Reduced Glucose Transporter at the Blood-Brain Barrier and in Cerebral Cortex in Alzheimer Disease

We studied the hexose transporter protein of the frontal and temporal neocortex, hippocampus, putamen, cerebellum, and cerebral microvessels (which constitute the blood-brain barrier) in Alzheimer disease and control subjects by reversible and covalent binding with [3H]cytochalasin B and by immunological reactivity. In Alzheimer disease subjects, we found a marked decrease in the hexose transporter in brain microvessels and in the cerebral neocortex and hippocampus, regions that are most affected in Alzheimer disease, but there were no abnormalities in the putamen or cerebellum. Hexose transporter reduction in cerebral microvessels of Alzheimer subjects is relatively specific because other enzyme markers of brain endothelium were not significantly altered. The low density of the hexose transporter at the blood-brain barrier and in the cerebral cortex in Alzheimer disease may be related to decreased in vivo measurements of cerebral oxidative metabolism.     

Down''s Syndrome Individuals Begin Life with Normal Levels of Brain Cholinergic Markers

We measured the activities of the cholinergic marker enzymes choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) in autopsied brains of seven infants (age range 3 months to 1 year) with Down's syndrome (DS), a disorder in which virtually all individuals will develop by middle age the neuropathological changes of Alzheimer's disease accompanied by a marked brain cholinergic reduction. When compared with age-matched controls cholinergic enzyme activity was normal in all brain regions of the individuals with infant DS with the exception of above-normal activity in the putamen (ChAT) and the occipital cortex (AChE). Our neurochemical observations suggest that DS individuals begin life with a normal complement of brain cholinergic neurons. This opens the possibility of early therapeutic intervention to prevent the development of brain cholinergic changes in patients with DS.     

Characterization of Cellular Transport, Subcellular Distribution, and Secretion of the Neurotoxicant 1-Methyl-4-Phenylpyridinium in Bovine Adrenomedullary Cell Cultures

Cultures of bovine adrenomedullary chromaffin cells accumulated 1-[methyl-3H]methyl-4-phenylpyridinium ([3H]MPP+) in a time- and concentration-dependent manner with an apparent Km of 0.7 microM and a Vmax of 3 pmol/min/10(6) cells. The uptake was sodium dependent and sensitive to inhibitors of the cell-surface catecholamine transporter. At low concentrations of MPP+, the subcellular distribution was identical to that of endogenous catecholamines in the catecholamine-containing chromaffin vesicles. However, at a higher concentration of MPP+, a larger proportion of the toxicant was recovered in the cytosolic fraction, with less in the chromaffin vesicle fractions. When cells were prelabeled with [3H]MPP+, at 1 and 300 microM, and then permeabilized with digitonin in the absence of Ca2+, there was a proportionally greater release of MPP+ from the cells labeled at the higher concentration of the toxicant. In the presence of Ca2+, cell permeabilization induced a time-dependent secretion of catecholamines and a parallel secretion of MPP+. Under these conditions, the secretion of endogenous catecholamines was unaffected by the presence of MPP+. When the permeabilization studies were carried out in the presence of tetrabenazine, a massive release of MPP+ was observed in the absence of Ca2+ and was not further increased by Ca2+. In intact cells prelabeled with 300 microM [3H]MPP+, the secretagogues nicotine and veratridine elicited a Ca2+ -dependent secretion of catecholamines and MPP+ from the cells in similar proportions to their cellular contents. Barium-induced release of both species was independent of external Ca2+.(ABSTRACT TRUNCATED AT 250 WORDS)     

Carbachol-Induced Cosecretion of Immunoreactive Atrial Natriuretic Peptides with Catecholamines from Cultured Bovine Adrenal Medullary Cells

The distribution and secretion of atrial natriuretic peptides (ANPs) were investigated in bovine adrenal medulla. (1) Cultured bovine adrenal medullary cells (2 x 10(6)/dish) contained 100.4 +/- 6.0 fmol of immunoreactive ANP (IR-ANP) and 207.3 +/- 6.6 nmol of catecholamines as epinephrine plus norepinephrine. (2) Stimulation of nicotinic but not muscarinic acetylcholine receptors caused a cosecretion of IR-ANP and catecholamines corresponding to the ratio of IR-ANP to catecholamines in cultured bovine adrenal medullary cells. (3) Carbachol-stimulated secretion of IR-ANP was dependent on the presence of extracellular Ca2+. (4) Chromaffin granules isolated from bovine adrenal medulla contained large amounts of IR-ANP and catecholamines, in the same ratio as did cultured adrenal medullary cells. (5) Reverse-phase HPLC analysis showed that both stored and secreted IR-ANP consisted of two components, which eluted at the position of ANP(99-126) or ANP(1-126). These results indicate that ANPs are stored as ANP(99-126) and ANP(1-126) in chromaffin granules, and are cosecreted in parallel with catecholamines in a Ca2+-dependent manner by the stimulation of nicotinic acetylcholine receptors.     

Paleohistology of Paget's disease in two medieval skeletons.

Paget's disease has been ascribed several times to specimens of archeological bone but, in the absence of microscopic examination, the evidence remains insubstantial. Suspected metabolic bone disease is described here in the archeological remains of a skeleton from a 16th century burial ground at Wells Cathedral, England and from a single medieval sacrum recovered from a large deposit of disarticulated bones from a churchyard at Barton-on-Humber, England. Radiographs showed apparent structural abnormality in one femoral shaft and calcaneus and in the isolated sacrum. Histomorphometry on undecalcified bone cores confirmed the regions of abnormality and showed not only increased trabecular width but also areas of "mosaic" woven bone together with extensive resorption cavities; these features contrasted with the normal structure and organized lamellar bone from sites elsewhere. Despite post-interment changes in surrounding tissues, the morphological stability of some of the osteocytes was remarkable. Preservation of the histology was sufficient to permit the assignment of a metabolic bone disorder and the nature of the sclerosis was consistent with Paget's disease.     

Sensitive detection of mycoplasmalike organisms in field-collected and in vitro propagated plants of Brassica, Hydrangea and Chrysanthemum by polymerase chain reaction

A polymerase chain reaction (PCR) protocol, previously designed for amplification of a DNA fragment from aster yellows mycoplasmalike organism (MLO), was employed to investigate the detection of MLO DNA in field-collected and in vitro micropropagated plants. PCR with template DNA extracted from symptomatic, naturally-infected samples of Brassica, Chrysanthemum and Hydrangea, each yielded a DNA band corresponding to 1.0 Kbp. However, no DNA product was observed when either infected Ranunculus (with phyllody disease) or Gladiolus with (symptoms of ‘germs fins’) was used as source of template nucleic acid for PCR; further experiments indicated absence of target DNA in the case of Ranunculus and the presence of substances in Gladiolus which inhibited the PCR. The MLO-specific DNA was detected by PCR using less than 95 pg of total nucleic acid (equivalent to total nucleic acid from 1.9, ug tissue) in the case of field-collected Hydrangea and less than 11.4 pg of nucleic acid (equivalent to total nucleic acid from 19 ng of tissue) in the case of field-collected Brassica. The findings illustrate highly sensitive detection of MLOs in both field-grown and in vitro micropropagated infected plants.     

Activation of m1 Muscarinic Acetylcholine Receptor Regulates τ Phosphorylation in Transfected PC12 Cells

Abstract: Hyperphosphorylated τ proteins are the principal fibrous component of the neurofibrillary tangle pathology in Alzheimer's disease. The possibility that τ phosphorylation is controlled by cell surface neurotransmitter receptors was examined in PC12 cells transfected with the gene for the rat m₁ muscarinic acetylcholine receptor. Stimulation of m₁ receptor in these cells with two acetylcholine agonists, carbachol and AF102B, decreased τ phosphorylation, as indicated by specific τ monoclonal antibodies that recognize phosphorylation-dependent epitopes and by alkaline phosphatase treatment. The muscarinic effect was both time and dose dependent. In addition, a synergistic effect on τ phosphorylation was found between treatments with muscarinic agonists and nerve growth factor. These studies provide the first evidence for a link between the cholinergic signal transduction system and the neuronal cytoskeleton that can be mediated by regulated phosphorylation of τ microtubule-associated protein.     

Brain S-Adenosylmethionine Levels Are Severely Decreased in Alzheimer's Disease

Abstract: S -Adenosylmethionine is an essential ubiquitous metabolite central to many biochemical pathways, including transmethylation and polyamine biosynthesis. Reduced CSF S -adenosylmethionine levels in Alzheimer's disease have been reported; however, no information is available regarding the status of S -adenosylmethionine or S -adenosylmethionine-dependent methylation in the brain of patients with this disorder. S -Adenosylmethionine concentrations were measured in postmortem brain of 11 patients with Alzheimer's disease. We found decreased levels of S -adenosylmethionine (−67 to −85%) and its demethylated product S -adenosylhomocysteine (−56 to −79%) in all brain areas examined (cerebral cortical subdivisions, hippocampus, and putamen) as compared with matched controls (n = 14). S -Adenosylmethionine and S -adenosylhomocysteine levels were normal in occipital cortex of patients with idiopathic Parkinson's disease (n = 10), suggesting that the decreased S -adenosylmethionine levels in Alzheimer's disease are not simply a consequence of a chronic, neurodegenerative condition. Reduced S -adenosylmethionine levels could be due to excessive utilization in polyamine biosynthesis. The severe reduction in levels of this essential biochemical substrate would be expected to compromise seriously metabolism and brain function in patients with Alzheimer's disease and may provide the basis for the observations of improved cognition in some Alzheimer's patients following S -adenosylmethionine therapy.     

Polymerization of τ into Filaments in the Presence of Heparin: The Minimal Sequence Required for τ - τ Interaction

Abstract: Paired helical filaments isolated from the brains of patients with Alzheimer's disease are composed of a major protein component, the microtubule-associated protein termed τ, together with other nonprotein components, including heparan, a glycosaminoglycan, the more extensively sulfated form of which is heparin. As some of these nonprotein components may modulate the assembly of τ into filamentous structures, we have analyzed the ability of the whole τ protein or some of its fragments to self-assemble in the presence of heparin. Different τ fragments, all of them containing some sequences of the tubulin-binding motif, can assemble in vitro into filaments. We have also found formation of polymers with the 18-residue-long peptide corresponding to the third tubulin-binding motif of τ. This suggests that the ability of τ for self-assembly could be localized in a short sequence of amino acids present in the tubulin-binding repeats of the τ molecule.