Jasmonate- and salicylate-induced defenses in wheat affect host preference and probing behavior but not performance of the grain aphid,Sitobion avenae

Jasmonate and salicylatemediated signaling pathways play significant roles in induced plant defenses, but there is no sufficient evidence for their roles in monocots against aphids. We exogenously applied methyl jasmonate （MeJA） and salicylic acid （SA） on wheat seedlings and examined biochemical responses in wheat and effects on the grain aphid, Sitobion avenae （Fab.）. Application of MeJA significantly increased levels of wheat＇s polyphenol oxidase, peroxidase and proteinase inhibitor 1, 2 and 6 days after treatment. In twochoice tests, adult aphids preferred control wheat leaves to MeJA or SA treated leaves. Electrical penetration graph （EPG） recordings of aphid probing behavior revealed that on MeJAtreated plants, the duration of aphid＇s first probe was significantly shorter and number of probes was significantly higher than those on control plants. Also total duration of probing on MeJAtreated plants was significantly shorter than on control plants. Total duration of salivation period on SAtreated plants was significantly longer, while mean phloem ingestion period was significantly shorter than on control plants. However, no significant difference in total duration of phloem sap ingestion period was observed among treatments. The EPG data suggest that MeJAdependent resistance factors might be due to feeding deterrents in mesophyll, whereas the SAmediated resistance may be phloembased. We did not observe any significant difference of MeJA and SA application on aphid development, daily fecundity, intrinsic growth rate and population growth. The results indicate that both MeJA and SAinduced defenses in wheat deterred S. avenae colonization processes and feeding behavior, but had no significant effects on its performance.     

Effects of the Application of Different Concentrations of NaN3 for Different Times on the Morphological and Cytogenetic Characteristics of Barley （Hordeum vulgate L.） Seedlings

Sodium azide （NAN3） has been used in many biological studies as a mutagen. In the present study, the morphological and cytogenetic effects of NaN3 on barley （Hordeum vulgare L.） seedlings were investigated. Seeds of barley were treated with different concentrations of NaN3 （0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mmol/L） and applied for different periods of time （3 and 4 h）. Parameters investigated, except for the mitotic index, were determined on Days 7 and 14. Increasing concentrations of NaN3 affected germination rates on Days 7 and 14 following application for 3 and 4 h. Although the length of the roots and leaves was affected by treatment with NaN3 on Day 14 of the germination period, coleoptile length was affected by NaN3 treatment on Day 7. Increasing concentrations of NaN3 and increased treatment period decreased the mitotic index compared with the untreated control. The inhibitory effects of NaN3 on the mitotic index indicate that NaN3 can have genotoxic and mutagenic effects on barley seedlings.     

重铬酸钾对蚕豆根尖细胞致畸效应的研究

以蚕豆根尖为材料,研究重铬酸钾对蚕豆根尖细胞的致畸效应。采用蚕豆根尖细胞的微核试验和染色体畸变试验方法,以不同浓度的重铬酸钾为诱变剂,测定蚕豆根尖细胞的微核率和染色体畸变率。结果表明：重铬酸钾能诱发较高频率的微核率,即在一定浓度范围内,其微核率随重铬酸钾处理浓度的升高而增加,但高于一定浓度后反而呈下降趋势;不同浓度的重铬酸钾均使蚕豆根尖细胞有丝分裂指数增大;重铬酸钾还能诱导蚕豆根尖细胞产生较高频率的染色体畸变,且产生多种类型的染色体畸变。结论是重铬酸钾对蚕豆根尖细胞具有明显的致畸效应。Abstract：We studied the aberrant effects of different concentrations of potassium dichromate on Vicia Faba root tip cells. The micronucleus and chromosome aberration assay was conducted to determine the micronucleus rate and chromosome aberration rate of Vicia faba root tip cells induced by potassium dichromate. The result indicated that potassium dichromate could increase the micronucleus rate of Vicia faba root tip cells. Within certain range of concentration the rate of micronucleus was found to be increased with the increase of potassium dichromate concentration,but beyond this range the rate of micronucleus decreased with further increase of potassium dichromate concentration. The potassium dichromate at different concentrations could increase the cell mitosis index. Besides,it also caused various types of chromosome aberration,and the rates of chromosome aberration were always higher than that of the control group. The conclusion of this study was that potassium dichromate has obvious teratogenic effect on vicia faba root tip cells.     

Influence of pH on Cd and Cu uptake, distribution and their effect on nitrate reductase activity in cucumber (Cucumis sativus L.) seedling roots

Influence of different pH solutions (5.0 and 7.0) on Cu²⁺ and Cd²⁺ absorption and distribution in root cells as well as effects of these metals on nitrate reductase activity (NR) in roots of cucumber seedlings were estimated. The absorption of Cu and Cd by roots measured as metal depletion in uptake solution was similar, both metal absorption was independent of the pH of solution. However, after rinsing of roots in distilled water (30 minutes), more Cu than Cd was found in protoplasts of root cells. More Cu was measured in all cell fractions when Cu was uptaken from pH 5.0 than from 7.0. The nitrate reductase activity after one hour of metal treatments was drastically decreased by Cu. The strongest reduction of enzyme activity was observed in roots treated with Cu in buffer with pH 5.0. Influence of Cd on the enzyme activity was weaker and was independent of the pH of solution. Lower concentration of Cd in solution (20 μM) increased NR activity. The data obtained prove the higher mobility of Cu than Cd into the cells of root. The mobility of Cu depends on pH of solution. Cu ions, but not Cd, influenced membrane permeability (K leakage). Cu acted more drasticly than Cd on NR activity.     

Experimental Visualization of Chromoneme as a Higher Level of Chromatin Compactization in the Mitotic Chromosome

We succeeded to visualize the chromoneme or a filamentous chromatin structure, with the mean thickness 0.1–0.2 μm, as a higher level of chromatin compactization in animal and plant cells at different stages of chromosome condensation at mitotic prophase and during chromatid decondensation at telophase. Under the natural conditions, chromoneme elements are not detected in the most condensed chromatin of metaphase chromosomes on ultrathin sections. We studied the ultrastructure and behavior of the chromatin of mitotic chromosomes in situ in cultured mouse L-197 cells under the conditions selectively demonstrating the chromoneme structure of the mitotic chromosomes in the presence of Ca²⁺. Loosely packaged dense chromatin bands, ca. 100 nm in diameter, chromonemes, were detected in chromosome arms in a solution containing 3 mM CaCl₂. When transferred in a hypotonic solution containing 10 mM tris-HCl, these chromosomes swelled, lost the chromoneme level of structure, and rapidly transformed in loose aggregates of elementary DNP fibrils, 30 nm in diameter. After this decondensation in the low ionic strength solution, the chromoneme structure of mitotic chromosomes was restored when they were transferred in a Ca₂₊ containing solution. The morphological characteristics of the chromoneme and pattern of its packaging in the chromosome were preserved. However, when the mitotic cells with chromosomes, in which the chromoneme structure was visualized with the help of 3 mM CaCl₂, were treated with a photosensitizer, ethidium bromide, and illuminate with a light with the wavelength 460 nm, chromatic decondensation under the hypotonic solution was not observed. The chromoneme elements in a stabilized chromatin of the mitotic chromosome preserved specific interconnection and the general pattern of their packaging in the chromatid was also preserved. The chromoneme elements in the chromosomes stabilized by light preserved their density and diameter even in a 0.6 M NaCl solution, which normally leads to chromoneme destruction. An even more rigid treatment of the stabilized chromosomes with a 2 M NaCl solution, which normally fully decondenses the chromosomes, made it possible to detect a 3D reticular skeleton devoid of any axial structures. __________ Translated from Ontogenez, Vol. 36, No. 5, 2005, pp. 323–332. Original Russian Text Copyright ? 2005 by Burakov, Tvorogova, Chentsov.     

The effect of jasmonic acid on the accumulation of ABA,proline and spermidine and its influence on membrane injury under water deficit in two barley genotypes

Seedlings of two barley genotypes (‘Maresi’ and wild form of Hordeum spontaneum) were treated with jasmonic acid (JA 5 μM and 15 μM) for 24 h, and then subjected to water stress (PEG 6000 solution of − 1.5 MPa). JA caused an increase in the content of ABA but not in that of proline and spermidine in the two studied genotypes. The effect of the treatment did not depend on the applied JA concentration. The pre-stress treatment with JA changed plant response to water deficit with regard to membrane injury. Treatment with a lower JA concentration (5 μM) caused a substantial reduction of the stress-induced membrane damage in the both genotypes. A higher JA concentration (15 μM) caused the reduction of membrane injury only in H. spontaneum and was ineffective in ‘Maresi’. JA had no influence on the leaf water status in water-stressed plants. A possible role of JA in leaf ABA accumulation and alleviation of cell membrane injury under water deficit is discussed. The work was partly supported by the Polish Committee For Scientific Research, grant No 5 PO6A 036 18     

Wear Behavior of Plasma Oxidized CoCrMo Alloy under Dry and Simulated Body Fluid Conditions

In this study, CoCrMo alloy was oxidized in plasma environment at the temperatures of 600 ℃ to 800 ℃ for 1 h to 5 h with 100% 02 gas and its tribological behavior was investigated. After the plasma oxidizing process, the compound and diffusion layers were formed on the surface. XRD results show that Cr203, a-Co and ε-Co phases diffracted from the modified layers after plasma oxidizing. The untreated and treated CoCrMo samples were subjected to wear tests both in dry and simulated body fluid conditions, and normal loads of 2 N and 10 N were used. For the sliding wear test, alumina balls were used as counter materials. It was observed that the wear resistance of CoCrMo alloy was increased after the plasma oxidizing process. The lowest wear rate was obtained from the samples that were oxidized at 800 ℃ for 5 h. It was detected that both wear environment and load have significant effects on the wear behavior of this alloy, and the wear resistance of oxidized CoCrMo alloy is higher when oxide-based counterface is used. The wear rates of both untreated and plasma oxidized samples increase under high loads.     

Fitness traits and underlying genetic variation related to host plant specialization in the aphid Sitobion avenae

Sitobion avenae （E） is an important cereal pest worldwide that can survive on various plants in the Poaceae, but divergent selection on different host plants shouldpromote the evolution of specialized genotypes or host races. In order to evaluate their resource use strategies, clones of S. avenae were collected from oat and barley. Host-transfer experiments for these clones were conducted in the laboratory to compare their fitness traits. Our results demonstrated that barley clones had significantly lower fecundityand tended to have longer developmental times when transferred from barley to oat. However, oat clones developed faster after they were transferred to barley. Clones fromoat and barley had diverged to a certain extent in terms of fecundity and developmental time of the nymphs. The separation of barley clones and oat clones of S. avenae was alsoevident in a principal component analysis. Barley clones tended to have higher broad-sense heritabilities for fitness traits than oat clones, indicating the genetic basis of differentiationbetween them. Barley clones showed significantly higher extent of specialization compared to oat clones from two measures of specialization （i.e., Xsp and Ysp）. Therefore, barleyclones were specialized to a certain extent, but oat clones appeared to be generalized. The fitness of S. avenae clones tended to increase with higher extent of specialization. Theevolution toward ecological specialization in S. avenae clones, as well as the underlying genetic basis, was discussed.     

Joint effects of acetochlor and urea on germinating characteristics of crop seeds

In order to evaluate ecological risk of agrochemicals in common use, joint toxic effects of acetochlor and urea on germinating characteristics of Chinese cabbage (Brassica Pe-kinensis Rupr) seeds were investigated using the water-culture method and the soil-culture method. The results indicated(that excessive application of acetochlor and urea, when the concentrations were higher than 31.3 mg ·kg-1 for acetochlor and 500 mg ·kg-1 for urea, had strong inhibitory effects on the rate of seed germination, root elongation and hypocotyl length of Chinese cabbage. The inhibitory rate of the germinating characteristics of Chinese cabbage seeds was significantly increased with an increase in the concentration of acetochlor or urea. The two agrochemicals in water had a stronger toxicity than these in the soil at the same concentration. Among the three indexes, hypocotyl length was the most sensitive to the toxicity of acetochlor and urea.     

Mechanisms of salt tolerance in transgenic Arabidopsis thaliana constitutively overexpressing the tomato 14-3-3 protein TFT7

A hydroponics experiment was conducted to investigate the effects of iron plaque on root surfaces with respect to selenite uptake and translocation within the seedlings of two cultivars of rice (Oryza sativa L. cv Xiushui48 and Bing9652). Different amounts of iron plaque were formed by adding 0, 10, 30, 50, 70 mg Fe l⁻¹ in the nutrient solution. After 24 h of growth, the amount of iron plaque was positively correlated with the Fe²⁺ addition to the nutrient solution. These concentrations of Fe, inducing plaque, had no significant effect on the shoot and root growth of rice plants in 50 μg Se l⁻¹ nutrient solution. The amount of Se accumulated in iron plaque was positively correlated to the amount of iron plaque. Increasing iron plaque decreased the selenium concentration in shoots and in roots. At the same time, the translocation of Se from roots to shoots was reduced with increasing amounts of iron plaque. At both the shorter and longer exposure times, the ratio of root- to-shoot selenium was higher than in the controls. More Se stayed in the roots at the longer exposure time than at the shorter time. The concentration of selenium in the xylem sap was sharply decreased with increasing amount of iron plaque on the rice roots. The DCB (dithionite-citrate-bicarbonate)-extracted Se was up to 89.9–91.1% of the total Se when roots with iron plaque (Fe 70) were incubated in 50 μg Se l⁻¹ solution for 30 min. This DCB-extracted Se, however, accounted for only 21.9–28.7% of total Se when roots with iron plaque were incubated in the same solution for 3 days. Se adsorbed in iron plaque can be desorbed by low-molecular-weight organic acids, similar to the desorption of Se from ferrihydrite. These results suggest that iron plaque might act as a ‘buffer’ for Se in the rhizosphere.     

NaCl对大麦幼苗生长及姊妹染色单体交换的影响

研究了NaCl胁迫下大麦幼苗生长及根端分生细胞的姊妹染色单体交换(SCE),当NaCl浓度提高时,SCE频率明显增大而细胞分裂指数却下降,实验组主胚根及幼苗的生长速度减慢。对细胞分裂和幼苗生长的抑制强度与处理浓度间呈正相关。实验结果表明,高浓度NaCl对幼苗生长和细胞分裂是有害的,它能引起细胞内的DNA损伤,因而具有潜在的诱变或致畸作用。     

NaCl诱导大麦细胞微核及异常有丝分裂的研究

大麦幼苗生长在含NaCl的介质中[c(NaCl)=0, 0.05, 0.10, 0.15, 0.20, 0.25mol/L],其根尖细胞有丝分裂指数下降,各NaCl处理组的微核率均有不同程度地增加,并诱发产生了如染色体断片、后期染色体桥及"不均等分裂"等异常分裂。诱发微核及异常分裂细胞的比率与NaCl浓度和作用时间呈正相关,浓度提高或作用时间延长则微核千分率与异常分裂细胞的比率增高。     

Flow Cytometric Analysis and Chromosome Sorting of Barley (Hordeum vulgare L.)

Flow cytometric analysis was systematically performed to optimize the concentration and duration of hydroxyurea (DNA synthesis inhibitor) and trifluralin (metaphase blocking reagent) treatments for synchronizing the cell cycle and accumulating metaphase chromosomes in barley root tips. A high metaphase index (76.5% in the root tip meristematic area) was routinely achieved. Seedlings of about 1.0-cm length were treated with 1.25 mM hydroxyurea for 14 h to synchronize the root tip meristem cells at the S/G2 phase. After rinsing with hydroxyurea, the seedlings were incubated in a hydroxyurea-free solution for 2 h and were treated with 1 microM trifluralin for 4 h to accumulate mitotic cells in the metaphase. The consistent high metaphase index depended on the uniform germination of seeds prior to treatment. High-quality and high-quantity isolated metaphase chromosomes were suitable for flow cytometric analysis and sorting. Flow karyotypes of barley chromosomes were established via univariate and bivariate analysis. A variation of flow karyotypes was detected among barley lines. Two single chromosome types were identified and sorted. Bivariate analysis showed no variation among barley individual chromosomes in AT and GC content.     

SCE induction and cell-cycle delay by toxaphene

Toxaphene is genotoxic in mammalian cell systems and also inhibits cell replication. It was therefore used to investigate possible masking of SCE induction due to cell-cycle delay. In this study, toxaphene-treated Chinese hamster lung (Don) cells exhibited a dose-dependent decrease in cell-cycle progression compared with untreated cells. At high, nontoxic toxaphene levels (15 micrograms/ml), cell cycling also slowed as the toxaphene treatment time was increased. Toxaphene induced significantly higher numbers of SCEs in treated cells, demonstrating a dose- and treatment time-relationship. Slopes of dose-response curves were 0.29, 0.43 and 0.77 SCE/micrograms toxaphene for 20.5 h, 24.5 h and 28.5 h incubation, respectively. There were no changes in SCE values in control cultures even when slower dividing cells were sampled e.g. at longer incubation times. Thus, higher SCE values in Chinese hamster cells were not associated per se with slower or more delayed cells. The results demonstrate that longer toxaphene treatment times were not necessary for obtaining sufficient harlequin-stained cells for SCE analysis, but that higher numbers of SCEs occurred in slower dividing cells, following prolonged incubation of cultures treated with toxaphene.     

Comparison of baseline sister-chromatid exchanges (SCE), cyclophosphamide-, ethylnitrosourea (ENU)-induced SCE, ENU-induced cell-cycle delay and chromosome aberrations between Peru and laboratory mice

The baseline sister-chromatid exchange (SCE) frequency and sensitivity to the effects of the mutagens cyclophosphamide (CPP) and ethylnitrosourea (ENU) in bone-marrow cells of descendants of wild mice trapped from Rimac valley in Peru (Peru mice) were studied and compared to the same effects in laboratory mice. Baseline SCE of the Peru mice were significantly higher than those of the C57BL/6J and DBA/2 mice. The average SCE/cell of 4 Peru mice was 5.4 (range 3.8-7.6), while the average of SCE/cell of either 4 C57BL or 5 DBA mice was 3.2 (range 3.0-3.4). The variation of SCE/cell among Peru mice studied was statistically significant whereas among C57BL or DBA mice it was not. SCE frequencies of primary cultures derived from the ear tissue of 10 Peru (mean SCE/cell = 8.5) were also significantly higher than those of 6 C57BL mice (mean SCE/cell = 7.4). CPP treatment resulted in a dose-dependent increase of SCE frequencies in bone-marrow cells of all the mice. However, some of Peru mice treated with CPP had significantly higher SCE than the other Peru mice and than all of the C57BL and DBA mice treated with equivalent dose. ENU induced increased SCE frequencies in Peru and C57BL mice. Again some of Peru mice either had significantly higher SCE, greater extent induced cell-cycle delay or chromosome aberrations (CA) than other Peru mice and than of all the C57BL mice treated with equivalent dose.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mutagenic activity of anticancer agent cis-dichlorodiammine platinum-II.

cis-Dichlorodiamminoplatinum-II (cis-DDP) has been widely used as an anticancer chemotherapeutic agent. The mutagenicity of cis-DDP was investigated in vitro and in vivo using sister-chromatid exchange analysis and the analysis of chromosomal aberrations. Parallel human lymphocyte cultures were incubated with and without the addition of BrdU at 4 concentrations of cis-DDP. Significant increases in SCE rate were observed at 0.25 micrograms/ml and higher, showing a clear dose-response relation between SCE rate and cis-DDP concentration. A significant increase in chromosome breakage and tetraradial figures was observed in BrdU free cultures treated with cis-DDP again showing a dose dependency. Analysis of the distribution of cells in the first, second and third division in cis-DDP treated cultures demonstrated the depressing effect of the drug on mitotic activity. In vivo analysis of SCE and chromosome aberrations in mouse showed that 13.85 mg/kg i.p. of cis-DDP produces significant increases in the rate of SCE and chromosome aberrations in bone-marrow cells.     

Sister-chromatid exchanges and cell-cycle kinetics in human lymphocyte cultures exposed to alkylating mutagens: apparent deformity in dose-response relationships

Experiments have been carried out using human whole-blood cultures to determine the effects of sampling times and of the duration of 5-bromodeoxyuridine (BrdUrd) treatment before fixation on sister-chromatid exchange (SCE) frequencies following exposure to mitomycin C (MMC). Cells were pulse treated for 1 h with 3 X 10(-6) M MMC at G1, and then sampled at 4-h intervals up to 88 h after stimulation of cultures with phytohemagglutinin (PHA). Results showed that this MMC treatment induced a 5-6 h proliferation delay per cell cycle, and that SCE frequencies first increased with time of fixation, peaking at 68 h, and then decreased. When cells were similarly treated with MMC, but subsequently exposed to BrdUrd for various times before fixation of cultures at 72 h, the SCE frequencies markedly increased with increasing durations of BrdUrd incubation times. These data indicate that, in mutagen-treated cultures, lymphocytes having relatively longer cell-cycle times show a higher mean frequency of SCEs. In a subsequent experiment, cells were treated for 1 h with increasing doses of MMC or 4-nitroquinoline 1-oxide (4NQO) at 0, 24, or 48 h, and then fixed at 72 h after PHA stimulation. Results showed that the optimal treatment times at which the agents could most efficiently produce SCEs were different for MMC and 4NQO, and that the dose-response curves tended to 'bend down' at very high doses; that is, treatments with very high doses induced smaller than expected numbers of SCEs. However, cells similarly treated with very high doses showed a higher, expected frequency of SCEs when sampled at 84 h, but again had a lower than expected SCE frequency when fixed at 96 h. The results indicate that there is an optimal time for sampling at which one can observe the maximum increase in SCE frequencies following mutagen exposure, and strongly suggest that the higher the dose, the later the optimal sampling time. Because of the apparent deformity of dose-response curves obtained after various treatments and sampling times, it seems necessary that extra fixation-time points be included in test protocols so as to avoid false negatives or confirm possible positives.     

Flow Cytometric Analysis and Chromosome Sorting of Barley (Hordeum vulgare L.)

Flow cytometric analysis was systematically performed to optimize the concentration and duration of hydroxyurea (DNA synthesis inhibitor) and trifluralin (metaphase blocking reagent) treatments for synchronizing the cell cycle and accumulating metaphase chromosomes in barley root tips. A high metaphase index (76.5% in the root tip meristematic area) was routinely achieved. Seedlings of about 1.0-cm length were treated with 1.25 mM hydroxyurea for 14 h to synchronize the root tip meristem cells at the S/G2 phase. After rinsing with hydroxyurea, the seedlings were incubated in a hydroxyurea-free solution for 2 h and were treated with 1 M trifluralin for 4 h to accumulate mitotic cells in the metaphase. The consistent high metaphase index depended on the uniform germination of seeds prior to treatment. High-quality and high-quantity isolated metaphase chromosomes were suitable for flow cytometric analysis and sorting. Flow karyotypes of barley chromosomes were established via univariate and bivariate analysis. A variation of flow karyotypes was detected among barley lines. Two single chromosome types were identified and sorted. Bivariate analysis showed no variation among barley individual chromosomes in AT and GC content.     

NaCl concentration alters temporal patterns of drinking and eating by rats

To obtain an understanding of the role of taste in NaCl preference-aversionunder standard laboratory feeding conditions, we characterizedthe eating and drinking patterns of rats maintained on powderedfood, water, and NaCl solution. The concentration of NaCl wasvaried systematically from 0.01 to 0.4 M with a single concentrationpresent for four consecutive days. In addition to daily intake,the number and duration of ingestion bouts, and the number ofswitches between food and fluid and between water and salinewere recorded throughout the day/night cycle. The availabilityof NaCl solution did not alter the typical pattern of night-timefeeding and prandial (drinking after a meal) drinking. As shownpreviously, NaCl intake was highest for 0.15 M NaCl and declinedat both stronger and weaker concentrations. Variations in drinkingbout number and duration determined amount consumed. Drinkingbout duration was highest for 0.2 M NaCl then declining progressivelyat both stronger and weaker concentrations. The number of drinkingbouts was highest for 0.04 M NaCl, a concentration slightlyabove the adapting salivary sodium concentration, declininglinearly thereafter with stronger NaCl concentrations. The availabilityof NaCl solution influenced the amount of food consumed, aswell as the number and duration of food bouts. Food bout numberwas highest in the presence of the weakest 0.01 M NaCl solution,while food bout duration was highest in the presence of hypertonicNaCl concentrations. Most switching behavior occurred betweenmeal consumption and drinking and little between drinking fluids.When 0.01–0.08 NaCl solutions were available, the ratsdrank saline after a meal; when hypertonic 0.3–0.4 M NaClsolutions were available, they drank water after a meal. Inthe presence of intermediate NaCl concentrations (0.15–0.20),the choice of fluid consumed after a meal was more equivocalto the extent that there was increased switching between waterand saline and vice versa. The significance of these differencesin the micromolar features of eating and drinking are discussedin relationship to taste and postingestional control mechanismsof ingestion.     

Cytotoxic and genotoxic effects of extracellular generated singlet oxygen in human lymphocytes in vitro

The induction of sister-chromatid exchanges (SCE) together with the proliferation rate index (PRI) were studied in human lymphocytes in vitro after treatment with singlet oxygen. When produced outside the cells, singlet oxygen can increase the duration of the cellular cycle as measured by an enhancement of the differences between the proliferation rate indexes of the control and the treated cells. A dose-dependent increase in the SCE rate per chromosome was also detected after contact between the singlet oxygen and lymphocytes.