Neurotoxicity of a fragment of the amyloid precursor associated with Alzheimer's disease

Amyloid deposition in senile plaques and the cerebral vasculature is a marker of Alzheimer's disease. Whether amyloid itself contributes to the neurodegenerative process or is simply a by-product of that process is unknown. Pheochromocytoma (PC12) and fibroblast (NIH 3T3) cell lines were transfected with portions of the gene for the human amyloid precursor protein. Stable PC12 cell transfectants expressing a specific amyloid-containing fragment of the precursor protein gradually degenerated when induced to differentiate into neuronal cells with nerve growth factor. Conditioned medium from these cells was toxic to neurons in primary hippocampal cultures, and the toxic agent could be removed by immunoabsorption with an antibody directed against the amyloid polypeptide. Thus, a peptide derived from the amyloid precursor may be neurotoxic.     

Tissue plasminogen activator reduces neurological damage after cerebral embolism

Intravenous administration of tissue plasminogen activator immediately after the injection of numerous small blood clots into the carotid circulation in rabbit embolic stroke model animals caused a significant reduction in neurological damage. In vitro studies indicate that tissue plasminogen activator produced substantial lysis of clots at concentrations comparable to those expected in vivo, suggesting that this may be the mechanism of action of this drug. Drug-induced hemorrhages were not demonstrable. Tissue plasminogen activator may be of value for the immediate treatment of embolic stroke.     

Polar lightning and decadal-scale cloud variability on Jupiter

Although lightning has been seen on other planets, including Jupiter, polar lightning has been known only on Earth. Optical observations from the New Horizons spacecraft have identified lightning at high latitudes above Jupiter up to 80 degrees N and 74 degrees S. Lightning rates and optical powers were similar at each pole, and the mean optical flux is comparable to that at nonpolar latitudes, which is consistent with the notion that internal heat is the main driver of convection. Both near-infrared and ground-based 5-micrometer thermal imagery reveal that cloud cover has thinned substantially since the 2000 Cassini flyby, particularly in the turbulent wake of the Great Red Spot and in the southern half of the equatorial region, demonstrating that vertical dynamical processes are time-varying on seasonal scales at mid- and low latitudes on Jupiter.     

Evidence for the occurrence of induced resistance to pitch canker,caused by Gibberella circinata (anamorph Fusarium circinatum), in populations of Pinus radiata

Pitch canker, caused by Gibberella circinata, was discovered in California in 1986. Although initially quite damaging to Monterey pines (Pinus radiata), the severity of pitch canker has moderated in areas where the disease was first observed and some trees appear to have recovered completely. The absence of symptoms on trees that were once severely affected implies they have become more resistant to the disease. Experimental work has shown that P. radiata can manifest systemic induced resistance (SIR) in response to infection by the pitch canker pathogen and observations of disease remission may indicate that SIR is operative under natural conditions as well. As a test of this hypothesis, the susceptibility of trees in remission was assessed by inoculating them with G. circinata and recording the extent of lesion development. In addition, randomly selected trees in areas that differed in residence time of pitch canker were inoculated to determine if trees with a longer period of exposure to the pathogen were more resistant to the disease. The results of these tests showed that 89% of trees observed to be in remission sustained very limited lesion development, consistent with resistance to pitch canker. Furthermore, trees in areas where pitch canker was well established tended to be more resistant than trees in areas where the disease was of more recent occurrence. In sum, these findings support the view that SIR occurs in P. radiata and is contributing to a moderation of the impact of pitch canker under natural conditions.     

Haplotypes of “<Emphasis Type="Italic">Candidatus</Emphasis> Liberibacter solanacearum” suggest long-standing separation

Three haplotypes of the recently discovered bacterium species “Candidatus Liberibacter solanacearum” are described and related to geographic ranges. The first two are associated with Zebra Chip/Psyllid Yellows of potatoes and other solanaceous plants, vectored by the tomato/potato psyllid Bactericera cockerelli in North and Central America and New Zealand. The third is associated with diseased carrots in Finland and vectored by the carrot psyllid Trioza apicalis. The haplotypes are described by SNPs on the 16s rRNA, 16s/23s ISR and 50s rplJ and rplL ribosomal protein genes. These SNPs are inherited as a package across the three genes. Haplotype “a” has been found primarily from Honduras and Guatemala through western Mexico to Arizona and California, and in New Zealand. Haplotype “b” is currently known from eastern Mexico and northwards through Texas to south central Washington. These haplotypes show some range overlap in Texas, Kansas and Nebraska. The haplotypes are not yet known to elicit biological differences in the plant or insect hosts. These apparently stable haplotypes suggest separate bacterial populations of long standing.     

Iron mobilization by heathland plant extracts

Aqueous extracts of leaves and shoots of Calluna vulgaris, Erica tetralix, and Betula pendula were reacted with iron compounds in the laboratory. Extracts of B. pendula were found to be most active in solubilizing iron. The iron mobilizing capacity of extracts of C. vulgaris depended upon plant age, season, and soil conditions. C. vulgaris shoots were found to be more readily leached of their soluble organic matter than those of B. pendula but yielded little soluble inorganic material. C. vulgaris extracts were the most acid (pH 4.2–4.5) of those examined.     

Accumulation of Cadmium,Chromium, and Zinc by the Moss Sphagnum Papillosum Lindle

In a series of laboratory experiments employing radiotracer methodology, the uptake of Cd,Cr, and Zn by Sphagnum papillosum Lindle moss from solutions of deionized water and bogwater was investigated. Bioaccumulation of the metals was a passive process, since living anddead moss accumulated metal equally. No significant differences were found in metal uptake ratesfrom single metal solutions and mixed metal solutions, suggesting insignificant competitionbetween the metals occurred at the low concentration range used (10-10 to 10-7 M). Metaluptake conformed with Freundlich adsorption isotherms. Concentration factors of metals inSphagnum papillosum in bog water (103 for Cd and Zn, 102 for Cr) were lower than in deionizedwater (104 for Cd and Zn, 103 for Cr), possibly due to metal complexation by dissolved organicmatter, competition by other major cations present in the bog water (Na+, K+, Mg2+, Ca2+) orcomplexation by chlorides in the bog water. While earlier studies have demonstrated the potentialof using sphagnum mosses for monitoring environmental metal contamination, these experimentsare the first to assess metal uptake in moss using low, environmentally realistic metalconcentrations. The results confirm that mosses would be very effective bioindicators ofenvironmental metal concentrations because the concentration of metal in the moss rapidly anddirectly reflects the metal concentrations in the ambient water.     

Rehabilitation of degraded dry heather [Calluna vulgaris (L.) Hull] moorland by controlled sheep grazing

Many areas of heathland in Europe have seen a decline in the area and condition of Calluna vulgaris (heather)-dominated vegetation, with subsequent declines in the associated faunal interest. Grazing, alongside burning, is still the predominant means of managing heathland vegetation, and, therefore, it is by manipulating this management that cost-effective improvements in vegetation condition can be made. This paper investigates the suitability of different grazing treatments for rehabilitating degraded ‘dry heath’. Treatments varied in the intensity (0-1.9 sheep ha⁻¹ year⁻¹) and timing (summer vs. winter) of sheep grazing. These treatments were compared with the behaviour of vegetation outside the fenced area kept under the previous management (open access all year round). As rabbits were common on the site, fences were erected to prevent access to the sheep grazed plots. Vegetation composition remained stable outside the fenced area, whilst all the fenced treatments showed a decrease in heather utilisation and an increase in the relative frequency of heather over the 5 years of the experiment. The increase was in proportion to the reduction in stocking rate, with only slow increases in relative frequency observed in the high grazing treatments (winter and summer). Other species that benefited from reducing grazing included Empetrum nigrum and Vaccinium myrtillus, whilst declines were observed for Agrostis capillaris and total monocotyledonous species. Only small overall differences were observed between the winter low, summer low and no sheep grazing treatments. However, a difference in response was present between the sheep exclosures and the sheep+rabbit exclosures, indicating that rabbits were having a noticeable effect on heather recovery at this site. On this degraded ‘dry heath’ system, imposing a reduction in stocking density improved the condition of the dwarf shrubs present and reduced the grass component of the vegetation. There was little effect of the timing of grazing, such that a reduction in sheep numbers to 0.8/0.9 sheep ha⁻¹ year⁻¹, to give utilisation levels of below 20%, can achieve the desired result of improving vegetation condition whilst still achieving some economic return from grazing. However, the wide range of ‘sustainable’ stocking densities for different heathland systems highlights the need to base effective management on measured utilisation rather than on stock numbers.