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Biomedical subjects

M J Berry

Publications and source records attributed to M J Berry.

At least 37 records · Page 2Linked to original sources
PubMed2000

The relationship between %HRpeak and %VO2peak in patients with chronic obstructive pulmonary disease.

PURPOSE: The relationship between the percent peak oxygen consumption (%VO2peak) and percent peak heart rate (%HRpeak) has been suggested as a method for exercise prescription. According to the American College of Sports Medicine (ACSM), 50, 60, 80, and 85% of VO2peak represent 62, 70, 85, and 90% of HRpeak, respectively. Recent research with young healthy adults has shown that this relationship is not as ACSM suggests. Furthermore, it has been suggested that this relationship be examined in populations with low functional capacity. METHODS: The present study evaluated the relationship between %HRpeak and %VO2peak in 125 patients with chronic obstructive pulmonary disease before and then after 3 months of exercise intervention. RESULTS: The mean percentages of HRpeak for the COPD patients at baseline were 70, 76, 87, and 90% at 50, 60, 80, and 85% of VO2peak. Percentages of HRpeak at 50, 60, and 80% of VO2peak were significantly different from those suggested by ACSM. The mean percentages of HRpeak after the 3-month exercise intervention were 71, 77, 87, and 90% at 50, 60, 80, and 85% of VO2peak. Percentages of HRpeak at 50, 60, and 80% of VO2peak were significantly different from those suggested by ACSM. There were no significant differences between the slopes and the intercepts of the two equations used to describe the relationship between %HRpeak and %VO2peak. Therefore, we pooled the data from the pre- and post-intervention tests to form the following equation to describe the relationship between %HRpeak and %VO2peak for COPD patients: %HRpeak = 0.55 (+/- 0.01)%VO2peak + 43.2 (+/- 1.4). CONCLUSION: In conclusion, the relationship between %HRpeak and %VO2peak described by ACSM is not applicable to patients with COPD. Furthermore, this relationship does not change with exercise training and can be described by a single equation.

Aged↗
PubMed2000

Cost-effectiveness analysis methods for the REACT Study.

The Reconditioning Exercise and Chronic Obstructive Pulmonary Disease Trial (REACT) is a two-arm randomized clinical trial designed to compare short-term versus long-term exercise intervention in terms of physical function, acute exacerbation of chronic obstructive pulmonary disease, health-related quality of life, and cost-effectiveness. Clinical trials such as REACT are now routinely paired with economic analyses, and nurses can expect to play a growing role in the conduct of these studies. This article describes a model that is useful for structuring economic evaluations of health care interventions, and illustrates a cost-effectiveness analysis that is being conducted in conjunction with the REACT study. An in-depth description of collection methods and procedures is provided, as well as a summary of recruitment and retention experience to date.

Aged↗
PubMed1999

Regulation of human thioredoxin reductase expression and activity by 3'-untranslated region selenocysteine insertion sequence and mRNA instability elements.

Thioredoxin reductases function in regulating cellular redox and function through their substrate, thioredoxin, in the proper folding of enzymes and redox regulation of transcription factor activity. These enzymes are overexpressed in certain tumors and cancer cells and down-regulated in apoptosis and may play a role in regulating cell growth. Mammalian thioredoxin reductases contain a selenocysteine residue, encoded by a UGA codon, as the penultimate carboxyl-terminal amino acid. This amino acid has been proposed to carry reducing equivalents from the active site to substrates. We report expression of a wild-type thioredoxin reductase selenoenzyme, a cysteine mutant enzyme, and the UGA-terminated protein in mammalian cells and overexpression of the cysteine mutant and UGA-terminated proteins in the baculovirus insect cell system. We show that substitution of cysteine for selenocysteine decreases enzyme activity for thioredoxin by 2 orders magnitude, and that termination at the UGA codon abolishes activity. We further demonstrate the presence of a functional selenocysteine insertion sequence element that is highly active but only moderately responsive to selenium supplementation. Finally, we show that thioredoxin reductase mRNA levels are down-regulated by other sequences in the 3'-untranslated region, which contains multiple AU-rich instability elements. These sequences are found in a number of cytokine and proto-oncogene mRNAs and have been shown to confer rapid mRNA turnover.

3' Untranslated Regions↗
PubMed1999

The Caenorhabditis elegans homologue of thioredoxin reductase contains a selenocysteine insertion sequence (SECIS) element that differs from mammalian SECIS elements but directs selenocysteine incorporation.

Thioredoxin reductases (TRR) serve critical roles in maintaining cellular redox states. Two isoforms of TRR have been identified in mammals: both contain a penultimate selenocysteine residue that is essential for catalytic activity. A search of the genome of the invertebrate, Caenorhabditis elegans, reveals a gene highly homologous to mammalian TRR, with a TGA selenocysteine codon at the corresponding position. A selenocysteyl-tRNA was identified in this organism several years ago, but no selenoproteins have been identified experimentally. Herein we report the first identification of a C. elegans selenoprotein. By (75)Se labeling of C. elegans, one major band was identified, which migrated with the predicted mobility of the C. elegans TRR homologue. Western analysis with an antibody against human TRR provides strong evidence for identification of the C. elegans selenoprotein as a member of the TRR family. The 3'-untranslated region of this gene contains a selenocysteine insertion sequence (SECIS) element that deviates at one position from the previously invariant consensus "AUGA." Nonetheless, this element functions to direct selenocysteine incorporation in mammalian cells, suggesting conservation of the factors recognizing SECIS elements from worm to man.

Amino Acid Sequence↗
PubMed1999

Anticipation of moving stimuli by the retina.

A flash of light evokes neural activity in the brain with a delay of 30-100 milliseconds, much of which is due to the slow process of visual transduction in photoreceptors. A moving object can cover a considerable distance in this time, and should therefore be seen noticeably behind its actual location. As this conflicts with everyday experience, it has been suggested that the visual cortex uses the delayed visual data from the eye to extrapolate the trajectory of a moving object, so that it is perceived at its actual location. Here we report that such anticipation of moving stimuli begins in the retina. A moving bar elicits a moving wave of spiking activity in the population of retinal ganglion cells. Rather than lagging behind the visual image, the population activity travels near the leading edge of the moving bar. This response is observed over a wide range of speeds and apparently compensates for the visual response latency. We show how this anticipation follows from known mechanisms of retinal processing.

Animals↗
PubMed1999

Cloning, sequencing and functional expression of a novel human thioredoxin reductase.

The DNA sequence encoding a novel human thioredoxin reductase has been determined. The protein is predicted to have 524 amino acids including a conserved -Cys-Val-Asn-Val-Gly-Cys catalytic site and a selenocysteine containing C-terminal -Gly-Cys-SeCys-Gly. The predicted molecular mass is 56.5. The newly identified TR sequence exhibits 54% identity to a previously reported human thioredoxin reductase and 37% identity to human glutathione reductase. Transient transfection of human embryonal kidney cells results in a 5-fold increase in thioredoxin reductase activity but no increase in glutathione reductase activity.

Amino Acid Sequence↗
PubMed1999

Two distinct SECIS structures capable of directing selenocysteine incorporation in eukaryotes.

Translation of UGA as selenocysteine requires specific RNA secondary structures in the mRNAs of selenoproteins. These elements differ in sequence, structure, and location in the mRNA, that is, coding versus 3' untranslated region, in prokaryotes, eukaryotes, and archaea. Analyses of eukaryotic selenocysteine insertion sequence (SECIS) elements via computer folding programs, mutagenesis studies, and chemical and enzymatic probing has led to the derivation of a predicted consensus structural model for these elements. This model consists of a stem-loop or hairpin, with conserved nucleotides in the loop and in a non-Watson-Crick motif at the base of the stem. However, the sequences of a number of SECIS elements predict that they would diverge from the consensus structure in the loop region. Using site-directed mutagenesis to introduce mutations predicted to either disrupt or restore structure, or to manipulate loop size or stem length, we show that eukaryotic SECIS elements fall into two distinct classes, termed forms 1 and 2. Form 2 elements have additional secondary structures not present in form 1 elements. By either insertion or deletion of the sequences and structures distinguishing the two classes of elements while maintaining appropriate loop size, conversion of a form 1 element to a functional form 2-like element and of a form 2 to a functional form 1-like element was achieved. These results suggest commonality of function of the two classes. The information obtained regarding the existence of two classes of SECIS elements and the tolerances for manipulations of stem length and loop size should facilitate designing RNA molecules for obtaining high-resolution structural information about these elements.

Animals↗
PubMed1999

Exercise rehabilitation and chronic obstructive pulmonary disease stage.

To determine the extent to which patients with Stage I COPD experience improvements in physical performance and quality of life as a result of exercise training, and to compare these improvements with those seen in Stage I and II patients, 151 patients with COPD underwent a 12-wk exercise program. Outcomes were measured at baseline and follow-up. Physical performance was evaluated by means of a 6-min walk, treadmill time, an overhead task, and a stair climb. General health-related quality of life was assessed in terms of the domains of Social Function, Health Perceptions, and Life Satisfaction. Disease-specific health-related quality of life was assessed with the Chronic Respiratory Disease Questionnaire (CRQ). Six-minute walk distance increased significantly in Stage I (200.5 ft [95% CI: 165.4, 235.7]), Stage II (238.3 ft [143.3, 333.3]), and Stage III (112.1 ft [34.6, 189.6]) participants. Treadmill time increased significantly in Stage I (0.42 min [0.20, 0.64]) and Stage II (0.64 min [0.14, 1.4]) participants. Time to complete the overhead task decreased significantly in Stage I (0.91 s [1.72, 0. 11]) and Stage II (1.39 s [2.66, 0.13]) participants. None of the measures of general health-related quality of life improved in any of the three groups. Participants in Stages I, II, and III all experienced improvements in the CRQ domains of dyspnea (0.72 [0.53, 0.91], 0.47 [0.02, 0.91], and 0.46 [0.05, 0.87], respectively) and fatigue (0.49 [0.33, 0.66], 0.54 [0.20, 0.87], and 0.55 [0.05, 1.05], respectively). These results suggest that all patients with COPD will benefit from exercise rehabilitation. Berry MJ, Rejeski WJ, Adair NE, Zaccaro D. Exercise rehabilitation and chronic obstructive pulmonary disease stage.

Aged↗
PubMed1999

Disruption of selenoprotein biosynthesis affects cell proliferation in the imaginal discs and brain of Drosophila melanogaster.

The patufet gene encodes the Drosophila melanogaster homologue of selenophosphate synthetase, an enzyme required for selenoprotein synthesis, and appears to have a role in cell proliferation. In this paper we analyse the expression pattern of patufet during the development of imaginal discs and brain as well as the function of this gene in relation to cell proliferation. Wild-type organisms showed a highly dynamic pattern of ptuf mRNA expression during larval and pupal development. Co-localization analysis of ptuf mRNA expression and BrdU incorporation showed high levels of ptuf mRNA in dividing cells and low or undetectable levels in non-dividing cells. In addition, [(75)Se] incorporation revealed a major selenoprotein band of 42 kDa. Mutant organisms showed no selenoprotein synthesis, lower levels of cell proliferation, a higher proportion of cells arrested in G(2) as seen by cyclin B labeling and increased levels of reactive oxygen species (ROS). Because most selenoproteins identified so far are antioxidants, the role of ptuf in cell proliferation through the control of the cellular redox balance is discussed.

Animals↗
PubMed1999

Polarized targeting of epithelial cell proteins in thyrocytes and MDCK cells.

Polarized trafficking signals may be interpreted differently in different cell types. In this study, we have compared the polarized trafficking of different proteins expressed endogenously in primary porcine thyroid epithelial cells to similar proteins expressed in MDCK cells. As in MDCK cells, NH4Cl treatment of filter-grown thyrocytes caused mis-sorted soluble proteins to exhibit enhanced secretion to the apical medium. In independent studies, thrombospondin 1 (a thyroid basolaterally secreted protein) was secreted basolaterally from MDCK cells. Likewise, the 5'-deiodinase (a thyroid basolateral membrane protein) encoded by the DIO1 gene was also distributed basolaterally in transfected MDCK cells. Consistent with previous reports, when the secretion of human growth hormone (an unglycosylated regulated secretory protein) was examined from transfected MDCK cells, the release was nonpolarized. However, transfected thyrocytes secreted growth hormone apically in a manner dependent upon zinc addition. Moreover, two additional regulated secretory proteins expressed in thyrocytes, thyroglobulin (the major endogenous glycoprotein) and parathyroid hormone (an unglycosylated protein expressed transiently), were secreted apically even in the absence of zinc. We hypothesize that while cellular mechanisms for interpreting polarity signals are generally similar between thyrocytes and MDCK cells, thyrocytes allow for specialized packaging of regulated secretory proteins for apical delivery, which does not require glycosylation but may involve availability of certain ions as well as appropriate intracellular compartmentation.

Animals↗
PubMed1998

Refractoriness and neural precision.

The response of a spiking neuron to a stimulus is often characterized by its time-varying firing rate, estimated from a histogram of spike times. If the cell's firing probability in each small time interval depends only on this firing rate, one predicts a highly variable response to repeated trials, whereas many neurons show much greater fidelity. Furthermore, the neuronal membrane is refractory immediately after a spike, so that the firing probability depends not only on the stimulus but also on the preceding spike train. To connect these observations, we investigated the relationship between the refractory period of a neuron and its firing precision. The light response of retinal ganglion cells was modeled as probabilistic firing combined with a refractory period: the instantaneous firing rate is the product of a "free firing rate, " which depends only on the stimulus, and a "recovery function," which depends only on the time since the last spike. This recovery function vanishes for an absolute refractory period and then gradually increases to unity. In simulations, longer refractory periods were found to make the response more reproducible, eventually matching the precision of measured spike trains. Refractoriness, although often thought to limit the performance of neurons, may in fact benefit neuronal reliability. The underlying free firing rate derived by allowing for the refractory period often exceeded the observed firing rate by an order of magnitude and was found to convey information about the stimulus over a much wider dynamic range. Thus, the free firing rate may be the preferred variable for describing the response of a spiking neuron.

Action Potentials↗
PubMed1998

Ultraviolet-induced cell death blocked by a selenoprotein from a human dermatotropic poxvirus.

Selenium, an essential trace element, is a component of prokaryotic and eukaryotic antioxidant proteins. A candidate selenoprotein homologous to glutathione peroxidase was deduced from the sequence of molluscum contagiosum, a poxvirus that causes persistent skin neoplasms in children and acquired immunodeficiency syndrome (AIDS) patients. Selenium was incorporated into this protein during biosynthesis, and a characteristic stem-loop structure near the end of the messenger RNA was required for alternative selenocysteine decoding of a potential UGA stop codon within the open reading frame. The selenoprotein protected human keratinocytes against cytotoxic effects of ultraviolet irradiation and hydrogen peroxide, providing a mechanism for a virus to defend itself against environmental stress.

Apoptosis↗
PubMed1998

Functionality of mutations at conserved nucleotides in eukaryotic SECIS elements is determined by the identity of a single nonconserved nucleotide.

In eukaryotes, the specific cotranslational insertion of selenocysteine at UGA codons requires the presence of a secondary structural motif in the 3' untranslated region of the selenoprotein mRNA. This selenocysteine insertion sequence (SECIS) element is predicted to form a hairpin and contains three regions of sequence invariance that are thought to interact with a specific protein or proteins. Specificity of RNA-binding protein recognition of cognate RNAs is usually characterized by the ability of the protein to recognize and distinguish between a consensus binding site and sequences containing mutations to highly conserved positions in the consensus sequence. Using a functional assay for the ability of wild-type and mutant SECIS elements to direct cotranslational selenocysteine incorporation, we have investigated the relative contributions of individual invariant nucleotides to SECIS element function. We report the novel finding that, for this consensus RNA motif, mutations at the invariant nucleotides are tolerated to different degrees in different elements, depending on the identity of a single nonconserved nucleotide. Further, we demonstrate that the sequences adjacent to the minimal element, although not required for function, can affect function through their propensity to base pair. These findings shed light on the specific structure these conserved sequences may form within the element. This information is crucial to the design of strategies for the identification of SECIS-binding proteins, and hence the elucidation of the mechanism of selenocysteine incorporation in eukaryotes.

Base Sequence↗
PubMed1997

Effects of cardioselective beta blockers on ventilation and gas exchange in patients with heart disease during ramp treadmill testing.

The effects of cardioselective beta blockade on ventilation and gas exchange were investigated in 12 male subjects with coronary artery disease during ramp treadmill testing. Patients were able to maintain much of their functional capacity as measured by oxygen consumption in the beta-blocked condition, and also maintained minute ventilation by increasing respiratory rate despite a decrease in tidal volume.

Adrenergic beta-Antagonists↗
PubMed1997

The structure and precision of retinal spike trains.

Assessing the reliability of neuronal spike trains is fundamental to an understanding of the neural code. We measured the reproducibility of retinal responses to repeated visual stimuli. In both tiger salamander and rabbit, the retinal ganglion cells responded to random flicker with discrete, brief periods of firing. For any given cell, these firing events covered only a small fraction of the total stimulus time, often less than 5%. Firing events were very reproducible from trial to trial: the timing jitter of individual spikes was as low as 1 msec, and the standard deviation in spike count was often less than 0.5 spikes. Comparing the precision of spike timing to that of the spike count showed that the timing of a firing event conveyed several times more visual information than its spike count. This sparseness and precision were general characteristics of ganglion cell responses, maintained over the broad ensemble of stimulus waveforms produced by random flicker, and over a range of contrasts. Thus, the responses of retinal ganglion cells are not properly described by a firing probability that varies continuously with the stimulus. Instead, these neurons elicit discrete firing events that may be the fundamental coding symbols in retinal spike trains.

Action Potentials↗
PubMed1997

Adaptation of retinal processing to image contrast and spatial scale.

Owing to the limited dynamic range of a neuron's output, neural circuits are faced with a trade-off between encoding the full range of their inputs and resolving gradations among those inputs. For example, the ambient light level varies daily over more than nine orders of magnitude, whereas the firing rate of optic nerve fibres spans less than two. This discrepancy is alleviated by light adaptation: as the mean intensity increases, the retina becomes proportionately less sensitive. However, image statistics other than the mean intensity also vary drastically during routine visual processing. Theory predicts that an efficient visual encoder should adapt its strategy not only to the mean, but to the full shape of the intensity distribution. Here we report that retinal ganglion cells, the output neurons of the retina, adapt to both image contrast-the range of light intensities-and to spatial correlations within the scene, even at constant mean intensity. The adaptation occurs on a scale of seconds, one hundred times more slowly than the immediate light response, and involves 2-5-fold changes in the firing rate. It is mediated within the retinal network: two independent sites of modulation after the photoreceptor cells appear to be involved. Our results demonstrate a remarkable plasticity in retinal processing that may contribute to the contrast adaptation of human vision.

Action Potentials↗
PubMed1997

A randomized trial comparing aerobic exercise and resistance exercise with a health education program in older adults with knee osteoarthritis. The Fitness Arthritis and Seniors Trial (FAST).

OBJECTIVE: To determine the effects of structured exercise programs on self-reported disability in older adults with knee osteoarthritis. SETTING AND DESIGN: A randomized, single-blind clinical trial lasting 18 months conducted at 2 academic medical centers. PARTICIPANTS: A total of 439 community-dwelling adults, aged 60 years or older, with radiographically evident knee osteoarthritis, pain, and self-reported physical disability. INTERVENTIONS: An aerobic exercise program, a resistance exercise program, and a health education program. MAIN OUTCOME MEASURES: The primary outcome was self-reported disability score (range, 1-5). The secondary outcomes were knee pain score (range, 1-6), performance measures of physical function, x-ray score, aerobic capacity, and knee muscle strength. RESULTS: A total of 365 (83%) participants completed the trial. Overall compliance with the exercise prescription was 68% in the aerobic training group and 70% in the resistance training group. Postrandomization, participants in the aerobic exercise group had a 10% lower adjusted mean (+/- SE) score on the physical disability questionnaire (1.71 +/- 0.03 vs 1.90 +/- 0.04 units; P<.001), a 12% lower score on the knee pain questionnaire (2.1 +/- 0.05 vs 2.4 +/- 0.05 units; P=.001), and performed better (mean [+/- SE]) on the 6-minute walk test (1507 +/- 16 vs 1349 +/- 16 ft; P<.001), mean (+/-SE) time to climb and descend stairs (12.7 +/- 0.4 vs 13.9 +/- 0.4 seconds; P=.05), time to lift and carry 10 pounds (9.1 +/- 0.2 vs 10.0 +/- 0.1 seconds; P<.001), and mean (+/-SE) time to get in and out of a car (8.7 +/- 0.3 vs 10.6 +/- 0.3 seconds; P<.001) than the health education group. The resistance exercise group had an 8% lower score on the physical disability questionnaire (1.74 +/- 0.04 vs 1.90 +/- 0.03 units; P=.003), 8% lower pain score (2.2 +/- 0.06 vs 2.4 +/- 0.05 units; P=.02), greater distance on the 6-minute walk (1406 +/- 17 vs 1349 +/- 16 ft; P=.02), faster times on the lifting and carrying task (9.3 +/- 0.1 vs 10.0 +/- 0.16 seconds; P=.001), and the car task (9.0 +/- 0.3 vs 10.6 +/- 0.3 seconds; P=.003) than the health education group. There were no differences in x-ray scores between either exercise group and the health education group. CONCLUSIONS: Older disabled persons with osteoarthritis of the knee had modest improvements in measures of disability, physical performance, and pain from participating in either an aerobic or a resistance exercise program. These data suggest that exercise should be prescribed as part of the treatment for knee osteoarthritis.

Activities of Daily Living↗