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At least 1,261 records · Page 70Linked to original sources
PubMed1980

Organochlorine residues and shell thicknesses in eggs of the clapper rail, common gallinule, purple gallinule, and limpkin (class Aves), eastern and southern United States, 1972-74.

Organochlorine residues and shell thicknesses were surveyed in eggs of the clapper rail (Rallus longirostris), purple gallinule (Porphyrula martinica), common gallinule (Gallinula chloropas), and limpkin (Aramus guarauna) from the eastern and southern United States. Clapper rail eggs were collected during 1972-73 in New Jersey, Virginia, and South Carolina. During 1973-74, gallinule eggs were collected in Florida, South Carolina, and Louisiana, and limpkin eggs were collected in Florida. Egg contents were analyzed for residues of organochlorine pesticides, including DDT, TDE, DDE, dieldrin, mirex, heptachlor epoxide, oxychlordane, cis-chlordane (and/or trans-nonachlor), cis-nonachlor, hexachlorobenzene (HCB), toxaphene, and endrin, and for polychlorinated biphenyls (PCBs). Shell thicknesses of recent eggs of these species were compared with archival eggs that had been collected before 1947. With the exception of the limpkin, the majority of eggs analyzed contained residues of p,p'-DDE and PCBs. Geometric means ranged from 0.10 ppm to 1.3 ppm. Small amounts (less than 1.0 ppm) of mirex, dieldrin, cis-chlordane (and/or trans-nonachlor), TDE, and DDT were detected in a few eggs. No evidence of eggshell thinning was found for any of the species studied. DDE residues in clapper rail eggs were higher in New Jersey and Virginia than in South Carolina.

Animals↗
PubMedDate not supplied

Preincubation dipping of turkey hatching eggs. II. Effect of shell treatment on hatachability.

The effects of various egg-shell treatments on the hatchability of turkey eggs were investigated. Hatchability was not effected significantly by drilling a hole in the large end, or removing cuticle with dilute acid from the entire shell surface of from either end. Embryo deaths were increased significantly (P less than 0.005), however, by a pinhole pierced in the large end. Sealing the drill or pinhole with Duco cement did not significantly alter the hatchability. Hatchability of treated or untreated eggs was not effected adversely by dipping for 2.5 minutes after preheating to 36 C, or for 10 minutes without preheating.

Animals↗
PubMed1980

Growth and differentiation of chicken embryos in simplified shell-less cultures under ordinary conditions of incubation.

The growth and differentiation of chicken embryos maintained in evaporating dishes as shell-less cultures were compared to that of control embryos in ovo under the same conditions of incubation. The development of cultured embryos appears to be indistinguishable from that of embryos in ovo up to 10 days of total incubation. Thereafter, the growth of shell-less embryos is significantly retarded as evidenced by morphological criteria of the Hamburger-Hamilton stages of development, body weight, tibia length, and total protein content. Cultured embryos are smaller in size than controls, but show normal morphological features including a fully-differentiated skeleton. Skeletal defects and other anomalies were not detected in any of the specimens studied. Limitations as to the use of the simplified method of culture are evaluated and discussed.

Animals↗
PubMed1985

Simmons' tamponade shell for leaking filtration blebs.

We used the Simmons' tamponade shell to successfully treat four of five patients who had leaking filtration blebs after glaucoma surgery. Bleb leaks in both the immediate postoperative period as well as many years following surgery were treated. In each case, previous pressure patching had been unsuccessful. Permanent closure of the leaks with the shell tamponade occurred within three days. Use of this technique is an effective alternative to surgical repair.

Adult↗
PubMed1989

Conjunctival flap-cosmetic shell-ptosis procedure. Treatment of blepharoptosis in severe keratopathy.

The correction of marked blepharoptosis in patients with severe or potential keratopathy will worsen the keratopathy and possibly lead to the complications of corneal ulceration and endophthalmitis. The conjunctival flap--cosmetic shell--ptosis procedure is well suited to this difficult management problem. Patients are initially treated with a conjunctival flap to protect their cornea. Subsequently they are fit with a cosmetic shell, and finally they undergo surgery to correct their ptosis. This three-stage procedure has produced excellent cosmetic and functional results in two patients, one of whom had ptosis and severe radiation-induced keratopathy following the treatment of a rhabdomyosarcoma; the other patient had severe ptosis associated with lack of corneal sensation and orbicularis function following removal of a cerebral meningioma.

Blepharoptosis↗
PubMed1998

Shell-vial culture and pp65 antigenemia assay in the detection of cytomegalovirus in the first blood sample of renal transplant recipients.

The aim of the study was to compare the efficacy of pp65 antigenemia assay and the shell-vial culture (SVC; viremia) for the diagnosis of cytomegalovirus (CMV) infection in renal transplant recipients, comparing the results obtained in the first blood sample and the total number of blood samples analyzed in this group of patients. During the study period, 70 renal transplant recipients were studied: 44 (62.8%) with CMV infection. The method of sedimentation in a dextran solution for leukocyte extraction was used in the pp65 antigenemia assay. The MRC-5 shell-vial assay was used for CMV isolation from leukocytes (viremia). Eighty blood samples were examined from 70 renal transplant recipients: Of the 44 positive samples studied, in 77.5% of cases, both the antigenemia assay and the SVC were positive. In 16.2%, only the antigenemia assay was positive, and, in 6.2%, only the SVC was positive. In all blood samples studied, the antigenemia was present in 93.7% of cases, and the SVC was present in 83.7% (P = 0.04). If the results obtained in only the first blood sample taken for the diagnosis are studied, then we observe that the antigenemia assay was positive in 39 patients (88.6%), whereas the SVC was positive in 41 patients (93.1%), although the difference was not statistically significant (P = 0.39). It is concluded that the inoculation of all of the leukocytes extracted from blood samples in the SVC seems to produce a slight increase in the sensitivity of the cell culture and that the SVC becomes positive before the antigenemia for the detection of CMV in peripheral blood, especially in the first blood sample.

Antibodies, Monoclonal↗
PubMed1996

F-actin forms transient perinuclear shells at the mitosis-interphase transition.

Intermediate filaments and microtubules are known to be involved in establishing and maintaining nuclear shape. F-actin may also be involved in determining nuclear shape, since we have found it associated with reforming nuclei very briefly after cell division. We stained cells from vertebrate tissue cultures (3T3 and NRK-49F) and epidermal cells from an insect with rhodamine-phalloidin and Hoechst #33342 to localize F-actin in relation to the nucleus. We found that F-actin forms shells only around nuclei during reorganization in late mitosis and early interphase. We suggest that perinuclear F-actin shells may be generally present in eukaryotes, but that they are easily missed because of their delicacy and transience.

3T3 Cells↗
PubMed2002

T(h)-symmetrical hexakisadducts of C(60) with a densely packed pi-donor shell can act as energy- or electron-transducing systems.

For the first time several T(h)-symmetrical hexakisadducts of C(60) bearing up to six electro- and photoactive o-phenylene diamine or 9,10-dialkoxyanthracene moieties were synthesized and subjected to photoinduced electron/energy-transfer studies. Both donors form a densely packed pi-donor shell surrounding the fullerene core. In these novel core-shell ensembles (7 and 19), either an efficient energy transfer from the dialkoxyanthracene periphery, or an electron transfer from the o-phenylene diamine periphery transduces the flow of excited-state energy or electrons, respectively, to the fullerene moiety, which resides in the central core. Due to the relatively high reduction potential of the fullerene core, which is anodically shifted by approximately equal to 0.7 V, compared with that of pristine C(60), the outcome of these intramolecular reactions depends mainly on the donor ability of the peripheral system. Interestingly, the charge-separated state in the o-phenylene diamine heptad (7; tau=2380 ns in benzonitrile) is stabilized by a factor of 20 relative to the corresponding o-phenylene diamine dyad (6; tau=120 ns in benzonitrile), an effect that points unequivocally to the optimized storage of charges in this highly functionalized fullerene ensemble.

Journal Article↗
PubMed2002

Hollow polymer shells from biological templates: fabrication and potential applications.

Three-dimensional ultrathin polymer shells have been produced by a combination of step-by-step adsorption of polyelectrolytes on glutaraldehyde-treated human erythrocytes and subsequent solubilization of the cytoplasmatic constituents by means of a deproteinizing agent. The obtained hollow films preserve both the size and shape of the templating cells. This opens a pathway for the fabrication of polymeric capsules within a wide range of size and shape by using various biological templates. They may have exciting potential applications, such as templates for nanocomposites, as containers for a large class of materials, or as cages for chemical reactions. The thickness of the films can be adjusted over a large range: from a few nm up to several tens of nm. The polymer shells are permeable to small molecules and ions but not to macromolecules. An increase in the ionic strength of the solution up to 100 mmol make the capsules permeable for proteins. Permeability and conductivity studies have provided evidence that the adsorption of lipids on polyelectrolyte layers is a means of producing capsules with controlled permeability properties. 6-Carboxyfluorescein and Rhodamin 6G were precipitated within the capsules.

Biotechnology↗
PubMed1982

Electron spin resonance dating of human bones from Brazilian shell-mounds (Sambaquís).

Electron spin resonance (ESR) signals from bone increase with exposure to radiation. This permits the dating of ancient bone from its exposure to natural radiation over the centuries. The ESR technique was used for dating human bones from Brazilian shell mounds. The results were compared with 14C dates on charcoal found near the bone. The natural radiation dose rate of the bones was about 0.01 Gy/year (1 rad/year), similar to that found in Japanese shell-mounds. Ages of the bone samples dated ranged from 2000-5000 years BP.

Bone and Bones↗
PubMed2004

Reactions under autogenic pressure at elevated temperature (RAPET) of various alkoxides: formation of metals/metal oxides-carbon core-shell structures.

The RAPET reaction at 700 degrees C, of different alkoxides (Ti, V, and Si) led to three different nanocomposites. Carbon is the element common to all three structures. Carbon was found as the core in the decomposition of TEOS, as the shell in the decomposition of VO(OEt)3 and embedded in, or mixed completely with, TiO2 in the decomposition of Ti(OiPr)4. This novel method using only metallic alkoxide precursor, in the absence of catalyst, leads in a one-step process to core-shell structures.

Carbon↗
PubMed2005

A small cavity with reactive internal shell atoms spanned by four {As(W/V)9}-type building blocks allows host-guest chemistry under confined conditions.

The reaction of [H2As(III)W18O60]7- with VO2+ and SO4(2-) ions in aqueous solution leads to a V(IV)/V(V) mixed-valence cluster anion containing the {As4M40O140}-type cryptand which has a high formation tendency. An important result is that it exhibits a new type of reactive internal cavity shell. The correspondingly obtained compound Na(NH4)20[{(V(IV)O(H2O))(V(IV)O)2(SO4)2}{(As(III)W9O33)2(As(III)W7.5V(V)1.5O31)2(WO2)4}] x 40 H2O (1), which can also be synthesized from a precursor with the preorganized cryptand, was characterized by elemental and thermogravimetric analyses (determination of crystal water content), redox titrations (determination of the number of V(IV) centers), electronic absorption as well as vibrational spectra, single-crystal X-ray structure analysis (including bond valence sum calculations), and magnetic susceptibility measurements. The relatively small central cavity--formed by the linking of four {AsM9}-type lacunary units (M = W/V) by four WO6 octahedra--allows positioning of a variety of cationic as well as anionic "guests" under confined conditions according to a new approach: replacement of some of the W by V atoms leads to high reactivity of the internal cavity shell as a result of relatively weak VO bonds compared to the WO bonds. This allows an interesting "encapsulation chemistry" with new options. In the present case the cavity contains besides an arrangement of three V(IV) centers, two sulfate groups that replace O atoms of the {AsM9} units as well as an interesting hydrogen bond situation.

Journal Article↗
PubMed2005

Synthesis and characterization of core-shell selenium/carbon colloids and hollow carbon capsules.

A novel Se/C nanocomposite with core-shell structures has been prepared through a facile one-pot microwave-induced hydrothermal process. The new material consists of a trigonal-Se (t-Se) core and an amorphous-C (a-C) shell. The Se/C composite can be converted to hollow carbon capsules by thermal treatment. These products were characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED), energy-dispersive X-ray (EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS).

Journal Article↗
PubMed2006

Mollusk shell formation: a source of new concepts for understanding biomineralization processes.

The biological approach to forming crystals is proving to be most surprising. Mollusks build their shells by using a hydrophobic silk gel, very acidic aspartic acid rich proteins, and apparently also an amorphous precursor phase from which the crystals form. All this takes place in a highly structured chitinous framework. Here we present ideas on how these disparate components work together to produce the highly structured pearly nacreous layer of the mollusk shell.

Animals↗
PubMed2006

Pyrene as chromophore and electrophore: encapsulation in a rigid polyphenylene shell.

Starting from the fourfold ethynyl-substituted chromophore 1,3,6,8-tetraethynylpyrene as core, a series of polyphenylene dendrimers was prepared in high yield by combining divergent and convergent growth methods. The fluorescence quantum yields (Q(f)>0.92) of the encapsulated pyrene chromophore were independent of the size of the polyphenylene shell. Fluorescence quenching studies and temperature-dependent fluorescence spectroscopy were performed to investigate the site isolation of the core. They indicate that a second-generation dendrimer layer is needed to efficiently shield the encapsulated pyrene and prevent aggregate formation. Alkali-metal reduction of the encapsulated pyrene core was carried out to afford the corresponding pyrene radical anions, for which hampered electron transfer to the core was observed with increasing dendrimer generation, which is further proof of the site isolation due to the polyphenylene shell. To improve film formation and solubility of the material, solubilizing alkyl chains were introduced on the periphery of the spherical particles. Furthermore, highly transparent films obtained by a simple drop-casting method showed blue emission mainly from the unaggregated species. The materials presented herein combine high quantum efficiency, good solubility, and improved film-forming properties, which make them possible candidates for several applications in electronic devices.

Journal Article↗
PubMed2007

Dissecting the general physicochemical properties of noncovalent interactions involving tyrosine side chain as a second-shell ligand in biomolecular metal-binding site mimetics: an experimental study combining fluorescence, 13C NMR spectroscopy and ESI mass spectrometry.

Detailed physicochemical features inherent in the dynamic cation-pi interactions of aromatic amino acid side chains in the secondary coordination spheres around metal ions were extracted and mapped by intrinsic tyrosine fluorescence titration experiments with two homologous, artificially engineered metal-binding scaffolds which mimic metal-binding sites in metalloproteins. A newly formulated method for the treatment of fluorescence titration data allows straightforward assessment of both the magnitudes and properties of metal-chelation-assisted cation-aromatic interactions (K2) underlying a proposed two-step metallosupramolecular association process. The unprecedented linear platform-motif correlations between the two contrasting scaffolds in their changes in tyrosine fluorescence on binding of 3d metal cations help to elucidate the properties of general cation-arene recognition corresponding to the metal-responsive characteristics of the second-shell Tyr residue surrounding the metal-binding sites in the supramolecular context, and thereby define a new noncovalent design principle for metal-ion recognition in aqueous solution. As supported by NMR spectroscopic and ESI-MS analyses and molecular mechanics force field calculations, the systematic study exemplifies the concept of using steady-state tyrosine fluorescence as a powerful tool for comprehensive descriptions of cation-pi interactions in the extended environment of a metal-binding site. We established that the physicochemical properties pertaining to indirect metal-arene interactions are highly dependent on the electronic properties of the metal ions. This work suggests that second-shell cation-pi interactions may play more diverse roles, including modulation of structure, reactivity, and function of metal-binding sites, than the previously well-established direct cation-pi interactions involving hard cations (e.g., alkali metal ions). Moreover, such a study will continue to complement theoretical predications and/or the early experimental investigations in organic solvents.

Biomimetics↗
PubMed1988

Unfertilized sea urchin eggs contain a discrete cortical shell of actin that is subdivided into two organizational states.

Changes in the distribution and organizational state of actin in the cortex of echinoderm eggs are believed to be important events following fertilization. To examine the initial distribution and form of actin in unfertilized eggs, we have adapted immunogold-labeling procedures for use with eggs of Strongylocentrotus purpuratus. Using these procedures, as well as fluorescence microscopy, we have revealed a discrete 1-micron-thick concentrated shell of actin in the unfertilized egg cortex. This actin is located in the short surface projections of unfertilized eggs and around the cortical granules in a manner that suggests it is associated with the cortical granule surface. The actin in the short surface projections appears to be organized into filaments. However, most if not all of the actin surrounding the cortical granules is organized in a form that does not bind phalloidin, even though it is accessible to actin antibody. The lack of phalloidin binding is consistent with either the presence of nonfilamentous actin associated with the cortical granules or the masking of actin-filament phalloidin-binding sites by some cellular actin-binding component. In addition to the concentrated shell of actin found in the cortex, actin was also found to be concentrated in the nuclei of unfertilized eggs.

Actins↗