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1.
We have studied the torsional elastic constant (alpha) of short DNA (27mer) oligomers of various sequence by fluorescence polarization anysotropy (FPA) measurements. The lowest alpha values were found in samples with sequence rich in AA dinucleotides or containing the alternating d(A-T) x d(A-T) motif. The torsional rigidity of our DNA samples was compared to that calculated according to the current values of twist angle fluctuations derived for ten dinucleotide steps by recent analyses of DNA crystal structure database. The values of torsional rigidity derived from crystals are higher than our experimental ones, obtained by FPA analysis, suggesting that packing force in crystals may notably hinder the dinucleotide twist angle fluctuations that occur in solution. This behaviour is more evident for samples containing AA, TA and AT steps. In all the samples there is about a twofold change of the alpha value in the 10-40 degrees C range. An activation enthalpy (Delta H (#)) of about 17.4 kJ mol(-1), on average, was obtained for the temperature dependence of eight of the ten samples studied. A correlation with the stacking energy is discussed. 相似文献
2.
3.
Dario Cremaschi Giuliano Meyer Carlo Rossetti Guido Bottà Paola Palestini 《The Journal of membrane biology》1987,95(3):209-218
Summary Cl– influx at the luminal border of the epithelium of rabbit gallbladder was measured by 45-sec exposures to36Cl– and3H-sucrose (as extracellular marker). Its paracellular component was evaluated by the use of 25mm SCN– which immediately and completely inhibits Cl– entry into the cell. Cellular influx was equal to 16.7eq cm–2 hr–1 and decreased to 8.5eq cm–2 hr–1 upon removal of HCO
3
–
from the bathing media and by bubbling 100% O2 for 45 min. When HCO
3
–
was present, cellular influx was again about halved by the action of 10–4
m acetazolamide, 10–5 to 10–4
m furosemide, 10–5 to 10–4
m 4-acetamido-4-isothiocyanostilbene-2,2-disulfonate (SITS), 10–3
m amiloride. The effects of furosemide and SITS were tested at different concentrations of the inhibitor and with different exposure times: they were maximal at the concentrations reported above and nonadditive. In turn, the effects of amiloride and SITS were not additive. Acetazolamide reached its maximal action after an exposure of about 2 min. When exogenous HCO
3
–
was absent, the residual cellular influx was insensitive to acetazolamide, furosemide and SITS. When exogenous HCO
3
–
was present in the salines, Na+ removal from the mucosal side caused a slow decline of cellular Cl– influx; conversely, it immediately abolished cellular Cl– influx in the absence of HCO
3
–
. In conclusion, about 50% of cellular influx is sensitive to HCO
3
–
, inhibitable by SCN–, acetazolamide, furosemide, SITS and amiloride and furthermore slowly dependent on Na+. The residual cellular influx is insensitive to bicarbonate, inhibitable by SCN–, resistant to acetazolamide, furosemide, SITS and amiloride, and immediately dependent on Na+. Thus, about 50% of apical membrane NaCl influx appears to result from a Na+/H+ and Cl–/HCO
3
–
exchange, whereas the residual influx seems to be due to Na+–Cl– contranport on a single carrier. Whether both components are simultaneously present or the latter represents a cellular homeostatic counterreaction to the inhibition of the former is not clear. 相似文献
4.
Dario Beruto Margherita Beruto Carlo Ciccarelli Pierre Debergh 《Physiologia plantarum》1995,94(1):151-157
A new method for evaluating the matric potential of gelled media has been developed. The method allows the derivation of the matric potential as a limit of a series of measurements of water potential values from gelled media prepared without added components, from agar powders progressively cleaned of mineral impurities. Three commercial agar brands were tested, and for these the matric potential was found to contribute only between 1 and 2% of their total water potential. Thermodynamic features relating matric and osmotic potentials are described. New hypotheses for understanding the water flux mechanism from gel to tissue cultured explants are discussed. Movement of water along polymeric chains is postulated to be a facilitated step in comparison with bulk movement. 相似文献
5.
Zuccotti M Sebastiano V Garagna S Redi CA 《Molecular reproduction and development》2005,71(2):245-246
Mammalian oocytes are thought to be neutral as for X- or Y-bearing sperm selection is concerned, and penetration of an oocyte by an X- or a Y-bearing sperm is considered a random event. This assumption is mainly based on a posteriori evidences of a nearly equal sex ratio at birth, but it has never been experimentally demonstrated. We have designed a simple experiment, which allowed the penetration of an oocyte by more than one sperm and the further sexing by PCR of each single pronucleus present within the ooplasm. For the first time, we provide experimental evidence that mammalian oocytes do not play a selecting role since a single oocyte may be simultaneously fertilised by both X- and Y-bearing sperm. 相似文献
6.
Gianfranco De Feo Giacomo Chiabrando Nunzia Cannovo Antonio Galluccio Carlo Tomino 《PloS one》2012,7(11)
Aim
The high variability of “centre-specific” documentation required by Independent Ethics Committee (IEC) plays a role in the time required for activation of participating centres of multicentre clinical trials. This study (a) provides a picture of the different activities, structural requirements and resources dedicated to the operation of the local IEC in Italy; (b) defines a detailed list of “centre-specific” documents considered as essential by the IEC for issuing its opinion and (c) suggests a “single document” to reduce the variability of the “centre-specific” documents required by the IEC.Methodology
Two surveys were conducted through the portal of National Monitoring Centre of Clinical Trials (https://oss-sper-clin.agenziafarmaco.it/). The first survey focused on the local IEC resources and on the “centre-specific” documentation that local IEC required from the Sponsor and local Principal Investigator (PI). The second focused on “single document” required in the form of statements from the Sponsor and the PI. Answers were discussed and extended during regular scheduled teleconferences and plenary meeting.Principal Findings
From 22/07/2009 to 15/12/2009, and from 19/04/2010 to 14/05/2010, 131 and 125 IECs responded to the first and the second surveys, respectively. 67% and 51% of IECs consider the structural requirements and the staff dedicated to the activity of the IECs as sufficient, respectively. Most of the IECs consider the “centre-specific” documentation as necessary for issuing the opinion, and a high percentage of IECs consider the proposed documentation as acceptable in substitution to any other “centre-specific” documentation already in use.Conclusions
The harmonization of IECs practice in Italy is the first step to facilitate multicentre clinical trials. Similar efforts should be directed to reduce the total number of IECs and to standardize clinical trials approval procedures, focusing on administrative procedures as well. 相似文献7.
Giampaolo Barone Angela Ruggirello Alessio Terenzi 《Journal of inorganic biochemistry》2010,104(7):765-773
The photophysical and photochemical properties of the cationic ZnII complex of 5-triethyl ammonium methyl salicylidene ortho-phenylendiimine (ZnL2+) interacting with native DNA were investigated by steady state and time-resolved fluorescence spectroscopies. Experimental results indicate that, in the presence of DNA, ZnL2+ is efficiently protected from a photochemical process, which occurs when it is in the free state dispersed in aqueous solution. The analysis of the absorption and emission spectra of ZnL2+, both stored in the dark and after exposure to tungsten lamp light for 24 h, corroborated by quantum chemical calculations, allowed us to point out that ZnL2+ undergoes a photoinduced two-electron oxidation process. According to this picture, the protective action of DNA toward the intercalated ZnL2+ was attributed to an effective inhibition of the ZnL2+ photooxidation. In this context, it can be considered that DNA-intercalated ZnL2+ is located in a region more hydrophobic than that sensed in the bulk water solvent. Moreover, by a thorough analysis of steady state and time-resolved fluorescence spectra, the interaction process can be consistently explained in terms of a complete intercalation of the complex molecules and that the polarity of the environment sensed by intercalated ZnL2+ is comprised between that of methanol and ethanol. 相似文献
8.
Zala Lužnik Claudia Breda Vanessa Barbaro Stefano Ferrari Angelo Migliorati Enzo Di Iorio Barbara Ferrari Carlo Griffoni Andrea Grassetto Hossein Mostafa Elbadawy Marina Bertolin 《Cell and tissue banking》2017,18(4):461-474
Isolated limbal epithelial stem cells (LESCs) were cultured with or without a 3T3 murine fibroblast feeder-layer (FL) in 4 different culture media on culture plates or on denuded human amniotic membrane (AM) support and fibrin gel support: (1) control medium supplemented with fetal bovine serum; (2) control medium supplemented with the synthetic serum “XerumFree? XF205” (XF); (3) CnT-20 medium supplemented with “XerumFree? XF205” (CnT-XF) and (4) CnT-20 medium supplemented with human AB serum (CnT-AB). The three xenogeneic media were compared to standard condition (control + FL) and parameters assessed included cell morphology, proliferative potential, number of passages, assessment of clonogenic and abortive colonies, life span, ?Np63α expression and epithelial morphology on AM. During serial cultivation of LESCs, most of the tested xeno-free media supported similar numbers of cell passages, total colony number, cumulative cell doublings (CCD) rates and expression of ?Np63α compared to control. The conditions cultivated with a FL showed a non-statistically significant higher number of cell passages and CCD rates before senescence when compared to the same conditions cultured without FL. Except for the control medium, only XF medium enabled the growth of cells on AM. The expression of ?Np63α was comparable in all the cultures grown onto AM, when compared to the controls on fibrin gel. In conclusion, the xeno-free media enabled LESC culture both on plastic and on denuded human AM. Despite the analyses were carried out in a statistically low number of samples and need re-assessment in a larger cohort, our results suggest that the production of a completely xeno-free LESC graft could be beneficial for future clinical applications. 相似文献
9.
Silvia Uccella Roberta Cerutti Davide Vigetti Daniela Furlan Rita Oldrini Ileana Carnevali Giuseppe Pelosi Stefano La Rosa Alberto Passi Carlo Capella 《The journal of histochemistry and cytochemistry》2006,54(8):863-875
Histidine decarboxylase (HDC) and vesicular monoamine transporter 2 (v-MAT2) are involved in the biosynthesis and storage of histamine. DOPA decarboxylase (DDC) is involved in the biosynthesis of a variety of amines and shares a high degree of homology with HDC. HDC and v-MAT2 immunoreactivities (IR) have recently been detected in well-differentiated neuroendocrine tumors (WDNETs) and poorly differentiated neuroendocrine carcinomas (PDNECs) of various sites and have been proposed as general endocrine markers. We evaluated HDC and v-MAT2 IR in a series of 117 WDNETs and PDNECs from different sites. Western blotting analysis was performed to verify the specificity of anti-DDC and anti-HDC antibodies. Real-time RT-PCR was performed using specific probes for HDC and DDC on 42 cases, examined also for DDC IR. HDC and v-MAT2 IR were observed in the majority of WDNETs and PDNECs of all sites and HDC-IR cases were always also DDC-IR. In contrast, high levels of HDC mRNA were detected only in the gastroenteropancreatic WDNETs, which did not show increased DDC mRNA levels. On the other hand, bronchial carcinoids and lung PDNECs showed high DDC mRNA levels, but nearly undetectable HDC mRNA levels. Western blotting analysis showed a cross-reaction between anti-HDC and anti-DDC antibodies. HDC should not be considered as a general endocrine marker and HDC IR in bronchial carcinoids and PDNECs of the lung can probably be attributed to a cross-reaction with DDC. 相似文献
10.
ABSTRACT A phytosociological study of the shrubland communities which colonise abandoned terraced olive groves in the Tyrrhenian district of Central Italy is presented here. The vegetational analysis was carried out using the Braun Blanquet phytosociological approach. Two main types of shrubland communities characterising distinct environmental conditions occur within abandoned terraced olive groves. On the one hand, there are those scrub types which tend to occupy the central part of the terrace; on the other hand, there are the scrubs types which develop along the stone walls bordering the terrace. Different phytosociological associations, sub-associations, and variants ranging from Pistacio-Rhamnetalia alaternii to Prunetalia spinosae are recognised and described. In the warm dry areas, both Myrto-Lentiscetum and Rhamno-Euphorbietum dendroidis occur. Also, a new Oleo-Ceratonion sub-association (Myrto-Lentiscetum spartietosum junceii) is presented here for the first time. In the inner zones of the study area, a range of aspects characterising a new Pruno-Rubion ulmifolii community type (Roso-Rubetum ulmifolii ass. nova) are identified. 相似文献