Present systems and future needs for risk assessment of veterinary biologicals in Australia: the perspective of the regulator

The increasing range and complexity of biologicals, and the greater demand for these products, have resulted in a greater volume of trade in animal-based biological material. This has given rise, in turn, to many approaches to the regulation of importation of these materials, as countries seek protection against the introduction of disease. Harmonization of these regulatory approaches would contribute significantly to the availability of veterinary biologicals, to their manufacture and trade, and to disease security. Australia has developed systems for the categorisation and evaluation of biologicals, control by import permits, and specific procedures at point-of-entry and in institutions where these products are used. Computerised records and precedents assist in evaluation and in the issuing of permits. Recognition that some materials must be subject to further control has led to a system of registration of institutions based on levels of biosecurity, and approved use and disposal programmes. Institutions vary from high-security animal health laboratories to human in vitro fertilisation clinics, which use animal-derived media and materials. Such institutions are regulated through quality assurance contracts. Quarantine authorities have linkages with other agencies which have an interest in these products. These linkages reflect the administrative structures of government in Australia, and provide for management of all forms of risk. The author describes these systems and overviews their biological basis.     

The role of enzyme distortion in the single displacement mechanism of family 19 chitinases

By using molecular dynamics simulations, we have examined the binding of a hexaNAG substrate and two potential hydrolysis intermediates (an oxazoline ion and an oxocarbenium ion) to a family 19 barley chitinase. We find the hexaNAG substrate binds with all sugars in a chair conformation, unlike the family 18 chitinase which causes substrate distortion. Glu 67 is in a position to protonate the anomeric oxygen linking sugar residues D and E whereas Asn 199 serves to hydrogen bond with the C2' N-acetyl group of sugar D, thus preventing the formation of an oxazoline ion intermediate. In addition, Glu 89 is part of a flexible loop region allowing a conformational change to occur within the active site to bring the oxocarbenium ion intermediate and Glu 89 closer by 4-5 A. A hydrolysis product with inversion of the anomeric configuration occurs because of nucleophilic attack by a water molecule that is coordinated by Glu 89 and Ser 120. Issues important for the design of inhibitors specific to family 19 chitinases over family 18 chitinases also are discussed.     

Key amino acids in the gamma subunit of the gamma-aminobutyric acidA receptor that determine ligand binding and modulation at the benzodiazepine site

Pharmacological analyses of gamma-aminobutyric acidA (GABAA) receptor subtypes have suggested that both the alpha and gamma subunits, but not the beta subunit, contribute to the benzodiazepine binding site. We took advantage of the different pharmacological properties conferred by the inclusion of different gamma subunits in the receptor macromolecule to identify amino acids gamma2Phe77 and gamma2Met130 as key determinants of the benzodiazepine binding site. gamma2Phe77 was required for high affinity binding of the benzodiazepine site ligands flumazenil, CL218,872, and methyl-beta-carboline-3-carboxylate but not flunitrazepam. This amino acid was, however, required for allosteric modulation by flunitrazepam, as well as other benzodiazepine site ligands. In contrast, gamma2Met130 was required for high affinity binding of flunitrazepam, clonazepam, and triazolam but not flumazenil, CL218, 872, or methyl-beta-carboline-3-carboxylate and did not affect benzodiazepine efficacy. Introduction of the phenylalanine and methionine into the appropriate positions of gamma1 was not sufficient to confer high affinity for the benzodiazepine site ligand zolpidem. These data show that gamma2Phe77 and gamma2Met130 are necessary for high affinity binding of a number of benzodiazepine site ligands. Although most previous studies have focused on the contribution of the alpha subunit, we demonstrated a critical role for the gamma subunit at the benzodiazepine binding site, indicating that this modulatory site is located at the interface of these two subunits. Furthermore, gamma2Phe77 is homologous to alpha1Phe64, which has been previously shown to be a key determinant of the GABA binding site, suggesting a conservation of motifs between different ligand binding sites on the GABAA receptor.     

Delayed postoperative tethering of the cervical spinal cord

Tethering of the spinal cord in the lumbar and sacral regions of children with congenital anomalies is a well-recognized problem; however, tethering in the cervical region has rarely been reported. A search of the literature revealed no reports of symptomatic postoperative cervical spinal cord tethering. The authors present five cases of delayed postoperative cervical spinal cord tethering and discuss the benefit of detethering in these patients. All five patients were young (16 to 42 years of age) at presentation. All had done well after an initial surgical procedure but returned between 1 and 31 years postoperatively with symptoms including severe headache, upper-extremity pain, and progressive neurological deficits. In each case, magnetic resonance imaging indicated dorsal tethering of the cord in the cervical region. Surgical exploration with microscopic sharp detethering of the cervical cord was performed on each patient with favorable results. To avoid retethering, wide Tutoplast duraplasty is recommended.     

Blastomycosis in dogs: 115 cases (1980-1995)

OBJECTIVE: To characterize diagnostic results, treatment, and outcome of dogs with blastomycosis during a 15-year period in Louisiana. DESIGN: Retrospective case series. ANIMALS: 115 dogs with blastomycosis. PROCEDURE: Medical records were reviewed for dogs with blastomycosis examined between 1980 and 1995. Additional data were collected from the state veterinary diagnostic laboratory, via telephone interviews of owners, and by use of a random survey of the hospital population. RESULTS: Blastomycosis was detected mainly in young, large-breed dogs. Proximity to a body of water was a significant risk factor for affected dogs. Most dogs were affected in January and August through October. Clinical signs and results of physical examination reflected the multisystemic nature of the disease. Commonly affected systems included the respiratory tract and lymphatic, ocular, and cutaneous systems. Nodular interstitial and interstitial patterns were common findings on thoracic radiographs. Cytologic examination was successful in identifying organisms in samples from vitreous, skin, and lymph nodes. Similar results were achieved for dogs treated with a combination of amphotericin B and ketoconazole, compared with dogs treated with itraconazole. CLINICAL IMPLICATIONS: Results of this study should assist veterinarians with the recognition and management of blastomycosis in dogs. Blastomycosis should be considered as a differential diagnosis for large-breed dogs that live close to a body of water in areas in which the disease is endemic or in dogs with a history of being transported to endemic areas that subsequently develop signs of pulmonary, ocular, lymphatic, or cutaneous disease. Treatment with itraconazole was as effective as treatment with a combination of amphotericin B and ketoconazole.     

A military application of a medical self-care program

The cost of health care is a growing concern to the military. Many military clinic appointments and emergency department visits are unnecessary; they are for minor, self-limiting illnesses and injuries that could be treated at home. Military health care can no longer afford the luxury of treating minor illnesses and injuries in the hospital setting. This paper examines one method for military beneficiaries to obtain health care services appropriately. A selected group of military family members received a medical self-care book and an education session, which resulted in more appropriate decision-making about when to use the health care system. This was a 6-month, experimental study using control and experimental groups, with surveys before and after the study period. The self-care book was used 628 times to help make more informed decisions about when to seek medical care. The mean number of clinic and emergency room visits (p = 0.02) decreased for those using the medical self-care book.