Effects of low temperature on diapause termination and body colour change in adults of a stink bug, Plautia stali

Abstract. Diapause adults of Plautia stali Scott maintained at 20°C under short day conditions (LD 12:12 h) were exposed to four temperatures of 5–20°C to examine the effect on diapause development which was assessed in terms of oviposition. Diapause adults kept at 20°C under short day conditions changed their body colour gradually from brown to green and started egg laying after a prolonged preoviposition period. Those transferred to either 10 or 15°C also showed colour change but did not lay eggs. Bugs exposed to 5°C underwent neither body colour change nor oviposition and died more rapidly than those kept at higher temperatures. When 30-day-old diapause adults were chilled at 5, 10 or 15°C for 30 or 60 days and returned to 20°C and long day conditions (LD 16:8 h), the preoviposition period varied primarily depending on the chilling, but not on the temperature. On the other hand, when 60day-old diapause adults chilled for 30 days were observed at 20°C and long day conditions, their preoviposition period tended to be longer as the chilling temperature was lower In this case, a temperature of 10°C appeared to intensify diapause. Therefore, the effect of chilling on diapause development varied depending on the age at which insects were chilled. When chilled bugs were transferred to short day conditions at 20°C, most females failed to lay any eggs and some turned green, then after a while, some green bugs changed to brown again. These results indicate that bugs remained sensitive to short day conditions even after a 60-day chilling at 10 or 15°C.     

Inactivation of Escherichia coli and Lactobacillus plantarum in relation to membrane permeabilization due to rapid chilling followed by cold storage

The relationship between membrane permeabilization and loss of viability by chilling depending on the chilling rate was investigated in two bacterial models: one Gram-positive bacterium, Lactobacillus plantarum, and one Gram-negative bacterium, Escherichia coli. Cells were cold shocked slowly (2°C/min) or rapidly (2,000°C/min) from physiological temperature to 0°C and maintained at this temperature for up to 1 week. Loss of membrane integrity was assessed by the uptake of the fluorescent dye propidium iodide (PI). Cell death was found to be strongly dependent on the rate of temperature downshift to 0°C. Prolonged incubation of cells after the chilling emphasized the effect of treatment on the cells, as the amount of cell death increased with the length of exposure to low temperature, particularly when cells were rapidly chilled. More than 5 and 3-log reductions in cell population were obtained with L. plantarum and E. coli after the rapid cold shock followed by 7-day storage, respectively. A correlation between cell inactivation and membrane permeabilization was demonstrated with both bacterial strains. Thus, loss of membrane integrity due to the chilling treatments was directly involved in the inactivation of vegetative bacterial cells.     

Control of diapause and supercooling by the retrocerebral complex inPyrrhocoris apterus

Effects of external (photoperiod, temperature) and internal (retrocerebral complex, diapause condition) factors on supercooling were studied inPyrrhocoris apterus (L.) (Heteroptera: Pyrrhocoridae) adults. An increase in supercooling capacity is associated with the induction of diapause by short-day photoperiod or cardiacallatectomy of long-day non-diapause insects in spite of a high temperature of 26°C. The induction of diapause is a prerequisite for a further increase in supercooling capacity by cold acclimation. Post-diapause adults show low values of the supercooling point also in late January or early February, although their developmental potential is fully restored. Evidently the ability to supercool associated with diapause induction is maintained by a low ambient temperature in spite of diapause termination. The supercooling point increases rapidly when these adults are transferred to a high temperature of 26°C and cold re-acclimation is then no longer possible. The inhibition of morphogenesis (maturation of gonads) by cardiacallatectomy does not prevent the supercooling point from increasing in post-diapause adults at the high temperature.     

Separation of induction and expression of tight junction formation mediated by proteinases

The formation of tight junctions can be induced in the human adenocarcinoma cell line HT 29 by treatment with trypsin at 37°C. In contrast, after treatment of the cells with trypsin at low temperature (3°C), no tight junctions were observed. However, abundant formation of tight junctions occurred when cells were treated with trypsin at 3°C, washed with soybean trypsin inhibitor, and subsequently incubated at 37°C. Thus, this protocoi allows for the first time the temporal separation of the induction and assembly of tight junctions.     

Environmental induction of larval diapause and life-history consequences of post-diapause development in the Large Copper butterfly,Lycaena dispar (Lepidoptera: Lycaenidae)

Many insects in temperate zones withstand the adverse conditions of winter through entering diapause and the two most important environmental stimuli that induce diapause are photoperiod and ambient temperature. The Large Copper butterfly, Lycaena dispar Haworth (Lepidoptera: Lycaenidae), is a Palearctic butterfly that hibernates as larvae. Since this butterfly is a near threatened species in some regions, there has been a growing need for a standardized protocol for mass rearing of this butterfly based on the adequate knowledge of its ecology. In the present study, we first identified that L. dispar larvae were sensitive to the photoperiodic induction of diapause during their first larval instar. We then investigated to what extent the diapause-inducing effects of photoperiod could be modified by ambient temperatures in L. dispar larvae by exposing them to the range of day-lengths (L:D 14:10, 12:12, 10:14 and 8:16) at three different temperatures (15, 20 and 25 °C). All larvae were induced to enter diapause at low ambient temperature (15 °C) regardless of photoperiod, whereas most of them (86 %) exhibited direct development when temperature was high (25 °C). The photoperiodic induction of diapause was evident when day-length was shorter than 14 h at intermediate temperature (20 °C). Pre-diapause development was prolonged at low temperatures. Finally, we found that post-diapause development of L. dispar larvae was determined by both the chilling temperature experienced by diapausing larvae and the duration of larval diapause. Adult emergence was enhanced when larvae were chilled at 8 °C and when they had been under the state of diapause for 20 days before they were treated to terminate diapause.     

Changes in the activity of enzymes of phenylpropanoid metabolism in tomatoes stored at low temperatures

A large increase in the activity of an enzyme involved in chlorogenic acid metabolism, hydroxycinnamyltransferase occurs in tomatoes stored at low temperatures. In contrast, the activity of the enzyme remains constant or falls slightly during normal ripening at 20°. The rise in activity occurs at temperatures below 10° and fails to occur at 15° or 20°. This increase in activity during low temperature storage occurs with fruit at all stages of ripening from mature green to fully ripe. The hydroxycinnamyltransferase of chilled tomatoes falls rapidly on transfer to 20° with a lag of about 4–8 hr and within 48 hr returns to that of unchilled fruit. The effects of such warming treatments are reversible since when a chilling period is resumed following warming to 20°, the rise in hydroxycinnamyltransferase activity is also resumed. Of the 5 other enzymes of phenylpropanoid metabolism studied, only PAL shows a similar increase in activity during low temperature storage although the activity of the other enzymes was maintained at higher levels in fruit at 2° than at 20°. The possible relationship between the behaviour of hydroxycinnamyltransferase activity at various temperatures and the known susceptibility of tomatoes to chilling injury is discussed.     

Effects of lipid-phase separation on the filipin action on membranes of ergosterol-replaced Tetrahymena cells,as studied by freeze-fracture electron microscopy

The effects of lipid-phase separation on the filipin action on pellicle membranes of ergosterol-replaced Tetrahymena pyriformis cells were studied by freeze-fracture electron microscopy. The pellicle membranes with phase separations induced by chilling from 34°C (growth temperature) to lower temperatures (30, 22 and 15°C) were treated with filipin. This produced filipin-induced lesions (“pits”) only in the particulated (liquid) regions along the margin between solid and liquid domains, while they were produced in the particle-free (solid) areas when membranes were chilled to 15°C. The pellicle membranes with lesions induced by filipin at 34°C were chilled to 22°C. This chilling raised larger particle-free areas and more condensed particle-aggregations on the membranes than on the membranes without the filipin treatment. These results suggest that the membrane fluidity affects induction and development of the ergosterol-filipin complex in the membrane.     

Effect of photoperiod experienced by parents on diapause induction in Trichogramma cacoeciae

In the genus Trichogramma, the prepupal stage can survive the cold season in diapause. However, optimal conditions for the induction of this cessation of development during the process of mass production of the parasitoid in a biological control program depend on the species. In Trichogramma cacoeciae Marchal (Hymenoptera: Trichogrammatidae), diapause is induced more easily if the parents are reared under short‐day conditions (L10:D14), and if the temperature is 10 °C rather than 13 °C. However, the effect of parental photoperiod on diapause induction is weaker at lower temperatures (10 °C). Following diapause induction, individuals can be stored at 3 °C for several months, up to 1 year. Non‐optimal conditions led to the establishment of a quiescent state in some or all individuals. In such cases, it was necessary to reduce the storage period to 1 or 2 months only, to prevent high mortality rates and low fecundity.     

Ribonuclease activity in roots of soybean seedlings subjected to chilling stress and recovery

Many developmental and physiological changes, including alterations of enzyme activities, occur in plants under low temperature stress. In this study the total ribonuclease activity was determined in crude extracts from root tips of soybean seedlings germinated at 25 °C, subjected to chilling conditions (10°C) and recovered at optimal temperature (25°C). Measurements of RNase activity were performed every 24 hours starting from the third to the 10-th day of growth. We found that chilling caused a considerable increase in ribonuclease activity (in comparison with the control), with an activity peak on the fourth day of the cold treatment. The enzyme activity in root extracts of the plants recovered after cold stress decreased along with the time of recovery. No differences were found in approximate molecular weight (35 kDa) and pH optimum (6.0) for ribonucleases extracted from control and chilled soybean roots.     

Effects of assay and acclimation temperatures on incorporation of amino acids into protein of isolated hepatocytes from the european eel, Anguilla anguilla L.

Hepatocytes of adult eels acclimated to 5° C, 10° C and 20° C, respectively were isolated by perfusion of the liver with collagenase. The liver-somatic index and the protein content of liver cells showed significantly higher values in fish kept at the lower temperatures. However, in the adenine nucleotide content and energy charge no significant differences were observed between the 5° C and the 20° C acclimation groups. The incorporation of radioactivity from a ¹⁴C-labelled amino acid mixture into perchloric acid precipitates was used as an estimate of over-all protein synthesis. When eel hepatocytes were incubated in Hanks' solution containing tracer amounts of amino acids, labelling of perchloric acid precipitates showed linear time courses over at least 60 min at 10° C and 20° C assay temperatures. The total cellular radioactivity, however, exhibited non-linear time courses. In the measurement range from 5° C to 25° C Arrhenius plots of protein labelling exhibited a discontinuity in both groups of fish. Hepatocytes from 10° C-acclimated eel showed almost twice the incorporation rates of amino acids as those from the 20° C-acclimated fish. It is concluded that high temperature dependencies in the low temperature range require an increase in the capacity of the apparatus for protein synthesis during cold acclimation.     

Importance of membrane fluidity in the induction of alkaline phosphatase,a periplasmic enzyme,in Escherichiacoli

An unsaturated fatty acid auxotroph was supplemented with either elaidate or oleate. After derepression of alkaline phosphatase by phosphate limitation at 38°C, the cells were shifted to incubation at various temperatures. Arrhenius plots of the rate of enzyme induction gave a steeper negative slope in the temperature range from 30°C to 35°C with elaidate-supplemented cells than with oleate-supplemented cells. At 25°C the induction was arrested in the former cells, while it was continued at a considerable rate in the latter. The arrest was released upon shift-back to 38°C, and precursors convertible to the active enzyme were not accumulated during incubation at 25°C. There was no marked difference in slope of Arrhenius plots of the rate of bulk protein synthesis between both types of cells, and the slope was almost equal to that of the rate of enzyme induction in the oleate-supplemented cells. The rate of β-galactosidase induction in the elaidate cells showed a similar temperature dependence to that of bulk protein synthesis.     

Influences of Temperature and Desiccation on Breaking Diapause in the Gemmules of Eunapius fraqilis (Leidy)

Summary

Most specimens of Eunapius fraqilis in Gallup Pond (Connecticut) apparently formed gemmules in September and then died. The gemmules were initially in a protracted diapause which was gradually broken during the winter. They germinated in the pond between late March and late April. Gemmules collected during the fall did not germinate during four months when they were kept at 20°C. Other gemmules from the same collections, which were kept at 5°C for several months before they were placed at 20°C, exhibited good germination. Finally, gemmules that did not germinate following a cold treatment could be activated by drying them at 20°C for seven days and then maintaining them in pond water at 20°C. These results suggest that low temperature and desiccation are effective in breaking gemmule diapause of Eunapius fraqilis.     

Cell-mediated mineralization in culture at low temperature associated with subtle thermogenic response

In both the growth plate and in marrow stromal cell cultures cell-mediated mineralization is preceded by characteristics of anaerobic and low efficiency energy metabolism. Reagents that increase mineralization like malonate and dexamethasone (DEX) also increase the mitochondrial membrane potential (MtMP) especially 1 week after DEX stimulation. Contrarily, levamisole, which decreases mineralization, also decreases MtMP. Modulation of MtMP and energy metabolism could be linked to regulation of mineralization by the uncoupling of oxidative phosphorylation. This uncoupling should be associated with thermogenesis in cells that induce mineralization. We examined whether cold temperature affects mineralization, and whether cellular thermogenesis takes place at cold temperature in parallel to changes in MtMP. Osteoprogenitor cells (OPC) induced, in DEX stimulated rat marrow stroma, higher mineralization at 33°C than at 37°C. Increased mineralization by cold temperature required long incubation since incubation in the cold during short intervals, 3–4 days, did not increase mineralization relative to (37°C) controls. Marrow stromal cells in the presence of valinomycin responded to incubation at 33°C by retaining all the vital dye after 4 h, unlike the cells at 37°C; however, after 24 h the level of dye retention at 33°C was the same as at 37°C. The delayed response of the temperature-dependent (> 37°C) K⁺ ionophor to incubation in the cold indicated that certain cells may respond to low temperature by local intracellular heating, and by heat conduction to the plasma membrane. DEX-stimulated stromal cells, unlike unstimulated cells, showed increased mitochondrial rhodamine 123 retention in the presence of valinomycin after 24 h in the cold, which corresponds to day 4 of OPC induction. This is consistent with the concept that valinomycin-induced cell damage is mediated by (cold-induced) local heating. The mechanism of this cell damage should selectively prefer non-thermogenic (rhodamine retaining) over thermogenic (rhodamine leaking) cells such as OPC. At cold temperature DEX-stimulated stromal cells showed the best anti-OPC selection under exposure to valinomycine between days 3–7, concurrent with the period of rhodamine leakage from the mitochondria. These results indicate that thermogenesis is enhanced during the period of low MtMP in mineralizing cells, and prolonged exposure to cold increases mineralization also due to induction of subtle thermogenesis. © 1996 Wiley-Liss, Inc.     

Synergy Between Low Temperature and Dessication in Breaking Gemmule Diapause of Eunapius fragilis (Leidy)

Summary

Gemmules of Eunapius fragilis collected during the fall and kept at 20° C for up to 6 months did not germinate. Freshly collected gemmules, which were dried at 20° C for 7 days and then rehydrated, also exhibited a very low capacity for germination. However, gemmules, stored at 20° C for several months and then dried, showed a much higher level of germination (but usually no more than 50%) after they were returned to pond water. Gemmules, stored at 4–5° C for 4 to 6 weeks, exhibited at most very little germination when they were tested at 20° C. On the other hand, gemmules, which were chilled at 4–5° C for 4 to 6 weeks and then dried for 7 days, underwent rapid and nearly complete germination upon rehydration. These results provide clear evidence for a synergistic effect between low temperature and desiccation in breaking gemmule diapause. It is suggested that in temporary habitats where E. fragilis often survives the dry summer as gemmules, drying may be the primary agent releasing the gemmules from diapause so that they germinate in the fall upon the return of water. A brief exposure of the gemmules to low temperatures before and/or during the dry period may enhance the effect of desiccation.     

Activation of a specific phospholipid fatty acyl hydrolase in Dunaliella salina microsomes during acclimation to low growth temperature

Dunaliella salina microsomes, but not chloroplasts, contain a fatty acyl hydrolase with high activity towards endogenous or exogenous phosphatidylglycerol and phosphatidylethanolamine. There is relatively little activity towards other phospholipids or added monogalactosyldiacylglycerol. Lipolysis is most active in the presence of 10 mM Ca²⁺ and is enhanced by added calmodulin. Microsomal acyl hydrolase activity in 30°C-grown cells is low when measured in vitro at 12°C but increases rapidly after cells are chilled to 12°C, finally attaining more than 13-times the pre-chilling value. The changing capacity for lipolysis may explain the key role of microsomes in the acclimation of Dunaliella to low temperature.     

Temperature influence on Arctic charr (Salvelinus alpinus L.) antibody response to a cellular antigen

In order to elucidate the immune responses of Arctic charr in relation to temperature, groups were acclimated to a moderate (9°C) and a cold temperature regime (4°C), as well as subjected to a temperature decrease (from 9 to 4°C) immediately prior to an immunization with sheep red blood cells. The charr kept at 9°C responded with increased primary and secondary antibody titres, as seen by direct haemagglutination, while fish at 4°C, as well as the fish subjected to a temperature reduction, displayed lower and lowest antibody titres, respectively, and only after a second immunization. It is concluded that Arctic charr can respond to a cellular antigen with a humoral immune response typical for other teleosts, but that the immune response is delayed and diminished at low temperatures. This temperature-induced immune suppression is intensified if the fish have not been acclimated to cold water prior to immunization. Accepted: 10 October 1999     

Chlorophyll fluorescence and anthocyanin content in chilled maize plants after return to a non- chilling temperature under various irradiances

The effect of irradiance on the ratio of variable to maximum fluorescence (F_v/F_m) and on the anthocyanin content of chilled (0.5 °C) young maize plants was investigated after returning the plants to a non-chilling temperature (25 °C). Compared to control plants grown throughout at 25 °C in the light, the F_v/F_m hardly changed during chilling or when returned to a non-chilling temperature in the dark, but there was a decrease in this parameter if the plants were shifted to the light after the cold treatment. Similarly, compared to the control plants there was no change in the anthocyanin content either at low temperature or after transfer to 25 °C in the dark. However, there was a sudden increase in the anthocyanin level after returning the plants from dark cold conditions to a non-chilling temperature in the light.     

Expression of a New Cold Shock Protein of 21.5 kDa and of the Major Cold Shock Protein by Streptococcus thermophilus After Cold Shock

Streptococcus thermophilus is widely used in food fermentations; it commonly suffers diverse stress challenges during manufacturing. This study investigated the cold shock response of S. thermophilus when the cell culture temperature shifted from 42°C to 15°C or 20°C. The growth of cells was affected more drastically after cold shock at 15°C than at 20°C. The generation time was increased by a factor of 19 when the temperature was lowered from 42° to 20°C, and by a factor of 72 after a cold shock at 15°C. The two-dimensional electrophoretic protein patterns of S. thermophilus under cold shock conditions were compared with the reference protein pattern when cells were grown at optimal temperature. Two proteins of 21.5 and 7.5 kDa synthesized in response to cold shock were characterized. N-terminal sequencing and sequence homology searches have shown that the 7.5-kDa protein belonged to the family of the major cold shock proteins, while no homology was found for the new cold shock protein of 21.5 kDa. Received: 4 June 1999 / Accepted: 6 July 1999