Rigid following of dogma will not be best for all patients.
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Decision Making↗
Biomedical subjects
D Taylor
Publications and source records attributed to D Taylor.
Fatigue of bone and bones: an analysis based on stressed volume.
The measured fatigue strength of a material can be affected by specimen size:tests using a large stressed volume may show a low fatigue strength due to the increased probability of finding weak regions. A Weibull analysis revealed an important size effect in bone and predicted this effect with an accuracy of 12%. This approach also explained apparent inconsistencies in the published data and made it possible to separate and quantify the effects of frequency, loading mode, and material source. The effect of frequency is the same for human and bovine bone, and the differences between different types of loading (tension, compression, and bending) are small (maximum: 12%). By extrapolating to the volume of whole bones, it is concluded that large bones will have a fatigue strength much lower, by a factor of 2-3, than that measured by conventional tests. Failure within 10(5) cycles is expected to occur at cyclic stresses of 23-30 MPa in human long bones and of 32-43 MPa in bovine bones. Repair is therefore needed to prevent failure at physiological stress levels.
Animals↗
Simple models for excitable and oscillatory neural networks.
Chains of coupled oscillators of simple "rotator" type have been used to model the central pattern generator (CPG) for locomotion in lamprey, among numerous applications in biology and elsewhere. In this paper, motivated by experiments on lamprey CPG with brainstem attached, we investigate a simple oscillator model with internal structure which captures both excitable and bursting dynamics. This model, and that for the coupling functions, is inspired by the Hodgkin-Huxley equations and two-variable simplifications thereof. We analyse pairs of coupled oscillators with both excitatory and inhibitory coupling. We also study traveling wave patterns arising from chains of oscillators, including simulations of "body shapes" generated by a double chain of oscillators providing input to a kinematic musculature model of lamprey.
Animals↗
Microcrack growth parameters for compact bone deduced from stiffness variations.
This paper shows how information on the fatigue behaviour of microcracks can be obtained by the analysis of stiffness changes measured during cyclic loading. Relationships between crack length, growth rate and cyclic stress intensity were deduced, and compared with previous empirical equations. Results show that the crack growth rate decreases rapidly with increasing length; this behaviour is typical of short-crack fatigue in many materials and is interpreted in terms of microstructural barriers to growth. Implications for the role of microcracks in remodelling and adaptation phenomena are discussed.
Adaptation, Physiological↗
Measuring the shape and size of microcracks in bone.
Microcracks in bone are normally measured from two-dimensional, transverse sections but this provides incomplete information about their three-dimensional shape and size. The methods of stereology can usefully be applied in such a case. This problem has been addressed using a theoretical model and a numerical simulation. Results show that the data are consistent with a crack shape which is elliptical, with axis ratio approximately 4.5:1 and with size variation (expressed as the ratio of standard deviation to mean length) of at least 0.1. Measured lengths will, on average, be smaller and have more scatter than true lengths. Errors caused by omitting small cracks are relatively unimportant. Knowledge of the true crack dimensions, and their variability, is important for the analysis of damage, stress fracture, remodelling and adaptation.
Adaptation, Physiological↗
The maternal and child health sites' practices regarding HIV education, counseling, and testing of women of reproductive age in Chicago: barriers to universal implementation.
OBJECTIVES: Women of reproductive age are increasingly at risk for human immunodeficiency virus (HIV) infection. Recent advances in reducing perinatal transmission have resulted in official guidelines on universal HIV education, counseling, and voluntary testing of women of reproductive age, especially pregnant women. This study assesses to what extent the maternal child health (MCH) sites are implementing these guidelines with their female patient population (including pregnant women) and examines the barriers that prevent them from implementing these guidelines. METHOD: The study uses survey data from 92 hospitals and community health centers offering MCH services in Chicago regarding their providers' practices on HIV education, counseling, and testing, implementation of zidovudine (ZDV) therapy to reduce perinatal transmission, and the barriers to implementing these services. In addition, 20 taped in-depth interviews were conducted with experts to examine the barriers to universal implementation. RESULTS: Almost half (45% of perinatal care and 50% of family planning providers) of the institutions are not consistently offering HIV testing. One-third of those institutions that offer testing are not offering pretest counseling. Thirty-nine percent of the perinatal care providers in these institutions are not providing posttest counseling to HIV-negative women. Over one-third (35%) of these institutions reported that they are not set up to implement ZDV therapy during labor and delivery. Almost half (49%) had no protocols for ZDV therapy in place. Barriers to implementation included lack of provider training, limited staff time, physician resistance, unavailability or avoidance to seek perinatal care by high-risk women, cost, absence of a statewide and hospital-specific plan, lack of reproductive choice focus in posttest counseling, lack of provider knowledge about the administration of ZDV or its availability during labor, and lack of consumer education on perinatal risk reduction. CONCLUSIONS: MCH sites and their providers need assistance to overcome many barriers they face to implement universal HIV education, counseling, and testing of women of reproductive age.
AIDS Serodiagnosis↗
Characteristics of children having multiple Medicaid-paid asthma hospitalizations.
OBJECTIVES: We undertook this population-based study to describe the characteristics of poor children with multiple asthma hospitalizations and to discern if poor minority children have a greater risk for these events than poor white children. METHODS: We conducted a retrospective analysis of 1994 California hospital discharge data for asthma hospitalizations among 1 to 12-year-old Medicaid patients (N = 6844 discharges). Risk factors for multiple Medicaid asthma hospitalizations were calculated by using logistic regression procedures. RESULTS: In 1994, asthma hospitalizations accounted for 11.6% of Medicaid-funded hospitalizations for 1 to 12-year-olds in California. These hospitalizations had a mean length of 2.7 days and a mean hospital charge of $6532. After we controlled for source of admission and length of stay, African American children (OR, 1.93; 95% CI 1.49-2.49) and Latino children (OR, 1.34; 95% CI 1.04-1.72) had a higher risk of multiple Medicaid-paid hospitalizations for asthma than did white children. Adjusted odds ratios for multiple asthma hospitalizations were 1.35 (CI, 1.05-1.74) for children with emergency room admissions, and 1.16 (CI, 0.97-1.39) for children having hospital stays of at least 5 days duration. CONCLUSIONS: Among children with Medicaid-paid hospitalizations for asthma, the risk for multiple asthma hospitalizations within a year was greater among African Americans and Latinos than among whites. Programs attempting to decrease repeat hospitalizations for asthma may benefit by focusing on these populations.
Black or African American↗
Capillary haemangiomas in association with morning glory disc anomaly.
PURPOSE AND METHOD: Capillary haemangiomas in children are usually isolated, but may have systemic associations. This accords with our finding of ocular malformations, especially "morning glory disc anomaly" (MGDA), in three children which are described. RESULTS: All three children had extensive capillary haemangiomas in combination with MGDA in one eye. One of the children also had microphthalmos in one eye and a partial agenesis of the corpus callosum. Another child had sclerocornea in one eye and congenital heart defects. CONCLUSION: An association of extensive capillary haemangiomas with MGDA is described. The embryological timing of such defects as well as investigation of the children is discussed. Extensive haemangiomas have not previously, to our knowledge, been described in association with MGDA.
Abnormalities, Multiple↗
Acute onset bilateral cataracts in an infant with vertically transmitted HIV with CMV retinitis despite treatment.
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AIDS-Related Opportunistic Infections↗
The Doyne Lecture. Congenital cataract: the history, the nature and the practice.
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Cataract↗
Early VEP and ERG evidence of visual dysfunction in autosomal recessive osteopetrosis.
Autosomal recessive (AR) osteopetrosis has a rapid course and manifests in the first months of life. Visual loss occurs because of optic nerve compromise, and more rarely retinal dysfunction (which may be a part of a primary neurodegeneration). The only curative treatment currently available is bone marrow transplantation (BMT). It has been suggested that BMT is contraindicated if AR osteopetrosis is associated with a primary neurodegeneration. Visual impairment tends to be irreversible after BMT. The young age of the patients makes reliable, objective tests of visual function especially important. We have reviewed the flash electroretinograms (ERGs) and flash and pattern visual evoked potentials (VEPs) recorded without sedation from 15 patients with AR osteopetrosis, 11 of whom were recorded longitudinally. The most frequent, early indication of visual dysfunction was a delay in the pattern or flash VEP latency. This first affects the pattern reversal VEP to small checks. Importantly this often preceded fundal changes of optic disc pallor, and evidence of optic nerve compression on neuroimaging. Only two patients had ERG evidence of retinal dysfunction affecting both rods and cones. One of these patients had a distinctive fundal appearance, but did not have evidence of associated neuronal degenerative disease. The other patient was lost to follow-up. In the patients reviewed in this study successful BMT and optic nerve decompression did not result in VEP improvement. Fundoscopy, VEP and ERG testing are indicated when the diagnosis of AR osteopetrosis is suspected and provide a useful means of monitoring visual involvement.
Bone Marrow Transplantation↗
Medical school admission committee members' evaluations of and impressions from recommendation letters.
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Evaluation Studies as Topic↗
Co-administration of citalopram and clozapine: effect on plasma clozapine levels.
Antidepressants are frequently used in the treatment of depressive symptoms associated with schizophrenia. In patients taking clozapine, choice of antidepressant is complicated by additive pharmacodynamic effects and by pharmacokinetic interactions. We predicted that citalopram would not elevate plasma clozapine levels when the two drugs were co-administered because it does not inhibit the relevant enzyme systems. In this preliminary study of five patients given citalopram and clozapine there was no overall change in mean clozapine levels. Based on this limited evidence, citalopram might be the antidepressant of choice in patients taking clozapine.
Adolescent↗
Antidepressant interactions with warfarin.
The interactions between warfarin and antidepressants can have potentially serious consequences resulting from enhanced or reduced anticoagulant activity. Information about such interactions was obtained from a Medline and hand search of the published literature, and by directly contacting manufacturers. The different classes of antidepressants are discussed in turn. The possible mechanisms are considered with particular reference to the cytochrome p450 system. From currently available data on the newer antidepressants our conclusions are that citalopram, nefazodone and sertraline may be relatively less likely to interact with warfarin. Fluoxetine, fluvoxamine, paroxetine and moclobemide appear to have the highest potential of the antidepressants for interactions. There is insufficient data on venlafaxine to make a prediction. The clinical implications of these findings are discussed and specific recommendations for International Normalized Ratio monitoring are suggested.
Animals↗
Autologous vein-covered stent repair of a cervical internal carotid artery pseudoaneurysm: technical case report.
OBJECTIVE AND IMPORTANCE: Stenting of a cervical internal carotid pseudoaneurysm is presented using a stent covered with saphenous vein. This procedure resulted in immediate exclusion of the aneurysm and maintained patency of the carotid artery. CLINICAL PRESENTATION: A gunshot to the neck resulted in airway obstruction and respiratory arrest with neurological injury in a male patient. Angiographic investigation revealed an enlarging cervical internal carotid pseudoaneurysm, possibly the source of a cerebral embolism. Anticoagulation had to be stopped because of bleeding complications. A decision was made to conduct definitive percutaneous treatment of the pseudoaneurysm. TECHNIQUE: A Palmaz stent (JJIS, Warren, NJ) was covered with saphenous vein harvested from the patient's leg. Using standard technique and a simple innovation for stent construct introduction into the sheath, the vein-covered stent was placed across the opening of the aneurysm and dilated into position with a balloon. CONCLUSION: Immediate exclusion of a cervical internal carotid pseudoaneurysm was performed using an autologous vein-covered stent. One-month follow-up confirmed continued exclusion of the pseudoaneurysm and carotid patency without stenosis.
Adult↗
Frontonasal dysplasia with optic disc anomalies and other midline craniofacial defects: a report of six cases.
The association of optic disc abnormalities with basal encephaloceles, specifically of the sphenoethmoidal type, and midline facial clefts has rarely been reported, although the association of midline facial clefts with encephaloceles is well described. We now report six cases of children, three males and three females, presenting with a sphenoethmoidal encephalocele, optic disc anomalies, midline facial clefting, hypertelorism, complete or partial agenesis of the corpus callosum, and endocrinological disturbances, including diabetes insipidus and pituitary dysfunction. This report underlines the importance of careful ophthalmic and endocrinological investigation of children with midline clefts associated with basal encephaloceles. These cases may represent a distinct entity within the spectrum of frontonasal dysplasia.
Abnormalities, Multiple↗
A high-resolution microsatellite map of the mouse genome.
The European Collaborative Interspecific Backcross (EUCIB) resource was constructed for the purposes of high-resolution genetic mapping of the mouse genome (). The large Mus spretus/C57BL/6 backcross of 982 progeny has a genetic resolution of 0.3 cM at the 95% confidence level ( approximately 500 kb in the mouse genome). We have used the EUCIB mapping resource to develop a genome-wide high-resolution genetic map incorporating 3368 microsatellites. The microsatellites are distributed among 2302 genetically separated bins with 1.46 markers per bin on average. Average bin separation is 0.61 cM. This high-resolution genetic map will aid the construction of a robust physical map of the mouse genome.
Animals↗
New developments in a consolidating health care industry.
The current health care industry has recently seen a great deal of consolidation in the form of mergers and acquisitions. These mergers and acquisitions invariably result in a loss of jobs. This paper focuses on two strategies that health care companies use to reduce workforce under these circumstances. Specifically, the paper will focus on the mergers between SmithKline Beckman and Beecham plc in the late 1980s, FHP Health Care and TakeCare Health Plans, and PacifiCare's recent acquisition of FHP Health-care. It will compare and contrast theory, strategy and practices of these six companies as they endeavoured to merge or acquire each other.
Drug Industry↗