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Biomedical subjects

R F Harrison

Publications and source records attributed to R F Harrison.

At least 55 records · Page 3Linked to original sources
PubMed1996

Application of the fuzzy ARTMAP neural network model to medical pattern classification tasks.

This paper presents research into the application of the fuzzy ARTMAP neural network model to medical pattern classification tasks. A number of domains, both diagnostic and prognostic, are considered. Each such domain highlights a particularly useful aspect of the model. The first coronary care patient prognosis, demonstrates the ARTMAP voting strategy involving 'pooled' decision-making using a number of networks, each of which has learned a slightly different mapping of input features to pattern classes. The second domain, breast cancer diagnosis, demonstrates the model's symbolic rule extraction capabilities which support the validation and explanation of a network's predictions. The final domain, diagnosis of acute myocardial infarction, demonstrates a novel category pruning technique allowing the performance of a trained network to be altered so as to favour predictions of one class over another (e.g. trading sensitivity for specificity or vice versa). It also introduces a 'cascaded' variant of the voting strategy intended to allow identification of a subset of cases which the network has a very high certainty of classifying correctly.

Artificial Intelligence↗
PubMed1996

A randomized prospective study of early follicular or midluteal initiation of long protocol gonadotropin-releasing hormone in an in vitro fertilization program.

OBJECTIVE: To determine the optimum menstrual cycle time to initiate a long-protocol gonadotropin-releasing hormone agonist (GnRH-a) down-regulation regimen before hMG stimulation before IVF. DESIGN: Randomized, prospective, single, first cycle study. SETTING: University teaching hospital. PATIENTS: Eighty-six infertile couples undergoing IVF-ET attempt under rules for Ireland. INTERVENTION: Gonadotropin-releasing hormone agonist administered intranasally from day 1 or 21 of menstrual cycle. Human menopausal gonadotropin commenced when pituitary down-regulation was confirmed. MAIN OUTCOME MEASURES: Ovarian response, cancellation, fertilization, and pregnancy rates. RESULTS: No significant differences found between day 1 and day 21 initiation. But starting on day 1 is more easily recognizable by patients and avoids the possibility of administering GnRH-a in the presence of an unsuspected pregnancy. CONCLUSIONS: Both follicular and luteal phase initiation of GnRH-a long-protocol down-regulation are equally efficacious. In our clinical context, patients and management favor commencing on day 1.

Adult↗
PubMed1996

Microbial contamination in an in vitro fertilization-embryo transfer system.

OBJECTIVE: To determine sources and transmission of microorganisms in IVF-ET and efficacy of in-place controlling systems. DESIGN: Prospective study. SETTING: In Vitro Fertilization-Embryo Transfer Unit at a university teaching hospital. PATIENTS: Twenty-eight couples undergoing 30 completed IVF-ET cycles. INTERVENTIONS: Gamete and embryo processing in a penicillin and streptomycin-rich medium. MAIN OUTCOME MEASURES: Presence of microorganisms at various stages of IVF-ET. Fertilization, cleavage, and pregnancy rates. RESULTS: In 50% of cycles no microorganisms were isolated and in the other 50% microbes were cultured from various loci. Cultures of four preprocessed semen samples were positive and corresponding postprocessed samples negative. Microbes were detected in 27% of needle washes after oocyte collection; in 40% and 32% of follicular fluids from left and right ovaries, respectively; and in two culture media from egg-sperm incubations at 20 hours after insemination. No microorganisms were grown from media from zygote incubations. Fertilization, cleavage, and pregnancy rates were independent of microbial presence. CONCLUSION: Seminal fluid and transvaginally collected oocytes are potential sources of microbial contamination of the IVF-ET culture system. A penicillin- and streptomycin-rich culture medium is effective in removing contaminating microbes. End point measures are not affected by commensal contamination.

Culture Media↗
PubMed1996

Early diagnosis of acute myocardial infarction using clinical and electrocardiographic data at presentation: derivation and evaluation of logistic regression models.

The aim of this study was to determine which, and how many, data items are required to construct a decision support algorithm for early diagnosis of acute myocardial infarction using clinical and electrocardiographic data available at presentation. Logistic regression models were derived using data items from 600 consecutive patients at one centre (Edinburgh), then tested prospectively on 510 cases from the same centre and 662 consecutive cases from another centre (Sheffield). Although performance of the models increased with progressive addition of data inputs when applied to training data, a simple six-factor model was the most effective on test data, yielding accuracies of 84.3 and 83.6% on the two test sets. A model constructed solely of electrocardiographic data performed nearly as well as those incorporating clinical data. Previously published logistic regression models did not perform so well as the models derived from data collected for this study.

Adolescent↗
PubMed1996

Tubo-peritoneal factor infertility: a distant sequel to intrauterine transfusion for rhesus disease.

A patient presented with infertility 28 years after receiving four intrauterine transfusions as a fetus for rhesus haemolytic disease. Extensive adhesions were found in the peritoneal cavity affecting in particular the ovarian retrieval mechanism. No other possible cause for the situation could be discerned. Patients who have undergone pioneering techniques such as this are now adults and may be trying to conceive. When confronted by such a history there is therefore a need for early thorough investigation of the tubal peritoneal factor.

Adult↗
PubMed1996

'Fragile' liver and massive hepatic haemorrhage due to hereditary amyloidosis.

The first case of amyloidosis is reported in which spontaneous massive hepatic haemorrhage necessitated emergency liver transplantation. Liver transplantation, as a treatment for a failing liver due to amyloidosis has not been previously reported. At transplantation, the liver tissue was uncharacteristically friable, although the subsequent vascular and biliary anastomoses were uncomplicated. Histological examination of the liver showed a surprisingly modest amount of amyloid, which was shown immunohistochemically to be derived from lysozyme, and a striking absence of reticulin staining. Both the patient's father and paternal grandfather had died from spontaneous hepatic haemorrhage, and histological review of their liver tissue showed similarly modest deposition of lysozyme-derived amyloid associated with loss of reticulin staining. In each case the quantity of amyloid was far less than would be expected to interfere with the mechanical integrity of the liver. This is the only report of hepatic disintegration associated with absence of reticulin staining, and it is probable that the mechanism represents a novel secondary effect of the amyloid deposits in the livers of this family.

Adolescent↗
PubMed1995

Course and outcome of IVF pregnancies and spontaneous conceptions within an IVF setting.

The study determines mortality and morbidity levels during pregnancy and the perinatal period in those conceiving through IVF in the Republic of Ireland in comparison with other parts of the world and a peer infertile group conceiving spontaneously whilst on the IVF clinic books. Six hundred and sixty couples had 187 IVF pregnancies from whom 220 babies were born to 151 deliveries. There were also 78 spontaneous conceptions which produced 78 offspring from 73 deliveries. The majority had trouble free pregnancies. The incidence of all complications was less than has been reported elsewhere. Of the IVF group, 16.5% aborted completed as did 5% of the spontaneous conceptions. A further 7% and 3.8%, respectively, aborted one sac of a multiple pregnancy. Of the IVF deliveries, 35.8% were multiple as were 6.8% of the spontaneous conceptions. Higher order multiple presence detrimentally influenced delivery mode, gestational age and birth weights in the IVF group. Of IVF patients, 55.7% were section deliveries as were 10.9% of the spontaneous conceptions. Incidence of IVF-group significant congenital abnormality was 1.8%. The perinatal mortality rate was 4.2 per 1000 births. This series suggests the final take-home baby outlook of 81% from conception by IVF is not as poor as previously portrayed. However, attention should be given to abortion, section and multiple pregnancy rates.

Adult↗
PubMed1995

The value of subcellular elemental analysis in the assessment of human spermatozoa.

The conventional sperm parameters of concentration, motility and morphology are descriptive and have proved of little value in predicting the fertilization potential of semen. New complementary tests of sperm function are required. Previous studies evaluating the subcellular elemental composition of spermatozoa using X-ray microanalysis with electron microscopy suggested that this technique may have the potential to confirm spermatozoal intracellular normality. This study compares the semen from 18 men of subfertile relationships and from 10 men of proven fertility with reference to concentration, motility, morphology and the elemental composition of spermatozoa. The elements phosphorus, sodium, potassium, chlorine and sulphur were detected and there were large intra- and intersample variations in the concentrations of these elements. There was no statistically significant difference in the elemental composition between the two groups. This study suggests that the spermatozoa of fertile and subfertile men are similar in subcellular elemental composition and in the maintenance of an ionic gradient. This test is therefore not a useful predictor of sperm function.

Acrosome↗
PubMed1995

Hepatitis C virus infection in the asymptomatic British blood donor.

Blood donor screening for hepatitis C virus (HCV) antibodies is now routine. Most blood transfusion services recommend that seropositive donors are referred for further investigation. Southern European studies suggest that many asymptomatic seropositive donors have clinically significant liver disease. Seropositive donors in areas of high prevalence may not, however, be representative of British donors. We have prospectively examined the prevalence and severity of HCV infection in a British volunteer blood donor population. During a 14 month period, only 0.35% (999/287,332) of all donors in the West Midlands were anti-HCV (screening assay) positive. Only 5% (52/999) of these were confirmed true seropositive. Nearly 80% (41/52) of seropositive donors were referred to the Queen Elizabeth Hospital Liver Unit for further investigation. Most underwent complete investigation, including liver biopsy. Forty of forty-one donors had biochemical, histological, or virological evidence of persistent viral infection. Histological changes were generally mild and none was cirrhotic. Covertly infected patients had less severe disease than those with an overt risk factor for HCV exposure. In the British Midlands, the prevalence of blood donor seropositivity is low. In contrast with seropositive Southern European donors, the British donor is more likely to belong to an at-risk group for parenteral exposure and is less likely to have severe histological changes. This study highlights the importance of developing locally relevant guidelines for the counselling and investigation of anti-HCV-positive blood donors.

Adult↗
PubMed1995

Stathmin is expressed by the proliferating hepatocytes during liver regeneration.

Aim-To determine the liver cell populations that express the phylogenetically conserved cytosolic protein stathmin during liver regeneration.Methods-Double immunostaining for stathmin and the Ki67 antigen was performed on sections of formaldehyde fixed, paraffin wax embedded tissues from 31 liver specimens. These included a variety of disease conditions characterised by some degree of hepatocyte regeneration. Quantitative western blot analysis was performed on 22 of these specimens.Results-Variable amounts of stathmin protein were detected by western blotting in all of the specimens examined. Stathmin was not detected in three cases of histologically normal liver. On immunostaining, stathmin was demonstrated in a proportion of hepatocytes as well as lymphoid inflammatory cells and other tissue elements. In all cases most of these stathmin positive cells showed nuclear positivity for the Ki67 antigen.Conclusions-Stathmin is expressed by proliferating hepatocytes but not by resting hepatocytes. Thus, it is likely that the protein has a function important to cell proliferation as opposed to cell differentiation.

Journal Article↗
PubMed1994

The role of dynamic and morphological studies in the assessment of potential liver donors.

In a prospective study, 66 donor livers were evaluated by monoethylglycinexylidide (MEGX) dynamic clearance and semiquantitative scoring of pathological changes in liver biopsies. The median MEGX level in 63 donors was 89 mcg/L (range 16-250 mcg/L); fifteen had MEGX levels < 50 mcg/L, 17 between 50 and 90 mcg/L, and 31 > 90 mcg/L. There were no cases of primary nonfunction, and no deaths were related to poor graft function. There was no statistically significant difference in peak aspartate aminotransferase (AST), day 5 AST, peak bilirubin, or lowest prothrombin time among the 3 groups. Liver biopsies were assessed in 61 donors: 33 (54%) were normal and 17 (28%) showed mild, 8 (13%) showed moderate, and 3 (5%) showed severe steatosis. Postperfusion biopsy assessing the extent of preservation injury was essentially normal or showed minimal change in 16 (26%), mild change in 29 (48%), moderate in 13 (21%) and severe abnormalities in 3 (5%). The latter 3 biopsies all had severe steatosis. There was no significant difference in early graft function or outcome between moderate/severe groups and normal/minimal groups, although the former had a higher peak AST (P < 0.02) and peak bilirubin (P < 0.004). This detailed prospective analysis suggests that MEGX and the morphological studies may assist in the assessment of potential liver donors but they do not provide a basis on which grafts should be discarded.

Adolescent↗