Exercise intensities modulate cognitive function in spontaneously hypertensive rats through oxidative mediated synaptic plasticity in hippocampus

Background

Oxidative damage in the brain may lead to cognitive impairments. There was considerable debate regarding the beneficial effects of physical exercise on cognitive functions because exercise protocols have varied widely across studies.

Purpose

We investigated whether different exercise intensities alter performance on cognitive tasks.

Methods

The experiment was performed on spontaneously hypertensive rats (6 months at the established phase of hypertension) distributed into 3 groups: sedentary, low-intensity exercise, and high-intensity exercise.

Results

Systolic blood pressure measurements confirmed hypertension in spontaneously hypertensive rats. In comparison to normotensive Wistar-Kyoto rats, sedentary spontaneously hypertensive rats had similar escape latencies and a similar preference for the correct quadrant in the probe trial. Compared to the sedentary group, the low-intensity exercise group had significantly better improvements in spatial memory assessed by Morris water maze. Low-intensity exercise was associated with attenuated reactive oxygen species, as measured by dihydroethidine fluorescence and nitrotyrosine staining in the dentate gyrus of the hippocampus. This was coupled with increased numbers of neurons and dendritic spines as well as a significant upregulation of synaptic density. In contrast, the beneficial effects of low-intensity exercise are abolished in high-intensity exercise as shown by increased free radical levels and an impairment in spatial memory.

Conclusions

We concluded that exercise is an effective strategy to improve spatial memory in spontaneously hypertensive rats even at an established phase of hypertension. Low-intensity exercise exhibited better improvement on cognitive deficits than high-intensity exercise by attenuating free radical levels and improving downstream synaptic plasticity.

Funding Acknowledgement

Type of funding sources: None.

Comparing shade tolerance measures of woody forest species

Shade tolerance, the minimum light requirement for plant survival, is a key trait for understanding community assembly and forest dynamics. However, it is poorly defined for tree species to date. Current methods of measuring shade tolerance vary considerably in their performance. For instance, some measures of shade tolerance are unreliable except under some specific conditions. Therefore, it is necessary to compare the performance of these methods to provide guidance of choosing appropriate shade tolerance measures in future studies. We collected a large dataset of light traits and other life history traits for 137 understory wood species in a subtropical forest and tested the performance of five commonly used shade-tolerance indices. Results showed that all the shade-tolerance measures, except the low-light abundance index, performed poorly in distinguishing and ranking shade tolerance of the tested species. The shade tolerance quantified by the low-light abundance was consistent with empirical classification of shade-tolerance/intolerance groups and successional seral stages of species. Comparison of the shade tolerance between trees of different diameter at breast height (DBH) or height classes further confirmed the reliability of low-light abundance. We conclude that low-light abundance is the most objective and practical of the five most commonly-used methods for measuring and ranking shade tolerance of understory wood species in our study forest, and likely in other forests as well. The simplicity of the method should greatly facilitate the assessment of light niche differentiation between species and thus contribute to understanding coexistence of tree species in forests.

Effect of Load Deflection on Corrosion Behavior of NiTi Wire

For dental orthodontic applications, NiTi wires are used under bending conditions in the oral environment for a long period. The purpose of this study was to investigate the effect of bending stress on the corrosion of NiTi wires using potentiodynamic and potentiostatic tests in artificial saliva. The results indicated that bending stress induces a higher corrosion rate of NiTi wires in passive regions. It is suggested that the passive oxide film of specimens would be damaged under bending conditions. Auger electron spectroscopic analysis showed a lower thickness of passive films on stressed NiTi wires compared with unstressed specimens in the passive region. By scanning electron microscopy, localized corrosion was observed on stressed Sentalloy specimens after a potentiodynamic test at pH 2. In conclusion, this study indicated that bending stress changed the corrosion properties and surface characteristics of NiTi wires in a simulated intra-oral environment.

The use of oral sildenafil for management of right ventricular dysfunction after pediatric heart transplantation

High pulmonary vascular resistance index (PVRI) can lead to right ventricular dysfunction and failure of the donor heart early after pediatric heart transplantation. Oral pulmonary vasodilators such as sildenafil have been shown to be effective modifiers of pulmonary vascular tone. We performed a retrospective, observational study comparing patients treated with sildenafil ("sildenafil group") to those not treated with sildenafil ("nonsildenafil group") after heart transplantation from 2007 to 2012. Pre- and posttransplant data were obtained, including hemodynamic data from right heart catheterizations. Twenty-four of 97 (25%) transplant recipients were transitioned to sildenafil from other systemic vasodilators. Pretransplant PVRI was higher in the sildenafil group (6.8 ± 3.9 indexed Woods units [WU]) as compared to the nonsildenafil group (2.5 ± 1.7 WU, p=0.002). In the sildenafil group posttransplant, there were significant decreases in systolic pulmonary artery pressure, mean pulmonary artery pressure, transpulmonary gradient and PVRI (4.7 ± 2.9 WU before sildenafil initiation to 2.7 ± 1 WU on sildenafil, p=0.0007). While intubation time, length of inotrope use and time to hospital discharge were longer in the sildenafil group, survival was similar between both groups. Oral sildenafil was associated with a significant improvement in right ventricular dysfunction and invasive hemodynamic measurements in pediatric heart transplant recipients with high PVRI early after transplant.

Adolescent changes in the homeostatic and circadian regulation of sleep

Sleep deprivation among adolescents is epidemic. We argue that this sleep deprivation is due in part to pubertal changes in the homeostatic and circadian regulation of sleep. These changes promote a delayed sleep phase that is exacerbated by evening light exposure and incompatible with aspects of modern society, notably early school start times. In this review of human and animal literature, we demonstrate that delayed sleep phase during puberty is likely a common phenomenon in mammals, not specific to human adolescents, and we provide insight into the mechanisms underlying this phenomenon.

Effects of passivation treatments on titanium alloy with nanometric scale roughness and induced changes in fibroblast initial adhesion evaluated by a cytodetacher

Passivation treatments of titanium alloy alter not only its nanosurface characteristics of oxides and ion release but also surface roughness (Ra), and wettability as well, where nanosurface characteristics of oxides include chemistries of oxides, amphoteric-OH groups adsorbed on oxides, and oxide thickness. Consequently, the passivation treatment affects the alloy's cyto-comparability. In this study, we polish specimens to achieve nanometric scale roughness. In addition, treatment effects are evaluated for surface topology, roughness, wettability, and responses of fibroblasts consisting of MTT assay, initial adhesion strength, and morphology. The initial adhesion strength is measured using a cyto-detacher that achieves nano-Newton resolution. Results reveal that (1) the treatment effects on the percentage of Ti--OH basic groups and wettability are nearly collinear; (2) the Ra of passivated Ti-6Al-4V ranges from 1.9 to 7.4 nm; (3) the initial adhesion strength of fibroblast ranges from 58 to 143 nN, and it is negatively correlated to the Ra; (4) the passivation results in distinguishable morphologies, which further substantiate the negative correlation between cell initial adhesion force and Ra; and (5) our results fall short of confirming previous reports that found positively charged functional groups promoting fibroblast attachment and spread. Potential causes of the inconsistency are addressed.

Effects of nano-surface properties on initial osteoblast adhesion and Ca/P adsorption ability for titanium alloys

Titanium alloys (Ti6Al4V), while subjected to high temperature surface treatment, experience altered nano-surface characteristics. The effects of such surface treatments are examined, including the initial adhesion force experienced by osteoblasts, the Ca/P adsorption capability, and the nano-surface properties, including the amounts of amphoteric Ti-OH groups, surface topography, and surface roughness. The initial adhesion force is considered a quantitative indicator of cyto-compatibility in vitro. Previously, a cyto-detacher was applied in a pioneer attempt measuring the initial adhesion force of fibroblasts on a metal surface. Presently, the cyto-detacher is further applied to evaluate the initial adhesion force of osteoblasts. Results reveal that (1) titanium alloys subjected to heat treatment could promote the adsorption capability of Ca and P; (2) titanium alloys subjected to heat treatment could have higher initial osteoblast adhesion forces; (3) the adhesion strength of osteoblasts, ranging from 38.5 to 58.9 nN (nanonewtons), appears stronger for rougher surfaces. It is concluded that the heat treatment could have impacted the biocompatibility in terms of the initial osteoblast adhesion force and Ca/P adsorption capability.

Characteristics of hydroxyapatite coated titanium porous coatings on Ti-6Al-4V substrates by plasma sprayed method

A porous metal coating applied to solid substrate implants has been shown, in vivo, to anchor implants by bone ingrowth. Calcium phosphate ceramics, in particular hydroxyapatite [Ca(10)(PO(4))(6)(OH)(2), HA], are bioactive ceramics, which are known to be biocompatible and osteoconductive, and these ceramics deposited on to porous-coated devices may enhance bone ingrowth and implant fixation. In this study, bi-feedstock of the titanium powder and composite (Na(2)CO(3)/HA) powder were simultaneously deposited on a Ti-6Al-4V substrate by a plasma sprayed method. At high temperature of plasma torch, the solid state of Na(2)CO(3) would decompose to release CO(2) gas and then eject the molten Ti powder to induce the interconnected pores in the coatings. After cleaning and soaking in deionized water, the residual Na(2)CO(3) in the coating would dissolve to form the open pores, and the HA would exist at the surface of pores in the inner coatings. By varying the particle size of the composite powder, the porosity of porous coating could be varied from 25.0 to 34.0%, and the average pore size of the porous coating could be varied to range between 158.5 and 202.0 microm. Using a standard adhesive test (ASTM C-633), the bonding strength of the coating is between 27.3 and 38.2 MPa. By SEM, the HA was observed at the surface of inner pore in the porous coating. These results suggest that the method exhibits the potential to manufacture the bioactive ceramics on to porous-coated specimen to achieve bone ingrowth fixation for biomedical applications.

In vitro andin vivo biological responses of plasma-sprayed hydroxyapatite coatings with posthydrothermal treatment

This study was undertaken to evaluate the effect of post-hydrothermal treatment on the biological responses of the plasma-sprayed hydroxyapatite (HA)-coated Ti-6Al-4V implant system both in vitro and in vivo. After hydrothermal treatment, the HA coating (HAC) shows the high mechanical strength and indices-of-crystallinity, denser microstructure, lower concentrations of amorphous and impurity phases, when compared with the as-sprayed HAC. The in vitro cell-culture studies, using UMR106 osteoblast-like cell, demonstrated no signifiacnt cell growth on both surface of as-sprayed and hydrothermal-treated HACs during 10-day culture. The in vivo studies, using the transcortical implant model in the femora of goats, evaluated the histological responses of two coatings. After 6 week of implantation, using backscattered electron images, no substantial histological variations in the extents of new bone apposition and new bone healing between the two HACs were observed. However, the as-sprayed HAC, owing to the dissolution induced the granular particles dissociated from the HAC, showed the statically lower extent of new bone apposition than hydrothermal-treated HAC at 12 weeks. The results suggest that hydrothermal treatment could be used to improve the mechanical strength, crystallinity, and phase composition of HAC, which are important factors of long-term fixation and stability of implant. Besides, the treated HAC could also achieve the initial fixation of implant in clinical use.

Developmental programming in sheep: administration of testosterone during 60-90 days of pregnancy reduces breeding success and pregnancy outcome

Evidence suggests that exposure to excess steroids during critical periods of fetal development leads to reproductive disorders. Exposure of female lambs to excess testosterone (T) from Days 60 to 90 of gestation (T60-90; term, 147 days) delayed onset of the LH surge and resulted in to male-typical reproductive behavior. The objectives of this study were to test the ability of T60-90 ewes to mate, conceive and lamb during the first three breeding seasons (Years 1, 2 and 3). Pregnant Suffolk ewes were injected with T propionate in cottonseed oil (100mg, im twice weekly) or vehicle (control; C) from Days 60 to 90 of gestation. In Year 1, ewes (C=12, T60-90=12) were kept with a vasectomized ram for 3 months and markings/visual observation of copulations were recorded. Rams had paint applied to their chest to facilitate detection of estrus and mating. All C but only three T60-90 ewes were marked (P<0.001). All ewes were then estrus-synchronized with two injections of prostaglandin F2alpha (20mg, im) given 11 days apart and allowed to mate with a painted, fertile ram. Nine of 12 C and 4 of 12 T60-90 ewes (P=0.1) were mated. Based on estrus and long-term monitoring of progesterone, more C than T60-90 became pregnant (82 and 18%, respectively; P<0.01). In Year 2, to maximize ram exposure, two C and two T60-90 estrus-synchronized ewes were placed with a painted, fertile ram at a time and mated ewes were removed to a nearby pen to force mating with others. Twenty-four hour video monitoring revealed the rams mated more C than T60-90 ewes (83 and 25%, respectively; P=0.01). In both Years 1 and 2, the rams preferred C over T60-90 ewes; therefore in Year 3 rams were given access only to T60-90 ewes. Only four T60-90 estrus-synchronized ewes were placed with a painted ram at a time. Not given an option, 91% of the T60-90 ewes were marked resulting in 4 of 11 (36%; first-service pregnancy rate in the breeding herd was 91%) ewes becoming pregnant to the synchronized estrus. Collectively these studies showed that fertility in T60-90 females was severely compromised, even after overcoming ram preference for controls.

Microstructure and corrosion behavior of porous coatings on titanium alloy by vacuum-brazed method

The microstructural evolution and electrochemical characteristics of brazed porous-coated Ti-6Al-4V alloy were analyzed and compared with respect to the conventionally 1300 degrees C sintering method. The titanium filler metal of low-melting-point (934 degrees C) Ti-15Cu-15Ni was used to braze commercially pure (CP) titanium beads onto the substrate of Ti-6Al-4V alloy at 970 degrees C for 2 and 8 h. Optical microscopy, scanning and transmission electron microscopy, and X-ray diffractometry (XRD) were used to characterize the microstructure and phase of the brazed metal; also, the potentiostat was used for corrosion study. Experimental results indicate that the bead/substrate contact interface of the 970 degrees C brazed specimens show larger contact area and higher radius curvature in comparison with 1300 degrees C sintering method. The microstructure of brazed specimens shows the Widmanstätten structure in the brazed zone and equiaxed alpha plus intergranular beta in the Ti-6Al-4V substrate. The intermetallic Ti2Ni phase existing in the prior filler metal diminishes, while the Ti2Cu phase can be identified for the substrate at 970 for 2 h, but the latter phase decrease with time. In Hank's solution at 37 degrees C, the corrosion rates of the 1300 degrees C sintering and the 970 degrees C brazed samples are similar at corrosion potential (E(corr)) in potentiodynamic test, and the value of E(corr) for the brazed sample is noble to the sintering samples. The current densities of the brazed specimens do not exceed 100 microA/cm2 at 3.5 V (SCE). These results suggest that the vacuum-brazed method exhibits the potentiality to manufacture the porous-coated specimens for biomedical application.

Effect of passivation and surface modification on the dissolution behavior and nano-surface characteristics of Ti-6Al-4V in Hank/EDTA solution

The aim of the present study was to investigate the effects of passivation treatment (34% nitric acid passivation, 400 ( composite function)C heated in air, and aged in 100 ( composite function)C de-ionized water) and surface modification (2 hr and 8 hr vacuum-brazed treatments) on the ion dissolution and nano-surface characteristics of Ti-6Al-4V exposed in Hank's solution with 8.0 mM ethylene diamine tetra-acetic acid (EDTA) at 37 ( composite function)C. The results indicated that the original nano-surface characteristics and microstructure would influence the ion dissolution but not change the capability of the Ca and P adsorption upon immersion. Of the three passivated treatments, 400 ( composite function)C thermal treatment for both 2 hr brazed Ti-6Al-4V (B2) and 8 hr brazed Ti-6Al-4V (B8) exhibits a substantial reduction in the constituent release compared to the acid passivated and water aged treatment, because the thicker thickness and rutile structure of surface oxide could provide the better dissolution resistance for 400 ( composite function)C-treated specimens. Moreover, the reduced Ti(2)Cu and increased alpha -titanium structure in B8 specimen could also improve ion dissolution resistance in comparison with B2 specimen. After soaking in Hank/EDTA solution, the adsorbed non-elemental Ca and P for all groups of specimens were observed by XPS analysis, and the AES depth-profile analysis indicate that the oxide films of all groups of specimens thicken with the longer immersion periods. The increasing oxide thickness may be the factor in the improved dissolution resistance at the longer immersion periods. The relation between lower dissolution rate and thicker oxide films were observed for all groups of specimens. The results suggest that the dissolution kinetics was governed by the metal ion transport through the oxide film in this study.

Effect of anti-hypertensive drug dose frequency on the clinic-home blood pressure difference in patients with stage 1 treated hypertension

Clinic blood pressure (CBP) is generally used for diagnosis and treatment monitoring in hypertension, but target organ damage correlates more closely with home blood pressure (HBP). Eliminating the clinic-home blood pressure difference (CHBPD) would make conventional CBP a more accurate alternative to HBP. This prospective, randomized, open trial compared the effect of a once-daily versus a twice-daily regimen of anti-hypertensive therapy on CHBPD. After a 2-week wash-out period, 85 confirmed stage 1 hypertensive patients were randomized to receive 2 mg trichlormethiazide daily in one (40 subjects) or two (45 subjects) daily doses for 3 weeks. CBP and HBP measurements were taken during the third week of treatment and the CHBPD calculated. After treatment, the systolic and diastolic CHBPD values were significantly greater in the once-daily regimen than in the twice-daily regimen. Conventional CBP should not be used as an alternative to HBP for evaluating prognosis and monitoring anti-hypertensive therapy when using a once-daily regimen.

Glaucoma studies in the eyeless worm: stress responsiveness and temporal expression of the Caenorhabditis elegans myocilin-like gene, cof-2

Prolonged exposure to stress and the resulting over-stimulation of the HPA system are often detrimental to the homeostasis of an organism. In fact, chronic stress is believed to affect the pathology of several disease states including coronary heart disease and hypertension, diabetes and obesity. In humans, mutations in the GLC1A gene have been associated with primary open angle glaucoma. Previous studies on this gene have suggested that its expression is also affected by the same factors that mediate the stress response. With the ultimate goal of using the nematode, Caenorhabditis elegans, as an invertebrate model for glaucoma, we have measured the stress responsiveness of the cof-2 gene, one of two C. elegans proteins with significant homology to the myocilin olfactomedin domain. We show that both cof-2 mRNA and protein expression are developmentally regulated and that both are affected by heat shock stress.

Comparison of plasma-sprayed hydroxyapatite coatings and zirconia-reinforced hydroxyapatite composite coatings:In vivo study

The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has been widely adopted because the HA coating can achieve the firmly and directly biological fixation with the surrounding bone tissue. However, the long-term mechanical properties of HA coatings has been concern for the long-term clinical application. Previous research showed that the concept of adding ZrO2 as second phase to HA significantly increased the bonding strength of plasma-sprayed composite material. The present work aimed to explore the biological properties, including the histological responses and shear strength, between the plasma-sprayed HA and HA/ZrO2 coating, using the transcortical implant model in the femora of canines. After 6 and 12 weeks of implantation, the HA coating revealed the direct bone-to-coating contact by the backscattered electron images (BEIs) of scanning electron microscope (SEM), but the osseointegration was not observed at the surface of HA/ZrO2 coating. For new bone healing index (NBHI) and apposition index (AI), the values for HA implants were significantly higher than that for HA/ZrO2 coatings throughout all implant periods. After push-out test, the shear strength of HA-coated implants were statistically higher than HA/ZrO2 coated implants at 6- and 12-week implantation, and the failure mode of HA/ZrO2 coating was observed at the coating-bone interface by SEM. The results indicate that the firm fixation between bone and HA/ZrO2 has not been achieved even after 12-week implantation. Consequently, the addition of ZrO2 could improve the mechanical properties of coatings, while the biocompatibility was influenced by the different material characteristics of HA/ZrO2 coating compared to HA coatings.

Attachment and proliferation of neonatal rat calvarial osteoblasts on Ti6Al4V: effect of surface chemistries of the alloy

This study examined the cell attachment and proliferation of neonatal rat calvarial osteoblasts on Ti6Al4V alloy as affected by the surface modifications. The modifications could alter simultaneously the surface chemistries of the alloy (elemental difference of Ti, Al, V, Cu and Ni about 300-600mum thick examined by EDS) as well as the XPS nano-surface characteristics of oxides on the metal surface (chemistries of oxides, amphoteric OH group adsorbed on oxides, and oxide thickness). Three materials including two from modifications and a control were examined. It is argued that a slight change of the nano-surface characteristics of oxides as a result of the modifications neither alters the in vitro capability of Ca and P ion adsorption nor affects the metal ion dissolution behavior of the alloy. This implies that any influence on the cytocompatibility of the materials should only be correlated to the effect of surface chemistries of the alloy and the associated metal ion dissolution behavior of the alloy. The experimental results suggest that the cell response of neonatal rat calvarial osteoblasts on the Ti6Al4V alloy should neither be affected by the variation of surface chemistries of the alloy in a range studied.

Effect of surface chemistries and characteristics of Ti6Al4V on the Ca and P adsorption and ion dissolution in Hank's ethylene diamine tetra-acetic acid solution

This study examined the influence of chemistries and surface characteristics of Ti6Al4V on the adsorption of Ca and P species and ion dissolution behavior of the material exposed in Hank's solution with 8.0 mM ethylene diamine tetra-acetic acid at 37 degrees C. The variation of chemistries of the alloy and nano-surface characteristics (chemistries of nano-surface oxides, amphoteric OH group adsorbed on oxides, and oxide thickness) was effected by surface modification and three passivation methods (34% nitric acid passivation. 400 degrees C heated in air, and aged in 100 degrees C water). X-ray photoelectron spectroscopy and Auger electron spectroscopy were used for surface analyses. The chemistries of nano-surface oxides in a range studied should not change the capability of Ca and P adsorption. Nor is the capability affected significantly by amphoteric OH group and oxide thickness. However, passivations influence the surface oxide thickness and the early stage ion dissolution rate of the alloy. The rate-limiting step of the rate can be best explained by metal-ion transport through the oxide film, rather than hydrolysis of the film. Variation of the chemistries of titanium alloy alters the electromotive force potential of the metal, thereby affecting the corrosion and ion dissolution rate.

Paternal behavior is associated with central neurohormone receptor binding patterns in meadow voles (Microtus pennsylvanicus)

Paternal and nonpaternal voles (microtus) have different arginine-vasopressin (AVP) and oxytocin (OT) receptor patterns in the extended amygdala, a neural pathway associated with parental behavior. Using receptor autoradiography, the authors examined whether AVP and OT receptor patterns were associated with facultative paternal behavior in either sexually and parentally inexperienced or experienced meadow voles (Microtus pennsylvanicus). Experienced, in contrast to inexperienced, males had less AVP binding in the lateral septum (LS), more AVP binding in the anterior olfactory nucleus (AON), and more OT binding in the AON, bed nucleus of the stria terminalis, LS, and lateral amygdala. Thus, specific AVP receptor patterns, which co-occur with paternal care in consistently paternal voles, also may be associated with paternal care (when present) in typically nonpaternal species. This study also demonstrated a possible relationship between OT receptor patterns and paternal state in male mammals.

Efficacy and safety of barnidipine compared with felodipine in the treatment of hypertension in Chinese patients

The efficacy and safety profiles of barnidipine in the treatment of hypertension were evaluated in an open parallel-group study. Fifty-nine Chinese patients with mild-to-moderate essential hypertension were randomized to receive either barnidipine or felodipine (5 mg once daily, titrated to 10 mg or 15 mg once daily, as indicated) for 12 weeks. Both drugs reduced blood pressures significantly with > or = 68% of cases obtaining marked or moderate blood pressure reduction. Mean reductions in systolic and diastolic blood pressure for barnidipine treatment were 23.7 +/- 13.5 mmHg and 12.7 +/- 7.9 mmHg, and for felodipine, 24.3 +/- 18.4 mmHg and 14.5 +/- 10.0 mmHg, respectively. There was no significant difference between these two drugs in anti-hypertensive effect, heart rate, laboratory measurements or incidence of adverse events. The only difference was that more patients taking felodipine experienced palpitations. We conclude that barnidipine has similar efficacy and a similar safety profile to felodipine in the treatment of mild-to-moderate essential hypertension in Chinese patients.

The cell attachment and morphology of neonatal rat calvarial osteoblasts on the surface of Ti-6Al-4V and plasma-sprayed HA coating: effect of surface roughness and serum contents

The biocompatibility of material plays an important role in the bone-implant interface for the prosthetic implant fixation. The biocompatibility of implants is associated with the chemical composition, surface topography, surface energy and surface roughness of biomaterials. The effects of two factors, surface roughness and serum contents, on osteoblast behavior at the surface of Ti-6Al-4V and plasma sprayed HA coating were investigated in the experiment. The osteoblasts derived from neonatal rat calvarial were cultured in Dulbecco's modified Eagle medium (DMEM) with fetal bovine serum (FBS) on the surface of polished Ti-6Al-4V (Ti-p), grit-blasted Ti-6Al-4V (Ti-b), polished HA coating (HAC-p), and as-sprayed HA coating (HAC). Under culture medium containing 4% FBS, the level of cell attachment to the polished surface is significantly higher than the rough surface of the same experimental materials during all culture periods. Increasing the contents of FBS up to 10%, the difference of osteoblast attachment is not found between Ti-p and Ti-b. Under 4% serum condition, the cell morphology attached to smooth surfaces (Ti-p and HAC-p) is spread faster and are more flattened than the one to rough surface of the same experimental materials by SEM. After 24 h culture, the corroded cracks are easily observed at the surface of polished HA coatings, and the cell morphology on HAC-p coatings are elongated and less flattened compared with Ti-p. The result is consistent with statistical difference of cell attachment between Ti-p and HAC-p under 4% serum condition.

Biological responses of neonatal rat calvarial osteoblasts on plasma-sprayed HA/ZrO2 composite coating

Plasma-sprayed hydroxyapatite (HA) coating, applied to metal substrates, can induce a direct chemical bond with bone and hence achieve a biological fixation of the implant. However, the poor bonding strength between the HA coating and the substrate has been a concern for the orthopedists. In a previous study, the zirconia-reinforced hydroxyapatite composite coatings (HA/ZrO(2)) could significantly improve the mechanical strength before and after soaking in simulated body fluid. This study aims to investigate the biological responses of osteoblasts on plasma-sprayed HA/ZrO(2) coating. The osteoblasts derived from neonatal rat calvarial were cultured in Dulbecco's modified Eagle medium (DMEM) with fetal bovine serum (FBS) on the surface of plasma-sprayed HA coating, HA/ZrO(2) coating, and ZrO(2) coating, respectively. The biological responses were investigated by the cell growth (1, 3, 5, and 10 days) and the cell morphology under scanning electron microscopy (SEM) (3, 6, 12, 24 and 48 h). Examination by SEM revealed that osteoblasts on HA coatings exhibit less spreading during the medium phase (6 and 12 h), while, better morphologies were observed at the latter phases (24 and 48 h). This should be derived by the dissolution of HA coating in the culture medium. On HA/ZrO(2) coating, the cells showed the poor morphologies at the latter phases (24 and 48 h). This could be explained by the no apatite formed at the surface HA/ZrO(2) coating after soaking in simulated body fluid. The lower contents of ZrO(2) coating in HA coating and the addition of other solid solution (ZrO(2)-MgO, CaO-ZrO(2), ZrO(2)-CeO(2)) in HA coating are the two possible methods to improve the cytocompatibility of HA/ZrO(2) coating.

Temporal reorganization of the suprachiasmatic nuclei in hamsters with split circadian rhythms

A dual oscillator basis for mammalian circadian rhythms is suggested by the splitting of activity rhythms into two components in constant light and by the photoperiodic control of pineal melatonin secretion and phase-resetting effects of light. Because splitting and photoperiodism depend on incompatible environmental conditions, however, these literatures have remained distinct. The refinement of a procedure for splitting hamster rhythms in a 24-h light-dark:light-dark cycle has enabled the authors to assess the ability of each of two circadian oscillators to initiate melatonin secretion and to respond to light pulses with behavioral phase shifting and induction of Fos-immunoreactivity in the suprachiasmatic nuclei (SCN). Hamsters exposed to a regimen of afternoon novel wheel running (NWR) split their circadian rhythms into two distinct components, dividing their activity between the latter half of the night and the afternoon dark period previously associated with NWR. Plasma melatonin concentrations were elevated during both activity bouts of split hamsters but were not elevated during the afternoon period in unsplit controls. Light pulses delivered during either the nighttime or afternoon activity bout caused that activity component to phase-delay on subsequent days and induced robust expression of Fos-immunoreactivity in the SCN. Light pulses during intervening periods of locomotor inactivity were ineffective. The authors propose that NWR splits the circadian pacemaker into two distinct oscillatory components separated by approximately 180 degrees, with each expressing a short subjective night.

Social and environmental factors influence the suppression of pup-directed aggression and development of paternal behavior in captive meadow voles (Microtus pennsylvanicus)

During summer, female meadow voles (Microtus pennsylvanicus) maintain territories and males do not engage in paternal care. As day length shortens, territories dissolve and males nest with females and young. Because paternal behavior has never been studied in free-living meadow voles during colder months or in the laboratory under short photoperiods, the authors examined whether males housed in short day (SD) lengths exhibited more frequent or better quality paternal behavior than males housed in long day (LD) lengths. Sexually and parentally inexperienced (naive) SD males exhibited proportionally more and qualitatively better paternal care than naive LD males. SD males were more responsive than LD males to classic social cues associated with prepartum aggression inhibition and paternal onset. SD sires also displayed qualitatively better paternal behavior than LD sires. These data suggest that meadow vole paternal state is regulated by specific social and environmental cues that may contain reliable information about ecological conditions that favor paternal care.