DBA/2J Genetic Background Exacerbates Spontaneous Lethal Seizures but Lessens Amyloid Deposition in a Mouse Model of Alzheimer’s Disease

Alzheimer’s disease (AD) is a leading cause of dementia in the elderly and is characterized by amyloid plaques, neurofibrillary tangles (NFTs) and neuronal dysfunction. Early onset AD (EOAD) is commonly caused by mutations in amyloid precursor protein (APP) or genes involved in the processing of APP including the presenilins (e.g. PSEN1 or PSEN2). In general, mouse models relevant to EOAD recapitulate amyloidosis, show only limited amounts of NFTs and neuronal cell dysfunction and low but significant levels of seizure susceptibility. To investigate the effect of genetic background on these phenotypes, we generated APP^swe and PSEN1^de9 transgenic mice on the seizure prone inbred strain background, DBA/2J. Previous studies show that the DBA/2J genetic background modifies plaque deposition in the presence of mutant APP but the impact of PSEN1^de9 has not been tested. Our study shows that DBA/2J.APP^swePSEN1^de9 mice are significantly more prone to premature lethality, likely to due to lethal seizures, compared to B6.APP^swePSEN1^de9 mice—70% of DBA/2J.APP^swePSEN1^de9 mice die between 2-3 months of age. Of the DBA/2J.APP^swePSEN1^de9 mice that survived to 6 months of age, plaque deposition was greatly reduced compared to age-matched B6.APP^swePSEN1^de9 mice. The reduction in plaque deposition appears to be independent of microglia numbers, reactive astrocytosis and complement C5 activity.     

Preliminary crystallographic study of C-reactive protein from Limulus polyphemus

Crystals of C-reactive protein from Limulus polyphemus have been grown both with and without calcium. The space group for the calcium-free crystals is I422 or I4(1)22, and the cell parameters are a = b = 173.33 (4) A, c = 98.81 (3) A. The crystals diffract to at least 2.8 A resolution and are suitable for detailed structural studies.     

Evolutionary lines among Salmonella enteritidis phage types are identified by insertion sequence IS200 distribution

A survey was made of the presence, copy number and location of the Salmonella-specific DNA insertion element IS200, within the genomes of the 27 phage type strains of Salmonella enteritidis. All the phage type strains contained copies of IS200 revealed by genomic Southern blot hybridizations with a 300-bp DNA probe internal to the element. Restriction site variation around IS200 insertion sites was examined. Three fundamental patterns of hybridization corresponding to chromosomal IS200 loci were found. In terms of population genetics, these 'IS200 profiles' correspond to clonal lineages of recent evolutionary origin, and underline the phage-typing scheme for epidemiological subdivision of S. enteritidis. The molecular analysis is consistent with genetic selection pressures which are apparent in the observed epidemiological distribution of S. enteritidis, since each clonal lineage contained one of the phage types of major clinical importance in the U.K.     

A note onStreptomyces No. 6, a chitosanase-producing actinomycete

This communication reports the deposit ofStreptomyces No. 6 in the National Collection of Industrial Bacteria, Aberdeen, AB2 1RY, Scotland, UK (Accession number 13037) and gives some references on its use in lysing cell walls of fungi in the Mucorales leading to protoplast formation. Its use in biotechnological fields is also referred to.     

A submerged-coil heating apparatus for investigating thermal inactivation of micro-organisms

A novel apparatus has been designed for the investigation of the thermal inactivation of micro-organisms over the temperature range 20–90C. It comprises a stainless steel coil fully submerged in a thermostatically-controlled water bath which allows very rapid temperature equilibration of microbial suspensions. Automated repeat sampling is possible at short time intervals (variable between 6 and 999 s) by means of an electronically controlled displacement mechanism. Validation of the apparatus performance and typical death curves are described.     

Minimally-invasive Technique for Injection into Rat Optic Nerve

The rat optic nerve is a useful model for stem cell regeneration research. Direct injection into the rat optic nerve allows delivery into the central nervous system in a minimally-invasive surgery without bone removal. This technique describes an approach to visualization and direct injection of the optic nerve following minor fascial dissection from the orbital ridge, using a conjunctival traction suture to gently pull the eye down and out. Representative examples of an injected optic nerve show successful injection of dyed beads.