In vitro pharmacologic effect of two endothelin-1 antagonists on equine colonic arteries and veins

OBJECTIVE: To evaluate the effectiveness of 2 potential endothelin (ET)-1 antagonists in blocking the contractile responses of equine colonic vessels to increasing concentrations of ET-1. SAMPLE POPULATION: Mesenteric vessels from 6 clinically healthy horses. PROCEDURE: Colonic vessels (arterial and venous rings) were placed in organ baths with oxygenated Tyrode solution at 37 C. Each was attached to a force transducer interfaced with a polygraph, and 2 g of tension was applied and equilibrated for 45 minutes. Then, B-1 (PD 142893) and B-2 (PD 145065) ET-1 antagonists were tested. One ring from each vessel type was used as a control for determining concentration-response relationships of ET-1 (10(-10) to 10(-6)M). Three rings of each vessel type were incubated with 3 concentrations of each antagonist (10(-7), 10(-6), and 10(-5) M) for 30 minutes before ET induced contractions were determined. The maximum contractile response and pA2 values were determined. RESULTS: Vessels contracted in a concentration-dependent manner to ET-1. Arteries responded slowly but reached greater contractions. Veins responded immediately with sustained contractions. Both antagonists inhibited contractions in a concentration-dependent manner with significant differences at 10(-6) and 10(-5)M for arteries and 10(-5) M for veins. Complete blockade of contractions was observed with B-2 (10(-5)M). The pA2 values for B-1 were 8.26 and 6.82 for arteries and veins, respectively, whereas they were 8.25 and 7.21 for B-2. CONCLUSION AND CLINICAL RELEVANCE: Both antagonists effectively blocked ET-1-induced contractions of equine colonic vessels. Because B-2 is water soluble and caused complete blockade at 10(-5) M, it appears to be the preferred antagonist.     

Role of endothelium and nitric oxide in modulating in vitro responses of colonic arterial and venous rings to vasodilatory neuropeptides in horses

The objective of this study was to determine and compare the in vitro responses of equine large colon arterial and venous rings to vasodilatory neuropeptides; calcitonin gene-related peptide (CGRP); substance P (SP); vasoactive intestinal polypeptide (VIP); and acetylcholine (ACh), a standard nonpeptide endothelium-dependent vasodilator. Responses of vessel rings to graded concentrations (10(-11) M to 10(-5) M) of each drug were determined in endothelium-intact, denuded, and Nomega-nitro-L-arginine methyl ester (L-NAME, 10(-5) M)-treated rings that were pre-contracted with norepinephrine. Percentage maximal relaxation (PMR), defined as the % decrease from the contracted state, was determined. Because all rings did not relax at least 50%, EC50 values could not be consistently calculated. Arterial rings with intact endothelium were more sensitive to CGRP, compared with VIP and SP, and venous rings of all conditions were more sensitive to VIP than CGRP or SP. Overall, arteries had a greater PMR for ACh compared with SP and VIP. Intact and L-NAME treated arteries had a greater PMR than denuded arteries; there were no differences in PMR of intact and L-NAME treated arteries. Veins had a greater PMR for VIP than CGRP, SP, or ACh. Calcitonin gene-related peptide caused greater relaxation in intact arteries, whereas VIP causes greater relaxation in veins. Arterial relaxation was dependent upon the presence of intact endothelium. The response of veins to VIP among the conditions tested was not different, suggesting VIP has direct actions on venous smooth muscle. These neuropeptides modulate vasomotor tone via vasorelaxation in colonic arteries and veins.     

A B-cell targeting virus disrupts potentially protective genomic methylation patterns in lymphoid tissue by increasing global 5-hydroxymethylcytosine levels

The mechanisms by which viruses modulate the immune system include changes in host genomic methylation. 5-hydroxymethylcytosine (5hmC) is the catalytic product of the Tet (Ten-11 translocation) family of enzymes and may serve as an intermediate of DNA demethylation. Recent reports suggest that 5hmC may confer consequences on cellular events including the pathogenesis of disease; in order to explore this possibility further we investigated both 5-methylcytosine (5mC) and 5hmC levels in healthy and diseased chicken bursas of Fabricius. We discovered that embryonic B-cells have high 5mC content while 5hmC decreases during bursa development. We propose that a high 5mC level protects from the mutagenic activity of the B-cell antibody diversifying enzyme activation induced deaminase (AID). In support of this view, AID mRNA increases significantly within the developing bursa from embryonic to post hatch stages while mRNAs that encode Tet family members 1 and 2 reduce over the same period. Moreover, our data revealed that infectious bursal disease virus (IBDV) disrupts this genomic methylation pattern causing a global increase in 5hmC levels in a mechanism that may involve increased Tet 1 and 2 mRNAs. To our knowledge this is the first time that a viral infection has been observed to cause global increases in genomic 5hmC within infected host tissues, underlining a mechanism that may involve the induction of B-cell genomic instability and cell death to facilitate viral egress.     

A short review on sugarcane: its domestication,molecular manipulations and future perspectives

Sugarcane (Saccharum spp.) is a special crop plant that underwent anthropogenic evolution from a wild grass species to an important food, fodder, and energy crop. Unlike any other grass species which were selected for their kernels, sugarcane was selected for its high stem sucrose accumulation. Flowering in sugarcane is not favored since flowering diverts the stored sugar resources for the reproductive and developmental energy needs. Cultivars are vegetatively propagated and sugarcane breeding is still essentially focused on conventional methods, since the knowledge of sugarcane genetics has lagged that of other major crops. Cultivar improvement has been extremely challenging due to its polyploidy and aneuploidy nature derived from a few interspecific hybridizations between Saccharum officinarum and Saccharum spontaneum, revealing the coexistence of two distinct genome organization modes in the modern variety. Alongside implementation of modern agricultural techniques, generation of hybrid clones, transgenics and genome edited events will help to meet the ever-growing bioenergy needs. Additionally, there are two common biotechnological approaches to improve plant stress tolerance, which includes marker-assisted selection (MAS) and genetic transformation. During the past two decades, the use of molecular approaches has contributed greatly to a better understanding of the genetic and biochemical basis of plant stress-tolerance and in some cases, it led to the development of plants with enhanced tolerance to abiotic stress. Hence, this review mainly intends on the events that shaped the sugarcane as what it is now and what challenges ahead and measures taken to further improve its yield, production and maximize utilization to beat the growing demands.

     

Evolution of Marek's disease -- a paradigm for incessant race between the pathogen and the host

Marek's disease (MD) is a highly contagious lymphoproliferative disease of poultry caused by the oncogenic herpesvirus designated Marek's disease virus (MDV). MD has a worldwide distribution and is thought to cause an annual loss over 1 bn US dollars to the poultry industry. Originally described as a paralytic disease, today MD is mostly manifested as an acute disease with tumours in multiple visceral organs. MD is controlled essentially by the widespread use of live vaccines administered either in ovo into 18-day-old embryos or into chicks immediately after they hatch. In spite of the success of the vaccines in reducing the losses from the disease in the last 30 years, MDV strains have shown continuous evolution in virulence acquiring the ability to overcome the immune responses induced by the vaccines. During this period, different generations of MD vaccines have been introduced to protect birds from the increasingly virulent MDV strains. However, the virus has countered each new vaccine with ever more virulent strains. This continuous race between the virus and the host is making the control of this poultry health problem a major challenge for the future.     

In vitro evaluation of the contractile response to endothelin-1 of the circular and longitudinal myometrial layers of the uterine horn of nongravid mares

OBJECTIVE: To characterize the in vitro response of circular and longitudinal myometrial layers of the uterine horn (CMLH and LMLH, respectively) of horses to endothelin (ET)-1 by use of specific ETA (BQ-123) and ETB (IRL-1038) receptor antagonists. SAMPLE POPULATION: Uteruses from 10 nongravid mares in anestrus. PROCEDURE: Muscle strips from the CMLH and LMLH were suspended in tissue baths and connected to force-displacement transducers interfaced with a polygraph. Strips were incubated for 45-minute intervals with no antagonist (control specimens), and 3 concentrations (10(-9), 10(-7), and 10(-5)M) of BQ-123, IRL-1038, or BQ-123 and IRL-1038 before concentration-response curves to ET-1 were generated. Contractile response to cumulative concentrations of ET-1 (10(-9) to 10(-6)M) was quantified by measuring change in the area under the curve (AUC) for the 3-minute period after each ET-1 dose. RESULTS: ET-1 caused concentration-dependent contraction of the CMLH and LMLH specimens. Application of BQ-123 decreased AUC values for both layers. Application of IRL-1038 increased the AUC value for LMLH specimens but did not affect the CMLH value. The combination of BQ-123 and IRL-1038 decreased the AUC value for LMLH tissue and increased that for CMLH tissue. CONCLUSIONS AND CLINICAL RELEVANCE: ET-1 causes contraction of the CMLH and LMLH in nongravid horses. In both layers, ETA receptors mediate contraction but the role of ETB receptors remains unclear. In the LMLH, ETA receptors have a dominant role; the presence of another receptor or receptor subtype within this layer is suggested. These findings support a physiologic role for ET-1 in uterine contractility.     

Immunohistochemical determination of the expression of endothelin receptors in bronchial smooth muscle and epithelium of healthy horses and horses affected by summer pasture-associated obstructive pulmonary disease

OBJECTIVE: To immunohistochemically determine the expression of endothelin (ET) receptors in bronchial smooth muscle and epithelium of healthy horses and horses affected by summer pasture-associated obstructive pulmonary disease (SPAOPD). SAMPLE POPULATION: Tissue specimens obtained from 8 healthy and 8 SPAOPD-affected horses. PROCEDURE: Horses were examined and assigned to healthy and SPAOPD groups. Horses were then euthanatized, and tissue specimens containing bronchi of approximately 4 to 8 mm in diameter were immediately collected from all lung lobes, fixed in zinc-formalin solution for 12 hours, and embedded in paraffin. Polyclonal primary antibodies against ET-A or ET-B receptors at a dilution of 1:200 and biotinylated IgG secondary antibodies were applied to tissue sections, followed by the addition of an avidin-biotin immunoperoxidase complex. Photographs of the stained slides were digitally recorded and analyzed by use of image analysis software to determine the intensity of staining. Two-way ANOVA was used for statistical analysis. RESULTS: The left diaphragmatic lung lobe of SPAOPD-affected horses had a significantly greater area of bronchial smooth muscle that immunostained for ET-A, compared with that for healthy horses. All lung lobes of SPAOPD-affected horses, except for the right diaphragmatic lobe, had significantly greater staining for ET-B receptors in bronchial smooth muscle, compared with results for healthy horses. CONCLUSIONS AND CLINICAL RELEVANCE: This study revealed overexpression of ET-A and, in particular, ETB receptors in the bronchial smooth muscle of SPAOPD-affected horses, which suggested upregulation of these receptors. These findings improve our understanding of the role of ET-1 in the pathogenesis of SPAOPD.