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Biomedical subjects

J C Low

Publications and source records attributed to J C Low.

At least 55 records · Page 3Linked to original sources
PubMed1993

Characterization by Multilocus Enzyme Electrophoresis of Listeria monocytogenes Isolates Involved in Ovine Listeriosis Outbreaks in Scotland from 1989 to 1991.

Initial results from a study of five small ovine listeriosis outbreaks in Scotland in 1989 to 1991 are presented. Forty-eight isolates including three from silage were typed at 10 polymorphic enzyme loci by using multilocus enzyme electrophoresis resulting in the identification of 12 electrophoretic types. Phylogenetic analysis partitioned the 12 electrophoretic types into two statistically distinct divisions distinguishing 1/2a serotypes from non-1/2a serotypes.

Journal Article↗
PubMed1992

Chromaticity of synaptic inputs to H1 horizontal cells in carp retina: analysis by voltage-clamp and spectral adaptation.

Cone photoreceptor inputs to H1 horizontal cells (H1 HCs) in carp retina were studied by measuring light-modulated currents (IL) to monochromatic stimuli (460, 533, 688 nm) under a voltage-clamp condition. By using double-barrelled micro-electrodes H1 HCs were voltage-clamped whilst perfusing with dopamine to uncouple the cells. The IL of the H1 HCs driven by each cone input was segregated by selective chromatic adaptation, and differences in the kinetics of the IL of the H1 HCs were revealed. Thus, all together, three types of IL were observed: (1) a 'fast outward' current to the long-wavelength stimulus; (2) a 'slow outward' current to the middle-wavelength stimulus; and (3) a 'delayed inward' current that followed the peak of 'slow outward' current to the short-wavelength stimulus. The reversal potentials of the three currents were estimated to be at least 20 mV more positive than the dark resting potential by extrapolation of the IL-V curve. These observations are consistent with the idea that the H1 HCs receive sign-inverting, conductance decreasing synaptic input(s) from at least one other cone mechanism, in addition to the main conventional EPSP type synaptic input from red-sensitive cones.

Animals↗
PubMed1992

Pyrolysis mass spectrometry of Listeria monocytogenes isolates from sheep.

Forty-eight isolates of Listeria monocytogenes from sheep and silage, involved in five small outbreaks of listeriosis, were compared by pyrolysis mass spectrometry (PyMS). The method clustered isolates from single animals, and showed that epidemiologically associated isolates were closely related to each other. PyMS is a simple technique capable of analysing large numbers of samples daily, and its application in veterinary studies should help to elucidate the epidemiology of listeriosis.

Animals↗
PubMed1992

Purification of listeriolysin O and development of an immunoassay for diagnosis of listeric infections in sheep.

A protein of 58,000-Da molecular mass was purified from the supernatant fluid of a dialysis sac culture of Listeria monocytogenes by cation-exchange chromatography. The purified protein, homogeneous by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and possessing the characteristics of listeriolysin O (LLO), was used to develop an indirect enzyme-linked immunosorbent assay. Anti-LLO antibodies were shown to be consistently produced in sheep after experimental challenge with L. monocytogenes serovar 4b. The assay also successfully detected and measured specific anti-LLO antibodies in the sera of silage-fed sheep among which listeric enteritis and abortions had occurred.

Animals↗
PubMed1991

Nutritional factors associated with vaginal prolapse in ewes.

Serum calcium, magnesium and phosphate values of ewes recently affected by vaginal prolapse were compared with unaffected ewes in four flocks. Subclinical hypocalcaemia was demonstrated in some affected and unaffected ewes in three flocks. Magnesium and phosphate values were normal. In two flocks the body condition of ewes recently affected by vaginal prolapse was variable and reflected the variation in condition found in the flock. In a third flock affected ewes had significantly lower body condition scores than unaffected ewes (P less than 0.001). Analysis of the fourth flock was not possible. Oestrogenic mycotoxins were not detected in any of the feed samples taken from these flocks. The following year the management, nutrition and energy, and the protein and calcium status of ewes in 12 flocks of greyface/mule ewes with a history of a regular high (greater than 3 per cent) or low (less than 1 per cent) prevalence of vaginal prolapse were compared. A high prevalence was not associated with any particular feedstuff. A high or intermediate (1 to 3 per cent) prevalence of vaginal prolapse was found in three of the four flocks managed as a single group and these three flocks were fed on an unrestricted basis. Body condition scoring and beta-hydroxybutyrate estimation confirmed that ewes in these flocks were overfed. The prevalence of vaginal prolapse in the flocks was not related to the serum albumin, calcium or urea of the ewes. Therefore subclinical hypocalcaemia was probably a consequence of vaginal prolapse rather than a cause.

Animal Feed↗
PubMed1991

Identification of cattle infected with bovine virus diarrhoea virus using a monoclonal antibody capture ELISA.

A monoclonal antibody capture enzyme linked immunosorbent assay (ELISA) has been developed to detect pestivirus-specific antigen in the leucocytes of cattle infected with bovine virus diarrhoea virus (BVDV). A blind trial was conducted to compare the specificity of the ELISA with conventional tissue culture virus isolation on 215 blood samples submitted for BVDV diagnosis from cattle throughout Scotland. One hundred and sixty seven samples were negative by both ELISA and virus isolation and 47 samples were positive by both tests. One blood was negative by ELISA and positive by virus isolation.

Animals↗
PubMed1991

Clinical and serum antibody responses to lambs to infection by Listeria monocytogenes.

Oral dosing of lambs with 1 x 10(10) colony forming units of Listeria monocytogenes daily for three days produced no clinical signs but protected the animals against bacteraemia following subsequent homologous subcutaneous challenge. Following the subcutaneous injections, comparison with controls revealed significantly lower rectal temperatures and a significant difference in positive blood cultures. In both groups signs of systemic illness were unremarkable. However, two and 10 days after the subcutaneous challenges neurological signs developed in two lambs. L monocytogenes was isolated from the brain of one lamb and histopathological lesions of listeric encephalomyelitis were demonstrated in both. After oral infection antibodies to L monocytogenes whole cell antigen were detectable in serum agglutination tests and by ELISA. Serological responses to flagellin were examined by ELISA and to listeriolysin O by immunoblotting. The responses of the animals to flagellin were weak and inconsistent, but antibodies to listeriolysin O were detectable after both oral and subcutaneous challenge. The subclass of antibody involved in this response was shown to be predominantly IgG1.

Agglutination Tests↗
PubMed1991

Voltage clamp study of electrophysiologically-identified horizontal cells in carp retina.

Passive membrane properties and electromotive force of light modulated currents of L-, R/G-type and rod-driven horizontal cells were studied by voltage-clamp using double-barrelled micro-electrodes whilst perfusing with 5 microM dopamine to uncouple the gap junctions. Input impedances of horizontal cells in darkness were 31 +/- 1.4 M omega (mean +/- SE, n = 63); the resting potentials were -37 +/- 1.3 mV. Current-voltage relationships had regions of both inward and outward rectification and a region of negative resistance was commonly observed. Reversal potentials of light modulated currents were estimated on average to be -7 +/- 4 mV (n = 14), which is consistent with the involvement of K+ and Na+ and/or Ca2+ gradients. Importantly in R/G cells both depolarizing and hyperpolarizing components of the response had essentially the same reversal potential.

Animals↗
PubMed1989

A myopathy of sheep associated with sarcocystis infection and monensin administration.

An outbreak of muscle disease affected approximately 20 of 600 ewes in spring 1987 in south-east Scotland. The clinical signs were a flaccid paralysis of the hind limbs and in severe cases collapse. Serum creatine kinase and aspartate aminotransferase activities were increased. Clinically affected sheep had a mean reciprocal serum antibody titre in a sarcocystis immunofluorescence antibody test of 557 whereas 22 sheep from the same flock, sampled one year earlier, showed a mean reciprocal titre of only 51. Histologically a heavy infestation of sarcocysts, myodegeneration and a non-suppurative myositis centred on degenerating sarcocysts were observed in a wide range of skeletal muscles and myocardium from four affected sheep. Monensin sodium had been inadvertently included in the protein pellet used in the feed for one week before the onset of the disease.

Animal Feed↗
PubMed1989

Acute nephropathy in young lambs.

Acute renal failure was diagnosed by clinical, necropsy and histological criteria in 39 flocks (20 low ground, 13 hill and six marginal upland) in areas served by six veterinary investigation centres. Forty-eight lambs of 12 different breeds or crosses were investigated. The mean age of affected lambs was 38 days (range seven to 84 days); 21 lambs (44 per cent) were aged seven to 28 days, while only eight (17 per cent) were older than two months. Mortality in clinically affected lambs was almost 100 per cent, with no response to various treatments. Histological examination showed that 40 lambs (83 per cent) had nephrosis, while the rest had toxic tubular necrosis, interstitial nephritis or tubular damage associated with oxalate crystal deposits. Only about half of the lambs had any evidence of enteric infections or enteropathy. Acutely ill lambs had azotaemia, haemoconcentration and proteinuria; some lambs had glycosuria or haematuria. Samples of plasma from 22 lambs with nephrosis were compared with similar samples from 82 incontact but asymptomatic lambs. The clinically affected group had significantly elevated plasma urea, creatinine, total protein, globulin, phosphorus and chloride concentrations and significantly reduced plasma calcium concentrations compared with healthy lambs. Affected lambs had a significant reduction also in the calcium:phosphorus ratio. No significant differences between groups was found in plasma concentrations of albumin, glucose, lactate, glycerol, creatine kinase, alkaline phosphatase, sodium, potassium or magnesium.

Acute Kidney Injury↗
PubMed1989

Binocular fields with lateral-eyed vision.

A simple geometrical model is constructed of the binocular field in animals with laterally directed eyes (such as the pigeon). Height and width are derived as a function of elevation, for eye-centred and for cyclopean co-ordinates. Stereoscopic vision in the frontal field is considered, and it is pointed out that convergence movements can facilitate stereopsis even in an afoveate periphery.

Animals↗