Altered synaptic glutamate homeostasis contributes to cognitive decline in young APP/PSEN1 mice.

Non-convulsive epileptiform activity is a common and under-studied comorbidity of Alzheimer's disease that may significantly contribute to onset of clinical symptoms independently of other neuropathological features such as ß-amyloid deposition. We used repeated treatment with low dose kainic acid (KA) to trigger sub-threshold epileptiform activity in young (less than 6 months) wild-type (WT) and APP/PSEN1 mice to test the role of disruption to the glutamatergic system in epileptiform activity changes and the development of memory deficits. Short-term repeated low-dose KA (five daily treatments with 5 mg/kg, IP) impaired long-term potentiation in hippocampus of APP/PSEN1 but not WT mice. Long-term repeated low-dose KA (fourteen weeks of bi-weekly treatment with 7.5-10 mg/kg) led to high mortality in APP/PSEN1 mice. KA treatment also impaired memory retention in the APP/PSEN1 mice in a Morris water maze task under cognitively challenging reversal learning conditions where the platform was moved to a new location. Four weeks of bi-weekly treatment with 5 mg/kg KA also increased abnormal spike activity in APP/PSEN1 and not WT mice but did not impact sleep/wake behavioral states. These findings suggest that hyperexcitability in Alzheimer's disease may indeed be an early contributor to cognitive decline that is independent of heavy ß-amyloid-plaque load, which is absent in APP/PSEN1 mice under 6 months of age.

Full-Gap Superconductivity Robust against Disorder in Heavy-Fermion CeCu_{2}Si_{2}.

A key aspect of unconventional pairing by the antiferromagnetic spin-fluctuation mechanism is that the superconducting energy gap must have the opposite sign on different parts of the Fermi surface. Recent observations of non-nodal gap structure in the heavy-fermion superconductor CeCu_{2}Si_{2} were then very surprising, given that this material has long been considered a prototypical example of a superconductor where the Cooper pairing is magnetically mediated. Here we present a study of the effect of controlled point defects, introduced by electron irradiation, on the temperature-dependent magnetic penetration depth λ(T) in CeCu_{2}Si_{2}. We find that the fully gapped state is robust against disorder, demonstrating that low-energy bound states, expected for sign-changing gap structures, are not induced by nonmagnetic impurities. This provides bulk evidence for s_{++}-wave superconductivity without sign reversal.

Observation of the non-linear Meissner effect.

A long-standing theoretical prediction is that in clean, nodal unconventional superconductors the magnetic penetration depth λ, at zero temperature, varies linearly with magnetic field. This non-linear Meissner effect is an equally important manifestation of the nodal state as the well studied linear-in-T dependence of λ, but has never been convincingly experimentally observed. Here we present measurements of the nodal superconductors CeCoIn5 and LaFePO which clearly show this non-linear Meissner effect. We further show how the effect of a small dc magnetic field on λ(T) can be used to distinguish gap nodes from non-nodal deep gap minima. Our measurements of KFe2As2 suggest that this material has such a non-nodal state.

PDGF ligand and receptor gene expression during repair of arterial injury.

Smooth muscle cells (SMC) in rat carotid artery leave the quiescent state and proliferate after balloon catheter injury, but the signals for mitogenesis are not known. In this study, the possibility that cells within damaged arteries produce a growth factor that could act locally to stimulate SMC replication and repair was examined. We found that the genes for PDGF-A and -B (ligand) and PDGF receptor (alpha and beta subunits) were expressed in normal and injured carotid arteries and were independently regulated during repair of carotid injury. Two phases of PDGF ligand and receptor gene expression were observed: (a) In the early stage, a large decrease in PDGF beta-receptor mRNA levels preceded 10- to 12-fold increases in PDGF-A transcript abundance in the first 6 h after wounding. No change in PDGF alpha-receptor or PDGF-B gene expression was found at these times. (b) In the chronic phase, 2 wk after injury, neointimal tissue had lower levels of PDGF alpha-receptor mRNA (threefold) and higher levels of PDGF beta-receptor mRNA (three- to fivefold) than did restored media. Moreover, in situ hybridization studies identified a subpopulation of neointimal SMC localized at or near the luminal surface with a different pattern of gene expression than the underlying carotid SMC. Luminal SMC were strongly positive for PDGF-A and PDGF beta-receptor transcripts, while showing little or no hybridization for PDGF-B or PDGF alpha-receptor. Immunohistochemical studies showed strongly positive staining for PDGF-A in SMC along the luminal surface. These data show that changes in PDGF ligand and receptor expression occur at specific times and locations in injured carotid artery and suggest that these changes may play a role in regulating arterial wound repair.

Solar structure and terrestrial weather.

If there is indeed an effect of the variable sun on the weather, the physical cause for it remains quite elusive (12). We should keep in mind the possibility that there may be several causes and several effects. The situation may change through the 11-year sunspot cycle and the 22-year solar magnetic cycle, as well as on longer time scales. Work is proceeding at a lively pace at the institutions mentioned in this article and at many others around the world. The Soviet Union has long had considerably more workers interested in this field than has any other country. A bilateral agreement between the Soviet Union and the United States has considerably increased the interactions between workers interested in this subject, including an exchange of extended visits between the two countries. A detailed knowledge of solar causes of geomagnetic activity is only now beginning to emerge after many years of scientific efforts. This suggests that a possible successful solution to the sun-weather problem will require a similar magnitude of effort. We look forward with interest and optimism to the results of the next few years.

The spiral interplanetary magnetic field: a polarity and sunspot cycle variation.

Spacecraft observations near the earth of the average direction of the interplanetary magnetic field during the sunspot maximum year 1968 showed a deviation from the spiral field of Parker's classical description. The included angle between the average field direction when the field polarity was away from the sun and the average direction when the field polarity was toward the sun was 168 degrees , rather than 180 degrees as predicted by Parker. This effect appears to have a sunspot cycle variation.

Solar flare acceleration of solar wind: influence of active region magnetic field.

The direction of the photospheric magnetic field at the site of a solar flare is a good predictor of whether the flare will accelerate solar wind plasma. If the field has a southward component, high-speed solar wind plasma is usually observed near the earth about 4 days later. If the field has a northward component, such high-speed solar wind is almost never observed. Southward-field flares may then be expected to have much larger terrestrial effects than northward flares.

Origin of the warped heliospheric current sheet.

The warped heliospheric current sheet for early 1976 is calculated from the observed photospheric magnetic field by a potential field method. Comparisons with measurements of the interplanetary magnetic field polarity for early 1976 obtained at several locations in the heliosphere by Helios 1, Helios 2, Pioneer 11, and at the earth show a rather detailed agreement between the computed current sheet and the observations. It appears that the large-scale structure of the warped heliospheric current sheet is determined by the structure of the photospheric magnetic field and that "ballerina skirt" effects may add small-scale ripples.

Solar Magnetic Sector Structure: Relation to Circulation of the Earth's Atmosphere.

The solar magnetic sector structure appears to be related to the average area of high positive vorticity centers (low-pressure troughs) observed during winter in the Northern Hemisphere at the 300-millibar level. The average area of high vorticity decreases (low-pressure troughs become less intense) during a few days near the times at which sector boundaries are carried past the earth by the solar wind. The amplitude of the effect is about 10 percent.

Regulation of pro-opiomelanocortin gene transcription in individual cell nuclei.

A nonrepetitive complementary RNA probe specific for an intervening sequence of the rat pro-opiomelanocortin (POMC) gene primary transcript was used to analyze the hormonal regulation of POMC gene transcription in individual cell nuclei in the rat pituitary by in situ hybridization. This probe recognized only full-length POMC heterogeneous nuclear RNA, as verified by Northern blots of pituitary RNA. When pituitary sections were hybridized with this 3H-labeled POMC intron A probe, silver grains were predominantly localized over the nuclei of cells that expressed POMC in the anterior and intermediate lobes. Adrenalectomy increased both the average grain density over corticotroph nuclei and the number of cells in the anterior pituitary with significant numbers of silver grains over their nucleus. Dexamethasone administration to intact or adrenalectomized rats results in the rapid (within 30 minutes) disappearance of silver grains over the nuclei of corticotrophs in the anterior lobe, suggesting that POMC gene transcription had been inhibited. However, adrenalectomy or dexamethasone administration did not alter the silver grain density over nuclei of intermediate lobe melanotrophs. Thus, this in situ hybridization assay utilizing an intervening sequence-specific POMC probe can measure rapid physiological changes in POMC heterogeneous nuclear RNA in individual cell nuclei.

Interplanetary Magnetic Field Polarity and the Size of Low-Pressure Troughs Near 180{degrees}W Longitude.

When the interplanetary magnetic field is directed away from the sun, the area of wintertime low-pressure (300-millibar) troughs near 180 degrees W longitude is significantly larger than when the field is toward the sun. This relation persists during most of the winters of 1951 to 1973.

The hypogonadal mouse: reproductive functions restored by gene therapy.

The hypogonadal (hpg) mouse lacks a complete gonadotropin-releasing hormone (GnRH) gene and consequently cannot reproduce. Introduction of an intact GnRH gene into the genome of these mutant mice resulted in complete reversal of the hypogonadal phenotype. Transgenic hpg/hpg homozygotes of both sexes were capable of mating and producing offspring. Pituitary and serum concentrations of luteinizing hormone, follicle-stimulating hormone, and prolactin were restored to those of normal animals. Immunocytochemistry and in situ hybridization showed that GnRH expression was restored in the appropriate hypothalamic neurons of the transgenic hpg animals, an indication of neural-specific expression of the introduced gene.

Strong anion exchange for studying protein-DNA interactions by H/D exchange mass spectrometry.

The use of mass spectrometry to study protein-ligand interactions is expanding into more complex systems including protein-DNA interactions. The excess amount of a model DNA or, more typically, an oligodeoxynucleotide (ODN), needed to study such interactions in an amide hydrogen-deuterium (H/D) exchange experiment, for example, causes serious signal suppression in the protein analysis. We describe here a modification of the traditional H/D exchange protocol whereby we utilize a strong anion exchange column to rapidly remove the ODN from solution before MS analysis. We showed the successful incorporation of such a column in a study of two protein-ODN systems: (1) the DNA-binding domain of human telomeric repeat binding factor 2 with a telomeric oligodeoxynucleotide and (2) thrombin with the thrombin-binding aptamer. The approach gave no appreciable difference in back-exchange compared to a method in which no strong anion exchange (SAX) is used.

Monocyte chemoattractant protein-1 in human atheromatous plaques.

Monocytes appear to be central to atherogenesis both as the progenitors of foam cells and as a potential source of growth factors mediating intimal hyperplasia, but the chemical messages which stimulate the influx of monocytes into human atheroma remain unknown. Monocyte chemoattractant protein-1 (MCP-1) is a recently described molecule with powerful monocyte chemotactic activity expressed by monocytes, vascular endothelial cells, and smooth muscle cells in culture. To begin to address the role of MCP-1 in vivo, we examined 10 normal arteries and 14 diseased human arteries for MCP-1 expression by in situ hybridization. MCP-1 mRNA was detected in 16% of 10,768 cells counted in human carotid endarterectomy specimens with highest expression seen in organizing thrombi (33%) and in macrophage rich areas bordering the necrotic lipid core (24%) as compared to the fibrous cap (8%) and the necrotic lipid core itself (5%). Based on immunohistochemical staining of serial sections and on cell morphology, MCP-1 mRNA appeared to be expressed by vascular smooth muscle cells (VSMC), mesenchymal appearing intimal cells (MICs), and macrophages. By contrast, few cells expressing MCP-1 mRNA were found in normal arteries (less than 0.1%). These data suggest a potential role for MCP-1 in mediating monocytic infiltration of the artery wall.

Changes in aquaporin-2 protein contribute to the urine concentrating defect in rats fed a low-protein diet.

Low-protein diets cause a urinary concentrating defect in rats and humans. Previously, we showed that feeding rats a low (8%) protein diet induces a change in urea transport in initial inner medullary collecting ducts (IMCDs) which could contribute to the concentrating defect. Now, we test whether decreased osmotic water permeability (Pf) contributes to the concentrating defect by measuring Pf in perfused initial and terminal IMCDs from rats fed 18 or 8% protein for 2 wk. In terminal IMCDs, arginine vasopressin (AVP)-stimulated osmotic water permeability was significantly reduced in rats fed 8% protein compared to rats fed 18% protein. In initial IMCDs, AVP-stimulated osmotic water permeability was unaffected by dietary protein. Thus, AVP-stimulated osmotic water permeability is significantly reduced in terminal IMCDs but not in initial IMCDs. Next, we determined if the amount of immunoreactive aquaporin-2 (AQP2, the AVP-regulated water channel) or AQP3 protein was altered. Protein was isolated from base or tip regions of rat inner medulla and Western analysis performed using polyclonal antibodies to rat AQP2 or AQP3 (courtesy of Dr. M.A. Knepper, National Institutes of Health, Bethesda, MD). In rats fed 8% protein (compared to rats fed 18% protein): (a) AQP2 decreases significantly in both membrane and vesicle fractions from the tip; (b) AQP2 is unchanged in the base; and (c) AQP3 is unchanged. Together, the results suggest that the decrease in AVP-stimulated osmotic water permeability results, at least in part, in the decrease in AQP2 protein. We conclude that water reabsorption, like urea reabsorption, responds to dietary protein restriction in a manner that would limit urine concentrating capacity.

Platelet-derived growth factor mRNA detection in human atherosclerotic plaques by in situ hybridization.

Platelet-derived growth factor (PDGF) mRNA, and mRNA for its receptor, have been localized to specific cell types within the human atherosclerotic plaque, using in situ hybridization. The predominant cell types found to express PDGF A and B chain mRNA are mesenchymal-appearing intimal cells and endothelial cells, respectively, with little or no expression detected in macrophages. The distribution of PDGF receptor mRNA containing cells was also examined and found to be localized predominantly in the plaque intima.

Platelet-derived growth factor activity and mRNA expression in healing vascular grafts in baboons. Association in vivo of platelet-derived growth factor mRNA and protein with cellular proliferation.

In a baboon graft model of arterial intimal thickening, smooth muscle cells (SMC) have been observed to proliferate underneath an intact monolayer of endothelium and in the absence of platelet adherence. Because platelets are not present and therefore cannot be a major source of growth stimulus, we have proposed that the vascular wall cells in the graft intima express mitogens and regulate SMC proliferation. To test this hypothesis, we assayed the grafts for mitogenic activity and expression of growth factor genes. Segments of healing graft and of normal artery, when perfused ex vivo, released mitogenic activity into the perfusate. The graft released more mitogen than the normal arterial segment, and some of the activity was inhibitable with an antibody to human platelet-derived growth factor (PDGF). In addition, Northern analysis of total RNA demonstrated higher expression of PDGF-A chain mRNA in the graft intima compared to normal artery. PDGF-B chain mRNA was barely detectable in both tissues. PDGF mRNA levels within the graft interstices were not measured. In situ hybridization of 7.5- or 12-wk grafts indicated that some luminal endothelial cells and adjacent intimal SMC contained PDGF-A chain mRNA. By thymidine autoradiography, intimal SMC were observed to be proliferating in the inner third of the intima. These data demonstrate a difference in the pattern of PDGF transcript expression and luminal perfusate activity in graft as compared with control arteries. The association of intimal smooth muscle cell proliferation with intimal PDGF mRNA expression and release of PDGF-like protein supports the hypothesis that factors from cells that have grown into the graft or populated its surface rather than platelets may regulate intimal smooth muscle cell proliferation in this model.

Regional expression of the platelet-derived growth factor and its receptors in a primate graft model of vessel wall assembly.

Healing baboon polytetrafluoroethylene grafts express PDGF mRNA in the neointima. Perfusates of graft segments also contain PDGF-like mitogenic activity. To extend these findings, we studied the expression and regional distribution of the PDGF protein isoforms and their receptors in this prosthetic graft model. By immunohistochemistry, as well as ELISA and Western blot analysis of tissue extracts, both PDGF-A and PDGF-B were identified in macrophages within the interstices of the synthetic material. In contrast, the neointima contained predominantly PDGF-A localized to the endothelial surface and the immediate subjacent smooth muscle cell layers. Tissue extracts of neointima and graft material were mitogenic for baboon aortic smooth muscle cells in culture; nearly all of this proliferative activity was blocked by a neutralizing anti-PDGF antibody. PDGF receptor beta-subunit mRNA and protein were easily detectable in the neointima and graft material. PDGF receptor alpha-subunit mRNA was also observed in the graft matrix and at lower levels in the neointima. This pattern of ligand and receptor expression further implicates locally produced PDGF as a regulator of neointimal smooth muscle cell growth in this model. The coexpression of ligand and receptor in the macrophage-rich matrix also suggests that PDGF may participate in the foreign body response.

Developmental expression of transforming growth factors alpha and beta in mouse fetus.

Expression of mRNA for transforming growth factor alpha (TGF-alpha) and TGF-beta 1 during the fetal development of mice was evaluated by in situ hybridization. TGF-alpha mRNA was detected in 9- and 10-day fetuses but was absent in older fetuses. TGF-alpha mRNA-containing cells were found in the placenta, otic vesicle, oral cavity, pharyngeal pouch, first and second branchial arches, and developing kidneys. mRNA for TGF-beta 1 was present in hematopoietic cells of blood islands and capillaries and in the liver as it began to bud off on day 10 and function as a hematopoietic organ.

Differential regional expression of three natriuretic peptide receptor genes within primate tissues.

The natriuretic peptide receptors are three homologous cell surface proteins, each with a single transmembrane domain. The atrial natriuretic peptide receptor type A (ANPRA) and the homologous receptor type B (ANPRB) are both membrane guanylyl cyclases that synthesize cyclic GMP as an intracellular second messenger. The third receptor in this family, the atrial natriuretic peptide receptor type C (ANPRC), is not coupled to cyclic GMP production. We report on the distribution of the ANPRA, ANPRB, and ANPRC mRNAs in rhesus monkey tissues assayed by in situ hybridization. ANPRA mRNA is most abundantly expressed in the kidney glomerulus, adrenal zona glomerulosa, pituitary, cerebellum, and endocardial endothelial cells of the right and left atrium and right ventricle. In contrast, abundant ANPRB expression appears to be confined to the adrenal medulla, pituitary, and cerebellum. ANPRC mRNA appeared to be expressed very differently than ANPRA and ANPRB. In the heart, ANPRC mRNA is expressed most prominently in endocardial endothelial cells of all four chambers but is also found throughout the myocardium only in the right atrium. These data identify major sites of natriuretic peptide receptor mRNA expression and suggest that there may be prominent cell type-specific differential distribution of these receptors in central and peripheral targets for the natriuretic peptides.