Clinical and radiological characteristics of acute pulmonary embolus in relation to 28-day and 6-month mortality.

BACKGROUND: Patients with acute pulmonary embolism (PE) exhibit a wide spectrum of clinical and laboratory features when presenting to hospital and pathophysiologic mechanisms differentiating low-risk and high-risk PE are poorly understood. OBJECTIVES: To investigate the prognostic value of clinical, laboratory and radiological information that is available within routine tests undertaken for patients with acute PE. METHODS: Electronic patient records (EPR) of patients who underwent Computed Tomography Pulmonary Angiogram (CTPA) scan for the investigation of acute PE during 6-month period (01.01.2016-30.06.2016) were examined. Data was gathered from EPR for patients that met inclusion criteria and all CTPA scans were re-evaluated. Biochemical thresholds of low-grade and high-grade inflammation, serum CRP >10mg/L and >150mg/L and serum albumin concentrations <35g/L and <25 g/L, were combined in the Glasgow Prognostic Score (GPS) and peri-operative Glasgow Prognostic Score (poGPS) respectively. Neutrophil Lymphocyte ratio (NLR) was also calculated. Pulmonary Embolus Severity Index score was calculated. RESULTS: Of the total CTPA reports (n = 2129) examined, 245 patients were eligible for inclusion. Of these, 20 (8%) patients had died at 28-days and 43 (18%) at 6-months. Of the 197 non-cancer related presentations, 28-day and 6-month mortality were 3% and 8% respectively. Of the 48 cancer related presentations, 28-day and 6-month mortality were 29% and 58% respectively. On univariate analysis, age ≥65 years (p<0.01), PESI score ≥100(p = <0.001), NLR ≥3(p<0.001) and Coronary Artery Calcification (CAC) score ≥ 6 (p<0.001) were associated with higher 28-day and 6-month mortality. PESI score ≥100 (OR 5.2, 95% CI: 1.1, 24.2, P <0.05), poGPS ≥1 (OR 2.5, 95% CI: 1.2-5.0, P = 0.01) and NLR ≥3 (OR 3.7, 95% CI: 1.0-3.4, P <0.05) remained independently associated with 28-day mortality. On multivariate binary logistic regression analysis of factors associated with 6-month mortality, PESI score ≥100 (OR 6.2, 95% CI: 2.3-17.0, p<0.001) and coronary artery calcification score ≥6 (OR 2.3, 95% CI: 1.1-4.8, p = 0.030) remained independently associated with death at 6-months. When patients who had an underlying cancer diagnosis were excluded from the analysis only GPS≥1 remained independently associated with 6-month mortality (OR 5.0, 95% CI 1.2-22.0, p<0.05). CONCLUSION: PESI score >100, poGPS≥1, NLR ≥3 and CAC score ≥6 were associated with 28-day and 6-month mortality. PESI score ≥100, poGPS≥1 and NLR ≥3 remained independently associated with 28-day mortality. PESI score ≥100 and CAC score ≥6 remained independently associated with 6-month mortality. When patients with underlying cancer were excluded from the analysis, GPS≥1 remained independently associated with 6-month mortality. The role of the systemic inflammatory response (SIR) in determining treatment and prognosis requires further study. Routine reporting of CAC scores in CTPA scans for acute PE may have a role in aiding clinical decision-making regarding treatment and prognosis.

Functional and developmental expression of a zebrafish Kir1.1 (ROMK) potassium channel homologue Kcnj1.

The zebrafish, Danio rerio, is emerging as an important model organism for the pathophysiological study of some human kidney diseases, but the sites of expression and physiological roles of a number of protein orthologues in the zebrafish nephron remain mostly undefined. Here we show that a zebrafish potassium channel is orthologous to the mammalian kidney potassium channel, ROMK. The cDNA (kcnj1) encodes a protein (Kcnj1) that when expressed in Xenopus laevis oocytes displayed pH- and Ba2+-sensitive K+-selective currents, but unlike the mammalian channel, was completely insensitive to the peptide inhibitor tertiapin-Q. In the pronephros, kcnj1 transcript expression was restricted to a distal region and overlapped with that of sodium­chloride cotransporter Nkcc, chloride channel ClC-Ka, and ClC-Ka/b accessory subunit Barttin, indicating the location of the diluting segment. In a subpopulation of surface cells, kcnj1 was coexpressed with the a1a.4 isoform of the Na+/K+-ATPase, identifying these cells as potential K+ secretory cells in this epithelium. At later stages of development, kcnj1 appeared in cells of the developing gill that also expressed the a1a.4 subunit.Morpholino antisense-mediated knockdown of kcnj1 was accompanied by transient tachycardia followed by bradycardia, effects consistent with alterations in extracellular K+ concentration in the embryo.Our findings indicate that Kcnj1 is expressed in cells associated with osmoregulation and acts as a K+ efflux pathway that is important in maintaining extracellular levels of K+ in the developing embryo.

Molecular characterization of the mercurial sensitivity of a frog urea transporter (fUT).

The amphibian urea transporter (fUT) shares many properties with the mammalian urea transporters (UT) derived from UT-A and UT-B genes. The transport of urea by fUT is inhibited by the mercurial agent p-chloromercuribenzenesulfonic acid (pCMBS). We found that in oocytes expressing cRNA encoding fUT, a 5-min preincubation in 0.5 mM mercury chloride (HgCl2) also significantly reduced urea uptake. The transport of urea by fUT was rendered mercury (Hg2+) insensitive by mutating either of the residues C185 or H187, both of which lie within the M-I region (close to the hypothetical UT pore). In oocytes expressing a mixture of the C185 and H187 mutants, Hg2+ sensitivity was reestablished. The transport of urea by the mouse UTs mUT-A2 and mUT-A3 was not sensitive to Hg2+. Introducing cysteine residues analogous to that mutated in fUT into mUT-A2 or mUT-A3 did not induce Hg2+ sensitivity. Additionally, introducing the double cysteine, histidine mutations into mUT-A2 or mUT-A3 still did not induce Hg2+ sensitivity, indicating that a region outside of the M-I region also contributes to the Hg2+-induced block of fUT. Using a series of chimeras formed between UT-A3 and fUT, we found that as well as C185 and H187, residues within the COOH terminal of fUT determine Hg2+ sensitivity, and we propose that differences in the folding of this region between fUT and mUT-A2/mUT-A3 allow access of Hg2+ to the fUT channel pore.

The basolateral expression of mUT-A3 in the mouse kidney.

Facilitative UT-A urea transporters play a central role in the urinary concentrating mechanism. There are three major UT-A isoforms found in the mouse kidney: mUT-A1, mUT-A2, and mUT-A3. The major aim of this study was to identify the location and function of mUT-A3. UT-A proteins were investigated using three novel mouse UT-A-targeted antibodies: ML446, MQ2, and ML194. ML446 detected mUT-A1 and mUT-A3. ML194 detected mUT-A1 and mUT-A2. Importantly, MQ2 was found to be selective for mUT-A3. MQ2 detected a 45- to 65-kDa signal in the mouse kidney inner medulla, which was deglycosylated to a 40-kDa protein band. Immunolocalization studies showed that mUT-A3 was strongly detected in the papillary tip, mainly in the basolateral regions of inner medullary collecting duct (IMCD) cells. Immunoblotting of subcellular fractions of inner medullary protein suggested that in mouse kidney mUT-A3 was present in plasma membranes. Consistent with this, immunoelectron microscopy demonstrated that mUT-A3 was predominantly localized at the basal plasma membrane domains of the IMCD cells in mouse kidney. Heterologous expression of mUT-A3-enhanced green fluorescent protein in Madin-Darby canine kidney cells showed that the protein localized to the basolateral membrane. In conclusion, our study indicates that mUT-A3 is a basolateral membrane transporter expressed in IMCD cells.

Regulation and identity of intracellular calcium stores involved in membrane cross talk in the early distal tubule of the frog kidney.

The early distal tubule (EDT) of the frog nephron, similar to the thick ascending limb in mammals, mediates the transepithelial absorption of NaCl. The continued absorption of NaCl in the face of varying Na(+) load is maintained by coordination of the activity of ion-transporting proteins in the apical and basolateral membranes, so-called pump-leak coupling. Previous studies identified intracellular Ca(2+), originating from an intracellular Ca(2+) store, as playing a key role in pump-leak coupling in the EDT (Cooper GJ, Fowler MR, and Hunter M. Pflügers Arch 442: 243-247, 2001). The purpose of the experiments described in this paper was to identify the intracellular Ca(2+) storage pools in the renal diluting segment. Store Ca(2+) movements were monitored by the fluorescence of mag-fura 2 in permeabilized segments of frog EDTs. The presence of both ATP and Ca(2+) was required to maintain store Ca(2+) content. Removal of either of these substrates resulted in a passive leak of Ca(2+) from the stores. The uptake of Ca(2+) into the store was sensitive to the SERCA inhibitor 2,5-di(tert-butyl) hydroquinone, whereas Ca(2+) release from the store was stimulated by IP(3) but not cADPR. Store Ca(2+) was insensitive to the mitochondrial ATP synthase inhibitor oligomycin, and, under conditions that energized Deltapsi(m), the complex 1 inhibitor rotenone and the protonophore FCCP. Ionomycin was able to mobilize store Ca(2+) following exposure to IP(3). These results suggest that the endoplasmic reticulum is a dominant Ca(2+) store in the frog EDT. A second pool, sensitive to ionomycin but not IP(3), may overlap with the IP(3)-sensitve pool. The data also rule out any contribution by mitochondria to EDT Ca(2+) cycling.

Relationship between intracellular pH and chloride in Xenopus oocytes expressing the chloride channel ClC-0.

During maturation of oocytes, Cl(-) conductance (G(Cl)) oscillates and intracellular pH (pH(i)) increases. Elevating pH(i) permits the protein synthesis essential to maturation. To examine whether changes in G(Cl) and pH(i) are coupled, the Cl(-) channel ClC-0 was heterologously expressed. Overexpressing ClC-0 elevates pH(i), decreases intracellular Cl(-) concentration ([Cl(-)](i)), and reduces volume. Acute acidification with butyrate does not activate acid extrusion in ClC-0-expressing or control oocytes. The ClC-0-induced pH(i) change increases after overnight incubation at extracellular pH 8.5 but is unaltered after incubation at extracellular pH 6.5. Membrane depolarization did not change pH(i). In contrast, hyperpolarization elevates pH(i). Thus neither membrane depolarization nor acute activation of acid extrusion accounts for the ClC-0-dependent alkalinization. Overnight incubation in low extracellular Cl(-) concentration increases pH(i) and decreases [Cl(-)](i) in control and ClC-0 expressing oocytes, with the effect greater in the latter. Incubation in hypotonic, low extracellular Cl(-) solutions prevented pH(i) elevation, although the decrease in [Cl(-)](i) persisted. Taken together, our observations suggest that KCl loss leads to oocyte shrinkage, which transiently activates acid extrusion. In conclusion, expressing ClC-0 in oocytes increases pH(i) and decreases [Cl(-)](i). These parameters are coupled via shrinkage activation of proton extrusion. Normal, cyclical changes of oocyte G(Cl) may exert an effect on pH(i) via shrinkage, thus inducing meiotic maturation.

Transport of volatile solutes through AQP1.

For almost a century it was generally assumed that the lipid phases of all biological membranes are freely permeable to gases. However, recent observations challenge this dogma. The apical membranes of epithelial cells exposed to hostile environments, such as gastric glands, have no demonstrable permeability to the gases CO2 and NH3. Additionally, the water channel protein aquaporin 1 (AQP1), expressed at high levels in erythrocytes, can increase membrane CO2 permeability when expressed in Xenopus oocytes. Similarly, nodulin-26, which is closely related to AQP1, can act as a conduit for NH3. A key question is whether aquaporins, which are abundant in virtually every tissue that transports O2 and CO2 at high levels, ever play a physiologically significant role in the transport of small volatile molecules. Preliminary data are consistent with the hypothesis that AQP1 enhances the reabsorption of HCO3- by the renal proximal tubule by increasing the CO2 permeability of the apical membrane. Other preliminary data on Xenopus oocytes heterologously expressing the electrogenic Na+-HCO3- cotransporter (NBC), AQP1 and carbonic anhydrases are consistent with the hypothesis that the macroscopic cotransport of Na+ plus two HCO3- occurs as NBC transports Na+ plus CO3(2-) and AQP1 transports CO2 and H2O. Although data - obtained on AQP1 reconstituted into liposomes or on materials from AQP1 knockout mice - appear inconsistent with the model that AQP1 mediates substantial CO2 transport in certain preparations, the existence of unstirred layers or perfusion-limited conditions may have masked the contribution of AQP1 to CO2 permeability.