Biomedical subjects
Publications and source records attributed to T Nishida.
Three of 21 newborn baboons injected intraocularly with human adenovirus type 12 developed an intravitreal mass 12 to 36 months later. Two of the masses were indistinguishable from human retinoblastoma, a retinal tumor that afflicts children. To our knowledge this is the first time a retinoblastoma-like tumor has been induced experimentally by adenovirus type 12 in a nonhuman primate.
Comparison of about 50 pairs of homologous nucleotide sequences for different genes revealed that the substitutions between synonymous codons occurred at much higher rates than did amino acid substitutions. Furthermore, five pairs of mRNA sequences for different genes were compared in species that had diverged at the same time. The evolutionary rate of synonymous substitution was estimated to be 5.1 X 10(-9) per site per year on the average and is approximately constant among different genes. It also is suggested that this property would be suitable for a molecular clock to determine the evolutionary relationships and branching order of duplicated genes. Each functional block of the noncoding region evolves with a rate that is almost constant, regardless of the types of genes. The intervening sequence and the 5' portion of the 3' noncoding region show considerable divergence, the extent of which is almost comparable to that in the synonymous codon sites, whereas the other blocks consisting of the 5' noncoding region and the 3' portion of the 3' noncoding region are strongly conserved, showing approximatley half of the divergence of the synonymous sites. This strong sequence preservation might be due to the functional requirements for transcription and modification of mRNA.
Behaviors in relation with water are described in detail for wild chimpanzees of the Manhale Mountains, Tanzania: drinking, wading streams, feeding, responses to rain, etc. When the results are compared with those of Gombe National Park, some behavioral differences emerge: drinking directly from the lake, feeding on aquatic plants, back/shoulder rubbing behavior by making day-beds, etc. are observed only for chimpanzees of the Mahale Mountains, while sponging to obtain water is observed only for those of Gombe. These may be examples of "tradition drift' in wild chimpanzees. Moreover, it is suggested that there is no innate hydrophobia among any of the African great apes.
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The primary formation of germinal centers was induced in the chick spleen by intravenous injection of sheep red blood cells (SRBC) at 21 days of age. In the spleen, SRBC were trapped in the ellipsoids soon after injection. The number of cells of periellipsoidal lymphoid tissues (PELT) was gradually depleted. Large pyroninophilic cells appeared in the periphery of periarterial lymphatic sheaths (PALS) 4 hrs after injection. Then they increased in number and migrated centralward in the PALS. On the 4th day they were accumulated in the vicinity of the central arteries to make nodular structures. Morphologically mature germinal centers encapsulated by connective tissue were formed for the first time on the 6th day after injection. They were most numerous on the 8th day and then decreased gradually. It was presumed that the primary germinal centers in the chick spleen might have been formed by the cells of the PELT which were originally derived from the bursa of Fabricius. The process of proliferation of germinal centers in the secondary immune response was discussed.
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Seven spontaneously hypertensive rats (SHR) and 14 Wistar inbred Kyoto strain rats (WKR) were used. Seven WKR were made diabetic by a single intravenous injection of streptozotocin (50 mg/kg body weight); the seven untreated WKR served as controls. The choroidal vessels of all rats were observed by electron microscopy after 12 months. The choroidal capillaries of control rats showed focal accumulation of basement (BM) in the subendothelial space. Two distinct types of BM lesions were noted: homogeneous thickening and sparse, interlacing branches, or ramifications, of BM. Increased BM caused indentations in the vascular wall. In diabetic rats, BM of capillaries, small arteries, and small veins showed arabesque ramification of BM which represented advanced forms of the sparse, interlacing ramifications seen in normal controls. Contiguous lesions of ramified BM, separated by narrow cytoplasmic processes projecting from the endothelial cells, resembled a scalloped border. In hypertensive rats, the arabesque ramifications were most conspicuous in the small veins. Homogeneous thickening of BM was noted in choroidal capillaries, small arteries, and small veins of SHR, although ramified BM was seen adjacent to it. Endothelial cell proliferation was seen in the small arteries of diabetic and hypertensive rats. The cytoplasm of endothelial cells at the lesion of proliferation was broadened, and cell nuclei appeared cubic or spherical. Consequently, the arterial lumina were narrowed. Complete occlusion was seldom seen in the choroidal arteries of diabetic rats, but it was observed in small arteries of SHR, accompanited by hypertrophy of medial smooth muscle cells and endothelial proliferation. Basement membrane accumulation and endothelial proliferation were common to both groups of rats, but the overall effect of pathological changes was more profound in hyptertension than in diabetes.
Four Wistar inbred rats made diabetic by an injection of streptozotocin and four control rats were killed after an experimental period of 12 months. Eye tissues were prepared for examination and detection of acid phosphatase (AcPase) by electron microscopy. In the retina of control animals, the Müller cell cytoplasm had a small number of highly electron-dense bodies. AcPase reaction products were seen on these dense bodies and on Golgi lamellae of Müller cells. In the diabetic rat retina, a greater number of these lysosome-like bodies were seen, especially in cell processes adjacent to capillaries and in those at the vitreoretinal interface. Increased deposits of AcPase reaction products were detected on Golgi lamellae, smooth endoplasmic reticulum, and highly electron-dense bodies. The functional significance of a marked increase in lysosomal enzymes within Müller cells is uncertain. The phenomenon may occur in order to eliminate cellular debris derived from necrotic pericytes and to digest excessive glycogen accumulated in the retina under diabetic conditions.
The interaction of phosphatidylcholine dispersions with acid soluble collagen separated from the skin of one month-old swine was studied to define the conditions facilitating the association of the collagen with lipids. When acid soluble collagen and phosphatidylcholine dispersions were incubated in 75 mM citrate buffer of pH 3.7 at 25 degrees C, the reisolated collagen fibrils did not contain appreciable amounts of phosphatidylcholine. However, the presence of n-propanol greatly promoted the retention of phosphatidylcholine, the amount of phosphatidylcholine associated being nearly 30% of collagen on a weight basis under optimal conditions. In contrast, methanol, ethanol, isopropanol, and n-butanol did not appreciably enhance the association of phosphatidylcholine with collagen. A limited inhibition of phosphatidylcholine retention was observed upon addition of sodium chloride to the propanol medium. The interaction of phosphatidylcholine with acid soluble collagen decreased sharply when temperature was increased above 30 degrees C; almost no phosphatidylcholine-collagen association occured at 40 degrees C. It appears that the enhanced association in the presence of n-propanol is due to a looseing of the collagen triple helix that exposes hydrophobic sites necessary for the interaction. However, the conversion of the triple helical structure to the random coil conformation by heating prevents the association of phosphatidylcholine with acid soluble collagen.
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A simple and convenient method for the purification of human plasma lecithin-cholesterol acyltransferase was developed. The method involves the adsorption of the enzyme from diluted human plasma on DEAE-Sephadex, treatment with 1-butanol in the presence of (NH4)2SO4, DEAE-Sephadex chromatography, treatment with dextran sulfate in the presence of Ca2+, and hydroxyapatite chromatography. The enzyme purified showed a single main band by polyacrylamide gel electrophoresis in the presence and absence of sodium dodecyl sulfate. In addition, the enzyme obtained was stable for more than four weeks, when it was kept at 4 degrees C under N2 in a buffer of low ionic strength. The purified enzyme was used to study its specificity toward the acyl acceptor. This specificity was found to be broad in that not only sterols but also long chain primary alcohols exhibited considerable acceptor activity. Furthermore, in agreement with our previous observations with crude enzyme (Piran, U. and Nishida, T. (1976) J. Biochem. (Tokyo) 80, 887-889), the purified enzyme was found to be capable of hydrolyzing the ester linkage at the carbon-2 position of phosphatidylcholine. The transesterification, as well as the hydrolytic reaction, required the presence of the cofactor polypeptide, apolipoprotein A-I.
Highly purified lecithin-cholesterol acyltransferase of human plasma was used to study the utilization of various sterols as the acyl acceptor. The esterification of sterols was facilitated by the presence of a 3beta-hydroxyl group and the trans configuration of the A/B rings, as was evident from the lack of acceptor activity of all 3 alpha-hydroxy sterols tested and coprostanol. Cholesterol analogs in which the side chain is modified, such as campesterol, beta-sitosterol, desmosterol and stigmasterol, were less effective than cholesterol as acyl acceptors. However, androstan-3 beta-ol, which completely lacks the side chain, was found to be more active than cholesterol. The transfer of the acyl group to all effective sterols required the presence of the cofactor peptide apolipoprotein A-I.
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