Monolayer cultures of perikarya isolated from postnatal rat cerebellum

Summary Viable cerebellar perikarya of mixed cell type obtained from 7–9-day-old rats were maintained in monolayer culture for up to 12 days. During this time extensive neurite formation and outgrowth occurred. The large majority of the cells developing in culture were tentatively identified as granule neurons. This identification was based on the large number isolated from the starting tissue, and the cells general morphological features in culture such as perikaryal and nuclear size, the bipolar nature of neurite extension, and their migratory behaviour.D.N. Currie was supported by a grant from Hoechst Pharmaceuticals, Ld, U.K.J.C. was supported by an S.R.C. Grant to S.P.R. RoseThe authors would like to thank Kathleen Tear for excellent technical assistance and members of the Brain Research Group for helpful discussions.     

Natural engineering principles of electron tunnelling in biological oxidation-reduction

We have surveyed proteins with known atomic structure whose function involves electron transfer; in these, electrons can travel up to 14 A between redox centres through the protein medium. Transfer over longer distances always involves a chain of cofactors. This redox centre proximity alone is sufficient to allow tunnelling of electrons at rates far faster than the substrate redox reactions it supports. Consequently, there has been no necessity for proteins to evolve optimized routes between redox centres. Instead, simple geometry enables rapid tunnelling to high-energy intermediate states. This greatly simplifies any analysis of redox protein mechanisms and challenges the need to postulate mechanisms of superexchange through redox centres or the maintenance of charge neutrality when investigating electron-transfer reactions. Such tunnelling also allows sequential electron transfer in catalytic sites to surmount radical transition states without involving the movement of hydride ions, as is generally assumed. The 14 A or less spacing of redox centres provides highly robust engineering for electron transfer, and may reflect selection against designs that have proved more vulnerable to mutations during the course of evolution.     

Observation of coherent optical information storage in an atomic medium using halted light pulses

Electromagnetically induced transparency is a quantum interference effect that permits the propagation of light through an otherwise opaque atomic medium; a 'coupling' laser is used to create the interference necessary to allow the transmission of resonant pulses from a 'probe' laser. This technique has been used to slow and spatially compress light pulses by seven orders of magnitude, resulting in their complete localization and containment within an atomic cloud. Here we use electromagnetically induced transparency to bring laser pulses to a complete stop in a magnetically trapped, cold cloud of sodium atoms. Within the spatially localized pulse region, the atoms are in a superposition state determined by the amplitudes and phases of the coupling and probe laser fields. Upon sudden turn-off of the coupling laser, the compressed probe pulse is effectively stopped; coherent information initially contained in the laser fields is 'frozen' in the atomic medium for up to 1 ms. The coupling laser is turned back on at a later time and the probe pulse is regenerated: the stored coherence is read out and transferred back into the radiation field. We present a theoretical model that reveals that the system is self-adjusting to minimize dissipative loss during the 'read' and 'write' operations. We anticipate applications of this phenomenon for quantum information processing.     

The effects of primary afferent depolarization on excitability fluctuations of Ia terminals within the motor nucleus

Résumé Sur la préparation de chat spinal aigue, les réponses antidromiques des fibres afférentes la dans un noyeau de motoneurones montrent des fluctuations considérables réduites par des volées afférentes qui provoquent une dépolarisation des afférences primaires. Les réponses provoquées par activation directe des motoneurones sont très stables, et leurs fluctuations non affectées par la stimulation afférente. Ces faits suggèrent que la variabilité du réflexe monosynaptique est principalement due aux fluctuations du potentiel de membrane des parties terminales des fibres afférentes Ia.     

The impact of economic growth in mortality modelling for selected OECD countries

The health of a population is affected by social, environmental, and economic factors. Pension providers and consultants, insurance companies, government agencies and individuals in the developed world have a vested interest in understanding how the economic growth will impact on the life expectancy of their population. Therefore, changes in death rates may occur due to climate and economic changes. In this study, we extend a previous study into excess deaths as a result of climate change to also provide a comprehensive investigation of the impact of economic changes using annual female and male data for 5 developed OECD countries. We find that there is strong negative relationship between mortality index, and climate and economic proxies. This model shows to provide better fitting and forecasting results both for females and males, and for all countries studied.     

The use of cell free extracts derived from fungal protoplasts in the study of aflatoxin biosynthesis.

A supernatant fraction derived from protoplasts of Aspergillus flavus was shown to be capable of converting both sterigmatocystin and versiconal hemiacetal acetate to aflatoxin B1. Versicolorin A was not converted under the same conditions.     

Reversible redox energy coupling in electron transfer chains

Reversibility is a common theme in respiratory and photosynthetic systems that couple electron transfer with a transmembrane proton gradient driving ATP production. This includes the intensely studied cytochrome bc1, which catalyses electron transfer between quinone and cytochrome c. To understand how efficient reversible energy coupling works, here we have progressively inactivated individual cofactors comprising cytochrome bc1. We have resolved millisecond reversibility in all electron-tunnelling steps and coupled proton exchanges, including charge-separating hydroquinone-quinone catalysis at the Q(o) site, which shows that redox equilibria are relevant on a catalytic timescale. Such rapid reversibility renders popular models based on a semiquinone in Q(o) site catalysis prone to short-circuit failure. Two mechanisms allow reversible function and safely relegate short-circuits to long-distance electron tunnelling on a timescale of seconds: conformational gating of semiquinone for both forward and reverse electron transfer, or concerted two-electron quinone redox chemistry that avoids the semiquinone intermediate altogether.