Stimulation by transforming growth factor-β of epidermal growth factor-dependent growth of aged human fibroblasts: Recovery of high affinity EGF receptors and growth stimulation by EGF

Summary The stimulatory effects of transforming growth factor β (TGF-β) on epidermal growth factor (EGF)-dependent growth of adult and newborn human fibroblasts were investigated. EGF-stimulated growth in low serum of dermal fibroblasts from a 41 year-old adult (HSF-41) was less than half that of newborn foreskin fibroblasts (HFF). The EGF-stimulated growth of HFF after 55 population doublings (HFF-55) was similarly reduced. The decreased growth response to EGF of fibroblasts, agedin vivo andin vitro appeared to result principally from a decreased sensitivity to EGF due to a decreased number and affinity of high affinity EGF receptors (H-EGFR). Pre-incubation of HSF-41 and HFF-55 with 25 pM TGF-β enhanced the growth responses of these cells to EGF and increased the levels of high affinity EGF-binding by these cells Thus, the stimulation by TGF-β of EGF-dependent growth of human fibroblasts agedin vivo orin vitro is mediated by increased levels of high affinity EGF binding. This research was supported in part by a grant-in-aid for scientific research (61480388) and a special project research grant to Okayama University from the Japanese Ministry of Education, Science and Culture. Editor's statement TGF beta interaction with its receptor is known to affect EGF receptors. In this paper a functional biological association is established.     

The evolution of growth trajectories: what limits growth rate?

According to life‐history theory, growth rates are subject to strong directional selection due to reproductive and survival advantages associated with large adult body size. Yet, growth is commonly observed to occur at rates lower than the maximum that is physiologically possible and intrinsic growth rates often vary among populations. This implies that slower growth is favoured under certain conditions. Realized growth rate is thus the result of a compromise between the costs and advantages of growing rapidly, and the optimal rate of growth is not equivalent to the fundamental maximum rate. The ecological and evolutionary factors influencing growth rate are reviewed, with particular emphasis on how growth might be constrained by direct fitness costs. Costs of accelerating growth might contribute to the variance in fitness that is not attributable to age or size at maturity, as well as to the variation in life‐history strategies observed within and among species. Two main approaches have been taken to study the fitness trade‐offs relating to growth rate. First, environmental manipulations can be used to produce treatment groups with different rates of growth. Second, common garden experiments can be used to compare fitness correlates among populations with different intrinsic growth rates. Data from these studies reveal a number of potential costs for growth over both the short and long term. In order to acquire the energy needed for faster growth, animals must increase food intake. Accordingly, in many taxa, the major constraint on growth rate appears to arise from the trade‐off between predation risk and foraging effort. However, growth rates are also frequently observed to be submaximal in the absence of predation, suggesting that growth trajectories also impact fitness via other channels, such as the reallocation of finite resources between growth and other traits and functions. Despite the prevalence of submaximal growth, even when predators are absent, there is surprisingly little evidence to date demonstrating predator‐independent costs of growth acceleration. Evidence that does exist indicates that such costs may be most apparent under stressful conditions. Future studies should examine more closely the link between patterns of resource allocation to traits in the adult organism and lifetime fitness. Changes in body composition at maturation, for example, may determine the outcome of trade‐offs between reproduction and survival or between early and late reproduction. A number of design issues for studies investigating costs of growth that are imposed over the long term are discussed, along with suggestions for alternative approaches. Despite these issues, identifying costs of growth acceleration may fill a gap in our understanding of life‐history evolution: the relationships between growth rate, the environment, and fitness may contribute substantially to the diversification of life histories in nature.     

The role of growth rate, redox-state of the plastoquinone pool and the trans-thylakoid ΔpH in photoacclimation of Chlorella vulgaris to growth irradiance and temperature

The long-term photoacclimation of Chlorella vulgaris Beijer (UTEX 265) to growth irradiance and growth temperature under ambient CO₂ conditions was examined. While cultures grew at a faster rate at 27 than at 5 °C, growth rates appeared to be independent of irradiance. Decreases in light-harvesting polypeptide accumulation, increases in xanthophyll pool size and changes in the epoxidation state of the xanthophyll cycle pigments were correlated linearly with increases in the relative reduction state of Q_A, the primary quinone receptor of photosystem II, when estimated as 1−q_P under steady-state growth conditions. However, we show that there is also a specific temperature-dependent component, in addition to the redox-state of the Q_A, involved in regulating the content and composition of light-harvesting complex II of C. vulgaris. In contrast, modulation of the epoxidation state of the xanthophyll pool in response to increased 1−q_P in cells grown at 5 °C was indistinguishable from that of cells grown at 27 °C, indicating that light and temperature interact in a similar way to regulate xanthophyll cycle activity in C. vulgaris. Because C. vulgaris exhibited a low-light phenotype in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), but a high-light phenotype upon addition of 2,5-dibromo-6-isopropyl-3-methyl-1,4-benzoquinone, we conclude that the plastoquinone pool acts as a sensor regulating the accumulation of light-harvesting polypeptides in C. vulgaris. However, concomitant measurements of non-photochemical fluorescence quenching (q_N) and the epoxidation state of the xanthophyll pool appear to indicate that, in addition to the redox-state of the plastoquinone pool, the trans-thylakoid ΔpH may also contribute to sensing changes in irradiance and temperature that would lead to over-excitation of the photosynthetic apparatus. We suggest that sink capacity as reflected in photosynthate utilization and cell growth ultimately regulate photoacclimation in C. vulgaris. Received: 17 April 2000 / Accepted: 23 May 2000     

Developmental growth patterns of the filter-feeder pterosaur, Pterodaustro guiñazui

Life-history parameters of pterosaurs such as growth and ontogenetic development represent an enigma. This aspect of pterosaur biology has remained perplexing because few pterosaur taxa are represented by complete ontogenetic series. Of these, Pterodaustro is unique in that besides being represented by hundreds of individuals with wing spans ranging from 0.3 to 2.5m, it includes an embryo within an egg. Here we present a comprehensive osteohistological assessment of multiple skeletal elements of a range of ontogenetic sizes of Pterodaustro, and we provide unparalleled insight into its growth dynamics. We show that, upon hatching, Pterodaustro juveniles grew rapidly for approximately 2 years until they reached approximately 53% of their mature body size, whereupon they attained sexual maturity. Thereafter, growth continued for at least another 3-4 years at comparatively slower rates until larger adult body sizes were attained. Our analysis further provides definitive evidence that Pterodaustro had a determinate growth strategy.     

Effects of transforming growth factor β on growth of human mammary epithelial cells in culture

Summary Normal human mammary epithelial cells (HMEC) from different individual reduction mammoplasty specimens were all growth inhibited, and showed a flattened, elongated morphology in response to human recombinant transforming growth factor β1 (TGFβ). The degree of growth inhibition varied among specimens, but none of the normal HMEC maintained growth in the continued presence of TGFβ. The degree of growth inhibition also varied with cell age in vitro, cells closer to senescence being more sensitive. TGFβ sensitivity was additionally assayed in two established cell lines derived from one of the reduction mammoplasty specimens after exposure to benzo(a)pyrene. Although varying degrees of growth inhibition and morphologic changes were observed in the cell lines, both lines contained populations that maintained active growth in the presence of TGFβ. Subclones of these lines demonstrated a great plasticity in their growth response to TGFβ, with individual clones ranging from strongly growth inhibited to nearly unaffected. These results suggest that multiple factors influence the extent of TGFβ-induced growth effects on both normal and transformed mammary epithelial cells, and that some of these factors may act through epigenetic mechanisms. This work was supported by CA24844 from the National Institutes of Health, Bethesda, MD, and the Office of Energy Research, Office of Health and Environmental Research of the U.S. Department of Energy under contract DE-AC03-76SF00098.     

Cellular senescence: A reflection of normal growth control,differentiation, or aging?

Normal cells, with few exceptions, cannot proliferate indefinitely. Cell populations--in vivo and in culture--generally undergo only a limited number of doublings before proliferation invariably and irreversibly ceases. This process has been termed the finite lifespan phenotype or cellular senescence. There is long-standing, albeit indirect, evidence that cellular senescence plays an important role in complex biological processes as diverse as normal growth control, differentiation, development, aging, and tumorigenesis. In recent years, it has been possible to develop a molecular framework for understanding some of the fundamental features of cellular senescence. This framework derives primarily from the physiology, genetics, and molecular biology of cells undergoing senescence in culture. Our understanding of senescence, and the mechanisms that control it, is still in its infancy. Nonetheless, recent data raise some intriguing possibilities regarding potential molecular bases for the links between senescence in culture and normal and abnormal growth control, differentiation, and aging.     

Metabolomic profiling of CHO fed-batch growth phases at 10, 100, and 1,000 L

Established bioprocess monitoring is based on quick and reliable methods, including cell count and viability measurement, extracellular metabolite measurement, and the measurement of physicochemical qualities of the cultivation medium. These methods are sufficient for monitoring of process performance, but rarely give insight into the actual physiological states of the cell culture. However, understanding of the latter is essential for optimization of bioprocess development. Our study used LC-MS metabolomics as a tool for additional resolution of bioprocess monitoring and was designed at three bioreactors scales (10 L, 100 L, and 1,000 L) to gain insight into the basal metabolic states of the Chinese hamster ovary (CHO) cell culture during fed-batch. Metabolites characteristics of the four growth stages (early and late exponential phase, stationary phase, and the phase of decline) were identified by multivariate analysis. Enriched metabolic pathways were then established for each growth phase using the CHO metabolic network model. Biomass generation and nucleotide synthesis were enriched in early exponential phase, followed by increased protein production and imbalanced glutathione metabolism in late exponential phase. Glycolysis became downregulated in stationary phase and amino-acid metabolism increased. Phase of culture decline resulted in rise of oxidized glutathione and fatty acid concentrations. Intracellular metabolic profiles of the CHO fed-batch culture were also shown to be consistent with scale and thus demonstrate metabolomic profiling as an informative method to gain physiological insight into the cell culture states during bioprocess regardless of scale.     

Rôle of single amino acids in phagostimulation,growth, and survival of Acyrthosiphon pisum

Twelve amino acids and amides at 0·1 to 0·75 or 1·0% in 35% sucrose solution were individually tested for their rôle in phagostimulation, growth, and survival in Acyrthosiphon pisum. Leucine and phenylalanine were phagostimulatory at all concentrations tested, tryptophan and valine at 0·1, 0·2, and 0·5%, and threonine at 0·1% only. Methionine was reported earlier by us to be phagostimulatory at 0·05 to 0·5%. Histidine and isoleucine had no effect, whereas arginine and lysine HCl reduced uptake when compared to sucrose alone. The non-essential amino acids, canavanine sulphate and glutamine, reduced uptake at all concentrations, whereas homoserine was phagostimulatory at 0·1 and 0·75%.Arginine, canavanine sulphate, glutamine, histidine, homoserine, isoleucine, leucine, and valine increased weight and prolonged survival, whereas lysine HCl, phenylalanine, threonine, and tryptophan neither promoted growth nor increased survival. Radioactive leucine (¹⁴C(U)) was incorporated into the protein fraction of the larval body and exuviae indicating that it took part in protein synthesis. This seems to be the first report in insects where peptide or protein synthesis occurred from single amino acids in sucrose.     

Annual growth rings and long-term growth patterns of mangrove trees from the Bragança peninsula,North Brazil

Ring analysis was carried out on 39 Rhizophora mangle trees from two salineand one brackish forest sites on apeninsula in north Brazil. All trees showedconstant growth over their entire lifespan, however the distinctiveness of growthrings was greater in trees from the salineareas than in trees from the brackish site.The mean radial increments form a patternof three distinct groups (`fast', `medium',and `slow' growth). Although all threegrowth groups contained trees from eachstudy site, trees from the brackish and thefrequently inundated saline area presenteda significantly higher growth rate (3.3 mmy^-1) than the trees growing in asaline, seldom inundated area. Radiocarbonanalysis showed that R. mangle formsannual rings in the region. The mean age ofeach forest, derived from the mean stemradius, the growth rates, and the treeaffiliation to each growth group, explainsforest's density and basal area. For thetrees from a saline area belonging to themedium growth group (mean increment 2.5 mmy^-1), the cambial growth correlatessignificantly with the precipitation in thetransition months between the dry and therainy season. The slowest growing trees(1.2 mm y^-1) showed a closerelationship between the ring width and thenumber of months with rainfall < 50 mm.Based on these results, we propose that thelocal abiotic factors influence theindividual growth rates but their effect onthe forest structure is modified by bioticfactors, such as neighborhoodcompetition.     

In vitro effect of pesticides on the germination, vegetative growth, and conidial production of two strains of Metarhizium anisopliae

Entomopathogenic fungi are widely used as biological control agents against a broad range of insect and arachnid pests. However, the control efficacy of entomopathogenic fungi is variable because of unfavourable and fluctuating environmental conditions and intrinsic factors. One strategy to enhance entomopathogenic fungi efficacy is a combined use of entomopathogenic fungi and low dosages of pesticides. These sub-lethal dosages of chemicals can increase the control efficiency of entomopathogenic fungi but only if they do not affect the fungi. Adverse effects could include the inhibition of germination and/or vegetative growth as well as conidiogenesis. The present study investigated the in vitro effects of different concentrations of fipronil, permethrin, imidacloprid, NeemAzal, and amitraz as potential candidates for combined applications on two strains of the entomopathogenic fungus Metarhizium anisopliae (MA). MA was inoculated on a medium amended with five different concentrations (0.32-200 ppm) of the abovementioned pesticides. The germination, vegetative growth, and sporulation were evaluated. The results showed, according to a physiology parameter compatibility classification, that all pesticides were compatible with both tested MA strains. Only fipronil in the higher dose rates of 40 and 200 ppm was close to moderately toxic to MA-7. Furthermore, only higher concentrations of the pesticides caused a slight inhibition (about 15%) of conidial germination and a reduction in colony size. Sporulation was reduced at most by approximately 50% by 40 or 200 ppm of fipronil or amitraz, respectively. Therefore, it is possible to use the tested pesticides in combination with either strain of MA for an integrated pest management approach. Studies on the effect of these combinations on target organisms are in progress.     

Sex-related,growth–climate association of Araucaria angustifolia in the neotropical ombrophilous woodlands of Argentina

Araucaria angustifolia is a dioecious dominant tree in araucaria forests in Brazil and Argentina, South America. The species is nowadays critically endangered by deforestation and global climate change. The goal of this study was to analyse the dynamics of radial growth in this species and its association with climatic variables, according to the sex, at its western range boundary in Argentina. Standard dendrochronological techniques were applied on stem disks from female and male trees. Xylem anatomical anomalies made the tree-ring dating process difficult. Female and male trees showed growth patterns that changed over time, not being significant in the 1950–1990 period and highly significant from the 1990s onwards (p < 0.1) when female trees had a higher growth rate. Female and male trees showed a different association with climatic variables. No significant effect of temperature and precipitation was identified on female trees. For male trees, rainfall had a positive effect in August, before the growing season, and a negative effect at the end of the growing season (March). Temperature had a negative effect on male trees, before and during the growing season (February and January, respectively). No effect of SOI was detected on both sexes. Results emphasised the usefulness of A. angustifolia for dendrochronological studies and the value of dioecious species for the study of sex-related growth–climate association.     

Influence of He−Ne laser irradiation of soybean seeds on seed mycoflora, growth, nodulation, and resistance toFusarium solani

Laser irradiation of soybean seeds for 3 min caused a clear reduction in the number of seed-borne fungi which became more pronounced as the irradiation time was extended. Pretreatment of the seeds with methylene blue, methyl red and carmine enhanced the effect of laser.Rhizoctonia solani, Alternaria tenuissima, Cercospora kikuchii andColletotrichum truncatum were completely eliminated when the seeds were pretreated with a dye and irradiated for 10 min. Seed germination was stimulated on exposure of the seed to 1-min irradiation. At such dose, most of the dyes were accelerators while the higher doses were inhibitory to seed germination. Chlorophylla, chlorophyllb and carotenoid content of developed plants differed, depending on the irradiation dose and dye treatment of the seeds. In seeds irradiated for 1 or 3 min, chlorophylla formation was less affected than chlorophyllb formation. In seeds irradiated for 10 min, both the chlorophyll contents were decreased especially in the presence of some applied dyes. On the other hand, there was an increase in carotenoid content of soybean leaves when the laser dose increased. The number and dry mass of nodules were mostly greater (as compared to the corresponding control), when the seeds irradiated for 1 or 3 min were pretreated with methyl red, chlorophenol red, crystal violet and methylene blue. Irradiation of pre-sowing seeds greatly protected soybean stands againstF. solani. The disease incidence differed somewhat when the irradiated seeds were pretreated with dyes. The reduction in disease incidence was accompanied by accumulation of high proline and phenol levels in the infected root tissues of soybean, suggesting that these compounds have a certain role in the prevention of disease development.     

Effects of immobilization on growth,substrate consumption, β-galactosidase induction,and byproduct formation inEscherichia coli

Summary Some metabolic properties of both suspended and immobilized aerobically and anaerobically growingEscherichia coli cells were investigated. Metabolic activity was found to be substantially different whenE. coli cells were immobilized in alginate. Cells grown immobilized in alginate, and then released from the gel, synthesized 1.6 (aerobic growth) and 4.9 (anaerobic growth) times as much -galactosidase per cell in response to induction as did suspended cells. Under both aerobic and anaerobic conditions, the cell yield from glycerol for immobilized cells was half that for suspended cells. At specific growth rates that were not significantly different from those of suspended cells, immobilized cells consumed glycerol at twice the rate of suspended cells. Immobilized cells produced elevated quantities of acetate, pyruvate, and lactate. Interpretation of these findings is discussed in terms of the kinetics of energy metabolism and the regulation of inducible protein synthesis inE. coli.     

Effect of uniconazole and limited water on growth,water relations,and mineral nutrition of “Lalandei” Pyracantha

Pyracantha (Pyracantha coccinea M. J. Roem. Lalandei) plants were treated with uniconazole at 0.5 mg ai container^–1 as a medium drench, 150 mg ai L^–1 as a foliar spray, or left untreated. Plants from all treatments were placed under three water regimes: drought acclimated, nonacclimated and later exposed to drought, or nonstressed. Acclimated plants were conditioned by seven 4-day stress cycles (water withheld), while nonacclimated were well watered prior to a single 4-day stress cycle at the same time as the seventh drought cycle of acclimated plants. Nonstressed plants were well watered throughout the study. Nonstressed plants had higher leaf water potentials and leaf conductances than acclimated and nonacclimated plants, and transpiration rates were higher in nonacclimated than acclimated plants. Uniconazole did not affect leaf water potential, leaf conductance, or transpiration rate. Acclimated plants had smaller leaf areas and leaf, stem, and root dry weights than nonacclimated or nonstressed plants. Plants drenched with uniconazole had the lowest stem and root dry weights. Acclimated plants also contained higher N concentrations than nonacclimated or nonstressed plants, and higher P concentrations than nonacclimated plants. Uniconazole medium drench treatments increased levels of Mn and P. Calcium concentration was increased in plants receiving either medium drench or foliar applications.     

Regulation of gene expression,growth,and cell survival by IL—4：Contribution of multiple signaling pathways

Interleukin-4 is a cytokine produced by activated T cells,mast cells,and basophils that elicits many important biological responses[1](see Tab 1).These responses range from the regulation of helper T cell differentiation[2] and the production of IgE[3] to the regulation of the adhesive properties of endothelial cells via VCAM-1[4],In keeping with these diverse biological effects,high-affinity binding sites for IL-4(Kd 20 to 300pM) have been detected on many hematopoietic and non-hematopoietic cell types at levels ranging from 50 to 5000 sites per cell[5].This review will focus on the discrete signal transduction pathways activated by the IL-4 recxeptor and the coordination of these individual pathways in the regulation of a final biological outcome.