Probing of the combined effect of bisquaternary ammonium antimicrobial agents and acetylsalicylic acid on model phospholipid membranes: differential scanning calorimetry and mass spectrometry studies

A model molecular biosystem of hydrated dipalmitoylphosphatidylcholine (DPPC) bilayers that mimics cell biomembranes is used to probe combined membranotropic effects of drugs by instrumental techniques of molecular biophysics. Differential scanning calorimetry reveals that doping of the DPPC model membrane with individual bisquaternary ammonium compounds (BQAC) decamethoxinum, ethonium, thionium and acetylsalicylic acid (ASA) leads to lowering of the membrane melting temperature (Tm) pointing to membrane fluidization. Combined application of the basic BQAC and acidic ASA causes an opposite effect on Tm (increase), corresponding to the membrane densification. Thus, modulation of the membranotropic effects upon combined use of the drugs studied can be revealed at the level of model membranes. Formation of noncovalent supramolecular complexes of the individual BQACs and ASA with DPPC molecules, which may be involved in the mechanism of the drug-membrane interaction at the molecular level, is demonstrated by electrospray ionization (ESI) mass spectrometry. In the ternary (DPPC + ASA + BQAC) model systems, the stable complexes of the BQAC dication with the ASA anion, which may be responsible for modulation of the membranotropic effects of the drugs, were recorded by ESI mass spectrometry. The proposed approach can be further developed for preliminary evaluation of the combined effects of the drugs at the level of model lipid membranes prior to tests on living organisms.

Alkane isomers: presence in petroleum ether and complexity

The presence and absence of alkane isomers in petroleum and petroleum derivatives depend on the complexity of these structures. It was assumed that the more complex the structure is the less probable it is that that the molecule can be detected in any petroleum derivative. Complexity is a vague concept, which has not been defined in quantitative terms yet, and therefore there is no experimental method, which could be used to determine 'complexity'. Mass spectrometry and infrared spectroscopy in combination with gas chromatography were used to identify the various structural isomers of alkanes in petroleum ether. The isomers were categorised in quantitative terms by using topological indices and linear discriminant analysis. It was found that alkanes possessing a more complex, highly branched structure are less probable to be detected in petroleum ether than isomers with a simpler backbone structure. It was proposed that the experimental 'measure' of the complexity of isomer(i) should be proportional to 1/C(i), where C(i), denotes the concentration of isomer(i) in a (primary) petroleum derivative.

Mechanistic investigation of the interaction between bisquaternary antimicrobial agents and phospholipids by liquid secondary ion mass spectrometry and differential scanning calorimetry

Mechanisms of interaction between the antimicrobial drugs decamethoxinum and aethonium, which are based on bisquaternary ammonium compounds, and a phospholipid component of biological membranes, dipalmitoylphosphatidylcholine, were studied by means of liquid secondary ion mass spectrometry (LSIMS) and differential scanning calorimetry (DSC). Supramolecular complexes of the drugs with this phospholipid were recorded under secondary ion mass spectrometric conditions. The dependence of the structures of these complexes on structural parameters of the dications of the bisquaternary ammonium compounds was demonstrated. Tandem mass spectrometric investigations of the metastable decay of doubly charged ions of decamethoxinum and aethonium complexes with dipalmitoylphosphatidylcholine allowed estimation of structural parameters of these complexes in the gas phase. Interactions of decamethoxinum and aethonium with model membrane assemblies built from hydrated dipalmitoylphosphatidylcholine were studied using DSC. It was shown that while both drugs can interact with model membranes, the mechanisms of such interactions for decamethoxinum and aethonium differ. The correlation between the nature of these interactions and structural and electronic parameters of the dications of the two bisquaternary agents is discussed. Interpretation of combined mass spectrometric and calorimetric experimental data led to proposals that the molecular mechanisms of antimicrobial action of bisquaternary ammonium compounds are related to their effect on the membrane phospholipid components of microbial cells.

An alternative solid phase peptide fragment condensation protocol with improved efficiency

The success of solid phase peptide synthesis is often limited by the aggregation of the growing peptide chains on the resin. Working from the results of a study of model coupling reactions in solution between Z-Gly-Phe-OH and H-Phe-OBzl, we have achieved higher efficiency in the repetitive solid phase fragment condensation of VGVAPG, in a 3:1 chloroform-phenol solvent system, using diisopropylcarbodiimide (DIC) as coupling agent, and a combination of 3-hydroxy-3,4-dihydro-4-oxo-1,2,3-benzotriazine (HODhbt) and its tetrabutyl ammonium salt as additive, than in DMF with DIC and HODhbt alone.

Investigations on the flucloxacillin levels in human serum, lung tissue, pericardial fluid and heart tissue

Following intramuscular administration of 500 mg flucloxacillin, the levels of this antibiotic were measured in the serum, lung, and heart tissue as well as pericardial fluid obtained during 24 lung and 19 heart operations. Between 55 and 160 min following administration, the intact, inflamed, and tumorous lung tissue pieces contained 3.3-4.0, 2.0-2.7, and 1.5-2.4 mcg/g flucloxacillin, respectively, representing 16-36, 13-16, and 10-18% of the actual serum levels. Pericardial fluid contained practically no flucloxacillin. The cardiac auricle contained 2.3-3.5 mcg/g between 35 and 130 min after administration; the mitral valve showed 1.1-2.5 mcg/g between 90 and 170 min afterward, whereas in the aortic valve 1.6 mcg/g was found between 105-220 min later. These concentrations represented 16-20, 7-22, and 12% of the actual serum levels. Both the serum and tissue levels proved to be higher than those of oxacillin at the same dosage. The flucloxacillin levels of the serum and tissues studied were much higher than the minimum inhibiting concentrations for the sensitive bacteria. Therefore, flucloxacillin is considered an excellent antibiotic for the treatment of respiratory infections and endocarditis, whereas its levels in the pericardial fluid show it insufficient for treatment of pericarditis.

Amikacin: in vitro bacteriological studies, levels in human serum, lung and heart tissue, and clinical results

The amikacin sensitivity of bacteria cultured from 3282 clinical cases of mixed type was determined. Gentamicin and amikacin were equally effective against E. coli strains. Amikacin inhibited the growth of more Pseudomonas aeruginosa strains than did gentamicin. Against Gram-positive bacteria gentamicin proved to be more effective. Many of the gentamicin-resistant strains were sensitive to amikacin. Amikacin levels were measured during 21 pulmonary and 14 heart operations, subsequent to a intramuscular administration of 500 mg amikacin. The serum contained 17-20 microgram/ml amikacin, in the intact, inflamed and tumourous parts of removed lung tissue 9, 6 and 6 microgram/g concentrations were detected, respectively, whereas the cardiac auricle and the pericardial fluid contained 3-4 and 2-4 microgram/ml, respectively. These amikacin levels reach or in most cases even exceed the minimal inhibiting concentrations against the bacteria. Therefore, amikacin is excellent for the treatment of respiratory infections, pericarditis and endocarditis caused by Gram-negative, gentamicin-resistant bacteria. Amikacin treatment of 8 patients with grave diseases as well as the successful local administration of amikacin based on the therapy of 55 cases of surgical suppurations is reported.

Embolism of heart tissue to the middle cerebral artery as a complication of heart surgery

After suture closure of an intraarterial septal defect an atrioventricular block occurred in a 6 years old child. Therefore, the suture was removed and the defect closed by a Dacron patch. The sinus rhythm returned. After the operation convulsions occurred, the patient died after 16h which was considered to be due to cerebral air embolism. Autopsy confirmed a correct operation, but the right middle cerebral artery has been found to be completely occluded by heart muscle and pericardial fat tissue.

An operated case of Holt-Oram syndrome with autosomal dominant inheritance

This report is concerned with a patient successfully operated for Holt-Oram syndrome. The disorder is inherited dominantly with complete penetrance and variable expressivity. It is pointed out that in cases of congenital heart disease familial cumulation must be borne in mind which can easily be verified by pedigree investigation. After demonstrating autosomal dominant inheritance, suitable inferences must be drawn for genetic counseling. Attention is drawn to the heart-surgical significance of the rhythm disorders so often associated with the syndrome.