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Biomedical subjects

M S Baker

Publications and source records attributed to M S Baker.

At least 37 records · Page 2Linked to original sources
PubMed1999

The medical department in military operations other than war. Part II: Medical Civic Assistance Program in Southeast Asia.

It is a short trip by air from Bangkok, Thailand, to Phnom Penh, Cambodia, but a dramatic contrast. A Medical Civic Assistance Program (MEDCAP) visit was conducted in conjunction with Exercise Flash Canoe 97, the first U.S. Navy mission to Cambodia in more than 22 years. Nearly 3,000 patients were seen by the MEDCAP team members. Medical and dental care, medications, educational materials, and training were provided. The mission was an exceptional training opportunity for U.S. Medical Department personnel, who learned to function outside of the hospital and clinic environment and to deal with limited logistic backup, austere field conditions, a hostile environment, and an overwhelming number of patients, many of them with infectious diseases. Cambodia lacks public health infrastructure and has uncertain communications, difficult travel conditions, and an unstable political climate. Using the planning checklists described in Part I, the team completed the "in-country" part of the mission with minimal logistic and support problems, maximizing the effectiveness of the health care providers. The MEDCAP is an important instrument of U.S. foreign policy and friendship with other peoples.

Adolescent↗
PubMed1998

Loss of cell viability dramatically elevates cell surface plasminogen binding and activation.

The plasminogen activation cascade is focused at the cell surface by virtue of the presence of plasminogen and plasminogen activator receptors. We have utilized flow cytometric plasminogen (plg) binding and activation assays to examine both plasminogen binding and activation on the surface of specific subpopulations of U937 cells (viable, apoptotic, and dead cells). A direct relationship was found to exist between cell viability (propidium iodide uptake) and the magnitude of lysine-dependent plasminogen binding, with apoptotic and dead subpopulations of cells binding up to 100-fold more plasminogen than viable cells. Despite the high level of lysine-dependent plasminogen binding on dead cells, plasminogen activation was minimal due to low levels of cell-surface urokinase plasminogen activator. Plasminogen activation readily occurred on the surface of apoptotic cells because of a dramatic increase in both lysine-dependent plasminogen binding and endogenous urokinase plasminogen activator. These results indicate that colocalization of plasminogen and urokinase plasminogen activator are paramount for plasminogen activation to proceed on the cell surface. Our data also strongly implicate the involvement of the plasminogen activation cascade in apoptosis, especially on urokinase plasminogen activator-expressing cell types. The current study clearly supports the important role of flow cytometry in cellular plasminogen binding and activation studies.

Amino Acid Chloromethyl Ketones↗
PubMed1998

Immunological detection of conformational neoepitopes associated with the serpin activity of plasminogen activator inhibitor type-2.

The physiological roles of plasminogen activator inhibitor-2 (PAI-2) are not yet well understood. Kinetic studies suggest a role in the regulation of plasminogen activator-driven proteolysis in many cell types. This study describes a monoclonal antibody (2H5), which uniquely recognizes neoepitope determinants on PAI-2 appearing after thermodynamic relaxation of the molecule. Enzyme-linked immunosorbent assays and native polyacrylamide gel electrophoresis immunoblotting confirmed the specificity of 2H5 for urokinase type plasminogen activator.PAI-2 complexes. Examination of the affinity of 2H5 for complexes formed between PAI-2 and a synthetic 14-mer reactive site loop peptide, PAI-2 treated with tissue plasminogen activator, or thrombin suggests that the 2H5 epitope is determined exclusively by sequences found only on PAI-2 following proteolytic cleavage of the Arg380-Thr381 bond and insertion of the reactive site loop into beta-sheet A. Peptides lacking both the P13 (Glu368) and P14 (Thr367) residues did not induce a conformational change or affect the inhibitory activity of PAI-2, indicating that one or both of these residues are critical for PAI-2 function. To our knowledge, this is the first description of a monoclonal antibody that can distinguish conformational changes in PAI-2 related specifically to its potential biological function(s).

Antibodies, Monoclonal↗
PubMed1998

Differentiating cells of murine stratified squamous epithelia constitutively express plasminogen activator inhibitor type 2 (PAI-2).

In stratified squamous epithelia a critical balance among cell proliferation, differentiation, and death must be maintained in order for these tissues to fulfill their barrier function. Previous studies have demonstrated that plasminogen activator inhibitor 2 (PAI-2) is a product of differentiating epidermal keratinocytes, suggesting a role for this inhibitor during squamous differentiation. Furthermore, in certain tumor cell lines, overexpression of PAI-2 confers resistance to the induction of programmed cell death, suggesting cytoprotective function(s). In the present study we demonstrate that PAI-2 mRNA and protein are constitutively and uniquely expressed in differentiating cells of murine stratified squamous epithelia, including epidermis, esophagus, vagina, oral mucosa, and tongue. PAI-2 immunohistochemical localization patterns suggest a predominantly cytosolic distribution, consistent with biochemical identification of the major PAI-2 species as a 43-kDa, presumably non-glycosylated protein. Functional analysis shows that the majority of epithelial PAI-2 is active. In contrast to the high levels of PAI-2 expression in stratified squamous epithelia, little or no PAI-2 is detectable in simple epithelia. These findings suggest that epithelial PAI-2 may mediate inhibition of intracellular proteinases associated with events during terminal differentiation and death that are unique to stratified squamous epithelia.

Animals↗
PubMed1998

Increased plasminogen binding is associated with metastatic breast cancer cells: differential expression of plasminogen binding proteins.

Overexpression of urokinase-type plasminogen activator and its receptor correlates with metastatic capacity in breast cancer. In this study we show that the urokinase/urokinase receptor-overexpressing, metastatic human breast cancer cell line MDA-MB-231 (1) bound significantly more cell-surface plasminogen in a lysine-dependent manner and (2) was capable of generating large amounts of plasmin compared with the non-metastatic cell lines MCF-7 and T-47D. In addition, distinct plasminogen binding proteins were detected in the plasma membranes of the cell lines, suggesting heterogeneity of binding proteins. Plasminogen binding was analysed using a combination of dual-colour fluorescence flow cytometry and ligand histochemistry (for comparative and cellular localization of ligand binding), and fluorimetry (for Scatchard analysis). Apart from revealing the greater plasminogen binding capacity of MDA-MB-231 cells, flow cytometry and histochemistry also revealed that, in all three cell lines, non-viable or permeabilized cells bound significantly more plasminogen in a lysine-dependent manner than viable or non-permeabilized cells. Viable MDA-MB-231 cells bound plasminogen with moderate affinity and high capacity (Kd = 1.8 microM, receptor sites per cell 5.0 x 10(7). Our results indicate that differences in cell surface-specific plasminogen binding capacity between cell lines may not be detectable with binding techniques that cannot distinguish between viable and non-viable cells.

Breast Neoplasms↗
PubMed1998

Localization of plasminogen activator inhibitor type 2 (PAI-2) in hair and nail: implications for terminal differentiation.

Plasminogen activator inhibitor type 2 (PAI-2) is an unusual serine proteinase inhibitor in that it is largely retained within the cell and is found in high concentrations in the upper viable layers of human epidermis. Studies using transfected cell lines that express high levels of PAI-2 have suggested that this inhibitor may confer protection against programmed cell death. To test the hypothesis that PAI-2 may protect epithelial cells in vivo from premature programmed cell death, we determined expression patterns of PAI-2 in murine hair and nail. These epidermal derivatives are comprised of numerous epithelial cell types with distinct differentiation pathways. Furthermore, the cyclic nature of the follicular epithelium makes it ideal for studying sequential stages of cell differentiation and death. PAI-2 mRNA and protein were detected in the differentiating cells of the outer root sheath and medulla of the follicle during the anagen phase of the hair growth cycle. PAI-2 was also detected in the permanent portion of the catagen follicle. In the telogen phase of the hair growth cycle, PAI-2 was limited to the postmitotic cells of the outer root sheath directly abutting the club hair. In the nail, PAI-2 was detected in the differentiating cells of the matrix and nail bed. This consistent, selective distribution of PAI-2 in the postmitotic, maturing cells prior to terminal keratinization and death suggests that (i) PAI-2 may be considered as a differentiation marker for many epithelial cell types, and (ii) PAI-2 is appropriately positioned to protect epithelial cells from premature demise.

Animals↗
PubMed1998

Gene expression of plasminogen activation cascade components in human term gestational tissues with labour onset.

The plasminogen activation cascade is thought to play a critical role in labour-associated remodelling events, such as fetal membrane rupture and placental separation. The aim of this study was to quantify, by Northern analysis, the gene expression of urokinase plasminogen activator (UPA), urokinase receptor (UPAR) and plasminogen activator inhibitor type-2 (PAI-2) in human gestational tissues. Amnion, choriodecidua and placenta were collected from women before, during and after spontaneous-onset labour at term. The expression of UPAR mRNA was significantly (P < 0.05) increased in amnion tissue during and after labour and delivery, compared with the before-labour group. In contrast, UPAR gene expression in choriodecidua and placenta was not significantly altered in association with labour onset. PAI-2 mRNA expression was also significantly (P < 0.05) increased in amnion after labour. No statistically significant differences were observed in choriodecidua or placenta PAI-2 mRNA with labour onset. Neither was any significant effect of labour status on UPA mRNA identified in any of the tissues examined. This study is the first to describe a significant increase in UPAR and PAI-2 gene expression in human amnion tissue with labour. These data are consistent with the hypothesis that, during labour, up-regulation of UPAR expression in amnion serves to localize active UPA at the cell surface, thereby increasing proteolytic activity in fetal membranes. Increased PAI-2 in amnion after labour may provide a regulatory 'switch' to cease further proteolysis in this tissue type. In conclusion, the data obtained support the proposal that the plasminogen activation cascade contributes to the rupture of fetal membranes during active labour.

Amnion↗
PubMed1997

The human ENO1 gene product (recombinant human alpha-enolase) displays characteristics required for a plasminogen binding protein.

Plasminogen binds with low affinity in a lysine-dependent manner to many cell types. Previously, a 54 kDa plasminogen receptor found on the surface of U-937 cells was identified as an alpha-enolase-like molecule. The aims of this study were to determine whether recombinant alpha-enolase (r-alpha-enolase), encoded by ENO1, was a plasminogen binding protein and to generate polyclonal antibodies against this antigen. Plasminogen specifically bound r-alpha-enolase with a Kd 1.9 microM and approached saturation at 10 microM. Lysine-dependent plasminogen binding to r-alpha-enolase was demonstrated by a greater than 80% inhibition of binding by the lysine analogues epsilon-amino caproic acid and tranexamic acid, whilst only 14% inhibition occurred with the arginine analogue benzamidine. Removal of the C-terminal lysine residue of r-alpha-enolase with carboxy-peptidase B significantly reduced its plasminogen binding capacity, suggesting that binding required C-terminal lysine residue of r-alpha-enolase. Binding to r-alpha-enolase enhanced the activation rate of plasminogen by urokinase but prevented alpha 2-antiplasmin from binding plasminogen. Taken together, these data suggest that the gene product of human ENO1 encodes an authentic plasminogen binding protein.

Binding, Competitive↗
PubMed1997

Tissue-specific expression of the relaxed conformation of plasminogen activator inhibitor-2 and low-density lipoprotein receptor-related protein in human term gestational tissues.

The relaxed conformation of plasminogen activator inhibitor-2 (PAIr) is formed during inactivation of the matrix-degrading enzyme urokinase plasminogen activator (uPA). The presence of PAIr in tissues, therefore, indicates the in situ inhibition of uPA-mediated proteolysis. In addition, PAIr functions as a ligand for the clearance receptor low-density lipoprotein receptor-related protein (LRP), thereby promoting internalization of receptor-bound uPA-PAIr complexes from the cell surface. The rapid internalization of receptor-bound, inactivated uPA has been suggested to be characteristic of invasive cell phenotypes. The aims of this study were to characterize the immunohistochemical localization of PAIr in human term gestational tissues (amnion, choriodecidua, and placenta) and to establish its co-expression with other components of the uPA cascade. The results obtained indicate that PAIr immunoreactivity was exclusively localized to amnion epithelial cells, with only minimal staining in the underlying chorion. PAIr immunoreactivity was not detectable in any of the trophoblastic tissues examined (villous and extravillous). The tissue-specific expression of PAIr immunoreactivity was not significantly altered in association with labor onset. uPA and PAI-2 staining was localized predominantly to amnion epithelial cells, underlying chorion, and trophoblast cells of villous and extravillous tissue. Amnion and trophoblasts of extravillous and chorionic tissue showed uPAR immunoreactivity, whereas staining in placenta was absent. Immunoreactive LRP was confined to trophoblasts of the chorion, and the villous and extravillous tissue. For the first time, localization of PAIr at the tissue level has been identified. The data obtained are consistent with the hypothesis that cells of invasive phenotype, although expressing all components of the uPA cascade, do not accumulate immunoreactive PAIr, because it is rapidly internalized from the cell surface. Conversely, cells of noninvasive phenotype will accumulate PAIr immunoreactivity only in the absence of LRP expression. We propose that the presence of PAIr and the absence of LRP at the cell surface are putative markers of noninvasive phenotypes.

Amnion↗
PubMed1997

A treadmill protocol to investigate independently the metabolic and mechanical stress of exercise.

The purpose of this study was to describe an experimental treadmill model for the independent assessment of metabolic and mechanical stress associated with exercise. Eight well-trained male runners (VO2max 61.2 ml.kg-1.min-1) undertook, on different days, three 40 min bouts (consisting of 8 x 5 min work intervals) of treadmill running: uphill, downhill and near-level. Mean %VO2 max was 90.0, 52.7 and 52.2 for uphill, near-level and downhill running respectively. Oxygen uptake increased (p < 0.05) across the eight work intervals during uphill running, with non-significant increases in both near-level and downhill running. In contrast, heart rate increased (p < 0.05) with uphill and downhill, but not near-level running. Blood lactate concentration was higher (p < 0.01) and plasma pH lower (p < 0.01) after uphill running compared with downhill and near-level running. Plasma creatine kinase activity was elevated (p < 0.05) immediately after uphill running and 24 hours after downhill running (p < 0.05). Subjective rating of delayed onset muscle soreness was elevated (p < 0.05) at 24 and 48 hours after downhill running only. There were no significant changes in the plasma concentration of the inflammatory mediators interleukin-1beta, complement component C3a and C reactive protein. Given the observed differences in cardiorespiratory responses and indicators of muscle damage and soreness, this experimental model could be employed to investigate, independently, the metabolic and mechanical stress of exercise.

Adult↗
PubMed1996

Evidence of oxidant-induced injury to epithelial cells during inflammatory bowel disease.

Evidence of in vivo oxidant-induced injury in inflammatory bowel disease (IBD) is largely indirect. Colon epithelial crypt cells (CEC) from paired specimens of histologically normal and inflamed bowel from IBD patients with active disease were examined for altered protein thiol redox status as an indicator of oxidative damage. When CEC preparations from 22 IBD patients were labeled with the reduced-thiol-specific probe [14C]-iodoacetamide (IAM), there was decreased labeling of a number of proteins indicating oxidation of thiol groups in CEC from inflamed mucosa compared to paired normal mucosa, especially the loss of thiol labeling of a 37-kD protein which was almost completely lost. The loss of reduced protein thiol status for the 37-kD band was paralleled by loss of epithelial cell glyceraldehyde-3-phosphate dehydrogenase (GAPDH, EC 1.2.1.12) enzyme activity, an enzyme known to contain an essential reduced cysteine (Cys149) at the active site. The identity of the 37-kD protein as GADPH monomer was confirmed by NH2-terminal amino acid sequence analysis. To examine whether this type of in vivo injury could be attributed to biologically relevant oxidants produced by inflammatory cells, CEC prepared from normal mucosa were exposed to H2O2, OCl-, nitric oxide (NO), and a model chloramine molecule chloramine T (ChT) in vitro. Dose-dependent loss of IAM labeling and GAPDH enzyme activity was observed. The efficacy (IC50) against IAM labeling was OCl- >> ChT > H2O2 > NO (52 +/- 3, 250 +/- 17, 420 +/- 12, 779 +/- 120 microM oxidant) and OCl- >> ChT > NO > H2O2 (89 +/- 17, 256 +/- 11, 407 +/- 105, 457 +/- 75 microM oxidant), respectively, for GAPDH enzyme activity. This study provides direct evidence of in vivo oxidant injury in CEC from inflamed mucosa of IBD patients. Oxidation and inhibition of essential protein function by inflammatory cells is a potential mechanism of tissue injury that may contribute to the pathogenesis of the disease and supports the exploration of compounds with antioxidant activity as new therapies for IBD.

Amino Acid Sequence↗
PubMed1996

Exercise and the neutrophil oxidative burst: biological and experimental variability.

The effect of acute bouts of moderate-intensity running and cycling on the neutrophil oxidative burst was examined. Eight well-trained male runners in group 1 each undertook, on different days, either two 40-min bouts of running (run 1 and run 2) separated by a 1-h recovery period, or 40 min of moderate cycling. Blood leucocyte (+49%) and granulocyte (+57%) counts increased (P < 0.05) with moderate running, but only the leucocyte count (+27%) was elevated significantly during moderate cycling. Chemiluminescence activity and superoxide anion release decreased after run 1 (-61%, P < 0.05) and after 30 min of cycling (-53%, P < 0.05), with no significant changes in the intracellular release of hydrogen peroxide. The same measures were also assessed at rest in a group of eight male volunteers (group 2) with no significant difference in neutrophil activity for samples treated in parallel or 1 h apart. These data suggest that while neutrophils are mobilised into the circulation in the first few hours following moderate exercise, their oxidative burst is temporarily inhibited. These effects were due to exercise per se and not to temporal variability or intra-assay variation.

Adult↗
PubMed1996

Clusterin, a putative complement regulator, binds to the cell surface of Staphylococcus aureus clinical isolates.

The ability of Staphylococcus aureus Cowan I strain and a number of S. aureus clinical isolates to bind to the human blood glycoprotein clusterin was investigated. Binding of clusterin to these strains was tested by both enzyme-linked immunosorbent assay and flow cytometry. All of the S. aureus strains examined appeared to bind clusterin to some extent, while nonpathogenic control strains Bacillus subtilis BR151 and Escherichia coli JM109 did not. Three S. aureus isolates were selected for more detailed study; binding of labeled clusterin was saturable, inhibited in the presence of excess unlabeled clusterin, and prevented by pretreatment of bacteria with proteases. From the saturation binding studies, estimates of the affinity constants for the binding of clusterin to the bacteria ranged from 31 to 57 nM. Addition of clusterin to S. aureus cultures was also found to result in aggregation of the bacterial cells; aggregation was not detected when clusterin was added to B. subtilis BR151 or E. coli JM109 cultures. These results suggest that at least some S. aureus strains possess specific proteinaceous receptors for clusterin. Such receptors may be an important new bacterial virulence determinant for S. aureus, as clusterin has been proposed to have a role in the regulation of complement activity.

Clusterin↗
PubMed1996

Moderate exercise triggers both priming and activation of neutrophil subpopulations.

We investigated how moderate exercise affects neutrophil microbicidal activity and whether exercise-induced responses are associated with changes in growth hormone (GH) secretion. Biological fluctuations were controlled for and GH secretion was manipulated by glucose ingestion. In eight men, 1 h of moderate exercise increased intracellular H2O2 generation in response to phorbol 12-myristate 13-acetate stimulation by threefold (P = 0.025) and complement receptor expression by 20% (P = 0.045). These responses were accompanied by a twofold increase in the plasma concentration of elastase, a marker of neutrophil activation in vivo. The plasma concentration of GH increased 10-fold after exercise, but this was reduced to 3-fold by glucose ingestion (P < 0.001), which also blunted elastase release (P < 0.001). Although the magnitude of H2O2 generation increased in proportion to the increase in plasma GH concentration, it declined progressively once this exceeded 20 ng/ml. The net response of neutrophils to exercise may represent a balance between the individual responses of subpopulations that are unaffected, primed, or fully activated by circulating mediators that respond to exercise and to dietary glucose intake.

Adult↗
PubMed1996

Combat care in 1995: implications in a changing world.

The military is changing in size, composition, and mission requirements. Military medical care will require changes to support mission requirements and keep pace with tactical situations. The echelon system of care will need great flexibility and medical personnel will require enhanced training in wartime skills to provide needed care closer to the battlefield.

Military Medicine↗
PubMed1996

Management of soft-tissue wounds, burns, and hand injuries in the field setting.

In combat, the tactical situation can prevent rapid evacuation to definitive care, or casualty overload can tie up the surgical teams. All medical personnel and their supporting cadre should have the ability to manage wounds and burns. Controlling bleeding and airways, cleaning and debriding wounds, and dressing or splinting injuries is essential knowledge and training for enlisted and officer personnel of all medical departments.

Burns↗
PubMed1996

Military medicine in operations other than war. Part I: Use of deployable medical systems facilities to assist in urban crises and enhance reserve medical training.

Navy medicine is challenged to provide ongoing and realistic training for medical personnel who will be deployed to provide battlefield care. Current events in this country suggest that the need for realistic training could be met while simultaneously providing support to civilian communities with great need. Deployable Medical Systems hospital modules could be set up in areas where the medical care system is overwhelmed and provide real patient management on the deployment platform. This innovative approach to providing "mutual support" to our own citizens will also enhance the cooperation between the civilian and military sectors should a civil disaster occur.

Disaster Planning↗