Search PubMed⌕ Search

Biomedical subjects

J C Low

Publications and source records attributed to J C Low.

At least 19 recordsLinked to original sources
PubMed1996

Voltage dependency of light-evoked on-off transient amacrine cell responses in carp retina.

The voltage dependency of the ON and the OFF components of transient amacrine cell responses was studied using two-electrode voltage-clamp and current-clamp techniques in the isolated retina of the carp. The two independent approaches gave similar data. When cells were voltage clamped near their resting potentials, both response components were associated with transient inward currents. Hyperpolarization increased response size (current or voltage) whilst depolarization decreased it. Response reversal, or a tendency for it, occurred at membrane potentials significantly more positive than the resting level with some quantitative variability. These data support the view that the ON-OFF depolarizations represent basically excitatory postsynaptic potentials and that the transience of the responses cannot mainly be due to any voltage-dependent conductance.

Animals↗
PubMed1996

Concurrent bovine viral diarrhoea virus and Salmonella typhimurium DT104 infection in a group of pregnant dairy heifers.

Two days after being imported into the United Kingdom one of a group of 30 pregnant dairy heifers showed clinical signs of bovine viral diarrhoea virus (BVDV) infection and subsequently died. Before it died the heifer was BVDV antigen-positive and antibody-negative. The gross post mortem findings were suggestive of mucosal disease but in addition to noncytopathic BVD virus, Salmonella typhimurium DT104 was cultured from tissues and gut contents. The other heifers were screened for S typhimurium by culturing faeces, and serology showed that 13 (45 per cent) of the group seroconverted to BVDV in the three weeks between samplings and the remainder were seropositive, indicating previous exposure. During this period four heifers showed clinical signs of acute BVDV infection but recovered uneventfully. Four animals (14 per cent) were positive for S typhimurium DT104 on faecal culture, and three of these excretors concurrently seroconverted to BVDV. Of the 29 heifers remaining in the group, one aborted in late gestation, 26 bore live calves and two delivered stillborn calves. Pre-colostral blood samples from the calves showed that their dams' pre-existing antibody titres correlated well with in utero fetal protection. In non-immune dams, exposure to BVDV between 69 and 120 days of gestation led to the birth of live persistently viraemic calves. Infection between 120 and 140 days of gestation led to the birth of live calves with evidence of congenital damage to the central nervous system, and infection later than 140 days of gestation led to the birth of live, normal calves with high pre-colostral antibody titres to BVDV. One calf which sucked colostrum was antibody and virus antigen-positive when sampled at 12 hours old but regular blood sampling failed to detect viraemia again until the calf was seven weeks old when it became persistently viraemic.

Animals↗
PubMed1996

Sulphur-induced polioencephalomalacia in lambs.

An outbreak of polioencephalomalacia affected 16 of 46 Swaledale lambs and five of 25 Scottish blackface lambs 15 to 32 days after they were introduced to an ad libitum concentrate ration containing 0.43 per cent sulphur. The clinical signs were acute and included depression central blindness and head-pressing, but no hyperaesthesia, nystagmus, dorsiflexion of the neck or opisthotonos were observed. Treatment of the affected lambs with vitamin B1, dexamethasone and antibiotics was associated with a prolonged recovery period, though no further cases were identified after vitamin B1 had been given parenterally to all the lambs at risk.

Animal Feed↗
PubMed1995

Prevalence of Actinobacillus seminis in the semen of rams in the United Kingdom.

A survey was conducted to establish the prevalence of Actinobacillus seminis in ovine semen and the possible importance of the organism as a cause of ram infertility. A seminis was isolated from three of 16 infertile rams and the infected animals had lesions of the genital tract and produced poor quality semen. A seminis was also isolated from two of 96 fertile rams used as donors of semen for artificial insemination programmes. The strains of A seminis could be identified on the basis of their API ZYM profiles. The results suggest that in the United Kingdom A seminis should be considered as a common cause of infertility in rams.

Actinobacillus↗
PubMed1995

Development and evaluation of an indirect ELISA to detect antibodies to abortion strains of Chlamydia psittaci in sheep sera.

A novel indirect enzyme-linked immunosorbent assay (ELISA) for antibodies against abortion strains of Chlamydia psittaci (C. psittaci) has been developed. The antigen used was chlamydial elementary bodies treated sequentially with N-lauroyl sarcosine and n-octyl-beta-D-glucopyranoside and finally solubilized with N-lauroyl sarcosine and dithiothreitol. Treating the antigen with sodium periodate after coating of the plates increased the specificity for antibodies to abortion strains. The test was evaluated initially with sera from experimentally infected sheep and an uninfected control group. These sheep were monitored for lambing performance and infection status. When used in conjunction with the indirect micro-immunofluorescence test (MIF), the ELISA was able to identify as negative all twenty-five sera from ewes that had no typical placental lesions and identified as positive twenty of twenty-one sera from infected ewes that had either typical placental lesions or had been found positive by isolation of chlamydia in cell culture. The combination of ELISA and MIF was also able to discriminate correctly groups of sera from six flocks with a history of infection from four known uninfected flocks.

Abortion, Veterinary↗
PubMed1994

Serological evidence implicating Neospora species as a cause of abortion in British cattle.

By means of an immunofluorescence antibody test (IFAT), using in vitro cultured parasites as antigen, antibodies to Neospora species at titres > or = 1/1280 were found in 11 of 120 Scottish cattle that had recently aborted but in only one of 97 cattle from herds in which there had been no recent abortions (P < 0.01). The specificity of the antibodies was confirmed by the lack of cross reactivity between samples with high titres to Neospora and toxoplasma antigen in a direct agglutination test, and by the absence of reactivity at > or = 1/640 in the IFAT of convalescent sera from cattle infected experimentally with Toxoplasma gondii, Sarcocystis cruzi, Eimeria bovis, E alabamensis, Cryptosporidium parvum and Babesia divergens. These results demonstrate that Neospora species infection occurs commonly in aborting cattle in Britain, and that the IFAT may be a useful tool for investigating the infection.

Abortion, Veterinary↗
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

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↗