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PubMed2005

The functional divide for primary reinforcement of D-amphetamine lies between the medial and lateral ventral striatum: is the division of the accumbens core, shell, and olfactory tubercle valid?

When projection analyses placed the nucleus accumbens and olfactory tubercle in the striatal system, functional links between these sites began to emerge. The accumbens has been implicated in the rewarding effects of psychomotor stimulants, whereas recent work suggests that the medial accumbens shell and medial olfactory tubercle mediate the rewarding effects of cocaine. Interestingly, anatomical evidence suggests that medial portions of the shell and tubercle receive afferents from common zones in a number of regions. Here, we report results suggesting that the current division of the ventral striatum into the accumbens core and shell and the olfactory tubercle does not reflect the functional organization for amphetamine reward. Rats quickly learned to self-administer D-amphetamine into the medial shell or medial tubercle, whereas they failed to learn to do so into the accumbens core, ventral shell, or lateral tubercle. Our results suggest that primary reinforcement of amphetamine is mediated via the medial portion of the ventral striatum. Thus, the medial shell and medial tubercle are more functionally related than the medial and ventral shell or the medial and lateral tubercle. The current core-shell-tubercle scheme should be reconsidered in light of recent anatomical data and these functional findings.

Animals↗

PubMed1999

Efficacy of disinfection of shell eggs externally contaminated with Salmonella enteritidis. Implications for egg testing.

Experimental contamination of the surface of shell eggs by dipping in a culture of Salmonella enteritidis resulted in the presence of Salmonella enteritidis in/on the shells as well as shell membranes but not in the egg content. Disinfection with Lugol's solution, chlorhexidine, ethanol, quarternary ammonium solutions or flaming after dipping in ethanol failed to achieve complete decontamination of the shell and membranes with resulting false positives when eggs were broken for culturing of the content. Dipping eggs for three seconds in boiling water resulted in complete destruction of Salmonella enteritidis in shells and membranes but sometimes caused the eggs to crack. A method of aseptically opening eggs without risk of contaminating the content from the shell or membrane was developed. Salmonella enteritidis deposited in/on the shell and membranes did not multiply during storage of the eggs at 20 degrees C for four weeks, the counts seemed to decrease. No Salmonella enteritidis was detected in the contents of any contaminated eggs.

Animals↗

PubMed2002

The origin of lactation as a water source for parchment-shelled eggs.

Available evidence indicates that mammary gland secretions first evolved in synapsids that laid parchment-shelled eggs. Unlike the rigid-shelled eggs of birds and some other sauropsids, parchment-shelled eggs lose water very rapidly when exposed to ambient air of lower vapor pressure, whether due to differences in relative humidity or to differences in temperature. This precludes endothermic incubation of parchment-shelled eggs in an open nest. Synapsids may have avoided egg desiccation by incubating eggs in a pouch, but this would limit maternal activity. Parchment-shelled eggs are able to take up liquid water across the eggshell. I propose that mammary secretion originally evolved as a means of supplying water to eggs, and as such was essential to the evolution of endothermy among the egg-laying cynodonts that were ancestral to mammals. It is possible that synapsid eggs, like parchment-shelled squamate eggs, were also capable of uptake of some nutrients, such as sodium and ionic calcium. Living monotremes still produce parchment-shelled eggs. The porous eggshell and bilaminar yolk sac membrane of these eggs permit substantial uptake of uterine secretions during the intrauterine period, and might also facilitate uptake of mammary secretions during egg incubation. In its simplest form, mammary secretion may be an ancient trait of egg-laying synapsids, having had an important role long before milk became obligatory for suckling young.

Animals↗

PubMed1986

Calcium intake in relation to ovulation and oviposition when access to oyster shell is time-restricted or unrestricted.

White Leghorn hens were fed either a conventional diet containing 40 gCa/kg from oyster shell, or one low in Ca (3 g/kg) with oyster shell offered separately. In experiment 1 access to oyster shell was unrestricted; in experiment 2. Access was time-restricted to the first 6 h of the photophase of the 14L:10D photoperiod. Irrespective of time-restriction, hens offered oyster shell laid heavier eggs, but shell thickness was reduced. On days on which only ovulation occurred, time-restricted hens consumed significantly less Ca than unrestricted hens. In contrast, on days on which only oviposition occurred, time-restricted hens consumed significantly more Ca than unrestricted hens. These results suggest that when access to oyster shell is time-restricted to morning hours Ca consumption occurs in response to a Ca deficit persisting from the previous period of shell calcification.

Animals↗

PubMed1986

Categorisation and causes of abnormal egg shells: relationship with stress.

Concern regarding the proportion of brown eggs being laid with abnormal egg shells led to an investigation of the relationship between disturbance or stress and egg shell appearance and quality. The abnormalities fell into two main classes: misshapen or bulging eggs and eggs coated with a superficial layer of amorphous calcium, variously termed dusted, white banded, chalky or pink eggs. Translocation of hens from pens to cages resulted in a decrease in egg production and an increase in the proportion of abnormal eggs over the succeeding 18 d. Disturbance to flocks on deep litter resulted in an increase in the proportion of eggs laid with abnormal shells on the following day, not only in the flocks directly affected but also in an adjacent flock. Exclusion from their nests of birds accustomed to laying in nest boxes resulted in disturbed prelaying behaviour, retention of eggs in the shell gland and an increased proportion of coated eggs. Administration of 0.1, 0.25 or 1.0 mg of adrenaline subcutaneously resulted in the retention of eggs currently in the hens' shell glands and in an increased proportion of eggs with abnormal egg shells being laid during the following 10 d. A dose response effect was apparent. There was evidence that the nature of the particular abnormality produced was dependent on the stage of egg formation at which the disturbance was imposed and, if retention followed, upon the length of time the egg was retained. Disturbances when eggs were only lightly calcified tended to result in misshapen eggs, while those occurring when oviposition was imminent tended to result in coated eggs. Dusted or pink eggs followed moderate retention whereas white banded eggs were seen after prolonged retention. These observations may provide a basis for a non-invasive method of assessing stress in laying hens as well as helping to account for hitherto inexplicable occurrences of declining egg shell quality.

Animals↗

PubMed1987

Progesterone and testosterone elicit increases in the duration of shell formation in domestic hens.

Injection of progesterone or testosterone in hens 4 and 10 h after ovulation increased the intervals between ovipositions and shell weights. The effects were dose-dependent. Expulsion of the egg from treated hens at the expected time of oviposition suppressed the increase in shell weight and deposition of the cuticle. The duration of shell formation had therefore been increased by the injections of progesterone or testosterone. Injections of progesterone 16 h or of testosterone 15 h after ovulation advanced oviposition and reduced shell weight. Testosterone propionate was more efficient than testosterone in its action on the duration of shell formation. Oestradiol was ineffective. Indomethacin delayed oviposition but did not change the duration of shell formation. These results suggest that the duration of shell formation is under the control of hormonal factors and that the larger follicles of the ovary, may be involved in its control.

Animals↗

PubMed1996

Egg-shell deposition and blood plasma inorganic phosphorus concentration in individual laying hens.

1. The relationship between plasma inorganic phosphorus measured at the end of the dark period and the weight of the next egg shell produced was investigated in 30 Hisex Brown hens. 2. Hens received an adequate conventional layers' diet and the lighting pattern was conventional (17 L: 7 D). Observations were made early (31 to 40 weeks) and late (62 to 68 weeks of age) in the laying period. 3. Eggs were classified by position in the clutch sequence and significant negative correlations were found between shell weights of early eggs in the sequence and plasma phosphate at the end of the dark period. 4. No significant trends were found in plasma total calcium. 5. No significant differences were found in bone compositions of birds producing consistently more or less than average shell weight during the laying period. 6. The negative correlations between plasma phosphate and shell weight are consistent with the observations of Sauveur and Mongin (1983) and show that impairment of shell deposition is associated with skeletal mobilisation as indicated by increase in plasma phosphate. This is consistent with the observations on bone composition and indicates that selection for shell quality will tend to select birds which are not dependent on excessive skeletal mobilisation during shell formation.

Analysis of Variance↗

PubMed1982

Effect of p-p'-DDE administered in vivo and in vitro on Ca2+ binding and Ca2+-Mg2+-ATPase activity in egg shell gland mucose of ducks.

Thinning of the egg shell is produced by p-p'-DDT and DDE in several species of birds. A study was made of the effect of DDE administered in vitro and in vivo on the Ca2+ binding and Ca2+-Mg2+-activated ATPase of a homogenate of the egg shell gland of ducks (Anas platyrhynchos var.). The concentration of Ca2+ was 1 X 10(-4) M and that of MgATP 1 X 10(-3) M. In vitro, DDE in concentrations of 2-16 micrograms/ml of incubation medium inhibited the Ca2+-Mg2+-activated ATPase in a concentration-dependent manner, whereas Mg2+-activated ATPase was not affected by these concentrations. The Ca2+ binding by the homogenate was reduced by DDE in the same concentrations. The sodium azide sensitive Ca2+ binding was most sensitive. In vivo, DDE administered in a concentration of 40 mg/kg dry weight of the food for 45 days reduced the egg shell index by 18% in comparison to controls. After 45 days of treatment the DDE concentrations in the egg shell gland mucosa was 1.20 +/- 0.16 micrograms/g of wet weight, while no DDE was detected in the controls. The Ca2+-Mg2+-activated ATPase was reduced by 32%, whereas the Mg2+-ATPase was not changed. The Ca2+ binding by the homogenate was reduced by 29%, the sodium azide sensitive part being most vulnerable, DDE increased the total Ca content of the egg shell gland mucosa by 44%. Since Ca is transported against a concentration gradient between blood plasma, and the lumen of the shell gland, it is suggested that DDE, by inhibiting the Ca2+-Mg2+-activated ATPase, decreased the Ca translocation over the egg shell gland mucosa.

Animals↗

PubMed1991

Localization of progesterone receptors in the shell gland of laying and nonlaying chickens.

The aim of the present study was to localize the progesterone receptor (PR) in the shell gland of the chicken and to determine if the localization and the amount of PR in the shell gland change with egg laying activity. White Leghorn hens laying regularly or out of lay for more than 2 wk were used. Localization of PR in the shell gland was done by immunocytochemistry. The amount of PR in the shell gland mucosal tissues was measured by Western blot analysis. Monoclonal antibodies to the chicken PR, PR6, and PR13 were used in both experiments. The PR were present in the nuclei of the surface epithelial cells, tubular gland cells, stromal fibroblasts, and smooth muscle cells in the arterial wall and myometrium of laying hens. The PR were localized in the same tissues of the shell gland of nonlaying hens as in laying hens. However, the density of PR-positive cells in nonlaying hens was greater, possibly because the tissues were atrophied. Western blot analysis indicated that the amount of PR was greater in nonlaying hens than in laying hens when equal amounts of proteins were used, whereas the molecular weights of PR of laying and nonlaying hens were identical. These results suggest that progesterone acting through its receptor may regulate the secretory activity of the surface epithelium and tubular gland cells for shell formation and the contractile activity of the myometrium. Moreover, once the cells of the shell gland differentiate and become responsive to progesterone, these cells maintain this responsiveness even during the nonlaying period.

Animals↗

PubMed2000

Ultrastructural characteristics of ostrich eggshell: outer shell membrane and the calcified layers.

The ultrastructure of the eggshell of the domestic hen has been well researched and structural studies of other avian species, such as the ostrich, often base their interpretation of egg shell structure on that of the chicken. In the ostrich, lowered hatchability and hatching trauma may be due to shell ultrastructural abnormalities. In the present study the ultrastructure of the calcified portion, and the outer shell membrane (OSM), of domesticated ostrich eggshells was investigated using standard electron microscopic techniques. Transmission and scanning electron microscopy studies demonstrated intimate contact between cup-shaped structures present on the OSM and the mammillary layer of the calcified portion of the shell. The initial calcium carbonate growth of the calcified shell was of a dendritic nature with nucleation sites on the surface of the cup's contents. The dendritic growth gave way to a more randomly-orientated, smaller crystallite growth structure, which changed in form as it neared the vertical crystal layer (VCL). The VCL is described as being both amorphous and 'crumbly' depending on the plane of fracture. These observations suggest that firstly, initial calcification is contained within the cups and is then directed outwards to form the shell and that secondly, the VCL may contain an evolutionary, calcified cuticular layer. These observations serve as a baseline for studies investigating the effect of shell structure and strength on hatchling trauma and the influence of maternal diet.

Animals↗

PubMed1987

Scanning electron microscopy of early dinosaur egg shell structure: a comparison with other rigid sauropsid eggs.

Fossil eggs attributable to dinosaur (probably prosauropod) parentage that have been recovered from the early Jurassic Elliot Formation sediments at the Rooidraai locality possess shells that are similar to those of birds and crocodilians, and distinctly unlike those of chelonians and gekkonids. The preserved shell is very thin, and distinct mammillary processes are lacking, although the inner surface displays an undulating contour. The absence of these processes may be attributable to the inner portion of the shell having been at least partially decalcified during incubation and not preserved in the fossil state. The shells appear to be composed of broadly wedge-shaped, albeit ill-defined calcareous units, and they are similar to those of birds and other dinosaurs in the pattern of cleavage shown by the tabular calcite crystals of the palisade layer, and in the absence of the dominant horizontal lamellae that characterize crocodilian shells. The differential resemblance of these early Jurassic shells to the eggs of other closely related sauropsid taxa may be pertinent to questions concerning the evolution of egg shell structure within this clade.

Alligators and Crocodiles↗

PubMed2002

Mollusc larval shell formation: amorphous calcium carbonate is a precursor phase for aragonite.

The larval shells of the marine bivalves Mercenaria mercenaria and Crassostrea gigas are investigated by polarized light microscopy, infrared spectroscopy, Raman imaging spectroscopy, and scanning electron microscopy. Both species contain similar shell ultrastructures. We show that larval shells contain amorphous calcium carbonate (ACC), in addition to aragonite. The aragonite is much less crystalline than non-biogenic aragonite. We further show that the initially deposited mineral phase is predominantly ACC that subsequently partially transforms into aragonite. The postset juvenile shell, as well as the adult shell of Mercenaria also contains aragonite that is less crystalline than non-biogenic aragonite. We conclude that ACC fulfills an important function in mollusc larval shell formation. It is conceivable that ACC may also be involved in adult shell formation.

Animals↗

PubMed1993

Developmental changes in the cell columns and trophoblastic shell of the macaque placenta: an immunohistochemical study localizing type IV collagen, laminin, fibronectin and cytokeratins.

Developmental changes in the organization of cells and extracellular matrix in the cell columns and trophoblastic shell of macaque placentas have been examined between 37 days of gestation and term. Between 37 and 53 days a thickened basement membrane developed between the trophoblast cells of the proximal cell columns and the mesenchymal cores of contiguous anchoring villi. This layer stained strongly for type IV collagen and laminin, but weakly for fibronectin. Large "lakes" of extracellular matrix immunoreactive for all 3 of these antigens were present in the distal columns, while smaller amounts were distributed between cells of the proximal columns. During this period the trophoblast cells in the proximal shell reorganized, forming strands of cells that were separated by bands of matrix immunoreactive for type IV collagen, laminin, and fibronectin. Staining for these antigens decreased abruptly at the junction between fetal and maternal tissues. Between 66 and 104 days the thick basement membrane of the proximal columns persisted, but stained only weakly for each of the 3 extracellular matrix antigens. The large lakes of matrix in the distal columns characteristic of earlier stages gradually disappeared. The cell columns became progressively shorter and the tips of the anchoring villi became embedded in the trophoblastic shell. The matrix of the shell decreased in immunostaining intensity except for narrow rims around the trophoblast cells. Gestational ages later than 104 days showed few additional changes in the distribution of the matrix antigens or cell organization of the columns and shell. The thick basement membrane-like layer persisted to term although it continued to stain weakly for the 3 matrix antigens. The distal ends of most anchoring villi were embedded in the trophoblastic shell. The developmental changes in the organization of the columns and shell may be related to changes in placental growth rate.

Animals↗

PubMed2006

Differential impact of pavlovian drug conditioned stimuli on in vivo dopamine transmission in the rat accumbens shell and core and in the prefrontal cortex.

RATIONALE: Conditioned stimuli (CSs) by pavlovian association with reinforcing drugs (US) are thought to play an important role in the acquisition, maintenance and relapse of drug dependence. OBJECTIVE: The aim of this study was to investigate by microdialysis the impact of pavlovian drug CSs on behaviour and on basal and drug-stimulated dopamine (DA) in three terminal DA areas: nucleus accumbens shell, core and prefrontal cortex (PFCX). METHODS: Conditioned rats were trained once a day for 3 days by presentation of Fonzies filled box (FFB, CS) for 10 min followed by administration of morphine (1 mg/kg), nicotine (0.4 mg/kg) or saline, respectively. Pseudo-conditioned rats were presented with the FFB 10 h after drug or saline administration. Rats were implanted with microdialysis probes in the shell, core and PFCX. The effect of stimuli conditioned with morphine and nicotine on DA and on DA response to drugs was studied. RESULTS: Drug CSs elicited incentive reactions and released DA in the shell and PFCX but not in the core. Pre-exposure to morphine CS potentiated DA release to morphine challenge in the shell but not in the core and PFCX. This effect was related to the challenge dose of morphine and was stimulus-specific since a food CS did not potentiate the shell DA response to morphine. Pre-exposure to nicotine CS potentiated DA release in the shell and PFCX. CONCLUSION: The results show that drug CSs stimulate DA release in the shell and medial PFCX and specifically potentiate the primary stimulant drug effects on DA transmission.

Animals↗

PubMed1998

Shell differentiation and engrailed expression in the Ilyanassa embryo.

We have used in situ hybridization and immunocytochemistry to study the expression of the engrailed-related gene, Ily-en in embryos of the marine mud snail Ilyanassa obsoleta. We find that Ily-en is only expressed in shell gland cells. Only mRNAs localized in the shell gland hybridize to an antisense probe of the Ily-en homeobox. Similarly, only shell gland cells or shell-forming cells are stained by the monoclonal antibody 4D9, which was raised to the engrailed-class protein from Drosophila. Ilyanassa embryos made deficient in vegetal cytoplasm by removing the third polar lobe fail to differentiate an organized external shell. They do however make some randomly oriented internal shell fragments in which Ily-en is expressed. Because Ily-en is expressed in shell gland cells of both normal and lobeless embryos, we conclude that the determinant(s) required for Ily-en expression are not exclusively localized in the polar lobe.

Animals↗

PubMed1991

Generation of infectious nucleocapsids by in vitro assembly of the shell protein on to the polymerase complex of the dsRNA bacteriophage phi 6.

A method for the in vitro uncoating of the phi 6 nucleocapsid (NC) was developed. The resulting particle, designated as the NC core, containing the genomic double-stranded (ds) RNA segments and the proteins P1, P2, P4 and P7, was not infectious but had a highly enhanced in vitro transcriptase activity compared to that of the intact NC. The NC shell protein P8 was purified by immunoaffinity chromatography, and it was shown to self-assemble to shell-like structures upon addition of calcium ions. The conditions for the self-assembly of the shell were optimized. Shell reassembly on to the NC cores restored the infectivity but resulted in a decrease of transcriptase activity. No reassembly of the shell on to RNA-less cores (procapsids) produced from a cDNA construction in Escherichia coli was observed. Our results suggest that the intracellular uncoating of the NC is the event activating the phi 6 dsRNA transcriptase and that the NC shell is necessary for infectivity, probably for the passage of the NC through the host cytoplasmic membrane. Packaging of the dsRNA segments into the procapsid appears to be a prerequisite for NC shell assembly.

Bacteriophages↗

PubMed1991

Rotavirus morphogenesis: domains in the major inner capsid protein essential for binding to single-shelled particles and for trimerization.

A cell-free system containing rotavirus subviral particles (SVPs), rabbit reticulocyte lysate, and [35S]methionine was programmed to synthesize viral protein by the addition of messenger RNA (mRNA). Electrophoretic analysis of single-shelled particles recovered from the system by CsCl centrifugation showed that newly made VP6 assembled into the particles in vitro. Electrophoretic analysis also showed that the newly made VP6 which bound to single-shelled particles in vitro was arranged in trimeric units. To identify the domain within VP6 essential for assembly into single-shelled particles, amino- and carboxyl-truncated species of VP6 were assayed for the ability to associate with single-shelled particles in the cell-free system. The truncated proteins were introduced into the system by adding VP6 mRNAs containing 5'- and 3'-terminal deletions. The terminally deleted mRNAs were prepared using SP6 RNA polymerase to transcribe portions of cDNAs of the rotavirus SA11 gene for VP6 (gene 6). Analysis of the ability of truncated VP6 to associate with single-shelled particles showed that a domain essential for assembly resides at the carboxyl-end of VP6 located between amino acid residues 251 and 397. To contrast the domain for assembly with that for trimerization, amino- and carboxyl-truncated species of VP6 were also examined by electrophoretic assay for the ability to trimerize in vitro. The results showed that the domain for trimerization resides near the center of VP6 located between amino acid residues 105 and 328. Comparison of the domains for assembly and trimerization showed that they are unique but may overlap. The fact that some truncated species of VP6, although able to bind to single-shelled particles were unable to form trimers in vitro, suggests that trimerization of VP6 is not prerequisite for the assembly of single-shelled particles.

Animals↗

PubMed1992

Pharmacological characterization of dopamine systems in the nucleus accumbens core and shell.

Recent anatomical data suggest that the nucleus accumbens can be parcellated into a core region, related to the caudate-putamen, and a shell region, associated with the limbic system. We have used pharmacological methods to characterize the dopamine innervations of the nucleus accumbens core and shell in the rat. Concentrations of both dopamine and serotonin were significantly greater in the nucleus accumbens shell than the nucleus accumbens core. Metabolite: amine ratios suggested that both dopamine and serotonin utilization are greater in the core. However, dopamine turnover (as determined by measuring the rate of decline of dopamine after alpha-methyl-p-tyrosine treatment) was not significantly different in the two accumbal sectors. Dopamine concentrations in the two nucleus accumbens sectors were decreased to an equivalent degree at both 4 and 18 h after reserpine administration. In contrast, serotonin concentrations were decreased to a significantly greater degree in the nucleus accumbens core than nucleus accumbens shell at 4 h, but not 18 h, after reserpine administration. Administration of haloperidol increased dopamine utilization in both nucleus accumbens sectors, but augmented utilization to a significantly greater degree in the nucleus accumbens core. Clozapine increased dopamine utilization to an equivalent degree in both nucleus accumbens regions. Short duration immobilization stress selectively increased dopamine utilization in the nucleus accumbens shell. These data indicate that there are significant differences between the nucleus accumbens core and nucleus accumbens shell in basal dopamine metabolism, and indicate that the core and shell dopamine innervations can be distinguished on the basis of response to both pharmacological and environmental challenges.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗