Bacillus thuringiensis potency bioassays against Heliothis armigera, Earias insulana, and Spodoptera littoralis larvae based on standardized diets

Bacillus thuringiensis screening programs based on the official potency bioassay using third-instar larvae and on a neonate bioassay were developed for Heliothis armigera, Earias insulana, and Spondoptera littoralis. In these bioassays, the diets were standardized to be suitable, with minor modifications, for feeding of the three lepidopterans. The bioassay protocol was based on determination of the LC50 of the microbial standard HD-1-S-80 in the insects susceptible to B. thuringiensis var. kurstaki strains. This was followed by preliminary screening of B. thuringiensis strains at the LC50 of the B. thuringiensis standard. The B. thuringiensis strains causing 100% mortality at this LC50 in the larvae were selected for potency determinations. The neonate bioassay was suitable for accurate determinations of potencies also in S. littoralis--a representative of insects weakly susceptible to the HD-1 standard. The role of the official and the neonate bioassays in developing microbial control programs is discussed.     

Genetic identification of non-specific esterases of the mouse cauda epididymidis and description of esterase-28, a new carboxylesterase isoenzyme (EC 3.1.1.1)

Twenty-five (25) electrophoretic bands with esterase activity were distinguished in supernatants of cauda epididymidis of DBA/2J mice. Twenty (20) of these were assigned to 10 genetically defined esterases (ES-1, ES-2, ES-3, ES-6, ES-7, ES-11, ES-14, ES-17, ES-19, ES-22) which were already known from investigations of other mouse tissues. Furthermore, ES-10 was identified in cauda supernatants after isoelectric focussing. A hitherto genetically undefined esterase was assigned to locus Es-28 which was expressed solely in the epididymis. Three phenotypes were distinguished: ES-28A was present in the majority of the inbred strains examined. ES-28B was observed in AKR/Han mice and ES-28C was found in SEG/1 mice.     

Nucleotide sequences of the fecBCDE genes and locations of the proteins suggest a periplasmic-binding-protein-dependent transport mechanism for iron(III) dicitrate in Escherichia coli.

The fec region of the Escherichia coli chromosome determines a citrate-dependent iron(III) transport system. The nucleotide sequence of fec revealed five genes, fecABCDE, which are transcribed from fecA to fecE. The fecA gene encodes a previously described outer membrane receptor protein. The fecB gene product is formed as a precursor protein with a signal peptide of 21 amino acids; the mature form, with a molecular weight of 30,815, was previously found in the periplasm. The fecB genes of E. coli B and E. coli K-12 differed in 3 nucleotides, of which 2 gave rise to conservative amino acid exchanges. The fecC and fecD genes were found to encode very hydrophobic polypeptides with molecular weights of 35,367 and 34,148, respectively, both of which are localized in the cytoplasmic membrane. The fecE product was a rather hydrophilic but cytoplasmic membrane-bound protein of Mr 28,189 and contained regions of extensive homology to ATP-binding proteins. The number, structural characteristics, and locations of the FecBCDE proteins were typical for a periplasmic-binding-protein-dependent transport system. It is proposed that after FecA- and TonB-dependent transport of iron(III) dicitrate across the outer membrane, uptake through the cytoplasmic membrane follows the binding-protein-dependent transport mechanism. FecC and FecD exhibited homologies to each other, to the N- and C-terminal halves of FhuB of the iron(III) hydroxamate transport system, and to BtuC of the vitamin B12 transport system. FecB showed some homology to FhuD, suggesting that the latter may function in the same manner as a binding protein in iron(III) hydroxamate transport. The close homology between the proteins of the two iron transport systems and of the vitamin B12 transport system indicates a common evolution for all three systems.     

Pituitary and ovarian responses of post-partum acyclic beef cows to continuous long-term GnRH and GnRH agonist treatment

Post-partum acyclic beef cows received continuous long-term treatment with GnRH (200 or 400 ng/kg body wt/h) or the GnRH agonist buserelin (5.5 or 11 ng/kg body wt/h) using s.c. osmotic minipumps which were designed to remain active for 28 days. All treatments increased circulating LH concentrations whereas FSH remained unchanged. Ovulation and corpus luteum (CL) formation as judged by progesterone concentrations greater than or equal to 1 ng/ml occurred in 0/5 control, 4/5 200 ng GnRH, 4/4 400 ng GnRH, 4/5 5.5 ng buserelin and 3/5 11 ng buserelin cows. The outstanding features of the progesterone profiles were the synchrony, both within and across groups, in values greater than or equal to 1 ng/ml around Day 6, and the fact that most CL were short-lived (4-6 days). Only 3 cows, one each from the 400 ng GnRH, 5.5 ng buserelin and 11 ng buserelin groups, showed evidence of extended CL function. Cows failed to show a second ovulation which was anticipated around Day 10 and this could have been due to insufficient FSH to stimulate early follicular development, or the absence of an endogenously driven LH surge. The highest LH concentrations for the respective groups were observed on Days 2 and 6 and by Day 10 LH was declining, although concentrations did remain higher than in controls up to Day 20.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tissue distribution of cocaine in the pregnant rat

Cocaine hydrochloride was administered by single intraperitoneal (IP) doses to pregnant rats at day 18 or 19 of gestation. Plasma and tissue cocaine and norcocaine concentrations were measured by high-pressure liquid chromatography. Pharmacokinetic analysis of concentration versus time data showed rapid distribution of cocaine and its metabolite to maternal and fetal tissues. The area under the cocaine concentration versus time curve (AUC) in fetus compared to maternal plasma was 3.33. The half-life of cocaine in the maternal plasma and fetus was 46 and 55 minutes, respectively, similar to values reported for cocaine elimination half-life in human plasma. The order of cocaine concentrations was placenta greater than fetal liver greater than maternal heart greater than whole fetus greater than fetal brain greater than maternal brain = maternal plasma. Norcocaine concentrations were usually less than 20% of cocaine concentrations in plasma and tissues. These results support extensive fetal exposure to cocaine following administration to pregnant rodents. Pharmacodynamic studies of cocaine in pregnancy should consider the effects of the drug on the developing fetus.     

Brefeldin A affects the cellular distribution of endocytic receptors differentially.

The cell surface expression of three endocytic receptors was studied in human hepatoma Hep G2 cells treated with brefeldin A (BFA). Ligand binding and cell surface iodination revealed that BFA increased the number of mannose 6-phosphate/insulin-like growth factor II receptors twofold and decreased the amount of asialoglycoprotein and transferrin receptors by 40-60%. The altered expression of receptors at the cell surface was paralleled by changes in the respective ligand uptake. The implications of this finding on our understanding of intracellular trafficking are discussed.     

Effects of abscisic acid on somatic embryo maturation of hybrid larch

Somatic embryos of hybrid larch (Larixleptoeuropaea) whichhad been matured for 4 weeks on maturation medium, developednormally on medium supplemented with 60 µM ABA, but abnormallyon medium with no ABA. A comparative structural and histochemicalinvestigation was carried out on these two types of mature embryos.At the light microscope level, differences between both treatmentswere visible only after 2–3 weeks of maturation. At aroundthis time, abnormal development becomes evident macroscopically:ABA-minus embryos remain rather stubby as opposed to the morecylindrically shaped ABA-plus embryos. Whereas somatic embryosmatured with ABA consist of densely cytoplasmic cells showinga high rate of cell division, ABA-minus embryos are largelymade up of expanded and highly vacuolate cells, indicating thatgrowth in the latter is mainly due to cell expansion and notdivision. After 4 weeks of maturation, ABA-minus embryos beginto elongate in the hypocotyl region, and precocious germinationwas observed frequently. Again, these morphogenetic events werelargely due to abnormal timing of cell expansion. Histochemically,storage proteins were found only in somatic embryos maturedfor 4 weeks with ABA. This observation is in line with resultsobtained by total protein analysis, yielding significantly lowertotal protein contents in ABA-minus embryos both on a freshweight and a per embryo basis after 4–5 weeks of maturation.Deposition of starch grains mainly in the cortex tissue of thehypocotyl region was observed within 2 weeks of maturation invarying amounts regardless of ABA supply. Polyphenols, in particularcatechins and proanthocyanidins, were present in all embryosfrom the very onset of development. They were localized preferentiallyin the proximal suspensor cells and the basal region of theembryo. However, accumulation of polyphenols was generally muchmore pronounced in embryos matured without ABA, indicating alack of biochemical regulatory competence in those embryos. Key words: Abscisic acid, embryonal development, somatic embryo, storage protein, polyphenols