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PubMed2005

Methodological problems in pressure profile calculations for lipid bilayers.

From molecular dynamics simulations of a dipalmitoyl-phosphatidyl-choline (DPPC) lipid bilayer in the liquid crystalline phase, pressure profiles through the bilayer are calculated by different methods. These profiles allow us to address two central and unresolved problems in pressure profile calculations: The first problem is that the pressure profile is not uniquely defined since the expression for the local pressure involves an arbitrary choice of an integration contour. We have investigated two different choices leading to the Irving-Kirkwood (IK) and Harasima (H) expressions for the local pressure tensor. For these choices we find that the pressure profile is almost independent of the contour used, which indicates that the local pressure is well defined for a DPPC bilayer in the liquid crystalline phase. This may not be the case for other systems and we therefore suggest that both the IK and H profiles are calculated in order to test the uniqueness of the profile. The second problem is how to include electrostatic interactions in pressure profile calculations when the simulations are conducted without truncating the electrostatic potential, i.e., using the Ewald summation technique. Based on the H expression for the local pressure, we present a method for calculating the contribution to the lateral components of the local pressure tensor from electrostatic interactions evaluated by the Ewald summation technique. Pressure profiles calculated with an electrostatic potential truncation (cutoff) from simulations conducted with Ewald summation are shown to depend on the cutoff in a subtle manner which is attributed to the existence of long-ranged charge ordering in the system. However, the pressure profiles calculated with relatively long cutoffs are qualitatively similar to the Ewald profile for the DPPC bilayer studied here.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2002

Irving S. Cooper and his role in intracranial stimulation for movement disorders and epilepsy.

Dr. Irving Cooper (1922-1985) was a pioneer in the field of functional neurosurgery. After years of treating patients with tremor by creating deep lesions with either anterior choroidal artery ligation or cryogenic thalamotomy, he began to utilize methods of electrical cerebral stimulation as treatment for a variety of disorders. Chronic cerebellar stimulation was employed for patients with epilepsy, cerebral palsy, and dystonia. While Dr. Cooper believed his results to be significant, there still remain many challenges to his claims. Later in his career, he placed deep brain electrodes in the internal capsule and thalamus for epilepsy and dystonia. His encouraging results from this small series were often overlooked. This paper reviews the science behind Dr. Cooper's work, his case series, and the controversies surrounding his results.

Electric Stimulation↗
PubMed2006

On-line drug metabolism in capillary electrophoresis. 1. Glucuronidation using rat liver microsomes.

A rat liver microsome pseudostationary phase has been used for the on-line capillary electrophoresis monitoring of glucuronidation. Uridine diphosphate glucuronosyltransferase (EC 2.4.1.17) containing microsomes was isolated from rat liver and directly injected onto neutrally coated capillary containing polymeric replaceable gels followed by injection of the substrate mixture. On-line glucuronidation was observed within 15 min without any sample preparation. The factors affecting the separation of glucuronides and parent compounds were investigated by varying the applied electric fields and the size (length and internal diameter) of capillary. The Michaelis-Menten parameters (Km and Vmax) for the glucuronidation of 4-methyl-7-hydroxy coumarin and 4-nitrophenol were determined using the CE method and by off-line microsomal incubation. No significant differences were observed for Km and Vmax values for 4-methyl-7-hydroxycoumarin and 4-nitrophenol between on-line and off-line glucuronidation of these two compounds. This method was also used to determine the inhibition constant (IC50 value) for the competitive inhibition of morphine glucuronidation by codeine, IC50 (on-line) = 170 vs 580 microM (off-line). The results demonstrate that this method can be used to screen for the glucuronidation of test compounds and should reduce the time required for this screening process.

Animals↗
PubMed1983

Development of simple standard assay procedures for the characterization of snake venom.

In accordance with the recommendations of the report of a WHO Coordination Meeting on Venoms and Antivenoms, methods have been developed for the assessment of lethal, defibrinogenating, procoagulant, haemorrhagic, and necrotizing properties of venoms, and used to study 53 venoms from 30 different species of snakes of medical importance throughout the world. The venoms studied included Echis carinatus (Iran), Naja naja kaouthia (Thailand), Notechis scutatus (Australia), Trimeresurus flavoviridis (Japan), Vipera russelli (Thailand), and Crotalus atrox (USA), which comprise six of the eight venoms designated by WHO as international reference venoms (IRVs). (C. atrox venom replaced C. adamanteus venom, as an adequate supply of the latter was not available.) The tests used were simple and should be reproducible in other laboratories throughout the world. Procedures for assaying neuromuscular paralytic activity and systemic myotoxic activity have yet to be developed.The tests will be used to assay the neutralizing potency of both international standard antivenoms (raised using the IRVs) and new and currently available commercial antivenoms. Such studies should result in the production of more potent antivenoms for use in both developing and developed countries, and improve the understanding and management of snake bite throughout the world.

Animals↗
PubMed1975

Weight carrying after myocardial infarction.

The blood-pressure responses to carrying a 15 kg. weight in a shoppong basket, and in a rucksack on the back, were compared in 13 ambulant male patients who were convalescing from an uncomplicated myocardial infarction. In 8 of the patients a sustained-handgrip test was also performed. Carrying the weight in the hand produced a distinct increase in blood-pressure, which did not occur when the weight was carried on the back. There was also a significant increase in blood-pressure during sustained handgrip. In view of the lack of symptoms with these circulatory changes, it is concluded that more specific advice about the possible dangers of sustained static exercise should be given to patients recovering from myocardial infarction.

Activities of Daily Living↗
PubMed1988

In vivo determination of ATP in tumors using 31P inversion spin transfer.

The in vivo exchange kinetics of creatine kinase in the hind leg muscle of rats containing a transplanted mammary adenocarcinoma has been investigated using 31P magnetic resonance spectroscopy. Using a solenoid coil, the adenosine triphosphate (ATP) resonances arising from the tumor could be distinguished from ATP resonances arising from the muscle surrounding the tumor by use of inversion spin transfer techniques. This procedure affords a specific method of evaluating ATP metabolism of tumors in vivo.

Adenocarcinoma↗
PubMed1995

Manometric asymmetry in the anal canal in controls and patients with fecal incontinence.

PURPOSE: This study was designed to ascertain the existence of manometric asymmetry in the anal canal in controls and in patients with fecal incontinence. METHODS: A computerized manometric technique with an eight-channel perfusion catheter was used. Coefficient of variation (CV, a mathematical expression of the degree or magnitude of deviation of a set of data points from the mean) was developed in this study as an index of anal canal manometric asymmetry. RESULTS: At 1 cm from the anal verge, mean CV was 9.3 and 8.7 percent in asymptomatic control males and females, respectively. During a maximum voluntary squeeze effort, mean CV in control males was 9.3 percent and was not significantly different (P = 0.28) from that in control females (7.8 percent). In 14 consecutive female patients with fecal incontinence, mean CV at rest (1 cm from the anal verge) was 21 percent and was significantly higher (P < 0.01) than in control females. Similarly, during a maximum voluntary squeeze effort, mean CV in patients with fecal incontinence was 20.5 percent and was significantly higher (P < 0.01) than in the female control group (7.8 percent). CONCLUSION: It is concluded that CV, a method of expressing anal sphincter manometric asymmetry, is a useful manometric parameter in the assessment of anorectal function.

Adult↗
PubMed1984

Rapid determination of whole-body bicarbonate kinetics by use of a digital infusion.

Accurate determination of substrate oxidation rates from breath 13CO2 levels often requires information on the bicarbonate status of the subject. We have developed a rapid method to obtain a complete set of bicarbonate kinetic parameters, prime bicarbonate pools with 13C, clamp breath 13CO2 levels rapidly and accurately with predetermined ranges, and provide a steady base-line enrichment of 13C for a subsequent substrate oxidation measurement. The method consists of administering NaH13CO3 intravenously as a combination of a bolus dose, an exponentially decreasing infusion, and a constant infusion. A Harvard model 2729 microprocessor-controlled syringe pump was modified for external control and coupled to a Hewlett-Packard HP-85 desk-top computer to deliver the complex infusion. An infusion algorithm that would rapidly attain and maintain an increase of 50% 13C enrichment of breath CO2 was derived by using the SAAM-27 program to interrogate a three-compartmental model of bicarbonate kinetics in normal, fasted, resting adult subjects. When the method was tested on five adult fasted subjects who had rested for 1.5 h, plateau enrichments were achieved within 10-20 min. The bicarbonate pool sizes and kinetic parameters obtained by compartmental analysis of their 13CO2 data were used to obtain a refined infusion protocol, which resulted in more rapid attainment of plateau enrichments. If carried out immediately before a substrate oxidation test, the method can provide a complete description of bicarbonate kinetics for use in the compartmental and noncompartmental analysis of substrate catabolism.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2006

Estimated progression rates in three United Kingdom hepatitis C cohorts differed according to method of recruitment.

OBJECTIVES: To estimate hepatitis C virus (HCV) progression rates between disease stages prior to cirrhosis, using data from liver biopsies in three observational cohorts. To demonstrate how the method of cohort recruitment can influence the estimation of HCV-progression rates. STUDY DESIGN AND SETTING: Data came from three United Kingdom observational cohorts, assembled from different referral sources. In total, 987 HCV-infected patients with an estimated (or known) date of infection and at least one histologically scored liver biopsy were eligible for inclusion in the analysis. Liver biopsy scores were used to determine the stage of HCV-related liver disease. A three-state continuous time Markov model was used to estimate covariate-specific average probabilities of progression of disease. RESULTS: After adjusting for confounders, considerably different rates of disease progression were estimated in the three cohorts. For a group of patients with the same demographics, the estimated 20-year probability of progression to cirrhosis was 12% (95% confidence interval CI = 6-22) in a hospital-based cohort, 6% (95% CI = 3-13) in a posttransfusion cohort, and 23% (95% CI = 14-37) in a cohort recruited from a tertiary referral center. CONCLUSION: Researchers using estimates of disease progression should be aware that the method of cohort recruitment has considerable influence on the progression rates that are derived.

Cohort Studies↗
PubMed1994

Automated reticulocyte counting and measurement of reticulocyte cellular indices. Evaluation of the Miles H*3 blood analyzer.

This study evaluated reticulocyte counting and measurement of reticulocyte cellular indices with the Miles H*3 blood analyzer, a new instrument that combines the Technicon/Miles technology for blood cells counting with a staining technique allowing counting of reticulocytes, quantification of staining intensity and measurement of reticulocyte cellular indices. Reticulocyte counts obtained with the Miles H*3 analyzer were compared with those obtained by manual counting, flow cytometry (thiazole orange method) and by the Sysmex R-3000 (Baxter Diagnostics) reticulocyte analyzer. Reticulocyte counting with the Miles H*3 showed excellent precision, and linearity in the range tested (1.1-49% and 1-72% reticulocytes, respectively, with two different protocols) with no significant carryover. Reticulocyte counts were stable after storing blood samples for 72 hours at 4 degrees C. Comparison of the four different methods, showed an acceptable intraclass correlation between Miles H*3 and Sysmex R-3000 (intraclass correlation coefficient, [ri] = .952), Miles H*3 and flow cytometry (ri = .922), and Sysmex R-3000 and flow cytometry (ri = .938). There was no satisfactory correlation between any of the three automated methods and the values obtained with manual counting of reticulocytes (ri = .538-.755), consistent with the well known imprecision of the manual technique. For a group of normal pediatric subjects, age 1-10, we obtained the following values (+/- SD) of reticulocyte indices: mean corpuscular volume 97.6 +/- 4.7 fL; cell hemoglobin concentration mean 28.2 +/- 1.4 g/dL; cell hemoglobin content 26.7 +/- 1.6 pg. We determined the direct cost, including depreciation, of the manual and instrumental methods. Cost/test varied from $1.61 for manual method to $6.03 for the Sysmex R-3000. Cost/test for flow cytometry and Miles H*3 were $3.34 and $3.49, respectively.

Child↗
PubMed2006

Emergency department visits among pediatric patients for sports-related injury: basic epidemiology and impact of race/ethnicity and insurance status.

OBJECTIVES: (1) To characterize the demographics and external causes of pediatric sports injury-related visits (SIRVs) to emergency departments (EDs). (2) To analyze the effect of race/ethnicity and insurance on SIRVs to EDs. METHODS: A stratified random-sample cross-sectional survey of EDs in the National Hospital Ambulatory Medical Care Survey was conducted from 1997-2001; for patients younger than 19 years, we used all visits [n = 33,654; injury-related visits (IRVs) = 13,496, SIRVs = 2990]. We examined both the external cause codes and the actual verbatim text of all IRVs. National estimates of pediatric IRVs were obtained using the assigned patient visit weights in the National Hospital Ambulatory Medical Care Survey databases and SUDAAN 9.1 software (SAS Institute, Inc., Cary, NC). RESULTS: Sports injuries resulted in 2.5 million visits annually, or 23% of ED IRVs. Male sex, older age (6-18 years), and white race/ethnicity are associated with higher rates of SIRVs. Cycling, basketball, playground injuries, and football resulted in the largest numbers of ED SIRVs. Leading diagnoses for SIRVs included fractures and dislocations, sprains and strains, open wounds, and contusions. Hispanic race/ethnicity was associated with lower rates of SIRVs across all insurance types. After controlling for demographic factors and insurance, Hispanic children were less likely to have an SIRV than white children (odds ratio, 0.7; 95% confidence interval, 0.6-0.9). CONCLUSIONS: Sports and recreation are the leading causes of pediatric ED IRVs. Hispanic children, regardless of insurance status, had lower rates of SIRVs than white children, which helps explain the lower rate of nonfatal IRVs to EDs among Hispanic youth.

Adolescent↗
PubMed2004

Facilitation of primary coronary angioplasty by early start of a glycoprotein 2b/3a inhibitor: results of the ongoing tirofiban in myocardial infarction evaluation (On-TIME) trial.

AIM: Although primary angioplasty is effective despite additional transportation delay, improved patency before PCI might be obtained by starting pharmacological pre-treatment before transportation. METHODS AND RESULTS: From June 2001 to November 2002, 507 patients with acute myocardial infarction, who were transferred to a PCI centre, were randomised to early, pre-hospital initiation of Tirofiban (Early) or to initiation in the catheterisation laboratory (Late). The primary end-point was TIMI flow grade 3 of the infarct-related vessel (IRV) at initial angiography, as assessed by an independent core-lab. The effect of Tirofiban on each TIMI flow component, the presence of thrombus at initial angiography and pre-PCI myocardial blush grade were secondary end-points. A large proportion of patients (41%) was diagnosed and randomised in the ambulance, without intervention of a physician. In the Early group, Tirofiban was administered a median of 59 min (range 11-178 min) earlier than in the Late group. At initial angiography, TIMI 3 flow was present in 19% the Early group and in 15% in the Late group (P = 0.22). The combined incidence of TIMI 2 or 3 flow was present in 43% in the Early group and in 34% in the Late group, respectively (P = 0.04). Thrombus or a fresh occlusion was present in 60% and 73% in the Early and Late group, respectively (P = 0.002). A pre-PCI myocardial blush grades 2 or 3 was more often present in the Early group (30% vs. 22%, P = 0.04). However, no difference in TIMI 3 flow or myocardial blush grade was found between the groups, post-PCI. At one-year follow-up, the combined incidence of death or recurrent MI was not different between the groups (7.0% vs. 7.0%, P = 0.99). CONCLUSION: Early initiation of Tirofiban did not improve initial TIMI 3 flow of the IRV significantly. Despite a better patency (TIMI 2 or 3 flow), a lower prevalence of thrombus or fresh occlusion and a better myocardial perfusion in the infarct-related region pre-PCI, no beneficial effect on post-PCI angiographic or clinical outcome was found, as compared to initiation of Tirofiban in the catheterisation laboratory.

Aged↗
PubMed2002

Phase III study of ibuprofen versus placebo for radiation-induced genitourinary side effects.

PURPOSE: On the basis of our anecdotal clinical observations that nonsteroidal anti-inflammatory agents relieved dysuria during radiotherapy for patients with prostate cancer, we conducted a Phase III randomized trial of ibuprofen vs. placebo for patients who had an increase in acute urinary symptoms. Our in vitro and in vivo laboratory data with a higher concentration of ibuprofen than achievable in this study demonstrated radiosensitization. This study examined whether the inflammatory response within the prostate during radiotherapy would respond to the standard dose of ibuprofen as assessed by a symptom score. METHODS AND MATERIALS: Patients were registered to the study and were followed weekly with a formal symptom assessment. A double-blind randomization to ibuprofen, 400 mg q.i.d., vs. placebo for 7 days was done at a time when the severity score increased. The symptom response was evaluated at the end of the week. RESULTS: Between 1995 and 1998, 100 patients were entered, 28 did not have a sufficient change in symptom score to be randomized, and 19 were either unable to take ibuprofen or withdrew before randomization. Of the 53 patients randomized, 27 received placebo and 26 ibuprofen. No statistically significant differences were found between the placebo and ibuprofen groups between baseline and randomization or between randomization and the 1-week posttreatment assessment. Neither group had a change in symptom severity between randomization and the 1-week posttreatment evaluation. CONCLUSION: The standard anti-inflammatory dose of ibuprofen did not relieve the acute urinary or rectal symptoms during radiotherapy for prostate cancer. The nonsteroidal anti-inflammatory drugs are potential radiation sensitizers with the mechanism of action as yet unknown. Clinical trials of the cyclooxygenase inhibitors as radiation sensitizers should explore a range of doses and evaluate potential mechanisms of action, including cyclooxygenase inhibition and other non-cyclooxygenase mechanisms.

Aged↗
PubMed2003

Quantitative determination of the enantiomers of methadone and its metabolite (EDDP) in human saliva by enantioselective liquid chromatography with mass spectrometric detection.

A sensitive enantioselective liquid chromatographic assay with mass spectrometric detection (LC-MS) has been developed and validated for the simultaneous determination of saliva concentrations of (R)- and (S)-methadone (Met) and (R)- and (S)-2-ethylidene-1,5-dimethyl-3,3-diphenyl-pyrrolidine (EDDP, a primary metabolite of Met). Saliva specimens were collected using Salivette devices (Sarsedt), and centrifuged; collected saliva was then spiked with deuterated internal standards, D3-Met and D3-EDDP, and directly injected into the LC-MS. Enantioselective separations were achieved on a liquid chromatographic chiral stationary phase (CSP) based upon immobilized alpha(1)-acid glycoprotein (AGP) using a mobile phase composed of acetonitrile: ammonium acetate buffer (10mM, pH 7.0) in a ratio of 18:82 (v/v), a flow rate of 0.9 ml/min and a temperature of 25 degrees C. Under these conditions, enantioselective separations were observed for methadone (alpha=1.30) and EDDP (alpha=1.17) within 15 min. Met, EDDP, D3-Met and D3-EDDP were detected using selected ion monitoring at m/z 310.20, 278.20, 313.20 and 281.20, respectively. Linear relationships between peak height ratio and drug-enantiomer concentrations were obtained for methadone in the range of 5.0-600.0 ng/ml, and for EDDP from 0.5 to 15.0 ng/ml per enantiomer with correlation coefficients better than 0.9994, where lower limit of quantification (LLOQ) for Met was 5 ng/ml and for EDDP 0.5 ng/ml. Acceptable intra- and inter-day precision of the method (CVs<4.0%) and accuracy (CVs<4.0%) were obtained. These findings demonstrate the accuracy and precision of the method used to successfully analyze saliva obtained from patients enrolled in a methadone-maintenance program.

Chromatography, Liquid↗
PubMed2004

Spectroscopic sensing of cancer and cancer therapy: current status of translational research.

Various types of optical spectroscopy have been investigated as methods to effect a non-invasive, real-time in-situ assessment of tissue pathology. All of these methods have one basic principle in common: the optical spectrum of a tissue contains information about the biochemical composition and/or the structure of the tissue, and that information conveys diagnostic information. The biochemical information can be obtained by measuring absorption, fluorescence, or Raman scattering signals. Structural and morphological information may be obtained by techniques that assess the elastic-scattering properties of tissue. These basic approaches are useful for the detection of cancer as well as for other diagnostic applications such as hemoglobin saturation, intra-luminal detection of atherosclerosis, and simply the identification of different tissue types during procedures. Optical spectroscopic measurements can also be employed in the management of disease treatment. The site-specific pharmacokinetics of chemotherapy and photodynamic therapy agents can be used to customize dosage to the patient, and diagnostic spectroscopy can be used to monitor response to treatment. In recent years clinical studies have provided indications of potential efficacy, and some of these modalities are now entering a translational research stage, with an eye to approval and commercialization. A benefit of these methods is their inherent low cost and ease of implementation, generally mediated with small portable instruments, not requiring any specialized facilities, and eventually not requiring expert interpretation. This paper reviews briefly the most common methods of diagnostic optical spectroscopy, and reviews in greater depth recent clinical translational research invoking scattering spectroscopy as the enabling technology, which has been the experience of the authors.

Antineoplastic Agents↗
PubMed2005

Calculation of local pressure tensors in systems with many-body interactions.

Local pressures are important in the calculation of interface tensions and in analyzing micromechanical behavior. The calculation of local pressures in computer simulations has been limited to systems with pairwise interactions between the particles, which is not sufficient for chemically detailed systems with many-body potentials such as angles and torsions. We introduce a method to calculate local pressures in systems with n-body interactions (n=2,3,4,) based on a micromechanical definition of the pressure tensor. The local pressure consists of a kinetic contribution from the linear momentum of the particles and an internal contribution from dissected many-body interactions by infinitesimal areas. To define dissection by a small area, respective n-body interactions are divided into two geometric centers, effectively reducing them to two-body interactions. Consistency with hydrodynamics-derived formulas for systems with two-body interactions [J. H. Irving and J. G. Kirkwood, J. Chem. Phys. 18, 817 (1950)], for average cross-sectional pressures [B. D. Todd, D. J. Evans, and P. J. Daivis, Phys. Rev. E 52, 1627 (1995)], and for volume averaged pressures (virial formula) is shown. As a simple numerical example, we discuss liquid propane in a cubic box. Local, cross-sectional, and volume-averaged pressures as well as relative contributions from two-body and three-body forces are analyzed with the proposed method, showing full numerical equivalence with the existing approaches. The method allows computing local pressures in the presence of many-body interactions in atomistic simulations of complex materials and biological systems.

Journal Article↗
PubMed2002

Signal recovery in free induction decay imaging using a stimulated spin echo.

A novel pulse sequence for acquiring a stimulated spin echo (SSE) is devised and implemented to recover the initial portion of the signal that is usually blanked or distorted in MRI using free induction decays (FIDs). The receiver-phase offset, center of the k-space, and time frame coordinates of the FID data points can be accurately determined from the SSE. A simple numerical method of signal recovery is formulated which can merge the FID and the SSE data for higher extrapolation accuracy. The application of the signal recovery method is demonstrated using the rotating ultrafast imaging sequence (RUFIS). The result shows the importance of experimentally finding the correct time origin of the FID signal.

Artifacts↗