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Biomedical subjects

J N Whitaker

Publications and source records attributed to J N Whitaker.

At least 127 records · Page 7Linked to original sources
PubMed1986

Multiple epitopes in a dodecapeptide of myelin basic protein determined by monoclonal antibodies.

Three custom synthesized myelin basic protein (MBP) peptides, bovine peptide 79-88, human peptide 80-89, and human peptide 82-91, were used to produce four murine monoclonal antibodies (MAb) that were selected on the basis of reaction in a solid phase radioimmunoassay (SRIA) with human MBP. The MAb were compared with respect to antigen specificity against intact MBP and 10 overlapping MBP peptides. One MAb recognized an epitope near the amino-terminus of bovine MBP peptide 79-88. A second MAb was directed towards an epitope that is more reactive in human MBP peptide 45-89 than in intact MBP, but is not recognized in any of the small MBP peptides examined. The third MAb detected an epitope near the middle of human MBP peptide 80-89, whereas the fourth MAb reacted with the carboxyl-terminal portion of human MBP peptide 82-91. Epitopes recognized in SRIA were sometimes not detected by the same MAb in a fluid phase double antibody radioimmunoassay. These results demonstrate the multiplicity of potential epitopes in a dodecapeptide of MBP and do not support the concept of a single, dominant epitope in the region of MBP peptide 80-89.

Amino Acid Sequence↗
PubMed1986

Epitopes of immunoreactive myelin basic protein in human cerebrospinal fluid.

To define in more detail the features of the immunoreactive myelin basic protein (MBP) present in cerebrospinal fluid (CSF) of humans following acute injury to central nervous system myelin, the epitopes of MBP recognized by three different antisera, each capable of detecting immunoreactive MBP in CSF, were examined. All three antisera reacted well with human MBP and human MBP peptide 45-89. Only in radioimmunoassays in which the MBP peptide 45-89 served as the radioligand could clearly elevated values of immunoreactive MBP be measured in CSF specimens from 5 patients with multiple sclerosis during or immediately after an exacerbation. The two antisera that reacted well with MBP peptide 80-89 resulted in higher levels of immunoreactive MBP measured in CSF. An epitope present in human MBP peptide 80-89 but sharing a conformation with both MBP and MBP peptide 45-89 is present in CSF following acute central nervous system myelin damage in multiple sclerosis.

Cross Reactions↗
PubMed1986

Isolation and characterization of cathepsin B from bovine brain.

Cathepsin B (EC 3.4.22.1) was purified 746-fold with a 21% recovery from bovine brain by autolysis, fractional precipitation with acetone, carboxy-methyl-Sephadex chromatography, affinity chromatography on a cystamine containing column and gel filtration chromatography. The purified cathepsin B eluted on gel filtration with an apparent molecular weight of 27,000 but was resolved into three bands of 30,000, 25,000 and 5,000 molecular weight by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE). Antibodies to cathepsin B, raised against the 30,000 dalton band, were shown by immunoblots to react with both the 30,000 and 25,000 dalton proteins with results suggesting that the former predominated as the immunoreactive form in bovine brain homogenates. Isoelectric focusing demonstrated multiple bands, ranging from pH 4.75-5.2 with the major band at pH 5.1-5.2, all of which were capable of degrading N alpha-carbobenzoxy-L-arginyl-L-arginine 4-methoxy-beta-naphthylamide. The cathepsin B activity against N alpha-benzoyl-DL-arginine beta-naphthylamide (BANA) and bovine myelin basic protein (MBP) had a pH optimum of pH 6.0. The Km for the degradation of BANA was 1.0 mM and 5.1 mM when assayed in the presence of 1% and 2.5% dimethylsulfoxide, respectively. Cathepsin B from bovine brain has many properties similar to cathepsin B isolated from other organs. The degradative effect of cathepsin B on MBP suggests a role for this proteinase in inflammatory demyelination.

Animals↗
PubMed1986

Analysis of the primary sequence of human myelin basic protein peptides 1-44 and 90-170 by fast atom bombardment mass spectrometry.

The originally described sequence of human myelin basic protein peptide 45-89 has recently been shown to contain two errors which have now been resolved. In the present study fast atom bombardment mass spectrometry was utilized to analyze the primary sequence of the other portions, peptides 1-44 and 90-170 of human myelin basic protein. The results obtained confirm the accuracy of the primary sequence published for both of these terminal peptides.

Amino Acid Sequence↗
PubMed1985

Hormonal and drug effects on the degradation of human myelin basic protein peptide 43-88 by alkaline proteolytic activity in the rat kidney.

The microsomal brush-border fraction of rat renal tissue contains enzymatic activity, optimally active at pH 9, that is capable of degrading human myelin basic protein (BP) peptide 43-88. In the present study, this degradation and the effect on it of selected drugs and hormones were examined further. Of the substances tested, 10(-2) M chloroquine and 10(-5) M ACTH 1-24 were found to be the most effective inhibitors followed by 10(-5) M ACTH 1-39; parathormone, glucagon and insulin were found to be inhibitors an order of magnitude weaker than ACTH 1-24. Hydrocortisone, dexamethasone, maleic acid and ACTH 4-10 were found to have minimal or no inhibitory effect on the peptide degrading activity. Gel filtration of the degradation products indicated that the rate of degradation of BP peptide 43-88 at pH 9 had been retarded by ACTH 1-24. These studies indicate that the clearance and catabolism of this peptide may be altered by available therapeutic agents.

Adrenocorticotropic Hormone↗
PubMed1985

Polyneuropathy and IgM monoclonal gammopathy: studies on the pathogenetic role of anti-myelin-associated glycoprotein antibody.

Attention has recently been directed toward patients having a polyneuropathy and a monoclonal IgM anti-myelin-associated glycoprotein (anti-MAG) antibody. The possibility of a pathogenetic role for the anti-MAG antibody in the evolution of the polyneuropathy and in the development of central nervous system signs, including tremor and ataxia, remains unresolved. In 5 patients with this syndrome whose clinical courses were followed closely, in 1 of whom a complete postmortem examination of the nervous system was performed, we made the following observations: the anti-MAG antibody did not localize to the compact layer of the myelin sheath in affected nerves, but did localize to areas of myelin splitting; anti-MAG antibody present in the sural nerve of an affected individual for 7 years was not associated with progressive pathology; anti-MAG antibody was not deposited in the central nervous system of an affected individual, although the antibody did bind to these same tissues in vitro; deposition of anti-MAG antibody observed at postmortem examination did not correlate with the degree of pathological change; and study of the peripheral nervous system favored a primary axonal neuropathy with secondary demyelination.

Adult↗
PubMed1985

A derivative of myelin-associated glycoprotein in cerebrospinal fluid of normal subjects and patients with neurological disease.

A procedure for quantitating the myelin-associated glycoprotein (MAG) in cerebrospinal fluid (CSF) was developed. The procedure involved immunoprecipitation with rabbit polyclonal anti-MAG antiserum followed by immune staining of electroblots with the monoclonal antibody HNK-1. This method could detect as little as 2 ng of MAG per ml of CSF and could accurately measure levels of 5 ng/ml or greater. No intact MAG was detected in any of the CSF samples examined, but all samples contained the 90K dalton proteolytic derivative of MAG called dMAG. Samples from normal volunteers and patients with demyelinating diseases contained levels of dMAG ranging from 2 to 13 ng/ml. There was no correlation of dMAG levels with levels of myelin basic protein or with active demyelinating disease. The relatively high levels of dMAG, even in control CSF samples, probably resulted from normal physiological turnover of MAG and could possibly obscure any additional increments of MAG or dMAG release that might occur as a result of demyelination.

Demyelinating Diseases↗
PubMed1985

Plasma exchange and prednisone in acute inflammatory polyradiculoneuropathy: a controlled randomized trial.

A controlled-randomized trial of plasma exchange combined with prednisone was compared to supportive care alone in patients with acute inflammatory polyradiculoneuropathy (AIP). The design of this study differs from other reported trials of plasma exchange in AIP because prednisone was used in the treatment group to prevent the possibility of antibody rebound. Furthermore, in this study, detailed muscle strength testing formed the principal basis for assessment of therapeutic efficacy while in the British, North American, and French studies, a functional assessment scale was used. Analysis of our data revealed no significant improvement in the treated group over the controls. The sample size, albeit small (12 treated and 13 controls), had the power (95% chance) to detect a change of two British Medical Research Council grades of strength between the groups. The difference in our results versus others (North American and French studies) probably reflects the adverse effects of prednisone on recovery in AIP. An additional consideration is that plasma exchange may have an overall modest effect on the course of AIP, less appreciated when individual muscles are tested compared to assessment by large functional categories.

Acute Disease↗
PubMed1985

Rat neural tissue cathepsin D: ultrastructural immunocytochemistry.

The cellular and subcellular localization of cathepsin D, an aspartyl endopeptidase, was investigated in the central and peripheral nervous systems of the rat by light and electron microscopic immunocytochemistry. The reaction of rabbit anti-rat brain cathepsin D within ventral cervical spinal cord, cerebellum, corpus callosum, caudate nucleus, optic nerve, trigeminal ganglion, fifth cranial nerve and sciatic nerve was localized with an indirect immunoperoxidase technique. A number of tissue processing methods were utilized, but only in tissues fixed in paraformaldehyde-lysine-periodate and sectioned at thicknesses of 25-50 micron could antibody penetration, enzyme protein immunoreactivity and intact morphology be reliably attained. Immunoreactive cathepsin D was present in lysosomes and pleomorphic dense bodies of neurons in the anterior horn of spinal cord, cerebellar Purkinje and granule cell layers, caudate nucleus and trigeminal ganglion. Lysosomal localization of cathepsin D was also documented in oligodendrocytes, astrocytes, endothelial cells and Schwann cells. Reaction product was not observed in microglia although its presence there would be expected. With these methods, reaction product was not detected in the Golgi saccules of any cell type.

Aging↗
PubMed1985

Plasma exchange and prednisone in Guillain-Barré syndrome: a controlled randomized trial.

A controlled randomized trial of plasma exchange combined with prednisone was compared with supportive care alone in patients with Guillain-Barré syndrome (GBS). There was no significant improvement in the treated group over the controls. The sample size, albeit small (12 treated and 13 controls), had the power (95% chance) to detect a change of 2 British Medical Research Council grades of strength between the groups. The difference in our results and others that indicated a beneficial effect of plasma exchange may reflect an adverse effect of prednisone on recovery in GBS. Failure to find a benefit of plasma exchange in our patients also raises the possibility that GBS may be a heterogeneous disorder with humoral factors playing a role in some but not all patients.

Adolescent↗
PubMed1985

[Myelin basic protein in cerebrospinal fluid in neurocysticercosis].

Cerebrospinal fluid (CSF) from 115 patients with several neurological disorders were tested for the presence of myelin basic protein (MBP), fragment P1 43-88. Cases were divided into groups according to neurological diagnosis. The control group (50 patients with chronic headache) presented normal CSF composition and presented no evidence of the presence of MBP. MBP was found in: four cases of the 44 of neurocysticercosis; three of the 8 cases of multiple sclerosis; one case of schistosomiasis with spinal cord involvement. Neuroimmunological data are discussed considering results found in this investigation.

Central Nervous System Diseases↗
PubMed1985

Cellular distribution of cathepsin D in childhood tumors.

Cathepsin D is an acidic endopeptidase that has been found in the cytoplasm of neurons and other cells. To test the hypothesis that the cellular content or distribution of cathepsin D may serve as a marker of neuronal differentiation in childhood neoplasia, we performed an immunocytochemical study of the cathepsin D content of tumors that occurred in 49 pediatric patients. We found diffuse, moderate to heavy staining primarily in differentiating neurogenous tumors and minimal staining in one Wilms' tumor, one Ewing's sarcoma, and one rhabdomyosarcoma. Benign reactive histiocytes stained intensely in most tumors. We concluded that although the presence of cathepsin D in malignant cells is not diagnostic of neural tumors, it may serve as a marker for cellular maturation in neuroblastomas and as a marker of macrophage infiltration in human tumors.

Adolescent↗
PubMed1984

Amino acid sequence of human myelin basic protein peptide 45-89 as determined by mass spectrometry.

In order to resolve the uncertainties about the primary structure of human myelin basic protein at residues 45-89, the sequence of this peptide and its tryptic fragments were reinvestigated by fast atom bombardment mass spectrometry. The sequence at positions 77-78 was found to be His-Gly and the sequence at positions 83-84 was shown to be Glu-Asn. The Ser at position 56 was not phosphorylated, whereas the residue at position 46 or 47 showed a heterogeneity of Gly and Ser in this peptide fragment in one of two protein preparations from different patients. These results demonstrate the usefulness of fast atom bombardment mass spectrometry for primary structure information. The corrected sequence of human basic protein peptide 45-89 will permit a more detailed immunochemical analysis of this peptide and its in vivo degradation products.

Amino Acid Sequence↗