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PubMed2003

Multi-technique characterization of retrieved bone cement from revised total hip arthroplasties.

The purpose of this study was to assess the chemical composition, structure and degree of double bond conversion of retrieved bone cement from 29 total hip replacement revision arthroplasties, employing a multi-technique approach. Scanning electron microscopy revealed a porous cement surface, which replicated the characteristics of bone or femoral stem surface irregularities. Fourier transform infrared spectroscopy indicated that the retrieved bone cement samples were covered by a well-organized proteinaceous film rich in amides and alcohols, probably because of the adsorption of species from body tissues and fluids. X-ray fluorescence spectrometry showed the presence of potassium, sodium, calcium and phosphorus, implying the development of a mineralization process of the adsorbed biofilm. X-ray microtomography demonstrated a dense porous network in the bulk material comprised of macropores with a mean diameter >1 mm. FTIR analysis of the degree of double bond conversion of retrieved samples was in the order of 70%, similar to that of samples prepared in vitro in air, but 30% lower relative to their counterparts mixed in vitro and set in water. The effect of the adsorption of species onto bone cement surface on the reactivity of the material with the surrounding tissues and materials, is currently unknown. The results of this investigation reveal that the in vivo aging pattern of bone cements may involve alterations, which cannot be simulated under current in vitro protocols, emphasizing the necessity for adopting in vivo approaches including retrieval studies in assessing bone cement properties.

Journal Article↗
PubMedDate not supplied

Prognostic validation of a 17-segment score derived from a 20-segment score for myocardial perfusion SPECT interpretation.

BACKGROUND: Recently, a 17-segment model of the left ventricle has been recommended as an optimally weighted approach for interpreting myocardial perfusion single photon emission computed tomography (SPECT). Methods to convert databases from previous 20- to new 17-segment data and criteria for abnormality for the 17-segment scores are needed. METHODS AND RESULTS: Initially, for derivation of the conversion algorithm, 65 patients were studied (algorithm population) (pilot group, n = 28; validation group, n = 37). Three conversion algorithms were derived: algorithm 1, which used mid, distal, and apical scores; algorithm 2, which used distal and apical scores alone; and algorithm 3, which used maximal scores of the distal septal, lateral, and apical segments in the 20-segment model for 3 corresponding segments of the 17-segment model. The prognosis population comprised 16,020 consecutive patients (mean age, 65 +/- 12 years; 41% women) who had exercise or vasodilator stress technetium 99m sestamibi myocardial perfusion SPECT and were followed up for 2.1 +/- 0.8 years. In this population, 17-segment scores were derived from 20-segment scores by use of algorithm 2, which demonstrated the best agreement with expert 17-segment reading in the algorithm population. The prognostic value of the 20- and 17-segment scores was compared by converting the respective summed scores into percent myocardium abnormal. Conversion algorithm 2 was found to be highly concordant with expert visual analysis by the 17-segment model (r = 0.982; kappa = 0.866) in the algorithm population. In the prognosis population, 456 cardiac deaths occurred during follow-up. When the conversion algorithm was applied, extent and severity of perfusion defects were nearly identical by 20- and derived 17-segment scores. The receiver operating characteristic curve areas by 20- and 17-segment perfusion scores were identical for predicting cardiac death (both 0.77 +/- 0.02, P = not significant). The optimal prognostic cutoff value for either 20- or derived 17-segment models was confirmed to be 5% myocardium abnormal, corresponding to a summed stress score greater than 3. Of note, the 17-segment model demonstrated a trend toward fewer mildly abnormal scans and more normal and severely abnormal scans. CONCLUSION: An algorithm for conversion of 20-segment perfusion scores to 17-segment scores has been developed that is highly concordant with expert visual analysis by the 17-segment model and provides nearly identical prognostic information. This conversion model may provide a mechanism for comparison of studies analyzed by the 17-segment system with previous studies analyzed by the 20-segment approach.

Aged↗
PubMed2001

Phenotypic analysis of hMSH2 mutations in mouse cells carrying human chromosomes.

Conversion of diploidy to haploidy is a method that allows the generation of stable murine/human hybrid cell lines carrying selected human chromosomes in only a single copy. In this setting, it is possible to detect genetic mutations with greater sensitivity and reliability than in diploid cells. Using this method, we were able to identify mutations in the human mismatch repair (MMR) gene hMSH2 in hereditary nonpolyposis colon cancer families, which have escaped detection by the conventional methods. In this report, we show that such hybrid cell lines can also be a valuable tool in the study of the mutated MMR proteins, in particular the variants found in hereditary nonpolyposis colon cancer families that carry missense mutations and where it is unclear whether they predispose to colon cancer. This analysis is made possible by the fact that the human hMSH2 protein is able to complement the MMR defect in the host murine cell line.

Alleles↗
PubMedDate not supplied

Cost considerations of converting to digital photography.

OBJECTIVES: To provide the practicing surgeon with data to make an informed economic decision regarding conversion from analog to digital photography. METHODS: A cost analysis of photography based on 35-mm vs digital platforms (low-, medium-, and high-cost hardware). RESULTS: Break-even thresholds for the investment in a digital platform of low, medium, and high costs were 3674, 15,789, and 34,000 images, respectively. CONCLUSION: Given the current excellent image quality and ongoing refinements in digital photography, a digital photography platform may be cost-effective for a busy facial plastic surgery practice.

Analog-Digital Conversion↗
PubMed1994

Quantitative analysis of human movement synergies: constructive pattern analysis for gait.

To record three-dimensional coordinates of the joints from normal human subjects during locomotion, we used a digital motion analysis system (ELITE). Recordings were obtained under several different conditions, which included normal walking and stepping over obstacles. Principal component analysis was used to analyze coordinate data after conversion of the data to segmental angles. This technique gave a stable summary of the redundancy in gait kinematic data in the form of reduced variables (principal components). By modeling the shapes of the phase plots of reduced variables (distortion analysis) and using a limited number of model parameters, good resolution was obtained between subtly different conditions. Hence, it was possible to accurately resolve small distributed changes in gait patterns within subjects. These methods seem particularly suited to longitudinal studies in which relevant movement features are not known a priori. Assumptions and neurophysiological applications are discussed.

Journal Article↗
PubMed1995

Biosynthetic origin of mycobacterial cell wall arabinosyl residues.

Designing new drugs that inhibit the biosynthesis of the D-arabinan moiety of the mycobacterial cell wall arabinogalactan is one important basic approach for treatment of mycobacterial diseases. However, the biosynthetic origin of the D-arabinosyl monosaccharide residues themselves is not known. To obtain information on this issue, mycobacteria growing in culture were fed glucose labeled with 14C or 3H in specific positions. The resulting radiolabeled cell walls were isolated and hydrolyzed, the arabinose and galactose were separated by high-pressure liquid chromatography, and the radioactivity in each sugar was determined. [U-14C]glucose, [6-3H]glucose, [6-14C]glucose, and [1-14C]glucose were all converted to cell wall arabinosyl residues with equal retention of radioactivity. The positions of the labeled atoms in the arabinose made from [1-14C]glucose and [6-3H]glucose were shown to be C-1 and H-5, respectively. These results demonstrated that the arabinose carbon skeleton is formed via the nonoxidative pentose shunt and not via hexose decarboxylation or via triose condensations. Since the pentose shunt product, ribulose-5-phosphate, is converted to arabinose-5-phosphate as the first step in 3-keto-D-manno-octulosonic acid biosynthesis by gram-negative bacteria, such a conversion was then searched for in mycobacteria. However, cell-free enzymatic analysis using both phosphorous nuclear magnetic resonance spectrometry and colorimetric methods failed to detect the conversion. Thus, the conversion of the pentose shunt intermediates to the D-arabino stereochemistry is not via the expected isomerase but rather must occur via novel metabolic transformations.

Arabinose↗
PubMed1999

Normative data for the Novaco Anger Scale from a non-clinical sample and implications for clinical use.

OBJECTIVES: To provide non-clinical normative data for the Novaco Anger Scale. To identify the ability of the scale to discriminate between clinical and non-clinical populations. DESIGN: Postal survey of individuals from a non-clinical sample. METHOD: A non-clinical sample of 212 NHS employees was sent a questionnaire pack, including the Novaco Anger Scale. A clinical sample of 58 outpatient anger-management referrals was identified from a retrospective case-note analysis. RESULTS: Descriptive data are presented for both samples. t-score conversions are provided, based on the non-clinical data. Results from a discriminant function analysis demonstrated that the Novaco Anger Scale classified participants as clinical or non-clinical with 94% accuracy. CONCLUSION: From this study it appears that the Novaco Anger Scale is able to discriminate between clinical and non-clinical populations. These data offer further support to the validity of the Novaco Anger Scale and its use in clinical assessment.

Adult↗
PubMed1979

Gene conversion of the mating-type locus in Saccharomyces cerevisiae.

Tetrad analysis of MATa/MAT alpha diploids of Saccharomyces cerevisiae generally yields 2 MATa:2MAT alpha meiotic products. About 1 to 1.8% of the tetrads yield aberrant segregations for this marker. Described here are experiments that determine whether the aberrant meiotic segregations at the mating-type locus are ascribable to gene conversions or to MAT switches, that is, to mating-type interconversions. Diploid strains incapable of switching MATa to MAT alpha, or the converse, nevertheless display changes of MATa to MAT alpha, or the reverse. These events must be attributed to gene conversion. Further, we suggest that MATa and MAT alpha alleles may represent nonhomologous sequences of DNA since they fail to display postmeiotic segregations.

Genes↗
PubMed1988

Physical lengths of meiotic and mitotic gene conversion tracts in Saccharomyces cerevisiae.

Physical lengths of gene conversion tracts for meiotic and mitotic conversions were examined, using the same diploid yeast strain in all experiments. This strain is heterozygous for a mutation in the URA3 gene as well as closely linked restriction site markers. In cells that had a gene conversion event at the URA3 locus, it was determined by Southern analysis which of the flanking heterozygous restriction sites had co-converted. It was found that mitotic conversion tracts were longer on the average than meiotic tracts. About half of the tracts generated by spontaneous mitotic gene conversion included heterozygous markers 4.2 kb apart; none of the meiotic conversions included these markers. Stimulation of mitotic gene conversion by ultraviolet light or methylmethanesulfonate had no obvious effect on the size or distribution of the tracts. Almost all conversion tracts were continuous.

Chromosome Mapping↗
PubMedDate not supplied

Hospital organizational change and financial status: costs and outcomes of care in Philadelphia.

Two recent changes in Philadelphia-area hospital organizations are consolidation into systems and acquisition of 2 medical school hospitals by a for-profit chain. This study explored whether such consolidation and conversion affected costs and outcomes of care. The analysis included 1,617,581 discharges from 49 acute-care hospitals from 1997 to 1999. Analyses within and between medical school hospitals examined trends in discharges, case mix, length of stay, and mortality. The study addressed 2 questions: whether, as hospitals consolidate into medical school hospital-based systems, volume, severity, length of stay, and mortality increase in those hospitals; and whether for-profit conversion redistributes complex, high-cost admissions to nonprofit hospitals. The 2 medical school hospitals that became for-profit experienced decreases in volume and resource intensity, coupled at one with an increase in severity. However, these patterns were produced more by the system's financial instability than by consolidation or conversion.

Academic Medical Centers↗
PubMed2001

[Computers in biomedical research: I. Analysis of bioelectrical signals].

A personal computer equipped with an analog-to-digital conversion card is able to input, store and display signals of biomedical interest. These signals can additionally be submitted to ad-hoc software for analysis and diagnosis. Data acquisition is based on the sampling of a signal at a given rate and amplitude resolution. The automation of signal processing conveys syntactic aspects (data transduction, conditioning and reduction); and semantic aspects (feature extraction to describe and characterize the signal and diagnostic classification). The analytical approach that is at the basis of computer programming allows for the successful resolution of apparently complex tasks. Two basic principles involved are the definition of simple fundamental functions that are then iterated and the modular subdivision of tasks. These two principles are illustrated, respectively, by presenting the algorithm that detects relevant elements for the analysis of a polysomnogram, and the task flow in systems that automate electrocardiographic reports.

Algorithms↗
PubMed2000

Standardization of surgeon-controlled variables: impact on outcome in patients with acute cholecystitis.

OBJECTIVE: To examine the effect of standardization of surgeon-controlled variables on patient outcome after cholecystectomy for two cohorts of patients with acute cholecystitis (AC). SUMMARY BACKGROUND DATA: Laparoscopic cholecystectomy (LC), when performed efficiently and safely, offers patients with AC a more rapid recovery and decreases the length of stay, thus reducing the health care utilization. Numerous studies have focused on the characteristics of patients with AC that may predict the conversion of LC to open cholecystectomy. However, analysis of these factors offers little insight for improving the outcome of patients with AC, because patient-controlled variables are difficult to influence. In the present study, treatment variables that were under the surgeon's control were standardized and the effects of these changes on the outcome of patients with AC were quantified. METHODS: Beginning in August 1997, a standardized treatment protocol was initiated for patients with suspected AC. LC was initiated as early as practical from the time of admission. All operations were performed in a specially equipped and staffed laparoscopic surgery suite, and all patients were supervised by one of two attending surgeons with a special interest in laparoscopic interventions. Two cohorts of patients with AC were retrospectively analyzed: 39 patients from the 12 months before initiation of this protocol (period 1) and 49 patients from the 12 months after its inception (period 2). Medical records were reviewed for demographic, perioperative, and outcome data. Surgical reports were reviewed to ascertain the reason for conversion and whether laparoscopic technical modifications were used. RESULTS: No significant difference was noted between the groups with regard to patient demographics, clinical presentation, or radiologic or laboratory parameters. After protocol initiation, patients received definitive treatment closer to the time of admission and had a greater percentage of laparoscopically completed cholecystectomies. Furthermore, the patients in period 2 had a significantly decreased postoperative length of stay and hospital charges than the earlier ones. Complications were infrequent and not significantly different between the groups. Two or more laparoscopic technical modifications were used in 95% of the successful LCs during period 2 versus 33.3% during period 1. CONCLUSIONS: By controlling when, where, and by whom LC for AC was performed, the authors have significantly improved the percentage of cholecystectomies that were completed laparoscopically. This has led to improved outcomes and lower hospital charges for patients with AC at this municipal hospital.

Acute Disease↗
PubMed2000

Estimating factors to convert Chinese 'Total Dust' measurements to ACGIH respirable concentrations in metal mines and pottery industries.

Historical data on the dust exposures of Chinese workers in metal mines (iron/copper, tin, tungsten) and pottery industries are being used in an ongoing joint Chinese/United States epidemiological study to investigate the exposure-response relationship for the development of silicosis, lung cancer, and other diseases. The historical data include 'total dust' concentrations determined by a Chinese method. Information about particle size distribution and the chemical and mineralogical content of airborne particles is generally not available. In addition, the historical Chinese sampling strategy is different from a typical American eight-hour time-weighted average (TWA) sampling strategy, because the Chinese samples were collected for approximately 15 minutes during production so the sample could be compared to their maximum allowable concentration (MAC) standard. Therefore, in order to assess American respirable dust exposure standards in light of the Chinese experience, factors are needed to convert historical Chinese total dust concentrations to respirable dust concentrations. As a part of the joint study to estimate the conversion factors, airborne dust samples were collected in 20 metal mines and 9 pottery factories in China during 1988 and 1989 using three different samplers: 10mm nylon cyclones, multi-stage 'cassette' impactors, and the traditional Chinese total dust samplers. More than 100 samples were collected and analysed for each of the three samplers. The study yielded two different estimates of the conversion factor from the Chinese total dust concentrations (measured during production processes) to respirable dust concentrations. The multivariate analysis of variance (MANOVA) reveals that, with a fixed sampling/analysis method, conversion factors were not statistically different among the different job titles within each industry. It also indicates that conversion factors among the industries were not statistically different. However, the two estimates consistently showed that conversion factors were the lowest in the pottery industry. Average conversion factors were then calculated for each of the estimates across the industries studied. A pooled mean conversion factor, 0.25+/-0.04, was then derived for all the job titles and industries. Respirable dust levels were estimated from the historical 'total dust' concentrations collected between 1952 and 1992 by adopting the American standard.

Air Pollutants, Occupational↗
PubMed1998

Gas chromatographic profiling and pattern recognition analysis of urinary organic acids from uterine myoma patients and cervical cancer patients.

An efficient organic acid profiling and pattern recognition method is described for the correlation between urinary organic acid profiles and uterine cervical cancer. After methoximation of keto acids in alkalinized urine samples, all free organic acids were recovered by a dual solid-phase extraction procedure, followed by conversion to tert.-butyldimethylsilyl derivatives for the profiling analysis by dual-capillary column gas chromatography (GC) with subsequent screening for acids by retention index (I) library matching. A total of 50 organic acids were positively identified in urine samples (0.25 ml) from 12 uterine myoma (benign tumor group) and 14 uterine cervical cancer (malignant tumor group) patients studied. When the GC profiles were simplified to their corresponding organic acid I spectra in bar graphical form, characteristic patterns were obtained for each average of benign and malignant tumor groups. Stepwise discriminant analysis performed on the GC data selected 16 acids as the variables discriminating between the two groups. Canonical discriminant analysis applied to these 16 variables correctly classified 26 urine samples into two separate clusters according to tumor types in the canonical plot.

Adult↗
PubMed2002

Apolipoprotein B-100 kinetics in visceral obesity: associations with plasma apolipoprotein C-III concentration.

Obesity is strongly associated with dyslipidemia, which may account for the associated increased risk of atherosclerosis and coronary disease. We aimed to test the hypothesis that kinetics of hepatic apolipoprotein B-100 (apoB) metabolism are disturbed in men with visceral obesity and to examine whether these kinetic defects are associated with elevated plasma concentration of apolipoprotein C-III (apoC-III). Very-low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), and low-density lipoprotein (LDL) apoB kinetics were measured in 48 viscerally obese men and 10 age-matched normolipidemic lean men using an intravenous bolus injection of d(3)-leucine. ApoB isotopic enrichment was measured using gas chromatography-mass spectrometry (GCMS). Kinetic parameters were derived using a multicompartmental model (Simulation, Analysis, and Modeling Software II [SAAM-II]). Compared with controls, obese subjects had significantly elevated plasma concentrations of plasma triglycerides, cholesterol, LDL-cholesterol, VLDL-apoB, IDL-apoB, LDL-apoB, apoC-III, insulin, and lathosterol (P <.01). VLDL-apoB secretion rate was significantly higher (P =.034) in obese than control subjects; the fractional catabolic rates (FCRs) of IDL-apoB and LDL-apoB (P <.01) and percent conversion of VLDL-apoB to LDL-apoB (P <.02) were also significantly lower in obese subjects. However, the decreased VLDL-apoB FCR was not significantly different from the lean group. In the obese group, plasma concentration of apoC-III was significantly and positively associated with VLDL-apoB secretion rate and inversely with VLDL-apoB FCR and percent conversion of VLDL to LDL. In multiple regression analysis, plasma apoC-III concentration was independently and significantly correlated with the secretion rate of VLDL-apoB (regression coefficient [SE] 0.511 [0.03], P =.001) and with the percent conversion of VLDL-apoB to LDL-apoB (-0.408 [0.01], P =.004). Our findings suggest that plasma lipid and lipoprotein abnormalities in visceral obesity may be due to a combination of overproduction of VLDL-apoB particles and decreased catabolism of apoB containing particles. Elevated plasma apoC-III concentration is also a feature of dyslipidemia in obesity that contributes to the kinetic defects in apoB metabolism.

Adult↗
PubMed1996

Factors affecting conversion of laparoscopic cholecystectomy to open surgery.

OBJECTIVE: To identify the risk factors predictive of conversion of laparoscopic cholecystectomy to open surgery. DESIGN: Demographic, ultrasonographic, and operative data of patients who underwent laparoscopic cholecystectomy were analyzed. Factors affecting conversion to open surgery were identified with statistical analysis. SETTING: A tertiary referral center. PATIENTS: Five hundred patients who underwent laparoscopic cholecystectomies at our institution between March 1991 and July 1994. The patients' data had been prospectively collected. INTERVENTION: Standard laparoscopic techniques with selective preoperative endoscopic retrograde cholangiopancreatography. MAIN OUTCOME MEASURE: Conversion of laparoscopic cholecystectomy to open surgery for management of technical difficulties or intraoperative complications. RESULTS: Increased risk of conversion with statistical significance was found in patients older than 65 years, obese patients, patients who underwent interval elective laparoscopic cholecystectomy for acute cholecystitis, patients with ultrasonographic findings of thickened gallbladder wall, patients seen during the early learning phase of the series, and patients whose surgery was performed by senior surgeons. Increased risk of conversion was not found with patients' sex, previous lower abdominal surgery, history of acute pancreatitis or cholangitis, impaired liver function on presentation, or emergency laparoscopic cholecystectomy for acute cholecystitis. CONCLUSIONS: Risk factors, including patient factors, presentation, preoperative ultrasonography, and surgical experience, all contributed to the possibility of conversion. Knowledge of these factors may help in arranging the operating schedule, psychological preparation for the procedure, and planning of the duration of convalescence.

Adult↗
PubMed1997

Liquid chromatographic analysis of amphetamine and related compounds in urine using solid-phase extraction and 3,5-dinitrobenzoyl chloride for derivatization.

A chromatographic method for the analysis of amphetamine and related compounds in urine using 3,5-dinitrobenzoyl chloride (3,5-DNB) as a labeling reagent is presented. This assay is based on the employment of solid-phase extraction (SPE) cartridges for sample cleanup and derivatization. Experimental conditions are optimized for the simultaneous derivatization of ephedrine, norephedrine, pseudoephedrine, beta-phenylethylamine, amphetamine, methamphetamine, and 3-phenylpropylamine. The derivatives formed are separated in a LiChrospher 1000 RP18 (125 x 4-mm i.d., 5-microns film thickness) analytical column using a water-acetonitrile gradient elution and detected at 254 nm. Derivatization in C18 SPE disks is found to be the best option for analysis of urine samples; this method provides analyte conversions that are about 85-102% of those obtained by the analogous solution derivatization. Because the 3,5-DNB reagent is a strong pi-acid, the described method can be used in combination with a Pirkle-type donor column for chiral analysis. The practicality of the described approach is illustrated by determining amphetamine enantiomers using a Supelcosil LC-(S)-naphtylurea (250 x 4.6-mm i.d., 5-microns film thickness) column and a mobile phase of n-hexane-acetonitrile-ethyl acetate. Under these conditions, good linearity and reproducibility are observed over the 0.5-10 micrograms/ml concentration range; the limit of detection is 50 ng/mL.

Amphetamines↗