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PubMed1998

Relationship between blood serum insulin-like growth factor I concentration and postweaning feed efficiency of crossbred cattle at three levels of dietary intake.

Blood serum concentration of IGF-I was analyzed to determine its relationship with individual postweaning feed efficiency (gain/feed) of 36 crossbred steer calves fed at three levels of feed intake (n = 12 at each level). Diets consisted of a corn silage-based growing diet for 84 d followed by a 91% concentrate finishing diet for 56 d. Dietary intake levels were at 80, 90, or 100% of ad libitum. Diets were formulated to ensure equal daily intake of protein, vitamins, and minerals across intake treatment levels. Intake was measured daily; ADG, DMI, and feed efficiency were calculated at 28-d intervals, through d 140. Individual weights and serum samples were collected at the beginning of the study and at 28-d intervals thereafter. The IGF-I concentrations were determined with a RIA. Data were analyzed as a multivariate split-plot in time. Imposed dietary intake restrictions did not affect serum IGF-I concentration (P = .90) or individual feed efficiency (P = .36), even though the least squares means for IGF-I concentration tended to decrease and the feed efficiency means tended to increase under the restricted intake levels. Serum IGF-I concentration, ADG, and feed efficiency were affected (P < .001) by collection date. Residual correlations between IGF-I concentrations at adjacent 28-d sampling times averaged .72. Diet intake level x sampling time interactions existed for ADG (P = .02) and feed efficiency (P < .001). Positive residual correlations of .28 (P < .001) and .16 (P = .07) existed between IGF-I and ADG and between IGF-I and feed efficiency, respectively. Regression analysis indicated that a 1 ng/mL increase in serum IGF-I concentration was associated with a .00135 kg/d increase in ADG (P < .001) and a .0001 kg gain/kg feed increase in feed efficiency (P = .04). These results support the hypothesis that serum IGF-I plays a role in growth and in efficiency of feed utilization in beef cattle.

Animal Feed↗

PubMed2001

Early weaning and postweaning nutritional management affect feedlot performance of angus x simmental heifers and the relationship of 12th rib fat and marbling score to feed efficiency.

Early-weaned Angus x Simmental heifers were used to evaluate the effects of postweaning nutritional management on feedlot performance, carcass merit, and the relationship of intramuscular and subcutaneous fat deposition to the feed efficiency among heifers fed for a high-quality market. Sixteen heifers were weaned at 73+/-5.5 d of age and grazed on endophyte-infected tall fescue for 18 mo before entering the feedlot (early-weaned-P). Eighty heifers from the following year's calf crop were weaned at 71+/-5.5 d of age and allowed either ad libitum access to a 25% concentrate diet (early-weaned-25C) or limit-fed a 90% concentrate diet (early-weaned-90C) to achieve a similar ADG. Following a 119-d growing period, 16 early-weaned-90C and 16 early-weaned-25C calves were paired based on BW and growth rate and individually fed during the finishing period along with the early-weaned-P heifers. Ultrasound measurements of s.c. and i.m. fat were recorded at approximately 60-d intervals throughout the finishing period. Feed efficiency was regressed against s.c. and i.m. fat, and i.m. fat was regressed on s.c. fat. Despite a similar ADG, early-weaned-90C calves gained more efficiently (P < or = 0.05) in the feedlot than early-weaned-25C calves. Heifers finished as yearlings tended (P < or = 0.10) to gain faster but gained less efficiently (P < or = 0.01) than early-weaned-90C heifers finished as calves. The rate of s.c. and i.m. fat deposition was similar between early-weaned-90C and early-weaned-25C heifer calves. The calves were grouped together for comparison to yearlings. Feed efficiency decreased quadratically (P < or = 0.01) as s.c. fat cover increased. The rate at which feed efficiency decreased relative to increasing s.c. fat cover was similar regardless of age at feedlot entry. However, heifers finished as calves gained more efficiently (P < or = 0.01) than yearlings at any given fat thickness. Feed efficiency decreased linearly (P < or = 0.01) as i.m. fat increased among heifers finished as calves. Additionally, heifers finished as calves deposited i.m. fat at a faster rate relative to s.c. fat (P < or = 0.01) than yearlings. These data suggest that heifers finished as calves produce high-quality carcasses with less s.c. fat cover while gaining more efficiently than heifers finished as yearlings.

Adipose Tissue↗

PubMed1984

Phenotypic relationships among early life traits and lifetime ewe production efficiency.

In least-squares analyses of variance, 10 ewe lamb traits were used, singly and in various combinations, to predict lifetime production efficiency. Ewes belonged to eight crossbred groups and were raised on two management systems for either 4 or 5 yr of production. Lifetime production efficiency components were total feed and ewe ownership cost, gross income and net revenue. A ewe lamb's type of birth, actual and adjusted weaning weight (WWt and AWWt), postweaning weight (PWWt) and first year gross income (FGROS) were significantly phenotypically related to one or more components of lifetime production efficiency. While triplets were better than either of the other two birth types, single-born ewes were better than twin-born ewes for lifetime production efficiency. Any of the three ewe lamb weights (AWWt, WWt or PWWt) appeared to be an accurate estimator of lifetime production efficiency. The effect of first year productivity was largely a part-whole relationship with lifetime production because the regression coefficients of subsequent lifetime production efficiency (not including first year production) on first year productivity were near zero. Postweaning average daily gain, ewe age at first estrus and date of first lambing (at approximately 12 mo of age) did not have significant relationships with lifetime production efficiency. When type of birth, date of birth, weaning weight and first year gross income were analyzed simultaneously, weaning weight and FGROS had the greatest effect on lifetime production efficiency. When AWWt and type of birth were considered simultaneously, both had significant relationships with lifetime production efficiency.

Age Factors↗

PubMed1992

Evaluation of various measures of and factors influencing feed efficiency of dairy cattle.

Early part records for milk yield and feed consumption of 2230 first lactation purebred and crossbred dairy cows were analyzed to evaluate various measures of feed efficiency. Corrected milk yield was estimated by adjusting the second 8 wk of milk yield for differences in weight of TDN consumed during wk 9 to 16, percentage of TDN derived from concentrate, and BW.75. Corrected milk yield is an estimate assuming that cows are the same size and consume the same amount of feed. Hence, it represents an expression of feed efficiency. Net feed efficiency, gross efficiency, corrected milk yield, and wk 9 to 16 milk were analyzed simultaneously. Coefficient of determination for net efficiency (.51) and gross efficiency (.72) were lower than that of milk (.82), whereas corrected milk yield had a coefficient of determination similar to that of milk. Hence, the use of ratios to define feed efficiency was less accurate than using corrected milk yield. Effects of genetic groups, stations, season of freshening, year of freshening, and heterosis were similar for gross efficiency and corrected milk yield, but different from those for milk. Therefore, corrected milk yield performed the same function as feed efficiency with higher accuracy.

Animals↗

PubMed2002

[Effect of drought stress on apparent resource utilization efficiency of Quercus mongolica].

To study the effect of drought stress on the physiological characteristics and resource utilization efficiency of Quercus mongolica, a dominant species in the Korean pine broad-leaved forest in Changbai Mountain, a comparative experiment was carried out under three soil moisture gradients as 85%-100% (high water, CK), 65%-85% (Medium water, MW), and 45%-65% (low water, LW) of field water-bolding capacity. The results showed that net photosynthetic rate, stomatal conduction, transpiration rate, water utilization efficiency, apparent CO2 utilization efficiency and apparent light utilization efficiency of the seedlings of Quercus mongolica were all significantly influenced by simulated drought stress. Stomatal conduction, water utilization efficiency and net photosynthetic rate of large tress of Quercus mongolica were affected by the soil drought stress, while transpiration rate, apparent CO2 utilization efficiency, and apparent light utilization efficiency were not influenced. Moderate soil water condition could greatly increase gas exchange and water utilization efficiency. These results indicated that the responses of gas exchange and resource utilization efficiency to various water stresses were different. Quercus mongolica was a species with variable resistance to drought stress, and the resistance would be improved by drought stress, especially moderate water stress.

Carbon Dioxide↗

PubMed1984

Unusually efficient tumor cell lysis by human effectors of antibody-dependent cellular cytotoxicity mediated by monoclonal antibodies.

Concentrations ranging between 0.01 and 10 pg per cell of certain monoclonal antibodies (MAbs) are shown to constitute 4-hr 50% lethal doses for tumor cells mixed with human effectors of antibody-dependent cellular cytotoxicity (ADCC). This efficient and rapid tumor cell lysis is achieved at low effector cell levels (effector:target ratios, less than or equal to 25:1) at which the effectors are nonadherent peripheral blood leukocytes (PBL) enriched by density centrifugation. Comparable MAb-mediated ADCC efficiency has not been reported previously, probably because most MAbs (e.g., 10 of 13 tested in this study) are typically inefficient or completely inactive in mediating ADCC, even at 100-fold greater concentrations. By analyzing the ADCC efficiencies of several MAbs specific for murine cell surface alloantigens, it is shown that murine IgG2a and IgG3 MAbs and a rat IgG2b MAb are very efficient mediators of ADCC. However, ADCC efficiency was found not to correlate strictly with subclass, since 4 of 6 murine IgG2a MAbs tested were completely inactive, even though they all bound the target cells readily. It is shown that the relative differences in ADCC efficiencies are not accounted for directly by antibody affinity for antigen; one MAb was very efficient in ADCC but had demonstrably low antigen affinity, while a second MAb showed no ADCC activity in spite of its high affinity for the same target antigen. These results point to other experimentally testable properties of MAbs and of MAb-antigen complexes which may be critical for efficient ADCC reactions. This study underscores an important immunotherapeutic value which certain MAbs potentially have for mediating tumor cell lysis: in low concentrations (and without toxic drug modification), some MAbs efficiently mediate the lysis of tumors by ADCC, which itself is as effective as other immune lytic processes but which requires no prior immunological education of effector cells.

Adult↗

PubMed1996

Endogenous adenosine increases O2 utilisation efficiency in isoprenaline-stimulated canine myocardium.

OBJECTIVE: We have previously demonstrated that myocardium is capable of down-regulating its O2 requirements and thus avoiding ischaemia when O2 supply is limited. The present study tested the hypothesis that endogenous adenosine produced this protective response when O2 supply was decreased by moderate coronary hypoperfusion or moderate coronary hypoxaemia. METHODS: In anaesthetised dogs, hearts were exposed by left thoracotomy and instrumented for measuring intraventricular pressure and regional myocardial segment length. The left anterior descending coronary artery was isolated, cannulated, and extracorporeally perfused. Coronary O2 supply was moderately reduced by lowering coronary perfusion pressure from 100 to 60 mmHg or by lowering coronary arterial O2 content by 50%. Hearts were treated with intracoronary infusions of adenosine, adenosine deaminase to degrade endogenous adenosine or with erythro-9-(2-hydroxy-3-nonyl)-adenine x HCl (EHNA) to inhibit adenosine degradation by endogenous adenosine deaminase, during beta-adrenergic stimulation with isoprenaline. Cardiac power in the left anterior descending perfusion territory was indexed by the product of heart rate x left ventricular peak systolic pressure x percent systolic segment shortening. O2 utilisation efficiency was taken as the ratio of power index/myocardial O2 consumption. RESULTS: Prior to a reduction in O2 supply, isoprenaline did not alter O2 utilisation efficiency. Intracoronary adenosine increased O2 utilisation efficiency during isoprenaline stimulation by 23% (P < 0.05). EHNA slightly increased O2 utilisation efficiency during isoprenaline stimulation (10%; P < 0.05); adenosine deaminase was without effect. When coronary perfusion pressure was decreased, adenosine deaminase sharply lowered cardiac power and O2 utilisation efficiency during isoprenaline stimulation, whereas EHNA augmented isoprenaline-enhanced power and increased efficiency. During hypoxaemia, adenosine deaminase lowered regional power but not efficiency during isoprenaline infusion; EHNA did not affect power but lowered O2 consumption and increased efficiency. Myocardial lactate extraction and contractile function during isoprenaline stimulation were not attenuated by reduced O2 supply, indicating that myocardial ischaemia did not occur under these conditions. CONCLUSION: Endogenous adenosine increases myocardial O2 utilisation efficiency during beta-adrenergic stimulation, and thus helps avert ischaemia when myocardial O2 supply is reduced.

Adenine↗

PubMed2001

Assessing efficiency in the UK breast screening programme: does size of screening unit make a difference?

The UK breast screening programme (UK BSP) is organised into a large number of individual screening units. Decision makers need to ensure these units are producing efficiently, particularly as the programme is anticipated to expand. Data envelopment analysis (DEA) was applied to investigate: the relative efficiency of screening units; the impact of screening unit size on efficiency; and how individual units could improve. Sixty-four screening units were categorised into 33 large and 31 small. Data were collected using a national survey and routinely collected data. The overall median efficiency score was 91%, 39 units were inefficient. Variation in efficiency scores was wide. Large units had a median efficiency score of 100% and 12 units were inefficient. Smaller units had a median efficiency score of 95% and 19 were inefficient. This difference was not statistically significant (Mann-Whitney, P=0.076). Forty-two percent of large units and 21% of small units were operating at constant returns to scale (mean difference 0.20, 95% CI: 0.15-0.43). Although there is no systematic difference in efficiency by size of screening unit there are inefficiencies in both large and small units and there is scope for many individual units to improve their use of current resources. It will be necessary for decision-makers to examine the practices of individual screening units before considering options for how best to improve their resource use. DEA can help to identify feasible options.

Breast Neoplasms↗

PubMed1995

Efficiency and quality in the public and private sectors in Senegal.

It is often argued that the private sector is more efficient than the public sector in the production of health services, and that government reliance on private provision would help improve the efficiency and equity of public spending in health. A review of the literature, however, shows that there is little evidence to support these statements. A study of government and non-governmental facilities was undertaken in Senegal, taking into account case mix, input prices, and quality of care, to examine relative efficiency in the delivery of health services. The study revealed that private providers are highly heterogeneous, although they tend to offer better quality services. A specific and important group of providers--Catholic health posts--were shown to be significantly more efficient than public and other private facilities in the provision of curative and preventive ambulatory services at high levels of output. Policies to expand the role of the private sector need to take into account variations in types of providers, as well as evidence of both high and low quality among them. In terms of public sector efficiency, findings from the study affirm others that indicate drug policy reform to be one of the most important policy interventions that can simultaneously improve efficiency, quality and effectiveness of care. Relationships that this study identified between quality and efficiency suggest that strategies to improve quality can increase efficiency, raise demand for services, and thereby expand access.

Efficiency, Organizational↗

PubMed2002

A national study of efficiency for dialysis centers: an examination of market competition and facility characteristics for production of multiple dialysis outputs.

OBJECTIVE: To examine market competition and facility characteristics that can be related to technical efficiency in the production of multiple dialysis outputs from the perspective of the industrial organization model. STUDY SETTING: Freestanding dialysis facilities that operated in 1997 submitted cost report fonns to the Health Care Financing Administration (HCFA), and offered all three outputs--outpatient dialysis, dialysis training, and home program dialysis. DATA SOURCES: The Independent Renal Facility Cost Report Data file (IRFCRD) from HCFA was utilized to obtain information on output and input variables and market and facility features for 791 multiple-output facilities. Information regarding population characteristics was obtained from the Area Resources File. STUDY DESIGN: Cross-sectional data for the year 1997 were utilized to obtain facility-specific technical efficiency scores estimated through Data Envelopment Analysis (DEA). A binary variable of efficiency status was then regressed against its market and facility characteristics and control factors in a multivariate logistic regression analysis. PRINCIPAL FINDINGS: The majority of the facilities in the sample are functioning technically inefficiently. Neither the intensity of market competition nor a policy of dialyzer reuse has a significant effect on the facilities' efficiency. Technical efficiency is significantly associated, however, with type of ownership, with the interaction between the market concentration of for-profits and ownership type, and with affiliations with chains of different sizes. Nonprofit and government-owned Facilities are more likely than their for-profit counterparts to become inefficient producers of renal dialysis outputs. On the other hand, that relationship between ownership form and efficiency is reversed as the market concentration of for-profits in a given market increases. Facilities that are members of large chains are more likely to be technically inefficient. CONCLUSIONS: Facilities do not appear to benefit from joint production of a variety of dialysis outputs, which may explain the ongoing tendency toward single-output production. Ownership form does make a positive difference in production efficiency, but only in local markets where competition exists between nonprofit and for-profit facilities. The increasing inefficiency associated with membership in large chains suggests that the growing consolidation in the dialysis industry may not, in fact, be the strategy for attaining more technical efficiency in the production of multiple dialysis outputs.

Ambulatory Care Facilities↗

PubMed2002

An initial investigation of efficiency in endoscopy delivery.

OBJECTIVE: The demand for endoscopic services is increasing rapidly. Of the several potential mechanisms to improve the supply of endoscopic procedures, improved efficiency in the endoscopy unit has received little attention. METHODS: We invited 20 experienced endoscopists to participate in an initial evaluation of endoscopy efficiency, in which they were observed performing procedures in their own unit. Procedure volume per unit time was used as the measure of efficiency. Medical directors and head nurses at each endoscopy unit were interviewed regarding factors they perceived as most important in limiting procedure volume. RESULTS: There was a greater than 3-fold variation in procedure volume score between the least efficient and most efficient endoscopists. The clearest trend predicting procedure volume score was short room turnover time (p = 0.0004). There was a trend toward improved procedure volume among endoscopists using another professional to sedate their patients and using two procedure rooms. The surveys of medical directors and head nurses suggested that multiple factors contribute to limiting procedure volume, but on average each perceived number of available doctors is the least important factor in limiting volume. CONCLUSIONS: Improving the efficiency of some endoscopists appears to be an important potential mechanism to meet the rising demand for endoscopic services. Increasing the resources that provide the opportunity for efficiency may be an important mechanism for increasing the availability of endoscopic services. Specific measures associated with improved efficiency include reduced room turnover times, and possibly use of two rooms per endoscopist and sedation by persons other than the endoscopist.

Efficiency, Organizational↗

PubMed2026

Investigating mechanisms of divergent feed efficiency in dairy cows.

Objectives were to investigate the associations between residual DMI (RFI), calculated as the difference between observed minus predicted DMI, with rumen microbiome, digestion, behavior, and metabolism that might explain the differences in RFI in lactating cows. One hundred 50 genotyped Holstein cows in 3 cohorts were used in this cohort study in which exposure was RFI. Rumen microbiota from 114 cows were sequenced, and a subset of 30 cows was used for hepatic mitochondrial respiration analysis. Cows were ranked by RFI and grouped into quartiles (Q1, most efficient, to Q4, least efficient) according to phenotypic (pQ) or genomic (gQ) quartiles of RFI for data presentation. Statistical models fitted the linear and quadratic RFI as continuous explanatory variables. Increasing efficiency, i.e., from larger to smaller RFI values, whether phenotypic or genomic, were associated with reduced DMI, a 3.0 kg/d difference between Q4 and Q1 according to phenotypic RFI (pRFI) and 1.9 kg/d according to genomic RFI (gRFI) without compromising ECM or body tissue reserves. These differences between Q4 and Q1 of pRFI and gRFI resulted in increased feed conversion ratio by an additional 200 and 100 g of ECM/kg DMI, respectively. Both pRFI and gRFI were associated with FA profiles in milk fat, with decreasing proportions of de novo and mixed FA and increasing proportions of pre-formed FA, particularly monounsaturated FA, as efficiency improved. Additionally, pRFI and gRFI were moderately correlated (r = 0.48) and ranking of cows was consistent across the 2 grouping methods (ρ = 0.44). Reducing RFI was associated with less total rumination time, but greater rumination time per kg of DMI by 2.0 and 1.7 min/kg between the extreme quartiles of pRFI and gRFI, respectively. Phenotypically and genomically more efficient cows were associated with less microbial α diversity based on inverse Simpson index. A total of 57 amplicon sequence variant groups were differentially abundant between Q1 and Q4 classified based on pRFI and gRFI, with Prevotella and Succinivibrionaceae shared between phenotypic and genomic RFI classifications. Increasing phenotypic and genomic efficiency was associated with an increased concentration of ruminal NH3-N. Genomically more efficient cows tended to have reduced ruminal pH (gQ1 to gQ4; 6.42 vs. 6.47 vs. 6.43 vs. 6.53) despite eating less. Decreasing pRFI was associated with reduced microbial N yield whereas, it tended to increase microbial N yield relative to the amount of N intake. Collectively, phenotypic and genomic RFI have a moderate degree of agreement matching the estimated heritability of the trait, and mechanisms underlying improved feed efficiency were linked with differences in ruminal microbiota and fermentation, and with increased rumination per kg of DM rather than total-tract digestibility or hepatic mitochondrial respiration.

dairy cow↗

PubMed2001

Technical efficiency of public clinics in Kwazulu-Natal Province of South Africa.

BACKGROUND: In sub-Saharan Africa (SSA) much of the attention of policy makers, health care managers, health systems researchers and donors is focussed almost solely on mobilising additional resources and not on efficiency in their use. OBJECTIVE(S): To investigate the technical inefficiencies among 155 primary health care clinics in Kwazulu-Natal Province of South Africa; and to draw policy implications. DESIGN: Cross-sectional provincial health clinic survey. SELLING: Kwazulu-Natal Provincial Department of Health Clinics survey, 1996. SUBJECTS: The analysis is based on 155 public clinics. INTERVENTIONS: Non-intervention Data Envelopment Analysis (DEA) study. MAIN OUTCOME MEASURES: Technical and scale efficiency scores. RESULTS: Forty seven (30%) were found to be technically efficient. Among the 108 (70%) technically inefficient facilities, 16% had an efficiency score of 50% or less. The presence of inefficiencies indicates that a clinic has excess inputs or insufficient outputs compared to those clinics on the efficiency frontier. To achieve technical efficiency, Kwazulu-Natal clinics would, in total have to decrease inputs by 417 nurses and 457 general staff. Alternatively, outputs would have to be increased by 115,534 antenatal visits, 1,010 births (deliveries), 179,075 child care visits, 5,702 dental visits, 121,658 family planning visits, 36,032 psychiatric visits, 56,068 sexually transmitted disease visits and 34,270 tuberculosis visits. CONCLUSION: There is need for more detailed studies in a number of the relativdy efficient clinics to determine why they are efficient with a view of documenting attributes of 'best practise' that other clinics can emulate. The potential benefit of replicating this kind of study in other provinces, and indeed, other SSA countries cannot be overemphasised.

Community Health Centers↗

PubMed2005

Transfection efficiency and uptake process of polyplexes in human lung endothelial cells: a comparative study in non-polarized and polarized cells.

BACKGROUND: Following systemic administration, polyplexes must cross the endothelium barrier to deliver genes to the target cells underneath. To design an efficient gene delivery system into lung epithelium, we evaluated capture and transfection efficiencies of DNA complexed with either Jet-PEI (PEI-polyplexes) or histidylated polylysine (His-polyplexes) in human lung microvascular endothelial cells (HLMEC) and tracheal epithelial cells. METHODS: After optimizing growth conditions to obtain a tight HLMEC monolayer, we characterized uptake of polyplexes by flow cytometry and evaluated their transfection efficiency. Polyplexes were formulated as small particles. YOYO-labelled plasmid fluorescence intensity and luciferase activity were used as readouts for uptake and gene expression, respectively. RESULTS: PEI-polyplexes were more efficiently taken up than His-polyplexes by both non-polarized (2-fold) and polarized HLMEC (10-fold). They were mainly internalized by a clathrin-dependent pathway whatever the cell state. In non-polarized cells, His-polyplexes entered also mainly via a clathrin-dependent pathway but with an involvement of cholesterol. The cell polarization decreased this way and a clathrin-independent pathway became predominant. PEI-polyplexes transfected more efficiently HLMEC than His-polyplexes (10(7) vs. 10(5) relative light units (RLU)/mg of proteins) with a more pronounced difference in polarized cells. In contrast, no negative effect of the cell polarization was observed with tracheal epithelial cells in which both polyplexes had comparable efficiency. CONCLUSIONS: We show that the efficiency of polyplex uptake by HLMEC and their internalization mechanism are polymer-dependent. By contrast with His-polyplexes, the HLMEC polarization has little influence on the uptake process and on the transfection efficiency of PEI-polyplexes.

Benzoxazoles↗

PubMed2005

Unique features of a pH-sensitive fusogenic peptide that improves the transfection efficiency of cationic liposomes.

BACKGROUND: One of the critical steps in intracellular gene delivery using cationic liposomes is the endosomal escape of the plasmid/liposome complexes to the cytosol. The addition of GALA, a pH-sensitive fusogenic peptide, is a promising method to accelerate this step in order to enhance the expression of the desired proteins. Detailed studies on the methods of enhancement would broaden the horizon of its application. METHODS: Using representative commercially available cationic liposomes (Lipofectin, Lipofectamine, and Lipofectamine 2000), the effects of GALA on transfection efficiency were studied by luciferase assay and confocal microscopic observations. RESULTS: A concentration-dependent increase in the transfection efficiency was observed for GALA. Addition of 0.1 microM GALA to the plasmid/liposome complex significantly increased the transfection efficiency, especially in the case of Lipofectin, but higher concentration of GALA decreased transfection efficiency. Successful reduction in the liposomal dosage was attained by employing GALA while maintaining a high transfection efficiency. Interestingly, although the transfection efficiency was higher in the presence of GALA, a lower amount of the plasmid DNA was taken up by the cells. Confocal microscopic observations of the rhodamine-labeled plasmid did not show a significant difference in the cellular localization among cells incubated in the presence or absence of GALA, suggesting that a slight increase in GALA-induced release of the plasmid to the cytosol may cause a significant change in the transfection efficiency. CONCLUSION: The unique features of GALA to mediate improved transfection efficiencies were identified.

Animals↗

PubMed2004

Efficient gene targeting in Kluyveromyces lactis.

Integration of a DNA fragment in a host genome requires the action of a double-strand break (DSB) repair mechanism. Homologous recombination (HR) is initiated by binding of Rad52p to DNA ends and results in targeted integration. Binding of the Ku heterodimer (Ku70p/Ku80p) results in random integration via non-homologous end joining (NHEJ). In contrast to Saccharomyces cerevisiae, the budding yeast Kluyveromyces lactis shows variable, but in general low, gene targeting efficiency. To study and to improve gene targeting efficiency, K. lactis has been used as a model. The KlRAD51, KlRAD52 and KlKU80 genes have been isolated and deletion mutants for these genes have been constructed. Efficiency of gene targeting was determined at the KlADE2 locus using targeting constructs with different lengths of homologous flanking sequences. In wild-type K. lactis, the gene targeting efficiency ranged from 0% with 50 to 88% with 600 bp flanks. The Klku80 mutant, however, showed >97% gene targeting efficiency independently of the size of the homologous flanks. These results demonstrate that deletion of the NHEJ mechanism results in a higher gene targeting efficiency. Furthermore, increased gene targeting efficiency was achieved by the transformation of wild-type K. lactis with the KlADE2 deletion construct in the presence of excess small DNA fragments. Using this method, PCR-generated deletion constructs containing only 50 bp of homologous flanking sequences resulted in efficient targeted gene replacement.

Antigens, Nuclear↗

PubMed1992

Myocardial oxygen consumption and mechanical efficiency of a perfused dogfish heart preparation.

Oxygen consumption of an in-pericardium heart preparation from the spiny dogfish (Squalus acanthias) was linearly related to cardiac power output. Basal oxygen consumption, predicted from the regression, was 0.127 microliters.s-1.g ventricle mass-1 and increased by 0.189 microliters.s-1.g ventricle mass-1 per milliwatt of power generated. From the relationship between cardiac power output and mechanical efficiency, mechanical efficiency was predicted to increase with cardiac power output to a maximum of 21%. Mechanical efficiency was measured during volume loading and pressure loading at two power outputs (50% and 72% of maximum power output). At 50% of maximum power output, mechanical efficiency increased significantly by 2.87%, from 11.9 +/- 0.3% to 14.8 +/- 0.5% (n = 7), when flow was halved and output pressure doubled to achieve the same power output. Similarly, at 72% of maximum power output, mechanical efficiency increased from 14.74 +/- 0.92% to 17.61 +/- 0.84% (n = 6) when flow was halved and output pressure doubled to generate the same higher level of power output. The increased mechanical efficiency at higher output pressures is believed to result from cardiac myocytes working within a length range where they are able to generate the most tension during contraction and are most efficient. We speculate that the loss of mechanical efficiency associated with large changes in sarcomere length, when stroke volume is large, is a driving force behind the use of frequency as the principal means of increasing cardiac output as observed in more active fishes, birds and mammals.

Animals↗

PubMed1998

Ventilatory efficiency and exercise tolerance in 101 healthy volunteers.

The ventilatory equivalent for CO2 defines ventilatory efficiency largely independent of metabolism. An impairment of ventilatory efficiency may be caused by an increase in either anatomical or physiological dead space, the latter being the most important mechanism in the hyperpnoea of heart failure, pulmonary embolism, pulmonary hypertension and the former in restrictive lung disease. However, normal values for ventilatory efficiency have not yet been established. We investigated 101 (56 men) healthy volunteers, aged 16-75 years, measuring ventilation and gas exchange at rest (n = 64) and on exercise (modified Naughton protocol, n = 101). Age and sex dependent normal values for ventilatory efficiency at rest defined as the ratio ventilation:carbon dioxide output (VE:VCO2), exercise ventilatory efficiency during exercise, defined as the slope of the linear relationship between ventilation and carbon dioxide output (VE vs VCO2 slope), oxygen uptake at the anaerobic threshold and at maximum (VO2AT, VO2max, respectively) and breathing reserve were established. Ventilatory efficiency at rest was largely independent of age, but was smaller in the men than in the women [VE:VCO2 50.5 (SD 8.8) vs 57.6 (SD 12.6) P < 0.05]. Ventilatory efficiency during exercise declined significantly with age and was smaller in the men than in the women (men: (VE vs VCO2 slope = 0.13 x age + 19.9; women: VE vs VCO2 slope = 0.12 x age + 24.4). The VO2AT and VO2max were 23 (SD 5) and 39 (SD 7) ml O2 x kg x min(-1) in the men and 18 (SD 4) and 32 (SD 7) in the women, respectively, and declined significantly with age. The VO2AT was reached at 58 (SD 9)% VO2max. Breathing reserve at the end of exercise was 41% and was independent of sex and age. It was concluded from this study that ventilatory efficiency as well as peak oxygen uptake are age and sex dependent in adults.

Adolescent↗