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Biomedical subjects

S L MacDonald

Publications and source records attributed to S L MacDonald.

7 recordsLinked to original sources
PubMed1998

Virus removal from bioproducts using ultrafiltration membranes modified with latex particle pretreatment.

Ultrafiltration is an attractive process for virus removal from bioproducts owing to its high throughput as well as the fact that the operation is carried out under ambient conditions (damage to proteins is highly limited). The principal concern regarding the adoption of conventional ultrafiltration membranes for virus removal is the possibility of the virus passing through abnormally large pores or surface imperfections on the membrane surface. The chief principle behind the present work is to pretreat the membrane by blocking the abnormally large pores using latex particles. Experimental work was conducted to validate this pretreatment using the bacteriophage phi x 174 as a model virus. The results attained were highly encouraging. Different sizes of latex particles were tested by treating a 100 KD molecular weight cut-off membrane, and the transmission of phage (suspended in buffer) through this membrane assessed. In the absence of any particle pretreatment, a virus clearance of 4.78 log reduction value was observed for this membrane. The transmission of phage through the membrane could be reduced by an order of magnitude using 0.11 micron latex particles, or two orders of magnitude using a combination of 0.11 and 0.50 micron particles. The application of latex particles did not hinder the transport of protein through the 100 KD membrane. Protein sieving coefficients obtained using this membrane were 91%, 16% and 2%, for lysozyme, HSA and IgG, respectively.

Bacteriophage phi X 174↗
PubMed1993

Caries prevalence in xerostomic individuals.

Saliva, via its lubricating, cleansing, remineralizing, antibacterial, and buffering actions, is an important protective factor for both dentition and soft tissue. Xerostomia is commonly found in older individuals due to the use of medications or medical conditions, such as Sjögren's, which directly affect salivary gland function. A xerostomic subgroup (n = 60), mean age = 60, 66 per cent female) of the Nutrition and Oral Health Study (n = 370) was reexamined for caries. Unstimulated and two-per-cent citric-acid stimulated parotid and submandibular/sublingual salivary flow rates were determined. This group was matched for number of teeth, age, sex, and alcohol and smoking habits with a medication-free subgroup (n = 60). Active root and coronal caries were found to be significantly higher in the xerostomic subgroup than in a matched subgroup of medication-free individuals. The mean DFS for the xerostomic subgroup was 45.4 +/- 21.7 for coronal caries and 5.3 +/- 5.8 for root caries. The mean number of teeth was 21.8. The mean DFS in the medication-free subgroup was 36.5 +/- 22.1 for coronal caries and 3.2 +/- 3.2 for root caries. The mean DFS in the xerostomic subgroup for coronal and root caries was statistically significantly higher (p < 0.05). The odds ratio was 2.89 for coronal caries and 3.27 for root caries in the xerostomic versus the medication-free subgroup. Caries varied inversely with salivary flow rate. The difference in flow rates for those in the lowest and highest quartile for coronal caries experience (DFS) in the xerostomic subgroup was found to be statistically significant (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Hypotensive effects of stroma-free haemoglobin solutions attributable to adenine nucleotides.

Aqueous solutions of stroma-free human haemoglobin are being evaluated as potential oxygen-carrying resuscitation fluids. There are indications, however, that such solutions may produce toxic side-effects in vivo. Stroma-free haemoglobin solution produced a 50% fall in mean arterial pressure when infused into a small animal model despite containing very low levels of non-haem protein and phospholipid contaminants. This effect was not produced by haemoglobin solutions after extensive dialysis. Red cell-derived adenine nucleotides were found to be present in concentrations high enough to cause such a response (80-85 micrograms/ml). We have developed a chromatographic assay capable of predicting hypotension in our animal model and consider that the complete absence of adenine nucleotides must be confirmed in all studies concerning the possible toxic side-effects of stroma-free haemoglobin solutions.

Adenine Nucleotides↗
PubMed1984

Statistical clustering procedures applied to low-cost speech recognition.

A new generation of low-cost speech recognition devices are appearing, which offer much promise for useful applications in biomedical engineering. These devices are statistical pattern recognizers. Input utterances are classified by comparison with a set of templates derived during 'speaker training'. For useful application of these devices, recognition accuracy must be high and speaker training must not be unacceptably complicated or tedious. This paper investigates techniques which consider the statistical nature of the input utterances, used to improve recognition accuracy. Word classification based on the Mahalonobis distance metric, and using templates derived from cluster analysis of the training inputs, was found to give results superior to the other strategies studied. This classifier was unsuitable for implementation in a real-time, low-cost system but the principle of clustering was successfully applied to produce an adaptive system which tracked changes in the user's voice. This allowed training to be drastically simplified by updating templates during normal operation. The adaptive system achieved 98.8% recognition accuracy on a 32 word vocabulary compared to 94.8% without adaptation.

Biomedical Engineering↗