g Factor of the ^{99}Zr (7/2^{+}) Isomer: Monopole Evolution in the Shape-Coexisting Region

The gyromagnetic factor of the low-lying E=251.96(9)  keV isomeric state of the nucleus ^{99}Zr was measured using the time-dependent perturbed angular distribution technique. This level is assigned a spin and parity of J^{π}=7/2^{+}, with a half-life of T_{1/2}=336(5)  ns. The isomer was produced and spin aligned via the abrasion-fission of a ^{238}U primary beam at RIKEN RIBF. A magnetic moment |μ|=2.31(14)μ_{N} was deduced showing that this isomer is not single particle in nature. A comparison of the experimental values with interacting boson-fermion model IBFM-1 results shows that this state is strongly mixed with a main νd_{5/2} composition. Furthermore, it was found that monopole single-particle evolution changes significantly with the appearance of collective modes, likely due to type-II shell evolution.

[A case report of pulmonary blastoma--biphasic pulmonary blastoma]

We report a biphasic pulmonary blastoma in a 77-year-old man. In a routine chest radiographic examination, in the left upper lung field, a massive shadow that had been entirely absent one year before was detected. The preoperative imaging films showed a 10 x 8 cm, well-circumscribed solid tumor in the upper lobe of the left lung. A preoperative clinical diagnosis of primary lung cancer was considered. The intraoperative findings were that the tumor had invaded the visceral pleura with adhesion to the parietal pleura. Left upper lobectomy with lymph node sampling was performed, and since invasion of the pulmonary artery wall was confirmed, complete removal of tumor was not possible. The postoperative diagnosis was biphasic pulmonary blastoma. The patient was treated with radiotherapy up to a limit of 50 Gy, covering the area around of the left hilum. At the latest follow-up, 1 year postoperatively, the patient was clinically and radiologically free of the disease.

Characterization of single actomyosin rigor bonds: load dependence of lifetime and mechanical properties

Load dependence of the lifetime of the rigor bonds formed between a single myosin molecule (either heavy meromyosin, HMM, or myosin subfragment-1, S1) and actin filament was examined in the absence of nucleotide by pulling the barbed end of the actin filament with optical tweezers. For S1, the relationship between the lifetime (tau) and the externally imposed load (F) at absolute temperature T could be expressed as tau(F) = tau(0).exp(-F.d/k(B)T) with tau(0) of 67 s and an apparent interaction distance d of 2.4 nm (k(B) is the Boltzmann constant). The relationship for HMM was expressed by the sum of two exponentials, with two sets of tau(0) and d being, respectively, 62 s and 2.7 nm, and 950 s and 1.4 nm. The fast component of HMM coincides with tau(F) for S1, suggesting that the fast component corresponds to single-headed binding and the slow component to double-headed binding. These large interaction distances, which may be a common characteristic of motor proteins, are attributed to the geometry for applying an external load. The pulling experiment has also allowed direct estimation of the number of myosin molecules interacting with an actin filament. Actin filaments tethered to a single HMM molecule underwent extensive rotational Brownian motion, indicating a low torsional stiffness for HMM. From these results, we discuss the characteristics of interaction between actin and myosin, with the focus on the manner of binding of myosin.

Position-dependent linkages of fibronectin- integrin-cytoskeleton

Position-dependent cycling of integrin interactions with both the cytoskeleton and extracellular matrix (ECM) is essential for cell spreading, migration, and wound healing. Whether there are regional changes in integrin concentration, ligand affinity or cytoskeleton crosslinking of liganded integrins has been unclear. Here, we directly demonstrate a position-dependent binding and release cycle of fibronectin-integrin-cytoskeleton interactions with preferential binding at the front of motile 3T3 fibroblasts and release at the endoplasm-ectoplasm boundary. Polystyrene beads coated with low concentrations of an integrin-binding fragment of fibronectin (fibronectin type III domains 7-10) were 3-4 times more likely to bind to integrins when placed within 0.5 microns vs. 0.5-3 microns from the leading edge. Integrins were not concentrated at the leading edge, nor did anti-integrin antibody-coated beads bind preferentially at the leading edge. However, diffusing liganded integrins attached to the cytoskeleton preferentially at the leading edge. Cytochalasin inhibited edge binding, which suggested that cytoskeleton binding to the integrins could alter the avidity for ligand beads. Further, at the ectoplasm-endoplasm boundary, the velocity of bead movement decreased, diffusive motion increased, and approximately one-third of the beads were released into the medium. We suggest that cytoskeleton linkage of liganded integrins stabilizes integrin-ECM bonds at the front whereas release of cytoskeleton-integrin links weakens integrin-ECM bonds at the back of lamellipodia.

Imaging of thermal activation of actomyosin motors

We have developed temperature-pulse microscopy in which the temperature of a microscopic sample is raised reversibly in a square-wave fashion with rise and fall times of several ms, and locally in a region of approximately 10 micrometers in diameter with a temperature gradient up to 2 degrees C/micrometers. Temperature distribution was imaged pixel by pixel by image processing of the fluorescence intensity of rhodamine phalloidin attached to (single) actin filaments. With short pulses, actomyosin motors could be activated above physiological temperatures (higher than 60 degrees C at the peak) before thermally induced protein damage began to occur. When a sliding actin filament was heated to 40-45 degrees C, the sliding velocity reached 30 micrometers/s at 25 mM KCl and 50 micrometers/s at 50 mM KCl, the highest velocities reported for skeletal myosin in usual in vitro assay systems. Both the sliding velocity and force increased by an order of magnitude when heated from 18 degrees C to 40-45 degrees C. Temperature-pulse microscopy is expected to be useful for studies of biomolecules and cells requiring temporal and/or spatial thermal modulation.

[Bilateral carotid endarterectomy for patients with bilateral carotid artery stenosis]

In a couple of recent randomized trials, the benefits of unilateral carotid endarterectomy (CEA) have been reevaluated in symptomatic patients with severe stenosis. In contrast, the operative indication, procedure, and perioperative management of bilateral CEAs for patients with bilateral carotid artery stenosis are still controversial. In this report, we reviewed 7 patients who underwent bilateral CEAs at out institute during the last 10 years, with regard to the clinical feature, angiographical findings, operative procedure, surgical results and long-term prognosis. The patients ranged from 52 to 73 years in age, and included six males and one female. Clinical symptoms were asymptomatic in 1 patient, transient ischemic attack in 2, reversible ischemic neurological deficits in 2, minor completed stroke in 1, and major completed stroke in 1. The angiographical carotid artery stenosis in the dominant side of symptomatic cases was 50% in 3, 70% in 1, 90% in 2, and ulceration in 4 cases. The stenosis in the non-dominant side of symptomatic cases was 60% in 1, 70% in 3, 90% in 2, and 4 cases with ulceration. One case among the asymptomatic cases had bilateral 80-90% stenosis. We staged bilateral CEAs, in the dominant side first except in one case among the symptomatic cases and on the more severely stenotic side first in the asymptomatic cases. During CEA, an external shunt was placed in 1 case, but no internal shunt was used in any of the cases. Perioperative complications were found in 2 patients, transient bilateral hypoglossal nerve palsy and local hemorrhage in the other case. Totally, all of 7 cases (14 consecutive CEAs) have been performed with satisfactory results. No mortality and no permanent morbidity has resulted. In the follow-up period (mean: 38.3 month), 1 patient was found to have developed cerebral infarction in the ipsilateral carotid artery territory. From our own small experience and from that in the literature, CEAs for bilateral carotid artery stenosis should be performed in the dominant side first. Then, after a certain period, from 2 to 6 weeks, the CEA should be performed in the non-dominant side.

Unbinding force of a single motor molecule of muscle measured using optical tweezers

The unbinding and rebinding of motor proteins and their substrate filaments are the main components of sliding movement. We have measured the unbinding force between an actin filament and a single motor molecule of muscle, myosin, in the absence of ATP, by pulling the filament with optical tweezers. The unbinding force could be measured repeatedly on the same molecule, and was independent of the number of measurements and the direction of the imposed loads within a range of +/- 90 degrees. The average unbinding force was 9.2 +/- 4.4 pN, only a few times larger than the sliding force but an order of magnitude smaller than other intermolecular forces. From its kinetics we suggest that unbinding occurs sequentially at the molecular interface, which is an inherent property of motor molecules.

Mechanical measurements of single actomyosin motor force

To elucidate the mechanism of force generation by actomyosin motor, a measuring system was constructed, in which an in vitro motility assay was combined with an optical trapping technique. An actin filament of several micron long was attached to a gelsolin-coated polystyrene bead, and was allowed to interact with a small number (approximately 1/1 micron actin filament) of rabbit skeletal heavy meromyosin (an active subfragment of myosin) molecules bound to a nitrocellulose-coated coverglass. The bead position was determined at 33-ms intervals. We measured the force generation event at relatively low (100-400 nM) ATP concentration so that the occurrence of individual force generation events could be detected with our time resolution. The actin-bound bead held in the optical trap moved in a stepwise manner in the direction of the actin filament only in the presence of ATP. At the trap strength of 0.3 pN/nm, the maximum size of the step was 11 nm, and the maximum force associated with the movement was 3.3 pN.

Mechanical properties of single protein motor of muscle studied by optical tweezers

Images

Stepwise motion of an actin filament over a small number of heavy meromyosin molecules is revealed in an in vitro motility assay

In order to determine the relative motions of an actin filament and a myosin molecule upon hydrolysis of one ATP, an in vitro motility assay, in which individual actin filaments slide over heavy meromyosin molecules bound to a substrate, was combined with an optical trapping technique. An actin filament, attached to a gelsolin-coated bead, was captured with an optical trap. The surface-bound heavy meromyosin molecules pulled the filament against the trapping force, which resulted in back and forth motions of the actin-bound bead. The number of heavy meromyosin molecules interacting with an actin filament (at most 1/micron filament) and the ATP concentration (< or = 0.5 microM) were chosen so as to facilitate detection of each "pull." Calculation of the centroid of the bead image revealed abrupt displacements of the actin filament. The frequency of such displacements was between 0.05 and 0.1 per 1 s per 1 micron actin filament, being consistent with calculated values based on the reported bimolecular binding constants of ATP and the actomyosin rigor complex. The distribution of the displacements peaked around 7 nm at a trapping force of 0.016 pN/nm, but it became broader, and some displacements were as large as 30 nm, when the trapping force was reduced to 0.0063 pN/nm, suggesting that the force generation due to the structural change of a myosin head may be insufficient to explain such displacements.

Right-handed rotation of an actin filament in an in vitro motile system

Muscle contraction occurs by mutual sliding between thick (myosin) and thin (actin) filaments. But the physical and chemical properties of the sliding force are not clear; even the precise direction of sliding force generated at each cross-bridge is not known. We report here the use of a recently developed in vitro motile assay system to show supercoiling of an actin filament in which the front part of the filament was fixed to a glass surface through cross-linked heavy-meromyosin and the rear part was able to slide on a track of heavy-meromyosin. A left-handed single turn of superhelix formed just before supercoiling, suggesting that the sliding force has a right-handed torque component that induces the right-handed rotation of an actin filament around its long axis. The presence of the torque component in the sliding force will explain several properties of the contractile system of muscle.

Orientation of actin monomers in moving actin filaments

We have visualized, under an optical microscope, the orientations of actin monomers in individual actin filaments undergoing Brownian motion in solution, actively sliding past myosin molecules, or immobile on a surface. For the visualization, two strategies have been adopted. One is to exploit the fluorescence polarization of a fluorescent probe firmly attached to actin. Using the probe phalloidin-tetramethylrhodamine, the fluorescence was clearly polarized along the filament axis, showing alignment of the probe molecules along the filament axis. Within our temporal resolution of 33 ms and spatial resolution of better than 1 micron (average over approximately 10(2) actin monomers), the orientation of the probe (hence of actin monomers) did not change upon interaction of the filament with heavy meromyosin; myosin-induced reorientation was estimated to be a few degrees at most. This first method, while highly sensitive to small reorientations of monomers off or toward the filament axis, does not report on reorientations around the axis. To detect rotation around the filament axis, we adopted the second strategy in which we attached small plastic beads to the actin filaments. Axial turns would be immediately apparent from the movement of the beads. Preliminary observations indicate that actin filaments can slide over a heavy meromyosin-coated surface without axial rotations. Since rotations have been implicated in different experiments, we are currently investigating the source of the apparent discrepancy. The attached bead also serves as a handle through which we can apply force, via optical tweezers, on the filament. By letting the sliding actin filament pull the bead against the optical force, we were able to estimate the sliding force and its fluctuation.

Dual-view microscopy with a single camera: real-time imaging of molecular orientations and calcium

A new microscope technique, termed "W" (double view video) microscopy, enables simultaneous observation of two different images of an object through a single video camera or by eye. The image pair may, for example, be transmission and fluorescence, fluorescence at different wavelengths, or mutually perpendicular components of polarized fluorescence. Any video microscope can be converted into a dual imager by simple insertion of a small optical device. The continuous appearance of the dual image assures the best time resolution in existing and future video microscopes. As an application, orientations of actin protomers in individual, moving actin filaments have been imaged at the video rate. Asymmetric calcium influxes into a cell exposed to an intense electric pulse have also been visualized.

[Direct surgical obliteration of a persistent trigeminal artery aneurysm]

A successful case of ruptured aneurysm of the persistent trigeminal artery (PTA) treated with direct operation is reported. Only 14 cases out of ever-reported 400 cases with persistent trigeminal artery have aneurysms developing from PTA itself or its junction. These aneurysms originate most frequently from the trunk portion of the PTA. In our case, aneurysms are found at the rt. internal carotid-PTA junction and the rt. IC-PC junction. Six out of 14 are associated with another intracranial aneurysms, indicating high multiplicity. Of 14 cases, only 2 including our case are treated by direct surgery. Since the internal carotid-PTA junction aneurysm is located in the cavernous sinus, special consideration is needed during the operation. Surgical keypoints in opening the cavernous sinus under normothermia and getting the landmark for orientation are described.

[The relation of intracranial air to C.S.F. rhinorrhoea in the traumatic pneumocephalus (intracerebral and ventricular) (author's transl)]

The relation of intracranial air to C.S.F. rhinorrhoea in our four cases, one intracerebral and the others intracerebral-ventricular pneumocephalus, were investigated on their clinical course, operative findings and RI-cisternographic findings. In the occurrence of the pneumocephalus, it seemed important for the damaged brain to herniate into the defect of the bone and dura matar. Clinically in the stage of an intracerebral pneumocephalus, the C.S.F. rhinorrhoea was not recognized as a rule. And next stage, the sudden effusions of C.S.F. appeared when the intracerebral pneumocephalus developed to the intracerebral-ventricular pneumocephalus.

[A case of hypertensive intracerebral hemorrhage associated with cerebral arteriovenous malformation and aneurysm (author's transl)]

A 45-year-old man suddenly developed right hemiparesis and aphasia during work and lost conciousness next day, when he was admitted to us. Lumbar puncture showed bloody C.S.F. with the initial pressure of 220 mm H2O. Physical examination revealed hypertension and arteriosclerosis. Cerebral angiogram revealed an arteriovenous malformation in the left frontoparietal-parasagittal region and a saccular aneurysm at the left internal carotid-posterior communicating artery junction. In addition, the existence of putaminal hematoma was suspected on account of the displacement of the left anterior cerebral artery and the left lenticulostriate arteries. On the fourth day after admission his consciousness returned and the right hemiparesis gradually improved. One month later the disappearance of the displacement of the anterior cerebral artery was demonstrated by cerebral angiogram. A frontoparietal craniotomy was done and no hematoma was found around the arteriovenous malformation and the basis of the aneurysm did not adhere to the temporal lobe. Taking these findings into consideration, it is presumed that the hematoma in putaminal region was due to neither arteriovenous malformation nor aneurysm but was a hypertensive intracerebral hemorrhage.