Candida albicans growth on thermal cycled materials for maxillofacial prostheses in vitro

In the present study, the growth of a single isolate of Candida albicans on saliva-, serum-coated or protein free (uncoated), thermocycled (4-70 degrees C for 1 min, respectively; 0, 1000 and 10 000 times) 15 commercial maxillofacial materials was investigated, by monitoring pH changes in growth media. The inhibitory effect of the tissue conditioners on fungal growth was analysed using three parameters viz: (i) delay in the onset of the rapid decline in pH (ii) reduction in the rate of pH change and (iii) the pH minima reached. In the case of control materials (non-thermocycled and uncoated), significant antifungal effect was observed with two products. However, the antifungal effect of the materials was significantly reduced both by thermal cycling (Analysis of covariance [ANOVA]; P < 0.01) and a layer of protein coating (saliva, P < 0.05; serum, P < 0.01). When the interrelation between three parameters of fungal growth and the surface hydrophobicity of the materials were analysed, minimum pH of fungal growth on 10 000-thermocycled materials correlated well with the contact angles of the materials (Student t-test, P < 0.01), suggesting that thermocycling process reduced the unpolymerized components of the materials which showed the antifungal effects, resulted in that the cell growth depends on the surface hydrophobicity of the specimens. These results, taken together, suggest that the ageing of the materials and the biological fluids of the host enhanced the fungal growth on maxillofacial materials.     

Kr:F准分子激光对牙体硬组织的热效应研究

目的：评价Kr:F准分子激光照射牙齿后，对牙体硬组织的影响。方法；通过测量Kr:F准分子激光照射后牙齿硬组织的温度，并与Nd:YAG激光照射组进行比较。结果：10s,60s时，Kr:F准分子激光组牙齿硬组织的温度升高值明显低于Nd：YAG激光照射组（P＜0．01）。在照射10s-60s时间内，Kr:F准分子激光照射后牙齿硬组织的温度变化值也明显低于Nd:YAG激光照射组（P＜0．01）。结论：Kr:F准分子激光牙齿产热较少。     

内外兼治法对血瘀气滞型腰痛病腰腿痛症状改善的影响

目的:观察外治法、外治法+口服药物治疗气滞血瘀型腰腿痛的远期疗效。方法:选取北京中医医院顺义医院2015年1月至2016年4月共74例符合:血瘀气滞证型的腰痛病且诊断腰椎间盘突出症住院的患者,随机分成治疗、对照组各自37例。对照组外治(磁振热理疗仪)、观察组内外兼治(身痛逐瘀汤口服、磁振热理疗仪外用)。分别计算治疗前及治疗后3个月患者的腰腿VAS评分。结果:3个月后腰腿痛VAS评分观察组治疗后VAS评分(3.17±1.02)分、对照组治疗后为(4.28±1.21)分,优良率及总有效率,观察组优于对照组(P0.05)。结论:应用内外兼治法治疗血瘀气滞型腰痛病具有较好的远期临床疗效。     

基于藏医白脉理论的中风病诊疗规律探析

藏医将人体的经脉分为黑脉和白脉。藏医认为因季节环境、饮食不当、瘟毒热邪侵入脉道,或外伤等损害白脉,导致三因素中的隆和血液紊乱而诱发白脉病。白脉病是藏医白脉系统遭受致病因素的影响后所致的一系列疾病的总称,临床上很多疾病归属于“白脉病”。中风病是藏医白脉病的一种,临症时需根据疾病的寒热属性、发病时间、病位及其三因素（赤巴、隆、培根）归属情况,据理选药、对治疾病,是藏医辨治白脉病的基本规律,临床时应按照藏医的诊疗规律、综合诊查病因、把握疾病证候变化规律来施治用药。     

超声造影联合声辐射力脉冲弹性成像评估微波消融治疗大鼠肝泡型棘球蚴病

目的 观察超声造影（CEUS）联合声辐射力脉冲（ARFI）弹性成像技术评价微波消融（MWA）治疗大鼠肝泡型棘球蚴病（HAE）效果的价值。方法 将40只HAE大鼠模型分为实验组（n=30）和对照组（n=10）。实验组予超声引导下MWA,对照组仅常规饲养。术前及术后1个月采用二维超声、CEUS和ARFI测量2组病灶最大径,以及实验组病灶边缘带平均灰阶比值与剪切波速度（SWV）。完成检测后处死大鼠,对组织切片行常规HE染色、CD34免疫组织化学染色及Masson染色,计数病灶边缘带微血管密度（MVD）及纤维化面积。结果 术后1个月,3种方法所测实验组病灶最大径均较术前缩小（P均<0.001）,对照组病灶最大径均较入组时增大（P均<0.001）;CEUS、ARFI所测病灶最大径均大于二维超声（P均<0.05）,CEUS与ARFI组间差异无统计学意义（P均>0.05）。术后1个月实验组病灶边缘带平均灰阶比值低于术前,平均SWV高于术前（P均<0.001）;病灶边缘带MVD低于而纤维化面积高于对照组（P均<0.001）,MVD与病灶边缘带灰阶比值呈正相关（r=0.541,P=0.011）,SWV与纤维化面积呈正相关（r=0.494,P=0.023）。结论 CEUS联合ARFI对评估MWA治疗大鼠HAE效果具有一定应用价值。     

Manipulating the Properties of Poly(1,4‐Cyclohexylenedimethylene Terephthalate) (PCT) Just by Tuning Steric Configuration of 1.4‐Cyclohexanedimethanol (CHDM)

The properties of poly(1,4‐cyclohexylenedimethylene terephthalate) (PCT) are manipulated only by tuning the steric configuration of 1,4‐cyclohexanedimethanol (CHDM). The chemical structures and compositions of PCTs are confirmed by nuclear magnetic resonance (¹H NMR and ¹³C NMR) before their thermal and mechanical properties are investigated by differential scanning calorimeter, thermogravimetric analyzer, and dynamic mechanical analysis. Results show that the ratio of cis‐ to trans‐CHDM in PCTs has significant influences on their properties. The melting temperature of PCTs is varied from 251 to 313 °C, and the glass transition temperature is increased from 73 to 92 °C when the content of trans‐CHDM in PCTs is increased from 10% to 96%. In addition, the crystallizability of PCT is also increased with the content of trans‐CHDM. However, its thermal stability is decreased seriously when the melting temperature of PCT is higher than 280 °C. It is concluded that when the content of trans‐CHDM is lower than 50% (PCT‐10, PCT‐28, and PCT‐46), the balance of melting temperature, glass transition temperature, and thermal stability for PCT can be achieved. Just by varying the cis/trans ratio of CHDM, rather than the addition of other components, the properties of PCT can be manipulated.     

Volcano-induced regime shifts in millennial tree-ring chronologies from northeastern North America

Dated records of ice-cap growth from Arctic Canada recently suggested that a succession of strong volcanic eruptions forced an abrupt onset of the Little Ice Age between A.D. 1275 and 1300 [Miller GH, et al. (2012) Geophys Res Lett 39(2):L02708, 10.1029/2011GL050168]. Although this idea is supported by simulation experiments with general circulation models, additional support from field data are limited. In particular, the Northern Hemisphere network of temperature-sensitive millennial tree-ring chronologies, which principally comprises Eurasian sites, suggests that the strongest eruptions only caused cooling episodes lasting less than about 10 y. Here we present a new network of millennial tree-ring chronologies from the taiga of northeastern North America, which fills a wide gap in the network of the Northern Hemisphere''s chronologies suitable for temperature reconstructions and supports the hypothesis that volcanoes triggered both the onset and the coldest episode of the Little Ice Age. Following the well-expressed Medieval Climate Anomaly (approximately A.D. 910–1257), which comprised the warmest decades of the last millennium, our tree-ring-based temperature reconstruction displays an abrupt regime shift toward lower average summer temperatures precisely coinciding with a series of 13th century eruptions centered around the 1257 Samalas event and closely preceding ice-cap expansion in Arctic Canada. Furthermore, the successive 1809 (unknown volcano) and 1815 (Tambora) eruptions triggered a subsequent shift to the coldest 40-y period of the last 1100 y. These results confirm that series of large eruptions may cause region-specific regime shifts in the climate system and that the climate of northeastern North America is especially sensitive to volcanic forcing.Tree-ring chronologies are the type of proxy record most used to develop climate reconstructions covering the last millennium (1). These chronologies have been integrated into large-scale networks, often with additional proxies, to document the amplitude, duration, and forcing mechanisms of the Medieval Climate Anomaly, the Little Ice Age, and the recent warming trend. However, the spatial coverage of long tree-ring records must be improved to allow a better understanding of regional variations in past climate (1, 2). For example, in eastern North America, millennial climate reconstructions have been constructed from tree species and sites sensitive to drought and precipitation (3), whereas temperatures were inferred solely from low-resolution proxies, such as pollen data (4, 5). Furthermore, only tree-ring-based climate reconstructions shorter than a millennium or using chronologies poorly replicated before A.D. 1500 have been published for the entire North American boreal forest (6, 7), whereas several millennial, highly replicated, temperature-sensitive tree-ring records have been developed across the Eurasian boreal zone. This lack of data is an important issue that causes the poor representation of North America in long-term, large-scale temperature reconstructions (1, 4).The feasibility of reconstructing volcanic forcing from tree-ring data has been debated, especially in regards to large and successive eruptions. Two of the largest eruptions of the last millennium, the A.D. 1257 Samalas and A.D. 1815 Tambora events, were both closely followed and preceded by additional large eruptions in 1227, 1275, 1284, 1809, and 1835 (8−11). Whereas general circulation model experiments suggest that the impacts of large and successive eruptions might have influenced climate systems for periods ranging from 20 y to several decades, or even centuries (12–16), Northern Hemisphere tree-ring-based temperature reconstructions only display negative temperature anomalies lasting between 2 and 10 y (17–20). Region-specific responses of the climate system to volcanic forcing may in part explain this discrepancy (17). For example, large and successive eruptions may have had stronger impacts on summer temperatures in northeastern North America (hereafter NENA) than elsewhere. An extensive Northern Hemisphere network of tree-ring density chronologies supports this idea, showing that the coldest 1816 temperature anomalies occurred over the Quebec-Labrador Peninsula (21), where they may have persisted for several decades (7). The idea is also supported by the abrupt acceleration of ice-cap growth in the Eastern Canadian Arctic during A.D. 1275–1300, at the onset of the Little Ice Age, as a consequence of a series of eruptions (22). However, the lack of millennial, well-replicated, and temperature-sensitive tree-ring chronologies in the NENA sector precludes the examination of the volcano−temperature relationship in a long-term context with an annual resolution.In this study, we have built a network of six highly replicated millennial tree-ring chronologies from large stocks of black spruce [Picea mariana (Mill.) B.S.P.] subfossil trees preserved in lakes of the NENA taiga from which we developed a millennial reconstruction (A.D. 910–2011) of regional July−August temperatures. For this purpose, we selected homogeneous sites with infrequent and well-documented ecological disturbances (23), and sampled homogeneous subfossil and living samples to maximize the robustness of our reconstruction. We then used a Bayesian mixture of probability distributions with dependence (also referred to as hidden Markov models or Markov switching models; see refs. 24 and 25) to detect possible regime shifts in summer temperatures triggered by series of large eruptions and to provide new insights concerning the climate history of NENA during the last 1,100 y.     

Comparison of the isomerization mechanisms of human melanopsin and invertebrate and vertebrate rhodopsins

Comparative modeling and ab initio multiconfigurational quantum chemistry are combined to investigate the reactivity of the human nonvisual photoreceptor melanopsin. It is found that both the thermal and photochemical isomerization of the melanopsin 11-cis retinal chromophore occur via a space-saving mechanism involving the unidirectional, counterclockwise twisting of the =C11H-C12H= moiety with respect to its Lys340-linked frame as proposed by Warshel for visual pigments [Warshel A (1976) Nature 260(5553):679–683]. A comparison with the mechanisms documented for vertebrate (bovine) and invertebrate (squid) visual photoreceptors shows that such a mechanism is not affected by the diversity of the three chromophore cavities. Despite such invariance, trajectory computations indicate that although all receptors display less than 100 fs excited state dynamics, human melanopsin decays from the excited state ∼40 fs earlier than bovine rhodopsin. Some diversity is also found in the energy barriers controlling thermal isomerization. Human melanopsin features the highest computed barrier which appears to be ∼2.5 kcal mol⁻¹ higher than that of bovine rhodopsin. When assuming the validity of both the reaction speed/quantum yield correlation discussed by Warshel, Mathies and coworkers [Weiss RM, Warshel A (1979) J Am Chem Soc 101:6131–6133; Schoenlein RW, Peteanu LA, Mathies RA, Shank CV (1991) Science 254(5030):412–415] and of a relationship between thermal isomerization rate and thermal activation of the photocycle, melanopsin turns out to be a highly sensitive pigment consistent with the low number of melanopsin-containing cells found in the retina and with the extraretina location of melanopsin in nonmammalian vertebrates.For a long time it was assumed that the human retina contains only two types of photoreceptor cells: the rods and cones responsible for dim-light and daylight vision, respectively. However, recent studies have revealed the existence of a small number of intrinsically photosensitive retinal ganglion cells (ipRGCs) that regulate nonvisual photoresponses (1). ipRGCs express an atypical opsin-like protein named melanopsin (2, 3) which plays a role in the regulation of unconscious visual reflexes and in the synchronization of endogenous physiological responses to the dawn/dusk cycle (circadian rhythms) (4, 5).Melanopsins are unique among vertebrate photoreceptors because their amino acid sequence shares greater similarity to invertebrate than vertebrate rhodopsin (i.e., the photoreceptor of rods) (6, 7). Like rhodopsins, melanopsins feature an up–down bundle architecture of seven transmembrane α-helices incorporating the 11-cis isomer of retinal as a covalently bound protonated Schiff base (PSB11 in Fig. 1A). Light-induced (i.e., photochemical) isomerization of PSB11 to its all-trans isomer (PSBAT) triggers an opsin conformational change that, ultimately, activates the receptor and signaling cascade (8, 9). However, similar to invertebrate and in contrast to vertebrate rhodopsins, melanopsins are bistable (10). Indeed, although vertebrate rhodopsins need a retinoid cycle (11) to regenerate PSB11, melanopsins have an intrinsic light-driven chromophore regeneration function via PSBAT back-isomerization. Furthermore, past studies have shown that melanopsins use an invertebrate-like signal transduction cascade (12).Open in a separate windowFig. 1.PSB11 chromophore reactivity. (A) Chromophore structure and isomerization to PSBAT. (B) Schematic representation of the photochemical (full arrows) and thermal (dashed arrows) isomerization paths. The CI is located energetically above the TS, features a different geometrical structure, and drives a far-from-equilibrium process. ΔE_S1-S0, τ_cis→trans, and Ea^T (in red) are the fundamental quantities computed in the present work.Melanopsins are held responsible for photoentrainment, using the changes of irradiance and spectral composition to adjust the circadian rhythm (13). The different studies carried out so far on melanopsin light sensitivity do not lead to consistent results. Although Do et al. (14) argue that ipRGCs work at extremely low irradiation intensities showing a single-photon response larger than rods, Ferrer et al. (15) conclude that the melanopsin has a reduced sensitivity relative to visual pigments. On the other hand, these photoreceptors would be expected to display high light sensitivity (14). In the vertebrate retina their density is 10⁴ times lower than that of rhodopsins. Moreover, the receptor is not confined in a dedicated cellular domain such as the outer segment of rods and cones, resulting in a ipRGCs photon capture more than 10⁶-fold lower than that of rods and cones per unit of retina illumination. A high sensitivity of melanopsins would also be consistent with their presence in extraretina locations such as in pineal complex, deep brain, and derma of nonmammalian vertebrates (e.g., amphibian) (16–18). The amount of light that can penetrate into such regions is limited and enriched in the red component due to light scattering by the surrounding tissues (14).The molecular-level understanding of the primary light response of melanopsin is a prerequisite for the comprehension of more complex properties such as its activation and sensitivity. Despite numerous studies carried out since its discovery (16), there is presently little information on the molecular mechanism of melanopsin activation. The common PSB11 chromophore of melanopsins and rhodopsins does not guarantee that the same mechanism operates in both photoreceptors. This not only concerns light-induced activation but also thermal activation: a process whose rate limits the photoreceptor light sensitivity and that is currently associated with thermal, rather than photochemical, PSB11 isomerization (19–24).The mechanism of light-induced PSB11 isomerization in vertebrate rhodopsins has been extensively investigated. Spectroscopic studies have shown that in bovine rhodopsin (Rh) the isomerization occurs on a subpicosecond timescale (25–27). Moreover, the observation of ground state (S₀) vibrational coherence (28) is consistent with a direct transfer of the excited state (S₁) population to the photoproduct (Fig. 1B) passing through a conical intersection (CI). Such a path has been located along the S₁ potential energy surface by constructing a multiconfigurational quantum chemistry (MCQC) based computer model of the photoreceptor (29–31) and spectroscopically supported by probing in the infrared (31). More recently (32), the same computer model has been used to map the Rh thermal isomerization path (Fig. 1B) providing information on the transition states controlling the reaction.Here we present a computational study focusing on the mechanism of photochemical and thermal isomerization of human melanopsin (hMeOp). This would require the construction of a computer model of hMeOp starting from the receptor crystal structure. However, the lack of hMeOp crystallographic data does not allow the use of the protocol previously applied in Rh studies. The significant sequence similarity between squid rhodopsin (sqRh), whose crystal structure is available (PDB code: 2Z73) (33), and hMeOp (40%, SI Appendix, Fig. S1) provides the fundamentals for constructing a structural model of hMeOp at a significant atomic resolution. Building on a study by Batista and coworkers (34) on murine melanopsin, we combine comparative modeling of hMeOp with MCQC to construct a quantum mechanics/molecular mechanics (QM/MM) computer model capable of simulating the photochemical and thermal isomerization reactions of hMeOp. The results are then compared with those found using Rh and sqRh models constructed using the same protocol. Such a comparison is expected to provide information on the differences in spectral and functional properties of these evolutionary distant pigments. As we will show below, the models indicate that hMeOp has a faster photochemical isomerization dynamics and a higher thermal isomerization barrier than both Rh and sqRh.     

Temperature-influenced dimensional change of different molar anatomical areas

ObjectiveTo analyse the linear coefficient of thermal expansion (LCTE) of different tooth regions using thermal mechanical analysis (TMA).MethodsSpecimens (n = 12) were sectioned from different anatomical areas from recently extracted molars using a slow-speed diamond saw. During analysis the specimens were kept saturated with phosphate-buffered saline using a specially designed quartz container that was placed inside the TMA unit. Specimens were subjected to a 15–50 °C heating cycle as well as a 50–15 °C cooling cycle at a 5 °C/min rate. LCTE was determined using the slope of each respective cycle with each specimen being run three times with the mean representing the LCTE of each specimen. Mean results between heating and cooling for each sample were compared with paired t-test while results between regions were compared with ANOVA and Tukey post hoc (p = 0.05).ResultsSignificant differences in LCTE were noted between tooth regions with caries-affected dentine, cervical, and root surfaces exhibited significantly lower LCTE. Furthermore, cooling LCTE was significantly greater than heating in all areas.ConclusionsUnder the conditions of this study, molar LCTE was found not to be uniform in all areas. Furthermore, cooling LCTE was found to be greater than heating.