Behavioral and neurotransmitter changes in the urease-infused rat: a model of congenital hyperammonemia

Rats implanted with subcutaneous or intraperitoneal osmotic minipumps infusing 0.8-1.25 IU urease/kg/h develop sustained hyperammonemia (range 137-497 microM, controls 88 +/- 51 microM +/- SD) for 5-7 days. Glutamine levels are also significantly elevated in plasma (677 +/- 166 versus 428 +/- 122 microM) and cerebral cortex (13.2 +/- 9.8 versus 4.7 +/- 2.8 nmol/mg tissue). Neurobehavioral abnormalities include decreased food intake and increased stereotypic activity. Increased serotonin turnover was suggested by elevated levels of tryptophan and 5-hydroxyindoleacetic acid in cerebral cortex, brain stem, and cerebellum of urease-infused compared to sham-operated animals. There were no changes in norepinephrine or gamma aminobutyric acid, and there was no correlation between the degree of hyperammonemia or glutaminemia and brain levels of tryptophan or biogenic amines. Animals receiving a tryptophan-deficient diet had significantly lower levels of tryptophan and 5-hydroxyindoleacetic acid in brain regions compared to animals receiving a normal tryptophan intake, under both control and hyperammonemic conditions. Despite the prevention of increased serotonin flux in hyperammonemic animals receiving a tryptophan-deficient diet, food intake and weight declined and there was increased stereotypic behavior.     

The use of a specific dna probe for detection of Mycoplasma gallisepticum in field outbreaks

A specific DNA probe (pMG4) was used to diagnose M. gallisepticum (MG) infection in field outbreaks in chicken and turkey breeder flocks in Israel. Dot-blot hybridisation of tracheal swab suspensions with the probe enabled positive identification of MG as early as 4 days after sampling, even in flocks at an early stage of infection when no other specific indications of infection were available.     

Reinnervation of the hippocampal perforant pathway zone in Alzheimer's disease

The perforant pathway originates from the entorhinal cortex of the anterior parahippocampal gyrus and terminates on the outer dendritic branches of the granule cells of the dentate gyrus and pyramidal cells of the subiculum and hippocampus. It carries the principal cortical input to the hippocampal formation. Destruction of the perforant pathway in experimental animals leads to a partial deafferentation of its target neurons, followed by a robust sprouting of acetylcholinesterase (AChE) terminals in the deafferented perforant pathway zone. In Alzheimer's disease, the cells of origin of the perforant pathway are laden with neurofibrillary tangles. AChE staining in the terminal zone of the perforant pathway in Alzheimer's disease shows several distinct patterns that are not found in control brains. These changes are consistent with the results of experimental studies demonstrating reinnervation in laboratory mammals, including nonhuman primates. The results suggest that in Alzheimer's disease sprouting of AChE-containing systems occurs in the hippocampal formation in response to disease-related cellular damage in the entorhinal cortex.     

Apolipoprotein E ϵ4 allele is not associated with earlier age at onset in amyotrophic lateral sclerosis

Apolipoprotein E allele 4 (apo E ?4) is known to be in genetic disequilibrium with Alzheimer's disease and is associated with an earlier age at onset of dementia. Whether apo E ?4 is a specific risk factor for Alzheimer's disease or is a more general susceptibility factor that shifts the age at onset of neurodegenerative diseases to earlier ages is unknown. To test these possibilities, we determined the apolipoprotein E genotypes of subjects with familial or sporadic amyotrophic lateral sclerosis (ALS). ApoE allele frequencies of the the apoE gene of the ALS subjects (n = 170, ?2 = 0.071, ?3 = 0.771, ?4 = 0.159) were found to be comparable to the allele frequencies of the general population. Furthermore, no significant association was observed between the age at onset or the duration of ALS and the inheritance of apoE ?4: subjects with at least one copy of ?4 (sporadic ALS: n = 15, onset at 57.7 ± 13.9 years; familial ALS: n = 23, onset at 53.6 ± 9.5 years, duration [n = 14] of 2.6 ± 1.6 years) had comparable ages at onset and durations to subjects without ?4 (sporadic ALS: n = 28, onset at 53.1 ± 17.0 years; familial ALS: n = 56, onset at 50.8 ± 12.1 years, duration [n = 30] of 1.9 ± 0.8 years). The lack of association of apoE ?4 with the age at onset and the duration of ALS suggests that apoE ?4 does not have a global effect on the pathogenesis of other neurodegenerative diseases.