Survival of the Halophilic Archaeon Halovarius luteus after Desiccation, Simulated Martian UV Radiation and Vacuum in Comparison to Bacillus atrophaeus.

Extraterrestrial environments influence the biochemistry of organisms through a variety of factors, including high levels of radiation and vacuum, temperature extremes and a lack of water and nutrients. A wide variety of terrestrial microorganisms, including those counted amongst the most ancient inhabitants of Earth, can cope with high levels of salinity, extreme temperatures, desiccation and high levels of radiation. Key among these are the haloarchaea, considered particularly relevant for astrobiological studies due to their ability to thrive in hypersaline environments.

The value of cone beam computed tomography in the detection of salivary stones prior to sialendoscopy.

This study aimed to assess the value of cone beam computed tomography (CBCT) in the detection of salivary stones in patients with signs and symptoms of salivary gland obstruction. A total of 142 major salivary glands were analysed in a cohort of 127 patients with signs and symptoms of salivary gland obstruction. CBCT scans were performed in order to determine the presence of one or more salivary stones.

Release of nitric oxide, but not prostaglandin E2, by bone cells depends on fluid flow frequency.

Loading frequency is an important parameter for the stimulation of bone formation in vivo. It is still unclear how the information of external loading characteristics is conveyed to osteoblasts and osteoclasts. Osteocytes are thought to detect mechanical loads by sensing fluid flow through the lacuno-canalicular network within bone and to translate this information into chemical signals.

Fibrodysplasia ossificans progressiva. An unusual cause of restricted mandibular movement.

A 9-year-old girl is presented who was initially misdiagnosed and finally diagnosed with fibrodysplasia ossificans progressiva only after presentation with progressive limitation of her mouth opening. The clinical, histopathological, and molecular biological aspects of this uncommon disorder will be discussed. Furthermore, dental and surgical guidelines will be described.

BIOPACK: the ground controlled late access biological research facility.

Future Space Shuttle flights shall be characterized by activities necessary to further build the International Space Station, ISS. During these missions limited resources are available to conduct biological experiments in space. The Shuttles' Middeck is a very suitable place to conduct science during the ISS assembly missions or dedicated science missions.

Centrifuges and inertial shear forces.

Centrifuges are often used in biological studies for 1 x g control samples in space flight microgravity experiments as well as in ground based research. Using centrifugation as a tool to generate an Earth like acceleration introduces unwanted inertial shear forces to the sample. Depending on the centrifuge and the geometry of the experiment hardware used these shear forces may contribute as much as 99% to the total force acting on the cells or tissues.

Osteocyte and bone structure.

The osteocyte is the most abundant cell type of bone. There are approximately 10 times as many osteocytes as osteoblasts in adult human bone, and the number of osteoclasts is only a fraction of the number of osteoblasts. Our current knowledge of the role of osteocytes in bone metabolism is far behind our insight into the properties and functions of the osteoblasts and osteoclasts.

Stimulation of bone cell differentiation by low-intensity ultrasound--a histomorphometric in vitro study.

Several investigations have established a stimulatory effect of low-intensity ultrasound treatment on osteogenesis and fracture healing. The objective of this study was to examine whether the stimulatory effect of low-intensity ultrasound results in increased bone cell activity and/or proliferation. Twenty-four paired triplets of metatarsal bone rudiments of twelve 17-days-old fetal mice were dissected and divided into two groups.

Inertial shear force and the impact on facilities for the International Space Station.

Inertial shear force is a surface force that is generated in centrifuges especially with attached samples on flat surfaces and plays a significant role in gravitational and space research. The magnitude of this force is proportional to the radius of the centrifuge and surface area of the sample compartment. In gravitational research we want to study the impact of weight onto a system.

Microgravity and bone cell mechanosensitivity.

The capacity of bone tissue to alter its mass and structure in response to mechanical demands has long been recognized but the cellular mechanisms involved remained poorly understood. Bone not only develops as a structure designed specifically for mechanical tasks, but it can adapt during life toward more efficient mechanical performance. Mechanical adaptation of bone is a cellular process and needs a biological system that senses the mechanical loading.

Mechanotransduction of bone cells in vitro: mechanobiology of bone tissue.

Mechanical force plays an important role in the regulation of bone remodelling in intact bone and bone repair. In vitro, bone cells demonstrate a high responsiveness to mechanical stimuli. Much debate exists regarding the critical components in the load profile and whether different components, such as fluid shear, tension or compression, can influence cells in differing ways.

Inertial shear forces and the use of centrifuges in gravity research. What is the proper control?

Centrifuges are used for 1 x g controls in space flight microgravity experiments and in ground based research. Using centrifugation as a tool to generate an Earth like acceleration introduces unwanted inertial shear forces to the sample. Depending on the centrifuge and the geometry of the experiment hardware used these shear forces contribute significantly to the total force acting on the cells or tissues.

Mechanotransduction in bone cells proceeds via activation of COX-2, but not COX-1.

Cyclooxygenase (COX) is the key enzyme in the production of prostaglandins, which are essential for the response of bone to mechanical loading. We determined which COX-isoform, COX-1 or COX-2, determines loading-induced prostaglandin production in primary bone cells in vitro. Mouse and human bone cells reacted to 1 h of pulsating fluid flow (PFF, 0.

Hypergravity studies in the Netherlands.

It looks like that with the utilization phase of the International Space Station (ISS) scientists will have the possibility to perform long duration and more sophisticated microgravity experiments than could be performed previously. In preparation for these spaceflight studies, ground based experiment tools for simulated (or real) microgravity and hypergravity are important. To provide the infrastructure and user support necessary to perform these ground based studies we have setup the Dutch Experiment Support Center, DESC.

Cost-effectiveness of screening for the possible development of cancer in patients with oral lichen planus.

Introduction: Several authors have expressed the view that patients with oral lichen planus (OLP) are at increased risk of developing oral cancer. Since OLP cannot be effectively treated, regular screening for the possible development of oral cancer might be considered.

Objectives: (i) To calculate costs and effectiveness of screening for oral cancer in OLP patients with a decision model; (ii) to compare the cost-effectiveness of different screening scenarios; and (iii) to perform a sensitivity analysis of several variables used in this model.

Characteristics of the parallel-plate flow chamber for mechanical stimulation of bone cells under microgravity.

We show the use of a dimensionless parameter alpha h, in properly downscaling a parallel-plate flow chamber system for flow stimulation of bone cells under microgravity. The proper experimental regime for exposing cells to predictable levels of dynamic fluid shear stress requires: 1) alpha h < 2, based on the consequent quasi-parabolic form of the velocity profile in this regime, and 2) fo m View Article and Find Full Text PDF

The production of nitric oxide and prostaglandin E(2) by primary bone cells is shear stress dependent.

Loading-induced flow of interstitial fluid through the lacuno-canalicular network is a likely signal for bone cell adaptive responses. However, the nature of the stimulus that activates the cell is debated. Candidate stimuli include wall shear stress, streaming potentials, and chemotransport.

Responses of bone cells to biomechanical forces in vitro.

In this paper, we review recent studies of the mechanism by which mechanical loading of bone is transduced into cellular signals of bone adaptation. Current biomechanical theory and in vivo as well as in vitro experiments agree that the three-dimensional network of osteocytes and bone-lining cells provides the cellular basis for mechanosensing in bone, leading to adaptive bone (re)modeling. They also agree that flow of interstitial fluid through the lacunar-canalicular porosity of bone, as a result of mechanical loading, most likely provides the stimulus for mechanosensing, and informs the bone cellular network about the adequacy of the existing bone structure.

Different responsiveness of cells from adult and neonatal mouse bone to mechanical and biochemical challenge.

Neonatal rodent calvarial bone cell cultures are often used to study bone cell responsiveness to biochemical and mechanical signals. However, mechanical strains in the skull are low compared to the axial and appendicular skeleton, while neonatal, rapidly growing bone has a more immature cell composition than adult bone. In the present study, we tested the hypothesis that bone cell cultures from neonatal and adult mouse calvariae, as well as adult mouse long bones, respond similarly to treatment with mechanical stress or 1,25-dihydroxyvitamin D3 (1,25(OH)2 D3).

Bone morphogenetic proteins in human bone regeneration.

Recently, the first clinical reports on bone regeneration by two recombinant human bone morphogenetic proteins (rhBMPs), BMP-2 and BMP-7 (also named osteogenic protein-1, OP-1) have been published (1-4). Although both BMPs were able to support bone regeneration, a significant variation in individual response was observed with both proteins. Animal studies and laboratory experiments reveal a number of conditions that influence the osteoinductivity of BMP, such as BMP concentration, carrier properties and influence of local and systemic growth factors and hormones.

Mechanical stress induces COX-2 mRNA expression in bone cells from elderly women.

Mechanical loading-induced fluid flow in the lacuno-canalicular network is a possible signal for bone cell adaptive responses. In an earlier study we found that pulsating fluid flow (PFF, 0.7+/-0.

Mechanotransduction in bone--role of the lacuno-canalicular network.

The capacity of bone tissue to alter its mass and structure in response to mechanical demands has long been recognized but the cellular mechanisms involved remained poorly understood. Over the last several years significant progress has been made in this field, which we will try to summarize. These studies emphasize the role of osteocytes as the professional mechanosensory cells of bone, and the lacuno-canalicular porosity as the structure that mediates mechanosensing.

Signal transduction pathways involved in fluid flow-induced PGE2 production by cultured osteocytes.

To maintain its structural competence, the skeleton adapts to changes in its mechanical environment. Osteocytes are generally considered the bone mechanosensory cells that translate mechanical signals into biochemical, bone metabolism-regulating stimuli necessary for the adaptive process. Prostaglandins are an important part of this mechanobiochemical signaling.