Discharge properties of morphologically identified vestibular neurons recorded during horizontal eye movements in the goldfish.

Computational capability and connectivity are key elements for understanding how central vestibular neurons contribute to gaze-stabilizing eye movements during self-motion. In the well-characterized and segmentally distributed hindbrain oculomotor network of goldfish, we determined afferent and efferent connections along with discharge patterns of descending octaval nucleus (DO) neurons during different eye motions. Based on activity correlated with horizontal eye and head movements, DO neurons were categorized into two complementary groups that either increased discharge during both contraversive (type II) eye (e) and ipsiversive (type I) head (h) movements (eIIhI) or vice versa (eIhII). Matching time courses of slow-phase eye velocity and corresponding firing rates during prolonged visual and head rotation suggested direct causality in generating extraocular motor commands. The axons of the dominant eIIhI subgroup projected either ipsi- or contralaterally and terminated in the abducens nucleus, Area II, and Area I with additional recurrent collaterals of ipsilaterally projecting neurons within the parent nucleus. Distinct feedforward commissural pathways between bilateral DO neurons likely contribute to the generation of eye velocity signals in eIhII cells. The shared contribution of DO and Area II neurons to eye velocity storage likely represents an ancestral condition in goldfish that is clearly at variance with the task separation between mammalian medial vestibular and prepositus hypoglossi neurons. This difference in signal processing between fish and mammals might correlate with a larger repertoire of visuo-vestibular-driven eye movements in the latter species that potentially required a shift in sensitivity and connectivity within the hindbrain-cerebello-oculomotor network. NEW & NOTEWORTHY We describe the structure and function of neurons within the goldfish descending octaval nucleus. Our findings indicate that eye and head velocity signals are processed by vestibular and Area II velocity storage integrator circuitries whereas the velocity-to-position Area I neural integrator generates eye position solely. This ancestral condition differs from that of mammals, in which vestibular neurons generally lack eye position signals that are processed and stored within the nucleus prepositus hypoglossi.

[Comparative study of blood lead and urine alanine in workers exposed to high concentrations of environmental lead]. / Estudio comparativo de la Plumbemia y la Alanuria en operarios expuestos a elevadas concentraciones de plomo ambiental.

The increase of the levels of lead in the blood and ALA in the urine in 40 workers whose jobs entail their coming into contact with lead salts has been studied over a four-year period, it having been observed that although the level of lead found in the blood varied in a majority of cases, it has been found to be approximately 30 micrograms per 100 ml, the ALA in the urine ranging around 0.40 mg per 100 ml. When these same workers were given medical checkups, no significant variations were found with regard to the type of work in which they were involved.

[Embryonic development of the teeth]. / Aportaciones al estudio del desarrollo embrionario del diente.

Embrionary evolution of the tooth in the rat continues four times very clearly. The first of them or "dentair esbozo" it takes place about the 16th day. The second one of them or "caperuza time" between the 17th and 18th day. The third one of them or "bell time" it takes place 19th, 20th and 21th days. At the end the fourth one of then or "of resolution" it takes place the 22 and first of the afterborn days.

[Changes in blood lead, urinary alanine and coproporphyrins in workers exposed to high concentrations of environmental lead]. / Modificaciones de la plumbemia, alanuria y coproporfirinas en trabajadores expuestos a elevadas concentraciones de plomo ambiental.

A study was conducted on a total of 200 workers whose duties bring them into contact with lead, to determine levels of total alanuria, plumbemia and coproporphyrins in urine, basophil spotting and Burton's fringe. It was noted that in all cases these levels exceeded the maximum permitted environmental concentration. 80% (?) presented high figures for alanuria and 84% had very high plumbaemia levels. Coproporphyrins were also high in more than 60% and also in more than 60% of cases, basophil spotting was found. On the other hand, Burton's fringe was only detected in a few. Lastly, an important fact which emerged was the high rate of absenteeism among this group of workers.