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.     

The antigen-binding capacity of mouse lymphocytes. II. Changes during the early immune response

The interaction of antigen with specific receptor sites of primed murine spleen lymphocytes has been estimated quantitatively. The antigen-specific receptors are restricted to a small segment of the entire spleen cell population, one which may be enriched by centrifugation of the cells in a discontinuous density gradient. The specificity of the receptors, their variable affinities for the specific ligand, their quantitative fluctuations following immunization, have been investigated. Attempts have also been initiated for their isolation. The possibility that these receptors may represent passively adherent cytophilic immunoglobulins was excluded. The results of these experiments suggest that the union of antigen with a portion of cell membrane receptors initiates a sequence of reaction steps involving DNA production and multiplication, leading to a small net synthesis of immunoglobulins. The continued presence of antigen during this period leads to complex formation with these immunoglobulins. The resulting immune complexes bind to both adherent and nonadherent cells, thereby amplifying the immune response.     

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.