Alternating Rabacfosadine/Doxorubicin: Efficacy and Tolerability in Naïve Canine Multicentric Lymphoma

Background

Standard of care treatment for multicentric lymphoma in dogs remains doxorubicin (DOX)‐based combination chemotherapy, but owners may hesitate to commit the time and financial resources to complete such a protocol, typically requiring 12–16 visits. Rabacfosadine (RAB), a double prodrug of the nucleotide analog 9‐(2‐phosphonylmethoxyethyl) guanine, has substantial single‐agent activity in dogs with lymphoma, and a different mechanism of action than DOX.

Hypothesis/Objectives

Our objective was to evaluate the efficacy and adverse effect (AE) profile of alternating doses of RAB and DOX in dogs with naïve multicentric lymphoma.

Animals

Fifty‐four dogs with previously untreated lymphoma.

Methods

Open‐label, multicenter prospective clinical trial. Dogs received alternating RAB (1.0 mg/kg IV weeks 0, 6, 12) and DOX (30 mg/m² IV weeks 3, 9, 15). Dogs that achieved complete response (CR) were followed by monthly evaluations. Complete clinicopathological evaluation and assessment of remission and AEs were performed every 21 days.

Results

The overall response rate was 84% (68%; CR; 16%; partial response [PR)]. The overall median progression‐free interval (PFI) was 194 days (216 for CR and 63 for PR). Most AEs were mild and self‐limiting: gastrointestinal and hematologic AEs were most common. Thirteen dogs experienced dermatologic AEs, and 2 dogs developed grade 5 pulmonary fibrosis.

Conclusions and Clinical Importance

Alternating RAB/DOX generally was well tolerated and resulted in PFIs comparable to standard DOX‐based multi‐agent protocols, with fewer treatment visits. Most adverse events were mild or moderate and self‐limiting. Further studies are warranted to explore long‐term outcome and other RAB chemotherapy combinations.

Downregulation of CXCR4 Expression and Functionality After Zoledronate Exposure in Canine Osteosarcoma

Background

The establishment and progression of metastases remains the life‐limiting factor for dogs diagnosed with osteosarcoma (OS). The pattern of metastases is likely regulated through interactions between chemokine receptors and chemokines, and perturbations in these signaling cascades responsible for cytoskeletal organization and directional migration have the potential to alter metastatic cell trafficking behaviors.

Hypothesis

Zoledronate will impair directional migration of OS cells through downregulation of chemokine (C‐X‐C motif) receptor 4 (CXCR4) expression and functionality.

Samples

Nineteen archived tumor specimens and plasma from 20 dogs with OS.

Methods

Prospectively, the expressions of CXCR4 were studied in OS cell lines and spontaneous tumor samples. The effect of zoledronate on CXCR4 expression and functionality was investigated by characterizing responses in 3 OS cell lines. In 19 OS specimens and 20 dogs with OS, changes in CXCR4 expression and circulating CXCR4 concentrations were characterized in response to zoledronate therapy respectively.

Results

All canine OS cells express CXCR4, and zoledronate reduces CXCR4 expression and functionality by 27.7% (P < .0001), through augmented proteasome degradation and reduced prenylation of heterotrimeric G‐proteins in 33% of tumor cell lines evaluated. In OS‐bearing dogs, zoledronate reduces CXCR4 expressions by 40% within the primary tumor compared to untreated controls (P = .03) and also decreases the circulating concentrations of CXCR4 in 18 of 20 dogs with OS.

Conclusions and clinical importance

Zoledronate can alter CXCR4 expression and functionality in OS cells, and consequent perturbations in CXCR4 intracellular signaling cascades might influence patterns of metastases.

The Association of Endothelin-1 Signaling with Bone Alkaline Phosphatase Expression and Protumorigenic Activities in Canine Osteosarcoma

Background

Canine osteosarcoma (OS) is an aggressive sarcoma characterized by pathologic skeletal resorption and pulmonary metastases. A number of negative prognostic factors, including bone alkaline phosphatase, have been identified in dogs with OS, but the underlying biologic factors responsible for such observations have not been thoroughly investigated. Endothelin‐1‐mediated signaling is active during bone repair, and is responsible for osteoblast migration, survival, proliferation, and bone alkaline phosphatase expression.

Hypothesis

The endothelin‐1 signaling axis is active in canine OS cells, and this pathway is utilized by malignant osteoblasts for promoting cellular migration, survival, proliferation, and bone alkaline phosphatase activities.

Animals

45 dogs with appendicular OS.

Methods

The expressions of endothelin‐1 and endothelin A receptor were studied in OS cell lines and in samples from spontaneously occurring tumors. Activities mediated by endothelin‐1 signaling were investigated by characterizing responses in 3 OS cell lines. In 45 dogs with OS, bone alkaline phosphatase concentrations were correlated with primary tumor osteoproductivity.

Results

Canine OS cells express endothelin‐1 and endothelin A receptor, and this signaling axis mediates OS migration, survival, proliferation, and bone alkaline phosphatase activities. In OS‐bearing dogs, circulating bone alkaline phosphatase activities were positively correlated with primary tumor relative bone mineral densities.

Conclusions and Clinical Importance

Canine OS cells express endothelin‐1 and functional endothelin A receptors, with the potential for a protumorigenic signaling loop. Increases in bone alkaline phosphatase activity are associated with osteoblastic OS lesions, and might be an epiphenomenon of active endothelin‐1 signaling or excessive osteoproduction within the localized bone microenvironment.

The immunotherapy of canine osteosarcoma: a historical and systematic review

Osteosarcoma is a malignant mesenchymal neoplasm that accounts for the majority of primary bone tumors in dogs and shares biological and clinical similarities with osteosarcoma in humans. Despite dose intensification with conventional cytotoxic therapies, survival times for dogs and humans diagnosed with high‐grade osteosarcoma have not changed in the past 20 years, with the principal cause of mortality being the development of pulmonary metastases. Given the therapeutic plateau reached for delaying metastatic progression with cytotoxic agents, exploration of alterative adjuvant therapies for improving management of osteosarcoma micrometastases is clinically justified. Evidence suggests that osteosarcoma is an immunogenic tumor, and development of immunotherapies for the treatment of microscopic lung metastases might improve long‐term outcomes. In this review, the history and foundational knowledge of immune interactions to canine osteosarcoma are highlighted. In parallel, immunotherapeutic strategies that have been explored for the treatment of canine osteosarcoma are summarized. With a greater understanding and awareness for how the immune system might be redirected toward combating osteosarcoma metastases, the rational development of diverse immune strategies for managing osteosarcoma holds substantial promise for transforming the therapeutic landscape and improving disease management in both dogs and human beings.

Expression of nociceptive ligands in canine osteosarcoma

Background

Canine osteosarcoma (OS) is associated with localized pain as a result of tissue injury from tumor infiltration and peritumoral inflammation. Malignant bone pain is caused by stimulation of peripheral pain receptors, termed nociceptors, which reside in the localized tumor microenvironment, including the periosteal and intramedullary bone cavities. Several nociceptive ligands have been determined to participate directly or indirectly in generating bone pain associated with diverse skeletal abnormalities.

Hypothesis

Canine OS cells actively produce nociceptive ligands with the capacity to directly or indirectly activate peripheral pain receptors residing in the bone tumor microenvironment.

Animals

Ten dogs with appendicular OS.

Methods

Expression of nerve growth factor, endothelin‐1, and microsomal prostaglandin E synthase‐1 was characterized in OS cell lines and naturally occurring OS samples. In 10 dogs with OS, circulating concentrations of nociceptive ligands were quantified and correlated with subjective pain scores and tumor volume in patients treated with standardized palliative therapies.

Results

Canine OS cells express and secrete nerve growth factor, endothelin‐1, and prostaglandin E2. Naturally occurring OS samples uniformly express nociceptive ligands. In a subset of OS‐bearing dogs, circulating nociceptive ligand concentrations were detectable but failed to correlate with pain status. Localized foci of nerve terminal proliferation were identified in a minority of primary bone tumor samples.

Conclusions and Clinical Importance

Canine OS cells express nociceptive ligands, potentially permitting active participation of OS cells in the generation of malignant bone pain. Specific inhibitors of nociceptive ligand signaling pathways might improve pain control in dogs with OS.

Pro-tumorigenic effects of transforming growth factor beta 1 in canine osteosarcoma

BACKGROUND

Transforming growth factor beta 1 (TGFβ1) is a pleiotropic cytokine that contributes to reparative skeletal remodeling by inducing osteoblast proliferation, migration, and angiogenesis. Organic bone matrix is the largest bodily reservoir for latent TGFβ1, and active osteoblasts express cognate receptors for TGFβ1 (TGFβRI and TGFβRII). During malignant osteolysis, TGFβ1 is liberated from eroded bone matrix and promotes local progression of osteotropic solid tumors by its mitogenic and prosurvival activities.

HYPOTHESIS

Canine osteosarcoma (OS) cells will possess TGFβ1 signaling machinery. Blockade of TGFβ1 signaling will attenuate pro-tumorigenic activities in OS cells. Naturally occurring primary OS samples will express cognate TGFβ1 receptors; and in dogs with OS, focal malignant osteolysis will contribute to circulating TGFβ1 concentrations.

ANIMALS

Thirty-three dogs with appendicular OS.

METHODS

Expression of TGFβ1 and its cognate receptors, as well as the biologic effects of TGFβ1 blockade, was characterized in OS cells. Ten spontaneous OS samples were characterized for TGFβRI/II expressions by immunohistochemistry. In 33 dogs with OS, plasma TGFβ1 concentrations were quantified and correlated with bone resorption.

RESULTS

Canine OS cells secrete TGFβ1, express cognate receptors, and TGFβ1 signaling blockade decreases proliferation, migration, and vascular endothelial growth factor secretion. Naturally occurring OS samples abundantly and uniformly express TGFβRI/II, and in OS-bearing dogs, circulating TGFβ1 concentrations correlate with urine N-telopeptide excretion.

CONCLUSIONS AND CLINICAL IMPORTANCE

Canine OS cells possess TGFβ1 signaling machinery, potentially allowing for the establishment of an autocrine and paracrine pro-tumorigenic signaling loop. As such, TGFβ1 inhibitors might impede localized OS progression in dogs.

Evidence-based medicine: the design and interpretation of noninferiority clinical trials in veterinary medicine

Noninferiority trials are clinical studies designed to demonstrate that an investigational drug is at least as effective as an established treatment within a predetermined margin. They are conducted, in part, because of ethical concerns of administering a placebo to veterinary patients when an established effective treatment exists. The use of noninferiority trial designs has become more common in veterinary medicine with the increasing number of established veterinary therapeutics and the desire to eliminate potential pain or distress in a placebo-controlled study. Selecting the appropriate active control and an a priori noninferiority margin between the investigational and active control drug are unique and critical design factors for noninferiority studies. Without reliable historical knowledge of the disease response in the absence of treatment and of the response to the selected active control drug, proper design and interpretation of a noninferiority trial is not possible. Despite the appeal of conducting noninferiority trials to eliminate ethical concerns of placebo-controlled studies, there are real limitations and possible ethical conundrums associated with noninferiority trials. The consequences of incorrect study conclusions because of poor noninferiority trial design need careful attention. Alternative trial designs to typical noninferiority studies exist, but these too have limitations and must also be carefully considered.

Association between absolute tumor burden and serum bone-specific alkaline phosphatase in canine appendicular osteosarcoma

BACKGROUND

In dogs with appendicular osteosarcoma (OSA), increased pretreatment serum bone-specific alkaline phosphatase (BALP) activity is a negative prognostic factor, associated with shorter disease-free intervals and survival times, but a biologic basis for observed differential serum BALP activities in canine OSA patients remains incompletely defined.

OBJECTIVE

Serum BALP activity will correlate with absolute tumor burden in dogs with OSA.

ANIMALS

This study included 96 client-owned dogs with appendicular OSA.

METHODS

In canine OSA cell lines, the expression and membranous release of BALP was evaluated in vitro. The correlation between serum BALP activity and radiographic primary tumor size was evaluated in OSA-bearing dogs. In dogs developing visceral OSA metastases, serial changes in serum BALP activities were evaluated in relation to progression of macroscopic metastases, and visceral metastatic OSA cells were evaluated for BALP expression.

RESULTS

In vitro, BALP expression was not associated with either tumorigenic or metastatic phenotype, rather the quantity of membranous BALP released was proportional with cell density. In dogs devoid of macroscopic metastases, there was a positive correlation between serum BALP activity and absolute primary tumor size. In dogs with progressive OSA metastases, serum BALP activity increased and coincided with the development of macroscopic metastases. OSA cells derived from visceral metastatic lesions retained BALP expression.

CONCLUSIONS AND CLINICAL IMPORTANCE

Tumor burden is a determinant of serum BALP activity in dogs with appendicular OSA. The association between increased pretreatment BALP activity and negative clinical prognosis may simply be attributed to greater initial tumor burden, and consequently more advanced tumor stage.

Canine osteosarcoma cell lines from patients with differing serum alkaline phosphatase concentrations display no behavioural differences in vitro

Osteosarcoma is an aggressive malignancy and represents the most frequent primary bone malignancy of dogs and humans. Prognostic factors reported for osteosarcoma include tumour size, presence of metastatic disease and serum alkaline phosphatase (ALP) concentration at the time of diagnosis. To date, there have been no studies to determine whether the behaviour of osteosarcoma cells differ based on serum ALP concentration. Here, we report on the generation of six canine osteosarcoma cell lines from osteosarcoma-bearing dogs with differences in serum ALP concentration. To determine whether in vitro behaviour differs between primary osteosarcoma cell lines generated from patients with normal or increased serum ALP, assays were performed to evaluate proliferation, migration, invasion and chemosensitivity. There were no significant differences in cell proliferation, migration, invasion or chemosensitivity between cell lines associated with normal or increased serum ALP concentration.

Double-blind placebo-controlled trial of adjuvant pamidronate with palliative radiotherapy and intravenous doxorubicin for canine appendicular osteosarcoma bone pain

BACKGROUND

Canine osteosarcoma (OSA) causes focal malignant osteolysis leading to severe pain. Despite the documented efficacy of radiotherapy or IV aminobisphosphonates for managing cancer bone pain, their potential combined therapeutic value has not been reported in OSA-bearing dogs.

HYPOTHESIS

Pamidronate combined with standardized palliative therapy will improve pain control and bone biologic effects in OSA-bearing dogs.

ANIMALS

Fifty dogs with appendicular OSA treated with standardized palliative therapy and either pamidronate or sterile saline.

METHODS

Randomized, prospective, double-blinded, placebo-controlled study. Treatment responses for dogs receiving standardized palliative therapy with (n = 26) or without (n = 24) adjuvant pamidronate were serially evaluated for changes in subjective pain scores, urine N-telopeptide (NTx) excretion, primary tumor relative bone mineral density (rBMD), and computerized pressure platform gait analysis.

RESULTS

Median duration of subjective pain relief for dogs treated with adjuvant pamidronate or placebo was 76 and 75 days, respectively (P= .39). Forty percent (20/50; pamidronate [11/26] and placebo [9/24]) of dogs experienced durable analgesia, defined by pain alleviation > or =112 days. For patients achieving durable pain control, dogs treated with pamidronate achieved greater reductions in NTx excretion and larger increases in rBMD compared with placebo controls. Changes in peak vertical force assessed by computerized pressure platform gait analysis correlated with pain alleviation in OSA-bearing dogs.

CONCLUSIONS AND CLINICAL IMPORTANCE

Combining pamidronate with standardized palliative therapy is safe, but does not clearly improve pain alleviation. However, in dogs achieving durable pain control, adjuvant pamidronate appears to decrease focal bone resorption in the local tumor microenvironment.

In vivo and in vitro efficacy of zoledronate for treating oral squamous cell carcinoma in cats

BACKGROUND

Feline oral squamous cell carcinoma (OSCC) may cause painful bone destruction. Given the local invasiveness and rapid clinical progression of OSCC, conventional therapies are often palliative. In human cancer patients, zoledronate exerts anticancer effects by inhibiting tumor-induced angiogenesis and malignant osteolysis.

HYPOTHESIS

Zoledronate will exert in vitro and in vivo anti-angiogenic and antiresorptive effects in feline OSCC.

ANIMALS

Eight cats with OSCC were prospectively treated with zoledronate and conventional treatment modalities.

METHODS

In vitro, zoledronate's effects in modulating soluble vascular endothelial growth factor (VEGF) secretion and receptor activator of nuclear factor kappaB (NF-kappaB) ligand (RANKL) expression were investigated in a feline OSCC cell line (SCCF1). In vivo, basal serum C-telopeptide (CTx) concentrations were compared among normal and OSCC-bearing cats, and the biologic effects of zoledronate administration in cats with naturally occurring OSCC were quantified by serially assessing circulating serum VEGF and CTx concentrations.

RESULTS

In vitro, zoledronate concentrations greater than 3 microM reduce soluble VEGF secretion in the SCCF1 cell line. The expression of RANKL in the SCCF1 cell line was also modulated by zoledronate, with low concentrations (3 microM) decreasing but higher concentrations (30 microM) increasing RANKL expression in comparison with untreated cells. In vivo, cats with bone-invasive OSCC had greater serum CTx concentrations in comparison with geriatric, healthy controls. Treatment with zoledronate rapidly decreased circulating serum VEGF and CTx concentrations in cats with spontaneously occurring OSCC.

CONCLUSIONS AND CLINICAL IMPORTANCE

Zoledronate exerts in vitro and in vivo effects that may favor the slowing of tumor growth and pathologic bone turnover associated with OSCC.

Investigating TrkA expression in canine appendicular osteosarcoma

BACKGROUND

The tropomyosin-related kinase A (TrkA) proto-oncogene encodes for a receptor that binds with high affinity to the neurotrophin ligand, nerve growth factor (NGF). Intracellular signaling mediated by the TrkA/NGF axis orchestrates neuronal cell differentiation, mitogenesis, and survival. Interestingly, TrkA also is expressed by bone forming cells, and its signaling promotes antiapoptotic effects in actively dividing osteoblasts.

HYPOTHESIS

In canine immortalized cell lines and naturally occurring tumor samples, osteosarcoma (OSA) cells will express TrkA. In canine OSA cell lines, TrkA signaling will promote cell mitogenesis and survival.

METHODS

In vitro, TrkA expression in canine OSA cell lines was assessed by reverse transcriptase-polymerase chain reaction, flow cytometry, and immunocytochemistry. In vitro, the involvement of TrkA-mediated signaling for cell mitogenesis and survival were investigated with commercially available assays. In vivo, TrkA expression was evaluated in primary tumors and pulmonary metastases with immunocytochemistry and immunohistochemistry, respectively.

RESULTS

In vitro, canine OSA cells expressed TrkA mRNA and protein. Ligation of TrkA with exogenous NGF did not induce mitogenesis. Blockade of TrkA signaling with either a protein kinase inhibitor or NGF-neutralizing antibody induced apoptosis of canine OSA cell lines. In vivo, the majority (10/15) of canine OSA primary tumors and pulmonary metastases (9/12) expressed TrkA protein.

CONCLUSIONS AND CLINICAL IMPORTANCE

Canine OSA cells express TrkA, and its signaling protects against apoptosis. Most dogs with spontaneously arising OSA express TrkA within their primary tumors and pulmonary metastatic lesions, warranting further investigations with TrkA antagonists as a novel treatment option for canine OSA.

Investigating CXCR4 expression in canine appendicular osteosarcoma

BACKGROUND

Chemokine receptors (CXCRs) are transmembrane proteins classically studied for their participation in leukocyte homing. By their binding of cognate ligands, CXCRs orchestrate key cellular processes, including directional migration. Several different CXCRs are expressed on cancer cells and dictate tissue-specific metastases. In pediatric osteosarcoma (OSA), CXCR4 expression by tumor cells may participate in metastasis to tissues containing CXCL12, the partnering ligand for CXCR4. Canine and pediatric OSA share many biological similarities, including preferential metastasis to lung, bone, and lymph node.

HYPOTHESIS

In canine immortalized cell lines and naturally occurring tumor samples, OSA cells will express CXCR4. In canine OSA cell lines, CXCR4 will participate in directional cell migration.

METHODS

In vitro, CXCR4 expression in canine OSA cell lines was assessed by reverse-transcriptase polymerase chain reaction, Western blot analysis, flow cytometry, and immunocytochemistry. In vitro, involvement of CXCR4-mediated signaling for directional migration was investigated with a commercial assay. In vivo, CXCR4 expressions were evaluated in primary tumors and pulmonary metastases with immunocytochemistry and immunohistochemistry, respectively.

RESULTS

In vitro, canine OSA cells express CXCR4 mRNA and protein. Ligation of CXCR4 with exogenous CXCL12 results in directional migration of canine OSA cell lines. In vivo, majority (8/11) of the canine OSA primary tumors, but minority (2/8) of the pulmonary metastases express CXCR4 protein.

CONCLUSIONS AND CLINICAL IMPORTANCE

Canine OSA cells express CXCR4, and its signaling participates in directional migration. Most dogs with spontaneously arising OSA express CXCR4 within their primary tumors.

The bone biologic effects of zoledronate in healthy dogs and dogs with malignant osteolysis

BACKGROUND

Malignant osteolysis is a process whereby cancer cells in concert with osteoclasts erode bone matrix. Aminobisphosphonates (NBPs) such as zoledronate induce osteoclast apoptosis and thereby decrease malignant skeletal destruction, severity of bone pain, and frequency of pathologic fracture.

HYPOTHESIS

IV-administered zoledronate will reduce homeostatic bone turnover in healthy dogs and pathologic bone resorption in dogs diagnosed with primary and secondary bone tumors.

ANIMALS

Six healthy dogs and 20 dogs with naturally occurring primary or metastatic bone tumors were administered zoledronate IV.

METHODS

Prospective study: In all dogs, healthy (n = 6) and with malignant osteolysis (n = 20), the bone biologic effects of zoledronate were evaluated by quantifying changes in serum C-telopeptide (CTx) or urine N-telopeptide (NTx) concentrations or both. In dogs with osteosarcoma (OSA) (n = 10), serial changes in tumor relative bone mineral density (rBMD) assessed by dual-energy x-ray absorptiometry were used to characterize zoledronate's antiresorptive effects within the immediate tumor microenvironment. Additionally, the biochemical tolerability of zoledronate was assessed in 9 dogs receiving multiple (> or =2) consecutive treatments.

RESULTS

All dogs had significant reductions in serum CTx or urine NTx concentrations or both after zoledronate administration. In a subset of dogs with appendicular OSA, reduced urine NTx concentrations and increased primary tumor rBMD coincided with improved limb usage as reported by pet owners in dogs treated with zoledronate and concurrent oral analgesics. Multiple zoledronate infusions were not associated with biochemical evidence of toxicosis.

CONCLUSIONS AND CLINICAL IMPORTANCE

In dogs with skeletal neoplasms, IV-administered zoledronate exerts bone biologic effects, appears safe, and can provide pain relief.

Effect of weight loss on the ECG of normotensive morbidly obese patients

BACKGROUND

Morbid obesity produces a variety of ECG alterations, including leftward shifts of the P-wave, QRS, and T-wave axes; disproportionately high frequencies of low QRS voltage; left ventricular hypertrophy and left atrial abnormality; and a high frequency of T-wave flattening in the inferior and lateral leads. This study was designed to assess the effects of substantial weight loss on the ECG in morbid obesity.

METHODS

We performed a resting 12-lead ECG on 60 normotensive patients (48 women and 12 men; mean +/- SD age, 37 +/- 7 years), whose body weight was twice their ideal body weight prior to and at the time of maximum weight loss after bariatric surgery.

RESULTS

Mean weight decreased from 136 +/- 7 to 85 +/- 3 kg. Weight loss produced significant decreases in the frequencies of low QRS voltage; Romhilt-Estes point score > or = 5 points; SV(1) + RV(5) or V(6) > 35 mm; RV(5) or V(6) > 26 mm; RaVL > 11 mm; RaVL > or = 7.5 mm; SaVR > 14 mm; P-terminal force more negative than - 0.04 mm.s in lead V(1); and T-wave flattening in the inferior, lateral, and inferolateral leads. Weight loss significantly shifted the mean P-wave, QRS, T-wave axes rightward, and significantly reduced mean RaVL and mean SaVR voltage.

CONCLUSION

Substantial weight loss is capable of reversing many of the ECG alterations associated with morbid obesity.

The electrocardiogram in morbid obesity

Electrocardiographic variables that occurred with significantly higher frequency in morbidly obese patients than in lean controls were low QRS voltage, leftward shift of the P, QRS, and T axes and multiple electrocardiographic criteria for left ventricular hypertrophy and left atrial enlargement. P-terminal force, RaVL, SaVR, and R/S ratio in lead V1 values were significantly higher in morbidly obese than in lean subjects.

Peliosis hepatis in a dog infected with Bartonella henselae

A 6-year-old spayed female Golden Retriever was examined because of generalized weakness and abdominal distention. Abdominal ultrasonography revealed a large quantity of peritoneal fluid. In addition, the liver appeared larger than normal and contained multiple, small, nodular masses and cyst-like structures. Abdominal exploratory surgery was performed, and 5 L of serosanguineous peritoneal fluid was removed. Gross lesions were not found in the stomach, kidneys, intestines, adrenal glands, or urinary bladder. There were diffuse cystic nodules in all liver lobes. The dog did not recover from anesthesia. A diagnosis of peliosis hepatis was made on the basis of gross and histologic appearance of the liver. A polymerase chain reaction assay revealed Bartonella henselae DNA in liver specimens. To our knowledge, this is the first report of molecular evidence of B henselae infection in a dog with peliosis hepatis.

Intestinal haemorrhage associated with colonic vascular ectasia (angiodysplasia) in a dog

An eight-year-old, sexually intact, male, 37 kg crossbred dog was referred for investigation of two acute episodes of intestinal bleeding and severe anaemia within a five-month period. There was no evidence of coagulopathy or underlying systemic disease. Technetium-labelled red blood cell scintigraphy suggested the colon as the site of bleeding. Colonoscopy identified a focal area of dilated and tortuous mucosal blood vessels. Histopathology of the resected colon revealed vascular ectasia (angiodysplasia). At nine months post-resection, the dog remained healthy and free of any overt intestinal haemorrhage.

Calcipotriol toxicity in a dog

A six-month-old Labrador retriever was presented for investigation of acute polyuria, polydipsia and haematemesis six hours following ingestion of a tube of the topical antipsoriatic vitamin D analogue, calcipotriol. Transient hypercalcaemia, azotaemia, proteinuria, thrombocytopenia and ventricular arrhythmias ensued. Abdominal ultrasonography and echocardiography revealed evidence of diffuse soft tissue mineralisation. Despite 13 days of intensive supportive care, the dog was euthanased due to continued haematemesis and anorexia. Necropsy confirmed mineralisation and necrosis of multiple organ systems consistent with vitamin D toxicity.

Cardiac morphology and left ventricular function in normotensive morbidly obese patients with and without congestive heart failure, and effect of weight loss

To assess cardiac morphology and left ventricular (LV) function in normotensive morbidly obese patients with and without congestive heart failure (CHF) we performed a physical examination and obtained a transthoracic echocardiogram and cardiac Doppler studies before and after substantial weight loss in patients whose actual body weight was initially equal to or more than twice their ideal body weight and who were free from systemic hypertension and underlying organic heart disease. There were 24 patients with CHF, 14 of whom were studied after weight loss. There were 50 patients without CHF, 39 of whom were studied after weight loss. Compared to patients without CHF, those with CHF had significantly greater mean LV internal dimension in diastole, LV end-systolic wall stress, LV mass/height index values, left atrial dimension and right ventricular internal dimension values, significantly lower mean LV fractional shortening, and transmitral Doppler E/A ratio values, and significantly longer mean transmitral E-wave deceleration time and duration of morbid obesity than patients without CHF. Substantial weight loss in those with and without CHF produced comparable reductions in mean LV internal dimension in diastole, LV end-systolic wall stress, LV mass/height index, transmitral Doppler E-wave deceleration time, and left atrial dimension, and comparable increases in LV fractional shortening and transmitral Doppler E/A ratio. Linear regression analysis identified duration of morbid obesity as the strongest predictor of CHF (p <0.00000002). Thus, LV mass is greater and LV systolic function and diastolic filling are more impaired in normotensive morbidly obese subjects with CHF than in those without CHF. Duration of morbid obesity is the strongest predictor of CHF among the variables studied. Substantial weight loss produces comparable changes in cardiac morphology and function in those with and without CHF.

Chronic beta-adrenoceptor blockade prevents the development of beta-adrenergic subsensitivity in experimental right-sided congestive heart failure in dogs

BACKGROUND

The reductions of myocardial beta-adrenergic receptor density and responsiveness to catecholamines in congestive heart failure are associated with excessive sympathetic stimulation. The purpose of this study was to determine whether the myocardial changes could be prevented by beta-receptor blockade.

METHODS AND RESULTS

We administered the oral beta-receptor blocking agent nadolol (40 mg/day) to dogs during an early stage of experimental right heart failure and to sham-operated dogs for 5 weeks. Animals receiving no nadolol were studied concurrently. Nadolol treatment did not prevent right ventricular hypertrophy or elevated concentrations of plasma norepinephrine that occurred in right heart failure, nor did it affect the decrease in myocardial norepinephrine content and norepinephrine uptake activity, suggesting that the hemodynamic stress imposed on the right ventricle of dogs with right heart failure was similar regardless of the presence or absence of beta-receptor blockade. Resting heart rate, right atrial pressure, aortic pressure, cardiac output, right ventricular dP/dt, and left ventricular dP/dt and dP/dt/P measured 5 days after discontinuation of nadolol did not differ significantly from those without nadolol treatment in either right heart failure or sham-operated animals. Sham-operated dogs also showed no changes in myocardial beta-receptor or adenylate cyclase activity after nadolol treatment. However, nadolol treatment prevented the reduction of myocardial beta-receptor density and attenuated the decrease in the cardiac beta-adrenergic sensitivity that occurred in right heart failure.

CONCLUSIONS

Excessive sympathetic stimulation may play an important role in the development of beta-receptor downregulation and beta-adrenergic subsensitivity in right heart failure.