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Based on establishing a mathematical model of the system provided system parameters, using the discrete-time Markov chain and a function set by a nonnegative integer random variable as probabilistic methods, the discrete time variable, two-queue different-gated polling system is fully analyzed, the low- and higher-order properties and cycle period of the system are deduced, and the average queue pair length and average waiting delay for message packets are calculated accurately. The simulation experiments agree well with the theoretical calculations. The analysis further deepens the understanding of the asymmetric threshold polling system, lays the foundation for research on the asymmetric threshold polling system, and has positive significance for a better and more flexible control periodic query polling work system. [ABSTRACT FROM AUTHOR]

Iron overload has been associated with acute/chronic organ failure, but whether iron overload induces liver injury remains unclear. The objectives of this study were to assess the relationship between urinary iron and serum alanine aminotransferase (ALT, a biomarker for liver injury), and investigate the potential mediating roles of lipid peroxidation and oxidative DNA damage in such association. Levels of urinary iron, serum ALT, and urinary biomarkers of lipid peroxidation (8-iso-prostaglandin-F2α [8-iso-PGF2α]) and oxidative DNA damage (8-hydroxy-deoxyguano-sine [8-OHdG]) were measured among 5386 observations of 4220 participants from the Wuhan-Zhuhai cohort. The relationships of urinary iron with serum ALT and risk of hyperALT were evaluated by linear mixed model and logistic regression model, respectively. The mediating roles of 8-iso-PGF2α and 8-OHdG were assessed by mediation analyses. This cross-sectional analysis found that urinary iron was positively associated with ALT (β = 0.032; 95% CI: 0.020, 0.044) and hyperALT prevalence (OR = 1.127; 95% CI: 1.065, 1.192). After 3 years of follow-up, participants with persistent high iron levels had increased risk of developing hyperALT (RR = 3.800; 95% CI: 1.464, 9.972) when compared with those with persistent low iron levels. In addition, each 1% increase in urinary iron was associated with a 0.146% (95% CI: 0.128%, 0.164%) increase and a 0.192% (95% CI: 0.154%, 0.229%) increase in 8-iso-PGF2α and 8-OHdG, respectively. Urinary 8-iso-PGF2α (β = 0.056; 95% CI: 0.039, 0.074) was positively associated with ALT, while the association between 8-OHdG and ALT was insignificant. Furthermore, increased 8-iso-PGF2α significantly mediated 22.48% of the urinary iron-associated ALT increment. Our study demonstrated that iron overload was significantly associated with liver injury, which was partly mediated by lipid peroxidation. Controlling iron intake and regulating lipid peroxidation may help in preventing liver injury. [ABSTRACT FROM AUTHOR]

Non-keratinizing nasopharyngeal carcinoma (NPC) is a malignancy with a poor prognosis for relapsing patients and those with metastatic disease. Here, we identify a novel disease mechanism of NPC which may be its Achilles' heel that makes it susceptible to immunotherapy. CD137 is a potent costimulatory receptor on activated T cells, and CD137 agonists strongly enhance anti-tumor immune responses. A negative feedback mechanism prevents overstimulation by transferring CD137 from T cells to CD137 ligand (CD137L)-expressing antigen presenting cells (APC) during cognate interaction, upon which the CD137-CD137L complex is internalized and degraded. We found ectopic expression of CD137 on 42 of 122 (34.4%) NPC cases, and that CD137 is induced by the Epstein-Barr virus latent membrane protein (LMP) 1. CD137 expression enables NPC to hijack the inbuilt negative feedback mechanism to downregulate the costimulatory CD137L on APC, facilitating its escape from immune surveillance. Further, the ectopically expressed CD137 signals into NPC cells via the p38-MAPK pathway, and induces the expression of IL-6, IL-8 and Laminin γ2. As much as ectopic CD137 expression may support the growth and spread of NPC, it may be a target for its immunotherapeutic elimination. Natural killer cells that express a CD137-specific chimeric antigen receptor induce death in CD137+ NPC cells, in vitro, and in vivo in a murine xenograft model. These data identify a novel immune escape mechanism of NPC, and lay the foundation for an urgently needed immunotherapeutic approach for NPC. [ABSTRACT FROM AUTHOR]

The effect of caffeine exposure on children's health remains poorly understood. We aimed to characterize the associations of caffeine and caffeine metabolites with adiposity outcomes among children and adolescents. We performed cross-sectional analyses of 1,447 children and adolescents aged 6–19 years from the 2009–2014 National Health and Nutrition Examination Survey. The linear regression and weighted quantile sum (WQS) regression were used to explore the associations of urinary caffeine and 14 caffeine metabolites with adiposity outcomes, including body mass index (BMI) z-score, waist circumference (WC), obesity, and overweight. In linear regression models, compared with the participants who consumed low caffeine, higher BMI z-score, WC, and risks of obesity and overweight were more likely among those who consumed high caffeine (P < 0.05). In WQS regression models, an interquartile range increase in the weighted caffeine index was significantly associated with increased BMI z-score (β = 0.10, 95% CI = 0.01, 0.17) and WC (β = 1.20, 95% CI = 0.31, 2.09), and risks of obesity (OR = 1.09, 95% CI = 1.02, 1.17). Totally, no modification effect of age or gender was observed in the linear regression model. Nonetheless, in WQS models, the positive associations of caffeine exposure with WC and risks of obesity and overweight were significant in children aged 6–11 years rather than 12–19 years. When stratified by gender, caffeine exposure was significantly associated with BMI z-score and WC in both boys and girls. These results add novel evidence that caffeine exposure might be associated with adverse adiposity outcomes among children and adolescents. [ABSTRACT FROM AUTHOR]

Background: The adverse effects of polycyclic aromatic hydrocarbon (PAHs), a group of common environmental pollutants, on mental health are unclear. This study is developed to evaluate the potential association of urinary PAH metabolites with depression in US adults. Methods: Measurement of 8 urinary PAH metabolites and assessment of depression were available for 9625 adults in the National Health and Nutritional Examination Survey 2005–2016. Multiple logistic regression models and weighted quantile sum (WQS) regression models were applied to evaluate the association between urinary PAH metabolites and depression. Results: Among 9625 individuals with a weighted geometric mean age of 42.63 years, 801 participants suffered from depression. Significant positive dose–response relationships were observed between specific urinary PAH metabolites and the risk of depression after adjusting for potential confounders. Urinary 1-hydroxynaphthalene was positively and dose-dependently associated with the risk of depression among total participants (odds ratio: 1.188; 95% confidence interval: 1.096–1.288). In addition, each 1-unit increase of ln-transformed urinary 1-hydroxynaphthalene, 2-hydroxynaphthalene, 3-hydroxyfluorene, 2-hydroxyfluorene, 1-hydroxyphenanthrene, 2&3-hydroxyphenanthrene, 1-hydroxypyrene, and total PAH metabolites was associated with a 23.3%, 32.6%, 23.3%, 29.4%, 30.8%, 22.8%, 29.4%, and 31.7% increment in the risk of depression in smokers, respectively (all P and P trend < 0.05). Of note, the positive WQS index was also significantly associated with the increased risk of depression in smokers (1.122, 1.059–1.188). Conclusion: Exposure to PAHs may elevate the risk of depression among US adults. More studies are warranted to investigate the underlying mechanism by which PAHs induce the development of depression. [ABSTRACT FROM AUTHOR]

We expected to explore the associations of hearing loss and hearing thresholds at different frequencies with total and cause-specific mortality. In this study, 11,732 individuals derived from the National Health and Nutrition Examination Survey (NHANES) 1999–2012 were included. Data of death was extracted from the NHANES Public-Use Linked Mortality File through December 31, 2015. Cox proportional hazards models were used to explore the associations between hearing loss, hearing thresholds at different frequencies, and total or cause-specific mortality. A total of 1,253 deaths occurred with a median follow-up of 12.15 years. A significant positive dose-response relationship between hearing loss in speech frequency and total mortality was observed, and the HRs and 95% CIs were 1.16 (0.91, 1.47), 1.54 (1.19, 2.00), and 1.85 (1.36, 2.50), respectively, for mild, moderate, and severe speech-frequency hearing loss (SFHL) with a Ptrend of 0.0003. In addition, moderate (HR: 1.90, 95% CI: 1.20–3.00) and greater (3.50, 1.38–8.86) SFHL significantly elevated risk of heart disease mortality. Moreover, hearing thresholds of >25 dB at 500, 1000, or 2000 Hz were significantly associated with elevated mortality from all causes (1.40, 1.17–1.68; 1.44, 1.20–1.73; and 1.33, 1.10–1.62, respectively) and heart disease (1.89, 1.08–3.34; 1.95, 1.21–3.16; and 1.89, 1.16–3.09, respectively). Hearing loss is associated with increased risks of total mortality and heart disease mortality, especially for hearing loss at speech frequency. Preventing or inhibiting the pathogenic factors of hearing loss is important for reducing the risk of death. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the associations between sleep duration and atherosclerotic cardiovascular disease (ASCVD) risk and the potential mechanism. Methods: Overall, 24,471 subjects without ASCVD were included from Dongfeng-Tongji (DFTJ) cohort. Data collection included questionnaires and general medical examinations. We used logistic regression models and generalized linear models to examine the associations between sleep duration, peripheral white blood cell (WBC) counts, and 10-year ASCVD risk. Mediation analyses were further performed to assess the potential role of peripheral WBC counts in the associations between sleep duration and 10-year ASCVD risk. Results: Increased risk of 10-year ASCVD was observed as sleep duration extended. After adjusting for potential confounders, the odds ratios (ORs) and 95% confidence intervals (CIs) for the risk of 10-year ASCVD were 1.24 (1.11–1.38), 1.12 (1.03–1.22), and 1.21(1.08–1.36) for individuals with nighttime sleeping duration of ≥ 9 h, daytime napping duration of > 30 min, and daily sleep duration of ≥ 9 h, respectively. Peripheral WBC counts mediated 14.1%, 14.5%, and 12.6% in the associations of nighttime sleep duration of ≥ 9 h, daytime napping duration of > 30 min and daily sleep duration of ≥ 9 h with 10-year ASCVD risk, respectively. Conclusions: Extended sleep durations are associated with the increased 10-year ASCVD risk, and the associations are partially mediated by peripheral WBC counts. [ABSTRACT FROM AUTHOR]

Exciting phenomena may emerge in non-centrosymmetric two-dimensional electronic systems when spin–orbit coupling (SOC)1 interplays dynamically with Coulomb interactions2,3, band topology4,5 and external modulating forces6–8. Here we report synergetic effects between SOC and the Stark effect in centrosymmetric few-layer black arsenic, which manifest as particle–hole asymmetric Rashba valley formation and exotic quantum Hall states that are reversibly controlled by electrostatic gating. The unusual findings are rooted in the puckering square lattice of black arsenic, in which heavy 4p orbitals form a Brillouin zone-centred Γ valley with pz symmetry, coexisting with doubly degenerate D valleys of px origin near the time-reversal-invariant momenta of the X points. When a perpendicular electric field breaks the structure inversion symmetry, strong Rashba SOC is activated for the px bands, which produces spin–valley-flavoured D± valleys paired by time-reversal symmetry, whereas Rashba splitting of the Γ valley is constrained by the pz symmetry. Intriguingly, the giant Stark effect shows the same px-orbital selectiveness, collectively shifting the valence band maximum of the D± Rashba valleys to exceed the Γ Rashba top. Such an orchestrating effect allows us to realize gate-tunable Rashba valley manipulations for two-dimensional hole gases, hallmarked by unconventional even-to-odd transitions in quantum Hall states due to the formation of a flavour-dependent Landau level spectrum. For two-dimensional electron gases, the quantization of the Γ Rashba valley is characterized by peculiar density-dependent transitions in the band topology from trivial parabolic pockets to helical Dirac fermions.Two-dimensional electronic systems in few-layer black arsenic show gate-tunable Rashba bands with unique spin–valley flavours and unconventional quantum Hall states due to synergetic spin–orbit coupling and the Stark effect. [ABSTRACT FROM AUTHOR]

In order to make the system can obtain better throughput rate at low energy consumption under high load on the basis of limited adhere, p-detection and subsection control thought, the paper puts forward a new analysis of MAC protocol on wireless sensor network with muti-probability and joint-control random access, aiming at clustering wireless sensor networks based on event-driving and large amounts of emergent transfer data. The paper adopts average cycle analysis method to model analysis and performance index analysis, obtaining expressions of system throughput rate, average delay and communication energy consumption, etc. Performing simulation of indicators such as system throughput and communication energy consumption by MATLAB, simulation are in accord with theoretical results. MPCMA control protocol can effectively improve performance indicators of wireless sensor network based on random muti-address access under the rough load.The study lays the theoretical foundation for the application of wireless sensor network protocol combined control based on multi-probability under heavy load circumstance [ABSTRACT FROM AUTHOR]

In this study, based on depolymerization solution of commercially available sodium lignosulfonate under mild conditions, an efficient method for the chromatographic separation of lignosulfonate depolymerization products was firstly established. The self-built database contains 18 lignin-based standards and the information on their names, formulas, structures, retention times, fragments, and corresponding MSE data was developed. By searching the online spectral data in a novel informatics database, a total of nine aromatic lignin depolymerization products were identified automatically. Thus, a fast standard protocol for detection and identification of real lignin degradation products was preliminary built. [ABSTRACT FROM AUTHOR]

Spot continual induction hardening (SCIH) is a surface heat treatment process, which can strengthen more than one small area or relative large area on complicated component surface. In order to investigate the microstructure and mechanical properties of gray cast iron with curved surface after SCIH, the microstructure, microhardness and residual stresses were analyzed under different process conditions. The results showed that the martensite grain in hardened region of concave surface was larger than that of convex surface. The domain sizes of concave and convex surfaces were smaller than that of matrix region due to the high heating rate in SCIH process. The phase transformation depth increased with the increasing of convex surface radius but decreased with the increasing of concave surface radius. The maximum values of residual tensile and compressive stresses increased with the increasing of feed velocity for convex and concave surfaces, respectively. The appearance positions of maximum tensile and compressive stresses were closer to center for convex and concave surfaces, respectively, when feed velocity increased from 1 to 5 mm/s. The achieved results indicated that the SCIH with relatively low feed velocity was more suitable for improving the mechanical properties of gray cast iron. Compared with convex surface, the concave surface of workpiece can obtain better mechanical properties under the same feed velocity of inductor. [ABSTRACT FROM AUTHOR]

Cu doping of ZnTe, which is an important semiconductor for various optoelectronic applications, has been successfully achieved previously by several techniques. However, besides its electrical transport characteristics, other physical and chemical properties of heavily Cu-doped ZnTe have not been reported. We found an interesting self-assembled formation of crystalline well-aligned Cu-Te nano-rods near the surface of heavily Cu-doped ZnTe thin films grown via the molecular beam epitaxy technique. A phenomenological growth model is presented based on the observed crystallographic morphology and measured chemical composition of the nano-rods using various imaging and chemical analysis techniques. When substitutional doping reaches its limit, the extra Cu atoms favor an up-migration toward the surface, leading to a one-dimensional surface modulation and formation of Cu-Te nano-rods, which explain unusual observations on the reflection high energy electron diffraction patterns and apparent resistivity of these thin films. This study provides an insight into some unexpected chemical reactions involved in the heavily Cu-doped ZnTe thin films, which may be applied to other material systems that contain a dopant having strong reactivity with the host matrix. [ABSTRACT FROM AUTHOR]

The prismy YFeO with (202)-preferred orientation was successfully synthesized through hydrothermal process at 240 C for 9 h with the ratio 1:1 of Y:Fe. The prepared YFeO powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), physical properties measurement system (PPMS), and differential scanning calorimetry (DSC), respectively. The results show the prepared YFeO has (202)-preferred orientation. The prismatic YFeO powders mainly consist of three elements (Y, Fe, and O), and atom ratio matched well with the formula. YFeO can simultaneously present obvious weak ferromagnetic and antiferromagnetic properties. In addition, the Néel temperature of YFeO is 349 C. [ABSTRACT FROM AUTHOR]

Background and aims: Estimating the distribution of soil organic carbon (SOC) is essential for improving SOC sequestration. Our objectives were (1) to quantify the dependency of SOC stocks on vegetation type; (2) to identify in which aggregate sizes and chemical forms the SOC was stored; and (3) to determine which vegetation type was the most effective at sequestering SOC. Methods: The studied vegetation types were shrubland CK16 (16-year-old Caragana korshinskii Kom.), shrubland CK26 (26-year-old C. korshinskii Kom.), shrubland AS ( Armeniaca sibirica Lam.), natural grassland and artificial pasture. We investigated SOC stocks and measured soil carbon, in <0.25, 0.25-1, 1-2, 2-5 and 5-8 mm sized aggregates, and carbon fractions [humus (HS-C), humic acid (HA-C), fulvic acid (FA-C)] from CK shrublands, natural grassland and cropland. Results: The SOC stocks were the greatest for CK shrublands and natural grassland. Compared with cropland, shrubland CK caused increases in >2 mm sized aggregate C stocks. The 1-2, 2-5, 5-8 mm size aggregate C stocks were the highest in the natural grassland. HS-C was 1.4, 3.1, and 4.1 Mg ha greater in shrubland CK16, shrubland CK26, and natural grassland, respectively, than in cropland. Conclusions: Conversion to C. korshinskii shrublands and protection of natural grassland should be promoted to improve the contribution of vegetation to SOC sequestration. [ABSTRACT FROM AUTHOR]

In the present study, we investigated the potential pathogenesis of coxsackievirus B3 (CVB3)-induced viral myocarditis and the promising protective effect of silencing RNA (small interfering RNA, siRNA). One hundred and twenty mice were included in the study, and 30 mice were intraperitoneally inoculated with CVB3 to establish an acute viral myocarditis model. The survival rate was observed for the CVB3-infected mouse model (MOD), and myocardial injury was examined by HE (hematoxylin and eosin) staining assay. Real-time PCR (RT-PCR) and Western blot assay were selected to detect the toll-like receptor 4 (TLR4) expression in myocardial tissues. The TLR4 gene was silenced for the MOD mice, and the effects of this treatment were observed. The results indicate that the expression of TLR4 mRNA and the protein significantly and persistently increased during the progression of CVB3-induced myocarditis. The activities of cardiac enzymes including CK, LDH, AST, and CK-MB were also enhanced in CVB3-induced myocardial tissues. Interestingly, when the TLR4 gene was silenced, the CVB3-induced TLR4 production was significantly decreased and the severity of myocarditis was significantly lessened. In conclusion, CVB3 may induce viral myocarditis by upregulating toll-like receptor 4 expression. The viral myocarditis can be ameliorated by silencing the TLR4 gene in the CVB3 viral myocarditis model, which may be a feasible therapeutic method for treatment of viral myocarditis. [ABSTRACT FROM AUTHOR]

A large number of diesel vehicles carrying gravel and sand shuttle back and forth every day on the major thoroughfares (Tai-16 and Tai-21) from Shinyi to Jiji in Nantou, Taiwan. A total of 10 stations along the major thoroughfares were selected as the exposure sites, whereas a small village located ∼9 km from a main traffic route was selected as the control site. Outdoor and indoor aerosol samples were collected using high-volume samplers and Harvard samplers, respectively. The metal concentrations of outdoor and indoor PM10 at the exposure sites were, respectively, higher than those at the control site. The plots between metal contents in the aerosols and road dust showed that diesel vehicles contributed significant amounts of metals to the outdoor and indoor aerosols at the exposure sites. Household dust samples along the roadside within 30 m of the main road in the small towns were collected using the wipe method. Based on the results of principal component analysis (PCA), three major components for household dust were identified: resuspended from road dust, brake wear and diesel emissions. Enrichment factors were applied to assess the contribution of pollution sources to household dust. These factors were calculated with respect to unpolluted river dust samples (EFriver) and road dust (EFroad). The differences between EFriver and EFroad could be mainly attributed to the effects of resuspension by passing vehicles. Approximately 72%, 68%, 68%, 73% and 86% of the vehicle-related metals Pb, Zn, Cu, Ni and Mo content, respectively, in household dust were the result of the resuspension of road dust by passing vehicles. The data of daily intakes of five metals (i.e., Fe, Pb, Cu, Ni and Mo) from inhalation and ingestion pathways showed that the doses from the ingestion pathway were much higher than those from the inhalation pathway. [ABSTRACT FROM AUTHOR]

Killer cell Ig-like receptors (KIRs) modulate the cytotoxic effects of natural killer cells. In primates, the KIRs are highly diverse as a consequence of variation in gene content, alternative domain composition, and loci polymorphism. We analyzed a bacterial artificial chromosome (BAC) clone draft sequence spanning the owl monkey KIR cluster. The draft sequence had seven ordered yet unconnected contigs containing six full-length and two partial gene models, flanked by the LILRB and FcAR framework genes. Gene models were predicted to encode KIRs with inhibitory, activating, or dual functionality. Four gene models encoded three Ig domain receptors, while three others encoded molecules with four Ig domains. The additional domain resulted from an insertion in tandem of a 2,101 bp fragment containing the last 289 bp of intron 2, exon 3, and intron 3, resulting in molecules with two D0 domains. Re-screening of the owl monkey BAC library and sequencing of partial cDNAs from an owl monkey yielded five additional KIRs, four of which encoded receptors with short cytoplasmic domains with premature stop codons due to either a single nucleotide substitution or deletion or the absence of exon 8. Phylogenetic analysis by domains showed that owl monkey KIRs were monophyletic, clustering independently from other primate KIR lineages. Retroelements found in introns, however, were shared by KIRs from different primate lineages. This suggests that the owl monkey inherited a KIR cluster with a rich history of exon shuffling upon which positive selection for ligand binding operated to diversify the receptors in a lineage-specific fashion. [ABSTRACT FROM AUTHOR]

A study has been carried out on water soluble ions, trace elements, as well as PM2.5 and PM2.5–10 elemental and organic carbon samples collected daily from Central Taiwan over a one year period in 2005. A source apportionment study was performed, employing a Gaussian trajectory transfer coefficient model (GTx) to the results from 141 sets of PM2.5 and PM2.5–10 samples. Two different types of PM10 episodes, local pollution (LOP) and Asian dust storm (ADS) were observed in this study. The results revealed that relative high concentrations of secondary aerosols (NO, SO and NH) and the elements Cu, Zn, Cd, Pb and As were observed in PM2.5 during LOP periods. However, sea salt species (Na+ and Cl−) and crustal elements (e.g., Al, Fe, Mg, K, Ca and Ti) of PM2.5–10 showed a sharp increase during ADS periods. Anthropogenic source metals, Cu, Zn, Cd, Pb and As, as well as coarse nitrate also increased with ADS episodes. Moreover, reconstruction of aerosol compositions revealed that soil of PM2.5–10 elevated approximately 12–14% in ADS periods than LOP and Clear periods. A significantly high ratio of non-sea salt sulfate to elemental carbon (NSS-SO/EC) of PM2.5–10 during ADS periods was associated with higher concentrations of non-sea-salt sulfates from the industrial regions of China. Source apportionment analysis showed that 39% of PM10, 25% of PM2.5, 50% of PM2.5–10, 42% of sulfate and 30% of nitrate were attributable to the long range transport during ADS periods, respectively. [ABSTRACT FROM AUTHOR]

Measurements of atmospheric fine aerosols, acidic gases and ammonia were made at National Chung Hsing University (Urban) and Huisun forest area (Forest) sites in central Taiwan region during October (highest ozone month). Annular Denuder System (ADS) was used for sampling gaseous (nitrous acid, nitric acid, sulfur dioxide and ammonia) and fine aerosol species (ammonium, nitrate and sulfate). The results showed a significant diurnal variation in nitrous acid and nitric acid concentrations. Nitric acid was produced primarily during daytime in both sites. In the urban site, the average concentration of nitric acid during daytime was 5.8 times higher compared to nighttime while the average nitrous acid concentration during daytime was lower compared to nighttime, due to the photo-dissociation of nitrous acid. Sulfate, nitrate and ammonium were the major constituents of PM2.5. Higher concentrations of nitrous acid, nitric acid, particulate nitrate and ammonium were recorded at urban site. [ABSTRACT FROM AUTHOR]

A CD-ROM consisting of videos of two lessons by different teachers demonstrating exemplary science teaching was used to elicit, develop and track the changing conceptions of good science teaching of student teachers enrolled for the one-year Postgraduate Diploma in Education (PGDE) at several stages during the programme. It was found that the videos acted as an effective probe to elicit student teachers’ conceptions and had significant impact on those conceptions at different stages of the programme through the provision of teacher models demonstrating exemplary teaching. The experience has extended novice teachers’ awareness of alternative teaching methods and approaches not experienced in their own schooling, broadened their awareness of different classroom situations, provided proof of existence of good practices and prompted them to reflect on their current conceptions of good science teaching. Most importantly, the strategy of asking student teachers to watch the same videos on three separate occasions at different times of the course was recognized by them as a crucial element in facilitating their reflection on their changing conceptions of good science teaching. [ABSTRACT FROM AUTHOR]

Fifty-six Fischer 344 rats bearing subcutaneous 9L-gliosarcoma tumours were studied to determine if Misonidazole (MISO), combined with photodynamic therapy (PDT), would be more effective than PDT alone. PDT, like conventional radiation, is potentiated by oxygen, and if there are areas of hypoxic cells within the tumour it is possible that the addition of the radiosensitizing drug should make the treatment more effective. Thirty-nine rats were divided into eight groups as controls. Seventeen rats were divided into three groups and received MISO combined with PDT, five rats were exposed to a laser dose of (nm = 630) 300 J at 300 mW, seven rats to a laser dose of 600 J at 600 mW and five rats to a laser dose of 2160 J at 600 mW. The tumours were approximately 1 cm when treated. Animals treated with either PDT at 300 J or 600 J failed to show any effect on growth of the tumour. At 2160 J a definite delay in growth was observed but addition of MISO did not potentiate this effect. The results indicate this combined therapy did not slow the growth rate of the tumours in this model. The implication of these results are discussed. [ABSTRACT FROM AUTHOR]

Suspensions of 9L-gliosarcoma cells were inoculated into the brain or flank of rats and photoradiation therapy (PRT) was applied to the resulting tumors. The PRT consisted of hematoporphyrin derivative (HpD), type I or II, followed by single-fiber laser energy 24, 48, or 72 h later. Necrotic foci in brain tumors were most numerous following laser exposure 24 h after HpD; they were more than twice as common, and with less damage to healthy tissue, after HpD II than after HpD I with the same laser dose. Neither lifespan nor the final weight of brain tumor was affected by the type of HpD or whether PRT was applied once or twice. In rats with flank tumor, multiple PRT (up to × 4) did not delay tumor growth; also, 11 of 12 PRT-treated flank tumors grew after implantation at various sites in healthy rats. We conclude that HpD II is a more effective photosensitizer than HpD I. However, the value of PRT will be limited until a lethal dose of laser energy can be delivered throughout a tumor without destroying vital healthy tissue. [ABSTRACT FROM AUTHOR]

Brain and glioma tissue levels of tritiated hematoporphyrin derivative (H-HPD) were measured in normal and 9L intracerebral glioma-bearing rats at 24 hours following administration ofH-HPD 2-20 mg/kg and at 24-120 hours afterH-HPD 10 mg/kg. Levels ofH-HPD in blood, liver, spleen and muscle were also measured. Tissue levels ofH-HPD increased progressively as the dose was increased. In animals given 10 mg/kg, gradual decreases in tissue levels occurred between 24 and 72 hours but thereafter remained stable. TheH-HPD level in gliomas was consistently 2-3 × greater than in brain tissue, despite changes in dosage and time interval. High levels of activity were measured in normal brain tissue at all dosage levels, and subsequent clearance of theH-HPD from brain, glioma, and other tissues was slow; at 120 hours after administration of 10 mg/kg, approximately 50% of the 24 hour level was still present. These results indicate that although a dose- and time-independent preferential uptake of hematoporphyrin derivative occurs in intracerebral gliomas, persistent high levels may be present in the surrounding brain. The disadvantages of using hematoporphyrin derivative rather than its individual components in studies of HPD uptake and photosensitization in the brain are discussed. [ABSTRACT FROM AUTHOR]