Quantitative fluorometric analysis of plant and microbial chitosanases.

A quantitative fluorometric assay for chitosanase activity in bacterial and plant tissues was developed. The assay can be conducted with either finely milled preparations of chitosan in suspension or dissolved chitosan; activity is based on measurements of glucosamine (GlcN) or oligomers of GlcN. GlcN is detected fluorometrically after reaction with fluorescamine with detection in the nanomole range. Fluorescence measurements of chitosanase activity and radioassay of chitinase in commercial preparations of chitinase from Streptomyces griseus revealed that both activities were present. Specific activities for the S. griseus chitosanase using suspended and soluble chitosans were respectively 1.24 and 6.4 mumol GlcN.min-1.mg protein-1. Specific activity of the S. griseus chitinase was 0.98 mumol GlcN.min-1.mg protein-1. Sweet orange callus tissue was tested for chitosanase and chitinase activity. It was necessary to remove small amine-containing molecules from the callus preparations before chitosanase activity could be assayed. The specific activity for chitinase and chitosanase in desalted extracts of nonembryogenic Valencia sweet orange callus tissue was determined to be 18.6 and 89.4 nmol GlcN.min-1.mg protein-1, respectively.     

The importance of oedema in acute radiation injury to the cerebral cortex of rats: An electron microscope study

Summary The oedematous changes in the cerebral cortex of rats after acute irradiation are described. The importance of these changes in the over-all injury is discussed. Swelling and rupture of clear glial cells without expansion of the extracellular space are seen during the early phases of injury. Not all of the clear glia become swollen, but those that do eventually undergo complete dissolution, initiating small foci of severe damage. The necrosis that ultimately encompasses the entire irradiated field may spread from these initial sites of injury. Clear glial cells that do not undergo swelling show an unusual type of reaction before they become necrotic.This work was supported by the U.S. Atomic Energy Commission and formed a part of a dissertation submitted in partial fulfillment for the degree of Doctor of Philosophy to the faculty of the Graduate School of Loyola University, Chicago, Illinois.The author wishes to express his indebtedness to Dr. F. Wassermann of Argonne National Laboratory, and Dr. D. S. Jones of Stritch School of Medicine, Loyola University, for their advice and guidance during the course of this study.Dedicated to Professor Friedrich Wassermann with admiration and affection on the occasion of his 80th birthday.     

Phenotypic profiling of mGlu7 knockout mice reveals new implications for neurodevelopmental disorders

Neurodevelopmental disorders are characterized by deficits in communication, cognition, attention, social behavior and/or motor control. Previous studies have pointed to the involvement of genes that regulate synaptic structure and function in the pathogenesis of these disorders. One such gene, GRM7, encodes the metabotropic glutamate receptor 7 (mGlu₇), a G protein‐coupled receptor that regulates presynaptic neurotransmitter release. Mutations and polymorphisms in GRM7 have been associated with neurodevelopmental disorders in clinical populations; however, limited preclinical studies have evaluated mGlu₇ in the context of this specific disease class. Here, we show that the absence of mGlu₇ in mice is sufficient to alter phenotypes within the domains of social behavior, associative learning, motor function, epilepsy and sleep. Moreover, Grm7 knockout mice exhibit an attenuated response to amphetamine. These findings provide rationale for further investigation of mGlu₇ as a potential therapeutic target for neurodevelopmental disorders such as idiopathic autism, attention deficit hyperactivity disorder and Rett syndrome.     

Comparison of biodiversity and ground cover between a commercial rotationally grazed property and an adjacent nature reserve in semi‐arid rangeland

Continuous livestock grazing can have negative effects on biodiversity and landscape function in arid and semi‐arid rangelands. Alternative grazing management practices, such as rotational grazing, may be a viable option for broad‐scale biodiversity conservation and sustainable pastoral management. This study compared ground cover, plant species composition and floristic and functional diversity along gradients of grazing intensity between a pastoral property rotationally grazed by goats and an adjacent nature reserve (ungrazed by commercial livestock) in semi‐arid south‐eastern Australia. Understorey plant species composition differed significantly between the rotationally grazed property and the nature reserve, with a greater proportion and frequency of palatable species recorded in the nature reserve. Understorey plant species richness, diversity, functional biodiversity measures and ground cover declined with increasing grazing pressure close to water points under commercial rotational grazing management. However, at a whole‐paddock scale, there were few differences in plant biodiversity and ground cover between the rotationally grazed property and the nature reserve, despite differences in overall plant species composition. Flexible, adaptive, rotational grazing should be investigated further for its potential to achieve both socio‐economic and biodiversity conservation outcomes in semi‐arid rangelands to complement existing conservation reserves.     

Advancing ecological risk assessment on genetically engineered breeding stacks with combined insect-resistance traits

Transgenic Research - To inform the ecological risk assessment (ERA) of a transgenic crop with multiple insecticidal traits combined by conventional breeding (breeding stack), a comparative field...     

Age‐related variation in the trophic characteristics of a marsupial carnivore,the Tasmanian devil Sarcophilus harrisii

Age‐related changes in diet have implications for competitive interactions and for predator–prey dynamics, affecting individuals and groups at different life stages. To quantify patterns of variation and ontogenetic change in the diets of Tasmanian devils Sarcophilus harrisii, a threatened marsupial carnivore, we analyzed variation in the stable isotope composition of whisker tissue samples taken from 91 individual devils from Wilmot, Tasmania from December 2014 to February 2017. Both δ¹³C and δ¹⁵N decreased with increasing age in weaned Tasmanian devils, indicating that as they age devils rely less on small mammals and birds, and more on large herbivores. Devils <12 months old had broader group isotopic niches, as estimated by Bayesian standard ellipses (SEA_B mode = 1.042) than devils from 12 to 23 months old (mode = 0.541) and devils ≥24 months old (mode = 0.532). Devils <24 months old had broader individual isotopic niches (SEA_B mode range 0.492–1.083) than devils ≥24 months old (mode range 0.092–0.240). A decrease in δ¹⁵N from the older whisker sections to the more recently grown sections in devils <24 months old likely reflects the period of weaning in this species, as this pattern was not observed in devils ≥24 months old. Our data reveal changes in the isotopic composition of devil whiskers with increasing age, accompanied by a reduction in isotopic variation both among population age classes and within individuals, reflecting the effect of weaning in early life, and a likely shift from an initially diverse diet of small mammals, birds, and invertebrates towards increasing consumption of larger herbivores in adulthood.