A hidden square-root boundary between growth rate and biomass yield

Although the theoretical value of biomass yield can be calculated from metabolic network stoichiometry, the growth rate is difficult to predict. Since the rate and yield can vary independently, no simple relationship has been discovered between these two variables. In this work, we analyzed the well-accepted enzyme kinetics and uncovered a hidden boundary for growth rate, which is determined by the square-root of three physiological parameters: biomass yield, the substrate turnover number, and the maximum synthesis rate of the turnover enzyme. Cells cannot grow faster than the square-root of the product of these parameters. This analysis is supported by experimental data and involves essentially no assumptions except (i) the cell is not undergoing a downshift transition, (ii) substrate uptake enzyme activity is proportional to its copy number. This simple boundary (not correlation) has escaped notice for many decades and suggests that the yield calculation does not predict the growth rate, but gives an upper limit for the growth rate. The relationship also explains how growth rate is affected by the yield and sheds lights on strain design for product formation.     

Qiliqiangxin regulates the balance between tumor necrosis factor-α and interleukin-10 and improves cardiac function in rats with myocardial infarction

The study investigated the effects of traditional Chinese drug Qiliqiangxin on cardiac function and the expression of pro/anti-inflammatory cytokines TNF-α/IL-10 in rats with myocardial infarction (MI). Rats with MI were randomly divided into drug-treated group (MI-Q) and control group (MI-C) compared with sham-operated group (S). Rats in the MI-Q group were treated with crude drug of oral Qiliqiangxin 24 h after operation at the dosage of 4 g/kg/day for 4 weeks, while in MI-C group and S group were treated with normal saline at the same time. Echocardiography and hemodynamic parameters, histopathologic changes and the expression of myocardial cytokines including TNF-α and IL-10 were assessed 4 weeks after the drug therapy. The results indicated that rats of the MI-C group exhibited decreased cardiac function and increased ratio of TNF-α/IL-10 which principally secreted by myocardium compared with those of the S group and Qiliqiangxin treatment significantly improved cardiac function and histopathologic changes with down-regulated ratio of TNF-α/IL-10. These data suggests that Qiliqiangxin may improve cardiac function of rats with MI through regulation the balance between TNF-α and IL-10.     

Pyrrolo[2,1-c][1,4]benzodiazepine and indole conjugate (IN6CPBD) has better efficacy and superior safety than the mother compound DC-81 in suppressing the growth of established melanoma in vivo

Melanoma is one of the most chemo-resistant cancers. The remission rate of current therapy remains low. Pyrrolo[2,1-c][1,4]benzodiazepines (PBDs) are a group of antitumor antibiotics that binds to N2 of guanine to form a DNA adduct. However, significant cardiotoxicity hampers their clinical use. We have previously synthesized a PBD indole conjugate (IN6CPBD) that induced apoptosis in several cancer cell lines. The purpose of this study was to assess the efficacy and safety of the IN6CPBD for established murine melanoma cells in vivo. IN6CPBD induced more apoptosis than DC-81 as evidenced by sub-G1 distribution, annexin V positivity, and decrease mitochondrial membrane potential (ΔΨ_mt). The melanomas were established in C57BL/6 mice by injecting B16F10 cells via the tail vein. Three courses of therapy were instituted after day 5 and the mice were sacrificed at day 20. The tumor growth rate in the foot pad was significantly reduced in IN6CPBD-treated mice than that in DC-81- and PBS-treated mice. The tumor burden in the lungs was also reduced significantly in IN6CPBD-treated mice accompanied with the most prominent TUNEL staining. Renal function, and cardiac enzymes were not altered significantly by IN6CPBD or DC-81, however, robust deterioration of liver function was noticed in the DC-81-treated mice. In summary, potent apoptosis could be elicited by the PBD indole conjugate IN6CPBD, accompanied with a better efficacy and less liver function impairment than the mother compound DC-81 in treating established melanoma metastasis in vivo.     

Trafficking of receptor tyrosine kinases to the nucleus

It has been known for at least 20 years that growth factors induce the internalization of cognate receptor tyrosine kinases (RTKs). The internalized receptors are then sorted to lysosomes or recycled to the cell surface. More recently, data have been published to indicate other intracellular destinations for the internalized RTKs. These include the nucleus, mitochondria, and cytoplasm. Also, it is recognized that trafficking to these novel destinations involves new biochemical mechanisms, such as proteolytic processing or interaction with translocons, and that these trafficking events have a function in signal transduction, implicating the receptor itself as a signaling element between the cell surface and the nucleus.     

A new Cu-Mn heterobinuclear complex exhibiting magnetization relaxation

A new heterometallic complex [CuMn(5-Brsap)₂(MeOH)(Ac)] ⋅ CH₃OH (1) (5-Brsap = 5-bromo-2-salicylideneamino-1-propanol) has been synthesized and characterized structurally as well as magnetically. Complex 1 has an alkoxo-bridged Cu(II) and Mn(III) heterobinuclear core, where the Mn(III) and Cu(II) ions have elongated octahedral and square-pyramidal geometries, respectively. In dc magnetic susceptibility measurements reveal that there is strong ferromagnetic interaction between the Mn(III) and Cu(II) ions with an exchange coupling constant J = 67.64 cm⁻¹. The ac magnetic susceptibility measurements, frequency dependence in both the real and imaginary signals is observed, which indicates slow relaxation of magnetization. An Arrhenius plot gave the effective anisotropy barrier Δ/k_B = 11.58 K and the pre-exponential factor ι₀ = 1.28 × 10⁻⁶ s.     

Synthesis, crystal structure and magnetic properties of a one-dimensional Mn(III) Schiff-base complex bridged by derivative of tetracyano-p-quinodimethane

A new one-dimensional manganese(III) Schiff-base complex [Mn(III)(salophen) (MeOTCNQ)] · CH₃CN 1 (salophen = N,N′-bis(salicylidene)phenylenediamine) bridged by 7-methoxy-7,7,8,8-tetra-cyano-p-quinodimethane (MeOTCNQ), has been synthesized and characterized by X-ray crystallography and magnetic studies. Crystal structure study reveals that complex 1 has a 1D manganese(III) chain bridged by MeOTCNQ ligand which was obtained unexpectedly from tetracyano-p-quinodimethane (TCNQ) reacting with methanol. Noticeably, MeOTCNQ molecules in complex 1 adopt an unusual cis-syn coordination mode. The analysis of magnetic data indicates that a weak intrachain antiferromagnetic interaction exists in complex 1.     

Synergistic effect of indomethacin and NGX6 on proliferation and invasion by human colorectal cancer cells through modulation of the Wnt/β-catenin signaling pathway

This study was designed to investigate whether indomethacin and NGX6 synergistically inhibit the growth and invasiveness of human colon cancer cells (HT-29 and SW620) and to elucidate the molecular mechanism of their action. Cell proliferation was assessed by MTT assay. Cell apoptosis was assessed by acridine orange/ethidium bromide staining (AO–EB) and annexin-V-FITC/PI assay. Invasive behaviors of colorectal cancer cells were examined by cell adhesion, migration, and invasion assays. Gap junctional intercellular communication (GJIC) was assessed by the scrape-loading/dye transfer technique. The subcellular localization and expression of β-catenin protein was examined by immunofluorescence staining and western blot analysis, respectively. Indomethacin and NGX6 had a synergistic effect on inhibiting proliferation and invasiveness of colon cancer HT-29 and SW620 cells, restoring GJIC of HT-29 and SW620, and suppressing translocation of β-catenin from the nucleus and cytoplasm to the plasma membrane. However, they did not have synergistic effects on enhancing apoptosis and suppressing extracellular matrix adhesion of HT-29 and SW620 cells. Indomethacin and NGX6 inhibit the proliferation and invasiveness of HT-29 and SW620 colon cancer cells by attenuating the WNT/ß-catenin signaling pathway.     

Functional role of EF-hands 3 and 4 in membrane-binding of KChIP1

The aim of the present study is to explore whether membrane targeting of K⁺ channel-interacting protein 1 (KChIP1) is associated with its EF-hand motifs and varies with specific phospholipids. Truncated KChIP1, in which the EFhands 3 and 4 were deleted, retained the α-helix structure, indicating that the N-terminal half of KChIP1 could fold appropriately. Compared with wild-type KChIP1, truncated KChIP1 exhibited lower lipid-binding capability. Compared with wild-type KChIP1, increasing membrane permeability by the use of digitonin caused a marked loss of truncated KChIP1, suggesting that intact EF-hands 3 and 4 were crucial for the anchorage of KChIP1 on membrane. KChIP1 showed a higher binding capability with phosphatidylserine (PS) than truncated KChIP1. Unlike that of truncated KChIP1, the binding of wild-type KChIP1 with membrane was enhanced by increasing the PS content. Moreover, the binding of KChIP1 with phospholipid vesicles induced a change in the structure of KChIP1 in the presence of PS. Taken together, our data suggest that EF-hands 3 and 4 of KChIP1 are functionally involved in a specific association with PS on the membrane.     

Role and relationship of nitric oxide and hydrogen peroxide in adventitious root development of marigold

Several lines of evidence suggest that nitric oxide (NO) and hydrogen peroxide (H₂O₂) are important signal molecules involved in plant development and other physiological processes. Marigold (Tagetes erecta L. ‘Marvel’) was used to understand the role and relationship of NO and H₂O₂ in adventitious root development of plants. The results showed that the effects of H₂O₂ or NO on adventitious root organogenesis of explants were dose dependent, with maximal biological responses at 200 μM H₂O₂ or 50 μM NO donor sodium nitroprusside (SNP). The results also indicated the importance of both putative NO synthase (NOS)-like and nitrate reductase (NR) enzymes, which might be responsible for the production of NO in explants during rooting. Additionally, guanosine 3′, 5′ -cyclic monophosphate (cGMP) was involved in NO- induced root formation of marigold, but it was not involved in H₂O₂- mediated rooting process. The root number and length of explants treated with NO and H₂O₂ simultaneously were significantly higher than those of explants treated with H₂O₂ or NO alone. Moreover, NO treatments enhanced endogenous H₂O₂ levels in hypocotyls. Together, these results indicate that NO and H₂O₂ play crucial roles in the adventitious root development of marigold explants both synergistically and independently.     

Intervention of cardiomyocyte death based on real-time monitoring of cell adhesion through impedance sensing

Cardiomyocyte death caused by proinflammatory cytokines, such as Tumor necrosis factor α (TNF-α), is one of the hot topics in cardiovascular research. TNF-α can induce multiple cell processes that are dependent on the treatment time although the long-term treatment definitely leads to cell death. The ability to intervene in cell death will be invaluable to reveal the effects of short-term TNF-α treatment to cardiomyocytes. However, a real-time monitoring technique is needed to guide the intervention of cell responses. In this work, we employed the impedance-sensing technique to real-time monitor the equivalent cell–substrate distance of cardiomyocytes via electrochemical impedance spectroscopy (EIS) and electrical cell–substrate impedance sensing (ECIS). In the stabilized cardiomyocyte culture, the sustained TNF-α treatment caused strengthened cell adhesion in the first 2 h which was followed by the transition to cell detachment afterwards. Considering cell detachment was an early morphological evidence of cell death, we removed TNF-α from the cardiomyocyte culture before the transition to achieve the intervention of cell responses. The result of this intervention showed that cell adhesion was continuously strengthened before and after the removal of TNF-α, indicating the short-term treated cardiomyocytes did not undergo death processes. It was also demonstrated in TUNEL and TBE tests that the percentages of apoptosis and cell death were both lowered.