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Biomedical subjects

K E Zachariassen

Publications and source records attributed to K E Zachariassen.

15 recordsLinked to original sources
PubMed2005

Isolation and characterization of hemolymph antifreeze proteins from larvae of the longhorn beetle Rhagium inquisitor (L.).

We describe a simple and effective procedure to isolate antifreeze proteins (AFPs) from the hemolymph of larvae of the longhorn beetle Rhagium inquisitor, and present some characteristics of their structures. Several AFPs were isolated from the hemolymph of this species by heat and acid extraction followed by cation exchange. The hemolymph contains at least six AFPs ranging in size from 12.5 to 12.8 kDa. Of these, three were separated to purity by the ion exchange step, as indicated by mass spectrometry. The remaining three forms were further separated by size exclusion chromatography, but could not be isolated to purity. All AFPs in the hemolymph of this species appears to have isoelectric points above 8.00. The dominant form, RiAFP(H4), was purified by the ion exchange step. Its amino acid composition reveals a lower level of cysteine and a higher level of threonine, arginine, alanine and glycine than seen in other insect AFPs. Its trypsin fingerprint does not match that of any known protein. It interacts with ice both in the anionic and cationic state.

Alanine↗
PubMed2001

Metal accumulation and metallothionein in brown trout, Salmo trutta, from two Norwegian rivers differently contaminated with Cd, Cu and Zn.

In this work we have studied the accumulation of heavy metals in two brown trout (Salmo trutta) populations in their natural environment and the participation of metal binding to metallothionein (MT) in this process. Cd, Cu and Zn concentrations, total MT (including Cu MT) and Cd/Zn MT were measured in the gills, liver and kidney of trout inhabiting two rivers, one Cu-contaminated and the other Cd/Zn-contaminated, located at Røros, Central Norway. In both populations, high levels of Cu were found in the liver, whereas Cd was accumulated in liver and particularly in the kidney. The proportions of Cd/Zn MT and Cu MT in liver and kidney, but not in gills, reflected the accumulated and the environmental concentrations of these metals. The total Cu MT concentrations in the investigated tissues, however, were highest in trout from the river with the lowest ambient Cu concentration. It is suggested that MTs are of less importance in Cu-acclimated trout. The data also suggest that acclimation to a Cu-rich environment involves reduced Cu accumulation or increased Cu elimination. In trout from the Cd-rich environment, this metal was mainly bound to MT, whereas in trout from the Cu-rich environment Cd was also associated with non-MT proteins. These findings emphasize the importance to determine both Cd/Zn MT and Cu MT levels, when the participation of this protein in metal handling in trout tissues is investigated.

Animals↗
PubMed2000

Ice nucleation and antinucleation in nature.

Plants and ectothermic animals use a variety of substances and mechanisms to survive exposure to subfreezing temperatures. Proteinaceous ice nucleators trigger freezing at high subzero temperatures, either to provide cold protection from released heat of fusion or to establish a protective extracellular freezing in freeze-tolerant species. Freeze-avoiding species increase their supercooling potential by removing ice nucleators and accumulating polyols. Terrestrial invertebrates and polar marine fish stabilize their supercooled state by means of noncolligatively acting antifreeze proteins. Some organisms also depress their body fluid melting point to ambient temperature by evaporation and/or solute accumulation.

Acclimatization↗
PubMed2000

Effects of ethoxyquin on the blood composition of turbot, Scophthalmus maximus L.

Ethoxyquin (6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (EQ) is a synthetic antioxidant used for preventing rancidity in animal foodstuffs. Three groups of ten fish were given a diet containing respectively 75 (control group with the commercial food), 200 and 400 ppm EQ for 16 days. The control group had a plasma osmolality and chloride concentration within the normal range of marine teleosts, but sodium concentrations of only about 110 mM, indicating the presence in the plasma of substantial amounts of another cation. Fish given food with 400 ppm EQ displayed a 70 mM increase in the plasma concentration of sodium. This indicates that EQ has disturbed the iono-regulatory mechanisms, probably by reducing the ATP production or inhibiting directly the Na/K-ATPase in the gills. The large increase in plasma sodium concentration was not accompanied by any significant increase in plasma osmolality, indicating that at least a part of the sodium added to the plasma is made osmotically inactive. In spite of the elevated plasma sodium concentration, the sodium content of erythrocytes of the 400-ppm EQ fish was reduced to half, while the content of calcium was unaffected. The transmembrane energy gradient of sodium in the EQ exposed turbot obviously increased, allowing them to use a sodium coupled antiport system to keep the cellular calcium content low when the Ca-ATPases is blocked. A mechanism of this kind is also likely to be important to turbot that experience hypoxia under natural conditions. The 400-ppm group also displayed a substantial increase in liver weight, but the physiological significance of this effect is not clear. The leucocyte counts indicated the absence of obvious immunological effects.

Animal Feed↗
PubMed1992

Pollutant-induced depression of the transmembrane sodium gradient in muscles of mussels.

This study deals with the effects of chemical pollutants on the transmembrane potential difference for sodium (delta mu Na) in smooth muscle cells of Mytilus edulis. A method for indirect determination of extracellular space, intracellular ion concentrations and delta mu Na has been developed and is applied in the investigations. The determination is based on concentration data from haemolymph and muscle tissue samples. The precision of the method used was tested by direct measurements of the apparent intracellular concentration of sodium and the membrane potential. On the basis of these tests, the method was evaluated as reasonably good. The method was used to study the sensitivity of the transmembrane delta mu Na in Mytilus edulis to 96 h exposures to various sublethal concentrations of formaldehyde, methanol and mercury. Both formaldehyde and mercury induced a depression of delta mu Na. The observed depressions could be ascribed to a change in both the electrogenic and the chemical components of delta mu Na. A depression of delta mu Na was associated with subsequent clinical injury and death. Methanol did not cause death or any changes in delta mu Na. Because of the observed correlation between depression of delta mu Na and clinical injury, delta mu Na is suggested to have a potential as an indicator of toxicity.

Animals↗
PubMed1991

Physiological parameters in ecotoxicology.

1. Regulated physiological parameters are normally maintained at a constant level by regulatory mechanisms. Acute toxic effects develop whenever a pollutant causes a regulated parameter to be displaced beyond tolerated limits, and thus, regulated parameters may be convenient toxicity parameters. The present study indicates that delta mu Na+ across the adductor muscle membrane of Mytilus edulis is a regulated parameter, and that injuries develop whenever this parameter drops below -700 J/mole. 2. Regulatory physiological parameters may display quick and substantial changes when regulatory mechanisms are activated to counteract variations in the regulated parameters. Thus, regulatory parameters may be used as sensitive alarm parameters in environmental monitoring. The present results indicate that the phosphate index [(ATP x P-arginine)/(Pi)2], metabolic rate and strombine may be used as alarm parameters. 3. The combined response of all parameters may provide a pollutant-specific fingerprint in environmental monitoring.

Animals↗
PubMed1991

Measurements of oxygen consumption in Mytilus edulis during exposure to, and recovery from, high sublethal concentrations of formaldehyde, benzene and phenol.

1. The rate of oxygen consumption has been monitored continuously in M. edulis during acute exposure to high sublethal concentrations of formaldehyde, phenol and benzene and subsequent recovery periods of 96 hr. 2. The results are discussed in relation to changes in the electrochemical potential difference of sodium, the content of ATP and the tissue concentration of strombine. 3. After exposure to benzene and phenol, an increase in the rate of oxygen consumption that could not be explained by oxygen debt from the exposure period was observed. 4. Depression of the rate of oxygen consumption after exposure to formaldehyde may be explained by a reduced ability to extract oxygen from the water. 5. The pattern of oxygen consumption and behavioural responses, as well as the combined changes in the biochemical markers, were distinctly different in the three cases.

Animals↗
PubMed1991

The effects of organic and inorganic pollutants on intracellular phosphate compounds in blue mussels (Mytilus edulis).

1. The effects of sublethal concentrations of organic and inorganic pollutants on intracellular energy-rich phosphates in blue mussels, Mytilus edulis, were investigated by in vivo 31P-NMR. 2. Formaldehyde (30 and 10 mg/l), phenol, pyridine, mercury and cadmium gave marked reductions in phosphoarginine and, in some cases, the ATP amounts. The reduction in high-energy phosphate was accompanied by an increase in inorganic phosphate in all groups. 3. A "phosphorus index", the product of the ratios between phosphoarginine and inorganic phosphate, and ATP and inorganic phosphate, is suggested, which might serve as an early warning ("alarm") parameter in environmental monitoring. 4. Diversity in the responses to different pollutants make phosphorus compounds in M. edulis also an interesting element in a finger print parameter system designed to distinguish between pollutants in the marine environment.

Adenosine Triphosphate↗
PubMed1991

Hypothermia and cellular physiology.

Temperature has pronounced and complex effects on cellular physiology. Rates of enzymatic processes display an exponential change with temperature, as expressed by the Q10 relationship. The basis of these effects may be temperature induced phase transitions in membrane lipids and protein associated water, effects on bulk water and effects on the relationship between water and inorganic solutes. Hypothermia may be lead to a collapse in ionic regulation, leading to an uncontrollable and lethal calcium influx. Subfreezing temperatures may cause injury due to cellular freezing with subsequent excessive osmotic swelling, lyotropic effects or excessive osmotic shrinking due to extracellular freezing. Cells may protect themselves by freeze avoidance accomplished by removal of ice nucleators, production of proteinaceous antifreeze agents and accumulation of polyols. Alternatively they may secure extracellular freezing by production of extracellular ice nucleating agents, and counteract lyotropic effects and osmotic shrinking by accumulation of polyols which reduce ice content in a colligative manner.

Cells↗
PubMed1985

Physiology of cold tolerance in insects.

From the available experimental data a relatively clear picture can be established with regard to the physiological importance of some of the mechanisms involved in insect cold hardening. In freeze-avoiding insects, all potent ice-nucleating agents are removed or inactivated, leading to a depression of the supercooling points to about 20 degrees C. Accumulation of polyols causes a further depression with a magnitude of about twice the corresponding melting-point depression. Production of thermal hysteresis factors causes a stabilization of the supercooled state. In freeze-tolerant insects, potent ice-nucleating agents are produced in the extracellular body fluid, ensuring a protective extracellular freezing at a few degrees below zero. Accumulation of polyols causes a steep drop in the lethal temperature, due to a reduction of the amount of ice by a colligative mechanism. However, there is still much to be learned about the mechanisms by which ice-nucleating agents, polyols, and thermal hysteresis agents are acting. Furthermore, the regulatory mechanisms involved in the production and elimination of these components from the body fluid of the insects are not understood. Also, when it comes to the influence of environmental factors, like photoperiod and temperature, there is much to be learned. In addition to giving attention to these topics, future research should be focused on the possible role of other factors in cold hardening such as bound water, dehydration, low-molecular-weight solutes other than polyols, and the biochemical mechanisms forming the basis of the seasonal changes in the cold hardiness of insects.

Adaptation, Physiological↗
PubMed1983

Total calorimetric measurements in the rat: influences of the sleep-wakefulness cycle and of the environmental temperature.

Rates of production as well as dry and evaporative heat loss during the sleep-wakefulness cycle were studied in 11 male, adult albino rats with chronically implanted electrodes and thermocouple re-entrant tubes. Two groups of animals chronically acclimated to 6 or 23 degrees C were acutely studied at 15, 20, 25, 30 and 35 degrees C. Statistical analysis of the data shows that rates of heat production and dry heat loss differ with respect to acclimation and acute environmental temperatures, and show significant differences depending on the states of the sleep-wakefulness cycle. Rate of heat production was highest during wakefulness, intermediate during synchronized sleep and lowest during paradoxical sleep. Rate of dry heat loss of 15 degrees C was maximal during paradoxical sleep. Rate of evaporative heat loss apparently did not change with the states of the sleep-wakefulness cycle. Heat storage estimated from difference in rates of heat production and heat loss was positive during wakefulness, slightly negative during synchronized sleep and markedly negative during paradoxical sleep. The data presented suggest a clear although partial suppression of thermoregulatory mechanisms during paradoxical sleep in the white rat.

Acclimatization↗