The manipulation of polar head group composition of phospholipids in the wheat Miranovskaja 808 affects frost tolerance

Caryopses of the frost-resistant cultivar of the wheat Triticum aestivum L., Miranovskaja 808, were germinated and grown in the presence of various concentrations of choline chloride. Changes in the composition of leaf total phospholipids and leaf total fatty acids at two extreme temperatures (25°C and 2°C) as well as changes in frost resistance were followed. A choline chloride concentration-dependent accumulation of phosphatidyl choline was observed in the leaves. Seedlings grown at 2°C accumulated more phosphatidyl choline at each choline chloride concentration than those grown at 25°C. There was an inverse relationship between the contents of phosphatidyl choline and phosphatidic acid in the leaves. Neither the temperature nor choline chloride seemed to affect fatty-acid composition. Modification of polar-head group composition of phospholipids affected frost tolerance: Seedlings grown in the presence of 15 mM choline chloride at 25°C exhibited a freezing resistance equal to that of hardened controls. The data indicate that the polar-head group composition of membrane phospholipids in plants can be easily manipulated and point to the importance of phosphatidyl choline in cold adaptation processes.     

Coordinate induction by UV light of stilbene synthase,phenylalanine ammonia-lyase and cinnamate 4-hydroxylase in leaves of vitaceae

A stilbene synthase catalyzing the formation of resveratrol from 4-hydroxycinnamoyl-CoA and malonyl-CoA was found in the leaves of several Vitaceae. This stilbene synthase and two other enzymes functioning on the route from phenylalanine to stilbenes were induced concurrently upon irradiation of the leaves with UV light. With leaves of Cissus antarctica, an increase of stilbene synthase activity, more than hundred-fold, was observed with a maximum appearing 15 h after the induction with UV light.Abbreviations EDTA Na₂-ethylenediaminotetraacetate - Hepes 4-(2-Hydroxyethyl)-1-piperazineethanesulfonic acid - Mes morpholinoethanesulfonic acid     

An analysis of the action of light on betalain synthesis in the seedling of Amaranthus caudatus,var. viridis

Accumulation of betalain (amaranthin) in the seedling of Amaranthus caudatus, var. viridis, is inducible by light. Since the apparent lag-phase of amaranthin accumulation after the onset of light is of the order of 3 h, light induction experiments could be performed up to 3 h after the onset of light without interference with actual synthesis. The intricate induction phenomena can be explained as follows: The inductive light operates through phytochrome and through a blue/UV photoreceptor (cryptochrome). A phytochrome-dependent High Irradiance Reaction is of minor importance. However, there is a strong, specific interaction between the light effects mediated through phytochrome and cryptochrome in the sense that the extent of the reversible response — (response obtained with a particular light treatment terminated with a saturating red light pulse) minus (response obtained with the same light treatment when terminated with a saturating 756 nm light pulse) —increases with increasing P_fr level and total fluence rate during the induction period. It is concluded that light induced amaranthin synthesis is, in fact, a convenient biochemical model system of photomorphogenesis in the case when phytochrome and cryptochrome operate simultaneously in mediating photomorphogenesis. Abbreviations: see Table 1 and 2 Materials and Medthods     

Repair of damage by ultraviolet radiation in xeroderma pigmentosum cell strains of complementation groups E and F

The xeroderma pigmentosum fibroblast strains XP2RO, complementation group E, and XP23OS, group F, were compared with normal human primary fibroblasts with regard to repair of damage induced by 254-nm UV. In XP2RO cells, repair DNA synthesis, measured by autoradiography (unscheduled DNA synthesis = UDS), was about 50% of the value found in normal human cells. In these cells also the removal of UV-induced sites recognized by a specific UV-endonuclease proceeds at a reduced rate. By having BUdR incorporated into the repaired regions, followed by the induction of breaks in these patches by 313-nm UV, it was shown that the reduced repair synthesis is not caused by a shorter length of the repair regions in XP2RO, but is solely due to a reduction in the number of sites removed by excision repair. In XP23OS a discrepancy was observed between the level of UDS, which was about 10% of the normal value, and other repair-dependent properties such as UV survival, host-cell reactivation and removal of UV-endonuclease-susceptible sites, which were less reduced than could be expected from the UDS level. However, when UDS was followed over a longer period than the 2 or 3 h normally used in UDS analysis, it appeared that in XP23OS cells, the rate of UDS remained constant whereas the rate decreased in normal control cells. Consequently, the residual level of UDS varies with the period over which it is studied.     

Repair of DNA damage after exposure to 4-nitroquinoline-1-oxide in heterokaryons derived from xeroderma pigmentosum cells

Xeroderma pigmentosum (XP) cells are dificient in the repair of damage induced by ultraviolet irradiation. Excision-repair-deficient XP cell strains have been classified into 7 distinct complementation groups, according to results of studies on cell fusion and UV irradiation. XP cells are not only abnormally sensitive to UV, but also to a variety of chemical carcinogens, including 4-nitroquinoline-1-oxide (4NQO). Complementation analysis with XP strains from 4 different complementation groups with respect to the repair of 4NQO-induced DNA damage revealed that the classification of the strains into complementation groups with respect to 4NQO-induced repair coincides with the classification based on the repair of UV damage.     

Analgesic effect of antagonists of substance P

[D-Pro²,D-Phe⁷,D-Trp⁹]-SP and [D-Pro²,D-Trp^7,9]-SP havebeen shown to be antagonists of substance P. The hindlimb scratching syndrome of mice, known to be caused by substance P was absent when these peptides were injected into substance P-treated mice. Substance P shortens “tail withdrawal time” from hot water; the two peptides greatly prolonged tail withdrawal time. Antidromic stimulation of the saphenous nerve (rat), known to release substance P and to induce vasodilatation plasma extravasation, was also greatly inhibited by [D-Pro²,D-Phe⁷,D-Trp⁹]-SP. These peptides presumably cause anti-nociceptor effects (analgesia) by inhibition of substance P at receptors and favor the concept that substance P is a sensory neurotransmitter of nociceptive messages.     

Rate of acclimation of the tropical salt-marsh fish Cyprinodon dearborni to temperature changes

The acclimation rates of temperature changes in Cyprinodon dearborni, collected from Laguna Los Patos, Cumana, Venezuela, were determined by the critical thermal maximum method. At an increase in temperature (from 24 to 31°C) fish started to gain acclimation level after 3 hours and took 3 days to fully get up to a higher level of resistance to heat death; however, at a decrease in temperature (from 3 t to 24°C) fish began to lose its acclimation level after 12 days and required 39 days to reach a lower level of resistance to thermal death.     

A laboratory study on the thermal tolerance of four southeastern stream insect species (Trichoptera,Ephemeroptera)

The acute thermal tolerances of four southeastern stream insect species, Ephemerella invaria (Walker), Stenonema ithaca (Clemens and Leonard), Symphitopsyche morosa (Hagun), and Brachycentrus lateralis (Say) were determined using an artificial stream enclosure. All species were acclimated at 10°C for 72 hours prior to instantaneous immersion into heated water for 96 hours. Percent mortality was recorded and the temperature at which 50% mortality occurred determined (LT5o). Data were subjected to standard statistical analysis.Thermal tolerance values were compared between species tested and to results from previous investigations using similar methodologies. The evolution and life histories of these species were also discussed in relation to their thermal tolerance values.