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Biomedical subjects

C A McLean

Publications and source records attributed to C A McLean.

At least 37 records · Page 2Linked to original sources
PubMed2000

Recent advances in the pre-mortem diagnosis of Creutzfeldt-Jakob disease.

Included in the spectrum of human transmissible spongiform encephalopathies are Creutzfeldt-Jakob disease (CJD) and the new variant form (vCJD), Gerstmann-Sträussler-Scheinker syndrome, fatal familial insomnia, kuru and various less distinct neuropsychiatric disorders. Progress in our understanding of this group of disorders continues at a prodigious rate, although important vexing practical issues persist. The definitive confirmation of symptomatic prion disease still requires pathological examination, most reliably performed post-mortem. However, paralleling the recent advances in the molecular biological understanding of normal prion protein (PrP(c)) function and the pathophysiology of prion diseases, there have been worthwhile developments in the pre-mortem diagnosis of CJD. Efforts to develop less invasive but very reliable ante-mortem diagnostic tests have received an additional impetus because of the potential epidemic of vCJD. Historically, the ancillary investigation of most merit has been the EEG, whereas the recent advances have encompassed a broader range of technologies, including both magnetic resonance and radioisotopic neuroimaging, and immunoassays for a range of non-specific marker proteins in both CSF, and less commonly, blood. However, given the recent refinement of sophisticated immunoassays, it is envisaged that the pathognomonic, protease-resistant, disease-associated isoforms of the prion protein (PrPres) may soon be directly detectable in the blood and tissues of patients manifesting or incubating a spongiform encephalopathy.

Biomarkers↗
PubMed2000

Creutzfeldt-Jakob disease: diagnostic utility of 14-3-3 protein immunodetection in cerebrospinal fluid.

With the aim of improving the pre-mortem diagnostic accuracy of sporadic Creutzfeldt-Jakob disease (CJD), there has been considerable recent interest in the merit of immunodetecting 14-3-3 proteins in the cerebrospinal fluid (CSF) using Western blotting, with cumulative support for the utility of this technique. As a corollary, during a 20 month period, CSF samples from an unselected prospective series of 124 patients in whom sporadic CJD was a differential diagnostic possibility were examined by the Australian Creutzfeldt-Jakob disease Registry (ACJDR) for the presence of 14-3-3 proteins. Follow up to achieve a final diagnosis or clinical outcome was successful in 119. For definite and probable sporadic CJD combined, a positive result was 91.4% sensitive, while the sensitivity for the pathologically verified group alone was 96.0%. A negative outcome was 92.5% specific with false positive results seen in five patients with diagnoses which included inflammatory CNS disorders, cerebral ischaemia and dementia with Lewy bodies (DLB). Immunodetectable 14-3-3 proteins were present in three of four symptomatic patients with prion protein gene (PRNP) mutations. CSF samples containing significant amounts of blood were confirmed as suboptimal, with weak or qualitatively unusual positive results found in greater than 50% of such specimens, with only one of 14 such cases ultimately classified as definite or probable CJD.

14-3-3 Proteins↗
PubMed2000

Altered glycosylation of acetylcholinesterase in lumbar cerebrospinal fluid of patients with Alzheimer's disease.

As clinical diagnosis of Alzheimer's disease is only 80%-90% accurate, there is a need to identify biochemical markers of Alzheimer's disease. Previous studies have shown an abnormality in the glycosylation of acetylcholinesterase (AChE) in the CSF collected postmortem from patients with Alzheimer's disease. This abnormality was very specific for Alzheimer's disease, as it was not detected in other illnesses causing dementia. We report here that the glycosylation of AChE is also altered in lumbar CSF collected antemortem. The altered glycosylation was due to increased concentrations of a minor AChE isoform that does not bind to concanavalin A (Con A). Glycosylation of AChE may eventually be of diagnostic value, especially when used in combination with other CSF markers.

Acetylcholinesterase↗
PubMed2000

Ischemic heart disease in black South African stroke patients.

BACKGROUND AND PURPOSE: Stroke patients in western countries frequently have coronary artery disease (CAD). In black Africans, CAD has been reported as being rare in both stroke patients and the general population. In this study, an attempt has been made to determine the prevalence of CAD in a black South African stroke population. METHODS: The prevalence of CAD was determined by indicators identified through a series of 5 observational studies in black patients diagnosed with stroke. CAD indicators included (1) bedside diagnosis in 741 patients; (2) resting ECG in 555 consecutively admitted patients; (3) a combination of clinical examination, cardiac ultrasound, radionuclide scintigraphy, and multigated blood pool studies in 102 consecutively admitted patients; (4) thallium scintigraphy in 60 patients; and (5) necropsy in 23 patients. RESULTS: On bedside questioning, only 0.7% complained of previous angina. There was no history given of myocardial infarction (MI), but documentation of this was found in the clinical notes of 0.7% of the patients. In the resting ECG study, evidence of myocardial ischemia was present in 14.6% and MI in 2.1%. In the combined study, cardiac ischemia was documented on ECG in 12.7% of patients and evidence of previous MI in 5.8%. Cardiac scintigraphic studies revealed changes of myocardial ischemia in 31.7% and MI in 13.3% of the 60 patients studied. Four (17.4%) of 23 patients in the necropsy study had histological evidence of previous MI, and 50% of all patients had evidence of >50% atherosclerotic stenosis in 1, 2, or 3 coronary arteries. CONCLUSIONS: The prevalence of CAD in black African stroke patients is significantly higher than has been documented in the general nonstroke black population as well as in stroke patients. Black stroke patients may have a risk for CAD similar to that of their white counterparts.

Adult↗
PubMed1999

Aqueous dissolution of Alzheimer's disease Abeta amyloid deposits by biometal depletion.

Zn(II) and Cu(II) precipitate Abeta in vitro into insoluble aggregates that are dissolved by metal chelators. We now report evidence that these biometals also mediate the deposition of Abeta amyloid in Alzheimer's disease, since the solubilization of Abeta from post-mortem brain tissue was significantly increased by the presence of chelators, EGTA, N,N,N',N'-tetrakis(2-pyridyl-methyl) ethylene diamine, and bathocuproine. Efficient extraction of Abeta also required Mg(II) and Ca(II). The chelators were more effective in extracting Abeta from Alzheimer's disease brain tissue than age-matched controls, suggesting that metal ions differentiate the chemical architecture of amyloid in Alzheimer's disease. Agents that specifically chelate copper and zinc ions but preserve Mg(II) and Ca(II) may be of therapeutic value in Alzheimer's disease.

Alzheimer Disease↗
PubMed1999

Early-onset Alzheimer's disease caused by a novel mutation at codon 219 of the presenilin-1 gene.

Mutations in the presenilin 1 (PS1) gene are responsible for approximately 50% of early onset autosomal-dominant Alzheimer's disease cases. A PCR based mutation detection method, chemical cleavage of mismatch, was used to detect a novel PS1 mutation in the coding sequence of the PS1 gene. Sequencing confirmed a T to C transition altering a leucine to proline at codon 219 of the PS1 gene. This is a novel mutation in exon 7 of the PS1 gene occurring outside the transmembrane regions of IV and V.

Age of Onset↗
PubMed1999

Soluble pool of Abeta amyloid as a determinant of severity of neurodegeneration in Alzheimer's disease.

Genetic evidence strongly supports the view that Abeta amyloid production is central to the cause of Alzheimer's disease. The kinetics, compartmentation, and form of Abeta and its temporal relation to the neurodegenerative process remain uncertain. The levels of soluble and insoluble Abeta were determined by using western blot techniques, and the findings were assessed in relation to indices of severity of disease. The mean level of soluble Abeta is increased threefold in Alzheimer's disease and correlates highly with markers of disease severity. In contrast, the level of insoluble Abeta (also a measure of total amyloid load) is found only to discriminate Alzheimer's disease from controls, and does not correlate with disease severity or numbers of amyloid plaques. These findings support the concept of several interacting pools of Abeta, that is, a large relatively static insoluble pool that is derived from a constantly turning over smaller soluble pool. The latter may exist in both intracellular and extracellular compartments, and contain the basic forms of Abeta that cause neurodegeneration. Reducing the levels of these soluble Abeta species by threefold to levels found in normal controls might prove to be a goal of future therapeutic intervention.

Aged↗
PubMed1999

Non-Abeta component of Alzheimer's disease amyloid (NAC) revisited. NAC and alpha-synuclein are not associated with Abeta amyloid.

alpha-Synuclein (alphaSN), also termed the precursor of the non-Abeta component of Alzheimer's disease (AD) amyloid (NACP), is a major component of Lewy bodies and Lewy neurites pathognomonic of Parkinson's disease (PD) and dementia with Lewy bodies (DLB). A fragment of alphaSN termed the non-Abeta component of AD amyloid (NAC) had previously been identified as a constituent of AD amyloid plaques. To clarify the relationship of NAC and alphaSN with Abeta plaques, antibodies were raised to three domains of alphaSN. All antibodies produced punctate labeling of human cortex and strong labeling of Lewy bodies. Using antibodies to alphaSN(75-91) to label cortical and hippocampal sections of pathologically proven AD cases, we found no evidence for NAC in Abeta amyloid plaques. Double labeling of tissue sections in mixed DLB/AD cases revealed alphaSN in dystrophic neuritic processes, some of which were in close association with Abeta plaques restricted to the CA1 hippocampal region. In brain homogenates alphaSN was predominantly recovered in the cytosolic fraction as a 16-kd protein on Western analysis; however, significant amounts of aggregated and alphaSN fragments were also found in urea extracts of SDS-insoluble material from DLB and PD cases. NAC antibodies identified an endogenous fragment of 6 kd in the cytosolic and urea-soluble brain fractions. This fragment may be produced as a consequence of alphaSN aggregation or alternatively may accelerate aggregation of the full-length alphaSN.

Alzheimer Disease↗
PubMed1999

Intracellular accumulation of detergent-soluble amyloidogenic A beta fragment of Alzheimer's disease precursor protein in the hippocampus of aged transgenic mice.

To study amyloid beta-protein (A beta) production and aggregation in vivo, we created two transgenic (Tg) mouse lines expressing the C-terminal 100 amino acids of human amyloid precursor protein (APP): Tg C100.V717F and Tg C100.WT. Western blot analysis showed that human APP-C100 and A beta were produced in brain and some peripheral tissues and A beta was produced in serum. Using antibodies specific for the A beta C terminus we found that Tg C100.V717F produced a 1.6-fold increase in A beta42/A beta40 compared with Tg C100.WT. Approximately 30% of total brain A beta (approximately 122 ng/g of wet tissue) was water-soluble. The remaining 70% of A beta partitioned into the particulate fraction and was completely sodium dodecyl sulfate-soluble. In contrast, human Alzheimer's disease brain has predominantly sodium dodecyl sulfate-insoluble A beta. Immunohistochemistry with an A beta(5-8) antibody showed that A beta or A beta-containing fragments accumulated intracellularly in the hippocampus of aged Tg C100.V717F mice. The soluble A beta levels in Tg brain are similar to those in normal human brain, and this may explain the lack of microscopic amyloid deposits in the Tg mice. However, this mouse model provides a system to study the intracellular processing and accumulation of A beta or A beta-containing fragments and to screen for compounds directed at the gamma-secretase activity.

Aging↗
PubMed1999

Molecular isoform distribution and glycosylation of acetylcholinesterase are altered in brain and cerebrospinal fluid of patients with Alzheimer's disease.

The glycosylation of acetylcholinesterase (AChE) in CSF was analyzed by lectin binding. AChE from Alzheimer's disease (AD) patients was found to bind differently to two lectins, concanavalin A and wheat germ agglutinin, than AChE from controls. As multiple isoforms of AChE are present in both CSF and brain, we examined whether the abnormal glycosylation of AD AChE was due to changes in a specific molecular isoform. Globular amphiphilic dimeric (G2a) and monomeric (G1a) isoforms of AChE were found to be differentially glycosylated in AD CSF. Glycosylation of AChE was also altered in AD frontal cortex but not in cerebellum and was also associated with an increase in the proportion of light (G2 and G1) isoforms. This study demonstrates that the glycosylation of AChE is altered in the AD brain and that changes in AChE glycosylation in AD CSF may reflect changes in the distribution of brain isoforms. The study also suggests that glycosylation of AChE may be a useful diagnostic marker for AD.

Acetylcholinesterase↗
PubMed1998

Acetylcholinesterase is increased in the brains of transgenic mice expressing the C-terminal fragment (CT100) of the beta-amyloid protein precursor of Alzheimer's disease.

Acetylcholinesterase (AChE) expression is markedly affected in Alzheimer's disease (AD). AChE activity is lower in most regions of the AD brain, but it is increased within and around amyloid plaques. We have previously shown that AChE expression in P19 cells is increased by the amyloid beta protein (A beta). The aim of this study was to investigate AChE expression using a transgenic mouse model of A beta overproduction. The beta-actin promoter was used to drive expression of a transgene encoding the 100-amino acid C-terminal fragment of the human amyloid precursor protein (APP CT100). Analysis of extracts from transgenic mice revealed that the human sequences of full-length human APP CT100 and A beta were overexpressed in the brain. Levels of salt-extractable AChE isoforms were increased in the brains of APP CT100 mice. There was also an increase in amphiphilic monomeric form (G1A) of AChE in the APP CT100 mice, whereas other isoforms were not changed. An increase in the proportion of G1A AChE was also detected in samples of frontal cortex from AD patients. Analysis of AChE by lectin binding revealed differences in the glycosylation pattern in APP CT100 mice similar to those observed in frontal cortex samples from AD. The results are consistent with the possibility that changes in AChE isoform levels and glycosylation patterns in the AD brain may be a direct consequence of altered APP metabolism.

Acetylcholinesterase↗
PubMed1998

Comparative neuropathology of Kuru with the new variant of Creutzfeldt-Jakob disease: evidence for strain of agent predominating over genotype of host.

The three major influences on the phenotype of the transmissible spongiform encephalopathies are believed to be strain of agent, route of infection and host genotype. We have compared the pathologic profiles and genotypes of the new variant of Creutzfeldt-Jakob disease (vCJD) and kuru. The comparison reveals that there are distinct lesional differences particularly in the prion protein (PrP) load and distribution as seen by immunohistochemistry. The clinico-pathologic phenotypes and the genotypes of these two diseases are sufficiently different to suggest that the strain of agent may play a greater role than any presumptive common route of peripherally acquired infection.

Adolescent↗
PubMed1997

The D178N (cis-129M) "fatal familial insomnia" mutation associated with diverse clinicopathologic phenotypes in an Australian kindred.

Fatal familial insomnia (FFI) is an inherited prion disease characterized by progressive insomnia and dysautonomia with only modest cognitive impairment early in the disease, associated with atrophy and gliosis in the medial thalamus, but without spongiform change. FFI is associated with an aspartic acid to asparagine mutation at codon 178 of the PrP gene (D178N) in conjunction with methionine at the codon 129 polymorphic site on the mutant allele (cis-129M). We report a pedigree with this genotype in which marked clinicopathologic phenotypic heterogeneity occurred including typical Creutzfeldt-Jakob disease, FFI, and what was thought to be an autosomal dominant cerebellar ataxia (ADCA)-like-illness, suggesting that the genotype-phenotype correlation is not as tight for this mutation as is frequently supposed.

Adult↗
PubMed1997

Viliuisk encephalomyelitis--review of the spectrum of pathological changes.

Viliuisk encephalomyelitis (VE) is an unique neurological disease occurring in the Iakut (Sakha) people of Siberia. Evolution of the disease follows one of three broad clinical forms: subacute, slowly progressive or chronic. Death occurs within 3 to 6 months in subacute cases and within 6 years in the slowly progressive cases. Chronic cases lack a subacute phase but show a slowly progressive dementia associated with bradykinesia, dysarthria and spastic paraparesis that stabilizes late in the disease process. In subacute and slowly progressive cases, focal necrotizing encephalomyelitis is seen at necropsy. Chronic cases show multifocal areas of lysis with a gliotic margin, predominantly within grey matter, lacking associated chronic inflammatory changes seen in the other forms of the disease. Epidemiological studies are consistent with a disease of low-grade communicability, but laboratory studies have so far failed to reveal an infectious organism. The spectrum of neuropathological changes are reviewed in this examination of 11 cases. Although the aetiology of VE remains obscure, further studies are warranted since it may represent a novel disease process.

Acute Disease↗
PubMed1997

Key features distinguishing post-transplantation lymphoproliferative disorders and acute liver rejection.

Post-transplantation lymphoproliferative disorder (PTLD) and acute rejection are two serious complications of orthotopic liver transplantation that can have a similar histologic appearance. We undertook the present study to assess the best way to distinguish these two entities. We studied histologic features, immunophenotyping, and Epstein-Barr virus (EBV) status, as assessed by immunohistochemical stain and in situ hybridization (ISH), in three groups: Group I, 8 cases of PTLD post-orthotopic liver transplantation with liver involvement; Group II, 15 cases diagnosed with acute liver rejection (control group); and Group III, a subset of 6 biopsy specimens from 4 patients of Group I whose graft rejection was diagnosed within the 2 months preceding the diagnosis of PTLD. The mean proportion of plasma to plasmacytoid cells in most cases from Group I was more than 40%, whereas from Group II it was less than 25% (P = .0001). There was a higher number of B lymphocytes than T lymphocytes in Group I. The numbers of mitotic figures and immunoblasts were significantly different in the two groups (P < .0001 and P = .0005, respectively), being higher in the patients with PTLD. EBV immunostain was most specific for the diagnosis of PTLD (75% positive in Group I, negative in Group II). ISH for EBV-encoded RNA was positive in 87% of cases in Group I and only 6.6% of cases in Group II (P = .0005). In Group III, four of the six liver biopsy specimens had a low plasma cell count and were negative for EBV studies. The other two biopsy specimens in this group had 70 to 80% plasma cell infiltrate, in addition to positive EBV immunostain and ISH in one, for which tissue was available for study. We conclude that viral studies and assessment of the number of plasma cells and B lymphocytes can help to distinguish between acute rejection and early PTLD.

Adult↗