Search PubMed⌕ Search

Biomedical subjects

S Abbas

Publications and source records attributed to S Abbas.

At least 37 records · Page 2Linked to original sources
PubMed1991

Non-reducing terminal linkage position determination in intact and permethylated synthetic oligosaccharides having a penultimate amino sugar: fast atom bombardment ionization, collisional-induced dissociation and tandem mass spectrometry.

Certain linkage positions in oligosaccharides can be discerned by collision-activated dissociation mass spectrometry, rationalized by molecular modelling. Previous work on synthetic oligosaccharides has suggested that daughter ion patterns can distinguish among intact compounds which terminate in alpha-L-fucose and have a penultimate amino sugar. The current study indicates that these observations can be extended to oligosaccharides terminating in beta-D-galactose. In addition, we have observed that protonated, ammoniated and lithiated molecular ions all produce linkage-specific daughter ion spectra in these two sets of oligosaccharides. Sodiated molecular ions could be fragmented usefully under high collision energy offset conditions; potassiated ions were stable and not dissociable under conditions available in a triple-quadrupole instrument. We also show linkage discernment among the permethylated set of these six synthetic oligosaccharides. Methylated derivatives of this set of compounds give more useful product ions, including a 3-linkage specific ion. A novel relationship was noted by a plot of collision energy against (daughter ion/parent ion) ratio, which gave a unique slope for each of the non-reducing terminal linkage positions 3, 4 and 6 in the set of six compounds. The slope of this plot is related to the ability of each linkage position in the oligosaccharide to absorb collisional energy. Rotational freedom of the individual glycosidic linkage is hypothesized to play a role in this phenomenon.

Amino Sugars↗
PubMed1984

A morphologic and histochemical study of metaplastic polyps of the colorectum.

A combined morphologic and histochemical study of metaplastic polyps of the colorectum was undertaken. With increasing size, these lesions showed alterations in architecture and differentiation, increased secretion of carcinoembryonic antigen and a reduced secretion of O-acylated sialomucin. These functional changes are also observed in colorectal cancers, but not in tubular adenomas showing low-grade dysplasia. Since there is little clinical evidence for a metaplastic polyp-carcinoma sequence, it is suggested that the sets of factors which lead to adenoma and metaplastic polyp formation in the colorectum are both required to induce malignant transformation.

Carcinoembryonic Antigen↗
PubMed1984

Sialomucins and carcinoembryonic antigen in the evolution of colorectal cancer.

We have explored the merit of a simultaneous study of sialomucin content and carcinoembryonic antigen (CEA) expression in the identification of early malignancy in adenomas. One hundred and thirteen colorectal adenomas were investigated by histochemical and immunocytochemical techniques. We compared adenomas from 'high risk' patients having synchronous carcinoma and 'low risk' groups with incidental polyps only. Twenty-three metaplastic and eight inflammatory polyps were also included. Our data suggest that size and dysplasia are not always closely related and that synchronous adenomas seem to carry a higher malignant potential than incidental polyps irrespective of size. The degree of O-acylation of sialic acids appears to be a sensitive indicator of early malignant change: loss of O-acylation was seen in all II adenomas with highly atypical foci ('focal carcinoma') but noted in only four of the remaining polyps with lower grade dysplasia (P less than 0.005). By contrast the intensity of staining for CEA was a gradual phenomenon and showed no statistically significant increase with the onset of malignancy. Inflammatory polyps showed staining characteristics similar to normal mucosa. Metaplastic polyps, however, revealed increased expression of CEA and reduced O-acylation with increased size which may reflect a disorder of growth and differentiation. Finally, by comparing these profiles of staining with those of normal mucosa, 'transitional' mucosa adjacent to carcinoma and carcinoma, we further illustrate a progression of changes occurring in colonic mucosa in carcinogenesis.

Adenocarcinoma↗
PubMed1984

Chest pain in women: a study of prevalence and mortality follow up in south Wales.

The London School of Hygiene cardiovascular questionnaire was administered by interviewers in a community survey of 1428 women aged 45-74 living in the Rhondda Fach in south Wales. The results were analysed after a 12 year follow up for mortality. The prevalence of angina was similar to that of a Swiss population, where the method of administration of the questionnaire was similar. The risk of dying associated with angina was some 50% higher than that for women without angina, significant at the 5% level. The risk was greatest for women aged 45-54 when angina accounted for some 15% of deaths in the follow up period. Grade 2 angina was associated with a higher mortality from coronary heart disease, with more than double the risk. The overall risk of dying associated with angina did not appear to decline with time.

Adult↗