Revising a priority list based on cost-effectiveness: the role of the prominence effect and distorted utility judgments

BACKGROUND

People sometimes object to the results of cost-effectiveness analysis when the analysis produces a ranking of options based on both cost and benefit. We suggest 2 new reasons for these objections: the prominence effect, in which people attend mostly to a more prominent attrbute (benefit as opposed to cost), and distortion of utility judgments.

METHOD

We simulated the production of a cost-effectiveness ranking list in 3 experiments using questionnaires on the World Wide Web. Subjects rated the utility of 16 health benefits using either rating scale or person trade-off elicitation methods. In some experiments, subjects were asked to rate the utility of the health benefits with attention also to the cost of achieving the benefits. In all experiments, at the end, subjects were shown a priority list based on their own utility judgments and were asked whether they wanted to move any of the health benefits up or down the list.

RESULTS

In all experiments, subjects wanted to give higher priority to treatments with higher benefit, even when they also had higher cost. They thus wanted to give less weight to high cost (which would, by itself, lead to lower ranking) and more weight to benefit than the weight implied by their own prior judgments. The desire for revision was reduced when subjects made their utility judgments after indicating whether the utility was above or below the midpoint of the scale (a manipulation previously found to reduce distortion).

CONCLUSION

The desire to change cost-effectiveness rankings is in part a preference reversal phenomenon that occurs because people attend mainly to the benefit of health interventions as opposed to cost, when they examine the ranking. People should be wary of tinkering with priority lists by examining the lists themselves.

Allocation of transplantable organs: do people want to punish patients for causing their illness?

Some people believe patients with alcoholic cirrhosis should not receive equal priority for scarce transplantable organs. This may reflect a belief that these patients (1) are personally responsible for causing their own illnesses, (2) have poor transplant prognoses, or (3) are unworthy because they have engaged in socially undesirable behavior. We explore the roles that social desirability and personal responsibility have in people's judgments about transplant allocation. We presented prospective jurors with 4 scenarios, asking them to distribute 100 transplantable organs among 2 groups of 100 patients each. In each scenario, 1 group of patients, but not the other, was described as having a history of unhealthy behavior (alcohol or cigarette use) associated with a poorer prognosis. In some scenarios, alcohol or cigarette use was said to cause the organ failure. In others, it only contributed to the patients' transplant prognosis. We also obtained self-reports of subjects' own smoking status. Subjects allocated significantly fewer than half the organs to those with unhealthy behaviors and worse prognoses (33%; P <.001), but the specific behavior (alcohol versus cigarette use) was not significantly associated with subjects' allocation choices. Significantly fewer organs were allocated to patients with behavior responsible for causing their diseases than to other patients (P <.0001). Subjects who never smoked discriminated the most and current smokers discriminated the least against patients with a history of unhealthy behavior (P <.0001). The public's transplantation allocation preferences are influenced by whether patients' behaviors are said to have caused their organ failure.

Effects of estrogen on growth plate senescence and epiphyseal fusion

Estrogen is critical for epiphyseal fusion in both young men and women. In this study, we explored the cellular mechanisms by which estrogen causes this phenomenon. Juvenile ovariectomized female rabbits received either 70 microg/kg estradiol cypionate or vehicle i.m. once a week. Growth plates from the proximal tibia, distal tibia, and distal femur were analyzed after 2, 4, 6, or 8 weeks of treatment. In vehicle-treated animals, there was a gradual senescent decline in tibial growth rate, rate of chondrocyte proliferation, growth plate height, number of proliferative chondrocytes, number of hypertrophic chondrocytes, size of terminal hypertrophic chondrocytes, and column density. Estrogen treatment accelerated the senescent decline in all of these parameters. In senescent growth plates, epiphyseal fusion was observed to be an abrupt event in which all remaining chondrocytes were rapidly replaced by bone elements. Fusion occurred when the rate of chondrocyte proliferation approached zero. Estrogen caused this proliferative exhaustion and fusion to occur earlier. Our data suggest that (i) epiphyseal fusion is triggered when the proliferative potential of growth plate chondrocytes is exhausted; and (ii) estrogen does not induce growth plate ossification directly; instead, estrogen accelerates the programmed senescence of the growth plate, thus causing earlier proliferative exhaustion and consequently earlier fusion.

Guidelines for counselling in infertility: outline version

The Guidelines for Counselling in Infertility describe the purpose, objectives, typical issues and communication skills involved in providing psychosocial care to individuals using fertility services. The Guidelines are presented in six sections. The first section describes how infertility consultations differ from other medical consultations in obstetrics and gynaecology, whereas the second section addresses fundamental issues in counselling, such as what is counselling in infertility, who should counsel and who is likely to need counselling. Section 3 focuses on how to integrate patient-centred care and counselling into routine medical treatment and section 4 highlights some of the special situations which can provoke the need for counselling (e.g. facing the end of treatment, sexual problems). Section 5 deals exclusively with third party reproduction and the psychosocial implications of gamete donation, surrogacy and adoption for heterosexual and gay couples and single women without partners. The final section of the Guidelines is concerned with psychosocial services that can be used to supplement counselling services in fertility clinics: written psychosocial information, telephone counselling, self-help groups and professionally facilitated group work. This paper summarizes the different sections of the Guidelines and describes how to obtain the complete text of the Guidelines for Counselling in Infertility.

Do nonpatients underestimate the quality of life associated with chronic health conditions because of a focusing illusion?

BACKGROUND

A number of studies show that the general public often estimates that the quality of life (QOL) associated with various health conditions is worse than patients say it is. These studies raise the possibility that people overestimate the impact that unfamiliar health conditions will have on their quality of life. One possible reason people overestimate this is because they are susceptible to a focusing illusion--when asked to imagine themselves in unfamiliar circumstances, people overestimate the emotional impact of those features of their life that would change.

METHODS

The authors surveyed members of the general public to test the hypothesis that their QOL ratings of hypothetical health conditions would be higher (indicating a better quality of life) after thinking about how the health condition would affect a broad range of life domains. Across 3 experiments, the authors varied the health conditions people were asked to consider (either paraplegia, below-the-knee amputation, or partial blindness), the life domains they were asked to consider, the response mode with which they evaluated how each health condition would affect each life domain, whether subjects rated the health condition before and after considering life domains or only after, and whether subjects rated their own current quality of life first.

RESULTS

Across 3 experiments, using 10 different questionnaire versions, only 1 instance was found in which subjects' ratings were significantly higher after thinking about the effect of the health condition on life domains than before, and the magnitude of this increase was small.

CONCLUSION

It could not be established that a focusing illusion contributes significantly to the discrepancy in QOL ratings of patients and nonpatients. Further research should explore other factors that could contribute to the discrepancy or other ways of testing for the influence of a focusing illusion.

Preference for equity as a framing effect

BACKGROUND

In previous studies, the authors found that most people, given a fixed budget, would rather offer a less effective screening test to 100% of a Medicaid population than a more effective test to 50% of the population. In a subsequent study, the authors found that the number of people preferring the less effective screening test was dramatically reduced when the percentage of Medicaid enrollees receiving it was less than 100. In this article, 2 new studies are reported that explore whether people's preferences for equity versus efficiency are susceptible to a framing effect.

METHODS

In 2 studies, the authors presented subjects with multiple scenarios involving screening tests that vary in the proportion of people who could receive the tests within a budget constraint and the number of people whose lives each test would save. Across scenarios, the proportion of Medicaid enrollees who could receive each test was varied, as was the question of whether scenarios involved Medicaid enrollees from the same or a different state. In addition, the authors varied the order in which subjects received the scenarios.

RESULTS

In the 1st study, people's preferences for equity over efficiency varied significantly depending on the way situations were framed. Preference for equity was stronger when the more widely distributed choice covered the entire population than when it covered only half the population (P < 0.001). In addition, people's preferences were susceptible to order effects, with preference for equity being significantly stronger when the 1st scenario received by subjects involved 1 screening test that could be offered to the entire population (P < 0.001). In the 2nd study, preferences for equity over efficiency diminished even when the different framings were descriptions of identical circumstances--preference for equity was significantly reduced when the population to be screened was framed broadly, in terms of the percentage of patients across 2 states who could receive testing rather than narrowly, in terms of the percentages of patients in 1 state who could receive testing (P = 0.04).

CONCLUSION

Policy planners should be careful about accepting public preferences for equity over efficiency at face value, because such preferences can be dramatically influenced by framing effects and order effects.

Effect of growth hormone treatment on testicular function, puberty, and adrenarche in boys with non-growth hormone-deficient short stature: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

To evaluate the effect of growth hormone (GH) therapy on pubertal onset, pubertal pace, adult testicular function, and adrenarche in boys with non-GH-deficient short stature.

STUDY DESIGN

Randomized, double-blind, placebo-controlled trial. GH (0.074 mg/kg, subcutaneously, 3 times per week) or placebo treatment was initiated in prepubertal or early pubertal boys and continued until near final height was reached (n = 49). Statistical significance was assessed by survival analysis, repeated-measures analysis of variance, and Student t test.

RESULTS

GH therapy did not affect the age at pubertal onset, defined either by testicular volume >4 mL or by testosterone concentration >1.0 nmol/L (30 ng/dL). GH treatment also did not affect the pace of puberty, defined either by the rate of change in testicular volume or testosterone concentration during the 4 years after pubertal onset. In boys followed up to age > or =16 years during the study, there were no significant differences in final testicular volume or in plasma testosterone, luteinizing hormone, or follicle-stimulating hormone concentrations. The pace of adrenarche, assessed by change in dehydroepiandrosterone sulfate levels over time, also did not differ significantly between the GH and placebo groups.

CONCLUSION

Our findings suggest that GH treatment does not cause testicular damage, alter the onset or pace of puberty, or alter the pace of adrenarche in boys with non-GH-deficient short stature.

Regulation of growth plate chondrogenesis by bone morphogenetic protein-2

Bone morphogenetic proteins (BMPs) regulate embryonic skeletal development. We hypothesized that BMP-2, which is expressed in the growth plate, also regulates growth plate chondrogenesis and longitudinal bone growth. To test this hypothesis, fetal rat metatarsal bones were cultured for 3 days in the presence of recombinant human BMP-2. The addition of BMP-2 caused a concentration-dependent acceleration of metatarsal longitudinal growth. As the rate of longitudinal bone growth depends primarily on the rate of growth plate chondrogenesis, we studied each of its three major components. BMP-2 stimulated chondrocyte proliferation in the epiphyseal zone of the growth plate, as assessed by [(3)H]thymidine incorporation. BMP-2 also caused an increase in chondrocyte hypertrophy, as assessed by quantitative histology and enzyme histochemistry. A stimulatory effect on cartilage matrix synthesis, assessed by (35)SO(4) incorporation into glycosaminoglycans, was produced only by the highest concentration of BMP-2. These BMP-2-mediated stimulatory effects were reversed by recombinant human Noggin, a glycoprotein that blocks BMP-2 action. In the absence of exogenous BMP-2, Noggin inhibited metatarsal longitudinal growth, chondrocyte proliferation, and chondrocyte hypertrophy, which suggests that endogenous BMPs stimulate longitudinal bone growth and chondrogenesis. We conclude that BMP-2 accelerates longitudinal bone growth by stimulating growth plate chondrocyte proliferation and chondrocyte hypertrophy.

Tethered-function analysis reveals that elF4E can recruit ribosomes independent of its binding to the cap structure

The cap-binding complex elF4F is involved in ribosome recruitment during the initiation phase of translation and is composed of three subunits: elF4E, -4G, and -4A. The m7GpppN cap-binding subunit eIF4E binds the N-terminal region of eIF4G, which in turn contacts eIF4A through its central and C-terminal regions. We have previously shown, through a tethered-function approach in transfected HeLa cells, that the binding of eIF4G to an mRNA is sufficient to drive productive translation (De Gregorio et al., EMBO J, 1999, 18:4865-4874). Here we exploit this approach to assess which of the other subunits of elF4F can exert this function. eIF4AI or mutant forms of eIF4E were fused to the RNA-binding domain of the lambda phage antiterminator protein N to generate the chimeric proteins lambda4A, lambda4E-102 (abolished cap binding), and lambda4E-73-102 (impaired binding to both, the cap and eIF4G). The fusion proteins were directed to a bicistronic reporter mRNA by means of interaction with a specific lambda-N binding site (boxB) in the intercistronic space. We show that lambda4E-102, but neither the double mutant lambda4E-73-102 nor lambda4A, suffices to promote translation of the downstream gene in this assay. Coimmunoprecipitation analyses confirmed that all lambda-fusion proteins are capable of interacting with the appropriate endogenous eIF4F subunits. These results reveal that eIF4E, as well as eIF4G, can drive ribosome recruitment independent of a physical link to the cap structure. In spite of its interaction with endogenous eIF4G, lambda4A does not display this property. eIF4A thus appears to supply an essential auxiliary function to eIF4F that may require its ability to cycle into and out of this complex.

The inclusion of patient testimonials in decision aids: effects on treatment choices

BACKGROUND

Decision aids often provide statistical information and patient testimonials to guide treatment choices. This raises the possibility that the testimonials will overwhelm the statistical information.

METHODS

Prospective jurors in Philadelphia County were presented with hypothetical statistical information about the percentage of angina patients who benefit from angioplasty and bypass surgery (50% and 75%, respectively). They were also given written testimonials from hypothetical patients who had benefited or not benefited from each of the two treatments. The numbers of patients benefiting and not benefiting were varied to be either proportionate to the statistical information or disproportionate. In study 1, all participants received 1 testimonial from a patient who had benefited from angioplasty and 1 from a patient who had not. Participants receiving the proportionate questionnaire version were also given 3 testimonials from patients who benefited from bypass surgery and 1 from a patient who did not, coinciding with the hypothetical statistical information. In contrast, participants receiving the disproportionate questionnaire version received only 1 testimonial from a patient who benefited from surgery and 1 from a patient who did not. In study 2, all participants received 2 examples of patients who benefited from angioplasty and 2 who did not. Participants with the proportionate questionnaire version received the same testimonials regarding surgery as in study 1. Those receiving the disproportionate questionnaire version received 2 testimonials from patients who benefited from bypass and 2 from patients who did not. Finally, a separate set of participants in study 2 received a questionnaire with no testimonials.

RESULTS

In study 1, 30% of participants receiving the disproportionate questionnaire version chose bypass surgery versus 44% of those receiving the proportionate questionnaire (P = 0.002 by chi2). In study 2, 34% of participants receiving the disproportionate questionnaire version chose bypass surgery versus 37% of those receiving the proportionate questionnaire (P = 0.59 by chi2). Of those receiving no patient testimonials, 58% chose bypass surgery.

CONCLUSIONS

The inclusion of written patient testimonials significantly influenced hypothetical treatment choices. Efforts to make the mix of positive versus negative testimonials proportionate to statistical information may, under some circumstances, affect choices in ways that cannot automatically be assumed to be optimal.

Topographical projection from the superior colliculus to the nucleus of the brachium of the inferior colliculus in the ferret: convergence of visual and auditory information

The normal maturation of the auditory space map in the deeper layers of the ferret superior colliculus (SC) depends on signals provided by the superficial visual layers, but it is unknown where or how these signals influence the developing auditory responses. Here we report that tracer injections in the superficial layers label axons with en passant and terminal boutons, both in the deeper layers of the SC and in their primary source of auditory input, the nucleus of the brachium of the inferior colliculus (nBIC). Electron microscopy confirmed that biocytin-labelled SC axons form axodendritic synapses on nBIC neurons. Injections of biotinylated dextran amine in the nBIC resulted in anterograde labelling in the deeper layers of the SC, as well as retrogradely labelled superficial and deep SC neurons, whose distribution varied systematically with the rostrocaudal placement of the injection sites in the nBIC. Topographical order in the projection from the SC to the ipsilateral nBIC was confirmed using fluorescent microspheres. We demonstrated the existence of functional SC-nBIC connections by making whole-cell current-clamp recordings from young ferret slices. Both monosynaptic and polysynaptic EPSPs were generated by electrical stimulation of either the superficial or deep SC layers. In addition to unimodal auditory units, both visual and bimodal visual-auditory units were recorded in the nBIC in vivo and their incidence was higher in juvenile ferrets than in adults. The SC-nBIC circuit provides a potential means by which visual and other sensory or premotor signals may be delivered to the nBIC to calibrate the representation of auditory space.

Can we use human judgments to determine the discount rate?

It has been suggested that the long-term discount rate for environmental goods should decrease at longer delays. One justification for this suggestion is that human judgments support it. This article presents an experiment showing that judgments concerning discount rates are internally inconsistent. These results point to potential problems with the use of judgments referenda for determining discount rates in cost-benefit analyses.

How serious are expressions of protected values?

People think that some things that they value should be protected from trade-offs with other things. For example, people think that no economic gain is great enough to justify clear-cutting old-growth forest. The authors probed the stability of these protected values (PVs) in several ways. Subjects were asked to think of counterexamples, and this had some effect on PVs. Subjects were then asked how they would resolve conflicts between 2 PVs. Resolutions did not differ from those between other values, but subjects tended to feel that conflicts between PVs did not occur in reality. Despite people's claims that PVs are unchanged by variation in quantity, expression of PVs was reduced when the magnitude or probability of the violation of a PV was smaller. In summary, PVs appear to be labile and amenable to challenge. Despite earlier concerns, apparent PVs may not always preclude the use of valuation measures in cost-effectiveness analysis or negotiated agreement on controversial issues.

How serious are expressions of protected values?

People think that some things that they value should be protected from trade-offs with other things. For example, people think that no economic gain is great enough to justify clear-cutting old-growth forest. The authors probed the stability of these protected values (PVs) in several ways. Subjects were asked to think of counterexamples, and this had some effect on PVs. Subjects were then asked how they would resolve conflicts between 2 PVs. Resolutions did not differ from those between other values, but subjects tended to feel that conflicts between PVs did not occur in reality. Despite people's claims that PVs are unchanged by variation in quantity, expression of PVs was reduced when the magnitude or probability of the violation of a PV was smaller. In summary, PVs appear to be labile and amenable to challenge. Despite earlier concerns, apparent PVs may not always preclude the use of valuation measures in cost-effectiveness analysis or negotiated agreement on controversial issues.

Determinants of priority for risk reduction: the role of worry

One hundred twenty-two members (experts) of the Society for Risk Analysis completed a mailed questionnaire and 150 nonexperts completed a similar questionnaire on the World Wide Web. Questions asked included those about priorities on personal and government action for risk reduction, badness of the risk, number of people affected, worry, and probabilities for self and others. Individual differences in mean desire for action were largely explained in terms of worry. Worry, in turn, was largely affected by probability judgments, which were lower for experts than for nonexperts. Differences across risks in the desire for action, within each subject, were also determined largely by worry and probability. Belief in expert knowledge about the risk increased worry and the priority for risk reduction. A second study involving 91 nonexperts (42 interviewed and 49 on the Web) replicated the main findings for nonexperts from the first study. Interviews also probed the determinants of worry, attitudes toward government versus personal control, and protective behaviors.

Recruiting subjects in cancer prevention and control studies

Recruitment of subjects is a critical aspect of prevention trials that is often overlooked by investigators. As a consequence, accrual time is often extended, workloads may become heavy, and resource utilization is increased in an effort to complete projects. Recruitment of healthy subjects in cancer prevention and control studies presents unique issues that need to be considered. The barriers to recruitment include participant issues, physician variables, features of the study design, and characteristics of the health care system in the United States. The authors provide their experience in overcoming these difficulties.

Catch-up growth: possible mechanisms

Many systemic diseases impair linear growth. If remission occurs, growth will often accelerate beyond the normal rate for age, a phenomenon termed "catch-up growth." As a result, final height is improved, although this recovery of adult stature is frequently incomplete. Two principal models have been proposed to explain catch-up growth. The first model postulates a central nervous system mechanism that compares actual body size with an age-appropriate set-point and then adjusts growth rate accordingly. However, there is recent evidence that growth inhibition in a single growth plate is followed by local catch-up growth, a finding not readily explained by the neuroendocrine model. Thus, a new model has been proposed that places the mechanism within the growth plate itself. According to this model, growth-inhibiting conditions decrease proliferation of growth plate stem cells, thus conserving their proliferative potential. Additional research is needed to determine whether the mechanisms governing catch-up growth are local, systemic, or both.

Are preferences for equity over efficiency in health care allocation "all or nothing"?

BACKGROUND

In a previous study we showed that within a budget constraint, most people would rather offer a less effective screening test to 100% of a Medicaid population, thereby saving 1,000 lives, than a more effective test to 50% of the population, thereby saving 1,100 lives. We present here a study exploring whether this preference for equity over efficiency persists when neither test can be offered to the entire population.

METHODS

Members of Physicians' Online and prospective jurors at the Philadelphia County Courthouse randomly received 1 of 3 questionnaires (Q1, Q2, or Q3) describing a limited budget to screen Medicaid enrollees for colon cancer. In all questionnaires, test 1 was said to save 1,000 lives, and test 2, a more effective and more expensive test, was said to save 1,100. In Q1, test 1 was offered to 100% and test 2 to 50% of the population. In Q2, the 2 tests could be offered to 50% and 25%, respectively; in Q3, to 90% and 40%, respectively. Respondents indicated which test they recommended and provided justification.

RESULTS

The majority of physicians (59%) and the general public (56%) receiving Q1 favored the less effective screening test However, of those receiving Q2, only 26% of physicians and 27% of the general public recommended the less effective screening test. And of those receiving Q3, only 38% of physicians and 28% of the general public recommended the less effective test. Justifications for these recommendations were based largely on concerns for equality of treatment among those who chose the less effective test and concerns for saving the most lives among those who preferred the more effective test.

CONCLUSIONS

Although most respondents show a preference for equity over efficiency when equity means that 100% of a population can receive a service, many fewer respondents maintain this preference when equity is no longer absolute. This result suggests that the preference for equity is sometimes "all or none."

Suppression and recovery of GH secretion after GH injection in non-GH deficient short children

OBJECTIVE

To identify the effect of exogenous GH on endogenous GH secretion in 48 non-GH deficient short children participating in a placebo-controlled trial of GH therapy on final adult height.

DESIGN

Night GH secretion (mean of levels every 20 min from 20.00 to 08.00 h) was evaluated at baseline, 6 months before starting placebo or GH (somatotropin, 0.222 mg/kg/ week, divided into 3 doses each week). At 6 months after starting injections, blood samples for GH were obtained hourly for 24 h after an injection, and every 20 min on each of the next two nights (with no additional placebo or GH injection).

RESULTS

IGF-I levels in the treatment group were elevated at 12 and 24 h but not at 36 h compared to the placebo group. Mean GH levels in the placebo group did not vary significantly among the four sampling periods. In the treatment group, the mean serum GH rose to a supraphysiological peak at an average time of 4 h after injection. Subsequently, mean GH level was significantly suppressed compared to placebo on the second night following GH injection, but returned to normal by the third night.

CONCLUSION

After 6 months of a thrice weekly GH treatment regimen in non-GH deficient short children, endogenous GH secretion was reduced from 24 to 36 h after injection compared to placebo and returned to control levels by 48 to 60 h after injection.

[Extravasation injuries and subcutaneous aspiration in children]

Complications of extravasation of intravenous fluid are not rare in pediatric practice, and their local (skin necrosis) and regional (vasculo nervous) implications can be severe. Two cases are presented in order to discuss the different treatments options and to describe the subcutaneous aspiration technique, which can be immediately efficient if proposed in a short delay.

Regulation of fetal rat bone growth by C-type natriuretic peptide and cGMP

C-type natriuretic peptide (CNP) and its high affinity receptor-B are expressed in fetal bones. Here we show that CNP accelerates longitudinal growth of fetal rat metatarsal bones in organ culture by several mechanisms. First, CNP stimulates chondrocyte proliferation in the proliferative zone as assessed by [3H]thymidine incorporation. Second, CNP stimulates cell hypertrophy as assessed by quantitative histology. Third, CNP stimulates cartilage matrix production as assessed by incorporation of 35SO4 into glycosaminoglycans. Natriuretic peptide receptor-B contains an intracellular guanylyl cyclase catalytic domain. We therefore hypothesized that cyclic GMP (cGMP) would reproduce the effects of CNP on fetal bones. Consistent with this hypothesis, we found that 8-Br-cGMP, like CNP, stimulates longitudinal growth and glycosaminoglycan synthesis. However, unlike CNP, cGMP inhibits proliferation of growth plate chondrocytes and has no effect on hypertrophy. We conclude that CNP stimulates longitudinal bone growth by increasing chondrocyte proliferation, chondrocyte hypertrophy, and cartilage matrix production. cGMP, a second messenger for CNP, reproduces some but not all of the effects of CNP, suggesting that other signal transduction mechanisms may also be involved.

Retinoic acid is a potent regulator of growth plate chondrogenesis

Vitamin A deficiency and excess both cause abnormalities in mammalian longitudinal bone growth. Because all-trans retinoic acid (RA) is synthesized from vitamin A, we hypothesized that RA regulates growth plate chondrogenesis. Consistent with this hypothesis, a single oral dose of RA reduced the height of the rat proximal tibial growth plate. To determine whether RA acts directly on growth plate, fetal rat metatarsal bones were cultured in the presence of RA. In this system, RA inhibited longitudinal bone growth by three mechanisms: 1) decreased chondrocyte proliferation, (assessed by 3H-thymidine incorporation), particularly in the proliferative zone of the growth plate; 2) decreased matrix synthesis (assessed by 35SO4 incorporation into glycosaminoglycans); and 3) decreased cell hypertrophy (determined histologically). The growth-inhibiting effects of RA were completely reversed by a retinoic acid receptor (RAR) antagonist. In the absence of exogenous RA, this antagonist accelerated bone growth, as did an RA-specific neutralizing antibody, suggesting that endogenous RA negatively regulates growth plate chondrogenesis. We conclude that RA, acting through RARs, negatively regulates longitudinal bone growth by inhibiting growth plate chondrocyte proliferation, chondrocyte hypertrophy, and matrix synthesis.

Continuing medical education for life: eight principles

Continuing medical education (CME) is being pressured to change in response to increasing and changing educational needs of practicing physicians, fostered by technical innovations, evolution of practice styles, and the reorganization of health care delivery. Leadership in the reform of CME falls primarily to the medical specialty societies in light of their traditional responsibilities for accrediting CME and maintaining professional standards. To address the need for reform, the American College of Obstetricians and Gynecologists in 1997 organized a conference to assemble CME program administrators from several medical specialties and academicians with expertise in postgraduate learning. At the conference, issues facing CME were examined. The authors, who were conference participants, state and explain eight principles that emerged from conference discussions. (For example: "Educational activities should be supportive of and coordinated with the transition to evidence-based medicine.") The principles reflect the interspecialty and interdisciplinary consensus achieved by the conference participants and can serve as useful guideposts for educators as they work to improve CME in their institutions. The authors conclude by noting the need for a more systematic and rigorously analytic approach, where CME content is determined according to assessed needs and CME is evaluated by measuring outcomes; for this to happen, CME educators and faculty must be brought up to date through training, including the use of problem-based learning. CME must also instill collegiality, interaction, and collaboration into the learning environment instead of being a solitary learning activity. Finally, CME must not only emphasize the acquisition of knowledge but also instruct physicians in the process of decision making to help them better use their knowledge as they make clinical judgments.

Autosomal dominant hypoparathyroidism associated with short stature and premature osteoarthritis

Familial hypoparathyroidism is an unusual and genetically heterogeneous group of disorders that may be isolated or may be associated with congenital or acquired abnormalities in other organs or glands. We have evaluated a family with a novel syndrome of autosomal dominant hypoparathyroidism, short stature, and premature osteoarthritis. A 74-yr-old female (generation I) presented with hypoparathyroidism, a movement disorder secondary to ectopic calcification of the cerebellum and basal ganglia, and a history of knee and hip replacements for osteoarthritis. Two members of generation II and one member of generation III were also documented with hypoparathyroidism, short stature, and premature osteoarthritis evident as early as 11 yr. Because of the known association between autosomal dominant hypoparathyroidism and activating mutations of the calcium-sensing receptor (CaR) gene, further studies were performed. Sequencing of PCR-amplified genomic DNA revealed a leucine to valine substitution at position 616 in the first transmembrane domain of the CaR, which cosegregated with the disorder. However, this amino acid sequence change did not affect the total accumulation of inositol phosphates as a function of extracellular calcium concentrations in transfected HEK-293 cells. In conclusion, a sequence alteration in the coding region of the CaR gene was identified, but is not conclusively involved in the etiology of this novel syndrome. The cosegregation of hypoparathyroidism, short stature, and osteoarthritis in this kindred does suggest a genetic abnormality involving a common molecular mechanism in parathyroid, bone, and cartilage.

[Pineal cyst in MRI: clinical symptoms and analysis]

Application of magnetic resonance imaging (MRI) in radiology allows to estimate and analyse pineal gland and pineal region pathology more precisely. We report 47 MRI brain studies of patients in whom pineal cyst was recognized as the only pathologic finding. MRI of the brain was performed because of clinical symptoms as headaches (32%), vertigo (26%) and altered behaviour (13%). Because of the common occurrence of pineal cyst in MRI brain imaging it seems to be important to decide whether these patients need neurosurgical intervention, especially if together with morphologic abnormality definite clinical symptoms exist.

Protected Values and Omission Bias

Protected values (PVs) are those that people think should not be traded off. Baron and Spranca (1997) proposed that such values result from rules concerning actions (as opposed to values for outcomes). This proposal implies that PVs should show a particularly large bias against harmful acts that undermine the value in question, as opposed to harmful omissions (omission bias). We found this correlation between PVs and omission bias in 3 experiments, using stimuli of the sort that we used before to demonstrate omission bias. In 2 experiments, we also found a weak tendency for PVs to be associated with lack of concern for the number of acts involved, which is analogous to earlier results showing an association with lack of concern for the quantity of outcomes. Finally, 1 experiment showed that some people are willing to sacrifice values to prevent losses more than they are willing to sacrifice these values for gains. Copyright 1999 Academic Press.

Safety of perioperative subcutaneous heparin for prophylaxis of venous thromboembolism in patients undergoing craniotomy

OBJECTIVE

To determine whether perioperative subcutaneous heparin is safe to use for patients undergoing craniotomy and to determine the incidence of venous thromboembolism in patients undergoing craniotomy.

METHODS

Perioperative prophylaxis with subcutaneous heparin, 5000 U every 12 hours, was begun at induction of anesthesia for craniotomy and continued for 7 days postoperatively or until the patient was ambulating. Entry criteria to the study included patient age over 18 years and no evidence of deep vein thrombosis (DVT) preoperatively as judged by lower limb duplex ultrasound. Patients were excluded if they had duplex evidence of DVT or clinical evidence of pulmonary embolus (PE) preoperatively, had hypersensitivity to heparin or related products, had sustained a penetrating head injury, or refused informed consent. Any patient undergoing craniotomy was eligible, including patients with a ruptured aneurysm or arteriovenous malformation and those with spontaneous intracranial hemorrhage. Patients underwent duplex study 1 week after surgery and 1 month of clinical follow-up. Records were also kept on 68 nonstudy patients who refused consent. All patients were treated with lower limb pneumatic compression devices.

RESULTS

One hundred six patients were treated. No differences were noted between study and nonstudy patients in some individual risk factors for DVT or PE, such as obesity, smoking, paralysis, infection, pregnancy or postpartum state, varicose veins, heart failure, or previous DVT or PE. Significantly more (43 of 106) patients in the study group had a history of risk factors for DVT or PE, particularly malignancy, however, compared with nonstudy patients (20 of 68 patients; chi2, P < 0.01). There were no differences between groups in intraoperative blood loss, transfusion requirements, or postoperative platelet counts. Four clinically significant hemorrhages occurred during surgery in patients receiving heparin. Three resulted from intraoperative aneurysm rupture and one from intraventricular bleeding during resection of an arteriovenous malformation. These events were believed to be related to known complications of these operations, not to heparin. Of the study patients, two developed symptomatic DVT and one developed a nonfatal PE during the 1-month postoperative period. One additional study patient developed DVT below the popliteal veins, which was not treated. Four study patients developed DVT 1 to 2 months after surgery. In nonstudy patients, three developed DVT and two developed PE (one fatal, one nonfatal).

CONCLUSION

Perioperative heparin may be safe to administer to patients undergoing craniotomy, but a larger study is needed to demonstrate efficacy.

[Chosen function of peripheral blood neutrophils in workers operating X-ray equipment]

Examinations were carried out in 44 persons (29 women and 15 men) who operated X-ray equipment in radiology departments. Neutrophil adherence and spontaneous migration of leukocytes were estimated in this group. Investigations' results were compared with the results in the control group. In the group of employees who operated X-ray units, the examinations were additionally performed taking sex into consideration. In the persons employed in radiology departments statistically significant reduction of neutrophil adherence was shown, which especially in the subgroup of men was observed. Statistically significant reduction of spontaneous migration area of leukocytes was revealed and it concerned both the subgroup of men and subgroup of women. On the basis of the obtained results the following conclusions were drawn: leukocyte spontaneous migration estimated in three-hour test decreases in employees who operated X-ray units; it may be used as the estimation test of influence of the X-ray on employees operating X-ray equipment when the routine tests are in the normal range.

Control of Bone Growth by Fibroblast Growth Factors

Fibroblast growth factors (FGFs) and their receptors (FGFRs) negatively regulate longitudinal bone growth. Activating FGFR3 mutations impair growth, causing human skeletal dysplasias, whereas inactivating mutations stimulate growth. Systemic administration of FGF-2 to mice stimulates bone growth at low doses but inhibits growth at high doses. In organ culture, FGF-2 inhibits growth by decreasing growth plate chondrocyte proliferation, hypertrophy and cartilage matrix synthesis. Local FGF-2 infusion accelerates ossification of growth plate cartilage. Thus, FGFs may regulate both growth plate chondrogenesis and ossification.

Determinants of spatial polarity in the growth plate

Growth of long bones occurs at the growth plate, a layer of cartilage that separates the epiphysis from the metaphysis. Growth plate exhibits spatial polarity. Proliferative chondrocytes undergo terminal differentiation when they approach the metaphyseal, but not the epiphyseal, border of the growth plate. The adjacent bone also exhibits spatial polarity. Metaphyseal, but not epiphyseal, blood vessels and bone cells invade the adjacent growth plate, remodeling it into bone. As a result, the metaphysis, but not the epiphysis, elongates over time. To determine whether cartilage polarity determines bone polarity and/or whether bone polarity determines cartilage polarity, rabbit distal ulnar growth plates were excised, inverted, and reimplanted in their original beds. Thus, cartilage polarity was inverted relative to bone polarity. Histological examination showed that the inverted cartilage polarity was maintained over time. In contrast, the polarity of the adjacent bone reversed after surgery, to match that of the cartilage. Blood vessel and bone cell invasion ceased in the metaphysis and arose in the epiphysis. Longitudinal bone growth (measured with weekly radiographs) occurred at the epiphyseal, not at the metaphyseal, surface of the growth plate. We conclude that the polarity of growth plate cartilage is determined by intrinsic factors. The cartilage polarity then determines the polarity of the adjacent bone and, consequently, the functional polarity of longitudinal bone growth.

[Angiographic findings in hereditary hemorrhagic teleangiectasia: a case study of Rendu-Osler-Weber disease]

A case of Rendu-Osler-Weber disease in 48 year old male was described. Selective arteriography of superior mesenteric artery revealed its widening (including intestine branches), numerous anastomoses in the form of microhaemangioma and fast venous return with broad superior mesenteric and portal vein.

The colonoscopic miss rate and true one-year recurrence of colorectal neoplastic polyps. Polyp Prevention Study Group

OBJECTIVE

Studies of tandem colonoscopies have reported that 15-25% of neoplastic polyps <1 cm in size and 0-6% of larger polyps are overlooked at the time of colonoscopy. We determined the miss rate and "true" 1-yr recurrence of neoplastic polyps in a population of patients reflecting a broad spectrum of different gastroenterology practice settings.

METHODS

Patient data from several sources were examined for repeat colonoscopies performed on the same patient within 120 days of each other. Examination pairs were included for analysis if both colonoscopies had good preps and reached the cecum. The miss rate was calculated by two methods: 1) a pooled rate, the total number of polyps on all second examinations divided by the total number on both examinations, and 2) a within-person rate, the average of the individual miss-rates. We estimated a "true" 1-yr recurrence rate by subtracting the proportion of patients with a missed neoplastic polyp from the proportion of patients with a neoplastic polyp found at 1 yr.

RESULTS

A total of 76 colonoscopy pairs a mean 47 days apart (range, 1-119 days) were identified from a total of approximately 15,000 examinations and used to calculate the overall miss rates. For the category "all polyps" (neoplastic and nonneoplastic polyps), 17% by the pooled method and 11% by the within-person method were missed. The corresponding rates for neoplastic polyps were 12% by the pooled method and 8% by the within-person method. A total of 17% of patients had one or more neoplastic polyps missed on the initial examination. The observed 1-yr recurrence rate was determined from 1,314 colonoscopy pairs performed a mean of 379 days apart and found to be 28% for neoplastic polyps. By comparing this to the proportion of patients with one or more missed neoplastic polyps, we found the true 1-yr recurrence of neoplastic polyps to be 11%.

CONCLUSION

There is a significant colonoscopic miss rate for neoplastic polyps and "all polyps" in clinical practice that is comparable to that previously stated in special research settings. The within-person rate more accurately reflects the true colorectal polyp miss rate for any given colonoscopic exam than does the pooled rate. The difference between the observed 1-yr recurrence rate and the proportion of patients with a missed polyp represents the true 1-yr recurrence of neoplastic polyps.

Gamma probe-guided sentinel node biopsy--optimal timing for injection

AIMS

We initiated a Phase I feasibility study using a gamma-detecting probe (GDP) and radiolabelled colloid to localize the sentinel lymph node (SLN) in breast cancer. The aim of the study was to establish the ideal timing for injection and examine any possible exclusion criteria for this method.

METHODS

Thirty breast cancer patients diagnosed by fine needle aspiration (FNA) were included in this study. All were injected with 60 MBq rhenium colloid labelled with 99mTc (Tck-17). Scintigraphy was done 20 min, 2, 6 and 25 hours post-injection. Patients were then taken to surgery where they were injected with patent blue dye. During surgery, the SLN was located with a GDP (Neoprobe Model 1000). In 28 patients, the SLN was identified by scintigraphy 2 hours after injection, identical to the images seen after 24 hours.

RESULTS

In all 28 patients, the SLN was found by the GDP during surgery. In 26 patients the SLN was dyed blue. The two patients with no SLN localization had received prior radiation. Pathology disclosed SLNs with metastases in seven patients. Two patients had a negative SLN but had an axillary lymph node replaced by tumour.

CONCLUSIONS

Two to 24 hours prior to surgery is suitable timing for injection. Previous radiotherapy predicts failure for this procedure. Further studies are needed to find the exact false-negative rate of this method for breast cancer.

Generation and subcellular distribution of histamine in human blood monocytes and monocyte subsets

OBJECTIVE AND DESIGN

This study was designed to establish the sites of formation and storage of histamine and histidine decarboxylase (HDC) in human monocytes and two of their subsets.

MATERIALS AND METHODS

The experiments were carried out using monocytes from buffy coats of healthy blood donors. Histamine was quantitated by RIA, HDC activity by the formation of histamine.

RESULTS

The monocyte subtype RM3/1 contained significantly more histamine than the subset 27E10 (0.041+/-0.025 vs. 0.005+/-0.004 pg/cell, p < 0.05) and also more HDC activity and HDC mRNA. After fractionation of monocyte homogenates in a discontinuous Percoll gradient or by differential centrifugation more than 80% of both, HDC activity and histamine, were recovered from the cytosolic fractions. About 50% of this histamine was found to be bound to proteins.

CONCLUSIONS

In monocytes histamine and HDC are colocalized in the cytoplasm indicating a subcellular distribution different from mast cells or basophils. The data also show that histamine is synthesized by the monocytes themselves.

Attitudes of obstetricians and gynecologists toward hormone replacement therapy

OBJECTIVE

To determine the attitudes of obstetricians and gynecologists toward hormone replacement therapy (HRT), and the beliefs and intuitions that affected those attitudes.

DESIGN

A questionnaire was sent to 1,000 gynecologists in the United States; 328 replies were received. The questionnaire asked about effects of HRT, practices concerning HRT, and decisions in hypothetical scenarios.

RESULTS

The respondents strongly favored HRT, and they were well informed about its effects on osteoporosis, cardiovascular disease, and breast cancer. They were aware of conflicting findings concerning breast cancer. The strength of their recommendation of HRT was sensitive to patient differences in risk factors. The respondents also showed four biases hypothesized to cause resistance to HRT: omission bias (more concern about harmful acts than harmful omissions); proportionality bias (attention to relative risk rather than risk differences); naturalness bias (preference for the natural); and ambiguity (avoiding options with missing information). Proportion bias, naturalness bias, and (weakly) omission bias were related to less favorable attitudes toward HRT.

CONCLUSION

Although specialists are highly favorable toward HRT in general, some negativity toward HRT may result from decision biases.

Molecular biology and clinical importance of the Ca(2+)-sensing receptor

The Ca(2+)-sensing receptor (CaR) is a member of the seven-transmembrane domain, G protein-coupled receptor super-family. In the parathyroid gland, it mediates the inhibitory effects of extracellular Ca2+ on the secretion of parathyroid hormone. In the kidney, activation of the CaR causes decreased reabsorption of Ca2+ from the tubular lumen. Mutations in the CaR gene produce abnormalities of Ca2+ homeostasis. Heterozygous loss-of-function mutations cause familial hypocalciuric hypercalcemia. Homozygous loss-of-function mutations cause neonatal severe hyperparathyroidism. In contrast, gain-of-function CaR mutations result in autosomal dominant and sporadic hypoparathyroidism. The resulting hypoparathyroidism and hypocalcemia can range from asymptomatic to life-threatening. Patients with hypocalcemia due to CaR mutations also show disproportionate hypercalciuria that may increase the risk of nephrocalcinosis, nephrolithiasis, and renal insufficiency.

Heterotypic recognition of recombinant FMDV proteins by bovine T-cells: the polymerase (P3Dpol) as an immunodominant T-cell immunogen

In this study we have examined the recognition of VP0, VP1, VP2, VP3 and P3Dpol by PBMC and CD4+ T-cells from infected, vaccinated-challenged, and multiply-vaccinated (O1, A24, C1 or ASIA1) cattle using recombinant proteins of an O1 serotype virus. The structural protein VP1 was recognised in an homotypic context whereas VP2, VP3, VP4 and P3Dpol were also recognised by T-cells from animals exposed to heterotypic viruses. Only the non-structural protein P3Dpol was consistently recognised by T-cells from the majority of animals examined and heterotypic recognition correlated with the presence of serologically detectable P3Dpol in purified virus. Thus, P3Dpol is a major cross-reactive immunodeterminant of FMDV, eliciting heterotypic T-cell responses and, therefore, with possible potential for inclusion in a subunit vaccine.

Activating mutations of the Ca2+-sensing receptor

The Ca2+-sensing receptor (CaR) is a member of the seven-transmembrane domain, G-protein-coupled receptor superfamily. It is expressed in parathyroid, kidney, and other tissues. In parathyroid, activation of the CaR by extracellular Ca2+ negatively regulates the secretion of parathyroid hormone. In the the thick ascending limb of Henle's loop, receptor activation decreases renal reabsorption of Ca2+. Heterozygous inactivating mutations of the CaR cause familial benign hypocalciuric hypercalcemia while homozygous inactivating mutations cause neonatal severe hyperparathyroidism. Conversely, activating mutations of the CaR cause autosomal dominant and sporadic hypoparathyroidism. Affected individuals have hypocalcemia which ranges from mild and asymptomatic to life-threatening. They also show a greater tendency to hypercalciuria than do other patients with hypoparathyroidism. Most, but not all, of the reported activating mutations occur in the amino-terminal, extracellular domain of the receptor. When expressed in cultured cells, mutant receptors can show both increased receptor sensitivity to Ca2+ and increased maximal signal transduction capacity.

Use of an ultrasensitive recombinant cell bioassay to determine estrogen levels in girls with precocious puberty treated with a luteinizing hormone-releasing hormone agonist

Although treatment of girls with precocious puberty should ideally restore estradiol levels to the normal prepubertal range, treatment effectiveness has usually been monitored by gonadotropin levels because estradiol RIAs have lacked sufficient sensitivity to monitor treatment effectiveness. We hypothesized that a recently developed ultrasensitive recombinant cell bioassay for estradiol would have sufficient sensitivity to demonstrate a dose-dependent suppression of estradiol during LH-releasing hormone agonist treatment and to determine whether currently used doses are able to suppress estradiol levels to the normal prepubertal range. Twenty girls with central precocious puberty were assigned randomly to receive deslorelin for 9 months at a dose of 1, 2, or 4 micrograms/ kg.day. A significant dose-response relationship was observed, with mean +/- SD estradiol levels of 16.7 +/- 6.1, 7.9 +/- 1.6, and 6.5 +/- 0.7 pmol/L at the doses of 1, 2, and 4 micrograms/kg.day, respectively (P < 0.01). The highest dose suppressed estradiol levels to just above the 95% confidence limits for normal prepubertal girls (< 0.07-6.3 pmol/L). We conclude that the ultrasensitive bioassay for estradiol has sufficient sensitivity for monitoring the response to LH-releasing hormone agonist treatment of central precocious puberty. Additionally, the observation that the deslorelin dose of 4 micrograms/kg.day did not fully restore estradiol levels to the normal prepubertal range suggests that some girls with precocious puberty may require higher doses to receive the maximal benefit of treatment. We suggest that restoration of estradiol levels to the normal prepubertal range should be the ultimate biochemical measure of efficacy, as estradiol is the key hormone that accelerates growth rate, bone maturation rate, and breast development in girls with precocious puberty.

Evaluation of an attenuation correction method for thallium-201 myocardial perfusion tomographic imaging of patients with low likelihood of coronary artery disease

BACKGROUND

Image artifacts caused by nonuniform photon attenuation are a source of error in interpretation of images during myocardial perfusion single photon emission computed tomography (SPECT). A newly introduced attenuation correction method was evaluated for improvement in image homogeneity during 201Tl SPECT. The method was assessed with a cardiac phantom and in examinations of 42 patients (29 men) with a low likelihood of coronary disease.

METHODS AND RESULTS

Simultaneous transmission-emission SPECT was performed with a moving collimated 153Gd line source synchronized with a moving electronic acquisition window for transmission imaging and a novel variable-width electronic exclusion window for emission imaging designed to avoid transmission-to-emission cross talk. The resulting uncorrected and corrected polar maps were analyzed visually and divided into 31 segments for quantitative analysis. Visual analysis of the color-coded mean polar maps showed clear improvement in homogeneity after correction among the phantom, male patients, female patients, and 42 patients combined at stress and redistribution. The male and female mean polar maps showed very little differences in regional count distribution after correction. Quantitative analysis of the mean polar maps showed the following mean segmental counts (%SD) before and after attenuation correction: phantom 88 (9) to 90 (7.5), P = .00005; men at stress 83 (10) to 88 (6), P = .0007, and at redistribution 84 (8) to 88 (6), P = .01; women at stress 86 (7) to 90 (5), P = .0002, and at redistribution 87 (5) to 88 (7), P = .3; patients combined at stress 84 (8) to 88 (6), P = .0004, and at redistribution 85 (7) to 87 (7), P = .03. Inferior/anterior count ratio for men at stress increased after correction from 0.82 to 0.99 and septal/lateral count ratio from 0.94 to 1.02. Inferior/anterior count ratio for men at redistribution increased from 0.86 to 1.06 and septal/lateral count ratio from 0.97 to 1.04. Inferior/anterior count ratio for women at stress increased from 0.95 to 1.03 and septal/lateral count ratio from 0.93 to 1.00. Inferior/anterior count ratio for women at redistribution increased from 1.04 to 1.10, and septal/lateral count ratio decreased from 1.02 to 1.00.

CONCLUSION

Improvement in image homogeneity was demonstrated with this attenuation correction method with a cardiac phantom and for patients with low likelihood of coronary artery disease. The slight relative increase in inferior wall counts at redistribution was most likely caused by scatter from the relatively higher liver activity compared with the situation during stress and emphasizes the need for scatter correction. The close similarity in count distribution for the mean male and female polar maps supports use of a sex-independent normal database for quantitative analysis. The reduced variation in corrected images from patient to patient implies increased accuracy for detection of myocardial defects.

Immunohistochemical demonstration of beta-naphthoflavone-inducible cytochrome P450 1A1/1A2 in rat intrahepatic biliary epithelial cells

Although intrahepatic biliary epithelial cells are targets for certain hepatotoxic chemicals, including some procarcinogens, their ability to monooxygenate, and thereby bioactivate and inactivate xenobiotics, remains to be established. Thus, the present study was undertaken to immunohistochemically determine if cytochrome P450 (CYP) 1A1/1A2 is present and can be induced within these nonparenchymal liver cells. Immunoperoxidase and immunofluorescent staining for CYP1A1/1A2 was detected within intrahepatic biliary epithelial cells as well as hepatocytes of control rats and was markedly enhanced in both cell types by beta-naphthoflavone (BNF). Color confocal laser microscopic analyses of dual immunofluorescent staining for CYP1A1/1A2 and cytokeratins 6 and 9 (56 and 64 kd, respectively) provided unequivocal evidence for the presence and induction of CYP1A1/1A2 within intrahepatic bile duct epithelia. Moreover, microdensitometric analyses of immunoperoxidase staining intensities for CYP1A1/1A2 revealed that intrahepatic biliary epithelial cells of control rats contain 44%, 56%, and 58% as much CYP1A1/1A2 as do centrilobular, midzonal, and periportal hepatocytes, respectively. These analyses further revealed that BNF increased the content of CYP1A1/1A2 in biliary epithelial cells by approximately 120%, while CYP1A1/1A2 levels in centrilobular, midzonal, and periportal hepatocytes were increased by 82%, 159%, and 160%, respectively. The results of this study represent the first in situ demonstration that mammalian intrahepatic biliary epithelial cells contain a CYP isoform, and further that CYP1A1/1A2 can be induced in these cells by BNF. These findings therefore indicate that intrahepatic biliary epithelial cells can oxidatively metabolize xenobiotics in situ and that their ability to bioactivate and inactivate xenobiotics can be significantly enhanced by CYP1A1/1A2 induction.

Effects of fibroblast growth factor-2 on longitudinal bone growth

In vivo, fibroblast growth factor-2 (FGF-2) inhibits longitudinal bone growth. Similarly, activating FGF receptor 3 mutations impair growth in achondroplasia and thanatophoric dysplasia. To investigate the underlying mechanisms, we chose a fetal rat metatarsal organ culture system that would maintain growth plate histological architecture. Addition of FGF-2 to the serum-free medium inhibited longitudinal growth. We next assessed each major component of longitudinal growth: proliferation, cellular hypertrophy, and cartilage matrix synthesis. Surprisingly, FGF-2 stimulated proliferation, as assessed by [3H]thymidine incorporation. However, autoradiographic studies demonstrated that this increased proliferation occurred only in the perichondrium, whereas decreased labeling was seen in the proliferative and epiphyseal chondrocytes. FGF-2 also caused a marked decrease in the number of hypertrophic chondrocytes. To assess cartilage matrix synthesis, we measured 35SO4 incorporation into newly synthesized glycosaminoglycans. Low concentrations (10 ng/ml) of FGF-2 stimulated cartilage matrix production, but high concentrations (1000 ng/ml) inhibited matrix production. We conclude that FGF-2 inhibits longitudinal bone growth by three mechanisms: decreased growth plate chondrocyte proliferation, decreased cellular hypertrophy, and, at high concentrations, decreased cartilage matrix production. These effects may explain the impaired growth seen in patients with achondroplasia and related skeletal dysplasias.

Underestimation of extent and severity of coronary artery disease by dipyridamole stress thallium-201 single-photon emission computed tomographic myocardial perfusion imaging in patients taking antianginal drugs

OBJECTIVES

This study evaluated the diagnostic value of dipyridamole plus low level treadmill exercise (dipyridamole stress) thallium-201 single-photon emission computed tomography (SPECT) in patients taking antianginal drugs.

BACKGROUND

Dipyridamole stress is the major substitute for maximal exercise in patients referred for myocardial perfusion imaging. Although antianginal drugs are commonly suspended before exercise, dipyridamole stress is usually performed without discontinuing these drugs.

METHODS

Twenty-six patients underwent two dipyridamole perfusion studies: the first without (SPECT-1) and the second with (SPECT-2) antianginal treatment. Twenty-one patients (81%) received calcium antagonists, 19 (73%) received nitrates, and 8 (31%) received beta-blockers. Eighteen of the patients underwent coronary angiography. Data are presented as the mean value +/- SD.

RESULTS

Visual scoring yielded significantly larger and more severe reversible perfusion defects for SPECT-1 than for SPECT-2. Quantitative analysis showed larger perfusion defects on stress images of SPECT-1 in the left anterior descending coronary artery (LAD) (25 +/- 21% vs. 17 +/- 15%, p = 0.003), left circumflex coronary artery (LCx) (56 +/- 35% vs. 48 +/- 36%, p = 0.03) and right coronary artery (RCA) (36 +/- 27% vs. 25 +/- 24%, p = 0.008) territories. Individual vessel sensitivities in the LAD, LCx and RCA territories were 93%, 79% and 100% for SPECT-1 and 64%, 50% and 70% for SPECT-2, respectively. These differences were highly significant for the LAD (p = 0.004) and LCx (p = 0.00004) territories. The overall individual vessel sensitivity of SPECT-1 was significantly higher than that of SPECT-2 (92% vs. 62%, p = 0.000003). Specificity was not significantly different in SPECT-1 compared with SPECT-2 (80% and 93%, p = 0.33).

CONCLUSIONS

Continued use of antianginal drugs before dipyridamole plus low level treadmill exercise thallium-201 SPECT may reduce the extent and severity of myocardial perfusion defects, resulting in underestimation of coronary artery disease.

The construction flagperson: a target for injury

A road construction 'flagger' is a construction crew member whose responsibility it is to safely co-ordinate vehicle traffic through road worksites. Flaggers are suffering injuries and fatalities at the worksite as a result of being struck by moving vehicles, both construction and commuter. These incidents are largely preventable with a more defensive flagger training programme. A cross-Canada provincial survey of occupational health and safety organizations revealed no national co-ordination and standardization in flagperson training. Statistics concerning flagger injury and fatality are disjointed and incomplete, and as such are not useful for evaluating and validating training and job performance. We recommend a revisiting of flagperson training standards and that greater effort is taken in gathering data specifically on flagger injuries and fatalities.