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PubMed2003

Enhancement of polyethylene glycol (PEG)-modified cationic liposome-mediated gene deliveries: effects on serum stability and transfection efficiency.

In this study, we modified cationic liposomes either by polyethylene glycol (PEG)-grafting or PEG-adding methods, and compared the physical properties of transfection complexes and transfection efficiency in-vitro and prolonged circulation in-vivo. The PEG-grafted transfection complexes were prepared by mixing plasmid DNA with PEG-grafted cationic liposomes, which were composed of DSPE-PEG 2000 and cationic lipids. The PEG-added transfection complexes were prepared by adding DSPE-PEG 2000 to the mixture of cationic liposomes and plasmid DNA. The particle sizes of the PEG-modified transfection complexes (approximately 200 nm) changed a little over 4 weeks compared with the conventional transfection complexes. In the presence of serum, the transfection efficiency of the conventional transfection complexes was lowered whereas the transfection efficiency of the PEG-modified transfection complexes was maintained. Moreover, the transfection efficiency of the conventional transfection complexes was significantly reduced when they were stored. However, the transfection efficiency was stable for the PEG-modified transfection complexes, even after two weeks of storage. Of the in-vitro transfection efficiencies, there was no difference between PEG-grafted and PEG-added transfection complexes. When the conventional, PEG-grafted, and PEG-added transfection complexes were administered into mice by the tail vein, the PEG-added transfection complexes showed a prolonged circulation of plasmid DNA compared with other transfection complexes. These results suggest that the PEG-added transfection complexes could be a useful non-viral vector because of their simplicity in preparation, enhanced stability and prolonged circulation compared with the conventional transfection complexes.

Cations↗

PubMed1995

The mechanical power output and hydromechanical efficiency of northern pike (Esox lucius) fast-starts

The mechanical power output and hydrodynamic efficiency of northern pike, Esox lucius, during acceleration from rest (fast-start) are calculated from hydrodynamic theory for two kinematic patterns, C-starts (used in escape) and S-starts (used in prey capture). The Weihs model is employed and modified to calculate the mechanical power produced by a fish during a fast-start. A term is included for the power required to accelerate body sections laterally. Lateral deceleration of fish body sections and their associated added mass are expressed as an active process requiring energy expenditure or as a passive process requiring no energy expenditure. In addition, two methods of calculating useful power (the power used to accelerate the virtual mass of the fish, i.e. fish body mass + longitudinal added mass, in the direction of motion), one derived from the Weihs model and the second by summing the changes in kinetic energy of the virtual mass of the fish during a fast-start, are compared and found to give similar estimates of useful power (not significantly different; differences average 22 %). Comparisons of the kinematics and performance of C- and S-starts reveal that C-starts are consistently terminated after two tail flips (stages 1 and 2) whereas S-starts continue for 36 tail flips (stages 36). In addition, acceleration during C-starts is more rapid and velocities are higher (2.32.8 m s-1) than during S-starts (0.81.8 m s-1) over the first 100 ms. However, the peak velocities achieved during S-starts and C-starts are similar over the duration of a fast-start. The superior acceleration rates achieved during the initial stages of a C-start can be explained, in part, by the use of greater maximum angles of attack, higher lateral and perpendicular velocities and larger maximum forces by the caudal fin. Hydrodynamic efficiencies for fast-starts range from 0.16 to 0.39, values that are lower than those observed during either burst-and-coast or steady swimming. Efficiencies are lower for S-starts than for C-starts during the first two tail beats. S-start efficiencies increase with each subsequent tail flip and the maximum efficiencies realised are similar to those achieved during C-starts. Power output during C- and S-starts (449.0 and 394.9 W kg-1 muscle fibre, respectively) approaches the theoretical maximum for vertebrate striated muscle (500 W kg-1). Also, the inferred muscle stress is close to the predicted optimum for maximum power output, at 30 % of the maximum isometric stress recorded for isolated fast muscle fibres. These measurements suggest that fast-start performance is near a physiological limit and is probably constrained by muscle function. The superior acceleration rates achieved by C-starts over S-starts are explained in part by differences in hydrodynamic efficiency, whereas power outputs are similar.

Journal Article↗

PubMed2001

Physical factors affecting the cost and efficiency of sound production in the treefrog Hyla versicolor.

The metabolic cost, energy output and efficiency (i.e. the ratio of energy output to metabolic cost) of sound production were compared among male grey treefrogs (Hyla versicolor) as a function of body size and temperature. The effects of call length (in notes per call) and dominant frequency (in kHz) were also considered. Cost, determined from the amount of oxygen consumed, averaged 12.1 mJ per note and was dependent only upon body mass. Acoustic energy per note, determined from oscillograms of recorded calls, averaged 0.34 mJ and was dependent only upon temperature. Conventional theory suggests that the efficiency of sound production should be a function of the ratio of the linear size of the radiating structures to the wavelength of the sound generated (i.e. efficiency is assumed to be a function of the product of mass(0.33) and frequency), but efficiency in H. versicolor was found to be a function of the product of temperature(2.1) and mass(-1.08). Adjusting for temperature and body mass, the efficiency of sound production in H. versicolor (average 2.4 %) is greater than the efficiency of other frog species for which data are available. Temperature may affect acoustic energy output because trunk muscle contraction speed increases with temperature, which increases the velocity of airflow across the vocal cords.

Animals↗

PubMed2006

Efficiency of synaptic transmission of single-photon events from rod photoreceptor to rod bipolar dendrite.

A rod transmits absorption of a single photon by what appears to be a small reduction in the small number of quanta of neurotransmitter (Q(count)) that it releases within the integration period ( approximately 0.1 s) of a rod bipolar dendrite. Due to the quantal and stochastic nature of release, discrete distributions of Q(count) for darkness versus one isomerization of rhodopsin (R*) overlap. We suggested that release must be regular to narrow these distributions, reduce overlap, reduce the rate of false positives, and increase transmission efficiency (the fraction of R* events that are identified as light). Unsurprisingly, higher quantal release rates (Q(rates)) yield higher efficiencies. Focusing here on the effect of small changes in Q(rate), we find that a slightly higher Q(rate) yields greatly reduced efficiency, due to a necessarily fixed quantal-count threshold. To stabilize efficiency in the face of drift in Q(rate), the dendrite needs to regulate the biochemical realization of its quantal-count threshold with respect to its Q(count). These considerations reveal the mathematical role of calcium-based negative feedback and suggest a helpful role for spontaneous R*. In addition, to stabilize efficiency in the face of drift in degree of regularity, efficiency should be approximately 50%, similar to measurements.

Animals↗

PubMed2006

Efficiency of playback for assessing the occurrence of five bird species in Brazilian Atlantic Forest fragments.

Playback of bird songs is a useful technique for species detection; however, this method is usually not standardized. We tested playback efficiency for five Atlantic Forest birds (White-browed Warbler Basileuterus leucoblepharus, Giant Antshrike Batara cinerea, Swallow-tailed Manakin Chiroxiphia caudata, Whiteshouldered Fire-eye Pyriglena leucoptera and Surucua Trogon Trogon surrucura) for different time of the day, season of the year and species abundance at the Morro Grande Forest Reserve (South-eastern Brazil) and at thirteen forest fragments in a nearby landscape. Vocalizations were broadcasted monthly at sunrise, noon and sunset, during one year. For B. leucoblepharus, C. caudata and T. surrucura, sunrise and noon were more efficient than sunset. Batara cinerea presented higher efficiency from July to October. Playback expanded the favourable period for avifaunal surveys in tropical forest, usually restricted to early morning in the breeding season. The playback was efficient in detecting the presence of all species when the abundance was not too low. But only B. leucoblepharus and T. surrucura showed abundance values significantly related to this efficiency. The present study provided a precise indication of the best daily and seasonal periods and a confidence interval to maximize the efficiency of playback to detect the occurrence of these forest species.

Animals↗

PubMed2002

Low efficiency of the Moloney murine leukemia virus reverse transcriptase during reverse transcription of rare t(8;21) fusion gene transcripts.

The resolving power of RT-PCR is limited by the efficiency of RNA-to-cDNA conversion. Methods to determine this efficiency, using a real-time PCR assay for quantifying AML1-MTG 8 [t(8;21)] fusion gene transcripts, are described. The efficiency is shown to be directly proportional to RNA template levels. The Moloney murine leukemia virus (MMLV) reverse transcriptase enzyme's conversion efficiency was calculated to be approximately 20%. The efficiency was even lower (6%) when target templates were rare (single molecules) in the RT reactions. Levels of nonspecific or background RNA present in the RT reaction reduced the reverse transcriptase's conversion efficiency. This background effect was particularly pronounced when the specific template was present in rare amounts.

Core Binding Factor Alpha 2 Subunit↗

PubMed2005

Improvement of recombination efficiency by mutation of red proteins.

The Red recombination system of the bacteriophage lambda is a useful tool for engineering bacterial artificial chromosomes (BACs) because desired mutations can be made in any part of the DNA, even in large DNAs, independent of the presence of appropriate restriction enzyme sites. Many have tried changing the inducible promoter or decreasing the copy number of Red genes in Escherichia coli to improve the recombination efficiency. Here we describe a novel method for increasing the recombination efficiency of the Red system by mutating the Red proteins. Mutant Red alpha and Red beta independently increased recombination efficiency. We found that the 18-bp 5' untranslated region (UTR) upstream from the ATG initiation codon of Gam protein is important for recombination efficiency. Although low rates of recombination have been observed in systems using high copy number plasmids, when we performed Red recombination using a high copy number plasmid containing 5'-UTR, mutant Red alpha, and mutant Red beta, recombination increased approximately 145-fold. The novel possibility that mutant Red alpha and Red beta can increase recombination efficiency indicates a new direction for improving recombination efficiency of expression systems that use low or high copy number plasmids or a defective prophage integrated into the E. coli chromosome.

5' Untranslated Regions↗

PubMed1996

Fluorescence in situ hybridization method for measuring transfection efficiency.

We describe here the use of fluorescence in situ hybridization (FISH) to measure the transfection efficiency of the transient expression vector pCMVcat in lymphoblasts and fibroblasts. By using a pCMVcat probe, we can visualize the location of the plasmid after transfection and thus determine transfection efficiency. In this report, we show that, for transfection of pCMVcat by the diethylaminoethyl-dextran method, the transfection efficiency was about 15 and 70 times greater in fibroblasts and lymphoblasts, respectively, when measured by the FISH method as compared to the efficiency measured by cotransfection with pCMV beta gal. Based on these results, we conclude that the FISH method is a highly sensitive, specific and direct measure of transfection efficiency of a transient expression vector and that it may be useful for evaluating laboratory assays in which the quantitative aspects of transfection and the effect of plasmid DNA damage on transfection efficiency are important.

Cell Line↗

PubMed1996

Physiological factors associated with efficiency in high intensity exercise.

Information about mechanical efficiency during intense exercise is limited, which is partly due to the difficulties that exist in quantifying anaerobic energy production. Based on human studies examining the isolated quadriceps muscle, the mechanical efficiency during intense dynamic exercise has been estimated to be around 22 to 26%. For cycling, the mechanical efficiency shows a wider range (14 to 34%) which, to a large extent, can be attributed to the uncertainties regarding the mass of the muscles used and whether muscle biopsy material is representative for the muscles involved in the exercise. Data from studies of the isolated quadriceps muscle suggest that mechanical efficiency increases as intense exercise is continued and that mechanical efficiency is greater when high intensity exercise is repeated, even with a rest period of 1 hour between exercise bouts. It is unclear whether a period of training can affect mechanical efficiency during intense exercise.

Energy Metabolism↗

PubMed2000

Effects of repetitive brief ischemia on contractile efficiency and oxygen cost of contractility in dog heart.

It is unclear whether preceding repetitive brief ischemia causes any improvement in the energy efficiency of intracellular calcium cycling or crossbridge cycling that may lead to cardioprotection after subsequent sustained ischemia/reperfusion, a phenomenon called ischemic preconditioning. To address this issue, left ventricular (LV) contractility (E(max)) and the relation between myocardial oxygen consumption (VO(2)) and pressure-volume area (PVA, a measure of LV total mechanical energy) were assessed before (Control) and 20 min (Rep-20) and 60 min (Rep-60) after repetitive brief ischemia in 11 isolated, blood-perfused dog hearts. At Rep-20, E(max) and PVA-independent VO(2) (nonmechanical energy expenditure) decreased by 23.0 +/- 19.5 and 13.9 +/- 18.0%, respectively (both p < 0.05). However, at Rep-60, both E(max) and PVA-independent VO(2) recovered to their respective control levels. The oxygen cost of contractility (the slope of the PVA-independent VO(2)-E(max) relation during CaCl(2) loading) remained constant (Control 0.0019 +/- 0.0009 vs. Rep-60 0.0018 +/- 0.0013 ml O(2) x ml x mmHg(-1) x beat(-1) x 100 g(-2), ns), suggesting unchanged efficiency in Ca(2+) cycling. Also, the contractile efficiency (the reciprocal of the slope of the VO(2)-PVA relation, reflecting the efficiency of crossbridge cycling) was the same between the Control and Rep-60 (53.7 +/- 16.7 vs. 55.4 +/- 14.4%, ns). Basal metabolism VO(2) during KCl arrest was also similar to that in the normal heart. Nonmechanical energy expenditure was reduced in proportion to the decrease in LV contractility after repetitive brief ischemia, while both the contractile efficiency and oxygen cost of contractility remained constant. These results indicate that the heart, after repetitive brief ischemia but before sustained ischemia, has normal efficiencies of crossbridge cycling and Ca(2+) cycling despite the transiently reduced contractility.

Animals↗

PubMed2004

Masticatory efficiency before and after surgery in oral cancer patients: comparative study of glossectomy, marginal mandibulectomy and segmental mandibulectomy.

This study evaluated the effect of oral cancer surgery on masticatory efficiency. Masticatory efficiency was measured using the ATP absorption method. Eating ability was measured using a questionnaire. Two groups were employed as controls: The "normal occlusion group" consisted of subjects who had a complete set of natural maxillary teeth opposed to mandibular teeth, and the "unilateral occlusion group" consisted of subjects who had lost their molar and premolar teeth on one side of the mandible as a result of caries or periodontal diseases. Three treatment groups, each of 6 patients, were studied: a glossectomy group, a marginal mandibulectomy group and a segmental mandibulectomy group. There were no differences in masticatory efficiency between two control groups. Masticatory efficiencies of the three oral cancer treatment groups were lower than in the unilateral occlusion group, even 12 months after surgery. Masticatory efficiency of the glossectomy group was significantly higher 12 months after surgery compared with pre-surgery. Masticatory and eating abilities of the marginal mandibulectomy group and the segmental mandibulectomy were reduced at 3 and 6 months after surgery. The masticatory efficiency 12 months after surgery was higher in the marginal mandibulectomy group than the segmental mandibulectomy group, although the difference was not statistically significant. The self assessed eating ability 12 months after surgery was significantly higher in the marginal mandibulectomy group than the segmental mandibulectomy group. These results suggest that discontinuation of the mandible may lead patients to eat only foods that do not require a substantial amount of chewing. Hence, the quality of life of patients in the marginal mandibulectomy group was considered to be better than that in the segmental mandibulectomy group.

Adenosine Triphosphate↗

PubMed1996

Efficient gene transfer to dispersed human pancreatic islet cells in vitro using adenovirus-polylysine/DNA complexes or polycationic liposomes.

The establishment of gene delivery systems that result in efficient transfection of the pancreatic beta-cells may generate an important tool for the study of IDDM and may also represent one critical step toward a clinical application of gene transfer for the prevention or early treatment of the disease. Using the reporter gene vectors pCAT and pCMV beta-gal, we have investigated the efficiency of transfection mediated by calcium phosphate precipitation, the monocationic liposome Lipofectin, the polycationic liposome Lipofectamine, and adenovirus-polylysine (AdpL) DNA complexes in human, mouse, rat, and fetal porcine islet cells. In all species studied, calcium phosphate-mediated transfection resulted in lower chloramphenicol acetyl transferase (CAT) activities than the other methods. Intact human, mouse, and rat islets were poorly transfected by Lipofectin, Lipofectamine, and AdpL. When dispersed by trypsin treatment, however, human, mouse, rat, and fetal pig islect cells were efficiently transfected by Lipofectamine. Moreover, transfection of dispersed human and mouse islet cells using AdpL, also resulted in high CAT activities. The percentage of cells staining positively for beta-galactosidase after transfection with Lipofectamine was 49% for mouse, 56% for rat, and 57% for dispersed human islet cells. Transfection of human islet cells using AdpL, however, yielded 70% beta-gal-positive cells. Fluorescence-activated cell sorting-purified rat islet alpha- and beta-cells were transfected with similar efficiency using Lipofectamine. CAT expression in human islet cells transfected with either Lipofectamine or AdpL reached a peak value after 5-7 days, followed by a gradual decline. It is concluded that transfection with AdpL or Lipofectamine are both efficient means to achieve transient expression of gene constructs in human and mouse islet cells, while for rat and fetal porcine islet cells, Lipofectamine is the most efficient of the agents investigated in this study.

Analysis of Variance↗

PubMed2004

A possible link between skeletal muscle mitochondrial efficiency and age-induced insulin resistance.

The transition from young to adult age is associated with decreased insulin sensitivity. To investigate whether changes in skeletal muscle mitochondrial function could be involved in the development of insulin resistance, we measured the oxidative capacity and energetic efficiency of subsarcolemmal and intermyofibrillar mitochondria isolated from the skeletal muscle of 60- and 180-day-old rats. Mitochondrial efficiency was tested by measuring the degree of thermodynamic coupling and optimal thermodynamic efficiency, as well as mitochondrial proton leak, which was determined in both the absence (basal) and the presence (fatty acid induced) of palmitate. Serum glucose, insulin, and HOMA index were also measured. The results show that in adult rats, concomitant with increased HOMA index, skeletal muscle mitochondria display higher respiratory capacity and energy efficiency. In fact, thermodynamic coupling and optimal thermodynamic efficiency significantly increased and fatty acid-induced proton leak was significantly lower in the skeletal muscle mitochondria from adult than in younger rats. A deleterious consequence of increased mitochondrial efficiency would be a reduced utilization of energy substrates, especially fatty acids, leading to intracellular triglyceride accumulation and lipotoxicity, thus contributing to the onset of skeletal muscle insulin resistance.

Adult↗

PubMed1993

Economical and biological efficiencies of beef cattle differing in level of milk production.

Economical and biological efficiencies of beef production to weaning and to slaughter were estimated in three groups, different in milk available (low, medium, and high) to the calves but with the same potential for growth. Data from different breed groups of cows (low [L] = Hereford x Angus, medium [M] = Red Poll x Angus, and high [H] = Milking Shorthorn x Angus) were used. Economical efficiency was the ratio of income to expenses and biological efficiency was the ratio of calf weight to total feed energy required. Income was derived from cull cows and calves at weaning or carcasses of calves fed to slaughter. Feed and non-feed expenses for the cowherd and for calves to weaning or to slaughter were included in economical efficiency. Efficiencies were estimated assuming observed reproductive rates and energy requirements for maintenance, as well as for equal reproductive rates and equal energy requirements for maintenance in the M and H groups. With the observed reproductive rates and maintenance requirements, biological efficiencies to weaning and to slaughter were 28.1, 27.2, and 27.5 g of weaning weight and 22.0, 20.4, and 20.3 g of carcass weight per megacalorie of ME for L, M, and H, respectively; the corresponding values using equal reproduction and equal maintenance in M and H were 28.3, 27.2, and 27.4 g of weaning weight and 22.1, 20.5, and 20.5 g of carcass weight per megacalorie of ME.(ABSTRACT TRUNCATED AT 250 WORDS)

Agriculture↗

PubMed1999

Direct and correlated responses to selection for efficiency of lean gain in mice.

Improvement in feed efficiency when selection is based on gain:feed ratio has often been accompanied by a reduction in feed intake. The following four criteria were used in mass selection for improved lean gain efficiency in mice with an objective of evaluating changes in lean gain and intake: 1) gain deviation, animals selected had the greatest gain in fat-free mass (FFM) after adjustment to a constant intake; 2) intake deviation, mice selected had the least feed intake after adjustment to a constant gain in FFM; 3) intrinsic efficiency, similar to the second criterion except that adjustment was also made for average weight maintained during the period; and 4) a positive control that used the ratio of gain in FFM: feed intake as the selection criterion. A fifth line, in which a male and a female were selected at random from each litter, served as a negative control. Experimental animals were outbred mice of the CF1 strain. Two replicates of the five lines were included in the study. Twelve males and females were pair-mated within each line-replicate combination each generation. Feed disappearance was measured from 25 to 42 d. Mice were scanned to obtain an electrical conductivity measurement for prediction of FFM. After six generations of selection, realized heritabilities for gain:feed, gain deviation, intake deviation, and intrinsic efficiency were .00 +/- .04, .04 +/- .29, .35 +/- .08, and .28 +/- .06, respectively. There were no differences among lines for gain:feed ratio. The correlated response in feed intake reduction was significant in the intake deviation and intrinsic efficiency lines (-.17 +/- .05 and -.21 +/- .04 g x d(-1) x generation(-1), respectively). The realized genetic correlations between the ratio and gain deviation, intake deviation, and intrinsic efficiency were .83 +/- .15, .01 +/- .04, and .21 +/- .12, respectively. Litter size was depressed in all selected lines.

Animals↗

PubMed2004

Preweaning efficiency for mature cows of breed crosses from tropically adapted Bos indicus and Bos taurus and unadapted Bos taurus breeds.

Production data were collected on mature cows produced by mating Angus and Hereford (pooled AH), Brahman (Bh) and Boran (Br), and Tuli, a tropically adapted Bos taurus, sires by AI or natural service to Angus and Hereford cows. These cows were mated to Charolais bulls for the purpose of this study. Within each sire breed of cow, cows were assigned randomly to one of three feeding rates, 49 or 76 g of DMI/ BW0.75 or ad libitum (10 to 12 cows/feeding rate group), with weekly individual animal feed consumption recorded. Lactation yields were recorded via the weigh-suckle-weigh protocol at approximately 14, 28, 56, 84, 112, 140, 168, and 196 d postpartum for each cow/calf pair. Means for milk yield at peak lactation, total milk yields, calf birth weight, age-adjusted weaning weights, preweaning daily gain, and feed efficiency were estimated. Peak yield (kg/d) for Bh (10.3 +/- 0.36) was greater (P < 0.05) than for Tuli (9.0 +/- 0.31). Total yield (kg, 212 d) for Bh (1802 +/- 68) was greater (P < 0.05) than for Tuli (1532 +/- 59). Birth weight of AH (44 +/- 0.9) was heavier than for Bh and Br (P < 0.05). Preweaning daily calf gain (g/d) and adjusted weaning weight (kg) of Bh (813 +/- 28, 212 +/- 6.1) and Br (766 +/- 24, 202 +/- 5.1) differed (P < 0.05) from AH (589 +/- 24, 169 +/- 5.2) and Tuli (634 +/- 24, 176 +/- 5.3). Efficiency estimates (grams of adjusted weaning weight/kilograms DMI of the cow) for Bh (88 +/- 2.5) and Br (85 +/- 2.1) exceeded (P < 0.05) those for Tuli (74 +/- 2.1) and AH (73 +/- 2.1). Bos indicus breed crosses exhibited greater peak and total yield, lower birth weight, greater daily gain and adjusted weaning weight, and higher feed efficiency than did Bos taurus breed crosses (P < 0.05). Total yield, daily gain, adjusted weaning weight, and feed efficiency were higher (P < 0.05) for cows sired by bulls from tropically adapted breeds, and the peak yield was less (P < 0.10). Tuli exhibited lower total yield and birth weight than did Angus/Hereford (P < 0.05). The efficiency of crossbred Tuli cows did not differ from Angus/Hereford F1 females, but neither equaled the efficiency of crossbred cows produced using Bos indicus breeds.

Adaptation, Physiological↗

PubMed1980

Estimates of partial efficiency of young beef bulls.

Gain, feed consumption and feed efficiency records of 1,409 bulls that were individully fed at central test stations were analyzed. Feed for maintenance and feed for gain were estimated and used to study partial and gross efficiency and relative feed intake. Among the eight breed groups represented there was a range of 3.4% in the breed means for partial efficiency and of 1.6% in the means for gross efficiency. Relative feed consumption ranged from 2.82 to 3.10 times maintenance among the eight breed groups. Effects associated with location, year, breed and the interactions among these effects were significant for traits related to partial efficiency. If the bulls presented to these central tests are representative of their respective breeds, these results emphasize the importance of making comparisons within tests and finding more efficient cattle within the breed of choice.

Animal Feed↗

PubMed2002

Stimulatory and inhibitory effects of protein amino acids on growth rate and efficiency of mixed ruminal bacteria.

Mixed ruminal bacteria were incubated in vitro with glucose, xylose, cellobiose, and various protein amino acids replaced isonitrogenously with 25% (i.e., 25 mg of N/L) of ammonia-N, to determine the growth rate and the amount of sugar consumed in the exponential growth phase. The growth rate and efficiency (grams of bacteria per gram of sugars) increased by 46 and 15%, respectively, when a mixture of 20 amino acids was added. On the other hand, neither growth rate nor efficiency increased when any one of these amino acids was added singly, except for Glu and Gln, each of which produced significant but small improvements. The stimulatory effect of the combined amino acids on bacterial growth declined when each of Leu, Trp, Tyr, Glu, Met, Phe, and Val was removed from the original group of 20. When a mixture of only these seven amino acids was used as a supplement, their stimulatory effects on growth rate and efficiency were only 21 and 25%, respectively, of the effects that the mixture of 20 amino acids showed. The effects increased to 76 and 72% on growth rate and efficiency, respectively, when Gly, Cys, and His were supplied in addition to the seven amino acids. The growth rate and efficiency of the ruminal bacteria were inhibited by an addition of each of Ile, Thr, Cys, Phe, Leu, Lys, or Val to ammonia-N, and the effects of the first five of these amino acids were highly significant. Isoleucine, threonine, and phenylalanine were each inhibitory even at a low concentration (1 mg of NL), while cysteine and leucine showed inhibitory effects at higher concentrations (more than 10 mg of N/L). A higher growth rate of the ruminal bacteria when supplemented with amino acid mixtures was accompanied with a higher growth efficiency, which was attributable to a relatively smaller proportion of energy expended on maintenance according to the Pirt derivation.

Amino Acids↗