Blood pressure thresholds for the diagnosis of hypertensive disorders of pregnancy in sickle cell disease

In this retrospective cohort study of singleton pregnancies in people with sickle cell disease (SCD) delivered at two academic centres between 1990 and 2021, we collected demographic and SCD-related data, pregnancy outcomes, and the highest systolic and diastolic blood pressure (SBP and DBP) at seven time periods. We compared the characteristics of subjects with new or worsening proteinuria (NWP) during pregnancy to those without. We then constructed receiver operating characteristic (ROC) curves to determine the blood pressure (BP) that best identifies those with NWP. The SBP or DBP thresholds which maximized sensitivity and specificity were 120 mmHg SBP (sensitivity: 55.2%, specificity: 73.5%) and 70 mmHg DBP (sensitivity: 27.6%, specificity: 67.7%). The existing BP threshold of 140/90 mmHg lacked sensitivity in both genotype groups (HbSS/HbSβ0 : SBP = 21% sensitive, DBP = 5.3% sensitive; HbSS/HbSβ+ : SBP = 10% sensitive, DBP = 0% sensitive). Finally, percent change in SBP, DBP and MAP were all poor tests for identifying NWP. Existing BP thresholds used to diagnose hypertensive disorders of pregnancy (HDP) are not sensitive for pregnant people with SCD. For this population, lowering the BP threshold that defines HDP may improve identification of those who need increased observation, consideration of early delivery and eclampsia prophylaxis.

Natural history of blood pressure in sickle cell disease pregnancy

In this retrospective cohort study of singleton pregnancies in people with sickle cell disease (SCD) delivered at two academic centres between 1990 and 2021, we collected demographic and SCD-related data, pregnancy outcomes, and the highest systolic and diastolic blood pressure (SBP and DBP) at seven time periods. We compared blood pressure values and trajectories in the composite cohort and in each genotype group to control values in a non-SCD pregnancy dataset. There were 290 pregnancies among 197 patients with SCD. Sixteen per cent (n = 47) of pregnancies had a hypertensive disorder of pregnancy (HDP); the rates did not differ by genotype. The mean SBP and DBP were lower in the HbSS/HbSβ0 group than in the non-SCD control group at all timepoints. Mean SBP and DBP trajectories were similar between the HbSS/HbSβ0 group and non-SCD controls, whereas the mean SBP and DBP in the HbSC/HbSβ+ group decreased between the first and second trimesters and plateaued between the second and third trimesters. There were no differences in blood pressure trajectory by haemoglobin >/< 10 gm/dL or by chronic transfusion status. Overall, pregnant people with SCD have lower blood pressure than unaffected pregnant people, raising the possibility that HDP are underdiagnosed, particularly in people with HbSS/HbSβ0 .

Pyruvate kinase activators: targeting red cell metabolism in thalassemia

Thalassemia is an inherited red blood cell disorder whereby the qualitative and/or quantitative imbalance in α- to β-globin ratio results in hemolysis and ineffective erythropoiesis. Oxidative stress, from the precipitated excess globin and free iron, is a major factor that drives hemolysis and ineffective erythropoiesis. Pyruvate kinase activity and adenosine triphosphate availability are reduced due to the overwhelmed cellular antioxidant system from the excessive oxidative stress. Mitapivat, a pyruvate kinase activator in development as a treatment for thalassemia, was shown to increase hemoglobin and reduce hemolysis in a small phase 2 single-arm trial of patients with α- and β-thalassemia. The ongoing phase 3 studies with mitapivat and the phase 2 study with etavopivat will examine the role of pyruvate kinase activators as disease modifying agents in thalassemia.

Go the Distance

This overview of reproductive and sexual health care concerns for people with sickle cell disease (SCD) addresses clinical concerns that can be complex and are inherently multidisciplinary. Clinicians must be prepared to initiate reproductive health care discussions, as these intimate concerns may not be volunteered by patients. SCD is associated with delayed onset of puberty, sickle pain during menstruation, disease-specific contraceptive considerations, high-risk pregnancy, priapism, erectile dysfunction, and offspring who inherit a hemoglobinopathy trait from affected parents. Reproductive health considerations are underrecognized, undertreated, and understudied. They need attention in primary care and specialty SCD, urology, and obstetrics and gynecology clinics.

Multiple Testing in the Context of Gene Discovery in Sickle Cell Disease Using Genome-Wide Association Studies

The issue of multiple testing, also termed multiplicity, is ubiquitous in studies where multiple hypotheses are tested simultaneously. Genome-wide association study (GWAS), a type of genetic association study that has gained popularity in the past decade, is most susceptible to the issue of multiple testing. Different methodologies have been employed to address the issue of multiple testing in GWAS. The purpose of the review is to examine the methodologies employed in dealing with multiple testing in the context of gene discovery using GWAS in sickle cell disease complications.

Mechanism of asynchronous Ca(2+) waves underlying agonist-induced contraction in the rat basilar artery

BACKGROUND AND PURPOSE

Uridine 5'-triphosphate (UTP) is a potent vasoconstrictor of cerebral arteries and induces Ca(2+) waves in vascular smooth muscle cells (VSMCs). This study aimed to determine the mechanisms underlying UTP-induced Ca(2+) waves in VSMCs of the rat basilar artery.

EXPERIMENTAL APPROACH

Isometric force and intracellular Ca(2+) ([Ca(2+)](i)) were measured in endothelium-denuded rat basilar artery using wire myography and confocal microscopy respectively.

KEY RESULTS

Uridine 5'-triphosphate (0.1-1000 micromol.L(-1)) concentration-dependently induced tonic contraction (pEC(50) = 4.34 +/- 0.13), associated with sustained repetitive oscillations in [Ca(2+)](i) propagating along the length of the VSMCs as asynchronized Ca(2+) waves. Inhibition of Ca(2+) reuptake in sarcoplasmic reticulum (SR) by cyclopiazonic acid abolished the Ca(2+) waves and resulted in a dramatic drop in tonic contraction. Nifedipine reduced the frequency of Ca(2+) waves by 40% and tonic contraction by 52%, and the nifedipine-insensitive component was abolished by SKF-96365, an inhibitor of receptor- and store-operated channels, and KB-R7943, an inhibitor of reverse-mode Na(+)/Ca(2+) exchange. Ongoing Ca(2+) waves and tonic contraction were also abolished after blockade of inositol-1,4,5-triphosphate-sensitive receptors by 2-aminoethoxydiphenylborate, but not by high concentrations of ryanodine or tetracaine. However, depletion of ryanodine-sensitive SR Ca(2+) stores prior to UTP stimulation prevented Ca(2+) waves.

CONCLUSIONS AND IMPLICATIONS

Uridine 5'-triphosphate-induced Ca(2+) waves may underlie tonic contraction and appear to be produced by repetitive cycles of regenerative Ca(2+) release from the SR through inositol-1,4,5-triphosphate-sensitive receptors. Maintenance of Ca(2+) waves requires SR Ca(2+) reuptake from Ca(2+) entry across the plasma membrane via L-type Ca(2+) channels, receptor- and store-operated channels, and reverse-mode Na(+)/Ca(2+) exchange.

Structure determination of the hexagonal quasicrystal approximant μ′-(Al,Si)4Cr by the strong reflections approach

A number of different crystalline phases have been found in Al-rich Al-Cr-Si alloys by transmission electron microscopy (TEM). Among these, the new hexagonal phase micro'-(Al,Si)(4)Cr (a=2.01 and c=1.24 nm) often found coexisting with the hexagonal micro-(Al,Si)(4)Cr (a=1.998 and c=2.4673 nm, isostructural with micro-Al(4)Mn) and also with the hexagonal lambda-(Al,Si)(4)Cr (a=2.839 and c=1.239 nm, isostructural with lambda-Al(4)Mn). It is evident from their electron diffraction patterns that the structures of these three phases are related. The strong reflections in all three are distributed in a similar way. They all exhibit a pseudo-icosahedral symmetry. The structure factor amplitudes and phases for the strong reflections of the micro' phase could therefore be adopted from those of the lambda phase, according to the strong reflections approach. A structure model of the micro' phase is thus deduced from the known lambda-Al(4)Mn. micro' consists of chains of 3+3 or 4+2 interpenetrated icosahedra along the 100 directions. Similar to the lambda phase, there are two flat layers (F) and four puckered layers (P) in each unit cell of micro', stacked along the c-axis in a sequence of PFP(PFP)' where the (PFP)' block is related to the PFP block by a 6(3) screw.

Structure model for the τ(μ) phase in Al–Cr–Si alloys deduced from the λ phase by the strong-reflections approach

There are very obvious common features in the electron diffraction patterns of the λ and τ(μ) phases in the Al–Cr–Si system. The positions of the strong reflections and their intensity distributions are similar for the two structures. The relation of the reciprocal lattices of the λ and τ(μ) phases is studied. By applying the strong-reflections approach, the structure factors of τ(μ) are deduced from the corresponding structure factors of the known λ phase. Rules for selecting reflections for the strong-reflections approach are described. Similar to that of λ, the structure of τ(μ) contains six layers stacked along the c axis in each unit cell. There are 752 atoms in each unit cell, 53 of them are unique. The corresponding composition of the τ(μ) model is Al3.82 − x CrSi x . Simulated electron diffraction patterns from the structure model are in good agreement with the experimental ones. The arrangement of interpenetrated icosahedral clusters in the τ(μ) phase is discussed.

Three-dimensional reconstruction of the ν-AlCrFe phase by electron crystallography

The three-dimensional (3D) structure of the huge quasicrystal approximant nu-AlFeCr (space group P6(3)/m, a = 40.687 and c = 12.546 A) was solved by electron crystallography. High-resolution transmission-electron-microscopy (HREM) images and selected-area electron diffraction patterns from 13 different zone axes were combined to give a 3D potential map. 124 out of 129 unique atoms were found in the 3D map. Procedures for ab initio structure determination by 3D reconstruction are given. It is demonstrated that 3D reconstruction from HREM images is very powerful for solving structures--even very complicated ones. There is no limit in terms of the number of unique atoms in a structure that can be solved by 3D reconstruction.

Surface reaction of stoichiometric and calcium-deficient hydroxyapatite in simulated body fluid

In the present study, the immersion behavior of two kinds of sintered HA with different Ca/P ratios in two different extracellular simulated solutions (Tris buffer and Hank's solutions) was investigated and compared. Results indicated that an as-received Ca-deficient HA (FHA) had a lower Ca/P ratio, larger linear shrinkage and higher density than a stoichiometric HA (MHA). When FHA powder was calcined at 900 degrees C, its Ca-deficient apatite structure was unstable and a significant amount of beta-TCP phase was formed. When heated to 1250 degrees C in air, the highly crystalline apatite structure of MHA was still stable without any noticeable decomposition. The FTIR spectra indicated that both immersed MHA and FHA in Hank's solution were gradually covered with a layer of precipitated apatite during immersion. When immersed in Tris buffer solution, neither HA showed significant changes in their FTIR spectra. SEM observation indicated that the precipitation rate on immersed FHA surface was much higher than that on MHA surface when immersed in Hank's solution. The weight loss and pH data confirmed the higher dissolution rate of FHA than MHA in Hank's solution.

Myosin thick filament lability induced by mechanical strain in airway smooth muscle

Airway smooth muscle adapts to different lengths with functional changes that suggest plastic alterations in the filament lattice. To look for structural changes that might be associated with this plasticity, we studied the relationship between isometric force generation and myosin thick filament density in cell cross sections, measured by electron microscope, after length oscillations applied to the relaxed porcine trachealis muscle. Muscles were stimulated regularly for 12 s every 5 min. Between two stimulations, the muscles were submitted to repeated passive +/- 30% length changes. This caused tetanic force and thick-filament density to fall by 21 and 27%, respectively. However, in subsequent tetani, both force and filament density recovered to preoscillation levels. These findings indicate that thick filaments in airway smooth muscle are labile, depolymerization of the myosin filaments can be induced by mechanical strain, and repolymerization of the thick filaments underlies force recovery after the oscillation. This thick-filament lability would greatly facilitate plastic changes of lattice length and explain why airway smooth muscle is able to function over a large length range.

Direct observation of molecular images of lanthanide phthalocyanines: III. Structural defects

The crystal imperfections in thin films of lanthanide phthalocyanines (LnPc2H, Ln = Nd, Tb, Er, Tm, Yb, and Lu) grown expitaxially on KCl have been observed by molecular imaging. Grain and twin boundaries, stacking faults, point defects, vacancies, mosaic structures, and sometimes even some amorphous islands exist in the well-crystallized specimens. Combined with the results reported earlier, the packing characteristics of planar LnPc2H molecules can be well understood.

High-resolution electron microscopic investigation of supported platinum particles reduced at high temperatures

High-resolution electron microscopy has been used to characterize the platinum particles supported on TiO2 or ZnO. After reduction at elevated temperatures, the metallic particles display a regular, faceted shape, and several superstructures, Pt3 Ti(C), Pt3 Ti(H), PtTi, and PtZn, have been found. These results, which may involve strong metal-support interaction, have been confirmed by optical diffraction and image simulation.

Structural studies of lanthanide phthalocyanines by high-resolution electron microscopy

Epitaxial films of lanthanide phthalocyanines (LnPc2H, Ln = Nd, Tb, Er, Tm, Yb, or Lu) formed on a KCl or NaCl crystal have been studied by means of high-resolution electron microscopy. These complexes are isomorphous and have both tetragonal and base-centered orthorhombic structures. Though radiation damage makes it difficult to study these beam-sensitive materials by electron microscopy, the behaviors of thin film growth and details of structural defects can still be identified at the molecular level.

Quasicrystals and noncrystallographic symmetry

New findings on quasicrystals with icosahedral, octagonal, decagonal, and dodecagonal symmetries obtained recently in the Beijing Laboratory of Electron Microscopy, Chinese Academy of Sciences, are presented. Special emphasis is put on the relation between quasicrystalline and crystalline structures. The important role played by electron diffraction and high-resolution electron microscopy in revealing these quasiperiodic structures is pointed out.

Coactivation of synergistic muscles of different fiber types in fast and slow contractions

The electrical activity of four pairs of synergistic muscles-the long head of triceps brachii and anconeus, lateral gastrocnemius and soleus, the long and short heads of biceps brachii, and rectus femoris and vastus medialis-was studied during isometric contractions of varying speed. Each muscle pair consists of a two-joint muscle and a one-joint muscle. Two of the one-joint muscles, anconeus and soleus, are composed predominantly of red muscle fibers and are called red muscles; all the remaining muscles are composed predominantly of pale fibers and are therefore called pale muscles. Synergistic pairs of muscles in which the muscles are both pale become active simultaneously in movement of all speeds. No difference in usage of such muscles was found as a function of movement speed. In synergistic muscle pairs composed of a red and a pale muscle, a slow movement was always initiated by the red muscle, whose electrical activity predominated throughout the movement. In a rapid movement, the pale muscle could be initially most active. However, movements of equal speed could be initiated by the red muscle. Thus the speed of a contraction is a necessary but not a sufficient condition for reversals of muscle activation.

Modification of valinomycin-mediated bilayer membrane conductance by 4,5,6,7-tetrachloro-2-methylbenzimidazole

The compound 4,5,6,7-tetrachloro-2-methylbenzimidazole (TMB), has been found to markedly modify the steady-state valinomycin-mediated conductance of potassium (K+) ions through lipid bilayer membranes. TMB alone does not contribute significantly to membrane conductance, being electrically neutral in solution. In one of two classes of experiments (I), valinomycin is first added to the aqueous phases, then changes of membrane conductance accompanying stepwise addition of TMB to the water are measured. In a second class of experiments (II), valinomycin is added to the membrane-forming solution, followed by TMB additions to the surrounding water. In both cases membrane conductance shows an initial increase with increasing TMB concentration which is more pronounced at lower K+ ion concentration. At TMB concentrations in excess of 10(-5) M, membrane conductance becomes independent of K+ ion concentration, in contrast to the linear dependence observed at TMB concentrations below 10(-7) M. This transition is accompanied by a change of high field current-voltage characteristics from superlinear (or weakly sublinear) to a strongly sublinear form. All of these observations may be correlated by the kinetic model for carrier-mediated transport proposed by Läuger and Stark (Biochim. Biophys. Acta 211:458, 1970) from which it may be concluded that valinomycin-mediated ion transport is limited by back diffusion of the uncomplexed carrier at high TMB concentrations. Experiments of class I reveal a sharp drop of conductance at high (greater than 10(-5) M) TMB concentration, not seen in class II experiments, which is attributed to blocked entry of uncomplexed carrier from the aqueous phases. Valinomycin initially in the membrane is removed by lateral diffusion to the surrounding torus. The time dependence of this removal has been studied in a separate series of experiments, leading to a measured coefficient of lateral diffusion for valinomycin of 5 x 10(-6) cm2/sec at 25 degrees C. This value is about two orders of magnitude larger than the corresponding coefficient for transmembrane carrier diffusion, and provides further evidence for localization of valinomycin in the membrane/solution interfaces.

Blocking of valinomycin-mediated bilayer membrane conductance by substituted benzimidazoles

Valinomycin selectively transports alkali cations, e.g. potassium ions, across lipid bilayer membranes. The blocking of this carrier-mediated transport by four substituted benzimidazoles has been investigated. The compounds are 4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazole, (TTFB); 4,5,6,7,-tetrachloro-2-methylbenzimidazole, (TMB); 2-trifluoromethylbenzimidazole, (TFB); and 2-methylbenzimidazole, (MBM). Because of its low acidic dissociation constant (pKa = 5.04), the blocking efficiency of TTFB in both neutral and anionic forms in the aqueous phase could be studied. The compounds exhibit the blocking efficiency sequence, TTFB- greater than TTFB0 greater than TMB0 greater than TFB0 greater than MBM0. The corresponding scale of decreasing lipophilicity, as determined by octanol/water partitioning, is TTFB0 greater than TMB0 greater than TTFB- greater than TFB0 greater than MBM0. Comparison of neutral species establishes a positive correlation of blocking efficiency with lipophilicity, with the latter being conferred primarily by chlorination of the benzenoid nucleus. Anionic TTFB, on the other hand, is the most effective blocking agent studied in spite of the fact that its dissociation in the aqueous phase markedly impedes its entry (presumably as a neutral species) into a bulk hydrocarbon phase. This observation suggests that the blocking of valinomycin-mediated bilayer membrane conductance takes place at the membrane/solution interface.