A covalently linked recombinant albumin dimer is more rapidly cleared in vivo than are wild-type and mutant C34A albumin

Mammalian albumins are abundant plasma proteins that exhibit a relatively slow terminal clearance. For this reason they have been fused to potentially therapeutic proteins with rapid terminal clearance to produce fusion proteins with more desirable clearance profiles. A disulfide-linked albumin dimer has been described, but its abundance and stability in plasma are uncertain. To determine whether an obligatory albumin dimer incapable of dissociation would clear less rapidly than monomeric albumin, we expressed 3 recombinant rabbit serum albumin (RSA) polypeptides: H6RSA, RSA modified by the addition of an N-terminal hexahistidinyl tag; H6RSA(C34A), H6RSA with a single cysteine (Cys) 34-to-alanine (Ala) substitution (C34A); and DiRSA, H6RSA(C34A) joined by way of its C-terminus to RSA(C34A) through an intervening hexaglycine spacer. The C34A mutation was introduced to eliminate the possibility of disulfide bond-mediated dimerization. We expressed the proteins with the use of the yeast Pichia pastoris and purified them using nickel-chelate, ion exchange, and gel-filtration chromatography. After radioiodination and injection into rabbits, H6RSA and H6RSA(C34A) exhibited indistinguishable terminal catabolic half-lives (4.9 +/- 0.7 and 4.8 +/- 0.5 days, mean +/- SD), whereas that of DiRSA was reduced to 3.0 +/- 0.3 days (p<.05). The three proteins circulated in intact form, and their distributions in liver, lung, kidney, heart, and spleen did not differ 24 hours after injection. Although more DiRSA than H6RSA(C34A) was present in urine, in both cases it was in acid-soluble form. Ethyl palmitate treatment reduced the relative acceleration of DiRSA clearance compared with that of H6RSA(C34A), suggesting a role for the reticuloendothelial system in the differential clearance of the larger protein. Our results suggest that an albumin fusion protein should include only a single copy of albumin; that if the fusion protein exceeds a certain size, it may not acquire the slow clearance profile of native albumin; and that albumin dimerization through Cys34 probably does not contribute substantially to albumin metabolism in vivo.     

Atropine-Induced Multilevel Block in Acute Inferior Myocardial Infarction A Possible Indication for Prophylactic Pacing

The degree of A-V block increased after intravenous administration of atropine in 10 nondigitalized patients with acute inferior myocardial infarction who had narrow QRS complexes during periods of 1:1 A-V conduction. Short episodes of 3:1, 4:1 and 5:1 A-V block were seen to emerge: (a) in 6 patients, directly from Wenckebach periods; (b) in 3 patients, from alternating Wenckebach periods; and (c) in 1 patient, from a 3:2 Wenckebach period which led to a short-lived alternating Wenckebach period. Apparently, the predominance of the chronotropic effects on the sinus node over the dromotropic effects on the A-V node led to a tachycardia-dependent (more ischemic than vagal) process, exposing or producing multi- (two, three or four) level block involving the A-V node (and perhaps the His bundle). Subsequently, therapeutic pacing was instituted in 9/10 patients because they developed spontaneous symptomatic advanced A-V block. Therefore, it is possible that the early effects of atropine identified a narrowly-defined subset of patients in whom prophylactic pacing may be indicated. However, more studies are necessary to corroborate these assumptions.     

Longitudinal Dissociation in the His Bundle: A Possible Mechanism of Two Distinct Cycle Lengths in Atrioventricular Reentrant Tachycardia

Two wide QRS tachycardias with identical morphology but different cycle lengths (CLs) developed in a 63-year-old man. Electrophysiological study demonstrated inducible atrioventricular reentrant tachycardia (AVRT) due to a concealed left posterior accessory pathway (AP), which was successfully ablated by radiofrequency application. Neither dual AV nodal pathways nor other APs were documented. Splitting of the His-bundle electrogram was shown, and programmed stimulation induced sudden prolongation of intra-hisian conduction time. These results suggest longitudinal dissociation in the His bundle may be responsible for two distinct CLs in AVRT without dualAV nodal physiology.     

His Bundle Ablation with the Laser Thermal Probe ("Hot Tip"): A Feasibility Study

Successful percutaneous ablation of the bundle of His requires accurate localization together with delivery of the minimum effective energy to avoid unwanted effects. The energy output from laser sources can be controlled very precisely but is not easily directed to the bundle of His using conventional fiber optics. The laser thermal probe ("hot tip") consists of an optical fiber and a terminal metal cap that is rapidly heated during energy delivery. When applied to cadaver hearts at energies of 100-150 joules (10 watts for 10-15 seconds) the 2.0-mm diameter peripheral artery probe was able to damage the bundle of His without extensive surrounding damage. The right ventricular free wall and interventricular septum were perforated during some applications at these energies leaving a tract with a diameter of less than 2.0 mm. The atrioventricular (AV) membranous septum, Foramen Ovale, right atrial appendage, and septal leaflet of the tricuspid valve were more resistant at these energy levels and perforations were always less than 1.0 mm in diameter. The probe was modified for use during electrophysiological studies and good quality unipolar electrograms were recorded from the metal cap confirming that the probe could be accurately positioned adjacent to the bundle of His. The laser thermal probe deserves further study as a "self directing" ablation tool.     

The ECG diagnosis of acute myocardial infarction in the presence of left bundle branch block

The electrocardiographic diagnosis of ischemic heart disease is made more difficult in the setting of confounding patterns, including left bundle branch block (LBBB). The electrocardiographic detection of abnormalities arising from acute ischemic cardiac disease in this setting is possible in certain cases, contrary to popular medical opinion. Several strategies are available to assist in the correct interpretation of the electrocardiogram (ECG) with LBBB and potential acute ischemia, including: (1) a knowledge of the anticipated ST segment-T wave morphologies of LBBB and, consequently, the ability to recognize ischemic changes; (2) the performance of serial ECGs demonstrating dynamic change; and (3) a comparison to previous ECGs. The first strategy, an awareness of the anticipated ST segment morphologies of LBBB, is the most important and not dependent on additional diagnostic testing or past medical records.     

Combination of ventilator care bundle and regular oral care with chlorhexidine was associated with reduction in ventilator associated pneumonia

BackgroundVentilator associated pneumonia (VAP) is an important source of morbidity and mortality in patients receiving mechanical ventilation. VAP is associated with prolongation of mechanical ventilation, ICU and hospital stay and increases in costs.MethodsQuality improvement project. Mechanically ventilated patients received oral care every 8 h with chlorhexidine 2%. A formal process was developed to evaluate compliance with the following ventilator bundle initiatives: head of the bed elevation to 30–45°, daily sedation vacation and assess the readiness to extubate, providing peptic ulcer disease prophylaxis and providing deep vein thrombosis prophylaxis (unless contraindicated).ResultsThe rate of VAP before starting the project, in the first 6 months of year 1431H, was 16.2 cases/1000 ventilator days. Six month after inception of the quality improvement project, the VAP rates decreased to 5.6 cases/1000 ventilator days at the end of 1431H, and at the end of 1432H, it was 5.5 cases/1000 ventilator days. This leads to significant reduction in mortality (adjusted according to APACHE II) from 23.4% to 19.1% (p value 0.024) and the length of stay in ICU from 9.7 to 6.5 days (p value 0.00002).ConclusionThe combination of regular oral hygiene with chlorhexidine 2% and rigorous implementation of ventilator care bundle was associated with significant reduction in VAP rate in mechanically ventilated patients. This has led to reduction in length of stay in ICU from 9.7 to 6.5 days and reduction in mortality from 23.4% to 19.1%.     

Modelling of the Guillotine Cutting Process by Means of a Symmetrical Blade with the Defined Geometry

This paper modelled the cutting process of a bundle consisted of ultra-thin cold-rolled steel sheets using a guillotine. The geometry of a cutting tool with given dimensions was assumed. A bundle of sheets being cut was modelled as deformable, the cutting tool was rigid, and the finite element method along with computer system LS-DYNA was employed. Numerical simulations of the complex state of stress and of the corresponding complex state of strain were carried out. Cutting processes belong to fast changing physical phenomena, and therefore, highly nonlinear dynamical algorithms were applied in order to solve this particular problem. Experimental investigations were also conducted by means of the scanning electron microscopy. It was found that the fracture region consisted of two distinct zones: brittle and ductile separated from each other by the interfacial transition. Morphological features of the brittle, ductile, and the transition regions were identified. The ductile and brittle zones were separated at the depth of ca. 1/5 thickness of the cut steel sheet. Finally, the numerical results obtained by usage of the finite element method as well as experimental ones in the form of microscopic images were compared, showing quite good agreement.