Effects of chloride conductance inhibitors on fluid secretion into ligated ileal and jejunal loops in pigs   总被引：1，自引：0，他引：1  

G W Forsyth  S E Gabriel 《American journal of veterinary research》1990,51(10):1551-1555

Compounds that prevent chloride transport in membrane vesicles have been tested for in vivo activity against the effects of intestinal secretory agents. Chloride channel blockers including diphenylamine-2-carboxylate, 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonate, 5-nitro-2-(2-phenylethylamino)benzoic acid, and alpha-phenylcinnamic acid were tested for effects on jejunal or ileal secretion in weanling pigs. Secretion was studied in ligated intestinal loops in a control state, during exposure to secretory concentrations of theophylline, and after prior treatment with cholera toxin. Increases in net fluid flux induced by either theophylline or cholera toxin were not prevented by adding chloride channel blockers into the intestinal lumen. Channel blocker concentrations that reduced chloride transport by greater than 50% in pig jejunal brush border vesicles did not cause significant changes in unidirectional blood to lumen chloride flux measured in situ. Several routes of administration of the specific chloride channel blocker alpha-phenylcinnamate failed to reduce fluid secretion induced by theophylline. Chloride channel blocker effectiveness appears to be significantly different between in vitro and in vivo experimental models. In contrast to the chloride channel blockers, loperamide significantly reduced net fluid and chloride flux in ileal loops secreting fluid in response to theophylline. Antagonism of the production or actions of second messenger by loperamide was more effective than the chloride channel blockers in reducing conductive chloride transport associated with intestinal secretion.  相似文献   

Calcium mediation of the pig jejunal secretory response.          下载免费PDF全文

G W Forsyth  P H Wong    D D Maenz 《Canadian journal of veterinary research》1985,49(2):179-185

The involvement of Ca++ ions as secretory mediators in pig jejunal epithelia has been investigated with an in vitro system. Omission of Ca++ from the Ringer-HCO3 bathing media on both sides of the tissue had minor effects on the basal electrical activity of pig jejunal mucosa. There were only slight decreases in transepithelial potential difference and increases in conductance with Ca++ free media. Low EGTA concentrations which reversibly blocked potential difference responses to secretory agents also had minimal effects on basal electrical activity. The in vitro secretory responses to A23187, to theophylline, and to Escherichia coli heat-stable enterotoxin were all eliminated by Ca++ depletion and restored by replacing normal Ca++ concentrations in the bathing media. Dantrolene prevented the secretory response but not the potential difference increases caused by heat-stable enterotoxin and A23187, suggesting that intracellular Ca++ stores may be reservoirs of secretory signal agent. Verapamil only blocked the secretory response to heat-stable enterotoxin. Chlorpromazine had negligible effects on basal conditions, but totally blocked both the secretory response and the Ca++-dependent effects of A23187 and heat-stable enterotoxin on potential difference. The response to theophylline was only partially inhibited by chlorpromazine, implying some involvement of both cAMP and Ca++ as secretory signals for theophylline. Cytoplasmic Ca++ concentrations appear to be at least as important as cyclic nucleotides in regulating the secretory effects of pig jejunum.  相似文献   

A survey of anaesthetic equipment in veterinary practices in New Zealand     

Scuffham AM  Forsyth SF  Jones BR 《New Zealand veterinary journal》1995,43(1):16-20

Sixty-four anaesthetic machines and 89 breathing circuits were surveyed in New Zealand veterinary practices. Each machine and circuit was tested for correct function. Sixty-six percent of machines checked were 10 years or older and vaporiser out-of-circuit machines totalled 72% of machines surveyed. Twenty-five percent of the temperature compensated vaporisers had been serviced within the previous 1 year, 33% serviced between 1 and 10 years ago, while the remaining 42% had no service record or had not been serviced for over 10 years. Sixty-six percent of machines had some type of scavenging device. Nineteen percent of machines had a leak in the high pressure system. Thirty percent of the anaesthetic machine low pressure systems leaked and 76% of the patient breathing circuits leaked. Overall, 91% of all anaesthetic machines and breathing circuits showed malfunctions which could increase practice operating costs, increase the exposure of practice personnel to anaesthetic agents, and increase patient morbidity.  相似文献   

THE VETERINARIAN AND NATIONAL SERVICE     

D. Forsyth  Stewart 《Australian veterinary journal》1942,18(5):216-217

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TWO MORTALITIES AMONG SHEEP DUE TO INFECTION WITH SPECIES OF THE SALMONELLA GROUP OF BACTERIA     

D. Forsyth  Stewart B.V.Sc.  Dip.Bact. 《Australian veterinary journal》1940,16(4):169-172

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Liposomes targeted to deliver antisecretory agents to jejunal mucosa.          下载免费PDF全文

R R Uwiera  D A Romancyia  J P Wong    G W Forsyth 《Canadian journal of veterinary research》1992,56(3):249-255

The B subunit of cholera toxin has been covalently attached to the surface of liposomes made from a mixture of phosphatidylethanolamine, phosphatidylcholine and cholesterol. Adenylate cyclase inhibitors and chloride conductance inhibitors were encapsulated within the liposomes. These "targeted" liposomes were used to study the combined effects of this novel delivery system, and a limited number of possible antisecretory agents, on net fluid flux into the pig jejunum. A state of net secretory fluid flux was induced in isolated jejunal loops in weanling pigs by adding theophylline or cholera toxin to the lumen of the isolated loops. There was no reduction in net fluid secretion when liposome suspensions without encapsulated secretory inhibitors were added to fluid in the lumen of loops treated with theophylline. There was also no reduction in net fluid secretion when miconazole, alpha-phenylcinnamate or 5 nitro-2-(3-phenethylamino)benzoate were encapsulated within targeted liposomes added to isolated jejunal loops. The net fluid flux induced by exposure of jejunal loops to theophylline was significantly reduced by adding targeted liposomes containing 2'-deoxy-3'-AMP. The reduction involved a reversal of net secretory fluid flux to an absorptive value. The net fluid secretory response to treatment of loops with cholera toxin was also inhibited by treating loops with targeted liposomes containing 2'-deoxy-3'-AMP. However, the reversal of secretion was less complete for secretion induced by cholera toxin than for secretion induced by theophylline. The reduced antisecretory efficacy versus cholera toxin was not improved by encapsulating higher concentrations of 2'-deoxy-3'-AMP.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

Differences in expression of retinal pigment epithelium mRNA between normal canines          下载免费PDF全文

Heather L.J. Hanik  Matthew E. Loewen  Greg D. Appleyard  Bruce H. Grahn    George W. Forsyth 《Canadian journal of veterinary research》2004,68(3):201-207

A reference database of differences in mRNA expression in normal healthy canine retinal pigment epithelium (RPE) has been established. This database identifies non-informative differences in mRNA expression that can be used in screening canine RPE for mutations associated with clinical effects on vision. Complementary DNA (cDNA) pools were prepared from mRNA harvested from RPE, amplified by PCR, and used in a subtractive hybridization protocol (representational differential analysis) to identify differences in RPE mRNA expression between canines. The effect of relatedness of the test canines on the frequency of occurrence of differences was evaluated by using 2 unrelated canines for comparison with 2 female sibling canines of blue heeler/bull terrier lineage. Differentially expressed cDNA species were cloned, sequenced, and identified by comparison to public database entries. The most frequently observed differentially expressed sequence from the unrelated canine comparison was cDNA with 21 base pairs (bp) identical to the human epithelial membrane protein 1 gene (present in 8 of 20 clones). Different clones from the same-sex sibling RPE contained repetitions of several short sequence motifs including the human epithelial membrane protein 1 (4 of 25 clones). Other prevalent differences between sibling RPE included sequences similar to a chicken genetic marker sequence motif (5 of 25), and 6 clones with homology to porcine major histocompatibility loci. In addition to identifying several repetitively occurring, noninformative, differentially expressed RPE mRNA species, the findings confirm that fewer differences occurred between siblings, highlighting the importance of using closely related subjects in representational difference analysis studies.  相似文献   

Nitric oxide causes the macroschizonts of Theileria annulata to disappear and host cells to become apoptotic     

Richardson  J.O.  Forsyth  L.M.G.  Brown  C.G.D.  Preston  P.M. 《Veterinary research communications》1998,22(1):31-45

The proliferation of Theileria annulata macroschizont-infected cell lines in vitro was significantly inhibited by nitric oxide (NO) generated by S-nitroso-N-acetyl-DL-penicillamine (SNAP). Incubation with SNAP caused the macroschizonts to disappear and host cells to become apoptotic. SNAP-derived NO also significantly inhibited the incorporation of tritiated thymidine by cultures of cells in which the schizonts had been induced to differentiate into merozoites by maintenance at 41°C instead of 37°C, the temperature used for culturing macroschizont-infected cells. These results point to NO as the mediator of macrophage anti-T. annulata activity and provide new evidence that the protective immune mechanisms which allow cattle to recover from primary infection and resist challenge may be attributed principally to the products of activated macrophages. These findings indicate that effective inactivated vaccines against T. annulata should include antigens able to stimulate the type of CD4+ T cell response which elicits macrophage activation and NO synthesis.  相似文献   

Letter: Ulceration of the sole in cattle.     

H Forsyth 《The Veterinary record》1975,96(20):457-458

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BLOOD GLUTATHIONE PEROXIDASE ACTIVITY IN HORSES IN RELATION TO MUSCULAR DYSTROPHY AND SELENIUM NUTRITION     

I. W. Caple  S. J. A. Edwards  W. M. Forsyth  †  Pam  Whiteley‡  R. H. Selth  § L. J. Fulton  ¶ 《Australian veterinary journal》1978,54(2):57-60

The activity of glutathione peroxidase, a selenium containing enzyme, was measured in the blood of horses to determine its usefulness as an indicator of selenium status. In 15 horses the enzyme activity was positively related to the blood selenium concentration (P<.001, r - 0.98) over the range of enzyme activities of 8.2 to 140 units (μmoles NADP-oxidised/min/gHb) and selenium concentrations of 0.24 to 2.74 μmol/k1. In a group of 8 horses which 2 foals had died with lesions of muscular dystrophy the enzyme activity increased from a mean of 11.8 units before treatment with selenium to 34.5 units after 2 intravenous injections of sodium selenite given one month apart. Another group of 8 horses grazing paddocks adjacent to this affected group did not receive any selenium treatment and had a mean enzyme activity of 11.9 units. Blood glutathione peroxidase activity was measured in 50 pasture-fed horses and 180 stallfed horses. The range of activities found (7 to 158 units) indicated that selenium intake in horses varied widely between localities. All pasture-fed horses grazing areas where muscular dystrophy had occurred in foals had low activities (less than 20 units). In stall-fed horses the enzyme activity was influenced by selenium treatment, and horses which had been treated usually had higher activities than horses in the same stable with no history of selenium treatment. It was concluded that blood glutathione peroxidase is a suitable indicator of selenium status in horses.  相似文献