Immp2l Enhances the Structure and Function of Mitochondrial Gpd2 Dehydrogenase.

'Inner mitochondrial membrane peptidase 2 like' (IMMP2L) is a nuclear-encoded mitochondrial peptidase that has been conserved through evolutionary history, as has its target enzyme, 'mitochondrial glycerol phosphate dehydrogenase 2' (GPD2). IMMP2L is known to cleave the mitochondrial transit peptide from GPD2 and another nuclear-encoded mitochondrial respiratory-related protein, cytochrome C1 (CYC1). However, it is not known whether IMMP2L peptidase activates or alters the activity or respiratory-related functions of GPD2 or CYC1. Previous investigations found compelling evidence of behavioural change in the Immp2lKD-/- KO mouse, and in this study, EchoMRI analysis found that the organs of the Immp2lKD-/- KO mouse were smaller and that the KO mouse had significantly less lean mass and overall body weight compared with wildtype littermates (p < 0.05). Moreover, all organs analysed from the Immp2lKD-/- KO had lower relative levels of mitochondrial reactive oxygen species (mitoROS). The kidneys of the Immp2lKD-/- KO mouse displayed the greatest decrease in mitoROS levels that were over 50% less compared with wildtype litter mates. Mitochondrial respiration was also lowest in the kidney of the Immp2lKD-/- KO mouse compared with other tissues when using succinate as the respiratory substrate, whereas respiration was similar to the wildtype when glutamate was used as the substrate. When glycerol-3-phosphate (G3P) was used as the substrate for Gpd2, we observed ~20% and ~7% respective decreases in respiration in female and male Immp2lKD-/- KO mice over time. Together, these findings indicate that the respiratory-related functions of mGpd2 and Cyc1 have been compromised to different degrees in different tissues and genders of the Immp2lKD-/- KO mouse. Structural analyses using AlphaFold2-Multimer further predicted that the interaction between Cyc1 and mitochondrial-encoded cytochrome b (Cyb) in Complex III had been altered, as had the homodimeric structure of the mGpd2 enzyme within the inner mitochondrial membrane of the Immp2lKD-/- KO mouse. mGpd2 functions as an integral component of the glycerol phosphate shuttle (GPS), which positively regulates both mitochondrial respiration and glycolysis. Interestingly, we found that nonmitochondrial respiration (NMR) was also dramatically lowered in the Immp2lKD-/- KO mouse. Primary mouse embryonic fibroblast (MEF) cell lines derived from the Immp2lKD-/- KO mouse displayed a ~27% decrease in total respiration, comprising a ~50% decrease in NMR and a ~12% decrease in total mitochondrial respiration, where the latter was consistent with the cumulative decreases in substrate-specific mediated mitochondrial respiration reported here. This study is the first to report the role of Immp2l in enhancing Gpd2 structure and function, mitochondrial respiration, nonmitochondrial respiration, organ size and homeostasis.

Metabolic scaling: individual versus intraspecific scaling of Nile tilapia (Oreochromis niloticus).

We examined intraspecific scaling of the resting metabolic rate (RMR) of Nile tilapia (Oreochromis niloticus) under different culture conditions and further explored the allometric relationships between organ mass (heart, liver, brain, gills, viscera, and red muscles) and blood parameters (erythrocyte size and red blood cell counts) and body mass. Oreochromis niloticus were bred in individual and group cultures. The scaling exponent of the RMR in the individual cultures was b = 0.620-0.821 (n = 30) and that in the group culture was b = 0.770 [natural logarithm (ln) RMR = 0.770 ln M - 1.107 (n = 76)]. The results of the two experimental methods were similar and were not significantly different from 0.75 (3/4), as predicted by the metabolic theory of ecology. The active and inactive organs were scaled with body mass by an exponent of 0.940 and 1.012, respectively. There was no significant relationship between the blood parameters and body mass. These results suggest that the differences in the culture methods may not have affected the allometric scaling of O. niloticus metabolism. The proportion of active and inactive organs contributed to allometric changes in the metabolic rate with body mass. Red blood cells in fish are not generally representative, and cell size can only partially explain the allometric scaling of metabolism.

Study on the laboratory historical control values of biological indicators in SD rats with 28-day repeated dose oral toxicity tests / 中国职业医学

OBJECTIVE: To establish the laboratory historical control values for biological indicators in SD rats with 28-day repeated dose oral toxicity tests. METHODS: The body mass, blood routine indexes, serum biochemical indexes, organ mass and organ coefficient of 10 batches of specific pathogen free SD rats in the control group and the control additional group were collected for 28-day repeated dose oral toxicity tests, and the historical control values was established. RESULTS: The body mass of both male and female SD rats increased with the increasing age(all P<0.01). The body mass of male rats was higher than that of female rats each week(all P<0.01). The body mass, blood routine and serum biochemical indexes, organ mass and organ coefficient of SD rats were affected by the age and gender of rats to varying degrees. The effects of age and gender on organ mass and organ coefficient were not consistent. The laboratory historical control values of body mass, blood routine indexes, serum biochemical indexes, organ mass and organ coefficient of SD rats were established according to the age measured in weeks and the gender of rats. CONCLUSION: The laboratory control values of biological indicators of SD rats should be established according to different weekly age and the gender of rats. Organ coefficient is more suitable as an observation index for toxicological safety evaluation compared with organ mass.

Scaling of organ masses in mammals and birds: phylogenetic signal and implications for metabolic rate scaling.

The persistent enigma of why the whole-body metabolic rate increases hypoallometrically with body mass should be solved on both the ultimate and proximate levels. The proximate mechanism may involve hyperallometric scaling of metabolically inert tissue/organ masses, hypoallometric scaling of metabolically expensive organ masses, a decrease in mass-specific metabolic rates of organs or a combination of these three factors. Although there are literature data on the tissue/organ masses scaling, they do not consider phylogenetic information. Here, we analyse the scaling of tissue/organ masses in a sample of 100 mammalian and 22 bird species with a phylogenetically informed method (PGLS) to address two questions: the role of phylogenetic differences in organ/tissue size scaling and the potential role of organ/tissue mass scaling in interspecific metabolic rate scaling. Strong phylogenetic signal was found for the brain, kidney, spleen and stomach mass in mammals but only for the brain and leg muscle in birds. Metabolically relatively inert adipose tissue scales isometrically in both groups. The masses of energetically expensive visceral organs scale hypoallometrically in mammals, with the exception of lungs, with the lowest exponent for the brain. In contrast, only brain mass scales hypoallometrically in birds, whereas other tissues and organs scale isometrically or almost isometrically. Considering that the whole-body metabolic rate scales more steeply in mammals than in birds, the mass-specific metabolic rate of visceral organs must decrease with body mass much faster in birds than in mammals. In general, studying whole-body metabolic rate is not adequate for explaining its scaling, and measuring metabolic rates of organs, together with their contribution to body mass, is urgently required.

Modest Regulation of Digestive Performance Is Maintained through Early Ontogeny for the American Alligator, Alligator mississippiensis.

The American alligator, Alligator mississippiensis, is an opportunistic carnivore that experiences an ontogenetic shift in food and feeding habits with an increase in body size. Alligators frequently feed on invertebrates and small fish as neonates and transition to feeding less frequently on larger vertebrates as they grow. We hypothesized that alligators experience an ontogenetic shift in the regulation of intestinal performance-modest regulation with frequent feeding early in life and wider regulation with less frequent feeding as they increase in body size. We tested this hypothesis by comparing postprandial responses in metabolic rate, organ masses, intestinal histology, digestive hydrolase activities, and intestinal nutrient uptake rates among neonate, juvenile, and subadult alligators. With feeding, alligators of all three age classes experienced a rapid increase in metabolic rate that peaked within 2 d and thereafter declined more slowly to prefeeding rates. Specific dynamic action increased with body mass and was equivalent to 32% of meal energy. For each age class, the majority of organs did not change in wet and dry mass with feeding. For subadult alligators, luminal gut pH varied regionally due to the acidic stomach, which continued to remain acidic with fasting. With feeding, epithelial enterocytes are remodeled from a pseudostratified to a stratified architecture and become infiltrated with lipid droplets. Feeding did not generate any significant change in the thickness of intestinal tissues, though it did induce an increase in enterocyte width and volume for subadults. For each age class, feeding generally did not result in significant changes in pancreatic trypsin, intestinal aminopeptidase, and intestinal nutrient uptake activities and capacities. Mass-specific nutrient uptake rates varied among age classes due to the higher rates exhibited by neonates. Among age classes, intestinal uptake capacities scaled allometrically (mass exponents <1) with body mass. Across these three age classes, the modest regulation of digestive performance with feeding and fasting for alligators appears to be ontogenetically conserved.

Physiological and Biochemical Thermoregulatory Responses in Male Chinese Hwameis to Seasonal Acclimatization: Phenotypic Flexibility in a Small Passerine.

Many small birds living in regions with seasonal fluctuations and ambient temperatures typically respond to cold by increasing metabolic thermogenesis, internal organ mass and the oxidative capacity of certain tissues. In this study, we investigated seasonal adjustments in body mass, resting metabolic rate (RMR), evaporative water loss (EWL), the mass of selected internal organs, and two indicators of cellular aerobic respiration (mitochondrial state-4 respiration and cytochrome c oxidase activity) in Chinese hwamei (Garrulax canorus) that had been captured in summer or winter from Wenzhou, China. RMR and EWL were higher in winter than in summer. State-4 respiration in the heart, liver, kidneys and pectoral muscle, as well as cytochrome c oxidase activity in the liver, kidneys and pectoral muscle were also higher in winter than summer. In addition, there was a positive correlation between RMR and EWL, and between RMR and indicators of cellular metabolic activity in the heart, liver, kidneys and pectoral muscle. This phenotypic flexibility in physiological and biochemical thermoregulatory responses may be important to the hwamei's ability to survive the unpredictable, periodic, cold temperatures commonly experienced in Wenzhou in winter.

Scaling of major organs in hatchling female American alligators (Alligator mississippiensis).

Allometric equations represent relationships between morphological/physiological traits and body mass Y = aMb , where Y is the trait, a is elevation, b is the exponent describing the shape of the line, and M is body mass. We measured visceral organ masses in hatchling alligators (Alligator mississippiensis) from five clutches from approximately 45 to 500 g wet body mass. The interaction between initial egg mass and clutch identity was significant for initial hatchling mass, but only egg mass, not clutch, had a significant effect on initial snout-vent and head length. Kidney and liver mass showed biphasic scaling with body mass, as determined by "breakpoint" analyses, with the breakpoint at 120 g wet body mass. Kidney and liver wet mass showed slopes b > 1.0 as animals increased approximately 45-120 g, with significantly lower b approximately 0.8-0.9 for alligators 120-500 g. Within kidney and liver mass, below and above the breakpoint, organ mass slopes tended to be similar across clutches. Lung and heart wet mass did not show biphasic scaling, with b approximately 0.8-0.9. Within lung and heart mass, clutches had statistically identical slopes. Combined clutch data for wet mass showed distinct regressions with b > 1.4 for approximately 45-120 g alligators' kidney and liver mass, compared with approximately 120-500 g alligators' kidney, liver, lung, and heart mass b < 1.0. Alligators show rapid kidney and liver growth following hatching, with higher rates than lung or heart tissue. Clutch, egg mass, and hatchling size influence organ size, and each factor should be accounted for in future studies exploring reptile morphology and physiology to assess environmental versus clutch contributions.

Physiological Responses to Fasting and Estivation for the Three-Toed Amphiuma (Amphiuma tridactylum).

Species of Amphiuma enter a state of subterranean estivation with the drying of their aquatic habitat. Characteristic of amphibian fasting and estivation is an initial depression of metabolism and tissue mass and function with fasting, followed by a more pronounced adaptive decrease in metabolism and tissue function with estivation. We hypothesized that Amphiuma likewise experiences a two-stage set of responses to estivation. Therefore, we examined the physiological responses of the three-toed amphiuma (Amphiuma tridactylum) to fasting and estivation treatments. Recently fed A. tridactylum served as controls for fasting treatments of 1, 3, and 6 mo (in water) and estivation treatments of 3 and 6 mo (buried in dried substrate). After a 1-mo fast, A. tridactylum experienced no further depression of metabolic rate following 3 or 6 mo of fasting or estivation. For all fasting and estivation trials, A. tridactylum maintained blood chemistry homeostasis, with the exception of an increase in blood urea following 6 mo of estivation. Compared with fed controls, the mass of most organs did not vary even after 6 mo of fasting and estivation. Only the small intestine (decreasing) and the full gall bladder (increasing) experienced significant changes in mass with fasting or estivation. The fasting decrease in small intestinal mass was in part due to enterocyte atrophy, which resulted in a decrease in mucosa/submucosa thickness. In contrast to many estivating anurans and the ecologically convergent sirens, A. tridactylum does not surround itself in a cocoon of dried skin or mucus during estivation. The thickness and architecture of their skin remains unchanged even after 6 mo of estivation. Following months of fasting or estivation, individuals still maintain gastric acid production, pancreatic enzyme activity, and intestinal enzyme and transporter activities. Contrary to our hypothesis that A. tridactylum experiences two stages of metabolic depression and tissue downregulation, first with fasting and second with estivation, we observed a relatively modest single-stage response to both. Rather than becoming dormant and engaging in mechanisms to depress metabolism and tissue performance with estivation, A. tridactylum employs an alternative strategy of remaining alert and possibly eating to survive extended periods when their aquatic habitats become dry.

The effects of neonicotinoid exposure on embryonic development and organ mass in northern bobwhite quail (Colinus virginianus).

Since their emergence in the early 1990s, neonicotinoid use has increased exponentially to make them the world's most prevalent insecticides. Although there has been considerable research concerning the lethality of neonicotinoids, their sub-lethal and developmental effects are still being explored, especially with regard to non-mammalian species. The goal of this research was to investigate the effects of the neonicotinoid imidacloprid on the morphological and physiological development of northern bobwhite quail (Colinus virginianus). Bobwhite eggs (n=390) were injected with imidacloprid concentrations of 0 (sham), 10, 50, 100, and 150mg/kg of egg mass, which was administered at day 0 (pre-incubation), 3, 6, 9, or 12 of growth. Embryos were dissected, weighed, staged, and examined for any overt structural deformities after 19days of incubation. The mass of the embryonic heart, liver, lungs and kidneys was also recorded. The majority of treatments produced no discernible differences in embryo morphology; however, in some instances, embryos were subject to increased frequency of anatomical deformity and altered organ masses. Some impacts were more pronounced in specific dosing periods, implying that there may be critical windows of development when embryos are more susceptible to neonicotinoid exposure. This investigation suggests that imidacloprid has the potential to impact bobwhite quail embryonic development and chick survival.

Changes in skeletal muscle and organ size after a weight-loss intervention in overweight and obese type 2 diabetic patients.

BACKGROUND: The effect of a weight-loss intervention on the masses of lean tissues and organs in humans is not well known. OBJECTIVE: We studied the effects of a diet and exercise weight-loss intervention on skeletal muscle (SM) mass and selected organs over 2 y using MRI in overweight adults with type 2 diabetes. DESIGN: Participants were 53 women and 39 men [mean ± SD: age 58 ± 7 y; body mass index (BMI; in kg/m2) 32 ± 3] enrolled in the Look AHEAD (Action for Health in Diabetes) trial and randomly assigned to an intensive lifestyle intervention (ILI) or diabetes support and education (DSE) on whom 2 y of data were collected. MRI-derived measurements of SM, heart, liver, kidney, spleen, and pancreas were acquired. RESULTS: Adjusted for baseline weight, height, age, sex, and ethnicity, the ILI group weighed (mean ± SE) 6.6 ± 0.7 kg less after 1 y and 5.2 ± 0.7 kg less after 2 y, whereas the DSE group did not change significantly (-0.4 ± 0.6 and -1.0 ± 0.7 kg after 1 and 2 y, respectively; P-interaction < 0.001). Total SM decreased in both groups during year 1 (-1.4 ± 0.2 kg; P < 0.001) with appendicular SM regained during year 2. Liver and spleen masses decreased in the ILI group (-0.12 ± 0.02 and -0.006 ± 0.003 kg, respectively) but were unchanged in the DSE group (0.00 ± 0.02 and 0.004 ± 0.003 kg, respectively). Kidney mass decreased by 0.013 ± 0.003 kg (P < 0.001) over 2 y in both groups. CONCLUSIONS: Decreases in liver (in Caucasians but not African Americans) and spleen were detected after a 6.2-kg weight reduction compared with a control group. SM and kidney mass decreased in both groups. Appendicular SM was regained during the second year whereas trunk SM was not. No evidence of a disproportionate loss of high-metabolic rate organs (heart, liver, kidney, spleen) compared with SM was found.

Short photoperiod increases energy intake, metabolic thermogenesis and organ mass in silky starlings Sturnus sericeus.

Environmental cues play important roles in the regulation of an animal's physiology and behavior. One such cue, photoperiod, plays an important role in the seasonal acclimatization of birds. It has been demonstrated that an animal's body mass, basal metabolic rate (BMR), and energy intake, are all affected by photoperiod. The present study was designed to examine photoperiod induced changes in the body mass, metabolism and metabolic organs of the silky starling, Sturnus sericeus. Captive silky starlings increased their body mass and BMR during four weeks of acclimation to a short photoperiod. Birds acclimated to a short photoperiod also increased the mass of certain organs (liver, gizzard and small intestine), and both gross energy intake (GEI) and digestible energy intake (DEI), relative to those acclimated to a long photoperiod. Furthermore, BMR was positively correlated with body mass, liver mass, GEI and DEI. These results suggest that silky starlings increase metabolic thermogenesis when exposed to a short photoperiod by increasing their body and metabolic organ mass, and their GEI and DEI. These findings support the hypothesis that bird species from temperate climates typically display high phenotypic flexibility in thermogenic capacity.

Effects of wet corn distillers grains with solubles on visceral organ mass, trace mineral status, and polioencephalomalacia biomarkers of individually-fed cattle.

Twenty-four steers (initial BW = 385 ± 1.1 kg) were blocked by BW and randomly assigned to 3 dietary treatments (0, 30, or 60% wet distillers grains with solubles [WDGS]; DM basis) and were fed individually to determine the effect of WDGS on live growth and carcass performance, visceral organ mass, trace mineral status, and polioencephalomalacia biomarkers. Steers were slaughtered at 125, 150, 164, and 192 d (2 blocks/slaughter date) when external fat depth was approximately 1.3 cm based on visual appraisal. Steers fed 30% WDGS had greater DMI than those fed 0 or 60% WDGS (P < 0.05), and steers fed 60% WDGS had the lowest carcass-adjusted ADG (P < 0.09) of the 3 treatments. Nonetheless, WDGS concentration did not alter feed efficiency (P > 0.41) on either live or carcass-adjusted basis. Steers fed 30% WDGS had greater liver S and Mn concentrations (DM basis) and lower liver Fe concentrations than control steers (P < 0.10; initial values used as a covariate), and feeding 60% WDGS decreased liver Cu and increased liver Fe (P < 0.10) compared with feeding 30% WDGS. Cytochrome c oxidase (COX) activity in brain tissue tended to be decreased with 60 vs. 30% WDGS (P = 0.12), and COX activity decreased linearly (P = 0.06) in lung tissue as dietary WDGS concentration increased. Likewise, gut fill linearly increased (P = 0.01) with increasing WDGS concentration. Feeding 30% WDGS increased fractional mass (g/kg of empty BW) of the small intestine (P < 0.10) compared with controls, whereas 60% WDGS increased fractional kidney mass (P < 0.10) compared with 30% WDGS. Overall, results suggest that gut fill, Cu status, and COX activity seem to be compromised by WDGS when fed at 60% of diet DM in diets based on steam-flaked corn, which suggests a greater susceptibility to polioencephalomalacia.

Effect of rate of body weight gain of steers during the stocker phase. II. Visceral organ mass and body composition of growing-finishing beef cattle.

Two experiments were conducted to examine the effect of rate of BW gain during the stocker phase on visceral organ mass and body composition of growing-finishing cattle that had grazed dormant native range (DNR) or winter wheat pasture (WP). In each experiment, fall-weaned steers were allotted randomly to 1 of these stocker production programs: 1) control, 1.02 kg · steer(-1) · d(-1) of a 40% CP cottonseed meal-based supplement during grazing of DNR (CON); 2) corn/soybean meal-based supplement fed at 1% of BW during grazing of DNR (CORN); 3) grazing WP at a high stocking rate to achieve a reduced rate of BW gain (LGWP); and 4) grazing WP at a low stocking rate to achieve an increased rate of BW gain (HGWP). In Exp. 1, 3 steers per treatment were harvested after winter grazing (138 d). The remaining WP steers were transitioned into a finishing phase and DNR steers were allowed to graze the same pastures for another 115 d before entering a feedyard. In Exp. 2, steers grazed respective pastures until each treatment reached an estimated HCW of 200 kg (262, 180, 142, and 74 d, respectively, for CON, CORN, LGWP, and HGWP treatments), at which time 4 steers per treatment were randomly selected for intermediate harvest before finishing. At the end of the finishing period, 4 additional steers from each treatment were randomly selected for final carcass measurements. All steers were fed to a common 12th rib fat thickness of 1.27 cm. After winter grazing in Exp. 1, HGWP steers had the greatest (P < 0.01) mesenteric/omental fat, total viscera, total splanchnic tissue mass, and carcass and empty body fat, compared with the other treatments. In Exp. 2 at intermediate harvest, WP steers had greater (P < 0.03) mesenteric/omental fat, total viscera, and total splanchnic tissue mass, compared with CORN steers, with CON steers being intermediate. Also, the WP steers had greater (P < 0.02) carcass and empty body fat, compared with CORN steers, with CON steers being intermediate. At final harvest in Exp. 2, LGWP steers had the least total viscera and total splanchnic tissue mass, compared with the other treatments. However, there were no differences (P > 0.53) among treatments for carcass or empty body fat. Stocker systems using WP or DNR result in cattle with differences in body fat and visceral organ mass before finishing; this may influence feedlot efficiency, even though there were no differences in body fat and visceral organ mass at the end of the finishing period.

Issues in characterizing resting energy expenditure in obesity and after weight loss.

UNLABELLED: Limitations of current methods: Normalization of resting energy expenditure (REE) for body composition using the 2-compartment model fat mass (FM), and fat-free mass (FFM) has inherent limitations for the interpretation of REE and may lead to erroneous conclusions when comparing people with a wide range of adiposity as well as before and after substantial weight loss. EXPERIMENTAL OBJECTIVES: We compared different methods of REE normalization: (1) for FFM and FM (2) by the inclusion of %FM as a measure of adiposity and (3) based on organ and tissue masses. RESULTS were compared between healthy subjects with different degrees of adiposity as well as within subject before and after weight loss. RESULTS: Normalizing REE from an "REE vs. FFM and FM equation" that (1) was derived in obese participants and applied to lean people or (2) was derived before weight loss and applied after weight loss leads to the erroneous conclusion of a lower metabolic rate (i) in lean persons and (ii) after weight loss. This is revealed by the normalization of REE for organ and tissue masses that was not significantly different between lean and obese or between baseline and after weight loss. There is evidence for an increasing specific metabolic rate of FFM with increasing %FM that could be explained by a higher contribution of liver, kidney and heart mass to FFM in obesity. Using "REE vs. FFM and FM equations" specific for different levels of adiposity (%FM) eliminated differences in REE before and after weight loss in women. CONCLUSION: The most established method for normalization of REE based on FFM and FM may lead to spurious conclusions about metabolic rate in obesity and the phenomenon of weight loss-associated adaptive thermogenesis. Using %FM-specific REE prediction from FFM and FM in kg may improve the normalization of REE when subjects with wide differences in %FM are investigated.

METABOLIC AND DIGESTIVE RESPONSES TO ARTIFICIAL SELECTION IN CHICKENS.

Compared to ancestral wild jungle fowl, domestic broiler chickens have been consciously selected for large body size, relatively large pectoral muscles, rapid growth, and high feed efficiency. Hence intraspecific comparisons of these two strains could help identify consequences of unconscious artificial selection, trade-offs in energy allocation, and factors limiting energy budgets. We therefore compared our measurements of many corresponding parameters in both strains: growth rate, energy intake, digestive efficiency, metabolic rate and its components, organ masses, and intestinal brush-border nutrient transporter and hydrolase activities and capacities, as functions of age and body mass in zero- to nine-week-old chicks. Both strains prove to have the same digestive efficiency. Compared to equal-sized jungle fowl, broilers have higher daily energy intake and activity costs. Broilers have relatively longer and wider, hence heavier, small intestines, and their other gut compartments are also relatively larger. Offsetting these increases, broilers have relatively smaller brains and leg bones, these being much less important to a captive bird than to a wild bird exposed to predators. Broilers have generally lower intestinal transporter activities, but relatively higher transporter capacities because of their larger guts. Among domestic chicken strains, comparison of broilers with layers, the former having been consciously selected for much higher growth rates, yields generally similar conclusions. Thus, as recognized in broad outline by Darwin, domestication provides clear examples of conscious selection, of unconscious selection for traits prerequisite to the consciously selected traits, and of unconscious selection against traits rendered less important or competing for space or energy.