Characterization of the receptor for platelet-derived growth factor on human fibroblasts. Demonstration of an intimate relationship with a 185,000-Dalton substrate for the platelet-derived growth factor-stimulated kinase

The receptor for platelet-derived growth factor (PDGF) on human foreskin fibroblasts has been characterized. The molecular weight of the PDGF-receptor complex was estimated by affinity labeling techniques to about 200,000, as determined by sodium dodecyl sulfate-gel electrophoresis performed under reducing conditions. Subtraction of the Mr of reduced PDGF (18,000 to 15,000) gives a Mr for the receptor proper of 185,000 (+/- 10,000). The mobility in sodium dodecyl sulfate-gel electrophoresis was similar whether or not reducing agents were present, suggesting that the receptor may be a single chain protein. The hydrodynamic size of the 125I-PDGF-receptor complex after solubilization with Triton X-100, corresponded to a Mr of approximately 320,000, as determined by gel chromatography. Subtraction of the Mr contributions from Triton X-100 and PDGF, respectively, gives a Mr of approximately 200,000 for the receptor itself, an estimate in good agreement with the value obtained from the affinity-labeling experiments. Several lectins were analyzed for their ability to inhibit binding of 125I-PDGF to its receptor. It was found that wheat germ agglutinin and a lectin from Crotalaria juncea were effective inhibitors and that their inhibitory effects could be neutralized by N-acetylglucosamine and galactose, respectively, suggesting that the receptor contains these sugars. The properties of the receptor were compared with those of a 185,000-Da component, being the major substrate for the membrane-bound PDGF-stimulated kinase. It was found that the 185,000-Da component behaved similar to the PDGF receptor in sodium dodecyl sulfate-gel electrophoresis, performed with or without reducing agents present. Further, the 185,000-Da component co-eluted with the PDGF receptor on a Sepharose 6B column, and had affinity for the same lectins that inhibited the binding of 125I-PDGF to its receptor. Finally, the 185,000-Da component had affinity for PDGF immobilized on Sepharose beads, suggesting that it has PDGF-binding activity. We conclude that the PDGF receptor and the 185,000-Da substrate for the PDGF-dependent kinase are intimately related and probably identical molecules.     

Specific localization of scallop gill epithelial calmodulin in cilia

Calmodulin has been isolated and characterized from the gill of the bay scallop aequipecten irradians. Quantitative electrophoretic analysis of epithelial cell fractions show most of the calmodulin to be localized in the cilia, specifically in the detergent- solubilized membrane-matrix fraction. Calmodulin represents 2.2 +/- 0.3 percent of the membrane-matrix protein or 0.41 +/- 0.5 percent of the total ciliary protein. Its concentration is at least 10(-4) M if distributed uniformly within the matrix. Extraction in the presence of calcium suggests that the calmodulin is not bound to the axoneme proper. The ciliary protein is identified as a calmodulin on the basis of its calcium- dependent binding to a fluphenazine-sepharose affinity column and its comigration with bovine brain calmodulin on alkaline-urea and SDS polyacrylamide gels in both the presence and absence of calcium. Scallop ciliary calmodulin activates bovine brain phosphodiesterase to the same extent as bovine brain and chicken gizzard calmodulins. Containing trimethyllysine and lacking cysteine and tryptophan, the amino acid composition of gill calmodulin is typical of known calmodulins, except that it is relatively high in serine and low in methionine. Its composition is less acidic than other calmodulins, in agreement with an observed isoelectric point approximately 0.2 units higher than that of bovine brain. Comparative tryptic peptide mapping of scallop gill ciliary and bovine brain calmodulins indicates coincidence of over 75 percent of the major peptides, but at least two major peptides in each show no near-equivalency. Preliminary results using ATP-reactivated gill cell models show no effect of calcium at micromolar levels on ciliary beat or directionality of the lateral cilia, the cilia which constitute the vast majority of those isolated. However, ciliary arrest will occur at calcium levels more than 150 muM. Because calmodulin usually functions in the micromolar range, its role in this system is unclear. Scallop gill ciliary calmodulin may be involved in the direct regulation of dyneintubule sliding, or it may serve some coupled calcium transport function. At the concentration in which it is found, it must also at least act as a calcium buffer.     

Utilization of the white-rot fungus Sporotrichum pulverulentum for water purification and protein production on mixed lignocellulosic wastewaters

A process has been developed that allows a direct conversion of lignocellulosic materials into fungal biomass. The thermotolerant white-rot fungus Sporotichum pulverulentium has been used in continuous laboratory fermentations as well as in a 25 m³ batch fermentation. Fungal cell mass for feeding trials was produced and the economics of the process were estimated. The investigation shows that the process works satisfactorily on the small continuous scale as well as in the large batch culture. The process also seems easy to scale up. The economic evaluations show the conversion of solid lignocellulosic materials to protein feed is not feasible by our process unless the material to be fermented has a certain negative value. A mixed wastewater, such as the white water system in paper and fiber board mills, containing both water soluble mono- and oligosaccharides and solid lignocellulosic material, can, however, be fermented in an economically feasible way due to the combined effect of protein production and water purification. Data on the nutritional value of the product are presented in an accompanying paper.     

Effect of felodipine on renal hemodynamics and excretion in the dog

The effects of felodipine on renal hemodynamics and excretion were evaluated in the anesthetized dog. Unilateral renal arterial infusion of felodipine produced ipsilateral increases in the absolute and fractional excretion of sodium and water which were greater than those of potassium; these effects occurred in the absence of changes in mean arterial pressure, renal blood flow, or glomerular filtration rate. There were no significant effects on renal hemodynamic or excretory function in the contralateral kidney. The unilateral renal arterial infusion of isotonic saline or vehicle produced no significant effects on renal hemodynamic or excretory function in either ipsilateral or contralateral kidney. Felodipine, a calcium antagonist with vasodilator antihypertensive properties, in doses which do not affect systemic or renal hemodynamics in the dog, increased urinary flow rate and sodium excretion by decreasing renal tubular water and sodium reabsorption. As a vasodilator antihypertensive agent, felodipine possesses potentially advantageous diuretic and natriuretic properties.     

Substrate profiling of deubiquitin hydrolases with a positional scanning library and mass spectrometry

Deconjugation of ubiquitin from cellular proteins is catalyzed by the deubiquitin hydrolase (DUB) family of enzymes and is an important component of the ubiquitin regulatory system affecting cellular function beyond simple maintenance of monomeric pools of ubiquitin. Specific deconjugation of ubiquitinated substrates has been described, but substrate recognition is poorly understood. To determine whether specificity may be conferred by recognition of a primary cognate sequence, the substrate preferences of two DUBs, UCH-L3 and isopeptidase T (IsoT), were profiled using a positional scanning branched peptide library. The sequence of the library was based on K48-branched diubiquitin, RLXXXXK(GGRLRLVL)QLEDGR, where X denotes a diversified position in the library (P1' '-P4' ' numbered from K48). Hydrolysis of the branched peptide was indicative of DUB activity and was detected and quantified by mass spectrometry. IsoT was active toward the library but demonstrated little preference for the diversified positions. In contrast, UCH-L3 exhibited minor amino acid preferences at P2' ' and P4' ' and a 10-fold preference for the basic residues Arg and Lys at P3' '. Kinetic analysis of substrates with optimized and suboptimized sequences (as defined by the library profile) confirmed the preference at P3' '. Substrate inhibition of UCH-L3 but not IsoT was noted for the optimized sequence at concentrations greater than 5 microM and with an IC(50) of 12.2 microM; the inhibition was determined to be competition with Ub-AMC (ubiquitin C-terminal 7-amido-4-methylcoumarin).     

902 MHz mobile phone does not affect short term memory in humans

We studied the effects of an electromagnetic field (EMF) as emitted by a 902 MHz mobile phone on human short term memory. This study was a replication with methodological improvements to our previous study. The improvements included multi-centre testing and a double blind design. A total of 64 subjects (32 men) in two independent laboratories performed a short term memory task (n-back) which poses a varying memory load (0-3 items) on the subjects' memory. They performed the task twice, once each under EMF and sham exposure. Reaction times (RTs) and accuracy of the responses were recorded. The order of exposure and memory load conditions were counterbalanced across subjects and gender. There were no statistically significant differences in performance between the two laboratories. We could not replicate our previous results: the EMF had no effect on RTs or on the accuracy of the subjects' answers. The inability to replicate previous findings could have been caused by lack of actual EMF effects or the magnitude of effects being at the sensitivity threshold of the test used.     

Multi-Band Plasmonic Platform Utilizing UT-Shaped Graphene Antenna Arrays

Plasmonics - In this work, we introduce a plasmonic platform based on UT-shaped graphene antenna arrays. The proposed multi-resonant platform shows three different resonances, which can be...     

Carbon and nitrogen flow in silver birch and Norway spruce connected by a common mycorrhizal mycelium

 Spruce and birch seedlings were grown together in boxes filled with unsterile peat. Both seedlings were colonized by the ectomycorrhizal fungus Scleroderma citrinum. The two plants thus shared a common external mycelium. ¹⁵N-labelled ammonium was supplied exclusively to the fungus, while the birch or the spruce plant was continuously fed with ¹³C-labelled CO₂ for 72 h. The carbon and nitrogen transfer rates were strikingly different for birch and spruce seedlings. The mycorrhizal mycelium received carbohydrates mainly from the birch plant and the nitrogen transfer by the fungus to the plants was largely directed towards the birch. Carbon assimilates were also transferred in both directions between birch and spruce; however, there was no conclusive evidence for a net transfer of carbon between the plants. Accepted: 20 September 1996