scholarly journals Evolutionary stability of antibiotic protection in a defensive symbiosis

2018 ◽  
Vol 115 (9) ◽  
pp. E2020-E2029 ◽  
Author(s):  
Tobias Engl ◽  
Johannes Kroiss ◽  
Marco Kai ◽  
Taras Y. Nechitaylo ◽  
Aleš Svatoš ◽  
...  
Keyword(s):  
Polyketide Synthase ◽  
Complex Mixture ◽  
Natural Setting ◽  
Human Pathogens ◽  
Biosynthesis Gene Cluster ◽  
Defensive Symbiosis ◽  
Mechanistic Basis ◽  
Main Components ◽  
High Degree

The increasing resistance of human pathogens severely limits the efficacy of antibiotics in medicine, yet many animals, including solitary beewolf wasps, successfully engage in defensive alliances with antibiotic-producing bacteria for millions of years. Here, we report on the in situ production of 49 derivatives belonging to three antibiotic compound classes (45 piericidin derivatives, 3 streptochlorin derivatives, and nigericin) by the symbionts of 25 beewolf host species and subspecies, spanning 68 million years of evolution. Despite a high degree of qualitative stability in the antibiotic mixture, we found consistent quantitative differences between species and across geographic localities, presumably reflecting adaptations to combat local pathogen communities. Antimicrobial bioassays with the three main components and in silico predictions based on the structure and specificity in polyketide synthase domains of the piericidin biosynthesis gene cluster yield insights into the mechanistic basis and ecoevolutionary implications of producing a complex mixture of antimicrobial compounds in a natural setting.

A High Angle, Double Tilting Cold Stage for the AEI EM7

1974 ◽  
Vol 32 ◽  
pp. 450-451
Author(s):  
P.R. Swann ◽  
A.E. Lloyd
Keyword(s):  
Habit Plane ◽  
Temperature Control ◽  
Tilt Angle ◽  
Cooling System ◽  
Thermal Drift ◽  
High Angle ◽  
Cold Stage ◽  
High Degree ◽  
Better Than

Figure 1 shows the design of a specimen stage used for the in situ observation of phase transformations in the temperature range between ambient and −160°C. The design has the following features a high degree of specimen stability during tilting linear tilt actuation about two orthogonal axes for accurate control of tilt angle read-out high angle tilt range for stereo work and habit plane determination simple, robust construction temperature control of better than ±0.5°C minimum thermal drift and transmission of vibration from the cooling system.

scholarly journals In-Situ Synthesis of TiO2@GO Nanosheets for Polymers Degradation in a Natural Environment

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2158
Author(s):  
Yueqin Shi ◽  
Zhanyang Yu ◽  
Zhengjun Li ◽  
Xiaodong Zhao ◽  
Yongjun Yuan
Keyword(s):  
Natural Environment ◽  
New Technologies ◽  
Separation Efficiency ◽  
Basic Mechanism ◽  
Chemical Degradation ◽  
Natural Environments ◽  
Additional Energy ◽  
Photogenerated Electrons ◽  
Main Components

Plastic photodegradation naturally takes 300–500 years, and their chemical degradation typically needs additional energy or causes secondary pollution. The main components of global plastic are polymers. Hence, new technologies are urgently required for the effective decomposition of the polymers in natural environments, which lays the foundation for this study on future plastic degradation. This study synthesizes the in-situ growth of TiO2 at graphene oxide (GO) matrix to form the TiO2@GO photocatalyst, and studies its application in conjugated polymers’ photodegradation. The photodegradation process could be probed by UV-vis absorption originating from the conjugated backbone of polymers. We have found that the complete decomposition of various polymers in a natural environment by employing the photocatalyst TiO2@GO within 12 days. It is obvious that the TiO2@GO shows a higher photocatalyst activity than the TiO2, due to the higher crystallinity morphology and smaller size of TiO2, and the faster transmission of photogenerated electrons from TiO2 to GO. The stronger fluorescence (FL) intensity of TiO2@GO compared to TiO2 at the terephthalic acid aqueous solution indicates that more hydroxyl radicals (•OH) are produced for TiO2@GO. This further confirms that the GO could effectively decrease the generation of recombination centers, enhance the separation efficiency of photoinduced electrons and holes, and increase the photocatalytic activity of TiO2@GO. This work establishes the underlying basic mechanism of polymers photodegradation, which might open new avenues for simultaneously addressing the white pollution crisis in a natural environment.

scholarly journals Intermittent pneumatic leg compressions enhance muscle performance and blood flow in a model of peripheral arterial insufficiency

2012 ◽  
Vol 112 (9) ◽  
pp. 1556-1563 ◽  
Author(s):  
Bruno T. Roseguini ◽  
Arturo A. Arce-Esquivel ◽  
Sean C. Newcomer ◽  
Hsiao T. Yang ◽  
Ronald Terjung ◽  
...  
Keyword(s):  
Blood Flow ◽  
Exercise Tolerance ◽  
Citrate Synthase ◽  
Arterial Disease ◽  
Muscle Performance ◽  
Sprague Dawley ◽  
Arterial Insufficiency ◽  
Mechanistic Basis ◽  
Peripheral Arterial

Despite the escalating prevalence in the aging population, few therapeutic options exist to treat patients with peripheral arterial disease. Application of intermittent pneumatic leg compressions (IPC) is regarded as a promising noninvasive approach to treat this condition, but the clinical efficacy, as well the mechanistic basis of action of this therapy, remain poorly defined. We tested the hypothesis that 2 wk of daily application of IPC enhances exercise tolerance by improving blood flow and promoting angiogenesis in skeletal muscle in a model of peripheral arterial insufficiency. Male Sprague-Dawley rats were subjected to bilateral ligation of the femoral artery and randomly allocated to treatment or sham groups. Animals were anesthetized daily and exposed to 1-h sessions of bilateral IPC or sham treatment for 14–16 consecutive days. A third group of nonligated rats was also studied. Marked increases in treadmill exercise tolerance (∼33%, P < 0.05) and improved muscle performance in situ (∼10%, P < 0.05) were observed in IPC-treated animals. Compared with sham-treated controls, blood flow measured with isotope-labeled microspheres during in situ contractions tended to be higher in IPC-treated animals in muscles composed of predominantly fast-twitch white fibers, such as the plantaris (∼93%, P = 0.02). Capillary contacts per fiber and citrate synthase activity were not significantly altered by IPC treatment. Collectively, these data indicate that IPC improves exercise tolerance in a model of peripheral arterial insufficiency in part by enhancing blood flow to collateral-dependent tissues.

scholarly journals Liquid chromatography–mass spectrometry analysis of dyes formed by in situ oxidative methods then purified by absorption and extraction from hair wefts

2020 ◽  
pp. 174751982097862
Author(s):  
M John Plater ◽  
Andrea Raab
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
Complex Mixture ◽  
Ammonium Salts ◽  
Mass Spectrometry Analysis ◽  
Liquid Chromatography Mass Spectrometry ◽  
Spectrometry Analysis ◽  
Chromatography Mass Spectrometry ◽  
Didecyldimethylammonium Chloride

The dye mixtures formed from three commercial hair colour formers were purified by absorption onto human hair wefts, washed and dried, extracted with dichloromethane:trifluoroacetic acid (75:25) and then analysed by liquid chromatography–mass spectrometry. Only 1–2 dyes were identified from each complex mixture of commercial aromatic amines along with a broad UV absorption mainly consisting of mixtures of quaternary ammonium salts from shampoos and some surfactants. Mecetronium ethyl sulfate and didecyldimethylammonium chloride were the main ammonium salts.

DNA—RNA hybridization

1975 ◽  
Vol 272 (915) ◽  
pp. 147-157 ◽  
Keyword(s):  
Nucleic Acid ◽  
Complex Mixture ◽  
Nucleic Acid Hybridization ◽  
Biological Research ◽  
Specific Sequence ◽  
Different Populations ◽  
Higher Eukaryotes ◽  
High Degree ◽  
Kinetics Of ◽  
Specific Sequences

Interest in nucleic acid hybridization stems mainly from its great power as a tool in biological research. It is used in several quite distinct ways. Because of the high degree of specificity that they show, hybridization techniques can be used to measure the amount of one specific sequence within a very heterogeneous mixture of sequences. Measurements of 1/10 6 -10 7 have been recorded. In extension of this, various properties of a specific sequence can often be studied. Secondly, because the kinetics of nucleic acid hybridization are quite well understood, it can be used to characterize both a pure sequence and a very complex mixture of sequences, like the genome of a vertebrate. Thirdly, again because of its specificity, it can be used to measure homologies between different populations of nucleic acids. Lastly, in conjunction with other techniques, it can be used as a basis for the fractionation of nucleic acid populations and the purification of specific sequences. Specific examples of these applications are given, with special reference to the organization of the genome in higher eukaryotes.

Distinguishing L from M photopigment coding sequences by hybridization to novel locked nucleic acid (LNA) oligonucleotide probes

2008 ◽  
Vol 25 (3) ◽  
pp. 283-287
Author(s):  
CHRISTINA PETTAN-BREWER ◽  
LI FU ◽  
SAMIR S. DEEB
Keyword(s):  
Nucleic Acid ◽  
Locked Nucleic Acid ◽  
Macaca Nemestrina ◽  
Oligonucleotide Probes ◽  
Coding Sequences ◽  
Cone Mosaic ◽  
Target Nucleic Acid ◽  
High Degree

Many attempts have been made over the years to distinguish human and primate L (long-wavelength sensitive) from M (middle-wavelength sensitive) cone photoreceptors using either immunohistochemistry or in situ hybridization. These attempts have been unsuccessful due to the very high degree of identity between the sequences of the L and M proteins and encoding mRNAs. The recent development of chemically modified oligonucleotide probes, referred to as locked nucleic acid (LNA) probes, has shown that they hybridize with much greater affinity and specificity to the target nucleic acid. This has greatly increased the potential for differentiating L from M cones by in situ hybridization. We have designed LNA oligonucleotide probes that are complementary to either the L or M coding sequences located in exon 5 of the Macaca nemestrina L and M pigment genes. We have shown that the LNA-M and LNA-L probes hybridize specifically to their respective target nucleic acid sequences in vitro. This result strongly suggests that these probes would be instrumental in rapidly distinguishing L from M cone in the entire retina, and in defining the cone mosaic during development and in adults.

Molecular interactions shaping the tetraspanin web

2017 ◽  
Vol 45 (3) ◽  
pp. 741-750 ◽  
Author(s):  
Sjoerd J. van Deventer ◽  
Vera-Marie E. Dunlock ◽  
Annemiek B. van Spriel
Keyword(s):  
Molecular Interactions ◽  
Intracellular Signaling ◽  
Spatial Organization ◽  
Complex Mixture ◽  
Point Of View ◽  
Intramolecular Interactions ◽  
Fundamental Understanding ◽  
High Degree ◽  
Partner Proteins ◽  
Insight Into

To facilitate the myriad of different (signaling) processes that take place at the plasma membrane, cells depend on a high degree of membrane protein organization. Important mediators of this organization are tetraspanin proteins. Tetraspanins interact laterally among themselves and with partner proteins to control the spatial organization of membrane proteins in large networks called the tetraspanin web. The molecular interactions underlying the formation of the tetraspanin web were hitherto mainly described based on their resistance to different detergents, a classification which does not necessarily correlate with functionality in the living cell. To look at these interactions from a more physiological point of view, this review discusses tetraspanin interactions based on their function in the tetraspanin web: (1) intramolecular interactions supporting tetraspanin structure, (2) tetraspanin–tetraspanin interactions supporting web formation, (3) tetraspanin–partner interactions adding functional partners to the web and (4) cytosolic tetraspanin interactions regulating intracellular signaling. The recent publication of the first full-length tetraspanin crystal structure sheds new light on both the intra- and intermolecular tetraspanin interactions that shape the tetraspanin web. Furthermore, recent molecular dynamic modeling studies indicate that the binding strength between tetraspanins and between tetraspanins and their partners is the complex sum of both promiscuous and specific interactions. A deeper insight into this complex mixture of interactions is essential to our fundamental understanding of the tetraspanin web and its dynamics which constitute a basic building block of the cell surface.

Colonization of depopulated crinoids by symbionts: who comes from the bottom and who from the water column?

2015 ◽  
Vol 95 (8) ◽  
pp. 1607-1612 ◽  
Author(s):  
E.S. Mekhova ◽  
P.Y. Dgebuadze ◽  
V.N. Mikheev ◽  
T.A. Britayev
Keyword(s):  
Water Column ◽  
Field Experiments ◽  
Dispersal Ability ◽  
Long Distance ◽  
Sandy Substrate ◽  
Limited Dispersal ◽  
Set Up ◽  
Almost All ◽  
High Degree

Previous experiments with the comatulid Himerometra robustipinna (Carpenter, 1881) demonstrated intensive host-to-host migration processes for almost all symbiotic species both within host aggregations and among hosts separated by several metres. The aim of this study was to check the ability of symbionts to complete long-distance migrations, by means of two in situ experiments which depopulated the crinoid host. Two different sets of field experiments were set up: exposure of depopulated crinoids (set 1) on stony ‘islands’ isolated from native crinoid assemblages by sandy substrate, and (set 2) in cages suspended in the water column. Hosts from set 1 were exposed for 1, 2, 3 and 4 weeks to assess whether substrate has an influence on the symbionts' long-distance migrations. In set 2 cages were exposed for 10–11 days, aiming to check whether symbionts were able to disperse through the water column with currents. These experiments allow the conclusion that post-settled symbionts can actively migrate among their hosts. Symbionts are able to reach their hosts by employing two different ‘transport corridors’, by drifting or swimming in water column, and by moving on the bottom. Comparison of experimental results allows the division of symbionts into two conventional groups according to the dispersal ability of their post-settled stages: (1) species able to complete long-distance migrations, (2) species unable to migrate or having limited dispersal ability. The finding of the free-living shrimp Periclimenes diversipes Kemp, 1922 in set 2 raises the question about the factors that affect such a high degree of specialization of crinoid assemblages.

Integration of cornea and cardiorespiratory afferents in the nucleus of the solitary tract of the rat

2002 ◽  
Vol 282 (4) ◽  
pp. H1278-H1287 ◽  
Author(s):  
Pedro Boscan ◽  
Julian F. R. Paton
Keyword(s):  
Electrical Stimulation ◽  
Solitary Tract ◽  
Peripheral Chemoreceptor ◽  
Single Unit Recordings ◽  
Degree Of Convergence ◽  
High Degree ◽  
Working Heart ◽  
Stimulation Of ◽  
Nerve Discharge

We determined the activity of neurons within the nucleus of the solitary tract (NTS) after stimulation of the cornea and assessed whether this input affected the processing of baroreceptor and peripheral chemoreceptor inputs. In an in situ, unanesthetized decerebrate working heart-brain stem preparation of the rat, noxious mechanical or electrical stimulation was applied to the cornea, and extracellular single unit recordings were made from NTS neurons. Cornea nociceptor stimulation evoked bradycardia and an increase in the cycle length of the phrenic nerve discharge. Of 90 NTS neurons with ongoing activity, corneal stimulation excited 51 and depressed 39. There was a high degree of convergence to these NTS neurons from either baroreceptors or chemoreceptors. The excitatory synaptic response in 12 of 19 baroreceptive and 10 of 15 chemoreceptive neurons was attenuated significantly during concomitant electrical stimulation of the cornea. This inhibition was GABAA receptor mediated, being blocked by pressure ejection of bicuculline. Thus the NTS integrates information from corneal receptors, some of which converges onto neurons mediating reflexes from baroreceptors and chemoreceptors to inhibit these inputs.

scholarly journals The surface albedo of the Greenland ice sheet: satellite-derived and in situ measurements in the Søndre Strømfjord area during the 1991 melt season

1996 ◽  
Vol 42 (141) ◽  
pp. 364-374 ◽  
Author(s):  
Wouter H. Knap ◽  
Johannes Oerlemans
Keyword(s):  
Surface Albedo ◽  
Near Infrared ◽  
Broad Band ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Zone Ii ◽  
High Degree ◽  
Pixel Scale ◽  
Very High

AbstractThe temporal and spatial variation in the surface albedo of the Greenland ice sheet during the ablation season of 1991 is investigated. The study focuses on an area east of Søndre Strømfjord measuring 200 km by 200 km and centred at 67°5′ N, 48° 13′W. The analysis is based on satellite radiance measurements carried out by the Advanced Very High Resolution Radiometer (AVHRR). The broad-band albedo is estimated from the albedos in channel 1 (visible) and channel 2 (near-infrared). The results are calibrated with the surface albedo of sea and dry snow.Satellite-derived albedos are compared with GIMEX ground measurements at three stations. There is a high degree of consistency in temporal variation at two of the three stations. Large systematic differences are attributed to albedo variations on sub-pixel scale.In the course of the ablation season four zones appear, each parallel to the ice edge. It is proposed that these are, in order of increasing altitude: (I) clean and dry ice, (II) ice with surface water, (III) superimposed ice, and (IV) snow. An extensive description of these zones is given on the basis of the situation on 25 July 1991. Zones I, III and IV reveal fairly constant albedos (0.46, 0.65 and 0.75 on average), whereas zone II is characterised by an albedo minimum (0.34). Survey of the western margin of the Greenland ice sheet (up to 71° N) shows that the zonation occurs between 66° and 70° N.

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