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Biomedical subjects

M K Robinson

Publications and source records attributed to M K Robinson.

At least 19 recordsLinked to original sources
PubMed1995

Antibodies that activate beta 2 integrins can generate different ligand binding states.

A human erythroleukemic cell line (K562) that does not normally express beta 2 integrins has been transfected with the genes encoding these integrins. The resulting cell lines show minimal background adhesion but can be stimulated to bind to appropriate substrates when activated with either of two different antibodies to CD18. The two antibodies appear to generate different ligand binding states in LFA-1 such that different members of the ICAM family are recognized. Antibody-activated complement receptor type 3 and p150,95-transfected cells bind protein-coated surfaces, although they require slightly different activation conditions for optimal binding.

Antibodies, Monoclonal↗
PubMed1995

Two-dimensional protein electrophoresis and multiple hypothesis testing to detect potential serum protein biomarkers in children with fetal alcohol syndrome.

Fetal alcohol syndrome (FAS) surveillance and intervention efforts are hampered by the lack of a specific biochemical test for diagnosis of the syndrome. Based on the hypothesis that abnormalities in growth and development (key features of FAS) involve altered protein metabolism, we analyzed serum proteins by two-dimensional gel electrophoresis and image analysis to search for potential protein biomarkers of FAS. Serum samples from 12 participants in whom FAS had been diagnosed and 8 sex- and age-matched participants whose mothers did not consume alcohol were analyzed in duplicate to determine whether the integrated intensities of matched proteins are significantly altered in children with FAS. Multiple hypothesis testing on 34 of the gels consisting of more than 1700 spots per gel revealed 21 proteins that we classified as potential protein biomarkers of FAS on the basis of significant t-test differences at p < 0.02. We classified 8 of the proteins as candidate biomarkers on the basis of significant concentration differences between case and control subjects at p < 0.01. One of the proteins is clearly an isoform of retinol binding protein; two appear in the area of the gel where alcohol dehydrogenase is expected to appear; one appears to be an isoform of alpha-1-antitrypsin; three appear to be isoforms of the beta-chain of haptoglobin; three may be forms of immunoglobulin light chains; and several others have not been associated with known proteins. No single protein differentiated all case subjects from control subjects, but stepwise canonical discriminant analyses revealed four groups of spots that distinguished between FAS case and control subjects with no misclassifications.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomarkers↗
PubMed1995

Porcine E-selectin: cloning and functional characterization.

E-selectin, a member of the selectin family, is believed to play an important role in mediating the initial adhesive events between leucocytes and the endothelium during inflammation. A monoclonal antibody against human E-selectin was found to cross-react with the porcine equivalent, a glycoprotein of 92,000 MW. Isolation of the cDNA for porcine E-selectin showed that it was 71% homologous with human E-selectin but had two less short consensus repeats. The porcine adhesion molecule could also support the adhesion of both porcine and human neutrophils. Expression of E-selectin on interleukin-1 alpha (IL-1 alpha)- or tumour necrosis factor-alpha (TNF-alpha)-activated porcine aortic endothelial cells in culture was prolonged, persisting for up to 48 hr. Binding studies using a chimeric molecule consisting of the lectin domain of porcine E-selectin and the epidermal growth factor (EGF) domain of human E-selectin fused to the human IgG constant region, further characterized porcine E-selectin as recognizing mainly granulocytic leucocytes and a subpopulation of lymphocytes.

Animals↗
PubMed1994

Cloning and expression kinetics of porcine vascular cell adhesion molecule.

Human vascular cell adhesion molecule is believed to play a key role in recruiting leukocytes to sites of injury. Here we report the identification of a homologous molecule in the pig which has five Ig domains and an overall 77% homology with the human protein. The expression of this protein was also characterised on porcine endothelial cells. Like the human adhesion molecule, the porcine protein could be induced by LPS, TNF and IL-1 alpha, although differences were noted in the kinetics of expression.

Amino Acid Sequence↗
PubMed1992

Comparison of L-selectin and E-selectin ligand specificities: the L-selectin can bind the E-selectin ligands sialyl Le(x) and sialyl Le(a).

The L- and E-selectins are leukocyte and endothelial cell surface molecules which mediate leukocyte-endothelial cell adhesion by interacting with carbohydrate ligands. In the present study we find that L-selectin, like E-selectin, can interact with synthetic neoglycoproteins containing Sialyl Le(x) (Neu5Ac alpha 2-3Gal beta 1-4[Fuc alpha 1-3]GlcNAc beta-R), or Sialyl Le(a) (Neu5Ac-alpha 2-3Gal beta 1-3[Fuc alpha 1-4]GlcNAc beta-R). Additionally, both the E-selectin and L-selectin can bind the peripheral lymph node addressin, a high endothelial venule ligand for L-selectin. Despite overlapping interactions, the L- and E-selectins discriminate between their native ligands. The peripheral lymph node addressin is a preferential ligand for L-selectin; and furthermore, L-selectin expressing cells do not interact detectably with the cutaneous lymphocyte antigen, a native glycoprotein ligand for E-selectin found on a subset of lymphocytes associated with the skin.

Animals↗
PubMed1992

Antibody against the Leu-CAM beta-chain (CD18) promotes both LFA-1- and CR3-dependent adhesion events.

The Leukocytic cell-adhesion molecule (beta 2 integrin) family of adhesion molecules play a key role in the intercellular adhesive interactions necessary for normal immune cell function. In this study, we report an antibody that recognizes an epitope on the Leukocytic cell-adhesion molecule common beta-chain (CD18) and promotes both lymphocyte function-associated Ag-1- and CR3-dependent adhesion events. The antibody recognizes a temperature-sensitive epitope that is not dependent on the presence of divalent cations. It is proposed that antibody binding promotes a conformational change in both lymphocyte function-associated Ag-1 and CR3, which may mimic a natural activation mechanism, resulting in increased cellular adhesion.

Antibodies, Monoclonal↗
PubMed1992

Neutrophil adhesion: a point for therapeutic intervention?

It has become increasingly clear over the last 20 years that the potential exists to modulate inflammatory responses with compounds that interfere with intercellular adhesion. This review highlights the adhesion interactions that occur during neutrophil extravasation and indicates some of the possible ways of disrupting these interactions.

Animals↗
PubMed1992

Glutamine preserves liver glutathione after lethal hepatic injury.

Glutathione (GSH) is a major antioxidant that protects tissues from free radical injury. Glutamine augments host defenses and may be important in GSH synthesis. Acetaminophen toxicity causes hepatic GSH depletion and hepatic necrosis. The authors hypothesized that glutamine-supplemented nutrition would enhance liver GSH stores and diminish hepatic injury and death after acetaminophen overdose. Wistar rats received either a standard total parenteral nutrition (TPN) solution (STD) or an isocaloric, isonitrogenous glutamine-supplemented solution (GLN). On the 5th day of feeding, animals were given acetaminophen (400 mg/kg intraperitoneally) and then killed at various time points. Standard TPN solution animals had a rapid depletion of hepatic glutathione, whereas GLN animals were resistant to this drop and rapidly repleted hepatic GSH stores. Glutamine-supplemented animals maintained higher plasma glutamine concentrations, had lesser elevations in hepatic enzymes, and sustained significantly fewer complications compared with STD animals. The authors conclude that glutamine-supplemented nutrition preserves hepatic glutathione, protects the liver, and improves survival during acetaminophen toxicity. Glutamine may augment host defenses by enhancing antioxidant protection.

Acetaminophen↗
PubMed1992

Hypercholesterolemia: case finding in family practice.

The recommendations of the expert panel of the National Cholesterol Education Program (NCEP) have been endorsed by national medical organizations as standards for the detection and treatment of hypercholesterolemia, yet information on how these recommendations are being followed in primary care settings is limited. This study was done to determine how family physicians in four primary care clinics associated with a teaching hospital in a large southern city follow the NCEP guidelines. Of the total patient sample (N = 817), about 60% had at least one total serum cholesterol measurement. Patients in the younger age groups were less likely to have a cholesterol determination than older patients. Of those in the "self-pay" category only 33% had a cholesterol determination. Variability by clinic and provider type was also noted, with physician assistants showing the highest compliance with screening guidelines (75%), whereas only 43% of patients seen by family practice residents had a cholesterol measurement. Of patients who should have had a lipoprotein analysis, based on total serum cholesterol and risk factors, only 23% actually had a lipid profile. Our study and other similar ones point out that case finding varies considerably and that efforts to improve case finding need to continue.

Adult↗
PubMed1992

Retinal vein occlusion.

Retinal vein occlusion is a common form of retinal vascular disease, especially in middle-aged and older individuals. The diagnosis is based on the funduscopic finding of retinal vein dilatation in association with retinal hemorrhages and cotton-wool spots. The pathology can involve the entire venous system or can be limited to a branch of the central retinal vein. Retinal vein occlusion can be distinguished clinically from diabetic retinopathy and other retinal diseases. Treatment for the acute phase of retinal vein occlusion has been disappointing. However, some late complications, such as persistent macular edema and neovascularization of the iris and retina, respond well to retinal photocoagulation. The family physician has an important role in detecting and controlling risk factors for retinal vein occlusion, including hypertension, diabetes mellitus and hyperviscosity syndromes.

Adult↗
PubMed1992

Glutathione deficiency increases organ dysfunction after hemorrhagic shock.

BACKGROUND: Reactive oxygen metabolites contribute to tissue destruction in a wide variety of diseases. Glutathione, a potent endogenous antioxidant, neutralizes the destructive potential of free radicals, but this tripeptide may be depleted during illness. We hypothesized that glutathione deficiency would amplify organ dysfunction after shock in rats. METHODS: Rats received either diethyl maleate to deplete tissue glutathione or a control solution intraperitoneally. The animals were subsequently bled to and maintained at a mean arterial pressure of 40 mm Hg for 30 minutes and then fully resuscitated. Sham animals underwent blood pressure monitoring only. Tissue glutathione, liver and renal function tests, organ bacterial content, and mortality rates were determined 4 and 24 hours after shock. RESULTS: Normal rats subjected to shock and sham animals had similar laboratory chemistry results, organ culture results, and mortality rates. However, glutathione-depleted animals subjected to shock had elevated liver and renal function tests, increased organ bacteria, and a dramatic increase in mortality rates compared with control shock and sham animals. CONCLUSIONS: We conclude that glutathione deficiency predisposes animals to organ failure and death after an otherwise nonlethal period of hypotension. Because glutathione deficiency is associated with severe injury and sepsis, treatment strategies that maintain glutathione stores may decrease the incidence of multisystem organ failure.

Animals↗
PubMed1991

The cutaneous lymphocyte antigen is a skin lymphocyte homing receptor for the vascular lectin endothelial cell-leukocyte adhesion molecule 1.

A skin-associated population of memory T lymphocytes, defined by expression of the cutaneous lymphocyte antigen (CLA), binds selectively and avidly to the vascular lectin endothelial cell-leukocyte adhesion molecule 1 (ELAM-1), an interaction that may be involved in targeting of CLA+ T cells to cutaneous sites of chronic inflammation. Here we present evidence that CLA itself is the (or a) lymphocyte homing receptor for ELAM-1. Antigen isolated with anti-CLA monoclonal antibody HECA-452 from human tonsillar lysates avidly binds ELAM-1 transfected mouse cells. Anti-CLA antibody blocks T lymphocyte binding to ELAM-1 transfectants. HECA-452 and ELAM-1 binding to lymphocytes or to isolated tonsillar HECA-452 antigen is abrogated by neuraminidase treatment implying a prominent role for sialic acid in CLA structure and function. The dominant form of CLA on T cells is immunologically distinct from the major neutrophil ELAM-1 ligand, the sialyl Lewis x (sLex) antigen (NeuAc alpha 2-3Gal beta 1-4[Fuc alpha 1-3]GlcNAc), which is absent, weakly expressed, or masked on T cells. However, neuraminidase treatment of CLA+ T cells, but not of CLA- T cells, reveals Lewis x (CD15) structures. In combination with the known requirement for terminal NeuAc alpha 2-3Gal and fucose residues attached to N-acetylglucosamine for ELAM-1 and HECA-452 binding, this finding suggests that CLA may comprise an additionally sialylated or otherwise modified form of sLex. The identification of a lymphocyte homing receptor for skin may permit novel approaches to the diagnosis and therapy of cutaneous and inflammatory disorders.

Animals↗
PubMed1991

A carbohydrate domain common to both sialyl Le(a) and sialyl Le(X) is recognized by the endothelial cell leukocyte adhesion molecule ELAM-1.

The specificity of endothelial cell leukocyte adhesion molecule-1, ELAM-1, for binding to a panel of carbohydrate structures was determined by a sensitive cell binding assay with immobilized synthetic glycoconjugates. ELAM-1 cDNA transfectants were found to bind Sialyl Lea (sialylated lacto-N-fucopentaose II) or sialylated Lewis a antigen (NeuAc alpha 2-3Gal beta 1-3(Fuc alpha 1-4)GlcNAc), as well as or slightly better than Sialyl Lex (sialylated lacto-N-fucopentaose III) or sialylated Lewis X antigen (NeuAc alpha 2-3 Gal beta 1-4(Fuc alpha 1-3)GlcNAc). A monoclonal antibody, HECA-452, which has been identified recently as recognizing ELAM-1 ligands in addition to those containing Sialyl Lex, was also found to bind both Sialyl Lex and Sialyl Lea. Hard sphere exo-anomeric (HSEA) calculations were performed on these two hexasaccharides. The conformations indicate that Sialyl Lea and Sialyl Lex show a high degree of similarity in both the nonreducing and reducing termini. As Lea and Lex show much weaker reactivity, the determinants recognized by ELAM-1 and HECA-452 probably involve neuraminic acid and fucose residues which on one face of both Sialyl Lex and Sialyl Lea can be similarly positioned. The finding that Sialyl Lea is a potent ligand for ELAM-1 is important, as circulating Sialyl Lea and Sialyl Lex containing mucins which are elevated in the serum of many cancer patients may block leukocyte interactions with ELAM-1 and may contribute to the pathological immunodepression observed in these patients.

Animals↗
PubMed1991

Evaluation of the primary skin irritation and allergic contact sensitization potential of transdermal triprolidine.

A transdermal patch for the OTC antihistamine, triprolidine (TP), might provide benefits in terms of increased efficacy and reduced sedative side effects. However, concerns over potential irritant or allergic contact sensitization (ACS) skin reactions necessitated through skin toxicity testing before and during initial clinical development. Initial effort was expended on development of a binary vehicle delivery system comprised of TP in 0.5% oleic acid (OA) in propylene glycol (PG). Rabbit skin irritation and Buehler guinea pig skin sensitization testing indicated that this TP/OA/PG formula had both skin irritation and ACS potential. Both tests underestimated, to some degree, the skin toxicities observed in later clinical testing. In clinical tests, skin irritation was due mainly to the OA/PG vehicle, but was enhanced in the presence of high TP concentrations. Of 26 subjects enrolled in a rising dose clinical pharmacokinetics study, one subject exposed twice to TP/OA/PG presented with delayed skin reactions suggestive of ACS. Positive diagnostic patch test results for this subject and four out of five other twice-exposed study subjects suggested that the TP/OA/PG formula had a very high ACS potential. Subsequent predictive clinical patch testing was conducted with a buffered aqueous TP formula which provided in vitro skin penetration of the drug equivalent to the TP/OA/PG formula. These clinical studies demonstrated that TP itself had no significant irritation potential but still induced ACS reactions in a high proportion of test subjects. The incidence of adverse skin reactions to TP was considered to be too high relative to the degree of improved therapeutic benefit of this delivery form. On this basis, all technology development effort was discontinued.

Administration, Cutaneous↗
PubMed1991

The human peripheral lymph node vascular addressin is a ligand for LECAM-1, the peripheral lymph node homing receptor.

The trafficking of lymphocytes from the blood and into lymphoid organs is controlled by tissue-selective lymphocyte interactions with specialized endothelial cells lining post capillary venules, in particular the high endothelial venules (HEV) found in lymphoid tissues and sites of chronic inflammation. Lymphocyte interactions with HEV are mediated in part by lymphocyte homing receptors and tissue-specific HEV determinants, the vascular addressins. A peripheral lymph node addressin (PNAd) has been detected immunohistologically in mouse and man by monoclonal antibody MECA-79, which inhibits lymphocyte homing to lymph nodes and lymphocyte binding to lymph node and tonsillar HEV. The human MECA-79 antigen, PNAd, is molecularly distinct from the 65-kD mucosal vascular addressin. The most abundant iodinated species by SDS-PAGE is 105 kD. When affinity isolated and immobilized on glass slides, MECA-79 immunoisolated material binds human and mouse lymphocytes avidly in a calcium dependent manner. Binding is blocked by mAb MECA-79, by antibodies against mouse or human LECAM-1 (the peripheral lymph node homing receptor, the MEL-14 antigen, LAM-1), and by treatment of PNAd with neuraminidase. Expression of LECAM-1 cDNA confers PNAd binding ability on a transfected B cell line. We conclude that LECAM-1 mediates lymphocyte binding to PNAd, an interaction that involves the lectin activity of LECAM-1 and carbohydrate determinants on the addressin.

Antigens, Surface↗
PubMed1991

Factors affecting inorganic mercury transport and toxicity in the isolated perfused proximal tubule.

The effects of cysteine (80 microM), glutathione (80 microM), rabbit albumin (100 microM), and an ultrafiltrate of rabbit plasma on the toxicity and transport of inorganic mercury (Hg2+; 18.4 microM) in isolated perfused S1, S2, and S3 segments of the renal proximal tubule from the rabbit were studied. Cellular and tubular injuries were assessed qualitatively by light microscopy observations and quantitatively by the tubular leak of the volume marker 3H-glucose. The lumen-to-bath transport of inorganic mercury was assessed by measuring both the rate of disappearance of inorganic mercury from the luminal fluid and the rate of appearance of inorganic mercury in the bath. When glutathione was added to the perfusate containing the inorganic mercury, no signs of epithelial cell necrosis or injury were detected in any of the three segments of the proximal tubule. There was also an absence of or a decrease in cellular injury in the epithelium of the same tubular segments when either cysteine or the ultrafiltrate was present in the perfusate. However, when rabbit albumin and inorganic mercury were present in the perfusate, severe degenerative and necrotic changes occurred very rapidly in the epithelium of all three segments of the proximal tubule. In almost every instance where glutathione, cysteine, or the plasma ultrafiltrate were present in the perfusate, the disappearance flux of inorganic mercury from the tubular lumen into the tubular epithelium was lowered. It was concluded that glutathione, cysteine, and the ultrafiltrate of rabbit plasma provide isolated perfused S1, S2, and S3 segments of the proximal tubule varying degrees of protection from the toxic effects of inorganic mercury. This protection appears to be related to a decrease in the movement of inorganic mercury across the luminal membrane of the tubular epithelial cells.

Albumins↗