Clonal production and organization of inhibitory interneurons in the neocortex

The neocortex contains excitatory neurons and inhibitory interneurons. Clones of neocortical excitatory neurons originating from the same progenitor cell are spatially organized and contribute to the formation of functional microcircuits. In contrast, relatively little is known about the production and organization of neocortical inhibitory interneurons. We found that neocortical inhibitory interneurons were produced as spatially organized clonal units in the developing ventral telencephalon. Furthermore, clonally related interneurons did not randomly disperse but formed spatially isolated clusters in the neocortex. Individual clonal clusters consisting of interneurons expressing the same or distinct neurochemical markers exhibited clear vertical or horizontal organization. These results suggest that the lineage relationship plays a pivotal role in the organization of inhibitory interneurons in the neocortex.     

Transpiration and forest structure in relation to soil waterlogging in a Hawaiian montane cloud forest

Transpiration, leaf characteristics and forest structure in Metrosideros polymorpha Gaud. stands growing in East Maui, Hawaii were investigated to assess physiological limitations associated with flooding as a mechanism of reduced canopy leaf area in waterlogged sites. Whole-tree sap flow, stomatal conductance, microclimate, soil oxidation-reduction potential, stand basal area and leaf area index (LAI) were measured on moderately sloped, drained sites with closed canopies (90%) and on level, waterlogged sites with open canopies (50-60%). The LAI was measured with a new technique based on enlarged photographs of individual tree crowns and allometric relationships. Sap flow was scaled to the stand level by multiplying basal area-normalized sap flow by stand basal area. Level sites had lower soil redox potentials, lower mean stand basal area, lower LAI, and a higher degree of soil avoidance by roots than sloped sites. Foliar nutrients and leaf mass per area (LMA) in M. polymorpha were similar between level and sloped sites. Stomatal conductance was similar for M. polymorpha saplings on both sites, but decreased with increasing tree height (r(2) = 0.72; P < 0.001). Stand transpiration estimates ranged from 79 to 89% of potential evapotranspiration (PET) for sloped sites and from 28 to 51% of PET for level sites. Stand transpiration estimates were strongly correlated with LAI (r(2) = 0.96; P < 0.001). Whole-tree transpiration was lower at level sites with waterlogged soils, but was similar or higher for trees on level sites when normalized by leaf area. Trees on level sites had a smaller leaf area per stem diameter than trees on sloped sites, suggesting that soil oxygen deficiency may reduce leaf area. However, transpiration per unit leaf area did not vary substantially, so leaf-level physiological behavior was conserved, regardless of differences in tree leaf area.     

Tree establishment and management on farms in the drylands: evaluation of different systems adopted by small-scale farmers in Mutomo District,Kenya

Agroforestry systems in Sub-Saharan African drylands are complex and heterogeneous in nature even under similar biophysical conditions. This can be attributed to household needs and socioeconomic status which influence the species and utility of the adopted trees. This has an impact on the trees establishment and management system through planting or Farmer Managed Natural Regeneration (FMNR). This study evaluates how trees for different utilities are managed and which socioeconomic factors influence these decisions. The study used primary data collected in Mutomo District, Kenya through a household survey based on a structured questionnaire. A paired sample t-test was done to assess the preferred mode of adopting trees for different utilities while factor analysis was used to characterize the households as either planting trees or practicing FMNR. Multiple linear regression using household regression factor scores as independent variables and socioeconomic indicators as dependent variables was done to ascertain which socioeconomic factors affect tree adoption. The results show that trees planted were mostly exotic species valued for their nutrition and commercial value, while FMNR was used for subsistence products and environmental services. Household size, livestock levels and mobility had a positive correlation with tree planting, while income, access to markets and roads had an inverse correlation. Access to natural woodland, distance to the nearest motorable road and land size had a positive correlation with tree protection. It is hoped that this knowledge will act as a reference point when designing agroforestry projects in similar areas to ensure they are more aligned to specific site and household conditions.     

Einfluß von SO2 und HF auf freie Aminosäuren der Fichte (Picea abies [L.] Karsten)

The influence of SO₂ and HF on free amino acids of spruce . The influence of the air pollutants SO₂ and HF on composition and amount of free amino acids was investigated. Distinct differences in the pattern of amino acids are caused, particularly in glutaminic acid and compounds based on it.     

Chemical and sensory quantification of geosmin and 2-methylisoborneol in rainbow trout (Oncorhynchus mykiss) from recirculated aquacultures in relation to concentrations in basin water

Globally, aquaculture systems with water recirculation experience increasing problems with microbial taste and odor compounds (TOCs) such as geosmin and 2-methylisoborneol (MIB). This study investigated the content of geosmin and MIB in water and the flesh of 200 rainbow trouts from eight recirculated aquaculture systems in Denmark. TOC content in the fish flesh was measured by a dynamic headspace extraction method and was evaluated by a sensory panel. The results showed significant correlations between TOC content in water and fish and between chemical analysis and sensory perception. When geosmin exceeded 20 ng/L in the water, 96% of the fish had an intense muddy flavor, but below 10 ng geosmin/L, 18% of the fish (only 3% in special depuration ponds) had an intense muddy flavor. The results indicate that TOC levels <10 ng/L will ensure that a negligible portion of the fish obtains an unpalatable taste and flavor due to TOCs.     

The incredible fungal genus —Drechslera — and its phytotoxic ophiobolins

ManyDrechslera species that haveCochliobolus sp. as a perfect stage produce a related group of ophiobolins, sesterterpenoids (C-25’s), which are phytotoxic to a wide range of plants. One of the most toxic ophiobolins is 6-epiophiobolin A and it is produced by all of theDrechslera species thus far studied. On the other hand, some novel ophiobolins have been found inD. oryzae: ophiobolin J, 6-epiophiobolin I, and 8-deoxyophiobolin J. Potentially, genetic crosses made between these fungi could yield novel organisms, producing novel combinations of the ophiobolins, and thus new pathotypes. Ophiobolins are being used in tissue culture systems to screen plants for sensitivity to these toxins. Paper presented at the Bat-Sheva Seminar on Host - Fungus Interaction, Jerusalem, Israel (March 14–25,1988).     

Genotypic and phenotypic screening of high and low virulence Staphylococcus aureus isolates from rabbits for biofilm formation and MSCRAMMs

At rabbit flock level, two types of Staphylococcus aureus infections can be distinguished. In the first type, caused by low virulence strains, the infection remains limited to a small number of animals. The second type of infection is caused by the high virulence strains, which spread throughout the rabbitry. The pathogenetic capacity of a particular S. aureus strain is attributed to a combination of extracellular factors and invasive properties such as adherence and biofilm formation. Twenty eight high virulence and 34 low virulence S. aureus isolates recovered from rabbits between 1998 and 2003 were used to study slime production on Congo red Agar (CRA) and prevalence of bap, icaA and icaD associated with biofilm formation. Furthermore these strains were screened for the presence of bbp, clfA, clfB, cna, ebpS, eno, fnbA, fnbB and fib encoding microbial surface components recognizing adhesive matrix molecules (MSCRAMMs). The presence of icaA and icaD was not correlated with slime production on CRA. Bap was absent in all strains. All rabbit S. aureus strains harboured clfA and clfB. The prevalences of ebpS, eno, fnbA and fib did not reveal striking differences between high and low virulence strains. FnbB prevalence in high virulence isolates was lower than in low virulence isolates and cna was absent in high virulence strains. It was remarkable that only high virulence strains were positive for bbp. Further research is necessary to elucidate the significance of bbp in the pathogenesis of high virulence strains.