Biomedical subjects

D Popescu

Publications and source records attributed to D Popescu.

At least 19 recordsLinked to original sources

PubMed2006

Usefulness of teicoplanin for preventing methicillin-resistant Staphylococcus aureus infections in orthopedic surgery.

In order to gather more data on the use of teicoplanin for reducing MRSA infections in high-risk populations, the present study was conducted. At a hospital in Barcelona, Spain, there was a high prevalence of MRSA infections among patients who underwent surgery for femoral neck fracture during the first 5 months of 2002 (period A) when cefuroxime was the antibiotic prophylaxis. During the following 12 months (period B) 600 mg of teicoplanin was added to cefuroxime. The rates of overall and MRSA infection during period A were 5.07 and 2.73%, respectively. Pulsed-field gel electrophoresis demonstrated there was no clonal relationship among MRSA strains. No nasal carriers of MRSA were detected among health workers. During period B the rates of overall and MRSA infection were 2.36 and 0.19%, respectively. Both rates were statistically significantly lower than those in period A (p<0.05). These results suggest teicoplanin may be useful in patients undergoing orthopedic surgery when the prevalence of MRSA is high.

Aged, 80 and over↗

PubMed2002

[How can we improve mortality records in primary care?].

OBJECTIVE: To calculate whether the introduction for systematic use of an epicrisis form for deaths improved the quality of mortality records in a primary care centre (PCC). DESIGN: Before and after study. SETTING: Urban, with a population of 31 000. Patients and other participants. All the deaths recorded at the PCC before 1996 (N=396) and in the period from January 1999 to August 2000 (N=160). MAIN MEASUREMENTS AND RESULTS: The number of deaths recorded at the PCC represents only 32.5% of the official data obtained from the municipal registry in the 1996 evaluation, and 51.5% in the 2000 evaluation. In 2000 the epicrisis forms were filled out in 76.8% (95% CI, 65.0-88.6%) of all deaths. In the 1996 evaluation the place of death was not recorded in 65.5% (95% CI, 59.0-71.8%) of cases, but in 2000 this figure was 22.5% (95% CI, 19-26%). Undefined causes of death dropped from 37% (95% CI, 33.4-40.6%) in 1996 to 30.5% (95% CI, 25.8-35.2%) in 2000. Recording of cause of death rose from 64% (95% CI, 57.8-70.4%) in 1996 to 73% (95% CI, 61.8-84.4%) in 2000. CONCLUSIONS: Official data reveal under-recording of mortality at the PCC. The introduction of an epicrisis form for deaths has improved the quality of the centres mortality records.

Aged↗

PubMed2000

Hydrodynamic effects on the solute transport across endothelial pores and hepatocyte membranes.

In this short note we propose a simple and rapid procedure to calculate the net quantity of metabolites absorbed by hepatocytes from blood plasma. The blood movement through sinusoids determines an opposed circulation of plasma through the space of Disse. Hydrodynamic considerations lead to the conclusion that hepatocytes absorb for their own synthesis processes a quantity of metabolites in a volume flow of the order of 10(-12) nl s(-1) through a sieve plate surface with an area of 1 microm2. At pathological temperature (40 degrees C), the excess of the net absorbed volume flow for the entire sinusoidal surface of the mammalian liver may be as high as 1.9 nl s(-1). Some observations on the effect of red and white blood cells on the chylomicron traffic through endothelial pores are made.

Animals↗

PubMed1997

Selective association of phospholipids as a clue for the passive flip-flop diffusion through bilayer lipid membranes.

We showed that the investigation of the selective association of phospholipids might contribute to the insight of the flip-flop diffusion processes. The process of selective association was studied quantitatively by testing the association probabilities for both parallel and anti-parallel orientations of the polar headgroups. The model of double chain binary mixture confirms a high capacity of phospholipids for self-association in parallel configuration of the electric dipole moments whether the cross-sectional area of the polar headgroups are in an usual range of 25-55 A2. It is demonstrated that the aggregation of a class of phospholipids from a binary mixture is strongly dependent on the dipole-dipole interaction between the same phospholipids and is modulated by the magnitude of the electric dipole moment of the other phospholipids from that binary mixture. There are a great number of mechanisms involved in the transbilayer movement of phospholipids. We referred here only to the passive transport of lipids from one monolayer to the other. The flip-flop mechanisms raised in this paper are the breakdown of bilayer due to the increase of the packing density and the inversion of the coupled phospholipids from the opposite monolayers of the same bilayer. Thus, the pair formation promoting a drop in occupied volume decreases the packing pressure in the respective monolayer and consequently triggers a flip-flop into the other direction since the packing pressure in the other monolayer has not dropped. According to the present model for the binary mixtures of double-chain lipids, the rate of the flip-flop diffusion decreased by increasing the number of the methylene groups added to the acyl chain. This dependence may be perturbed whether the phospholipids possesses a very high cross-section area of the polar headgroups (a > 55 A2). We think that the selective association of phospholipids is neither exclusively, nor only involved in promoting the transbilayer diffusion of phospholipids. Most probably, the selective association determines some phospholipid domains that attract certain particular proteins so that it can modulate the protein activity.

Diffusion↗

PubMed1995

Differential length effects in a binary mixture of single chain amphiphiles in planar monolayers. A three-dimensional approach.

The purpose of this work was to investigate the selective association into a binary lipid mixture having the acyl chain lengths of the two components as variables. A more adequate parameter that can describe the selectivity of the association processes into a binary lipid mixture is the mean association probability. In the present paper, we used a three-dimensional approach by evaluating the mean probabilities of association of single chain amphiphile molecules for a group of 36 binary mixtures. The possible correlations between the hydrophobic chain lengths and the association processes have been carried out by using the differential mean association probabilities. These results allowed us to uncover some significant rules that govern the selective association between the two components from a single chain binary mixture. We have found that in a binary mixture of single chain amphiphiles, the distance where the dispersion forces become effective during association processes is about 8.89 A.

In Vitro Techniques↗

PubMed1995

Aspects of self- and cross-association hydrophobicity in a single chain binary mixture. A computer study.

The differential scanning calorimetry (DSC) traces for binary mixtures of single chain amphiphiles present more than one transition temperature, while the traces for pure single chain amphiphiles have a single (or at most two) transition temperature(s). These secondary transition temperatures can appear owing to the selective association processes between the components of the lipid mixtures. This paper presents an attempt to examine theoretically the association of single chain amphiphiles between (a) two identical molecules (self-association) and (b) two different molecules (cross-association). Association probabilities, the mean association probabilities and the overall ratio of efficiency, were evaluated for 36 binary mixtures of single chain amphiphiles. A test system for evaluation of differential effects of the hydrophobic chain length on the mean association probabilities was considered. Self-association of longer hydrophobic chains and cross-association phenomena show a high probability compared with the self-association of shorter hydrophobic chains. We found that "the efficacious length of association" in a binary mixture of single chain amphiphiles is 8 methylene groups.

Calorimetry, Differential Scanning↗

PubMed1993

Association probabilities between the single-chain amphiphiles into a binary mixture in plan monolayers (II).

A test system of homologous binary mixtures of single-chain amphiphiles was considered. The dependence of the association probabilities on the hydrophobic chain length, and on the dipole moment of the shorter chain component when the longer chain component has a low dipole moment, was studied. The free-end effect of each hydrophobic chain on the association probability was also analysed. Generally, both the shorter chain end effect and the longer chain end effect on the association process are independent of their own initial chain length, but are dependent on the chain length of the other component and dipole moment. The changes in every association probability produced by the addition of one methylene group to the shorter chain and to the longer chain are unequal and opposite. For this reason the efficiency ratios were defined and analysed. The thermotropic behaviour of lipid mixtures can be related to association processes.

Electrochemistry↗

PubMed1991

Calculation of the optimal surface area for amphiphile molecules using the hard core method.

In this work, we have calculated the optimal surface area per amphiphile molecule using a two-dimensional gas of electric dipoles interacting with hard The optimal surface area can be evaluated according to a formula (in the two-body approximation) or as a root of an equation (in the three-body approximation). If the equation has more than one positive root, which is greater than the hard core area, then a polydisperse dimensional distribution of supramolecular aggregates is possible.

Journal Article↗

PubMed1990

Association probabilities between the single chain amphiphiles into a binary mixture in planar monolayers.

In this work, we have calculated the probabilities of selfassociation of single chain amphiphile molecules for 36 binary mixtures of molecules having an even number of carbon atoms (from 8 to 24 carbon atoms). The association probabilities depend on the dipole moment of head groups, the length of chains and the mole fraction of the mixture of both types of amphiphile. These calculations are useful for the quantitative and qualitative explanation of the cluster formation on the surface of the mono- or bilayers.

Electrochemistry↗

PubMed1987