The 5-lipoxygenase inhibitor tepoxalin induces oxidative damage and altered PTEN status prior to apoptosis in canine osteosarcoma cell lines.

The 5-lipoxygenase (5-LOX) inhibitor tepoxalin has been shown to slow canine osteosarcoma (OSA) tumour xenografts growth, yet the mechanisms are poorly elucidated. Further examination of tepoxalin in canine OSA cell lines shows that tepoxalin treated cells undergo apoptosis through caspase-3 activation and annexin staining. Interestingly, apoptosis is superseded by an increase in reactive oxygen species (ROS), as measured by activation of dihydrorhodamine 123 and mitosox. This increase in ROS appears to be related to the 5-LOX inhibitor regardless of cellular 5-LOX status, and was not observed after treatment with the tepoxalin metabolite RWJ20142. Additionally, 5-LOX inhibition by tepoxalin appears to increase phosphatase and tensin (PTEN) homolog activity by preventing its alkylation or oxidation. PTEN modification or inhibition allows phosphoinositide-3 (PI3) kinase activity thereby heightening activation of protein kinase B (AKT) phosphorylation. Our data suggest that off target oxidation and LOX inhibition play roles in the apoptotic response.

The effects of baicalein on canine osteosarcoma cell proliferation and death.

Flavonoids are a group of modified triphenolic compounds from plants with medicinal properties. Baicalein, a specific flavone primarily isolated from plant roots (Scutellaria baicalensis), is commonly used in Eastern medicine for its anti-inflammatory and antineoplastic properties. Previous research shows greater efficacy for baicalein than most flavonoids; however, there has been little work examining their effects on sarcoma cells, let alone canine cells. Three canine osteosarcoma cell lines (HMPOS, D17 and OS 2.4) were treated with baicalein to examine cell viability, cell cycle kinetics, anchorage-independent growth and apoptosis. Results showed that osteosarcoma cells were sensitive to baicalein at concentrations from approximately 1 to 25 µM. Modest cell cycle changes were observed in one cell line. Baicalein was effective in inducing apoptosis and did not prevent doxorubicin cell proliferation inhibition in all the cell lines. The mechanism for induction of apoptosis has not been fully elucidated; however, changes in mitochondrial permeability supersede the apoptotic response.

Effect of intravenous lidocaine administration on laminar inflammation in the black walnut extract model of laminitis.

REASONS FOR PERFORMING STUDY: Laminitis is a serious complication of horses suffering from sepsis/endotoxaemia-related events. Laminitis in horses and organ injury in human sepsis are both reported to involve inflammatory injury to the laminae/organs including early activation of endothelium and leucocytes leading to emigration of neutrophils into the tissue interstitium. In the black walnut extract (BWE) model, systemic inflammatory events coincide with marked increase in laminar mRNA concentrations of inflammatory genes including proinflammatory cytokines (i.e. IL-1beta, IL-6), COX-2, chemokines (i.e. IL-8) and endothelial adhesion molecules (i.e. ICAM-1 and E-selectin). In models of human sepsis, i.v. lidocaine has been reported to decrease leucocyte and endothelial activation, and the expression of proinflammatory cytokines and chemokines. OBJECTIVES: To evaluate the effect of i.v. lidocaine therapy on the inflammatory processes documented to occur in the BWE model of laminitis. METHODS: Twelve horses were administered BWE and treated immediately with either lidocaine (1.3 mg/kg bwt bolus, followed by 0.05 mg/kg bwt/min CRI, n=6) or saline (n=6) for 10 h. At 10 h post BWE administration, laminar samples were obtained under general anaesthesia for assessment of proinflammatory gene expression (using RT-qPCR) and leucocyte emigration (via CD13 immunohistochemistry). At 0, 3 and 10 h post BWE administration, skin samples were obtained for assessment of leucocyte emigration (via calprotectin immunohistochemistry). RESULTS: No significant differences between groups were noted for inflammatory gene mRNA concentrations (IL-1beta, IL-6, IL-8, COX-2) or for number of leucocytes present within the laminar interstitium or skin dermis. Increased (P<0.05) laminar E-selectin mRNA concentrations were present in the LD group (vs. SAL group). CONCLUSIONS: Continuous administration of i.v. lidocaine does not inhibit inflammatory events in either the laminae or skin in the horse administered black walnut extract. POTENTIAL RELEVANCE: This work questions the use of continuous i.v. administration of lidocaine as an effective anti-inflammatory therapy for systemic inflammation.

Tissue concentrations of 4-HNE in the black walnut extract model of laminitis: indication of oxidant stress in affected laminae.

In the septic horse prone to laminitis, a similar activation of the innate immune system appears to occur as reported in the septic human prone to organ failure. Because oxidant injury plays a central role in organ failure occurring due to an overzealous innate immune response in human sepsis, this study was performed to determine whether there was evidence of oxidant stress in the laminar tissue in the early stages of laminitis. 4-Hydroxy-2-nonenal (4-HNE), a lipid aldehyde that forms due to lipid peroxidation occurring during episodes of oxidant stress, readily forms adducts with cellular proteins; these adducts can be assessed as a marker of oxidant stress in the form of lipid peroxidation. In this study, a slot blot technique was used to assess 4-HNE adduct concentrations in the laminae, lung, liver, and intestinal tract in the black walnut extract (BWE) model of laminitis. Significant increases in laminar 4-HNE adduct concentrations were identified at two early stages in the BWE model, in the absence of such changes in the other tissues. These data indicate that oxidant stress may play an important role in the laminar failure in laminitis, and further support the concept that a poor antioxidant response in the laminae relative to other equine tissues may be responsible for failure of the laminae in the septic horse. In contrast, tissues such as the lung and liver that undergo oxidant injury in human sepsis appear to be relatively protected in horses.

Laminar xanthine oxidase, superoxide dismutase and catalase activities in the prodromal stage of black-walnut induced equine laminitis.

UNLABELLED: REASONS FOR STUDY: Xanthine oxidase (XO)-dependent production of superoxide anion and hydrogen peroxide, a characteristic of ischaemia-reperfusion injury, may contribute to the development of equine laminitis. OBJECTIVE: To determine the levels of XO and antioxidant enzymes (catalase, superoxide dismutase [SOD]) in the digital laminae of normal horses (CON) and horses in the developmental stage of laminitis using the black walnut extract (BWE) model. METHODS: Healthy horses (n = 12) were administered BWE (BWE group, n = 6), or water (CON group, n = 6) through a nasogastric tube. At the onset of leucopenia in the BWE-treated animals, all horses were anaesthetised, digital laminae and other samples collected rapidly and flash frozen, and the animals subjected to euthanasia. Extracts of the frozen tissues were assayed for the 2 conformational forms of xanthine: oxygen oxidoreductase (XOR), namely, xanthine dehydrogenase (XDH) and xanthine oxidase (XO), as well as the antioxidant enzymes, SOD and catalase. RESULTS: Extracts of liver, lungs and skin, but not digital laminae, from either CON or BWE-treated horses had endogenous SOD, whereas all had endogenous XO and catalase. The levels of XDH, XO and catalase were similar in extracts of laminae from CON and BWE-treated horses as was the ratio of XDH to XO in extracts. CONCLUSIONS AND POTENTIAL RELEVANCE: The absence of increased XO activity suggest against the involvement of this reactive oxygen intermediate-generating system in the development of laminar pathology in BWE-treated horses. Conversely, the absence of SOD from extracts of equine digital laminae, but not other tissues, suggests that the equine digital laminae are highly susceptible to damage by superoxide anion, produced, for example, by emigrant inflammatory leucocytes.

A comparison of the effects of lamotrigine on neuroma-induced action potential firing and normal behaviour in rat: implications for establishing a pre-clinical 'therapeutic index'.

The effects of lamotrigine on rat neuroma and behavioural paradigms were evaluated to determine a pre-clinical therapeutic index. Lamotrigine blocked neuroma-induced burst pattern firing at a free plasma concentration of 13.7+/-1.7 microM (n=5). Oral dosing of lamotrigine (50-200 mg/kg) had no significant effects on behaviour but measurements of plasma concentrations of free drug showed non-linear oral absorption and lower than predicted drug levels (5-27 microM). Given intravenously (10-100 mg/kg), lamotrigine did affect behaviour at a free plasma concentration of 42.0 microM (n=2). By comparing free plasma concentrations, a therapeutic index of 3 was calculated, which is lower than published data based on comparing oral doses. We propose that a therapeutic index should only be derived with reference to plasma drug concentrations to prevent non-linear or incomplete drug absorption from confounding accurate estimation.

Carotid endarterectomy: a comparison of regional versus general anesthesia in 500 operations.

The outcomes of 489 patients undergoing 500 carotid endarterectomies were reviewed to compare results from using general anesthesia with those from using regional (cervical block) anesthesia. From September 1982 to May 1998, 228 procedures (221 patients) were performed under general anesthesia and 272 procedures (268 patients) were performed under local anesthesia. A detailed comparison of the two groups revealed close similarity in age, sex, presenting symptoms, and associated risk factors. Overall, perioperative mortality was 0.8%. In comparison to regional anesthesia, the general anesthesia group had greater overall morbidity (23.3 vs. 13. 6%, p < 0.008) and more frequent use of postoperative vasoactive drugs to control blood pressure (40.4 vs. 26.1%, p < 0.001). Furthermore, anesthesia time, operative time, and frequency of shunt use were significantly greater in the general anesthesia group (p < 0.03).

Surgical management of gastrointestinal carcinoid tumors.

While carcinoid tumors of the gastrointestinal tract continue to intrigue physicians and surgeons, the medical and surgical management of these tumors continues to evolve. Summarizing the current literature, patients should undergo local excision for incidental tumors of the stomach, rectum, and appendix, provided the tumor measures less than 2 cm in greatest dimension and does not demonstrate muscular invasion or lymph node metastases. Curative radical resection should be attempted, even in the presence of hepatic metastases, in patients with symptomatic or incidentally discovered carcinoid tumors of the small intestine, or in patients with large (> 2 cm) or invasive tumors. Palliative radical resection should be performed for patients with metastatic carcinoid tumors in light of the indolent tumor growth characteristics and the incapacitating symptoms related to tumor bulk and hormone production. Liver dearterialization should be considered only if resection cannot be safely accomplished. Carcinoid heart disease can be safely managed surgically and early intervention prior to the development of irreversible myocardial dysfunction is advocated. Medical therapy, primarily octreotide, should be offered to patients with disseminated tumors, and should be administered and available during the perioperative period to patients undergoing resection or liver dearterialization. With the use of new radioimmunoimaging techniques, earlier diagnosis, improved follow-up, and potentially targeted chemotherapy will be possible. As is evident, the treatment for gastrointestinal carcinoid tumors can be simple, as with small appendiceal tumors, or complex, as with disseminated small intestinal tumors. All surgeons should be familiar with the treatment options for these patients, as most can be treated by simple endoscopic excision or appendectomy. For the unusual patient with a disseminated carcinoid tumor, a multidisciplinary approach is required, combining the expertise of surgeons, oncologists, anesthesiologists, and radiologists for effective results.

Trends in morbidity and mortality of hepatic resection for malignancy. A matched comparative analysis.

OBJECTIVE: The authors define more clearly the trends in morbidity and mortality after hepatic resection for malignant disease in matched patient groups during two discrete time periods. SUMMARY BACKGROUND DATA: Recent reports have shown improvement in operative morbidity and mortality associated with hepatic resection; however, results often included resections for benign disease and trauma. Furthermore, specific factors contributing to the improvement in operative risks between the last two decades have not been defined. METHODS: A retrospective matched comparative analysis was conducted of patients with primary and metastatic hepatic malignancy resected with curative intent between two periods (1976 to 1980 and 1986 to 1990). Eighty-one patients met our inclusion criteria in the early period; this group was matched with 81 patients from the latter period by the following four parameters: age, gender, type of malignant disease, and extent of resection. Records of these two patient groups were abstracted for clinical presentation, co-morbid factors, operative techniques, and perioperative morbidity and mortality. RESULTS: The authors found a significant decrease in operative morbidity, median perioperative transfusion, and length of hospital stay in the latter period (1986 to 1990). The incidence of postoperative subphrenic abscess and intra-abdominal hemorrhage was significantly lower during this period. Operative mortality rate was similar for both periods, 4.9% and 1.2%, respectively (p > 0.05). CONCLUSION: Hepatic resection for malignant disease currently can be performed with a low morbidity and mortality in the hands of trained and experienced hepatic surgeons; operative risks of hepatic resection should not deter its application in the treatment of primary and metastatic malignant disease of the liver.

Sinistral portal hypertension. Splenectomy or expectant management.

Splenectomy has been considered the treatment of choice for patients with bleeding from sinistral portal hypertension (SPH) and varices, but is controversial for asymptomatic patients. To further define the role of splenectomy for SPH, the authors compared the clinical presentations and outcomes of 25 patients treated with splenectomy with those of 12 observed patients. Clinical features were similar except for transfusions administered (60% vs. 25%, p < 0.05), hemoglobin (9.8 +/- 2.2 g/dL vs. 12.5 +/- 2.1 g/dL, p < 0.05), and history of prior bleeding episodes (56% vs. 8%, p < 0.05), splenectomy versus no splenectomy, respectively. At 3 years, neither survival (78% vs. 64%, p = 1.0) nor new or recurrent bleeding (16% vs. 24%, p = 0.2) differed, splenectomy versus no splenectomy, respectively. The authors conclude that in the absence of prior bleeding episodes, anemia, or severe hemorrhage, observation of patients with SPH is justified.

Atrial natriuretic factor inhibits hypertonic saline-mediated decreases in renal hemodynamics.

The present study in the anesthetized dogs was designed to test the hypothesis that atrial natriuretic factor (ANF) attenuates whole kidney tubuloglomerular feedback (TGF) mediated decreases in renal blood flow (RBF) and glomerular filtration rate (GFR) produced by hypertonic saline (HS). Secondly, as adenosine (AD) has been implicated as a metabolic mediator of TGF, we also hypothesized that ANF would antagonize the renal actions of AD. To test this hypothesis, RBF and GFR were assessed in response to hypertonic saline (HS, 16%, i.r.) or adenosine (AD, 0.1 mumol/min, i.r.) in the presence and absence of exogenous ANF (100 ng/kg/min, i.r.). ANF attenuated HS-mediated reductions in GFR (HS, -39.6 +/- 9.8 ml/min vs. HS + ANF, -14.3 +/- 4.5 ml/min, P less than 0.05) and in RBF (HS, -143 +/- 35 ml/min vs. HS + ANF, -5 +/- 22 ml/min, P less than 0.05). GFR was reduced by AD (-9.2 +/- 3.0 ml/min, P less than 0.05), but maintained by AD + ANF (-0.4 +/- 2.0 ml/min, NS). A transient adenosine-mediated vasoconstriction was attenuated by ANF (AD, -54.5 +/- 3.6 ml/min vs. AD + ANF, -3.7 +/- 3.1 ml/min, P less than 0.005). We conclude that ANF at pharmacologic concentrations attenuates at the whole kidney level hypertonic saline and adenosine-mediated reductions in RBF and GFR.

Space: exploration-exploitation and the role of man.

The early years of space activity have emphasized a crew role similar to that of the test pilot or the crew of a high performance aircraft; even the Apollo lunar exploration missions were dominated by the task of getting to and from the moon. Skylab was a prototype space station and began to indicate the range of other functional roles man will play in space. The operation of the Space Shuttle has the elements of the operation of any other high performance flight vehicle during launch and landing; but in its on-orbit operations, it is often a surrogate space station, developing techniques and demonstrating the role of a future space station in various functions. In future space systems, the role of the crew will encompass all of the activities pursued in research laboratories, manufacturing facilities, maintenance shops, and construction sites. The challenge will be to design the tasks and the tools so that the full benefit of the opportunities offered by performing these functions in space can be attained.