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PubMed1995

Proliferative responses of T cells from the skin and nerve lesions of leprosy patients.

In the current study we compared the mitogenic responses of T cells from skin and nerve biopsies of leprosy patients with those of peripheral blood mononuclear cells (PBMC). Lymphocytes from these sources were cultured at < or = 100 cells/well in the presence of PHA, irradiated autologous feeder cells, and IL-2, and proliferation was assessed after 6 to 12 days. Whereas PBMC were capable of vigorous responses, the growth of cells from skin and nerve was markedly reduced. The diminished response was independent of the clinical status of leprosy patients and was also observed in skin-infiltrating lymphocytes from patients suffering from other disorders. Analysis of proliferative responses at 1 cell/well suggested both a reduction in precursor frequency and a decrease in mean burst size. Analysis of lymphokine production suggested that cultured cells from skin lesions had reduced IL-w and IL-4 production relative to PBMC generated under similar conditions. Equal numbers of CD3+ cells were present in each source, but lesion cells were enriched in CD45RA- "memory" T cells, as well as CD3+CD28+ T cells. However, these alterations in subpopulation distribution could not account for the substantial differences in proliferative potential. We conclude that significant differences exist in the activation potential of cells from different tissue sources.

CD28 Antigens↗
PubMed1984

Allostery without conformational change. A plausible model.

A general model is presented whereby ligand-induced changes in protein dynamics could produce allosteric communication between distinct binding sites, even in the absence of a macromolecular conformational change. Theoretical analysis, based on the statistical thermodynamics of ligand binding, shows that cooperative interaction free energies amounting to several kJ . mol-1 may be generated by this means. The effect arises out of the possible changes in frequencies and amplitudes of macromolecular thermal fluctuations in response to ligand attachment, and can involve all forms of dynamic behaviour, ranging from highly correlated, low-frequency normal mode vibrations to random local anharmonic motions of individual atoms or groups. Dynamic allostery of this form is primarily an entropy effect, and we derive approximate expressions which might allow the magnitude of the interaction in real systems to be calculated directly from experimental observations such as changes in normal mode frequencies and mean-square atomic displacements. Long-range influence of kinetic processes at different sites might also be mediated by a similar mechanism. We suggest that proteins and other biological macromolecules may have evolved to take functional advantage not only of mean conformational states but also of the inevitable thermal fluctuations about the mean.

Allosteric Regulation↗
PubMed1991

Reoxygenation-induced arrhythmogenic transient inward currents in isolated cells of the guinea-pig heart.

Transient inward currents (Iti), activated by a rise in intracellular Ca concentration, are believed to trigger cardiac arrhythmias in reperfused hearts. In this report, Iti in isolated cardiocytes from the guinea-pig were evoked by reoxygenation following a period of anoxia of between 4 min and 35 min. Reoxygenation was performed 1 min after the full development of an anoxia-induced time-independent K current. This current disappeared within 2-6 s and in the following 10 s Iti developed to maximum amplitude. Iti were evoked using a constant pulse pattern (holding potential Vh = -45 mV; test potential Vt = +10; pulse duration 350 ms; frequency 1 Hz). In more than 95% of the cells, Iti at the holding potential Iti (-45 mV) declined with a time constant of tau = 670 +/- 240 ms (mean +/- SD, n = 17). In two cells, undamped oscillatory currents were observed. The amplitude of Iti (-45 mV) was proportional to the amplitude and duration of the preceding depolarizing test pulse. Test pulses of long duration (500 ms and 1000 ms, mean +/- SD) to potentials positive to +10 mV produced slowly decaying tail currents (tau = 391 +/- 51 ms, mean +/- SD), which superimposed with Iti (-45 mV). The current/voltage relationship of Iti peaked between -30 mV and -10 mV and approximated zero at the most positive potentials, i.e. no reversal of Iti was found up to +80 mV. Using double-pulse protocols (prepulse potential +40 mV), Iti were enhanced at potentials negative to -30 mV and were also present in the range of the normal resting potential of ventricular heart cells. The instantaneous current-voltage relationship was monotone between -50 mV and +40 mV. Because of the dependence of Iti on the preceding depolarization, the instantaneous current-voltage relationship provides more reliable information on the voltage dependence of Iti. The interval between two subsequent Iti (-45 mV) values was 237 +/- 35 ms (mean +/- SD, n = 27) and depended on the amplitude of Iti (-45 mV) to increase by 5.2 +/- 0.5% (mean +/- SD) per 100 pA decrease in Iti (-45 mV). A simple noise analysis showed that if one assumes that ionic channels are responsible for the generation of Iti (-45 mV), their unitary conductance cannot exceed 0.36 pS. We conclude that reoxygenation-induced Iti are triggered by a cyclic release of Ca from the sarcoplasmic reticulum and provide evidence that they are mediated by the electrogenic Na/Ca exchanger.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2004

One year outcomes and costs following a vertebral fracture.

Vertebral fractures are believed to be important predictors for future vertebral and other fractures, leading to at least a 4- to 5-fold increase in the risk of subsequent fractures. However, little is known about their associated near-term costs. The purpose of this study was to quantify the subsequent fracture and cost outcomes emanating from patients with an incident vertebral fracture. A probabilistic decision analysis model was developed to estimate the expected cost of all subsequent fractures. We ran Kaplan-Meier time-to-event models on placebo patients in risedronate's pivotal phase III clinical trial data to determine the cumulative incidence or probabilities of all fractures within one year of an incident vertebral fracture. Unit costs for health care payers in the USA and Sweden for vertebral, hip, other, and forearm/wrist fractures were multiplied by fracture probabilities to generate the expected costs of new fractures within one year of incident vertebral fractures. Our analysis found that that 26.1% of vertebral fracture patients with a mean age of 74 years refractured within 1 year (vertebral 17.4%; hip 3.6%; "other" 3.5%; forearm/wrist 1.6%). The calculated medical costs for those patients who refracture within 1 year was $5906 and 3670 euros for the USA and Sweden, respectively, while the weighted average cost across all patients (refracture and non-fracture) within a year of their incident fracture was $1541 (USA) and 958 euros (Sweden). These results suggest that therapies with proven, rapid efficacy may offer important economic value to healthcare payers, providers and patients.

Aged↗
PubMed2001

Models of central pattern generators for quadruped locomotion. I. Primary gaits.

In this paper we continue the analysis of a network of symmetrically coupled cells modeling central pattern generators for quadruped locomotion proposed by Golubitsky, Stewart, Buono, and Collins. By a cell we mean a system of ordinary differential equations and by a coupled cell system we mean a network of identical cells with coupling terms. We have three main results in this paper. First, we show that the proposed network is the simplest one modeling the common quadruped gaits of walk, trot, and pace. In doing so we prove a general theorem classifying spatio-temporal symmetries of periodic solutions to equivariant systems of differential equations. We also specialize this theorem to coupled cell systems. Second, this paper focuses on primary gaits; that is, gaits that are modeled by output signals from the central pattern generator where each cell emits the same waveform along with exact phase shifts between cells. Our previous work showed that the network is capable of producing six primary gaits. Here, we show that under mild assumptions on the cells and the coupling of the network, primary gaits can be produced from Hopf bifurcation by varying only coupling strengths of the network. Third, we discuss the stability of primary gaits and exhibit these solutions by performing numerical simulations using the dimensionless Morris-Lecar equations for the cell dynamics.

Animals↗
PubMed1987

Description of the sub-miniature endplate potential distribution, determination of subunit size and number of subunits in the adult frog neuromuscular bell-miniature endplate potential.

Miniature endplate potentials were recorded from the isolated pectoralis cutaneous muscle of the frog during very stable recording conditions and low noise levels. Two to 5 x 10(3) miniature endplate potentials were filmed at eight unstressed junctions that met rigorous experimental criteria for analysis. Seven junctions generated enough sub-miniature endplate potentials (1-3%) to produce a bell-shaped amplitude distribution. The sub-miniature endplate potential means were usually 9-10 times smaller than the modal bell-miniature endplate potential values. The standard deviation of the sub-miniature endplate potential class was calculated by subtracting the noise and measurement error from the measured sub-miniature endplate potential distribution. The coefficients of variation of the sub-miniature endplate potential distribution were 9-16%. Half of the bell-miniature endplate potential amplitude distributions showed 4-6 integral peaks in the central part of the distributions and the positions of these peaks were maintained with increasing sample size. The remaining distributions were not smooth and suggested integral peaks. The intervals between the peaks were about the same size as the sub-miniature endplate potential mode. These data provide further evidence for the subunit hypothesis of the quantum of transmitter release and describe the amplitude distribution of the sub-miniature endplate potential class of the adult preparation.

Action Potentials↗
PubMed2005

Spectral moments of the long-term average spectrum: sensitive indices of voice change after therapy?

Voice clinicians require an objective, reliable, and relatively automatic method to assess voice change after medical, surgical, or behavioral intervention. This measure must be sensitive to a variety of voice qualities and severities, and preferably should reflect voice in continuous speech. The long-term average spectrum (LTAS) is a fast Fourier transform-generated power spectrum whose properties can be compared with a Gaussian bell curve using spectral moments analysis. Four spectral moments describe features of the LTAS: Spectral mean (Moment 1) and standard deviation (Moment 2) represent the spectrum's central tendency and dispersion, respectively. Skewness (based on Moment 3) and kurtosis (based on Moment 4) represent the spectrum's tilt and peakedness, respectively. To examine whether the first four spectral moments of the LTAS were sensitive to perceived voice improvement after voice therapy, this investigation compared pretreatment and posttreatment voice samples of 93 patients with functional dysphonia using spectral moments analysis. Inspection of the results revealed that spectral mean and standard deviation lowered significantly with perceived voice improvement after successful behavioral management (p < 0.001). However, changes in skewness and kurtosis were not significant. Furthermore, lowering of the spectral mean uniquely accounted for approximately 14% of the variance in the pretreatment to posttreatment changes observed in perceptual ratings of voice severity (p < 0.001), indicating that spectral mean (ie, Moment 1) of the LTAS may be one acoustic marker sensitive to improvement in dysphonia severity.

Adolescent↗
PubMed2002

Computed tomography perfusion imaging in acute stroke.

The development of thrombolytic and neuroprotective agents for the treatment of acute stroke has created an imperative for improved imaging techniques in the assessment of acute stroke. Five cases are presented to illustrate the value of perfusion CT in the evaluation of suspected acute stroke. To obtain the perfusion data, a rapid series of images was acquired without table movement following a bolus of contrast medium. Cerebral blood flow, cerebral blood volume and mean transit time were determined by mathematically modelling the temporal changes in contrast enhancement in the brain and vascular system. Pixel-by-pixel analysis allowed generation of perfusion maps. In two cases, CT-perfusion imaging usefully excluded acute stroke, including one patient in whom a low-density area on conventional CT was subsequently proven to be tumour. Cerebral ischaemia was confirmed in three cases, one with an old and a new infarction, one with a large conventional CT abnormality but only a small perfusion defect, and one demonstrating infarct and penumbra. Perfusion CT offers the ability to positively identify patients with non-haemorrhagic stroke in the presence of a normal conventional CT, to select those cases where thrombolysis is appropriate, and to provide an indication for prognosis.

Acute Disease↗
PubMed1987

Insertion and deletion mutagenesis of the human cytomegalovirus genome.

Studies on human cytomegalovirus (CMV) have been limited by a paucity of molecular genetic techniques available for manipulating the viral genome. We have developed methods for site-specific insertion and deletion mutagenesis of CMV utilizing a modified Escherichia coli lacZ gene as a genetic marker. The lacZ gene was placed under the control of the major beta gene regulatory signals and inserted into the viral genome by homologous recombination, disrupting one of two copies of this beta gene within the L-component repeats of CMV DNA. We observed high-level expression of beta-galactosidase by the recombinant in a temporally authentic manner, with levels of this enzyme approaching 1% of total protein in infected cells. Thus, CMV is an efficient vector for high-level expression of foreign gene products in human cells. Using back selection of lacZ-deficient virus in the presence of the chromogenic substrate 5-bromo-4-chloro-3-indolyl beta-D-galactoside, we generated random endpoint deletion mutants. Analysis of these mutants revealed that CMV DNA sequences flanking the insert had been removed, thereby establishing this approach as a means of determining whether sequences flanking a lacZ insertion are dispensable for viral growth. In an initial test of the methods, we have shown that 7800 base pairs of one copy of L-component repeat sequences can be deleted without affecting viral growth in human fibroblasts.

Bacterial Proteins↗
PubMed2001

Polymorphism of human Alpha class glutathione transferases.

The recognition of the importance and utility of single nucleotide polymorphisms has generated an interest in the development of new strategies for their identification. Analysis of the Expressed Sequence Tag (EST) database can provide a rapid and efficient means of identifying polymorphisms. Screening of the Alpha class glutathione transferases (GSTs) in the EST database identified 10 putative polymorphisms in the coding region of the GSTA1 and GSTA2 genes, six of which were subsequently verified by sequence analysis. Polymerase chain reaction/restriction fragment length polymorphism analysis revealed the existence of three variants, a silent base substitution, K125K (G365A) in GSTA1, and T112S and E210A in GSTA2, in European Australian, African and Chinese populations. The variant isoforms of GSTA2 were expressed in Escherichia coli, purified, and enzymatically characterized. Modelling of the two GSTA2 polymorphisms into a three-dimensional structure of GSTA2, and characterization of their enzymatic properties, has shown that the structure and function of the wild-type GSTA2-2 isoenzyme is not significantly altered by these polymorphisms. This report demonstrates that analysis of the EST database provides a rapid and efficient means of identifying variant proteins.

Alleles↗
PubMed1985

The genetics of schizophrenia: new perspectives.

Despite the evidence for genetic factors in schizophrenia, the underlying hereditary defect is unknown. The author reviews recent advances in genetic research methodologies and discusses their strengths and limitations. He concludes that in the face of genetic heterogeneity current models of segregation analysis are not likely to unravel the mode of inheritance of schizophrenia. The author underscores the potential contribution of both molecular genetics (as a means to generate DNA markers) and studies with biologic vulnerability traits to identifying and quantitating the genetic component in the transmission of schizophrenia.

Chromosome Mapping↗
PubMed1987

The sound of two hands clapping: an exploratory study.

Clapping is a little-studied human activity that may be viewed either as a form of communicative group behavior (applause) or as an individual sound-generating activity involving two "articulators"--the hands. The latter aspect was explored in this pilot study by means of acoustical analyses and perceptual experiments. Principal components analysis of 20 subjects' average clap spectra yielded several dimensions of interindividual variation that were related to observed hand configuration. This relationship emerged even more clearly in a similar analysis of a single clapper's deliberately varied productions. In perception experiments, subjects proved sensitive to spectral properties of claps: For a single clapper, at least, listeners were able to judge hand configuration with good accuracy. Besides providing some general information on individual variations in clapping, the present results support the general hypothesis that sound emanating from a natural source informs listeners about the changing states of the source mechanism.

Adult↗
PubMedDate not supplied

The benefit of negative tests in non-ulcer dyspepsia.

OBJECTIVES: Negative diagnostic tests are usually evaluated by their ability to advance a diagnostic search, or they are considered redundant expenditures in establishing a definitive diagnosis. It has remained difficult to assess their benefit in terms of their own merit and the reassurance that they provide to a patient. The aim of the present study is to develop a mathematical model for quantifying the impact of diagnostic tests on a patient's health-related quality of life (HRQL). METHODS: An influence diagram is used to model how non-ulcer dyspepsia (NUD) and its medical care affect HRQL. Diagnostic tests and medical therapy benefit HRQL by alleviating fear of disease and NUD symptoms. Medical care can also adversely affect HRQL, lead to expenses in time and money, and compromise a patient's sense of autonomy. HRQL is modeled as the focal point of multiple influences detracting from its value. RESULTS: Negative diagnostic tests can improve HRQL in NUD. The improvement of HRQL by diagnostic tests depends on a multitude of individual influences and the interactions between them, such as the severity of NUD symptoms andfear of disease, as well as the impact of medical care itself on HRQL. If a patient harbors a strong fear of serious disease or cancer, more extensive testing is likely to improve the patient's well-being and appears a worthwhile endeavor. Other patients, however, would be served perfectly well by empirical therapy only. For the vast majority of subjects with NUD who never seek medical advice, the unpleasantness of the disease itself does not outweigh the anticipated downside of obtaining medical care. CONCLUSION: The analysis illustrates the applicability of the influence diagram in modeling disease behavior. This method helps to assess the benefit of negative tests beyond their means of generating information.

Attitude to Health↗
PubMed1995

Best interests: a concept analysis and its implications for ethical decision-making in nursing.

The purpose of this paper is to analyse the concept of 'best interest' in order to give nurses, who use it to justify their actions, a clear picture of what this means, and to identify the skills needed for doing so. The process for concept analysis developed by Walker and Avant was used in the analysis of data generated from the literature. Themes were identified from which the defining attributes, antecedents and consequences emerged. The congruence of the findings with current values in nursing, such as promotion of patient autonomy, and the nurse as advocate, are discussed, together with the underpinning ethics theory. The skills needed for nursing practice are identified and recommendations for nurse education are made.

Beneficence↗
PubMedDate not supplied

Observer sensitivity to retinal vessel diameter and tortuosity in retinopathy of prematurity: a model system.

BACKGROUND: Abnormally increased diameter and tortuosity of retinal blood vessels in the posterior pole, or "plus disease," is recognized as a powerful predictor of poor outcome in eyes with retinopathy of prematurity (ROP). Although the diagnosis of plus disease depends upon the examiner's ability to examine retinal blood vessels, the ability of the human observer to identify changes in retinal blood vessel diameter and tortuosity accurately has not been studied. METHODS: Using computer-aided analysis of fundus photographs from eyes with a wide range of ROP severity, we generated tracings of posterior pole blood vessels which varied by quintiles of mean vessel diameter and tortuosity. Subjects (23 naive and 12 expert observers) ranked groups of tracings in order of increasing mean vessel diameter and tortuosity. These ranking tests were performed on tracings derived from the same fundus and tracings derived from distinct fundi. In a similar fashion, subjects also compared one designated standard fundus tracing with 25 distinct fundus tracings. RESULTS: Vessel diameter was assessed correctly more often than vessel tortuosity, both among similar (> 99% vs 92% of the time, respectively, P < 0.001), or among distinct (88% vs 78% of the time, respectively, P < 0.001) fundus images. The mean vessel diameter and tortuosity of 25 distinct fundus images were correctly ranked versus a standard image in 89% of attempts. Assessments of increments in vessel diameter and tortuosity were independent. Naive and expert subjects performed indistinguishably on all tests. CONCLUSIONS: Intelligent human observers have considerable ability to discern clinically relevant increments in blood vessel diameter and tortuosity. This ability may facilitate standardization in the diagnosis of plus disease in ROP.

Computer Simulation↗
PubMed2005

Variation of fetal nasal bone length in second-trimester fetuses according to race and ethnicity.

OBJECTIVE: The purpose of this study was to determine the influence of race and ethnicity on the expected nasal bone length (NBL) based on biparietal diameter (BPD) measured in second-trimester fetuses. METHODS: We searched our ultrasound, obstetric, and cytogenetic databases for all second-trimester fetuses with measured NBLs. Fetuses with Down syndrome were identified and excluded from the analysis. Linear regression curves were generated for NBL by BPD according to race and ethnicity. Categories used were African American, Hispanic, Asian, and white. Analysis of variance was used to compare mean variation of observed from expected NBL by BPD according to race and ethnicity. RESULTS: There were 717 fetuses with NBL-by-BPD pairs who were available for analysis in our population, including 139 African American, 58 Hispanic, 22 Asian, and 498 white fetuses. Nasal bone length was highly correlated with BPD for each race (P < .001). Mean variances of observed from expected NBL by BPD were statistically different according to race or ethnicity (P = .0092). CONCLUSIONS: Race and ethnicity significantly affect the mean regression line of expected NBL by BPD among fetuses in the second trimester. Genetic sonographic norms, therefore, appear to require race- and ethnicity-specific formulas for NBL.

Black or African American↗
PubMed2004

Growth centiles for Omani premature infants born at 26 weeks of gestation.

OBJECTIVE: The present growth chart used in the Sultanate of Oman does not contain centile measurements for infants born at 26-weeks of gestation. With the increased survival of these premature infants, there is a growing need to develop such a chart. The present study was conducted with the aim to look at the anthropometric measurements (weight, length and head circumference) of Omani premature infants born at 26-weeks of gestation and to develop centile charts for these measurements. METHODS: The study was conducted at the Special Care Baby Unit (SCBU) of the Royal Hospital, one of the major perinatal institutions in Muscat, Oman. A computerized database is maintained for all the admissions from 1996. We extracted the required anthropometric data for all 26-week gestation premature Omani infants admitted to SCBU from January 1996 to November 2003. A total of 49 babies were admitted during that period. Out of these, 43 had complete information on the growth parameters, including birth weight, length and head circumference. These parameters were noted down and by using the statistical package, an analysis was performed to get the normal distribution curve. By using the Microsoft Excel program, graphs were generated for all the 3 growth parameters. RESULTS: The mean birth weight for the premature infants born at 26-week gestation was noted to be 908 +/- 156 grams, with length and head circumference of 33.5 +/- 2.5 and 24.5 +/- 1.7 centimeters. The normal distribution curve was obtained with minimal skewing. CONCLUSION: We were able to generate centile charts of the anthropometric measurements for Omani infants born at 26-weeks of gestation. The next step is to collect the national data from other institutions in Oman and then incorporate it into the present growth chart to make the charts more valid, reliable and applicable.

Anthropometry↗