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Dr. Emiko Matsumoto Kazushige Hirosawa Kiyoshi Takagawa Yoshiki Hotta 《Cell and tissue research》1988,252(2):293-300
Summary A Drosophila visual mutant rdgA has photoreceptive cells which degenerate gradually after eclosion. Fine structure of the retinular cells of rdgA
KS60
and rdgA
K014
was studied during early stages of degeneration to determine the initial morphological defects. The retinular cells of these two alleles showed the following structural abnormality within 1 day after eclosion: (1) rhabdomeres were small and irregular in shape; (2) cisternae of the rough endoplasmic reticulum were more numerous than those in normal retinular cells; (3) submicrovillar cisternae were absent; and (4) lysosomes were fewer than normal. Three-dimensional reconstruction of serial sections of the ommatidia showed that the degeneration of mutant rhabdomeres proceeds more rapidly in regions remote from the nuclei. These results suggest that the process of turnover of rhabdomeric microvilli is abnormal in rdgA. We also confirmed an increase of lysosomes and destruction of cellular organelles, as reported by previous investigators at more advanced stages of degeneration. 相似文献
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Hiroshi Yanagawa Yoko Ogawa Kiyotsugu Kojima Masahiko Ito 《Origins of life and evolution of the biosphere》1988,18(3):179-207
We have developed experimental approaches for the construction of protocellular structures under simulated primitive earth conditions and studied their formation and characteristics. Three types of envelopes; protein envelopes, lipid envelopes, and lipid-protein envelopes are considered as candidates for protocellular structures. Simple protein envelopes and lipid envelopes are presumed to have originated at an early stage of chemical evolution, interaction mutually and then evolved into more complex envelopes composed of both lipids and proteins.Three kinds of protein envelopes were constructedin situ from amino acids under simulated primitive earth conditions such as a fresh water tide pool, a warm sea, and a submarine hydrothermal vent. One protein envelope was formed from a mixture of amino acid amides at 80 °C using multiple hydration-dehydration cycles. Marigranules, protein envelope structures, were produced from mixtures of glycine and acidic, basic and aromatic amino acids at 105 °C in a modified sea medium enriched with essential transition elements. Thermostable microspheres were also formed from a mixture of glycine, alanine, valine, and aspartic acid at 250 °C and above. The microspheres did not form at lower temperatures and consist of silicates and peptide-like polymers containing imide bonds and amino acid residues enriched in valine. Amphiphilic proteins with molecular weights of 2000 were necessary for the formation of the protein envelopes.Stable lipid envelopes were formed from different dialkyl phospholipids and fatty acids.Large, stable, lipid-protein envelopes were formed from egg lecithin and the solubilized marigranules. Polycations such as polylysine and polyhistidine, or basic proteins such as lysozyme and cytochromec also stabilized lipid-protein envelopes. 相似文献
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Interleukin-4 downregulates interleukin-6 production by human alveolar macrophages at protein and mRNA levels. 总被引:2,自引:0,他引:2
Effects of interleukin-4 (IL-4) on IL-6 production by human alveolar macrophages (AM) obtained by bronchoalveolar lavage from healthy donors was examined at the protein and gene levels. IL-6 production was quantitated by enzyme immunoassay (EIA) and bioassay using the IL-6 dependent murine hybridoma cell line MH60.BSF2. Results showed that when activated with LPS, AM released significantly more biologically active IL-6 than blood monocytes. Human rIL-4 significantly suppressed IL-6 production by AM and monocytes stimulated with LPS. Northern blot analysis revealed that IL-4 reduced the expression of IL-6 mRNA in LPS-stimulated AM and monocytes. The inhibitory effect was most pronounced when IL-4 was added with LPS or within the first 4 hr after LPS to AM or monocytes. The suppressive effect of IL-4 was completely neutralized by pretreatment with anti-IL-4 antibody. IL-4 also showed a suppressive effect on IL-6 production by macrophages generated in vitro by maturation of blood monocytes with granulocyte-macrophage colony stimulating factor (GM-CSF). These observations suggest that IL-4 may play a critical role in in situ regulation of immune responses through suppression of IL-6 production. 相似文献
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Cyanogen bromide (BrCN) condensed oligoadenylates [oligo(A)] on a poly(uridylic acid) [poly(U)] template in an aqueous solution. Imidazole and divalent metal ions such as Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Mg2+, and Fe2+ were required for the condensation. Chain length of oligo(A) and reaction temperature affected the coupling yield. Hexaadenylate [(pA)6] was converted to (pA)12, (pA)18, (pA)24, (pA)30, (pA)36, (pA)42, and (pA)48 in a 68% overall yield for 20 h at 25 degrees C. The coupling yield increased with increase in the poly(U) concentration. Five- to sevenfold molar excess of uridylyl residues of poly(U) to adenylyl residues of oligo(A) gave the best yield (68%). Metal ions affected the formation of linkage isomers of the phosphate bonds: The 2',5'- and 3',5'-phosphodiester bonds were predominant in the presence of Co2+, Zn2+, and Ni2+ and the 5',5'-pyrophosphate bond was predominant in the presence of Mn2+. In particular, Ni2+ gave the highest ratio of the 3',5'-phosphodiester bond (30%). N-Cyanoimidazole (1), N,N'-iminodiimidazole (2), and N-carboxamidoimidazole (3) were formed in a reaction of imidazole with BrCN in an aqueous solution. 1 and 2 had much the same condensing activity for the polymerization of adenylates as BrCN. A reaction pathway was proposed in which 1 and 2 are not only intermediates for the production of 3 but also the true condensing agent in the coupling reaction of oligo(A). Phosphorimidazolide derivative was detected in a reaction of 5'-AMP with either 1 or 2. The condensation would proceed by way of N-cyanoimidazole-phosphate adduct, the phosphorimidazolide derivative, or both. 相似文献
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Summary Polypeptides, synthesized from a mixture of amino acid amides by microwave heating during repeated hydration-dehydration cycles, showed hydrolase- and oxidoreductase-like catalytic activities. Poly(GAVDH), polypeptides synthesized from an equimolar mixture (each 0.1 M) of glycinamide,l-alaninamide,l-valinamide,l-aspartic acid -amide, andl-histidinamide, catalyzed the hydrolysis of PNPAc. The hydrolytic rate of PNPAc with poly(GAVDH) was the quadruple of that ofl-histidine alone. Though the kcat values of different resulting polypeptides were 103–106 times less than those of native hydrolases, the Km value of the polypeptides further containing phenylalanine residues was nearly equal to that of the esterase. This result indicates the presence of hydrophobic interaction between a substrate and the polypeptides. Resulting polypeptides also showed catalytic activity for the reduction of ferricyanide ion [Fe(CN)3–] with NADH. The polypeptides seemed to have a strong affinity for adenine nucleotides, because the reaction was inhibited by adenine derivatives such as NAD+ and AppA. A hypothesis for the emergence of primitive protein enzymes is discussed. 相似文献
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Hiroshi Yanagawa Kiyotsugu Kojima Masahiko Ito Nobuhiko Handa 《Journal of molecular evolution》1990,31(3):180-186
Summary Amino acid amides effectively reacted to produce polypeptides in response to microwave heating during repeated hydration-dehydration cycles. The polypeptides, formed from a mixture of glycinamide, alaninamide, valinamide, and aspartic acid -amide, had molecular weights ranging from 1000 to 4000 daltons. Amino acids were incorporated into the polypeptides in proportion to the starting concentrations, with the exception of glycine whose incorporation was 1.5 times higher than that of the other amino acids. The polypeptides had some definite secondary structure, such as -helix and -sheet, in aqueous solution. This reaction provides not only a convenient method for abiotic peptide formation but also a convenient method for the chemical synthesis of peptides. 相似文献