摘要:

ABSTRACT.Micronuclear mitosis in livingSpirostomum tereshas been studied by sensitive polarization microscopy, and the dynamic aspects of micronuclear division are described. The small, spherical, interphase micronuclei lie in form‐fitting depressions in the macronuclear surface. Nuclear division begins with the rounding and slight swelling of the macronucleus and, coincidentally, the micronuclei move out of the depressions and away from the macronucleus, increase in size, and become weakly birefringent. As mitosis proceeds, the micronuclei increase in uniaxial birefringence and elongate to form irregular ovoids that convert to angular structures displaying principal axes of positive birefringence so divergent as to appear oriented at a right angle to one another. Micronuclei maintain this appearance for as long as 60 min and then abruptly change to rectangular‐shaped structures, increase in uniaxial birefringence, and begin anaphase elongation. The somewhat dumbbell‐shaped micronuclei lengthen at the constant rate of 2.0 μm/min to reach lengths>70 μm. It appears that little half‐spindle shortening occurs during spindle elongation. Accompanying the changes in micronuclear spindle length are changes in birefringence. Just before elongation begins, presumably metaphase, the micronucleus is uniformly and intensely birefringent. At the magnifications employed, a chromosome plate is not clearly visible as a region of reduced birefringence. As elongation begins, the putative half‐spindles are more birefringent than is the interzone, a condition that is maintained until the spindles have achieved ∼30% elongation, at which time a region of increased birefringence develops at the center of the interzone. This pattern persists for a very short time, then gives way to a uniform birefringence of the entire separation spindle that is maintained until elongation is completed. The rate of micronuclear spindle elongation, changes in micronuclear dimensions, and corresponding changes in birefringence are discussed with respect to possible mechanis

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb05309.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACT.Allantosoma intestinalis, a suctorian ciliate isolated from the intestine of the horse, was studied utilizing light and electron optical methods. These small sausage‐shaped organisms have a varying number of tentacles (between one and 12) located at each extremity of the body. The microtubular axoneme of each tentacle in cross‐section consists of two files of microtubules arranged in a daisy‐like configuration. Haptocysts occur in the tentacle shaft, abutted to the plasma membrane of the knob of the tentacle, and in the cell body. The haptocysts are bottle‐shaped, with prominent annular striations around their midportion. The cell is covered by three membranes, an outer plasma membrane, an outer alveolar, and an inner alveolar membrane. A thin epiplasmic layer is found beneath the inner alveolar membrane, and a single row of microtubules underlies the epiplasm. The subpellicular microtubules are arranged parallel to each other forming a corset around the cell along the long axis: such a system is not characteristic of suctorians. A field of diminutive kinetosomes (each 180 nm long, max. of 15 per field), lacking cilia, was found below the cortex. The function of these prokinetosomes is unknown. A ciliated swarmer has not been observed, only the nonciliated adult. The characteristics ofAllantosomaare compared with those of other suctorian

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb05310.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACT.Amphidinium carteriwas unable to grow on nutrient‐enriched seawater in the presence of 200 μg/ml fluoride (F) but could be adapted to grow successfully on this F concentration when repeatedly cultured with stepwise increases in sub‐inhibitory F concentration. Electron microscopic investigation of the F‐adapted dinoflagellate cells showed abnormal ultrastructural features in the chloroplast (especially the pyrenoid), mitochondria, and nucleus. Simultaneous comparison with the F‐inhibited dinoflagellate cells showed that thylakoid formation was extremely disorganized by fluoride and that F‐adaptation conferred a prolamellar‐like configuration on the thylakoids in the center of the pyrenoid. This unexpected appearance of lamellae formation in the F‐adapted cells suggested that the pyrenoid may be a center for thylakoid assembly. Such cells also showed large, intensely osmiophilic inclusions in the mitochondria. Microbodies are found in close juxtaposition to the mitochondria and chloroplast, suggesting an increased metabolic dependence on photorespiration. The F‐adapted nucleus showed dark and light concentric rings in the nucleolus region, accompanied by other signs of mitotic activity, which were not observed in the F‐inhibited cells. It was inferred that the F‐adaptation may have required some form of genetic change resulting presumably in the development o

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb05311.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACT.Conjugating cells ofEuplotes vannus(syngens Naples and Barcarès) were investigated for Con A‐binding sites by means of fluorescence microscopy. Cells fixed with 0.4% paraformaldehyde and incubated with 15 μg/ml FITC‐Con A showed a distinct region of strong fluorescence, the size, shape and localization of which characteristically changed during the course of conjugation, first appearing at courtship stage (cells contact without forming pairs) and vanishing soon after the migration pronuclei have been exchanged, but before cells have separated. Con A binding and conjugation were blocked by cyclohexamide and α‐galactosidase. Con A‐binding was also inhibited by α‐mannosidase, α‐glucosidase and β‐galactosidase without affecting conjugation except a delay of pair formation. The results suggest an involvement of newly formed or translocated glycoconjugates in cell pairing

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb05312.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACT.Temperature shifts have been used to block critical points in the conjugation sequence ofParamecium 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

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb05313.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACT.Sporocysts of the coccidianSarcocystis tenellawere originally isolated in the feces of a coyote. Sporocysts used for inoculation of lambs were obtained from experimentally infected dogs. At 14, 16, and 19 days postinoculation (DPI) of lambs with the sporocysts, various developmental stages of first‐generation meronts were found within cells located between the endothelium and internal elastic membrane of mesenteric arteries. At 19, 21, and 25 DPI, second‐generation merogony occurred in cells associated with capillaries and arterioles of kidney glomeruli and convoluted tubules. Meronts of both generations were bounded by a double pellicular membrane and were situated free in the host cell cytoplasm. Merozoites formed by endopolygeny that involved multiple intranuclear spindles of a single, large irregular nucleus. First‐generation meronts measured 22.6 × 17.1 μm (19–28.7 × 7.5–24 μm) and contained 120–240 merozoites, which measured 7.1 × 1.6 μm (4.8–7.5 × 1.3–1.8 μm). Corresponding values for second‐generation meronts were 13.2 × 9.2 μm (8.3–15 × 7–13.5 μ), 32–80, and

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb05314.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACT.The development ofSarcocystis cruziwas studied in an 11‐day‐old calf killed seven days postinoculation with 5 × 108sporocysts from feces of coyotes. Uninucleate zoites were found in arteries of mesenteric lymph nodes but not in other organs. Zoites measured 4.9 × 3.0 (3.5–7.0 × 2.1–3.5) μm. Of the 36 zoites studied, 31 were in endothelial cells, four were in macrophages in the lumen of arteries, and one was free in the lumen of an artery. Infected endothelial cells were two to three times larger than uninfected cells. Zoites appeared structurally similar to sporozoites. The occurrence of zoites in macrophages suggests that sporozoites ofSarcocystismight use such cells to reach the site of their fir

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb05315.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACT.The large fresh‐water microaerobic amoebaPelomyxa palustrisdoes not contain mitochondria, but three types of bacterial endosymbionts are always present. Thus, it is of interest in the discussion of the possible origin of mitochondria from primitive prokaryotes. Gas exchanges (O2, CO2) and concentration of endosymbionts were determined in individual amoebae, in which the life cycle stage was noted. Grey type (stationary phase) amoebae had a lower O2uptake and lower endosymbiont concentration than light type (growth phase) amoebae, and highest O2uptake was found in centrifugal pieces of light typePelomyxa, centrifuged in vivo, which contained nearly all of the endosymbionts. In light type amoebae, the respiratory activity was independent of O2concentration between 1 and 21%, and, when compared on the basis of dry weight and protein, of the same order as that of other free‐living protozoa. The R.Q. was slightly higher than 1, indicating that glycolysis does not play a significant role in energy metabolism. It is concluded thatP. palustrisis fully aerobic, and suggestions are presented as to the role of the endosymbionts in its respiratory metabol

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb05316.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACT.[14C]chimyl and [3H]batyl alcohols were added toCrithidia fasciculatacultures during the mid‐log phase of cell growth, and the lipid extracts of the cells were analyzed for degradation products.C. fasciculatacells were able to take up exogenous glyceryl ethers, and in amounts as high as the endogenous lipid content. The glyceryl ether taken up by the cells was incorporated into lipids either prior to the ether bond cleavage or after degradation to fatty acid. The extent of degradation and the degree of incorporation of degradation products into cellular lipid were higher for chimyl than for batyl alcohol. Batyl alcohol was not metabolized efficiently, leading to the formation of large intracellular pools of free substrate. One product of glyceryl ether degradation was identified as alkyl‐dihydroxy acetone, and was detected inside and outside of the cells. The data strongly suggest that this product is the first stable intermediate in the degradation process and indicate that the extracellular formation of alkyl‐dihydroxy acetone is due to the action of exocnzyme; ecteted by the cells. The constant detection of alk I cnyl glycerol among the degradation products indicates the existence of a second mechantsm inC. fasciculatafor converting the alkyl‐to alkenyl

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb05317.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACT.The enzyme that catalyzes the critical conversion of the proposed reductive thymidine catabolic end product, P‐aminoisobutyric acid, to the initial anabolic reutilization substrate, probably methylmalonic semialdehyde, was investigated to un‐ ambiguously substantiate the operation of a reductive pyrimidine catabolic and reutilization pathway inTetrahymena pyriformisstrain GL. Although most of the studies on the further metabolism of P‐aminoisobutyric acid in other organisms suggested transamination of p‐aminoisobutyric acid to methylmalonic semialdehyde followed by its further oxidation to methylmalonic acid, such a transaminating system could not be demonstrated. By means of a sensitive fluorometric assay system, however, a low, but significant amount of P‐aminoisobutyric acid oxidase activity was detected. This enzymatic activity exhibited the following characteristics in homogenates: good activity in alkaline 0.2 M Tris‐HCI buffer with a rather broad pH optimum ranging from 7.8 to 9.0; optimum activity at a temperature of 37°C; stimulation on the addition of exogenous FAD; inhibition on the addition of divalent cations, EDTA, or PCMB; little stimulation on the addition of detergents; and no increase in activity on repeated freezing and thawing. In addition, crude preparations of this oxidase were found to be relatively stable when stored up to one week either refrigerated or frozen, to have a specific activity of 2.8 nmoles/min/mg of protein, and to have a K, of 3.6 × 10−M ford,l‐β‐aminoisobutyric acid. Whether this high Km, is physiologically significant or not, however, will have to await further investigation. Preliminary (NH4)2SO4fractionation and affinity chromatography studies also indicated that this enzyme appears to be a unique and specific oxidase whose activity is separable from other marker enzymes, incl

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1981.tb05318.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY