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The Research Foundations of Graduate Education
This title is part of UC Press's Voices Revived program, which commemorates University of California Press's mission to seek out and cultivate the brightest minds and give them voice, reach, and impact. Drawing on a backlist dating to 1893, Voices Revived makes high-quality, peer-reviewed scholarship accessible once again using print-on-demand technology. This title was originally published in 1993.
eBook
Rapid emergence of life shown by discovery of 3,700-million-year-old microbial structures
Stromatolite fossils formed around 3,700 million years ago in what is now Greenland predate the previous oldest fossil evidence for life on Earth by more than 200 million years.
Signs of life on an ancient Earth
Stromatolites are sedimentary formations created by the layered growth of microorganisms in shallow marine settings. Fossil stromatolites constitute some of the earliest evidence for life on Earth. Allen Nutman
et al
. describe metamorphosed stromatolites deposited around 3,700 million years ago in what is now Greenland. This is more than 200 million years older than the previous record-holders for earliest-known fossils, so these stromatolites rank as the Earth's earliest fossils by some margin. Although there is indirect evidence from isotope geochemistry that the pedigree of life on Earth is even older, this report is likely to be controversial.
Biological activity is a major factor in Earth’s chemical cycles, including facilitating CO
2
sequestration and providing climate feedbacks. Thus a key question in Earth’s evolution is when did life arise and impact hydrosphere–atmosphere–lithosphere chemical cycles? Until now, evidence for the oldest life on Earth focused on debated stable isotopic signatures of 3,800–3,700 million year (Myr)-old metamorphosed sedimentary rocks and minerals
1
,
2
from the Isua supracrustal belt (ISB), southwest Greenland
3
. Here we report evidence for ancient life from a newly exposed outcrop of 3,700-Myr-old metacarbonate rocks in the ISB that contain 1–4-cm-high stromatolites—macroscopically layered structures produced by microbial communities. The ISB stromatolites grew in a shallow marine environment, as indicated by seawater-like rare-earth element plus yttrium trace element signatures of the metacarbonates, and by interlayered detrital sedimentary rocks with cross-lamination and storm-wave generated breccias. The ISB stromatolites predate by 220 Myr the previous most convincing and generally accepted multidisciplinary evidence for oldest life remains in the 3,480-Myr-old Dresser Formation of the Pilbara Craton, Australia
4
,
5
. The presence of the ISB stromatolites demonstrates the establishment of shallow marine carbonate production with biotic CO
2
sequestration by 3,700 million years ago (Ma), near the start of Earth’s sedimentary record. A sophistication of life by 3,700 Ma is in accord with genetic molecular clock studies placing life’s origin in the Hadean eon (>4,000 Ma)
6
.
Journal Article
BMI is a poor predictor of adiposity in young overweight and obese children
Background
The body mass index (BMI) is a simple and widely utilized screening tool for obesity in children and adults. The purpose of this investigation was to evaluate if BMI could predict total fat mass (TFM) and percent body fat (%FAT) in a sample of overweight and obese children.
Methods
In this observational study, body composition was measured by dual energy x-ray absorptiometry (DXA) in 663 male and female overweight and obese children at baseline within a multidisciplinary, pediatric fitness clinic at an academic medical center. Univariate and multivariate regression analyses were conducted to evaluate whether BMI z-score (BMIz) predicts TFM or %FAT.
Results
The BMIz, sex and age of subjects were identified as significant predictors for both TFM and %FAT. In subjects younger than 9 years, the BMIz was a weak to moderate predictor for both TFM (R
2
= 0.03 for males and 0.26 for females) and %FAT (R
2
= 0.22 for males and 0.38 for females). For subjects between 9 and 18 years, the BMIz was a strong predictor for TFM (R
2
between 0.57 and 0.73) while BMIz remained only moderately predictive for %FAT (R
2
between 0.22 and 0.42).
Conclusions
These findings advance the understanding of the utility and limitations of BMI in children and adolescents. In youth (9-18y), BMIz is a strong predictor for TFM, but a weaker predictor of relative body fat (%FAT). In children younger than 9y, BMIz is only a weak to moderate predictor for both TFM and %FAT. This study cautions the use of BMIz as a predictor of %FAT in children younger than 9 years.
Journal Article
A Phase 3 Randomized Trial of Voxelotor in Sickle Cell Disease
In a trial evaluating two daily-dose levels of voxelotor, which binds to sickle hemoglobin and prevents polymerization under hypoxic conditions, hemoglobin levels increased by more than 1 g per deciliter in approximately half the patients who received the drug, and markers of hemolysis decreased. Toxic effects were mainly low grade and not different from those with placebo.
Journal Article
Long-term benefits and risks of frontline nilotinib vs imatinib for chronic myeloid leukemia in chronic phase: 5-year update of the randomized ENESTnd trial
In the phase 3 Evaluating Nilotinib Efficacy and Safety in Clinical Trials–Newly Diagnosed Patients (ENESTnd) study, nilotinib resulted in earlier and higher response rates and a lower risk of progression to accelerated phase/blast crisis (AP/BC) than imatinib in patients with newly diagnosed chronic myeloid leukemia in chronic phase (CML-CP). Here, patients’ long-term outcomes in ENESTnd are evaluated after a minimum follow-up of 5 years. By 5 years, more than half of all patients in each nilotinib arm (300 mg twice daily, 54%; 400 mg twice daily, 52%) achieved a molecular response 4.5 (MR
4.5
;
BCR-ABL
⩽0.0032% on the International Scale) compared with 31% of patients in the imatinib arm. A benefit of nilotinib was observed across all Sokal risk groups. Overall, safety results remained consistent with those from previous reports. Numerically more cardiovascular events (CVEs) occurred in patients receiving nilotinib vs imatinib, and elevations in blood cholesterol and glucose levels were also more frequent with nilotinib. In contrast to the high mortality rate associated with CML progression, few deaths in any arm were associated with CVEs, infections or pulmonary diseases. These long-term results support the positive benefit-risk profile of frontline nilotinib 300 mg twice daily in patients with CML-CP.
Journal Article