Biological interactions mediate context and species-specific sensitivities to salinity.

Toxicants have both sub-lethal and lethal effects on aquatic biota, influencing organism fitness and community composition. However, toxicant effects within ecosystems may be altered by interactions with abiotic and biotic ecosystem components, including biological interactions. Collectively, this generates the potential for toxicant sensitivity to be highly context dependent, with significantly different outcomes in ecosystems than laboratory toxicity tests predict. We experimentally manipulated stream macroinvertebrate communities in 32 mesocosms to examine how communities from a low-salinity site were influenced by interactions with those from a high-salinity site along a gradient of salinity. Relative to those from the low-salinity site, organisms from the high-salinity site were expected to have greater tolerance and fitness at higher salinities. This created the potential for both salinity and tolerant-sensitive organism interactions to influence communities. We found that community composition was influenced by both direct toxicity and tolerant-sensitive organism interactions. Taxon and context-dependent responses included: (i) direct toxicity effects, irrespective of biotic interactions; (ii) effects that were owing to the addition of tolerant taxa, irrespective of salinity; (iii) toxicity dependent on sensitive-tolerant taxa interactions; and (iv) toxic effects that were increased by interactions. Our results reinforce that ecological processes require consideration when examining toxicant effects within ecosystems.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'.

Does thalidomide prolong survival in dogs with splenic haemangiosarcoma?

OBJECTIVES: To investigate thalidomide as an adjuvant treatment for canine haemangiosarcoma. MATERIALS AND METHODS: Fifteen dogs with splenic haemangiosarcoma, initially treated by splenectomy, were included. Following recovery from surgery, all dogs received thalidomide continuously until their death. Tumour stage was established using CT scans of the chest and abdomen immediately before starting thalidomide treatment and again three months later. Cause of death was confirmed by post mortem examination. RESULTS: The median survival time of dogs receiving thalidomide was 172 days (95% confidence interval: 93 to 250 days). Five dogs (33% of the population receiving thalidomide) survived more than 1 year (range 458 to 660 days) after surgery. Dogs with stage 2 disease that received thalidomide also had a longer survival time than dogs with stage 3 disease (median survival time 303 versus 40 days). Of 15 dogs, 13 died from metastatic haemangiosarcoma. CLINICAL SIGNIFICANCE: Treatment using thalidomide may improve survival of dogs with splenic haemangiosarcoma and should be considered a possible adjuvant therapy.

Soft tissue sarcoma in the dog - Part 2: surgical margins, controversies and a comparative review.

Soft tissue sarcoma constitutes a heterogeneous group of mesenchymal tumours. Although they are common in the dog, many uncertainties surround the best options for clinical management. Despite recent improvements in outcome, approximately one in five patients may still die as a result of their disease. There is some evidence that wide surgical excision may not be required for every soft tissue sarcoma but, conversely, complacency in treatment may adversely affect outcomes for patients with aggressive disease. The purpose of this review is to examine the issues affecting the management of canine soft tissue sarcoma, and to evaluate the human literature for lessons that may guide future treatment directions for dogs. Comparative lessons from human soft tissue sarcoma that may be important for the canine patient in the future include (1) understanding the oncogenic potential of the pseudocapsule to better predict tumour behaviour and optimal surgical margins, (2) recognising the importance of planned multi-modality therapy for improving tumour control, (3) considering a role for compartmental resection strategies and (4) improving the accuracy of pretreatment analysis of the tumour to better predict behaviour and optimal treatment options.

Soft tissue sarcoma in the dog - part 1: a current review.

Soft tissue sarcomas are derived from tissues of mesenchymal origin. Although local recurrence following surgical resection is the characteristic challenge in their management, 40% dogs with high-grade tumours may also develop metastatic disease, despite successful local control. Soft tissue sarcoma is a complex disease and there are many uncertainties regarding the biology and optimal clinical management. There are currently no diagnostic tests that can reliably predict the amount of surgical margin required for a particular tumour, so there can be a mismatch between treatment and disease. Historically, the tendency has been to always recommend wide excision margins but this is not fully supported by recent evidence. A selection bias for less aggressive soft tissue sarcomas in primary care practice can account for good outcomes that are achieved despite narrow surgical excision margins. On the other hand, inappropriately conservative treatment will adversely affect outcomes for patients with more aggressive disease. This review provides an update on the current understanding of management of canine soft tissue sarcomas.

Histological evaluation of the soft palate in dogs affected by brachycephalic obstructive airway syndrome.

AIMS: To histologically examine tissue obtained from the thick rostral portion of the soft palate in severely affected brachycephalic dogs, and to quantitatively compare the histological findings with a similar region in control dogs. METHODS: Nine dogs examined for treatment of brachycephalic obstructive airway syndrome (BOAS) were prospectively recruited into the study. Four mesaticephalic dogs were also recruited following euthanasia for reasons unrelated to respiratory or gastrointestinal disease. Palatine tissue was harvested using an elliptical incision extending from the junction with the hard palate to the free caudal edge, and passing axial to the tonsilar crypts. The resected portion was fixed in formalin and stained using H&E. Tissues were examined in transverse section and assessments of the palatinus muscles, interstitium, lamina propria and salivary tissue were recorded. Quantitative analysis of the proportions of palatinus muscle, salivary tissue and stroma was performed using ImageJ image analysis software. RESULTS: When compared to the control dogs, the histological findings of the clinically affected dogs showed a marked increase in acute and chronic muscle degeneration and necrosis. This was typified by swollen, hypereosinophilic fibres with centralised nuclei, myofibre atrophy, loss of cross striations and fragmented sarcoplasm. There was reduced proportions of palatinus muscle (p<0.001) and increased proportions of collagenous stroma (p=0.004) and salivary gland tissue (p=0.046) in the clinical samples, compared to control dogs. CONCLUSIONS: Increased thickness of the palate in dogs with BOAS was not due to muscle hypertrophy but was due to increased stroma within the lamina propria, and increased proportions of salivary tissue. There was also a reduction of muscle mass, especially within the paired palatinus muscles, that may have consequences for palate function. CLINCAL RELEVANCE: The results of this study enable us to start investigating the aetiology of the changes seen in brachycephalic compared to mesaticephalic dogs, which will impact timing and extent of treatment of clinical cases.

Pedicle ligation in ovariohysterectomy: an in vitro study of ligation techniques.

OBJECTIVES: Ligature failure is an important complication following ovariohysterectomy in the bitch. The aim of this study was to assess the differences between five individual ligation techniques in their ability to attenuate a bulky vascular model. METHODS: A vascular model was constructed that enabled the occlusive ability of five different ligation techniques to be measured including the square knot, surgeon's knot, slip knot, modified transfixing ligature and the single-double other side knot. Each was constructed using both USP-0 polyglyconate and polyglactin 910 suture material. The extent of attenuation of the vascular model that was achieved by each technique was assessed using pressure transducers. RESULTS: In this model, the slip knot, modified transfixing ligature and the single-double other side knot outperformed the square and surgeon's knots. CLINICAL SIGNIFICANCE: The results of this study suggest that utilising a knot design that has more inherent resistance to slippage of the first throw (e.g. the modified transfixing ligature, slip or single-double other side knots) may be preferable over square and surgeon's knots when tying a ligature on a bulky vascular pedicle like the ovarian stump in a large bitch.

Ability to work and owner satisfaction following surgical repair of common calcanean tendon injuries in working dogs in New Zealand.

AIM: To report the long-term outcome (return to work and owner satisfaction) following surgical treatment of common calcanean tendon (Achilles tendon) injuries in working dogs in New Zealand. METHODS: Ten New Zealand Huntaway or Heading dogs (working Collies) with complete or partial tears of the common calcanean tendon, were treated using locking-loop suturing and casting, with (7) or without (3), a calcaneo-tibial screw. All dogs were actively in work on sheep or cattle farms at the time of injury, and return to work was the desired outcome. Ability to work and owner satisfaction were investigated using a telephone questionnaire at a mean followup interval of 14.6 months. RESULTS: Overall, 7/10 dogs returned to full or substantial levels of work. Post-operative complications occurred in two dogs that did not return to full or substantial levels of work. Moderate persistent lameness (score 3 on a scale of 0-5) was present in 2/7 dogs that returned to full or substantial levels of work, equating to a 71% good-to-excellent functional outcome within this group. Seven owners felt the financial investment in opting for surgical repair was worthwhile. A screw and cast method of rigid immobilisation was thought to be superior to casting alone. CONCLUSIONS: Surgical treatment of common calcanean tendon injury in working dogs carries a good prognosis if an appropriate tenorrhaphy technique is used and rigid immobilisation is achieved for 6 weeks. Care must be taken to limit post-operative complications. CLINICAL RELEVANCE: This study justifies the use of surgical repair of such injuries in the working dog even when return to work is the only acceptable outcome.

Bicipital tendinitis and tenosynovitis in the dog: a study of 15 cases.

AIM: To describe the clinical, radiographic, and sonographic features of 15 dogs with bicipital tendinitis and tenosynovitis, classify them according to cause, and evaluate the long-term efficacy of treatment. METHODS: Dogs exhibiting forelimb lameness with pain localised to the biceps tendon were included in the study. Sonographic examination of the tendon and tendon sheath, and radiographic examination including positive contrast arthrograms of the shoulder joint were performed, and assessed for features consistent with biceps tendon disease. In some cases, synovial-fluid analysis and surgical investigation were also undertaken. The causes of the conditions were classified as either traumatic, mechanical, neoplastic or inflammatory. Dogs were treated conservatively with rest and anti-inflammatory drugs, or surgically by either transection of the transverse humeral ligament or tenodesis of the biceps tendon. Assessment of the effects of treatment was made by re-examination at six weeks and from information gained by telephone interview with the dog's owner at longer-term follow-up. RESULTS: Bicipital tendinitis and tenosynovitis were common causes of forelimb lameness in active, middle-aged or older, medium to large-breed dogs. The most sensitive physical tests for localising pain to the biceps apparatus were shoulder flexion with the elbow extended, focal digital pressure applied directly to the biceps origin, and the biceps retraction test. Sonographic assessment was found to be more sensitive than shoulder radiography or arthrography for characterising the lesion. Conservative treatment of 11 traumatic cases resulted in good or excellent function at long-term follow-up. One mechanical bicipital tendinitis secondary to mineral deposits within the supraspinatus tendon improved following transection of the transverse humeral ligament and removal of the deposits. One of two cases of inflammatory tendinitis/ tenosynovitis improved following tenodesis. One dog with neoplastic disease did not improve and was euthanased. CONCLUSIONS: The diagnosis of bicipital tendinitis and tenosynovitis requires a careful examination using a combination of physical tests. Of the ancillary tests, sonography was the most reliable, however information gained from all tests was useful in fully evaluating the biceps apparatus and shoulder joint. The classification system employed in this study was helpful in selecting a treatment protocol and determining the likely prognosis.

Ultrasonographic examination of the pharynx and larynx of the normal dog.

Real-time ultrasonographic examination of the canine larynx was performed in 12 normal dogs using a 7.5-mHz mechanical sector scanner combined with a stand-off. A variety of breeds and ages were examined. All examinations were performed in nonsedated, conscious animals. Transverse scans were found to provide the most reliable and interpretable images. Identification of laryngeal structures included the epiglottis, laryngeal and cricoid cartilages, and the vocal cords. In conscious animals, abduction and adduction of the vocal cords associated with respiration could be identified if the animal was made to pant during the examination. Movement of the vocal cords could also be quantified by pulse-wave Doppler recording. In all animals, recordings were made during inspiration only, with muscular vibration at a rate less than 0.1 m/s.

Use of omental pedicle grafts in the management of non-healing axillary wounds in 10 cats.

A retrospective analysis of the clinical case histories of 10 domestic shorthaired cats that underwent omentalisation, using a vascular pedicle of greater omentum, of chronic non-healing axillary wounds was carried out. Wounds were debrided and closed in a primary fashion following omentalisation. The cats had undergone a modal number of three previous repair attempts over a three- to 18-month period (mean 11 months) before referral. Further dehiscence occurred in eight cases, requiring a modal number of one further attempt at closure of the wound. Other complications included incisional herniation (two cats), serous exudate from the axillary wound (two cats) and paracostal abscessation (one cat). Long-term cure was achieved in seven of the 10 cases, with wounds finally having healed at a mean of 24 days post-omentalisation. Chronic axillary wounds are particularly difficult to treat and there are no reports of consistently successful techniques for their repair. This report suggests that omentalisation of these wounds may be a step towards such a repair procedure.

Treatment of canine nasal aspergillosis with a new non-invasive technique. Failure with enilconazole.

A new, non-invasive technique recently described for the treatment of canine nasal aspergillosis was performed on four dogs. The antimycotic agent used was a 10 per cent enilconazole suspension, with the drug left in situ for a period of one hour. None of the dogs responded to single treatment. One dog died from an acute septic response secondary to pyelonephritis and bacterial endocarditis eight days after a second treatment. A second dog responded completely to a second treatment and remained free of fungal disease for a follow-up period of 11 months. In the remaining two dogs, extensive and profuse fungal growth was seen on rhinoscopic re-examination. Conventional treatment, with tube implantation into the frontal sinuses and nasal irrigation for two weeks, was performed. Successful resolution of infection was obtained. Although the new, non-invasive technique was simple to carry out and well tolerated by the dogs, instillation of 10 per cent enilconazole appears to have poor therapeutic efficacy and exacerbated fungal growth in two of the animals.

The canine intervertebral disk: part one: structure and function.

Intervertebral disk disease continues to be a common and debilitating condition of dogs. In the first of a two-part article on the canine intervertebral disk, the microscopic and ultrastructural anatomy of the normal, nonchondrodystrophoid disk is described. Specific attention is placed on elements of the structure which impart important functional attributes. Finally, the role of the intervertebral disk in providing flexibility to the vertebral column is discussed, with a description of its biomechanical properties and reaction to compressive loads.

The canine intervertebral disk. Part Two: Degenerative changes--nonchondrodystrophoid versus chondrodystrophoid disks.

In the second of a two-part article on the canine intervertebral disk, the morphological changes which occur within the disk during aging and degeneration are described. Degeneration of the intervertebral disk appears to be a self-perpetuating process as a consequence of disruption to the annulus fibrosus, cellular remodeling, altered biomechanical loading, and nutritional deficiencies. In the nonchondrodystrophoid disk, premature acceleration of the aging process can occur following traumatic disruption to the annulus fibrosus. This degeneration usually occurs in isolated disks along the length of the vertebral column. By contrast, disk degeneration in the chondrodystrophoid breeds occurs simultaneously in all disks along the vertebral column and usually is well advanced by two years of age. Ultrastructural differences between the intervertebral disk of the nonchondrodystrophoid dog and that of the chondrodystrophoid dog may explain the rapidity and severity of degenerative changes in the latter breeds.

Partial resection and omentalization: a new technique for management of prostatic retention cysts in dogs.

OBJECTIVE: The purpose of this study was to determine the results of a new technique for management of prostatic retention cysts in dogs. STUDY DESIGN: A retrospective clinical study. ANIMALS: Eighteen client-owned dogs. METHODS: Dogs with prostatic retention cysts were treated by celiotomy and drainage of the cysts. The majority of the cyst wall was resected and residual cyst cavities were packed with omentum. All dogs were castrated. RESULTS: Long-term resolution of clinical signs was achieved in all dogs, with follow-up periods ranging from 6 to 42 months. Five dogs developed urinary incontinence postoperatively. This persisted in two dogs, but was well controlled with phenylpropanolamine. In the remaining dogs, the incontinence was transient and resolved within 2 months of surgery. CONCLUSIONS: Partial cyst resection combined with omentalization and castration was a simple and effective means of managing prostatic retention cysts. The incidence of serious complications, including postoperative urinary incontinence, was low.

Corrective osteotomy for bilateral forelimb varus deformities in a working dog.

Bilateral varus antebrachial deformity in a 7-month-old working dog was surgically corrected. The deformity was a sequela to premature closure of the distal radial physes after trauma to the forelimbs. Treatment was by ulnectomy and oblique radial osteotomy. Stabilisation of the fractures was maintained by an external fixation device. The treatment was successful and the dog returned to work as a sheep dog.

Estimation of minimum alveolar concentration (MAC) for halothane, enflurane and isoflurane in spontaneously breathing guinea pigs.

MAC for halothane, enflurane and isoflurane was determined in guinea pigs (Cavia porcellus) exposed to constant anesthetic concentrations (2.5 hours each) in a flow-through glass chamber. The following values were obtained (N = 8 for each anesthetic): 1.01 +/- 0.03 vol% for halothane, 2.17 +/- 0.04 vol% for enflurane, and 1.15 +/- 0.05 vol% for isoflurane. In guinea pigs, MAC for halothane and enflurane are similar to those reported for other rodents, while MAC for isoflurane is lower. The data indicate that guinea pigs possibly are more susceptible to isoflurane's anesthetic actions than other rodents.

Myocardial recovery from the cardiac depressant effects of enflurane and halothane.

Recovery from the cardiac depressant effects of enflurane and halothane was examined in the dog heart-lung preparation (HLP) and in right ventricular muscle isolated from guinea pig hearts. In the HLP. recovery was studied under two conditions: (1) After a two-hour exposure to anesthetic concentrations increasing from 0.36 to 1.2 MAC, and (2) after a one-hour exposure to a single concentration that raised the left atrial pressure (LAP) to 9 to 10 mmHg. Under either condition, +dP/dtmax. was significantly less depressed with enflurane and returned to preanesthetic control levels, while recovery with halothane remained significantly below control. Following the longer exposure. recovery of the LAP and left ventricular function curves (LVFC) was significantly less with halothane; however, this difference was not observed after the shorter exposure period. In electrically paced, isometrically contracting right ventricular strips exposed for one hour to 2.25 vol% enflurane (a concentration that reduced contractility by 45%), force development returned within 60 minutes to values above preanesthetic control values. After an identical depression for one hour with halothane (0.80 vol%), force development recovered to values less than those observed following enflurane. These data indicate that the recovery from anesthetic-induced negative inotropic effects in isolated cardiac preparations is better with enflurane than halothane.

Comparison of Streptomyces albus muramidase-extracted streptococcal antigen with acid-extracted M antigen and with pepsin-extracted T antigen.

Purified Streptomyces albus lytic enzyme was used in an attempt to extract type-specific antigen from a type 1, group A streptococcus. The presumably type-specific antigen was purified by ammonium sulfate fractionation followed by chromatography on O-(carboxymethyl)-cellulose columns. Comparison of the enzyme-extracted substance with acid-extracted material showed it to be serologically different from M protein. In addition, the extract obtained by enzyme treatment was resistant to trypsin as well as to the lytic enzyme. It was inactivated partially by pepsin and totally by papain. Comparison of the enzyme extract with pepsin-extracted T antigen showed these two preparations to be serologically identical. Subtle differences in their susceptibility to heat and acid treatment were noted. Immunodiffusion analyses of acid-extracted M protein and pepsin-extracted T protein, as well as with the enzyme extract, clearly established that the M-protein preparation contained a component serologically identical with one of the precipitinogens common to the other two extracts.