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A simple modification of nuclear staining after acid hydrolysis has been made which provides easy identification of quail nuclear markings in a chick-quail chimera. This method also improves the histologic detail normally seen with hematoxylin and eosin when compared to the more commonly used Feulgen reaction. Embryonic tissues can be fixed in Zenker's or Helly's solution and the sections obtained are hydrolyzed in acid (3.5 N HCl at 37 C for 40-50 min). After acid hydrolysis the sections are stained with hematoxylin and eosin rather than Schiff reagent and fast green. The interphase nuclei of chick cells show homogeneous or mottled purplish blue staining, while quail nuclei contain a dark blue spot. This staining corresponds to the reddish purple staining of the quail's heterochromatin seen adjacent to the nucleolus in the standard Feulgen stain. This new technique facilitates identification of quail cell types in the chick host and provides superior histology of the chick tissues by demonstrating cytoplasmic detail. 相似文献
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The interpretation of central 3,4-dihydroxyphenylethylamine (dopamine, DA) metabolism, as indicated by determinations in rat cisternal CSF, was investigated using intrastriatal injection of the DA neurotoxin 6-hydroxydopamine (6-OHDA) and intraperitoneal injection of the noradrenergic neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4). DA turnover was subsequently determined by measurement of the rate of accumulation of total 3,4-dihydroxyphenylacetic acid and homovanillic acid (DOPAC + HVA) in the CSF after probenecid was given. Two days later the rats were killed, and metabolism of DA and 5-hydroxytryptamine (5-HT) was investigated by determining levels of the amines and their metabolites in brain regions. Although 6-OHDA greatly decreased striatal DA metabolism, this was not paralleled by DA turnover as indicated by CSF, as this fell only moderately and approximately in parallel with results for the brain as a whole. 5-HT metabolism was essentially unaltered. DSP4 considerably depleted noradrenaline and caused smaller decreases of 5-HT metabolism in some regions. However, DA metabolism was not significantly affected, either in brain or CSF, which suggests that noradrenaline neurones make only a small contribution to central DA metabolism. Results as a whole suggest that DOPAC and HVA concentrations in rat cisternal CSF reflect whole brain DA metabolism and derive predominantly from DA neurones in extrastriatal regions of the brain. 相似文献
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We address the question of the long term coexistence of three interacting species whose dynamics are governed by the ordinary differential equations x
i
= X
i
f
i
(i = 1, 2, 3). In order for any theory in this area to be useful in practice, it must utilize as little information as possible concerning the forms of the f
i
, in view of the great difficulty of determining these experimentally. Here we obtain, under rather general conditions on the equations, a criterion for judging whether the species will coexist in a biologically realistic manner. This criterion depends only on the behaviour near the one or two species equilibria of the two dimensional subsystems, the behaviour there being relatively easy to examine experimentally. We show that with the exception of one class of cases, which is a generalization of a classical example of May and Leonard [21], invasibility at each such equilibrium suitably interpreted is both necessary and sufficient for a strong form of coexistence to hold. In the exceptional case, a single additional condition at the equilibria is enough to ensure coexistence. 相似文献
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The question of whether all species in a multispecies community governed by differential equations can persist for all time is one of the most important in theoretical ecology. However, criteria for this property vary widely, asymptotic stability and global asymptotic stability being two of the conditions most widely used. In fact neither of these criteria appears to reflect intuitive concepts of persistence in a satisfactory manner: the first because it is only a local condition, the second because it rules out cyclic behavior. We argue here that a more realistic criterion is that of “permanent coexistence,” which essentially requires that there should be a region separated from the boundary (corresponding to a zero value of the population of at least one species) which all orbits enter and remain within. A mathematical technique for establishing permanent coexistence is illustrated by an application to the long-standing problem of predator-mediated coexistence in a two-prey one-predator community. 相似文献
9.
The development and assessment of DNA and oligonucleotide probes for the specific detection of Bacillus anthracis 总被引:1,自引:0,他引:1
R.A. Hutson C.J. Duggleby J.R. Lowe R.J. Manchee P.C.B. Turnbull 《Journal of applied microbiology》1993,75(5):463-472
Two DNA probes and a number of oligonucleotide probes were designed from the virulence factor genes of Bacillus anthracis. These probes were tested for specificity against 52 B. anthracis strains and 233 Bacillus strains encompassing 23 other species. A rapid slot blotting technique was used for screening the large numbers of isolates involved. All probes tested appeared to be specific for B. anthracis under high stringency conditions. These probes could differentiate between virulent and avirulent strains. The probes were also applied to the detection of B. anthracis in routine environmental and clinical samples. A non-radioactive hybridization and detection system based on digoxigenin-11-dUTP was developed. 相似文献
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In synchronized Chlorella sorokiniana cells, the NH4+ inducibleNADP-specific glutamate dehydrogenase enzyme (NADP-GDH) accumulatedin a linear manner throughout the first cell cycle. Early inthe following second cell cycle, an increase in its rate ofaccumulation occurred that was proportional to the increasein total cellular DNA in the previous cell cycle. In synchronizedbacterial cells, increases in rate of linear accumulation ofinducible enzymes coincide with the time of replication of theirstructural genes. To determine whether the rate change in NADPGDHaccumulation resulted from a delay in replication of its nuclearstructural gene (gdhN) in fully induced C. sorokiniana cells,the cell cycle timing of replication of this gene was comparedto that of another nuclear gene, nitrate reductase (nia), andof a chloroplast gene, ribulose bisphosphate carboxylase large-subunit(rbcL), in synchronized cells cultured in NH4+ or NO3(uninduced) medium. The gdhN and nia genes replicated withinthe period of nDNA synthesis and rbcL within the period of ctDNAsynthesis in cells growing in either nitrogen source. Therefore,the delayed rate change in enzyme accumulation results froma process that regulates expression of the gdhN gene after itsreplication. (Received July 16, 1994; Accepted November 28, 1994) 相似文献