Possible triggers for phase transformation in zirconia hip balls.

The clinical history of yttria-stabilized, zirconia (Zr) ceramic has been controversial. In the patient, combinations of hydrothermal and mechanical shocks may trigger detrimental changes in Zr balls that have inferior metastability. Transformations from tetragonal to monoclinic phase may be influenced by impingement, dislocation, and disassociation in certain patients.

Wear in molded tibial inserts: knee simulator study of H1900 and GUR1050 polyethylenes.

Hi-fax 1900 tibial inserts were used in the IB-1 total knee replacement (TKR) beginning 1978, soon followed by the AGC design. Such direct compression molded (DCM) inserts was relatively immune to oxidation. Unfortunately the Hi-fax 1900 resin (H1900) was taken off the market in year 2004.

Neural connectivity in the mediobasal hypothalamus of the sheep brain.

The ventromedial nucleus of the hypothalamus (VMN) and the arcuate nucleus (ARC) are two centres regulating energy balance and food intake, but inter-connectivity of these nuclei is not well defined in non-rodent species. In this study, we performed retrograde tracing and immunohistochemistry in the ovine brain with ewes receiving FluoroGold (FG) injections into either ARC or VMN for the mapping of retrogradely labelled cells. Strong reciprocal connections were found between the two regions.

Redefining the limits of day length responsiveness in a seasonal mammal.

At temperate latitudes, increases in day length in the spring promote the summer phenotype. In mammals, this long-day response is mediated by decreasing nightly duration of melatonin secretion by the pineal gland. This affects adenylate cyclase signal transduction and clock gene expression in melatonin-responsive cells in the pars tuberalis of the pituitary, which control seasonal prolactin secretion.

Kisspeptin neurons in the arcuate nucleus of the ewe express both dynorphin A and neurokinin B.

Kisspeptin is a potent stimulator of GnRH secretion that has been implicated in the feedback actions of ovarian steroids. In ewes, the majority of hypothalamic kisspeptin neurons are found in the arcuate nucleus (ARC), with a smaller population located in the preoptic area. Most arcuate kisspeptin neurons express estrogen receptor-alpha, as do a set of arcuate neurons that contain both dynorphin and neurokinin B (NKB), suggesting that all three neuropeptides are colocalized in the same cells.

Rapid in vivo effects of estradiol-17beta in ovine pituitary gonadotropes are displayed by phosphorylation of extracellularly regulated kinase, serine/threonine kinase, and 3',5'-cyclic adenosine 5'-monophosphate-responsive element-binding protein.

We have determined the time course of phosphorylation of MAPK/ERK, cAMP-responsive element-binding protein (CREB), and serine/threonine kinase (Akt) in ovine pituitary gonadotropes after in vivo injection (iv) of either 25 mug estradiol-17beta (E17beta) or vehicle. In ovariectomized ewes, E17beta increased the number of gonadotropes expressing phosphorylated (p)ERK-1/2 and pCREB immunoreactivity (-IR) within 90 min, as assessed by immunohistochemistry. By Western blot, we also showed that pERK-1/2, pCREB, and pAkt (ser 473) proteins were up-regulated by E17beta.

Kisspeptin synchronizes preovulatory surges in cyclical ewes and causes ovulation in seasonally acyclic ewes.

We determined whether kisspeptin could be used to manipulate the gonadotropin axis and ovulation in sheep. First, a series of experiments was performed to determine the gonadotropic responses to different modes and doses of kisspeptin administration during the anestrous season using estradiol-treated ovariectomized ewes. We found that: 1) injections (iv) of doses as low as 6 nmol human C-terminal Kiss1 decapeptide elevate plasma LH and FSH levels, 2) murine C-terminal Kiss1 decapeptide was equipotent to human C-terminal Kiss1 decapeptide in terms of the release of LH or FSH, and 3) constant iv infusion of kisspeptin induced a sustained release of LH and FSH over a number of hours.

Serotype 1 and 2 bovine noroviruses are endemic in cattle in the United kingdom and Germany.

The genomically and antigenically distinct bovine noroviruses Bo/Jena/1980/DE and Bo/Newbury2/1976/UK have been associated with calf diarrhea. In the present seroprevalence study, both were found to be endemic in cattle from Germany and the United Kingdom, a finding in contrast to previous virus prevalence studies. They were less common than group A rotaviruses, particularly in calves, suggesting a different epidemiology.

Recovery of infectious murine norovirus using pol II-driven expression of full-length cDNA.

Noroviruses are the major cause of nonbacterial gastroenteritis in humans. These viruses have remained refractory to detailed molecular studies because of the lack of a reverse genetics system coupled to a permissive cell line for targeted genetic manipulation. There is no permissive cell line in which to grow infectious human noroviruses nor an authentic animal model that supports their replication.

Changes in insulin, glucose and ketone bodies, but not leptin or body fat content precede restoration of luteinising hormone secretion in ewes.

The reproductive system, including pulsatile luteinising hormone (LH) secretion, is inhibited by deficits in energy availability and restored by energy surfeits. Plasma LH, insulin, leptin, ghrelin, glucose, ketone body, and nonesterified fatty acid concentrations were measured in ovariectomised, food-restricted ewes before and after return to ad libitum feeding to determine the factors that change in time to account for the restoration of pulsatile LH secretion. At 07.

Dose effects of cross-linking polyethylene for total knee arthroplasty on wear performance and mechanical properties.

Wear performance and mechanical properties of cross-linking polyethylene (XLPE) tibial inserts were investigated using a knee simulator, scanning electron microscopy (SEM), and a small punch test (SPT). Ultrahigh molecular weight PE made from GUR1050 resin was irradiated at doses ranging from 0 to 200 kGy and then machined into tibial inserts followed by annealing. The knee simulator was run for up to four million cycles.

Intracellular parasitism of chlamydiae: specific infectivity of chlamydiaphage Chp2 in Chlamydophila abortus.

The obligate intracellular nature of chlamydiae presents challenges to the characterization of its phages, which are potential tools for a genetic transfer system. An assay for phage infectivity is described, and the infectious properties of phage Chp2 were determined.

Surface micro-analyses of long-term worn retrieved "Osteal" alumina ceramic total hip replacement.

We analyzed wear pattern of long-term retrieved alumina-alumina hip prostheses from Osteal, which were implanted for 15-19 years. A comparison was carried out with our previous study of 17-year Biolox alumina-on-alumina hip prostheses, (Shishido et al., J Biomed Mater Res B 2003;67:638-647) and all-alumina total hip replacement run under microseparation simulator tests.

Chemical genetics reveals a complex functional ground state of neural stem cells.

The identification of self-renewing and multipotent neural stem cells (NSCs) in the mammalian brain holds promise for the treatment of neurological diseases and has yielded new insight into brain cancer. However, the complete repertoire of signaling pathways that governs the proliferation and self-renewal of NSCs, which we refer to as the 'ground state', remains largely uncharacterized. Although the candidate gene approach has uncovered vital pathways in NSC biology, so far only a few highly studied pathways have been investigated.

Kisspeptin expression in the brain: catalyst for the initiation of puberty.

In 2003, two independent groups of researchers discovered almost simultaneously that inactivating mutations of the G protein coupled receptor, GPR54, cause hypogonadotropic hypogonadism in mice and men. Since this discovery, kisspeptins, the natural ligands for GPR54, have been thrust into the reproductive neuroendocrine spotlight, as major regulators of GnRH function. Kisspeptins are the peptide products of the KiSS-1 gene, and potently stimulate gonadotrophin secretion when administered either centrally or peripherally.

Genotypic and physiological characterization of Saccharomyces boulardii, the probiotic strain of Saccharomyces cerevisiae.

Saccharomyces boulardii, a yeast that was isolated from fruit in Indochina, has been used as a remedy for diarrhea since 1950 and is now a commercially available treatment throughout Europe, Africa, and South America. Though initially classified as a separate species of Saccharomyces, recent publications have shown that the genome of S. boulardii is so similar to Saccharomyces cerevisiae that the two should be classified as conspecific.

Isolation and restraint stress results in differential activation of corticotrophin-releasing hormone and arginine vasopressin neurons in sheep.

This study investigated sex differences in the stress-induced activation of neurons containing corticotrophin-releasing hormone (CRH), arginine vasopressin (AVP) and enkephalin in the paraventricular nucleus (PVN) of gonadectomized male and female sheep. Groups (n=3) of both sexes were either subjected to 90 min isolation and restraint stress (stress group) or were not stressed. Blood samples were taken every 10 min for 90 min prior to and after stress to monitor cortisol levels in plasma.

Characterizing a mammalian circannual pacemaker.

Many species express endogenous cycles in physiology and behavior that allow anticipation of the seasons. The anatomical and cellular bases of these circannual rhythms have not been defined. Here, we provide strong evidence using an in vivo Soay sheep model that the circannual regulation of prolactin secretion, and its associated biology, derive from a pituitary-based timing mechanism.

KiSS-1 messenger ribonucleic acid expression in the hypothalamus of the ewe is regulated by sex steroids and season.

The KiSS-1 gene encodes a family of peptides called kisspeptins, which are endogenous ligands for the G protein-coupled receptor GPR54. Kisspeptin function appears to be critical for GnRH secretion and the initiation of puberty. To test the hypothesis that steroid hormones regulate KiSS-1 mRNA expression in the ewe, we examined the brains of ovary-intact (luteal phase) and ovariectomized (OVX) ewes, as well as OVX ewes that received estradiol (E) or progesterone (P) replacement.

Projections to the preoptic area from the paraventricular nucleus, arcuate nucleus and the bed nucleus of the stria terminalis are unlikely to be involved in stress-induced suppression of GnRH secretion in sheep.

Stress compromises reproductive function and the major physiological system activated during stress is the hypothalamo-pituitary-adrenal axis. Corticotrophin-releasing hormone and arginine vasopressin (AVP), which are produced in neurones of the paraventricular nucleus (PVN), drive the hypothalamo-pituitary-adrenal axis and are also implicated in the suppression of the reproductive axis. We used retrograde tracing and Fos labelling to map the projections from the PVN to the preoptic area (POA) where most gonadotrophin releasing hormone (GnRH) neurones are found.

Leptin inhibits bone formation not only in rodents, but also in sheep.

Unlabelled: This study examines the effect of long-term ICV administration of leptin in ewes. We found that central application significantly decreased osteoblast activity as measured by serum analysis as well as by histomorphometry, resulting in decreased trabecular bone volume. These data provide additional evidence that bone formation and therefore bone remodeling is at least in part centrally controlled.

IQGAP1 protein specifies amplifying cancer cells in glioblastoma multiforme.

The accurate identification and thorough characterization of tumorigenic cells in glioblastomas are essential to enhance our understanding of their malignant behavior and for the design of strategies that target this important cell population. We report here that, in rat brain, the scaffolding protein IQGAP1 is a marker of brain nestin+ amplifying neural progenitor cells. In a rat model of glioma, IQGAP1 also characterizes a subpopulation of nestin+ amplifying tumor cells in glioblastoma-like tumors but not in tumors with oligodendroglioma features.

Elevated KiSS-1 expression in the arcuate nucleus prior to the cyclic preovulatory gonadotrophin-releasing hormone/lutenising hormone surge in the ewe suggests a stimulatory role for kisspeptin in oestrogen-positive feedback.

Kisspeptins are encoded by the gene KiSS-1 and regulate gonadotrophin-releasing hormone (GnRH) and gonadotrophin secretion in various species, including humans. Here, we quantify gene expression of KiSS-1 in the arcuate nucleus (ARC) across the ovine oestrous cycle and demonstrate an increase in the caudal division of the ARC during the preovulatory period. These data strongly suggest that kisspeptins are involved in the generation of the preovulatory GnRH and luteinising hormone surge.

Sex difference in the suppressive effect of cortisol on pulsatile secretion of luteinizing hormone in sheep.

We tested the hypothesis that there are sex differences in the inhibitory effect of cortisol on pulsatile LH secretion and pituitary responsiveness to GnRH in gonadectomized sheep. In experiment 1, pulsatile LH secretion was examined in gonadectomized ewes and rams infused with either saline, a low (250 microg/kg.h) or a high (500 microg/kg.

The effect of penicillin on Chlamydia trachomatis DNA replication.

Chlamydia trachomatis L2 was used to infect BGMK cells at an m.o.i.