Mott Transition in the A15 Phase of Cs_{3}C_{60}: Absence of a Pseudogap and Charge Order.

We present a detailed NMR study of the insulator-to-metal transition induced by an applied pressure p in the A15 phase of Cs_{3}C_{60}. We evidence that the insulating antiferromagnetic (AFM) and superconducting (SC) phases coexist only in a narrow p range. At fixed p, in the metallic state above the SC transition T_{c}, the ^{133}Cs and ^{13}C NMR spin-lattice relaxation data are seemingly governed by a pseudogaplike feature. We prove that this feature, also seen in the ^{133}Cs NMR shift data, is rather a signature of the Mott transition which broadens and smears out progressively for increasing (p,T). The analysis of the variation of the quadrupole splitting ν_{Q} of the ^{133}Cs NMR spectrum precludes any cell symmetry change at the Mott transition and only monitors a weak variation of the lattice parameter. These results open an opportunity to consider theoretically the Mott transition in a multiorbital three-dimensional system well beyond its critical point.

NMR study of the superconducting gap variation near the Mott transition in Cs3C60.

Former extensive studies of superconductivity in the A3C60 compounds, where A is an alkali metal, have led one to consider that Bardeen-Cooper-Schrieffer electron-phonon pairing prevails in those compounds, though the incidence of electronic Coulomb repulsion has been highly debated. The discovery of two isomeric fulleride compounds Cs3C60 which exhibit a transition with pressure from a Mott insulator (MI) to a superconducting (SC) state clearly reopens that question. Using pressure (p) as a single control parameter of the C60 balls lattice spacing, one can now study the progressive evolution of the SC properties when the electronic correlations are increased towards the critical pressure p(c) of the Mott transition. We have used 13C and 133Cs NMR measurements on the cubic phase A15-Cs3C60 just above p(c)=5.0(3) kbar, where the SC transition temperature Tc displays a dome shape with decreasing cell volume. From the T dependence below T(c) of the nuclear spin lattice relaxation rate (T1)(-1) we determine the electronic excitations in the SC state, that is 2Δ, the gap value. The latter is found to be largely enhanced with respect to the Bardeen-Cooper-Schrieffer value established in the case of dense A3C60 compounds. It even increases slightly with decreasing p towards p(c), where T(c) decreases on the SC dome, so that 2Δ/k(B)T(c) increases regularly upon approaching the Mott transition. These results bring clear evidence that the increasing correlations near the Mott transition are not significantly detrimental to superconductivity. They rather suggest that repulsive electron interactions might even reinforce elecron-phonon superconductivity, being then partly responsible for the large T(c) values, as proposed by theoretical models taking the electronic correlations as a key ingredient.

Efficient NMR measurement and data analysis supported by the Bayesian inference: The case of the heavy fermion compound YbCo2Zn20.

We propose a data-driven technique to infer microscopic physical quantities from nuclear magnetic resonance (NMR) spectra, in which the data size and quality required for the Bayesian inference are investigated. The 59Co-NMR measurement of YbCo2Zn20 single crystal generates complex spectra with 28 peaks. By exploiting the site symmetry in the crystal structure, the isotropic Knight shift Kiso and nuclear quadrupole resonance (NQR) frequency νQ were respectively estimated to be Kiso=0.7822±0.0090% and νQ=2.008±0.016 MHz (T=20 K and H≃10.2 T) by analyzing only 30 data points from one spectrum. The estimated νQ is consistent with the precise value obtained in the NQR experiment. Our method can significantly reduce the measurement time and the computational cost of data analysis in NMR experiments.

The characteristics of karyotype and telomeric satellite DNA sequences in the cricket, Gryllus bimaculatus (Orthoptera, Gryllidae).

The chromosomes derived from the Japanese population of Gryllus bimaculatus were characterized by C-banding and Ag-NOR staining. The chromosome number, 2n = 28 + XX (female)/XO (male), corresponded with that of other populations of G. bimaculatus, but the chromosome configuration in idiograms varied between the populations. NORs were carried on one pair of autosomes and appeared polymorphous. The positive C-bands located at the centromere of all chromosomes and the distal regions of many chromosome pairs, and the size and the distribution pattern of the distal C-heterochromatin showed differences among the chromosomes. In addition, this paper reports on the characteristics of HindIII satellite DNA isolated from the genome of G. bimaculatus. The HindIII repetitive fragments were about 0.54 kb long, and localized at the distal C-bands of the autosomes and the interstitial C-bands of the X chromosome. Molecular analysis showed two distinct satellite DNA sequences, named the GBH535 and GBH542 families, with high AT contents of about 67 and 66%, respectively. The two repetitive families seem to be derived from a common ancestral sequence, and both families possessed the same 13-bp palindrome sequence. The results of Southern blot hybridization suggest that the sequence of the GBH535 family is conserved in the genomic DNAs of Gryllus species, whereas the GBH542 family is a species-specific sequence.

Niemann-Pick disease: coupling and uncoupling of inhibited sphingomyelinase activity and exogenous cholesterol esterification in fibroblasts by ionophore treatment.

In order to elucidate a biochemical relationship between sphingomyelin and cholesterol metabolisms, we examined the effects of several ionophores (monensin, nigericin, A23187, ionomycin, lasalocid) on sphingomyelinase activity and cholesterol esterification in cultured human fibroblasts. Phase-contrast microscopy showed the presence of foamy cells with monensin and nigericin treatments only. Electron microscopic examination revealed lamellated membranous bodies and cytoplasmic vacuoles in cells treated with monensin and nigericin. Monensin and nigericin treatments led to reduction of acid sphingomyelinase activity and disturbance of the esterification of lipoprotein-derived cholesterol in cultured fibroblasts, which is compatible with the biochemical changes of Niemann-Pick disease, type C. A23187, ionomycin, and lasalocid treatments showed only sphingomyelinase reduction in treated fibroblasts. Experimental models in this culture system could be produced in these ways, mimicking subtypes of Niemann-Pick disease, type A, B and type C.

A case of adrenal tumor producing renin, aldosterone, and sex steroid hormones.

A 27-year-old woman with an adrenal tumor that produced renin and aldosterone, associated with hypertension and adrenogenital syndrome, is described. Severe hypertension, cardiomegaly, a low serum potassium level, clinical symptoms of adrenogenital syndrome, and a left upper abdominal tumor also were found. Endocrinological studies showed that plasma and urinary levels of sex steroid hormones such as dehydroepiandrosterone, androsterone, and testosterone were markedly increased. Plasma renin activity, plasma angiotensin II, and plasma aldosterone levels also were increased markedly, although deoxycorticosterone levels remained within the normal range. The possibility of renovascular hypertension was excluded by angiography of the renal artery and by venous sampling of plasma renin activity. Abnormal elevations in plasma aldosterone levels persisted despite normalization of plasma angiotensin II by converting enzyme inhibitor administration. It was suspected that this patient had an adrenal tumor producing renin as well as sex steroids and aldosterone. Microscopy of the resected tumor revealed that the tumor was composed mostly of cells with large nuclei and light cytoplasm. The tumor contained dehydroepiandrosterone, dehydroepiandrosterone sulfate, testosterone, aldosterone, and renin. Immunohistochemical study showed that some of the tumor cells produced renin. Biopsy of the left renal tissue showed evident atrophy of the juxtaglomerular cells and pronounced arteriosclerosis. After resection of the tumor, all blood and urinary levels of the abnormally increased hormones returned to a normal range and an apparent fall of blood pressure was noted. To our knowledge, this is the first report of a renin and aldosterone-producing adrenal tumor associated with hypertension and adrenogenital syndrome.

Infantile bilateral striatal necrosis. Clinicopathological classification.

Two cases of infantile bilateral striatal necrosis (IBSN) were studied retrospectively, and the literature was reviewed. The two children had presented with progressive neurologic signs of involuntary movements or muscle hypertonia from infancy. Initial computed tomography scans showed mild atrophy of the caudate nuclei or basal ganglia, and the neuropathologic examination revealed diffuse neuronal loss with some patchy preservation and marked astrogliosis in the striatum and globus pallidus. The 27 reported cases of IBSN were divided into three groups with characteristic clinical and pathologic features: early, acute onset (four cases); early, gradual onset (16 cases); and late onset (seven cases). Although metabolic changes in the developing corpus striatum may be important in the pathogenesis of IBSN, the origin is uncertain.

Ouabain-sensitive Na-K ATPase response in the rabbit iris-ciliary body after lensectomy-vitrectomy.

We studied ouabain-sensitive Na-K adenosine triphosphatase (ATPase) activities in the iris-ciliary body of rabbit eyes after lensectomy-vitrectomy. Changes in enzyme activities were quantitatively investigated in the plasma membrane of iris-ciliary body at 0 or 7 hours and at days 1, 3, 7, and 14. The specific activity of Na-K ATPase rose to significantly higher levels than the control value at 7 hours following surgery, but returned to the baseline value after 7 days. In addition, we evaluated enzyme activities after lensectomy-vitrectomy during which SF6 or silicone oil was injected. The specific activity of Na-K ATPase following the injection of SF6 or silicone oil was significantly higher than the control value at 7 hours and did not return to the normal value even after 14 days. Consensual reaction, demonstrated by increased Na-K ATPase activity, also was found in the contralateral unoperated eyes of SF6- and silicone oil-injected rabbits. The increased Na-K ATPase activity in the iris-ciliary body after experimental surgery may play an important role in restoring swollen tissues.

Alteration of active Na-K transport on protein kinase C activation in cultured ciliary epithelium.

PURPOSE: Experiments were conducted to test whether protein kinase C activation causes changes in active sodium-potassium transport in an established SV-40 transformed line (ODM2) of cultured human nonpigmented ciliary epithelial cells. METHODS: Rubidium-86 (86Rb) uptake was measured and the data used to determine the rate of potassium entry into the cells. RESULTS: Protein kinase C activator, phorbol dibutyrate (PDBu), caused a stimulation of ouabain-sensitive 86Rb uptake. Inhibition of protein kinase C by 1-(5-isoquinolinylsulfonyl) 2-methylpiperazine (H-7), or down-regulation of protein kinase C activation by prolonged exposure of PDBu, decreased the PDBu response. These results suggest that protein kinase C plays a role in Na-K pump activation. The Na/H+ exchanger inhibitor, amiloride, also reduced the stimulation of the ouabain-sensitive 86Rb uptake by PDBu. 86Rb efflux was not altered by protein kinase C activation. At the same time that PDBu increased the ouabain-sensitive 86Rb uptake, it also decreased the ouabain-insensitive 86Rb uptake. The ouabain-insensitive 86Rb uptake component could be inhibited by bumetanide, suggesting that protein kinase C activation decreases the activity of a Na/K/2Cl cotransporter. CONCLUSIONS: These findings suggest that activation of protein kinase C may stimulate Na,K-ATPase activity mainly by a mechanism involving increased Na+ influx mediated by the Na+/H+ exchanger.

Immunocytochemical localization of ornithine aminotransferase in rat ocular tissues.

Gyrate atrophy of the choroid and retina is a rare inherited form of chorioretinal degeneration due to a deficiency of ornithine aminotransferase (OAT). We localized the enzyme in rat ocular tissues using immunocytochemical procedures. Immunoreactivity was observed in the epithelia of ciliary body, iris, and lens. Retinal pigment epithelium and Müller cells were immunoreactive in the retina. A little immunoreactive product was found in the choroid. Our findings suggested that OAT plays an important role in ornithine metabolism in these ocular tissues.

Immunocytochemical localization of ornithine aminotransferase in human ocular tissues.

Gyrate atrophy of the choroid and retina is a rare inherited form chorioretinal degeneration caused by a deficiency of ornithine aminotransferase. We localized the enzyme in human ocular tissues using immunocytochemical procedures. Immunoreactivity was observed in the nonpigmented epithelium of the ciliary body and lens epithelium. In the retina, ganglion cells and some amacrine cells were immunoreactive. Pigmented granules made it difficult to identify immunoreactive products in the iris, pigmented epithelium of the ciliary body, choroid, and retinal pigment epithelium. Our findings suggested that ornithine aminotransferase plays an important role in ornithine metabolism in these oculartissues.

Immunohistochemical study of ferritin-positive cells in the cerebellar cortex with subarachnoidal hemorrhage in neonates.

Ferritin immunohistochemistry was performed on the cerebellar cortex with subarachnoidal hemorrhage (SAH) in preterm and term neonates, in comparison with anti-glial fibrillary acidic protein (GFAP) for astrocytes and Ricinus communis agglutinin-1 (RCA-1) immunostaining for microglia. The ferritin-positive cells were increased in the cortex with SAH. The predominant cell type which was labeled with antiserum to ferritin in the human cerebellar molecular layer with SAH was the microglia, which were stained with RCA-1 but not with GFAP. Ferritin-positive microglia may be induced by ischemia with vasospasms, and be related to the loss of Purkinje cells.

Developmental immunohistochemistry of membrane proteins in the brain coded by a gene on human chromosome 21.

A monoclonal antibody, OK-2, against membrane proteins coded by a gene on chromosome 21 was obtained using hamster/human hybrid cells as an antigen, and used for a developmental study on the brains of Down's syndrome (DS) cases. The membrane proteins recognized by OK-2 were expressed earlier in neurons and vessels of DS brains than in normal brains, the difference being more marked in the temporal lobe than in the frontal lobe. This over-expression of the membrane proteins in DS brains, especially in the temporal lobe, may be related to the pathogenesis of or predisposition to Alzheimer type dementia in elderly DS cases.

Pathogenesis of periventricular white matter hemorrhages in preterm infants.

Periventricular white matter hemorrhage (PWMH) was frequently found in very low-birth weight infants with perinatal asphyxia or respiratory distress. Primary PWMH with or without intraventricular rupture was found at the deep arterial borderzones of the frontal or occipital lobes. The ischemic tissue damage induced by hypoperfusion may be a predisposing factor for PWMH. However, the high incidence of visceral intravascular thrombi and the fan-shaped appearance of hemorrhage suggested venous hemorrhagic infarction. Venous thrombosis with coagulopathy may be an important factor for the pathogenesis of PWMH.

Endotoxin, cerebral blood flow, amino acids and brain damage in young rabbits.

The effects of bacterial endotoxin (lipopolysaccharide; LPS) on the cerebral blood flow (CBF), amino acid levels and brain histology were studied in young rabbits. The CBF was slightly decreased in the cerebral cortex and markedly decreased in the cerebral white matter at 60 and 120 min after LPS administration. Histological examination revealed only slightly pyknotic neurons around small vessels at 24 hours, and multifocal necrosis in the deep cerebral cortex and white matter at 72 hours. Some amino acids were increased in the plasma and brain regions at 24 hours after LPS administration, most of which were essential amino acids. GABA in the cerebral white matter was decreased at 24 hours. At 72 hours, most non-essential and glucogenic amino acids were decreased. These results suggest that the brain histological changes are related mainly to hypoperfusion and vascular damage in the brain. The amino acid changes may also be related to inappropriate amino acid metabolism associated with brain cell damage.

Vascular dysplasia in Down syndrome: a possible relationship to moyamoya disease.

The brain of a child with Down syndrome (DS) and vascular abnormalities is described. Neuropathological examination showed a large cerebral infarction. In the circle of Willis there was hypoplasia of the left middle and posterior communicating cerebral arteries, and microscopically there was thickening of intima and focal disruption of internal elastica in some areas of the circle of Willis. Several reports suggest that the incidence of moyamoya disease is higher in children with DS than in other children. The high incidence of congenital heart disease in DS suggests an abnormality of vascular development that may manifest intracranially as a structural vascular defect, creating a vulnerability to unknown factors important in the pathogenesis of the moyamoya abnormality.

Ferritin immunohistochemical study on pontine nuclei from infants with pontosubicular neuron necrosis.

Immunohistochemical ferritin staining was performed on pontine nuclei of the brains of 17 infants with pontosubicular neuron necrosis (PSN), aged 23 to 42 weeks of gestation. Ferritin-positive cells were increased in cases of karyorrhexis with spongy changes and gliosis, but not in those of selective karyorrhexis. Ferritin-positive cells were more increased in the cases with extensive karyorrhectic neurons. Iron may be released to the damaged pontine tissue as a catalyst and microglia may play an important role in the repair of the tissue.

Development of ferritin-containing cells in the pons and cerebellum of the human brain.

The distribution and development of ferritin-containing cells were studied in the pons and cerebellum of human fetuses up to adults, using an immunohistochemical method. The predominant cell type labeled with antiserum to ferritin in the pons and cerebellum was morphologically oligodendrocytes. In the pons, positive cells appeared at 21 weeks of gestation in the reticular formation, and longitudinal and transverse fibers, and at 25 weeks of gestation in pontine nuclei. They increased with age from 33 weeks to infancy. In the cerebellum, positive cells appeared at 25 weeks of gestation in the cerebellar white matter and granular layer. They increased from 29 to 40 weeks of gestation in the white matter, and to childhood in the granular layer. The time of appearance of positive cells in the pons and cerebellum is earlier than in the cerebrum, like myelination. This development of ferritin-positive glia may be related to maturation of oligodendrocytes as well as being the basis of myelination.

The effects of prostaglandin E1 and nicardipine on cerebral blood flow, blood volume and oxygenation in young rabbits.

The effects of the vasodilators, prostaglandin E1 and nicardipine, on cerebral blood flow (CBF), cerebral blood volume and oxygenation were studied in young rabbits of 2 weeks of age using the hydrogen clearance method and near infrared spectrophotometry. Prostaglandin E1 decreased CBF in the cerebral cortex. However, cerebral oxygenation through oxyhemoglobin and cytochrome a, a3 was not affected by the drug. On the other hand, nicardipine increased CBF in the cerebral white matter and diencephalon in spite of the fall in blood pressure and the decreased cerebral blood volume due to deoxyhemoglobin. Oxidized cytochrome a, a3 variably increased. These results suggest that nicardipine, a calcium channel antagonist, may cause dilation of cerebral arterioles, increase CBF and cellular oxidation, and cause constriction of cerebral veins, in contrast to the little effect of prostaglandin E1 on cerebral vessels.