In vivo toxicity of nano-alumina on mice neurobehavioral profiles and the potential mechanisms

The rapid development and expanding applications of nanotechnology have led to enhanced exposure of human body to nanoparticles. It is, therefore, necessary to address the safety issue via rigorous toxicological evaluation and to understand the underlying interaction mechanism. However, only a few studies to date have evaluated the safety of nano-sized materials and their potential adverse effects on biological systems. In this study, we sought to investigate the potential toxicity of aluminum oxide (alumina) nanoparticles in ICR strained mice, focusing on potential neurobehavioral defects and the possible mechanisms. The results demonstrated that nano-alumina impaired neurobehavioral functions, including lengthened escape latency, shorter time spent in the target quadrant and reductions in the number of platform crossing. In addition, it induced cell necrosis and apoptosis, which were likely mediated by the reduction of MMP and ROS, and the induction of the caspase-3 gene. Our results implicated that mitochondrial impairment plays a key role in neurotoxicity of nano-alumina, sequent oxidative damage and neural cell loss, especially necrosis, may be direct causes for the neurobehavioral defects. Collectively, nano-alumina presents a strong pro-cell death effect on ICR mice in vivo, suggesting that nano-alumina may serve as an inducer for neural toxicology. Findings in the present study indicating that surface chemical characteristics and nanoscale sizes of nano-alumina could co-contribute significantly to neurotoxicity. The impaired neurobehavioral patterns indicate that nano-alumina particles are more toxic to the cerebrum than those of nano-carbon with the same nanoparticle size and micro-alumina with the same surface chemical characteristics.

Establishment of a poisoned animal model of toxic encephalopathy induced by 1,2-dichloroethane

1,2-dichloroethane(1,2-DCE) is toxic, especially by inhalation due to its high vapour pressure. Inhalation of concentrated 1,2-DCE vapor can induce effects on the human nervous system, even encephalopathy. However, 1,2-DCE toxic encephalopathy has seldom been reported, and no adequate data were available to evaluate the encephalopathy of 1,2-DCE in experimental animals. The aim of the present study was to establish a toxic experimental animal model induced by 1,2-DCE. Dose effect and time effect of 1,2-DCE on the nervous system were detected. The rats were treated by 1,2-DCE at various concentrations of 0, 2.5, 5.0, 10.0 g/m3 for 6 h and treatment of rats at 10.0 g/m3 for 0, 3, 6, and 12 h. Morphology of brain tissue was observed by HE staining and TEM under light and electron microscope, besides water contents in the cortex and medulla of rats were analyzed. The results indicated that 1,2-DCE induced abnormal histopathology, and significantly higher water content were confirmed in the cerebral cortex of toxic animal model in a dose- and time-dependent manner. To declare that 1,2-DCE could induce toxic encephalopathy with a pathological feature of cerebral edema is very important for the medical rescue in urgent toxic accidents.

Abstract P3-12-07: Polymorphisms in the UDP-Glucuronosyltransferase 2B Gene Family and Risk of Breast Cancer in Women of African Descent

Background: The UDP-glucuronosyltransferase 2B (UGT2B) enzymes catalyze glucuronidation, which is an important clearance pathway of steroid hormones, and medications, and potential carcinogens. As steroid hormones play a central role in breast cancer development, genetic polymorphisms in the UGT2B gene family may affect breast cancer susceptibility.

Methods: We evaluate two missense mutations in UGT2B15 (rs1902023, D85Y and rs4148269, K523T), one missense mutation in UGT2B7 (rs7439366, H268Y), and one single nucleotide polymorphism (SNP) 497 bp upstream to UGT2B4 (rs13129471) using pooled case-control studies of breast cancer, which included 1,287 cases and 851 controls. Cases and controls were enrolled in Nigeria, Barbados, and the US, and all are women of African ancestry.

Results: All four SNPs followed Hardy-Weinberg equilibrium in each ethnicity group. We found the rs13129471 SNP was significantly associated with breast cancer risk after adjusting for ethnicity (P=0.003). Compared with homozygous genotype for the A-rs13129471 allele, the odds ratio for heterozygous genotype and homozygous genotype for the G-rs13129471 allele was 1.02 (95% CI: 0.81-1.28) and 1.50 (1.15-1.95), respectively. The association was stronger in Nigerian women (P=4x10- 5) and the corresponding odds ratio was 1.13 (95% CI: 0.85-1.49) and 2.39 (1.61-3.55). No significant association was found for the other three non-synonymous SNPs.

Conclusion: Our results suggest that polymorphism in the UGT2B4 gene may be associated with breast cancer risk in women of African ancestry and the association may follow a recessive model. The finding needs to be confirmed in other populations.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-12-07.

Safety in Construction Yards: Perception of Occupational Risk by Italian Building Workers

The purpose of this study is to analyse the perception of occupational risk by building workers in an area of Central Italy. Three hundred male building workers compiled questionnaires including 7 different types of dangers: falling from height, cuts and wounds to body and eyes, manual handling of loads, noise, vibrations and dust inhalation. The workers quantified, on a scale of one to five, the potential injury and frequency of occurrence of each risk, as well as providing information on the possibility of checking/avoiding the risk. Furthermore, attendance of the workers at previous specific courses on accident prevention and the effectiveness of these was evaluated. A possible correlation between the perception of job risk and having had previous injuries was also assessed. The results showed that about 35% of workers do not consider their job hazardous; moreover, the risk perception is higher regarding dangers producing immediate injury, as opposed to those producing occupational illnesses. Moreover, there is no direct relationship between considering the job dangerous for health and having attended training courses, while the relationship between risk perception and past injuries is more marked. In conclusion, accident prevention training is essential for building workers; however, it is even more important to improve the quality of workers' information in order to increase their awareness of danger.

Bax gene silencing: a potential intervention in aluminum-induced neural cell death

There is a vast amount of evidence indicating that Bax plays a major role in the development, maintenance, and survival of neurons and neuron-supporting cells such as glial cells. The high potency of Bax small interfering RNA (siRNA), as shown by many experimental studies, makes it a rational candidate as a co-therapeutic agent in apoptotic cell death. To investigate whether Bax RNA interference (RNAi) may serve as a potential intervention in neural cell death induced by aluminum, we herein established aluminum (Al)-treated gliatoma (C6) cells as a model for evaluating neurotoxic injury on normal glia. Using the cell model, we undertook a different approach by inducing glial cell death with Al and then using Bax gene RNAi to suppress glial cell death. Combining cell viability assays and expression analyses by quantitative real-time PCR (qRT-PCR) and immunocytochemistry, we selected and validated the optimal siRNA from 3 candidate siRNAs for the Bax gene. Sequenced reduction of neural cell death was determined with flow cytometry. Our data identified siRNA1 as the most effective siRNA. The optimal concentration of the transfection agent was 20 nM and the optimal incubation period was 72 h. The transfection and knockdown efficiencies were 95 percent and 62 percent, respectively, which closely correlated with Bax protein expression and also the cell apoptosis intervention. Taken together, Bax is essential for apoptosis induced by aluminum. Inactivation of the Bax gene could be an effective strategy for delaying the onset of apoptosis induced by Al. Our results reveal promising therapeutic potential for Bax gene silencing in Al-induced neurodegeneration.

Genetic Risks for Breast Cancer in African American Women: Analysis of Candidate Single Nucleotide Polymorphisms from Association Studies

Background: African American breast cancer patients present with more aggressive disease than Caucasian women. They are also more likely to experience earlier onset of illness and tumors that are resistant to current treatment options due to their high grade and negative hormone receptor status. These attributes are correlated with greater mortality. The different frequencies of these indicators in African American and Caucasian patients have been associated with genetic susceptibility and genetically driven progression of breast cancer. However, these studies have focused on well-known breast cancer genes, not the low-penetrance mutations identified by genome-wide association studies (GWAS).Aims: This pilot case-control replication study investigated both the overall and attribute-based breast cancer risk of African American women associated with three single nucleotide polymorphisms (SNPs) selected through previously published association studies, including a genome-wide association study by Gold et al. (2008), and predicted high odds ratios and high minor allele frequencies in the African American population compared to the original study populations. We hypothesized that rs2180341 and rs7776136, located in 6q22.33 and associated with risk in a GWAS of Ashkenazi Jewish familial breast cancer cases, would contribute to overall risk in a case-control cohort of African American women. We also hypothesized that rs3741378, a SNP in SIPA1 previously associated with hormone-receptor negative tumors, would contribute to this outcome in the same cohort. These SNPs were additionally studied for relevance to other clinical outcomes.Methods: Two hundred and eighteen cases and 105 controls from the University of Chicago Cancer Risk Clinic were genotyped for these three SNPs using SNaPshot multiplex. Clinical information, including age of diagnosis, family history, hormone receptor status, survival, and tumor grade and stage, was also collected. Statistical analysis was performed using Pearson's χ2 test, Fisher's exact test, logistic regression and supplementary tests in Stata.Results: Unlike other populations, the African American population showed allelic odds ratios of approximately 1.0 for all SNPs tested, indicating no statistically significant association between these SNPs and breast cancer risk. We also found no association with age of diagnosis, hormone receptor status, tumor stage and grade. However, the minor allele of rs2180341 was associated with decreased survival in patients with a hazard ratio of 3.991 (p=0.044, 95% CI: 1.038-15.337) for the homozygous minor allele genotype.Conclusion: This pilot study represents one of the first forays into the translation of breast cancer GWAS results to populations of African ancestry. Based on our preliminary findings, future studies on a larger cohort of breast cancer cases of African ancestry will be needed to identify risk factors that may be particular to this patient population.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3068.

Therapeutic potential of BAK gene silencing in aluminum induced neural cell degeneration

Previous studies have demonstrated robust BAK gene silencing via RNA interference (RNAi). To investigate whether BAK RNAi may serve as a co-therapeutic agent in neural cell death, we herein established a cell degeneration model using a human neuroblastoma cell line (SH-SY5Y) treated by aluminum (Al). Combining cell viability assays and expression analyses by QRT (quantitative real-time)-PCR and immunocytochemistry, we selected and validated the optimal small interfering RNA (siRNA) from three candidate siRNAs for the BAK gene. Our data identified siRNA1 as the most effective siRNA; the optimal concentration of the transfection agent was 10nM and the optimal incubation period was 24h. The transfection and knockdown efficiency was 93% and 58%, respectively, which closely correlated with the BAK protein expression. SH-SY5Y cells with BAK knockdown showed a clear resistance against cell death and Al-induced apoptosis. These results indicate that genetic inactivation of BAK could be an effective strategy in delaying the onset of apoptosis in Al-treated cells, and exemplify the therapeutic potential of RNAi-based methods for the treatment of neural cell degeneration.

Is necroptosis a death pathway in aluminum-induced neuroblastoma cell demise?

Besides being an aggravating factor secondary to major physiological alterations in degenerative diseases, aluminum has also been considered as a risk factor in the etiology. Although many in vivo and in vitro data are in favor of apoptosis and necrosis being involved in Al induced neurodegenerative processes, there is considerable evidence that very complex events may contribute to neural cell death. Necroptosis, a novel cell death pathway, was recently reported to contribute to ischemia brain injury. It is different from, but associated with, apoptosis and necrosis, the two common major pathways of cell demise. In the present study, SH-SY5Y cells were put under stress by Al, a potential degenerative cell death inducer. Nec-1, a specific inhibitor, was used to identify necroptosis. The characteristics observed in Nec-1 and Al treated SH-SY5Y cells showed that necrotic morphological changes were reduced, and a sharp decrease of necrotic rate was detected. Besides, there were Al-induced mitochondria membrane potential decreasing, reactive oxygen species remaining, and autophagosomes declining. The mechanism of Nec-1s effect on cell death may be related to caspases pathways. To our best knowledge, this is the pioneer report on necroptosis in mixed human neural cell death pathways, which might offer a novel therapeutic target for neurodegenerative diseases, and an extended window for neuroprotection.

How Do Rat Cortical Cells Cultured with Aluminum Die: Necrosis or Apoptosis?

Aluminum (Al) exposure has been implicated as the cause of neural cells loss in several neurodegenerative diseases. Therefore, defining the mechanism of neural cell death in Al toxicity and degenerative diseases might lead to the development of therapeutic agents which promote neural cell survival. Furthermore, knowledge of cell death pathways might facilitate the discovery of treatments for neurodegeneration. However, the death mode of neural cells triggered by Al has not been firmly established. The present study focuses on understanding the pathway of cells death in cultured cortical cells treated with Al. Primary neurons cultured alone, astrocytes cultured alone, and neuron/astrocyte co-cultures obtained from newborn rats were incubated with Al at the concentrations of 0, 0.5,1.0, or 2.0 mM for 72 h. Morphological changes were observed with an inverted phase microscope, a fluorescent microscope, and an electron microscope. Simultaneously, the rate of apoptosis was quantified with flow cytometry. Morphological characteristics of apoptosis such as cell shrinkage, aggregation and fragmentation of chromatin, membrane buds, and formation of membrane-bound apoptotic bodies were observed in Al-treated neurons, while none of these characteristics were found in Al-treated astrocytes. Quantitative results of apoptotic rates detected with flow cytometry indicated a typical apoptosis progression in neurons at various dosages. A concentration-dependent relationship between Al concentration and apoptotic rates confirmed that apoptosis is the prominent cause of cell death in primary cultured neurons, even at a concentration lower than 2 mM. Both necrosis and apoptosis are evident in neuron/astrocyte co-cultures, but the intensity of apoptosis is much less compared with that of neurons, suggesting that astrocytes may be especially important for neuronal survival in the presence of Al.

Scanning tunneling spectroscopy of Ag films: the effect of periodic versus quasiperiodic modulation

By using scanning tunneling spectroscopy to probe a silver thin film that contains both periodic and quasiperiodic modulation, and by using Fourier analysis, we unravel the influences of individual Fourier components of the scattering potential (periodic versus quasiperiodic) on the electronic structure of a one-dimensional quasiperiodically modulated thin Ag film. Along the periodically modulated direction, a Bragg reflection-induced energy gap is observed in k space. On the other hand, the exotic E vs k spectrum with many minigaps was observed along the quasiperiodic direction.

Aluminum impairs rat neural cell mitochondria in vitro

Exposure to aluminum has been reported to lead to neurotoxicity. Mitochondria are important organelles involved in maintaining cell function. This study investigates the effect of aluminum on mitochondria in rat neural cells. The ultrastructure of mitochondria was observed, and the cell death rate (CDR), reactive oxygen species (ROS), mitochondrial membrane potential (MMP) and 3-[4,5demethyl-2-thiazalyl]-2,-5diphenyl-2H-tetrazolium bromide (MTT) were measured to investigate the effect of aluminum on the mitochondrial structure and its function in neural cells. Results observed from the mitochondrial ultrastructure show that aluminum may impair the mitochondrial membrane and cristae. Increased CDR, enhanced ROS, decreased MMP, and decreased enzyme activity in mitochondria were observed in the Al-exposed neurons (100 500 microM). The present study demonstrates that alteration in the mitochondrial structure and function plays an important role in neurotoxic mechanisms induced by aluminum.

The Role of Alteration of Glutamic Acid and Gaba in Learning and Memory Impairment of Rats Induced by Aluminum

Aluminum exposure has been reported to be related to learning and memory impairment. This study examines the role of aluminum in alterating amino acids of the cerebral cortex of rats. The Step-down type tests were performed to investigate the alteration of learning and memory of rats induced by aluminum. The amino acids in the cerebral cortex were detected by high performance liquid chromatography (HLPC). Results show that the amounts of aluminum in the cerebral cortex increased by 5.0mgAl3+/(Kg·BW) group and 10.0mg Al3+/(Kg·BW) group. In the Step-down type test, the EN1 increased significantly in the Al3+ 10.0mg/(Kg·BW) group. The latency shortened obviously and the EN2 increased significantly in the 10.0mg Al3+/(Kg·BW) group. The content of Glu (Glutamic acid) increased but the content of GABA (gamma-aminobutyric acid) decreased significantly in the 10.0mg Al3+/(Kg·BW) group. This present study shows evidence that the disorder of amino acid neurotransmitters system plays an important role in the impairment of learning and memory of rats induced by aluminum.

Semiclassical spin transport in spin-orbit-coupled bands

Motivated by recent interest in novel spintronics effects, we develop a semiclassical theory of spin transport that is valid for spin-orbit coupled bands. Aside from the obvious convective term in which the average spin is transported at the wave packet group velocity, the spin current has additional contributions from the wave packet's spin and torque dipole moments. Electric field corrections to the group velocity and carrier spin contribute to the convective term. Summing all terms we obtain an expression for the intrinsic spin-Hall conductivity of a hole-doped semiconductor, which agrees with the Kubo formula prediction for the same quantity. We discuss the calculation of spin accumulation, which illustrates the importance of the torque dipole near the boundary of the system.

Universal intrinsic spin Hall effect

We describe a new effect in semiconductor spintronics that leads to dissipationless spin currents in paramagnetic spin-orbit coupled systems. We argue that in a high-mobility two-dimensional electron system with substantial Rashba spin-orbit coupling, a spin current that flows perpendicular to the charge current is intrinsic. In the usual case where both spin-orbit split bands are occupied, the intrinsic spin-Hall conductivity has a universal value for zero quasiparticle spectral broadening.

Neurotoxicity Assessment of Chemicals on Exposed Workers — A Review of Neurobehavioral and Neurophysilogical Tests

With the wide utilization of neurotoxic substances, more and more people are exposed to them occupationally or environmentally. Neurotoxicity has been defined as any adverse effect on the structure or function of the central and /or peripheral nervous system by biological, chemical and physical agent. Neurotoxic effect may be permanent or reversible, caused by neuropharmacological or neurodegenerative properties of a neurotoxicant. The nervous system is very sensitive and fragile to chemicals. The early adverse effects should be detected as early as possible because they are reversible, functional and chemical, not structural. A multidisciplinary approach is necessary to assess neurotoxicity because of the complexity and diverse functions of the nervous system. Many of the relevant effects can be measured directly by neurochemical, neurophysiological, and neuropathological techniques, whereas, others must be inferred from observed behavior and psychic performance. Neurotoxicity in humans is most commonly measured by relatively noninvasive neurophysiological and neurobehavioral methods that assess cognitive, affective, sensory, and motor function. The biomarker assay can be complement. In general, due to the speciality and difficult accessibility, the biomarkers that manifest the neurotoxicity of chemicals in nervous system are difficult to obtain, but a number of biochemical and molecular parameters similar to those involved as toxicity targets in the nervous system are also present in more easily accessible tissues, such as cerebrospinal fluid (CSF), blood, plasma and peripheral blood cells. These tissues can be surrogate indicators. With the multidisciplinary approach, the neurotoxicity of chemicals can be assessed or screened sensitively and practically.

Metallic phase in quantum Hall systems due to inter-Landau-band mixing

The electronic eigenstates of a quantum Hall (QH) system are chiral states. Strong inter-Landau-band mixings among these states can occur when the bandwidth is comparable to the spacing of two adjacent Landau bands. We show that mixing of localized states with opposite chirality can delocalize electronic states. Based on numerical results, we propose the existence of a metallic phase between two adjacent QH phases and between a QH phase and the insulating phase. This result is consistent with nonscaling behaviors observed in recent experiments on a quantum Hall liquid-to-insulator transition.

[Cytokines in experimental cancer cachexia]

OBJECTIVE

To investigate the relationship between cytokine IL-6, IL-1, TNF-alpha and experimental cancer cachexia as well as observe the effect of indomethacin on the cachectic mice.

METHODS

T739 mice bearing lung adenocarcinoma LA795 were used as murine tumor cachexia model. In this experiment, serum IL-6, IL-1, TNF-alpha, glucose, protein and triglyceride levels and body weight in different stages of cancer cachexia were monitored. Thirty-two mice were randomized into four groups for comparison, with eight mice in each group: no tumor (NTB) group, tumor without treatment (NT) group, tumor with normal saline (NST) group and tumor with indomethacin (INDT) group. For the last group, intraperitoneal infusion of indothacin 1 microgram/gm was given once every day for six days starting from the 14 th day of tumor implantation.

RESULTS

Compared with the NTB group, the NT group showed higher serum of IL-6, IL-1, TNF-alpha and lower total protein, triglyceride and glucose (P < 0.01). After treatment with indomethacin, the INDT mice gave higher serum glucose, protein and lipid levels. Meanwhile, the serum level of IL-6, TNF-alpha and IL-1 in the INDT group was found to be significantly low in comparison with the NST group.

CONCLUSION

(1) IL-6, IL-1 and TNF-alpha appear to be involved in experimental cancer cachexia. (2) The positive effects of indomethacin by inhibiting the growth of these cytokines indicate that indomethacin is able to improve the condition of cancer cachexia.

[Relationship between serum matrix metalloproteinase-2 and metastasis and recurrence following radical hepatic resection in hepatocellular carcinoma]

OBJECTIVE

To study the relationship between serum matrix metalloproteinase-2 (MMP-2) and metastasis and recurrence following radical hepatic resection in hepatocellular carcinoma (HCC).

METHODS

Cox's proportional hazard model was used to determine the significant clinical factor of prognosis. Meanwhile, enzyme linked immunoadsordent assay (ELISA) and northern blot analysis were adopted to detect serum and tumor tissue levels of MMP-2 respectively in HCC patients.

RESULTS

Cox's proportional hazard model showed that tumor size and tumor number were significant prognostic factors of HCC patients following hepatic resection (P=0.022 and P=0.040). According to this result, we divided HCC patients into high-tendency to metastasis recurrence and low-tendency to metastasis recurrence groups. Serum levels of MMP-2 in high-tendency to metastasis recurrence following radical hepatic resection group were significantly higher than those in low-tendency group (26.39ng/m+/-2.64ng/ml vs 24.86ng+/-1.95ng/ml, P<0.05). Serum levels of MMP-2 in HCC patients performed non-radical hepatic resection group were also significantly higher than those in HCC patients performed radical hepatic resection group (29.43ng+/-3.12 ng/ml vs 25.72ng+/-2.45ng/ml, P<0.01). Northern blot analysis revealed that the changes of MMP-2 level in the serum were consistent with those of its mRNA level in the tumor tissue of HCC patients.

CONCLUSIONS

Serum MMP-2 level is an indicator for metastatic recurrence following radical hepatic resection in HCC. The high levels of MMP-2 in the serum are due to high MMP-2 mRNA expression in the tumor tissue of HCC patients.

Trichloroethylene in urine as biological exposure index

Occupational exposure to trichloroethylene (TRI) was studied by analysis of environmental air and urine from 49 workers operating in a special printing house on glass. For the measurement of environmental concentration of TRI (Cenv), the ambient air was sampled using personal passive dosimeters. The activated charcoal was desorbed with carbon disulfide and injected into a gas-cromatograph - mass spectrometer (GC-MSD). The biological monitoring of exposed workers was conducted by determining the concentration of TRI in urine (Curine) Urine concentration of TRI was determined by headspace analysis using GC-MSD. Significant correlation was found between the environmental TRI concentration and urinary TRI concentration. The use of a regression equation between Curine (microg/l) and Cenv (mg/m3) (Curine = 0.081 x Cenv + 4.27) resulted in a value of Curine corresponding to Threshold Limit Value-Time Weighted Average (TLV-TWA) exposure value (269 mg/m3) of 26.0 microg/L.

An evaluation of the colorimetric assays based on enzymatic reactions used in the measurement of human natural cytotoxicity

In recent years colorimetric assays based on an enzymatic reaction such as the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay have been used in an attempt to replace the conventional isotopic assay for cell-mediated cytotoxicity. To clarify the problems in the colorimetric assays for natural cytotoxicity, K562 cells were employed as target cells and peripheral mononuclear cells (PBMCs) from cancer patients were used as effector cells. No correlation was found between the 51Cr assay and the MTT assay (P>0.05) or the N-acetyl-beta-D-glycosaminidase (NAG) release assay (P>0.05) in 16 cancer patients. Labeling effector cells showed that the 51Cr release levels of such cells in 19 chemotherapy patients were significantly higher than the levels from target cells in this group (P<0.01) and from effector cells in the control group (P<0.01). There was no correlation between the positive and negative 51Cr assays (P>0.05). The sensitivity of the MTT assay was greatly decreased by washing K562 cells prior to loading MTT solution. Enzyme release occurs as a result of cell metabolism and elevated enzyme release is associated with freezing. These findings indicate that the colorimetric assays based on an enzymatic reaction are not suitable for the detection of natural cytotoxicity in all populations, and are especially not suitable for the assay of natural cytotoxicity in chemotherapy patients.

Shape of the quantum diffusion front

We show that quantum diffusion has well-defined front shape. After an initial transient, the wave packet front (tails) is described by a stretched exponential P(x,t) = A(t)exp(-absolute value of [x/w](gamma)), with 1 < gamma < infinity, where w(t) is the spreading width which scales as w(t) approximately t(beta), with 0 < beta < or = 1. The two exponents satisfy the universal relation gamma = 1/(1-beta). We demonstrate these results through numerical work on one-dimensional quasiperiodic systems and the three-dimensional Anderson model of disorder. We provide an analytical derivation of these relations by using the memory function formalism of quantum dynamics. Furthermore, we present an application to experimental results for the quantum kicked rotor.

[Effect on manganese exposure on blood prolactin and plasma renin activity]

In order to study the adverse effects of manganese on neuro-endocrine and cardiovascular system, radioimmunoassay (RIA) was used to test the blood prolactin concentration and plasma renin activity among manganese-exposed workers. The result showed that the blood prolactin concentration and Plasma renin activity in manganese exposed workers were significantly higher than those of control group. It suggested that manganese exposure might affect the function at tubero-infundibular area and renin-angiotensin aldosterone system.

Effect of circular motion exercise on bone modeling and bone mass in young rats: an animal model of isometric exercise

The aims of the study are to develop a non-invasive animal model of circular motion exercise and to evaluate the effect of this type of exercise on bone turnover in young rats. The circular motion exercise simulates isometric exercise using an orbital shaker that oscillates at a frequency of 50 Hz and is capable of speeds from 0-400 rpm. A cage is fixed on top of the shaker and the animals are placed inside. When the shaker is turned on, the oscillatory movement should encourage the animals to hold on to the cage and use various muscle forces to stabilize themselves. Rats at 8 weeks of age were trained on the shaker for 6 weeks and static and dynamic histomorphometric analyses were performed for the proximal tibial metaphysis and the tibial shaft. The exercise resulted in no significant effect on animal body weight, gastrocnemius muscle weight and femoral weight. Although the bone formation rate of cancellous and cortical periosteum was increased by the exercise, trabecular bone volume was decreased. The exercise increased periosteal and marrow perimeters and the cross-sectional diameter of cortical bone from medial to lateral without a significant increase in the cortical bone area. These results suggest that circular motion exercise under force without movement or additional weight loading will cause bone-modeling drift with an increase in bone turnover to reconstruct bone shape in adaptation to the demand in strength. Since there is no additional weight loading during circular motion exercise, the net mass of bone is not increased. The bone mass lost in trabecular bone could possibly be due to a re-distribution of mineral to the cortical bone.

A comprehensive neurobehavioral and neurophysiological study for low level lead-exposed workers

A comprehensive neurobehavioral and neurophysiological study was performed to evaluate the adverse effect of low level lead-exposure, and to compare the sensibility, easiness of the test methods utilized. The tests were: WHO recommended Neurobehavioral Core Test Battery (NCTB), Autonomic Nouvers System Function (ANS) Test Battery, Brain Electricity Active Mapping (BEAM), and Nerve Conduction Velocity. 44 lead-exposed workers were selected, with 34 age, education degree, family economic level, smoking and drinking matched referents.

RESULT

The mean blood lead concentration of lead-exposed workers was 1.3870 mumol/L, whereas that of referents was 0.6080 mumol/L, the difference was very significant. The negative Profile of Mood State (POMS) score of lead-expose workers was higher than that of referents, whereas the positive POMS score of the referents was higher than that of lead-exposed group, with a covariance analysis. The lead-exposure affected some NCTB test items, such as simple reaction time (SRT), digital symbol (DSY), correct dots (PAC) and total dots (PA). The heart-rate response to Valsalva manoeuvre (HR-V), heart-rate response to deep breathing (HR-DB), and blood-pressure response to immediate standing (BP-IS) were lowered in lead-exposed workers significantly. Some abnormal brain electric waves (dominant beta frequency, semetry-diffuse abnormal and non semetry-diffuse abnormal wave distribution, dominant low wave amplitude) appeared in lead-exposed workers. Left ulnar nerve maximal conduction velocity was significantly lowered in lead-exposed group.

CONCLUSION

The NCTB (including POMS), and ANS function test should be the regular screening battery for low level lead-exposed workers. The threshold blood lead concentration for health surveillance should be 30 micrograms/dL, or 1.4 mumol/L.