Saverio G. Condò

Oxygen transport in extreme environments

Evolution has adopted different strategies to solve the problem of transporting oxygen to respiring tissues, according to needs dictated by the environment. A thermodynamic analysis of haemoglobins of organisms living in extreme polar environments (mammals and fish) provides elegant examples of such adaptations.

Arctic adaptation in reindeer The energy saving of a hemoglobin

Previous results [(1988) Arct. Med. Res. 47, 83–88] have shown that hemoglobin from reindeer is characterized by a low overall heat of oxygenation. This particular aspect has been investigated further in a series of precise oxygen equilibrium experiments. The results obtained show a peculiar dependence of the temperature effect on the fractional saturation of hemoglobin with oxygen, which could be regarded as a very interesting case of molecular adaptation to extreme environmental conditions.

Sexual and seasonal variability of lobster hemocyanin

Abstract 1. 1. Hemocyanin from the mediterranean lobster Palinurus elephas has been shown to change in subunit composition with relation with the sex of the animal and the period of the year. 2. 2. The sexual difference, consisting of the presence of a specific subunit in the hemocyanin from female animals, is not linked to any evident functional property of the pigment. 3. 3. On the contrary, the season dependent variations in the subunit composition, which consist of the appearance of several catodic bands on electropherograms from both male and female animals, produce obvious functional effects; in particular an increase of the cooperativity of oxygen binding has been consistently found during the summer. 4. 4. The concentration of the pigment is also season and sex dependent, being higher in male animals and during the winter. 5. 5. Hemocyanin from a closely related lobster, Palinurus mauritanicus, does not show sexual and seasonal differences in subunit composition. This difference is tentatively attributed to the difference in the habitat of the two species.

Reduced sensitivity of O2 transport to allosteric effectors and temperature in loggerhead sea turtle hemoglobin: functional and spectroscopic study

The functional and spectroscopic (EPR and absorbance) properties of the adult loggerhead sea turtle (Caretta caretta) hemoglobin have been studied with special reference to the action of allosteric effectors and temperature. Present results indicate that turtle Hb displays a very low O2 affinity and a very small sensitivity to allosteric effectors and temperature. Furthermore, the amplitude of the Bohr effect for O2 binding is strongly reduced. In parallel, EPR and absorbance spectroscopic properties of the nitrosylated derivative of turtle Hb suggest that the hemoprotein is in a low-affinity conformation, even in the absence of allosteric effectors. These findings suggest the existence of unusual molecular mechanisms modulating the basic reaction of Hb with O2, which may be linked to specific physiological needs related to the diving behavior of the turtle.

Thermodynamics of oxygen binding to arctic hemoglobins. The case of reindeer.

The most surprising characteristic of reindeer hemoglobin (Hb) concerns its response to changes in temperature. Thus, the shape of the oxygen-binding curve is strongly temperature dependent due to the difference in the enthalpy of oxygenation between the T and R state of the molecule. In fact, delta H of oxygen binding to the T state is strongly exothermic whereas that of the R state is very close to zero or possibly positive after correction for the heat of oxygen solubilization. Moreover, the allosteric transition T0----R0 has been found to display a negative delta H and a contemporaneous decrease in entropy, a behavior which is precisely the opposite of what has been reported for other hemoglobins. As a whole, reindeer Hb represents a beautiful example of the significance that comparative studies may have in assessing the general validity of the main properties of the hemoglobin molecule.

Alumina and zirconia based ceramics for load-bearing applications

This chapter reviews the structure, mechanical properties, and biocompatibility of load-bearing ceramics used in dentistry. The development of this class of ceramic biomaterials is traced from the late sixties when alumina was introduced in dentistry. The literature on both polycrystalline and single crystal alumina dental implants is reviewed. The use of alumina declined when zirconia-toughened ceramics were introduced in orthopedics in the eighties. The use of yttria partially-stabilized tetragonal zirconia (Y-TZP) in dentistry allowed the production not only of dental implants and abutments, but also a broad range of load-bearing fixed partial dentures, such as multi-unit bridges and crowns, thanks to the development of CAD/CAM technology. Today, the trend is to use alumina and zirconia ceramics for making more aesthetic parts by improving their optical translucency.

THE PRIMARY STRUCTURE OF HEMOGLOBIN FROM REINDEER (RANGIFER TARANDUS TARANDUS) AND ITS FUNCTIONAL IMPLICATIONS

The primary structures of alpha- and beta-chains of hemoglobin from reindeer (Rangifer tarandus tarandus) were determined. Comparison of the reindeer hemoglobin sequence with those of human and bovine hemoglobins showed 50 and 29 substitutions per alpha beta dimer, respectively. The influence of replacements on the modulation of hemoglobin oxygen affinity by heterothopic ligands and temperature, as well as their importance on the structure-function relationships in hemoglobin are discussed.

Arctic life adaptation—II. the function of musk ox (Ovibos muschatos) hemoglobin

1. The hemoglobin system from musk ox (Ovibos muschatos) has been characterized from the functional point of view with special regard to the effect of organic phosphates and temperature. 2. The results are similar to those previously obtained in the case of reindeer and confirm that hemoglobins from arctic animals may display very low enthalpy change for the reaction with oxygen. 3. This finding is considered an example of molecular adaptation of respiratory pigments to extreme environmental conditions.

Arctic life adaptation--I. The function of reindeer hemoglobin

1. The functional properties of hemoglobin from the reindeer (Rangifer tarandus tarandus L.) are characterized as a function of pH, temperature and organic phosphate concentration. 2. Alongside overall similarities shared with most vertebrate hemoglobins, hemoglobin from the reindeer shows significant differences with respect to the effect of both organic phosphates and chloride anions. 3. The limited effect of temperature on oxygen binding (delta H = -4 kcal/mol O2) could be regarded as an interesting case of molecular adaptation to extreme environmental conditions.

Flight and heat dissipation in birds a possible molecular mechanism

Birds during normal sustained flight must be able to dissipate more than 8 times as much heat as during rest in order not to be overheated. The experiments reported in this note on the hemoglobin systems from two different birds indicate the existence of a molecular mechanism by which hemoglobin is used simultaneously for oxygen transport and heat dissipation.