Genetic Ecotoxicology III: the Relationship Between DNA Strand Breaks and Genotype in Mosquito Fish Exposed to Radiation

DNA polymorphism in mosquito fish (Gambusia affinis), as revealed by RAPD (randomly amplified polymorphic DNA) and allozyme analysis, was compared to relative amounts of DNA strand breakage in blood and liver tissues. Mosquito fish were exposed to radionuclide contamination in situ and to X-rays in the laboratory. The types of RAPD metrics used were the number of RAPD bands per individual and the frequency of certain RAPD bands. In a previous study, it was noted that in some instances the number of RAPD bands and the frequency of certain RAPD bands were elevated in radionuclide-contaminated sites relative to reference sites. In the present study, it was found that the median molecular length (MML) of the DNA (which is inversely proportional to the amount of DNA strand breakage) was correlated in several cases to the number of RAPD bands per individual. In addition, for those RAPD bands that occurred at a higher frequency in mosquito fish from radionuclide-contaminated sites, DNA strand breakage was often lower for those fish with than without these RAPD bands. RAPD data obtained on mosquito fish exposed to X-rays in the laboratory paralleled those from the field. Furthermore, analysis showed that heterozygotes for the allozyme locus nucleoside phosphorylase were more prevalent in radionuclide-contaminated sites and had fewer DNA strand breaks than did homozygotes. These results provide additional evidence that changes in population genetic structure of mosquito fish exposed to a genotoxicant (radiation) can be detected at the DNA level.     

Effect of cinoxacin on cellular metabolism and p-aminohippurate transport in kidney cortical slices in terms of its nephrotoxic action

Cinoxacin is a drug which, at very high doses, causes renal damage only in rats. This study compared the in vitro effects of cinoxacin and nalidixic acid on cellular metabolism and p-aminohippurate (PAH) transport in renal cortical slices. Cinoxacin had no effect on Na+ transport, ATP content, oxygen consumption, inulin space and tissue water content, in rat renal cortical slices in vitro, while nalidixic acid affected most of the parameters tested. PAH uptake by slices from rats pre-treated with a nephrotoxic dose of cinoxacin was decreased. This renal damage appeared to be due to physical trauma resulting from deposition of cinoxacin crystals in the urinary tract.     

Measurement of cerebral vascular extraction fractions in the rat using intracarotid injection techniques

A small volume (5 μl) common carotid arterial injection method is described for the quantitation of cerebral vascular extraction fractions (E_t) of diffusion limited tracer molecules in the rat. The method is a modification of a technique diffusion duced by Oldendorf and widely used for the study of blood-brain barrier phenomena. While the Oldendorf technique has proven valuable for estimating the relative permeabilities of substances, it is limited in measuring E_t under conditions of physiologically or pharmacologically altered permeability or blood flow. The method described in this paper — using a small volume (5 μl) common carotid injection, a freely diffusible reference tracer, [¹⁴C]butanol, and a 5 sec circulation time — allows for measurements of E_t that reflect changes in blood flow and small differences in permeability. The modified method is important for the study of the regulation of cerebral vascular permeability and flow in an inexpensive animal model.     

Effects of acute or chronic administration of low doses of a dopamine agonist on drinking and locomotor activity in the rat

Low doses of piribedil (0.25–5.0 mg/kg) administered acutely produced reliable decrements in locomotor activity in thirsty and non-thirsty animals, the greatest effect occurring at the highest dose. A sequence of ten daily injections of piribedil produced indications of the development of tolerance, at the two highest doses (2.5 and 5.0 mg/kg) in thirsty animals. The smallest doses used, given either acutely or chronically, produced a weak enhancement of drinking behaviour within the first 15 min of a drinking test, as shown by a reduction in latency to drink and an increase in the amount of water consumption. Tolerance did develop with respect to drinking behaviour; animals treated chronically with piribedil displayed higher levels of drinking at several dose levels when compared with acutely treated subjects. The tolerance displayed at the two highest doses could have a close affinity with that shown with regard to locomotor activity.     

Amine accumulation in behavioural pathology

When nigro-striatal and meso-cortical neurons degenerate there is a loss of dopamine in the terminal fields and an accumulation of amines in the axons of these systems as they traverse the hypothalamus through the medial forebrain bundle. Traditional lines of thought have attributed the occurrence of motor and consummatory deficits which occur after dopamine neuron degeneration to the loss of functional dopamine neurotransmitter in the terminal fields. However we have hypothesized that hypothalamic amine accumulation represents an area of brain tissue where processes such as neurotransmitter release ephaptic transmission or local axon swelling may be affecting adjacent neurons and may thereby participate in the production of behavioural deficits. There is a considerable amount of evidence from studies on both peripheral and central catecholamine-containing neurons indicating that when their axons degenerate a release of functional neurotransmitter can occur. Information from neuropharmacological studies indicates that several drugs which facilitate behavioural recovery from dopamine-depleting lesions may do so by affecting amine release or receptor sensitivity near areas of accumulation rather than depleted terminal fields. We conclude that amine accumulation is a component of dopamine neuron degeneration which should be considered when assessing the role of the central catecholamine systems in the control of various behavioural and physiological processes.     

Food and water intake and weight regulation in the pigeon

The interaction of eating and drinking and the relation between intake and body weight was examined in pigeons maintained under laboratory conditions in order to obtain normative data on intake and weight regulation in this species. Under ad lib conditions food and water intake values are correlated, while deprivation of either nutrient leads to a reduction in the intake of the other. A linear relation between the log food intake and the log body weight was found under both ad lib and deprivation conditions. Following a period of food deprivation the pigeon shows both a short-term and a long-term compensatory increase in food intake whose magnitude is directly proportional to the degree of body weight loss produced by deprivation. The findings for the pigeon are similar in many respects to those reported for the rat and are discussed in relation to weight regulation and motivational mechanisms in hunger and thirst.     

Capacitive sensor for lick-by-lick recording of drinking.

An electronic device senses the touching of water by the animal's tongue; and each lick is recorded distinctly as a deflection on paper by an ascillograph. From these traces lick rate and any variations therein may be determined.     

Physiological and behavioral effects of parachlorophenylalanine in the rat

The effect of parachlorophenylalanine (PCPA 300 mg/kg i.p.) on several physiological and behavioral parameters was investigated with telemetric methods in the unrestrained rat. Body temperature did not change with the exception of an immediate and short-lasting decrease after drug injection. Food and water intake were maximally depressed on the day following drug administration, and recovered gradually during the subsequent days, drinking more rapidly than feeding. Click-evoked potentials recorded from the auditory cortex and inferior colliculus maintained their typical waveforms during synchronized and desynchronized sleep indicating that PCPA does not produce a qualitative change of the sleep stages. A short-lasting increase of the potentials was observed after drug injection. PCPA exerted profound changes on motor activity. The activity during the light periods was significantly increased. However, motor behavior was altered more in its temporal pattern than in intensity, especially during the dark periods. The circadian rhythms of feeding, drinking and motor activity were attenuated. Since the time-course of these changes corresponds to that known for serotonin depletion in the brain, serotoninergic neuronal mechanisms may play a major role in the organization of behavioral rhythms.This study was supported by the Swiss National Science Foundation, grant no. 3.693.71, and by the Hartmann-Mueller Foundation. Parachlorophenylalanine was supplied by the courtesy of Pfizer AG, Zürich.     

Osmotic water permeability of the apical membrane of proximal straight tubular (PST) cells

Osmotic steps, C, were produced across the apical cell membrane of isolated rabbit PST by perfusing their lumens with double barreled micropipettes at a rate of 0.5–0.8 nl/s. C=15–46 mOsmolar were induced with mannitol. Changes in luminal diameter were recorded as a function of time with a TV camera and an integrator-processor system with space and time resolutions of 0.03 m and 0.0167 s (3). The tubules were bathed with oil. Outer tubule diameter was time invariant. P _os ^ca , the apical cell osmotic permeability was therefore calculated from cell volume changes with time in units of 10^–4 cm³/cm². s. Osmolar. P _os ^ca was independent of C. The mean is 22.8±1.3 (n=55). With a basolateral permeability of 50.4 (3,12), the transcellular permeability is 14 (same units) smaller than the transepithelial values available. This leads to the conclusion that a significant paracellular water osmotic permeability must exist.     

Structural changes in the course of bone conservation measured by pulsed nuclear magnetic resonance techniques

Summary Conservation of bone leads to structural changes of the tissues, such as increase of SH-groups and acidity. At the same time, a decrease in enzyme activity is observed. These alterations in the macromolecular structures are accompanied by changes of distribution of the tissue water. Using the technique of pulsed nuclear magnetic resonance (NMR), it is possible to evaluate the state of water in the tissue.In this work we measured the spin-lattice relaxation times (T₁) of tissue water protons as a parameter for structural changes in the course of conservation. Three different techniques of bone conservation were applied, in which the results of all measurements showed a significant decrease of T₁. In addition, we found a slight but not significant increase in the total tissue water content during the conservation period.By using the method we present, evidence of structural changes in bone tissue can be obtained in a simple but effective manner.

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Résumé La conservation de l'os entraîne des changements de la structure tissulaire, tels qu'une augmentation des groupements SH et une élévation du pH. On observe simultanément une diminution de l'activité enzymatique. Ces altérations des structures macromoléculaires s'accompagnent de changements dans la répartition de l'eau tissulaire. Grâce à la technique de résonance magnétique nucléaire pulsée (RMN) il est possible d'estimer l'état de l'eau dans les tissus.Dans le présent travail, on a mesuré les temps de relaxation du réseau du spin (T₁) des protons de l'eau tissulaire comme critère des changements structuraux lors de la conservation. Trois différentes techniques de conservation osseuse ont été utilisées; les mesures des T₁ ont montré que ces trois techniques déterminent une diminution significative de ce paramètre. Par ailleurs, les auteurs ont trouvé que la quantité totale d'eau tissulaire augmente légèrement mais de façon non significative lors de la période de conservation.En utilisant la méthode exposée ici, la preuve de changements structuraux dans le tissu osseux peut être obtenue de manière simple mais certaine.