Hepatic Gene Expression of Angiogenic and Regeneration Markers in Cats with Congenital Portosystemic Shunts (CPSS).

Congenital portosystemic shunts (CPSS) are vascular anomalies resulting in liver hypoplasia and hepatic insufficiency. Cats with CPSS typically show signs of hepatic encephalopathy associated with increased ammonia, inflammatory cytokines, and oxidative stress. Surgical attenuation of the CPSS results in improved liver function, resolution of clinical signs, and increased portal blood flow. Hepatic gene expression has not previously been investigated in cats with CPSS. Here, we compared the hepatic expression of genes involved in the urea cycle (CPS1, NAGS), angiogenesis (VEGFR2, NPPA, NPR1, NPPC, NPR2, HIF1a), liver regeneration (SERPINB1, HGF, TGFß), and metabolism (FGF21) from a small series of cats (n = 18) with CPSS to that of control cats (n = 10). The expression of TGFß, VEGFR2, HGF, FGF21, and CPS1 was significantly elevated in liver biopsies from cats with CPSS. Cats that could only tolerate partial closure of their CPSS had increased hepatic expression of SERPINB1, HIF1a, and NPR2 compared with those that could tolerate complete ligation. Furthermore, there were no significant correlations between gene expression and pre-operative plasma ammonia concentrations in cats with CPSS. The changes in hepatic gene expression in cats with CPSS are in direct contrast to those seen in dogs with CPSS, suggesting alternative mechanisms may be involved in mediating hepatic changes in cats with CPSS.

Long-term outcome and quality of life of dogs that developed neurologic signs after surgical treatment of a congenital portosystemic shunt: 50 cases (2005-2020).

OBJECTIVE: To determine survival time and quality of life of dogs that developed postattenuation neurologic signs (PANS) after surgical treatment of a single congenital portosystemic shunt and survived at least 30 days and identify whether neurologic signs present at the time of discharge would resolve or reoccur. ANIMALS: 50 client-owned dogs. PROCEDURES: Medical records were retrospectively reviewed, and follow-up data relating to neurologic signs and seizure activity were obtained. Owners were asked to complete a questionnaire related to the presence of neurologic signs, including seizures, and their dog's quality of life. RESULTS: Thirty of the 50 (60%) dogs had postattenuation seizures with or without other nonseizure neurologic signs, and 20 (40%) had neurologic signs other than seizures. Neurologic signs had fully resolved by the time of discharge in 24 (48%) dogs. Signs resolved in 18 of the remaining 26 (69%) dogs that still had PANS other than seizures at the time of discharge. Seizures reoccurred in 15 of the 30 dogs that had postattenuation seizures. Twenty-seven of 33 (82%) owners graded their dog's long-term (> 30 days after surgery) quality-of-life as high. Forty-five (90%) dogs survived > 6 months. Most (29/43 [67%]) neurologic signs (other than seizures) present at the time of hospital discharge resolved. CLINICAL RELEVANCE: Findings highlighted that survival times of > 6 months and a high QOL can be achieved in most dogs with PANS that survive at least 30 days. Most neurologic signs other than seizures resolved within 1 month postoperatively. Half of the dogs with postattenuation seizures had a reoccurrence.

Sensitivity of the Natriuretic Peptide/cGMP System to Hyperammonaemia in Rat C6 Glioma Cells and GPNT Brain Endothelial Cells.

C-type natriuretic peptide (CNP) is the major natriuretic peptide of the central nervous system and acts via its selective guanylyl cyclase-B (GC-B) receptor to regulate cGMP production in neurons, astrocytes and endothelial cells. CNP is implicated in the regulation of neurogenesis, axonal bifurcation, as well as learning and memory. Several neurological disorders result in toxic concentrations of ammonia (hyperammonaemia), which can adversely affect astrocyte function. However, the relationship between CNP and hyperammonaemia is poorly understood. Here, we examine the molecular and pharmacological control of CNP in rat C6 glioma cells and rat GPNT brain endothelial cells, under conditions of hyperammonaemia. Concentration-dependent inhibition of C6 glioma cell proliferation by hyperammonaemia was unaffected by CNP co-treatment. Furthermore, hyperammonaemia pre-treatment (for 1 h and 24 h) caused a significant inhibition in subsequent CNP-stimulated cGMP accumulation in both C6 and GPNT cells, whereas nitric-oxide-dependent cGMP accumulation was not affected. CNP-stimulated cGMP efflux from C6 glioma cells was significantly reduced under conditions of hyperammonaemia, potentially via a mechanism involving changed in phosphodiesterase expression. Hyperammonaemia-stimulated ROS production was unaffected by CNP but enhanced by a nitric oxide donor in C6 cells. Extracellular vesicle production from C6 cells was enhanced by hyperammonaemia, and these vesicles caused impaired CNP-stimulated cGMP signalling in GPNT cells. Collectively, these data demonstrate functional interaction between CNP signalling and hyperammonaemia in C6 glioma and GPNT cells, but the exact mechanisms remain to be established.

Incidence and risk factors for neurological signs after attenuation of a single congenital portosystemic shunt in 50 cats.

OBJECTIVE: To determine the incidence, outcome, and risk factors for postattenuation neurological signs (PANS) in cats treated for single congenital portosystemic shunts (CPSS). STUDY DESIGN: Retrospective cohort study. ANIMALS: Cats (n = 50) with a single CPSS. METHODS: Medical records of cats treated by surgical attenuation of a single CPSS between 2003 and 2017 were reviewed for signalment, surgical technique, preoperative management and postoperative clinical outcomes. Binary logistic regression was performed to investigate risk factors for occurrence of PANS and seizures. RESULTS: Congenital portosystemic shunts in 50 cats included 40 extrahepatic and 10 intrahepatic shunts. Postattenuation neurological signs were recorded in 31 (62%) cats and graded as 1 in 10 cats, 2 in nine cats, and 3 in 12 cats. Postattenuation neurological signs included seizures in 11 cats. Five of 31 cats with PANS did not survive to discharge. No association was detected between PANS or seizures and the type of CPSS (intrahepatic or extrahepatic), degree of attenuation, age, or the use of perioperative levetiracetam or hepatic encephalopathy immediately preoperatively. Osmolality at a median 24 hours postoperatively was lower in cats with PANS (P < .049, Wald 3.867, odds ratio [Exp(B)] 0.855, CI 0.732-0.999). CONCLUSION: Postattenuation neurological signs are common complications in cats treated for CPSS. Preoperative levetiracetam did not prevent the occurrence of PANS or seizures. The only risk factor for PANS detected was lower postoperative Osmolality in cats with PANS at 24 hours. CLINICAL SIGNIFICANCE: Postattenuation neurological signs including seizures occur frequently in cats undergoing surgical attenuation of a CPSS. Preoperative levetiracetam did not protect against the development of PANS.

Prospective comparison of perioperative wound and pain score parameters in cats undergoing flank vs midline ovariectomy.

OBJECTIVES: The aim of this study was to prospectively compare perioperative pain score and wound parameters, inclusive of postoperative swelling and erythema, between flank and midline ovariectomy (OVE) in cats, performed by final-year veterinary students. METHODS: Healthy cats presented for routine OVE were randomly assigned to either the midline or flank group after owner consent to participate in the study. Perioperative protocols were standardised for both groups. Clinical data were collected prior to surgery, intraoperatively, at 1 h postoperatively, at the time of discharge, and at 3 and 10 day postoperative re-examination appointments. Data recorded included duration of surgery and anaesthesia, intraoperative complications, Feline Acute Pain Scale (FAPS) scores, a simple descriptive scale of reaction to wound palpation (SDSwound), a dynamic and interactive visual analogue scale assessment of pain (DIVAS), and both a simple descriptive scale (SDSswelling) and a visual analogue scale (VASswelling) of surgical wound swelling. RESULTS: Thirty-eight cats received a flank OVE and 37 received a midline OVE. Duration of surgery, duration of anaesthesia and intraoperative complications did not vary significantly between the two groups. Cats in both groups had significantly higher FAPS scores after surgery (P = 0.0002), with cats receiving a flank OVE having significantly higher pain scores compared with a midline OVE at 1 h postoperatively (P = 0.0004) and at discharge (P = 0.002). Swelling of the surgical wound (SDSswelling) was significantly higher in cats receiving a midline OVE at the time of discharge (P = 0.048), as well as at the 3 day (P <0.0001) and 10 day (P = 0.001) postoperative re-examinations. FAPS scores were significantly higher in cats receiving a midline OVE at the 3 day (P = 0.016) and 10 day re-examinations (P = 0.045). No cats in either group suffered a wound breakdown or infection. CONCLUSIONS AND RELEVANCE: Our study does not support advocating a preferred surgical approach for feline OVE within a teaching environment.

Indications, complications, and outcomes associated with subdermal plexus skin flap procedures in dogs and cats: 92 cases (2000-2017).

OBJECTIVE: To describe indications, complications, and outcomes associated with subdermal plexus skin flap (SPSF) procedures in dogs and cats. ANIMALS: 53 dogs and 20 cats that received SPSFs for reconstruction of skin defects from 2000 to 2017. PROCEDURES: Medical record data were collected and summarized regarding patient signalment, indication for the SPSF procedure, type and location of SPSF, complications, and outcome. RESULTS: 92 SPSF procedures (64 in dogs and 28 in cats) were included. Indications for the procedures included tumor excision (n = 37 [40%]), acute wound (14 [15%]) or chronic wound (28 [30%]) reconstruction, surgical scar revision (7 [8%]), and other reasons (6 [7%]). Types of SPSFs included advancement (31 [34%]), axillary fold (20 [22%]), inguinal fold (20 [22%]), rotation (16 [17%]), transposition (3 [3%]), and distant direct (2 [2%]). Complications were noted for 47 (51%) procedures at a mean ± SD of 6.9 ± 4.0 days after surgery and were classified as minor (34 [37%]) or major (13 [14%]). Outcome was considered excellent for 44 (48%) procedures, good for 33 (36%), fair for 13 (14%), and poor for 2 (2%). CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that approximately half of SPSF procedures in dogs and cats can be expected to be followed by a complication, occurring at a mean of 1 week after surgery, and yet with appropriate management of these complications, a good to excellent outcome was possible. Owners should be counseled about the likely need for additional visits and costs associated with treatment of postoperative complications.

Regulation and Function of C-Type Natriuretic Peptide (CNP) in Gonadotrope-Derived Cell Lines.

C-type natriuretic peptide (CNP) is the most conserved member of the mammalian natriuretic peptide family, and is implicated in the endocrine regulation of growth, metabolism and reproduction. CNP is expressed throughout the body, but is particularly abundant in the central nervous system and anterior pituitary gland. Pituitary gonadotropes are regulated by pulsatile release of gonadotropin releasing hormone (GnRH) from the hypothalamus, to control reproductive function. GnRH and CNP reciprocally regulate their respective signalling pathways in αT3-1 gonadotrope cells, but effects of pulsatile GnRH stimulation on CNP expression has not been explored. Here, we examine the sensitivity of the natriuretic peptide system in LßT2 and αT3-1 gonadotrope cell lines to continuous and pulsatile GnRH stimulation, and investigate putative CNP target genes in gonadotropes. Multiplex RT-qPCR assays confirmed that primary mouse pituitary tissue express Nppc,Npr2 (encoding CNP and guanylyl cyclase B (GC-B), respectively) and Furin (a CNP processing enzyme), but failed to express transcripts for Nppa or Nppb (encoding ANP and BNP, respectively). Pulsatile, but not continuous, GnRH stimulation of LßT2 cells caused significant increases in Nppc and Npr2 expression within 4 h, but failed to alter natriuretic peptide gene expression in αT3-1 cells. CNP enhanced expression of cJun, Egr1, Nr5a1 and Nr0b1, within 8 h in LßT2 cells, but inhibited Nr5a1 expression in αT3-1 cells. Collectively, these data show the gonadotrope natriuretic peptide system is sensitive to pulsatile GnRH signalling, and gonadotrope transcription factors are putative CNP-target genes. Such findings represent additional mechanisms by which CNP may regulate reproductive function.

Surgical management of an adrenal gland tumor that had extended into the thoracic portion of the caudal vena cava in a dog.

CASE DESCRIPTION: A 14-year-old neutered female Border Collie with a 3-week history of collapse during exercise was evaluated because of recumbency, tachycardia, and hypotension. CLINICAL FINDINGS: Results of biochemical testing indicated the presence of a pheochromocytoma, and CT revealed an enlarged right adrenal gland mass that extended down the right phrenicoabdominal vein into the posthepatic thoracic portion of the caudal vena cava. TREATMENT AND OUTCOME: A midline celiotomy and median sternotomy were performed to allow en bloc removal of the right adrenal gland tumor and its tumor thrombus extension within the caudal vena cava. Temporary occlusion of the thoracic and abdominal portions of the caudal vena cava and both renal veins and the dual inflow to the liver (Pringle maneuver) were required. The venotomy and tumor and thrombus extractions required a 25-minute period of vascular occlusion. The dog had no major postsurgical complications. Histologic findings indicated that direct adrenal tumor invasion into the caudal vena cava wall had occurred along the established route of tumor extension down the phrenicoabdominal vein. CLINICAL RELEVANCE: For the dog of this report, an adrenal tumor thrombus that extended into the thoracic portion of the caudal vena cava was surgically managed with a combined median sternotomy and midline celiotomy approach and temporary occlusion of the hepatic artery, portal vein, and abdominal and thoracic portions of the caudal vena cava. This facilitated successful manual manipulation of the tumor and enabled venotomy of sufficient size for tumor thrombus extraction.

Intraoperative and major postoperative complications and survival of dogs undergoing surgical management of epiglottic retroversion: 50 dogs (2003-2017).

OBJECTIVE: To report intraoperative and major postoperative complications in dogs treated surgically for epiglottic retroversion (ER), compare the incidence of major postoperative complications between procedures, and report survival of surgically treated dogs. STUDY DESIGN: Multi-institutional retrospective study. SAMPLE POPULATION: Fifty dogs treated with 78 procedures. METHODS: Medical records of dogs diagnosed and surgically treated for ER from 2003 to 2017 at 11 institutions were reviewed. Complications were divided into intraoperative and major postoperative complications. RESULTS: Intraoperative complications occurred during 2 of 78 (2.6%) procedures. Thirty-six major postoperative complications were documented in 22 dogs after 36 of 74 (48.7%) procedures. Postoperative complications occurred after 7 of 12 (58.3%) nonincisional epiglottopexy, 23 of 43 (53.5%) incisional epiglottopexy, 2 of 4 (50%) partial epiglottectomy, 2 of 12 (16.7%) subtotal epiglottectomy, and 2 of 3 (66.7%) other surgical procedures. Epiglottopexy failure was the most common major postoperative complication. The incidence of major postoperative complications did not differ between procedures (P = .1239), although, when combined, epiglottopexy procedures (30/55) had a higher incidence of complications than epiglottectomy procedures (4/16; P = .048). Thirty (60%) dogs were alive at a median of 928 days (range, 114-2805), 8 (16%) were lost to follow-up after 411 days (range, 43-1158), and 12 (24%) were dead/euthanized after 301.5 days (range, 3-1212). Median survival time was not reached after a median of 716 days. CONCLUSION: Although intraoperative complications were uncommon, major postoperative complications were common, especially after epiglottopexy procedures. CLINICAL SIGNIFICANCE: Although surgical treatment of ER is associated with a high rate of major postoperative complications, especially epiglottopexy procedures, long-term survival can be achieved.

Variations in surgical technique for adrenalectomy with caudal vena cava venotomy in 19 dogs.

OBJECTIVE: To describe surgical techniques, caval occlusion times, and short-term outcomes in dogs undergoing adrenalectomy with caval venotomy. STUDY DESIGN: Retrospective case series. ANIMALS: Dogs undergoing adrenalectomy with caval venotomy between October 1, 2010 and May 31, 2018. METHODS: Medical records of dogs undergoing adrenalectomy with caval venotomy were reviewed for signalment, perioperative management, surgical details, perioperative complications, mortality, and histopathology. Computed tomography images were reviewed to describe tumor morphology and signs of thrombus extension. RESULTS: Nineteen dogs had adrenal tumor thrombi extending into the prehepatic (14 dogs, 74%), hepatic (3 dogs, 16%), and posthepatic (2 dogs, 11%) caudal vena cava. Tumors occurred in left (11) and right (8) adrenal glands. Median caval occlusion was 6.5 minutes (range, 2-25). Two to six vascular tourniquets were used. Venotomy closure was performed under full caval occlusion in 11 dogs and by using a partial occlusion clamp in 8 dogs. Left ureteronephrectomy was performed in 5 dogs. Perioperative mortality rate was 21% (4 dogs). CONCLUSION: Extension of caval tumor thrombus beyond the hepatic hilus did not preclude a good outcome. Longer caval occlusion than has been previously reported was tolerated in some cases. Number of vascular tourniquets used reflected the location of phrenicoabdominal vein insertion on the cava and length of the caval tumor thrombus. Venotomy closure under full occlusion was often required for right adrenal tumors. When required, ureteronephrectomy was left sided. CLINICAL SIGNIFICANCE: Dogs with adrenal tumors extending beyond the hepatic hilus and those requiring a long caval occlusion time can survive adrenalectomy.

Incidence and risk factors for neurological signs after attenuation of single congenital portosystemic shunts in 253 dogs.

OBJECTIVE: To determine the incidence, outcome, and risk factors for postattenuation neurological signs (PANS) and seizures after attenuation of single congenital portosystemic shunts (CPSS) in dogs. STUDY DESIGN: Retrospective cohort study. SAMPLE POPULATION: Dogs (N = 253) with single CPSS. METHODS: Medical records of dogs treated by surgical attenuation of a single CPSS between February 2000 and July 2015 were reviewed for signalment and preoperative and postoperative clinical outcomes, including the occurrence of PANS. Univariable and multivariable binary logistic regression was used to assess risk factors for PANS and for seizures. RESULTS: Twenty-eight (11.1%) dogs developed PANS, including 12 (4.7%) dogs with seizures. Five (17.9%) dogs with PANS did not survive to discharge. Risk factors for PANS included the presence of hepatic encephalopathy (HE) immediately preoperatively (P = .038, odds ratio [OR] 2.704, CI 1.057-6.922) and increasing age (P < .001, OR 1.476, CI 1.223-1.780). Risk factors for seizures included the presence of HE immediately preoperatively (P = .048, OR 3.538, CI 1.013-12.363) and increasing age (P = .009, OR 1.364, CI 1.082-1.720). No association was found between the location of portosystemic shunts (extrahepatic and intrahepatic) and post-operative PANS (P = .532) or seizures (P = .620). Similarly, preemptive administration of levetiracetam did not influence the risk of PANS (P = .991) or seizures (P = .752). CONCLUSION: Preoperative HE and older age in dogs with a CPSS increased the odds of developing PANS and seizures in our population. Preemptive administration of levetiracetam did not protect dogs against the development of PANS or seizures. CLINICAL SIGNIFICANCE: Surgical attenuation of a single CPSS should not be excessively delayed, and surgeons should stabilize the clinical signs of HE before surgery to prevent postoperative PANS and seizures.

Natriuretic peptide activation of extracellular regulated kinase 1/2 (ERK1/2) pathway by particulate guanylyl cyclases in GH3 somatolactotropes.

The natriuretic peptides, Atrial-, B-type and C-type natriuretric peptides (ANP, BNP, CNP), are regulators of many endocrine tissues and exert their effects predominantly through the activation of their specific guanylyl cyclase receptors (GC-A and GC-B) to generate cGMP. Whereas cGMP-independent signalling has been reported in response to natriuretic peptides, this is mediated via either the clearance receptor (Npr-C) or a renal-specific NPR-Bi isoform, which both lack intrinsic guanylyl cyclase activity. Here, we report evidence of GC-B-dependent cGMP-independent signalling in pituitary GH3 cells. Stimulation of GH3 cells with CNP resulted in a rapid and sustained enhancement of ERK1/2 phosphorylation (P-ERK1/2), an effect that was not mimicked by dibutryl-cGMP. Furthermore, CNP-stimulated P-ERK1/2 occurred at concentrations below that required for cGMP accumulation. The effect of CNP on P-ERK1/2 was sensitive to pharmacological blockade of MEK (U0126) and Src kinases (PP2). Silencing of the GC-B1 and GC-B2 splice variants of the GC-B receptor by using targeted short interfering RNAs completely blocked the CNP effects on P-ERK1/2. CNP failed to alter GH3 cell proliferation or cell cycle distribution but caused a concentration-dependent increase in the activity of the human glycoprotein α-subunit promoter (αGSU) in a MEK-dependent manner. Finally, CNP also activated the p38 and JNK MAPK pathways in GH3 cells. These findings reveal an additional mechanism of GC-B signalling and suggest additional biological roles for CNP in its target tissues.

Attenuation of congenital portosystemic shunt reduces inflammation in dogs.

Liver disease is a major cause of morbidity and mortality. One of the most significant complications in patients with liver disease is the development of neurological disturbances, termed hepatic encephalopathy. The pathogenesis of hepatic encephalopathy is incompletely understood, which has resulted in the development of a wide range of experimental models. Congenital portosystemic shunt is one of the most common congenital disorders diagnosed in client owned dogs. Our recent studies have demonstrated that the pathophysiology of canine hepatic encephalopathy is very similar to human hepatic encephalopathy, which provides strong support for the use of dogs with a congenital portosystemic shunt as a naturally occurring model of human hepatic encephalopathy. Specifically, we have demonstrated an important role for ammonia and inflammation in the development of hepatic encephalopathy in dogs with a congenital portosystemic shunt. Despite the apparent importance of inflammation in driving hepatic encephalopathy in dogs, it is unclear whether inflammation resolves following the successful treatment of liver disease. We hypothesized that haematological and biochemical evidence of inflammation, as gauged by neutrophil, lymphocyte and monocyte concentrations together with C-reactive protein concentrations, would decrease following successful treatment of congenital portosystemic shunts in dogs. One hundred and forty dogs with a congenital portosystemic shunt were enrolled into the study. We found that the proportion of dogs with a monocyte concentration above the reference range was significantly greater in dogs with hepatic encephalopathy at time of initial diagnosis. Importantly, neutrophil and monocyte concentrations significantly decreased following surgical congenital portosystemic shunt attenuation. We also found a significant decrease in C-reactive protein concentrations following surgical attenuation of congenital portosystemic shunts. Our study demonstrates that haematological and biochemical indices of inflammation reduce following successful treatment of the underlying liver disorder.

Markers of hepatic regeneration associated with surgical attenuation of congenital portosystemic shunts in dogs.

Dogs with congenital portosystemic shunts (CPSS) have liver hypoplasia and hepatic insufficiency. Surgical CPSS attenuation results in liver growth associated with clinical improvement. The mechanism of this hepatic response is unknown, although liver regeneration is suspected. This study investigated whether markers of liver regeneration were associated with CPSS attenuation. Dogs treated with CPSS attenuation were prospectively recruited. Residual liver tissue was collected for gene expression analysis (seven genes) from 24 CPSS dogs that tolerated complete attenuation, 25 dogs that tolerated partial attenuation and seven control dogs. Relative gene expression was measured using quantitative polymerase chain reaction (qPCR). Blood samples were collected before, 24 h and 48 h post-surgery from 36 CPSS dogs and from 10 control dogs. Serum hepatocyte growth factor (HGF) concentration was measured using a canine specific enzyme-linked immunosorbent assay (ELISA). HGF mRNA expression was significantly decreased in CPSS compared with control dogs (P = 0.046). There were significant increases in HGF (P = 0.050) and methionine adenosyltransferase 2 A (MAT2A; P = 0.002) mRNA expression following partial CPSS attenuation. Dogs with complete attenuation had significantly greater MAT2A (P = 0.024) mRNA expression compared with dogs with partial attenuation. Serum HGF concentration significantly increased 24 h following CPSS attenuation (P < 0.001). Hepatic mRNA expression of two markers of hepatocyte proliferation (HGF and MAT2A) was associated with the response to surgery in dogs with CPSS, and serum HGF significantly increased following surgery, suggesting hepatocyte proliferation. These findings support the concept that hepatic regeneration is important in the hepatic response to CPSS surgery.

Homologous and heterologous desensitization of guanylyl cyclase-B signaling in GH3 somatolactotropes.

The guanylyl cyclases, GC-A and GC-B, are selective receptors for atrial and C-type natriuretic peptides (ANP and CNP, respectively). In the anterior pituitary, CNP and GC-B are major regulators of cGMP production in gonadotropes and yet mouse models of disrupted CNP and GC-B indicate a potential role in growth hormone secretion. In the current study, we investigate the molecular and pharmacological properties of the CNP/GC-B system in somatotrope lineage cells. Primary rat pituitary and GH3 somatolactotropes expressed functional GC-A and GC-B receptors that had similar EC50 properties in terms of cGMP production. Interestingly, GC-B signaling underwent rapid homologous desensitization in a protein phosphatase 2A (PP2A)-dependent manner. Chronic exposure to either CNP or ANP caused a significant down-regulation of both GC-A- and GC-B-dependent cGMP accumulation in a ligand-specific manner. However, this down-regulation was not accompanied by alterations in the sub-cellular localization of these receptors. Heterologous desensitization of GC-B signaling occurred in GH3 cells following exposure to either sphingosine-1-phosphate or thyrotrophin-releasing hormone (TRH). This heterologous desensitization was protein kinase C (PKC)-dependent, as pre-treatment with GF109203X prevented the effect of TRH on CNP/GC-B signaling. Collectively, these data indicate common and distinct properties of particulate guanylyl cyclase receptors in somatotropes and reveal that independent mechanisms of homologous and heterologous desensitization occur involving either PP2A or PKC. Guanylyl cyclase receptors thus represent potential novel therapeutic targets for treating growth-hormone-associated disorders.

Successful surgical management of a perforating oesophageal foreign body in a cat.

UNLABELLED: CASE PRESENTATION AND SURGICAL INTERVENTION: a 3-year-old cat was presented with a recent history of dysphagia and intermittent regurgitation. Radiography revealed a bony oesophageal foreign body at the level of the thoracic inlet. Endoscopic retrieval was attempted but resulted in severe dyspnoea due to the development of pneumomediastinum, pneumothorax and subcutaneous emphysema secondary to perforation of the oesophageal wall. Immediate surgical exploration was carried out. Extensive necrosis of the oesophagus resulting from the presence of the foreign body led to a decision to perform an oesophageal resection and anastomosis. CLINICAL RELEVANCE: this is the first clinical report of a cat treated successfully by oesophagectomy following oesophageal perforation due to an obstructive foreign body. The authors suggest that prompt surgical intervention, the ability to convert to a surgical procedure under the same anaesthetic as a non-surgical retrieval, placement of a gastrostomy tube and the availability of advanced anaesthetic and critical care support are important factors to consider when managing feline patients with a perforating oesophageal foreign body.

Association of mesenteric portovenographic findings with outcome in cats receiving surgical treatment for single congenital portosystemic shunts.

OBJECTIVE: To determine whether hepatic portal vascularity assessed via intraoperative mesenteric portovenography (IMP) is related to outcome in cats undergoing surgical attenuation of a congenital portosystemic shunt (CPSS). DESIGN: Retrospective case series. ANIMALS: 25 cats, each with 1 CPSS, in which IMP was performed before and after temporary complete occlusion of the shunting vessel to provide complete (n=9) or partial (16) shunt attenuation. PROCEDURES: Medical records were reviewed for signalment, clinical history, postoperative complications, clinical outcome, and results of bile acids stimulation testing. Portovenograms obtained before and after shunt occlusion were graded to determine whether degree of intrahepatic portal branching was correlated with degree of shunt attenuation, clinical or biochemical factors, postoperative complications, or outcome. In 12 of the 16 cats that had partial CPSS attenuation, procedures were later repeated to achieve complete (n=9) and additional partial (1) CPSS attenuation. RESULTS: Degree of opacification of the intrahepatic portal vessels increased significantly (higher portovenogram grade) after CPSS attenuation. The median portovenogram grade assigned after temporary shunt occlusion at the first surgery was significantly higher in cats that did not have postattenuation neurologic complications or neurologic signs at follow-up than in cats that did. It was also higher in cats that had a better clinical response to surgery versus those that had a poor response and in cats with reduced preprandial and postprandial serum bile acids concentrations at follow-up versus those that did not. CONCLUSIONS AND CLINICAL RELEVANCE: IMP may be used to help predict complications and outcome following surgical treatment of CPSS in cats.

Use of a latissimus dorsi myocutaneous flap for one-stage reconstruction of the thoracic wall after en bloc resection of primary rib chondrosarcoma in five dogs.

OBJECTIVE: To describe a thoracic wall reconstructive technique using a latissimus dorsi myocutaneous flap after en bloc resection of primary rib chondrosarcoma and report outcome in 5 dogs. STUDY DESIGN: Retrospective study. ANIMALS: Dogs (n=5) with primary rib chondrosarcoma. METHODS: Medical records (2003-2005) were reviewed for signalment, staging investigations, surgical findings, complications, and outcomes. Owners and veterinary surgeons were contacted for outcome information. RESULTS: A latissimus dorsi myocutaneous flap provided an air-tight thoracic wall closure after chondrosarcoma resection. Paradoxical respiratory movement of the flap occurred; however, from physical examination and blood gas analysis (2 dogs), ventilation was adequate. All flaps survived, 1 had superficial skin necrosis distally and 2 had minor wound dehiscence. One dog without tumor-free margins died of tumor-related disease 56 days after surgery. Tumor recurrence did not occur in 4 dogs with tumor-free margins. One dog was euthanatized 10 months after surgery for unrelated disease; 3 dogs were alive at writing (median follow-up: 20 months; range, 18-27 months) and all had a satisfactory functional and cosmetic outcome. CONCLUSIONS: Reconstruction of ventral thoracic wall defects using a latissimus dorsi myocutaneous flap yields a functional, cosmetic outcome. CLINICAL RELEVANCE: A latissimus dorsi myocutaneous flap can be used as a successful 1-stage reconstructive technique for ventral thoracic wall defects.

Outcome of and complications associated with tube cystostomy in dogs and cats: 76 cases (1995-2006).

OBJECTIVE: To determine indications for cystostomy tube use in dogs and cats, complications associated with their use, and outcome of dogs and cats in which cystostomy tubes had been inserted. DESIGN: Retrospective case series. ANIMALS: 37 dogs and 39 cats. PROCEDURES: Information was obtained from medical records. Long-term follow-up information was obtained by use of a client questionnaire. RESULTS: Indications for cystostomy tube placement were bladder dysfunction, urinary tract rupture, obstructive urinary tract neoplasia, urinary diversion following urogenital surgery, obstructive urolithiasis, and feline lower urinary tract disease. Median time tubes were in place was 11 days, but duration of tube use was significantly longer for animals with bladder dysfunction than for animals with urinary tract trauma, urinary diversion, or urinary tract obstruction. Thirty-seven (49%) animals had tube complications. Development of complications was not significantly associated with species, age, body weight, duration of tube use, or tube type, except that animals were significantly more likely to develop complications following long-rather than short-term use. In 42 animals, the underlying condition resolved and the tube was removed; 22 animals died or were euthanatized with the tube in place. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that cystostomy tubes may be used for animals with various conditions related to problems with urine outflow. Nearly half the animals in the study developed complications related to the cystostomy tube, suggesting that potential complications should be discussed with owners prior to tube placement. However, most complications were easily resolved.

Association of portovenographic findings with outcome in dogs receiving surgical treatment for single congenital portosystemic shunts: 45 cases (2000-2004).

OBJECTIVE: To determine whether hepatic portal vascularity, as assessed by intraoperative mesenteric portovenography (IMP), is related to outcome in dogs undergoing attenuation of single congenital portosystemic shunts (CPSSs). DESIGN: Retrospective case series. ANIMALS: 45 dogs, each with a single CPSS, in which IMP was performed before and after temporary complete occlusion of the shunting vessel and that underwent complete (17 dogs) or partial (28 dogs) CPSS attenuation (surgery 1). PROCEDURES: Medical records were reviewed for signalment, clinical history, and bile acids stimulation test results. Intrahepatic portal vessel (IPV) opacification in pre- and postocclusion portovenograms was graded to determine whether the degree of opacification was correlated with the degree of shunt attenuation, clinical or biochemical factors, or long-term clinical outcome. In 17 of 28 dogs that had partial CPSS attenuation, these procedures were subsequently repeated (surgery 2) to achieve complete (14 dogs) or further partial (3 dogs) CPSS attenuation. RESULTS: Compared with preattenuation findings, IPV opacification increased significantly after partial or complete CPSS attenuation. The degree of IPV opacification before and after CPSS occlusion (surgery 1) was greater in dogs that tolerated complete versus partial CPSS attenuation and was correlated positively with age. The degree of IPV opacification following CPSS occlusion (surgery 1) was maximal in all dogs without encephalopathy and was correlated negatively with follow-up preprandial serum bile acids concentrations and positively with clinical improvement. CONCLUSIONS AND CLINICAL RELEVANCE: Data suggest that IMP can be used to assess changes in IPV blood flow and help predict outcome following attenuation of single CPSSs in dogs.