Identification of a Distal Nerve Sheath Tumour by a Caudolateral Approach to the Caudal Compartment of the Stifle Joint

Numerous approaches to the stifle joint have been described for therapy of bone and joint diseases. The ease of these techniques, the adequacy of their exposure, and the presence of the neurovascular plexus in the caudal region of the stifle joint make a caudal approach impractical for routine use. Diseases of the caudal compartment of the stifle joint or neuro-vascular plexus may, however, necessitate surgery in this region. In the case presented, development of an approach to the caudal region was necessary for diagnosis of a distal nerve sheath tumour of a branch of the tibial nerve.

Nerve sheath tumours in the dog occur most commonly in the brachial plexus or nerve roots. They infrequently occur in distal nerves and present with chronic and often severe pain. In this case a nerve sheath tumour of the tibial nerve was identified after a 16-month history of lameness and pain. Diagnosis required development of a caudolateral approach to the caudal compartment of the stifle joint. Amputation of the left hind limb was performed after confirmation of the diagnosis.

Elevated parathyroid hormone-related protein and hypercalcemia in two dogs with schistosomiasis

Two adult dogs were evaluated for hypercalcemia. Diagnostic evaluation identified elevated parathyroid hormone-related protein (PTHrP) and presumptive humoral hypercalcemia of malignancy. At necropsy, schistosomiasis was diagnosed. North American schistosomiasis is caused by Heterobilharzia americana. Clinical findings may include dermatitis, coughing, diarrhea, and anorexia. Clinicopathological findings may include hypercalcemia, hyperglobulinemia, hypoalbuminemia, anemia, and eosinophilia. Diagnosis by fecal examination is difficult. Praziquantel or fenbendazole treatment may be curative or palliative. These are the first reported cases of hypercalcemia with elevated PTHrP in animals without diagnosed malignancy. Elevation of PTHrP has not been previously reported in hypercalcemic humans or in animals with granulomatous inflammation.

Neutropenia in dogs and cats: a retrospective study of 261 cases

Case records of 232 dogs and 29 cats with neutropenia were reviewed to examine the spectrum of underlying etiologies causing the neutropenia. Six etiological categories included nonbacterial infectious disease; increased demand due to marked inflammation, bacterial sepsis, or endotoxemia; drug-associated neutropenia; primary bone-marrow disease; immune-mediated neutropenia; and diseases of unclear etiology. The largest single category associated with the development of neutropenia was nonbacterial infectious disease (e.g., feline leukemia virus [FeLV], feline immunodeficiency virus [FIV], histoplasmosis, cryptococcosis, and parvovirus), with parvovirus infection accounting for 47.1% of all cases. The least common (0.38%) cause was naturally occurring immune-mediated neutropenia.

Telomerase enzyme activity as a diagnostic tool to distinguish effusions of malignant and benign origin

Telomerase enzyme activity is high in populations of cells that are dividing, and is low or undetectable in quiescent cell populations. Activation of telomerase in tissues that normally lack the capacity for self-renewal is strongly correlated with neoplasia. Telomerase activity can be detected in samples containing very small numbers of cells and studies of human patients suggest that measurement of telomerase activity may be useful for the evaluation of samples that can be obtained in a minimally invasive manner. This study compares the presence or absence of telomerase activity with cytologic evaluation of body cavity effusions, to determine if neoplasia is the underlying cause for the effusion in dogs and cats. Detection of telomerase in effusions was no more sensitive than cytologic evaluation for the identification of underlying neoplasia, and was less specific (telomerase assay: sensitivity = 50%, specificity = 83%; cytology: sensitivity = 50%, specificity = 100%). We conclude that although the telomerase assay may constitute a useful adjunctive test for the diagnosis of neoplasia in some dogs and cats with body cavity effusions, the results of this assay are not sufficiently reliable to be used as a sole diagnostic test.

Platelet aggregation and adenosine triphosphate secretion in dogs with untreated multicentric lymphoma

Whole-blood platelet aggregation and adenosine triphosphate secretion were measured in 15 dogs with untreated multicentric lymphoma and 10 normal control dogs to determine if dogs with lymphoma have altered platelet function. Dogs with quantitative platelet disorders (ie, thrombocytopenia or thrombocytosis) or with clinical evidence of a bleeding disorder were excluded from the study. Platelets from affected dogs had significantly greater maximum aggregation than those from control dogs, suggesting that platelets from dogs with lymphoma are hyperactive. Platelet hyperactivity may play a role in the development of hemostatic disorders (eg, disseminated intravascular coagulation) or in tumor metastasis. Further investigation is needed to determine if modification of platelet function in patients with lymphoma affects disease progression or outcome.

Transmissible venereal tumor: a retrospective study of 29 cases

Twenty-nine cases of naturally occurring, transmissible venereal tumor were studied retrospectively. The external genitalia was the primary site of tumor involvement in 27 dogs, with the remaining two dogs having primary intranasal involvement. Extragenital tumor involvement was identified in six cases, including five cases with metastatic disease. Fifteen cases were treated effectively with radiation therapy alone. Radiation therapy also was effective in four cases that were resistant to chemotherapy. Four of five cases treated with at least four doses of vincristine as a solitary agent also achieved complete remissions. Transmissible venereal tumor remains a unique canine tumor that often is curable despite the development of extragenital primary lesions or metastasis.

Nephrotic syndrome resulting in thromboembolic disease and disseminated intravascular coagulation in a dog

Thromboembolic disease and progression to disseminated intravascular coagulation (DIC) are potential life-threatening complications for dogs with nephrotic syndrome. Platelet count, prothrombin time (PT), activated partial thromboplastin time (APTT), plasma concentration of fibrinogen degradation products (FDPs), antithrombin III (ATIII), protein C, and plasminogen were used to identify hemostatic abnormalities in a dog with nephrotic syndrome. Pulmonary thromboembolic disease was diagnosed by thoracic radiography, arterial blood gas analysis, and pulmonary scintigraphy. Prompt recognition and treatment of hemostatic complications is necessary in dogs with nephrotic syndrome.

Feline cutaneous squamous cell carcinoma of the nasal planum and the pinnae: 61 cases

Cutaneous squamous cell carcinoma is a common tumor in cats and frequently occurs on the nasal planum and the pinnae. The medical records of 61 cats were reviewed for this retrospective study. Typical presentation was an older (median age, 12 years) cat with an erythematous, crusty, and erosive lesion. Methods of treatment included surgery, radiation, and cryotherapy. Disease-free interval and survival time were calculated for each case and grouped according to lesion location and treatment type. All treatments were found to be effective, with surgery resulting in the longest disease-free interval (median, 594 days).

Active form of Pseudomonas mevalonii 3-hydroxy-3-methylglutaryl coenzyme A reductase

Based on multiple gel permeation chromatographic experiments, we report a Stokes radius of 59.7 A for Pseudomonas mevalonii 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase; EC 1.1.1.88) and its His381Asn, His381Gln, and His381Lys mutant enzymes. Comparison of this Stokes radius with the radius calculated from the crystal structure indicated that the active form of P. mevalonii HMG-CoA reductase was a hexamer and not a dimer as previously thought. The Stokes radius, an S26,w of 11.0, and an estimated V of 0.723 were used in the Svedberg equation to calculate an anhydrous molecular mass of 270,084 Da for P. mevalonii HMG-CoA reductase (monomer mass 45,538 Da), consistent with the enzyme being a hexamer in solution. The Stokes radii of all standard proteins examined correlated with the inverse error function complement of their partition coefficient, Kd. Kd did not correlate with logarithm of the standard protein's molecular weight. Eight nonstandard proteins had Stokes radii that matched their crystallographic radii of longest axis. This indicated that the frozen conformation of a protein in its crystal form can dictate restraints on its shape in solution.

Factors affecting treatment decisions and satisfaction of owners of cats with cancer

Cancer in cats is being diagnosed with increasing frequency. Euthanasia or an active intervention such as chemotherapy, radiation therapy, or surgery are treatment choices for the owner at diagnosis of the cat's disease. In this study, 2 interviews with cat owners, one soon after diagnosis of cancer in the cat and one 6 months later, were used to identify owner characteristics associated with a decision of euthanasia or intervention, to identify factors associated with an owner's satisfaction with euthanasia or intervention, and to evaluate inappropriate expectations of the owners who selected an intervention. The study included 89 owners from 3 referral hospitals. In logistic regression analysis, significant factors were not found that affected the owner's decision to euthanatize the cat versus intervene. Satisfaction with the decision to euthanatize the cat was associated with the ability of the cat to groom itself, eat, and play at the first interview. Among owners who selected an intervention, 4 combinations of factors were associated with being satisfied. The first combination was clinic of origin (CLIN), having a live cat at the 6-month follow-up interview (LIVE), and understanding the number of return visits required for the intervention. The second was CLIN, LIVE, and type and frequency of adverse effects from the intervention at the 6-month interview. The third was CLIN, LIVE, and feeling guilty at the 6-month interview. The fourth was CLIN, LIVE, and whether the cat had a good or excellent quality of life at the first interview. Thirty percent (21/69) of the owners tended to overestimate their cats' life expectancy. Owners also felt they had reasonably accurate estimations of adverse effects of treatment and number of return visits, but underestimated the costs required for an intervention. For owners who elect an intervention, a reminder from the veterinarian that emotional upheavals may develop even after the decision has been made is important. To provide optimal patient care and client education, veterinarians must find a middle ground between being knowledgeable, practical, and informed, and being compassionate and approachable.

Squamous cell carcinoma of the canine nasal cavity and frontal sinus: eight cases

Squamous cell carcinoma of the canine nasal cavity and frontal sinus was diagnosed in eight cases between May 1988 and April 1994. The most common presenting complaints were nasal discharge, including epistaxis; sneezing; and facial deformity or exophthalmos. Metastasis was not identified in any case, but bone lysis and invasion into tissues outside the nasal cavity were noted in five cases. Computed tomograms were performed in five cases and were more useful than radiographs in determining the extent of neoplastic involvement. Euthanasia was performed within one week of diagnosis in three cases at the owner's request; one case died at home within one month; and the remaining four cases were euthanized within eight months due to progressive clinical signs. The mean survival time in these eight cases was three months, with a range of zero weeks to eight months.

Tracheal defect and embryonal rhabdomyosarcoma in a young dog

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Mast cell tumors: dilemmas of diagnosis and treatment

Making the most appropriate choices for diagnosis and treatment of canine and feline mast cell tumors remains challenging. An understanding of the heterogeneity of the disease process, the associated paraneoplastic disorders, and the known prognostic indicators can be helpful in making rational decisions regarding each individual case. A multimodality approach may be needed for optimal care of some patients, but the effectiveness of current medical treatment strategies continues to limit our ability to cure disseminated forms of disease.

Splenic vein thrombosis resulting in acute anemia: an unusual manifestation of nephrotic syndrome in a Chinese shar pei with reactive amyloidosis

Nephrotic syndrome in a seven-year-old Chinese shar pei resulted in oliguric renal failure, coagulopathy, and acute anemia. Renal amyloidosis and widespread thromboses were diagnosed postmortem. Splenic vein thrombosis caused significant splenic congestion, coagulative necrosis, and acute anemia. Splenic vein thrombosis is reported here as an unusual consequence of nephrotic syndrome in the dog.

Squamous cell carcinoma of the canine nasal planum: eight cases (1988-1994)

Squamous cell carcinoma of the nasal planum was diagnosed in eight dogs between March 1988 and January 1994. Epistaxis, sneezing, and ulceration or swelling of the nasal planum were the most common presenting complaints. Although no evidence of metastasis was identified, the primary tumor in all cases was locally invasive with extensive involvement of underlying tissues. Advanced imaging procedures performed in three cases indicated that physical examination may underestimate the local extent of the neoplasm. Euthanasia was performed in six cases due to progressive neoplastic disease with worsening epistaxis and sneezing; the mean survival time in these cases was 5.4 months.

Chylothorax associated with right-sided heart failure in five cats

Chylothorax associated with right-sided congestive heart failure was diagnosed in 5 cats. One cat had restrictive pericardial disease, with mild pericardial effusion, and a heart-base chemodectoma. Two other cats had congestive cardiac disease (tetralogy of Fallot and tricuspid regurgitation in 1 cat, and endocardial cushion defect and tricuspid dysplasia in the other), and 2 cats had idiopathic cardiomyopathy. All cats had jugular venous distention, and echocardiographic evaluation helped define the nature of the cardiac disease in these cats. Subtotal pericardiectomy resulted in resolution of the chylothorax in the cat with the heart-base tumor, whereas medical management of the right-sided heart failure temporarily decreased pleural effusion in the cat with tetralogy of Fallot and in the 2 cats with cardiomyopathy.

Lack of hormonal stimulation of pyridoxine metabolism in isolated rat hepatocytes

Isolated hepatocytes obtained from Sprague-Dawley rats (145-175 g) were incubated for 15 min at 30 degrees C in Krebs-Henseleit bicarbonate buffer, pH 7.4, containing 0.5 mM concentration of each of the 20 natural amino acids and either 4.5 or 23 microM [U-14C]pyridoxine. Pyridoxine, pyridoxal, pyridoxal phosphate, and pyridoxic acid separated by an anion-exchange chromatographic technique were quantified using a phosphate analyzer and a liquid scintillation counter. The conversion of [U-14C]pyridoxine to its metabolites was more than doubled by increasing the amount of pyridoxine (4.5 to 23 microM) in the incubation medium. Insulin (10 mU/ml), glucagon (1 nM), or epinephrine (10 microM) did not have any significant effect on the conversion of [14C]-pyridoxine to pyridoxal, pyridoxal phosphate, or pyridoxic acid. Our earlier observations of a large decrease in serum pyridoxal phosphate in the diabetic rat cannot be explained by any direct hormonal effects on pyridoxine metabolism.

Cholangiohepatitis in a dog

Cholangiohepatitis was diagnosed in a dog with a 4-day history of anorexia, vomiting, fever, and icterus. Additional findings included signs of depression, dehydration, hepatosplenomegaly, and abdominal discomfort. Exploratory laparotomy was performed, and specimens of liver, spleen, and bile were obtained. Histologic evaluation of liver and spleen revealed acute, suppurative cholangio-hepatitis and splenitis, respectively. Cultures of liver and bile yielded Klebsiella sp. The dog responded to rehydration and intravenous administration of chloramphenicol. Although uncommon, cholangiohepatitis should be suspected in dogs with anorexia, fever, vomiting, icterus, and signs of abdominal discomfort. Definitive diagnosis requires bacterial cultures of liver and bile. Administration of an appropriate antibiotic should resolve clinical signs.

Rectal hemorrhage associated with vascular ectasia in a young dog

Rectal bleeding in a 7-month-old 13-kg sexually intact female mixed-breed dog was determined to be associated with vascular ectasia of the small intestine, descending colon, rectum, and anus. Microscopically, the telangiectasia was associated with lymphangiectasia and focal ulceration. Surgical intervention resulted in incomplete resection of the lesion and only temporary amelioration of clinical signs. The dog's age was compatible with a congenital origin for the defect, but an acquired cause could not be excluded.

Effects of lithium carbonate administration to healthy cats

Lithium carbonate administration to healthy cats was evaluated in 2 controlled studies (a dose-response study and a bone marrow evaluation study) to determine the effectiveness of lithium as a bone marrow stimulant. Lithium carbonate was administrated at dosage ranging from 300 to 1,050 mg/m2 of body surface/d. Complete blood count, serum lithium concentration determination, serum biochemical analysis, urinalysis, and bone marrow aspiration and biopsy were periodically performed. Serum lithium concentration greater than 2 mEq/L was associated with significant decrease in numbers of circulating segmented neutrophils (less than 1,200 cells/microliter; P less than 0.01) and lymphocytes (less than 1,300 cells/microliter; P less than 0.0001), as well as significant (P less than 0.05) decrease in urine specific gravity. Bone marrow evaluation revealed apparent maturation arrest of the neutrophil cell line. Coincident with the changes in laboratory values, the lithium-treated cats became ill. Changes in behavior and vocalization were seen, followed by anorexia, vomiting, and diarrhea. In later stages of intoxication, cats became hyperexcitable and manifested coarse muscular tremors. It was concluded that lithium carbonate does not have potential value as a bone marrow stimulant and is toxic to cats at serum concentration greater than 2 mEq/L.

Effects of single-dose L-asparaginase on coagulation values in healthy dogs and dogs with lymphoma

Ten healthy dogs and 10 dogs with multicentric lymphoma were given a single dose of L-asparaginase at a rate of 10,000 IU/m2 of body surface. Assessment of concentrations of contributors to the coagulation process and of the ability to coagulate including antithrombin III, one-stage prothrombin time, prothrombin-proconvertin time, activated partial thromboplastin time, plasminogen, fibrinogen, and platelet number were performed prior to drug administration (day 0). These tests were repeated 24 hours (day 1), 48 hours (day 2), and 7 days after treatment with L-asparaginase. Antithrombin-III concentrations were significantly lower in the dogs with lymphoma than in healthy dogs on days 0, 1, 2, and 7; however, with the exception of day 1, mean values remained within normal limits. There was also a difference between the 2 groups in prothrombin/proconvertin values on day 7 and in platelet number on day 2, with the lymphoma group having significantly shorter prothrombin/proconvertin time than healthy dogs, and the difference in platelet numbers being associated with increased counts in the healthy dogs. Data obtained from the healthy dogs and dogs with lymphoma for each coagulation test were pooled for each treatment day (0, 1, 2, and 7), and day-0 values for each coagulation test were compared with data obtained on days 1, 2, and 7. Antithrombin-III concentration on day 7 was significantly lower than on day 0, prothrombin/proconvertin time on day 1 was significantly longer than on day 0, and fibrinogen concentrations on days 1 and 2 were significantly lower than on day 0.(ABSTRACT TRUNCATED AT 250 WORDS)

Extracellular phosphate requirement for insulin action on isolated rat hepatocytes

Isolated rat hepatocytes were prepared in KHB buffer, pH 7.4; were centrifuged and washed twice in KHB buffer containing various amounts of phosphate and calcium; and were incubated at 30 degrees in the presence of tracer [2,3-14C]succinate and a 0.5 mM concentration of each of the 20 natural amino acids. Hepatocytes washed and incubated in KHB buffer containing less than 0.1 mM phosphate failed to show any insulin stimulation of [2,3-14C]succinate oxidation or protein incorporation of tracer carbons. The absence or presence of extracellular phosphate did not alter the specific activity of 32P-adenine nucleotides; they remained the same in the presence or absence of insulin. The maximal insulin stimulatory effect on succinate oxidation and tracer incorporation into protein was observed in the presence of 1.18 mM phosphate and 1.9 mM calcium ion. The lack of external phosphate did not prevent the stimulation of succinate oxidation by either glucagon on epinephrine, whereas removal of calcium from the medium abolished their hormonal effects. The lack of medium calcium also prevented the insulin stimulation of succinate oxidation and protein synthesis. Our data indicate that a diminished insulin responsiveness in hypophosphatemic patients may be due to the insensitivity of mitochondria to insulin in the hypophosphatemic state.

Comparison of four methods of estimating glomerular filtration rate in cats

Four methods of evaluating renal function were performed in 6 cats anesthetized with halothane in oxygen. Glomerular filtration rate (GFR) was measured simultaneously in each cat by exogenous creatinine clearance (ECC), bolus inulin clearance, and 99mTc(Sn)-diethylene-triaminepentaacetic acid (DTPA) clearance determined by 2 different methods. In the first DTPA clearance method (DTPA-1), we measured radioactivity in serial blood specimens to construct plasma disappearance curves for calculation of GFR. In the second DTPA clearance method (DTPA-2), we used serial external head counts of radioactivity and a single blood specimen to construct plasma disappearance curves for calculation of GFR. Bolus inulin clearance was calculated from plasma disappearance curves using a 1-compartment open pharmacokinetic model (IN-1) and a 2-compartment open pharmacokinetic model (IN-2). Glomerular filtration rates were measured over 3 hours, for creatinine and DTPA methods, and over 4 hours for the inulin methods. The GFR obtained with the reference method (ECC) was 2.56 +/- 0.61 ml/min/kg of body weight (mean +/- SD). Values for GFR determined by ECC and DTPA-1 were significantly correlated (r = 0.852; P less than or equal to 0.05). Correlation between ECC and DTPA 2 was not as good (r = 0.783; P less than or equal to 0.10), but the 2 DTPA methods significantly correlated with one another (r = 0.897; P less than or equal to 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosis and treatment of chylothorax associated with lymphoblastic lymphosarcoma in four cats

Chylothorax was diagnosed in 4 cats with lymphoblastic lymphosarcoma. Clinical findings included dyspnea, muffled heart sounds, and noncompressibility of the cranial portion of the thorax. All cats had high pleural fluid triglyceride concentration. Lymphosarcoma was diagnosed by cytologic evaluation of pleural fluid in 3 cats and by histologic evaluation of a cranial cervical lymph node in 1 cat. Two cats were euthanatized prior to any treatment, and the other 2 cats were managed by thoracic drainage, chemotherapy, and/or irradiation.

Lack of insulin stimulation on Percoll-prepared or high-speed-centrifuged rat liver hepatocytes

Rat liver hepatocytes isolated from a 30-31% percoll density gradient at 10,000g are refractory toward insulin stimulation of 14CO2 formation and 14C-incorporation into protein from [2,3-14C]succinate. Basal hepatocyte oxidation of succinate was not impaired by the presence of 5% percoll in the incubation medium nor was it impaired when percoll-free hepatocytes were used that had been isolated after centrifugation at 9000g; however, in both instances the stimulatory effect of insulin was lost. Hepatocyte damage may have occurred in these processes. This is in contrast to previous work which shows that insulin (10 mU/ml) will stimulate [2,3-14C]succinate oxidation and [2,3-14C]succinate carbon incorporation into protein in non-percoll-treated hepatocytes (isolated by centrifugation at 10g) by about 29%. We conclude that the latter procedure although more time consuming is the more gentle method of choice and leaves the hepatocyte in a form more closely related to an in vivo state than does treatment with a percoll density gradient at 10,000g.

Lymphosarcoma with disseminated skeletal involvement in a pup

Lymphoblastic lymphosarcoma with disseminated skeletal involvement was diagnosed in a 15-week-old Golden Retriever. The skeletal disease was characterized by diffuse, irregular areas of radiolucency most evident in the diaphyseal portion of long bones and was associated with gait abnormalities and signs of pain. Necropsy also revealed involvement of the spleen, liver, kidneys, and mesenteric lymph nodes.

Hydrazine stress in the diabetic: ornithine decarboxylase activity

Streptozotocin-induced diabetes of 7 weeks duration increased male Sprague-Dawley rat kidney ornithine decarboxylase activity by 4.8-fold but did not affect the liver enzyme. Hydrazine treatment of 4 hr duration stimulated equally kidney ornithine decarboxylase activities of nondiabetic and diabetic rats. Hydrazine treatment increased liver ornithine decarboxylase activity in the nondiabetic rat but did not increase it in the diabetic rat. Since hydrazine stimulates ornithine decarboxylase activity prior to polyamine and protein syntheses, we speculate that the lack of hydrazine stimulation of ornithine decarboxylase in the diabetic liver may be related in part to the unrestrained gluconeogenesis and depressed Kreb's cycle activity: the latter being required for protein synthesis.

Tumors of the ear canal

This discussion will focus on the clinical presentation, diagnostic evaluation, expected biologic behavior, and therapeutic options for tumours of the ear canal in the dog and cat. Particular emphasis will be placed on neoplasia of the ceruminous glands, squamous cell carcinoma, and non-neoplastic mass lesions.

Effects of single-dose and three-day trimethoprim-sulfadiazine and amikacin treatment of induced Escherichia coli urinary tract infections in dogs

Efficacy of single-dose and 3-day trimethoprim-sulfadiazine (TMS) and amikacin treatment regimens for induced Escherichia coli urinary tract infections (UTI) in dogs was evaluated. Using each regimen, effects of giving TMS combination or amikacin were compared in males and females, and the response of treated dogs was compared with that of nontreated controls. Response to treatment was evaluated, using results of quantitative urine cultures and urinalyses obtained on 4 occasions. Abacteriuria was identified by finding a lack of bacterial organisms in specimens collected for the initial and final posttherapy evaluations. Before treatments, magnitudes of bacteriuria were similar in all experimental groups, and UTI persisted in all nontreated dogs. Single-dose treatment regimens did not reliably eradicate UTI in males or females, whether amikacin or TMS was administered. Magnitude of bacteriuria often diminished immediately after single-dose treatment, and such reductions of bacteriuria persisted in 2 of 8 dogs. However, no male dogs and only 1 of 4 females became abacteriuric after a single-dose treatment regimen. The single female in which UTI was eradicated was treated with a single dose of amikacin. The 3-day TMS treatment regimen eradicated UTI in each of 4 females, but the 3-day amikacin treatment regimen resulted in abacteriuria in only 1 of 4 females. Three-day treatment regimens were not effective in male dogs, regardless of the antimicrobial drug used. Of the short-course treatments for canine UTI evaluated by this model, only 3-day TMS treatment of females was consistently effective.

Lack of influence of vitamin D deficiency on insulin release from the isolated pancreatic islets of rats

Pancreatic islets were isolated from young (100 g) and adult (390 g), normal and vitamin D deficient male Sprague-Dawley rats. The release of insulin from leucine-stimulated or glucose-stimulated islet was not altered by vitamin D deficiency. The in vitro addition of either 25-hydroxy- or 1,25-dihydroxyvitamin-D had no effect on insulin release from either normal or vitamin D deficient islets. We conclude that the earlier report (Normal et al., Science 209 (1980) 823-825) on vitamin D deficiency depressing insulin secretion from the perfused pancreas must be related to the vitamin's effect on insulin synthesis and not the islet's release of insulin.

Insulinoma in a ferret

Insulinoma was diagnosed in a 7-year-old female ferret examined because of generalized seizures, intermittent paraplegia, and abnormal behavior. Low serum glucose, high serum insulin, and infinite amended insulin/glucose ratio values in this ferret supported the clinical diagnosis of insulinoma. Histologic examination of the pancreas confirmed the diagnosis of insulinoma. The clinical signs and laboratory evaluations in this case and in a previously reported case of insulinoma in a ferret were consistent with variations reported in dogs with insulinoma.

Experimental diabetes causes mitochondrial loss and cytoplasmic enrichment of pyridoxal phosphate and aspartate aminotransferase activity

The streptozotocin diabetic rat was selected as a model to study how insulin deficiency alters vitamin B6 utilization by focusing on pyridoxal phosphate levels and aspartate aminotransferase activities in liver tissues. Diabetes of 15 weeks' duration lowered plasma pyridoxal phosphate levels by 84%. Normal plasma pyridoxal phosphate was 480 pmole/ml. Fractionation of liver into mitochondrial and extramitochondrial compartments demonstrated that diabetes caused a 43% diminution in mitochondrial pyridoxal phosphate per gram of liver. There was no cytoplasmic change in these diabetic rats. Mitochondrial aspartate aminotransferase activity was decreased 53% per gram of diabetic liver and cytoplasmic aspartate aminotransferase activity was elevated 3.4-fold. Damage to diabetic mitochondria during preparation procedures could not account for the rise in cytoplasmic aspartate aminotransferase activity. Electrophoresis showed that in the diabetic cytoplasm both cathodal and anodal forms of the enzyme were elevated. Speculations concerning mitochondrial loss and cytoplasmic gain of enzyme activity as well as those on the reduction of plasma pyridoxal phosphate in the diabetic rat are presented.

Metabolic and mitochondrial disturbances in streptozotocin-treated Sprague-Dawley and Sherman rats

This study provides explanation for conflicting evidence in the literature relating to changes in mitochondrial function and metabolic parameters during chemically induced diabetes. Diabetes of 3 days' duration (early ketosis) did not alter heart, kidney, or liver mitochondrial respiratory rates with glutamate or succinate even though serum glucose and triglycerides were elevated. Diabetes of 5 weeks' duration did not alter kidney or liver mitochondrial function in the fed adult rat although weight gain was depressed. The amount of kidney mitochondrial protein isolated per gram of tissue was increased by 30% in the diabetic. This increase was reversed by insulin treatment as were the other biochemical modalities measured. Superimposition of a 24-hr fast resulted in enhanced gluconeogenesis as measured by an animal weight loss of 17% within 24 hr (liver weight loss, 21%) and an elevation of serum urea nitrogen by 180% compared to fasted control. Respiratory rates of diabetic kidney mitochondria with glutamate were unaffected in the fasted animal whereas diabetic liver mitochondrial respiratory rates during succinate oxidation were reduced by 43%. Respiratory control was unchanged in the fasted diabetic rat. All the observed changes were reversed by insulin. Variation in the serum and liver metabolic indices (urea nitrogen, creatinine, glycerol, free fatty acids, free amino acids, triglycerides, and glucose) and liver mitochondrial responses to 7 weeks of chemically induced diabetes was affected by the rat strain, Sprague-Dawley versus Sherman, and rat weight, 72 g versus 222 g. Liver mitochondrial respirations in fed Sherman rats were not depressed by diabetes. Both rat strains had elevated liver free fatty acids and glutamate dehydrogenase activity in the diabetic state. Serum leucine, isoleucine, and valine were more elevated and serum lysine and arginine were more depressed in the diabetic Sprague-Dawley rat than in the Sherman rat. Conjectures on these results are presented in the text.

Localization of L-lactate dehydrogenase in mitochondria

Relatively small but persistent amounts of L-lactate dehydrogenase (LDH) activity were found in mitochondrial preparations isolated from liver of the rat. Using a variety of cytosolic markers, it was found that essentially no cytosolic contamination was present. Respiratory velocities and respiratory control with L-lactate were somewhat lower than with glutamate, but equal or superior to those with pyruvate. Agarose gel electrophoresis showed LDH isoenzymes in mitochondria similar to that in corresponding cytosol. Subtilisin BPN', a bacterial protease, was incubated with intact mitochondria and enzyme activities were measured. Following mitochondrial disruption, the proteolytic treatment was repeated. Digitonin was also used in the fractionation of mitochondria. These techniques helped to determine the location of the LDH in the mitochondria as being mainly in the outer membrane and periplasmic space.

Influence of genetic predisposition to diabetes and obesity on mitochondrial function

Inbred mice with the mutation diabetes C57BL/KsJ db+/db+ and the mutation obese C57BL/6J ob/ob displayed a total liver mitochondrial capacity to oxidize glutamate or succinate which was approximately eight times greater than the capacity of the C57BL/6J +/+ control mice. This increase in oxidation capacity was estimated by multiplying the observed twofold increase in each of the following components: total liver weight, the mitochondrial protein content per gram of liver, and glutamate or succinate respiration activity per milligram of liver mitochondrial protein. No significant difference in liver mitochondrial function and capacity for oxidation was observed between db+/db+ and ob/ob mutants, which indicated that these results may be primarily mediated by the genetic factors responsible for obesity and hyperphagia in these mutants, and not by the genetic traits associated with diabetes. These findings may provide a biochemical foundation in support of the thrifty gene hypothesis.

3-Hydroxykynurenine, 3-hydroxyanthranilic acid, and o-aminophenol inhibit leucine-stimulated insulin release from rat pancreatic islets

Individual islets were isolated from rat pancreas to study the effects of tryptophan and its metabolites on leucine-stimulated release of insulin. 3-Hydroxykynurenine, 3-hydroxyanthranilic acid, and o-aminophenol were inhibitors at concentrations below 10 mM whereas tryptophan, kynurenine, kynurenic acid, xanthurenic acid, and anthranilic acid were ineffective inhibitors at concentrations up to 10 mM. A structure-activity analysis of these metabolites demonstrated that vicinal aromatic hydroxy and amino groups with their concomitant electron donating properties are required for inhibition of insulin release. Inhibition of islet insulin release by the three kynurenine metabolites may be involved in the depressed insulin levels found in vitamin B6-deficient rats by other workers.

Differential inhibition of mitochondrial respiratory control by N-1-substituted, 3-,4-substituted pyridinium halides

Several N-1-alkyl-, 3-, and 4-carbamidopyridinium halides were synthesized and determined to be inhibitors of mitochondrial oxidative phosphorylation. L-Glutamate respiration was most depressed by N-1-dodecylpyridinium bromide whereas succinate respiration was most depressed by N-1-dodecylisonicotinamide bromide. Combination of inhibitors with mitochondrial sites may involve lipophilic interactions as modified by steric restrictions.

Influence of dietary cholesterol on mitochondrial function in the rat

Rat-liver mitochondrial cholesterol ester levels were increased nine-fold and free cholesterol levels were doubled by feeding 10% lard and 2% cholesterol with Purina rabbit chow pellets to weanling male Sprague-Dawley rats for 5 weeks. This resulted in depression of State 3 (ADP-stimulated) glutamate respiration and reduced sensitivity to inhibition of phosphyorylation by tetrabutylammonium bromide and oligomycin. Brain, heart, lung, spleen, kidney and testis mitochondrial functions were not responsive to changes in dietary cholesterol nor were increases noted in free cholesterol content; mitochondrial cholesterol esters in these six tissues remained at extremely low levels regardless of treatment. Inclusion of 0.01% oleyl-p-decylbenzene sulfonate (a hypocholesterolemic agent) in the 10% lard and 2% cholesterol diet prevented elevation of rat-liver cholesterol esters and restored "normal" mitochondrial functions of respiratory control. This compound had no lowering effect on the raised level of liver mitochondrial free cholesterol nor on the reduced mitochondrial sensitivity to the phosphorylation inhibitors. We concluded that cholesterol esters were associated with depression of liver mitochondrial respiratory control and that free cholesterol was related to desensitization of mitochondria to the phosphorylation inhibitors.

Depression by ethionine of phosphorylating oxidation in hepatic mitochondria

Induction of hepatic steatosis and suppression of hepatic ATP levels, protein synthesis and gluconeogenesis subsequent to administration of ethionine may be consequences of interference by this compound with mitochondrial phosphorylation of ADP. The mitochondrial dysfunction is not a direct action of ethionine on the organelle.

Lipophilic and respiratory properties of NADH and succinate dehydrogenase sites in mitochondria from various tissues of the rat

Mitochondria were isolated from heart, liver, kidney, spleen, and brain of the rat. With overall regard to both resting and activated respiratory velocities with either glutamate or succinate, as well as the respective degrees of respiratory control, kidney mitochondria were most efficient and spleen mitochondria least so. A probe of mitochondrial inner membrane lipophilicity with tetrabutylammonium bromide showed that NADH dehydrogenases from liver and heart were similar, as were also those from kidney and spleen. With the exception of brain, only small differences were observed in lipophilic properties of succinate dehydrogenases from the various other tissues. Variation in lipophilic characteristics of the two sites on the mitochondrial inner membranes could not be correlated with embryological origin of the tissue.

Mitochondrial functional changes during hepatic hyperplasia and azo dye carcinogenesis

Resting and active-state respiratory velocities, respiratory control, high amplitude volume changes, and latent ATPase activities were examined in hepatic mitochondria from rats fed 3'-methyl-4-dimethylaminoazobenzene (3'MeDAB) for production of liver tumors and from rats in three phases of liver regeneration subsequent to subtotal hepatectomies. Tetrabutylammonium bromide, a lipophilic probe capable of selectively inhibiting phosphorylating oxidation or uncoupling oxidation from phosphorylation, was used to detect subtle alterations in lipophilicity characteristics of the organelles and it was concluded that mitochondria from pre-hyperplastic, hyperplastic, and neoplastic tissues had a higher than normal degree of membrane lipophilicity at specific functional sites. Control of respiration by ADP was markedly augmented in all experimental groups; this behavior, plus depressed sensitivity to swelling agents and energized contraction, were similar in mitochondria from hepatomas and from 3-day regenerating livers. These mitochondrial functions were even more pronounced, however, in cells in pre-hyperplastic states (6 and 16 h subsequent to partial hepatectomy). Many forms of liver damage result in mitochondrial alterations which elevate the capacity for oxidative phosphorylation. Such changes associated with induction of azo dye oncogenesis are mimicked by the degree of hyperplasia in the tissue following the first mitotic wave of regeneration; implications relevant to hepatocarcinogenesis are discussed.

Synthesis of 5-substituted isophthalic acids and competitive inhibition studies with bovine liver glutamate dehydrogenase

Isophthalic acid, 5-carboxy-, 5-hydroxy-, 5-methoxy-, 5-fluoro-, 5-bromo-, 5-cyano-, and 5-methylisophthalic acid were inhibitors competitive with L-glutamate for bovine liver glutamate dehydrogenase. The extent of inhibition by the derived compounds was not much greater than that obtained with the parent compound, isophthalic acid. A plot of pKi versus pH showed the presence of an ionizable group (pKa 7.4-7.8) at the enzyme active site which interacted with the substitutent at the 5 position of the substituted isophthalates.

Respiratory control depression by tetraalkylammonium bromides in rat liver mitochondria

Six different lipophilic (hydrophobic) organic cations, tetraethyl-, tetrapropyl, tetrabutyl-, tetrapentyl-, tetrahexyl-, and tetraheptylammonium bromide, depressed respiratory control in rat liver mitochondria. Evaluation of mitochondrial responses in terms of a quadratic equation in log P (an index of lipophilicity) indicated that the NADH dehydrogenase receptor site for inhibitor (diminution of control of glutamate, alpha-ketoglutarate, and beta-hydroxybutyrate respiration) was more lipophilic than receptor sites for flavin-linked substrates (reduction of control of succinate, choline and alpha-glycerophosphate respiration). The succinate dehydrogenase receptor site for inhibition by the tetraalkylammonium bromides was more hydrophillic (less lipophilic) than the choline or alpha-glycerophosphate dehydrogenase receptor sites. Depression of respiratory control may be a function of charge density and of lipophilicity at specific inner membranal sites and the susceptible site may differ for different respiratory substrates.