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31.
Michael G. Gabridge Marlene J. Bright Helen R. Richards 《In vitro cellular & developmental biology. Plant》1982,18(1):55-62
Summary Cell monolayer cultures were prepared from hamster tracheal explants by a collagenase exposure and subsequent incubation in
Waymouth’s MAB 87/3 medium. The epithelial outgrowth occurred on glass cover slips. Cilia on the monolayers continued to beat
normally after the “parent” explant was removed. Monolayer cultures infected withMycoplasma pneumoniae had significant amounts of attachment. A morphological analysis of the attachment was conducted with scanning electron microscopy.
Clusters, cocci, and filaments ofM. pneumoniae all attached to the epithelial cells, but the filaments were especially common. Mycoplasmas were seen in association with
both ciliated and nonciliated cell membranes. On ciliated cells, mycoplasmas were on the ciliary strands and on the cell membrane.
When located immediately adjacent to or in between cilia, mycoplasmas were oriented vertically with the constricted attachment
tip oriented down toward the host cell membrane. When located more than a micron away from the ciliary fibers, mycoplasmas
lay horizontally along the epithelial cell membrane. The photographic data suggest that clusters or “sperules” of mycoplasmas
may liberate individual mycoplasmas that attach to the cell membrane. It appears that the receptor sites forM. pneumoniae are rather uniformly distributed along the ciliated cell membrane, and are not restricted to the interciliary areas.
Electron microscopy was done with the cooperation of Dr. R. Macleod and the staff of the Center for Electron Microscopy at
the University of Illinois. Critical editorial review was provided by C. Dayton.
This investigation was supported in part by grants to M. G. G. from the National Institute of Allergy and Infectious Diseases
(AI 12559) and the National Heart, Lung, and Blood Institute (HL 23806), Bethesda, Maryland. 相似文献
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The migration of 51Cr-labeled nylon-wool separated mouse thoracic duct T cells has been followed in order to determine whether there is a circulation of small (nondividing) T cells through the small intestine. Approximately 6% of the injected dose of T-TDL localized in the small intestine (minus Peyer's patches). Experiments revealed that this gut-localizing cell population consisted almost entirely, if not exclusively, of lymphoblasts present in mouse T-TDL. When lymphoblasts and small lymphocytes from mouse T-TDL were separated by velocity sedimentation, and the migration of separated fractions was studied, we found large cells (66% blasts) migrated well to the gut but poorly to the lymph nodes, whereas small cells (2% blasts) showed minimal migration to the gut but localized randomly in lymph nodes and spleen. The in vivo distribution of small cells from T-TDL was similar to that of T-PLN. Furthermore, the recirculatory patterns of both 51Cr-labeled T-TDL and T-PLN were found to be identical as accessed by their rate of recovery in the thoracic duct lymph of recipient mice. These results support the notion that the vast majority of T-TDL and T-PLN are part of a common pool of recirculating T cells which recirculate randomly through lymph nodes and spleen and not the small intestine. 相似文献
34.
Dr. Wanderley de Souza Marlene Benchimol Cecilia Somlo Raul Dodsworth Machado Aida Hasson-Voloch 《Cell and tissue research》1979,202(2):275-281
Summary Membranes were isolated from the main electric organ of Electrophorus electricus and studied by means of cytochemistry and freezefracture. The membrane fractions consisted of vesicles inside-in as determined by localization of anionic sites using colloidal iron and cationized ferritin particles. The anionic sites were not homogeneously distributed on the surface of the vesicle. Freeze-fracture showed the presence of intramembranous particles associated with either protoplasmic (P) or extracellular (E) faces of the membrane. Regions of the membrane without particles were observed. The results are discussed in relation to the existence of association between intramembranous particles and membrane receptors.For all correspondence 相似文献
35.
S O Andrade H O da Silva Lopes M de Almeida Barros G G Leite S M Dias M Saueressig D Nobre J A Temperini 《Arquivos do Instituto Biológico》1978,45(2):117-136
Aspects of photosensitization in bovines grazing on pastures of Brachiaria decumbens Stapf infested with Pithomyces chartarum (Berk. & Curt.) M.B. Ellis infested all pastures 45(2):117-136, 1978. This paper reports experimental studies on photosensitization in bovines grazing on different pastures of Brachiaria decumbens Stapf in the "Cerrados" region (Planaltina, DF). Climatic conditions, zinc content and occurence of fungi on pastures were investigated. Pithomyces chartarum (Berk. & Curt.) M.B. Ellis infested all pastures examined. Photosensitization was observed in one animal maintained on a pasture of B. decumbens formed with seeds from Australia. Clinical and necropsy data were similar to those related in literature for sporidesmin-intoxicated animals. An isolate of P. chartarum and samples of bovine bile were assayed for sporidesmin presence. 相似文献
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37.
Michael E. Joesten Moira E. Royston Marlene Jimenez Axel Wadewitz Diana Melian Richard A. Lockshin 《Journal of insect physiology》1982,28(7):589-599
Larvae of Manduca sexta, (Sphingidae) increase their weight approx. 50% just before pupation and then secrete this fluid during the formation of their burrows. Time-lapse cinematography indicates that the fluid is ejected into the walls of the final burrow. It may offer some mechanical support; it is not particularly repellent to ants or mice, and it contains only small amounts of the alkaloids ingested from its preferred food plants. Comparison to other species indicates that the gain and loss of water is associated with burrowing behaviour; the fluid appears to be used in providing hydraulic pressure for burrowing, in forming and cementing the pupal chamber, and in acting as a CO2 trap underground. The secretion is a hypertonic, highly alkaline solution containing KHCO3 and small amounts of Na+, Ca2+, Mg2+, PO4?3 and some proteins. Haemolymph levels of K+ decrease, and those of Ca2+ increase, during the secretory phase. When radioactive calcium is injected into mature larvae, it appears promptly in the secretion. If however, the injection is given more than 24 hr before the animal begins secreting, then the calcium is bound to haemolymph protein and does not appear in the secretion. 相似文献
38.
Cintia Camila Silva Angelieri Christine Adams-Hosking Katia Maria Paschoaletto Micchi de Barros Ferraz Marcelo Pereira de Souza Clive Alexander McAlpine 《PloS one》2016,11(1)
A mosaic of intact native and human-modified vegetation use can provide important habitat for top predators such as the puma (Puma concolor), avoiding negative effects on other species and ecological processes due to cascade trophic interactions. This study investigates the effects of restoration scenarios on the puma’s habitat suitability in the most developed Brazilian region (São Paulo State). Species Distribution Models incorporating restoration scenarios were developed using the species’ occurrence information to (1) map habitat suitability of pumas in São Paulo State, Southeast, Brazil; (2) test the relative contribution of environmental variables ecologically relevant to the species habitat suitability and (3) project the predicted habitat suitability to future native vegetation restoration scenarios. The Maximum Entropy algorithm was used (Test AUC of 0.84 ± 0.0228) based on seven environmental non-correlated variables and non-autocorrelated presence-only records (n = 342). The percentage of native vegetation (positive influence), elevation (positive influence) and density of roads (negative influence) were considered the most important environmental variables to the model. Model projections to restoration scenarios reflected the high positive relationship between pumas and native vegetation. These projections identified new high suitability areas for pumas (probability of presence >0.5) in highly deforested regions. High suitability areas were increased from 5.3% to 8.5% of the total State extension when the landscapes were restored for ≥ the minimum native vegetation cover rule (20%) established by the Brazilian Forest Code in private lands. This study highlights the importance of a landscape planning approach to improve the conservation outlook for pumas and other species, including not only the establishment and management of protected areas, but also the habitat restoration on private lands. Importantly, the results may inform environmental policies and land use planning in São Paulo State, Brazil. 相似文献
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