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Biomedical subjects

A W Ritchie

Publications and source records attributed to A W Ritchie.

At least 19 recordsLinked to original sources
PubMed2000

Phosphine generation by mixed- and monoseptic-cultures of anaerobic bacteria.

A microbial basis for bioreductive generation of phosphine is proposed, which could account at least in part for the presence of this toxic gas in natural anaerobic environments and in sewage and landfill gases. Phosphine generation under anaerobic growth conditions was dependent upon both the culture inoculum source (animal faeces) and enrichment culture conditions. Phosphine was detected in headspace gases from mixed cultures under conditions promoting fermentative growth of mixed acid and butyric acid bacteria, either in the presence or absence of methane generation. Monoseptic cultures of certain mixed acid fermentors (Escherichia coli, Salmonella gallinarum, and Salmonella arizonae) and solvent fermentors (Clostridium sporogenes, Clostridium acetobutyricum and Clostridium cochliarium) also generated phosphine. Such fermentative bacteria participate in the multi-stage process of methanogenesis in nature. Generation of phosphine by these bacteria, rather than by methanoarchaea themselves, could explain the apparent correlation between methanogenesis and the formation of phosphine in nature.

Bacteria, Anaerobic↗
PubMed1999

An audit of positive findings in flexible and rigid check cystoscopy.

Both flexible and rigid cysto-urethroscopy are routinely used in the surveillance of transitional cell bladder tumours. This study addressed the issue of patient selection for either rigid or flexible cystoscopy. What proportion of positive findings at flexible cystoscopy and negative findings at rigid cystoscopy are acceptable? Standards were set of 10% for the former and 50% for the latter and our practice was then audited. A retrospective analysis of 800 patients undergoing check cystoscopy revealed a positive finding rate of 8.3% using the flexible instrument and 48.1% using the rigid instrument.

Carcinoma, Transitional Cell↗
PubMed1995

Computerized angiographic analysis of the outcome of peripheral thrombolysis.

BACKGROUND: Catheter-directed peripheral thrombolysis is used increasingly for the management of acute limb ischemia. The comparison of different agents and techniques has proven difficult because of the variations in patient presentation, vessel involvement, and treatment methods. METHODS: A computerized database in which angiographic information is stored on computerized arterial maps has been designed to record details of thrombolysis. RESULTS: A total of 201 patients who presented with rest pain were recorded on the database, and their angiograms were analyzed. There were 123 native-vessel and 78 graft occlusions. Immediate success of lysis and 30-day outcome were not dependent on the site of the occlusion. If an underlying stenosis was revealed, limb salvage rates were significantly greater than when none was found (82% versus 58%, P < 0.01). The presence of at least 1 run-off vessel increased limb salvage rates by 30% (P < 0.001). If more than 5 arterial segments were occluded on the prelysis angiogram, limb salvage was worse than if there were fewer than 5 (57% versus 85%, P < 0.0001). For grafts, less than 5 segments of occlusion led to limb salvage rates of 90%, and more than 5 segments of occlusion led to rates of 72% (P = 0.07). CONCLUSIONS: This simple and user-friendly system of computerized angiographic analysis will enable detailed examination of thrombolytic practice and assist in the prediction of success.

Adult↗
PubMed1995

NATALI--a model for National Computer Databases in the investigation of new therapeutic techniques.

New medical treatments are often introduced without the benefit of randomized trials. We describe how a national computerized database was produced, by the Thrombolysis Study Group, for monitoring one such new treatment: peripheral arterial thrombolysis. A novel method for transferring angiograms to computer generated arterial maps that can help in the classification and analysis of the outcome of thrombolysis is also described. Data provided by prospective collection from 14 hospitals within the UK was entered onto the database (Auditbase for Windows), to give contributing members a continual audit of their own results and complications that can be compared with that of the group as a whole. This system may be an appropriate model for other forms of multi-centre audit and the monitoring of new treatments.

Computer Graphics↗
PubMed1992

Mechanisms responsible for diminished fragmentation of ureteral calculi: an experimental and clinical study.

We molded 24 synthetic stones (mean weight 680 mg., range 641 to 715) from a commercial mixture of gypsum, silica, cellulose and polyvinyl acetate. Each stone was subjected to 400 shocks on a Wolf 2300 Piezolith and groups of 6 stones were treated in 4 different modes. Mean amounts fragmented were 243 +/- 18 mg. in a free environment, 62 +/- 18 mg. confined loosely in a latex tube, 22 +/- 8 mg. impacted in the tube and 30 +/- 8 mg. impacted alongside a 7F stent. During a 30-month period 118 patients received in situ extracorporeal shock wave lithotripsy for ureteral calculi using the same lithotriptor. The mean stone burden was 11.4 mm. (range 4 to 29). Success was greater for patients with calculi 10 mm. or less than for those with stones greater than 10 mm. (71% versus 51%, p less than 0.05), despite the former group receiving less shocks (5,404 versus 7,491). The influence of size was then excluded by studying the number of shocks delivered per mm. of calculus. Patients receiving 500 to 699 shocks per mm. showed a higher success rate than those receiving a smaller number of shocks per mm. Treatment with a greater number of shocks per mm. did not improve success rate. The experimental study demonstrated that confinement and impaction significantly diminish the rate of fragmentation of calculi. However, the clinical study suggested that there may be an optimum number of shocks per mm. that should be delivered. Treatment beyond this point fails to improve results. The 28% failure rate even in those receiving the highest number of shocks per mm. suggests that large, impacted calculi are unsuitable for treatment with in situ shock wave lithotripsy on this machine.

Adolescent↗
PubMed1992

An investigation of factors influencing the in vitro induction of LAK activity against a variety of human bladder cancer cell lines.

We investigated the sensitivity of transitional cell carcinoma cells, derived from the human bladder, to lymphokine activated killer cells. Recombinant interleukin-2 activated peripheral blood mononuclear cells were studied for their ability to mediate the cytolysis of a panel of four established human bladder transitional cell carcinoma cell lines. Lymphokine activated killer activity was assessed using a standard four hour chromium release assay. All four bladder cancer cell lines proved to be susceptible to lymphokine activated killer mediated cytolysis. This was found to be dependent upon the dose of cytokine and upon the duration of the activation period. The four cell lines were differentially susceptible to lysis (specific cytotoxicity at effector to target ratio of 40:1; RT112 = 22.9%, RT4 = 49.2%, MGH-U1 = 49.1%, EJ18 = 62.3%). The varying susceptibility of lymphokine activated killer mediated cytotoxicity was found to be independent of the histological grade of the parent tumour or the donor of effector cells. Both interferon-alpha and tumour necrosis factor-alpha also elicited lymphokine activated killer cell activity, although the maximum specific cytotoxicity achieved was considerably lower than that obtained with interleukin-2 alone. Interleukin-2, at optimal concentration, and tumour necrosis factor-alpha were found to behave synergistically in the generation of lymphokine activated killer effectors. However, concentrations of tumour necrosis factor-alpha higher than 100 Uml.-1 resulted in a decrease in specific cytotoxicity. These findings suggest a possible use of adoptive immunotherapy in human bladder cancer and indicate the optimum conditions for the generation of such effector cells.

Carcinoma, Transitional Cell↗
PubMed1992

J-wire facilitates retrograde manipulation of ureteric calculi prior to extracorporeal shock wave lithotripsy.

During a 13-month period, 55 patients underwent attempted retrograde manipulation for ureteric lying above the pelvic brim. The mean stone burden was 11 mm (range 5-21); 41 stones (75%) were primary ureteric calculi and 14 (25%) were fragments resulting from extracorporeal shock wave lithotripsy to renal calculi. The method of retrograde manipulation was recorded prospectively. Retrograde flushing through an 8F angiography catheter with a mixture of saline and lignocaine gel was successful in 27 patients (49%). The insertion of a J-wire through the angiocath allowed for successful manipulation in a further 17 patients (31%). Retrograde manipulation was impossible in 11 patients (20%). There were 4 complications (7%), none attributable to the use of a J-wire.

Adolescent↗
PubMed1991

The effects of recombinant human interferon-gamma on a panel of human bladder cancer cell lines.

We have examined the Major Histocompatibility Complex class II antigen inducing capabilities of recombinant human interferon-gamma, on a panel of human transitional cell carcinoma lines which have been raised from original tumours of varying histological grades: RT4 (grade 1), RT112 (grade 2) and MGH-U1 (grade 3). Cells were examined for class II antigens using an indirect immunofluorescent staining method and analysed on a fluorescence activated cell sorter. Twenty percent of RT4 cells constitutively expressed class II antigen. Both RT112 and MGH-U1 were repeatedly found to be negative for this antigen prior to treatment with interferon-gamma. Following treatment with interferon-gamma all three lines showed an increase in class II antigen expression, which was consistently dependent on both the length of incubation and concentration of interferon-gamma. A differential susceptibility was found amongst the three cell lines which may relate to the histological grade of the parent tumor.

Carcinoma, Transitional Cell↗
PubMed1991

The impact of extracorporeal piezoelectric lithotripsy on the management of ureteric calculi: an audit.

The presentation and management of 153 patients with ureteric calculi requiring active treatment over a 12-month period were reviewed; 74% of patients had primary ureteric calculi and 26% had ureteric calculi composed of fragments resulting from extracorporeal piezoelectric shockwave lithotripsy (EPL) to renal calculi; 32 patients (21%) had more than 1 calculus or a steinstrasse. The primary procedures included were in situ EPL (n = 54), push-bang (44), retrograde ureteroscopy (40), Dormia basket extraction (6), push-pull (1), antegrade ureteroscopy (1) and combinations of these (7). The success of the primary procedure could not be predicted from stone size, site or duration in the ureter, but upper tract dilatation was significantly less (p less than 0.01) in the successful group. The overall success rate for complete stone extraction was 97%, but 54 patients (35%) required more than 1 procedure to achieve this. In situ EPL and push-bang, as either primary or secondary procedures, were successful in treating 79 patients (52%); 2 patients required ureterolithotomy (1.3%). The overall complication rate was 18%. Since EPL is only successful in treating approximately half of ureteric calculi, a range of other treatments should be available to maintain a low rate of open surgery.

Adolescent↗
PubMed1991

Prognostic value of raised prostatic acid phosphatase and negative skeletal scintigraphy in prostatic cancer.

Of 438 consecutive cases of newly diagnosed prostate cancer, 178 (41%) had skeletal metastases (T0-4 M1) at the time of diagnosis according to skeletal scintigraphy; 139 men had serum prostatic acid phosphatase (PAP) greater than twice the upper limit of normal on 2 separate occasions at the time of diagnosis and 65% of them had metastases on bone scan. However, 49 men with normal bone scans were found to have similarly raised serum PAP. (Such patients are defined as having skeletal metastases in the current Medical Research Council immediate versus deferred orchiectomy study and stratified accordingly). The actuarial survival of this group was calculated by life table methods and was compared with that of 2 other subgroups: those patients having metastases demonstrated on bone scan, and those patients having both normal bone scans and normal serum PAP. The survival of the "metastatic by acid phosphatase" group was significantly better than that of the "metastatic by bone scan" group but did not differ from that of patients having both normal scans and PAP. For patients with no scintigraphic evidence of skeletal metastases at diagnosis, those with a raised PAP were at a significantly greater risk of scan conversion, although this was more powerfully predicted by high histological grade.

Acid Phosphatase↗
PubMed1991

Does further extracorporeal lithotripsy promote clearance of small residual fragments?

Small persistent fragments (less than or equal to 4 mm) following extracorporeal shock wave lithotripsy have been termed clinically insignificant residual fragments (CIRF), but their presence may be associated with an increased rate of development of recurrent symptomatic renal calculi. We have adopted a policy of further extracorporeal piezoelectric shock wave lithotripsy (EPL) for patients with CIRF in an attempt to promote complete clearance. A series of 22 patients with a mean initial stone burden of 16 mm (range 7-48) developed CIRF after a median of 2 EPL treatment sessions (range 1-9). CIRF were in the lower calices (n = 20), middle calices (n = 1) and upper calices (n = 1). These calices were normal (n = 6), slightly dilated (n = 9), moderately dilated (n = 2) or grossly dilated (n = 5). After 6 to 14 months, patients underwent a further session of EPL. One month later, 3 patients with normal calices showed a considerable reduction in CIRF, but all other patients showed no change. When CIRF form in normal calices a further session of EPL may promote clearance. However, when calices containing CIRF are significantly dilated, further EPL is of no value.

Adult↗
PubMed1990

Measures of mortality in prostatic cancer.

The use of different expressions of mortality in prostate cancer can lead to difficulty in comparing reported data. We have used different measures of mortality in the same group of 438 patients presenting consecutively with histologically proven adenocarcinoma of the prostate, in order to assess the values and deficiencies of each method. The use of expected and relative survival is shown to be valuable in allowing indirect but objective assessment of disease specific mortality in prostatic cancer.

Adenocarcinoma↗
PubMed1990

De-differentiation with time in prostate cancer and the influence of treatment on the course of the disease.

There is little information on histological changes in prostate cancer during the course of the disease. We have studied 74 patients with carcinoma of the prostate who required 2 transurethral resections of the prostate (mean interval between resections 2.4 years). They constituted 18.4% of all patients with carcinoma of the prostate presenting to our clinic between January 1978 and April 1988. All tumours were staged by conventional methods and graded using the Gleason system. The Gleason sum score in those patients with tumour in both specimens increased in 49, remained constant in 12 and decreased in 7. Within this group were 34 patients who were treated expectantly. The mean Gleason sum scores in this group increased, with a concomitant increase in local tumour stage and development of metastases. Although this was not a randomised trial, there was no significant difference in survival between patients having "deferred" management and those treated immediately, either from time of diagnosis or from time of second resection. There was, however, a significant difference in the time to second resection, with the "deferred" group requiring repeat resection on average 1 year earlier. This study confirmed the concept of tumour de-differentiation with time and showed that this phenomenon occurs in both treated and untreated tumours. Although overall survival was not influenced by the type of initial therapy or its timing, local progression, as assessed by the need for further TURP, occurred earlier in those not receiving immediate therapy.

Aged↗
PubMed1990

Lithotripsy for calculi in caliceal diverticula?

There is continuing debate about the optimum management of patients with calculi in caliceal diverticula. Extracorporeal piezoelectric lithotripsy (EPL) has the advantage of being non-invasive, whereas endourological management can treat the underlying anatomical problem. A total of 20 patients with calculi in caliceal diverticula were treated with EPL. Twelve of 16 patients with symptoms (75%) were rendered symptom-free but only 5 (25%) became stone-free. This information should be of value in counselling patients before selecting the appropriate treatment.

Adult↗