Hypomagnesemia: a clinical perspective Pham, Phuong-Chi T; Pham, Phuong-Anh T; Pham, Son V ...
International journal of nephrology and renovascular disease,
01/2014, Letnik:
7, Številka:
default
Journal Article
Recenzirano
Odprti dostop
Although magnesium is involved in a wide spectrum of vital functions in normal human physiology, the significance of hypomagnesemia and necessity for its treatment are under-recognized and ...underappreciated in clinical practice. In the current review, we first present an overview of the clinical significance of hypomagnesemia and normal magnesium metabolism, with a focus on renal magnesium handling. Subsequently, we review the literature for both congenital and acquired hypomagnesemic conditions that affect the various steps in normal magnesium metabolism. Finally, we present an approach to the routine evaluation and suggested management of hypomagnesemia.
Background
Osmotic demyelination syndrome (ODS) is a complication generally associated with overly rapid correction of hyponatremia. Traditionally, nephrologists have been trained to focus solely on ...limiting the correction rate. However, there is accumulating evidence to suggest that the prevention of ODS is beyond achieving slow correction rates.
Methods
We (1) reviewed the literature for glial intracellular protective alterations during hyperosmolar stress, a state presumed equivalent to the rapid correction of hyponatremia, and (2) analyzed all available hyponatremia-associated ODS cases from PubMed for possible contributing factors including correction rates and concurrent metabolic disturbances involving hypokalemia, hypophosphatemia, hypomagnesemia, and/or hypoglycemia.
Results
In response to acute hyperosmolar stress, glial cells undergo immediate extracellular free water shift, followed by active intracellular Na
+
, K
+
and amino acid uptake, and eventual idiogenic osmoles synthesis. At minimum, protective mechanisms require K
+
, Mg
2+
, phosphate, amino acids, and glucose. There were 158 cases of hyponatremia-associated ODS where both correction rates and other metabolic factors were documented. Compared with the rapid correction group (>0.5 mmol/L/h), the slow correction group (≤0.5 mmol/L/h) had a greater number of cases with concurrent hypokalemia (49.4 vs. 33.3 %,
p
= 0.04), and a greater number of cases with any concurrent metabolic derangements (55.8 vs. 38.3 %,
p
= 0.03).
Conclusion
Glial cell minimizes volume changes and injury in response to hyperosmolar stress via mobilization and/or utilization of various electrolytes and metabolic factors. The prevention of ODS likely requires both minimization of correction rate and optimization of intracellular response during the correction phase when a sufficient supply of various factors is necessary.
Single crystal structures of six thiophene-containing molecules, endowed with strong electron-accepting groups, are reported. Each of the reported compounds is endowed with either one or two strong ...electron-accepting groups. These groups are dicyanovinyl (DCV) or –CHC(CN)2; tricyanovinyl (TCV) or –C(CN)(CN)2; cyanophenyl −Ph-CN and nitro −NO2. The molecules in this study are 2-(2,2′-bithiophen-5-ylmethylene)malononitrile or 2T-DCV (1); 2-(thieno3,2-bthiophen-2-ylmethylene)malononitrile or thienothiophene-DCV (2); 2,2′-(2,2′-bithiophene-5,5′-diylbis(methanylylidene))dimalononitrile or DCV-2T-DCV (3); 4,4′-(thiophene-2,5-diyl)dibenzonitrile (4); 2-(5″-(p-tolyl)2,2′:5′,2″-terthiophen-5-yl)ethene-1,1,2-tricarbonitrile (5); and 5,5′-dinitro-2,2′-bithiophene (6). A common and most noticeable feature found in these structures is the impact of the electron-accepting groups on promoting planarity and directing molecular packing in the solid state favoring the formation of π-stacks with varying distances ranging from 3.267 Å in 2 to 3.447 Å in 1. The presence of phenyl groups seems to result in less planar structures and favors herringbone motifs as seen in compounds 4 and 5. Planarity, close π-stacks, and the presence of additional strong interplanar and inter-stack interactions such as C–H···NC distances of 2.610 Å are also observed in 1–3 and 6. Hydrogen bonding between adjacent stacks was also observed. Intramolecular CN···S interactions with distances ranging from 3.267 to 3.364 Å were exhibited in all compounds with DCV or TCV groups. Such structural features are thought to be conducive to better charge transport in organic semiconductors. Our study found that fused thiophenes do not necessarily lead to more planar molecules in the presence of DCV groups presumably due to intramolecular N···S interactions. Case in point is compound 1, and a linear bithiophene derivative is found to be more planar than the fused bithiophene 2 even though both are endowed with the same electron-accepting group (DCV), as evident from experimental torsion angles. CCDC numbers are 2208323, 2208322, 2289032, 2270158, 2289048, and 2270317, for compounds 1–6, respectively.
We report herein on the solid-state structures of three closely related triphenylamine derivatives endowed with tricyanovinyl (TCV) and dicyanovinyl (DCV) groups. The molecules described contain ...structural features commonly found in the design of functional organic materials, especially donor–acceptor molecular and polymeric architectures. The common feature noticeable in these structures is the impact of these exceptionally strong electron-accepting groups in forcing partial planarity of the portion of the molecule carrying these groups and directing the molecular packing in the solid state, resulting in the formation of π-stacks of dimers within the unit cell of each. Stacks are formed between phenyl groups bearing electron-accepting groups on two adjacent molecules. Short π–π stack distances ranging from 3.283 to 3.671 Å were observed. Such motif patterns are thought to be conducive for better charge transport in organic semiconductors and enhanced device performance. Intramolecular charge transfer is evident from the shortening of the observed experimental bond lengths in all three compounds. The nitrogen atoms (of the cyano groups) have been shown to be extensively involved in short contacts in all three structures, primarily through C–H···NC interactions with distances as short as 2.462 Å. The compounds reported here are (3,3-dicyano-2-(4-(diphenylamino)phenyl)-1λ3-allylidene)amide or tricyanovinyltriphenylamine, Ph3NTCV (1); 2-(4-(diphenylamino)benzylidene)-malononitrile or dicyanovinyltriphenylamine, Ph3NDCV (2); and (3,3-dicyano-2-(4-(di-p-tolylamino)phenyl)-1λ3-allylidene)amide or dimethyltricyanovinyltriphenylamine, Me2Ph3NTCV (3). Results of density functional theory calculations using DFT-B3LYP/6-31G(d,p) indicate the lowering of LUMO levels as a result of the introduction of these groups with band gaps of 3.13, 2.61, and 2.55 eV for compounds 1–3, respectively, compared with 4.65 eV calculated for triphenylamine. This is supported by the electronic and fluorescence spectra of these molecules with absorption λmax of 483, 515, and 545 nm for compounds 1, 2, and 3, respectively.
We report herein on the competing inter- and intramolecular interactions in seven structurally related thiophene and ethyelenedioxythiophene (EDOT) molecules, substituted with bromine and/or ...tricyanovinyl (TCV) groups in various combinations, using single crystal structural analyses. Br···Br Interactions of less than 3.5 Å appear to be dominant in the crystal structures of the dibromo EDOT molecules and yet are almost nonexistent in 5,5″-dibromoterthiophene (shortest Br···Br distances are >4.2 Å), indicating a cooperative role involving the Br and the ethylenedioxy moiety. Short Br···Br distances of 3.5 Å within stacks and between adjacent stacks of molecules in crystalline dibromo EDOT dimer (6) could be utilized for the preparation of highly ordered polymers with the perfectly planar EDOT dimer as repeating unit, similar to the work reported by Wudl. On the other hand, new dimeric motifs are formed in Br-EDOT-TCV as strong S···N (3.03 Å) intermolecular interactions in TCV-EDOT are replaced by competing N···Br (2.99 Å) interactions. Short intramolecular N···S distances ranging from 3.2 to 3.3 Å are associated with small dihedral angles between the TCV and thiophene planes ranging from 0.80 to 4.3 deg. A slight enhancement of molecular planarity apparently has a profound impact on the extent of conjugation as evident from the CC bond lengths (1.34–1.40 Å) and C–C (1.37–1.44 Å) within the thiophene rings. These findings suggest that N···S, N···Br, and Br···Br inter- and intramolecular interactions could be utilized as additional crystal engineering tools to promote molecular planarity and arrangement of higher oligomers in the solid state prior to polymerization of thiophene-based molecular materials. On the basis of the current study, these interactions appear to also enhance the stability of the structure and influence intramolecular charge transfer and π-stack formation patterns.
The goal of this work is to examine the solid state structures of compounds that have been designed for increased conjugation and solubility, as these factors are important if these compounds are to ...be used in the solid state. The impact of three commonly employed molecular design strategies on the solid state structures of three thiophene derivatives is reported herein. These strategies include: (i) introduction of a strong electron accepting group (2T–TCV, 1 ); (ii) increase in conjugation by introducing a vinylene bridge in the presence of a strong electron accepting group (2T–TCV with both a TCV group and a CC bridge, 2 ); and (iii) enhancing the solubility by introducing n -butyl side chain groups in the presence of both a strong electron accepting group and a CC bridge (2T–TCV containing a strong electron accepting group, a CC bridge and four n -butyl groups, 3 ). Compounds 1 and 2 crystallize with four molecules in the unit cell while the unit cell of compound 3 contains only two molecules. The torsion between the two thiophene rings increases from 4.39° to 5.50° to 5.75° for 1 , 2 , and 3 , respectively. The short distances between adjacent molecules within the unit cell also increase from 2.84 Å in 2 to 3.47 Å in 3 . We also note that while the sulfur atoms assume a syn conformation in both 1 and 2 , they favor the anti -conformation in 3 . DFT calculations show a small energy difference between the syn and anti -conformation for 1 and 2 , i.e. 3.18 kJ mol −1 and 3.19 kJ mol −1 , respectively; this energy difference is found to be greater for compound 3 with the anti -conformation being 17.47 kJ mol −1 more stable than the syn conformation.
A series of three dicyanovinyl (DCV)-substituted oligothiophenes (referred to collectively as DCV-nT-DCV, where n = 1−3) were prepared and their electrochemical and structural properties were ...examined. The introduction of this group results in favorable structural features: planarity, π-stack formation, and close intermolecular interactions as revealed from X-ray single crystal analysis. Electrochemical measurements suggest that these molecules are easy to both oxidize and reduce and thus are expected to show ambipolar charge transport properties similar to those we reported earlier on a closely related series of oligthiophenes endowed with the tricyanovinyl group (TCV).
Continuing medical education (CME) is a compulsory requirement for every health professional. However, to date, little is known about the effectiveness of CME in Vietnam. This study assessed CME ...programs based on attendees' perception and evaluation.
A cross-sectional study was conducted during a five-month period in all 62 CME courses at a university hospital. A self-report, anonymous questionnaire was distributed to the participants during the course and was collected at the end of the course. The questionnaire included questions about demographic characteristics, experiences during the course and participants' perception and evaluation as measured by the 19-item Program Evaluation Instrument (PEI). A higher score on the PEI indicates a higher level of positive reaction toward CME programs.
Among 1312 participants in the analysis, the majority were females (58.1%) with a mean age of 34.5 (SD = 10.6) years. Almost all participants had good, positive perceptions toward CME. However, about 5% of participants reported CME a waste of time. Participants reported a high score on the PEI (95.0±8.9) and all four dimensions including program objectives (20.7±2.2), learner's objectives (18.8±2.3), teacher's behavior (25.7±2.7) and program satisfaction (29.7±3.4). While there was no association between demographic characteristics and PEI score, attendance rate during the courses and perceptions toward CME were positively associated with PEI score.
CME programs receive positive reaction and evaluation from healthcare professionals and are helpful in providing and updating knowledge, attitude and practice in Vietnam. However, further studies are needed in other settings and specialties to fully understand the effectiveness of CME in Vietnam.
Hyponatremia is one of the most common electrolyte abnormalities linked to adverse outcomes and increased mortality in hospitalized patients. While the differential diagnosis for hyponatremia is ...diverse, most cases stem from arginine vasopressin (AVP) dysregulation, where hypoosmolality fails to suppress AVP synthesis and release. The physiological effects of AVP are currently known to depend on its interaction with any of 3 receptor subtypes V1A, V2, and V1B. Activation of V2 by AVP is the key in renal water regulation and maintenance of total body volume and plasma tonicity. Despite the long-recognized problem with excess AVP in euvolemic and hypervolemic hyponatremia, traditional therapeutic options have relied on nonspecific and potentially problematic strategies. More recently, a new class of drugs, introduced as "aquaretics," has gained great attention among clinicians because of its ability to correct hyponatremia via direct competitive inhibition of AVP at V2 receptors to induce renal electrolyte-free water excretion. In this paper, we aim to review available clinical data on the only FDA-approved aquaretic, dual V1A/V2 receptor antagonist conivaptan, discuss its clinical indications, efficacy, safety profile, and comment on its clinical limitations.
1,4-Bis(4-nitro-styr-yl)benzene Pham, Phuong-Truc T
Acta crystallographica. Section E, Structure reports online,
07/2009, Letnik:
65, Številka:
Pt 8
Journal Article
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The complete molecule of the title compound, C(22)H(16)N(2)O(4), is generated by a crystallographic centre of inversion. The plane of the central aromatic ring is tilted by 11.85 (4)° with respect to ...the outer aromatic ring. The crystal packing is determined by van der Waals inter-actions, with stair-like stacking between adjacent aromatic rings. The stacks are staggered and each layer is approximately 3.8 Å from the next. The closest inter-molecular contact (approximately 2.42 Å) is between an O atom and a vinyl H atom.
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