草地螟滞育幼虫的蛋白和核酸含量变化

为了阐明草地螟Loxostege sticticalis 滞育的分子调控基础, 本研究应用Trizol法、 DNA和蛋白质定量试剂盒、 SDS-PAGE电泳技术分别对进入滞育1, 2, 3和4个月、 解除滞育以及非滞育草地螟老熟幼虫中的核酸含量、 总蛋白含量和组分的变化进行了测定。结果表明： 滞育不同月份幼虫的总RNA含量显著低于非滞育幼虫的总RNA含量（P＜0.05）; 解除滞育幼虫的总RNA含量显著高于滞育2, 3和4个月的幼虫, 但仍显著低于非滞育的对照组。滞育不同月份、 非滞育以及解除滞育幼虫的总DNA含量没有显著差异（P＞0.05）。RNA/DNA比值随滞育的开始而显著下降, 随着滞育的结束而显著上升。滞育不同月份的幼虫总蛋白含量显著高于非滞育幼虫的总蛋白含量（P<0.05）, 但解除滞育与非滞育幼虫的总蛋白含量无显著差异。利用SDS-PAGE电泳分析发现滞育幼虫体内存在滞育关联蛋白, 蛋白条带在24 kDa左右, 但非滞育和已经解除滞育的幼虫则没有该蛋白条带。这些结果表明, 总RNA含量的降低、 RNA/DNA比值下降、 总蛋白含量的升高, 以及24 kDa蛋白的存在是草地螟幼虫滞育的主要生理特征。     

Ontogenetic patterns of cold-hardiness and glycerol production in Sarcophaga crassipalpis

Developmental patterns of low-temperature tolerance and glycerol production were determined for larval, pupal and adult stages of the flesh fly Sarcophaga crassipalpis Macquart (Diptera: Sarcophagidae). Both diapause and non-diapause-destined flies were reared at relatively high temperatures, 20° or 25°C, prior to testing. Cold tolerance was greatest for diapause pupae aged 12–35 days after pupariation. Among non-diapause-destined flies, pupae exhibited a greater level of low temperature tolerance than larvae or adults. Although diapause pupae were more tolerant than non-diapause pupae maximal cold tolerance was not attained in either group until 10 days after pupariation. Non-diapause-destined feeding and wandering larvae had higher glycerol levels than larvae destined for diapause. During the first 6 weeks after pupariation glycerol titres increased steadily in diapause pupae. Rapid loss of glycerol is associated with the termination of pupal diapause.     

Cold-induced mitochondrial degradation and cryoprotectant synthesis in freeze-tolerant arctic caterpillars

Summary The larvae ofGynaephora groenlandica, a long-lived moth endemic to the high arctic, are perennially freeze-tolerant and able to increase their freeze-tolerance by synthesizing glycerol. Cold-induced mitochondrial changes were correlated (using electron microscopy, DNA staining, cytochrome c assay, and oxygen uptake) with glycerol production (using NMR spectroscopy) in larvae under different acclimations and in the field. Hypometabolism in summer- or warm-acclimated larvae led to glycerol accumulation. Extended exposure to near-zero or freezing temperatures caused mitochondrial degradation and glycerol accumulation. Rapid freezing of warm-acclimated larvae did not result in mitochondrial breakdown. Mitochondrial reconstitution upon warm-acclimation occurred much more rapidly (<1 week) than did degradation (>2 months). Concomitant with mitochondrial breakdown was reduced oxidative metabolism, but the cytochrome c concentration remained independent of acclimation temperature. The adaptive response to cold by mitochondrial degradation and glycerol accumulation byG. groenlandica may be linked to diapause in other species of ectotherms.     

大斑芫菁滞育幼虫在滞育不同阶段体内糖类和醇类含量的变化

在以卵滞育的昆虫中昆虫滞育时的生理代谢特点已经得到了大量研究。本文对以末龄幼虫（5龄）滞育的大斑芫菁Mylabris phalerate（Pallas）在不同滞育阶段体内糖类和醇类代谢的特征进行了研究。结果表明： 滞育个体血淋巴中的海藻糖含量高于非滞育个体,且随滞育时间的加大逐渐升高,滞育5个月时达到最大值,为5.61 μmol/mL。糖原的含量随滞育的进程逐渐减少,滞育初期（0.5个月）为0.72 mg/mL,到滞育末期（5个月）时仅为0.1 mg/mL。滞育个体脂肪体中的海藻糖含量都高于非滞育个体,滞育1个月时为非滞育个体的3倍,至滞育末期时达非滞育个体的5倍,为2.5 μmol/g脂肪体。糖原含量总体变化趋势是随滞育时间的加大逐渐减少,滞育早期和中期都高于非滞育个体。在滞育过程中血淋巴积累的小分子多元醇主要为甘油,其次是山梨醇;而在脂肪体中主要为甘油,其次是甘露醇,少量积累山梨醇：表明大斑芫菁滞育幼虫主要积累的是海藻糖和一些小分子多元醇。滞育幼虫在准备滞育时储备了大量糖原,这些糖原可能为滞育期间海藻糖、山梨醇和甘油的代谢提供了原料。     

Lipid metabolism during aging of high-alpha-linolenate-phenotype potato tubers

Previous studies demonstrated that high levels of alpha-linolenate in cell membranes of potato tubers (achieved by overexpressing fatty acid desaturases) enhances lipid peroxidation, oxidative stress, and tuber metabolic rate, effectively accelerating the physiological age of tubers. This study details the changes in lipid molecular species of microsomal and mitochondrial membranes from wild-type (WT) and high-alpha-linolenate tubers during aging. The microsomal and mitochondrial polar lipids of high-alpha-linolenate tubers were dominated by 18:3/18:3 and 16:0/18:3 molecular species. Relative to WT tubers, high-alpha-linolenate tubers had a substantially higher 16:0/18:n to 18:n/18:n molecular species ratio in mitochondria and microsomes, potentially reflecting a compensatory response to maintain membrane biophysical properties in the face of increased unsaturation. Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) accounted for 53 and 37% of polar lipids, respectively, in mitochondria from younger WT and high-alpha-linolenate tubers. The relative proportions of these phospholipids (PL) did not change during aging of WT tubers. In contrast, PE increased to dominate the PL pool of mitochondria during aging of high-alpha-linolenate tubers. While aging effected an increase in mitochondrial 18:3-bearing PCs and PEs in WT tubers, the concentration of 18:3-bearing PCs fell with a concomitant increase in 18:3-bearing PEs during aging of high-alpha-linolenate tubers. These age- and high-alpha-linolenate-induced changes had no effect on the respiration rate and functional integrity of isolated mitochondria. Differential increases in the respiration rates of WT and high-alpha-linolenate tubers during aging were therefore a consequence of unsaturation-dependent alterations in the microenvironments of cells. Microsomal 18:3-bearing PCs, PEs, digalactosyldiacylglycerols (DGDG), and monogalactosyldiacylglycerols all increased in WT tubers during aging. In contrast, a selective loss of 18:3-bearing PCs and DGDGs from microsomes of high-alpha-linolenate tubers likely reflects a greater susceptibility of membranes to peroxidative catabolism during aging. Aging resulted in an increase in sterol/PL ratio in microsomes from WT tubers, due primarily to a decline in PL. In high-alpha-linolenate tubers, the increase in sterol/PL ratio during aging was due to increases in Delta 5-avenasterol and stigmasterol, indicating membrane rigidification and likely contributing to increased membrane permeability. Age-induced changes in 18:3-bearing lipids in membranes of transformed tubers are discussed relative to the development of oxidative stress and accelerated aging.     

Phospholipid species containing long and very long polyenoic fatty acids remain with rhodopsin after hexane extraction of photoreceptor membranes

About one-fourth the phosphatidylcholines (PCs) from bovine disk photoreceptor membranes contain very long chain (24-36 carbons) polyunsaturated (4, 5, and 6 double bonds) fatty acids of the n-3 and n-6 series (VLCPUFA). Such fatty acids, exclusively occurring in dipolyunsaturated species, are esterified to the sn-1 position of their glycerol backbone, docosahexaenoate being the major fatty acid at sn-2. Chromatographically, such PCs display a weakly polar character relative to other species, ascribable to their exceedingly large number of carbons. After hexane extraction of lyophilized disks, PC is the major component of the fraction of lipids that remains associated with rhodopsin, followed by phosphatidylserine, while a large proportion of the phosphatidylethanolamine is removed. The fatty acid composition of the hexane-removable and protein-bound lipid fractions markedly differs, the latter being enriched in lipid species containing long-chain and very long chain polyenes. This is observed for all lipid classes except free fatty acids. VLCPUFA-containing PCs are the most highly concentrated species in the rhodopsin-associated lipid fraction. The very long chain polyenes these PCs have at sn-1 may account for their resistance to being separated from the protein. It is hypothesized that their unusually long polyenoic fatty acids could be well suited to partially surround alpha-helical segments of rhodopsin.     

Relationship between the fatty acids of fat body triacylglycerol and lipophorin diacylglycerol of non-diapause and diapause larvae of the southwestern corn borer,Diatraea grandiosella

The fatty acids of the triacylglycerol reserves in the fat body and of the diacylglycerol of lipophorin in the hemolymph of non-diapause and diapause larvae of D. grandiosella were compared. For both non-diapause and diapause larvae palmitate, palmitoleate, oleate, and linoleate were the predominant fatty acids present in fatty body triacylglycerol, and palmitate, oleate, and linoleate were the predominant fatty acids present in lipophorin diacylglycerol. However, differences were detected in the relative amounts of oleate and linoleate present in lipophorin diacylglycerol of non-diapause and diapause larvae. The relative amount of linoleate in lipophorin diacylglycerol declined during diapause, whereas that of oleate remained relatively high during diapause. The fatty acid profile of lipophorin diacylglycerol from non-diapause larvae treated with a juvenile hormone analog to induce a diapause-like state more closely matched that of diapause larvae than that of non-diapause larvae. The differences detected in the fatty acid composition of lipophorin diacylglycerol in non-diapause and diapause larvae appear to be due mainly to the different physiological states rather than to the different rearing temperatures employed. The results are discussed in relation to the essential role fatty acids, especially oleate, play in the survival of diapause larvae.     

Activity of NAD-sorbitol dehydrogenase is caused by biosynthesis of enzyme protein in diapause and non-diapause eggs of the silkworm,Bombyx mori

• 1.1. Using SDS-PAGE and immunoblotting analyses with anti-sorbitol dehydeogenase (EC 1.1.1.14, SDH) serum, changes in amount of SDH protein were examined in diapause and non-diapause eggs of the silkworm, Bombyx mori.
• 2.2. When diapause eggs were exposed to 5°C from 2 days after oviposition to break the diapause gradually, SDH protein appeared after 50-day chilling, and then the amount increased along with chilling period. This changing pattern paralleled that in SDH activity.
• 3.3. In diapause eggs treated with HCl after chilling at 5°C for 30 days to break the diapause quickly, and non-diapause eggs, changing patterns in amount of SDH protein also paralleled those in SDH activity.
• 4.4. These results showed that SDH activity was caused by biosynthesis of SDH protein, independent of diapause or non-diapause eggs.
• 5.5. Occurrence of SDH correlates with the three developmental phases: diapause termination, embryonic growth, and larval differentiation. In larva, SDH was mainly localized in the fat-body.

     

A novel RNA helicase-like protein during early embryonic development in silkworm Bombyx mori: molecular characterization and intracellular localization

In order to understand the molecular mechanism of development during early embryogenesis in diapause and non-diapause of the silkworm, mRNA from diapause and non-diapause eggs was compared using the differential display technique. We cloned the full length of a cDNA encoding a novel RNA helicase-like (RHL) protein by the RACE method using a cDNA fragment which was one of the specific cDNAs in the non-diapause eggs. A BLAST search using the predicted amino acid sequence of RHL revealed a low homology (21–25% identity of its partial length) with that of the DEAD-box RNA helicase. Gene expression of the RHL gene of the diapause and non-diapause eggs was investigated by RT-PCR until 60 h after oviposition. Amplified RHL cDNA was observed through all the stages in the non-diapause eggs, while in the diapause eggs, cDNA was found in eggs 0–12 h after oviposition but disappeared 24–60 h after oviposition. When the diapause eggs were activated by HCl treatment after chilling at 4 °C for 6 days from 48 h after oviposition (artificial diapause termination), cDNA was observed from 12 h after HCl treatment. We also investigated the immunohistochemical distribution and localization of RHL in non-diapause eggs using anti-recombinant His-tag RHL antiserum. RHL was distributed in blastoderm cells and yolk cells and was localized in the nucleus and the cytosol of yolk cells. These data suggest that RHL has an important role in the early embryo of the silkworm.     

Effect of photoperiod on the induction and maintenance of diapause and on development of the predatory bugPodisus maculiventris (Hem.: Pentatomidae)

The predatory bugPodisus maculiventris Say displays a reproductive diapause. In the laboratory, at 23±1°C, when the pre-imaginal stages were reared on larvae ofGalleria melonella L. (Lepidoptera: Pyralidae) under a short photoperiod of 8L: 16D, diapause was induced in all adult females, whereas under a long photoperiod of 16L: 8D none entered diapause. Nymphal development was faster under the diapause-inducing short photoperiod than under the diapause-averting long photo-period. By contrast, embryonic development was faster under the long than under the short photoperiod. Diapause maintenance was also under the control of photoperiod. After a 10-d-period of chilling at 4°C, diapause was quickly terminated in adults kept under long photoperiod whereas it was maintained in most of those kept under short photoperiod. The predation rate of non-diapause or post-diapause adult females was much higher than that of diapause females.     

中红侧沟茧蜂寄生对寄主粘虫血淋巴糖类、脂类和蛋白质含量的影响

为揭示寄生蜂寄生对其寄主的生理调控机制, 室内对中红侧沟茧蜂Microplitis mediator寄生与未被寄生寄主粘虫Mythimna separata幼虫血淋巴中糖类、脂类和蛋白含量变化进行了测定。结果显示: 在滞育与非滞育条件下, 被寄生的粘虫血淋巴中糖原浓度均比未被寄生的粘虫高。滞育条件下寄生后12 d差异显著（P<0.05）, 被寄生粘虫糖原含量为7.93 μg/mL, 未被寄生粘虫糖原含量为4.70 μg/mL; 非滞育条件下寄生后6 d差异显著（P<0.05）, 被寄生粘虫糖原含量为14.35 μg/mL, 未被寄生粘虫糖原含量为5.47 μg/mL。海藻糖含量测定结果显示, 在滞育条件下寄生蜂对被寄生粘虫无明显影响, 而非滞育条件下影响效果差异显著（P<0.05）, 寄生后4 d被寄生粘虫海藻糖含量为46.82 μg/mL, 未被寄生粘虫含量为26.72 μg/mL。在滞育与非滞育两种条件下, 寄生与未被寄生寄主脂类和蛋白含量没有显著性差异。结果说明: 寄生蜂的存在使寄主血淋巴中的糖原含量增高; 非滞育条件是影响被寄生粘虫海藻糖含量变化主要因素; 粘虫对中红侧沟茧蜂的寄生表现相当强的适应性和忍受力。     

Cold hardiness of larvae of the southwestern corn borer, Diatraea grandiosella

The cold-hardening capacity of field-collected larvae from southeast Missouri and laboratory-reared larvae of the southwestern corn borer, Diatraea grandiosella Dyar, was examined. Supercooling points of non-diapause and diapause larvae collected from maize plants grown in Missouri (36°30 N lat.) were ca.-7.0°C. The hemolymph melting points of diapause field larvae (-0.8°C) were significantly lower than those of non-diapause larvae collected in July (-0.5°C). The supercooling points of hemolymph from non-diapause and diapause field larvae ranged randomly from-10° to-18°C. Supercooling points of non-diapause laboratory larvae increased from-13° to-10°C prior to pupation, whereas those of diapause larvae increased similarly before the onset of diapause, but then decreased during diapause to ca.-17°C. No change in supercooling points or capacity to survive in the presence of ice was observed in diapause laboratory larvae acclimated at 4°C for 63 days. Laboratory and field larvae began to freeze at ca.-1.5°C in the presence of ice, but survived to several degrees below their melting points. The high supercooling points of field larvae appeared to be due to the presence of an environmental ice-nucleator. Although data for laboratory larvae indicate sufficiently low supercooling points to permit winter survival in southeastern Missouri, considerable larval mortality occurs in the field due to inoculative freezing and the presence of an ice-nucleator.     

SOME PHYSIOLOGICAL CHARACTERISTICS IN DIAPAUSE LARVAE OF ASIAN CORN BORER, OSTRINIA FURNACALIS (LEPIDOPTERA:PYRALIDAE)

Abstract  The physiological and biochemical characteristics of the diapause larvae of Asian corn borer Ostrinia furnacalis , were investigated. The molecular weight of diapause associated protein in hemolymph was determined. The development of male reproductive system, the body water content, the tolerance to suffocation and the rates of respiration of the diapause and non-diapause larvae were compared. The results revealed that the diapause larvae have the following characteristics: 1. There is a diapause associated protein in heamolymoph; its molecular weights of two polypeptide chains are 72,000 and 84,000 Dal. respectively. 2. The male reproductive organ is underdeveloped. 3. The body water content is lowered. 4. A much higher tolerance to suffocation is exhibited after submergence under water at room temperature. 5. A low rate of respiration prevailed.     

亚洲玉米螟滞育幼虫的一些生理特征(英文)

对亚洲玉米螟,Ostrinia furnacalis(Guenee)(Lepidoptera:Pyralidae),末龄滞育幼虫的生理生化指标进行了研究。确定了血淋巴滞育关联蛋白的分子量,微量呼吸仪测定了幼虫的呼吸量。同时,对体内水分含量,幼虫对水的耐受性,以及雄性精巢的大小亦进行了分析和观察。发现相应于非滞育幼虫,滞育幼虫有如下特点:1.滞育幼虫的血淋巴中具有一种滞育关联蛋白,它的两个亚肽的分子量分别为72000和840000道尔顿。2.雄性生殖器官发育不完全。3.体内水分含量占体重的比率较低,相对应干重较高。4.在室温下对浸水窒息的耐受性高。5.幼虫呼吸微弱,氧的消耗较小。     

Juvenile hormone and the induction of larval polymorphism and the diapause of the southwestern corn borer, Diatraea grandiosella

The southwestern corn borer, Diatraea grandiosella, enters diapause as an immaculate mature larva which is a polymorphic variant of the spotted non-diapause larva. Because dormant immaculate larvae could be obtained by treating last stage non-diapause larvae with a juvenile hormone mimic (JHM), experiments were conducted to determine whether these hormonally induced immaculate larvae (HIL) were physiologically comparable to the normal environmentally induced immaculate diapause larvae (EIL). Comparative data obtained about pupation rates, response to JHM, metabolic reserves, oxygen consumption, and the state of spermatogenesis of HIL and EIL led to the conclusion that the HIL were physiologically similar to the EIL. The results demonstrate that the developmental programme of non-diapause larvae could be switched and ‘diapause’ induced solely by the topical application of JHM. We believe that the data further support our hypothesis that the larval diapause of D. grandiosella is initiated and maintained by the juvenile hormone.     

Temperature and photoperiodic regulation of diapause of the southwestern corn borer,Diatraea grandiosella

The effect of temperature and photoperiod on the onset and termination of the mature larval diapause of the southwestern corn borer, Diatraea grandiosella, was examined. The results showed that diapause induction was an extremely temperature-dependent process. Larvae reared at 23°C under short days all entered diapause whereas 90 per cent of those reared at 27°C developed continuously. A photoperiodic response was only demonstrable at 25°C, when diapause was instituted following larval exposure to daily photophases ranging from 8 to 14 hr. An examination of the sensitivity of immature larvae to low temperatures revealed that all instars showed some susceptibility to low temperature induction of diapause. No intermediate instar was found in which the developmental programme could be switched entirely from a diapause to a non-diapause one, or vice versa.Diapause development was also found to be primarily temperature regulated. The rate of termination of diapause at 30°C was significantly higher than that at 25 or 23°C. Continuous exposure to light rather than a daily photoperiod produced the highest rate of diapause development. It was also shown that a period of chilling (5°C) did not accelerate diapause development. The significance of the results in relation to the evolution and geographical distribution of the species is discussed.     

Diapause development in Bombyx eggs in relation to ‘esterase A’ activity

Diapause is broken by hydrochloric acid treatment and also terminated by long chilling of eggs in the silkworm, Bombyx mori. One of esterases in silkworm eggs named ‘esterase A’ is closely related to diapause of this insect.Hydrochloric acid treatment of diapause eggs induced a prompt elevation of esterase A activity. The elevation was observed within 30 min after treatment. This HCl treatment effectively stimulated the eggs to hatch. This indicates that the increase of esterase A activity is correlated with an active resumption of morphogenesis.The question was examined of whether chilling also increases esterase A activity or not. It was found that chilling also caused an increase of esterase A activity. This increase occurred before the re-appearance of glycogen in eggs, which indicates the termination of diapause in this insect. In fact, the establishment of hatchability in chilled eggs was observed after esterase A activity has reached the maximum level. Thus the increase of esterase A activity could be regarded as associated with the termination of diapause per se but not with the subsequent process of post-diapause development. This change in esterase A activity was observed only in chilled diapause eggs and was not observed in diapause eggs without chilling and non-diapause eggs.These results suggest that the increase of esterase A activity during chilling may be a kind of activity that occurs during the diapause stage in preparation for resumption of morphogenesis or diapause development.     

Comparison of the circadian eclosion rhythm between non-diapause and diapause pupae in the onion fly, Delia antiqua: the change of rhythmicity

When pupae of Delia antiqua were transferred to constant darkness (DD) from light-dark (LD) cycles or constant light (LL), the sensitivity to light of the circadian clock controlling eclosion increased with age. The daily rhythm of eclosion appeared in both non-diapause and diapause pupae only when this transfer was made during late pharate adult development. When transferred from LL to DD in the early pupal stage, the adult eclosion was weakly rhythmic in non-diapause pupae but arrhythmic in diapause pupae. However, the sensitivity of the circadian clock to temperature cycles or steps was higher in diapause pupae than in non-diapause pupae; in the transfer to a constant 20 degrees C from a thermoperiod of 25 degrees C (12 h)/20 degrees C (12 h) on day 10 after pupation or from chilling (7.5 degrees C) in DD, the adult eclosion from diapause pupae was rhythmic but that from non-diapause pupae arrhythmic. In a transfer to 20 degrees C from the thermoperiod after the initiation of eclosion, rhythmicity was observed in both types of pupae. The larval stage was insensitive to the effect of LD cycle initiating the eclosion rhythm. In D. antiqua pupae in the soil under natural conditions, therefore, the thermoperiod in the late pupal stage would be the most important 'Zeitgeber' for the determination of eclosion timing.     

Repeated cycles of chilling and warming effectively terminate prolonged larval diapause in the chestnut weevil, Curculio sikkimensis

Curculio sikkimensis (Coleoptera: Curculionidae) requires one or more years to complete its life cycle, owing to prolonged larval diapause. To compare the effects of temperature cycles and total periods of chilling on the termination of prolonged diapause, larvae were subjected to different chilling (5 degrees C) and warming (20 degrees C) cycles ranging from 30 to 720 days, and all cycles were repeated until the sum of chilling and warming periods reached 720 days. The prolonged diapause of C. sikkimensis was more effectively terminated by repeated cycles of chilling and warming than by prolonging the continuous chilling period. However, extremely short temperature cycles were not highly effective in enhancing diapause termination, even when such cycles were repeated many times. To examine the role of warming periods on diapause termination, diapause larvae were subjected to a sequence of chilling (120 days at 5 degrees C) and warming (240 days at 20 degrees C) with a warming period (0-120 days at 20 degrees C) inserted in the chilling period. Diapause larvae that were not reactivated in the first chilling period required exposure to a certain period of warming before they were able to complete diapause development in the subsequent chilling. Thus, C. sikkimensis appears to spread its reactivation times over several years in response to seasonal temperature cycles.     

Thermal behavior of liposomes containing PCs with long and very long chain PUFAs isolated from retinal rod outer segment membranes

About one-fourth the phosphatidylcholines (PC) from retina photoreceptor rod outer segment (ROS) membranes contain docosahexaenoic acid (22:6n-3) at sn-2 and a very long chain polyunsaturated fatty acid (VLCPUFA) (C24 to C36) at the sn-1 position of the glycerol backbone. In order to study the thermotropic behavior of these PCs, subfractions and molecular species of PC (16:0/22:6, 18:0/22:6, 22:6/22:6, 32:5/22:6, 32:6/22:6, 34:5/22:6), were isolated from bovine ROS, and liposomes containing different proportions of these PCs and dimyristoyl-PC (DMPC) or dipalmitoyl PC (DPPC) were compared using the fluorescence probes Laurdan and 1,6-diphenyl-1,3,5-hexatriene (DPH). With both probes, the 22:6n-3 containing PCs from ROS, in all proportions tested, decreased the transition temperature (Tt) of both DMPC and DPPC. Below the transition temperature, coexistence of phases was evidenced in all cases. Liposomes formed with 100% of any of these PCs did not show phase transitions in the temperature range studied (8 degrees C to 50 degrees C). At physiological temperatures, as it is likely to be the case in ROS membranes, all of these PC species were in the liquid-crystalline state. With Laurdan, all dipolyunsaturated PCs seemed to behave similarly: despite the large number of double bonds per molecule, all of them decreased the Tt of DPPC less than did the hexaenoic PCs. With DPH, an ample difference was detected between the dipolyunsaturates, 22:6/22:6-PC and VLCPUFA/22:6-PCs, and between the latter and hexaenoic PCs throughout the temperature range studied. This difference is consistent with the interpretation that the largest "disorder" produced by PCs containing a VLCPUFA like 32:6n-3 at the sn-1 position occurs toward the center of the membrane.