Search Results - (Author, Cooperation:E. Doherty)

2016-01-07

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

1432-0614

Springer Online Journal Archives 1860-2000

Biology

Process Engineering, Biotechnology, Nutrition Technology

Abstract  The effective diffusivity of O2 inside immobilised cell particles has been much discussed. Most reported estimates are based on fitting a mass-transfer reaction model to measured total oxygen uptake rates. The particle diameter has the largest single influence in such models, but its accurate measurement has probably received insufficient attention. We have studied sorbitol and glucose oxidation by cells of Gluconobacter suboxydans entrapped in calcium alginate gel beads. These beads were found to shrink rapidly in air, so that size measurement under water is essential. By comparison with rigid particles of similar known size, it was shown that measurement of the microscopic image gives a systematic underestimate. In consequence, the fitted oxygen diffusivity will be around 20% too low. Careful attention to size measurement gave good agreement between diffusivity estimates from beads with different mean sizes and cell loadings, with a best value of 2.51×109 m2s-1, 92% of the value for pure water. The estimated diffusivity is not significantly affected by a distribution of bead sizes with up to 10% standard deviation about the same mean.

Electronic Resource

1432-1440

Familial combined hyperlipidaemia ; Lipoproteins ; Lipoprotein lipase ; Hepatic lipase

Springer Online Journal Archives 1860-2000

Medicine

Abstract The aetiology of familial combined hyperlipidaemia remains obscure, with both genetic and environmental factors contributing to the phenotype, which is frequently associated with premature coronary heart disease. We have studied lipoprotein lipase (LPL) activity and hepatic lipase (HL) activity in patients with coronary heart disease to determine whether variation in lipase activities contributes to this phenotype. Forty-one patients (mean age 50 years; 30 male) were selected on the basis of cholesterol levels above 6.5 mmol/l and triglyceride levels above 2.2 mmol/1, with apoprotein B values over the 90th percentile. There was a family history of premature coronary heart disease in 78% and a personal history in 64%, at mean age 44, the patient group therefore predominantly corresponded to the common definition of familial combined hyperlipidaemia, appropriate in the absence of molecular markers. None of the patients was diabetic; hypertension and smoking were not over represented. Blood samples were taken following intravenous administration of heparin (100IU/kg body wt), and LPL and HL activities were measured. Mean post-heparin LPL was significantly lower in patients than controls 10 min after heparin administration (2.98 ± 1.04 and 3.86 ± 0.93 μmol ml-1 h-1, respectively, P = 0.001), and 37% patients had values below the 10th percentile of controls. Both male and female patients had significantly higher HL activities than their respective controls at 5, 10, 20 and 30 minutes postheparin. As expected, both female patients and controls had lower HL activities than males, although this sex difference did not reach statistical significance in the patient group. Mean lipid and lipoprotein results were: cholesterol 8.2 mmol/1; triglycerides 4.2 mmol/l; high-density lipoprotein cholesterol 0.90 mmol/1; apoprotein Al 122 mg/dl; apoprotein B 171 mg/dl; lipoprotein (a) 23 mg/dl (median 10 mg/dl). High-density lipoprotein cholesterol and triglycerides were negatively correlated (r = -0.26, P = 0.05). HL was significantly related to body mass index at all time points whereas the negative correlation between post-heparin LPL and body mass index was significant only 30 min after heparin administration. Post-heparin LPL was only weakly correlated with triglycerides 10 and 20 min after heparin administration. These lipid and lipoprotein results are clearly potentially atherogenic as indicated by the extent of premature coronary heart disease in the group described. A decrease in LPL activity may contribute to this pattern.

Electronic Resource