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1.
Transverse alternating field electrophoresis (TAFE) 总被引:3,自引:0,他引:3
The rapid development of electrophoretic technology during the past five years has given us a stream of improvements in the area of pulsed-field separation techniques. This progression has culminated in the conception of TAFE, a simple, high resolution technique providing straight lane geometry and separation of fragments up to 9 million base pairs in length. Pulsed-field techniques will unquestionably play a major role in the forthcoming analysis of the human genome by facilitating restriction mapping and cloning of large fragments. We have no doubt that TAFE will allow scientists to do this type of genetic analysis, faster and better than ever before. 相似文献
2.
Susanna Voltolini Giovanni Orengo Luigi Fontana Arsenio Corrado Negrini 《Aerobiologia》1992,8(3):349-354
Summary Fifty workers from two grain elevator terminals were examined to evaluate the prevalence of respiratory symptoms and their relationship with grain dust exposure.Fifty per cent of subjects complained of respiratory symptoms (rhinitis, asthma, chronic cough and dyspnea on exertion). In 34% of the workers the ventilatory function revealed some abnormalities (slight or moderate obstruction).Twenty-two (44%) showed a positive cutaneous reaction to one or more of the allergens tested, mostly towardsDermatophagoides and storage mites. The self-measurement of PEF over 14 days in 27 workers, showed significant differences between symptomatic and asymptomatic subjects. In particular, the results obtained from the cutaneous reactions could suggest a bronchial hypereactivity, worsened by the working exposure to dusts. The monitoring of PEF appears to be a simple and useful method for investigating the relationship between respiratory symptoms and the working environment. 相似文献
3.
In Drosophila neuroblast cells, which give rise to the embryonic nervous system, undergo a limited number of asymmetric cell divisions. These cell lineages result in the formation of clusters of neurons when neuroblasts are isolated and cultured. A significant proportion of these neural cell clusters (NCC) arise from individual precursor cells. The formation of NCC containing more than two neurons is repressed when DNA synthesis is inhibited. Cell division during NCC development was examined by [3H]thymidine autoradiography. The pattern of DNA synthesis by neural cells was that expected based on observations in situ. The pattern in individual NCC was consistent with single precursor origins for more than 80% of NCC, under our conditions of culture. Based on this, we show that the largest neural precursors at gastrulation undergo the most cell divisions in culture. The neuroblast cell division cycle averages approximately 1.5 hr, and is similar to that of blastoderm cells. 相似文献
4.
Abdullah Jaffer Brian Harvey Vivienne Ann Russell Machteld Elizabeth Carstens Anna Susanna de Villiers Joshua Joachim Fransua Taljaard 《Neurochemical research》1993,18(10):1057-1061
Chronic treatment of rats with lithium chloride was examined in order to determine its effect on hypothalamic monoamine and metabolite content, basal thyrotropin (TSH) secretion and thyroid function. The hypothalamic concentrations of noradrenaline (NA), dopamine (DA) and its metabolites, dihydroxyphenylacetic acid. (DOPAC) and homovanillic acid (HVA) in the lithium treated rats remained unaltered when compared to control levels. NA turnover and the NA metabolite, 3-methoxy-4-hydroxyphenylglycol (total MHPG), were significantly lower (p<0.01), whereas both serotonin (5-HT) and its metabolite, 5-hydroxyindole-3-acetic acid (5-HIAA), were significantly higher (p<0.01 and p<0.02, respectively) in the lithium treated rat hypothalami than in controls. Chronic lithium treatment significantly elevated basal TSH levels (p<0.05). This effect was antagonized by methylp-hydroxybenzoate (methylparaben, p<0.01), which did not itself affect basal TSH levels. Free serum T3 and T4 levels were not significantly affected by chronic lithium treatment, although T4 tended to be slightly lower than control levels. The monoamine changes observed in the hypothalamus of lithium treated rats did not appear to account for the elevated TSH levels observed in these rats since NA activity which is generally regarded as stimulatory was decreased and 5-HT which has an inhibitory effect on TSH secretion, was increased. The elevated TSH levels may have been due to a reduced negative feedback inhibition of TSH release by the mildly reduced circulating T4 levels caused by chronic lithium treatment. A further possibility is that the pituitary cGMP (and hence TSH) response to TRH may have been enhanced by chronic lithium treatment and methylparaben may have antagonized this effect. 相似文献
5.
6.
Charles A. Tyson Carol E. Green Susanna E. LeValley Robert J. Stephens 《In vitro cellular & developmental biology. Plant》1982,18(11):945-951
Summary Hepatocytes from livers of rats loaded by Fe-dextran treatment were isolated by an in situ collagenase perfusion technique
and evaluated for their biochemical, cytochemical, and morphological characteristics in cell culture. Iron loads 15 times
higher than in normal rat liver cells isolated in the same way were retained in the preparations with 40% present as hemosiderin.
A simple centrifugation-mathematical approach is described for the calculation of Fe content in the hepatocyte (95%) and reticuloendothelial
(5%) fractions in the isolates. The cells were cultured for 22 h without loss of protein synthesis capability or significant
changes in cell count, viability, endogenous glutamate-oxaloacetate transaminase (GOT) or Fe and were morphologically similar
in most respects to unloaded (normal) hepatocytes similarly cultured. Studies are in progress to assess the utility of these
preparations as a model for Fe mobilization from Fe-loaded animals.
This work is supported by National Institutes of Health Grants AM 25647-03 (M. Dawson, Principal Investigator) and GM 28158-01
(C. Tyson, Principal Investigator). The technical assistance of Mr. Jack E. Dabbs, Mr. Charles Hart, and Mr. Randy Douglas
is acknowledged. 相似文献
7.
A. A. Garfunkel T. N. Harris Susanna Harris 《Cancer immunology, immunotherapy : CII》1980,8(2-3):87-93
Summary Alloantibody-containing globulins that can suppress the production of hemolytic antibody plaques by antigenically stimulated Balb/c spleen cells were tested for their effect on Balb/c plasmacytoma cells. Two plasmacytomas, MOPC 21 and MOPC 315, which normally produce IgGl and IgA, respectively, were treated with CBA anti-Balb/c globulin from which the cytotoxic antibody had been largely removed by differential absorption. The effects on synthesis of the Ig's were studied in three experimental modes.1. When the tumor cells were pretreated with the antibody before incubation with 3H-thymidine labeled aminoacids, there was suppression of the synthesis of immunoglobulins, as measured in both the cell contents and the medium. The suppression was most marked at the highest concentration of antibody and decreased progressively with dilution. In the case of other or smaller peptides not precipitated by anti-Ig but precipitable by TCA, this could be demonstrated only in the most recently synthesized peptides, those found within the cells.2. When the exposure to the suppressive antibody was simultaneous with the incubation of tumor cells and labeled aminoacids suppression was again demonstrated, indicating that the suppressive effect was expressed as early as the synthesis of the peptides.3. Even when the exposure to labeled aminoacids began before the incubation with antibody, the cell contents, which included the most recently synthesized peptides, still showed the same effects of the successive dilutions of the suppressive antibody as the cell contents from the other modes of exposure. In the medium, however, there was an additional effect under these experimental conditions. Labeled material appeared in amounts that increased with increasing concentration of the suppressive antibody, suggesting the release from the cells of the peptides whose synthesis was interrupted by the antibody. 相似文献
8.
Growth effects of lithium chloride in BALB/c 3T3 fibroblasts and madin-darby canine kidney epithelial cells 总被引:2,自引:0,他引:2
The ability of LiCl to initiate DNA synthesis was studied in Madin-Darby canine kidney (MDCK) cells, and mouse BALB/c 3T3 fibroblasts. In a defined culture medium lacking serum, LiCl increased DNA synthesis in BALB/c 3T3 cells 100–200% over control values. Maximum DNA synthesis was observed with concentrations of LiCl between 10 and 25 mM and increases from 40–50% over control were observed with concentrations as low as 1 mM. Exposure of BALB/c 3T3 cultures to LiCl resulted in an increase in the percentage of cells initiating DNA synthesis, total DNA content and cell number. Lithium chloride, in combination with insulin or epidermal growth factor (EGF), had either an additive or synergistic effect upon the growth of BALB/c 3T3 fibroblasts. MDCK cells proved refractory to the growth actions of LiCl, although they responded to EGF and insulin with increased DNA synthesis. Lithium chloride appears to have a direct effect on cell proliferation in some but not all cell types. 相似文献
9.
10.
Metabolic engineering of isoprenoid biosynthesis in Arabidopsis for the production of taxadiene, the first committed precursor of Taxol 总被引:1,自引:0,他引:1
Besumbes O Sauret-Güeto S Phillips MA Imperial S Rodríguez-Concepción M Boronat A 《Biotechnology and bioengineering》2004,88(2):168-175
Paclitaxel (Taxol) is a widely used anticancer isoprenoid produced by the secondary metabolism of yew (Taxus sp.) trees. However, only limited amounts of Taxol or related metabolites (taxoids) can be obtained from the currently available sources. In this work we have taken the first step toward genetically engineering the biosynthesis of taxoids in angiosperms. The first committed step in Taxol biosynthesis is the production of taxadiene from geranylgeranyl diphosphate (GGPP), catalyzed by the plastid-localized enzyme taxadiene synthase (TXS). A recombinant T. baccata TXS lacking the putative plastid targeting peptide and fused to a C-terminal histidine (His) tag was shown to be enzymatically active in Escherichia coli. Constitutive production of the full-length His-tagged enzyme in Arabidopsis thaliana plants led to the accumulation of taxadiene and concomitant growth retardation and decreased levels of photosynthetic pigment in transgenic plants. Although these phenotypes may derive from a toxic effect of taxadiene, the lower accumulation of endogenous plastid isoprenoid products such as carotenoids and chlorophylls in transgenic plants also suggests that the constitutive production of an active TXS enzyme might alter the balance of the GGPP pool. Induction of transgene expression using a glucocorticoid-mediated system consistently resulted in a more efficient recruitment of GGPP for the production of taxadiene, which reached levels 30-fold higher than those in plants constitutively expressing the transgene. This accomplishment illustrates the possibility of engineering the production of taxoids and other GGPP-derived isoprenoids in crop plants despite the constraints associated with limited knowledge with regard to regulation of GGPP availability. 相似文献