Crystallization of human plasma apo-retinol-binding protein

Crystals of three forms of human plasma apo-retinol-binding protein have been obtained using the procedure described for the holoprotein. The apoprotein was prepared by a novel method, which uses hydrophobic interaction and immobilized dye chromatography. The three forms were separated by fast protein liquid chromatography. All of the crystals are isomorphous and diffract to 2.5 Å resolution. These crystals will be useful for studies of the mechanism of binding of retinol to its carrier using X-ray diffraction techniques.     

A computer program for enzyme kinetics that combines model discrimination, parameter refinement and sequential experimental design.

A method of model discrimination and parameter estimation in enzyme kinetics is proposed. The experimental design and analysis of the model are carried out simultaneously and the stopping rule for experimentation is deduced by the experimenter when the probabilities a posteriori indicate that one model is clearly superior to the rest. A FORTRAN77 program specifically developed for joint designs is given. The method is very powerful, as indicated by its usefulness in the discrimination between models. For example, it has been successfully applied to three cases of enzyme kinetics (a single-substrate Michaelian reaction with product inhibition, a single-substrate complex reaction and a two-substrate reaction). By using this method the most probable model and the estimates of the parameters can be obtained in one experimental session. The FORTRAN77 program is deposited as Supplementary Publication SUP 50134 (19 pages) at the British Library (Lending Division), Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1986) 233, 5.     

The Formation of Otoliths in the Frog Rana esculenta. Scanning Electron Microscopic and X-Ray Diffraction Studies

Two crystal forms of calcium carbonate were observed: calcite (utricle) and aragonite (saccule, lagena, endolymphatic sac). The first step in otolith formation is the appearance of organic structures in the macula. The subsequent step is characterized by fast growing primitive crystals with a prismatic habitus that successively transform into adult or mature crystals. With the metamorphosis, the aragonite crystals of the endolymphatic organ show clear signs of erosion that can be related to a process of CaCO₃ mobilization from such deposits.     

Crystallization and preliminary X-ray data of human plasma retinol-binding protein

Crystals of human plasma retinol-binding protein have been obtained from 4.5 m-NaCl buffered at pH 6.8 with 20 mm-cacodylate. The crystals are trigonal with space group R3 and unit cell dimensions, referred to the hexagonal system. $\text{a = b = 104.2}\text{A}\text{?}\text{and}\text{c = 74.5}\text{A}\text{?}$. The crystals diffract to a resolution of 2.0 Å.     

Tubular structures associated with the endothelial endoplasmic reticulum in glomerular capillaries of Rhesus monkey and nephritic man

Summary Round bodies, tubular profiles and crystalline images have been studied by electron microscopy in the endothelium of seven normal young Rhesus monkeys and in the renal glomerular endothelium of two nephritic human patients. The crystalline images are most frequently formed by aggregation of round bodies, 200–240 Å in diameter. In Rhesus monkeys a variety of crystalline images are seen. On the contrary, in nephritic patients round bodies and tubular profiles are rare and less organized. In the glomerular endothelium of two normal men they were not found.The results obtained suggest that the round bodies, the tubular profiles and the crystalline images result from sectioning of a system of undulating tubules associated with the smooth endoplasmic reticulum. In nephritic patients the formation of such a tubular system could represent a change taking place within the affected cells as a pathologic response to the disease.This work was supported by U.S. Public Health Service (N.H.I.), Grant AI-04527-03-04, and by the Consiglio Nazionale delle Ricerche (C.N.R.), Contributo 115/0815/0-1365. The Authors are greatly indebted to Miss Hermina Spiele for skilful technical assistance.     

Beiträge zur Frage der lichtmikroskopischen Sichtbarkeit des endoplasmatischen Retikulums in Pflanzenzellen

Zusammenfassung Die an Innenepidermiszellen der Zwiebelschuppe vonAllium cepa zu beobachtenden schlauchförmigen intraplasmatischen Vakuolen, in der vorliegenden Arbeit kurz als Schläuche bezeichnet, werden näher untersucht. Sie heben sich im Protoplasma im Phasenkontrast als nichtkontrastierte, massearme Zonen ab. Diese Gebilde werden als Elemente des endoplasmatischen Retikulums (ER) angesprochen. Vergleichende Literaturstudien bekräftigen diese Ansicht.An tierischen Zellen wurden mehrfach im positiven Phasenkontrast dunkle, längliche oder netzförmige Gebilde als Elemente des ER erkannt. Die bei Pflanzenzellen auftretenden, äußerlich sehr ähnlichen Gebilde sind dagegen Plasmaleisten. Sie entstehen zwischen vergrößerten vakuolenartigen Elementen des ER.In jedem Fall ist es notwendig, streng zwischen dem ER sensu strictu, welches aus den Membranen und der von diesen umschlossenen intrazisternalen Phase (IZP) besteht, und dem Grundplasma, der extrazisternalen Phase (EZP), in der die Organellen liegen, zu unterscheiden. Im Lichtmikroskop (Phasenkontrast) werden an erwachsenen Pflanzenzellen die Membranen des ER nicht aufgelöst. Wenn die Membranen aber auseinanderweichen und die IZP durch Wasseraufnahme ein größeres Volumen einnimmt, kann man den Kontrastunterschied zwischen IZP und EZP sehen.Wir danken den optischen Werken C. Reichert A. G., Wien, für die leihweise Überlassung einer phasenoptischen Ausrüstung und der Firma Werfft-Chemie, Wien, für das Tetracyclin-Präparat Achromycin- Lederle.