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Biomedical subjects

C Schwab

Publications and source records attributed to C Schwab.

At least 55 records · Page 3Linked to original sources
PubMed1996

Distinct distribution of apolipoprotein E and beta-amyloid immunoreactivity in the hippocampus of Parkinson dementia complex of Guam.

The distribution of apolipoprotein E (ApoE) was studied in the brain tissue of cases of the amyotrophic lateral sclerosis-parkinsonism-dementia complex of Guam, locally known as lytico bodig disease (LB), and compared with cases of Alzheimer's disease (AD) and normal brain tissue. In both LB and AD, strong ApoE immunostaining was observed in association with pathological lesions. In LB, these were mainly extracellular neurofibrillary tangles (eNFTs) which were intensely immuno-positive for ApoE. Occasional diffuse beta-amyloid protein (beta AP) deposits appear in this disorder and they were moderately immunopositive. In AD, senile plaques and diffuse beta AP deposits were intensely immunopositive, while eNFTs were only moderately immunopositive. The reason for the strong association of ApoE with the pathological entities in LB and AD is unknown, but may be related to a scavenger function which does not involve lipid metabolism. In both LB and AD, subpial and layer I diffuse deposits were ApoE negative but beta AP positive. Intracellular NFTs were mostly ApoE negative. A few showed weak positive staining. These data suggest that ApoE appears in LB and AD pathological lesions only after they are well established. In all controls, as well as all LB and AD cases, strong ApoE immunoreactivity was observed in unidentifiable structures in capillaries. Weak staining in a few neurons and very weak staining of an occasional astrocyte was observed. The source of ApoE which is deposited on extracellular pathological structures in LB and AD is unknown.

Adult↗
PubMed1995

Relationship of amyloid beta/A4 protein to the neurofibrillary tangles in Guamanian parkinsonism-dementia.

The Chamorro population of the island of Guam is highly susceptible to a disease called lytico-bodig (LB), which clinically resembles a mixture of amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD) and Alzheimer disease (AD). The disease is characterized by the widespread development of neurofibrillary tangles in the central nervous system. These tangles have an immunohistochemical profile indistinguishable from that seen in AD. We studied by immunohistochemistry the occurrence of intracellular and extracellular neurofibrillary tangles in LB in the entorhinal cortex, hippocampus and substantia nigra using antibodies to tau protein and ubiquitin. We also studied the relationship of these tangles to amyloid precursor protein (APP) and its beta-amyloid fragment (BAP), using multiple antibodies to BAP and other APP sequences. In advanced cases of LB, the development of neurofibrillary tangles was far more severe than in advanced cases of AD. Virtually all neurons of CA-1 and the subiculum were lost and only ghost tangles remained. In areas dominated by such extracellular tangles, BAP deposits were frequently observed developing around the fibers of ghost tangles. In some cases, the deposits covered only a few of the fibers, but in others, they seemed to envelope the complete tangle. The deposits were thioflavin S and Congo red positive, indicating that the BAP was in a consolidated form. We describe these entities as "tangle-associated amyloid deposits". Such BAP deposits have previously been described in some cases of AD, dementia pugilistica and LB. However, we found them in all cases of LB with dementia in the hippocampal-entorhinal areas and in most cases in the substantia nigra. They do not evolve from diffuse BAP deposits since they are remote from them, and they do not trap dystrophic neurites. The fact that extracellular tangle material can act as a nidus for BAP build-up in LB suggests that further consideration needs to be given to the ways in which extracellular BAP deposits are formed.

Adult↗
PubMed1994

Genuine and apparent cross-reaction of polyclonal antibodies to proteins and peptides.

Antiserum to a native protein may cross-react with the corresponding denatured protein or with peptides. The cross-reaction is either a genuine property of the antibodies or caused by antibodies produced against some unfolded protein contaminating the native protein used for immunization. Appropriate conformation-sensitive immunoassays must be employed to distinguish a genuine from an apparent cross-reaction. In the present study, we have analyzed critically the cross-reaction of rabbit antisera against proteins and peptides. We have distinguished between genuine and apparent cross-reaction with the help of the protein A antibody-capture ELISA, a new conformation-sensitive ELISA format. Three systems were analyzed: cross-reaction of antisera to native yeast and horse cytochrome c with unfolded apo-cytochrome c; cross-reaction of antisera to a coiled-coil leucine-zipper peptide with a homologous random-coil peptide obtained by introducing two proline residues into the leucine-zipper sequence; cross-reaction of antisera to two peptides that correspond to the N-terminal and an internal sequence of ferredoxin: NADP+ reductase (FNR), with the native enzyme. The reaction of the anti-(cytochrome c) sera was clearly due to antibodies produced against unfolded protein, it was an apparent and not a genuine cross-reaction. Furthermore, the apparently cross-reactive antibodies to horse cytochrome c did not discriminate against sequence-related proteins from dog, beef, rabbit and pigeon. In contrast, antibodies to the leucine-zipper peptide did cross-react in a genuine way with the homologous random-coil peptide, that is, the cross-reactive antibodies do not seem to have been produced against the unfolded form of the leucine-zipper peptide. Of the two anti-peptide sera the one against the unstructured and highly accessible N-terminal segment reacted strongly with the native protein. The second serum against a solvent-accessible turn-like sequence of FNR showed apparent cross-reactivity: antibodies recognizing the native protein were directed against a minor conformational isoform of the free peptide and did not react with the principal form(s) of the free peptide. The generation of cross-reactive antibodies depends on the conformational stability and integrity of the immunogen and on the molecular form of its application, i.e., free, polymerized or carrier-bound. The results clarify the different nature of cross-reactivity of antisera to proteins and peptides. This knowledge is crucial if antisera are to be used as conformation-specific probes.

Amino Acid Sequence↗
PubMed1994

Postmortem changes in the levels and localization of microtubule-associated proteins (tau, MAP2 and MAP1B) in the rat and human hippocampus.

The neuronal cytoskeleton is disrupted in neurodegenerative disorders such as Alzheimer's disease. Due to the lack of suitable animal models, studies examining the events involved in the neurodegeneration have relied on postmortem human brain tissue obtained from individuals with the disease and from normal controls. However, it is uncertain if the neuronal cytoskeleton is stable during the postmortem interval. Immunohistochemistry and immunoblots were used to examine the microtubule-associated proteins tau, MAP2, and MAP1B in the rat hippocampus at various times after death. Shortly after death, tau immunoreactivity was lost from axons and accumulated in somatodendritic compartments. MAP2 and MAP1B also accumulated in neuronal cell bodies prior to a loss of immunostaining in some regions, notably subiculum. Immunoblots confirmed a loss of MAP2 and MAP1B within a few hours after death. Tau levels remained constant during the 8-hour postmortem interval examined, although the electrophoretic mobility of some tau bands was altered. Human brain tissue obtained at autopsy and at surgery demonstrated similar cytoskeletal alterations in postmortem tissue. These results demonstrate that microtubules and associated proteins are not stable postmortem.

Adolescent↗
PubMed1994

Alterations in tau immunostaining in the rat hippocampus following transient cerebral ischemia.

Previous studies in gerbils have shown that cytoskeletal disruption and a loss of the dendritic microtubule-associated protein, MAP2, may occur after short periods of transient global ischemia. tau, a predominantly axonal microtubule-associated protein, has not been examined following ischemia. We compared neuronal damage with alterations in MAP2, tau, and 72-kD heat shock protein (HSP72) immunostaining at various reperfusion times following 20 min of ischemia in the rat four-vessel occlusion model. tau accumulated in neuronal cell bodies throughout the hippocampal formation 30 min to 2 h after the ischemic insult. Perikaryal tau immunostaining was transient in most regions, but persisted in polymorphic hilar neurons. This was accompanied by a loss of immunostaining in the target of many hilar neurons, the inner molecular layer of the dentate gyrus. The same neuronal populations that exhibited increased tau immunostaining of perikarya later displayed an induction of HSP72 immunoreactivity. In contrast, loss of MAP2 immunostaining was not consistently observed before neuronal death and did not correspond to HSP72 induction. The altered tau immunostaining is not the direct result of excitotoxic insult, as intrahippocampal injection of kainic acid did not cause the somal accumulation of tau, but did cause disruption of MAP2 immunostaining. Taken together, the results suggest that the somal accumulation of tau is an early, sensitive, and selective marker of ischemic insult.

Animals↗
PubMed1993

Mapping antibody binding sites on cytochrome c with synthetic peptides: are results representative of the antigenic structure of proteins?

Crystallographic work on antigen-antibody complexes has revealed that extensive surface areas of proteins may interact with antibodies. On the other hand, most experimental approaches to locate and define antigenic determinants of protein antigens rely on the linear sequence of the polypeptide chain. Hence the question arises whether mapping of antibody binding sites by analysis of the reactivity of anti-protein antibodies with synthetic peptides can provide a representative picture of the antigenic structure of a protein antigen. We have addressed this question using yeast iso-1 cytochrome c as a protein antigen against which antisera were raised in rabbits. The reaction of the antisera with 103 synthetic hexapeptides covering the entire sequence of cytochrome c was tested by the pepscan procedure in which peptides are coupled to polyethylene rods and tested by ELISA. For the assay, anti-cytochrome c antibodies were fractionated by affinity chromatography on native yeast iso-1 cytochrome c and on apo-cytochrome c; the latter is a random coil. It was found that only antibodies retained by the apo-cytochrome c affinity column react with synthetic peptides. These antibodies comprise a small fraction, probably less than 2%, of all cytochrome c-specific antibodies. The majority of antigenic determinants, which seem to consist of strongly conformation-dependent topographic epitopes, could not be uncovered by the peptide approach. Epitope mapping with short peptides seems of limited usefulness in the case of small, globular, and conformationally stable proteins like cytochrome c.

Antibodies↗
PubMed1992

Caveats for the use of surface-adsorbed protein antigen to test the specificity of antibodies.

Rabbit antisera against apo-cytochrome c, which was prepared by removal of the covalently bound heme prosthetic group from yeast iso-1 cytochrome c, were tested for reactivity against native yeast iso-1-cytochrome c. When the antigen was adsorbed to a microtiter plate in a conventional enzyme-linked immunosorbent assay (ELISA), the antisera were unable to distinguish between their cognate antigen apo-cytochrome c, a random coil protein, and native cytochrome c, a small globular protein of remarkable conformational stability in solution. However, when the assay was conducted under conditions where antigen and antibody were free to associate in solution, that is in a solution-phase radioimmunoassay (RIA), the antisera were highly specific for apo-cytochrome c. Similarly, antibodies induced by native cytochrome c and discriminating strongly between native and apo-cytochrome c in a solution-phase RIA, did not distinguish between native and apo-cytochrome c in a solid-phase ELISA. This discrepancy of results obtained by different immuno assay procedures clearly indicates that adsorption to plastic alters the antigenic structure of even a conformationally stable protein such as cytochrome c. A conventional solid-phase ELISA strongly selects for those antibodies that recognize the unfolded antigen. The results presented warrant serious thoughts about previous reports on anti-peptide antibodies reacting with native whole protein molecules, as tested by those ELISA procedures that have the protein antigen adsorbed to plastic.

Adsorption↗
PubMed1992

Autoradiography of muscarinic cholinergic receptors in cortical and subcortical brain regions of C57BL/6 and DBA/2 mice.

Mice of the inbred strains C57BL/6 and DBA/2 show strain-dependent behavioural differences which have been correlated with variations in brain cholinergic systems. In the present study, the density of muscarinic cholinergic receptors in both strains of mice was determined by autoradiographic methods using [3H]quinuclidinyl benzilate (QNB) and [3H]pirenzepine as ligands. C57BL/6 mice showed a significantly lower [3H]QNB binding level in the frontal cortex by one third as compared to DBA/2 mice. In the striatum and the cholinergic pontomesencephalic nucleus laterodorsalis tegmenti the [3H]QNB binding was lower in C57BL/6 by 28% and 31%, respectively. The [3H]pirenzepine binding level was found to be significantly higher in C57BL/6 temporal cortex (by 22%). These results are discussed in relation to interstrain differences in cholinergic cell density and in the activity of cholinergic enzymes.

Animals↗
PubMed1992

Competencies of novice nurse educators.

Appropriate preparation for the nurse faculty role has been debated for many years. Currently, the master of science in nursing (MSN) is considered to be the minimal acceptable preparation. The focus of most MSN programs, however, is advanced knowledge and skill in clinical nursing. The purpose of this study is to identify the perceptions of novice nurse faculty concerning nurse faculty competencies, to ascertain the extent to which novice nurse faculty demonstrate the competencies, and to determine mechanisms through which competencies are obtained. The findings indicate that many novice nurse faculty are not educationally prepared for the faculty role.

Attitude↗
PubMed1992

Parvalbumin and calbindin immunoreactivity in the rat brain: a double-immunolabelling method.

Parvalbumin and calbindin, two calcium binding proteins in the nervous system, are present in certain neuronal subpopulations. In the present study a method for a simultaneous demonstration of the both antigens was developed, which labels parvalbumin- and calbindin-containing structures in contrasting colours. A horseradish peroxidase-conjugated second antibody was used for the visualization of the monoclonal anticalbindin antibody, whereas the biotinylated anti-parvalbumin antibody was demonstrated by means of a biotin-streptavidine-alkaline phosphatase system. The method may be useful to classify neuronal populations and to study their morphological relationship.

Animals↗
PubMed1991

Epitope mapping employing immobilized synthetic peptides. How specific is the reactivity of these peptides with antiserum raised against the parent protein?

Peptides synthesized onto polyethylene pins can be directly used to map the antigenic structure of proteins by ELISA (Geysen et al., 1987, J. Immunol. Methods 102, 259-274). The specificity of the reaction between anti-cytochrome c antibodies (IgG) and pin-bound hexapeptides of cytochrome c was tested using a competitive ELISA in which free and pin-bound peptides competed for the antibody. Competition was specific for many of the pin-bound peptides: only free peptides having the same sequence as the pin-bound peptides were able to compete for antibody-binding. However, non-specific reactivity was observed with pin-bound peptides whose sequence corresponded to the N terminal segment of cytochrome c. This segment is predicted to be particularly antigenic because of its high mobility and the nature of its amino acid sequence. In one case no competition by the free peptide could be observed even though the pin-bound peptide reacted strongly with anti-cytochrome c antibodies.

Animals↗
PubMed1991

Histology and transmission electron microscopy of the cornea in xeroderma pigmentosum type C.

Xeroderma pigmentosum is a very rare precancerous skin disease that is triggered by sunlight. It is caused by a defect in the DNA repair system and causes benign and malignant transformations. Only eye tissues that come into contact with UV light are affected, such as the lids, conjunctiva and cornea. We describe a patient who suffered from xeroderma pigmentosum type C, showing the typical skin alterations but no sign of malignancy. A perforating keratoplasty was performed on both eyes because of the dense opacity of the corneas. The corneal buttons obtained were examined by light and transmission electron microscopy. Degeneration was found only in the basal-cell layer of the corneal epithelium. The most severe morphological changes were seen in Bowman's layer, the subepithelial stroma, Descemet's membrane and the corneal epithelium. Bowman's layer was often interrupted or replaced by a degenerative pannus, which extended into the underlaying stroma. Subepithelial "channels" were localized in the basal epithelium and protruded into the subepithelial stroma. In both corneas, Descemet's membrane contained different amounts of so-called lattice collagen, and the remaining endothelial cells in the left cornea contained numerous melanin granules.

Adult↗