Biomedical subjects

K R Parsons

Publications and source records attributed to K R Parsons.

At least 55 records · Page 3Linked to original sources

PubMed1989

Evidence that blood-borne infection is involved in the pathogenesis of bovine pneumonic pasteurellosis.

Five calves were inoculated intravenously with 10(8) colony forming units (cfu) of Pasteurella haemolytica A1; the mean score for pneumonic consolidation 3 days post-inoculation was 28%, and the mean clinical score was 7.8. Five calves inoculated intratracheally with 10(9) cfu of the same strain of P. haemolytica had comparable scores (34% and 8.8). Histological lesions of fibrinous pneumonia were similar in all calves. P. haemolytica was recovered from all but one of the affected lungs. From one calf killed in extremis 3 hours after intravenous inoculation, numbers of bacteria recovered from lung were 1,000-fold greater than from liver and spleen. A similar difference in bacterial numbers was also obtained from a gnotobiotic calf killed in extremis, 12 hours after intravenous inoculation of 10(8) cfu P. haemolytica. Evidence from these experiments supports the hypothesis that the blood-borne route is important in the pathogenesis of bovine pneumonic pasteurellosis.

Animals↗

PubMed1989

Investigation of bovine gut associated lymphoid tissue (GALT) using monoclonal antibodies against bovine lymphocytes.

Gut associated lymphoid tissue of the small and large intestine of calves and cows has been compared morphologically and quantitatively using monoclonal antibodies to bovine lymphocytes. B cells were significantly decreased in the ileum of the cow compared to the calf. Significantly increased numbers of T cells were present in cell suspensions of all lymphoid areas of the cow compared to the calf. T lymphocyte subsets were quantified into cryostat sections of lymphoid tissues expressing BoT4, and BoT8 antigens demonstrated increased numbers in follicular and dome areas of the discrete Peyer's patches of the small and large intestine of the cow. BoT4+, BoT8+, and the non-BoT4/BoT8+ T cell subsets were increased in the mucosa of the cow as compared to the calf. Similarities in structure and lymphocyte composition of the discrete Peyer's patches of the small intestine, cecum and colon and isolated single follicles in the large intestine suggest similar functional properties.

Analysis of Variance↗

PubMed1989

Effects of dietary change and rotavirus infection on small intestinal structure and function in gnotobiotic piglets.

The combined effects of weaning and rotavirus infection on small intestinal structure and function and on growth rate were studied in 28 gnotobiotic piglets. There was little damage by rotavirus to the proximal small intestine, some damage to the mid small intestine and relatively severe damage to the distal small intestine; villi were stunted, crypts lengthened and activities of all brush border enzymes decreased. The damage was short-lived despite the synchronisation of rotavirus infection with simulated weaning. There was no evidence of persistent damage to the small intestine and growth rate was unaffected.

Animals↗

PubMed1988

Two monoclonal antibodies (CC17, CC29) recognizing an antigen (Bo5) on bovine T lymphocytes, analogous to human CD5.

Two new monoclonal antibodies (CC17 and CC29) raised against bovine thymocytes are described. The antibodies, both of which were IgG1, recognize a molecule of approximately 67,000 molecular weight on bovine T cells. They react T cells in peripheral blood, the lymph node paracortex and the periateriolar lymphoid sheath in the spleen. Both the cortex and medulla of the thymus are stained but the medulla reacts more intensely. They do not stain B cells in peripheral blood, the ileal Peyer's patch, the cortex or the primary follicles in lymph nodes. No activity was found on cells outside the lymphoid system, i.e. monocytes, alveolar macrophages or endothelial and epithelial tissue. The antigen recognized is considered to be the bovine homologue of CD5 (T1) in humans and Lyt1 in mice. The mAbs appear to be particularly useful for detecting cells in the peripheral blood of young calves which are of the T cell lineage but do not express BoT2 or the mature pan T cell antigen recognized by mAb IL-A27 and may thus allow identification of a population of bovine lymphocytes previously described as null cells.

Animals↗

PubMed1988

Histochemical localization and possible antibacterial role of xanthine oxidase in the bovine mammary gland.

Xanthine oxidase (XO) was demonstrated to be present in the teat canal and secretory tissue of the bovine mammary gland by histochemical techniques. Homogenates of these tissues were able to replace XO in an antibacterial assay with Streptococcus uberis. The action of XO on its substrate hypoxanthine was shown to provide an essential component for anti-streptococcal activity mediated by lactoperoxidase. A mechanism is proposed whereby the interaction of XO, lactoperoxidase and thiocyanate may provide antibacterial activity in the teat canal.

Animals↗

PubMed1988

Characterization of a bovine thymic differentiation antigen analogous to CD1 in the human.

Three monoclonal antibodies (MoAb), TH97A, CC13, and CC14, define a thymic differentiation antigen in cattle. The antigen is expressed on 50-60% of bovine thymocytes, located mainly in the cortical areas, but is not expressed on peripheral blood mononuclear cells (PBMC). In cryostat sections of lymph node, the antibodies react with large dendritic-like cells in the paracortical regions. They also react with a proportion of the large 'frilly' cells in afferent lymph and with dendritic-like cells in the dermis. The antibodies apparently do not react with cells in the epidermis. Biochemical analysis of the antigen recognized by MoAb TH97A reveals two bands of 44 kDa and 12 kDa under reducing conditions. These polypeptides are distinct from bovine class I major histocompatibility complex molecules reactive with the MoAb w6/32. The tissue distribution of positive cells together with results of biochemical analyses indicate that the antigen recognized by these MoAb is the bovine analogue of the human CD1.

Animals↗

PubMed1988

Pathology of calves with diarrhoea in southern Britain.

Twenty-one moribund calves with diarrhoea were purchased from 11 farms, their faeces examined for enteropathogens and samples of intestinal tissue removed under anaesthesia. Lesions and presence of enteropathogens on the mucosal surface were scored by histological examination of immunostained paraffin sections. Two or more enteropathogens were detected in 19 calves. Cryptosporidium appeared to be the principal cause of diarrhoea in six calves, rotavirus in four, Salmonella typhimurium in two, bacteria adherent to the surface of the large intestine in two, coronavirus in one and K99+ Escherichia coli in one calf. Diarrhoea in four calves was the consequence of mixed infections in which no one enteropathogen appeared to predominate. In one calf no enteropathogen was detected. Diarrhoea was associated with infections and lesions throughout the small and large intestines. The enteropathogens most frequently associated with lesions in the small intestines were rotavirus, coronavirus and cryptosporidium; in the large intestines they were coronavirus and bacteria apparently adherent to the mucosal surface.

Animals↗

PubMed1988

Role of immunoglobulin and peritoneal phagocytes in the protection of rats against salmonella infection.

Intradermal vaccination of rats with heat-killed Salmonella dublin protected against an intraperitoneal challenge of live S dublin. Serum from vaccinated animals administered intraperitoneally protected normal rats against intraperitoneal challenge with S dublin and four other serotypes. Protection was attributed to opsonic antibodies which promoted phagocytosis by mononuclear phagocytes. The opsonin was identified as IgG2a which prevented lysis of macrophages and enabled them to contain the pathogen at the site of infection. In vitro, mononuclear phagocytes killed S dublin for up to two hours after phagocytosis in the presence of immune rat serum.

Animals↗

PubMed1987

Immune response of cattle to respiratory mycoplasmas.

M. bovis and M. dispar produce very different types of response in the calf lung. The immune response of the host plays a major role in the formation of the lesion induced by M. bovis and this response is predominantly Ig mediated. In contrast M. dispar produces a much milder reaction in the lung which may be related to an ability of the mycoplasma to inhibit the host's immune response. Recovery from infection appears to be primarily mediated by IgG present in the lung and functioning in conjunction with alveolar macrophages. The immunity following vaccination which is observed in experimental studies and field trials is also likely to be mediated by the same mechanism.

Animals↗

PubMed1987

Growth of Mycoplasma bovis in organ cultures of bovine foetal trachea and comparison with Mycoplasma dispar.

Inoculation of tracheal organ cultures from bovine foetuses with Mycoplasma bovis resulted in a loss of cellular structure of the lamina propria, followed 20-22 days later by lifting and detachment of overlying epithelium. The effect was associated with large numbers of M. bovis, identified by immunoperoxidase labelling and electromicroscopy, infiltrating between the epithelial cells and amassing in the lamina propria, especially in the region of the basement membrane of the epithelium. Ciliary activity was undiminished for up to 18 days following inoculation and little or no cytopathic effect on the ciliated epithelium was seen in spite of the close proximity of large numbers of organisms. In contrast, M. dispar was restricted to the margin of the ciliated epithelium where, as previously reported, it caused pyknosis, sloughing and flattening of the epithelium with consequent loss of ciliary activity. The cytopathology observed for each mycoplasma bore a close similarity to the behaviour of the two mycoplasmas in vivo and it is suggested that the organ culture system may be a useful and relevant system to elucidate the pathogenic mechanisms for each mycoplasma.

Animals↗

PubMed1987

Comparative pathogenicity of Mycoplasma bovis and Mycoplasma dispar for the respiratory tract of calves.

Mycoplasma bovis and M. dispar are both important in the etiology of calf respiratory disease, but marked differences are evident in the pathogenesis of disease caused by the two species. Both attach to bovine cells but vary in their invasiveness. M. bovis is capable of invading the lung parenchyma from the airways, while M. dispar predominantly infects the ciliated epithelial cells lining the respiratory tract. M. dispar causes ciliostasis in fetal-bovine tracheal organ cultures, whereas M. bovis does not have the same dramatic effect on ciliary activity. The immunological response of the host contributes to the lesions produced by M. bovis. Both T- and B-lymphocytes accumulate in the lung, which becomes a site for the production of antibody. In contrast, M. dispar produces a mild cellular response in the lungs of calves and may have immunosuppressive properties.

Animals↗

PubMed1986

Systemic and local immune responses of gnotobiotic calves to respiratory infection with Mycoplasma bovis.

Gnotobiotic calves were inoculated by the intratracheal route with Mycoplasma bovis and the specific antibody response in sera and tracheo-bronchial washings examined by radioimmunoassay. In sera an IgM response which reached a peak two weeks post infection was followed by IgG1 and IgG2 antibody responses. Low levels of IgA antibody were detected in sera three and four weeks after infection. The predominant antibody in tracheo-bronchial washings 2 weeks after infection was IgA. Four weeks after infection IgG1 antibody predominated, but IgG2 and IgA antibodies were also present. Cells containing Ig were present in the cellular accumulations around the necrotic zones produced by M. bovis in the lung parenchyma two and four weeks after infection. IgG1 containing cells predominated in these cellular infiltrates. IgG2 producing cells were the next in frequency. It is concluded that the lung lesion caused by M. bovis is partly due to the host's immune response, presumably contributing to the control of the infection, and that the cells infiltrating the lung are a major source of the local and systemic IgG antibody that is detected after infection. IgA staining cells were observed in the submucosa of tissues from nasal cavity and trachea. These cells are probably the source of IgA in tracheo-bronchial washings and sera since IgA-producing cells were not a predominant component of the lesion in the lung parenchyma.

Animals↗

PubMed1986

Dysentery in calves caused by an atypical strain of Escherichia coli (S102-9).

Dysentery lasting 4-8 days was produced in five 4-day-old colostrum-fed calves, after inoculation with an atypical strain of Escherichia coli S102-9; peak excretion of S102-9 occurred during the period of dysentery. Two calves were killed when clinical signs were most severe and bacteria were seen attached to the surfaces of enterocytes in the large intestine; microscopic lesions were seen in these areas. The lesions were identical to those previously reported in a natural outbreak of dysentery in calves, from which E. coli S102-9 was isolated, and to those seen in gnotobiotic calves experimentally infected with S102-9. Reinfection of the three surviving calves 16-20 days later with S102-9 and primary infection of two calves aged 24 and 51 days did not cause dysentery. Four of 659 coliforms isolated from field outbreaks of calf diarrhoea resembled the atypical strain S102-9. These four isolates and S102-9 did not produce heat-stable enterotoxin, but all produced a toxin cytopathic for Vero and HeLa cells. Two of the four isolates were inoculated alone into 4-day-old gnotobiotic calves deprived of colostrum; neither calf developed dysentery but microscopic lesions identical to those produced by S102-9 were detected in the large intestines of both animals.

Animals↗

PubMed1986

Mycoplasma bovis infection in gnotobiotic calves and combined infection with respiratory syncytial virus.

Mycoplasma bovis was inoculated alone or in combination with respiratory syncytial virus into the respiratory tracts of 12 gnotobiotic calves. Clinical signs ranged from transient pyrexia to protracted fever accompanied by severe lower respiratory signs and in one case, arthritis. Pulmonary lesions included foci of coagulative necrosis surrounded by mononuclear cells and suppurative bronchiolitis with varying degrees of lympho-reticular hyperplasia. No enhancement of lesions occurred in the combined infections of M. bovis and respiratory syncytial virus. M. bovis was identified by immunoperoxidase labelling in lesions of necrosis, especially at interfaces between the lesion and mononuclear cells and in bronchiolar exudates. Organisms were also located in necrotic lesions of joint capsules, in tonsillar crypts, and in liver.

Animals↗

PubMed1986

Antibody-containing cells and specialised epithelial cells in the bovine teat.

Tissue from the ends of teats of dry, periparturient and lactating cows were studied using light and electron microscopy. Accumulations of infiltrating leucocytes mainly in the folds of the distal rosette of the teat cistern (Furstenberg's rosette) were detected; plasma cells predominated. The latter were classified by the type of immunoglobulin (Ig) which they synthesised. Plasma cells synthesising IgG1 were found to be the major antibody producing cell type of the teat. Neither the number of stromal plasma cells present nor the class of Ig which they synthesised was significantly altered by changes in mammary gland secretory activity. Scanning electron microscopy revealed areas of epithelium of Furstenberg's rosette that contained cells differing in surface characteristics from epithelial cells of adjacent areas of the teat cistern.

Animals↗

PubMed1985

Studies on the relationship between coronaviruses from the intestinal and respiratory tracts of calves.

An immunofluorescence test on smears of nasal epithelial cells was used to detect coronavirus infection in the respiratory tract of calves. Thirteen gnotobiotic calves were infected with coronavirus isolates derived from faeces or respiratory material: virus was detected in faeces and nasal swabs from all animals. In 115 calves from a field survey, there was a significant association between coronavirus excretion from both respiratory and enteric routes in calves with diarrhoea. In a further 12 calves, at necropsy, the predilection sites for coronavirus growth were the distal small intestine, large intestine and the epithelia of the nasal cavity and trachea. Antigen was not found in lung tissue by immunofluorescence or immunoperoxidase staining. Infection with enteric coronavirus induced immunity to reinfection and to heterologous challenge with two coronavirus isolates derived from the respiratory tract. Nine coronaviruses were cultivated, cloned and antisera to three were prepared in pigs. There was complete virus neutralisation in tests with homologous sera and significant cross reactions with the eight other isolates which were of intestinal and respiratory origin. Thus, these bovine coronavirus isolates belonged to the same serotype despite the source of virus.

Animals↗

PubMed1985

Dysentery caused by Escherichia coli (S102-9) in calves: natural and experimental disease.

A dysentery syndrome was recognized among the Institute's calves at 18 to 21 days of age. It was reproduced experimentally in gnotobiotic calves with an atypical Escherichia coli (S102-9) isolated from the affected calves. In both natural and experimental disease the calves passed copious bright red blood in the feces and developed diarrhea. Walls of the colon and rectum were thickened, and the mucosa was reddened and covered by an exudate that contained mucus and blood clots. Bacteria were seen closely adherent to the luminal surfaces of enterocytes, often in cup-shaped depressions or on cytoplasmic pedestals. Microvilli were distorted, disorientated or absent. There was exfoliation of infected enterocytes and a mild acute inflammation of the underlying lamina. In two of five calves with natural disease, the adherent bacteria did not stain by the immunoperoxidase method with antisera raised against E. coli (S102-9). This indicated that there was possibly more than one bacterial cause of the syndrome. Lesions in experimentally infected calves were indistinguishable from those produced by some E. coli which are enteropathogenic for man, rabbits, and pigs.

Animals↗

PubMed1985

Pathology of natural rotavirus infection in clinically normal calves.

During a longitudinal study of the epidemiology of rotavirus infection in a calf rearing unit, excretion of virus in faeces was detected by enzyme-linked immunosorbent assay in 40 of 48 (83 per cent) unweaned calves aged between three days and five weeks. Fifty per cent of the infected calves had no clinical signs of disease. Enterocytes containing rotavirus antigen and intestinal lesions were found in all of 12 clinically normal calves selected for necropsy between days 1 and 4 of virus excretion. Stunting and fusion of villi, exfoliation, disarrangement and vacuolation of enterocytes and the presence of cuboidal enterocytes were observed in infected calves but not in rotavirus-free control calves. Lesions predominated in the upper small intestine, where rotavirus was most abundant, especially on the first two days of virus excretion. The numbers of enterocytes infected with rotavirus diminished before the lesions resolved.

Animals↗