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Biomedical subjects

G A Hall

Publications and source records attributed to G A Hall.

At least 55 records · Page 3Linked to original sources
PubMed1983

Quantitation of small intestinal structure and function in unthrifty piglets.

Litters of piglets were weighed at birth, weaning and five weeks later; pairs of thrifty and unthrifty weaned pigs were identified. Small intestinal structure and function were studied in 28 eight-week-old age-matched littermate pairs and in 16 weight-matched littermates. A comparison of age-matched piglets showed changes in mucosal structure in unthrifty piglets, a slight reduction in absorptive function but no biochemical evidence of small intestinal disease. Morphometric studies of weight-matched piglets revealed no differences between thrifty and unthrifty piglets, suggesting that the differences in the age-matched groups may have been an effect of body-weight. If unthrifty pigs grew slowly as a result of small intestinal damage and malfunction immediately after weaning no evidence of it remained when they were studied five weeks later.

Animals↗
PubMed1981

Responses of fluke-infected and fluke-free cattle to experimental reinfection with Salmonella dublin.

Cattle, aged nine to 18 months, were given sublethal doses of Salmonella dublin either intravenously, orally on two occasions, or by contact for 19 to 22 weeks with a persistent excretor. When challenged by intravenous injection of 10(9) S dublin at 10 to 22 weeks after their first exposure to S dublin 22 out of 36 animals survived. All similarly challenged cattle, which had not been previously exposed to S dublin, died. Infection with Fasciola hepatica did not alter the ability of cattle to survive reinfection with S dublin but the bacteria persisted in the tissues and were excreted in the faeces of fluke-infected animals for longer than in fluke-free animals. The ability to survive reinfection and to eliminate S dublin from the tissues was apparently unrelated to agglutinating antibody titres or delayed hypersensitivity.

Agglutinins↗
PubMed1979

Transport of cyclic adenosine 3',5'-monophosphate across Escherichia coli vesicle membranes.

The uptake and efflux of cyclic adenosine 3',5'-monophosphate (3',5'-cAMP) by Escherichia coli membrane vesicles were studied. Metabolic energy was not required for the uptake process and was found to actually decrease the amount of 3',5'-cAMP found in the vesicles. 3',5'-cAMP uptake exhibits saturation kinetics (Km = 10 mM, Vmax = 2.8 nmol/mg of protein per min) and was competitively inhibited by a number of 3',5'-cAMP analogs. The uptake of 3',5'-cAMP was found to be sharply affected by a membrane phase transition. The excretion of 3',5'-cAMP was studied by using everted membrane vesicles. Efflux in this system was dependent upon metabolic energy and was reduced or abolished by uncouplers. Different energy sources powered efflux at different rates, showing a relationship between the degree of membrane energization and rate of excretion of 3',5'-cAMP. The efflux process also displayed saturation kinetics (Km = 10.0 mM, Vmax = 0.98 nmol/mg of protein per min) and was competitively inhibited by the same 3',5'-cAMP analogs and to the same degree as was the uptake process. 3',5'-cAMP was found to be chemically unaltered by both the uptake and excretion processes. These data are interpreted as showing that the uptake and excretion of 3',5'-cAMP in E. coli membrane vesicles are carrier-mediated phenomena, possibly employing the same carrier system. Uptake is by facilitated diffusion whereas efflux is via an energy-dependent, active transport process. Evidence is presented showing that cells can regulate the number of 3',5'-cAMP transport carriers. The rate of 3',5'-cAMP excretion is possibly regulated by both the degree of membrane energization and the number of carriers present per cells.

Biological Transport↗
PubMed1979

Immunological responses of fluke-infected and fluke-free cattle to Salmonella dublin and other antigens.

Immune responses to heat-killed Brucella abortus strain 19 and to ovalbumin were compared in 15 fluke-infected and 15 fluke-free Friesian heifers. B abortus was injected 16 weeks and ovalbumin 19 weeks after the oral administration of 1000 metacercariae of Fasciola hepatica. Agglutinating antibody responses to B abortus were similar in both groups. Immediate type hypersensitivity to ovalbumin was apparently suppressed in fluke-infected animals when assessed by active and passive cutaneous anaphylaxis two weeks after sensitisation. However, when assessed by Schultz-Dale responses of intestine, in vitro, 36 weeks after sensitisation there was no difference between the groups. The heifers were subsequently given live Salmonella dublin intravenously. The fluke-infected animals which became carriers of S dublin had the most persistently elevated titres of agglutinating antibodies in their sera and the highest incidence of immediate-type hypersensitivity, as assessed by Schultz-Dale responses of intestine, but the weakest cutaneous delayed hypersensitivity reactions to S dublin. The latter might have been related to lymphopenia which developed after fluke infection. The increased susceptibility of fluke-infected cattle to S dublin cannot be attributed to impaired agglutinin responses but may result from effects on cell-mediated mechanisms.

Agglutinins↗
PubMed1978

A study of the susceptibility of cattle to oral infection by salmonellas contained in raw sewage sludge.

Raw sewage sludge, containing up to 10(5) naturally occuring salmonellas/1, was included in the diet of one group of cattle at the rate 1 ]/animal/day and in a second group at the rate of 1 ]/animal/week. Sterilized sludge, to which had been added 10(5) S. dublin/litre, was included in the diet of a third group of animals at the rate of 1 ]/animal/day. Salmonellas were isolated from all samples of raw sewage sludge but were not isolated from the faeces or carcasses of animals fed on the sludge. Salmonellas were isolated from the faeces of one animal and the carcasses of two animals fed on sterilized sludge to which S. dublin had been added.

Animal Feed↗
PubMed1978

The serology of experimental Salmonella dublin infections of cattle.

Agglutinating antibodies to somatic "O" and flagellar "H" antigens of S. dublin were measured in the serum of 43 pregnant heifers before intravenous or oral infection with S. dublin and in the serum of 21 uninfected control animals. The data from these animals were analysed statistically and a titre of 1/80, to both antigens, has been interpreted as of doubtful significance and a titre of 1/160 to both antigens, has been interpreted as significantly raised. Animals in which fetal infection occurred after challenge by either the intravenous or oral route developed significant increases in "H" and "O" titres indicating the value of measure "H" titres in the diagnosis of S. dublin abortion. In animals which were infected orally and in which infection appeared to be confined to the alimentary tract the "H" titre did not become significantly raised. Lack of correlation between antibody titres and faecal excretion of S. dublin and persistence of infection in carcasses confirms that the serum agglutination test is of no value in detecting latent carriers.

Abortion, Veterinary↗
PubMed1978

Investigation of a cutaneous delayed hypersensitivity response as a means of detecting Salmonella dublin infection in cattle.

Delayed hypersensitivity reactions developed 48 to 96 h after intradermal injection of killed Salmonella dublin in 25 of 28 cattle which had been inoculated intravenously, and in five of 10 cattle which had been inoculated orally with S dublin 24 to 493 days previously. Control animals showed no delayed hypersensitivity reactions. Persistence of infection in five of the intravenously inoculated and in four of the orally inoculated animals was confirmed by isolation of S dublin from the carcases at necropsy one week after skin testing. Failure to isolate the organism from the carcases of 21 animals which had reacted positively to the intradermal test did not eliminate the possibility of their being carriers of S dublin. Skin testing was concluded to be a reliable means of identifying animals which had been, and possibly still were, infected systemically with S dublin. However recovered animals might be falsely identified as infected. Repeated testing gave misleading results.

Administration, Oral↗
PubMed1976

The isolation of reovirus-like agents (rota-viruses) from acute gastroenteritis of piglets.

Isolations of reovirus-like agents (rotaviruses) were made from nine of 23 outbreaks of piglet diarrhoea on different farms and from both weaned and unweaned piglets. The viruses were shown to be morphologically and anti-genically similar to the rotaviruses of children and calves. Gnotobiotig piglets given intranasal inoculations of five different isolates developed acute gastroenteritis, and the virus was re-isolated from the faeces or intestinal contents. The piglet virus was not adapted to replicate in cell culture. We conclude that the pig rotavirus is commonly associated with outbreaks of gastroenteritis and is probably an important aetiological factor in this disease.

Animals↗
PubMed1976

Gnotobiotic piglets experimentally infected with neonatal calf diarrhoea reovirus-like agent (Rotavirus).

Gnotobiotic piglets were infected with a strain of rotavirus that had been isolated from a calf and passaged four times in piglets. The resulting disease was studied by light and electron microscopy at 21, 44 and 68 h after inoculation. In the small intestine infection caused desquamation of the epithelial cells of the villi resulting in severe stunting. There was severe damage to microvilli and accumulation of lipid within the cytoplasm. Virus particles were seen in epithelial cells covering the stunted villi. Infection also caused desquamation of the superficial epithelial cells of the stomach mucosa and of the epithelial cells of the bronchi, bronchioles, and alveoli of the lungs.

Animals↗
PubMed1976

Seminal plasma proteins and the reaction of spermatozoa from intact boars and from boars without seminal vesicles to cooling.

Spermatozoa from intact boars and from boars without seminal vesicles were resuspected in diluent and cooled at different rates to 0 degrees C. Glutamic oxaloacetic transaminase and lactate dehydrogenase activities were greater in the diluents which had contained spermatozoa from intact boars than in those which contained spermatozoa from animals without seminal vesicles. The incubation of seminal plasma from an intact boar with spermatozoa from a vesiculectomized animal before cooling also increased the enzyme activity in the diluent. The factors responsible for this effect were associated with the basic protein fractions of boar seminal plasma, in particular the proteins with haemagglutinating activity which may have been adsorbed onto the spermatozoa. Spermatozoa were exposed to colloidal Fe(OH)2+ to determine by electron microscopy the charge on the surface of the plasma membrane of washed epididymal spermatozoa and ejaculated spermatozoa from intact and vesiculectomized boars. Epididymal spermatozoa bound the positively charged particles more readily than the ejaculated spermatozoa from the intact boars, due to the absence of membrane-bound protein.

Animals↗