Biphasic Growth Research Articles

A neural‐network based model of bioreaction kinetics

AbstractA neural‐network based model of the kinetics in a fermentation process is presented. In the development and application of the model, the state of the process was estimated by an independent model based on elemental balances and an electroneutrality condition. The aim of the work was a model that describes the overall kinetic relations well enough to be used for on‐line simulation and prediction. Both feed‐forward and partially recurrent networks were investigated. The networks were trained off‐line, but in the on‐line application they are adapted to the process conditions by adjusting a set of correction factors. The approach is illustrated on a number of batch runs of Saccharomyces cerevisiae, where the networks are demonstrated to be able to accurately describe the biphasic growth.

The significance of heregulin in breast cancer tumor progression and drug resistance.

The erbB-2 receptor plays an important role in the prognosis of breast cancer and is expressed at high levels in nearly 30% of tumors in breast cancer patients. While evidence accumulates to support the relationship between erbB-2 overexpression and poor overall survival in human breast cancer, understanding of the biological consequence(s) of erbB-2 overexpression remains elusive. The discovery of heregulin has allowed us to identify a number of related but distinct biological endpoints which appear responsive to signal transduction through the erbB-2/4 receptor. These endpoints of growth, invasiveness, and differentiation have clear implications for the emergence, maintenance, and/or control of malignancy, and represent established endpoints in the assessment of malignant progression in human breast cancer. Preliminary studies in vitro have shown that heregulin induces a biphasic growth effect on cells with erbB-2 overexpression. Interestingly, we observed that expression of heregulin correlates with a more aggressive/invasive, vimentin-positive phenotype in breast cancer cells lines. Therefore, we have postulated that heregulin is involved in breast cancer tumor progression. We have shown that heregulin induces in vitro chemoinvasion and chemotaxis of breast cancer cells as well as growth in an anchorage dependent and independent manner. Interestingly, a heregulin neutralizing antibody inhibits chemotaxis and results in cell growth inhibition and blockade of the invasive phenotype. Strikingly, genetically engineered cells which constitutively express heregulin demonstrate critical phenotypic changes that are associated with a more aggressive phenotype. Specifically, these cells are no longer dependent on estrogen for growth and are resistant to tamoxifen in vitro and in vivo, and moreover these cells metastasize to lymph nodes in athymic nude mice. These tumors appear to have lost bcl-2 expression as compared with the control tumors. In addition, presumably by activation/regulation of topoisomerase II, the heregulin-transfected cells become exquisitely sensitive to doxorubicin and VP-16. Clearly, mechanistic aspects of the erbB-2/4 and heregulin interaction need to be understood from a therapeutic standpoint which could provide additional insights into synergistic treatments for certain patients, or improve treatment regimens for a large number of women. The study of heregulin and its co-expression with erbB-2/4 receptor and the assessment of its involvement in the progression from the in situ stage of breast tumors to the invasive one will additionally increase the relevance of heregulin as a prognostic/diagnostic factor. We believe that our studies provide new insights into breast cancer diagnosis, prognosis, and treatment.

Biphasic transforming growth factor-β production flanking the pro-inflammatory cytokine response in cerebral trauma

We determined the time-course of the production of transforming growth factor-beta (TGF-beta) after fluid-percussion injury using a bioassay. Biophasic production of TGF-beta composed mainly of TGF-beta 2 was detected in the ipsilateral cortex, with a first peak 30 min and a second peak 48 h after the lesion, flanking the transient production of tumor necrosis factor-alpha and interleukin-6 occurring between 5 and 18 h after trauma. This temporal pattern suggested that TGF-beta plays alternatively a pro- and anti-inflammatory role in the regulation of the brain cytokine network in response to injury, providing an endogenous mechanism for the control of the inflammatory reaction in traumatic brain injury.

Biphasic actions of estrogen on colon cancer cell growth: possible mediation by high- and low-affinity estrogen binding sites

The present experiments were carried out to investigate the possible direct effects of estrogens (E) on the growth of colon cancer cells. Estradiol exhibited a concentration-dependent biphasic growth effect on a mouse colon cancer cell line (MC-26). Low concentrations of estradiol (10(-10) M: to 10(-8) M: ) had a growth-stimulatory effect, while higher concentrations (10(-7) M: to 10(-6) M: ) were growth-inhibitory. Estrogen receptor (ER) mRNA as well as specific, saturable binding of estradiol to ER (K(d)=0.3NM: , B(max)=0.72 fmol/μg DNA) was identified in these cells. In addition to the classical high affinity ER, lower affinity, higher capacity estrogen binding sites (K(d)=35MM: , B(max)=30 fmol/μg DNA) were also characterized in MC-26 cells. These two types of estrogen binding sites exhibited distinct binding specificities for E and antiestrogens. Treatment of MC-26 cells with an oligodeoxy-nucleotide antisense to the translation start codon of ER mRNA did not alter the grown-inhibitory effect of 10(-6) M: estradiol, demonstrating that the growth-inhibitory effect of high concentrations of E was not mediated by ER; we have previously shown that under the same conditions, ER antisense oligonucleotides do block the growth-stimulatory effects of 10(-9) M: E(2) in MC-26 cells. The data suggest that physiological concentrations of estradiol acting via the classical ER may have a proliferative effect on the growth of colon cancer cells. However, in situations where there are high luminal concentrations of estrogenic compounds, they may act on low affinity estrogen binding sites that mediate the growth-inhibitory effect.

Growth and nitrogenase activity of Azotobacter vinelandii in chemically-defined media containing glucose and p-hydroxybenzoic acid

Azotobacter vinelandii was cultured in chemically-defined media supplemented with p-hydroxybenzoic acid, either in the presence or absence of glucose. Growth, oxygen consumption, nitrogenase activity and utilization of the carbon sources were investigated. When the microorganism was cultured in media containing p-hydroxybenzoic acid and glucose, a biphasic growth curve could be observed, in which glucose was used as primary carbon source. Nitrogenase activity was higher in absence of glucose. Oxygen consumption, however, was lower in media without glucose, suggesting that under these culture conditions the hypothesis of respiratory protection of nitrogenase is not supported.

Influence of growth rate and precursor availability on spiramycin production inStreptomyces ambofaciens

The development of a culture medium in which the growth rate was limited by initial phosphate concentration permitted spiramycin production during the growth phase. The influence of the growth rate on spiramycin production in this medium was studied. Addition of glycerol before spiramycin production increased the growth rate by 100% and spiramycin production began at a low rate. Spiramycin production yield was decreased by 50%. Addition of fatty acids such as hexanoate before spiramycin production increased the global yield of spiramycin by 47% and a high level of acetate excretion was observed just before spiramycin production. The development of a biphasic growth medium increased the spiramycin global yield. In this biphasic growth medium, in the first phase there was fast growth during which no acetate was excreted and no spiramycin was detected. During a second phase of slow growth, acetate excretion preceded spiramycin production and the spiramycin biosynthetic rate was maintained at a high level.Key words: Streptomyces ambofaciens, spiramycin, electrophoresis, nitrogen source, regulation.

New mode of Dunaliella biotechnology: two-phase growth for β-carotene production

Attempts to adapt the laboratory experience of bi-phasic growth and carotenogenesis in Dunaliella to large-scale conditions were highly successful. Algae were initially cultivated in stage one for optimizing biomass production of cells containing a low β-carotene to chlorophyll ratio. The culture was then transferred to stage two, diluted to about one third and induced for carotenogenesis. The bi-phase cultivation increased β- carotene productivity to 450 mg m-2 d-1 in stage one and to 300 mg m-2 d-1 in stage two, compared to the relatively low productivity of below 200 mg β- carotene m-2 d-1, in the conventional one phase type of cultivation. The results indicate that a selected algal product can be promoted specifically by growth manipulation of the alga and its environment.

Amniotic sac, fetal heart area, fetal curvature, and other morphometrics using first trimester vaginal ultrasonography and color Doppler imaging.

Ultrasonographic morphometric measurements were obtained with transvaginal ultrasonography from 121 patients with first trimester singleton pregnancies. Amniotic and gestational sac diameters, fetal heart area, and fetal length increased in a linear rate relative to crown-rump length, whereas the amniotic and gestational sac volumes increased at an exponential rate. The yolk sac exhibited a biphasic growth pattern with a peak at a crown-rump length of 3.5 cm. The ratio of crown-rump length to anteroposterior dimension increased over the first trimester, suggesting less curvature in older fetuses. In conclusion, vaginal ultrasonography permits accurate measurement of many new morphometric parameters.

Annual cycles of growth and reproduction in hatchery–reared Florida largemouth bass, Micropterus salmoides floridanus, raised on forage or pelleted diets

Annual cycles of growth and reproduction of hatchery–reared Florida largemouth bass, Micropterus salmoides floridanus, were investigated. Animals were raised on either forage (goldfish, Carassius auratus) or a pelleted salmon feed. Male and female year–class 1 largemouth bass were sampled throughout one complete yearly cycle (January–December). A biphasic growth cycle was observed in both forage–fed and pellet–fed fish. No increase in body length or weight was observed until approximately midway through the spawning period (May), after which fish grew at a consistent rate for the remainder of the study. The reproductive cycle of forage–fed fish was characterized by a rapid increase in gonadosomatic index (GS1) between January and April, followed by a prolonged spawning period (April–July) during which GSI progressively declined. Fully regressed gonads were observed in September and October, and a resumption of gonadal recrudescence was observed between October and December. Visceral adipose deposits (expressed as mesenteric fat index; MFI) were resorbed during gonadal growth and the initial stages of the spawning period, and restored during the post–spawning phase. Fish raised on pelleted feed had growth and reproductive cycles that parallelled those of forage–fed fish, but several significant differences were observed between the two diet groups. During the growth phase of the cycle, pellet–fed largemouth bass grew significantly faster than forage–fed largemouth bass, and had significantly larger MFIs than forage–fed largemouth bass at all times of the year. Pellet–fed fish also had significantly larger GSIs than forage–fed fish. These data indicate that diet composition may be an important determinant of growth and reproductive function in this species.

Modulation of breast cancer progression and differentiation by the gp30/heregulin [correction of neregulin

In the last decade we have come to understand that the growth of cancer cells in general and of breast cancer in particular depends, in many cases, upon growth factors that will bind to and activate their receptors. One of these growth factor receptors is the erbB-2 protein which plays an important role in the prognosis of breast cancer and is overexpressed in nearly 30% of human breast cancer patients. While evidence accumulates to support the relationship between erbB-2 overexpression and poor overall survival in breast cancer, understanding of the biological consequence(s) of erbB-2 overexpression remains elusive. Our recent discovery of the gp30 has allowed us to identify a number of related but distinct biological endpoints which appear responsive to signal transduction through the erbB-2 receptor. These endpoints of growth, invasiveness, and differententiation te have clear implications for the emergence, maintenance and/or control of malignancy, and represent established endpoints in the assessment of malignant progression in breast cancer. We have shown that gp30 induces a biphasic growth effect on cells with erbB-2 over-expression. We have recently determined the protein sequence of gp30 and cloned its full length cDNA sequence. We have also cloned two additional forms to the ligand, that are believed to be different isoforms. We are currently expressing the different forms in order to determine their biological effects. To elucidate the cellular mechanisms underlying cell growth inhibition by gp30, we tested the effect of this ligand on cell growth and differentiation of the human breast cancer cells which overexpress erbB-2 and cells which express low levels of this protooncogene.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of adenylate cyclase-cyclic AMP-dependent signal transduction in the ACTH-induced biphasic growth effect of rat adrenocortical cells in primary culture.

ACTH has a biphasic effect on the proliferation of fetal rat adrenocortical cells in primary culture. Dramatic changes occurred during the first 72 h of ACTH stimulation, when incorporation of bromodeoxyuridine was used as an indicator of proliferation. The primary effect of ACTH was the inhibition of proliferation during the first 24 h, which was followed by an intense stimulatory phase during the third day of ACTH treatment. Cycloheximide (a protein synthesis inhibitor) prevented both the inhibitory and the stimulatory effects of ACTH, but did not affect the basal proliferation of unstimulated zona glomerulosa-like cells. Although adrenocortical cells stimulated with cyclic AMP (cAMP) derivatives, 8-bromo cAMP (8-Br cAMP) or dibutyryl cAMP ((Bu)2cAMP), differentiated morphologically into fasciculata-like cells, and secreted corticosterone and 18-OH-deoxycorticosterone, as did ACTH-stimulated cells, neither of the derivatives inhibited proliferation during the first 24 h of treatment. In contrast to ACTH, (Bu)2cAMP had a stimulatory effect on bromodeoxyuridine incorporation during the first 24 h of treatment. 8-Br cAMP did not change proliferation during the 24 h of treatment, but had a stimulatory effect after 72 h, which was not seen with (Bu)2cAMP. Thus, these results suggest that (1) differentiation, steroid hormone synthesis and the mitogenic effect of ACTH are transduced through the cAMP-mediated system, (2) the antimitogenic effect of ACTH is transduced via a cAMP-independent pathway and (3) both antimitogenic and mitogenic effects of ACTH are dependent on protein synthesis.

Fermentation of lactose by yeast cells secreting recombinant fungal lactase.

Strains of Saccharomyces cerevisiae transformed with a yeast multicopy expression vector carrying the cDNA for Aspergillus niger secretory beta-galactosidase under the control of ADH1 promoter and terminator were studied for their fermentation properties on lactose (V. Kumar, S. Ramakrishnan, T. T. Teeri, J. K. C. Knowles, and B. S. Hartley, Biotechnology 10:82-85, 1992). Lactose was hydrolyzed extracellularly into glucose and galactose, and both sugars were utilized simultaneously. Diauxic growth patterns were not observed. However, a typical biphasic growth was observed on a mixture of glucose and galactose under aerobic and anaerobic conditions with transformants of a haploid S. cerevisiae strain, GRF167. Polyploid distiller's yeast (Mauri) transformants were selected simply on the basis of the cloned gene expression on X-Gal (5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside) plates. Rapid and complete lactose hydrolysis and higher ethanol (0.31 g/g of sugar) and biomass (0.24 g/g of sugar) production were observed with distiller's yeast grown under aerobic conditions. A constant proportion (10%) of the population retained the plasmid throughout the fermentation period (48 h). Nearly theoretical yields of ethanol were obtained under anaerobic conditions on lactose, glucose, galactose, and whey permeate media. However, the rate and the amount of lactose hydrolysis were lower under anaerobic than aerobic conditions. All lactose-grown cells expressed partial galactokinase activity.

Growth pattern in the Apert syndrome.

In this paper, we demonstrate that a discernible and unique growth pattern characterizes the Apert syndrome. The keys to understanding Apert newborn measurement values are brain size and cranial configuration. Both true megalencephaly and coronal synostosis are present at birth. Thus, the head is unusually heavy and the cranium is disproportionately high. Mean newborn length and weight are above the normal 50th centile. Of our newborn patients, 16% exceeded 4,000 g in weight. Preterm infants were appropriate or slightly large for gestational age. A biphasic linear growth pattern was found. In childhood, deceleration of linear growth occurs so that most values fall between the 5th and 50th centiles. From adolescence to adulthood, deceleration becomes more pronounced. This 2-step linear growth deceleration results in large measure from rhizomelic shortness of the lower limbs. Puberty takes place within the normal time frame. Although a disproportionate amount of the megalencephaly accounts for the dramatic increase in head height, the widely patent midline calvarial defect, allowing the brain to expand anteriorly into the metopic area, and some increase in the head breadth permit the mean head circumference at birth to normalize slightly above the 50th centile. During the growth period, the head circumference was studied in surgically unoperated Apert patients from the 1960s and earlier. The natural history of the growing cranium consists of gradual deceleration in head circumference from slightly above the 50th centile at birth to within or at -2 SD later on.

Growth pattern and ginsenoside production of Agrobacterium-transformed Panax ginseng roots

Panax ginseng roots transformed by Agrobacterium rhizogenes grew rapidly in a hormone-free medium. The transformed roots showed biphasic growth: rapid during the first two weeks and slower thereafter. Sucrose in the medium was almost all converted to glucose and fructose during the first two weeks, and the root growth slowed down after the depletion of sucrose in the medium. Periodic changes of the medium maintained the high growth rate, and the dry weight increased by 31 times in 32 days, which is the highest growth rate so far reported for cultured tissues of ginseng. The medium exchange also increased the ginsenoside content in the roots. Effective scale-up of the root culture was achieved in a turbine-blade type bioreactor.

Growth characteristics of Glycyrrhiza glabra cell suspension cultures

Callus and cell suspension cultures of licorice (Glycyrrhiza glabra) have been established in Gamborg's B5 medium supplemented with 2% sucrose, 1.0 mg 1-1 2,4-dichlorophenoxyacetic acid and 0.1 mg 1-1 kinetin. Biomass accumulation was affected by the density and age of inoculum, vessel size and sucrose level. 8% sucrose medium in 2-1 flasks induced biphasic growth, with fructose as the only source of carbon and energy in the second phase.

Magnitude and Kinetics of Stem Elongation Induced by Exogenous Indole-3-Acetic Acid in Intact Light-Grown Pea Seedlings.

Exogenously applied indole-3-acetic acid (IAA) strongly promoted stem elongation over the long term in intact light-grown seedlings of both dwarf (cv Progress No. 9) and tall (cv Alaska) peas (Pisum sativum L.), with the relative promotion being far greater in dwarf plants. In dwarf seedlings, solutions of IAA (between 10-4 and 10-3 M), when continuously applied to the uppermost two internodes via a cotton wick, increased whole-stem growth by at least 6-fold over the first 24 h. The magnitude of growth promotion correlated with the applied IAA concentration from 10-6 to 10-3 M, particularly over the first 6 h of application. IAA applied only to the apical bud or the uppermost internode of the seedling stimulated a biphasic growth response in the uppermost internode and the immediately lower internode, with the response in the latter being greatly delayed. This demonstrates that exogenous IAA effectively promotes growth as it is transported through intact stems. IAA withdrawal and reapplication at various times enabled the separation of the initial growth response (IGR) and prolonged growth response (PGR) induced by auxin. The IGR was inducible by at least 1 order of magnitude lower IAA concentrations than the PGR, suggesting that the process underlying the IGR is more sensitive to auxin induction. In contrast to the magnitude of the IAA effect in dwarf seedlings, applied IAA only doubled the growth in tall seedlings. These results suggest that endogenous IAA is more growth limiting in dwarf plants than in tall plants, and that auxin promotes stem elongation in the intact plant probably by the same mechanism of action as in isolated stem segments. However, since dwarf plants to which IAA was applied failed to reach the growth rate of tall plants, auxin cannot be the only limiting factor for stem growth in peas.

Utilisation of maltose and glucose by lactobacilli isolated from sourdough

The utilisation of glucose and maltose was investigated with Lactobacillus strains isolated from sourdough starters. These preparations have been in continuous use for a long period to produce sourdough from rye, wheat and sorghum. The major metabolic products formed by resting cells from glucose or maltose were lactate, ethanol and acetate. Upon fermentation of maltose, resting cells of Lactobacillus sanfrancisco, L. reuteri, L. fermentum and Lactobacillus ep. released up to 13.8 mM glucose after 8 h. The ratio of released glucose per mol of utilised maltose was up to 1:1. Glucose formation was high when starved cells of L. sanfrancisco and Lactobacillus sp. were used. This is consistent with maltose utilisation via maltose phosphorylase which phosphorylates maltose without the expenditure of ATP and thus allows the cell to waste glucose in the presence of abundant maltose. The glucose formed may be utilised by the lactobacilli or other microorganisms, e.g. yeasts. However, the release of glucose into the medium by sourdough lactobacilli prevents competitors from utilising the abundant maltose by glucose repression. In strains of L. sanfrancisco, maltose utilisation was very effective and not subject to glucose repression. Therefore, they overgrow other microorganisms sharing this habitat. Wild isolates of L. sanfrancisco were initially unable to grow on glucose. Upon growth on maltose such strains required adaptation times of up to 150 h to grow on glucose. After subsequent transfer of glucose-grown cells to fresh medium the strains resumed growth both on glucose or maltose. They readily lost their ability to grow on glucose upon exposure to maltose. L. sanfrancisco exhibited biphasic growth characteristics on media containing glucose, maltose or both carbon sources. Evidence is provided that biphasic growth and metabolite formation are dependent on the redox potential.

Utilisation of maltose and glucose by lactobacilli isolated from sourdough

The utilisation of glucose and maltose was investigated with Lactobacillus strains isolated from sourdough starters. These preparations have been in continuous use for a long period to produce sourdough from rye, wheat and sorghum. The major metabolic products formed by resting cells from glucose or maltose were lactate, ethanol and acetate. Upon fermentation of maltose, resting cells of Lactobacillus sanfrancisco, L. reuteri, L. fermentum and Lactobacillus ep. released up to 13.8 mM glucose after 8 h. The ratio of released glucose per mol of utilised maltose was up to 1:1. Glucose formation was high when starved cells of L. sanfrancisco and Lactobacillus sp. were used. This is consistent with maltose utilisation via maltose phosphorylase which phosphorylates maltose without the expenditure of ATP and thus allows the cell to waste glucose in the presence of abundant maltose. The glucose formed may be utilised by the lactobacilli or other microorganisms, e.g. yeasts. However, the release of glucose into the medium by sourdough lactobacilli prevents competitors from utilising the abundant maltose by glucose repression. In strains of L. sanfrancisco, maltose utilisation was very effective and not subject to glucose repression. Therefore, they overgrow other microorganisms sharing this habitat. Wild isolates of L. sanfrancisco were initially unable to grow on glucose. Upon growth on maltose such strains required adaptation times of up to 150 h to grow on glucose. After subsequent transfer of glucose-grown cells to fresh medium the strains resumed growth both on glucose or maltose. They readily lost their ability to grow on glucose upon exposure to maltose. L. sanfrancisco exhibited biphasic growth characteristics on media containing glucose, maltose or both carbon sources. Evidence is provided that biphasic growth and metabolite formation are dependent on the redox potential.

Herbivory and Its Consequences.

We argue that herbivores often induce nonlinear or biphasic growth and development in plants. Collectively these individual responses translate into a system-level optimization curve wherein at low levels of herbivory overall community responses show increases in production potential, whereas extreme herbivory causes extreme reduction in productivity. The transition between these two states defines a point of optimal herbivory in respect to C and N processes.We present four case examples from the literature demonstrating such nonlinear responses, suggesting a widespread existence for this herbivore-plant phenomenon. The nonlinear responses appear to demonstrate temporal and spatial scale dependencies.

The role of erbB2 signal transduction pathways in human breast cancer

The erbB2 receptor is expressed at very high levels in nearly 30% of human breast cancer patients and plays an important role in the transformation and the prognosis of breast cancer. While evidence accumulates to support the relationship between erbB2 overexpression and poor overall survival in human breast cancer, understanding of the biological consequence(s) of erbB2 overexpression remains elusive. Our recent discovery, cloning, sequencing, and expression of the erbB2 ligand (gp30) has allowed us to identify a number of related but distinct biological endpoints which appear responsive to signal transduction through the erbB2 receptor. These endpoints of growth, invasiveness, and differentiation have clear implications for the emergence, maintenance, and/or control of malignancy, and represent established endpoints in the assessment of malignant progression in breast cancer. Studies in vitro have shown that gp30 induces a biphasic growth effect (induction of growth at low concentrations and inhibition of growth at high concentrations) on cells with erbB2 over-expression. Strikingly, we have recently observed that the erbB2 signalling pathway can be modulated by estrogen acting through the estrogen receptor (ER). Conversely, we observed that down regulation of erbB2 by estrogen can be blocked by gp30 acting through the erbB2 receptor. Clearly, mechanistic aspects of the erbB2/ligand interaction need to be understood from a therapeutic standpoint, and may furthermore provide additional insights into treatment synergy for particular patients. We think that these studies will facilitate the emergence of erbB2-targeted therapy.