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Biomedical subjects

F Ashton

Publications and source records attributed to F Ashton.

13 recordsLinked to original sources
PubMed1991

Restriction enzyme analysis of Listeria monocytogenes strains associated with food-borne epidemics.

Listeria monocytogenes (serotype 4b) has caused four major food-borne epidemics in North America. In this study, L. monocytogenes isolates from the Nova Scotia (Canada), Boston (Mass.), and Los Angeles (Calif.) outbreaks were examined by restriction enzyme analysis with the endonuclease HhaI. Human isolates (n = 32) from the 1981 Canadian outbreak were compared with a strain recovered from coleslaw, which was epidemiologically incriminated as the vehicle of infection. After HhaI digestion, 29 of 32 isolates exhibited the restriction enzyme pattern of the reference coleslaw isolate. The restriction enzyme patterns of the nine clinical isolates from the 1983 Massachusetts outbreak were identical to each other but differed from those of raw milk isolates recovered from sources supplying the pasteurizer. Isolates (n = 48) from the 1985 California outbreak were evaluated. The restriction enzyme patterns of the L. monocytogenes isolates from humans and from the suspect cheese samples were identical to those of four of five cheese factory environmental isolates. Isolates from each of these outbreaks exhibited a restriction enzyme pattern that was characteristic of that outbreak. The case with which restriction enzyme analysis can be applied to all serotypes of L. monocytogenes argues for its use in the epidemiology of L. monocytogenes.

DNA, Bacterial↗
PubMed1991

Variability in growth of Neisseria polysaccharea on colistin-containing selective media for Neisseria spp.

In a prospective survey of 773 healthy schoolchildren in southern Alberta, Canada, Neisseria polysaccharea was isolated from the pharynxes of only 4 (0.5%) subjects, whereas Neisseria lactamica and Neisseria meningitidis were isolated from 110 (14%) and 15 (2%) children, respectively. These strains of N. polysaccharea, together with three other sporadic isolates from Alberta, Canada, were compared with the type strain from France and strains from Spain and Germany. All strains were phenotypically identical, except that the Canadian and German strains, for which the colistin MICs were 1 mg/liter, failed to grow on Thayer-Martin medium (TMM), whereas the type strain and the Spanish strains, for which the colistin MICs were greater than 7.5 mg/liter, were not inhibited. Multilocus enzyme electrophoresis indicated that six distinct electrophoretic types were present among the seven Canadian strains. Our results show that growth on gonococcal selective media which contain colistin is a variable feature of this taxon.

Adolescent↗
PubMed1990

Hepatocidal toxicity of Listeria species.

A novel rat hepatocidal test, based on morphological changes in monolayer culture and the percentage of lactate dehydrogenase (LDH) released into the medium after exposure to culture filtrates of Listeria spp. was used to determine listerial toxicity and pathogenicity. Primary cultures of rat hepatocytes exposed to brain heart infusion (BHI) culture filtrates from ATCC strains of Listeria monocytogenes and L. ivanovii, released 91-92% and 95% of LDH after 3 h and 18.5 h, respectively. Cultured monolayers changed from normal hepatocytes into nonviable round forms. Brain heart infusion broth and BHI culture filtrates of other Listeria spp. were nontoxic to hepatocytes. The rat hepatocidal test is a quantitative and rapid system for studying listerial toxicity and pathogenicity.

Animals↗
PubMed1986

Atherosclerosis in vascular grafts for peripheral vascular disease. Part 2. Synthetic arterial prostheses.

Thirty-nine synthetic (32 Dacron and 7 Teflon) arterial prostheses (from 38 patients with peripheral arterial disease) removed after periods between 2 months and 18 years, were examined by histology and immuno-histology. The grafts were initially permeated by thrombus containing platelet antigens and this became organised and converted to granulation, and then to fibrous, tissue. The newly-formed tissue contained 'foreign-body' giant-cells in contact with the plastic prosthesis and showed evidence of permeation by plasma proteins. In grafts of over 2 years duration, this reactive tissue no longer contained platelet antigens but invariably revealed bound lipid, identifiable as apolipoprotein-B-containing lipoproteins (LpB), and fibrinogen-related antigens (FRA), in a distribution resembling that seen in atherosclerotic arteries. LpB and FRA were also seen in organised, or partially organised, mural thrombi in older grafts. The oldest grafts additionally showed stenosis, calcification or aneurysm formation. Lipid deposition increases with the age of grafts; is independent of the nature of the plastic fibre used or its mode of fabrication; and sometimes contributes to graft failure. Immuno-histology indicates that this is an insudative process indistinguishable from 'true' atherosclerosis which occurs in graft-linings of prostheses of long duration and in old mural thrombi in grafts and that the lipid in these lesions derives from plasma LpB rather than from platelets. This source for the lipid suggests that the insudative and thrombogenic theories of atherogenesis can be reconciled.

Adult↗
PubMed1979

Long term results of autogenous vein bypass grafts in femoropopliteal arterial occlusion.

The results of 329 consecutive autogenous vein grafts carried out between January 1962 and June 1973 have been reviewed. The 5- and 10-year mortality rates were 14.6 per cent and 18.7 per cent respectively. The corresponding patency rates were 70 per cent at 5 years and 34 per cent at 10 years, the lowest patency (27.8 per cent) occurring in below-knee anastomoses with grafts of 5 mm or less in diameter. As other have noted, the state of the popliteal--tibial run-off vessels had a considerable influence on long term patency rates. In severely ischaemic limbs, the limb salvage rate following this operation was 77 per cent. An analysis of symptoms, associated disease and complications is presented and discussed. No valid conclusions could be made regarding the effect of lumbar sympathectomy and postoperative anticoagulants on long term patency. This review has confirmed the findings of earlier studies that a satisfactory 5-year patency rate and a gratifying limb salvage rate can be achieved with an extremely low operative mortality rate of 0.37 per cent. Despite the presence of widespread atherosclerotic arterial disease, the 5-year mortality rate is 14.6 per cent, indicating that an attempt at reconstructive surgery is usually well worth while.

Adult↗
PubMed1975

Studies on gonococcal infection. I. Electron microscopic studies on phagocytosis of Neisseria gonorrhoeae by macrophages.

Macrophages from mice were infected with Neisseria gonorrhoeae type 1 cells, and their ultrastructure was studied by electron microscopy. The macrophages showed various stages of engulfment and digestion of gonococci 2 hr after infection. Infected macrophages seemed to develop pseudopodia for phagocytosis, and could engulf more than 30 gonococcal cells. Some engulfed bacteria appeared morphologically intact, while others appeared lysed and some structures resembling the L form of N. gonorrhoeae were also seen. These observations suggest that gonococcal cells may be able to survive intracellularly with normal or altered forms of morphology, and that macrophages containing these bacteria may disseminate gonococcal infection in man.

Animals↗
PubMedDate not supplied

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Creativity↗
PubMedDate not supplied

Abdominal aortic aneurysms complicated by spontaneous iliocaval or duodenal fistulae.

Seven hundred and twenty one abdominal aortic aneurysms were treated between 1960 and 1985. Twenty one of these (2.9%) were complicated by the development of a spontaneous primary fistula, 16 (2.2%) into the vena cava or iliac veins and 5 (0.7%) into the duodenum. A correct preoperative diagnosis was made in only four instances, two aorto-caval and two aorto-duodenal fistulae. Hospital mortality was 44% for aorto-caval and 60% for aorto-duodenal fistulae. Despite the lack of a precise preoperative diagnosis in the majority of cases, the prognosis for aorto-caval fistula remained comparable to that for patients undergoing emergency surgery for uncomplicated ruptured aortic aneurysms. The mortality of spontaneous aorto-duodenal fistulae was appreciably higher and the aneurysmal contents of 4 out of these 5 cases had positive bacterial cultures.

Aged↗
PubMedDate not supplied

Peripheral arterial embolism. A 20 year review.

Two hundred and forty eight peripheral arterial emboli occurring in 221 patients during a period of 20 years have been retrospectively reviewed. Best results are seen following early surgery with the balloon catheter but, in the clinical absence of tissue necrosis, late embolectomy is worthwhile. Atrial fibrillation and post-myocardial thrombus are the major sources of emboli, but tumour and septic emboli do occur and histological and bacteriological examination of retrieved material is essential. Patients who have sustained myocardial infarction have an increased risk of embolism in the first two weeks and despite modern therapy its incidence remains unchanged. Distinguishing true embolism from acute arterial thrombosis is a continuing problem and different surgical regimes for the two conditions are discussed. Embolectomy following anticoagulation has a high limb salvage rate and a low mortality; anti-coagulation as an adjuvant to surgery also improves prognosis for these patients who have lower amputation rates than those not anticoagulated.

Adult↗