Bioavailability of organic chemicals in the aquatic environment

• 1.1. Bioavailability in the aquatic environment can be defined as the external availability of a chemical to an organism. The availability of sediment-sorbed chemicals to organisms is a particularly important aspect of this phenomena.
• 2.2. Various experiments described in the literature, such as toxicity and accumulation experiments, have investigated the influence of suspended sediment in the aqueous phase on bioavailability.
• 3.3. The bioavailability of a chemical appears to be influenced by the chemical, the sediment, and the organism being examined. Thus, describing “the bioavailability” of a chemical in the aquatic environment is not a simple process.

     

Short-term osmotic responses of cells and tissues of the sea anemone,Condylactis gigantea

• 1.1. Cells of tentacles and body wall of the sea anemone Condylactis gigantea behaved as simple osmometers during 5hr exposure to 50, 67, 83, 100 and 125% sea-water.
• 2.2. All intracellular water appeared to be osmotically active.
• 3.3. Cell sodium, chloride and total osmolyte content remained invariable, with taurine decreasing and potassium increasing as sea-water concentration was reduced.
• 4.4. Tissues, as a whole, exhibited a pseudoregulatory response to changes in salinity as the large and osmotically inert extracellular space buffered volume changes to a considerable extent.

     

The effect of osmotic and ion-osmotic stresses on the blood and urine composition and urine flow of rainbow trout (Salmo gairdneri)

• 1.1. Changes in urine and plasma concentrations (sodium, potassium, magnesium, calcium and total osmotic) and urine production were determined in fish exposed to various concentrations of an ionically active substance, sodium chloride, and a non-electrolyte, mannitol, as well as freshwater.
• 2.2. Responses occurred for the most part over a short crisis period preceeding establishment of new stable conditions.
• 3.3. It was shown that plasma homeostasis was not maintained in response to changing ion-osmotic and osmotic gradients.
• 4.4. Urinary osmotic and ionic concentrations were unaffected and urine production was shown to be inversely related to the external concentration.
• 5.5. It is suggested that ionic shifts between body compartments are an important aspect of ion-osmotic adaptation.

     

Activities of hexokinase,phosphofructokinase and pyruvate kinase in the body wall,pyloric caeca and tube feet of Asterias vulgaris: Evidence of body wall as a major source of glycolytic activity

• 1.1. The activities of hexokinase (HK) and pyruvate kinase (PK) were significantly higher than the activity of phosphofructokinase (PFK) in the body wall, pyloric caeca and tube feet.
• 2.2. When expressed as a function of wet weight, the specific activity of HK was highest in the pyloric caeca. When expressed as a function of cytosolic protein, the specific activity of HK was highest in the body wall.
• 3.3. Specific activities PFK and PK, expressed as functions of cytosolic protein, were highest in the tube feet. These enzyme activities should reflect the high energetic requirements of the tube feet.
• 4.4. Highest total activity of PFK was found in the body wall. These results support the conclusion that the body wall is a metabolically active organ and that the energetic requirement of the body wall is a significant component of the energetic requirements of the organism.

     

A simple procedure for evaluating the protein degradation rate in mussel (Mytilus galloprovincialis Lam.) tissues and its application in a study of phenanthrene effects on protein catabolism

• 1.1. An improved, simple method for the evaluation of the protein catabolic rate in the tissues of the lamellibranch mollusc Mytilus galloprovincialis Lam. is presented.
• 2.2. This procedure, which utilizes the technique of the decay curve of a labeled amino acid (¹⁴C-leucine) in the tissues, exploits the capacity of these organisms to rapidly take up soluble compounds from sea-water.
• 3.3. When mussels are exposed to ¹⁴C-leucine in the sea-water, the labeled amino acid is rapidly accumulated into the cell proteins.
• 4.4. A further addition of unlabeled leucine to the sea-water drastically decreases the specific activity of soluble amino acids into the cells, so that the reincorporation of the labeled leucine into the proteins becomes negligible, allowing a correct estimation of the degradation rate of the proteins.
• 5.5. This procedure was utilized to evaluate the effect of phenanthrene on the rate of catabolism of cytosolic proteins in the digestive gland of mussels, and to study the relationship between the protein degradation rate and the activity of lysosomes, which play a well-established role in the catabolism of macromolecules.

     

Sodium balance in adult atlantic salmon (Salmo salar L.) during migration into neutral and acid fresh water

• 1.1. In sea-water, adult salmon (S. salar) exchange an average of 12.6% of total body sodium/hr.
• 2.2. Following transfer to fresh water sodium uptake follows Michaelis-Menton kinetics. F_max = 2.40 mmol Na/1 ECF/hr, K_m = 0.26 mmol Na/1. The uptake system is fully activated immediately following transfer to fresh water.
• 3.3. Post smolts adapted to sea-water for 3 months take up sodium at only one third of the rate of adult fish following return to fresh water.
• 4.4. The concentration of prolactin in the plasma is low in sea-water adapted fish and does not rise during the first 8 hr in fresh water.
• 5.5. At pH 5 sodium uptake is reduced by almost 90%, even in the absence of aluminium, but recovers immediately on return to neutral water.
• 6.6. At pH 5 and 20 μmol Al/1 there is little further effect on sodium uptake but after 6 hr in aluminium the inhibition of sodium uptake continues after return to neutral aluminium fresh water and uptake is only 50% of normal 24 hr later.

     

Osmotic regulation in aqueous humor and blood in the euryhaline fish,Eugerres plumieri

• 1.1. The estuarine fish Eugerres plumieri was acclimated to sea-water concentrations ranging from 6 to 85% sea-water.
• 2.2. Serum and aqueous humor osmolalities were moderately well regulated over the range of concentrations studied.
• 3.3. Serum osmolality and aqueous humor osmolalities conformed to the following relations: serum osmolality = (319 ± 3) + (0.56 ± 0.03) (% sea-water); aqueous humor osmolality = (314 ± 4) + (0.35 ± 0.04) (% sea-water).
• 4.4. Aqueous humor osmolality was more strictly regulated than that of serum, indicating that the retina and nervous system of the fish, which are encased in inextensible structures, are well protected from variations in sea-water concentration in order to minimize osmotically induced changes in cell volume.

     

The respiratory gas carrying capacity of ascidian blood

• 1.1. The respiratory function of ascidian blood as an oxygen carrier is marginal and equal to sea-water.
• 2.2. The main gas flux is by diffusion.

     

Sea-water tolerance in freshwater-resident arctic charr (Salvelinus alpinus)

• 1.1. Freshwater-resident Arctic charr acclimated for 2 months at 8°C, 15% were divided into four experimental groups in July and exposed to 1 and 8°C in 15 and 34% salinity.
• 2.2. Only slight changes in gill Na-K-ATPase activity, blood plasma osmolality and blood plasma concentrations of Cl⁻ and Mg²⁺ were found for the fish exposed to 1 or 8°C in brackish water.
• 3.3. When exposed to sea-water at 8°C, an increase in osmolality and in concentrations of Cl⁻ and Mg²⁺ took place during the first 2–3 days, after which it levelled off.
• 4.4. If exposed to sea-water at 1°C, however, marked increases were found for all parameters measured and all the fish were dead within 5 days of exposure.
• 5.5. These results show that freshwater-resident Arctic charr—if acclimated to brackish water—can survive in sea-water during summer if the environmental temperature is not too low.

     

The effect of total environmental CO2 concentrations on the ion-permeability of shore crabs,Carcinus maenas (L.)

• 1.1. Salt exchange characteristics (permeability, half-time for salinity adaptation and net salt flux after a change in salinity) of adult shore crabs were studied in relation to experimentally increased external CO₂ (TCO₂ = carbon dioxide, carbonic acid, bicarbonate and carbonate) concentrations.
• 2.2. Up to about 15mM TCO₂/1, elevated external TCO₂ concentrations induce an increase in the salt permeability of shore crabs, resulting in higher passive salt fluxes across the body wall. The effect is most pronounced in larger animals (body weight > 25 g).
• 3.3. When external TCO₂ concentrations exceed internal TCO₂ concentrations, then permeability and salt exchange drop to low values, comparable to those observed in control animals. The results clarify a connection between blood gas transport and salt transport.
• 4.4. Elevated CO₂ levels are unfavourable by inhibiting the chloride/bicarbanate pump (thus disturbing the removal of metabolically produced CO₂ and the salt uptake in a hypotonic environment). High TCO₂ levels, up to about 20 mmol TCO₂/1, cause stress but Carcinus maenas can survive, at least temporarily, at the expense of metabolic energy.

     

Mechanical properties of the stalk and cirri of the sea lily Cenocrinus asterius

• 1.1. The mechanical properties of the stalk and cirri of Cenocrinus asterius L. were analysed using freshly autotomized stalk segments.
• 2.2. When tested in bending, the proximal portions of the stalk had a lower flexural stiffness than the medial/distal portions. The difference between the proximal and medial/distal regions was less than an order of magnitude.
• 3.3. The rate of plastic deformation (creep) of stalk segments and cirri subjected to a constant load was used to calculate the coefficient of viscosity. Measurements taken while the samples were bathed in sea-water, distilled water, or potassium enriched sea-water produced no obvious differences in the viscous properties of the samples.

     

Hyperosmotic properties of the fluids of the perivisceral coelom and water vascular system of starfish kept under stable conditions

• 1.1. Osmotic measurements were made on the perivisceral coelomic and water vascular fluids of 4 species of northwest Pacific starfish and their stable sea-water media.
• 2.2. Mean levels of both fluids were hyperosmotic in every species, often at statistically significant levels.
• 3.3. For all species combined, mean hyperosmolality (mosmol/kg ± SE) of perivisceral coelomic fluid was 1.49 ± 0.17, and water vascular fluid 6.07 ± 0.74.
• 4.4. The hyperosmotic nature of these fluids contributes to water balance, working in conjunction with madreporitic inflow and other factors.

     

Water loss and haemolymph osmolarity of Potamon potamios,an aquatic land crab,under stress of dehydration and salinity

• 1.1. Small crabs survived over 18% water loss and large crabs 21% when in dry air. Size, temperature and relative humidity affected this rate.
• 2.2. Haemolymph osmolarity of newly collected crabs ranged from 530 to 630 mOsm/kg, depending on their size and the season.
• 3.3. When dehydrated, haemolymph osmolarity rose to over 700 mOsm/kg, and ion concentration increased by over 10%.
• 4.4. Crabs survived in sea-water for at least two weeks. Haemolymph osmolarity rose and ion concentration increased. The acclimation pattern affected the haemolymph osmolarity.

     

Internal reference standards in ionic regulation and the predictability of ionic concentrations in animals

• 1.1. The regulation of ions at similar concentrations in most individuals of a species suggests the existence of internal reference standards.
• 2.2. Few have been identified, but many probably relate to cell membrane properties, including potentials, surface charge densities and equilibrium constants of receptor molecules.
• 3.3. Solubility may sometimes determine the product [Ca²⁺][CO₃²⁻].
• 4.4. Reference standards must generally each relate to more than one ionic species.
• 5.5. For some concentrations, including osmolality, there may be no direct reference standard.

     

Salt-dependent effects of juvenile hormone and related compounds in larvae of the brine shrimp,Artemia

• 1.1. Molting in state III larvae of the brine shrimp. Anemia, is interrupted, or even accelerated, when populations are exposed to various concentrations of juvenile hormone, methyl farnesoate, or methoprene in artificial sea-water.
• 2.2. The effects are believed to be salt-dependent, because exposure to these compounds in sea-water that is isotonic to larval hemolymph had no effect. This suggests that the juvenoids may target the ion transporting epithelia.

     

The temperature of the air within the external auditory meatus compared with esophageal temperature during anaesthesia and surgery

• 1.1.|Air temperature within the external auditory meatus, sensed by a thermistor insulated from the walls of the aural canal, was compared with the temperature recorded from a probe in the esophagus in patients under general anaesthesia.
• 2.2.|In the first study of 14 patients, aural temperatures at the time of induction of anaesthesia were more than 3°C lower, and the changes during surgery were more variable, than those recorded from the esophagus.
• 3.3.|In a second study of 35 patients in which heat loss from the external ear was reduced by ear protectors, there was also a poor correlation between temperatures of the ear and esophagus. Aural temperature was initially lower and rose over time in most cases whereas esophageal temperature generally decreased.
• 4.4.|These results suggest that air temperature within the aural canal is not a useful estimate of deep body temperature since it reflects mainly skin temperature.

     

Breast,hips, and buttocks revisited: Honest fatness for honest fitness

This paper comments on: Low, B. S., Alexander, R. D., and Noonan, K.M. Human hips, breast, and buttocks: Is fat deceptive? Ethology and Sociobiology 8: 249-247, 1987. In it I argue that:

• 1.1. Sexual selection has probably not been the most important selection pressure on
• 2.female human body shape.
• 3.2. Male humans in different cultures find different aspects of the female body attractive
• 4.and therefore are unlikely to have exerted consistent directional sexual selection on
• 5.the female body.
• 6.3. Breast size is not correlated with lactation success.
• 7.4. Visible hip width is not correlated with parturition success.
• 8.5. Women would lower their fitness if they tried to deceive men about their internal
• 9.pelvic dimensions.
• 10.6. There are many alternative hypothesis to explain the existence of fat onwomen's
• 11.breast, hips, and buttocks.

     

Viscosity increase of holothurian body wall in response to photic stimulation

• 1.1. The dermis of body wall of Holothuria leucospilota Brandt rapidly increased in viscosity in response to a flashlight.
• 2.2. The response was inhibited in a preparation from which the epidermis had been removed or in a preparation anaesthetized with menthol.
• 3.3. The results strongly suggest that the viscosity of the connective tissue is controlled through nervous activities.

     

Ventilatory rate in the butterfish (Pholis gunnellus) as a consequence of temperature and previous emersion

• 1.1. Observation of ventilation in immersed Pholis gunnellus showed a linear relationship between ventilatory rate and temperature between 8 and 20°C.
• 2.2. At 13°C and after 30 min emersion, ventilatory rate was initially lower than prior to emersion, providing evidence of adequate uptake of O₂ for standard metabolism during the emersion period.
• 3.3. This species has a laterally elongate body form with reduced scales and extensive mucus secretion.
• 4.4. During emersion, gaping behaviour probably exposes the gills and extensively vascularised oesophageal regions to air.
• 5.5. These are considered to be morphological and behavioural adaptations by P. gunnellus, to aerial respiration in the intertidal habitats occupied by this species.

     

Electrical-ionic control of gene expression

• 1.1. Changes in turgor, in cell volume, in membrane potential, in intracellular ionic activities and, more recently, in spontaneous electrical activity have been reported to be causally linked to the expression of specific genes.
• 2.2. As a result, it has become clear that changes in membrane properties and/or in the intracellular “ionic environment” can play an important role in generating cell type specific physiological responses which indirectly—or maybe directly—affect gene expression.
• 3.3. Possible targets of the ionic “environment” are: the selective transport across biological membranes; the activity of certain (regulatory) enzymes; the conformation of some (regulatory) proteins; of chromatin; of the cytoskeleton; of the nuclear matrix; the association of the cytoskeleton with plasmamembrane proteins or RNA; the association chromatin-nuclear matrix; protein-DNA and protein-protein interactions etc. All these sites may be instrumental to “fine or coarse” tuning of gene expression.
• 4.4. The exact mechanisms by which changes in intracellular ionic environment are transduced, directly or indirectly, into alterations of the activity of trans-acting factors have not yet been fully uncovered. Changes in the degree of phosphorylation of regulatory proteins and/or of trans -acting factors may provoke fine tuning effects on cell type specific gene expression activity.
• 5.5. The intranuclear ionic environment is difficult to measure in an exact way. It can be influenced in a number of ways. The location of a gene, as determined by the position of the nucleus in the cytoplasm and by the association of chromatin to the nuclear matrix may be especially important in cells which can generate some type of intracellular gradient or in excitable cells.
• 6.6. In some somatic cell types—germinal vesicles may behave differently—the intranuclear inorganic ionic “environment” has been reported to be distinct from the cytoplasmic one. This challenges the widespread assumption that the nuclear envelope is always freely permeable to small molecules and inorganic ions.
• 7.7. It can be expected that the fast progress in the cloning of “electrically” controlled genes, in the identification of trans-acting factors, in their mode of interaction with genes and in the precise localization of genes within the nucleus may soon lead to substantial progress in this domain.