Clinical performance of occlusal onlays made of lithium disilicate ceramic in patients with severe tooth wear up to 11 years.

OBJECTIVES: Evaluation of survival and complication rate of monolithic occlusal onlays made of lithium disilicate ceramic used in patients with severe tooth wear up to 11years of clinical service. METHODS: In a prospective non-randomized clinical study 7 patients (4 male, 3 female; median age: 44.3±6.56years old) were restored full mouth with a total of 103 adhesively bonded occlusal onlays made of lithium disilicate ceramic (IPS e.max Press, Ivoclar Vivadent, Schaan, Liechtenstein). All restorations were examined during annual recall visits using periodontal parameters according to the modified United States Public Health Service (USPHS) criteria: (a) marginal discoloration, (b) secondary caries, (c) marginal integrity, (d) surface texture, (e) restoration fracture, and (f) occlusal wear, rating with Alpha, Bravo and Charlie over an observation period up to 11years (68-139 months; median: 94.9±26.1 months). Data was statistically analyzed using the Kaplan-Meier estimation. RESULTS: Monolithic lithium disilicate occlusal onlays presented a 100% survival rate. Four restorations within one patient (3.9%) presented marginal discoloration, one after 60 and three after 108 months (all rated Bravo). One restoration (1%) showed a marginal crack formation (technical complication) after 120 months, rated Bravo. No biological complication, debonding or secondary caries could be found and tested periodontal parameters showed excellent results. SIGNIFICANCE: Based on the analyzed data up to 11years, monolithic occlusal onlays made of lithium disilicate ceramic can be considered as a reliable treatment option for full-mouth rehabilitations in patients with severe tooth wear.

Diving development in nursing harbour seal pups.

This study investigated physiological and behavioural aspects of diving development in pups of the harbour seal Phoca vitulina. Behavioural data (4280 h, 6027 dives) from time/depth recorders (N=13) deployed on pups aged 0-19 days are presented concomitantly with physiological measurements (N=8, sampled both early and late in the nursing period) of blood oxygen stores and body composition. Pups grew from 12.6+/-1.8 kg (mean age 2 days, total body fat 16+/-4 %) to 22.2+/-2.5 kg (mean age 16 days, total body fat 35+/-5 %; means +/- S.D.) over the duration of the experiment. Pups less than 5 days of age had an elevated haematocrit and reduced plasma volume compared with older pups. Although plasma volume and blood volume increased, mass-specific blood oxygen stores (total haemoglobin) fell during the study period. Simultaneously, the following behavioural indicators of diving ability increased: the proportion of time spent in the water, dive depth, dive duration, bottom time and maximum daily swimming velocity. In addition, the proportion of dives that were identified by cluster analyses as being U-shaped increased significantly with age. On the basis of the measured blood oxygen stores, less than 1 % of the recorded dives exceeded the calculated aerobic dive limit. Thus, development in blood oxygen stores or rates of oxygen consumption did not seem to restrain the rate of neonatal dive development in harbour seals. It appears that behavioural modifications (experience and learning) may be the primary rate-limiting factors for ontogeny of diving skills in neonates of this species.

Genetic variation and functional properties of Atlantic cod hemoglobins: introducing a modified tonometric method for studying fragile hemoglobins.

Hemoglobin polymorphism in Atlantic cod has been investigated with respect to physiological performance at 10, 15 and 20 degrees C applying a modified tonometric method for O2 equilibrium analysis with full control of the equilibrating gas mixture. The results did not indicate any dissociation of the hemoglobins by a reduction in cooperativity and a parallel increase in affinity during the analytical procedure in contrast to the original tonometric method. With the applied preparation technique, we could store the hemolysate for 70 days at -25 degrees C without any significant changes in the O2 binding properties (P < 0.05) demonstrating the high quality of this procedure for analysing fragile fish hemoglobins. The present investigation demonstrates that the oxygen affinity of the hemoglobins varied between the genotypes. At all temperatures, except 20 degrees C and pH 8.0, Hb-I(2/2) had a higher O2 affinity than Hb-I(1/1). These results conform with previous results (16), suggesting Hb-I(2/2), the genotype which is the dominant allele in northern areas, to be the most efficient O2 carrier at low temperatures. The highest O2 affinity, however, was found for Hb-I(2/2b), supporting the results of Fyhn et al. (9), that this genotype is more restricted to coastal and warmer water and thus a better marker of the coastal population. Our results further suggest a correlation between genotype specific growth rates and oxygen affinities at all temperatures studied, with the highest growth rates observed in those genotypes having the highest O2 affinities. In conclusion, the hemoglobin polymorphism of cod seems to be correlated with physiological performance.

Functional characterisation of Eskimo dog hemoglobin: I. Interaction of Cl- and 2,3-DPG and its importance to oxygen unloading at low temperature.

The oxygen binding properties of hemoglobin and some hematological parameters in Eskimo dogs (belonging to Canis lupus familiaris) in Ilulissat/Jacobshavn, Greenland were analysed. The average [2,3-DPG] and [Hb] (n = 16) were 3.14 +/- 0.34 mmol l-1 blood and 9.53 +/- 0.65 g dl-1 (1.49 mmol l-1), respectively, giving a stoichiometric ratio of 2.11 mol 2,3-DPG/mol Hb. Oxygen binding analysis carried out on hemolysate in HEPES buffer at 20 and 37 degrees C revealed a high oxygen affinity (1.2 mmHg at pH 7.4, 20 degrees C) in the desalted condition, which decreased markedly in the presence of chloride and 2,3-DPG. A low apparent equilibrium constant for the binding of 2,3-DPG (1.0 x 10(-5) mol l-1) was found at pH 7.2 and 20 degrees C in the absence of chloride. Moreover, we show that chloride ions have an additive effect on oxygen affinity in the concentration range 10-300 mmol l-1 in the presence of 3 mmol l-1 2,3-DPG at low pH and temperature (pH < 7.4 and 20 degrees C). This feature may be of physiological importance to oxygen unloading under acidotic conditions when tissue temperature is low. Thermodynamic analysis reveal that in the presence of 3 mmol l-1 2,3-DPG and 100 mmol l-1 chloride, the Eskimo dog hemoglobin exhibits a low heat of oxygenation, which places this animal close to arctic ruminants with respect to the influence of temperature on oxygen binding in vivo.

Functional characterisation of Eskimo dog hemoglobin: II. The interplay of HCO(3)- and Cl-.

Hemoglobin (Hb) from the Eskimo dog (belonging to Canis lupus familiaris) showed similar Bohr effect (delta log P50/delta pH) to human HbA in the presence of 100 mmol l-1 NaCl at 20 degrees C. The presence of 7% carbon dioxide in the desalted condition caused a positive (reversed) Bohr effect in the pH range 7.1-7.5 on Eskimo dog Hb, whereas in human HbA there was no Bohr effect within this pH range. A positive Bohr effect on Eskimo dog Hb in this condition was also observed at 37 degrees C. This could indicate differences in the pK values of the amino terminal residues of the two hemoglobins, with possible pH-dependent binding of both bicarbonate (HCO(3)-) and carbamate. Analysis of the effect of CO2 on oxygen affinity of Eskimo dog Hb in the pH range 6.7-7.6 in the presence of chloride and/or 2,3-diphosphoglycerate (2,3-DPG) support this theory. Our results indicate a competition between HCO(3)- and Cl- in affecting oxygen binding. Thermodynamic analysis reveals that bicarbonate binding lowers the apparent heat of oxygenation in Eskimo dog Hb nearly as much as chloride does in the presence of 2,3-DPG at physiological pH. This safeguards an effective oxygen unloading at lowered red blood cell concentrations of chloride. Moreover, we show that the oxygen affinity at high O2 saturation is less dependent on temperature in the presence than in the absence of CO2-.

Synergistic modulation by chloride and organic phosphates of hemoglobin from bear (Ursus arctos).

The oxygen binding properties of hemoglobin (Hb) from brown bear (Ursus arctos) have been studied focussing on the effect of heterotropic ligands, and the behaviour has been compared with that of human HbA, taken as a prototype of mammalian Hbs. It has been observed that in bear Hb chloride ions and 2,3-diphosphoglyceric acid (Gri(2,3)P2) can modulate the oxygen affinity in a synergistic way such that their individual effect is enhanced whenever they are both present in saturating amounts. The thermodynamic analysis of such a feature indicates that in bear Hb there are two classes of chloride binding sites, one acting synergistically with Gri(2,3)P2 and another one, which likely overlaps with the organic phosphate interaction cleft, and is therefore fully operative only in the absence of Gri(2,3)P2. The behaviour of the last site is similar to that observed in human HbA, where the effect of Cl- and Gri(2,3)P2 is mutually exclusive. The interaction energy between chloride and Gri(2,3)P2 synergistic binding sites appears to be O2-linked so that the interplay may have a relevant physiological role in modulating the oxygen transport in brown bear. This behaviour is associated with a marked pH-dependence of the oxygenation enthalpy in bear Hb, such that under acidotic and hypercloruremic conditions, oxygen supply to peripheral tissues could be maintained essentially unaltered even under low temperature conditions.

Physiological relevance of the overall delta H of oxygen binding to fetal human hemoglobin.

Human fetal hemoglobin is known to display, at 20 degrees C, a lower affinity than human adult hemoglobin for oxygen when both proteins are in the absence of organic phosphates. The physiologically important reverse situation is achieved at 37 degrees C upon addition of 2,3-bisphosphoglycerate (DPG), whose lower effect on fetal hemoglobin is related to some amino acid substitutions present in gamma-chains. However, the difference in oxygen affinity observed at 37 degrees C is not solely due to the different modulation power of DPG with respect to adult and fetal hemoglobins. In fact, the results presented here reveal new aspects linked to the interplay of temperature and organic phosphates. In particular, the lower effect of DPG on fetal hemoglobin renders almost identical the oxygen affinity of the two hemoglobins at 20 degrees C, abolishing the difference observed in the absence of the effector. Successively on going from 20 degrees C to 37 degrees C, by virtue of the lower overall heat of oxygenation (delta H) displayed by fetal hemoglobin when in the presence of DPG, adult hemoglobin shows a lower oxygen affinity, as it should if oxygen has to be transferred from maternal to fetal blood.

The interplay of temperature and protons in the modulation of oxygen binding by squid blood.

An extensive set of data relating to the binding of oxygen by haemocyanin from the squid Todarodes sagittatus has been collected under various experimental conditions. The results obtained show that, within the range of physiological pH, the concentration of protons affects mainly the high-affinity state of the molecule without significantly affecting the low-affinity state. As far as the effect of temperature is concerned, the data show a characteristic feature which is very similar to that previously described in the case of haemoglobins from Arctic mammals such as reindeer (Rangifer tarandus) and musk ox. (Ovibos moschatus). The shape of the oxygen equilibrium curve shows strong temperature-dependence, since the overall heat of the binding of oxygen to the low-affinity state of the molecule is strongly exothermic and that to the high-affinity state is very close to zero. The results provide an outline of the intramolecular compromise that, through the interplay of temperature and protons, optimizes the loading and unloading of oxygen under the various environmental conditions experienced by this species of squid.

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.

Interaction of hemoglobin with chloride and 2,3-bisphosphoglycerate. A comparative approach.

The equilibrium oxygen-binding properties of hemoglobins from reindeer (Rangifer tarandus tarandus), musk ox (Ovibos muschatos) and a bat (Rousettus aegyptiacus) have been investigated with special reference to the effect of heterotrophic ligands such as chloride and 2,3-bisphosphoglycerate [Gri(2,3)P2]. The results obtained with hemoglobins from reindeer and musk ox indicate that their low oxygen affinity and their insensitivity to Gri(2,3)P2 are not only an intrinsic property of the molecule, as proposed in the case of ruminant hemoglobins, but also the results of the interplay between chloride and Gri(2,3)P2 interactions. In other words, insensitivity of reindeer and musk ox hemoglobins to Gri(2,3)P2 is mainly due to a decreased affinity constant for this cofactor and to an increased affinity constant for chloride anions; this renders more effective the competition of chloride for th anion-binding site. On the other hand bat hemoglobin behaves in a completely different way and could be regarded as a type case of low-affinity hemoglobin since its functional properties are modulated neither by chloride nor by Gri(2,3)P2. The results are discussed in the light of the amino acid residues which are known to be involved in the binding of organic phosphates.

Temperature modulation of oxygen transport in a diving mammal (Balaenoptera acutorostrata).

The functional properties of haemoglobin from the Lesser Rorqual whale (Balaenoptera acutorostrata) have been characterized as a function of the heterotropic effector concentrations and temperature. The results obtained suggest the existence of sophisticated modulation mechanisms based on the interplay of organic phosphates, carbon dioxide, lactate and temperature. These, together with the very small apparent heat of oxygenation (delta H) of oxygen binding, have been physiologically interpreted on the basis of the specific metabolic needs of this diving mammal.

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.

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.

Arctic adaptation in whale hemoglobin: interplay of carbon dioxide and temperature in the oxygen unloading.

The functional properties of hemoglobin from the whale Balaenoptera acutorostrata have been characterized as a function of pH, CO2, organic phosphates and temperature. Carbon dioxide effect does not depend on the presence of organic phosphates such as 2,3-DPG and P6-inositol while it is strongly affected by temperature, so that at 37 degrees C it is completely abolished. This, together with the very small delta H of oxygen binding (delta H = -4 to -2 Kcal/mol of oxygen at pH 7.4) has been physiologically interpreted on the basis of the specific metabolic needs of fins and tail which are the place of a great muscular activity.

Differences between horse and human haemoglobins in effects of organic and inorganic anions on oxygen binding.

Despite the fact that the horse is one of the more common domesticated animals, there are few reports dealing with the properties of its blood, and no comprehensive study has been performed on the reactivity of horse haemoglobin towards organic and inorganic ions. Here we report data on the effects of the organic phosphates D-glycerate-2,3-bisphosphate (2,3-DPG) and InsP6, and of chloride on the properties of horse haemoglobin. Thus the effect of saturating concentrations of 2,3-DPG on the oxygen affinity of horse haemoglobin is about 60% lower than with human adult haemoglobin under the same experimental conditions. The same applies also to InsP6, whose effect on oxygen binding to horse haemoglobin is decreased by about 55% compared with human adult haemoglobin. On the whole, horse haemoglobin appears to be much less sensitive to organic phosphates than previously believed. These results are discussed in the light of the primary structure of the molecule.

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

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 degrees C. The temperature sensitivity of reindeer and muskox blood expressed by the apparent heat of oxygenation, delta 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.

Lactate does facilitate oxygen unloading from the hemoglobin of the whale, Balaenoptera acutorostrata, after diving.

The present study reports on a specific effect of lactate on the oxygen binding properties of the hemoglobin from the whale, Balaenontera acutorostrata. In fact 0.1 mM lactate may increase the amount of oxygen unloaded to the tissues as much as 30%. Under these conditions the Bohr shift, of the magnitude of about -1, does not alter the oxygen affinity, but plays an important role in the isohydric transport of carbon dioxide.

The chloride shift may facilitate oxygen loading and unloading to/from the hemoglobin from the brown bear (Ursus arctos L.).

1. The oxygen binding properties of hemolyzed bear blood were studied in 0.1 M Tris and 0.1 M Hepes buffer with respect to the possible effects of temperature, pH, pCO2, 2,3-DPG, and chloride ions. 2. There was a significant Bohr shift with a Bohr factor (delta log P50/delta pH) of the magnitude of -0.5. The temperature sensitivity expressed by the apparent heat of oxygenation minus the heat of oxygen in solution was about -8.1 kcal/mol at pH 7.4. 3. Chloride ions decreased the oxygen affinity in the concentration range 50-200 mM, and there was a marked increase in the co-operativity of oxygenation up to a chloride concentration of about 200 mM. 4. There were no effects of pCO2 and 2,3-DPG in the presence of 200 mM Cl-, while in the absence of Cl-, 2,3-DPG had the same effect as 200 mM Cl- at 37 degrees C and pH 7.4. 5. Our results suggests at least two different binding sites for the chloride ion, one high affinity site which may also bind 2,3-DPG in the absence of chloride, and one or more low affinity sites, which only binds chloride. 6. The results further show, that a chloride shift of about 33 mM may account for as much as a 40% increase in O2 unloading, without taking into account the additional effect of the Bohr shift.