Molecular dosimetry of DNA and hemoglobin adducts in mice and rats exposed to ethylene oxide.

Experiments involving ethylene oxide (ETO) have been used to support the concept of using adducts in hemoglobin as a surrogate for DNA adducts in target tissues. The relationship between repeated exposures to ETO and the formation of N-(2-hydroxyethyl)valine (HEtVal) in hemoglobin and 7-(2-hydroxyethyl)guanine (7-HEG) in DNA was investigated in male rats and mice exposed by inhalation to 0, 3, 10, 33, or 100 ppm ETO for 6 hr/day for 4 weeks, or exposed to 100 ppm (mice) or 300 ppm (rats) for 1, 3, 5, 10, or 20 days (5 days/week). HEtVal was determined by Edman degradation, and 7-HEG was quantitated by HPLC separation and fluorescence detection. HEtVal formation was linear between 3 and 33 ppm ETO and increased in slope above 33 ppm. The dose-response curves for 7-HEG in rat tissues were linear between 10 and 100 ppm ETO and increased in slope above 100 ppm. In contrast, only exposures to 100 ppm ETO resulted in significant accumulation of 7-HEG in mice. Hemoglobin adducts were lost at a greater rate than predicted by normal erythrocyte life span. The loss of 7-HEG from DNA was both species and tissue dependent, with the adduct half-lives ranging from 2.9 to 5.8 days in rat tissues (brain, kidney, liver, lung, spleen, testis) and 1.0 to 2.3 days in all mouse tissues except kidney (t1/2 = 6.9 days). The concentrations of HEtVal were similar in concurrently exposed rats and mice, whereas DNA from rats had at least 2-fold greater concentrations of 7-HEG than DNA from mice.(ABSTRACT TRUNCATED AT 250 WORDS

Multiple Routes of Pesticide Exposure for Honey Bees Living Near Agricultural Fields

Populations of honey bees and other pollinators have declined worldwide in recent years. A variety of stressors have been implicated as potential causes, including agricultural pesticides. Neonicotinoid insecticides, which are widely used and highly toxic to honey bees, have been found in previous analyses of honey bee pollen and comb material. However, the routes of exposure have remained largely undefined. We used LC/MS-MS to analyze samples of honey bees, pollen stored in the hive and several potential exposure routes associated with plantings of neonicotinoid treated maize. Our results demonstrate that bees are exposed to these compounds and several other agricultural pesticides in several ways throughout the foraging period. During spring, extremely high levels of clothianidin and thiamethoxam were found in planter exhaust material produced during the planting of treated maize seed. We also found neonicotinoids in the soil of each field we sampled, including unplanted fields. Plants visited by foraging bees (dandelions) growing near these fields were found to contain neonicotinoids as well. This indicates deposition of neonicotinoids on the flowers, uptake by the root system, or both. Dead bees collected near hive entrances during the spring sampling period were found to contain clothianidin as well, although whether exposure was oral (consuming pollen) or by contact (soil/planter dust) is unclear. We also detected the insecticide clothianidin in pollen collected by bees and stored in the hive. When maize plants in our field reached anthesis, maize pollen from treated seed was found to contain clothianidin and other pesticides; and honey bees in our study readily collected maize pollen. These findings clarify some of the mechanisms by which honey bees may be exposed to agricultural pesticides throughout the growing season. These results have implications for a wide range of large-scale annual cropping systems that utilize neonicotinoid seed treatments

The promoter of ZmMRP-1, a maize transfer cell-specific transcriptional activator, is induced at solute exchange surfaces and responds to transport demands

Transfer cells have specializations that facilitate the transport of solutes across plant exchange surfaces. ZmMRP-1 is a maize (Zea mays) endosperm transfer cell-specific transcriptional activator that plays a central role in the regulatory pathways controlling transfer cell differentiation and function. The present work investigates the signals controlling the expression of ZmMRP-1 through the production of transgenic lines of maize, Arabidopsis, tobacco and barley containing ZmMRP-1promoter:GUS reporter constructs. The GUS signal predominantly appeared in regions of active transport between source and sink tissues, including nematode-induced feeding structures and at sites of vascular connection between developing organs and the main plant vasculature. In those cases, promoter induction was associated with the initial developmental stages of transport structures. Significantly, transfer cells also differentiated in these regions suggesting that, independent of species, location or morphological features, transfer cells might differentiate in a similar way under the influence of conserved induction signals. In planta and yeast experiments showed that the promoter activity is modulated by carbohydrates, glucose being the most effective inducer

The Chromosome Number of Maize

The wide-spread interest in the genetics of maize, coupled with the uncertainty as to the number of chromosomes occurring in this species prompted the investigation which is here reported. From a review of the literature it appears that Kuwada (1911, 1915, 1919) is the only worker who has reported extensive counts of maize chromosomes. His results are summarized in table 1. Variations were reported in the number of chromosomes both within and between varieties as well as between different cells of individual plants. He concluded that sweet varieties are usually characterized by having twelve chromosomes, and starchy varieties by having ten, as the haploid number. Several exceptions were recorded, as shown in the table. With one exception his sweet X starchy hybrids were considered as having a haploid number of ten chromosomes. The pollen mother cells of a single plant of Black Mexican had one univalent and eleven bivalent chromosomes, while cells of the root-tip had twenty-three chromosomes. He considered that this had been caused by non-disjunction. According to Kuwada\u27s counts the haploid number varied as much as six chromosomes within some varieties. Since completing the investigation which follows, a brief paper has appeared by Longley (1924) concerning chromosome numbers in maize and related species. Four varieties including Chinese and Tepic maize are reported as each having a haploid number of 10 chromosomes

The Segregation of Carbohydrates in Crosses between Waxy and Starchy Types of Maize

The purpose of this paper is to report the Mendelian segregation of waxy and starchy carbohydrates in both the sporophytic and gametophytic generations of maize. This is of especial genetic interest because the counts of segregate waxy kernels have very commonly been short of the expected numbers, although this character appears to be a simple Mendelian recessive. Collins (1909) was the first to point out the physical difference in the endosperm of waxy and ordinary starchy varieties. While the exact difference in their chemical nature has not been established, Weatherwax (1922) considered that the waxy carbohydrate was erythrodextrin because of its reddish color reaction to iodine as compared with the bluish staining of the endosperms of ordinary starchy varieties. Demerec (1924), Brink and MacGillivray (1924), and Longley (1924) have each established a corresponding differential staining of the pollen grains of the two maize sorts. Brink (1925) has more recently reported finding the same chemical distinction for the carbohydrates of the embryo sacs. In a publication of earlier results the writers (1925) failed, through faulty technique, to observe the differential staining of the pollen, but later results conform with those of the above investigators. Our earlier observations as to the wide distribution of starch throughout the sporophytic vegetative tissues have been confirmed. Taking into consideration the observations of all investigators, it appears that the waxy carbohydrate is restricted to haploid or 1x tissue including pollen, embryo sac, and possibly the tissue developed from the antipodals, and to the 3x tissue of the endosperm. Only ordinary starch has been found in the diploid or 2x tissues which make up the rest of the plant. The results of this investigation as well as those of Demerec, Brink and MacGillivray, and Longley indicate that those segregated plants following hybridization which come true to endosperm type also come true to the same sort of carbohydrate in the pollen. This is evidence that a single chromosome factor controls both or else that they are very closely linked characters with no observed crossing over

The Occurrence of Starch and Erythrodextrin in Maize and Their Segregation in the Pollen of Hybrids

A variety of maize (Zea mays) differing from other known sorts in the texture of its endosperm was described by Collins (1909). The type of endosperm of this variety was designated as “waxy” in contrast with the starchy and sweet types of other maize. It has since been shown by Weatherwax (1922) that the carbohydrate of this waxy endosperm is erythrodextrin which can be distinguished from other carbohydrates by its red color reaction with iodine. It has recently been reported by Demerec (1924) and Brink and MacGillivray (1924) that this carbohydrate is also present in the pollen of this Chinese waxy variety. With plants homozygous for endosperm type, these authors found that iodine stains the pollen from starchy and waxy maize blue and reddish, respectively. When the pollen from plants heterozygous for these characters was stained with iodine, nearly equal numbers of blue and reddish pollen grains resulted. They interpreted this as a segregation of the waxy and starchy characters in the pollen grains. Longley (1924) has reported such segregation, also determined by the iodine test, in crosses of Chinese maize with starchy maize, and with annual and perennial teosinte, and in crosses between starchy and glutinous Coix. Similar results had previously been reported by Parnell (1921) for glutinous and starchy varieties of rice and their hybrids