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Biomedical subjects

G Lamont

Publications and source records attributed to G Lamont.

18 recordsLinked to original sources

Guidelines for the diagnosis and management of hereditary spherocytosis.

Hereditary spherocytosis (HS) is a heterogeneous group of disorders with regard to clinical severity, protein defects and mode of inheritance. It is relatively common in Caucasian populations; most affected individuals have mild or only moderate haemolysis. There is usually a family history, and a typical clinical and laboratory picture so that the diagnosis is often easily made without additional laboratory tests. Atypical cases may require measurement of erythrocyte membrane proteins to clarify the nature of the membrane disorder and in the absence of a family history, occasionally molecular genetic analysis will help to determine whether inheritance is recessive or non-dominant. It is particularly important to rule out stomatocytosis where splenectomy is contraindicated because of the thrombotic risk. Mild HS can be managed without folate supplements and does not require splenectomy. Moderately and severely affected individuals are likely to benefit from splenectomy, which should be performed after the age of 6 years and with appropriate counselling about the infection risk. In all cases careful dialogue between doctor, patient and the family is essential. Laparoscopic surgery, when performed by experienced surgeons, can result in a shorter hospital stay and less pain.

Folic Acid↗

Peri-operative blood lactate concentrations in pre-term babies with necrotising enterocolitis.

AIM: Hyperlactaemia has been shown to predict mortality in preterm babies undergoing intensive care. The value of such measurement has not been evaluated in babies undergoing laparotomy for necrotising enterocolitis (NEC). The aim of this study was to determine whether peri-operative blood lactate measurements (L) can be used to predict outcome in preterm babies with necrotising enterocolitis. METHODS: Clinical and laboratory data in 24 babies who underwent laparotomy for NEC over 3 years were collected. The data were analysed to correlate blood lactate level with the clinical outcome. RESULTS: There were no statistically significant differences between babies who died and those who survived in terms of gestation, birth weight, condition at birth, etc. There was no difference in pre-operative acid-base status parameters between the groups. Median (range) of pre- and post-operative blood lactate measurements (L) are shown: Pre-op Lactate: 0.9 (0.3 to 2.4) n = 15 (Survivors); 2.7 (0.5 to 10.9) n = 5, p = 0.05 (Non-survivors). Post-op Lactate: 1.2 (0.5 to 6) n = 19 (Survivors); 4.7 (0.2 to 19.5) n = 5, p = 0.06 (Non-survivors). Babies with pre-operative hyperlactaemia ([L] > 1.6 mmol/L) were more likely to die. (Odd's Ratio 22, Confidence Interval 1.54 to 314.3, p = 0.04). Pre-operative L was not higher in babies who subsequently had bowel resection compared to those who had no bowel resection ([L] = 0.88 mmol/L [0.3 to 10.9] vs. 1.6 mmol/L [0.6 to 2.7], [p = 0.2]). Post-operative L was generally higher than pre-operative L but was a less useful predictor of death. CONCLUSION: This study suggests that elevation of L in the pre-operative period carries a poor prognosis in babies with NEC. As L was not significantly different between babies who had necrotic bowel and those who had a healthy bowel, we postulate that it reflects inadequate global tissue oxygen delivery rather than local disease process. Pre-operative optimisation of oxygen delivery has been shown to reduce mortality in high-risk adult surgical patients. Babies with NEC may also benefit from further peri-operative resuscitation.

Enterocolitis, Necrotizing↗

Prolonged monitoring of the upper gastrointestinal tract using echo planar magnetic resonance imaging.

Upper gastrointestinal motility and transit has been studied in five human volunteers with the ultra high speed, magnetic resonance imaging (MRI) technique MBEST (Modulus Blipped Echo-planar Single pulse Technique), a variant of echo planar imaging. Snapshot images requiring a data acquisition time of only 64-128 msec allowed visualisation of peristalsis in the antrum and duodenum in real time, without motional image degradation, as would normally be seen using conventional MRI. Gastroduodenal flow of the luminal contents was visualised using water as a contrast medium, with appropriate adjustment of the time constant (T2) weighting of the system. Rapid (0.3 Hz) imaging of gastroduodenal motility in both transverse and coronal planes was achieved by respiratory gating to the imaging frequency, allowing repetition rates of up to 20 frames per minute for 2-3 hours. Fast replay of stored images, to produce a 'movie loop', allowed identification of fasting motility patterns of the gastric antrum and proximal small intestine, with depiction of the phases of the migrating motor complex. Images of the fed patterns after the ingestion of a test meal showed good separation of solid and liquid particulate matter and mixing waves in the gastric body. The potential for quantitative measurements with this new imaging modality of the gastrointestinal tract is under development, which will allow us to measure transit and correlate this with motility data.

Adult↗

Long-term results of the Belsey Mark IV antireflux operation in relation to the severity of esophagitis.

A retrospective analysis of the results of the Belsey Mark IV operation has been conducted, relating these to the degree of esophagitis present preoperatively. Analysis of 89 patients showed a 91.7% success rate in patients without esophagitis. Good results diminished steadily as the severity of esophagitis increased, giving 76.5%, 75%, 66.7%, and 50% success rates for first-, second-, third-, and fourth-degree esophagitis, respectively. We believe that shortening of the esophagus is an important factor in this. Shortening is obvious in third- and fourth-degree esophagitis but subtle in first- and second-degree esophagitis. We conclude that the Belsey operation is adequate for patients without esophagitis, but for patients with any degree of esophagitis more effective reflux control is needed.

Adult↗

Gastrointestinal tract: dynamic MR studies with echo-planar imaging.

Gastrointestinal (GI) tract motility was depicted in four human volunteers with the high-speed echo-planar imaging technique: modulus blipped echo-planar single-pulse technique (MBEST). Data acquisition times of 64 and 128 msec obviate image degradation due to motion without the need for gut paralysis and allow imaging of the GI tract in real time. Peristaltic patterns of the gastric antrum and proximal small intestine were depicted for fasting and fed subjects and subjects in whom peristalsis had been pharmacologically stimulated. The potential for quantitative measurements of GI tract motion with this new technique was demonstrated.

Adult↗

Effect of cimetidine on prognosis after simple closure of perforated duodenal ulcer.

A prospective controlled study in 60 patients undergoing simple closure of perforated duodenal ulcer demonstrated a significant (P less than 0.05) benefit following postoperative cimetidine treatment, in terms of avoiding subsequent dyspeptic symptoms and complications of peptic ulcer disease. Thus cimetidine is recommended in the follow-up management of perforated duodenal ulcers.

Aged↗

Decreased membrane deformability in Melanesian ovalocytes from Papua New Guinea.

We examined the ability of Melanesian ovalocytes from Papua New Guinea to be deformed in order to probe the resistance of these cells to invasion by several species of malaria parasite. We found ovalocytes were refractile to drug-induced endocytosis, that they formed abnormal rouleaux, showed reduced deformability when aspirated into 0.6-micron diameter pores in polycarbonate sieves, and failed to crenate when mounted under a glass coverslip. No substantial differences were found between normocytes and ovalocytes in their initial rate of filtration through 4.5-micron pore polycarbonate sieves, their membrane fluidity as measured by the rate of depolarization of fluorescent probes or the rate of extraction of cytoskeletal proteins in low ionic strength buffers. We conclude that the resistance of ovalocytes to undergo localized deformation might be significant in explaining the resistance of these cells to invasion by malarial merozoites.

Chlorpromazine↗

Resistance of Melanesian elliptocytes (ovalocytes) to invasion by Plasmodium knowlesi and Plasmodium falciparum malaria parasites in vitro.

Erythrocytes from humans with Melanesian elliptocytosis are resistant to invasion by Plasmodium falciparum in vitro and epidemiological evidence suggests they may be resistant to P. vivax and P. malariae. We have examined the ability of P. knowlesi merozoites to invade Melanesian elliptocytes in vitro as a definitive means of examining these cells for resistance to invasion by malarial species with different receptor requirements. The Melanesian elliptocytes were highly resistant to invasion by P. knowlesi merozoites showing that the resistance associated with this erythrocyte variant lies at a level common to the invasion pathway(s) of P. falciparum and P. knowlesi. This makes Melanesian elliptocytosis unique as no other human erythrocyte variant has been shown to be resistant to invasion by both species.

Elliptocytosis, Hereditary↗

Comparison of in vitro pyrimethamine assays and in vivo response to sulphadoxine-pyrimethamine in Plasmodium falciparum from Papua New Guinea.

The in vitro pyrimethamine sensitivity of 20 Plasmodium falciparum isolates from Papua New Guinea children was determined. The children were treated with sulphadoxine-pyrimethamine and six were found to have clinically resistant malaria. The P. falciparum isolated from these subjects were more resistant to pyrimethamine in vitro than 13 of the isolates from sensitive cases. These results suggest that pyrimethamine sensitivity alone may be a good indicator of in vitro response to sulphadoxine-pyrimethamine.

Child↗

Ovalocytic erythrocytes from Melanesians are resistant to invasion by malaria parasites in culture.

Ovalocytic erythrocytes from Melanesians in Papua New Guinea have been demonstrated to be resistant to infection by malaria parasites (Plasmodium falciparum) in culture by using a double-label fluorescence assay of merozoite invasion. That merozoites do not bind irreversibly to ovalocytes has been demonstrated by an assay that measures competition between ovalocytes and normocytes. Analysis of behavior on thermal deformation has demonstrated that ovalocytes are more more thermostable than normocytes, suggesting that there is a major difference in cytoskeletal structure. These findings with P. falciparum and epidemiological data demonstrating clinical resistance to P. vivax and P. malariae suggest that the membrane alterations(s) in these ovalocytes affect(s) invasion step(s) common to all three species of malaria parasite.

Animals↗

Plasmodium falciparum strains from Papua New Guinea: culture characteristics and drug sensitivity.

Seven strains of Plasmodium falciparum from Papua New Guinea have been established in continuous in vitro culture. Samples with a high initial parasitaemia were more likely to form continuous lines, possibly due to the time required for transport of infected blood samples from Papua New Guinea to laboratories in Australia. Most but not all established lines were resistant to chloroquine and all were resistant to pyrimethamine, possibly reflecting the parasite strain characteristics in that region.

Adolescent↗

A simple method for ECG and VCG assessment of the severity of pulmonary valve stenosis.

In patients with isolated pulmonary valve stenosis, the right ventricular (RV) hypertrophy is related to the hemodynamic severity of their lesions. We estimated the peak RV pressure noninvasively in 112 patients with isolated pulmonary valve stenosis by a Frank lead vectorcardiogram (VCG), an orthogonal electrocardiogram (ECG), and a standard scalar ECG. In 78 randomly assigned patients, 10 ECG measurements and 13 VCG measurements were correlated with the peak RV pressure at cardiac catheterization; the best multiple linear regression equation used the R wave in standard lead 1 (ECG), maximal rightward voltage in the terminal part of the frontal vector loop (VCG), and the Q wave in the orthogonal Z lead, giving R = 0.66 (SEM 25). The equation was validated in the other 34 patients; correlation of estimated with actual peak RV pressure was r = 0.64. A nomogram for clinical use was devised from this regression equation.

Adolescent↗