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Biomedical subjects

M Lester

Publications and source records attributed to M Lester.

16 recordsLinked to original sources
PubMed2006

Kinetic study of the thermoluminescence of KMgF3:LaF3 compounds employing the general one trap model.

The parameters characterising the trap centres involved in the thermoluminescence of KMgF3:LaF3 compounds have been found by deconvolving the glow curve with the General One Trap model (GOT). For the fitting procedure the Levenberg-Marquardt method has been employed. Tm-T(stop) measurements along with initial rise measurements were performed in order to estimate the number of peaks the glow curve is made up of, and the corresponding activation energies. Instead of the Runge-Kutta method, a novel algorithm has been employed to integrate the differential equation of the GOT model, which reduces the computational time nearly 30 times with respect to the former when the glow curve is recorded with a lineal heating rate profile. The strong computational time reduction makes feasible a large number of runs with different guess values. An interesting result is that the concentration of disconnected deep traps is much less than the concentration of trap centres.

Computer Simulation↗
PubMed2006

A next generation, pilot-scale continuous sterilization system for fermentation media.

A new continuous sterilization system was designed, constructed, started up, and qualified for media sterilization for secondary metabolite cultivations, bioconversions, and enzyme production. An existing Honeywell Total Distributed Control 3000-based control system was extended using redundant High performance Process Manager controllers for 98 I/O (input/output) points. This new equipment was retrofitted into an industrial research fermentation pilot plant, designed and constructed in the early 1980s. Design strategies of this new continuous sterilizer system and the expanded control system are described and compared with the literature (including dairy and bio-waste inactivation applications) and the weaknesses of the prior installation for expected effectiveness. In addition, the reasoning behind selection of some of these improved features has been incorporated. Examples of enhancements adopted include sanitary heat exchanger (HEX) design, incorporation of a "flash" cooling HEX, on-line calculation of F(o) and R(o), and use of field I/O modules located near the vessel to permit low-cost addition of new instrumentation. Sterilizer performance also was characterized over the expected range of operating conditions. Differences between design and observed temperature, pressure, and other profiles were quantified and investigated.

Bioreactors↗
PubMed2004

The anticonvulsant and proconvulsant effects of alpha2-adrenoreceptor agonists are mediated by distinct populations of alpha2A-adrenoreceptors.

The alpha2-adrenoreceptor (AR) is the most investigated noradrenergic receptor with regard to modulation of seizure activity. However, because of the complexity of multiple alpha2-AR subtypes and their distribution, the exact role of this receptor in modulating seizure activity is not clear. alpha2A- and alpha2C-ARs function as both autoreceptors (presynaptic) on noradrenergic neurons, where they regulate norepinephrine (NE) release, and as postsynaptic receptors on neurons that receive noradrenergic innervation, where they regulate the release of other neurotransmitters (heteroreceptor). The nonselective alpha2-AR agonist clonidine produced a proconvulsant effect on seizure susceptibility, while the selective alpha2A-AR agonist guanfacine was anticonvulsant. The effects of both alpha2-AR agonists were absent in alpha2a knockout mice, suggesting that the alpha2A-AR mediates the proconvulsant and anticonvulsant effect of alpha2-AR agonists on seizure susceptibility. To determine whether the alpha2-AR agonists were acting on inhibitory presynaptic autoreceptors to decrease NE release or on postsynaptic receptors on NE target neurons, the effects of clonidine and guanfacine were determined in dopamine beta-hydroxylase knockout (Dbh -/-) mice that lack NE. The anticonvulsant effect of guanfacine persisted in Dbh -/- mice, suggesting that guanfacine may act preferentially on alpha2A-postsynaptic receptors that regulate the action of NE on target neurons. In contrast, the proconvulsant effect of clonidine was lost in Dbh -/- mice, suggesting that clonidine may act on presynaptic autoreceptors to decrease NE release. We hypothesize that the alpha2A-presynaptic autoreceptor is responsible for the proconvulsant effect of alpha2-AR agonists, while the alpha2A-postsynaptic receptor is responsible for the anticonvulsant effect of alpha2-AR agonists. These data help to clarify the inconsistent effects of alpha2-AR agonists on seizure activity.

Adrenergic alpha-Agonists↗
PubMed2002

Use of frozen bagged seed inoculum for secondary metabolite and bioconversion processes at the pilot scale.

Frozen bagged seed inoculum was prepared, thawed and tested for seven cultures. Thawing techniques were developed and other key influences on thawing rate were quantified; seed bag thawing without a water bath rarely required more than 4 to 5 h and was as short as 0.5 to 1 h for lower fill volume bags. Testing included growth of bagged seed as a function of bag fill volume (0.5, 1.0, 2.0, and 3.5 L), comparison of culture age at time of bagging, growth of bagged versus laboratory-prepared seed, productivity of production cultures derived from bagged versus laboratory-prepared seed, growth of bagged seed as a function of volume percent glycerol added at time of bagging, and growth of bagged seed as a function of frozen storage time and temperature. For each culture tested, conditions were developed such that seed tanks inoculated with bagged seed showed only minimal delay in attaining the target oxygen uptake rate (OUR) relative to seed tanks inoculated with laboratory-prepared inoculum. Although the bag fill volume did influence culture growth in some cases, bag fill volumes required were reasonable (typically 2.0 to 3.5 L) compared with laboratory seed inoculum volumes of 2.0 L. In the most remarkable example, frozen bagged seed was prepared from a second-stage seed-tank cultivation of Glarca lozoyensis, then thawed and inoculated into first-stage seed medium. It grew to the desired OUR in a similar timeframe as laboratory-prepared inoculum inoculated into first-stage seed medium. Thus, the frozen bagged seed replaced an existing laboratory inoculum preparation period of 7 days without an appreciable delay in either of the two subsequent seed-tank growth stages. Furthermore, productivities were found to be comparable for bagged-seed-derived and laboratory-seed-derived production cultivations for four different fermentation processes.

Bioreactors↗
PubMed2001

Resonant radiation pressure on neutral particles in a waveguide.

A theoretical analysis of electromagnetic forces on neutral particles in a hollow waveguide is presented. We show that the effective scattering cross section of a very small (Rayleigh) particle can be strongly modified inside a waveguide. The coupling of the scattered dipolar field with the waveguide modes induces a resonant enhanced backscattering state of the scatterer-guide system close to the onset of new modes. The particle effective cross section can then be as large as the wavelength even far from any transition resonance. As we will show, a small particle can be strongly accelerated along the guide axis while being highly confined in a narrow zone of the cross section of the guide.

Journal Article↗
PubMed2000

Hypertension, hormones, and aging.

The most rapidly growing segment of the United States population is the geriatric group, especially those above 75 years of age. Hypertension, diabetes mellitus, and dyslipidemia increase with advancing years in Westernized, industrialized societies such as the United States. These disorders contribute significantly to strokes and myocardial infarctions and associated morbidity and mortality in our elderly population. The increase in these chronic disease processes with aging is related, in part, to increasing obesity, reductions in physical activity, and medications that predispose to these conditions (ie, nonsteroidal inflammatory agents and hypertension). Hypertension in the elderly is characterized by high peripheral vascular resistance/reduced cardiac output, impaired baroflex sensitivity, relatively greater systolic pressures, increased blood pressure variability, and a propensity to salt sensitivity. Type 2 diabetes in the elderly is related to alterations in body composition (ie, increased central adiposity and decreased lean body mass) and to reduced physical activity. There is an increasing body of evidence that aggressive treatment of hypertension and dyslipidemia in the elderly results in comparable, if not greater, reductions in cardiovascular morbidity and mortality in the elderly as in younger counterparts.

Aged↗
PubMed1995

Ketoconazole 2 percent cream in the treatment of tinea pedis, tinea cruris, and tinea corporis.

Thirty-five dermatologists enrolled 256 patients to assess the safety and efficacy of ketoconazole 2 percent cream, applied once daily, in the treatment of tinea pedis, tinea cruris, and tinea corporis. Of these, 232 were eligible for efficacy evaluation based on mycologic evidence. Symptoms were assessed after four and eight weeks of treatment; relapse was assessed four weeks after the end of treatment. Total symptom scores decreased significantly during the treatment period. A marked or excellent response to treatment was observed in 82 percent of the cases. At the end of treatment 113 patients had all of their symptoms scored as absent or mild. Of these, three patients relapsed (2.7 percent) and had at least one symptom scored as moderate or severe at the follow-up visit. Only 7.2 percent (six of eighty-three) of the patients with negative findings on potassium hydroxide examination at the end of treatment showed positive findings at the follow-up visit. Three patients reported local irritant reactions to ketoconazole, two of whom discontinued treatment.

Administration, Cutaneous↗
PubMed1990

MRI quantitation of edema in focal cerebral ischemia in cats: correlation with cytochrome aa3 oxidation state.

1H MRI permits detection of edema in the brain. In a middle cerebral artery stroke model in the cat, we found a significant correlation between an edema index based on MRI and a sensitive metabolic index of ischemia, the in vivo oxidation status of mitochondrial cytochrome aa3 determined by near-infrared reflectance spectrophotometry (r = -0.70, alpha = 0.001). This result suggests that a simple, noninvasive study using MRI can provide an index of the extent of ischemic damage in an experimental acute stroke model.

Animals↗
PubMed1990

Nurses' knowledge of opioid analgesic drugs and psychological dependence.

Inadequate knowledge of opioid analgesic drugs and the incidence of psychological dependence are major barriers to nursing management of patients in pain. This study analyzed data obtained from 27 workshops on pain across 14 states (2,459 nurses) to determine current nursing knowledge of pharmacological management of pain. Results indicate that nurses lack knowledge in classification of opioids ranging from 23 to 98% correct response across seven analgesic drugs. Less than 25% of nurses correctly identified the frequency of psychological dependence. Further analysis revealed significant differences in basic versus advanced learners and geographical differences in knowledge. Implications are made for nursing education and practice.

Attitude of Health Personnel↗
PubMedDate not supplied

Design and installation of a next generation pilot scale fermentation system.

Four new fermenters were designed and constructed for use in secondary metabolite cultivations, bioconversions, and enzyme production. A new PC/PLC-based control system also was implemented using GE Fanuc PLCs, Genius I/O blocks, and Fix Dynamics SCADA software. These systems were incorporated into an industrial research fermentation pilot plant, designed and constructed in the early 1980s. Details of the design of these new fermenters and the new control system are described and compared with the existing installation for expected effectiveness. In addition, the reasoning behind selection of some of these features has been included. Key to the design was the goal of preserving similarity between the new and previously existing and successfully utilized fermenter hardware and software installations where feasible but implementing improvements where warranted and beneficial. Examples of enhancements include strategic use of Inconel as a material of construction to reduce corrosion, piping layout design for simplified hazardous energy isolation, on-line calculation and control of nutrient feed rates, and the use of field I/O modules located near the vessel to permit low-cost addition of new instrumentation.

Algorithms↗