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PubMed2003

Relationship of employee-reported work limitations to work productivity.

BACKGROUND: Work limitation rates are crucial indicators of the health status of working people. If related to work productivity, work limitation rates may also supply important information about the economic burden of illness. OBJECTIVE: Our objective was to assess the productivity impact of on-the-job work limitations due to employees' physical or mental health problems. RESEARCH DESIGN: Subjects were asked to complete a self-administered survey on the job during 3 consecutive months. Using robust regression analysis, we tested the relationship of objectively-measured work productivity to employee-reported work limitations. SUBJECTS: We attempted to survey employees of a large firm within 3 different jobs. The survey response rate was 2245 (85.9%). Full survey and productivity data were available for 1827 respondents. MEASURES: Each survey included a validated self-report instrument, the Work Limitations Questionnaire (WLQ). The firm provided objective, employee-level work productivity data. RESULTS: In adjusted regression analyses (n = 1827), employee work productivity (measured as the log of units produced/hour) was significantly associated with 3 dimensions of work limitations: limitations handling the job's time and scheduling demands (P = 0.003), physical job demands (P = 0.001), and output demands (P = 0.006). For every 10% increase in on-the-job work limitations reported on each of the 3 WLQ scales, work productivity declined approximately 4 to 5%. CONCLUSION: Employee work limitations have a negative impact on work productivity. Employee assessments of their work limitations supply important proxies for the economic burden of health problems.

Adolescent↗
PubMed1991

Limitations of Photosynthesis in Pinus taeda L. (Loblolly Pine) at Low Soil Temperatures.

The relative importance of stomatal and nonstomatal limitations to net photosynthesis (A) and possible signals responsible for stomatal limitations were investigated in unhardened Pinus taeda seedlings at low soil temperatures. After 2 days at soil temperatures between 13 and 7 degrees C, A was reduced by 20 to 50%, respectively. The reduction in A at these moderate root-chilling conditions appeared to be the result of stomatal limitations, based on the decrease in intercellular CO(2) concentrations (c(i)). This conclusion was supported by A versus c(i) analysis and measurements of O(2) evolution at saturating CO(2), which suggested increases in stomatal but not biochemical limitations at these soil temperatures. Nonuniform stomatal apertures, which were demonstrated with abscisic acid, were not apparent 2 days after root chilling, and results of our A versus c(i) analysis appear valid. Bulk shoot water potential (psi) declined as soil temperature dropped below 16 degrees C. When half the root system of seedlings was chilled, shoot psi and gas-exchange rates did not decline. Thus, nonhydraulic root-shoot signals were not implicated in stomatal limitations. The initial decrease in leaf conductance to water vapor after root chilling appeared to precede any detectable decrease in bulk fascicle psi, but may be in response to a decrease in turgor of epidermal cells. These reductions in leaf conductance to water vapor, which occurred within 30 minutes of root chilling, could be delayed and temporarily reversed by reducing the leaf-to-air vapor-pressure deficit, suggesting that hydraulic signals may be involved in initiating stomatal closure. By independently manipulating the leaf-to-air vapor-pressure deficit of individual fascicles, we could induce uptake of water vapor through stomata, suggesting that nonsaturated conditions occur in the intercellular airspaces. There was an anomaly in our results on seedlings maintained for 2 days at soil temperatures below 7 degrees C. Lower A appeared primarily the result of nonstomatal limitations, based on large increases in calculated c(i) and A versus c(i) analysis. In contrast, measurements of O(2) evolution at saturating CO(2) concentrations implied nonstomatal limitations per se did not increase at these temperatures. One explanation for this paradox is that calculations of c(i) are unreliable at very low gas-exchange rates because of inadequate measurement resolution, and limitations of A are predominantly stomatal. An alternative interpretation is that increases in c(i) are real and the results from O(2)-evolution measurements are in error. The high CO(2) concentration used in O(2)-evolution measurements (15%) may have overcome nonstomatal limitations by enzymes that were down-regulated by a feedback mechanism. In this scenario, carbohydrate feedback limitations may be responsible for nonstomatal reductions in A after 2 days at soil temperatures below 7 degrees C.

Journal Article↗
PubMed1993

Safety limits for nutrient intakes: concepts and data requirements.

The possible quantitative methods calculating safety limits for nutrient intakes are related conceptually to those used to calculate safe limits for exposure to environmental chemicals and to the therapeutic index used to assess the relative safety of drugs. The impact of using a fixed SF has been compared with the use of variable SFs. Of the methods identified, the SRM gives lower limits than does the MPM. However, neither of these methods calculates safety limits below the RDA, even for nutrients with narrow margins of safety. The acceptability criteria for toxicity data for use in identifying safety limits are an issue of major importance and must be resolved before calculated limits may be used to support policy or regulatory decisions. An advantage of adopting a standard formula involving systematically varying SFs to calculate safety limits is that the margin of safety below the expected range of toxicity for each nutrient would be systematic, without having the safety limit for any nutrient regress below its RDA. Once the data acceptability criteria were met, the safety limit would be identified objectively. The confidence in and reasonableness of safety limits, regardless of the method used to define them, will be enhanced if the objectives, data criteria, and the quantitative method have been agreed upon ahead of time by groups responsible for nutrition and health policy. Even with such agreement, the confidence in using such procedures to support policy decisions will be improved by the extent and quality of the data base on toxicity and adverse reactions associated with consumption of excessive levels of the nutrients under consideration.

Adult↗
PubMed1974

Ribonucleic acid regulation in amino acid-limited cultures of Escherichia coli grown in a chemostat.

The regulation of ribonucleic acid (RNA) synthesis was examined in cultures of bacteria whose growth was limited in the chemostat by the supply of a required amino acid. Strains possessing the relaxed (relA) mutation accumulated excess RNA (relative to protein) at low growth rates when growth was limited by arginine, histidine, or cysteine but not when limited by methionine. In contrast, stringent (relA(+)) strains maintained a constant RNA/protein ratio with decreasing growth rate regardless of the amino acid used to limit growth. The presence of excess RNA in relaxed strains was accompanied by an absence of increase in RNA production upon addition of chloramphenicol, a lag upon shift-up in growth by addition of excess of the limiting amino acid, and a decreased rate of production of beta-galactosidase upon induction. Analysis of the RNA accumulated in relaxed strains indicated it was present as transfer RNA as well as 50S and 30S ribosomal subunits. Microscope examination of the relaxed strains during histidine-, arginine-, or cysteine-limited growth in the chemostat showed them to be 10 to 20 times longer in size than the stringent strains. Also, cell density was reduced to one-tenth when the increased size was observed. An analysis of the amount of ppGpp present in all slow-growing amino acid-limited cultures (relaxed and stringent) demonstrated that only basal levels of ppGpp were made. These data are consistent with the hypothesis that when growth is limited in the chemostat by an initiation event in protein synthesis, i.e., limited methionine, RNA regulation occurs in relaxed as well as stringent strains. Also, when other amino acids are limiting in concentration during translation, errors occur in relaxed strains, resulting in misread proteins.

Amino Acids↗
PubMed1994

Detection of expiratory flow limitation during mechanical ventilation.

Two new methods, application of negative pressure at the airway opening during expiration (NEP) and reduction of flow resistance by bypassing the expiratory line of the ventilator by exhaling into the atmosphere (ATM), were used to detect expiratory flow limitation in 12 semirecumbent (45 degree) mechanically ventilated patients, seven with chronic airway obstruction (CAO). An increase of expiratory flow with NEP or ATM, relative to the preceding control breath, was taken as indicating absence of expiratory flow limitation. By contrast, the portion of the tidal expiration over which there was no change in flow with NEP or ATM was considered as flow-limited. With NEP, nine patients exhibited flow limitation, six (all with CAO) were flow-limited over most of the tidal expiration (> 70% VT), and three at < 60% VT. Although the results with NEP and ATM were in general in good agreement, in the three non-flow-limited patients the ATM method gave erroneous results. Six patients were also studied supine, including two who were not flow-limited when semirecumbent: both became flow-limited when supine. We conclude that NEP provides a simple method to detect flow limitation in mechanically ventilated patients. The supine position enhances flow limitation.

Aged↗
PubMed1998

Assessment of inspiratory flow limitation invasively and noninvasively during sleep.

To define the standard of airway flow limitation, pharyngeal pressure and flow rate were measured during wakefulness and sleep in seven habitual snorers with widely varying degrees of sleep-induced increases in upper airway resistance. Inspiratory pressure:flow relationships were used to group breaths into four categories of flow limitation, including linear (Level 1), mildly alinear (Level 2), constant flow rate with no pressure dependence (Level 3), and decreasing flow rate throughout significant portions of inspiration, i.e., negative pressure dependence (Level 4). These pressure:flow rate gold standards of flow limitation were used to evaluate a flow limitation index derived from the time profile (or "shape") of three noninvasive estimates of flow rate: (1) pneumotach flow rate, (2) differentiated sum respiratory inductance plethysmography (RIP), and (3) nasal pressure. A nonflow limited template for each of these noninvasive measurements was taken from awake breaths and the difference in area determined between the template breath and each of the noninvasive signals measured during nonrapid eye movement (NREM) sleep. The noninvasive flow limitation indices were found to be effective in differentiating severe types of inspiratory flow limitation, i.e., Level 1 versus Level 3 or Level 4 (sensitivity/specificity > 80%). On the other hand, these indirect indices were not able to consistently detect mild levels of flow limitation (Level 1 versus Level 2; sensitivity/specificity = 62 to 72%); nor were these noninvasive estimates of flow rate "shape" sensitive to breaths with a high but fixed resistance throughout inspiration. The area index derived from measurements of pressure at the nares (Pn) was the most sensitive, nonperturbing, noninvasive measure of flow rate and flow limitation, and we recommend its use for recognizing most of the common types of moderate to severe levels of airway flow limitation in sleeping subjects.

Adult↗
PubMed2002

Design, limitations and sustained metabolic rate: lessons from small mammals.

Physiological limitations affect an organism's capacity to acquire and expend energy over long periods of activity. These limitations could be related to the central machinery used for acquiring, processing and allocating energy, or by the energy-consuming machinery. Another possibility is that the capacities of central and peripheral organs and tissues are co-adjusted, implying an optimized design. Given the important consequences that rates of energy expenditure have on many ecological aspects of animal life, we need to understand which factors impose ceilings on sustained metabolic rate. Ceilings on sustainable energy expenditure represent the limit below which all the activities performed by an individual must occur. There have been many studies of design constraints on energy budgets, but the different procedures used to identify the type of physiological limitation do not necessarily resolve which factors actually impose metabolic ceilings in small mammals, which precludes a clear understanding of the ecological and evolutionary consequences of design constraints on energy budgets. We propose that the following steps are necessary to identify the physiological limits on sustained metabolic rate: (1) combining peak energy demands to differentiate a central limitation from a peripheral limitation; (2) pushing the animals to their physiological limits (e.g. asymptotic food intake); (3) testing for a central excess capacity (if the limit is set peripherally), or a peripheral excess capacity (if there is a central limitation); (4) utilizing different levels of energy demand to test for symmorphosis.

Animals↗
PubMed2006

Clinical and radiographic indices associated with airflow limitation in patients with sarcoidosis.

BACKGROUND: Airflow limitation is found in some patients with sarcoidosis, and it is associated with a poor prognosis. The aim of this study was to investigate clinical and radiographic indices associated with airflow limitation in patients with sarcoidosis. METHODS: A prospective, observational study was performed on 228 consecutive sarcoidosis patients followed up at our patient clinic at the Central Clinic of Kyoto. Patients underwent pulmonary function tests, and high-resolution CT (HRCT) of the lung was evaluated for the presence of lymph node enlargement, lung opacity, reticular shadow, and thickening of bronchovascular bundles (BVB). Airflow limitation was defined as FEV(1)/FVC < 70%. Airway reversibility was tested in subjects with airflow limitation. The frequency of airflow limitation was evaluated, and clinical and radiographic parameters were compared between patients with and without airflow limitation. RESULTS: Among all 228 subjects, 20 subjects (8.8%) had airflow limitation, and none showed airway reversibility. Patients with airflow limitation were predominantly male, smokers, and had advanced chest radiographic stage, increased frequency of lung opacities, reticular shadows, and thickened BVB on HRCT. Stepwise regression analysis showed that chest radiographic stage IV, higher age, smoking, and thickened BVB were independently associated with lower FEV(1)/FVC. CONCLUSION: The frequency of airflow limitation was 8.8% in Japanese sarcoidosis patients. Chest radiographic stage IV, higher age, smoking, and thickened BVB were associated with airflow limitation in patients with sarcoidosis.

Adult↗
PubMedDate not supplied

Limited joint mobility in childhood diabetes: family studies.

We examined 204 persons with insulin-dependent diabetes mellitus (IDDM), aged 7-23 yr, and 336 of their first-degree relatives, to determine whether there is a genetic component to the development of limited joint mobility. Simple and multiplex pedigrees with IDDM were studied along with normal controls. Only 1 of 90 normal controls had joint stiffness. Among 225 nondiabetic parents of children with IDDM, 7 (3%) had joint limitation, compared with 42 (21%) of children and youth with IDDM. Only 1 of 108 nondiabetic siblings of diabetic probands had limitation. Three parents had adult-onset diabetes and all had limited joint mobility. None of the 8 nondiabetic relatives with joint limitation had diabetic probands with joint involvement; 5 of these 8 tested were negative for islet cell auto-antibodies. There were 11 IDDM multiplex families with at least one member having joint limitation. The concordance rate for limited joint mobility of persons with diabetes for more than 5 yr who were over 12 yr of age was 56%, not different from the 48% frequency in patients with IDDM who met these age and duration criteria. Thus, evidence that limited joint mobility is a metabolic consequence of diabetes includes the virtual absence of limitation among first-degree relatives of probands, including probands with joint stiffness, and that the frequency of joint involvement is not increased in first-degree relatives of patients with IDDM. Furthermore, two brothers with pancreatic hypoplasia and a non-HLA-associated form of IDDM were affected with limited joint mobility. Nonetheless, the expression of this complication must be influenced by host factors, since not all persons with IDDM develop it, and those who do have variable ages of onset without correlation to control measures.

Adolescent↗
PubMed2001

Limitation of life support in the critically ill: the Hong Kong perspective.

INTRODUCTION: Patients admitted to the intensive care unit (ICU) may not benefit from the life support provided and it may result in prolonged and unnecessary suffering. Limiting life-support therapy in this situation is an ethically acceptable practice in Western countries. Statements produced by professional bodies have been generally made from a Western perspective. Cultural influences, aspects of management and resource limitations may create differences, yet there is little information available on the ethical decision making processes involved in limitation of life support in Asian countries. This article reviews the processes involved in the limitation of life support in critically ill intensive care patients in the predominantly Chinese population of Hong Kong. METHODS: Direct and computerised search of locally available and international published research articles and opinions. RESULTS: Limitation of life-support therapy occurs in 23% to 61% of critically ill Chinese patients that die within the ICU which is comparable to figures presented in the Western literature. Relatives wish to be part of the decision making process when limitation of therapy is to be considered. A staff attitude of caring towards patient and family, a need for information from the doctor and staff, and competence in providing adequate treatment have been identified as important factors by relatives when limitation of life-support therapy was being discussed. CONCLUSIONS: Limitation of therapy in dying Chinese patients occurs in ICUs and, patients and relatives concur in 95% of cases with medical decisions to limit therapy in these patients. The importance of communication as well as a desire to participate in the decision-making process regarding limitation of therapy suggest similarities between Western and Asian expectations. More comprehensive data are required regarding end-of-life issues in the Asian context, especially in relation to the general population's perception as to the processes involved.

Critical Illness↗
PubMed2005

Prevalence of musculoskeletal activity limitation and associated factors among adults in the general population in the 1998 Quebec Health Survey.

OBJECTIVE: To estimate the prevalence of short term and longterm musculoskeletal activity limitation among the general adult population of the province of Quebec, and to identify which factors are associated with these limitations. METHODS: We analyzed cross-sectional data from the 1998 Quebec Health Survey. Logarithmic binomial regression models were used to estimate prevalence ratios of (1) short term activity limitation related to musculoskeletal disorders (MSD); and (2) longterm activity limitation related to MSD in relation to demographic and behavioral variables and comorbidity factors. RESULTS: About one-fifth of participants reporting short term activity limitation and one-third of participants reporting longterm activity limitation mentioned MSD as a cause. Multivariate analyses showed that higher age, lower income, being overweight, ill defined nervousness, and the number of traumatic events that occurred before age 18 years were significantly associated with short term and longterm activity limitation related to MSD, whereas being in the minority ethnic group was protective for both outcomes. Female sex, physical inactivity, being a former alcohol drinker, and mental disorders were also associated with longterm activity limitation. CONCLUSION: MSD are a major cause of activity limitation among adults from Quebec. With the aging population and the increasing prevalence of obesity, increasing prevalence of activity limitation related to MSD is to be expected.

Activities of Daily Living↗
PubMed1988

Limits of movement in the human knee. Effect of sectioning the posterior cruciate ligament and posterolateral structures.

We applied specific forces and moments to the knees of fifteen whole lower limbs of cadavera and measured, with a six degrees-of-freedom electrogoniometer, the position of the tibia at which the ligaments and the geometry of the joint limited motion. The limits were determined for anterior and posterior tibial translation, internal and external rotation, and varus and valgus angulation from zero to 90 degrees of flexion. The limits were measured in the intact knee and then the changes that occurred with removal of the posterior cruciate ligament, the lateral collateral ligament, the popliteus tendon at its femoral attachment, and the arcuate complex were measured. The cutting order was varied, allowing us to determine the changes in the limits that occurred when each structure was cut alone and the amount of motion of the joint that was required for each structure to become taut and to limit additional motion when the other supporting structures had been removed. Removal of only the posterior cruciate ligament increased the limit for posterior tibial translation, with no change in the limits for tibial rotation or varus and valgus angulation. The additional posterior translation was least at full extension and increased progressively, reaching 11.4 millimeters at 90 degrees of flexion. The progressive increase in posterior translation with flexion was apparently due to slackening of the posterior portion of the capsule, as the translation nearly doubled when the posterolateral structures subsequently were removed. Removal of only the posterolateral extra-articular restraints increased the amount of external rotation and varus angulation. The average increase in external rotation depended on the angle of flexion; it was greatest at 30 degrees of flexion and decreased with additional flexion. At 90 degrees of flexion, the intact posterior cruciate ligament limited the increase in external rotation to only 5.3 degrees, less than one-half of the 13.0-degree increase that occurred at 30 degrees of flexion. Subsequent removal of the posterior cruciate ligament markedly increased external rotation at 90 degrees of flexion, resulting in a total increase of 20.9 degrees. The limit for varus angulation was normal as long as the lateral collateral ligament was intact. When the lateral collateral ligament was cut, the limit increased 4.5 degrees (approximately 4.5 millimeters of additional joint opening) when the knee was partially flexed (to 15 degrees).(ABSTRACT TRUNCATED AT 400 WORDS)

Biomechanical Phenomena↗
PubMed2005

The influence of functional limitations and various demographic factors on self-reported activity restriction at older ages.

PURPOSE: The study analysed some differentials in self-reported restrictions for personal care activities. Activity restrictions are the result of basic functional limitations (vision, mobility...), but such limitations do not evenly reduce activity performance. We assessed how age, sex and the place of residence (household or institutions) changed the risk of reporting restrictions for similar functional problems. METHOD: We used the French disability survey data on personal care activity restrictions and functional limitations (physical, visual, time orientation) for people aged 55 years and older (n=16961). A logistic regression model shows the separate impact of the nature of functional limitations and of age, gender and residence on the risk of reported restrictions. RESULTS: Half of the people aged 55 and older reported functional problems; 20% of them also reported personal care activity restrictions. The probability of reporting restrictions was higher for people with several types of limitations, especially orientation and physical controlling for such limitations, the probability of restriction increased with age beyond 70, was higher for men than women below 70, and was higher in institutions than in households. CONCLUSION: Self-reported activity restrictions are not solely related to functional limitations but also to various demographic variables likely to modify the impact of these limitations on activity performance. These findings suggest studying differentials in the resources allowing to compensate limitations and to prevent reported restrictions.

Activities of Daily Living↗
PubMed2003

Limited versus severe Wegener's granulomatosis: baseline data on patients in the Wegener's granulomatosis etanercept trial.

OBJECTIVE: To report baseline data on 180 patients with Wegener's granulomatosis (WG) enrolled in the WG Etanercept Trial (WGET), and to examine demographic and clinical differences between patients with limited disease and those with severe disease. METHODS: Definitions of limited and severe disease were agreed upon by consensus of the investigators at a pretrial meeting and were incorporated into the protocol as a stratification criterion. These data were applied prospectively to the WGET patient cohort, based on clinical features and the intention to treat patients according to disease activity. Data related to disease onset, date of diagnosis, clinical features, antineutrophil cytoplasmic antibody assays, tissue biopsy findings, and other medical history were collected on a baseline medical history form. Physician-investigators from each center participated in the development of this form, and all were certified in its use prior to the start of the trial. Selected data on patients who were screened for the trial but were not enrolled were also collected. RESULTS: Several significant differences between the limited and severe disease subsets were observed. Patients with limited disease were nearly a decade younger at disease onset compared with patients with severe disease. Thirty-three percent of patients with severe disease were women, compared with 58% of those with limited disease. Despite their younger age at symptom onset, patients with limited disease tended to have longer disease duration, a greater likelihood of experiencing exacerbation of previous disease following a period of remission, and a higher prevalence of destructive upper respiratory tract disorders at the time of enrollment (e.g., saddle-nose deformity). Patients with limited WG were less likely than those with severe disease to have antibodies to either proteinase 3 or myeloperoxidase. Patients with severe disease had a higher likelihood of previous thyroid disease, particularly either Graves' disease or Hashimoto thyroiditis, suggesting the possibility of different pathogenetic factors within these disease subsets. Other observed differences between these subsets, such as the greater frequency of alveolar hemorrhage in the severe disease group, were related to the a priori definitions of limited and severe disease. CONCLUSION: There are significant differences between patients with limited WG and those with severe WG with regard to sex, age, the likelihood of recurrent disease, the risk of damage in certain organ systems, and, possibly, etiologic factors. These differences (and perhaps other differences that are currently unrecognized) in patient subsets may have implications for mechanisms of pathogenesis, prognosis, response to treatment, and the design of future clinical investigations.

Adult↗
PubMed2005

Reducing symptom limitations: a cognitive behavioral intervention randomized trial.

Until now, little research has been conducted examining the reactive dimension, or the degree to which a symptom limits an individual's life, in a multiplicity of symptoms. This research examines how problem-solving therapy organizes an intervention to decrease symptom limitations. The purpose was threefold: to determine if a cognitive behavioral intervention decreases the impact of symptom limitations among individuals newly diagnosed with cancer, who are receiving chemotherapy; to determine, after adjusting for covariates, how symptom limitations change over time; and to describe which symptoms are most limiting. This randomized control trial was conducted in two comprehensive and four community cancer centers. Two hundred thirty-seven individuals, aged 31-87, newly diagnosed with solid tumor cancers, participated. The experimental group (118 individuals) received a 10-contact, 18-week cognitive behavioral intervention focused on cancer- and chemotherapy-related symptoms. The control group (119 individuals) received conventional care. Interviews occurred at baseline, 10, 20, and 32 weeks. Data analysis used a two-level hierarchical linear model. Participants receiving the cognitive behavioral intervention had lower scores of symptom limitation than did participants in the control group. At the onset of the study, younger patients reported more symptom limitations than their older counterparts; however, this was reversed by the end of the study. The cognitive behavioral intervention was key to decreasing symptom limitations. Findings also suggest that nursing interventions may be particularly helpful to younger individuals in managing cancer-related symptom limitations.

Adult↗
PubMed1995

Induction of a metabolic switch in insect cells by substrate-limited fed batch cultures.

Insect cell metabolism was studied in substrate-limited fed batch cultures of Spodoptera frugiperda (Sf-9) cells. Results from a glucose-limited culture, a glutamine-limited culture, a culture limited in both glucose and glutamine, and a batch culture were compared. A stringent relation between glucose excess and alanine formation was found. In contrast, glucose limitation induced ammonium formation, while, at the same time, alanine formation was completely suppressed. Simultaneous glucose and glucosamine limitation suppressed both alanine and ammonium formation. Although the metabolism was influenced by substrate limitation, the specific growth rate was similar in all cultures. Alanine formation must involve incorporation of free ammonium, if ammonium formation is mediated by glutaminase and glutamate dehydrogenase, as our data suggest. On the basis of the results, two possible pathways for the formation of alanine in the intermediary metabolism are suggested. The cellular yield on glucose was increased 6.6 times during glucose limitation, independently of the cellular yield on glutamine, which was increased 50-100 times during glutamine limitation. The results indicate that alanine overflow metabolism is energetically wasteful and that glutamine is a dispensable amino acid for cultured Sf-9 cells. Preliminary data confirm that glutamine can be synthesized by the cells themselves in amounts sufficient to support growth.

Alanine↗
PubMed1995

Evaluation of noise-induced hearing loss by reference to the upper limit of hearing.

We have defined the upper limit of hearing as the maximum audible frequency measured with fixed intensity and changing frequency. We have previously established the standard upper limit ageing curves from the normal age variation in the upper limit of hearing. In the present study, we sought to clarify the effects of occupational noise on the upper limit of hearing. We measured the upper limit of hearing in 239 healthy male workers (478 ears) exposed to intensive occupational noise. Their age variation in the upper limit of hearing was compared with the standard upper limit ageing curves in males. There were statistically significant deteriorations. Even if the ears that had normal hearing levels (35 dB or less) were selected, deterioration in the upper limit of hearing was noticeable. The upper limit of hearing may serve as clinically useful information on the hearing impairment that precedes noticeable hearing impairment in conventional audiometry for workers exposed to intensive occupational noise.

Adolescent↗
PubMed1986

The effect of the dissolved oxygen concentration and anabolic limitations on the behaviour of Rhizobium ORS571 in chemostat cultures.

Chemostat cultures of Rhizobium ORS571 limited by the supply of oxygen or an anabolic substrate contained poly-beta-hydroxybutyrate (PHB). Low amounts of PHB (about 10%) were present in ammonia- or nitrate-limited cultures; higher amounts were found in Mg++-limited cultures (about 20%) and in oxygen-limited nitrogen-fixing cultures (37%). A method is described to calculate YATP values (g PHB-free biomass . mol-1 ATP) from the Ysucc values (g dry wt . mol-1 succinate) measured. Ysucc and YATP values in cultures limited by the supply of an anabolic substrate and in the oxygen-limited ammonia-assimilating culture were much lower than the values found in the PHB-free succinate-limited cultures. This shows that uncoupling of growth and energy production occurred. Therefore, H2/N2 ratio (mol hydrogen formed per mol nitrogen fixed) in nitrogen-fixing cultures could not be calculated from the comparison of the YATP value found in the nitrogen-fixing culture and the value found in the corresponding ammonia-assimilating culture. Although the optimal dissolved oxygen concentration (d.o.c.) for nitrogen-fixing cultures of Rhizobium ORS571 is 5 or 10 microM, nitrogen-fixing cultures could be obtained up to a d.o.c. of 40 microM. Not only nitrogenase but also hydrogenase was active at this d.o.c. However, accumulation of PHB (10%) may indicate that cultures grown at unfavourable oxygen concentrations (15-40 microM O2) were N-limited rather than energy-limited, which may be the result of partial inactivation or repression of nitrogenase at a higher d.o.c.

Adenosine Triphosphate↗