Evidence for glutamatergic ganglion cells in the avian retina

This dissertation presents structural, immunochemical and neurochemical evidence for glutamatergic retinotectal synaptic transmission, augmenting and extending previous physiological and anatomical studies. The evidence is especially striking when the laminar patterns of ($\sp3$H) L-glutamate receptor binding, ($\sp3$H) L-glutamate high affinity uptake (HAU) and glutamate immunoreactivity (GLIR) of the dorsal tectum are compared. All show high activity in the tectal SGFS, with a peak in the most superficial laminae of SGFS followed by dip in the b-c region, and a second broad peak in deeper SGFS. Uptake and immunoreactivity bear a stronger resemblance to one another than either does to receptor binding, consistent with the fact that HAU and GLIR are localized in the same structures: glutamatergic terminals, intrinsic cell bodies and their processes. Receptor binding, as attested by the lack of enucleation effects, is a marker of postsynaptic receptors. In summary, these results are consistent with the hypothesis that most of the retinal projection to the optic tectum is glutamatergic: (1) A glutamate/aspartate HAU system exists in the superficial laminae, and it is dependent upon an intact retinal input, as shown developmentally and by retinal ablation; (2) Glutamate-like immunoreactivity appears in retinorecipient tectal regions (partially responsive to enucleation), in cell bodies of retinal ganglion cells and displaced ganglion cells, and in a non-tectal ganglion cell projection, the ectomammilary nucleus; (3) Sodium-independent glutamate receptor binding (which remains unchanged by enucleation) is most intense in the retinorecipient regions of the tectum and the ectomammilary nucleus. This binding is pharmacologically typical of a CNS sensory structure, being dominated by the quisqualate/kainate receptor subclass. Thus, as with other sensory systems, a portion of the retinotectal projection has been shown to include glutamatergic afferents with the distribution and properties expected of the primary projection ^

Fibrillins: Sequence, phylogeny and carboxy terminal domain proteolytic processing

Fibrillin-1 and -2 are large secreted glycoproteins that are known to be components of extracellular matrix microfibrils located in the vasculature, basement membrane and various connective tissues. These microfibrils are often associated with a superstructure known as the elastic fiber. During the development of elastic tissues, fibrillin microfibrils precede the appearance of elastin and may provide a scaffolding for the deposition and crosslinking of elastin. Using RT/PCR, we cloned and sequenced 3.85Kbp of the FBN2 gene. Five differences were found between our contig sequence and that published by Zhang et al. (1995). Like many extracellular matrix proteins, the fibrillins are modular proteins. We compared analogous domains of the two fibrillins and also members of the latent TGF-$\beta$ binding protein (LTBP) family to determine their phylogenetic relationship. We found that the two families are homologous. LTBP-2 is the most similar to the fibrillin family while FBN-1 is the most similar to the LTBP family. The fibrillin-1 carboxy terminal domain is proteolytically processed. Two eukaryotic protein expression systems, baculoviral and CHO-K1, were developed to examine the proteolytic processing of the carboxy terminal domain of the fibrillin-1 protein. Both expression systems successfully processed the domain and both processed a mutant less efficiently. In the CHO-K1 cells, processing occurred intracellularly. ^

AVIAN ROTAVIRUSES

The prevalence of antirotavirus antibodies in chickens and turkeys in the Gonzales, Texas and Llano, Texas areas was studied. Caged layer chicken flocks were found to have a prevalence of 64% when samples were taken randomly. This compares to 45% in chicken broiler breeder flocks and 92% in turkey breeding flocks. The natural occurrence of turkey rotavirus infection in two separate field studies showed an increase in mortality varying from 9% to 45% above expected death losses. Clinically, pasted vents, lacitude, and general malaise were noted in affected poults. Lesions noted on post mortem examination were; slight ballooning of the small intestine, excessively large ceca, and mild hyperemia of the small and large intestines.^ The use of maternal antibody from simian rotavirus immunized chickens' eggs for preventing murine rotavirus infection in infant mice was investigated. There was a reduction from 91% to 15% incidence when infant mice were treated twice daily with egg yolk immunoglobulin.^ The need for a convenient, easily grown and rapidly reproducing model for avian and mammalian rotaviruses led to the use of coturnix chicks. The turkey rotavirus was adapted to the quail chicks be serial passage. Transmission and scanning electron microscopy as well as micropathological methods were used in the study of the pathogenesis of rotavirus infection in quail and infant mice. ^

The development of poultry farms risk assessment tool for avian influenza in Imo State, Nigeria

Background: Nigeria was one of the 13 countries where avian influenza outbreak in poultry farms was reported during the 2006 avian influenza pandemic threat and was also the first country in Africa to report the presence of H5N1influenza among its poultry population. There are multiple hypotheses on how the avian influenza outbreak of 2006 was introduced to Nigeria, but the consensus is that once introduced, poultry farms and their workers were responsible for 70% of the spread of avian influenza virus to other poultry farms and the population. ^ The spread of avian influenza has been attributed to lack of compliance by poultry farms and their workers with poultry farm biosecurity measures. When poultry farms fail to adhere to biosecurity measures and there is an outbreak of infectious diseases like in 2006, epidemiological investigations usually assess poultry farm biosecurity—often with the aid of a questionnaire. Despite the importance of questionnaires in determining farm compliance with biosecurity measures, there have been few efforts to determine the validity of questionnaires designed to assess poultry farms risk factors. Hence, this study developed and validated a tool (questionnaire) that can be used for poultry farm risk stratification in Imo State, Nigeria. ^ Methods: Risk domains were generated using literature and recommendations from agricultural organizations and the Nigeria government for poultry farms. The risk domains were then used to develop a questionnaire. Both the risk domain and questionnaire were verified and modified by a group of five experts with a research interest in Nigeria's poultry industry and/or avian influenza prevention. Once a consensus was reached by the experts, the questionnaire was distributed to 30 selected poultry farms in Imo State, Nigeria that participated in this study. Survey responses were received for all the 30 poultry farms that were selected. The same poultry farms were visited one week after they completed the questionnaires for on-site observation. Agreement among survey and observation results were analyzed using a kappa test and rated as poor, fair, moderate, substantial, or nearly perfect; and internal consistency of the survey was also computed. ^ Result: Out of the 43 items on the questionnaire, 32 items were validated by this study. The agreement between the survey result and onsite observation was analyzed using kappa test and ranged from poor to nearly perfect. Most poultry farms had their best agreements in the contact section of the survey. The least agreement was noted in the farm management section of the survey. Thirty-two questions on the survey had a coefficient alpha > 0.70, which is a robust internal consistency for the survey. ^ Conclusion: This study developed 14 risk domains for poultry farms in Nigeria and validated 32 items from the original questionnaire that contained 43 items. The validated items can be used to determine the risk of introduction and spread of avian influenza virus in poultry farms in Imo State, Nigeria. After further validations in other states, regions and poultry farm sectors in Nigeria; this risk assessment tool can then be used to determine the risk profile of poultry farms across Nigeria.^