Comparison of the cytotoxicity of molybdenum as powder and as alloying element in a niobium-molybdenum alloy.

Commercially pure metal niobium (c.p. Nb) as well as niobium-molybdenum (Nb-Mo) alloys were produced following several powder metallurgical routes.

New aspects of signal transduction in the Xenopus laevis melanotrope cell.

Light and temperature stimuli act via various brain centers and neurochemical messengers on the pituitary melanotrope cells of Xenopus laevis to control distinct subcellular activities such as the biosynthesis, processing, and release of alpha-melanophore-stimulating hormone (alphaMSH). The melanotrope signal transduction involves the action of a large repertoire of neurotransmitter and neuropeptide receptors and the second messengers cAMP and Ca(2+). Here we briefly review this signaling mechanism and then present new data on two aspects of this process, viz.

Role of the forkhead transcription family member, FKHR, in thymocyte differentiation.

While performing a large-scale analysis of mRNA transcripts in the murine thymus, our attention was drawn to the forkhead family transcription factor FKHR. Here we demonstrate that FKHR is expressed in thymocytes, most prominently in those that are undergoing positive selection. Interestingly, FKHR transcripts show a highly regionalized pattern of expression, concentrated in the innermost areas of the medulla.

Critical size defect in the goat's os ilium. A model to evaluate bone grafts and substitutes.

Bone defects and their treatment are a well known problem in orthopaedic surgery. A critical size defect is a suitable model to study bone replacement materials. This study describes a critical size defect in the goal and the evaluation of three bone fillers (particulate autograft, particulate allograft, and a polyethylene oxide/polybutylene terephthalate copolymer) in this defect.

Application of porous PEO/PBT copolymers for bone replacement.

A range of polyethylene oxide/polybutylene terephthalate (PEO/PBT) copolymers (70-30% PEO) was investigated for nonloadbearing bone replacement application. Porous PEO/PBT cylinders (d = 5 mm, h = 7 mm) were implanted transcortically in the diaphyseal femur of 10 goats, and the animals were sacrificed at 3, 6, 9, 12, and 26 weeks. Qualitative evaluation was performed using light and fluorescence microscopy, scanning electron microscopy, and back-scatter electron imaging with an attached X-ray microanalysis system.

Inhibition of alpha-MSH secretion is associated with increased cyclic-AMP egress from the neurointermediate lobe of Xenopus laevis.

Cyclic-AMP is known to be released from cells and tissues and the amounts released have been reported to reflect intracellular cAMP levels. To measure cAMP release the phosphodiesterase inhibitor IBMX is often used to increase the amount of cAMP to a detectable level. Using this method to follow cAMP dynamics of melanotrope cells in the neurointermediate pituitary lobe of the amphibian Xenopus laevis we show that the alpha-MSH secreto-inhibitors baclofen (GABAB receptor agonist) and dopamine inhibit cAMP release, confirming the idea that these factors inhibit alpha-MSH secretion by reducing adenylyl cyclase activity.

Bone-bonding behaviour of poly(ethylene oxide)-polybutylene terephthalate copolymer coatings and bulk implants: a comparative study.

A range of poly(ethylene oxide)-polybutylene terephthalate (PEO-PBT) copolymers (70-30% PEO), both as coating on titanium alloy as well as bulk cylinders, was press-fit implanted in the diaphyseal femur of 16 goats. At early survival times (4 wk), a high degree of cortical bone contact was observed for bulk implants using light microscopy and this was confirmed by backscatter electron microscopy. This was attributed to the swelling behaviour of PEO-PBT copolymers.

Crystal structure of the adenovirus DNA binding protein reveals a hook-on model for cooperative DNA binding.

The adenovirus single-stranded DNA binding protein (Ad DBP) is a multifunctional protein required, amongst other things, for DNA replication and transcription control. It binds to single- and double-stranded DNA, as well as to RNA, in a sequence-independent manner. Like other single-stranded DNA binding proteins, it binds ssDNA, cooperatively.

Interfacial behavior of PEO/PBT copolymers (Polyactive) in a calvarial system: an in vitro study.

Polyactive, a polyethylene oxide/polybutylene terephthalate (PEO/PBT) copolymer, has been reported to display bone-bonding behavior. Although a detailed description of the in vivo bone/Polyactive interface is available, the underlying bone-bonding mechanism is still largely unknown. In this in vitro study, a calvarial envelope method has been adopted to reproduce the in vivo bone-bonding phenomenon and subsequently to obtain information on the biological effect of varying PEO/PBT segment ratios.

Interface reactions to PEO/PBT copolymers (Polyactive) after implantation in cortical bone.

The bone reaction at the interface of a range of PEO/PBT copolymers (Polyactive) after press-fit implantation in the diaphyseal femur of 20 goats was investigated. The animals were sacrificed at 1, 4, 12, 26, and 52 weeks. Undecalcified histologic sections were prepared, evaluated qualitatively, and quantified with the aid of an image analysis system.

Differential effects of coexisting dopamine, GABA and NPY on alpha-MSH secretion from melanotrope cells of Xenopus laevis.

The secretion of alpha-MSH from the intermediate lobe of the pituitary gland of the amphibian Xenopus laevis is under complex neural control. Three neurotransmitters, dopamine, GABA and NPY, coexist in nerve terminals that contact the melanotrope cells. All three neurotransmitters inhibit alpha-MSH release.

The CRF-related peptide sauvagine stimulates and the GABAB receptor agonist baclofen inhibits cyclic-AMP production in melanotrope cells of Xenopus laevis.

Release of alpha-MSH from the pars intermedia melanotrope cells of Xenopus laevis is regulated by various classical neurotransmitters and neuropeptides. We have examined the effect of two of these regulatory substances, the neurotransmitter GABA and the CRF-related peptide sauvagine, on the adenylate cyclase system of the melanotrope cells. Sauvagine treatment, which stimulates alpha-MSH release, lead to an elevation in the level of cyclic-AMP, an effect which was potentiated by cholera toxin.

Evidence for Independently Regulated Secretory Pathways of Proopiomelano-cortin-Related Peptides in the Mouse Pars Intermedia.

The existence of multiple secretory pathways within endocrine cells has been receiving increasing attention (1-5). In some cases there is evidence for independently regulated pathways, for example in prolactin-producing cells (6) and parathyroid hormone-producing cells (7, 8). These pathways concern newly synthesized hormone versus hormone sequestered in mature secretory compartments.

Biosynthetic response of mouse intermediate pituitary gland to induced drinking and dehydration.

There are indications that the intermediate lobe peptide alpha-MSH is involved in the regulation of the hydromineral balance in mice and other mammals. The purpose of our studies was to determine whether manipulation of this balance in the mouse could lead to changes in either the rate of POMC biosynthesis in the pars intermedia or to changes in the direction of the processing of the precursor protein to form bioactive peptides. The results show that excess drinking, induced by substitution of drinking water by a 5% glucose solution, causes a rapid increase in POMC synthesis, whereas dehydration has the opposite effect; no evidence could be found that the above treatments have any effect on the processing of POMC, although strain differences were found in level of N-terminal acetylation of newly synthesized melanotropins and endorphins.

Time-resolved fluorescence studies of flavodoxin. Fluorescence decay and fluorescence anisotropy decay of tryptophan in Desulfovibrio flavodoxins.

The time-resolved fluorescence characteristics of tryptophan in flavodoxin isolated from the sulfate-reducing bacteria Desulfovibrio vulgaris and Desulfovibrio gigas have been examined. By comparing the results of protein preparations of normal and FMN-depleted flavodoxin, radiationless energy transfer from tryptophan to FMN has been demonstrated. Since the crystal structure of the D.

Y-chromosomal influences on renal and adrenal measures in mice.

From a four-way cross between unrelated inbred strains of mice, a random-breeding line was developed that segregated at two coat-color loci and carried Y chromosomes from different sources. Adult males were used for measurements of body weight, kidney weight, renal papilla length, and adrenal gland weight. Clear evidence was obtained of Y-linked influences on papilla length and adrenal weight, whereas direct effects of Autosome 9 were indicated with regard to adrenal weight only.

A slow and a fast secretory compartment of POMC-derived peptides in the neurointermediate lobe of the amphibian Xenopus laevis.

1. Peptide release from the neurointermediate lobe of Xenopus laevis has been studied using dual pulse-chase incubation, superfusion and HPLC techniques. 2.