Combined VEGF and bFGF loaded nanofiber membrane protects against neuronal injury and hypomyelination in a rat model of chronic cerebral hypoperfusion

Currently, there are no effective therapeutic targets for the treatment of chronic cerebral hypoperfusion(CCH)-induced cerebral ischemic injury. Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) are discovered as the inducers of neurogenesis and angiogenesis. We previously made a nanofiber membrane (NFM), maintaining a long-term release of VEGF and bFGF up to 35 days, which might make VEGF and bFGF NFM as the potential protective agents against cerebral ischemic insult. In this study, the effects of VEGF and bFGF delivered by NFM into brain were investigated as well as their underlying mechanismsin a rat model of CCH. VEGF + bFGF NFM application increased the expressions of tight junction proteins, maintained BBB integrity, and alleviated vasogenic cerebral edema. Furthermore, VEGF + bFGF NFM sticking enhanced angiogenesis and elevated CBF. Besides, VEGF + bFGF NFM treatment inhibited neuronal apoptosis and decreased neuronal loss. Moreover, roofing of VEGF + bFGF NFM attenuated microglial activation and blocked the launch of NLRP3/caspase-1/IL-1β pathway. In addition, VEGF + bFGF NFM administration prevented disruption to the pre/postsynaptic membranes and loss of myelin sheath, relieving synaptic injury and demyelination. Oligodendrogenesis, neurogenesis and PI3K/AKT/mTOR pathway were involved in the treatment of VEGF + bFGF NFM against CCH-induced neuronal injury and hypomyelination. These findings supported that VEGF + bFGF NFM application constitutes a neuroprotective strategy for the treatment of CCH, which may be worth further clinical translational research as a novel neuroprotective approach, benifiting indirect surgical revascularization.

[The status and influencing factors of presenteeism among clinical nurses: a systematic review]

Objective: To systematically review the status and factors influencing presenteeism among clinical nurses. Methods: In December 2021, CNKI, CBM, Wanfang, VIP, Web of Science, PubMed, Embase, The Cochrane Library, CINAHL, PsyclNFO and other databases were electronically searched to cross sectional studies on the current situation and factors influencing the occurrence of presenteeism among clinical nurses. The search terms mainly included presenteeism, sick at work, Stanford Presenteeism Scale, nurse, level, risk factor, influence, et al. And the search time was from the establishment of the database to November 30, 2021. Literature screening, data extraction and evaluation of the risk of bias in the included literature were done independently by two researchers, and meta-analysis was performed using Stata 15.1 software. Results: A total of 29 studies involving 13 535 clinical nurses were included.The results of the meta-analysis showed that the score of presenteeism was 17.99 [95% CI (17.02-18.95), P =0.000]. Subgroup analysis showed that presenteeism scores were higher in articles published before 2020 (ES=19.28, 95%CI: 18.41-20.15, P=0.000) and in the group of nurses aged 36 to 40 years (ES=19.27, 95%CI: 17.35~21.19, P=0.000), female (ES= 17.04, 95%CI: 14.70-19.39, P=0.000), secondary school education (ES=21.01, 95%CI: 17.76-24.26, P= 0.007), married (ES=17.49, 95%CI: 15.13-19.85, P=0.000), working for 5 to 10 years (ES=17.78, 95%CI: 16.54-19.02, P=0.000), contract (ES=17.05, 95%CI: 15.23-18.87, P=0.000), working in pediatrics (ES= 16.65, 95% CI: 15.31-17.99, P=0.000) and European region (ES =21.21, 95% CI: 20.50-21.93, P=0.000) . Conclusion: Current evidence suggests that clinical nurses are at high risk of presenteeism, which is affected by variety of factors. The managers should pay attention to the physical and mental health of nurses, identify high-risk factors as early as possible and take measures to reduce the occurrence of presenteeism and improve the quality of nursing.

VEGF loaded nanofiber membranes inhibit chronic cerebral hypoperfusion-induced cognitive dysfunction by promoting HIF-1a/VEGF mediated angiogenesis

We investigated the potential effects and mechanisms of vascular endothelial growth factor (VEGF)-nanofiber membranes (NFMs) treatment in a rat model of chronic cerebral hypoperfusion (CCH). VEGF-NFMs treatment promoted angiogenesis in surgical temporal cortex and hippocampus, alleviating decreased CBF in these two cerebral regions. VEGF-NFMs application improved reduced NAA/Cr ratio, preventing neuronal loss. VEGF-NFMs sticking decreased the number of TUNEL-positive cells in surgical temporal cortex, ameliorated impaired synaptic plasticity, and inhibited the release of pro-inflammatory cytokines and the activation of microglia and astrocytes in surgical temporal cortex and hippocampus. Furthermore, BDNF-TrkB/PI3K/AKT, BDNF-TrkB/ERK and HIF-1a/VEGF/ERK pathways were involved in the treatment of VEGF-NFMs against CCH-induced neuronal injury. These results showed the neuroprotective effects of VEGF-NFMs sticking may initiate from neurovascular repairing followed by inhibition of neuronal apoptosis and neuronal and synaptic damage, eventually leading to the suppression of cognitive dysfunction, which provided theoretical foundation for further clinical transformation of VEGF-NFMs.

Fecal microbiota transplantation and replenishment of short-chain fatty acids protect against chronic cerebral hypoperfusion-induced colonic dysfunction by regulating gut microbiota, differentiation of Th17 cells, and mitochondrial energy metabolism

BACKGROUND

Little is known about the association between gut microbiota and intestinal injury under a state of chronic cerebral hypoperfusion (CCH). Here, the effects of gut microbiota and short-chain fatty acids (SCFAs), as important metabolic products, on intestinal function and potential mechanisms after CCH were investigated.

METHODS

Rats were subjected to bilateral common carotid artery occlusion (BCCAo) to induce CCH. The gut microbiota and metabolites of SCFAs were assessed by 16S rRNA sequencing and targeted metabolomics, respectively. Transcriptomic analysis of colon tissues was also conducted. Subsequently, potential molecular pathways and differentially expressed genes were verified by western blot, immunoprecipitation, and immunofluorescence analyses. Furthermore, the integrity of the colonic barrier was evaluated by hematoxylin and eosin and mucin 2 staining and expression levels of tight junction proteins. Besides, colonic inflammation was further assessed by flow cytometry and expression levels of inflammatory cytokines. In addition, colonic mitochondrial dysfunction was analyzed via membrane potential, reactive oxygen species, electron transport chain (ETC) activities, adenosine triphosphate content, and mitochondrial ultrastructure.

RESULTS

CCH modified gut microbial composition and microbial metabolism of SCFAs, which may be associated with inhibition of mitochondrial ETC activities and oxidative phosphorylation, leading to dysregulation of mitochondrial energy metabolism. Furthermore, CCH induced differentiation of pathogenic Th17 cells, promoted the formation of complexes of interferon regulatory factor 4 and signal transducer and activator of transcription 3 (STAT3), and increased the phosphorylation of STAT3. This was associated with an impairment of colonic barrier function and chronic colonic inflammation. In contrast, FMT and SCFA replenishment ameliorated CCH-induced gut microbial dysbiosis by increasing the intestinal content of Ruminococcus_sp_N15_MGS_57 and modulating microbial metabolism of SCFAs by increasing acetic acid contents associated with an improvment of the balance between Tregs and Th17 cells, mitochondrial ETC activities, and oxidative phosphorylation to prevent colonic inflammation and dysregulation of mitochondrial energy metabolism.

CONCLUSION

These findings indicate that FMT and SCFA replenishment present a promising therapeutic strategy against colonic dysfunction under a state of chronic cerebral ischemia.

Preservation of spatial memory and neuroprotection by the fatty acid amide hydrolase inhibitor URB597 in a rat model of vascular dementia

Background

Chronic cerebral hypoperfusion (CCH) is a major risk factor for vascular dementia (VaD). There are currently no broadly effective prevention or treatment strategies for VaD, but recent studies have reported promising results following vascular bypass surgery and pharmacomodulation of the brain endocannabinoid system (ECS). In this study, early effects of encephalomyosynangiosis (EMS) bypass surgery and augmented endocannabinoid signaling on CCH-induced cognitive dysfunction and neuronal damage were investigated.

Methods

An animal model of VaD was established by bilateral common carotid artery occlusion (BCCAO). Cannabinoid signaling was upregulated by treatment with the fatty acid amide hydrolase inhibitor URB597 (URB). Spatial learning and memory, cerebral blood flow (CBF), revascularization, brain-derived neurotrophic factor (BDNF)-tropomyosin receptor kinase B (TrkB) signaling, and apoptosis were compared among Sham, BCCAO, BCCAO + EMS, BCCAO + URB, and BCCAO + URB + EMS groups. Spatial learning and memory were evaluated using the Morris water maze (MWM). The CBF in cortex and hippocampus was evaluated by 3-dimensional arterial spin labeling. The neovascularization was visualized by CD34 immunofluorescence staining, and BDNF-TrkB signaling protein expression levels were assessed by Western blotting.

Results

Treatment with URB597 but not EMS alone reversed the spatial learning and memory deficits induced by BCCAO. Neovascularization was enhanced after EMS surgery but not by URB597. Alternatively, there were no significant differences in CBF among treatment groups. Expression levels of BDNF and TrkB were significantly reduced by CCH compared to Sham treatment, and downregulation of both proteins was reversed by URB597 treatment but not EMS. BCCAO enhanced neuronal apoptosis, which was also reversed by URB597.

Conclusions

Augmentation of endogenous cannabinoid signaling but not EMS protects against CCH-induced neurodegeneration and preserves spatial learning and memory, possibly by activating BDNF-TrkB signaling.

[Electroacupuncture improves learning-memory ability possibly by suppressing apoptosis and down-regulating expression of apoptosis-related proteins in hippocampus and cerebral cortex in immature mice with Alzheimer's disease]

OBJECTIVE

To investigate the effect of electroacupuncture (EA) at "Baihui"(GV20), "Fengfu"(GV16) and bilateral "Shenshu"(BL23) on learning-memory ability, apoptosis in the hippocampus and expression of Aβ, Caspase 3, Bax and Bcl-2 proteins in the hippocampus and cerebral cortex in immature mice with Alzheimer's disease (AD), so as to explore its mechanism underlying improvement of AD.

METHODS

Forty APP/PS1 transgenic male young mice were equally randomized into model and EA groups and 20 C57BL/6J male young mice were used as the normal control. EA (10 Hz, about 2 mA) was applied to GV20-BL23 and GV16-BL23 for 20 min, once daily, 6 days a week for 16 weeks. The Morris water maze swimming test was used to evaluate the animals' learning-memory ability. Congo red staining and immunohistochemical staining were used to detect senile plaques in the hippocampus (dentate gyrus) and cerebral cortex tissues. Terminal deoxynucleotidyl transferase-mediated dUTP Nick-end Labeling (TUNEL) was used to detect the cellular apoptosis of hippocampus. The expression levels of apoptosis related factors Caspase 3, Bax and Bcl-2 were detected by Western blot.

RESULTS

After modeling, the escape latency of place navigation test of Morris water maze swimming tasks was significantly increased (P<0.05), while the number of platform crossing and residence time in the platform quadrant of spatial exploration test were significantly decreased in the model group in contrast to the normal control group (P<0.05). The number of apoptotic cells in the hippocampus and expression levels of Aβ, Caspase 3 and Bax proteins in the hippocampus and cerebral cortex were significantly up-regulated in the model group relevant to the normal control group (P<0.05). Following EA intervention, the escape latency of place navigation test of Morris water maze swimming tasks was significantly decreased (P<0.05), while the number of platform crossing and residence time in the platform quadrant of spatial exploration test were significantly increased in the EA group in contrast to the model group (P<0.05). The hippocampal apoptotic cells, the expression of Aβ, Caspase 3 and Bax proteins in hippocampus and cerebral cortex were evidently down-regulated in the EA group in contrast to the model group (P<0.05). Whereas the ratio of Bcl-2/Bax was significantly decreased in the model group relevant to the normal control group (P<0.05) and considerably increased in the EA group in contrast to the model group (P<0.05). No significant changes were found in the expression levels of Bcl-2 after modeling and after EA intervention (P>0.05).

CONCLUSION

EA of GV20, GV16 and BL23 can effectively improve the learning-memory ability in AD mice, which may be related to its function in inhibiting neuronal apoptosis in the hippocampus and down-regulating the expression levels of Aβ, Caspase 3 and Bax proteins in both hippocampus and cerebral cortex.

Neuroprotective effects of andrographolide on chronic cerebral hypoperfusion-induced hippocampal neuronal damage in rats possibly via PTEN/AKT signaling pathway

To explore the potential effects of andrographolide on chronic cerebral hypoperfusion (CCH)-induced neuronal damage as well as the underlying mechanisms. Rat CCH model was established by 2-vessel occlusion (2VO). The CCH rats received andrographolide treatment for 4 weeks. The neuron loss was detected by using neuronal nuclei (NeuN) immunofluorescent staining. The expression levels of phospho-phosphatase and tensin homolog deleted on chromosome ten (p-PTEN), protein kinase B (AKT), p-AKT, and cysteinyl aspartate specific proteinase-3 (Caspase-3) proteins were accessed by Western blotting. Moreover, the neuronal apoptosis of hippocampus tissues was detected via terminal deoxynucleotidyl transferase- mediated dUTP nick end labeling (TUNEL) staining. CCH reduced the number of NeuN-positive cells, while the number was significant increased after andrographolide treatment. CCH increased the proteins expression level of p-PTEN, Caspase-3, and decreased the p-AKT, which were reversed by andrographolide treatment. Furthermore, andrographolide treatment also down-regulated CCH-induced TUNEL-apoptosis rate. Our results suggest that the PTEN/AKT pathway may be modulated by andrographolide and the damaging effects of CCH on hippocampus may be ameliorated by andrographolide treatment. Andrographolide may act as a potential therapeutic approach for chronic ischemic insults.

[Effects of different concentrations of calcitonin gene-related peptide on long-term depression of hippocampus in mice]

The purpose of this study was to explore the effects of calcitonin gene-related peptide (CGRP) on the long-term depression (LTD) of hippocampus in mice. Sixty C57BL/6J mice (30 days old) were randomly divided into control group, three CGRP (50, 100, and 200 nmol/L) groups, CGRP + CGRP_8-37 group and CGRP + APV group (10 mice for each group). The effects of exogenous application of different concentrations of CGRP on synaptic plasticity and LTD in hippocampus of mice were detected by in vitro recording of local field potential. The results showed that higher doses (100 and 200 nmol/L) of CGRP significantly enhanced the induction of LTD in the hippocampus. Moreover, CGRP increased the magnitude of N-methyl-D-aspartate (NMDA) receptor-mediated excitatory postsynaptic currents. The above-mentioned effects of CGRP were blocked by either CGRP selective antagonist CGRP_8-37 or NMDA receptor antagonist APV. These results suggest that CGRP can dose-dependently enhance the induction of LTD in hippocampus of mice, and the underlying mechanism involves the mediation of NMDA receptor function.

URB597 protects against NLRP3 inflammasome activation by inhibiting autophagy dysfunction in a rat model of chronic cerebral hypoperfusion

Background

Previous studies reported that URB597 (URB) had therapeutic potential for treating chronic cerebral hypoperfusion (CCH)-induced neuroinflammation and autophagy dysfunction. However, the interaction mechanisms underlying the CCH-induced abnormal excessive autophagy and neuroinflammation remain unknown. In this study, we investigated the roles of impaired autophagy in nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing (NLRP) 3 inflammasome activation in the rat hippocampus and the underlying mechanisms under the condition of induced CCH as well as the effect of URB treatment.

Methods

The CCH rat model was established by bilateral common carotid artery occlusion (BCCAo), and rats were randomly divided into 11 groups as follows: (1) sham-operated, (2) BCCAo; (3) BCCAo+autophagy inhibitor 3-methyladenine (3-MA), (4) BCCAo+lysosome inhibitor chloroquine (CQ), (5) BCCAo+microglial activation inhibitor minocycline, (6) BCCAo+ROS scavenger N-acetylcysteine (NAC), (7) BCCAo+URB, (8) BCCAo+URB+3-MA, (9) BCCAo+URB+CQ, (10) BCCAo+URB+minocycline, (11) BCCAo+URB+NAC. The cell localizations of LC3, p62, LAMP1, TOM20 and NLRP3 were assessed by immunofluorescence staining. The levels of autophagy-related proteins (LC3, p62, LAMP1, BNIP3 and parkin), NLRP3 inflammasome-related proteins (NLRP3, CASP1 and IL-1β), microglial marker (OX-42) and proinflammatory cytokines (iNOS and COX-2) were evaluated by western blotting, and proinflammatory cytokines (IL-1β and TNF-a) were determined by ELISA. Reactive oxygen species (ROS) were assessed by dihydroethidium staining. The mitochondrial ultrastructural changes were examined by electron microscopy.

Results

CCH induced microglial overactivation and ROS accumulation, promoting the activation of the NLRP3 inflammasome and the release of IL-1β. Blocked autophagy and mitophagy flux enhanced the activation of the NLRP3-CASP1 inflammasome pathway. However, URB alleviated impaired autophagy and mitophagy by decreasing mitochondrial ROS and microglial overactivation as well as restoring lysosomal function, which would further inhibit the activation of the NLRP3-CASP1 inflammasome pathway.

Conclusion

These findings extended previous studies indicating the function of URB in the mitigation of chronic ischemic injury of the brain.

[Effect of different courses of electroacupuncture intervention on recognition memory and proliferation and differentiation of hippocampal neural stem cells in mice with radiation-induced brain injury]

OBJECTIVE

To observe the influence of different courses of electroacupuncture (EA) intervention on recognition memory and the proliferation and differentiation of hippocampal neural stem cells in mice with radiation-induced brain injury, so as to explore its mechanisms underlying improving radiation-induced brain injury.

METHODS

Se-venty 30-day old C57BL/6J mice were randomly divided into control, model and EA groups, and the latter two groups were further divided into 1 week (W), 2 W and 3 W subgroups (n=10 in the control group and each subgroup). The ra-diation-induced brain injury model was established by radiating the mouse' left head at a dose of 8 Gy for 10 min by using a radiation linear accelerator. EA (1.5 V, 2 Hz/10 Hz) was applied to "Baihui" (GV20), "Fengfu" (GV14) and bilateral "Shenshu" (BL23) for 30 min, once daily for 1, 2 and 3 weeks, respectively. The learning-cognition memory ability was detected by using novel object recognition test in an open test box to record the time for exploring a novel object (TN) and a familiar object and to calculate the recognition index (RI). The neural stem cells' proliferation and differentiation in the hippocampus tissues were evaluated by counting the number of bromodeoxyuridine (BrdU)-labeled cells, neuronal nuclei (NeuN)/BrdU-positive cells and BrdU/glia fibrillary acidic protein (GFAP)-positive cells under microscope after immunofluorescence stain.

RESULTS

After modeling, the TN at 90 min and 24 h and RI of the model subgroup 3 W at 90 min and RI of the model subgroup 1, 2 and 3 W at 24 h were significantly decreased in comparison with those of the control group (P<0.01, P<0.05). Moreover, the number of BrdU-positive cells in the model subgroup 1 W and 2 W, the BrdU/NeuN double-labeled cells in the 3 model subgroups and BrdU/GFAP double-labeled cells in the model subgroup 1 W and 3 W were significantly decreased (P<0.01, P<0.05). Following EA interventions, the TN in the 3 EA subgroups at both 90 min and 24 h, and RI of EA subgroup 3 W at 90 min and EA subgroup 2 W and 3 W at 24 h were considerably increased compared with those of the corresponding 3 model subgroups (P<0.05, P<0.01). The numbers of BrdU-positive cells as well as BrdU/NeuN and BrdU/GFAP double-labeled cells were significantly increased in the 3 EA subgroups (P<0.05, P<0.01, P<0.001).

CONCLUSION

EA of GV20, GV14 and BL23 can improve the recognition memory ability of mice with radiation-induced brain injury, which may be related to its effect in promoting the proliferation and differentiation of stem cells in the hippocampus.

[Effects and mechanisms of electro-acupuncture on proliferation and differentiation of neural stem cells in C57 mice exposed to different doses of X-ray radiation]

The present study was aimed to investigate the effects and mechanisms of electro-acupuncture (EA) on proliferation and differentiation of neural stem cells in the hippocampus of C57 mice exposed to different doses of X-ray radiation. Thirty-day-old C57BL/6J mice were randomly divided into control, irradiation, and EA groups. The control group was not treated with irradiation. The irradiation groups were exposed to different doses of X-ray (4, 8 or 16 Gy) for 10 min. The EA groups were electro-acupunctured at Baihui, Fengfu and bilateral Shenyu for 3 courses of treatment after X-ray radiation. Immunohistochemistry was used to evaluate proliferation and differentiation of the hippocampal neural stem cell. RT-PCR and Western blot were used to detect mRNA and protein expressions of Notch1 and Mash1 in the hippocampus, respectively. The results showed that, compared with the control group, the numbers of BrdU positive cells (4, 8 Gy subgroup) and BrdU/NeuN double-labeling positive cells (3 dose subgroups) were decreased significantly in the irradiation group, but the above changes could be reversed by EA. Compared with the control group, the number of BrdU/GFAP double-labeling positive cells in each dose subgroup of irradiation group was decreased significantly, while EA could reverse the change of 4 and 8 Gy dose subgroups. In addition, compared with the control group, the expression levels of Notch1 mRNA and protein in hippocampus were up-regulated, and the expression levels of Mash1 mRNA and protein were significantly decreased in each dose subgroup of irradiation group. Compared with irradiation group, the expression levels of Notch1 mRNA and protein in hippocampus of EA group were decreased significantly in each dose subgroup, and the expression levels of Mash1 mRNA and protein were increased significantly in 4 and 8 Gy subgroups. These results suggest that irradiation affects the proliferation and differentiation of neural stem cells in hippocampus of mice, whereas EA may significantly increase the proliferation and differentiation of hippocampal neural stem cells via the regulation of Notch signaling pathway.

Andrographolide enhances hippocampal BDNF signaling and suppresses neuronal apoptosis, astroglial activation, neuroinflammation, and spatial memory deficits in a rat model of chronic cerebral hypoperfusion

Andrographolide is a medical herbal compound with documented anti-inflammatory activity and therapeutic efficacy in animal models of Alzheimer's disease, traumatic brain injury, and ischemic stroke. The present study examined the potential therapeutic effects of andrographolide on chronic cerebral hypoperfusion (CCH)-induced hippocampal neuronal damage and cognitive dysfunction. A CCH model was established in male Sprague Dawley (SD) rats using 2-vessel occlusion (2VO). After 4 weeks of CCH, spatial learning and memory were assessed in the Morris water maze and structural damage to the hippocampus by hematoxylin and eosin (HE) staining. Astrocyte activation was examined by immunohistochemical staining and Western blotting for glial fibrillary acid protein (GFAP), while expression levels of the pro-inflammatory cytokine-tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β), the apoptosis effector cysteinyl aspartate specific proteinase-3 (caspase-3), and the neuroprotectant brain-derived neurotrophic factor (BDNF) and the TrkB receptor were estimated by Western blotting. After 4 weeks of CCH, the hippocampus of 2VO rats exhibited marked neurodegeneration as well as elevated GFAP, TNF-α, IL-1β, and caspase-3 compared to Sham controls. In addition, spatial learning was impaired compared to Sham controls. Andrographolide treatment during CCH suppressed astrocyte activation as evidenced by reduced GFAP expression, enhanced expression of BDNF and TrkB, improved impaired spatial learning and memory, and reversed upregulated TNF-α, IL-1β, and caspase-3 expression. These results reveal a potential neuroprotective effect of andrographolide on hippocampal neuronal damage and cognitive impairment from CCH due to suppression of astrocyte activation and enhancement of BDNF-TrkB signaling.

The potential protective effects of cannabinoid receptor agonist WIN55,212-2 on cognitive dysfunction is associated with the suppression of autophagy and inflammation in an experimental model of vascular dementia

Vascular dementia (VaD) is characteristic of chronic brain ischemia and progressive memory decline, which has a high incidence in the elderly. However, there are no effective treatments for VaD, and the underlying mechanism of its pathogenesis remains unclear. This study investigated the effects of a synthetic cannabinoid receptor agonist WIN55,212-2 (WIN) on VaD, and molecular mechanisms of the effects. VaD model was induced by 2-vessel occlusion (2VO). Spatial reference learning was evaluated by the Morris water maze, and recognition memory was assessed using the novel object recognition test. Autophagy-related proteins [microtubule-associated protein 1 light chain 3 (LC-3) and Beclin-1] were examined by immunohistochemistry and Western blot. Caspase-3 was detected by Western blot. Inflammatory factors, tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β), were estimated by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. VaD increased the levels of LC-3, Beclin-1, and inflammatory factors, which were reversed by chronic treatment with WIN. WIN decreased the expression of Capase-3, and improved the learning and memory impairment of VaD rats. These data indicate that WIN exerts a neuroprotective effect on the cognitive deficits of VaD rats, which may be associated with the suppression of excessive autophagy and inflammation.

[Effect of different concentrations of calcitonin gene-related peptide on the long-term potentiation in hippocampus of mice]

The purpose of this study was to explore the effects of different concentrations of calcitonin gene-related peptide (CGRP) on long-term potentiation (LTP) in the hippocampus of mice. C57BL/6J mice (30 days old) were randomly divided into control group, three CGRP groups, and CGRP + CGRP_8-37 group (10 mice for each group). Different concentrations of CGRP (50, 100 and 200 nmol/L) were given to the hippocampal slices of mice. The presynaptic release of neurotransmitters and the induction of LTP were measured by extracellular field recording techniques. The result showed that different concentrations of CGRP did not affect the presynaptic release of neurotransmitters, but 100 and 200 nmol/L CGRP increased the amplitude of LTP induced in the hippocampus of mice. This facilitation effect of CGRP was blocked by its specific antagonist CGRP_8-37. These results suggest that CGRP dose-dependently facilitates the induction of LTP in the hippocampus of mice through its specific receptor.

[Effect of curcumin on intestinal mucosal mechanical barrier in rats with non-alcoholic fatty liver disease]

Objective: To investigate the effect of curcumin on intestinal mucosal mechanical barrier in rats with non-alcoholic fatty liver disease. Methods: A total of 30 male Sprague-Dawley rats were equally divided into normal control group, model group, and curcumin intervention group. The rats in the model group and the curcumin intervention group were given high-fat feed for 16 weeks, and those in the curcumin intervention group were given curcumin 200 mg/kg/day by gavage once a day after 8 weeks of high-fat feeding. The rats were sacrificed at the end of week 16. A light microscope was used to observe pathological changes in the liver, an electron microscope was used to observe the tight junction of the intestinal mucosa, an automatic biochemical analyzer was used to measure the serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), chromogenic substrate Limulus amebocyte lysate assay was used to measure plasma lipopolysaccharide (LPS) level, spectrophotometric method was used to measure the activity of serum diamine oxidase, ELISA was used to measure the serum level of tumor necrosis factor-α (TNFα), and immunohistochemistry was used to measure the expression of the tight junction protein occludin. One-way ANOVA test and SNK-q test were used for statistical analysis. Results: Under the light microscope, the control group had no hepatocyte steatosis, the model group had significant hepatocyte steatosis and inflammatory cell infiltration, and the curcumin intervention group had reduced hepatocyte steatosis and inflammatory cell infiltration. Under the electron microscope, the control group had a clear and complete structure of the tight junction of the intestinal mucosa and normal structures of mitochondria and endoplasmic reticulum; in the model group, the structure of the tight junction of the intestinal mucosa was destroyed, the intercellular space was widened, the desmosomes had a loose structure, there was edema in some mitochondria, and the endoplasmic reticulum was dilated; the curcumin intervention group had improvements in the structure of tight junction of the intestinal mucosa, intercellular space, edema in the mitochondria, and dilation of the endoplasmic reticulum. Compared with the control group, the model group had significant increases in the serum levels of AST, ALT, DAO, TNFα, and LPS (q = -15.918, -14.402, -33.700, -8.944, and -10.832, P < 0.05); compared with the model group, the curcumin intervention group had significant reductions in the serum levels of AST, ALT, DAO, TNFα, and LPS (q = 10.457, 7.752, 18.802, 5.202, and 4.279, P < 0.05). In the control group, occludin showed a linear distribution along the top of small intestinal mucosal epithelial cells. The model group had a significant reduction in positive staining compared with the control group, and the curcumin intervention group had a significant increase in positive staining compared with the model group. The relative expression of occludin was 0.29±0.03 in the control group, 0.12±0.02 in the model group, and 0.21±0.02 in the curcumin intervention group (P < 0.05). Conclusion: Intestinal mucosal mechanical barrier is impaired in rats with NAFLD. Curcumin can reduce such damage, and its mechanism of action may be related to up-regulating the expression of occludin in the intestinal mucosa and reducing the levels of TNFα and LPS.

Cannabinoid receptor agonist WIN55,212-2 and fatty acid amide hydrolase inhibitor URB597 ameliorate neuroinflammatory responses in chronic cerebral hypoperfusion model by blocking NF-κB pathways

The present study explored the protective effects of cannabinoid receptor agonist WIN55,212-2 (WIN) and fatty acid amide hydrolase inhibitor URB597 (URB) against neuroinflammation in rats with chronic cerebral hypoperfusion (CCH). Activated microglia, astrocytes, and nuclear factor kappa B (NF-κB) p65-positive cells were measured by immunofluorescence. Reactive oxygen species (ROS) was assessed by dihydroethidium staining. The protein levels of cluster of differentiation molecule 11b (OX-42), glial fibrillary acidic protein (GFAP), NF-κB p65, inhibitor of kappa B alpha (IκB-a), IκB kinase a/β (IKK a/β), phosphorylated IKK a/β (p-IKK a/β), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), tumor necrosis factor (TNF)-α, and interleukin-1β (IL-1β) were examined by western blotting or enzyme-linked immunosorbent assay. All the protein levels of OX-42, GFAP, TNF-a, IL-1β, COX-2, and iNOS are increased in CCH rats. WIN and URB downregulated the levels of OX-42, GFAP, TNF-α, IL-1β, COX-2 and iNOS and inhibited CCH-induced ROS accumulation in CCH rats, indicating that WIN and URB might exert their neuroprotective effects by inhibiting the neuroinflammatory response. In addition, the NF-κB signaling pathway was activated by CCH in frontal cortex and hippocampus, while the aforementioned changes were reversed by WIN and URB treatment. These findings suggest that WIN and URB treatment ameliorated CCH-induced neuroinflammation through inhibition of the classical pathway of NF-κB activation, resulting in mitigation of chronic ischemic injury.

[Glucose excursion in senior patients with type 2 diabetes mellitus and coronary artery disease]

Objectives: To explore glucose excursion and incidence of hypoglycemia in senior patients with type 2 diabetes mellitus (T2DM) and coronary artery disease (CAD) with different hemoglobin A1c (HbA1c) values. Methods: Eighty-nine outpatients [58 male, 31 female, aged 69.0 (66.0, 73.0) years] diagnosed with T2DM and CAD in Beijing Anzhen Hospital between June 2013 and March 2016 were divided into group A (HbA1c<6.5%, n=25) and group B (HbA1c≥6.5%, n=64). Every patient wore continuous glucose monitoring system (CGMS) for 72 h. Glucose excursion parameters and incidence of hypoglycemia from CGMS readings were calculated. Results: Compared with group B, patients in group A experienced shorter diabetes duration [8.0 (3.5, 15.0) vs 15.0 (8.0, 20.0) years, Z=-2.222, P=0.026], lower standard deviation (SD) of blood glucose from CGMS, mean amplitude of glycemic excursions(MAGE) and mean of the daily differences(MODD) (P=0.001, 0.003, 0.001). However, incidence of hypoglycemia was significantly increased [56.0% (14/25) vs 32.8% (21/64), χ(2)=4.051, P=0.044] in group A. Compared to those who had not experienced hypoglycemia, patients with hypoglycemia had higher SD [1.8(1.4, 2.4) mmol/L vs 1.4(1.1, 1.8) mmol/L, Z=-3.198, P=0.001] and MAGE [6.0(3.2, 7.4) mmol/L vs 3.9(2.7, 4.8 )mmol/L, Z=-2.768, P=0.006] which were appropriate tools for assessing intraday glycemic variability. No statistical difference were found in MODD which was the index for estimating interday glycemic variability. Conclusions: Intensive glycemic control in senior patients with T2DM and CAD had higher incidence of hypoglycemia. Those with hypoglycemia experienced greater intraday glucose excursion.

Cognitive function, depression, anxiety and quality of life in Chinese patients with untreated unruptured intracranial aneurysms

Detected unruptured intracranial aneurysms (UIA) are becoming more common with the increased utilization of CT angiography, MR angiography and digital subtraction angiography. A proportion of patients with UIA remain untreated. We investigated to assess cognitive function, depression, anxiety and quality of life (QoL) in Chinese patients with untreated UIA. Thirty one Chinese patients with untreated UIA and 25 healthy controls were identified and matched for variables including age, sex, and living area. Cognitive function was evaluated with the Montreal Cognitive Assessment (MoCA). Depression, anxiety and QoL were screened with the Self-Rating Depression Scale, Self-Rating Anxiety Scale, and Short Form-36, respectively. Non-parametric tests were used for comparisons between groups. No patient had cognitive dysfunction at 1 month or 1 year after detection of UIA. However, a significant decrease of overall MoCA subscores was found in 30 (97%) of 31 patients 5 years after UIA discovery, suggestive of mild cognitive impairment. A significant decrease in depression and anxiety was found in patients over time. QoL in patients was reduced most prominently in psychosocial function and social activities 1 year after detection of UIA, but these improved to within normal limits at the end of the follow-up period. For Chinese patients with untreated UIA, depression, anxiety and reduced QoL may be short-term complications. Mild cognitive impairment may be a long-term complication.

Elevated C-reactive protein levels may be a predictor of persistent unfavourable symptoms in patients with mild traumatic brain injury: a preliminary study

The pathogenesis of persistent unfavourable outcomes following mild traumatic brain injury (mTBI) are not fully understood. Low-grade systemic inflammation might contribute to the development of persistent unfavourable outcomes in patients with mTBI. We used plasma high-sensitivity C-reactive protein (CRP) levels as the biomarker of systemic inflammation to investigate whether elevated CRP levels were associated with persistent adverse outcomes in these patients. A total of 213 consecutive patients with mTBI were identified in our study. Plasma high-sensitivity CRP levels were measured at baseline, 1month, 2months and 3months after initial traumatic brain injury. The study endpoints included persistent postconcussion syndrome (PCS), persistent psychological problems (depression and anxiety), persistent physiological problems (frequent headache, nausea, insomnia, dizziness and fatigue) and persistent cognitive impairment, which were screened by International Classification of Diseases (ICD-10), diagnostic and statistical manual of mental disorders (DSM-IV), Beck anxiety inventory (BAI), Beck depression inventory (BDI) and montreal cognitive assessment (MoCA) 3months post-injury. The associations between baseline CRP levels and persistent unfavourable outcomes were estimated from multiple regression models adjusting for various confounding covariates. Elevated baseline CRP levels were associated with a significant increase in the incidence of persistent PCS (odds ratio [OR], 2.719; 95% confidence interval [CI], 1.609-4.594; p=0.000), persistent psychological problems (OR, 1.535; 95% CI, 1.063-2.216; p=0.022), and persistent cognitive impairment (OR, 1.687; 95% CI, 1.135-2.507; p=0.010). However, elevated CRP levels were not associated with persistent physiological problems (OR, 1.330; 95% CI, 0.905-1.956; p=0.146). Furthermore, three adjusted models did not essentially affect the OR of elevated CRP levels for these persistent unfavourable outcomes. Among patients with mTBI, baseline elevated CRP levels may be an independent predictor of persistent persistent PCS, psychological problems and cognitive impairment.

Effects of statins-use for patients with aneurysmal subarachnoid hemorrhage: a meta-analysis of randomized controlled trials

Aneurysmal subarachnoid hemorrhage (aSAH)-induced cerebral vasospasm and delayed ischemic neurological deficit (DIND) are the major causes of morbidity and mortality in patients with aSAH. The effects of statins-use for patients with aSAH remain controversial. Here,a total of 249 patients from six randomized controlled trials(RCTs) were subjected to meta-analysis. No significant decrease was found in the incidence of vasospasm(RR, 0.80; 95% CI, 0.54-1.17), with substantial heterogeneity (I(2) = 49%, P = 0.08), which was verified by the further sensitivity analysis and subgroup meta-analysis. Furthermore, no significant difference was presented in the incidence of poor neurological outcome(RR, 0.94; 95% CI, 0.77-1.16), and potential side effects(RR, 2.49; 95% CI, 0.75-8.33). Nevertheless, significant difference was reported in the occurrence of DIND(RR, 0.58; 95% CI, 0.37-0.92) and mortality(RR, 0.30; 95% CI, 0.14-0.64). At present, although statins-use in the patients with aSAH should not be considered standard care at present, statins-use may have the potential effects in the prevention of mortality in patients with aSAH.

The effects of intracranial pressure monitoring in patients with traumatic brain injury

Background

Although international guideline recommended routine intracranial pressure (ICP) monitoring for patients with severe traumatic brain injury(TBI), there were conflicting outcomes attributable to ICP monitoring according to the published studies. Hence, we conducted a meta-analysis to evaluate the efficacy and safety of ICP monitoring in patients with TBI.

Methods

Based on previous reviews, PubMed and two Chinese databases (Wangfang and VIP) were further searched to identify eligible studies. The primary outcome was mortality. Secondary outcomes included unfavourable outcome, adverse events, length of ICU stay and length of hospital stay. Weighted mean difference (WMD), odds ratio (OR) and 95% confidence intervals (CIs) were calculated and pooled using fixed-effects or random-effects model.

Results

two randomized controlled trials (RCTs) and seven cohort studies involving 11,038 patients met the inclusion criteria. ICP monitoring was not associated with a significant reduction in mortality (OR, 1.16; 95% CI, 0.87–1.54), with substantial heterogeneity (I² = 80%, P<0.00001), which was verified by the sensitivity analyses. No significant difference was found in the occurrence of unfavourable outcome (OR, 1.40; 95% CI, 0.99–1.98; I² = 4%, P = 0.35) and advese events (OR, 1.04; 95% CI, 0.64–1.70; I² = 78%, P = 0.03). However, we should be cautious to the result of adverse events because of the substantial heterogeneity in the comparison. Furthermore, longer ICU and hospital stay were the consistent tendency according to the pooled studies.

Conclusions

No benefit was found in patients with TBI who underwent ICP monitoring. Considering substantial clinical heterogeneity, further large sample size RCTs are needed to confirm the current findings.

Multispecies coexistence of trees in tropical forests: spatial signals of topographic niche differentiation increase with environmental heterogeneity

Neutral and niche theories give contrasting explanations for the maintenance of tropical tree species diversity. Both have some empirical support, but methods to disentangle their effects have not yet been developed. We applied a statistical measure of spatial structure to data from 14 large tropical forest plots to test a prediction of niche theory that is incompatible with neutral theory: that species in heterogeneous environments should separate out in space according to their niche preferences. We chose plots across a range of topographic heterogeneity, and tested whether pairwise spatial associations among species were more variable in more heterogeneous sites. We found strong support for this prediction, based on a strong positive relationship between variance in the spatial structure of species pairs and topographic heterogeneity across sites. We interpret this pattern as evidence of pervasive niche differentiation, which increases in importance with increasing environmental heterogeneity.

A dural arteriovenous fistula in cavernous sinus developed from viral meningitis

Although hormonal influences, inflammation, trauma, sinus thrombosis, venous hypertension, and congenital origin have been proposed as sources of dural arteriovenous fistulas (DAVFs) in cavernous and sigmoid sinuses, the etiology of these lesions remains controversial. We present a case with a cavernous sinus DAVF developed from viral meningitis which has not been previously described. A 24-year-old male was admitted to our institute because of periorbital pain, decreased vision, pulsatile tinnitus, chemosis, and exophthalmos on the right side after he had suffered viral meningitis four months before. Cerebral angiography demonstrated a cavernous sinus DAVF, which was successfully obliterated with several platinum coils using a transvenous approach. The viral meningitis most likely caused the inflammation, that may be responsible for the occurrence of the cavernous sinus DAVF. Prompt treatment for inflammation may help to prevent the development of DAVFs.

Chronic cerebral hypoperfusion in rats causes proteasome dysfunction and aggregation of ubiquitinated proteins

The deposition of abnormal protein aggregates is a feature of several neurodegenerative diseases. We have employed a rat model to investigate whether chronic cerebral hypoperfusion (CCH) induces proteasome dysfunction and the accumulation of ubiquitinated proteins and aggregates in the CNS. Protein aggregation was analyzed by ethanolic phosphotungstic acid (EPTA) electron microscopy (EM), immunogold EM, laser-scanning confocal microscopy, and Western blotting. Proteasome peptidase activity was studied by peptidase activity assays. EPTA EM and immunogold EM revealed that CCH led to the accumulation of protein aggregates in rat hippocampal CA1 neurons. High-resolution confocal microscopy demonstrated the presence of ubiquitin-positive protein aggregates surrounding nuclei and along dendrites. Western blotting revealed that levels of free ubiquitin were significantly reduced and that levels of ubiquitinated proteins were markedly increased in the hippocampus of CCH rats. Direct activity measurements revealed that proteasome peptidase activity in the hippocampal region of rats was decreased after CCH induction. These data suggest that reduced proteasome activity following CCH could impair the removal of abnormally folded proteins via the ubiquitin-proteasome pathway, leading to the accumulation of potentially toxic protein aggregates that could contribute to neurodegeneration.

Successful heart transplantation after 13 hours of donor heart ischemia with the use of HTK solution: a case report

INTRODUCTION

For heart transplantation (HTx), the recommended ischemic time (IT) for donor heart is not to exceed 6 hours. Though Dr Christiaan Barnard used a donor heart with IT of 16 hours, 50 minutes with a portable hypothermic perfusion system in 1981, the recorded IT of donor hearts reported recently is 8 hours, with no adverse effects.

CASE REPORT

The patient, a 14-year-old boy of blood type O, was diagnosed with cardiomyopathy at age 12. In early September 2003, the patient was recommended for HTx. His condition deteriorated 18 days later with low CO, elevated pulmonary vascular resistance, and frequent ventricular tachycardia, further complicated by pneumonia and multiorganism infections, which were contraindications for HTx. On September 22, 2003, a donor heart of blood type O was available 370 km away. Another patient of blood type B with severe heart failure was matched for the HTx. During the intervening time, another donor heart of blood type B became available locally. We matched the type B donor heart to the type B recipient. Since the type O donor heart seemed to be wasted, we performed HTx for the boy. Though preserved for 12 hours in cold cardioplegia, the donor heart was implanted with biatrial anastomosis that took 1 hour. The total IT of this donor heart was 13 hours. The recipient recovered and was discharged 3 months later.

CONCLUSIONS

The IT of 13 hours for this donor heart is believed to be a world record. Our experience demonstrates that preservation time of donor heart may exceed 6 hours.

Successful heart transplantation after 13 hours of donor heart ischemia with the use of HTK solution: a case report

INTRODUCTION

For heart transplantation (HTx), the recommended ischemic time (IT) for donor heart is not to exceed 6 hours. Though Dr Christiaan Barnard used a donor heart with IT of 16 hours, 50 minutes with a portable hypothermic perfusion system in 1981, the recorded IT of donor hearts reported recently is 8 hours, with no adverse effects.

CASE REPORT

The patient, a 14-year-old boy of blood type O, was diagnosed with cardiomyopathy at age 12. In early September 2003, the patient was recommended for HTx. His condition deteriorated 18 days later with low CO, elevated pulmonary vascular resistance, and frequent ventricular tachycardia, further complicated by pneumonia and multiorganism infections, which were contraindications for HTx. On September 22, 2003, a donor heart of blood type O was available 370 km away. Another patient of blood type B with severe heart failure was matched for the HTx. During the intervening time, another donor heart of blood type B became available locally. We matched the type B donor heart to the type B recipient. Since the type O donor heart seemed to be wasted, we performed HTx for the boy. Though preserved for 12 hours in cold cardioplegia, the donor heart was implanted with biatrial anastomosis that took 1 hour. The total IT of this donor heart was 13 hours. The recipient recovered and was discharged 3 months later.

CONCLUSIONS

The IT of 13 hours for this donor heart is believed to be a world record. Our experience demonstrates that preservation time of donor heart may exceed 6 hours.

C57BL/6 and BALB/c bronchoalveolar macrophages respond differently to exercise

Macrophages from prototypical Th1 strains (e.g., C57BL/6) and Th2 strains (e.g., BALB/c) are classified as M-1 and M-2 phenotypes. We investigated the different phagocytic responses between M-1 and M-2 bronchoalveolar macrophages (BAMs) under resting and two various exercise conditions. At rest, M-1 BAMs showed higher phagocytic capacity of unopsonized particles, higher expression of MARCO (macrophage receptor with collagenous structure), and higher generation of NO than M-2 BAMs. Severe exercise, but not moderate exercise, significantly enhanced both phagocytosis of unopsonized particles and expression of MARCO in M-2 BAMs. In contrast, M-1 BAMs were unaffected by either exercise protocol. The phagocytosis of unopsonized particles was largely mediated by MARCO, especially in M-1 BAMs. Secreted products from cultured M-2 BAMs isolated after severe exercise, but not those from M-1 BAMs, enhanced BAM phagocytosis. The cultured M-1 BAMs secreted phagocytosis inhibitors, and this effect could be blocked by NO antagonists. Moreover, the extent of phagocytosis suppression induced by M-1 BAM-secreted products correlated with their production of nitrite/nitrate. Exogenous NO donors as well as NO derivatives, nitrite and nitrate, suppressed the BAM phagocytosis. We propose that while the severe exercise-enhanced phagocytosis in M-2 BAMs was largely mediated by MARCO up-regulation and secretion of stimulators, the lack of exercise effect in M-1 BAMs could be partially due to the constitutive secretion of NO-related suppressors. In conclusion, genetically different mice use different strategies in regulating BAM activity under resting conditions and in response to various exercise paradigms.

Antimicrobial coatings: a remedy for medical device-related infections

This article discusses the mechanisms involved in the different approaches to antimicrobial coatings and reports on a new application that seems to offer an antimicrobial surface that is effective for long-term medical implants and suitable for a variety of drugs.

Role of cupric ions in the H2O2/UV oxidation of humic acids

The purpose of this study is to reveal the role of cupric ions as a natural water contaminant in the H2O2/UV oxidation of humic acids. Humic acids are naturally occurring organic matter and exhibit a strong tendency of complexation with some transition metal ions. Chlorination of humic acids causes potential health hazards due to formation of trihalomethane (THM). The removal of THM precursors has become an issue of public concern. The H2O2/UV process is capable of mineralizing humic acids due to formation of a strong oxidant, hydroxyl radicals, in reaction solution. Experiments were conducted in a re-circulated photoreactor. Different cupric concentrations (0-3.8 mg/l) and different pH values (4-9) were controlled to determine their effects on the degradation of humic acids, UV light absorbance at 254 nm, and H2O2. The presence of cupric ions inhibits humic mineralization and decreases the rate of destruction of humic acids which absorb UV light at 254 nm. On the other hand, the higher the cupric concentration, the lower the H2O2 decomposition rate. In the studied pH range, the minimum of total organic carbon (TOC) removal occurs at pH = 6 in the presence of 2.6 mg/l of cupric ions; both acidification (pH = 4) and alkaline condition (pH = 9) lead to a better removal of TOC. It is inferred from this study that the cupric-complexed form of humic acids is more refractory than the non-complexed one.

Severe exercise enhances phagocytosis by murine bronchoalveolar macrophages

Because physical activity affects the immune competency of individuals by an unknown mechanism, we investigated the effect of acute exercise on phagocytosis of bronchoalveolar macrophages (BAMs). Male BALB/c mice, 7-9 weeks old, ran on a treadmill to exhaustion (severe exercise, SE) or at a final speed of 17 m/min for 30 min (moderate exercise, ME). Although both exercise protocols induced differential leukocytosis, 95% leukocytes from lung lavages of both groups were BAMs. The BAM phagocytic capacity of nonopsonized beads increased immediately after SE but not after ME, gradually returning to the basal level after 4 h. SE upregulates the macrophage scavenger receptors (SR-A type I/II and MARCO), CR3, and ICAM-1, but not Fc gammaR. Although the blocking effect of MARCO antibody was most pronounced, that of ICAM-1 antibody was totally reversed by cross-linking CR3. Our results showed that SE, but not ME, activated BAMs and that the enhanced nonopsonized phagocytosis was mainly mediated by scavenger receptors and ICAM-1/CR3.

Probabilistic approach to ranking sources of uncertainty in ELF magnetic field exposure limits

There is a need to improve the biological data, dosimetry, and risk assessment methodology used for setting guidelines for occupational exposures to extreme-low-frequency magnetic fields. This paper illustrates how a probabilistic approach can be used to determine priorities for future research based upon the analysis of biological and dosimetric variables that affect stimulation of the heart by magnetically-induced currents. A model was constructed to predict a level of whole-body magnetic-field exposure below which no cardiac stimulation is expected (Bncs). For each iteration of the model, a value was selected from cardiac stimulation threshold, shape factor, and conductivity distributions by Latin Hypercube sampling, and a value for Bncs was computed. The very wide range of simulated Bncs magnetic-field values obtained indicates that there is considerable uncertainty about what constitutes a "safe" level of exposure. The results show that the major occupational-exposure guidelines are very conservative with respect to risks of cardiac stimulation. The minimum Bncs value computed (0.01 T) by either a circular-loop model or an ellipsoid dosimetric model is ten times the highest recommended workday exposure value in a guideline. The lowest 5% Bncs value calculated for a circular-loop model is about 50-times the ICNIRP occupational exposure limit; the lowest 5% Bncs value calculated for an ellipsoid model is more than 100 times the ACGIH occupational exposure limit. A new finding is that the method specified by several guidelines for determining guideline compliance when exposures occur at multiple frequencies (additive weighting of harmonics) leads to substantially lower Bncs estimates relative to a probably more valid rms-weighting method. Probabilistic sensitivity analyses indicate that lack of knowledge of the threshold for cardiac stimulation is the greatest source of uncertainty as to what is a "safe" level of exposure to extreme-low-frequency magnetic fields. Additional research to address this source of uncertainty may be expected to have the greatest potential impact to reduce overall uncertainty about safe magnetic field exposures.

Interactions of vancomycin resistant enterococci with biomaterial surfaces

Enterococci are a frequent cause of nosocomial infections and are often found adherent to indwelling catheters. Concern about such device associated infections has increased with the appearance of vancomycin resistant (VR) enterococci. However, the possible influence of vancomycin resistance in the pathogenesis of biomaterial centered infection has not yet been assessed. Using polyethylene terephthalate (PET) disks as model surfaces, the authors evaluated possible differences in the adherence and persistence of vancomycin sensitive (VS) and VR strains of Enterococcus faecium and Enterococcus faecalis on biomaterial surfaces in vitro and in vivo. The results indicate that: 1) as expected, the clearance of free VR and VS organisms after intraperitoneal injection into normal mice is equally efficient. 2) In vitro, VR bacteria are roughly twice as adherent to plasma coated PET surfaces as are VS organisms. 3) However, in vivo persistence of VS organisms preadherent to biomaterial implants is 5- to 10-fold better than that of preadherent VR organisms. The authors now believe that a discrete change in bacterial cell wall composition between VR and VS enterococci may contribute to the substantial differences in bacterial adhesion and survival of adherent organisms.

Summary and evaluation of guidelines for occupational exposure to power frequency electric and magnetic fields

Major U.S. and international guidelines for limiting occupational exposures to EMF are evaluated. These safety guidelines are designed to prevent short-term adverse effects by maintaining bulk-tissue current densities below 10 mA m(-2) (rms). Above this level, effects of induced currents and electric fields can include stimulation of neural and cardiac tissues. The models and input data used by guideline-setting organizations to relate 50/60-Hz magnetic-field exposures to induced current densities differ significantly. In order to develop a better understanding of such differences, the current densities derived from exposure guideline models are compared to minimum thresholds for cardiac stimulation and fibrillation. The nominal minimum thresholds for cardiac stimulation and ventricular fibrillation are 100 times and 200 times greater, respectively, than the current density of 10 mA m(-2) used as a dosimetric limit. However, the assumed relationship between the 10 mA m(-2) dose limit and magnetic field exposure limits introduces additional uncertainty. The ratios between the threshold for cardiac stimulation and the calculated induced current density at the exposure limit vary between a low of 50 and a high of 526, depending upon the guideline. These ratios, as indicators of implicit safety factors, are larger than those recommended to protect against adverse effects of induced current density, including cardiac stimulation, in magnetic resonance imaging or against adverse effects of toxic chemical exposures. This review and assessment of EMF occupational exposure guidelines suggests that several scientific and compliance issues remain ambiguous or unresolved. Recommendations are made for guideline organizations to strengthen and clarify the scientific basis for the guideline process. These recommendations include the documentation of supporting data, development of operational definitions for guidelines, examination of dosimetric models, clarification of safety factors, and identification of high priority topics for future research.

Uncertainty and variation in indirect exposure assessments: an analysis of exposure to tetrachlorodibenzo-p-dioxin from a beef consumption pathway

Indirect exposures to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and other toxic materials released in incinerator emissions have been identified as a significant concern for human health. As a result, regulatory agencies and researchers have developed specific approaches for evaluating exposures from indirect pathways. This paper presents a quantitative assessment of the effect of uncertainty and variation in exposure parameters on the resulting estimates of TCDD dose rates received by individuals indirectly exposed to incinerator emissions through the consumption of home-grown beef. The assessment uses a nested Monte Carlo model that separately characterizes uncertainty and variation in dose rate estimates. Uncertainty resulting from limited data on the fate and transport of TCDD are evaluated, and variations in estimated dose rates in the exposed population that result from location-specific parameters and individuals' behaviors are characterized. The analysis indicates that lifetime average daily dose rates for individuals living within 10 km of a hypothetical incinerator range over three orders of magnitude. In contrast, the uncertainty in the dose rate distribution appears to vary by less than one order of magnitude, based on the sources of uncertainty included in this analysis. Current guidance for predicting exposures from indirect exposure pathways was found to overestimate the intakes for typical and high-end individuals.

Paraspinal muscle evoked cerebral potentials in patients with unilateral low back pain

Cerebral somatosensory evoked potentials (SEPs) were elicited by magnetic stimulation of paraspinal muscles unilaterally at the L2 and L5 levels in 20 healthy subjects and 16 patients with low back pain and unilateral muscle spasm. A magnetic coil with a mean diameter of 4.7 cm was placed tangentially to the skin. The stimulus strength was sufficient to induce a visible muscle twitch without producing muscle contraction in the legs. The potentials recorded over the scalp consisted of several components (P30, N40, P55, N70, and P90) and were elicited in all subjects. In both healthy and patient subjects, paraspinal muscle evoked potentials were readily elicited. Vibration applied to paraspinal muscles, as well as voluntary contraction of paraspinal muscles, was associated with attenuation of the evoked potentials. This finding suggests that muscle spindle receptors provide the afferent input responsible for the early components of the magnetically evoked cerebral potentials. In patients with unilateral muscle spasm, the amplitudes of P30-N40, N40-P50, and P50-N70 were decreased significantly on the affected side when compared with values on stimulation of the unaffected side, as well as those obtained from control subjects. The cerebral evoked potentials returned to normal amplitude when the muscle spasm subsided following a period of time and after the application of spinal manipulative therapy. The technique has potential for quantitative evaluation of muscle spasm in low back pain.

Effects of palmatine on motor activity and the concentration of central monoamines and its metabolites in rats

We used behavioral and biochemical methods to investigate the sedative effect of palmatine on locomotor activity and the concentration of monoamine in rats. It was found that palmatine enhanced the hypomotility induced by alpha-methyl-p-tyrosine, reserpine and 5-hydroxytryptophan, but reduced the hypermotility produced by L-dopa plus benserazide and p-chlorophenylalanine. Furthermore, palmatine significantly decreased the concentration of dopamine and homovanillic acid in the cortex and the concentration of serotonin in the brain stem, and it increased the concentration of 5-HT in the cortex and 5-hydroxyindole acetic acid in the brain stem. These results suggest that the sedative mechanism of palmatine may be related to the decrease in the concentration of catecholamine in the cortex and serotonin in brain stem and the increase in the concentration of 5-HT in the cortex.

The H-reflex to magnetic stimulation of lower-limb nerves

We elicited H-reflexes by magnetic and electrical stimulation of several different nerves in 10 healthy subjects and two patients with S-1 radiculopathy. The posterior tibial nerve at the popliteal fossa and the femoral nerve at the inguinal ligament were tested with both electrical and magnetic stimulation; the proximal sciatic nerve was tested only with magnetic stimulation. Muscle activity was recorded from the soleus muscle for posterior tibial and sciatic nerve stimulation and from the vastus medialis muscle for femoral nerve stimulation. No significant difference was found between the latency of H-reflexes evoked by magnetic or electrical stimulation. With magnetic stimulation, the mean (+/- SD) Ia sensory fiber conduction velocity in the proximal segment of the sciatic nerve was 72.4 +/- 3.3 m/s, while the motor nerve fiber conduction velocity in the same portion of the nerve was significantly slower, at 60.6 +/- 2.0 m/s. In two patients with unilateral S-1 radiculopathy, the latency of the H-reflex from the soleus muscle to both magnetic and electrical stimulation of the posterior tibial nerve was absent or prolonged on the affected side. Magnetic stimulation can be used to study the H-reflex and Ia fiber conduction velocity and is particularly advantageous when testing deeply located nerve trunks.