Glutathione, Cysteine, and Ascorbate Concentrations in Clinically Ill Dogs and Cats

Case report: Suspected propofol associated Heinz body anemia in five mechanically ventilated dogs: a historical case series

Objective

The aim of this report is to raise awareness of the risk of oxidant-induced erythrocyte injury, including Heinz body (HB) anemia, in critically ill dogs by describing the condition in five dogs receiving constant rate infusions of propofol.

Case summary

This case series describes five dogs with suspected propofol-induced HB anemia undergoing mechanical ventilation (MV) for lower motor neuron disease. Four of the five dogs were treated for tick paralysis (Ixodes holocyclus) and one was treated for suspected eastern brown snake (Pseudonaja textilis) envenomation. Propofol constant rate infusions were administered as part of total intravenous anesthesia. All five dogs became anemic, and a complete blood count and blood smear interpretation by a specialist clinical pathologist confirmed the presence of oxidative red blood cell injury (eccentrocytosis and HBs). The duration of MV ranged from 76 to 131 h, with HBs identified within 47-96 h of commencing propofol. All five dogs survived to discharge, with one dog requiring a blood transfusion.

Discussion

While propofol-induced HB anemia is a recognized phenomenon in cats, to the author's knowledge, this is the first case series detailing multiple occurrences in dogs. Veterinarians should be aware of the risk of propofol-induced oxidative erythrocyte injury in dogs receiving prolonged infusions of propofol, and consider risk mitigation by using propofol as part of multiagent intravenous anesthesia, keeping dose rates as low as possible, and daily monitoring of blood smears and red blood cell indices.

Oxidative stress in dogs with chronic inflammatory enteropathy treated with allogeneic mesenchymal stem cells

The search for new biomarkers in patients with chronic inflammatory enteropathy (CIE) is ongoing in the human and veterinary medicine fields. Oxidative stress biomarkers (malondialdehyde [MDA], reduced glutathione [GSH], and albumin) have been studied in humans with chronic enteropathies, but among them, only albumin has been studied in dogs with CIE. Moreover, the effect of mesenchymal stem cell (MSCs) treatment with or without prednisone on these parameters has never been studied in dogs with CIE. These parameters were compared between healthy dogs (n = 12) and dogs with CIE, and before and 1, 3, 6, and 12 months after the treatment with MSCs alone (n = 9) or together with prednisone (n = 11). The relationship between the Canine Inflammatory Bowel Disease Activity Index (CIBDAI) and oxidative stress was evaluated. Albumin was the only parameter that significantly differed between dogs with CIE and healthy dogs (p = 0,037). Differences were observed only in albumin values after combined treatment with MSCs and prednisone. No differences were observed in MDA and GSH after treatment with MSCs with or without prednisone. Albumin could help stage canine CIE, as well as its prognosis, as has already been demonstrated, although it is essential to evaluate this parameter for its antioxidant capacity, and therefore it could be a good biomarker of oxidative stress in this pathology. However, the treatment with MSCs seems unable to modify any of the analyzed oxidative stress parameters.

Beyond the Bowl: Understanding Amino Acid Requirements and Digestibility to Improve Protein Quality Metrics for Dog and Cat Foods

The determination of amino acid (AA) requirements for mammals has traditionally been done through nitrogen (N) balance studies, but this technique underestimates AA requirements in adult animals. There has been a shift toward researchers using the indicator amino acid oxidation (IAAO) technique for the determination of AA requirements in humans, and recently in dogs. However, the determination of AA requirements specific to adult dogs and cats at maintenance is lacking and the current requirements outlined by the National Research Council are based on a dearth of data and are likely underreporting the requirements of indispensable AA (IAA) for the population. To ensure the physiological requirements of our cats and dogs are met, we need methods to accurately and precisely measure digestibility. In vivo methods, such as ileal cannulation, are most commonly used, however, due to ethical considerations, we are moving away from animal models and toward in vitro methods. Harmonized static digestion models have the potential to replace in vivo methods but work needs to be done to have these methods more accurately represent the gastrointestinal tract (GIT) of cats and dogs. The Digestible IAA Score (DIAAS) is one metric that can help define protein quality for individual ingredients or mixed diets that uses AA SID estimates and ideally those can be replaced with in vitro AA digestibility estimates. Finally, we need accurate and reliable laboratory AA analyses to measure the AA present in complete diets, especially those used to quantify methionine (Met) and cysteine (Cys), both often limiting AAs in cat and dog diets. Together, this will guide accurate feed formulation for our companion animals to satisfy requirements while avoiding over-supplying protein, which inevitably contributes to excess N excretion, affecting both the environment and feed sustainability.

Differences in selected blood parameters between brachycephalic and non-brachycephalic dogs

Introduction

Cranial and upper-airway anatomy of short-nosed, flat-faced brachycephalic dogs predisposes them to brachycephalic obstructive airway syndrome (BOAS). Periodic apnoea increased inspiratory resistance, and an inability to thermoregulate effectively are characteristic of BOAS, but internationally accepted objective markers of BOAS severity are missing. The objective of this study was to compare the selected blood parameters between non-brachycephalic (NC) and brachycephalic (BC) dogs, exploring the possibility of developing a blood test for BOAS severity grading in the future.

Methods

We evaluated blood biochemistry, complete blood cell counts, red blood cell (RBC) indices, reticulocyte counts, a blood-born marker of intermittent hypoxia (glutathione, NO production), RBC hydration, deformability, and blood markers of metabolic changes and stress between BC (n = 18) and NC (meso- and dolichocephalic, n = 22) dogs.

Results

Reticulocyte counts and the abundance of middle-fluorescence immature reticulocytes were significantly (p < 0.05) higher in BC dogs compared to NC dogs. BC dogs had significantly more NO-derived NO2 - /NO3 - in plasma than NC dogs. RBCs of BC dogs were shedding significantly more membrane, as follows from the intensity of eosin maleimide staining, and had a significantly higher mean corpuscular hemoglobin concentration than NC dogs. Intracellular reduced glutathione content in RBCs of BC dogs was significantly lower, while plasma lactate was significantly higher in BC dogs compared to NC dogs. Plasma cholesterol and triglycerides were significantly lower, and cortisol was significantly higher in BC dogs compared to NC dogs. Eosinophil counts were significantly lower and the neutrophil-to-lymphocyte ratio was higher in BC dogs compared to NC dogs.

Discussion

Taken together, our findings suggest that the brachycephalic phenotype in dogs is associated with alterations at the level of blood cells and, systemically, with oxidation and metabolic changes. The parameters identified within this study should be further investigated for their potential as objective indicators for BOAS.

Antioxidant Effect of a Dietary Supplement Containing Fermentative S-Acetyl-Glutathione and Silybin in Dogs with Liver Disease

Oxidative stress is often involved in liver disease progression. Liver is the primary site for the synthesis of glutathione (GSH), the major intracellular antioxidant. GSH erythrocyte concentration can decrease in case of liver damage. So, the use of food supplements with antioxidant capacity has been reported in the veterinary literature. In this case-control study, we tested a new supplement containing S-acetyl-glutathione (SAG), silybin, and other antioxidant ingredients in dogs affected by liver disease. After two weeks of supplement administration, we were able to report a significant increase in the level of erythrocyte GSH in the treated (TRT) group, nearly reaching the physiological limit at the end of the study. In addition, most of the key liver parameters are significantly reduced in the TRT group by the end of the trial. The results of this study support the effectiveness of the tested complementary feed, which may be helpful in managing dogs with liver conditions.

Selected biomarkers of oxidative stress in healthy Beagle dogs: A preliminary study

Introduction

While oxidative stress has been studied in pathologic conditions in dogs, data in presumably healthy dogs and standardized protocols are lacking. This work purposed to bridge the gap by presenting provisional physiological ranges for oxidative stress biomarkers in a group of Beagle dogs.

Methods

Based on our long-standing clinical expertise in the field of oxidative stress, nine plasma biomarkers of oxidative stress were evaluated for their concentrations (mean ± SD) in 14 healthy adult Beagle dogs.

Results

Selected biomarkers were: vitamins C (7.90 ± 1.36 μg/mL) and E (34.1 ± 6.63 μg/mL), zinc (0.80 ± 0.17 mg/L), copper (0.54 ± 0.048 mg/L), selenium (256 ± 25.7 μg/L), total and oxidized glutathione (822 ± 108 μM and 3.56 ± 1.76 μM), myeloperoxidase (67.4 ± 56.2 ng/mL), and isoprostanes (340 ± 95.3 ng/mL). Glutathione peroxidase activity and superoxide anion production in whole blood were also measured. Glutathione peroxidase activity was 473 ± 34.0 IU/g of hemoglobin and superoxide anion production in whole blood was 18,930 ± 12,742 counts per 30 min. Reduced glutathione/oxidized glutathione and copper/zinc ratios were, respectively, 280 ± 139 and 0.70 ± 0.15. Sex-related differences were recorded for zinc (p = 0.0081), copper/zinc ratio (p = 0.0036) and plasma isoprostanes (p = 0.0045).

Conclusion

Provisional physiological norms covering 95% of our group were proposed for each biomarker and should be of interest for future studies of canine oxidative stress.

Management of Feline Hyperthyroidism and the Need to Prevent Oxidative Stress: What Can We Learn from Human Research?

Feline hyperthyroidism is a clinical syndrome related to an excessive production of thyroid hormones, and it is considered as a spontaneous animal model for human thyrotoxicosis. Many shared features between the feline and the human disease have been identified so far, including pathogenesis, clinical signs, and treatment options. Although methimazole is considered the first-choice drug in both species, several side effects have been described. Furthermore, methimazole could interfere with the oxidative status, already perturbated by the disease. It has been reported in humans that dietary management, mainly through antioxidant supplementation, could mitigate this oxidative burden. The purpose of the review is to describe current therapeutic options in the course of feline hyperthyroidism and to summarize the state of the art relationship between dietary antioxidants administration and the reduction of methimazole side-effects in humans to support the use of this approach also in cats.

Safety and efficacy of a ribose-cysteine supplement to increase erythrocyte glutathione concentration in healthy dogs

OBJECTIVE

To evaluate the safety of oral administration of a d-ribose-l-cysteine (RibCys) supplement to dogs and the effect of this supplementation on erythrocyte glutathione (GSH) concentration.

ANIMALS

24 healthy adult dogs.

PROCEDURES

In a randomized, double-blinded, controlled trial, dogs received 500 mg of a RibCys supplement or placebo (n = 12/group), PO, every 12 hours for 4 weeks. Dogs were evaluated weekly by means of a physical examination, CBC, serum biochemical analysis, urinalysis, and owner-completed quality-of-life questionnaire. Erythrocyte GSH concentration was measured on day 0 (ie, the day before treatment began) and weekly during supplementation.

RESULTS

No dose-limiting adverse effects were noted in any dog. Two dogs in each group had mild, self-limiting diarrhea and anemia. No significant increase in erythrocyte GSH concentration was noted in either group at any time point. Two dogs in the RibCys group had improved skin and coat health and improved clinical signs of osteoarthritis. No clinical or owner-perceived improvements were noted in the placebo group.

CONCLUSIONS AND CLINICAL RELEVANCE

The RibCys supplement was safe and well tolerated in all dogs. Owners reported improvements in dermatologic and orthopedic conditions in some dogs in the RibCys group. No significant differences were observed in erythrocyte GSH concentration before or after RibCys treatment. This lack of significant differences may have been attributable to the use of healthy dogs, which would not be expected to have depleted GSH concentrations. Given the observed safety profile of RibCys, additional research is warranted to explore the potential usefulness of RibCys supplementation in dogs with cancer and those undergoing treatment for cancer.

Oxidative red blood cell damage associated with propofol and intravenous lipid emulsion therapy in a dog treated for 5-fluorouracil toxicosis

OBJECTIVE

To describe the first documented case of oxidant-induced anemia in a dog associated with propofol and IV lipid emulsion (IVLE) treatment for 5-fluorouracil (5-FU) toxicosis.

CASE SUMMARY

A 2-year-old male intact mixed breed dog was presented for evaluation after ingestion of 5% 5-FU cream. Refractory reactive seizures rapidly developed, and treatment with benzodiazepines, propofol, levetiracetam, and IVLE was initiated. The dog was euthanized due to development of marked oxidant-induced anemia.

NEW INFORMATION PROVIDED

This report documents the first instance of oxidant-induced anemia in the dog, associated with propofol and IVLE infusion therapy prescribed for treatment of 5-FU toxicosis.

Vitamin C in Health and Disease: A Companion Animal Focus

Vitamin C is synthesized in the liver in most species, including dogs and cats, and is widely distributed through body tissues. Vitamin C has an important physiologic role in numerous metabolic functions including tissue growth and maintenance, amelioration of oxidative stress, and immune regulation. It is also a co-factor in the production of important substances such as catecholamines and vasopressin. Decreased vitamin C levels have been documented in a wide variety of diseases, and in critically ill human patients may be associated with increased severity of disease and decreased survival. Intravenous supplementation with vitamin C has been proposed as a potential life-saving treatment in conditions such as septic shock, and results of small some human trials are promising. Data in companion in animals is very limited, but the possible benefits and , seemingly low risk of adverse effects , and the low cost of this treatment make vitamin C therapy a promising area of future investigation in critically ill dogs and cats.

Antioxidant supplementation during illness in dogs: effect on oxidative stress and outcome, an exploratory study

OBJECTIVES

To assess whether combination antioxidant supplementation for 30 days in systemically ill dogs alters antioxidant status, degree of lipid peroxidation, clinical score and survival.

MATERIALS AND METHODS

Forty client-owned systemically-ill hospitalised dogs were eligible for inclusion. Dogs were randomised to no supplementation (NS; n=19) or supplementation with N-acetylcysteine/S-adenosylmethionine/silybin and vitamin E (AS; n=20) for 30 days. Clinical score and oxidative biomarkers including glutathione, cysteine, vitamin E, selenium and urine isoprostanes/creatinine (F₂ -IsoPs/Cr) were determined on days 0 and 30. Glutathione, cysteine, vitamin E and urine F₂ -IsoPs/Cr were quantified by high-performance liquid chromatography, and selenium concentrations determined using atomic absorption spectroscopy.

RESULTS

Thirty-two dogs completed the study (NS, n=16; AS, n=16). Vitamin E concentrations were significantly greater in the supplemented compared to the non-supplemented group. No other markers of oxidative stress significantly changed with supplementation. There was no difference in Day 30 clinical scores or survival between the two groups.

CLINICAL SIGNIFICANCE

In this population of systemically-ill hospitalised dogs, combination antioxidant supplementation did not alter redox state or clinical outcome.

Redox unbalance in the hyperthyroid cat: a comparison with healthy and non-thyroidal diseased cats

Background

Feline hyperthyroidism, the most common endocrinopathy in older cats, provides a spontaneous model for human thyrotoxicosis. Human thyrotoxicosis is associated with redox unbalance, which may result in organ damage. The redox status of hyperthyroid cats is largely unknown. The aims of the present study were to compare the redox status of cats with hyperthyroidism with that of healthy cats and cats with chronic non-thyroidal illness.

Results

Forty cats with untreated hyperthyroidism (group H), 45 chronically ill cats with non-thyroidal illness (group I), and 39 healthy cats (group C) were recruited for this observational cross-sectional study. All cats were screened for redox status markers. Determinable reactive oxygen metabolites (d-ROMs) were used as oxidative stress markers. Antioxidant status was determined using the OXY-Adsorbent test to quantify the plasma barrier to oxidation. The Oxidative Stress index (OSi) was calculated as the ratio of d-ROMs and OXY-Adsorbent test values. Data were compared by ANOVA with Tukey’s multiple comparisons post-hoc test. The dROMs of group H (193 ± 47 CarrU) were significantly higher (p &lt; 0.001) than those of the healthy cats (103 ± 17 CarrU). The OXY-Adsorbent test results in group H (265 ± 68 μmol HClO/ml) were significantly lower than those in healthy cats (390 ± 83 μmol HClO/ml; p &lt; 0.01) and chronically ill cats (306 ± 45 μmol HClO/ml, p &lt; 0.05). Moreover, the Osi value in group H (0.8 ± 0.2 CarrU/μmol HClO/ml) was significantly higher (p &lt; 0.001) than that of the healthy cats (0.3 ± 0.1 CarrU/μmol HClO/ml).

Conclusions

As described in humans with hyperthyroidism, feline hyperthyroidism is associated with redox unbalance. Free radical production is increased in hyperthyroid cats and their antioxidant depletion seems to be more severe than in cats with non-thyroidal illnesses. Our results support the rationale for a clinical trial investigating the potential positive effects of antioxidant supplementation to cats with hyperthyroidism.

Electronic supplementary material

The online version of this article (10.1186/s12917-019-1896-7) contains supplementary material, which is available to authorized users.

The development of antioxidant system in the intestinal tract of broiler chickens

The gastrointestinal tract is the site for the uptake of nutrients from the external environment. We hypothesized that the antioxidant system in the intestinal tract has a vital protective role from the oxidative damage induced by oxidants in foods. The aim of this study was to investigate the development of the antioxidant system in the intestine of chickens. The activity and gene expression of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) and the content of the non-enzymatic substance glutathione (GSH) were measured in the duodenum, jejunum, and ileum of chickens at 1, 3, 7, 11, 14, 21, 35, and 42 d of age. The results showed that the small intestinal tract had relatively higher SOD activity and GSH concentration and lower CAT and GSH-Px activities, compared with those of other visceral organs. CAT and GSH-Px activities and GSH concentration showed a decreasing trend with age, whereas SOD activity was not significantly influenced by age. The gene expression of SOD1, SOD2, and GSH-Px7 showed a dramatic decrease from 3 d of age. The results indicated that SOD and GSH were highly expressed in the first week of age after hatching. To conclude, the results suggest that SOD and GSH play a vital protective role in the small intestine after hatching, which contributes to rapid development of the intestine.

Biomarkers of oxidative stress as an assessment of the redox status of the liver in dogs

Background

Oxidative stress is associated with a diverse group of liver disorders across species.

Objectives

Determine whether glutathione (GSH) concentration in plasma and red blood cells correlates with liver GSH concentration in dogs and evaluate whether other markers of systemic oxidative stress, plasma vitamin E and urine 8‐isoprostanes/creatinine (F₂‐IsoPs/Cr) concentrations, correlate with liver GSH.

Animals

Thirty‐four client‐owned dogs undergoing clinically indicated liver biopsy and 15 healthy control dogs.

Methods

Prospective, observational cross‐sectional study. Urine and blood were collected before liver biopsy. Plasma, erythrocyte, and liver GSH were measured using high performance liquid chromatography (HPLC); vitamin E was measured by HPLC, and F₂‐IsoPs/Cr was measured by gas chromatography/mass spectrometry.

Results

All dogs were treated at the discretion of the attending clinician (24/34 received antioxidants; 4/34 fed therapeutic liver diet), which included dogs with primary or secondary liver disease (inflammatory (n = 21), metabolic (n = 9), vascular (n = 2), and neoplastic (n = 2)). Median GSH concentrations in plasma, erythrocyte, and liver were 0.18 mg/dL (range 0.14 to 0.56 mg/dL), 56.7 mg/dL (18.3 to 79.2 mg/dL), and 181 mg/dL (39.9 to 527 mg/dL), respectively. No significant correlations were found between liver GSH and erythrocyte GSH, plasma GSH, vitamin E, or F₂‐IsoPs/Cr. Dogs undergoing clinically indicated liver biopsy had significantly higher urine F₂‐IsoPs/Cr than did healthy controls (5.89 vs 2.98 ng/mg; P < .0001).

Conclusions and Clinical Importance

Erythrocyte and plasma GSH are not indicative of liver GSH concentration in dogs. In addition, dogs undergoing clinically indicated liver biopsy have evidence of increased systemic oxidative stress compared to healthy controls.

Metabolic Differences between Dogs of Different Body Sizes

Introduction

The domesticated dog, Canis lupus familiaris, has been selectively bred to produce extreme diversity in phenotype and genotype. Dogs have an immense diversity in weight and height. Specific differences in metabolism have not been characterized in small dogs as compared to larger dogs.

Objectives

This study aims to identify metabolic, clinical, and microbiota differences between small and larger dogs.

Methods

Gas chromatography/mass spectrometry, liquid chromatography/tandem mass spectrometry, clinical chemistry analysis, dual-energy X-ray absorptiometry, and 16S pyrosequencing were used to characterize blood metabolic, clinical, and fecal microbiome systems, respectively. Eighty-three canines from seven different breeds, fed the same kibble diet for 5 weeks, were used in the study.

Results

449 metabolites, 16 clinical parameters, and 6 bacteria (at the genus level) were significantly different between small and larger dogs. Hierarchical clustering of the metabolites yielded 8 modules associated with small dog size.

Conclusion

Small dogs had a lower antioxidant status and differences in circulating amino acids. Some of the amino acid differences could be attributed to differences in microflora. Additionally, analysis of small dog metabolites and clinical parameters reflected a network which strongly associates with kidney function.

Glutathione Peroxidase Activity, Plasma Total Antioxidant Capacity, and Urinary F2- Isoprostanes as Markers of Oxidative Stress in Anemic Dogs

Background

Oxidative stress plays a role in the pathophysiology of several diseases and has been documented as a contributor to disease in both the human and veterinary literature. One at‐risk cell is the erythrocyte, however, the role of oxidative stress in anemia in dogs has not been widely investigated.

Hypothesis/Objective

Anemic dogs will have an alteration in the activity of glutathione peroxidase (GPx), a decrease in of total antioxidant capacity (TAC), and an increased concentration of urinary 15‐F₂‐isoprostanes (F₂‐IsoP) when compared to healthy dogs.

Animals

40 client‐owned dogs with anemia (PCV <30%) age‐matched to 40 client‐owned healthy control dogs.

Methods

Prospective, cross‐sectional study. Whole blood GPx activity, plasma TAC, and urinary F₂‐isoprostane concentrations were evaluated in each dog and compared between groups.

Results

Anemic dogs had significantly lower GPx activity (43.1 × 10³ +/‐ 1.6 × 10³ U/L) than did dogs in the control group (75.8 × 10³ +/‐ 2.0 × 10³ U/L; P < 0.0001). The GPx activity in dogs with hemolysis (10³ +/‐ 0.8 × 10³ U/L) was not significantly different (P = 0.57) than in dogs with nonhemolytic anemia (43.5 × 10³ +/‐ 1.1 × 10³ U/L). The TAC concentrations (P = 0.15) and urinary F₂‐isoprostanes (P = 0.73) did not significantly differ between groups.

Conclusions and Clinical Importance

Glutathione peroxidase activity was significantly decreased in anemic dogs indicating oxidative stress. Additional studies are warranted to determine if antioxidant supplementation would improve survival and overall outcome as part of a therapeutic regimen for anemic dogs.

Biomarkers for differentiation of causes of respiratory distress in dogs and cats: Part 2--Lower airway, thromboembolic, and inflammatory diseases

OBJECTIVES

To review the current veterinary and relevant human literature regarding biomarkers of respiratory diseases leading to dyspnea and to summarize the availability, feasibility, and practicality of using respiratory biomarkers in the veterinary setting.

DATA SOURCES

Veterinary and human medical literature: original research articles, scientific reviews, consensus statements, and recent textbooks.

HUMAN DATA SYNTHESIS

Numerous biomarkers have been evaluated in people for discriminating respiratory disease processes with varying degrees of success.

VETERINARY DATA SYNTHESIS

Although biomarkers should not dictate clinical decisions in lieu of gold standard diagnostics, their use may be useful in directing care in the stabilization process. Serum immunoglobulins have shown promise as an indicator of asthma in cats. A group of biomarkers has also been evaluated in exhaled breath. Of these, hydrogen peroxide has shown the most potential as a marker of inflammation in asthma and potentially aspiration pneumonia, but methods for measurement are not standardized. D-dimers may be useful in screening for thromboembolic disease in dogs. There are a variety of markers of inflammation and oxidative stress, which are being evaluated for their ability to assess the severity and type of underlying disease process. Of these, amino terminal pro-C-type natriuretic peptide may be the most useful in determining if antibiotic therapy is warranted. Although critically evaluated for their use in respiratory disorders, many of the biomarkers which have been evaluated have been found to be affected by more than one type of respiratory or systemic disease.

CONCLUSION

At this time, there are point-of-care biomarkers that have been shown to reliably differentiate between causes of dyspnea in dogs and cats. Future clinical research is warranted to understand of how various diseases affect the biomarkers and more bedside tests for their utilization.

Characterization of feline serum-cobalt binding

BACKGROUND

Oxidative stress inhibits albumin's ability to complex with cobalt. Feline serum-cobalt binding has not been described.

OBJECTIVES

The objective was to develop a cobalt binding test for use with feline serum, and correlate the results with other biochemical and cellular constituents in blood, and with clinical diseases of cats.

METHODS

A colorimetric test of cobalt binding, based on the oxidation-reduction reaction of Co(+2) and dithiothreitol, was developed using feline serum. The test was used to measure cobalt binding in stored serum from 176 cats presented to the University of Illinois Veterinary Teaching Hospital for a variety of disease conditions. Time-matched hematology and biochemical data, and clinical information, were obtained from the medical record of each cat and correlated with the serum-cobalt binding results.

RESULTS

Serial dilution of feline serum with phosphate-buffered saline resulted in a highly linear decrease in serum-cobalt binding (r(2)  = .9984). Serum-cobalt binding of the clinical samples also correlated with albumin concentrations in a stepwise linear regression model (r(2)  = .425), and both cobalt binding and albumin were significantly decreased in cases of inflammation. Albumin and cobalt binding also shared significant correlations with several erythron variables, and serum concentration of total calcium and bilirubin.

CONCLUSIONS

The correlation of cobalt binding measured by a colorimetric test with albumin concentration in the clinical samples and with serum dilution is consistent with feline albumin-cobalt complex formation. Hypoalbuminemia is the likely cause of reduced serum-cobalt binding in inflammation and the correlations observed between cobalt binding and other variables.

Role of Rhipicephalus microplus cheliceral receptors in gustation and host differentiation

Rhipicephalus microplus is considered the most economically important ectoparasite of cattle worldwide. It is known that zebuine breeds of cattle are less susceptible to tick infestation than taurine breeds. Contact chemoreceptors in the cheliceral pit sensilla of ticks respond selectively to phagostimulant compounds, however their role in blood feeding relative to host susceptibility to infestation remains to be fully understood. We addressed this topic by conducting taste electrophysiology experiments with cheliceral pit sensilla preparations of R. microplus females. Solutions of five known ixodid tick phagostimulants were tested at different concentrations: sodium (NaCl), and potassium chloride (KCl) (10(-3)-10(-1)M); glucose (10(-4)-10(-1)M); adenosine triphosphate (ATP) (10(-6)-10(-2)M); and reduced l-glutathione (GSH) (10(-6)-10(-2)M). Serum samples from six susceptible animals of the Girolando breed (5/8 Bos indicus×3/8 B. taurus) and six resistant Nelore bovines (pure B. indicus) were also tested. A dose-dependent response of gustatory neurons associated with the chelicerae sensillum to NaCl, glucose, GSH, and ATP were observed. Responses by the cheliceral inner digit pit sensilla of R. microplus to KCl and glucose were also observed and they are reported here for the first time. In addition to an electrophysiological response to known phagostimulants, chemoreceptors in the chelicera of R. microplus responded differently to serum from cattle susceptible and resistant to infestation. The cheliceral pit neurons were more responsive to serum of R. microplus resistant bovines with a higher mean spike frequency (53.5±2spikess(-1)) than to serum samples from susceptible cattle (40.3±2spikess(-1)). The implications of chemosensation during tick blood feeding are discussed.

In vivo reduction of cell-free methemoglobin to oxyhemoglobin results in vasoconstriction in canines

BACKGROUND

Cell-free hemoglobin (Hb) in the vasculature leads to vasoconstriction and injury. Proposed mechanisms have been based on nitric oxide (NO) scavenging by oxyhemoglobin (oxyHb) or processes mediated by oxidative reactions of methemoglobin (metHb). To clarify this, we tested the vascular effect and fate of oxyHb or metHb infusions.

STUDY DESIGN AND METHODS

Twenty beagles were challenged with 1-hour similar infusions of (200 μmol/L) metHb (n = 5), oxyHb (n = 5), albumin (n = 5), or saline (n = 5). Measurements were taken over 3 hours.

RESULTS

Infusions of the two pure Hb species resulted in increases in mean arterial blood pressure (MAP), systemic vascular resistance index, and NO consumption capacity of plasma (all p < 0.05) with the effects of oxyHb being greater than that from metHb (MAP; increase 0 to 3 hr; 27 ± 6% vs. 7 ± 2%, respectively; all p < 0.05). The significant vasoconstrictive response of metHb (vs. albumin and saline controls) was related to in vivo autoreduction of metHb to oxyHb, and the vasoactive Hb species that significantly correlated with MAP was always oxyHb, either from direct infusion or after in vivo reduction from metHb. Clearance of total Hb from plasma was faster after metHb than oxyHb infusion (p < 0.0001).

CONCLUSION

These findings indicate that greater NO consumption capacity makes oxyHb more vasoactive than metHb. Additionally, metHb is reduced to oxyHb after infusion and cleared faster or is less stable than oxyHb. Although we found no direct evidence that metHb itself is involved in acute vascular effects, in aggregate, these studies suggest that metHb is not inert and its mechanism of vasoconstriction is due to its delayed conversion to oxyHb by plasma-reducing agents.

Effect of N-acetylcysteine supplementation on intracellular glutathione, urine isoprostanes, clinical score, and survival in hospitalized ill dogs

BACKGROUND

Antioxidant depletion and lipid peroxidation have been correlated with disease severity and associated with poor outcomes.

HYPOTHESIS/OBJECTIVES

Supplementing dogs with N-acetylcysteine (NAC) during the first 48 hours of hospitalization will increase cysteine, normalize glutathione concentrations, and decrease the degree of lipid peroxidation associated with illness.

ANIMALS

Sixty systemically ill hospitalized client-owned dogs and 14 healthy control dogs.

METHODS

Randomized investigator-blinded, placebo-controlled prospective study. Dogs were randomized to treatment with NAC (n = 30) versus placebo (n = 30). Antioxidants, urine 8-isoprostane/creatinine (IP/Cr), and clinical score were determined before and after treatment with NAC. Glutathione, cysteine, and vitamin E concentrations were quantified using high-performance liquid chromatography. Atomic absorption spectroscopy and enzyme-linked immunosorbent assays were used to quantify selenium and isoprostane concentrations, respectively.

RESULTS

Ill dogs had significantly lower vitamin E concentrations (27 versus 55 μg/mL; P = .0005) as well as elevated IP/Cr ratios (872 versus 399 pg/mg; P = .0007) versus healthy dogs. NAC supplementation significantly increased plasma cysteine (8.67 versus 15.1 μM; P < .0001) while maintaining glutathione concentrations. Dogs in the placebo group experienced a statistically significant decrease in glutathione concentrations (1.49 versus 1.44 mM; P = .0463). Illness severity and survival were unchanged after short duration NAC supplementation.

CONCLUSIONS

Ill dogs experience systemic oxidative stress. Supplementation with NAC during the first 48 hours of hospitalization stabilized erythrocyte glutathione concentrations. The clinical impact of this supplementation and glutathione concentration stabilization was undetermined.

Short-term culture of ovarian cortex pieces to assess the cryopreservation outcome in wild felids for genome conservation

Background

Cryopreservation of ovarian tissue has the potential to preserve female germ cells of endangered mammals. In the present study, a freezing protocol successfully used for human tissue, was adapted for preserving ovarian tissue of domestic and non-domestic felids. Ovaries from non-domestic felid species were obtained from seven freshly euthanized and two recently deceased wild felids kept in different European Zoos. In addition, ovaries from domestic cats were obtained after ovariectomy from local veterinary clinics for methological adaptations.

Ovarian cortex was dissected and uniform sized pieces of 2 mm diameter were obtained. Using a slow freezing protocol (-0.3°C per min) in 1.5 mol/L ethylene glycol, 0.1 mol/L sucrose, the pieces were cultured for up to 14 days both before and after cryopreservation. The integrity of primordial follicles was assessed by histology, and the impact of different protein sources (FCS or BSA) and Vitamin C was determined during two weeks of culture.

Results and conclusion

During culture the number of primordial follicles decreased within the ovarian pieces (p < 0.05). This effect was less pronounced when FCS was used as the protein source instead of BSA. Supplementation with Vitamin C had a detrimental effect on follicle survival. Since the procedure of cryopreservation had no effect on the follicle survival after one week of culture we conclude that the freezing protocol was suitable for felids. This is the first report of preserving a huge amount of follicles within ovarian tissue by slow freezing performed in several wild feline species.

Antioxidant status in hyperthyroid cats before and after radioiodine treatment

BACKGROUND

Reversible antioxidant depletion is found in hyperthyroid humans, and antioxidant depletion increases the risk of methimazole toxicosis in rats.

OBJECTIVES

To determine whether abnormalities in concentrations of blood antioxidants or urinary isoprostanes were present in hyperthyroid cats, and were reversible after radioiodine treatment. To determine whether or not antioxidant abnormalities were associated with idiosyncratic methimazole toxicosis.

ANIMALS

Hyperthyroid cats presented for radioiodine treatment (n = 44) and healthy mature adult control cats (n = 37).

METHODS

Prospective, controlled, observational study. Red blood cell glutathione (GSH), plasma ascorbate (AA), plasma free retinol (vitamin A), α-tocopherol (vitamin E), and urinary free 8-isoprostanes in hyperthyroid cats were compared to healthy cats and to hyperthyroid cats 2 months after treatment.

RESULTS

Blood antioxidants were not significantly different in hyperthyroid cats (mean GSH 1.6 ± 0.3 mM; AA 12.8 ± 4.9 μM, and vitamin E, 25 ± 14 μg/mL) compared to controls (GSH 1.4 ± 0.4 mM; AA 15.0 ± 6.6 μM, and vitamin E, 25 ± 17 μg/mL). Urinary isoprostanes were increased in hyperthyroid cats (292 ± 211 pg/mg creatinine) compared to controls (169 ± 82 pg/mg; P = .006), particularly in hyperthyroid cats with a USG < 1.035. Plasma free vitamin A was higher in hyperthyroid cats (0.54 ± 0.28 μg/mL versus 0.38 ± 0.21 in controls; P = .007). Both abnormalities normalized after radioiodine treatment. No association was found between oxidative status and prior idiosyncratic methimazole toxicosis.

CONCLUSION AND CLINICAL IMPORTANCE

Increased urinary isoprostane could reflect reversible renal oxidative stress induced by hyperthyroidism, and this requires additional evaluation.

Oxidative stress and neutrophil function in cats with chronic renal failure

BACKGROUND

Oxidative stress is an important component in the progression of chronic renal failure (CRF) and neutrophil function may be impaired by oxidative stress.

HYPOTHESIS

Cats with CRF have increased oxidative stress and decreased neutrophil function compared with control cats.

ANIMALS

Twenty cats with previously diagnosed renal failure were compared with 10 age-matched control cats.

METHODS

A biochemical profile, CBC, urinalysis, antioxidant capacity, superoxide dismutase (SOD) enzyme activity, reduced to oxidized glutathione ratio (GSH : GSSG), and neutrophil phagocytosis and oxidative burst were measured. Statistical comparisons (2-tailed t-test) were reported as mean +/- standard deviation.

RESULTS

The CRF cats had significantly higher serum blood urea nitrogen, creatinine, and phosphorus concentrations than control cats, and significantly lower PCV and urine specific gravity than control cats. The GSH : GSSG ratio was significantly higher in the CRF group (177.6 +/- 197, 61.7 +/- 33; P < .02) whereas the antioxidant capacity was significantly less in the CRF group (0.56 +/- 0.21, 0.81 +/- 0.13 Trolox units; P < .005). SOD activity was the same in control and CRF cats. Neutrophil oxidative burst after Escherichia coli phagocytosis, measured as an increase in mean fluorescence intensity, was significantly higher in CRF cats than controls (732 +/- 253, 524 +/- 54; P < .05).

CONCLUSIONS

The higher GSH : GSSG ratio and lower antioxidant capacity in CRF cats is consistent with activation of antioxidant defense mechanisms. It remains to be determined if supplementation with antioxidants such as SOD beyond the level of control cats would be of benefit in cats with CRF.