False-positive results and the polymerase chain reaction.
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Biomedical subjects
Publications and source records attributed to K A Fleming.
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Metastases from a carcinoid tumor to the pituitary gland have, to our knowledge, not been described. We present a 49-year-old woman diagnosed as having a primary carcinoid tumor arising in the submucosa of a large bronchus who 8 years later presented with multiple metastases including one to the pituitary gland, which was in partial failure of pituitary function. This case illustrates than when confronted with a pituitary tumor resembling an adenoma but negative for pituitary hormones, the possibility of a metastasis from a carcinoid tumor should be considered.
This study reports high incidence tumourigenic activity of the pSV2neo plasmid demonstrated by transfection of NIH 3T3 cells. The plasmid is frequently used as a dominant selectable marker for confirming successful gene transfection, and the findings indicate a need for caution in interpretation and design of assays for oncogenes which use co-transfection and subsequent selection with neomycin.
A method for efficient simultaneous extraction of high-molecular-weight DNA and RNA from solid mammalian tissues including clinical biopsies is described. It is based on the disruption and subsequent melting of deep frozen tissue in the presence of frozen phenol and nucleic acid extraction buffer; this allows for simultaneous disruption of tissue and inactivation of nucleases. The yield is about 0.7-5.8 mg of DNA and 0.5-8.1 mg of total RNA/g of tissue depending upon the tissue type; this is higher than the yield of other methods tested. Analysis of total RNA by denaturing gel electrophoresis, and of DNA and poly(A)+ RNA by Southern and Northern blot hybridization using 32P and biotinylated probes, indicated that c-Ha-ras gene and its transcripts were undegraded. Biotinylated and 32P probes had approximately the same sensitivity in detecting nucleic acids on Southern and Northern blots. This extraction procedure is simple and, when used with biotinylated probes, is rapid, inexpensive, and nonhazardous. The methodology can be modified for use with other clinical samples and cells grown in culture.
The expression of HLA class I (HLA-A, B, C) and class II (HLA-DR) antigens on the biliary epithelium of 10 patients (nine men) with primary sclerosing cholangitis (PSC) was investigated using an immunoperoxidase technique on cryostat sections. Five patients were staged as grade II and five grade III on hepatic histology. None were cirrhotic. as grade II and five grade III on hepatic histology. None were cirrhotic. Controls were nine patients with primary biliary cirrhosis (PBC), five with extra hepatic biliary obstruction, 15 with other forms of chronic liver disease and six with normal livers. Bile ducts from the normal subjects and patients with chronic liver disease did not express HLA-DR antigens. In contrast, all 10 of the PSC biopsies showed varying degrees of HLA-DR staining of the biliary epithelium. Expression of DR antigens was also found on the bile ducts of all five patients with extra hepatic biliary obstruction and in six of nine patients with PBC. Expression of HLA class I antigens was seen on the biliary epithelium of all the biopsies examined. Increased numbers of helper and suppressor T-cells were seen in the portal tracts of all the PSC patients. This study has confirmed that aberrant expression of HLA-DR may occur on the biliary epithelium of some, but not all, patients with PBC. In addition, the study has shown that aberrant expression of HLA-DR always occurs in PCS at an early stage of histological liver damage. While this may be important in the pathogenesis of PSC, the aberrant expression in extra hepatic biliary obstruction suggests that it may be a secondary phenomenon.
Lung tissue from 13 cases of unexplained non-immunological hydrops fetalis was examined by in situ hybridisation to detect parvovirus. Four specimens contained parvovirus DNA in cells in the blood vessel lumina and alveoli. Twenty six control cases were negative for parvovirus DNA. As there was no known epidemic of parvovirus infection during the study period, this suggests that parvovirus is a relatively common cause of non-immunological hydrops fetalis. In situ hybridisation may have a role in clinical medicine, particularly for retrospective investigations.
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We report a case of a long-standing subcutaneous nodule of the scalp in a young man, with the histological features of a primary cutaneous meningioma. The results of an immunohistological study using a panel of monoclonal antibodies gave a similar pattern to that seen in intracranial meningiomas, and distinct from other cutaneous lesions which may be considered in the differential diagnosis.
Immunohistology was used for the detection of Legionella pneumophila serogroup I in necropsy tissue. Study of pneumonic lung from the recent Stafford outbreak has shown that this technique has a high sensitivity. A retrospective postmortem examination showed that L pneumophila serogroup 1 was an unusual cause of pneumonia in Oxfordshire during the study period. L pneumophila serogroup 1 can be successfully subgrouped, using a panel of monoclonal antibodies on formalin fixed paraffin embedded sections. Immunohistological methods have a potentially useful role in the diagnosis of Legionellosis at postmortem examination and in the epidemiological investigation of individual cases and outbreaks.
In analysing human papilloma virus (HPV) infection of the cervix in formalin fixed paraffin sections by non-isotopic in situ hybridisation two main problems were found: detachment of sections from the glass during hybridisation and probe detection; inadequate sensitivity and inability to assess sensitivity of the in situ procedure. The first problem was investigated by assessing the efficiency of various tissue adhesives individually and in combination. The second problem was addressed by optimising conditions for DNA unmasking, hybridisation, and biotinylated probe detection. Sensitivity of the final in situ procedure developed was assessed by using the detection of pHY2.1 repeats as a built-in control. Extrapolation of data showed that less than 10 copies of HPV DNA can be visualised by these procedures. HPV nucleic acid, mainly in the form of DNA, was detected not only in koilocytic nuclei but also in suprabasal cells in condylomas and CIN lesions. HPV mRNA was also visualised in the cytoplasm (and probably also nuclei) of the same cell types. These non-isotopic in situ procedures give results comparable to those obtained with radiolabelled probes, but they are less time consuming and provide better morphological resolution.
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One hundred and eighty five consecutive liver biopsies were immunostained using anti-alpha-1-antitrypsin to assess the use of routine immunohistochemistry in the diagnosis of alpha-1-antitrypsin (AAT) deficiency. About half the livers showed staining of hepatocytes for alpha-1-antitrypsin, but most of these livers showed a panlobular pattern, possibly indicating increased synthesis of AAT. Only ten contained periportal granules, said to be typical of AAT deficiency. In cases in which serum was also available for quantitation and phenotyping there was no absolute relation between staining pattern, phenotype, and serum concentrations: the immunohistological screening technique, therefore, has limitations in the diagnosis of AAT deficiency in liver biopsy specimens.
Thirteen meningiomas of varying light microscopic features were studied immunohistologically using a panel of monoclonal antibodies directed against epithelial, mesenchymal, and neural components. All 13 meningiomas showed expression of epithelial membrane antigen, vimentin, and S100 protein, as did normal meninges. Five of the 13 meningiomas also showed focal expression of cytokeratins, with double labelling showing expression of cytokeratins and vimentin by different cells. The cytokeratin expression was especially noticeable in cells surrounding the hyaline bodies of meningiomas. These results provide further evidence that meningiomas have features of both mesenchymal and epithelial tissues.
A sensitive method for detecting biotinylated DNA probes on dot and Southern blots is described which is based on the principle outlined by Leary et al (1). This system has two main components: detection of biotinylated DNA by a two-step procedure with streptavidin and poly(alkaline phosphatase); and blocking background with Tween 20. 32fg and 80fg of lambda phage DNA was detected on dot and Southern blot hybridizations respectively. 150fg of beta-globin was detected on Southern blots of genomic DNA. This method is fast, reproducible and can detect single copy genes in 0.25 micrograms genomic DNA on Southern blots.