Unit responses of the lateral geniculate body to light flashes in free moving unrestrained cats

Riassunto È stata eseguita la registrazione di singole unità della parte dorsale del corpo genicolato laterale, in gatti non anestetizzati liberi di muoversi. Si dimostra che nella maggiore parte dei casi, le risposte ad un lampo di luce espresse in «spikes»/sec sono minime nel sonno sincronizzato, aumentano nella veglia e sono massime nel sonno desincronizzato. Qualora le risposte vengano riferite all'attività «spontanea» precedente il flash, il rapporto risposta-attività spontanea è maggiore nella veglia rispetto agli altri stati.

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The research reported in this document has been sponsored by the Air Force Office of Scientific Research through the European Office of Aerospace Research (OAR), United States Air Force Grant AF EOAR 67-7 and by the Consiglio Nazionale delle Ricerche.

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Moscow University, Chair of Higher Nervous Activity Physiology. Exchange Fellowship of the Italian Ministero degli Affari Esteri.     

lambda Repressor and cro--components of an efficient molecular switch

In a lysogen, most genes of phage lambda are repressed; in response to a transient induction signal, they are efficiently switched on. The switch, which consists in part of a tripartite operator to which two regulatory proteins bind, depends not only on DNA--protein interactions, but also on effects transmitted from one DNA-bound protein to another. lambda Exemplifies a strategy that facilitates efficient switching between two physiological states in response to a transient signal.     

Effect of trace metal availability on coccolithophorid calcification

The deposition of atmospheric dust into the ocean has varied considerably over geological time. Because some of the trace metals contained in dust are essential plant nutrients which can limit phytoplankton growth in parts of the ocean, it has been suggested that variations in dust supply to the surface ocean might influence primary production. Whereas the role of trace metal availability in photosynthetic carbon fixation has received considerable attention, its effect on biogenic calcification is virtually unknown. The production of both particulate organic carbon and calcium carbonate (CaCO3) drives the ocean's biological carbon pump. The ratio of particulate organic carbon to CaCO3 export, the so-called rain ratio, is one of the factors determining CO2 sequestration in the deep ocean. Here we investigate the influence of the essential trace metals iron and zinc on the prominent CaCO3-producing microalga Emiliania huxleyi. We show that whereas at low iron concentrations growth and calcification are equally reduced, low zinc concentrations result in a de-coupling of the two processes. Despite the reduced growth rate of zinc-limited cells, CaCO3 production rates per cell remain unaffected, thus leading to highly calcified cells. These results suggest that changes in dust deposition can affect biogenic calcification in oceanic regions characterized by trace metal limitation, with possible consequences for CO2 partitioning between the atmosphere and the ocean.