scholarly journals Adaptive benefits from small mutation supplies in an antibiotic resistance enzyme

2017 ◽  
Vol 114 (48) ◽  
pp. 12773-12778 ◽  
Author(s):  
Merijn L. M. Salverda ◽  
Jeroen Koomen ◽  
Bertha Koopmanschap ◽  
Mark P. Zwart ◽  
J. Arjan G. M. de Visser
Keyword(s):  
Antibiotic Resistance ◽  
High Resistance ◽  
Artificial Selection ◽  
Fitness Landscape ◽  
Adaptive Landscape ◽  
Clinical Settings ◽  
Short Term ◽  
Theory Lead

Populations with large mutation supplies adapt via the “greedy” substitution of the fittest genotype available, leading to fast and repeatable short-term responses. At longer time scales, smaller mutation supplies may in theory lead to larger improvements when distant high-fitness genotypes more readily evolve from lower-fitness intermediates. Here we test for long-term adaptive benefits from small mutation supplies using in vitro evolution of an antibiotic-degrading enzyme in the presence of a novel antibiotic. Consistent with predictions, large mutant libraries cause rapid initial adaptation via the substitution of cohorts of mutations, but show later deceleration and convergence. Smaller libraries show on average smaller initial, but also more variable, improvements, with two lines yielding alleles with exceptionally high resistance levels. These two alleles share three mutations with the large-library alleles, which are known from previous work, but also have unique mutations. Replay evolution experiments and analyses of the adaptive landscape of the enzyme suggest that the benefit resulted from a combination of avoiding mutational cohorts leading to local peaks and chance. Our results demonstrate adaptive benefits from limited mutation supplies on a rugged fitness landscape, which has implications for artificial selection protocols in biotechnology and argues for a better understanding of mutation supplies in clinical settings.

Ultrastructural investigations of MDL 19,660-induced effects on the canine platelet and megakaryocyte

1990 ◽  
Vol 48 (3) ◽  
pp. 374-375
Author(s):  
D.E. Loudy ◽  
J. Sprinkle-Cavallo ◽  
J.T. Yarrington ◽  
F.Y. Thompson ◽  
J.P. Gibson
Keyword(s):  
Antidepressant Drug ◽  
Beagle Dogs ◽  
Long Term Effects ◽  
Short Term ◽  
Platelet Counts ◽  
Toxicological Studies ◽  
Induced Aggregation ◽  
Internal Architecture

Previous short term toxicological studies of one to two weeks duration have demonstrated that MDL 19,660 (5-(4-chlorophenyl)-2,4-dihydro-2,4-dimethyl-3Hl, 2,4-triazole-3-thione), an antidepressant drug, causes a dose-related thrombocytopenia in dogs. Platelet counts started to decline after two days of dosing with 30 mg/kg/day and continued to decrease to their lowest levels by 5-7 days. The loss in platelets was primarily of the small discoid subpopulation. In vitro studies have also indicated that MDL 19,660: does not spontaneously aggregate canine platelets and has moderate antiaggregating properties by inhibiting ADP-induced aggregation. The objectives of the present investigation of MDL 19,660 were to evaluate ultrastructurally long term effects on platelet internal architecture and changes in subpopulations of platelets and megakaryocytes.Nine male and nine female beagle dogs were divided equally into three groups and were administered orally 0, 15, or 30 mg/kg/day of MDL 19,660 for three months. Compared to a control platelet range of 353,000- 452,000/μl, a doserelated thrombocytopenia reached a maximum severity of an average of 135,000/μl for the 15 mg/kg/day dogs after two weeks and 81,000/μl for the 30 mg/kg/day dogs after one week.

Introduction

2017 ◽  
Author(s):  
Igor Galynker
Keyword(s):  
Risk Assessment ◽  
At Risk ◽  
Suicide Risk ◽  
Assessment Methods ◽  
Suicidal Patient ◽  
Clinical Settings ◽  
Short Term ◽  
Imminent Risk ◽  
Intended Use

One of the most difficult determinations a psychiatrist makes is whether the chronically suicidal patient is at risk for imminent suicide. The Introduction presents the challenges of the imminent risk assessment and explains the purpose of The Suicidal Narrative—the first clinical guide to such an assessment. It introduces the distinction between long-term and short-term suicide risk, highlights the lack of structured instruments for imminent risk assessment, and discusses the advantages of multimodal and multi-informant assessment methods. It then describes intended uses of the guide, lists its inherent limitations, and identifies possible areas of unintended misuse. The Introduction concludes by naming the main intended use of The Suicidal Narrative: as a roadmap for a comprehensive assessment of imminent suicide risk in diverse clinical settings.

Short-term effect of aldosterone on NEM-sensitive ATPase in rat collecting tubule

1989 ◽  
Vol 257 (2) ◽  
pp. F177-F181 ◽  
Author(s):  
C. Khadouri ◽  
S. Marsy ◽  
C. Barlet-Bas ◽  
A. Doucet
Keyword(s):  
Atpase Activity ◽  
Affinity Constant ◽  
Short Term ◽  
Collecting Tubule ◽  
Lag Period ◽  
In Vitro Effects ◽  
Collecting Tubules

Because previous studies indicated that in the collecting tubule, N-ethylmaleimide (NEM)-sensitive ATPase, the biochemical equivalent of the proton pump, is controlled by mineralocorticoids in the long term, the present study was designed to investigate whether such control also exists in the short term. Therefore we investigated the in vivo and in vitro effects of aldosterone on the enzyme activity in cortical and outer medullary collecting tubules (CCT and MCT, respectively) from adrenalectomized rats. Administration of aldosterone (10 micrograms/kg body wt) markedly stimulated NEM-sensitive ATPase activity in the CCT and MCT within 3 h. Similarly, incubating CCT or MCT for 3 h in the presence of 10(-8) M aldosterone enhanced NEM-sensitive ATPase activity up to values similar to those previously measured in the corresponding nephron segments of normal rats. In vitro stimulation of NEM-sensitive ATPase was dose dependent in regard to aldosterone (apparent affinity constant approximately 10(-9) M), appeared after a 30-min lag period, and reached its maximum after 2-2.5 h. Finally, actinomycin D and cycloheximide totally abolished the in vitro action of aldosterone, demonstrating the involvement of protein synthesis in this process.

Adaptation to calcium deprivation in the rat: effects of parathyroidectomy.

1977 ◽  
Vol 232 (3) ◽  
pp. E336
Author(s):  
J T Pento ◽  
L C Waite ◽  
P J Tracy ◽  
A D Kenny
Keyword(s):  
Adaptive Response ◽  
Calcium Transport ◽  
Parathyroid Tissue ◽  
Adaptation Period ◽  
Short Term ◽  
High Calcium

The role of parathyroid hormone (PTH) in the adaptive response in gut calcium transport to calcium deprivation has been studied in the rat using both the in vitro everted duodenal sac and the in situ ligated duodenal segment technique. Intact or parathyroidectomized (PTX) young rats were placed on a low calcium (0.01%) diet for 7-, 14-, or 21-day adaptation periods and compared with control rats maintained on a high calcium (1.5%) diet. Prior PTX (3 days before the start of the adaptation period) abolished the adaptive response (enhanced calcium transport) induced by calcium deprivation for a 7-day adaptation period, but did not abolish a response after a 21-day period. A 14-day adaptation period gave equivocal results. It is concluded that PTH appears to be necessary for short-term (7-day) adaptation, but not for long-term (21-day) adaptation to calcium deprivation. However, if accessory parathyroid tissue is present, the data could be interpreted differently: the essentiality of PTH for the adaptive response might be independent of the length of the adaptation period. The data also contribute to a possible resolution of the controversy concerning the involvement of PTH in the regulation of intestinal calcium transport in the rat.

scholarly journals Performance of Polyester-Based Electrospun Scaffolds under In Vitro Hydrolytic Conditions: From Short-Term to Long-Term Applications

Nanomaterials ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 786 ◽  
Author(s):  
Oscar Gil-Castell ◽  
José David Badia ◽  
Jordi Bou ◽  
Amparo Ribes-Greus
Keyword(s):  
Molar Mass ◽  
Pure Water ◽  
Phosphate Buffer Solution ◽  
Short Term ◽  
Buffer Solution ◽  
Electrospun Scaffolds ◽  
The Stability ◽  
Short Time

The evaluation of the performance of polyesters under in vitro physiologic conditions is essential to design scaffolds with an adequate lifespan for a given application. In this line, the degradation-durability patterns of poly(lactide-co-glycolide) (PLGA), polydioxanone (PDO), polycaprolactone (PCL) and polyhydroxybutyrate (PHB) scaffolds were monitored and compared giving, as a result, a basis for the specific design of scaffolds from short-term to long-term applications. For this purpose, they were immersed in ultra-pure water and phosphate buffer solution (PBS) at 37 °C. The scaffolds for short-time applications were PLGA and PDO, in which the molar mass diminished down to 20% in a 20–30 days lifespan. While PDO developed crystallinity that prevented the geometry of the fibres, those of PLGA coalesced and collapsed. The scaffolds for long-term applications were PCL and PHB, in which the molar mass followed a progressive decrease, reaching values of 10% for PCL and almost 50% for PHB after 650 days of immersion. This resistant pattern was mainly ascribed to the stability of the crystalline domains of the fibres, in which the diameters remained almost unaffected. From the perspective of an adequate balance between the durability and degradation, this study may serve technologists as a reference point to design polyester-based scaffolds for biomedical applications.

scholarly journals Effect of polyphenols on the intestinal and placental transport of some bioactive compounds

2010 ◽  
Vol 23 (1) ◽  
pp. 47-64 ◽  
Author(s):  
Fátima Martel ◽  
Rosário Monteiro ◽  
Conceição Calhau
Keyword(s):  
Bioactive Compounds ◽  
Biological Effects ◽  
Alcoholic Beverages ◽  
Short Term ◽  
Intestinal Epithelia ◽  
The Past ◽  
Cell Culture Systems ◽  
Epithelial Barriers

Polyphenols are a group of widely distributed phytochemicals present in most foods of vegetable origin. A growing number of biological effects have been attributed to these molecules in the past few years and only recently has their interference with the transport capacity of epithelial barriers received attention. This review will present data obtained concerning the effect of polyphenols upon the transport of some compounds (organic cations, glucose and the vitamins thiamin and folic acid) at the intestinal and placental barriers. Important conclusions can be drawn: (i) different classes of polyphenols affect transport of these bioactive compounds at the intestinal epithelia and the placenta; (ii) different compounds belonging to the same phenolic family often possess opposite effects upon transport of a given molecule; (iii) the acute and chronic/short-term and long-term exposures to polyphenols do not produce parallel results and, therefore, care should be taken when extrapolating results; (iv) the effect of polyphenolics in combination may be very different from the expected ones taking into account the effect of each of these compounds alone, and so care should be taken when speculating on the effect of a drink based on the effect of one component only; (v) care should be taken in drawing conclusions for alcoholic beverages from results obtained with ethanol alone. Although most of the data reviewed in the present paper refer to in vitro experiments with cell-culture systems, these studies raise a concern about possible changes in the bioavailability of substrates upon concomitant ingestion of polyphenols.

Long- and short-term in vitro D-dimer stability measured with INNOVANCE D-Dimer

2010 ◽  
Vol 103 (02) ◽  
pp. 461-465 ◽  
Author(s):  
Martina Böhm-Weigert ◽  
Thomas Wissel ◽  
Heidrun Muth ◽  
Bettina Kemkes-Matthes ◽  
Dirk Peetz
Keyword(s):  
Frozen Storage ◽  
Percentage Change ◽  
Short Term ◽  
Term Stability ◽  
Long Term Stability ◽  
Repeated Freezing ◽  
The Mean ◽  
D Dimer

Summary In vitro D-dimer stability in plasma is widely assumed, but has not yet been documented by systematic studies using samples covering a wide range of D-dimer. We investigated the short- and long-term stability of D-dimer in clinical citrated plasma samples with normal and pathological levels. The short-term stability was analysed by measuring D-dimer fresh, after storage of plasma for 4 hours at room temperature (RT) and after an additional 24 h storage at +2 to +8°C (n=40). Long-term stability samples (n=40) were measured fresh and after storage for 19, 25 and 36 months at ≤-60°C. The effect of repeated freezing was analysed by measuring samples (n=50) fresh and after four consecutive freeze-thaw cycles. D-dimer was measured on the BCS System using the INNOVANCE D-Dimer assay (Siemens Healthcare Diagnostics Products GmbH, Marburg, Germany). D-dimer values at baseline ranged from 0.23–22.2 mg/l FEU. The mean percentage change after storage for 4 hours at RT and additional 24 hours at +2 to +8°C was +3.8% and +2.7%, respectively. The mean percentage change after frozen storage for 19, 25 and 36 months at ≤-60°C was –11.7%, –4.8% and –9.3%, respectively. The small decrease of D-dimer values after frozen storage was not time-dependent. Repeated freezing did not significantly alter D-dimer values (mean change ≤5%). The data demonstrate stability of D-dimer in plasma prior to freezing for up to 4 hours at RT and for up to 24 hours at +2 to +8°C as well as in plasma stored for up to three years at ≤-60°C.

Assessing the Likelihood of Recurrence during RNA Evolution in Vitro

2004 ◽  
Vol 10 (1) ◽  
pp. 1-22 ◽  
Author(s):  
Niles Lehman
Keyword(s):  
Fitness Landscape ◽  
Initial Point ◽  
Living System ◽  
Test Tube ◽  
Adaptive Landscape ◽  
Local Optimum ◽  
Evolution Experiment ◽  
Efficient Selection ◽  
Insight Into

Recurrence is the possibility of resulting in the same endpoint multiple times when a living system is allowed to evolve repeatedly starting from a given initial point. This concept is of concern to both evolutionary theoreticians and molecular biologists who use nucleic acid selection techniques to mimic biotic and computorial processes in the test tube. Using the continuous in vitro evolution methodology, many replicate experimental evolutionary lineages with populations of catalytic RNA were performed to gain insight into the parameters that could affect recurrence. The likelihood that the same genotype will result in parallel trials of an evolution experiment in vitro depends on several factors, including the phenotype under selection, the size and composition of the initial diverse pool of nucleic acids used in the experiment, the degree of mutation possible during the experiment, the shape of the fitness landscape through which the population evolves, and the strategies used to invoke selection and to search the landscape, among others. By considering these factors, it can be predicted that recurrence is more likely when a small, wild-type-based starting pool is used with efficient selection and search strategies involving little online mutagenesis within a rugged adaptive landscape with a strong local optimum. The recurrence experiments performed here on the 150-nucleotide ligase ribozyme demonstrate that it repeatedly jumps from one peak in a fitness landscape to another, apparently hurdling a deep fitness valley. These predictions can and should be tested by additional multiple replicates of actual evolution experiments in the laboratory.

Direct upregulation of parathyroid calcium-sensing receptor and vitamin D receptor by calcimimetics in uremic rats

2009 ◽  
Vol 296 (3) ◽  
pp. F605-F613 ◽  
Author(s):  
Francisco J. Mendoza ◽  
Ignacio Lopez ◽  
Rocio Canalejo ◽  
Yolanda Almaden ◽  
David Martin ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Term Treatment ◽  
Parathyroid Cell ◽  
Calcium Sensing Receptor ◽  
Short Term ◽  
Calcium Sensing ◽  
Long Term Treatment ◽  
Acute Increase

To investigate whether the effect of the calcimimetic AMG 641 and calcitriol on CaSR and VDR expression could be separated from their ability to reduce parathyroid cell proliferation, five-sixth nephrectomized (5/6 Nx) rats received vehicle, AMG 641, calcitriol, or AMG 641+calcitriol either daily for 13 days (long-term protocol) or in a single dose (short-term protocol). In the long-term protocol, AMG 641, calcitriol, and their combination significantly reduced the percentage of proliferating parathyroid cells. Proliferation was uncontrolled in the short-term protocol. A significant increase in CaSR mRNA (% vs. β-actin) was detected in rats treated with both calcitriol (1.60 ± 0.30) and AMG 641 (1.66 ± 0.25) for 13 days ( P = 0.01 vs. 5/6 Nx+vehicle, 0.89 ± 0.09); and there was a further increase when both drugs were administered simultaneously (2.46 ± 0.33). In the short-term protocol, only rats receiving AMG 641 alone (2.01 ± 0.33, P < 0.001) showed increased expression of CaSR mRNA, whereas the combination (1.81 ± 0.20) produced no additional benefit. AMG 641 also increased CaSR mRNA expression in vitro. Changes in VDR mRNA paralleled those of CaSR mRNA. In the long-term treatment, both AMG 641 (0.87 ± 0.14) and calcitriol (0.99 ± 0.12) increased VDR mRNA ( P < 0.05 vs. 5/6 Nx+vehicle, 0.49 ± 0.10), and the increase was more accentuated when the drugs were combined (1.49 ± 0.45). In the short-term protocol, only treatment with AMG 641, alone (1.52 ± 0.41) or combined with calcitriol (1.86 ± 0.24), increased VDR mRNA. In conclusion, our results demonstrate an acute increase in CaSR mRNA and VDR mRNA in the parathyroid glands of uremic rats treated with AMG 641, in which cell proliferation was uncontrolled, thus supporting a direct effect of calcimimetics on CaSR and VDR expression by hyperplastic parathyroid cells.

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