The geometric structure of the brain fiber pathways

The structure of the brain as a product of morphogenesis is difficult to reconcile with the observed complexity of cerebral connectivity. We therefore analyzed relationships of adjacency and crossing between cerebral fiber pathways in four nonhuman primate species and in humans by using diffusion magnetic resonance imaging. The cerebral fiber pathways formed a rectilinear three-dimensional grid continuous with the three principal axes of development. Cortico-cortical pathways formed parallel sheets of interwoven paths in the longitudinal and medio-lateral axes, in which major pathways were local condensations. Cross-species homology was strong and showed emergence of complex gyral connectivity by continuous elaboration of this grid structure. This architecture naturally supports functional spatio-temporal coherence, developmental path-finding, and incremental rewiring with correlated adaptation of structure and function in cerebral plasticity and evolution.     

Disseminated pheochromocytoma in a North American river otter (Lontra canadensis)

A 21-yr-old male North American river otter (Lontra canadensis) with a chronic history of degenerative osteoarthritis was evaluated for acute posterior paralysis. Because no definitive cause was identified and a poor prognosis was expected, the otter was euthanatized. A malignant neoplasm of adrenal gland origin with disseminated metastases to the central nervous system, lymph nodes, diaphragm, pancreas, spleen, and liver was diagnosed on postmortem examination. No clinical signs of disseminated neoplasia had been noted throughout the otter's history. The adrenal neoplasm was composed of nests of epithelial cells surrounded by a fine fibrovascular stroma. Neoplastic cells were immunohistochemically positive for chromogranin A, PGP9.5, metencephalin, and endorphin and negative for melan A and inhibin, confirming a diagnosis of a malignant pheochromocytoma. On the basis of the necropsy finding, metastasis of the pheochromocytoma might have contributed to the observed clinical signs.     

Genetic variation in the 5′UTR of the KRT2.13 gene of sheep

KRT2.13 is a type II keratin wool intermediate filament (IF) protein. Extensive variation was revealed in the 5′ untranslated region (UTR) of the ovine KRT2.13 gene (KRT2.13) using polymerase chain reaction – single strand conformational polymorphism (PCR‐SSCP) analysis. Nine unique PCR‐SSCP patterns were obtained with individual sheep having either one (homozygous), or a combination of two (heterozygous) of these patterns. Seven of the amplicons that produced the apparently homozygous patterns were successfully sequenced (GenBank FJ217670 – FJ217676), revealing eight single nucleotide insertions, 10 single nucleotide substitutions, a nucleotide deletion and a 16 nucleotide insertion that occurred in only one of the sequences. The seven sequences showed between 85% and 95% homology to the previously identified KRT2.13 sequence (GenBank X72379). This study emphasizes the power of PCR‐SSCP analysis in genotyping, as this extensive variation was found in only 100 sheep, of a variety of breeds. Since variation in the 5′UTR of genes may affect their expression, this genetic variation needs to be further studied to establish its role if any, in influencing gene expression and consequently wool traits.     

Comparison of antigen detection and quantitative PCR in the detection of chlamydial infection in koalas (Phascolarctos cinereus)

The gold standard method for detecting chlamydial infection in domestic and wild animals is PCR, but the technique is not suited to testing animals in the field when a rapid diagnosis is frequently required. The objective of this study was to compare the results of a commercially available enzyme immunoassay test for Chlamydia against a quantitative Chlamydia pecorum-specific PCR performed on swabs collected from the conjunctival sac, nasal cavity and urogenital sinuses of naturally infected koalas (Phascolarctos cinereus).The level of agreement for positive results between the two assays was low (43.2%). The immunoassay detection cut-off was determined as approximately 400 C. pecorum copies, indicating that the test was sufficiently sensitive to be used for the rapid diagnosis of active chlamydial infections.