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Biomedical subjects

D F Lewis

Publications and source records attributed to D F Lewis.

167 records · Page 10Linked to original sources
PubMedDate not supplied

Neonatal outcome when delivery follows a borderline immature lecithin to sphingomyelin ratio.

OBJECTIVE: Occasionally, clinicians are presented with a complicated preterm pregnancy where fetal pulmonary maturity testing might be used to help guide management decisions. However, should delivery be allowed if the lecithin to sphingomyelin ratio (L/S ratio) is not quite mature? The incidence of newborn complications after delivery with L/S ratio values of 1.8 and 1.9 is unknown. The purpose of this study was to evaluate the neonatal morbidity and mortality in patients that delivered with these borderline immature results. STUDY DESIGN: All patients who underwent fetal pulmonary maturity testing were prospectively recorded in log books. An L/S ratio of > or = 2.0 was considered mature. Patients with an L/S ratio of 1.8 or 1.9 were considered "borderline immature." These borderline immature cases were evaluated for the gestational age at amniocentesis, the gestational age at delivery, and neonatal outcome. RESULTS: During the 9-year study period, L/S ratio testing was performed on 2038 patients. Of these, 162 preterm patients (7.9%) had an L/S ratio of 1.8 or 1.9 A total of 63 of these 162 patients delivered < 72 hours after the amniocentesis and met study criteria. The pregnancies ranged from 27 to 36 weeks' gestation. There was a 13% incidence (95% confidence interval (CI) of 4% to 30%) of major neonatal morbidity and a 3% incidence (95% CI of 0% to 17%) of neonatal mortality in the 30 pregnancies with an L/S ratio of 1.8. The incidence of major neonatal morbidity was only 3% (95% CI of 0% to 15%) in the 33 patients with an L/S ratio of 1.9, with no cases of mortality (95% CI of 0% to 9%). CONCLUSION: Based on 95% CIs, the data of this study reveal that the maximum risk for major morbidity is < or = 15%, with a mortality risk of < 10% in a preterm newborn delivered with a 1.9 L/S ratio value. The maximum risk is 30% for major morbidity and 17% for mortality in preterm newborns delivered with a 1.8 L/S ratio. This information may help in the decision-making process of whether to deliver or to observe when faced with a borderline immature L/S ratio result in a complicated preterm pregnancy.

Amniocentesis↗
PubMedDate not supplied

Studies on a toxic metabolite from the mould Wallemia.

While monitoring the occurrence of toxigenic moulds in foods, using a bioassay screen, it was shown that an isolate of Wallemia sebi produced toxic effects in several of the bioassays. The toxic metabolite was isolated and purified using solvent extraction, TLC and HPLC coupled with the brine shrimp assay to monitor the toxic fractions. The purified toxin, which we propose to call walleminol A, has been partially characterized by mass spectroscopy, nuclear magnetic resonance, ultraviolet and infrared spectroscopy. It can be provisionally interpreted as a tricyclic dihydroxy compound, C15H24O2, with structural features characteristic of a sesquiterpene with an isolated double bond, but further work is required to characterize this compound unequivocally. The minimum inhibitory dose of walleminol A in the bioassays is approximately 50 micrograms/ml, which is comparable with a number of mycotoxins such as citrinin and penicillic acid.

Animals↗
PubMedDate not supplied

Safety aspects of food preservatives.

The use of food preservatives, such as benzoic acid, nitrites, and sulphites, as antimicrobials, and butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), ascorbic acid and tocopherols, as antioxidants, has probably changed food production patterns and eating habits more than has the use of any other class of food additive. These food preservative chemicals confer substantial benefits on man, not only by the preservation and increased palatability of food, but also by affording protection against the pathological effects of reactive oxygen species (ROS) which are associated with cancer, cardiovascular disease and aging. Nevertheless, although most preservatives are now considered to be without potential adverse effects and are classified as GRAS, there have been problems concerning the safety of some of these chemicals, including the possibility of allergies from benzoic acid and sulphites, the formation of carcinogenic nitrosamines from nitrites, and the possible rodent carcinogenicity of BHA and BHT. The mechanisms of this toxicity at high dosage, the roles of the cytochromes P450, and the generation and scavenging of ROS in the toxicity of these chemicals, are reviewed and discussed.

Animals↗
PubMedDate not supplied

Quantitative structure-activity relationships and COMPACT analysis of a series of food mutagens.

Quantitative structure-activity relationships between chemical structure and Ames mutagenicity for a group of 24 food mutagens, including 17 cooked-food heterocyclic amines, have been determined. For the TA98 strain of Salmonella typhimurium (frameshift mutagens) the best correlation of mutagenicity is with molecular diameter (R = 0.91), while for the TA100 strain (base-pair mutations) the best correlation is with delta E, the energy difference between the lowest unoccupied and highest occupied molecular orbitals. High mutagenicity is related to high values of molecular diameter, hence to planarity and to high values of the COMPACT ratio ([area/depth2]/delta E). High mutagenicity is also related to low values of delta E. Consequently, highly mutagenic and potentially carcinogenic food chemicals can readily be identified as substrates of cytochrome P4501 (CYP1) and may therefore be detected by the COMPACT procedure. Highly mutagenic compounds also exhibit high values of dipole moment.

Carcinogens↗