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Biomedical subjects

B Elliott

Publications and source records attributed to B Elliott.

At least 37 records · Page 2Linked to original sources
PubMed1998

c-Src kinase activity is required for hepatocyte growth factor-induced motility and anchorage-independent growth of mammary carcinoma cells.

Overexpression and amplification of hepatocyte growth factor (HGF) receptor (Met) have been detected in many types of human cancers, suggesting a critical role for Met in growth and development of malignant cells. However, the molecular mechanism by which Met contributes to tumorigenesis is not well known. The tyrosine kinase c-Src has been implicated as a modulator of cell proliferation, spreading, and migration; these functions are also regulated by Met. To explore whether c-Src kinase is involved in HGF-induced cell growth, a mouse mammary carcinoma cell line (SP1) that co-expresses HGF and Met and a nonmalignant epithelial cell line (Mv1Lu) that expresses Met but not HGF were used. In this study, we have shown that c-Src kinase activity is constitutively elevated in SP1 cells and is induced in response to HGF in Mv1Lu cells. In addition, c-Src kinase associates with Met following stimulation with HGF. The enhanced activity of c-Src kinase also correlates with its ability to associate with Met. Expression of a dominant negative double mutant of c-Src (SRC-RF), lacking both kinase activity (K295R) and a regulatory tyrosine residue (Y527F), in SP1 cells significantly reduced c-Src kinase activity and strongly blocked HGF-induced motility and colony growth in soft agar. In contrast, expression of the dominant negative c-Src mutant had no effect on HGF-induced cell proliferation on plastic. Taken together, our data strongly suggest that HGF-induced association of c-Src with Met and c-Src activation play a critical role in HGF-induced cell motility and anchorage-independent growth of mammary carcinomas and further support the notion that the presence of paracrine and autocrine HGF loops contributes significantly to the transformed phenotype of carcinoma cells.

Animals↗
PubMed1998

Autocrine secretion of TGF-beta 1 and TGF-beta 2 by pre-adipocytes and adipocytes: a potent negative regulator of adipocyte differentiation and proliferation of mammary carcinoma cells.

We have developed an in vitro system to examine the influence of adipocytes, a major mammary stromal cell type, on the growth of a murine mammary carcinoma, SP1. Previously, we have shown that 3T3-L1 adipocytes release a mitogenic factor, hepatocyte growth factor, which strongly stimulates proliferation of SP1 cells. We now show that 3T3-L1 pre-adipocytes secrete active inhibitory molecules which inhibit DNA synthesis in SP1 cells. In addition, latent inhibitory activity is present in conditioned media (CM) from both pre-adipocytes and adipocytes, and is activated following acid treatment. CM also inhibited DNA synthesis in Mv1Lu wild type epithelial cells, but not DR27 mutant epithelial cells which lack TGF-beta type II receptor. Inhibitory activity of CMs was partially abrogated by neutralizing anti-TGF-beta1 and anti-TGF-beta2 antibodies, and was removed following ultrafiltration through membranes of 10,000 Mr but not 30,000 Mr pore size. These results show that the inhibitory effect on DNA synthesis is mediated by TGF-beta1-like and TGF-beta2-like molecules. In addition, acid-treated CM as well as purified TGF-beta inhibited differentiation of pre-adipocytes. Untreated pre-adipocyte CM, but not mature adipocyte CM, spontaneously inhibited adipocyte differentiation. Together, these findings indicate that pre-adipocytes spontaneously activate their own secreted TGF-beta, whereas mature adipocytes do not, and suggest that activation of TGF-beta has a potent negative regulatory effect on adipocyte differentiation and tumor growth. Thus, TGF-beta may be an important modulator of tumor growth and adipocyte differentiation via both paracrine and autocrine mechanisms. These findings emphasize the importance of adipocyte-tumor interactions in the regulation of tumor microenvironment.

3T3 Cells↗
PubMed1998

Gene conversion tracts from double-strand break repair in mammalian cells.

Mammalian cells are able to repair chromosomal double-strand breaks (DSBs) both by homologous recombination and by mechanisms that require little or no homology. Although spontaneous homologous recombination is rare, DSBs will stimulate recombination by 2 to 3 orders of magnitude when homology is provided either from exogenous DNA in gene-targeting experiments or from a repeated chromosomal sequence. Using a gene-targeting assay in mouse embryonic stem cells, we now investigate the effect of heterology on recombinational repair of DSBs. Cells were cotransfected with an endonuclease expression plasmid to induce chromosomal DSBs and with substrates containing up to 1.2% heterology from which to repair the DSBs. We find that heterology decreases the efficiency of recombinational repair, with 1.2% sequence divergence resulting in an approximately sixfold reduction in recombination. Gene conversion tract lengths were examined in 80 recombinants. Relatively short gene conversion tracts were observed, with 80% of the recombinants having tracts of 58 bp or less. These results suggest that chromosome ends in mammalian cells are generally protected from extensive degradation prior to recombination. Gene conversion tracts that were long (up to 511 bp) were continuous, i.e., they contained an uninterrupted incorporation of the silent mutations. This continuity suggests that these long tracts arose from extensive degradation of the ends or from formation of heteroduplex DNA which is corrected with a strong bias in the direction of the unbroken strand.

Animals↗
PubMed1998

Decreasing length of stay: are there effects on outcomes of psychiatric hospitalization?

OBJECTIVE: The authors compared hospital outcomes for depressed patients hospitalized between 1988 and 1996. METHOD: Between 1988 and 1996, 206 depressed patients in three cohorts were evaluated at admission; of these, 161 (78.2%) were evaluated at discharge and 119 (78.3% of those followed [N = 152]) 1 month later. Evaluation consisted of measures of symptoms, global functioning, self-concept, ego defenses, work and social functioning, and readmission. RESULTS: Lengths of stay significantly declined over time (26.5 versus 19.5 versus 8.3 days). At discharge, the most recently hospitalized group showed higher residual depression and lower residual global functioning scores than the other groups. Other measures did not differ among the groups at discharge. One month after discharge, the shortest-stay group continued to show lower global functioning, as well as lower quantity of work functioning. Readmission rates were equal. Within the shortest-stay group, no differences in outcome were found between patients treated in a partial hospital and those not so treated. CONCLUSIONS: Improvement during very brief admission is comparable to that in longer stays on many aspects of functioning. However, depressed patients discharged more quickly show significantly higher residual levels of depressive symptoms and lower levels of global functioning, which may place them at greater risk for adverse outcomes in the immediate posthospital period.

Adult↗
PubMed1998

Useful sites on the Internet.

Internet medical sites offer the physician opportunities to improve patient care, to obtain continuing education and medical management services, and the ability to communicate with colleagues. This paper discusses how to choose the best sites, and highlights some valuable federal, university and commercial medical sites found on the Internet.

Computer Communication Networks↗
PubMed1998

Full text core medical journals on the Internet.

Peer reviewed, core medical journals have an increasing presence on the Internet. A significant number of them offer full text articles without fees. This paper indexes these resources, and discusses ways to keep the list current.

Computer Communication Networks↗
PubMed1998

Complementary or Alternative medicine and the Internet.

Complementary or Alternative Medicine (CAM) is being used with increasing frequency in the United States. This paper describes what CAM is, and catalogues mainstream medical Web sites. These online resources contain extensive information on CAM, and will provide a means to stay current with this sometimes-new yet often ancient area of medicine.

Complementary Therapies↗
PubMed1997

Screening for domestic violence in a rural family practice.

This study evaluates the effectiveness of a screening form used to assess the incidence of current and past domestic abuse among patients seen in a rural family practice. Two of nine family physicians screened most adult women they saw at a rural primary care clinic for three months in early 1996. Of the 280 women who completed surveys, 94(34%) reported experiencing physical or emotional abuse at some time in the past. Twenty-three (8%) reported physical abuse within the past year. Fourteen women (5%) reported being currently afraid of their partner or someone else. Although current or past abuse was seen across all groups, women reporting abuse were more likely to be unmarried, younger, and on medical assistance. They were also more likely to have children at home. We concluded that the prevalence of women reporting current abuse in a rural family practice is sufficient to warrant mass screening.

Adult↗
PubMed1996

Phosphatidylinositol 3-kinase activity is required for hepatocyte growth factor-induced mitogenic signals in epithelial cells.

Phosphatidylinositol (PI) 3-kinase is an important enzyme implicated in growth factor-stimulated intracellular signaling. In this study we have shown that hepatocyte growth factor (HGF) induces a rapid tyrosine phosphorylation of PI 3-kinase and association with HGF receptor/Met in Mv1Lu epithelial cells. Murine mammary carcinoma (SP1) cells, which co-express HGF and HGF receptor/Met, showed sustained phosphorylation of PI 3-kinase. Wortmannin, a potent inhibitor of PI 3-kinase, inhibited HGF-induced PI 3-kinase activity, proliferation of Mv1Lu cells, and spontaneous growth of SP1 cells in a dose-, and time-dependent manner. Transfection of a dominant negative mutant p85 (Deltap85) subunit of PI 3-kinase into SP1 cells strongly inhibited HGF-stimulated proliferation and PI 3-kinase activity. However, wortmannin did not influence HGF-induced c-Jun expression. Furthermore, HGF stimulated S6 kinase activity, but its activity was not required for HGF-induced proliferation. Overall, these results suggest that HGF-induced PI 3-kinase activity is important for the mitogenic action of HGF in epithelial cells and further demonstrate that expression of c-Jun is not influenced by inhibition of PI 3-kinase activity.

Animals↗
PubMed1996

Fibronectin fibrils and growth factors stimulate anchorage-independent growth of a murine mammary carcinoma.

Stromal cells are important regulators of mammary carcinoma growth and metastasis. We have previously shown that a 3T3-L1 adipocyte cell line secretes hepatocyte growth factor (HGF), which stimulates proliferation of a murine mammary carcinoma (SP1) in monolayer cultures (DNA Cell Biol. 13, 1189-1897, 1994). We now examine the role of growth factors and the extracellular matrix protein fibronectin in stimulation of anchorage-independent growth of SP1 cells. Purified transforming growth factor-beta (TGF-beta) stimulated significant colony growth in soft agar cultures, whereas HGF had a lesser effect. Analysis by confocal microscopy revealed that carcinoma cell colonies contained extracellular microfibrils composed of fibronectin. Partial depletion of fibronectin from 7% FBS/agar cultures reduced the number of colonies; colony growth could be recovered by adding back exogenous fibronectin. Addition of the 70-kDa N-terminal fragment of fibronectin, which inhibits fibronectin fibril formation, reduced growth of SP1 cell colonies, but an 85-kDa fragment containing the cell binding domain did not inhibit colony growth. These findings indicate that deposition of extracellular fibronectin fibrils is necessary, but not sufficient, for anchorage-independent growth of SP1 mammary carcinoma cells; growth factors are also required. SP1 cells had less fibronectin mRNA and secreted less fibronectin protein under anchorage-independent conditions than under anchorage-dependent conditions, as determined by Northern blotting and immunoprecipitation analysis. Thus, both growth factors (HGF and TGF-beta) and fibronectin may be important regulators of paracrine stimulation by stromal cells of anchorage-independent growth of mammary carcinoma cells.

3T3 Cells↗
PubMed1996

Hepatocyte growth factor (HGF) is a copper-binding protein: a facile probe for purification of HGF by immobilized Cu(II)-affinity chromatography.

Hepatocyte growth factor (HGF) is a multifunctional protein expressed in a variety of cell types and tissues. Here we describe a novel one-step method to separate and identify HGF, based on a unique interaction between HGF and Cu(II). Conditioned medium (CM) from mouse 3T3-L1 adipocytes which contains HGF or purified human recombinant HGF was used for analysis. Mouse 3T3-L1 adipocyte CM was applied to a Cu(II)-affinity column and rinsed with equilibration buffer. HGF was then eluted with 10 mM imidazole. Fractions eluted from the column were analyzed by SDS-PAGE. Analysis by silver staining revealed an 85kDa protein. Further analysis by Western blotting with polyclonal anti-HGF IgG demonstrated that this protein corresponded to HGF. Human recombinant HGF, when applied to a Cu(II)-affinity column, showed a stronger affinity to Cu(II) than did mouse HGF. Human recombinant HGF was not eluted from the Cu(II) column with either 10 or 20 mM imidazole; however, it was readily eluted with 40 mM imidazole. The percentages of recovery of both human and mouse HGF were greater than 90%. Both mouse HGF and human recombinant HGF eluted from the Cu(II)-affinity column retained their biological activity as measured by HGF-induced cell proliferation of Mv1Lu cells. Our findings provide the first evidence that HGF is a copper-binding protein and that a Cu(II)-affinity column can be used for efficient one-step purification of biologically active HGF.

Adipocytes↗
PubMed1996

The role of upper limb segment rotations in the development of racket-head speed in the squash forehand.

In the squash forehand drive, the contribution that each of the upper limb segment's anatomical rotations make to racket-head velocity towards the front wall (x-direction) during the forward swing and at impact were calculated. Eight squash players (3 females, 5 males) capable of hitting a high-performance squash forehand drive were filmed at a nominal rate of 300 Hz by two phase-locked Photosonics cameras. The three-dimensional displacement histories of 12 selected landmarks were then calculated using the direct linear transformation approach and three-dimensional individual segment rotations were calculated using vector equations. Internal rotation of the upper arm at the shoulder joint (46.1%), hand flexion at the wrist joint (18.2%) and forearm pronation at the radio-ulnar joint (12.0%) were the major contributors to the mean 30.8 m s-1 x-direction velocity of the centre of the racket-head at impact. Pronation of the forearm at the radio-ulnar joint and extension at the elbow joint both played a significant role in generating racket velocity in the period prior to impact.

Arm↗
PubMed1996

Synergy between trehalose and Hsp104 for thermotolerance in Saccharomyces cerevisiae.

We isolated a mutant strain unable to acquire heat shock resistance in stationary phase. Two mutations contributed to this phenotype. One mutation was at the TPS2 locus, which encodes trehalose-6-phosphate phosphatase. The mutant fails to make trehalose and accumulates trehalose-6-phosphate. The other mutation was at the HSP104 locus. Gene disruptions showed that tps2 and hsp104 null mutants each produced moderate heat shock sensitivity in stationary phase cells. The two mutations were synergistic and the double mutant had little or no stationary phase-induced heat shock resistance. The same effect was seen in the tps1 (trehalose-6-phosphate synthase) hsp104 double mutant, suggesting that the extreme heat shock sensitivity was due mainly to a lack of trehalose rather than to the presence of trehalose-6-phosphate. However, accumulation of trehalose-6-phosphate did cause some phenotypes in the tps2 mutant, such as temperature sensitivity for growth. Finally, we isolated a high copy number suppressor of the temperature sensitivity of tps2, which we call PMU1, which reduced the levels of trehalose-6-phosphate in tps2 mutants. The encoded protein has a region homologous to the active site of phosphomutases.

Amino Acid Sequence↗
PubMed1996

Physician detection of family violence. Do buttons worn by doctors generate conversations about domestic abuse?

Family violence is ubiquitous in our society and, thus, is encountered in all medical practices. The purpose of this study was to ascertain whether physicians wearing buttons with an anti-abuse message have more conversations about violence compared with physicians not wearing such buttons. Six of 11 family practice residents wore Minnesota Medical Association buttons that invited conversations about abuse. For four weeks, all 11 residents recorded daily the number of conversations about violence that occurred in the medical setting. Analyses comparing the two groups showed that the physicians wearing buttons had significantly more conversations than those not wearing buttons (c2 = 9.040, p < 0.005). Physicians wearing buttons had a higher percentage of days with conversations about domestic violence than physicians without buttons (c2 = 7.695, p < 0.01). From the significant p-values documented, we conclude that wearing the buttons increases conversations about family violence and makes physicians more consistent in talking about violence with patients.

Curriculum↗
PubMed1996

Identification of a hepatocyte growth factor autocrine loop in a murine mammary carcinoma.

Constitutive activation of growth factor receptors through autocrine/paracrine mechanisms occurs frequently in human cancers and is thought to play an important role in carcinogenesis. We have demonstrated previously that hepatocyte growth factor (HGF) is a potent mitogenic factor for murine mammary carcinoma (SP1) cells in vitro. We report here an autocrine HGF loop in SP1 cells. HGF receptor/Met is expressed in SP1 cells and is constitutively tyrosine phosphorylated. The phosphorylation of HGF receptor/Met is inhibited when cells are exposed to suramin or anti-HGF IgG. This finding suggests that constitutive tyrosine phosphorylation of HGF receptor/Met is sustained by an extracellular factor, most likely HGF. Using Northern blot and Western blot analysis, we detected expression of a 6-kb HGF mRNA in SP1 cells and a M(r) 85,000 HGF protein in SP1-conditioned medium, respectively. In vitro translation of mRNA from SP1 cells and metabolic labeling confirmed expression and synthesis of HGF by SP1 cells. SP1 cells also invade through Matrigel-coated transwell membranes in an in vitro invasion assay, and invasion of these cells was inhibited by neutralizing anti-HGF IgG. In addition, SP1-conditioned medium induced scatter activity of Madin-Darby canine kidney epithelial cells, and this activity was inhibited by neutralizing anti-HGF IgG. We have also shown that several signaling molecules including phosphatidylinositol 3-kinase, Src, focal adhesion kinase, and phospholipase C-gamma in SP1 cells are constitutively tyrosine phosphorylated, suggesting that coexpression of HGF and HGF receptor/Met may in part contribute to sustained tyrosine phosphorylation of these cytoplasmic proteins in SP1 cells. Our observations in the SP1 model suggest that HGF contributes to growth and invasive phenotypes of mammary carcinomas via both paracrine and autocrine mechanisms.

3T3 Cells↗