Oxygen transport in the blood of arctic mammals: adaptation to local heterothermia

Summary The oxygen binding of whole blood from humans and two arctic mammals, reindeer and muskox, has been studied as a function of carbon dioxide and temperature. All bloods display a marked Bohr effect with Bohr coefficients in the range –0.44––0.73. The Bohr effect is more pronounced at 20°C. The temperature sensitivity of reindeer and muskox blood expressed by the apparent heat of oxygenation, H, is almost three times lower than that of human HbA under the same experimental conditions. This thermodynamic difference gives special benefits to arctic mammals with large heterothermy by safeguarding oxygen unloading at very low ambient temperatures.     

In vitro tests for the measurement of veterinary clostridial toxins, toxoids and antisera. I. Titration of Clostridium septicum toxins and antitoxins in cell culture

The assay of Clostridium septicum antitoxin currently requires the inoculation of test mixtures intravenously into mice or intradermally into guinea-pig skin. An alternative indicator system based on the use of cell cultures is described. Evidence is presented to show that the toxins detected by the in vivo and in vitro indicators are indistinguishable in terms of molecular weight, charge and hydrophobicity and that there is a close agreement between the two methods of titration. Cell culture indicators are more sensitive than their in vivo counterparts, permitting detection of substantially lower titres than is possible using in vivo indicators. It is suggested that cell culture indicators may prove useful for the titration of Cl septicum antitoxin in sera from vaccine field trials and potency tests. Cell culture methods could also be used for the potency testing of antitoxin preparations.     

Significant extension in northern Australia of the known geographic range of the Shield Shrimp Triops australiensis (Crustacea: Notostraca)

The program BIOCLIM predicts the total geographic distribution of species, based upon the biogeoclimatic characteristics common to the localities at which they are known to occur. Field studies in the Northern Territory have located the Shield Shrimp Triops australiensis at localities substantially north of its known and predicted geographic distribution.     

Measurement of vitellogenin,a biomarker for exposure to oestrogenic chemicals,in a wide variety of cyprinid fish

There is increasing concern about man-made chemicals in the aquatic environment that mimic oestrogens because they may disrupt reproductive function. Vitellogenin, a precursor of egg-yolk in fish and other oviparous animals, may be used as a biomarker for “oestrogen” exposure. This study investigated the use of a radioimmunoassay developed to carp (Cyprinus carpio) vitellogenin to measure vitellogenin in other species of fish, especially cyprinids that would be of value for field and laboratory studies on oestrogenic xenobiotics. Of the nine families of fish studied, only vitellogenin from cyprinids (to which the carp belongs) showed good cross-reactivity in the carp vitellogenin radioimmunoassay. Vitellogenin from cyprinids native to Europe that cross reacted in the carp vitellogenin radioimmunoassay included: bream (Abramis brama), roach (Rutilus rutilus), rudd (Scardinius erythropthalmus), gudgeon (Gobio gobio) and minnow (Phoxinus phoxinus). Vitellogenin from cyprinids used widely in ecotoxicology that cross reacted in the carp vitellogenin radioimmunoassay included: fathead minnow (Pimephales promelas), zebrafish (Brachydanio rerio) and goldfish (Carassius auratus). In the cyprinids studies, the concentrations of vitellogenin in mature females were between a few hundred and a thousand microgram per millilitre. Concentrations of plasma vitellogenin in immature females were always greater than 200 ng·m^-1, whereas in males (with the exception of the fathead minnow) plasma vitellogenin concentrations were less than 20 ng·ml^-1 (and generally, much lower). The results suggest that the structure of vitellogenin is highly conserved within the cyprinid family and that the carp vitellogenin radioimmunoassay may be used to measure the concentrations of vitellogenin in plasma from a wide variety of cyprinids.     

Eicosanoids and their role in immune modulation in fish—a brief overview

Eicosanoids have been demonstrated to play a central role in immune regulation in mammals brought about by their direct effects on cells such as macrophages and lymphocytes or by their indirect effects via cytokines. Studies have shown that fish mononuclear phagocytes, granulocytes and thrombocytes synthesize and release both cyclooxygenase- and lipoxygenase-derived products such as prostaglandin E₂, leukotriene B₄ and lipoxin A₄. Whether lymphocytes have the ability to generate leukotrienes and lipoxins is still unclear but they do appear to have 12-lipoxygenase activity that leads to the generation of 12-hydroxy fatty acid derivatives. As in mammals, leukotriene and lipoxin biosynthesis requires the presence of a 5-lipoxygenase activating protein-like molecule that is sensitive to the action of the specific inhibitor, MK-886. The prostaglandin-generating ability of trout macrophages can be altered by incubation with lipopolysaccharide suggesting the possible presence of an inducible cyclooxygenase activity. Prostaglandins have been found to suppress the mitogen-induced proliferation of trout leucocytes and the generation of humoral antibody and plasma cells both in vivo and in vitro. The lipoxygenase products, leukotriene B₄ and lipoxin A₄ have more variable effects ranging from inhibition to stimulation depending on the assay system employed. Overall, there is clear evidence that eicosanoids play a role in immune regulation in fish in a similar way to that reported in mammals.     

Palisade mesophyll cell expansion during leaf development in Zinnia elegans (Asteraceae)

Temporal and spatial patterns of palisade mesophyll cell expansion in Zinnia elegans were characterized as a basis for developing a suspension culture model for mesophyll cell expansion. Our objectives were to 1) identify the leaf regions from which cells in various stages of expansion could be selectively isolated for culture, and 2) develop a basis for comparison of rate and extent of mesophyll cell expansion in culture with that in the leaf. Palisade mesophyll cells were isolated from expanding leaves by gentle physical maceration without the use of enzymes. Isolated cells from leaves in different stages of expansion were then measured by computer image analysis. Analysis of size frequency distributions showed that unexpanded cells can be isolated from the entire blade of small leaves or the basal regions of partially expanded leaves. Fully expanded cells can be obtained from the apical and middle regions of partially expanded leaves. Within the leaf, Zinnia mesophyll cells expanded from about 400 μm² to about 2.300 μm² at an estimated rate of 160 μm² d^-1. The percent increase in cell length exceeded the percent increase in cell width. Expansion of mesophyll cells continued for 6–8 d after epidermal expansion ceased. This difference in the timing of cell expansion in epidermal and mesophyll cells indicates that different regulatory factors may be operating in these adjacent tissues and underscores the importance of investigating the regulation of mesophyll cell expansion at the cellular level.     

Triplet repeat expansion at the FRAXE locus and X-linked mild mental handicap.

We have recently shown that the expression of the FRAXE fragile site in Xq28 is associated with the expansion of a GCC trinucleotide repeat. In the families studied, FRAXE expression is also associated with mild mental handicap. Here we present data on families that previously had been diagnosed as having the fragile X syndrome but that later were found to be negative for trinucleotide repeat expansion at the FRAXA locus. In these families we demonstrate the presence of a GCC trinucleotide repeat expansion at the FRAXE locus. Studies of the FRAXE locus of normal individuals show that they have 6-25 copies of the repeat, whereas affected individuals have > 200 copies. As in the fragile X syndrome, the amplified CpG residues are methylated in affected males.