Standardization of a Videofluoroscopic Swallow Study Protocol to Investigate Dysphagia in Dogs.

BACKGROUND: Videofluoroscopic swallow study (VFSS) is the gold standard for diagnosis of dysphagia in veterinary medicine but lacks standardized protocols that emulate physiologic feeding practices. Age impacts swallow function in humans but has not been evaluated by VFSS in dogs. HYPOTHESIS/OBJECTIVES: To develop a protocol with custom kennels designed to allow free-feeding of 3 optimized formulations of contrast media and diets that address limitations of current VFSS protocols. We hypothesized that dogs evaluated by a free-feeding VFSS protocol would show differences in objective swallow metrics based on age. ANIMALS: Healthy juvenile, adult, and geriatric dogs (n = 24). METHODS: Prospective, experimental study. Custom kennels were developed to maintain natural feeding behaviors during VFSS. Three food consistencies (thin liquid, pureed food, and dry kibble) were formulated with either iohexol or barium to maximize palatability and voluntary prehension. Dogs were evaluated by 16 swallow metrics and compared across age groups. RESULTS: Development of a standardized VFSS protocol resulted in successful collection of swallow data in healthy dogs. No significant differences in swallow metrics were observed among age groups. Substantial variability was observed in healthy dogs when evaluated under these physiologic conditions. Features typically attributed to pathologic states, such as gastric reflux, were seen in healthy dogs. CONCLUSIONS AND CLINICAL IMPORTANCE: Development of a VFSS protocol that reflects natural feeding practices may allow emulation of physiology resulting in clinical signs of dysphagia. Age did not result in significant changes in swallow metrics, but additional studies are needed, particularly in light of substantial normal variation.

Specific mesenchymal/epithelial induction of olfactory receptor, vomeronasal, and gonadotropin-releasing hormone (GnRH) neurons.

We asked whether specific mesenchymal/epithelial (M/E) induction generates olfactory receptor neurons (ORNs), vomeronasal neurons (VRNs), and gonadotropin-releasing hormone (GnRH) neurons, the major neuron classes associated with the olfactory epithelium (OE). To assess specificity of M/E-mediated neurogenesis, we compared the influence of frontonasal mesenchyme on frontonasal epithelium, which becomes the OE, with that of the forelimb bud. Despite differences in position, morphogenetic and cytogenic capacity, both mesenchymal tissues support neurogenesis, expression of several signaling molecules and neurogenic transcription factors in the frontonasal epithelium. Only frontonasal mesenchyme, however, supports OE-specific patterning and activity of a subset of signals and factors associated with OE differentiation. Moreover, only appropriate pairing of frontonasal epithelial and mesenchymal partners yields ORNs, VRNs, and GnRH neurons. Accordingly, the position and molecular identity of specialized frontonasal epithelia and mesenchyme early in gestation and subsequent inductive interactions specify the genesis and differentiation of peripheral chemosensory and neuroendocrine neurons.

Human olfactory epithelial cells generated in vitro express diverse neuronal characteristics.

The olfactory epithelium constitutes the sole source of regenerating neural cells that can be obtained from a living human. As such, primary cultures derived from human olfactory epithelial biopsies can be utilized to study neurobiological characteristics of individuals under different conditions and disease states. Here, using such human cultures, we report in vitro generation of cells that exhibit a complex neuronal phenotype, encompassing receptors and signaling pathways pertinent to both olfaction and other aspects of CNS function. Using in situ hybridization, we demonstrate for the first time the native expression of olfactory receptors in cultured cells derived from human olfactory epithelial tissue. We further establish the presence and function of olfactory transduction molecules in these cells using immunocytochemistry, calcium imaging and molecular methods. Western blot analysis revealed the expression of neurotransmitter receptors for dopamine (D2R), 5-HT (5HT2C) and NMDA subtypes 1 and 2A/2B. Stimulation with dopamine or 5-HT enhanced receptor G protein activation in a subtype specific manner, based on 35S-guanosine triphosphate incorporation assay. Functional characteristics of the cultured cells are demonstrated through enhanced tyrosine phosphorylation of NMDAR 2A/2B and recruitment of signaling partners in response to NMDA stimulation. The array of neuronal characteristics observed here establishes that proliferating cells derived from the human olfactory epithelium differentiate in vitro to express functional and molecular attributes of mature olfactory neurons. These cultured neural cells exhibit neurotransmitter pathways important in a number of neuropsychiatric disorders. Their ready availability from living humans thus provides a new tool to link functional and molecular features of neural cells with clinical characteristics of individual living patients.

A speculative essay on retinoic acid regulation of neural stem cells in the developing and aging olfactory system.

Circulating signals like the acidic derivative of vitamin A: retinoic acid (RA) may regulate resident stem cells in the adult nervous system, particularly in the olfactory pathway. RA is an essential factor for inducing neural stem or precursor cells that give rise to olfactory receptor neurons (ORNs) and olfactory bulb (OB) interneurons (OBINs) during embryonic development. Similar precursors in the adult brain constantly generate new ORNs and OBINs, and embryonic signaling pathways, like that via RA, may be retained or reactivated for this purpose. We have shown that RA regulates neural precursors in the embryonic and adult olfactory pathway. Moreover, RA administration after olfactory system damage stimulates an immune response and yields a more rapid recovery of olfactory-guided behavior. We suggest that olfactory integrity may be maintained by RA-mediated regulation of neurogenesis as well as local immune responses, and that aging compromises these mechanisms. The chemical senses, particularly olfaction, decline in aged individuals, and RA (via vitamin A) levels may also decline, perhaps due to changes in appetite and food intake. This synergy may result in a high prevalence of olfactory pathology in aged individuals.

Once and again: retinoic acid signaling in the developing and regenerating olfactory pathway.

Retinoic acid (RA), a member of the steroid/thyroid superfamily of signaling molecules, is an essential regulator of morphogenesis, differentiation, and regeneration in the mammalian olfactory pathway. RA-mediated teratogenesis dramatically alters olfactory pathway development, presumably by disrupting retinoid-mediated inductive signaling that influences initial olfactory epithelium (OE) and bulb (OB) morphogenesis. Subsequently, RA modulates the genesis, growth, or stability of subsets of OE cells and OB interneurons. RA receptors, cofactors, and synthetic enzymes are expressed in the OE, OB, and anterior subventricular zone (SVZ), the site of neural precursors that generate new OB interneurons throughout adulthood. Their expression apparently accommodates RA signaling in OE cells, OB interneurons, and slowly dividing SVZ neural precursors. Deficiency of vitamin A, the dietary metabolic RA precursor, leads to cytological changes in the OE, as well as olfactory sensory deficits. Vitamin A therapy in animals with olfactory system damage can accelerate functional recovery. RA-related pathology as well as its potential therapeutic activity may reflect endogenous retinoid regulation of neuronal differentiation, stability, or regeneration in the olfactory pathway from embryogenesis through adulthood. These influences may be in register with retinoid effects on immune responses, metabolism, and modulation of food intake.

Immunolocalization of retinoic acid receptors in the mammalian olfactory system and the effects of olfactory denervation on receptor distribution.

All-trans retinoic acid (ATRA), a metabolite of vitamin A, binds to retinoic acid receptors (RARs) to mediate gene transcription in target cells. We previously found that an ATRA supplement enhanced olfactory recovery rate in adult mice after olfactory bulb deafferentation. In this study, we examined the cellular localization of RARalpha, RARbeta, and RARgamma and the effects of surgery and ATRA treatment using immunocytochemistry. Mice received a left olfactory nerve transection with the right side serving as internal control. One day after surgery, the mice were given either ATRA mixed with sesame oil or just sesame oil. In the unoperated olfactory bulb, only RARalpha immunoreactivity (ir) was observed. In the unoperated right olfactory epithelium, RARalpha-ir was found in flask-shaped cells located in the supporting cell layer, in cell clusters above the basal cell layer, in cells in the lamina propria, in some respiratory cells and in the olfactory bulb. The flask-shaped cells did not immunostain for either neurons or sustentacular cells. RARbeta-ir was localized only in the respiratory cells while no RARgamma-ir was observed in the olfactory epithelium. The density of RARalpha-ir cells was higher in the operated left olfactory epithelium and highest after ATRA treatment. This study demonstrates the presence of RARs in the olfactory system, provides additional support that the ATRA-signaling pathway may be involved in the recovery of the olfactory epithelium after injury, and suggests a role for an unstudied cell type in that process.

Preliminary results of olfactory testing in rats without deprivation.

Although rodents are nocturnal, their behavior is usually tested during the day. The authors present the results of a preliminary study, which suggest that altering the animals' day:night cycle might be the key to eliminating the need for food or water deprivation prior to testing.

Ethical issues in pharmacoepidemiologic research using Saskatchewan administrative health care utilization data.

PURPOSE: To describe the process of obtaining access to the administrative health care utilization data of the Canadian province of Saskatchewan and the ethical issues involved. METHODS: The report focuses on the process of obtaining data for two recent studies. In the first, associations between aplastic anemia and agranulocytosis and prior drug use were evaluated, while the second is an examination of anti-arrhythmia drug utilization. In these studies, data from files containing computerized information on prescription drug use, hospitalizations, physician services and cancer registrations were linked together and also with information from hospital charts, physician records and death registrations. RESULTS: Data on individual patients are available from the Saskatchewan data-files after the removal of identifying variables, and access to external information from hospitals, physicians, death registrations and the patients themselves is possible. However, researchers must accept that data considered to be only indirectly relevant to the objectives of the study or which, due to small numbers, may potentially identify either patients or physicians will only be released in aggregate form. CONCLUSIONS: Access to the Saskatchewan data-files and to external information from hospitals, physicians and death registrations is normally straightforward. Restrictions that are applied are discussed.

Could conditional release of new drugs provide the information required to study drug effectiveness? - A discussion paper.

Conditional release is the approval of a new drug onto the market, subject to specific conditions relating to effectiveness and safety that, if achieved, will lead to full approval. Conditional approval of a new drug, during which time it is used in normal clinical practice, should allow the collection of data on effectiveness and safety to provide a genuine cost effectiveness evaluation. Proposals put forward in 1977 in the United Kingdom for approving a drug on a conditional basis while monitoring for adverse drug reactions are examined, and issues that would affect a present day conditional release scheme are identified. These issues are: who would do the evaluation and who would pay for it; how would patients be identified and registered; would all new drugs be monitored and for how long; what data would be reported and evaluated; and who would do the reporting? How a conditional release scheme would work in Canada in light of these questions is considered and a method based on pharmacists registering patients and on physicians and/or patients reporting data to an independent organization funded by governments and the pharmaceutical industry is outlined. Under certain conditions, conditional release would provide the information to allow true cost effectiveness and safety assessments instead of the current inadequate predictions based on efficacy and safety data from clinical trials. It is important that academics and drug approval and monitoring agencies work together to develop active systems to improve the postapproval evaluation of effectiveness, safety and cost effectiveness of new drugs in Canada.

Characteristics of odorant elicited calcium changes in cultured human olfactory neurons.

An important step in establishing and utilizing a cell culture system for the in vitro study of olfaction is assessing whether the cultured cells possess physiological properties similar to those of mature olfactory neurons. Various investigators have successfully established proliferating cell lines from olfactory tissue, but few have demonstrated the characteristics of odor sensitivity of these cells. We successfully established cultured cell lines from adult human olfactory tissue obtained using an olfactory biopsy procedure and measured their ability to respond to odor stimulation using calcium imaging techniques. A subset of the human olfactory cells in culture displayed a distinct morphology and specifically expressed immunocytochemical markers characteristic of mature human olfactory neurons such as OMP, G(olf), NCAM and NST. Under defined growth conditions, these cultured cells responded to odorant mixes that have been previously shown to elicit intracellular calcium changes in acutely-isolated human olfactory neurons. These odorant-elicited calcium responses displayed characteristics similar to those found in mature human olfactory neurons. First, cultured cells responded with either increases or decreases in intracellular calcium. Second, increases in calcium were abolished by removal of extracellular calcium. Third, inhibitors of the olfactory signal transduction cascades reversibly blocked these odorant-elicited intracellular calcium changes. Our results demonstrate that cultures of adult human olfactory cells established from olfactory biopsies retain some of the in vivo odorant response characteristics of acutely isolated cells from the adult olfactory epithelium. This work has important ramifications for investigation of olfactory function and dysfunction using biopsy procedures and in vitro assays of odor sensitivity.

Retinoic acid enhances the rate of olfactory recovery after olfactory nerve transection.

In the olfactory system, retinoic acid (RA) plays an important role in development and may affect growth in the adult animal. To explore the potential effects of RA on recovery after injuries, adult mice were trained in a buried food paradigm and were given a single oral supplement of RA after olfactory nerve transection. Results demonstrate that RA accelerates the recovery of olfactory functions after injury.

Concordance on the recording of cancer in the Saskatchewan Cancer Agency Registry, hospital charts and death registrations.

Accurate and complete registries are an important source of knowledge about cancer. The concordance of the recording of neoplasms in the Saskatchewan cancer registry with that in hospital charts and death registrations was evaluated for 368 patients. The agreement between registry and hospital charts or death registrations was excellent (kappa: 0.93; 95% confidence interval: 0.89, 0.97), with 91.3% of those with cancer having the same neoplasm recorded in their chart or death registration as in the registry. There was only one patient whose hospital chart indicated cancer who was not in the registry and one apparent major discrepancy relating to the cancer site, which was due to the recording of the primary site in the registry and a secondary in the hospital chart. Although based on a relatively small number of patients, these results suggest a high degree of consistency between cancer registry, hospital charts and death registrations in Saskatchewan.

New drug approval times and 'therapeutic potential' in Canada, Australia, Sweden and the United States during the period 1992 to 1998.

In two previous studies, the times required to approve new drugs in Canada, Australia, Sweden, the United Kingdom and the United States during the periods 1992 to 1995 and 1996 to 1998 were compared. However, during each of these two periods, only a fraction of the drugs that were approved in any of the countries were approved in all of them. Because an analysis based solely on drugs approved in all the countries would provide additional information, data from the previous studies have been used to compare drugs approved in each of Canada, Australia, Sweden and the United States during the period 1992 to 1998. In addition, applications that received a 'priority' or a 'standard' review by the United States Food and Drug Administration were analyzed separately to determine whether differences between the countries diminished for drugs considered to be of potentially greater therapeutic value. For the 87 drugs identified as being approved for marketing in all four countries during the period 1992 to 1998, approval times in Canada and Australia were not significantly different, but both Canada and Australia had significantly longer times than those of the United States and Sweden (P<0.001). Of the 87 drugs, 37 (43%) received a priority review in the United States. In both the priority and standard review categories, the Australian and Canadian median approval times were significantly longer than those in Sweden and the United States. The results demonstrate that, in general, both priority and standard new drug applications are reviewed more expeditiously in Sweden and the United States than in Canada. Canadian patients continue to experience delayed access to potentially valuable medicines.

Expression of mRNAs encoding for two different olfactory receptors in a subset of olfactory receptor neurons.

Evidence has accumulated to support a model for odorant detection in which individual olfactory receptor neurons (ORNs) express one of a large family of G protein-coupled receptor proteins that are activated by a small number of closely related volatile chemicals. However, the issue of whether an individual ORN expresses one or multiple types of receptor proteins has yet to be definitively addressed. Physiological data indicate that some individual ORNs can be activated by odorants differing substantially in structure and/or perceived quality, suggesting multiple receptors or one nonspecific receptor per cell. In contrast, molecular biological studies favor a scheme with a single, fairly selective receptor per cell. The present studies directly assessed whether individual rat ORNs can express multiple receptors using single-cell PCR techniques with degenerate primers designed to amplify a wide variety of receptor sequences. We found that whereas only a single OR sequence was obtained from most ORNs examined, one ORN produced two distinct receptor sequences that represented different receptor gene families. Double-label in situ hybridization studies indicated that a subset of ORNs co-express two distinct receptor mRNAs. A laminar segregation analysis of the cell nuclei of ORNs labeled with the two OR mRNA probes showed that for one probe, the histogram of the distribution of the cell nuclei along the depth of the epithelium was bimodal, with one peak overlapping the (unimodal) histogram for the other probe. These results are consistent with co-expression of two OR mRNAs in a population of single ORNs.

Modulation of odor-induced increases in [Ca(2+)](i) by inhibitors of protein kinases A and C in rat and human olfactory receptor neurons.

Protein kinases A and C have been postulated to exert multiple effects on different elements of signal transduction pathways in olfactory receptor neurons. However, little is known about the modulation of olfactory responses by protein kinases in intact olfactory receptor neurons. To further elucidate the details of the modulation of odorant responsiveness by these protein kinases, we investigated the action of two protein kinase inhibitors: H89, an inhibitor of protein kinase A, and N-myristoylated EGF receptor, an inhibitor of protein kinase C, on odorant responsiveness in intact olfactory neurons. We isolated individual olfactory neurons from the adult human and rat olfactory epithelium and measured responses of the isolated cells to odorants or biochemical activators that have been shown to initiate cyclic AMP or inositol 1,4,5-trisphospate production in biochemical preparations. We employed calcium imaging techniques to measure odor-elicited changes in intracellular calcium that occur over several seconds. In human olfactory receptor neurons, the protein kinase A and C inhibitors affected the responses to different sets of odorants. In rats, however, the protein kinase C inhibitor affected responses to all odorants, while the protein kinase A inhibitor had no effect. In both species, the effect of inhibition of protein kinases was to enhance the elevation and block termination of intracellular calcium levels elicited by odorants. Our results show that protein kinases A and C may modulate odorant responses of olfactory neurons by regulating calcium fluxes that occur several seconds after odorant stimulation. The effects of protein kinase C inhibition are different in rat and human olfactory neurons, indicating that species differences are an important consideration when applying data from animal studies to apply to humans.

Time required for approval of new drugs in Canada, Australia, Sweden, the United Kingdom and the United States in 1996-1998.

BACKGROUND: The timeliness with which national regulatory agencies approve new drugs for marketing affects health care professionals and patients. An unnecessarily long approval process delays access to new medications that may improve patients' health status. The author compared drug approval times in Canada, Australia, Sweden, the United Kingdom and the United States. METHODS: Application and approval dates of new chemical or biological substances (excluding diagnostic products, and new salts, esters, dosage forms and combinations of previously approved substances) approved for marketing in the 5 countries from January 1996 to December 1998 were requested from the relevant pharmaceutical companies. Data on new drug approvals during the study period were also obtained from the national drug regulatory agencies in Canada, Australia and Sweden and from publications of the US Food and Drug Administration. RESULTS: A total of 219 new drugs were identified as being approved in at least one of the countries during the study period: 23 (10.5%) in all 5 countries, 23 (10.5%) in 4, 27 (12.3%) in 3, 42 (19.2%) in 2, and 104 (47.5%) in 1 country. By individual nation, 97 drugs were identified as being approved in Canada, 94 in Australia, 107 in Sweden, 55 in the UK and 123 in the US. Approval times in Canada and Australia were similar (medians 518 and 526 days respectively), but both countries had significantly longer approval times than Sweden (median 371 days), the UK (median 308 days) and the US (median 369 days). This pattern was consistent across all 3 years and for the 23 new drugs approved in all 5 countries during the 3-year period. Median approval times in Canada were similar in all of the reviewing divisions of Health Canada's Therapeutic Product Program (539-574 days) except the Central Nervous System Division (428 days) and the Bureau of Biologics and Radiopharmaceuticals (698 days). INTERPRETATION: Median drug approval times during 1996-1998 decreased by varying amounts from the 1995 values in all 5 countries. However, the median approval time in Canada continues to be significantly longer than the times achieved in Sweden, the UK and the US, and it remains considerably longer than Canada's own target of 355 days for all new drugs.

Acute adverse event signalling scheme using the Saskatchewan Administrative health care utilization datafiles: results for two benzodiazepines.

Linked administrative health care utilization databases offer potential benefits for postmarketing surveillance. The value of the Saskatchewan datafiles in an acute adverse event signalling scheme has been evaluated using two benzodiazepines. The first 20,000 patients dispensed lorazepam and the first 8525 patients dispensed alprazolam were followed through the datafiles over the year after their initial prescription of the relevant drug, and all medical services occurring during treatment were recorded. The most frequent adverse drug reactions to benzodiazepines are drowsiness, depression, impaired intellectual function and memory, lethargy, impaired coordination, dizziness, nausea and/or vomiting, skin rash, and respiratory disturbance. Data from our study showed that sleep disorders, depressive disorders, dizziness and/or vertigo, respiratory symptoms, esophagus and stomach disorders, and inflammatory skin conditions occurred significantly more often in the first 30 days after the initial prescription than in the succeeding six months in both drug groups, indicating that they are important adverse events. There are several limitations to the methodology; however, the results of the analysis indicate that the use of administrative health care utilization datafiles in a systematic assessment to signal potential acute adverse drug reactions is a feasible proposition, but further studies are required to assess whether events are real adverse reactions.

Cell and molecular biology of olfaction.

Genetics, experience, environment, and health can all affect the anatomic and physiologic components of the olfactory system and thereby influence olfactory performance. Large individual differences exist among subjects with respect to olfactory sensitivity and identification ability, which may result in both qualitative and quantitative differences in perceptual ability.

Olfactory neuron-specific expression of NeuroD in mouse and human nasal mucosa.

Human olfactory neuroepithelium (OE) is situated within the olfactory cleft of the nasal cavity and has the characteristic property of continually regenerating neurons during the lifetime of the individual. This regenerative ability of OE provides a unique model for neuronal differentiation, but little is known about the structure and biology of human olfactory mucosa. Thus, to better understand neurogenesis in human OE, we studied the expression of olfactory marker protein (OMP), TrkB and NeuroD in human nasal biopsies and autopsy specimens and compared these data with those obtained from normal and regenerating mouse OE. We show that NeuroD and TrkB are coordinately expressed in human OE. Thus, by using these markers we have been able to extend the known boundaries of the human OE to include the inferior middle turbinate. In normal mouse OE, TrkB and OMP expression overlap in cells closest to the superficial layer, but TrkB is expressed more strongly in the lower region of this layer. In contrast, NeuroD expression is more basally restricted in a region just above the globose basal cells. These characteristic expression patterns of OMP, TrkB and NeuroD were also observed in the regenerating mouse OE induced by axotomy. These results support a role of NeuroD and brain-derived neurotrophic actor (BDNF), the preferred ligand for TrkB, in the maintenance of the olfactory neuroepithelium in humans and mice.