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Biomedical subjects

N Craven

Publications and source records attributed to N Craven.

At least 19 recordsLinked to original sources

Familial Klippel-Trenaunay syndrome: a case report.

We present a case of familial occurrence of Klippel-Trenaunay syndrome (thought to be the first such reported in a family from the UK), and the results of an investigation into associated abnormalities in related family members. The findings are compatible with recent suggestions that the syndrome may be inherited, and that isolated naevi flammei may, at least in some instances, have a similar genetic basis, possibly representing a forme fruste of the syndrome.

Child, Preschool↗

Regulation of phagolysosome pH in bovine and human neutrophils: the role of NADPH oxidase activity and an Na+/H+ antiporter.

Fluorescein-labelled Staphylococcus aureus were used to follow changes in phagolysosome (PL) pH of bovine and human neutrophils following phagocytosis. Under aerobic conditions there was an alkalinisation of the PL followed by a slow decline. Under anaerobic conditions no alkalinisation of the PL was seen, and pharmacological inhibition of the NADPH oxidase with diphenyleneiodonium (DPI) resulted in a rapid acidification of the PL following phagocytosis. The inclusion of amiloride, an inhibitor of Na+/H+ antiporter activity, produced a more rapid alkalinisation phase following phagocytosis under aerobic conditions and reduced, but did not abolish, the acidification phases seen under anaerobic conditions or following treatment of neutrophils with DPI. The results suggest that PL pH is influenced by NADPH oxidase activity and to a lesser extent by a Na+/H+ antiporter. The antibacterial effectiveness of neutrophil granule proteins may be affected under conditions that influence the functioning of these two systems.

Amiloride↗

Pathological changes following implantation of intramammary devices (IMD) and immunological mediator release by cells on recovered IMDs.

Implantation of abraded polyethylene intramammary devices (IMD) for six months in the mammary glands of cows resulted in macroscopic and microscopic pathological changes in udder tissue. These changes were characterised by hyperplasia and metaplasia of the epithelial cells and hypertrophy of the subepithelial connective tissue examined by light and electron microscopy (EM). Quarters containing IMDs also had increased numbers of neutrophils and macrophages in the subepithelial stroma compared with control quarters. IMDs recovered six months after implantation were shown by transmission and scanning EM to be covered with plaque and cells. These cells were mainly macrophages, although other leucocytes were also present. In vitro culture of recovered IMDs in the presence of lipopolysaccharide resulted in the release of neutrophil chemotactic factor, or factors, and interleukin-1. Some quarters with IMDs also had concurrent infections at the time of slaughter. In these cases both the pathological changes seen in the tissues and the release of soluble mediators following in vitro culture of the IMDs were significantly increased compared with sterile quarters containing IMD.

Animals↗

Oxygen concentration in milk of healthy and mastitic cows and implications of low oxygen tension for the killing of Staphylococcus aureus by bovine neutrophils.

The partial pressure of O2 in milk from normal cows and from cows with mastitis was measured and the concentrations of O2 calculated. Oxygen levels of milk from normal cows were similar to those in venous plasma, but inflammation of the mammary gland led to a dramatic drop in O2 concentration to less than 10% of control values. Intracellular survival of Staphylococcus aureus strain M60 in bovine neutrophils was greater under anaerobic than aerobic conditions. The implications of low O2 concentrations in milk from infected mammary glands for the bactericidal activity of bovine neutrophils is discussed.

Animals↗

Effect of pH changes on the killing of Staphylococcus aureus and other mastitis pathogens by bovine neutrophil granule extracts.

A partly purified extract of granules from bovine neutrophils was used to investigate killing of mastitis pathogens by the non-oxidative killing system of the neutrophil. Eight strains of Staphylococcus aureus, two of Escherichia coli and two of Streptococcus uberis were used. Different strains of bacteria had different sensitivities to killing by the extract, three strains of staphylococci being particularly resistant. Whereas E coli were killed most effectively at pH 6.0, little or no killing of S aureus took place below pH 6.5 and, although S uberis were also killed better above neutral pH, significant killing also took place at acidic pH levels. Resistance to killing by the extract was not significantly correlated with that by intact neutrophils.

Animals↗

Antimicrobial drug susceptibility of Staphylococcus aureus isolated from bovine mastitis.

Isolates of Staphylococcus aureus (106) from bovine mastitis were tested for susceptibility to antimicrobial agents. beta-lactamase was produced by 69.8 per cent of isolates and 7.5 per cent were resistant to streptomycin (minimum inhibitory concentration more than 32 micrograms/ml). Resistance to other agents was rare. Intrinsic resistance or tolerance to beta-lactam antibiotics was not found.

Animals↗

Chemotactic factors for bovine neutrophils in relation to mastitis.

The chemotactic effect of a variety of agents for bovine blood polymorphonuclear neutrophils (PMN) was evaluated in vitro in assays of migration under agarose. Activated serum and leukotriene B4 showed significant chemotactic activity whereas various bacterial products, formyl peptides, casein and platelet activating factor failed to attract bovine PMN. In vitro cultures of bovine mammary gland macrophages released chemotactic activity for homologous PMN when stimulated by addition of opsonised, killed Staphylococcus aureus, Escherichia coli or Zymosan or sterile E. coli culture filtrates or endotoxin. No significant activity was produced by unstimulated macrophages. Pharmacological levels of various inhibitors or arachidonic acid oxygenation had no significant effect on the generation of PMN chemoattractants by mammary macrophages.

Animals↗

The influence of extracellular and phagolysosomal pH changes on the bactericidal activity of bovine neutrophils against Staphylococcus aureus.

The influence of the pH of suspending medium on bovine neutrophil (PMN) function was assessed in tests of phagocytosis and killing of Staphylococcus aureus. Intracellular killing was markedly inhibited by moderate extracellular acidification whereas phagocytosis was little affected, except at the lowest pH level (pH 5.0). The killing of S. aureus by extracts of isolated PMN lysosomal granules showed a similar pH dependence and was optimal at pH levels above neutrality. Survival of S. aureus within PMN from different cows varied significantly and the relative differences in PMN bactericidal efficiency were maintained at all pH levels. The acidification of extracellular medium during incubation which resulted from metabolic activity of the PMN themselves, increased with increasing ratios of bacteria:PMN and varied significantly among cows. Addition of methylamine (10 mM) to elevate phagolysosomal pH inhibited phagocytosis and had no effect on intracellular survival of S. aureus. However, a lower concentration (1.5 mM) did not affect phagocytosis, but reduced bacterial survival without altering the relative differences in efficiency of PMN from different cows. It is suggested that the acidity of the extracellular medium may both reflect and influence the pH changes occurring within PMN phagosomes and, thereby, modulate the efficiency of intracellular destruction of S. aureus.

Animals↗

Assessment in the mouse of cefoperazone as a treatment for mastitis.

The value of cefoperazone in mastitis therapy was assessed in the mouse model of mastitis primarily by its effect on bacterial cell numbers in the gland. In addition histological studies showed that the drug was not an irritant in the mammary gland. Pharmacokinetic studies showed that it was slowly absorbed from the gland (six days to absorb 500 micrograms) but was easily removed by milking. In ascending order of efficacy cefoperazone (500 micrograms/gland) was active against four-hour-old intramammary infections caused by Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Streptococcus agalactiae and Strep uberis. The effect against Staph aureus was titrated down to a dose of 50 micrograms/gland. Cefoperazone was not bactericidal against intracellular staphylococci but it did sensitise them to the action of lytic enzyme. Cefoperazone and cloxacillin behaved similarly against progressive staphylococcal mastitis. Both antibiotics significantly reduced the bacterial numbers when four-hour-old infections were treated but the effect on 26-hour-old infections was perceptible only when each antibiotic was assayed against saline treatment in the mouse. The results suggest that further studies in dairy cattle should be undertaken.

Animals↗

Recruitment of neutrophils by an encapsulated coagulase-negative strain of Staphylococcus simulans in the mammary gland of the mouse.

The encapsulated coagulase-negative strain of Staphylococcus simulans (strain 76) was inoculated into the mammary glands of lactating mice. In contrast to the coagulase-positive encapsulated Staphylococcus aureus (strain M), which elicited a neutrophil response within 18 hr, strain 76 organisms multiplied in the glands but failed to elicit a neutrophil response for 3 days; they were then eliminated from the gland by 8 days. When strain 76 was inoculated into mice whose offspring had been removed 3 days earlier, a neutrophil response was induced within 18 hr and, although phagocytic ingestion was resisted for at least 42 hr, the organisms were eliminated from most glands within 5 days. Inoculation of a naturally occurring double-stranded RNA (BRL 5907) into the mammary gland induced a macrophage infiltration of the alveolar lumen that was qualitatively similar to 3 days involution. Intramammary inoculation of strain 76 18 hr after BRL 5907 resulted in a neutrophil infiltration within 6 hr. In vitro, strain 76 stimulated the release of chemotactic factors for neutrophils from bovine mammary gland macrophages. The results suggest that the recruitment of neutrophils by strain 76 in the mammary gland of the mouse is mediated by macrophages.

Animals↗

Phagocytosis of Staphylococcus aureus by bovine mammary gland macrophages and intracellular protection from antibiotic action in vitro and in vivo.

Macrophages isolated from the involuted bovine mammary gland were cultured in vitro. Phagocytosis of opsonized Staphylococcus aureus occurred rapidly, but intracellular killing of bacteria was slow. Many intracellular staphylococci survived for up to 4 d exposure to extracellular cloxacillin and emerged from within the macrophages to multiply extracellularly when the antibiotic was inactivated. Rifampicin was significantly more efficient than cloxacillin in killing intracellular S. aureus after 18 h incubation, but it too failed to sterilize the cultures within 3 d. Staphylococci, which had remained viable within macrophages during 20 h incubation with extracellular cloxacillin, showed an increased sensitivity to dilute lysostaphin on subsequent exposure. A 3 d course of intramammary therapy with cloxacillin, commencing simultaneously with an infecting inoculum of approximately 10(8) colony forming units (c.f.u.) S. aureus, apparently eliminated the infection from one quarter of the udders of each of three lactating cows, but bacteria were re-isolated from two cows after a delay of several days. However, when other quarters of the same cows were infected with approximately 10(8) c.f.u. S. aureus which had been phagocytosed by autologous mammary macrophages, similar simultaneous antibiotic therapy failed to affect these infections. The in vitro and in vivo findings indicate the significance of intracellular survival of S. aureus as a factor contributing to failure of antibiotic therapy.

Animals↗