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Michael J Lewis

Publications and source records attributed to Michael J Lewis.

24 records · Page 2Linked to original sources

Variations of lactoperoxidase activity and thiocyanate content in cows' and goats' milk throughout lactation.

Lactoperoxidase activity and thiocyanate content were monitored in the milks of seven individual cows and six goats during lactation. Lactoperoxidase activity exhibited a cyclic pattern with alternating peaks and troughs throughout lactation. Extremely large variations were observed between and within animals. For example, lactoperoxidase activity ranged from 0.05-5.60 U/ml for one cow on different sampling days. Variations between cows were also large, ranging from 0.98-5.1 U/ml on a specific sampling day. Mean lactoperoxidase activity in cows ranged from 1.5-2.7 U/ml with an overall mean of 2.3 +/- 1.0 U/ml while the thiocyanate concentration ranged from 6.0-10.2 micrograms/ml with an overall average of 8.5 +/- 5.1 micrograms/ml. Lactoperoxidase activity means for goats ranged from 0.04-0.16 U/ml with a grand mean of 0.1 +/- 0.06 U/ml while the thiocyanate content means ranged from 6.6-8.2 micrograms/ml with a grand mean of 7.0 +/- 2.59 micrograms/ml. There was no correlation between lactoperoxidase activity and thiocyanate content in either cows' (R2 = 0.011) or goats' (R2 = 0.015) milk. These experiments have revealed that lactoperoxidase activity is affected by many factors including the individual animals, species, feed and stage of lactation. Therefore the exogenous supply of thiocyanate and hydrogen peroxide needed to activate the lactoperoxidase system for raw milk preservation will vary in quantity depending on these factors.

Animals↗

Effect of hydrodynamic and physicochemical changes on critical flux of milk protein suspensions.

The critical flux during ultrafiltration of whey protein concentrate and sodium caseinate suspensions was investigated. The weak form of critical flux was found for both suspensions. Critical flux of sodium caseinate was higher than that of whey protein concentrate. This could be due to the differences in particle size of the suspensions, resulting in a slower particle back transportation for small particles (whey proteins) compared to the larger casein micelles. Critical flux increased as crossflow velocity increased and decreased as concentration increased, suggesting that critical flux was determined by competition between rate of particle removal from the membrane surface and rate of particle movement towards the membrane surface. Influence of changing pH, addition of NaCl and CaCl2 on the critical fluxes of both protein suspensions was also studied. Increasing pH led to an increase in critical flux for both protein suspensions, suggesting that electrostatic repulsive forces are involved in determining critical flux in both cases. Addition of NaCl gave rise to a decrease in electrostatic interactions due to an increase in ionic strength and zeta potential, and resulted in a decrease in critical flux for sodium caseinate, but had no significant effect for whey protein concentrate. Addition of CaCl2 resulted in a decrease in the critical flux and had a more pronounced influence than NaCl. These results suggest that, in addition to electrostatic repulsive forces, other factors such as structure of protein may be involved in determining the critical flux.

Animals↗

A new yeast endosomal SNARE related to mammalian syntaxin 8.

We report the identification of a yeast SNARE that has escaped notice because of an apparent error in the genome sequence and because it is functionally redundant. It is encoded by an extended version of ORF YAL014c, and since its SNARE motif is related to mammalian syntaxin 8 we term the gene SYN8. Syn8p is in endosomes. Co-precipitation indicates a set of complexes containing Pep12p, Vti1p, either Syn8p or Tlg1p and either Snc1p or Ykt6p. Analysis of growth and trafficking defects demonstrates that in the absence of Tlg1p, Syn8p is required for Pep12p function. Conversely, when Tlg1p is present, Syn8p can be removed without loss of Pep12p function, or induction of any other obvious trafficking defect. Syn8p thus appears to be a functional homolog of mammalian syntaxin 8, but Tlg1p can, amongst other roles, provide an equivalent function.

Amino Acid Motifs↗

Ongoing faculty evaluations: developmental gain or just more pain?

PURPOSE: We continue to increase the amount of evaluations to improve the outcomes of our residency programs. Although ongoing faculty evaluations clearly are an important part of faculty development, their value in terms of improving the program needs to be evaluated. The questions asked were as follows: (1) Do faculty evaluations continue to improve the faculty over the course of successive evaluation periods? (2) Are there groups of faculty who would benefit the most from faculty evaluation feedback? (3) Are there any specific objective categories within the evaluation that carry more value and may help to shorten this form? METHODS: Forty-two faculty members were evaluated by 40 surgical residents with an assessment form developed by surgical residents that assessed faculty members by 10 different criteria. The initial set of data was collected, and attending surgeons were given an intervention in the form of a letter detailing how they had been assessed in each of the 10 categories. The attending surgeons were evaluated again 6 months later and were given an intervention in the form of verbal feedback regarding their evaluations. The attending faculty members were then assessed 1 year after that. One way analyses of variance and Fisher Protected Least Significant Difference (PLSD) were used to analyze the resulting data to determine if there were significant differences in the faculty evaluations. A part-whole correlation was performed that correlated the 10 evaluation criteria against the mean score on each evaluation, and partial eta-squared analysis was used to determine which criterion had the largest effect on the overall means. RESULTS: The means for the 42 faculty members as a whole continued to improve from the first to the final evaluation period, with 30 faculty members increasing their mean score (18 significantly) and 12 decreasing their mean score (4 significantly). Seven of the 10 evaluation criteria's means improved sequentially by feedback session. These were (1) Didactic Teaching, (2) Teaching Rounds, (3) Attendance at Didactic Activities, (4) Allows [Resident] Autonomy to Make Independent Decisions, (5) Provides Feedback, (6) Stimulates Critical Thinking with Use of Literature, and (7) Encourages and Maintains an Atmosphere of Professional Mutual Respect for All Members of Health Care Team (Role Model). The faculty group with the lowest evaluations improved significantly more than those of both the middle and the role model group, with the middle and the role model groups improving, but not significantly differently from each other. Of the criteria that improved, only Provides Feedback improved significantly from the first to second and the second to third evaluation periods. The three criteria with the highest correlation coefficients were Role Model (0.76), Provides Feedback (0.75), and Stimulates Critical Thinking (0.74). The results from the partial eta-squared test showed that the criterion with the largest effect size was Provides Feedback (0.28). These analyses indicate that the criterion Provides Feedback was both highly correlated with the average score on a faculty member's evaluation and was more responsible than any other criteria for the overall improvement in the mean evaluation score of the faculty members. CONCLUSIONS: (1) Ongoing faculty evaluations indeed are a powerful tool to improve the faculty as a whole. (2) The faculty members with the lowest evaluations showed the largest amount of improvement. (3) Providing feedback to the residents seems to be the most valued factor by the residents for faculty evaluations and perhaps could become the basis of the evaluation for the most accomplished faculty.

Faculty, Medical↗

Heart rate variability analysis: a tool to assess cardiac autonomic function.

Heart rate monitoring is commonly used to provide an acute indicator of an individual's cardiovascular status and responsiveness. An increasingly popular technique involves quantifying the very small amounts by which the heart rate changes from one cardiac cycle to the next. This "heart rate variability (HRV) analysis" provides a substantial amount of additional information about the cardiovascular system and enables quantification of cardiac regulatory influences on the autonomic nervous system. The autonomic nervous system consists of two main components: the sympathetic system and the parasympathetic system. The relative influence of these two components on the sino-atrial node of the heart determines the heart rate. A number of physiological factors, including blood pressure and respiratory rate, can have a profound effect on this autonomic "balance." HRV analysis therefore provides a noninvasive method for investigating the dynamic influence of changing physiological parameters on cardiac regulation.

Autonomic Nervous System↗