Nagina Parmar

Microbially Mediated Calcium Carbonate Precipitation: Implications for Interpreting Calcite Precipitation and for Solid-Phase Capture of Inorganic Contaminants

Microbial degradation of urea was investigated as a potential geochemical catalyst for Ca carbonate precipitation and associated solid phase capture of common groundwater contaminants (Sr, UO2, Cu) in laboratory batch experiments. Bacterial degradation of urea increased pH and promoted Ca carbonate precipitation in both bacterial control and contaminant treatments. Associated solid phase capture of Sr was highly effective, capturing 95% of the 1 mM Sr added within 24 h. The results for Sr are consistent with solid solution formation rather than discrete Sr carbonate phase precipitation. In contrast, UO2 capture was not as effective, reaching only 30% of the initial 1 mM UO2 added, and also reversible, dropping to 7% by 24 h. These results likely reflect differing sites of incorporation of these two elements-Ca lattice sites for Sr versus crystal defect sites for UO2. Cu sequestration was poor, resulting from toxicity of the metal to the bacteria, which arrested urea degradation and concomitant Ca carbonate precipitation. Scanning electron microscopy (SEM) indicated a variety of morphologies reminiscent of those observed in the marine stromatolite literature. In bacterial control treatments, X-ray diffraction (XRD) analyses indicated only calcite; while in the presence of either Sr or UO2, both calcite and vaterite, a metastable polymorph of Ca carbonate, were identified. Tapping mode atomic force microscopy (AFM) indicated differences in surface microtopography among abiotic, bacterial control, and bacterial contaminant systems. These results indicate that Ca carbonate precipitation induced by passive biomineralization processes is highly effective and may provide a useful bioremediation strategy for Ca carbonate-rich aquifers where Sr contamination issues exist.Microbial degradation of urea was investigated as a potential geochemical catalyst for Ca carbonate precipitation and associated solid phase capture of common groundwater contaminants (Sr, UO2, Cu) in laboratory batch experiments. Bacterial degradation of urea increased pH and promoted Ca carbonate precipitation in both bacterial control and contaminant treatments. Associated solid phase capture of Sr was highly effective, capturing 95% of the 1 mM Sr added within 24 h. The results for Sr are consistent with solid solution formation rather than discrete Sr carbonate phase precipitation. In contrast, UO2 capture was not as effective, reaching only 30% of the initial 1 mM UO2 added, and also reversible, dropping to 7% by 24 h. These results likely reflect differing sites of incorporation of these two elements-Ca lattice sites for Sr versus crystal defect sites for UO2. Cu sequestration was poor, resulting from toxicity of the metal to the bacteria, which arrested urea degradation and concomitant Ca carbonat...

Chronic transfusion practices for prevention of primary stroke in children with sickle cell anemia and abnormal TCD velocities

Chronic transfusions are recommended for children with sickle cell anemia (SCA) and abnormal transcranial Doppler (TCD) velocities ( 200 cm/sec) to help prevent the occurrence of a primary stroke [1]. The goal is usually to maintain the sickle hemoglobin concentration (HbS) <30%; however, this goal is often difficult to achieve in clinical practice. The NHLBI-sponsored trial ‘‘TCD With Transfusions Changing to Hydroxyurea (TWiTCH)’’ will compare standard therapy (transfusions) to alternative therapy (hydroxyurea) for the reduction of primary stroke risk in this patient population. Transfusions will be given according to current transfusion practices at participating sites. To determine current academic community standards for primary stroke prophylaxis in children with SCA, 32 clinical sites collected data on 340 children with abnormal TCD velocities receiving chronic transfusions to help prevent primary stroke. The average (mean ± 1 SD) pretransfusion HbS was 34 ± 11% (institutional average 23–48%); the 75th and 90th percentiles were 41 and 50%, respectively. Lower %HbS was associated with higher pretransfusion Hb values and receiving transfusions on time. These data indicate variable current transfusion practices among academic pediatric institutions and in practice, 30% HbS may not be an easily attainable goal in this cohort of children with SCA and abnormal TCD. Children with sickle cell anemia (SCA) compose a high risk group for the development of stroke. If untreated, 11% will experience a clinical stroke by 20 years of age [2]. Adams et al. have shown that children with SCA who are at risk for primary stroke can be identified by measuring time-averaged mean blood flow velocities in the internal carotid or middle cerebral arteries by TCD [3]. Abnormal TCD velocities ( 200 cm/sec) are associated with high risk for stroke and warrant transfusion therapy to reduce the risk of primary stroke. First stroke can be successfully prevented in 90% of children with SCA and abnormal TCD velocities by the use of chronic transfusion therapy, with a goal of keeping HbS concentrations less than 30% [1]. TCD with Transfusions Changing to Hydroxyurea (TWiTCH) is an NHLBIsponsored, Phase III, multicenter trial comparing standard therapy (monthly transfusions) to alternative therapy (daily hydroxyurea) to reduce the risk of primary stroke in children with SCA and documented abnormal TCD velocities. Since transfusions compose the standard treatment arm, accurate %HbS values achieved in actual clinical practice were needed for protocol development. The majority of our information about transfusing patients with SCA to prevent stroke comes from secondary stroke prevention, i.e., the use of chronic red blood cell transfusions to prevent a second stroke after a first clinical stroke has occurred. Classically, transfusions are administered at 4-week intervals to maintain HbS at less than 30%. After several years of transfusion therapy, a few centers increase transfusion interval to 5–6 weeks and allow HbS to increase toward 50% in selected patients [4,5]. Our previous study in 295 children with SCA who received transfusions for secondary stroke prevention revealed an average pretransfusion HbS of 35 ± 11% with highly variable institutional %HbS levels ranging from 22 to 51% [6] In order to determine the current clinical standard of transfusion therapy for primary stroke prevention for elevated TCD velocities, we performed a larger survey of potential TWiTCH sites. We hypothesized that average pretransfusion HbS values achieved at pediatric academic centers would be higher than 30%. This study defines the current practice at academic medical centers in provision of chronic transfusion therapy to help reduce the risk of primary stroke in children with SCA. A total of 340 children with SCA and history of abnormal TCD velocities receiving chronic PRBC transfusions for primary stroke prophylaxis were identified at 32 institutions (Table I). The number of patients per site ranged from 3 to 33 (median 9 per site). A total of 3,970 transfusions were administered over the 12-month period, with a mean of 11.7 ± 2.8 transfusions per patient. Results were similar when analyzed by each patient contributing equally or each transfusion contributing equally (Table II). The predominant transfusion type by patient was defined as the technique used 6 times over the 12-month period. Most children (79%) received primarily simple transfusions, while 19% had primarily exchange transfusions (11% partial / manual exchange, 8% erythrocytapheresis), and 2% multiple transfusion types. The transfusion goal was <30% at almost all sites (84%), while at five sites, the %HbS was allowed in selected patients to increase to 50% after a period of clinical stability. The majority (95%) of the transfusions were administered within the defined 7-day window. On average, late transfusions were given 1.3 ± 5.5 days after the defined 7-day window. Thirty percent of the patients had at least one late transfusion and 14% had 2 or more late transfusions in the 1-year period. For the 3,653 transfusions with reported %HbS values (representing 92% of the 3,970 transfusions), the mean pretransfusion HbS percentage was 33.2 ± 14.0% (median 32%). The 75th percentile for HbS values was 41%, while the 90th percentile was 51%. There were substantial differences among institutional pretransfusion %HbS values, ranging from 23 ± 14% HbS at one institution where HbS was reported for 103 transfusions given to nine patients during the 12-month period, to 48 ± 15% at another institution where HbS was reported for 95 transfusions administered to nine patients during the same time frame (Table III). The five sites with increased HbS goals to 50% in selected patients did not have higher values than others. For each transfusion, subjects were less likely to have pretransfusion HbS <30% if they were older [OR 0.92 for each year increase in age, 95% CI (0.89, 0.96)] and on transfusions for a longer period of time [OR 0.90 for each year increase in duration, 95% CI (0.86, 0.94)]. Patients with higher pretransfusion Hb levels were more likely to have pretransfusion HbS <30% [OR 1.63 for each g/dL increase in Hb, 95% CI (1.46, 1.83)] and late transfusions were less likely to be associated with a pretransfusion HbS <30% [OR 0.27, 95% CI (0.18, 0.41)]. The Hb result does not appear to be a function of late transfusions since both covariates remained significant when modeled jointly. History of alloor autoantibodies, TCD velocity, and erythrocytapheresis use were not significant predictors of a pretransfusion HbS <30%. During the initial STOP study, transfusions were given to maintain pretransfusion HbS values at less than 30% [3]. However, there were frequent transient rises of HbS above this level [7]. Furthermore, extended follow-up results from the STOP study showed that pretransfusion %HbS values during the post-trial follow-up were higher than those during the STOP study [8]. The average %HbS per patient was 27.5 ± 12.4, still within the desired goal of 30%. However, pretransfusion HbS levels were 30–34.9% in 12%, 35–39.9% in 7%, and greater than 40% in 12% of the transfusions. In the STOP2 study, where children with abnormal TCD velocities whose Doppler readings became normal were randomly assigned to continue or stop transfusions, 24% of the patients had pretransfusion HbS levels greater than 30% [9]. These findings indicate that even in the context of a prospective clinical trial, maintaining HbS <30% was difficult to achieve. With the subsequent recommendation to treat all children with SCA who are at risk for primary stroke with transfusions to maintain HbS <30%, the feasibility of this approach in actual clinical practice is not known. Possible Letters

Solid phase capture of strontium by the iron reducing bacteria Shewanella alga strain BrY

Abstract The impact of the Fe (III)-reducing bacteria Shewanella alga on the solid phase partitioning of dissolved Sr 2+ was investigated in a series of experiments using live cells, dead cells (heat-treated at 80°C) and isolated cell envelope fractions. The synthetic hydrous ferric oxide (HFO) used in the experiments was prepared in the laboratory by titration of FeCl 3 with NaOH. The presence of dissolved Fe (II) was observed only in response to the reductive dissolution of HFO by S. alga in experiments conducted with live cells, nor was the production of dissolved Fe (II) by the live cells inhibited by 1 mM Sr 2+ . pH increased in each of the bacterial systems (live, dead, cell envelope) as well as in the abiotic control (HFO, no bacteria) over the time course of the experiment (5 days) due presumably to a pCO 2 drawdown of the culture medium in response to equilibration with the N 2 atmosphere of the anaerobic chamber used in the investigation. In the presence of the live Fe (III)-reducing bacteria, the pH increase was sufficient to bring about supersaturation with respect to siderite after approximately 2 days. Solid phase Sr 2+ capture was greatest in the live cell systems (60%) followed by dead cell and cell envelope treatments (40%), and least in the abiotic control (10%). The greater percentage solid phase capture of Sr 2+ in the presence of the live cells is due to both sorption and precipitation processes occurring in this experimental system. These results show that non-viable S. alga cells and cell envelopes can sorb significantly greater quantities of Sr 2+ compared to HFO alone, and that siderite precipitation in live S. alga cultures enhances the solid phase partitioning of Sr 2+ .

Pregnancy outcomes in women with thalassemia in North America and the United Kingdom

Improved survival in thalassemia has refocused attention on quality of life, including family planning. Understanding the issues associated with infertility and adverse pregnancy outcomes may impact clinical care of patients with thalassemia. We report the number and outcomes of pregnancies among subjects enrolled in Thalassemia Clinical Research Network (TCRN) registries and examine variables associated with successful childbirth. We identified 129 pregnancies in 72 women among the 264 women, age 18 years or older in our dataset. Over 70% of pregnancies resulted in live births and 73/83 (88%) of live births occurred at full term. Most pregnancies (78.2%) were conceived without reproductive technologies. Most (59.3%) pregnancies occurred while on chronic transfusion programs, however only 38.9% were on iron chelation. Four women developed heart problems. Iron burden in women who had conceived was not significantly different from age‐ and diagnosis‐matched controls that had never been pregnant. There was also no difference in pregnancy outcomes associated with diagnosis, transfusion status, diabetes or Hepatitis C infection. Pregnancies occurred in 27.3% of women with thalassemia of child‐bearing age in the TCRN registries, a notable increase from our previous 2004 report. With optimal health maintenance, successful pregnancies may be achievable. Am. J. Hematol. 88:771–773, 2013.

The Influence of Age on in vitro Plasmin Generation in the Presence of Fibrin Monomer

Background and Objectives: The components of the fibrinolytic system interact to generate plasmin from its zymogen form, plasminogen. At birth, all the components of the fibrinolytic system are present but with differing plasma concentrations. The present study was undertaken to explore the effect of physiological, age-dependent factors of the fibrinolytic system during childhood on the capacity to generate plasmin. Design and Methods: Total plasmin generation was measured in venous plasma from umbilical cords and adults, on plastic and cell surfaces, in the presence of fibrin monomer, Desafib. Plasminogen, its inhibitors α2-antiplasmin and plasminogen activator inhibitor type 1, and plasmin-α2-antiplasmin complex in the time samples were assayed by enzyme-linked immunosorbent assay. The effect of addition of plasminogen on the plasmin generation in cord plasma and the effect of lipoprotein on adult and cord plasmin generation were measured. Results: On the surface of human umbilical vein endothelial cells, onset of plasmin generation was earlier (40 min) compared to plastic (60 min) but total plasmin generation was similar on both surfaces. The addition of plasminogen to cord plasma increased plasmin generation. Supplementation of lipoprotein in adult plasma had an inhibitory effect, but there was no significant effect in cord plasma. Interpretations and Conclusions: Plasmin generation is reduced in newborn compared to adult plasma. Decreased plasmin generation in cord plasma is likely due to decreased plasminogen concentration. The antifibrinolytic effect of lipoprotein is more pronounced in adults as compared to newborns due to the presence of higher plasminogen concentration.

Education and Employment Status of Children and Adults with Thalassemia in North America

Advances in the management of thalassemia have resulted in increased life expectancy and new challenges. We conducted the first survey of education and employment status of people with thalassemia in North America.

Randomization is not associated with socio-economic and demographic factors in a multi-center clinical trial of children with sickle cell anemia

Few studies have investigated factors influencing participation rates for minority children with a chronic disease in clinical trials. The Silent Cerebral Infarct Multi‐Center Clinical (SIT) Trial provides an opportunity to study the impact of demographic and socio‐economic factors on randomization in a clinical trial among Black children. Our primary objective was to characterize the factors associated with successful randomization of children with sickle cell disease (SCD) and silent cerebral infarct (SCI) in the SIT Trial after initial consent.

Effect of covalent antithrombin-heparin complex on developmental mechanisms in the lung

We have developed a potent antithrombin (AT)-heparin conjugate (ATH) that is retained in the lung to prevent pulmonary thrombosis associated with respiratory distress in premature newborns. During continuing maturation, pulmonary angiogenesis in premature infants would be a crucial process in lung development. A naturally occurring latent form of antithrombin (L-AT) has antiangiogenic effects on lung vascularization. However, impact of latent ATH (L-ATH) on developing lung vascularization is unknown. Thus, effects of L-AT and L-ATH on fetal murine lung development were compared. Lung buds from embryonic day 11.5 (E11.5) Tie2-LacZ mouse embryos were incubated in DMEM plus FBS supplemented with PBS, AT, L-AT, heparin, ATH, or L-ATH. Vasculature of cultured explants was quantified by X-galactosidase staining. RNA was analyzed with murine gene probes for angiopoietin (Ang)-1, Ang-2, fibroblast growth factor 2 (FGF2), platelet endothelial cell adhesion molecule (PECAM), and vascular endothelial growth factor (VEGF). FGF2-supplemented medium was used to test contribution to effects of L-AT and L-ATH on angiogenesis. Epithelial branching morphogenesis was inhibited by L-AT (P = 0.003) and heparin (P < 0.001). L-AT and heparin decreased relative vascular area compared with PBS, ATH, and L-ATH. Expressions of all genes studied were downregulated by L-AT. However, L-AT and L-ATH inhibited branching morphogenesis and vasculature with added FGF2. These findings indicate that covalent linkage of AT to heparin negates disruptive effects of these moieties on lung morphology, vascularization, and growth factor gene expression. ATH may have enhanced safety as an anticoagulant during vascular development.

Quantitative analysis of catheter roughness induced by cutting and manipulation : a potential prothrombotic risk

Thrombosis is a major complication of central venous access devices, its incidence depending on material, diameter, tip position, and tip surface. Catheters are usually cut to the appropriate length for accurate positioning. Cutting is not recommended, however, as rough surfaces can serve as a nidus for thrombosis. The present study was performed to assess the roughness of catheter tips provided by various manufacturers versus the roughness once cut and handled. Three types of catheters (Hickman, Port-a-Cath, and Per Q Cath) were cut by scissors, iris scissors, or scalpel, and were handled with debakey forceps, a needle driver, adson with teeth or adson without teeth, to determine the damage created on the catheter. The uncut manufactured tip was compared as a control. Scanning electron microscopy was used for imaging of all samples, and roughness was quantified by atomic force microscopy for the cutting methods. Qualitative results by scanning electron microscopy showed that scalpel-cut and manufactured ends appeared smoother relative to those cut with scissors or iris scissors. This complemented the roughness analysis by atomic force microscopy. Catheters handled by debakey forceps and adsons with teeth showed most roughness, visible as deep holes or a grainy surface when observed by high-magnification scanning electron microscopy. Overall, the smoothest result was produced by scalpel, followed by the manufactured end, scissors, and iris scissors. Handling should be minimized, and use of adsons with teeth, needle drivers and debakey forceps should be avoided, as they can leave permanent damage. Adsons without teeth appeared the least damaging.