM) is an essential metabolite in all living organisms. In clinical research, SAM has also been suggested as a chemotherapeutic agent in various diseases. The main problem of SAM is its instability at high temperatures, at neutral and alkaline pH, and in the presence of humidity. SAM retention in spray-dried powder was determined under various conditions of spray-drying. The highest SAM retention was obtained when maltodextrin (dextrose equivalent, DE, of 25) was used as the carrier solid with the SAM feed liquid at pH 4.0. The water content in the powder had a significant effect on the stability of SAM. SAM powder with lower water content exhibited higher stability.     

A 5-bp Insertion in Mip Causes Recessive Congenital Cataract in KFRS4/Kyo Rats

We discovered a new cataract mutation, kfrs4, in the Kyoto Fancy Rat Stock (KFRS) background. Within 1 month of birth, all kfrs4/kfrs4 homozygotes developed cataracts, with severe opacity in the nuclei of the lens. In contrast, no opacity was observed in the kfrs4/+ heterozygotes. We continued to observe these rats until they reached 1 year of age and found that cataractogenesis did not occur in kfrs4/+ rats. To define the histological defects in the lenses of kfrs4 rats, sections of the eyes of these rats were prepared. Although the lenses of kfrs4/kfrs4 homozygotes showed severely disorganised fibres and vacuolation, the lenses of kfrs4/+ heterozygotes appeared normal and similar to those of wild-type rats. We used positional cloning to identify the kfrs4 mutation. The mutation was mapped to an approximately 9.7-Mb region on chromosome 7, which contains the Mip gene. This gene is responsible for a dominant form of cataract in humans and mice. Sequence analysis of the mutant-derived Mip gene identified a 5-bp insertion. This insertion is predicted to inactivate the MIP protein, as it produces a frameshift that results in the synthesis of 6 novel amino acid residues and a truncated protein that lacks 136 amino acids in the C-terminal region, and no MIP immunoreactivity was observed in the lens fibre cells of kfrs4/kfrs4 homozygous rats using an antibody that recognises the C- and N-terminus of MIP. In addition, the kfrs4/+ heterozygotes showed reduced expression of Mip mRNA and MIP protein and the kfrs4/kfrs4 homozygotes showed no expression in the lens. These results indicate that the kfrs4 mutation conveys a loss-of-function, which leads to functional inactivation though the degradation of Mip mRNA by an mRNA decay mechanism. Therefore, the kfrs4 rat represents the first characterised rat model with a recessive mutation in the Mip gene.     

Radial dose distribution for 18.3 MeV/n alpha beams in tissue-equivalent gas

Experimental measurements of the radial restricted linear energy transfer (LETr) for alpha beams of 18.3 MeV/n in tissue-equivalent gas were presented. The radial dose distribution for the alpha beam was deduced from the restricted LET measurements. A differential W value for the alpha particle in the tissue-equivalent gas was also deduced. The result for the differential W value was 29.0 +/- 0.9 eV/ion pair. The radial dose varied according to an inverse-square function with distance from the track center for radii larger than 0.026 micron. The maximum extension of the track, the penumbra radius, as 2.73 +/- 1.67 microns, which was less than predicted by calculations (7-9 microns).     

Quantitative analysis of development of mitochondrial ultrastructure in differentiating mouse hepatocytes during postnatal period

Between birth and 10 days of age, the volume density (volume/unit cytoplasmic volume) of the matrix, and the surface density (area/unit cytoplasmic volume) of the inner membrane and cristae increased in both periportal and perihepatic hepatocytes, and did not differ significantly between the cells of the two zones. After 10 days of age, however, the volume density of the matrix decreased in perihepatic cells and remained unchanged in periportal cells, and, therefore, it became greater in periportal cells than in perihepatic cells in 20-day-old and adult animals. The surface density of the inner membrane and cristae decreased in the cells of both zones. Further, the hepatocyte volume increased markedly, especially in perihepatic zones between 20 days of age and the adult. The results show that, in postnatally differentiating hepatocytes, mitochondria are likely to develop during early postnatal period, then the structural heterogeneity of mitochondria arises, and hepatocyte volume increases markedly during late postnatal period after weaning. Thus, the process of postnatal hepatocyte differentiation includes such several phases of development.     

Heterogeneity and tissue-specific expression of eukaryotic transcription factor S-II-related protein mRNA

Two new cDNA clones for S-II-related proteins were isolated from a mouse liver cDNA library. Analyses of these clones suggested that S-II proteins are a family of proteins with relatively conserved C-terminal regions but variable N-terminal regions, and that some members of this family are expressed in a tissue-specific manner.     

Mechanisms of modulation of neuronal nicotinic receptors by substance P and OAG

Substance P is known to modulate neuronal nicotinicacetylcholine receptors (nAChRs) in the sympathetic nervous system.There are two conflicting proposals for the mechanism of this effect, an indirect action mediated by protein kinase C (PKC) and a direct interaction with receptor subunits. We studied the mechanisms of thiseffect in PC-12 cells. Substance P enhanced the decay of thenicotine-induced whole cell current. This effect was fast in its onsetand was not antagonized by guanosine5'-O-(2-thiodiphosphate), a G protein blocker, orstaurosporine, a nonselective PKC blocker. Staurosporine failed toreverse the inhibition by 1-oleoyl-2-acetyl-sn-glycerol (OAG), a synthetic diacylglycerol analog known to activate PKC. Theinhibitory effects of the peptide and OAG were preserved in excisedpatches, but substance P applied to the extra patch membrane wasineffective in the cell-attached patch configuration. We conclude thatsubstance P modulates neuronal nAChRs most likely by direct interactions with the receptors but independently from activation ofPKC or G proteins and that PKC does not participate in modulation by OAG.

     

Estimation of interaction function gamma(x) with sparsely ionizing radiation

The interaction function gamma(chi), which was introduced in the theory of dual radiation action as the probability that two energy transfers separated by distance chi combine with each other to produce a lesion, was estimated with sparsely ionizing radiation (60Co gamma rays and 40 kV X rays). Gamma(chi) was deduced on the assumption that the sensitive matrix is made up of small spherical flocculi distributed over the cell nucleus. The diameter of a flocculus was estimated at (4.0-11.2) X 10(-8) m when the diameter of the cell nucleus d was assumed to be 5 microns, and (4.0-11.4) X 10(-8) m when d was assumed to be 10 microns. It seems reasonable to hypothesize that the flocculus corresponds to the linker DNA in the chromatin structure of DNA, because the size of the linker DNA as a target (about 40 nm) is consistent with the diameter of flocculi obtained in this study.