Optically detected magnetic resonance of high-density ensemble of NV- centers in diamond.

Optically detected magnetic resonance (ODMR) is a way to characterize the ensemble of NV-centers. Recently, a remarkably sharp dip was observed in the ODMR with a high-density ensemble of NV centers. The model (Zhu et al 2014 Nat. Commun. 5 3424) indicated that such a dip was due to the spin-1 properties of the NV- centers. Here, we present many more details of the analysis to show how this model can be applied to investigate the properties of the NV- centers. By using our model, we have reproduced the ODMR with and without applied external magnetic fields. Additionally, we investigate how the ODMR is affected by the typical parameters of the ensemble NV- centers such as strain distributions, inhomogeneous magnetic fields, and homogeneous broadening width. Our model provides a way to characterize the NV- center from the ODMR, which would be crucial to realize diamond-based quantum information processing.

Surface pitting of heart valve disks tested in an accelerated fatigue tester.

There are various reports on the fracture of mechanical heart valves implanted in humans or animals and it has been pointed out that fractures are induced by erosion of the disk surface due to cavitation bubbles. Cavitation erosion on mechanical heart valves was studied using our originally designed accelerated fatigue tester. Several valve housings with different compliance values were used. The number and position of pits on the valve disk were measured using an optical microscope. Disk-closing velocity was measured and cavitation bubbles were monitored by a high-speed video camera. It was found that disk-closing velocity increased and cavitation erosion was enhanced with an increase in compliance of the valve holder. Therefore, careful attention should be paid to the compliance of an accelerated fatigue tester.

Effect of the sinus of valsalva on the closing motion of bileaflet prosthetic heart valves.

Conventional bileaflet prosthetic mechanical heart valves close passively with backflow. Naturally, the valve has problems associated with closure, such as backflow, water hammer effect, and fracture of the leaflet. On the other hand, in the case of the natural aortic valve, the vortex flow in the sinus of Valsalva pushes the leaflet to close, and the valve starts the closing motion earlier than the prosthetic valve as the forward flow decelerates. This closing mechanism is thought to decrease backflow at valve closure. In this study, we propose a new bileaflet mechanical valve resembling a drawbridge in shape, and the prototype valve was designed so that the leaflet closes with the help of the vortex flow in the sinus. The test valve was made of aluminum alloy, and its closing motion was compared to that of the CarboMedics (CM) valve. Both valves were driven by a computer controlled hydraulic mock circulator and were photographed at 648 frames/s by a high speed charge-coupled device (CCD) camera. Each frame of the valve motion image was analyzed with a personal computer, and the opening angles were measured. The flow rate was set as 5.0 L/min. The system was pulsed with 70 bpm, and the systolic/diastolic ratio was 0.3. Glycerin water was used as the circulation fluid at room temperature, and polystyrene particles were used to visualize the streamline. The model of the sinus of Valsalva was made of transparent silicone rubber. As a result, high speed video analysis showed that the test valve started the closing motion 41 ms earlier than the CM valve, and streamline analysis showed that the test valve had a closing mechanism similar to the natural one with the effect of vortex flow. The structure of the test valve was thought to be effective for soft closure and could solve problems associated with closure.

Effect of vesicle size on in vivo release of daunorubicin from hydrogenated egg phosphatidylcholine-based liposomes into blood circulation.

The effect of the vesicle size on in vivo release of daunorubicin, an anthracycline anticancer drug, from liposomes into the circulation was studied in rats. The liposomes were prepared from hydrogenated egg phosphatidylcholine (HEPC) or egg phosphatidylcholine (EPC), cholesterol and dicetylphosphate at a molar ratio of 5:4:1, and their mean vesicle sizes were adjusted to about 50 and 100 nm. The drug retained in the liposomes and the drug that leaked were separated from plasma by gel filtration. On the assumption that the lipid content does not change, the drug release from each liposome preparation was estimated from the latency (%) calculated from the drug/lipid concentration ratio of the liposome preparation. From HEPC-liposomes with a diameter of 50 nm, the drug was released gradually after intravenous administration, and the cumulative percent release of the drug reached 40% after 240 min. However, from EPC-liposomes with the same size, 50% of the drug was released within 5 min, and more than 90% of the drug was released within 60 min. From HEPC-liposomes with a diameter of 100 nm, no drug release was observed for 240 min after administration. These findings indicate that the vesicle size and the lipid composition of liposome preparation affect the in vivo drug release.

Immunohistochemical detection of the laminin receptor polypeptide, a putative precursor of 67-kda-laminin receptor, in human lung-cancer.

Laminin receptor polypeptide was immunodetected in human lung cancer with a polyclonal antibody raised against a 20-mer peptide of the putative high-affinity laminin receptor of 67 kDa (Wewer et al: Cancer Res 47: 5691-5698, 1987). As a result, immunoreactivity was recognized specifically in cancer cells both in freshly-prepared cell samples and in paraffin-embedded tissue specimens. It was shown that immunodetection of the laminin receptor polypeptide with this antipeptide antibody could be applied to diagnostic use for lung cancer. The results also suggest that the laminin receptor polypeptide is not necessarily a membrane-associated protein and may function without further processing to the 67 kDa-laminin receptor.

Solubilization by Triton X-100 makes possible complete recovery of lipids from liposomes in enzymatic assay.

We have developed an accurate and sensitive method for enzymatically determining phosphatidylcholine (PC) and cholesterol (CHOL) in liposomes. Solubilizing liposomes with a high concentration (80%) of Triton X-100 at 65 degrees C for 5 min led to the complete recovery of the lipids by current assay using commercial kits. The method had good linearity in a range of 0.004-0.4 mumol PC. Using this method, PC and CHOL were completely recovered from various liposomes. We conclude that PC and CHOL in liposomes can be determined accurately and sensitively by this method.

Effects of fluidity and vesicle size on antitumor activity and myelosuppressive activity of liposomes loaded with daunorubicin.

The effects of fluidity and vesicle size on the antitumor activity and myelosuppressive activity of liposomes loaded with daunorubicin, an anthracycline antitumor drug, were investigated in Yoshida sarcoma-bearing rats. Liposomes composed of egg phosphatidylcholine (EPC) or hydrogenated egg phosphatidylcholine (HEPC), cholesterol and dicetyl phosphate in a molar ratio of 5:4:1 were injected intravenously into rats 5 d after subcutaneous inoculation of Yoshida sarcoma. At non-effect dosage in free drug, HEPC-liposomes with a diameter of 58 or 142 nm showed the greatest inhibitory effect against Yoshida sarcoma among liposomes tested, whereas larger ones (272 nm) had weaker effect. Small EPC-liposomes (57 nm) had no effect. Larger HEPC-liposomes (especially 142 nm) greatly decreased the number of peripheral white blood cell compared with free drug at the same dose, indicating relatively strong myelosuppressive toxicity. However, small EPC- and HEPC-liposomes with a diameter of 57 and 58 nm, respectively, showed toxic effects comparable to that of free drug. Examination of the dose-dependency of therapeutic effects and toxicity indicated encapsulation of daunorubicin in the small HEPC-liposomes to enhance the therapeutic index about 3 times that of free drug. These findings indicate the possibility of using small HEPC-liposome as a drug carrier for targeting solid tumors.

Significant stabilization of the phosphatidylcholine bilayer structure by incorporation of small amounts of cardiolipin.

The effects of the negatively charged phospholipid cardiolipin on the structural properties of egg-yolk phosphatidylcholine (EyPC) liposomal membranes were studied by monitoring the water permeability of the liposomes caused by osmotic shrinkage in hypertonic glucose solution. Incorporation of small amounts of bovine heart cardiolipin (BhCL) into the EyPC membranes caused a significant decrease in their water permeability associated with stabilization of the membrane structure. Much evidence obtained by attenuated total reflection IR spectroscopy suggested that incorporation of BhCL into the EyPC membranes causes a cooperative conformational change in the EyPC polar head groups, but does not alter the fluidity of the bilayer structure in the fluid liquid crystalline state. Incorporation of small amounts of BhCL stabilized the intermolecular hydrogen-bonded network including water molecules of the hydration layers at the bilayer surface that are important for the stable bilayer configuration of the EyPC molecules. The antisymmetric PO2- frequencies of the EyPC membrane with incorporated BhCL suggested that the BhCL content of 50 mol% induced a change in the phase behaviors of mixed BhCL/EyPC membranes.

Modification of the frictional surfaces of artificial joints.

To overcome the wear problems associated with artificial joint materials, new surface structures with regular patterning were designed and fabricated. The lubrication properties were studied to evaluate the wear of the frictional surfaces. The surface structure was a pattern of "dents" with a diameter of 0.2-1.0 mm and a pitch of 0.6-2.0 mm. The pattern was fabricated on the stainless steel (SUS) surface by a photochemical etching technique with 3 microns depth, and on an ultrahigh molecular weight polyethylene (UHMWPE) surface by mechanical processes. The time dependent changes of frictional force between SUS and UHMWPE were measured, and the surface morphologic changes were observed. The patterned surface showed lower frictional force than the smooth non-patterned surface, and less wear occurred on the patterned sample than on the sample without a pattern. There were optimum sizes for the diameter and the pitch of the pattern. These results demonstrated that lubrication properties could be improved by patterning of the frictional surfaces. The surface patterning was effective in preventing wear of the frictional surface, and the life of an artificial joint could be extended by such patterning.

The lipophilic weak base (Z)-5-methyl-2-[2-(1-naphthyl)ethenyl]-4-piperidinopyridine (AU-1421) is a potent protonophore type cationic uncoupler of oxidative phosphorylation in mitochondria.

The lipophilic weak base AU-1421 acts as a simple protonophoric uncoupler of oxidative phosphorylation in rat liver mitochondria judging from the following observations. In the absence of any carrier lipophilic anions or P(i), AU-1421 stimulated the rate of state 4 respiration maximally about 7-fold at a concentration of 30 nmol/mg mitochondrial protein. At the same maximum effective concentration, it also inhibited ATP synthesis, released oligomycin-inhibited state 3 respiration, dissipated the proton motive force in the energized state, and activated latent H(+)-ATPase. AU-1421 also allowed proton conduction in both mitochondrial membranes and liposomes. These actions of AU-1421 resemble those of the typical anionic uncoupler SF6847. A marked difference between the two was, however, that ATPase activation by AU-1421 was not suppressed at higher concentrations of AU-1421, whereas ATPase activated by SF6847 was suppressed on increase of the SF6847 concentration. The finding that this simple protonophoric cation acts as an uncoupler at a micromolar concentration is significant, because all true (i.e., protonophore type) uncouplers known so far are anionic not cationic. Thus, AU-1421 is a unique uncoupler of the protonophore type.

Increase in water permeability of negatively charged liposomal membrane by local anesthetics.

Effect of the local anesthetics dibucaine, tetracaine, lidocaine and procaine on the water permeability of phospholipid membrane was examined using liposomes composed of bovine heart cardiolipin and egg yolk phosphatidylcholine in a molar ratio of 2/98 by monitoring the osmotic shrinkage of liposomes in hypertonic glucose solution at pH 7.3 and 30 degrees C. These local anesthetics greatly accelerated the water permeability by destabilizing the membrane structure. The effect was found to be governed by the hydrophobicity of the anesthetics. There was also a significant correlation between the membrane destabilizing actions and the anesthetic activities.

The local anesthetic tetracaine destabilizes membrane structure by interaction with polar headgroups of phospholipids.

The effect of the local anesthetic tetracaine at less than 10 mM on the water permeability of the phospholipid membrane was examined using liposomes composed of various molar ratios of negatively charged cardiolipin to electrically neutral phosphatidylcholine by monitoring their osmotic shrinkage in hypertonic glucose solution at 30 degrees C. The concentration of tetracaine causing the maximum velocity of shrinkage of liposomes increased with increase in the molar ratio of cardiolipin. Tetracaine increased the zeta-potential of the negatively charged liposomal membrane toward the positive side due to the binding of its cationic form to the negatively charged polar headgroups in the membrane. The maximum velocity of water permeation induced by osmotic shock was observed at essentially the same tetracaine concentration giving a zeta-potential of the liposomal membrane of 0 mV. These concentrations were not affected by change in the sort of acyl-chain of phospholipids in the liposomes when their negative charges were the same. These results suggests that the membrane integrity is governed mainly by the electrical charge of phospholipid polar headgroups when phospholipid bilayers are in the highly fluid state, and that positively charged tetracaine molecules neutralize the negative surface charge, lowering the barrier for water permeation through phospholipid bilayers.

Investigation of parameter estimator and adaptive controller for assist pump by computer simulation.

The multi-output adaptive controller of a left ventricular assist device (LVAD) was studied by computer simulation. The controller regulated two outputs--mean aortic pressure (mAoP) and mean atrial pressure (mLAP)--by regulating vacuum pressure (input). The autoregressive models were used to describe the circulatory system. The parameters of the models were estimated by the recursive least squares method. Based on the autoregressive models, the vacuum pressure minimizing a performance index was searched. The index used was the weighted summation of the square errors. Responses of the adaptive controller were simulated when the contractility of the left ventricle was decreased at various rates and the peripheral resistance was changed. Both the mAoP and mLAP were controlled to their predicted values in the steady state. The steady-state errors of the mAoP were less than a few mm Hg, and those of the mLAP were lower than 1 mm Hg. Consequently, the estimated parameters can be regarded as true parameters, and the adaptive controller has the potential to control more than two outputs. The multioutput adaptive controller studied is useful in controlling the LVAD according to the change in circulatory condition.

The effect of left ventricular assist device (LVAD) on cardiac reserve in dogs.

The effect of LVAD on the preservation of cardiac reserve against ischemic damage was studied using Sarnoff's ventricular function curve. An LVAD was implanted between the canine left atrium and the aorta. Left ventricular function was measured by changing the height of the reservoir connected to the left atrium. The left ventricular function curve (LVFC) was drawn by plotting left ventricular stroke work (LVSW) against left atrial pressure (LAP). The coronary artery was occluded under a pump-on (ON group) or pump-off (OFF group). After reperfusion, measurements were repeated and changes in the LVFC caused by ischemia were compared in both groups. The gradient of the LVFC was significantly reduced by ischemia (107 +/- 15 ml/beat----80 +/- 14, n = 13) but not in the ON group. LVSW under normal preload did not significantly change in either group. This suggests that the LVAD preserved cardiac reserve against ischemic damage.

Electrical oscillation and fluctuation in phospholipid membranes. Phospholipids can form a channel without protein.

Fluctuations and/or step-wise changes in membrane potential and electrical current were observed in bilayer membranes of dioleoylphosphatidylcholine (DOPC) in the absence of any channel protein. The DOPC membranes consisted of three types: black lipid membranes, pipette-clamp membranes and lipid membranes transferred to porous filter paper by conventional Langmuir-Blodgett techniques. This finding is significant since phospholipids are the main constituents of biomembranes. Lipid molecules with a cis double bond in their carbon skeleton are suggested to be important in the gating or excitation of biomembranes.

Stable phospholipid membrane supported on porous filter paper.

A novel method to construct a stable and uniform phospholipid membrane of large area and good manipulability is reported. Using the Langmuir-Blodgett (LB) technique, a monolayer of phospholipid can be transferred to filter paper. The electrical conductance across the pores of the lipid membrane is about 1.8 X 10(-9) S/cm2, corresponding to the conductance of 10(-7)-10(-10) S/cm2 reported for bilayer lipid membranes (BLM) of phospholipids. A scanning electron micrograph demonstrated that the phospholipid membrane on the filter paper was uniform.