Heptachlor: toxicity to and uptake by several estuarine organisms

Technical-grade heptachlor (65% heptachlor, 22% trans-chlordane, 2% cis-chlordane, and 2% nonachlor) was tested in 96-hr bioassays to determine its toxicity to estuarine animals. The test organisms and the 96-hr LC50 or EC50s based on measured concentrations in water) are as follows: American oyster (Crassostrea virginica), 1.5 mug/liter; pink shrimp (Penaeus duorarum), 0.11 mug/liter; grass shrimp (Palaemonetes vulgaris), 1.06 mug/liter; sheepshead minnow (Cyprinodon variegatus), 3.68 mug/liter; pinfish (Lagodon rhomboides), 3.77 mug/liter; and spot (Leiostomus xanthurus), 0.85 mug/liter. Analytical-grade heptachlor (99.8% heptachlor) and heptachlor epoxide (99%) were also studied. The analytical-grade heptachlor 96-hr LC50 for pink shrimp and spot was 0.03 mug/liter and 0.86 mug/liter, respectively, while that for pink shrimp exposed to heptachlor epoxide was 0.04 mug/liter. Heptachlor was accumulated and some metabolized to its epoxide by all animals tested. Fish and oysters accumulated heptachlor in their tissues 2,800-21,300 times the measured concentration in water; shrimp, only 200-700 times.     

Time study of effects of pregnant mare's serum gonadotropin on surface characteristics of granulosa cells in rat ovaries

A single injection of pregnant mare's serum gonadotropin (PMSG) into immature female rats was used to stimulate graafian follicle growth. The surface of granulosa cells in the growing follicles was examined at 12-hour intervals for 72 hours by scanning electron microscopy. Between 24 and 36 hours after injection of PMSG, microvillous processes appeared on the surface of the cells. These villous processes became fully developed at 48 hours and remained for at least 72 hours after PMSG injection. The significance of this PMSG-induced microvilli formation on granulosa cells is discussed.     

Pooling of urine samples for screening for Neisseria gonorrhoeae by ligase chain reaction: accuracy and application

The accuracy of detection of genital Neisseria gonorrhoeae infection in pooled urine samples by ligase chain reaction (LCR) was examined in three populations. Firstly, urine specimens from 300 female military recruits (FMR) were tested by LCR individually and in pools of four and six. Secondly, 300 urine specimens from middle-school students (MSS) were tested individually by LCR, and then the processed specimens were stored frozen for subsequent testing in pools of 4 and 10. Thirdly, 600 frozen urine specimens from high-school students (HSS) were tested by using the LCR pooling algorithm, i.e., testing processed specimens in pools of four in one test unit dose, and retesting individual specimens from positive pools. Finally, the pooling algorithm results were compared to culture results for a subset of 344 students from the original 600 HSS from whom cervical or urethral samples were taken at the discretion of the school nurse practitioners. Compared to individual testing of specimens by LCR in the FMR population, the pooling-by-four algorithm was 100% sensitive (5 of 5) and 100% pool specific (70 of 70), and the pool-by-six algorithm was 100% sensitive (5 of 5) and 100% pool specific (45 of 45). In the MSS population, the pool-by-4 algorithm was 95.8% sensitive (23 of 24) and 100% (52 of 52) pool specific, and the pool-by-10 algorithm was 95.8% sensitive (23 of 24) and 100% (17 of 17) pool specific. In the subset of 344 HSS from whom endocervical or urethral specimens were collected for culture, 31 were positive by LCR in urine and 26 were positive by culture. After results discrepant between culture and LCR were adjudicated by a confirmatory LCR test, the pooling algorithm was 93.8% (30 of 32) sensitive and 99.7% (311 of 312) specific. Culture from these 344 HSS was 81.3% (26 of 32) sensitive. The pooling algorithm reduced the cost of the N. gonorrhoeae LCR assay by 60% compared to individual testing of the HSS specimens and was both sensitive and specific.     

Mannopinic acid and agropinic acid catabolism region of the octopine-type Ti plasmid pTi15955

Octopine-type Ti plasmids such as pTi15955, pTiA6 and pTiR10 direct the catabolism of at least eight compounds called opines that are released from crown gall tumours. Four of these compounds are denoted mannityl opines, each of which possesses a D-mannityl substituent on the nitrogen atom of either glutamate or glutamine. We have analysed a 20 kb region of the Ti plasmid pTi15955 that is required for the catabolism of two such opines, mannopinic acid and agropinic acid. A total of 12 genes in four operons were identified by DNA sequence analysis. Transposons Tn5lacZ and MudK were used to mutagenize these genes and to create aga-lacZ and moa-lacZ translational fusions. The expression of all fusions was induced by agropinic acid and by mannopinic acid. One of these four operons encodes an agropinic acid permease, whereas a second one encodes a mannopinic acid permease. A third operon contains three genes encoding probable catabolic enzymes, two of which (AgaF and AgaG) are thought to convert agropinic acid to mannopinic acid, while the third (AgaE) probably converts mannopinic acid to mannose and glutamate. AgaE resembles a bacterial amino acid deaminase, whereas AgaF and AgaG resemble two bacterial proteins that together catabolize substituted hydantoins, whose chemical structure resembles that of agropinic acid. The remaining operon encoded the MoaR protein, a negative regulator of itself and of the other three operons.     

Phospholipase D and its product, phosphatidic acid, mediate agonist-dependent raf-1 translocation to the plasma membrane and the activation of the mitogen-activated protein kinase pathway

The primary known function of phospholipase D (PLD) is to generate phosphatidic acid (PA) via the hydrolysis of phosphatidylcholine. However, the functional role of PA is not well understood. We report here evidence that links the activation of PLD by insulin and the subsequent generation of PA to the activation of the Raf-1-mitogen-activated protein kinase (MAPK) cascade. Brefeldin A (BFA), an inhibitor of the activation of ADP-ribosylation factor proteins, inhibited insulin-dependent production of PA and MAPK phosphorylation. The addition of PA reversed the inhibition of MAPK activation by BFA. Overexpression of a catalytically inactive variant of PLD2, but not PLD1, blocked insulin-dependent activation of PLD and phosphorylation of MAPK. Real time imaging analysis showed that insulin induced Raf-1 translocation to cell membranes by a process that was inhibited by BFA. PA addition reversed the effects of BFA on Raf-1 translocation. However, PA did not activate Raf-1 in vitro or in vivo, suggesting that the primary function of PA is to enhance the recruitment of Raf-1 to the plasma membrane where other factors may activate it. Finally, we found that the recruitment of Raf-1 to the plasma membrane was transient, but Raf-1 remained bound to endocytic vesicles.     

Early fraction calculation ability

Three- to 7-year-olds' ability to calculate with whole-number, fraction, and mixed-number amounts was tested using a nonverbal task in which an amount was displayed and then hidden (J. Huttenlocher, N. C. Jordan, & S. C. Levine, 1994). Next, an amount was added to or subtracted from the hidden amount. The child's task was to determine the hidden amount that resulted from the transformation. Although fraction problems were more difficult than whole-number problems, competence on all problem types emerged in the early childhood period. Furthermore, there were striking parallels between the development of whole-number and fraction calculation. This is inconsistent with the hypothesis that early representations of quantity promote learning about whole numbers but interfere with learning about fractions (e.g., R. Gelman, 1991; K. Wynn, 1995, 1997).