Betty E. Skipper

Development of the aging cell surface: variation in the distribution of intramembrane particles with progressive age of human diploid fibroblasts.

Cell membranes of early and late passage human embryo fibroblasts were freeze-fractured and the distribution of intramembrane particles was compared using statistical methods. Aged cells do not exhibit dramatic differences in total numbers of intramembrane particles when compared to younger cells. However, significant alterations develop with age between the distribution of particles on P and E fracture faces. Younger cells exhibit more particles on their P faces than corresponding membrane halves from older cells. In contrast, the E fracture faces of aged cells have significantly more particles than do corresponding surfaces of younger cell membranes. The observations suggest that properties of membrane fluidity may change with increased cellular age.

Development of the aging cell surface: Reduction of gap junction-mediated metabolic cooperation with progressive subcultivation of human embryo fibroblasts (IMR-90)

Abstract Gap junctions develop between IMR-90 fibroblasts in cultures which have been serially subcultivated until reduced proliferative rates are produced. However, distribution is sparse and the junctions exhibit relatively few component subunits. To investigate whether a concomitant reduction in the ability of senescent cells to maintain metabolic coupling occurs, autoradiography was used to determine the relative exchange of [ 3 H]uridine nucleotides between early and late passage cells. In addition, the rate of reappearance of gap junctions between dissociated cells of both sample groups was examined by freeze-fracturing and electron microscopy. Gap junctions form between young cells approx. 1 h after reassociation in culture. Structurally complete gap junctions are present within 2 h. In contrast, membranes of cells in senescent cultures do not exhibit particle arrays typical of forming junctions until one or more hours of incubation. Small but assembled junctions are observed after 4 or more hours of reassociation. Autoradiography reveals some 70% of young cells to be receiving label from young donors following a 4 h period of metabolic exchange, whereas only 30% of older cells receive label after comparable periods of incubation. Statistical analyses of reciprocal experiments using young donor/old recipients and old donor/young recipients suggest that recipient cells may have a slightly larger effect on the exchange reaction than donor cells. We conclude that contact-mediated metabolic cooperation is reduced with increased serial subcultivation of cells.

Phase II and pharmacokinetic study of high-dose methotrexate in the treatment of advanced gynecologic malignancy: A Southwest Oncology Group trial

Fifteen patients with advanced or recurrent gynecologic malignancy were treated with high-dose methotrexate (HDMTX) (1-8 g/M2) and citrovorum factor rescue (10-100 mg/M2). One complete response (13%) and two improved responses occurred in eight patients (25%) with squamous cell carcinoma and one of seven patients (14%) with nonsquamous nontrophoblastic carcinoma had stable disease for 7 months. The median duration of survival in the squamous group was 9 months and in the nonsquamous groups 6.5 months. Mean serum MTX concentrations were proportional to the doses administered and typical two compartment plasma disappearance curves were seen. Adverse toxic reactions were not observed at serum MTX levels less than 7.8 X 10(-7) M at 24 hr and 1 X 10(-7) M at 48 hr post-MTX. Hematopoietic toxicity occurred most frequently with leukopenia observed in 19.5% of courses. Hepatic, renal, gastrointestinal, and dermatologic toxicities were observed infrequently. Drug-induced nephrotoxicity occurred in one patient and possibly related leukoencephalopathy occurred in another patient. On the basis of the relatively low response rate observed in this trial and the high expense of HDMTX therapy, the value of such therapy may be limited in advanced nontrophoblastic gynecologic cancer.

The impact of revisions in vitamin a content data on estimates of nutrient intake

Abstract We have assessed the implications for epidemiological investigations of replacing old USDA Handbook 8 values by the new ones. Using food frequency data on 34 foods rich in vitamin A from 1252 subjects, indices of average daily intake of retinol, carotene and total vitamin A were calculated using the old and new contents. The carotene and total vitamin A indices based on the new data were significantly increased whereas the retinol index decreased slightly. However, the relative intakes among the subjects for all three nutrients were stable. Spearman rank correlation coefficients between old and new indices were all above 0.90. Agreement of old and new index terciles was 77% for total vitamin A, 79% for carotene, and 89% for retinol. Implications for nutritional research are discussed.

Suppression of rabbit peritoneal macrophage migration by heat-labileE. coli toxin

Migration of rabbit peritoneal macrophages toward casein-serum was inhibited by preincubation of the cells with heat-labile toxin ofEscherichia coli in direct relationship to the concentration of toxin in the incubation mixture. Cells preincubated with heated toxin or with toxin-antiserum migrated the same as those which had been incubated in toxin-free media. Toxin-preincubated cells had levels of cyclic AMP which were increased in direct relationship to the concentration of toxin in the preincubation mixture. Heated toxin failed to induce increased levels of cAMP in the cells at the highest concentration tested.