Immunohistochemical characterization of delta crystallin-containing retina/optic nerve "boundary" cells in the chick embryo

The term "transdifferentiation" has been used to describe the apparent phenotypic conversion of chick embryo neural retina Müller glial cells into lens-like cells in vitro. This phenotypic conversion is characterized by expression of such lens-specific proteins as delta crystallin and has been viewed as an example of cells transforming from the phenotype of a given tissue to that of another. We have identified a population of neuroglia-like cells in the embryonic chick retina which express high levels of delta crystallin as a function of normal development. The position and morphology of these cells is quite distinctive in that they form a loose meshwork which defines the boundary between the neural retina and the optic nerve head. These "boundary" cells are detectable as early as Day 5 of development through hatching. However, the meshwork structure formed by the cells is only readily observed between Days 8 and 9 of development. Double-immunolabeling procedures comparing delta crystallin staining to that of glial and neuronal markers suggest that these cells are a form of retinal Müller glial cell. The results show that under appropriate microenvironmental conditions, expression of delta crystallin falls into the normal repertoire of retinoblast cells. The results also demonstrate the presence of a cellular boundary defining the junction between the neural retina and the optic nerve, tissues that are ontogenetically and structurally continuous but functionally distinct.     

Neutrophil migration into the bovine uterine lumen following intrauterine inoculation with killed Haemophilus somnus.

Polymorphonuclear neutrophils (PMN) in bovine uterine flushings following intrauterine deposition of killed bacteria were measured and the effect of immune status on the influx of PMN into the uterine lumen during oestrus was determined. Holstein heifers were immunized with a 270-kDa outer-membrane protein (omp-270) from Haemophilus somnus. During oestrus, immunized heifers (n = 21) received an intrauterine inoculum of either a heat-killed suspension of a homologous strain of H. somnus containing omp-270 (n = 7), a heterologous strain of H. somnus lacking omp-270 (n = 7), or phosphate-buffered saline (n = 7). Five additional heifers were inseminated with extended bovine semen. Uterine contents were collected in saline lavage immediately before inoculation (t0) and at 6, 24, 48, 72, 96, and 120 h after inoculation. The semen-inoculated heifers were lavaged only at t120. All groups experienced PMN infiltration which peaked 6 h after inoculation and tended to decline thereafter. Differences were not observed between treatment groups, indicating that neither bacterial inoculation nor immune status was as important in eliciting PMN effusion as the flushing procedure itself.     

Mechanism of adhesion of Alysiella bovis to glass surfaces

Alysiella bovis adheres to surfaces by means of short, ruthenium red-staining, rod-like fimbriae. The fimbriae remain associated with the cell envelope of A. bovis, even when sonicated or exposed sequentially to toluene, Triton X-100, lysozyme, ribonuclease, and deoxyribonuclease. Adhesion of outer membrane-derived cell wall ghosts of A. bovis to glass was inhibited by IO4-, sodium dodecyl sulfate, urea, pronase, and trypsin. Protease treatment digested the fimbriae from the distal end, and exposure to sodium dodecyl sulfate depolymerized the fimbriae. Exposure of ghosts to 1% sodium dodecyl sulfate preferentially solubilized a 16,500-dalton protein which was subsequently purified by gel filtration and demonstrated to be a glycoprotein (ca. 17% carbohydrate). Antibodies raised against the 16,500-dalton glycoprotein agglutinated whole cells and inhibited adhesion of ghosts to glass.     

Aberrant nuclear morphology in the mouse myeloma SP2/0 cell line

The mouse myeloma SP2/0 cell line when grown in supplemented Dulbecco's modified Eagle's media spontaneously produced aberrant nucleated cells which increased in frequency with cell culture age. These cells underwent cytological changes associated with apoptosis, that is, the condensation of chromatin followed by karyorrhexis and the production of small apoptotic bodies. Aberrant cells were induced by media changes, centrifugation, and temperature shocking. The rapid induction of aberrant cells by a media change suggests that the mechanism of fragmentation was not associated with cell division.     

Studies on the Analysis of Fluorescence Decay Data by the Method of Moments

The method of moments, as presented by Isenberg and Dyson (1969; Biophys. J. 9:1337) has been shown to be a reliable way of obtaining the amplitudes and time constants of several simultaneously emitting species, even in the presence of an overlapping excitation. Recent improvements in the method include (a) a component incrementation test for determining the number of relaxations, (b) a procedure, which we call exponential depression, for dramatically improving convergence, and (c) a new algorithm for implementing the method of moments on a digital computer with a high degree of flexibility and efficiency. These improvements, as well as new general theory, are described and tested using both synthetic and real experimental data. Component incrementation consists of examining models with increasing numbers of exponential terms. Given adequate precision, we find that an analysis for N + 1 components, of data that are actually represented by N components, provides the correct amplitudes and time constants plus an N + 1 term with an insignificant amplitude. Exponential depression is a transformation in which the original excitation and fluorescence, E(t) and F(t), are multiplied by exp (-λt), where λ is an arbitrary parameter. While the convolution is invariant to this transformation, the proper choice of λ greatly reduces the number of iterations necessary to obtain the amplitudes and time constants and may even improve their accuracy. In addition, an appendix by John P. Mullooly presents a statistical analysis of the effect of counting error on the method of moments estimates of fluorescence decay parameters, applicable when data are obtained by the monophoton technique. Formulas are derived that give the approximate precision of the decay parameters for the general case of N exponential components, with calculational details for one and two component systems.     

Map location of arginyl-tRNA synthetase mutations in Escherichia coli K-12

Summary Mutants of Escherichia coli K-12 previously isolated in the authors' laboratory have reduced arginyl-tRNA synthetase activity. The mutants fall into two classes. All mutants grow slowly on arginine-free medium. On arginine-supplemented medium some mutants grow at a normal rate (Class I) while others still grow slowly (Class II). Matings were performed to located a Class I and a Class II mutation on the E. coli chromosome map, and on the basis of our results we have assigned both to one locus, argS.