Predator detection and avoidance by starlings under differing scenarios of predation risk

Practically all animals must find food while avoiding predators.An individual's perception of predation risk may depend on manyfactors, such as distance to refuge and group size, but it isunclear whether individuals respond to different factors ina similar manner. We tested whether flocks of foraging starlingsresponded in the same way to an increased perception of predationrisk by assessing three factors: (1) neighbor distances, (2)habitat obstruction, and (3) recent exposure to a predator.We found that in all three scenarios of increased risk, starlingsreduced their interscan intervals (food-searching bouts), whichincreased the frequency of their vigilance periods. We thenexamined how one of these factors, habitat obstruction, affectedescape speed by simulating an attack with a model predator.Starlings were slower to respond in visually obstructed habitats(long grass swards) and slower when they had their head downin obstructed habitats than when they had their head down inopen habitats. In addition, reaction times were quicker whenstarlings could employ their peripheral fields of vision. Ourresults demonstrate that different sources of increased riskcan generate similar behavioral responses within a species.The degree of visibility in the physical and social environmentaffects both the actual and perceived risk of predation.     

Purification of mammalian tumor (L1210) thymidylate synthetase by affinity chromatography on stable biospecific adsorbent. Stabilization of the enzyme with neutral detergents.

Thymidylate synthetase from mouse leukemic L1210 cells was purified to electrophoretic homogeneity with 70% yield as a result of an affinity chromatography procedure based on reversible deoxyuridylate-dependent binding of the enzyme to a stable biospecific adsorbent, 10-formyl-5,8-dideazafolate, immobilized on aminoethyl-Sepharose. The presence of neutral detergents, Triton X-100, or Nonidet P40 stabilized thymidylate synthetase during purification. Analytical electrophoresis of the enzyme treated with an excess of 5-fluorodeoxyuridylate and 5,10-methylenetetrahydrofolate showed the presence of two forms of thymidylate synthetase--5-fluorodeoxyuridylate.5,10-methylenetetrahydrofolate complex, indicating that there are two binding sites for 5-fluorodeoxyuridylate present on the enzyme molecule. Molecular weight of native thymidylate synthetase was found to be 75,000, whereas that for the monomer was 38,500.     

Genetic transformation of filamentous fungi

Many filamentous fungi of all taxa can now be subject to DNA-mediated transformation. Many dominant selectable markers are available and the range available is increasing as new genes are cloned. Transformation is especially valuable in cloning genes defined by mutations with selectable phenotypes and is allowing investigation of many problems in fungi with good genetic systems. Increasingly sophisticated techniques for inactivating genes, targetingin vitro generated mutations to specific loci, and altering gene expression and its regulation are being developed. These approaches are being used to investigate the wealth of basic and applied biological problems available in filamentous fungi.     

Direct selection for curing and deletion of Rhizobium plasmids using transposons carrying the Bacillus subtilis sacB gene

We have constructed derivatives of the transposon Tn5 carrying the mob site (oriT) of plasmid RP4, and an nptI-sacB-sacR cassette [Ried and Collmer, Gene 57 (1987) 239-246]. The mob site, in conjunction with the antibiotic-resistance markers carried on the transposons, allows identification of transposon inserts in cryptic plasmids by mobilisation to other strains. The sacB-sacR genes allow direct selection for the loss or curing of plasmids, because only strains which no longer contain an active sacB gene are able to grow on media containing sucrose. We have tested these transposons in four strains of Rhizobium leguminosarum and two strains of Rhizobium meliloti, and have been able to demonstrate curing of several large cryptic plasmids, and generation of large deletions in many other plasmids. This method has enabled us to show that the R. leguminosarum plasmids pRL12JI and pR1eVF39f carry auxotrophic markers, and that the plasmid pR1eVF39c carries genes which affect colony morphology.     

Substrate specificity of mammalian folylpoly-gamma-glutamate synthetase for 5,8-dideazafolates and 5,8-dideaza analogues of aminopterin

The substrate specificity of pig liver folylpolyglutamate synthetase (tetrahydrofolate:L-glutamate gamma-ligase (ADP-forming), EC 6.3.2.17) for classical 5,8-dideaza analogues of folic acid, isofolic acid aminopterin and isoaminopterin has been investigated. 5,8-Dideazafolate and 5,8-dideazaaminopterin are very effective substrates with activities approaching those of the best reduced folate substrates. The analogous isofolate analogues are less effective substrates, but still better than folic acid. The 5-chloro substituent is the only modification that consistently increases the on rate, with 5-chloro-5,8-dideazaaminopterin being the most effective substrate found, thus far, for the enzyme. Methylation at positions 9 or 10 generally decreases binding, while 5-methylation increases the binding of 4-oxoquinazolines, but decreases the binding of their 4-amino counterparts. The presence of a formyl group at N9 or N10 has the opposite effect, decreasing the binding of 4-oxo analogues while increasing the rate for 4-amino derivatives. Increases in on rate with methyl, formyl or 4-amino substitutions are only significant when the parent compound is a poor substrate, suggesting that these groups do not interact directly with the enzyme but cause conformational changes in the structure of the substrate that influence binding to the enzyme.     

Differential reduction of morphine-withdrawal body shakes by butaclamol enantiomers

Rats withdrawn from continuous morphine infusion showed reliable occurrence of withdrawal body shakes. This sign of narcotic withdrawal was inhibited by the neuroleptic drug, (+) butaclamol. (?) Butaclamol was inactive. (+) Butaclamol activity was not antagonized by naloxone (5 mg/kg). The anti-withdrawal mechanism of (+) butaclamol is discussed in terms of effects on dopamine and narcotic receptors.The butyrophenone neuroleptic, haloperidol, has been used successfully to reduce signs of narcotic withdrawal in laboratory animals (1–4) and human addicts (5). Other neuroleptics of the butyrophenone type also show anti-withdrawal action (6, 7). The mechanism of action of these neuroleptics in blocking narcotic withdrawal is not understood. Butaclamol is a new neuroleptic drug that is available in two enantiomers and only (+) butaclamol possesses neuroleptic activity (8–10). Because of its demonstrated stereo-specificity in producing its pharmacological action, we employed this drug to establish specificity of action of neuroleptics in blocking narcotic withdrawal.     

Expression and secretion in Aspergillus nidulans and Aspergillus niger of a cell surface glycoprotein from the cattle tick, Boophilus microplus, by using the fungal amdS promoter system.

A cell surface glycoprotein (Bm86) from cells of the digestive tract of the cattle tick Boophilus microplus, which has been shown to elicit a protective immunological response in vaccinated cattle, was expressed and secreted in the filamentous fungi Aspergillus nidulans and Aspergillus niger by using the fungal amdS promoter system. The cloned gene coded for the Bm86 secretory signal and all of the Bm86 mature polypeptide except for the hydrophobic carboxy-terminal segment. High levels of Bm86 mRNA were detected in the transformed cells. Bm86 polypeptide was secreted from the cells in a soluble form and it was glycosylated, probably to a similar extent to the native glycoprotein. The recombinant product had an apparent molecular mass of 83 to 87 kilodaltons, whereas that predicted from the amino acid sequence was 69 kilodaltons. The Bm86 was expressed at levels of up to 1.8 mg/liter, or approximately 6% of secreted protein under the growth conditions used. No intracellular Bm86 was detected. A general relationship was observed between transformants containing a high number of copies of the expression plasmid and high expression levels.     

The location of proteins labeled by the 125I-lactoperoxidase system in the NIL 8 hamster fibroblast.

NIL 8 hamster fibroblast cells were labeled by lactoperoxidase-catalyzed iodination. Their membranes were fractionated by sedimentation-rate and isopycnic zonal centrifugation. All the iodinated proteins except the very prominently labeled high molecular weight protein (greater than 200,000 daltons) were located in a fraction identified enzymically and compositionally as plasma membrane. The high molecular weight protein that was previously shown to be sensitive to virus transformation (Hynes, 1973) is concentrated in a very high density particle (rho equals 1.253-1.259) which contains mainly carbohydrate and protein and very low levels of lipid. 5'-nucleotidase was the only enzyme reproducibly demonstrated in this fraction, and electron micrographs revealed a predominantly amorphous morphology together with a few membraneous structures. The iodine label in this fraction was very sensitive to trypsinization prior to homogenization. All the available evidence indicates that this fraction is derived from the surface coat. Mitochondria, nuclei, and soluble protein were labeled to an insignificant extent. The presence of the iodinated surface proteins associated with the endoplasmic reticulum fraction is discussed in the light of these results.