Oxygen consumption in rat skeletal muscle at various rates of oxygen delivery

Summary Resting oxygen consumption of the vascularly isolated gracilis anticus muscle of the rat perfused by natural circulation via the femoral artery with diluted or undiluted blood depends on oxygen delivery (the product of flow rate and arterial oxygen concentration-DO₂) only when DO₂ falls below 16 l/min/g.     

The effect of D-6-methyl-8-[β-isopropylaminoethyl] ergoline-I on the lactation in nursing rats

D-6-Methyl-8-[-isopropylaminoethyl] ergoline-I [VÚFB-10726], beginning from the dose of 0.05 mg/kg p.o., suppresses lactation through the inhibition of prolactin secretion in nursing rats.     

Aerobic bacterial pyrite oxidation and acid rock drainage during the Great Oxidation Event

The enrichment of redox-sensitive trace metals in ancient marine sedimentary rocks has been used to determine the timing of the oxidation of the Earth's land surface. Chromium (Cr) is among the emerging proxies for tracking the effects of atmospheric oxygenation on continental weathering; this is because its supply to the oceans is dominated by terrestrial processes that can be recorded in the Cr isotope composition of Precambrian iron formations. However, the factors controlling past and present seawater Cr isotope composition are poorly understood. Here we provide an independent and complementary record of marine Cr supply, in the form of Cr concentrations and authigenic enrichment in iron-rich sedimentary rocks. Our data suggest that Cr was largely immobile on land until around 2.48?Gyr ago, but within the 160?Myr that followed--and synchronous with independent evidence for oxygenation associated with the Great Oxidation Event (see, for example, refs 4-6)--marked excursions in Cr content and Cr/Ti ratios indicate that Cr was solubilized at a scale unrivalled in history. As Cr isotope fractionations at that time were muted, Cr must have been mobilized predominantly in reduced, Cr(III), form. We demonstrate that only the oxidation of an abundant and previously stable crustal pyrite reservoir by aerobic-respiring, chemolithoautotrophic bacteria could have generated the degree of acidity required to solubilize Cr(III) from ultramafic source rocks and residual soils. This profound shift in weathering regimes beginning at 2.48?Gyr ago constitutes the earliest known geochemical evidence for acidophilic aerobes and the resulting acid rock drainage, and accounts for independent evidence of an increased supply of dissolved sulphate and sulphide-hosted trace elements to the oceans around that time. Our model adds to amassing evidence that the Archaean-Palaeoproterozoic boundary was marked by a substantial shift in terrestrial geochemistry and biology.     

Studies on proteolytic digestion of myosin from red and white skeletal muscles of the rabbit

Zusammenfassung Der Vergleich der tryptischen und chymotryptischen Myosinspaltungen aus weissem und rotem Kaninchenmuskel ergibt: Nichteiweißstickstoffbildung zeigt durch Trypsin eine schnellere Myosinspaltung im weissen Muskel; Chymotrypsin spaltet beide Myosine mit gleicher Geschwindigkeit.     

An age-colour relationship for main-belt S-complex asteroids

Asteroid collisions in the main belt eject fragments that may eventually land on Earth as meteorites. It has therefore been a long-standing puzzle in planetary science that laboratory spectra of the most populous class of meteorite (ordinary chondrites, OC) do not match the remotely observed surface spectra of their presumed (S-complex) asteroidal parent bodies. One of the proposed solutions to this perplexing observation is that 'space weathering' modifies the exposed planetary surfaces over time through a variety of processes (such as solar and cosmic ray bombardment, micro-meteorite bombardment, and so on). Space weathering has been observed on lunar samples, in Earth-based laboratory experiments, and there is good evidence from spacecraft data that the process is active on asteroid surfaces. Here, we present a measurement of the rate of space weathering on S-complex main-belt asteroids using a relationship between the ages of asteroid families and their colours. Extrapolating this age-colour relationship to very young ages yields a good match to the colour of freshly cut OC meteorite samples, lending strong support to a genetic relationship between them and the S-complex asteroids.     

Structure of a ligand-binding intermediate in wild-type carbonmonoxy myoglobin

Small molecules such as NO, O2, CO or H2 are important biological ligands that bind to metalloproteins to function crucially in processes such as signal transduction, respiration and catalysis. A key issue for understanding the regulation of reaction mechanisms in these systems is whether ligands gain access to the binding sites through specific channels and docking sites, or by random diffusion through the protein matrix. A model system for studying this issue is myoglobin, a simple haem protein. Myoglobin has been studied extensively by spectroscopy, crystallography, computation and theory. It serves as an aid to oxygen diffusion but also binds carbon monoxide, a byproduct of endogenous haem catabolism. Molecular dynamics simulations, random mutagenesis and flash photolysis studies indicate that ligand migration occurs through a limited number of pathways involving docking sites. Here we report the 1.4 A resolution crystal structure of a ligand-binding intermediate in carbonmonoxy myoglobin that may have far-reaching implications for understanding the dynamics of ligand binding and catalysis.     

The evaluation of biologically active supernatants of cultures of lymphoid cells from rabbits with delayed (cellular) hypersensitivity on a macrophage layer

Zusammenfassung Supernatanten aus Kulturen überempfindlicher Lymphozyten und dem spezifischen Antigen mit MIF-Aktivität können die Entstehung der Pseudopodien normaler Makrophagen verhindern und zeigen nach längerem Kultivieren zuweilen toxische Eigenschaften.