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Biomedical subjects

W Phillips

Publications and source records attributed to W Phillips.

46 records · Page 3Linked to original sources
PubMed1979

Development of a ceramic surface replacement for the hip. An experimental Sialon model.

The objective of this study was to investigate the design and fixation advantages of Sialon ceramic surface replacements implanted without acrylic bone cement. The biocompatibility and friction and wear properties of Sialon ceramic were compared with more conventional prosthetic materials such as stainless steel and alumina. A functional load-bearing canine hip surface replacement model was established to test Sialon femoral cups designed for fixation by bone ingrowth. The results of the polyethylene wear tests on highly polished ceramic and stainless steel counterfaces were essentially similar. These laboratory data indicated that the in-vivo polyethylene wear performance on metal or ceramic prosthetic surfaces could be expected to be indistinguishable, i.e. the ceramic/polyethylene combination would not offer any improved wear resistance in-vivo. It was found possible to get bone ingrowth into the macrokeying areas of the ceramic femoral cups but not into the microporous surfaces due to the presence of a fibrous membrane lining their internal surfaces. The biocompatability specimens also appeared to be invested with a fibrous membrane. Further studies are under way to determine the relationship between reaming procedures, micro motion at the interfaces and Sialon biocompatibility.

Aluminum↗
PubMed1976

Automatic control of the artificial heart.

An automatic control system has been developed to balance and control the output of an artificial heart. The system consisted of 2 linked negative feedback loops. The left ventricle was controlled by a Servo-Stroke Optimizer, which insured complete filling and full stroke operation of the left pump with each beat and changed the beat rate in accord with changes in aortic pressure. The right ventricle was controlled by a Servo-Variable Systolic Duration unit, which changed the stroke of the right ventricle to maintain the left atrial pressure within a preset band. In the initial animal studies, control pressures (aortic and left atrial pressure) were obtained from implanted transducers. More recently, a method has been devised whereby the control pressures were obtained from specific points on the left air line pressure wave, obviating the need for implanted transducers. The control system has been evaluated in a mock circulatory loop and in 9 calves with implanted artificial hearts. The system has provided balance of the 2 implanted ventricles and changes in flow rate in response to changes in peripheral resistance. The need for an operator to make manual adjustment to the power units has been considerably reduced. Further studies are indicated to evaluate the function of the control system in animals performing moderate-to-maximal exercise. Furthermore, the ultimate benefits of full stroke operation vs fill limited mode operation remain to be delineated.

Animals↗
PubMedDate not supplied

A novel kainate receptor ligand [3H]-(2S,4R)-4-methylglutamate: pharmacological characterization in rabbit brain membranes.

Since kainate evokes large non-desensitizing currents at alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, kainate is of limited use in discriminating between AMPA and kainate receptors. Following recent reports that (2S,4R)-4-methylglutamate is a kainate receptor-selective agonist, we have radiolabelled and subsequently characterized the binding of [3H]-(2S,4R)-4-methylglutamate to rabbit whole-brain membranes. [3H]-(2S,4R)-4-methylglutamate binding was rapid, reversible and labelled two sites (KD1 = 3.67+/-0.50 nM/Bmax1 = 0.54+/-0.03 pmol/mg protein and KD2 = 281.66+/-12.33 nM/ Bmax2 = 1.77+/-0.09 pmol/mg protein). [3H]-(2S,4R)-4-methylglutamate binding was displaced by several non-NMDA receptor ligands: domoate > kainate >> L-quisqualate > or = L-glutamate > 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) >> (S)-AMPA = (S)-5-fluorowillardiine > NMDA. Neither the metabotropic glutamate receptor agonists (1S,3R)-ACPD or L-AP4, together with the L-glutamate uptake inhibitor L-trans-2,4-PDC, influenced binding when tested at 100 microM. We conclude that [3H]-(2S,4R)-4-methylglutamate is a useful radioligand for labelling kainate receptors. It possesses high selectivity, and possesses a pharmacology similar to that for rat cloned low-affinity (Glu5 and 6) kainate receptor subunits.

Animals↗
PubMedDate not supplied

Discocyte--echinocyte reversibility in blood stored in CPD over a period of 56 days.

Blood collected with CPD and stored was examined with optical (LM) and scanning electron microscopy (SEM) before and after reversal of echinocytes into discocytes. Reversal was achieved by incubation of the red blood cells at 37 C in an adenosine containing medium. The transformation of discocytes into echinocytes occurred rapidly during the first three weeks of storage. A shape/density relationship was observed in the various fractions. The denser cells were found to have the more advanced echinocytic changes. After incubation with adenosine, most of the cells reversed into discocytes and early stages of stomatocytes. When spheroechinocytes I and II were present, they reversed into spherostomatocytes. No echinocytogenic property was found in plasma during 5 weeks of storage at 4 C and no immediate reversion of echinocytes was obtained in fresh plasma, therefore the initial discocyte--echinocyte transformation was explained by intracellular changes. The data from the various fractions showed that the more dense cells were more spherocytic. We suggest that removal of this part of the population of stored red blood cells might improve the survival of transfused cells.

Adenosine↗
PubMedDate not supplied

The bispectral index monitor: a new tool for air medical personnel.

The bispectral index monitor (BIS) is commonly used in the operating room to help anesthesiologists quantitate the level of anesthesia. The BIS has been shown to reduce the incidence of anesthetic overuse and decrease costs. The device has made its way into critical care areas, where it has proven effective in monitoring sedation levels, specifically in reducing the incidence of oversedation. This article explores the possibility of using the monitor in the air medical environment.

Air Ambulances↗
PubMedDate not supplied

Data collection in continence care.

Evaluation is an important component of any project. However, where change is complex and the time and resources available for collecting data are scarce, considerable thought needs to be given to how evaluation is best carried out. This article discusses some of the issues that arose during the setting up of a service to promote continence.

Aged↗