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PubMed1998

Improving ion-trap GC-MS quantitation limits for therapeutic agents extracted from rat plasma.

Insufficient quantitation limits using ion-trap gas-chromatography mass-spectrometry (GC-MS) prevented the assay of some samples during a preliminary screening of preclinical rat plasma samples (50 microliter) containing novel, polar therapeutic agents. Few options were available for improving the lower limit of quantitation. The limited amount of sample available precluded the extraction additional plasma. Lipid-liquid extraction recoveries were greater than 90% throughout the range of the standard curve (500-2000 ng ml-1). Chromatography was optimized and multiple, equivalent sites for analyte fragmentation were precluded, using MS-MS to improve assay sensitivity. Quantitation limits were decreased 10-fold however, by using a larger syringe to increase the injection volume from 5 to 50 microliter, in combination with a universal programmable injector. These large injection volumes required changes in the injector events program and in column plumbing. Additionally, evaluation of injection liner packing material demonstrated a 2-fold improvement in sensitivity, using carbofrit, relative to silanized glass wool. Converting to inert ion-trap electrodes did not appear to affect the detection limit, perhaps due to over-riding peak broadening during gas chromatography. The changes described produced a 20-fold improvement in the lower limit quantitation.

Animals↗
PubMed2003

70-mph speed limit and motor vehicular fatalities on interstate highways.

In May 1996, Alabama increased the rural interstate highways speed limit to 70 mph. This study was conducted to determine if the faster speed limit had any influence on the number of motor vehicular crash (MVC) deaths. The null hypothesis was that no significant change occurred in the number of deaths since the faster speed was introduced. Using MVC fatality data collected by the Alabama Department of Public Safety and published by the state of Alabama from 1984 to 1999, a time-series study designed was used to examine the number of MVC deaths before and after the speed limit change. The trend of MVC deaths was examined for both rural and urban interstate highways and those occurring on Federal and state highways. There were 174 interstate MVC deaths in 1997 and 165 in 1999; both figures represent a significant increase (P <.05) from the trend of previous years' results. State and Federal highways demonstrated no significant change. By 1998 the number of interstate highway MVC deaths dropped to 114, falling back within the expected trend established by the results of the previous years. The number of rural interstate MVC deaths was found to be significant in 1997 and 1999. The faster speed limit was associated with an increase in MVC deaths for the first year after the speed limit increase. The decline in the number of MVC deaths for 1998 was unanticipated. There are many other factors that need to be evaluated before determining the cause and effect that higher speed limits have on MVC fatalities.

Accidents, Traffic↗
PubMed2003

Time requirements of the standard echocardiogram: implications regarding limited studies.

BACKGROUND: Although no formal detailed definitions exist, a standard echocardiogram should easily be differentiated from a limited examination by its comprehensive nature and time requirement. OBJECTIVE: We evaluated the time required to perform each specific component of a comprehensive echocardiography examination and applied these data to compare the time required to complete 3 limited imaging protocols. METHODS: In all, 7 experienced sonographers were timed in their performance of a comprehensive echocardiographic examination on a healthy patient. A total of 3 limited imaging protocols were then constructed to evaluate for pericardial effusion, wall motion, and left ventricle size. The time necessary to complete each protocol was calculated by adding the average time required to perform all of its components and was compared with the comprehensive examination. RESULTS: The imaging time required to complete a standard study was 26 +/- 5.4 minutes (range: 20-32). The percentage of total study time spent on 2-dimensional imaging, M-mode, color Doppler, and spectral components was 31 +/- 2.9%, 11 +/- 3.6%, 17 +/- 2.9%, and 39 +/- 5.0%, respectively. The calculated time needed to perform a limited protocol was less than 5 minutes, resulting in a greater than 80% reduction in time compared with the standard examination. CONCLUSION: Time analysis of components of the standard echocardiography examination can be used to construct appropriate, time-efficient, limited, cardiac ultrasound imaging examinations and differentiate limited from comprehensive studies.

California↗
PubMed1997

Physical activity, functional limitations, and the risk of fall-related fractures in community-dwelling elderly.

This case-control study examines the association of vigorous and mild physical activity with fall-related fractures in a community-dwelling population age 65 and older in South Florida. Vigorous physical activity was defined as exercising, doing heavy housecleaning, or other hard labor three or more times per week in the month prior to the index date; mild physical activity was defined as the number of hours per day subjects reported spending on their feet. A case was any subject who sustained a fall-related fracture (ICD-9CM-800 through ICD-9CM-829) over a 21-month period (n = 471). Controls were at 10% random sample selected from the Health Care Financing Administration Medicare files (n = 712). The presence of any limitation in activities of daily living (ADL) significantly modified the effect of vigorous physical activity. Physically active subjects with no limitations (ADL = 0) were less likely to sustain a fall-related fracture than were inactive subjects with an adjusted odds ratio (aOR) of 0.6, (0.5-0.8 95% CI), and active subjects with any limitation (ADL > or = 1) had an aOR of 3.2 (1.1-9.8 95% CI). Limiting this analysis to 159 hip fracture cases produced similar results. Mild physical activity was not associated with fracture. These results suggest that vigorous physical activity is associated with a lower fracture risk among elderly persons who have no limitation in ADL and with a higher risk among those with any limitations.

Accidental Falls↗
PubMed2004

Diagnosis of pulmonary vascular limit to exercise by cardiopulmonary exercise testing.

BACKGROUND: Given the recent development of newer and less-invasive treatments for pulmonary hypertension, and the long wait for lung transplantation, early and correct diagnosis of this condition is increasingly important. The purpose of this study was to determine and improve the accuracy of a non-invasive, cardiopulmonary exercise-testing algorithm for detecting a pulmonary vascular limit to exercise. METHODS: We performed 130 consecutive, incremental cycling-exercise tests for exertional symptoms with pulmonary and radial artery catheters in place. Pulmonary vascular limit was defined as pulmonary vascular resistance at maximum exercise >120 dynes. sec/cm(5) and a peak-exercise systemic oxygen delivery <80% predicted, without a pulmonary mechanical limit or poor effort. We applied a previously reported non-invasive exercise-test-interpretation algorithm to each patient and sequentially manipulated branch point threshold values to maximize accuracy. RESULTS: The sensitivity of the original non-invasive algorithm for pulmonary vascular limit was 79%, specificity was 75%, and accuracy was 76%. Sensitivity did not change with systematic alteration of branch-point threshold values, but specificity and accuracy improved to 88% and 85%, respectively. Accuracy improved most by modifying the threshold values for percent predicted maximum oxygen uptake and carbon dioxide output ventilatory equivalents at lactate threshold. CONCLUSION: Non-invasive cardiopulmonary exercise testing is a useful tool for detecting and excluding a pulmonary vascular limit and for determining whether abnormal pulmonary hemodynamics limit aerobic capacity.

Adult↗
PubMed2002

Hydrazine detection limits in the cigarette smoke matrix using infrared tunable diode laser absorption spectroscopy.

Infrared absorption lines of hydrazine are broad and typically not baseline resolved, with line strengths approximately 100 times weaker than the more widely studied compound ammonia. Hardware and software improvements have been made to a two-color infrared tunable diode laser (IR-TDL) spectrometer in order to improve the limit of detection (LOD) of hydrazine (N2H4) in the cigarette smoke matrix. The detection limit in the smoke matrix was improved from 25 parts-per-million-by-volume (ppmv) to 4.2 ppmv using a 100 m pathlength cell with acquisition of background spectra immediately prior to each sample and 100 ms temporal resolution. This study did not detect hydrazine in cigarette smoke in the 964.4-964.9 cm(-1) spectral region, after mathematically subtracting the spectral contributions of ethylene, ammonia, carbon dioxide, methanol, acrolein, and acetaldehyde. These compounds are found in cigarette smoke and absorb in this spectral region. The LOD is limited by remaining spectral structure from unidentified smoke species. The pseudo random noise (root mean square) in the improved instrument was 2 x 10(-4) absorbance units (base e) which is equivalent to a 0.09 ppmv hydrazine gas sample in the multipass cell. This would correspond to a detection limit of 0.44 ppmv of hydrazine, given the dilution of the smoke by a factor of 5 by the sampling system. This is a factor of 10 less than the 4.2 ppmv detection limit for hydrazine in the smoke matrix, and indicates that the detection limit is primarily a result of the complexity of the matrix rather than the random noise of the TDL instrument.

Hydrazines↗
PubMedDate not supplied

Limited sonography in collaborative midwifery practice.

In 1996, the American College of Nurse Midwives published guidelines for midwives who wish to incorporate limited third trimester sonography into their practices. First, however, certain didactic and clinical content needs to be disseminated through basic and continuing midwifery education. To assist the busy practitioner, information is offered related to recommended methods of obtaining learning validation and continuing competency in limited sonography. This article discusses various clinical situations in which the assessment and management of a patient's condition might be improved by having ultrasonographic information immediately available. In addition, selected data obtained by limited sonography that may necessitate physician collaboration are described through clinical case presentations. The pitfalls of limited sonography are also discussed by use of case descriptions detailing some of the risks inherent in performing a limited ultrasonogram. The recommendation of performing a complete uterine survey with each limited ultrasonogram is emphasized. Finally, some of the controversies surrounding routine sonography in pregnancy and sonograms for entertainment are addressed.

Adult↗
PubMed2001

Metabolism of 2,4-dinitrotoluene (2,4-DNT) by Alcaligenes sp. JS867 under oxygen limited conditions.

Transformation of 2,4-dinitrotoluene (2,4-DNT) by Alcaligenes JS867 under varying degrees of oxygen limitation was examined. Complete 2,4-DNT removal was observed under oxygen excess with near stoichiometric release (83%) of nitrite. Average kinetic parameters were estimated based on a dual-Monod biokinetic model with 2,4-DNT and O2 as growth limiting substrates. The negative impact of nitrite accumulation on the reaction rate was adequately described by inclusion of a noncompetitive inhibition term for NO2-. Under aerobic conditions, mumax, KsDNT, and KiNO were 0.058 (0.004)hr(-1), 3.3(+/-1.3) mg 2,4-DNT/L, and 1.2(+/-0.2)hr(-1), respectively. At increasing oxygen limitation, rates of 2,4-DNT disappearance and nitrite production decreased and incomplete removal of 2,4-DNT commenced. JS867 was able to use NO2- as a terminal electron acceptor when grown on glucose or succinate under anaerobic conditions. However, during growth on 2,4-DNT and under O2-limited conditions, JS867 did not use released nitrite as electron acceptor. The nearly constant molar ratios of DNT removed over NO2- released under various degrees of oxygen limitation suggested that oxygenolytic denitration pathways continued. No evidence of nitroreduction was obtained under the examined oligotrophic conditions. JS867 displayed a high affinity for oxygen consumption with K(SO2) value of 0.285(+/-0.198) mg O2/L. Our results indicate that under oligotrophic conditions with 2,4-DNT as dominant carbon source, oxygen availability and nitrite accumulation may limit 2,4-DNT biomineralization, but the accumulation of reduced 2,4-DNT transformation products will be small.

Alcaligenes↗
PubMed2004

Novel scaled average bioequivalence limits based on GMR and variability considerations.

PURPOSE: i) To develop novel approaches for the construction of bioequivalence (BE) limits incorporating both the intrasubject variability and the geometric mean ratio (GMR), and ii) to assess the performance of the novel approaches in comparison to several scaled BE procedures and the classic unscaled average BE. METHODS: Plots of the BE limits or the extreme GMR values accepted as a function of the coefficient of variation (CV) were constructed for published and the developed scaled procedures. Two-period crossover BE investigations with 12, 24, or 36 subjects were simulated with assumptions of a CV 10%, 20%, 30%, or 40%. The decline in the percentage of accepted studies was recorded as the true GMR for the two formulations was raised from 1.00 to 1.50. Acceptance of BE was evaluated by published and the developed scaled procedures, and, for comparison, by the unscaled average BE. RESULTS: Two GMR-dependent BE limits are proposed for the evaluation of average BE: i) BELscG1 with Ln(Upper, Lower BE limit) = +/-[(5 - 4GMR)0.496s + Ln(1.25)], and ii) BELscG2 with Ln(Upper, Lower BE limit) = +/-[(3 - 2GMR)(0.496s + Ln(1.25))], where s is the square root of the intrasubject variance. The range of BE limits becomes narrower as GMR values deviate from unity, and increases with variability. The two new approaches exhibit the highest statistical power at low CV values. At high levels of variability, BELscG1 and BELscG2 show high statistical power, as well as the lowest percentages of acceptance among the scaled methods when GMR = 1.25. The latter becomes more obvious when a large number of subjects is incorporated in the studies. CONCLUSIONS: The GMR and CV estimates of the BE study can be used in conjunction with the GMR vs. CV plot for the assessment of average BE. The new approaches, BELscG1 and BELscG2, appear to be highly effective at all levels of variation investigated.

Algorithms↗
PubMed2004

Increased parent limits on teen driving: positive effects from a brief intervention administered at the Motor Vehicle Administration.

The purpose of this study was to determine whether exposure to a brief intervention administered at the Motor Vehicle Administration (MVA) increases parental limits on teen driving. A total of 658 parents and their 16-year-old adolescents were recruited from a local MVA site as adolescents successfully tested for provisional licenses. At the MVA, participating parents completed written surveys about expected teen driving during the 1st month of provisional licensure. One month later, 579 parent-teen dyads completed follow-up telephone interviews about teen driving within the past month. On weeks assigned as intervention, parents were exposed to a video and given the video and a driving agreement to take home. In multivariate linear regression analyses, the results indicated that when controlling for selected demographic and baseline psychosocial variables, intervention parents reported more driving rules, restricted driving, limits for high-speed roads, weekend night restrictions, and overall driving limits than did parents in the control group. When compared to control teens, intervention teens reported more limits on passengers, high-speed roads, and night driving, and on overall driving limits, but there were no differences for overall driving or driving under high-risk conditions. In addition, intervention parents were about 3 times, and intervention teens were about 5 times, more likely than controls to report using a parent-teen driving agreement. These results indicate that brief exposure to intervention at an MVA office may help increase parental limits on teen driving.

Adolescent↗
PubMed2000

Role of inspiratory capacity on exercise tolerance in COPD patients with and without tidal expiratory flow limitation at rest.

Expiratory flow limitation promotes dynamic hyperinflation during exercise in chronic obstructive pulmonary disease (COPD) patients with a consequent reduction in inspiratory capacity (IC), limiting their exercise tolerance. Therefore, the exercise capacity of patients with tidal expiratory flow limitation (FL) at rest should depend on the magnitude of IC. The presented study was designed to evaluate the role of FL on the relationship between resting IC, other respiratory function variables and exercise performance in COPD patients. Fifty-two patients were included in the study. Negative expiratory pressure (NEP) uptake (VO2,max) were measured during an incremental symptom-limited cycle exercise. Twenty-nine patients were FL at rest. The IC was normal in all non-FL patients, while in most FL subjects it was decreased. Both WRmax and VO2,max were lower in FL patients (p<0.001, each). A close relationship of WRmax and O2,max to IC was found (r=0.73 and 0.75, respectively; p<0.0001, each). In the whole group, stepwise regression analysis selected IC and forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) (% predicted) as the only significant contributors to exercise tolerance. Subgroup analysis showed that IC was the sole predictor in FL patients, and FEV1/FVC in non-FL patients. Detection of flow limitation provides useful information on the factors that influence exercise capacity in chronic obstructive pulmonary disease patients. Accordingly, in patients with flow limitation, inspiratory capacity appears as the best predictor of exercise tolerance, reflecting the presence of dynamic hyperinflation.

Aged↗
PubMed1997

Para-aminobenzoic acid used as a marker for completeness of 24 hour urine: assessment of control limits for a specific HPLC method.

OBJECTIVE AND DESIGN: The study comprised three protocols. Protocol 1 compared a HPLC method with the commonly employed colorimetric diazocoupling method. Protocol 2 examined, if the last dosage of p-aminobenzoic acid (PABA) could be advanced in the old to allow for a delayed age-dependent urinary excretion of PABA. Protocol 3 established limits for recovery of PABA in 24 h urine applying the HPLC method. SUBJECTS AND SETTING: A total of 151 healthy volunteers participated in the study of which 140 were accepted. In protocol 1: 37 subjects aged 20-78 y were included. All subjects took PABA as recommended (80 mg orally at 08.00, 12.00 and 18.00 h). Protocol 2: compared urinary PABA excretion in two groups of 80 y old subjects who had their last PABA dosage administered at 15.00 h (n = 16) and at 18.00 h (n = 31), respectively. Protocol 3: comprised 56 subjects aged 20-80 y. In the younger age group (20-59 y; n = 34) PABA was taken as recommended, whereas in the older age group (60-80 y; n = 22) the last PABA dosage was advanced three hours. RESULTS: Protocol 1: HPLC gave significantly lower PABA recovery results compared to colorimetry, the difference between methods being 23.9 +/- 8.5 mg/24 h (P < 0.001). Protocol 2: higher PABA recoveries were demonstrated with the advanced dosage schedule compared to the recommended schedule (208 +/- 14 mg/24 h vs 181 +/- 22 mg/24 h; P < 0.001). Protocol 3: PABA recovery with HPLC was 211 +/- 12 mg/24 h, and the lower limit comprising 95% of subjects was 187 mg/24 h. Similar PABA recoveries were demonstrated in the younger subjects and the older subjects (211 +/- 11 mg/24 h vs 211 +/- 13 mg/24 h; NS). CONCLUSION: An advanced dosage schedule for PABA in the aged is recommended. Because of lower recoveries with HPLC, the low limit for recovered PABA in a complete 24 h urine differs from the limit based on colorimetry. This study found a limit of 187 mg/24 h corresponding to the lower 95% confidence limit for a single subject.

4-Aminobenzoic Acid↗
PubMed2005

Abdominal fat distribution and functional limitations and disability in a biracial cohort: the Atherosclerosis Risk in Communities Study.

OBJECTIVE: To examine the associations of abdominal fat and obesity with functional limitations and disability in late adulthood. DESIGN: Longitudinal, cohort study. PARTICIPANTS: African American and white men and women aged 45-64 y at baseline with measured waist circumference, waist-to-hip ratio (WHR), and body mass index (BMI) who participated in the Atherosclerosis Risk in Communities (ARIC) Study (n = 9416). OUTCOME MEASURES: Self-reported functional limitations, activities of daily living (ADLs), and instrumental activities of daily living (IADLs) at ages 52-75 y. RESULTS: Waist circumference, WHR, and BMI were positively associated with functional limitations and ADL and IADL impairment approximately 9 y later among African American and white men and women. For example, in African American women the odds ratios (95% CI) associated with a one standard deviation (s.d.) increment in waist circumference (13.3 cm) for severe functional limitations and ADL and IADL impairment were 2.36 (2.00-2.79), 1.41 (1.25-1.58), and 1.49 (1.34-1.66), respectively. In white women, the odds ratios (95% CI) were 2.66 (2.39-2.96), 1.60 (1.47-1.74), and 1.42 (1.31-1.53), respectively. Similar associations were found in men. A 1 s.d. increment in WHR (0.08 U) and BMI (5.06 kg/m2) produced similar results. The associations of waist circumference and WHR with functional limitations and ADL and IADL impairment were attenuated but, in general, remained statistically significant when BMI was added to the models. CONCLUSIONS: Maintaining a healthy body weight and avoiding increases in abdominal fat should be investigated for their potential to reduce the risk of functional limitations and disability in an aging population.

Abdominal Fat↗
PubMed1997

Effects of medium composition and nutrient limitation on loss of the recombinant plasmid pLG669-z and beta-galactosidase expression by Saccharomyces cerevisiae.

The effects of medium composition, nutrient limitation and dilution rate on the loss of the recombinant plasmid pLG669-z and plasmid-borne beta-galactosidase expression were studied in batch and chemostat cultures of Saccharomyces cerevisiae strain CGpLG. The difference in growth rates between plasmid-free and plasmid-containing cells (delta mu) and the rate of segregation (R) were determined and some common factors resulting from the effect of medium composition on plasmid loss were identified. Glucose-limited chemostat cultures of CGpLG grown on defined medium were more stable at higher dilution rates and exhibited delta mu-dominated plasmid loss kinetics. Similar cultures grown on complex medium were more stable at lower dilution rates and exhibited R-dominated plasmid loss kinetics. Overall plasmid stability was greatest in phosphate-limited chemostat cultures grown on defined medium and was least stable in magnesium-limited cultures grown on defined medium. delta mu decreased and R increased with increased dilution rate, irrespective of medium composition. Increased plasmid loss rates at high or low dilution rates would appear to be characteristic of loss kinetics dominated by R or delta mu, respectively. Growth of glucose-limited chemostat cultures on complex medium decreased delta mu values but increased R values, in comparison to those cultures grown on defined medium. Any increased stability that a complex medium-induced reduction of delta mu may have conferred was counteracted by an increased R value. Increased beta-galactosidase productivity was correlated with increased plasmid stability only in glucose-limited chemostat cultures grown on defined medium and not in those grown on complex medium. Previous studies have yielded contrasting responses with regard to the effect of dilution rate on recombinant plasmid loss from S. cerevisiae. Our findings can account for these differences and may be generally valid for the stability of similar yeast plasmid constructs. This information would facilitate the design of bioprocesses, where recombinant plasmid instability results in reduced culture productivity.

Culture Media↗
PubMed2000

Identification of transcription activators that regulate gonococcal adaptation from aerobic to anaerobic or oxygen-limited growth.

Analysis of the Neisseria gonorrhoeae DNA sequence database revealed the presence of two genes, one encoding a protein predicted to be 37. 5% identical (50% similar) in amino acid sequence to the Escherichia coli FNR protein and the other encoding a protein 41% and 42% identical (54 and 51% sequence similarity) to the E. coli NarL and NarP proteins respectively. Both genes have been cloned into E. coli and insertionally inactivated in vitro. The mutated genes have been transformed into gonococci and recombined into the chromosome. The fnr mutation totally abolished and the narP mutation severely diminished the ability of gonococci to: (i) grow anaerobically; (ii) adapt to oxygen-limited growth; (iii) initiate transcription from the aniA promoter (which directs the expression of a copper-containing nitrite reductase, AniA, in response to the presence of nitrite); and (iv) reduce nitrite during growth in oxygen-limited media. The product of nitrite reduction was identified to be nitrous oxide. Immediately upstream of the narL/narP gene is an open reading frame that, if translated, would encode a homologue of the E. coli nitrate- and nitrite-sensing proteins NarX and NarQ. As transcription from the aniA promoter was not activated during oxygen-limited growth in the presence of nitrate, the gonococcal two-component regulatory system is designated NarQ-NarP rather than NarX-NarL. As far as we are aware, this is the first well-documented example of a two-component regulatory system working in partnership with a transcription activator in pathogenic neisseria. A 45 kDa c-type cytochrome that was synthesized during oxygen-limited, but not during oxygen sufficient, growth was identified as a homologue of cytochrome c peroxidases (CCP) of other bacteria. The gene for this cytochrome, designated ccp, was located, and its regulatory region was cloned into the promoter probe vector pLES94. Transcription from the ccp promoter was repressed during aerobic growth and induced during oxygen-limited growth and was totally FNR dependent, suggesting that the gonococcal FNR protein is a transcription activator of at least two genes. However, unlike AniA, synthesis of the CCP homologue was insensitive to the presence of nitrite during oxygen-limited growth.

Adaptation, Physiological↗
PubMed2001

Short- and long-term changes in proteome composition and kinetic properties in a culture of Escherichia coli during transition from glucose-excess to glucose-limited growth conditions in continuous culture and vice versa.

To investigate the ability of Escherichia coli K12 MG1655 to cope with excess and limitation of a carbon and energy source, we studied the changes in kinetic properties and two-dimensional (2D) gel protein patterns of an E. coli culture. The population was transferred from glucose-excess batch to glucose-limited continuous culture (D = 0.3 h(-1)), in which it was cultivated for 500 h (217 generations) and then transferred back to glucose-excess batch culture. Two different stages to glucose-limitation were recognized: a short-term physiological adaptation characterized by a general effort in enhancing the cell's substrate scavenging ability and mutations resulting in a population exhibiting increased glucose affinity. Physiological short-term adaptation to glucose-limitation was achieved by upregulation of 12 proteins, namely MglB, MalE, ArgT, DppA, RbsB, YdcS, LivJ (precursor), UgpB (precursor), AceA, AldA, AtpA and GatY. Eight of these proteins are periplasmic binding proteins of ABC transporters. Most of them are not involved in glucose transport regulons, but rather in chemotaxis and transport of other substrates, whereas MalE and MglB have previously been shown to belong to transport systems important in glucose transport under glucose-limited conditions. Evolution under low glucose concentration led to an up to 10-fold increase in glucose affinity (from a K(s) of 366 +/- 36 microg l(-1) at the beginning to 44 +/- 7 microg l(-1)). The protein pattern of a "500-h-old" continuous culture showed a highly increased expression of MglB and MalE as well as of the regulator protein MalI. When adapted cells taken from the "500-h-old" continuous culture were transferred to batch culture, an increased expression of MalE was observed, compared with cells from un-adapted batch-grown cells. Otherwise, no significant changes were observed in the protein pattern of batch-grown populations before and after 500 h of evolution in the glucose-limited continuous culture.

Biological Evolution↗
PubMed2001

The relationship between body mass index and self-reported functional limitation among older adults: a gender difference.

OBJECTIVES: To determine whether there is a gender difference in how body mass index (BMI) relates to self-reported functional limitation. Also, to evaluate whether the method of categorizing BMI changes the observed results. DESIGN: Cross-sectional cohort study. SETTING: Rural Pennsylvania. PARTICIPANTS: A total of 7,120 male (n = 3,312) and female (n = 3,808) community-dwelling older adults enrolled in a Medicare managed-risk contract. MEASUREMENTS: All subjects completed a modified Level II Nutrition Risk Screen upon enrollment in the health plan. Height and weight were obtained by nursing personnel during an enrollment clinic visit. Subjects who reported 10 or more pounds weight loss in the previous 6 months were excluded. Logistic regression was used to evaluate the relationship between BMI and self-reported functional limitation separately for each sex, adjusting for age, depression, and polypharmacy. Two schemes were used to categorize BMI: equally distributed sex-specific quintiles and arbitrary division based on National Institutes of Health (NIH) Obesity Guidelines. RESULTS: How BMI relates to functional limitation depends upon both sex and method of categorizing BMI. When BMI was considered in gender-specific quintiles, women in the highest quintile of BMI had increased risk of functional impairment; there was no relationship between BMI and functional limitation for men. When BMI was categorized by the NIH obesity guidelines, both men and women with BMI >40 had significantly increased risk of functional limitation. CONCLUSIONS: The mechanisms behind gender discrepancy in self-reported functional limitation remain unclear. Studies may need to consider men and women separately, because how BMI relates to function depends on gender. Further research is needed to evaluate how changes in weight and body composition during middle and old age affect functional status.

Aged↗
PubMed2002

Percentage of body fat and body mass index are associated with mobility limitations in people aged 70 and older from NHANES III.

OBJECTIVES: To assess the association between functional limitations and body composition indices, including percentage of body fat, muscle mass, and body mass index (BMI). DESIGN: A cross-sectional, population-representative sample. SETTING: All noninstitutionalized people living in the United States (National Health and Nutrition Examination Survey). Data were collected between 1988 and 1994. PARTICIPANTS: One thousand five hundred twenty-six women and 1,391 men aged 70 and older. MEASUREMENTS: Independent variables included BMI, muscle mass, and percentage of body fat; the latter two were assessed using predictive equations. The dependent variable, functional limitations, was defined as difficulty in performing at least three of five functional living tasks, such as carrying a 10-pound bag of groceries. RESULTS: Women in the highest quintile for percentage of body fat and women with a BMI of 30 or greater were two times more likely to report functional limitations than women in the comparison groups. Similar, but weaker, relationships were found among men; men in the highest quintile for body fat and men with a BMI of 35 or greater were 1.5 times more likely to report limitations. Low muscle mass (sarcopenia) and sarcopenia in combination with high percentage of body fat (sarcopenic obesity) were not associated with a greater likelihood of reporting functional limitations. CONCLUSIONS: Prevention of excessive accumulation of body fat and maintenance of a BMI in the normal range may reduce the likelihood of functional limitations in old age.

Adipose Tissue↗