Effect of time delay in specific growth rate on the periodic operation of bioreactors with input multiplicities

The effect of time delay in specific growth rate () on the periodic operation of bioreactors with input multiplicities is theoretically analyzed for productivity improvement. A periodic rectangular pulse is applied either in feed substrate concentration (S_f) or in dilution rate (D). Periodic operation under feed substrate concentration cycling gives improvement in productivity at lower value of ¯S_f of the two steady-state multiplicities of S_f only when the time delay in is larger. Whereas the larger value of ¯S_f gives improvement in average productivity for all values of time delay. Dilution rate (D) cycling gives an improvement in average productivity particularly for larger time delay in . This improvement in average productivity is obtained only at smaller value of dilution rate out of the two steady-state input multiplicities of D.List of Symbols D 1/h dilution rate - F memory function - g dummy variable - K_i g/l substrate inhibition constant - K_m g/l substrate saturation constant - P g/l product concentration - P_m g/l product saturation constant - Q g/(hl) product cell produced per unit time - S g/l substrate concentration - S_f g/l feed substrate concentration - S_f,p g/l feed substrate concentration during fraction of a period - X g/l biomass concentration - Y_X/S g/g cell mass yield - w variable either S or Z - Z g/l weighted average of substrate concentration Greek Letters 1/h time delay parameter - ₁ , ₂ product yield parameters, g/g and 1/h - pulse width expressed as a fraction of a period - 1/h specific growth rate - _m 1/h maximum specific growth rate - h period of oscillation - – average value     

Different binding of RNA polymerase to individual promoters

Summary The amount of E. coli RNA polymerase which can be bound to individual promoters on pgal and dgal phage DNA in a stable heparin-resistant form was measured by assessing its capacity to transcribe, upon addition of the nucleoside triphosphates, the RNA sequences starting at these promoters. These RNA species were analysed by competition hybridization to separated single strands of , pgal and dgal phage DNA.Individual promoters bind, at saturation, different numbers of polymerase molecules. From the amount of polymerase necessary to saturate all promoters (Fig. 3), from the proportions of RNA synthesized at the individual promoters (Table 1) and from the amounts of -³²P-ATP or-GTP label incorporated into the different RNA species (Tables 2 and 3) we calculate polymerase storage capacities for the promoters as follows: gal: 6 molecules; l-strand specific: 3–5 molecules starting with ATP and 1 molecule starting with GTP; r-strand specific: 3–5 molecules starting with ATP (and perhaps one molecule starting with GTP); these estimates are lower limits and may be too small by a factor of up to three.The heparin resistant binding of six polymerase molecules to the gal promoter is dependent on CGA protein and cAMP, but ATP and GTP can allow one polymerase to bind to the same site or to a very close one.Several parameters of polymerase binding are different with the individual promoters tested.     

Adaptive phenotypic plasticity in the Midas cichlid fish pharyngeal jaw and its relevance in adaptive radiation

Background  

Phenotypic evolution and its role in the diversification of organisms is a central topic in evolutionary biology. A neglected factor during the modern evolutionary synthesis, adaptive phenotypic plasticity, more recently attracted the attention of many evolutionary biologists and is now recognized as an important ingredient in both population persistence and diversification. The traits and directions in which an ancestral source population displays phenotypic plasticity might partly determine the trajectories in morphospace, which are accessible for an adaptive radiation, starting from the colonization of a novel environment. In the case of repeated colonizations of similar environments from the same source population this "flexible stem" hypothesis predicts similar phenotypes to arise in repeated subsequent radiations. The Midas Cichlid (Amphilophus spp.) in Nicaragua has radiated in parallel in several crater-lakes seeded by populations originating from the Nicaraguan Great Lakes. Here, we tested phenotypic plasticity in the pharyngeal jaw of Midas Cichlids. The pharyngeal jaw apparatus of cichlids, a second set of jaws functionally decoupled from the oral ones, is known to mediate ecological specialization and often differs strongly between sister-species.     

Cochlear function in mice following inhalation of brevetoxin-3

Brevetoxin-3 was shown previously to adversely affect central auditory function in goldfish. The present study evaluated the effects of exposure to this agent on cochlear function in mice using the 2f₁-f₂ distortion-product otoacoustic emission (DPOAE). Towards this end, inbred CBA/CaJ mice were exposed to a relatively high concentration of brevetoxin-3 (~400 g/m³) by nose-only inhalation for a 2-h period. Further, a subset of these mice received a second exposure a day later that lasted for an additional 4 h. Mice exposed only once for 2 h did not exhibit any notable cochlear effects. Similarly, mice exposed two times, for a cumulative dose of 6 h, exhibited essentially no change in DPOAE levels.     

Anti‐Helicobacter pylori therapy in localized gastric mucosa‐associated lymphoid tissue lymphoma: A prospective,nationwide, multicenter study in Japan

Background

Helicobacter pylori eradication therapy was approved in Japan for the first‐line, standard treatment of H. pylori‐positive gastric mucosa‐associated lymphoid tissue (MALT) lymphoma. Although several retrospective studies or small‐scale single‐center studies have been reported, a prospective, large‐scale, nationwide, multicenter study has not been reported from Japan.

Materials and Methods

We conducted a prospective, nationwide, multicenter study to evaluate the clinical efficacy of rabeprazole‐based triple H. pylori eradication therapy for patients with localized gastric MALT lymphoma in practice‐based clinical trial. A total of 108 H. pylori‐positive patients with stage I/II₁ gastric MALT lymphoma underwent H. pylori eradication therapy. The primary endpoints were complete remission (CR) rate and the rate of transfer to secondary treatment. The secondary endpoints were CR maintenance duration and overall survival (OS).

Results

CR of lymphoma was achieved in 84 of 97 patients (86.6%), during the period 2.0‐44.7 months (median, 5.3 months) after starting H. pylori eradication treatment. CR was maintained in 77 of 81 patients (95.1%) for 0.4‐53.2 months (median, 33.1 months). Secondary treatments (radiotherapy, rituximab, or gastrectomy) for gastric MALT lymphoma were needed in 10 of the 97 patients (10.31%). During follow‐up, OS rate was 96.9% (94/97) and the causes of 3 deaths were not related to lymphoma.

Conclusions

Rabeprazole‐based H. pylori eradication therapy demonstrated a high CR rate, long CR maintenance, and a good OS for patients with localized gastric MALT lymphoma in this prospective, practice‐based, multicenter study.     

Cloning and characterization of cDNAs encoding putative CTCFs in the mosquitoes, <Emphasis Type="Italic">Aedes aegypti</Emphasis> and <Emphasis Type="Italic">Anopheles gambiae</Emphasis>

Background  

One of the many ascribed functions of CCCTC-binding factor (CTCF) in vertebrates is insulation of genes via enhancer-blocking. Insulation allows genes to be shielded from "cross-talk" with neighboring regulatory elements. As such, endogenous insulator sequences would be valuable elements to enable stable transgene expression. Recently, CTCF joined Su(Hw), Zw5, BEAF32 and GAGA factor as a protein associated with insulator activity in the fruitfly, Drosophila melanogaster. To date, no known insulators have been described in mosquitoes.     

MIF‐173G/C (rs755622) polymorphism as a risk factor for acute lymphoblastic leukemia development in children

Background

Macrophage inhibitory factor (MIF) is a pro‐inflammatory cytokine modulating monocyte motility and a pleiotropic regulator of different biological and cellular processes. The MIF‐173G/C (rs755622) polymorphism is found in the promoter region and affects its activity. The present study investigated the MIF polymorphism as a risk factor for the development of acute lymphoblastic leukemia (ALL) in Egyptian children.

Methods

We analyzed the MIF‐173G/C (rs755622) polymorphism in 180 ALL cases and 150 healthy control children by amplification of the gene using a polymerase chain reaction followed by restriction endonuclease digestion and running on an agarose gel for visualization of the product.

Results

We found a significant incidence of the homozygous polymorphic (CC) genotype and the combined polymorphic genotypes (GC + CC) in ALL patients compared to healthy controls (p = 0.001 and p = 0.007, respectively), whereas the wild‐type genotype (GG) was more common in healthy controls (p = 0.006). Multivariate logistic regression analysis adjustment for MIF different genotypes and other potential risk factors such as age, sex and parental smoking indicated that the CC genotype is the only significant risk factor for the test (p = 0.02). We also noted that, by increasing the C‐allele representation within the gene [GC, CC], there was an increase in total leukocytic count (p = 0.09 and p = 0.001, respectively) that may reflect the bad prognostic impact of the polymorphic allele, although further studies are needed.

Conclusions

The results of the present study indicate that the MIF‐173G/C (rs755622) polymorphism is a risk factor for childhood ALL development with respect to both homozygous and combined polymorphic genotypes. In addition, the increased leukocytic count in synchronization with the increased representation of the polymorphic C‐allele may reflect its bad prognostic impact.     

Embryonic sympathoblasts transiently express TrkB <Emphasis Type="Italic">in vivo</Emphasis> and proliferate in response to brain-derived neurotrophic factor <Emphasis Type="Italic">in vitro</Emphasis>

Background  

Nerve growth factor and neurotrophin-3 are involved in the development of sympathetic neurons; however, whether brain derived neurotrophic factor also plays a role is not known. The purpose of this study was to determine whether BDNF and its receptor, TrkB, are expressed during the development of paravertebral sympathetic ganglia in vivo and to determine the effect of BDNF in vitro.     

Structural aspects of the cytochromeb 6 f complex; structure of the lumen-side domain of cytochromef

The following findings concerning the structure of the cytochromeb ₆ f complex and its component polypeptides, cytb ₆, subunit IV and cytochromef subunit are discussed:

FGF10 maintains distal lung bud epithelium and excessive signaling leads to progenitor state arrest,distalization, and goblet cell metaplasia

Background  

Interaction with the surrounding mesenchyme is necessary for development of endodermal organs, and Fibroblast growth factors have recently emerged as mesenchymal-expressed morphogens that direct endodermal morphogenesis. The fibroblast growth factor 10 (Fgf10) null mouse is characterized by the absence of lung bud development. Previous studies have shown that this requirement for Fgf10 is due in part to its role as a chemotactic factor during branching morphogenesis. In other endodermal organs Fgf10 also plays a role in regulating differentiation.     

Identification of two proteins that interact with the Erp virulence factor from Mycobacterium tuberculosis by using the bacterial two-hybrid system

Background  

The exported repetitive protein (erp) gene encodes a secreted 36-kDa protein with a central domain containing several proline-glycine-leucine-threonine-serine (PGLTS) repeats. It has been demonstrated that erp is a virulence-associated factor since the disruption of this gene impairs the growth of Mycobacterium bovis and Mycobacterium tuberculosis in mice.     

The hemolytic and cytolytic activities of Serratia marcescens phospholipase A (PhlA) depend on lysophospholipid production by PhlA

Background  

Serratia marcescens is a gram-negative bacterium and often causes nosocomial infections. There have been few studies of the virulence factors of this bacterium. The only S. marcescens hemolytic and cytotoxic factor reported, thus far, is the hemolysin ShlA.