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S McQuaid

Publications and source records attributed to S McQuaid.

At least 19 recordsLinked to original sources
PubMed1995

Microwave antigen retrieval for immunocytochemistry on formalin-fixed, paraffin-embedded post-mortem CNS tissue.

Microwave antigen retrieval methods were assessed for a panel of antibodies on formalin-fixed, paraffin-embedded sections from a range of human central nervous system (CNS) tissues taken at post-mortem. The immunoreactivity of a number of antigens (synaptophysin, PGP9.5, GFAP, carbonic anhydrase II, CD68, ferritin, HLA-DR, alpha beta-crystallin, measles and herpes viruses) was markedly enhanced by this procedure compared with other methods of antigen unmasking, such as trypsinization. Enhancement was noted both by an increased number of positive cells and by the intensity of reactions within individual cells and their processes. Furthermore, the microwave method produced uniform immunostaining over large surface area sections with no loss of morphological detail. Large cryostat sections of CNS tissue can be difficult to obtain with good morphology. The ability to retrieve a wide range of antigen in formalin-fixed, paraffin-embedded CNS tissue will greatly increase the range of investigations that can be carried out on this type of stored material.

Antigens↗
PubMed1995

A comparison of digoxigenin and biotin labelled DNA and RNA probes for in situ hybridization.

A number of in situ hybridization protocols using digoxigenin or biotin labelled probes were assessed for viral nucleic acid detection in formalin fixed, paraffin embedded tissue. Single-step detection protocols for biotin labelled probes produced low sensitivity; however, enzyme based one-step detection protocols for digoxigenin probes produced high sensitivity for both RNA and DNA systems. For both probe types, multistep detection protocols produced equally high sensitivity. Use of an enhanced APAAP procedure for digoxigenin labelled probes achieved maximal sensitivity without use of biotin-strep-tavidin reactions. The sensitivity of nucleic acid detection obtained with a digoxigenin labelled probe is comparable to that obtained using biotin. Digoxigenin labelled probes for nucleic acid detection are recommended for tissues with endogenous biotin.

Animals↗
PubMed1994

Association of measles virus with neurofibrillary tangles in subacute sclerosing panencephalitis: a combined in situ hybridization and immunocytochemical investigation.

Neurofibrillary tangle formation, a cardinal characteristic of Alzheimer's disease, is also a feature of several other neurodegenerative disorders, including subacute sclerosing panencephalitis (SSPE). In the present study the association of measles virus genome with neurofibrillary tangle formation has been studied in five cases of SSPE, using in situ hybridization (measles genome) and immunocytochemistry (tau, ubiquitin and beta/A4 amyloid). In two cases with duration of disease less than one year, neurofibrillary tangle formation was not observed. However, in those cases in which the disease was of several years duration, numerous tau- and ubiquitin-positive neurofibrillary tangles were demonstrated. In the two cases of longest duration, double-labelling techniques demonstrated the frequent association of neurofibrillary tangle formation with neuronal measles virus genome positivity. Immunocytochemistry for beta/A4 amyloid failed to demonstrate amyloid in any of the five cases. These findings support the hypothesis that neurofibrillary tangle formation can occur independently of amyloid formation and that this mechanism may operate in both Alzheimer's disease and in virally-induced disease.

Adolescent↗
PubMed1992

Detection protocols for biotinylated probes: optimization using multistep techniques.

Recent studies using biotinylated in situ hybridization (ISH) have utilized a wide range of detection protocols for the biotinylated hybrids, leading to conflicting reports in the literature regarding sensitivity. In this study we compared 11 different detection protocols for biotinylated ISH using a measles virus-specific RNA probe on formalin-fixed, paraffin-embedded central nervous system tissue infected with measles virus. Maximum sensitivity was achieved with five-step detection protocols incorporating the use of a monoclonal antibody to biotin. Single-step detection protocols were found to be insensitive, as shown by their failure to detect viral nucleic acid in infected white-matter cells. Only by increasing the number of steps in the detection protocols were these infected cells demonstrable. Unless pre-hybridization, hybridization, and detection protocols are optimized, the results obtained in pathogenicity studies using ISH could be misinterpreted, leading to false conclusions about nucleic acid distribution. This also applies to the ever-increasing use of ISH for diagnostic purposes.

Antibodies, Monoclonal↗
PubMed1992

Salivary insulin-like growth factor-I originates from local synthesis.

Insulin-like growth factor-I (IGF-I) is a GH-dependent growth factor found in its highest concentrations in plasma. It is also measurable in saliva. The origins of salivary IGF-I concentrations were studied. Intracardial administration of Sprague-Dawley rats with 125I-labelled IGF-I and subsequent analysis of plasma and saliva samples by exclusion gel chromatography and SDS-PAGE, followed by autoradiography, demonstrated the apparent inability of IGF-I to cross from the plasma pool through to saliva. 125I-Labelled IGF-I was not chromatographed immediately before injection, resulting in administration of free iodide along with the iodinated peptide. This free iodide was demonstrable in saliva, indicating that movement of substances from plasma to saliva was measurable using the levels of 125I activity administered. Free iodide in saliva was not contributed to by 125I-labelled IGF-I degradation since 125I-labelled IGF-I was shown to be stable in saliva over 24 h. These data indicated that IGF-I in saliva is produced locally. Identification of a 4.7 kb IGF-I mRNA transcript in rat parotid salivary gland was consistent with IGF-I synthesis within that tissue.

Animals↗
PubMed1991

Comparison of reporter molecules for viral in situ hybridization.

A number of streptavidin-linked reporter molecules at the endpoint of a five-step detection protocol for viral in situ hybridization using biotinylated probes were examined. DNA-DNA and RNA-RNA model systems were used. Streptavidin linked to either peroxidase or fluorescein was found to be optimal in terms of sensitivity and resolution within individual cells. All other reporter molecules labelled similar numbers of cells with low background reaction. However, streptavidin-5 nm gold followed by silver enhancement gave very high background staining making interpretation of positive signals very difficult.

Alkaline Phosphatase↗
PubMed1991

Cerebral endothelial cell infection by measles virus in subacute sclerosing panencephalitis: ultrastructural and in situ hybridization evidence.

Infection of vascular endothelium plays a central role in the pathogenesis of acute measles virus infection outside the central nervous system (CNS) but has not been described in the human CNS. An ultrastructural survey was made of blood vessels in five cases of subacute sclerosing panencephalitis (SSPE) to determine whether or not infection of cerebral vascular endothelium occurred in this persistent fatal CNS disease caused by measles virus. Morbillivirus nucleocapsids were found in a few endothelial cells in three necropsy cases but not in the limited tissue available from two biopsies. In a severe parenchymal lesion in one necropsied case, endothelial cells hybridized in situ with a biotinylated probe specific for the N genomic RNA of measles virus. It is concluded that human cerebral endothelium is susceptible to measles virus infection.

Cerebrovascular Circulation↗
PubMed1990

N-myc oncogene amplification in paediatric tumours.

DNA, extracted from tumours arising in 29 paediatric patients [14 neuroblastoma, 9 Wilms tumour (nephroblastoma), 6 miscellaneous] was investigated for evidence of N-myc amplification, using pNb-1, a recombinant plasmid containing a 1.0 Kb fragment homologous to the 5' end of the human N-myc gene. Within the neuroblastoma group, 4 patients had 15 or more copies of N-myc which correlated with advanced disease stage, and 3 other patients showed low grade amplification (2-5 copies). Low grade amplification was also observed in one patient with stage III unfavourable histology Wilms tumour, resistant to treatment. N-myc was present at single copy level in all other tumours studied. It is concluded that N-myc activation by amplification confers aggressive properties on a variety of embryonal tumours, rather than being restricted to initiation of neoplasia in tumours of neuroectodermal origin. A greater understanding of the complex interaction of a number of oncogenes involved in neuroblastoma may enable more effective therapeutic strategies to be devised.

Child↗
PubMed1990

A study of glutamine synthetase in normal human brain and intracranial tumours.

Glutamine synthetase (GS) activity was measured in selected areas of three normal brains and in 262 biopsies from patients with suspected intracranial tumours. In general, levels were higher in grey matter than in white matter and the highest activities of all were found in the hypothalamus which is consistent with its high glutamatergic activity. In the biopsy material, GS activity was greatest in gliotic brain, in keeping with the predominantly astrocytic localization of the enzyme. High levels were also found in astrocytomas and oligodendrogliomas but there was considerable variation between tumours, suggesting a random loss of GS expression during neoplastic transformation or heterogeneity in their cellular origin. The immunocytochemical demonstration of GS in neoplastic oligodendrocytes and in meningioma cells argues against absolute cell-type specificity for this enzyme.

Brain↗
PubMed1990

Use of immunocytochemistry and biotinylated in situ hybridisation for detecting measles virus in central nervous system tissue.

Optimised immunocytochemical (ICC) and in situ hybridisation (ISH) protocols for long term, formalin fixed, central nervous system tissue infected with measles virus were developed. The effectiveness of 10 proteases for the enzymatic unmasking of formalin fixed antigen and nucleic acid was investigated. Protease VIII gave maximal signal generation with optimal tissue preservation and no background staining for both techniques. The use of a microwave oven as an additional pre-hybridisation step for RNA-RNA in situ hybridisation produced a significant increase in the number of cells labelled for genomic RNA. The ability to show the presence of antigen and nucleic acid in long term, formalin fixed tissue facilitates the use of stored necropsy material available in pathology departments for ICC and ISH investigations.

Antigens, Viral↗
PubMed1989

Examination of eight cases of multiple sclerosis and 56 neurological and non-neurological controls for genomic sequences of measles virus, canine distemper virus, simian virus 5 and rubella virus.

In situ hybridization studies have been carried out on brain samples from eight cases of multiple sclerosis (MS) and 56 non-neurological and neurological controls, using single-stranded 35S-labelled RNA probes prepared against genomic RNA sequences of measles virus, canine distemper virus, rubella virus and simian virus 5. Foci of hybridization were found using probes against the measles virus nucleocapsid protein (N), phosphoprotein and fusion protein gene sequences in two of the MS cases, and also in one control, a case of disseminated cytomegalovirus infection with spinal cord necrosis. This result was confirmed using biotinylated probes prepared against the measles virus N genomic sequence. No hybridization was found in any of the MS or control cases using any of the other viral genome-specific probes.

Astrocytoma↗
PubMed1988

Long-term dosing studies using mutagenic carcinogens indicate a highly significant correlation between elevations in the level of rat glutathione S-transferase P messenger RNA and liver tumours of hepatocellular origin.

We have investigated levels of transcript homologous with glutathione S-transferase P (GST-P; GST 7-7) in tumours and hyperplastic lesions induced in the livers of rats by long-term gavage dosing with diethylnitrosamine (DEN) and 6-p-dimethylaminophenylazobenzothiazole (6BT). Detailed histopathological examination of the livers of the 90 animals used in this study at 6-8 months after initiation of daily dosing revealed that, of the 30 animals treated with carcinogen, 15 had developed tumours or hyperplastic lesions. Of these, 11 were areas of fibrosarcoma/fibrous hyperplasia. The remaining four were hepatocellular carcinomas. Northern blotting of total RNA purified from these tissues revealed the presence of transcripts of 3 and 0.75 kb. Evidence is presented to indicate that the former is a hitherto-undetected precursor of the 3-kbp rat GST-P gene, the latter representing the previously characterized mature GST-P transcript. Large elevations of the 0.75-kb transcript (30-35-fold) were encountered in all of the hepatocellular carcinomas, but in none of the other lesions, indicating a highly significant correlation (P = less than 0.001) between high elevations in levels of GST-P mRNA and liver tumours of hepatocellular origin. Minor elevations in transcript level (less than or equal to 5-fold) were encountered in several of the non-hepatocellular lesions. In regenerating livers, small increases in the level of the 3-kb transcript (approximately 3-fold) were routinely detected in total RNA from all partial hepatectomies, a concomitant decrease of approximately similar magnitude occurring in the 0.75-kb transcript, suggesting that minor elevations in levels of GST-P transcript, where encountered in non-hepatocellular lesions, are related to pre-neoplasia rather than to the proliferative rate of hyperplastic cells per se. The data extend previous observations, carried out largely using short-term regimes, to an analysis of transcripts homologous with GST-P in hyperplastic, pre-neoplastic and neoplastic lesions induced by long-term dosing with genotoxic carcinogens, and strongly lend support to the concept that high (30-fold) elevations in GST-P transcript correlate most strikingly with tumours of hepatocellular origin.

Animals↗