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PubMed1993

The relationship between comfortable and most metabolically efficient walking speed in persons with unilateral above-knee amputation.

Walking is most efficient when the least energy is spent over a certain distance. In six normal male subjects and 11 males with above-knee amputation the comfortable self-selected walking speeds and the most metabolically efficient walking speeds were determined. For that purpose energy expenditure was measured per second and per meter at six incremental walking speeds. Heart and step rate were registrated also at each walking speed. The results showed that in subjects who have not undergone amputation the comfortable walking speed is the same as the most efficient walking speed. However, in the above-knee amputee group, the comfortable walking speed is lower than the most efficient walking speed. When both groups walked at their own efficient walking speed they had the same energy expenditure per second.

Amputation, Surgical↗

PubMed1985

The efficiency of matching in case-control studies of risk-factor interactions.

We have examined the relative efficiency of matching vs not matching on a binary exposure variable in a case-control study of its interaction with another binary exposure variable. Interaction is treated as a parameter measuring departure from multiplicativity. Efficiency is considered both in the presence and absence of other matching variables, the former case requiring use of matched-pair estimators. In most circumstances examined, matching on one variable led to a less efficient estimator of the interaction parameter. If both variables were related to disease, the only circumstance in which matching always improved efficiency was when the high-risk level of the matching variable was uncommon and not positively associated with the high-risk level of the other variable. Matching always appeared to harm efficiency when the high risk level of the matching variable was common. Other disadvantages of matching are that it precludes estimation of the main effect of the matching variable and fitting of non-multiplicative models, and increases the difficulty of control selection.

Epidemiologic Methods↗

PubMed1980

Dust in dental laboratories. Part III: Efficiency of ventilation systems and face masks.

The efficiency of local and electrostatic ventilation systems installed in dental laboratories has been measured. With local exhaust systems, dust amounts could be reduced in breathing air close to the emission source to levels lower than threshold limit values for various elements or compounds in dust produced through cutting, grinding, or polishing various dental materials such as chromium-cobalt, nickel, or gold alloys, porcelain, gypsum models, or denture base material. However, the local exhaust system did not enable a dust reduction from handling amalgam dies consistent with criteria of threshold limit values for mercury and silver. The efficiency of electrostatic filters installed in dental laboratories for general ventilation purposes was found to range from 37% to 73% based on weight reduction. Various ventilation systems with bag filters possessing a high efficiency based on weight reductions allowed small, respirable particles less than 5 micrometers to recirculate within the working environment. The efficiency of face masks for the reduction of inhaled dust revealed efficiencies for two commercial masks ranging from 70% to 95% based on weight reduction. However, such masks only partly retained the respirable dust.

Air Movements↗

PubMed1992

No persistent effect of preweaning nutrition on postweaning food intake, feeding efficiency, or body energy stores in Long-Evans rats.

The purpose of this study was to determine the relative importance of pre- and postweaning nutrition on body mass, body fat, and feeding efficiency in Long-Evans rats up to a period of 18 weeks following weaning. Female rats were bred and pups were redistributed to form large (14-19 pups), normal (11-13 pups) and small (4 pups) litter groups. Weaned rats were housed as pairs (40 pairs) or singletons (n = 16) and fed either a mixed-fat diet (36.6% fat) or a standard chow diet (13.5% fat). Food intake, body mass, and feeding efficiency were measured at 4, 8, 12, and 18 weeks postweaning. Total body fat and depot fat pad mass were also measured at 18 weeks postweaning. At weaning, pups from small litters were fatter (p less than 0.001), and had a greater mass (p less than 0.03) than pups from large litters. There were no persistent effects of preweaning litter size after covarying for preweaning mass on body mass, and postweaning growth, food intake, feeding efficiency, or body fat accretion. Male rats ingesting the mixed-fat diet had a greater body mass (p less than 0.05), greater body fat accretion (p less than 0.008) and a higher feeding efficiency (p less than 0.001) than their chow-fed counterparts, despite an overall lower energy intake (p less than 0.05). Female rats ingesting the mixed-fat diet had a lower food energy intake (p less than 0.005) and a greater feeding efficiency (p less than 0.001) than chow-fed rats during the early postweaning period, only. Thus, postweaning nutrition may play a more important role in postweaning adult mass and depot fat in freely eating rats than early nutritional experiences.

Adipose Tissue↗

PubMed1988

Biosynthesis of reovirus-specified polypeptides: effect of point mutation of the sequences flanking the 5'-proximal AUG initiator codons of the reovirus S1 and S4 genes on the efficiency of mRNA translation.

The effect on translation of site-directed nucleotide substitutions around the 5'-proximal AUG initiation codon of the reovirus s1 mRNA specifying polypeptide sigma 1 and the reovirus s4 mRNA specifying polypeptide sigma 3 was examined. The efficiency of synthesis of the S1-encoded sigma 1 polypeptide and the S4-encoded sigma 3 polypeptide was analyzed in transfected simian COS cells. Mutant s1 mRNAs possessing either GCU AUG G or GCA AUG G sequences surrounding the 5'-proximal sigma 1 AUG were translated with an efficiency comparable to that of the wild-type s1 mRNA which possesses the flanking sequence CCU AUG G. Mutant s4 mRNAs possessing either CCU AUG G or CCA AUG G sequences surrounding the 5'-proximal sigma 3 AUG were translated with an efficiency comparable to that of wild-type s4 mRNA which possesses the flanking sequence GCA AUG G. The s4 mRNAs, both wild-type and mutant, were translated in vivo about five times more efficiently than the s1 mRNAs, both wild-type and mutant. These results suggest that nucleotide positions other than the -3, -2, -1, and +4 positions relative to the 5'-proximal initiator AUG, where the A is +1, play a dominant role in determining the efficiency of translation of these two reovirus mRNAs in vivo.

Codon↗

PubMed1981

Differential translation efficiency explains discoordinate expression of the galactose operon.

We have used an mRNA-dependent E. coli S-30 translation system to compare the translation efficiencies of two polycistronic transcripts of the galactose operon, the CRP-cAMP-dependent mRNA (P1) and the CRP-cAMP-independent mRNA (P2). The RNAs were prepared in vitro, quantitated by hybridization or gel analysis and translated in a cell free system. The specific protein products were measured, and their quantities were compared with the amount of input mRNA. Our results show that the P2 mRNA synthesizes epimerase, the 5'-proximal gene product of the gal operon, four times more efficiently than the P1 mRNA. The 5'-distal gene products, transferase and kinase, are translated with the same efficiency from both transcripts. Thus the ratio of epimerase to kinase synthesis is four times higher for the P2 mRNA than for the P1 mRNA. This change in epimerase to kinase ratio is identical to that observed in vivo when the cellular cAMP level falls and gal transcription is believed to switch from P1 to P2. We suggest that it is the differential translation efficiency of the epimerase gene on the two different gal transcripts that accounts for this discoordinate expression. Moreover, since the P2 mRNA differs from the P1 mRNA only by the addition of five nucleotides at the 5' terminus and these nucleotides are outside the ribosome binding region we determine for epimerase, the selective difference in the translation efficiency of epimerase is probably mediated by RNA conformation.

Carbohydrate Epimerases↗

PubMed1990

Comparison of the efficiencies of true blue and diamidino yellow as retrograde tracers in the peripheral motor system.

The abilities of the fluorescent retrograde tracers true blue and diamidino yellow to label motor neurons of the rat sciatic nerve were compared quantitatively. Following injection of a mixture of the 2 tracers into the sciatic nerve, diamidino yellow was found only in double-labelled neurons, while 28% of labelled neurons contained true blue alone. The relative labelling efficiency of diamidino yellow, at only 72%, was significantly lower than that of true blue. When the tracers were injected separately a difference in the labelling efficiency was still observed but, in addition, there were significantly fewer diamidino yellow-labelled neurons than when a mixture had been injected. This suggests that the presence of true blue in the mixture had enhanced the uptake, transport or visualisation of diamidino yellow. When a mixture of true blue and diamidino yellow was applied to the cut sciatic nerve, the relative labelling efficiency of diamidino yellow (77%) was again found to be lower than that of true blue, but positive identification of diamidino yellow-labelled cells was hampered by chromatolytic changes in the cell bodies. Injection of the tracer mixture into the gastrocnemius muscle resulted in a diamidino yellow labelling efficiency (36%) significantly lower than that obtained with either nerve injection or nerve dipping. Thus, compared to true blue, diamidino yellow was either less capable of reaching the motor endplates within the muscle, or it was taken up less efficiently by axon terminals than by the axons themselves.

Amidines↗

PubMed1996

Efficiency of heating during radiofrequency catheter ablation of accessory atrioventricular pathways.

Adequate heating with myocardial thermal injury is necessary for successful ablation. This study was designed to examine the relationship between power, temperature, and efficiency of heating during radiofrequency catheter ablation of accessory pathways in 76 patients. During each application of radiofrequency energy, temperature was continually monitored by use of an ablation catheter with a thermistor embedded in the tip of the distal electrode. The efficiency of heating varied by location, with the greatest efficiency of heating for posteroseptal energy applications (2.7 +/- 2.3 degrees C/W), which were significantly greater than for left-sided (2.1 +/- 1.9 degrees C/W, P < 0.01) or right-sided (1.0 +/- 1.1 degrees C/W, P < 0.01) applications. For patients with left free wall and posteroseptal pathways, the temperature, radiofrequency power, time to peak temperature and efficiency of heating were similar between the successful and unsuccessful pulses. However, the mean temperature (53.5 +/- 4.5 vs. 45.1 +/- 5.1 degrees C, P < 0.01) and radiofrequency power (49.6 +/- 5.2 vs. 40.3 +/- 10.2 watt, P < 0.05) differed significantly between the successful and unsuccessful ablation pulses in patients with right free wall pathways. To achieve greater efficiency of heating and higher temperature, it is reasonable to use higher power outputs (40-50 W) in radiofrequency ablation of right free wall pathways, whereas less power outputs (30-40 W) are likely to produce adequate heating of posteroseptal and left free wall pathways, and minimize the risk of impedance rise and coagulum formation.

Adolescent↗

PubMed1990

Frog virus 3-mediated translational shut-off: frog virus 3 messages are translationally more efficient than host and heterologous viral messages under conditions of increased translational stress.

Frog virus 3 rapidly and selectively blocks host cell translation while synthesizing more than 60 virus-specific polypeptides. Previous work indicated that virus infection led to activation of a kinase that phosphorylated and, as a consequence, inactivated eIF-2. Although phosphorylation of eIF-2 could explain the rapid decline in host cell translation, it could not explain how viral protein synthesis persisted in the face of host shut-off. To explain this phenomenon, we speculated that viral messages, either as a consequence of their higher translational efficiency or their greater abundance, were able to outcompete host messages for the remaining translational initiation complexes. To test this hypothesis, the relative translational efficiency of three characteristic FV3 messages was measured against that of several model messages. Translational efficiency was determined by monitoring the resistance (and hence the competitiveness) of a given transcript to increasing concentrations of salt in vitro and in vivo. In both rabbit reticulocyte lysates and wheat germ extracts, FV3 messages were more resistant to supra-optimal concentrations of potassium acetate than globin message and three BMV transcripts. In vivo, FV3 polypeptides were synthesized in the presence of salt concentrations that blocked host cell protein synthesis. These results suggest that the selective translation of FV3 messages in virus-infected cells may partly be due to the higher translational efficiency of viral messages. Structural features that contribute to translational efficiency are discussed.

Acetates↗

PubMed1982

Encapsulation, with high efficiency, of radioactive metal ions in liposomes.

The encapsulation of radioactive metalic cations, such as 111In3+ or 67Ga3+, in the internal aqueous compartment of liposomes can be achieved with an efficiency of about 90%. The efficient loading of a high specific activity of cations into liposomes involves the transport of 111In3+ or 67Ga3+ through the lipid bilayer to an encapsulated strong chelate, such as nitrilotriacetic acid, by 8-hydroxyquinoline, in conjunction with an efficient anion-exchange resin technique for the removal of the external cations. The efficiency of loading cations to liposomes is affected markedly by the concentration of 8-hydroxyquinoline-metal, and the presence of the chelating agents in the loading incubation mixture. However, the loading efficiency is not affected by the pH of the internal aqueous compartment of liposomes over a range of pH 5-9, the concentration of the liposomes, the method of liposomal preparation, the lamellar structure of the liposomes, and the composition of liposomes. Furthermore, the loading procedures do not appear to affect the size and the permeability of liposomes. There is a good agreement in the tissue distributions of the liposomes prepared by the present loading methods and those by the conventional method of encapsulation by sonication. Liposomes entrapping high specific activity of 67Ga3+ or 111In3+ will be useful for future studies of the in vivo kinetics of liposomes by the combined techniques of scintigraphic imaging and the gamma-ray perturbed angular correlation.

Animals↗

PubMed1993

Simple and efficient generation of marked clones in Drosophila.

BACKGROUND: Cell lineage analysis and mosaic analysis of mutations are important techniques that are used to study the development of many organisms. Unfortunately, the methods employed for such analyses are usually inefficient, technically demanding or labor intensive. In Drosophila, the most common methodology used for the generation of mosaic animals is mitotic recombination, which is induced by X-rays. Although this technique is simple, it has the undesirable characteristics of a low efficiency and a high rate of cell death. Furthermore, although a large number of marker systems has been employed to detect mitotic recombinants, none allows easy identification of clones for all cell types. RESULTS: A system is described here that allows a highly efficient generation of clones with the concomitant expression of an easily detectable cellular marker. This method can be applied to cell lineage and mosaic analysis in Drosophila. The site-specific yeast FLP recombinase, under the control of a heat shock-inducible promoter, efficiently catalyses mitotic recombination specifically at the site of a FLP recombination target (FRT). In this system, recombination fuses the alpha-tubulin promoter to the lacZ gene, allowing transcription of the marker. Recombinant cells and their progeny can, therefore, be detected by standard assays for beta-galactosidase. Of particular importance is the fact that only the cells of interest stain, thus allowing their simple detection in any tissue. CONCLUSIONS: We demonstrate that, by intermolecular recombination, we can use FLIP recombinase to generate marked clones efficiently in embryonic, larval and adult tissues. This simple and efficient technique is well suited to cell-lineage analysis and can be easily extended to the generation and detection of mutant clones in mosaic animals.

Journal Article↗

PubMed2004

Myocardial blood flow and efficiency in concentric and eccentric left ventricular hypertrophy.

BACKGROUND: It is not clearly understood why concentric left ventricular hypertrophy (increased left ventricular mass and relative wall thickness) is associated with higher cardiovascular risk than eccentric hypertrophy (increased left ventricular mass but normal relative wall thickness). Possible reasons include lower myocardial efficiency or perfusion reserve in concentric than in eccentric hypertrophy. We compared myocardial perfusion reserve and efficiency in normotensive controls and in hypertensive patients with concentric and with eccentric hypertrophy. METHODS: Study subjects comprised 16 patients with hypertension-induced left ventricular hypertrophy and 10 normotensive controls. We measured myocardial perfusion reserve and oxygen consumption by positron emission tomography. We calculated myocardial efficiency by dividing left ventricular minute work by myocardial oxygen consumption. RESULTS: There was no significant difference in myocardial perfusion reserve between patients with concentric (n = 9) as compared to eccentric (n = 7) hypertrophy. However, myocardial perfusion reserve in both patient groups were lower than in controls. Although myocardial efficiency in patients with eccentric hypertrophy and in controls were not different, both values were higher than measurements in patients with concentric hypertrophy (18% +/- 6% v 16% +/- 3% v 13% +/- 4%, eccentric hypertrophy versus controls versus concentric hypertrophy, respectively, P =.04 for both eccentric versus concentric hypertrophy and for controls versus concentric hypertrophy). CONCLUSIONS: Myocardial efficiency but not perfusion reserve is lower in hearts with concentric compared with eccentric left ventricular hypertrophy. This might be an explanation for the higher cardiovascular morbidity and mortality associated with concentric left ventricular hypertrophy.

Adult↗

PubMed2006

The surgical efficiency score: a feasible, reliable, and valid method of skills assessment.

BACKGROUND: Technical skills assessments are being increasingly used in surgical residency programs, with the objectivity and validity of several techniques well established. However, many of these methods are labor and time intensive, limiting their feasibility. This study aims to compare more efficient techniques of skills appraisals with an established gold standard. METHODS: Thirty surgeons completed 2 previously validated laboratory-based surgical models: small bowel anastomosis and vein patch insertion. Gold standard evaluation was the Objective Structured Assessment of Technical Skills (OSATS) method. "Efficient" techniques used were (1) quality of final product (FP); (2) snapshot assessment (SS), in which task performance was edited to a 2-minute sound bite and scored with OSATS; and (3) the surgical efficiency score (SES), a combination of final product quality and hand-motion analysis. All human observer evaluations used retrospective video analysis with 3 trained observers. Nonparametric tests were used to analyze the results. RESULTS: With respect to small bowel anastomosis, correlations with OSATS were as follows: FP 0.341 (P=.07), SS 0.577 (P<.001), and SES 0.842 (P<.001). For vein patch insertion, the correlations were as follows: FP 0.545 (P=.001), SS 0.609 (P<.001), and SES 0.700 (P<.001). Interobserver concordance was high for both models with respect to FP (Cronbach's alpha 0.80 for small bowel anastomosis and 0.84 for vein patch insertion). With respect to SS, interobserver reliability was high for vein patch insertion (Cronbach's alpha 0.80) but only moderate for small bowel anastomosis (0.59). CONCLUSIONS: The surgical efficiency score and snap shot assessments both show significant correlations with the traditional OSATS appraisals and suggest that skills assessment can be made more feasible. Correlations were closer with the former and interobserver concordance more variable with the latter, suggesting the surgical efficiency score as the most reliable of the methods evaluated.

Anastomosis, Surgical↗

PubMed2005

Inpatient rehabilitation of patients requiring hemodialysis: improving efficiency of care.

OBJECTIVE: To determine if reducing missed therapy sessions by patients requiring hemodialysis will reduce the length of stay (LOS) and improve the efficiency of care in an inpatient rehabilitation unit. DESIGN: Retrospective study. SETTING: Inpatient rehabilitation unit at a university medical center. PARTICIPANTS: All patients discharged from the Albany Medical Center rehabilitation unit between January 1, 2003, and June 30, 2004. The total number of patients was 955, 40 of whom required hemodialysis. INTERVENTION: On January 1, 2003, Albany Medical Center began providing hemodialysis in the late afternoon, allowing patients to complete a full 3-hour program without missing therapy sessions to attend dialysis. We compared the outcomes of 915 patients who did not require hemodialysis with the outcomes of 40 patients who required hemodialysis. We also compared the outcomes of patients treated on the rehabilitation unit in 2003-2004 to the outcomes of patients treated on the rehabilitation unit before dialysis was available at times that did not conflict with therapy (calendar year 2001). MAIN OUTCOME MEASURES: LOS, improvement on the FIM instrument, and FIM efficiency score. RESULTS: The LOS of the hemodialysis patients changed from 16.0 in 2001 to 12.1 in 2003-2004 (P<.05), and the FIM efficiency score of the hemodialysis patients improved from 1.8 in 2001 to 2.9 in 2003-2004 (P<.05). The FIM efficiency score of the nondialysis group in 2003-2004 was 4.0. This was significantly greater (P<.05) than that of dialysis patients in 2003-2004. CONCLUSIONS: A program to reduce conflicts between medical treatments such as hemodialysis and therapy sessions may result in reduced LOS and improved efficiency on an inpatient rehabilitation unit.

Activities of Daily Living↗

PubMed2006

Enhancement of operational efficiencies for people with high cervical spinal cord injuries using a flexible integrated pointing device apparatus.

OBJECTIVE: To investigate the effectiveness of a universal integrated pointing device apparatus (IPDA), which can integrate numerous commercial pointing devices and can be controlled by various combinations of available movements, for people with cervical spinal cord injury (SCI) who cannot operate standard computer pointing devices. DESIGN: An exploratory quasi-experimental design. All subjects were required to perform specific mouse-operating (continuous-clicking, target-acquisition, drag-and-drop) tasks. People with SCI received clinical assessments and were classified into 2 groups based on pointing device used: group A, who used standard mouse devices, and group B (IPDA combinations), who were unable to use standard mouse devices. The measures of group A and group B were compared. SETTING: Rehabilitation science center of a medical institution. PARTICIPANTS: Thirty-seven people with high cervical SCI and 30 able-bodied subjects. INTERVENTION: The IPDA. MAIN OUTCOME MEASURES: The efficiency of the people with SCI in each mouse-operation task was expressed as a percentage of that for able-bodied subjects (%NL). RESULTS: Group B displayed similar operational efficiency in performing the drag-and-drop tasks ( approximately 30% NL) to group A, although they exhibited worse efficiency than group A in performing the other tasks (P<.05). Operational efficiencies of all tasks had negative relationships with age by using linear regression analysis (adjusted r(2)>.36, P<.001). The use of pointing devices was associated with American Spinal Injury Association Impairment Scale (P<.001), completeness (P<.001), and muscle strength (P<.01), particularly finger flexor muscle strength, but not with neurologic level or muscle tone. CONCLUSIONS: The IPDA could help most people with high cervical SCI who could not use commercial mouse devices to achieve acceptable operational efficiencies. Pointing devices were assigned based on the underlying SCI severity and muscle strength, particularly finger flexor muscle strength.

Activities of Daily Living↗

PubMedDate not supplied

Comparison of ionization chamber efficiencies for activity measurements.

The calibration of ionization chamber measuring systems in terms of activity is described. The energy-dependent efficiency curves of three chambers at the Bureau International des Poids et Mesures, the National Physical Laboratory and the Physikalisch-Technische Bundesanstalt are determined and compared using a fitting procedure for the experimental radionuclide efficiencies by the Microsoft (MS) EXCEL Solver program. An estimation of the uncertainty of the efficiency curves and the deviations of experimental and calculated radionuclide efficiencies are given. By this fitting method, discrepancies in the efficiency determination can be detected at a level of about one percent. Systematic deviations entering into the calculations either from emission probabilities per decay or from absolute activity standardization are discussed.

Algorithms↗

PubMed2006

Experimental determination of the extrinsic sensitivity and counting efficiency of a nuclear gamma camera using a homogeneous circular planar source.

Two important operational parameters of medical gamma cameras are the extrinsic counting efficiency and sensitivity. Historically, for practical reasons these two parameters have been defined using a point source of radiation at a certain distance from the detector. This definition has the disadvantage of producing measurements of limited clinical relevance since real patients are not point sources of radiation. In this work, we propose a more clinically relevant method of determining efficiency and sensitivity, using a planar, circular, homogeneous source. For this purpose, a gamma camera of 39 cm diameter, and a circular, homogeneous, 36.5 cm diameter Co-57 source with an activity of 5.5+/-0.7%mCi were employed. The source was placed coaxially with the detector at distances of 50, 100, and 150 cm. Data were acquired using a medium and a high-resolution collimator. The efficiency was found to depend directly on the solid angle subtended by the detector. Computed values for the sensitivity are in the range of 5-6 kcts/sec-mCi, and values for the efficiency were found to range between 0.2% and 2%. The results show an approximate 2:1 ratio in sensitivity and efficiency between the medium and high-resolution collimators regardless of source-detector distances.

Algorithms↗

PubMed2004

KLN-5: a safe monocationic lipophosphoramide to transfect efficiently haematopoietic cell lines and human CD34+ cells.

The safe and efficient delivery of nucleic acids into haematopoietic stem cells (HSCs) has a wide range of therapeutic applications. Although viruses are being used in most clinical trials owing to their high transfection efficacy, recent results highlight many concerns about their use. Synthetic transfection reagents, in contrast, have the advantage of being safe and easy to manage while their low transfection efficiency remains a hurdle that needs to be addressed before they can be widely used. Using information on transfection mechanisms, a new family of monocationic lipids called lipophosphoramides was synthesized. Their efficiency to transfer genes into haematopoietic cell lines (K562, Jurkat and Daudi) and CD34+ cells was assessed. In this study, we report that one of these new compounds, KLN-5, leads to more efficient transfection activity than one of our previously most efficient reagents (EG-308) and the commercially available monocationic lipids (DC-CHOL and DOTAP/DOPE) (P<0.05). In addition, only a slight toxicity related to the chemical structure of the new compounds is observed. Moreover, we show that KLN-5 can successfully carry the transgene into haematopoietic progenitor cells (CD34+). These results demonstrate that synthetic transfection reagents represent a viable alternative to viruses and could have potential practical utility in a number of applications.

Amides↗