The marine sponge metabolite mycothiazole: A novel prototype mitochondrial complex I inhibitor

A natural product chemistry-based approach was applied to discover small-molecule inhibitors of hypoxia-inducible factor-1 (HIF-1). A Petrosaspongia mycofijiensis marine sponge extract yielded mycothiazole (1), a solid tumor selective compound with no known mechanism for its cell line-dependent cytotoxic activity. Compound 1 inhibited hypoxic HIF-1 signaling in tumor cells (IC₅₀ 1 nM) that correlated with the suppression of hypoxia-stimulated tumor angiogenesis in vitro. However, 1 exhibited pronounced neurotoxicity in vitro. Mechanistic studies revealed that 1 selectively suppresses mitochondrial respiration at complex I (NADH-ubiquinone oxidoreductase). Unlike rotenone, MPP⁺, annonaceous acetogenins, piericidin A, and other complex I inhibitors, mycothiazole is a mixed polyketide/peptide-derived compound with a central thiazole moiety. The exquisite potency and structural novelty of 1 suggest that it may serve as a valuable molecular probe for mitochondrial biology and HIF-mediated hypoxic signaling.     

Prey life-history and bioenergetic responses across a predation gradient

To evaluate the importance of non-consumptive effects of predators on prey life histories under natural conditions, an index of predator abundance was developed for naturally occurring populations of a common prey fish, the yellow perch Perca flavescens, and compared to life-history variables and rates of prey energy acquisition and allocation as estimated from mass balance models. The predation index was positively related to maximum size and size at maturity in both male and female P. flavescens, but not with life span or reproductive investment. The predation index was positively related to size-adjusted specific growth rates and growth efficiencies but negatively related to model estimates of size-adjusted specific consumption and activity rates in both vulnerable (small) and invulnerable (large) size classes of P. flavescens. These observations suggest a trade-off between growth and activity rates, mediated by reduced activity in response to increasing predator densities. Lower growth rates and growth efficiencies in populations with fewer predators, despite increased consumption suggests either 1) a reduction in prey resources at lower predator densities or 2) an intrinsic cost of rapid prey growth that makes it unfavourable unless offset by a perceived threat of predation. This study provides evidence of trade-offs between growth and activity rates induced by predation risk in natural prey fish populations and illustrates how behavioural modification induced through predation can shape the life histories of prey fish species.     

The spatial heterogeneity of diatoms in eight southeastern Ohio streams: how far does a single riffle reach?

Periphyton is a commonly used biomonitoring tool for streams. Often only one or few riffles are sampled and assumed to be representative of a stream reach. Current literature focuses on periphyton heterogeneity at small scales, on individual rocks within a riffle, and larger scales, within watersheds or ecoregions. The intermediate scales, within single riffles or among riffles, have not been adequately addressed. The purpose of this research was to determine how many riffles must be sampled in order to represent a reach and whether the number of necessary riffles varied with stream health. Since periphyton is sensitive to habitat change, it was hypothesized that heterogeneity would be primarily partitioned among riffles. Eight to ten consecutive riffles were sampled at eight individual stream reaches. Sampled reaches were categorized based on previously collected bioassesment data: three non-attaining, three partially-attaining, and two fully-attaining water quality standards as defined by the Ohio Environmental Protection Agency. Data were analyzed using the Bray-Curtis Similarity Index, Hill’s N₂ dominance diversity index, and the Acid Mine Drainage Diatom Index of Biotic Integrity. Diatoms appeared to be patchily distributed within a reach. This patchiness often led to varied relative abundance of common species and the introduction or loss of rare species among riffles. To account for this variation within a reach, at least two riffles should be sampled. However, a multimetric index may correctly classify a stream based on a one-riffle sample. Variation does not appear to correspond directly to stream health, but to species richness and diversity.     

Maintenance of pluripotency in human embryonic stem cells cultured on a synthetic substrate in conditioned medium

Realizing the potential clinical and industrial applications of human embryonic stem cells (hESCs) is limited by the need for costly, labile, or undefined growth substrates. Here we demonstrate that trypsin passaging of the hESC lines, HUES7 and NOTT1, on oxygen plasma etched tissue culture polystyrene (PE‐TCPS) in conditioned medium is compatible with pluripotency. This synthetic culture surface is stable at room temperature for at least a year and is readily prepared by placing polystyrene substrates in a radio frequency oxygen plasma generator for 5 min. Modification of the polystyrene surface chemistry by plasma etching was confirmed by X‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS), which identified elemental and molecular changes as a result of the treatment. Pluripotency of hESCs cultured on PE‐TCPS was gauged by consistent proliferation during serial passage, expression of stem cell markers (OCT4, TRA1‐60, and SSEA‐4), stable karyotype and multi‐germlayer differentiation in vitro, including to pharmacologically responsive cardiomyocytes. Generation of cost‐effective, easy‐to‐handle synthetic, defined, stable surfaces for hESC culture will expedite stem cell use in biomedical applications. Biotechnol. Bioeng. 2010;105: 130–140. © 2009 Wiley Periodicals, Inc.     

Immunoregulatory effects of freeze injured whole tumour cells on human dendritic cells using an in vitro cryotherapy model

Tumour cryotherapy has been described as both immunostimulatory and immunoinhibitory in previous studies. However, previous studies have not accurately reproduced the precise conditions of current clinical cryotherapy. The objective of this study is to assess the immunological effects of cryotreated whole tumour cells on dendritic cells (DC) maturation and function using an in vitro model. Prostate cancer cells were cooled using Endocare cryo-system to mimic temperatures achieved during clinical cryotherapy. Human DC were prepared from cluster of differentiation (CD) 14 monocytes and matured with lipopolysaccharide (LPS). Cryotreated cancer cells were added to DC on day 3. On day 7, DC were harvested and phenotyped. Cytokine gene expression was assessed using real time quantitative polymerase chain reaction (RT-PCR). Functional activity of DC was assessed in allogenic mixed lymphocyte reaction (MLR) and the molecular changes using gene microarray technology. There was statistically significant upregulation of costimulatory molecules and maturation markers (CD86, CD83, CD80 and CL II) in DC loaded with cryotreated whole tumour cells compared to both control DC and DC matured with LPS (P < 0.001). There was a significant increase in stimulatory cytokines gene expression (IL-2, IL-12, IL-15, IL-18 and IFN-γ). However, IL-10 and TGF-β expression reduced significantly. The effect of different freezing temperature was equal. cDNA microarray analysis showed upregulation of interleukin 1 (IL-1) and cycline dependent kinase inhibitor 1A (CDKN1A (p21) and downregulation of Caspase 8 and BCL2. Overall, our findings suggest that the effect of cryotherapy is generally stimulatory to DC which may enhance anti-tumour effects. Therefore, the combination of cryotherapy and DC vaccine may represent a novel method to increase the efficacy of cryotherapy especially at the peripheral zones of the prostate where cells are exposed to sub-lethal temperature.     

Nosema pyrausta and Cry1Ab‐incorporated diet led to decreased survival and developmental delays in European corn borer

The high dose/refuge strategy for delaying evolution of resistance to Bt maize [Zea mays L. (Poaceae)] relies on random mating between resistant European corn borers, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), and susceptible O. nubilalis from the refuge. However, differences in developmental rate caused by feeding on Bt maize, or infection with the microsporidium Nosema pyrausta Paillot (Microsporida: Nosematidae) may result in assortative mating. Developmental delays and mortality caused by infection with N. pyrausta and feeding on Bt maize were quantified alone and in combination in Cry1Ab‐resistant and susceptible O. nubilalis. Feeding on Cry1Ab‐incorporated diet significantly increased number of days from hatch to pupation and decreased survival in the resistant population. Infection with N. pyrausta increased mortality and lengthened development in both the resistant and susceptible populations. The combination of Cry1Ab‐incorporated diet and infection with N. pyrausta in resistant O. nubilalis lengthened development and increased mortality to a greater extent than either factor alone. Greater larval delays of resistant O. nubilalis feeding on Bt maize could lead to temporal isolation from adults emerging from refuge maize. The resulting assortative mating would hasten the evolution of resistance. Developmental delays caused by infection with N. pyrausta may increase the likelihood of mating between resistant and infected susceptible adults emerging from refuge maize, producing infected offspring that are also more susceptible to Bt maize.     

Arterial compliance of rowers: implications for combined aerobic and strength training on arterial elasticity

Regular endurance exercise increases central arterial compliance, whereas resistance training decreases it. It is not known how the vasculature adapts to a combination of endurance and resistance training. Rowing is unique, because its training encompasses endurance- and strength-training components. We used a cross-sectional study design to determine arterial compliance of 15 healthy, habitual rowers [50 +/- 9 (SD) yr, 11 men and 4 women] and 15 sedentary controls (52 +/- 8 yr, 10 men and 5 women). Rowers had been training 5.4 +/- 1.2 days/wk for 5.7 +/- 4.0 yr. The two groups were matched for age, body composition, blood pressure, and metabolic risk factors. Central arterial compliance (simultaneous ultrasound and applanation tonometry on the common carotid artery) was higher (P < 0.001) and carotid beta-stiffness index was lower (P < 0.001) in rowers than in sedentary controls. There were no group differences for measures of peripheral (femoral) arterial stiffness. The higher central arterial compliance in rowers was associated with a greater cardiovagal baroreflex sensitivity, as estimated during a Valsalva maneuver (r = 0.54, P < 0.005). In conclusion, regular rowing exercise in middle-aged and older adults is associated with a favorable effect on the elastic properties of the central arteries. Our results suggest that simultaneously performed endurance training may negate the stiffening effects of strength training.