A slab gel electrophoresis technique for measurement of plasma retinol-binding protein, cellular retinol-binding and retinoic-acid-binding proteins in human skin

At least four different proteins that bind retinoids could be present in a vitamin A target tissue like the skin. In order to separate cellular retinoid-binding proteins (CRBP and CRABP) from serum retinol-binding protein (RBP) and albumin, a one-step procedure was devised. The technique is based on slab polyacrylamide gel electrophoresis (PAGE) of the extracted proteins incubated with tritiated retinoids. The procedure was used to study binding proteins in the skin. The results show that epidermal extracts (the epithelial part of the skin) contain no RBP activities whereas dermal extracts (the mesenchymal part of the skin) contain 1.6 +/- 0.81 pmol/mg protein of RBP. This technique further showed higher levels of CRABP in both epidermal (9.05 +/- 1.16 pmol/mg protein) and dermal (1.5 +/- 0.54 pmol/mg protein) extracts than those previously determined by other less specific techniques. On the other hand CRBP levels were found to be lower in the two tissues (epidermis 0.2 +/- 0.1 pmol/mg and dermis 0.12 +/- 0.05 pmol/mg protein). New conditions to measure specifically CRABP with the charcoal/dextran technique could be developed and analyzed by the PAGE technique; a dissociation constant of 13.7 nM was then calculated for epidermal CRABP. This PAGE technique appears to be the most appropriate method for the study of retinoid-binding proteins including RBP in human skin.     

Effect of linolenate on photosynthesis by intact spinach chloroplasts II. Influence of preillumination of leaves on the inhibition of photosynthesis by linolenate

The inhibitory effect of linolenate on intact spinach chloroplastsdepends on the level of the internal pool of metabolites. Chloroplastsfrom preilluminated leaves or chloroplasts artificially loadedwith 3-phosphoglyceric acid required higher concentrations oforthophosphate for maximal rates of CO₂ dependent O₂ evolutionthan untreated chloroplasts. The loaded chloroplasts were moresensitive to linolenate, and in the presence of linolenate theoptimal phosphate concentration was shifted toward lower values.We propose that the inhibition of photosynthesis by linolenateis due to inhibition of the "phosphate translocator". ¹ Part of this work has been published in the Book of Abstracts,4th International Congress on Photosynthesis, Reading, U.K.,1977, p. 265–266. ² This work is part of a doctoral programme carried out by L.Mv6 Akamba in this laboratory. ³ To whom reprint requests should be adressed. (Received October 14, 1978; )     

Relationship between the ATP content measured at three imbibition times and germination of onion seeds during storage at 3, 15 and 30C

The possibility of using ATP content as an indicator of seedquality was studied in onion seeds {Allium cepa cv. Wdenswil).The percentage germination and ATP content of imbibed seedswere compared during 145 weeks of storage at three temperatures(3, 15 and 30C). ATP content, which was undetectable in airdriedseeds (moisture content: 9%, w/w), increased rapidly as a functionof imbibition time, as did the fresh weight and respirationrate, reaching a steady-state level after about 17 h. After36 weeks of storage, the rate of ATP formation was greater forthe seeds stored at 3C than for those kept at 15 and 30C.Furthermore, the onset of ATP synthesis was delayed. These phenomena,which are likely to be an expression of seed ageing, are usefulindicators, allowing the prediction of the loss of seed viabilitybefore the decrease in percentage germination which occurredbeyond 36 weeks of storage. In addition, the correlation betweenATP content and germination capacity of seeds during 145 weeksof storage was excellent (r=0.95 at 15C and 0.97 at 30C),provided that a 17 h-imbibition time, specific for onion seeds,was chosen. These results are discussed in terms of the controversyconcerning the correlation between the ATP content and germinationpercentage of seeds. Key words: Allium cepa, ageing, bioenergetic metabolism, seed quality, temperature storage     

Phosphate Uptake in an Obligately Marine Fungus II. Role of Culture Conditions, Energy Sources, and Inhibitors

Phosphate uptake in the obligately marine fungus, Thraustochytrium roseum, is maximal at pH 7.5 to 7.8, is dependent on temperature, and varies with phosphate concentration. Pyruvate and succinate stimulate phosphate uptake, although they do not increase respiration. The uncoupling agents, 2,4-dinitrophenol and dicoumerol, inhibit phosphate uptake but stimulate oxygen consumption only in the presence of NaCl. Oligomycin inhibits both processes. Among the inhibitors of protein synthesis, chloramphenicol reduces phosphate uptake without affecting respiration. Puromycin is unique in that it greatly enhances phosphate uptake and abolished the lag period associated with this phenomenon. It does not affect respiration.     

Aversive responses of captive sandbar sharks Carcharhinus plumbeus to strong magnetic fields

This experimental study focused on the possible deterrent effect of permanent magnets on adult sandbar sharks Carcharhinus plumbeus. Results showed that the presence of a magnetic field significantly reduced the number of approaches of conditioned C. plumbeus towards a target indicating that adult C. plumbeus can be deterred by strong magnetic fields. These data, therefore, confirm that the use of magnetic devices to reduce shark by‐catch is a promising avenue.     

Carbon balance of a European mountain bog at contrasting stages of regeneration

Carbon dioxide and methane (CH4) fluxes were measured in a cutover bog of the Jura Mountains (France) together with biotic and abiotic variables for two entire vegetation periods in order to compare the carbon balance of the bog at three stages of regeneration. Among all factors, air temperature and vegetation index (including leaf area of vascular plants, bryophyte density and bryophyte desiccation) were the two main determinants of ecosystem respiration and gross photosynthesis at light saturation. During 2004 and 2005, the vegetated plots acted as carbon sinks. Net carbon exchange ranged between 67 and 166 g C m(-2) yr(-1) for the Eriophorum-dominated plots and between 93 and 183 g C m(-2) yr(-1) for the Sphagnum-dominated plots. The bare peat plots represented a net carbon source (between -19 and -32 g C m(-2) yr(-1)). Methane fluxes accounted for a very small part of the total carbon efflux (< 2%). The recovery of vegetation in our naturally regenerating bog was beneficial for the carbon sequestration after the relatively short period of 20 yr.     

Seasonal Net Ecosystem Carbon Exchange of a Regenerating Cutaway Bog: How Long Does it Take to Restore the C‐Sequestration Function?

We measured the net ecosystem exchange (NEE) and respiration rates and modeled the photosynthesis and respiration dynamics in a cutover bog in the Swiss Jura Mountains during one growing season at three stages of regeneration (29, 42, and 51 years after peat cutting; coded sites A, B, and C) to determine if reestablishment of Sphagnum suffices to restore the C‐sequestration function. From the younger to the older stage Sphagnum cover increased, while net primary Sphagnum production over the growing season decreased (139, 82, and, 67 g m^?2 y^?1 for A, B, and C respectively), and fen plant species were replaced by bog species. According to our NEE estimations, over the vegetation period site A was a net CO₂‐C source emitting 40 g CO₂‐C/m² while sites B and C were accumulating CO₂‐C, on average 222 and 209 g CO₂‐C/m², respectively. These differences are due to the higher respiration in site A during the summer, suggesting that early regeneration stages may be more sensitive to a warmer climate. Methane fluxes increased from site A to C in parallel with Eriophorum vaginatum cover and vascular plant leaf area. Our results show that reestablishing a Sphagnum cover is not sufficient to restore a CO₂‐sequestrating function but that after circa 50 years the ecosystem may naturally regain this function over the growing season.     

Derivation of high purity neuronal progenitors from human embryonic stem cells

The availability of human neuronal progenitors (hNPs) in high purity would greatly facilitate neuronal drug discovery and developmental studies, as well as cell replacement strategies for neurodegenerative diseases and conditions, such as spinal cord injury, stroke, Parkinson's disease, Alzheimer's disease, and Huntington's disease. Here we describe for the first time a method for producing hNPs in large quantity and high purity from human embryonic stem cells (hESCs) in feeder-free conditions, without the use of exogenous noggin, sonic hedgehog or analogs, rendering the process clinically compliant. The resulting population displays characteristic neuronal-specific markers. When allowed to spontaneously differentiate into neuronal subtypes in vitro, cholinergic, serotonergic, dopaminergic and/or noradrenergic, and medium spiny striatal neurons were observed. When transplanted into the injured spinal cord the hNPs survived, integrated into host tissue, and matured into a variety of neuronal subtypes. Our method of deriving neuronal progenitors from hESCs renders the process amenable to therapeutic and commercial use.