An Invisibility Cloak Using Silver Nanowires

In this paper, we use the parameter retrieval method together with an analytical effective medium approach to design a well-performed invisible cloak, which is based on an empirical revised version of the reduced cloak. The designed cloak can be implemented by silver nanowires with elliptical cross sections embedded in a polymethyl methacrylate host. This cloak is numerically proved to be robust for both the inner hidden object as well as incoming detecting waves and is much simpler, thus easier to manufacture when compared with the earlier one proposed by Cai et al. (Nat Photon 1: 224, 2007).     

A Polymethyl Methacrylate Method for Large Specimens of Mineralized Bone with Implants

A simple modified polymethyl methacrylate method is described for large mineralized bone specimens with implants and bioactive materials which produces consistently good histological preservation of the interface between bone and implant. Human femoral heads, whole rabbit condyles and canine tibias and femurs containing implants consisting of hydroxyapatite, smooth polyethylene, porous polyethylene and carbon were dehydrated in ascending grades of ethanol and cleared with xylene on an automated tissue processor which alternated vacuum and pressure for 22 hr. Infiltration was done with washed polymethyl methacrylate at 4 C under vacuum for 13 days. Polymerization was carried out in wide-mouth glass jars at 38 C for 36 hr so that the total processing time was less than 20 days. The only important modification was in the polymethyl methacrylate, which had less plasticizer than usual in order to give a harder block. This enabled production of 4 μm sections with good preservation of mineralized and cellular areas for the study of metabolic bone diseases, morphometry, fluorochrome labelling and interface analysis with the implant in situ.     

A polymethyl methacrylate method for large specimens of mineralized bone with implants

A simple modified polymethyl methacrylate method is described for large mineralized bone specimens with implants and bioactive materials which produces consistently good histological preservation of the interface between bone and implant. Human femoral heads, whole rabbit condyles and canine tibias and femurs containing implants consisting of hydroxyapatite, smooth polyethylene, porous polyethylene and carbon were dehydrated in ascending grades of ethanol and cleared with xylene on an automated tissue processor which alternated vacuum and pressure for 22 hr. Infiltration was done with washed polymethyl methacrylate at 4 C under vacuum for 13 days. Polymerization was carried out in wide-mouth glass jars at 38 C for 36 hr so that the total processing time was less than 20 days. The only important modification was in the polymethyl methacrylate, which had less plasticizer than usual in order to give a harder block. This enabled production of 4 micron sections with good preservation of mineralized and cellular areas for the study of metabolic bone diseases, morphometry, fluorochrome labelling and interface analysis with the implant in situ.     

Synthesis of protein-containing polymers in organic solvents

Subtilisin has been modified with polyethylene glycol (PEG) monomethacrylate (MW 8000) by reductive alkylation, and incorporated into polymethyl methacrylate durring free-radical initiated polymerization. The activity and stability of the PEG-modified enzymes have been determined in aqueous buffer and organic solvents. The K(m) and V(max) values for unmodified, singly and doubly modified subtilisin were compared in these environments, and the half-lives of both modified enzymes were remarkably high (up to 2 months). The protein-containing polymer was analyzed for activity and polymer properties, and our results indicate that active subtilisin can be incorporated into polymethyl methacrylate during polymerization in organic solvents while retaining its activity and stability. (c) 1995 John Wiley & Sons, Inc.     

低浓度万古霉素复合PMMA骨水泥的细胞毒性研究

目的:研究低浓度万古霉素(1%)复合聚甲基丙烯酸甲酯PMMA骨水泥对SD仔鼠原代成骨细胞的增殖以及凋亡的影响。方法:采用分离SD仔鼠颅骨与胰酶消化法获取SD仔鼠原代成骨细胞,通过细胞爬片碱性磷酸酶染色对原代成骨细胞进行鉴定;利用CCK-8法检测低浓度万古霉素复合PMMA及纯PMMA骨水泥浸提液对SD大鼠原代成骨细胞的增殖影响、流式细胞仪检测万古霉素复合PMMA及纯PMMA骨水泥浸提液对对SD大鼠原代成骨细胞的凋亡影响。结果:SD大鼠原代成骨细胞在低浓度万古霉素复合PMMA骨水泥浸提液中第1、2、3天的增殖更明显(P0.05),在纯PMMA骨水泥浸提液中第1、5天凋亡显著增加(P0.05)。结论:低浓度万古霉素复合PMMA骨水泥相比PMMA骨水泥具有较低的细胞毒性,在临床应用于骨缺损伴局部骨感染的治疗方面具有一定的优势。     

N-butyl Methacrylate and Paraffin as an Embedding Medium for Light Microscopy

A method of tissue embedding using n-butyl methacrylate and paraffin is described. Following alcohol dehydration and infiltration with the methacrylate monomer, tissues are embedded in gelatin capsules in a mixture consisting of 3.5 g of paraffin for each 10 ml of methacrylate. Benzoyl peroxide (0.2 g for each 10 ml of monomer) is added as the catalyst and the methacrylate polymerized in a 50 C oven for 18-24 h. Following polymerization the block is trimmed and embedded in paraffin to provide a firm support during sectioning. A water trough attached to the microtome knife is essential to facilitate the handling of sections and ribbons. For serial sections a mixture of equal weights of beeswax and paraffin is used to make the sections adhere to each other. Usual staining procedures can be used since the embedding medium is readily soluble in xylene.     

N-Butyl methacrylate and paraffin as an embedding medium for light microscopy.

A method of tissue embedding using n-butyl methacrylate and paraffin is described. Following alcohol dehydration and infiltration with the methacrylate monomer, tissues are embedded in gelatin capsules in a mixture consisting of 3.5 g of paraffin for each 10 ml of methacrylate. Benzoyl peroxide (0.2 g for each 10 ml of monomer) is added as the catalyst and the methacrylate polymerized in a 50 C oven for 18--24 h. Following polymerization the block is trimmed and embedded in paraffin to provide a firm support during sectioning. A water trough attached to the microtome knife is essential to facilitate the handling of sections and ribbons. For serial sections a mixture of equal weights of beeswax and paraffin is used to make the sections adhere to each other. Usual staining procedures can be used since the embedding medium is readily soluble in xylene.     

The Application of Miller's Elastic Stain to Glycol Methacrylate Tissue Sections

The application of Miller's dilute elastic stain followed sequentially by Gill's III hematoxylin and a fast green counterstain produced a reliable and consistent method for differentially staining elastic fibers, nuclei, muscle and collagen in glycol methacrylate tissue sections. Evaluation of different methods of fixation and conditions of staining on animal tissue sections showed that elastic fibers in both perfusion and immersion fixed tissues can be intensely stained. The stability of Miller's elastic stain offers the potential of a commercially available histological stain reagent for coarse and fine elastic fibers in glycol methacrylate tissue sections.     

The application of Miller's elastic stain to glycol methacrylate tissue sections

The application of Miller's dilute elastic stain followed sequentially by Gill's III hematoxylin and a fast green counterstain produced a reliable and consistent method for differentially staining elastic fibers, nuclei, muscle and collagen in glycol methacrylate tissue sections. Evaluation of different methods of fixation and conditions of staining on animal tissue sections showed that elastic fibers in both perfusion and immersion fixed tissues can be intensely stained. The stability of Miller's elastic stain offers the potential of a commercially available histological stain reagent for coarse and fine elastic fibers in glycol methacrylate tissue sections.     

Silver Methenamine Staining for Scanning Electron Microscopy of Bone Sections Containing Biomaterials

Sections of tissue containing orthopedic materials are currently used to study the compatibility of those materials and to perform electron probe microanalysis at the material-tissue interface. Identification of the cells in contact with the material by Scanning electron microscopy (SEM) is of interest. We have developed a method for staining cells and tissue structures embedded in polymethyl methacrylate with silver methenamine once the sections have been obtained. Sections were prepared by grinding, and the silver methenamine was applied after oxidation with periodic acid. The procedure was carried out in a microwave oven. Backscatter SEM showed staining of the cell nucleus membrane, chromatin, the nuclear organizers, and the chromosomes of dividing cells. The cytoplasm and the cytoplasmic membrane were also stained. Collagen fibers of the extracellular matrix and the mineralized matrix of bone were labeled. Material particles in the macrophages were easily recognizable and Energy-Dispersive Spectrometer were not impaired by the presence of silver in the preparation.     

Combined Lectin Binding and PAS/Alcian Blue Staining in Glycol Methacrylate Sections

Evaluation of cryofixation and paraffin and glycol methacrylate embedding showed that lectin binding was essentially independent of the embedding medium. Fluorescence intensity increased in the following order: glycol methacrylate, paraffin and cryostat sections, The optical resolution increased in the reverse order. Semi-thin glycol methacrylate sections provided satisfactory fluorescence intensities and the best resolution of all embedding techniques applied. Furthermore the lectin treated sections can be stained further using routine histological or specific histochemical methods. The potassium hy-droxide/alcian blue/periodic acid-phenylhydra-zine-Schiff method was used successfully to demonstrate sulfated and nonsulfated sialomucins. Lectins combined with mucin histochemistry allowed visualization of specific sugar residues in the same glycol methacrylate plastic section.     

REDUCTION OF HEATING ARTIFACTS IN THIN SECTIONS EXAMINED IN THE ELECTRON MICROSCOPE

Certain phenomena affecting contrast obtained from tissue sections with the electron microscope have been investigated and a technique is described for reducing destruction by the electron beam of fine details in sections. It has been concluded that loss of embedding material is slightly higher at exposed surfaces of sections than it is at surfaces covered by substrate film. Covering of both surfaces of sections with thin films of formvar, collodion, or carbon materially improves the general appearance, reduces distortion, and sometimes reduces loss of tissue mass from the section as result of exposure to the electron beam. This improvement is considered to result from the relatively high melting-point of the covering films which serve to eliminate or reduce surface-tension or other forces operating in methacrylate softened by the electron beam.     

Postmortem diagnostics of renal diseases from semithin sections.

For the light microscopic postmortem study of mostly glomerular renal diseases, in addition to the paraffin technique, 0.5 mu thick (semithin) sections from material fixed in buffered formaldehyde and embedded in methacrylate or Durcupan ACM were used. The method allows for eventual electron microscopic examinations. The semithin sections were stained with methylene blue combined with basic fuchsin, as well as with periodic acid-silver methamine. The method is not a substitution, but the supplementation of the paraffin technique and is suited for the clarification of numerous fine details: in some cases the exact diagnosis was made in this way.     

Method for histological preparation of bone sections containing titanium implants

A thin sectioning technique involving hand grinding has been developed to produce 20-40-microns-thick sections of bone-titanium implant sites. Components include: 1) surface staining of sections prior to mounting on slides so bone labels (oxytetracycline-HCl and 2,4-bis(N,N-dicarbomethyl)aminomethylfluorescein (DCAF] can be seen in sections viewed with transmitted light, 2) a pneumatic sample press for bonding sections to slides with a thin, uniform glue line and without trapped air bubbles, and 3) bonding methyl methacrylate embedded sections to clear acrylic slides with methyl methacrylate monomer to provide enhanced bond strength and grinding properties compared to those obtainable with glass slides. Sample cracking and distortion is minimized and the tissue-implant interface can be kept intact. The expense of start-up equipment for this technique is minimal.     

Assessment of Demyelination in Glycol Methacrylate Sections: A New Protocol for Cresyl Fast Violet Staining

A simple staining technique for nervous tissue is described. Tissue perfused with glutaraldehyde and formaldehyde and postfixed with osmium tetroxide is embedded in glycol methacrylate. One-micrometer sections are stained with 0.05% cresyl fast violet aqueous solution at 60 C for 5 min, washed with tap water and air dried. With this method the details of all nervous tissue elements are clearly demonstrated. The technique is particularly useful for assessing demyelination because the staining of axoplasm allows demyelinated axons to be well visualized.     

Assessment of demyelination in glycol methacrylate sections: a new protocol for cresyl fast violet staining

A simple staining technique for nervous tissue is described. Tissue perfused with glutaraldehyde and formaldehyde and postfixed with osmium tetroxide is embedded in glycol methacrylate. One-micrometer sections are stained with 0.05% cresyl fast violet aqueous solution at 60 C for 5 min, washed with tap water and air dried. With this method the details of all nervous tissue elements are clearly demonstrated. The technique is particularly useful for assessing demyelination because the staining of axoplasm allows demyelinated axons to be well visualized.     

Histoautoradiographic Localization of Calcium in Oat Plant Tissues

The leaching of water-soluble and exchangeable calcium in histoautoradiog-raphy of oat tissue can be prevented by using acetone as the dehydration fluid (freeze substitution technique) and by keeping the tissue sections, while stretching on water, embedded in the methacrylate matrix. Ca⁴⁵ was either added to the mineral solution on which the oat plants were grown (75 μc), or applied on the leaf surface (8 μc). After freezing in melting isopentane, specimens of 1-2 mm dimensions are fixed for 24 hr in an acetone-OsO₄ (1%) solution at—80 C. Dehydration is obtained by transferring the material every day for 6 successive days to a fresh acetone solution at—80 C. The material is infiltrated by a three-time renewed monomer methacrylate mixture (methylmethacrylate I, butylmethacrylate 4) at—50 C. The specimens are embedded in the polymerizing methacrylate mixture at room temperature. Sections of 4-8 μ are easily cut with a rotating microtome. If the methacrylate is not removed from the sections, they can be stretched on water without leaching of calcium. The presence of methacrylate in no way hinders microscopic observation nor effective histoautoradiography.     

Notes of Technic

The leaching of water-soluble and exchangeable calcium in histoautoradiog-raphy of oat tissue can be prevented by using acetone as the dehydration fluid (freeze substitution technique) and by keeping the tissue sections, while stretching on water, embedded in the methacrylate matrix. Ca⁴⁵ was either added to the mineral solution on which the oat plants were grown (75 μc), or applied on the leaf surface (8 μc). After freezing in melting isopentane, specimens of 1-2 mm dimensions are fixed for 24 hr in an acetone-OsO₄ (1%) solution at—80 C. Dehydration is obtained by transferring the material every day for 6 successive days to a fresh acetone solution at—80 C. The material is infiltrated by a three-time renewed monomer methacrylate mixture (methylmethacrylate I, butylmethacrylate 4) at—50 C. The specimens are embedded in the polymerizing methacrylate mixture at room temperature. Sections of 4-8 μ are easily cut with a rotating microtome. If the methacrylate is not removed from the sections, they can be stretched on water without leaching of calcium. The presence of methacrylate in no way hinders microscopic observation nor effective histoautoradiography.     

A Plastic Embedding Medium for Thin Sectioning in Light Microscopy

Tissue blocks with surface areas up to 2 cm² can be sectioned at 1 or 2 μ after embedding in a medium consisting of: methyl methacrylate, 27 ml; polyethylene glycol distearate MW 1540, 6 gm; dibutyl phthalate, 4 ml; and Plexiglas molding powder A-100, 9 gm (added last). The methacrylate mixture is polymerized at 50° C by benzoyl peroxide, 0.8 gm/ 100 ml of methacrylate. The polymerized matrix is transparent and the blocks can be cut on a rotary microtome with a steel knife. The plastic can be removed from sections with acetone prior to staining. Artifacts caused by embedding and sectioning are negligible     

Method for Histological Preparation of Bone Sections Containing Titanium Implants

A thin sectioning technique involving hand grinding has been developed to produce 20—40-μn-thick sections of bone-titanium implant sites. Components include: 1) surface staining of sections prior to mounting on slides so bone labels (oxytetracycline-HCI and 2,4-bis(N,N-dicarbometnyl) aminomethylfluorescein (DCAF)) can be seen in sections viewed with transmitted light, 2) a pneumatic sample press for bonding sections to slides with a thin, uniform glue line and without trapped air bubbles, and 3) bonding methyl methacrylate embedded sections to clear acrylic slides with methyl methacrylate monomer to provide enhanced bond strength and grinding properties compared to those obtainable with glass slides. Sample cracking and distortion is minimized and the tissue-implant interface can be kept intact The expense of start-up equipment for this technique is minimal.