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At least 217 records · Page 12Linked to original sources

PubMed1989

Behavioural differences between laying hen populations selected for high and low efficiency of food utilisation.

1. The effects on behaviour of selecting light-hybrid laying hens for high and low efficiency of food utilisation were investigated. Efficiency of food utilisation was measured as the proportional deviation of observed food consumption from expected food consumption. 2. Videograms of the day-time behaviour of 48 to 53-week-old individually caged hens from the F3 generation were analysed by instantaneous sampling. 3. Low-efficiency hens spent more time food-pecking, walking, pacing, and showing escape and aggressive behaviour than did high-efficiency hens. High-efficiency hens spent more than twice as much time resting and sleeping, and were never observed pacing prior to laying. 4. These differences were larger during the 2 h before laying than at other times of day. 5. Low-efficiency hens had poorer plumage, especially on the neck and the breast, and the poorer the plumage the more agitation they showed. 6. Time spent food-pecking was negatively correlated with laying frequency. 7. Differences in the occurrence of specific behaviour patterns, particularly those symptomatic of pre-laying frustration, partly explained differences in efficiency of food utilisation. Selection for higher efficiency of food utilisation might eliminate hens which are most frustrated prior to laying in cages.

Aggression↗

PubMed2006

Dust collection efficiency analysis in a two-dimensional circulating granular bed filter.

Dust collection efficiency data were analyzed to determine better operating conditions for a two-dimensional circulating granular bed filter (CGBF). The dust collection efficiency in the granular bed was affected by the following operating parameters: the louver angle, the solids mass flow rate, and the particle size of the bed material. Experimental results showed that higher dust collection efficiency occurs when the solids mass flow rates were 20.34 +/- 0.24, 21.50 +/- 0.11, and 30.51 +/- 0.57 g/sec at louver angles of 45 degrees, 30 degrees, and 20 degrees, respectively. Optimal dust collection efficiency peaked with a louver angle of 30 degrees. Average particle sizes of bed material by sieve diameters (microm) of 795 microm had higher dust collection efficiency than the average collector particle size of 1500 microm. Dust collection efficiency is influenced by bed material attrition phenomenon, causing dust collection efficiency to decrease rapidly. The dust collection efficiency analysis not only found the system free of design defects but also assisted in the operation of the two-dimensional CGBF system.

Air Pollutants↗

PubMed2001

Control of DNA excision efficiency in Paramecium.

Programmed excision of internal eliminated sequences (IESs) occurs at thousands of sites in ciliate genomes. How this is controlled is largely unknown. Here, we report the characterization of the non-efficiently excised 156psiG-11 IES from Paramecium primaurelia strain 156 and that of the efficiently excised 168psiG-11 IES, an allelic variant from strain 168. Then, we report a genetic and molecular analysis of IES excision efficiency in F(1) progeny derived from interstrain crosses and in F(2) homozygous progeny derived from F(1) autogamy. IES 168psiG-11 excision efficiency was approximately 100% in all cases. IES 156psiG-11 excision efficiency was 19 +/- 13% in F(1) progeny and 0.6 +/- 1.1% in F(2) progeny. No trans-excision event between IESs 156psiG-11 and 168psiG-11 was detected within the F(1) progeny. These data demonstrate that the excision efficiency of this IES is variable and controlled by a cis-acting element. This should encompass positions 8 and/or 9 of the right IES end, which display allele differences. Finally, the 30-fold stimulation of IES 156psiG-11 excision efficiency within F(1) progeny relative to F(2) progeny demonstrates that Paramecium IES excision efficiency is sensitive either to a conjugation-specific trans-acting factor provided by the zygotic genome, or to homologous chromosome cross-talk.

Alleles↗

PubMed2001

Shoot structure and photosynthetic efficiency along the light gradient in a Scots pine canopy.

We examined the effects of structural and physiological acclimation on the photosynthetic efficiency of Scots pine (Pinus sylvestris L.) shoots. We estimated daily light interception (DLI) and photosynthesis (DPHOT) of a number of sample shoots situated at different positions in the canopy. Photosynthetic efficiency (epsilon) was defined as the ratio of DPHOT to the potential daily light interception (DLI(ref)) defined as the photosynthetically active radiation (PAR) intercepted per unit area of a sphere at the shoot location. To calculate DLI(ref), DLI and DPHOT, the radiation field surrounding a shoot in the canopy was first modeled using simulated directional distributions of incoming PAR on a clear and an overcast day, and estimates of canopy gap fraction in different directions provided by hemispherical photographs. A model of shoot geometry and measured data on shoot structure and photosynthetic parameters were used to simulate the distribution of PAR irradiance on the needle surface area of the shoot. Photosynthetic efficiency (epsilon) was separated into light-interception efficiency (epsilon(I) = DLI/DLI(ref)) and conversion efficiency (epsilon(PHOT) = DPHOT/DLI). This allowed us to quantify separately the effect of structural acclimation on the efficiency of photosynthetic light capture (epsilon(l)), and the effect of physiological acclimation on conversion efficiency (epsilon(PHOT)). The value of epsilon increased from the top to the bottom of the canopy. The increase was largely explained by structural acclimation (higher epsilon(I)) of the shade shoots. The value of epsilon(PHOT) of shade foliage was similar to that of sun foliage. Given these efficiencies, the clear-day value of DPHOT for a sun shoot transferred to shade was only half that of a shade shoot at its original position. The method presented here provides a tool for quantitatively estimating the role of acclimation in total canopy photosynthesis.

Light↗

PubMed2001

Delta efficiencies of running and cycling.

PURPOSE: The purpose of the present study was to compare delta efficiencies of running with cycling, while several factors that can possibly influence delta efficiency were excluded. METHODS: Twelve subjects performed a submaximal running and cycling test on subsequent days. Delta efficiencies of running and cycling were compared at equal metabolic intensities. Furthermore, rest periods were included in the protocol to avoid fatigue. Pedaling and stride frequencies were held constant during the tests. Finally, the influence of two ways of applying extra external load (inclination of treadmill and horizontal impeding forces) on the delta efficiency of running and cycling was investigated. RESULTS: The results of the present study show that the mean delta efficiency of running (45.5%) is still significantly higher than the mean delta efficiency of cycling (25.7%). The way extra external load is applied does not influence delta efficiency. CONCLUSION: The way of loading and the difference in metabolic intensity can be excluded as causes for the observed difference in delta efficiency between running and cycling. It is suggested that a different contribution in the metabolic load attributable to muscular activity of the arms and/or trunk that does not directly contribute to the work needed to overcome the amount of applied external load may be a relevant factor.

Adult↗

PubMed2002

Arm mechanical efficiency and arm exercise capacity are relatively preserved in chronic obstructive pulmonary disease.

PURPOSE: Previous studies indicate that energy expenditure related to physical activity is enhanced and that mechanical efficiency of leg exercise is reduced in patients with chronic obstructive pulmonary disease (COPD). However, it is yet unclear whether an inefficient energy expenditure is also present during other activities in COPD. This study was carried out to examine arm efficiency and peak arm exercise performance relative to leg exercise in 33 (23 male) patients with COPD ((mean +/- SEM) age: 61 +/- 2 yr; FEV : 40 +/- 2% of predicted) and 20 sex- and age-matched healthy controls. METHODS: Body composition, pulmonary function, resting energy expenditure (REE), and peak leg and arm exercise performance were determined. To calculate mechanical efficiency, subjects performed submaximal leg and arm ergometry at 50% of achieved peak loads. During exercise testing, metabolic and ventilatory parameters were measured. RESULTS: In contrast to a reduced leg mechanical efficiency in patients compared with controls (15.6 +/- 0.6% and 22.5 +/- 0.6%, respectively; < 0.001), arm mechanical efficiency was comparable in both groups (COPD: 18.3 +/- 0.9%, controls: 21.0 +/- 1.2%; NS). Arm efficiency was not related to leg efficiency, pulmonary function, work of breathing, or REE. Also, arm exercise capacity was relatively preserved in patients with COPD (ratio arm peak work rate/leg peak work rate in patients: 89% vs 53% in controls; < 0.001). CONCLUSION: Mechanical efficiency and exercise capacity of the upper and lower limbs are not homogeneously affected in COPD, with a relative preservation of the upper limbs. This may have implications for screening of exercise tolerance and prescription of training interventions in patients with COPD. Future studies need to elucidate the mechanism behind this observation.

Arm↗

PubMed2000

Iterative crystal efficiency calculation in fully 3-D PET.

The calculation of the intrinsic efficiency of individual crystals is one of the steps needed to obtain accurate images of the radioisotope distribution in positron emission tomography (PET). These efficiencies can be computed by comparing the number of coincidence counts obtained when the crystals are equally illuminated by the same source. However, because the number of coincidence counts acquired for one crystal also depends on the efficiency of the other crystals in coincidence, most methods of crystal efficiency calculation need to assume that the influence of the other crystals is negligible. If there are large crystal efficiency variations, this approximation may lead to systematic errors. We have recently implemented an iterative method for a single ring of detectors that does not rely on this assumption. In this paper, we describe a fully three-dimensional (3-D) iterative method that better exploits the sensitivity of the tomograph and allows reduced acquisition times or the use of narrow energy windows. We compare the performance of the iterative method (single-ring and extended to fully 3-D) with noniterative techniques for different acquisition times of a uniform cylinder. Two different energy windows were used to assess the performance of each method with different levels of variations of crystal efficiency. The results showed that the iterative methods are more accurate when large efficiency variations exist and that only the fully 3-D methods provided good efficiency estimates with very low duration scans. We, thus, conclude that iterative fully 3-D methods provide the best estimations and can be used in a larger range of situations than can the other methods tested.

Algorithms↗

PubMed1997

Mapping of pump efficiency on the pressure-flow curve of a centrifugal blood pump.

Because pump efficiency is closely related to heat generation and blood trauma in a centrifugal blood pump, it is quite important to study pump efficiencies in a variety of conditions. In the present study, pump efficiencies were mapped on the pressure head-flow rate curves of 4 different pumps; BioMedicus BioPump (BP-80), Nikkiso (NK), Gyro C1E3, and Gyro PI601 (diameter of the impeller, NK: 50 mm, C1Ee3: 65 mm, and PI601: 50 mm). The mapping of pump efficiency revealed the following findings. First, the cone type (BP-80) has less pump efficiency than the impeller type (NK and C1E3); second, the miniaturization of the C1E3 to the PI601 has resulted in an increase in pump efficiency; and third, the diameter of the impeller may contribute to the pump efficiency of an im peller type pump. The mapping of the pump efficiency, as demonstrated in this study, is useful for the analysis of hydraulic pump performance in a wide range of clinically applied conditions.

Blood Flow Velocity↗

PubMed1983

The influence of dilution rate, temperature, and influent substrate concentration on the efficiency of steady-state biomass production in continuous microbial culture.

The efficiency of steady-state biomass production was defined as the ratio of the biomass produced at steady state to the biomass that would be produced if influent substrate were completely and permanently incorporated. The scope of analysis was confined to microbial growth processes described by a Monod reaction mechanism. A thermo-kinetic analysis of this mechanism with coefficient values estimated from experimental data showed: (table; see text) (1) As the dilution rate was increased, the efficiency passed through a single peak. Raising the temperature did not markedly change the peak efficiency, but did broaden and shift the peak toward higher dilution rates. In contrast, elevating the influent substrate concentration significantly improved the peak efficiency while still broadening and shifting the peak toward higher dilution rates. (2) As the temperature was raised, the efficiency also showed a single peak. Increasing the dilution rate did not significantly alter the peak value or breadth, but did shift the peak to higher temperatures. In contrast, elevating the influent substrate concentration substantially improved the peak efficiency and caused the peak to shift toward lower temperatures without broadening. (3) As the influent substrate concentration was elevated, the peak efficiency improved and asymptotically approached unity. These results suggested that relatively high influent substrate concentrations, low temperatures, and moderate dilution rates would be needed to optimize the efficiency of steady-state biomass production by Monod processes with coefficient values similar to those used in this paper.

Bacteria↗

PubMed2004

Large efficiency improvements in BEAMnrc using directional bremsstrahlung splitting.

The introduction into the BEAMnrc code of a new variance reduction technique, called directional bremsstrahlung splitting (DBS), is described. DBS uses a combination of interaction splitting for bremsstrahlung, annihilation, Compton scattering, pair production and photoabsorption, and Russian Roulette to achieve a much better efficiency of photon beam treatment head simulations compared to the splitting techniques already available in BEAMnrc (selective bremsstrahlung splitting, SBS, and uniform bremsstrahlung splitting, UBS). In a simulated 6 MV photon beam (10 x 10 cm2 field) photon fluence efficiency in the beam using DBS is over 8 times higher than with optimized SBS and over 20 times higher than with UBS, with a similar improvement in electron fluence efficiency in the beam. Total dose efficiency in a central-axis depth-dose curve improves by a factor of 6.4 over SBS at all depths in the phantom. The performance of DBS depends on the details of the accelerator being simulated. At higher energies, the relative improvement in efficiency due to DBS decreases somewhat, but is still a factor of 3.5 improvement over SBS for total dose efficiency using DBS in a simulated 18 MV photon beam. Increasing the field size of the simulated 6 MV beam to 40 x 40 cm2 (broad beam) causes the relative efficiency improvement of DBS to decrease by a factor of approximately 1.7 but is still up to 7 times more efficient than with SBS.

Algorithms↗

PubMed2025

Robust and highly efficient transformation method for a minimal mycoplasma cell.

UNLABELLED: Mycoplasmas have been widely investigated for their pathogenicity, as well as for genomics and synthetic biology. Conventionally, transformation of mycoplasmas was not highly efficient, and due to the low transformation efficiency, large amounts of DNA and recipient cells were required for that purpose. Here, we report a robust and highly efficient transformation method for the minimal cell JCVI-syn3B, which was created through streamlining the genome of Mycoplasma mycoides. When the growth states of JCVI-syn3B were examined in detail by focusing on such factors as pH, color, absorbance, colony forming unit, and transformation efficiency, it was found that the growth phase after the lag phase can be divided into three distinct phases, of which the highest transformation efficiency was observed during the early exponential growth phase. Notably, the transformation efficiency of up to 4.4 × 10-2 transformants per cell per microgram of plasmid DNA was obtained. A method to obtain several hundred to several thousand transformants with less than 0.2 mL of culture with approximately 1 × 107-108 cells and 10 ng of plasmid DNA was developed. Moreover, a transformation method using a frozen stock of transformation-ready cells was established. These procedures and information could simplify and enhance the transformation process of minimal cells, facilitating advanced genetic engineering and biological research using minimal cells. IMPORTANCE: Mycoplasmas are parasitic and pathogenic bacteria for many animals. They are also useful bacteria to understand the cellular process of life and for bioengineering because of their simple metabolism, small genomes, and cultivability. Genetic manipulation is crucial for these purposes, but transformation efficiency in mycoplasmas is typically quite low. Here, we report a highly efficient transformation method for the minimal genome mycoplasma JCVI-syn3B. Using this method, transformants can be obtained with only 10 ng of plasmid DNA, which is around one-thousandth of the amount required for traditional mycoplasma transformations. Moreover, a convenient method using frozen stocks of transformation-ready cells was established. These improved methods play a crucial role in further studies using minimal cells.

Transformation, Bacterial↗

PubMed1991

A cellular function can enhance gene expression and plating efficiency of a mutant defective in the gene for ICP0, a transactivating protein of herpes simplex virus type 1.

ICP0 transactivates herpes simplex virus type 1 genes of all classes as well as a number of heterologous viral and cellular genes, yet it is not essential for virus replication in vitro or in vivo. Stocks of ICP0 deletion mutants, however, exhibit significantly lower plating efficiencies on standard 24-h-old Vero cell monolayers than do stocks of wild-type virus. In an attempt to determine whether the growth status of cells in the monolayer affects the ability of ICP0 mutants to initiate plaque formation, the plating efficiencies and abilities of an ICP0 null mutant (7134) and of wild-type virus (KOS) to express selected viral proteins were determined on Vero cell monolayers whose growth had been arrested either by contact inhibition-trypsinization or by isoleucine deprivation and had then been released from growth arrest. The proportion of cells cycling synchronously after release from growth arrest was assessed by flow cytometry. The results of these studies indicate that the plating efficiency of 7134 was greatest on Vero cell monolayers 8 h after release from growth arrest induced by either treatment. Monolayers of both types released from growth arrest at other times supported 7134 plaque formation less efficiently. In contrast, the plating efficiency of KOS was nearly equal on monolayers at all times after release from growth arrest. Notably, both KOS and 7134 were equally efficient in entering cells and inducing expression of the immediate-early protein ICP4 in either 8- or 24-h monolayers. Relative to KOS, however, 7134 was significantly impaired in the expression of selected early and late genes in cells at 24 h postrelease. When the plating efficiencies of 7134 and KOS were examined in 0-28 cells (Vero cells that are stably transformed with the ICP0 gene) whose growth had been arrested and then released, no differences in the plating efficiencies of the two viruses as a function of growth status were noted. These findings suggest that a cellular function expressed maximally in cells 8 h after release from growth arrest can substitute operationally for ICP0 to enhance plaque formation and viral gene expression by 7134. They further suggest that one role of ICP0 in viral infection is to facilitate virus replication in cells that do not express this function.

Animals↗

PubMed2001

Dichloroacetate improves cardiac efficiency after ischemia independent of changes in mitochondrial proton leak.

Dichloroacetate (DCA) is a pyruvate dehydrogenase activator that increases cardiac efficiency during reperfusion of ischemic hearts. We determined whether DCA increases efficiency of mitochondrial ATP production by measuring proton leak in mitochondria from isolated working rat hearts subjected to 30 min of ischemia and 60 min of reperfusion. In untreated hearts, cardiac work and efficiency decreased during reperfusion to 26% and 40% of preischemic values, respectively. Membrane potential was significantly lower in mitochondria from reperfused (175.6 +/- 2.2 mV) versus aerobic (185.8 +/- 3.1 mV) hearts. DCA (1 mM added at reperfusion) improved recovery of cardiac work (1.9-fold) and efficiency (1.5-fold) but had no effect on mitochondrial membrane potential (170.6 +/- 2.9 mV). At the maximal attainable membrane potential, O(2) consumption (nmol O(2) x mg(-1) x min(-1)) did not differ between untreated or DCA-treated hearts (128.3 +/- 7.5 and 120.6 +/- 7.6, respectively) but was significantly greater than aerobic hearts (76.6 +/- 7.6). During reperfusion, DCA increased glucose oxidation 2.5-fold and decreased H(+) production from glucose metabolism to 53% of untreated hearts. Because H(+) production decreases cardiac efficiency, we suggest that DCA increases cardiac efficiency during reperfusion of ischemic hearts by increasing the efficiency of ATP use and not by increasing the efficiency of ATP production.

Adenosine Triphosphate↗

PubMed1986

Renal autoregulatory efficiency during angiotensin-converting enzyme inhibition in dogs on a low sodium diet.

Autoregulatory efficiency of renal blood flow (RBF) and glomerular filtration rate (GFR) was evaluated in 12 anesthetized dogs that had been maintained on low-sodium diet during control conditions and following infusion of an angiotensin-converting enzyme inhibitor (captopril). Converting enzyme inhibition (CEI) decreased systemic blood pressure by 15.5 +/- 3.5%, increased RBF by 36.3 +/- 6.5%, and increased GFR by 25.9 +/- 10.7%. In response to reductions in renal arterial pressure, RBF was efficiently autoregulated and did not change significantly until the 89- to 75-mm Hg range during the control period and the 74- to 54-mm Hg range during CEI. Overall GFR autoregulatory efficiency was generally well maintained during CEI; however, evaluation of the coupled autoregulatory efficiency of RBF and GFR indicated that during angiotensin blockade, there was a greater incidence of a dissociation between RBF and GFR autoregulatory efficiency. Six of the 12 dogs showed reduced GFR autoregulatory efficiency at renal arterial pressures where RBF was still well maintained. Thus, while the data indicate that blockade of the renin-angiotensin system does not abolish the basic capability of the kidney to autoregulate either RBF or GFR efficiently, more subtle influences on the coupling of RBF and GFR autoregulatory efficiency were observed at the lower level of the autoregulatory range.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed2004

Vocal efficiency measurements in subjects with vocal polyps and nodules: a preliminary report.

Vocal efficiency is a quantitative measure of the ability of the larynx to convert subglottal power to acoustic power. On the basis of the scant previous literature and clinical intuition, we tested the hypothesis that vocal efficiency, as an indicator of the functional status of the larynx, is abnormally reduced in persons with vocal nodules and polyps. Because the most difficult aspect of obtaining measures of vocal efficiency has been the determination of subglottal pressure, we applied a noninvasive airflow interruption technique for this purpose. Subjects with normal voices (n = 22), vocal polyps (n = 14), and vocal nodules (n = 16) phonated at different intensities into a mask connected by way of piping to a flow meter, a pressure transducer, and an acoustic microphone. Inflation of a balloon-type valve located within the piping provided interruption of phonation. The intraoral pressure plateau occurring during flow interruption was used to estimate subglottal pressure. Subglottal power and acoustic power were determined, and their quotient provided a measure of vocal efficiency. The vocal efficiency in the normal subjects averaged 1.15 x 10(-5) at 70 dB, 3.17 x 10(-5) at 75 dB, 7.52 x 10(-5) at 80 dB, and 1.41 x 10(-4) at 85 dB. The vocal efficiency in the patients with vocal polyps averaged 3.62 x 10(-6) at 70 dB, 8.34 x 10(-6) at 75 dB, 2.10 x 10(-5) at 80 dB, and 4.26 x 10(-5) at 85 dB. The vocal efficiency in the patients with vocal nodules averaged 4.32 x 10(-6) at 70 dB, 1.57 x 10(-5) at 75 dB, 4.26 x 10(-5) at 80 dB, and 8.34 x 10(-5) at 85 dB. As compared to the normal subjects, the patients with laryngeal polyps or vocal nodules had significantly reduced vocal efficiency. These results provide quantitative verification of the clinical impression of inefficient phonation in patients with mass lesions of the vocal folds.

Adult↗

PubMed1994

The influence of anesthesia on myocardial oxygen utilization efficiency in patients undergoing coronary bypass surgery.

A maximum efficiency of myocardial oxygen utilization is desirable, especially in patients with limited coronary blood supply. Little is known about the effects of anesthesia on the efficiency of myocardial oxygen utilization. The aim of this retrospective study was to investigate the effects of different types of anesthesia on myocardial efficiency in patients undergoing coronary bypass surgery. Myocardial blood flow (Argon wash in technique), myocardial oxygen uptake, and standard hemodynamics were measured awake, after induction of anesthesia, and during sternal spread. Myocardial oxygen utilization efficiency was calculated from the ratio of external work divided by myocardial oxygen consumption. Sixty-five patients in eight groups with different anesthetic techniques were studied: 1) halothane/nitrous oxide, 2) enflurane/nitrous oxide, 3) high-dose morphine, 4) high-dose fentanyl, 5) fentanyl/midazolam, 6) high-dose sufentanil, 7) sufentanil/nitrous oxide, and 8) propofol. In all groups induction of anesthesia was associated with a decrease of cardiac work (from 86 +/- 17 to 55 +/- 16 J/min in pooled data) which resulted from a decrease of both stroke volume index and blood pressure. However, myocardial oxygen consumption did not decrease proportionally (from 11.2 +/- 3.0 to 8.5 +/- 2.3 mL.min-1 x 100 g-1 in pooled data) and myocardial oxygen utilization efficiency was therefore decreased in all groups (from 29.2% +/- 2.5% at awake state to 23.9% +/- 5.8% after induction of anesthesia in pooled data). Surgical stimulation by sternotomy and sternal spread was associated with different patterns of hemodynamic response between groups. Blood pressures and external work tended to be higher in the high-dose narcotic groups while it remained less affected in the other groups. However, myocardial efficiency remained depressed in all groups (22.2% +/- 8.2% in pooled data) and with respect to myocardial efficiency no differences between anesthetic techniques were found. We conclude that the specific anesthetic technique does not influence impairment of myocardial oxygen utilization efficiency by anesthesia.

Anesthesia↗

PubMed2001

Spectral luminous efficiency as a function of age.

Spectral luminous efficiency function for a 2-deg field at a photopic level (100 Td) was measured for 91 observers by flicker photometry (FP) and for 97 observers by direct brightness matching (DBM), to find age-related change in the efficiency function as well as to obtain a reliable data set to be used in photometry. Observers ranged in age from 11 to 78 years. A gradual reduction of luminous efficiency with age was observed for both functions by FP and by DBM in the short-wave region, which was expected because of the age-related increase of optical density of eye lens. A similar age-related reduction of efficiency was observed in the long-wave region for the function obtained by DBM; this reduction was regarded as being due to reduced chromatic contribution to brightness with age. Principal components analysis on the spectral efficiency data and an analysis of the efficiency difference between the data obtained by DBM and FP confirmed this conclusion. Assuming a log-linear change in efficiency with age for any wavelength throughout the life span, spectral luminous efficiency function at any age was derived for photometric use.

Adolescent↗

PubMed2005

Optimization of high-efficiency transfection of adult human mesenchymal stem cells in vitro.

With the advent of recent protocols to isolate multipotent human mesenchymal stem cells (MSCs), there is a need for efficient transfection methodologies for these cells. Most standard transfection methods yield poor transfection efficiencies for MSCs (<1%). Here we have optimized a high-efficiency transfection technique for low passage MSCs derived from adult human bone marrow. This technique is an extension of electroporation, termed amaxa Nucleofection, where plasmid DNA is transfected directly into the cell nucleus, independent of the growth state of the cell. With this technique, we demonstrate up to 90% transfection efficiency of the viable population of MSCs, using plasmid construct containing a standard cytomegalovirus (CMV) early promoter driving expression of green fluorescent protein (GFP). Although little variation in transfection efficiency was observed between patient samples, a 2-fold difference in transfection efficiency and a 10-fold difference in expression levels per cell were seen using two distinct CMV-GFP expression plasmids. By fluorescence-activated cell sorting, the GFP expressing cells were sorted and subcultured. At 2 wk posttransfection, approx 25% of the population of sorted cells were GFP positive, and by 3 wk, nearly 10% of the cells still retained GFP expression. Transfection of these cells with plasmid containing either the collagen type I (Col1a1) promoter or the cartilage oligomeric matrix protein (COMP) promoter, each driving expression of GFP, produced a somewhat lower transfection efficiency (approx 40%), due in part to the lower activity of transcription from these promoters compared to that of CMV. Transfection with the collagen type II (Col2a1) promoter linked to GFP exhibited low expression, due to the fact that collagen type II is not expressed in these cells. Upon culturing of the Col2a1-GFP transfected cells in a transforming growth factor-beta3-containing medium known to induce mesenchymal chondrogensis, a significant enhancement of GFP level was seen, indicating the ability of the transfected cells to differentiate into chondrocytes and express cartilage-specific genes, such as Col2a1. Taken together, these data provide evidence of the applicability of this technique for the efficient transfection of MSCs.

Adult↗