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PubMed2003

Msx genes are expressed in the carapacial ridge of turtle shell: a study of the European pond turtle, Emys orbicularis.

The turtle shell forms by extensive ossification of dermis ventrally and dorsally. The carapacial ridge (CR) controls early dorsal shell formation and is thought to play a similar role in shell growth as the apical ectodermal ridge during limb development. However, the molecular mechanisms underlying carapace development are still unknown. Msx genes are involved in the development of limb mesenchyme and of various skeletal structures. In particular, precocious Msx expression is recorded in skeletal precursors that develop close to the ectoderm, such as vertebral spinous processes or skull. Here, we have studied the embryonic expression of Msx genes in the European pond turtle, Emys orbicularis. The overall Msx expression in head, limb, and trunk is similar to what is observed in other vertebrates. We have focused on the CR area and pre-skeletal shell condensations. The CR expresses Msx genes transiently, in a pattern similar to that of fgf10. In the future carapace domain, the dermis located dorsal to the spinal cord expresses Msx genes, as in other vertebrates, but we did not see expansion of this expression in the dermis located more laterally, on top of the dermomyotomes. In the ventral plastron, although the dermal osseous condensations form in the embryonic Msx-positive somatopleura, we did not observe enhanced Msx expression around these elements. These observations may indicate that common mechanisms participate in limb bud and CR early development, but that pre-differentiation steps differ between shell and other skeletal structures and involve other gene activities than that of Msx genes.

Animals↗

PubMed1996

The marsupial shell membrane: an ultrastructural and immunogold localization study.

In the dasyurid marsupial, Sminthopsis crassicaudata, as the oocytes/embryos travel down the female reproductive tract two extracellular coats, the mucoid and shell membrane, come to surround them. Embryos recovered from the oviduct have a mucoid coat but no shell membrane which is only found surrounding uterine embryos. Initially, the shell membrane has a compact granular consistency but it later thins and becomes fibrous in texture with fibres oriented mainly in the plane of the membrane. Immunogold labelling with polyclonal antibodies raised against the extracellular coats was employed to determine the location and ultrastructural appearance of the secretory granules which contain mucoid and shell membrane precursors. Secretory granules in the luminal epithelium of the ampulla of the oviduct are of irregular electron density, while those in the isthmus are electron-dense and homogeneous. Both types give rise to the mucoid coat. Secretory granules in the epithelia of the utero-tubal junction and some endometrial glands are electron-lucent and contain some flocculent material which, after exocytosis, gives rise to the shell membrane.

Animals↗

PubMed2001

Effect of 1alpha-hydroxyvitamin D3 and egg-shell calcium on bone metabolism in ovariectomized osteoporotic model rats.

Egg-shell calcium (Ca) is one of the effective Ca sources for bone metabolism. In the present study, we investigated whether egg-shell Ca had similar effects compared with calcium carbonate (CaCO3) when vitamin D3 (1alpha(OH)D3) treatment was given to an osteoporotic rat model. In both 1alpha(OH)D3-supplemented and -unsupplemented rats, the bone mineral density (BMD) of the lumber spine in the vitamin-supplemented group increased significantly compared with the unsupplemented group. In a Ca balance study, there were also significant differences in intestinal Ca absorption, urinary Ca and fecal Ca between the vitamin-supplemented and -unsupplemented groups. These results show that egg-shell Ca could have similar effects to CaCO3 on bone metabolism. In contrast with CaCO3, vitamin D3 supplementation did not significantly increase serum Ca levels in the egg-shell Ca group; however, the mechanism of Ca absorption is still unclear. Our results suggest that egg-shell Ca may be an effective nutrient in Ca metabolism for people treated with vitamin D3.

Animals↗

PubMed1975

The nature of metal-ligand bonding in the primary hydration shell and in ionophores with alkali metal ions.

1. Trasport of alkali ions in model membranes mediated by ionophores is associated with at least two basic problems: (a) a conceivable physical model for the metal-ligand bonding in the primary hydration shell and (b) migration of ions from the primary hydration shell to ionophores to form ion complexes. 2. The nature of metal-ligand bonding both in the primary hydration shell and in the ionophores has been found to be around 80% ionic and 20% covalent in both cases by indepdnent investigation. Clearly the energetics being equivalent in both systems, ions will not migrate from the former to the latter. 3. A novel model is proposed in terms of hydrogen bonding in the primary hydration shell for Li+ and Na+ so that the migration of these ions to ionophores is easily envisaged. Hydrogen bonding contribures 18% and 5% of the energy to the total hydration shell energy of Li+ and Na+, respectively.

Acetamides↗

PubMed1992

An electron microscopic morphometric comparison of tyrosine hydroxylase immunoreactive innervation in the neostriatum and the nucleus accumbens core and shell.

The synaptic targets and size distributions of the sectioned profiles of tyrosine hydroxylase immunoreactive fibers and boutons in the neostriatum and shell and core of the nucleus accumbens were evaluated. Significantly more synaptic contacts where dendrite shafts are the postsynaptic element were observed in the shell than in the core of the nucleus accumbens or neostriatum. Relative to the core and neostriatum, a significantly greater proportion of the tyrosine hydroxylase immunoreactive innervation of the accumbal shell consisted of thin fiber and small bouton profiles. Thus, with regard to the morphometric parameters evaluated, the core of the nucleus accumbens is aligned with neostriatum and the shell is different from the core and neostriatum. In the light of these data, it is probably that the effects of the dopaminergic innervation in the core resemble the effects in neostriatum more than do those in the shell.

Animals↗

PubMed1994

Modulation of locomotor activity by NMDA receptors in the nucleus accumbens core and shell regions of the rat.

Two subdivisions of the nucleus accumbens (NAC), the core and the shell, have been recently identified on the basis of immunohistochemical differences and neural connections. A major neural input to the NAC is provided by glutamatergic afferents of allocortical origin and there is evidence that glutamate can modulate psychomotor activation and drug reinforcement. This study was undertaken to explore whether selective pharmacological blockade of NMDA neurotransmission within the core and the shell region affected differentially spontaneous and cocaine-induced locomotor activity. We report that intra-NAC microinfusion of aminophosphonovaleric acid (AP-5) (0.75-3.0 micrograms/side, 1.5-6.0 micrograms total dose) within the core but not the shell region reduced cocaine-induced locomotion in a dose-dependent manner. In contrast, microinfusion of the same doses of AP-5 within the shell region caused a dose-dependent increase of spontaneous locomotion, while microinfusion within the core region was ineffective. These results indicate that blockade of NMDA receptors in the core and the shell of the NAC elicited different effects on spontaneous and cocaine-induced locomotion. This suggests that these substructures may subserve different functions within the integrated output of the NAC, functions that may vary according to the state of arousal.

2-Amino-5-phosphonovalerate↗

PubMed1996

Sensorimotor gating in rats is regulated by different dopamine-glutamate interactions in the nucleus accumbens core and shell subregions.

The amplitude of the acoustic startle reflex is normally reduced when the startling stimulus is preceded by a weak click or "prepulse'. Prepulse inhibition (PPI) of acoustic startle has been used as an operational measure of sensorimotor gating or inhibition, and is reduced in schizophrenia patients and in rats with central dopamine (DA) activation. The DA agonist-induced disruption of PPI in rats may thus offer a useful animal model to study impaired sensorimotor gating in schizophrenia. We have previously reported that DA-glutamate interactions in the nucleus accumbens (NAC) regulate PPI. The NAC has at least two major subregions-the core and shell-that have distinct anatomical and neurochemical properties. In this study, we compared changes in PPI after manipulations of DA-glutamate activity in these two NAC subregions. Consistent with previous findings, infusion of the non-NMDA agonist AMPA into the NAC core subregion significantly reduced PPI, and this effect was opposed by systemic administration of the D2 antagonist haloperidol. Also consistent with previous reports, infusion of the non-NMDA antagonist CNQX into the NAC core subregion did not alter PPI, but its co-infusion with D-amphetamine (AMPH) attenuated the AMPH-disruption of PPI. In contrast, while PPI was reduced after AMPA infusion into the NAC shell subregion, this effect of AMPA could not be blocked by pretreatment with haloperidol. Infusion of either AMPH or CNQX into the NAC shell subregion reduced PPI independently. The PPI-disruptive effects of intra-shell CNQX infusion were not blocked by haloperidol. The present results suggest striking differences between the NAC core and shell subregions in their neurochemical modulation of sensorimotor gating of acoustic startle in the rat.

Acoustic Stimulation↗

PubMed1994

A fast method for forward computation of multiple-shell spherical head models.

Using a combination of 3 suitably located dipoles in a homogeneous sphere, the scalp potential due to a dipole source in a 4-shell spherical head model can be approximated with a high degree of precision and a more than 30-fold increase in computing speed. Magnitudes and locations of the 3 equivalent dipoles can be fitted in a homogeneous sphere to data generated from a source at one location in a 4-shell head model. The resulting parameters are used to compute scalp potentials for sources at other locations and orientations. Residual variance measures showed close agreement between the new approximation and a standard 4-shell computation method. Further tests of the method used scalp data from 500 randomly selected pairs of sources generated by the standard 4-shell computation and fitted using, for forward computations, the new approximation and the single-shell Ary-corrected head model. Errors with the new approximation were marginally larger than with the standard computation, but sources were located within 0.5 mm and 0.6 degrees of the original position in 99% of the fits. 99% error limits for the Ary model were up to 18 mm and 25 degrees and depended on the head model parameters.

Brain↗

PubMed1996

Behavioural effects of 7-OH-DPAT are solely due to stimulation of dopamine D2 receptors in the shell of the nucleus accumbens; jaw movements.

The goal of this study was to determine whether the dopamine D3 receptor in limbic structures plays a role in the shell-specific and dopamine-dependent display of jaw movements in rats. When combined with the dopamine D1 receptor agonist (+/-)-6-chloro-7,8-dihydroxy-3-allyl-1- phenyl-2,3,4,5-tetrahydro-1 H-3-benzazepine (SKF 82958, 5 micrograms), the putative dopamine D3 receptor agonist (+/-)-7-hydroxy-N, N-di-n-propyl-2-aminotetralin (7-OH-DPAT, 10 micrograms) produced repetitive jaw movements following injection into the shell, but not the core, of the nucleus accumbens. This behaviour was only partially inhibited by local blockade of dopamine D1 receptors (R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1 H-3-benzazepine, SCH 23390, 500 ng), dopamine D2 receptors (domperidone, 50 and 100 ng) or dopamine D2/3 receptors (l-sulpiride, 25 ng). Combined blockade of both dopamine D1 and D2 receptors in the shell completely antagonized the jaw movements elicited by the cocktail of SKF 82958 and 7-OH-DPAT. Replacing 7-OH-DPAT by another putative dopamine D3 receptor agonist, S(+)-(4aR, 10bR)-3,4,4a,10b-tetrahydro-4-propyl-2H,5H-[I]benzopyrano[4, 3-b]-1, 4-oxazin-9-ol (PD 128,907, 10 micrograms), in the cocktail did not produce jaw movements, when administered into the shell. Injection of the cocktail of SKF 82958 and 7-OH-DPAT into the ventrolateral striatum, which contains nearly no dopamine D3 receptors, also elicited jaw movements. It is concluded that mesolimbic dopamine D3 receptors play no role in the dopamine-dependent and shell-specific jaw movements: the contribution of 7-OH-DPAT in the cocktail of SKF 82958 and 7-OH-DPAT to the display of jaw movements is solely due to its ability to activate dopamine D2 receptors.

Animals↗

PubMed1985

Characterization of lamina-bound chromatin in the nuclear shell isolated from HeLa cells.

The structure and the polypeptide composition of the nuclear shell isolated from interphase HeLa cells have been investigated and compared to those of the intranuclear material. The isolated nuclear shell contains chromatin superstructures (28-32 nm thick fibres) made of tightly packed nucleosomes that resist low ionic strength conditions and that are associated with the three nuclear lamins. Chromatin in the nuclear shell exhibits very simple chemical composition. Especially, non-histone proteins are lacking. The results presented here rule out the possibility that the nuclear shell results from contamination of lamina by intranuclear elements. They suggest that the lamins are directly involved in the specific properties and in the organization of chromatin in the nuclear shell.

Cell Fractionation↗

PubMed1978

Fine structure of muscle insertions on the larval shell and operculum of the nudibranch Phestilla sibogae (Mollusca: Gastropoda) before and during metamorphosis.

In Phestilla, the attachment of the larval body to shell and operculum occurs at muscle insertion sites. Attachment zones are specialized areas of squamous epithelium wherein the cells contain structures considered to be cytoplasmic anchors. The anchors are intracellular organelles consisting of apical and basal hemidesmosomal plaques connected by bundles of tonofilaments which traverse the cells. Muscle-to-epithelium and epithelium-to-shell adhesion is probably due to an extracellular cement. At metamorphosis, both shell and operculum are lost. Electron microscopic investigation of shell and opercular attachment sites during metamorphosis has demonstrated that apical hemidesmosomes lose their integrity and tonofilament bundles pull away from the apical plasmalemma of the epithelial cells as the cells lose contact with the shell or operculum.

Animals↗

PubMed1980

A scanning electron microscopic study of the inorganic and organic matrices comprising the mature shell of Amblema, a fresh-water mollusc.

The scanning electron microscope has been used to describe the morphology of the mature shell in a fresh-water bivalve. The structure of the organic and inorganic components within the nacre, the myostracum, and the prismatic layer is described. A transitional or intermediate zone, interposed between the prismatic layer and the nacre, was identified. In demineralized samples, the organic component of the nacre was found to consist of parallel matricial sheets interconnected by irregular transverse bridges. The structure of the mineral component of the nacre was found to vary with the method of specimen preparation. With polished-etched samples, brick-like units were seen. When shells were simply broken and fixed in osmium, the layers of nacreous material consisted of fusing rhomboidal crystals of aragonite which demonstrated subconchoidal fractures. On the inner surface of the shell, the rhomboidal crystals showed an apparent spiral growth pattern. The myostracum was characterized by regions of modified nacreous structure consisting of enlarged aragonite crystals with a pyramidal morphology. The peripheral aspect of the muscle scars was characterized by rhomboidal crystals, the latter fusing to form the typical nacreous laminae. The uniqueness of the anterior adductor scar is exemplified by the presence of pores, each pore walled by pyramidal units, for the insertion of adductor fibres. In most regions of the shell, the prismatic layer consisted of one prism unit thickness with a height of approximately 225--250 micrometer. However, in two specialized regions of the shell, this layer was seen to consist of multiple layers of stacked prisms. The organic matrices of the prismatic layer are arranged in a honeycomb-like arrangement and packed with mineralized spherical subunits.

Animals↗

PubMed1984

Shell formation and calcium transport in the barnacle Chthamalus fragilis.

The mantle epithelium of the barnacle Chthamalus fragilis (Darwin) exhibits several ultrastructural features which may serve to regulate the calcification process. At the basis-mural plate and intermural plate junctions where rapid shell growth occurs, cells are characterized by long apical cytoplasmic projections and large intercellular spaces. These features may increase the functional surface area of the epithelium and enable more rapid deposition of calcium. The cells underlying the general shell surfaces contain numerous electron-dense inclusion bodies and show frequent cellular disintegration near the growing shell interface. Release of the granular contents of these inclusion bodies has been observed in both disintegrating and non-disintegrating cells. X-ray microanalysis revealed significantly higher calcium levels in the inclusion bodies than in the surrounding cytoplasm. This suggests a calcium transport role for these inclusion bodies. Cellular debris produced as a result of the disintegration of the mantle cells near the shell may play some role in the formation of the organic matrix of the shell. The presence of large numbers of mitochondria and well-developed apical microvilli in the cells of the inner mantle epithelium suggest that these cells serve to transport calcium into the mantle from the ambient sea water.

Animals↗

PubMed1989

Characterization of rotavirus replication intermediates: a model for the assembly of single-shelled particles.

The segmented double-stranded (ds)RNA genome of the rotaviruses is replicated asymmetrically with viral mRNA serving as the template for minus-strand RNA synthesis. To identify intermediate structures in rotavirus replication, subviral particles (SVPs) purified from the cytoplasm of simian rotavirus SA11-infected cells were assayed for RNA polymerase activity in a cell-free system that supports viral RNA replication. Intact SVPs containing newly made RNA were resolved by electrophoresis under nondenaturing conditions on 0.6% agarose gels (50 mM Tris-glycine, pH 8.8). This gel system was found to separate without disrupting SA11 single- and double-shelled virions and virion-derived core particles. SVPs from the cell-free system that contained newly made dsRNA migrated in the agarose gels at positions between virion-derived cores and intermediate of single- and double-shelled virions. SVPs containing newly made dsRNA were eluted from the gel and analyzed for protein content by electrophoresis on polyacrylamide gels. The results showed that three distinct types of replication intermediates (RIs) were present in SA11-infected cells. The smallest intermediate (precore RI, 45 nm, 220 S) contained the structural proteins VP1, VP3, and VP9 and the nonstructural proteins NS53, NS35, and NS34. A second intermediate (core RI, 60 nm, 310 S) contained the core proteins VP1, VP2, and VP3 and the proteins VP9, NS35 and NS34. The largest RI (single-shelled RI, 75 nm, 420 S) contained the inner shell proteins VP1, VP2, VP3, and VP6 and the proteins VP9, NS35 and NS34. Analysis of the formation and turnover of RIs in infected cells pulse-labeled with 35S-amino acids supports a hypothesis that rotavirus single-shelled particles are assembled in vivo by the sequential addition of VP2 and VP6 to precore RIs consisting of VP1, VP3, VP9, NS35, and NS34.

Animals↗

PubMed1991

Modulation of quail intestinal and egg shell gland calbindin (Mr 28,000) gene expression by vitamin D3, 1,25-dihydroxyvitamin D3 and egg laying.

The effects of vitamin D3 sources, egg production and egg cycle on the genomic expression of calbindin (Mr 28,000) in the intestine and egg shell gland (ESG) of quail were characterized by Northern blot and solution hybridization, using synthetic oligonucleotide probe. In vitamin D3- or 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3)-fed quail, onset of egg production induced duodenal and ESG calbindin mRNA and calbindin synthesis. Duodenal calbindin mRNA was slightly higher during the period of shell calcification as compared with the period during which shells were not formed (ESG inactivity). ESG calbindin mRNA was markedly higher during the period of shell calcification than of ESG inactivity. Increasing dietary intake of [3H]1 alpha-hydroxyvitamin D3 increased the duodenal, but not ESG, content of 1,25-(OH)2D3 and calbindin. Duodenal calbindin and its mRNA were absent in vitamin D-deficient quail and were not affected by egg laying. ESG calbindin in the vitamin D-deficient quail was not affected by egg laying, but calbindin mRNA increased in the vitamin D-deficient birds during shell calcification. The results suggest that: (a) intestinal calbindin mRNA and calbindin are induced and/or regulated, either directly or indirectly, by 1,25-(OH)2D3; (b) intestinal calbindin and its mRNA are further induced at the onset of egg laying by an additional stimulator besides 1,25-(OH)2D3; (c) 1,25-(OH)2D3 is required for the expression of the latter stimulator; (d) ESG calbindin mRNA and calbindin are induced in egg-laying birds by a stimulator associated with the egg cycle; and (e) the induction of ESG calbindin mRNA does not need vitamin D metabolites, but 1,25-(OH)2D3 is required for the translation of the mRNA.

Animals↗

PubMed1993

Comparison of MRC-5 and A-549 cells in conventional culture tubes and shell vial assays for the detection of varicella-zoster virus.

A-549 and MRC-5 cells were compared for the detection of varicella-zoster virus (VZV) by conventional tube cell culture and by shell vial assay using fresh specimens. VZV was detected in 33 (32.4%) of 102 specimens by one or all of these methods. In conventional tube culture, seven (21.2%) of 33 were positive in MRC-5 cells and 24 (72.7%) of 33 were positive in A-549 cells, a threefold increase in sensitivity. In shell vial assay, 30 (90.9%) of 33 were positive in MRC-5 cells and 31 (93.9%) of 33 were positive in A-549 cells. The samples tested by A-549 shell vial assay had more positives showing plaque formation. The two shell vial procedures gave the highest levels of sensitivity. A-549 cells provided a more sensitive method of detecting VZV in clinical specimens in both conventional tubes and shell vial assays than did MRC-5 cells.

Cell Line↗

PubMedDate not supplied

A serious skin sulfur mustard burn from an artillery shell.

Despite the Geneva Protocol of 1925 and the Paris Conference on Prohibition of Chemical Weapons in 1989, sulfur mustard and other chemical weapons continue to pose a hazard to both civilians and soldiers. The presence of artillery shells containing sulfur mustard, both in waters where these shells were dumped and in old battlefields, presents a problem in times of peace, especially for those who collect wartime memorabilia. Past literature has reported several hundred incidents involving fishermen who inadvertently pulled leaking shells aboard their fishing vessels, thereby exposing themselves to the vesicant chemical. Other literature reports exposure to children who found the chemical shells in old battlefields. The purpose of this article is to report the first case of a serious sulfur mustard burn that occurred after removing the detonator from an old artillery shell in a historic battle field near Verdun, France. The circumstances surrounding the injury, the diagnosis and management of injuries secondary to sulfur mustard, and the long-term consequences to the patient are presented and discussed. Although skin grafting has been used in the management of other chemical burn injuries, this report is the first to describe the need for split-thickness skin grafts in the management of a patient with sulfur mustard burns.

Burns, Chemical↗

PubMed2006

Ultrastructural and immunohistochemical observations on the process of horny growth in chelonian shells.

The process of growth of horny scutes of the carapace and plastron in chelonians is poorly understood. In order to address this problem, the shell of the terrestrial tortoise Testudo hermanni, the freshwater turtle Chrysemys picta, and the soft shelled turtle Trionix spiniferus were studied. The study was carried out using immunohistochemistry, electron microscopy and autoradiography following injection of tritiated histidine. The species used in the present study illustrate three different types of shell growth that occur in chelonians. In scutes of Testudo and Chrysemys, growth mainly occurs in the hinge regions by the production of cells that accumulate beta-keratin and incorporate tritiated histidine. Newly produced bundles of alpha- and beta-keratin incorporate most of the histidine. No keratohyalin is observed in the epidermis of any of the species studied here. In Testudo, newly generated corneocytes containing beta-keratin form a corneous layer to form the growing rings of scutes. In Chrysemys, newly generated corneocytes containing beta-keratin form the new, expanded corneous layer. In the latter species, at the end of the growing season (autumn/fall), thin corneocytes containing little beta-keratin are produced underneath the corneous layer, and gradually form a scission layer. In the following growing season (spring-summer) the shedding layer matures and determines the loss of the outer corneous layer. In this way, scutes expand their surface at any new molt. In Trionix, no distinct scutes and hinge regions are present and during the growing season, new corneocytes are mainly produced along the perimeter of the shell. Corneocytes of Trionix contain little beta-keratin and form a thick corneous layer in which cells resemble the alpha-layer of the softer epidermis of the limbs, tail and neck. Neither keratohyalin nor specific histidine incorporation was observed in these cells. Corneocytes are gradually lost from the epidermal surface. Dermal scutes are absent in Trionix, but the dermis is organized in 6-10 layers of plywood-patterned collagen bundles. The stratified layers gradually disappear toward the growing border of the shell. The mode of growth of horny scutes in these different species of chelonians is discussed.

Animals↗