Rotational occlusion of the vertebral artery at the atlantoaxial joint: is it truly physiological?

We present a patient with vertebrobasilar insufficiency, with vertigo and horizontal nystagmus, induced by turning the head to the right. Angiography demonstrated transient occlusion of the left vertebral artery at the atlantoaxial joint during rotation of the head. The pathogenesis and angiographic findings are discussed.     

Regulation of phospholipase A2 in human leukemia cell lines: its implication for intracellular signaling.

Permeabilized human leukemia HL-60 and U-937 cells suspended in an acidic or alkaline medium release various unsaturated fatty acids, most abundantly oleic and arachidonic acids. Concomitant production of lysophospholipids suggests that phospholipases A2 play a major role in this fatty acid release reaction. The fatty acid release at acidic conditions depends on the intracellular Ca2+ concentrations at the 10(-8)-10(-7) M range and is enhanced by membrane-permeant diacylglycerols, although this enhancement seems independent of protein kinase C activation. On the other hand, the fatty acid release at alkaline conditions is potentiated by vanadate, and this potentiation is counteracted by genistein, suggesting a role of tyrosine phosphorylation in this release reaction. GTP[gamma S], an activator of G proteins, greatly enhances the fatty acid release. Aluminum fluoride, another activator of heterotrimeric G proteins, also greatly potentiates this release reaction. Phorbol ester increases the fatty acid release at alkaline conditions, to some extent, whereas it counteracts the vanadate-induced potentiation of fatty acid release. The results imply that several phospholipases A2 are coupled to receptors for their activation, thereby functioning in the transmembrane control of cellular events.     

Fatal necrotic enteritis associated with Clostridium perfringens in wild crows (Corvus macrorhynchos)

Sporadic outbreaks of fatal enteritis occurred among free-living wild crows (‘large billed’ or ‘wok’ crow; Corvus macrorhynchos) in an open-air park in Japan in 2002. Eight crows were found dead during February, followed by two more in September, and five of the eight were examined histopathologically. At necropsy, all cases showed a markedly dilated small intestine, especially the jejunum and ileum, with large amounts of gas, and dark red to greenish–brown soft content. The necrotic intestinal wall was markedly thickened with multifocal haemorrhages. All cases had multifocal white foci in the liver, and four cases showed marked splenomegaly. Histologically, there was severe necrotic enteritis characterized by extensive mucosal necrosis and multifocal haemorrhages, as well as inflammatory cell infiltrations. A prominent pseudo-membrane formation was noted in the affected intestine. Severe adhesive peritonitis was also observed in three cases. Gram-positive bacilli were present in large numbers in the lumen, and in and around necrotic lesions in the affected intestine. The bacilli were positive for Clostridium perfringens enterotoxin type A by immunohistochemistry, and were also positive for C. perfringens type A using the immunofluorescence method. C. perfringens was isolated by anaerobic culture from the intestinal contents. The present enteritis was thought to be induced by proliferated C. perfringens in the intestine, and to be the cause of death.     

cAMP-independent decrease of ATP-sensitive K+ channel activity by GLP-1 in rat pancreatic β-cells

Using the patch-clamp method, we studied the mechanism of depolarization of rat pancreatic beta-cells induced by glucagon-like peptide 1 (7-36) amide (GLP-1). GLP-1 caused depolarization in a concentration-dependent manner (0.2-100 nM). Exendin (9-39) amide, a GLP-1 receptor antagonist, prevented the GLP-1-induced depolarization. GLP-1 reduced tolbutamide-sensitive membrane currents evoked by voltage ramps from -90 to -50 mV, recorded in the perforated whole-cell configuration, suggesting that GLP-1 decreased the activity of the ATP-sensitive K+ channel (KATP). This GLP-1 effect was prevented by exendin (9-39) amide. In cells treated with Rp-cAMPS, an inhibitor of the cAMP-dependent protein kinase (PKA), GLP-1 still caused depolarization and reduced the whole-cell membrane current through KATP. Examined in the cell-attached configuration, 20 nM GLP-1, applied out of the patch, had little effect on KATP activity. In the inside-out configuration, the open time probability and the single-channel conductance of KATP in the absence of ATP inside the membrane were unaffected by the presence of 20 nM GLP-1 in the pipette. In both conditions, application of ATP to the inside of the membrane reduced KATP activity. The half-maximal concentrations (ki) of ATP were 11.6 microM without and 5.6 microM with 20 nM GLP-1 in the pipette (P<0.05). The values of the Hill coefficient (h) were 1.03 without and 1.01 with GLP-1. We conclude that GLP-1 reduces KATP activity by elevating the sensitivity of KATP to ATP, resulting in depolarization of pancreatic beta-cells. This GLP-1 action is independent of the cAMP signalling pathway.     

Diffusion coefficient of water through dental composite resin

Water sorption of polymer filling materials affects dimensional stability, mechanical properties and bonding strength with tooth structures. To clarify the effect of the degradation on service life and micro-leakage, the diffusion coefficient of water through the resin should be identified. Distributions of time-dependent water concentrations in the resin were computed. Water sorption of composite resin discs with different thicknesses was measured and compared with the solution of Fick's second law. The diffusion coefficient of water through the resin discs was computed to be D=3.9-5.0 x 10(-13)m(2)/s from the measurements of specimens with different thicknesses. Results of water sorption measurements for the discs with different thicknesses were in good agreement with the theoretical results. The relationship among the thickness of the disc, the diffusion coefficient and the water sorption ratio was shown clearly. The testing method for water sorption by International Standard ISO 4049 for resin-based filling materials was discussed.     

Porous Ti-6Al-4V alloy fabricated by spark plasma sintering for biomimetic surface modification

Porous compacts with both biological and biomechanical compatibilities and high strength were developed. Spherical powders of Ti-6Al-4V alloy, which were either as received or surface modified with the use of calcium ions by hydrothermal treatment (HTT), were fabricated by a spark plasma sintering process. The porous compacts of pure Ti were used as reference materials. Porosity was approximately 30%, and compressive strengths were 113 and 125 MPa for the as-received Ti alloy powders and those modified by the HTT process, respectively. The bending strength and elastic modulus of as-received Ti alloy powders were 128-178 MPa and 16-18 GPa, respectively. Each of the compacts was immersed in simulated body fluid (SBF). The amount of adsorption/precipitation of calcium phosphate through the compacts was measured by weight change and was observed by SEM. The compacts were covered with calcium phosphate after 2 weeks of immersion in SBF. The compacts of Ti alloy had plenty of precipitated apatite crystals, and modification by HTT accumulated more precipitation. Because calcium phosphate is a mineral component of bone, apatite, which is precipitated on the surface of the compacts, could adsorb proteins and/or drugs such as antibiotics. It is expected that a large amount of proteins and/or drugs could be impregnated when the porous compacts developed are used.     

Masked excitatory action of noradrenaline on rat islet β-cells via activation of phospholipase C

The effect of noradrenaline (NE) on rat islet -cells was examined. NE reduced insulin secretion from rat islets exposed to extracellular solutions containing glucose at 5.5 or 16.6 mM. In islets treated with pertussis toxin (PTX), however, NE increased insulin secretion. The NE-induced augmentation of insulin secretion was inhibited by prazosin. In intact islets, NE increased phospholipase C (PLC) activity, an effect that was prevented by treatment of islets with U-73122. NE elevated intracellular [Ca²⁺] ([Ca²⁺]_i) in isolated -cells independently of PTX. Although this NE effect was inhibited by prazosin, phenylephrine did not mimic it. The [Ca²⁺]_i response to NE was also prevented by the treatment of cells with U-73122. NE produced depolarization of -cells followed by nifedipine-sensitive action potentials. NE reduced the whole-cell membrane currents through ATP-sensitive K⁺ channels (K_ATP), responsible for the depolarization. This NE effect was prevented by treatment of -cells with U-73122 or BAPTA/AM. Although at least some of our results imply the presence of ₁-adrenoceptors, -cells were not stained by a polyclonal IgG antibody recognizing all adrenergic ₁-receptor subtypes so far identified. These results suggest that an interaction of NE with an unknown type of receptor activates rat islet -cells via a PLC-dependent signal pathway. This effect is, however, masked by the inhibitory action via a PTX-sensitive pathway also activated by NE.     

Identification of p46 Shc expressed in the nuclei of hepatocytes with high proliferating activity: Study of regenerating rat liver

The adaptor molecule Shc is a proto-oncogene product, and it is known to be associated with cell proliferation. However, the role of Shc in the proliferation and regeneration of hepatocytes remains unknown. In the present study, we report that p46 Shc is specifically expressed in the nuclei of proliferative (or regenerative) hepatocytes, suggesting that p46 Shc protein plays a role in hepatocellular proliferation. The expression of Shc was analyzed in liver tissue after partial hepatectomy (PH) or sham operation in Wistar rats by using immunohistochemistry and/or Western blot analysis. In addition, the expression of various cell cycle-related proteins, such as Cdk4, cyclin D1, PCNA, and Cdk1 was analyzed in the tissues of regenerating rat liver. Furthermore, the tyrosine phosphorylation of Shc was studied in liver tissue after PH or sham operation by immunoprecipitation using a monoclonal phosphotyrosine antibody. Although the protein levels of p52 Shc were unchanged in liver tissues after PH or sham operation, tyrosine phosphorylation was detected only in the regenerating rat liver after PH. The levels of p46 Shc protein were markedly increased in liver tissues during the liver regenerative process. In contrast, p66 Shc was not detected in the liver tissues after PH or sham operation. Western blotting and immunohistochemistry showed that the main location of p46 Shc was in the nuclei of proliferating hepatocytes after PH. These data suggest that p46 Shc expressed in hepatocellular nuclei may be closely related to the proliferation of hepatocytes. Therefore, it is suggested that p46 Shc expressed in hepatocellular nuclei may be a useful marker for detecting hepatocytes with high proliferative activity.     

Correlation between microstructure of Ag-Pd-Au-Cu alloy and changes in shape on aging

An investigation has been carried out to study changes in shape on aging in plastic deformed Ag-Pd-Au-Cu alloys. The changes in shape were measured in order to establish a relationship to the aging heat treatments. Their microstructure was observed in order to clarify this phenomenon at the same time. They were also investigated quantitatively using a feature analysis system. The changes in shape were interpreted as the shrinkage in volume resulting from the formation of the ordered phase. They were smaller at aging temperatures below 673 K. The change in microstructure was different at aging temperature between 573 and 773 K. These phenomena were due to the following: First, nodules which nucleated at the grain boundaries would have grown into the grains well before the formation of the ordered phase, and second, the shrinkage in volume would have been of a different kind that the ordered phase. Therefore aging treatments should be carried out at low temperature in order to minimize the changes in shape. Also, nodular growth should be inhibited in order to maximize the hardening in Ag-rich alloys.     

A study on the effect of (2"R)-4'-O-tetrahydropyranyladriamycin, a new antitumor antibiotic, on reproduction. I. Its effect on the fertility of rats

The effect of a new antitumor antibiotic on the fertility was studied using SD rats. (2"R)-4'-O-Tetrahydropyranyladriamycin (THP) was administered to each rat at 0.01, 0.03 or 0.1 mg/kg daily. Males were given the drug intravenously for 63 days prior to mating and during the mating period; females were given the drug intravenously from 14 days prior to mating until day 7 of pregnancy. All the pregnant rats were sacrificed on day 20 of pregnancy, followed by external, visceral and skeletal observations of their fetuses. Results were summarized as follows. THP, at 0.1 mg/kg, suppressed body weight gain in females during the late period of pregnancy but did not affect body weight gain in males. THP, at 0.1 mg/kg, increased the numbers of dead fetuses and of resorptions. It caused no external, visceral or skeletal anomalies at any dose levels. The results suggest that, in rats, the maximum "no effect" dose of THP is 0.03 mg/kg/day intravenously regarding fertility and fetal development.