DNA replication, transcription, and H3K56 acetylation regulate copy number and stability at tandem repeats

Tandem repeats are inherently unstable and exhibit extensive copy number polymorphisms. Despite mounting evidence for their adaptive potential, the mechanisms associated with regulation of the stability and copy number of tandem repeats remain largely unclear. To study copy number variation at tandem repeats, we used two well-studied repetitive arrays in the budding yeast genome, the ribosomal DNA (rDNA) locus, and the copper-inducible CUP1 gene array. We developed powerful, highly sensitive, and quantitative assays to measure repeat instability and copy number and used them in multiple high-throughput genetic screens to define pathways involved in regulating copy number variation. These screens revealed that rDNA stability and copy number are regulated by DNA replication, transcription, and histone acetylation. Through parallel studies of both arrays, we demonstrate that instability can be induced by DNA replication stress and transcription. Importantly, while changes in stability in response to stress are observed within a few cell divisions, a change in steady state repeat copy number requires selection over time. Further, H3K56 acetylation is required for regulating transcription and transcription-induced instability at the CUP1 array, and restricts transcription-induced amplification. Our work suggests that the modulation of replication and transcription is a direct, reversible strategy to alter stability at tandem repeats in response to environmental stimuli, which provides cells rapid adaptability through copy number variation. Additionally, histone acetylation may function to promote the normal adaptive program in response to transcriptional stress. Given the omnipresence of DNA replication, transcription, and chromatin marks like histone acetylation, the fundamental mechanisms we have uncovered significantly advance our understanding of the plasticity of tandem repeats more generally.

The role of gene dosage in budding yeast centrosome scaling and spontaneous diploidization

Ploidy is the number of whole sets of chromosomes in a species. Ploidy is typically a stable cellular feature that is critical for survival. Polyploidization is a route recognized to increase gene dosage, improve fitness under stressful conditions and promote evolutionary diversity. However, the mechanism of regulation and maintenance of ploidy is not well characterized. Here, we examine the spontaneous diploidization associated with mutations in components of the Saccharomyces cerevisiae centrosome, known as the spindle pole body (SPB). Although SPB mutants are associated with defects in spindle formation, we show that two copies of the mutant in a haploid yeast favors diploidization in some cases, leading us to speculate that the increased gene dosage in diploids ‘rescues’ SPB duplication defects, allowing cells to successfully propagate with a stable diploid karyotype. This copy number-based rescue is linked to SPB scaling: certain SPB subcomplexes do not scale or only minimally scale with ploidy. We hypothesize that lesions in structures with incompatible allometries such as the centrosome may drive changes such as whole genome duplication, which have shaped the evolutionary landscape of many eukaryotes.

Ploidy is the number of whole sets of chromosomes in a species. Most eukaryotes alternate between a diploid (two copy) and haploid (one copy) state during their life and sexual cycle. However, as part of normal human development, specific tissues increase their DNA content. This gain of entire sets of chromosomes is known as polyploidization, and it is observed in invertebrates, plants and fungi, as well. Polyploidy is thought to improve fitness under stressful conditions and promote evolutionary diversity, but how ploidy is determined is poorly understood. Here, we use budding yeast to investigate mechanisms underlying the ploidy of wild-type cells and specific mutants that affect the centrosome, a conserved structure involved in chromosome segregation during cell division. Our work suggests that different scaling relationships (allometry) between the genome and cellular structures underlies alterations in ploidy. Furthermore, mutations in cellular structures with incompatible allometric relationships with the genome may drive genomic changes such duplications, which are underly the evolution of many species including both yeasts and humans.

Translation of small downstream ORFs enhances translation of canonical main open reading frames

In addition to canonical open reading frames (ORFs), thousands of translated small ORFs (containing less than 100 codons) have been identified in untranslated mRNA regions (UTRs) across eukaryotes. Small ORFs in 5′ UTRs (upstream (u)ORFs) often repress translation of the canonical ORF within the same mRNA. However, the function of translated small ORFs in the 3′ UTRs (downstream (d)ORFs) is unknown. Contrary to uORFs, we find that translation of dORFs enhances translation of their corresponding canonical ORFs. This translation stimulatory effect of dORFs depends on the number of dORFs, but not the length or peptide they encode. We propose that dORFs represent a new, strong, and universal translation regulatory mechanism in vertebrates.

Hypo-osmotic-like stress underlies general cellular defects of aneuploidy

Aneuploidy, which refers to unbalanced chromosome numbers, represents a class of genetic variation that is associated with cancer, birth defects and eukaryotic micro-organisms1-4. Whereas it is known that each aneuploid chromosome stoichiometry can give rise to a distinct pattern of gene expression and phenotypic profile4,5, it remains a fundamental question as to whether there are common cellular defects that are associated with aneuploidy. Here we show the existence in budding yeast of a common aneuploidy gene-expression signature that is suggestive of hypo-osmotic stress, using a strategy that enables the observation of common transcriptome changes of aneuploidy by averaging out karyotype-specific dosage effects in aneuploid yeast-cell populations with random and diverse chromosome stoichiometry. Consistently, aneuploid yeast exhibited increased plasma-membrane stress that led to impaired endocytosis, and this defect was also observed in aneuploid human cells. Thermodynamic modelling showed that hypo-osmotic-like stress is a general outcome of the proteome imbalance that is caused by aneuploidy, and also predicted a relationship between ploidy and cell size that was observed in yeast and aneuploid cancer cells. A genome-wide screen uncovered a general dependency of aneuploid cells on a pathway of ubiquitin-mediated endocytic recycling of nutrient transporters. Loss of this pathway, coupled with the endocytic defect inherent to aneuploidy, leads to a marked alteration of intracellular nutrient homeostasis.

County-level access to opioid use disorder medications in medicare Part D (2010-2015)

OBJECTIVE

To identify geographic disparities in access to opioid use disorder (OUD) treatment medications and county demographic and economic characteristics associated with access to buprenorphine and oral naltrexone prescribers in Medicare Part D.

DATA SOURCES/STUDY SETTING

We utilized data from the Medicare Part D Prescription Drug Event Standard Analytic File (2010-2015).

STUDY DESIGN/DATA COLLECTION

We used logistic regression to examine county-level access to OUD medication prescribers.

PRINCIPAL FINDINGS

There was a 5.6 percentage point increase in counties with access to an OUD prescriber over the study period. However, in 2015, 60 percent of US counties lacked access to a Medicare Part D buprenorphine prescriber and over 75 percent lacked access to an oral naltrexone prescriber. Increased access to OUD prescribers was largely concentrated in urban counties. Results of logistic regression indicate regional differences and potential racial disparities in access to OUD prescribers.

CONCLUSIONS

To improve access to buprenorphine and naltrexone treatment for Medicare Part D enrollees, CMS may consider implementing educational and training initiatives focused on OUD treatment, offering training to obtain a buprenorphine waiver at no cost to providers, and sending targeted information to providers in low OUD treatment capacity areas.

Aneuploidy as a cause of impaired chromatin silencing and mating-type specification in budding yeast

Aneuploidy and epigenetic alterations have long been associated with carcinogenesis, but it was unknown whether aneuploidy could disrupt the epigenetic states required for cellular differentiation. In this study, we found that ~3% of random aneuploid karyotypes in yeast disrupt the stable inheritance of silenced chromatin during cell proliferation. Karyotype analysis revealed that this phenotype was significantly correlated with gains of chromosomes III and X. Chromosome X disomy alone was sufficient to disrupt chromatin silencing and yeast mating-type identity as indicated by a lack of growth response to pheromone. The silencing defect was not limited to cryptic mating type loci and was associated with broad changes in histone modifications and chromatin localization of Sir2 histone deacetylase. The chromatin-silencing defect of disome X can be partially recapitulated by an extra copy of several genes on chromosome X. These results suggest that aneuploidy can directly cause epigenetic instability and disrupt cellular differentiation.

Analysis of membrane proteins localizing to the inner nuclear envelope in living cells

Understanding the protein composition of the inner nuclear membrane (INM) is fundamental to elucidating its role in normal nuclear function and in disease; however, few tools exist to examine the INM in living cells, and the INM-specific proteome remains poorly characterized. Here, we adapted split green fluorescent protein (split-GFP) to systematically localize known and predicted integral membrane proteins in Saccharomyces cerevisiae to the INM as opposed to the outer nuclear membrane. Our data suggest that components of the endoplasmic reticulum (ER) as well as other organelles are able to access the INM, particularly if they contain a small extraluminal domain. By pairing split-GFP with fluorescence correlation spectroscopy, we compared the composition of complexes at the INM and ER, finding that at least one is unique: Sbh2, but not Sbh1, has access to the INM. Collectively, our work provides a comprehensive analysis of transmembrane protein localization to the INM and paves the way for further research into INM composition and function.

Karyotyping human and mouse cells using probes from single-sorted chromosomes and open source software

Multispectral karyotyping analyzes all chromosomes in a single cell by labeling them with chromosome-specific probes conjugated to unique combinations of fluorophores. Currently available multispectral karyotyping systems require the purchase of specialized equipment and reagents. However, conventional laser scanning confocal microscopes that are capable of separating multiple overlapping emission spectra through spectral imaging and linear unmixing can be utilized for classifying chromosomes painted with multicolor probes. Here, we generated multicolor chromosome paints from single-sorted human and mouse chromosomes and developed the Karyotype Identification via Spectral Separation (KISS) analysis package, a set of freely available open source ImageJ tools for spectral unmixing and karyotyping. Chromosome spreads painted with our multispectral probe sets can be imaged on widely available spectral laser scanning confocal microscopes and analyzed using our ImageJ tools. Together, our probes and software enable academic labs with access to a laser-scanning spectral microscope to perform multicolor karyotyping in a cost-effective manner.

Targeting the adaptability of heterogeneous aneuploids

Aneuploid genomes, characterized by unbalanced chromosome stoichiometry (karyotype), are associated with cancer malignancy and drug resistance of pathogenic fungi. The phenotypic diversity resulting from karyotypic diversity endows the cell population with superior adaptability. We show here, using a combination of experimental data and a general stochastic model, that the degree of phenotypic variation, thus evolvability, escalates with the degree of overall growth suppression. Such scaling likely explains the challenge of treating aneuploidy diseases with a single stress-inducing agent. Instead, we propose the design of an "evolutionary trap" (ET) targeting both karyotypic diversity and fitness. This strategy entails a selective condition "channeling" a karyotypically divergent population into one with a predominant and predictably drugable karyotypic feature. We provide a proof-of-principle case in budding yeast and demonstrate the potential efficacy of this strategy toward aneuploidy-based azole resistance in Candida albicans. By analyzing existing pharmacogenomics data, we propose the potential design of an ET against glioblastoma.

Delayed correlation of mRNA and protein expression in rapamycin-treated cells and a role for Ggc1 in cellular sensitivity to rapamycin

To identify new molecular targets of rapamycin, an anticancer and immunosuppressive drug, we analyzed temporal changes in yeast over 6 h in response to rapamycin at the transcriptome and proteome levels and integrated the expression patterns with functional profiling. We show that the integration of transcriptomics, proteomics, and functional data sets provides novel insights into the molecular mechanisms of rapamycin action. We first observed a temporal delay in the correlation of mRNA and protein expression where mRNA expression at 1 and 2 h correlated best with protein expression changes after 6 h of rapamycin treatment. This was especially the case for the inhibition of ribosome biogenesis and induction of heat shock and autophagy essential to promote the cellular sensitivity to rapamycin. However, increased levels of vacuolar protease could enhance resistance to rapamycin. Of the 85 proteins identified as statistically significantly changing in abundance, most of the proteins that decreased in abundance were correlated with a decrease in mRNA expression. However, of the 56 proteins increasing in abundance, 26 were not correlated with an increase in mRNA expression. These protein changes were correlated with unchanged or down-regulated mRNA expression. These proteins, involved in mitochondrial genome maintenance, endocytosis, or drug export, represent new candidates effecting rapamycin action whose expression might be post-transcriptionally or post-translationally regulated. We identified GGC1, a mitochondrial GTP/GDP carrier, as a new component of the rapamycin/target of rapamycin (TOR) signaling pathway. We determined that the protein product of GGC1 was stabilized in the presence of rapamycin, and the deletion of the GGC1 enhanced growth fitness in the presence of rapamycin. A dynamic mRNA expression analysis of Deltaggc1 and wild-type cells treated with rapamycin revealed a key role for Ggc1p in the regulation of ribosome biogenesis and cell cycle progression under TOR control.

A comprehensive library of histone mutants identifies nucleosomal residues required for H3K4 methylation

Methylation of histone 3 lysine 4 (H3K4) by yeast Set1-COMPASS requires prior monoubiquitination of histone H2B. To define whether other residues within the histones are also required for H3K4 methylation, we systematically generated a complete library of the alanine substitutions of all of the residues of the four core histones in Saccharomyces cerevisiae. From this study we discovered that 18 residues within the four histones are essential for viability on complete growth media. We also identified several cis-regulatory residues on the histone H3 N-terminal tail, including histone H3 lysine 14 (H3K14), which are required for normal levels of H3K4 trimethylation. Several previously uncharacterized trans-regulatory residues on histones H2A and H2B form a patch on nucleosomes and are required for methylation mediated by COMPASS. This library will be a valuable tool for defining the role of histone residues in processes requiring chromatin.

An inexpensive gel electrophoresis-based polymerase chain reaction method for quantifying mRNA levels

In order to engage their students in a core methodology of the new genomics era, an ever-increasing number of faculty at primarily undergraduate institutions are gaining access to microarray technology. Their students are conducting successful microarray experiments designed to address a variety of interesting questions. A next step in these teaching and research laboratory projects is often validation of the microarray data for individual selected genes. In the research community, this usually involves the use of real-time polymerase chain reaction (PCR), a technology that requires instrumentation and reagents that are prohibitively expensive for most undergraduate institutions. The results of a survey of faculty teaching undergraduates in classroom and research settings indicate a clear need for an alternative approach. We sought to develop an inexpensive and student-friendly gel electrophoresis-based PCR method for quantifying messenger RNA (mRNA) levels using undergraduate researchers as models for students in teaching and research laboratories. We compared the results for three selected genes measured by microarray analysis, real-time PCR, and the gel electrophoresis-based method. The data support the use of the gel electrophoresis-based method as an inexpensive, convenient, yet reliable alternative for quantifying mRNA levels in undergraduate laboratories.

Idiopathic hyperammonemia following an unrelated cord blood transplant for mucopolysaccharidosis I

Bone marrow transplantation (BMT) has been shown to reverse or stabilize some manifestations of mucopolysaccharidosis I (Hurler syndrome). Idiopathic hyperammonemia (IHA) is a rare complication of solid organ and BMT that is characterized by elevated serum ammonia, normal liver enzymes, and abrupt onset of neurologic deterioration. We present the case of a 14-month-old male patient with Hurler syndrome who developed fatal IHA (ammonia = 2297 micromol/L) 31 days after a cord blood transplant. A complete autopsy was performed, with examination of both frozen and formalin-fixed paraffin-embedded (FFPE) tissues using a variety of special stains and electron microscopy. Hyperammonemia was documented by analysis of antemortem serum and postmortem cerebrospinal and vitreous fluid. Other causes of hyperammonemia, including Reye syndrome, were excluded. Histologic changes included centrilobular microvesicular steatosis of the liver and storage product present in multiple organs. The highly water-soluble mucopolysaccharide (MPS) storage product was best identified by colloidal iron staining of FFPE and unfixed air-dried fresh frozen liver sections. Alcian blue stains failed to convincingly demonstrate MPS in any of the liver sections. This is the first published report, to our knowledge, of IHA in a posttransplant patient younger than 18 years old or following transplantation for Hurler syndrome. Demonstration of the hepatic centrilobular microvesicular steatosis characteristic of IHA was complicated by the diffuse storage of MPS within the liver. MPS storage can be best detected in the liver using colloidal iron staining. Oil-red-O staining may be useful to document microvesicular steatosis in cases with a clinical history of hyperammonemia following solid organ or BMT. Determining if certain subsets of children are at increased risk for IHA requires further study.

Testing efficacy with detection controlled estimation: an application to telemedicine

Detection controlled estimation (DCE) is a powerful new econometric estimator in the family of missing data estimators. By collecting measures from a variety of inspectors or inspection technologies, DCE is able to make inferences about the entire population, even when that population is not directly observed. Using this innovative method, we were able to assess whether telemedicine technology could be substituted for in-person visits when providing maintenance care for patients with hypertension. Our findings indicate that there is no support for the proposition that telemedicine is less effective than in-person visits for determining whether patients have high blood pressure. Indeed, our results imply that telemedicine misses 7% fewer cases of high blood pressure than in-person visits do. The results of this study indicate that DCE may be an effective tool for use in cost-effectiveness or cost-benefit analysis in health care.

Predictors of costs of caring for elderly patients discharged with heart failure

BACKGROUND

Investments in programs to improve outcomes and reduce readmissions for patients who survive hospitalization with heart failure will be economically most favorable for those who have the highest risk. Little information is available, however, to stratify the risk of these patients incurring costs after discharge. In this study, we sought to determine correlates of costs in a representative sample of patients with heart failure in the 6 months after discharge.

METHODS

We reviewed medical records of 2181 patients aged > or = 65 years who were discharged alive from 18 Connecticut hospitals in 1994 and 1995 with a principal discharge diagnosis of heart failure. Outcomes 6 months after discharge, including all-cause readmission and cost, heart failure-related readmission and cost, and death, were obtained from the Medicare administrative database. A 2-stage sample selection model was used to identify the independent correlates of cost. Risk scores were calculated to identify subsets of patients at risk for generating high costs.

RESULTS

On average, patients discharged with heart failure incurred costs of $2388 resulting from heart failure-related admissions and $7101 resulting from admissions from any cause during the 6 months after discharge. An average admission for heart failure cost $7174, whereas an admission resulting from any cause cost $8589. The multivariate models explained 7% of the variation in cost, although clinical characteristics such as recent heart failure admissions, kidney failure, and hypertension were significant independent correlates of increased cost. Older age and a history of stroke were independently associated with decreased cost. Patients without any of the risk factors associated with increased costs still incurred $1500 to $5000, on average, in the 6 months after discharge.

CONCLUSIONS

Patients with heart failure generate substantial hospital costs in the 6 months after discharge. Given the emerging evidence for effective programs to reduce readmission, investments in interventions that produce even modest reductions in risk would be economically favorable.

Quality of medical care and excess mortality in older patients with mental disorders

BACKGROUND

This study investigated whether differences in quality of medical care might explain a portion of the excess mortality associated with mental disorders in the year after myocardial infarction.

METHODS

This study examined a national cohort of 88 241 Medicare patients 65 years and older who were hospitalized for clinically confirmed acute myocardial infarction. Proportional hazard models compared the association between mental disorders and mortality before and after adjusting 5 established quality indicators: reperfusion, aspirin, beta-blockers, angiotensin-converting enzyme inhibitors, and smoking cessation counseling. All models adjusted for eligibility for each procedure, demographic characteristics, cardiac risk factors and history, admission characteristics, left ventricular function, hospital characteristics, and regional factors.

RESULTS

After adjusting for the potential confounding factors, presence of any mental disorder was associated with a 19% increase in 1-year risk of mortality (hazard ratios [HR], 1.19; 95% confidence interval [CI], 1.04-1.36). After adding the 5 quality measures to the model, the association was no longer significant (HR, 1.10; 95% CI, 0.96-1.26). Similarly, while schizophrenia (HR, 1.34; 95% CI, 1.01-1.67) and major affective disorders (HR, 1.11; 95% CI, 1.02-1.20) were each initially associated with increased mortality, after adding the quality variables, neither schizophrenia (HR, 1.23; 95% CI, 0.86-1.60) nor major affective disorder (HR, 1.05; 95% CI, 0.87-1.23) remained a significant predictor.

CONCLUSIONS

Deficits in quality of medical care seemed to explain a substantial portion of the excess mortality experienced by patients with mental disorders after myocardial infarction. The study suggests the potential importance of improving these patients' medical care as a step toward reducing their excess mortality.

Correlates and impact on outcomes of worsening renal function in patients > or =65 years of age with heart failure

1.5 mg/dl. Based on the number of these factors, a patient's risk for developing worsening renal function ranged between 16% (< or =1 factor) and 53% (> or =5 factors). After adjusting for confounding effects, worsening renal function was associated with a significantly longer length of stay by 2.3 days, higher in-hospital cost by $1,758, and an increased risk of in-hospital mortality (odds ratio 2.72; 95% confidence interval 1.62 to 4.58). In conclusion, worsening renal function, an event that frequently occurs in elderly patients hospitalized with heart failure, confers a substantial burden to patients and the healthcare system and can be predicted by 6 admission characteristics.

Variations in and correlates of length of stay in academic hospitals among patients with heart failure resulting from systolic dysfunction

OBJECTIVE

Given the high cost of caring for patients with congestive heart failure, there are strong incentives to decrease hospital costs by shortening length of hospital stay. We sought to identify factors associated with length of stay among patients admitted for the treatment of heart failure resulting from systolic dysfunction.

STUDY DESIGN

Retrospective cohort study.

METHODS

We examined data from patients with a principal discharge diagnosis of congestive heart failure who had been admitted to 1 of the 49 academic hospitals across the United States that participated in the CHF Benchmark Project, a large collaborative quality improvement project coordinated by the University HealthSystem Consortium. Patients were discharged between January 1 and June 30, 1996. We obtained patient characteristics and hospitalization data by retrospectively reviewing medical records. We used linear regression models to identify major determinants of length of stay.

RESULTS

Among the 1046 patients eligible for the study, 59% were women, 55% were white, and 58% were aged 65 years or older. Adjusting for patient demographic and admission clinical characteristics, the mean length of stay was 4.9 +/- 0.9 days. Length of stay varied significantly among hospitals, even after adjusting for differences in patient characteristics. In multivariate regression models, factors that were independently associated with a significantly longer length of stay were prior renal failure, peripheral edema, atrial fibrillation, hyponatremia, urinary catheter on admission, initiation of an antiarrhythmic or warfarin, and major complications. Patient characteristics and hospital events combined explained 16% of the variation in the length of stay. Adjusting for the individual hospitals explained an additional 10% of the variation in the length of stay.

CONCLUSIONS

Although a number of patient and hospitalization factors were associated with length of stay in patients with congestive heart failure resulting from systolic dysfunction, much unexplained variation remained. Clinical factors alone explained about 50% more variation than did factors specific to the individual hospitals.

Under-utilisation of beta-blockers after acute myocardial infarction. Pharmacoeconomic implications

We reviewed the literature on the efficacy and effectiveness of beta-blocker therapy and examined the economic consequences of under-utilisation. Despite the literature documenting the value of beta-blockers, the therapy is not prescribed at the appropriate rates. Approximately half of acute myocardial infarction (AMI) survivors who are eligible for the therapy do not receive it. There are 3 sources of costs that may arise from such under-utilisation: (i) increased morbidity and mortality associated with under-use; (ii) increased demand for related medical resources when the health state following an AMI is suboptimal due to under-use of beta-blocker therapy; and (iii) increased cost due to substitution of higher cost and/or less effective treatments for beta-blockers. For the first category, there is evidence suggesting that around 2900 to 5000 lives are lost in the US in the first year following an AMI due to underprescription. There is very little evidence on the second category of costs; 1 recent study does address this issue and indicates that beta-blocker therapy can lead to a 22% relative risk reduction for hospital readmission during the first year. Several studies also show a decrease in reinfarction. There is no information that addresses the third category of costs adequately (though 1 study does present evidence of substitution of calcium channel-blockers for beta-blockers). We conclude that there is a dearth of evidence on the economic consequences of the under-utilisation of beta-blocker therapy. What does exist suggests that the net costs to society may be substantial.

Relative inefficiencies in production between solo and group practice physicians

Health economists have hypothesized for some time that physicians produce medical care in an inefficient manner. Further, whether solo or group practice physicians are relatively more inefficient has been a question of particular interest. Theoretical considerations suggest that solo and group practice physicians face different behavioural and production constraints, implying that they may produce care at different levels of efficiency; which is more efficient is an empirical question. We employed stochastic production frontier estimation to address this issue.

Career characteristics of graduates of a Medical Scientist Training Program, 1970-1990

PURPOSE

To describe the career characteristics of the graduates of the Medical Scientist Training Program (MSTP) at Duke University School of Medicine.

METHOD

Surveys and information at administrative offices were used to collect data on all the 1970-1990 MSTP graduates in the summer of 1995. Of the 147 graduates, all but three had completed postgraduate training. In addition, data were available for 35 recent graduates (1991-1995), most of whom were in transition from training and fellowship positions to career positions.

RESULTS

Of the 144 graduates from 1970 through 1990, 84 (58%) had selected careers in internal medicine or pathology. A total of 106 (74%) were involved in careers in academic medicine or research. Of these, 87 (82%) held full-time faculty appointments and devoted major efforts to basic or clinical research. Of this group, 59 (68%) were primary investigators receiving grant support from the National Institutes of Health (NIH). Of the 12 women graduates, 11 had careers in academic medicine or research, and seven were primary investigators on NIH grants. At the present time, 11 of 43 (26%) of the matriculating MSTP students are women. Five of the seven underrepresented-minority students in the MSTP have entered in the last five years.

CONCLUSION

This study reinforces and extends previous conclusions concerning the success of federally funded MSTPs in producing physician scientists who compete favorably for NIH funding.

Infantile sialic acid storage disease: a rare cause of cytoplasmic vacuolation in pediatric patients

We report a case of infantile sialic acid storage disease (ISSD) in a black infant presenting in utero with nonimmune hydrops, ascites, and anemia requiring intrauterine transfusion. Upon birth, the patient had prominent edema, large anterior fontanelle, partial absence of the rectus abdominis, clubbing of the left foot, gingival hypertrophy, short first metatarsals, prominent scrotal raphe, right heart dilatation, and left ventricular dysfunction. Radiographs showed pulmonary hypoplasia and epiphyseal stippling. He died of respiratory failure at day 2. Autopsy demonstrated capillary hemangiomata, remote cerebral hemorrhages, and central nervous system periventricular leukomalacia, as well as severe cardio- and hepatosplenomegaly. Multiple single membrane-limited vacuoles consistent with enlarged lysosomes were present in virtually all cell types examined, with striking involvement of liver, myocardium, and placenta. Vacuolar contents were not identifiable by electron microscopy. Demonstration of elevated free sialic acid in urine, amniotic fluid, and cultured fibroblasts confirmed the diagnosis of ISSD. Characteristics of sialic acid storage diseases and their diagnosis are reviewed. ISSD should be considered in infants with empty cytoplasmic vacuoles in multiple tissue types.

Solo versus group practice in the medical profession: the influence of malpractice risk

While Partnerships are a significant form of business organization in many sectors of the economy, relatively little is known about the incentives which lead to their formation. This paper explores the formation of partnerships among office based physicians when facing some risk of malpractice litigation. Theoretical results indicate that malpractice exposure can increase the incentives to shirk within a partnership, and so exert a significant influence on the decision to form a partnership. Empirical results find that malpractice risk has the expected negative effect on some partnership formation.

Coexisting endogenous and exogenous lipoid pneumonia and pulmonary alveolar proteinosis in a patient with neurodevelopmental disease

We report a unique case of coexisting exogenous lipoid pneumonia, endogenous lipoid pneumonia (ELP), and pulmonary alveolar proteinosis (PAP) in a 5-year-old patient with severe neurodevelopmental disease. The patient presented with gastroesophageal reflux and presumed chronic lung disease resulting from recurrent aspiration pneumonias and succumbed to respiratory failure. The autopsy showed lipid-laden macrophages and periodic acid-Schiff-positive granular material in alveolar spaces and multilamellated structures within both alveolar macrophages and extracellular debris. These findings were similar to those in previous reports of coexisting ELP and PAP in the setting of gastroesophageal reflux. However, the present case differed by the presence of scattered large osmiophilic extracellular lipid vacuoles. Besides strengthening the association between ELP and PAP and their relationship to gastroesophageal reflux, this case suggests that they may arise together with exogenous lipoid pneumonia, through related mechanisms, in the setting of neurodevelopmental disease.

Endocardial fibroelastosis with coronary artery thromboembolus and myocardial infarction

We report a case of an 18-month-old male, born to a woman with third trimester febrile illness, who had a history of congestive heart failure and respiratory distress, cardiomegaly, and electrocardiographic (ECG) findings suggestive of cardiomyopathy and myocarditis. After gradual improvement in heart size and function with pharmacologic therapy, he developed a terminal episode of respiratory distress and cardiogenic shock, with ECG findings of an anterolateral infarct. At autopsy it was found that endocardial fibroelastosis with mural thrombi in the left ventricle had been complicated by thromboembolism to the left anterior descending coronary artery, resulting in transmural infarction of the anteroseptal region of the left ventricle. Myocardial infarction is a potential but unusual thromboembolic complication of endocardial fibroelastosis. A high index of suspicion for coronary artery thromboemboli should be maintained in pediatric patients with cardiomyopathy and suspected myocardial infarction.

Variant of atelosteogenesis? Report of a 20-week fetus

We report on a 20-week fetus with manifestations similar, but not identical, to those of atelosteogenesis. The present fetus had rhizomelic micromelia with absence of ossification in the humerus, radius, ulna, and cervical and upper thoracic vertebral bodies; coronal clefts in the ossified thoracic vertebral bodies; and talipes equinovarus. The physes were relatively normal on histologic examination.

Rocky mountain spotted fever: hepatic lesions in childhood cases

We studied 16 fatal childhood cases of Rocky Mountain spotted fever (RMSF). Hepatic histologic lesions with statistically significant differences from age- and sex-matched controls were portal triaditis consisting of polymorphonuclear leukocytes and large mononuclear cells, portal vasculitis, sinusoidal leukocytosis, erythrophagocytosis by Kupffer cells, and gross hepatic weight. Hepatocellular necrosis, cholestasis, and congestion were not more frequent in RMSF than in controls. Using immunofluorescence microscopy, we were able to demonstrate rickettsial organisms in portal blood vessels and sinusoidal lining cells of 7 cases.

Pulmonary pathology of Rocky Mountain spotted fever (RMSF) in children

Despite infrequent respiratory symptoms, histopathologic changes were identified in the lungs of 15 of 16 children dying of Rocky Mountain spotted fever (RMSF). Gross examination demonstrated increased lung weight, edema, congestion, focal hemorrhage, and bronchopneumonia in a few cases. Paraffin sections were stained with hematoxylin and eosin and phosphotungstic acid-hematoxylin, and available blocks were examined by direct immunofluoresence for Rickettsia rickettsii. Cases and controls matched for age and sex were randomized and examined blindly for pathologic changes. In addition, morphometric measurements of mean alveolar septal thickness were made in each case. The histopathologic findings include (1) diffuse interstitial mononuclear (lymphocyte and macrophage) inflammatory infiltrate in 15/16 cases of RMSF (5/10 controls), (2) pulmonary edema and intraalveolar hemorrhage in 11/16 cases of RMSF (2/10 controls), and (3) vasculitis of small pulmonary venules and arterioles in 5/16 RMSF cases (0/10 controls). Rickettsia rickettsii were identified in 4/8 RMSF cases by direct fluorescent antibody technique. Although pulmonary disease is not always clinically apparent in children with RMSF, involvement of the pulmonary microcirculation is a frequent event in fatal cases and may contribute to the development of non-cardiogenic pulmonary edema.

Multiple congenital septal atresias of the intestine: histomorphologic and pathogenetic implications

Congenital atresias of the gastrointestinal tract are usually single and divided into three forms on a morphologic basis. The septal or diaphragmatic type (type I) is the least common. We report an infant with multiple type I atresias involving both the small and large intestine and describe the unique histologic features of the septa: fragmentation of muscularis mucosa, multiple septal cysts lined by columnar epithelium, circular and longitudinal muscular layers, and absence of inflammation. This infant had a sibling who died with multiple intestinal atresias of the septal type. The histologic features suggest that type I gastrointestinal atresias may be due to failure of complete recanalization rather than result from healing of vascular of inflammatory events.

Fatal Rocky Mountain spotted fever. Hematologic and lymphoreticular observations

Generalized histiocytic proliferation with a component of phagocytosis and thrombocytopenia accompanies a number of infectious diseases and malignant neoplasms. Its extent and occurrence were studied in the hematopoietic and lymphoreticular tissues of fatal childhood cases of Rocky Mountain spotted fever. Its frequent occurrence and morphologic similarities to other associated causes were documented.

Comparative demonstration of pulmonary fat emboli by "en bloc" osmium tetroxide and oil red O methods

The presence and localization of fat in human lung tissue was evaluated by the "en bloc" staining procedure with osmium tetroxide performed with formalin fixed tissue with subsequent paraffin sectioning and with the oil red O technique performed with frozen sections. Fifty-one autopsy cases were divided into three clinical groups: group A, consisting of 17 patients with severe skeletal trauma; group B, consisting of 14 patients with minor skeletal trauma; and group C, consisting of 20 control patients without trauma. Adjacent sections of lung were selected from all cases, stained with the "en bloc" osmium tetroxide and oil red O methods, coded, and examined under the light microscope without knowledge of the clinical grouping, Stainable fat was graded on a 1 to 4+ scale, and attention was given to histologic localization in tissue sections. The "en bloc" osmium tetroxide technique revealed greater amounts of stainable lipid in clinical groups A and B and was most effective in demonstrating lipid when present in small quantities (group B). Since the method permits the employment of paraffin sections, evaluation of fine histologic detail is an advantage that is not always obtained in frozen sections. It is concluded that the "en bloc" osmium tetroxide technique is superior to the oil red O technique in terms of visualization and histologic localization of minute amounts of lipid in lung tissue.

Progressive hepatic injury in prolonged parenteral alimentation

A morphologic sequence of progressive hepatic injury is demonstrated in an immature infant who received TPN for 148 days. Because immature infants are susceptible to multiple pathophysiologic insults, it is presently impossible to isolate a single etiologic agent responsible for hepatic dysfunction. It is important for physicians caring for immature infants to establish through biochemical and morphologic monitoring that appropriate duration for TPN which is not likely to lead to irreversible hepatic injury.

Bilateral adrenal neuroblastoma

Bilateral adrenal neuroblastoma is extremely rare, with isolated case reports considered to represent metastatic spread rather than simultaneous occurrence. This patient was found to have synchronous, separate, and equal size neoplasms that morphologically and ultrastructurally are neuroblastoma. We believe that these findings represent the unusual occurrence of simultaneous primary adrenal neuroblastoma reflecting multicentric origin of this neoplasm.

Asymptomatic cecal stenosis after necrotizing enterocolitis

Survival of infants with necrotizing enterocolitis may be complicated by intestinal stricture(s) as a result of healing of ischemic segments of bowel. An asymptomatic cecal stenosis not visible on barium enema was identified at operation for reestablishment of intestinal continuity. Infants recovering from acute necrotizing enterocolitis deserve continued surveillance for mechanical and functional abnormalities of the gastrointestinal tract. Patency of the intestinal lumen distal to the ostomy site should be clearly demonstrated by the surgeon when continuity is reestablished.

Kidney lesions in Rocky Mountain spotted fever: a light-, immunofluorescence-, and electron-microscopic study

The essential pathologic lesion in Rocky Mountain spotted fever (RMSF) is a vasculitis that may involve the kidneys as well as the heart, brain, skin, and subcutaneous tissues. Histopathologic information concerning the response of the kidneys in RMSF is rather limited, however. In this study renal tissue from 17 children who died of RMSF was examined by light, electron, and immunofluorescence microscopy. A lymphocytic or mixed inflammation, or both, involving vessels and interstitium of the kidney was found in all patients. In addition, 10 patients had histologic evidence of acute tubular necrosis, and another 3 had glomerular lesions consisting of focal segmental tuft necrosis or increased cellularity secondary to neutophilic infiltration, or both. Immunofluorescence- and electron-microscopic studies failed to demonstrate immune-complex deposition within glomeruli, a finding that suggests that immunoglobulin and classic immune complexes were not involved in the pathogenesis of the renal lesions at the time of death. These findings suggest the possibility that the pathogenesis of the renal lesion in RMSF may be due to a direct action of the organism (Rickettsia rickettsii) on the vessel wall.

Myocardial involvement in Rocky Mountain spotted fever

Rocky Mountain spotted fever (RMSF), an acute febrile exanthematous illness caused by Rickettsia rickettsii and transmitted by ticks, is endemic in the southern Atlantic states. This report is based on the clinical and pathological findings of myocardial involvement in 16 children who died with severe RMSF. All 16 children had myocardial lesions to some degree, but it was not believed that these could be evaluated in terms of cardiac function and death in the face of the usual peripheral vascular collapse caused by the widespread vascular lesions throughout the body.

Rocky mountain spotted fever in childhood

Experience with 138 cases of Rocky Mountain spotted fever indicates that the major clinical features of characteristic rash, fever, and tick bite, in combination with low serum sodium concentration and thrombocytopenia, are helpful in recognizing this serious and potentially lethal infectious disease.

The impact of an elective curriculum in pathology

Under the revised medical curriculum at Duke University, elective courses were offered in the third and fourth years beginning in 1968-1969. Departmental electives in autopsy, surgical, and systemic pathology were offered as major courses, and the subspecialty courses in cardiovascular, renal, pulmonary, pediatric, and neuropathology were taught by specialists in those areas. Special topics in subcellular and molecular pathology, neoplasia, environmental diseases, and experimental pathology were subscribed by medical and graduate students alike. To determine the impact of elective courses in pathology, these electives were compared to those offered by other basic science disciplines. Tabulation of total courses offered, student enrollment, and total academic credit hours were constructed for each basic science area. The data show that over the six year study period the students elected more courses in pathology than in any other basic science. The most heavily subscribed electives in pathology were those that were clinically oriented, such as cardiovascular or renal pathology. One impact of this elective system may be to enhance recruitment. During the period studied, 29 Duke graduates interned in pathology compared to six under a comparable time period in the traditional curriculum.

Cellular autophagocytosis induced by deprivation of serum and amino acids in HeLa cells

Morphologic alterations in HeLa cells deprived of serum and amino acids were studied by light and electron microscopy. After complete deprivation for 1, 3, or 6 hours, many cells contained autophagic vacuoles enclosing clearly recognizable cell organelles. The proportion of cells showing autophagy rose from 4 to 37% in the first 3 hours of deprivation. Acid phosphatase reaction product was localized within many of the autophagic vacuoles by a modified Gomori method. After 12 to 24 hours of deprivation, many membranous residual bodies were noted within the starved HeLa cells. These electron microscopic studies indicate that complete deprivation of serum and amino acids provides a useful model for the further study of cellular autophagocytosis.

Iron metabolism and cell membranes. III. Iron-induced alterations in HeLa cells

The morphologic characteristics of acute iron loading were studied in HeLa cells incubated in an iron-enriched Eagle's medium containing 500 mug/ml of iron. Chemical studies showed that ferritin synthesis was rapidly induced and the concentration of intracellular ferritin increased up to 72 hours. Closely coupled with an increase in HeLa cell ferritin was a marked decrease in the rate of cell multiplication. The significant ultrastructural findings of iron-induced HeLa cell injury are characterized by the appearance of both autophagic multivesicular and residual bodies over the first 72 hours of iron incubation. The prominence of multivesicular bodies was noted after only 4 hours' incubation, with iron and myelin figures first appearing after 6 hours. Thus, the partial arrest of cell multiplication was associated with an increase in cytoplasmic residual bodies containing iron and other debris. The distribution of intracellular ferritin within HeLa cells differs significantly from the distribution described previously in hepatic parenchymal cells. In HeLa cells, ferritin particles were confined to lysosomal vesicles and were not identified in cell sap, endoplasmic reticulum, or Golgi apparatus.