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ABSTRACTLeprosy is an infectious disease caused by Mycobacterium leprae, which is a noncultivable bacterium. One of the principal goals of leprosy research is to develop serological tests that will allow identification and early treatment of leprosy patients. M. habanais a cultivable nonpathogenic mycobacterium and candidate vaccine for leprosy, and several antigens that cross-react between M. lepraeand M. habanahave been discovered. The aim of the present study was to extend the identification of cross-reactive antigens by identifying M. habanaproteins that reacted by immunoblotting with antibodies in serum samples from leprosy patients but not with antibodies in sera from tuberculosis (TB) patients or healthy donors (HDs). A 28-kDa antigen that specifically reacted with sera from leprosy patients was identified. To further characterize this antigen, protein spots were aligned in two-dimensional polyacrylamide gels and Western blots. Spots cut out from the gels were then analyzed by mass spectrometry. Two proteins were identified: enoyl-coenzyme A hydratase (lipid metabolism; ML2498) and antigen 85B (Ag85B; mycolyltransferase; ML2028). These proteins represent promising candidates for the design of a reliable tool for the serodiagnosis of lepromatous leprosy, which is the most frequent form in Mexico.

Since 1980, the yellow-eyed penguin Megadyptes antipodes has had three seasons of poor breeding success or low adult survival. Causes for poor seasons are not identified but could be related to climate - in particular, the El Nino-Southern Oscillation event, which affects ocean currents and climate over the penguins' range. We carried out an exploratory analysis to determine whether fluctuations in penguin population variables were correlated with fluctuations in climate variables. Population variables across breeding areas showed consistently strong correlations with rainfall and sea surface temperature. We modelled changes in climate variables and penguin population variables to test whether the effect could be explained as a chance correlation. Investigations using these models indicated that the observed relationship was unlikely to have been due to chance. The models also suggested that fledge-ling success increased in seasons that were slightly cooler and wetter than average. Modelling studies were also carried out on a historical dataset of penguin population variables in the 1930s. It was found that the population tended to increase in seasons that were warmer and drier than average. Average temperatures have risen and average precipitation levels have become highly variable in the study area during this time. Therefore, long term climate change in general, rather than the El Nino-Southern Oscillation events in particular, could be among the underlying causes of gradual decline in yellow-eyed penguin numbers.

The electrosensory system of elasmobranchs is extremely sensitive to weak electric fields, with behavioral thresholds having been reported at voltage gradients as low as 5 nV/cm. To achieve this amazing sensitivity, the electrosensory system must extract weak extrinsic signals from a relatively large reafferent background signal associated with the animal's own movements. Ventilatory movements, in particular, strongly modulate the firing rates of primary electrosensory afferent nerve fibers, but this modulation is greatly suppressed in the medullary electrosensory processing nucleus, the dorsal octavolateral nucleus. Experimental evidence suggests that the neural basis of reafference suppression involves a common-mode rejection mechanism supplemented by an adaptive filter that fine tunes the cancellation. We present a neural model and computer simulation results that support the hypothesis that the adaptive component may involve an anti-Hebbian form of synaptic plasticity at molecular layer synapses onto ascending efferent neurons, the principal output neurons of the nucleus. Parallel fibers in the molecular layer carry a wealth of proprioceptive, efference copy, and sensory signals related to the animal's own movements. The proposed adaptive mechanism acts by canceling out components of the electrosensory input signal that are consistently correlated with these internal reference signals.

1.A pseudorandom binary sequence electrical pulse rate stimulus was delivered to the abducens nerve of an elasmobranch preparation. Ipsilateral eye movements were recorded using a position-sensitive photodiode to measure the position of a reflective patch attached to the fish's eye.2.Eye position data was cross-correlated with the stimulus pattern, and exponential decay curves were fitted to the cross-correlograms to estimate the time constant of a linear first order low-pass filter model. The cross-correlograms were transformed into the frequency domain using a Digital Fourier Transform, and Bode plots of eye dynamics were plotted.3.Eye motor plant dynamics in the elasmobranchCephaloscyllium isabella can be accurately characterised by a linear first order low-pass filter model with a corner frequency of 0.73±0.10 Hz. Non-minimum phase lag reaches 90‡ at about 4 Hz, indicating a time delay of some 50–60 ms.4.Integration of the canal signal is not required for producing compensatory eye movements above the characteristic frequency of the eye motor plant. However, the canal signal may be integrated to ensure that the vestibulo-ocular reflex is compensatory at lower frequencies. Substantial phase compensation or prediction is required for effective control of the vestibulo-ocular reflex.

Eye movements were produced in an elasmobranch preparation by electrical stimulation of the horizontal canal ampullary nerves. A pseudorandom binary sequence of stimulus pulse trains was delivered bilaterally. Eye position during this stimulus was cross-correlated with the stimulus pattern to obtain a linear model of the response. Sums of exponential functions were fitted to the crosscorrelogram data to estimate time-constants and transfer functions. The data was examined in the frequency domain by using Fourier transformation.

The dogfish oculomotor system can be modelled as a first order linear system (Montgomery, 1983) and hence can be specified by its characteristic frequency and gain. This paper describes the effect of temperature on these two parameters. The characteristic frequency is directly related to temperature, and decreases from 0·31 Hz at 20°C to 0·15 Hz at 10°C. The gain is inversely related to temperature, increasing approximately 2·5 times over a temperature drop from 20 °C to 10 °C. It is argued that the increase in gain with falling temperature can be attributed to an increase in relaxation time of the muscle, and that it is likely to be of biological significance in maintaining reflex performance in a poikilothermic animal.