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Biomedical subjects

S P Wolfe

Publications and source records attributed to S P Wolfe.

7 recordsLinked to original sources
PubMed2001

Effect of flow configuration and membrane characteristics on membrane fouling in a novel multicoaxial hollow-fiber bioartificial liver.

A novel "multicoaxial hollow fiber bioreactor" has been developed consisting of four concentric tubes, the two innermost tubes are called hollow fibers. Bioartificial livers are created by culturing liver progenitors in the space between the two innermost hollow fibers and with culture media contained in the two compartments (intracapillary and extracapillary) sandwiching the cell compartment. The outermost compartment is used for gas exchange. A hydrodynamic model has recently been established to predict the optimum hydraulic permeability and bioreactor operational parameters to create the physicochemical environment found in the liver acinus. However, perfusion with serum-free hormonally-defined media and inoculation of cells introduces membrane fouling into the equation, and this parameter must be incorporated into the model. Using commercially available semipermeable hollow fibers (1 mm [0.65 microm pores] and 3 mm [0.1 microm pores] outer diameters [o.d]), the primary cause of resistance is the middle hollow fiber. Preliminary studies using bioreactors inoculated with isolated rat hepatocytes and perfused with serum-containing culture media demonstrated that the middle hollow fiber is the primary site of fouling, and this fouling ultimately causes cell mortality by blocking the transfer of nutrients. Experiments were performed to determine the best commercially available middle hollow fiber for construction of bioreactors and two 3-mm outer-diameter middle hollow fibers were compared: polypropylene and polysulfone, with 0.2 microm and 0.1 microm pore sizes, respectively. Dead-ended and cross flow configurations were compared for their effectiveness at reducing membrane fouling in the middle hollow fiber by determining the change in resistance with time. The results demonstrate that the 0.2-microm pore size polypropylene hollow fiber is the best choice for construction of the multicoaxial hollow-fiber bioreactor, and that cross flow results in two orders of magnitude lower resistance than dead-ended flow after 36 h.

Animals↗
PubMed1995

'Prevention programmes'--a dietetic minefield.

Food allergy and intolerance (FAI) is undoubtedly a controversial subject surrounded by a great deal of publicity. One of the most confusing issues arises when considering the value of allergy prevention programmes. Although prevention strategies have now been extensively studied the results are still inconclusive. In childhood, atopic disorders eg asthma, eczema, dermatitis, urticaria, rhinitis and gastrointestinal related symptoms are relatively common with estimates of their prevalence ranging from two to 20 per cent (Mallet & Henocq, 1992). In addition, the proportion of young children with allergies seems to be increasing, although the extent to which food allergens contribute remains unclear (Hide, 1991; Croner, 1992; DoH, 1994). In many of these cases, prevention of unpleasant, socially and psychologically disruptive and sometimes life threatening symptoms can be achieved by dietary modification. If atopic and gastrointestinal symptoms can be prevented growth failure may not be a problem, children may miss less schooling, and if long term prevention is achieved there may be a substantial reduction in the cost of medical care these children would otherwise require. Before prevention programmes are introduced, however, careful thought should be given to the implications of dietary treatment. The programmes are difficult to administrate in terms of both resources and expense. Specifically, from a nutritional point of view, the diets employed are often socially disruptive which inevitably leads to problems with compliance. Nutritional adequacy may also be difficult to achieve unless there is close supervision by a dietitian who is experienced in the management of the complex dietary manipulations involved. Unfortunately the dietetic resources essential for the safety of the programmes may be lacking in many hospitals. Preventive practice may be aimed at either the general population or at specially identified group who are considered to be at a greater risk of developing atopic disorders. Dietary intervention studies looking at prevention in this 'at risk' group have considered maternal dietary modification during pregnancy and lactation, the use of soya and hydrolysed protein feeds and the weaning diet. The nutritional consequences of these methods of dietary manipulation will be discussed in more detail.

Breast Feeding↗
PubMed1993

A double blind lipase for lipase comparison of a high lipase and standard pancreatic enzyme preparation in cystic fibrosis.

A standard acid resistant microsphere pancreatic enzyme preparation was compared with identical capsules half filled with mini-tablets of a new high lipase preparation in a randomised double blind crossover study in children with cystic fibrosis. Each patient received his/her usual number of capsules and the same dose of lipase during each period of the study. Eighteen patients completed the study. There were fewer gastrointestinal symptoms when pancreatic enzyme was supplied as the high lipase preparation. There was also a significant improvement in fat absorption (17%, 95% confidence interval (CI) 6 to 27), reduction in faecal fat output (15.8 g/day, 95% CI 6.4 to 22.5), and faecal energy loss (789 kJ/day, 95% CI 211 to 1384). It is concluded that half filled capsules of the new high lipase preparation are more effective than the standard preparation and it is likely that filled capsules would allow patients to use fewer than half the number of pancreatic enzyme capsules.

Adolescent↗
PubMed1993

Resting energy expenditure and substrate oxidation rates in cystic fibrosis.

The resting energy expenditure (REE) and substrate oxidation rates in 16 patients with cystic fibrosis who had mild chest disease and 11 healthy controls were measured using indirect calorimetry. The mean REE (% predicted) in the patients with cystic fibrosis was 11% greater than in the controls. Five patients with cystic fibrosis were hypermetabolic but only one of these had a clinically significant reduction of respiratory function. A greater proportion of REE was derived from carbohydrate oxidation in the cystic fibrosis patients (43.5% v 29.9%). However, the 24 hour dietary intake of carbohydrate was greater in the cystic fibrosis group (49.6 v 45.8% of energy intake). These data suggest that a high dietary intake of carbohydrate may contribute to the increased oxidation of carbohydrate in these cystic fibrosis patients. All patients with cystic fibrosis, including those with apparently mild lung disease, should continue to receive a high energy diet.

Adolescent↗
PubMedDate not supplied

Control of malabsorption in cystic fibrosis.

Intestinal malabsorption is severe and of early onset in virtually all people who have cystic fibrosis. The main cause is deficiency of pancreatic enzymes, but bicarbonate deficiency, abnormalities of bile salts, mucosal transport and motility, and anatomical structural changes are other contributory factors. Appropriate pancreatic replacement therapy will achieve normal or near normal absorption in many patients. It is important to identify both malabsorption and evidence of a pancreatic lesion in all patients who are to receive pancreatic enzymes. All who have evidence of fat malabsorption are deemed pancreatic insufficient and candidates for enzyme replacement therapy. Effective treatment should allow a normal diet to be taken, control symptoms, correct malabsorption and achieve a normal nutritional state and growth. The occurrence of fibrosing colonopathy in some patients receiving very high doses of those enzymes that have the copolymer Eudragit L30 D55 in their covering has resulted in guidelines in the UK to avoid dosages greater than the equivalent of 10,000 IU lipase/kg/day for all patients and also to avoid preparations containing this copolymer in children and adolescents. For patients not responding to 10,000 IU lipase/kg/day, review of adherence to treatment, change of enzyme preparation, variation of the time of administration and reduction in gastric acid may improve absorption. The importance of excluding other gastrointestinal disorders as a cause of the patient's symptoms and the need for early investigations, rather than merely increasing the dosage of enzymes, is stressed. With modern enzymes, adequate control of gastrointestinal symptoms and absorption can be achieved at dosages of 10,000 IU lipase/kg/day or only slightly more, and a normal nutritional state and growth rate maintained in most patients with cystic fibrosis.

Child↗