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Molecular dynamics simulations of phosphate-based glasses P2O5-CaO-Na2O have been carried out, using an interatomic force field that has been parameterized to reproduce the structural and mechanical properties of crystalline phosphorus pentoxide, o′(P2O5)∞ orthorhombic phase. Polarization effects have been included through the shell-model potential and formal charges have been used to aid transferability. A modification to the DL_POLY code (version 2.20) was used to model the high temperature shell dynamics. Structural characterizations of three biomedically applicative molar compositions, (P2O5)0.45(CaO)x(Na2O)0.55-x (x = 0.30, 0.35, and 0.40), have been undertaken. Good agreement with available experimental and ab initio data is obtained. The simulations show that, dependent on composition, the phosphorus atoms are primarily bonded to two or three oxygens that in turn bridge to neighbouring phosphorus atoms. Na+ and Ca2+ modifiers are found to occupy a pseudo-octahedral bonding environment with mean oxygen coordination numbers of 6.55 and 6.85, respectively, across all compositions studied. [ABSTRACT FROM AUTHOR]

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The general trend in biomaterials is to use and employ materials that play an active role in tissue regeneration rather than passive and inert materials. Therefore, understanding how a material interacts with the surrounding environments, including cells and tissue fluid, allows material design to be tailored so that implants can be constructed to promote a specific biological response, helping them better perform their function. This class of materials has been described as the “Third Generation” of biomaterials. Phosphate based glasses fall into this category and it has been shown that the properties of these glasses can be tuned viatheir composition according to the desired end application. These glasses can be prepared as melt-quenched or sol-gel bulk form suitable for potential hard tissue engineering applications and as vehicles for antimicrobial agents. They can also be prepared as fibres suitable for soft tissue engineering applications such as those involving muscle, ligaments, and tendon, where, like the fibres, the tissue has a high degree of anisotropy. [ABSTRACT FROM AUTHOR]

Using the immunohistochemical technique, we attempted to identify the source of secretion of steroid hormones between the mid- and late-terms of gestation in dogs by investigating steroid converting enzymes such as cholesterol side-chain cleavage enzyme (SCC), 3 β-hydroxysteroid dehydrogenase/isomerase (3 β-HSD), 17 α-hydroxylase/C17, 20lyase (c17), and aromatase in the ovaries and placenta. Aromatase positive cells were slightly confirmed in luteal cells in the mid-term of gestation (day 40), whereas, in the late-stage (day 50 and 60), the number of aromatase positive cells had increased. However, the oestrogen precursor (c-17 positive cells), could barely be identified in the marginal regions of the corpora lutea (CL) and completely disappeared in the late-stage of gestation. The androgen precursors, convertase SCC and 3 β-HSD, were confirmed in all regions of the CL during the mid-stage of gestation (day 40), showing particularly strong cell reactions in the marginal region of the CL. Yet, these positive reactions of SCC and 3 β-HSD in the marginal region of the CL disappeared in the late-stage of gestation. Moreover, it was discovered that the number of SCC and 3 β-HSD positive cells had decreased in all regions of the CL. None of the enzymes were detected in the placenta. The above results indicated that the source of oestrogen secretion in pregnant dogs is considered to be the CL, and that, compared with the mid-stage of gestation, there was an increased number of oestrogen synthesizing cells within the CL in the late-stage. However, the biosynthetic site of oestrogen precursors from the luteal cells during the late-stage of gestation is still unknown. [ABSTRACT FROM AUTHOR]

Adrenoceptor mechanisms in the extrinsic uterine arteries from late pregnant guinea-pigs were characterized pharmacologically and compared with contractile responses of uterine arteries from non-pregnant and oophorectomized control, progesterone and oestrogen treated animals. Pregnancy caused an increase in diameter of the arteries, more pronounced the more distal they were. There was no change in potassium-evoked maximum contractions during pregnancy. Noradrenaline (10 nM to 1 mM), in the presence of cocaine (1 μM) and propranolol (0.1 μM), induced concentration-dependent contractions of the arterial segments, with approximately similar pD2 values. The maximum responses (Emax) were significantly increased during pregnancy and hormone supplementation. Prazosin (10 nM to 1 μM), but not rauwolscine (10 nM to 1 μM), antagonized noradrenaline-evoked contractions of the arteries. Isoprenaline (10 nM to 1 μM), in the presence of prazosin (0.1 μM) and cocaine (1 μM), had no relaxant effect on arteries contracted submaximally by prostaglandin F2α, (5 μM). Neither cocaine nor normetanephrine modified noradrenaline-evoked contractions of the uterine artery. The results indicate that guinea-pig uterine vasoconstriction is mediated by α1-adrenoceptors while relaxant β-adrenoceptor effects, neuronal and extraneuronal uptake mechanisms are of minor importance. The observed increase in Emax may be due either to an increase in the number of α1-adrenoceptors or to an enhanced pharmaco-mechanical coupling, which conceivably is regulated by sex steroids since this response was reproduced in castrated animals by hormone supplementation. [ABSTRACT FROM AUTHOR]

The effects of histamine have been studied on separated circular and longitudinal myometrial layers from the guinea-pig. Virgin guinea-pigs in dioestrus were (1) untreated, (2) treated for 14 days thrice weekly with oestradiol cypionate 20 μg/kg s.c., or (3) treated as in (2) but in addition with progesterone 3 mg/animal s.c. daily for 4 days before use. Preparations were field-stimulated (60 V 2 ms 30 Hz for 5 s every 100 s) to elicit regular contractions. Histamine was equipotent in producing enhancement of evoked contractions of circular myometrium from animals in each treatment group (pD=5.03, 5.05 and 4.95 in groups 1, 2 & 3 respectively), and enhanced contractility in all but two longitudinal myometrial preparations. Treatment with oestradiol alone, and with oestradiol and progesterone following oestradiol priming enhanced the magnitude of maximal response and produced a small decrease in the potency of histamine on the longitudinal myometrium. pA estimates for mepyramine as an antagonist were similar (8.6) in preparations of longitudinal myometrium from each group of animals. Metiamide (1-10 μmol/l) did not antagonise the effects of histamine in this layer. These results, taken together, indicate that ovarian steroids act selectively on the longitudinal myometrial layer to amplify the action of histamine, but do not alter the histamine receptor subtype which in this layer is exclusively H. [ABSTRACT FROM AUTHOR]

It is without any doubt that the theatre historian in Britain is greatly indebted to visitors from other lands, for evidence found in their letters, diaries and sketches has informed us of theatre architecture, plays and performances of which our own countrymen, neglecting to record what for them was a commonplace, made no mention. Now it is possible to reciprocate with material to be found in the sketch-book diary of Sir James Thornhill concerning the Hôtel de Bourgogne. The purpose of this article is to examine two sketches in that diary by Thornhill and consider them in the light of data already collected concerning that theatre. [ABSTRACT FROM PUBLISHER]