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Biomedical subjects

J R Wilson

Publications and source records attributed to J R Wilson.

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

An empirical approach to characterizing trunk muscle coactivation using simulation input modeling techniques.

Accurately describing trunk muscle coactivation is fundamental to quantifying the spine reaction forces that occur during lifting tasks and has been the focus of a great deal of research in the spine biomechanics literature. One limitation of previous approaches has been a lack of consideration given to the variability in these coactivation strategies. The research presented in this paper is an empirical approach to quantifying and modeling trunk muscle coactivation using simulation input modeling techniques. Electromyographic (EMG) data were collected from 28 human subjects as they performed controlled trunk extension exertions. These exertions included isokinetic (10 and 45 degrees /s) and constant acceleration (50 degrees /s/s) trunk extensions in symmetric and asymmetric (30 degrees ) postures at two levels of trunk extension moment (30 and 80Nm). The EMG data were collected from the right and left pairs of the erector spinae, latissimus dorsi, rectus abdominis, external obliques and internal obliques. Each subject performed nine repetitions of each combination of independent variables. The data collected during these trials were used to develop marginal distributions of trunk muscle activity as well as a 10x10 correlation matrix that described how the muscles cooperated to produce these extension torques. These elements were then combined to generate multivariate distributions describing the coactivation of the trunk musculature. An analysis of these distributions revealed that increases in extension moment, extension velocity and sagittal flexion angle created increases in both the mean and the variance of the distributions of the muscular response, while increases in the rate of trunk extension acceleration decreased both the mean and variance of the distributions of activity across all muscles considered. Increases in trunk asymmetry created a decrease in mean of the ipsi-lateral erector spinae and an increase in the mean of all other muscles considered, but there was little change in the variance of these distributions as a function of asymmetry.

Acceleration↗
PubMed2000

Bacterial metal-resistance proteins and their use in biosensors for the detection of bioavailable heavy metals.

We have expressed and purified metal-resistance and metal regulatory proteins from the bacterial determinants of resistance to heavy metals and utilised these in the development of biosensors for heavy metals. Both the metallothionein from the cyanobacterium Synechococcus PCC 7942 and the MerR regulatory protein from transposon Tn501 allow the detection of non-specific metal binding down to 10(-15) M concentrations of Hg(II), Cu(II), Zn(II) and Cd(II) in pure solution. Differential effects of the metals can be detected at both low and high concentrations, and the shape of the capacitance curves may reflect biologically relevant responses of the proteins to metals. Further work is required to establish the relationship between the detected binding of metal and the biological response of the protein, or to provide biosensors of use in the natural environment.

Bacterial Proteins↗
PubMed2000

Development of process equipment to separate nonthermal and thermal effects of RF energy on microorganisms.

We developed a modified radio frequency (RF) dielectric heater, as a component of a continuous process, for isolating thermal and nonthermal effects of RF energy on microorganisms in liquid foods. The concept combines instantaneous input of RF energy to the food system with rapid removal of thermal energy. We used a double tube heat exchanger as an integral part of the RF heater. The outer tube was Teflon. The inner tube was stainless steel which was grounded in the RF circuit. Product flowed through the annular region between the two concentric tubes. Cooling water flowed through the grounded stainless steel tube. The RF energy was absorbed by the process fluid in the annular region. The cooling water flowing in the inner tube removed the thermal energy from the process fluid controlling the temperature.

Food Microbiology↗
PubMed2000

Quantitative and functional characterization of muscarinic receptor subtypes in insulin-secreting cell lines and rat pancreatic islets.

Expression of muscarinic receptors in rat islets, RINm5F cells, and INS-1 cells was established by reverse transcriptase-polymerase chain reaction (RT-PCR) and quantified by RNase protection. Both methods indicated that m3 and m1 receptors were expressed approximately equally in the various cellular preparations and to a much greater extent than the m5 subtype. However, the cell lines, especially RINm5F cells, expressed less of a given receptor subtype than did islets. Immunohistochemistry indicated that m3 receptors were expressed throughout the islet core. Binding studies using the radiolabeled muscarinic receptor antagonist QNB demonstrated a maximal binding capacity of INS-1 cells of 23.0+/-2.9 fmol/mg protein. Functional analyses were undertaken using INS-1 cells stably transfected with either m1 or m3 receptor cDNAs. Overexpression of either receptor did not affect basal responses but markedly enhanced maximal responses to the muscarinic receptor agonist carbachol. Although maximal hydrolysis of phosphatidylinositol 4,5-bisphosphate (Ptd InsP2) was twofold greater in m1-transfectants as compared with m3-transfectants, cell lines overexpressing either receptor gave essentially equivalent secretory responses to a full range of carbachol doses. The results demonstrate that both m1 and m3 muscarinic receptors are well expressed in pancreatic beta-cells, functionally linked to signaling pathways, and capable of initiating insulin secretion with equal potencies.

Animals↗
PubMed1999

Pulmonary hypertension and exercise intolerance in patients with heart failure.

OBJECTIVES: This study was undertaken to investigate the relationship between pulmonary hypertension and exercise performance in patients with heart failure. BACKGROUND: The exercise capacity of patients with heart failure is frequently reduced. Pulmonary hypertension may contribute to this exercise intolerance by impairing blood flow through the pulmonary circulation. METHOD: Three hundred twenty patients with heart failure underwent upright treadmill exercise testing with hemodynamic monitoring. The incidence of pulmonary hypertension and the relationship between pulmonary vascular resistance (PVR) and exercise cardiac output and minute oxygen consumption (VO2) were examined. RESULTS: Pulmonary vascular resistance was normal (<1.5 Wood Units; Group 1) in 28% of the patients, mildly elevated (1.5 to 2.49 Wood Units; Group 2) in 36%, moderately elevated (2.5 to 3.49 Wood Units; Group 3) in 17% and severely elevated (>3.5 Wood Units; Group 4) in 19%. Increasing PVR was associated with significantly lower peak exercise VO2 (Group 1: 13.9+/-3.7; 2:13.7+/-3.4; 3: 11.8+/-2.4; 4: 11.5+/-2.6 L/min, p<0.01 Groups 3 and 4 vs. 1) and lower peak exercise cardiac output (Group 1: 10.0+/-2.8, 2:9.0+/-3.0; 3: 7.4+/-2.1; 4: 6.3+/-2.0 L/min, p<0.05, Groups 2, 3 and 4 vs. 1). The pulmonary wedge pressure decreased during exercise, consistent with impaired left ventricular filling, in 36% of patients with severe pulmonary hypertension (Group 4) versus only 13% of patients with normal PVR (p<0.01). CONCLUSIONS: Pulmonary vascular resistance is frequently increased in heart failure and is associated with a reduced cardiac output response to exercise, suggesting that pulmonary hypertension impairs exercise performance in heart failure.

Adult↗
PubMed1999

Comparison of cholinergic and histaminergic axons in the lateral geniculate complex of the macaque monkey.

The cholinergic and histaminergic projections have important neuromodulatory functions in the ascending visual pathways, so we compared the pattern and mode of innervation of the two projections in the lateral geniculate complex (dorsal lateral geniculate nucleus and pregeniculate nucleus) of the macaque monkey. Brain tissue from macaques was immunoreacted by means of antibodies to choline acetyltransferase (ChAT) or to histamine and processed for light and electron microscopy. A dense plexus of thin, highly branched ChAT-immunoreactive axons laden with varicosities was found in all layers of the dLGN including the koniocellular laminae and in the pregeniculate nucleus. ChAT label was more dense in magnocellular layers 1 and 2 than in parvocellular layers 3-6 and relatively sparse in the interlaminar zones. Varicosities associated with the cholinergic axons had an average of three conventional asymmetric synapses per varicosity, and these appeared to contact dendrites of both thalamocortical cells and interneurons. Histamine-immunoreactive axons were distributed homogeneously throughout all laminar and interlaminar zones of the dLGN, but were denser in the pregeniculate nucleus than in the dLGN. Histaminergic axons branched infrequently and were typically larger in caliber than cholinergic axons. The overwhelming majority of varicosities were found en passant and rarely displayed conventional synapses, despite the abundance of synaptic vesicles, and were not associated preferentially with specific cellular structures. The innervation of the macaque dLGN complex by cholinergic and histaminergic systems is consistent with their proposed role in state dependent modulation of thalamic activity. The dense and highly synaptic innervation by cholinergic axons supports the proposal of additional involvement of these axons in functions related to eye movements.

Animals↗
PubMed1999

The utility of exercise testing after cardiac transplantation in older patients.

BACKGROUND: The criteria for cardiac transplantation recipient selection, including the appropriate recipient upper age limit, continue to expand with an increasing number of recipients greater than 60 years of age. While others have reported their transplant experience in older recipients in terms of quality of life assessment, we have examined the role of exercise cardiopulmonary testing post-transplantation in older cardiac transplant recipients. METHODS: We reviewed inpatient and outpatient charts of 28 patients 60 years of age or older who underwent orthotopic heart transplantation at Vanderbilt University Medical Center. RESULTS: In this population, perioperative mortality of 7.1% and Kaplan-Meier survival at 1 and 5 years of 89 and 77%, respectively, were similar to the institutional 1-year (89%) and 5-year (75%) survival among younger adult transplant recipients. Exercise cardiopulmonary testing results were available in 22/25 patients surviving greater than 1 year. Both peak oxygen consumption and percentage of maximum VO2 were significantly greater among patients reporting NYHA Class 1 or 2 functional status, in comparison with those NYHA Class 3 or greater. CONCLUSION: Following cardiac transplantation, survival of patients greater than 60 years of age is equivalent to that of younger patients at our institution. Exercise testing provides an objective measure of performance and correlates with subjective status following heart transplantation. Most patients demonstrate good functional status, with minimal symptoms and good exercise capacity. These results, although retrospective, suggest that cardiac transplantation remains a reasonable therapeutic option for patients greater than 60 years of age with end-stage cardiomyopathy.

Aged↗
PubMed1999

Virtual environments applications and applied ergonomics.

The usability of virtual environments has attracted considerable efforts from ergonomists. Work has included studies of the side or after effects of participation in a virtual environment (VE) as well as the appropriateness of the Virtual Reality hardware and software interfaces and the understanding of factors which determine participant performance. Equally important for applied ergonomics is to understand how best to specify, build, implement and evaluate virtual environment solutions to everyday industrial, commercial, educational and medical problems. The potential value of ergonomics applied to virtual environments, and vice versa, are discussed. Two particular instances of VE development relevant to applied ergonomics are described - structured development and evaluation of industrial training and participatory redesign of workplaces. This paper is one of a number of contributions to a special issue on ergonomics in the study and use of virtual environments.

Ergonomics↗
PubMed1999

Relationship between exertional symptoms and functional capacity in patients with heart failure.

OBJECTIVES: The present study was undertaken to investigate the relationship over time between exertional symptoms in heart failure and functional capacity. BACKGROUND: Most clinicians rely on exertional symptoms rather than on exercise testing to assess functional capacity in heart failure. However, it remains uncertain whether the subjective symptoms reported by patients provide a reliable index of functional capacity. METHODS: Fifty patients with heart failure underwent serial cardiopulmonary exercise testing and evaluation of exertional fatigue and dyspnea over a period of one to four years. Exercise testing was performed using the Naughton treadmill protocol and a MedGraphics metabolic cart. Fatigue and dyspnea were each scored from 0 to 3 (p = none, 1 = mild, 2 = moderate, 3 = severe). A composite symptom score was determined by adding together the fatigue and dyspnea scores. RESULTS: Patients underwent a total of 185 tests at an average interval of 4.3 months (average tests/patient = 3.7). Composite symptom scores noted at the time of exercise testing correlated significantly with peak exercise minute oxygen consumption (VO2) (r = 0.47, p < 0.01). In addition, the change in symptoms scores and change in peak VO2 noted between the baseline and final exercise test correlated significantly (r = 0.50, p < 0.01). However, patients reported few or no symptoms (symptom score < or =2) 45% of the time when peak VO2 was <14 ml/min/kg, consistent with a severe functional disability, and 72% of the time when peak VO2 was 14 to 18 ml/min/kg, consistent with moderate functional disability. CONCLUSIONS: Exertional symptoms reported by patients with heart failure generally correlate with maximal exercise capacity. However, exertional symptoms frequently underestimate the severity of functional disability. Cardiopulmonary exercise testing rather than symptoms should be used to assess functional capacity in heart failure.

Adult↗
PubMed1999

Comparison of soft tissue profile changes in serial extraction and late premolar extraction.

To assess soft tissue profile changes through time, a comparison was made of patients treated by serial extraction without subsequent orthodontic treatment (n=28), patients treated with serial extraction and orthodontic treatment (n=30), and patients treated orthodontically with late extraction (n=30). Cephalometric radiographs were traced and digitized; linear and angular measurements were made with a custom computer program that allowed digitization of specific soft tissue points. Maxillary, mandibular, and overall cephalometric superimpositions and linear measurements of change from the superimpositions were done by hand. Statistical analyses were made to determine if significant differences existed within each group at each time period and between groups at each time period, as well as between males and females at each time period. Data were also analyzed to determine if significant correlations existed between any hard tissue variable and any soft tissue variable, or between any soft tissue variable and any other soft tissue variable. It was found that in those patients treated with late premolar extraction, the most labial point of the mandibular incisor was more posterior from pretreatment to posttreatment than in the serial extraction group. While a great number of associations existed between variables, no significant differences were found between the soft tissue profiles of these three groups of patients. The gender differences that were found to exist were most likely due to normal maturational changes, not the treatment itself.

Adolescent↗
PubMed1999

Increases in phosphorylation of the myosin II heavy chain, but not regulatory light chains, correlate with insulin secretion in rat pancreatic islets and RINm5F cells.

Although cytoskeletal proteins such as myosin II are implicated in the control of insulin secretion, their precise role is poorly understood. In other secretory cells, myosin II is predominantly regulated via the phosphorylation of the regulatory light chains (RLC). The current study was aimed at investigating RLC phosphorylation in beta-cells. In both the insulin-secreting cell line RINm5F and rat pancreatic islets, the RLC was basally phosphorylated on the myosin light chain kinase sites (Ser19/Thr18). Phosphorylation at these sites was not consistently increased by either metabolic stimuli (glyceraldehyde/glucose) or the depolarizing agent KCl. The RLC sites phosphorylated by protein kinase C (PKC) (Ser1/Ser2) were unphosphorylated in the basal state, not affected by nutrients or KCl, and only slightly increased by the PKC activator phorbol 12-myristate 13-acetate (PMA). Like the other insulin secretagogues, however, PMA did promote serine phosphorylation of the myosin heavy chain (MHC) in RINm5F cells. Phosphopeptide mapping suggested that the same peptide was phosphorylated under both PMA and glyceraldehyde stimulation, which further extends our previous study of the Ca2+-dependent phosphorylation of this protein (Wilson JR, Ludowyke RI, Biden TJ: Nutrient stimulation results in a rapid Ca2+-dependent threonine phosphorylation of myosin heavy chain in rat pancreatic islets and RINm5F cells. J Biol Chem 273:22729-22737, 1998). Overall, our results demonstrate that in RINm5F cells and rat pancreatic islets, MHC phosphorylation correlates better with insulin secretion than phosphorylation of the RLC. We therefore propose that in beta-cells, in contrast to other secretory cells, phosphorylation of the MHC is more important than that of the RLC for regulation of the myosin II protein complex during insulin secretion.

Animals↗
PubMed1999

Asymmetric responses in cortical visually evoked potentials to motion are not derived from eye movements.

PURPOSE: Normal neonates and many adults after abnormal visual development have directional preferences for visual stimulus motions; i.e., they give better responses for optokinetic nystagmus (OKN) and visually evoked potentials (VEPs) in one direction than to those in the opposite direction. The authors tested whether the VEP responses were asymmetrical because of abnormal eye movements. METHODS: VEPs were recorded from the visual cortices of five macaque monkeys: one normal, one neonate, and three reared with alternating monocular occlusion (AMO). They were lightly anesthetized, followed by paralysis to prevent eye movements. They then had "jittered" vertical grating patterns presented in their visual fields. The steady state VEPs were analyzed with discrete Fourier transforms to obtain the amplitudes and phases of the asymmetries. RESULTS: The normal, control monkey had small, insignificant amplitudes of its asymmetrical Fourier component and random phases that were not 180 degrees out of phase across the left and right eyes. The neonatal monkey and the AMO monkeys all had large, significant asymmetries that were approximately 180 degrees out of phase between the left and right eyes. CONCLUSIONS: The neonate and abnormally reared monkeys continued to have asymmetrical responses even after their eyes were paralyzed. Therefore, eye movements cannot be the source of the asymmetrical amplitudes of the VEPs, and the visual cortex is at least one source responsible for asymmetries observed in neonates and adults reared under abnormal visual inputs.

Animals↗
PubMed1998

Impact of a nurse practitioner on the cost of managing inpatients with heart failure.

We examined the impact on hospital costs of having a nurse practitioner manage uncomplicated patients hospitalized for decompensated heart failure. This strategy was associated with a significant decrease in total hospital costs ($6,659+/-5,843 vs $5,211+/-4,137 [p < 0.03]), a trend toward decreased length of stay (4.0+/-3.0 vs 3.4+/-2.4 days [p = 0.13]), and no significant change in the 30-day readmission rate (13% of patients vs 16% of patients [p = NS]).

Adult↗
PubMed1998

Nutrient stimulation results in a rapid Ca2+-dependent threonine phosphorylation of myosin heavy chain in rat pancreatic islets and RINm5F cells.

Activation of protein kinases plays an important role in the Ca2+-dependent stimulation of insulin secretion by nutrients. The aim of the present study was to identify kinase substrates with the potential to regulate secretion because these have been poorly defined. Nutrient stimulation of the rat insulinoma RINm5F cell line and rat pancreatic islets resulted in an increase in the threonine phosphorylation of a 200-kDa protein. This was secondary to the gating of voltage-dependent Ca2+ channels because it was reproduced by depolarizing KCl concentrations and blocked by the Ca2+ channel antagonist, verapamil. The peak rises in [Ca2+]i preceded or were coincident with the maximal threonine phosphorylation in response to both glyceraldehyde and KCl. In digitonin-permeabilized RINm5F cells a rise in Ca2+ from 0.1 to 0.15 microM was sufficient to increase phosphorylation. Protein kinase C, protein kinase A, and Ca2+/calmodulin-dependent kinase II did not appear to be responsible for the phosphorylation, yet the Ca2+ dependence of the response suggests possible involvement of other members of the Ca2+/calmodulin-dependent kinase family. The 200-kDa protein was identified as myosin heavy chain by immunoprecipitation with a polyclonal nonmuscle myosin antibody. Phosphopeptide mapping indicated that the site of phosphorylation on myosin heavy chain was the same for both KCl- and glyceraldehyde-stimulated cells. Phosphoamino acid analysis confirmed a low basal phosphothreonine content of myosin heavy chain, which increased 6-fold in response to KCl. A lesser (2-fold) increase in serine phosphorylation was also detected using this technique. Although myosin IIA and IIB were shown to be present in RINm5F cells and rat islets, myosin IIA was the predominant threonine-phosphorylated species, suggesting that the two myosin species might be independently regulated. Our results identify myosin heavy chain as a novel kinase substrate in pancreatic beta-cells and suggest that it might play an important role in the regulation of insulin secretion.

Amino Acids↗
PubMed1998

Frequency of low-risk hospital admissions for heart failure.

Heart failure is one of the most common reasons for admission to acute care hospitals. A proportion of these admissions are probably low risk and could be managed in subacute care facilities, resulting in substantial cost savings. To investigate the proportion of low-risk hospital admissions for heart failure, all admissions for heart failure to Vanderbilt University Medical Center between July 1993 and June 1995 were identified (n = 743). One hundred twenty of these admissions were randomly selected, reviewed, and classified into a high-risk versus low-risk group on admission based on the severity of heart failure and the presence of life-threatening complications. Of the 120 admissions, 57 (48%) were classified as high risk based on the presence of moderate to severe heart failure for the first time or recurrent heart failure with a major complicating factor. Sixteen admissions (28%) were associated with adverse outcomes, including myocardial infarction in 5 (9%), intubation in 6 (11%), and death in 4 (7%). Sixty-three admissions (52%) were classified as low risk based on the presence of new-onset mild heart failure or mild to moderate recurrent heart failure with no complicating factors. Most of these admissions were for dyspnea without any life-threatening complication; 57 (91%) had no evidence of interstitial or alveolar pulmonary edema, and arterial oxygen saturation averaged 95 +/- 3%. Only 3 of these low risk admissions (5%) were associated with an adverse cardiovascular event. None of the patients died. These data suggest that over half of the patients admitted for heart failure to an acute care facility are low risk and probably could be managed in a subacute care setting, resulting in large cost savings.

Aged↗
PubMed1998

Conduction velocity versus amplitude analysis: evidence for demyelination in diabetic neuropathy.

Motor conduction velocities (CVs) were correlated with distal compound muscle action potential (CMAP) amplitudes for tibial, peroneal, and median nerves in patients with biopsy-proven chronic inflammatory demyelinating polyneuropathy (CIDP), diabetic neuropathy, and amyotrophic lateral sclerosis. Only in the diabetic patients did CV significantly correlate with CMAP amplitude. The data show that diabetic neuropathy produces conduction velocity slowing that cannot be explained by axon loss alone, and that differentiation between diabetic neuropathy and CIDP in an individual nerve is difficult.

Action Potentials↗