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Biomedical subjects

A Tuck

Publications and source records attributed to A Tuck.

8 recordsLinked to original sources
PubMed2000

Chronic lymphocytic leukemia lymphocytes lack the capacity to repair UVC-induced lesions.

Cells from chronic lymphocytic leukemia (CLL) patients and from healthy individuals were irradiated with UVC and incubated for varying periods of time. The number of single strand breaks and alkali-labile sites was determined by comet analysis. Unirradiated CLL and healthy cells exhibited no significant numbers of single strand breaks. The extent of DNA damage was found to increase with dose for both healthy and CLL cells. However, the CLL cells had much more extensive DNA fragmentation than healthy cells at each dose. Deoxyribonucleoside supplemented medium inhibited comet formation in both cell types. Thymidine alone produced the same effect. In healthy cells, repair of lesions was complete after 4 h of incubation as indicated by the absence of comet formation. The CLL cells exhibited no significant repair even after 48 h. CLL lymphocytes are killed by very low doses of UVC radiation. The results reported here suggest that this hypersensitivity results from the inability of CLL cells to repair UVC-induced DNA damage and a contributing factor is the low amounts of intracellular deoxyribonucleosides.

Comet Assay↗
PubMed1999

Hypersensitivity of lymphocytes from chronic lymphocytic leukemia patients to ultraviolet light-C radiation.

Chronic lymphocytic leukemia (CLL) results in the accumulation of mature immunologically defective lymphocytes in GO phase. Lymphocytes from CLL patients were exposed to UVC radiation to determine whether these cells are capable of undergoing apoptosis, as a response to DNA damage. Lymphocytes from CLL patients were found to be readily killed by ultraviolet light-C (UVC) radiation. Cells from healthy donors were minimally affected by doses of UVC ten times higher then those which caused dramatic drops in the metabolism of CLL cells. At four hours after irradiation, the reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) had dropped by 50% for CLL cells exposed to a dose of 10 J/m2. In contrast, there was no significant drop for healthy cells exposed to 100 J/m2. Cell death was measured by trypan blue staining, flow cytometry of Annexin V-PI stained cells, and Wright staining. By 24 hours after irradiation, significant amounts of cell death were observed in CLL cells at doses which had no significant effects on viability of healthy lymphocytes. The extreme sensitivity of CLL lymphocytes to UVC indicates that phototherapy should be explored as a potential treatment for this neoplasm.

Apoptosis↗
PubMed1996

Localization of platelet-derived growth factor beta receptor expression in the periepithelial stroma of human breast carcinoma.

Platelet-derived growth factor (PDGF) BB is secreted by most human breast carcinoma cells; however, only recently have PDGF beta receptors been demonstrated in malignant breast tissue. In the present study, the tissue localization of PDGF beta receptor expression was studied in human breast carcinoma and nonmalignant breast tissues stained using both immunofluorescence and immunoperoxidase techniques. We examined a total of 29 cases of breast carcinomas, which showed both in situ and invasive components. PDGF beta receptor staining was localized in the periepithelial stroma and was particularly intense in regions immediately adjacent to carcinoma in situ components in all tumors examined. A diffuse low level of PDGF beta receptor staining was seen throughout the stroma of eight nonmalignant breast tissues as well as of nonmalignant regions of tumor tissues. Image analysis was used to assess the coincidence of staining of PDGF beta receptor with epithelial or stromal cells in 13 of the 29 tumor tissues studied. Less than 5% of malignant ductal epithelium or myoepithelium showed PDGF beta receptor staining. Analysis with stromal cell type-specific markers indicated significant localization of PDGF beta receptor primarily within alpha smooth muscle actin-staining cells (32%) and vascular endothelial cells (41%) in the periepithelial stroma. PDGF beta receptor positivity was strongly associated with periepithelial stromal cells adjacent to the basement membrane surrounding regions of carcinoma in situ but was less intense in regions of invasive carcinoma where basement membrane was degraded. The absence of PDGF beta receptors on carcinoma cells and their presence in the surrounding stroma suggest a paracrine stimulation of adjacent stromal tissue by malignant epithelial cells in human breast tumors.

Actins↗
PubMed1992

Autoantibodies to endogenous growth hormone in short children (the Wessex Growth Study).

Small stature is associated with low growth hormone secretion, but in most cases the reason is unknown. The commonest cause of hormone insufficiency is autoimmunity, and autoantibodies to hormones are often found where there is autoimmune disease of the corresponding gland. Displaceable growth hormone binding by the sera of 125 short (< 3rd centile) but otherwise normal school entrants was significantly higher (P < 0.05) than by the sera of 100 age-matched children of normal height (10th-90th centile), and binding in 21 (17%) of the small children exceeded the upper limit of 95% of the normal population. Furthermore, urinary growth hormone excretion was significantly lower in the small children (total overnight output 0.6-1.7 ng) compared with controls (1.5-3.7 ng) (P < 0.05) even when corrected for body surface area. Thus, growth hormone binding and growth hormone excretion discriminated between two groups of children selected only on the basis of height. The assay used for growth hormone binding was specific for IgG, suggesting that the binding factor was antibody. Autoimmunity merits further investigation as a basis for poor growth.

Autoantibodies↗
PubMed1990

A medium for the isolation, enumeration and rapid presumptive identification of injured Clostridium perfringens and Bacillus cereus.

A blood-free egg yolk medium (BCP) containing pyruvate, inositol, mannitol and a bromocresol purple indicator in a nutrient agar base has been developed to initiate the growth of Clostridium perfringens. It is comparable to blood agar for the growth of normal, chilled stored vegetative cells and heat-injured spores of Cl. perfringens and Bacillus cereus. It has the advantage over blood agar in exhibiting presumptive evidence of Cl. perfringens (production of lecithinase and inositol fermentation) after an overnight incubation at 43 degrees - 45 degrees C. Pyruvate, catalase and other hydrogen peroxide degraders were found to remove toxins rapidly formed in media exposed to air and light. Free radical scavengers of superoxide, hydroxyl ions and singlet oxygen were ineffective. Without scavengers the formation of 10-20 micrograms/ml hydrogen peroxide in the exposed medium was indicated and found lethal to injured Cl. perfringens. The BCP medium has been used successfully for the rapid identification and enumeration of Cl. perfringens in foods and faeces from food poisoning outbreaks and cases of suspected infectious diarrhoea. Greater recovery of severely injured vegetative Cl. perfrigens could be obtained by pre-incubation at 37 degrees C of inoculated media for 2-4 h followed by overnight incubation at 43 degrees - 45 degrees C. Tryptose-sulphite-cycloserine and Shahidi-Ferguson-perfringens agar base were found to inhibit the growth of several strains of injured vegetative Cl. perfringens. This was not completely overcome by the addition of pyruvate. The inclusion of mannitol also allows the medium to be used for the presumptive identification of B. cereus. Growth and lecithinase activity are profuse on BCP. Heat-injured spores are recovered equally well on BCP and blood agar. A scheme for the identification of some other clostridia on BCP is presented.

Bacillus cereus↗
PubMed1989

An enzyme-linked immunosorbent assay (ELISA) for the measurement of serum antibodies to growth hormone. The Wessex Growth Study.

A solid-phase enzyme-linked immunosorbent assay for measuring antibodies to growth hormone (GH) was developed, with occasional use and long shelf-life in mind. With coating protein concentration optimised, the standard curve was linear over a 25-fold range of concentration. The interassay coefficient of variation ranged from 14.4% to 9.3%. The specificity of the assay was confirmed by the substitution of insulin for GH as coating protein and by preabsorption of sera with GH coupled covalently to Sepharose beads. There was no binding signal with insulin and absorption was dose dependent, maximum (greater than 80% complete) with 2 x 10(4) micrograms GH/ml undiluted serum. The assay was simple to perform, cheap and reliable.

Antibodies↗
PubMed1985

Nucleolar cycles during the fifth stadium in Manduca epidermis.

The changing pattern of nucleolar structure in the epidermal cells of Manduca sexta has been correlated with hormonal changes taking place during the fifth stadium. The epidermal nucleoli show three cycles of development, the first and third of which occur at the beginnings of the intermoult and moult phases respectively and are related to larval and pupal syntheses. The second phase occurs in the middle of the stadium but prior to the onset of wandering and commitment to pupation. A phase of mitosis separates the second and third cycles. The three cycles thus correspond in time to those found in Calpodes. The three cycles of nucleolar change are superimposed over nuclear changes relating to the degree of ploidy. Each phase begins with an expansion of the condensed nucleoli to form lobed rings and then necklaces. In the first phase (day 0-3), the rings and necklaces progress to form threaded networks. Both rings and networks have many ribosomal precursor granules that are lacking in condensed nucleoli. The rings and networks are therefore presumed to be more active in rRNA synthesis than the condensed state. The first and third phases of nucleolar change occur after elevated titres of haemolymph ecdysteroid. Post-thoracic ligation of animals at ecdysis blocks nucleolar changes as well as the appearance of polyploid nuclei. Nucleolar changes may be a primary response of the epidermis to stimulation by ecdysone.

Animals↗