Some of the studies conducted by Purdue and BAS scientists using the new bone ultrafiltration probe include:
• Measurement of baseline concentrations of the bone minerals, calcium, magnesium and phosphate in bone, skeletal muscle, subcutaneous tissue and blood.
• Measurement of changes in interstitial calcium, magnesium and phosphate in bone, skeletal muscle, subcutaneous tissue and blood after infusion of either calcium or EDTA.
• Study of the effect of different dietary levels of calcium on interstitial bone minerals.
The Bone Ultrafiltration Probe consists of semi-permeable membrane fibers attached to a microbore conducting tube. The membrane fibers are implanted into the bone. On the tubing are two cuffs of porous material, which promote tissue growth and help stabilize the position of the probe. In addition to the cuffs, there are suture retainers at 5-cm intervals to further facilitate anchoring or the probe in place. A kink resistant sheath at the fiber-tubing junction facilitates subcutaneous tunneling of the probe at the bone exit site.
After the probe has been implanted into the bone, there are two methods of sampling from an implanted bone probe. For studies in freely moving unrestrained animals the probes can be connected to a needle hub (72-6957) which can be inserted into a Vacutainer™
(72-6958) to provide the negative pressure. For this sampling method animals wear jackets with pockets to hold the Vacutainers.
If frequent samples will be collected over a short period of time the use of a mini-peristaltic pump (72-6954) and a fraction collector (BS4 72-6909) may be more convenient. To use the bone probe with the pump and fraction collector the hub adapter segment of the bone probe is removed and the probe tubing is connected directly to the mini-pump and the mini-pump is connected to the HoneyComb Refrigerated Fraction Collector.
Uses of the BAS Bone Ultrafiltration Probe
It has long been possible to study the changes in bone structure and mineralization in the living animal with the use of such physical measurements as x-ray and ultrasound. However, it has not previously been possible to monitor ongoing chemical changes in the extracellular fluid of bone in the living, moving animal. That will now be possible with the BAS Bone Probe (72-6956) developed by a collaborative effort of BAS and Purdue University Scientists.
The Bone Probe adds to the BAS line of specialty membrane probes, which allow sampling from many different tissues in the awake, living animals. These probes are designed to be used in large animals and can be used for studies lasting for several weeks. The bone probes can be used with a hub assembly and Vacutainers™ to permit complete mobility of the subject or with a small peristaltic pump to permit automated faction collection
The Bone Probe was developed under a NASA contract using the sheep as a model. NASA’s interest in bone physiology is related to the problems of bone loss suffered by astronauts during protracted weightlessness. For humans to spend protracted periods in space and return to gravity to live healthy normal lives, it will be necessary to prevent the microgravity induced bone loss. In order to do this it will be necessary to understand the physical and chemical changes induced by microgravity and to develop methods to prevent these changes. Prevention of bone loss will involve the evaluation of the effectiveness of a number of counter measures, both physical, nutritional and pharmaceutical.
It has been possible to monitor changes is bone density and mineralization by traditional methods but monitoring the chemical changes in the interstitial fluid of bone over time in the living animal has not previously been possible. With this new device one can monitor most low molecular weight chemicals of 3 kD or less.