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Biomedical subjects

M Duncan

Publications and source records attributed to M Duncan.

54 records · Page 3Linked to original sources
PubMed1987

Arrested larval development in cattle nematodes.

Most economically important cattle nematodes are able to arrest their larval development within the host - entering a period of dormancy or hypobiosis. Arrested larvae have a low death rate, and large numbers can accumulate in infected cattle during the grazing season. Because of this, outbreaks of disease caused by such nematodes can occur at times when recent infection with the parasites could not have occurred, for example during winter in temperature northern climates when cattle are normally housed. The capacity to arrest is a heritable trait. It is seen as an adaptation by the parasite to avoid further development to its free-living stages during times when the climate is unsuitable for free-living survival. But levels of arrestment can vary markedly in different regions, in different cattle, and under different management regimes. Climatic factors, previous conditioning, host immune status, and farm management all seem to affect arrestment levels. In this article, James Armour and Mary Duncan review the biological basis of the phenomenon, and discuss the apparently conflicting views on how it is controlled.

Journal Article↗
PubMed1986

Ulcerative balanoposthitis associated with non-syphilitic spirochaetal infection.

Ulcerative balanoposthitis associated with non-syphilitic spirochaetal infection was found in 41 (12%) of 344 consecutive men with genital ulcer disease in two clinics in South Africa. All patients with non-syphilitic spirochaetal infection were uncircumcised. Non-syphilitic treponemes were seen in only two of 60 uncircumcised men who had urethritis without genital ulceration. In 14 patients with ulcerative balanoposthitis no cause of genital ulceration could be identified. Most patients presented with large, serpiginous, superficial, foul smelling, and tender ulcers, the base of which was purulent with undermined edges. Non-tender inguinal lymphadenopathy was present in seven of 14 patients. One female sexual partner of a patient with non-syphilitic spirochaetal infection had a vaginal infection with non-syphilitic spirochaetes.

Humans↗
PubMed1984

Dopamine infusion studies in patients with pathological hyperprolactinemia: evidence of normal prolactin suppressibility but abnormal dopamine metabolism.

The cause of pathological hyperprolactinemia (PHP) is not known, although it has been postulated that lactotroph refractoriness to dopamine (DA) is an important factor. We, therefore, studied PRL suppressibility in response to iv DA administered in a dose designed to achieve peripheral plasma DA concentrations in the range reported in rat pituitary portal plasma. Nine normal subjects and 14 patients (8 with probable microadenomas and 6 with macroadenomas) with PHP were studied during a 4-h infusion of 0.5 micrograms/kg X min DA. Serum PRL levels decreased in normal subjects to 18 +/- 3% (mean +/- SEM) of initial basal levels, not significantly different from the fall to 22 +/- 2% of basal levels found in patients with PHP. Maximal PRL suppression in patients with probable microadenomas (21 +/- 2%) was not significantly different from that in those with macroadenomas (22.8 +/- 2.0%). Upon cessation of DA infusion, there was a rapid rebound in PRL release, which was significantly greater (P less than 0.05) in patients (155 +/- 15%) than in normal subjects (118 +/- 13%). Plasma DA levels were measured by gas chromatography/mass spectroscopy and were significantly higher (P less than 0.05) in patients than in normal subjects during the infusion. The MCR for DA in normal subjects (12.5 +/- 2.8 liters/kg X h) was significantly greater (P less than 0.005) than that in patients (6.2 +/- 0.5 liters/kg X h). The data show that the release of PRL in patients with PHP is not refractory to physiological concentrations of DA, but that there is an abnormality of peripheral DA metabolism in these patients. We conclude that the development of PHP is unlikely to be due to insensitivity of lactotrophs to endogenous DA and that patients with PHP have a systemic disturbance of DA metabolism.

Adenoma↗
PubMed1982

Loss of hypothalamic dopaminergic control of prolactin secretion in the hyperprolactinaemic rat.

The possibility that chronic hyperprolactinaemia results in loss of the ability of hypothalamic dopamine activity to inhibit prolactin secretion was studied in rats. Two degrees of hyperprolactinaemia (moderate and gross) were induced in the animals following the chronic administration of two different doses of oestradiol valerate. In rats with high chronic serum prolactin concentrations (approximately 20 times normal) there was a profound increase in prolactin secretion following inhibition of brain dopamine (DA) synthesis by 3-iodo-L-tyrosine, indicating intact and highly active hypothalamic DA-inhibitory control of prolactin release. However, the degree of hypothalamic inhibition of prolactin release relative to normal controls was significantly reduced. In animals with grossly elevated chronic serum prolactin concentrations (approximately 100 times normal) a prolactin response to DA synthesis inhibition was absent despite a highly significant reduction in hypothalamic DA concentrations induced by 3-iodo-L-tyrosine. These observations show that chronic and gross hyperprolactinaemia in the rat results in loss of hypothalamic DA inhibitory control of prolactin secretion. The use of 3-iodo-L-tyrosine to block brain DA synthesis in these studies has provided significant new data relating to prolactin control in hyperprolactinaemic states and indicates that this compound could be a useful clinical tool in the study of human hyperprolactinaemia.

Animals↗
PubMed1981

Trial of daunomycin in acute promyelocytic leukemia of childhood: a Southwest Oncology Group Study.

Children with acute promyelocytic leukemia were treated with aggressive daunomycin induction and 6-mercaptopurine and methotrexate maintenance. The remission rate was 8 out of 10 fully evaluable patients. Three are still alive up to 32 months. With vigorous induction therapy, occurrence of disseminated intravascular coagulation was rare. Only one case of DIC was seen in a child who had pseudomonas sepsis at time of diagnosis. Since current protocols are more aggressive, future chemotherapy include patients with acute promyelocytic leukemia.

Adolescent↗
PubMedDate not supplied

Morphological changes in atrial appendages removed during the maze procedure: a comparison with autopsy controls.

Atrial fibrillation (AF) is commonly encountered in clinical practice and typically it is treated with pharmacological agents. Some patients whose arrhythmias are resistant to pharmacological therapy undergo the maze procedure, which is a surgical treatment. The atrial appendages are removed as part of the surgical procedure. These appendages often demonstrate mycocyte hypertrophy, vacuolar degeneration and other changes that may be seen in cardiomyopathies. We examined 19 of these appendages and compared them with 17 autopsy controls, 12 of whom had documented coronary atherosclerotic disease and 5 of whom did not. We semiquantitatively measured the amount of vacuolar degeneration, interstitial fibrosis, myocyte hypertrophy and intramyocardial adipose tissue. Univariate and multivariate analysis was performed and revealed that vacuolar degeneration were significantly more common in appendages of patients with arrhythmias than the autopsy controls (P<.0004). The other three histological features studied were not significantly different in the three groups. Ultrastructural studies on atrial tissue excised during the maze procedure, retrieved from the paraffin blocks, revealed degenerative changes similar to cardiomyopathic myocardial tissue. Vacuolar degeneration is commonly seen in atrial appendages removed in patients with chronic AF. Myocyte hypertrophy is a nonspecific finding and may occur in patients with arrhthymias and coronary artery disease.

Adipose Tissue↗
PubMedDate not supplied

Emergency room management of minor burn injuries: a quality management evaluation.

The vast majority of acute burns are initially seen and treated in emergency departments (EDs). Most of the individuals caring for these patients have little or no specialized training in the multidisciplinary approach to the burned patient. Burns of limited severity are treated immediately and then followed on an outpatient basis; therefore reviews of documented practices in emergency departments were not found. It was hypothesized that follow-up care may be suboptimal in this population. The medical records of 791 patients treated at three EDs in a Midwestern regional referral area from January 1991 through December 1991 were evaluated to assess the documentation of care provided. The three hospitals included a tertiary care teaching facility, a pediatric facility, and a community-based teaching hospital. Only the charts of patients treated and released from the ED were evaluated. The data demonstrate that there was suboptimal documentation of diagnosis, treatment, and follow-up care of the thermally injured patients who were initially treated in these EDs. Burn team members should develop educational and clinical relationships with EDs in the referral area to optimize both the delivery and documentation of outpatient burn care. This is especially important in today's health care environment, in which reimbursement is based on services rendered.

Adult↗
PubMedDate not supplied

A broader vision for managed care, Part 2: A typology of community benefits.

Applying a "community benefit" standard to managed care is difficult because prevailing definitions of community benefit have been drawn largely from the hospital industry, which has different operating practices and capabilities than managed care plans do. To formulate a more comprehensive and appropriate typology for managed care, we describe four different conceptual perspectives on community benefit and identify actual plan practices that match each perspective. We propose a "balanced model" for encouraging community benefit through public and private policies.

Charities↗
PubMedDate not supplied

A programme for computer aided identification of phlebotomine sandflies of the Americas (CIPA)--presentation and check-list of American species.

The CIPA programme is a collaborative project including two entomologists from France and seven from South and Central America countries. Its objective is the development of an expert system for computer aided identification of phlebotomine sandflies from the Americas. It also includes the formation of data bases for bibliographic, taxonomic and biogeographic data. Participant consensus on taxonomic prerequisites, standardization in bibliographic data collections and selection of descriptive variables for the final programme has been established through continuous communication among participants and annual meetings. The adopted check-list of American sandflies presented here includes 386 specific taxa, ordered into three genera and 28 sub-genera or species groups.

Animals↗