Obstetrical levator ani muscle avulsion is detected after 10%–30% of vaginal deliveries and is associated with pelvic organ prolapse later in life. However, the mechanism by which levator avulsion ...may contribute to prolapse is unknown.
This study investigated the extent by which size of the levator hiatus and pelvic muscle weakness may explain the association between levator avulsion and pelvic organ prolapse.
This was a supplementary study of a longitudinal cohort of parous women enrolled 5–10 years after first delivery and assessed annually for prolapse (defined as descent beyond the hymen) for up to 9 annual visits. For this substudy, vaginally parous participants were assessed for levator avulsion using 3-dimensional transperineal ultrasound. Ultrasound was performed at a median interval of 11 years from delivery. Ultrasound volumes also were used to measure levator hiatus area with Valsalva. Pelvic muscle strength was measured with perineometry. Women with and without pelvic organ prolapse were compared for levator avulsion, levator hiatus area, and pelvic muscle strength, using multivariable logistic regression yielding a measure of mediation. Bootstrap methods were used to calculate the confidence interval corresponding to the measure of mediation by hiatus area and pelvic muscle strength.
Prolapse was identified in 109 of 429 (25%) and was significantly associated with levator avulsion (odds ratio, 4.17; 95% confidence interval, 2.28–7.31). Prolapse also was associated with levator hiatus area (odds ratio, 1.52 per 5 cm2; 95% confidence interval, 1.34–1.73) and inversely with muscle strength (odds ratio, 0.87 per 5 cm H2O; 95% confidence interval, 0.81–0.94). In a multivariable logistic model including levator avulsion, levator hiatus area, and strength, the association between levator avulsion and prolapse was substantially attenuated and indeed was no longer statistically significant (odds ratio, 1.75; 95% confidence interval, 0.91–3.39). Hiatus area and strength mediated 61% (95% confidence interval, 34%–106%) of the association between avulsion and prolapse. Furthermore, since the 95% confidence interval for this estimate contained 100%, it cannot be ruled out that the 2 markers fully mediate the effect of avulsion on prolapse.
The strong association between pelvic organ prolapse and levator avulsion can be explained to a large extent by a larger levator hiatus and weaker pelvic muscles after levator avulsion.
Since Sn86− was discovered from the solid‐state phase in 2000, its solution chemistry has been elusive due to the high charges and chemical activity. Herein, we report the synthesis and ...characterization of an inverse sandwich‐type cluster dimer {K2ZnSn8(ZnMes)2}4− (1 a), in which the highly charged Sn86− is captured by mixed‐valence ZnI/ZnII to form the dimer {closo‐Zn2Sn8}2 moieties bridged by a Zn‐Zn bond. Such Zn‐Sn cluster not only exhibits a novel example of mixed‐valence ZnI/ZnII for stabilizing highly active anion species, but also indicates the Sn86− cluster can act as a novel bridging ligand, like arene, with a η4:η4‐fashion. Theoretical calculations indicate that a significant delocalization of electrons over Zn atoms plays a vital role in the stabilization of the Sn86− species. The AdNDP and magnetic response analyses clearly showed the presence of local σ‐aromaticity in three cluster fragments: two ZnSn4 caps and Sn8 square antiprism.
An inverse sandwich‐type cluster dimer of K(2,2,2‐crypt)4{K2ZnSn8(ZnMes)2} was synthesized. The highly charged Sn86− is captured by mixed‐valence ZnI/ZnII to form the closo‐Zn2Sn8 bridged by a ZnI‐ZnI bond. The Zn–Sn compound not only indicates the Sn86− can act as a novel bridging ligand like arene, but shows the interdisciplinary integration of cluster chemistry and zinc chemistry.
The chemical bonding of Zintl clusters is still an evolving and hot topic in modern chemistry. In this paper we synthesized a novel K(2.2.2crypt)4In8Bi13 complex in a condensed phase. The quantum ...chemical calculations and X‐ray data revealed that the compound consists of the 1:1 mixture of Bi@In8Bi123− and Bi@In8Bi125− clusters. To the date, those clusters are the largest binary clusters composed of In and Bi elements. Herein, we introduce a spherical aromatic description of chemical bonding for such clusters. We show through AdNDP, ELF, and induced magnetic field and quantitative NICS analyzes that both clusters are spherically aromatic which explains their high symmetry, stability, and peculiar magnetic properties. We believe that this work will help researchers in the further development and understanding of chemical bonding in Zintl clusters.
The chemical bonding pattern of novel Bi@In8Bi123−/5− clusters was analyzed (see figure). The highly symmetric structures and peculiar magnetic shielding properties could be explained by involving the “spherically aromatic nature” of the bonding in Bi@In8Bi123−/5−. Those clusters are the largest synthesized binary In/Bi clusters isolated from the solution known to the date.
Anions are associated with several biological processes in nature and act as catalysts in chemical and fuel production. Non-covalent interactions are useful tools for driving molecular processes. ...Recently, compounds containing halogen bond (XB) donors enhanced by hydrogen bonds (HBs) have been highlighted in the literature. Here, bonds between selected structures, capable of HB-enhanced XB (HBeXB), and anions (Cl
−
, Br
−
, and I
) have been investigated. EDA-NOCV analysis shows that increasing the X halogen donor atom (Cl < Br < I) or decreasing the X
−
anion (I
−
> Br
−
> Cl
−
) sizes favors C-X X
−
non-covalent interactions. Molecules containing HBeXB interact more favorably with anions because of more attractive electrostatic and/or less intense Pauli repulsion C-X X
−
interactions. The electron-acceptor groups (-NO
2
) present in the receptor structure support more attractive non-covalent bonds with Cl
−
. This is because the C-X bond is polarized by the -NO
2
group and/or N-H I interaction. The improvement from a mono to double HBeXB system favors anion recognition due to more attractive C-I (Cl
−
, Br
−
or I
−
) bonds polarized through N-H I interactions. Our results contribute significantly to gain further insight into the mechanism of action of compounds with anion sensing properties, aiding in the design of compounds with improved properties.
Anions have relevant roles in nature and in the chemistry industry. Here, structures containing halogen bond donors enhanced by hydrogen bonds have been tuned aiming to improve the anionic recognition.
In recent years, endohedral metallofullerenes involving the C50 cages have been observed experimentally to encapsulate several metal atoms. This is the last step in a bottom-up growing mechanism to ...produce the most commonly observed large metallofullerenes. Nonetheless, currently, there is a lack of theoretical rationalization of such compounds. We now report, for the first time, a comprehensive theoretical study extending the experimentally known M@C50 species to endohedral group 3 and 4 elements using dispersion-corrected density functional theory. For C50 fullerene, isomers C s (266) and D 5h (271) are the most energetically favorable cages to host these metals, despite being far from the ground state of neutral C50 fullerene. Interestingly, properties of these endohedral compounds are highly comparable to those of the tri- and tetra-anions of the correspondent hollow fullerene cages. It is found that metal–cage binding energies larger than −5 eV are directly related to relative abundances experimentally measured for the group 3 endohedral metallofullerenes. In addition, hypothetical group 4 metallofullerenes are also expected to be stable. Our results show that the resulting metal atoms transfer charge to the cage, to partially covalent-ionic compounds, which is the nature of the metal encapsulation within the C50 cage, where the ionic bond character increases for the heavier elements. In all cases, highest occupied molecular orbital–lowest unoccupied molecular orbital gaps smaller than 0.4 eV are found, in accordance with the high reactivity imposed by the need for further growth. Aromaticity NICS(0)iso indices reveal that some carbon rings close to the enclosed metal M are not fully aromatic and some are even antiaromatic, even though hollow C50 fullerene cages are fully aromatic. Thus, the stabilities of the endohedral M@C50 compounds are not fully ruled by the aromatic character of the carbon cage but instead by the energy characteristics of the metal–cage interactions, which are fully characterized by means of energy decomposition analyses. Such results can be useful to guide further experimental explorative synthetic efforts toward more diverse metal species encapsulated within the higher intermediate C50 cage, which can be extended to other intermediate species already experimentally detected.
New Equations to Estimate GFR in Children with CKD SCHWARTZ, George J; MUNOZ, Alvaro; SCHNEIDER, Michael F ...
Journal of the American Society of Nephrology,
03/2009, Letnik:
20, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The Schwartz formula was devised in the mid-1970s to estimate GFR in children. Recent data suggest that this formula currently overestimates GFR as measured by plasma disappearance of iohexol, likely ...a result of a change in methods used to measure creatinine. Here, we developed equations to estimate GFR using data from the baseline visits of 349 children (aged 1 to 16 yr) in the Chronic Kidney Disease in Children (CKiD) cohort. Median iohexol-GFR (iGFR) was 41.3 ml/min per 1.73 m(2) (interquartile range 32.0 to 51.7), and median serum creatinine was 1.3 mg/dl. We performed linear regression analyses assessing precision, goodness of fit, and accuracy to develop improvements in the GFR estimating formula, which was based on height, serum creatinine, cystatin C, blood urea nitrogen, and gender. The best equation was: GFR(ml/min per 1.73 m(2))=39.1height (m)/Scr (mg/dl)(0.516) x 1.8/cystatin C (mg/L)(0.294)30/BUN (mg/dl)(0.169)1.099(male)height (m)/1.4(0.188). This formula yielded 87.7% of estimated GFR within 30% of the iGFR, and 45.6% within 10%. In a test set of 168 CKiD patients at 1 yr of follow-up, this formula compared favorably with previously published estimating equations for children. Furthermore, with height measured in cm, a bedside calculation of 0.413*(height/serum creatinine), provides a good approximation to the estimated GFR formula. Additional studies of children with higher GFR are needed to validate these formulas for use in screening all children for CKD.
Bis- and tris-pyridyl borate ligands containing pyridyl donor arms, a methylated boron cap, and a fluorine-lined coordination pocket have been prepared and utilized in coinage metal chemistry. The ...tris(pyridyl)borate ligand has been synthesized using a convenient boron source, NBu4MeBF3. These N-based ligands permitted the isolation of group 11 metal–ethylene complexes MeB(6-(CF3)Py)3M(C2H4) and Me2B(6-(CF3)Py)2M(C2H4) (M = Cu, Ag, Au). The gold complexes display the largest coordination-induced upfield shifts of the ethylene 13C resonance relative to that of the free ethylene in their NMR spectra, while the silver complexes show the smallest shift. Solid-state structures of five of these metal–ethylene complexes as well as the related free ligands were established by X-ray crystallography. Surprisingly, all three MeB(6-(CF3)Py)3M(C2H4) adopt the rare κ2 coordination mode rather than the typical κ3 coordination mode of facial capping tridentate ligands. Computational analyses indicate that κ2 coordination mode is favored over the κ3-mode in these coinage metal–ethylene complexes and point to the effects CF3-substituents have on κ2/κ3-energy difference. The M–C and M–N bond distances of MeB(6-(CF3)Py)3M(C2H4) follow the trend expected based on covalent radii of M(I) ions. The calculated ethylene–M interaction energy of κ2-MeB(6-(CF3)Py)3M(C2H4) indicated that the gold(I) forms the strongest interaction with ethylene. A comparison to the related poly(pyrazolyl)borates is also presented.
The Chronic Kidney Disease in Children study is a cohort of about 600 children with chronic kidney disease (CKD) in the United States and Canada. The independent variable for our observations was a ...measurement of glomerular filtration rate (GFR) by iohexol disappearance (iGFR) at the first two visits 1 year apart and during alternate years thereafter. In a previous report, we had developed GFR estimating equations utilizing serum creatinine, blood urea nitrogen, height, gender, and cystatin C measured by an immunoturbidimetric method; however, the correlation coefficient of cystatin C and GFR (-0.69) was less robust than expected. Therefore, 495 samples were re-assayed using immunonephelometry. The reciprocal of immunonephelometric cystatin C was as well correlated with iGFR as was height/serum creatinine (both 0.88). We developed a new GFR estimating equation using a random 2/3 of 965 person-visits and applied it to the remaining 1/3 as a validation data set. In the validation data set, the correlation of the estimated GFR with iGFR was 0.92 with high precision and no bias; 91 and 45% of eGFR values were within 30 and 10% of iGFR, respectively. This equation works well in children with CKD in a range of GFR from 15 to 75ml/min per 1.73m2. Further studies are needed to establish the applicability to children of normal stature and muscle mass, and higher GFR.
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![[Sn8]6−‐Bridged Mixed‐Valen...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1433-7851/small "[Sn8]6−‐Bridged Mixed‐Valence ZnI/ZnII in {[K2ZnSn8(ZnMes)]2}4− Inverse Sandwich‐Type Cluster Supported by a ZnI−ZnI Bond")
