Refinements of and commentary on the silver staining techniques of Fernández-Galiano

The original ammoniacal silver carbonate staining technique and subsequent modification developed by Fernández-Galiano are useful for investigating ciliate protozoan systematics and/or ciliate cortical structure and morphogenesis. The technique is complicated, however, by both uncertainties arising from the need to count drops of reagents and subjective control of the staining intensity. I have resolved these complications by defining volumes of reagents rather than using drops and by defining a range of staining times. I also comment on various steps of the techniques. My techniques are simplified and refined to produce consistent, high quality staining results.     

Stereological Study of Amygdala Glial Populations in Adolescents and Adults with Autism Spectrum Disorder

The amygdala undergoes aberrant development in autism spectrum disorder (ASD). We previously found that there are reduced neuron numbers in the adult postmortem amygdala from individuals with ASD compared to typically developing controls. The current study is a comprehensive stereological examination of four non-neuronal cell populations: microglia, oligodendrocytes, astrocytes, and endothelial cells, in the same brains studied previously. We provide a detailed neuroanatomical protocol for defining each cell type that may be applied to other studies of the amygdala in neurodevelopmental and psychiatric disorders. We then assess whether cell numbers and average volumes differ between ASD and typically developing brains. We hypothesized that a reduction in neuron numbers in ASD might relate to altered immune function and/or aberrant microglial activation, as indicated by increased microglial number and cell body volume. Overall, average non-neuronal cell numbers and volumes did not differ between ASD and typically developing brains. However, there was evident heterogeneity within the ASD cohort. Two of the eight ASD brains displayed strong microglial activation. Contrary to our original hypothesis, there was a trend toward a positive correlation between neuronal and microglial numbers in both ASD and control cases. There were fewer oligodendrocytes in the amygdala of adult individuals with ASD ages 20 and older compared to typically developing controls. This finding may provide a possible sign of altered connectivity or impaired neuronal communication that may change across the lifespan in ASD.     

Addressing barriers to improve biocrust colonization and establishment in dryland restoration

Methods to reduce soil loss and associated loss of ecosystem functions due to land degradation are of particular importance in dryland ecosystems. Biocrusts are communities of cyanobacteria, lichens, and bryophytes that are vulnerable to soil disturbance, but provide vital ecosystem functions when present. Biocrusts stabilize soil, improve hydrologic function, and increase nutrient and carbon inputs. Methods to reestablish biocrust rapidly, when lost from ecosystems, have the potential to restore important dryland ecosystem functions and thereby increase probability of successful rehabilitation. The aim of this study was to identify habitat ameliorations to enhance the success of biocrust inoculation by: (1) reducing physiological stress on biocrusts and increasing resource availability (using shade, soil surface roughening, and watering), and (2) stabilizing mobile soils (using straw borders, three soil tackifiers [soil stabilizers], and a combination of shade, water, roughening, and tackifier). In the Great Basin Desert on the Utah Test and Training Range near Salt Lake City, we applied field‐harvested biocrust material to experimental plots on coarse‐ and fine‐textured soils with the top 2 cm of soil and biocrust removed. Habitat ameliorations were applied with and without biocrust addition. Shade provision increased biocrust cover 50% over controls. Biocrust cover and soil stability were 65% lower in straw border plots relative to controls. Soil tackifiers, alone and in combination with resource augmentation and stress reduction, did not improve cover and stabilization over inoculated controls. We found variability in recovery by time and between soil types. These results suggest plausible strategies to improve success of biocrust inoculation.     

Estimation of molecular weight by polyacrylamide gel electrophoresis using heat stable fluorophors

The utilization of 2-methoxy-2,4-diphenyl-3(2H)-furanone (MDPF) as a fluorescent label for proteins in SDS polyacrylamide gel electrophresis is described. The procedure is very sensitive and detects disks containing as little as 1 ng of protein. The fluorescence signal is linear with concentration of protein to 500 ng. Emphasis is placed on the use of MDPF-labeled proteins as standards for the estimation of molecular weights of fluorescamine-labeled proteins. Data are provided which demonstrate the need for only three standard proteins in the molecular weight curve. Finally, the relative mobilities of proteins from nonreplicate determinations exhibited an average variation of only 3.9%.     

Ecophysiological traits of invasive alien Acacia cyclops compared to co‐occuring native species in Strandveld vegetation of the Cape Floristic Region

Tree invasions of Mediterranean‐climate ecosystems pose a significant threat to both biodiversity and functioning, by excluding native species, altering soil nutrient status and depleting water resources. In order to attain greater relative biomass associated with successful invasion in these characteristically resource‐poor environments, invasive species must have novel traits that enable better acquisition (e.g. deep roots) or exploitation of different resources (e.g. N₂ fixation) and/or more efficient use of available resources than native species. We compared the ecophysiological and morphological traits of three abundant native species to those of the invasive Australian tree species, Acacia cyclops. This species is widely invasive in the Mediterranean‐climate coastal vegetation of South Africa that includes the Strandveld vegetation type. A. cyclops had 30–50% greater foliar N concentrations (P < 0.001) in comparison with the native species and lower foliar δ¹⁵N values that may indicate N₂ fixation. Additionally, A. cyclops maintained higher photosynthetic rates over the dry summer season (ca. 15 μmol m^?2 s^?1) than the native species. These higher photosynthetic rates may result from sustained access to water due to deeper rooting abilities as indicated by the more negative δD values (P < 0.001) of A. cyclops (?43‰) in comparison with the some native species (?29 to ?37‰). Acacia cyclops did not, however, exhibit greater water use efficiencies or photosynthetic nitrogen use efficiencies (P > 0.05) compared to native species. Invasiveness of A. cyclops into this resource‐limited Mediterranean‐climate ecosystem appears to be supported by greater resource acquisition, possibly partially through N₂ fixation and greater rooting depth, rather than greater resource use efficiency or conservation.     

Effect of preconditioning to the soil environment on the performance of 20 cyanobacterial strains used as inoculum for biocrust restoration

Biological soil crusts are complex communities of organisms that develop on the top layer of dryland soils where they enhance important ecosystem services, including soil fertility and protection from erosion. Regrettably, a range of human activities such as cattle grazing, off‐road driving, hiking, and global warming result in significant deterioration of biocrust cover and their associated services. This scenario has prompted efforts to develop effective biocrust restoration strategies, which often involve the production of biocrust inoculum, both in greenhouse and in laboratory settings. Sometimes this inoculum is preconditioned in a process of “hardening” at considerable expense and effort in order to improve its fitness under harsh field conditions. But the positive effects of such hardening procedures have yet to be rigorously demonstrated. Here, we compared the growth performance of 20 cultured strains of biocrust cyanobacteria in outdoor tests on native soils as a function of preconditioning regimes consisting of increasingly high exposure to solar radiation, temperature and illumination daily variability, and recurrent wet‐dry cycles. Preconditioning improved performance in 13 out of 20 strains, particularly among pioneer crust‐forming Microcoleus spp. (eight out of eight). Improvements were variable among heterocystous strains (three out of four Scytonema spp., two out of four Tolypothrix spp., and none out of four Nostoc spp.). Based on these results, we recommend the inclusion of preconditioning treatments to increase inoculum survival rate and speed of cyanobacterial biocrust recovery in restoration of dryland soils.     

Microsite enhancements for soil stabilization and rapid biocrust colonization in degraded drylands

In dryland ecosystems, natural recovery of biological soil crusts (biocrusts) following disturbance may be slow or inhibited, necessitating active restoration practices. While biocrusts can be readily propagated under environmentally controlled conditions, rehabilitation in the field is complicated by environmental stresses which may be particularly acute in degraded, destabilized soils with harsh climatic conditions at the soil surface. In this study, we first present the results of a field trial at a severely degraded rangeland site examining the stabilizing effects of various soil amendments (polysaccharide glues and polyacrylamides) in combination with biocrust inoculum. We found that a psyllium compound was the only amendment to maintain effectiveness after 19 months, and the only treatment that maintained biocrust inoculum throughout the trial. In a subsequent short‐term experiment where plots were shaded and watered, we examined how biocrust inoculation rate (0, 20, and 40% initial cover) and the psyllium‐based amendment affected biocrust growth. After 4 months, visible biocrust cover in inoculated plots was greater than in controls, but only chlorophyll a exhibited a dosage‐response to inoculum application rate, indicating preferential establishment of cyanobacteria. Psyllium did not affect biocrust development but did improve soil stability. Shade and watering buffered against temperature extremes (up to 15°C) and increased the duration of moist surface conditions necessary for biocrust growth by up to 30%, mimicking conditions more common in the fall and winter months. Our results suggest that inducing early successional biocrusts on a highly degraded site is possible with suitable microclimate conditions.     

The statistical distribution of trichostrongylid nematodes in grazing lambs

Barger I. A. 1985. The statistical distribution of trichostrongylid nematodes in grazing lambs. International Journal for Parasitology15: 645–649. Worm counts of the genera Haemonchus, Ostertagia, Trichostrongylus and Nematodirus from 104 naturally-infected lambs were found to follow negative binomial distributions. Although mean counts covered a 10-fold range, k values did not differ significantly among the four genera. It was concluded that all genera were equally overdispersed. Some implications of this overdispersion for flock productivity and for parasite control were examined