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11.
A Bardoni M P Pagliula G Pallavicini S Rindi A A Castellani G De Luca 《The Italian journal of biochemistry》1989,38(5):360-368
UDP-glucose dehydrogenase (UDPGDH) was extracted and partially purified from different rat tissues and the kinetic parameters and some properties of the enzyme were determined and compared. The pH optimum ranged between 8.6 and 9.4 for liver and kidney UDPGDH and between 8.4 and 8.6 for skin and lung UDPGDH. Liver and kidney enzymes showed a similar affinity for both UDPG and NAD. Lung and skin enzymes also showed similar affinity for both substrates, which differed however from that of liver and kidney UDPGDH. Both liver and kidney enzymes had a higher heat stability and a different electrophoretic mobility compared to skin and lung UDPGDH. These data suggest the existence of different tissue specific forms of the enzyme. 相似文献
12.
Targeting of T7 RNA polymerase to tobacco nuclei mediated by an SV40 nuclear location signal 总被引:9,自引:0,他引:9
Michael W. Lassner Aubrey Jones Steve Daubert Luca Comai 《Plant molecular biology》1991,17(2):229-234
We have expressed two T7 RNA polymerase genes by electroporation into tobacco protoplasts. One of the genes was modified by inserting nucleotides encoding a viral nuclear localization signal (NLS) from the large T antigen of SV40. Both T7 RNA polymerase genes directed synthesis of a ca. 100 kDa protein in the electroporated protoplasts. T7 RNA polymerase activity was detected in extracts of protoplasts electroporated with both genes. Immunofluorescence analysis of these protoplasts indicated that only the polymerase carrying the NLS accumulated in the cell nucleus. These experiments suggest that mechanisms involved in the transport from the cytoplasm to the nucleus are similar in plant and animal cells. This system demonstrates the feasibility of T7 RNA polymerase-based approaches for the high-level expression of introduced genes in plant cells. 相似文献
13.
Phorbol esters enhance attachment of NIH/3T3 cells to laminin and type IV collagen substrates 总被引:2,自引:0,他引:2
The effect of phorbol esters on the adhesive properties of NIH/3T3 mouse fibroblasts was investigated using plastic substrates precoated with the extracellular matrix proteins fibronectin, collagen, and laminin. Treatment with phorbol 12-myristate 13-acetate (PMA) enhanced NIH/3T3 cell attachment to laminin and type IV collagen substrates but had little or no effect on attachment to fibronectin and type I collagen substrates. The effect of PMA in enhancing cell attachment to laminin and type IV collagen substrates was dose dependent between 10(-9) and 10(-7) M. PMA was effective as early as 30 min; the effect reached a maximum at 2 h and decreased gradually. Phorbol 12, 13-dibenzoate and phorbol 12, 13-diacetate were effective but to a lesser extent and phorbol 12-myristate and phorbol 13-acetate showed little or no effect. These results suggest that PMA may enhance NIH/3T3 cell adhesion through effects on laminin and type IV collagen receptors. Retinoic acid, which itself requires at least 6 h to show an effect on attachment, did not have any effect on cell attachment in 2 h and, if anything, slightly inhibited PMA-enhanced cell attachment to laminin and type IV collagen substrates. 相似文献
14.
G De Luca M E Tira S Rindi R Salvini G Cetta A A Castellani 《The Italian journal of biochemistry》1984,33(6):403-412
The PGs produced in the growth medium by skin fibroblast cultures from two O.I. affected patients were investigated. After density gradient centrifugation, in the most dense fraction two main families of molecules appeared. The patient with the more severe clinical picture showed a lower content of the PGs with the highest molecular weight. The GAG composition of PGs was different in the two patients. The more severely affected one showed an increase of HS and a decrease of ChS content, in agreement with the lower value of galactosamine to glucosamine ratio in urinary GAGs. 相似文献
15.
Renny T. Franceschi Hector F.De Luca Donna L. Mercado 《Archives of biochemistry and biophysics》1983,222(2):504-517
The interaction of the 1α,25-dihydroxyvitamin D3 receptor with immobilized calf thymus DNA has been compared with its sedimentation properties on hypotonic sucrose gradients. Forty to sixty percent of total hormone:receptor complexes formed at 4 °C were retained by DNA-cellulose and could be eluted by 0.18 to 0.2 m KCl. In contrast, heating preparations to 25 °C rapidly and irreversibly converted receptor to a form which bound hormone and DEAE-cellulose normally, but was unable to associate with DNA. Similarly, the ability of receptor to aggregate to a 6 S species was labile at 25 °C. Stabilization of receptor in the DNA binding aggregating form was accomplished using Ca2+, Mg2+, Mn2+, or Na2MoO4 while several protease and phosphatase inhibitors were ineffective. An examination of DNA binding properties of aggregating and nonaggregating receptor forms revealed that only receptor competent to enter into aggregates could bind DNA suggesting that a functional nucleic acid binding site, and, hence, a nucleic acid interaction is necessary for aggregate formation. Consistent with this view, an RNA:receptor interaction appears to be involved in formation of the 6 S complex since removal of RNA by ribonuclease treatment or purification of receptor reduced aggregation, an effect that could be reversed by addition of purified RNA. 相似文献
16.
In the presence of Mn(II) ions, the u.v. absorption spectrum of retinyl phosphate (Ret-P) solubilized in Triton X-100 micelles, phosphatidylcholine liposomes or rat liver microsomes exhibited a shift from the maximum of 330 nm to 287 nm. The effect of Mn(II) was reversed by adding EDTA or phosphate buffer. The same spectral change was found in the presence of poly-L-lysine in place of Mn(II) ions. The e.s.r. spectrum of Mn(II) in the presence or in the absence of Ret-P clearly showed that approx. 75% of the initial concentration of Mn(II) ions is bound to Ret-P when the molar ratio of Ret-P to Mn(II) ions is 4:1; no such binding occurred in the presence of retinol or retinoic acid. The appearance of two isosbestic points at 303 and 368 nm, in the presence of Mn(II) ions, suggests the existence of an equilibrium between an Mn(II)-bound monomer and an Mn(II)-bound dimer of Ret-P in Triton X-100 micelles. The same effect on the u.v.-absorption spectrum of Ret-P was also induced by Co(II), Cr(II), Zn(II) and Fe(II), but not by Mg2+ or Cu(II). The formation of the 'metachromatic complex' between Ret-P and Mn(II) or Co(II) inhibited the synthesis of retinyl phosphate mannose (Ret-P-Man) from exogenous and endogenous Ret-P and guanosine diphosphate [14C]mannose when bovine serum albumin was added after the metal ion. However, the order of addition did not influence Ret-P-Man synthesis in incubations containing MgCl2, which does not form the metachromatic complex with Ret-P. These results suggest that the bioavailability of proteins, polyamines and metal ions may control the extent to which Ret-P can be mannosylated in the intact membrane. 相似文献
17.
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19.
Dr. Luca Martire 《Facies》1996,35(1):209-236
Summary The red, pelagic limestones of the Rosso Ammonitico Veronese (Upper Bajocian-Tithonian) of the Altopiano di Asiago area can
be subdivided into eight facies. They differ from each other in structure (bedding style, presence and type of nodularity)
and texture (nature of components, grain-vs mud-support, compactional features). Several discontinuities could be recognized,
based on sedimentological or biostratigraphic evidence. In the context of a drowned platform, where sediments essentially
consist of skeletal remains of both planktonic and benthic organism, the different facies are interpreted as reflecting a
varying influence of currents on the winnowing of micrite and on triggering early cementation. Early cementation in turn,
controlled the patterns of bioturbation and the response of sediments to later compaction and pressure-dissolution. At times,
microbial mats, of unidentified nature, were important in trapping and binding sediment, giving rise to early lithified nodules
and layers of stromatolitic aspect.
The Rosso Ammonitico Veronese can be subdivided into three units: lower Rosso Ammonitico (RAI: Upper Bajocian-Lower Callovian),
middle Rosso Ammonitico (RAM: Upper Callovian-Middle Oxfordian), and upper Rosso Ammonitico (RAS: Lower Kimmeridgian-Tithonian).
Frequent ammonite moulds allow the precise dating of the base and top of each unit, and the documentation of facies heteropies
and hiatusses in the more fossiliferous RAS. The lower unit (RAM) is massive and essentially nodular; the middle unit (RAM)
is well bedded, non-nodular, and cherty; the upper unit (RAS) is richer in clay and typically nodular. The RAI and the RAS
are present everywhere, though significant facies and thickness changes affect particularly the RAS; the RAM is much more
variable, ranging from 0 to 10 metres. These variations, that may be gradual or abrupt, are inter-preted as the result of
Middle-Late Callovian block-faulting which generated an irregular sea floor topography where the swells were more exposed
to currents that continuously removed sediments, inducing long-lasting periods of nondeposition. Sediments preferentially
accumulated in the adjacent lows. A confirmation of this hypothesis is provided by evidence of synsedimentary tectonics, described
for the first time in the Rosso Ammonitico Veronese. Neptunian dykes, both vertical and horizontal, are developed at the top
of the RAI and are filled with laminated sediments or collapse breccias. Glides of metre-size blocks and slumps are present
at the top of the RAI and at the base of the RAM, respectively. Cm-thick layers of mud supported breccias are intercalated
in the upper part of the RAI and within the RAM: they are interpreted as seismites. All these features document a tensional
regime that generated fractures in more or less lithified sediments and failure along steep fault scarps or gently dipping
slopes of tilted fault blocks. Recognition of this Callovian-Oxfordian tectonic activity shows that, after the Bajocian drowning,
the Trento Plateau did not simply experience a uniform and general foundering: a small-scale block-faulting was still active
and affected the pattern of facies distribution. 相似文献
20.
Pierre Taberlet Luca Fumagalli Jacques Hausser 《Evolution; international journal of organic evolution》1994,48(3):623-636
The shrews of the Sorex araneus group have undergone a spectacular chromosome evolution. The karyotype of Sorex granarius is generally considered ancestral to those of Sorex coronatus and S. araneus. However, a sequence of 777 base pairs of the cytochrome b gene of the mitochondrial DNA (mtDNA) produces a quite different picture: S. granarius is closely related to the populations of S. araneus from the Pyrenees and from the northwestern Alps, whereas S. coronatus and S. araneus from Italy and the southern Alps represent two well-separated lineages. It is suggested that mtDNA and chromosomal evolution are in this case largely independant processes. Whereas mtDNA haplotypes are closely linked to the geographical history of the populations, chromosomal mutations were probably transmitted from one population to another. Available data suggest that the impressive chromosome polymorphism of this group is quite a recent phenomenon. 相似文献