Ultraparamagnetic cells formed through intracellular oxidation and chelation of paramagnetic iron

Making cells magnetic is a long‐standing goal of chemical biology, aiming to enable the separation of cells from complex biological samples and their visualization in vivo using magnetic resonance imaging (MRI). Previous efforts towards this goal, focused on engineering cells to biomineralize superparamagnetic or ferromagnetic iron oxides, have been largely unsuccessful due to the stringent required chemical conditions. Here, we introduce an alternative approach to making cells magnetic, focused on biochemically maximizing cellular paramagnetism. We show that a novel genetic construct combining the functions of ferroxidation and iron chelation enables engineered bacterial cells to accumulate iron in “ultraparamagnetic” macromolecular complexes, allowing these cells to be trapped with magnetic fields and imaged with MRI in vitro and in vivo. We characterize the properties of these cells and complexes using magnetometry, nuclear magnetic resonance, biochemical assays, and computational modeling to elucidate the unique mechanisms and capabilities of this paramagnetic concept

Effect of co-trimoxazole on mortality in HIV-exposed but uninfected children in Botswana (the Mpepu Study): a double-blind, randomised, placebo-controlled trial

Background Co-trimoxazole prophylaxis reduces mortality among HIV-infected children, but efficacy in HIV-exposed but uninfected (HEU) children in a non-malarial, low-breastfeeding setting with a low risk of mother-to-child transmission of HIV is unclear. Methods HEU children in Botswana were randomly assigned to receive co-trimoxazole (100 mg/20 mg once daily until age 6 months and 200 mg/40 mg once daily thereafter) or placebo from age 14–34 days to age 15 months. Mothers chose whether to breastfeed or formula feed their children. Breastfed children were randomly assigned to breastfeeding for 6 months (Botswana guidelines) or 12 months (WHO guidelines). The primary outcome, analysed by a modified intention-to-treat approach, was cumulative child mortality from treatment assignment to age 18 months. We also assessed HIV-free survival by duration of breastfeeding. This trial is registered with ClinicalTrials.gov, number NCT01229761. Findings From June 7, 2011, to April 2, 2015, 2848 HEU children were randomly assigned to receive co-trimoxazole (n=1423) or placebo (n=1425). The data and safety monitoring board stopped the study early because of a low likelihood of benefit with co-trimoxazole. Only 153 (5%) children were lost to follow-up (76 in the co-trimoxazole group and 77 in the placebo group), and 2053 (72%) received treatment continuously to age 15 months, death, or study closure. Mortality after the start of study treatment was similar in the two study groups: 30 children died in the co-trimoxazole group, compared with 34 in the placebo group (estimated mortality at 18 months 2·4% vs 2·6%; difference –0·2%, 95% CI –1·5 to 1·0, p=0·70). We saw no difference in hospital admissions between groups (12·5% in the cotrimoxazole group vs 17·4% in the placebo group, p=0·19) or grade 3–4 clinical adverse events (16·5% vs 18·4%, p=0·18). Grade 3–4 anaemia did not differ between groups (8·1% vs 8·3%, p=0·93), but grade 3–4 neutropenia was more frequent in the co-trimoxazole group than in the placebo group (8·1% vs 5·8%, p=0·03). More co-trimoxazole resistance in commensal Escherichia coli isolated from stool samples was seen in children aged 3 or 6 months in the co-trimoxazole group than in the placebo group (p=0·001 and p=0·01, respectively). 572 (20%) children were breastfed. HIV infection and mortality did not differ significantly by duration of breastfeeding (3·9% for 6 months vs 1·9% for 12 months, p=0·21). Interpretation Prophylactic co-trimoxazole seems to offer no survival benefit among HEU children in non-malarial, low-breastfeeding areas with a low risk of mother-to-child transmission of HIV

Cotrimoxazole Prophylaxis and Risk of Severe Anemia or Severe Neutropenia in HAART-Exposed, HIV-Uninfected Infants

Background: Prophylactic cotrimoxazole is recommended for infants born to HIV-infected mothers. However, cotrimoxazole may increase the risk of severe anemia or neutropenia. Methods: We compared the proportion of HIV-exposed uninfected (HIV-EU) infants experiencing incident severe anemia (and separately, severe neutropenia) between a prospective cohort receiving prophylactic cotrimoxazole from 1 to 6 months vs. infants from two prior trials who did not receive cotrimoxazole. Infants were from rural and urban communities in southern Botswana. Results: A total of 1705 HIV-EU infants were included. Among these 645 (37.8%) were fed with iron-supplemented formula from birth. Severe anemia developed in 87 (5.1%) infants, and severe neutropenia in 164 (9.6%) infants. In an analysis stratified by infant feeding method, there were no significant differences in the risk of severe anemia by prophylactic cotrimoxazole exposure–risk difference, −0.69% (95% confidence interval [CI] −2.1 to 0.76%). Findings were similar in multivariable analysis, adjusted odds ratio (aOR) 0.35 (95% CI 0.07 to 1.65). There were also no significant differences observed for severe neutropenia by cotrimoxazole exposure, risk difference 2.0% (95% CI −1.3 to 5.2%) and aOR 0.80 (95% CI 0.33 to 1.93). Conclusions: Severe anemia and severe neutropenia were infrequent among HIV-exposed uninfected infants receiving cotrimoxazole from 1–6 months of age. Concerns regarding hematologic toxicity should not limit the use of prophylactic cotrimoxazole in HIV-exposed uninfected infants. ClinicalTrials.gov Registration Numbers NCT01086878 (http://clinicaltrials.gov/show/NCT01086878), NCT00197587 (http://clinicaltrials.gov/show/NCT00197587), and NCT00270296 (http://clinicaltrials.gov/show/NCT00270296)

Birth Weight for Gestational Age Norms for a Large Cohort of Infants Born to HIV-Negative Women in Botswana Compared with Norms for U.S.-Born Black Infants

Background: Standard values for birth weight by gestational age are not available for sub-Saharan Africa, but are needed to evaluate incidence and risk factors for intrauterine growth retardation in settings where HIV, antiretrovirals, and other in utero exposures may impact birth outcomes. Methods: Birth weight data were collected from six hospitals in Botswana. Infants born to HIV-negative women between 26-44 weeks gestation were analyzed to construct birth weight for gestational age charts. These data were compared with published norms for black infants in the United States. Results: During a 29 month period from 2007-2010, birth records were reviewed in real-time from 6 hospitals and clinics in Botswana. Of these, 11,753 live infants born to HIV-negative women were included in the analysis. The median gestational age at birth was 39 weeks (1st quartile 38, 3rd quartile 40 weeks), and the median birth weight was 3100 grams (1st quartile 2800, 3rd quartile 3400 grams). We constructed estimated percentile curves for birth weight by gestational age which demonstrate increasing slope during the third trimester and leveling off beyond 40 weeks. Compared with black infants in the United States, Botswana-born infants had lower median birth weight for gestational age from weeks 37 through 42 (p < .02). Conclusions: We present birth weight for gestational age norms for Botswana, which are lower at term than norms for black infants in the United States. These findings suggest the importance of regional birth weight norms to identify and define risk factors for higher risk births. These data serve as a reference for Botswana, may apply to southern Africa, and may help to identify infants at risk for perinatal complications and inform comparisons among infants exposed to HIV and antiretrovirals in utero

Decoherence produces coherent states: an explicit proof for harmonic chains

We study the behavior of infinite systems of coupled harmonic oscillators as t->infinity, and generalize the Central Limit Theorem (CLT) to show that their reduced Wigner distributions become Gaussian under quite general conditions. This shows that generalized coherent states tend to be produced naturally. A sufficient condition for this to happen is shown to be that the spectral function is analytic and nonlinear. For a rectangular lattice of coupled oscillators, the nonlinearity requirement means that waves must be dispersive, so that localized wave-packets become suppressed. Virtually all harmonic heat-bath models in the literature satisfy this constraint, and we have good reason to believe that coherent states and their generalizations are not merely a useful analytical tool, but that nature is indeed full of them. Standard proofs of the CLT rely heavily on the fact that probability densities are non-negative. Although the CLT generally fails if the probability densities are allowed to take negative values, we show that a CLT does indeed hold for a special class of such functions. We find that, intriguingly, nature has arranged things so that all Wigner functions belong to this class.Comment: Final published version. 17 pages, Plain TeX, no figures. Online at http://astro.berkeley.edu/~max/gaussians.html (faster from the US), from http://www.mpa-garching.mpg.de/~max/gaussians.html (faster from Europe) or from [email protected]

High Prevalence of Hypertension and Placental Insufficiency, but No In Utero HIV Transmission, among Women on HAART with Stillbirths in Botswana

Background: Increased stillbirth rates occur among HIV-infected women, but no studies have evaluated the pathological basis for this increase, or whether highly active antiretroviral therapy (HAART) influences the etiology of stillbirths. It is also unknown whether HIV infection of the fetus is associated with stillbirth. Methods: HIV-infected women and a comparator group of HIV-uninfected women who delivered stillbirths were enrolled at the largest referral hospital in Botswana between January and November 2010. Obstetrical records, including antiretroviral use in pregnancy, were extracted at enrollment. Verbal autopsies; maternal HIV, CD4 and HIV RNA testing; stillbirth HIV PCR testing; and placental pathology (blinded to HIV and treatment status) were performed. Results: Ninety-nine stillbirths were evaluated, including 62 from HIV-infected women (34% on HAART from conception, 8% on HAART started in pregnancy, 23% on zidovudine started in pregnancy, and 35% on no antiretrovirals) and 37 from a comparator group of HIV-uninfected women. Only 2 (3.7%) of 53 tested stillbirths from HIV-infected women were HIV PCR positive, and both were born to women not receiving HAART. Placental insufficiency associated with hypertension accounted for most stillbirths. Placental findings consistent with chronic hypertension were common among HIV-infected women who received HAART and among HIV-uninfected women (65% vs. 54%, p = 0.37), but less common among HIV-infected women not receiving HAART (28%, p = 0.003 vs. women on HAART). Conclusions: In utero HIV infection was rarely associated with stillbirths, and did not occur among women receiving HAART. Hypertension and placental insufficiency were associated with most stillbirths in this tertiary care setting

The Kiloparsec-Scale Kinematics of High-Redshift Star-Forming Galaxies

We present the results of a spectroscopic survey of the kinematic structure of star-forming galaxies at redshift z ~ 2 - 3 using Keck/OSIRIS integral field spectroscopy. Our sample is comprised of 12 galaxies between redshifts z ~ 2.0 and 2.5 and one galaxy at z ~ 3.3 which are well detected in either HAlpha or [O III] emission. These observations were obtained in conjunction with the Keck laser guide star adaptive optics system, with a typical angular resolution after spatial smoothing ~ 0.15" (approximately 1 kpc at the redshift of the target sample). At most five of these 13 galaxies have spatially resolved velocity gradients consistent with rotation while the remaining galaxies have relatively featureless or irregular velocity fields. All of our galaxies show local velocity dispersions ~ 60 - 100 km/s, suggesting that (particularly for those galaxies with featureless velocity fields) rotation about a preferred axis may not be the dominant mechanism of physical support. While some galaxies show evidence for major mergers such evidence is unrelated to the kinematics of individual components (one of our strongest merger candidates also exhibits unambiguous rotational structure), refuting a simple bimodal disk/merger classification scheme. We discuss these data in light of complementary surveys and extant UV-IR spectroscopy and photometry, concluding that the dynamical importance of cold gas may be the primary factor governing the observed kinematics of z ~ 2 galaxies. We conclude by speculating on the importance of mechanisms for accreting low angular-momentum gas and the early formation of quasi-spheroidal systems in the young universe.(abridged)Comment: 34 pages, 13 figures. Revised version accepted for publication in the Astrophysical Journal. Version with full-resolution figures is available at http://www.astro.ucla.edu/~drlaw/Papers/OSIRIS_data2.pd