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61.
Giorgio Bianchi Pinarosa Avato Paolo Bertorelli Giuseppe Mariani 《Phytochemistry》1978,17(5):999-1001
The epicuticular waxes of the two sorghum varieties Alliance A and SD 102 have been analyzed, after separation of the leaf blades from the sheaths. The major constituents were found to be free fatty acids but small amounts of esters, aldehydes, alcohols, n-alkanes and sterols were also detected. The typical chain lengths of aldehydes, free alcohols and free fatty acids were C28 and C30. 相似文献
62.
Enkephalin-binding systems in human plasma 总被引:1,自引:0,他引:1
Roberta Possenti Valeria De Marco Ornella Cherubini L. Giorgio Roda 《Neurochemical research》1983,8(4):423-432
Three amino acid-containing fractions present in human plasma are shown to bind both leu and met-enkephalin: serum albumin and two species of a much lower molecular weight, in all likelihood polypeptides. The amount of enkephalin associated with serum albumin seems comparatively smaller than that associated with the two low molecular weight systems. These systems jointly are apparently capable of binding a significant part of the circulating enkephalins. The possibility is suggested that the interactions described may play a role in maintaining the integrity of circulating enkephalins. 相似文献
63.
Paul A. del Giorgio Alicia L. Vinocur Ruben J. Lombardo Hector G. Tell 《Hydrobiologia》1991,224(3):129-154
The phytoplankton of the River Lujan (Buenos Aires, Argentina) was studied for a period of 18 months, together with physical and chemical variables, in relation to a pollution gradient. 167 taxa were recorded within a seasonal succession characterized by dominance of diatoms with a brief summer green algae facies. A combination of several biotic indices and multivariate analysis was employed to assess the impact of pollution on the phytoplankton community. The biotic indices used were species diversity and richness, algal quotients (green algae/diatom ratio, Centrales/Pennales ratio) and the SD succession rate index. Multivariate procedures included cluster analysis and ordination by PCA of both species and samples, stepwise discriminant analysis and multiple discriminant analysis of variance (MANOVA). Results indicate that community dynamism is attenuated at the more polluted sites, concomitant with an increased predominance of a broad-tolerance algal assemblage, co-dominated by Cyclotella meneghiniana and Nitzschia stagnorum. The changes in the community structure and dynamics described herein involved alterations in the distribution and relative proportions of the algae, rather than modifications in the basic species composition. These changes may not be readily detectable by methods which over-simplify the ecological information, such as systems of indicator species and biotic indices, designed to assess the degree of pollution. The suitability of multivariate analysis and biotic indices in river phytoplankton studies is further discussed. 相似文献
64.
Bruno Samorì Giorgio Lenaz Maurizio Battino Giancarlo Marconi Ida Domini 《The Journal of membrane biology》1992,128(3):193-203
Summary A general approach is developed to interpret linear dichroism (LD) spectra of ubiquinones (Q
n) in host bilayers. Information is reported in terms of guest-host mutual orientation and localization. The overall orientational anisotropy of guest ubiquinone molecules is described by a basic set of limiting orientation/localization modes. Assignments of the UV transitions of the ubiquinone chromophore were obtained by the liquid crystal-linear dichroism technique and molecular orbital (CNDO/S) calculations. The LD spectra of Q
n in the bilayers provided by the lyotropic nematic mesophase exhibited by water solutions of potassium laurate and decanol were interpreted on the basis of the above assignments. The resulting experimental evidence showed a multisite distribution in the host bilayer for the aromatic heads of all the investigated Q
n derivatives except Q0. The orientational distribution suggested by the LD spectra fits the solubilization model recently proposed by G. Lenaz [J. Membrane Biol. (1988) 104:193–209] for ubiquinone in lipid membranes. Within this model Q
n molecules are located in the midplane and their headgroups oscillate transversally across the membrane. Q
0 instead has a single site location, close to the polar bilayer interface. Experimental evidence that the headgroup carbonyls tend to grasp the polar interface of the host bilayer was also obtained. Orientation and location distributions of Q
n guest molecules are therefore likely to result from the tendency of their aromatic heads to grasp the polar heads of the host bilayer and from the concurrent tendency of their chains to settle into the hydrocarbon host interior.abbreviations AA
average absorption
- OD, OD
optical densities for plane polarized radiations parallel () and perpendicular () to the sample optical axis
- OD
OD — OD
- EPR
electron paramagnetic resonance
- LC-LD
liquid crystal-linear dichroism
- LD
linear dichroism
-
LD
r
reduced linear dichroism.
- MO
molecular orbital
- N
nematic
- NMR
nuclear magnetic resonance
-
S
jj
order parameters of the directions j of the transition moments of the guest chromophore
-
S
ii
order parameters of the orientational axes i of the guest molecule with respect to the magnetic field
-
S
ii
order parameters of the axes i of the guest molecules with respect to the bilayer axis a
-
S
a
order parameters of the host bilayer axis a with respect to the orienting magnetic field
-
j,i
deflection angles between the directions j and the axes i
-
O
i
optical factors of the i axis see Eq. (A4)]
- Qn
ubiquinone whose isoprenoid chain contains n isoprenoid units
Dr. A. Rossi is gratefully acknowledged for the t.e.m. reduction of the spectra. Ubiquinone homologs were kind gifts from Eisai Co., Tokyo, Japan. This work was supported by M.U.R.S.T., and C.N.R. Target Project on Biotechnology and Bioinstrumentation, Rome, Italy. 相似文献
65.
The relationship between ETS (electron transport system) activity and oxygen consumption in lake plankton: a cross-system calibration 总被引:4,自引:0,他引:4
The ETS (electron transport system) assay to measure respirationof aquatic organisms has been widely applied in studies of marinemetabolism, but its use in freshwaters has been much more limited.This method calculates oxygen consumption from the measuredETS activity using an empirical conversion factor. This factorhas been calculated for various marine organisms, and for naturalplankton communities, but calibrations for freshwater organismsare lacking. The aim of this paper was to determine the relationshipbetween lake plankton respiration and ETS activity, based onmeasured epilimnetic plankton oxygen uptake and ELS activityin 20 southern Quebéc lakes. The relationship betweenplankton oxygen consumption and ETS varies significantly bothwithin lakes over the growing season, and among lakes. The magnitudeof the error associated with calculating respiration from ETSis, however, similar to the error in other standard limnologicalprocedures used in plankton carbon flow studies. Oxygen consumptionis not a linear function of ETS across the range of lakes, butis rather a power function. The respiration:ETS ratio for lakeplankton therefore not constant: it is high in oligotrophicand colored lakes, and declines with trophy. These results areconsistent with the changes expected in the structure of theplankton along trophic gradients. 相似文献
66.
The effects of elongational stress exposure on the activation and aggregation of blood platelets. 总被引:1,自引:0,他引:1
Hemodynamic shear is known to stimulate blood and endothelial cells and induce platelet activation. Many studies of shear-induced platelet stimulation have employed rotational viscometers in which secondary flow effects are assumed to be negligible. Shear induced platelet activation occurs at elevated shear rates where secondary flows may contribute a significant percentage of the total hydrodynamic force experienced by the sample. Elongational stress, one component of this secondary flow, has been shown to alter transmembrane ion flux in intact cell and the permeability of synthetic membrane preparations. Elongational flow also occurs in the vasculature at sites of elevated shear stress. Secondary flow components may contribute to platelet activation induced during shear stress application in rotational viscometry. A unique 'constrained convergence' elongational flow chamber was designed and fabricated to study platelet response to elongational stress exposure. The elongational flow chamber was capable of producing an elongation rate of 2.1 s-1 with a corresponding volume averaged shear rate of 58.33 s-1. Significant changes were observed in the total platelet volume distribution and measured response to added chemical antagonists after elongational stress exposure. The total platelet volume histogram shifted toward larger particle sizes, suggesting the formation of large aggregates as a result of elongational stress exposure. Platelets exposed to elongational stress demonstrated a dose dependent decrease in added ADP-induced aggregation rate and extent of aggregation. 相似文献
67.
Giuseppe Fossati Andrea Balsari Donatella Taramelli Maria Luisa Sensi Giuseppe Pellegris Maurizio Nava Giorgio Parmiani 《Cancer immunology, immunotherapy : CII》1982,14(2):99-104
Summary Peripheral blood lymphocytes (PBL) of melanoma patients were sensitized in vitro with lymphocytes of a single donor or with a pool of lymphocytes of 5–20 different donors. After 6–7 days, the cytotoxic activity of the sensitized PBL was tested against cultured autologous tumor cells and lymphocytes in a 51Cr-release assay. Tumor lysis was observed in 13 of 16 cases in which patients' PBL (Pt-PBL) were stimulated by a pool of allogeneic lymphocytes and in five out of seven cases when single sensitization was performed. In no case was lysis of autologous normal lymphocytes or blasts seen. Cultivation of Pt-PBL with irradiated autologous tumor cells never led to the induction of lymphocytes cytotoxic to melanoma cells. Lysability by pool-activated autologous Pt-PBL of fresh cryopreserved tumor cells was compared to that of short-term cultured tumor cells, and no significant differences were observed. Cold-target inhibition experiments indicated that the cytotoxicity of Pt-PBL was tumor-restricted since only autologous melanoma cells but not lymphocytes were able to inhibit the reaction. These results indicate that activation of Pt-PBL is necessary in order to elicit or amplify their antitumor activity. 相似文献
68.
Robert C. Jennings Flavio M. Garlaschi Paolo D. Gerola Rachel Etzion-Katz Giorgio Forti 《BBA》1981,638(1):100-107
Lowering the pH of the incubation medium to pH 5.4 leads to grana formation morphologically similar to that induced by metal cations. The same phenomenon is observed in EDTA-washed chloroplasts, indicating that it is not due in part to electrostatic ‘masking’ by residual cations associated with the membranes. Digitonin fractionation studies have indicated that the distribution of the major chlorophyll-protein complexes between granal and stromal membrane regions is similar at pH 5.4 in the absence of Mg2+, and at pH 7.4 in the presence of Mg2+. Chlorophyll fluorescence induction studies have indicated that the primary photochemistry of Photosystem II (PS II) is stimulated by lowering the pH to 5.4, just as it is upon metal cation addition at higher pH values. The failure to observe such an increase at pH 5.4 by measuring electron transport to ferricyanide is attributed to a combination of an inhibition by this pH of electron transport at a site after Q reduction and an increase in the number of PS II centres detached from the plastoquinone pool. We conclude that the stacked configuration of chloroplast membranes leads to increased PS II primary photochemistry, which is most simply explained in terms of a redistribution of excitation energy towards PS II. 相似文献
69.
Of 59 patients who underwent operative correction of congenital coronary artery fistulas from May 1956 through May 1980 at our institution, three had fistulas that arose from the coronary artery and terminated in the left heart. The chief indication for surgical correction in such patients is the presence of symptoms or the development of complications, which include rupture, endocarditis, and congestive heart failure. The principal objective of repair is closure or obliteration of the fistulous communication and preservation of distal myocardial perfusion. Because symptoms and complications tend to occur with age, elective ligation is warranted during childhood, even in asymptomatic patients. The three cases described here, as well as the reviewed series of left heart fistulas, substantiate this fact. All three patients were symptomatic before operation and asymptomatic afterward. 相似文献
70.