Influence of prey species and stages on predatory efficiency and development of two phytoseiid mites

The effect of prey species and the different stages of prey on the predatory efficiency and biology of the phytoseiid mites,Amblyseius gossipi Elbadry andTyphlodromus mangiferus sp. n. was studied. It was found that feeding either predator onTetranychus cucurbitacearum (Sayed) promoted faster development and a higher rate of oviposition than rearing on the twospotted spider mite,T. urticae (Koch). Different stages of both prey species also produced different responses in the biological activities of these predaceous mites.

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Résumé On a étudié l'effet de l'espèce de la proie et de ses différents stades sur l'efficacité et la biologie des acariens phytoseiides,Amblyseius gossipi Elbadry etTyphlodromus mangiferus sp. n. Il a été constaté que l'alimentation des 2 prédateurs avecTetranychus cucurbitacearus (Sayed) assure un dévelopment plus rapide et une fécondité plus élevée que leur élevage surT. urticae (Koch). Les différents stades de ces 2 proies produisent des réponses différentes dans les activités biologiques des 2 acariens prédateurs.

     

The distribution and abundance of species of Danthonia DC on the New England Tablelands (Australia)

The distribution and percent frequency of the 13 species and one variety of Danthonia recorded on the New England Tablelands were examined in a survey of 110 predominantly pastoral sites. The relationships between site factors and the presence and percent frequency of the different Danthonia species were subjected to canonical correlation analysis. Individual species were found to have particular sets of environmental factors associated with their distribution and percent frequency; a fact not well recognized in the past. The most common factor associated with the abundance of Danthonia was either a long time since the last cultivation or no cultivation at all. Other factors such as altitude, drainage, soil parent material, soil texture and total soil phosphorus status were also of some importance. The six species most commonly recorded throughout the New England Tablelands were D. racemosa RBr, D. pilosa RBr, D. laevis J. Vickery, D. linkii Kunth., D. richardsonii Cashmore and D. tenuior (Steud.) Conert. Of these the first three are ecologically wide species. The first two can coexist with other naturalized species under grazing while D. laevis tends to disappear with disturbance. D. linkii and D. richardsonii require fairly narrow habitat conditions but these conditions and consequently these species are common. Both species respond positively to disturbance. Danthonia linkii increases with cultivation and D. richardsonii colonizes eroded soil surfaces. Danthonia tenuior has more restricted requirements and is not so frequent The other seven species and one variety did not occur often enough for detailed study and the occurrence of two of these species, D. carphoides and D. caespitosa must be considered as rare.     

Isozymes of Ipomoea batatas catechol oxidase differ in catalase-like activity.

The amino acid sequences of two isozymes of catechol oxidase from sweet potatoes (Ipomoea batatas) were determined by Edman degradation of BrCN cleavage fragments of the native protein and by sequencing of amplified cDNA fragments. Sequence alignment and phylogenetic analysis of plant catechol oxidases revealed about 80% equidistance between the two I. batatas catechol oxidases and approximately 40--60% to catechol oxidases of other plants. When H(2)O(2) was applied as substrate the 39 kDa isozyme, but not the 40 kDa isozyme, showed catalase-like activity. The structure of the 40 kDa isozyme was modeled on the basis of the published crystal structure of the 39 kDa isozyme [T. Klabunde et al., Nat. Struct. Biol. 5 (1998) 1084]. The active site model closely resembled that of the 39 kDa isozyme determined by crystallography, except for a mutation of Thr243 (40 kDa isozyme) to Ile241 (39 kDa isozyme) close to the dimetal center. This residue difference affects the orientation of the Glu238/236 residue, which is thought to be responsible for the catalase-like activity of the 39 kDa isozyme for which a catalytic mechanism is proposed.     

Human dynein and sperm pathology

Human spermatozoa with normal structure and with different axonemal deficiencies (absence of axoneme, of arms, or of central structures) were studied by electron microscopy, SDS-polyacrylamide gel electrophoresis, and ATPase activity measurements. Normal human sperm possess a complement of high molecular weight polypeptides with an electrophoretic migration similar to that of sea urchin and other mammalian sperm dyneins. Human high molecular weight bands are numbered one to four in order of increasing of electrophoretic mobility; all of them are absent in spermatozoa that lack axoneme. The absence of doublet arms, coincides with the absence of bands 2, 3, and 4; the absence of central structures coincides with a reduction in intensity of band 2. In the latter two abnormal conditions, band 1 has an increased intensity. The data are tentatively interpreted by attributing the polypeptides forming bands 3 and 4 to the arm structure, whereas band 2 is supposed to contain a mixture of polypeptides localized in the arms and in the central structures; these abnormal sperm contain modified polypeptides which gather in band 1. Histochemical ATPase stainings indicate that this enzyme is localized mainly in the doublet arms and, to a minor extent, in the central structures.     

Comparative in vitro and in vivo beta-oxidation of N-nitrosodiethanolamine in different animal species

The metabolism of N-nitrosodiethanolamine (NDELA) was studied to assess whether the formation of the beta-oxidated metabolites N-(2-hydroxyethyl)-N-(formylmethyl)nitrosamine (EFMN) and N-(2-hydroxyethyl)-N-(carboxymethyl)nitrosamine (ECMN) is involved in the mechanism of tumor induction in various animal species with different susceptibility to NDELA carcinogenicity. In vitro studies using liver S9 fractions from rats, hamster, B6C3F1 and CD-1 mice and rabbits showed that all the animal species metabolize NDELA through the beta-oxidation pathway, although to different extents. Urinary excretion of NDELA and its metabolite ECMN in rats, hamsters and mice after 5 mg X kg-1 NDELA i.p. confirmed these findings. The results suggest there is no correlation between carcinogenesis by NDELA and its beta-oxidation. The possibility that ECMN formation might represent a detoxifying metabolic pathway for NDELA is discussed.     

Radioimmunoassay of chenodeoxycholic acid-3-sulfate in urine

A sensitive and specific radioimmunoassay (RIA) for the measurement of urinary total chenodeoxycholic acid-3-sulfate (SCDCA) was developed and the accuracy was confirmed. SCDCA bound to bovine serum albumin as the antigen and emulsified with Freund's complete adjuvant was injected into rabbits. The antiserum obtained was capable of binding 75% of [11,12-3H]SCDCA at 1:1000 dilution. The percentage of bound radioactivity decreased linearly with logarithmic increases in unlabeled SCDCA, from 8 to 200 pmol/ml. The antiserum showed an extremely high specificity for SCDCA (free and conjugated), and the values determined by RIA indicated a close correlation with those found by gas-liquid chromatography. The daily urinary SCDCA level was determined using SCDCA-RIA in 12 disease-free humans and 74 patients with chronic liver diseases. In the normal subjects the daily urinary SCDCA level was 0.74 +/- 0.83 mg/day and increased levels were evident in all groups with chronic liver diseases. The daily urinary SCDCA level corresponds closely with the extent of hepatic dysfunction.     

Comparative incidence of reticuloendothelial tumors in C57BL mice after exposure to tritiated water

A total of 2,377 C 57 Bl/6M mice were assigned to control groups and experimental groups exposed to tritiated water administered as a pulse injection or in drinking water, at a dose of 1.0 microCi per injection or per ml of drinking water. Weanlings were observed for the duration of life span. Data analysis was based on two coefficient estimates (1) individual carcinogenic induction coefficient and (2) specific tumorigenic induction coefficient. The carcinogenic potency of tritium was found to be dual in nature in enhancing the absolute induction of lymphocytic lymphomas in both sexes as well as their relative induction in competition with reticulo-endothelial tumors of other types.