Prostaglandin E2 and reactive oxygen metabolite damage in the cecum in a pony model of acute colitis

The objective of this project was to determine early tissue biochemical events associated with increased colonic secretion during the acute stage of castor-oil-induced colitis by measuring cecal mucosal and submucosal malondialdehyde (MDA) and prostaglandin E₂ (PGE₂), levels in ponies. Intestinal tissue (inflamed or healthy) samples were obtained from 4 age- and sex-matched Shetland ponies. Biochemical methods were used to determine MDA and PGE₂ levels in intestinal tissue samples from inflamed and healthy equine intestine. Inflamed tissue MDA and PGE₂ levels increased with time after castor oil challenge and correlated with granulocyte infiltration, as determined by myeloperoxidase levels in a companion study. Elevated intestinal tissue MDA levels suggest that lipid peroxidation could be attributed to reactive oxygen metabolites (ROM) released from stimulated, recruited, and resident granulocytes. Tissue levels of MDA and PGE₂ suggest a role for granulocyte-derived mediators of intestinal inflammation in the massive secretory response in cases of acute equine colitis. Tissue MDA and PGE₂ levels may be useful laboratory tools to quantify and characterize intestinal secretory inflammatory responses in acute inflammatory conditions in the equine colon.     

Growth and its partitioning in Prunus rootstocks in response to root zone temperature

Rootstocks for stone fruit varieties differentially influence tree physiology and one possible explanation for these differences is that varieties vary in their response to root zone temperature (RZT). To examine the effects of RZT, two trials using actively growing plants of five different Prunus rootstocks with chill requirements between 100 and 1100 h were undertaken. Plants were grown at RZTs of 5, 13 and 19 °C for 6 weeks after which total dry matter accumulation and its partitioning amongst roots, stems and leaves was determined. In general, the magnitude of total dry matter and its component parts positively correlated with RZT and significant differences were found among varieties in the magnitude of total dry matter accumulation. Individual varieties ranked differently at the three RZTs with respect to total dry matter: in general, the same ranking was also seen in the ranking of each growth component. RZT significantly influenced partitioning causing differences in leaf, stem and root mass ratios. These differences were greatest at low RZTs and became less as RZT increased. Several patterns of partitioning were found. Firstly, the low chill varieties (Okinawa and Flordagold) were little affected by RZT with similar partitioning occurring at each RZT. Secondly, the higher chill varieties, Green Leaf Nemaguard (GL), Golden Queen (GQ) and Fay Elberta (FE), reacted more strongly to RZT and were particularly affected by the lowest RZT. For these varieties, the root mass ratio rose and stem mass ratio fell as RZT increased. However, with respect to leaf mass ratio, two different trends were found: the leaf mass ratio for FE and GQ positively correlated with RZT whilst the relationship for GL was negative. These findings suggest that the response to RZT is related to a variety's chill requirement; offer an explanation for differences in performance of rootstock–scion combinations at different locations; and will aid the development of more accurate tree performance models by taking RZT into account.     

Why are there not more herbicide-tolerant crops?

Herbicide-tolerant (HT) varieties of corn, soybean, canola (oilseed rape) and cotton have been grown since the mid-1990s, and have been widely adopted by farmers in several countries. HT genes have been inserted into or selected for in many other species, including almost all major crop species in the world and many minor crops and ornamental species. In some cases this has been done specifically to introduce the HT trait, whereas in others the HT gene has been used as a selectable marker (eg the bar gene, conferring glufosinate-ammonium tolerance). However, in very few cases have the HT crops generated been commercialized, despite the weed-control advantages that many such crops would offer. There are several reasons for this, including the high research and development costs associated with developing the new HT crop cultivars, the high cost of obtaining regulatory clearance for the HT crops or products derived from them, international trade issues relating to genetically modified crops, and issues surrounding the expanded herbicide registration for the new use and the potential impact of this on the existing registration status of the herbicide. New HT crops are unlikely to be developed unless they offer a sufficiently large advantage to farmers and a substantial assured market to justify the associated development and regulatory costs.     

Mechanism of action and fate of the fungicide chlorothalonil (2,4,5,6-tetrachloroisophthalonitrile) in biological systems: I. Reactions with cells and subcellular components of Saccharomyces pastorianus

The mechanism and sequence of reaction of chlorothalonil in cells of Saccharomyces pastorianus was investigated by the use of either ¹⁴C-labeled fungicide or Na₂³⁵SO₄-labeled cells. The initial uptake of fungicide resulted in rapid formation of substituted chlorothalonil-reduced glutathione (GSH) derivatives. Chlorothalonil reacted with proteins during derivative formation but decreased cell viability did not occur until all the GSH was reacted and inhibition of specific NAD thiol-dependent glycolytic and respiratory enzymes occurred. It is postulated that enzyme activity and cell viability are controlled either directly or indirectly by the concentration of GSH. The loss of GSH through derivative formation with chlorothalonil and the lack of regeneration of the reduced thiol could be an important feature in the sequence of toxicity of the fungicide. The general mechanism of action of chlorothalonil resembles the trichloromethyl sulfenyl fungicides in that treated cells accumulate large concentrations of fungicide; reactions involve both low and high molecular-weight thiols, with the formation of glutathione-fungicide derivatives; and toxicity resides ultimately with the inhibition of thiol-dependent enzymes.     

Effects of continuous rate intravenous infusion of butorphanol on physiologic and outcome variables in horses after celiotomy

A randomized, controlled, blinded clinical trial was performed to determine whether butorphanol administered by continuous rate infusion (CRI) for 24 hours after abdominal surgery would decrease pain and surgical stress responses and improve recovery in horses. Thirty-one horses undergoing exploratory celiotomy for abdominal pain were randomly assigned to receive butorphanol CRI (13 microg/kg/h for 24 hours after surgery; treatment) or isotonic saline (control). All horses received flunixin meglumine (1.1 mg/kg IV q12h). There were no significant differences between treatment and control horses in preoperative or operative variables. Treatment horses had significantly lower plasma cortisol concentration compared with control horses at 2, 8, 12, 24, 36, and 48 hours after surgery. Mean weight loss while hospitalized was significantly less for treatment horses than control horses, whether expressed as total decrease in body weight (13.9+/-3.4 and 27.9+/-4.5 kg, respectively) or as a percentage decrease in body weight (2.6+/-0.7 and 6.3+/-1.1%, respectively). Treatment horses were significantly delayed in time to first passage of feces (median times of 15 and 4 hours, respectively). Treatment horses had significantly improved behavior scores during the first 24 hours after surgery, consistent with the conclusion that they experienced less pain during that time. Butorphanol CRI during the immediate postoperative period significantly decreased plasma cortisol concentrations and improved recovery characteristics in horses undergoing abdominal surgery.     

Altered target sites as a mechanism of herbicide resistance

Over 200 distinct herbicide resistant weed biotypes have evolved worldwide. In most of these, resistance is conferred by an altered target site, i.e. a modified target protein with reduced affinity for the herbicide(s) in question. This has been documented for herbicides that target most major known sites of action, including those that inhibit photosynthetic electron transfer at photosystem II, acetyl-CoA carboxylase, acetolactate synthase, and tubulin polymerization. Patterns of cross-resistance to structurally similar herbicides and those from other chemical classes that target the same site vary, depending on the mutation and its effect on protein steric and electronic properties. Mechanisms of target site-based herbicide resistance are reviewed, with emphasis on the biochemical and molecular basis for resistance.