Atmospheric Production of Glycolaldehyde Under Hazy Prebiotic Conditions

The early Earth’s atmosphere, with extremely low levels of molecular oxygen and an appreciable abiotic flux of methane, could have been a source of organic compounds necessary for prebiotic chemistry. Here, we investigate the formation of a key RNA precursor, glycolaldehyde (2-hydroxyacetaldehyde, or GA) using a 1-dimensional photochemical model. Maximum atmospheric production of GA occurs when the CH₄:CO₂ ratio is close to 0.02. The total atmospheric production rate of GA remains small, only 1×10⁷ mol yr^???1. Somewhat greater amounts of GA production, up to 2 × 10⁸ mol yr^???1, could have been provided by the formose reaction or by direct delivery from space. Even with these additional production mechanisms, open ocean GA concentrations would have remained at or below ~1 μM, much smaller than the 1–2 M concentrations required for prebiotic synthesis routes like those proposed by Powner et al. (Nature 459:239–242, 2009). Additional production or concentration mechanisms for GA, or alternative formation mechanisms for RNA, are needed, if this was indeed how life originated on the early Earth.     

Dual role of p53 amyloid formation in cancer; loss of function and gain of toxicity

The tumor suppressor p53 plays an important role in genome integrity. It is frequently mutated in all types of human cancers, making p53 a key factor in cancer progression. Two phenotypic consequences of these alterations are dominant; a loss of function and a gain of function of p53, which, in several cases, accumulates in intracellular aggregates. Although the nature of such aggregates is still unclear, recent evidence indicates that p53 can undergo conformational transitions leading to amyloid formation. Amyloid diseases, such as, Alzheimer’s disease, are characterized by the accumulation of insoluble aggregates displaying the fibrillar conformation. We decided to investigate the propensity of wild type p53 to aggregate and its consequent assembly into different amyloid species, such as oligomers and fibrils; and to determine if these changes in conformation lead to a loss of function of p53. Furthermore, we analyzed cases of Basal Cell Carcinoma (BCC), for the presence of p53 amyloids. Here, we show that p53 forms amyloid oligomers and fibrils, which coincide with p53 inability of binding to DNA consensus sequences. Both p53 amyloid oligomers and fibrils were detected in BCC cancer samples. Additionally, we demonstrate that p53 oligomers are the most cytotoxic to human cell cultures.Our study reveals p53 amyloid formation and demonstrates its dual role in the pathogenesis of cancer by producing a loss of protein function and a gain of toxic function, extensively described in several amyloidogenic diseases. Our results suggest that under certain circumstances, cancer could be considered a protein-conformation disease.     

Design,synthesis and structure–activity relationship of rhenium 2-arylbenzothiazoles as β-amyloid plaque binding agents

To continue our efforts toward the development of ^99mTc PiB analogs, we have synthesized 24 neutral and lipophilic Re (as a surrogate of ^99mTc) 2-arylbenzothiazoles, and explored their structure–activity relationship for binding to Aβ_1–40 fibrils. These Re complexes were designed and synthesized via the integrated approach, so their ^99mTc analogs would have a greater chance of crossing the blood–brain barrier. While the lipophilicities (log P_C18 = 1.59–3.53) of these Re 2-arylbenzothiazoles were all within suitable range, their binding affinities (K_i = 30–617 nM) to Aβ_1–40 fibrils varied widely depending on the selection and integration of the tetradentate chelator into the 2-phenylbenzothiazole pharmacophore. For potential clinical applications, further refinement to obtain Re 2-arylbenzothiazoles with better binding affinities (<10 nM) will likely be needed. The integrated approach reported here to generate compact, neutral and lipophilic Re 2-arylbenzothiazoles could be applied to other potent pharmacophores as well to convert other current Aβ PET tracers to their ^99mTc analogs for more widespread application via the use of SPECT scanners.     

A road map for molecular ecology

The discipline of molecular ecology has undergone enormous changes since the journal bearing its name was launched approximately two decades ago. The field has seen great strides in analytical methods development, made groundbreaking discoveries and experienced a revolution in genotyping technology. Here, we provide brief perspectives on the main subdisciplines of molecular ecology, describe key questions and goals, discuss common challenges, predict future research directions and suggest research priorities for the next 20 years.     

Genetic analysis of a contact zone between two lineages of the ocellated lizard (Lacerta lepida Daudin 1802) in south‐eastern Iberia reveal a steep and narrow hybrid zone

Measuring the diffusion of genes between diverging taxa through zones of secondary contact is an essential step to understand the extent and nature of the reproductive isolation that has been achieved. Previous studies have shown that the ocellated lizard (Lacerta lepida Daudin, 1802) has endured repeated range fragmentation associated with the climatic oscillations of the Plio‐Pleistocene that promoted diversification of many different evolutionary units within the species. However, the oldest divergence within the group is estimated to have occurred much earlier, during the Miocene, around 9 Ma and corresponds to the split between the subspecies Lacerta lepida nevadensis Buchholz (1963) and Lacerta lepida lepida Daudin (1802). Although these two evolutionary units have documented genetic and morphological differentiation, most probably accumulated during periods of allopatry, little is known about patterns of gene flow between them. In this study, we performed a population genetic analysis of a putative area of secondary contact between these two taxa, using mtDNA and microsatellite data. We assessed levels of gene flow across the contact zone to clarify to what extent gene flow may be occurring. Hybridization between the subspecies was observed by the presence of genetically introgressed individuals. However, the overall coincidence of mitochondrial and multilocus nuclear clines and generally steep clines support the idea that this contact zone is acting as a barrier to gene flow. Taken together, these results suggest that L. l. lepida and L. l. nevadensis are in independent evolutionary trajectories and should be considered as two different species.     

Growth, nitrogen utilization and biodiesel potential for two chlorophytes grown on ammonium, nitrate or urea

Nitrogen removal from wastewater by algae provides the potential benefit of producing lipids for biodiesel and biomass for anaerobic digestion. Further, ammonium is the renewable form of nitrogen produced during anaerobic digestion and one of the main nitrogen sources associated with wastewater. The wastewater isolates Scenedesmus sp. 131 and Monoraphidium sp. 92 were grown with ammonium, nitrate, or urea in the presence of 5 % CO₂, and ammonium and nitrate in the presence of air to optimize the growth and biofuel production of these chlorophytes. Results showed that growth on ammonium, in both 5 % CO₂ and air, caused a significant decrease in pH during the exponential phase causing growth inhibition due to the low buffering capacity of the medium. Therefore, biological buffers and pH controllers were utilized to prevent a decrease in pH. Growth on ammonium with pH control (synthetic buffers or KOH dosing) demonstrated that growth (rate and yield), biodiesel production, and ammonium utilization, similar to nitrate- and urea-amended treatments, can be achieved if sufficient CO₂ is available. Since the use of buffers is economically limited to laboratory-scale experiments, chemical pH control could bridge the gap encountered in the scale-up to industrial processes.     

S100A8/A9 (Calprotectin) Negatively Regulates G2/M Cell Cycle Progression and Growth of Squamous Cell Carcinoma

Malignant transformation results in abnormal cell cycle regulation and uncontrolled growth in head and neck squamous cell carcinoma (HNSCC) and other cancers. S100A8/A9 (calprotectin) is a calcium-binding heterodimeric protein complex implicated in cell cycle regulation, but the specific mechanism and role in cell cycle control and carcinoma growth are not well understood. In HNSCC, S100A8/A9 is downregulated at both mRNA and protein levels. We now report that downregulation of S100A8/A9 correlates strongly with a loss of cell cycle control and increased growth of carcinoma cells. To show its role in carcinogenesis in an in vitro model, S100A8/A9 was stably expressed in an S100A8/A9-negative human carcinoma cell line (KB cells, HeLa-like). S100A8/A9 expression increases PP2A phosphatase activity and p-Chk1 (Ser345) phosphorylation, which appears to signal inhibitory phosphorylation of mitotic p-Cdc25C (Ser216) and p-Cdc2 (Thr14/Tyr15) to inactivate the G2/M Cdc2/cyclin B1 complex. Cyclin B1 expression then downregulates and the cell cycle arrests at the G2/M checkpoint, reducing cell division. As expected, S100A8/A9-expressing cells show both decreased anchorage-dependent and -independent growth and mitotic progression. Using shRNA, silencing of S100A8/A9 expression in the TR146 human HNSCC cell line increases growth and survival and reduces Cdc2 inhibitory phosphorylation at Thr14/Tyr15. The level of S100A8/A9 endogenous expression correlates strongly with the reduced p-Cdc2 (Thr14/Tyr14) level in HNSCC cell lines, SCC-58, OSCC-3 and UMSCC-17B. S100A8/A9-mediated control of the G2/M cell cycle checkpoint is, therefore, a likely suppressive mechanism in human squamous cell carcinomas and may suggest new therapeutic approaches.     

Evaluation of a Model for Glycemic Prediction in Critically Ill Surgical Patients

We evaluated a neural network model for prediction of glucose in critically ill trauma and post-operative cardiothoracic surgical patients. A prospective, feasibility trial evaluating a continuous glucose-monitoring device was performed. After institutional review board approval, clinical data from all consenting surgical intensive care unit patients were converted to an electronic format using novel software. This data was utilized to develop and train a neural network model for real-time prediction of serum glucose concentration implementing a prediction horizon of 75 minutes. Glycemic data from 19 patients were used to “train” the neural network model. Subsequent real-time simulated testing was performed in 5 patients to whom the neural network model was naive. Performance of the model was evaluated by calculating the mean absolute difference percent (MAD%), Clarke Error Grid Analysis, and calculation of the percent of hypoglycemic (≤70 mg/dL), normoglycemic (>70 and <150 mg/dL), and hyperglycemic (≥150 mg/dL) values accurately predicted by the model; 9,405 data points were analyzed. The models successfully predicted trends in glucose in the 5 test patients. Clark Error Grid Analysis indicated that 100.0% of predictions were clinically acceptable with 87.3% and 12.7% of predicted values falling within regions A and B of the error grid respectively. Overall model error (MAD%) was 9.0% with respect to actual continuous glucose modeling data. Our model successfully predicted 96.7% and 53.6% of the normo- and hyperglycemic values respectively. No hypoglycemic events occurred in these patients. Use of neural network models for real-time prediction of glucose in the surgical intensive care unit setting offers healthcare providers potentially useful information which could facilitate optimization of glycemic control, patient safety, and improved care. Similar models can be implemented across a wider scale of biomedical variables to offer real-time optimization, training, and adaptation that increase predictive accuracy and performance of therapies.     

Establishment and Biological Characterization of a Panel of Glioblastoma Multiforme (GBM) and GBM Variant Oncosphere Cell Lines

Objective

Human tumor cell lines form the basis of the majority of present day laboratory cancer research. These models are vital to studying the molecular biology of tumors and preclinical testing of new therapies. When compared to traditional adherent cell lines, suspension cell lines recapitulate the genetic profiles and histologic features of glioblastoma multiforme (GBM) with higher fidelity. Using a modified neural stem cell culture technique, here we report the characterization of GBM cell lines including GBM variants.

Methods

Tumor tissue samples were obtained intra-operatively and cultured in neural stem cell conditions containing growth factors. Tumor lines were characterized in vitro using differentiation assays followed by immunostaining for lineage-specific markers. In vivo tumor formation was assayed by orthotopic injection in nude mice. Genetic uniqueness was confirmed via short tandem repeat (STR) DNA profiling.

Results

Thirteen oncosphere lines derived from GBM and GBM variants, including a GBM with PNET features and a GBM with oligodendroglioma component, were established. All unique lines showed distinct genetic profiles by STR profiling. The lines assayed demonstrated a range of in vitro growth rates. Multipotency was confirmed using in vitro differentiation. Tumor formation demonstrated histologic features consistent with high grade gliomas, including invasion, necrosis, abnormal vascularization, and high mitotic rate. Xenografts derived from the GBM variants maintained histopathological features of the primary tumors.

Conclusions

We have generated and characterized GBM suspension lines derived from patients with GBMs and GBM variants. These oncosphere cell lines will expand the resources available for preclinical study.