Structure and variability of the individual odor trail in Solenopsis geminata Fabr. (Hymenoptera,Formicidae)

Journal of Comparative Physiology A -     

Recombinant HIV Envelope Proteins Fail to Engage Germline Versions of Anti-CD4bs bNAbs

Vaccine candidates for HIV-1 so far have not been able to elicit broadly neutralizing antibodies (bNAbs) although they express the epitopes recognized by bNAbs to the HIV envelope glycoprotein (Env). To understand whether and how Env immunogens interact with the predicted germline versions of known bNAbs, we screened a large panel (N:56) of recombinant Envs (from clades A, B and C) for binding to the germline predecessors of the broadly neutralizing anti-CD4 binding site antibodies b12, NIH45-46 and 3BNC60. Although the mature antibodies reacted with diverse Envs, the corresponding germline antibodies did not display Env-reactivity. Experiments conducted with engineered chimeric antibodies combining the mature and germline heavy and light chains, respectively and vice-versa, revealed that both antibody chains are important for the known cross-reactivity of these antibodies. Our results also indicate that in order for b12 to display its broad cross-reactivity, multiple somatic mutations within its VH region are required. A consequence of the failure of the germline b12 to bind recombinant soluble Env is that Env-induced B-cell activation through the germline b12 BCR does not take place. Our study provides a new explanation for the difficulties in eliciting bNAbs with recombinant soluble Env immunogens. Our study also highlights the need for intense efforts to identify rare naturally occurring or engineered Envs that may engage the germline BCR versions of bNAbs.     

Probabilistic computation by neuromine networks

In this paper, we address the question, can biologically feasible neural nets compute more than can be computed by deterministic polynomial time algorithms? Since we want to maintain a claim of plausibility and reasonableness we restrict ourselves to algorithmically easy to construct nets and we rule out infinite precision in parameters and in any analog parts of the computation. Our approach is to consider the recent advances in randomized algorithms and see if such randomized computations can be described by neural nets. We start with a pair of neurons and show that by connecting them with reciprocal inhibition and some tonic input, then the steady-state will be one neuron ON and one neuron OFF, but which neuron will be ON and which neuron will be OFF will be chosen at random (perhaps, it would be better to say that microscopic noise in the analog computation will be turned into a megascale random bit). We then show that we can build a small network that uses this random bit process to generate repeatedly random bits. This random bit generator can then be connected with a neural net representing the deterministic part of randomized algorithm. We, therefore, demonstrate that these neural nets can carry out probabilistic computation and thus be less limited than classical neural nets.     

Thresholding technique for accurate analysis of density and geometry in QCT, pQCT and microCT images

Computed tomography (CT) is widely used in the assessment of bone parameters in live patients and animals as well as bone samples. Quantitative analysis requires the segmentation of the bone from the surrounding tissue, and most segmentation methods rely on some type of thresholding technique. The aim of this communication is to highlight the influence of threshold selection on various bone parameters and recommend appropriate thresholds. Two types of information are of interest in bone analysis from images: geometric parameters and density parameters. We know from imaging theory that blurring is an inherent byproduct of all imaging methods. Depending on the threshold used for segmentation, the object boundary moves in space due to the sloping edge. It is, thus, critical to select the threshold that creates an object boundary that reflects the actual object size. Similarly, due to blurring, the imaged density shows erroneous values at the object boundaries. Such values must not be included for an accurate representation of the object density. Using a pQCT scanner and a bone phantom with known density and geometry, we show that the thresholds for geometry and density are different. The threshold for accurate geometric segmentation was 49% of the difference of the density between the adjacent tissues. The threshold for accurate density assessment was 95% of the maximum density value of the bone. These specific thresholds are valid only for the scanner tested; however, the principle for selecting the thresholds is valid across scanner platforms and scale of imaging.     

Reduced titres of ecdysone following juvenile hormone treatment in the German cockroach, Blattella germanica

Changes in ecdysone titre of the larvae of the German cockroach, Blattella germanica, exposed continuously to the juvenile hormone (JH), or to the insect growth regulator (IGR) with JH activity, can be correlated with the nature of the substance applied, its dose, and the time of application. The younger larvae exposed to the high dose of the IGR die in the next ecdysis, whereas the same treatment induces a diapause-like stage of developmental arrest in the last larval stage. The affected larvae have very little or no ecdysone, the synthesis of which takes place in the second part of the instar. The same treatment after this period has a lesser effect. The extent of the effect is correlated to the amount of ecdysone synthesized before the application of IGR. Last instar larvae exposed to the lower dose of the IGR or JH lack the peak of ecdysone normally found in the controls at the end of the second third of the instar when metamorphosis takes place. In these insects the first rise of the ecdysone titre begins towards the end of the instar, and ecdysis into the supernumerary larval stage is initiated when the ecdysone titre reached a level permitting ecdysis.A direct or indirect antagonism between these hormones, both fundamental to insect development, can explain the morphogenetic, inhibitory, and lethal effects observed in insects treated with JH or IGR with JH activity.