β-D-galactosidase activity of viable, non-culturable coliform bacteria in marine waters

The β-D-galactosidase activity of viable but non-culturable (vnc) Escherichia coli cells in seawater was investigated using a rapid fluorimetric enzyme assay. Results from microcosm studies showed that loss of culturability did not necessarily result in loss of the ability to produce the galactosidase enzyme. Even when no culturable cells were detected, a positive enzyme assay response was observed and the activity of the inducible enzyme over time more closely reflected the number of vnc cells present.     

Regulation of Rat Dopamine Transporter mRNA and Protein by Chronic Cocaine Administration

This study describes a direct comparison of dopamine transporter (DAT) mRNA and protein, as well as its binding sites, in tissue from the same animals after chronic cocaine administration. Rats were treated twice daily with 25 mg/kg cocaine or with saline. After 8 days of cocaine administration, changes in DAT mRNA levels in the substantia nigra pars compacta and ventral tegmental area were measured by in situ hybridization, and DAT protein in the striatum was quantified by immunoblotting. Whereas chronic cocaine treatment significantly reduced levels of DAT mRNA in the substantia nigra pars compacta and ventral tegmental area as compared with vehicle-treated controls, cocaine treatment did not alter DAT protein levels in the striatum. Furthermore, the density of DAT binding sites was also measured in the striatum by quantitative autoradiography using two DAT radioligands, 33-(4-[125I]iodophenyl)tropane-2-carboxylic acid methyl ester ([125I]RTI-55) and [3H]propanoyl-3beta-(4-tolyl)tropane ([3H]PTT). Similar to the results of immunoblotting of DAT protein, [1251]RTI-55 and [3H]PTT binding site levels also remained unaltered. These results indicate a dissociation in the regulation of DAT mRNA and its protein levels as a result of cocaine administration in rats. This study also indicates that the DAT ligands [3H]PTT and [125I]RTI-55 provide an accurate assessment of DAT protein levels.     

False Memory ≠ False Memory: DRM Errors Are Unrelated to the Misinformation Effect

The DRM method has proved to be a popular and powerful, if controversial, way to study ‘false memories’. One reason for the controversy is that the extent to which the DRM effect generalises to other kinds of memory error has been neither satisfactorily established nor subject to much empirical attention. In the present paper we contribute data to this ongoing debate. One hundred and twenty participants took part in a standard misinformation effect experiment, in which they watched some CCTV footage, were exposed to misleading post-event information about events depicted in the footage, and then completed free recall and recognition tests. Participants also completed a DRM test as an ostensibly unrelated filler task. Despite obtaining robust misinformation and DRM effects, there were no correlations between a broad range of misinformation and DRM effect measures (mean r  = −.01). This was not due to reliability issues with our measures or a lack of power. Thus DRM ‘false memories’ and misinformation effect ‘false memories’ do not appear to be equivalent.     

Consequences of defaunation for a tropical tree community

Hunting affects a considerably greater area of the tropical forest biome than deforestation and logging combined. Often even large remote protected areas are depleted of a substantial proportion of their vertebrate fauna. However, understanding of the long‐term ecological consequences of defaunation in tropical forests remains poor. Using tree census data from a large‐scale plot monitored over a 15‐year period since the approximate onset of intense hunting, we provide a comprehensive assessment of the immediate consequences of defaunation for a tropical tree community. Our data strongly suggest that over‐hunting has engendered pervasive changes in tree population spatial structure and dynamics, leading to a consistent decline in local tree diversity over time. However, we do not find any support for suggestions that over‐hunting reduces above‐ground biomass or biomass accumulation rate in this forest. To maintain critical ecosystem processes in tropical forests increased efforts are required to protect and restore wildlife populations.     

The binding of lipopolysaccharide from Escherichia coli to mammalian cell membranes and its effect on liposomes

The kinetics of the absorption of ³²P- or ¹⁴C-labelled lipopolysaccharide from Escherichia coli NCTC 8623, serotype 0 125, chemotype XII, to erythrocytes, leukocytes, peritoneal macrophages and peritoneal lymphocytes was examined. Under variable conditions maximal levels of binding were found due to saturation of receptor sites on the cell membrane or steric hindrance by bound lipopolysaccharide. During adsorption slight leakage of haemoglobin was found but complete lysis of erythrocytes was ruled out after noting the effect of lipopolysaccharide on artificial lipid bilayers.The affinity of lipopolysaccharide to cell membranes revealed a consistent pattern of cyclic fluctuation between adsorption and desorption. A model was proposed to explain this cyclic fluctuation in binding based on membrane reorganization. It was significant that the cycle of lipopolysaccharide adsorption-desorption proceeded to completion even if the process was interrupted. The indication was that, once triggered, membrane reorganization occurred independently without influence from the test environment.     

An analysis of the association of collagen based on structural models.

The existence and distribution of vertical, interacting edges on cylindrical surfaces, which were derived from the basic structural features of the collagen molecule, have been examined as a function of the angle θ of the superhelix. Over the range θ = 26°–33° and near θ = 36°, the strongest intermolecular association was detected at 29.95°. This model exhibited three similar, self-interacting edges, separated by approximately 120°. The potential for three similar but nonidentical edges lies in the geometry of the collagen molecule, but the existence of such edges and their ability to self-associate is dependent upon the unique amino acid sequence. The relative strengths of association of each edge with itself and with the other edges are not identical, but the present analysis does not permit a judgment as to whether this variation could result in functional specificity in such interactions. All three chains participate in each edge though their contribution to the relative interaction strength is not identical. These edges showed distinct maxima when displaced past one another by integral intervals of D, where D = 233 residue positions (quarter-stagger). The strongest relative interaction occurs at a displacement of 1D.