Membrane lipids and ethanol tolerance in the mouse. The influence of dietary fatty acid composition

Mice of the TO Swiss strain received diets containing different amounts of saturated or unsaturated fat throughout life. These diets produced characteristic changes in cardiac phospholipid fatty acid composition, but produced no significant differences in fatty acid composition of phospholipids from a crude membrane fraction of brain. When littermates of these animals were exposed to ethanol vapour in an inhalation chamber it was observed that mice which had received a diet high in saturated fat lost the righting reflex at an estimated concentration of ethanol in blood higher than that required for mice receiving a control diet, or a diet rich in polyunsaturated fat. Analysis of the brain membrane fraction from those animals which had received ethanol revealed that mice receiving the highly saturated fat diet now had a significantly greater proportion of saturated fatty acids in brain membrane phospholipids. These results are discussed in relation to the hypothesis that brain membrane lipid composition may influence the behavioural response to ethanol.     

The altered pattern of amylose accumulation in the endosperm of low-amylose barley cultivars is attributable to a single mutant allele of granule-bound starch synthase I with a deletion in the 5'-non-coding region

Reasons for the variable amylose content of endosperm starch from waxy cultivars of barley (Hordeum vulgare) were investigated. The mature grains of most such cultivars contain some amylose, although amounts are much lower than in wild-type cultivars. In these low-amylose cultivars, amylose synthesis starts relatively late in grain development. Starch granules in the outer cell layers of the endosperm contain more amylose than those in the center. This distribution corresponds to that of granule-bound starch synthase I (GBSSI), which is more severely reduced in amount in the center of the endosperm than in the outer cell layers, relative to wild-type cultivars. A second GBSSI in the barley plant, GBSSIb, is not detectable in the endosperm and cannot account for amylose synthesis in the low-amylose cultivars. The change in the expression of GBSSI in the endosperm of the low-amylose cultivars appears to be due to a 413-bp deletion of part of the promoter and 5'-untranslated region of the gene. Although these cultivars are of diverse geographical origin, all carry this same deletion, suggesting that the low-amylose cultivars have a common waxy ancestor. Records suggest a probable source in China, first recorded in the 16th century. Two further families of waxy cultivars have no detectable amylose in the endosperm starch. These amylose-free cultivars were selected in the 20th century from chemically mutagenized populations of wild-type barley. In both cases, 1-bp alterations in the GBSSI gene completely eliminate GBSSI activity.     

Bioluminescent Listeria monocytogenes provide a rapid assay for measuring biocide efficacy

Abstract A recombinant derivative of Listeria monocytogenes 23074, engineered to express the luxAB genes of Vibrio fischeri MJ1, has a bioluminescent phenotype that provides a rapid monitor of microbial viability. The antibacterial activity of phenol and chlorhexidine diacetate (Hibitane) was measured using both bioluminescence and viable counts. Concentration exponents were assessed as 7.3 for phenol and 2.63 for chlorhexidine diacetate using plate counts. The rapidity of bioluminescence measurement constitutes a major advantage in biocide assessment.     

Mechanisms of action of disinfectants

Disinfectants and biocides are a chemically diverse group of agents which are generally considered to exhibit poor selective toxicity. This should not be mistaken for poor target specificity, however, and much is now known concerning the damaging interactions which may arise between bacterial cell and disinfectant agent. Critical governing features of these interactions are the physicochemical characteristics of the chemical agent, cell morphology, and the physiological status of the microorganism. Antibacterial events include membrane disruption, macromolecule dysfunction, and metabolic inhibition; the consequential effect is determined by the relative contribution(s) of the target(s) to microbial cell survival and the possible initiation of self-destructive processes. Disinfection kinetics offer a measure to differentiate between physiochemical and chemical interactions.Increasingly demanding disinfectant applications require more sophisticated use of biocidal systems. Approaches include: agents in combination, whereby a knowledge of mechanism of action assists in designing optimal mixtures; intracellular biocide delivery, using cellular transport processes to overcome cellular barriers; and targeted donation of biocide from delivery systems, requiring an understanding of target reactivity.A knowledge of disinfection mechanisms provides a basis from which novel chemistries and synergistic combinations may be developed.     

Control of microbial contamination of Franz diffusion cell receptor phase in the development of transcutaneous breast cancer therapeutics

Aims:  To determine the micro-organism contamination of excised porcine (pig) ear, and evaluate the use of Cyclopore track-etched membranes (CTEM) for preventing ingress into Franz-type diffusion cells.
Methods:  Swabs were taken from four locations and used to inoculate Tryptone Soya Agar (TSA) and Sabouraud Dextrose Agar (SDA) plates. Diffusion cells were assembled to include porcine skin with and without CTEM, and the receptor phase sampled periodically and spread onto plates.
Results:  Five distinct colony types were isolated after incubation of all swabs on TSA plates at 37°C; on SDA plates, one fungal colony was found at 30°C and one at 37°C. The SDA agar plate incubated at 30°C resulted in the growth of a large diffused white fungal colony. No regional differences were observed. Without the CTEM, the receptor phase became contaminated within 6 h. With the CTEM present, microbial ingress was substantially retarded with visible presumptive fungal growth occurring at 24 h and detectable contamination on both microbiological media at 48 h.
Conclusions:  As expected, the native porcine ears were considerably contaminated. The ingress of contamination into the diffusion cell receptor phases can be largely, but not entirely, eliminated using CTEM. The addition of antimicrobial agents was necessary to eliminate micro-organisms that were observed at later time points.
Significance and Impact of the Study:  This article, while highlighting the presence of a high number of micro-organisms on native porcine skin, presents a practical means to reduce the risk of microbial contamination in transdermal/transcutaneous permeation studies, particularly in the study of cell cultures grown within Franz diffusion cell receptor compartments.     

Reciprocal role of the inward currents ib, Na and i(f) in controlling and stabilizing pacemaker frequency of rabbit sino-atrial node cells.

Experiments and computations were done to clarify the role of the various inward currents in generating and modulating pacemaker frequency. Ionic currents in rabbit single isolated sino-atrial (SA) node cells were measured using the nystatin-permeabilized patch-clamp technique. The results were used to refine the Noble-DiFrancesco-Denyer model of spontaneous pacemaker activity of the SA node. This model was then used to show that the pacemaker frequency is relatively insensitive to the magnitude of the sodium-dependent inward background current ib, Na. This is because reducing ib, Na hyperpolarizes the cell and so activates more hyperpolarizing-activated current, i(f), whereas the converse occurs when ib, Na is increased. The result is that i(f) and ib, Na replace one another and so stabilize nodal pacemaker frequency.