Communication using eye roll reflective signalling.

Body reflections in the ultraviolet (UV) are a common occurrence in nature. Despite the abundance of such signals and the presence of UV cones in the retinas of many vertebrates, the function of UV cones in the majority of taxa remains unclear. Here, we report on an unusual communication system in the razorback sucker, Xyrauchen texanus, that involves flash signals produced by quick eye rolls. Behavioural experiments and field observations indicate that this form of communication is used to signal territorial presence between males. The flash signal shows highest contrast in the UV region of the visual spectrum (lambdamax approximately 380 nm), corresponding to the maximum wavelength of absorption of the UV cone mechanism in suckers. Furthermore, these cones are restricted to the dorsal retina of the animal and the upwelling light background is such that their relative sensitivity would be enhanced by chromatic adaptation of the other cone mechanisms. Thus, the UV cones in the sucker have optimal characteristics (both in terms of absorbance and retinal topography) to constitute the main detectors of the flash signal. Our findings provide the first ecological evidence for restricted distribution of UV cones in the retina of a vertebrate.

Sperm motility of externally fertilizing fish and amphibians.

We review the phylogeny, sperm competition, morphology, physiology, and fertilization environments of the sperm of externally fertilizing fish and amphibians. Increased sperm competition in both fish and anurans generally increases sperm numbers, sperm length, and energy reserves. The difference between the internal osmolarity and iconicity of sperm cells and those of the aquatic medium control the activation, longevity, and velocity of sperm motility. Hypo-osmolarity of the aquatic medium activates the motility of freshwater fish and amphibian sperm and hyperosmolarity activates the motility of marine fish sperm. The average longevity of the motility of marine fish sperm (~550 seconds) was significantly (P < 0.05) greater than that of freshwater fish sperm (~150 seconds), with the longevities of both marine and freshwater fish being significantly (P < 0.05) lower than that of anuran sperm (~4100 seconds). The average velocity of anuran sperm (25 µm/s) was significantly (P < 0.05) lower than that of marine fish (140 µm/s) or freshwater fish (135 µm/s) sperm. The longevity of the sperm of giant salamanders (Cryptobranchoidea) of approximately 600 seconds was greater than that of freshwater fish sperm but much lower than anuran sperm. Our research and information from the literature showed that higher osmolarities promote greater longevity in anuran sperm, and some freshwater fish sperm, and that anuran and cryptobranchid sperm maintained membrane integrity long after the cessation of motility, demonstrating a preferential sharing of energy reserves toward the maintenance of membrane integrity. The maintenance of the membrane integrity of anuran sperm in fresh water for up to 6 hours showed an extremely high osmotic tolerance relative to fish sperm. The very high longevity and osmotic tolerance of anuran sperm and high longevity of cryptobranchid sperm, relative to those of freshwater fish, may reflect the complex fertilization history of amphibian sperm in general and anurans reversion from internal to external fertilization. Our findings provide a greater understanding of the reproductive biology of externally fertilizing fish and amphibians, and a biological foundation for the further development of reproduction technologies for their sustainable management.

[Opioid addiction: P300 assessment in treatment by methadone substitution]. / Toxicomanie aux opiacés: étude au moyen de la P300 du sevrage et du traitement de substitution par la méthadone.

The aim of this study was to assess cognitive functions in two clinical conditions, namely during heroin detoxification and during substitution treatment by methadone. Two groups of chronic heroin user inpatients, meeting DSM-III-R criteria for concurrent opiate dependence, were tested using an auditory oddball paradigm of P300. The first group (four women and six men) were drug-free and the second (five women, ten men) received methadone treatment. Patients were also compared to a control group of non-dependent healthy subjects (five women, nine men). The patients were recorded 6-10 days after the beginning of either detoxification or methadone treatment. There were significant P300 alterations in the two patient groups, with amplitude decrease and latency increase, at a time when self-reported signs of withdrawal were absent or minimal. Paradoxically, the reaction time was accelerated in the two groups of patients, who also showed increased discrimination errors. These abnormalities were found with a lesser degree in the methadone-treated group than in detoxification patients.

[Polymorphism of the continuous muscle fibers activity syndrome. Possible relationship with Morvan's fibrillary chorea (author's transl)]. / Polymorphisme du syndrome d'activité continue des fibres musculaires Relation possible avec la chorée fibrillaire de Morvan.

Two cases presenting the main features of the continuous muscle activity syndrome (neuromyotonia) are reported. The clinical particularities between the two patients are under lined. The second case is special because of its acute and reversible evolution and the possible role of gold salts in its etiology. This latter point suggests Morvan's fibrillary chorea. The possible relationships between the two syndrome are discussed.

Effects of postural changes of the upper limb on reflex transmission in the lower limb. Cervicolumbar reflex interactions in man.

The influence of passive changes in upper limb position on the excitability of three myotatic arc reflexes (soleus, quadriceps, and biceps femoris) of the lower limb has been explored on 42 volunteers. The results indicate that the excitability of the three myotatic arcs can be influenced at a distance by postural modifications of the upper limb. When the ipsilateral upper limb is forwards or the contralateral backwards, a facilitation of both soleus and quadriceps tendon reflexes is observed while the biceps femoris reflexes are reduced. This pattern of facilitation and inhibition is reversed when the ipsilateral upper limb is backwards or the contralateral forwards. The facilitations as well as inhibitions of proximal myotatic arc reflexes are quantitatively more marked than that of the soleus reflex. Facilitation and inhibition are not linearly related to the angle of the arm with the trunk. Effects begin at a considerable angle, become maximal at 45 degrees, and progressively disappear for greater values. It is suggested that the distinct pattern of facilitation and inhibition which is exerted in reciprocal fashion on extensor and flexor motor nuclei might depend on the long propriospinal neurones connecting cervical and lumbar enlargements.