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OBJECTIVE: To evaluate a prototype dynamic laryngoplasty system (DLPS) in a static airflow model. STUDY DESIGN: Experimental. SAMPLE POPULATION: Ten equine larynges. METHODS: The right arytenoid was fixed in abduction in all specimens. A left-sided laryngoplasty was performed with No. 2 Fiberwire and a FASTakII anchor. Each larynx was tested in a static airflow model. The system was adjusted to a flow rate of 55 L/s and prelaryngeal pressure of 12 mm Hg prior to testing in maximal arytenoid abduction. In phase 1, the left suture was loosened, shortened, and tested in 3-mm steps from 0 to 30 mm. In phase 2, the suture was tied with the DLPS in position at a target left-to-right quotient angle (LRQ) of 0.5. The DLPS was activated to target psi of 0, 25, and 50 for testing. Translaryngeal impedance (TLI), LRQ, cross-sectional areas (CSA), and resultant change in LRQ and CSA between, before, and during airflow testing were calculated. RESULTS: In phase 1, TLI was reduced by suture shortening up to 6 mm (P = .001) but not by additional shortening (P > .05). In phase 2, activation of the DLPS reduced the TLI from 0 psi (0.43 ± 0.08 mm Hg/L/s) to 25 psi (0.16 ± 0.04 mm Hg/L/s, P < .001), but no further reduction was detected at maximal psi (P = .10). CONCLUSION: Activation of the DLPS effectively reduced TLI. CLINICAL SIGNIFICANCE: These results justify further investigation of the DLPS to assess its clinical applicability.
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Cartilagem Aritenoide/cirurgia , Cavalos/cirurgia , Laringoplastia/veterinária , Laringe/cirurgia , Técnicas de Sutura/veterinária , Animais , Cadáver , Laringoplastia/instrumentação , Laringoplastia/métodos , VácuoRESUMO
Venous thromboembolism is a common complication of cancer. Based on recent evidence that (1) growth arrest-specific 6 (Gas6) regulates the expression of tissue factor during venous thrombosis, and (2) cancer promotes a procoagulant milieu, we hypothesize that Gas6 may be involved in cancer-induced coagulopathy. Venous thrombi were induced in both wild-type (WT) and Gas6-deficient ((-/-)) mice with cancer. WT mice with cancer developed larger thrombi than their healthy counterparts; these larger thrombi induced by cancer were not seen in Gas6(-/-) mice. Whole genome microarray analysis of differential gene expression in WT and Gas6(-/-) endothelial cells exposed to M27 murine lung carcinoma cells reveal that Gas6 increases prostaglandin E synthase (Ptges) expression in endothelial cells. This was confirmed using real-time polymerase chain reaction and immunofluorescence staining. Culture of WT endothelial cells with M27 increases the secretion of prostaglandin E2 (PGE2), the enzymatic product of Ptges, in WT but not in Gas6(-/-) endothelial cells. In WT endothelial cells, Ptges expression was regulated through extracellular signal-regulated kinase 1/2 phosphorylation (ERK1/2). In vitro, PGE2 activates platelets after binding to its receptor, EP3. In vivo, EP3 receptor antagonism reversed the effect of cancer-induced thrombosis in WT mice. These results show that Gas6, through upregulation of PGE2, contributes to cancer-induced venous thrombosis.
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Peptídeos e Proteínas de Sinalização Intercelular/fisiologia , Oxirredutases Intramoleculares/genética , Neoplasias/complicações , Trombose Venosa/etiologia , Animais , Células Cultivadas , Dinoprostona/efeitos adversos , Dinoprostona/metabolismo , Regulação Enzimológica da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Peptídeos e Proteínas de Sinalização Intercelular/genética , Oxirredutases Intramoleculares/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neoplasias/genética , Neoplasias/patologia , Prostaglandina-E Sintases , Regulação para Cima , Trombose Venosa/genética , Trombose Venosa/patologiaRESUMO
OBJECTIVE: Coagulation and inflammation are inter-related. Gas6 (growth arrest-specific 6) promotes venous thrombosis and participates to inflammation through endothelial-innate immune cell interactions. Innate immune cells can provide the initiating stimulus for venous thrombus development. We hypothesize that Gas6 promotes monocyte recruitment during venous thrombosis. APPROACH AND RESULTS: Deep venous thrombosis was induced in wild-type and Gas6-deficient (-/-) mice using 5% FeCl3 and flow reduction in the inferior vena cava. Total monocyte depletion was achieved by injection of clodronate before deep venous thrombosis. Inflammatory monocytes were depleted using an anti-C-C chemokine receptor type 2 (CCR2) antibody. Similarly, injection of an anti-chemokine ligand 2 (CCL2) antibody induced CCL2 depletion. Flow cytometry and immunofluorescence were used to characterize the monocytes recruited to the thrombus. In vivo, absence of Gas6 was associated with a reduction of monocyte recruitment in both deep venous thrombosis models. Global monocyte depletion by clodronate leads to smaller thrombi in wild-type mice. Compared with wild type, the thrombi from Gas6-/- mice contain less inflammatory (CCR2hiCX3CR1lo) monocytes, consistent with a Gas6-dependent recruitment of this monocyte subset. Correspondingly, selective depletion of CCR2hiCX3CR1lo monocytes reduced the formation of venous thrombi in wild-type mice demonstrating a predominant role of the inflammatory monocytes in thrombosis. In vitro, the expression of both CCR2 and CCL2 were Gas6 dependent in monocytes and endothelial cells, respectively, impacting monocyte migration. Moreover, Gas6-dependent CCL2 expression and monocyte migration were mediated via JNK (c-Jun N-terminal kinase). CONCLUSIONS: This study demonstrates that Gas6 specifically promotes the recruitment of inflammatory CCR2hiCX3CR1lo monocytes through the regulation of both CCR2 and CCL2 during deep venous thrombosis.
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Quimiotaxia de Leucócito , Inflamação/metabolismo , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Monócitos/metabolismo , Receptores CCR2/metabolismo , Receptores de Quimiocinas/metabolismo , Veia Cava Inferior/metabolismo , Trombose Venosa/metabolismo , Animais , Receptor 1 de Quimiocina CX3C , Células Cultivadas , Quimiocina CCL2/genética , Quimiocina CCL2/metabolismo , Quimiotaxia de Leucócito/efeitos dos fármacos , Ácido Clodrônico/farmacologia , Modelos Animais de Doenças , Células Endoteliais/metabolismo , Predisposição Genética para Doença , Inflamação/genética , Inflamação/patologia , Inflamação/prevenção & controle , Peptídeos e Proteínas de Sinalização Intercelular/deficiência , Peptídeos e Proteínas de Sinalização Intercelular/genética , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Monócitos/efeitos dos fármacos , Comunicação Parácrina , Fenótipo , Receptores CCR2/genética , Transdução de Sinais , Veia Cava Inferior/efeitos dos fármacos , Veia Cava Inferior/patologia , Trombose Venosa/genética , Trombose Venosa/patologia , Trombose Venosa/prevenção & controleRESUMO
BACKGROUND: Phenylbutazone is often prescribed to manage pain caused by hyperinsulinemia-associated laminitis, but in diabetic people nonsteroidal anti-inflammatory drugs increase insulin secretion and pancreatic activity. HYPOTHESIS/OBJECTIVES: Investigate the effect of phenylbutazone administration on insulin secretion in horses. It was hypothesized that phenylbutazone will increase insulin secretion in horses with insulin dysregulation (ID). ANIMALS: Sixteen light breed horses, including 7 with ID. METHODS: Randomized cross-over study design. Horses underwent an oral glucose test (OGT) after 9 days of treatment with phenylbutazone (4.4 mg/kg IV q24h) or placebo (5 mL 0.9% saline). After a 10-day washout period, horses received the alternative treatment, and a second OGT was performed. Insulin and glucose responses were compared between groups (ID or controls) and treatments using paired t test and analyses of variance with P < .05 considered significant. RESULTS: In horses with ID, phenylbutazone treatment significantly decreased glucose concentration (P = .02), glucose area under the curve (2429 ± 501.5 vs 2847 ± 486.1 mmol/L × min, P = .02), insulin concentration (P = .03) and insulin area under the curve (17 710 ± 6676 vs 22 930 ± 8788 µIU/mL × min, P = .03) in response to an OGT. No significant effect was detected in control horses. CONCLUSION AND CLINICAL IMPORTANCE: Phenylbutazone administration in horses with ID decreases glucose and insulin concentrations in response to an OGT warranting further investigation of a therapeutic potential of phenylbutazone in the management of hyperinsulinemia-associated laminitis beyond analgesia.
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Dermatite , Doenças dos Cavalos , Hiperinsulinismo , Animais , Glicemia/análise , Dermatite/veterinária , Glucose , Teste de Tolerância a Glucose/veterinária , Doenças dos Cavalos/tratamento farmacológico , Cavalos , Hiperinsulinismo/tratamento farmacológico , Hiperinsulinismo/veterinária , Insulina/metabolismo , Secreção de Insulina , Fenilbutazona/uso terapêuticoRESUMO
Equine thyroid disorders pose a diagnostic challenge in clinical practice because of the effects of nonthyroidal factors on the hypothalamic-pituitary-thyroid axis, and the horse's ability to tolerate wide fluctuations in thyroid hormone concentrations and survive without a thyroid gland. While benign thyroid tumours are common in older horses, other disorders like primary hypothyroidism or hyperthyroidism in adult horses and congenital hypothyroidism in foals are rare. There is a common misunderstanding regarding hypothyroidism in adult horses, especially when associated with the clinical profile of obesity, lethargy, and poor performance observed in dogs and humans. Low blood thyroid hormone concentrations are often detected in horses as a secondary response to metabolic and disease states, including with the nonthyroidal illness syndrome; however, it is important to note that low thyroid hormone concentrations in these cases do not necessarily indicate hypothyroidism. Assessing equine thyroid function involves measuring thyroid hormone concentrations, including total and free fractions of thyroxine (T4) and triiodothyronine (T3); however, interpreting these results can be challenging due to the pulsatile secretion of thyroid hormones and the many factors that can affect their concentrations. Dynamic testing, such as the thyrotropin-releasing hormone stimulation test, can help assess the thyroid gland response to stimulation. Although true hypothyroidism is extremely rare, thyroid hormone supplementation is commonly used in equine practice to help manage obesity and poor performance. This review focuses on thyroid gland pathophysiology in adult horses and foals, interpretation of blood thyroid hormone concentrations, and evaluation of horses with thyroid disorders. It also discusses the use of T4 supplementation in equine practice.
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Doenças do Cão , Doenças dos Cavalos , Hipotireoidismo , Doenças da Glândula Tireoide , Humanos , Cavalos , Animais , Cães , Tireotropina/fisiologia , Hormônios Tireóideos/fisiologia , Doenças da Glândula Tireoide/diagnóstico , Doenças da Glândula Tireoide/tratamento farmacológico , Doenças da Glândula Tireoide/veterinária , Tiroxina/uso terapêutico , Tri-Iodotironina/fisiologia , Hipotireoidismo/diagnóstico , Hipotireoidismo/veterinária , Obesidade/veterinária , Doenças dos Cavalos/diagnóstico , Doenças dos Cavalos/tratamento farmacológico , Suplementos NutricionaisRESUMO
BACKGROUND: The thyrotropin-releasing hormone (TRH) stimulation test is used to diagnose pituitary pars intermedia dysfunction (PPID) using 10- or 30-min protocols. Imprecise sampling time for the 10-min protocol can lead to misdiagnoses. OBJECTIVES: To determine the effect of imprecise sampling time for the 30-min protocol of the TRH stimulation test. STUDY DESIGN: In vivo experiment. METHODS: Plasma immunoreactive adrenocorticotropin (ACTH) concentrations were measured 9, 10, 11, 29, 30 and 31 min after intravenous administration of 1 mg of TRH in 15 control and 12 PPID horses. Differences in ACTH concentrations between sampling times, variability in ACTH concentrations between protocols, and diagnostic classification of PPID were assessed using Friedman's test, Bland-Altman plots, and Fisher's exact test, respectively, with 95% confidence intervals reported and significance set at p < 0.05. RESULTS: Imprecise sampling time resulted in variable ACTH concentrations, but significant differences in absolute ACTH concentrations were not detected for imprecise sampling within each protocol or between protocols. Imprecise sampling changed PPID diagnostic classification for 3/27 (11 [4-28] %) horses for both protocols. Using the 30-min protocol as a reference, 1/12 (8 [1-35] %) horses returned a negative test result and 5/12 (42 [19-68] %) horses returned equivocal test results that would be considered positive in practice due to the presence of supportive clinical signs. MAIN LIMITATIONS: Limited sample size and inter-horse variability reduced the ability to detect small but potentially relevant differences. CONCLUSIONS: Overall, the impact of imprecise sampling was not significantly different between the 10- and 30-min TRH stimulation test protocols. However, diagnostic classification for PPID would have varied between the 10- and 30-min protocols in this population, if clinical signs had been ignored. Precise timing during TRH stimulation tests and contextual interpretation of ACTH concentrations remain fundamental for the diagnosis of PPID.
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Doenças dos Cavalos , Doenças da Hipófise , Adeno-Hipófise Parte Intermédia , Cavalos , Animais , Hormônio Liberador de Tireotropina , Doenças da Hipófise/diagnóstico , Doenças da Hipófise/veterinária , Hormônio Adrenocorticotrópico , Administração Intravenosa/veterinária , Doenças dos Cavalos/diagnósticoRESUMO
BACKGROUND: Insulin dysregulation (ID) is central to equine metabolic syndrome. There are limited epidemiological studies investigating dynamic testing of ID in ponies. OBJECTIVES: To evaluate prevalence and risk factors for ID through dynamic testing of hyperinsulinaemia (DHI) and insulin resistance (IR). STUDY DESIGN: Cross-sectional. METHODS: Sex, age, breed, height, cresty neck score (CNS), body condition score (BCS), laminitis, HMGA2:c.83G>A genotype and pituitary pars intermedia dysfunction (PPID) status were documented. Dynamic hyperinsulinaemia was diagnosed with an oral sugar test (OST) and IR with an insulin tolerance test (ITT). Owners completed surveys reporting activity, laminitis history and perception of body condition using a (1-9) visual analogue scale (VASo). Ordinal scores were converted to binary outcomes for CNS (≤2/5 or ≥3/5), BCS and VASo (≤6/9 or ≥7/9). Variables associated with insulin concentrations, glucose reduction after the ITT and laminitis were evaluated with mixed effects regression models accounting for random effects of farms. RESULTS: Among 167 ponies tested, median (range) age was 9 (4-21) years and BCS was 6 (4-8). Prevalence (95% confidence interval [CI]) of ID was 61 (53-68)%. Factors associated with insulin concentrations (estimate [95% CI]; µIU/mL) 60 min post-OST were: age (1.07 [1.02-1.11]), CNS (≥3/5, 1.52 [1.04-2.23]) and VASo (≥7/9, 1.75 [1.09-2.79]); and 90 min post-OST were: age (1.08 [1.03-1.12]), CNS (≥3/5, 1.80 [1.22-2.64]), VASo (≥7/9, 2.49 [1.52-4.08]) and sex (male, 0.64 [0.45-0.91]). Factors associated with glucose reduction after the ITT (estimate [95% CI]; %) were: age (-1.34 [-2.01 to -0.67]), sex (female, -6.21 [-11.68 to -0.74]) and VASo (≥7/9, -1.74 [-18.89 to -4.78]). Factors associated with laminitis (odds ratio [95% CI]) were DHI (4.60 [1.68-12.58]), IR (3.66 [1.26-10.61]) and PPID (11.75 [1.54-89.40]). MAIN LIMITATIONS: Single time-point sampling, laminitis definition and diet analysis. CONCLUSIONS: Ageing, being female and owner-perceived obesity were associated with ID.
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Doenças dos Cavalos , Hiperinsulinismo , Resistência à Insulina , Doenças da Hipófise , Cavalos , Animais , Feminino , Masculino , Insulina/metabolismo , Estudos Transversais , Hiperinsulinismo/veterinária , Doenças da Hipófise/veterinária , Austrália/epidemiologia , Glucose , Doenças dos Cavalos/diagnósticoRESUMO
BACKGROUND: Venous thromboembolism is associated with endothelial cell activation that contributes to the inflammation-dependent activation of the coagulation system. Cellular damage is associated with the release of different species of extracellular RNA (eRNA) involved in inflammation and coagulation. TLR3 (toll-like receptor 3), which recognizes (viral) single-stranded or double-stranded RNAs and self-RNA fragments, might be the receptor of these species of eRNA during venous thromboembolism. Here, we investigate how the TLR3/eRNA axis contributes to venous thromboembolism. METHODS AND RESULTS: Thrombus formation and size in wild-type and TLR3 deficient (-/-) mice were monitored by ultrasonography after venous thrombosis induction using the ferric chloride and stasis models. Mice were treated with RNase I, with polyinosinic-polycytidylic acid, a TLR3 agonist, or with RNA extracted from murine endothelial cells. Gene expression and signaling pathway activation were analyzed in HEK293T cells overexpressing TLR3 in response to eRNA or in human umbilical vein endothelial cells transfected with a small interference RNA against TLR3. Plasma clot formation on treated human umbilical vein endothelial cells was analyzed. Thrombosis exacerbated eRNA release in vivo and increased eRNA content within the thrombus. RNase I treatment reduced thrombus size compared with vehicle-treated mice (P<0.05). Polyinosinic-polycytidylic acid and eRNA treatments increased thrombus size in wild-type mice (P<0.01 and P<0.05), but not in TLR3-/- mice, by reinforcing neutrophil recruitment (P<0.05). Mechanistically, TLR3 activation in endothelial cells promotes CXCL5 (C-X-C motif chemokine 5) secretion (P<0.001) and NFκB (nuclear factor kappa-light-chain-enhancer of activated B cells) activation (P<0.05). Finally, eRNA triggered plasma clot formation in vitro (P<0.01). CONCLUSIONS: We show that eRNA and TLR3 activation enhance venous thromboembolism through neutrophil recruitment possibly through secretion of CXCL5, a potent neutrophil chemoattractant.
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Modelos Animais de Doenças , Células Endoteliais da Veia Umbilical Humana , Camundongos Endogâmicos C57BL , Camundongos Knockout , Infiltração de Neutrófilos , Receptor 3 Toll-Like , Trombose Venosa , Animais , Receptor 3 Toll-Like/metabolismo , Receptor 3 Toll-Like/genética , Trombose Venosa/metabolismo , Trombose Venosa/genética , Trombose Venosa/patologia , Humanos , Células Endoteliais da Veia Umbilical Humana/metabolismo , Transdução de Sinais , Células HEK293 , Lesões do Sistema Vascular/metabolismo , Lesões do Sistema Vascular/genética , Lesões do Sistema Vascular/patologia , Neutrófilos/metabolismo , RNA/genética , Masculino , Camundongos , Poli I-C/farmacologia , Coagulação SanguíneaRESUMO
Crofton weed (Ageratina adenophora) is a global and highly invasive weed, with ingestion causing severe respiratory disease in horses, leading to irreversible and untreatable pulmonary fibrosis and oedema. While reports of equine pneumotoxicity remain common in Australia and New Zealand, equine pneumotoxicity may be underdiagnosed in other countries where Crofton weed is endemic but poorly differentiated. The pathogenesis of Crofton weed toxicity following ingestion has been well described in a number of different animal models, including rodents, rabbits, and goats. However, induced toxicity is organ-selective across different animal species, and these vastly differ from the pathogenesis described in horses, both clinically and after experimental exposure. Sources of variation may include species-specific susceptibility to different toxins present in the plant, different mechanistic processes of toxicity, and species differences in toxin biotransformation and bioactivation across different organs. Considering disease severity and Crofton weed's invasiveness globally, assessing published toxicological and exposure data is necessary to advance research, identify specific toxins for horses, and possible prophylactic and therapeutic strategies. This review presents an overview of the available literature on equine toxicity, parallels between toxicity in horses and other animal species, and important aspects to be included in the future research agenda.
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BACKGROUND: Sirolimus, a mechanistic target of rapamycin inhibitor, suppresses insulin production in other species and has therapeutic potential for hyperinsulinemia in horses. HYPOTHESIS/OBJECTIVE: Determine the pharmacokinetics (PKs) of sirolimus and evaluate its effect on insulin dynamics in healthy and insulin dysregulation (ID) horses. ANIMALS: Eight Standardbred geldings. METHODS: A PK study was performed followed by a placebo-controlled, randomized, crossover study. Blood sirolimus concentrations were measured by liquid chromatography-mass-spectrometry. PK indices were estimated by fitting a 2-compartment model using nonlinear least squares regression. An oral glucose test (OGT) was conducted before and 4, 24, 72, and 144 hours after administration of sirolimus or placebo. Effects of time, treatment and animal on blood glucose and insulin concentrations were analyzed using mixed-effects linear regression. Sirolimus was then administered to 4 horses with dexamethasone-induced ID and an OGT was performed at baseline, after ID induction and after 7 days of treatment. RESULTS: Median (range) maximum sirolimus concentration was 277.0 (247.5-316.06) ng/mL at 5 (5-10) min and half-life was 3552 (3248-4767) min. Mean (range) oral bioavailability was 9.5 (6.8-12.4)%. Sirolimus had a significant effect on insulin concentration 24 hours after a single dose: median (interquartile range) insulin at 60 min (5.0 [3.7-7.0] µIU/mL) was 37 (-5 to 54)% less than placebo (8.7 [5.8-13.7] µIU/mL, P = .03); and at 120 min (10.2 [8.4-12.2] µIU/mL) was 28 (-15 to 53)% less than placebo (14.9 [8.4-24.8] µIU/mL, P = .02). There was minimal effect on glucose concentration. Insulin responses decreased toward baseline in ID horses after 7 days of treatment. CONCLUSION AND CLINICAL IMPORTANCE: Sirolimus decreased the insulinemic response to glucose and warrants further investigation.
Assuntos
Doenças dos Cavalos , Insulina , Cavalos , Animais , Masculino , Teste de Tolerância a Glucose/veterinária , Estudos Cross-Over , Glicemia/análise , GlucoseRESUMO
BACKGROUND: The HMGA2:c.83G>A variant was identified in Welsh ponies having pleiotropic effects on height and insulin concentration. OBJECTIVE: Determine whether the HMGA2:c.83G>A variant is associated with decreased height and higher basal insulin concentrations across pony breeds. ANIMALS: Two hundred thirty-six ponies across 6 breeds. METHODS: Cross-sectional study. Ponies were genotyped for the HMGA2:c.83G>A variant and phenotyped for height and basal insulin concentrations. Stepwise regression was performed for model analysis using a linear regression model for height and mixed linear model for insulin with farm as a random effect. Coefficient of determination, pairwise comparison of the estimated marginal means and partial correlation coefficients (parcor) were calculated to assess the relationship between HMGA2 genotype and height or insulin. RESULTS: Breed and genotype accounted for 90.5% of the variation in height across breeds, and genotype explained 21% to 44% of the variation within breeds. Breed, genotype, cresty neck score, sex, age, and farm accounted for 45.5% of the variation in insulin, with genotype accounting for 7.1%. The HMGA2 A allele frequency was 62% and correlated with both height (parcor = -0.39; P < .001) and insulin (parcor = 0.22; P = .02). Pairwise comparisons found A/A ponies were >10 cm shorter than other genotypes. Compared with G/G individuals, A/A and G/A individuals had 4.3 µIU/mL (95% confidence interval [CI]: 1.8-10.5) and 2.7 µIU/mL (95% CI: 1.4-5.3) higher basal insulin concentrations, respectively. CONCLUSIONS AND CLINICAL IMPORTANCE: These data demonstrate the pleiotropic effects of the HMGA2:c.83G>A variant and its role in identifying ponies at increased risk for insulin dysregulation.
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Proteína HMGA2 , Doenças dos Cavalos , Resistência à Insulina , Animais , Estudos Transversais , Genótipo , Doenças dos Cavalos/genética , Cavalos , Insulina , Resistência à Insulina/fisiologia , Fenótipo , Proteína HMGA2/genéticaRESUMO
Pituitary pars intermedia dysfunction (PPID) is an endocrinopathy commonly affecting old horses. It is a spontaneously occurring, progressive disease that is still poorly understood. Previous studies have observed neurodegeneration of the dopaminergic inhibition of melanotrophs, which leads to decreased dopamine (DA) in the pars intermedia (PI) and increased pro-opiomelanocortin-derived peptides circulating in plasma. However, rats knockout for the dopamine D2 receptor (D2r) similarly develop PI hypertrophy and hyperplasia. Thus, based on the current pathophysiological theory of PPID, whether the decreased DA or the D2r dysfunction leads to PPID is still unclear. To test this, a total of 28 retrospective cases of horses with PPID were collected, graded and the expression of tyrosine hydroxylase (TH) and D2r in the PI were determined. The histological and immunohistochemical results demonstrated that horses with higher tumor histological grades had reduced TH expression with increased D2r immunoreactivity colocalized in the PI (p < 0.001, p < 0.05 respectively). This correlation supports the role of DA in the pathogenesis of continuous unregulated proliferation of neoplastic cells in PI and indicates the efficiency of D2r agonists as a treatment for PPID.
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Doenças dos Cavalos , Doenças da Hipófise , Adeno-Hipófise Parte Intermédia , Doenças dos Roedores , Cavalos , Animais , Ratos , Dopamina/metabolismo , Estudos Retrospectivos , Doenças dos Cavalos/patologia , Doenças da Hipófise/genética , Doenças da Hipófise/veterinária , Doenças da Hipófise/metabolismo , Receptores de Dopamina D2/genética , Receptores de Dopamina D2/metabolismo , Adeno-Hipófise Parte Intermédia/metabolismo , Adeno-Hipófise Parte Intermédia/patologiaRESUMO
Pituitary pars intermedia dysfunction (PPID) is diagnosed by increased basal or post thyrotropin-releasing hormone (TRH) stimulation ACTH concentrations. ACTH is known to be unstable; however, the effect of different temperatures and TRH stimulation on equine ACTH stability is poorly described. In total, 15 horses, including 8 PPID positive (ACTH > 35 pg/mL at baseline or >65 pg/mL 30 min after TRH stimulation), were divided into 2 groups: 9, including 5 PPID positive, with basal ACTH concentrations and 6, including 3 PPID positive, with post TRH stimulation ACTH concentrations. Whole blood was stored for 1 h at 4, 20, 30, 40, or 70 °C. After centrifugation, immunoreactive ACTH concentrations were determined using a chemiluminescent assay. Linear mixed effect models were used to detect the effects of temperature, PPID status, and TRH stimulation on the immunoreactive ACTH concentration. Temperature had a significant effect (p = 0.003) on immunoreactive ACTH concentrations, and this effect was greater in PPID-negative horses (p = 0.01), with the changes in immunoreactive ACTH concentrations being slightly unpredictably higher or lower than samples stored at 4 °C. Even at 20 °C, mean immunoreactive ACTH concentrations minimally changed by 5% in PPID horses and 12% in non-PPID horses after 1 h. No significant effect of TRH stimulation was identified. Although ACTH concentrations should ideally be determined from samples kept at 4 °C, samples inadvertently left at temperatures of up to 40 °C can provide valid results if analyzed within 1 h; however, this increases the risks of altered ACTH concentrations, occasionally influencing the diagnosis of PPID.
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Although there are many hormonal changes associated with reproduction, the effects of ovulation and early pregnancy on adrenocorticotropic hormone (ACTH) and insulin concentrations are poorly described. We hypothesise that both ovulation and early pregnancy will alter ACTH and insulin concentrations in healthy mares. Eighteen mares showing no clinical signs suggestive of, or laboratory findings consistent with, pituitary pars intermedia dysfunction PPID and insulin dysregulation (ID) are enrolled. ACTH, cortisol, insulin and glucose concentrations are measured over their peri-ovulatory period, as determined via ultrasounds and progesterone concentrations. The mares are grouped by age and gestation status, and a two-way repeated-measures ANOVA is used to determine the effects of age and early pregnancy, along with the peri-ovulatory period, on analyte concentrations. No significant effect of age, ovulation or early pregnancy is detected on the mares' cortisol, insulin or glucose concentrations; however, there is a significant effect of early pregnancy and ovulation on ACTH concentrations (p = 0.04 and p = 0.04 respectively). ACTH concentrations change around ovulation and with early pregnancy. Therefore, knowledge of a mare's reproductive status might be beneficial when interpreting ACTH concentrations.
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BACKGROUND: Pituitary pars intermedia dysfunction (PPID) is a common endocrinopathy of horses diagnosed with a thyrotropin-releasing hormone (TRH) stimulation test. HYPOTHESIS/OBJECTIVES: Describe the repeatability of TRH stimulation in horses with and without PPID in winter and autumn. ANIMALS: Twenty adult horses; 6 controls and 6 with PPID tested in autumn, 8 controls and 6 with PPID tested in winter with 3 controls and 3 with PPID tested in both seasons. METHODS: Thyrotropin-releasing hormone stimulation was performed on 2 consecutive occasions, 1 week before and 1 week after the winter solstice and the autumn equinox. Blood was collected before and 30 minutes after IV injection of 1 mg of TRH. ACTH concentration was determined by a chemiluminescent assay. Repeatability and test-retest reliability were assessed by repeated measures analysis of variance, intraclass correlation coefficient and within-horse coefficients of variation (CV). Bland-Altman plots were generated to visualize agreement between repetitions. RESULTS: In winter, no week effect was detected on the results of the TRH simulation and the test had an excellent test-retest reliability. In autumn, after-TRH ACTH concentrations were significantly lower on week 2 (P = .02) and the test only had a good test-retest reliability. There were significantly larger within-horse CV during autumn (P = .04) and after TRH stimulation (P = .04). There were 2 misclassifications in winter and 4 in autumn. CONCLUSIONS AND CLINICAL IMPORTANCE: The TRH stimulation test was repeatable when performed 2 weeks apart in winter; however, in autumn, more variability in after-TRH ACTH concentrations resulted in decreased repeatability.
Assuntos
Doenças dos Cavalos , Doenças da Hipófise , Adeno-Hipófise Parte Intermédia , Hormônio Adrenocorticotrópico/metabolismo , Animais , Doenças dos Cavalos/diagnóstico , Cavalos , Doenças da Hipófise/diagnóstico , Doenças da Hipófise/veterinária , Reprodutibilidade dos Testes , Hormônio Liberador de TireotropinaRESUMO
BACKGROUND: Diagnosis of pituitary pars intermedia dysfunction (PPID) is problematic because of large variations in ACTH concentrations. HYPOTHESIS/OBJECTIVES: Compare the test characteristics of baseline and post-thyrotropin-releasing hormone (TRH) stimulation plasma ACTH concentrations in horses using diagnostic cutoff values (DCOVs) and reference intervals (RIs) and determine the clinical consequences of using each method. ANIMALS: One hundred six mature horses: 72 control cases and 34 PPID cases. METHODS: Prospective case-controlled study. Horses underwent monthly TRH stimulation tests. Diagnostic cutoff values were determined monthly by receiver operating characteristic curves using the Youden index. Reference intervals were determined monthly by a robust method. For each case age, sex and body condition score (BCS) were recorded. RESULTS: Baseline ACTH concentrations varied by month (P < .001) with significant "month × age" (P = .003), "month × sex" (P = .003), and "month × BCS" (P = .007) effects. Baseline ACTH concentrations were accurate to diagnose PPID (0.91 ± 0.06) with DCOVs increasing the test sensitivity (0.61 ± 0.21 to 0.87 ± 0.05, P = .002) and RI increasing test specificity (0.85 ± 0.12 to 0.98 ± 0.01, P = .01). Thyrotropin-releasing hormone stimulation improved test accuracy (0.91 ± 0.06 to 0.97 ± 0.03, P = .004). CONCLUSIONS AND CLINICAL IMPORTANCE: ACTH concentrations follow a circannual rhythm and vary with physiological factors. As using DCOVs increases the ability to detect mild cases and using RI decreases the risk of unnecessary treatments, ACTH concentrations should be interpreted within a specific clinical context. The TRH stimulation test improves the diagnosis of PPID.
Assuntos
Doenças dos Cavalos , Doenças da Hipófise , Adeno-Hipófise Parte Intermédia , Hormônio Adrenocorticotrópico/metabolismo , Animais , Doenças dos Cavalos/diagnóstico , Cavalos , Doenças da Hipófise/diagnóstico , Doenças da Hipófise/veterinária , Estudos Prospectivos , Hormônio Liberador de TireotropinaRESUMO
BACKGROUND: Endocrinopathic laminitis develops in association with insulin dysregulation, but the role of insulin in the pathogenesis remains unclear. Hyperinsulinemia can cause hypoaminoacidemia, which is associated with integumentary lesions in other species and therefore warrants investigation as a potential mechanism in laminitis. OBJECTIVE: Evaluate plasma amino acid concentrations in the euglycemic-hyperinsulinemic clamp (EHC) and prolonged glucose infusion (PGI) laminitis models. ANIMALS: Sixteen Standardbred horses. METHODS: Prospective experimental study. Plasma amino acid concentrations were measured in samples collected every 6 hours from horses that underwent a 48-hour EHC (n = 8) or 66-hour PGI (n = 8) after a 24- or 6-hour baseline period in EHC and PGI groups, respectively. RESULTS: Fifteen of the 20 measured amino acid concentrations decreased over time in both EHC and PGI horses (P < 0.001). The median percentage change from baseline for these amino acids was: histidine (EHC: 41.5%; PGI: 43.9%), glutamine (EHC: 51.8%; PGI: 35.3%), arginine (EHC: 51.4%; PGI: 41%), glutamic acid (EHC: 52.4%; PGI: 31.7%), threonine (EHC: 62.8%; PGI: 25.2%), alanine (EHC: 48.9%; PGI: 19.5%), proline (EHC: 56.2%; PGI: 30.3%), cystine (EHC: 34.9%; PGI: 31.2%), lysine (EHC: 46.4%; PGI: 27.8%), tyrosine (EHC: 27.5%; PGI: 16.9%), methionine (EHC: 69.3%; PGI: 50.8%), valine (EHC: 50.8%; PGI: 34.4%), isoleucine (EHC: 60.8%; PGI: 38.7%), leucine (EHC: 48.2%; PGI: 36.6%), and phenylalanine (EHC: 16.6%; PGI: 12.1%). CONCLUSIONS AND CLINICAL IMPORTANCE: Hypoaminoacidemia develops in EHC and PGI laminitis models. The role of hypoaminoacidemia in the development of hyperinsulinemia-associated laminitis warrants further investigation.
Assuntos
Doenças do Pé , Casco e Garras , Doenças dos Cavalos , Hiperinsulinismo , Aminoácidos , Animais , Doenças do Pé/veterinária , Doenças dos Cavalos/etiologia , Cavalos , Hiperinsulinismo/veterinária , Estudos ProspectivosRESUMO
Prudent use of antimicrobials is paramount to slow the development of resistance and for successful treatment. The use of cumulative antibiograms will allow evidence-based antimicrobial selection with consideration of local resistance patterns. We generated a "first-isolate-per-patient" cumulative antibiogram for a regional equine referral hospital. Bacterial organisms cultured from horses between 2011 and 2018, sample origin, antimicrobial susceptibilities, and multidrug-resistant (MDR) status were tabulated. Of 1,176 samples, 50% were culture positive. Overall, 93 of 374 (25%) were MDR. Of the MDR isolates, 11 (12%) were susceptible to high-importance antimicrobials only (as defined by the Australian Strategic and Technical Advisory Group on antimicrobial resistance). ß-hemolytic streptococci were uniformly susceptible to penicillin (76 of 76); 17 of 20 (85%) non-ß-hemolytic Streptococcus spp. were susceptible to penicillin. Despite veterinary-specific challenges in constructing an antibiogram, our study provides an exemplar of the clinical utility of regional-, farm-, or hospital-specific cumulative antibiograms for evidence-based empirical antimicrobial selection by veterinarians prior to susceptibility result availability.
Assuntos
Bactérias/isolamento & purificação , Cavalos/microbiologia , Testes de Sensibilidade Microbiana/veterinária , Animais , Bactérias/efeitos dos fármacos , Farmacorresistência Bacteriana Múltipla , Hospitais Veterinários/estatística & dados numéricos , Testes de Sensibilidade Microbiana/estatística & dados numéricos , QueenslandRESUMO
BACKGROUND: In metabolically stable horses, alpha-2-agonists suppress insulin secretion with transient hyperglycemia and rebound hyperinsulinemia. In horses with insulin dysregulation (ID), the effect of alpha-2-agonists has not been investigated; however, both the alpha-2-agonist-induced suppression of insulin secretion and rebound hyperinsulinemia could have clinical relevance. HYPOTHESIS/OBJECTIVES: In horses with ID, alpha-2-agonists will alter insulin and glucose dynamics. ANIMALS: Seven horses with ID and 7 control horses. METHODS: In this randomized crossover study, xylazine hydrochloride (1.1 mg/kg) or detomidine hydrochloride (30 µg/kg) were administered IV, and blood was collected for glucose and insulin concentrations at 0, 15, 30, 45, 60, 90, 120, 150, 180, and 300 minutes after administration. Horses received each drug in a random order with a 24-hour washout period between drugs. Percent change in glucose and insulin concentrations was compared between groups, drugs, and over time with P < .05 considered significant. RESULTS: A significant time-dependent effect of both alpha-2-agonists on glucose and insulin concentrations in control and ID horses was identified (P = .01 for all comparisons). There was no significant effect of sedative selection and endocrine status on blood glucose concentration in either group; however, in ID horses, xylazine administration resulted in severe rebound hyperinsulinemia whereas detomidine administration did not (P = .02). CONCLUSIONS AND CLINICAL IMPORTANCE: Alpha-2-agonists have a significant effect on glucose and insulin concentrations in horses. In ID horses, detomidine could minimize hyperinsulinemia when compared to xylazine.
Assuntos
Agonistas de Receptores Adrenérgicos alfa 2/farmacologia , Glicemia/efeitos dos fármacos , Sedação Consciente/veterinária , Cavalos/fisiologia , Hipnóticos e Sedativos/farmacologia , Imidazóis/farmacologia , Insulina/sangue , Xilazina/farmacologia , Animais , Estudos Cross-Over , Feminino , Cavalos/sangue , MasculinoRESUMO
BACKGROUND: Determination of plasma adrenocotrophic hormone (ACTH) concentration (endogenous or thyrotropin-releasing hormone [TRH] stimulation test) is the most commonly used diagnostic test for pituitary pars intermedia dysfunction (PPID) in horses. Because ACTH is unstable, samples often are frozen to be shipped to laboratories or to allow for batch analysis of research samples. However, the effect of multiple freeze-thaw cycles on equine ACTH is unknown. OBJECTIVE: To determine the effects of multiple freeze-thaw cycles on immunoreactive ACTH concentration. ANIMALS: Twenty-eight horses ranging from 10 to 27 years of age were used. METHODS: Prospective study. Horses were divided into 4 groups: group 1, PPID-negative, without TRH stimulation; group 2, PPID-negative, with TRH stimulation; group 3, PPID-positive, without TRH stimulation; and group 4, PPID-positive, with TRH stimulation. Whole blood was collected from each horse at baseline or 30 minutes after TRH stimulation. Immunoreactive plasma ACTH concentration was determined using a chemiluminescence assay. Plasma samples then were frozen at -80°C >24 hours, thawed at 4°C and reanalyzed for 5 freeze-thaw cycles. Changes in plasma ACTH concentration were analyzed using a linear mixed-effect model. RESULTS: Significant effects of freeze-thaw cycles (P = .001) and PPID status (P = .04) on plasma ACTH concentration were observed, but no significant effect of TRH stimulation was identified. CONCLUSIONS AND CLINICAL IMPORTANCE: The plasma ACTH concentration is altered by freeze-thaw cycles, and the effect is observed sooner in horses with PPID. To diagnose PPID, multiple freeze-thaw cycles should be avoided when measuring plasma ACTH concentration.