Biomedical subjects

C Soto

Publications and source records attributed to C Soto.

At least 55 records · Page 3Linked to original sources

PubMed1999

Expression of dominant-negative src-homology domain 2-containing protein tyrosine phosphatase-1 results in increased Syk tyrosine kinase activity and B cell activation.

The Src-homology domain 2 (SH2)-containing cytoplasmic tyrosine phosphatase, SHP-1 (SH2-containing protein tyrosine phosphatase-1), interacts with several B cell surface and intracellular signal transduction molecules through its SH2 domains. Mice with the motheaten and viable motheaten mutations are deficient in SHP-1 and lack most mature B cells. To define the role of SHP-1 in mature B cells, we expressed phosphatase-inactive SHP-1 (C453S) in a mature B cell lymphoma line. SHP-1 (C453S) retains the ability to bind to both substrates and appropriate tyrosine-phosphorylated proteins and therefore can compete with the endogenous wild-type enzyme. We found that B cells expressing SHP-1 (C453S) demonstrated enhanced and prolonged tyrosine phosphorylation of proteins with molecular masses of 110, 70, and 55-60 kDa after stimulation with anti-mouse IgG. The tyrosine kinase Syk was hyperphosphorylated and hyperactive in B cells expressing SHP-1 (C453S). SHP-1 and Syk were coimmunoprecipitated from wild-type K46 cells, K46 SHP-1 (C453S) cells, and splenic B cells, and SHP-1 dephosphorylated Syk. Cells expressing SHP-1 (C453S) showed increased Ca2+ mobilization, extracellular signal-regulated kinase activation, and homotypic adhesion after B cell Ag receptor engagement. Thus, SHP-1 regulates multiple early and late events in B lymphocyte activation.

Animals↗

PubMed1999

Alzheimer's and prion disease as disorders of protein conformation: implications for the design of novel therapeutic approaches.

Several lines of evidence suggest that a defective protein folding is a central event in both Alzheimer's and prion disease. Although the two disorders are very different clinically, neuropathologically, and biochemically, the molecular event that may trigger the disease process appears to be the same: the formation of an altered protein conformer composed of a high content of beta-sheet structure. Compounds with the ability to prevent and to reverse protein conformational changes may be useful as novel therapeutic approaches for Alzheimer's disease, prion disease, and other disorders of defective protein folding.

Alzheimer Disease↗

PubMed1999

Plaque busters: strategies to inhibit amyloid formation in Alzheimer's disease.

Alzheimer's disease is a devastating degenerative disorder of the brain for which there is no cure or effective treatment. Although the etiology of Alzheimer's disease is not fully understood, recent research suggests that deposition of cerebral amyloid plaques is central to the disease process. Therefore, an attractive therapeutic strategy for Alzheimer's disease is to prevent, reduce or reverse amyloid deposition in the brain. Several small chemical compounds, synthetic peptides and natural proteins have been described that inhibit amyloid formation or amyloid neurotoxicity in vitro. The effect of these and other compounds now needs to be tested in vivo and the ability of amyloid inhibitors to halt the progression of Alzheimer's disease in humans needs to be evaluated.

Alzheimer Disease↗

PubMed1999

[MLL rearrangements in acute leukemias].

PURPOSE: In present study we have studied MLL rearrangements in a serie of acute myeloid, lymphoblastic and biphenotypic leukaemias. PATIENTS AND METHODS: We analyzed a total of 11 cases: 9 acute myeloid leukaemias (M4 and M5 subtypes in FAB classification), 1 lymphoid leukaemia, and 1 acute biphenotypic leukaemia. We studied bone marrow samples from all patients by using conventional cytogenetic techniques and fluorescence in situ hybridization (FISH) with an MLL probe. We also analyzed the correlation between clinical features and genetic results. RESULTS: Cells from 6 patients showed to contain MLL rearrangements and these arose in all types of leukaemias included in this study. Some MLL rearrangements were detected by FISH in kariotypically normal cases or without cytogenetic evidence of 11q23 aberration. MLL gene duplication has been observed in two cases with M4 and biphenotypic leukaemia, respectively. The presence of MLL gene rearrangements does not shape a group of patients with a common clinical pattern. CONCLUSIONS: MLL rearrangements occurs in a wide variety of leukemias. These rearrangements should be screened by FISH techniques, taking into account that gene duplications could arise in cases with normal karyotype. MLL rearrangements appear to have a considerable clinicopathologic heterogeneity.

Adult↗

PubMed1998

Alzheimer's beta-amyloid vasoactivity: identification of a novel beta-amyloid conformational intermediate.

The beta-amyloid (A beta) peptide has previously been shown to enhance phenylephrine or endothelin-1 induced constriction of aortic rings in vitro. The characteristics of A beta vasoactivity (dose, fragment length, timing) suggest that the mechanism is distinct from A beta cytotoxicity. To identify which properties of A beta determine its biological activity on vessels, we investigated a number of A beta analogues and fragments, individually and in combination, including those that are known to be associated with Alzheimer's disease (A beta(1-42)) and hereditary cerebral hemorrhage with amyloidosis--Dutch type (A beta(22Q)(1-40)). The vasoactivity appears to be related to the conformation adopted by the peptide in solution. The beta-pleated sheet rich A beta(1-42) and A beta(22Q)(1-40) were each less vasoactive than the mainly random coil wild type A beta(1-40). However, the most vasoactive A beta peptides were combinations which contain mixtures of random coil and beta-sheet structure. The finding that peptides containing low or high levels of beta-pleated conformation are less vasoactive than those containing intermediate amounts of this structural motif allows us to propose the existence of a transitional form between random coil and beta-pleated that is the vasoactive species of A beta. This is the first time that A beta conformational intermediates have been identified and a biological activity associated with them.

Amyloid beta-Peptides↗

PubMed1998

Beta structure motif recognition by anti-gliadin antibodies in coeliac disease.

A 20-amino acid synthetic peptide from the N-terminal region of gamma3 avenin yields a surprisingly strong reactivity with anti-gliadin antibodies (AGA) of coeliac sera, comparable to that of a gliadin extract. In contrast, a low reactivity is observed with five similar peptides derived from alpha-gliadin, gamma70 and omega1 secalins. Circular dichroism studies of these peptides show that the avenin peptide displays the highest beta-turn content (30%), while other peptides yield much lower values. In agreement with circular dichroism data, nuclear magnetic resonance data point to the presence of a beta-turn in the avenin peptide DPSEQ segment, a sequence with a high statistical beta-turn preference. A strong linear dependence between AGA reactivity and beta-turn content was observed for these peptides, indicating for the first time a role of beta-turn motifs in anti-gliadin antibodies recognition in coeliac disease. This suggests that circulating AGA in coeliac patients comprise not only linear but also conformational antibodies against beta-turn motifs. Polyclonal antibodies raised against the avenin peptide containing beta-turn motifs react by immunoblotting with all gliadin, hordein and secalin proteins, which are rich in beta-turn conformations, despite that their primary structures are unrelated to that of the peptide.

Antibodies↗

PubMed1998

Inhibition of Alzheimer beta-fibrillogenesis by melatonin.

It is generally postulated that the amyloid beta protein (Abeta) plays a central role in the progressive neurodegeneration observed in Alzheimer's disease. Important pathologic properties of this protein, such as neurotoxicity and resistance to proteolytic degradation, depend on the ability of Abeta to form beta-sheet structures or amyloid fibrils. We report that melatonin, a hormone recently found to protect neurons against Abeta toxicity, interacts with Abeta1-40 and Abeta1-42 and inhibits the progressive formation of beta-sheets and amyloid fibrils. These interactions between melatonin and the amyloid peptides were demonstrated by circular dichroism and electron microscopy for Abeta1-40 and Abeta1-42 and by nuclear magnetic resonance spectroscopy for Abeta1-40. Inhibition of beta-sheets and fibrils could not be accomplished in control experiments when a free radical scavenger or a melatonin analog were substituted for melatonin under otherwise identical conditions. In sharp contrast with conventional anti-oxidants and available anti-amyloidogenic compounds, melatonin crosses the blood-brain barrier, is relatively devoid of toxicity, and constitutes a potential new therapeutic agent in Alzheimer's disease.

Alzheimer Disease↗

PubMed1998

Beta-sheet breaker peptides inhibit fibrillogenesis in a rat brain model of amyloidosis: implications for Alzheimer's therapy.

Inhibition of cerebral amyloid beta-protein deposition seems to be an important target for Alzheimer's disease therapy. Amyloidogenesis could be inhibited by short synthetic peptides designed as beta-sheet breakers. Here we demonstrate a 5-residue peptide that inhibits amyloid beta-protein fibrillogenesis, disassembles preformed fibrils in vitro and prevents neuronal death induced by fibrils in cell culture. In addition, the beta-sheet breaker peptide significantly reduces amyloid beta-protein deposition in vivo and completely blocks the formation of amyloid fibrils in a rat brain model of amyloidosis. These findings may provide the basis for a new therapeutic approach to prevent amyloidosis in Alzheimer's disease.

Alzheimer Disease↗

PubMed1998

The prionoses and other conformational disorders.

The basic pathogenesis of numerous neurodegenerative disorders is now thought to be related to abnormal protein conformation. The common theme in all these diseases is the conversion of a normal cellular and/or circulating protein into an insoluble, aggregated, beta-sheet rich form which is deposited in the brain, sometimes in the form of amyloid. These deposits are toxic and produce neuronal dysfunction and death. The most common of these illnesses is Alzheimer's disease (AD), in which a central event is the conversion of the normal soluble amyloid beta (sA beta) peptide to amyloid beta (A beta) within neuritic plaques and cerebral vessels. A unique category of the conformational conditions are prion related diseases (or prionoses), where the etiology is thought to be related to conversion of the normal prion protein, PrPC, into an infectious and pathogenic form, PrPSc. In the case of AD and the prionoses, the conformational change can be influenced by the presence of mutations in various gene products, as well as by chaperone proteins. Apolipoprotein E is thought to act as such a chaperone protein in AD; however, among the prionoses such a protein has been hypothesized to exist only by indirect evidence and is called "protein X". Our growing understanding of the mechanisms involved in this category of diseases, raises the possibility of therapeutic approaches based directly on the prevention and reversal of pathologic protein conformation.

Alzheimer Disease↗

PubMed1997

Detection of apolipoprotein E/dimeric soluble amyloid beta complexes in Alzheimer's disease brain supernatants.

The inheritance of the apolipoprotein (apo) E4 allele is an important risk factor for late-onset Alzheimer's disease (AD). A major component of the Alzheimer's disease neuritic plaques is amyloid beta (A beta). We previously identified apoE/A beta complexes within neuritic plaques (1). It was not known if this interaction takes place before or after A beta peptides become incorporated into neuritic plaques. To address this question we sought evidence of apoE complexes with brain soluble A beta peptides in AD and control patients. In addition, numerous proteins have been shown to bind A beta peptides in vitro. It is not know if any of these bind brain sA beta in vivo. We found evidence for the presence of apoE/dimeric sA beta complexes in the AD brain and could not detect complexes with other A beta peptide binding proteins. The binding of sA beta to apoE may be one factor influencing its clearance from the brain and/or its conformational state.

Alzheimer Disease↗

PubMed1997

An intracellular protein that binds amyloid-beta peptide and mediates neurotoxicity in Alzheimer's disease.

Amyloid-beta is a neurotoxic peptide which is implicated in the pathogenesis of Alzheimer's disease. It binds an intracellular polypeptide known as ERAB, thought to be a hydroxysteroid dehydrogenase enzyme, which is expressed in normal tissues, but is overexpressed in neurons affected in Alzheimer's disease. ERAB immunoprecipitates with amyloid-beta, and when cell cultures are exposed to amyloid-beta, ERAB inside the cell is rapidly redistributed to the plasma membrane. The toxic effect of amyloid-beta on these cells is prevented by blocking ERAB and is enhanced by overexpression of ERAB. By interacting with intracellular amyloid-beta, ERAB may therefore contribute to the neuronal dysfunction associated with Alzheimer's disease.

3-Hydroxyacyl CoA Dehydrogenases↗

PubMed1997

Modulation of oscillator interactions in the crab stomatogastric ganglion by crustacean cardioactive peptide.

The modulation of the pyloric rhythm of the stomatogastric ganglion of the crab, Cancer borealis, by crustacean cardioactive peptide (CCAP) is described. CCAP activated pyloric rhythms in most silent preparations, and altered the phase relationships of pyloric motor neuron firing in all preparations. In CCAP, the pyloric rhythms were characterized by long lateral pyloric (LP) neuron bursts of action potentials. The threshold for CCAP action was approximately 10(-10) M, with increasing effects at higher CCAP concentrations. The changes in motor pattern evoked by CCAP produced significant changes in LP-innervated muscle movement. These movements were additionally potentiated by CCAP applications to isolated nerve-muscle preparations. Thus, enhanced motor neuron firing and increase of the gain of the neuromuscular junctions are likely to operate coordinately in response to hormonally released CCAP. High CCAP concentrations sometimes resulted in modification of the normal 1:1 alternation between the pyloric dilator (PD) and LP neurons to patterns of 2:1, 3:1, or 4:1 alternation. CCAP seems to activate slow intrinsic oscillations in the LP neuron, as well as enhance faster oscillations in the pacemaker group of PD/anterior burster (AB) neurons. Simulations of fast and slow oscillators with reciprocal inhibitory coupling suggest mechanisms that could account for the mode switch from 1:1 alternation to multiple PD bursts alternating with one LP neuron burst.

Action Potentials↗

PubMed1997

Effect of portal vein ligation and silymarin treatment on aspirin metabolism and disposition in rats.

The influence of portal hypertension on the metabolism and pharmacokinetics of aspirin was evaluated after the administration of a single oral dose of acetylsalicylic acid (20 mgkg(-1)) in portal-vein-ligated (PVL) rats. Experiments were also performed in control (sham-operated rats) and in rats that received an oral daily dose (150 mgkg(-1)) of silymarin from the tenth day after surgery for 7 d. Plasma concentration profiles of all groups exhibited monoexponential decay but with important changes in pharmacokinetic parameters. The aspirin elimination constant (k) for PVL rats was lower than for control rats, whereas the plasma half-life and area under the curve were greater than those in the control group. However, Cmax was comparable with that of the control rats. Urinary excretion of the metabolites (salicylic acid and glucuronides) was significantly altered in PVL rats: the urinary glucuronides were reduced and urinary salicylic acid was increased. The activities of plasma and liver esterases were increased significantly in PVL rats, while the activity of p-nitroanisole-O-demethylase was not affected. Depletion of cytochrome P 450 was also noted in the same group of rats. Silymarin markedly reversed the alterations found in the PVL group.

Administration, Oral↗

PubMed1997

An experimental study on the pathogenesis of gastroesophageal reflux after repair of diaphragmatic hernia.

BACKGROUND/PURPOSE: Gastroesophageal reflux (GER) is increasingly reported after surgical repair of congenital diaphragmatic hernia (CDH) and eventration. The aim of this study was to test the hypothesis that transdiaphragmatic pressure gradients are increased and that the antireflux barrier is weakened after plication of a previously paralyzed diaphragm. METHODS: Abdominal and esophageal pressures as well as lower esophageal sphincter pressures (LESP) and diaphragmatic pinchcock pressure (DPP) were measured before and after diaphragmatic plication in 16 rats in which the diaphragm had been previously eventrated by phrenic nerve section. RESULTS: This maneuver increased the transdiaphragmatic inspiratory pressure gradient from 2.75 +/- 0.54 to 4.51 +/- 0.86 mm Hg (P < .05) by rising both the inspiratory (-2.02 +/- 0.39 v -3.11 +/- 0.92 mm Hg, P < .05) and the expiratory (1.47 +/- 0.87 v 0.51 +/- 0.41 mm Hg, P < .05) intrathoracic pressures. At the same time, the antireflux barrier was weakened because LESP decreased from 17.5 +/- 5.59 to 10.59 +/- 5.74 mm Hg (P < .05) and DPP tended to decrease from 13.57 +/- 8.67 to 6.07 +/- 1.72 mm Hg (ns). CONCLUSIONS: Plication of the previously paralyzed diaphragm in the rat reinforces the GER driving forces while weakening the antireflux barrier. This may explain why reflux is frequent in children surviving repair of diaphragmatic hernia and eventration.

Animals↗

PubMed1997

Identification of diaphragmatic crural component of gastroesophageal barrier in the rat.

Manometric assessment of the diaphragmatic contribution to the human gastroesophageal barrier is difficult because it overlaps with that of the lower esophageal sphincter. Our aim was to investigate the barrier components in the rat in which the gastroesophageal junction is widely separated from the hiatus. Rats under anesthesia (N = 119) and after muscle relaxation (N = 14) underwent stationary and pull-through perfusion manometry. Inspiratory transdiaphragmatic pressure gradient was 5.79 +/- 1.69 mm Hg and lower esophageal sphincter pressure was 14.76 +/- 8.63 mm Hg. A 13.78 +/- 3.13-mm intraabdominal segment of the esophagus was interposed cranially between the sphincter and a group of phasic oscillations with frequency identical to the respiratory rate and pressure of 13.81 +/- 6.54 mm Hg, which disappeared after muscle relaxation. Both components of the gastroesophageal barrier in the rat are widely separated by a long intraabdominal esophagus. This arrangement allows investigation of the behavior of both components under challenging conditions.

Animals↗

PubMed1996

The length of amyloid-beta in hereditary cerebral hemorrhage with amyloidosis, Dutch type. Implications for the role of amyloid-beta 1-42 in Alzheimer's disease.

In hereditary cerebral hemorrhage with amyloidosis, Dutch type (HCHWA-D), a genetic variant (E22Q) of amyloid beta (Abeta) accumulates predominantly in the small vessels of leptomeninges and cerebral cortex, leading to fatal strokes in the fifth or sixth decade of life. Abeta deposition in the neuropil occurs mainly in the form of preamyloid, Congo red negative deposits, while mature neuritic plaques and neurofibrillary tangles, hallmark lesions in Alzheimer's disease (AD), are characteristically absent. A recent hypothesis regarding the pathogenesis of AD states that Abeta extending to residues 42-43 (as opposed to shorter species) can seed amyloid formation and trigger the development of neuritic plaques followed by neuronal damage in AD. We characterized biochemically and immunohistochemically Abeta from three cases of HCHWA-D to determine its length in vascular and parenchymal deposits. Mass spectrometry of formic acid-soluble amyloid, purified by size-exclusion gel chromatography, showed that Abeta 1-40 and its carboxyl-terminal truncated derivatives were the predominant forms in leptomeningeal and cortical vessels. Abeta 1-42 was a minor component in these amyloid extracts. Immunohistochemistry with antibodies S40 and S42, specific for Abeta ending at Val-40 or Ala-42, respectively, were consistent with the biochemical data from vascular amyloid. In addition, parenchymal preamyloid lesions were specifically stained with S42 and were not labeled by S40, in agreement with the pattern reported for AD, Down's syndrome, and aged dogs. Our results suggest that in HCHWA-D the carboxyl-terminal Abeta heterogeneity is due to limited proteolysis in vivo. Moreover, they suggest that Abeta species ending at Ala-42 may not be critical for the seeding of amyloid formation and the development of AD-like neuritic changes.

Alzheimer Disease↗

PubMed1996

Inhibition of Alzheimer's amyloidosis by peptides that prevent beta-sheet conformation.

Amyloid beta-peptide (A beta) is a major fibrillar component of neuritic plaques in Alzheimer's disease (AD) brains and is related to the pathogenesis of the disease. We hypothesized that amyloid formation could be inhibited by peptides homologous to A beta (position 17-21) with a similar degree of hydrophobicity, but with a very low propensity to adopt a beta-sheet conformation by incorporating proline residues (anti-beta-sheet peptides or beta-sheet inhibitors). An 11-residue peptide with these characteristics binds to A beta, inhibits A beta fibril formation and partially disaggregates preformed fibrils in vitro. Shorter anti-beta-sheet peptides and analogs containing D-amino acids are also able to inhibit A beta fibrillogenesis. The latter are more resistant to proteolytic degradation and may serve as a starting point to design more efficient peptides derivatives to inhibit amyloidogenesis in vivo.

Alzheimer Disease↗

PubMed1996

Apolipoprotein J and Alzheimer's amyloid beta solubility.

Apolipoprotein J (apoJ) has been found associated with soluble amyloid beta (sA beta) in plasma and cerebrospinal fluid in normal individuals and co-deposited with fibrillar A beta in Alzheimer's cerebrovascular and parenchymal lesions. Although studies in vitro and in vivo indicate that apoJ is a major carrier protein for sA beta, its role in the fibrillogenesis process is not known. We report herein that apoJ in its native high-density lipoprotein lipidic environment is fully active to interact with A beta peptides. Furthermore, apoJ prevents aggregation and polymerization of synthetic A beta in vitro. The interaction was stable for at least 14 days at 37 degrees C in physiologic buffers, and the peptide retrieved after complex dissociation at low pH retained its inherent aggregation properties. In addition, the binding to apoJ protects synthetic A beta from proteolytic degradation; both A beta 1-42 and A beta 1-40 were more resistant to proteolysis by trypsin and chymotrypsin when complexed to apoJ. The data suggest that the interaction may preclude sA beta aggregation in biological fluids and point to a protecting role of apoJ for complexed A beta species.

Alzheimer Disease↗