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Biomedical subjects

N J Watt

Publications and source records attributed to N J Watt.

At least 37 records · Page 2Linked to original sources
PubMed1995

Distribution and quantitation of lung parenchymal contractile tissue in ovine lentivirus-induced lymphoid interstitial pneumonia. Do tissue forces limit lung distensibility?

BACKGROUND: Lymphoid interstitial pneumonia (LIP) is frequently identified in sheep infected with the ovine lentivirus, maedi-visna virus (MVV). Functional consequences of this condition include a reduction in lung distensibility that cannot be explained by the density of surface forces within the lung parenchyma. A potential source of tissue forces to account for this functional deficit is the substantial parenchymal smooth muscle hyperplasia that is a feature of the lung pathology. This investigation examines the relationship between lung distensibility and the quantity and distribution of smooth muscle hyperplasia in MVV-induced LIP. EXPERIMENTAL DESIGN: Immunohistochemical localization of alpha-smooth muscle actin (ASMA) was used to identify parenchymal contractile tissue. The distribution and morphometric quantitation of ASMA in lung parenchyma was determined in normal sheep lungs and in lungs from sheep seropositive for MVV. The relationship between the volume density of ASMA in lung parenchyma (Vv'ASMA') and static lung compliance (Cst) and lung distensibility (K) was examined. RESULTS: In normal lungs, ASMA was expressed by typical smooth muscle cells surrounding airways and blood vessels, by cells at the alveolar septal tips protruding into the alveolar ducts, and, rarely, by individual cells within septa. In MVV-seropositive sheep with minimal histopathology, increased ASMA expression occurred in association with early interstitial infiltrates and was located both at septal tips and within septa. With more severe pathology, ASMA-expressing cells became organized into bundles within obviously thickened septa and septal tips. In maedi, Vv'ASMA' is negatively correlated with K and Cst (rs = -0.614; p < 0.005; and rs = -0.504; p < 0.025, respectively). However, partial correlation coefficients indicate that Vv'ASMA' and lung parenchymal tissue density (Vvt) are strongly interdependent. CONCLUSIONS: ASMA expression in normal sheep lung parenchyma follows a similar pattern of distribution to that described for human lungs. The quantity of ASMA in lung parenchyma in LIP associated with MVV infection is negatively correlated with lung distensibility; however, whether this is a causal association remains undetermined.

Actins↗
PubMed1994

Sequence and chromosomal localisation of the gene encoding ovine latent transforming growth factor-beta 1.

Transforming growth factor-beta 1 (TGF-beta 1) plays important roles in pathologic processes. To further investigate the actions of this cytokine in sheep, the entire 1170-bp ovine TGF-beta 1 pro-protein-encoding sequence has been determined by the cloning and sequencing of specific polymerase-chain-reaction amplification products of TGF-beta 1 cDNA sequences. In addition, these sequences have been used to estimate the length of the TGF-beta 1 mRNA as 1.5-1.7 kb by Northern blot hybridization and determine that the ovine TGF-beta 1 gene occupies a single locus in the sheep genome by chromosomal in situ hybridization.

Amino Acid Sequence↗
PubMed1994

Necrotic enteritis of unknown aetiology in young beef calves at pasture.

An enteric disease has occurred for four consecutive years (1989 to 1992) in a spring-calving beef suckler herd in east central Scotland affecting seven- to 12-week-old beef calves. The affected animals remained pyrexic (40 to 42 degrees C) with an acute enteritis which progressed in some cases to severe mucohaemorrhagic colitis. Despite intensive antibiotic and fluid therapy 25 per cent of the affected calves died after five to 10 days of illness. Post mortem examination revealed ulceration and necrosis of the mucosa of the abomasum and small and large intestine. Haematological examinations revealed a severe, non-regenerative neutropenia. Histopathological examination of gut and associated lymphoid tissue revealed lesions similar to those described in bovine viral diarrhoea/mucosal disease (BVD/MD) infection but detailed investigations failed to reveal evidence of active BVD virus infection in the herd. No aetiological agent has been found in association with this disease, for which the term necrotic enteritis is proposed.

Abomasum↗
PubMed1994

Quantitative analysis of immunohistological changes in the synovial membrane of sheep infected with Maedi-Visna virus.

We have carried out a quantitative immunohistological analysis of synovial membrane from the joints of clinically arthritic sheep naturally infected with Maedi-Visna virus (MVV) and compared the results to subclinically affected joints (carpal and tarsal) from infected sheep and to joints from a control population. Significantly elevated numbers of all three T lymphocyte subsets (CD4+, CD8+ and gamma delta) were found in the synovia from clinically arthritic sheep compared to controls. There was also a significant increase in the number of CD8+ T lymphocytes in the carpal synovium of subclinically arthritic animals. In both clinically arthritic and subclinical disease states CD8+ T cells predominated over CD4+ T cells and T cells bearing the gamma delta T cell receptor. Significant increases were also observed in the numbers of cells staining for MHC class II antigens in the synovial lining cell layer and subintimal cell populations of synovia from clinically arthritic sheep. These increases were apparent in the subintimal cell population at the subclinical stage of disease. Macrophage-like cells staining for the viral core protein p15 were observed in some of the most inflamed samples. The data are thus consistent with a disease process driven by chronic viral antigen presentation to infiltrating T cells, and could serve as a model for elucidating the mechanisms underlying some types of inflammatory joint disease in man.

Animals↗
PubMed1994

Exponential analysis of the pressure-volume characteristics of ovine lungs.

Static pressure-volume curves were generated from data obtained from 18 normal anaesthetized adult sheep. Lung volumes were determined by helium dilution. An exponential curve of the form V = Vmax - Ae-KP was fitted to the pressure-volume data from each sheep where P is the static recoil pressure, Vmax represents the volume asymptote, A is the difference between Vmax and the intercept on the volume axis and K defines the slope and hence the shape of the P-V curve. Quality of fit of the data was assessed visually, by means of a sign test and a runs test and by the coefficient of determination (r2). Exponential equations were found to adequately describe the shape of the pressure-volume curve in sheep. The exponent K was not correlated with effective alveolar volume (VAeff) (rs = 0.183; P > 0.05). Static lung compliance was determined over a volume range from the end-expiratory level (VEEL) to VEEL plus 400 ml. Measurements of static lung compliance were significantly correlated with measurements of effective alveolar volume (VAeff) (rs = 0.505; P < 0.025). In the ovine, the exponent K, an index of distensibility, is independent of lung volume and offers a means of assessing lung distensibility in this species.

Air Pressure↗
PubMed1994

A technique for the sequential isolation of RNA and DNA from embryos developed for screening for viruses.

A technique has been developed to detect RNA or DNA viruses in single embryos. This technique is based on sequential RNA and DNA isolation from the embryo and analysis of this nucleic acid by polymerase chain reaction. A constitutively expressed embryo gene (alpha subunit ATPase) is also analysed as an internal standard. Extraction of RNA was more efficient than that of DNA, however, positive results were obtained for the internal standard gene for 84% (RNA) and 30% (DNA) of embryos tested.

Animals↗
PubMed1994

A temporal study of RNAs produced in maedi-visna virus infection of choroid plexus cells.

We have examined the types and cellular distribution of transcripts of maedi-visna virus during infection of choroid plexus fibroblasts. Early in infection (19 hours post infection) only small spliced transcripts are found in the cytoplasm. Little virus specific RNA is detected in the nucleus at this stage. Later in infection structural gene transcripts are detectable in the cytoplasm as well as the nucleus. We have measured the half life of each type of transcript in total cellular RNA late in infection by two different methods (northern blotting or S1 protection assays after alpha-amanitin treatment, or specific hybridisation after pulse chase). Both of these methods suggest half lives for unspliced viral RNAs of 8-12 hours. Although the gel based methods were unsuitable for the accurate determination of half life for the shorter transcripts, they did confirm a long half life for these transcripts: pulse chase measurements suggested that this was similar to that seen for the unspliced transcripts. These observations are consistent with the virus exerting temporal control on protein synthesis by a method analogous to that of the HIV Rev protein.

Animals↗
PubMed1994

Respiratory syncytial virus-associated bronchopneumonia in a young chimpanzee.

A fatal bronchopneumonia in a captive, 14-month-old female chimpanzee (Pan troglodytes) is reported. Clinical, necropsy and histopathological findings, together with immunofluorescence and virus isolation studies implicated respiratory syncytial virus as the causative agent. The probable pathogenesis is discussed.

Animals↗
PubMed1994

Pathophysiologic correlations in lymphoid interstitial pneumonia.

Effective alveolar volume, diffusing capacity for carbon monoxide (DCOsb), volume-corrected diffusing capacity (D/VA), static lung compliance (Cst), and lung distensibility were measured in 16 sheep seropositive for maedi-visna virus (MVV) immediately before they were killed. Lungs were inflation-fixed, and the left lung was randomly sampled for morphometric analysis. The total lung weight, total fixed lung volume, volume densities of tissue (Vvt) and air (Vva), and the alveolar surface density were measured and correlated with the physiologic measurements. The density of surface forces could not account for the variation in the distensibility of the lungs, indicating that tissue-related forces may be important in determining lung distensibility in lymphoid interstitial pneumonia (LIP) associated with MVV infection. Possible sources of tissue-related forces are the contractile tissue associated with lung parenchyma, airways, or vasculature. When DCOsb was corrected for volume, a strong negative correlation with Vvt was noted, indicating that factors distinct from lung-volume reduction are important in limiting gas exchange in LIP associated with MVV infection. More sheep demonstrated abnormal D/VA values than any other physiologic measurement, with reduced values being apparent even in sheep considered clinically normal and with little or no morphometric evidence of lung disease. Measurements of diffusing capacity are thus considered the most sensitive functional index of disease progression.

Animals↗
PubMed1994

Ovine lentivirus (maedi-visna virus) protein expression in sheep alveolar macrophages.

The expression of gag (p15, p25) and env gene products in ovine lentivirus-infected cells was studied in 20 adult Texel ewes seropositive to maedi-visna virus and 10 seronegative matched controls. Bronchoalveolar lavage was performed to recover alveolar cell pools from which cytocentrifuge preparations were made. Single and double immunocytochemical techniques were applied to study viral replication and coexpression of viral markers with markers for macrophages, lymphocytes, and major histocompatibility complex (MHC) class II. Aveolar macrophages of eight of 20 infected sheep (40%) were positive for viral protein expression. The percentage of positive macrophages varied from < 1% to 12% of the total population of macrophages. Viral protein expression was not detected in lymphocytes or other cell types. A relationship between virus-replicating macrophages and differential expression of MHC class II molecules, upregulated in ovine lentivirus infection, could not be established. Pathology was evaluated in nine infected ewes. Animals with the highest levels of positive cells had moderate or severe lymphoid interstitial pneumonia. However, sheep with similar degrees of lesions had lower percentages of positive macrophages or were negative for viral protein detection. These results support the idea that a partial or even a complete loss in the restriction mechanism of maedi-visna virus in lungs can occur in some individuals.

Animals↗
PubMed1993

Autoimmune reactivity in sheep induced by the visna retrovirus.

Sheep, either naturally or experimentally infected with visna virus, were examined for the production of autoantibodies. Elevated titres of IgM and IgG antiglobulins and rheumatoid factors as well as antibodies to ssDNA, cardiolipin or histones were found in serum of both groups of animals using ELISA techniques. IgA autoantibodies were usually absent or present in low titres. The specificity of the autoantibody reactivities was confirmed by inhibition assays, affinity chromatography, Western blotting and agglutination methods. Antiglobulin titres were slightly elevated in synovial fluids, although the levels of the other autoantibodies were not raised. No significant correlations were observed between autoantibody and immunoglobulin concentrations. In a separate group of sheep infected experimentally, small but significant rises in the levels of all IgM autoantibodies, except anti-histone antibodies, were observed during and subsequent to the primary immune response to the virus. The autoantibody profiles tended to parallel each other, suggesting a common stimulus for their induction and/or a high degree of polyreactivity. The results thus show that the visna retrovirus induces, either directly or indirectly, autoimmune reactivities that are commonly observed in human autoimmune diseases such as rheumatoid arthritis or systemic lupus erythematosis.

Animals↗
PubMed1993

Lung compliance, lung volume and transfer factor for carbon monoxide in anaesthetised sheep: normal values and reproducibility of measurements.

Measurements of quasistatic compliance (Cqst), effective alveolar volume (VA,eff) and single-breath transfer factor for carbon monoxide (TL,CO, 'sb') were completed in 16 normal, anaesthetised, adult Texel ewes. Regression equations were computed for these variables as a function of bodyweight and the optimal equations selected. The 95 per cent prediction intervals for the equations were calculated such that normal lung function in similar sheep could be accurately predicted. The long term reproducibility of these measurements was assessed in nine sheep, measured at monthly intervals over a period of five months. Although measurements made in individual sheep were often highly variable, the variation between repeated measurements on the separate days for the group was insignificant.

Anesthesia, General↗
PubMed1993

An extended outbreak of infectious peritonitis in a closed colony of European wildcats (Felis silvestris).

Feline infectious peritonitis is a multisystemic disease of domestic and exotic cats caused by a coronavirus. An outbreak of feline infectious peritonitis was investigated in a closed colony of European wildcats (Felis silvestris) at a zoological garden. Over a six-year period, a putative fading kitten syndrome occurred in six of 11 litters born and severe lesions of infectious peritonitis occurred in five of the eight wildcats retained in the colony during this period. Lesions were more acute in the early stages of the outbreak and included perivascular pyogranulomatous inflammation with exudative serositis. Lesions occurred only in males. Vascular lesions were common in the liver of all affected wildcats, serositis occurred in the abdominal and thoracic cavities in most cases and meningeal lesions were present in two cases. Immunohistochemistry with specific antisera detected viral antigen within macrophages in all lesions. This outbreak demonstrates that the lesions of feline infectious peritonitis can become modified over time and that the virus can persist in a closed colony, possibly via carrier wildcats.

Animals↗
PubMed1993

Protozoan encephalomyelitis causing pelvic limb paresis in a yearling sheep.

A pelvic limb paresis of 6 weeks duration in a yearling sheep resulted from protozoan encephalomyelitis involving the spinal cord at the thoracolumbar junction. An elevated lumbosacral cerebrospinal fluid protein concentration but normal cisternal cerebrospinal fluid protein concentration indicated the presence of a thoracolumbar inflammatory lesion resulting in cord compression which obstructed the rostral flow of the cerebrospinal fluid. Under general anaesthesia, myelography at the lumbo-sacral site demonstrated blockage to the rostral flow of contrast medium at T13/L1. At necropsy, there were no gross pathological changes at T13/L1, but histopathology revealed non-tract specific lymphocytic perivascular cuffing, axonal swelling and oedema in the spinal cord, characteristic of a protozoal encephalomyelitis. No parasites were detected in the multiple spinal cord sections examined but immunocytochemistry identified antigens cross-reactive with Sarcocystis spp. antigens in glial cells in these lesions.

Journal Article↗
PubMed1993

Phenotypic analysis of cells in bronchoalveolar lavage fluid and peripheral blood of maedi visna-infected sheep.

A phenotypic analysis of bronchoalveolar lavage fluid (BALF) and peripheral blood (PB) cells in maedi visna virus (MVV)-infected sheep has been performed. The differential cell count in BALF from MVV-infected animals was characterized by a significant increase (P < 0.05) in lymphocytes and neutrophils. Lymphocyte phenotyping in BALF from MVV-infected sheep showed a significant decrease (P < 0.05) of CD4+ cells, a significant increase (P < 0.05) of CD8+ cells and a significant inversion (P < 0.001) of the CD4+/CD8+ ratio. CD5+ lymphocytes were also significantly decreased (P < 0.05). Gamma delta T cells and B cells did not differ significantly when compared with the controls. No correlation was observed between BALF and PB lymphocyte phenotypes. BALF macrophages from MVV-infected animals showed increased MHC class II expression and BALF lymphocytes from the same animals demonstrated up-regulation of LFA-1 and LFA-3 expression. These findings and their relationship with lentiviral pathogenesis are discussed.

Animals↗
PubMed1993

Simple technique for detecting RNA viruses by PCR in single sections of wax embedded tissue.

The detection of specific RNA species in wax-embedded tissue sections using the polymerase chain reaction (PCR) means that gene expression can be studied and RNA viruses detected in stored histological tissue samples. This technique potentially allows the distribution of gene expression and viral replication to be studied in finely subdivided tissues. A technique is presented that has been used successfully to detect short RNA target sequences (130-420 bases) from proto-oncogene Abelson, human enteroviruses, and the sheep retrovirus Maedi-Visna virus using RNA PCR in single wax sections (20-30 microns). Various tissues were used which had not been deliberately prepared for this purpose. In a simple procedure hot xylene dewaxing is followed by acid phenol extraction of RNA and RNA PCR.

Abelson murine leukemia virus↗