Effects of imipramine and reserpine on body size and organ size in euthyroid and hyperthyroid growing rats.
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A matter of size: developmental control of organ size in plants.
The intrinsic size of plant organs is determined by developmental signals, yet the molecular and genetic mechanisms that control organ size are largely unknown. Ongoing functional analysis of Arabidopsis genes is defining important regulators involved in these mechanisms. Key features of this control are the coordinated activation of growth and cell division by growth regulators and the maintenance of meristematic competence by the ANT gene, which acts as an organ-size checkpoint. Alterations of genome size by polyploidization and endoreduplication can reset this checkpoint by ploidy-dependent, epigenetically regulated differential gene expression. In addition, the regulation of polarized growth and phytohormone signaling also affect final organ size. These findings reveal unique aspects of plant organ-size control that are distinct from animal organ-size control.
Arabidopsis↗
The pleiotropic Arabidopsis frd mutation with altered coordination of chloroplast biogenesis, cell size and differentiation, organ size and number.
In higher plants, plastid development must be tightly coordinated with cell and organ development. In this paper, a novel T-DNA-mutagenized Arabidopsis line showing chlorotic leaves and minute stature was identified in a genetic screen for altered chloroplast development. The mutation corresponded to a single locus on chromosome IV and was associated with insertion of the T-DNA. This locus was named FARFADET and resulted in pleiotropic effects on chloroplast biogenesis, cell size and differentiation, organ size and number. Thus, in contrast with previously described chlorotic mutants, frd mutants were affected not only in chloroplast development and chlorophyll accumulation, but also in cell and organ development. Alteration of differentiation affected different cell types such as leaf epidermal cells, trichomes, mesophyll cells, and columella cells. A major effect on mesophyll cell differentiation was the lack of palisadic parenchyma and absence of grana stacks. Moreover, meristem size and lateral meristem initiation were affected. Genetic and molecular characterisation showed that the T-DNA insertion generated 41 bp deletion in a potential miRNA precursor. The predicted miRNA target genes were involved in plant development and stress. It is therefore hypothesized that the frd mutation had affected coordination of cell developmental span and the control of the division-differentiation balance.
Arabidopsis↗
Plant organ size control: AINTEGUMENTA regulates growth and cell numbers during organogenesis.
The control of cell proliferation during organogenesis plays an important role in initiation, growth, and acquisition of the intrinsic size of organs in higher plants. To understand the developmental mechanism that controls intrinsic organ size by regulating the number and extent of cell division during organogenesis, we examined the function of the Arabidopsis regulatory gene AINTEGUMENATA (ANT). Previous observations revealed that ANT regulates cell division in integuments during ovule development and is necessary for floral organ growth. Here we show that ANT controls plant organ cell number and organ size throughout shoot development. Loss of ANT function reduces the size of all lateral shoot organs by decreasing cell number. Conversely, gain of ANT function, via ectopic expression of a 35S::ANT transgene, enlarges embryonic and all shoot organs without altering superficial morphology by increasing cell number in both Arabidopsis and tobacco plants. This hyperplasia results from an extended period of cell proliferation and organ growth. Furthermore, cells ectopically expressing ANT in fully differentiated organs exhibit neoplastic activity by producing calli and adventitious roots and shoots. Based on these results, we propose that ANT regulates cell proliferation and organ growth by maintaining the meristematic competence of cells during organogenesis.
Arabidopsis↗
Regulation of imaginal disc cell size, cell number and organ size by Drosophila class I(A) phosphoinositide 3-kinase and its adaptor.
BACKGROUND: Class I(A) phosphoinositide 3-kinases (PI 3-kinases) have been implicated in the regulation of several cellular processes including cell division, cell survival and protein synthesis. The size of Drosophila imaginal discs (epithelial structures that give rise to adult organs) is maintained by factors that can compensate for experimentally induced changes in these PI 3-kinase-regulated processes. Overexpression of the gene encoding the Drosophila class I(A) PI 3-kinase, Dp110, in imaginal discs, however, results in enlarged adult organs. These observations have led us to investigate the role of Dp100 and its adaptor, p60, in the control of imaginal disc cell size, cell number and organ size. RESULTS: Null mutations in Dp110 and p60 were generated and used to demonstrate that they are essential genes that are autonomously required for imaginal disc cells to achieve their normal adult size. In addition, modulating Dp110 activity increases or reduces cell size in the developing imaginal disc, and does so throughout the cell cycle. The inhibition of Dp110 activity reduces the rate of increase in cell number in the imaginal discs, suggesting that Dp110 normally promotes cell division and/or cell survival. Unlike direct manipulation of cell-cycle progression, manipulation of Dp110 activity in one compartment of the disc influences the size of that compartment and the size of the disc as a whole. CONCLUSIONS: We conclude that during imaginal disc development, Dp110 and p60 regulate cell size, cell number and organ size. Our results indicate that Dp110 and p60 signalling can affect growth in multiple ways, which has important implications for the function of signalling through class I(A) PI 3-kinases.
Animals↗
The Arabidopsis auxin-inducible gene ARGOS controls lateral organ size.
During plant development, the final size of an organ is regulated and determined by various developmental signals; however, the molecular mechanisms by which these signals are transduced and the mediators involved are largely unknown. Here, we show that ARGOS, a novel Arabidopsis gene that is highly induced by auxin, is involved in organ size control. Transgenic plants expressing sense or antisense ARGOS cDNA display enlarged or reduced aerial organs, respectively. The alteration in organ size is attributable mainly to changes in cell number and the duration of organ growth. Ectopic expression of ARGOS prolongs the expression of AINTEGUMENTA (ANT) and CycD3;1 as well as the neoplastic activity of leaf cells. Moreover, organ enlargement in plants overexpressing ARGOS can be blocked by the loss of function of ANT, implying that ARGOS functions upstream of ANT to affect the meristematic competence of organ cells. The induction of ARGOS by auxin is attenuated or abolished in auxin-resistant1 (axr1), and overexpression of ARGOS partially restores axr1 organ development. These results suggest that ARGOS may transduce auxin signals downstream of AXR1 to regulate cell proliferation and organ growth through ANT during organogenesis.
Amino Acid Sequence↗
Gross and microscopic visceral anatomy of the male Cape fur seal, Arctocephalus pusillus pusillus (Pinnipedia: Otariidae), with reference to organ size and growth.
The gross and microscopic anatomy of the Cape fur seal heart, lung, liver, spleen, stomach, intestine and kidneys (n = 31 seals) is described. Absolute and relative size of organs from 30 male seals are presented, with histological examination conducted on 7 animals. The relationship between log body weight, log organ weight and age was investigated using linear regression. Twenty five animals were of known age, while 6 were aged from counts of incremental lines observed in the dentine of tooth sections. For the range of ages represented in this study, body weight changes were accurately described by the exponential growth equation, weight = w(o)r(t), with body weight increasing by 23 % per annum until at least 9-10 y of age. Organ weight increased at a rate of between 25 % and 33 % per annum until at least 9-10 y of age, with the exception of the intestines, where exponential increase appeared to have ceased by about 7 y. The relationship between body weight and organ weight was investigated using logarithmic transformations of the allometric equation, y = ax(b), where the exponent b is 1 if organ weight is proportional to body weight. Most organs increased in proportion to the body. However, the heart, liver and spleen had exponents b > 1, suggesting that these organs increased at a faster rate than the body. The basic anatomical features of the viscera were similar to those of other pinnipeds, with some exceptions, including the arrangement of the multilobed lung and liver. Apart from the large liver and kidneys, relative size of the organs did not differ greatly from similar sized terrestrial carnivores. The histological features of the organs were generally consistent with those previously described for this species and other otariids. The heart, as in other pinnipeds, was unlike that of cetacea in not having unusually thick endocardium or prominent Purkinje cells. Notable histological features of the lungs included prominent fibrous septa, prominent smooth muscle bundles, cartilage extending to the level of the alveolar sacs and ample lymphoid tissue. The spleen had a thick capsule, well developed trabeculae and plentiful plasma cells. Abundant parietal cells were present in the fundic glands and lymphoid follicles were present in the gastric lamina propria, particularly in the pyloric region. Small intestinal villi were very long but this could have resulted from underlying chronic inflammation. Lymphoid follicles were prominent in the colon. The kidney reniculi each had a complete cortex, medulla and calyx, but a sportaperi medullaris musculosa was not identified.
Animals↗
Fat cadherin modulates organ size in Drosophila via the Salvador/Warts/Hippo signaling pathway.
BACKGROUND: The atypical Fat cadherin has long been known to control cell proliferation and organ size in Drosophila, but the mechanism by which Fat controls these processes has remained elusive. A newly emerging signaling pathway that controls organ size during development is the Salvador/Warts/Hippo pathway. RESULTS: Here we demonstrate that Fat limits organ size by modulating activity of the Salvador/Warts/Hippo pathway. ft interacts genetically with positive and negative regulators of this pathway, and tissue lacking fat closely phenocopies tissue deficient for genes that normally promote Salvador/Warts/Hippo pathway activity. Cells lacking fat grow and proliferate more quickly than their wild-type counterparts and exhibit delayed cell-cycle exit as a result of elevated expression of Cyclin E. fat mutant cells display partial insensitivity to normal developmental apoptosis cues and express increased levels of the anti-apoptotic DIAP1 protein. Collectively, these defects lead to increased organ size and organism lethality in fat mutant animals. Fat modulates Salvador/Warts/Hippo pathway activity by promoting abundance and localization of Expanded protein at the apical membrane of epithelial tissues. CONCLUSIONS: Fat restricts organ size during Drosophila development via the Salvador/Warts/Hippo pathway. These studies aid our understanding of developmental organ size control and have implications for human hyperproliferative disorders, such as cancers.
Animals↗
The E3 ubiquitin ligase BIG BROTHER controls arabidopsis organ size in a dosage-dependent manner.
Organ growth up to a species-specific size is tightly regulated in plants and animals. Final organ size is remarkably constant within a given species, suggesting that a species-specific size checkpoint terminates organ growth in a coordinated and timely manner. Phytohormones influence plant organ size, but their precise functions in size control are unclear because of their pleiotropic and complex developmental roles. The Arabidopsis transcription factors AINTEGUMENTA and JAGGED promote organ growth by maintaining cellular proliferation potential. Loss of the Antirrhinum transcription factor CINCINNATA causes leaf overgrowth, yet also leads to a highly abnormal leaf shape. Thus, no dedicated factor that limits the final size of plant organs has been isolated. Here, we identify the novel RING-finger protein BIG BROTHER (BB) as a repressor of plant organ growth. Small changes in BB expression levels substantially alter organ size, indicating a central regulatory role for BB in growth control. Recombinant BB protein has E3 ubiquitin-ligase activity that is essential for its in vivo function, suggesting that BB acts by marking cellular proteins for degradation. Our data indicate that plants limit the duration of organ growth and ultimately organ size by actively degrading critical growth stimulators.
Amino Acid Sequence↗
Phenotypic flexibility in a novel thermal environment: phylogenetic inertia in thermogenic capacity and evolutionary adaptation in organ size.
The goal of our work was to understand the role of a novel thermal environment in shaping the phenotypic expression of thermogenic capacity and organ size. To examine this we compared two populations of the South American rodent Phyllotis darwini from different altitudes (Andean and valley populations), taking advantage of the fact that this genus originated at high altitude in the Andean plateau. DNA mitochondrial analysis showed that the two populations were separated and then experienced different thermal regimens for at least the last 450,000 yr. We expected the two populations of P. darwini to present more metabolic and organ size similarities if phylogenetic inertia had been an important factor. In this sense, phylogenetic inertia means that the valley population would retain evolutionary adaptations of high altitude: a greater phenotypic flexibility in both physiological and morphological traits. In general, our results indicate that the actual thermogenic capacities (magnitude and flexibility) of the valley population are a consequence of phylogenetic inertia. On the other hand, results for organ size (magnitude and flexibility) could suggest that this population would have adapted to the less seasonal central valley.
Adaptation, Physiological↗
Influence of dietary aflatoxin, zinc, and copper on bone size, organ weight, and body weight in hamsters and rats.
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Aflatoxins↗
Lymphoid organ size varies among inbred lines 6(3) and 7(2) and their thirteen recombinant congenic strains of chickens with the same major histocompatibility complex.
The objective was to evaluate lymphoid organ size in chickens from a series of 13 recombinant congenic strains (RCS) and their highly inbred parental lines (6(3) and 7(2)). The parental line 6(3) was selected for resistance to tumors induced by Marek's disease virus and avian leukosis viruses, whereas line 7(2) was selected for susceptibility to these tumors. Each RCS on the average contains a random one-eighth of genome from the donor line 7(2). Previous studies have shown that lines 6(3) and 7(2) differ in the size of primary lymphoid organs; i.e., the bursa of Fabricius (BF) and the lobes of the thymus (T) are smaller in line 6(3) than line 7(2). In the current study, the relative size of the T, BF, and spleen was first examined in about 15 males from each of 13 RCS and the 2 parental lines at 60 to 69 d of age. The differences of relative BF, T, and spleen size among the RCS and the parental lines 6(3) and 7(2) differed significantly (P < 0.001). Males and females from 4 RCS and the 2 parental lines were evaluated a second time, and differences in the relative sizes in lymphoid organs among the RCS and parental lines were consistent. In 2 RCS, the size of the T and BF was comparatively large as in line 7(2), leading to the conclusion that different allelic forms at 1 or more loci in these RCS regulate the size of both organs. In 2 other RCS, the BF was large compared with the T, suggesting that allelic forms at some loci in these RCS influence the BF independent of the T. The relative lymphoid organ size among the RCS appeared to cosegregate with the concentration of IgG in the plasma measured previously. The evaluation of genomic variability of these lines is underway, and the RCS are available for research on traits that differ between lines 6(3) and 7(2).
Animals↗
Adjusting energy expenditures to energy supply: food availability regulates torpor use and organ size in the Chilean mouse-opossum Thylamys elegans.
We studied how food abundance and consumption regulates torpor use and internal organ size in the Chilean mouse-opossum Thylamys elegans (Dielphidae), a small nocturnal marsupial, endemic in southern South America. We predicted that exposure to food rations at or above the minimum energy levels necessary for maintenance would not lead to any signs of torpor, while reducing food supply to energy levels below maintenance would lead to marked increases in frequency, duration and depth of torpor bouts. We also analyzed the relationship between food availability and internal organ mass. We predicted a positive relationship between food availability and internal organ size once the effect of body size is removed. Animals were randomly assigned to one of two groups and fed either 70, 100 or 130% of their daily energy requirement (DER). We found a positive and significant correlation between %DER and body temperature, and also between %DER and minimum body temperature. In contrast, for torpor frequency, duration and depth, we found a significant negative correlation with %DER. Finally, we found a significant positive correlation between the %DER and small intestine and ceacum dry mass. We demonstrate that when food availability is limited, T. elegans has the capacity to reduce their maintenance cost by two different mechanisms, that is, increasing the use of torpor and reducing organ mass.
Adaptation, Physiological↗
Digestive organ sizes and enzyme activities of refueling western sandpipers (Calidris mauri): contrasting effects of season and age.
We examined seasonal and age-related variation in digestive organ sizes and enzyme activities in female western sandpipers (Calidris mauri) refueling at a coastal stopover site in southern British Columbia. Adult sandpipers exhibited seasonal variation in pancreatic and intestinal enzyme activities but not in digestive system or organ sizes. Spring migrants had 22% higher total and 67% higher standardized pancreatic lipase activities but 37% lower total pancreatic amylase activity than fall migrants, which suggests that the spring diet was enriched with lipids but low in glycogen. Spring migrants also had 47% higher total intestinal maltase activity as well as 56% higher standardized maltase and 13% higher standardized aminopeptidase-N activities. Spring migrants had higher total enzymic capacity than fall migrants, due primarily to higher total lipase and maltase activities. During fall migration, the juvenile's digestive system was 10% larger than the adult's, and it was composed differently: juveniles had a 16% larger small intestine but a 27% smaller proventriculus. The juvenile's larger digestive system was associated with lower total enzymic capacity than the adult's due to 20% lower total chitinase and 23% lower total lipase activities. These results suggest that juvenile western sandpipers may process food differently from adults and/or have a lower-quality diet.
Age Factors↗
Flexible remodeling of organ size during spring migration of the garden warbler (Sylvia borin).
The energetic demands of long-distance migratory birds change drastically, depending on the stage of their life cycle. Changing demands are reflected in the up and down regulation of adipose tissue and organ mass. This paper presents new data on organ size changes during different stages of spring migration of garden warblers (Sylvia borin). Phenotypic mass changes were quantified in 13 organs of birds caught in Tanzania, Ethiopia and Egypt. We also sampled birds after a simulated stopover in Egypt. Some organs increased in mass up to about 1.5-fold during migration from Tanzania to Ethiopia, while some remained unchanged or even decreased in mass. During flight across the Sahara, nearly all organ masses including heart and flight muscles were reduced. Exceptionally large reductions (approximately 50%) were observed for liver, bile, spleen, kidney and digestive tract organs. The only exceptions were the testes, which increased 4-fold in mass. During the simulated stopover in Egypt, a significant recovery was observed for kidney, liver, heart, proventriculus, and small intestine. The testes continued to increase in mass. Flexible remodeling of organ size in the course of spring migration thus comprises significant changes for all quantified organs, with a variety of organ-specific patterns. Individual organ patterns are differentially shaped by functional aspects according to the different organ requirements in the alternation of flight and stopover phases, energetics, future demands, and protein requirements. Anticipatory mechanisms account for the size change of the testes, and we suggest the same for the kidney and the gall bladder.
Analysis of Variance↗
EBP1 regulates organ size through cell growth and proliferation in plants.
Plant organ size shows remarkable uniformity within species indicating strong endogenous control. We have identified a plant growth regulatory gene, functionally and structurally homologous to human EBP1. Plant EBP1 levels are tightly regulated; gene expression is highest in developing organs and correlates with genes involved in ribosome biogenesis and function. EBP1 protein is stabilised by auxin. Elevating or decreasing EBP1 levels in transgenic plants results in a dose-dependent increase or reduction in organ growth, respectively. During early stages of organ development, EBP1 promotes cell proliferation, influences cell-size threshold for division and shortens the period of meristematic activity. In postmitotic cells, it enhances cell expansion. EBP1 is required for expression of cell cycle genes; CyclinD3;1, ribonucleotide reductase 2 and the cyclin-dependent kinase B1;1. The regulation of these genes by EBP1 is dose and auxin dependent and might rely on the effect of EBP1 to reduce RBR1 protein level. We argue that EBP1 is a conserved, dose-dependent regulator of cell growth that is connected to meristematic competence and cell proliferation via regulation of RBR1 level.
Adaptor Proteins, Signal Transducing↗
Mating-induced reduction in accessory reproductive organ size in the stalk-eyed fly Cyrtodiopsis dalmanni.
BACKGROUND: Internal reproductive organ size is an important determinant of male reproductive success. While the response of testis length to variation in the intensity of sperm competition is well documented across many taxa, few studies address the importance of testis size in determining other components of male reproductive success (such as mating frequency) or the significance of size variation in accessory reproductive organs. Accessory gland length, but not testis length, is both phenotypically and genetically correlated with male mating frequency in the stalk-eyed fly Cyrtodiopsis dalmanni. Here we directly manipulate male mating status to investigate the effect of copulation on the size of both the testes and the accessory glands of C. dalmanni. RESULTS: Accessory gland length was positively correlated with male mating frequency. Copulation induced a significant decrease in accessory gland size. The size of the accessory glands then recovered slowly over the next 8-48 hours. Neither testis length nor testis area was altered by copulation. CONCLUSION: These results reveal that the time course of accessory gland recovery corresponds to field observations of mating behaviour and suggest that accessory gland size may limit male mating frequency in C. dalmanni.
Animals↗
Local reduction of organ size in transgenic mice expressing a soluble insulin-like growth factor II/mannose-6-phosphate receptor.
Genetic evidence suggests that the insulin-like growth factor II (IGF-II)/mannose-6-phosphate receptor (IGF2R) slows growth. A soluble form of IGF2R (sIGF2R) is produced by proteolytic cleavage of the intact cellular receptor and is found at high levels in fetal and neonatal plasma. To test the hypothesis that sIGF2R modulates organ size in vivo, we generated transgenic mice expressing a mouse Igf2r complementary DNA in which the transmembrane domain sequence was deleted. The transgene was driven by the keratin-10 promoter and was expressed at the highest levels in the skin and alimentary canal. Transgenics showed disproportionately reduced size of the alimentary canal, where the wet weight was decreased by 9-20% and the dry weight was decreased by 20-30%, whereas the water content per unit dry weight was not significantly changed. In addition, the circulating levels of IGF-II and the latent form of transforming growth factor-beta1 were increased by 58-77% and 56-140%, respectively, whereas plasma epidermal growth factor levels showed a 24-35% reduction. The serum and tissue activities of four lysosomal enzymes were not affected, with the exception of the colon in the line expressing the transgene at highest levels, where enzyme activities were decreased compared with control values. These results support a significant role for the sIGF2R in local modulation of organ size in vivo.
Animals↗