Biomedical subjects
Publications and source records attributed to P R Williams.
Endocast analysis of the brain Homo floresiensis by Falk et al. (Reports, 8 April 2005, p. 242) implies that the hominid is an insular dwarf derived from H. erectus, but its tiny cranial capacity cannot result from normal dwarfing. Consideration of more appropriate microcephalic syndromes and specimens supports the hypothesis of modern human microcephaly.
The rheological behaviour of coagulating human blood has been measured using multiple strain wave frequencies. The results indicate that coagulating blood, prior to the point of incipient clot formation, can be modelled by a modified form of the Gross-Marvin 'ladder' model, and the benefits of such modeling for blood coagulation are discussed.
We performed a comparison of the effects of two bisphosphonates, pamidronate and zoledronic acid, on regenerate bone mineral content in distraction osteogenesis in an immature rabbit model. Single dose zoledronic acid was found to be 18 times more potent at producing an increase in bone mineral content than pamidronate per mg/kg of drug infused at surgery. Histological examination of all rabbit kidneys was performed at trial completion. Nephrocalcinosis was identified in 14 of 20 kidneys of rabbits infused with pamidronate, but was not detected in the 20 kidneys of those rabbits infused with zoledronic acid. A further 20 kidneys from rabbits given a second dose of zoledronic acid were also found to be free of signs of nephrocalcinosis. Three of 40 control kidneys exhibited signs of nephrocalcinosis. The increased potency of zoledronic acid allowed us to give one-tenth the dose of pamidronate, with increased therapeutic efficacy and no evidence of nephrocalcinosis.
Public risk perceptions and demand for safer food are important factors shaping agricultural production practices in the United States. Despite documented food safety concerns, little attempt has been made to elicit consumers' subjective risk judgments for a range of food safety hazards or to identify factors most predictive of perceived food safety risks. In this study, over 700 conventional and organic fresh produce buyers in the Boston area were surveyed for their perceived food safety risks. Survey results showed that consumers perceived relatively high risks associated with the consumption and production of conventionally grown produce compared with other public health hazards. For example, conventional and organic food buyers estimated the median annual fatality rate due to pesticide residues on conventionally grown food to be about 50 per million and 200 per million, respectively, which is similar in magnitude to the annual mortality risk from motor vehicle accidents in the United States. Over 90% of survey respondents also perceived a reduction in pesticide residue risk associated with substituting organically grown produce for conventionally grown produce, and nearly 50% perceived a risk reduction due to natural toxins and microbial pathogens. Multiple regression analyses indicate that only a few factors are consistently predictive of higher risk perceptions, including feelings of distrust toward regulatory agencies and the safety of the food supply. A variety of factors were found to be significant predictors of specific categories of food hazards, suggesting that consumers may view food safety risks as dissimilar from one another. Based on study findings, it is recommended that future agricultural policies and risk communication efforts utilize a comparative risk approach that targets a range of food safety hazards.
BACKGROUND AND OBJECTIVES: As the financial performances of US academic health centers have faltered under managed care and the Balanced Budget Act of 1997, increasing attention has been paid to the costs and benefits of operating primary care networks. This study examines the indirect revenues to a university hospital and faculty group practice that result from such a primary care network using a method of abstracting billing data. METHODS: A primary care patient cohort was identified by selecting all patients who generated at least one charge in any of the 10 primary care clinics in the network over a 15-month period. All charges from the hospital and the faculty practice group for this cohort were then examined during a 6-month period, and the total charges generated in the primary care setting were compared with charges generated elsewhere in the health system. RESULTS: The primary care patient cohort included 56,459 patients and generated a total of $7,243,312 in charges for primary care services, $43,559,741 of charges in the hospital billing system for non-primary care services, and $8,825,611 of charges for services from specialty faculty. This cohort accounted for 18.5% of the gross charges for hospital care and 17.6% of charges generated by the specialty physicians. CONCLUSIONS: Using a simple and replicable methodology, this study estimates a substantial financial benefit to the hospital and specialty practices from a primary care network.
Food safety concerns and the demand for organically grown produce have increased significantly in the United States over the last decade. Key differences in lifestyle characteristics, food safety attitudes and beliefs, perceived food safety risks, and valuation of health risk reductions between organic and conventional food buyers remain largely unknown, however. To better characterize how buyers of organic fresh produce differ from their conventional counterparts, over 700 food shoppers were sampled from ten major retail stores in the Boston area. Survey results show that self-reported organic buyers are more likely than conventional buyers to engage in a variety of health-promoting and environmentally friendly behaviors. Organic buyers are less trusting of federal food safety agencies than are conventional buyers, and perceive greater benefits associated with organically grown produce than do their conventional counterparts. Further, organic buyers have significantly higher risk perceptions than do conventional buyers for food safety hazards associated with conventionally grown produce. Compared to conventional buyers, organic produce buyers also perceive significant risk reductions associated with switching to organically grown produce and are willing to pay a higher price to reduce perceived food safety risks. Few sociodemographic differences between buyer types were observed, possibly due to how organic and conventional food stores were matched. Survey findings highlight the need for greater public education about a range of food safety issues and farming practices to ensure that consumers are making informed decisions in the marketplace.
In symptomatic patients with recurrent anterior sternoclavicular dislocation, surgery may be required to stabilise the joint. Posterior sternoclavicular dislocations may also require open reduction and stabilisation due to the complications that may arise. We present a new, 'safe' technique of surgical stabilisation of the sternoclavicular joint that is not technically demanding and does not require exposure of the first rib, as is often the case in other methods described. The repair was tested in cadavers before being employed in three patients and was found to be effective under both static and dynamic loading. The early clinical results prove encouraging.
Between January 1987 and December 1988 there were 7575 births in the Swansea maternity unit. Of these 823 (10.9%) were considered to be at 'high risk' for developmental dysplasia of the hip (DDH). Static ultrasound examination was performed in each case and the results classified on the basis of the method of Graf. A total of 117 type III-IV hips in 83 infants was splinted using the Aberdeen splint. Radiographs of these hips were taken at six and 12 months. Hilgenreiner's measurements of the acetabular angle were made in all cases and the development of the femoral capital epiphysis was assessed by measuring the epiphyseal area. The effect of splintage on the acetabular angle and the epiphyseal area between the normal and abnormal splinted hips was compared. Radiographs of 16 normal infants (32 normal unsplinted hips) were used as a control group. This cohort has now been followed up for a minimum of nine years. There have been no complications as a result of splintage. The failure rate was 1.7% or 0.25 per 1000 live births. No statistical difference was found when comparing the effect of splintage on the acetabular angle and epiphyseal area between normal and abnormal splinted hips and normal unsplinted hips. Our study has shown that while the Aberdeen splint had a definite but small failure rate, it was safe in that it did not produce avascular necrosis. The current conventional view that a low rate of splintage is always best is therefore brought into question if the Aberdeen splint is chosen for the management of neonatal DDH.
Debate continues over the use of compartment pressure monitoring devices in the diagnosis of compartment syndrome. We present the results of a survey that was designed to explore this issue. The majority of UK trauma and orthopaedic surgeons surveyed advocate making the diagnosis of compartment syndrome by a combination of clinical acumen and compartment pressure measurements. Less than half of the trauma centres surveyed had pressure monitoring equipment available. There is marked variation in opinion regarding the threshold level for surgery when monitoring is applied.
Debate continues over implant selection when surgical intervention is deemed necessary in the management of diaphyseal fractures of the humerus. We present a series of patients in which we used an elastic intramedullary nail to manage a variety of difficult humeral fractures and discuss the theoretical advantages which we feel this method offers.
We report findings from studies of water subjected to tension by pulsed dynamic stressing which may have significance in the context of assessing the safety of biomedical applications of low-frequency ultrasound. When incident on bubbles near a free surface (or a flexible membrane), shockwaves generated by cavitation bubble collapse are found to lead to the production of liquid jets which are directed towards the surface. Tension pulses generated by reflection of these shockwaves at a free surface initiate, and propagate, the growth of further cavitation bubbles. Estimates of the tensile strength of water, Fc, from measurements of the velocity of these pulses suggest that Fc is far higher than has previously been reported for experiments involving the reflection of low-frequency ultrasound; and the estimate of Fc reported here considerably exceeds the values of tension thought to be generated by ultrasound in many biomedical applications.
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A burst-superimposition technique was used to assess the strength of the quadriceps femoris muscle in three groups of patients. Group 1 comprised twenty patients who had had a torn anterior cruciate ligament of the knee and had a reconstruction of the ligament one to six months after the injury. Group 2 comprised twelve patients who had had a torn anterior cruciate ligament for an average of three months (a subacute tear). Group 3 comprised eight patients who had had a torn anterior cruciate ligament for an average of two years (a chronic tear). The patients in Groups 2 and 3 had not had an operation for the torn ligament. The patients in Groups 1 and 3 had no evidence of failure of activation of the involved quadriceps, but nine of the twelve patients in Group 2 had reflex inhibition of contraction of the muscle.
The responses of quadriceps femoris muscles to an electrically elicited fatigue test were recorded from both lower extremities of 18 patients who had recently undergone unilateral, anterior cruciate ligament reconstruction. The fatigue test consisted of 40 pps, 13-pulse electrical trains that were repeated once per second for 3 min. The intensity of stimulation was set for each extremity to produce 20% of the maximum voluntary isometric contraction of the uninvolved muscle. The uninvolved quadriceps femoris muscle showed a significantly greater rate of decline in force over the first minute than the involved muscle (0.803%.s-1 for uninvolved muscle vs 0.620%.s-1 for involved muscle). Similarly, the average forces produced over the last minute were significantly lower for the uninvolved than the involved quadriceps femoris muscle (uninvolved = 42.6%, involved = 50.4% of their original forces). These surprising results showed that the involved quadriceps femoris muscles were more endurant than the uninvolved muscles. It is suggested that the increases in endurance of the involved muscle may have been due, in part, to greater recruitment of Type I fibers with electrical stimulation or selective Type II fiber atrophy in the involved muscle.
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Twenty two operations have been performed on 20 patients for the relief of symptoms due to bullous lung disease. Open intubation drainage of the bullae was used in all patients, the technique initially devised by Monaldi for the treatment of intrapulmonary tuberculous abscesses having been modified. Three patients died after surgery. Mortality was associated with low preoperative FEV1 (median 350 ml) and higher preoperative arterial carbon dioxide tension (PaCO2) (median 7.8 kPa). Symptomatic improvement was reported by 16 of the remaining 17 patients and was maintained over a median follow up period of 1.6 years. This was accompanied by objective improvement in lung function with a 22% median improvement in FEV1, an 11% median reduction in total lung capacity, and a 26% median reduction in residual volume. In one patient symptoms were unchanged after surgery. The technique described provides a simple method for decompressing bullae by means of a minimally invasive surgical procedure. It also allows for the treatment of further bullae at a later date by closed intubation under local anaesthetic. It has proved a suitable approach for all but those with the poorest lung function and is now our treatment of choice.