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Biomedical subjects

I H Brown

Publications and source records attributed to I H Brown.

At least 37 records · Page 2Linked to original sources
PubMed1994

Isolation of an influenza A virus of unusual subtype (H1N7) from pigs in England, and the subsequent experimental transmission from pig to pig.

A novel H1N7 influenza virus (A/swine/Eng/191973/92) was isolated from nasal swabs collected from two pigs on a farm where there had been recent clinical disease due to infection with an H1N1 virus (A/swine/Eng/195852/92). Antigenically, the haemagglutinin (HA) of the H1N7 virus was related most closely to the HA of A/USSR/90/77, whilst the neuraminidase (NA) appeared to be related most closely to the NA of A/equine/Prague/1/56 (H7N7). Pigs infected experimentally with A/swine/Eng/191973/92 developed mild clinical signs, excreted virus into the nasal passages for up to nine days after infection, appeared normal at necropsy, transmitted the virus to sentinel pigs, but seven out of eight pigs failed to seroconvert. These findings suggest that the H1N7 virus has a low pathogenicity for pigs, resulting in limited virus multiplication which is insufficient to stimulate a detectable primary humoral immune response.

Animals↗
PubMed1993

Pathogenicity of a swine influenza H1N1 virus antigenically distinguishable from classical and European strains.

An H1N1 strain of influenza virus (A/swine/England/195852/92) isolated recently from clinical epizootics in pigs was transmitted experimentally to six-week-old specific pathogen-free pigs. Between one and four days after inoculation the infected pigs developed pyrexia and showed signs of coughing, sneezing and anorexia. Seroconversion was detected seven days after infection. Virus was isolated from nasal swabs and tissues up to four days after infection, but was not recovered from faeces. Virus was isolated from serum samples taken from each infected animal for a period of only one day between one and three days after infection. The pathology was characterised by a widespread interstitial pneumonia for up to 21 days after infection, lesions in the bronchi and bronchioles for up to seven days after infection, and haemorrhagic lymph nodes. Epithelial damage in the bronchial generations as a result of the virus infection was demonstrated by immunocytochemistry and electron microscopy.

Animals↗
PubMed1993

Alloy particle shape and sensitivity of high-copper amalgams to manipulative variables.

Compressive strength, dimensional change during hardening and residual mercury content of three high-copper spherical particle amalgams (Tytin, Logic and Valiant), two admix amalgams (Dispersalloy and Permite C) and a conventional lathe-cut amalgam (New True Dentalloy) were determined as a function of condensation pressure and trituration time. The properties of the three amalgams containing non-spherical particles were markedly dependent on condensation pressure in the range 3 MPa to 14 MPa. Specimens condensed at 3 MPa showed substantially lower strength, greater expansion during hardening and higher residual mercury contents than did specimens condensed at 14 MPa. The three high-copper spherical particle amalgams, on the other hand, were comparatively insensitive to condensation pressure. Variations in trituration time between 5 and 12 seconds had little effect on the properties of any of the amalgams.

Copper↗
PubMed1993

Variation in condensation pressure during clinical packing of amalgam restorations.

Clinical measurements were made of the condensation pressures applied by a specialist prosthodontist to each amalgam increment during the packing of two pinned Class II restorations. The technique employed involved taking simultaneous video recordings of the operative procedures and the output of a strain gauge stress measuring system attached to the plugger. The condensation pressure applied during each thrust of the plugger could then be related directly to a particular stage of the packing process. In Cavity A, a maxillary left second premolar, an "admix" amalgam containing both spherical and lathe-cut particles was used while Cavity B, a mandibular right first molar, was filled with a spherical particle amalgam. The measurements indicated that the condensation pressures applied decreased substantially as the filling of each cavity proceeded. A marked reduction accompanied the change from a 1.5 mm diameter to a 2.5 mm diameter plugger but in addition, the dentist modified the force applied to each plugger according to the particular task which he was undertaking. For Cavity A, the condensation pressure applied during the filling of the base of the mesial proximal box was 12.6 +/- 1.9 MPa whereas the final increment was subjected to a condensation pressure of only 2.2 +/- 0.7 MPa. Corresponding figures for Cavity B were 7.6 +/- 2.0 MPa and 1.9 +/- 0.5 MPa.

Dental Alloys↗
PubMed1992

Pathogenicity of concurrent infection of pigs with porcine respiratory coronavirus and swine influenza virus.

Combinations of porcine respiratory coronavirus (PRCV) and either of two swine influenza viruses (H1N1 or H3N2) were administered intranasally and by aerosol to six- to eight-week-old specific pathogen-free pigs. The clinical responses, gross respiratory lesions and growth performances of these pigs were studied and compared with those of single (PRCV, H1N1 or H3N2) and mock-infected animals. PRCV infection caused fever, growth retardation and lung lesions, but no respiratory symptoms. Infection with swine influenza viruses caused rather similar, mild symptoms of disease, with H1N1 infection being the least severe. Combined infections with influenza viruses and PRCV did not appear to enhance the pathogenicity of these viruses. Furthermore, viruses were isolated more frequently from tissues and nasal swabs taken from 'single' than 'dual' infected animals, suggesting a possible in vivo interference between replication of PRCV and swine influenza virus.

Animals↗
PubMed1992

Isolation of a Lelystad virus-like agent from British pigs and scanning electron microscopy of infected macrophages.

Six, one-week-old gnotobiotic piglets were inoculated with tissues or sera collected from field cases of porcine reproductive and respiratory syndrome. The piglets showed little or no illness, and two that were necropsied at 8 and 9 days post infection appeared grossly normal. However, a Lelystad virus-like agent was isolated from most of the inoculated pigs using porcine alveolar macrophage cultures. Seroconversion to the Lelystad virus was observed and some animals developed microscopically detectable interstitial pneumonias. Scanning electron microscopy was used to study the in vitro cytopathic effect of the Lelystad virus on porcine alveolar macrophages.

Abortion, Veterinary↗
PubMed1991

Serological studies of transmissible gastroenteritis in Great Britain, using a competitive ELISA.

A competitive ELISA which differentiates between transmissible gastroenteritis virus (TGEV) and porcine respiratory coronavirus (PRCV) was used to detect non-neutralising antibodies to the peplomer protein of TGEV in porcine sera. The test was shown to be TGEV specific, having a relative specificity of 100 per cent, and to have a relative sensitivity of 94.9 per cent when compared with the virus neutralisation test. The prevalence of TGEV in Great Britain is low; only 0.6 per cent of sows sampled in 1990 were seropositive to TGEV. Seroconversion to the virus neutralisation test occurred in a closed herd in 1984, with no apparent spread, but later testing by the ELISA did not detect any blocking antibodies. The possibility of the existence of a less contagious strain of PRCV is discussed. All British isolates of TGEV tested by the indirect fluorescent antibody test were recognised by the monoclonal antibody 1D.B12, the indicator antibody in the ELISA.

Animals↗
PubMed1990

Sows infected in pregnancy with porcine respiratory coronavirus show no evidence of protecting their sucking piglets against transmissible gastroenteritis.

Eighteen litters of sucking piglets were challenged with one of two strains of transmissible gastroenteritis virus (TGEV). During pregnancy, their seronegative dams had been either inoculated intranasally with porcine respiratory coronavirus (PRCV), inoculated orally with TGEV or left untreated. On the basis of weight gain, clinical signs and survival, no differences in response to challenge was detected when piglets suckled by PRCV inoculated sows were compared with those suckled by uninoculated sows. Such a difference was evident when the litters of sows successfully pre-immunized with TGEV were compared with those of uninoculated or PRCV-inoculated sows. The possibility of transplacental transmission of PRCV was investigated in two litters born to sows that had been inoculated with this virus in late pregnancy. All sixteen live-born piglets were seronegative for the virus at birth and PRCV was not isolated from tissues taken from two stillborn piglets.

Animals↗
PubMed1983

Growth and endocrine function after treatment for medulloblastoma.

Children with medulloblastoma in Bristol are treated surgically and with craniospinal irradiation, and in some cases chemotherapy. Thirteen medium or long term survivors were investigated to determine their growth and endocrine function. Their rate of growth was considerably reduced through the first year of their illness and after spinal irradiation spinal growth was poor. Nine children developed growth hormone deficiency. They were clinically euthyroid but 7 had raised basal thyroid stimulating hormone values. Gonadal function was abnormal in all but the youngest child. The rate of survival is increasing in children with medulloblastoma but this is associated with appreciable endocrine abnormalities. Some of these problems are present shortly after treatment ends but others may develop later and long term surveillance is therefore essential.

Adolescent↗