The relative toxicity of a spore preparation of Bacillus thuringiensis var. israelensis against fourth instar larvae of Aedes aegypti and Toxorhynchites amboinensis: suspension feeding compared with enemas and forced feeding

The toxic effect of a spore preparation of Bacillus thuringiensis var. israelensis Berliner Serotype H-14 (Bti) on 4th instar larvae of Aedes aegypti L. and Toxorhynchites amboinensis (Doleschall) was observed when given either in a suspension feeding test or when injected orally as a forced feeding or via the anus as an enema. The A. aegypti larvae showed the greater sensitivity to Bti both because they greatly concentrate the toxin by filter feeding and they are more sensitive to Bti than are the larvae of T. amboinensis. The latter appeared approximately two-fold less sensitive to Bti than the former after taking into account their greater body weight.

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Résumé La toxicité sur des larves de 4ème stade de A. aegypti et T. amboinensis, d'une préparation de spores de B. thuringiensis var. israelensis Berliner sérotype H-14, a été examinée après: injection orale par alimentation forcée, injection anale comme lavement, — le témoin étant une alimentation à partir d'une suspension de spores.Les larves de A. aegypti ont présenté la plus grande sensibilité au Bti d'une part parce qu'elles concentrent beaucoup la toxine avec leur alimentation par filtration, et parce qu'elles sont plus sensibles sensu stricto au Bti. Même en tenant compte de leur poids plus élevé, T. amboinensis est apparu comme deux fois moins sensible au Bti.

     

Infant feeding practices: 1984-85 versus 1977-78.

In 1979 and 1980 the Canadian Paediatric Society''s Nutrition Committee published guidelines for professionals counselling mothers of infants on feeding practices. The practices in 1984-85 of mothers in Toronto were determined for comparison with the practices identified in a similar study conducted in Toronto and Montreal in 1977-78 to ascertain if practices had changed in favour of the recommendations. Between July 1984 and February 1985, 404 metropolitan Toronto mothers of infants were interviewed. Compared with the 1977-78 group of mothers, more of the 1984-85 mothers had chosen to breast-feed and fewer had stopped breast-feeding in the first month. As well, fewer of the 1984-85 infants had been fed unmodified cow''s milk in the first 6 months of life and introduced to solid foods before 4 months of age. We conclude that major changes in infant feeding practices had occurred since 1977-78 and that the 1984-85 practices corresponded closely to the infant feeding guidelines.     

Computer modelling of DNA structures involved in chromosome maintenance.

Sequence-dependent DNA bending of synthetic and natural molecules was studied by computer analysis. Modelling of synthetic oligonucleotides and of 107 kb of natural sequences gave results which closely resembled published electrophoretic data, demonstrating the powerful predictive capacity of the procedure. The analysis was extended to the study of DNA structures involved in chromosome maintenance. Centromeric DNAs from yeast were found to have sequences in their functional elements which cause them to be unusually straight. Autonomous replicating sequences were found to have two structural domains, one consisting of unusually straight sequences surrounding the consensus and the other of bending elements in flanking DNA. In addition to a structural homology, centromeric and autonomous replicating sequences share common sequence elements. These observations show that computer modelling of natural sequences is a viable approach to the study of the biological implications of alternative DNA structures.     

Glutamine-dependent carbamoyl-phosphate synthetase and other enzyme activities related to the pyrimidine pathway in spleen of Squalus acanthias (spiny dogfish).

The first two steps of urea synthesis in liver of marine elasmobranchs involve formation of glutamine from ammonia and of carbamoyl phosphate from glutamine, catalysed by glutamine synthetase and carbamoyl-phosphate synthetase, respectively [Anderson & Casey (1984) J. Biol. Chem. 259, 456-462]; both of these enzymes are localized exclusively in the mitochondrial matrix. The objective of this study was to establish the enzymology of carbamoyl phosphate formation and utilization for pyrimidine nucleotide biosynthesis in Squalus acanthias (spiny dogfish), a representative elasmobranch. Aspartate carbamoyltransferase could not be detected in liver of dogfish. Spleen extracts, however, had glutamine-dependent carbamoyl-phosphate synthetase, aspartate carbamoyltransferase, dihydro-orotase, and glutamine synthetase activities, all localized in the cytosol; dihydro-orotate dehydrogenase, orotate phosphoribosyltransferase, and orotidine-5'-decarboxylase activities were also present. Except for glutamine synthetase, the levels of all activities were very low. The carbamoyl-phosphate synthetase activity is inhibited by UTP and is activated by 5-phosphoribosyl 1-pyrophosphate. The first three enzyme activities of the pyrimidine pathway were eluted in distinctly different positions during gel filtration chromatography under a number of different conditions; although complete proteolysis of inter-domain regions of a multifunctional complex during extraction cannot be excluded, the evidence suggests that in dogfish, in contrast to mammalian species, these three enzymes of the pyrimidine pathway exist as individual polypeptide chains. These results: (1) establish that dogfish express two different glutamine-dependent carbamoyl-phosphate synthetase activities, (2) confirm the report [Smith, Ritter & Campbell (1987) J. Biol. Chem. 262, 198-202] that dogfish express two different glutamine synthetases, and (3) provide indirect evidence that glutamine may not be available in liver for biosynthetic reactions other than urea formation.     

A survey of the accumulation of novel polyhydroxyalkanoates by bacteria

Summary A wide range of bacterial strains were examined for their ability to accumulate polyhydroxyalkanoates (PHA) from various carbon sources. Strains were selected from those reported to accumulate poly-3-hydroxybutyrate (PHB), related organisms and laboratory stocks. Other strains known to utilize n-alkanes, n-alcohols or n-acids were chosen to investigate their ability to produce long-chain PHAs. Five strains accumulated only PHB, 13 accumulated PHAs containing only C₄ and C₅ units and 7 accumulated PHAs containing 3-hydroxyacid units in the range C₅ to C₁₀.     

Rats reproduce and rear litters during chronic exposure to 150-kV/m, 60-Hz electric fields

Mature female rats and their subsequent litters were exposed either to 112- or to 150-kV/m, 60-Hz electric fields or sham-exposed for 19 h daily through pre-breeding, breeding, and rearing periods of experimentation. Exposed females mated in equal percentages and reared litters of equal numbers, and mean body masses of pups were the same as those of sham-exposed animals. Thus, experiments to investigate electric-field effects on reproduction and development in rats are feasible at effective field strengths of 112 and 150 kV/m.     

Trophoblast/leukocyte-common antigen is expressed by human testicular germ cells and appears on the surface of acrosome-reacted sperm

The murine monoclonal antibody H316 reacts with a cell-surface antigen of human trophoblast, leukocytes, certain epithelia, and several malignant cell types. We have found that the H316 antibody also recognizes an antigen synthesized by pre- and post-meiotic human testicular germ cells and is expressed in the acrosomal region of methanol-fixed testicular, epididymal, and ejaculated sperm. The antigen is poorly expressed on the surface of fresh ejaculated motile sperm, but is detectable on most viable sperm after a 6-h incubation in medium containing human serum albumin (HSA), or 60-min incubation with the calcium ionophore A23187 (both treatments induce sperm acrosomal changes termed capacitation and acrosome reaction). We found that antigen recognized by H316 is immunoprecipitated as a single, broad 50 kDa band from radiolabeled ionophore-treated sperm extracts and that preincubation of HSA-capacitated sperm with this antibody causes a moderate, but significant, inhibition of hamster egg penetration. These data indicate that the antigen recognized by the H316 monoclonal antibody is synthesized by testicular germ cells and is surface-expressed on capacitated/acrosome-reacted sperm populations. Its potential as a human sperm acrosome reaction marker, and possible biological role in sperm-egg or sperm-lymphocyte interactions, warrants further investigation.     

The Tc3 Family of Transposable Genetic Elements in Caenorhabditis Elegans

We describe genetic and molecular properties of Tc3, a family of transposable elements in Caenorhabditis elegans. About 15 Tc3 elements are present in the genomes of several different wild-type varieties of C. elegans, but Tc3 transposition and excision are not detected in these strains. Tc3 transposition and excision occur at high frequencies, however, in strain TR679, a mutant identified because of its highly active Tc1 elements. In TR679, Tc3 is responsible for several spontaneous mutations affecting the unc-22 gene. Tc3-induced mutations are unstable, and revertants result from precise or nearly precise excision of Tc3. Although Tc3 is very active in TR679, it is not detectably active in several other mutator mutants, all of which exhibit high levels of Tc1 activity. Tc3 is 2.5 kilobases long, and except for sequences near its inverted repeat termini, it is unrelated to Tc1. The termini of Tc3 are inverted repeats of at least 70 base pairs; the terminal 8 nucleotides of Tc3 are identical to 8 of the terminal 9 nucleotides of Tc1.     

Chemotaxis in Methanospirillum hungatei

Methanospirillum hungatei gave a positive chemotactic response to acetate.