Comparison of Cesium-137 and X-ray Irradiators by Using Bone Marrow Transplant Reconstitution in C57BL/6J Mice

Mice are used extensively in transplantation studies involving bone marrow ablation. Due to the increasing security issues and expenses involved with γ irradiators, self-contained X-ray irradiators have been increasing in popularity. We hypothesized that bone marrow ablation by irradiation of mice with a ¹³⁷Cs irradiator would be comparable to that from an X-ray source irradiator. A lethal-dose curve was obtained by irradiating C57BL/6J mice with 500, 700, 900, and 1100 cGy from either source. These data were used to determine the lethal radiation exposure range for a noncompetitive bone marrow engraftment curve for each source. At 90 d after reconstitution, the bone marrow engraftment curves revealed significant differences between the 2 sources in the establishment of B cell, myeloid, and T cell lineages. Murine B cell reconstitution after exposure to a ¹³⁷Cs source was greater than that after X-ray exposure at each dose level, whereas the converse was true for myeloid cell reconstitution. At the 1050- and 1100-cGy doses, mice irradiated by using the X-ray source demonstrated higher levels of T cell reconstitution but decreased survival compared with mice irradiated with the ¹³⁷Cs source. We concluded that although both sources ablated endogenous bone marrow sufficiently to enable stem cell engraftment, there are distinct physiologic responses that should be considered when choosing the optimal source for use in a study and that irradiation from the ¹³⁷Cs source was associated with lower overall morbidity due to opportunistic infection.Abbreviations: B3, barrier level; B4, barrier level 4; BMT, bone marrow transplantationStudies of hematopoietic stem cell transplantation have evolved over the past 60 y.^1,9 Many preclinical investigations involving cell and gene therapy and hematopoietic stem cell function are performed in mouse models, and techniques such as adoptive cell transfer and bone marrow transplant are commonly used in these studies. Such techniques often require a supralethal dose of irradiation to ensure adequate engraftment with donor cells and subsequent survival. Conventional γ-emitting irradiators (¹³⁷Cs and ⁶⁰Co sources) have been used to deliver myeloablative doses of radiation prior to bone marrow transplantation (BMT). After the terrorist attack of 11 September 11 2001, security measures regarding active radioactive source irradiators have been heightened. In 2005, the US Congress passed the Energy Policy Act, in which the US Nuclear Regulatory Commission was assigned to evaluate and prevent malicious misuse of radioactive materials. As a result, increased security controls were imposed on radioactive material sources and quantities of concern, including shielded active source irradiators.¹⁴ Mandated security measures now include fingerprinting and a criminal-history record check to allow persons unescorted access to various radioactive materials.¹⁵ Background checks and fingerprinting procedures can be time-consuming and present an additional expense that usually is passed on to individual investigators. These enhanced security measures have significantly increased the expense associated with use of these irradiators, and federal regulations as proposed in 10 CFR Part 37 are likely to become more stringent in coming years.¹⁶ This situation has correspondingly led to an increased interest in the use of X-ray irradiators as a substitute for γ-ray sources such as ¹³⁷Cs, and many animal facilities across the country have begun to purchase these units, even though there is no unbiased comparative information regarding the effectiveness of the instruments.In addition to decreased security requirements, X-ray irradiators are substantially less expensive to purchase than are active-source irradiators. After reviewing quotes, we estimate that the initial purchase price of an X-ray irradiator is about one sixth that of a cesium source. These figures do not include the costs of shipping, installation, or disposal of old active-source machines, and thus actual starts up costs are much higher. Annual maintenance as well as annual or semiannual dosimetry assessment costs are relatively comparable between the 2 sources. X-ray irradiators offer an additional financial advantage in that they do not require the strict security measures required for active γ-source irradiators. Given the number of disadvantages for the possession and use of γ-emitting irradiators, the use of X-ray irradiators in research likely will increase in the future.Extensive review of the literature did not reveal any studies in which bone marrow transplantation (BMT) efficiencies, kinetics, or overall responses in mice were compared between ¹³⁷Cs and X-ray irradiators. We hypothesized that both the ¹³⁷Cs and X-ray sources would ablate the bone marrow effectively and allow for comparable donor bone marrow reconstitution, and we sought to compare any differences in cell population engraftment after the use of each source. Recipient hematologic recovery after irradiation and reconstitution with bone marrow was assessed by determining the percentages of B and T lymphocytes and myeloid cells in the peripheral blood at 90 d after engraftment. In light of previously published work, we hypothesized that using the X-ray source before BMT would require a reduced dosage of radiation compared with that for the ¹³⁷Cs source.^4,6,9Historically, lethal-dose curves have been generated to calculate the dose which is lethal for 50% of the irradiated animals (mice, in this case) over a 30-d period (that is, the LD_50:30); this method allows approximation of the radiation sensitivity of a cohort of experimental mice.¹¹ A mouse in which 100% of the bone marrow has been ablated will be unable to recover hematopoietic function and will die. A priori, if the animal dies, one can assume that the minimal lethal dose has been reached or exceeded; conversely, if the mouse survives, the minimal lethal dose was not achieved. Because of the number of mice needed to calculate an accurate LD_50:30, we elected to perform a broad lethal-dose curve (1100 to 500 cGy in 200-cGy increments) to determine the point at which 100% death was reached for both sources. We then used this information as the lower radiation exposure limit for a bone marrow reconstitution curve (refined into 50-cGy increments), thereby allowing us to examine the bone marrow reconstitution response after differing radiation exposures.⁹ There is ample support in the literature for the broad lethal-dose test range chosen in this study.^4,9 Previous work with thymocyte reconstitution after bone marrow ablation has demonstrated that irradiation exposures of approximately 400 cGy are required to establish a population of donor-derived thymocytes in the recipient.⁵ Therefore, we used a dosage test range above 400cGy in the current study. The dose range for this study was 500 to 1100 cGy, and we expected to see morbidity and mortality primarily due to bone marrow failure between 8 and 20 d in the lethal-dose curve.¹²     

Detection of Hepatitis E Virus Antibodies in Dogs in the United Kingdom

Hepatitis E virus (HEV) genotypes 3 and 4 are zoonotic pathogens, with pigs predominantly implicated in disease transmission. The rapid rise in human cases in developed countries over the past decade indicates a change in epidemiology of HEV, and it has been suggested that additional animal species may be involved in transmission of infection. Multiple studies have identified contact with dogs as a risk factor for HEV infection in industrialised nations, and a low seroprevalence to HEV has previously been reported in dogs in low-income countries. In this study we aimed to evaluate the possibility that dogs are susceptible to HEV, and determine the frequency with which this occurs. Serum samples from UK dogs with and without hepatitis were screened for HEV-specific antibodies, and canine liver and stool samples were analysed by qPCR for the presence of HEV RNA. We describe evidence to show HEV infection occurs at low levels in dogs in the UK, but the strain of origin is undetermined. The low seroprevalence level of HEV in dogs implies the risk of zoonotic disease transmission is likely to be limited, but further investigations will be required to determine if HEV-infected dogs can transmit HEV to man.     

The Scirtothrips dorsalis Species Complex: Endemism and Invasion in a Global Pest

Invasive arthropods pose unique management challenges in various environments, the first of which is correct identification. This apparently mundane task is particularly difficult if multiple species are morphologically indistinguishable but accurate identification can be determined with DNA barcoding provided an adequate reference set is available. Scirtothrips dorsalis is a highly polyphagous plant pest with a rapidly expanding global distribution and this species, as currently recognized, may be comprised of cryptic species. Here we report the development of a comprehensive DNA barcode library for S. dorsalis and seven nuclear markers via next-generation sequencing for identification use within the complex. We also report the delimitation of nine cryptic species and two morphologically distinguishable species comprising the S. dorsalis species complex using histogram analysis of DNA barcodes, Bayesian phylogenetics, and the multi-species coalescent. One member of the complex, here designated the South Asia 1 cryptic species, is highly invasive, polyphagous, and likely the species implicated in tospovirus transmission. Two other species, South Asia 2, and East Asia 1 are also highly polyphagous and appear to be at an earlier stage of global invasion. The remaining members of the complex are regionally endemic, varying in their pest status and degree of polyphagy. In addition to patterns of invasion and endemism, our results provide a framework both for identifying members of the complex based on their DNA barcode, and for future species delimiting efforts.     

Helicobacter pylori,HIV and Gastric Hypochlorhydria in the Malawian Population

Background

HIV and Helicobacter pylori are common chronic infections in sub-Saharan Africa. Both conditions can predispose to gastric hypochlorhydria that may be a risk factor for enteric infections and reduced drug absorption. We have investigated to what extent HIV and H. pylori infections are associated with hypochlorhydria in a Malawian cohort of patients undergoing endoscopy.

Methods

104 sequential symptomatic adults referred for gastroscopy at Queen Elizabeth Central Hospital, Blantyre, Malawi, had blood taken for rapid HIV testing and fasting serum gastrin analysis. Gastric fluid was aspirated for pH testing, and gastric biopsies were taken.

Results

After 9/104 HIV-infected patients who were already established on anti-retroviral therapy were excluded, 17/95 (25.0%) were seropositive for untreated HIV, and 68/95 (71.6%) patients were H. pylori positive by histology. Hypochlorhydria (fasting gastric pH>4.0) was present in 55.8% (53/95) of patients. H. pylori infection was significantly associated with hypochlorhydria (OR 2.91, [1.02-7.75], p=0.046). While single infection with HIV was not significantly independently associated with hypochlorhydria. H. pylori and HIV co-infection was more strongly associated with hypochlorhydria (OR 6.25, [1.33-29.43], p=0.020) than either infection alone, suggesting an additive effect of co-infection. HIV infection was associated with higher serum gastrin levels (91.3pM vs. 53.1pM, p=0.040), while H. pylori infection was not (63.1pM vs. 55.1pM, p=0.610). Irrespective of H. pylori and HIV status, most patients (>90%) exhibited pangastritis. Only three patients had histological evidence of gastric atrophy, of which only one was HIV-infected.

Conclusion

H. pylori infection was associated with fasting hypochlorhydria, while HIV was not independently associated. HIV and H. pylori co-infection, however, was more strongly associated with hypochlorhydria than H. pylori infection alone. The mechanism of this apparent additive effect between HIV and H. pylori remains unclear, but appears to be related to chronic pangastritis rather than gastric atrophy, and associated with hypergastrinaemia in HIV-infected individuals.     

Ethnic Disparities in Emergency Severity Index Scores among U.S. Veteran’s Affairs Emergency Department Patients

BackgroundThe goal of these analyses was to determine whether there were systematic differences in Emergency Severity Index (ESI) scores, which are intended to determine priority of treatment and anticipate resource needs, across categories of race and ethnicity, after accounting for patient-presenting vital signs and examiner characteristics, and whether these differences varied among male and female Veterans Affairs (VA) ED patients.ConclusionsThe findings suggest the possibility that subgroups of VA patients receive different ESI ratings in triage, which may have cascading, downstream consequences for patient treatment quality, satisfaction with care, and trust in the health equity of emergency care.     

Investigating Devonian trees as geo‐engineers of past climates: linking palaeosols to palaeobotany and experimental geobiology

We present the rationale for a cross‐disciplinary investigation addressing the ‘Devonian plant hypothesis’ which proposes that the evolutionary appearance of trees with deep, complex rooting systems represents one of the major biotic feedbacks on geochemical carbon cycling during the Phanerozoic. According to this hypothesis, trees have dramatically enhanced mineral weathering driving an increased flux of Ca²⁺ to the oceans and, ultimately, a 90% decline in atmospheric CO₂ levels through the Palaeozoic. Furthermore, experimental studies indicate a key role for arbuscular mycorrhizal fungi in soil–plant processes and especially in unlocking the limiting nutrient phosphorus in soil via Ca‐phosphate dissolution mineral weathering. This suggests co‐evolution of roots and symbiotic fungi since the Early Devonian could well have triggered positive feedbacks on weathering rates whereby root–fungal P release supports higher biomass forested ecosystems. Long‐standing areas of uncertainty in this paradigm include the following: (1) limited fossil record documenting the origin and timeline of the evolution of tree‐sized plants through the Devonian; and (2) the effects of the evolutionary advance of trees and their in situ rooting structures on palaeosol geochemistry. We are addressing these issues by integrating palaeobotanical studies with geochemical and mineralogical analyses of palaeosol sequences at selected sites across eastern North America with a particular focus on drill cores from Middle Devonian forests in Greene County, New York State.     

What's Inside That Seed We Brew? A New Approach To Mining the Coffee Microbiome

Coffee is a critically important agricultural commodity for many tropical states and is a beverage enjoyed by millions of people worldwide. Recent concerns over the sustainability of coffee production have prompted investigations of the coffee microbiome as a tool to improve crop health and bean quality. This review synthesizes literature informing our knowledge of the coffee microbiome, with an emphasis on applications of fruit- and seed-associated microbes in coffee production and processing. A comprehensive inventory of microbial species cited in association with coffee fruits and seeds is presented as reference tool for researchers investigating coffee-microbe associations. It concludes with a discussion of the approaches and techniques that provide a path forward to improve our understanding of the coffee microbiome and its utility, as a whole and as individual components, to help ensure the future sustainability of coffee production.