Elimination of 15N-thymidine after oral administration in human infants.

BACKGROUND: We have developed a new clinical research approach for the quantification of cellular proliferation in human infants to address unanswered questions about tissue renewal and regeneration. The approach consists of oral 15N-thymidine administration to label cells in S-phase, followed by Multi-isotope Imaging Mass Spectrometry for detection of the incorporated label in cell nuclei. To establish the approach, we performed an observational study to examine uptake and elimination of 15N-thymidine. We compared at-home label administration with in-hospital administration in infants with tetralogy of Fallot, a form of congenital heart disease, and infants with heart failure. METHODS: We examined urine samples from 18 infants who received 15N-thymidine (50 mg/kg body weight) by mouth for five consecutive days. We used Isotope Ratio Mass Spectrometry to determine enrichment of 15N relative to 14N (%) in urine. RESULTS/FINDINGS: 15N-thymidine dose administration produced periodic rises of 15N enrichment in urine. Infants with tetralogy of Fallot had a 3.2-fold increase and infants with heart failure had a 4.3-fold increase in mean peak 15N enrichment over baseline. The mean 15N enrichment was not statistically different between the two patient populations (p = 0.103). The time to peak 15N enrichment in tetralogy of Fallot infants was 6.3 ± 1 hr and in infants with heart failure 7.5 ± 2 hr (mean ± SEM). The duration of significant 15N enrichment after a dose was 18.5 ± 1.7 hr in tetralogy of Fallot and in heart failure 18.2 ± 1.8 hr (mean ± SEM). The time to peak enrichment and duration of enrichment were also not statistically different (p = 0.617 and p = 0.887). CONCLUSIONS: The presented results support two conclusions of significance for future applications: (1) Demonstration that 15N-thymidine label administration at home is equivalent to in-hospital administration. (2) Two different types of heart disease show no differences in 15N-thymidine absorption and elimination. This enables the comparative analysis of cellular proliferation between different types of heart disease.

Use of stable isotope-tagged thymidine and multi-isotope imaging mass spectrometry (MIMS) for quantification of human cardiomyocyte division.

Quantification of cellular proliferation in humans is important for understanding biology and responses to injury and disease. However, existing methods require administration of tracers that cannot be ethically administered in humans. We present a protocol for the direct quantification of cellular proliferation in human hearts. The protocol involves administration of non-radioactive, non-toxic stable isotope 15Nitrogen-enriched thymidine (15N-thymidine), which is incorporated into DNA during S-phase, in infants with tetralogy of Fallot, a common form of congenital heart disease. Infants with tetralogy of Fallot undergo surgical repair, which requires the removal of pieces of myocardium that would otherwise be discarded. This protocol allows for the quantification of cardiomyocyte proliferation in this discarded tissue. We quantitatively analyzed the incorporation of 15N-thymidine with multi-isotope imaging spectrometry (MIMS) at a sub-nuclear resolution, which we combined with correlative confocal microscopy to quantify formation of binucleated cardiomyocytes and cardiomyocytes with polyploid nuclei. The entire protocol spans 3-8 months, which is dependent on the timing of surgical repair, and 3-4.5 researcher days. This protocol could be adapted to study cellular proliferation in a variety of human tissues.

Control of cytokinesis by ß-adrenergic receptors indicates an approach for regulating cardiomyocyte endowment.

One million patients with congenital heart disease (CHD) live in the United States. They have a lifelong risk of developing heart failure. Current concepts do not sufficiently address mechanisms of heart failure development specifically for these patients. Here, analysis of heart tissue from an infant with tetralogy of Fallot with pulmonary stenosis (ToF/PS) labeled with isotope-tagged thymidine demonstrated that cardiomyocyte cytokinesis failure is increased in this common form of CHD. We used single-cell transcriptional profiling to discover that the underlying mechanism of cytokinesis failure is repression of the cytokinesis gene ECT2, downstream of ß-adrenergic receptors (ß-ARs). Inactivation of the ß-AR genes and administration of the ß-blocker propranolol increased cardiomyocyte division in neonatal mice, which increased the number of cardiomyocytes (endowment) and conferred benefit after myocardial infarction in adults. Propranolol enabled the division of ToF/PS cardiomyocytes in vitro. These results suggest that ß-blockers could be evaluated for increasing cardiomyocyte division in patients with ToF/PS and other types of CHD.

Variability of subsurface structure and infiltration hydrology among surface coal mine valley fills.

Surface coal mining alters landscapes including creating waste-rock fills or dumps. In Appalachia USA, mines fill valleys with waste rock, constructing valley fills that affect water quality and aquatic ecology downstream. Total dissolved solids (TDS) in mine effluent are elevated from exposure of mineral surfaces to weathering. Understanding TDS variability requires understanding valley fill internal structure and its effect on hydrology, yet prior studies focused on point measurements or did not address patterns among fills. Here we investigated subsurface structure and hydrologic flowpaths in two dimensions within four valley fills using electrical resistivity imaging (ERI). We used artificial rainfall to investigate the location and transit time of preferential flowpaths through the fills. We corroborated our ERI interpretations using borehole logs, downhole video, and shallow soil excavation. ERI results indicated variability in substrate type and widespread presence of preferential flowpaths. We estimated an average preferential flowpath vertical length of 6.6 m, average transit time of water along the flowpath of 1.4 h, and average minimum water velocity of 5.1 m/h (0.14 cm/s). These rates are higher than typical for undisturbed lands, and resemble highly preferential flow in karst terrain. ERI successfully distinguished fills using conventional loose-dump construction from experimental controlled-material compacted-lift construction. Conventional fills exhibited finer particles that retain water at the surface, with larger rocks and larger voids at depth. Conventional fills had greater ranges of subsurface resistivity (i.e. substrate types) and greater interior accumulation of water during artificial rainfall, indicating more quick/deep preferential infiltration flowpaths. We show experimental construction significantly alters hydrologic response, which in combination with use of low-TDS waste rock, may affect downstream water quality relative to conventional loose-dump methods. Our soil boring and pits corroborated ERI interpretation, thus demonstrating ERI to be a robust non-invasive technique that provides reliable information on valley fill structure and hydrology.

Impact of Heated Humidified High Flow Air via Nasal Cannula on Respiratory Effort in Patients with Chronic Obstructive Pulmonary Disease.

Background: High flow nasal cannula therapy (HFNC) has been widely adopted for respiratory distress, and evidence suggests that purging dead space of the upper airway improves gas fractions in the lung. This study tests the hypothesis that HFNC with room air could be as effective as low flow oxygen in chronic obstructive pulmonary disease (COPD). Methods: Thirty-two COPD patients prescribed 1 - 2 L/min of oxygen were studied. The conditions tested consisted of a control (CTRL; no therapy), then in random order HFNC and prescribed low flow oxygen (LFO). HFNC was the highest flow tolerated up to 35 L/min without supplemental oxygen. Arterial blood gases (ABGs), respiratory rate (RR), heart rate (HR) and tidal volume (VT) were measured at the end of each condition. Results: Arterial oxygen (PaO2) was greater (p < 0.001) for LFO than both HFNC and CTRL (CTRL=57.4±6.1mmHg, HFNC=58.6±8.3mmHg, LFO=72.6±10.2mmHg). HFNC reduced RR by 11% (p<0.05) from CTRL and LFO (CTRL=20.2±3.8br/min, HFNC=17.9±3.3br/min, LFO=20.2±3.7br/min) with no differences in VT. There were no differences between arterial carbon dioxide (PaCO2) (CTRL=45.5±4.9mmHg, HFNC=45.0±5.3mmHg, LFO=46.0±3.9mmHg). Conclusions: HFNC resulted in a clinically relevant reduction in ventilatory effort with no change in ABG indicating a gas equilibrium effect of purging anatomical dead space. Clinical Trial Registration: ClinicalTrials.gov ID: NCT00990210.

The safe use of children's toys within the healthcare setting.

Toys are classed as a potential source of infection because they can become contaminated with microorganisms from unwashed hands, body fluids or from children putting them in their mouths. Environmental audits by infection control teams have shown that toys kept in healthcare settings are often dirty and not subject to the recommended cleaning protocols.

Legionellosis: epidemiology, management and prevention.

Legionellosis is an acute bacterial pneumonia, which is associated with a mortality rate of approximately 10-15 per cent in healthy individuals. It was first identified in the USA following an outbreak of pneumonia among delegates at a legionnaires' convention. Antibiotics provide effective treatment. Outbreaks continue to occur and have the most significant effects on older people and other vulnerable groups.

A brief guide to anthrax.

Anthrax is an acute infectious disease caused by Bacillus anthracis. The organism is found in soil and is directly transmissible to humans via skin abrasions or by inhalation or ingestion of airborne spores. This article provides an overview of the history, microbiology and epidemiology of anthrax, and the various types of the disease. The article also discusses diagnosis and treatment as well as vaccination and infection control issues. In light of recent publicity over the use of anthrax as a form of bioterrorism, all health care workers should develop sufficient knowledge of anthrax, including how it is spread and the risk to the general public, in order to be able to provide appropriate information if necessary.