Relationship between Carbon Isotope Discrimination and Grain Yield in Spring Wheat Cultivated under Different Water Regimes

In C3 plants, carbon isotope discrimination (△) has been proposed as an indirect selection criterion for grain yield. Reported correlations between △ and grain yield however, differ highly according to the analyzed organ or tissue, the stage of sampling, and the environment and water regime. In a first experiment carried out in spring wheat during two consecutive seasons in the dry conditions of northwest Mexico (Ciudad Obregon, Sonora), different water treatments were applied,corresponding to the main water regimes available to spring wheat worldwide, and the relationships between △ values of different organs and grain yield were examined. Under terminal (post-anthesis) water stress, grain yield was positively associated with △ in grain at maturity and in leaf at anthesis, confirming results previously obtained under Mediterranean environments. Under early (pre-anthesis) water stress and residual moisture stress, the association between grain △ and yield was weaker and highly depended on the quantity of water stored in the soil at sowing. No correlation was found between △ and grain yield under optimal irrigation. The relationship between △ and grain yield was also studied during two consecutive seasons in 20 bread wheat cultivars in the Ningxia region (Northern China), characterized by winter drought(pre-anthesis water stress). Wheat was grown under rainfed conditions in two locations (Guyuan and Pengyang) and under irrigated conditions in another two (Yinchuan and Huinong). In Huinong, the crop was also exposed to salt stress.Highly significant positive associations were found between leaf and grain △ and grain yields across the environments.The relationship between △ and yield within environments highly depended on the quantity of water stored in the soil at sowing, the quantity and distribution of rainfall during the growth cycle, the presence of salt in the soil, and the occurrence of irrigation before anthesis. These two experiments confirmed the value of △ as an indirect selection criterion for yield and a phenotyping tool under post-anthesis water stress (including limited irrigation).     

Genetic Control of Water Use Efficiency and Leaf Carbon Isotope Discrimination in Sunflower (Helianthus annuus L.) Subjected to Two Drought Scenarios

High water use efficiency (WUE) can be achieved by coordination of biomass accumulation and water consumption. WUE is physiologically and genetically linked to carbon isotope discrimination (CID) in leaves of plants. A population of 148 recombinant inbred lines (RILs) of sunflower derived from a cross between XRQ and PSC8 lines was studied to identify quantitative trait loci (QTL) controlling WUE and CID, and to compare QTL associated with these traits in different drought scenarios. We conducted greenhouse experiments in 2011 and 2012 by using 100 balances which provided a daily measurement of water transpired, and we determined WUE, CID, biomass and cumulative water transpired by plants. Wide phenotypic variability, significant genotypic effects, and significant negative correlations between WUE and CID were observed in both experiments. A total of nine QTL controlling WUE and eight controlling CID were identified across the two experiments. A QTL for phenotypic response controlling WUE and CID was also significantly identified. The QTL for WUE were specific to the drought scenarios, whereas the QTL for CID were independent of the drought scenarios and could be found in all the experiments. Our results showed that the stable genomic regions controlling CID were located on the linkage groups 06 and 13 (LG06 and LG13). Three QTL for CID were co-localized with the QTL for WUE, biomass and cumulative water transpired. We found that CID and WUE are highly correlated and have common genetic control. Interestingly, the genetic control of these traits showed an interaction with the environment (between the two drought scenarios and control conditions). Our results open a way for breeding higher WUE by using CID and marker-assisted approaches and therefore help to maintain the stability of sunflower crop production.     

The Effect of Vapour Pressure Deficit on Carbon Isotope Discrimination in the Desert Shrub Larrea tridentata(Creosote Bush)

Larrea tridentata (creosote bush) seedlings were subjected tothree regimens of atmospheric humidity in a growth chamber experiment.Relative humidity was varied to achieve daytime vapour pressuredeficits (VPD) during growth of 29, 48 and 77 kPa. Photosyntheticgas exchange, carbon isotope composition and biomass productionwere measured after 8–10 weeks of treatment. Whereas stomatalconductance (g) declined linearly with increasing ambient VPD,CO₂ assimilation rate (A) was not measurably affected by changesin ambient VPD. This resulted in a decrease in intrinsic wateruse efficiency (ratio of CO₂ assimilation to stomatal conductance;A/_g) with increasing VPD. Leaf carbon isotope discrimination(A) was negatively correlated (r² = 088) with A/g ratios. Carbonisotope discrimination also correlated positively with ratiosof internal (C₁) to ambient (c_a) CO₂ levels determined by gasexchange measurements (c₁/c). The ratio of c₁ to c_a was lowerat higher VPD levels. Leaf biomass decreased with increasingambient VPD and correlated positively with. Root to leaf biomassratio increased at higher VPD levels and correlated negativelywith. Key words: Larrea tridentata, vapour pressure deficit, carbon isotope discrimination, intrinsic water-use efficiency     

Signal Divergence is Correlated with Genetic Distance and not Environmental Differences in Darters (Percidae: Etheostoma)

Speciation research focuses on the evolutionary mechanisms responsible for the origin of species, and recent treatments have distinguished ecological and mutation-order speciation as distinct evolutionary processes. Using a research framework that considers ??speciation phenotypes?? (sensu Shaw and Mullen in Genet 139(5):649?C661, 2011) and a modified hierarchy of speciation models, we address whether speciation in benthic fishes commonly called darters proceeds under divergent ecological selection or a mutation-order process. We examined neutral genetic divergence, sexual signal (male color) divergence, environmental differences, and geographic distance in 66 species pair comparisons. Modified Mantel tests detected significant relationships between genetic distance and overall male color differences, as well as geographic distance and overall male color differences; however, after accounting for the correlation of male color and geographic distance with genetic distance using a partial Mantel test, no relationship was observed between male color and geographic distance. Neither microhabitat nor climatic measures of environmental differences correlated with overall male color differences. Color difference scores for discrete color categories (i.e., red/orange/yellow, black, and blue/green) differed in their correlations with explanatory variables, implying different selection regimes may be influencing each component of darter color patterns. Our results do not support a primary role for divergent ecological selection shaping early divergence of darter sexual signals. Instead, a model of mutation-order speciation may best explain the clock-like manner of changes in male color among darter species.     

Photoregulation of Phenylalanine Ammonia Lyase is not Correlated with Anthocyanin Induction in Photomorphogenetic Mutants of Tomato(Lycopersicon esculentum)

Photoregulation of phenylalanine ammonia lyase (PAL)(EC 4.3.1.5 [EC] )was analyzed in wild type (WT) and mutants: phytochrome dencient-awrea(au), high pigment exhibiting exaggerated phytochrome response(hp) and the double mutant (au.hp) of tomato (Lycopersicon esculentum(Mill.) cv. Ailsa Craig). Red light, acting via phytochrome,stimulates PAL activity in cotyledons and hypocotyls of tomatoseedlings. The time course of photoinduction of PAL in cotyledonsof the mutants (au and au.hp) and WT seedlings has a peak ofactivity at 4 h, after which the activity falls sharply, exceptin hp seedlings where activity is maintained at a high level.In hypocotyls, photoinduction of PAL also shows an initial rise,reaching a maximum at 3 h, followed by a sharp decline in themutants (au and au.hp) and WT seedlings. However in hp seedlingsphotoinduction of PAL is about 3 fold that in WT. The photoinductionof PAL appears to be dependent on de novo synthesis of proteinand nucleic acids. The use of a PAL specific inhibitor a-aminooxyß-phenylpropionic acid indicated that PAL is an essentialcomponent of the anthocyanin biosyn-thetic pathway in the tomatoseedlings. However, a comparison of anthocyanin biosynthesis[Adamse et al. (1989) Photochem. Photobiol. 50: 107] and PALphotoinduction data revealed that phytochrome mediated inductionof PAL and anthocyanin in the tomato seedlings are not correlated.While au and au.hp mutant seedlings show a similar increasein PAL level as in the WT, there is little formation of anthocyaninin these mutant seedlings. The results indicate that, in contrastto the photoregulation of anthocyanin synthesis which is dependenton the presence of the labile phytochrome (IP) pool in tomatoseedlings, the photoinduction of PAL is mediated via a smallpool of phytochrome in au mutant: stable phytochrome (sP) ora residual /P pool. (Received August 6, 1991; Accepted September 27, 1991)     

Correlation between the Carbon Isotope Discrimination in Leaf Starch and Sugars of C(3) Plants and the Ratio of Intercellular and Atmospheric Partial Pressures of Carbon Dioxide

Carbon isotope discrimination (Δ) was analyzed in leaf starch and soluble sugars, which represent most of the recently fixed carbon. Plants of three C₃ species (Populus nigra L. × P. deltoides Marsh., Gossypium hirsutum L. and Phaseolus vulgaris L.) were kept in the dark for 24 hours to decrease contents of starch and sugar in leaves. Then gas exchange measurements were made with constant conditions for 8 hours, and subsequently starch and soluble sugars were extracted for analysis of carbon isotope composition. The ratio of intercellular, p_i, and atmospheric, p_a, partial pressures of CO₂, was calculated from gas exchange measurements, integrated over time and weighted by assimilation rate, for comparison with the carbon isotope ratios in soluble sugars and starch. Carbon isotope discrimination in soluble sugars correlated strongly (r = 0.93) with p_i/p_a in all species, as did Δ in leaf starch (r = 0.84). Starch was found to contain significantly more ¹³C than soluble sugar, and possible explanations are discussed. The strong correlation found between Δ and p_i/p_a suggests that carbon isotope analysis in leaf starch and soluble sugars may be used for monitoring, indirectly, the average of p_i/p_a weighted by CO₂ assimilation rate, over a day. Because p_i/p_a has a negative correlation with transpiration efficiency (mol CO₂/mol H₂O) of isolated plants, Δ in starch and sugars may be used to predict differences in this efficiency. This new method may be useful in ecophysiological studies and in selection for improved transpiration efficiency in breeding programs for C₃ species.     

Stable Carbon Isotope Discrimination Is under Genetic Control in the C4 Species Maize with Several Genomic Regions Influencing Trait Expression

In plants with C₄ photosynthesis, physiological mechanisms underlying variation in stable carbon isotope discrimination (Δ13C) are largely unknown, and genetic components influencing Δ13C have not been described. We analyzed a maize (Zea mays) introgression library derived from two elite parents to investigate whether Δ13C is under genetic control in this C₄ species. High-density genotyping with the Illumina MaizeSNP50 Bead Chip was used for a detailed structural characterization of 89 introgression lines. Phenotypic analyses were conducted in the field and in the greenhouse for kernel Δ13C as well as plant developmental and photosynthesis-related traits. Highly heritable significant genetic variation for Δ13C was detected under field and greenhouse conditions. For several introgression library lines, Δ13C values consistently differed from the recurrent parent within and across the two phenotyping platforms. Δ13C was significantly associated with 22 out of 164 analyzed genomic regions, indicating a complex genetic architecture of Δ13C. The five genomic regions with the largest effects were located on chromosomes 1, 2, 6, 7, and 9 and explained 55% of the phenotypic variation for Δ13C. Plant development stage had no effect on Δ13C expression, as phenotypic as well as genotypic correlations between Δ13C, flowering time, and plant height were not significant. To our knowledge, this is the first study demonstrating Δ13C to be under polygenic control in the C₄ species maize.During photosynthesis, plants use light energy to convert atmospheric CO₂ and water into carbohydrates. For the element carbon, there are two stable isotopes, ¹²C and ¹³C. Due to the physical and chemical properties of photosynthetic CO₂ fixation, plants are depleted in ¹³C compared with atmospheric CO₂. In C₃ plants, this discrimination of stable carbon isotopes (Δ13C) has long been used to detect genetic differences of water use efficiency and has been shown to be an accurate predictor for yield under drought (Rebetzke et al., 2002). As Δ13C is linearly related to the ratio of intercellular to atmospheric CO₂ partial pressure (Farquhar et al., 1982), stomatal closure under drought stress is associated with reduced Δ13C. For C₄ plants, our knowledge about the mechanisms underlying Δ13C and about its association with water use efficiency is much more limited. Differences in Δ13C between genotypes of C₄ species have been reported, among others, for sorghum (Sorghum bicolor; Hubick et al., 1990) and maize (Zea mays; Monneveux et al., 2007). However, comprehensive studies analyzing the inheritance of Δ13C have not been performed to date.In C₃ plants, the important steps of CO₂ uptake include the diffusion of atmospheric CO₂ through the boundary layer and the stomata. Subsequently, CO₂ is taken up by the cell and enters the chloroplast, where carboxylation by Rubisco takes place. During photosynthetic carbon fixation, the strongest fractionation of carbon isotopes occurs during the carboxylation reaction of Rubisco (Roeske and O’Leary, 1984). A theoretical model of Δ13C in C₃ photosynthesis has been described by Farquhar et al. (1982), in which Δ13C depends linearly on the ratio of intercellular to ambient partial pressure of CO₂ (p_i p_a−1), and thus provides an indication of stomatal conductance and photosynthetic capacity. Additionally, the model includes the dependency of Δ13C on the fractionation of carbon isotopes during CO₂ diffusion in the air and on the enzymatic properties of the Rubisco enzyme.For rice (Oryza sativa), tomato (Solanum lycopersicum), and wheat (Triticum aestivum), it has been shown that genetic variation for Δ13C is quantitative, genotype-by-environment interaction is small, and the trait heritability is high (Condon and Richards, 1992; Rebetzke et al., 2002; Comstock et al., 2005; Impa et al., 2005). Quantitative trait loci (QTL) for Δ13C have been mapped (Handley et al., 1994; Price et al., 2002; Rebetzke et al., 2008), and in the model plant Arabidopsis (Arabidopsis thaliana), four genes have been identified that are associated with Δ13C. Two are involved in stomatal patterning and thus influence stomatal conductance (Masle et al., 2005; Nilson and Assmann, 2010), and one of them influences photosynthetic capacity as well (Masle et al., 2005). One gene plays a role in cuticular wax composition and is also associated with stomatal conductance (Lü et al., 2012), whereas the fourth gene encodes a cellulose synthase subunit, and mutations in this gene lead to decreased Δ13C. Presumably, this is the result of a decreased cell turgor due to a decreased water transport capacity of the xylem (Liang et al., 2010).For C₄ plants, our knowledge about the genetic mechanisms and physiological processes underlying Δ13C is much more limited, due to the more complex mechanism of CO₂ fixation. The first carboxylation step in C₄ plants takes place in mesophyll cells, in which CO₂ is fixed by phosphoenolpyruvate carboxylase (PEPC). During this reaction, combined with the fractionation of carbon isotopes during HCO₃⁻ formation, carbon is actually enriched in ¹³C (Farquhar, 1983). The C₄ organic acid formed by PEPC is transported to the bundle sheath cells, where CO₂ is released to be fixed by Rubisco in the second step. However, a fraction of CO₂ released in the bundle sheath can diffuse back to the mesophyll cells. The proportion of carbon fixed by PEPC that subsequently leaks out of the bundle sheath cells is termed leakiness (ϕ) and reduces the opportunity of Rubisco to discriminate against ¹³C in C₄ plants. According to the theoretical model by Farquhar (1983), Δ13C and p_i p_a−1 are also linearly related in C₄ plants, but the regression slope is determined by ϕ. Consequently, there can be a positive or a negative correlation of Δ13C and p_i p_a−1 depending on ϕ (Hubick et al., 1990). Regarding the entire fixation process, discrimination against ¹³C in C₄ plants is not as strong as in C₃ plants, and so far there have been few studies reporting a genetic variation of Δ13C in C₄ plants. In sorghum, small but significant differences in Δ13C have been observed among 12 cultivars (Hubick et al., 1990), and similar to C₃ plants, Δ13C has been shown to be correlated with transpiration efficiency (Henderson et al., 1998). Additionally, it has been shown for maize and sugarcane (Saccharum officinarum) that stress conditions lead to an increase in Δ13C (Bowman et al., 1989; Meinzer et al., 1994; Ranjith et al., 1995; Buchmann et al., 1996). Experiments under drought and under well-watered conditions showed higher values for Δ13C in drought-tolerant maize hybrids than in susceptible checks (Monneveux et al., 2007).The use of Δ13C as an indirect trait in breeding for drought tolerance in C₄ species would be highly beneficial, given a stable trait expression and high heritability similar to that in C₃ plants. To assess whether Δ13C can also be used in C₄ plants as an indirect selection trait for drought-tolerant lines, it needs to be shown that Δ13C is under genetic control, although the physiology and molecular mechanisms of Δ13C are not yet fully understood. In this study, we used an introgression library (IL; Eshed and Zamir, 1994) derived from two elite parents to analyze the genetic variation in Δ13C under well-watered conditions. ILs have been successfully used in genetics to identify QTL for various qualitatively and quantitatively inherited traits. An IL is a defined set of nearly isogenic inbred lines derived from repeated backcrosses with one of the parents (recurrent parent [RP]) and marker-assisted selection for single fragments (Supplemental Fig. S1). Ideally, each IL line carries a single chromosome fragment of a donor parent (DP) in the genetic background of an RP. Taken together, the different segments cover the whole donor genome, allowing estimation of the effects of single donor fragments in an otherwise identical genetic background (Eshed and Zamir, 1994). The RP of the IL under investigation originates from southeastern Europe and is an elite inbred line of the maize dent pool. As DP, we chose an unrelated maize line representative of the European flint pool. The IL (IL_01–IL_89) was genotyped using the Illumina MaizeSNP50 Bead Chip (Ganal et al., 2011) carrying 56,110 single-nucleotide polymorphism (SNP) markers.Kernel Δ13C of 77 IL lines was measured in the field and in the greenhouse (Δ13C is genetically controlled in the C₄ species maize. Our specific goals were (1) to characterize the genetic architecture of Δ13C (i.e. to determine the number of genomic regions associated with Δ13C), (2) to localize genomic regions influencing Δ13C, and (3) to assess the extent to which genotypic variation in Δ13C might be the result of differences in plant development.

Table I.

Overview of the experiments and experimental designs

Diffusional Contribution to Carbon Isotope Fractionation during Dark CO(2) Fixation in CAM Plants

A mathematical model is developed which can be used to predict in vivo carbon isotope fractionations associated with carbon fixation in plants in terms of diffusion, CO₂ hydration, and carboxylation components. This model also permits calculation of internal CO₂ concentration for comparison with results of gas-exchange experiments. The isotope fractionations associated with carbon fixation in Kalanchoë daigremontiana and Bryophyllum tubiflorum have been measured by isolation of malic acid following dark fixation and enzymic determination of the isotopic composition of carbon-4 of this material. Corrections are made for residual malic acid, fumarase activity, and respiration. Comparison of these data with calculations from the model indicates that the rate of carbon fixation is limited principally by diffusion, rather than by carboxylation. Processes subsequent to the initial carboxylation also contribute to the over-all isotopic composition of the plant.     

High Efficiency Production of germ-line Transgenic Japanese Medaka (Oryzias latipes) by Electroporation with Direct Current-shifted Radio Frequency Pulses

Although there have been several studies showing the production of transgenic fish through electroporation techniques, success rates have been low and few studies show germ-line integration and expression. When electroporation has been successful, the device used is no longer commercially available. The goal of this experiment was to find an alternative efficient method of generating transgenic Japanese medaka (Oryzias latipes) using a commercially available electroporation device. The Gene Pulser II and RF module (Bio-Rad Laboratories, USA), along with two reporter gene constructs, were used. In contrast to other electroporation devices, which are based on a single pulse with exponential decay or square wave technology, the Gene Pulser II incorporates a direct current (DC)-shifted radio frequency (RF) signal. With this technique, over 1000 embryos can be electroporated in less than 30 min. The plasmid pCMV-SPORT--gal (Invitrogen, USA) was used in the supercoiled form to optimize parameters for gene transfer into single-celled embryos, and resulted in up to 100% somatic gene transfer. Similar conditions were used to generate fish transgenic for both the pCMV-EGFP plasmid (Clontech, USA) and a cytomegalovirus (CMV) driven phytase-EGFP construct. The conditions used were a voltage of 25 V, a percent modulation of 100%, a radio frequency of 35 kHz, a burst duration of 10 ms, 3 bursts, and a burst interval of 1.0 s. Seventy percent of the embryos electroporated with the pCMV-EGFP construct survived to sexual maturity, and of those, 85% were capable of passing the transgene on to their offspring. Transgenic second generation back-crossed (BC₂) fry were subjected to Southern blot analysis, which confirmed germ-line integration, and observation for green fluorescence protein, which confirmed protein expression. DC-shifted RF pulses are effective and efficient in the production of transgenic medaka, and germ-line integration and expression can be achieved without linearization of the transgene vector.     

Stable Carbon Isotope Composition (deltaC), Water Use Efficiency, and Biomass Productivity of Lycopersicon esculentum, Lycopersicon pennellii, and the F(1) Hybrid

Three tomatoes, Lycopersicon esculentum Mill. cv UC82B, a droughttolerant wild related species, Lycopersicon pennellii (Cor.) D'Arcy, and their F₁ hybrid, were grown in containers maintained at three levels of soil moisture. Season-long water use was obtained by summing over the season daily weight losses of each container corrected for soil evaporation. Plant biomass was determined by harvesting and weighing entire dried plants. Season-long water use efficiency (gram dry weight/kilogram H₂O) was calculated by dividing the dry biomass by the season-long water use. The season-long water use efficiency was greatest in the wild parent, poorest in the domestic parent, and intermediate (but closer to the wild parent) in the F₁ hybrid. Instantaneous water-use efficiency (micromole CO₂/millimole H₂O) determined by gas exchange measurements on individual leaves was poorly correlated with season-long water use efficiency. However, the relative abundance of stable carbon isotopes of leaf tissue samples was strongly correlated with the season-long water use efficiency. Also, the isotopic composition and the season-long water use efficiency of each genotype alone were strongly negatively correlated with plant dry weight when the dry weight varied as a function of soil moisture.     

Effects of Salinity on Stomatal Conductance, Photosynthetic Capacity, and Carbon Isotope Discrimination of Salt-Tolerant (Gossypium hirsutum L.) and Salt-Sensitive (Phaseolus vulgaris L.) C(3) Non-Halophytes

The effects of salinity on growth, stomatal conductance, photosynthetic capacity, and carbon isotope discrimination (Δ) of Gossypium hirsutum L. and Phaseolus vulgaris L. were evaluated. Plants were grown at different NaCl concentrations from 10 days old until mature reproductive structures were formed. Plant growth and leaf area development were strongly reduced by salinity, in both cotton and bean. Stomatal conductance also was reduced by salinity. The Δ always declined with increasing external salinity concentration, indicating that stomatal limitation of photosynthesis was increased. In cotton plant dry matter, Δ correlated with the ratio of intercellular to atmospheric CO₂ partial pressures (p_l/p_a) calculated by gas exchange. This correlation was not clear in bean plants, although Δ showed a more pronounced salt induced decline in bean than in cotton. Possible effects of heterogeneity of stomatal aperture and consequent overestimation of p_l as determined from gas exchange could explain these results. Significant differences of Δ between leaf and seed material were observed in cotton and bean. This suggests different patterns of carbon allocation between leaves and seeds. The photon yield of O₂ evolution determined at rate-limiting photosynthetic photon flux density was insensitive to salinity in both species analyzed. The light- and CO₂-saturated rate of CO₂ uptake and O₂ evolution showed a salt induced decline in both species. Possible explanations of this observation are discussed. O₂ hypersensitivity was observed in salt stressed cotton plants. These results clearly demonstrate that the effect of salinity on assimilation rate was mostly due to the reduction of stomatal conductance, and that calculation of p_l may be overestimated in salt stressed plants, because of heterogeneity of stomatal aperture over the leaf surface.     

Male-specific Iridescent Coloration in the Pipevine Swallowtail (Battus philenor) is Used in Mate Choice by Females but not Sexual Discrimination by Males

We investigated the potential roles in behavioral interactions of sexually dichromatic iridescent blue coloration found on the dorsal hindwing of male Pipevine Swallowtails (Battus philenor). Behavioral experiments in a large enclosure addressed whether male dorsal hindwing coloration mediated sexual recognition by males, female choice of mates, or both. Models presented to males in the enclosure produced responses that show that males discriminate females from other males using chemical but not visual cues. In contrast, ablation of male dorsal iridescence significantly reduced male mating success with virgin females in the enclosure. The results support the hypothesis that male-specific iridescent coloration in this species is a signal that is important for females in assessing either male species identity or quality in intersexual interactions.     

Impaired glucose tolerance (IGT) is not associated with disturbed homocysteine metabolism

Summary. Elevated plasma total homocysteine (tHcy) has been suggested to be an additional risk factor for cardiovascular disease in subjects with impaired glucose tolerance (IGT) and Type 2 diabetes (T2D). In order to investigate whether an insulin resistant/chronic hyperinsulinemic situation in male diabetic and prediabetic subjects directly influences the tHcy metabolism, fasting tHcy and post-methionine load tHcy plasma levels (PML-tHcy) were determined in 15 men with IGT, 13 men with newly dia-gnosed T2D, and 16 normoglycemic controls (NGT). Fasting tHcy (IGT, 13.1 ± 4.6; T2D, 12.8 ± 4.0; NGT, 10.7 ± 4.4 μmol/L) and PML-tHcy (IGT, 46.5 ± 17.39; T2D, 41.1 ± 6.8; NGT, 38.0 ± 9.7 μmol/L) showed no differences between the groups. Fasting tHcy and PML-tHcy correlated with fasting proinsulin (r = 0.395, p < 0.05; r = 0.386, p< 0.05) and creatinine (r = 0.489, p < 0.01; r = 0.339, p < 0.05), resp. Multiple regression analysis showed only a relationship between fasting tHcy and creatinine. No relationships have been found between fasting tHcy and PML-tHcy, resp., and indicators of an insulin resistant state, e.g., insulin and proinsulin, as well as serum cobalamin and folate concentrations. In conclusion, our data suggest that the degree of glucose intolerance has no direct impact on the metabolism of homocysteine. However, tHcy levels tend to be elevated with the development of nephropathy, indicating an association between tHcy and renal function in these subjects. Received May 11, 1999     

Sleep microstructure is not altered in children with attention-deficit/hyperactivity disorder (ADHD)

The high rate of occurrence of sleep disturbances in children with attention-deficit/hyperactivity disorder (ADHD) prompted the idea that structural and neurotransmitter changes might give rise to specific sleep pattern abnormalities. The aim of this study was to evaluate the microstructure of sleep in children with ADHD who had no polysomnographically diagnosed sleep disorder, had never been treated for ADHD, and were free from any psychiatric comorbidity. Participants were 14 patients with ADHD (12 boys and 2 girls aged 7-12 years, mean age 9.6+/-1.6). ADHD was diagnosed according to DSM-IV criteria (Diagnostic and statistical manual of mental disorders). Psychiatric comorbidities were ruled out by detailed psychiatric examination. The patients underwent two consecutive overnight video-polysomnographic (PSG) recordings, with the sleep microstructure (cyclic alternating pattern - CAP) scoring during the second night. The data were compared with age- and sex-matched controls. Sleep microstructure analysis using CAP revealed no significant differences between the ADHD group and the controls in any of the parameters under study. In conclusions, no ADHD-specific alterations were found in the sleep microstructure.     

Using the Stable Carbon and Nitrogen Isotope Compositions of Vervet Monkeys (Chlorocebus pygerythrus) to Examine Questions in Ethnoprimatology

This study seeks to understand how humans impact the dietary patterns of eight free-ranging vervet monkey (Chlorocebus pygerythrus) groups in South Africa using stable isotope analysis. Vervets are omnivores that exploit a wide range of habitats including those that have been anthropogenically-disturbed. As humans encroach upon nonhuman primate landscapes, human-nonhuman primate interconnections become increasingly common, which has led to the rise of the field of ethnoprimatology. To date, many ethnoprimatological studies have examined human-nonhuman primate associations largely in qualitative terms. By using stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope analysis, we use quantitative data to understand the degree to which humans impact vervet monkey dietary patterns. Based on initial behavioral observations we placed the eight groups into three categories of anthropogenic disturbance (low, mid, and high). Using δ¹³C and δ¹⁵N values we estimated the degree to which each group and each anthropogenically-disturbed category was consuming C₄ plants (primarily sugar cane, corn, or processed foods incorporating these crops). δ¹³C values were significantly different between groups and categories of anthropogenic-disturbance. δ¹⁵N values were significantly different at the group level. The two vervet groups with the highest consumption of C₄ plants inhabited small nature reserves, appeared to interact with humans only sporadically, and were initially placed in the mid level of anthropogenic-disturbance. However, further behavioral observations revealed that the high δ¹³C values exhibited by these groups were linked to previously unseen raiding of C₄ crops. By revealing these cryptic feeding patterns, this study illustrates the utility of stable isotopes analysis for some ethnoprimatological questions.     

Poly(ADP-ribose) polymerase (PARP-1) is not involved in DNA double-strand break recovery

Background  

The cytotoxicity and the rejoining of DNA double-strand breaks induced by γ-rays, H₂O₂ and neocarzinostatin, were investigated in normal and PARP-1 knockout mouse 3T3 fibroblasts to determine the role of poly(ADP-ribose) polymerase (PARP-1) in DNA double-strand break repair.     

Photosynthetic Thermotolerance is Quantitatively and Positively Correlated with Production of Specific Heat-shock Proteins Among Nine Genotypes of Lycopersicon (Tomato)

We recently showed that the chloroplast small heat-shock protein (herein referred to as chlp Hsp24) protects photosystem 2 (PS2) during heat stress, and phenotypic variation in production of chlp Hsp24 is positively related to PS2 thermotolerance. However, the importance of chlp Hsp24 or other Hsps to other aspects of photosynthesis and overall photosynthetic thermotolerance is unknown. To begin investigating this and the importance of genetic variation in Hsp production to photosynthetic thermotolerance, the production of several prominent Hsps and photosynthetic thermotolerance were quantified in nine genotypes of Lycopersicon, and then the relationships between thermotolerance of net photosynthetic rate (P _N) and production of each Hsp were examined. The nine genotypes exhibited wide variation in P _N thermotolerance and production of each of the Hsps examined (chlp Hsp70, Hsp60, and Hsp24, and cytosol Hsp70). No statistically significant relationship was observed between production of chlp Hsp70 and P _N thermotolerance, and only a weak positive relationship between cytosolic Hsp70 and P _N was detected. However, significant positive relationships were observed between production of chlp Hsp24 and Hsp60 and P _N thermotolerance. Hence natural variation in production of chlp Hsp24 and Hsp60 is important in determining variation in photosynthetic thermotolerance. This is perhaps the first evidence that chlp Hsp60 is involved in photosynthetic thermotolerance, and these in vivo results are consistent with previous in vitro results showing that chlp Hsp24 protects PS2 during heat stress.