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.     

Methods of Measuring Phase Shifts: Why I Continue to Use an Aschoff Type II Procedure Despite the Skepticism of Referees

Figure 1 shows the test procedure used in many experiments from this laboratory on nonphotic clock resetting. The animal, a hamster, is in an LD cycle until the day when the stimulus is given. Very close to the time the stimulus is introduced the lights are turned off and remain off until the end of the test, usually just a few days later. This is a modification of Aschoff's (1) type II method for determining phase shifts and phase response curves (PRCs).     

Paraquat depresses the activity of angiotensin converting enzyme expressed by human umbilical vein endothelial cells in culture

The activity of angiotensin converting enzyme (ACE) in cell lysate of cultured human umbilical vein endothelial cells (HUVEC) after a 24-hour incubation with 10(-3) and 10(-4)M of paraquat (PQ) was decreased. However, LDH released into the culture medium of HUVEC during the 24-hour incubation with PQ was not increased. Many investigators show that the change in serum ACE activity reflects the impairment of vascular endothelial cells. We showed in this report that ACE was decreased even at an early stage of endothelial injury induced by PQ, when LDH release is not yet increased.     

A new method of isolation and a new form of transketolase from baker's yeast]

A new procedure for the isolation of homogeneous transketolase from baker's yeast based on the use of enzyme-specific antibodies immobilized on a insoluble matrix has been developed. The enzyme yield is 90% of its total content in the original yeast extract. The eluate from the immunocolumn was found to contain a previously unknown form of transketolase which represents an enzyme-RNA complex.     

Carbonmonoxy dopamine beta-hydroxylase. Structural characterization by Fourier transform infrared, fluorescence, and x-ray absorption spectroscopy

The carbon monoxide complex of ascorbate-reduced dopamine beta-hydroxylase has been prepared and characterized by Fourier transform infrared, fluorescence, and x-ray absorption spectroscopies. CO has previously been shown to be a competitive inhibitor with respect to O2, and binds to only one of the two copper atoms/active site (Blackburn, N. J., Pettingill, T. M., Seagraves, K. S., and Shigeta, R. T. (1990) J. Biol. Chem. 265, 15383-15386). Thus, it acts as an excellent probe of the O2-binding site. A single C-O infrared absorption band is observed at 2089 cm-1, shifting by 46 cm-1 to lower energy on substitution with either 13C16O or 12C18O. The 13C isotope shift is reversed to the position expected for 12CO upon vacuum flushing with 12CO gas, indicating that formation of the CO adduct is a fully reversible process. Binding of the substrate tyramine does not eliminate the infrared peak but causes a 3-cm-1 shift to lower energy. On the other hand, binding of a bifunctional inhibitor which cross-links the substrate and O2-binding site does eliminate the CO peak. These data, in conjunction with the competitive nature of CO binding with respect to O2, identify the CO-binding site as the O2-binding site, and place it in close proximity to the substrate-binding site. CO-dopamine beta-hydroxylase exhibits no luminescence in the visible region, suggesting a structure different from carbonmonoxy hemocyanin, and in all probability mononuclear. Analysis of extended x-ray absorption spectroscopy data is most consistent with an average coordination per Cu of 2-3 histidines, 0.5 CO, and 0.5 S atoms as ligands, and absorption edge comparisons indicates pseudo-4 coordination as the most likely geometry at each Cu(I) center. The results can be interpreted by a model involving inequivalent 4-coordination at each Cu(I) center in the CO adduct with CuAHis3S...CuBHis2CO-X as the coordination most consistent with all of the data.     

Acquisition of an additional internal cleavage site differentially affects the ability of pseudorabies virus to multiply in different host cells.

The translocation of the 325 leftmost bp of the genome of pseudorabies virus (PrV) to the internal junction between the L and S components confers upon the virus a growth advantage relative to wild-type PrV in chicken embryo fibroblasts (CEFs) and chickens and a growth disadvantage in rabbit kidney (RK) cells and mice. To clarify the molecular basis for the species-specific growth characteristics of the translocation mutants, we have compared several parameters of the virus growth cycle in CEFs and RK cells infected with wild-type PrV and with translocation mutants. The salient findings are as follows. (i) The synthesis of early-late and late proteins is not as effective in CEFs as it is in RK cells, and these proteins, in particular, the major capsid proteins, accumulate less abundantly in CEFs than in RK cells. (ii) Cleavage of concatemeric DNA to genome-size molecules is also not as effective in CEFs as it is in RK cells. (iii) The internal junction present in translocation mutants is a functional cleavage site. (iv) In RK cells, translocation mutants are hypercleaved and a significant proportion of the total viral DNA is cleaved into subgenomic fragments. (v) In CEFs infected with translocation mutants, subgenomic fragments also accumulate but most of the viral DNA remains in concatemeric form. A model which postulates that the cell-specific growth advantage or disadvantage of the translocation mutants is related to the presence of a second cleavage site within their genomes and is affected by the efficiency of cleavage of concatemeric DNA in particular infected cell types is presented. The significance of these findings as they relate to the evolution of herpesviruses with class 2- and class 3-like genomes is discussed.     

A search for quantitative trait loci for ovulation rate in cattle

Seventy-seven polymorphic microsatellites were analysed in offspring of three elite sires that were part of the foundation of an experimental population selected for twinning rate at the US Meat Animal Research Center, Clay Center, Nebraska. All females were assessed for ovulation rate by rectal palpation of corpora lutea over 8–10 consecutive oestrous cycles from approximately 12 to 18 months of age, and associations between ovulation rate and sire allele were examined in each of the three sire groups. A preliminary analysis was performed using selectively genotyped daughters of each sire. Markers found significant or approaching significance were also genotyped in all daughters, sons and granddaughters of these sires. A test of marker associations limited to the granddaughter data provided an independent confirmation of marker effect and significance relative to the initial test with daughter data. Putative ovulation rate quantitative trait loci were detected on chromosomes 7 and 23. Marker UWCA20 on chromosome 7 was associated with an effect in excess of one phenotypic standard deviation and accounted for approximately 10% of phenotypic variation ovulation rate. Marker CYP21 (steroid 21-hydroxylase) on chromosome 23 was associated with an effect of slightly less than half a phenotypic standard deviation and accounted for approximately 4% of phenotypic variation.