The two axes of the human eye and inversion of the retinal layers: The basis for the interpretation of the retina as a phase grating optical,cellular 3D chip

The question of why the human eye has two axes, a photopic visual axis, and an eye axis, is just as justified as the one of why the fovea is not on the eye axis, but instead is on the visual axis. An optical engineer would have omitted the second axis and placed the fovea on the eye axis. The answer to the question of why the design of the real eye differs from the logic of the engineer is found in its prenatal development. The biaxial structure was the only possible consequence of the decision to invert the retinal layers. Accordingly, this is of considerable importance. It, in turn, forms the basis of the interpretation of the retina as a cellular 3D phase grating, and can provide a grating-optical interpretation of adaptive effects (Purkinje shift) and aperture phenomena (Stiles-Crawford effects I and II, Bezold-Brücke phenomenon) and visual acuity data in photopic and scotopic vision.     

Flower colours along an alpine altitude gradient, seen through the eyes of fly and bee pollinators

Alpine flowers face multiple challenges in terms of abiotic and biotic factors, some of which may result in selection for certain colours at increasing altitude, in particular the changing pollinator species composition, which tends to move from bee-dominated at lower elevations to fly-dominated in high-alpine regions. To evaluate whether growing at altitude—and the associated change in the dominant pollinator groups present—has an effect on the colour of flowers, we analysed data collected from the Dovrefjell National Park in Norway. Unlike previous studies, however, we considered the flower colours according to ecologically relevant models of bee and fly colour vision and also their physical spectral properties independently of any colour vision system, rather than merely looking at human colour categories. The shift from bee to fly pollination with elevation might, according to the pollination syndrome hypothesis, lead to the prediction that flower colours should shift from more bee-blue and UV-blue flowers (blue/violet to humans, i.e. colours traditionally associated with large bee pollinators) at low elevations to more bee-blue-green and green (yellow and white to humans—colours often linked to fly pollination) flowers at higher altitude. However, although there was a slight increase in bee-blue-green flowers and a decrease in bee-blue flowers with increasing elevation, there were no statistically significant effects of altitude on flower colour as seen either by bees or by flies. Although flower colour is known to be constrained by evolutionary history, in this sample we also did not find evidence that phylogeny and elevation interact to determine flower colours in alpine areas. Handling editor: Neal Williams     

Inhibitors of human immunodeficiency virus-1 protease.

We have shown that the interaction of pepstatin A with human immunodeficiency virus-1 protease (HIV-1 protease) can be characterized by a high-affinity mode (Ki = 478 +/- 27 nM), resulting in pure competitive inhibition of the hydrolytic activity of HIV-1 protease toward the fluorogenic substrate. Binding of pepstatin in this mode induces a blue shift in the endogenous fluorescence arising from the tryptophan residues in HIV-1 protease. This shift is maximal in the presence of 10 microM pepstatin. Haloperidol, in contrast, interacts with HIV-1 protease with weaker affinity (Ki = 19 +/- 1 microM) in a mode which results in pure noncompetitive inhibition of the hydrolytic activity of HIV-1 protease. Binding of haloperidol in this mode induces a red shift in the endogenous fluorescence arising from the tryptophan residues in HIV-1 protease. This shift is maximal in the presence of 200 microM haloperidol. Addition of both pepstatin and haloperidol at concentrations in the range of their Ki values results in additive inhibition of the hydrolytic activity of HIV-1 protease, as well as an additive effect on the tryptophan fluorescence of protease. However, at saturating concentrations of pepstatin and haloperidol, the effect of haloperidol was predominant, as measured by the changes in the intrinsic fluorescence of HIV-1 protease.     

A comparative study of the relationship between light intensity and feeding ability in brown trout (Salmo trutta) and Arctic charr (Salvelinus alpinus)

1. Field observations indicate that the ability to feed at different light intensities may differ between brown trout and Arctic charr, and this is the first study to test this experimentally. To establish a background level of feeding in daylight at midday, trout and charr in two size groups were kept in tanks (one fish per tank) at three constant temperatures (5.0, 10.8 and 13.0 °C) and each fish was offered, one at a time, 50 freshly killed shrimps (Gammarus pulex), the number eaten being recorded. Shrimps could only be taken in the water column because a metal mesh prevented access to dead shrimps on the tank bottom. In a first series of experiments, individual fish were kept at one of 10 natural light intensities (range 0.001–50 lx). In a second series, conditions were similar except that the fish tank was covered in black polyethylene and had a light‐tight lid with a shutter so that light levels could be kept constant, using artificial illumination. In a third series, the fish were fed in total darkness, but the false bottom was removed, allowing access to dead shrimps on the tank bottom as well as in the water column. 2. The results of the first and second series differed interspecifically but were very similar intraspecifically, with no significant differences between the food intake for the two size groups or in the experiments at 10.8 and 13.0 °C. Food intake remained fairly constant at light intensities between 50 lx (dusk or dawn) and 0.03 lx and was similar to that of fish feeding at midday. At 10.8 and 13.0 °C, food intake between 0.03 and 50 lx was higher for trout than for charr, mean values for shrimps eaten per fish being 39.9 for trout (range 36–44, n = 100 fish) and 32.0 for charr (range 28–38, n = 100), but at 5.0 °C, the situation was reversed with mean values of 15.1 for trout (range 11–18, n = 50 fish) and 19.8 for charr (range 17–22, n = 50). 3. As light intensity decreased from 0.04 to 0.001 lx, feeding rate decreased exponentially but was always higher for charr than for trout, with a mean number of shrimps eaten at 0.001 lx of 9.3 for trout (range 5–13, n = 20 fish) and 13.6 for charr (range 9–20, n = 20) at 10.8 and 13.0 °C, and 2.0 for trout (range 1–4, n = 10 fish) and 5.5 for charr (range 2–8, n = 10) at 5.0 °C. In total darkness (false bottom fitted), none of the 50 shrimps was taken by either species. When the false bottom was removed in the third series, the mean number of shrimps consumed over 24 h was eight for trout (range 3–11, n = 20 fish) and 14.9 for charr (range 9–20, n = 20) at 10.8 and 13.0 °C, and two for trout (range 0–4, n = 10 fish) and five for charr (range 3–8, n = 10) at 5.0 °C. 4. Therefore, the feeding ability of trout was superior to that of charr when using photopic vision in daylight and mesotopic vision at dusk and dawn, but inferior to that of charr when using scotopic vision at low light intensity. Charr were also superior at low temperatures and when foraging for food in total darkness. Therefore, as light intensity decreases after dusk in their natural habitat, the advantage in feeding will shift from trout to charr, with the reverse occurring as light intensity increases after dawn.     

Influence of bulky substituents on the regioselective group-transfer reactions of diorganozinc compounds with N, N′-bis(2,6-di-isopropylphenyl)-1,4-diaza-1,3-butadiene

Diorganozinc compounds R₂Zn (R=alkyl or aryl) react with N,N′-bis(2,6-di-isopropylphenyl)-1,4-diaza-1,3-butadiene, (i-Pr₂Ph)N=CHCHp=N(i-Pr₂Ph) (i-Pr₂Ph-DAB) to give thermally unstable 1:1 coordination complexes R₂Zn(i-Pr2Ph-DAB), which subsequently undergo a slow regioselective alkyl or aryl group-transfer reaction from the zinc atom to an imine-nitrogen or a carbon atom of the NCCN system of the i-Pr₂Ph-DAB ligand. In the case of R=methyl, n-propyl, n-butyl, s-butyl, neopentyl and benzyl, C-alkylation occurs with a subsequent 1,2- hydrogen shift in the amino-imino skeleton affording RZn[(i-Pr₂Ph)N-CH₂-CR=N(i-Pr₂Ph)], whereas for R=t- butyl the C-alkylated product t-BuZn[(i-Pr₂Ph)N---CH(t-Bu)---CH=N(i-Pr₂Ph)] is stable. Surprisingly, diphenylzinc reacts with i-Pr₂Ph-DAB exclusively to give the N-arylated product PhZn[(i-Pr₂Ph)N=CHCH=N(Ph)(i-Pr₂Ph)].     

超连续谱激光可见谱段致人眼眩目效应研究

本文采用超连续谱激光光源滤除其红外部分仅输出可见谱段部分,在不超过国家安全标准允许的最大辐照量条件下,以正入射方式照射人眼后,记录并分析在明、暗适应条件下中心极限视力恢复时间、中心近极限视力恢复时间和视觉后像持续时间,明确超连续谱激光可见谱段对人眼的眩目效果。明适应下激光照射0.1 s导致人眼中心极限视力恢复时间为31~119 s,中心近极限视力恢复时间为19~76 s;暗适应下激光照射0.1 s导致人眼中心极限视力恢复时间为26~223 s,中心近极限视力恢复时间为13~123 s;明、暗适应下导致人眼眩目效应的最小功率密度值分别为0.055 mW/cm^2和0.005 mW/cm^2。结果表明,超连续谱激光可见谱段对人眼有良好的眩目效果,可导致数十秒至数百秒的中心视力下降,随着照射功率密度增高,眩目效应增强,显示出较好的量效关系,且相同功率密度时暗适应下人眼的眩目效果优于明适应。该研究探究了明、暗适应条件下超连续谱激光对人眼眩目效应,明确了超连续谱激光与人眼眩目的量效关系。     

Trivial influences: A doubly stochastic poisson process model permits the detection of arbitrarily small electromagnetic signals

If a weak, exogenous, extremely low-frequency (ELF) electric or magnetic field is to produce biological sequelae, then there must exist averaging sufficient to lift some primary effect of that field above the endogenous stochastic variations of the biological system. One way in which a field could accomplish this is by changing the intensity of some stochastic operation that controls an important and not trivially reversible biological transformation. In this paper, this operation is modeled as a doubly stochastic Poisson process. It is then shown, first, that (in theory) even a minuscule exogenous influence might appreciably shift the incidence of a sufficiently rare transformation and, second, that this shift might be observable if a trial were allowed to run long enough over a sufficiently large population of exposed entities. © 1995 Wiley-Liss, Inc.     

生态系统稳态转换检测研究进展

在气候变化、人类活动等影响下,生态系统结构和功能可能发生大规模的突变,导致生态系统从一个相对稳定的状态进入另一个稳定状态,这种现象称为稳态转换。由于生态系统的复杂性,准确刻画生态系统多稳态并界定其临界点尚存在挑战,提升对生态系统稳态转换的检测和预测能力依旧是生态学领域研究的热点和难题。基于多稳态理论和稳态转换经典概念框架,阐释了稳态转换检测的理论基础;归纳总结出四种稳态转换检测方法的原理和优劣势;鉴于稳态转换的尺度依赖性,梳理了单一生态系统、区域综合生态系统和全球生态系统不同尺度下的稳态转换检测方法、研究思路和应用案例。基于研究进展和问题现状,提出在未来研究中,亟待发展适应复杂系统的综合检测方法;创新稳态转换多尺度分析的技术方法体系;深化生态系统稳态转换驱动机制研究,构建多元耦合机理模型;进而深化稳态转换检测结果链接生态系统管理的实践研究;解析生态系统服务和可持续发展机制。     

The effect of a novel CCK-antagonist (lorglumide) on human and guinea pig gallbladder strips: a tensiometric study

The effect of a novel CCK-antagonist (lorglumide, CR 1409) was evaluated by "in vitro" tensiometric studies on 16 human (gallstone patients) and 12 guinea pig gallbladder smooth muscle strips. In the animal experiments, increasing doses of lorglumide (0.2-6.5 uM) caused a rightward shift of the dose-response curves of CCK-OP, with an increase of the ED50 from 8.2 nM +/- 1.62 SEM, n = 12; to 100 nM +/- 12, n = 4) without affecting the maximal effect (Emax). Schild plot gave an affinity constant of 7.19. In human gallbladders, the effect of lorglumide was also present (ED50 increased from 47 nM +/- 8 SEM, n = 16; to 300 nM +/- 10 SEM, n = 4) coexisting with a large inter-sample variation for CCK-OP ED50s and maximal contractions, most likely due to the histological changes of the wall in chronic cholecystitis. The affinity constant was similar to that found in animal experiments. We confirm the studies previously reported in animals on the existence of a competitive antagonism of lorglumide on CCK gallbladder receptors. Moreover, our results on gallbladders from gallstone patients show that lorglumide is a highly effective antagonist of CCK-induced contractions despite the presence of chronic cholecystitis. Our study might help for a better comprehension of the role of these new anti-CCK drugs in the treatment of biliary pain.     

How training and testing histories affect generalization: a test of simple neural networks

We show that a simple network model of associative learning can reproduce three findings that arise from particular training and testing procedures in generalization experiments: the effect of (i) 'errorless learning', (ii) extinction testing on peak shift, and (iii) the central tendency effect. These findings provide a true test of the network model which was developed to account for other phenomena, and highlight the potential of neural networks to study the phenomena that depend on sequences of experiences with many stimuli. Our results suggest that at least some such phenomena, e.g. stimulus range effects, may derive from basic mechanisms of associative memory rather than from more complex memory processes.     

双量子滤波（DQF）核磁共振研究细胞内钠

双量子滤波（ＤＱＦ）核磁共振研究细胞内钠屠萍官,张日清,赵南明（清华大学生物科学与技术系生物膜与膜生物工程国家重点实验室北京１０００８４）用核磁共振位移试剂实现了细胞内销的动态研究［１］。但由稀土元素组成的位移试剂是否具有毒性至今仍有争议［２－４］。...     

Cytogenetic damage in human lymphocytes following GMSK phase modulated microwave exposure.

The present study investigated, using in vitro experiments on human lymphocytes, whether exposure to a microwave frequency used for mobile communication, either unmodulated or in presence of phase only modulation, can cause modification of cell proliferation kinetics and/or genotoxic effects, by evaluating the cytokinesis block proliferation index and the micronucleus frequency. In the GSM 1800 mobile communication systems the field is both phase (Gaussian minimum shift keying, GMSK) and amplitude (time domain multiple access, TDMA) modulated. The present study investigated only the effects of phase modulation, and no amplitude modulation was applied. Human peripheral blood cultures were exposed to 1.748 GHz, either continuous wave (CW) or phase only modulated wave (GMSK), for 15 min. The maximum specific absorption rate (approximately 5 W/kg) was higher than that occurring in the head of mobile phone users; however, no changes were found in cell proliferation kinetics after exposure to either CW or GMSK fields. As far as genotoxicity is concerned, the micronucleus frequency result was not affected by CW exposure; however, a statistically significant micronucleus effect was found following exposure to phase modulated field. These results would suggest a genotoxic power of the phase modulation per se.     

Mechanistic prediction of food effects for Compound A tablet using PBPK model

Physiologically based pharmacokinetic (PBPK) modeling has been extensively used to study the factors of effect drug absorption, distribution, metabolize and extraction progress in human. In this study, Compound A(CPD A) is a BCS Class II drug, which has been extensive applied in clinical as lipid-lowering drug, administered orally after food, they displayed positive food effects in human, A PBPK model was built to mechanistic investigate the food effect of CPD A tablet in our study. By using gastroplus™ software, the PBPK models accurately predicted the results of food effects and predicted data were within 2-fold error of the observed results. The PBPK model mechanistic illuminated the changes of pharmacokinetic values for the positive food effects of the compound in human. Here in, the PBPK modeling which were combined with ACAT absorption models in it, successfully simulated the food effect in human of the drug. The simulation results were proved that PBPK model can be able to serve as a potential tool to predict the food effect on certain oral drugs.     

Sensory adaptation for timing perception

Recent sensory experience modifies subjective timing perception. For example, when visual events repeatedly lead auditory events, such as when the sound and video tracks of a movie are out of sync, subsequent vision-leads-audio presentations are reported as more simultaneous. This phenomenon could provide insights into the fundamental problem of how timing is represented in the brain, but the underlying mechanisms are poorly understood. Here, we show that the effect of recent experience on timing perception is not just subjective; recent sensory experience also modifies relative timing discrimination. This result indicates that recent sensory history alters the encoding of relative timing in sensory areas, excluding explanations of the subjective phenomenon based only on decision-level changes. The pattern of changes in timing discrimination suggests the existence of two sensory components, similar to those previously reported for visual spatial attributes: a lateral shift in the nonlinear transducer that maps relative timing into perceptual relative timing and an increase in transducer slope around the exposed timing. The existence of these components would suggest that previous explanations of how recent experience may change the sensory encoding of timing, such as changes in sensory latencies or simple implementations of neural population codes, cannot account for the effect of sensory adaptation on timing perception.     

Counteracting effects of urea and methylamines in function and structure of skeletal muscle myosin

Myosin is an asymmetric protein that comprises two globular heads (S1) and a double-stranded alpha-helical rod. We have investigated the effects of urea and the methylamines trimethylamine oxide (TMA-O) and glycine betaine (betaine) on activity and structure of skeletal muscle myosin. K(+) EDTA ATPase activity of myosin was almost completely inhibited by urea (2M); TMA-O stimulated myosin activity, whereas betaine had no effect. When combined with urea (0-2M), TMA-O or betaine (1 M) effectively protected the ATPase activity of myosin against inhibition. Intrinsic fluorescence measurements showed that in urea or TMA-O (0-2M), there were no shifts in the center of mass of the fluorescence spectrum of myosin, despite a decrease in fluorescence intensity. However, these osmolytes at concentrations above 2M produced a red shift in the emission spectrum. Betaine alone did not alter the center of mass at any concentration tested up to 5.2M. Thus, modifications in ATPase activity induced by low concentrations of solutes (<2M) are not directly correlated with the modifications in myosin structure detected by fluorescence. Both methylamines (>or=1M) were also able to protect myosin structure against urea-induced effects (2-8M). Protection was not observed for S1, supporting the hypothesis that these osmolytes have a biphasic effect on myosin: at lower concentrations there is an effect on the globular portion (S1), and at higher concentrations there is an effect on the coiled-coil (rod) portion of myosin.     

Psychomotor performance is not influenced by brief repeated exposures to mobile phones

The present study investigated the presence of a cumulative effect of brief and repeated exposures to a GSM mobile phone (902.40 MHz, 217 Hz modulated; peak power of 2 W; average power of 0.25 W; SAR = 0.5 W/kg) on psychomotor functions. To this end, after each of 3 15-min exposures, both an acoustic simple reaction time task (SRTT) and a sequential finger tapping task (SFTT) were administered to 24 subjects. The present study was unable to detect the cumulative effects of brief and repeated EMF exposure on human psychomotor performance, although there was a non-statistical trend to shorter reaction times. In summary, these data show an absence of effects with these particular exposure conditions; however, possible cognitive effects induced by different signal characteristics cannot be excluded.     

Identification of phosphorylethanolamine in 31P-NMR spectra of human peripheral blood lymphocytes

The 31P-NMR spectrum of intact human peripheral blood lymphocytes contains a large unidentified peak in the phosphomonoester region. The pH dependency of the 31P-NMR chemical shift of this peak in perchloric acid extracts of peripheral blood lymphocytes was recorded. It was compared to the pH dependency of the chemical shift of phosphorylethanolamine, phosphorylcholine, and ribose 5-phosphate in model solutions. An excellent agreement was found between the behavior of phosphorylethanolamine and the unidentified peak. To further substantiate this assignment phosphorylethanolamine was added to extracts and the pH titrations were repeated. The added phosphorylethanolamine gave exactly the same chemical shift as the unidentified peak and no difference was observed with pH titrations. The concentration of phosphorylethanolamine in human peripheral blood lymphocytes was estimated by 31P NMR to be 2.4 mumol/10(9) cells (range 0.9-4.3/10(9) cells, n = 4).     

Binding of the bovine basic pancreatic trypsin inhibitor (Kunitz inhibitor) to human and bovine factor Xa. A thermodynamic study

The effect of pH and temperature on the apparent association equilibrium constant (Ka) for the binding of the bovine basic pancreatic trypsin inhibitor (BPTI, Kunitz inhibitor) to human and bovine factor Xa (Stuart-Prower factor; EC 3.4.21.6) has been investigated. Under all the experimental conditions, values of Ka for BPTI binding to human and bovine factor Xa are identical. On lowering the pH from 9.5 to 4.5, values of Ka (at 21.0 degrees C) for BPTI binding to human and bovine factor Xa decrease, thus reflecting the acidic pK shift of the His57 catalytic residue from 7.1, in the free enzyme, to 5.2, in the proteinase-inhibitor complex. At pH 8.0, values of the apparent thermodynamic parameters for BPTI binding to human and bovine factor Xa are: Ka = 2.1 x 10(5)M-1 (at 21.0 degrees C), delta G degree = -29.7 kJ/mol (at 21.0 degrees C), delta S degree = +161 entropy units (at 21.0 degrees C), and delta H degree = +17.6 kJ/mol (temperature-independent over the explored range, from 5.0 degrees C to 45.0 degrees C). Thermodynamics of BPTI binding to human and bovine factor Xa have been analysed in parallel with those of related serine (pro)enzyme/Kazal- and /Kunitz-type inhibitor systems. Considering the known molecular models, the observed binding behaviour of BPTI to human and bovine factor Xa was related to the inferred stereochemistry of the proteinase/inhibitor contact region.     

CORNEAL SURFACE PROPERTIES OF TWO MARINE MAMMAL SPECIES1

Compared to the anterior surface of the normal human cornea, all Tursiops showed pronounced random, local curvature changes typical of old keratitis and scarring. Comparable but less severe findings apply to Zalophus. These irregularities were superimposed on the mild regular astigmatism of the spoon-shaped Tursiops cornea (mean central power is 26.8 D, SD = 3.8, N = 82). All Zalophus corneas showed no reliable regular astigmatism (overall mean power is 21.7 D, SD = 4.4, N = 53) but exhibited a flat, circular region about 6.5 mm in diameter along the nasal aspect of the horizontal meridian. Refraction through this cornea1 region showed aerial emmetropia, which accounts for equivalent marine and aerial visual resolution in this species.