Re-evaluation of the low-dose dexamethasone suppression test in dogs

OBJECTIVES

This study aims to re-evaluate the low-dose dexamethasone suppression test 8-hour cortisol cut-point for the diagnosis of hypercortisolism in dogs using a solid-phase, competitive chemiluminescent enzyme immunoassay.

MATERIALS AND METHODS

Twenty-seven client-owned dogs with naturally occurring hypercortisolism and 30 healthy control dogs were prospectively recruited. Performance of the low-dose dexamethasone suppression test was assessed using sensitivity, specificity and a receiver operating characteristic curve compared to a clinical diagnosis of hypercortisolism including response to treatment.

RESULTS

Twenty-four dogs were diagnosed with pituitary-dependent hypercortisolism and three with adrenal-dependent hypercortisolism. In 30 healthy control dogs, 8-hour post-dexamethasone cortisol concentrations ranged from 5.5 to 39 nmol/L. A receiver operating characteristic curve curve constructed from the 8-hour post-dexamethasone cortisol concentrations of hypercortisolism and control dogs demonstrated that the most discriminatory cut-point was more than 39 nmol/L with sensitivity of 85.2% (95% confidence interval, 67.5% to 94.1%) and specificity of 100% (95% confidence interval, 88.7% to 100.0%) and an area under the curve of 0.963.

CLINICAL SIGNIFICANCE

The optimal cut-point of more than 36 nmol/L proposed by this study is similar to the currently accepted 8-hour cortisol concentration cut-point for diagnosing hypercortisolism when using a solid-phase, competitive chemiluminescent enzyme immunoassay.

Co-impairment of autonomic and glucagon responses to insulin-induced hypoglycemia in dogs with naturally occurring insulin-dependent diabetes mellitus

This study aimed to investigate the contributions of two factors potentially impairing glucagon response to insulin-induced hypoglycemia (IIH) in insulin-deficient diabetes: 1) loss of paracrine disinhibition by intra-islet insulin and 2) defects in the activation of the autonomic inputs to the islet. Plasma glucagon responses during hyperinsulinemic-hypoglycemic clamps ([Formula: see text]40 mg/dL) were assessed in dogs with spontaneous diabetes (n = 13) and in healthy nondiabetic dogs (n = 6). Plasma C-peptide responses to intravenous glucagon were measured to assess endogenous insulin secretion. Plasma pancreatic polypeptide, epinephrine, and norepinephrine were measured as indices of parasympathetic and sympathoadrenal autonomic responses to IIH. In 8 of the 13 diabetic dogs, glucagon did not increase during IIH (diabetic nonresponder [DMN]; ∆ = -6 ± 12 pg/mL). In five other diabetic dogs (diabetic responder [DMR]), glucagon responses (∆ = +26 ± 12) were within the range of nondiabetic control dogs (∆ = +27 ± 16 pg/mL). C-peptide responses to intravenous glucagon were absent in diabetic dogs. Activation of all three autonomic responses were impaired in DMN dogs but remained intact in DMR dogs. Each of the three autonomic responses to IIH was positively correlated with glucagon responses across the three groups. The study conclusions are as follows: 1) Impairment of glucagon responses in DMN dogs is not due to generalized impairment of α-cell function. 2) Loss of tonic inhibition of glucagon secretion by insulin is not sufficient to produce loss of the glucagon response; impairment of autonomic activation is also required. 3) In dogs with major β-cell function loss, activation of the autonomic inputs is sufficient to mediate an intact glucagon response to IIH.NEW & NOTEWORTHY In dogs with naturally occurring, insulin-dependent (C-peptide negative) diabetes mellitus, impairment of glucagon responses is not due to generalized impairment of α-cell function. Loss of tonic inhibition of glucagon secretion by insulin is not sufficient, by itself, to produce loss of the glucagon response. Rather, impaired activation of the parasympathetic and sympathoadrenal autonomic inputs to the pancreas is also required. Activation of the autonomic inputs to the pancreas is sufficient to mediate an intact glucagon response to insulin-induced hypoglycemia in dogs with naturally occurring diabetes mellitus. These results have important implications that include leading to a greater understanding and insight into the pathophysiology, prevention, and treatment of hypoglycemia during insulin treatment of diabetes in companion dogs and in human patients.

Curricular Revision and Reform: The Process, What Was Important, and Lessons Learned

Beginning in 2005, the Doctor of Veterinary Medicine program at the University of California underwent major curricular review and reform. To provide information for others that follow, we have documented our process and commented on factors that were critical to success, as well as factors we found surprising, difficult, or problematic. The review and reform were initiated by the Executive Committee, who led the process and commissioned the committees. The planning stage took 6 years and involved four faculty committees, while the implementation stage took 5 years and was led by the Curriculum Committee. We are now in year 2 of the institutionalizing stage and no longer refer to our reform as the "new curriculum." The change was driven by a desire to improve the curriculum and the learning environment of the students by aligning the delivery of information with current teaching methodologies and implementing adult learning strategies. We moved from a department- and discipline-based curriculum to a school-wide integrated block curriculum that emphasized student-centered, inquiry-based learning. A limit was placed on in-class time to allow students to apply classroom knowledge by solving problems and cases. We found the journey long and arduous, requiring tremendous commitment and effort. In the change process, we learned the importance of adequate planning, leadership, communication, and a reward structure for those doing the "heavy lifting." Specific to our curricular design, we learned the importance of the block leader role, of setting clear expectations for students, and of partnering with students on the journey.

Evaluation of total dietary fiber concentration and composition of commercial diets used for management of diabetes mellitus, obesity, and dietary fat-responsive disease in dogs

OBJECTIVE

To determine total dietary fiber (TDF) concentration and composition of commercial diets used for management of obesity, diabetes mellitus, and dietary fat-responsive disease in dogs.

DESIGN

Cross-sectional study.

SAMPLE

Dry (n = 11) and canned (8) canine therapeutic diets.

PROCEDURES

Insoluble and soluble dietary fiber (IDF and SDF), high-molecular-weight SDF (HMWSDF), and low-molecular-weight SDF (LMWSDF) concentrations were determined. Variables were compared among diets categorized by product guide indication, formulation (dry vs canned), and regulatory criteria for light and low-fat diets.

RESULTS

SDF (HMWSDF and LMWSDF) comprised a median of 30.4% (range, 9.4% to 53.7%) of TDF; LMWSDF contributed a median of 11.5% (range, 2.7% to 33.8%) of TDF. Diets for diabetes management had higher concentrations of IDF and TDF with lower proportions of SDF and LMWSDF contributing to TDF, compared with diets for treatment of fat-responsive disease. Fiber concentrations varied within diet categories and between canned and dry versions of the same diet (same name and manufacturer) for all pairs evaluated. Diets classified as light contained higher TDF and IDF concentrations than did non-light diets. All canned diets were classified as low fat, despite providing up to 38% of calories as fat.

CONCLUSIONS AND CLINICAL RELEVANCE

Diets provided a range of TDF concentrations and compositions; veterinarians should request TDF data from manufacturers, if not otherwise available. Consistent responses to dry and canned versions of the same diet cannot necessarily be expected, and diets with the same indications may not perform similarly. Many diets may not provide adequate fat restriction for treatment of dietary fat-responsive disease.

Total dietary fiber composition of diets used for management of obesity and diabetes mellitus in cats

OBJECTIVE

To determine total dietary fiber (TDF) composition of feline diets used for management of obesity and diabetes mellitus.

DESIGN

Cross-sectional survey.

SAMPLE

Dry veterinary (n = 10), canned veterinary (12), and canned over-the-counter (3) feline diets.

PROCEDURES

Percentage of TDF as insoluble dietary fiber (IDF), high-molecular-weight soluble dietary fiber (HMWSDF), and low-molecular-weight soluble dietary fiber (LMWSDF) was determined.

RESULTS

Median measured TDF concentration was greater than reported maximum crude fiber content in dry and canned diets. Median TDF (dry-matter) concentration in dry and canned diets was 12.2% (range, 8.11% to 27.16%) and 13.8% (range, 4.7% to 27.9%), respectively. Dry and canned diets, and diets with and without a source of oligosaccharides in the ingredient list, were not different in energy density or concentrations of TDF, IDF, HMWSDF, or LMWSDF. Similarly, loaf-type (n = 11) and gravy-type (4) canned diets differed only in LMWSDF concentration. Disparities in TDF concentrations among products existed despite a lack of differences among groups. Limited differences in TDF concentration and dietary fiber composition were detected when diets were compared on the basis of carbohydrate concentration. Diets labeled for management of obesity were higher in TDF concentration and lower in energy density than diets for management of diabetes mellitus.

CONCLUSIONS AND CLINICAL RELEVANCE

Diets provided a range of TDF concentrations with variable concentrations of IDF, HMWSDF, and LMWSDF. Crude fiber concentration was not a reliable indicator of TDF concentration or dietary fiber composition. Because carbohydrate content is calculated as a difference, results suggested that use of crude fiber content would cause overestimation of both carbohydrate and energy content of diets.

Animal models of disease: classification and etiology of diabetes in dogs and cats

Diabetes mellitus is a common disease in dogs and cats. The most common form of diabetes in dogs resembles type 1 diabetes in humans. Studies suggest that genetics, an immune-mediated component, and environmental factors are involved in the development of diabetes in dogs. A variant of gestational diabetes also occurs in dogs. The most common form of diabetes in cats resembles type 2 diabetes in humans. A major risk factor in cats is obesity. Obese cats have altered expression of several insulin signaling genes and glucose transporters and are leptin resistant. Cats also form amyloid deposits within the islets of the pancreas and develop glucotoxicity when exposed to prolonged hyperglycemia. This review will briefly summarize our current knowledge about the etiology of diabetes in dogs and cats and illustrate the similarities among dogs, cats, and humans.

Clinical findings, diagnostic test results, and treatment outcome in cats with spontaneous hyperadrenocorticism: 30 cases

Background

Spontaneous hyperadrenocorticism (HAC) is rare in cats. Clinical findings, diagnostic test results, and response to various treatment options must be better characterized.

Objectives

To report the clinical presentation, clinicopathologic findings, diagnostic imaging results, and response to treatment of cats with HAC.

Animals

Cats with spontaneous HAC.

Methods

Retrospective descriptive case series.

Results

Thirty cats (15 neutered males, 15 spayed females; age, 4.0–17.6 years [median, 13.0 years]) were identified from 10 veterinary referral institutions. The most common reason for referral was unregulated diabetes mellitus; dermatologic abnormalities were the most frequent physical examination finding. Low‐dose dexamethasone suppression test results were consistent with HAC in 27 of 28 cats (96%), whereas ACTH stimulation testing was suggestive of HAC in only 9 of 16 cats (56%). Ultrasonographic appearance of the adrenal glands was consistent with the final clinical diagnosis of PDH or ADH in 28 of 30 cats (93%). Of the 17 cats available for follow‐up at least 1 month beyond initial diagnosis of HAC, improved quality of life was reported most commonly in cats with PDH treated with trilostane.

Conclusions and Clinical Importance

Dermatologic abnormalities or unregulated diabetes mellitus are the most likely reasons for initial referral of cats with HAC. The dexamethasone suppression test is recommended over ACTH stimulation for initial screening of cats with suspected HAC. Diagnostic imaging of the adrenal glands may allow rapid and accurate differentiation of PDH from ADH in cats with confirmed disease, but additional prospective studies are needed.

Changes in characteristics of inmates with latent tuberculosis infection

OBJECTIVES

Health and social characteristics place prisoners at high risk for progression from latent tuberculosis infection (LTBI) to tuberculosis (TB), but completion of LTBI therapy is low with many patients lost to follow-up after release. Despite decreases in active TB, demographic characteristics of active cases have remained relatively unchanged. This study investigated whether characteristics have changed in inmates diagnosed with LTBI in San Francisco, CA, USA.

STUDY DESIGN

Cross-sectional.

METHODS

Data from baseline interviews of randomized trials conducted in 1998-1999 and 2004-2007 were compared.

RESULTS

In both time periods, most subjects with LTBI (>60%) were Latinos, while the proportion in both the jail and San Francisco remained at 15-20%. Overall, the prisoners interviewed in 2004-2007 were less likely to have been on medication for LTBI previously, and expressed more likelihood of finishing their medication compared with those interviewed in 1998-1999. In 2004-2007, the foreign-born subjects were more likely to prefer English to Spanish, to have been in stable housing and to have been employed before jail compared with 1998-1999, while no such changes were seen between the two time periods for US-born subjects.

CONCLUSIONS

The pool of TB-infected individuals coming from a jail is not static, and understanding the changes over time is of importance for targeted programmes. Given the high infection rate and the predominance of foreign-born individuals who may have received bacillus Calmette-Guérin vaccination, screening with interferon-gamma release assay may be beneficial to identify those with true infection.

Serum 17alpha-hydroxyprogesterone concentrations during the reproductive cycle in healthy dogs and dogs with hyperadrenocorticism

OBJECTIVE

To determine concentrations of 17alpha-hydroxyprogesterone (17OHP) in serum of healthy bitches during various stages of the reproductive cycle and in bitches with hyperadrenocorticism and to compare the dynamics of 17OHP with those of progesterone.

DESIGN

Prospective evaluation study.

ANIMALS

15 healthy sexually intact bitches and 28 spayed bitches with hyperadrenocorticism.

PROCEDURES

11 healthy bitches were evaluated during estrus, nonpregnant diestrus, and anestrus (group 1); 4 other healthy bitches were evaluated during pregnancy and after ovariohysterectomy (group 2). Cycle stages were determined via physical examination, vaginal cytologic evaluation, and serum progesterone concentration. Bitches with hyperadrenocorticism were evaluated once at the time of diagnosis (group 3). Serum hormone concentrations were determined with immunoassays.

RESULTS

In group 1, the serum 17OHP concentration was significantly higher in diestrus (median, 1.8 ng/mL) than in estrus (median, 1.1 ng/mL) and anestrus (median, 0.2 ng/mL) and higher in estrus than in anestrus. Changes in serum progesterone concentrations accounted for 22% (estrus) or 23% (diestrus) of the variation in serum 17OHP concentrations. In group 2, 17OHP and progesterone concentrations were significantly higher during pregnancy than after ovariohysterectomy. The serum 17OHP concentration in group 3 was significantly lower (median, 0.2 ng/mL) than in group 1 in estrus and diestrus and in group 2 during pregnancy (median, 0.7 ng/mL) but was not different from 17OHP concentrations in anestrus or after ovariohysterectomy (median, 0.2 ng/mL).

CONCLUSIONS AND CLINICAL RELEVANCE

Serum 17OHP concentrations in healthy bitches increased during estrus, diestrus, and pregnancy and at those times were higher than in spayed bitches with hyperadrenocorticism.

Parental dietary effect on embryological development response to toxicants with the sea urchin Arbacia punctulata

The role of echinoid parental nutrition in early-life stage toxicity is not well understood. Arbacia punctulata were fed either a fresh diet consisting of organic lettuce and carrots or a dry feed. Embryos from parents fed the dry feed exhibited lower sensitivity to copper, whereas the opposite occurred with 1,3,5-trinitrobenzene and sodium dodecyl sulfate (SDS). EC(50) values for the dry and fresh feed treatments, respectively, were 41.0 and 29.9 microg/L for copper, 0.5 and 1.8 mg/L for 1,3,5-trinitrobenzene, and 3.5 and 5.6 mg/L for SDS. The data suggests that nutritional standardization for sea urchins in ecotoxicological laboratories needs to be addressed and further investigated.

Evaluation of six portable blood glucose meters for measuring blood glucose concentration in dogs

OBJECTIVE

To evaluate accuracy of 6 portable blood glucose meters (PBGMs) by comparing results of these meters with results obtained with a reference chemistry analyzer.

DESIGN

Evaluation study.

ANIMALS

49 dogs (158 blood samples). Procedures-Venous blood samples were tested with the 6 PBGMs, and results were compared with results of a commercially available analyzer that used a reference method based on the hexokinase reaction.

RESULTS

Plasma glucose concentrations obtained with the reference analyzer ranged from 41 to 639 mg/dL. There were significant correlations between blood glucose concentrations obtained with the 6 PBGMs and plasma glucose concentrations obtained with the reference analyzer (r > or = 0.96). However, for all 6 PBGMs, results differed from results for the reference analyzer, with the difference increasing as plasma glucose concentration increased. Significant differences in bias were found among meters. For 142 samples classified as hypoglycemic, euglycemic, or hyperglycemic on the basis of results of the reference analyzer, the percentage of samples that were misclassified on the basis of results of the PBGMs ranged from 2.1% to 38.7%.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of the present study suggested that there were substantial differences in the accuracy of currently available PBGMs when used to determine blood glucose concentration in dogs.

Serum insulin-like growth factor-I concentration in cats with diabetes mellitus and acromegaly

BACKGROUND

Serum insulin-like growth factor-I (IGF-I) has been used in place of serum growth hormone quantification for identifying acromegaly in diabetic cats. The utility of IGF-I as a screening test for acromegaly has not been critically evaluated. This retrospective study was performed to evaluate the usefulness of serum IGF-I concentration for identifying acromegaly.

HYPOTHESIS

Serum IGF-I is a useful screening test for acromegaly in diabetic cats.

ANIMALS

A review was made of the medical records of 74 diabetic cats that had serum IGF-I quantified. The diabetes was classified as well controlled (15 cats), poorly controlled because of problems with the insulin treatment regimen, concurrent disease, or both (40), or poorly controlled with clinical findings consistent with acromegaly (19).

METHODS

A review of medical records was made.

RESULTS

Serum IGF-I concentration was significantly (P < .0001) increased in acromegalic diabetic cats, compared with well-controlled and poorly controlled diabetic cats. Sensitivity and specificity for serum IGF-I concentration were 84% (95%/ confidence interval [CI] = 60.4-96.6%) and 92% (95% CI = 81.3-97.2%), respectively. There was no significant correlation between serum IGF-I concentration and duration of insulin treatment (r = 0.23, P = .089), insulin dosage (r = 0.14, P = .30), age (r = 0.16, P = .12), and pituitary volume (r = 0.40, P = .11), but a modest correlation was found between serum IGF-I concentration and body weight (r = 0.48, P < .0001).

CONCLUSIONS AND CLINICAL IMPORTANCE

Results support the use of serum IGF-I concentration as a screening test for acromegaly in diabetic cats that have clinical findings supportive of the disease.

Clinical features and heritability of hypoadrenocorticism in Nova Scotia Duck Tolling Retrievers: 25 cases (1994-2006)

OBJECTIVE

To evaluate the clinical features and heritability of naturally occurring hypoadrenocorticism in Nova Scotia Duck Tolling Retrievers (NSDTRs).

DESIGN

Retrospective case series.

ANIMALS

25 NSDTRs with hypoadrenocorticism.

PROCEDURES

Questionnaires completed by owners of NSDTRs with hypoadrenocorticism and medical records from veterinarians were reviewed for information regarding diagnosis, age at diagnosis, concurrent diseases, age at death, and cause of death. Pedigrees were analyzed for heritability and mode of inheritance of hypoadrenocorticism (including complex segregation analysis of pedigrees of 1,515 dogs).

RESULTS

On the basis of results of ACTH stimulation testing, hypoadrenocorticism was diagnosed in 16 female and 9 male NSDTRs (including 6 full siblings). Median age at diagnosis was 2.6 years; the diagnosis was made prior to 2 years of age in 11 dogs. Seventeen dogs had hyponatremia, hyperkalemia, or both, and serum electrolyte concentrations were within reference ranges for 8 dogs at the time of diagnosis. Median survival time after diagnosis for 4 dogs that died or were euthanized as a result of medical causes was 1.6 years. Heritability was calculated at 0.98 with no sex effect, and complex segregation analysis fit a major gene model with an autosomal recessive mode of inheritance.

CONCLUSIONS AND CLINICAL RELEVANCE

In NSDTRs, hypoadrenocorticism was diagnosed at an earlier age, compared with published reports of age at diagnosis among the general dog population. Among the study dogs, 32% had no serum electrolyte abnormalities at the time of diagnosis, and the disease appeared to have an autosomal recessive mode of inheritance in the breed.

Adrenalectomy and Caval Thrombectomy in a Cat With Primary Hyperaldosteronism

A 13-year-old, castrated male, domestic longhaired cat was diagnosed with primary hyperaldosteronism from an adrenal gland tumor and a thrombus in the caudal vena cava. Clinical signs included cervical ventriflexion, lethargy, weakness, inappetence, and diarrhea. Laboratory tests revealed hypokalemia, normonatremia, hyperglycemia, hypophosphatemia, and elevated creatine kinase activity. Hypokalemia worsened despite oral potassium supplementation. An adrenalectomy and caval thrombectomy were successfully performed utilizing deliberate hypothermia followed by progressive rewarming.

Comparison of serologic evaluation via agar gel immunodiffusion and fungal culture of tissue for diagnosis of nasal aspergillosis in dogs

OBJECTIVE

To compare the sensitivity and specificity of serologic evaluation and fungal culture of tissue for diagnosis of nasal aspergillosis in dogs.

DESIGN

Prospective study.

ANIMALS

58 dogs with nasal discharge and 26 healthy dogs.

PROCEDURES

Dogs with nasal discharge were anesthetized and underwent computed tomography and rhinoscopy; nasal tissues were collected for histologic examination and fungal culture. Sera were assessed for antibodies against Aspergillus spp (healthy dog sera were used as negative control specimens). Nasal aspergillosis was diagnosed in dogs that had at least 2 of the following findings: computed tomographic characteristics consistent with aspergillosis, fungal plaques detected during rhinoscopy, and histologically detectable fungal hyphae in nasal tissue. Histologic characteristics of malignancy were diagnostic for neoplasia. Without evidence of neoplasia or fungal disease, nonfungal rhinitis was diagnosed.

RESULTS

Among the 58 dogs, 21 had nasal aspergillosis, 25 had nonfungal rhinitis, and 12 had nasal neoplasia. Fourteen aspergillosis-affected dogs and 1 dog with nonfungal rhinitis had serum antibodies against Aspergillus spp. Fungal culture results were positive for Aspergillus spp only for 17 dogs with aspergillosis. With regard to aspergillosis diagnosis, sensitivity, specificity, and positive and negative predictive values were 67%, 98%, 93%, and 84%, respectively, for serum anti-Aspergillus antibody determination and 81%, 100%, 100%, and 90%, respectively, for fungal culture.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that seropositivity for Aspergillus spp and identification of Aspergillus spp in cultures of nasal tissue are highly suggestive of nasal aspergillosis in dogs; however, negative test results do not rule out nasal aspergillosis.

Relative adrenal insufficiency in dogs with sepsis

BACKGROUND

A syndrome of relative adrenal insufficiency has been identified in septic humans, and is associated with hypotension and death. Relative adrenal insufficiency is generally associated with basal serum cortisol concentration within or above the reference range and a blunted cortisol response to adrenocorticotropic hormone administration. It is unknown whether relative adrenal insufficiency occurs in septic dogs.

HYPOTHESIS

That relative adrenal insufficiency occurs in septic dogs, and that relative adrenal insufficiency is associated with hypotension and mortality.

ANIMALS

Thirty-three septic dogs admitted to a small animal intensive care unit.

METHODS

Dogs were included in the study if they had a known or suspected infectious disease and had systemic inflammatory response syndrome. Dogs were excluded if they had disease or medication history expected to affect the hypothalamic-pituitary-adrenal axis. Serum cortisol and endogenous plasma adrenocorticotropic hormone concentrations were measured before, and serum cortisol concentration measured 1 hour after, intramuscular administration of 250 microg of cosyntropin/dog. The change in cortisol concentration (delta-cortisol) before and after cosyntropin administration was determined in each dog.

RESULTS

Hypotension was associated with lower delta-cortisol values (OR 1.3; CI 1.0-1.9; P = .029). delta-Cortisol cutoff of 3.0 microg/dL was most accurate for predicting hypotension, survival to discharge, and 28-day survival. The rate of death in dogs with delta-cortisol < or = 3 microg/dL was 4.1 times that of dogs with delta-cortisol > 3 microg/dL (RR 4.1; CI 1.5-12.3; P = .01).

CONCLUSIONS AND CLINICAL RELEVANCE

Delta-cortisol < or = 3 microg/dL after adrenocorticotropic hormone administration is associated with systemic hypotension and decreased survival in septic dogs.

Comparable myelinated nerve pathology in feline and human diabetes mellitus

The occurrence of diabetic neuropathy in cats provides an opportunity to study the development and treatment of neurological complications not present in diabetic rodent models, where few pathological alterations are evident. The present study further defines pathological alterations in nerve biopsies from 12 cats with spontaneously occurring diabetes mellitus. Peroneal nerve biopsies displayed concurrent injury to both Schwann cells and axons of myelinated fibers that was remarkably similar to that present in human diabetic neuropathy. In addition to demyelination, remyelination (constituting 20-84% of the total myelinated fiber population) was indicated by fibers with inappropriately thin myelin sheaths. Unlike our previous investigations, striking axonal injury was apparent, and consisted of dystrophic accumulations of membranous debris or neurofilaments, as well as degenerative fiber loss resulting in a 50% decrease in myelinated fiber density. In spite of extensive fiber loss, regenerative clusters were apparent, suggesting that axonal regeneration was not completely frustrated. These data highlight the potential utility of feline diabetic neuropathy as a model that faithfully replicates the nerve injury in human diabetes mellitus.

Incidence of and risk factors for diabetes mellitus in cats that have undergone renal transplantation: 187 cases (1986–2005)

OBJECTIVE

To compare incidence of diabetes mellitus in cats that had undergone renal transplantation with incidence in cats with chronic renal failure, compare mortality rates in cats that underwent renal transplantation and did or did not develop diabetes mellitus, and identify potential risk factors for development of posttransplantation diabetes mellitus (PTDM) in cats.

DESIGN

Retrospective case series.

ANIMALS

187 cats that underwent renal transplantation.

PROCEDURES

Medical records were reviewed.

RESULTS

26 of the 187 (13.9%) cats developed PTDM, with the incidence of PTDM being 66 cases/1,000 cat years at risk. By contrast, the incidence of diabetes mellitus among a comparison population of 178 cats with chronic renal failure that did not undergo renal transplantation was 17.9 cases/1,000 cat years at risk, and cats that underwent renal trans-plantation were 5.45 times as likely to develop diabetes mellitus as were control cats with chronic renal failure. The mortality rate among cats with PTDM was 2.38 times the rate among cats that underwent renal transplantation but did not develop PTDM. Age, sex, body weight, and percentage change in body weight were not found to be significantly associated with development of PTDM.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that cats that undergo renal transplantation have an increased risk of developing diabetes mellitus, compared with cats with chronic renal failure, and that mortality rate is higher for cats that develop PTDM than for cats that do not.

Frequency and risk factors for urinary tract infection in cats with diabetes mellitus

BACKGROUND

Identification and control of infections are important in the management of diabetic cats. Urinary tract infections have not been well characterized in diabetic cats. This retrospective study was performed to review and characterize urinary tract infections in diabetic cats.

HYPOTHESIS

Urinary tract infections are common in diabetic cats.

ANIMALS

A review was made of the medical records of 141 diabetic cats that had had urine obtained for culture by antepubic cystocentesis and that had not been treated with antibiotics, undergone urinary tract catheterization or urinary tract surgery within 2 weeks of urine collection or had urethral obstruction at the time of urine collection.

METHODS

A review of medical records.

RESULTS

Urinary tract infection was identified in 18 of 141 diabetic cats. Escherichia coli was the most common isolate (67%). Female cats were at increased risk (prevalence odds ratios [POR], 3.7; 95% confidence interval [CI], 1.3 to 10.2; P = .013). Clinical signs of lower urinary tract disease and findings on urine sediment examination were good predictors of positive urine cultures.

CONCLUSIONS AND CLINICAL IMPORTANCE

Urinary tract infections are common in diabetic cats regardless of status of diabetic control, suggesting routine monitoring with urine sediment exams or urine culture is warranted.

Comparison of ultrasonographic characteristics of the thyroid gland in healthy small-, medium-, and large-breed dogs

OBJECTIVE

To determine ultrasonographic characteristics of the thyroid gland in healthy small-, medium-, and large-breed dogs and evaluate the relationships of thyroid gland size and volume with body weight and body surface area (BSA).

ANIMALS

72 dogs of small (6 Toy and 6 Miniature Poodles), medium (12 Beagles), and large breeds (12 Akitas and 36 Golden Retrievers).

PROCEDURE

Each dog's thyroid gland was examined ultrasonographically with a 10- to 5-MHz multifrequency linear-array transducer. Size, shape, echogenicity, and homogeneity of thyroid lobes were evaluated on longitudinal and transverse images. Thyroid lobe volume was estimated by use of the equation for an ellipsoid (pi/6 [length x height x width]).

RESULTS

Thyroid lobes appeared fusiform or elliptical on longitudinal images and triangular or round to oval on transverse images. In most dogs, thyroid lobes were hyperechoic or isoechoic, compared with surrounding musculature, and had a homogeneous echogenic pattern. Mean length, width, height, and volume of thyroid lobes were significantly greater in Akitas and Golden Retrievers, compared with findings in Beagles or Poodles; mean length, width, and height were significantly greater in Beagles, compared with findings in Poodles. Total thyroid gland volume correlated with body weight (r = 0.73) and BSA (r = 0.74).

CONCLUSIONS AND CLINICAL RELEVANCE

Among the dog breeds examined ultrasonographically, thyroid lobe size and volume were more variable than shape, echogenicity, and homogeneity. The correlation of thyroid gland volume with BSA suggests that size of the dog, rather than breed, should be considered when assessing thyroid glands ultrasonographically.

Inhaled flunisolide suppresses the hypothalamic-pituitary-adrenocortical axis, but has minimal systemic immune effects in healthy cats

Feline bronchial disease is commonly treated with oral glucocorticoids (OGC), which might be contraindicated in cats with certain infectious, endocrine, renal, or cardiac diseases. Inhalant GC (IGC) maximize local efficacy and minimize systemic bioavailability. We evaluated systemic endocrine and immune effects of IGC (flunisolide, 250 microg/puff q12h) versus OGC (prednisone, 10 mg/d PO) and placebo. Six healthy cats received each drug for 2 weeks followed by a 1-month washout. Testing included determination of single early morning cortisol concentration, results of ACTH stimulation, the urine cortisol-to-creatinine ratio (UC: Cr), lymphocyte phenotype, lymphocyte blastogenesis, serum total IgA and IgM concentrations, and cytokine profiles. Significant differences between treatments were not apparent for serum immunoglobulin concentrations, or expression (mRNA) for the cytokines, interleukin (IL-) 2, IL-4, and IL-10, or gamma interferon. Single early morning cortisol concentration was lower for IGC (0.68 - 0.74 microg/dL), compared with that associated with placebo (2.82 +/- 1.94 microg/dL; P = .033). The ACTH-stimulated peak cortisol concentrations were lower after treatment in cats receiving IGC (before, 8.5 +/- 50.2 microg/dL; after, 2.9 +/- 3.3 microg/dL, P = .0004), but not OGC (before, 8.0 +/- 6.1 microg/dL; after, 6.0 +/- 4.5 microg/dL, P = .07). Similarly, UC: Cr (0.8 +/- 0.8) before IGC was lower than the value (5.02 +/- 3.62; P = .019) after IGC. Compared with placebo, cats given OGC, but not IGC, had significantly lower total percentages of T and B cells. Lymphocyte proliferation was decreased in cats receiving OGC, but not IGC, in comparison with placebo (6.9 +/- 3.3; 24.0 +/- 6.5; 18.8 +/- 14.0, respectively). Significantly more IL-10 mRNA transcription was detected in cats administered OGC or IGC, compared with placebo. Although IGC suppress the hypothalamic-pituitary-adrenocortical axis, IGC had minimal effects on the systemic adaptive immune system.

Measurements of growth hormone and insulin-like growth factor 1 in cats with diabetes mellitus

Serum concentrations of insulin-like growth factor 1 (IGF-1) and growth hormone were measured in 25 cats with untreated diabetes mellitus (11 of which were used for follow-up measurements, one to three, four to eight, nine to 12 and 13 to 16 weeks after their treatment with insulin began), 14 diabetic cats that had previously been treated with insulin, and seven diabetic cats that also had hypersomatotropism, two of which had not previously been treated with insulin; 18 healthy cats were used as controls. In the untreated diabetic cats the concentration of IGF-1 ranged from 13.0 to 433.0 ng/ml (median 170.5 ng/ml), which was significantly lower than the concentrations in the control cats (196.0 to 791.0 ng/ml, median 452.0 ng/ml). Their IGF-1 concentrations increased significantly when they were treated with insulin and after four to eight weeks were not different from those in the control cats. In the diabetic cats that had previously been treated with insulin the IGF-1 concentrations were 33.0 to 476.0 ng/ml (median 316.0 ng/ml), which was significantly lower than the concentrations in the control cats, but significantly higher than in the untreated diabetic cats. The IGF-1 concentrations in the two previously untreated diabetic cats with hypersomatotropism were low and low-normal but increased markedly after treatment with insulin. In the five previously treated cats with hypersomatotropism the concentration of IGF-1 was above the normal range. The concentrations of growth hormone in the treated and untreated diabetic cats without hypersomatotropisms were not significantly different and there was an overlap in its concentrations in the diabetic cats with and without hypersomatotropism.

Evaluation of serum 17-hydroxyprogesterone concentration after administration of ACTH in dogs with hyperadrenocorticism

OBJECTIVE

To evaluate serum 17-hydroxyprogesterone (17-OHP) concentration measurement after administration of ACTH for use in the diagnosis of hyperadrenocorticism in dogs.

DESIGN

Prospective study.

ANIMALS

110 dogs.

PROCEDURE

Serum 17-OHP concentrations were measured before and after ACTH stimulation in 53 healthy dogs to establish reference values for this study. Affected dogs had pituitary-dependent (n = 40) or adrenal tumor-associated (12) hyperadrenocorticism or potentially had atypical hyperadrenocorticism (5; diagnosis confirmed in 1 dog). In affected dogs, frequency interval and borderline and abnormal serum 17-OHP concentrations after ACTH stimulation were determined. Serum cortisol concentrations were assessed via low-dose dexamethasone suppression and ACTH stimulation tests.

RESULTS

In healthy dogs, serum 17-OHP concentration frequency intervals were grouped by sex and reproductive status (defined as < 95th percentile). Frequency intervals of serum 17-OHP concentrations after ACTH stimulation were < 77, < 2.0, < 3.2, and < 3.4 ng/mL (< 23.3, < 6.1, < 9.7, and < 10.3 nmol/L) for sexually intact and neutered females and sexually intact and neutered males, respectively. In 53 dogs with confirmed hyperadrenocorticism, serum cortisol concentrations after ACTH stimulation and 8 hours after administration of dexamethasone and serum 17-OHP concentrations after ACTH stimulation were considered borderline or abnormal in 79%, 93%, and 69% of dogs, respectively. Two of 5 dogs considered to have atypical hyperadrenocorticism had abnormal serum 17-OHP concentrations after ACTH stimulation.

CONCLUSIONS AND CLINICAL RELEVANCE

Serum 17-OHP concentration measurement after ACTH stimulation may be useful in the diagnosis of hyperadrenocorticism in dogs when other test results are equivocal.

Ultrasonographic evaluation of the thyroid gland in healthy, hypothyroid, and euthyroid Golden Retrievers with nonthyroidal illness

Ultrasound evaluation of the thyroid gland was performed in healthy, hypothyroid, and euthyroid Golden Retriever dogs with nonthyroidal illness (NTI) to determine the diagnostic usefulness of ultrasound for differentiating between euthyroid and hypothyroid dogs. Thirty-six healthy, 11 hypothyroid, and 35 euthyroid dogs with NTI were evaluated. Each thyroid lobe was examined ultrasonographically for size, shape, echogenicity, and homogeneity. Thyroid lobe volume was estimated by using the equation for an ellipsoid: pi/6(length X height x width). No differences were found between healthy dogs and euthyroid dogs with NTI. In the majority of euthyroid dogs, the thyroid lobes were fusiform and triangular in shape in longitudinal and transverse planes, respectively. The thyroid capsule appeared smooth. The thyroid parenchyma had a homogeneous echogenic pattern and usually was hyperechoic or isoechoic compared with the surrounding musculature. Ultrasound findings in hypothyroid dogs were more variable, including a greater frequency of round to oval-shaped thyroid lobes in the transverse imaging plane (P < .05), hypoechogenicity of the thyroid parenchyma compared with surrounding musculature (P < .001), and a decrease in the size and volume of the thyroid lobes and total volume of the thyroid gland (P < .05) compared with euthyroid dogs. Other findings in hypothyroid dogs included an irregular surface to the thyroid capsule, a heterogeneous pattern to the thyroid parenchyma, and differences in the echogenic pattern between the left and right thyroid lobes. Results suggest that determination of thyroid size and volume by ultrasound may be a useful adjunctive test for differentiating between hypothyroid and euthyroid dogs with NTI.

Pretreatment clinical and laboratory findings in dogs with primary hyperparathyroidism: 210 cases (1987–2004)

OBJECTIVE

To evaluate pretreatment clinical and laboratory findings in dogs with naturally occurring primary hyperparathyroidism.

DESIGN

Retrospective study.

ANIMALS

210 dogs with primary hyperparathyroidism and 200 randomly selected, age-matched control dogs that did not have primary hyperparathyroidism.

PROCEDURE

Medical records for dogs with primary hyperparathyroidism were reviewed for signalment; clinical features; and results of clinicopathologic testing, serum parathyroid hormone assays, and diagnostic imaging.

RESULTS

Mean age of the dogs with primary hyperparathyroidism was 11.2 years (range, 6 to 17 years). The most common clinical signs were attributable to urolithiasis or urinary tract infection (ie, straining to urinate, increased frequency of urination, and hematuria). Most dogs (149 [71%]) did not have any observable abnormalities on physical examination. All dogs had hypercalcemia, and most (136 [65%]) had hypophosphatemia. Overall, 200 of the 210 (95%) dogs had BUN and serum creatinine concentrations within or less than the reference range, and serum parathyroid hormone concentration was within reference limits in 135 of 185 (73%) dogs in which it was measured. Urolithiasis was identified in 65 (31 %) dogs, and urinary tract infection was diagnosed in 61 (29%). Mean serum total calcium concentration for the control dogs-was significantly lower than mean concentration for the dogs with primary hyperparathyroidism, but mean BUN and serum creatinine concentrations for the control dogs were both significantly higher than concentrations for the dogs with primary hyperparathyroidism.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that urolithiasis and urinary tract infection may be associated with hypercalcemia in dogs-with primary hyperparathyroidism, but that development of renal insufficiency is uncommon.

Secretion of sex hormones in dogs with adrenal dysfunction

OBJECTIVE

To evaluate adrenal sex hormone concentrations in response to ACTH stimulation in healthy dogs, dogs with adrenal tumors, and dogs with pituitary-dependent hyperadrenocorticism (PDH).

DESIGN

Prospective study.

ANIMALS

11 healthy control dogs, 9 dogs with adrenal-dependent hyperadrenocorticism (adenocarcinoma [ACA] or other tumor); 11 dogs with PDH, and 6 dogs with noncortisol-secreting adrenal tumors (ATs).

PROCEDURE

Hyperadrenocorticism was diagnosed on the basis of clinical signs; physical examination findings; and results of ACTH stimulation test, low-dose dexamethasone suppression test, or both. Dogs with noncortisol-secreting ATs did not have hyperadrenocorticism but had ultrasonographic evidence of an AT. Concentrations of cortisol, androstenedione, estradiol, progesterone, testosterone, and 17-hydroxyprogesterone were measured before and 1 hour after i.m. administration of 0.25 mg of synthetic ACTH.

RESULTS

All dogs with ACA, 10 dogs with PDH, and 4 dogs with ATs had 1 or more sex hormone concentrations greater than the reference range after ACTH stimulation. The absolute difference for progesterone, 17-hydroxyprogesterone, and testosterone concentrations (value obtained after ACTH administration minus value obtained before ACTH administration) was significantly greater for dogs with ACA, compared with the other 3 groups. The absolute difference for androstenedione was significantly greater for dogs with ACA, compared with dogs with AT and healthy control dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Dogs with ACA secrete increased concentrations of adrenal sex hormones, compared with dogs with PDH, noncortisol-secreting ATs, and healthy dogs. Dogs with noncortisol-secreting ATs also have increased concentrations of sex hormones. There is great interdog variability in sex hormone concentrations in dogs with ACA after stimulation with ACTH.

Factors Affecting the Frequency of Value-Focused Health Activities and Policies by Employers

OBJECTIVE

We sought to gather employer perspectives about value-focused activities (VFAs), intentions to make decisions based on value, and other factors affecting decisions.

METHODS

Health decision-makers (n = 174), both American College of Occupational and Environmental Medicine members and corporate HR/benefits directors, responded to an Internet-based questionnaire.

RESULTS

Of a total of 32 listed VFAs, companies reported, on average, performing 5.2 activities currently and considering 2.6. Twenty-five percent of companies reported doing eight or more. The most common VFAs were providing access to flu shots, centers of excellence, and wellness programs. Greater access to detailed outcome data was associated with doing more VFAs, as was greater accountability for absence, disability, and productivity outcomes.

CONCLUSIONS

Employers vary widely in the number of VFAs in which they participate. Decision-makers with more information about, and accountability for, value outcomes reported doing more VFAs.

Comparison of serum-free thyroxine concentrations determined by standard equilibrium dialysis, modified equilibrium dialysis, and 5 radioimmunoassays in dogs

Measurement of serum-free thyroxine (fT4) concentration provides a more accurate assessment of thyroid gland function than serum thyroxine (T4) or 3,5,3'-triiodothyronine (T3). Techniques for measuring serum fT4 concentration include standard equilibrium dialysis (SED), radioimmunoassay (RIA), and a combination of both (modified equilibrium dialysis [MED]). This study compared results of serum fT4 measurements by means of SED, MED, and 5 RIAs in 30 healthy dogs, 10 dogs with hypothyroidism, and 31 euthyroid dogs with concurrent illness for which hypothyroidism was a diagnostic consideration. Serum fT4 concentrations were comparable when determined by the SED and MED techniques, and mean serum fT4 concentrations were significantly (P < .01) lower in dogs with hypothyroidism than in healthy dogs and euthyroid dogs with concurrent illness. Significant (P < .05) differences in fT4 concentrations were identified among the 5 RIAs and among the RIAs and MED and SED. Serum fT4 concentrations were consistently lower when fT4 was determined by the RIAs, compared with either equilibrium dialysis technique. Serum fT4 concentrations were significantly lower (P < .01) in dogs with hypothyroidism than in healthy dogs for all RIAs; were significantly lower (P < .05) in dogs with hypothyroidism than in euthyroid dogs with concurrent illness for 4 RIAs; and were significantly lower (P < .01) in euthyroid dogs with concurrent illness than in healthy dogs for 4 RIAs. RIAs had the highest number of low serum fT4 concentrations in euthyroid dogs with concurrent illness. This study documented differences in test results among fT4 assays, emphasizing the importance of maintaining consistency in the assay used to measure serum fT4 concentrations in the clinical or research setting.

Percutaneous ultrasound-guided radiofrequency heat ablation for treatment of hyperthyroidism in cats

OBJECTIVE

To determine efficacy and safety of percutaneous radiofrequency heat ablation for treatment of hyperthyroidism in cats.

DESIGN

Prospective study.

ANIMALS

9 cats.

PROCEDURE

Hyperthyroidism was diagnosed via clinical signs and high serum total (TT4) and free thyroxine (fT4) concentrations. One or 2 hyperfunctional cervical thyroid nodules were detected by use of scintigraphy and ultrasonography. If cats had 1 abnormal thyroid lobe, heat ablation was performed on that lobe; if cats had 2 abnormal lobes, heat ablation was applied to the larger lobe. Overall, heat ablation was performed 14 times in the 9 cats. Clinical signs and serum TT4, fT4, and calcium concentrations were monitored daily for 2 days after the procedure, weekly for the first month, and then monthly. Laryngeal function was evaluated and cervical ultrasonography and thyroid scintigraphy were also performed. Monitoring continued for as long as 9 months after heat ablation if a cat became euthyroid or until an owner chose an alternative treatment because of recurrence of hyperthyroidism.

RESULTS

Serum TT4 and fT4 concentrations transiently decreased after all 14 heat ablation procedures (< or = reference range after 10 of 14 treatments) within 2 days after the procedure. Cats were euthyroid for 0 to 18 months (mean, 4 months). Hyperthyroidism recurred in all cats. Adverse effects included transient Horner's syndrome (2 cats) and laryngeal paralysis without clinical signs (1 cat).

CONCLUSIONS AND CLINICAL RELEVANCE

Percutaneous heat ablation as a treatment for hyperthyroidism in cats is effective transiently but not permanently.

Surgical management of adrenal gland tumors with and without associated tumor thrombi in dogs: 40 cases (1994-2001)

OBJECTIVE

To compare pathologic findings and results of adrenalectomy for adrenal gland tumors in dogs with and without vena caval tumor thrombi.

DESIGN

Retrospective study.

ANIMALS

40 dogs with adrenal gland tumors.

PROCEDURE

Medical records were examined. An exact logistic regression analysis was used to evaluate associations between tumor type or right-sided versus left-sided tumor involvement and development of caval tumor thrombi and associations between tumor thrombi, tumor type, or right- versus left-sided location and perioperative complications and mortality rate. Survival was compared between dogs with and without tumor thrombi.

RESULTS

Caval thrombi were detected in 25% of dogs, including 3 of 28 (11%) dogs with an adrenocortical tumor and 6 of 11 dogs with a pheochromocytoma. A caval tumor thrombus was detected in 6 of 17 right-sided and 4 of 20 left-sided tumors. Sensitivity and specificity of abdominal ultrasonography for detection of caval thrombi were 80 and 90%, respectively. Intraoperative and postoperative complications developed in 15 and 51% of dogs, respectively. The mortality rate was 22%. There were no significant differences in perioperative morbidity and mortality rates between dogs with and without tumor thrombi.

CONCLUSIONS AND CLINICAL RELEVANCE

Caval thrombi associated with adrenal gland tumors are amenable to adrenalectomy and thrombectomy without significantly increased perioperative morbidity and mortality rates, assuming the surgeon is experienced in appropriate techniques.

Corneal sensitivity in dogs with diabetes mellitus

OBJECTIVE

To compare aesthesiometer-determined corneal sensitivity between diabetic and nondiabetic dogs and to investigate the correlation between corneal sensitivity and duration of diabetes or status of glycemic control, as estimated by use of glycated blood protein concentrations.

ANIMALS

23 diabetic and 29 nondiabetic normoglycemic dogs.

PROCEDURE

A Cochet-Bonnet aesthesiometer was used to measure corneal touch threshold (CTT) in 5 corneal regions of each dog. At the time of ocular examination, duration of diabetes mellitus was estimated from the history, and blood was drawn for assessment of blood glycosylated hemoglobin and serum fructosamine concentrations.

RESULTS

Median CTT for central, nasal, dorsal, temporal, and ventral corneal regions in nondiabetic dogs (1.6, 2.3, 2.8, 2.8, and 5.1 g/mm2, respectively) was significantly lower than in diabetic dogs (2.8, 4.0, 5.1, 5.1, and 6.6 g/mm2, respectively). Median regional CTT in diabetic dogs was not significantly correlated with estimated duration of diabetes mellitus or blood glycated protein concentrations. No significant difference was found in regional CTT between eyes of normoglycemic dogs with unilateral cataracts.

CONCLUSIONS AND CLINICAL RELEVANCE

Diabetic dogs have significantly reduced corneal sensitivity in all regions, compared with nondiabetic normoglycemic dogs. Regional variation in corneal sensitivity is similar in diabetic and normoglycemic dogs. Neither glycemic control nor duration of diabetes, as estimated, is significantly correlated with corneal hyposensitivity. Corneal nerve dysfunction may be associated with recurrent or nonhealing ulcers in diabetic dogs for which no other underlying cause can be found.

Streptozocin for treatment of pancreatic islet cell tumors in dogs: 17 cases (1989-1999)

OBJECTIVE

To determine toxic effects of streptozocin given in combination with a diuresis protocol in dogs and establish whether streptozocin is efficacious in treatment of pancreatic islet cell tumors in dogs.

DESIGN

Retrospective study.

ANIMALS

17 dogs.

PROCEDURE

Medical records were reviewed to obtain information regarding signalment, tumor stage and staging tests performed, number of streptozocin treatments, adverse effects, results of biochemical and hematologic monitoring during streptozocin treatment, tumor dimensions, duration of normoglycemia, and date of death, when applicable. Dogs were compared with a historical control group of 15 dogs treated surgically and medically.

RESULTS

58 treatments were administered to the 17 dogs. Only 1 dog developed azotemia. Serum alanine aminotransferase activity increased in some dogs but decreased when treatment was discontinued. Hematologic toxicoses were rare. Vomiting during administration was uncommon but occasionally severe. Two dogs developed diabetes mellitus after receiving 5 doses. Median duration of normoglycemia for 14 dogs with stage-II or -III insulinoma treated with streptozocin was 163 days (95% confidence interval, 16 to 309 days), which was not significantly different from that for the control dogs (90 days; 95% confidence interval, 0 to 426 days). Two dogs had rapid resolution of paraneoplastic peripheral neuropathy, and 2 others had measurable reductions in tumor size.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that streptozocin can be administered safely to dogs at a dosage of 500 mg/m2, IV, every 3 weeks when combined with a protocol for induction of diuresis and may be efficacious in the treatment of dogs with metastatic pancreatic islet cell tumors.

Mass Spectrometric Immunoassay

A new, general method of immunoassay is demonstrated. The approach is based on the microscale immunoaffinity capture of target antigens followed by mass-specific identification and quantitation using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Immunoaffinity capture of antigens effectively overcomes signal suppression effects typically encountered during traditional matrix-assisted laser desorption/ionization analysis of complex biological mixtures while simultaneously concentrating the analyte into a small volume. Mass spectrometric detection of antigens is unambiguous, as antigen signals are observed at characteristic mass-to-charge values in the mass spectrum, offering a high level of immunity to artifacts due to nonbiospecific retention of mixture components. However, the most important aspect of such mass-specific detection is the ability to use a single assay to screen biological systems for the presence of multiple, mass-resolved antigens. Analyte quantitation is possible by using a single antibody to capture both the antigen and an antigen variant which has been chemically modified to have a different mass. With proper calibration, the relative signal intensities of the two species in the mass spectrum can be used to determine the antigen concentration. Sample incubation and processing methods were such that a typical analysis could be performed in less than 1 h while subnanomolar sensitivities were maintained. The technique has been used for the rapid, selective, and quantitative screening of human blood for the presence of myotoxin a, and Mojave toxin form the venoms of the prairie rattlesnakes, Crotalus viridis viridis, and and the Mojave rattlesnake, Crotalus scutulatus scutulatus.

Analysis of native proteins from biological fluids by biomolecular interaction analysis mass spectrometry (BIA/MS): exploring the limit of detection, identification of non-specific binding and detection of multi-protein complexes

Biomolecular interaction analysis mass spectrometry (BIA/MS) is a two-dimensional analytical technique that quantitatively and qualitatively detects analytes of interests. In the first dimension, surface plasmon resonance (SPR) is utilized for detection of biomolecules in their native environment. Because SPR detection is non-destructive, analyte(s) retained on the SPR-active sensor surface can be analyzed in a second dimension using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. The qualitative nature of the MALDI-TOF MS analysis complements the quantitative character of SPR sensing and overcomes the shortcomings of the SPR detection stemming from the inability to differentiate and characterize multi-protein complexes and non-specific binding. In this work, the benefit of performing MS analysis following SPR sensing is established. Retrieval and detection of four markers present in biological fluids (cystatin C, beta-2-microglobulin, urinary protein 1 and retinol binding protein) was explored to demonstrate the effectiveness of BIA/MS in simultaneous detection of clinically related biomarkers and delineation of non-specific binding. Furthermore, the BIA/MS limit of detection at very low SPR responses was investigated. Finally, detection of in-vivo assembled protein complexes was achieved for the first time using BIA/MS.

Delineation of in vivo assembled multiprotein complexes via biomolecular interaction analysis mass spectrometry

Biomolecular interaction analysis mass spectrometry (BIA-MS) is a multiplexed bioanalytical approach used in analysis of proteins from complex biological mixtures. It utilizes surface-immobilized ligands for protein affinity retrieval, surface plasmon resonance for monitoring the ligand-protein interaction and matrix-assisted laser desorption/ionization-time of flight mass spectrometry for revealing the masses of the biomolecules retrieved by the ligand. In order to explore the utility of BIA-MS in delineation of multiprotein complexes, an in vivo assembled protein complex comprised of retinol binding protein (RBP) and transthyretin (TTR) was investigated. Antibodies to RBP and TTR were utilized as ligands in the analysis of the protein complex present in human plasma. The RBP-TTR complex was retrieved by the anti-RBP antibody as indicated by the presence of both RBP and TTR signals in the mass spectra. RBP signals were not observed in the mass spectra of the material retained on the anti-TTR derivatized surface. In addition, the mass-specific detection in BIA-MS allowed detection of RBP and TTR analyte variants.

Analysis of human urine protein biomarkers via biomolecular interaction analysis mass spectrometry

Biomolecular interaction analysis mass spectrometry (BIA/MS) is a two-dimensional chip-based analytical technique geared toward quantitative and qualitative analysis of small volumes of biological samples. Interactions between surface-immobilized ligands and solute-borne analytes are quantitatively viewed in real time through surface plasmon resonance sensing, followed by qualitative matrix-assisted laser desorption/ionization time-of-flight MS analysis of the analyte(s) affinity-retained on the sensor surface. In this work, BIA/MS was used in the detection of a number of protein biomarkers from human urine. Small volumes of human urine were analyzed for cystatin C, beta(2)-microglobulin, urinary protein 1, and retinol-binding protein (RBP). Multiaffinity sensor surfaces were created to simultaneously and rapidly detect all four proteins in a single BIA/MS analysis on a two-flow cell sensor chip configuration. Furthermore, RBP was analyzed separately from both urine and plasma samples. Results indicate that BIA/MS can be used successfully in rapid screening of a number of urinary proteins indicated as putative biological markers for renal dysfunction.

Determination of beta-2 microglobulin levels in plasma using a high-throughput mass spectrometric immunoassay system

A high-throughput mass spectrometric immunoassay (MSIA) system for the analysis of proteins directly from biological fluids is reported. A 96-well-format robotic workstation equipped with antibody-derivatized affinity pipet tips was used for the parallel extraction of specific proteins from samples and subsequent deposition onto 96-well arrayed matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) targets. Interferences from nonspecifically bound proteins were minimized through choice of appropriate affinity pipet tip derivatization chemistries. Sample preparation for MALDI-TOFMS was enhanced through the use of hydrophobic/hydrophilic contrasting targets, which also presented functionalities found to promote matrix/analyte crystal growth. Automated mass spectrometry was used in the unattended acquisition of data, resulting in an analysis rate of approximately 100 samples/h (biological fluid-->data). The quantitative MSIA of beta2m levels present in human plasma samples is given as illustration.

Oral chromium picolinate and control of glycemia in insulin-treated diabetic dogs

Chromium is an essential dietary trace mineral involved in carbohydrate and lipid metabolism. Chromium is required for cellular uptake of glucose, and chromium deficiency causes insulin resistance. Chromium supplementation may improve insulin sensitivity and has been used as adjunct treatment of diabetes mellitus in humans. In this study, 13 dogs with naturally acquired diabetes mellitus were treated with insulin for 3 months, then with insulin and chromium picolinate for 3 months. Dogs weighing <15 kg (33 lb: n = 9) were administered 200 microg of chromium picolinate PO once daily for I month, then 200 microg of chromium picolinate twice daily for 2 months. Dogs weighing >15 kg (n = 4) received 200 microg of chromium picolinate once daily for 2 weeks, then 200 microg twice daily for 2 weeks, then 400 microg twice daily for 2 months. Type of insulin, frequency of insulin administration, and diet were kept constant, and insulin dosage was adjusted, as needed, to maintain optimal control of glycemia. Mean body weight, daily insulin dosage, daily caloric intake, 10-hour mean blood glucose concentration, blood glycated hemoglobin concentration, and serum fructosamine concentration were not markedly different when dogs were treated with insulin and chromium picolinate, compared with insulin alone. Adverse effects were not identified with chromium picolinate administration. Results of this study suggest that, at a dosage range of 20-60 microg/kg/d, chromium picolinate caused no beneficial or harmful effects in insulin-treated diabetic dogs.