Application of multivariate methods to the conservation management of Hazel scrub in northeast Ireland

The plant species composition of seminatural woods in Northeast Ireland was recorded. Three main types of woodland were identified in habitats where combinations of steep slope, poor drainage and accumulations of large boulders have, in the past, made them unsuitable for agriculture. Despite these characteristics, clearance for agriculture is proceeding rapidly, but mainly in woods from poorly drained sites. Badly drained woods also have a relatively higher proportion of regionally rare plant species and there is, therefore, an argument for some priority for their conservation.

The population size-structures of trees were used to predict future changes in canopy composition, possibly originating from the introduction of myxomatosis to Ireland. Such changes may give rise to management problems associated with canopy closure and a subsequent reduction of species diversity.     

Aluminium toxicity and multiplication of Rhizobium trifolii in a defined growth medium

The responses of six strains of R. trifolii to pH, Ca, Al and phosphate were studied in the defined medium of Munns and Keyser (1981) supplemented with vitamins. Wild-type strains responded in the same way as rifampicin-resistant mutant strains. Multiplication was inhibited by acidity alone at pH4.3, and by 50 μM Al at pH 5.5 (despite the precipitation of Al). This inhibitory effect of Al was overcome by increasing the pH above 6.0, or by increasing the phosphate concentration from 10 to 100 μm. Ca concentration had no effect, nor did holding the medium at 22°C for 36 weeks before inoculation. There was variation between strains in their responses to concentrations of A1 < 50 μM. These responses indicate that the defined medium is a satisfactory model for the white clover rhizosphere.Results from these studies and from chemical analyses indicate that the inhibitory effect of Al under partially-neutralized conditions is not due to a direct effect of monomeric A1, nor to an indirect effect of polymeric A1 in reducing the concentration of phosphate, but is due to a direct effect of polymeric A1.     

Combined effects of best management practices on water quality in oxbow lakes from agricultural watersheds

Water quality conditions in three oxbow lakes were examined before and after best management practices (BMPs) implementation within the Mississippi Delta. Experimental design called for the development of structural and cultural treatments to reduce sediment and associated pollutants entering watershed oxbow lakes. Three watersheds were selected and developed with different levels of BMPs. Changes in lake water quality were used as measures of management success. Analyses of water quality data prior to the implementation of BMPs suggested the lakes were stressed and ecologically damaged due to excessive sediment inflow. Significant improvements in water quality were observed with the use of cultural and structural BMPs. Sediments decreased 34–59%, while Secchi visibility and chlorophyll generally increased. The most dramatic improvements in water quality occurred in the two watersheds that featured cultural practices and combinations of cultural and structural practices. Reducing suspended sediment concentrations in these oxbow lakes favored phytoplankton production resulting in increased chlorophyll concentrations and higher concentrations of dissolved oxygen. Cultural BMPs, more so than structural BMPs, play a vital role in improving lake water quality, and are needed in addition to structural measures to ensure improved water quality in oxbow lakes receiving agricultural runoff.     

Effects of thiopental sedation on learning and memory

Subjects who were administered thiopental showed a loss of memory for events discussed while they were under sedation. We tested the subjects for recognition memory of pictures and recall of associated pairs of letters and words, and found that the subsequent memory loss was correlated with the concentration of thiopental in the venous blood at the time the material was learned. Retention did not appear to be state-dependent because the subject, while under sedation, could recall material learned prior to sedation, and because recall was not facilitated by reinstatement of the sedation.     

A physiological basis for a theory of synapse modification

The functional organization of the cerebral cortex is modified dramatically by sensory experience during early postnatal life. The basis for these modifications is a type of synaptic plasticity that may also contribute to some forms of adult learning. The question of how synapses modify according to experience has been approached by determining theoretically what is required of a modification mechanism to account for the available experimental data in the developing visual cortex. The resulting theory states precisely how certain variables might influence synaptic modifications. This insight has led to the development of a biologically plausible molecular model for synapse modification in the cerebral cortex.     

Electroencephalographic evidence for retention of olfactory cues in homing coho salmon

Differences were observed in the magnitude of the evoked electroencephalographic response to 1 percent morpholine for homing coho salmon (Oncorhynchus kisutch) exposed to morpholine as fingerlings 1 month before smolting as compared to salmon not exposed to morpholine as fingerlings. These results indicate that olfactory information has been retained for 18 months, the period between smolting and the homeward migration.     

Crystal structure analysis of deamino-oxytocin: conformational flexibility and receptor binding

Two crystal structures of deamino-oxytocin have been determined at better than 1.1A resolution from isomorphous replacement and anomalous scattering x-ray measurements. In each of two crystal forms there are two closely related conformers with disulfide bridges of different chirality, which may be important in receptor recognition and activation.     

Experimental allergic encephalomyelitis in agammaglobulinemic chickens

White Leghorn chickens were subjected to bursectomy and total body irradiation at hatching, thus rendering them agammaglobulinemic. At 4 weeks of age, these chickens and control chickens received lyophilized bovine spinal cord emulsified with complete Freund's adjuvant. Agammaglobulinemic chickens developed the lesions of allergic encephalomyelitis with the same frequency and intensity as the controls. Our findings support the contention that antibodies are not necessary for the development of experimental allergic encephalomyelitis.