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Biomedical subjects

W L Dunn

Publications and source records attributed to W L Dunn.

At least 73 records · Page 4Linked to original sources
PubMed1977

A new histochemical technique of use in the interpretation and diagnosis of adenocarcinoma and villous lesions in the large intestine.

The periodic acid-thionin Schiff/potassium hydroxide/periodic acid-Schiff (PAT/KOH/PAS) procedure has been used to investigate the histochemical staining characteristics of the mucins found in adenocarcinoma and villous lesions of the large intestine. The 46 blocks examined represented 58 lesions from 37 patients, all of whom had had resections for carcinoma of the colon. tin sharp contrast to normal colon, none of the adenocarcinomas stained red with the PAT/KOH/PAS. With two exceptions the poorly and moderately differentiated adenocarcinomas stained blue, whereas of the well differentiated lesions half were blue and half purple. The malignant villous lesions demonstrated the same trends, although a larger percentage were purple. None of the benign lesions stained blue. It is suggested that malignancy in the colon is accompanied by an increase in blue staining in the PAT/KOH/PAS technique and that such staining may be of value in the interpretation of highly atypical adenoma where it might identify the onset of malignancy. This change in staining indicates a distinct alteration in the chemistry of the mucins which we interpret as a reduction in the degree of side chain O-acylation of their constituent sialic acids.

Adenocarcinoma↗
PubMed1977

Histochemical comparison of the epithelial mucins in the ileum in Crohn's disease and in normal controls.

A comparison of routine and special histochemical methods that were applied to the epithelial mucins of small intestine from patients with Crohn's disease and from normal controls showed that the normal small intestine (ileum) goblet cells secrete a predominantly non-sulphated sialomucin and that, in contradistinction to the colon, the neuraminidase insensitivity of the sialic acids of the small intestine was not due to either O-acylation at C4 or an ester substituent at C1. Presumably this implies that the protection against enzyme attack afforded to the mucosa by the mucin coat in the small intestine utilises a different mechanism from that in the colon and that, although in many respects the small intestinal mucins in Crohn's disease, and in normal controls are similar, there is an increase in side-chain O-acylated sialic acids in such mucins in Crohn's disease. This difference has not been described before, probably because it can be seen only after staining such sections by the PAT/KOH/PAS and the PBT/KOH/PAS techniques.

Crohn Disease↗
PubMed1977

A method for the simultaneous estimation of free and ketosidically bound sialic acids.

Various methods for the estimation of free and ketosidically bound sialic acid were investigated for accuracy and specificity. It was found that oxidation with 0.025 M sodium metaperiodate in pH 7.0 phosphate buffer at room temperature for 20 min provided a simple, rapid, sensitive method whereby both the free and the ketosidically bound acid present in a mixture could be quantitatively analyzed. On completion of the oxidation step, the bound sialic acid is estimated with resorcinol reagent and the free sialic acid with thiobarbituric acid reagent. Oxidation under these conditions permitted a facile analysis of mixtures of bovine submaxillary mucin and free N-acetylneuraminic acid, whereas the Warren thiobarbituric acid procedure gave an erroneous value for free sialic acid.

Animals↗
PubMed1976

The use of a transesterification technique to distinguish between certain neuraminidase resistant epithelial mucins.

The effects of potassium hydroxide and soidum methoxide treatments upon the Alcian blue staining and neuraminidase lability of certain neuraminidase resistant epithelial mucins have been studied. The results were interpreted as indicating that while the mucins of rat colon and rabbit Brunner's gland contain only 4-0-acetyl sialic acid, human colonic epithelial mucins may contain some sialic acid with esters at the C1 carboxyl group.

Animals↗
PubMed1976

A new histochemical method for the identification and visualization of both side chain acylated and nonacylated sialic acids.

A new histochemical method is described for the differentiation of mucins that utilizes two different Schiff reagents and allows single section identification of side chain O-acylated, and nonacylated, sialic acids in contrasting colors. In the event of mucins containing only one type of sialic acid, it may allow their specific identification (e.g., C7 or C8 side chain O-acylated). It has been shown to be useful in the identification of some metastases from adenocarcinomas of colon (where the primary is potassium hydroxide/periodic acid-Schiff positive) and should prove of great value in the investigation of diseases of the gastrointestinal tract and particularly those of the colon. It should also be valuable in the general field of epithelial mucin histochemistry, particularly for those mucins of the salivary and parotid glands, etc.

Animals↗
PubMed1975

A histochemical method of differentiating lower gastrointestinal tract mucin from other mucins in primary or metastatic tumours.

Epithelial mucins of the normal terminal ileum, caecum, colon, and rectum of man are unique in that they alone exhibit staining following the periodate-borohydride/KOH/PAS technique. Application of this technique enables one to differentiate those mucin-producting metastases arising from adenocarcinoma of the lower gastrointestinal tract from those arising elsewhere, and may occasionally be useful in determining the site of the primary tumour when it is in doubt. Furthermore, it was found to be especially useful in distinguishing between primary adenocarcinoma of the lung and metastases in the lung from adenocarcinoma of the lower gastrointestinal tract.

Adenocarcinoma↗
PubMed1975

The demonstration of O-acetylated sialic acids in colonic epithelial glycoproteins.

Glycoproteins have been isolated from a 1 M sodium chloride extract of the colonic epithelial cells of man and rat by a combination of Agarose gel and DEAE-cellulose chromatography; The glycoproteins contain O-acetylated or O-esterified sialic acids of at least four types: (a) unsubstituted or possible at position C-9, (b) substituted at C-4 and possibly at C-9, (c) substituted at C-7 and/or C-8, and (d) substituted at C-4 as well as at C-7 and/or C-8.

Animals↗
PubMed1975

Differences in chemical composition between the epithelial glycoproteins of the upper and lower halves of rat colon.

Analysis of the apparently homogeneous sulfated sialoglycoproteins isolated from the epithelial cells of the upper (proximal to the ileum) and lower (proximal to the rectum) halves of Wistar rat colon showed that whereas they were similar in overall carbohydrate and amino acid composition, they differed significantly in the O-acetyl substitution pattern of their constituent sialic acids. The glycoprotein from the upper half of the colon was found to contain a larger percentage of sialic acid substitued at C7 and/or C8, as well as at C4 and C7 and/or C8; it contained less sialic acid which was unsubstituted as well as less subsituted at C4 alone. It has been shown that differences in substitution at C7 and/or C8 can be detected by analysis of the 105 000 g supernatants prepared from homogenates of isolated epithelial cells or fresh or formol calcium fixed whole colonic tissue.

Animals↗