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121.
Sergio Sgorbati Marisa Levi Elio Sparvoli Federica Trezzi Giovanni Lucchini 《Physiologia plantarum》1986,68(3):471-476
Cytometry and flow cytometry were used to study characteristics of fluorescence of the DNA-DAPI complex in nuclei released from different fresh and formaldehyde-fixed pea ( Pisum sativum L. cv. Lincoln) tissues. The two methods of isolation are compared and discussed as well as their possible use for quantitative analysis of DNA in plant tissues. With fixed tissues it is possible to obtain a number of nuclei sufficient for the flow cytometric analysis, even using small amounts of plant tissue. 相似文献
122.
Dion tomasellii sp. nov. occurs with an interrupted distribution from Guerrero to central Sonora. It is characterized by falcate to subfalcate leaflets. The populations from Sonora and northern Sinaloa are segregated asD. tomasellii var.sonorense on the basis of their narrower and glaucous leaflets. 相似文献
123.
124.
125.
Production planning in flexible manufacturing may require the solution of a large-scale discrete-event dynamic stochastic optimization problem, due to the complexity of the system to be optimized, and to the occurrence of discrete events (new orders and hard failures). The production planning problem is here approached for a multistage multipart-type manufacturing shop, where each work cell can share its processing time among the different types of parts. The solution of this problem is obtained by an open-loop-feedback control strategy, updated each time a new event occurs. At each event time, two coupled problems are solved: 1) a product-order scheduling problem, conditioned on estimated values of the production capacities of all component work cells; and 2) a production-capacity planning problem, conditioned on predefined sequences of the product orders to be processed. In particular, the article aims at defining a production planning procedure that integrates both analytical tools, derived from mathematical programming, and knowledge-based rules, coming from experience. The objective is to formulate a hybrid (knowledge-based/analytical) planning architecture, and to analyze its use for multicell multipart-type manufacturing systems. 相似文献
126.
Effect of cytoplasmic acidification on the membrane potential of T-lymphocytes: Role of trace metals
Summary The effect of lowering intracellular pH on the membrane potential (E
m
) of rat thymic lymphocytes was studied using the potential-sensitive dyebis-oxonol. Cells were acid loaded by addition of the electroneutral K+/H+ exchanging ionophore nigericin. Acidification to pH 6.3 in Na+-free solution resulted in a biphasic change inE
m
: an early transient hyperpolarization followed by a sustained depolarization. These changes were associated with a rise in cytosolic free Ca2+ ([Ca2+]
i
). The hyperpolarization was eliminated when the change in [Ca2+]
i
was prevented using BAPTA, an intracellular Ca2+ chelator. Moreover, a similar hyperpolarization was elicited by elevation of [Ca2+]
i
at physiological pH
i
using ionomycin, suggesting involvement of Ca2+-activated K+ channels. In contrast, the depolarization phase could not be mimicked by raising [Ca2+]
i
with ionomycin. However, intracellular BAPTA effectively inhibited the acidificationinduced depolarization. Inhibition was also obtained by extracellular addition of EGTA or dithiothreitol, even when the external free Ca2+ concentration remained unaltered. These observations suggested a possible role of contaminating trace metals. Cytosolic acidification is envisaged to induce intracellular accumulation of one or more trace metals, which induces the observed changes inE
m
. Accordingly, similar changes inE
m
can be induced without acidification by the addition of small amounts of Cu2+ to the medium. The ionic basis of theE
m
changes induced by acidification and the significance of these observations are discussed. 相似文献
127.
Roberto Bovara Giacomo Carrea Sergio Riva Francesco Secundo 《Biotechnology letters》1996,18(3):305-308
Summary Cholic acid (3,7,12-trihydroxy-5-cholanoic acid) was completely and selectively transformed into 12-ketoursodeoxycholic acid (3,7-dihydroxy-12-oxo-5-cholanoic acid) by means of two consecutive enzymatic steps catalyzed, the first, by 7- and 12-hydroxysteroid dehydrogenase and, the second, by 7-hydroxysteroid dehydrogenase. Coenzyme regeneration was carried out with -ketoglutarate-glutamate dehydrogenase and glucose-glucose dehydrogenase, respectively. 相似文献
128.
Sergio Archangelsky 《Review of Palaeobotany and Palynology》1996,90(3-4):287-302
During the late Paleozoic and early Mesozoic the Gondwana Supercontinent underwent dramatic geographic and climatic changes. Geologic and biologic factors concurrently played an important role modelling the vegetation of that time. The gymnospermic component of plant assemblages shows significant variations in composition and in the distribution of different taxa. Analysis of the assemblages shows that some plant groups dominated the scenario, such as the pteridosperms, glossopterids, corystosperms and, to a lesser degree, cordaites and conifers. Ginkgophytes, bennettites or cycads were less important in the Paleozoic but their numbers increased in the Triassic. Paleozoic assemblages were extensively dominated by glossopterids that became extinct in the earliest Mesozoic. Pteridosperms crossed the P—M barrier and became dominant during the Triassic, at a time when corystosperms evolved and radiated. Other groups became extinct in the Paleozoic, namely dicranophylls and cordaites. Conifers were represented by different families, restricted either to the Paleozoic or the Mesozoic. They were not conspicuous in the analysed assemblages. In some areas of Gondwana, taxa of the Euramerican alliance are present through a migrational mechanism that occurred during continental displacements which produced global climatic changes. Recent studies have shown that there are far more common elements between Euramerica and Gondwana than suspected up to now. These elements find their distribution especially in the western part of Gondwana (Africa—South America). 相似文献
129.
Giuliano Callaini Maria Giovanna Riparbelli Marcella Cintorino Sergio Antonio Tripodi Giorgio Bianciardi Piero Tosi Romano Dallai 《Biology of the cell / under the auspices of the European Cell Biology Organization》1994,81(1):39-45
Summary— Immunofluorescence and immunoelectron microscopy indicated that the antibody raised against the nuclear antigen Ki-67 of mammalian cells recognized antigenic determinants of early Drosophila embryos, localized on the outside of the nuclear envelope. Hence, the nuclear envelope of Drosophila appears to share a similar epitope with the chromosome scaffold of mitotic mammalian cells. With the progression of mitosis the antigen persisted around the mitotic spindle region and was also found in the pole regions at metaphase and anaphase. The antibody also stained the equatorial regions of the spindles from anaphase to late telophase. The antibody may therefore be used as a biochemical marker of the nuclear envelope for studying nuclear membrane biogenesis and behavior during the mitotic divisions of the Drosophila embryo. 相似文献
130.
Marco Vinceti Sergio Rovesti Cristina Marchesi Margherita Bergomi Gianfranco Vivoli 《Biological trace element research》1994,40(3):267-275
In a part of the municipal territory of Reggio Emilia, northern Italy, selenium in drinking water decreased from 7 μg/L to
less than 1 μg/L. In a cohort of 4419 individuals, previously exposed for at least 5 yr to the drinking water with higher
selenium content, the 7-yr temporal distribution of deaths for coronary disease and for stroke was analyzed to examine a possible
relationship with changes in drinking water selenium. From January 1986 until August 1988, when tap water selenium was 7 μg/L,
deaths for coronary disease were one in males and two in females. After the decrease in drinking water selenium, 21 and 10
coronary deaths were observed, respectively, in males and in females from September 1988 to December 1992. No significant
difference in the temporal distribution of stroke deaths was observed both in males and in females. Even if an effect of chance
and aging in the temporal distribution of coronary deaths may not be excluded, findings of the study seem to be consistent
with the hypothesis of a beneficial effect of selenium on coronary disease mortality. 相似文献