Acetylcholine and Dopamine Promote the Production of Platelet Activating Factor in Immature Cells of Chick Embryonic Retina

We have previously shown that platelet-activating factor (PAF), a naturally occurring lipid mediator of cell-to-cell communication, was produced by 3-day-old chick retina stimulated with acetylcholine (ACh) and dopamine (DA), but not with other neurotransmitters. ACh and DA stimulated PAF synthesis via a dithiothreitol (DTT)-insensitive cholinephosphotransferase, without affecting the acetyltransferase pathway, which was stimulated only by the calcium ionophore A23187. Therefore, we attempted to study the effects of neurotransmitters on PAF production and on the activities of the DTT-insensitive cholinephosphotransferase and acetyltransferase in the developing chick embryo retina up to hatching. Our results show that PAF was produced already at 8 days of development, when retinal cells are still rather immature and ganglion and Mueller cells are the only differentiated cells. The stimulation of PAF production occurred with ACh and not with other neurotransmitters. In older stages, DA also stimulated PAF production, as already described in the chick after hatching. DTT-insensitive cholinephosphotransferase and acetyltransferase activities were present in 8-day-old embryos, the earliest stage analyzed. Both enzymatic activities increased with age; DTT-insensitive cholinephosphotransferase increased rapidly from day 12 up to day 18, whereas acetyltransferase activity increased linearly up to the time of hatching. To promote PAF production, ACh and DA activate DTT-insensitive cholinephosphotransferase, but not acetyltransferase.(ABSTRACT TRUNCATED AT 250 WORDS)     

European Society of Biomechanics S.M. Perren Award 2014: Safety factor of the proximal femur during gait: A population-based finite element study

It has been suggested that the mechanical competence of the proximal femur is preserved with respect to physiological loading conditions rather than accidental overloading, but the consequences of this adaptation for fracture risk in the elderly remain unclear. The goal of the present study was to analyse the safety factor of the human femur in the two most frequent daily activities, level walking and stair climbing, and to understand the dependence, if any, of this safety factor on age, volumetric bone mineral density (vBMD), and gender.     

A novel microhabitat for parasitic copepods: A new genus of Ergasilidae (Copepoda: Cyclopoida) from the urinary bladder of a freshwater fish

An endoparasitic copepod is reported from the urinary bladder of a fish for the first time. Endoparasitic copepods on fish hosts are extremely rare and the impact of colonization of this novel microhabitat on the biology of the parasite is discussed. This curious association was reported from two different host families of Neotropical freshwater fishes, Erythrinidae and Cichlidae, collected from the Cristalino River, a tributary of the Araguaia River, in Brazil. The copepod is fully described using light and scanning electron microscopy. Urogasilus brasiliensis n. g., n. sp. represents a new genus and species of the family Ergasilidae and can be distinguished from other genera by its unique tagmosis, in which the fourth and fifth pedigerous somites and the genital double-somite are all fused to form an elongate trunk. The anal somite is the only free abdominal somite present. The pattern of leg segmentation is also unique, with legs 1 to 3 each having a 2-segmented endopod and leg 4 reduced to a single seta. The discovery of ovigerous female ergasilids in the urinary bladder of a fish is novel and this discovery represents a good model for further studies on the adaptations to an endoparasitic lifestyle.     

Sensitivity of a subject-specific musculoskeletal model to the uncertainties on the joint axes location

Subject-specific musculoskeletal models have become key tools in the clinical decision-making process. However, the sensitivity of the calculated solution to the unavoidable errors committed while deriving the model parameters from the available information is not fully understood. The aim of this study was to calculate the sensitivity of all the kinematics and kinetics variables to the inter-examiner uncertainty in the identification of the lower limb joint models. The study was based on the computer tomography of the entire lower-limb from a single donor and the motion capture from a body-matched volunteer. The hip, the knee and the ankle joint models were defined following the International Society of Biomechanics recommendations. Using a software interface, five expert anatomists identified on the donor's images the necessary bony locations five times with a three-day time interval. A detailed subject-specific musculoskeletal model was taken from an earlier study, and re-formulated to define the joint axes by inputting the necessary bony locations. Gait simulations were run using OpenSim within a Monte Carlo stochastic scheme, where the locations of the bony landmarks were varied randomly according to the estimated distributions. Trends for the joint angles, moments, and the muscle and joint forces did not substantially change after parameter perturbations. The highest variations were as follows: (a) 11° calculated for the hip rotation angle, (b) 1% BW × H calculated for the knee moment and (c) 0.33 BW calculated for the ankle plantarflexor muscles and the ankle joint forces. In conclusion, the identification of the joint axes from clinical images is a robust procedure for human movement modelling and simulation.     

Expression of Immunoglobulin Receptors with Distinctive Features Indicating Antigen Selection by Marginal Zone B Cells from Human Spleen

Marginal zone (MZ) B cells, identified as surface (s)IgM^highsIgD^lowCD23^low/−CD21⁺CD38⁻ B cells, were purified from human spleens, and the features of their V(D)J gene rearrangements were investigated and compared with those of germinal center (GC), follicular mantle (FM) and switched memory (SM) B cells. Most MZ B cells were CD27⁺ and exhibited somatic hypermutations (SHM), although to a lower extent than SM B cells. Moreover, among MZ B-cell rearrangements, recurrent sequences were observed, some of which displayed intraclonal diversification. The same diversifying sequences were detected in very low numbers in GC and FM B cells and only when a highly sensitive, gene-specific polymerase chain reaction was used. This result indicates that MZ B cells could expand and diversify in situ and also suggested the presence of a number of activation-induced cytidine deaminase (AID)-expressing B cells in the MZ. The notion of antigen-driven expansion/selection in situ is further supported by the VH CDR3 features of MZ B cells with highly conserved amino acids at specific positions and by the finding of shared (“stereotyped”) sequences in two different spleens. Collectively, the data are consistent with the notion that MZ B cells are a special subset selected by in situ antigenic stimuli.