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Biomedical subjects

A F Williams

Publications and source records attributed to A F Williams.

At least 217 records · Page 12Linked to original sources
PubMed1981

Children killed in falls from motor vehicles.

In 1978 in the United States, 38 children aged 5 years or younger were killed when they fell from the passenger compartments of moving motor vehicles not involved in crashes. Twenty-eight children (74%) were boys. Eighteen (47%) were 2 years old; 35 (92%) were aged 1 to 3 years. Thirty-six children fell out through doors, one fell out of a window, and one fell through a hole in the floor. Sixteen falls occurred when the driver was making a turn or going around a curve, nine when someone opened the door, seven when the driver was proceeding straight ahead, five when the driver was backing out of a driveway, and one when the driver was swerving. All 38 children killed in falls from vehicles were unrestrained. Use of seat belts or child restraint systems would prevent falls even if doors came open, as well as providing protection in crashes. A recent study has shown that pediatricians, by routinely counseling parents to restrain children in cars, can have some effect in increasing child restraint use. Pediatricians should also encourage parents to transport children in rear seats and to check at the start of trips to ensure that all doors are completely closed and locked.

Accidents, Traffic↗
PubMed1980

The kinetics of antibody binding to membrane antigens in solution and at the cell surface.

The reaction kinetics of 125I-labelled mouse monoclonal antibodies binding to three cell-surface antigens of rat thymocytes (Thy-1.1, W3/25) were studied. The differences between bivalent and univalent interactions were determined by using antibody in the F(ab')2 or Fab' form and by using antigen in polymeric or monomeric forms. Association rate constants (k+1), dissociation rate constants (k-1) and equilibrium constants were determined. Also, the dissociation kinetics of rabbit antibodies against rat Thy-1 antigen were studied. The major findings were as follows. (i) With F(ab')2 antibody there was no simple relationship between antigen density at the cell surface and extent of bivalent binding. Extensive univalent binding was observed unless the antibody had a high k-1 for the univalent interaction, in which case all binding was bivalent. (ii) k+1 values were similar for F(ab')2 or Fab' antibody, and for the different antibodies were in the range 0.8 x 10(5)--1.1 x 10(6) M-1.s-1. These differences were sufficient to affect the interpretation of serological assays with the different antibodies. (iii) Antibody bound bivalently dissociated much more slowly than that bound univalently. However, the k-1 values for the univalently bound antibody were sufficiently low in most cases that the lifetime of the univalent complex was similar to or greater than the time needed for the assay. Thus the results could be interpreted on the basis of irreversible reactions. The overall conclusion from the study is that for an understanding of the binding of antibody to cell-surface antigens the kinetics of the interaction are of major importance and theories based on equilibrium binding are inappropriate.

Animals↗
PubMed1980

Two subsets of rat T lymphocytes defined with monoclonal antibodies.

A new monoclonal mouse antibody that recognizes a subset of rat peripheral T cells has been prepared by immunizing mice with rat thymocyte glycoprotein. This antibody, designated MRC OX 8, labels all peripheral T cells that are unlabeled by the previously described W3/25 monoclonal antibody. No peripheral T cells were found that bound both antibodies, but, in contrast, 90% of thymocytes were doubly labeled. Thoracic duct lymphocytes of congenitally athymic nude rats were not labeled by either antibody, but the spleens of such animals contained both W3/25+ cells and MRC OX 8+ cells. These splenocyte subpopulations did not overlap. Using the fluorescence-activated cell sorter to isolate cells binding MRC OX 8 antibody, the phenotype of T cells mediating various T cell functions was established. Combining the present results with those published previously, it is shown that the cells providing help for antibody responses and those mediating graft-vs.-host reactions are phenotypically W3/25+ MRC OX 8-. On the other hand, parental T cells that suppress antibody formation in F1 hosts were identified as W3/25- MRC OX 8+. The relationship between the rat T cell subsets defined by these antibodies and those in the mouse identified by the Ly series of alloantibodies is discussed and a comparison made between teh rat W3/25+ subset and a recently identified human T cell subset.

Absorption↗
PubMed1980

Immunosuppressive properties of rabbit antibodies against a major glycoprotein restricted to rat leukocyte membranes.

The role of antibodies to the rat leukocyte-common (LC) antigen in the immunosuppression induced by antilymphocyte serum (ALS) was tested in two ways. First, two batches of rabbit antisera to purified rat LC antigen and a conventional rabbit anti-rat thoracic duct lymphocyte serum (ALS) were compared for their ability to suppress the rejection of LEW (RT1l) kidney grafts transplanted to DA (RT1a) recipients. All three sera were able to suppress rejection completely. However, when the amount of lymphocyte-binding immunoglobulin necessary for effective immunosuppression was compared, the anti-LC sera were found to be 10-fold weaker than the conventional ALS. In the second experiment the conventional ALS was depleted of its anti-LC antibodies by incubating with pure LC antigen, and this was found not to diminish its immunosuppressive potency. It was concluded that anti-LC antibodies do not contribute significantly to the immunosuppressive potency of conventional ALS. This is despite the fact that anti-LC antibodies constituted 48% of the antibodies in the ALS used in the immunosuppression experiments, and in six other batches of ALS the proportion of anti-LC antibodies ranged from 25 to 49%. Because only a small component of the nonanti-LC antibodies are directed at leukocyte-specific antigens, it is concluded that the immunosuppressive properties of ALS are mediated by a minor component of the serum directed at as yet undefined antigens. In additional experiments, a mouse monoclonal antibody to the rat LC antigen, a mouse monoclonal antibody (W3/13) to a rat T lymphocyte-brain-granulocyte antigen, and rabbit antisera to pure rat Thy-1 were tested for their ability to suppress kidney graft rejection, but none had any effect at all, even in large doses.

Animals↗
PubMed1979

Purification with monoclonal antibody of a predominant leukocyte-common antigen and glycoprotein from rat thymocytes.

A leukocyte-common (L-C) antigen which can be dominant as an immunogen in rabbit anti-rat thoracic duct lymphocyte serum has been purified from rat thymocytes. Initially, an antigenic fragment of 100,000 apparent mol. wt. was prepared at 400 to 900-fold purification by lentil lectin affinity chromatography and gel filtration in deoxycholate. Mice were then immunized with this fraction, and a hybrid myeloma cell line secreting antibody to the L-C antigen was prepared by cell fusion. This antibody was used for affinity chromatography and gave pure L-C antigen at 1400-fold purification compared with thymocytes. The L-C antigen is a major membrane glyco-protein of rat thymocytes and has an apparent mol. wt. of 150,000 as determined by electrophoresis on polyacrylamide gels in sodium dodecyl sulfate. The antigen constitutes one of the three thymocyte glycoproteins which stain intensely for carbohydrate with periodic acid Schiff stain. It is present on greater than 95% of thymocytes, bone marrow cells and thoracic duct lymphocytes.

Animals↗
PubMed1979

Evaluation of the Tennessee Child Restraint Law.

In Tennessee a law came into force January 1, 1978 requiring parents to use child restraints properly when transporting their children who are less than four years old. Alternatively, the law permits children to be held in arms, a practice known to be hazardous rather than protective. Before and after the law went into force, observations were made of children in cars exiting from shopping centers in Knoxville and Nashville, Tennessee, and in Lexington and Louisville, Kentucky, an adjacent state not having a child restraint law. More than 80 per cent of Tennessee children observed in the fourth month the law was in force were not using child restraints anchored by seat belts, although use rates increased in Tennessee (8 to 16 per cent) to a greater extent than in Kentucky (11 to 15 per cent). Moreover, due to a large increase in children traveling in arms in Nashville, there was an increase in such travel in the two Tennessee cities studied (23 to 28 per cent) relative to a decrease in those studied in Kentucky (19 to 14 per cent).

Child Welfare↗
PubMed1978

T-lymphocyte heterogeneity in the rat: separation of functional subpopulations using a monoclonal antibody.

W3/25 antibody is the monoclonal product of a hybrid cell resulting from the fusion of a mouse myeloma cell line with spleen cells from a mouse immunized with rat thymocytes. Pure clones have been derived, and segregants free of parental myeloma chains have been isolated. Previous studies have shown that this antibody recognizes a subpopulation of T cells among rat thoracic duct lymphocytes. In the work reported here, three T-cell functions were assayed after separating rat thoracic duct lymphocytes on the fluorescence-activated cell sorter on the basis of labeling with W3/25 antibody. Two of the functional activities appeared to be completely segregated by this procedure. Thus, helper cell activity for an anti-hapten plaque-forming cell response was confined to the labeled population, whereas the allogeneic suppressive effect produced in a parental vector F1 adoptive transfer was mediated by cells in the unlabeled fraction. The third function, graft-versus-host activity, was almost entirely contained within the labeled subpopulation. It is concluded that the antigenic determinant recognized by the monoclonal antibody W3/25 is a differentiation marker for T-cell functional subpopulations.

Animals↗
PubMed1978

Glycoproteins and antigens of membranes prepared from rat thymocytes after lysis by shearing or with the detergent Tween-40.

In purification of cell surface antigens an efficient method for preparing membrane from large numbers of cells is needed. Such a method is described for preparing membranes from rat thymocytes after lysis in the non-ionic detergent Tween-40. Cell surface antigens were recovered at a yield of 30-50%, and a purification of 30-40-fold. By contrast enzyme markers for the other cell organelles were present in the membrane fraction in very low yield. The membrane obtained with the detergent method was compared with that resulting from the best of previously describes methods involving cell lysis by shearing. The detergent method compared favourably for simplicity as well as for yield and purification, and both membrane preparations contained similar protein and glycoprotein constituents. The main glycoprotein bands of membranes from thymocytes and thoracic duct lymphocytes were identified after polyacrylamide gel electrophoresis in dodecyl sulphate. In thymocyte membrane, three main bands at apparent molecular weights of 150 000, 84 000 and 25 000 were seen, and of these the 84 000 glycoprotein did not bind to the lentil lectin. In thoracic duct lymphocyte membrane the 25 000 glycoprotein was absent and a band at 95 000 was intensified in comparison with thymocytes.

Animals↗
PubMed1978

Molecular weights of the Thy-1 glycoproteins from rat thymus and brain in the presence and absence of deoxycholate.

1. The Thy-1 membrane glycoproteins from rat thymus and brain bound deoxycholate to 24% of their own weight as measured by equilibrium dialysis. The binding occurred co-operatively at the critical micelle concentration of deoxycholate, suggesting that the glycoproteins bind to a micelle, and not to the detergent monomer. 2. From sedimentation-equilibrium and deoxycholate-binding data the molecular weights of the glycoprotein monomers were calculated to be 18700 and 17500 for thymus and brain Thy-1 glycoprotein monomers were calculated to be 18700 and 17500 for thymus and brain Thy-1 glycoproteins respectively. The molecular weight of the polypeptide part of the glycoprotein is thus 12500. 3. In the absence of deoxycholate, brain or thymus Thy-1 glycoprotein formed large homogeneous complexes of mol. wt. 270000 or 300000 respectively. The sedimentation coefficient of these was 12.8 S. The complex was only partially dissociated by 4M-guanidinium chloride. 4. After cleavage of brain or thymus Thy-1 glycoprotein with CNBr, two peptides were clearly identified. They were linked by disulphide bonds and both contained carbohydrate. This cleavage suggests there is only one methionine residue per molecule, which is consistent with the above molecular weights and the known amino acid composition.

Alkylation↗