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61.
62.
ROBERT K. PECK 《The Journal of eukaryotic microbiology》1978,25(2):186-198
SYNOPSIS The membranes, epiplasm, and fiber systems are described in the somatic cortex of Glaucoma chattoni strain HZ-1. Kinetodesmal fibers, postciliary and transverse microtubular ribbons, basal microtubules, transverse fibers and transverse accessory material are associated with kinetosomes. Longitudinal microtubular ribbons and mitochondria occur interkinetally. In the buccal cortex, the membranes, epiplasm and fibers of the 3 membranelles, the paroral kinety, the ribbed wall, and the cytostome are described. Comparisons between G. chattoni and other ciliates reveal ultrastructural differences of possible systematic significance. In the somatic cortex of this and other tetrahymenines. Iongitudinal microtubular ribbons and basal microtubules occur concurrently. In the buccal cortex, alveoli are absent in tetrahymenine membranelles. A table is presented of the fiber systems associated with single somatic kinetosomes of various ciliates whose cortical ultrastructure has been studied to date. 相似文献
63.
Recent freshwater oscillatoriacean analogue of the Lower Palaeozoic calcareous alga Angulocellularia
ROBERT RIDING LARISA VORONOVA 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1982,15(2):105-114
Recent freshwater cyanophyte oncoids from Canandaigua Lake, New York, consist almost entirely of minute irregular, bush-like, micritic masses comparable with the calcareous alga Angulocellularia Vologdin from Lower Cambrian algal-arehaeocyathan bioherms and biostromes of the Siberian Platform and western Mongolia. The Recent specimens arc radially orientated within the oncoids and occasionally contain moulds of axial filaments 15 μm in diameter. Acid-residues of the oncoids yield abundant Schizothrix calcicola. The micritic bush-like masses are interpreted to have formed by the calcification of the sheaths of these cyanophytes. This analogue allows Angulocellularia to be reinterpreted as a calcified oscillatoriacean cyanophyte, rather than a rhodophyte as previously suggested. It indicates that filamentous cyanophytes can produce apparently solid calcareous fossils, not only porostromatc tubes. The occurrence of Angulocellularia has been overlooked in some previous studies of Cambrian and Ordovician bioherms. The generic diagnosis is emended. 相似文献
64.
The crustacean lacinia mobilis: a reconsideration of its origin, function and phylogenetic implications 总被引:1,自引:0,他引:1
The lacinia mobilis of the Crustacea Malacostraca is a more or less spine-like movable appendage of the medial mandibular edge, inserted near the base of the incisor process. It occurs in two or possibly three eumalacostracan superorders but is retained in the adult stage only in the Peracarida. The lacinia has been interpreted as the distal member of the spine-row found in many adult Malacostraca and/or their larvae, or alternatively as a derivative of a certain cusp ('cusp b') of the biting edge of the primitive lophogastrids. The distribution, ontogeny and function of the lacinia were studied in a variety of Eumalacostraca. There is great variability in the guiding and locking mechanisms involved in biting, within the subclass and even within single orders. A lacinia-based guiding and locking system is likely to function only in weak mandibles. New evidence is produced in favour of derivation of the lacinia from the spine-row, and the 'cusp b' derivation hypothesis is rejected, 'cusp b' being only a highly specialized lacinia. Doubt is cast upon the unity of the superorder Peracarida mainly because the place of the order Amphipoda within it is regarded as insecure. 相似文献
65.
The regional distribution of hydroxylase cofactor in rat brain 总被引:1,自引:0,他引:1
66.
Light initiated fruit body primordia of Coprinus congregatus Bull, ex Fr. grown at relatively high temperature (25°C) require a single dark period or low-temperature induction for completion of fruit-body development. The dark period requirement varied with the temperature regime during the inductive dark period A minimum requirement of 2.5 h was found al 15–20°C. Darkness always promotes development of fruit-body primordial, but cannot, be regarded as an absolute necessity until temperature exceeds about 17.5°C. Normal development of me primordia without darkness was obtained by lowering the temperature to 10°C for 6 h. It appeared that at high temperatures two successive stimuli were required for basidiocarp maturation, a light-off and a subsequent signal light-on signal. On the contrary, at 10°C a single low-temperature signal seemed to be involved. Thus, induction of fruit-body development could be produced by alternative pathways. These developmental features have been extended to other fungi and compared with the flowering processes of some short-day plants. 相似文献
67.
Effects of Glyphosate on Metabolism of Phenolic Compounds 总被引:1,自引:0,他引:1
Light enhanced the inhibiting effect of root-fed glyphosate (5 × 10?4M) on dry weight accumulation of soybean [Glycine max. (L.) Merr.] seedling axes. Inhibition of growth by light was greatest in hypocotyls, whereas by glyphosate it was greatest in roots. A synergistic effect of light and glyphosate on stimulation of phenylalanine ammonia-Iyase (PAL, E.C. 4.3.1.5) activity was also demonstrated. In continuous white light PAL activity increased linearly for 4 days in axes of seedlings exposed to glyphosate. Evidence of phytochrome involvement in the light effect was shown. The stimulatory effect of glyphosate on PAL activity was greater in roots than in hypocotyls. Soluble hydroxyphenolic compound levels were reduced by glyphosate but were increased by light on a per axis basis. On a fresh weight basis, hydroxyphenolics were more concentrated in glyphosate-treated than in control tissues in the light. When compared to other amino acids, disproportionate decreases in free pools of phenylalanine and tyrosine occurred in axes of seedlings treated with glyphosate and light. The effect of light on all measured parameters was mainly in the hypocotyl, while that of glyphosate was primarily in the root. In the light, glyphosate caused increases in levels of glutamine and other amino acids that may be the result of amination reactions, protecting from excess ammonia generated by enhanced PAL activity. These results suggest that PAL has a strong influence on its substrate levels in this system and/or that glyphosate inhibits synthesis of aromatic amino acids. 相似文献
68.
MICHAEL H. SILVER JEAN-MICHEL FOIDART ROBERT M. PRATT 《Differentiation; research in biological diversity》1981,18(1-3):141-149
Indirect immunofluorescence has been used to study the distribution of fibronectin and collagen types I, II, and III in the developing primary and secondary palatal processes and forelimb buds of the Swiss Webster (NIH) mouse. In the palatal processes fibronectin and types I and III collagen are distributed throughout the mesenchyme. Fibronectin is present in the basement membrane, while types I and III collagen are localized in a linear, discontinuous fashion beneath the basement membrane. Fibronectin is not observed in the epithelium, including the presumptive fusion areas. In the forelimb bud these components show a similar distribution prior to chondrogenesis (early day 11). When chondrogenesis commences (late day 11 or early day 12) fibronectin and, to a lesser degree, types I and III collagen are apparently concentrated in the core mesenchyme, suggesting that fibronectin has a role in initiating chondrogenesis, perhaps by increasing cellular aggregation. Type II collagen is observed only in chondrogenic regions. The codistribution of fibronectin and types I and III collagen supports in vitro studies which indicate that cells use fibronectin to bind to collagen in the matrix. The developing chondrogenic regions appear to lose fibronectin gradually, concomitant with the appearance of type II collagen, suggesting that fibronectin is not involved in the maintenance of functional chondrocytes in their matrices. 相似文献
69.
ROBERT D. HINRICHSEN 《The Journal of eukaryotic microbiology》1981,28(4):417-423
ABSTRACT. Temperature shifts have been used to block critical points in the conjugation sequence of Paramecium tetraurelia. Increasing temperatures above 27°C reduced ciliary agglutination, pair formation, and nuclear exchange; a complete inhibition of these stages occurred at 37°C. Temperatures below 19°C had no effect on ciliary agglutination or nuclear exchange but completely inhibited pair formation. The bases for the cells’ inability to form pairs at 19°C and 37°C were sought. Cells placed below 19°C were unable to deciliate or fuse membranes in the holdfast region; at 37°C, membrane fusion in both the holdfast and paroral regions was prevented. Time course studies on cross-fertilization reveal that temperatures 35°C block all stages of the process up to the actual exchange of pronuclei. After the exchange has begun, the process continues despite the elevated temperature. Temperature shifts are discussed as a means of conditionally blocking critical points in the developmental program of conjugation. 相似文献
70.
Theory can have many different kinds of use in illuminatingecological research. The examples sketched in this paper include:the uses and short-comings of population models currently usedin setting catch quotas for whales and for fisheries; the richarray of behaviour displayed by nonlinear equations and itsrelevance to understanding natural and managed populations;models for the interaction between populations (particularlythe regulation of natural populations by diseases); and somegeneral patterns of community organization. The paper concludeswith some remarks on the contrasts between public pieties about"The Scientific Method" and the way scientists actually work,from Darwin's day to our own. 相似文献