Steady Shear and Step Changes in Shear Stimulate Endothelium via Independent Mechanisms—Superposition of Transient and Sustained Nitric Oxide Production

We propose that fluid shear presents two distinct stimuli to endothelium—the rate of change of flow and flow itself, to which cells sense and respond via independent mechanochemical transduction pathways. We demonstrate that nitric oxide production occurs by two independent mechanisms; a G protein-dependent transient burst stimulated by rapid changes in flow, and a G protein-independent sustained production under steady or smoothly transitioned flow. The novel use of step, ramp, and impulse flow in this study to stimulate nitric oxide production allows the isolation of these individual production events. Impulse flow activates only the G protein-dependent transient burst, which ramp flow fails to stimulate yielding only the sustained response. Step flow, which contains both a rapid increase and a steady flow component, stimulates both pathways, with the response of the superposition of the transient burst and sustained production.     

Relaxation Kinetic Study of Eudragit? NM30D Film Based on Complex Modulus Formalism

This study is aimed at resolving and characterizing the primary (α) and secondary relaxations (β) in Eudragit® NM30D film based on apparent activation energies derived from complex modulus formalism using dielectric analysis (DEA). The glass transition (T_g) of the film was determined using differential scanning calorimetry (DSC). The α relaxation corresponding to T_g and the β relaxations occurring below T_g were probed using DEA. The occurrence of α and β relaxations in Eudragit® NM30D film was elucidated using the complex modulus of the dielectric response employing loss modulus and permittivity data. Activation energies of these relaxations and the fundamental frequency so determined support the assignment of the relaxation pattern in the Eudragit® NM30D film. DEA methodology of the complex modulus formalism is a useful tool for differentiating the α and β relaxation kinetics in Eudragits® not easily studied using traditional thermal methods such as DSC. The kinetics associated with α and β relaxations so determined will provide formulation design support for solid orals that incorporate Eudragit® polymers. As mobility changes can affect stability and diffusion, the dipolar α and β relaxations revealed through DEA analysis may enable a better correlation to functionality of Eudragit® based pharmaceutical dosage forms.KEY WORDS: activation energy, loss modulus, permittivity, primary relaxation, secondary relaxation     

Shear stress regulation of Krüppel-like factor 2 expression is flow pattern-specific

Flow patterns in blood vessels contribute to focal distribution of atherosclerosis; the underlying mechanotransduction pathways remain to be investigated. We demonstrate that different flow patterns elicit distinct responses of Krüppel-like factor-2 (KLF2) in endothelial cells (ECs) in vitro and in vivo. While pulsatile flow with a significant forward direction induced sustained expression of KLF2 in cultured ECs, oscillatory flow with little forward direction caused prolonged suppression after a transient induction. The suppressive effect of oscillatory flow was Src-dependent. Immunohistochemical studies on ECs at arterial branch points revealed that KLF2 protein levels were related to local hemodynamics. Such flow-associated expression patterns were also demonstrated in a rat aortic restenosis model. Inhibition of KLF2 with siRNA sensitized ECs to oxidized LDL-induced apoptosis, indicating a protective role of KLF2. In conclusion, differential regulation of KLF2 may mediate the distinct vascular effects induced by various patterns of shear stress.     

Platelet Transport Rates and Binding Kinetics at High Shear over a?Thrombus

Thrombus formation over a ruptured atherosclerotic plaque cap can occlude an artery with fatal consequences. We describe a computational model of platelet transport and binding to interpret rate-limiting steps seen in experimental thrombus formation over a collagen-coated stenosis. The model is used to compute shear rates in stenoses with growing boundaries. In the model, moving erythrocytes influence platelet transport based on shear-dependent enhanced diffusivity and a nonuniform platelet distribution. Adhesion is modeled as platelet-platelet binding kinetics. The results indicate that observed thrombus growth rates are limited by platelet transport to the wall for shear rates up to 6000 s⁻¹. Above 7000 s⁻¹, the thrombus growth rate is likely limited by binding kinetics (10⁻⁴ m/s). Thrombus growth computed from these rate-limiting steps match the thrombus location and occlusion times for experimental conditions if a lag time for platelet activation is included. Using fitted parameters, the model is then used to predict thrombus size and shape at a higher Reynolds number flow consistent with coronary artery disease.     

Shear stress modulation of IL-1β-induced E-selectin expression in human endothelial cells

Background

Endothelial cells (ECs) are continuously exposed to hemodynamic forces imparted by blood flow. While it is known that endothelial behavior can be influenced by cytokine activation or fluid shear, the combined effects of these two independent agonists have yet to be fully elucidated.

Methodology

We investigated EC response to long-term inflammatory cues under physiologically relevant shear conditions via E-selectin expression where monolayers of human umbilical vein ECs were simultaneously exposed to laminar fluid shear and interleukin-1ß (shear-cytokine activation) in a parallel plate flow chamber.

Results and Conclusion

Naïve ECs exposed to shear-cytokine activation display significantly higher E-selectin expression for up to 24 hr relative to ECs activated in static (static-cytokine). Peak E-selectin expression occurred after 8–12 hr of continuous shear-cytokine activation contrary to the commonly observed 4–6 hr peak expression in ECs exposed to static-cytokine activation. Cells with some history of high shear conditioning exhibited either high or muted E-selectin expression depending on the durations of the shear pre-conditioning and the ensuing shear-cytokine activation. Overall, the presented data suggest that a high laminar shear enhances acute EC response to interleukin-1ß in naïve or shear-conditioned ECs as may be found in the pathological setting of ischemia/reperfusion injury while conferring rapid E-selectin downregulation to protect against chronic inflammation.     

Shear stress regulates expression of death-associated protein kinase in suppressing TNFα-induced endothelial apoptosis

Death associated protein kinase (DAPK) is a positive regulator in tumor necrosis factor α (TNFα)‐induced apoptotic pathway, and DAPK expression is lost in cancer cells. In the vasculature, misdirected apoptosis in endothelial cells leads to pathological conditions such as inflammation and physiological shear stress is protective against apoptosis. Using bovine aortic endothelial cells, we found that DAPK expression increased, while the auto‐inhibitory phosphorylation of serine 308 decreased with shear stress at 12 dynes/cm² for 6 h. Quantitative RT‐PCR revealed a corresponding increase in DAPK mRNA [P < 0.01]. We found that after 18‐h TNFα induction, shearing cells for another 6 h significantly reduced apoptosis based on TUNEL staining [P < 0.05], although cell necrosis was not affected. Under the same conditions, we observed significantly decreased overall DAPK, as well as phospho‐serine 308 DAPK [P < 0.05] compared to TNFα treatment alone. Caspase‐3 and ‐7 activities downstream of DAPK were also attenuated. Shearing cells alone resulted in enhanced apoptosis, likely due to increased DAPK activity. Our findings were further supported by DAPK siRNA, which yielded contrary results. We present conclusive evidence for the first time that shear stress of up to 6 h up‐regulates DAPK expression and activation. However, in the presence of apoptotic stimuli such as TNFα, shear stress caused decrease in DAPK activity. In fact, long‐term shear stress of 24 h significantly reduced overall DAPK expression. Our findings strongly support a novel role for DAPK in mediating effects of shear stress in suppressing cytokine‐activated apoptosis. J. Cell. Physiol. 227: 2398–2411, 2012. © 2011 Wiley Periodicals, Inc.     

Where does heteroclisis come from? Evidence from Romanian dialects

This study examines some cases of heteroclisis in the history of Romanian dialects, and concludes that the data call for a reconsideration of Stump’s distinction (Language 82:279–322, 2006) between ‘cloven’ heteroclisis, where the intraparadigmatic ‘split’ is aligned with some morphosyntactic feature distinction, and ‘fractured’ heteroclisis, where this is not the case and the pattern of heteroclisis is purely morphological. Stump’s account creates the impression that the ‘cloven’ variety is universally predominant, and that the ‘fractured’ variety tends to follow very closely the available ‘cloven’ patterns of the language. I shall suggest, instead, that the ‘fractured-only’ situation may in fact underlie heteroclisis cross-linguistically, the phenomenon being in general sensitive not directly to morphosyntactic content, but rather to characteristic, and often purely ‘morphomic’, patterns of stem-allomorphy. Research for this paper was undertaken as part of the Arts and Humantities Research Council-funded project Autonomous Morphology in Diachrony: comparative evidence from the Romance Languages, currently being conducted at Oxford University.     

Message from the Editor-in-Chief

The current issue of Acta Biochimica et Biophysica Sinica (ABBS) has turned a new page of this journal since its publication forty five years ago. It is perhaps an appropriate time to share with our readers about the evolution of this journal, the changes that have taken place, and the future that we are looking forward to. ABBS was first established in 1958 with Professor Ying-Lai WANG as the founding Editor-in-Chief and has been ever since an     

What Do We Learn from Spheroid Culture Systems? Insights from Tumorspheres Derived from Primary Colon Cancer Tissue

Due to their self-renewal and tumorigenic properties, tumor-initiating cells (TICs) have been hypothesized to be important targets for colorectal cancer (CRC). However the study of TICs is hampered by the fact that the identification and culturing of TICs is still a subject of extensive debate. Floating three-dimensional spheroid cultures (SC) that grow in serum-free medium supplemented with growth factors are supposed to be enriched in TICs. We generated SC from fresh clinical tumor specimens and compared them to SC isolated from CRC cell-lines as well as to adherent differentiated counterparts. Patient-derived SC display self-renewal capacity and can induce serial transplantable tumors in immuno-deficient mice, which phenotypically resemble the tumor of origin. In addition, the original tumor tissue and established SC retain several similar CRC-relevant mutations. Primary SC express key stemness proteins such as SOX2, OCT4, NANOG and LGR5 and importantly show increased chemoresistance ability compared to their adherent differentiated counterparts and to cell line-derived SC. Strikingly, cells derived from spheroid or adherent differentiating culture conditions displayed similar self-renewal capacity and equally formed tumors in immune-deficient mice, suggesting that self-renewal and tumor-initiation capacity of TICs is not restricted to phenotypically immature spheroid cells, which we describe to be highly plastic and able to reacquire stem-cell traits even after long differentiation processes. Finally, we identified two genes among a sphere gene expression signature that predict disease relapse in CRC patients. Here we propose that SC derived from fresh patient tumor tissue present interesting phenotypic features that may have clinical relevance for chemoresistance and disease relapse and therefore represent a valuable tool to test for new CRC-therapies that overcome drug resistance.     

Production of steviol from steviol glucosides using β-glycosidase from Sulfolobus solfataricus

Steviol is a diterpene isolated from the plant Stevia rebaudiana that has a potential role as an antihyperglycemic agent by stimulating insulin secretion from pancreatic beta cells and also has significant potential to diminish the renal clearance of anionic drugs and their metabolites. In this study, the lacS gene, which encodes a thermostable β-glycosidase (SSbgly) enzyme from the extremely thermoacidophillic archaeon Sulfolobus solfataricus, was cloned and expressed in E. coli Rossetta BL21(DE3)pLyS using lactose as an inducer. Through fermentation, SSbgly was expressed as a 61 kDa protein with activity of 24.3 U/mg and the OD₆₀₀ of 23 was reached after 18 h induction with 10 mM lactose. Purified protein was obtained by Ni-Sepharose chromatography with a yield of 92.3%. SSbgly hydrolyzed steviol glycosides to produce steviol with a yield of 99.2%. The optimum conditions for steviol production were 50 U/ml SSbgly and 90 mg/ml Ste at 75 °C as determined by the response surface method.     

Skill Memory Escaping from Distraction by Sleep��Evidence from Dual-Task Performance

Background

Sleep facilitates off-line consolidation of memories, as shown for learning of motor skills in the absence of concomitant distractors. We often perform complex tasks focusing our attention mostly on one single part of them. However, we are equally able to skillfully perform other concurrent tasks. One may even improve performance on disregarded parts of complex tasks, which were learned implicitly. In the present study we investigated the role of sleep in the off-line consolidation of procedural skills when attention is diverted from the procedural task because of interference from a concurrent task.

Methodology/Principal Findings

We used a dual-task paradigm containing (i) procedural serial reaction time task (SRTT), which was labeled as subordinate and unimportant and (ii) declarative word-pair association task (WPAT), performed concomitantly. The WPAT served as a masked distractor to SRTT and was strongly reinforced by the instructions. One experimental and three control groups were tested. The experimental group was re-tested after two nights of sleep (sleep group, SG). The first control group had sleep deprivation on the first post-learning night (nighttime-awake group, NA), the second control group was tested in the morning and then re-tested after 12-hours (daytime-awake group, DA); the third one had the same assignments as DA but with a subsequent, instead of a concomitant, WPAT (daytime-awake-subsequent-WPAT group, DAs). We found SRTT performance gains in SG but not in NA and DA groups. Furthermore, SG reached similar learning gains in SRTT as the DAs group, which gained in SRTT performance because of post-training interference from the declarative task.

Conclusions/Significance

The results demonstrate that sleep allows off-line consolidation, which is resistant to deteriorating effects of a reinforced distractor on the implicit procedural learning and allowing for gains which are consistent with those produced when inhibited declarative memories of SRTT do not compete with procedural ones.     

Psychrophilic α-amylase from Aeromonas veronii NS07 isolated from farm soils

Among 120 isolates examined in this study, three isolates were selected for amylase production on starch agar plates following incubation at 10 °C. Identification by 16SrRNA on selected bacterium disclosed the highest similarity for protean regions of this gene as Aeromonas veronii NS07. A 63 kDa psychrophilic amylase enzyme from NS07 strain was purified by two-steps chromatography. The enzyme had the highest specific activity at pH 4 and was active at the range of temperatures from 0 to 50 °C, although the optimum temperature for enzyme activity was found at 10 °C. Analysis of the N-terminal amino acid sequencing disclosed 20 amino acids from purified amylase which had no similarity with other known α-amylases, indicating that the presented enzyme was novel. Amylase activity was enhanced in relation to optimum activity with the presence of sodium sulphate (161%), MnCl₂ (298%), CaCl₂ (175%), FeCl₂ (182%), MgCl₂ (237%), ZnCl₂ (169%), NiCl₂ (139%), NaCl (158%), each at 5 mM, while EDTA, phenylmethane sulphonylfluoride (PMSF) (3 mM), urea (8 M) and SDS (1%) inhibited the enzyme up to 5%, 2%, 80% and 18%, respectively. NS07 strain seems to be suitable as biocatalyst for practical use in liquefaction of starch at low temperatures, detergent and textile industries.     

Synthesis of cello-oligosaccharides from cellobiose with β-glucosidase II from Aspergillus niger

An extracellular -glucosidase II of Aspergillus niger catalysed the synthesis of cello-oligosaccharides from cellobiose (15%, w/v). The enzyme was stable at and below 4°C for at least 230 days and also stable at 30°C with the presence of 2.0% (w/v) cellobiose. The maximum yield of cello-oligosaccharides was about 30% (mol/mol), based on cellobiose (130 mg/mL) consumed. © Rapid Science Ltd. 1998     

Can phenotypic rescue from harvest refuges buffer wild sheep from selective hunting?

Human harvests can unwittingly drive evolution on morphology and life history, and these selective effects may be detrimental to the management of natural resources. Although theory suggests that harvest refuges, as sources of unselected animals, could buffer the effects of human exploitation on wild populations, few studies have assessed their efficiency. We analyzed records from >7000 trophy bighorn rams (Ovis canadensis) harvested in Alberta, Canada, between 1974 and 2011 to investigate if the movement of rams from refuges toward harvested areas reduced the effects of selective harvesting on horn size through phenotypic rescue. Rams taken near refuges had horns on average about 3% longer than rams shot far from refuges and were slightly older, suggesting migration from refuges into hunted areas. Rams from areas adjacent to and far from harvest refuges, however, showed similar declines in horn length and increases in age at harvest over time, indicating a decreasing rate of horn growth. Our study suggests that the influx of rams from refuges is not sufficient to mitigate the selective effects of sheep trophy harvest. Instead, we suggest that selective hunting of highly mobile animals may affect the genetic structure of populations that spend part of the year inside protected areas.     

Glycopeptides from human κ-chains

Glycopeptides have been isolated from tryptic digests of kappa-type light chains separated from human myeloma proteins obtained from the serum of two patients, Car and Rai. The glycopeptides are derived from the variable region of the chain in both cases, but from different sections. On the basis of homology it is deduced that glycopeptide from Car, kappaI type, is derived from position 25-31 whereas that from Rai, kappaII type, is from position 62-77, their sequences being respectively Ala-Ser-Gln-Asn-Ile-Ser and Phe-Ser-Gly-Ser-Gly-Ser-Gly(Thr,Asp)Phe-Thr-Leu-Asx-Ile-Ser-Arg. The significance of the results is discussed in connexion with the nature of the attachment site of carbohydrate to protein.     

Secreted β-galactosidase from a Flavobacterium sp. isolated from a low-temperature environment

The bacterial strain Flavobacterium sp. 4214 isolated from Greenland was found to express β-galactosidase (EC 3.2.1.23) at temperatures below 25°C. A chromosomal library of Flavobacterium sp. 4214 was constructed in Escherichia coli, and the gene gal4214-1 encoding a β-galactosidase of 1,046 amino acids (114.3 kDa) belonging to glycosyl hydrolase family 2 was isolated. This was the only gene encoding β-galactosidase activity that was identified in the chromosomal library. Expression levels in both Flavobacterium sp. 4214 and in initial recombinant E. coli strains were insufficient for biochemical characterization. However, a combination of T7 promoter expression and introduction of an E. coli host that complemented rare transfer RNA genes yielded 15 mg of β-galactosidase per liter of culture. Gal4214-1-His protein was found to be active in monomeric conformation. The protein was secreted from the cytoplasm, probably through an N-terminal signaling sequence. The Gal4214-1-His protein was found to have optimum activity at a temperature of 42°C, but with short-term stability at temperatures above 25°C.     

Synthesis of β-alanine from l-aspartate using l-aspartate-α-decarboxylase from Corynebacterium glutamicum

β-Alanine is mainly produced by chemical methods in current industrial processes. Here, panD from Corynebacterium glutamicum encoding l-aspartate-α-decarboxylase (ADC) was cloned and expressed in Escherichia coli BL21(DE3). ADC _C.g catalyzes the α-decarboxylation of l-aspartate to β-alanine. The purified ADC _C.g was optimal at 55 °C and pH 6 with excellent stability at 16–37 °C and pH 4–7. A pH–stat directed, fed-batch feeding strategy was developed for enzymatic synthesis of β-alanine to keep the pH value within 6–7.2 and thus attenuate substrate inhibition. A maximum conversion of 97.2 % was obtained with an initial 5 g l-aspartate/l and another three feedings of 0.5 % (w/v) l-aspartate at 8 h intervals. The final β-alanine concentration was 12.85 g/l after 36 h. This is the first study concerning the enzymatic production of β-alanine by using ADC.