Sub-lethal autolysis : Modification of cell periphery by lysosomal enzymes

Lysosomal activation was induced in dog kidney and HEp-2 cells by treatment with anticellular serum and high concentrations (20 μg/ml) of vitamin A alcohol. The morphological changes accompanying the release of enzymes from activated lysosomes were described. Measurements of cell coat thickness by ellipsometry revealed that lysosomal enzymes released extracellularly were able to digest the coat. The scale of enzyme release was an important factor in determining the amount of coat digested. Complement-sufficient anticellular sera and high concentrations of vitamin A induced marked lysosomal activation and extensive digestion of the coat. Complement-deficient anticellular serum produced significantly less lysosomal labilization and only limited digestion of the coat. The digestion of the cell coat induced by these agents was prevented by pretreatment of the cells with either hydrocortisone or chloroquine.     

Vascular wall resident progenitor cells: A review

The vessel wall has usually been thought to be relatively quiescent. But the discovery of progenitor cells in many tissues and in the vasculature itself has led to a reconsideration of the vascular biology. The presence of circulating endothelial and smooth muscle progenitors able to home to the injured vascular wall is a firm acquisition; less known is the notion, coming from embryonic and adult tissue studies, that stem cells able to differentiate into endothelial cells and smooth muscle cells also reside in the arterial wall. Moreover, the existence of a vasculogenic zone has recently been identified in adult human arteries; this niche-like zone is believed to act as a source of progenitors for postnatal vasculogenesis. From the literature it is already apparent that a complex interplay between circulating and resident vascular wall progenitors takes place during embryonal and postnatal life; a structural/functional disarray of these intimate stem cell compartments could hamper appropriate vascular repair, the development of vascular wall disease being the direct clinical consequence in adult life. This review gives an overview of adult large vessel progenitors established in the vascular wall during embryogenesis and their role in the maintenance of wall homeostasis.     

Intracellular pH electrode : Experiments on the giant squid axon

A new, easy method to produce and calibrate a 1-μm tip intracellular pH electrode is described. This antimony electrode and a micro-calomel electrode were inserted into the giant axon of Loligo pealii. The potential obtained when the axon was bathed in seawater corresponded to a pH of 7.0 ± 0.2. It was found that acidification of the external perfusate induced a drop in axoplasmatic pH leading to changes in the membrane electrical properties. Changes of resting or action potentials did not influence intracellular pH.     

Quantitative assessment of peptide-lipid interactions.: Ubiquitous fluorescence methodologies

Peptide-membrane interactions have been gaining increased relevance, mainly in biomedical investigation, as the potential of the natural, nature-based and synthetic peptides as new drugs or drug candidates also expands. These peptides must face the cell membrane when they interfere with or participate in intracellular processes. Additionally, several peptide drugs and drug leads actions occur at the membrane level (e.g., antimicrobial peptides, cell-penetrating peptides and enveloped viruses membrane fusion inhibitors). Here we explore fluorescence spectroscopy methods that can be used to monitor such interactions. Two main approaches are considered, centered either on the peptide or on the membrane. On the first, we consider mainly the methodologies based on the intrinsic fluorescence of the aminoacid residues tryptophan and tyrosine. Regarding membrane-centric approaches, we review methods based on lipophilic probes sensitive to membrane potentials. The use of fluorescence constitutes a simple and sensitive method to measure these events. Unraveling the molecular mechanisms that govern these interactions can unlock the key to understand specific biological processes involving natural peptides or to optimize the action of a peptide drug.     

Heterocycles from saccharide hydrazones : Part I. Saccharide 1,3,4-oxadiazoles

Oxidation, with iodine-mercuric oxide, of acetylated saccharide aroylhydrazones and of aromatic aldehyde hydrazones yields 5-aryl-2-(polyacetoxyalkyl)-1,3,4-oxadiazoles and 2,5-diaryl-1,3,4-oxadiazoles, respectively. On de-O-acetylation, saccharide oxadiazole acetates rearrange to the tautomeric, cyclic iminolactones which, on reacetylation, regenerate the starting oxadiazoles. Attempted dehydration of saccharide acetyl- and benzoyl-hydrazones by treatment with boiling acetic anhydride under reflux resulted in the formation of peracetylated N,N-diacetylhydrazones and-N-acetyl-N-benzoylhydrazones, respectively.     

Quinacrine fluorescence of metaphase chromosomes : Identical patterns in different tissues

The quinacrine mustard fluorescence patterns of the metaphase chromosomes of different tissues of the same plant species were found to be identical. Similar studies of the chromosome regions on human material gave the same result.     

Light scattering by cellulose : IV. Fibers with helical morphology

Solid-state light scattering has been used to study the scattering by the helically wound microfibrils in wood fibers. Scattering envelopes have been recorded from a section of Eastern spruce wood as well as a single fiber of Black spruce. Theoretical expressions for the intensity of light scattered by a continuous helix have been derived and found to be in fair agreement with the experimental results. A method of estimating the “pitch” and “tilt” of the helical segments is outlined.     

The oxidation of D-glucose and D-fructose with oxygen in aqueous,alkaline solutions : Part II. The overall kinetics

Based on a previously reported, integral reaction-scheme, a very simple, kinetic model for the homogeneous oxidation of D-glucose and D-fructose in aqueous, alkaline solutions has been developed. It involves the influence of the type and concentration of the hexose, the hydroxyl-ion concentration, the oxygen concentration in the liquid phase, and the temperature on the rate of formation of the acidic reaction products. No attention is paid to the product distribution.     

Immobilization antigens of Tetrahymena pyriformis : I. Assay and extraction

A method using immunodiffusion has been established to assay the two mutually exclusive temperature dependent immobilization antigens, H and T, of Tetrahymena pyriformis. Specific antiserum was obtained by exploitation of allelic or temperature induced variations among inbred strains for absorption of antisera prepared against whole cells. The antigens were extracted both from isolated cilia and from whole cell bodies. Mild detergent extraction was found to be more efficient than mechanical disruption of the cells by freeze-thawing. The sedimentation behavior in sucrose density gradients of active H antigen was the same, whether freeze-thaw or detergent extracted; similarly, the sedimentation behavior of T was the same following the two extraction methods. Extraction with acetic acid, as reported by others, solubilized the same material as the detergent, but the acid denatured the antigen. An estimate of the molecular weight of the antigen of 29 000 for H and 23 000 for T was made.     

Dispersal of adult female fig wasps 1. Arrivals and departures

Ficus burtt-davyi, like most other fig species (Ficus, Moraceae), is exclusively pollinated by its own unique species of fig wasp, in this caseElisabethiella baijnathi (Chalcidoidea, Agaonidae). Because fig crop development on any one tree is usually synchronised, the small and short-lived female wasps have to migrate and find other trees bearing figs which are at suitable stage of development for oviposition. However, the likelihood of successful location and subsequent arrival at a new host tree is dependent on distance and the effect of environmental factors such as wind and temperature. This study examines the relationship between ambient temperatures and the timing of fig wasps emergence from their natal figs and the commencement of their dispersal flight. The behaviour of the wasps arriving at figs which were ready to be pollinated was also examined. The female wasps did not appear to distinguish between the figs and other parts of the tree when in flight. However, after landing on the tree their search for figs was more directed as they visited more figs than leaves. Short-range recognition of figs appears to be by contact chemo-reception, but the wasps showed a preference for entering figs which did not already contain a female wasp.     

Metabolism of 2-deoxy-d-glucose by baker's yeast : IV. Incorporation of 2-deoxy-d-glucose into cell wall mannan

1.

1. Saccharomyces cerevisiae grown in the presence of 2-deoxy-d-glucose incorporate this glucose and mannose analogue into cell wall polysaccharides. Fractionation of cell walls to mannan- and glucan-containing fractions followed by analysis for glucose, mannose and deoxyglucose showed that deoxyglucose was incorported mainly, if not exclusively, into cell wall mannan.     

Proliferative versus apoptotic functions of caspase-8 : Hetero or homo: The caspase-8 dimer controls cell fate

Caspase-8, the initiator of extrinsically-triggered apoptosis, also has important functions in cellular activation and differentiation downstream of a variety of cell surface receptors. It has become increasingly clear that the heterodimer of caspase-8 with the long isoform of cellular FLIP (FLIP_L) fulfills these pro-survival functions of caspase-8. FLIP_L, a catalytically defective caspase-8 paralog, can interact with caspase-8 to activate its catalytic function. The caspase-8/FLIP_L heterodimer has a restricted substrate repertoire and does not induce apoptosis. In essence, caspase-8 heterodimerized with FLIP_L prevents the receptor interacting kinases RIPK1 and -3 from executing the form of cell death known as necroptosis. This review discusses the latest insights in caspase-8 homo- versus heterodimerization and the implication this has for cellular death or survival. This article is part of a Special Issue entitled: Proteolysis 50 years after the discovery of lysosome.     

Emission-wavelength-dependent decay of the fluorescent probe N-phenyl-1-naphthylamine

We have measured the fluorescence decay of $\text{N-}\text{phenyl}\text{-1-}\text{naphthylamine}$ using the phase-modulation method, in several solvent systems and egg phosphatidylcholine vesicles. The decay is monoexponential in pure solvents (both polar and non-polar) of low viscosity. In polar viscous solvents or in non-polar solvents containing an added polar solute, the decay is heterogeneous and emission wavelength dependent. In such cases, dielectric relaxation and/or excited-state complexing give rise to a shift of the emission spectrum on the nanosecond time scale. Emission-wavelength-dependent decay was also observed when $\text{N-}\text{phenyl}\text{-1-}\text{naphthylamine}$ was bound to egg phosphatidylcholine vesicles. From these results as well as the position of the emission spectral maximum, we conclude that $\text{N-}\text{phenyl}\text{-1-}\text{naphthylamine}$ probes the ester-carbonyl region of the phospholipid acyl chains, where it undergoes an excited-state reaction. This result contradicts the often made assumption that $\text{N-}\text{phenyl}\text{-1-}\text{naphthylamine}$ probes the deeper hydrocarbon region of the bilayer.     

Diffusion tensor imaging and cognition in cerebral small vessel disease : The RUN DMC study

Background

Cerebral small vessel disease (SVD) is very common in elderly and related to cognition, although this relation is weak. This might be because the underlying pathology of white matter lesions (WML) is diverse and cannot be properly appreciated with conventional FLAIR MRI. In addition, conventional MRI is not sensitive to early loss of microstructural integrity of the normal appearing white matter (NAWM), which might be an important factor. Diffusion tensor imaging (DTI) provides alternative information on microstructural white matter integrity and we have used this to investigate the relation between white matter integrity, in both WML and NAWM, and cognition among elderly with cerebral SVD.

Methods

The RUN DMC study is a prospective cohort study among 503 independently living, non-demented elderly with cerebral SVD aged between 50 and 85 years. All subjects underwent MRI and DTI scanning. WML were segmented manually. We measured mean diffusivity (MD) and fractional anisotropy (FA), as assessed by DTI in both WML and NAWM.

Results

Inverse relations were found between MD in the WML and NAWM and global cognitive function (β = −.11, p < 0.05; β = −.18, p < 0.001), psychomotor speed (β = −.15, p < 0.01; β = −.18, p < 0.001), concept shifting (β = −.11, p < 0.05; β = −.10, p < 0.05) and attention (β = −.12, p < 0.05; β = −.15, p < 0.001). The relation between DTI parameters in both WML and NAWM and cognitive performance was most pronounced in subjects with severe WML.

Conclusion

DTI parameters in both WML and NAWM correlate with cognitive performance, independent of SVD. DTI may be a promising tool in exploring the mechanisms of cognitive decline and could function as a surrogate marker for disease progression in therapeutic trials.This article is part of a Special Issue entitled: Imaging Brain Aging and Neurodegenerative disease.