Acute CO2 tolerance in fishes is associated with air breathing but not the Root effect, red cell ßNHE, or habitat.

High CO2 (hypercapnia) can impose significant physiological challenges associated with acid-base regulation in fishes, impairing whole animal performance and survival. Unlike other environmental conditions such as temperature and O2, the acute CO2 tolerance thresholds of fishes are not understood. While some fish species are highly tolerant, the extent of acute CO2 tolerance and the associated physiological and ecological traits remain largely unknown. To investigate this, we used a recently developed ramping assay, termed the Carbon Dioxide maximum (CDmax), that increases CO2 exposure until loss of equilibrium (LOE) is observed. We investigated if there was a relationship between CO2 tolerance and the Root effect, ß-adrenergic sodium proton exchanger (ßNHE), air-breathing, and fish habitat in 17 species. We hypothesized that CO2 tolerance would be higher in fishes that lack both a Root effect and ßNHE, breathe air, and reside in tropical habitats. Our results showed that CDmax ranged from 2.7 to 26.7 kPa, while LOE was never reached in four species at the maximum PCO2 we could measure (26.7 kPa); CO2 tolerance was only associated with air-breathing, but not the presence of a Root effect or a red blood cell (RBC) ßNHE, or fish habitat. This study demonstrates that the diverse group of fishes investigated here are incredibly tolerant of CO2 and that although this tolerance is associated with air-breathing, further investigations are required to understand the basis for CO2 tolerance.

Preferential intracellular pH regulation is a common trait amongst fishes exposed to high environmental CO2.

Acute (<96 h) exposure to elevated environmental CO2 (hypercarbia) induces a pH disturbance in fishes that is often compensated by concurrent recovery of intracellular and extracellular pH (pHi and pHe, respectively; coupled pH regulation). However, coupled pH regulation may be limited at CO2 partial pressure (PCO2 ) tensions far below levels that some fishes naturally encounter. Previously, four hypercarbia-tolerant fishes had been shown to completely and rapidly regulate heart, brain, liver and white muscle pHi during acute exposure to >4 kPa PCO2  (preferential pHi regulation) before pHe compensation was observed. Here, we test the hypothesis that preferential pHi regulation is a widespread strategy of acid-base regulation among fish by measuring pHi regulation in 10 different fish species that are broadly phylogenetically separated, spanning six orders, eight families and 10 genera. Contrary to previous views, we show that preferential pHi regulation is the most common strategy for acid-base regulation within these fishes during exposure to severe acute hypercarbia and that this strategy is associated with increased hypercarbia tolerance. This suggests that preferential pHi regulation may confer tolerance to the respiratory acidosis associated with hypercarbia, and we propose that it is an exaptation that facilitated key evolutionary transitions in vertebrate evolution, such as the evolution of air breathing.

The effect of substrate rearing on growth, aerobic scope and physiology of larval white sturgeon Acipenser transmontanus.

The effect of substratum on growth and metabolic rate was assessed in larval white sturgeon Acipenser transmontanus. Yolk-sac larvae (YSL) were reared in bare tanks or tanks with gravel as substratum from hatch until approximately 16 days post hatch (dph). The effect of an artificial substratum was also evaluated on growth alone. Substratum had a significant effect on mass, with larvae reared in gravel and artificial substrata being larger than those reared without substratum. Routine metabolic rates were significantly lower and relative aerobic scope (the difference between maximum and routine metabolic rate) was significantly higher for YSL and feeding larvae (FL) reared in gravel relative to those reared in bare tanks, particularly before fish started feeding exogenously. Furthermore, gravel-reared larvae had higher whole-body glycogen concentrations relative to bare-tank-reared larvae. Routine factorial scope (maximum metabolic rate divided by routine metabolic rate) was relatively low in all treatments (< 1·7) indicating a limited ability to elevate metabolic rate above routine early in development and mass exponents for metabolic rate exceeded 1. Taken together, these data indicate that YSL reared without substratum may divert more of their energy to non-growth related processes impairing growth. This finding underscores the importance of adequate rearing substratum for growth of A. transmontanus and may provide support for habitat restoration and alternative hatchery rearing methods associated with sturgeon conservation.

Preferential intracellular pH regulation represents a general pattern of pH homeostasis during acid-base disturbances in the armoured catfish, Pterygoplichthys pardalis.

Preferential intracellular pH (pHi) regulation, where pHi is tightly regulated in the face of a blood acidosis, has been observed in a few species of fish, but only during elevated blood PCO2. To determine whether preferential pHi regulation may represent a general pattern for acid-base regulation during other pH disturbances we challenged the armoured catfish, Pterygoplichthys pardalis, with anoxia and exhaustive exercise, to induce a metabolic acidosis, and bicarbonate injections to induce a metabolic alkalosis. Fish were terminally sampled 2-3 h following the respective treatments and extracellular blood pH, pHi of red blood cells (RBC), brain, heart, liver and white muscle, and plasma lactate and total CO2 were measured. All treatments resulted in significant changes in extracellular pH and RBC pHi that likely cover a large portion of the pH tolerance limits of this species (pH 7.15-7.86). In all tissues other than RBC, pHi remained tightly regulated and did not differ significantly from control values, with the exception of a decrease in white muscle pHi after anoxia and an increase in liver pHi following a metabolic alkalosis. Thus preferential pHi regulation appears to be a general pattern for acid-base homeostasis in the armoured catfish and may be a common response in Amazonian fishes.

Development of an electronic medical record based intervention to improve medical care of osteoporosis.

UNLABELLED: Osteoporosis is infrequently addressed during hospitalization for osteoporotic fractures. An EMR-based intervention (osteoporosis order set) was developed with physician and patient input. There was a trend toward greater calcium supplementation from July 2008 to April 2009 (s = 0.058); however, use of antiresorptives (13%) or discharge instructions for BMD testing and osteoporosis treatment (10%) remained low. INTRODUCTION: Osteoporosis is infrequently addressed during hospitalization for osteoporotic fractures. The study population consisted of patients over 50 years of age. METHODS: Northwestern Memorial Hospital is a tertiary care academic hospital in Chicago. This study was conducted from September 1, 2007 through June 30, 2009. RESULTS: Physicians reported that barriers to care comprised nonacute nature of osteoporosis, belief that osteoporosis should be addressed by the PCP, low awareness of recurrent fractures, and radiographs with terms such as "compression deformity", "wedge deformity", or "vertebral height loss" which in their opinion were not clearly indicative of vertebral fractures. An EMR-based intervention was developed with physician and patient input. Over the evaluation period, 295 fracture cases in individuals over the age of 50 years in the medicine floors were analyzed. Mean age was 72 ± 11 years; 74% were female. Sites of fracture included hip n = 78 (27%), vertebral n = 87 (30%), lower extremity n = 61 (21%), upper extremity n = 43 (15%) and pelvis n = 26 (9%). There was no increase in documentation of osteoporosis in the medical record from pre- to post-EMR implementation (p = 0.89). There was a trend toward greater calcium supplementation from July 2008 to April 2009 (p = 0.058); however, use of antiresorptives (13%) or discharge instructions for BMD testing and osteoporosis treatment (10%) remained low. CONCLUSION: An electronic medical record intervention without electronic reminders created with physician input achieves an increase in calcium supplementation but fails to increase diagnosis or treatment for osteoporosis at the time of hospitalization for a fragility fracture.

Patterns of nurse-physician communication and agreement on the plan of care.

BACKGROUND: Interdisciplinary communication is critically important to provide safe and effective care, yet it has been inadequately studied for hospitalised medical patients. Our objective was to characterise nurse-physician communication and their agreement on patients' plan of care. METHODS: During a one-month period, randomly selected hospitalised patients, their nurses and their physicians were interviewed. Nurses and physicians were asked to identify one another, whether communication had occurred, and about six aspects of the plan of care. Two internists rated nurse-physician agreement on aspects of the plan of care as none, partial or complete agreement. Measures included the percentage of nurses and physicians able to identify one another and reporting communication and the percentage of nurse-physician pairs in agreement on aspects of the plan of care. RESULTS: 310 (91%) and 301 (88%) of 342 eligible nurses and physicians completed interviews. Nurses correctly identified patients' physicians 71% of the time and reported communicating with them 50% of the time. Physicians correctly identified the patients' nurses 36% of the time and reported communicating with them 62% of the time. Physicians and nurses showed no agreement on aspects of the plan of care ranging from 11% for planned procedures to 42% for medication changes. CONCLUSIONS: Nurses and physicians did not reliably communicate with one another and were often not in agreement on the plan of care for hospitalised medical patients.

Complete intracellular pH protection during extracellular pH depression is associated with hypercarbia tolerance in white sturgeon, Acipenser transmontanus.

Sturgeons are among the most CO2 tolerant of fishes investigated to date. However, the basis of this exceptional CO2 tolerance is unknown. Here, white sturgeon, Acipenser transmontanus, were exposed to elevated CO2 to investigate the mechanisms associated with short-term hypercarbia tolerance. During exposure to 1.5 kPa Pco2, transient blood pH [extracellular pH (pHe)] depression was compensated within 24 h and associated with net plasma HCO3- accumulation and equimolar Cl- loss, and changes in gill morphology, such as a decrease in apical surface area of mitochondrial-rich cells. These findings indicate that pHe recovery at this level of hypercarbia is accomplished in a manner similar to most freshwater teleost species studied to date, although branchial mechanisms involved may differ. White sturgeon exposed to more severe hypercarbia (3 and 6 kPa Pco2) for 48 h exhibited incomplete pH compensation in blood and red blood cells. Despite pHe depression, intracellular pH (pHi) of white muscle, heart, brain, and liver did not decrease during a transient (6 h of 1.5 kPa Pco2) or prolonged (48 h at 3 and 6 kPa Pco2 blood acidosis. This pHi protection was not due to high intrinsic buffering in tissues. Such tight active cellular regulation of pHi in the absence of pHe compensation represents a unique pattern for non-air-breathing fishes, and we hypothesize that it is the basis for the exceptional CO2 tolerance of white sturgeon and, likely, other CO2 tolerant fishes. Further research to elucidate the specific mechanisms responsible for this tremendous pH regulatory capacity in tissues of white sturgeon is warranted.

The effects of variable water salinity and ionic composition on the plasma status of the Pacific Hagfish (Eptatretus stoutii).

Hagfish are the most pleisiomorphic extant craniates, and based on the similarity of ionic concentrations between their internal milieu and seawater (SW), they have long been touted as a model for osmo- and ionoconformation. As a result, the lack of direct symmetry between hagfish plasma and the environment with respect to [Na(+)], [Cl(-)], [Mg(2+)], and [Ca(2+)] have been left largely unexplored. In order to determine the capacity of hagfish to regulate their blood compartment, we exposed Pacific hagfish (Eptatretus stoutii) to 24, 32, 40, and 48 g/l salinity for 48 h, as well as to two treatments where a portion of the water [Na(+)] was replaced with either Mg(2+) or Ca(2+) at constant salinity for up to 6 days. Following exposure, we measured plasma ion status, pH, and total carbon dioxide (TCO(2)). As expected, our results indicated that hagfish had no capacity to regulate plasma osmolality, [Na(+)], or [Cl(-)], but they did maintain plasma [Mg(2+)] and [Ca(2+)] nearly constant despite fluctuation of environmental salinity or elevated water [Mg(2+)] and [Ca(2+)] (two- and sevenfold, respectively). Furthermore, exposure to elevated water [Mg(2+)] and [Ca(2+)] resulted in a large increase of plasma TCO(2) with little to no increase of plasma pH. We concluded that hagfish may control plasma [Mg(2+)] and [Ca(2+)] at levels below that of their environment via secretion of HCO(3) (-), similar to the mechanisms described in the intestine of teleosts. We speculate that secretion of HCO(3) (-) likely evolved to maintain plasma [Mg(2+)] and [Ca(2+)] below environmental levels (both of which negatively affect nervous function and muscle contraction if elevated), and was an exaptation for the development of water-absorption mechanisms in the intestine of marine osmoregulators. The ancestors of modern hagfish are thought to have never entered freshwater, thus investigations into their ionoregulatory ability potentially have profound implications regarding the evolution of fishes.

Structural study of K(x)Na(1 - x)NbO(3) (KNN) for compositions in the range x = 0.24-0.36.

The structure of the A-site substituted perovskite K(x)Na(1 - x)NbO(3), x = 0.24-0.36, where a phase boundary was previously reported, has been determined by high-resolution X-ray powder and neutron powder diffraction studies. The structure of the x = 0.3 compound was refined in the monoclinic space group Pm at 293 K and in P4mm at 523 K. The Glazer tilt system of the room-temperature monoclinic phase is a(0)b(+)c(0), which has implications for the nature of the next symmetry change with composition towards pure potassium niobate. A phase-coexistence region at the transition between monoclinic and tetragonal phases was also identified, consistent with a first-order phase boundary. There is also evidence for an intermediate oxygen-octahedra tilted tetragonal phase.

A validation of intracellular pH measurements in fish exposed to hypercarbia: the effect of duration of tissue storage and efficacy of the metabolic inhibitor tissue homogenate method.

This study assessed the effect of tissue storage duration and accuracy of the metabolic inhibitor tissue homogenate (MITH) method on intracellular pH (pHi) values of tissues of white sturgeon Acipenser transmontanus during hypercarbia. No effect of storage in liquid nitrogen of up to 30 days was observed and MITH appears appropriate for measurement of pH in fish exposed to up to 10% CO2 (10000 Pa pCO2).

Juvenile atlantic and shortnose sturgeons (family: Acipenseridae) have different hematological responses to acute environmental hypoxia.

Experiments were conducted to determine the behavioral and physiological responses to acute hypoxic challenges in Atlantic (Acipenser oxyrinchus) and shortnose (Acipenser brevirostrum) sturgeons. We measured the ventilatory rate following a 45-mmHg hypoxic challenge, as well as a variety of hematological parameters, including O2 transport and hormonal, ionic, and metabolic variables, following a 1-h exposure to either 75- or 30-mmHg hypoxic challenges. Compared to fish in normoxic conditions (Pwo2 150 mmHg), juveniles of both species increased their ventilatory rate by approximately 40% when exposed to a 1-h challenge at 45 mmHg Pwo2. Hematological variables (e.g., hematocrit, hemoglobin, and Na+ and Cl- levels) did not change substantially following a 1-h challenge at 75 mmHg Pwo2. Conversely, a severe hypoxic challenge of 30 mmHg caused changes in several hematological variables (e.g., whole blood glucose and plasma cortisol and lactate levels). Most of these hematological parameters returned to prehypoxic levels within 2 h. Severe environmental hypoxia elicited the same basic pattern of response in both species; however, maximal plasma lactate levels were higher in Atlantic sturgeons, and maximal cortisol levels were higher in shortnose sturgeons. Whether these species differences are related to dissimilar hypoxia-tolerance, ecological, and/or endocrinological characteristics between these two species is not entirely clear.

The effects of trace metal exposure on agonistic encounters in juvenile rainbow trout, Oncorhynchus mykiss.

The effects of five trace metals, copper, cadmium, nickel, zinc and lead (presented as soluble salts) on the ability of juvenile rainbow trout to form social relationships were investigated. Comparable concentrations of the five metals in relation to their acute 96 h LC50s (concentration at which population mortality=50% at 96 h) were used (i.e. 15% of the 96 h LC50) and water quality parameters (hardness=120 mg l(-1) as CaCO(3), pH 8; DOC=3 mg l(-1)) were kept constant throughout. In the first experiment, trout exposed to sublethal concentrations of cadmium for 24 h displayed significantly lower numbers of aggressive attacks during pair-wise agonistic encounters than fish paired in the copper, nickel, zinc, lead and control water. In a second experiment, fish were exposed to the same concentration of metal for 24 h, and then returned to normal water for 24 h. When these metal pre-exposed fish were paired with non-exposed fish only cadmium pre-exposure had a significant effect on social interaction. All of the cadmium pre-exposed fish became subordinate when paired with non-exposed fish, whereas the probability of a fish pre-exposed to copper, nickel, zinc or lead becoming subordinate did not significantly differ from random. Therefore, at around 15% of the 96 h LC50, different metals exert different effects on the social behaviour of fish, suggesting potential implications for social structure and population stability.

The effect of pneumonia on mortality among patients hospitalized for acute stroke.

OBJECTIVE: To determine the effect of pneumonia on 30-day mortality in patients hospitalized for acute stroke. METHODS: Subjects in the initial cohort were 14,293 Medicare patients admitted for stroke to 29 greater Cleveland hospitals between 1991 and 1997. The relative risk (RR) of pneumonia for 30-day mortality was determined in a final cohort (n = 11,286) that excluded patients dying or having a do not resuscitate order within 3 days of admission. Clinical data were obtained from chart abstraction and were merged with Medicare Provider Analysis and Review files to obtain deaths within 30 days. A predicted-mortality model (c-statistic = 0.78) and propensity score for pneumonia (c-statistic = 0.83) were used for risk adjustment in logistic regression analyses. RESULTS: Pneumonia was identified in 6.9% (n = 985) of all patients and in 5.6% (n = 635) of the final cohort. The rates of pneumonia were higher in patients with greater stroke severity and features indicating general frailty. Unadjusted 30-day mortality rates were six times higher for patients with pneumonia than for those without (26.9% vs 4.4%, p < 0.001). After adjusting for admission severity and propensity for pneumonia, RR of pneumonia for 30-day death was 2.99 (95% CI 2.44 to 3.66), and population attributable risk was 10.0%. CONCLUSION: In this large community-wide study of stroke outcomes, pneumonia conferred a threefold increased risk of 30-day death, adding impetus to efforts to identify and reduce the risk of pneumonia in patients with stroke.

Health literacy and performance on the Mini-Mental State Examination.

The objectives of the study were to determine the relationship between functional health literacy and performance on the Mini-Mental State Examination (MMSE). New Medicare managed-care enrollees aged 65 years and older, living independently in the community in four US cities (Cleveland, Houston, Tampa, and Fort Lauderdale/Miami), were eligible to participate. In-home interviews were conducted to determine demographics and health status, and interviewers then administered the Short Test of Functional Health Literacy in Adults (S-TOFHLA) and the MMSE. We then determined the relationship between functional health literacy and the MMSE, including total scores, subscale scores (orientation to time, orientation to place, registration, attention and calculation, recall, language, and visual construction), and individual items. Functional health literacy was linearly related to the total MMSE score across the entire range of S-TOFHLA scores (R(2) = 0.39, p < 0.001). This relationship between health literacy and MMSE was consistent across all MMSE subscales and individual items. Adjustment for chronic conditions and self-reported overall health did not change the relationship between health literacy and MMSE score. Health literacy was related to MMSE performance even for subscales of the MMSE that were not postulated to be directly dependent on reading ability or education (e.g. delayed recall). These results suggest that the lower MMSE scores for patients with low health literacy are only partly due to 'test bias' and also result from true differences in cognitive functioning. 'Adjusting' MMSE scores for an individual's functional health literacy may be inappropriate because it may mask true differences in cognitive functioning.

Lack of health insurance and decline in overall health in late middle age.

BACKGROUND: The number of adults in their 50s and 60s in the United States who do not have health insurance is increasing. This group may be particularly vulnerable to the ill effects of being uninsured. METHODS: We conducted a prospective cohort study using files from the Health and Retirement Study, a national survey of adults who were 51 to 61 years old in 1992. We determined the risks of a major decline in overall health and of the development of new physical difficulties between 1992 and 1996 for participants who were continuously uninsured (uninsured in 1992 and in 1994), those who were intermittently uninsured (uninsured either in 1992 or in 1994), and those who were continuously insured. We used logistic regression to determine the independent effects of being uninsured on health outcomes after adjustment for base-line sociodemographic factors, preexisting medical conditions, and types of health-related behavior such as smoking and alcohol use. RESULTS: We analyzed data for 7577 participants. The 717 continuously uninsured participants and the 825 intermittently uninsured participants were more likely than the 6035 continuously insured participants to have a major decline in overall health between 1992 and 1996 (21.6 percent, 16.1 percent, and 8.3 percent of the three groups, respectively; P<0.001 for both comparisons). According to a multivariate analysis, the adjusted relative risk of a major decline in overall health was 1.63 (95 percent confidence interval, 1.26 to 2.08) for continuously uninsured participants and 1.41 (95 percent confidence interval, 1.11 to 1.78) for intermittently uninsured participants, as compared with continuously insured participants. A new difficulty in walking or climbing stairs was also more likely to develop in the continuously or intermittently uninsured participants than in the continuously insured participants (28.8 percent, 26.4 percent, and 17.1 percent of the three groups, respectively; P<0.001 for both comparisons). The adjusted relative risk of such a new physical difficulty was 1.23 (95 percent confidence interval, 1.02 to 1.47) for the continuously uninsured participants and 1.26 (95 percent confidence interval, 1.01 to 1.54) for the intermittently uninsured participants. CONCLUSIONS: The lack of health insurance is associated with an increased risk of a decline in overall health among adults 51 to 61 years old.

Antihypertensive medication use in Hispanic adults: a comparison with black adults and white adults.

BACKGROUND: Variations in awareness, treatment, and control of hypertension among different racial/ethnic groups have been widely reported. It is unclear whether these differences are explained fully by differences in socioeconomic status, insurance coverage, health status, and health behaviors, or whether these differences indicate that racial/ethnic subgroups have unique barriers to hypertension control. OBJECTIVES: Determine whether there are significant differences between racial/ethnic groups in medication use for hypertension after adjusting for potentially confounding variables. RESEARCH DESIGN: Cross-sectional analysis of the 1992 Health and Retirement Study. SUBJECTS: 2450 non-Hispanic white, 939 non-Hispanic black, and 345 Hispanic participants, ages 51 to 61, reporting a history of hypertension. MEASURES: Self-reported current antihypertensive medication use. We used logistic regression to adjust for demographics, socioeconomic status, health status, insurance, and health risk behaviors. RESULTS: 63.6% of white adults, 72.6% of black adults, and 52.5% of Hispanic adults reported current medication use to control hypertension (P <0.001 across all three groups). In stratified analysis, the lower rate of use for Hispanic adults was consistent regardless of gender, insurance coverage, or health status. After controlling for all variables, the adjusted prevalence for Hispanic adults was 50.8% and 73.3% for black adults. CONCLUSIONS: The differences in antihypertensive medication use between white adults, black adults, and Hispanic adults, particularly the markedly lower rates among Hispanic adults, are not explained by differences in demographics, socioeconomic status, health insurance coverage, health status, or health risk behaviors. Alternative explanations for these results and areas for future research and intervention are explored.

Does physician gender affect satisfaction of men and women visiting the emergency department?

OBJECTIVE: To assess the association of physician gender with patient ratings of physician care. DESIGN: Interviewer-administered survey and follow-up interviews 1 week after emergency department (ED) visit. SETTING: Public hospital ED. PATIENTS/PARTICIPANTS: English- and Spanish-speaking adults presenting for care of nonemergent problems; of 852 patients interviewed in the ED who were eligible for follow-up, 727 (85%) completed a second interview. MEASUREMENTS AND MAIN RESULTS: We conducted separate ordered logistic regressions for women and men to determine the unique association of physician gender with patient ratings of 5 interpersonal aspects of care, their trust of the physician, and their overall ratings of the physician, controlling for patient age, health status, language and interpreter status, literacy level, and expected satisfaction. Female patients trusted female physicians more (P =.003) than male physicians and rated female physicians more positively on the amount of time spent (P =.01), on concern shown (P =.04), and overall (P =.03). Differences in ratings by female patients of male and female physicians in terms of friendliness (P =.13), respect shown (P =.74), and the extent to which the physician made them feel comfortable (P =.10) did not differ significantly. Male patients rated male and female physicians similarly on all dimensions of care (overall, P =.74; friendliness, P =.75; time spent, P =.30; concern shown, P =.62; making them feel comfortable, P =.75; respect shown, P =.13; trust, P =.92). CONCLUSIONS: Having a female physician was positively associated with women's satisfaction, but physician gender was not associated with men's satisfaction. Further studies are needed to identify reasons for physician gender differences in interpersonal care delivered to women.