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Biomedical subjects

D A Wolf

Publications and source records attributed to D A Wolf.

At least 55 records · Page 3Linked to original sources
PubMed1993

Reduced shear stress: a major component in the ability of mammalian tissues to form three-dimensional assemblies in simulated microgravity.

BHK-21 cells were cultured under various shear stress conditions in an Integrated Rotating-Wall Vessel (IRWV). Shear ranged from 0.5 dyn/cm2 (simulated microgravity) to 0.92 dyn/cm2. Under simulated microgravity conditions, BHK-21 cells complexed into three-dimensional cellular aggregates attaining 6 x 10(6) cells/ml as compared to growth under 0.92 dyn/cm2 conditions. Glucose utilization in simulated microgravity was reduced significantly, and cellular damage at the microcarrier surface was kept to a minimum. Thus, the integrated rotating wall vessel provides a quiescent environment for the culture of mammalian cells.

Animals↗
PubMed1993

Transcriptional and posttranscriptional regulation of human androgen receptor expression by androgen.

Autoregulation is a control mechanism common to several proteins of the steroid/thyroid hormone receptor superfamily. In this work, the effect of androgens and antiandrogens on the expression of the human androgen receptor (hAR) in prostate and breast cancer cell lines was studied. Northern blot analysis revealed a decrease in hAR steady state RNA levels in LNCaP cells by 3.3 nM of the synthetic androgen mibolerone. Maximal down-regulation of hAR RNA to 30% of control levels occurred 48 h after hormone addition. T47D breast cancer cells showed a similar effect with mibolerone, while hAR expression in normal skin fibroblasts did not respond to androgen treatment. As shown by nuclease S1 analysis, hAR transcripts initiate at three principal start sites, all of which are equally sensitive to androgen. Steroidal as well as nonsteroidal antiandrogens were capable of partially antagonizing androgen-mediated hAR RNA down-regulation in LNCaP and T47D cells, while not exerting a significant effect when administered alone. While hAR RNA stability was increased by hormone, nuclear run-on analysis revealed a 4-fold reduction of hAR gene transcription 96 h after androgen treatment. Although decreased hAR RNA levels did not coincide with a parallel decrease in AR protein levels, analysis of androgen-inducible reporter constructs demonstrated that prolonged androgen administration to cells results in a progressively impaired sensitivity of the intracellular androgen response mechanism. These results show that prolonged androgen exposure leads, besides its effect on hAR RNA levels, to functional inactivation of the AR. Thus, in vivo, posttranslational control of AR activity appears to be a novel mechanism of negative autoregulation of androgen effects on gene expression.

Androgens↗
PubMed1993

Rotating-wall vessel coculture of small intestine as a prelude to tissue modeling: aspects of simulated microgravity.

A new low shear stress, low turbulence microcarrier culture system has been developed at NASA's Johnson Space Center that permits large-scale three-dimensional tissue culture. Tissue culture bioreactors called rotating-wall vessels were used in conjunction with multicellular cocultivation to develop a unique in vitro tissue-modeling system. Normal small intestine epithelium and mesenchymal cells were cocultivated on Cytodex-3 microcarriers and were initiated in two phases. Normal small intestine mesenchymal cells were inoculated into the rotating-wall vessel at 2 x 10(5) cells/ml and allowed to attach and proliferate for 2 to 3 days. Normal small intestine epithelium was then added at an innoculum of 2 x 10(5) cells/ml and cultivation continued for 30 to 40 days. These cocultures attained cell numbers of 4-6 x 10(6) cells/ml and differentiated to form tissue-like masses of 0.4-0.5 cm with minimal necrosis. The masses displayed apical brush borders, differentiated epithelial cells, cellular polarity, extracellular matrix, and basal lamina. Verification of mesenchymal and epithelial cell expression was determined by immunocytochemistry and scanning electron microscopy. These data suggest that the rotating-wall vessel affords a new tissue culture model for investigation of growth, regulatory, and differentiation processes within normal tissues.

Biomarkers↗
PubMed1992

Cell culture for three-dimensional modeling in rotating-wall vessels: an application of simulated microgravity.

High-density, three-dimensional cell cultures are difficult to grow in vitro. The rotating-wall vessel (RWV) described here has cultured BHK-21 cells to a density of 1.1 X 10(7) cells/ml. Cells on microcarriers were observed to grow with enhanced bridging in this batch culture system. The RWV is a horizontally rotated tissue culture vessel with silicon membrane oxygenation. This design results in a low-turbulence, low-shear cell culture environment with abundant oxygenation. The RWV has the potential to culture a wide variety of normal and neoplastic cells.

Animals↗
PubMed1992

Morphologic differentiation of colon carcinoma cell lines HT-29 and HT-29KM in rotating-wall vessels.

A new low shear stress microcarrier culture system has been developed at NASA's Johnson Space Center that permits three-dimensional tissue culture. Two established human colon adenocarcinoma cell lines, HT-29, an undifferentiated, and HT-29KM, a stable, moderately differentiated subline of HT-29, were grown in new tissue culture bioreactors called Rotating-Wall Vessels (RWVs). RWVs are used in conjunction with multicellular cocultivation to develop a unique in vitro tissue modeling system. Cells were cultivated on Cytodex-3 microcarrier beads, with and without mixed normal human colonic fibroblasts, which served as the mesenchymal layer. Culture of the tumor lines in the absence of fibroblasts produced spheroidlike growth and minimal differentiation. In contrast, when tumor lines were co-cultivated with normal colonic fibroblasts, initial growth was confined to the fibroblast population until the microcarriers were covered. The tumor cells then commenced proliferation at an accelerated rate, organizing themselves into three-dimensional tissue masses that achieved 1.0- to 1.5-cm diameters. The masses displayed glandular structures, apical and internal glandular microvilli, tight intercellular junctions, desmosomes, cellular polarity, sinusoid development, internalized mucin, and structural organization akin to normal colon crypt development. Differentiated samples were subjected to transmission and scanning electron microscopy and histologic analysis, revealing embryoniclike mesenchymal cells lining the areas around the growth matrices. Necrosis was minimal throughout the tissue masses. These data suggest that the RWV affords a new model for investigation and isolation of growth, regulatory, and structural processes within neoplastic and normal tissue.

Adenocarcinoma↗
PubMed1992

Transcriptional down-regulation of c-myc in human prostate carcinoma cells by the synthetic androgen mibolerone.

The mechanism of down-regulation of c-myc RNA associated with androgen-induced suppression of the transformed phenotype in the human prostate carcinoma cell line LNCaP was investigated. The synthetic androgen mibolerone (7 alpha-17 alpha-Dimethyl-19-nortestosterone) reversibly inhibits the proliferation of LNCaP cells and, from 12-72 h after hormone addition reduces the level of c-myc transcripts to a few per cent of controls. P1, P2, and P0 c-myc transcripts decline at the same rate, whereas P3 transcripts are much less hormone sensitive. Nuclear run-on analysis revealed that c-myc is down-regulated at the level of transcription initiation in LNCaP cells. The level of c-myc transcripts prevailing in untreated control cells can be restored in androgen-induced cells by excess antiandrogen, indicating the involvement of the androgen receptor in c-myc down-regulation.

Blotting, Northern↗
PubMed1992

Transcriptional regulation of prostate kallikrein-like genes by androgen.

Using gene-specific synthetic oligonucleotides the expression and regulation of kallikrein-like genes in the human prostatic cancer cell line LNCaP were studied. Prostate-specific antigen (PSA) and human glandular kallikrein (hGK-1) together constitute a subfamily of serine proteases exclusively produced in the human prostate. RNA analysis revealed that both genes are expressed in LNCaP cells with PSA basal levels being 2-fold higher than hGK-1 levels. Both mRNAs are induced over a period of 24 h in the presence of 3.3 nM of the synthetic androgen mibolerone. Stimulation of PSA RNA is about 5-fold, whereas hGK-1 stimulation is less pronounced. Nuclear run-on analysis revealed that androgen induction of kallikrein-like genes in LNCaP cells is a rapid event (less than 3 h) occurring at the level of transcription initiation. Treatment of cells with cycloheximide demonstrates that, while PSA/hGK-1 basal transcription strictly depends on continuous protein synthesis, transcriptional induction by androgen does not. This suggests the direct involvement of the androgen receptor in the induction process independent of additional labile protein factors necessary for kallikrein basal transcription. A binding motif is present in the PSA and hGK-1 promoters, closely resembling the consensus sequence for steroid-responsive elements. The androgen antagonist cyproterone acetate was also able to stimulate transcription of kallikrein-like genes in LNCaP cells. In contrast, androgen-dependent transcriptional suppression of the protooncogene c-myc was strongly counteracted by cyproterone acetate. Thus, antiandrogens act differentially on androgen-regulated prostate-specific (PSA, hGK-1) and growth-related (c-myc) gene expression in LNCaP cells.

Androgen Antagonists↗
PubMed1991

Synthetic androgens suppress the transformed phenotype in the human prostate carcinoma cell line LNCaP.

Experiments have been designed to investigate hormonal effects on the human prostatic carcinoma cell line LNCaP in the presence of complete foetal calf serum. At physiological concentrations (3.3 x 10(-9)M), several derivatives of 17 alpha-methyl-testosterone led to a significant reduction of cell proliferation, inhibition of colony formation in soft agar, change of morphology, induction of a prostate specific mRNA and down-regulation of c-myc RNA. Two different antiandrogens, hydroxyflutamide and cyproterone acetate, were capable of reversing the effects exerted by the synthetic androgens on growth properties. The proliferation rate of control cells devoid of androgen receptor was not inhibited by synthetic androgens. Our results indicate that the cellular androgen response mechanism of LNCaP cells is intact and that synthetic androgens elicit androgen receptor mediated suppression of the transformed phenotype. Rare cases of remission of prostatic cancer on androgen treatment have been reported. LNCaP cells may be a model of an uncommon class of prostatic cancer which responds favourably to androgen treatment.

Antigens, Neoplasm↗
PubMed1991

Intergenerational transfers: a question of perspective.

Informal intergenerational transfers have traditionally been examined from the perspective of the older generation; more recent studies have proceeded from the perspective of adult children. Drawing upon principles of formal demography, we establish the mathematical relationship between the two generations' perspectives. We then consider the importance of generational perspective with regard to prevalence estimates of intrafamily transfers. Transfers examined include coresidence, household and financial assistance, and personal caregiving. Results have implications for projection of future trends in intrafamily transfers and for data collection.

Adult↗
PubMed1991

Correlations between frequencies of kin.

Recent years have seen the development of formal and microsimulation models of the structure and dynamics of kin networks. These models generally assume uncorrelated fertility within and across generations. Several sets of real data, however, show positive correlations between the frequencies of various categories of kin. This paper uses formal models to calculate the correlations that will exist between certain categories of kin even if mothers and daughters have independent fertility. Mechanisms by which fertility might be transmitted from mothers to their daughters are considered and the implications for kin correlations are evaluated.

Adolescent↗
PubMed1990

Family, households, and care arrangements of frail older women: a structural analysis.

Previous research has examined determinants of the living arrangements and the informal-care arrangements of older women; research on care arrangements has often taken living arrangements as given. Here we consider each separately, then go on to analyze the simultaneous determinants of living and care arrangements. Factors influencing these outcomes can be categorized as indicators of opportunities, resources, needs, or preferences. Of particular interest is the extent to which kin availability--specifically, the existence of living children--constrains opportunities, the role of financial resources, and the consequences of needs as revealed by levels of physical and mental disability. Our analysis consists of multinomial-logit models estimated with data from the 1982 National Long-Term Care Survey. The results indicate the importance of kin availability, with striking differences in the living and care arrangements between childless and other older women. Among those with children, there are less striking but consistent differences according to the number and sex composition of living children. Finally, variables representing needs for care are generally the strongest predictors of all the outcomes analyzed.

Activities of Daily Living↗
PubMed1990

Household patterns of older women. Some international comparisons.

Comparative analyses based on aggregate data have shown that the percentage of older women living alone has risen dramatically during recent decades, a pattern repeated in many European and North American countries. This article investigates the correlates of the decision to live alone, using individual-level data from five countries and a parallel analytic approach. The major categories of factors analyzed here are kin availability, financial resources, and disability and health status. Several common patterns of findings emerge for the group of countries considered: Larger kin networks and the presence of severe disabilities reduce the probability of living alone, whereas higher income increases the probability of living alone. Despite these similarities in individual-level correlates, there remain some differences across countries in the levels of single-person households, and these might be attributable to macrolevel forces such as housing and social welfare policies.

Aged↗
PubMed1989

Kinship patterns and household composition: older unmarried Hungarian women, 1984.

Household composition of older unmarried women in Hungary is analyzed using data from the 1984 microcensus. The principal determinants of household composition investigates are 1) kin availability--the number of living children, siblings, and parents; 2) health status; 3) marital status; 4) age; and 5) income. A multinomial logit model distinguishing among 5 household types reveals that number of children, severe disabilities, age, and income are all strongly related to household composition. Trends in fertility and mortality patterns suggest that kinship patterns will change in coming years; these results imply that household composition will, in turn, change as well.

Adult↗
PubMed1989

Living arrangements and family networks of older women in Italy.

As in many other industrialized countries, population aging in Italy is disproportionately a phenomenon associated with unmarried women, mainly widows. This article examines the extent to which older unmarried women live alone, and the extent to which they receive help in everyday tasks from others outside their households, using data from a large Italian household sample survey conducted in 1983. Older women can either live alone or with others, and may or may not receive external help in either case; thus there are four distinct combinations of outcomes analyzed. In both descriptive bivariate analysis and a multivariate model of the outcomes, we find pronounced differences in behavior according to region of residence, educational level, age, degree of disability, work experience, and pension receipt. The findings indicate the importance of family as a source of help and/or co-residence in situations of need.

Activities of Daily Living↗
PubMed1988

Case-control study of proximal and distal colon cancer and diet in Wisconsin.

The relationship between diet and subsite-specific colon cancer was investigated using dietary histories obtained from a statewide, population-based sample of 152 proximal colon cancer patients, 201 distal colon cancer patients and 618 general population controls. The results do not support hypotheses that (1) dietary fat and cholesterol are more strongly related to proximal colon cancer and (2) vegetables and other dietary sources of fiber are more strongly associated with distal colon cancer. Vegetable consumption over lifetime was consistently protective for both proximal and distal colon cancer. Odds ratios and 95% confidence intervals for the most significant dietary factors (based on high vs. low consumption) for proximal colon cancer were: salad, 0.29 (0.17, 0.48); miscellaneous vegetables, 0.58 (0.35, 0.97); cruciferous vegetables, 0.59 (0.35, 0.97); processed lunchmeat, 2.04 (1.31, 3.17); pan-fried foods, 1.79 (1.15, 2.80); eggs, 1.75 (1.02, 2.99) and for distal colon cancer they were: salad, 0.43 (0.28, 0.67); cruciferous vegetables, 0.44 (0.28, 0.71); cheese, 0.62 (0.40, 0.96); processed lunchmeat, 1.79 (1.17, 2.73); pan-fried foods, 1.55 (1.03, 1.27). The results support recommendations that the "prudent diet" (low-fat, high-vegetable) may reduce colon cancer risk.

Adolescent↗
PubMed1988

The multistate life table with duration-dependence.

"A method for generalizing the multistate, or increment-decrement, life table to include rates which depend upon duration of exposure to risk, as well as upon age, is proposed. The method is built upon the linear approximation, called the linear integration hypothesis, developed mainly by Rogers and his colleagues.... It is possible to derive several new summary indices of the life-table cohort's history, such as the mean and median time in current status, at any age. The method is illustrated using a simple four-state marital-status model which has appeared often in the literature; here, rates of divorce and widowhood vary by duration of marriage as well as age." An example is demonstrated using 1984 period data for women in Finland aged 15-50. (SUMMARY IN FRE)

Age Factors↗
PubMed1988

Household composition choices of older unmarried women.

This article extends previous research on the household composition of older unmarried women, using a statistical model that treats each of a woman's surviving children as a distinct potential provider of a shared household. Additional possibilities--living alone, living with other nuclear-family relatives, and living with others--are also recognized, providing a varied range of household-structure opportunities for older women. The approach allows us to identify individual child attributes associated with the propensity to coreside with the older unmarried mother. The results confirm earlier findings regarding the importance of income, age, and disability status as determinants of the household composition of older women. We find, however, that unmarried children, especially sons, are more likely to share a household with an elderly mother than are married children. Working reduces the likelihood that a married daughter will live with her older mother. Overall, the findings suggest that the attributes, more so than the sheer numbers, of living children influence the household structure of their mothers.

Aged↗