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91.
Pergolizzi B Peracino B Silverman J Ceccarelli A Noegel A Devreotes P Bozzaro S 《Developmental biology》2002,251(1):18-26
The Dictyostelium mutant HSB1 is temperature-sensitive for development, undergoing aggregation and fruiting body formation at temperatures below 18 degrees C but not above. In vivo G protein-linked adenylyl cyclase activation is defective in HSB1, and the enzyme is not stimulated in vitro by GTPgammaS; stimulation is restored upon addition of wild-type cytosol. Transfection with the gene encoding the cytosolic regulator PIA rescued the mutant. We excluded the possibility that HSB1 cells fail to express PIA and show that the HSB1 piaA gene harbors a point mutation, resulting in the amino acid exchange G(917)D. Both wild-type and HSB1 cells were also transfected with the HSB1 piaA gene. The piaA(HSB1) gene product displayed a partial inhibitory effect on wild-type cell development. We hypothesize that PIA couples the heterotrimeric G protein to adenylyl cyclase via two binding sites, one of which is altered in a temperature-sensitive way by the HSB1 mutation. When overexpressed in the wild-type background, PIA(HSB1) competes with wild-type PIA via the nonmutated binding site, resulting in dominant-negative inhibition of development. Expression of GFP-fused PIA shows that PIA is homogeneously distributed in the cytoplasm of chemotactically moving cells. 相似文献
92.
Maini PK 《Comptes rendus biologies》2004,327(3):225-234
One of the characteristics of biological systems is their ability to produce and sustain spatial and spatio-temporal pattern. Elucidating the underlying mechanisms responsible for this phenomenon has been the goal of much experimental and theoretical research. This paper illustrates this area of research by presenting some of the mathematical models that have been proposed to account for pattern formation in biology and considering their implications. 相似文献
93.
The social amoeba, Dictyostelium discoideum, produces a multicellular fruiting body and has become a model system for cell-cell interactions such as signalling, adhesion and development. However, unlike most multicellular organisms, it forms by aggregation of cells and, in the laboratory, forms genetic chimeras where there may be competition among clones. Here we show that chimera formation is also likely in nature, because different clones commonly co-occur on a very small scale. This suggests that D. discoideum will likely have evolved strategies for competing in chimeras, and that the function of some developmental genes will be competitive. Natural chimerism also makes D. discoideum a good model organism for the investigation of issues relating to coexistence and conflict between cells. 相似文献
94.
Kiran Gurung Bregje Wertheim Joana Falcao Salles 《Entomologia Experimentalis et Applicata》2019,167(3):156-170
Insects are associated with multiple microbes that have been reported to influence various aspects of their biology. Most studies in insects, including pest species, focus on the bacterial communities of the microbiome even though the microbiome consists of members of many more kingdoms, which can also have large influence on the life history of insects. In this review, we present some key examples of how the different members of the microbiome, such as bacteria, fungi, viruses, archaea, and protozoa, affect the fitness and behavior of pest insects. Moreover, we argue that interactions within and among microbial groups are abundant and of great importance, necessitating the use of a community approach to study microbial–host interactions. We propose that the restricted focus on bacteria very likely hampers our understanding of the functioning and impact of the microbiome on the biology of pest insects. We close our review by highlighting a few open questions that can provide an in‐depth understanding of how other components of the microbiome, in addition to bacteria, might influence host performance, thus contributing to pest insect ecology. 相似文献
95.
We have examined slime cell distribution on the surface of the achenes of some Artemisia and Neopallasia taxa, as well as slime composition, envelope formation during the hydration, and slime relation to different morphological features and environmental factors. The results of the studies show a characteristic pattern of slime cells distribution, which could differ between taxa. The slime in the taxa studied belongs to the cellulose type and consists of two components i.e., pectins and cellulose. Although all fruits contain slime cells, not all of them show the slime envelope formation. Plants occurring in dry habitats (such as A. barrelieri) or annual species (such as A. annua) are characterised by a large amount of slime and a fast process of slime envelope formation. Slime production has not been observed in some polyploid populations (A. campestris and A. campestris ssp. sericea) and in two species occurring in relatively fertile habitats (A. verlotiorum, A. vulgaris). A reason for this may be either the immaturity of polyploid fruits leading to the production of a scarce, not detectable slime amount or, alternatively, the occurrence of not functional slime cells. Slime facilitates and stimulates the germination, as well as the adherence of the fruits to the ground or to animals (for dispersal). The slime could play important role in the distribution and colonisation of new habitats in many Artemisia taxa. 相似文献
96.
Confocal imaging and phylogenetic considerations of the subcutaneous neurons in the Atlantic hagfish Myxine glutinosa
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Giacomo Zaccone Douglas S. Fudge Timothy M. Winegard Gioele Capillo Michal Kuciel Kengo Funakoshi Eugenia Rita Lauriano 《Acta zoologica》2015,96(2):209-217
We used confocal microscopy and immunohistochemistry to characterize the morphology of the subcutaneous neurons and the innervation of the slime glands and striated muscles in the hagfish Myxine glutinosa. A rich plexus of 5HT‐, ChAT‐ and TH‐positive neurons is described in the capsule of the slime glands. These neurons, like those of the subcutaneous plexus, receive pericellular terminations from the axons of central cells. Capsular neurons receive innervation from 5HT‐positive and nNOS‐positive nerve fibres. Other nerve endings belonging to two separate nerve populations are identified in the striated muscles. They contain TH and nNOS immunoreactivity. Due to the lack of any topographical labelling, the cell origin and the projections of the neurons into the cranial and spinal nerves are unknown. This study provides anatomical evidence of multiple (5HT and nNOS) peripheral innervation of the neurons. However, it does not provide information about the function of these neurons in the hagfish. We suggest that hagfish neurons have a phylogenetic relationship with the spinal group of the dorsal cells of lampreys and the supramedullary cells of teleosts. 相似文献
97.
Macrocyst formation in the sexual cycle was found in three dictyostelid species:Dictyostelium monochasioides, Polysphondylium candidum, andP. pseudo-candidum. Mating tests suggested thatD. monochasioides andP. pseudocandidum were heterothallic andP. candidum was homothallic. The primary walls of macrocysts had partially or fully degenerated, while the inner walls, believed to be
tertiary walls, showed an undulate structure. 相似文献
98.
We examined 12 important monoterpenes found on the forest floor underPinus thunbergii, and monitored their effect on the growth of a slime mold,Dictyostelium discoideum Ax-2. Four concentrations were tested for each compound (3.3, 0.33, 0.033, and 0.0033 μ/mL). Relative growth rates were determined
by comparing the cell counts of treated organisms with those from the controls. At a concentration of 3.3 μlml, (1S)-(-)-α-pinene,
(-)-menthone, (-)-camphene, (S)-(+)-carvone, and (1 R)-(-)-fenchone strongly inhibited the development of this slime mold.
In contrast, (+)-sabinene, (R)-(+)-limonene, and myrcene showed no inhibitory effects, even at the highest concentration tested.
By comparing individual growth rates with the control during the incubation period, we could classify these monoterpenes into
three groups: I., compounds that were able to inhibit Ax-2 growth at all concentrations; II., compounds that showed a strong
inhibitory effect at treatments between 3.3 and 0.033 μl/mL, and mild anti-microbial activity at the lowest concentration;
and III., compounds that inhibited growth at higher concentrations (3.3 and 0.33 μl/mL), but enhanced it at lower levels (0.033
and 0.0033 μ/ml.). Based on these results, we suggest that the inhibitory and enhancing effects of selected monoterpenes depend
upon the concentration of the individual compound. 相似文献
99.
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