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Biomedical subjects

F M Robertson

Publications and source records attributed to F M Robertson.

At least 55 records · Page 3Linked to original sources
PubMed1992

Induction of ornithine decarboxylase in specific subpopulations of murine epidermal cells following multiple exposures to 12-O-tetradecanoylphorbol-13-acetate, mezerein and ethyl phenylpropriolate.

Single applications of 12-O-tetradecanoylphorbol-13-acetate (TPA), mezerein or ethyl phenylpropriolate (EPP) to mouse skin at appropriate doses cause similar degrees of hyperplasia and comparable levels of induction of epidermal ornithine decarboxylase (ODC) activity. Multiple (n = 5) treatments with these agents, in contrast, resulted in large differences in induced ODC activity (TPA much greater than mezerein greater than EPP) with no differences in the degree of hyperplasia or [3H]thymidine pulse-labeling among the multiple treatment groups. To attempt to explain the cellular basis for the greater ODC-inducing ability of TPA relative to mezerein and EPP in chronic exposure protocols, immunocytochemical and flow cytometric analyses were performed. Immunocytochemistry using an ODC-specific polyclonal antibody revealed substantially different pattern of ODC-positive cells in chronically exposed epidermis than observed with single exposures. TPA treatment resulted in very pronounced immunostaining of the perifollicular cells, with little evidence of specific staining in the interfollicular epidermis mezerein treatment yielded staining in both interfollicular and some perifollicular areas, while EPP treatment produced the least amount of specifically stained cells, all of which were in the interfollicular epidermis. Flow cytometric analysis of keratinocytes isolated from chronically treated skin identified three distinct subpopulations that bound varying amounts of ODC antibody. Chronic treatment of CD-1 murine epidermis with TPA appeared to cause the expansion of an intermediate sized cell subpopulation that was not apparent with EPP or mezerein. Our results suggest that chronic treatment of murine epidermis with the potent complete tumor promoter TPA leads to the selective expansion of a keratinocyte subpopulation that is hyperinducible for ODC and may be identical to the cells in the perifollicular region previously identified. These observations also suggest that the weaker tumor promoters mezerein and EPP are less capable of causing expansion of this specific subpopulation, which may be an important target cell population for neoplastic transformation in mouse epidermis.

Alkynes↗
PubMed1992

Diagnosis and treatment of asthma in children: usefulness of a review of medical records.

In order to tackle the problems of underdiagnosis and undertreatment of asthma in childhood general practitioners need to be aware of which children in their practices have or might have asthma. In an effort to identify a cohort of asthmatic or potentially asthmatic children a trained audit facilitator studied all the medical records of children aged between one year and 15 years who were registered with 12 Tayside general practices. From a total of 10,685 medical records the frequency of 'key items' sometimes associated with asthma were as follows: one or more episodes of bronchospasm or wheeze 23.7% of children, persistent cough 23.2%, treatment with anti-asthma therapy in the past 20.0%, exercise induced cough or wheeze 5.2% and history of 'wheezy bronchitis' 4.6%. However, in only 896 children (8.4%) had a formal diagnosis of asthma been made. Of all the children, 5.4% had received a prescription for anti-asthma medication within the past three months. Only 1.2% were taking an inhaled corticosteroid and 1.0% sodium cromoglycate, but many more were taking inhaled bronchodilators (3.1%) and oral bronchodilators (1.7%). The findings suggest that a systematic review of medical records by a trained facilitator can identify those children who could benefit from clinical review. Practices who wish to know which of their children have or might have asthma should consider using medical record review to search for key items associated with asthma.

Adolescent↗
PubMed1992

Abdominal vascular trauma: a review of 106 injuries.

A retrospective analysis of acute abdominal vascular injuries was performed to review outcome variables and treatment principles. The authors review their most recent 5-year experience with 106 major abdominal vascular injuries in 64 patients treated at a combined Army and Air Force urban medical center. The majority of the patients were young men who sustained penetrating injuries. There were 41 (64%) gunshot wounds, 17 (27%) stab wounds, and 6 (9%) sustained blunt trauma. Forty-five patients (71%) came to the hospital in shock. The inferior vena cava in 26 patients (41%) and the aorta in 11 patients (17%) were injured most frequently. Suture repair was possible in 53 (50%) injuries. Ligation was performed in 41 (39%). Overall mortality for the series was 39 per cent. Hemorrhagic shock was the cause of death in 23 patients (92%) with only two late deaths. Transfusion requirement, presence of shock, and number of vessels injured all affected outcome. Immediate stabilization in the emergency department includes appropriate crystalloid and blood product resuscitation with minimal delay for diagnostic studies. Prompt abdominal exploration to control hemorrhage and particular attention to factors associated with coagulopathy remain the key elements in saving the lives of these severely injured patients.

Abdominal Injuries↗
PubMed1991

Distinct patterns of chemotactic peptide-induced calcium mobilization in differentiated myeloid leukemia cells and peripheral blood neutrophils.

Flow cytometry was used to compare intracellular calcium mobilization in mature neutrophilic granulocytes (PMN) with HL-60 promyelocytic leukemia cells induced to differentiate with dibutyryl cyclic adenosine 3',5'-monophosphate (dbcAMP). Using the calcium-specific probe indo-1 acetoxymethyl ester, we found that the ability of differentiating HL-60 cells to mobilize calcium in response to N-formyl-methionyl-leucyl-phenylalanine (fMLP) developed concomitantly with expression of receptors on the cells for this peptide. Mobilization of calcium in HL-60 cells, as well as in PMN, in response to fMLP was dose dependent and was related to the presence of calcium in the culture medium. In calcium-free medium, tenfold higher concentrations of fMLP were required to induce calcium mobilization than in calcium-containing medium. In HL-60 cells, calcium mobilization occurred more rapidly than in PMN and was independent of extracellular calcium. Furthermore, the response of HL-60 cells to fMLP was more prolonged than the response of PMN and was also of greater magnitude. Calcium mobilization in both HL-60 cells and PMN was partially inhibited by the calcium channel blocker, verapamil, but completely blocked by trimethylbenzoic acid 8-(diethylamino) octyl ester, an intracellular calcium antagonist. These results indicate that although both cell types mobilize calcium in response to fMLP, the characteristics of the responses are distinct. These differences may underlie distinct functional responses of PMN and differentiated HL-60 cells to fMLP.

Biological Transport, Active↗
PubMed1991

Peritoneal leukocyte response following placement of polyglycolic acid intestinal sling in patients with rectal carcinoma.

The intestinal sling procedure has been used successfully without the observance of pelvic infections. This procedure involves the implantation of polyglycolic acid (PGA) mesh to hold the bowel out of the pelvis to prevent radiation enteritis. We previously showed that PGA mesh has no intrinsic bactericidal activity. Since phagocytic leukocytes produce reactive oxygen intermediates during respiratory burst that are associated with oxygen-dependent bactericidal activity, we examined peritoneal cell types and their respiratory burst activity isolated from patients with biopsy-confirmed rectal carcinoma who underwent the intestinal sling procedure (N = 12) compared with patients who did not (N = 13). There was no significant difference in the cell types within the peritoneal cavity over the 7-day postoperative period examined. However, there was a significant increase in the ability of leukocytes isolated from mesh patients to produce hydrogen peroxide in the absence of an exogenous stimulus (P less than 0.05), as measured by flow cytometric quantitation of oxidation of the hydroperoxide-sensitive dye, 2',7'-dichlorofluorescin diacetate (DCFH-DA). Despite the higher endogenous DCFH oxidation by leukocytes from mesh patients, the cells retained the ability to oxidize DCFH following treatment with a membrane-active stimulant for respiratory burst activity, 12-O-tetradecanoyl-phorbol-13-acetate. These observations suggest that PGA mesh used for the intestinal sling procedure stimulates the respiratory burst activity of peritoneal leukocytes during the postoperative period in which bacterial proliferation and colonization occur. The stimulation of reactive oxygen intermediates involved in oxygen-dependent bactericidal activity by PGA mesh may be one of the mechanisms underlying the lack of infections observed with the use of PGA mesh in contaminated settings.

Bacterial Infections↗
PubMed1991

Induction of leukocyte activation by meshes surgically implanted in the peritoneal cavity.

The search for surgical prosthetics that do not act to promote infection has been frustrating. However, recent experience with the implantation of polyglycolic acid mesh (PGA) used as an intestinal sling has been associated with a lack of pelvic infections. To examine the basis for these observations, 1 x 1-cm pieces of biomaterials were sewn onto the peritoneal cavity of rats. The biomaterials examined included PGA mesh, a composite mesh composed of a permanent nonabsorbable Novafil inner layer coated with a PGA outer layer, polyvinyl alcohol sponge, and silicon elastomer. Biomaterials were removed at postoperative days 1, 2, 8, and 14, and examined for bacteriostatic and bactericidal activity by standard techniques. Mesh adherent leukocytes were evaluated for their ability to oxidize dichlorofluorescein diacetate (DCFH-DA), which is fluorescent in the presence of intracellular hydrogen peroxide produced by both polymorphonuclear cells and monocytes. PGA and the composite mesh had no intrinsic bacteriostatic or bactericidal activity. However, adherent leukocytes were induced to oxidize DCFH at levels 10-fold and 5-fold, respectively, by postoperative day 14, compared with earlier time points and other biomaterials. The ability of these PGA meshes to stimulate respiratory bursts by peritoneal cells may partly be responsible for the lack of infections associated with their use.

Animals↗
PubMed1991

Enhanced hydroperoxide production by peripheral blood leukocytes following exposure of murine epidermis to 12-O-tetradecanoylphorbol-13-acetate.

Previous studies have shown that the phorbol ester tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulates phagocytic leukocytes to produce reactive oxygen intermediates in vitro. The present studies focused on the production of reactive oxygen intermediates by peripheral blood leukocyte cell populations following in vivo exposure of murine epidermis to TPA. TPA induced a dose-dependent (0.2-20 micrograms) increase in polymorphonuclear cells (PMN) that appeared to be recruited from the marginal pools, while simultaneously decreasing the number of peripheral blood mononuclear cells. These alterations were detected as early as 2 h following topical application of TPA and persisted over a 21 day time period, using a twice-weekly TPA treatment schedule. The oxidation of 2',7'-dichlorofluorescin (DCFH) was used to examine the hydroperoxide production in peripheral blood PMN isolated from SENCAR mice treated with TPA. TPA stimulated a 2-fold increase in PMN-associated DCFH oxidation (645.4 +/- 118 fmol DCF) 4 h after topical application of 10 micrograms TPA when compared to PMN isolated from acetone-treated mice (339.0 +/- 35.8 fmol DCF). These observations suggest that topical application of TPA recruits PMN that are activated prior to their infiltration into the epidermis. Given the ability of these cells to migrate to local sites, they may serve as a primed cell population that significantly contributes to cutaneous alterations observed during acute and chronic inflammation following TPA exposure.

Administration, Cutaneous↗
PubMed1990

Production of hydrogen peroxide by murine epidermal keratinocytes following treatment with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate.

The ability of murine epidermal cells to produce intracellular hydrogen peroxide was analyzed by flow cytometry and the measurement of 2',7'- dichlorofluorescin (DCFH) oxidation. Epidermal cells isolated from acetone-treated CD-1 mice for 24 h were relatively homogeneous in cell size and density and oxidized low levels of DCFH. However, following 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment of mice (10 micrograms; 24 h), two cytokeratin-positive populations of cells were identified that were heterogeneous with respect to size and density. These two TPA-derived cell populations oxidized levels of DCFH that were time and dose dependent and were between 2- and 10-fold higher than levels of DCFH oxidized by cells isolated from acetone-treated mice. The ability of catalase, the enzyme that detoxifies hydrogen peroxide, to suppress DCFH oxidation to control levels suggested that intracellular hydrogen peroxide was responsible for the enhanced rate of DCFH oxidation in epidermal cells isolated from TPA-treated mice. The ability of mouse epidermal keratinocytes to oxidize DCFH in response to TPA treatment was confirmed using a cloned keratinocyte cell line. These results suggest that specific subpopulations of keratinocytes produce elevated levels of intracellular peroxides following treatment with TPA either in vivo or in culture.

Animals↗
PubMed1990

Identification of epidermal cell subpopulations with increased ornithine decarboxylase activity following treatment of murine epidermis with 12-O-tetradecanoylphorbol-13-acetate.

Ornithine decarboxylase (ODC), the initial enzyme in the polyamine biosynthetic pathway, has been used as a marker for the hyperplasia that occurs following exposure of mouse epidermis to the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Using flow cytometry in combination with polyclonal antibodies to ODC, we examined the levels of ODC-associated immunoreactive protein present within mouse epidermal cells at 4 and 24 h after a single topical application of TPA, as well as following chronic exposure to TPA and in papillomas. Basal levels of ODC-specific antibody binding were detectable in acetone-treated CD-1 mouse epidermis and were increased 3-fold at 4 h after TPA treatment. The amount of ODC antibody binding detected after exposure to 17 nmol TPA twice weekly for 3 weeks was similar to that detected within cells isolated from papillomas and was 2.5-fold higher than in cells isolated at 4 h after a single topical treatment of mice with TPA. These observations support the hypothesis that specific subpopulations of keratinocytes constitutively express high levels of ODC following chronic exposure to TPA. The novel method for ODC detection described in these studies provides a means to identify, isolate, and further characterize epidermal cells that may give rise to papillomas and carcinomas.

Animals↗
PubMed1990

Production of hydrogen peroxide by rabbit articular chondrocytes. Enhancement by cytokines.

Recent evidence suggests that reactive oxygen intermediates may play a role in the etiology of cartilage matrix degradation in arthritis. We have previously established that normal articular chondrocytes can functionally act as macrophages. These functions include expression of class II MHC Ag, presentation of Ag and induction of mixed and autologous lymphocyte stimulation. Inasmuch as the production of reactive oxygen intermediates is a hallmark of macrophage activity during inflammatory response, we were interested in examining the ability of normal articular chondrocytes to produce reactive oxygen intermediates. Using the trapped indicator 2',7'-dichlorofluorescin diacetate (DCFH-DA), we measured the levels of intracellular hydrogen peroxide within normal rabbit articular chondrocytes. We found that Concanavalin A induces chondrocytes to rapidly oxidize 2',7'-dichlorofluorescin diacetate to a highly fluorescent dichlorofluorescin in a dose- and time-dependent manner. Fluorescent dichlorofluorescin oxidation by chondrocytes was inhibited by the addition of catalase, an enzyme that detoxifies hydrogen peroxide. Exposure of rabbit chondrocytes to either IFN-gamma or TNF primed the chondrocytes to produce significantly greater amounts of hydrogen peroxide with or without further stimulation. Using scopoletin oxidation as a measure of the release of hydrogen peroxide, we confirmed that chondrocytes released this reactive oxygen intermediate after adherence to serum coated culture plates. Rabbit articular chondrocytes produced and released greater amounts of hydrogen peroxide than pulmonary alveolar macrophages, a well characterized macrophage cell type. These observations suggest that chondrocytes are an important source of reactive oxygen intermediates. Furthermore, the production of reactive oxygen intermediates by chondrocytes may be an important mechanism by which chondrocytes induce structural and functional alterations in cartilage matrix observed during arthritis.

Animals↗
PubMed1990

Differential production of interleukin 1 on the surface of biomaterials.

The production of cytokines on the surface of surgical biomaterials plays a major role in their biocompatibility. Membrane-associated interleukin 1 (mIL-1) is a cytokine found on the surface of macrophages activated by biomaterials. To better understand the host-foreign body interaction, we quantitated the production of mIL-1 on the surface of two materials commonly used in surgery, expanded polytef (ePTFE) and silicon elastomer (SE). The mean (+/- SD) level of mIL-1 produced by adherent cells to ePTFE significantly decreased from day 2 (13,746 +/- 3630 cpm per disk) compared with day 7 (2828 +/- 1304 cpm per disk). However, the level of mIL-1 produced by ePTFE-adherent cells was still markedly greater than the level of mIL-1 produced by cells adherent to SE (1877 +/- 1028 vs 1595 +/- 822 cpm per disk). These results indicate that ePTFE and SE elicit a differential host response in terms of cytokine production. This study may enhance our understanding of the cellular events on the surface of biomaterials that underlie clinical observations.

Animals↗
PubMed1990

Flow cytometric detection of ornithine decarboxylase activity in epidermal cell subpopulations.

Using flow cytometry in combination with membrane permeabilization techniques to enhance binding of antibodies with immunoreactive protein within the cytoplasm, we have developed a method to examine the ornithine decarboxylase (ODC) activity present within subpopulations of epidermal cells following acute and chronic exposure to the phorbol ester tumor promoter 12-0-tetradecanoylphorbol-13-acetate (TPA). The method described has the sensitivity to detect basal levels of ODC as well as increases in ODC at early time points following treatment with TPA and has the additional advantage of allowing subpopulation identification and characterization.

Animals↗
PubMed1990

Failure of F-Met-Leu-Phe to induce chemotaxis in differentiated promyelocytic (HL-60) leukemia cells.

Treatment of HL-60 promyelocytic leukemia cells with dibutyryl cyclic adenosine 3',5'-monophosphate (dbcAMP) induced these cells to differentiate toward mature neutrophilic granulocytes (PMN). DbcAMP was found to produce a rapid time- and dose-dependent inhibition of HL-60 cell proliferation, reaching a maximum after 48 hr treatment of the cells with 250-500 microM. This was associated with morphologic alterations consistent with maturing PMN. Using immunofluorescence and flow cytometry, we found that dbcAMP-treated HL-60 cells expressed some, but not all, surface markers characteristic of mature phagocytes. Thus receptors for the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP); the monocyte/granulocyte markers My-8, Mo-1, and Leu-15; as well as the monocyte markers Mo-2 and My-4 were identified on the cells. In contrast, dbcAMP-treated cells did not express the PMN-specific antigen DL1.2. We also found that dbcAMP-treated HL-60 cells produced hydrogen peroxide in response to the phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA). However, the magnitude of this response was significantly less than that observed in mature PMN. In contrast, fMLP-stimulated levels of hydrogen peroxide production were comparable in both cell types. In addition, despite the fact that dbcAMP-treated cells expressed fMLP receptors, they did not exhibit directed migration toward this chemotactic peptide. Taken together, these data suggest that dbcAMP-induced differentiation of HL-60 cells is incomplete.

Antigens, Surface↗
PubMed1990

Effect of mass screening mammography on staging of carcinoma of the breast in women.

In 1980, our institution began a screening mammography program. A retrospective review was done to document whether or not implementation of this program significantly changed the method of discovery of carcinoma of the breast and the stage of carcinoma of the breast at presentation in the patients we studied. Women diagnosed with carcinoma of the breast during a three year period, prior to the institution of the screening program (group 1) were compared with a similar set of patients diagnosed after establishment of the program (group 2). There were 165 patients in group 1 and 181 in group 2. The vast majority of cancers for those in group 1, 84.2 per cent, were discovered at self-examination, as compared with 46.3 per cent for those in group 2. Forty-eight per cent of the cancers for those in group 2 were first discovered by mammography as compared with 6.1 per cent in group 1. There was no statistical difference in the number of patients presenting with stage O, III and IV disease. The percentage of patients presenting with stage I disease rose significantly after the establishment of the mammography program (16.4 per cent in group 1 to 41.5 per cent in group 2). Findings from this study confirm that a mammographic screening program can have a marked effect on lowering the stage of carcinoma of the breast at presentation. The current recommendations for screening mammography should be implemented. Doing so will result in earlier detection and improved survival in this group of patients.

Breast↗
PubMed1987

Characterization of an immunosuppressive factor derived from colon cancer cells.

The colon cancer cell line, HT29, produces a soluble substance (HT29 factor) that blocks mitogen-induced T cell proliferation and the production of interleukin 2 (IL 2). Inhibition of T cell proliferation by the HT29 factor is reversible and is not due to a decline in cell viability or an alteration in the kinetics of T cell proliferation. It occurs even when the HT29 factor is added only 24 hr before terminating the T cell cultures, indicating that the factor affects cell division after activation of T cells has already occurred. No inhibitory activity was found in medium conditioned by human colonic epithelial cells or fibroblasts. The factor has an apparent m.w. of 56,000 and an isoelectric point of 7.9. It is sensitive to endopeptidases, heating to 56 degrees C, and extremes of pH. The HT29 factor also suppresses IL 2 production by T cells. However, low IL 2 availability alone cannot account for the suppressive effect of the factor on T cell proliferation, because the addition of exogenous IL 2 does not reverse the inhibition. This block in IL 2 responsiveness is not primarily due to a decrease in IL 2 receptors because Tac expression on activated T cells is minimally decreased during a 24-hr exposure to the HT29 factor. In addition, IL 2-induced proliferation of mitogen-activated T cells is inhibited only slightly by the HT29 factor, indicating that a block in the interaction of IL 2 with its receptor is not its main mechanism of action. Thus the inhibition of T cell proliferation is likely to be due primarily to a mechanism independent of IL 2.

Cell Line↗
PubMed1985

Renal responses to diuretics in the turtle.

We administered the diuretics furosemide and ethacrynic acid to conscious freshwater turtles to assess changes in renal function and plasma renin activity (PRA) in an animal which lacks a loop of Henle. Furosemide (2 and 5 mg/kg) produced no changes in blood pressure, hematocrit, plasma electrolytes, glomerular filtration rate (GFR), or PRA. Furosemide doubled urine volume while sodium excretion increased 20-fold and chloride and potassium excretion increased 12-fold (P less than 0.05 in each case). Net potassium secretion was observed. Ethacrynic acid (2 and 5 mg/kg) also produced no changes in blood pressure, hematocrit, plasma electrolytes, or PRA. At the lower dose GFR increased by 40% and urine volume nearly doubled (P Less than 0.05 in each case). Sodium, chloride, and potassium excretion increased roughly 10-fold (P less than 0.05 in each case). At the higher dose, GFR increased by 80% and urine volume more than doubled (P Less than 0.05 in each case). Sodium excretion rose 40-fold, chloride excretion rose 25-fold, and potassium excretion rose 10-fold (P less than 0.05 in each case). At both doses net potassium secretion occurred. The results demonstrate that both drugs inhibit tubular reabsorption in the turtle, acting primarily on distal segments of the nephron. The failure of either drug to alter PRA suggests that the turtle lacks a tubular mechanism for altering renin release.

Animals↗
PubMedDate not supplied

Activation of liver macrophages following phenobarbital treatment of rats.

Phenobarbital is a potent inducer of hepatic cytochrome P-450 and is a tumor promoter in the two-stage model of liver carcinogenesis. In the present studies, we show that phenobarbital also induces an accumulation of activated macrophages in the livers of treated rats. These macrophages are larger and more stellate than resident Kupffer cells and are highly vacuolated. In addition, macrophages isolated from livers of phenobarbital-treated rats display increased phagocytosis of sheep red blood cells, chemotaxis toward the complement fragment C5a and enhanced production of hydrogen peroxide. Biologically active mediators released by activated macrophages have been implicated in tumor promotion as well as in the regulation of cytochrome P-450-mediated drug biotransformation. We propose that the activated macrophages that accumulate in the liver following phenobarbital treatment may contribute, at least in part, to the biological responses to this drug.

Animals↗