Purification of the Chlorella HUP1 hexose—proton symporter to homogeneity and its reconstitution in vitro

A prokaryotic biotin acceptor domain was fused to the carboxy terminal end of the Chlorella hexose—proton sym- porter. The plant symporter is biotinylated in vivo when expressed in Schizosaccharomyces pombe. The extended biotinylated transport protein is fully active, catalyzes accumulation of d -glucose analogs and restores growth of a glucose-uptake-deficient yeast strain. Crude membranes were solubilized with octyl-β-d -glucoside in the presence of Escherichia colil -α-phosphatidylethanolamine. Biotinylated symporter was purified to homogeneity by biotinavidin affinity chromatography. The symporter protein was reconstituted together with cytochrome-c oxidase prepared from beef heart mitochondria into proteo-liposomes. Cytochrome-c oxidase is a redox-driven H⁺-pump generating a proton motive force (inside negative and alkaline) while transferring electrons from cytochrome-c to oxygen; this energy is used by the symporter to accumulate d -glucose at least 30-fold. In the absence of the driving force the transport protein facilitates diffusion of d -glucose until the concentration equilibrium is reached. It was shown that maximal transport activity depends highly on the amount of co-reconstituted cytochrome-c oxidase and that the symporter possesses 10% of its in vivo turnover number under optimized in vitro transport conditions.     

A personal computer-based system for online monitoring of neurologic intensive care patients]

In the management of neurological intensive care patients with an intracranial space-consuming process the measurement and recording of intracranial pressure together with arterial blood pressure is of special interest. These parameters can be used to monitor the treatment of brain edema and hypertension. Intracranial pressure measurement is also important in the diagnosis of the various subtypes of hydrocephalus. Not only the absolute figures, but also the recognition of specific pressure-patterns is of particular clinical and scientific interest. This new, easily installed and inexpensive system comprises a PC and a conventional monitor, which are connected by an AD-conversion card. Our software, specially developed for this system demonstrates, stores and prints the online-course and the trend of the measurements. In addition it is also possible to view the online-course of conspicuous parts of the trend curve retrospectively and to use these values for statistical analyses. Object-orientated software development techniques were used for flexible graphic output on the screen, printer or to a file. Though developed for this specific purpose, this system is also suitable for recording continuous, longer-term measurements in general.     

Intensive RNAi with lentiviral vectors in mammalian cells

RNAi is a powerful technology for analyzing gene function in human cells. However, its utility can be compromised by inadequate knockdown of the target mRNA or by interpretation of effects without rigorous controls. We review lentiviral vector-based methods that enable transient or stable knockdowns to trace mRNA levels in human CD4+ T cell lines and other targets. Critical controls are reviewed, including rescue of the pre-knockdown phenotype by re-expression of the targeted gene. The time from thinking about a potential knockdown target to analysis of phenotypes can be as short as a few weeks.     

Derivatives of the insect moulting hormone for affinity chromatography, and their biological activities.

Several derivatives of the arthropod moulting hormone have been synthesized which were coupled to AH Sepharose 4B yielding about 2 mumole ligand per g wet gel. As an indication of the suitability of the ligands for biological work the puff inducing capacity of their methyl esters was tested. The methyl ester of inokosterone-C-26-carboxylic acid possesses the highest biological activity; lower activities were obtained with the esters of ecdysterone-C-6-CM-oxime and ecdysterone hemisuccinates. Therefore, inokosterone-C-26-carbocylic acid should be a useful ligand for affinity chromatography of ecdysone recptors from insect tissues.     

The first study of human growth: Christian Friedrich Jampert

The circumstances surrounding the first study of human growth, published in 1754, are described. Jampert, who made this study, died young and his work was not recognised, indeed remained completely unknown between 1778 and 1981. The content of the work is briefly described.     

The determination of the membrane ptoential of Chlorella vulgaris. Evidence for electrogenic sugar transport.

From data on the accumulation of tetraphenylphosphonium within Chlorella vulgaris cells, it can be estimated that these cells possess a membrane potential of --120 to --150 mV (inside negative). Under anaerobic conditions as well as in the presence of uncoupling agents the membrane potential drops to about -60 to -80 mV. Nystatin (50 mug/ml) abolishes it almost completely. Since it took more than 1 h before the tetraphenylphosphonium equilibrium was reached, this method could not be used to measure relatively fast transient changes in membrane potential. However, the rate of influx of tetraphenylphosphonium is also directly dependent on membrane potential and can be followed within minutes. Using this phenomenon as an indicator for membrane potential a brief transient depolarisation was detected after the addition of sugars taken up by Chlorella via the proton cotransport system. The depolarisation was absent from cells not induced for sugar uptake and induced cells did not show it with substances not transported, like mannitol. The maximal depolarisation observed amounted to about 70 mV; after 1 min, however, the membrane potential returned to a value about 25 mV less negative than the one before sugars was added. The results demonstrate that sugar uptake in Chlorella is electrogenic. The delta pH plus membrane potential measured for Chlorella completely cover the energy required to explain the 1600-fold accumulation of 6-deoxyglucose experimentally observed.