A resonance Raman study of Ambystoma tigrinum hemoglobins: evidence for intraspecies hemepocket variations

Using resonance Raman difference spectroscopy, the Raman-active vibrational modes of hemoglobins from adult, neotenic, and larval forms of the salamander, Ambystoma tigrinum have been compared to each other and to human hemoglobin. The local heme environment of the adult and neotenic proteins were identical and differed from that of the larval protein. Differences were observed in modes sensitive to porphyrin pi electron density and axial ligation. Systematic differences were also observed between human and adult salamander hemoglobins particularly in modes sensitive to the heme vinyl environment. The relationship between these environmental differences, oxygen binding affinity, and the effects of allosteric modulators are discussed.     

Biosynthesis of rat insulin-like growth factor II. I. Immunochemical demonstration of a approximately 20-kilodalton biosynthetic precursor of rat insulin-like growth factor II in metabolically labeled BRL-3A rat liver cells

BRL-3A rat liver cells synthesize mature 7484-dalton rat insulin-like growth factor II (rIGF-II) as a approximately 22-kDa precursor, presumably prepro-rIGF-II. In the present study, we have biosynthetically labeled intact BRL-3A cells with [35S]cysteine and immunoprecipitated cell lysates and media with antisera to rIGF-II. A approximately 20-kDa protein was identified in immunoprecipitates of cell lysates having properties consistent with pro-rIGF-II. The approximately 20-kDa protein is precipitated by immune sera but not by nonimmune serum. Its immunoprecipitation is specifically inhibited by unlabeled rIGF-II but not by insulin. It is not precipitated from labeled lysates of a subclone of BRL-3A cells (BRL-3A2) that does not synthesize rIGF-II. The approximately 20-kDa protein is rapidly labeled intracellularly (10 min) but is not detected in BRL-3A media. In pulse-chase experiments, radioactivity in the approximately 20-kDa protein disappears during the chase and appears, at later times, in specifically immunoprecipitated approximately 19-, approximately 10-, approximately 8-, and approximately 7-kDa proteins in media and, to a limited extent, intracellularly. A protein with electrophoretic mobility identical to that of the approximately 20-kDa protein observed in cell lysates is immunoprecipitated from 35S-proteins whose synthesis is directed by BRL-3A RNA in a reticulocyte lysate cell-free translation system supplemented with microsomal membranes, and presumably arises by cotranslational removal of the signal peptide from approximately 22-kDa prepro-rIGF-II. Processing of the approximately 20-kDa protein in intact BRL-3A cells to intermediate and mature rIGF-II species appears to occur at the time of secretion and/or shortly thereafter, with the different forms appearing at approximately the same time.     

Plant Reactions to Inoculation of Roots with Fungi and Bacteria

The potential of 120 isolates of fungi and bacteria from plant rhizospheres to interfere with plant development and growth was studied in greenhouse experiments. The pure cultured isolates were obtained from plant roots in the field and applied as suspensions to the roots of eight test plant species. 10–20% of the isolates caused distinct symptoms on shoots, growth retardations without other symptoms or growth promotions. Responses of treated plants ranged from death of plants soon after treatment to up to about 40% higher shoot fresh weight than in control plants. Two bacterial isolates induced strong reactions in most of the plant species tested while other isolates showed a more or less pronounced specificity by giving reactions in only some of the plant species tested.     

Population dynamics in variable environments. II. Correlated environments,sensitivity analysis and dynamics

Mean and mean square number are studied for age-structured populations with serially correlated temporally fluctuating vital rates. Results are that (1) Moments of population number can be used effectively to analyse growth rates of the coefficient of variation and an approximate median population number. (2) Analytical approximations to the growth rates of moments reveal dynamic consequences of covarying phenotypic traits and of temporal correlation along environmental sequences. (3) Dynamic properties can be explicitly related to the static sensitivity of an average vital rate matrix. (4) The use of (1), (2) and (3) allows an extension of many applications of static vital rate theory to dynamics with fluctuating rates.     

On the purification of beta-bungarotoxin

It has recently been claimed that our beta-bungarotoxin preparation contained three contaminants, including a postsynaptic toxin. We have extended our purification procedure and found no evidence of such contaminants.