The topologic and chronologic patterns of hematopoietic cell seeding in host femoral bone marrow after transplantation.

The early stages of homing, seeding, and engraftment of hematopoietic stem and progenitor cells are poorly characterized. We have developed an optical technique that allows in vivo tracking of transplanted, fluorescent-tagged cells in the host femurs. In this study we used fluorescence microscopy to monitor the topologic and chronologic patterns of hematopoietic cell seeding in the femoral bone marrow (BM) of mice. PKH-labeled cells homed to the femur within minutes after injection into a peripheral vein. Most cells drifted within the marrow space and gradually seeded in clusters close to the endosteal surface of the epiphyseal cortex. Three days after transplantation 85% to 94% (14%) of PKH-labeled cells in the femoral marrow were located within 100 microm of the epiphyseal bone surface (P <.001 versus the more central cells), whereas labeled cells were absent in the femoral diaphysis. Primary seeding of juxtaendosteal, epiphyseal marrow occurred independently of recipient conditioning (myeloablated and nonconditioned hosts), donor-recipient antigen disparity, or the phenotype of the injected cells (whole BM and lineage-negative cells) and was consistently observed in secondary recipients of BM-homed cells. Seeding in regions close to the epiphyseal bone was also observed in freshly excised femurs perfused ex vivo and in femurs assessed without prior placement of optical windows, indicating that the site of primary seeding was not affected by surgical placement of optical windows. Four to 5 days after transplantation, cellular clusters appeared in the more central regions of the epiphyses and in the diaphyses. Centrally located cells showed decreased PKH fluorescence, suggesting that they were progeny of the seeding cells, and brightly fluorescent cells (quiescent first-generation seeding cells) were observed close to the bone surface for as long as 24 days after transplantation. These data indicate that the periphery of the femoral marrow hosts primary seeding and that quiescent cells continue to reside in the periphery for weeks and do not divide. The site of proliferation of transplanted cells is the center of the marrow space.     

Infection of Tick Cells and Bovine Erythrocytes with One Genotype of the Intracellular Ehrlichia Anaplasma marginale Excludes Infection with Other Genotypes

Anaplasma marginale, a tick-borne rickettsial pathogen of cattle, is endemic in several areas of the United States. Many geographic isolates of A. marginale that occur in the United States are characterized by the major surface protein 1a, which varies in sequence and molecular weight due to different numbers of tandem repeats of 28 or 29 amino acids. Recent studies (G. H. Palmer, F. R. Rurangirwa, and T. F. McElwain, J. Clin. Microbiol. 39:631-635, 2001) of an A. marginale-infected herd of cattle in an area of endemicity demonstrated that multiple msp1α genotypes were present but that only one genotype was found per individual bovine. These findings suggested that infection of cattle with other genotypes was excluded. The present study was undertaken to confirm the phenomenon of infection exclusion of A. marginale genotypes in infected bovine erythrocytes and cultured tick cells. Two tick-transmissible isolates of A. marginale, one from Virginia and one from Oklahoma, were used for these studies. In two separate trials, cattle inoculated with equal doses of the two isolates developed infection with only one genotype. Tick cell cultures inoculated with equal doses of the two isolates became infected with only the Virginia isolate of A. marginale. When cultures were inoculated with different ratios of the Oklahoma and Virginia isolates of A. marginale, the isolate inoculated in the higher ratio became established and excluded infection with the other. When cultures with established infections of one isolate were subsequently infected with the other, only the established isolate was detected. We documented infection exclusion during initial infection in cell culture by labeling each isolate with a different fluorescent dye. After 2 days in culture, only a single isolate was detected per cell by fluorescence microscopy. Finally, when Anaplasma ovis infections were established in cultures that were subsequently inoculated with the Virginia or Oklahoma isolate of A. marginale, A. marginale infection was excluded. These studies confirm that infection exclusion occurs with A. marginale in bovine erythrocytes and tick cells, resulting in the establishment of only one genotype, and appears to be the first report of infection exclusion for Anaplasma and Ehrlichia species.     

Genetic association of low density lipoprotein receptor and Alzheimer's disease

The low density lipoprotein receptor (LDLR) is an attractive candidate gene for genetic association with Alzheimer's disease (AD) because: (i) the LDLR is an apolipoprotein E (apoE) receptor, alleles of which have been associated with AD, (ii) LDLR resides at chromosome 19p13.3 within a region linked to AD, and (iii) LDLR modulates the homeostasis of cholesterol, which itself appears associated with AD. Therefore, we evaluated whether LDLR haplotypes alter the odds of AD by performing an association study examining three LDLR single nucleotide polymorphisms (SNPs) in 118 AD patients and 133 non-AD subjects. LDLR genotypes were obtained by TaqMan allelic discrimination assays. Although individual LDLR SNPs were not associated with AD, analyses of unambiguous haplotypes suggested the hypothesis that the 211 LDLR haplotype was associated with reduced odds of AD. We then evaluated this hypothesis in a second study cohort, i.e., the Religious Orders Study. These results supported the hypothesis that the 211 LDLR haplotype is associated with reduced odds of AD. Moreover, these data suggested further associations between LDLR variants and AD. Thus, LDLR variants appear significantly associated with AD and merit additional study.     

Smoking Cessation in the Chicago Coronary Prevention Evaluation Program

Quit-rates for cigarette smokers in a lifestyle intervention program aimed at reducing coronary risk were 24 percent for all participants and 34 percent for non-dropouts. Recidivism remained very low during participation in the program. Half of the smokers who quit did so after being in the program more than two years. These data suggest that while engaging in an effort to make other changes in lifestyle, many smokers can be helped to quit. Sustained antismoking efforts in the clinical practice of medicine can be expected to share these same positive aspects. While mass public health programs to eliminate smoking and prevent young people from taking up the habit are being developed, health practitioners can make a significant contribution by including vigorous efforts at smoking cessation as part of routine practice.     

Urban health: a look out our windows.

Approximately 80% of Americans live in cities or immediately adjacent communities. Such urban environments are complex amalgams of people of disparate backgrounds, economic status, and expectations, with extraordinary disparities in health status and outcomes between groups just blocks apart. Urban health as a framing paradigm is of recent vintage and offers a perspective on health and disease that integrates clinical medicine and public health and draws on the social and political sciences to seek understanding of the impact of cities on the health of populations and individuals. Ironically, disparate outcomes and increased mortality among poor minority populations in cities are not primarily related to the consequences of the urban epidemics of drugs and violence but rather are due to the increased prevalence and severity of common diseases such as asthma, cardiovascular disease, diabetes, and kidney disease. Several factors may be responsible for such disparities, including stress, racism, perceptions of deprivation, economic inequalities, and lack of access to quality health care. It is time for leaders in medical education and health care delivery to focus on the populations that surround their institutions in order to study urban health and meet the challenge of caring for all the residents of our cities.     

Astronomical reach of fundamental physics

Using basic physical arguments, we derive by dimensional and physical analysis the characteristic masses and sizes of important objects in the universe in terms of just a few fundamental constants. This exercise illustrates the unifying power of physics and the profound connections between the small and the large in the cosmos we inhabit. We focus on the minimum and maximum masses of normal stars, the corresponding quantities for neutron stars, the maximum mass of a rocky planet, the maximum mass of a white dwarf, and the mass of a typical galaxy. To zeroth order, we show that all these masses can be expressed in terms of either the Planck mass or the Chandrasekar mass, in combination with various dimensionless quantities. With these examples, we expose the deep interrelationships imposed by nature between disparate realms of the universe and the amazing consequences of the unifying character of physical law.     

Synthesis of a 35S‐labeled dinucleoside phosphorothioate prodrug,an orally bioavailable anti‐HBV agent

The ³⁵S‐labeled, dinucleoside phosphorothioate 1, an orally available agent against hepatitis B virus, was prepared in eight steps with high specific activity and radiochemical purity. Radiolabeled 3H‐benzodithiole‐3‐one‐1,1‐dioxide was synthesized in four steps from ³⁵S₈ and was used as the sulfurizing reagent. Copyright © 2012 John Wiley & Sons, Ltd.     

Surgical Volume and Center Effects on Early Mortality After Pediatric Cardiac Surgery: 25-Year North American Experience From a Multi-institutional Registry

Mortality after pediatric cardiac surgery varies among centers. Previous research suggests that surgical volume is an important predictor of this variation. This report characterizes the relative contribution of patient factors, center surgical volume, and a volume-independent center effect on early postoperative mortality in a retrospective cohort study of North American centers in the Pediatric Cardiac Care Consortium (up to 500 cases/center/year). From 1982 to 2007, 49 centers reported 109,475 operations, 85,023 of which were analyzed using hierarchical multivariate logistic regression analysis. Patient characteristics varied significantly among the centers. The adjusted odds ratio (OR) for mortality decreased more than 10-fold during the study period (1982 vs. 2007: OR, 12.27, 95 % confidence interval [CI], 8.52–17.66; p < 0.0001). Surgical volume was associated inversely with odds of death (additional 100 cases/year: OR, 0.84; 95 % CI, 0.78–0.90; p < 0.0001). In the analysis of interactions, this effect was fairly consistent across age groups, risk categories (except the lowest), and time periods. However, a volume-independent center effect contributed substantially more to the risk model than did the volume. The Risk Adjusted Classification for Congenital Heart Surgery, version 1 (RACHS-1) risk category remains the strongest predictor of postoperative mortality through the 25-year study period. In conclusion, center-specific variation exists but is only partially explained by operative volume. Low-risk operations are safely performed at centers in all volume categories, whereas regionalization or other quality improvement strategies appear to be warranted for moderate- and high-risk operations. Potentially preventable mortality occurs at centers in all volume categories studied, so referral or regionalization strategies must target centers by observed outcomes rather than assume that volume predicts quality.     

Counting primary loops in polymer gels

Much of our fundamental knowledge related to polymer networks is built on an assumption of ideal end-linked network structure. Real networks invariably possess topological imperfections that negatively affect mechanical properties; modifications of classical network theories have been developed to account for these defects. Despite decades of effort, there are no known experimental protocols for precise quantification of even the simplest topological network imperfections: primary loops. Here we present a simple conceptual framework that enables primary loop quantification in polymeric materials. We apply this framework to measure the fraction of primary loop junctions in trifunctional PEG-based hydrogels. We anticipate that the concepts described here will open new avenues of theoretical and experimental research related to polymer network structure.