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31.
Limited chymotryptic cleavage of soluble chicken gizzard desmin protofilaments allows the characterization of three structurally distinct domains. A surface-exposed very basic amino-terminal region (the headpiece) with an amino acid sequence excluding a-helical organization (7.5 kd) is separated from the perhaps globular carboxy-terminal 48 residues (the tailpiece) by a distinctly different middle domain of approximately 330 residues. This 38 kd domain is very rich in α-helix (at least 83%), and electron microscopy reveals a thin rod with a length of 500 ± 50 Å. Amino acid sequence data also show that the rod domain is interrupted by a nonhelical portion. An a-helical array is able to form a coiled-coil spanning the carboxy-terminal half of the 38 kd domain. The a-type diffraction pattern of 10 nm filaments arises from a coiled-coil conformation displayed through most but not all of the middle domain of the protofilaments. 相似文献
32.
Summary Light and dark adaptations were studied in the eye of Squilla mantis. Light adaptation is characterized by (1) a proximal shift of the distal pigment sheath (DPS) surrounding the proximal portion of the crystalline cone above its zone of contact with the rhabdom; (2) flattening of the distal pigment sheath; (3) lengthening of the crystalline cone correlated with shortening of the rhabdom; (4) a migration of screening pigment granules in retinula cells in the protoplasmic bridges crossing the perirhabdomal space. In animals kept in constant darkness, longitudinal displacements of the distal pigment sheath were found to be subject to a circadian rhythm characterized by a maximal light adaptation state at about 5 p.m. and a minimal one at 5 a.m. Screening pigment granule translocation in retinula cells does not show such rhythmic activity.Abbreviations a, b
maximal incidence angles in L.A., and D.A., respectively
- Cc
crystalline cone
- Dps
distal pigment sheath
- I
extreme incident light beam
- Prs
perirhabdomal space
- Rh
rhabdom
- Rp
reflecting pigment
This research has been supported by grant 3.012-76 of the Swiss National Science Foundation 相似文献
33.
Three strains (2ac9, 3ac10 and 4ac11) of oval to rodshaped, Gram negative, nonsporing sulfate-reducing bacteria were isolated from brackish water and marine mud samples with acetate as sole electron donor. All three strains grew in simple defined media supplemented with biotin and 4-aminobenzoic acid as growth factors. Acetate was the only electron donor utilized by strain 2ac9, while the other two strains used in addition ethanol and/or lactate. Sulfate served as electron acceptor and was reduced to H2S. Complete oxidation of acetate to CO2 was shown by stoichiometric measurements with strain 2ac9 in batch cultures using sulfate, sulfite or thiosulfate as electron acceptors. With sulfate an average growth yield of 4.8 g cell dry weight was obtained per mol of acetate oxidized; with sulfite or thiosulfate the growth yield on acetate was about twice as high. None of the strains contained desulfoviridin. In strain 2ac9 cytochromes of the b- and c-type were detected. Strain 2ac9 is described as type strain of the new species and genus, Desulfobacter postgatei. 相似文献
34.
Archives of Microbiology - A new strictly anaerobic, polarly flagellated, sporing, acetate-oxidizing, sulfate-reducing bacterium was isolated from anaerobic fresh or sea water mud samples. The... 相似文献
35.
Benvenuto Cestaro Elvira Pistolesi Norbert Hershkowitz Shimon Gátt 《生物化学与生物物理学报:生物膜》1982,685(1):13-20
A procedure is described which inserts asymmetrically cerebroside sulfate (‘sulfatide’) into the outer leaflet of bilayered phospholipid vesicles. Cerebroside sulfate is adsorbed onto a cellulose, filter-paper support and, when incubated with phosphatidylcholine vesicles is transferred to and inserted into the outer leaflet of these vesicles. This transfer occurs at, or above the transition temperature of the phospholipid and follows a similar pattern with small or larger (‘fused’) unilamellar vesicles. The transfer is linear with time for 1–2 h and is maximal after about 6 h, when the sulfatide content reaches about 6 mol% of the total quantity of phospholipid, corresponding to about 10 mol% of the phospholipids present in the outer layer. Initial rates of sulfatide transfer were somewhat increased when the vesicles contained a positively charged lipid (e.g. stearylamine) and decreased when this lipid was negatively charged (e.g. dicetyl phosphate) or hydrophobic (e.g. cholesterol). Divalent ions markedly inhibited sulfatide transfer and monovalent ions did so to a lesser degree. Once incorporated into the outer leaflet of the vesicle, the sulfatide could not be removed by washing with buffer, 1 M NaCl or 1 M urea. 相似文献
36.
Mhamed Sa?d El Kebbaj Norbert Latruffe Yves Gaudemer 《Biochemical and biophysical research communications》1982,108(1):42-50
In order to titrate and understand the role of arginyl residues of D-β-hydroxybutyrate dehydrogenase, arginyl specific reagents: butanedione, 1,2-cyclohexanedione and phenylglyoxal were incubated with three different forms of the enzyme; native enzyme (inner mitochondrial membrane bound), purified apoenzyme (phospholipid -free) and phospholipid-enzyme complex (reconstituted active form).After complete inactivation of the enzyme by [14C]-phenylglyoxal, the number of modified arginyl residues was different: one with the lipid-free apoenzyme and three with the phospholipid-enzyme complex, suggesting a conformational change of the enzyme triggered by the presence of phospholipids.After exhaustive chemical modification either of the apoenzyme or of the phospholipid-enzyme complex with [14C]-phenylglyoxal, four arginyl residues were titrated indicating that these residues are located in the hydrophilic part of the enzyme, not interacting with phospholipids.Reconstituted enzyme inactivated by butanedione could no longer bind a pseudosubstrate (succinate) which indicates that an arginyl residue is involved in the enzyme-substrate complex formation.The values of second order rate constants of D-β-hydroxybutyrate dehydrogenase inactivation by butanedione and 1,2-cyclohexanedione were unchanged with the three enzyme forms, suggesting that phospholipids are not involved in the substrate binding mechanism. 相似文献
37.
Zusammenfassung Bei dem ConchostracenLeptestheria dahalacensis kommen auf den ersten Antennen etwa 600 gleich aussehende Sinneshaare vor, die in Gruppen von jeweils 25–30 zusammengefaßt sind. Diese Sinneshaare sind in zwei Teile gegliedert, die durch das lichtmikroskopisch gut sichtbare Basalstück (basal bead) voneinander getrennt sind. Dieses bildet die Basis des Haares, dessen Wand im wesentlichen aus Epicuticula besteht. Apikal wird das Haar durch das Endkügelchen (terminal pellet) abgeschlossen. Das Basalstück wird von der untersten Lage der Epicuticula gebildet. Die 4–10 Receptorcilien, die jeweils einzeln ebensovielen Dendriten aufsitzen, ziehen aus dem inneren Teil des Rezeptors, der von insgesamt 5 Hüllzellen umgeben wird, durch das Basalstück, in dem sie stark eingeengt werden und verzweigen sich dann im äußeren Teil des Rezeptors. Sie ziehen bis zum Endkügelchen, in das sie durch einen Porus, den man als Häutungsporus ansprechen kann, eintreten. In der Häutungsvorbereitung wird der Haarbalg von der Hüllzelle 5, das Basalstück von der Hüllzelle 4, der Haarschaft dagegen von der Hüllzelle 3 gebildet. Dabei spaltet sich die Hüllzelle 3 ringspaltförmig auf, so daß in diesem Spalt der neuangelegte Haarschaft handschuhfingerförmig eingestülpt liegt. Die Hüllzelle 2 formt die Spitze des neuen Haares, während die Dendritenscheide von der Hüllzelle 1 abgegeben wird.
The receptors on the first antennae ofLeptestheria dahalacensis Rüppel (Crustacea, Conchostraca)
Summary On the antennulae ofLeptestheria dahalacensis (Conchostraca) nearly 600 sensory setae of one type are found. They are gathered in groups of 25–30. The single sensory seta is divided into two parts by the basal bead which is easily visible in the light microscope. The basal bead is the socket of the seta, whose wall is mainly built up by the epicuticle. The terminal pellet closes the tip of the seta. The basal bead is derived from the innermost layer of the epicuticle. 4–10 dendrites each with one receptorcilium innervate the receptor. The receptorcilia stretch through the interior part of the receptor and the basal bead into the exterior part, where they branch. They enter the terminal pellet in a porus, which seems to be a moulting porus. The interior part of the receptor is surrounded by 5 sheath cells. During the premoult it becomes obvious, that the socket of the seta is built by the sheath cell 5, the basal bead by the sheath cell 4 and the shaft by the sheath cell 3. For this the sheath cell 3 is divided into two parts. Between this two parts the newly formed cuticle is invaginated. The sheath cell 2 formes the tip and the sheath cell 1 the cuticular sheath of the new bristle.相似文献
38.
39.
40.
Vernon E. Walker Timothy R. Fennell Joyce A. Boucheron Norbert Fedtke Franoise Ciroussel James A. Swenberg 《Mutation research》1990,233(1-2):151-164
The results of efforts to identify and quantify macromolecular adducts of ethylene oxide (ETO), to determine the source and significance of background levels of these adducts, and to generate molecular dosimetry data on these adducts are reviewed. A time-course study was conducted to investigate the formation and persistence of 7-(2-hydroxyethyl)guanine (7-HEG; Fig. 1) in various tissues of rats exposed to ETO by inhalation, providing information necessary for designing investigations on the molecular dosimetry of adducts of ETO. Male F344 rats were exposed 6 h/day for up to 4 weeks (5 days/wk) to 300 ppm ETO by inhalation. Another set of rats was exposed for 4 weeks to 300 ppm ETO, and then killed 1–10 days after cessation of exposures. DNA samples from control and treated rats were analyzed for 7-HEG using neutral thermal hydrolysis, HPLC separation, and fluorescence detection. The adduct was detectable in all tissues of treated rats following 1 day of ETO exposure and increased approximately linearly for 3–5 days before the rate of increase began to level off. Concentrations of 7-HEG were greatest in brain, but the extent of formation was similar in all tissues studied. The adduct disappeared slowly from DNA, with an apparent half-life approx. 7 days. The shape of the formation curve and the in vivo half-life indicate that 7-HEG will approach steady-state concentrations in rat DNA by 28 days of ETO exposure. The similarity in 7-HEG formation in target and nontarget tissues indicates that the tissue specificity for tumor induction is due to factors in addition to DNA-adduct formation. 相似文献