Viscosity and gelation studies in deer hunting hemoglobins.

Sickling, viscosity and gelling properties of the red cells and the hemoglobins of three Virginia white-tailed deer homozygous for types II and III (the sickling types) and V (the nonsickling type), respectively, have been analyzed. The sickling of erythrocytes of deer with type II or III is inhibited by urea and cyanate at concentrations which are comparable to those used in in vitro studies of red cells from patients with sickle cell anemia. No differences were observed between the viscosities of the three deer hemoglobin types at temperatures of 12 degrees C or above. High concentrations of deer hemoglobin types II and III gelled at 1 degree C and at pH values of 7.4-7.7; the minimum gelling concentration of type II was 33.5 g% and of type III was 38 g%. Gel formation was not observed at pH values between 6.7-7.1. Hemoglobin type V did not gel and prevented the formation of gels of type II and III in mixtures at pH 7.6-7.7.     

Studies on bovine transferrin; isolation and partial characterization

Bovine serum transferrin (type Tf-A) was isolated by a series of four techniques; (a) precipitation with Rivanol; (b) chromatography of the soluble protein fraction on a column of Sephadex G-150; (c) chromatography of the transferrin containing protein zone on a column of DEAE-Sephadex; and (d) chromatography on a column of DEAE-Sephadex after transferrin was treated with neuraminidase.
It was found that an unidentified protein binds firmly to transferrin, and its removal is only possible after the release of the sialic acid residues with neuraminidase. It is possible that this protein is hemopexin. The occurrence of multiple transferrin components is, in part, dependent on the number of sialic acid residues; possible differences in molecular weight or size seem not to be a factor. The amino acid composition of bovine transferrin, and that of each of three subfractions, resembles that of human transferrin. The calculated mol. wt. of bovine transferrin was found to be 67,000 from sedimentation and viscosity data and 72,400 from sedimentation and diffusion measurements. Sedimentation and viscosity data in concentrated urea suggest that bovine transferrin is composed of two subunits, an observation which is in contrast to data from studies which suggest that human transferrin is composed of a single polypeptide chain.     

Towards a solution of the plankton paradox: the importance of physiology and life history

Phytoplankton communities reveal an astonishing biodiversity, whereas classical competition theory seems to suggest that only a few competing species can survive. Recently we suggested a new solution to this plankton paradox. In theory, at least, competition between multiple species can generate complex dynamics that can support a large number of species. How likely is it then, in reality, that competitive chaos indeed promotes biodiversity? To obtain some insight, we simulated multispecies competition according to five different physiological scenarios. For random species parameters, biodiversity was generally low. Assuming plausible physiological trade‐offs, the simulations revealed switches back and forth between equilibrium and nonequilibrium dynamics, and a higher biodiversity. An extremely high biodiversity, with sometimes more than 100 species on three resources, was observed in simulations that assumed a cyclic relation between competitive abilities and resource contents. We conclude that physiological and life‐history patterns have a major impact on the likelihood of nonequilibrium dynamics and on the biodiversity of plankton communities.     

Class III β-tubulin,a novel biomarker in the human melanocyte lineage

It is generally thought that class III β-tubulin expression is limited to cells of the neural lineage and is therefore often used to identify neurons amongst other cell types, both in vivo and in vitro. Melanocytes are derived from the neural crest and share both morphological features and functional characteristics with peripheral neurons. Here, we show that these similarities extend to class III β-tubulin (TUBB3) expression, and that human melanocytes express this protein both in vivo and in vitro. In addition, we studied the expression of class III β-tubulin in two murine melanogenic cell lines and show that expression of this protein starts as melanoblasts mature into melanocytes. Melanin bleaching experiments revealed close proximity between melanin and TUBB3 proteins. In vitro stimulation of primary human melanocytes by α-MSH indicated separate regulatory mechanisms for melanogenesis and to TUBB3 expression. Together, these observations imply that human melanocytes express TUBB3 and that this protein should be recognized as a wider marker for multiple neural crest-derived cells.