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Biomedical subjects

K Arnold

Publications and source records attributed to K Arnold.

At least 199 records · Page 11Linked to original sources
PubMed1983

Effect of poly(ethylene glycol) on phospholipid hydration and polarity of the external phase.

The hydration properties of phosphatidylcholine (PC)/water dispersions on the addition of poly(ethylene glycol) were studied by means of 2H-NMR. The quadrupole splittings and their temperature dependences correspond to measurements of PC/water dispersions at low water content. It is concluded that the bound water is partly extracted by poly(ethylene glycol) but the binding properties of the water in the inner hydration shell of about five water molecules are not changed. The ability of some phospholipid/water dispersions to undergo phase transitions to nonlamellar structures upon dehydration is discussed. Dipalmitoylphosphatidylcholine (DPPC) and egg phosphatidylcholine do not form nonlamellar structures on addition of purified poly(ethylene glycol), as was demonstrated by means of 31P-NMR. Poly(ethylene glycol) decreases the polarity of the aqueous phase and the partition of hydrophobic molecules between the membrane and the external phase is changed. This was demonstrated using the excimer fluorescence of pyrene in a ghost suspension. It is suggested that the changes in polarity and hydration on the addition of poly(ethylene glycol) can contribute to the alterations in the membrane surface observed under conditions of membrane contact and fusion.

Cell Fusion↗
PubMed1983

The plasma levels of chlormethiazole and two of its metabolites in elderly subjects after single and multiple dosing.

Plasma levels of chlormethiazole and two of its metabolites have been estimated in elderly subjects both after single and repeated oral dosage and on withdrawal. A sensitive analytical method was developed to permit the quantitation of chlormethiazole and its two major metabolites in plasma. The two major metabolites were positively identified against authentic standards as 5-acetyl-4-methylthiazole and 5-(1-hydroxyethyl)-4-methylthiazole. Chlormethiazole and its metabolites were shown to have accumulated to varying extents after seven nightly doses. On withdrawal of the drug, the plasma was free of chlormethiazole within 44 h and free of all traces of its metabolites within 84 h. The accumulation was not accompanied by any undue clinical effect and was not in itself considered to be detrimental to the normal use of chlormethiazole in the treatment of sleep disturbances in the elderly.

Journal Article↗
PubMed1983

[Artificial nutrition in neurology--indications and problems].

36 patients with severe neurological diseases (craniocerebral trauma, cerebrovascular insufficiency, meningo-encephalitis, polyneuropathy, paraplegia, intoxication etc.) received for more than 3 months monosaccharides and polyols (Triofusin E 1000) and a 10-%-concentration of crystalline amino acids (Aminofusin L10% kohlenhydratfrei) via the parenteral route in combination with / or exclusively a nutrient-defined diet (Biosorb). Exclusive enteral nutrition was given preference if possible. Numerous laboratory parameters, as for example blood counts, "hepatic enzymes", electrolytes, trace elements, plasma proteins, lipids, urea and creatinine were determined once a week. Substitutions and secondary complications were registered in addition. Iron and plasma proteins had to be substituted most frequently. It could be proved that hypoferremia was caused by insufficient iron supply in case of exclusive/prevailing parenteral nutrition, incorrect application of the iron preparations, inflammatory complications with iron moving into the R.E.S., as well as malabsorption syndromes probably induced by bacteria. Inflammatory complications were also the major cause of protein deficiency syndromes (hypoalbuminemia). In case of relatibely often occurring diarrhea, however, it could clearly be proved that it was not induced by nutrition but was produced by a broad-spectrum antibiosis. Chronically persistent diarrhea with colitis-like colonic changes required enteral feeding with an oligopeptide diet (z.B. Peptisorb) via jejunal feeding tube. Nitrogen balances which were determined after more than 3 months of artificial nutrition formed the basis of a nutritional plan differentiated according to diagnostic groups and stages of disease.

Adolescent↗
PubMed1983

Penicillinase-producing Neisseria gonorrhoeae isolates from different localities in south east Asia. Susceptibility to 15 antibiotics.

Sixty four penicillinase-producing Neisseria gonorrhoeae (PPNG) and 24 non-penicillinase-producing (non-PPNG) strains isolated from six different south east Asian localities were tested by the agar dilution method against 15 antibiotics. All isolates were susceptible to spectinomycin and sulphamethoxazole-trimethoprim (19:1 ratio). A large proportion of both PPNG and non-PPNG strains showed, however, a decreased susceptibility to tetracycline, kanamycin, and erythromycin: 49% with minimum inhibitory concentrations (MICs) of tetracycline greater than or equal to 2 micrograms/ml, 34% with MICs of kanamycin greater than or equal to 32 micrograms/ml, and 80% with MICs of erythromycin greater than or equal to 2 micrograms/ml. These MIC cut-off values were chosen since they are close to the highest concentrations of these antibiotics attainable in serum after drug administration. Resistance to these antibiotics was not related to penicillinase production and does not appear to be confined to gonococci isolated from one particular locality. Strains showing resistance concurrently to two or three of these drugs were often isolated from different south east Asian countries. All eight cephalosporins tested were effective against both PPNG and non-PPNG strains. On a weight to weight basis the new cephalosporins--namely, moxalactam, cefoperazone, cefotaxime, and ceftriaxone--were the most effective. In contrast to those of cefoxitin, cefuroxime, moxalactam, and cefoperazone the MICs of cefamandole, cefotaxime, and ceftriaxone were significantly affected when the inoculum size was increased from 10(3) to 10(6) colony forming units (cfu).

Anti-Bacterial Agents↗
PubMed1983

Influence of polyethylene glycol on the structure of the erythrocyte membrane: an ESR study.

Using a fatty acid spin label (I (10, 3)) it was found that the membrane fluidity of intact human erythrocytes is not influenced by polyethylene glycol (PEG) up to a concentration of 10 wt%. On the contrary a drastic effect of PEG on the spectrum of maleimide spin labeled membrane proteins of erythrocyte ghosts were detected. It is suggested that aggregation and/or conformational changes of membrane proteins were induced by PEG.

Blood Proteins↗
PubMed1982

Quantitative estimation of non-lamellar structures in membranes. A 31P-nmr and electron microscopical study of the influence of linolic acid on the erythrocyte membrane.

The influence of linolic acid on the phase behaviour of erythrocyte membranes has been studied using the 31P-nmr spectroscopy and freeze-fracture electron microscopy. For untreated membranes a lamellar arrangement is found in the nmr spectra as well as in electron micrographs. Incubation of erythrocytes with vesicles from linolic acid yields dramatic changes in membrane structure. Besides the lamellar structure there are non-lamellar phases of phospholipids. The percentage of lipids arranged in these structures can be estimated from the nmr spectra by computer simulation. A combination of freeze-fracture and nmr experiments indicates that hexagonal and micellar structures are involved in the non-lamellar phase.

Erythrocyte Membrane↗
PubMed1982

Structural transitions of the erythrocyte membrane: an ESR approach.

The effect of temperature and ionic strength on the ESR spectrum of the fatty acid spin label I (10,3) in membranes of freshly drawn human red blood cells has been investigated. The results suggest that the microviscosity of the membrane is not strongly influenced by the ionic strength. Discontinuities at various temperatures could be observed, which disappear after cholesterol treatment. The possible role of membrane lipids and proteins on the thermotropic membrane behaviour observed is discussed. It is assumed that the spectra are averaged signals from different regions of the membrane.

Blood Sedimentation↗
PubMed1981

31p-NMR investigations of phase separation in phosphatidylcholine/phosphatidylethanolamine mixtures.

A phase diagram of DPPC-DPPE mixture is constructed by an analysis of the temperature dependence of the anisotropy of chemical shift of the 31P-NMR signals of the individual components. At each temperature the phase state of the individual phospholipids is described. Thus 31P-NMR is more informative than other methods such as ESR, DSC and fluorescence. The measurements confirm the conclusion of other authors that there is a phase separation in the gel state. In the temperature range of the phase transition the molecules are exchanged rapidly between liquid-crystalline and solid regions. In addition to the phase diagram a theoretical approach is applied to estimate the relative distribution of like and unlike molecules in the liquid-crystalline state and a nonrandom distribution is found.

Magnetic Resonance Spectroscopy↗
PubMed1981

Neisseria gonorrhoeae strains isolated in Hong Kong: in vitro susceptibility to 13 antibiotics.

Fifty-five Neisseria gonorrhoeae strains isolated in Hong Kong over a period of 6 months were tested for their in vitro susceptibility to 13 antimicrobial agents by the agar dilution method. Six strains were beta-lactamase producing. In addition, five beta-lactamase strains from Singapore were tested. Among the non-beta-lactamase-producing strains, 34 (62%) had intermediate resistance to penicillin, with minimal inhibitory concentrations (MICs) ranging from 0.125 to 0.5 microgram/ml, and 15 strains were fully susceptible to penicillin (MICs, 0.015 to 0.06 microgram/ml). The MICs of penicillin for all beta-lactamase-producing strains were 2 microgram/ml, and the strains were resistant to ampicillin. Although a direct correlation between the MICs for resistance to penicillin and the other antibiotics tested was not observed, the gonococci isolated in Hong Kong were notably more resistant to tetracycline and streptomycin than has been reported elsewhere, with 78% of strains requiring for inhibition an MIC of tetracycline of greater than 2 microgram/ml and 51% of the isolates requiring an MIC of streptomycin of greater than 128 microgram/ml. All strains were susceptible to spectinomycin and kanamycin as well as to sulfamethoxazole-trimethoprim (ratio, 19:1). Among the cephalosporins, the order of effectiveness was cefuroxime, cefamandole, and cefoxitin. The older generation of cephalosporins, cephradine and cephalexin, was the least effective: 45 and 37% of the strains, respectively, required for inhibition MICs of greater than or equal to 8 microgram/ml. Cefotaxime, a new parenteral cephalosporin, was the most active; the median MIC was at least 10-fold lower than that of cefuroxime.

Anti-Bacterial Agents↗