Biomedical subjects

D Hecht

Publications and source records attributed to D Hecht.

14 recordsLinked to original sources

PubMed2000

PKC and ERK1/2 regulate amylase promoter activity during differentiation of a salivary gland cell line.

The addition of transforming growth factor alpha (TGFalpha) to a human submandibular gland cell line (HSG) cultured on basement membrane extract Matrigel, synergistically activates the acinar cell-specific salivary amylase promoter. Signaling through beta1 integrins and increased phosphorylation of ERK1/2 are involved in the increased promoter activity. Phorbol-12-myristate-13-acetate (PMA) and thapsigargin increase amylase promoter activity, suggesting that phorbol ester and calcium-dependent protein kinase C (PKC) pathways are also involved. The combination of specific inhibitors of PKC and MEK1 inhibits the amylase promoter. Inhibitors of the calcium-dependent PKC isoforms alpha, beta, and gamma decrease the promoter activity; however, PKCbeta is not detectable in HSG cells. TGFalpha alters the cellular localization of PKCalpha but not -gamma, suggesting PKCalpha is involved in TGFalpha upregulation of the amylase promoter. Furthermore, rottlerin, a PKCdelta-specific inhibitor, increases the promoter activity, suggesting PKC isoforms differentially regulate the amylase promoter. In conclusion, beta1-integrin and TGFalpha signaling pathways regulate the amylase promoter activity in HSG cells. In response to Matrigel and TGFalpha, the activation of both PKCalpha and phosphorylation of ERK1/2 results in synergistic activation of the amylase promoter. Published 2000 Wiley-Liss, Inc.

Amylases↗

PubMed2000

Effects of the novel alphav integrin antagonist SM256 and cis-platinum on growth of murine squamous cell carcinoma PAM LY8.

Increased density of proliferating and migrating tumor cells and neovascular endothelial cells has been associated with tumor progression and poor prognosis in patients with squamous cell carcinoma (SCC). Tumor and neovascular endothelial cells in squamous cell carcinoma have been reported to express integrin heterodimers containing the alphav subunit, which binds to vitronectin and other extracellular matrix proteins that contain the amino acid recognition sequence Arg-Gly-Asp (RGD). In the present study, we examined the effect of the novel non-peptide alphav integrin antagonist SM256 on growth of SCC line PAM LY8 in BALB/c SCID mice, and determined whether SM256 has direct inhibitory effects on growth of murine endothelial and PAM LY8 SCC cells in vitro. SM256 inhibits cell adhesion of murine cells expressing alphavbeta3 and alphavbeta5 integrins in vitro with an IC50 of 35 nM and 30 nM, respectively. Growth of Pam LY8 tumors in vivo was inhibited with 14-day continuous administration of SM256 by subcutaneous osmotic diffusion pump, during which a mean serum concentration of 56 nM was detected. While both murine aortic endothelial cells and PAM LY8 were found to express alphav integrins by fluorescence cytofluorometry, SM256 at 50 nM in MTT assay completely inhibited growth of endothelial cells, but had no significant direct effect on growth of PAM LY8 cells. We compared the effect on growth of PAM LY8 of SM256 infusion versus single agent or combination chemotherapy with a maximally tolerated dose of cis-platinum, which is used as a standard chemotherapy for SCC. When treatment was initiated at either 7 or 21 days following establishment of tumor, 14-day infusion of SM256 had an inhibitory effect on growth that was similar to that obtained with single dose cis-platinum, but no additive effect of concurrent therapy with SM256 and cis-platinum was observed. These results demonstrate the activity and feasibility of use of alphav antagonists such as SM256 for therapy of SCC.

Animals↗

PubMed1999

Late cytomegalovirus pneumonia in adult allogeneic blood and marrow transplant recipients.

To assess the impact of antiviral prophylaxis during the first 3 months after transplantation on the frequency, timing, and outcome of cytomegalovirus (CMV) pneumonia during the first year, 541 adult allogeneic blood and marrow transplant recipients were evaluated. Thirty-four patients (6.3%) developed 35 episodes of CMV pneumonia at a mean of 188 days after transplantation, with an associated mortality rate of 76%. Twenty-six episodes (74%) occurred late (after day 100). Of the patients with late CMV pneumonia almost all (92%) had chronic graft vs. host disease or had received T cell-depleted transplants. Fourteen late CMV pneumonias (54%) were associated with serious concurrent infections, and 100% of these episodes were fatal. In conclusion, although the frequency of CMV pneumonia in the early posttransplantation period may be substantially reduced by prophylaxis, CMV continues to be a major cause of morbidity and mortality in the late period. Some subsets of patients need more prolonged surveillance and prophylaxis and/or preemptive therapy.

Adolescent↗

PubMed1998

Differential binding characteristics and cellular inhibition by soluble VEGF receptors 1 and 2.

The FLT-1 and KDR genes encode transmembrane tyrosine kinases which function as high-affinity receptors for vascular endothelial growth factor (VEGF). We have used the baculovirus system to express the extracellular parts of the FLT-1 receptor and KDR receptor in soluble form (sFLT-1 and sKDR), for in vitro binding and competition assays. Here, we show that the binding of VEGF165 to sKDR but not sFLT-1 is dependent on heparin, regardless of whether VEGF165 or sKDR is immobilized. Further, only sFLT-1 acts as a receptor antagonist in solution and sKDR can neither compete with the binding of VEGF165 to human endothelial cells carrying both receptors nor block VEGF165 induced mitogenicity. Soluble KDR only partially inhibits cell migration even at high concentrations, in contrast to sFLT which can almost completely block (82%) VEGF-induced cell proliferation and migration. Taken together these results show that the two soluble VEGF receptor proteins, sFLT-1 and sKDR, despite binding the same ligand, behave very differently when immobilized with regard to their dependence on heparin for VEGF binding. In solution their respective ability to function as receptor antagonists is also strikingly different, possibly a reflection of their different dependency on heparin.

Animals↗

PubMed1998

Regional suppression of tumor growth by in vivo transfer of a cDNA encoding a secreted form of the extracellular domain of the flt-1 vascular endothelial growth factor receptor.

Vascular endothelial growth factor (VEGF), a potent angiogenic mediator, is overexpressed in most solid tumors. On the basis of the knowledge that solid tumor growth beyond a small volume is critically dependent on angiogenesis, and that adenovirus (Ad) vectors can mediate efficient in vivo gene transfer and expression, we hypothesized that Ad-mediated transfer of a secreted form of the extracellular domain of the flt-1 VEGF receptor (Adsflt) would suppress tumor growth on a regional basis. To evaluate this concept, three tumor models were examined using a murine colon carcinoma cell line and syngeneic BALB/c mice. First, mice with preestablished splenic CT26.CL25 tumors and liver metastases were given Adsflt on AdNull intravenously and, after 15 days, spleens and livers were harvested to quantify tumor burden. Adslft-treated animals had minimal residual splenic tumors and liver metastases; in contrast, control animals had bulky splenic tumors and extensive liver metastases (p < 0.003). Second, mice with preestablished lung metastases showed a significant reduction in pulmonary metastases with regionally administered Adslft (intratracheal, p < 0.02) but not when the vector was systemically administered (intravenous, p > 0.9). Finally, mice with primary subcutaneous tumors treated with intratumoral administration of Adslft showed significant tumor suppression (p < 0.05) not observed in AdNull-treated mice or mice given Adslft intravenously (p > 0.3). We conclude that Ad-mediated in vivo regional delivery of a secreted form of the extracellular domain of the flt-1 VEGF receptor can effectively inhibit regional tumor growth, a strategy that may provide a means to control tumor growth within the treated organ without the risk of systemic antiangiogenesis.

Adenoviridae↗

PubMed1996

Do topical antibiotics provide improved prophylaxis against bacterial growth in the presence of polypropylene mesh?

BACKGROUND: Herniorrhaphies using a foreign body such as mesh can become infected. An experiment was performed in rabbits to compare three methods of antibiotic treatment to prevent the growth of bacteria in mesh-containing wounds. METHODS: This experiment compared preoperative intravenous antibiotics (cefazolin), topical antibiotics applied intraoperatively (bacitracin), and their combination in preventing the quantitative growth of bacteria in a subcutaneous wound containing a polypropylene mesh inoculated with Staphylococcus aureus. The bacteria were inoculated in doses sufficient to deliberately cause the growth of 130.0 +/- 56.4 x 10(4) bacteria per gram of tissue in saline-treated control animals. Quantitative cultures of the mesh and surrounding tissues were obtained 5 days after insertion of the mesh and inoculation of the wound. RESULTS: Experimental data showed that treatment with systemic intravenous antibiotics, topical powdered antibiotics, or their combination all statistically significantly decreased the quantitative cultures grown from the inoculated tissues as compared with saline-treated controls (P<0.05). However, there were no statistically significant differences in quantitative growth among the three methods of antibiotic treatment. CONCLUSIONS: Antibiotics reduced the quantitative growth of bacteria in tissues excised from wounds inoculated with bacteria. However, preoperative intravenous antibiotics, topical powdered antibiotics, and their combination all were equally effective.

Animals↗

PubMed1996

Effects of granulocyte colony-stimulating factor in severe pancreatitis.

BACKGROUND: The effect of granulocyte colony-stimulating factor (G-CSF) on the rate of secondary infections in acute pancreatitis was evaluated in a canine model. Infectious complications are the major determinant of morbidity and mortality in severe pancreatitis. Bacterial translocation has been shown to be a cause of these secondary infections. The relative immunosuppression found with pancreatitis may promote translocation and the spread of bacteria to the pancreas. METHODS: Thirty-four mongrel dogs were studied. Pancreatitis was induced in 18 dogs; 9 were treated with 100 micrograms G-CSF/day and 9 were given only saline solution. Laparotomy alone was done in 16 dogs of which one half were given 100 micrograms G-CSF/day and one half were given saline solution. Daily blood counts and cultures were obtained. All dogs were killed on day 7, and the mesenteric lymph nodes, pancreas, liver, spleen, and peritoneal fluid were cultured and studied histologically. RESULTS: G-CSF caused a significant and sustained increase in mature granulocytes in dogs given pancreatitis. No difference was found in the rate of translocation to mesenteric lymph nodes in dogs given G-CSF (n = 4) versus dogs given saline solution (n = 6). However, a significant decrease occurred in the spread of bacteria to distant sites in dogs given G-CSF (1 versus 15, p < 0.05). CONCLUSIONS: Although G-CSF does not decrease the rate of translocation, it does decrease the rate of distant infection in severe acute pancreatitis.

Acute Disease↗

PubMed1995

Identification of fibroblast growth factor 9 (FGF9) as a high affinity, heparin dependent ligand for FGF receptors 3 and 2 but not for FGF receptors 1 and 4.

Fibroblast growth factors (FGF) are multifunctional, heparin binding polypeptides that share structural similarity, but differ in their target cell specificity and expression pattern. Here we describe the cloning and expression of the mouse homologue of FGF9, and the use of a panel of soluble FGF receptors and genetically engineered cells to study its receptor binding specificity. FGF9 is found to bind with high affinity (kd: 0.25 nM) to FGFR3, for which a specific ligand has not yet been identified. FGF9 can also bind, albeit with a lower affinity, to FGFR2 but does not bind FGFR1 or FGFR4. There is no significant binding to either FGFR3 or FGFR2, expressed either as soluble receptors or in heparin sulfate deficient cells, in the absence of heparin. Moreover, receptor binding of FGF9 requires heparin in a manner specific to the receptor type. In conclusion FGF9 presents a unique case of ligand-receptor specificity and fulfills the criteria as a high affinity, heparin-dependent ligand for FGFR3.

Amino Acid Sequence↗

PubMed1994

Perlecan, basal lamina proteoglycan, promotes basic fibroblast growth factor-receptor binding, mitogenesis, and angiogenesis.

A survey of defined species of cell surface and extracellular matrix heparan sulfate proteoglycans (HSPG) was performed in a search for cellular proteoglycans that can promote bFGF receptor binding and biological activity. Of the various affinity-purified HSPGs tested, perlecan, the large basement membrane HSPG, is found to induce high affinity binding of bFGF both to cells deficient in HS and to soluble FGF receptors. Heparin-dependent mitogenic activity of bFGF is strongly augmented by perlecan. Monoclonal antibodies to perlecan extract the receptor binding promoting activity from active HSPG preparations. In a rabbit ear model for in vivo angiogenesis, perlecan is a potent inducer of bFGF-mediated neovascularization. These results identify perlecan as a major candidate for a bFGF low affinity, accessory receptor and an angiogenic modulator.

Animals↗

PubMed1994

Elevated protein tyrosine phosphatase activity and increased membrane viscosity are associated with impaired activation of the insulin receptor kinase in old rats.

Insulin resistance is very common in the elderly, and may be associated with glucose intolerance or frank diabetes. In previous studies we demonstrated that insulin resistance in old Wistar rats is associated with decreased autophosphorylation and activation of the hepatic insulin receptor kinase (IRK) in vivo. We now show that this defect can be reproduced in vitro, where the extent of insulin-induced activation of IRK in liver membranes of old rats was decreased by approximately 50% compared with young controls. The defect could be largely abolished after solubilization of the membranes with Triton X-100. We also show that: (a) the viscosity of membranes from the old rats was significantly (P < 0.001, n = 4) higher (by 15%) compared with young controls; (b) incubation of plasma membranes from old animals with lecithin liposomes, which lowered their cholesterol levels, partially abolished the defect in IRK activation; and (c) Triton extracts of liver membranes prepared from old rats did not interfere with the activation of IRK derived from young controls. Additionally, non-membrane components did contribute to the development of this defect. We observed a significant (approximately 30%) (P < 0.001, n = 18) elevation of cytosolic protein tyrosine phosphatase (PTP) activity directed against the beta subunit of the insulin receptor in livers of old rats. No such elevation of PTP activity could be demonstrated with synthetic substrates. Our findings are consistent with a model in which increased membrane viscosity as well as enhancement of a cytosolic PTP activity both markedly inhibit the activation in vivo of the hepatic IRK in old animals.

Aging↗

PubMed1992

Selective inhibition of protein tyrosine phosphatase activities by H2O2 and vanadate in vitro.

Acute (10-30 min) treatment of intact rat hepatoma (Fao) cells with H2O2, inhibits in vivo protein tyrosine phosphatase activity. Vanadate markedly potentiates this effect although it has only trivial effects of its own. Here we show that H2O2 inhibits a protein tyrosine phosphatase activity, but not a p-nitro phenyl phosphate hydrolysing activity, in cytosolic extracts of these cells. This effect is completely reversed by 10 mM dithiothreitol. Other oxidants have similar inhibitory effects. Vanadate inhibits the protein tyrosine phosphatase activity in vitro, and its effects are additive with those of H2O2. These findings suggest that H2O2 and vanadate interact with the protein tyrosine phosphatases at two independent sites. They also suggest that in intact cells H2O2 has a direct inhibitory effect on protein tyrosine phosphatase activity and an indirect effect of facilitating the entry of vanadate.

Animals↗

PubMed1992

Mitomycin C-induced colitis in rats: a new animal model of acute colonic inflammation implicating reactive oxygen species.

The mechanism of the tissue damage induced by colonic inflammation in ulcerative colitis is not established. We therefore developed and characterized a simple new rat model of acute colonic inflammation induced by a single systemic injection of mitomycin C. After an intraperitoneal injection of mitomycin-C, colon histologic examination revealed transient (3 to 14 days) diffuse, colonic inflammation and injury that, like human ulcerative colitis, was limited to the mucosal layer. The rest of the gastrointestinal tract was spared. Gut permeability, as measured by urinary excretion of orally administered lactulose and mannitol, was unchanged 3 days after injection, when inflammation was already present; permeability was increased at 7 days, when inflammation was maximal. Mitomycin C did not produce inflammation in experimentally bypassed segments of small bowel despite the presence of colonic-type bacteria, suggesting that lack of intraluminal bacteria was not responsible for the absence of inflammation in the small intestine. Chemiluminescence, a means of estimating levels of reactive oxygen species, was greater in the intact, inflamed colon of mitomycin C-treated rats than in bypassed segments. Moreover, inflamed mucosal scrapings produced more in vitro luminol-enhanced chemiluminescence. Furthermore, the reactive oxygen species scavengers allopurinol, catalase, and WR-2721 decreased inflammation severity. We therefore conclude: (1) the mitomycin C-treated rat is a novel, easy to prepare animal model of acute inflammation of colonic mucosa, with morphologic similarities to the acute phase of ulcerative colitis in human beings; (2) increased gut permeability in mitomycin C-treated rats is the result, not the cause, of the inflammation; and (3) reactive oxygen species play an important role in colonic inflammation and tissue injury in this model, and possibly in human ulcerative colitis.

Animals↗

PubMed1988

The dimensional structure of medical students' perceptions of diseases.

First- and second-year medical students rated 35 diseases (e.g., cancer, heart attack, herpes, schizophrenia, alcoholism) on nine different rating scales (e.g., prognosis, ease of management). In order to uncover the underlying dimensional structure, mean ratings were subjected to multidimensional scaling analyses in which both diseases and rating scales were placed in the same configuration. The results indicated that a two-dimensional solution, accounting for 97% of the variance, was most appropriate. The first dimension distinguishes between diseases that appear to be more physiological in nature and those that have some psychological involvement as well. The second dimension seems most related to fear, seriousness, prognosis, patient desirability, and ease of management.

Attitude of Health Personnel↗

PubMed1986

Cancer Opinionnaire. Medical students' attitudes toward psychosocial cancer care.

A questionnaire assessing attitudes toward psychosocial cancer care (the Cancer Opinionnaire) was constructed. Factor analysis revealed five factors: outcome expectations; candor; interest in treating cancer; psychosocial concerns: role of the physician; and psychosocial concerns: importance to the patient. Reliabilities ranged from 0.68 to 0.82. A multivariate analysis of variance indicated that second-year students, who had been exposed to a required first-year course stressing biopsychosocial concerns of medical care, expressed more positive attitudes than did entering first-year students. Additionally, female medical students expressed more positive attitudes than did male students. Addressing biopsychosocial concerns in the beginning of medical education may help establish a more open and fertile ground upon which later training will be received.

Attitude of Health Personnel↗