Shivering in intact and spinal rabbits during spinal cord cooling

Zusammenfassung Bei spinalen wie auch bei intakten, leicht narkotisierten Kaninchen konnte durch Kühlung des Rückenmarkes Muskelzittern ausgelöst werden. Im Vergleich zu den intakten Tieren war der Effekt der Rückenmark-Kühlung bei spinalen Tieren schwächer, und die Temperatur zu Beginn und bei Beendïgung der elektromyographisch erfassten Aktivität war niedriger, bzw. streute in einem weiteren Temperaturbereich. Die während des Kältezitterns intakter Tiere häufig zu beobachtenden phasischen Aktivitätsschwankungen im Elektromyogramm waren bei spinalen Tieren nur selten nachweisbar.     

Response of respiration to selective heating of the spinal cord below partial transection

Conclusions The experiments indicate that the signals arising from thermal stimulation of the spinal cord are conducted to higher spinal and to supraspinal thermoregulatory effector systems by afferent fibers which run in the ventrolateral, but not in the dorsal portions of the spinal ascending tracts. This corresponds to the observation ofWünnenberg andBrück that shivering induced by external cooling is not inhibited by heating the lower cervical and upper thoracic spinal cord, if the ventral funiculi are transected at a higher cervical level. -These findings are parallel to the observation that the inhibitory effect on shivering of skin pressure is no longer present after contralateral transection of the ventrolateral funiculus at a higher level, i. e. after transection of the so-called ventral spinothalamic tract. Likewise, it has been observed that modifications of electrocortical activity following thermal stimulation of the skin or following changes of environmental temperature are abolished, if the ventrolateral funiculi are transected at the cervical level. -It may be suggested, therefore, that the afferent signals arising from spinal thermosensitive structures might follow the same ascending pathway as do the discharges of peripheral thermodetectors.

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Zusammenfassung Der Einfluss thermischer Reizung des Rückenmarks unterhalb einer Teildurchschneidung in Höhe von Th 4–Th 11 auf Atmung, Hautdurchblutung und motorische Aktivität wurde an leicht narkotisierten Kaninchen untersucht. Mittels Marchi-Färbung einige Tage nach Durchschneidung wurden die ausgeschalteten afferenten Bahnen ermittelt. Nach Durchschneidung der Hinterstränge und anschliessender Abschnitte der Seitenstränge konnte durch Rückenmarkwärmung unterhalb der Durchschneidung eine thermische Tachypnoe und eine Hautvasodilatation oberhalb der Durchschneidung ausgelöst werden. Diese Reaktion war nach Durchschneidung der Vorderseitenstränge erloschen.

     

Structure of a methyl-coenzyme M reductase from Black Sea mats that oxidize methane anaerobically

The anaerobic oxidation of methane (AOM) with sulphate, an area currently generating great interest in microbiology, is accomplished by consortia of methanotrophic archaea (ANME) and sulphate-reducing bacteria. The enzyme activating methane in methanotrophic archaea has tentatively been identified as a homologue of methyl-coenzyme M reductase (MCR) that catalyses the methane-forming step in methanogenic archaea. Here we report an X-ray structure of the 280?kDa heterohexameric ANME-1 MCR complex. It was crystallized uniquely from a protein ensemble purified from consortia of microorganisms collected with a submersible from a Black Sea mat catalysing AOM with sulphate. Crystals grown from the heterogeneous sample diffract to 2.1?? resolution and consist of a single ANME-1 MCR population, demonstrating the strong selective power of crystallization. The structure revealed ANME-1 MCR in complex with coenzyme M and coenzyme B, indicating the same substrates for MCR from methanotrophic and methanogenic archaea. Differences between the highly similar structures of ANME-1 MCR and methanogenic MCR include a F(430) modification, a cysteine-rich patch and an altered post-translational amino acid modification pattern, which may tune the enzymes for their functions in different biological contexts.     

A conspicuous nickel protein in microbial mats that oxidize methane anaerobically

Anaerobic oxidation of methane (AOM) in marine sediments is an important microbial process in the global carbon cycle and in control of greenhouse gas emission. The responsible organisms supposedly reverse the reactions of methanogenesis, but cultures providing biochemical proof of this have not been isolated. Here we searched for AOM-associated cell components in microbial mats from anoxic methane seeps in the Black Sea. These mats catalyse AOM rather than carry out methanogenesis. We extracted a prominent nickel compound displaying the same absorption spectrum as the nickel cofactor F430 of methyl-coenzyme M reductase, the terminal enzyme of methanogenesis; however, the nickel compound exhibited a higher molecular mass than F430. The apparent variant of F(430) was part of an abundant protein that was purified from the mat and that consists of three different subunits. Determined amino-terminal amino acid sequences matched a gene locus cloned from the mat. Sequence analyses revealed similarities to methyl-coenzyme M reductase from methanogenic archaea. The abundance of the nickel protein (7% of extracted proteins) in the mat suggests an important role in AOM.     

硅谷：美国高科技发展的标志

美国硅谷的发展在整个世界引起了广泛的兴趣和关注 ,硅谷已成为美国高科技发展的标志 ,任何其他国家和地区的高科技的发展都不能和硅谷相比。经济论坛硅谷位于海湾和山谷之间 ,东西宽１６公里 ,南北跨度５０公里 ,并且正在不断延长。硅谷有４０００家公司 ,他们都很小。８０年代后期 ,ＩＢＭ公司总裁访问了我大学 ,他告诉我硅谷３０００多家公司中只有少于１００家的年收入超过１亿美元。硅谷是从事信息技术的、小的、成长型公司的产地。直到硅半导体芯片运用于微电子工业 ,硅谷才成为美国乃至世界的高科技工业的中心。现在 ,许多大公司将生…