A method for introducing site-specific mutations using oligonucleotide primers and its application to site-saturation mutagenesis

Oligonucleotide primer-directed mutagenesis is a useful molecular biological tool, which is invalubable for the study of the structure/function relationships in proteins and for the creation of mutant proteins possessing modified or novel biological activities. Mutagenesis studies in which a site-saturation approach is employed require a high-efficiency mutagenesis procedure, which will generate a population of mutated molecules containing an even distribution of all possible amino acid changes, or a subset thereof. This article describes such a mutagenesis technique and discusses the adaptations that are necessary to perform sitesaturation mutagenesis.     

γ-Aminobutyric acid (GABA) and other amino acids in tissues of the tick,Amblyomma hebraeum (Acari: Ixodidae) throughout the feeding and reproductive periods

We assayed a variety of tick (Amblyomma hebraeum Koch; Acari, Ixodidae) tissues for a number of amino acids throughout the feeding and early reproductive periods. Our HPLC assay could detect as little as 2–5 pmol per sample of the following: GABA, glycine, serine, glutamine, alanine, taurine, glutamate and aspartate. All of these amino acids could be detected in the salivary gland, synganglion (=total CNS in acarines), haemolymph, Gené's organ, seminal receptacle and ovary. GABA reached high levels in the salivary gland of freshly engorged ticks (685 nmol g^-1) and in the synganglion it exceeded 1000 nmol g^-1 throughout most of the feeding cycle and the first week post-engorgement. GABA also reached a peak titre in the haemolymph of 40 nmol ml^-1. Taurine levels peaked at 1065 nmol g^-1 in the salivary gland from large partially fed ticks. Glutamate and aspartate were likewise found in the salivary gland and synganglion at high concentrations. For most of the amino acids there is insufficient information to correlate these titres (and fluctuations of titres) to neuromodulatory functions. It is possible, however, that the high GABA titre in the salivary gland of engorged ticks is correlated with an augmented level of fluid secretion.Deceased: Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9.     

University acknowledges special risks,introduces drug program for anesthetists.

Anesthetists are at special risk for becoming addicted to some of the drugs they work with. The problem was highlighted by the recent death of a physician in Comox, BC, and a doctor''s brush with death at a hospital near Ottawa. The University of Ottawa has responded with a program, the professional Assistance Program for the Impaired or Disabled Physician, that is in the final stages of approval. Although it will be aimed initially at anesthetists and anesthesia residents in the university''s teaching hospitals, there are hopes the program will spread eventually to other medical departments.     

Photochemical oxidation of tyrosinase

Dye sensitized photo-oxidation inactivates tyrosinases isolated from Neurospora and Agaricus. The rate of inactivation is enhanced by cyanide and is dependent on pH.     

The relative biological activities of α- and β-ecdysone and their 3 dehydro derivatives in the chromosome puffing assay

The relative biological activity of α- and β-ecdysone and their 3-dehydro derivatives in inducing changes in puffing activity in D. melanogaster salivary glands in vitro is approximately constant. Although the six different puffing assays differed considerably in their sensitivity to ecdysones, no stage-specific or locus-specific differential response to the four compounds was detected.     

Observations on the food and diel feeding behaviour of pelagic O-group gadoids in the northern North Sea

The diets and diel feeding behaviour of six O-group gadoid species are described, the cod Gadus morhua (L.), the haddock Melanogramus aeglefinus (L.), whiting Merlangius merlangus (L.), saithe Pollachius virens (L.), Norway pout Trisopterus esmarkii (L.) and the blue whiting Micromesistius poutassou (R.). There were differences, in the main food groups selected by each species with respect to the type, size and number. The main prey consumed did not vary with depth. Cod, saithe and Norway pout had only one period of feeding activity whereas haddock and whiting apparently had two. The diets of haddock and whiting varied in association with these two periods. It is suggested that the differences between the diets were the result of each species having a different feeding behaviour which reflects that adopted in adult life.