Changes In Temperature Sensitivity Research Articles

Understanding how variable thermal environments affect the molecular mechanisms underlying temperature-sensitive phenotypes: lessons from sex determination.

The thermal environment that organisms experience can affect many aspects of their phenotype. As global temperatures become more unpredictable, it is imperative that we understand the molecular mechanisms by which organisms respond to variable, and often transient, thermal environments. Beyond deciphering the mechanisms through which organisms respond to temperature, we must also appreciate the underlying variation in temperature-dependent processes, as this variation is essential for understanding the potential to adapt to changing climates. In this Commentary, we use temperature-dependent sex determination as an example to explore the mechanistic processes underlying the development of temperature-sensitive phenotypes. We synthesize the current literature on how variable thermal conditions affect these processes and address factors that may limit or allow organisms to respond to variable environments. From these examples, we posit a framework for how the field might move forward in a more systematic way to address three key questions: (1) which genes directly respond to temperature-sensitive changes in protein function and which genes are downstream, indirect responders?; (2) how long does it take different proteins and genes to respond to temperature?; and (3) are the experimental temperature manipulations relevant to the climate the organism experiences or to predicted climate change scenarios? This approach combines mechanistic questions (questions 1 and 2) with ecologically relevant conditions (question 3), allowing us to explore how organisms respond to transient thermal environments and, thus, cope with climate change.

Redox and temperature-sensitive changes in microbial communities and soil chemistry dictate greenhouse gas loss from thawed permafrost

Greenhouse gas (GHG) emissions from thawed permafrost are difficult to predict because they result from complex interactions between abiotic drivers and multiple, often competing, microbial metabolic processes. Our objective was to characterize mechanisms controlling methane (CH4) and carbon dioxide (CO2) production from permafrost. We simulated permafrost thaw for the length of one growing season (90 days) in oxic and anoxic treatments at 1 and 15 °C to stimulate aerobic and anaerobic respiration. We measured headspace CH4 and CO2 concentrations, as well as soil chemical and biological parameters (e.g. dissolved organic carbon (DOC) chemistry, microbial enzyme activity, N2O production, bacterial community structure), and applied an information theoretic approach and the Akaike information criterion to find the best explanation for mechanisms controlling GHG flux. In addition to temperature and redox status, CH4 production was explained by the relative abundance of methanogens, activity of non-methanogenic anaerobes, and substrate chemistry. Carbon dioxide production was explained by microbial community structure and chemistry of the DOC pool. We suggest that models of permafrost CO2 production are refined by a holistic view of the system, where the prokaryote community structure and detailed chemistry are considered. In contrast, although CH4 production is the result of many syntrophic interactions, these actions can be aggregated into a linear approach, where there is a single path of organic matter degradation and multiple conditions must be satisfied in order for methanogenesis to occur. This concept advances our mechanistic understanding of the processes governing anaerobic GHG flux, which is critical to understanding the impact the release of permafrost C will have on the global C cycle.

Proton Resonance Frequency Chemical Shift Thermometry: Experimental Design and Validation toward High-Resolution Noninvasive Temperature Monitoring and In Vivo Experience in a Nonhuman Primate Model of Acute Ischemic Stroke

Applications for noninvasive biologic temperature monitoring are widespread in biomedicine and of particular interest in the context of brain temperature regulation, where traditionally costly and invasive monitoring schemes limit their applicability in many settings. Brain thermal regulation, therefore, remains controversial, motivating the development of noninvasive approaches such as temperature-sensitive nuclear MR phenomena. The purpose of this work was to compare the utility of competing approaches to MR thermometry by using proton resonance frequency chemical shift. We tested 3 methodologies, hypothesizing the feasibility of a fast and accurate approach to chemical shift thermometry, in a phantom study at 3T. A conventional, paired approach (difference [DIFF]-1), an accelerated single-scan approach (DIFF-2), and a new, further accelerated strategy (DIFF-3) were tested. Phantom temperatures were modulated during real-time fiber optic temperature monitoring, with MR thermometry derived simultaneously from temperature-sensitive changes in the water proton chemical shift (∼0.01 ppm/°C). MR thermometry was subsequently performed in a series of in vivo nonhuman primate experiments under physiologic and ischemic conditions, testing its reproducibility and overall performance. Chemical shift thermometry demonstrated excellent agreement with phantom temperatures for all 3 approaches (DIFF-1: linear regression R(2) = 0.994; P < .001; acquisition time = 4 minutes 40 seconds; DIFF-2: R(2) = 0.996; P < .001; acquisition time = 4 minutes; DIFF-3: R(2) = 0.998; P < .001; acquisition time = 40 seconds). These findings confirm the comparability in performance of 3 competing approaches to MR thermometry and present in vivo applications under physiologic and ischemic conditions in a primate stroke model.

Co-precipitation synthesis of YAG:Dy nanophosphor and its thermometric properties

Dy3+ doped yttrium aluminum garnet (YAG) nanophosphors were synthesized by a co-precipitation method for potential thermographic applications in a liquid media dispersed with fluorescent nanoparticles. The doping concentration and annealing temperature on the structural and optical properties of YAG:Dy were investigated. Pure phase YAG:Dy nanophosphors were obtained by annealing the co-precipitated hydroxide products at above 900°C. Maximum photoluminescence intensity was observed from 6%Dy doped YAG samples. The effect of measuring temperature between 20 and 350°C on the photoluminescence spectra of nano YAG:Dy was investigated. A temperature-sensitive change in the peak intensity ratio of 496/457nm emission lines was demonstrated for such nanophosphors for the first time, suggesting potential applications in temperature monitoring of fuel spray.

Sensing using rare-earth-doped upconversion nanoparticles.

Optical sensing plays an important role in theranostics due to its capability to detect hint biochemical entities or molecular targets as well as to precisely monitor specific fundamental psychological processes. Rare-earth (RE) doped upconversion nanoparticles (UCNPs) are promising for these endeavors due to their unique frequency converting capability; they emit efficient and sharp visible or ultraviolet (UV) luminescence via use of ladder-like energy levels of RE ions when excited at near infrared (NIR) light that are silent to tissues. These features allow not only a high penetration depth in biological tissues but also a high detection sensitivity. Indeed, the energy transfer between UCNPs and biomolecular or chemical indicators provide opportunities for high-sensitive bio- and chemical-sensing. A temperature-sensitive change of the intensity ratio between two close UC bands promises them for use in temperature mapping of a single living cell. In this work, we review recent investigations on using UCNPs for the detection of biomolecules (avidin, ATP, etc.), ions (cyanide, mecury, etc.), small gas molecules (oxygen, carbon dioxide, ammonia, etc.), as well as for in vitro temperature sensing. We also briefly summarize chemical methods in synthesizing UCNPs of high efficiency that are important for the detection limit.

Particle Migration by Optical Scattering Force in Microfluidic System With Light-Absorbing Liquid

Optical force offers a promise of being applied as a noninvasive manipulation tool for microscopic objects without physical contact. Particle control in a microfluidic system is achieved by optics showing advantages over electric or the other methods. With optics, the fluid need not to be contamination free and there is no need for electrode fabrication. Particles can experience different forces depending on the optical configuration. The scattering force is predominant under parallel or gently focused irradiation, while the gradient force is predominant in tightly focused irradiation. This paper reports the experimental and theoretical investigations of the potential of optical scattering force for particle control technique in a microfluidic system with a light-absorbing liquid. The light-absorption of the incident laser beam in the liquid causes a temperature rise and induces the corresponding property changes of liquid and particles. The experiments were presented for particle migration using the scattering force exerted by a compact diode laser with a wavelength of 635 nm. The absorption of the light in the liquid was controlled by the concentration of dye substance added in a buffer solution. The velocities of polystyrene particles with a diameter of 1.9 μm and the temperature distributions of the liquid under laser irradiation were measured by tracking their movement and by temperature-sensitive fluorophore, respectively. When there is no light absorption in the liquid, the migration velocity of particles under the laser beam is linearly increased with the increase of the laser power, in agreement with the calculations based on ray optics theory. In the case of light-absorbing liquid, the migration speed of particles experiencing the optical force indicates a nonlinear increase as the laser power increases. This enhancement mainly attributes to the temperature-sensitive change of liquid viscosity resulting in a reduction of viscous drag for migrating particles. An appropriate arrangement of light absorption leads to an enhancement in the photophoretic velocity of particles, and eventual performance promotion of particle separation and/or sorting using the optical force.

Ambient temperature-dependent thermoregulatory role of REM sleep

Changes in ambient temperature produce complex effects on sleep–wakefulness. In order to find out the mechanisms involved in temperature-sensitive changes in sleep in rats, their thermal preference, body temperature and sleep were studied before and after the destruction of both peripheral and central warm receptors, by systemic administration of 375mg/kg capsaicin. Though the pre-treated rats preferred to stay mostly at the ambient temperature of 27°C, post-treated rats strayed freely into chambers having ambient temperature of 30°C and 33°C. Sleep and body temperature of these rats were studied for six hours each, when they were kept at an ambient temperature of 18–36°C. Total sleep time, especially REM sleep, was maximum at 30°C in pre-treated rats, but this REM sleep peak at 30°C disappeared after capsaicin administration. Body temperature increased sharply in post-treated rats, at ambient temperatures above 30°C. Apart from the ability to defend body temperature at high ambient temperature, avoidance of warm ambient temperature and increase in REM sleep are the behavioral measures which are lost in post-treated rats. Results of this study suggest that the ambient temperature-related increase in REM sleep at 30°C could be part of the thermoregulatory measures.

Validation of microtubule‐associated Tobacco mosaic virus RNA movement and involvement of microtubule‐aligned particle trafficking

Functional studies of Tobacco mosaic virus (TMV) infection using virus derivatives expressing functional, dysfunctional, and temperature-sensitive movement protein (MP) mutants indicated that the cell-to-cell transport of TMV RNA is functionally correlated with the association of MP with microtubules. However, the role of microtubules in the movement process during early infection remains unclear, since MP accumulates on microtubules rather late in infection and treatment of plants with microtubule-disrupting agents fails to strongly interfere with cell-to-cell movement of TMV RNA. To further test the role of microtubules in TMV cell-to-cell movement, we investigated TMV strain Ni2519, which is temperature-sensitive for movement. We demonstrate that the temperature-sensitive defect in movement is correlated with temperature-sensitive changes in the localization of MP to microtubules. Furthermore, we show that during early phases of recovery from non-permissive conditions, the MP localizes to microtubule-associated particles. Similar particles are found in cells at the leading front of spreading TMV infection sites. Initially mobile, the particles become immobile when MP starts to accumulate along the length of the particle-associated microtubules. Our observations confirm a role for microtubules in the spread of TMV infection and associate this role with microtubule-associated trafficking of MP-containing particles in cells engaged in the cell-to-cell movement of the TMV genome.

Geophysical consequences of the Cordillera–Craton thermal transition in southwestern Canada

There is a pronounced increase in heat flow and lithosphere temperatures across the transition from the stable North American Craton to the southeastern Canadian Cordillera. The heat flow increases from 40–60 mW m −2 in the Craton to 80–100 mW m −2 in the Cordillera. There are numerous reliable heat flow data in the Cordillera but measurements in the Western Canada Sedimentary Basin overlying the adjacent Craton are in petroleum exploration wells with inherent low accuracy and are affected by hydrological effects. However, the deep thermal boundary is well defined based upon contrasts in several other temperature-sensitive geophysical parameters. The boundary is located 100 km west of the mountain front in the region of the Rocky Mountain Trench, and it must occur over a distance of less than 200 km. Temperatures in the deep crust and upper mantle are first computed from the heat flow and radioactive heat generation data. These temperatures are then compared to those estimated from the temperature dependence of uppermost mantle seismic velocity, Pn, and from xenoliths in kimberlites for the Craton, and in Tertiary volcanics for the Cordillera. Pn velocities decrease from about 8.2 km s −1 in the exposed Craton to 7.8 km s −1 in the Cordillera. The temperatures just below the Moho are 400–500°C for the Craton and 900–1000°C beneath the Cordillera based upon all three constraints. Two temperature-sensitive changes across the thermal boundary are examined. There is a westward decrease in crustal thickness from 40–50 km for the Craton to 32–34 km for the Cordillera with no significant change in average elevation nor in gravity. Isostatic balance is maintained by thermal expansion and density reduction in the high-temperature Cordillera lithosphere. The average temperature to a depth of 150 km is about 400°C higher for the Cordillera compared to the Craton. There also is a pronounced westward decrease in lithosphere strength and thus deformation style. In the Craton, the crust and upper mantle are very strong to at least 100 km depth. As a result, the foreland belt deep crust and upper mantle have remained undeformed during late Mesozoic to early Tertiary tectonics. Shortening occurred primarily in overlying sedimentary thrust sheets, mediated by high pore fluid pressures. In the Cordillera hinterland, the high temperatures result in the rheological lithosphere with significant strength being limited to the upper 10–15 km of the crust. Mesozoic–Cenozoic shortening deformation and subsequent extension included this whole thin lithosphere.

Characterization of the rat colonic aldosterone receptor and its activation process.

Aldosterone increases sodium absorption, short circuit current, and transmural potential difference in rat colon. We studied the rat colonic aldosterone receptor using the synthetic glucocorticoid, 11 beta, 17 beta-dihydroxy-17 alpha-propynylandrosta-1,4,6-triene-3-one, to prevent binding to the glucocorticoid receptor. Specific aldosterone binding was found in proximal and distal colon. Heating to 25 degrees C decreased binding within 15 min, but the protease inhibitor, phenylmethylsulfonyl fluoride, stabilized binding. Binding was highest in terminal distal colon. Competitive binding assay showed aldosterone specificity compared to other competitors was greater at 30 than at 4 degrees C, suggesting temperature-sensitive changes in receptor specificity. Scatchard analysis revealed a straight line with a KD of 2.5 nM at 0 degrees C and 4.1 nM at 30 degrees C. Bmax was higher in distal than in proximal colon (30 degrees C, 156 +/- 33 versus 65 +/- 9 fmol/mg protein) and increased by 36% in proximal and 180% in distal colon at 30 degrees C compared to 0 degrees C. DEAE-cellulose chromatography of unactivated receptor demonstrated a single peak eluting at 200-250 mM KCl. Heat, ATP, and gel filtration did not activate the receptor, whereas increasing cytosolic salt concentration to 300 mM KCl, raising the pH to 8, or adding EGTA and EDTA caused increased DNA-cellulose binding and a new peak eluting at 30-80 mM KCl on DEAE-cellulose chromatography. There is a specific aldosterone receptor in colon with increasing number of binding sites from proximal to most distal segments paralleling aldosterone's physiological effects. Absence of receptor activation with heat, gel filtration, or ATP suggests differences between activation of the aldosterone receptor and other steroid hormone receptors.

Analysis of damage profiles in poly(methyl methacrylate) in terms of oxygen diffusion and consumption

Profiles of photolytically induced chain scissions in poly(methyl methacrylate) (PMMA) and oxygen diffusion and solubility parameters have been used to estimate the activation energy of the chain scission process. The resulting activation energy of 19 kcal/mol, which does not include contributions from the activation energies of oxygen diffusion and solubility, suggests that the temperature-sensitive changes in photolytic scission in PMMA arise from changes in the efficiency of the cage effect.

Temperature-sensitive changes in the structure of globin chromatin in lines of red cell precursors transformed by ts-AEV

Chicken bone marrow cells infected in vitro with a temperature-sensitive avian erythroblastosis virus fail to produce hemoglobin at 36°C. When the product or products of the transforming gene ( erb) are inactivated by a temperature shift to 42°C in culture, several different cloned lines of cells infected with the temperature-sensitive avian erythroblastosis virus begin to make hemoglobin. This shift in phenotype correlates with an increase in hemoglobin mRNA specific to both adult and embryonic α and β globin. The switch is accompanied by the acquisition of DNAase I-hypersensitive sites in one cell line (clone 2); however, a hypothetically more mature line (clone 3) has already acquired globin DNAase-hypersensitive sites but does not express hemoglobin until the temperature shift. Several (but not all) specific restriction sites associated with both the α and β domains become unmethylated after the switch from 36°C to 42°C. The magnitude of these methylation switches is small compared with changes that occur in these genes during normal avian erythropoiesis. The results suggest that changes in chromosomal structure precede transcription and are not a consequence of transcription. Since (presumptive) precursor cloned lines can be established with some, but not all, of the structural properties of active globin chromatin, it is likely that many of these properties can be independently established and are not obligatorily related.

Studies of membrane fusion II. fusion of human erythrocytes by sendai virus

ABSTRACT Thin section, negative stain and freeze-fracture electron microscopy have been used to study the fusion of human erythrocytes by Sendai virus. Sendai virus particles are shown to consist of an envelope covered with ∼ 12 nm-long projections or spikes which encloses a helical nucleocapsid. The spike complexes are dumbell-shaped and consist of 2 knobs, one ∼ 8 nm, the other ∼14 nm, in diameter connected by a narrow ∼ 3 nm-thick stalk, with the larger knob embedded in the lipid bilayer of the viral envelope. Virus particles bind to and agglutinate cells at 4 °C; fusion of viral envelopes with the erythrocyte membrane and extensive cell-cell fusion takes place following a brief incubation at 37 °C. At 4 °C most virus particles are roughly spherical and fractures through the viral envelope reveal concave E fracture faces with ∼ 14-nm-diameter intramembrane particles and convex P faces with a complementary arrangement of pits. Incubation at 37 °C results in a dramatic change in the structure of the viral envelope of many virus particles. Invaginations of the viral envelope give the virus a convoluted profile and such virus particles are characterized in freeze-fracture replicas by the presence of smooth linear ridges 30 nm wide and up to 0. ·5 μm long on E faces and by a complementary arrangement of linear grooves on P faces. Instead of ∼ 14 nm-diameter intramembrane particles on E faces, ∼ 8 nm particles are present on both P and E faces. These changes, which only take place when virus particles are bound to erythrocytes, are also accompanied by the disappearance of clearly defined surface spikes. Only virus particles having this altered morphology actually fuse with the erythrocyte membrane. The characteristic ‘ridged’ morphology of the viral envelope allows specific sites of viral envelope-cell fusion to be identified in freezefracture replicas and successive stages during the incorporation of the viral envelope to be reconstructed. These observations show that viral envelope-cell fusion is initiated by a cell- mediated temperature-sensitive change in the molecular organization of the viral envelope which allows the particle—denuded linear invaginations, possibly lipid bilayer, to interact and fuse with the erythrocyte membrane. Further observations suggest that cell-cell fusion does not occur directly between cells but is achieved by the simultaneous fusion of a virus particle with 2 adjacent erythrocytes.

Temperature-sensitive changes in surface modulating assemblies of fibroblasts transformed by mutants of Rous sarcoma virus.

The hypothesis that surface modulating assemblies containing microfilaments and microtubules and altered after cellular transformation was tested on cells infected with temperature-sensitive mutants of avian sarcoma virus. Untransformed cells (mouse 3T3 and chick fibroblasts), cells transformed by simian virus 40 (SV 3T3), and chick fibroblasts infected with Schmidt-Ruppin strain of Rous sarcoma virus (SR-RSV-A-infected cells) were first compared for differences in microfilament and microtubule patterns after treatment with fluorescein-labeled antibodies to actin and tubulin. Transformed cells showed disappearance of ordered stress microfilaments and thickened or diffuse alterations of microtubular arrays. At restrictive temperatures (41 degrees), chick fibroblasts infected with a temperature-sensitive mutant (ts 68) of Rous sarcoma virus showed normal patterns of stress fialments and radial microtubular arrays originating in 1 or 2 centrioles. At permissive temperatures (37 degrees), these patterns were disordered and resembled those of SR-RSV-A-infected cells. After a shift from 41 degrees to 37 degrees, the changes in microtubules were observed in the majority of cells within 1 hr. These changes were reversible and did not result from the inability of tubulin to polymerize. In ts 68-infected cells at permissive temperatures, concanavalin A induced much less surface modulation (inhibition of receptor mobility) than at restrictive temperatures. These results suggest that cellular transformation alters both the structure and function of surface modulating assemblies and prompt the hypothesis that products of viral transforming genes may affect these assemblies with a consequent loss of growth control.

A temperature-sensitive change in the energy of activation of hormone-stimulated hepatic adenylyl cyclase.

We describe an abrupt increase (at 32 degrees ) in the energy of activation for the reaction of hepatic adenylyl cyclase in the presence of glucagon or epinephrine. This increase is not seen in the presence of fluoride, prostaglandin E(1), or 1-propanol, or in the absence of cyclase stimulators. The change in energy of activation found with hormones is abolished by 1-propanol. This change does not represent differences in hormone or substrate binding at different temperatures, but seems to reflect interactions among elements of the cyclase stimulation sequence. Similar changes in energy of activation were not observed for alkaline phosphatase, cyclic AMP-phosphodiesterase, 5'-nucleotidase, or ouabain-sensitive ATPase. Since the mole fraction of cholesterol in liver membranes is sufficiently high to preclude a phase change in bulk membrane lipids, our observation suggests either that cyclase is restricted to cholesterol-poor membrane regions or that the change in its energy of activation is largely restricted to protein components of the cyclase apparatus. The data are compatible with fundamental differences in the stimulation process(es) for the hormones (glucagon and epinephrine) as compared with those for fluoride and prostaglandin E(1).

Changes in temperature-sensitivity of haemagglutinin and neuraminidase during adaptation of influenza virus to mice.

Temperature-sensitivity of haemagglutinin and neuraminidase of influenza A2 (H2 N2) strains was determined before and after mouse adaptation.

Isolation of temperature-sensitive mutants of murine sarcoma virus.

Three separate murine sarcoma virus nonproducer cell lines have been isolated which are temperature sensitive for the maintenance of transformation. In each case, a viral rather than a cellular genetic mutation is the reason for the temperature-sensitive effect. Superinfection of one of the mutants with murine leukemia virus overcomes the temperature-sensitive change in the transformed state.

Changes of Membrane Proteins and Their Relation to Deoxyribonucleic Acid Synthesis and Cell Division of Escherichia coli

Abstract Escherichia coli K-12 were treated in five ways to alter DNA synthesis, cell division, or both. Their membranes were then examined for changes. The bacteria were grown in the presence of radioactive l-arginine to label the membranes. 14C-Arginine was used for the experimental culture and 3H-arginine for the control, or vice versa. The cells were mixed, and their membranes were isolated and run on acrylamide gels in 0.5% sodium dodecyl sulfate to obtain a spectrum of proteins. Gel fractions were counted for both labels in order to find differences caused by the experimental treatment. Two principal changes were found in the membranes. At a position Y, corresponding to molecular weight 34,000, less protein appeared whenever DNA synthesis was inhibited. At a position X, molecular weight 39,000, extra protein appeared whenever bacterial division was inhibited. Rates of changes of Y and X were examined during thymidine deprivation to stop DNA synthesis, and after restoration of thymidine. Whereas DNA synthesis was rapidly affected, the changes of Y were gradual, suggesting that Y is not responsible for the synthesis of DNA; rather, its slowed rate of formation might be a consequence of arrested DNA synthesis. Changes of X were more immediate, and could possibly be responsible for altered cell division which is only affected after a lag. No significant changes in synthesis of X and Y were noted between cells near the beginning and end of the division cycle, suggesting that these proteins are normally made continuously or are not produced under normal conditions. Pulse chase experiments indicated that X and Y do not have a precursor-product relation. This is also suggested by the kinetic studies. Temperature-sensitive changes of membrane proteins in a previously described temperature-sensitive DNA synthesis mutant were further examined. The mutation appears to influence the formation of Y indirectly by stopping DNA synthesis. But production of X in the absence of DNA synthesis was much less in the mutant than in the wild type, which is compatible with ability of the mutant to divide even in the absence of DNA synthesis.