Newly generated cells are increased in hippocampus of adult mice lacking a serine protease inhibitor

Background  

Neurogenesis in the hippocampal dentate gyrus and the subventricular zone occurs throughout the life of mammals and newly generated neurons can integrate functionally into established neuronal circuits. Neurogenesis levels in the dentate gyrus are modulated by changes in the environment (enrichment, exercise), hippocampal-dependent tasks, NMDA receptor (NMDAR) activity, sonic hedgehog (SHH) and/or other factors.     

A poset hierarchy

This article extends a paper of Abraham and Bonnet which generalised the famous Hausdorff characterisation of the class of scattered linear orders. They gave an inductively defined hierarchy that characterised the class of scattered posets which do not have infinite incomparability antichains (i.e. have the FAC). We define a larger inductive hierarchy ^κℌ* which characterises the closure of the class of all κ-well-founded linear orders under inversions, lexicographic sums and FAC weakenings. This includes a broader class of “scattered” posets that we call κ-scattered. These posets cannot embed any order such that for every two subsets of size < κ, one being strictly less than the other, there is an element in between. If a linear order has this property and has size κ it is unique and called ℚ(κ). Partial orders such that for every a < b the set {x: a < x < b} has size ≥ κ are called weakly κ-dense, and posets that do not have a weakly κ-dense subset are called strongly κ-scattered. We prove that ^κℌ* includes all strongly κ-scattered FAC posets and is included in the class of all FAC κ-scattered posets. For κ = ℵ₀ the notions of scattered and strongly scattered coincide and our hierarchy is exactly aug(ℌ) from the Abraham-Bonnet theorem. The authors warmly thank Uri Abraham for his many useful suggestions and comments. Mirna Džamonja thanks EPSRC for their support on an EPSRC Advanced Fellowship.     

Experimental method to measure the effect of charge on bimolecular collision rates in electrolyte solutions

A stable, monoprotic nitroxide spin probe is utilized as a model to study molecular collisions in aqueous electrolyte solutions. The rate constants of bimolecular collisions, K(col) for 2,2,5,5-tetramethylpyrrolidin-1-oxyl-3-carboxylic acid (CP) when it is uncharged (at low pH) and K(col)? when it is charged (CP?; at high pH), are measured as functions of temperature and ionic strength. The ratio f* ≡ K(col)?/K(col) is a direct measure of the effect of charge on the collision rate. Neglecting the small differences in size and diffusion coefficients of CP and CP?, f* is the fractional change in collision rate due to Coulomb repulsion which was treated theoretically in Debye's classic paper [Trans. Electr. Chem. Soc. 1942, 82, 265]. K(col) and K(col)? are determined from EPR spectral changes due to spin-spin interactions which are dominated by Heisenberg spin exchange under the conditions of these experiments. Values of f* vary linearly with values of κ · d in the range 0.4 < κ · d < 1.8, where κ and d are the inverse Debye screening length and the distance at closest approach, respectively. Values of d obtained in two independent ways, (1) from rotational correlation times measured by EPR and (2) by insisting that the experimental results be consistent with the Debye theory at infinite dilution, yield similar results. As the ionic strength is increased (κ increased), the screening effect reduces the effect of the Coulomb barrier more slowly than predicted by the Debye theory. While values of K(col) and K(col)? vary substantially with T, approximately following the Stokes-Einstein-Smoluchowski equation, values of f* depend only slightly on temperature at a given value of κ · d, as is predicted by Debye's theory.     

Preparation of β-Silyl-α,β-unsaturated Esters and 3-Silyl Allyl Alcohols

Acylsilanes react with lithium α-silyl ester enolates to provide β-silyl-α,β-unsaturated esters having predominantly the (Z) geometry. These esters were reacted with Grignard reagents and with lithium aluminum hydride to give the corresponding (Z) 3-silyl allyl alcohols.     

♣ Does not imply the existence of a Suslin tree

We prove that ♣ does not imply the existence of a Suslin tree, so answering a question of I. Juhász. The authors thank the Israel Academy of Sciences and Humanities for partial support through the Basic Research Foundation Grant number 0327398. Mirna Džamonja would in addition like to thank The Hebrew University of Jerusalem and The Lady Davis Foundation for the Forchheimer Postdoctoral Fellowship during the academic year 1994/95, and Rutgers University for their hospitality during a visit in November 1995, when part of the research for this paper was conducted. Some of the research was also conducted while Mirna Džamonja was a visiting assistant professor at the University of Wisconsin-Madison. This publication is denoted [DjSh 604] in the list of publications of Saharon Shelah.     

Identification of a potent antibacterial factor isolated from bronchoalveolar lavage fluid: guanidine,N-[3-[(aminoiminomethyl)amino]propyl]-N-dodecyl-, a potential source of error in the analysis of antibacterial agents

The widespread use of antibiotics in modern society has encouraged the search for new antibacterial compounds. In this laboratory investigations are being made to identify and characterise novel antibacterial peptides. With this in mind, the antibacterial properties of human bronchoalveolar lavage (BAL) fluid from sarcoidosis patients is being investigated. In this communication we report on the identification and characterisation of a highly active non-peptide antibacterial compound isolated from BAL fluid. The structure of this active compound was elucidated by high-resolution accurate mass and tandem mass spectrometry to be guanidine, N-[3-[(aminoiminomethyl)amino]propyl]-N-dodecyl-. This compound does not appear to be endogenous, and its presence in BAL fluid extracts presents a potential source of error in analysis of antibacterial agents. The biological effects of guanidine, N-[3-[(aminoiminomethyl)amino]propyl]-N-dodecyl- have not previously been described in the literature.     

Epidermal lignin deposition in quinoa cotyledons in response to UV-B radiations

UV-B radiation (280-320 nm) is harmful to living organisms and has detrimental effects on plant growth, development and physiology. In this work we examined some mechanisms involved in plant responses to UV-B radiation. Seedlings of quinoa (Chenopodium quinoa Willd.) were exposed to variable numbers of UV-B radiation doses, and the effect on cotyledons was studied. We analyzed (1) cotyledons anatomy and chloroplasts ultrastructure; (2) peroxidase activity involved in the lignification processes; and (3) content of photosynthetic pigments, phenolic compounds and carbohydrates. Exposure to two UV-B doses induced an increase in the wall thickness of epidermal cells, which was associated with lignin deposition and higher activity of the peroxidase. The chloroplast ultrastructure showed an appearance typical of plants under shade conditions, likely in response to reduced light penetration into the mesophyll cells due to the screening effect of epidermal lignin deposition. Exposure to UV-B radiation also led to (1) enhancement in the level of phenolics, which may serve a protective function; (2) strong increase in the fructose content, a fact that might be related to higher requirement of erythrose-4P as a substrate for the synthesis of lignin and phenolics; and (3) reduction in the chlorophyll concentration, evidencing alteration in the photosynthetic system. We propose that the observed lignin deposition in epidermal tissues of quinoa is a resistance mechanism against UV-B radiation, which allows growing of this species in Andean highlands.     

Sulfide analysis by the silver sulfide-silver electrode

Summary The study was performed to evaluate the usefulness of the silver sulfide-silver electrode for measuringsulfldes in foods by means of the electromotive force of the cell saturated calomel electrode/S^2–/Ag₂S, Ag. The electrode response to sulfide ion activity over the pH interval 3 to 12 was determined, and procedures for the standardization of the silver sulfide-silver electrode are discussed.

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Sulfidanalyse mit Hilfe der Silbersulfid/Silberelektrode

Zusammenfassung Ziel der Untersuchungen ist es, die Silbersulfid/Silberelektrode auf ihre Verwendbarkeit zurMessung von Sulfiden in Lebensmitteln zu prüfen. Die vorliegende Mitteilung befaßt sich mit dem Einfluß des pH-Wertes im Bereich von 3–12 auf das Potential sowie mit den Möglichkeiten der Standardisierung des Elektrodensystems gesättigte Kalomelelektrode/S^2–/Ag₂S, Ag.

     

A novel bis-phenanthridine triamine with pH controlled binding to nucleotides and nucleic acids

The new bis-phenanthridine triamine is characterised by three pK(a) values: 3.65; 6.0 and >7.5. A significant difference in the protonation state of at pH = 5 (four positive charges) and at pH = 7 (less than two positive charges) accounts for the strong dependence of -nucleotide binding constants on nucleotide charge under acidic conditions, whereas at neutral pH all -nucleotide complexes are of comparable stability. All experimental data point at intercalation as the dominant binding mode of to polynucleotides. However, there is no indication of bis-intercalation of the two phenanthridine subunits in binding to double stranded polynucleotides, the respective complexes being most likely mono-intercalative. Thermal stabilisation of calf thymus DNA (ct-DNA) and poly A-poly U duplexes upon addition of is significantly higher at pH = 5 than at neutral conditions. This is not the case with poly dA-poly dT, indicating that the specific secondary structure of the latter, most likely the shape of the minor groove, plays a key role in complex stability. At pH = 5 acts as a fluorimetric probe for poly G (emission quenching) as opposed to other ss-polynucleotides (emission increase), while at neutral conditions this specificity is lost. One order of magnitude higher cytotoxicity of compared to its "monomer" can be accounted for by cooperative action of two phenanthridinium units and the charged triamine linker. The results presented here are of interest to the development of e.g. sequence-selective cytostatic drugs, and in particular for the possibility to control the drug activity properties over binding to DNA and/or RNA by variation of the pH of its surrounding.