[Probiotics, prebiotics and zinc in the therapy and prevention of acute infectious diarrhoea in children: state of the art]. / Probiotici, prebiotici e zinco nella terapia e prevenzione della diarrea acuta infettiva in età pediatrica: qual' è l'attuale evidenza?

Selected probiotics (mainly Lactobacilli, and particularly LGG, and Saccharomyces boulardii) have recently demonstrated a therapeutic efficacy in acute diarrhoea, if used in the early phase of infection and at high concentration. Further data are needed to clarify their effect for prevention and travellers' diarrhoea. The mechanisms of action of probiotics need to be fully elucidated but seem to include a complex interaction of epithelial, molecular, metabolic and immune responses. There is an increasing evidence that different micro-organisms show different properties and efficacy. An accurate identification and selection of the strains, the dose and the patients are thus crucial for a correct therapeutic approach. Prebiotics can modify the intestinal flora and interact with the immune system of the host against specific pathogens. However, clinical trials are currently limited and a beneficial effect of prebiotics in acute diarrhoea is still lacking. In developing countries zinc supplementation demonstrated a significant reduction of fecal excretion, duration, severity and persistency of diarrhoea. Moreover, zinc may improve immune status, intestinal permeability, epithelial and enzymatic functions, and transport of electrolytes. The use of zinc in addition to oral rehydration solution (ORS) could thus theoretically improve the treatment and reduce the complications of diarrhoea worldwide. However, in developed countries, no trial using zinc supplementation in patients with acute diarrhoea has been published yet and the cost-benefit ratio of zinc supplementation needs to be assessed.

Exogenous mesenchymal stem cells localize to the kidney by means of CD44 following acute tubular injury.

Mesenchymal stem cells (MSC) were recently shown to migrate to injured tissues when transplanted systemically. The mechanisms underlying the migration and homing of these cells is, however, unclear. In this study, we examine the role of CD44 and its major ligand, hyaluronic acid, in the trafficking of intravenously injected MSC in the glycerol-induced mouse model of acute renal failure (ARF). In vitro, hyaluronic acid promoted a dose-dependent migration of the stem cells that was inhibited by an anti-CD44 blocking monoclonal antibody. In vivo, stem cells injected into mice with ARF migrated to the injured kidney where hyaluronic acid expression was increased. Their presence correlated with morphological and functional recovery. Renal localization of the MSC was blocked by pre-incubation with the CD44 blocking antibody or by soluble hyaluronic acid. Stem cells derived from CD44 knockout mice did not localize to the injured kidney and did not accelerate morphological or functional recovery. Reconstitution by transfection of CD44 knockout stem cells with cDNA encoding wild-type CD44, but not a loss of function CD44 unable to bind hyaluronic acid, restored in vitro migration and in vivo localization of the cells to injured kidneys. We suggest that CD44 and hyaluronic acid interactions recruit exogenous MSC to injured renal tissue and enhance renal regeneration.

Role of glutamate delta -2 receptors in activity-dependent competition between heterologous afferent fibers.

A principle that regulates detailed architecture in the brain is that active terminals have a competitive advantage over less active terminals in establishing synaptic connections. This principle is known to apply to fibers within a single neuronal population competing for a common target domain. Here we uncover an additional rule that applies when two neuronal populations compete for two contiguous territories. The cerebellar Purkinje cell dendrites have two different synaptic domains with spines innervated by two separate excitatory inputs, parallel fibers (PFs) and climbing fibers (CFs). Glutamate delta-2 receptors are normally present only on the PF spines where they are important for their innervation. After block of activity by tetrodotoxin, numerous new spines form in the CF domain and become innervated mainly by PFs; all spines, including those still innervated by the CFs, bear delta-2 receptors. Thus, in the absence of activity, PFs gain a competitive advantage over CFs. The entire dendritic arbor becomes a uniform territory with the molecular cues associated with the PFs. To access their proper territory and maintain synaptic contacts, CFs must be active and locally repress the cues of the competitor afferents.

Control of spine formation by electrical activity in the adult rat cerebellum.

Dendritic spines are a key structure in neuronal plasticity. Enhanced activity is commonly associated with an increase in spine size and density. Purkinje cell dendrites are characterized by a proximal and a distal compartment on which climbing fibers and parallel fibers, respectively, impinge. The proximal region has a very low spine density, whereas the distal region has a high density. Previous experiments showed that after climbing fiber deletion, Purkinje cells become hyperactive, and a large number of spines develop on the proximal dendrites. Here we show that the same hyperspiny transformation occurs in the proximal dendrites of adult Purkinje cells by depressing electrical activity with tetrodotoxin. Thus, spines in different dendritic compartments are created or maintained independently from the level of Purkinje cell-firing rate and when the afferent activity is blocked. This conclusion supports the view that spinogenesis is the expression of an intrinsic program and the two regions of the dendritic tree respond differently to activity block because of differences in the inputs that they receive. On tetrodotoxin treatment, climbing fibers become atrophic and may sprout thin collateral ramifications directed mainly toward the granular layer. All changes are reversible on tetrodotoxin removal. Therefore, Purkinje cells provide a model where spines in different compartments of the same neuron are differently regulated by the activity of their local afferents. In addition, electrical activity is also essential to maintain the full climbing fiber innervation.

[The activity of the "Hygrobac DAR 352" filter in resuscitation patients]. / Riscontro dell'attività del filtro "Hygrobac DAR 352" nei pazienti in rianimazione.

The Authors clinically evaluated the efficacy of the "Hygrobac DAR 352" filter as an antibacterial barrier in a group of patients during mechanical ventilation. After 24 hours of IPVV, a cultural sample has been taken on both sides of the filter introduced in the breathing circuit (patient's side; ventilator's side). While bacteria has been isolated on "the patient's side" of the filter, they were not present on the surface of the "ventilator's side" of the filter. Therefore, the Authors emphasize that the Hygrobac DAR 352 filter represents a good barrier against the passage of bacteria, as it avoids the contamination of the mechanical ventilator by keeping pathogenic organisms coming from patient's airways inside the filter itself.