Low Experimental Temperature Research Articles

High‐quality polythiophene films prepared by electropolymerization of thiophene in BF3‐ethyl ether solution

AbstractPolythiophene films have been deposited on a platinum electrode surface by direct oxidation of thiophene in BF3‐ethyl ether solution containing a controlled amount of water (5 mM). The electric and mechanical properties of the films were studied. Experimental results demonstrated that the films prepared at low applied potentials were semiconductors with conductivities in the order of 10−1 s cm−1. The strengths of these films were high and comparable to those of some widely used engineering plastics such as poly(propylene) and poly(vinyl acetate). The conductivities of the PT films varied with the value of applied potential used for electrolysis and passed through a maximum of 19.13 s cm−1 at +1.6 V. At a given applied potential, low experimental temperature, and monomer concentration led to formation of films with high quality. © 1995 John Wiley & Sons, Inc.

Thermal evolution of pre‐adult life history traits in Drosophila melanogaster

AbstractReplicated lines of Drosophila melanogaster were allowed to evolve in population cage culture at 16.5° C or 25° C for five years. Their larval and pupal development times, larval growth rates, larval critical weights for pupariation and pre‐adult survival rates were then measured at both temperatures. Pre‐adult survival showed evidence of adaptation of the lines to their thermal selection regimes, with each set of lines showing superior survival when tested at the temperature at which they had been evolving. Pupal periods were similar for all lines when growing at 16.5° C but, at 25° C, the low temperature lines had the longer pupal periods. Irrespective of experimental temperature, low temperature lines grew faster and had shorter larval development periods than the high temperature lines. Larval critical weights for pupariation were higher in the low temperature lines at the low experimental temperature, and higher in the high temperature lines at the higher experimental temperature. The correlations between these traits induced by thermal evolution were in general different from or opposite to the genetic correlations found within a single temperature.

The effect of temperature on the metabolism of juvenile tuatara,Sphenodon punctatus

Abstract Resting metabolic rates of juvenile tuatara (1–2 year old) were found to be significantly affected by ambient temperature over the range 5–22.5°C. The younger, smaller animals had higher rates of mass‐specific metabolism than the older and larger juveniles, significantly so at the lower and higher experimental temperatures. There is evidence of a compensatory, temperature‐independent metabolic decline in juvenile tuatara in the mid‐temperature range, similar to that found in other cool‐temperate reptiles. The mass‐specific metabolic rates of juvenile tuatara are high when compared with a small data sample of metabolic rates for adult tuatara, but similar to those of some small New Zealand lizards.

Tectonic evolution of Proterozoic rocks in the Cimarron Mountains, northern New Mexico, USA

Abstract Portions of three Proterozoic tectonostratigraphic sequences are exposed in the Cimarron Mountains of New Mexico. The Cimarron River tectonic unit has affinities to a convergent margin plutonic/volcanic complex. Igneous hornblende from a quartz diorite stock records an emplacement pressure of 2–2.6 kbar. Rocks within this unit were subsequently deformed during a greenschist facies regional metamorphism at 4–5 kbar and 330 ± 50° C.The Tolby Meadow tectonic unit consists of quartzite and schist. Mineral assemblages are indicative of regional metamorphism at pressures near 4 kbar and temperatures of 520 ± 20° C. A low‐angle ductile shear zone separates this succession from gneisses of the structurally underlying Eagle Nest tectonic unit. Gneissic granite yields hornblende pressures of 6–8 kbar. Pelitic gneiss records regional metamorphic conditions of 6–7 kbar and 705 ± 15° C, overprinted by retrogression at 4 kbar and 530 ± 10° C. Comparison of metamorphic and retrograde conditions indicates a P–T path dominated by decompression and cooling. The low‐angle ductile shear zone represents an extensional structure which was active during metamorphism. This extension juxtaposed the Tolby Meadow and Eagle Nest units at 4 kbar and 520° C. Both units were later overprinted by folding and low‐grade metamorphism, and then were emplaced against the Cimarron River tectonic unit by right‐slip movement along the steeply dipping Fowler Pass shear zone.An argon isotope‐correlation age obtained from igneous hornblende dates plutonism in the Cimarron River unit at 1678 Ma. Muscovite associated with the greenschist facies metamorphic overprint yields a 40 Ar/39 Ar plateau age of 1350 Ma. By contrast, rocks within the Tolby Meadow and Eagle Nest units yield significantly younger argon cooling ages. Hornblende isotope‐correlation ages of 1394–1398 Ma are interpreted to date cooling during middle Proterozoic extension. Muscovite plateau ages of 1267–1257 Ma appear to date cooling from the low‐grade metamorphic overprint. The latest ductile movement along the Fowler Pass shear zone post‐dated these cooling ages. Argon released from muscovites of the Eagle Nest/Tolby Meadow composite unit, at low experimental temperatures, yields apparent ages of c. 1100 Ma. Similar ages are not obtained north‐east of the Fowler Pass shear zone, suggesting movement more recently than 1100 Ma.

Rapid dissociation and reassociation of actomyosin cross-bridges during force generation: a newly observed facet of cross-bridge action in muscle.

The force response of skinned fibers of the rabbit psoas muscle to stretches (and releases) was studied. At physiological ionic strength and low experimental temperature (5 degrees C) the force response to stretches apparently is affected neither by cross-bridges that occupy weak-binding states nor by transitions among various attached force-generating states. Plots of force vs. imposed length change (T plots) recorded during stretches suggest that cross-bridges even in force-generating states dissociate and reassociate rapidly from and to actin as had previously been proposed [Brenner, B. (1986) Basic Res. Cardiol. 81, 1-15]. Plots of fiber stiffness vs. speed of imposed length changes (stiffness-speed relations) imply rate constants for dissociation (k-) in the force-generating states ranging from 50 to 1000 s-1, while the rate constant for reassociation (k+) has to be at least an order of magnitude larger (high actin affinity). Rapidly reversible actin interaction of cross-bridges in force-generating states provides a mechanism for rapid detachment of force-generating cross-bridges during high-speed shortening which, in contrast with the hypothesis of A. F. Huxley [(1957) Prog. Biophys. 7, 255-318], and related cross-bridge models, does not require completion of the ATP-hydrolysis cycle and thus may account for the unexpectedly low ATPase activity during high-speed shortening.

40Ar/39Ar ages of detrital muscovite within early Paleozoic overstep sequences, Avalon composite terrane, southern New Brunswick: implications for extent of late Paleozoic tectonothermal overprint

Concentrates of coarse-grained detrital muscovite from the Ratcliffe Brook Formation (lowermost Cambrian) display internally discordant 40Ar/39Ar age spectra. Gas fractions evolved at intermediate and high experimental temperatures record apparent ages of ca. 610–620 Ma. These are interpreted as dating initial cooling through temperatures appropriate for intracrystalline retention of 40Ar and may indicate derivation from mylonite zones developed within proximal late Precambrian granitic rocks. Gas fractions evolved at lower experimental temperatures record patterns of spectra discordance that suggest the constituent grains experienced partial, intracrystalline diffusive loss of 40Ar during a late Paleozoic, low-grade thermal overprint. A muscovite concentrate from pelitic schist beneath the allochthonous, latest Precambrian Cranberry Head granite records a 40Ar/39Ar plateau age of 318 ± 1 Ma. This is interpreted as closely dating Late Carboniferous thrust emplacement of the allochthon.

K-Ar and 40Ar/39Ar whole-rock ages of slate/phyllite from allochthonous basement and cover in the tectonic windows of Finnmark, Norway: Evaluating the extent and timing of Caledonian tectonothermal activity

Slate/phyllite samples collected within allochthonous basement rocks (Raipas Super-group) exposed in the Komagfjord and Alfa-Kvaenangen tectonic windows in Finnmark, northern Norway, display variably discordant 40 Ar/ 39 Ar age spectra in which apparent ages systematically increase from ca. 400-425 Ma (recorded at low experimental temperatures) to dates as old as ca. 1750-1800 Ma (in some high-temperature increments). The apparent age variations are not matched by fluctuations in apparent K/Ca ratios and are therefore interpreted to reflect intracrystalline gradients in the concentration of 40 Ar within constituent fine-grained white mica. The gradients are suggested to have developed as a result of a variable Caledonian thermal rejuvenation of white-mica argon systems which had initially cooled through argon retention temperatures at ca. 1700-1800 Ma following the Sveco-karelian orogeny. The extent of whole-rock spectra discordancy is related to the proximity of the basal thrust of the structurally overlying Kalak Nappe Complex. Whole-rock sample suites were also collected structurally downward (0.6-20 m) from the Kalak Thrust within penetratively cleaved, allochthonous cover sequences (Lomvatn Formation) exposed along the northern edge of the Komagfjord window. These display discordant 40 Ar/ 39 Ar age spectra with most intermediate-temperature gas fractions recording mutually similar apparent 40 Ar/ 39 Ar ages of ∼410-430 m.y. Observed variations in K-Ar and 40 Ar/ 39 Ar ages suggest that a late Caledonian tectonothermal event (ca. 420-425 Ma) variably affected the allochthonous basement and cover units exposed in the two Finnmark windows. This thermal overprint is interpreted to have developed during emplacement of the structurally overlying Kalak Nappe Complex while it was maintained at post-Scandian metamorphic temperatures in excess of at least 350 °C. Although the effects of a Late Cambrian-Early Ordovician orogenic event have been described from portions of the Kalak Nappe Complex, no clear record of correlative tectonothermal activity has been documented within structurally underlying tectonic units. It is therefore likely that most of the Paleozoic metamorphism and deformation observed along the eastern margin of the Caledonide orogen in northern Scandinavia developed during eastward transport of previously assembled, composite Scandian nappes into their present structural position on the Baltoscandian platform between ca. 400 and 425 Ma.

Metabolic and Biochemical Correlates of Thermal Acclimation in the Rough-Skinned Newt Taricha granulosa

Taricha granulosa (the rough-skinned newt) exhibited no thermal acclimation of metabolism when measured at a low experimental temperature (ET) (5 C) but underwent pronounced acclimation at a high ET (20 C). Thermal acclimation markedly altered the substrate concentration at which enzyme activity was 50% of maximum activity ($K_{s}$) for two enzymes, lactate dehydrogenase (LDH) and malate dehydrogenase (MDH). In general, the $K_{s}$ decreased after acclimation to low temperatures. Maximum activity of both enzymes, by contrast, was unaffected by thermal acclimation. No qualitative differences in isozymes from warm-and cold-acclimated salamanders were evident from starch gel electrophoresis of LDH, MDH, or IDH (isocitrate dehydrogenase). Acclimation to cold temperatures had no effect on the proportions of most phospholipids in the liver but increased the proportions of unsaturated fatty acids and decreased sphingomyelin content. In most respects, Taricha granulosa resembled other ectothermic vertebrates in i...

Gas chromatographic study of the urea-cetyl alcohol adduct and its components. II. Urea as a selective stationary phase

The properties of urea (the host component in the inclusion compound with cetyl alcohol) as a stationary phase were studied. In contrast to an earlier work [2] it has been found that, by increasing the urea surface (by depositing on a suitable support or adsorbent) both its polar properties and the contribution made by the formation of inclusion compounds [3] can be followed chromatographically and utilized analytically. In the present case, with urea deposited on Chromosorb W, the strongly polar character of the phase predominated to such an extent that the clathration contribution was not observed. From the analytical point of view this is, however, an interesting and useful GSC system permitting very rapid analyses even at relatively low experimental temperatures.

Effect of synthetic luteinizing hormone-releasing hormone (LH-RH) on ovulation and pituitary cytology of the goldfish Carassius auratus.

Synthetic luteinizing hormone – releasing hormone (LH–RH) induces ovulation and stimulates release of secretory granules from the pituitary gonadotrophs of goldfish kept at 12 ± 1 °C, a temperature at which ovulation does not occur in control fish. Gonadal development is stimulated at doses too low to induce ovulation. Relatively high doses were required to induce ovulation; this may be related to the low experimental temperatures, although several other possibilities are discussed. Intracranial injections appeared to be only slightly more effective than intraperitoneal injections. A single type of gonadotroph containing two types of granules was identified at the ultrastructural level. Only the small, electron-dense granules are released after injection of synthetic LH–RH; the role of the large, less electron-dense granules is uncertain.

The effect of season and experimental temperature on the rates of oxidative phosphorylation of liver and muscle mitochondria from the tench, Tinca tinca

1. 1. The regulation of mitochondrial respiration in muscle and liver of tench ( Tinca tinca) was examined over the physiological temperature range in summer and winter. 2. 2. In winter animals the mitochondrial respiration is driven more efficiently by succinate in liver and by α-ketoglutarate (α-KG) in muscle. 3. 3. At low experimental temperatures winter rates are higher than summer rates in mitochondria of both tissues and with both substrates, whereas at high experimental temperatures summer rates are higher, particularly with α-KG as a substrate. 4. 4. There is no difference in temperature dependence between states 3 and 4 mitochondrial respiration. 5. 5. The Arrhenius curves of liver mitochondria respiration are linear over the temperature range tested; the curves for muscle mitochondria are either linear (with α-KG in winter) or show a break at 8°C (succinate in winter) or 12°C (α-KG in summer). 6. 6. Neither respiratory control indices (RCI) nor ADP:O ratios show systematic changes with experimental temperature. However, the RCI values of liver mitochondria are always higher in winter than in summer. 7. 7. At low experimental temperatures the K m -values of succinate driven mitochondrial respiration are much higher in the muscles than in the liver, particularly in winter fish. This explains the very low respiratory rate of muscle mitochondria in winter when the substrate is succinate.

Discontinuities in the arrhenius plots of mitochondrial membrane-bound enzyme systems from a poikilotherm: Acclimation temperature of carp affects transition temperatures

1. Evidence is presented for ‘breaks’ in the Arrhenius plots of succinate and cytochrome oxidase systems of mitochondria from carp liver and red epaxial muscle. 2. Arrhenius activation energies (Ea) of succinate and cytochrome oxidase systems above and below the transition temperatures (T*) are about half those reported for homoiotherms (Table 3). Succinate oxidase and cytochrome oxidase obey Michaelis-Menten kinetics. The Km-values for succinate and tetramethyl-p-phenylenediamine (TMPD) (25°C) are similar to those in homoiotherms; they are not affected by acclimation temperature (Table 2). 3. The change inEa of carp liver mitochondria (C.L.M.) occurs at low (high) experimental temperatures if carps are acclimated to low (high) ambient temperatures for at least 4 (3) weeks prior to the experiments (Fig. 1). 4. TheT* shift in Arrhenius plots following a change in acclimation temperature has been studied for succinate oxidation by carp liver mitochondria (Fig. 2). The time constant ofT* change was calculated as taccl.1/2=4.3 days (Fig. 3). Based on the concept of lipid protein interaction the acclimation temperature dependency ofT* is discussed as a possible consequence of a lipid adaptation. 5. Carp acclimated to 26°C and 10°C do not differ significantly with respect to specific activity of liver succinate oxidase determined at 25°C (Table 1). The same is true for the liver-somatic index and the amount of mitochondrial protein per gram of liver (Table 1). Changes, however, are observed in these parameters if carp are in a transitory state of temperature acclimation (early after changing from 26°C to 10°C; Table 1). 6. A bimodal action of temperature change during the process of acclimation is discussed combining the results in a model of succinate oxidase system of carp liver (Fig. 4).

Factors affecting oxygen consumption in the woodlouse Porcellio scaber latr

1. There is a well-defined time sequence in the oxygen consumption of Porcellio scaber. A maximal rate (the 'active rate') is obtained in woodlice subjected to the maximal disturbance of food presentation, handling and light. After initial exploratory activity has ceased, the oxygen consumption declines through a series of 'excited rates' towards the 'standard rate' which is approached after 2-3 hr equilibration in a respirometer. 2. The rate following starvation for 1-3 days is similar to the standard rate. 3. Thermal acclimation has no significant effect on the slope or the level of the rate: temperature curves for the excited or the standard rate of oxygen consumption of Porcellio scaber. 4. The rate: temperature curves for active, excited and standard oxygen consumption of Porcellio scaber have a double sigmoid form with high temperature coefficients at the extremes of the experimental temperature range. 5. The respiration rate of a homogenate of Porcellio scaber in the presence of 9.0 mM succinate is intermediate between the active and standard rate of the intact animal. 6. The maximum scope for activity is highest at 10-15°C and falls towards both higher and lower experimental temperatures. 7. The overall oxygen consumption of intact Porcellio scaber may reflect the summation of 'cellular' and 'organismic' metabolic components which account for approximately equal proportions of the total metabolism at the normal environmental temperature range of 10-15°C. Below this temperature the cellular component is predominant whilst at the upper limits of the experimental temperature range oxidative metabolism is represented solely by the organismic component.