In situ metal imaging and Zn ligand-speciation in a soil-dwelling sentinel: complementary electron microprobe and synchrotron microbeam X-ray analyses.

Understanding the relationships between accumulated metal speciation in cells and tissues of ecologically significant taxa such as earthworms will improve risk assessments. Synchrotron-based µ-focus X-ray spectroscopy was used to detect, localize, and determine ligand-speciation of Zn and Pb in thin sections of two epigeic earthworm species collected from a Pb/Zn-mine soil. The findings indicated that Zn and Pb partition predominantly as typical hard acids (i.e., strong affinities for O-donors) within liverlike chloragocytes. Moreover, Zn speciation was very similar in the chloragog and intestinal epithelia but differed subtly in the kidneylike nephridial tubules; neither Zn nor Pb was detectable in the ventral nerve cord. High resolution X-ray mapping of high pressure-frozen, ultrathin, freeze-substituted sections in a transmission electron microscope (TEM), combined with conventional TEM structural analysis, identified a new cell type packed with highly organized rough endoplasmic reticulum and containing deposits of Cd (codistributed with S); there was no evidence that these cells are major depositories of Zn or Pb. These data may be used in a systems biology approach to assist in the interpretation of metal-evoked perturbations in whole-worm transcriptome and metabolome profiles.

Expressions of depression in rural women with chronic illness.

INTRODUCTION: Globally, chronic conditions have become the most prevalent and costly of health problems, imposing a growing drain on healthcare delivery systems and healthcare financing. Depressive symptoms and disorders are one of the most common complications of chronic illness and negatively impact one's perceived quality of life. In recent years, depression has been recognized as a major health problem for rural women. The purpose of this article is to describe the experience of depression in a sample of chronically ill rural women who participated in an online social-support and health education research project. METHODS: Middle-aged rural women with at least one chronic condition were recruited from the western USA to participate in the Women to Women (WTW) project, a 22 week computer-based intervention of virtual support and health education. The presence of depression was measured quantitatively using the Center for Epidemiologic Studies Depression Scale (CES-D). Messages posted by the women (n=82) to the online support forum were carefully examined for evidence of depressive symptomatology, perceptions of the relationship of depression to their chronic illnesses, and their strategies for coping with their depression. RESULTS: Of the 82 women who participated in the support intervention, 47 (57%) demonstrated clinically significant psychological distress at the time of enrollment into the WTW project by scoring 16 or above on the CES-D (range=0-48; x=19.27; sd=11.25). At the end of the computer intervention, complete data were available on 57 women. Of these, 24 (42%) scored 16 or above on the CES-D (range=0-49; x=15.74; sd=11.55) indicating continuing psychological distress. In all, 59 messages were coded 'depression'. The women's messages included descriptions of symptoms consistent with the literature (feelings of worthlessness and guilt; helplessness and hopelessness; alterations in sleep patterns; loss of energy). The interrelationship of depression and illness, pain, and seasonal weather variations was acknowledged; traditional and complementary healthcare treatments were discussed; relationships with healthcare providers and family and friends were described; and a variety of strategies used in coping with their depression were shared. CONCLUSIONS: Rural women with chronic illness struggle with depression. The description of their depressive symptomatology provides insight into the experience and may facilitate healthcare providers' ability to recognize depression and identify strategies to ameliorate the negative impact of depression in chronically ill rural women.

Glial cells of the oligodendrocyte lineage express both kainate- and AMPA-preferring subtypes of glutamate receptor.

mRNAs for AMPA- and kainate-preferring glutamate receptor subunits are expressed abundantly in the CNS, yet functional studies of neurons and glia from brain suggest selective expression of AMPA receptors. We now show that glial cells of the O-2A lineage express rapidly desensitizing responses to kainate, mRNAs for GluR6, GluR7, KA-1, and KA-2, rapidly desensitizing responses to AMPA, and mRNAs for GluR-B, -C, and -D. Analysis of glutamate receptor currents in single cells reveals two receptor populations with high and low affinity for kainate and different sensitivity for potentiation by concanavalin A and for block of desensitization by cyclothiazide. Our experiments describe the characterization of native kainate-preferring receptors in glia and reveal coexpression in single cells of functional AMPA- and kainate-preferring receptors.

Selective modulation of desensitization at AMPA versus kainate receptors by cyclothiazide and concanavalin A.

Potentiation by cyclothiazide of recombinant glutamate receptor responses in Xenopus oocytes showed absolute selectivity for AMPA versus kainate receptors. In contrast, concanavalin A strongly potentiated responses at kainate but not AMPA receptors. Rapid desensitization in HEK 293 cells transfected with AMPA receptors was blocked by cyclothiazide, but only weakly attenuated by concanavalin A. Desensitization at kainate receptors was blocked by concanavalin A but unaffected by cyclothiazide. Selective effects of these modulators following coexpression of subunits from different families suggest independent assembly of functional AMPA and kainate receptors. Northern blot analysis of mRNA for dorsal root ganglia revealed a predominant expression of GluR5, indicating that modulation of desensitization by concanavalin A but not cyclothiazide in sensory neurons accurately predicts subunit expression for native glutamate receptors.

Identifying individual scaffolding molecules in the postsynaptic density.

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 - August 7, 2008.

Adult weight management across the community: population-level impact of the LOSE IT to WIN IT challenge.

Objective: Excess body weight negatively impacts health, but there are few evaluations of low-intensity weight management challenge programs in defined populations. This study examined weight change in adults who participated in the LOSE IT to WIN IT (LIWI) health challenge in a US community. The community-level impact on body mass index was also explored. Methods: Body weight was analysed over 1 year in the cohort of LIWI enrolees, stratified by participants who were healthy weight or overweight/obese at baseline. Secondarily, a multiple cross-sectional analysis compared the 2.5-year trends in body mass index between community adults who did vs. did not participate in LIWI. Results: LOSE IT to WIN IT participants who were overweight/obese lost a mean (95% confidence interval) 1.6 (1.2, 2.0) kg (~2%) over 1 year (p < 0.001), whereas healthy weight participants lost 0.7 (0.3, 1.1) kg. Across the community, LIWI participants and non-participants both gained 0.4 kg m-2 over the 2.5-year study period (p = 0.884). Conclusions: LOSE IT to WIN IT was modestly effective among enrolees, resulting in a small weight loss of 2% over 1 year among those who were overweight/obese. However, LIWI did not impact weight gain in the community. To slow such community-level weight gain trends, weight management challenges must reach larger fractions of the populations that they target.

Access to and use of research by rural nurses.

INTRODUCTION: The use of relevant research findings to inform clinical practice is important for nurses, regardless of setting. Although there have been studies addressing the use of research among various practitioners, little is known about how nurses in rural areas access health information (specifically research findings), nor how such findings are incorporated into daily practice. The purpose of this study was to explore rural nurses' access, use and perceived usefulness of research for rural practice. METHODS: The study was conducted in a sparsely populated state located in the western part of the USA. An ethnographic method was chosen to answer the research questions for this descriptive study. Semi-structured interviews were conducted with 29 rural nurses from nine communities by graduate nursing students enrolled in a rural nursing course following in-class instruction and practice. Field notes taken by the students supplemented the interview data. The students' notes included a windshield survey or description of the context and location within which the participants lived and/or practiced as well as the interviewers' observations, thoughts and impressions about the research project. Interviews were audiotaped and transcribed verbatim. Once transcribed, the interview narratives, windshield data and field notes were analyzed by the students for common themes; the students then wrote and submitted papers to the faculty addressing the themes that emerged from their interviews. The analysis conducted by the faculty members included four sources of data: transcriptions of interviews; field notes; windshield data; and students' papers. The process of identifying themes was facilitated by using the software program NUD*IST (QSR International; Melbourne, VIC, Australia). Demographic information was entered into the Statistical Package for Social Scientists (SPSS Inc; Chicago, IL, USA) to compile descriptive information about the sample. FINDINGS: Twenty-seven female and two male nurses participated in the study. The nurses' ages ranged from 31-72 years and their experience in nursing spanned 3-50 years with a range of 1 to 35 years in rural nursing. The interviews revealed that most of the nurses used the term 'research' to mean 'gathering information'. When asked how often they used 'research' the responses ranged from 2-3 times per day to 2-3 times per month. The preferred means of obtaining information was asking a colleague. Additional resources included work-place journals, books, in-services, conferences and the internet. Twenty-three of the nurses reported having internet access at work; 25 had internet access at home. Supportive supervisors and articles in general nursing journals were identified as helpful. Barriers to using research included: lack of knowledge of research methods; lack of time at work or at home to look up information; and the lack of computers and internet access on the nursing units. When computers were available, the nurses reported that poor computer literacy decreased their ability to quickly find and evaluate information. Additional barriers included diminishing financial support from employers and the long travel distances required to attend conferences. The nurses reported finding little clinical research specifically related to rural practice. CONCLUSIONS: Education and mentorship is needed about how to evaluate the types and strength of evidence, access research using the internet, interpret findings, and incorporate evidence in clinical practice. Interventions that foster the appreciation and use of research by staff nurses and managers are needed in order to build an evidence based culture. Research is needed, specifically as related to rural clinical practice.

Inhibition of phosphatase activity facilitates the formation and maintenance of NMDA-induced calcium/calmodulin-dependent protein kinase II clusters in hippocampal neurons.

The majority of hippocampal neurons in dissociated cultures and in intact brain exhibit clustering of calcium/calmodulin-dependent protein kinase II (CaMKII) into spherical structures with an average diameter of 110 nm when subjected to conditions that mimic ischemia and excitotoxicity [Neuroscience 106 (2001) 69]. Because clustering of CaMKII would reduce its effective concentration within the neuron, it may represent a cellular strategy to prevent excessive CaMKII-mediated phosphorylation during episodes of Ca2+ overload. Here we employ a relatively mild excitatory stimulus to promote sub-maximal clustering for the purpose of studying the conditions for the formation and disappearance of CaMKII clusters. Treatment with 30 microM N-methyl-D-aspartic acid (NMDA) for 2 min produced CaMKII clustering in approximately 15% of dissociated hippocampal neurons in culture, as observed by pre-embedding immunogold electron microscopy. These CaMKII clusters could be labeled with antibodies specific to the phospho form (Thr286) of CaMKII, suggesting that at least some of the CaMKII molecules in clusters are autophosphorylated. To test whether phosphorylation is involved in the formation and maintenance of CaMKII clusters, the phosphatase inhibitors calyculin A (5 nM) or okadaic acid (1 microM) were included in the incubation medium. With inhibitors more neurons exhibited CaMKII clusters in response to 2 min NMDA treatment. Furthermore, 5 min after the removal of NMDA and Ca2+, CaMKII clusters remained and could still be labeled with the phospho-specific antibody. In contrast, in the absence of phosphatase inhibitors, no clusters were detected 5 min after the removal of NMDA and Ca2+ from the medium. These results suggest that phosphatases type 1 and/or 2A regulate the formation and disappearance of CaMKII clusters.

A study of patient acceptance of double-contrast barium enema and colonoscopy. Which procedure is preferred by patients?

To our knowledge, no previous study has addressed the question of which method of evaluation of the lower gastrointestinal tract is preferred by patients, air-contrast barium enema or colonoscopy. Over a four-month period, we asked 189 consecutive patients who had undergone colonoscopy to express their preference for either air-contrast barium enema or colonoscopy. A clear preference for colonoscopy was expressed by our patients in terms of comfort and polyp detection despite higher cost. Time lost from work and post-procedure constipation were significantly less for colonoscopy than for barium enema. These factors should be considered in the evaluation of suspected lower gastrointestinal tract disease.

Syntaxin 4 is concentrated on plasma membrane of astrocytes.

Syntaxins are a family of transmembrane proteins that participate in SNARE complexes to mediate membrane fusion events including exocytosis. Different syntaxins are thought to participate in exocytosis in different compartments of the nervous system such as the axon, the soma/dendrites or astrocytes. It is well known that exocytosis of synaptic vesicles at axonal presynaptic terminals involves syntaxin 1 but distributions of syntaxins on neuronal somal and dendritic, postsynaptic or astroglial plasma membranes are less well characterized. Here, we use pre-embedding immunogold labeling to compare the distribution of two plasma membrane-enriched syntaxins (1 and 4) in dissociated rat hippocampal cultures as well as in perfusion-fixed mouse brains. Comparison of Western blots of neuronal cultures, consisting of a mixture of hippocampal neurons and glia, with glial cultures, consisting of mostly astrocytes, shows that syntaxin 1 is enriched in neuronal cultures, whereas syntaxin 4 is enriched in glial cultures. Electron microscopy (EM)-immunogold labeling shows that syntaxin 1 is most abundant at the plasma membranes of axons and terminals, while syntaxin 4 is most abundant at astroglial plasma membranes. This differential distribution was evident even at close appositions of membranes at synapses, where syntaxin 1 was localized to the plasma membrane of the presynaptic terminal, including that at the active zone, while syntaxin 4 was localized to nearby peri-synaptic astroglial processes. These results show that syntaxin 4 is available to support exocytosis in astroglia.

Increased circulating concentration of the N-terminus of the atrial natriuretic factor prohormone in persons with pheochromocytomas.

To investigate the possible relationship of hypertension and the N-terminus of the atrial natriuretic factor (ANF) prohormone which contains two peptides [i.e. pro ANF-(1-30) and pro-ANF-(31-67)] with blood pressure-lowering effects, we examined the circulating levels of the N-terminus of the ANF prohormone in three patients with pheochromocytomas before surgery, during an increase in their blood pressure with surgical manipulation of their tumors, and after surgery when their blood pressures returned to normal. The circulating levels of the whole N-terminus [amino acids 1-98; pro-ANF-(1-98)] and pro-ANF-(31-67) from the midportion of the N-terminus of the ANF prohormone were increased 2-fold in patients with both extraadrenal and intraadrenal pheochromocytomas. In both the intraadrenal and extraadrenal patients N-terminus [pro-ANF-(1-98)] and pro-ANF-(31-67) circulating levels increased further during surgical manipulation and returned to normal after surgical removal of their respective tumors. Each of these pheochromocytomas was found to have pro-ANF-(1-30) and -(31-67)-binding sites that were functional, since they could enhance the guanylate cyclase-cGMP system 2-fold in these pheochromocytomas. The entire 126 amino acids of the prohormone were present within each of the pheochromocytomas, since both the whole N-terminus and C-terminus (i.e. ANF) of the prohormone were present. Examination of the pheochromocytomas by electron microscopy revealed electron-dense granules similar to those in the heart, which have been associated with the synthesis and storage of the ANF prohormone. We conclude that 1) the whole N-terminus [pro-ANF-(1-98)] and pro-ANF-(31-67) of the ANF prohormone circulate at higher concentrations in persons with pheochromocytomas and return to normal with removal of the tumors; 2) pheochromocytomas contain specific binding sites for pro-ANF-(1-30) and -(31-67); 3) these binding sites are functional, since pro-ANF-(1-30) and -(31-67) could enhance the enzyme guanylate cyclase within these tumors; and 4) the entire 126 amino acids of the ANF prohormone are present within these tumors, which have electron-dense granules associated with polypeptide hormone synthesis, suggesting that the ANF prohormone is being synthesized within the pheochromocytomas.

Characterization of Leydig cell protein kinase. Further studies in hormone action.

Leydig cell cAMP-dependent protein kinase has been characterized using rapid fractionation and optimal conditions to minimize proteolysis. DEAE-cellulose analysis showed a single Type I peak of cAMP binding and enzyme activity that eluted at 0.1 M KCl. Photoaffinity labelling with 8-azido[32P]cAMP followed by SDS-PAGE showed a doublet with Mr 54000 and 51000 for the peak fraction, while the original extract exhibited only the smaller form. Autophosphorylation revealed a doublet of Mr 54000 +/- 573 and Mr 51000 +/- 710. To titrate the occupancy of regulatory subunits during hCG action, free cAMP receptors were measured by 8-azido[3H]cAMP binding under non-exchange conditions followed by photolysis. hCG treatment caused a dose-related decrease of free receptors and SDS-PAGE analysis of the 8-azido[32P]cAMP regulatory subunit from control and hCG treated cells also showed a hormone dependent decrease in a single band of Mr 50000. These results have shown that the Leydig cell protein kinase behaves as a Type I enzyme on DEAE analysis, but has the physical characteristics of the Type II enzyme. The dose-dependent fall in available receptor sites during hCG stimulation further indicates the central role of cAMP in hormone action in the Leydig cell.

The segregation and expression of glutamate receptor subunits in cultured hippocampal neurons.

The distribution and expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate-selective glutamate receptor subunits (GluR1-4) were studied in cultured hippocampal neurons using antibodies generated against peptides corresponding to the C-termini of GluR1, GluR2/3 and GluR4, and with a set of oligonucleotide probes designed complementary to specific pan, flip and flop GluR1-4 messenger RNA sequences. GluR1-4 subunit proteins were localized in fixed hippocampal neurons (2 h to three weeks after plating) by immunocytochemistry with light and electron microscopy. At early stages in culture, moderate staining with antibodies to GluR1 and GluR2/3 and very light staining with antibody to GluR4 was observed in cell bodies and proximal portions of all neurites of some neurons. Upon establishment of identified axons and dendrites by seven days in culture, staining was intense with specific antibodies to GluR1 and GluR2/3 and light with anti-GluR4 antibody in cell bodies and dendrites. Little or no staining was observed in axons. Cells at seven days in culture exhibited a variety of morphologies. However, we could not assign a pattern of staining to a particular type. As the cultures matured over two and three weeks, staining was limited to the somatodendritic compartment. The intensity of glutamate receptor subunit staining increased and the extent of staining proceeded to the distal extreme of many dendrites. Moreover, antibodies to GluR1-4 subunits were co-localized in neurons. Immunocytochemistry on living neurons did not result in any significant labeling, suggesting that the epitope is either not expressed on the surface of the neurons, or is present, but inaccessible to the antibody. Electron microscopy demonstrated receptor localization similar to that found in brain, with staining of postsynaptic membrane and density, dendritic cytoplasm and cell body, but not within the synaptic cleft. We examined the possible role of "cellular compartmentation" in the pattern of glutamate receptor expression in hippocampal neurons. Compartmentalization studies of the subcellular distribution of messenger RNAs encoding GluR1-4 subunits was determined in mature cultures by in situ hybridization. Significant silver grain appearance was restricted to the cell body, indicating that the synthesis of glutamate receptor subunits is limited largely to the neuronal cell body. The expression of microtubule-associated protein 2 was studied in parallel. Microtubule-associated protein 2 expression appeared 6 h after plating, while glutamate receptor subunit expression was present at 2 h. This indicates that microtubule-associated protein 2 does not regulate the initial distribution of glutamate receptor subunits into neurites.(ABSTRACT TRUNCATED AT 400 WORDS)

Sustained elevation of calcium induces Ca(2+)/calmodulin-dependent protein kinase II clusters in hippocampal neurons.

Treatment of cultured hippocampal neurons with the mitochondrial uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP) in the absence of glucose mimics ischemic energy depletion and induces formation of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) clusters, spherical structures with diameters of 75-175 nm [Dosemeci et al., J. Neurosci. 20 (2000) 3076-3084]. The demonstration that CaMKII clustering occurs in the intact, adult rat brain upon interruption of blood flow indicates that clustering is not confined to cell cultures. Application of N-methyl-D-aspartate (250 microM, 15 min) to hippocampal cultures also induces cluster formation, suggesting a role for Ca(2+). Indeed, intracellular Ca(2+) monitored with Fluo3-AM by confocal microscopy reaches a sustained high level within 5 min of CCCP treatment. The appearance of immunolabeled CaMKII clusters, detected by electron microscopy, follows the onset of the sustained increase in intracellular Ca(2+). Moreover, CaMKII does not cluster when the rise in intracellular Ca(2+) is prevented by the omission of extracellular Ca(2+) during CCCP treatment, confirming that clustering is Ca(2+)-dependent. A lag period of 1-2 min between the onset of high intracellular Ca(2+) levels and the formation of CaMKII clusters suggests that a sustained increase in Ca(2+) level is necessary for the clustering. CaMKII clusters disappear within 2 h of returning the cultures to normal incubation conditions, at which time no significant cell death is detected. These results indicate that pathological conditions that promote sustained episodes of Ca(2+) overload result in a transitory clustering of CaMKII into spherical structures. CaMKII clustering may represent a cellular defense mechanism to sequester a portion of the CaMKII pool, thereby preventing excessive protein phosphorylation.

A prospective trial of short-course radiotherapy plus chemotherapy for palliation of dysphagia from advanced esophageal cancer.

PURPOSE: Between 1994 and 1997, 22 patients with dysphagia from advanced incurable esophageal cancer were enrolled in a phase I/II prospective study to assess the palliative benefit and toxicity of a short course of radiotherapy with chemotherapy. METHODS: The study population included 17 men and five women with a median age of 69 (range 43-84). Patients were treated with 30 Gy in ten fractions to the mediastinum with a concurrent single course of chemotherapy (5-FU, 1000 mg/m(2), days 1-4 and mitomycin-C 10 mg/m(2), day 1). Swallowing ability was recorded each day on a self-administered diary card using the five point dysphagia index of the MRC (UK). The median baseline MRC swallowing score was 4 (cannot swallow solids). RESULTS: Treatment was generally well tolerated, but seven (32%) patients had transient worsening of dysphagia scores immediately following treatment because of esophagitis; fifteen (68%) achieved a complete response (score 1: no difficulty on swallowing) with a median time to normalization of swallowing of 5 weeks. For these patients, the median dysphagia-free interval from time of onset of improvement was 11 weeks (range 1-131 weeks) and 11 (73%) remained dysphagia-free until death. The remaining patients had no or marginal improvement. Univariate analysis showed no difference between responders and non-responders with respect to age, gender, or histology. Median survival for the entire study population was 20 weeks (range 3-135 weeks). CONCLUSIONS: This prospective trial shows that a short course of radiotherapy plus chemotherapy may produce complete relief of swallowing difficulties in a substantial proportion of patients with acceptable toxicity.

The N-terminus of the atrial natriuretic factor prohormone in the pleural fluid of congestive heart failure patients.

To investigate the possibility that the prohormone of atrial natriuretic factor might be secreted into the pleural fluid of patients with congestive heart failure who are known to have high concentrations of both the N-terminus and C-terminus of this prohormone circulating in their plasma, six patients with class 2 New York Heart Association classified congestive heart failure had the simultaneous measurement of plasma and pleural fluid N-terminal and C-terminal atrial natriuretic factor prohormone concentrations. The 98 amino acid (aa) N-terminus, the midportion of the N-terminus consisting of aa 31-67 of the 126 aa ANF prohormone (ie, pro ANF 31-67), and the C-terminus (aa. 99-126, ANF) were found in high concentrations in the pleural fluid of all of these patients. The concentrations of the N-terminus (ie, pro ANF 1-98), and pro ANF 31-67 in pleural fluid were nearly equal to their concentration in plasma of these patients. Their plasma levels were more than double the plasma concentrations of pro ANFs 1-98 and 31-67 in 54 persons without congestive heart failure. These preliminary findings demonstrate that all 126 amino acids of the ANF prohormone are present in pleural fluid of patients with congestive heart failure since both the 98 aa N-terminus and the C-terminus (aa 99-126) are present. Whether or not the N-terminus, which contains diuretic and natriuretic peptides, secretion into pleural fluid helps clear the fluid present in the lung in congestive heart failure could not be determined from the present investigation.

Atrial natriuretic factor in the pleural fluid of congestive heart failure patients.

To investigate the possibility that atrial natriuretic factor might be secreted into the pleural fluid of patients with congestive heart failure who are known to have high concentrations of this new peptide hormone circulating in their plasma, six patients with class 2 New York Heart Association classified congestive heart failure had simultaneos measurement of plasma and pleural fluid atrial natriuretic factor concentrations. Atrial natriuretic factor was found in high concentrations in the pleural fluid of all of these patients. The concentration of atrial natriuretic factor in pleural fluid was nearly equal to the concentration in plasma of these patients. Their plasma levels were double the plasma concentration of this peptide hormone in 54 persons without congestive heart failure. These preliminary findings demonstrate that atrial natriuretic factor is present in pleural fluid of patients with congestive heart failure, but whether or not this secretion of atrial natriuretic factor into the pleural fluid helps the lung clear the fluid present in the lung in congestive heart failure cannot be determined from the present investigation.

Increased release of the N-terminus of the atrial natriuretic factor prohormone with increasing absolute atmospheres of pressure in a hyperbaric chamber and reversal with oxygen therapy.

Increasing atmospheres of absolute pressure (ATA) on the cardiopulmonary system results in a marked diuresis. The present investigation was designed to determine if the diuresis observed with increasing ATA is associated with increased release of the N-terminus of the atrial natriuretic factor (ANF) prohormone that contains two potent diuresis-producing hormones consisting of amino acids (aa) 1-30 (pro ANF 1-30; long-acting sodium stimulator) and aa 31-67 (pro ANF 31-67; vessel dilator) of this 126 aa prohormone. Seven healthy volunteers (mean age, 31 years) had the circulating concentration of the N-terminus of the ANF prohormone evaluated at 1, 2, and 3 ATA in a monoplace hyperbaric chamber by two specific and sensitive radioimmunoassays that immunologically recognize (1) the whole 98 aa N-terminus and (2) the midportion of the N-terminus consistent with aa 31-67 (pro ANF 31-67). With increasing ATA from 1 (sea level) to 2 (equivalent to 33 feet of sea water), the circulating concentrations of both the whole N-terminus and pro ANF 31-67 increased threefold. At 3 ATA (66 feet of sea water), their circulating concentrations increased sixfold over their concentrations, at 1 ATA. With the addition of 100 percent O2 while at 3 and 2 ATA, the circulating concentrations of both the whole N-terminus and pro ANF 31-67 immediately decreased to their prehyperbaric ATA levels and remained there with further decompression to 1 ATA and removal of O2 supplementation. The increased circulating concentration of the N-terminus of the ANF prohormone containing two peptides with potent diuretic effects during increasing atmospheres of absolute pressure may help to explain the diuresis that has been observed with increasing ATA.

Pharmacokinetic characterization of the postdistribution phase of prohormone atrial natriuretic peptides amino acids 1-98, 31-67, and atrial natriuretic factor during and after rapid right ventricular pacing in dogs.

Release rate constants and disappearance rate constants were determined for three atrial natriuretic peptides consisting of amino acids 1-98 (i.e., proANF 1-98), the midportion of the ANF prohormone consisting of amino acids 31-67 (i.e., proANF 31-67) and amino acids 99-126 (i.e., ANF) after right ventricular pacing at 100, 125, 150, and 180 bpm in six male mongrel dogs. Right atrial and femoral vein blood was obtained at baseline, and at 5, 12, 19, 26, 56, 86, 116, 146, and 206 minutes after right ventricular pacing. Resulting plasma concentration-time data derived parameters were compared. The disappearance rate constants for atrial and femoral venous proANF 1-98 were 0.0144 +/- 0.0087 (X +/- SD) and 0.0175 +/- 0.0075 min-1, respectively (t = 0.6158) and release rate constants were 0.1569 +/- 0.1504 and 0.0670 +/- 0.0393 min-1, respectively (t = 1.8269; P greater than .05). The proANF 31-67 disappearance rate constants were 0.0139 +/- 0.0082 and 0.0148 +/- 0.0132 min-1, respectively (t = 0.1192) and release rate constants were 0.0957 +/- 0.0414 and 0.1984 +/- 0.1762 min-1, respectively (t = 1.4812). The ANF elimination phase disappearance rate constants were 0.0663 +/- 0.0273 and 0.1116 +/- 0.0539 min-1 (t = 2.0923, P greater than .05), respectively, and the release rate constants were 0.1335 +/- 0.0532 and 0.1638 +/- 0.0520 min-1 (t = 0.7878, P greater than .05), respectively. These data indicate that proANF 1-98 and proANF 31-67 circulating beta post-distribution half-lives are approximately 45 minutes whereas beta half-life of ANF is 10 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

The accuracy of the TriTrac-R3D accelerometer to estimate energy expenditure.

PURPOSE: This study examined the reliability and validity of the TriTrac-R3D triaxial accelerometer to estimate energy expenditure during various modes of exercise. METHODS: Twenty subjects (age = 21.5+/-3.4 yr; body mass index = 23.3+/-3.6 kg x m(-2)) performed five exercises (treadmill walking, treadmill running, stepping, stationary cycling, and slideboard), with each lasting 20-30 min and workload increased at 10-min intervals. To test the inter-TriTrac reliability, two TriTrac-R3D accelerometers were worn during each exercise period, and to examine validity, a simultaneous measurement of energy expenditure was made using indirect calorimetry (SensorMedics 2900 Metabolic Cart). RESULTS: Results showed a significant correlation between the two TriTrac-R3D accelerometers during all exercises. The difference in estimated energy expenditure between the two accelerometers during the walking, stepping, and slideboard exercises was less than 1 kcal x min(-1) but statistically significant (P<0.05). There was also a significant correlation between energy expenditure estimated by each of the TriTrac-R3D accelerometers and indirect calorimetry during walking, running, stepping, and slideboard exercise (P<0.05). The interaction of Method x Workload was significant (P<0.05) for each exercise, indicating that the TriTrac-R3D underestimates energy expenditure and that the magnitude of this underestimation increases as workload increases. CONCLUSIONS: Therefore, energy expenditure estimated via triaxial accelerometry does not increase with increasing workloads. These results suggest that there are limitations to using triaxial accelerometry to quantify energy expenditure.