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81.
82.
Infection of BALB/c mice with the M variant of encephalomyocarditis virus resulted in the development of a paralytic syndrome in 7 to 10 days. The paralysis was maximal during the period of viral clearance; most of the animals recovered from the initial deficit and showed no delayed recurrences. Pathologically, the white matter of brain and spinal cord showed well-demarcated areas of perivascular cuffing, demyelination, and, during recovery, remyelination by oligodendrocytes--all suggestive of postinfectious encephalomyelitis. Depletion of either the CD4 or CD8 subset of T cells in vivo with the appropriate monoclonal antibody, GK1.5 or 2.43, respectively, administered one day (24 h) prior to infection was sufficient to limit the development of the paralytic syndrome by 79% (GK1.5) and 82% (2.43).  相似文献   
83.
This report concerns development of a cell-free system from rat liver to study transport of membrane constituents from the Golgi apparatus to the plasma membrane. Highly purified Golgi apparatus as donor and a mixture of sheets and vesicles as plasma membrane acceptor fractions were combined to analyze requirements for lipid and protein transport. In the reconstituted system, the Golgi apparatus donor was in suspension. To measure transfer, membrane constituents of the donor membranes were radiolabeled with [3H]acetate (lipids) or [3H]leucine (proteins). The plasma membrane vesicles were used as the acceptor and were unlabeled and immobilized on nitrocellulose for ease of recovery and analysis. The reconstituted cell-free transfer was dependent on temperature, but even at 37 degrees C, the amount of transfer did not increase with added ATP, was not specific for any particular membrane fraction or subfraction nor was it facilitated by cytosol. ATP was without effect both in the presence or absence of a cytosolic fraction capable of the support of cell-free transfer in other systems. In contrast to results with ATP, NADH added to the reconstituted system resulted in an increased amount of transfer. A further increase in transfer was obtained with NADH plus a mixture of ascorbate and dehydroascorbate to generate ascorbate free radical. The transfer of labeled membrane constituents from the Golgi apparatus to the plasma membrane supported by NADH plus ascorbate radical was stimulated by a cytosol fraction enriched in less than 10 kDa components. This was without effect in the absence of NADH/ascorbate radical or with ATP as the energy source. Specific transfer was inhibited by both N-ethylmaleimide and GTP gamma S. The findings point to the possibility of redox activities associated with the trans region of the Golgi apparatus as potentially involved in the transport of membrane vesicles from the Golgi apparatus to the cytoplasmic surface of the plasma membrane.  相似文献   
84.
In this paper, we describe a study of the role of turbulencein the loss by sedimentation of phytoplankton cells from themixed layer. The approach presented allows the quantificationof the sedimentation rate of phytoplankton in the whole rangeof turbulence levels of this layer. Two types of phytoplanktercan be distinguished according to the effect that turbulencecan exert on their sedimentation rate. The rate of those cellswhose settling velocity is lower than –1 m day–1will not be modified by turbulence. The sedimentation rate ofcells with higher settling velocities can, however, be modifiedby the level of turbulence. A set of dimensionless numbers isgiven to delimit several processes that are important in thedynamics of phytoplankton sedimentation in a turbulent regime.The use of these dimensionless numbers suggests that an increasein the turbulence level in the mixed layer does not always implya decrease in the sedimentation rate of phytoplankton cells.  相似文献   
85.
A genetic linkage map of Theobroma cacao (cocoa) has been constructed from 131 backcross trees derived from a cross between a single tree of the variety Catongo and an F1 tree from the cross of Catongo by Pound 12. The map comprises 138 markers: 104 RAPD loci, 32 RFLP loci and two morphologic loci. Ten linkage groups were found which cover 1068 centimorgans (cM). Only six (4%) molecular-marker loci show a significant deviation from the expected 11 segregation ratio.The average distance between two adjacent markers is 8.3 cM. The final genome-size estimates based on two-point linkage data ranged from 1078 to 1112 cM for the cocoa genome. This backcross progeny segregates for two apparently single gene loci controlling (1) anthocyanidin synthesis (Anth) in seeds, leaves and flowers and (2) self-compatibility (Autoc). The Anth locus was found to be 25 cM from Autoc and two molecular markers co-segregate with Anth. The genetic linkage map was used to localize QTLs for early flowering, trunk diameter, jorquette height and ovule number in the BC1 generation using both single-point ANOVA and interval mapping. A minimum number of 2–4 QTLs (P<0.01) involved in the genetic expression of the traits studied was detected. Coincident map locations of a QTL for jorquette height and trunk diameter suggests the possibility of pleiotropic effects in cocoa for these traits. The combined estimated effects of the different mapped QTLs explained between 11.2% and 25.8% of the phenotypic variance observed in the BC1 population.  相似文献   
86.
Abstract: Formation of the definitive kidney in Macaca fascicularis embryos was investigated using light and electron microscopy. Appearance of the definitive kidney at stage 14 was indicated by the ureteric bud invading the metanephrogenic blastema. Glomerular capillaries originate from the connective tissue that surrounds the developing renal vesicle. At 46–100 days gestational age the more developed glomeruli show thinning of the capillary endothelium, thickening of the basal membrane, and presence of pedicels, suggesting a capability of renal function.  相似文献   
87.
Drought signal transduction in plants   总被引:5,自引:0,他引:5  
Water deficit is one of the most common environmental limitations of crop productivity by affecting growth through alterations in metabolism and gene expression. The mechanisms involved in drought perception and signal transduction pathways are poorly understood. The participation of the plant hormone abscisic acid (ABA) has been well established. ABA levels increase when there are changes in the environment that result in cellular dehydration. Different approaches have been taken to understanding the molecular responses to desiccation and how ABA regulates gene expression. Recent efforts have identified particular topics of importance in the dissection of the signal transduction pathway which are summarized as follows: physiological approaches: identification of signalling molecules. Genetic approaches: the use of mutants, and Molecular approaches: promoter analysis.  相似文献   
88.
Pistachio fruit components, including hulls (mesocarps and epicarps), seed coats (testas), and kernels (seeds), all contribute to variable aflatoxin content in pistachios. Fresh pistachio kernels were individually inoculated with Aspergillus flavus and incubated 7 or 10 days. Hulled, shelled kernels were either left intact or wounded prior to inoculation. Wounded kernels, with or without the seed coat, were readily colonized by A. flavus and after 10 days of incubation contained 37 times more aflatoxin than similarly treated unwounded kernels. The aflatoxin levels in the individual wounded pistachios were highly variable. Neither fungal colonization nor aflatoxin was detected in intact kernels without seed coats. Intact kernels with seed coats had limited fungal colonization and low aflatoxin concentrations compared with their wounded counterparts. Despite substantial fungal colonization of wounded hulls, aflatoxin was not detected in hulls. Aflatoxin levels were significantly lower in wounded kernels with hulls than in kernels of hulled pistachios. Both the seed coat and a water-soluble extract of hulls suppressed aflatoxin production by A. flavus.  相似文献   
89.
The informativeness and inheritance of randomly amplified polymorphic DNA (RAPD) markers were investigated in an intraspecific F1 progeny derived from two heterozygous parents. The analysis confirmed the utility of RAPD markers for comparing candidate parents for the development of a molecular genetic map, and provided numerous markers for linkage analysis in a crop with a very limited history of classical or molecular genetic studies. Six potential parental lines (themselves F1 hybrid clones) showed between 1.82 and 0.62 segregating bands per primer in three hybrid families. Forty-three percent (309) of 722 primers produced polymorphic products in the most informative of these three crosses, revealing 328 single-dose (SD) markers segregating 1:1 for presence/absence in a progeny of 90 individuals. A second class of informative markers were those present in both parents but segregating in the progeny. Fifty-seven or 67% of the monomorphic but segregating markers exhibited the 3:1 ratio expected for SD dominant markers in a cross between heterozygotes. Linkage groups were constructed from the segregation of SD RAPD markers originating in the female (TMS 30572) and the male (CM2177-2) parent. Key words : RAPDs, molecular markers, genetic segregation, Manihot, single-dose markers.  相似文献   
90.
Contamination studies by ochratoxin A on pork kidney and chicken liver has been carried out in Catalonia (Spain). 73% of the pork kidney samples analyzed did not contain an amount of ochratoxin A over our detection limit (0.5 ng/g) whereas only 7% had contamination higher than 1 ng/g. None of the chicken samples analyzed were contaminated by this toxin above the detection limit. All contamination levels found are below the maximum levels accepted by several countries for this kind of material. A confirmative test is necessary before discarding false positive samples.  相似文献   
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