Plant height–crown radius and canopy coverage–density relationships determine above-ground biomass–density relationship in stressful environments

Debate continues in theoretical ecology over whether and why the scaling exponent of biomass–density (M–N) relationship varies along environmental gradients. By developing a novel geometric model with assumptions of allometric growth at the individual level and open canopy at the stand level, we propose that plant height–crown radius and canopy coverage–density relationships determine the above-ground M–N relationship in stressful environments. Results from field investigation along an aridity gradient (from eastern to western China) confirmed our model prediction and showed that the above-ground M–N scaling exponent increased with drought stress. Therefore, the ‘universal’ scaling exponents (−3/2 or −4/3) of the M–N relationship predicted by previous models may not hold for above-ground parts in stressful environments.     

IGF-1 Regulates Cyr61 Induced Breast Cancer Cell Proliferation and Invasion

Background

Studies from our laboratory and others have shown that cysteine-rich 61 (Cyr61) may be involved in tumor proliferation and invasion. In earlier studies, we demonstrated increased insulin-like growth factor-I (IGF-1) is associated with breast tumor formation and poor clinical outcomes. In our current study we have investigated IGF-1 regulation of Cyr61 and whether targeting IGF-1 could inhibit Cyr61 induced tumor growth and proliferation.

Methods

Several ATCC derived normal and breast cancer cell lines were used in this study: MDA-MB231, BT474, MCF-7, and SKBR3. We also tested cells stably transfected in our laboratory with active Akt1 (pAkt; SKBR3/AA and MCF-7/AA) and dominant negative Akt1 (SKBR3/DN and MCF-7/DN). In addition, we used MCF-7 cells transfected with full length Cyr61 (CYA). Monolayer cultures treated with IGF-1 were analyzed for Cyr61 expression by RT-PCR and immunohistochemical staining. Migration assays and MTT based proliferation assays were used to determine invasive characteristics in response to IGF-1/Cyr61 activation.

Results

Cells with activated Akt have increased levels of Cyr61. Conversely, cells with inactive Akt have decreased levels of Cyr61. IGF-1 treatment increased Cyr61 expression significantly and cells with high level of Cyr61 demonstrate increased invasiveness and proliferation. Cyr61 overexpression and activation led to decrease in E-cadherin and decrease in FOXO1. Inhibition of the PI3K and MAPK pathways resulted in significant decrease in invasiveness and proliferation, most notably in the PI3K pathway inhibited cells.

Conclusion

The findings of this study show that IGF-1 upregulates Cyr61 primarily through activation of the Akt-PI3K pathway. IGF-1 induced MAPK plays a partial role. Increase in Cyr61 leads to increase in breast cancer cell growth and invasion. Hence, targeting Cyr61 and associated pathways may offer an opportunity to inhibit IGF-1 mediated Cyr61 induced breast cancer growth and invasion.     

Taxol induced apoptosis regulates amino acid transport in breast cancer cells

A major outcome from Taxol treatment is induction of tumor cell apoptosis. However, metabolic responses to Taxol-induced apoptosis are poorly understood. In this study, we hypothesize that alterations in specific amino acid transporters may affect the Taxol-induced apoptosis in breast cancer cells. In this case, the activity of the given transporter may serve as a biomarker that could provide a biological assessment of response to drug treatment. We have examined the mechanisms responsible for Taxol-induced neutral amino acid uptake by breast cancer cells, such as MCF-7, BT474, MDAMB231 and T47D. The biochemical and molecular studies include: (1) growth-inhibition (MTT); (2) transport kinetics: (3) substrate-specific inhibition; (4) effect of thiol-modifying agents NEM and NPM; (5) gene expression of amino acid transporters; and (6) apoptotic assays. Our data show that Taxol treatment of MCF-7 cells induced a transient increase in Na⁺-dependent transport of the neutral amino acid transporter B0 at both gene and protein level. This increase was attenuated by blocking the transporter in the presence of high concentrations of the substrate amino acid. Other neutral amino acid transporters such as ATA2 (System A) and ASC were not altered. Amino acid starvation resulted in the expected up-regulation of System A (ATA2) gene, but not for B0 and ASC. B0 was significantly down regulated. Taxol treatment had no significant effect on the uptake of arginine and glutamate as measured by System y⁺ and X⁻ _GC respectively. Tunel assays and FACS cell cycle analysis demonstrated that both Taxol- and doxorubicin-induced upregulation of B0 transporter gene with accompanying increase in cell apoptosis, could be reversed partially by blocking the B0 transporter with high concentration of alanine, and/or by inhibiting the caspase pathway. Both Taxol and doxorubicin treatment caused a significant decrease in S-phase of the cell cycle. However, Taxol-induced an increase primarily in the G2 fraction while doxorubicin caused increase in G1/G0 together with a small increase in G2. In summary, our study showed that Taxol induced apoptosis in several breast cancer cells results in activation of amino acid transporter System B0 at both gene and protein level. Similar response was observed with another chemotherapeutic agent Doxorubicin, suggesting that this increase is in response to apoptosis, and not only due to changes in cell cycle related events. Drs. Wu and Shen contributed equally to this study.     

Effect of constant and fluctuating temperature on the circadian foraging rhythm of the red imported fire ant,Solenopsis invicta Buren (Hymenoptera: Formicidae)

Understanding circadian foraging rhythms activity of the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae) foragers at different temperatures is an important step towards developing control measures in Integrated Pest Management (IPM) programs. In this study, the circadian foraging rhythm activities of S. invicta foragersat different temperature were investigated under laboratory and field conditions. Results indicated that the foraging activity increased after sunrise, and maximum foraging occurred at 14:00 (foraging rate was 69.22 ± 0.57 and 72.58 ± 1.15 foragers/min in the first and second year, respectively) in the tea fields of Guangzhou during autumn. Furthermore, foragers demonstrated circadian rhythms and exhibited a unimodal after 24 h. A significant correlation was found between foraging activity and temperature. S. invicta colonies were active at moderate soil temperatures (approximately 26.65 °C to 29.24 °C). The preferred temperature of the colonies was 26 °C, followed by 22 °C and 18 °C in the laboratory. The individual S. invicta activity was maximum at 17:00 (18.67 ± 1.66 times /10 min) and minimum at 5:00 (8.33 ± 2.51 times/10 min) at 26 °C. The fluctuating temperature had a significant impact on individual locomotor activity (r = 0.8979, P < 0.01) but did not alter the rhythm activity. Our results demonstrated that temperature might play an important role in circadian foraging rhythms activity of S. invicta. These results may have implications for the development of more effective fire ant management strategies.     

Beta-1,3-glucan inducible expression of prophenoloxidase-activating proteinase from eri-silkworm, Samia cynthia ricini

A cDNA clone encoding possible prophenoloxidase-activating serine protease (PAP) was isolated by screening the cDNA library from immunized larval fat body of the wild silkmoth, Samia cynthia ricini. The cDNA encodes a 438 amino acid open reading frame with a predicted 20 residue signal peptide. Samia PAP has high sequence similarity to Bombyx mori and Manduca sexta PAPs, which contain two amino terminal clip domains followed by a carboxyl-terminal catalytic domain. The expression of the gene was barely detectable in the fat body of naive larvae, but induced after injection of the larvae with beta-1,3-glucans or bacterial cells.     

A robust approach for electronic health record–based case-control studies with contaminated case pools

We consider analyses of case-control studies assembled from electronic health records (EHRs) where the pool of cases is contaminated by patients who are ineligible for the study. These ineligible patients, referred to as “false cases,” should be excluded from the analyses if known. However, the true outcome status of a patient in the case pool is unknown except in a subset whose size may be arbitrarily small compared to the entire pool. To effectively remove the influence of the false cases on estimating odds ratio parameters defined by a working association model of the logistic form, we propose a general strategy to adaptively impute the unknown case status without requiring a correct phenotyping model to help discern the true and false case statuses. Our method estimates the target parameters as the solution to a set of unbiased estimating equations constructed using all available data. It outperforms existing methods by achieving robustness to mismodeling the relationship between the outcome status and covariates of interest, as well as improved estimation efficiency. We further show that our estimator is root-n-consistent and asymptotically normal. Through extensive simulation studies and analysis of real EHR data, we demonstrate that our method has desirable robustness to possible misspecification of both the association and phenotyping models, along with statistical efficiency superior to the competitors.