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Biomedical subjects

K Olden

Publications and source records attributed to K Olden.

At least 37 records · Page 2Linked to original sources
PubMed1995

Environmental health science research and human risk assessment.

Environmental health science research, with its focus on fundamental science and disease prevention, is important for the development of rational and cost-effective public health and regulatory policies related to environmental protection. Environmentally related diseases are preventable, yet they impose a major burden on society in terms of human suffering and costs related to health care. Similarly, the expenditure of hundreds of billions of dollars for regulatory compliance is a major economic concern. There is considerable debate regarding current regulatory risk assessment practices for environmental agents. Implicit in all risk assessment schemes is the need to extrapolate from high-exposure studies to low-exposure situations and from known risks in rodents to probable risks in people. Both extrapolations are fraught with uncertainties. These uncertainties are accommodated in risk-assessment schemes by the incorporation of arbitrary "safety factors" and other default approaches. Since these factors are not derived experimentally, they may overestimate or under estimate actual risks. Risk-assessment methodology, its relevance to the human condition, and its use in protecting human health will greatly improve when our expanding knowledge of the basic biology of environmental effects is incorporated into toxicological testing and risk-assessment schemes. Moreover, exciting opportunities now exist to advance our understanding of the environmental and genetic bases of many common diseases and to design effective prevention and intervention strategies to combat their development. This report discusses some of the current opportunities and challenges.

Cell Communication↗
PubMed1995

Fibronectin and integrins in invasion and metastasis.

The adhesive glycoprotein fibronectin and integrin receptors appear to play important roles in the progression of metastatic disease. Fibronectin is a multifunctional extracellular glycoprotein that has at lest two independent cell adhesion regions with different receptor specificities. The cell adhesive region in the central portion of fibronectin is comprised of at least two minimal amino acid sequences--an Arg-Gly-Asp (RGD) sequence and a Pro-His-Ser-Arg-Asn (PHSRN) sequence--which function in synergy. Another cell adhesive region is located near the carboxy-terminus in the alternatively spliced IIICS module. The critical minimal sequences for this region Leu-Asp-Val (LDV) and Arg-Glu-Asp-Val (REDV) which function in an additive rather than synergistic fashion. Integrins are heterodimeric, transmembrane cell adhesion receptors for fibronectin and other extracellular matrix molecules. Several different integrins bind to fibronectin. The alpha 5 beta 1 fibronectin-specific integrin binds to the central RGD/PHSRN site. The alpha 4 beta 1 integrin binds to the IIICS site. Fibronectin-integrin interactions are important in tumor cell migration, invasion, and metastasis. In addition to promoting cell adhesion to the extracellular matrix, these proteins may also function in chemotaxis and control of proliferation. Peptide and antibody inhibitors of fibronectin and integrin functions have been shown to be effective inhibitors of metastasis, and are potentially important reagents for the study and control of cancer.

Amino Acid Sequence↗
PubMed1995

Activation of resident tissue-specific macrophages by swainsonine.

The induction of macrophage tumoricidal activity by swainsonine (8a beta-indolizidine-1 alpha, 2 alpha, 8 beta-triol), an indolizidine alkaloid, has been implicated as possibly an important immune effector mechanism involved in the suppression of tumor growth and metastasis in vital organs such as the lung, liver and spleen (Olden, K. et al. The potential importance of swainsonine in therapy for cancers and immunology. Pharmacol. Ther. 50:285-290; 1991). The present study further explores this possibility by determining whether resident tissue-specific macrophages of several mouse strains can be rendered tumoricidal by systemic administration of swainsonine. We found that systemically administered swainsonine could increase the tumoricidal activity of both alveolar (lung) and splenic macrophages. The activity was enhanced as much as 3- to 4-fold over that obtained with macrophages from organs of control animals and was both dose- and time-dependent. The level and extent of activation by swainsonine was comparable to that achieved with traditional macrophage-activating agents, such as lipopolysaccharide and interferon-gamma. The fact that swainsonine activated highly purified (> 95%) cultures of macrophages from the various sources suggests a direct mechanism of activation. Furthermore, the in vivo activation of macrophages in immune-compromised animals (SCID and nude) lends credence to this suggestion. These findings provide a plausible explanation for the observations that systemically administered swainsonine inhibits organ colonization of metastatic cells and growth of SC tumor xenografts, whereas the growth of tumor cells is not inhibited by swainsonine in culture.

Adjuvants, Immunologic↗
PubMed1993

Environmental risks to the health of American children.

The major environmental health issue for children today is the extremely high prevalence of unacceptable exposure to lead, especially in inner cities, but occurring throughout the country. It is now generally accepted that lead is toxic to the developing nervous system at levels that were thought only a decade ago to be without effect. Children are more susceptible to the effects of lead than the adults who live in the same environments. Although lead-based paint is no longer used and lead is now removed from gasoline, children will continue to live in housing with the potential for lead poisoning for perhaps another generation. Research into the prevention of exposure and prevention of the consequences of unavoidable exposure is now under way.

Adolescent↗
PubMed1993

Adhesion molecules and inhibitors of glycosylation in cancer.

Expression of aberrant oligosaccharide moieties of glycoproteins and glycolipids is a typical characteristic of essentially all animal and human tumors, irrespective of the carcinogenic mechanism. Evidence is presented to document that transformation-associated alternations in the oligosaccharide moieties of surface and adhesive glycoproteins are responsible, at least in part, for expression of the malignant phenotype. However, the contribution of carbohydrates to tumor progression and metastasis cannot be fully assessed until more information is available concerning the multiple mechanisms that regulate cell adhesion and carbohydrate biosynthesis. Nevertheless, our rudimentary understanding of the carbohydrate-dependent events involved in cell adhesion and metastasis has resulted in animal studies to develop novel and exciting approaches to cancer therapy.

Animals↗
PubMed1991

Protective effects of swainsonine on murine survival and bone marrow proliferation during cytotoxic chemotherapy.

We have investigated the ability of swainsonine, an indolizidine alkaloid with pleiotropic in vivo effects, to confer protection against the cytotoxic effects of both cell cycle-specific and cell cycle-nonspecific cytotoxic anticancer agents. The intraperitoneal administration of swainsonine decreased the lethality of methotrexate (MTX), fluorouracil (5-FU), cyclophosphamide (CPM), and doxorubicin (DOX) in non-tumor-bearing C57BL/6 mice. The increased survival rate was found to correlate with stimulation of bone marrow cell proliferation, as measured by increases in 1) bone marrow cellularity, 2) in vivo and in vitro colony-forming activity, and 3) engraftment efficiency. These responses were critically dependent on the dose, sequence, and timing of swainsonine administration. If these results are confirmed in humans, swainsonine may offer promise in future intensive chemotherapy programs, allowing increased dosage and/or frequency of administration of cytotoxic agents without increasing toxic effects in bone marrow.

Alkaloids↗
PubMed1991

The potential importance of swainsonine in therapy for cancers and immunology.

Swainsonine, an indolizidine alkaloid, was initially used in biomedical research as a tool to investigate the biosynthesis and function of asparagine-linked 'complex' type oligosaccharide moieties of glycoproteins. Recently, swainsonine has generated interest in its potential use as an anticancer agent with reports that it (i) inhibits tumor growth and metastasis, (ii) augments natural killer (NK) and macrophage-mediated tumor cell killing, and (iii) stimulates bone marrow cell proliferation. The antineoplastic activity of swainsonine can be explained at least in part by augmentation of immune effector mechanisms. The potential application of swainsonine as an anticancer agent is discussed.

Animals↗
PubMed1991

Monoclonal antibody characterization of two distant sites required for function of the central cell-binding domain of fibronectin in cell adhesion, cell migration, and matrix assembly.

Site-directed mutagenesis studies have suggested that additional peptide information in the central cell-binding domain of fibronectin besides the minimal Arg-Gly-Asp (RGD) sequence is required for its full adhesive activity. The nature of this second, synergistic site was analyzed further by protein chemical and immunological approaches using biological assays for adhesion, migration, and matrix assembly. Fragments derived from the cell-binding domain were coupled covalently to plates, and their specific molar activities in mediating BHK cell spreading were compared with that of intact fibronectin. A 37-kD fragment purified from chymotryptic digests of human plasma fibronectin had essentially the same specific molar activity as intact fibronectin. In contrast, other fragments such as an 11.5-kD fragment lacking NH2-terminal sequences of the 37-kD fragment had only poor spreading activity on a molar basis. Furthermore, in competitive inhibition assays of fibronectin-mediated cell spreading, the 37-kD fragment was approximately 325-fold more active than the GRGDS synthetic peptide on a molar basis. mAbs were produced using the 37-kD protein as an immunogen and their epitopes were characterized. Two separate mAbs, one binding close to the RGD site and the other to a site approximately 15 kD distant from the RGD site, individually inhibited BHK cell spreading on fibronectin by greater than 90%. In contrast, an antibody that bound between these two sites had minimal inhibitory activity. The antibodies found to be inhibitory in cell spreading assays for BHK cells also inhibited both fibronectin-mediated cell spreading and migration of human HT-1080 cells, functions which were also dependent on function of the alpha 5 beta 1 integrin (fibronectin receptor). Assembly of endogenously synthesized fibronectin into an extracellular matrix was not significantly inhibited by most of the anti-37-kD mAbs, but was strongly inhibited only by the antibodies binding close to the RGD site or the putative synergy site. These results indicate that a second site distant from the RGD site on fibronectin is crucial for its full biological activity in diverse functions dependent on the alpha 5 beta 1 fibronectin receptor. This site is mapped by mAbs closer to the RGD site than previously expected.

Amino Acid Sequence↗
PubMed1991

Swainsonine stimulation of the proliferation and colony forming activity of murine bone marrow.

Swainsonine, an indolizidine alkaloid, was recently reported to exhibit both antineoplastic and immunomodulatory activities (Humphries, M.J.; Olden, K. Asparagine-linked oligosaccharides and tumor metastasis. Pharmacol. Ther. 44:85-105; 1989). In this study, we show that systemically administered swainsonine promoted the proliferation of murine bone marrow (BM) cells. Animals that received swainsonine intravenously exhibited a significant increase (approximately 5-10 fold) in BM cellularity, engraftment efficiency, and colony forming unit activity using in vitro or in vivo assays. BM cells derived from swainsonine-treated animals or treated with swainsonine in vitro also exhibited a 4-5 fold increase in [3H]-thymidine incorporation, suggesting that a larger fraction of the cells was in the S-phase of the cell cycle. This provides the first evidence that swainsonine, which stimulates the production of cytokines by cells of the immune system, promoted the proliferation of BM progenitor cells. These results suggest that swainsonine could prove valuable in patients undergoing intensive chemoradiotherapy or autologous BM transplantation by decreasing or possibly eliminating leukopenia or myelosuppression often associated with these procedures; it may also be a useful probe to investigate the mechanism of normal hematopoieses.

Alkaloids↗
PubMed1991

Failure of initial 24-hour esophageal pH monitoring to predict refractoriness and intractability in reflux esophagitis.

Prolonged esophageal pH monitoring is considered to be the most sensitive and specific test for the diagnosis of gastroesophageal reflux disease (GERD). However, the role of pH monitoring in predicting the clinical and endoscopic response of reflux esophagitis is not well defined. In this study, 106 patients with moderate to severe symptoms of GERD and esophagitis (grades 0-IV) by endoscopy were initially studied by ambulatory esophageal pH monitoring, and their clinical response to standard H2 antagonist therapy was monitored at 8 wk. Refractory patients were defined as those who failed to heal and/or had intractable reflux symptoms after 8 wk of H2 antagonist therapy, and who required continuous therapy with higher doses of H2 antagonists, addition of prokinetic agents, or omeprazole. There was a positive correlation (r = 0.89) between endoscopic severity of esophagitis upon entry into the study and refractoriness to standard medical therapy. However, there were no differences in the various pH parameters analyzed between the 58 patients who responded and the 48 patients who were refractory to medical therapy, regardless of the endoscopic grading of their esophagitis. We conclude that 24-h ambulatory esophageal pH monitoring does not predict refractoriness of reflux esophagitis to standard therapy. The decision for more aggressive methods of treatment probably requires assessment of symptomatic and endoscopic response after 8 week standard H2 antagonist therapy.

Adult↗