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A H Clark

Publications and source records attributed to A H Clark.

33 records · Page 2Linked to original sources
PubMed1981

Infrared and laser-Raman spectroscopic studies of thermally-induced globular protein gels.

Infrared and laser-Raman spectroscopy have been used to follow secondary structure changes during the heat-set gelation of a number of aqueous (D2O) globular protein solutions. Measurements of the infrared Amide I' absorption band around 1650 cm-1, for BSA gels of varying clarity and texture, have shown that the very considerable variations in network structure underlying these materials are not reflected in obvious differences in secondary structure. In all cases aggregation is accompanied by development of beta-sheet of a kind common in fibrous protein systems, but for BSA at least this does not appear to vary significantly in amount from one gel type to another. Infrared studies of gels formed from other protein systems have confirmed this tendency for beta-sheet to develop during aggregation, and the tendency is further substantiated by laser-Raman evidence which provides the extra information that in most of the examples studied alpha-helix content simultaneously falls. From these, and other observations, some generalisations are made about the thermally-induced sol-to-gel transformations of globular proteins.

Chymotrypsin↗
PubMed1981

Electron microscopy of network structures in thermally-induced globular protein gels.

Thin sections of heat-set proteins gels formed from bovine serum albumin, insulin, lysozyme, ribonuclease, and alpha-chymotrypsin, have been studied by transmission electron microscopy. Micrographs have been interpreted as showing protein networks with strands between one and two times as thick as the native protein diameters. Considerable differences in the persistence characteristics, and frequencies of cross-linking, of the strands are observed, and there are variations in network homogeneity over long distances which correlate well with changes in gel opacity caused by alterations in pH and ionic strength. Evidence that artefacts are unlikely to have influenced these interpretations has been obtained in the BSA case in particular, by studying the aggregation process in solution, using alternative microscope approaches such as heavy-metal shadowing and negative staining. assuming that artefacts are absent, gel section micrographs have been simulated by a computer procedure, and the results suggest that, in most cases, the simplest interpretation of the microscope data is in terms of a "string of beads" model for the aggregation process, involving only moderately unfolded, and still globular, protein molecules. Other structural interpretations cannot be ruled out, however, as the degree of protein unfolding, and the exact mode of incorporation of the monomers into the network filaments, cannot be established by the microscope technique alone.

Chymotrypsin↗
PubMed1980

Small-angle x-ray scattering studies of thermally-induced globular protein gels.

Small-angle X-ray scattering has been applied to gels formed by heating globular proteins, in aqueous solution, above their unfolding temperatures. A number of BSA gels, previously characterized by electron microscopy, have been studied, and, by setting up theoretical models for the scattering process, the X-ray data have been shown to be consistent with the microscope conclusions regarding network structure. It is concluded that the networks form by a linearly-directed aggregation of unfolded, disc-like, protein molecules, three-dimensional geometry being achieved by occasional branching, and/or cross-linking. Long-range inhomogeneities in network structure, easily observed by electron microscopy, and correlated with variations in pH or ionic strength, have an effect on X-ray scattering, and hence the x-ray method is sensitive not only to different network strand thicknesses, but to different degrees of uniformity as well.

Animals↗
PubMed1922

Animal Evolution.

Explore the source record for details and available documents.

Journal Article↗
PubMedDate not supplied

COX-1 and COX-2 expression in stage I and II invasive cervical carcinoma: relationship to disease relapse and long-term survival.

COX-1 and COX-2 are members of the cyclooxygenase (COX) family, which influence tumor invasion and apoptosis. The objective of the study was to assess the relationship between COX-1 and COX-2 expression in early-stage disease and subsequent disease relapse and long-term survival. Women with FIGO stage I and II cervical carcinoma, younger than 50 years, treated between 1981 and 1990 were included. COX-1 and COX-2 expressions in the tumors were assessed by immunohistochemistry. COX-1 and COX-2 were expressed in 61% (17/28) and 57% (16/28) of tumors, respectively. COX-1 nonexpressers showed an improved overall survival compared to expressers (log-rank test, P= 0.09). There was no significant difference in the overall survival in COX-2 nonexpressers compared to expressers (P= 0.6). Out of eight women with disease relapse, COX-1 or COX-2 expression was noted in six of eight tumors, and both were expressed in five of eight tumors. Our preliminary data suggest an adverse prognosis with COX-1 expression in early-stage cervical carcinoma and a trend toward COX-1 expression in disease relapse. The association between COX-2 expression and a worse prognosis was not proven in this study.

Adult↗
PubMedDate not supplied

Current manpower pool in cytotechnology.

Data are presented on the manpower shortage in the field of cytotechnology and the lack of sufficient training programs to meet current needs, and the fiscal bases of these problems are discussed. The workload placed on cytotechnologists is also analyzed in financial terms, emphasizing the pressures for high productivity in frequently less-than-optimal conditions. Screening accuracy is also considered. All of these issues need attention to produce adequate numbers of accurate screeners.

Cell Biology↗
PubMedDate not supplied

Early endocervical glandular neoplasia. I. Histomorphology and cytomorphology.

A study is presented of 36 cases of early endocervical glandular neoplasia comprising three specific entities: endocervical adenocarcinoma in situ, microinvasive adenocarcinoma and adenocarcinoma limited to a single polypoid structure. A clinical profile is developed that reveals a typical patient population. The histomorphologic and cytomorphologic features of early endocervical glandular neoplasia are discussed in detail. The consistently reproducible cytologic appearance described may be accurately detected microscopically. Early detection of endocervical adenocarcinoma could produce a dramatic decrease in patient morbidity and mortality, such as has occurred with squamous epithelial malignancies.

Adenocarcinoma↗
PubMedDate not supplied

Early endocervical glandular neoplasia. II. Morphometric analysis of the cells.

A morphometric analysis was performed on the cells of early endocervical glandular neoplasia, including adenocarcinoma in situ and microinvasive adenocarcinoma, in cytologic preparations. The measurements were compared with those of cells from the normal endocervix and cells from other lesions that enter into the differential diagnosis. The morphometric profile developed for the cells of early glandular neoplasia proved to be useful, reliable and reproducible. Not only could the cells of normal endocervical samples be distinguished from those of early endocervical glandular neoplasia, but the measurements also seemed capable of making the visually difficult distinction between adenocarcinoma in situ and microinvasive adenocarcinoma. The latter point requires further confirmation since only a few cases of microinvasive adenocarcinoma were available for study.

Adenocarcinoma↗
PubMedDate not supplied

A morphometric study of primary adenocarcinoma of the vagina.

Primary adenocarcinoma of the vagina accounts for approximately 1% of all invasive carcinomas of the female genital tract. This paper reports on a study of four cases of primary adenocarcinoma (including one with in utero diethylstilbestrol exposure) of the vagina from the files of the Medical University of South Carolina. Both tissue sections and cytologic preparations from each case were evaluated in order to delineate the morphologic characteristics of the cells that compose the lesions. Histologically, the lesions primarily presented the tubular cystic pattern; solid and papillary growth patterns were also seen in one case. The constituent cells included clear cells, hobnail cells and secretory and nonsecretory tubular cystic cells. All specimens were examined for the following parameters: cell population, nuclear area, cytoplasmic area, nuclear/cytoplasmic (N/C) proportions, nuclear and cytoplasmic characteristics. While a fairly detailed profile of the morphologic criteria for hobnail cells was developed, the cellular profiles of the other malignant glandular cells originating in primary vaginal adenocarcinoma remain less certain.

Adenocarcinoma↗