Specific Effects Of Temperature Research Articles

Environmental Influence on the Infection of Wheat byMycosphaerella graminicola

Mycosphaerella graminicolo (anamorph, Septoria tritici), the causal agent of Septoria tritici blotch on wheat, can cause a significant yield loss for most commercially grown wheat cultivars and in many wheatgrowing areas. Environmental factors which affect infection and disease development such as light intensity, temperature, and moisture have been studied extensively. Yet, reports on specific effects of temperature and leaf wetness period on the infection process are limited []

Influence of column temperature on the electrophoretic behavior of myoglobin and .alpha.-lactalbumin in high-performance capillary electrophoresis

The influence of column temperature on the electrophoretic behavior of myoglobin and alpha-lactalbumin in high-performance capillary electrophoresis (HPCE) is presented. The major effect of temperature is to shorten the analysis time by decreasing the viscosity, but specific temperature effects on the protein migration behavior were also observed. Myoglobin, under high field (350 V/cm), was essentially temperature stable from 20 to 45 degrees C, but at constant current, a second form of myoglobin could be detected at both 214 and 410 nm. The initial form appeared to correspond to the Fe3+ and the second to the Fe2+ oxidation state of the heme iron. The rate of conversion from Fe3+ to the reduced Fe2+ in myoglobin, under given electrophoretic conditions, followed first-order kinetics with a rate constant at 30 degrees C of 304 s-1. A second protein, alpha-lactalbumin type III, demonstrated a conformational transition that resulted in asymmetric peaks and sigmodial mobility plots versus temperature in the transition region.

Direct Effects of Low Temperature upon Components of Fructan Metabolism in Leaves of Lolium temulentum L.

Summary Specific effects of temperature upon fructan metabolism were measured in intact leaves of Lolium temulentum L. held at 5°C by comparing them with leaves where fructan accumulation at 20 °C had been induced by excision. Changes in fructose 2,6-bisphosphate contents differed markedly, with leaves at 5 °C showing a sustained decrease and excised leaves a marked increase, even though both treatments caused increased rates of sucrose accumulation in the tissue. Activity of cytoplasmic fructose-1,6-bisphosphatase, which is inhibited by fructose-2,6-bisphosphate, remained constant for 8 h following excision but increased by 64 % in chilled leaves. Measurements of incorporation of 14 CO 2 into oligosaccharides showed that chilled and excised leavesdiffered in the patterns of accumulation of radioactivity in trisaccharide isomers and the relative abundance of labelled tetra- and pentasaccharides, but not in the progressive movement of radioactivity from sucrose to high molecular weight fructan. Low incubation temperatures also affected the relative proportions of the different isomeric trisaccharides produced in vitro by crude SST and purified invertase preparations supplied with sucrose, mainly by increased accumulation of kestose. These results are discussed in relation to the effects of different environmental conditions during the induction of fructan synthesis in leaves of temperate gramineae.

Accumulation and turnover of abscisic acid in osmotically stressed cotton leaf tissue in relation to temperature

Leaf discs of cotton ( Gossypium hirsutum L. cv. Deltapine 70) were osmotically stressed by floating them on solutions of polyethylene glycol 8000. The tissue produced copious amounts of abscisic acid (ABA) when stressed. Accumulation of ABA depended strongly upon temperature during the incubation, displaying a maximum at 20°C. At 35°C, the amount of ABA accumulated after 24 h was 45–80% less than at 20°C. Temperature did not affect leakage of ABA into the medium. Turnover rate of [ 14C]ABA was more than 3 times greater at 35°C than at 20°C. This rapd turnover at 35°C could account for the decreased ABA accumulation. Three 14C-containing metabolites of ABA were extracted from the tissue. At 20°C, two of these accumulated and retained substantial 14C over 16 h. At 35°C, though, the 14C in one of these compounds was almost completely lost during the last 8 h of the incubation. Although the metabolites are not identified, the results show some specific effects of temperature on ABA metabolism. The strong effect of temperature on ABA accumulation may contribute to patterns of ABA-dependent processes (such as stomatal closure) during water stress.

The pathophysiology of acute experimental allergic encephalomyelitis in the rabbit.

Clinical, histological and electrophysiological studies were performed on rabbits with acute experimental allergic encephalomyelitis (EAE). The clinical features were similar to those previously described, with the notable exception of the new findings of areflexia, respiratory slowing and hypothermia. The histological findings were also similar to those previously reported, with inflammatory demyelinating lesions both in the central and peripheral nervous system, especially the dorsal root ganglia. Electrophysiological studies performed one to nine days after the onset of neurological signs demonstrated conduction block in a high proportion of the large diameter afferents in the lumbosacral and thoracic dorsal root ganglia. Single fibre studies with spike-triggered averaging confirmed the conduction block in the dorsal root ganglia. That the conduction block was due to demyelination was indicated by slowing of conduction in large diameter fibres, normal conduction in unmyelinated fibres and the specific effects of temperature and of the potassium channel blocking agent, 4-aminopyridine. These conduction abnormalities in the peripheral nervous system, focused on the dorsal root ganglia, account for the postural disturbance, hypotonia, ataxia and areflexia in rabbits with EAE. Such conduction block is likely to mask the expression of any lesions of the central nervous system that alone could produce similar signs. The implications of these findings for the human demyelinating diseases are discussed.

The influence of temperature on the force-velocity relationship in rabbit papillary muscle.

AbstractThe force‐velocity relationship was determined at the moment of isometric peak twitch force in rabbit papillary muscles using the damped‐release technique described previously. The analysis was carried out in each muscle at two or three temperatures within the range 22–338deg; C. The experimental data were fitted with Hill's equation by means of a computer program using the least squares method. Lowering of the temperature caused an increase of the isometric peak twitch force (Po) and also, generaliy, an increase of the extrapolated value of Vmax (the shortening velocity at zero load). The temperature‐induced changes of the force‐velocity curve were interpreted as being the net result of two opposing effects: I. an altered degree of activation of the contractile system caused by a change in the amount of activator‐calcium bound to the contractile proteins (‘inotropic temperature effect’), and 2. a change in the rate of interaction between the A and I filaments independent of the degree of activation (‘specific temperature effect’). The analysis indicated a Q10 of 1.9 for the specific temperature effect. This value accords with the temperature dependence of Vmax that has been observed during tetanic contraction of skeletal muscle.

Specific effects of temperature on recombination in Schizophyllum commune

Specific effects of temperature on recombination in Schizophyllum commune

The chlorination of pyridine: Investigations on pyridine and quinoline derivatives 41st. Communication

AbstractOn chlorinating pyridine in the gas phase at 270° a good yield of 2‐chloropyridine is obtained together with a small quantity of 2:6‐dicloropyridine. At 400° the main product is 2:6‐dichloropyridine.It is shown that among the products produced in the chlorination at 270°, a small amount of a pyridylpyridinium compound must be present, for 2‐aminopyridine is obtained on hydrolysis of the reation product.Chlorination in the gas phase takes place very slowly at about 200° at this temperature 3:5‐dichloropyridine is obtained together with 3:4:5‐trichloropyridine.On chlorinating fused pyridine hydrochloride at about 170° a considerable yield of 3:5‐dichloropyridine is produced along with a small amount of 3:4:5‐trichloropyridine and pentachloropyridine.Thus in the chlorination of pyridine a specific temperature effect on the type of substitution is observed as in the bromination of pyridine. In the chlorination, the temperature limits for both types of substitution lie near together.2‐Aminopyridine is obtained on heating 2‐chloropyridine with aqueous ammonia and copper sulphate. 2‐Amino‐6chloropyridine is obtaines on heating 2:6‐dichloropyridine with aqueous ammonia.

THE EFFECT OF LOW TEMPERATURES ON COLD‐BLOODED ANIMALS

1. Frogs freeze at a temperature of −0·44° ±0·02° C. in a manner very similar to that of solutions isotonic with their body‐fluid.2. Specimens of R. pipiens obtained from the neighbourhood of Chicago will survive a temperature of −1° C. They will not survive a temperature of −1·8° C.3. The heart tissue, whether exsected or in vivo, of these frogs survives a temperature of −2·5°, but is killed by a temperature of −3·0° C.4. Since this is the case, and since similar experiments by other observers have shown that muscular tissue will survive a temperature of −2·9° C., while the peripheral nerves are not killed by much lower temperatures, it appears probable that the cause of death is connected with a specific temperature effect on the brain or cord.5. It is unlikely that frogs survive the low temperatures of the air and superficial layers of the earth of a Manitoban winter. Their winter quarters are probably situated in a layer of mud or soil which retains a temperature in the neighbourhood of 0° C.