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91.
Kari Hovind-Hougen Marina Cinco Godfried M. Roomans Aksel Birch-Andersen 《Archives of microbiology》1981,130(5):339-343
The morphology of cells of strain Muggia, a slightly halophilic leptospire, was examined by the negative staining technique.The ultrastructure of the cells was rather similar to that of cells of Leptonema illini, i. e. the cells possessed cytoplasmic tubules. The basal complex of their flagella, however, was similar to the corresponding part of flagella on Gramnegative bacteria. The interior of the cells was densely packed with inclusions, except for the two outermost wavelengths at each end where these inclusions were absent.X-ray microanalysis showed that the inclusions contained sodium and chlorine as their main constituents. The inclusions disappeared upon storage of the cultures at room temperature. 相似文献
92.
93.
Ulrich Schlüter Hartwig Holst Kurt Chr. Rönnau 《Journal of invertebrate pathology》1982,39(3):362-372
The effect of the antibiotic Nikkomycin was investigated on the Malpighian tubules and the gut of fourth-instar larvae of the Mexican bean beetle, Epilachna varivestis. Within the Malpighian tubules, three different stages in cell alterations can be recognized. A stage of increased activity (Stage A), and two stages of dedifferentiation (Stages B and C) which are distinguishible by characteristic mitochondrial morphology. In Stage C individuals, when Malpighian tubule function stops entirely, alterations in the midgut take place, that are signs of increased activity. Measurements of hemolymph osmotic pressure showed that there is a considerable increase to a higher level which is maintained. Compared with the ultrastructural data, the regulation of osmotic pressure on a higher level may, in part, be the result of compensation for the failure of Malpighian tubule function by the midgut. 相似文献
94.
The larval Malpighian tubules of the saline-water mosquito Aedes taeniorhynchus were examined using light and electron microscopy. The tubules contain two cell types: primary cells and stellate cells. Primary cells are characterized by their size (70 μm × 70 μm × 10 μm) and an abundance of intracellular membranebound crystals. Two types of microvilli are found on the luminal surface of the primary cells: (1) small microvilli containing core microfilaments and extensions of endoplasmic reticulum, and (2) larger microvilli (≈3 μm in length) which in addition to the above components contain a mitochondrion along their entire length. Both microvillar types have abundant knobs lining the cytoplasmic surface of the microvillar membrane. These knobs, which are often found in insect ion transporting tissues, have been termed ‘portasomes’ by Harvey (1980). The possible role of these structures in ion transport and mitochondrial positioning is discussed. The stellate cells are much smaller than the primary cells, and lack intracellular crystals. Their microvilli are smaller as well (≈0.6 μm in length) and contain no endoplasmic reticulum. mitochondria or knobs. The cells types found in the saline-water mosquito larva, Aedes taeniorhynchus, are identical to those found in Aedes aegypti, indicating that the unique capacity of saline-water mosquito larvae to transport Mg2+ and SO4|post|staggered|2− is not associated with the presence of an additional cell type. 相似文献
95.
Thomas M. Clark Timothy J. Bradley 《Archives of insect biochemistry and physiology》1997,34(2):123-141
Two environmental parameters, feeding status and salinity, are expected to affect water and ion balance of the aquatic larvae of Aedes aegypti. Evidence was obtained for regulation of Malpighian tubule fluid secretion rates in response to changes in each of these parameters. Exposure to increased salinity induces release into the hemolymph of material with diuretic effects on Malpighian tubules. Diuretic material is present in hemolymph of larvae raised in higher salinities, rapidly appears in the hemolymph of larvae following transfer from dilute water to higher salinity, and rapidly disappears from the hemolymph following transfer from higher salinity to dilute water. Feeding status affects diuretic properties of both hemolymph and Malpighian tubules. Feeding causes hemolymph to become diuretic relative to hemolymph from nonfeeding larvae. Malpighian tubules removed from feeding larvae have greater basal fluid secretion rates and also appear to have greater maximal fluid secretion capacity than do tubules removed from nonfeeding larvae. Larval hemolymph [5-HT] was found to increase fivefold in response to elevated salinity but was unaffected by feeding status. Methiothepin, a 5-HT receptor antagonist, inhibited stimulation of fluid secretion by 5-HT and blocked the diuretic effects of hemolymph from larvae exposed to higher salinity but was without effect on stimulation of fluid secretion by diuretic peptide. During the course of this investigation, a preliminary pharmacological characterization of the 5-HT receptor on Aedes Malpighian tubules, suggesting that this receptor may be pharmacologically distinct from other described insect 5-HT receptors, was obtained. Arch. Insect Biochem. Physiol. 34:123–141, 1997. © 1997 Wiley-Liss, Inc. 相似文献
96.
Dallai R Carapelli A Nardi F Fanciulli PP Lupetti P Afzelius BA Frati F 《Tissue & cell》2004,36(4):233-244
The spermatozoon of Coletinia sp. has a bilayered acrosome, a short nucleus (4 microm) and a relatively short sperm tail with two mitochondrial derivatives. The chromatin is uniformly dense except for several electron-lucid channels or strands which permeate the nucleus and which originate in the spermatid as invaginations of the nuclear envelope. The invaginations occur mostly or exclusively along two meridians of the spermatid that are also characterized by the presence of a longitudinal rod of medium electron density. The two rods (designated as 'mid-spermatid rods') evidently are instrumental in the formation of the electron-lucid channels. The significance of this elaborate system of intranuclear channels is not understood. The sperm tail has a 9 + 9 + 2 axoneme with each of the nine microtubular doublets accompanied by an accessory microtubule; scant intertubular material can also be distinguished. Hence, the tail axoneme resembles that of many pterygote insects. Each of the two mitochondrial derivatives contains a crystalline inclusion that has periodically spaced layers going in different directions on either side of the midline. Two synapomorphic traits appear to be shared by Ateluridae and Nicoletiidae, namely the invaginations of the nuclear membrane along two meridians of the nucleus and the shape of the crystalline inclusions of the mitochondrial derivatives. Four species from the family Lepismatidae were also examined as to their sperm ultrastructure. Three of them, Allacrotelsa kraepelini, Ctenolepisma longicaudata and Ctenolepisma sp., were found to be very similar to the two previously examined lepismatids, Thermobia domestica and Lepisma saccharina. On the other hand, spermatozoa of Tricholepisma aurea were aggregated in small groups rather than pairwise joined as seen in the other lepismatids. Sperm characters are also used to reconstruct a phylogenetic hypothesis which suggests a close relationship between Ateluridae and Nicoletiidae. 相似文献
97.
In vitro formation of the endoplasmic reticulum occurs independently of microtubules by a controlled fusion reaction 总被引:1,自引:0,他引:1
We have established an in vitro system for the formation of the endoplasmic reticulum (ER). Starting from small membrane vesicles prepared from Xenopus laevis eggs, an elaborate network of membrane tubules is formed in the presence of cytosol. In the absence of cytosol, the vesicles only fuse to form large spheres. Network formation requires a ubiquitous cytosolic protein and nucleoside triphosphates, is sensitive to N-ethylmaleimide and high cytosolic Ca(2+) concentrations, and proceeds via an intermediate stage in which vesicles appear to be clustered. Microtubules are not required for membrane tubule and network formation. Formation of the ER network shares significant similarities with formation of the nuclear envelope. Our results suggest that the ER network forms in a process in which cytosolic factors modify and regulate a basic reaction of membrane vesicle fusion. 相似文献
98.
99.
Role of curvature and phase transition in lipid sorting and fission of membrane tubules 总被引:2,自引:0,他引:2
We have recently developed a minimal system for generating long tubular nanostructures that resemble tubes observed in vivo with biological membranes. Here, we studied membrane tube pulling in ternary mixtures of sphingomyelin, phosphatidylcholine and cholesterol. Two salient results emerged: the lipid composition is significantly different in the tubes and in the vesicles; tube fission is observed when phase separation is generated in the tubes. This shows that lipid sorting may depend critically on both membrane curvature and phase separation. Phase separation also appears to be important for membrane fission in tubes pulled out of giant liposomes or purified Golgi membranes. 相似文献
100.
Binary lipid monolayers consisting of equimolar proportions of a phosphoinositide and a nickel-chelating lipid formed helical tubular vesicular structures, which appeared to be induced and/or stabilized by myelin basic protein (MBP). Another basic polypeptide, poly-L-lysine, had a similar effect but not to as great a degree as MBP; the proteins thus appeared to act as polycations. Although, the nickel-chelating lipid is a synthetic product, other endogenous divalent cations such as Zn(2+), as well as phosphoinositides, are integral and dynamic components of the myelin sheath in vivo. There, comparable helical tubular structures might represent a means for sequestration of these lipids into domains of high local concentration, perhaps in regions where the membrane is greatly curved. 相似文献