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71.
72.
Summary In the noctuid moth Spodoptera exempta, the distribution of visual pigments within the fused rhabdoms of the compound eyes was investigated by electron microscopy. Each ommatidium regularly contains eight receptor cells belonging to three morphological types: one distal, six medial, and one basal cell (Meinecke 1981); four different visual pigments — absorption maxima at approximately 355, 465, 515, and 560 nm — are known to occur within the eye (Langer et al. 1979). The compound eyes were illuminated in situ by use of monochromatic light of different wavelengths. This illumination produced a wide scale of structural changes in the microvilli of the rhabdomeres of individual cells. Preparation of eyes by freeze-substitution revealed the structural changes in the rhabdomeres to be effects of light occurring in vivo.The degree of structural changes may be considerably different in rhabdomeres within the same ommatidium; it was found to depend on the wavelength and the duration of illumination, the intensity received by the ommatidia as well as the spectral sensitivity of the receptor cells. Therefore, it was possible to estimate the spectral sensitivities of the morphological types of receptor cells. Generally, all medial cells are green receptors and all basal cells red receptors; distal cells are blue receptors in about two-thirds of the ommatidia, while in the remaining third of them distal cells are sensitive to ultraviolet light.Supported by Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 114 (Bionach) 相似文献
73.
Helmut Klocker Bernhard Auer Helmut J. Burtscher Monica Hirsch-Kauffmann Manfred Schweiger 《Molecular & general genetics : MGG》1982,188(2):309-312
Summary The UV photoproduct, thymine dimer (
), is excorporated with a remarkably low rate from the DNA of human fibroblasts grown in cell culture. An UV dose of 18 J/m2 creates 0.045%
(related to thymine). Within the first two days of repair logarithmically growing and quiescent fibroblasts exhibit the same repair rates; thereafter, the proportion of
is lower in growing cells due to recovery of DNA replication. Only about 50% of the lesions are excised within 24 h. In quiescent cells, 13% of the thymine dimers originally present can be detected as late as a week after UV-irradiation. Two distinct first-order rate constants indicate that approximately half of the dimers are less accessible to repair. Repair measured by the nucleoid decondensation technique corresponds to the faster repair rate, whereas the slow repair rate cannot be detected by this method. Saturation of repair is found beyond 27 J/m2. The remarkably slow rate of excision indicates that thymine dimers are not lethal lesions in human fibroblasts. 相似文献
74.
Microbodies of the algaMougeotia were isolated in a linear sucrose gradient. The organelles, which moved to the density 1.24 g cm–3, contained about 70% of the glycolate oxidase (EC 1.1.3.1) found in this alga. The enzyme oxidized glycolate, utilizing either oxygen or 2,6-dichlorophenolindophenol (DCPIP) as the electron acceptor. L-Lactate was an alternate substrate; almost no D-lactate was utilized. In the presence of O2, a Km of 415 M was determined for glycolate, whereas the Km for L-lactate was about 5,000 M. In the presence of DCPIP, lower concentrations of glycolate and L-lactate were sufficient to obtain the highest rates of enzyme activity.Abbreviations DCPIP
2,6-dichlorophenolindophenol
Supported by the Deutsche Forschungsgemeinschaft 相似文献
75.
Helmut Wombacher 《Molecular and cellular biochemistry》1980,30(3):157-164
Summary Soluble cyclic nucleotide 3:5 monophosphate phosphodiesterase (PDE) (EC 3.1.4.17) obtained from beef adrenal cortex as the 100,000 g/1.5 h supernatant is usually regarded as a very hydrophilic protein. However, when subjected to hydrophobic chromatography on Octyl-Sepharose CL 413 it reveals strong hydrophobic interaction with the column matrix. The chromatographic procedure leads to multiple but distinct forms of PDE which degrade cAMP beyond 5AMP to inosine, via adenosine. The same metabolic pathway was previously observed with a membrane bound multienzyme sequence. Even the soluble PDE forms separated by gel chromatography (Sephadex G 200, Sepharose S 200 and Sepharose 6B) and soluble PDE of other tissue (heart) displayed the same metabolic pattern. These findings indicate a linkage between PDE, nucleotidase and deaminase activities. The intimate association of the enzyme is additionally supported by the phenomenon of kinetic advantage clearly observed with the most hydrophobic PDE form. Its end product, inosine, is formed more rapidly from CAMP than from the intermediate 5AMP. This paradoxical phenomenon is explained by close physical proximity between the enzymes involved in the metabolic pathway. Furthermore, when the most hydrophobic PDE form was immobilized on Octyl-Sepharose, rather than loss of catalytic activity even higher enzyme activities were measured. It is suggested that the so-called multiple forms of soluble PDE-at least in part-represent more or less preserved forms of a native, membrane bound, multienzyme sequence which degrades cyclic nucleotides. 相似文献
76.
Helmut Bertrand Frank E. Nargang Richard A. Collins Cheryl A. Zagozeski 《Molecular & general genetics : MGG》1977,153(3):247-257
Summary We have isolated twenty-six nuclear, singlegene cytochrome-deficient mutants of Neurospora crassa as an initial step toward the study of the structural components and regulatory mechanisms involved in the biogenesis of the mitochondrial cytochrome system. These mutants, together with two previously described mutants, cyt-1 and cyt-2, have been classified into six distinct groups on the basis of cytochrome phenotype: a) cytochrome aa
3
deficiency (due to mutations affecting loci designated cya); b) cytochrome b deficiency (cyb-1 locus); c) cytochrome b deficiency with a partial deficiency of cytochrome aa
3
(cyb-2 locus); d) deficiency of both cytochromes aa
3
and b (cyt loci); e) deficiency of both cytochromes aa
3
and c (cyt-2 locus); and f) partial deficiency of cytochromes aa
3
and c (cyt-12 locus).Four of seven mutations affecting cya loci have been mapped and are located on linkage groups I, II, V, and VI. It is not yet known whether these genes code for structural components of cytochrome oxidase or have a regulatory function that affects synthesis or assembly of the enzyme. The cyb-1 and cyb-2 genes are located on linkage groups V and VI, respectively, and appear to code for regulatory elements that control the biogenesis of cytochromes b and aa
3
. The positions of the cyt mutations that cause a simultaneous deficiency of cytochromes aa
3
and b are dispersed throughout the genome, except for two gene clusters on the left arm of linkage group I. Some of these mutants may be deficient in mitochondrial protein synthesis. Two mutations, cyt-2 and cyt-12, are located on linkage groups VI and II, respectively, and appear to affect genes that code for components of a regulatory system that controls the biogenesis of cytochromes aa
3
and c. 相似文献
77.
The electron impact mass spectra of 19 trimethyl silylated flavonol mono-, di- and -triglycosides are reported for the first time. All spectra show wel 相似文献
78.
Helmut Hölder 《Pal?ontologische Zeitschrift》1978,52(3-4):280-304
The Parapatocerates from the Süntel (Weser mountains, Northwest Germany) are described being an utmost variable subspecies respectively geographical raceParapatoceras distans (?) bentzi (Potonié) with two possibly modificatorily separated form groups. They differ from the similarP. distans(?) crioconus (Buckman) (=Crioconites Buckman) of Chippenham (England) in primary quadrilobaty and further characteristics accessible only by precise analysis. To establish the speciesdistans Baugier & Sauzé and with this the genusParapatoceras, recovery of the holotype or a determination of a neotype is required. A very similar but probably quinquelobate specimen (Parapatoceras sp.) from the Macrocephalus oolite of Hanover seems to accentuate once more the taxonomically minor degree of the quadri- or quinquelobaty inParapatoceras. 相似文献
79.
Summary A heme-nonapeptide (H-9-P)1, applicable to electron microscopic cytochemistry via peroxidase-like activity, was prepared by passing horse heart cytochrome c through a column with Sepharose and covalently attached trypsin. After purification by column chromatography (Sephadex G50 Superfine, Biogel P-2) a maximal yield of 50% and purity of >99% was achieved. A concise schedule allows for inexpensive preparation of H-9-P with standard laboratory equipment. H-9-P has the following properties: Its structure is (14) Cys-Ala-Gln-Cys-His-Thr-Val-Glu-Lys (22) with heme attached to Cys (14) and (17). MW=1630, pI=4.95,
E(max)
pH 7
= 397.5 nm,
22 °C, pH 7
397.5 nm
= 1.11 × 105 [Liter/Mole x cm]. With the use of a diaminobenzidine-H2O2-medium — as applied for cytochemistry — we determined spectrophotometrically a pHopt=12.5 and an apparent K5 = 3.14 × 10– 3 [M]. Glutardialdehyde leads to considerable de-activation and, according to SDS-polyacrylamide-gel-electrophoresis, to diffuse crosslinking accompanied by a shift of the active pH-region towards neutral pH values. An attempt was made to optimize the cytochemical assay. The peroxidase-like activity of H-9-P is well comparable to that of other heme-tracers; only horseradish peroxidase has a higher turnover number. When injected to mice or added to cell suspensions, even high concentrations of H-9-P did not entail any signs of toxicity.Abbreviations AAA
amino acid analysis
- AHC
ammoniumhydrogencarbonate
- BSA
bovine serum albumin
- Cyt c
cytochrome c
- DAB
5,3-diaminobenzidine
- GA
glutardialdehyde
- H-8-P
heme-octapeptide
- H-9-P
heme-nonapeptide
- H-11-P
heme-undecapeptide
- HR-POX
horseradish peroxidase
- MW
molecular weight
- PAGE
polyacrylamid-gel-electrophoresis
- pI
isoelectric point
- SDS
sodiumdodecylsulphate
- SG-TLC
silicagel-thin-layer-chromatography
This work was supported by the Österreichische Forschungsfonds 相似文献
80.
Helmut Zacharias 《Chromosoma》1990,99(1):24-35
Drosophila nasutoides has an extraordinary genome since 62% of its DNA resides in chromosome4. This element mainly consists of constitutive heterochromatin which does not polytenize. Earlier studies of heterochromatin attributed little attention to the fact that condensed chromosomes often vary in condensation. This paper reports that chromosomes of the same complement display different degrees and kinetics of condensation. InD. nasutoides, even sex specific differences can be observed. The results of a comparative microphotometric study on neuroblast metaphases in both sexes revealed the following picture. The process of chromosome condensation is not restricted to mitotic prophase but continues into the metaphase. The mean condensation is not equal for all chromosomes. In the metaphase of the female, Feulgen density increases from theX chromosome, via3 and2, to chromosome4. In the male, the order isX, 2, 3, Y, and4. During the metaphase of the male, chromosomes condense with similar kinetics. In contrast, chromosomes of the female display asynchrony as monitored by area and length determinations. TheX chromosomes of the female probably have enhanced shortening during prophase. This would explain the metaphase of the female where theX chromosomes shorten less than the autosomes, and why each of theX chromosomes is 15% shorter than theX chromosome in the metaphase of the male. Further differences were observed in the longitudinal and lateral compaction of the chromosomes in males and females. The sex chromosomes and chromosome3 condense by shortening, while chromosomes2 and4 preferentially reduce their diameter. The large amount of DNA engaged in heteropycnosis and the isochromosome nature allow the identification of chromosome4 during interphase. At this stage, a new category of extreme DNA packaging was detected. The interphase density of chromosome4 can exceed that of metaphase by a factor of up to 8. Two events account for this high degree of condensation:(1) the homologues are particularly associated due to somatic pairing and (2) the arms are further tightened as a result of pericentric folding. The features of the isochromosome suggest that the interaction of chromatids during interphase is essentially caused by specific DNA sequences. The data confirm that heteropycnosis not only interferes with gene expression but also strongly inhibits DNA synthesis in endocycles. 相似文献