Determination of the maximum specific uptake capacities for glucose and oxygen in glucose-limited fed-batch cultivations of Escherichia coli

A simple pulse-based method for the determination of the maximum uptake capacities for glucose and oxygen in glucose limited cultivations of E. coli is presented. The method does not depend on the time-consuming analysis of glucose or acetate, and therefore can be used to control the feed rate in glucose limited cultivations, such as fed-batch processes. The application of this method in fed-batch processes of E. coli showed that the uptake capacity for neither glucose nor oxygen is a constant parameter, as often is assumed in fed-batch models. The glucose uptake capacity decreased significantly when the specific growth rate decreased below 0.15 h(-1) and fell to about 0.6 mmol g(-1) h(-1) (mmol per g cell dry weight and hour) at the end of fed-batch fermentations, where specific growth rate was approximately 0.02 h(-1). The oxygen uptake capacity started to decrease somewhat earlier when specific growth rate declined below 0.25 h(-1) and was 5 mmol g(-1) h(-1) at the end of the fermentations. The behavior of both uptake systems is integrated in a dynamic model which allows a better fitting of experimental values for glucose in fed-batch processes in comparison to generally used unstructured kinetic models.     

Catalysis of electron transfer by selenocysteine

Selenium is an essential element that is involved in biological redox processes. The electrode potentials of the selenocysteine half-reactions RSe(*) + e(-) --> RSe-, (RSeSeR)(*)(-) + e(-) --> 2 RSe(-), and RSeSeR + 2 e(-) --> 2 RSe(-) [E degrees' (pH 7)] are +0.43, +0.18, and -0.38 V, respectively, at pH 7. The spectra of RSe(*) and (RSeSeR)(*)(-) are characterized by absorption maxima at 460 nm (epsilon = 560 M(-)(1) cm(-)(1)) and 455 nm (epsilon = 7100 M(-)(1) cm(-)(1)), respectively. The bond dissociation energy of RSe-H has been calculated, and the value of 310 kJ/mol is in agreement with literature values. In comparison with the sulfur analogue cysteine, the more facile accessibility of the radical oxidation state is striking and may have biological implications, such as in mediation of one-electron- and two-electron-transfer processes, as illustrated by catalysis by selenocysteine of the electron transfer between dithiothreitol and benzyl viologen.     

Structural and functional characteristics of S1P receptors

The sphingosine-1-phosphate (S1P) family of G protein-coupled receptors (GPCR) regulates essential cellular processes such as proliferation, migration, cytoskeletal organization, adherens junction assembly, and morphogenesis. S1P, a product from the breakdown of sphingomyelin, binds to the five members of this receptor family, S1P(1), S1P(2), S1P(3), S1P(4), and S1P(5), previously referred to as endothelial differentiation gene (EDG)-1, -5, -3, -6, and -8. S1P receptors are widely expressed in different tissues, so it is not surprising that the S1P receptor family regulates many physiological processes, such as vascular maturation, cardiac development, lymphocyte trafficking, and vascular permeability. FTY720, a new S1P receptor agonist, is undergoing clinical trials as an immunosuppressor. Understanding the physiological role of these receptors and the basics of the ligand-receptor interaction will potentially provide new therapies to control a variety of diseases.     

Microbial processes of the carbon and sulfur cycles in the Chukchi Sea

The research performed in August 2004 within the framework of the Russian-American Long-term Census of the Arctic (RUSALCA) resulted in the first data concerning the rates of the key microbial processes in the water column and bottom sediments of the Bering strait and the Chukchi Sea. The total bacterial counts in the water column varied from 30 x 10(3) cells ml(-1) in the northern and eastern parts to 245 x 10(3) cells ml(-1) in the southern part. The methane content in the water column of the Chukchi sea varied from 8 nmol CH4 l(-1) in the eastern part of the sea to 31 nmol CH4 l(-1) in the northern part of the Herald Canyon. Active microbial processes occurred in the upper 0-3 cm of the bottom sediments; the methane formation rate varied from 0.25 to 16 nmol CH4 dm(-3) day(-1). The rates of methane oxidation varied from 1.61 to 14.7 nmol CH4 dm(-3) day(-1). The rates of sulfate reduction varied from 1.35 to 16.2 micromol SO4(2-) dm(-3) day(-1). The rate of methane formation in the sediments increased with depth, while sulfate reduction rates decreased (less than 1 micromol SO4(2-) dm(-3) day(-1)). These high concentrations of biogenic elements and high rates of microbial processes in the upper sediment layers suggest a specific type of trophic chain in the Chukchi Sea. The approximate calculated balance of methane emission from the water column into the atmosphere is from 5.4 to 57.3 micromol CH4 m(-2) day(-1).     

Thermodynamics of the hydrolysis of sucrose

A thermodynamic investigation of the hydrolysis of sucrose to fructose and glucose has been performed using microcalorimetry and high-pressure liquid chromatography. The calorimetric measurements were carried out over the temperature range 298-316 K and in sodium acetate buffer (0.1 M, pH 5.65). Enthalpy and heat capacity changes were obtained for the hydrolysis of aqueous sucrose (process A): sucrose(aq) + H2O(liq) = glucose(aq) + fructose (aq). The determination of the equilibrium constant required the use of a thermochemical cycle calculation involving the following processes: (B) glucose 1-phosphate2-(aq) = glucose 6-phosphate2-(aq); (C) sucrose(aq) + HPO4(2-)(aq) = glucose 1-phosphate2-(aq) + fructose(aq); and (D) glucose 6-phosphate2-(aq) + H2O(liq) = glucose(aq) + HPO4(2-)(aq). The equilibrium constants determined at 298.15 K for processes B and C are 17.1 +/- 1.0 and 32.4 +/- 3.0, respectively. Equilibrium data for process D was obtained from the literature, and in conjunction with the data for processes B and C, used to calculate a value of the equilibrium constant for the hydrolysis of aqueous sucrose. Thus, for process A, delta G0 = -26.53 +/- 0.30 kJ mol-1, K0 = (4.44 +/- 0.54) x 10(4), delta H0 = -14.93 +/- 0.16 kJ mol-1, delta So = 38.9 +/- 1.2 J mol-1 K-1, and delta CoP = 57 +/- 14 J mol-1 K-1 at 298.15 K. Additional thermochemical cycles that bear upon the accuracy of these results are examined.     

Measurement of ingestion rate of Hydrobia ulvae (Pennant) on intertidal epipelic microalgae: the effect of mud snail density

The individual mean ingestion rate of Hydrobia ulvae was measured experimentally in controlled microcosms, in the dark to avoid primary production during measurement and at constant temperature. The experimental design was based on the addition of prelabelled epipelic microalgae to microcosms in a constant proportion with unlabelled diatoms, and in such a way that algal food availability was not a limiting factor within the range of tested densities (0.3 to 4.1 snails cm(-2)). Results show that the individual mean ingestion rate decreased significantly from 26.6+/-1.1 ng Chl a snail(-1) h(-1) to 22.4+/-1.0 ng Chl a snail(-1) h(-1) between 0.7 and 3 snails cm(-2). We hypothesize that this sharp decrease (the threshold density was between 1.4 and 2.5 snails cm(-2)) may account for a density-dependent effect. We have tested this hypothesis by using a simple random walk model including basic behavioural processes such as a break in feeding activity when two individuals contact each other. The model represents quantitatively well the threshold effect, suggesting that behavioural processes have to be taken into account for estimating a global feeding activity of H. ulvae populations.     

JNK1 is required for maintenance of neuronal microtubules and controls phosphorylation of microtubule-associated proteins

Microtubules (MTs) play an important role in elaboration and maintenance of axonal and dendritic processes. MT dynamics are modulated by MT-associated proteins (MAPs), whose activities are regulated by protein phosphorylation. We found that a member of the c-Jun NH(2)-terminal protein kinase (JNK) subgroup of MAP kinases, JNK1, is involved in regulation of MT dynamics in neuronal cells. Jnk1(-/-) mice exhibit disrupted anterior commissure tract formation and a progressive loss of MTs within axons and dendrites. MAP2 and MAP1B polypeptides are hypophosphorylated in Jnk1(-/-) brains, resulting in compromised ability to bind MTs and promote their assembly. These results suggest that JNK1 is required for maintaining the cytoskeletal integrity of neuronal cells and is a critical regulator of MAP activity and MT assembly.     

Receptor-induced degradation of atrial natriuretic peptide by a rabbit carotid artery smooth muscle cell

We have used a smooth muscle cell line isolated from rabbit carotid artery (RCA) as a model system with which to study the expression of atrial natriuretic peptide (ANP) receptors and, in addition, the receptor-mediated degradation of ANP. RCA cells bind rat alpha ANP-(1-28) reversibly at 37 C, apparently to a single class of high affinity (Kd approximately equal to 50 pM) binding sites (approximately equal to 20,000 sites per cell). Binding of rat alpha ANP-(1-28) elicits rapid accumulation of intracellular cGMP. However, the concentrations of rat alpha ANP-(1-28) and related peptides, abbreviated at the N- and C-terminals, required to stimulate cGMP synthesis are substantially greater than those required for binding. Analysis by HPLC of 125I-labeled rat alpha ANP-(1-28) bound to RCA cells at 37 C illustrates the rapid and continuous degradation of the radioiodinated rat alpha ANP-(1-28) to two radiolabeled products, one of which, 125I-labeled tyrosine is the major radiolabeled component that dissociates from the cells. Measurement of rat alpha ANP-(1-28) interaction with RCA cells by radioligand binding techniques therefore subsumes several processes. One of these processes is the rapid and continuous degradation of specifically bound ANP by these cells and perhaps also other target cells that respond to ANP.     

Disposition of norepinephrine and epinephrine in jejunum of WLH chicken.

Disposition of (-)-norepinephrine and (-)-epinephrine in jejunum of WLH chicken was studied using oil-immersion technique. The relative rate of different routes of disposition of catecholamines was in the following order: for (-)-NE COMT greater than or equal to MAO greater than or equal to U2 greater than U1, for (-)-Epi U2 greater than or equal to COMT greater than MAO greater than U1. The role of enzymatic degradation is almost equal to that of uptake processes for (-)-Epi, but it was greater for (-)-NE.     

Cutting edge: a small molecule antagonist of LFA-1-mediated cell adhesion.

LFA-1 (CD18,CD11a) is a cell-adhesion molecule that mediates critical immunological processes. In this paper we report the discovery and characterization of (R)-5-(4-bromobenzyl)-3-(3, 5-dichlorophenyl)-1,5-dimethylimidazolidine-2,4-dione (BIRT 377), an orally bioavailable small molecule that interacts specifically with LFA-1 via noncovalent binding to the CD11a chain and prevents LFA-1 from binding to its ligand, ICAM-1. BIRT 377 inhibits lymphocyte activity both in vitro and in vivo, in functional assays that require LFA-1-mediated cell adhesion. These results demonstrate that LFA-1-mediated leukocyte adhesion can be antagonized with noncharged, low m.w. molecules and suggest that the potential therapeutic value of adhesion inhibitors can be attained with a small, orally bioavailable compound.     

Mash1 is required for generic and subtype differentiation of hypothalamic neuroendocrine cells

The neuroendocrine hypothalamus regulates a number of critical biological processes and underlies a range of diseases from growth failure to obesity. Although the elucidation of hypothalamic function has progressed well, knowledge of hypothalamic development is poor. In particular, little is known about the processes underlying the neurogenesis and specification of neurons of the ventral nuclei, the arcuate and ventromedial nuclei. The proneural gene Mash1 is expressed throughout the basal retrochiasmatic neuroepithelium and loss of Mash1 results in hypoplasia of both the arcuate and ventromedial nuclei. These defects are due to a failure of neurogenesis and apoptosis, a defect that can be rescued by ectopic Ngn2 under the control of the Mash1 promoter. In addition to its role in neurogenesis, analysis of Mash1(-/-), Mash1(+/-), Mash1(KINgn2/KINgn2), and Mash1(KINgn2/+) mice demonstrates that Mash1 is specifically required for Gsh1 expression and subsequent GHRH expression, positively regulates SF1 expression, and suppresses both tyrosine hydroxylase (TH) and neuropeptide Y (NPY) expression. Although Mash1 is not required for propiomelanocortin (POMC) expression, it is required for normal development of POMC(+) neurons. These data demonstrate that Mash1 is both required for the generation of ventral neuroendocrine neurons as well as playing a central role in subtype specification of these neurons.     

Studies on the transport of aliphatic glucosides by hamster small intestine in vitro.

It has been found (1) that glucosides with a long alkyl chain (2-18 carbon atoms) as the aglycone can be transported by carrier-mediated processes in the hamster small intestine in vitro, (2) that these glucosides interact with the glucose carrier, and (3) that they compete with glucose and analogs for the binding to the carrier. The are Na+- and phlorizin-insensitive components of uptake for the long chain alkyl glucosides which suggest additional interactions or uptake processes.     

The scoliosis (sco) mouse: a new allele of Pax1

We describe the spontaneous mutant mouse scoliosis (sco) that carries a new allele of Pax1 (un-i, undulated intermediate). The Pax1(un-i) allele is lacking the 5'-flanking region and exon 1 to 4 which is mapped to nt -2636 to -640 and -272 to 4271 of the Pax1 gene. Homozygous mice show a mild form of the known phenotypes of other Pax1 mutants. Adult mice have a lumbar scoliosis and kinky tails. In homozygous embryos the skeleton ossifies early, ossification centers of the vertebral bodies are fused with the ossification centers of the pedicles. Neural arches and spinous processes are underdeveloped but the pedicles and transverse processes are overdeveloped which is in contrast to other Pax1 mutants. In the scapula, the acromion is missing and the deltoid tuberosity of the proximal humerus is shortened and thickened. Among the inner organs the thymus development is affected. In late embryos, the thymus is small and thymocyte numbers are reduced. T-cell development from CD4- and CD8- double negative (DN) to CD4+ and CD8+ double positive (DP) is decelerated. The percentage of CD90+ cells is also reduced but in contrast to other Pax1 mutants no alteration of the expression level of the CD90 (Thy-1) could be found.     

Long noncoding RNA LEF1-AS1 silencing suppresses the initiation and development of prostate cancer by acting as a molecular sponge of miR-330-5p via LEF1 repression

Prostate cancer (PCa) is one of the major cancers affecting males with high mortality around the world. Recent studies have found that some long noncoding RNAs play a critical part in the cellular processes of PCa. In our study, aberrant expressed lymphoid enhancer-binding factor-1 antisense RNA 1 (LEF1-AS1), microRNA-330-5p (miR-330-5p), and lymphoid enhancer-binding factor-1 (LEF1) were screened out from a microarray database, the role of the novel noncoding RNA regulatory circuitry in the initiation and development of PCa was investigated. LEF1-AS1 and LEF1 were highly expressed while miR-330-5p was poorly expressed in PCa. Following that, the PCa PC-3 cell line was adopted for subsequently experiments, in which the expression of LEF1-AS1 and miR-330-5p was subsequently altered by means of exogenous transfection. After that, the effects of up- or downregulation of LEF1-AS1 and miR-330-5p on epithelial–mesenchymal transition (EMT) and the cell ability for proliferation, invasion, migration in vitro, and tumorigenesis and lymph node metastasis (LNM) in vivo were evaluated. RNA crosstalk revealed that LEF1-AS1 bound to miR-330-5p and LEF1 was the target gene of miR-330-5p. Silenced LEF1-AS1 or elevated miR-330-5p exhibited inhibited EMT processes, reduced ability of proliferation, invasion and migration, coupling with decreased tumorigenesis and LNM in nude mice. The key findings of this study collectively propose downregulation of LEF1-AS1 competing with miR-330-5p to inhibit EMT, invasion and migration of PCa by LEF1 repression.     

Proteomics Study of COI1-regulated Proteins in Arabidopsis Flower

Jasmonates (JAs) are a new class of plant hormone that regulate expression of diverse genes to mediate various plant responses. The Arabidopsis F-box protein COM is required for plant defense and male fertility in JA signal pathway. To further investigate the regulatory role of COM in male fertility, we compared the proteomics profiles of Arabidopsis wild type (WT) flowers with coi1-1 mutant male-sterile flowers using two-dimensional difference gel electrophoresis coupled with matrix-assisted laser desoption/ionization-time-of-flight mass spectrometry. Sixteen proteins with potential function in specific biological processes such as metabolism processes and defense/stress responses were differentially expressed in WT and coi1-1 mutant flowers. Verification on a phi class glutathione transferase AtGSTF9, one out of these 16 identified proteins, revealed that the expression of AtGSTF9 was severely downregulated in flowers of coi1-1 mutant compared with that of WT. Further function analyses of these genes would provide new insights into the molecular basis of COI1-regulated male fertility.     

The effect of angiotensin 1-7 on tyrosine kinases activity in rat anterior pituitary

Angiotensin 1-7 (Ang 1-7) is a peptide originated from Ang II. It is known that in vessels Ang 1-7 shows opposite effects to Ang II. Ang 1-7 can modify processes of proliferation. However, Ang 1-7 action in pituitary gland cells was never studied. Moreover, the specific binding sites for Ang 1-7 are still unknown. The aim of this study was to examine the effects of Ang 1-7 on tyrosine kinases (PTKs) activity in the anterior pituitary. The reaction of phosphorylation was carrying out in presence of different concentration of Ang 1-7 and losartan (antagonist of AT1 receptor) and PD123319 (antagonist of AT2). Our results show that Ang 1-7 inhibited activity of PTK to 60% of basic activity. Losartan did not change the Ang 1-7-induced changes in PTKs activity. The presence of PD123319 together with Ang 1-7 caused stronger inhibition PTKs activity than Ang 1-7 alone. These observations suggest that Ang 1-7 binds to the novel, unknown, specific for this peptide receptor.     

The relationship of regulatory proteins and DNase I hypersensitive sites in the yeast GAL1-10 genes.

We have used yeast strains containing a disrupted positive (GAL4) and/or a disrupted negative (GAL80) regulatory gene to investigate the relationship of these regulatory proteins to the hypersensitive sites upstream of their target genes, GAL1-10. We find that neither of these regulatory proteins is required for the formation of the hypersensitive region. There is positive regulatory protein (dependent) binding to a portion of the hypersensitive region when GAL1 and 10 are expressed. However, similar binding can also occur under conditions in which the genes are not expressed. Thus, such binding is necessary but not sufficient for expression of GAL1 and 10 and control of GAL1-10 expression must also include processes which occur subsequent to GAL4/DNA binding. The negative regulatory protein GAL80 plays a significant role in these processes.     

Bacterial transformation and biodegradation processes simulation in horizontal subsurface flow constructed wetlands using CWM1-RETRASO

The performance and reliability of the CWM1-RETRASO model for simulating processes in horizontal subsurface flow constructed wetlands (HSSF CWs) and the relative contribution of different microbial reactions to organic matter (COD) removal in a HSSF CW treating urban wastewater were evaluated. Various different approaches with diverse influent configurations were simulated. According to the simulations, anaerobic processes were more widespread in the simulated wetland and contributed to a higher COD removal rate [72-79%] than anoxic [0-1%] and aerobic reactions [20-27%] did. In all the cases tested, the reaction that most contributed to COD removal was methanogenesis [58-73%]. All results provided by the model were in consonance with literature and experimental field observations, suggesting a good performance and reliability of CWM1-RETRASO. According to the good simulation predictions, CWM1-RETRASO is the first mechanistic model able to successfully simulate the processes described by the CWM1 model in HSSF CWs.