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Biomedical subjects

J A Lawrence

Publications and source records attributed to J A Lawrence.

At least 37 records · Page 2Linked to original sources
PubMed1996

Integrated tick and tick-borne disease control trials in crossbred dairy cattle in Malawi.

Crossbred dairy heifers on a farm in an East Coast fever (ECF) endemic area in Malawi were immunised against Theileria parva, Anaplasma spp., Babesia bigemina, Babesia bovis and Cowdria ruminantium. They were treated at infrequent intervals with chlorfenvinphos to limit infestation with adult ticks, without providing complete tick control. In one trial, which tested a threshold dipping regimen, 20 heifers were dipped only once in 6 months to control a flush of Boophilus microplus. Unimmunised controls showed serological evidence of exposure to T. parva and B. bigemina, and one died of ECF, but there were no incidents of tick-borne disease in the immunised group. In a second trial, which tested a strategic dipping regimen, 107 animals were dipped 9 times over a 6 month period. Despite heavy challenge by B. bovis and moderate challenge by B. bigemina and Anaplasma spp. demonstrated serologically, there was only a single clinical case of babesiosis. The observations provide encouragement for the introduction of integrated tick and tick-borne disease control programmes in improved cattle in ECF endemic areas.

Administration, Topical↗
PubMed1996

Nurses' representations of the positive and negative features of nursing.

Nurses' representations of their work are defined as their cognitive 'work spaces', a theoretical concept derived from Newell & Simon's (1977) problem-solving model and Lewin's (1935) concept of interacting positive and negative valences. Using a structural equation modelling technique, a network of positive and negative features in nurses' work spaces is described in patterns of response to a questionnaire eliciting nurses' ratings of their professional opportunities and difficulties. The modelling technique revealed the dominance of positive over negative features, and the overall significance of social recognition for encouraging nurses to remain in nursing. Comparative analyses revealed that dominant features of work space representations did not differ for nurses from four city and country hospitals, nor in relation to positions in the nursing hierarchy. The importance of understanding the perceptions of nurses is discussed in relation to changes and development in nursing as a profession.

Adult↗
PubMed1996

Malignant melanoma metastatic to the gastrointestinal tract.

Malignant melanoma, a common malignancy whose prevalence is increasing, represents 1-3% of cancers in the United States [1]. At autopsy, metastatic deposits to the gut are frequently found, but less than 9% of melanoma patients are diagnosed with gastrointestinal metastases while living [2]. Modern management includes aggressive surgical therapy to prolong survival and to palliate the disease [3]. Therefore, imaging of metastatic melanoma is clinically important to detect extent and determine whether the patient would benefit by surgery. Gastrointestinal metastases may manifest as mucosal or submucosal masses, serosal implants, or carcinomatosis [4]. They arise more commonly in the mesentery or distal small bowel than the proximal gastrointestinal tract or colon. The purpose of this essay is to illustrate the appearance of melanoma metastatic to the gastrointestinal tract on luminal contrast studies and on CT and to emphasize the importance of early investigation of gastrointestinal symptoms in a patient with a history of malignant melanoma.

Adult↗
PubMed1996

Field observations on the duration of immunity in cattle after vaccination against Anaplasma and Babesia species.

In an outbreak of Babesia bovis in a large herd of Friesian x Malawi Zebu cattle, which occurred after an interruption of intensive dipping, clinical or fatal babesiosis occurred in 54/299 (18.1%) animals which had never been vaccinated, as compared to 9/153 (5.9%) vaccinated animals. Eight of the nine affected vaccinates had been vaccinated more than 27 months previously. Sera were collected every 3-4 months from 33 Friesian x Malawi Zebu heifers maintained with intensive dipping and vaccinated with trivalent B. bovis, Babesia bigemina and Anaplasma centrale vaccine. After 2 years, 25% had become seronegative for B. bovis by indirect immunofluorescence, as compared to 97% for B. bigemina and 46% for A. centrale. Because of the evidence that immunity following vaccination against B. bovis declines after 2 years in the absence of tick challenge, it is recommended that tick control should be relaxed after immunity has been established, in order to save acaricide, reinforce immunity and avoid any need for revaccination.

Anaplasma↗
PubMed1996

Improving the specificity of indirect immunofluorescence for the serological diagnosis of bovine anaplasmosis.

Fluorescing inclusion appendages were detected consistently in preparations of Anaplasma centrale and Anaplasma marginale when they were used as antigen in indirect immunofluorescence serological tests for the diagnosis of anaplasmosis in cattle. The presence of the inclusion appendages made it possible to confirm the specificity of the immunofluorescent reaction and to determine end-points with accuracy.

Anaplasmosis↗
PubMed1995

Overexpression of cyclin D mRNA distinguishes invasive and in situ breast carcinomas from non-malignant lesions.

The elucidation of molecular alterations that occur during human breast cancer progression may contribute to the development of preventative strategies. Using in situ hybridizations on a cohort of 94 biopsy lesions, quantitatively increased cyclin D mRNA expression levels were observed in only 18% of benign lesions, which confer no or slightly increased breast cancer risk, and 18% of premalignant atypical ductal hyperplasias, which confer a four to fivefold increase in breast cancer risk. The transition to carcinoma was accompanied by frequent cyclin D mRNA overexpression in 76% of low-grade ductal carcinomas in situ, 87% of higher grade comedo ductal carcinomas in situ and 83% of infiltrating ductal breast carcinomas. The data identify a molecular event that may separate benign and premalignant human breast lesions from any form of breast carcinoma.

Breast Neoplasms↗
PubMed1995

Lower extremity spiral CT angiography versus catheter angiography.

Both catheter and spiral computed tomography (CT) angiography of the lower extremity vasculature were performed in six patients with clinically symptomatic peripheral vascular disease. Forty-eight arteries were studied and were independently evaluated for arterial stenoses and occlusions. Compared with catheter arteriography, CT angiography correctly depicted segmental occlusions and significant stenoses (> 50%) in 26 of 28 arteries, yielding a sensitivity of 92.9%, a specificity of 96.2%, and an overall accuracy of 95.5%.

Aged↗
PubMed1995

The serological response to heartwater immunization in cattle is an indicator of protective immunity.

A significant correlation was demonstrated in Friesian-cross steers between the serological response to previous vaccination with the Ball 3 strain of Cowdria ruminantium and the development of protective immunity against the Kalota isolate from Malawi. Of 10 animals which seroconverted after vaccination, all were completely or partially immune to challenge. Ten of the 14 animals which failed to seroconvert were immune but the proportion was not significantly different from that in the unvaccinated controls (4/10). Of 29 animals vaccinated and treated simultaneously with a slow-release doxycycline implant, 13 failed to seroconvert, and of these, four were completely susceptible to challenge.

Animals↗
PubMed1995

Reactions to heartwater vaccination in crossbred Zebu cattle.

One thousand and ninety-four crossbred Zebu cattle were immunized against heartwater with a sheep-blood vaccine containing the Ball 3 strain of Cowdria ruminantium. Animals experiencing febrile reactions were treated at various stages of the reaction with tetracycline. Four hundred and sixty-two (42.2%) reacted, six (0.6%) of which died. Deaths were significantly less frequent in cattle treated on the first day of reaction (2/323, 0.6%) than those treated at a later stage (4/61, 6,6%). The mean incubation period was 15,6 d (range 7-23 d). Incubation period and frequency of reactions varied significantly between farms, between vaccine batches and between vaccine doses. Variations in frequency of reactions, incubation period and severity of reaction did not affect the efficacy of immunization, as assessed by seroconversion.

Animals↗
PubMed1994

CT angiography: expanded clinical applications.

In this essay, the potential of vascular imaging with helical CT is explored. The speed and ease with which volumes of interest can be depicted with high resolution and the ability of CT to resolve small differences in electron density allow imaging of vascular territories with IV injection of iodinated contrast materials. Vascular and combined vascular/soft-tissue/bone imaging make CT a powerful clinical tool. The technique is predominantly used for evaluation of atherosclerotic disease of the carotid bifurcation, the renal arteries, and the major abdominal vessels. A variety of display options, such as surface rendering and maximum intensity projection (MIP), have different advantages and are often complementary. The time taken to produce clinically acceptable images has been markedly reduced to between 15 and 30 min. Some of the limitations are related to the length of vascular coverage, the contrast load, and the need for exact timing. On the other hand, the technique is not affected by flow artifacts. CT angiography is now a reliable and practical clinical test that may be a useful adjunct to conventional CT.

Angiography↗
PubMed1993

Binding of 5-HT1A receptor and 5-HT transporter ligands in rat cortex and hippocampus following cholinergic and serotonergic lesions.

The cellular localisation of 5-HT1A receptor and 5-HT transporter binding sites in the rat cortex and hippocampus has been examined. Lesions of either basal forebrain neurones or serotonergic neurones did not affect [3H]8-OH-DPAT binding, suggesting that 5-HT1A binding sites are not localised on cholinergic or serotonergic nerve terminals. The binding of the 5-HT transporter ligand, [3H]citalopram was unaffected by the cholinergic lesion whereas binding was reduced in both the hippocampus and cortex following serotonergic lesions. A reduction in binding site density rather than an alteration in affinity was responsible for this effect. While these data suggest that [3H]citalopram binding sites are located on serotonergic nerve terminals, the abolition of hippocampal binding sites contrasted with a 50% loss in cortical tissue.

5,7-Dihydroxytryptamine↗
PubMed1993

Efficacy of an Australian Babesia bovis vaccine strain in Malawi.

Three calves vaccinated with the Australian Ka strain of Babesia bovis were fully protected against experimental infection with an isolate from a farm on which four of 210 vaccinated cattle had died from B bovis infection. A degree of cross protection against the isolate was demonstrated in one calf which had been infected previously with Babesia bigemina.

Animals↗
PubMed1993

Extremity osteosarcoma in childhood: prognostic value of radiologic imaging.

PURPOSE: To evaluate previously described radiologic prognostic factors in extremity osteosarcoma. MATERIALS AND METHODS: In 47 pediatric patients, available images were evaluated for seven prognostic factors at diagnosis and seven additional factors after preoperative chemotherapy. These factors were correlated with histopathologic response and clinical outcome. The association of histopathologic response and outcome was also evaluated. RESULTS: Metastases at presentation and a > 20-cm-diameter soft-tissue mass were predictive of a poor outcome but occurred in few patients. Factors most predictive of < 90% tumor necrosis after chemotherapy included an increase or no change in soft-tissue mass size and increased bone destruction. Although a significant relationship (P < .05) was found between histopathologic response and outcome, no factors predictive of histopathologic response were also predictive of outcome. The accuracy of pathologic response in predicting outcome was 66%. CONCLUSION: Radiologic studies are of only limited use in predicting which patients with extremity osteosarcoma will have a poor response to chemotherapy or a poor outcome, and are not useful in predicting a good response or outcome.

Adolescent↗
PubMed1993

Use of serological response to evaluate heartwater immunization of cattle.

Frozen blood vaccine containing the Ball 3 strain of Cowdria ruminantium is prepared by an FAO/DANIDA Project in Malawi for the immunization of improved dairy cattle against heartwater. The immunogenicity of vaccine batches for cattle has been quantified and different regimens for immunization have been evaluated using indirect immunofluorescence to assess antibody responses. Infected endothelial cells grown in culture are used as antigen. The proportion of animals responding serologically has varied between different batches of vaccine tested in homogeneous cattle populations at the same time, presumably reflecting differences in immunogenicity of batches. The proportion of animals in a homogeneous population responding serologically to the same vaccine batch administered under different regimens has also varied. Indirect immunofluorescence testing has proved to be a useful method for assessing the immune response of cattle to immunization and has been adopted as a routine quality control procedure for heartwater vaccine production in Malawi.

Animals↗