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Biomedical subjects

M A Lawrence

Publications and source records attributed to M A Lawrence.

12 recordsLinked to original sources
PubMed2001

The use of sediment analogues to study the uptake of pollutants by chironomid larvae.

A technique is described that uses artificial resin beads with known surface properties to investigate the factors influencing the bioaccumulation of pollutants from sediments. One advantage of this technique is that it provides a standard procedure against which it is possible to calibrate natural sediments with their diverse properties. The method has been used on third instar larvae of the midge Chironomus riparius and the results are compared with previous studies on the worm Lumbriculus variegatus. The use of a standard test using resin beads as a substitute for natural sediment allows comparisons to be made between species and substrates. Thus, the bioaccumulation factors for the midge larvae are much smaller than those of the worm and this correlates with the ability of the insect larva to detoxify many pollutants. It is also possible to use the test to identify if ingestion of the sediment increases the bioaccumulation of contaminants and whether this involves the release of pollutants by digestive processes or not.

Animals↗
PubMed2000

Can adsorption isotherms predict sediment bioavailability?

The adsorption and desorption of 2,4-dichlorophenol (DCP) and pentachlorophenol (PCP) were studied for a range of synthetic particles, a dimethylditallowammonium exchanged clay and a natural sediment. The synthetic particles were Dowex 1X8400, Toyopearl Phenyl 650M and Toyopearl SP 650M. The bioaccumulation of the DCP and PCP from these particles was then studied using the oligochaete, Lumbriculus variegatus. There is a correlation between contaminant-particle interactions, as determined from adsorption and desorption isotherms, and bioaccumulation. Bioaccumulation by L. variegatus was found to be highest from the systems where differences in the classification of adsorption and desorption isotherms were observed.

Adsorption↗
PubMed2000

Tube gastrostomy after radical cystectomy and urinary diversion: surgical technique and experience in 709 patients.

We describe our surgical technique of tube gastrostomy and report our experience with 709 patients who underwent cystectomy and urinary diversion with gastrostomy tube placement from January 1988 to December 1997. This modified Stamm technique provides an effective means of gastric decompression without the discomfort associated with nasogastric decompression, is associated with a low complication rate (0.05%), and may be considered as the procedure of choice when gastric drainage is required after radical cystectomy and lower urinary tract reconstruction.

Cystectomy↗
PubMed1994

Iododoxorubicin in advanced breast cancer: a phase II evaluation of clinical activity, pharmacology and quality of life.

Iododoxorubicin 80 mg m-2 i.v. was given 3 weekly for a maximum of six cycles as first-line chemotherapy to 14 evaluable women with metastatic breast cancer. The response rate was 14% (95% confidence intervals 4-40%); median time to progression was 3.5 months (range 0.7 to > 9.3) and median survival was 10.2 months (range 2.3 to > 20.4). Neutropenia was the main toxicity but was not associated with severe sepsis. Two patients had a significant (> 10%) but asymptomatic fall in cardiac ejection fraction; other toxicities were mild. Plasma pharmacokinetics was studied during the first cycle of treatment. Iododoxorubicin was extensively metabolised to iododoxorubicinol. Neutropenia and thrombocytopenia were both significantly correlated with the area under the concentration-time curve (AUC) for iododoxorubicin and the total AUC for iododoxorubicin and iododoxorubicinol. Quality of life (QOL), evaluated by self-report questionnaire and interview, showed little evidence of benefit in terms of physical symptom relief, level of activity, psychological symptoms or global evaluation of QOL during treatment. Iododoxorubicin is subjectively less toxic than standard anthracyclines, but at the dose and schedule used has limited activity in metastatic breast cancer, possibly because iododoxorubicinol is not clinically active.

Adult↗
PubMed1989

Local excision for selected colorectal carcinomas.

In summary, local excision is a useful tool in the management of selected colorectal carcinomas. The advent of the fibreoptic colonoscope has revised the concept of local excision when dealing with carcinoma-containing polyps of the colon. The clinician now has the means of locally excising certain carcinomas which would have required laparotomy in the not so distant past. In dealing with carcinoma of the rectum, local excision is not advocated for all rectal carcinomas. In fact, when the previously discussed tumour related factors are considered, local excision should be the ultimate procedure in less than 5% of operations performed for rectal carcinomas. However, when appropriately used, local excision provides a less morbid alternative to more radical procedures without compromising patient survival rates or local recurrence rates.

Colorectal Neoplasms↗
PubMed1989

Lower gastrointestinal bleeding. A systematic approach to classification and management.

Early classification of lower gastrointestinal bleeding as occult, minor overt, or major overt allows a practical approach to evaluation and management. Localization of the bleeding site is the next step. In occult and minor overt bleeding, the cause can usually be determined from results of conventional diagnostic tests; however, angiography and even intraoperative endoscopy may be necessary in some particularly difficult cases. In contrast, major overt bleeding may only allow time for angiographic localization before surgery. Using this approach, the primary care physician can successfully manage most patients with lower gastrointestinal bleeding.

Gastrointestinal Hemorrhage↗
PubMed1988

Reference concentrations of serum selenium and manganese in healthy nulliparas.

Reference serum selenium and manganese concentrations were established for healthy nulliparas aged 18-23 years resident in Cape Town. Measurements were determined for selenium in 100 female students who had been taking low-dosage triphasic contraceptive medication for a minimum of 3 months and in 100 female students who were not on contraceptive therapy. Manganese concentrations were determined for 25 female students from each group. The mean serum selenium concentrations were 0.988 +/- 0.189 micrograms/l (78 +/- 15 micrograms/dl) and 0.925 +/- 0.177 mumol/l (73 +/- 14 micrograms/l) respectively for females taking and not taking oral contraceptives. The corresponding concentrations for manganese were 21.84 +/- 9.82 nmol/l (1.20 +/- 0.54 micrograms/l) and 21.66 +/- 7.64 nmol/l (1.19 +/- 0.42 micrograms/l) respectively. The differences in selenium were statistically significant (P = 0.0231) but not for manganese (P = 0.910).

Adolescent↗
PubMed1987

Reference values for serum copper, ceruloplasmin and zinc and haematological indices for healthy nulliparous females.

Reference serum copper, ceruloplasmin and zinc values were established for 100 healthy white nulliparous students aged 18-23 years resident in Cape Town who had been taking low-dosage triphasic contraceptives for a minimum period of 3 months, and in 100 female students not taking contraceptives. The mean serum copper values were 26.5 +/- 4.2 mumol/l and 16.9 +/- 2.7 mumol/l for those taking and not taking oral contraceptives respectively; corresponding values for ceruloplasmin were 181 +/- 43.9 IU/ml and 110 +/- 22.7 IU/ml respectively. Both differences were statistically significant. Serum zinc values for those on contraceptives were 14.1 +/- 2.1 mumol/l and for the others 14.7 +/- 2.0 mumol/l. There were no differences in the haematological parameters except for a significantly higher mean corpuscular volume in females taking oral contraceptives. Of possible clinical significance in this student population are prevalence rates of 2.2% for anaemia (haemoglobin value less than 11.5 g/dl), 7% for iron deficiency (serum ferritin less than 12 micrograms/l) and 6.6% for iron depletion (serum ferritin 12-20 micrograms/l).

Adult↗