Allen W. Hahn

Prevalence of and risk factors for hip dysplasia and cranial cruciate ligament deficiency in dogs

OBJECTIVE-To evaluate prevalence of and risk factors for hip dysplasia (HD) and cranial cruciate ligament deficiency (CCLD) in dogs and determine change in prevalence over time. DESIGN-Cross-sectional study. ANIMALS-1,243,681 Dogs for which information was reported to the Veterinary Medical Database between 1964 and 2003. PROCEDURES-Information on breed, sex, and age was collected, and prevalences and odds ratios were calculated. RESULTS-Castrated male dogs were significantly more likely than other dogs to have HD (odds ratio [OR], 1.21), and castrated male (OR, 1.68) and spayed female (OR, 2.35) dogs were significantly more likely to have CCLD. Dogs up to 4 years old were significantly more likely to have HD (OR for dogs 2 months to 1 year old, 1.22; OR for dogs > 1 to 4 years old, 1.48), whereas dogs > 4 years old were significantly more likely to have CCLD (OR for dogs > 4 to 7 years old, 1.82; OR for dogs > 7 years old, 1.48). In general, large- and giant-breed dogs were more likely than other dogs to have HD, CCLD, or both. Prevalences of HD and CCLD increased significantly over the 4 decades for which data were examined. CONCLUSIONS AND CLINICAL RELEVANCE-Results suggested that sex, age, and breed were risk factors for HD, CCLD, or both in dogs and that prevalences of HD and CCLD have increased over time.

Identification of the most common cutaneous neoplasms in dogs and evaluation of breed and age distributions for selected neoplasms

OBJECTIVE-To identify the most common cutaneous neoplasms in dogs and evaluate breed and age distributions for selected neoplasms. DESIGN-Retrospective epidemiological study. SAMPLE-Records available through the Veterinary Medical Database of dogs examined at veterinary teaching hospitals in North America between 1964 and 2002. PROCEDURES-Information on tumor type and patient breed and age was collected. Incidence and odds ratios with 95% confidence intervals were calculated. RESULTS-Records of 1,139,616 dogs were reviewed. Cutaneous neoplasms were diagnosed in 25,996 of these dogs; records for the remaining 1,113,620 dogs did not indicate that cutaneous neoplasms had been diagnosed, and these dogs were considered controls. The most frequent age range for dogs with cutaneous neoplasms was 10 to 15 years. Lipoma, adenoma, and mast cell tumor were the most common skin tumor types. CONCLUSIONS AND CLINICAL RELEVANCE-Results supported previously reported data regarding cutaneous neoplasia in dogs but provided updated information on the most common skin tumors and on age and breed distributions.

Hormonal and Sex Impact on the Epidemiology of Canine Lymphoma

The Surveillance Epidemiology and End Results data demonstrate that the risk of non-Hodgkin lymphoma is lower for women, but that the incidence increases after fifty years of age, at which menopause is regularly reached, suggesting that female hormones may be protective for NHL. This study examines the influence of sex on lymphoma risk in a relevant large animal model. Records for dogs in the Veterinary Medical Database were analyzed from 1964 to 2002. Risk ratios were calculated to evaluate associations between sex, neutering status, and lymphoma occurrence. A total of 14,573 cases and 1,157,342 controls were identified. Intact females had a significantly lower risk of developing lymphoma, Odds Ratio 0.69 (0.63–0.74) with a P < .001. We conclude that there is a sex effect on NHL risk in dogs similar to humans. We hypothesize that the hormone levels of intact females lower the risk of NHL. The possibility of a protective role of endogenous estrogens in the etiology of NHL should be investigated.

Glow Discharge Polymer Coated Oxygen Sensors

The need to measure reliably and accurately oxygen concentration in biological media is often crucial. Presently used commercially available and laboratory fabricated systems usually utilize polarographic sensors to measure oxygen partial pressure in aqueous media. These sensors use a noble metal (platinum or gold) cathode connected to a source of electrons, (commonly a battery) and are referenced to a suitable anode such as Ag/AgC1 to complete the circuit. Many methods have been used to improve sensor drift, sensitivity, and response time by permuting cathode geometry, construction details, membrane type and thickness, and electronic correction techniques. For a review of these methods the interested reader is referred to (1,2).

A Working Equation for Oxygen Sensing Disk Electrodes

For more than 35 years, noble metal electrodes have been employed to measure oxygen partial pressure in biological fluids and other media. Anyone who has attempted to use these types of electrodes is well aware of the instability and drift attendant to them. While a great deal of material can be found in the electrochemical and analytical chemical literature regarding the catalytic interaction of noble metal surfaces with oxygen, this literature usually pertains to large surfaces, non isotonic media and/or rotating ring-disc systems. Comparatively little has been published concerning the interaction between oxygen and noble metal surfaces for electrode sizes employed in biological applications.

Relationships between demographic variables and lead toxicosis in cattle evaluated at North American veterinary teaching hospitals

OBJECTIVE To determine associations between age, sex, breed, and month and year of admission and the diagnosis of lead toxicosis in cattle. DESIGN Retrospective case-control study. Sample Population-Records of all cattle evaluated at North American veterinary teaching hospitals during the years 1963 to 2002, which were available through the Veterinary Medical Database. PROCEDURES Logistic regression was used to evaluate the associations between postulated risk factors and the occurrence of lead toxicosis in cattle and predict the occurrence of the diagnosis of lead toxicosis in cattle. RESULTS 413 cases of lead intoxication and 202,363 control cattle were identified and met the inclusion criteria. Cattle < 4 years of age were at increased risk for the diagnosis of lead intoxication relative to cattle > or = 4 years of age. Cattle > or = 2 months and < 6 months of age had the greatest risk for lead intoxication (odds ratio, 12.3). Angus cattle were at greater risk for toxicosis (odds ratio, 1.95), compared with other breeds. The risk of lead toxicosis was greater before 1985 (odds ratio, 1.94) than the risk thereafter. The risk of lead toxicosis diagnosis was greatest in the months of May, June, July, and August. CONCLUSIONS AND CLINICAL RELEVANCE Lead toxicosis in cattle was associated with age < 4 years and the Angus breed. A seasonal pattern existed with peak occurrence in the late spring and summer. The occurrence of lead toxicosis has declined over time.

Variations on the Response Characteristics of Oxygen Electrodes

To summarize: The works presented in this and the previous paper (2) have produced an operational model for describing the oxygen reduction process in common medical grade sterile saline media at a platinum disc shaped electrode with a fairly specific surface conditioning. This paper has illustrated some of the variations possible in electrode current responses. An important feature of these data is that they are highly consistent and repeatable and can be discussed in terms of the model. However, the question still remains: What is the aging process? Is it due to a decrease of active sites for the electrochemical reduction process, brought about by the reduction process itself, or is it a process caused by other species in the media? To answer these questions, it may be necessary to employ some of the sophisticated techniques such as angle-resolved photoelectron spectroscopy (4) and extended x-ray absorption fine structure (5), available today for the study of atomic and molecular arrangements on solid surfaces.

Performance of implanted biogalvanic pacemakers.

Seventeen unipolar cardiac pacemakers powered by hybrid biogalvanic cells were implanted in dogs. Long term clinical effects and electrical performance in vivo of the generators were investigated. The biogalvanic cells were designed to provide 50 years of generator operation.

The Effect of Catalyst Concentration of the Cured Properties of a Medical Grade RTV Silicone Elastomert

Abstract Mechanical properties, degree of swelling, structural uniformity (by election microscopy), lipid uptake and implantation effects were studied on samples of silicone elastomers made with various catalyst concentrations and effects are presented.

Control of Electrode Aging by a Periodic Anodization Technique

The long-term use of noble metal electrodes for amperometrically monitoring oxygen tension in blood and tissue has been hampered by the unstable nature of the electrode calibration. Changes in sensitivity (current per unit oxygen tension) as rapid as 20% per hour have been reported [1]. If this drift were constant, it would, in principle, be simple to correct for; however, increasing and decreasing trends separated by plateau regions are most frequently encountered [2,3]. In some cases, changes in sensitivity have been attributed to protein deposition or to poisoning by sulfur-containing molecules [4], but such mechanisms cannot account for the drift observed with electrodes immersed in pure saline solutions [2,3]. The latter phenomenon, usually referred to as “electrode aging”, can best (and perhaps only) be explained by supposing an interrelationship between the electrode’s catalytic activity and its redox history. This, of course, is a concept well documented in the electrochemical literature [5]. Of particular importance here is that some electrochemical studies [6,7] suggest that, at least for Pt electrodes, strong oxidizing treatments, such as exposure to concentrated nitric acid or anodization at elevated potentials, may result in more stable electrode behavior. In this report, we present evidence, based on in vitro tests in physiological saline, indicating that the aging phenomenon can be controlled by periodically restoring the electrode surface to a pseudostable level of catalytic activity via in situ anodization.