Research needs, environmental concerns, and logistical considerations for incorporating livestock grazing into coastal upland habitat management.

Along the Gulf of Mexico (GoM) coast, natural resource managers continually struggle with managing coastal uplands due to front-end costs, prolonged maintenance, and habitat-specific ecological needs. Prescribed fire, mechanical removal, and chemical treatments are common habitat management techniques used to remove invasive species, clear understory, and achieve other management goals. However, rapid development and changing climate exacerbate the difficulty in using these techniques. A potential alternative or complementary technique is using livestock for habitat management (i.e., targeted or controlled grazing). In other regions of the world, using livestock for conservation or restoration of managed lands has shown to be a less intrusive and more financially viable alternative. To better understand the research needs, logistical, and environmental concerns related to using livestock for habitat management in the coastal uplands of the GoM, we developed and distributed a survey to three groups of land users, including natural resource managers, researchers, and livestock producers in the region. Survey results show that over 96% of respondents are interested in using livestock for habitat management, but less than 10% of respondents were aware of any information that could be used to inform grazing practices for coastal upland habitat management along the Gulf of Mexico coast. There were differences among surveyed groups, but generally small-sized cattle breeds and goats were identified as the livestock with the most potential for environmental benefit and ease of containment. General concerns and areas for further investigation were implementation (e.g., which livestock type to use and grazing intensity), logistical considerations (e.g., fencing and rotational frequency), impacts of grazing on water quality, wildlife, vegetation, and livestock nutrition. Survey respondents overwhelmingly (at least 75% of each group) indicated that livestock grazing ideally would not be a standalone management practice and should be used in conjunction with other habitat management techniques such as prescribed burns, mechanical clearing, or chemical treatments. The results of the survey could be used to develop applied research projects and guidance documents that directly address informational needs related to using livestock for habitat management of coastal uplands along the Gulf of Mexico coast.

Vaginal injuries after consensual sexual intercourse - a survey among office-based gynecologists in Hamburg, Germany.

Studies on the occurrence of injuries following consensual sexual intercourse (CSI) among patients treated by office-based gynecologists are lacking. This survey aimed to assess the presence and medical relevance of vaginal injuries after CSI in gynecological office-based practice, associated risk factors, and their significance for forensic medical assessment practice. All office-based gynecologists in Hamburg, Germany (n = 316), were asked to fill in a one-page questionnaire via a fax survey. The questionnaire covered various aspects such as having observed CSI-related injuries, injury severity, risk factors, and concomitant factors (bleeding, need for surgical care, hospitalization). Response rate was 43.2% (n = 115). Overall, 83.5% of office-based gynecologists reported having observed vaginal injuries after CSI at least once and 59.1% repeatedly. Regarding maximum injury severity, 52.1% observed mucosal erosions, 32.3% mucosa penetrating injuries, and 14.6% injuries penetrating the vagina. Having observed bleeding was reported by 56.3%, 28.1% had to perform surgical suture care, and hospital admission was initiated by 20.8%. Menopause (37.5%), use of objects (19.8%), alcohol, and/or drug use (16.7%) were reported as the most frequently observed associated risk factors. Vaginal injuries after CSI have been observed by the majority of office-based gynecologists in Hamburg involving a wide spectrum of severity, including the necessity of surgical care and hospital admission. Complementing published work in clinical and emergency medicine, these findings are highly relevant to the forensic evaluation of injuries in an allegation of sexual assault, as the severity of a vaginal injury in this setting does not necessarily support a conclusion on the issue of consent.

Energy-Spread Preservation and High Efficiency in a Plasma-Wakefield Accelerator.

Energy-efficient plasma-wakefield acceleration of particle bunches with low energy spread is a promising path to realizing compact free-electron lasers and particle colliders. High efficiency and low energy spread can be achieved simultaneously by strong beam loading of plasma wakefields when accelerating bunches with carefully tailored current profiles [M. Tzoufras et al., Phys. Rev. Lett. 101, 145002 (2008)PRLTAO0031-900710.1103/PhysRevLett.101.145002]. We experimentally demonstrate such optimal beam loading in a nonlinear electron-driven plasma accelerator. Bunches with an initial energy of 1 GeV were accelerated by 45 MeV with an energy-transfer efficiency of (42±4)% at a gradient of 1.3 GV/m while preserving per-mille energy spreads with full charge coupling, demonstrating wakefield flattening at the few-percent level.

Human- and infrastructure-associated bacteria in greywater.

Greywater, the wastewater from sinks, showers and laundry, is an understudied environment for bacterial communities. Most greywater studies focus on quantifying pathogens, often via proxies used in other wastewater, like faecal indicator bacteria; there is a need to identify more greywater-appropriate surrogates, like Staphylococcus sp. Sequencing-based studies have revealed distinct communities in different types of greywater as well as in different parts of greywater infrastructure, including biofilms on pipes, holding tanks and filtration systems. The use of metagenomic sequencing provides high resolution on both the taxa and genes present, which may be of interest in cases like identifying pathogens and surrogates relevant to different matrices, monitoring antibiotic resistance genes and understanding metabolic processes occurring in the system. Here, we review what is known about bacterial communities in different types of greywater and its infrastructure. We suggest that wider adoption of environmental sequencing in greywater research is important because it can describe the entire bacterial community along with its metabolic capabilities, including pathways for removal of nutrients and organic materials. We briefly describe a metagenomic dataset comparing different types of greywater samples in a college dormitory building to highlight the type of questions these methods can address. Metagenomic sequencing can help further the understanding of greywater treatment for reuse because it allows for identification of new pathogens or genes of concern.

The effects of different sampling techniques on peripheral post mortem tryptase levels: a recommended sampling method.

Different sampling techniques can impact on post mortem tryptase levels. A previous study demonstrated significantly lower femoral post mortem total tryptase levels in samples collected via transcutaneous aspiration compared with directly sampling during internal examination. However, an outlier with high tryptase level was noted in one transcutaneous aspiration sample. This 6-month prospective study compared total post mortem tryptase levels between 21 paired aspirated venous and arterial femoral blood samples, and 19 paired aspirated and cutdown femoral venous blood samples in non-anaphylactic deaths only. No statistical differences were demonstrated between the different sampling methods. However, four outlier cases with higher tryptase levels in aspirated arterial and femoral cutdown samples compared with aspirated venous femoral samples were noted. The reasons for the outliers may be due to the bloods collected from these two methods being contaminated by central arterial and venous blood with high tryptase levels respectively. None of the aspirated venous femoral post mortem tryptase levels were above recognized post mortem tryptase cutoff to diagnose anaphylaxis. This study recommends aspirating blood samples from a clamped femoral/external iliac vein for post mortem tryptase analysis should be defined as the gold standard. Further study using the recommended sampling method on post mortem tryptase levels in non-anaphylactic and anaphylactic cases is warranted.

PATHOLOGY OF PERIMACULAR FOLDS DUE TO VITREORETINAL TRACTION IN ABUSIVE HEAD TRAUMA.

PURPOSE: To demonstrate vitreoretinal traction as a mechanism for perimacular folds in abusive head trauma. METHODS: We performed gross and histopathologic examination of eyes of children with suspected abusive head trauma and identified those with typical perimacular folds. Information was collected regarding the incident that led to the child's death and systemic manifestations noted at autopsy. Eyes were prepared in a fashion that allowed for demonstration of the vitreoretinal interface. RESULTS: Ten eyes of five patients (2-13 months) were examined. All patients had systemic manifestations of abusive trauma including intracranial injury. All cases provided evidence of vitreoretinal traction producing perimacular folds. Condensed vitreous was seen attached to the apices of the retinal folds, and the detached internal limiting membrane comprising the inner surfaces of the schisis cavity. Four cases showed severe bilateral multilayered symmetric retinal hemorrhages extending to the ora serrata. All cases showed optic nerve sheath subdural hemorrhage and subarachnoid hemorrhage. Orbital hemorrhage was unilateral in two cases and bilateral in three cases. Four cases showed orbital fat hemorrhage. One case showed extraocular muscle sheath and cranial nerve sheath hemorrhage. Two cases showed juxtapapillary intrascleral hemorrhage. CONCLUSION: Vitreoretinal traction is the likely mechanism of perimacular folds in abusive head trauma.

Differences in sampling techniques on total post-mortem tryptase.

BACKGROUND: The measurement of mast cell tryptase is commonly used to support the diagnosis of anaphylaxis. In the post-mortem setting, the literature recommends sampling from peripheral blood sources (femoral blood) but does not specify the exact sampling technique. Sampling techniques vary between pathologists, and it is unclear whether different sampling techniques have any impact on post-mortem tryptase levels. AIM: The aim of this study is to compare the difference in femoral total post-mortem tryptase levels between two sampling techniques. METHODS: A 6-month retrospective study comparing femoral total post-mortem tryptase levels between (1) aspirating femoral vessels with a needle and syringe prior to evisceration and (2) femoral vein cut down during evisceration. RESULTS: Twenty cases were identified, with three cases excluded from analysis. There was a statistically significant difference (paired t test, p < 0.05) between mean post-mortem tryptase by aspiration (10.87 ug/L) and by cut down (14.15 ug/L). The mean difference between the two methods was 3.28 ug/L (median, 1.4 ug/L; min, - 6.1 ug/L; max, 16.5 ug/L; 95% CI, 0.001-6.564 ug/L). CONCLUSIONS: Femoral total post-mortem tryptase is significantly different, albeit by a small amount, between the two sampling methods. The clinical significance of this finding and what factors may contribute to it are unclear. When requesting post-mortem tryptase, the pathologist should consider documenting the exact blood collection site and method used for collection. In addition, blood samples acquired by different techniques should not be mixed together and should be analyzed separately if possible.

Characterization of the relative importance of human- and infrastructure-associated bacteria in grey water: a case study.

AIMS: Development of efficacious grey water (GW) treatment systems would benefit from detailed knowledge of the bacterial composition of GW. Thus, the aim of this study was to characterize the bacterial composition from (i) various points throughout a GW recycling system that collects shower and sink handwash (SH) water into an equalization tank (ET) prior to treatment and (ii) laundry (LA) water effluent of a commercial-scale washer. METHODS AND RESULTS: Bacterial composition was analysed by high-throughput pyrosequencing of the 16S rRNA gene. LA was dominated by skin-associated bacteria, with Corynebacterium, Staphylococcus, Micrococcus, Propionibacterium and Lactobacillus collectively accounting for nearly 50% of the total sequences. SH contained a more evenly distributed community than LA, with some overlap (e.g. Propionibacterium), but also contained distinct genera common to wastewater infrastructure (e.g. Zoogloea). The ET contained many of these same wastewater infrastructure-associated bacteria, but was dominated by genera adapted for anaerobic conditions. CONCLUSIONS: The data indicate that a relatively consistent set of skin-associated genera are the dominant human-associated bacteria in GW, but infrastructure-associated bacteria from the GW collection system and ET used for transient storage will be the most common bacteria entering GW treatment and reuse systems. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is the first to use high-throughput sequencing to identify the bacterial composition of various GW sources.

Emittance preservation in a plasma-wakefield accelerator.

Radio-frequency particle accelerators are engines of discovery, powering high-energy physics and photon science, but are also large and expensive due to their limited accelerating fields. Plasma-wakefield accelerators (PWFAs) provide orders-of-magnitude stronger fields in the charge-density wave behind a particle bunch travelling in a plasma, promising particle accelerators of greatly reduced size and cost. However, PWFAs can easily degrade the beam quality of the bunches they accelerate. Emittance, which determines how tightly beams can be focused, is a critical beam quality in for instance colliders and free-electron lasers, but is particularly prone to degradation. We demonstrate, for the first time, emittance preservation in a high-gradient and high-efficiency PWFA while simultaneously preserving charge and energy spread. This establishes that PWFAs can accelerate without degradation-an essential step toward energy boosters in photon science and multistage facilities for compact high-energy particle colliders.

SARS-CoV-2 monitoring at three sewersheds of different scales and complexity demonstrates distinctive relationships between wastewater measurements and COVID-19 case data.

Wastewater monitoring of SARS-CoV-2 presents a means of tracking COVID-19 community infection dynamics on a broader geographic scale. However, accounting for environmental and sample-processing losses may be necessary for wastewater measurements to readily inform our understanding of infection prevalence. Here, we present measurements of the SARS-CoV-2 N1 and N2 gene targets from weekly wastewater samples at three sites in Hamilton County, Ohio, during an increase and subsequent decline of COVID-19 infections. The concentration of N1 or N2 RNA in wastewater, measured over the course of six months, ranged from below the detection limit to over 104 gene copies/l, and correlated with case data at two wastewater treatment plants, but not at a sub-sewershed-level sampling site. We also evaluated the utility of a broader range of variables than has been reported consistently in previous work, in improving correlations of SARS-CoV-2 concentrations with case data. These include a spiked matrix recovery control (OC43), flow-normalization, and assessment of fecal loading using endogenous fecal markers (HF183, PMMoV, crAssphage). We found that adjusting for recovery, flow, and fecal indicators increased these correlations for samples from a larger sewershed (serving ~488,000 people) with greater industrial and stormwater inputs, but raw N1/N2 concentrations corresponded better with case data at a smaller, residential-oriented sewershed. Our results indicate that the optimal adjustment factors for correlating wastewater and clinical case data moving forward may not be generalizable to all sewersheds.

Reduced model of plasma evolution in hydrogen discharge capillary plasmas.

A model describing the evolution of the average plasma temperature inside a discharge capillary device including Ohmic heating, heat loss to the capillary wall, and ionization and recombination effects is developed. Key to this approach is an analytic quasistatic description of the radial temperature variation which, under local thermal equilibrium conditions, allows the radial behavior of both the plasma temperature and the electron density to be specified directly from the average temperature evolution. In this way, the standard set of coupled partial differential equations for magnetohydrodynamic (MHD) simulations is replaced by a single ordinary differential equation, with a corresponding gain in simplicity and computational efficiency. The on-axis plasma temperature and electron density calculations are benchmarked against existing one-dimensional MHD simulations for hydrogen plasmas under a range of discharge conditions and initial gas pressures, and good agreement is demonstrated. The success of this simple model indicates that it can serve as a quick and easy tool for evaluating the plasma conditions in discharge capillary devices, particularly for computationally expensive applications such as simulating long-term plasma evolution, performing detailed input parameter scans, or for optimization using machine-learning techniques.

Combining laser interferometry and plasma spectroscopy for spatially resolved high-sensitivity plasma density measurements in discharge capillaries.

Precise characterization and tailoring of the spatial and temporal evolution of plasma density within plasma sources are critical for realizing high-quality accelerated beams in plasma wakefield accelerators. The simultaneous use of two independent diagnostics allowed the temporally and spatially resolved detection of plasma density with unprecedented sensitivity and enabled the characterization of the plasma temperature in discharge capillaries for times later than 0.5 µs after the initiation of the discharge, at which point the plasma is at local thermodynamic equilibrium. A common-path two-color laser interferometer for obtaining the average plasma density with a sensitivity of 2 × 1015 cm-2 was developed together with a plasma emission spectrometer for analyzing spectral line broadening profiles with a resolution of 5 × 1015 cm-3. Both diagnostics show good agreement when applying the spectral line broadening analysis methodology of Gigosos and Cardeñoso in the temperature range of 0.5 eV-5.0 eV. For plasma with densities of 0.5-2.5 × 1017 cm-3, temperatures of 1 eV-7 eV were indirectly measured by combining the diagnostic information. Measured longitudinally resolved plasma density profiles exhibit a clear temporal evolution from an initial flat-top to a Gaussian-like shape in the first microseconds as material is ejected out from the capillary. These measurements pave the way for highly detailed parameter tuning in plasma sources for particle accelerators and beam optics.

Growth of factor-dependent hemopoietic precursor cell lines.

Cell lines have been produced from long-term cultures of mouse bone marrow that require a factor, present in WEHI-3 conditioned medium (CM) or in spleen CM, for their sustained growth. The cell lines were obtained from nonvirus-treated cultures, are nonleukemic, maintain a normal karyotype, and form colonies showing granulocyte maturation when plated in soft agar. Granulocyte/macrophage (GM) colony-stimulating factor is not the inductive moiety involved in the maintenance of proliferation of these cells. It is suggested that the cell lines represent a self-renewing population of cells ancestral to GM colony-forming cells, which may be responding to a hitherto unrecognized regulator.

Post mortem vitreous magnesium in adult population.

BACKGROUND: The study of post mortem vitreous magnesium (Mg) is less common than sodium (Na), chloride (Cl) and potassium (K) in the forensic literature. There is no accepted normal range for post mortem vitreous Mg and the relationship between post mortem vitreous Mg levels and post mortem interval (PMI), other electrolyte levels, disease conditions, age and sex have not been fully established. AIM: To investigate the relationship of post mortem vitreous Mg with age, sex, PMI, vitreous electrolyte levels and diabetic status. METHODS: A retrospective study of 20 consecutive cases of diabetics and 20 non-diabetic adult deaths was performed. Spearman correlation and the permutation test were used to explore the relationship between post mortem vitreous Mg and continuous and categorical variables respectively. RESULTS: The mean post mortem vitreous Mg was 1.03mmol/L (95%CI: 0.98-1.08mmol/L). The absolute Spearman correlation coefficients (rho) between post mortem vitreous Mg with PMI, age, and other vitreous electrolytes (Na, Cl, and K) ranged between 0.04-0.21 (p>0.19). Post mortem vitreous Mg was statistically higher in diabetics (mean difference: 0.08mmol/L; area-under-the-curve=0.65 on receiver-operator-characteristic curve). No statistical difference was demonstrated between sexes (p=0.92). CONCLUSIONS: In our adult population, post mortem vitreous Mg did not correlate with age, PMI, other vitreous electrolytes (sodium, chloride and potassium) or sex. It was higher in diabetics, however had limited utility as a surrogate marker. Overall, post mortem Mg is steady in the early post mortem period with a mean of 1.03mmol/L.

Post mortem tryptase cut-off level for anaphylactic death.

Serum mast cell tryptase is used to support the diagnosis of anaphylaxis. The recommended clinical cut-off for total tryptase (<11.4µg/L) appears unsuitable in the post mortem setting due to largely unknown processes which result in significantly elevated levels in these samples. Consequently there is no widely accepted tryptase cut-off level for diagnosing an anaphylactic death. This 5-year retrospective study compared total tryptase levels in post mortem femoral blood in anaphylactic deaths and control. Univariate and multivariate analysis was used to assess the relative contribution of other factors (age, gender, post mortem interval, and presence of resuscitation) on post mortem tryptase levels. Nine anaphylactic deaths and 45 controls were identified. Receiver-operating characteristic (ROC) curve analysis identified an optimal cut-off of 53.8µg/L, with sensitivity of 89%, and specificity of 93%, for total post mortem tryptase in femoral blood to diagnosis anaphylaxis. No other factors showed any statistical significant contribution to post mortem tryptase elevation. Femoral total post mortem tryptase level of 53.8µg/L and above is a useful ancillary test in diagnosing an anaphylactic death.

Improved latent tuberculosis therapy completion rates in refugee patients through use of a clinical pharmacist.

SETTING: Primary care clinic for refugees, Philadelphia, Pennsylvania, USA. OBJECTIVE: To assess the effect of a clinical pharmacist-run clinic for latent tuberculous infection (LTBI) on LTBI treatment completion rates in refugee patients. DESIGN: In 2012, a pharmacist-run LTBI clinic was established to improve adherence and completion rates among refugees. Before 2012, LTBI treatment completion rates were less than 30%. A structured model was developed to efficiently track patients and ensure completion within specified time ranges. Interventions made by the pharmacist were recorded. Completion reports were forwarded to the Philadelphia Department of Health for tracking and statistical purposes. RESULTS: Between 2012 and 2016, of 436 refugee patients screened, 121 (27.8%) were diagnosed with LTBI and 103 were referred to the pharmacist-run LTBI clinic to initiate treatment. Of those referred, 94% successfully completed LTBI treatment within the designated time frame, 40% of whom required an intervention from the pharmacist to remain adherent. CONCLUSION: LTBI treatment completion rates more than tripled after the implementation of a pharmacist-run LTBI clinic. This successful model indicates that incorporating clinical pharmacists into interdisciplinary health care teams can enhance medication adherence and completion rates in refugee populations, leading to improved public health outcomes.

Risk of morbidity following catheter removal among neonates with catheter associated bloodstream infection.

OBJECTIVE: We hypothesized that infectious morbidities following percutaneously inserted central venous catheter (PICC) removal would be greater among neonates with central-line associated bloodstream infection (CLBASI). STUDY DESIGN: This retrospective cohort study, included all neonates who required a PICC over a ten-year period. Outcomes assessed following PICC removal included: late bloodstream infection, rule-out sepsis workups, need for a subsequent PICC and antibiotic days and PICC days after PICC removal. Odds ratios (OR) and 95% confidence intervals (CI) were determined for outcomes. Regression analyses were used to control for confounders. RESULTS: Two-thousand nine hundred and thirteen neonates required at least one PICC during the study period. After adjusting for confounders neonates with CLABSI were 3.4 (95% confidence interval (CI) 2.5, 4.6) and 2.2 (95% CI 1.2, 4.0) times more likely respectively to require a subsequent PICC or develop a late bloodstream infection after PICC removal. Neonates with CLABSI required 1.33 (95% CI 0.77, 1.89) more days of antibiotic treatment and 6.85 (95% CI 5.34, 8.37) more PICC days following PICC removal than neonates without a CLABSI. CONCLUSIONS: Neonates with CLABSI are at risk for additional infectious morbidities after PICC removal. Future intervention studies aimed at reducing CLABSI should evaluate whether morbidities following catheterization are also reduced.

Elevation of post mortem vitreous humour sodium and chloride levels can be used as a reliable test in cases of suspected salt water drowning when the immersion times are less than one hour.

BACKGROUND: Previous studies in salt water drowning deaths (SWD) demonstrated an observable elevation of post mortem vitreous sodium and chloride (PMVSC) levels. It remains unclear what the underlying mechanism responsible for this change is: whether this is due to rapid electrolyte changes from salt water inhalation/ingestion during drowning or from electrolyte diffusion and/or osmosis across the outer coats of the eyeballs during immersion. A recent animal study using sacrificed bovine eyeballs immersed in salt water demonstrated no significant elevations in PMVSC when immersed for less than one hour. Assuming similar physical properties between human and bovine, we extrapolate that an elevation in PMVSC in SWD with immersion times of less than one hour (SWD-1) would not be from immersion, but from drowning. AIM: Investigate whether there is an elevation in PMVSC in SWD-1. METHODS: Retrospective study comparing PMVSC in SWD-1 with controls from 2012 to 2015 inclusive. RESULTS: PMVSC in SWD-1 was significantly elevated compared with controls. A PMVSC of 259mmol/L has a sensitivity, specificity and likelihood ratio of 0.9, 0.9 and 7.6, respectively. CONCLUSION: The elevation in PMVSC in SWD-1 is due to drowning. A PMVSC of 259mmol/L and above is a reliable ancillary test in diagnosing drowning in bodies immersed in salt water for less than one hour.

Rapid phosphorylation of a specific 33-kDa protein (p33) associated with growth stimulated by murine and rat IL3 in different IL3-dependent cell lines, and its constitutive expression in a malignant independent clone.

Protein phosphorylation mediated by murine IL3 and other factors has been studied in two different IL3-dependent lines, AC2 and 123. In both lines, responses to rat recombinant IL3 are enhanced or induced by growth in rat spleen lymphocyte conditioned medium. Growth stimulation by murine and rat IL3, by rat lymphokine(s), and by ATP in ATP-responsive cells is closely associated with the rapid (2-4 min) phosphorylation of a 33-kDa protein (p33) in all the cells examined. p33 phosphorylation is not stimulated by another lymphokine, IL4, nor by TPA or calcium ionophore alone, which are unable to stimulate growth by themselves, and is independent of serum. p33 phosphorylation is inhibited by trifluoperazine, an inhibitor of calcium-calmodulin, but is less sensitive to inhibition by H7, an inhibitor of protein kinase c, in AC2 cells. A spontaneous IL3-independent clone of AC2 (AC-) has been isolated. AC- cells are aggressively leukemic, do not produce detectable IL3, but phosphorylate p33 constitutively where it is associated with a particulate cell fraction. It is suggested that p33 is a common intermediate molecule involved in signal transduction by the various ligands which result in growth stimulation and that its constitutive phosphorylation may play a key role in the maintenance of the leukemic state.

Relationship of factor-induced proliferation to respiratory status in marrow progenitor cells.

We have examined the respiratory status of murine and human marrow progenitor cells proliferating in response to growth factors. Proliferation of fresh marrow cells, which are almost entirely entering terminal differentiation, depends on oxidative phosphorylation as determined by oxygen uptake, lactic acid production, and effect of mitochondrial poisons which within minutes completely prevent incorporation of thymidine. However, marrow progenitors responding to growth factors in in vitro assays can proliferate in the presence of high concentrations of mitochondrial poisons, with mixed granulocyte/macrophage colonies being almost refractory to inhibition. We suggest that marrow anaerobiosis may have a physiological significance and may be of relevance to the aberrant respiration of leukemic cells which are considered to be derived from progenitor populations.