Basal and glucagon-stimulated plasma C-peptide concentrations in healthy dogs, dogs with diabetes mellitus, and dogs with hyperadrenocorticism

Serum glucose and plasma C-peptide response to i.v. glucagon administration was evaluated in 24 healthy dogs, 12 dogs with untreated diabetes mellitus, 30 dogs with insulin-treated diabetes mellitus, and 8 dogs with naturally acquired hyperadrenocorticism. Serum insulin response also was evaluated in all dogs, except 20 insulin-treated diabetic dogs. Blood samples for serum glucose, serum insulin, and plasma C-peptide determinations were collected immediately before and 5, 10, 20, 30, and (for healthy dogs) 60 minutes after i.v. administration of 1 mg glucagon per dog. In healthy dogs, the patterns of glucagon-stimulated changes in plasma C-peptide and serum insulin concentrations were identical, with single peaks in plasma C-peptide and serum insulin concentrations observed approximately 15 minutes after i.v. glucagon administration. Mean plasma C-peptide and serum insulin concentrations in untreated diabetic dogs, and mean plasma C-peptide concentration in insulin-treated diabetic dogs did not increase significantly after i.v. glucagon administration. The validity of serum insulin concentration results was questionable in 10 insulin-treated diabetic dogs, possibly because of anti-insulin antibody interference with the insulin radioimmunoassay. Plasma C-peptide and serum insulin concentrations were significantly increased (P < .001) at all blood sampling times after glucagon administration in dogs with hyperadrenocorticism, compared with healthy dogs, and untreated and insulin-treated diabetic dogs. Five-minute C-peptide increment, C-peptide peak response, total C-peptide secretion, and, for untreated diabetic dogs, insulin peak response and total insulin secretion were significantly lower (P < .00l) in diabetic dogs, compared with healthy dogs, whereas these same parameters were significantly increased (P < .01) in dogs with hyperadrenocorticism, compared with healthy dogs, and untreated and insulin-treated diabetic dogs. Although not statistically significant, there was a trend for higher plasma C-peptide concentrations in untreated diabetic dogs compared with insulin-treated diabetic dogs during the glucagon stimulation test. Baseline C-peptide concentrations also were significantly higher (P < .05) in diabetic dogs treated with insulin for less than 6 months, compared with diabetic dogs treated for longer than 1 year. Finally, 7 of 42 diabetic dogs had baseline plasma C-peptide concentrations greater than 2 SD (ie, > 0.29 pmol/mL) above the normal mean plasma C-peptide concentration; values that were significantly higher, compared with the results in healthy dogs (P < .001) and with the other 35 diabetic dogs (P < .001). In summary, measurement of plasma C-peptide concentration during glucagon stimulation testing allowed differentiation among healthy dogs, dogs with impaired beta-cell function (ie, diabetes mellitus), and dogs with increased beta-cell responsiveness to glucagon (ie, insulin resistance). Plasma C-peptide concentrations during glucagon stimulation testing were variable in diabetic dogs and may represent dogs with type-1 and type-2 diabetes or, more likely, differences in severity of beta-cell loss in dogs with type-1 diabetes.

One-year follow-up evaluation of magnetic resonance imaging of the brain in dogs with pituitary-dependent hyperadrenocorticism

OBJECTIVE

To evaluate magnetic resonance imaging (MRI) brain scans of dogs with pituitary-dependent hyperadrenocorticism (PDH) and no signs of CNS dysfunction 1 year after diagnosis and initial MRI.

DESIGN

Prospective study of surviving dogs from a previous study.

ANIMALS

13 dogs underwent MRI of the brain at the time that PDH was diagnosed and prior to treatment. At that time, none of the dogs had clinical signs suggestive of an intracranial mass. Approximately 1 year after diagnosis and MRI, the brain was again evaluated by MRI.

RESULTS

On the initial MRI scan, 5 of the 13 dogs had normal findings, and 8 had evidence of a mass (tumor) in the area of the pituitary gland. Of the 5 dogs that had no visible pituitary mass on the initial MRI scan, 3 had a normal MRI brain scan 1 year later. Of the 5 dogs that had no visible pituitary mass on initial MRI scan, 2 had a visible pituitary mass at 1 year. The 8 dogs that had a visible mass on the initial MRI brain scan had easily identified pituitary masses on the second MRI scan. Of these 8 dogs, 4 had no apparent change in pituitary mass size, and 4 had obvious increase in vertical height of the pituitary mass. Of the 4 dogs, 2 developed signs of neurologic dysfunction within 1 year after diagnosis of PDH, presumably attributable to that mass. Of the 13 dogs, 12 were treated with mitotane soon after completion of the initial MRI scan. Sensitivity to mitotane and initial pituitary mass size or growth were not correlated. Of the 13 dogs evaluated initially and 1 year after diagnosis, 10 had pituitary masses identified on MRI brain scans.

CLINICAL IMPLICATIONS

The incidence of visible pituitary masses among dogs with PDH at the time of or within a year of diagnosis was > 75%. In 2 dogs, signs of CNS dysfunction developed within 1 year of PDH diagnosis when pituitary masses were > or = 10 mm.

Assessment of pseudarthrosis in pedicle screw fusion: a prospective study comparing plain radiographs, flexion/extension radiographs, CT scanning, and bone scintigraphy with operative findings

Twenty-five consecutive patients who had previously undergone lumbar fusion using stainless steel pedicle screw instrumentation and complained of persistent, severe pain were identified for prospective study. All patients had been scheduled for hardware removal and fusion inspection. Studies to rule out pseudarthrosis included plain radiography, flexion and extension radiography, computed tomography, and bone scintigraphy. Each preoperative radiographic study was then evaluated in a blinded fashion by a single independent radiologist and was determined to show fusion or pseudarthrosis. Each patient then underwent surgery, at which time the pedicle screw instrumentation was removed and the fusion was inspected. Using surgical inspection as absolute evidence of fusion or pseudarthrosis, statistical analysis was undertaken to evaluate the predictive value of the radiographic studies singly and in combination. No statistically significant correlation was found.

Outcome after Wiltse pedicle screw removal

Thirty-five patients were retrospectively reviewed after hardware removal after previous posterior lumbar spinal fusion by using Wiltse pedicle screw fixation. Pseudarthrosis was intraoperatively confirmed in 10 patients. Thirty of 35 patients were reviewed at an average of 17.5 months (range, 6-57 months). Of 30 patients, 30 had persistent back pain that limited activities and lumbar motion. Patients found to have pseudarthroses were significantly more likely to have less pain, use fewer narcotic medications, and have an improved quality of life after reoperation than patients found to have solid fusions. Postsurgical assessment of fusion is difficult, with instrumentation making exploration the most reliable method determining the state of arthrodesis. Accurate preoperative assessment of the fusion mass is the most important factor in deciding whether or not to reoperate on patients after Wiltse pedicle screw arthrodesis of the lumbar spine.

Rapid tryptic mapping using enzymatically active mass spectrometer probe tips

A method has been developed for rapid, sensitive, and accurate tryptic mapping of polypeptides using matrix-assisted laser desorption/ionization time-of-flight mass analysis. The technique utilizes mass spectrometer probe tips which have been activated through the covalent immobilization of trypsin. The enzymatically active probe tips were used for the tryptic mapping of chicken egg lysozyme and the results compared with those obtained using either free trypsin or agarose-immobilized trypsin. A significant increase in the overall sensitivity of the process was observed using the active probe tips, as well as the production of more characteristic proteolytic fragments and the elimination of background signals due to the autolysis of the trypsin. Further, probe tip digestions were found to be rapid and convenient.

Hypoglycemia in four dogs with smooth muscle tumors

Tumor-associated hypoglycemia has been reported in dogs with pancreatic beta-cell tumors, hepatic tumors, and, rarely, with other neoplasms. This article describes 4 dogs with marked hypoglycemia associated with smooth muscle tumors (jejunal leiomyoma, gastric leiomyoma and leiomyosarcoma, and splenic leiomyosarcoma). Presenting clinical signs included grand mal seizures, lethargy, weakness, ataxia, and, in 1 dog, polyuria/polydipsia. The serum insulin concentration was low in 1 dog and normal in the other dog evaluated. Immunohistochemical staining for insulin was negative in the 4 tumors; the 3 tumors arising from the stomach and jejunum stained diffusely positive for glucagon. Blood glucose concentrations rapidly returned to normal after complete surgical resection of the tumors, and clinical signs associated with hypoglycemia resolved. Long-term follow-up available in 3 of the 4 dogs found no recurrence of clinical signs related to hypoglycemia at 15, 31, and 38 months after surgery, respectively.

Adrenalectomy for treatment of hyperadrenocorticism in cats: 10 cases (1988-1992)

Outcome of and complications associated with bilateral adrenalectomy in 8 cats with pituitary-dependent hyperadrenocorticism and bilateral adrenocortical hyperplasia and outcome of and complications associated with unilateral adrenalectomy in 2 cats with adrenocortical tumor (adrenocortical adenoma, 1 cat; adrenocortical carcinoma, 1 cat) and unilateral adrenomegaly were determined. Glucocorticoids were administered to all cats at the time of surgery, and mineralocorticoids were administered to the 8 cats that underwent bilateral adrenalectomy. A ventral midline celiotomy was performed in all cats. Intraoperative complications did not develop in any cat. Postoperative complications developed in all cats and included abnormal serum electrolyte concentrations (n = 8), skin lacerations (n = 5), pancreatitis (n = 3), hypoglycemia (n = 2), pneumonia (n = 1), and venous thrombosis (n = 1). Three cats died within 5 weeks after surgery of complications associated with sepsis (n = 2) or thromboembolism (n = 1). Clinical signs and physical abnormalities caused by hyperadrenocorticism resolved in the remaining 7 cats 2 to 4 months after adrenalectomy. Insulin treatment was discontinued in 4 of 6 cats with diabetes mellitus. Median survival time for these 7 cats was 12 months (range, 3 to > 30 months). Two cats died of acute adrenocortical insufficiency 3 and 6 months after bilateral adrenalectomy, 2 cats were euthanatized because of chronic renal failure 3 and 12 months after bilateral (n = 1) or unilateral (n = 1) adrenalectomy, and 2 cats were alive 9 and 14 months after bilateral adrenalectomy. In the remaining cat, clinical signs recurred 10 months after the cat had undergone unilateral adrenalectomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Properties and developmental regulation of polysialyltransferase activity in the chicken embryo brain

The properties and developmental regulation of vertebrate polysialyltransferase (PST), an enzyme activity responsible for extension of alpha 2,8-linked sialic acid homopolymers (PSA) associated with the fifth Ig domain of the neural cell adhesion molecule (NCAM). have been studied. The assay for PST used exogenous NCAM as a substrate, with a PSA-specific endoneuraminidase as a control for specificity. Optimal conditions for PST activity at 37 degrees C were found to be pH 6.0 in the presence of divalent cations (Mn2+, 20mM). The enzyme Km was found to increase with increasing polymer length, ranging from 0.7 to 0.07 microns. The developmental regulation both of PST activity and of the addition of PSA to NCAM were studied in chick whole brain, tectum, and cerebellum and found to be precisely coordinated. In each tissue PSA and PST were highest during early stages of morphogenesis, followed by a decrease as development reached completion. The insertion of the VASE exon in the fourth Ig domain of NCAM was also found to parallel closely the developmental down-regulation of PSA, and on this basis could be considered a potential determinant in the specific polysialylation of NCAM. However in direct tests of this hypothesis in transfected cells the presence of VASE did not markedly alter the level of NCAM polysialylation or alter the affinity of PST for the NCAM substrate.

Pheochromocytoma and hyperadrenocorticism in dogs: six cases (1982-1992)

Pheochromocytoma was diagnosed in 4 dogs with pituitary-dependent hyperadrenocorticism and 2 dogs with hyperadrenocorticism caused by adrenocortical tumor. All dogs were examined initially because of clinical signs associated with hyperadrenocorticism. Pheochromocytoma was suspected in 2 dogs with pituitary-dependent hyperadrenocorticism that had ultrasonographic evidence of an adrenal gland mass, and in 1 dog suspected to have hyperadrenocorticism associated with an adrenocortical tumor after complications (systemic hypertension, cardiac arrhythmias) developed during induction of anesthesia. Pheochromocytoma was an unexpected finding at necropsy in the remaining 3 dogs. Two dogs collapsed suddenly and died before diagnostic tests could be performed; the other dog died during anesthesia for cobalt teletherapy of a pituitary macroadenoma. Hypertension, most notable during digital manipulation of the affected adrenal gland, developed during anesthesia and surgery in 3 dogs that underwent exploratory celiotomy.

Protein determinants for specific polysialylation of the neural cell adhesion molecule

Expression of polysialic acid (PSA) involves its specific attachment to the neural cell adhesion molecule (NCAM). Here we identify the amino acid residues within NCAM that are polysialylated and structural domains of the NCAM polypeptide that are required for addition of PSA in cells. Chicken NCAM cDNAs containing amino acid mutations, domain deletions, and domain substitutions were expressed in the F11 rat/mouse hybrid cell line, which can produce polysialylated NCAM. Polysialylation of the chicken NCAM was evaluated by immunopurification and electrophoresis. Mutation of all three potential N-glycosylation sites within the fifth immunoglobulin domain (Ig5) abrogated polysialylation. Analysis of paired mutations revealed that Asn-459 is heavily polysialylated, Asn-430 has a lower level of substitution, and Asn-404 receives little or no PSA. Analysis of domain deletions established that the intracellular domain, Ig domains 1-3, and the COOH-terminal fibronectin-type III (FNIII) repeat are not required for polysialylation, but that deletion of either the adjacent Ig4 or FNIII-type domain prevented addition of PSA. Accordingly, a minimal polypeptide for polysialylation was found to contain Ig domains 4 and 5, the adjacent FNIII repeat, plus a membrane attachment. These results suggest that although all PSA is located within Ig5, regions outside Ig5 also play a role in PSA addition to NCAM. Furthermore, molecular modeling indicates spatial proximity of Asn-430 and Asn-459 and a tight-locking arrangement between Ig4, Ig5, and FNIII#1 that would be consistent with their formation of a spatially discrete enzyme recognition site for polysialylation.

Effect of lente insulin for treatment of diabetes mellitus in 12 cats

Ultralente insulin has replaced protamine zinc insulin as the treatment of choice in treatment of diabetes mellitus in cats. There is variability in effectiveness of ultralente insulin and problems with glycemic control develop in some cats. Alternative insulin preparations are sought when ultralente insulin is ineffective. Twelve cats with insulin-dependent diabetes mellitus were treated with lente insulin. Clinical signs improved in 8 cats given lente insulin every 12 hours. Lente insulin was ineffective in 4 cats. Three of these cats were subsequently found to have an insulin resistant disorder. In 1 cat, lente insulin was ineffective because of short duration of action. Lente insulin is a viable treatment alternative when ultralente insulin is ineffective in achieving glycemic control. Ultralente insulin is still the insulin of choice for the initial treatment of diabetes in cats, because of the potential to establish glycemic control with once-a-day treatment.

Magnetic resonance imaging of the brain in dogs with recently diagnosed but untreated pituitary-dependent hyperadrenocorticism

Magnetic resonance imaging was used to determine the prevalence of visible pituitary masses in 21 dogs with recently diagnosed and untreated pituitary-dependent hyperadrenocorticism. All dogs had clinical signs and routine database values (CBC, serum biochemical panel, and urinalysis) consistent with a diagnosis of hyperadrenocorticism, and none had clinical signs suggestive of an intracranial mass. Each dog had plasma cortisol concentrations after adrenocorticotropic hormone administration or low-dose dexamethasone administration consistent with hyperadrenocorticism. Pituitary-dependent hyperadrenocorticism was confirmed by the finding of 2 equal-size adrenal glands on abdominal ultrasonography and by results of plasma endogenous adrenocorticotropic hormone concentration and high-dose dexamethasone suppression testing. Sagittal and transverse T1-weighted magnetic resonance images of the brain were obtained before and after IV administration of gadopentenate dimeglumine. Eleven dogs had visible masses, ranging in size from 4 to 12 mm at greatest vertical height. Mean age and body weight of dogs with a visible pituitary mass was not significantly different from dogs without a visible mass. There was no significant difference in endocrine test results when comparing dogs with a visible pituitary mass to dogs without. The prevalence of visible pituitary masses in dogs with pituitary-dependent hyperadrenocorticism was greater than suggested by the prevalence of clinical neurologic signs.

Magnetic resonance imaging for diagnosis of pituitary macrotumors in dogs

The value of magnetic resonance imaging (MRI) for the evaluation of dogs with pituitary-dependent hyperadrenocorticism (PDH) and CNS signs was assessed. Magnetic resonance imaging of the brain was performed in 13 dogs with PDH and neurologic signs. The diagnosis of PDH was made on the basis of results of adrenocortical function tests and abdominal ultrasonography, in conjunction with appropriate history, clinical signs, and clinicopathologic alterations. Eight dogs had been treated with the adrenocorticolytic agent, mitotane, for 1 to 30 months before the development of neurologic signs. Prior to MRI, each dog had progressive neurologic signs that could not be attributed to hypocortisolism or mitotane toxicosis. The neurologic signs most frequently detected were disorientation and ataxia. Mean age of dogs at the time neurologic signs developed was 9.5 years. Sex predilection was not detected; however, most were large-breed dogs, with 11 of the 13 dogs weighing more than 20 kg. A large mass in the pituitary gland, suprasellar region, or both was easily identified on the magnetic resonance images of each dog. The masses ranged from 8 to 24 mm in size. Expansion of tumors into the suprasellar region and compression of structures adjacent to the pituitary gland were readily detected by MRI. Contrast enhancement did not improve tumor identification, but did enable better delineation between tumor and surrounding structures. After the diagnosis of a macrotumor was made by MRI, radiotherapy was initiated in 9 dogs and was successfully completed in 6. Three dogs had a relapse of neurologic signs 8, 11, and 26 months after radiotherapy was completed.(ABSTRACT TRUNCATED AT 250 WORDS)

Peptide characterization using bioreactive mass spectrometer probe tips

A method has been developed for the rapid and sensitive mass spectrometric characterization of peptides. The approach uses bioreactive mass spectrometer probe tips, incorporating covalently bound enzymes, which are capable of modifying biomolecules for analytical purposes. In the demonstrated cases, enzymatic proteolysis is initiated upon application of analyte to the probe tips, time is allowed for digestion, and the products are analyzed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The probe tips have been used for proteolytic mapping and partial sequence determination of picomole quantities of peptide. Analysis times were approximately 30 min. Two methods of database search were utilized. The first used limited peptide sequence information and parent molecular weight, while the second used exclusively the molecular weights of a number of endoproteolytic fragments. A simple method of comparing the match of experimental data for a tryptic digest with the results of a search is described.

Cervical spine fusions for trauma. A long-term radiographic and clinical evaluation

Ninety-six successful cervical spine fusions performed for trauma, with a minimum of 5 years' follow-up, were retrospectively reviewed. Radiographic degenerative changes adjacent to fusion masses were assessed and correlated with clinical symptoms. The type of fusion, fusion extension, and final kyphosis of the involved segments were also analyzed. Twenty-eight patients had fusion masses aligned in 20 degrees or more of kyphosis. There was a significant increase in complaints of cervical pain in patients with neck fusions equal to or exceeding 20 degrees of kyphosis (P < 0.01). Evidence of mild degenerative changes adjacent to fusion masses was common, but did not correlate with symptoms.

Nonoperative management of upper thoracic spine fractures

We attempted to determine if nonsurgical treatment could be successful in treating instability of upper thoracic spine fractures, which may receive some stabilization and splinting from the ribs. From 1966 to 1989, the records of all patients treated at Rancho Los Amigos Medical Center for fractures from T-1 to T-8 were reviewed. Penetrating injuries and malignant lesions were excluded. A total of 118 patients were admitted during this period; 49 patients had nonsurgical treatment. Complications included 1 patient with neurologic worsening, brace-related skin necrosis in 8 cases, and deep venous thrombosis in 12 patients. No failure of arthrodesis was noted. Rib fractures did not adversely affect late stability. We conclude that orthotic treatment of thoracic spine instability from T-1 to T-8 can be successful, especially in cases where early surgery is not possible.

Comparative aspects of Cushing's syndrome in dogs and cats

Naturally occurring hyperadrenocorticism (Cushing's syndrome) is extremely common in dogs, with an incidence far greater than that in humans. The incidence of the syndrome in cats, much less frequently diagnosed than in dogs, probably is similar to that in humans. Many features of canine hyperadrenocorticism are strikingly similar to those in humans; however, several alterations in dogs are unique and not observed in other species. Clinical features and hospital testing abnormalities are reviewed in this article.

Mass determination of human immunoglobulin IgM using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Monoclonal human immunoglobulin IgM has been analyzed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Using a matrix of sinapinic acid with a laser wavelength of 355 nm, positive ions with 2 to 6 charges were observed in the mass spectra. Two major molecular species were present. The molecular weights estimated from the multiply-charged signals were found to decrease systematically with decrease in the charge state of the ion. This effect was determined to stem from the non-linear influence of the initial kinetic energy of desorption on the final kinetic energy of the multiply-charged species. A method of successive approximations, with the molecular weights and desorption velocities of the analytes as variables, was used to correct for these non-linearities. Mean molecular weights for the two IgM species were found to be 939,000 +/- 2000 and 982,000 +/- 2000 Da. An initial desorption velocity of 565 +/- 10 ms/s was determined for both.

Origin of the isoelectric heterogeneity of monoclonal immunoglobulin h1B4

The origin of the microheterogeneity of a highly purified antiinflammatory humanized monoclonal antibody prepared in mammalian cell culture has been investigated. This antibody is an IgG directed toward human CD18 (a subunit of leukocyte integrins). When the IgG preparation is subjected to isoelectric focusing, it is found to contain four major species with pI values ranging from 6 to 7. Although the relative amounts of each form differ and some species are present only in small quantities, each has been isolated by a combination of high-resolution anion-exchange chromatography and isoelectric focusing. Comparative studies reveal no detectable differences in overall secondary (far UV circular dichroism) or tertiary (intrinsic fluorescence) structure, molecular weight (laser-desorption mass spectroscopy), or antigen binding activity. When each of the isolated species is incubated under conditions which favor deamidation, it is converted to forms of lower pI which appear to correspond to naturally observed species. While the isolated light chain is relatively homogeneous, the heavy chain exhibits a pattern of isoelectric focusing bands similar to that of the intact immunoglobulin. These results suggest that in this case, charge microheterogeneity is due to the sequential deamidation of the immunoglobulin heavy chain.

Effect of an orally administered sulfonylurea, glipizide, for treatment of diabetes mellitus in cats

An orally administered sulfonylurea drug, glipizide, was evaluated for treatment of diabetes mellitus. Confirmation of diabetes was based on evidence of appropriate clinical signs, persistent hyperglycemia, and glucosuria. Glipizide (5 mg, PO, q 12 h) was administered to each cat. Sixteen cats were fed a commercial high-fiber diet and 4 cats were fed a commercial low-fiber diet. Insulin was not administered to any cat during the study. Each cat was evaluated 2, 4, 8, and 12 weeks after initiation of treatment. Three clinical responses to glipizide treatment were identified. Mean preprandial blood glucose concentration and mean blood glucose concentration during an 8-hour postprandial period decreased to < 200 mg/dl in 5 of 20 (25%) cats. In these 5 cats, glucosuria was no longer detected and clinical signs resolved by the 4-week reevaluation. Euglycemia was maintained after discontinuing glipizide treatment in 2 of these 5 cats. Glycemic control has been maintained in 2 of 5 of the responding cats for 5 and 7 months of glipizide treatment. One of 5 of the responding cats developed insulin-requiring diabetes mellitus after 6 months of glipizide treatment. Seven of 20 (35%) cats failed to respond to treatment. Mean preprandial blood glucose concentration and mean blood glucose concentration during an 8-hour postprandial period did not change from pretreatment values after 2 +/- 1 months; glucosuria persisted and clinical signs progressively worsened. Insulin treatment was required to establish glycemic control in these 7 cats. Eight of 20 (40%) cats partially responded to glipizide treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Prostaglandin induction of abortion in pregnant bitches after misalliance

Of 48 privately-owned bitches evaluated 30 to 35 days after a single, unplanned breeding, 30 (62%) dogs were determined not to be pregnant by abdominal ultrasonography and 18 dogs were confirmed to be pregnant. Each pregnant dog was hospitalized, allotted to a treatment group, and given prostaglandin F2 alpha, SC, at 1 of 3 dosages: group 1, 0.1 mg/kg of body weight, every 8 hours; group 2, 0.25 mg/kg, every 12 hours; and group 3, 0.1 mg/kg, every 8 hours for 2 days and then 0.2 mg/kg every 8 hours thereafter. Plasma from each dog was assayed for progesterone concentration before treatment and daily until abortion was completed. Physical examinations and abdominal ultrasonography were performed every 12 and 48 hours, respectively. Treatment was continued until abortion was complete as determined by results of abdominal ultrasonography. Ultrasonography was performed earlier than the scheduled 48 hours if abdominal contractions, fetuses, or bloody or dark colored vaginal discharge was observed. Dogs of 14 breeds were treated; body weight ranged from 5.4 to 37.7 kg. All dogs aborted all fetuses within 9 days of beginning treatment. Abdominal palpation was not satisfactory in confirming whether the abortion process had been completed; however, results of ultrasonography were a reliable indicator. Plasma progesterone concentrations prior to treatment were typical of the middle phase of gestation, with all concentrations > 6.0 ng/ml. The plasma progesterone concentration decreased significantly in each dog after the first 48 hours of therapy. None of the bitches aborted any fetal material until at least 24 hours after the plasma progesterone concentration was < 2.0 ng/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin resistance in three dogs with hypothyroidism and diabetes mellitus

Insulin resistance resolved in 3 dogs with hypothyroidism and diabetes mellitus after treatment with sodium levothyroxine. A thorough diagnostic evaluation failed to identify any other cause of insulin resistance in these dogs. Hypothyroidism was diagnosed in each dog on the basis of clinical signs, physical findings, hyperlipidemia, and results of thyrotropin or thyrotropin-releasing hormone stimulation test. Hypoglycemia was documented in each dog within 2 weeks of starting sodium levothyroxine administration. The insulin dosage was decreased by 60 to 62% during the ensuing months and good glycemic control was obtained at these lower insulin dosages in all dogs. These findings would suggest hypothyroidism-induced insulin resistance in these dogs.