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Biomedical subjects

G Albertini

Publications and source records attributed to G Albertini.

At least 19 recordsLinked to original sources
PubMed1995

Membrane fluidization by animycotic bifonazole.

Calorimetry, nuclear magnetic resonance and X-ray diffraction techniques have been used to obtain thermodynamic and structural information on dipalmitoyl phosphatidylcholine (DPPC) liposomes doped by the antimycotic drug bifonazole in the range 0 < R < 1, where R = moles of bifonazole/moles of DPPC. The technique of spin labeling electron spin resonance (ESR) has also been used to study permeability and fluidity properties. The decrease of the cooperativity at the gel to liquid crystalline phase transition, as shown by ESR an DSC measurements, indicates that bifonazole imparts higher fluidity to the lipid matrix. Increase in permeability of ascorbate ions, after incorporation of bifonazole in the membrane, has been detected by ESR experiments using spin label 5-SASL. 13C NMR spectra indicate that the drug molecule is highly immobilized. X-ray diffraction and freeze fracture TEM results show that the equilibrated phase at room temperature is lamellar and unidimensional together with the presence of small particles and pits of uniform size. A marked hysteresis is evident in the formation of this phase.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1992

Lipid-drug interaction: a structural analysis of pindolol effects on model membranes.

The ternary system constituted by distearoylphosphatidylcholine, pindolol (a vasodilator drug) and water has been investigated by using X-ray diffraction and calorimetric techniques. The structural modifications induced by the drug have been determined and a possible interaction model has been derived. In particular, the pindolol content-temperature dependent phase diagram shows the occurrence of two new phases: the first is an interdigitated gel, and the second is a lamellar structure presenting an unusual mixed disordered-ordered conformation of the hydrocarbon chains (L alpha beta). The comparative analysis of electron density profiles relative to the L alpha beta phase, reveals significant modifications in the paraffinic region of the lipid layer. In agreement with thermodynamic results, the structural data suggest that the drug induces a stiffening and a tightening of the hydrocarbon chains. Moreover, the hydrophilic properties of the membrane (particularly in P beta, and L alpha beta phases) present an evident dependence with the drug concentration.

Calorimetry↗
PubMed1992

Structural and functional relationships in 5'-nucleotidase from bull seminal plasma. A Fourier transform infrared study.

Fourier transform infrared spectroscopy (FTIR) was used to investigate the secondary structure of 5'-nucleotidase from bull seminal plasma (BSP). Spectra of protein in both D2O and H2O were analyzed by deconvolution and second derivative methods in order to observe the overlapping components of the amide I band. The protein, which is made up of two apparently identical subunits and which contains two zinc atoms, was studied in its native form, in the presence of dithiotreitol (DTT) and after removal of the two zinc atoms by means of nitrilotriacetic acid (NTA). Deconvolved and second derivative spectra of amide I band showed that the native protein contains mostly beta-sheet structure with a minor content of alpha-helix. The quantitative analysis of the amide I components was performed by a curve-fitting procedure which revealed 54% beta-sheet, 18% alpha-helix, 22% beta-turns and 6% unordered structure. The second derivative and deconvolved spectra of amide I band showed that no remarkable changes in the secondary structure of 5'-nucleotidase were induced by either DTT or NTA. These results were confirmed by the curve-fitting analysis where little or no changes occurred in the relative content of amide I components when the protein was treated with DTT or with NTA. Major changes, however, were observed in the thermal denaturation behavior of the protein. The native protein showed denaturation at temperatures between 70 and 75 degrees C, while the maximum of denaturation was observed between 65 and 70 degrees C and between 55 and 60 degrees C in the presence of NTA and DTT, respectively. The results obtained indicate that the two separate subunits of the protein have essentially the same secondary structure as that of the native enzyme.

5'-Nucleotidase↗
PubMed1992

Cognitive profiles in adolescents with mental retardation.

Cognitive profiles of performance were obtained from a selected group of adolescent subjects with mental retardation (MR) (n = 32; mean age: 15.4 years, S.D. = 3.7) by means of an ad hoc neuropsychological battery. On the basis of each subject's IQ, the experimental sample was divided into three homogeneous subgroups (severely, moderately and mildly retarded) and cognitive performances obtained in the battery tests were compared. Subsequently, in order to clarify the qualitative aspects of MR, the cognitive patterns of subjects with the same IQ and chronological age were examined. Altogether, from a neuropsychological point of view, the results of this study seem to support the hypothesis that MR is a heterogeneous condition of cognitive deficits (some abilities are better preserved than others) and indicate that a set of multiple tests exploring single cognitive functions is needed in order to describe cognitive profiles in MR.

Adolescent↗
PubMed1990

Interaction of the herbicide atrazine with model membranes. I: Physico-chemical studies on dipalmitoyl phosphatidylcholine liposomes.

Atrazine (2-chloro-4 ethylamino-6-(isopropylamino)-s-triazine) is one of the most widely used herbicides. Fourier transform infrared spectroscopy, differential scanning calorimetry and fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) and of its derivative 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) were used to study the interaction of atrazine with dipalmitoyl phosphatidylcholine liposomes used as a model for biological membranes. The results show that atrazine does not perturb the hydrophobic core of the lipid bilayer and suggest that the herbicide localizes near the glycerol backbone of the lipid.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1990

Thermodynamic and structural effects of propranolol on DPPC liposomes.

Some thermodynamic and structural aspects of propranolol-DPPC liposomes interaction were investigated by DSC and X-ray diffraction: the lamellar arrangement of the lipid matrix remains intact even at high concentrations of the drug (until 1:1 drug/lipid molar ratio). However, the bilayer thickness increases significantly and the chains become perpendicular to the lamellar planes, for increasing drug content. At still higher propranolol concentrations a hexagonal phase occurs followed by a lamellar phase, in which the liposomes are destroyed. Moreover, the presence of propranolol has been found to impart fluidity to the lipid matrix.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1987

Studies of structural modifications induced by gamma-irradiation in distearoylphosphatidylcholine liposomes.

An investigation of the structural and thermodynamical modifications induced by gamma-irradiation in model membranes is reported. Differential scanning calorimetry and X-ray diffraction were used to study the different phases and associated transitions of distearoylphosphatidylcholine multilamellar liposomes after 60Co gamma-irradiation. Changes were observed in the shape of the calorimetric peaks and in the corresponding phase transition temperatures. In particular a shoulder was observed at about 20 kGy. The three phases characteristic of lecithins with identical acyl chains were detected also for the highest radiation dose. The formation of lysolecithin and stearic acid upon phospholipid degradation was observed. The lysolecithin concentration increases as a function of irradiation dose, until a saturation value is reached at 40 kGy. These results correlate quite well with those obtained for interlayer and interchain distances and for the width of the main phase transition calorimetric peak. At the highest dose (approximately equal to 80 kGy) cross-linked adjacent radicals and other molecular species are also formed. Appreciable differences, and some similarities, in the behaviour of DSPC and DPPC liposomes under gamma-irradiation were observed.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1986

Clinical pharmacology of tritoqualine: a comparative study against dexchlorpheniramine in allergic rhinitis.

The effect of tritoqualine on seasonal allergic rhinitis caused by grass pollen was compared to that of dexchlorpheniramine maleate (DCPM) in 21 patients randomly allocated into two parallel groups. There were rapid improvements of all symptoms considered after treatment with either tritoqualine or DCPM. A significant reduction of plasma histamine concentrations was observed during the treatment with tritoqualine whereas no modification occurred with DCPM. Finally, it was shown that tritoqualine did not modify reaction times to visual and auditive stimuli whereas DCPM induced a significant slowing-down of the reaction time to visual stimuli. From this pilot study tritoqualine appears to have the same efficacy for the treatment of seasonal allergic rhinitis as classic anti-H1 antihistamines, but without central nervous system side-effects.

Adolescent↗
PubMed1985

X-ray diffractometry and calorimetry studies of structural modifications induced by gamma-irradiation in phosphatidylcholine multilamellar liposomes.

Experimental results are reported on structural and thermodynamic modifications induced by gamma-irradiation in model membranes. Differential scanning calorimetry (DSC) and X-ray diffraction were used to study the different phases and associated transitions of dipalmitoylphosphatidylcholine after 60Co gamma-irradiation. Changes were observed in the shape of calorimetric peaks and in the corresponding enthalpy. The repetition distance of the layers increases while the distances related to the aliphatic chains decrease as a function of gamma-irradiation time. Moreover, an increase in the hexagonal symmetry with increasing dose was detected. No disappearance of a pre-transition was detected even at high doses.

Calorimetry↗