Chromophore of Bacteriorhodopsin is Closer to the Cytoplasmic Surface of Purple Membrane: Fluorescence Energy Transfer on Oriented Membrane Sheets

Transmembrane location of the retinal chromophore, either native or reduced in situ to a fluorescent derivative, of the purple membrane of Halobacterium halobium was investigated with fluorescence energy transfer techniques. Single sheets of purple membrane, either native or reduced with borohydride, were adsorbed on polylysine-coated glass; the orientation, whether the exposed surfaces were cytoplasmic or extracellular, was controlled by adjusting the pH of the membrane suspension before the adsorption. On the exposed surface of the reduced membrane, a layer of cytochrome c, hemoglobin, or ferritin was deposited. The rate of excitation energy transfer from the fluorescent chromophore in the membrane to the colored protein was greater when the protein was on the cytoplasmic surface of the membrane than when it was on the extracellular surface. Analysis in which uniform distribution of the protein on the surface was assumed showed that the reduced chromophore is situated at a depth of <1.5 nm from the cytoplasmic surface. The location of the native retinal chromophore was examined by depositing a small amount of tris(2,2'-bipyridyl)ruthenium(II) complex on the native membrane adsorbed on the glass. Energy transfer from the luminescent complex to the retinal chromosphore was more efficient on the cytoplasmic surface than on the extracellular surface, suggesting that the native chromophore is also on the cytoplasmic side. From these and previous results we conclude that the chromophore, whether native or reduced, of bacteriorhodopsin is located at a depth of 1.0 +/- 0.3 nm from the cytoplasmic surface of purple membrane.

Percutaneous radio-frequency mandibular nerve rhizotomy guided by CT fluoroscopy

We describe a new method for radio-frequency mandibular nerve rhizotomy under CT fluoroscopy. A patient with cancer had severe intractable and drug-resistant pain in his left mandibular region. Because he had an anatomic deformity due to cancer invasion and radiation therapy, we planned a mandibular nerve rhizotomy under CT fluoroscopic imaging. The needle was advanced to the mandibular nerve just caudal to the foramen ovale under real-time CT fluoroscopy, avoiding the cancer region. Pain scores of the patient were reduced after the nerve rhizotomy, without any complications.

Changes in apparent systemic clearance of propofol during transplantation of living related donor liver

BACKGROUND

Propofol is used during living-related donor liver transplantation because its metabolism is not greatly affected by liver failure. However, the pharmacokinetics of propofol during liver transplantation have not been fully defined. The purpose of this study was to evaluate the apparent systemic clearance of propofol during the dissection, anhepatic and reperfusion phases of living-related donor liver transplantation, and to estimate the role of the small intestine and lung as extrahepatic sites for propofol disposition.

METHODS

Ten patients scheduled for living-related donor liver transplantation were enrolled in the study. Anaesthesia was induced with vecuronium 0.1 mg kg(-1) and propofol 2 mg kg(-1), and then maintained by 60% air, 0.5-1.5% isoflurane in oxygen and a constant infusion of propofol at 2 mg kg(-1) h(-1). Apparent systemic clearance during the dissection, anhepatic and reperfusion phases was calculated from the pseudo-steady-state concentration for each phase. Disposition in the small intestine was determined by measuring arteriovenous blood concentration in 10 liver transplantation donors. Pulmonary disposition was determined by measuring the arteriovenous blood concentration in 10 recipients during the anhepatic phase. The data are expressed as mean (sd).

RESULTS

Apparent systemic clearances in the dissection, anhepatic and reperfusion phases were 1.89 (sd 0.48) litre min(-1), 1.08 (0.25) litre min(-1) and 1.53 (0.51) litre min(-1), respectively. The concentration of propofol in the portal vein was lower than in the radial artery. The intestinal extraction ratio calculated from the concentration in the radial artery and portal vein was 0.24 (0.12). There were no significant differences in propofol concentrations between the radial and pulmonary arteries.

CONCLUSION

Apparent systemic clearance was decreased by approximately 42 (10)% during the anhepatic phase compared with the dissection phase. After reperfusion, liver allografts rapidly began to metabolize propofol. The small intestine also participates in the metabolism of propofol.

Propofol activates vanilloid receptor channels expressed in human embryonic kidney 293 cells

Propofol (2,6-diisopropylphenol) is an intravenous anesthetic agent structurally unrelated to any other intravenous anesthetics. We examined the effect of propofol on a rat vanilloid receptor that was expressed in the human embryonic kidney (HEK) 293 cells by using calcium imaging method. Propofol caused a concentration-dependent increase in [Ca(2+)](i) in the HEK293 cells with the receptor. These responses were inhibited by removing extracellular calcium ions. The propofol-evoked increase in [Ca(2+)](i) in the HEK293 cells with the receptor was partially inhibited by capsazepine, a competitive antagonist of capsaicin. We conclude that propofol acts as an agonist for the receptor.

Hydrothorax: an unexpected complication after laparoscopic myomectomy

We report a case of hydrothorax as a complication of laparoscopic myomectomy in an otherwise healthy woman. The most likely cause of the patient's hydrothorax was irrigation fluid moving from the peritoneal cavity into the pleural space via defects in the diaphragm. Anaesthesists and surgeons should consider hydrothorax as a potential complication in any patient undergoing laparoscopy.

[Successful management of a patient who developed intra-operative pulmonary tumor embolism]

A 68-year-old female with retroperitoneal tumor extending into the inferior vena cava (IVC) developed massive pulmonary tumor embolism during removal of the tumor. Because of her unstable hemodynamics, emergency pulmonary embolectomy under cardiopulmonary bypass was performed. Successful management of her intra- and post-operative persistent right heart failure led to a satisfactory postoperative course without serious neurological complications. In peri-operative management of a patient with an extended tumor into IVC, prevention of the embolism, detection of the pulmonary embolism and treatment of intra- and post-operative right heart failure are important.

Purification of ferredoxins and their reaction with purified reaction center complex from the green sulfur bacterium Chlorobium tepidum

Four ferredoxin (Fd) fractions, namely, FdA-D were purified from the green sulfur bacterium Chlorobium tepidum. Their absorption spectra are typical of 2[4Fe-4S] cluster type Fds with peaks at about 385 and 280 nm and a shoulder at about 305 nm. The A(385)/A(280) ratios of the purified Fds were 0.76-0.80. Analysis of the N-terminal amino acid sequences of these Fds (15-25 residues) revealed that those of FdA and FdB completely agree with those deduced from the genes, fdx3 and fdx2, respectively, found in this bacterium (Chung and Bryant, personal communication). The N-terminal amino acid sequences of FdC and FdD (15 residues) were identical, and agree with that deduced from the gene fdx1 (Chung and Bryant, personal communication). The A(385) values of these Fds were unchanged when they were stored for a month at -80 degrees C under aerobic conditions and decreased by 10-15% when they were stored for 6 days at 4 degrees C under aerobic conditions, indicating that they are not extremely unstable. In the presence of Fd-NADP(+) reductase from spinach, and a purified reaction center (RC) preparation from C. tepidum composed of five kinds of polypeptides, these Fds supported the photoreduction of NADP(+) at room temperature with the following K(m) and V(max) (in micromol NADP(+) micromol BChl a(-1) h(-1)): FdA, 2.0 microm and 258; FdB, 0.49 microM and 304; FdC, 1.13 microM and 226; FdD, 0.5 microM and 242; spinach Fd, 0.54 microM and 183. The V(max) value of FdB was more than twice that previously reported for purified RC preparations from green sulfur bacteria.

Propofol potentiates ATP-activated currents of recombinant P2X(4) receptor channels expressed in human embryonic kidney 293 cells

We examined the effects of a general anesthetic 2, 6-diisopropylphenol (propofol) on ATP- and alpha,beta-methylene ATP (alphabetameATP)-activated currents in the human embryonic kidney 293 (HEK 293) cells expressing recombinant P2X receptor channels, using the whole-cell patch-clamp method. Propofol at clinical relevant concentrations ( approximately 56 microM) potentiated the current responses through the P2X(4) receptor in a dose-dependent manner, whereas propofol did not affect the responses through the P2X(2) receptor or through the heterologous complex of the P2X(2) and P2X(3) (P2X(2+3)) receptor. These results suggest that activation of P2X(4) subtype in the brain and the motor neurons of the spinal anterior horn might be involved in the excitatory effect by propofol such as convulsion and unexpected movements.

An alpha-L-arabinofuranosidase from Trichoderma reesei containing a noncatalytic xylan-binding domain

L-Sorbose, an excellent cellulase and xylanase inducer from Trichoderma reesei PC-3-7, also induced alpha-L-arabinofuranosidase (alpha-AF) activity. An alpha-AF induced by L-sorbose was purified to homogeneity, and its molecular mass was revealed to be 35 kDa (AF35), which was not consistent with that of the previously reported alpha-AF. Another species, with a molecular mass of 53 kDa (AF53), which is identical to that of the reported alpha-AF, was obtained by a different purification procedure. Acid treatment of the ammonium sulfate-precipitated fraction at pH 3.0 in the purification steps or pepsin treatment of the purified AF53 reduced the molecular mass to 35 kDa. Both purified enzymes have the same enzymological properties, such as pH and temperature effects on activity and kinetic parameters for p-nitrophenyl-alpha-L-arabinofuranoside (pNPA). Moreover, the N-terminal amino acid sequences of these enzymes were identical with that of the reported alpha-AF. Therefore, it is obvious that AF35 results from the proteolytic cleavage of the C-terminal region of AF53. Although AF35 and AF53 showed the same catalytic constant with pNPA, the former showed drastically reduced specific activity against oat spelt xylan compared to the latter. Furthermore, AF53 was bound to xylan rather than to crystalline cellulose (Avicel), but AF35 could not be bound to any of the glycans. These results suggest that AF53 is a modular glycanase, which consists of an N-terminal catalytic domain and a C-terminal noncatalytic xylan-binding domain.

Structural analysis of muscle thin filament

Thin sheets of Ac-Tm-Tn paracrystals were prepared in the presence of high concentration of Ca2+ ion and three-dimensional image analysis was performed. The optical diffraction pattern of an electron micrograph showed spots up to 1/1.6 nm-1 in the radial direction and up to 1/2.5 nm-1 in the axial direction, the best resolution ever obtained so far. The translationally filtered image showed clear polarity of filament which looked like a "spearhead" per each crossover repeat of actin helix. The three-dimensionally reconstructed model looked very similar to the inner regions (A+B domains) of the Ac-Tm-S1 complex obtained by Toyoshima and Wakabayashi (14, 15) when they were placed so that the "spearhead" pattern of the Tc-Tm-Tn complex and the "arrowhead" pattern of the Ac-Tm-S1 complex pointed in the same direction. The myosin-binding site of actin was identified by comparison of the two structures. The model of actin molecule cut out from the thin filament model had a low density region within itself, which was located about 2.5 nm from the helix axis. That low density region divided actin molecule into two domains, a large and a small domain. A dense "pillar" was detected which connected two neighboring actin molecules along a left-handed generic helix 1 nm from the helix axis. Two actin-actin binding sites which were responsible for the connection through the "pillar" were located on the inner surface of actin molecule. To obtain better crystalline arrays of actin, we tried a method utilizing adsorption to lipid. A positively-charged monolayer of lipids was formed on the surface of a small volume of buffer solution which was put in a microwell. Solution of negatively-charged F-actin was then injected into the buffer solution and was allowed to be joined to the lipid monolayer by electrostatic attraction. Fluidity of the lipid monolayer enabled the two-dimensional crystallization of actin. Electron microscopy revealed that larger paracrystalline arrays were formed more rapidly (less than 1 hr) than those formed within solution, which demonstrated the advantage of this adsorption method.

Marine sterols. VIII. Isolation and structure of sarcosterol, a new sterol with a delta17(20)-double bond from the soft coral Sarcophyton glaucum

The sterol mixture of the southern Japan's soft coral, Sarcophyton glaucum, was found to contain 11 sterols including a novel sterol, 23,24 xi-dimethylcholesta-5,22-dien-3 beta-ol and a new diunsaturated C29 sterol. 22,23-Dihydrobrassicasterol and gorgosterol were the major components in free- and esterified sterols respectively. Brassicasterol was found in S. glaucum, in contrast to the ubiquity of 24-epibrassicasterol in the marine invertebrates in the northern districts. The new sterol (sarcosterol) was isolated; its structure as 23 xi, 24 xi-dimethylcholesta-5, 17(20)-trans-dien-3 beta-ol was based on spectra evidence and comparison with cholesta-5, 17(20)-trans-dien-3 beta-ol.