Metastable ripple phase of fully hydrated dipalmitoylphosphatidylcholine as studied by small angle x-ray scattering

Fully hydrated dipalmitoylphosphatidylcholine (DPPC) undergoes liquid crystalline to metastable P_β, phase transition in cooling. A small angle x-ray scattering study has been performed for obtaining further evidence about the structure of this phase. From a high-resolution observation of x-ray diffraction profiles, a distinct multipeak pattern has become obvious. Among them the (01) reflection in the secondary ripple structure is identified clearly. There are peaks assigned straightforwardly to (10) and (20) reflections in the primary ripple structure and peaks assigned to (10) and (20) reflections in the secondary ripple structure. Therefore the multipeak pattern is due to superposition of the reflections cause by the primary and secondary ripple structures. The lattice parameters are estimated as follows: for the primary ripple structure a = 7.09 nm, b = 13.64 nm, and γ = 95°, and for the secondary ripple structure a = 8.2 nm, b = 26.6 nm, and γ = 90°. The lattice parameters thus obtained for the secondary ripple structure are not conclusive, however. The hydrocarbon chains in the primary ripple structure have been reported as being tilted against the bilayer plane and, on the other hand, the hydrocarbon chains in the secondary ripple structure are likely to be perpendicular to the bilayer plane. This fact seems to be related to a sequential mechanism of phase transitions. On heating from the L_β, phase where the hydrocarbon chains are tilted the primary ripple structure having tilted hydrocarbon chains takes place and on cooling from the L_α phase where the hydrocarbon chains are not tilted the secondary ripple structure with untilted chains tends to be stabilized. It appears that the truly metastable ripple phase is expressed by the second ripple structure although in the course of the actual cooling transition both the secondary and primary ripple structures form and coexist.     

Hydrogen exchange kinetics of nucleic acids: Double and triple helices with Hoogsteen-type basepairs

The kinetics of hydrogen-tritium exchange reaction have been followed by a Sephadex technique of a double-helical poly(ribo-2-methylthio-adenylic acid)·poly(ribouridylic acid) complex with the Hoogsteen-type basepair. Only one hydrogen in every 2-methylthio-adenine·uracil basepair has been found to exchange at a measurably slow rate, 0.023 s^?1 (at 0°C), which is, however, much greater than that for a double-helix with the Watson-Crick type A·U pair. The kinetics of hydrogen-tritium exchange were also examined by triple-helical poly(rU)·poly(rA)·poly(rU) which involves both the Watson-Crick and Hoogsteen basepairings. Here, three hydrogens in every U·A·U base triplet have been found to exchange at a relatively slow rate, 0.0116 s^?1 (at 0°C). The kinetics of hydrogen-deuterium exchange reactions of these polynucleotide helices have also been followed by a stopped-flow ultraviolet absorption spectrophotometry at various temperatures. On the basis of these experimental results, the mechanism of the hydrogen exchange reactions in these helical polynucleotides was discussed. In the triple helix, the rate-determining process of the slow exchange of the three (one uracil-imide and two adenine-amino) hydrogens is considered to be the opening of the Watson-Crick part of the U·A·U triplet. This opening is considered to take place only after the opening of the Hoogsteen part of the triplet.     

Endothelial specific granules in the umbilical veins of the postnatal rabbit

Summary A remarkable increase in number of endothelial specific granules was observed in the rabbit umbilical veins between 2 and 5 days after birth. Electron microscopy indicated that the granules were segregated in the Golgi complex of the endothelial cells and released into the vascular lumen during the postnatal obliteration stage of this vessel.Incubation of the postnatal vessels in Ringer solution containing a histamine releasing compound induced remarkable morphological alterations of these cytoplasmic components; a reduction of their osmiophilia, swelling with a widened space separating the granular matrix from the limiting membrane, fusion to each other and expulsion of their contents into the vascular lumen, as in mast cell degranulation by this drug, were noted.High-performance liquid chromatography of the homogenized vessels demonstrated appreciable concentrations of histamine in the postnatal samples. There was a correlation between the histamine concentration and the quantity of granules in the respective postnatal samples.The present study strongly suggests that the granules are reservoirs of histamine and have an important role in the obliteration of this vessel.This work was supported in part by Grant in Aid for Scientific Research (# 448087) to S. Fujimoto from the Ministry of Education of Japan     

The “happy puppet” syndrome in two siblings

Summary Disomic and trisomic cells of a patient with Down syndrome mosaic were used to study the effect of the additional chromosome 21 against an identical genetic background. The frequency of Ag staining and the participation in satellite associations were determined for each pair of acrocentric chromosomes. The additional chromosome 21 of the trisomic cells and its homologues proved to be regularly Ag positive. Therefore the trisomic cells showed more Ag positive chromosomes and more satellite associations per cell than the diploid cells. Thus, no compensation for the additional rRNA-gene dose could be found in the cells of the trisomic line.     

The nucleotide sequence of 5S ribosomal RNA from Schizosaccharomyces pombe

The nucleotide sequence of 5S rRNA from the fission yeast, S. pombe, has been established by post labeling procedures combined with cataloging RNase T1- and A-oligonucleotides derived from unlabeled 5S rRNA. The sequence consists of 119 nucleotides without a modified base and shows more dissimilarities (at 38 positions) from that of S. cerevisiae than from that of humans (at 33 positions).     

Nucleotide sequence of 5S ribosomal RNA from Lingula anatina. A study on the molecular evolution of 5S ribosomal RNA from a living fossil

By chromatography on columns of DEAE-Sephadex A-50 and Sephadex G-100, and electrophoresis on polyacrylamide gel, 5S rRNA was purified from a low-molecular-weight RNA fraction extracted from the total tissues of Lingula anatina. Complete digests of the 5S rRNA with RNase T1 [EC 3.1.4.8] and pancreatic RNase [EC 3.1.4.22] were sequenced by conventional column chromatography procedures. The nucleotide sequence of this RNA was determined mainly by a chemical method for sequencing the RNA 3' end-labeled with 32P (1), with the complement of the oligonucleotide catalog obtained by the complete RNase digestions of the RNA. By comparing the sequences of several invertebrate, vertebrate, and Chlorella 5S rRNAs, a phylogenic tree of the rRNAs was constructed and the time of divergence of Lingula was estimated.     

Screening of microorganisms having high fumarase activity and their immobilization with carrageenan

Summary To develop an efficient method for continuous production of L-malic acid from fumaric acid using immobilized microbial cells, screening of microorganisms having high fumarase activity was carried out and cultural conditions of selected microorganisms were investigated. As a result of screening microorganisms belonging to the genera Brevibacterium, Proteus, Pseudomonas, and Sarcina were found to produce fumarase in high levels. Among these microorganisms Brevibacterium ammoniagenes, B. flavum, Proteus vulgaris, and Pseudomonas fluorescens were further selected for their high fumarase levels in the cultivation on several media. These 4 microorganisms were entrapped into a k-carrageenan gel lattice, and the resultant immobilized B. flavum showed the highest fumarase activity and operational stability.Cultural conditions for the fumarase formation and the operational stability of fumarase activity of immobilized B. flavum are detailed. Productivity for L-malic acid using immobilized B. flavum with k-carrageenan was 2.3 fold of that using immobilized B. ammoniagenes with polyacrylamide.Presented at the Annual Meeting of the Agricultural Chemical Society of Japan, Nagoya, April 3, 1978     

The fine structure of ventral prostatic secretory epithelial cells in older rats

Summary The ventral prostatic secretory epithelial cells in older rats were studied by light and electron microscopy. The cells vary in height in different parts of the same organ, and ultrastructurally they show the presence of a developed secretory apparatus such as well-developed Golgi body and abundant rough endoplasmic reticulum. They also show signs of a depressed secretory activity, involving occasional emiocytosis of apical secretory vacuoles and a paucity of condensing vacuoles in the Golgi region and above it. Further, they are characterized by the frequent occurrence of supra and paranuclear pleomorphic lysosomes.