Molecular model for DNA recognition by the family of basic-helix-loop-helix-zipper proteins.

The basic-helix-loop-helix-zipper (bHLH-Zip) motif is a conserved region of approximately 70 amino acids that mediates both sequence-specific DNA binding and protein dimerization. This motif is found in protein sequences from many eukaryotic organisms and is contained in the protein sequence of the oncogene myc and its partner max, and a shortened version of the motif (bHLH) is found in the muscle determination factor myoD and its partner E12. An evaluation of the conserved amino acids that define the motif coupled with the published mutagenic studies of this region has led to our formulation of a molecular model for the binding of this motif as a dimer to specific sequences of DNA. This model has the dimeric protein interacting with an abutted, dyad-symmetric DNA sequence. Helix 2 of each monomer is modeled as a coiled-coil extension of the C-terminal "leucine zipper." Helix 1 does not interact with helix 1 from its partner in the dimer but with the hydrophobic surface created when the helix 2 regions of the dimer interact with each other as a coiled-coil. Sequence-specific interactions are proposed between the basic region and the invariant cis elements that all bHLH-Zip proteins bind.     

Why species delimitation matters for fungal ecology: Colletotrichum diversity on wild and cultivated cashew in Brazil

Anthracnose is one of the most important plant diseases globally, occurring on a wide range of cultivated and wild host species. This study aimed to identify the Colletotrichum species associated with cashew anthracnose in Brazil, determine their phylogenetic relationships and geographical distribution, and provide some insight into the factors that may be influencing community composition. Colletotrichum isolates collected from symptomatic leaves, stems, inflorescences, and fruit of cultivated and wild cashew, across four Brazilian biomes, were identified as Colletotrichum chrysophilum, Colletotrichum fragariae, Colletotrichum fructicola, Colletotrichum gloeosporioides sensu stricto, Colletotrichum queenslandicum, Colletotrichum siamense and Colletotrichum tropicale. Colletotrichum siamense was the most dominant species. The greatest species richness was associated with cultivated cashew; leaves harbored more species than the other organs; the Atlantic Forest encompassed more species than the other biomes; and Pernambuco was the most species-rich location. However, accounting for the relative abundance of Colletotrichum species and differences in sample size across strata, the interpretation of which community is most diverse depends on how species are delimited. The present study provides valuable information about the Colletotrichum/cashew pathosystem, sheds light on the causal agents identification,and highlights the impact that species delimitation can have on ecological studies of fungi.     

The development and application of a radioimmunoassay for 18-hydroxy-corticosterone.

A sensitive and specific radioimmunoassay has been developed for 18-hydroxy-corticosterone (18-OH-B) and applied to the measurement of this steroid in peripheral plasma. High specific activity label (3H-18-OH-B) was prepared using the incubation of 3H-corticosterone with duck adrenal mitochondria. Antisera were produced by immunisation with 18-OH-B gamma-lactone 3-oxime conjugated to bovine serum albumin. The antibodies examined showed 100% cross-reactivity with 18-hydroxy-deoxycorticosterone gamma-lactone (18-OH-DOC gamma-lactone), but minimal cross-reactivity with other steroids. Paper chromatography was used to separate 18-OH-DOC gamma-lactone from 18-OH-B gamma-lactone. The interassay precision was 7.6% and the intra-assay precision 11.0%. The accuracy of the method was confirmed by showing a linear relationship between amounts of 18-OH-B added and amounts of 18-OH-B gamma-lactone measured (y = 0.854 X +15.1, r = 0.9. p less than 0.001). The mean plasma level in normal subjects on an ad libitum sodium intake was 225 +/- 92.7 (SD) pg/ml (n = 17) when standing, and 99 +/- 38.3 (SD) pg/ml (n = 6) after lying down for 30 minutes.     

Nuclear secretory particles associated with the calyx cells of the ichneumonid parasitoid Campoletis sonorensis (Cameron)

Summary The present study is an ultrastructural investigation of the calyx region of the ichneumonid endoparasitoid Campoletis sonorensis. It appears that synthesis of electrondense secretory particles occurs within nuclei of calyx cells. The particles consist of an ovocylindrical electron-dense inner core and a surrounding unit membrane. After their formation the particles pass from the nucleus by budding through both membranes of the nuclear envelope. The particles, along with fully developed parasitoid eggs concentrate within the lateral oviduct lumen. Feulgen histochemical studies suggest the presence of DNA within the calyx fluid. The possible function of the particles is discussed.Approved for publication as TA 11744 by the Director, Texas Agricultural Experiment Station. Conducted in cooperation with the USDA and supported in part by Cotton, Inc. Grant CI—199 with funds made available through the USDA. Appreciation is also expressed to Sigma Xi for its contribution of funds during this study.     

Isolation, identification and synthesis of host-seeking stimulants for Cardiochiles nigriceps, a parasitoid of tobacco budworm

Several methyl-branched saturated C₃₂, C₃₃, and C₃₄ hydrocarbons have been identified from larvae and mandibular glands of Heliothis virescens (F.) (Lepidoptera, Noctuidae) that trigger a short-range host-seeking response of its parasitoid, Cardiochiles nigriceps, Viereck (Hymenoptera: Branconidae). Although the individual components elicited a response, a mixture of the most active C₃₂, C₃₃, and C₃₄ hydrocarbons was significantly more active than the individual components; some mixtures were as active as the contents of the mandibular gland of the host.

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Zusammenfassung Isomere Monomethylalkane in den Larven und in der Mandibeldrüse von Heliothis virescens, die bei ihrem Parasitoid, Cardiochiles nigriceps, nach Kontakt eine wirtsuchende Wirkung besitzen, wurden identifiziert. Mischungen mehrerer, als aktiv erkannter Substanzen (z.B. 12-Methyl C₃₁+12-Methyl C₃₂+13-Methyl C₃₃, optimal zusammen 500 ng) wirkten stärker als die einzelnen Komponenten und konnten die Wirkung des Mandibulardrüseninhalts erreichen.

     

Diallel Analysis of Growth Traits in Mice

Two replications of a complete diallel cross experiment were performed among four partially inbred lines of mice. These inbred lines originated from a random-bred ICR strain and were produced by 12 generations of full sibbing (F congruent to 92%). Individual body weight was recorded for each animal at 12, 21, 42 and 56 days of age. Body weight gain traits were examined for intervals 12-21, 21-42 and 42-56 days. Simultaneous least squares analyses of inbred and linecrossed groups were used. Sex differences were highly significant for all traits. Replicate differences were significant but made a small contribution to the total variation. Inbred lines differed greatly. Crosses showed growth trends similar to their contemporary maternal and paternal inbreds. Heterosis was highly significant for all traits except 21-day weight. Inbreds were heavier at 12 days of age, but linecrossed progeny were superior to inbreds for all postweaning weights. General combining ability was highly significant for 12- and 56-day weights and 21-42-day gain. Specific combining ability was highly significant for 21-day weight, 12-21- and 42-56-day gain. Significant maternal effects were found for all individual weights but not for 12-21- and 21-42-day gain. Residual reciprocal effects were significant for all traits. Estimated variances among linecrossed groups contained a large maternal component, a fluctuating additive genetic component and consistent non-additive genetic influence on all growth parameters measured.     

Comparative flight behavior of parasitoids Campoletis sonorensis and Microplitis croceipes

Flight behavior of parasitoids Microsplitis croceipes Cresson (Braconidae) and Campoletis sonorensis (Cameron) (Ichneumonidae) was examined in a wind tunnel. Both species exhibited odor directed, oriented flights to cotton, although flight frequency was related to variation in wind velocity or differential cotton volatile emission with changes in wind velocity, or both. Flight frequency at constant wind velocity was affected by illumination. Microplitis croceipes was attracted to the wind borne odor of Heliothis virescens (F.) frass and larvae, whereas C. sonorensis was not. Possible interaction of the wind borne odors from the habitat and host is suggested for parasitoids.

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Résumé Le comportement de vol de M. croceipes Cres. (Hym. Braconidae) et de C. sonorensis Cam. (Hym. Icheumonidae) a été étudié en olfactométrie dans un tunnel à vent. Les femelles des deux espèces, et non les mâles, ont un vol orienté par l'odeur des feuilles fraîches de coton (Gossypium hirsutum L.). La fréquence d'envol est liée aux changements de vitesse du vent, aux variations d'émissions, par le cotonnier, des substances volatiles, en fonction de la vitesse du vent, ou aux deux. La fréquence d'envol à vitesse de vent constante dépend de l'éclairage. La fréquence d'envol de C. sonorensis augmente avec des intensités lumineuses relativement fortes et diminue avec des intensités relativement faibles. L'inverse est observé avec M. croceipes. Le vent chargé d'odeurs de larves ou d'extréments d'Heliothis virescens F., attire M. croceipes et non C. sonorensis. Nous suggérons une éventuelle interaction des odeurs portées par le vent et provenant de l'habitat et de l'hôte.

     

In vitro development of bovine morulae in bovine serum albumin, normal steer serum and uterine flushings

One hundred fifty-three excellent and good bovine morulae were cultured in Ham's F-10, supplemented with 10 % steer serum, bovine serum albumin, or uterine flushings (64 mg protein/ml) to compare embryo development. Embryos were observed every 12 h in culture. Treatment differences were evaluated by assigning a numerical value of 0 to 4 to each embryo representing the stage of development reached in vitro. The final morphological developmental score of the embryos was comparable for steer serum (2.66) and bovine serum albumin (2.50), but it differed significantly for uterine flushings obtained from ovariectomized, steroid-supplemented cows (< 0.1) or heat-treated uterine flushings (0.07). Since albumin alone was able to support development, it suggests that the albumin component of steer serum may be responsible for the observed development. Uterine fluids were unable to support growth of embryos, suggesting that incompatibility may be due to asynchrony between the early bovine embryo and uterine constituents, or a concentration of uterine components may exacerbate actions of inhibitory substances.     

Effect of the parasitoid, Campoletis sonorensis, on the growth of its host, Heliothis virescens

Growth of Heliothis virescens was stopped following parasitism by the ichneumonid parasitoid, Campoletis sonorensis. The source of the active factor was found to be the lateral oviducts of the female parasitoid. The active factor appears to be a protein.