Clinical evaluation and surgical intervention for diaphragmatic eventration mimicking peritoneopericardial hernia in a cat

A 2-year-old spayed female British Shorthair cat presented with an increased frequency and duration of cough since infant period. Based on radiographic, ultrasonographic, and computed tomography findings, peritoneopericardial diaphragmatic hernia was considered so that repair surgery was planned. During celiotomy, lax diaphragm was identified instead of defect. Transabdominal diaphragmatic plication was performed to resolve lax diaphragm and to prevent recurrence by overlapping relatively normal part of diaphragm. Diagnosed with diaphragmatic eventration postoperatively, the cat showed improvement in clinical signs and imaging results. Transabdominal diaphragmatic plication is a suitable treatment; the patient maintained normally during a 14-month follow-up period.

Fatigue analysis of canine tracheal stents using the finite element method

This study aimed to evaluate fatigue of three stent designs when various forces are applied and perform a comparative analyses. A computer simulation using the finite element method was performed. In particular, we constructed a three-dimensional finite element model of nitinol stents with three designs (S6: single-woven wire, wire diameter: 0.006 inch; D6: double-woven wire, wire diameter: 0.006 inch, and D7: double-woven wire, wire diameter: 0.007 inch) that are used to treat canine tracheal collapse (TC). The stents were subjected to a 200 mmHg compression force, a pure torsion force in a perpendicular direction, and a bending-torsion force combining perpendicular and axial forces. The von Mises stress was calculated to evaluate the extent of stent displacement, and Goodman diagrams were plotted to compare fatigue life cycles. D7 exhibited a longer fatigue life compared to S6 and D6. Under compression, pure torsion, and bending-torsion forces, displacement was the smallest for D7, followed by D6 and S6. Similarly, the fatigue life was the longest for D7, followed by D6 and S6. S6 showed the greatest displacement when subjected to external forces; among stents designed using the same wire, D6 displayed less displacement than S6, and D7 exhibited superior fatigue life when subjected to varying degrees of force. This study showed that the structural stability and fatigue life of stents could be effectively compared using finite element method D7 has the greatest stability and structural rigidity under cyclic load.

Double-wire woven nitinol stent for treating dogs with refractory tracheal collapse: A case series

This retrospective case series describes the signalments, clinical signs, diagnostic test results, and postoperative complications obtained from the medical records of 10 client-owned dogs that underwent treatment for grade IV tracheal collapse using double-wire woven nitinol stents between October 2017 and September 2021. Respiratory signs resolved in all dogs immediately after tracheal stent placement. Mild to moderate stent fractures were identified in five dogs, of which two showed concurrent respiratory distress necessitating re-stenting after several months. Minor complications, such as stent migration, were absent. The double-wire woven nitinol stent optimised for the canine trachea showed favourable outcomes and minimal complications.

Case report: Adjuvant therapy with toceranib for an incompletely resected renal cell carcinoma with suspected pulmonary metastasis in a dog

Primary renal neoplasia is rare in humans and dogs, with renal cell carcinoma (RCC) being the most common form of this cancer. As RCC is often diagnosed at an advanced stage, pulmonary metastasis is frequently observed. Tyrosine kinase inhibitors (TKIs) are the standard adjuvant treatments for metastatic RCC in humans. Similarly, in veterinary medicine, recent trials have employed TKIs for early-stage RCC patients who underwent complete surgical resection and showed no distant metastasis. However, the use of TKIs has not yet been reported commonly in cases of advanced RCC with metastasis. This case study presents the first clinical outcomes of TKI therapy in a dog with incompletely resected RCC and metastasis. A 5-year-old spayed female Chihuahua was referred to our hospital with a right renal mass and multiple pulmonary nodules suspected to be metastases. A portion of the renal mass was surgically removed, and histopathological examination revealed RCC with a high mitotic index. Adjuvant chemotherapy was administered, owing to incomplete resection with suspected pulmonary metastasis. An anticancer drug response prediction test was conducted using patient tissues. Since toceranib showed the most favorable responsiveness, it was selected as a therapeutic agent. Toceranib was orally administered at a dosage of 2.27 mg/kg every 48 h. Regular medical records for potential adverse effects were obtained, including systemic blood pressure, complete blood count, serum biochemical examination, and urinalysis. After 2 weeks of toceranib therapy, partial remission of pulmonary nodules continued for 2 months. The patient did not experience any adverse effects of the anticancer drug during the 4-month follow-up period. However, the patient died from an unidentified cause 6 months after the initial detection of the renal mass. This report describes the use of toceranib in dogs with RCC. In the present case, the patient showed an initial response to chemotherapy, and despite the presence of several poor prognostic factors, the dog survived beyond the expected 3-month lifespan to 6 months. Notably, no adverse events were observed during treatment.

The biomechanical and biological effect of supercooling on cortical bone allograft

BACKGROUND

The need for a storage method capable of preserving the intrinsic properties of bones without using toxic substances has always been raised. Supercooling is a relatively recently introduced preservation method that meets this need. Supercooling refers to the phenomenon of liquid in which the temperature drops below its freezing point without solidifying or crystallizing.

OBJECTIVES

The purpose of this study was to identify the preservation efficiency and applicability of the supercooling technique as a cortical bone allograft storage modality.

METHODS

The biomechanical effects of various storage methods, including deep freezing, cryopreservation, lyophilization, glycerol preservation, and supercooling, were evaluated with the three-point banding test, axial compression test, and electron microscopy. Additionally, cortical bone allografts were applied to the radial bone defect in New Zealand White rabbits to determine the biological effects. The degree of bone union was assessed with postoperative clinical signs, radiography, micro-computed tomography, and biomechanical analysis.

RESULTS

The biomechanical properties of cortical bone grafts preserved using glycerol and supercooling method were found to be comparable to those of normal bone while also significantly stronger than deep-frozen, cryopreserved, and lyophilized bone grafts. Preclinical research performed in rabbit radial defect models revealed that supercooled and glycerol-preserved bone allografts exhibited significantly better bone union than other groups.

CONCLUSIONS

Considering the biomechanical and biological superiority, the supercooling technique could be one of the optimal preservation methods for cortical bone allografts. This study will form the basis for a novel application of supercooling as a bone material preservation technique.

Anti-Staphylococcal Activity of Ligilactobacillus animalis SWLA-1 and Its Supernatant against Multidrug-Resistant Staphylococcus pseudintermedius in Novel Rat Model of Acute Osteomyelitis

Osteomyelitis caused by staphylococcal infection is a serious complication of orthopedic surgery. Staphylococcus pseudintermedius is the main causative agent of osteomyelitis in veterinary medicine. Methicillin-resistant S. pseudintermedius (MRSP) has been reported in companion animals, especially dogs. Multidrug-resistant S. pseudintermedius is an emerging pathogen and has acquired antibiotic resistance against various commercial antimicrobial agents. New antimicrobial compounds are urgently needed to address antibiotic resistance, and the development of novel agents has become an international research hotspot in recent decades. Antimicrobial compounds derived from probiotics, such as bacteriocins, are promising alternatives to classical antibiotics. In this study, the antibacterial activities of Ligilactobacillus animalis SWLA-1 and its concentrated cell-free supernatant (CCFS) were evaluated in vitro and in vivo. The CCFS of this bacterium showed no toxicity against osteoblast and myoblast cells in vitro, while significantly inhibiting the multidrug-resistant S. pseudintermedius KUVM1701GC strain in a newly established rat model. The CCFS significantly inhibited multidrug-resistant staphylococci both in vitro and in vivo. This suggests that CCFS derived from L. animalis SWLA-1 has potential as an alternative to classic antibiotics for staphylococcal infections in dogs.

Long-term adjuvant metronomic chemotherapy in a dog with recurrent maxillofacial osteosarcoma

Osteosarcoma (OSA) is the most common malignant bone tumour in dogs; however, OSA of the maxilla is uncommon compared to appendicular OSA. Oral melanoma also commonly occurs in dogs with frequent distant metastasis. The role of adjuvant chemotherapy has been questioned in maxillary OSA and melanoma. A 17-year-old English Cocker Spaniel was referred with a growing mass on the right maxilla and a right lower lip mass. Osteosarcoma was diagnosed after partial maxillectomy, and the right lower lip mass was diagnosed as oral melanoma. Metronomic chemotherapy (MC) was performed, and the number of doses was tapered due to side effects at 5 weeks after initiation of MC. After 130 weeks of MC, chemotherapy was suspended due to kidney disease. After the suspension of chemotherapy, findings suggesting recurrence and metastasis were detected. The dog suddenly died 193 weeks after surgery, which was 8-14 times longer than the expected survival time. To the best of our knowledge, this is the first case report of successful long-term combination therapy, including surgery and MC, in a dog with maxillary OSA and lip melanoma. Our results show that the survival time can be greatly extended if MC is performed with proper management.

A rabbit model of tracheal collapse for optimal self-expanding metal stents

Investigating the characteristics of tracheas can help the understanding of diseases related to the trachea, particularly tracheal collapse (TC) in dogs. This study aimed to compare the mechanical properties of tracheas from New Zealand White (NZW) rabbits and dogs and to introduce a method for inducing a model of TC in the normal trachea. Tracheal samples were obtained from NZW rabbit cadavers (n=5) weighing 3.62-3.92 kg and from dog cadavers (n=5) weighing 2.97-3.28 kg. Three live NZW rabbits weighing 3.5-4.0 kg were used to establish the model. The radial forces of both sample sets were measured using a digital force gauge and statistically compared. Subsequently, TC was surgically induced in three female NZW rabbits by physically weakening their tracheal cartilage under general anesthesia. Their clinical signs were monitored for 3 months, and radiographic examinations were performed monthly for 3 months. The mean radial forces of the two sample sets were comparable (P >0.05). The clinical signs, radiographic examinations, and macroscopic examinations were all comparable to those of dogs with TC. The cadaveric study between the rabbits and dogs demonstrated that the surgically induced rabbit model of TC is an excellent candidate for the experimental study of dogs with TC. This study also provides a reference of tracheal radial force values to enable selection of appropriate mesh types and wire diameters of self-expanding metal stents.

Adjuvant therapy with toceranib for hepatocellular carcinoma and cholangiocarcinoma in a Pomeranian

A 10-year-old spayed female Pomeranian dog was referred for hepatic mass evaluation. Blood tests revealed mildly elevated alkaline phosphatase activities. Computed tomography revealed a mass with multiple nodules on the right hepatic medial lobe adjacent to the caudal vena cava; histopathology confirmed mixed hepatocellular carcinoma (HCC) and cholangiocarcinoma (CC). Because of incomplete resection, adjuvant therapy was recommended. As tumour cells showed PDGFR-α, c-Kit, and FGFR1 overexpression, the anticancer effect of tyrosine kinase inhibitors was evaluated on the cells; toceranib was the most effective and was administered starting with an extra-labelled dose. The dog remained stable for 2.3 years with mild adverse effects. To our knowledge, this is the first successful clinical application of toceranib in a dog with mixed HCC-CC.

Case report: Toceranib as adjuvant chemotherapy in a dog with incompletely resected combined hepatocellular-cholangiocarcinoma

An 11-year-old intact female mixed breed dog was presented with abdominal distention and elevated hepatic enzyme levels. Computed tomography revealed a multicystic hepatic mass at the left medial lobe adjacent to the diaphragm and caudal vena cava. The mass was surgically removed with partial hepatectomy, but it could not be removed completely because of adhesion to the diaphragm. The tissue was submitted for histopathologic evaluation, and the patient was diagnosed with stage IIIA combined hepatocellular-cholangiocarcinoma (cHCC-CC). Considering the residual tumor tissue from incomplete surgical excision, adjuvant chemotherapy was recommended. Tumor tissue obtained from the patient was assessed using an anticancer drug response prediction test, and the results showed that toceranib phosphate was the most effective chemotherapeutic agent for this patient. Toceranib was initiated (3.1 mg/kg, PO, q48 h), and routine adverse effect assessment, including systemic blood pressure measurement, complete blood count, serum biochemical evaluations, and urinalysis were performed at two-week intervals for the first 2 months and every 2 months thereafter. Radiography and ultrasonography were conducted at one-month intervals for the first two months and then every 2 months subsequently. Concurrent hyperadrenocorticism was managed with trilostane (1 to 5 mg/kg, PO, q12h). The patient showed no critical adverse effects of chemotherapy, obvious recurrence, or metastasis. The response to toceranib was assessed as a partial response, and the patient is still alive over 23 months after tumor excision. This is the first case report describing chemotherapy for a dog with cHCC-CC.

Comparison of three different self-expanding metal stents using rabbit models for the treatment of tracheal collapse

Purpose:

To identify an optimal self-expandable metallic stent (SEMS) and verify whether a mechanically superior SEMS would result in better clinical outcomes in the treatment of tracheal collapse.

Methods:

We selected three SEMS (n = 8 each), including an S-type stent with a wire diameter of 0.006 inches (S6) and two D-type stents with wire diameters of 0.006 (D6) and 0.007 inches (D7). Twenty-four New Zealand White rabbits were divided into three equal groups. After the stents were deployed, the clinical signs were recorded daily, and radiographic examinations were performed monthly. All rabbits were euthanized after three months.

Results:

Two rabbits with S6 stents and one rabbit with a D7 stent died within three months because of stent migration or pneumonia. All rabbits with D6 stents survived for three months. On histological examination, the D6 group had the lowest inflammation score.

Conclusions:

Both clinically and histopathologically, the results with D-type stents with a wire diameter of 0.006 inches were superior to those of the other groups (p = 0.001). The use of an optimal intraluminal stent may improve the long-term clinical outcomes in the treatment of tracheal collapse in dogs.

Evaluation of mechanical properties of self-expanding metal stents for optimization of tracheal collapse in dogs

The objective of this study was to compare the mechanical properties, including radial, axial, and bending forces, of various self-expanding metal stents with different wire diameters. The radial forces generated through longitudinal and cylindrical compression, along with axial and bending forces, were measured and used to evaluate the mechanical properties of 3 types of self-expanding metal stents (n = 3); the most suitable type was further assessed with 4 different wire diameters (n = 3). The D-type stent (double-wire woven uncovered nitinol stent) had the highest radial force and the lowest axial force and hence, was the most suitable for clinical use; however, its bending force was the lowest, corroborating the results of the axial force measurements. Therefore, the D-type stent was further evaluated using the following wire diameters: i) 0.127, ii) 0.152, iii) 0.178, and iv) 0.203 mm. When the wire diameter was increased by 0.025 mm, the measured radial, axial, and bending forces increased significantly. Thus, the adequate wire diameter should be determined based on the anatomical structure of stents. The mechanical properties of self-expanding stents should be considered in selecting the optimal design for tracheal collapse in dogs.

Use of coccygeal vertebra autograft and platelet-rich plasma for treating a distal radial nonunion fracture in a small-breed dog

A 4.3-kg, 11-month-old, spayed female poodle was presented for treatment of a right radio-ulnar nonunion fracture. Clinical history included failed surgical correction of a radius fracture with internal fixation 1 mo before presentation. Radiographic examination revealed a 1.5-cm lytic lesion on the right distal radius. Surgery was planned with a coccyx autograft and platelet-rich plasma. A 2.8-cm-long bone defect was created, and the lytic lesion was removed. Caudectomy was performed; the 6th and 7th coccygeal bones were harvested, placed into the defect, and fixed to the radius with a locking plate. Remnants of coccygeal bone were ground, mixed with platelet-rich plasma, and used to fill the bone defects. There was no evidence of nonunion or delayed union at the 18-month follow-up examination. Key clinical message: Based on the study findings, we inferred that a coccyx autograft and platelet-rich plasma can be used for successful reconstruction of a distal radial defect.

Establishment of Canine Transitional Cell Carcinoma Cell Lines Harboring BRAF V595E Mutation as a Therapeutic Target

Transitional cell carcinoma (TCC) is the most common malignant tumor of the canine urinary tract and tends to have a poor prognosis due to its invasive potential. Recent studies have reported that up to 80% of canine urothelial carcinoma has the BRAF V595E mutation, which is homologous to the human V600E mutation. Activating the BRAF mutation is an actionable target for developing effective therapeutic agents inhibiting the BRAF/mitogen-activated protein kinase (MAPK) pathway in canine cancer as well as human cancer. We established novel canine TCC cell lines from two tumor tissues and one metastatic lymph node of canine TCC patients harboring the BRAF V595E mutation. Tumor tissues highly expressed the BRAF mutant and phosphorylated extracellular signal-related kinases (ERK)1/2 proteins. The derived cell lines demonstrated activated MAPK pathways. We also evaluated the cell lines for sensitivity to BRAF inhibitors. Sorafenib, a multiple kinase inhibitor targeting RAF/vascular endothelial growth factor receptor (VEGFR), successfully inhibited the BRAF/MAPK pathway and induced apoptosis. The established canine TCC cell lines responded with greater sensitivity to sorafenib than to vemurafenib, which is known as a specific BRAF inhibitor in human cancer. Our results demonstrated that canine TCC cells showed different responses compared to human cancer with the BRAF V600E mutation. These cell lines would be valuable research materials to develop therapeutic strategies for canine TCC patients.

Case Report: Trans-Articular External Skeletal Fixation of the Hip for a Highly Comminuted Juxta-Articular Fracture of the Proximal Femur Caused by Gunshot Injury in a Cat

This report describes a novel surgical technique for trans-articular external skeletal fixation (TA-ESF) of the hip to stabilize a rare, highly comminuted juxta-articular fracture of the proximal femoral segment involving the metaphysis and diaphysis in a cat. A 2-year-old, castrated male, Korean shorthair cat was admitted for a left femoral fracture caused by gunshot injury. Radiographs and computed tomography (CT) scans revealed a highly comminuted proximal femoral diaphyseal fracture that involved the femoral neck and the greater trochanter. The left femoral head was intact on CT. Under fluoroscopic guidance, an intramedullary Steinmann pin was placed to align the femur, and five positive-profile, end-threaded pins were placed in the left hemipelvis and distal femur. A triangulated frame of connecting bars was constructed using Steinmann pins and epoxy resin for TA-ESF. This secured the pins placed in the pelvis and femur as well as the intramedullary pin, providing proximal femoral stabilization by trans-articular fixation of the hip. The cat began placing weight on the left pelvic limb 4 days postoperatively, and progressively obtained near-normal limb function by day 112. The TA-ESF was partially dismantled to a linear tie-in construct on day 64 and was completely removed on day 161. Final radiographs on day 161 revealed lack of bone healing in the proximal segment, especially femoral head and neck, despite functional recovery of the injured leg. At one year postoperatively, the cat had normal limb function without any noticeable complications. On follow-up 29 months after surgery, the owner reported that the cat had normal limb function without any noticeable complications. Despite insufficient bone healing in the cat, TA-ESF of the hip allowed for satisfactory functional recovery of this challenging juxta-articular fracture of the proximal femur, which was not amenable to stabilization with a traditional non-load-sharing fixation system.

Surgical Reconstruction of the Metatarsal Pad Using Nonweight-Bearing Surfaces of the Footpads in a Dog

A 9 yr old mixed-breed dog weighing 6.3 kg was presented with degloving injuries and multiple lacerations on the footpads of both hindlimbs. After amputation of the left hindlimb and debridement of the necrotic footpads on the right hindlimb, the remaining pads were insufficient for ambulation. The complete carpal pads and the peripheral, nonweight-bearing portions of the second and fifth digital pads of both forelimbs were harvested for pad grafting. All segments were sutured on the cutaneous trunci muscle in the predetermined location of the right abdominal wall for the pouch flap. After detaching the flap, the grafted segments were gradually strengthened, and the dog was able to regain ambulation. When considering pad grafting, the entire carpal pad and crescent-shaped segments from the nonweight-bearing surfaces of digital pads are excellent candidates for free grafts without compromising the ambulation of other limbs.

Case Report: Surgical Correction of a Cystic Duct Stump Leakage Following Cholecystectomy Using an Autologous Rectus Sheath Graft in a Dog

A 2.7 kg, 13-year-old, castrated male Yorkshire Terrier was presented with bile peritonitis after cholecystectomy. Exploratory coeliotomy to identify and correct bile leakage revealed that the transected end of the cystic duct was open with no in-situ ligatures or vascular clips. The residual cystic duct stump was too short to ligate or seal directly. An autologous rectus sheath graft, harvested from the internal leaf of the rectus sheath, was used to patch the cystic duct stump. The graft was secured over the open duct using several simple interrupted sutures and covered with an omentalization. The clinical signs resolved after surgery, except for a transient increase in hepatobiliary enzyme levels and intrahepatic bile duct dilatation. The enzyme levels returned to near normal on day 25 after surgery. No intrahepatic bile duct dilatation was detected on day 55 after surgery. The owner was contacted for 3 years post-operatively and reported that the dog remained healthy without any long-term complications. Grafting using autologous rectus sheath can be used to treat cystic duct stump leakage that cannot be managed with direct closure using traditional modalities due to spatial constraints.

Comparative evaluation of canine cadaver embalming methods for veterinary anatomy education

Formalin-embalmed cadavers have been extensively used to teach anatomy. Although they ensure the preservation of anatomical structures without microbial contamination, they are considerably rigid and cannot be used to study the joint and muscle movements. Moreover, formalin irritates the eyes and airways and is carcinogenic on chronic exposure. To overcome the disadvantages of formalin-fixed cadavers, we investigated the usefulness of alternative embalming methods using saturated salt solution (SS) and Thiel's solution (TS). We compared the three solutions based on the following parameters: cost of the embalming solution; preservation of anatomical structure, color, flexibility, and texture; and microbial contamination. Convenience of anatomical structure identification and preferences in anatomical laboratory practice were evaluated using questionnaires answered by veterinary undergraduate students. Cost of the embalming solution was the lowest for formalin solution (FS) and most expensive for TS. All cadavers were successfully preserved without significant putrefaction and were useful for teaching veterinary anatomy. Cadavers embalmed with SS or TS were superior in facilitating joint and muscle movement. Compared to FS, the color and texture of muscles and internal organs were similar to those of living animals and there was no irritating and offensive smell in SS and TS cadavers. Students preferred the SS and TS cadavers for their usefulness in identification of anatomical structures, highlighting their usefulness in veterinary anatomy education.

Parotid Duct Ectasia in a Dog

A 3yr old spayed female Brittany was referred with a cylindrical mass on the right side of her face. Three months earlier, a small stone embedded in the right parotid duct was noted and removed through a ductal incision by the referring veterinarian. At referral, the dog's general physical condition was normal except for a cylindrical mass on the right cheek. Skull radiographs showed a possibly retained sialolith or dystrophic mineralization within the previous surgical site. Aspiration of the mass yielded a thick, yellow/tan, mucopurulent fluid. Cytology of the fluid demonstrated degenerative neutrophils without bacteria. The cylindrical mass was excised with a carbon dioxide laser. The caudal end of the mass was connected to the parotid salivary gland and the rostral one-third of the mass tapered to a point. The caudal end of the mass was ligated with 3-0 polydioxanone and excised immediately rostral to the ligation. Histopathology revealed that the mass was parotid duct ectasia. The dog completely recovered with some mild temporary facial paresis and had no recurrence of parotid duct ectasia at 4 mo follow-up. The case report describes a dog with an unusual parotid salivary duct ectasia caused by parotid duct sialolith removal.

Reconstruction of urethral defects using a fascia lata autograft in a dog

A castrated male Shih-Tzu dog was presented for evaluation of urine leakage after urethrotomy. A fistula with urine leakage was identified in the perineal region. On retrograde urethrography, the contrast extravasated from the penile urethra into the subcutaneous tissue of the perineum. Urine leakage with urethrocutaneous fistula was diagnosed. During surgery, the disrupted urethra wall and two urethral defects were identified. A fascia lata autograft was used, rather than primary repair of the urethra. Two pieces of fascia lata were harvested and sutured to the urethral defects. The fistula was treated with debridement and drainage. No evidence of urine leakage and dysuria was noted 6 months postoperatively. Thus, this case report describes successful urethral reconstruction using a fascia lata autograft.

Splenic malignant fibrous histiocytoma with concurrent hypertension and epistaxis in an Alaskan malamute dog

Background

Malignant fibrous histiocytoma has been uncommonly described in dogs. Several extranasal neoplasias have been reported to result hypertensive epistaxis. There are, however, no published case reports of extranasal malignant fibrous histiocytoma with concurrent hypertension and epistaxis in dogs.

Case presentation

A 10-year-old dog presented with a spontaneous massive epistaxis persisting for 5 days. The dog exhibited unstable hypertension, which was considered as a cause of epistaxis. The complete blood count, prothrombin time, and activated partial thromboplastin time were within the reference limits, and other systemic examination showed no abnormalities except for a splenic mass occupying more than one third of the abdomen. Histologic examination of the resected spleen revealed the characteristic features of a malignant fibrous histiocytoma. One week after splenectomy, the hypertension and epistaxis resolved clinically and did not recur on the 5-month follow-up.

Conclusions

The dog’s blood pressure and epistaxis normalized after malignant fibrous histiocytoma resection suggesting that hypertensive epistaxis may be a rare manifestation of canine malignant fibrous histiocytoma.

Successful management of lymphangiosarcoma in a puppy using a tyrosine kinase inhibitor

A puppy was diagnosed with lymphangiosarcoma associated with lymphedema based on lymphography and histopathology. The lesions resolved after toceranib therapy, and the dog remains in remission 1 year later. This is the first report of a successful outcome following oral toceranib as first-line therapy for lymphangiosarcoma in a dog.

Post-operative corticosteroid irrigation for chronic rhinosinusitis after endoscopic sinus surgery: A meta-analysis

BACKGROUND

Recently, topical steroid therapy delivery using high-volume sinonasal irrigations has been used more frequently, following endoscopic sinus surgery (ESS), to improve drug delivery into the paranasal sinuses.

OBJECTIVE

The goal of this study was to perform a systematic review with meta-analysis of the efficacy of steroid nasal irrigation on post-operative management of Chronic rhinosinusitis (CRS) following ESS.

METHODS

Five databases (PubMed, SCOPUS, Embase, Web of Science, and the Cochrane database) from inception to March 2017 were independently reviewed by two researchers. Studies that scored CRS endoscopic findings and CRS-related quality of life (QOL) post-operatively before and after steroid nasal irrigation and that compared the effects of steroid nasal irrigation (treatment groups) with saline alone irrigation (control group) were included in the analysis.

RESULTS

Twelve studies (n = 360) met inclusion criteria. Steroid nasal irrigation significantly reduced the endoscopic score compared with pre-treatment values and also improved QOL. Adverse effects following steroid nasal irrigation such as increased intraocular pressure (IOP) and hypothalamus-pituitary-adrenal (HPA) axis disturbance were not significant. However, compared with saline alone irrigation, the additional effects of steroid irrigation were not significant in the view of the endoscopic score and disease-specific QOL.

CONCLUSION

Although steroid nasal irrigation would not induce adverse effects related to systemic steroid absorption, the beneficial effects of additional steroids in saline irrigation were ambiguous in regard to endoscopic score and CRS-related QOL improvement compared with saline alone irrigation. However, further clinical trials with robust research methodologies should be conducted to confirm the results of this study.

Acute blindness in a dog with Acinetobacter-associated postencephalitic hydrocephalus

A 10-month-old male Welsh Corgi with a history of acute blindness underwent neuro-ophthalmological testing and magnetic resonance imaging (MRI). Vision testing revealed complete visual deficits but the electroretinograph and pupillary light reflex were normal in both eyes. The motor and sensory functions of the eyelids and eyes were also normal. The MRI revealed compression of the optic chiasm caused by severe ventriculomegaly in the lateral and third ventricles. Such lesions are associated with inflammatory stenotic lesions in the mesencephalic aqueduct. Moderate neutrophilic pleocytosis was observed during cerebrospinal fluid analysis and Acinetobacter lwoffii was isolated, leading to a diagnosis of Acinetobacter-positive obstructive hydrocephalus. This is the first reported case of culture-proven Acinetobacter-associated postencephalitic hydrocephalus with acute blindness in a dog.

Sterile Pyometra in Two Dogs

Two young dogs were referred to the Veterinary Medical Teaching Hospital of Konkuk University, one for examination of vaginal discharge and the other after being hit by a car. Dog 1 exhibited a high neutrophil count on Gram-stained vaginal smears, marked leukocytosis on a complete blood count, and uterine enlargement on ultrasonography. In dog 2, a markedly enlarged right uterine horn containing echogenic debris was found incidentally on ultrasonography. A tentative diagnosis of pyometra was made in both cases and ovariohysterectomy was performed. Purulent material was collected from each uterine horn and submitted separately for aerobic and anaerobic bacterial culture; all culture results were negative. The white blood cell count revealed normal limits 2 days post operation in dog 1 and 4 days post operation in dog 2. Positive bacterial cultures are usually obtained from dogs with pyometra, and antibiotic selection is based on the results of culture and sensitivity testing in the event of failure of empiric antibiotic therapy. However, in the cases reported here, no bacterial growth was identified from the uterine samples despite the presence of purulent material. A short course of empiric antibiotic therapy was administered. This is the first known report describing sterile pyometra in dogs.

Surgical management of parotid salivary duct rupture secondary to non-iatrogenic trauma in a dog

A 3-year-old French bulldog presented for evaluation of recurrent swelling and a fistula on the right cheek after a dog fight. A large volume of serous fluids was identified on the wound immediately after atropine drops. A diagnosis of parotid salivary duct rupture secondary to trauma was made. On surgical exploration, the thickened proximal segment of the severed duct was identified and circumferentially double ligated with 3–0 silk. No evidence of swelling and normal appearance of the parotid salivary gland were identified 4 months postoperative recheck. No further problems were noted 10 months postoperatively phone-call. To the author’s knowledge, this is the first reported case of successful proximal parotid duct ligation of parotid salivary duct rupture secondary to non-iatrogenic trauma.

Clinical Outcomes of Surgically Managed Spontaneous Tumors in 114 Client-owned Dogs

Medical records of 139 tumors from 114 dogs that underwent surgery from May 2010 through March 2015 were retrospectively reviewed. Among 114 dogs, females (64.9%) were significantly more common than males (35.1%) (p<0.05). Dogs aged 6 to 10 years were more presented than non-tumor patients, however, there was no significant difference. The mean age (±SD) was 10.3±3.0 years. Although we found no significant difference of breed predisposition, the most common breed was Maltese (19.3%), followed by Shih-Tzu (14.0%), and Yorkshire terrier (13.2%). Proportional morbidity ratios (PMRs) of mammary gland, oral cavity, and skin tumors were high in Poodles, Yorkshire terriers, and Golden retrievers, respectively. Mammary gland (36.0%) was the most common site, followed by skin and soft tissues (12.2%), oral cavity (10.8%), and digestive organs (8.6%), but there was no significant difference. The objectives of surgery were curative surgery (86.2%), biopsy (4.9%), and palliative surgery (6.5%). In this study, 123 of 139 tumors had histopathological diagnoses. Adenocarcinoma was the most common type (n=24), followed by adenoma (n=17), soft tissue sarcoma (n=13), benign mixed tumor (n=5), and others (n=64). Recurrence or suspected metastasis was identified in 26 dogs. Median survival times of malignant mammary gland tumors, skin and subcutaneous tumors, and splenic tumors were 1,563.0±1,201.7, 469, and 128 days, respectively.

Intercostal thoracotomy in 20 dogs: muscle-sparing versus traditional techniques

The levels of pain, duration of approaching and closure, and surgical exposure associated with intercostal thoracotomy were compared between muscle-sparing and traditional techniques in 20 dogs. Postoperative pain was assessed based on numerical pain scores using behavioral observation, heart rate, respiratory rate, and wound palpation. Time for approaching and closure were measured, and the extent of intrathoracic organ exposure for the surgical procedures was described for each technique. There were significant differences in numerical pain scores at 2 h as well as 1, 2, 3, 4, 5, 6, and 7 days after surgery between the two groups (p < 0.0001). There was no significant (p = 0.725) difference in times for approaching and closure between the two groups. Compared to the traditional method, the muscle-sparing technique also achieved the desired exposure without compromising exposure of the target organs. Our results suggest that the muscle-sparing technique is more effective than the traditional method for providing a less painful recovery during the first 7 days after intercostal thoracotomy. Additionally, the muscle-sparing technique is as effective as the traditional modality for providing an appropriate time for approaching and closure during intercostal thoracotomy as well as adequate organ exposure for the surgical procedures.

Primary cranial mediastinal hemangiosarcoma in a young dog

Primary cranial mediastinal hemangiosarcomas are uncommon tumors. A 30-kg, 2-year-old, intact female German shepherd was presented for evaluation of cachexia and respiratory distress of a few days’ duration. Lateral radiographic projection of the thorax revealed significant pleural effusion. Computed tomography revealed a cranial mediastinal mass effect adjacent to the heart. On surgical exploration, a pedunculated mass attached to the esophagus, trachea, brachiocephalic trunk, left subclavian artery and cranial vena cava without attachment to the right atrium and auricular appendage was removed and debrided by use of blunt dissection and dry gauzes, respectively. Histopathology results described the cranial mediastinal mass as hemangiosarcoma. At 8 months and 5 days post-operatively, the patient died. Primary cranial mediastinal hemangiosarcomas, although a seemingly rare cause of thoracic pathology in young dogs, should be considered in the differential diagnosis for pleural effusion and soft tissue mass effect in the cranial mediastinum. This is the first case report in a dog to describe primary cranial mediastinal hemangiosarcoma.

Comparison of techniques for transdiaphragmatic thoracic drainage after diaphragmatic defect closure in dogs: a cadaveric study

Four thoracic evacuation techniques for pneumothorax elimination after diaphragmatic defect closure were compared in 40 canine cadavers. After creating a defect in the left side of the diaphragm, thoracic drainage was performed by thoracostomy tube insertion through the defect and a small (DD-SP) or large (DD-LP) puncture created in the caudal mediastinum, or through both the diaphragmatic defect and intact contralateral diaphragm with a small (DI-SP) or large (DI-LP) puncture in made in the caudal mediastinum. Differences in intrapleural pressure (IPP) between the right and left hemithoraxes after air evacuation along with differences in IPP before making a defect and after air evacuation in each hemithorax were calculated. A difference (p ≤ 0.0011) in IPP between the left and right hemithoraxes after air evacuation as well as before making a defect and after air evacuation in the right hemithorax was detected for the DD-SP group. No significant differences (p ≥ 0.0835) were observed for the DI-LP, DD-LP, or DI-SP groups. Creation of a large mediastinal puncture or thoracic evacuation through both a diaphragmatic defect and intact contralateral diaphragm can facilitate proper pneumothorax elimination bilaterally after diaphragmatic defect closure in dogs with a small puncture in the caudal mediastinum.

Traumatic triceps tendon avulsion in a dog: magnetic resonance imaging and surgical management evaluation

We report here the clinical presentation, magnetic resonance imaging (MRI) findings and successful surgical management associated with triceps tendon avulsion in a dog. A definitive diagnosis of triceps tendon avulsion was made based on MRI with evidence of displacement of the triceps tendon. Surgical correction of triceps tendon avulsion was performed with two horizontal mattress sutures using polyester and two tunnels drilled in the olecranon to reattach the tendon to the proximal olecranon. At 9 months, there was no evidence of lameness on the left thoracic limb. This is the first case report to describe MRI evaluation for the diagnosis of the triceps tendon avulsion.

Synovial hemangioma accompanied by cruciate ligament injury in a dog

We report here the clinical presentation and successful surgical management of synovial hemangioma accompanied by cruciate ligament injury in a dog. Surgical correction of cruciate ligament injury was performed after removing torn cruciate ligaments, synovial mass and masses attached to the ligaments and distal femoral articular cartilage. At 10 months, the dog has showed no evidence of recurrence in the stifle joint. Synovial hemangioma, although a seemingly rare cause of stifle joint pathology, should be considered in the differential diagnosis for cruciate ligament injury when a circumscribed intra-articular soft tissue mass is evident radiographically with cranial or caudal drawer motion. This is the first case report in a dog to describe synovial hemangioma accompanied by cruciate ligament injury.

Hypertrophic osteopathy associated with pulmonary adenosquamous carcinoma in a dog

A six-year-old intact female Maltese dog weighing 3.8 kg presented with a history of mild lameness and swelling on both forelimbs. Radiographic and computed tomographic views revealed an extensive periosteal reaction in all four limbs and a large round mass on the right middle lung lobe. A total lobectomy was performed and pulmonary adenosquamous carcinoma was histologically confirmed. A diagnosis of hypertrophic osteopathy (HO) secondary to a lung tumor was made. Periosteal proliferation decreased significantly after surgery; however, there was evidence of dyspnea, mass recurrence, and periosteal reaction three months post-operatively. This is the first case report of pulmonary adenosquamous carcinoma with HO in a dog in which we describe clinical, imaging, surgical, and histological findings.

Surgical correction of an aberrant right subclavian artery in a dog

A diagnosis of an aberrant right subclavian artery was made in a 3-month-old Boston terrier. Surgical correction was performed after confirming adequate collateral circulation. Reports of surgical correction and evaluation of the perioperative thoracic limb blood pressure are rare in dogs.

Predictive value of intra-amniotic and serum markers for inflammatory lesions of preterm placenta

OBJECTIVE

To compare the relative predictive values of amniotic fluid (AF) matrix metalloproteinase-9 (MMP-9), interleukin-6 (IL-6), and serum C-reactive protein (CRP) for histologic chorioamnionitis and intra-amniotic infection in women with preterm labor or preterm premature rupture of membranes (PROM).

STUDY DESIGN

This retrospective cohort study included 99 consecutive women with preterm labor or preterm PROM (21-35 weeks' gestation) who delivered within 72 h of transabdominal amniocentesis. The AF was cultured for aerobic and anaerobic bacteria and for genital mycoplasmas and was assayed for MMP-9 and IL-6 levels. Maternal serum CRP was measured immediately after amniocentesis. The placentas were examined histologically.

MAIN OUTCOME MEASURES

histologic chorioamnionitis and intra-amniotic infection.

RESULTS

The prevalence of histologic chorioamnionitis and a positive AF culture was 44% (44/99) and 28% (28/99), respectively. In predicting intra-amniotic infection, AF MMP-9 had a significantly higher area under the curve (AUC: 0.94 [95% CI, 0.87-0.98]) than AF IL-6 (0.87 [95% CI, 0.78-0.84]; P < 0.05) and serum CRP (0.76 [95% CI, 0.66-0.84]; P < 0.001) and a higher sensitivity and specificity than serum CRP (P < 0.01, respectively). However, in predicting histologic chorioamnionitis, there were no significant differences in AUCs among the three tests (AF MMP-9: 0.78 [95% CI, 0.68-0.85]; AF IL-6: 0.76 [95% CI, 0.66-0.84]; serum CRP: 0.76 [95% CI, 0.66-0.84]). In a sub-analysis of 71 women without intra-amniotic infection, histologic chorioamnionitis was associated with an elevated serum CRP level (P < 0.05), but not with the level of AF IL-6 or MMP-9 (P = 0.232 and P = 0.402, respectively).

CONCLUSIONS

The AF MMP-9 has a better overall diagnostic performance than the AF IL-6 and maternal serum CRP in predicting intra-amniotic infection. However, the serum CRP level obtained up to 72 h before delivery appears to be an important marker for early identification of histologic chorioamnionitis in women without intra-amniotic infection.

Clinical effect of additional electroacupuncture on thoracolumbar intervertebral disc herniation in 80 paraplegic dogs

The clinical efficacy of electroacupuncture and acupuncture in combination with medication for the treatment of thoracolumbar intervertebral disc herniation was investigated in paraplegic dogs with intact deep pain perception. To evaluate the additional effect of electroacupuncture, dogs treated with conventional medicines alone were compared to dogs treated with electroacupuncture and acupuncture and conventional medicine. Medical records of 80 dogs were reviewed for this investigation and classified into two groups undergoing different treatment methods: (1) treatment with conventional medicine alone (Group C, n = 37) and (2) treatment with conventional medicine combined with electroacupuncture and acupuncture (Group CE, n = 43). Prednisone was the conventional medicine and electroacupuncture was applied at GV07 and GV02-1 at 0.5-2.5 mV, mixed Hz of 2 and 15 Hz for 25-30 min. Acupuncture was performed locally at urinary bladder meridian points near the lesion, and bilaterally distantly at GB30, GB34, and ST36. Treatment efficacy was evaluated by post-operative neurologic function, ambulation, relapse, complication, and urinary function. Ambulation recovery was more prevalent in Group CE than Group C (p = 0.01) and recovery of ambulation and back pain relief time was shorter in Group CE compared to Group C (p = 0.011 and 0.001, respectively). Relapse rate was significantly lower in Group CE (p = 0.031). The results suggest that a combination of electroacupuncture and acupuncture with conventional medicine is more effective than conventional medicine alone in recovering ambulation, relieving back pain, and decreasing relapse. Electroacupuncture and acupuncture is thus a reasonable option for the treatment of intervertebral disc herniation in paraplegic dogs with intact deep pain perception.

Bilateral ureteral ectopia with renal dysplasia and urolithiasis in a dog

A 7-month-old, 4.3-kg, spayed female bichon frise was referred for evaluation of chronic urinary incontinence. Abdominal radiographs revealed calculi within the right kidney and ureter. An ultrasound revealed a small right kidney. An abdominal computed tomography scan with contrast revealed that the left ureter was extramurally ectopic, inserting into the proximal urethra. A right intramural ectopic ureter was identified during cystotomy. Ureteronephrectomy was performed on the right, and ureteroneocystostomy was performed on the left. A telephone conversation with the owner 4 months after surgery revealed that the dog exhibited no evidence of urine dribbling, and urinary continence was maintained well on phenyl-propanolamine (1.75 mg/kg orally q 12 hours). This is the first report of successful surgical management of bilateral ureteral ectopia with concurrent, unilateral, renal dysplasia and urolithiasis.

Surgical correction of pectus excavatum in two cats

Two sexually intact male Bengal cats, one a 4-month-old weighing 2.8 kg and the other, a 3-month-old weighing 2.0 kg, were presented to the University of Missouri-Columbia Veterinary Teaching Hospital for evaluation of respiratory distress. On initial presentation, both cats were dyspneic, exercise intolerant, and had marked concave deformation of the caudal sternum. Surgical correction of pectus excavatum was performed using a cylindrical external splint and U-shaped external splint. Post-operative thoracic radiography revealed that there was decreased concavity of the sternum and increased thoracic height at the level of the caudal sternebrae in both cats.

The role of nitric oxide in ocular surface diseases

For the first time, the current series of studies provide a possible pathophysiologic mechanism of NO-induced ocular surface disease. NO is present in tear and aqueous humor and is suspected of having an important physiological role in maintaining normal homeostasis of the ocular surface. NO concentrations are higher in aqueous humor compared to tears, though some variability exists between different species. When inflammation was induced by PTK wounding or LPS, three forms of NOS expression were seen in corneal cells. Each isoform of NOS was expressed uniquely according to the specific location of inflammation. When concentrations of NO peaked, the levels of iNOS were markedly increased in fibroblasts and inflammatory cells. The correlation between NO and inflammation was confirmed by treatment with NOS inhibitor, which abrogated the amount of both NO and inflammation. The tissue damage by NO was measured by nitrotyrosine formation. Damage was detected mainly in inflammatory cells, especially those localized in and around the limbal vessel. It is likely that expression of iNOS in limbal fibroblasts has other roles related to survival of limbal stem cells and fibroblasts as well. Because the main source of NO are fibroblasts, we were able to determine the effect of various concentrations of NO on cell viability using a fibroblast culture system. Cell viability increased in dose dependent manner from 10 microM to 500 microM of the NO generator SNAP, but decreased at concentrations above 1000 microM, suggesting that the in vivo mechanism of cell death was indirect, through specific biologic pathways. Therefore, the pathophysiological mechanism of NO action is bimodal with a toxicological component in ocular surface diseases. Furthermore, its concentration and interaction with other oxygen mediators appear to vary depending on the degree of inflammation.

Identification of the GTP binding site of human glutamate dehydrogenase by cassette mutagenesis and photoaffinity labeling

It has been reported that the hyperinsulinism-hyperammonemia syndrome is caused by mutations in glutamate dehydrogenase (GDH) gene that affects enzyme sensitivity to GTP-induced inhibition. To identify the GTP binding site(s) within human GDH, mutant GDHs at Tyr-266 or Lys-450 position were constructed by cassette mutagenesis. More than 90% of the initial activities were remained at the concentration of GTP up to 300 microm for the Lys-450 mutant GDHs regardless of their size, hydrophobicity, and ionization of the side chains, whereas the wild type GDH and the Tyr-266 mutant GDHs were completely inhibited by 30 microm GTP. The binding of GTP to the wild type GDH or the mutant GDHs was further examined by photoaffinity labeling with 8-[gamma-(32)P]azidoguanosine 5'-triphosphate (8-N(3)-GTP). Saturation of photoinsertion with 8-N(3)-GTP occurred apparent K(d) values near 20 microm for the wild type GDH or the Tyr-266 mutant GDH, and the photoinsertion of 8-N(3)-[gamma-(32)P]GTP was significantly decreased in the presence of 300 microm GTP. Unlike the wild type GDH or the Tyr-266 mutant GDH, less than 10% of photoinsertion was detected in the Lys-450 mutant GDH, and the photoinsertion was not affected by the presence of 300 microm GTP. The results with cassette mutagenesis and photoaffinity labeling demonstrate selectivity of the photoprobe for the GTP binding site and suggest that Lys-450, but not Tyr-266, is required for efficient binding of GTP to GDH. Interestingly, studies of the steady-state velocity showed that both the wild type GDH and the Tyr-266 mutant GDHs were inhibited by ATP at concentrations between 10 and 100 microm, whereas less than 10% of the initial activities of the Lys-450 mutant GDHs were diminished by ATP. These results indicate that Lys-450, but not Tyr-266, may be also responsible for the ATP inhibition; therefore, ATP bound to the GTP site.

Effects of ADP on different inhibitory properties of brain glutamate dehydrogenase isoproteins by perphenazine

Incubation of glutamate dehydrogenase isoproteins (GDH I and GDH II) from bovine brains with perphenazine resulted in a time-dependent loss of enzyme activity. 2-Oxoglutarate and NADH, separately or together, gave partial but not complete protection against the inhibition. Although there were no detectable differences between GDH I and GDH II in inhibition by perphenazine in the absence of ADP, the sensitivities to the inhibition by the drug were significantly distinct for the two isoproteins in the presence of ADP. Low concentrations of ADP (0.05-0.20 mM) did not interfere with the inhibition of GDH I and GDH II by perphenazine. However, in the presence of high concentrations of ADP (0.5-1.0 mM), inhibitory effects of perphenazine on GDH isoproteins were significantly diminished as determined by enzyme kinetics and quantitative affinity chromatography on perphenazine-Sepharose. GDH I was more sensitively reacted with ADP than GDH II on the inhibition by perphenazine. Since physiological ADP levels can vary from 0.05 to > 1.0 mM depending on the rate of oxidative phosphorylation, our results suggest a possibility that two types of GDHs are differently regulated by the antipsychotic actions of perphenazine depending on the physiological concentrations of ADP. GTP and L-leucine, other well-known allosteric regulators, did not affect the inhibitory actions of perphenazine on bovine brain GDH isoproteins.

Cassette mutagenesis of lysine 130 of human glutamate dehydrogenase. An essential residue in catalysis

It has been suggested that reactive lysine residue(s) may play an important role in the catalytic activities of glutamate dehydrogenase (GDH). There are, however, conflicting views as to whether the lysine residues are involved in Schiff's base formation with catalytic intermediates, stabilization of negatively charged groups or the carbonyl group of 2-oxoglutarate during catalysis, or some other function. We have expanded on these speculations by constructing a series of cassette mutations at Lys130, a residue that has been speculated to be responsible for the activity of GDH and the inactivation of GDH by pyridoxal 5'-phosphate (PLP). For these studies, a 1557-bp gene that encodes human GDH has been synthesized and inserted into Escherichia coli expression vectors. The mutant enzymes containing Glu, Gly, Met, Ser, or Tyr at position 130, as well as the wild-type human GDH encoded by the synthetic gene, were efficiently expressed as a soluble protein and are indistinguishable from that isolated from human and bovine tissues. Despite an approximately 400-fold decrease in the respective apparent Vmax of the Lys130 mutant enzymes, apparent Km values for NADH and 2-oxoglutarate were almost unchanged, suggesting the direct involvement of Lys130 in catalysis rather than in the binding of coenzyme or substrate. Unlike the wild-type GDH, the mutant enzymes were unable to interact with PLP, indicating that Lys130 plays an important role in PLP binding. The results with analogs of PLP suggest that the aldehyde moiety of PLP, but not the phosphate moiety, is required for efficient binding to GDH.

Proteolytic processing of oligopeptides containing the target sequences by the recombinant tobacco vein mottling virus NIa proteinase

Tobacco vein mottling virus (TVMV) belongs to the potyviridae that consists of about 200 plant viruses. Potyviruses have RNA genomes of approximately 10,000 bases from which a single polyprotein is expressed from each virus upon infection. The NIa proteinase is known to process the polyprotein at seven distinct junctions between proteins. Kinetic constants were determined for the reactions of the recombinant TVMV NIa protease (27 kDa) with synthetic oligopeptides containing the sequences for the cleavage sites. For optimum activity, the substrate needs to have six amino acids (P6-P1) in the amino region and four (P1'-P4') in the carboxy region, including four conserved amino acids (V-R-F-Q) in P4-P1 positions. Mutation of any of four conserved amino acids to Gly made the substrate inert to the enzyme. Among the substrates, the oligopeptides containing the sequences for junctions, P3-6K1, NIa (VPg-Pro), and NIa-NIb were not processed by the NIa protease. Those junctions have Glu at P3, Glu at P1, and Thr at P2. The implications of high substrate specificity and size dependence in polyprotein processing and viral replication are discussed.

Fluorometric assay of turnip mosaic virus NIa protease

Turnip mosaic virus (TuMV) NIa protease cleaves the viral polyprotein at seven distinct junctions out of nine. The amino acid sequences of the seven cleavage sites have three conserved amino acids, V, H, Q in positions P4, P2, P1, respectively. Small molecules as well as conjugated peptides were tested for proteolytic activity of the enzyme. None of small molecules tested, such as methylumbelliferyl-p-guanidinobenzoate, p-nitrophenyl-p'-guanidinobenzoate, p-nitrophenyl acetate, and methylumbelliferyl-N-acetylglutamate, were hydrolyzed. Ac-V-Y-H-Q-Mca was also not hydrolyzed. Intramolecularly quenched fluorogenic substrates Dns-P-V-Y-H-Q-A-W-NH(2) and Dns-P-V-Y-H-Q-W-NH(2) emitted fluorescence after addition of TuMV NIa protease. The proteolysis rate of Dns-P-V-Y-H-Q-A-W-NH(2) was comparable to that of the tetradecapeptide with an optimum sequence, but Dns-P-V-Y-H-Q-W-NH(2) was hydrolyzed at a slower rate, which was confirmed independently by HPLC analysis. These results suggest that intramolecularly quenched fluorogenic substrates can be used for the continuous assay of TuMV NIa protease.

Photoaffinity labeling of brain glutamate dehydrogenase isoproteins with an azido-ADP

The ADP binding site within two types of bovine brain glutamate dehydrogenase isoproteins (GDH I and GDH II) was identified using photoaffinity labeling with [alpha-32P]8-azidoadenosine 5'-diphosphate (8N3ADP). 8N3ADP, without photolysis, mimicked the activatory properties of ADP on GDH I and GDH II activities, although maximal activity with 8N3ADP was about 75% of maximal ADP-stimulated activity. Saturation of photoinsertion with [alpha-32P]8N3ADP occurred at around 40 approximately 50 microM photoprobe with apparent Kd values near 25 and 40 microM for GDH I and GDH II, respectively. Photoinsertion of [alpha-32P]8N3ADP was decreased best by ADP in comparison with other nucleotides. With the combination of immobilized aluminum affinity chromatography and reversed-phase high performance liquid chromatography, photolabel-containing peptides generated by tryptic digestion were isolated. This identified a portion of the adenine ring binding domain of GDH isoproteins as in the region containing the sequence, EMSWIADTYASTIGHYDIN. Photolabeling of the peptide was prevented over 90% by the presence of 1 mM ADP during photolysis, while other nucleotides could not reduce the amount of photoinsertion as effectively as ADP. These results demonstrate selectivity of the photoprobe for the ADP binding site and suggest that the photolabeled peptide with the residues Glu179-Asn197 is within the ADP binding domain of the brain GDH isoproteins.

Identification of an NAD+ binding site of brain glutamate dehydrogenase isoproteins by photoaffinity labeling

Photoaffinity labeling with [32P]nicotinamide 2-azidoadenosine dinucleotide (2N3NAD+) was used to identify the NAD+ binding site within two types of glutamate dehydrogenase isoproteins (GDH I and GDH II) isolated from bovine brain. In the absence of photolysis, 2N3NAD+ is a substrate for the GDH isoproteins. When the enzymes were covalently modified by photolysis in the presence of saturating amounts of photoprobe, about 50% inhibition of the GDH activities was observed. Photoinsertion of probe was increased by GTP or glutarate and decreased by NAD+ or ADP. With the combination of immobilized boronate affinity chromatography and reversed-phase HPLC, photolabel-containing peptides generated with trypsin were isolated. This identified a portion of the adenine ring binding domain of GDH isoproteins as the region containing the sequence, CIAVGXSDGSIWNPDGIDPK for both GDH isoproteins, corresponding to Cys270 through Lys289 of the amino acid sequence of well known bovine liver GDH. The X indicates a position for which no phenylthiohydantoin-derivative could be assigned. The missing residue, however, can be designated as a photolabeled glutamate since the sequences including the glutamate residue in question have a complete identity with those of the other GDH species known. Photolabeling of these peptides was prevented by the presence of NAD+ during photolysis. These results demonstrate selectivity of the photoprobe for the NAD+ binding site and suggest that the peptide identified using the photoprobe is located in the NAD+ binding domain of the brain GDH isoproteins. Both amino acid sequencing and compositional analysis identified Glu275 as the site of photoinsertion.