The interacting roles of climate, soils, and plant production on soil microbial communities at a continental scale.

Soil microbial communities control critical ecosystem processes such as decomposition, nutrient cycling, and soil organic matter formation. Continental scale patterns in the composition and functioning of microbial communities are related to climatic, biotic, and edaphic factors such as temperature and precipitation, plant community composition, and soil carbon, nitrogen, and pH. Although these relationships have been well explored individually, the examination of the factors that may act directly on microbial communities vs. those that may act indirectly through other ecosystem properties has not been well developed. To further such understanding, we utilized structural equation modeling (SEM) to evaluate a set of hypotheses about the direct and indirect effects of climatic, biotic, and edaphic variables on microbial communities across the continental United States. The primary goals of this work were to test our current understanding of the interactions among climate, soils, and plants in affecting microbial community composition, and to examine whether variation in the composition of the microbial community affects potential rates of soil enzymatic activities. A model of interacting factors created through SEM shows several expected patterns. Distal factors such as climate had indirect effects on microbial communities by influencing plant productivity, soil mineralogy, and soil pH, but factors related to soil organic matter chemistry had the most direct influence on community composition. We observed that both plant productivity and soil mineral composition were important indirect influences on community composition at the continental scale, both interacting to affect organic matter content and microbial biomass and ultimately community composition. Although soil hydrolytic enzymes were related to the moisture regime and soil carbon, oxidative enzymes were also affected by community composition, reflected in the abundance of soil fungi. These results highlight that soil microbial communities can be modeled within the context of multiple interacting ecosystem properties acting both directly and indirectly on their composition and function, and this provides a rich and informative context with which to examine communities. This work also highlights that variation in climate, microbial biomass, and microbial community composition can affect maximum rates of soil enzyme activities, potentially influencing rates of decomposition and nutrient mineralization in soils.

Identifying determinants of nations' wetland management programs using structural equation modeling: an exploratory analysis.

Integrated management and policy models suggest that solutions to environmental issues may be linked to the socioeconomic and political characteristics of a nation. In this study, we empirically explore these suggestions by applying them to the wetland management activities of nations. Structural equation modeling was used to evaluate a model of national wetland management effort and one of national wetland protection. Using five predictor variables of social capital, economic capital, environmental and political characteristics, and land-use pressure, the multivariate models were able to explain 60% of the variation in nations' wetland protection efforts based on data from 90 nations, as defined by level of participation in the international wetland convention. Social capital had the largest direct effect on wetland protection efforts, suggesting that increased social development may eventually lead to better wetland protection. In contrast, increasing economic development had a negative linear relationship with wetland protection efforts, suggesting the need for explicit wetland protection programs as nations continue to focus on economic development. Government, environmental characteristics, and land-use pressure also had a positive direct effect on wetland protection, and mediated the effect of social capital on wetland protection. Explicit wetland protection policies, combined with a focus on social development, would lead to better wetland protection at the national level.

Depression in late life, cognitive decline and white matter pathology in two clinico-pathologically investigated cases.

CASE REPORTS: We report two cases of late life depression who became progressively more resistant to treatment, developed cognitive impairment, and began to exhibit neurological abnormalities and evidence of vascular disease. A discussion of the clinical features of the cases is accompanied by reports of neuropathology and neuroimaging findings. Extensive white matter lesions were present on computed tomography in both patients, and basal ganglia infarcts were seen in one. Neuropathology revealed evidence of cerebral atrophy, demyelination and white matter lesions in addition to cerebrovascular and generalised vascular disease. Neither patient exhibited Alzheimer pathology outwith the norm for their age. We believe this to be the first report of neuropathological findings in depression with white matter changes. LITERATURE REVIEW: The pathological basis of white matter lesions and their relationship to depression, its age of onset and clinical features is addressed in relation to the cases described. Pathological investigation of white matter lesions has not previously been carried out in depression and hypotheses regarding their nature in this illness are based on extrapolation from research in a variety of other disorders. The association of depression with vascular risk factors is considered, as is the relationship between depression and cognitive deficits. There is a need for further investigation in this area.

A comparison of sleep profiles in patients with dementia with lewy bodies and Alzheimer's disease.

INTRODUCTION: Sleep disturbances are common in healthy old age and in dementia syndromes. Polysomnography has demonstrated typical changes in both Alzheimer's disease (AD) and dementia with Lewy bodies (DLB) with AD being characterised by sundowning and sleep apnoea and DLB patients showing more disturbances of movement control during sleep. The technical difficulties associated with EEG sleep recordings mean that polysomnography is not possible out of specialist centres. OBJECTIVES: To use questionnaires to assess the frequency of sleep disturbances in patients with Alzheimer's disease and dementia with Lewy bodies. METHOD: The sleep profiles of twenty patients with AD and 17 with DLB were assessed using three questionnaires, one designed to assess night time sleep disturbance, one day time sleepiness and the last carer burden. The sleep questionnaires were repeated in a subgroup after treatment with a cholinesterase inhibitor (rivastigmine). RESULTS: Level of sleep disturbance in both groups was high. DLB patients had more overall sleep disturbance, more movement disorders whilst asleep and more abnormal day time sleepiness. Treatment with rivastigmine produced a trend towards normalisation of sleep profile in a small number of subjects. CONCLUSIONS: Both groups have extensive sleep problems. The DLB and AD groups have different sleep profiles that are of diagnostic importance and may suggest different treatment strategies. The results are consistent with those found from polysomnographic assessment and suggest that the questionnaires used are sensitive to detect differences previously documented with polysomnography.

The effects of gap size and disturbance type on invasion of wet pine savanna by cogongrass, Imperata cylindrica (Poaceae).

Cogongrass is a nonindigenous species perceived to threaten native communities of the southeastern United States through modification of species composition and alteration of community processes. To examine how gap size and disturbance type influence the invasion of wet pine savannas by cogongrass, we performed three field experiments to evaluate the response of cogongrass seeds and transplanted seedlings to four different gap sizes, four types of site disturbance, and recent burning of savanna vegetation. Cogongrass germinated, survived, and grew in all gap sizes, from 0 to 100 cm in diameter. Similarly, disturbance type had no effect on germination or seedling and transplant survival. Tilling, however, significantly enhanced transplanted seedling growth, resulting in a tenfold increase in biomass over the other disturbance types. Seedling survival to 1 and 2 mo was greater in burned savanna than unburned savanna, although transplant survival and growth were not affected by burning. Results of this study suggest that cogongrass can germinate, survive, and grow in wet pine savanna communities regardless of gap size or type of disturbance, including burning. Burning of savanna vegetation may enhance establishment by improving early seedling survival, and soil disturbance can facilitate invasion of cogongrass by enhancing plant growth.

Growth and invasive potential of Sapium sebiferum (Euphorbiaceae) within the coastal prairie region: the effects of soil and moisture regime.

The introduced tree Sapium sebiferum (Euphorbiaceae) is considered a serious threat to the preservation of the coastal prairie region of Louisiana and Texas, although it is currently uncommon in the western part of the region. The objective of this study was to evaluate the potential effects of location, soils, and available moisture on the growth and survival of S. sebiferum in coastal prairie. In a field experiment, S. sebiferum mortality was significantly greater at a western site than at central and eastern sites. The greatest mortality and least growth of surviving plants occurred on a soil from the western region, regardless of site. A greenhouse study also found that S. sebiferum growth was lowest on the western soil. Watering frequency significantly affected S. sebiferum growth, except on the western soil. Sapium sebiferum growth responded to both nitrogen and phosphorus additions for all soils. Soil analyses revealed the highest sand, sodium, and phosphorus contents, and much higher electrical conductivity in the western soil. It is concluded that the soil examined from the western region is unfavorable for S. sebiferum growth, though not to the extent to preclude S. sebiferum completely. Evidence suggests that soil salinity may be the primary cause of the poor S. sebiferum growth at the western site.

Rivastigmine in the treatment of dementia with Lewy bodies: preliminary findings from an open trial.

The objective of this study was to assess the tolerability and efficacy of rivastigmine in a group of patients with probable dementia with Lewy bodies (DLB), using an open label study. Open label treatment was with rivastigmine up to maximum tolerated dose (mean 9.6 mg daily, range 3-12 mg). Eleven patients with DLB, mean age 78.5 years, were treated with this cholinesterase inhibitor. After 12 weeks of treatment, mean Neuropsychiatric Inventory scores fell by 73% for delusions, 63% for apathy, 45% for agitation and 27% for hallucinations. Five of the patients (45%) experienced very significant clinical improvements that had not been achieved with other treatments, including low dose neuroleptics. Medication was well tolerated and parkinsonian symptoms tended to improve. Cholinesterase inhibition may be a safe and effective alternative to neuroleptic treatment in DLB. Such effects may also prove to be applicable to the management of neuropsychiatric symptoms in Parkinson's disease and Alzheimer's disease.

Macroglossia in the Beckwith-Wiedemann syndrome.

An infant with the Beckwith-Wiedemann syndrome is described, with emphasis placed on the occurrence of macroglossia and possible maxillofacial deformities. In addition to placing the syndrome among the clinical entities which result in macroglossia, attention is also brought to concurrent metabolic disorder through hypoglycemia and possible late-occurring visceral malignancy which may produce significant patient compromise.