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Biomedical subjects

M S Baker

Publications and source records attributed to M S Baker.

At least 19 recordsLinked to original sources
PubMed1992

Occupancy of the cancer cell urokinase receptor (uPAR): effects of acid elution and exogenous uPA on cell surface urokinase (uPA).

The development of a simple, sensitive fluorimetric assay for the measurement of cell surface-associated urokinase plasminogen activator (uPA) on viable, adherent HCT116 cells in microtitre plates, after a preincubation with purified human plasminogen is described. The assay determines plasmin activity by the cleavage of H-D-Val-Leu-Lys 4-aminomethyl coumarin under near physiological pH and ionic conditions with a sensitivity in the range of 5-100 mIU uPA/well at excitation 355 nm and emission 460 nm. Plasmin generated during the assay converted all cell-surface sc-uPA to tc-uPA, allowing the determination of total uPA activity. Inhibitor studies (PAI-2, amiloride or Glu-Gly-Arg chloromethylketone) confirmed the specificity of the uPA assay. Removal of these agents prior to assay allowed determination of the cell surface sc-uPA:tc-uPA ratio. Cell surface activity was only partially removed by acid elution. This corresponded with the loss of a number of proteins and uPA-containing species as detected by SDS-PAGE, gelatin enzymography and Western blotting. Although the major protein species eluted had a M(r) of 55 kDa, reacted with a commercial anti-human uPA mAb and correlated with the main lytic zone, other higher M(r) species were also eluted from HCT116 cells. Exogenous uPA increased cell-surface activity markedly on cells previously treated with acid. Following acid elution, cell surface uPA activity was restored after 30h in culture suggesting either de novo synthesis or release of pre-formed uPA with subsequent secretion and binding to uPAR. The assay has enabled studies on adherent cells to address questions about the regulation and expression of cell-surface uPA.

Aprotinin↗
PubMed1992

Cytokine immunoreactivity in plasma does not change after moderate endurance exercise.

We investigated whether increased concentrations of circulating cytokines may be responsible for exercise-induced priming of blood neutrophils (J. A. Smith et al. Int. J. Sports Med. 11: 179-187, 1990). The plasma concentrations of tumor necrosis factor-alpha, interleukin- (IL) 1 beta, IL-6, granulocyte-macrophage colony-stimulating factor, and neopterin in trained and untrained human subjects were measured by immunoassay before and after 1 h of cycling at 60% of maximal oxygen uptake. C-reactive protein and creatine kinase (CK) were also measured before and 24 h after exercise as markers of the "acute-phase response" and muscle damage (C. Taylor et al. J. Appl. Physiol. 62: 464-469, 1987), respectively. The small changes in the plasma concentrations of cytokines or neopterin observed after exercise in both trained and untrained subjects were not significantly different to those found in a control group of nonexercised subjects. However, untrained subjects did exhibit an acute-phase response (P = 0.04) 24 h after exercise without additional release of CK into plasma. Baseline training differences were confined to a twofold elevation in CK activity (P = 0.04). The results show that circulating cytokines are unlikely to be responsible for the priming of neutrophil microbicidal activity observed after moderate endurance exercise (J. A. Smith et al. Int. J. Sports Med. 11: 179-187, 1990).

Adult↗
PubMed1992

Free radical generation in hydroperoxide-treated erythrocytes monitored continuously by luminol-amplified chemiluminescence.

Organic hydroperoxides induce oxidative damage to mammalian cells. We describe how luminol-amplified chemiluminescence can be used to monitor free radical generation (following treatment of erythrocytes in vitro with organic hydroperoxides) throughout the entire time-course of oxidative stress. Enrichment of erythrocyte alpha-tocopherol levels increased the induction time by 25% and led peak chemiluminescence fall of 30%. Furthermore, ascorbate loading reduced the signal four-fold during the induction period. The catalytic role of haemoglobin was shown by the abolition of chemiluminescence by azide and a low (but detectable) signal in haemoglobin-depleted erythrocyte ghosts. Luminol-amplified chemiluminescence enables the kinetics of free radical generation to be monitored continuously. Furthermore, it may enable features of the mechanism of interaction between cellular antioxidants and antioxidant enzymes to be elucidated.

Cells, Cultured↗
PubMed1992

The wandering spleen.

Wandering spleen is an unusual entity, occurring in both sexes and at any age, but is more frequent in women of reproductive age and in children. Wandering spleen is probably most often a result of congenital anomalies of development of the dorsal mesogastrium, but acquired factors may have a role in certain instances. Patients present most commonly with an asymptomatic mass, mass and subacute abdominal or gastrointestinal complaints or with acute abdominal findings. Clinical diagnosis can be difficult, but noninvasive imaging procedures, such as sonography, nuclear scintigraphy, computed tomography and magnetic resonance imaging are usually diagnostic. Laboratory tests are usually nonspecific, but may occasionally reveal evidence of hypersplenism or functional splenia. Symptoms may remain limited or absent for long periods of time, but complications related to torsion or compression of abdominal organs by the spleen or the pedicle are quite common. Splenomegaly is usually a result of torsion of the pedicle and splenic sequestration. Significant morbidity and mortality rates seem to be considerably less than described in 1933 and limited primarily to patients presenting initially with acute abdominal findings. Management recommendations have varied, but recognition of a significant risk of postsplenectomy sepsis supports a conservative approach. Patients with limited symptomatology may be medically managed until they exhibit worsening symptoms indicating progressive splenic torsion or gastrointestinal compression. Detorsion and splenopexy may be considered a reasonable surgical option even in patients presenting with acute abdomen, if there is no evidence of infarction, thrombosis or hypersplenism. Splenic preservation is especially recommended in extremely young patients who are at particular risk for postsplenectomy sepsis. However, it should be noted that follow-up evaluation data on splenopexy patients are notably lacking. Splenectomy is ideally reserved for patients presenting with acute abdomen and splenic infarction or thrombosis or with hypersplenism and patients in whom splenopexy is technically unfeasible. Subtotal splenectomy and splenic autotransplantation may be of limited value. Pneumococcal, Hemophilus and meningococcal vaccines are indicated before elective splenectomy and shortly after nonelective splenectomy. Antibiotic prophylaxis is recommended for those at particular risk. Prospective studies are unlikely, but extended follow-up information on patients already reported, particularly those managed expectantly or with conservative surgical measures, is needed.

Congenital Abnormalities↗
PubMed1991

Oxidation of articular cartilage glyceraldehyde-3-phosphate dehydrogenase (G3PDH) occurs in vivo during carrageenin-induced arthritis.

Articular cartilage proteoglycan biosynthesis was substantially inhibited by the competitive glycolytic inhibitor 2-deoxyglucose (approximately 65% at 100 mM), but to a much lesser degree (approximately 10%) by the oxidative phosphorylation uncoupler, 2,4-dinitrophenol. These results confirm that articular cartilage proteoglycan synthesis mostly utilises ATP which is generated by glycolysis. In addition, we have utilised the loss of the relatively specific labelling of glyceraldehyde-3-phosphate dehydrogenase (G3PDH) by [3H]-iodoacetic acid to show that rabbit articular G3PDH is oxidised in vivo during the animal model of acute arthritis, carrageenin-induced arthritis, in the same way as we have previously shown that cartilage G3PDH is oxidised after in vitro exposure to sublethal doses of H2O2. The oxidation of rabbit G3PDH in vivo (18 hr post-injection) corresponds with the maximal influx of PMNL cells into the arthritic synovial fluid and with substantial inhibition of proteoglycan core protein synthesis. We propose that H2O2 released from "activated" PMNLs and macrophages is responsible for the "down-regulation" of biosynthetic processes found in cartilage during acute inflammation.

2,4-Dinitrophenol↗
PubMed1991

The effects of free radical scavengers on arachidonic acid metabolism by ovine placental microsomes.

1. The effect of free radical (superoxide and hydroxyl) and hydrogen peroxide scavengers on the formation of prostaglandin E2 by ovine placental microsomes was investigated. 2. Of the free radical scavengers tested only Mn Desferal, a low molecular weight (712 Da) superoxide scavenger, at concentrations of 0.5-5 mmol/l significantly (P less than 0.001) stimulated PGE2 formation by ovine placental microsomes. 3. This observation is consistent with the involvement of superoxide radicals in the inactivation of prostaglandin G/H synthase (PGHS). 4. The results obtained further suggest that if superoxide radicals are important regulators of PGHS activity in the ovine placenta, they are not accessible to large molecular weight free radical scavengers.

Animals↗
PubMed1991

The oxidant hypochlorite (OCl-), a product of the myeloperoxidase system, degrades articular cartilage proteoglycan aggregate.

The myeloperoxidase-derived oxidant, hypochlorite (OCl-) was shown to be able to degrade proteoglycan aggregate prepared from bovine articular cartilage. Exposure of proteoglycan aggregate to OCl- concentrations less than 10(-4) M resulted in a decrease in the size of the constituent proteoglycan monomers, which were unable to reaggregate with hyaluronate due to the loss of the hyaluronic acid binding region as indicated by immunoblotting using the monoclonal 1-C-6 antibody. Analysis of the [35S]-labeled core proteins by SDS/polyacrylamide electrophoresis and fluorography indicated a decrease in the size of the core protein. These data suggest that concentrations of OCl- below 10(-3) M results in the cleavage of the proteoglycan core protein in or near the hyaluronic acid binding region. The physiological consequences of these data are discussed. Exposure to higher concentrations (greater than 10(-3)) of OCl- caused more extensive degradation of the core protein; however, there was no evidence to suggest that OCl- cleaves glycosaminoglycan (GAG) chains.

Animals↗
PubMed1991

Estimating the treatment costs of breast and lung cancer.

The Continuous Medicare History Sample File (CMHSF) was used to derive an estimate of the lifetime direct medical expenses attributable to two chronic diseases, lung cancer and female breast cancer. These two cancers are the leading cancer causes of death in men and women in the United States. They inflict large costs on the population, both direct and indirect, but the costs have been difficult to measure. The primary obstacle to quantification is the intermittent and long-term nature of treatment for these diseases. A complete record of expenses cannot usually be obtained from one source, however, a review of all the national health surveys, as well as the Medicare statistical files identified the CMHSF, which is maintained by the Health Care Financing Administration in a format suitable for calculation of cumulative medical expenses. Some of the pertinent features of the CMHSF include the following: 1) it is a nationally representative sample of the Medicare population, 2) it is longitudinal covering an 8-year period from 1974 to 1981, 3) it captures the majority of medical expenses for each enrollee, and 4) it can be linked to other national data bases such as the National Death Index. Charges for three phases of cancer treatment were derived from the file: initial therapy, maintenance care, and terminal care. A method is described for computing the present value of life-time treatment costs from the phase-specific charges. The lifetime cost of treating breast cancer in 1984 dollars is $36,926 and lung cancer is $12,510.

Aged↗
PubMed1991

Medical aspects of Persian Gulf operations: environmental hazards.

Deployment of troops to the countries surrounding the Persian Gulf will result in exposure to a unique and dangerous environment. The austere and hostile environment is marked by extremes of temperature, dangerous snakes and scorpions, and hazardous marine conditions, in addition to the problems that will be faced by those potentially in combat. Proper education and training prior to deployment, reinforcement by the leadership, and common sense prevention measures will prevent most environmental casualties from occurring.

Animals↗
PubMed1991

Medical aspects of Persian Gulf operations: serious infectious and communicable diseases of the Persian Gulf and Saudi Arabian Peninsula.

The countries surrounding the Persian Gulf are remarkable for the variety of infectious and contagious diseases that will affect those deployed to this area. In addition to the common gastrointestinal problems often seen in deployed troops, they will be exposed to such unusual problems as malaria, schistosomiasis, leishmaniasis, and rabies. Medical personnel will need to consider diseases that they have never before treated or diagnosed, and will have to educate their troops regarding control of vectors, avoidance of exposure, and personal hygiene and sanitation. Proper predeployment vaccination, use of appropriate prophylaxis, and use of countermeasures such as insect repellent will keep the spread of disease minimal.

Diarrhea↗
PubMed1990

Inhibition of cancer cell urokinase plasminogen activator by its specific inhibitor PAI-2 and subsequent effects on extracellular matrix degradation.

Isotopically labeled [( 3H]serine, [3H]proline, and [35S]sulfate) subendothelial cell basement membranes were used to determine the role of urokinase plasminogen activator (uPA) and its specific inhibitor plasminogen activator inhibitor 2 (PAI-2) in colon cancer cell extracellular matrix degradation. Recombinant PAI-2 irreversibly inhibited low and high molecular weight purified human uPA in addition to both colon cancer cell-associated and secreted uPA, particularly if pro-uPA had been preactivated. Two selected lines (COLO394 and LIM1215) preferentially degraded differently labeled matrices in a time- and plasminogen-dependent manner. This process was inhibitable by PAI-2 in the medium at levels which suggested that some degree of "shielding" of cell surface uPA from inhibitor occurred. The ability of PAI-2 to regulate the invasive phenotype of cells which express cell surface or receptor-bound uPA is discussed.

Cell Line↗
PubMed1990

Plasminogen activator inhibitor 2 (PAI-2) is not inactivated by exposure to oxidants which can be released from activated neutrophils.

Purified recombinant human monocyte plasminogen activator inhibitor 2 (PAI-2) retained inhibitory activity after exposure to a number of oxidants, including hypochlorite anion (OCl-), chloramine-T (CT) and hydrogen peroxide (H2O2). Analysis of PAI-2 exposed to oxidants by gel filtration chromatography and SDS-PAGE indicated that although the protein could no longer be detected by silver staining, this was not due to fragmentation of the PAI-2 molecule. The sensitivity of a number of serine protease inhibitors (serpins), (eg. alpha 1 proteinase inhibitor (alpha 1PI) and plasminogen activator inhibitor 1 (PAI-1] to oxidative inactivation has been attributed to oxidation of reactive site methionine residues and/or tertiary structural modifications. The relevance of these phenomena and the potential for PAI-2 to be used as a therapeutic inhibitor of urokinase (uPA)-dependent proteolysis during inflammation and tumour metastasis is discussed.

Amino Acid Sequence↗
PubMed1990

Depolymerization of synovial fluid hyaluronic acid (HA) by the complete myeloperoxidase (MPO) system may involve the formation of a HA-MPO ionic complex.

Gel filtration analysis (Sephacryl S-1000) indicated that the Mr of purified equine synovial cell culture 3H-hyaluronic acid (HA) (Mr greater than 1.67 x 10(7) Da) decreased in a concentration dependent manner after exposure to hypochlorite (OCl-). Both high (equine) and medium (human, Mr = 5.5 x 10(5) Da) molecular weight HA were cleaved by the complete myeloperoxidase system (MPO/H2O2/Cl-). Purified human neutrophil myeloperoxidase (MPO) bound tightly to HA-Sepharose and we suggest that this is due to a strong ionic interaction between HA and MPO. The formation of such a complex did not disturb MPO activity. The significance of these results in relation to our previous studies concerning the reduction in viscosity and potential cleavage of HA by the product of the MPO/H2O2/Cl- system is discussed.

Cells, Cultured↗
PubMed1990

The acutely injured patient.

This article reviews the examination techniques and priorities for an injured patient. The format can be tailored to both the field setting and the hospital. Learning a concise method of examination and treatment is basic to trauma care and helps ensure that life-threatening injuries are not overlooked.

Critical Care↗
PubMed1990

Recognition of vascular injury in the trauma patient.

Medical personnel should be able to recognize vascular injuries. Knowing the key signs of ischemia, namely pallor, pulselessness, pain, paresis, and paresthesia and the soft signs of vascular injury will help to prevent limb loss.

Blood Vessels↗
PubMed1990

The inhibitory action of oxygen radical scavengers on proteinuria and glomerular heparan sulphate loss in the isolated perfused kidney.

The perfused isolated kidney is a partial ischemic system that is characterised by glomerular proteinuria and release of glomerular heparan sulfate. Metabolic changes associated with the levels of glutathione, xanthine oxidase and glyceraldehyde 3-dehydrogenase indicated that oxygen radical metabolites were being produced during the perfusion. We have demonstrated that a mixture of oxygen metabolite scavengers containing mannitol, superoxide dismutase and catalase included in the perfusion medium significantly reduced protein excretion. Similar results were obtained with the administration of allopurinol to the rat 24h prior to kidney removal and allopurinol in the perfusion medium. [35S]Heparan sulfate loss from the glomerulus was totally inhibited by the scavenger mixture. These results suggest that reactive oxygen metabolites may be involved in damage to renal capillaries, specifically to heparan sulfate proteoglycan, which leads to proteinuria as a result of partial ischemia produced during perfusion.

Animals↗