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Biomedical subjects

R J Connor

Publications and source records attributed to R J Connor.

At least 37 records · Page 2Linked to original sources
PubMed1990

Helminthosis in goats in southern Tanzania: investigations on epidemiology and control.

Investigations were conducted in naturally infected goats to determine the main epidemiological factors related to gastro-intestinal nematode infections in southern Tanzania with a view to making appropriate recommendations for control. Faecal worm egg counts rose during the single rainy season and then fell to remain low during the dry season. The beneficial effect of an anthelmintic treatment after the rains was demonstrated in weaner goats under traditional management and this should form the basis of rational control.

Animals↗
PubMed1990

Prospective evaluation of serum CA 125 levels in a normal population, phase I: the specificities of single and serial determinations in testing for ovarian cancer.

To determine the potential efficacy of the CA 125 assay as one component of a strategy for early detection of ovarian malignancy, serum CA 125 levels were determined in 1082 women 40 years of age or older in Stockholm. Initial serum CA 125 levels exceeded 35 U/ml in 36 women (3.3%) and 65 U/ml in 11 women (1.0%), placing the exact 95% upper confidence limits on false positive rates for a single screen at 4.3 and 1.7%, respectively. Follow-up CA 125 levels were obtained for those women with initially elevated levels and a group of age-matched controls. Mean CA 125 levels declined significantly for women with initially elevated levels (P = 0.0014). Interindividual variation and variation within individual subjects over the entire follow-up period were 52 and 35%, respectively. Of the 36 subjects with initially elevated serum CA 125 levels, only 2 showed a doubling of these levels; in only 1 of these 2 was this increase sustained. Intensive clinical follow-up with pelvic examination and ultrasonography, with investigators blinded to CA 125 results, led to the diagnosis of Stage III ovarian cancer in the latter individual. Diagnosis was made 21 months after the initially elevated serum CA 125 measurement and 15 months after the first measured doubling of that level. Because no other malignancies were identified at entry or during the follow-up period (median 560 days) in the women with elevated CA 125 levels, the specificity of the assay over that time period would have been 99.9% using the doubling of an initially elevated value as the criterion for determining positivity and 100% using as the criterion a sustained increase in level for those with initially elevated levels that doubled. These results support the continued investigation of longitudinally collected CA 125 levels to identify individuals at high risk for ovarian malignancy.

Adult↗
PubMed1990

Statistical considerations in cancer screening programs.

The goal of cancer screening is the early detection and treatment of disease, with a consequent reduction in the mortality rate. Evaluation of whether a particular screening program can achieve this goal is a difficult task. Two components of the screening process must be assessed. The first is the ability of the screening test to detect cancer early while minimizing the number of false-positive results. In this regard, the specificity of the test ordinarily must be very high, approaching 99%. No screening test for prostate cancer has yet been reported to have a specificity this high, indicating that any prostate cancer screening program using currently available tests will have to deal with the problem of a large number of false-positive findings. To evaluate the overall impact of a screening program, the best procedure is the randomized controlled trial with cancer-specific mortality as the endpoint. This endpoint is used because it avoids the lead time and length biases inherent in other outcome variables such as stage shift and case survival. The screening randomized controlled trial must be carefully planned and implemented, because it is lengthier and more costly than the usual therapy trial because of differences in study populations, trial design relative to the planned population intervention, and the extent of knowledge of disease natural history. A further important component of screening evaluation is cost. The decision to implement or continue a screening program can be aided by using cost-effectiveness analysis, which bases a decision on the ranking of cost-to-benefit ratios for the various programs contending for limited funds. Screening cost includes the cost of the test, the cost of side effects of the test, and the costs of biopsy and treatment, while screening benefit can be measured in terms of lives saved, life years saved, or quality-adjusted life years.

Cost-Benefit Analysis↗
PubMed1989

Bovine trypanosomiasis in southern Tanzania: investigation into the incidence of infection and duration of chemoprophylaxis.

Before implementing chemoprophylaxis to control bovine trypanosomiasis it is essential to have epidemiological data upon which to base control regimes. A study was conducted under natural tsetse challenge with two groups each of 12 calves grazing their first season. Group 1 received isometamidium treatments prophylactically at intervals during the rainy season and calves in group 2 were treated individually with diminazene as they become infected with trypanosomes. Infections were first detected in the unprotected calves and indicated that the onset of challenge was approximately four weeks after the rainy season began. Trypanosoma vivax accounted for 21 of the 30 infections detected in blood smears, and although one infection remained unspeciated, the remaining eight were T. congolense. It was concluded that a prophylactic regime beginning one month after the start of the rains with repeat treatments of isometamidium at 1 mg/kg at intervals of 10 weeks could be expected to give good control of trypanosomiasis at this location.

Age Factors↗
PubMed1989

Notes on the routine intravenous use of isometamidium in the control of bovine trypanosomiasis on the Kenya coast.

Various chemotherapeutic regimes were used to control trypanosomiasis in 3,000 Boran cattle on an estate on the Kenya coast. Recently the therapeutic use of isometamidium by the intravenous route was adopted to treat individual trypanosome-infected cattle. This was in order to overcome tissue reactions encountered after intramuscular injection and also to control a "thin cow" syndrome attributed to chronic trypanosomiasis. Toxic side effects were eliminated by careful attention to the intravenous technique which was safely used in calves, pregnant cattle and bulls. Weekly blood sampling and treatments of infected individuals resulted in a reduction of cases from 2,187 to 208 out of 46,495 and 46,329 samples examined in 1985 and 1986 respectively. The standard of management was very high and although this routine successfully controlled bovine trypanosomiasis on this estate its application elsewhere is likely to be limited.

Animals↗
PubMed1989

Stage-shift cancer screening model.

A stage-shift cancer screening model is developed in the context of a randomized controlled trial (RCT) of cancer screening. In the model, detection by screening causes the time of diagnosis of the cancer to be advanced so that either the stage at diagnosis is shifted from one stage to the next lower one or the stage of diagnosis is unchanged but the cancer is diagnosed earlier in the stage. These are called external and internal stage shifts, respectively. At each stage the extent of the external and internal shifts and any associated mortality benefits are estimated. Further, the model allows the interrelationships of these benefits within and between stages to be delineated. This then allows us to better understand the results of the RCT. Data from a completed breast cancer screening RCT are used to illustrate the application of the model and its value in improving our understanding of the trial's results.

Adult↗
PubMed1987

Bovine trypanosomiasis in southern Tanzania: parasitological and serological survey of prevalence.

In a survey for bovine trypanosomiasis blood smears from 1,617 cattle at 72 sites were examined. Trypanosomes were found in 93 cattle, representing 16% of the cattle in herds in which trypanosomiasis was confirmed. Of the positive cattle 56% had infections with T. congolense, 17% T. vivax and 2.2% T. brucei. Five cattle had mixed infections and in 18 cattle the species was not identified. Sera from 1,352 cattle were tested using microelisa. Ten out of 16 sites, at which no trypanosomes were found in blood smears and at which trypanocides were in use, had over 15% seropositive cattle compared with five of 19 sites at which trypanocides were not in use. It was concluded that the microelisa was a useful aid to the diagnosis of bovine trypanosomiasis and that there is a need for accurate records of drug use and livestock movements to be kept. The serious risk of drug resistant strains of trypanosomes emerging due to the uncontrolled use of trypanocides is emphasised.

Animals↗
PubMed1987

Comparing new and old screening tests when a reference procedure cannot be performed on all screenees. Example of automated cytometry for early detection of cervical cancer.

Direct determination of the sensitivity and specificity of a screening test requires use of a reference procedure (such as biopsy with histopathologic analysis) that provides an estimate of true disease status. The authors present a method for comparing the accuracy of a new screening test to an old one in situations when it is not feasible to apply the reference procedure to all screenees. This method requires that only those persons who test positive on old or new screening tests be further evaluated with the reference procedure. Ratios of sensitivities and specificities are derived for rapid comparison of the two screening tests. It is shown that McNemar's test can be used for significance testing of the differences in sensitivities and specificities between two screening tests. The required sample size for a study that compares the two tests is determined.

Female↗
PubMed1987

Sample size for testing differences in proportions for the paired-sample design.

Miettinen (1968, Biometrics 24, 339-352) presented an approximation for power and sample size for testing the differences between proportions in the matched-pair case. Duffy (1984, Biometrics 40, 1005-1015) gave the exact power for this case and showed that Miettinen's approximation tends to slightly overestimate the power or underestimate the sample size necessary for the design power. A simple alternative approximation that is more conservative is presented here. In many cases, the sample size for the independent-sample case provides a conservative approximation for the matched-pair design.

Research Design↗
PubMed1986

Concurrent outbreak of pseudo-lumpy skin disease and acute Trypanosoma vivax infection in cattle.

Pseudo-lumpy skin disease and acute Trypanosoma vivax infections occurred simultaneously in a dairy herd which had no previous history of trypanosomiasis. The onset of the outbreak was sudden and 29 out of the 40 adult Friesian and exotic x zebu cattle were found to have skin lesions. Five out of the nine animals sampled had fulminating T. vivax parasitaemias with packed red cell volumes ranging from 0.09 to 0.28 litres/litre. Whereas carried tsetse may have introduced T. vivax, the failure to trap tsetse and the presence of large numbers of biting flies strongly suggested that in this outbreak both aetiological agents were transmitted mechanically.

Animals↗
PubMed1982

Effect of various immunoregulatory substances on the growth inhibitory activity (GIA) of human monocytes against lymphoblastoid cell lines.

Human peripheral blood monocytes, isolated by adherence to plastic surfaces or elutriation by size, were tested for growth inhibitory activity (GIA) against human and mouse lymphoblastoid cell lines. Cells isolated by either method inhibited incorporation of 3H-thymidine of both target cells, but did not affect phytohemagglutinin-induced blasts. GIA was appreciably higher when the assays were performed in medium with human serum rather than fetal calf serum. Interferon significantly augmented GIA at a 10:1 effector:target (E/T) radio in a 24 hr assay, and at an E/T ratio of 30:1 in a 48 hr assay. Preincubation with phorbol myristate acetate (PMA) caused a threefold or greater increase in GIA by monocytes. Prostaglandins or indomethacin, as well as corticosteroids, did not influence GIA. Superoxide dismutase and catalase were not found to affect GIA when added to the assay. cytostatic activity by human monocytes is apparently subject to positive regulation, but not to suppression by prostaglandins. The mechanism responsible for GIA remains undetermined, but appears to be independent of superoxide radical generation.

Cell Line↗
PubMed1981

Removal of partially loosened fixed partial dentures.

The technique described offers maximum safety for the abutment tooth and the probability of salvage of the existing restoration. The options of reusing the restoration or recementing it as a temporary restoration are both attractive.

Dental Abutments↗
PubMed1981

A study of immunoregulation of BALB/c mice by Echinococcus granulosus equinus during prolonged infection.

Two models of intraperitoneal infection with E. granulosus equinus by protoscolices and by cyst passage in BALB/c mice were used to provide mesenteric lymph node cells for adoptive cell transfer into syngeneic recipient normal responder mice. The cell transfer inocula were shown to have depleted Thy-1 cells, but to be highly suppressive to the normal sheep erythrocyte response of the recipients. The nature of the depletion and non-specific suppression, and the infectious nature of the latter, are discussed in relation to other examples of mitogenic stimulation resulting in non-specific T cell suppressor activity. The functions of Ly-2,3+ cells, not only as suppressor, but as alloreactive cytotoxic cells, are discussed as a possible, autoimmune explanation for the longevity of the parasite within the mouse model, in contradistinction to the predictable early rejection of analogous xenografts.

Animals↗