The role of ganglioside GM3 in the modulation of conformation and activity of sarcoplasmic reticulum Ca(2+)-ATPase

Rabbit sarcoplasmic reticulum does contain trace amounts of gangliosides, and the main species is GM3. Incorporation of GM3 into the SR vesicles or addition of it to the soybean phospholipid used for reconstitution of proteoliposomes obviously increased ATP hydrolysis, as well as, Ca2+ uptake activity of sarcoplasmic reticulum Ca(2+)-ATPase. Conformation changes of Ca(2+)-ATPase induced by GM3 were also observed by circular dichroism, intrinsic fluorescence and fluorescence quenching measurements.     

The "allosteric three-site model" of elongation cannot be confirmed in a well-defined ribosome system from Escherichia coli

For the functional role of the ribosomal tRNA exit (E) site, two different models have been proposed. It has been suggested that transient E-site binding of the tRNA leaving the peptidyl (P) site promotes elongation factor G (EF-G)-dependent translocation by lowering the energetic barrier of tRNA release [Lill, R., Robertson, J. M. & Wintermeyer, W. (1989) EMBO J. 8, 3933-3938]. The alternative "allosteric three-site model" [Nierhaus, K.H. (1990) Biochemistry 29, 4997-5008] features stable, codon-dependent tRNA binding to the E site and postulates a coupling between E and aminoacyl (A) sites that regulates the tRNA binding affinity of the two sites in an anticooperative manner. Extending our testing of the two conflicting models, we have performed translocation experiments with fully active ribosomes programmed with heteropolymeric mRNA. The results confirm that the deacylated tRNA released from the P site is bound to the E site in a kinetically labile fashion, and that the affinity of binding, i.e., the occupancy of the E site, is increased by Mg2+ or polyamines. At conditions of high E-site occupancy in the posttranslocation complex, filling the A site with aminoacyl-tRNA had no influence on the E site, i.e., there was no detectable anticooperative coupling between the two sites, provided that second-round translocation was avoided by removing EF-G. On the basis of these results, which are entirely consistent with our previous results, we consider the allosteric three-site model of elongation untenable. Rather, as proposed earlier, the E site-bound state of the leaving tRNA is a transient intermediate and, as such, is a mechanistic feature of the classic two-state model of the elongating ribosome.     

Near-ohmic behavior for conducting polymers: extension beyond PEDOT on gold-plated platinum to other polymer-counterion/substrate combinations

Conducting polymers constitute a class of materials for which electrochemical and electron transport properties are a function not only of their chemical identity but also of their complex morphology. In this paper, we investigate and compare the frequency dependence behavior of the impedance of poly(3,4-ethylenedioxythiophene), or PEDOT, and that of poly(3,4-ethylenedioxypyrrole), or PEDOP, which are doped with a series of polyatomic anions during electrodeposition. We also contrast the behavior of PEDOT on Pt|Au, Pt, glassy carbon, and gold. Initial results for polycarbazole, PCz, electrodes are, in addition, included. Deposition parameters were adjusted to produce morphologically similar films for PEDOT, PEDOP, and PCz. In doing so, we have been successful in producing frequency-independent impedance behavior similar to that previously reported for PEDOT on Pt|Au. Although the impedance behavior of these polymers appears to be primarily determined by morphological features, the impact of counterion identity (beyond ionic charge transport) is also discussed. These studies suggest that choice of polymer/dopant combination and electrodeposition parameters can be manipulated to tune the impedance characteristics of electrodes, thereby optimizing them for capacitive or faradaic charge injection, or some combination of the two.     

Multiresolution biological transient extraction applied to respiratory crackles

Ketoprofen was encapsulated within poly-epsilon-caprolactone (PCL) and hydroxypropyl methylcellulose phthalate 50 (HPMCP50) microspheres (MS). Scanning electron microscopy (SEM) studies showed spherical particles without surface crystal formation and differential scanning calorimetry (DSC) supported these results. MS of PCL or HPMCP50 had a mean particle size of 10.7 +/- 2.2 and 10.9 +/- 2.0 mu m respectively, whereas a mixture of these polymers increased the MS particle size to 30 mu m. Greater incorporation efficiencies were found for HPMCP50 MS (98.1 +/- 0.7). MS of PCL and HPMCP50 mixtures showed a decreased drug entrapment as the amount of PCL was increased (96.0 +/- 0.2 for 25% PCL, 95.6 +/- 1.8 for 50% PCL, 80.2 +/- 0.7 for 75% PCL and 78.9 +/- 9.0 for 100% PCL). Size exclusion chromatography (SEC) studies revealed a weak interaction between ketoprofen and PCL and some polymer degradation was found during HPMCP50 MS storage, probably by breaking of the phthalic anhydride bond to be anyhydroglucose backbone. Four types of cryoprotectors (glucose, trehalose, mannitol and sorbitol, at 5 and 10% W/V) and two freezing conditions (-196 and -20 degrees C) were evaluated in freeze-drying studies. For HPMCP50, the sizes of MS after reconstitution of liophylizates were nearly the same as the initial ones. For PCL MS only, those formulations with sorbitol or glucose at 10% and frozen at -196 degrees C showed acceptable results. In contrast to the rapid release rate of ketoprofen from PCL MS as a result of carrier porosity (80% released within 15 min), the release from HPMCP50 MS could be controlled by means of pH (40% released in the first 15 min in simulated gastric fluid and nearly 100% ketoprofen delivered in the same time in simulated intestinal fluid).     

Auricular reconstruction with a postauricular myocutaneous island flap: flip-flop flap

Surgical defects of the concha-helix part of the ear larger than 2 cm may pose a reconstructive challenge. Split- or full-thickness skin grafts or local flaps may be used, and a number of these have been described. Yet cosmetic results are often unsatisfactory. Our experience with a postauricular myocutaneous island flap is described. Eleven patients (12 ears), aged 48 to 89 years, underwent the procedure under local anesthesia following excision of conchal bowl malignant tumors that included the cartilage underlying the skin. The surgical technique is described in detail. Few complications were encountered, and cosmetic results were excellent. In four ears, resection margins extended into the ear canal, and that portion was allowed to heal satisfactorily by secondary intention. We recommend the use of this flap for practical, safe, and early good cosmetic results.     

Time-related changes of cold-stored rat liver in University of Wisconsin solution. Effect of ursodeoxycholate

Livers of Wistar rats were stored between 0 and 36 hrs. in the University of Wisconsin preservation liquid in order to determine time-related biochemical and morphological hepatic changes. Ursodeoxycholate (100 microM) was also added in the medium to test the hepatoprotective properties of the bile salt. Biochemical assays were performed on hepatic microsomes, plasma and biliary canalicular membranes. Protein and lipid composition of the microsomal and baso-lateral plasma membranes remained stable. Protein and cholesterol content of the biliary canalicular membranes decreased, phospholipid/cholesterol ratio increased between 0 and 36 hrs.; it resulted in a leak of 5'-nucleotidase and leucine amino peptidase activity of these biliary canalicular membranes, especially up to 12 hrs. Between 0 and 36 hrs., the lipid and protein content remained stable in the plasma membranes, as well as both tested enzymatic activities. Observations under electron microscopy showed alterations and underlined fragility of the bile canaliculi, particularly after 24 hrs. preservation. Ultrastructure of sinusoidal membranes showed damaged microvilli. Endoplasmic reticulum remained unchanged, in relation to the stability of the microsomal lipidic, proteic content and hydroxymethylglutaryl-coenzyme A reductase activity, except the decreased protein content after preservation for 36 hrs without ursodeoxycholate. Ursodeoxycholate by itself did not protect against the described disturbances.     

The effect of image resolution on vessel signal in high-resolution magnetic resonance angiography

In this paper, the theoretical dependence of the signal of flowing fluids is considered in terms of the imaging parameters and the physical condition of the flowing fluid. For the vessel sizes, flow ranges, and imaging conditions studied, it is demonstrated that the fluid signal can be predicted from the solution of Bloch equations. For vessels on the order of the imaging resolution or smaller, the effects of the image resolution must be included