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.     

Neurons are replenished in cultures of embryonic chick optic tectum after immunomagnetic depletion

The effect of intercellular interactions on the determination and differentiation of early embryonic brain cells was tested by immunomagnetic cell separation techniques. Using the A2B5 monoclonal antibody, which in chick brain reacts with a neuron-specific surface ganglioside, we produced initially pure populations of optic tectum cells devoid of the antigen. A coincident depletion of neurofilament(+) cells (95%) and nonneuronal growth characteristics of the separated A2B5(-) cells indicated that the vast majority of neurons had been removed initially. Surprisingly, A2B5(+) cells rapidly appeared in separated A2B5(-) cell cultures. After 1 day, the percentage of A2B5(+) cells in separated cell cultures equalled those in unseparated cultures (approximately 50%). By a week in culture, A2B5(+) cells developed neuronal morphology and contained neurofilaments. A2B5(-) to (+) conversion was a regulated phenomenon in that removal of different proportions of the (+) cells resulted in different numbers of (-) to (+) conversions. New DNA synthesis was not required for the acquisition of cell surface A2B5 antigen or for differentiation of cells into definitive A2B5(+) neurons. Our results demonstrate that postmitotic embryonic brain contains cells which are capable of replacing depleted neurons in vitro.     

Über die Wirkung von Indol-3-Essigsäure auf das Längenwachstum von Keimlingen verschiedenerBrassica-Arten

Zusammenfassung Keimlinge vonBrassica-Arten, welche überaus wuchsstoffreiche Extrakte liefern, verhalten sich gegenüber von außen her (durch Pasten) zugefügten verschiedenen Konzentrationen von Indol-3-essigsäure ganz analog wie Keimlinge wuchsstoffarmer, andersartiger Pflanzen. Während Indol-3-essigsäure bei intakten Keimlingen fast ausschließlich Hemmungen des Längenwachstums bewirkte, zeigen dekapitierte (an pflanzeneigenem Wuchsstoff weitgehend verarmte) Pflanzen ausschließlich Förderungen.Mit 2 Textabbildungen     

Airway cellularity, lipid laden macrophages and microbiology of gastric juice and airways in children with reflux oesophagitis

Background and methods

Human metapneumovirus (hMPV) is a recently discovered respiratory virus associated with bronchiolitis, pneumonia, croup and exacerbations of asthma. Since respiratory viruses are frequently detected in patients with acute exacerbations of COPD (AE-COPD) it was our aim to investigate the frequency of hMPV detection in a prospective cohort of hospitalized patients with AE-COPD compared to patients with stable COPD and to smokers without by means of quantitative real-time RT-PCR.

Results

We analysed nasal lavage and induced sputum of 130 patients with AE-COPD, 65 patients with stable COPD and 34 smokers without COPD. HMPV was detected in 3/130 (2.3%) AE-COPD patients with a mean of 6.5 × 10⁵ viral copies/ml in nasal lavage and 1.88 × 10⁵ viral copies/ml in induced sputum. It was not found in patients with stable COPD or smokers without COPD.

Conclusion

HMPV is only found in a very small number of patients with AE-COPD. However it should be considered as a further possible viral trigger of AE-COPD because asymptomatic carriage is unlikely.     

Structural rearrangement of model membranes by the peptide antibiotic NK-2

We have developed a novel α-helical peptide antibiotic termed NK-2. It efficiently kills bacteria, but not human cells, by membrane destruction. This selectivity could be attributed to the different membrane lipid compositions of the target cells. To understand the mechanisms of selectivity and membrane destruction, we investigated the influence of NK-2 on the supramolecular aggregate structure, the phase transition behavior, the acyl chain fluidity, and the surface charges of phospholipids representative for the bacterial and the human cell cytoplasmic membranes. The cationic NK-2 binds to anionic phosphatidylglycerol liposomes, causing a thinning of the membrane and an increase in the phase transition temperature. However, this interaction is not solely of electrostatic but also of hydrophobic nature, indicated by an overcompensation of the Zeta potential. Whereas NK-2 has no effect on phosphatidylcholine liposomes, it enhances the fluidity of phosphatidylethanolamine acyl chains and lowers the phase transition enthalpy of the gel to liquid cristalline transition. The most dramatic effect, however, was observed for the lamellar/inverted hexagonal transition of phosphatidylethanolamine which was reduced by more than 10 °C. Thus, NK-2 promotes a negative membrane curvature which can lead to the collapse of the phosphatidylethanolamine-rich bacterial cytoplasmic membrane.     

Backbone assignment of perdeuterated proteins using long-range H/C-dipolar transfers

For micro-crystalline proteins, solid-state nuclear magnetic resonance spectroscopy of perdeuterated samples can provide spectra of unprecedented quality. Apart from allowing to detect sparsely introduced protons and thereby increasing the effective resolution for a series of sophisticated techniques, deuteration can provide extraordinary coherence lifetimes—obtainable for all involved nuclei virtually without decoupling and enabling the use of scalar magnetization transfers. Unfortunately, for fibrillar or membrane-embedded proteins, significantly shorter transverse relaxation times have been encountered as compared to micro-crystalline proteins despite an identical sample preparation, calling for alternative strategies for resonance assignment. In this work we propose an approach towards sequential assignment of perdeuterated proteins based on long-range ¹H/¹³C Cross Polarization transfers. This strategy gives rise to H/N-separated correlations involving C^α, C^β, and CO chemical shifts of both, intra- and interresidual contacts, and thus connecting adjacent residues independent of transverse relaxation times.     

AgCad2 cadherin in Anopheles gambiae larvae is a putative receptor of Cry11Ba toxin of Bacillus thuringiensis subsp. jegathesan

In an effort to study the mode of action of Cry11Ba, we identified toxin binding proteins in Anopheles gambiae larval midgut and investigated their receptor roles. Previously, an aminopeptidase (AgAPN2) and an alkaline phosphatase (AgALP1) were identified as receptors for Cry11Ba toxin in A. gambiae. However, an A. gambiae cadherin (AgCad1) that bound Cry11Ba with low affinity (K_d = 766 nM) did not support a receptor role of AgCad1 for Cry11Ba. Here, we studied a second A. gambiae cadherin (AgCad2) that shares 14% identity to AgCad1. Immunohistochemical study showed that the protein is localized on A. gambiae larval midgut apical membranes. Its cDNA was cloned and the protein was analyzed as a transmembrane protein containing 14 cadherin repeats. An Escherichia coli expressed CR14MPED fragment of AgCad2 bound Cry11Ba with high affinity (K_d = 11.8 nM), blocked Cry11Ba binding to A. gambiae brush border vesicles and reduced Cry11Ba toxicity in bioassays. Its binding to Cry11Ba could be completely competed off by AgCad1, but only partially competed by AgALP1. The results are evidence that AgCad2 may function as a receptor for Cry11Ba in A. gambiae larvae.     

Disintegration of Dung Pats from Cattle Treated with the Ivermectin Anthelmintic Bolus,or the Biocontrol Agent Duddingtonia flagrans

An experiment was performed during the grazing seasons of 1998, 1999 and 2000 to study the influence of the antiparasitic drug ivermectin and the nematophagous fungus Duddingtonia flagrans on cattle dung disintegration. The faeces originated from groups of animals that were part of a separate grazing experiment where different control strategies for nematode parasite infections were investigated. Each group consisted of 10 first-season grazing cattle that were either untreated, treated with the ivermectin sustained-release bolus, or fed chlamydospores of D. flagrans. Faeces were collected monthly on 4 occasions and out of pooled faeces from each group, 4 artificial 1 kg dung pats were prepared and deposited on nylon mesh on an enclosed pasture and protected from birds. The position of the new set of pats was repeated throughout the 3 years of the study. Each year, the dung pats were weighed 4, 6, 8 and 10 weeks after deposition and immediately afterwards replaced to their initial positions.

Results showed that there was no difference in faecal pat disintegration between groups. However, the time-lag between deposition and complete disintegration of the faeces varied significantly between deposition occasions. Dung pats disappeared within 2 weeks (visual observation) when subjected to heavy rainfall early after deposition, whereas an extended dry period coincided with faeces still remaining 12 months after deposition.