Rethinking Embryonic Germ Layers

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Live Algae in Deep Sediment Layers

Examination of sediment cores taken from shallow coastal regions of the Baltic showed that some algae were still alive at depths beyond the depth of light penetration. Their cells contained chlorophyll and photosynthesis resumed when they were exposed to light. Photosynthesis was detected by simultaneous measurement of oxygen production and ¹⁴C uptake. Autoradiography was used to detect incorporated ¹⁴C. The autoradiographic method was improved by a few modifications.     

Outer Layers of the Azotobacter vinelandii Cyst

Ruthenium red stained a capsule external to the exine of the Azotobacter cyst. The central body is therefore surrounded by three layers, the intine, the exine, and the capsule, all containing acid mucopolysaccharide. Vesicles that appear to originate from the contracting cell membrane of the central body may account for the lipid content of the intine. The exine is composed of laminated sheets that tend to fragment into hexagonal pieces.     

Bloch Oscillations of Surface Plasmon-Like Modes in Waveguide Arrays That Comprise Perforated Perfect Conductor Layers and Dielectric Layers

This study investigates the optical Bloch oscillations (OBOs) in waveguide arrays that consist of alternative perfect electric conductor (PEC) layers and dielectric layers by performing both numerical simulations and theoretical analyses. In PEC dielectric waveguide arrays (PDWAs), the PEC layers are perforated with square holes to support the surface plasmon-like (SPL) modes. The relative permittivities of the dielectric layers have a constant gradient across the waveguide arrays. The OBOs in the PDWAs arise because of the excitation and coupling of the SPL modes. The ray trajectories that are predicted using Hamiltonian optics are consistent with the simulated results. When the position of incidence is fixed, the period of oscillation varies as the reciprocal of the incident frequency. However, the amplitude of oscillation is almost independent of the frequency. For a fixed incident frequency, the amplitude and period of oscillation increases and decreases, respectively as the position of incidence moves toward the dielectric layers with higher relative permittivities.     

生物素-亲和素微模式表面的制备与细胞定位

细胞在模式化表面的定位培养对于组织工程、生物传感器技术和细胞生物学基础研究具有重要意义。研究基于软光刻技术的生物素-亲和素微模式表面快速制备方法,并用所制备的模式进行牛主动脉血管内皮细胞的定位培养。表明该技术可在细胞尺度上有效地控制细胞生长的空间位置。      

生物素-亲和素微模式表面的制备与细胞定位

细胞在模式化表面的定位培养对于组织工程,生物传感器技术和细胞生物学基础研究具有重要意义。研究基于软光刻技术的生物素－亲和素微模式表面快速制备方法,并用所制备的模式进行了牛主动脉血管内皮细胞的定位培养。表明该技术可在细胞尺度上有效地控制细胞生长的空间位置。     

Layers of symbiosis--visualizing the termite hindgut microbial community

Jared Leadbetter takes us for a nature walk through the diversity of life resident in the termite hindgut--a microenvironment containing 250 different species found nowhere else on Earth. Jared reveals that the symbiosis exhibited by this system is multi-layered and involves not only a relationship between the termite and its gut inhabitants, but also involves a complex web of symbiosis among the gut microbes themselves.     

Charge Displacements in Interfacial Layers Containing Reaction Centers

Reaction centers from the photosynthetic bacterium Rhodobacter sphaeroides were oriented in phospholipid interfacial layers adsorbed to a Teflon film separating two electrolyte-filled compartments of a Teflon cell. Light-induced voltage changes were measured as a function of time across electrodes immersed in the cell compartments. The experimental system is characterized both experimentally and theoretically to relate the measured signals to the light-induced displacement currents in the reaction centers. Mathematical relations between the measured signals and the distances and geometries of the charge-transfer reactions are derived. At pH 8.0 the reaction centers were found to be oriented with ∼60% of the population oriented with the donor facing the aqueous phase. The density of the reaction centers in the layer was ∼10¹¹ cm⁻², which is close to that found in the native system. Reconstitution of the secondary quinone, Q _B , in 90% of the RCs was achieved with an ∼100-fold excess of ubiquinone in the vesicle preparation. Received: 1 July 1997/Revised: 23 June 1998     

Reconstitution of Bacterial Spore Coat Layers In Vitro

The spore coat layers of Bacillus cereus T can be at least partially restored by mixing spores stripped of their coat with solubilized coat protein.     

Differential Convergence of Life-Cycle Inventories toward Upstream Production Layers

We present an input-output analysis of the life-cycle labor, land, and greenhouse gas (GHG) requirements of alternative options for three case studies: investing money in a new vehicle versus in repairs of an existing vehicle (labor), passenger transport modes for a trip between Sydney and Melbourne (land use), and renewable electricity generation (GHG emissions). These case studies were chosen to demonstrate the possibility of rank crossovers in life-cycle inventory (LCI) results as system boundaries are expanded and upstream production inputs are taken into account. They demonstrate that differential convergence can cause crossovers in the ranking of inventories for alternative functional units occurring at second-and higher-order upstream production layers. These production layers are often excluded in conventional process-type life-cycle assessment (LCA) by the delineation of a finite system boundary, leading to a systematic truncation error within the LCI. The exclusion of higher-order upstream inputs can be responsible for ranking crossovers going unnoticed. In this case, an incomplete conventional process-type LCA of two alternative options can result in preferences and recommendations to decision makers that are different from preferences and recommendations concluded from a complete hybrid input-output-based assessment. Therefore, the need to avoid misleading effects on the ranking of alternative functional units due to differential convergence supports the practice of hybrid input-output-based LCA techniques.     

An Algebraic Approach to Signaling Cascades with n Layers

Posttranslational modification of proteins is key in transmission of signals in cells. Many signaling pathways contain several layers of modification cycles that mediate and change the signal through the pathway. Here, we study a simple signaling cascade consisting of n layers of modification cycles such that the modified protein of one layer acts as modifier in the next layer. Assuming mass-action kinetics and taking the formation of intermediate complexes into account, we show that the steady states are solutions to a polynomial in one variable and in fact that there is exactly one steady state for any given total amounts of substrates and enzymes.     

Localizing Genes to Cerebellar Layers by Classifying ISH Images

Gene expression controls how the brain develops and functions. Understanding control processes in the brain is particularly hard since they involve numerous types of neurons and glia, and very little is known about which genes are expressed in which cells and brain layers. Here we describe an approach to detect genes whose expression is primarily localized to a specific brain layer and apply it to the mouse cerebellum. We learn typical spatial patterns of expression from a few markers that are known to be localized to specific layers, and use these patterns to predict localization for new genes. We analyze images of in-situ hybridization (ISH) experiments, which we represent using histograms of local binary patterns (LBP) and train image classifiers and gene classifiers for four layers of the cerebellum: the Purkinje, granular, molecular and white matter layer. On held-out data, the layer classifiers achieve accuracy above 94% (AUC) by representing each image at multiple scales and by combining multiple image scores into a single gene-level decision. When applied to the full mouse genome, the classifiers predict specific layer localization for hundreds of new genes in the Purkinje and granular layers. Many genes localized to the Purkinje layer are likely to be expressed in astrocytes, and many others are involved in lipid metabolism, possibly due to the unusual size of Purkinje cells.     

Plant Thin Cell Layers: A 40-Year Celebration

The concept of a thin cell layer (TCL) was initially presented by Tran Thanh Van in two key papers exactly 40 years ago. At that time, Nicotiana tabacum was the model plant used to establish three main pathways for de novo organogenesis by developing a flower, vegetative bud, and root “programme” from pedicel tissue. Over the last 40 years, a wealth of research in plant tissue culture based on TCLs has emerged, fortifying the importance of this very simple technique, and highlighting its fundamental importance as a key tool in plant cell and tissue differentiation as well as organ development. This review not only highlights the achievements made using TCLs in the plant kingdom over these 40 years, it also reports on the success of this technique in ornamentals, fruit and forestry species, vegetables, and medicinal plants. There is overwhelming evidence of the importance of this technique for plant biotechnology, and it provides one solution for the mass clonal propagation of plants, use in bioreactors, genetic transformation, or micropropagation.     

Oxygen Permeability of the Limiting Layers of the Cornea

Using polarography and suitable mathematical analysis, the oxygen permeability of an individual layer of a bilayered tissue may be determined if the oxygen consumption and permeability of the other layer are known. Results obtained on rabbit cornea indicate that the permeability of the epithelium is about four times that of the endothelium.     

Modulating Drug Release from Gastric-Floating Microcapsules through Spray-Coating Layers

Floating dosage forms with prolonged gastric residence time have garnered much interest in the field of oral delivery. However, studies had shown that slow and incomplete release of hydrophobic drugs during gastric residence period would reduce drug absorption and cause drug wastage. Herein, a spray-coated floating microcapsule system was developed to encapsulate fenofibrate and piroxicam, as model hydrophobic drugs, into the coating layers with the aim of enhancing and tuning drug release rates. Incorporating fenofibrate into rubbery poly(caprolactone) (PCL) coating layer resulted in a complete and sustained release for up to 8 h, with outermost non-drug-holding PCL coating layer serving as a rate-controlling membrane. To realize a multidrug-loaded system, both hydrophilic metformin HCl and hydrophobic fenofibrate were simultaneously incorporated into these spray-coated microcapsules, with metformin HCl and fenofibrate localized within the hollow cavity of the capsule and coating layer, respectively. Both drugs were observed to be completely released from these coated microcapsules in a sustained manner. Through specific tailoring of coating polymers and their configurations, piroxicam loaded in both the outer polyethylene glycol and inner PCL coating layers was released in a double-profile manner (i.e. an immediate burst release as the loading dose, followed by a sustained release as the maintenance dose). The fabricated microcapsules exhibited excellent buoyancy in simulated gastric fluid, and provided controlled and sustained release, thus revealing its potential as a rate-controlled oral drug delivery system.