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351.
THE VEGETATIONAL HISTORY OF PARTS OF SOUTH AND EAST DURHAM 总被引:7,自引:7,他引:0
352.
BARBARA B. ELLENBOGEN S. H. HUTNER KATHLEEN M. TAMBURRO 《The Journal of eukaryotic microbiology》1972,19(2):349-354
SYNOPSIS. An osmotic growth requirement for the trypanosomatid Crithidia fasciculata became conspicuous at 32 C. Osmo-supportive compounds were surveyed at 28 vs. 33 C, in “low-osmotic” defined medium. Effective osmotic support was provided by many compounds, e.g., glycerophosphate, sorbitol, mannitol, glycerol, Na isethionate, glycine, arginine, KCl, NaCl, NH4Cl, and K2SO4. The nonspecificity of the requirement was thus evident, but inactivity of the presumably poorly adsorbable pentaerythritol indicated that osmotic pressure was a likely but insufficient condition for satisfying the temperature-enhanced growth requirement most clearly expressed as a need for osmotic support. Fortification of the medium with a combination of glycerophosphate, glycine, glycerol, and Tween 80 permitted good growth at 35 C. Possible relations between the temperature-enhanced osmotic requirement cell membrane damage, and morphological phases of Trypanosoma and Leishmania are discussed. 相似文献
353.
In the context of a broader ecological investigation, food habits of giraffe were studied in Tsavo National Park (East). The only method employed was direct observation of feeding animals in the field. Each instance in which one animal fed on one individual plant was counted as one food record for this plant species; 4025 records are analysed. A total of sixty-six plant species was found to be eaten, the great majority being trees and shrubs, with a few creepers and vines. There were marked seasonal differences in the diet of giraffe, deciduous trees, shrubs and vines being dominant in the green season, evergreen plants (partly in riverine forest) in the dry season. All the trees and larger shrubs common in the study area were eaten by giraffe, while few records for very small shrubs and none for herbs and grasses were obtained. An analysis of the available vegetation was made in part of the dry-season habitat, and for twenty species the frequency in the habitat was compared with the frequency in the giraffe's diet, revealing selection for or against certain species. Giraffe utilized the upper vegetation layers, where available, but overall c. 50% of all browsing was below 2 m above ground, i.e. within reach of smaller browsers. Results of this study are compared with what is known on food habits of giraffe in other areas. Possible competition of giraffe with other browsers and the relationship between giraffe and their habitat are discussed. Continued survival of giraffe, and other browsers, in Tsavo National Park depends primarily on (1) adequate control of fire, and (2) the impact of future vegetation changes on the amount and variety of available browse plants. 相似文献
354.
Rapid detection and serotyping of prunus necrotic ringspot virus in perennial crops by enzyme-linked immunosorbent assay 总被引:5,自引:0,他引:5
Strains of prunus necrotic ringspot virus (NRSV) in hop and plum cultivars were rapidly and conveniently detected and serotyped by enzyme-linked immunosorbent assay. Antisera produced against the G isolate of NRSV from cherry and the Paradise isolate of apple mosaic virus (ApMV) from apple were used concurrently to ensure detection of all serotypes and to differentiate between them. Both NRSV and ApMV serotypes occurred in plum either as single or mixed infections. By contrast, the NRSV serotype was not found in hop, which contained either ApMV or a serotype intermediate between NRSV and ApMV. 相似文献
355.
Two aspects of hop latent viroid (HLVd) relevant to control were examined: the production of viroid-free plants from infected material and transmission of HLVd in the field. Plants free from HLVd were obtained by a combination of storing infected source plants at low temperature (2–4o C in the dark) for several months followed by meristem culture using small explants. A total of 77 plants of six cultivars and male pollinator clones were grown from meristems and 28 of these were free from HLVd. Tests showed that the cutting of stems (mimicking the use of tools) was more effective than abrasion (mimicking natural plant to plant contact) for the mechanical transmission of HLVd between hop plants. When field-grown test plants were inoculated, infection occurred more commonly in May before plants had grown large enough for significant contact between neighbouring plants than later in the season. The aphid Phorodon humuli could not be shown to transmit HLVd.
These results indicate that all hop varieties and pollinator clones can be made available to the industry free from HLVd and that the chances of infection can be reduced by avoiding early-season cultural operations that cut into hop shoots. 相似文献
These results indicate that all hop varieties and pollinator clones can be made available to the industry free from HLVd and that the chances of infection can be reduced by avoiding early-season cultural operations that cut into hop shoots. 相似文献
356.
We observed that Plasmodium berghei sporozoite-infected Anopheles stephensi was not impaired in its ability to locate blood on a host. When probing rats, infected mosquitoes took as long as non-infected mosquitoes to locate blood. Contrary to previous suggestions, infective mosquitoes delivered sporozoites into mineral oil even after extensively probing a vertebrate host. We observed that, in mosquitoes having probed a host, both the mean number of sporozoites ejected over 3 min into oil (35.9 v. 31.7 sporozoites) and the proportion of mosquitoes delivering sporozoites (60% v. 50%) were similar to mosquitoes not having probed. We then developed a model of sporozoite delivery, taking into account observations that sporozoites are clumped in the lumen of the glands as well as upon delivery, and that output is uneven and inconsistent. We conclude that clumping optimizes transmission, if a threshold of infection exists and the mean number of sporozoites per clump is greater than the threshold. 相似文献
357.
STUART M. KRASSNER JOHNNY CHANG SUNG PAK KIM-OANH LUC BARBARA GRANGER 《The Journal of eukaryotic microbiology》1993,40(2):224-230
ABSTRACT. The phorbol ester TPA (phorbol 12-myristate 13-acetate) substitutes for CO2 as an agonist for transforming Trypanosoma cruzi epimastigotes to the metacyclic trypomastigote stage in a starvation medium consisting of phosphate buffered saline + 10 mM proline, 10 mM sodium acetate and 0.035% NaHCO3. Since TPA is thought to stimulate protein kinase C by mimicking the activity of the secondary messenger diacylglycerol, the above result suggested that T. cruzi metacyclogenesis could be activated by a Ca2+-dependent protein kinase C signal induction pathway. Accordingly, cytosolic calcium flux ([Ca2+]i) in epimastigotes, activated with 5% CO2 or TPA (10-7 M), was measured with the Ca2+ molecular probe, fluo-3AM. In addition, [Ca2+]i was measured in cells incubated with putative metacyclogenic agonists (e.g. proline, glutamate, bioamines, ionophores and catecholamines). None of the compounds studied, except for EGTA, affected cytosolic Ca2+ levels. Control assays with 11 μM thapsigargin, which mobilizes noncytoplasmic Ca2+ stores by inhibiting endoplasmic reticulum Ca2+-ATPase. validated our fluorometric assay procedure. Although thapsigargin significantly increases cytoplasmic Ca2+ fluorescence, it has no effect on transformation. The protein kinase C inhibitors staurosporine, H-7 and HA 1004 were tested for their effect on T. cruzi metacyclogenesis. Low concentrations of staurosporine and HA 1004 significantly elevated Pent strain transformation while H-7 had no effect on Peru strain metacyclogenesis. Inhibitor H-7 did significantly depress CL transformation. the results indicate that induction of T. cruzi metacyclic trypomastigote formation by CO2 and TPA is not accompanied by changes in cytosolic Ca2+ and do not provide supporting evidence for participation of a protein kinase C-mediated phosphoinositide cascade in metacyclogenesis. 相似文献
358.
Abstract: Shark bite marks, including striae, sulci and abrasions, in a well‐preserved fossil dolphin skeleton referred to Astadelphis gastaldii (Cetacea, Delphinidae) from Pliocene sediments of Piedmont (northern Italy), are described in detail. The exceptional combination of a fossil dolphin having a significant part of the skeleton preserved and a large number of bite marks on the bones represents one of the few detailed documentations of shark attack in the past. Most bite marks have been referred to a shark about 4 m long with unserrated teeth, belonging to Cosmopolitodus hastalis, on the basis of their shape and their general disposition on the dolphin skeleton. According to our hypothesis, the shark attacked the dolphin with an initial mortal bite to the abdomen from the rear and right, in a similar way as observed for the living white shark when attacking pinnipeds. A second, less strong, bite was given on the dorsal area when the dolphin, mortally injured, probably rolled to the left. The shark probably released the prey, dead or dying, and other sharks or fishes probably scavenged the torn body of the dolphin. 相似文献
359.
BARBARA PETRIDOU MARGUERITE CUNY FRANOISE HAYES 《The Journal of eukaryotic microbiology》1983,30(3):573-577
Comparison of the electrophoretic migration patterns of proteins of active 40S and 60S ribosomal subunits isolated from nine amicronucleate strains of Tetrahymena of known phenoset revealed strain dependent differences which correlated with the phenoset classification of these strains as determined by Borden, Whitt & Nanney, who compared isoenzyme patterns. 相似文献
360.
BARBARA F. PALSER WILLIAM R. PHILIPSON F.L.S. MELVA N. PHILIPSON 《Botanical journal of the Linnean Society. Linnean Society of London》1989,101(4):363-393
PALSER, B. F., PHILIPSON, W. R. & PHILIPSON, M. N., 1989. Development of ovule, megagametophyte and early endosperm in Rhododendron L. (Ericaceae). Complete development of ovule, megagametophyte and early endosperm is compared for 15 species (almost complete for four additional species) representing all subgenera and most sections of Rhododendron. In all the ovule is anatropous, unitegmic, tenuinucellate with the lateral and micropylar nucellus disintegrating completely. The integument has a tanniniferous epidermis, starch around egg apparatus and micropyle, an endothelium and hypostase. Differences occur in time of closure of the micropyle and its final length, total proportion of ovule occupied by gametophyte and by formation of ovule tails only in section Vireya. Megagametophyte development follows the Polygonum pattern in all species. A single archesporial cell becomes the megaspore mother cell directly, and the chalazal spore of a linear tetrad functions. Between the eight-nucleate stage and maturity the micropylar end of the gametophyte elongates into the micropyle. Starch is characteristically present in the mature central cell. The pollen tube penetrates porogamously and double fertilization is rapid. Endosperm development starts promptly and is cellular, first forming a linear row of four cells. The zygote elongates slightly but does not divide during the stages followed. Differences may occur in time of enlargement, orientation of some mitoses, some cellular characteristics, amount of starch present and final size of megagametophyte. Rare abnormalities occur. 相似文献