Risk analysis of patients with an osteolytic acetabular defect after total hip arthroplasty using subject-specific finite-element modelling

Aims

Osteolysis, secondary to local and systemic physiological effects, is a major challenge in total hip arthroplasty (THA). While osteolytic defects are commonly observed in long-term follow-up, how such lesions alter the distribution of stress is unclear. The aim of this study was to quantitatively describe the biomechanical implication of such lesions by performing subject-specific finite-element (FE) analysis on patients with osteolysis after THA.

Patients and Methods

A total of 22 hemipelvis FE models were constructed in order to assess the transfer of load in 11 patients with osteolysis around the acetabular component of a THA during slow walking and a fall onto the side. There were nine men and two women. Their mean age was 69 years (55 to 81) at final follow-up. Changes in peak stress values and loads to fracture in the presence of the osteolytic defects were measured.

Results

The von Mises stresses were increased in models of those with and those without defects for both loading scenarios. Although some regions showed increases in stress values of up to 100%, there was only a moderate 11.2% increase in von Mises stress in the series as a whole. The site of fracture changed in some models with lowering of the load to fracture by 500 N. The most common site of fracture was the pubic ramus. This was more frequent in models with larger defects.

Conclusion

We conclude that cancellous defects cause increases in stress within cortical structures. However, these are likely to lead to a modest decrease in the load to fracture if the defect is large (> 20cm3) or if the patient is small with thin cortical structures and low bone mineral density. Cite this article: Bone Joint J 2018;100-B:1455–62.

Seasonal breeding in relation to dietary animal protein in deer mice (Peromyscus maniculatus)

We used stable carbon and nitrogen isotope compositions of hair and liver as a way of examining seasonal diet changes and explaining seasonal breeding in deer mice ( Peromyscus maniculatus (Wagner, 1845)). Summer and winter δ13C values differed, which is attributed to the availability of different plant tissues (C3 plants). The δ15N values of liver showed a decrease in consumed animal protein during winter, but the difference was not large enough to indicate a full trophic level change in diet from summer to winter. The δ15N values of hair remained constant across the seasons, which is attributed to a continuous level of moulting throughout the year. Our data indicate that lowered food quality in the form of reduced dietary animal protein intake may play a role in the cessation of breeding in deer mice in winter.

The effect of metabolic rate on stable carbon and nitrogen isotope compositions in deer mice, Peromyscus maniculatus

The stable isotopic compositions of nitrogen and carbon in animal tissues reflect diet. However, factors other than diet can also affect these stable isotope ratios, leading to misinterpretations of diet composition. To test the hypothesis that variation in metabolic rate alters the isotopic compositions of tissues, deer mice ( Peromyscus maniculatus (Wagner, 1845)) were kept at three temperatures (thermoneutral (23 °C), cool (5 °C), and cold (–10 °C)) and fed ad libitum. The changes in carbon and nitrogen isotope compositions of liver associated with the thermoneutral versus cool and cold conditions were very small in comparison with those arising from differences in diet. We conclude that temperature-induced variations in metabolic rate are insufficient to produce differences in the stable carbon or nitrogen isotope compositions that could be mistaken for changes in diet.

Conifer-seed preferences of small mammals

The preferences of the deer mouse ( Peromyscus maniculatus (Wagner, 1845)), southern red-backed vole ( Myodes gapperi (Vigors, 1830)), heather vole ( Phenacomys intermedius Merriam, 1889), long-tailed vole ( Microtus longicaudus (Merriam, 1888)), and meadow vole ( Microtus pennsylvanicus (Ord, 1851)) for lodgepole pine ( Pinus contorta Dougl. ex Loud.), white spruce ( Picea glauca (Moench.) Voss), and subalpine fir ( Abies lasiocarpa (Hook.) Nutt.) seeds were investigated using cafeteria-style feeding experiments. Seed selection by P. maniculatus and M. gapperi in the field was also studied. Peromyscus maniculatus, M. gapperi, M. longicaudus, and M. pennsylvanicus showed a distinct preference for lodgepole pine seeds and avoidance of subalpine fir seeds, and consumed the different species of seeds in similar relative proportions. Phenacomys intermedius behaved very differently from the other rodent species in that it did not show a preference among seed species, and consumed very few seeds in total. Findings from the field seed selection trials were consistent with laboratory results. We suggest that postdispersal seed predation by small mammals could limit the recruitment success of lodgepole pine and white spruce, but would not be a major problem in the regeneration of subalpine fir stands. This could provide an advantage for subalpine fir over neighbouring competitive species.

Carbon- and nitrogen-isotope tissue–diet discrimination and turnover rates in deer mice, Peromyscus maniculatus

The dietary habits of most small mammals are not well documented, and stable isotope measurements can provide information on when and how diets change. Here we document the discrimination and turnover times for carbon and nitrogen isotopes in blood, liver, muscle, hair, and milk from deer mice ( Peromyscus maniculatus (Wagner, 1845)) fed a controlled diet. Nonbreeding adults and pregnant females were livetrapped, maintained on a commercial laboratory chow, and had tissues sampled on a regular schedule. After adjusting to the laboratory diet, most tissues of nonbreeding adults were slightly depleted of 13C and enriched in 15N relative to diet (Δ13Ctissue–diet range = 0.3‰ to –1.1 ‰; Δ15Ntissue–diet range = 1.9‰ to 3.4‰). Liver (half-lives of 2.8 and 3.6 days for C and N, respectively) turned over more rapidly than blood (22.4 and 19.8 days for C and N, respectively) and muscle (18.7 and 24.8 days for C and N, respectively). The isotopic compositions of nonbreeding and breeding adults indicated tissue turnover at approximately the same rate, but juvenile tissues reflected the laboratory diet much more quickly than adult tissues.

The UKNG database: a simple audit tool for interventional neuroradiology

INTRODUCTION

The UK Neurointerventional Group (UKNG) has developed a unified database for the purposes of recording, analysis and clinical audit of neuroangiography and neurointerventional procedures. It has been in use since January 2002.

METHODS

The database utilizes an Access platform (Microsoft) comprising separate but linked programs for data collection and analysis. The program that analyses aneurysm therapy has been designed to mirror the criteria used in the International Subarachnoid Aneurysm Trial (ISAT).

RESULTS

Data entered into the main database immediately update the analysis program producing clinical outcome scores in the form of a report. Our local database (Wessex) now contains records on more than 1,750 patients including nearly 350 aneurysm coilings and a total of approximately 500 neurointerventional, vascular procedures. Every time a new piece of information is added to the main database the reporting database is automatically updated which allows 'real-time' audit and analysis of one's clinical practice. The clinical outcome scores for aneurysm treatment are presented in such a way that we can directly compare our results with the 'Clinical Standard' set by ISAT.

CONCLUSION

This database provides a unique opportunity to monitor and review practice at national level. The UKNG wishes to share this database with the wider neurointerventional community and a copy of the software can be obtained free of charge from the authors.

Microgeographic genetic structure in the yellow-pine chipmunk (Tamias amoenus)

While there is evidence for broad-scale genetic structure in small mammals, few studies have used variable DNA-based genetic markers to examine genetic differentiation at microgeographic (tens of kilometres) scales. Yellow-pine chipmunks (Tamias amoenus) live in the heterogeneous landscape of the Rockies in southwest Alberta and are generally restricted to areas of low elevation. We used seven microsatellite loci to determine whether chipmunks show evidence of population genetic structure among three closely situated sites (< 15 km) in the Kananaskis Valley, Alberta. We found evidence for genetic structure in the form of significant differences in allele frequencies among populations and significantly nonzero values of FST for both overall and pairwise population comparisons. However, FIS values for each population were not significantly different from zero, suggesting little evidence for inbreeding within populations. Genetic differentiation probably occurs as a result of the strong effect of drift in very small (N(e) approximately 25) populations of these animals even in the face of substantial immigration rates.

Sexual dimorphism in body composition of small mammals

Differences in reproductive roles between the sexes may lead to sexual dimorphism in body composition. Body size and composition of three species of small mammals (bushy-tailed wood rats (Neotoma cinerea Ord), deer mice (Peromyscus maniculatus Wagner), and red-backed voles (Clethrionomys gapperi Vigors)) were analyzed to test the predictions that (i) males will have more muscle mass than females and (ii) females will have more fat than males. Results supported the first prediction but not the second. For all three species, males had more lean dry mass relative to body size than females, but females did not have relatively more fat than males. Muscle mass of males may aid in mate-searching and mate-guarding activities, but fat content may not differ between the sexes because female small mammals depend on increased ingestion rates, rather than fat stores, to support reproduction.

Evaluating body condition in small mammals

Body condition (energy reserves) can have important fitness consequences. Measuring condition of live animals is typically done by regressing body mass on measures of body size and using the residuals as an index of condition. The validity of this condition index was evaluated by determining whether it reflected measured fat content of five species of small mammals (yellow-pine chipmunks (Tamias amoenus Allen), bushy-tailed wood rats (Neotoma cinerea Ord), deer mice (Peromyscus maniculatus Ord), red-backed voles (Clethrionomys gapperi Vigors), and meadow voles (Microtus pennsylvanicus Ord)). We also determined whether body water could predict fat content, enabling the use of hydrogen-isotope dilution for estimating condition. For all five species, condition estimates weakly predicted fat content and more accurately predicted variation in lean dry mass and water content. The relationship between body water and fat content was inconsistent among the five species, discouraging against the general use of isotope dilution in these animals. Although ecologically important, these indices are best interpreted as explaining variation in all constituents of body composition.

Early and periodic screening, diagnosis, and treatment examination completion rates for Oklahoma Medicaid managed care: 1995-1998

Although quality medical care is a goal of all health care providers, finding a means by which to take that idea from the abstract to the measurable is often an arduous task. The Oklahoma Health Care Authority and the Oklahoma Foundation for Medical Quality confronted that challenge when examining the state of Oklahoma's Early and Periodic Screening, Diagnosis, and Treatment (EPSDT) examination completion rates. Focused on measuring processes of care, the Oklahoma Health Care Authority (OHCA) and the Oklahoma Foundation for Medical Quality (OFMQ) used chart abstraction to track EPSDT examination rates for SoonerCare Plus Medicaid managed care recipients from 1995 through 1998. During the abstractions, an examination was interpreted as an EPSDT screen if a comprehensive health and development history plus a comprehensive unclothed physical examination were recorded. Examination rates have improved from 1995 when there was a documented 17.6% completion rate. The 1998 documented rate of completion was 60.0%. Trend analysis shows significant improvement over the four-year period. The results also suggest the necessity for continued improvement in the provision of documented EPSDT examinations to individuals in Medicaid managed care plans in Oklahoma.

Human triglyceride-rich lipoprotein apo E kinetics and its relationship to LDL apo B-100 metabolism

Apolipoprotein (apo) E is a multifunctional protein that can act as a ligand for lipoprotein receptors. The receptor-mediated clearance of the triglyceride-rich lipoproteins (TRL) chylomicrons and VLDL from plasma is, in part, dependent on apo E. Enrichment of VLDL with apo E is thought to enhance receptor-mediated clearance of VLDL resulting in a low rate of conversion of VLDL to LDL. However, the kinetic mechanism controlling the concentration of apo E in VLDL is not known. We conducted kinetic studies on apo E in the TRL fraction (d < 1.006 g/ml) and apo B-100 in the TRL and LDL (d = 1.019-1.063 g/ml) fractions to assess the kinetic determinants of apo E concentration in TRL and to determine the effects that TRL apo E production and clearance rates have on the production rate of LDL apo B-100. Nineteen males between the ages of 24 and 73 underwent a primed-constant infusion with deuterated leucine tracer in the constantly-fed state. Apo B-100 from TRL and LDL, and apo E from TRL were isolated and their tracer incorporation measured by gas chromatography/mass spectrometry. The residence time and production rates of each protein were determined from the kinetic data using the SAAM II modeling program. The residence time and production rate of TRL apo E were about one-half that of TRL apo B-100 (1.8 +/- 1.0 vs. 2.9 +/- 2.1 h and 14.5 +/- 11.0 vs. 27.6 +/- 17.3 mg/kg per day, respectively). The production rate of TRL apo E was weakly correlated with the production rate of TRL apo B-100 (r = 0.424, P = 0.07). Multiple regression analysis showed that the residence time of TRL apo B-100 and the relative TRL apo E production rate (relative to the TRL apo B100 production rate) were negatively associated with LDL apo B-100 production rate, accounting for 68% of its variability. We conclude that (1) the concentration of apo E in TRL is highly correlated to its production rate, suggesting that production rate regulates the TRL apo E concentration, and (2) individuals with a relatively short TRL apo B-100 residence time and those producing TRL with a relatively low apo E content have the highest LDL apo B-100 production rates.

Consultations owing to adverse drug reactions in a single practice

Data was collected over a six-month period on all patients presenting with a suspected adverse drug reaction. Analysis showed that this was a frequent reason for doctor-patient contact and that a large proportion of adverse reactions were owing to a small group of drugs.

The sialylation of plasma lipoproteins

Sialic acids are a family of amino sugars that are commonly found as terminal oligosaccharide residues on glycoproteins and glycolipids. Plasma lipoproteins are sialylated on their apolipoprotein and glycolipid constituents. The function of sialic acid on apolipoproteins is not completely understood but has been associated with secretion, lipid-binding, and plasma clearance for some apolipoproteins. The sialic acid content of individual apolipoproteins can vary in response to physiological conditions while the sialic acid content of individual sialylated glycolipids (gangliosides) is constant. Thus, the sialic acid content of plasma lipoproteins can differ considerably as a result of (1) variations in the sialylation of their apolipoprotein constituents, (2) variations in their content of sialylated apolipoproteins and gangliosides, and (3) modifications of the sialic acid on lipoprotein constituents while circulating in plasma. The significance of sialic acid on lipoproteins is not fully understood although associations have been made between sialic acid and charge (very low density lipoprotein), lipoprotein solubility, receptor binding and uptake, and interactions with vascular matrix (low density lipoprotein and Lp(a)) and with cholesterol efflux (high density lipoprotein). Further studies identifying sites of sialylation on apolipoproteins and characterizing the structures of sialylated oligosaccharides will aid in determining the enzymes responsible for their sialylation. Manipulations of the sialylation of apolipoproteins and of the quantity of apolipoproteins and gangliosides on lipoproteins will be useful methods in determining the role of lipoprotein sialic acid in the development of atherosclerosis.

Spontaneous dissection of the anterior inferior cerebellar artery

A patient presented with the clinical features of a brain stem infarct. MRI confirmed changes of infarction but also revealed an unusual lesion in the left cerebellopontine angle cistern. The evolution of this lesion on MRI, together with angiographic changes, indicated a dissecting aneurysm of the left anterior inferior cerebellar artery, a previously unreported phenomenon. The presentation, causes and diagnosis of intracranial dissection are discussed.

Consumer Assessment of Health Plans Survey (CAHPS) results for Oklahoma managed care Medicaid, 1997, 1998, and 1999

Consumer satisfaction surveys have become an important source of information for purchasers and consumers of health care and health care organizations themselves. Individuals receiving health care provide valuable information regarding access, use of services, and satisfaction with care that can be used for multiple evaluative purposes. The Oklahoma Health Care Authority has adopted the Consumer Assessment of Health Plans Survey (CAHPS) to measure patient satisfaction for the SoonerCare managed care programs. The Oklahoma Foundation for Medical Quality administered the surveys. The adult and child CAHPS core questionnaires served as the basis for the general surveys in 1997 and 1998. The CAHPS for Children with Special Needs survey results and the Pediatric Adaptation of the CAHPS Behavioral Health Survey results were administered in 1999 for baseline measures. Results indicated an overall increase in consumer satisfaction levels across the two CAHPS core questionnaires. Baseline measures for special needs populations were also established.

Immunization rate comparison for Oklahoma Medicaid managed care population by age two: 1995-1998

Processes of care are used as one measure for the quality of care rendered by providers. One example is the immunization of children by the age of two. The Oklahoma Health Care Authority, with the Oklahoma Foundation for Medical Quality, has been tracking childhood immunization rates from 1995 through 1998. The rate calculated included the medical record data and the Oklahoma Statewide Immunization Information System (OSIIS) data set. The standards were based on Advisory Committee on Immunization Practices recommendations and Quality Assurance Reform Initiative standards. The rate of provision of documented immunizations in the Medicaid managed care population under the age of two has improved markedly from 1995 to 1998. The trend analysis suggests there might be areas for continued improvement in the provision of immunization to individuals in Oklahoma's Medicaid managed care population. Further, the OSIIS data is critical for maintaining a uniform data set for immunization information.

Sialic acid-containing components of lipoproteins influence lipoprotein-proteoglycan interactions

Sialic acid is a negatively charged sugar associated with the protein and lipid portions of lipoproteins. Sialic acid has been hypothesised to play an anti-atherogenic role in lipoprotein metabolism through the electrostatic inhibition of lipoprotein interactions with chondroitin-6-sulphate-rich arterial proteoglycans (APG). We conducted a series of studies using native and modified lipoproteins (VLDL1 Sf 60-400, VLDL2 Sf 20-60, IDL1 Sf 16-20, IDL2 Sf 12-16, LDL(A) Sf 8-12, and LDL(B) Sf0-8) that vary in their sialic acid content to examine the relationship between lipoprotein sialic acid content and its interaction with APG. Lipoprotein sialic acid was greatest in VLDL1 and decreased progressively with particle density until the IDL2 fraction (VLDL1 > VLDL2 > IDL1 > IDL2 = LDL(A) = LDL(B)). The pattern of reactivity of each fraction with APG was different from the pattern observed for lipoprotein sialic acid content (IDL2 > LDL(A) > LDL(B) > IDL1 > VLDL2 > VLDL1). Levels of sialic acid were lower in subjects with CHD as compared to control subjects but the presence of CHD had no effect on lipoprotein-APG complex formation when sex and plasma triglyceride levels were taken into account. There was also no significant relationship between the lipoprotein sialic acid content and the reactivity with APG within each lipoprotein fraction. Treatment of hypertriglyceridaemic subjects with ciprofibrate decreased lipoprotein-APG complex formation in all lipoprotein fractions. This was associated with a decrease in the total sialic acid content of apo B100-containing lipoproteins suggesting that the total sialic acid content of apo B100-containing lipoproteins has no influence on lipoprotein-APG complex formation. We next conducted in vitro experiments to manipulate LDL sialic acid content. Enzymatic removal of sialic acid from LDL with neuraminidase resulted in an increase in LDL-APG complex formation. This was accompanied by an increase in the exposure of free amino groups on LDL possibly due to disruption of interactions between free amino groups and sialic acid-containing components on LDL. Increasing LDL sialic acid content through incubation with ganglioside resulted in a decrease in lipoprotein-APG complex formation without any changes in the exposure of free amino groups on LDL. We conclude that total sialic acid content of lipoproteins is not a major determinant of their binding to APG. However, specific sialic acid-containing components on lipoproteins can affect their interaction with APG.

Comparison of influenza immunization rates for Oklahoma Medicare patients: 1995, 1996 and 1997

The Health Care Financing Administration has reported influenza immunization rates since 1994. The Department of Health and Human Services has set a minimum national target rate for the annual immunization of the elderly population at 60 percent, as published in Healthy People 2000. The Oklahoma Foundation for Medical Quality analyzed the Medicare claims data for Oklahoma for the 1995, 1996, and 1997 influenza seasons. Additionally, we reviewed the Behavioral Risk Factor Surveillance System influenza immunization data for 1995. Claims data for the 1997 influenza season show the immunization rate for the Medicare population of Oklahoma is 41.4 percent. The immunization rate for the African-American Medicare population was 22.3 percent for 1997, compared with 42.2 percent for the Caucasian population. The ten most populous counties in the state had a 9-percent higher rate of immunization than the other 67 counties. The Medicare population in Oklahoma is not receiving the influenza vaccination at the target rate. Especially underserved are the African-American and non-urban populations. There appear to be opportunities for improvement in the provision of the influenza vaccination for the Medicare population of Oklahoma.

Proposal of a multicompartmental model for use in the study of apolipoprotein E metabolism

Apolipoprotein (apo) E is a 299-amino acid glycoprotein that serves a number of functions in lipoprotein metabolism. Apo E binds to the triglyceride-rich lipoproteins (TRL), very-low-density lipoprotein (VLDL), and chylomicrons, as they are lipolyzed, mediating their removal from plasma via lipoprotein receptors. Apo E is also found associated with high-density lipoprotein (HDL) and has been suggested to play a role in reverse cholesterol transport. Studies on the kinetic behavior of apo E from the TRL and HDL fractions provide insights into the metabolic relationships between TRL and HDL in vivo. We sought to develop a compartmental model that can be used for analysis of kinetic data in studies on the metabolism of TRL and HDL apo E. Using radioactive tracers, it has been previously observed that, in some instances, a portion of VLDL apo E that is removed from plasma subsequently reappears in VLDL. Four multicompartmental models were considered that could account for this type of behavior: model A, in which there is transfer of apo E from HDL to VLDL; model B, in which there is a bidirectional extravascular exchange; model C, in which there is removal and subsequent reintroduction of TRL apo E into plasma; and model D, in which there is secretion of TRL apo E into plasma directly and via an extravascular pathway. Models C and D provided the best fit to the experimental data. While no physiologically plausible analog to model C could be found, an extravascular delay, analogous to newly secreted apo E that enters the lymphatic system before appearing in plasma, was postulated for model D. It was this model that was used to analyze kinetic data from metabolic studies of apo E. The model was able to provide a satisfactory fit to kinetic data in studies in which subjects were given a primed-constant infusion of 2H3-leucine. It was determined that TRL apo E from the six subjects studied had a mean residence time of 0.11 +/- 0.05 days and a mean production rate of 10.6 +/- 7.2 mg/kg/d, while HDL apo E had a mean residence time of 2.96 +/- 0.99 days and a mean production rate of 0.07 +/- 0.07 mg/kg/d. We conclude that this model describes a potential pathway for the metabolism of a portion of apo E in plasma and can be used to calculate the residence time and production rate of TRL and HDL apo E under a variety of conditions.

Heterogeneity of apolipoprotein B-100-containing lipoproteins: what we have learnt from kinetic studies

Apolipoprotein B-100-containing lipoprotein assembly is dependent on the successive addition of triglyceride by microsomal transfer protein. Assembly may end at this point and the lipoprotein secreted or it may continue with the bulk addition of triglyceride by an unknown transfer process. These steps are independently regulated and result in the secretion of a spectrum of apolipoprotein B-100-containing particles. The production of small, dense LDL is determined by the type of VLDL secreted by the liver. Large, triglyceride-rich VLDL1 results in the formation of small, dense LDL through triglyceride exchange and subsequent hydrolysis. Small, dense LDL are cleared from plasma relatively slowly and tend to accumulate in the circulation where they exert their atherogenic effects.

Characteristics and hospital utilization of the Oklahoma Medicare population: 1994-1996

BACKGROUND AND OBJECTIVES

Epidemiologic surveillance reports that focus on hospital utilization are limited in number. The objective of this study was to provide a current profile of the demographic characteristics of the Oklahoma Medicare population and to profile trends in hospital utilization.

METHODS

Using the Medicare enrollment files and discharge claims data sets for 1994 through 1996, demographic characteristics and surveillance measures were calculated for enrollees based on age, sex, race/ethnicity, principal diagnosis, and primary procedure. In addition, average hospital charge and average reimbursement were evaluated by diagnosis-related group.

RESULTS

The Oklahoma Medicare population has grown by 2.5% from 1994 through 1996. The majority (87.5%) of the enrollees are aged 65 or greater. Of those less than 65 years of age, most are enrolled in the program because of disability. Less than 5% of the Medicare population was enrolled in a managed care plan during 1996. The overall length of stay, in-hospital mortality, and 30-day mortality rates have declined for all age groups and principal diagnoses profiled. More than one fifth of all of the Medicare discharge claims were related to heart disease.

CONCLUSIONS

The Medicare discharge claims files represent a useful source of data from which to conduct surveillance on this population. The declining rates of mortality and length of stay that were demonstrated for all Medicare age groups must be taken into account in any evaluation of health care services that seeks to address the impact of quality improvement or utilization management strategies over time.

Interaction of very-low-density, intermediate-density, and low-density lipoproteins with human arterial wall proteoglycans

The specific interaction of lipoproteins with arterial wall constituents, particularly proteoglycans (APG), is believed to play an important role in the development of atherosclerosis. The objective of this study was to examine the interaction of apolipoprotein B (apoB) containing lipoprotein subfractions (VLDL1, Sf 60 to 400; VLDL2, Sf 20 to 60; IDL1, Sf 16 to 20; IDL2, Sf 12 to 16; LDLA, Sf 8 to 12; and LDLB, Sf 0 to 8) prepared by cumulative density gradient centrifugation with chondroitin sulfate-rich APG. Eighteen subjects were studied, and a similar pattern of interaction between the lipoprotein species and APG was found in all. The order of reactivity (as measured by increased turbidity due to insoluble complex formation) was IDL Sf 12 to 16 > or = LDL Sf 8 to 12 > LDL Sf 0 to 8 > IDL Sf 16 to 20 >> VLDL Sf 20 to 60 > VLDL Sf 60 to 400. When the subjects were divided on the basis of their LDL subfraction profile, the extent of insoluble complex formation was highest in the group in which small, dense LDLIII was predominant; intermediate in the group whose LDL was mainly LDLII; and lowest in the group with a high proportion of LDLI (the mean reactivity, AU at 600 nm. of APG with IDL Sf 12 to 16 and LDL Sf 8 to 12 was 0.66; 0.62 and 0.46, 0.43 and 0.20, and 0.21 for the three groups, respectively). Fibrate lipid-lowering treatment decreased the percentage of LDLIII and increased the percentage of LDLI within total LDL and reduced the reactivity of all apoB-containing lipoprotein fractions toward APG. Sialic acid content varied in different lipoprotein subfractions, being the highest in VLDL and lowest in LDL. However, across lipoprotein species, it did not significantly correlate with APG-binding reactivity, suggesting that other factors are important in determining the interaction of lipoproteins with APG. Modification of LDL arginine and lysine residues abolished the ability of the lipoprotein to interact with APG, a finding that supports the hypothesis that the interaction is dependent on key positively charged amino acids on apoB. These findings demonstrate that (1) the overall reactivity of apoB-containing lipoproteins is greatest in individuals with small, dense LDL and (2) within an individual, IDL of Sf 12 to 16 is the most reactive species, and this may in part explain the positive correlation between IDL and risk of coronary heart disease.

Lovastatin decreases de novo cholesterol synthesis and LDL Apo B-100 production rates in combined-hyperlipidemic males

The effect of lovastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, on the kinetics of de novo cholesterol synthesis and apolipoprotein (apo) B in very-low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), and low-density lipoprotein (LDL) was investigated in five male patients with combined hyperlipidemia. Subjects were counseled to follow a Step 2 diet and were treated with lovastatin and placebo in randomly assigned order for 6-week periods. At the end of each experimental period, subjects were given deuterium oxide orally and de novo cholesterol synthesis was assessed from deuterium incorporation into cholesterol and expressed as fractional synthesis rate (C-FSR) and production rate (C-PR). Simultaneously, the kinetics of VLDL, IDL, and LDL apo B-100 were studied in the fed state using a primed-constant infusion of deuterated leucine to measure fractional catabolic rates (FCR) and production rates (PR). Drug treatment resulted in significant decreases in total cholesterol (-29%), VLDL cholesterol (-40%), LDL cholesterol (-27%), and apo B (-16%) levels and increases in HDL cholesterol (+13%) and apolipoprotein (apo) A-I (+11%) levels. Associated with these plasma lipoprotein responses was a significant reduction in both de novo C-FSR (-40%; P = .04) and C-PR (-42%; P = .03). Treatment with lovastain in these patients had no significant effect on the FCR of apoB-100 in VLDL, IDL, or LDL, but resulted in a significant decrease in the PR of apoB-100 in IDL and LDL. Comparing the kinetic data of these patients with those of 10 normolipidemic control subjects indicates that lovastatin treatment normalized apoB-100 IDL and LDL PR. The results of these studies suggest that the declines in plasma lipid levels observed after treatment of combined hyperlipidemic patients with lovastatin are attributable to reductions in the C-FSR and C-PR of de novo cholesterol synthesis and the PR of apoB-100 containing lipoproteins. The decline in de novo cholesterol synthesis, rather than an increase in direct uptake of VLDL and IDL, may have contributed to the decline in the PR observed.

MRI in the localization of CSF fistulae: is it of any value?

Coronal T2-weighted magnetic resonance imaging (MRI) has been reported to be a useful technique for the localization of both spontaneous and traumatic CSF (cerebro spinal fluid) fistulae. We reviewed the magnetic resonance imaging (MRI) scans of 50 patients with temporal lobe epilepsy in whom such sequences were routinely acquired to determine if this asymptomatic population fulfilled any of the criteria for the diagnosis of a CSF fistula. We found that a large proportion did and conclude that using MRI as the initial radiological investigation in the localization of CSF fistulae is of such low specificity that it is of little or no value.

Optimization of radiographic technique for chest radiography

Over 1500 patients undergoing chest radiography in the West Midlands have been monitored for entrance surface doses using lithium borate thermoluminescent dosemeters. In total 63 X-ray tubes were monitored from 30 hospital departments. The mean patient entrance surface dose is 0.15 mGy, and the 75th percentile entrance surface dose is 0.18 mGy. A reference level of 0.18 mGy has been recommended for PA chest radiography in the West Midlands. Image quality has been assessed on patient radiographs. Departmental radiologists were responsible for assessing radiographs taken within their hospital. Independent analysis was performed by a control radiologist. Film-screen processor sensitivity has been assessed on 48 film-screen processor combinations. Significant differences were observed between the nominally quoted sensitivities and the measured sensitivities. Only 26% of systems produced measured sensitivities within 10% of the nominal values. A four variable regression model, explaining 78% of the variance, provided the best description for the variation in patient dose. These variables were actual sensitivity, applied potential, generator waveform and radiographic quality. Four recommendations have been made to lower patient doses; these are: (1) an increase in applied potential to a minimum of 90 kVp; (2) a film-screen sensitivity of 400; (3) optimization of processor performance and (4) regular radiological audits to reduce repeat rates to a level of 5%. If all of these recommendations are followed, an estimated overall entrance surface dose saving of 53% would result. Changing the applied potential alone will see the variation in the mean entrance surface dose from non-gridded systems reduce from a factor of 4 to a factor of 2.

Impact of age on the metabolism of VLDL, IDL, and LDL apolipoprotein B-100 in men

Levels of plasma very low density lipoprotein (VLDL) and low density lipoprotein (LDL) constituents increase with age. In an attempt to further define the mechanisms responsible for these changes, kinetic studies of VLDL and LDL apolipoprotein (apo) B-100 were carried out in 19 normolipidemic male subjects with plasma total cholesterol and triglyceride levels below the 90th percentile whose ages ranged from 24 to 73 years. Subjects were maintained on standardized diets consisting of 47-49% of calories as carbohydrate, 15% protein, and 36-40% fat (15-17% saturated, 15-17% monounsaturated, 6% polyunsaturated) with 150 mg cholesterol/1000 kcal. At the end of the diet period, the metabolism of apoB-100 within VLDL, intermediate density lipoprotein (IDL), and LDL was studied in the fed state using a primed-constant infusion of [2H3]leucine. Data were fit to a multicompartmental model to determine residence times and production rates of apoB-100 in each fraction. There were significant positive correlations between age and VLDL, IDL, and LDL apoB-100 concentrations (r = 0.50, 0.62, and 0.69; P = 0.03, 0.004, and 0.001, respectively). There was a positive correlation between age and the production rate of VLDL apoB-100 (r = 0.50, P = 0.03), but there was no significant relationship between age and either IDL or LDL apoB-100 production rates. Age was also positively correlated with the residence time of LDL apoB-100 (r = 0.68 P = 0.001). Our data suggest that the age-associated increase in VLDL apoB-100 is due to an increased production rate of this constituent, whereas the age-associated increase in LDL apoB-100 is due to an increased residence time of these particles in plasma.

Contribution of apoB-48 and apoB-100 triglyceride-rich lipoproteins (TRL) to postprandial increases in the plasma concentration of TRL triglycerides and retinyl esters

After the ingestion of a fat-rich meal, there is a postprandial increase in the plasma concentration of both apolipoprotein B-48- and apoB-100-containing triglyceride-rich lipoproteins (apoB-48 and apoB-100 TRL). In order to determine the contribution of these lipoproteins to postprandial lipemia, the concentration of triglycerides (TG) and retinyl esters (RE) was measured in apoB-48 and apoB-100 TRL after an oral fat load. Six normolipidemic male subjects were fed heavy cream (1 g fat per kg body weight) containing vitamin A (3000 retinol equivalents). TRL were isolated by ultracentrifugation from plasma samples obtained at regular intervals after the meal, and apoB-100 TRL were separated from apoB-48 TRL by affinity chromatography using monoclonal antibodies. Postprandial increase in plasma TG concentration was due to an increase in TG in the TRL fraction, which in turn was predominantly (82 +/- 4%) due to an increase in TG in apoB-48 TRL. Contribution of apoB-100 TRL to postprandial increase in TRL TG was 3-27% in individual subjects. ApoB-100 TRL remained a significant carrier of total plasma triglyceride in the fed state, as reflected by similar apoB-100 and apoB-48 TRL TG concentrations at 2, 4, and 6 h after the fat meal. Retinyl esters were regularly detected in apoB-100 TRL. Seventy-five (+/- 9) percent of the increase in TRL-RE was due to RE in apoB-48 TRL and 25 +/- 9% was due to RE in apoB-100. These data suggest that RE in plasma are not always associated with apoB-48-containing lipoproteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of significant abnormalities on lumbar spine radiographs

The purpose of this study was to determine the proportion of significant abnormalities detected on anteroposterior (AP) and lateral radiographs of the lumbar spine when viewed separately, in a series of cases where the prevalence of abnormalities had been artificially increased. Five radiologists of varying experience were required to report separately on the AP and lateral films of 300 cases in which randomly included were 30 cases with metastatic disease, a disc infection or an inflammatory spondylitis. At a later date, unaware of their initial observations, the radiologists repeated the exercise reviewing all the films together. As might be expected the false positive rate was relatively high, particularly in the least experienced radiologists' responses. Nevertheless the overall results indicate that the majority of early inflammatory spondylitis cases will be missed on a solitary lateral film as will many of the metastases. Conversely, fractionally more of the disc infections were observed on the lateral film than on the AP. Further analyses in terms of sensitivity, specificity, positive and negative predictive values are presented. The authors conclude that it is preferable to reduce the overall number of lumbar spine examinations performed, by adherence to accepted guidelines, than to prejudice the detection of significant, albeit rare, abnormalities by restricting the routine series of radiographs.

Measurement of human apolipoprotein B-48 and B-100 kinetics in triglyceride-rich lipoproteins using [5,5,5-2H3]leucine

A primed-constant infusion of deuterated leucine was used in humans to determine the maximal level of enrichment at plateau of apolipoprotein (apo)B-48 and apoB-100 which are synthesized in the intestine and liver, respectively, and to compare the kinetics of these two proteins under identical conditions. Eight normal subjects (four post-menopausal females and four males) over the age of 40 were studied in the constantly fed state over a 20-h period by providing small hourly feedings of identical composition. [5,5,5-2H3]Leucine (10 mumol/kg body weight followed by 10 mumol/kg body weight per hour) was infused over 15 h intravenously. The enrichment of deuterated leucine in apoB-48 and apoB-100 triglyceride-rich lipoproteins isolated by ultracentrifugation (d less than 1.006 g/ml) was determined during the entire infusion period. The plateau level of enrichment in triglyceride-rich lipoprotein apoB-48 was 3.96 +/- 1.41 tracer/tracee ratio (%) which was 39.7% of the plasma leucine enrichment level. The plateau level of enrichment in triglyceride-rich lipoprotein apoB-100 was 7.23 +/- 1.17 tracer/tracee ratio (%) which was 72.5% of the plasma leucine enrichment level. Mean fractional secretion rates of triglyceride-rich lipoprotein apoB-48 and apoB-100 were 4.39 +/- 2.00 and 5.39 +/- 1.98 pools per day, respectively, with estimated residence times of 5.47 and 4.45 hours, respectively. The data indicate that in the fed state there is about a twofold difference in the plateau enrichment of an intestinally derived protein, as compared to one of hepatic origin, most likely attributable to differences in the enrichment of the intracellular leucine in the two organs.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence on the variation in initiation of breeding in Peromyscus maniculatus

Correlates of the initiation of breeding by female Peromyscus maniculatus borealis (Mearns) were examined to test the hypotheses that asynchronous breeding was related to age, weight, matriline, and nest-site habitat. Life-history data were collected by mark–recapture techniques and by monitoring natal nests over two breeding seasons in 1985 and 1986. Timing of initiation of breeding was related significantly to nest-site habitat and age, but not to matriline or weight. At approximately the same altitude, females nesting in dry rocky stream beds bred first, followed by those in open rock fields, then shrub areas, and last in subalpine forest. Youngest animals bred first in all habitats, although the relationship between age and initiation date was weak. Habitat effects appeared to be primarily related to microclimatic effects. The influence of habitat on the timing of initiation of breeding also had consequences for reproductive success, total reproductive output, and survival. Reproductive success of first litters was greatest for females nesting in rocky stream beds in the spring and least for females nesting in shrub and forest habitats. The apparent advantages of early breeding in rocky stream beds were offset by greater overwinter mortality.

Relocation of nest sites by female deer mice, Peromyscus maniculatus borealis

Nest-sites of female Peromyscus maniculatus borealis were monitored during 1985 and 1986 in the Kananaskis Valley, Alberta, Canada. Nest-site relocation by breeding overwintered adults and young of the year was common. There was no significant difference in the distance moved between years and sites or among reproductive-status groups. Nest relocations were most common in 1985, when population density was approximately half that in 1986. There were no differences in the numbers of relocations per season due to site or age. Females in breeding condition moved 3 times more frequently than did nonbreeders, which were young of the year. Relocations were most frequent at parturition and during early lactation, and thus may serve as a predator-avoidance mechanism. Some relocations by females may have served to leave former nest sites to offspring from previous litters.