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J C Morris

Publications and source records attributed to J C Morris.

At least 181 records · Page 10Linked to original sources
PubMed1995

No association found between Alzheimer's disease and a mitochondrial tRNA glutamine gene variant.

We have screened a large sample of patients with sporadic late-onset dementia of the Alzheimer type (DAT) and age-matched controls for a mitochondrial tRNA(Gln) variant previously reported to be associated with increased risk of developing Alzheimer's disease (AD). The frequency of an Ava II site gain was determined by restriction analysis of a PCR-amplified mitochondrial DNA product. One of 155 DAT cases and four of 105 age-matched controls carried the variant. Both the affected and control frequencies are statistically different from those previously reported. The mitochondrial lineage of those individuals harboring the variant was determined by sequencing a short region of the hypervariable mitochondrial D-loop. The affected individual and three of the four controls carrying the Ava II variant belong to the same mitochondrial lineage previously reported to be associated with AD.

Aged↗
PubMed1995

WT1-mediated transcriptional activation is inhibited by dominant negative mutant proteins.

The WT1 tumor suppressor gene encodes four isoforms of a zinc finger transcription factor with both activation and repression functions which are dependent upon promoter architecture. Using a simple HSV-tk promoter containing 5'-Egr-1/WT1-binding sites, we found that WT1 isoforms (A) and (B) strongly activated transcription. WT1(A) and (B) bound equally well to the Egr-1/WT1-binding site, but WT1(B), which contains a 17 amino acid insertion compared to WT1(A), was a consistently stronger activator of transcription than WT1(A). Transcriptional activation by wild-type WT1 was inhibited by coexpression of WT(PM) or WT(AR), genetically defined dominant negative alleles of WT1. In vitro, as well as in the yeast two-hybrid system, WT1 protein associated with itself and with dominant negative mutant proteins. The major domain required for self-association and inhibition of transcriptional activation mapped to the first 182 amino acids of WT1. Dominant negative WT1 alleles may play a role in tumorigenesis by associating with wild-type WT1 proteins and decreasing their transcriptional activity.

Animals↗
PubMed1995

Glycan requirements of glycosylphosphatidylinositol phospholipase C from Trypanosoma brucei. Glucosaminylinositol derivatives inhibit phosphatidylinositol phospholipase C.

Glycosylphosphatidylinositol phospholipase C (GPI-PLC) from Trypanosoma brucei and phosphatidylinositol phospholipase C (PI-PLC) from Bacillus sp. both cleave glycosylphosphatidylinositols (GPIs). However, phosphatidylinositol, which is efficiently cleaved by PI-PLC, is a very poor substrate for GPI-PLC. We examined GPI-PLC substrate requirements using glycoinositol analogs of GPI components as potential inhibitors. Glucosaminyl (alpha 1-->6)-D-myo-inositol (GlcN(alpha 1-->6)Ins), GlcN(alpha 1-->6)Ins 1,2-cyclic phosphate, GlcN(alpha 1-->6)-2-deoxy-Ins, and GlcN(alpha 1-->6)Ins 1-dodecyl phosphonate inhibited GPI-PLC. GlcN(alpha 1-->6)Ins was as effective as Man-(alpha 1-->4)GlcN(alpha 1-->6)Ins; we surmise that GlcN(alpha 1-->6)Ins is the crucial glycan motif for GPI-PLC recognition. Inhibition by GlcN(alpha 1-->6)Ins 1,2-cyclic phosphate suggests product inhibition since GPIs cleaved by GPI-PLC possess a GlcN(alpha 1-->6)Ins 1,2-cyclic phosphate at the terminus of the residual glycan. The effectiveness of GlcN(alpha 1-->6)-2-deoxy-Ins indicates that the D-myo-inositol (Ins) 2-hydroxyl is not required for substrate recognition, although it is probably essential for catalysis. GlcN(alpha 1-->6)-2-deoxy-L-myo-inositol, unlike GlcN(alpha 1-->6)-2- deoxy-Ins, had no effect on GPI-PLC; hence, GPI-PLC can distinguish between the two enantiomers of Ins. Surprisingly, GlcN(alpha 1-->6)Ins 1,2-cyclic phosphate was not a potent inhibitor of Bacillus cereus PI-PLC, and GlcN(alpha 1-->6)Ins had no effect on the enzyme. However, both GlcN(alpha 1-->6)Ins 1-phosphate and GlcN(alpha 1-->6)Ins 1-dodecyl phosphonate were competitive inhibitors of PI-PLC. These observations suggest an important role for a phosphoryl group at the Ins 1-position in PI-PLC recognition of GPIs. Other studies indicate that abstraction of a proton from the Ins 2-hydroxyl is not an early event in PI-PLC cleavage of GPIs. Furthermore, both GlcN(alpha 1-->6)-2-deoxy-Ins 1-phosphate and GlcN(alpha 1-->6)-2-deoxy-L- myo-inositol inhibited PI-PLC without affecting GPI-PLC. Last, the aminoglycoside G418 stimulated PI-PLC, but had no effect on GPI-PLC. Thus, these enzymes represent mechanistic subclasses of GPI phospholipases C, distinguishable by their sensitivity to GlcN(alpha 1-->6)Ins derivatives and aminoglycosides. Possible allosteric regulation of PI-PLC by GlcN(alpha 1-->6)Ins analogs is discussed.

Animals↗
PubMed1995

Auditory dysfunction in aging and senile dementia of the Alzheimer's type.

OBJECTIVE: To determine the prevalence and type of auditory dysfunction in older volunteer subjects with mild probable Alzheimer's disease (pAD). METHODS: Pure-tone thresholds, word recognition in quiet, Synthetic Sentence Identification with Ipsilateral Competing Message or Contralateral Competing Message, distortion-product otoacoustic emissions, and auditory brain-stem responses were done in 82 elderly volunteer subjects whose cognitive, psychologic, and neurologic status had been determined through annual testing in a research center. Based on clinical criteria and the Clinical Dementia Rating (CDR) scale, 40 subjects had been judged to be nondemented (CDR score, 0), and 42 had a clinical diagnosis of pAD, with 22 in the questionable (CDR score, 0.5) and 20 in the mild (CDR score, 1) categories. RESULTS: The mean age-adjusted pure-tone average thresholds (0.5, 1.0, and 2.0 kHz) were poorer in the subjects with pAD by 5.1 dB in the right ears and 6.1 dB in the left ears; these differences were not statistically significant. Word recognition in quiet did not differ by CDR category. The age-adjusted scores on the Synthetic Sentence Identification with Ipsilateral Competing Message or Contralateral Competing Message were significantly reduced in the subjects with mild pAD. Distortion-product otoacoustic emission amplitudes and auditory brain-stem response thresholds and latencies paralleled the pure-tone threshold results and did not differ across the CDR groups. CONCLUSIONS: Central auditory dysfunction was evident in subjects with even mild cases of pAD, whereas peripheral auditory function was not different from that in age-matched control subjects. Additional research is needed to delineate the mechanisms of central auditory dysfunction and to establish the sensitivity and specificity of auditory testing in subjects with Alzheimer's disease. We recommend auditory assessment, including Synthetic Sentence Identification with Ipsilateral Competing Message or Contralateral Competing Message, for older patients in general and in particular for those in whom dementia is suspected.

Aged↗
PubMed1995

Thyrotropin receptor T cell epitopes in autoimmune thyroid disease.

The human TSH receptor represents the primary target of thyroid-stimulating immunoglobulins responsible for the hyperthyroidism of Graves' disease. In the present series of investigations, the distribution of T cell epitopes has been mapped using synthetic peptides spanning the entire extracellular region of the human TSH receptor. In vitro proliferative responses of the mononuclear cells were measured using flow cytometric analysis of bromodeoxyuridine incorporation into nuclei. In 8 of 11 samples from patients with Graves' disease, at least one (and up to 9) regions of the human TSH receptor induced proliferation, with the mean stimulation index being 39.8 +/- 47.3. No single universal stimulatory peptide was identified. In contrast, stimulation was not observed in three control subjects, while one control subject showed minimal stimulation (index of 5.7) to peptides encompassing a limited area (amino acids 31-65). The immunodominant epitope of patients with recent-onset Graves' disease was localized between amino acids 271 and 365, whereas the immunodominant epitope of patients with disease duration greater than 1 year localized between amino acids 91 and 215. We conclude that the bromodeoxyuridine incorporation method is a useful and important tool for detecting antigen-induced lymphocyte proliferation. The TSH receptor-specific T cells from different Graves' disease patients recognize variable distinct sites within the extracellular region of the TSH receptor, and the immunodominant epitope apparently shifts toward the N-terminus of the receptor protein during the course of treated Graves' disease.

Bromodeoxyuridine↗
PubMed1995

TSH receptor sequences recognized by CD4+ T cells in Graves' disease patients and healthy controls.

Twenty-nine overlapping synthetic peptides, twenty residues long, representing the entire extracellular sequence of the human thyroid stimulating hormone receptor (hTSHr), were used to test the epitope repertoire of CD4+ T lymphocytes from patients with Graves' disease and from healthy subjects. The peptides were used to propagate and test short term CD4+ T cell lines specific for hTSHr epitopes, and to directly test CD8+ depleted, CD4+ enriched peripheral blood lymphocytes. Analysis of the response of short-term CD4+ T cells lines and CD8+ depleted peripheral blood lymphocytes to the individual peptides revealed that 14 of the 15 patients and nine of the ten controls responded to at least one hTSHr peptide. There was no common response pattern, nor any region of the hTSHr sequence that was predominantly recognized. Several peptides were recognized by both patients and controls. These results support the notion that immunological tolerance to hTSHr is due to peripheral tolerance of potentially autoreactive CD4+ T cells, not their clonal deletion. The presence of self-reactive, hTSHr-specific CD4+ T cells in healthy individuals implies that these cells are not permanently anergized, since they can be activated in vitro.

Adult↗
PubMed1995

Reduced expression of a naturally deleted form of human proopiomelanocortin complementary deoxyribonucleic acid after transfection into Chinese hamster ovary cells.

POMC is the precursor molecule for a number of hormones, ACTH, MSH, and beta-endorphin. The human genomic sequence has been elucidated, but to date the complete human complementary DNA (cDNA) sequence has not been published. Here we report the cloning and expression of human POMC cDNA from the anterior pituitary gland. Two forms of POMC cDNA have been identified; one sequence agrees with the cDNA sequence predicted from the published genomic sequence, and the second is a variant with a 9-base pair deletion (corresponding to the loss of three amino acids, Ser-Ser-Gly, between residues 67-73). Both POMC cDNA sequences have been expressed in Chinese hamster ovary cells. A significant difference was observed between the levels of expression in the cells and the amount secreted into the media of the two protein precursor molecules. The expression of the deleted variant in the cells was 16.4 +/- 0.9% of the level of normal POMC (P < 0.001), and in the media the deleted variant was 22.4 +/- 2.2% of the level of normal POMC (P < 0.001).

Amino Acid Sequence↗
PubMed1995

Defining the major antibody epitopes on the human thyrotropin receptor in immunized mice: evidence for intramolecular epitope spreading.

To evaluate the B cell response to the extracellular domain of the human TSH receptor (hTSHR-ecd), we used recombinant hTSHR-ecd to immunize BALB/c mice (group A) and CBA/J mice (groups B and C). Mice from groups A and B were boosted once, and mice from group C received three antigen boosts. All individual mice developed highly specific hTSHR-ecd antibodies (hTSHR-ecd-Ab), confirmed by Western blot analyses. The B cell epitopes recognized by these murine hTSHR-ecd-Ab were mapped by enzyme-linked immunoassays using 26 synthetic overlapping peptides spanning the entire mature hTSHR-ecd [amino acids (aa) 22-415], i.e. without the signal sequence. Although all BALB/c and CBA/J mice antisera recognized peptide 1 (aa 22-41), the hyperimmunized CBA/J mice (group C) demonstrated recognition of additional peptides (numbers 21-26) clustered toward the carboxyl-terminus of the hTSHR-ecd (aa 322-415). Furthermore, group C serum blocked the binding of [125I]bTSH to native porcine TSHR, whereas sera from groups A and B were inactive. We were also able to map the B cell epitopes of antisera from rabbits immunized repeatedly with hTSHR-ecd and found the same recognition pattern of peptide 1 and additional peptides clustered near the carboxyl-terminus of the hTSHR-ecd (aa 322-341 and 367-415). These rabbit antisera also inhibited the binding of [125I]bTSH to native porcine TSHR. These data provide a comprehensive B cell epitope-mapping study of induced hTSHR-ecd-Ab and demonstrate intramolecular spreading of the epitopes recognized. Although the N-terminal region was highly antigenic, repeated immunization induced hTSHR-ecd-Ab targeted to a region critical for TSH binding.

Animals↗
PubMed1995

Generation and characterization of monoclonal antibodies to the human thyrotropin (TSH) receptor: antibodies can bind to discrete conformational or linear epitopes and block TSH binding.

Splenocytes from female BALB/c mice immunized with a recombinant extracellular domain of the human TSH receptor (ETSHR) were used to generate a panel of 23 hybridomas that produce TSHR-specific monoclonal antibodies (mAbs). All mAbs were of the immunoglobulin G (IgG) isotype and belonged to different subclasses, including IgG1, IgG2a, and IgG2b. The antibodies bound to the ETSHR with relatively high affinity, and several of them blocked the binding of [125I]TSH to the TSHR, with some showing better blocking than others. Competitive binding studies with a subgroup of 4 biotinylated mAbs showed at least 3 different binding specificities. To determine the TSHR epitopes to which these mAbs were binding, we tested them against 37 overlapping synthetic peptides that span the entire ETSHR. mAb 47, which did not block TSH binding, bound to an epitope represented by amino acid residues 22-30. mAb 28, which had a TSH binding inhibitory index of 20%, bound to an epitope represented by amino acids 32-41. However, mAbs 37 and 49, with TSH binding inhibitory index values of 39% and 43%, respectively, showed no significant reactivity with any of the peptides, suggesting that they react with a conformational epitope. Together, these studies showed that mAbs with discrete binding specificities can interact with either linear or conformational epitopes and block TSH binding. The availability of these mAbs should facilitate identification of fine structures of the TSHR that are relevant for its function as well as pathogenesis of a number of thyroid disorders mediated by antibodies to TSHR.

Animals↗
PubMed1995

Thyrotropin receptor-specific antibodies in BALB/cJ mice with experimental hyperthyroxinemia show a restricted binding specificity and belong to the immunoglobulin G1 subclass.

Immunization with the extracellular domain of TSH receptor (TSHR) led to the development of hyperthyroxinemia in BALB/cJ, but not C57BL/6J, SJL/J, and B10.BR, mice. Earlier, human studies had shown that thyroid-stimulating antibodies are predominantly of the immunoglobulin G1 (IgG1) subclass with a narrow specificity to TSHR, and antibodies that block thyroid function could be of any subclass with a broader specificity. Therefore, antibody responses in susceptible (BALB/cJ) and resistant (SJL/J) mice were characterized. There were no significant differences in the titers, relative affinities, or isotypes of antibodies against the TSHR. BALB/cJ and SJL/J sera reacted with 2 and 7 of 26 overlapping peptides from the extracellular domain of the TSHR. The ability of sera from BALB/cJ and SJL/J mice to block TSH binding to TSHR was reversed by 1 and 6 of the reactive peptides, respectively. BALB/cJ mice showed predominantly an IgG1 response against the TSHR and peptides, whereas SJL/J mice showed varying levels of all IgG subclasses. Although SJL/J sera reacted with peptides to which blocking antibodies bind, they did not show hypothyroidism, suggesting that their sera contained a mixture of blocking and stimulating antibodies that negated the effects of each other. In contrast, some TSHR-specific antibodies in BALB/cJ probably represented stimulating antibodies.

Animals↗
PubMed1995

The CERAD experience, Part VIII: Neuroimaging-neuropathology correlates of temporal lobe changes in Alzheimer's disease.

We compared premortem neuroimaging findings with neuropathologic evidence of temporal lobe atrophy in 20 patients with Alzheimer's disease (AD) confirmed by autopsy. There were significant correlations between temporal horn enlargement observed by neuroimaging and hippocampal atrophy at autopsy, and between the overall cerebral atrophy severity on neuroimaging and scores on the Mini-Mental State Examination. This report confirms previous studies correlating temporal lobe atrophy on neuroimaging with a clinical diagnosis of AD, although more precise neuroimaging techniques are needed for use in multicenter studies of AD.

Alzheimer Disease↗
PubMed1995

The Consortium to Establish a Registry for Alzheimer's Disease (CERAD). Part XI. Clinical milestones in patients with Alzheimer's disease followed over 3 years.

The rate of cognitive decline, measured by psychometric testing, is widely used to track the progression of Alzheimer's disease (AD). As an alternative approach, we studied clinical measures as markers of the progression of dementia in 343 community-dwelling patients with probable AD enrolled in the multi-center Consortium to Establish a Registry for Alzheimer's Disease (CERAD) project. Subjects received standardized evaluations at entry and at annual follow-up. Decline on the Clinical Dementia Rating, loss of instrumental activities of daily living, failure to recall three words on the Mini-Mental State Examination (MMSE), and decline of the total MMSE score to below 10 were high-risk milestones, with cumulative frequencies exceeding 50% at 3 years. Loss of dressing and toileting activities occurred at intermediate rates, while loss of eating ability was rare. The risk of reaching clinical milestones and the annual rate of cognitive decline on the MMSE were directly correlated. Clinical milestones are useful indices of the progression of dementia in patients with AD.

Activities of Daily Living↗
PubMed1995

Identification of thyroid blocking antibodies and receptor epitopes in autoimmune hypothyroidism by affinity purification using synthetic TSH receptor peptides.

UNLABELLED: To examine the interaction of immunoglobulins from patients with newly diagnosed hypothyroidism with the TSH receptor (TSHr), we tested protein-A purified IgG in an ELISA assay with a series of peptides representing the entire extracellular domain (ECD) of human TSHr. Antibodies bound, on average, 4.1 peptides (range 0-16) per patient, and antibodies from 26 of 30 patients (86.6%) demonstrated binding to at least one peptide. Six of the 20-mer peptides (61, 151, 181, 301, 361, 376) were most frequently recognized. These were used to construct affinity columns and separate IgGs from 10 patients into bound and unbound fractions. All fractions were tested for their ability to stimulate and inhibit cAMP generation in FRTL-5 cells. Inhibitory IgGs were purified from 9 patients (90%), suggesting that the incidence of blocking antibodies (TBAb) in autoimmune hypothyroidism is higher than previously reported. 7 of 10 patients had antibodies that recognized peptide 361 further supporting the importance of this epitope in TBAb binding. Anti-microsomal and anti-thyroglobulin antibodies did not co-purify with inhibitory antibodies, and were always in the unbound fractions. We found no correlation between the pattern of antibody binding or bioactivity with clinical manifestations of hypothyroidism. CONCLUSIONS: (1) The majority of patients with autoimmune hypothyroidism have antibodies against the TSHr-ECD that recognized linear epitopes. Most have antibodies directed at more than one site and the pattern is quite heterogeneous. (2) Six sites (noted above) are most frequently recognized. (3) Inhibitory antibodies are distinct from anti-microsomal and anti-thyroglobulin antibodies.

Adolescent↗
PubMed1994

Delineation of amino acid residues within hTSHr 256-275 that participate in hormone binding.

The amino acid sequence 256-275 of the human thyrotropin (TSH) receptor extracellular domain has previously been shown to participate in a high affinity TSH binding site by a synthetic peptide approach as well as by site-directed mutagenesis. To further investigate this binding site, we synthesized a series of peptides with alanine substitutions for each residue in the native sequence. Peptides were also synthesized containing truncations or deletions of the native sequence. Each peptide was tested for its ability to inhibit 125I-bTSH binding to porcine thyroid membrane preparations, and the concentration at which 50% inhibition of binding occurred was determined (EC50). Alanine substitution at residues Tyr258, Cys262, Cys263, Phe265, Lys266, Asn267, Lys269, Lys270, and Arg272 all resulted in statistically significant decreases in activity when compared to the native sequence (p < 0.05). Alanine substitution of the remaining residues did not alter their activity. Comparison of this sequence with the corresponding sequences of the remaining glycoprotein hormone receptors (human lutropin and human follitropin receptors) reveals that these residues lie within one of the most highly conserved regions of the extracellular domain. We conclude that 9 specific amino acids within the sequence 256-275 of hTSHr (-Y--CC-FKN-KK-R--) participate in the interaction of the hTSHr-extracellular domain with TSH. This may represent a site in which the nonconserved residues are involved in the binding of the beta-subunit and the conserved residues are involved in the binding of the common alpha-subunit or a region of the beta-subunit that is common to all glycoprotein hormones.

Amino Acid Sequence↗
PubMed1994

Multiple-buffer-additive strategies for enhanced capillary electrophoretic separation of peptides.

A dodeca-peptide from the beta-subunit of thyroid stimulating hormone (TSH) was used as a model system for developing "multiple-buffer-additive" strategies to effect the separation of structurally-similar peptides. A series of synthetic peptides included six peptides with identical amino acid composition and two with multiple alanine substitutions at selected positions. Those with identical amino acid composition included the native and reverse sequences of residues 101-112 of the beta-TSH and four "computer-shuffled" amino acid sequences. Buffer additives such as acetonitrile (ACN), hexane sulfonic acid (HSA), and hexamethonium bromide (HxMBr), were shown to alter selectivity dramatically. HSA, an ion-pairing agent, and ACN, known to alter the hydrophobic environment of the solute, and HxMBr, which is thought to negate solute-wall interactions, are shown to independently effect only partial resolution of the mixture. It is shown that only with the proper combination of HSA and ACN are all mixture components resolved. These results re-affirm that CE selectivity may be altered by changes in buffer ionic strength or with the addition of HSA, but also show that further changes in selectivity can be achieved through alteration of buffer hydrophobicity. The observed changes in selectivity accompanying the addition of HSA and ACN may be due to differing electrophoretic mobilities resulting from nearest-neighbor effects or subtle differences in peptide secondary structure or solvation. This emphasizes the importance of employing multiple-buffer-additive strategies for effecting the resolution of peptide mixtures that are difficult to separate.

Amino Acid Sequence↗