Adult rats stressed as neonates show exaggerated behavioral responses to both pharmacological and environmental challenges.

Adult rats that were isolated from the mother and nest for 1 hr per day from Postnatal Day 2 to 9 were studied. Controls consisted of handled littermates as well as separate litters that were never handled. As adults, animals were given either a pharmacological challenge (1.0 or 2.0 mg/kg amphetamine) or an environmental challenge (restraint). Previously isolated animals demonstrated increased activity compared to controls at both drug doses. Similarly, isolated animals manifested exaggerated inhibition of activity after restraint. Previously isolated animals usually did not show differences compared to controls under baseline conditions (saline injection or no restraint). The neuroplastic changes that result from the neonatal experience are long lasting and appear when the system is challenged. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hydrogel/bioactive glass composites for bone regeneration applications: Synthesis and characterisation

Due to the deficiencies of current commercially available biological bone grafts, alternative bone graft substitutes have come to the forefront of tissue engineering in recent times. The main challenge for scientists in manufacturing bone graft substitutes is to obtain a scaffold that has sufficient mechanical strength and bioactive properties to promote formation of new tissue. The ability to synthesise hydrogel based composite scaffolds using photopolymerisation has been demonstrated in this study. The prepared hydrogel based composites were characterised using techniques including Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-dispersive X-ray spectrometry (EDX), rheological studies and compression testing. In addition, gel fraction, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), porosity and swelling studies of the composites were carried out. It was found that these novel hydrogel bioglass composite formulations did not display the inherent brittleness that is typically associated with bioactive glass based bone graft materials and exhibited enhanced biomechanical properties compared to the polyethylene glycol hydrogel scaffolds along. Together, the combination of enhanced mechanical properties and the deposition of apatite on the surface of these hydrogel based composites make them an ideal candidate as bone graft substitutes in cancellous bone defects or low load bearing applications.     

Effects of US duration on classical conditioning of the rabbit's nictitating membrane response.

Attempted to distinguish the effects of UCS duration based on explicit pairings with the CS from the consequences of sheer exposure to the UCS in the rabbit nictitating membrane response. 228 albino rabbits received various proportions of CS (a 1,000-Hz tone) and UCS (a 60-Hz shock). Exp I revealed that there was an inverse relation between the overall level of CR acquisition and UCS durations of 50, l,500, and 6,000 msec. In addition, decrements in CR likelihood occurred within the daily sessions of 90 CS–UCS trials, and the magnitude of these within-session decrements was directly related to UCS duration. In Exp II, UCS duration of 50 and 6,000 msec were paired with the CS. When UCS exposure was equated, the UCS duration paired with the CS had a positive effect on CR likelihood. Conversely, in Exp III, the duration of interpolated UCSs had inverse effects on the rate of CR acquisition. In Exp IV, the opportunity for within-session decrements was eliminated by presenting only 1 CS–UCS trial per day, which resulted in a positive relation between CR likelihood and UCS duration. Results are discussed in terms of associative and performance hypotheses. (54 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behaviorally functional opioid systems in infant rats: II. Evidence for pharmacological, physiological, and psychological mediation of pain and stress.

Two experiments, with 160 10-day-old Sprague-Dawley rat pups, examined the behavioral characteristics of the neonatal opioid system during distressful situations, using a modification of the hot-plate paw-lick test. Ss were analgesic to heat following intraperitoneal morphine (0.5 mg/kg). Subcutaneous naloxone (0.5 mg/kg) prevented the analgesia. Morphine analgesia was significantly greater in Ss group-isolated from the dam. Saline controls group-isolated from the dam exhibited longer latencies than their nest-housed siblings. Individual isolation for 5 min markedly increased paw-withdrawal latency, and this effect was naltrexone reversible. Analgesia was not seen when Ss were tested directly from the nest or when grouped with others for 5 min. It is suggested that the opioid systems for stress and pain are functional in 10-day-old rats and that short-term isolation from the dam is a probable natural stressor modulated by endogenous opioid release. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Composition-property relationships for an experimental composite nerve guidance conduit: evaluating cytotoxicity and initial tensile strength

The objective of this work was to examine the main (individual), combined (interaction) and second-order (quadratic) effects of: (i) poly(d,l-lactide-co-glycolide) (PLGA), (ii) F127, and (iii) a zinc-silicate based bioactive glass, on the cytotoxicity and ultimate tensile strength of an experimental nerve guidance conduit (NGC). The experimental plan was carried out according to a Box–Behnken design matrix. The effects of each compositional factor were quantified using response surface methodology (RSM) techniques. Linear and quadratic polynomial equations were developed to examine cytotoxicity (after incubation at 3, 7 and 28 days) and initial ultimate tensile strength (UTS₀). Multiple regression analyses showed that the developed models yielded a good prediction for each response examined. It was observed that the beneficial effects of PLGA and bioactive glass on controlling cytotoxicity appeared greater than that of F127. Furthermore, the experimental conduits (with the exception of CNGC-I and CNGC-K) generally showed superior cytocompatibility when compared with the comparable literature for the clinically used nerve guidance conduit Neurolac^?. In this investigation, optimal compositions for cell viability were obtained for the following composition: PLGA = 18.89 wt%/F127 = 0.52 wt%/glass = 12.71 wt%. The optimization of composition with respect to ultimate tensile strength was also established (desired UTS₀ being based on the properties of the control device Neurolac^? whose UTS is c.20 MPa). The desired UTS₀ of ≤20 MPa was found for the composition: PLGA = 18.63 wt%/F127 = 0.77 wt%/glass = 5.54 wt%. A UTS₀ ≤30 MPa was recorded for the composition: PLGA = 18.34 wt%/F127 = 0.62 wt%/glass = 9.83 wt%, such tensile strengths are comparable to, reported values for Neurolac^?. Examination of the composition–property relationships with respect to combining cell viability and UTS₀ indicated preferred compositions in the range 17.97–19.90 wt% PLGA, 0.16–1.13 wt% F127 and between 5.54 and ≤20 wt% glass. This research demonstrates the value of a design of experiments approach for the design of novel nerve guidance conduits, and shows that the materials examined may have potential for the repair of peripheral nerve discontinuities.     

Rehearsal and verbal reminders in facilitating compliance with safety rules

Accidents and incidents often occur, because a basic and seemingly simple rule is ‘forgotten’, either unintentionally (error, lapse) or with some degree of deliberate negligence (violation). The present experiment examined the utility of a rehearsal and a last-minute reminder in reducing the magnitude of deviations from an important safety rule by qualified, but relatively inexperienced pilots, specifically, remaining above an altitude of 500-ft. A single rehearsal flight entailing a search for a target on the ground increased the minimum altitude in later flights, but this positive effect did not completely generalize when the target on the ground was changed. These results suggest that the rehearsal flight was encoded in a context-specific manner. The addition of an explicit, last minute reminder about the mandated minimum altitude just before each test flight failed to significantly alter the pilots’ behavior. The results are discussed with respect to their theoretical and practical implications.     

Family physicians'' utilization of a brief smoking cessation program following reinforcement contact after training: a randomized trial

Viral infections may induce an acquired form of immunodeficiency, generally lasting a few weeks. In the more severe form, such as HIV infection, the immunodeficiency is permanent. Programmed death of T cells represents one of the mechanisms by which HIV determines the T cell functional impairment, finally resulting in the destruction of T cells. In this study, we evaluated whether an altered regulation of apoptosis was also implicated in the anergy associated with the common measles or varicella-zoster virus (VZV) infections in infancy. A spontaneous apoptosis of peripheral blood mononuclear cells was observed in children who had suffered from these infections as long as 6 mo after the acute disease. Apoptosis was demonstrated through analysis of cellular DNA content, morphologic evidence of cell nuclei shrinkage, and by analysis of DNA degradation. Stimulation of T cells through anti-CD4 MAb increased the number of apoptotic cells with a maximal effect 72 h after the stimulation. Our results suggest that apoptosis may account for the anergy that follows acute viral infections in infancy.     

Cocaine-induced effects on isolation stress in neonatal rats.

The effects of cocaine administration on isolation-induced vocalizations and activity levels in 10-day-old rat pups were examined. Day 10 pups given cocaine (1.25, 2.5, 5, 10, and 20 mg/kg ip) vocalized significantly less than their caffeine- (10 mg/kg) and saline-administered siblings during a 5-min isolation period. Cocaine- and caffeine-administered pups also demonstrated a significant increase in overall activity compared with controls. In addition, ip administration of the dopamine antagonist haloperidol (0.5 and 1.0 mg/kg) before 1.25 and 2.5 mg/kg cocaine produced a significant elevation in vocalizations compared with saline pretreatment, which indicates a blocking of cocaine's effect on calling behavior. These results suggest that the endogenous dopamine system involved with reinforcement and reward may quell the stress of isolation in the infant rat. (PsycINFO Database Record (c) 2010 APA, all rights reserved)