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Biomedical subjects

P L Rogers

Publications and source records attributed to P L Rogers.

At least 19 recordsLinked to original sources
PubMed2004

Evaluating longevity of composite beef females using survival analysis techniques.

Objectives were to 1) identify risk factors affecting the longevity of beef females, 2) evaluate the utility of measures collected early in life in predicting longevity, and 3) estimate the heritability of longevity when females were culled primarily for not being pregnant following a 45-d breeding season. Data were from 1,379 Composite Gene Combination (CGC; 1/2 Red Angus, 1/4 Charolais, 1/4 Tarentaise) cows born from 1982 through 1999 at the USDA-ARS, Fort Keogh Livestock and Range Research Laboratory, Miles City, MT, and first calving at approximately 2 yr of age. The length of productive life was modeled using Cox regression to identify factors affecting the longevity of beef females. Age at first calving and calf birth weight did not influence longevity. Cows that experienced dystocia were at greater risk of being culled than those that calved without assistance (P < 0.01). On average, as breeding value for cow weight increased, the risk of being culled decreased (P < 0.01), whereas the risk of being culled increased with increasing maternal breeding values for preweaning gain (P < 0.05). Traits measured before 1 yr of age were not useful in predicting the subsequent longevity of cows. The heritability of functional longevity was estimated to be 0.14. Relatively low heritability and the lack of indicators of longevity expressed early in life suggest that genetic improvement of longevity will be difficult. Matching the genetic potential of cows for size and milk production to the production environment such that rebreeding performance is not compromised by concurrent lactation seems to be a consideration in retaining beef females when open cows are culled.

Animals↗
PubMed2003

Screening, identification and kinetic characterization of a bacterium for Mn(II) uptake and oxidation.

Following sample collection and screening at a number of Mn-associated mine sites in Northern Australia, a microbial strain was selected for its enhanced rate of Mn uptake. The strain was identified by phylogenetic analysis as a Rhizobium sp. Kinetic studies of Mn(II) uptake and oxidation by this strain in glucose-based media established that the uptake of Mn(II) was much greater than the conversion of Mn(II) to Mn oxide. Chemical analysis and scanning electron microscopy confirmed the production of significant amounts of polysaccharides by this strain. These polysaccharides may play a role both in enhancing Mn(II) accumulation and in minimizing Mn oxide production.

Cell Division↗
PubMed2003

Anions effects on biosorption of Mn(II) by extracellular polymeric substance (EPS) from Rhizobium etli.

Microbial extracellular polymeric substances (EPS) are potential biosorbents for metal remediation and recovery. The Langmuir and Freundlich kinetics of Mn(II) binding by the EPS from a novel Mn(II) oxidising strain of Rhizobium etli were determined. Maximum manganese specific adsorptions (q(max)) decreased in the sequence: sulphate (62 mg Mn per g EPS) > nitrate (53 mg g(-1)) > chloride (21 mg g(-1)). Consideration of the anion during kinetic studies is usually neglected but is important in providing more practical and comparable data between different biosorbent systems.

Adsorption↗
PubMed2001

Production of asporogenous mutants of Bacillus sphaericus 2362 in continuous culture.

AIMS: To report the production of asporogenous mutants (Spo-) of Bacillus sphaericus 2362 in continuous culture. METHODS AND RESULTS: Microbial culture samples were taken at 0.05 h-1 dilution rate and plated out on nutrient agar plates. Translucent colonies were obtained with vegetative morphology under phase contrast microscope. Heat resistance evaluations at different temperature settings showed that the Spo- mutants had lower heat resistance than the Spo+ wild type. Western blots analyses carried out on both wild type and the mutants indicated the presence of binary protein toxins of 42 and 51 kDa in both. Bioassays carried out on the wild type and the Spo- mutants against mosquitoes showed the mutants to be 100-fold less toxic in comparison to the wild type. CONCLUSION: Existence and production of asporogenous mutants of Bacillus sphaericus 2362 in continuous culture at low dilution rates is demonstrated by this study. The organism's ability to produce toxins appears to be significantly reduced by the mutational process. SIGNIFICANCE AND IMPACT OF THE STUDY: The production of asporogenous mutants had not been reported previously among strains of Bacillus sphaericus. The present report on the toxigenic capability of asporogenous mutants also raises the possibility of using continuous culture to significantly improve the productivity of toxin production in future.

Animals↗
PubMed2001

Quantifying learning in medical students during a critical care medicine elective: a comparison of three evaluation instruments.

OBJECTIVE: To compare three different evaluative instruments and determine which is able to measure different aspects of medical student learning. DESIGN: Student learning was evaluated by using written examinations, objective structured clinical examination, and patient simulator that used two clinical scenarios before and after a structured critical care elective, by using a crossover design. PARTICIPATION: Twenty-four 4th-yr students enrolled in the critical care medicine elective. INTERVENTIONS: All students took a multiple-choice written examination; evaluated a live simulated critically ill patient, requested data from a nurse, and intervened as appropriate at different stations (objective structured clinical examination); and evaluated the computer-controlled patient simulator and intervened as appropriate. MEASUREMENTS AND MAIN RESULTS: Students' knowledge was assessed by using a multiple-choice examination containing the same data incorporated into the other examinations. Student performance on the objective structured clinical examination was evaluated at five stations. Both objective structured clinical examination and simulator tests were videotaped for subsequent scores of responses, quality of responses, and response time. The videotapes were reviewed for specific behaviors by faculty masked to time of examination. Students were expected to perform the following: a) assess airway, breathing, and circulation; b) prepare a mannequin for intubation; c) provide appropriate ventilator settings; d) manage hypotension; and e) request, interpret, and provide appropriate intervention for pulmonary artery catheter data. Students were expected to perform identical behaviors during the simulator examination; however, the entire examination was performed on the whole-body computer-controlled mannequin. The primary outcome measure was the difference in examination scores before and after the rotation. The mean preelective scores were 77 +/- 16%, 47 +/- 15%, and 41 +/- 14% for the written examination, objective structured clinical examination, and simulator, respectively, compared with 89 +/- 11%, 76 +/- 12%, and 62 +/- 15% after the elective (p <.0001). Prerotation scores for the written examination were significantly higher than the objective structured clinical examination or the simulator; postrotation scores were highest for the written examination and lowest for the simulator. CONCLUSION: Written examinations measure acquisition of knowledge but fail to predict if students can apply knowledge to problem solving, whereas both the objective structured clinical examination and the computer-controlled patient simulator can be used as effective performance evaluation tools.

Adult↗
PubMed2001

Etiology and treatment of achalasia in the pediatric age group.

Achalasia in children bears many similarities to the disorder in adults, both in terms of clinical features and in terms of the approach to therapy. Pharmacologic management is of limited temporary benefit until more definitive therapy is undertaken. Intrasphincteric injections of botulinum toxin provides safe but short-term relief from symptoms. Based on our review of the safety and effectiveness of pneumatic dilation, we advocate this procedure as the primary form of definitive therapy for achalasia in children. In patients who do not achieve satisfactory results from a series of graduated pneumatic dilations, Heller myotomy provides safe and effective surgical treatment.

Adolescent↗
PubMed2000

Medical students can learn the basic application, analytic, evaluative, and psychomotor skills of critical care medicine.

OBJECTIVE: To determine whether fourth-year medical students can learn the basic analytic, evaluative, and psychomotor skills needed to initially manage a critically ill patient. DESIGN: Student learning was evaluated using a performance examination, the objective structured clinical examination (OSCE). Students were randomly assigned to one of two clinical scenarios before the elective. After the elective, students completed the other scenario, using a crossover design. SETTING: Five surgical intensive care units in a tertiary care university teaching hospital. PARTICIPANTS: Forty fourth-year medical students enrolled in the critical care medicine (CCM) elective. INTERVENTIONS: All students evaluated a live "simulated critically ill" patient, requested physiologic data from a nurse, ordered laboratory tests, received data in real time, and intervened as they deemed appropriate. MEASUREMENTS AND MAIN RESULTS: Student performance of specific behavioral objectives was evaluated at five stations. They were expected to a) assess airway, breathing, and circulation in appropriate sequence; b) prepare a manikin for intubation, obtain an acceptable airway on the manikin, demonstrate bag-mouth ventilation, and perform acceptable laryngoscopy and intubation; c) provide appropriate mechanical ventilator settings; d) manage hypotension; and e) request and interpret pulmonary artery data and initiate appropriate therapy. OSCEs were videotaped and reviewed by two faculty members masked to time of examination. A checklist of key behaviors was used to evaluate performance. The primary outcome measure was the difference in examination score before and after the rotation. Secondary outcomes included the difference in scores at each rotation. The mean preelective score was 57.0%+/-8.3% compared with 85.9%+/-7.4% (p<.0001) after the elective. Significant improvement was demonstrated at each station except station I. CONCLUSION: Fourth-year medical students without a CCM elective do not possess the basic cognitive and psychomotor skills necessary to initially manage critically ill patients. After an appropriate 1-month CCM elective, students' thinking and application skills required to initially manage critically ill patients improved markedly, as demonstrated by an OSCE using a live simulated "patient" and manikin.

Catheterization, Swan-Ganz↗
PubMed2000

Compensation for teaching in critical care.

OBJECTIVES: To determine the financial or nonclinical time critical care program directors or teaching faculty members receive as compensation for their educational activities. To compare compensation types and amounts among critical care specialties and between university vs. nonuniversity sponsoring institutions. DATA SOURCES AND EXTRACTION: Survey returns (46%) from critical care fellowship directors listed in the American Medical Association Graduate Medical Education Directory. Information was stratified according to fellowship specialty and type of sponsoring hospital and compared by chi-square analysis and the Kruskal-Wallis test. CONCLUSIONS: Most program directors (77%) and faculty (82%) receive no specified compensation for education-related activities. Multidisciplinary programs are more likely to compensate faculty members than other specialty-specific programs (p = .006). Most programs sponsored by university or military/federal hospitals do not provide specified compensation (79% and 100%, respectively). Overall, community hospital-based programs provide a greater percentage of compensation to directors and faculty than university programs (for directors, p = .02; odds ratio, 3.85; for faculty, p = .001; odds ratio, 8.4). When compensation is specified, it is most often financial and it averages 18% of the salary (range, 5% to 100%) for directors and 19% of the salary for faculty (range, 5% to 50%). When reduced clinical time is provided (5% of program directors, 2% of faculty), it averages 13% (range, 8% to 18%) for directors and 18% (range, 10% to 25%) for faculty. Alternative methods for assigning educational compensation are discussed.

Critical Care↗
PubMed2000

Kinetic and nuclear magnetic resonance studies of xylose metabolism by recombinant Zymomonas mobilis ZM4(pZB5).

The specific rates of growth, substrate utilization, and ethanol production as well as yields of biomass and ethanol production on xylose for the recombinant Zymomonas mobilis ZM4(pZB5) were shown to be much less than those on glucose or glucose-xylose mixtures. Typical fermentations with ZM4(pZB5) growing on glucose-xylose mixtures followed two-phase growth kinetics with the initial uptakes of glucose and xylose being followed by slower growth and metabolic uncoupling on xylose after glucose depletion. The reductions in rates and yields from xylose metabolism were considered in the present investigation and may be due to a number of factors, including the following: (i) the increased metabolic burden from maintenance of plasmid-related functions, (ii) the production of by-products identified as xylitol, acetate, lactate, acetoin, and dihydroxyacetone by (13)C-nuclear magnetic resonance (NMR) spectroscopy and high-performance liquid chromatography, (iii) growth inhibition due to xylitol by the putative inhibitory compound xylitol phosphate, and (iv) the less energized state of ZM4(pZB5). In vivo (31)P-NMR studies have established that the levels of NTP and UDP sugars on xylose were less than those on glucose, and this energy limitation is likely to restrict the growth of the recombinant strain on xylose media.

Culture Media↗
PubMed2000

Characterization of a high-productivity recombinant strain of Zymomonas mobilis for ethanol production from glucose/xylose mixtures.

The fermentation characteristics of a recombinant strain of Zymomonas mobilis ZM4(pZB5) capable of converting both glucose and xylose to ethanol have been further investigated. Previous studies have shown that the strain ZM4(pZB5) was capable of converting a mixture of 65 g/L of glucose and 65 g/L of xylose to 62 g/L of ethanol in 48 h with an overall yield of 0.46 g/g. Higher sugar concentrations (e.g., 75/75 g/L) resulted in incomplete xylose utilization (80 h). In the present study, further kinetic evaluations at high sugar levels are reported. Acetate inhibition studies and evaluation of temperature and pH effects indicated increased maximum specific uptake rates of glucose and xylose under stressed conditions with increased metabolic uncoupling. A high-productivity system was developed that involved a membrane bioreactor with cell recycling. At sugar concentrations of approx 50/50 g/L of glucose/xylose, an ethanol concentration of 50 g/L, an ethanol productivity of approx 5 g/(L.h), and a yield (YP/S) of 0.50 g/g were achieved. Decreases in cell viability were found in this system after attainment of an initial steady state (40-60 h); a slow bleed of concentrated cells may be required to overcome this problem.

Aldose-Ketose Isomerases↗
PubMed2000

Nuclear magnetic resonance studies of acetic acid inhibition of rec Zymomonas mobilis ZM4(pZB5).

The fermentation characteristics and effects of lignocellulosic toxic compounds on recombinant Zymomonas mobilis ZM4(pZB5), which is capable of converting both glucose and xylose to ethanol, and its parental strain, ZM4, were characterized using 13C and 31P nuclear magnetic resonance (NMR) in vivo. From the 31P NMR data, the levels of nucleoside triphosphates (NTP) of ZM(pZB5) using xylose were lower than those of glucose. This can be related to the intrinsically slower assimilation and/or metabolism of xylose compared to glucose and is evidence of a less energized state of ZM4(pZB5) cells during xylose fermentation. Acetic acid was shown to be strongly inhibitory to ZM4(pZB5) on xylose medium, with xylose utilization being completely inhibited at pH 5.0 or lower in the presence of 10.9 g/L of sodium acetate. From the 31P NMR results, the addition of sodium acetate caused decreased NTP and sugar phosphates, together with acidification of the cytoplasm. Intracellular deenergization and acidification appear to be the major mechanisms by which acetic acid exerts its toxic effects on this recombinant strain.

Aldose-Ketose Isomerases↗
PubMed1998

A sandwich enzyme-linked immunosorbent assay for the Bacillus sphaericus binary toxin.

Bacillus sphaericus (Bs) binary toxin was purified from recombinant E. coli DH5alpha harboring the recombinant plasmid pAR5, which carries a 3.6-kb DNA fragment of Bs 1593M encoding mosquito larvicidal activity. The binary toxin preparation, designated BsEcAg, contained mainly 51- and 42-kDa toxin proteins and was toxic to 50% of Culex quinquefasciatus larvae at a concentration of 9.22 ng toxin protein/ml. This preparation was used to raise antibodies in sheep and mice. The sandwich ELISA used sheep antitoxin antibody as primary antibody (coating antibody), mouse antitoxin antibody as second antibody, and goat antimouse antibody as an alkaline phosphatase-conjugated detecting antibody. The assay sensitivity was 200 ng/ml for both BsEcAg and binary toxin antigen (BsAg) from Bs 2362 cells. There is a significant correlation between toxin level determined by ELISA and bioassay. This procedure has also been used to monitor toxin levels in batch fermentations of Bs 2362.

Antibodies, Bacterial↗
PubMed1998

Composition of the cell walls of several yeast species.

Cell walls, representing 26%-32% of the cell dry weight, were prepared from several strains of the yeasts Kloeckera apiculata, Debaryomyces hansenii, Zygosaccharomyces bailii, Kluyveromyces marxianus and Saccharomyces cerevisiae. Extraction of the walls with potassium hydroxide at 4 degrees C, followed by saturation of the alkali-soluble extract with ammonium sulphate gave fractions of mannoprotein, alkali-soluble glucan and alkali-insoluble glucan. Chitin was associated with the alkali-insoluble glucan. The proportions of the different fractions within the walls varied with the species and strain. Mannoprotein comprised between 25% and 34% of the walls, the content of alkali-insoluble glucan ranged from 15% to 48%, and the content of alkali-soluble glucan ranged from 10% to 48%. There was significant variation in the physical appearance of the alkali-soluble glucans and the relative viscosity of suspensions of these glucans. The yeasts could represent novel sources of polysaccharides with industrial and medical applications.

Cell Wall↗
PubMed1997

Partitioning and effects of silver in amended freshwater sediments.

Sediments that represented a wide range of characteristics were amended with silver compounds to observe partitioning and bioavailability. In laboratory studies, silver partitioning to particulates, sediment pore water, and overlying water was measured and bioavailability of silver was determined using Hyalella azteca in 10-day sediment toxicity tests. Three silver compounds were used as sources of silver for this study: silver nitrate, silver chloride, and silver thiosulfate complex. Sediment amendment procedures were adjusted as necessary depending on the characteristics of the individual compounds. Several sediment characteristics such as organic carbon, pH, redox, and acid volatile sulfides regulated silver partitioning and bioavailability. Bioavailability of silver was correlated with the overlying water concentration of silver. Ten-day LC50 values ranged from 1.62 to 379.7 mg Ag/kg for H. azteca exposed to sediments amended with AgNO3. In laboratory experiments, silver chloride and silver thiosulfate were orders of magnitude less toxic and bioavailable than silver nitrate, with 10-day LC50 values greater than the highest concentrations of AgCl and silver thiosulfate complex amended to sediments (2560 and 1125 mg Ag/kg, respectively.

Animals↗
PubMed1997

Biotransformation for L-ephedrine production.

L-ephedrine is widely used in pharmaceutical preparations as a decongestant and anti-asthmatic compound. One of the key intermediates in its production is L-phenylacetylcarbinol (L-PAC) which can be obtained either from plants (Ephedra sp.), chemical synthesis involving resolution of a racemic mixture, or by biotransformation of benzaldehyde using various yeasts. In the present review, recent significant improvements in the microbial biotransformation are assessed for both fed-batch and continuous processes using free and immobilised yeasts. From previous fed-batch culture data, maximal levels of L-PAC of 10-12 gl-1 were reported with yields of 55-60% theoretical based on benzaldehyde. However, recently concentrations of more than 22 gl-1 have been obtained using a wild-type strain of Candida utilis. This has been achieved through optimal control of yeast metabolism (via microprocessor control of the respiratory quotient, RQ) in order to enhance substrate pyruvate production and induce pyruvate decarboxylase (PDC) activity. Processes involving purified PDC have also been evaluated and it has been demonstrated that L-PAC levels up to 28 gl-1 can be obtained with yields of 90-95% theoretical based on the benzaldehyde added. In the review the advantages and disadvantages of the various strategies for the microbial and enzymatic production of L-PAC are compared. In view of the increasing interest in microbial biotransformations, L-PAC production provides an interesting example of enhancement through on-line control of a process involving both toxic substrate (benzaldehyde) and end-product (L-PAC, benzyl alcohol) inhibition.

Acetone↗
PubMed1997

Cloning and expression of the Bacillus sphaericus 2362 mosquitocidal genes in a non-toxic unicellular cyanobacterium, Synechococcus PCC6301.

Genes encoding the mosquitocidal binary toxin of Bacillus sphaericus 2362 were introduced into Synechococcus PCC6301, a cyanobacterium that can tolerate a number of potential variations in the mosquito breeding environment, and can serve as a food source for mosquito larvae. The toxin genes, preceded by a Synechococcus rbcL promoter, were located on a mobilizable Escherichia coli Synechococcus shuttle vector, which was introduced into Synechococcus PCC6301 at frequencies of 10(-5)-10(-7) exconjugants/recipient, depending on the selective conditions used. Recombinant Synechococcus exhibited significant toxicity against 2-day-old and 6-day-old Culex quinquefasciatus larvae, the concentration required to kill 50% of larvae (LC50) being 2.1 x 10(5) and 1.3 x 10(5) cells/ml respectively. Mosquitocidal activity decreased tenfold after 20 generations of non-selective growth.

Animals↗