Calcium mediation of the pig jejunal secretory response.

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.     

Observations on semen quality of dogs in the tropics

Semen was obtained from eight mongrels and 17 purebred dogs kept in a tropical climate. The mean spermatozoal output per ejaculate was 303.6 +/- 138.2 and 602.9 +/- 466.2 million, respectively. Values for individual progressive motility, live and abnormal spermatozoa were comparable with those obtained in temperate regions. The type and frequency of spermatozoal abnormalities are illustrated.     

Effects of exercise stress on various immune functions in horses.

Chemotactic locomotion and luminol-dependent chemiluminescence of neutrophils, mitogen-induced lymphocyte blastogenesis, serum cortisol concentration, immunoglobulin quantification, and leukocyte counts were determined to evaluate the effect of a single strenuous exercise in horses. Increased serum cortisol concentration (P less than 0.01) and an increased neutrophil-to-lymphocyte ratio (P less than 0.05) indicated that horses had been stressed. The chemotactic index and peak chemiluminescence production decreased significantly (P less than 0.05 and P less than 0.01, respectively) 1 day after exercise. Mitogen-induced blastogenesis of lymphocytes and serum immunoglobulin values remained unchanged in response to exercise. Results of this study indicated that a single bout of exercise may transiently impair neutrophil antimicrobial functions and nonspecific defense mechanisms, but not specific immunity in horses.     

Immunoglobulin E recognition of Dirofilaria immitis antigens is more specific than immunoglobulin G.

The chronological development of the serum IgE and IgG response to microfilaria, third and fourth stage larvae, and male and female adult Dirofilaria immitis was examined by enzyme-linked immunosorbent assay (ELISA) and enzyme-linked immunoelectrotransfer blot (EITB). Dirofilaria immitis-specific IgE and IgG levels peaked 16-18 weeks post-infection after increasing in response to the fourth larval molt. Specific IgG levels plateaued after patency, while IgE continued to decline. The use of ammonium sulfate cut sera showed there was no quenching or blocking of IgE binding by IgG in the ELISA and EITB methods used in this study. IgE-specific EITB showed 30-49 bands for the five respective extracts that were identified by M(r) or relative mobility. Eighty-five to 100 bands were visualized by IgG-specific EITB for the same five extracts. The isotype-specific ELISA and EITB were shown to be closely related by significant correlations (P < 0.0001) between S/N ratios and the number of bands found on blots. The isotype-specific EITB bands non-specifically recognized were greater in size than 21 kDa for IgG and 45 kDa for IgE. Recognition of bands changed over time with some bands being recognized only by prepatent sera. Ten antigen bands of seven M(r) were consistently and specifically recognized by IgE in the five-stage extracts by sera from prepatent and patent infections; only one such M(r) at 13.9 kDa, was described for IgG. A potentially diagnostic 31.9 kDa antigen band was identified on the IgE-specific EITB of D. immitis female extract and was shown to be recognized by IgE in sera from all infected dogs at all time points examined from 2 weeks until 1 year post-inoculation. Overall, IgE reactivity was more specific for D. immitis infections than IgG reactivity.     

Liposomes targeted to deliver antisecretory agents to jejunal mucosa.

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)     

Assessment of gastrointestinal nematode infection,anthelmintic usage and husbandry practices on two small-scale goat farms in Malaysia

Haemonchosis is a common problem on goat farms in tropical countries such as Malaysia. Prevention of production losses generally depends on the use of anthelmintic drugs, but is threatened by the emergence of anthelmintic resistance. This study investigates anthelmintic efficacy on small-scale Malaysian goat farms and describes putative risk factors. Adult goats had moderate to high pre-treatment faecal trichostrongyle egg counts, despite being housed on slatted floors and fed on cut-and-carry forage, raising questions about the source of nematode infection. Our results show multiple resistance to benzimidazole and macrocyclic lactone anthelmintic drugs and allow us to discuss the genetic origins of resistance with reference to farm husbandry and management. We conclude that improvement in Malaysian goat production efficiency will require the development of sustainable helminth control strategies, underpinned by a better understanding of the origins and population genetics of anthelmintic resistance.     

Repurposing Ionophores as novel antimicrobial agents for the treatment of bovine mastitis caused by Gram‐positive pathogens

Increasing reports of multidrug‐resistant bacterial infections in animals has created a need for novel antimicrobial agents that do not promote cross‐resistance to critically important antimicrobial classes used in human medicine. In response to the recent emergence of antimicrobial resistance in several bovine mastitis pathogens, in vitro antimicrobial susceptibility was determined for four polyether ionophores (lasalocid, monensin, narasin and salinomycin) against Staphylococcus spp. and Streptococcus spp. isolated from clinical cases. In addition, erythrocyte haemolysis and WST ‐1 cell proliferation assays were used to assess in vitro mammalian cell cytotoxicity and biofilm susceptibility testing was performed using the minimum biofilm eradication concentration (MBEC ?) biofilm assay. Lasalocid, monensin, narasin and salinomycin exhibited bacteriostatic antimicrobial activity against all pathogens tested, including methicillin‐resistant staphylococci, with MIC ₉₀ values <16 μg/ml. Narasin and monensin displayed the least toxicity against mammalian cell lines and all compounds significantly reduced viable cell numbers in a Staphylococcus aureus biofilm. Based on in vitro characterization, all four ionophores offer potentially novel treatments against bovine mastitis but in vivo studies will be essential to determine whether acceptable safety and efficacy is present following intramammary administration.