Lack Of Regrowth Research Articles

Quercus virginianaMill. Root Regrowth Following Linear Trenching

AbstractBackgroundAs long-lived organisms, urban trees often encounter development and redevelopment activities during their lifespans. These activities can damage tree roots, often through methods like root severing during trenching or excavation.MethodsIn 2017, we simulated trenching damage on matureQuercus virginianaMill. trees at 3 different distances from the base (3, 6, or 12 times the stem diameter). After 5 years, we revisited these trees to assess root regrowth based on the cut root’s cross-sectional area (CSA) and distance from the base.ResultsWe observed regrowth in all but 38 (6.7%) of the 557 cut roots revisited. The lack of regrowth in some roots was not associated with our original treatments, the CSA of the roots at the time of trenching, or distance between the cut root end and the trunk (minimumP-value = 0.841). On average, the observed CSA of the regrowth was 22.2% of the original root’s CSA. Only our initial trenching treatments (P-value = 0.024) and the distance between the trunk and the cut root end (P-value = 0.002) significantly predicted the level of regrowth observed 5 years after pruning.ConclusionsIn summary, our findings indicate that root systems require many years to recover from trenching damage. Increasing the distance between trenching activities and trees may have a minor effect on root regrowth.

Targeting dormant phenotype acquired mycobacteria using natural products by exploring its important targets: In vitro and in silico studies.

The dormant phenotype of Mycobacterium tuberculosis that develops during infection poses a major challenge in disease treatment, since these bacilli show tolerance to front-line drugs. An in vitro hypoxia dormancy model was established, which produced phenotypically dormant Mycobacterium smegmatis after prolonged incubation under conditions of low oxygen, low pH, and nutrient limitation. Bacilli in this model displayed the classical dormancy characters, including loss of acid fastness, altered morphology, and, most importantly, tolerance to front-line drugs. The dormant form of M. smegmatis was treated with drugs and phytomolecules. Three phytomolecules exhibited activity against dormant bacilli, as shown by lack of regrowth in solid and liquid media. Further investigation of dormancy-active hits was carried out using in silico approaches to understand the druggable targets of these phytomolecules in dormant bacilli. For this study, molecular docking, molecular dynamics simulations (MDS), and molecular mechanics-generalized born solvent accessibility (MM-GBSA)-based binding energy (ΔGbind) calculations were performed. Five different targets, namely, isocitrate lyase (ICL), GMP synthase, LuxR, DosR, and serine/threonine protein kinase (STPK), from M. smegmatis and M. tuberculosis were studied in details. DosR and STPK were found to be the common targets in both the species that were more prone to the phytomolecules. The standard DosR inhibitor, HC104A, showed a lower dock score and binding energy of -4.27 and -34.50 kcal/mol, respectively, compared to the natural products under study. The phytomolecule, icariin, showed better docking score (dock score = -5.92 kcal/mol with and binding energy ΔGbind= -52.96 kcal/mol) with DosR compared to known DosR inhibitor, HC104A (dock score = -4.27 kcal/mol and binding energy ΔGbind = -34.50 kcal/mol). Similarly, the known STPK inhibitor MRCT67127 showed a lower dock score and binding energy of -4.25 and -29.43 kcal/mol, respectively, compared to the phytomolecule, icariin (dock score = -5.74 kcal/mol and ΔGbind= -43.41 kcal/mol). These compounds might ultimately lead to new therapeutics or may be useful as adjuvants to the first-line drugs to reduce the lengthy anti-TB therapy in the future.

Fighting tuberculosis by drugs targeting nonreplicating Mycobacterium tuberculosis bacilli.

Current tuberculosis (TB) treatment requires 6 months of combination therapy with isoniazid (INH), rifampin (RIF), pyrazinamide (PZA), and ethambutol for active TB and 9 months of INH or 3 months of rifapentine (RFP) + INH for latent TB. The lungs of patients with active and latent TB contain heterogeneous mixtures of cellular and caseous granulomas harboring Mycobacterium tuberculosis bacilli ranging from actively replicating (AR) to nonreplicating (NR), phenotypically drug-resistant stages. Several in vitro models to obtain NR cells were reported, including exposure to hypoxia, nutrient starvation, acid + nitric oxide, and stationary phase. Overall, these models showed that RIF, RFP, PA-824 (PA), metronidazole (MZ), bedaquiline (BQ), and fluoroquinolones were the most active drugs against NR M. tuberculosis. In hypoxia at pH 5.8, some combinations killed AR plus NR cells, as shown by lack of regrowth in liquid media, whereas in hypoxia at pH 7.3 (the pH of the caseum), only RIF and RFP efficiently killed NR bacilli while several other drugs showed little effect. In conventional mouse models, combinations containing RFP, BQ, PA, PZA, moxifloxacin, sutezolid, linezolid, and clofazimine sterilized animals in ≤2 months, as shown by lack of viable bacilli in lung homogenates after 3 months without therapy. Drugs were less effective in C3HeB/FeJ mice forming caseous granulomas. Overall, in vitro observations and in vivo studies suggest that the search for new TB drugs could be addressed to low lipophilic molecules (e.g., new rpoB inhibitors with clogP < 3) killing NR M. tuberculosis in hypoxia at neutral pH and reaching high rates of unbound drug in the caseum.

Abstract 2595: Efficacy of cetuximab and mutant selective EGFR inhibitor WZ4002 in EGFR T790M and non-T790M models of erlotinib resistant non-small cell lung cancer

Abstract Background: EGFR kinase inhibitors, including erlotinib, are effective treatments for patients with EGFR mutant lung cancer. However, resistance inevitably develops, most commonly (60%) mediated by an EGFR secondary mutation EGFR T790M. Mutant selective EGFR inhibitors (WZ4002, AZD9291, CO-1686) are effective in preclinical models and clinically (AZD9291 &amp; CO-1686) in EGFR T790M patients (response rates (RR) &amp;gt; 50%) but are less effective in patients with non-T790M mediated drug resistance (AZD9291 RR ∼10%). Combination of afatinib and cetuximab is effective in both T790M (32% RR) and non-T790M (25% RR) mediated resistance but is associated with significant toxicity. We evaluated whether cetuximab could add to the efficacy of a mutant selective EGFR inhibitor and whether the combination was also effective in a model of non-T790M mediated resistance. Methods: Mice harboring xenografts from PC9GR (EGFR Del 19/T790M), H1975 (EGFR L858R/T790M), HCC827GR (EGFR Del 19/MET amplification) cells or genetically engineered mouse models (GEMMS) expressing EGFR L858R/T790M were treated with vehicle, WZ4002 alone, cetuximab alone or the combination. We compared the efficacy of the treatments and evaluated for tumor cures (defined as tumor disappearance and lack of regrowth following 6 weeks of drug withdrawal). In addition, we evaluated the impact of the treatments on EGFR signaling and apoptosis. Results: In the EGFR T790M xenograft models (PC9GR and H1975), the combination of WZ4002 and cetuximab was more effective than either single agent. Only the combination led to tumor cures (5/15 in PC9GR and 3/18 in H1975) while none were observed with the single agents. In the HCC827GR xenografts, the combination of WZ4002/cetuximab was more effective than the single agents but did not lead to any cures. Evaluation of the tumors from treated mice revealed that the efficacy of the combination correlates with effective degradation of EGFR and MET (in HCC827GR). In the L858R/T790M GEMMs, the combination led to significantly greater tumor shrinkage compared to single agents. Evaluation of treated tumors revealed enhanced apoptosis in the combination treated mice. Conclusions: The addition of cetuximab enhances the efficacy of the mutant selective EGFR inhibitor WZ4002 in vivo by increasing the single agent efficacy in both EGFR T790M and non-T790M models. Clinical trials of mutant selective EGFR inhibitors and cetuximab are warranted. Citation Format: Erin M. Tricker, Chunxiao Xu, Kwok-Kin Wong, Pasi A. Janne. Efficacy of cetuximab and mutant selective EGFR inhibitor WZ4002 in EGFR T790M and non-T790M models of erlotinib resistant non-small cell lung cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2595. doi:10.1158/1538-7445.AM2015-2595

Activities of Drug Combinations against Mycobacterium tuberculosis Grown in Aerobic and Hypoxic Acidic Conditions

Mycobacterium tuberculosis is exposed to hypoxia and acidity within granulomatous lesions. In this study, an acidic culture model of M. tuberculosis was used to test drug activity against aerobic 5-day-old (A5) and hypoxic 5-, 12-, and 19-day-old (H5, H12, and H19, respectively) bacilli after 7, 14, and 21 days of exposure. In A cultures, CFU and pH rapidly increased, while in H cultures growth stopped and pH increased slightly. Ten drugs were tested: rifampin (R), isoniazid (I), pyrazinamide (Z), ethambutol (E), moxifloxacin (MX), amikacin (AK), metronidazole (MZ), nitazoxanide (NZ), niclosamide (NC), and PA-824 (PA). Rifampin was the most active against A5, H5, H12, and H19 bacilli. Moxifloxacin and AK efficiently killed A5 and H5 cells, I was active mostly against A5 cells, Z was most active against H12 and H19 cells, and E showed low activity. Among nitrocompounds, NZ, NC, and PA were effective against A5, H5, H12, and H19 cells, while MZ was active against H12 and H19 cells. To kill all A and H cells, A5- and H5-active agents R, MX, and AK were used in combination with MZ, NZ, NC, or PA, in comparison with R-I-Z-E, currently used for human therapy. Mycobacterial viability was determined by CFU and a sensitive test in broth (day to positivity, MGIT 960 system). As shown by lack of regrowth in MGIT, the most potent combination was R-MX-AK-PA, which killed all A5, H5, H12, and H19 cells in 14 days. These observations demonstrate the sterilizing effect of drug combinations against cells of different M. tuberculosis stages grown in aerobic and hypoxic acidic conditions.

Management of cruciferous cover crops by mowing for soil and water conservation in southern Spain

Abstract In recent years, the use of cover crops in Mediterranean olive orchards has increased due to serious soil erosion problems and surface water contamination by herbicides. In these areas, the annual precipitation regime is strongly seasonal, with dry summers that require killing the cover crop before it competes with the trees for water. Cruciferous species are being introduced as cover crops in southern Spain, and their management by mowing could reduce the use of herbicides. However, the use of mowing as a management system requires an understanding of the phenology of these species to identify the most suitable mowing date to derive the greatest possible soil water content. The aims of this study were the following: (1) to assess the susceptibility of cruciferous species to mowing, their regrowth ability and the persistence of their residues on the soil surface after mowing, and (2) to identify the best mowing date for the cover crops in relation to the soil moisture content in the environmental conditions of southern Spain. For these purposes, the emergence, ground cover, biomass and regrowth after two mowing dates of common mustard (Sinapis alba L. subsp. mairei), rocket (Eruca vesicaria), radish (Raphanus sativus) and Ethiopian mustard (Brassica carinata) were evaluated in field trials during 2001/2002. In addition, during 2002/2003 and 2003/2004, the moisture content of soil sowed with common mustard and rocket cover crops was assessed at different mowing dates and compared with a bare soil control. Common mustard was the most favourable species for management by mowing due to its lack of regrowth after mowing. Early mowing (March 10th) reduced soil moisture due to the regrowth of the cover crop, fast decomposition of cover residues and weed proliferation. Late mowing (April 24th) led to little or no regrowth of the cover crops, large biomass and high persistence of cover residues, which provided effective soil ground cover, avoided the emergence of spring–summer weeds and helped retain soil moisture, reaching a similar water content to bare soil. These results suggest that cruciferous cover crops killed by mowing in late April can be used to replace no-tillage bare soil management systems to reduce the use of herbicides and preserve soil and water quality.

Activity of Drug Combinations against Dormant Mycobacterium tuberculosis

Aerobic (5-day-old cultures) and nonreplicating (dormant) Mycobacterium tuberculosis (5-, 12-, and 19-day-old cultures) bacteria were treated with rifampin (R), moxifloxacin (MX), metronidazole (MZ), amikacin (AK), or capreomycin (CP) for 7, 14, and 21 days. R-MX-MZ-AK and R-MX-MZ-CP killed both aerobic and dormant bacilli in 21 days, as shown by lack of regrowth in solid and liquid media. R-MX-MZ-AK and R-MX-MZ-CP also caused a strong decrease of nonreplicating bacilli in 7 days in a cell-based dormancy model.

Field observations on the occurrence of new indicators of disinfection efficiency

This paper summarizes studies on the presence of acid-fast and yeast organisms in wastewater and water treatment plants and in surface water. These organisms were found to satisfy three of Bonde's criteria for indicator organisms: presence whenever pathogens are likely to be present; resistance at least equal to that of pathogens; and lack of regrowth in the post-treatment environment. This, plus prior data, indicates that these organisms are at least as acceptable as indicators of disinfection efficiency than the coliform group.