Bioactive glass S53P4 and autograft bone in treatment of depressed tibial plateau fractures - a prospective randomized 11-year follow-up.

The clinical and radiological outcomes of bioactive glass (BAG)-S53P4 and autograft bone (AB) used as bone-graft substitutes in depressed tibial plateau fractures were evaluated in a prospective randomized 11-year follow-up study. All patients (n = 29) had sustained tibial plateau fractures with a joint-line depression of >3 mm. Fifteen patients (5 patients the BAG group, 10 patients in the AB group) participated in this long-term follow-up. X-rays were taken preoperatively, postoperatively, and at the long-term follow-up, and computed tomography (CT) scans were made at the long-term follow-up for evaluation of the bone substitute, osteoarthritis, the tibial-femoral angle, and deviation of mechanical axes. No material-dependent adverse effects were seen in any patient. The means of the articular surface depression on X-rays at the long-term follow-up were 1.4 mm (range: 0-2 mm) in the BAG group and 1.4 mm (range: 0-4 mm) in the AB group, and on CT scans the means were 2.2 mm (range: 2-3 mm), and 2.1 mm (range: 0-3), respectively. No significant difference in the tibial-femoral angle or deviation of mechanical axes was observed between the two groups. BAG-S53P4 can be used as a bone substitute in depressed lateral tibial plateau fractures with good functional and radiological long-term results.

Dioxygen transfer during vitamin K dependent carboxylase catalysis.

The vitamin K dependent carboxylase of liver microsomes is involved in the posttranslational modification of certain serine protease zymogens which are critical components of the blood clotting cascade. During coupled carboxylation/oxygenation this carboxylase converts glutamate residues, dihydrovitamin K, CO2, and O2 to a gamma-carboxyglutamyl (Gla) residue, vitamin K (2R,3S)-epoxide, and H2O with a stoichiometry of 1:1 for all substrates and products. In this paper we investigate the role of molecular oxygen in the reaction by following the course of the oxygen atoms using 18O2. Two different mass spectroscopic techniques, electron ionization positive ion mass spectrometry and supercritical fluid chromatography-negative ion chemical ionization mass spectrometry, were used to quantitate the amount of 18O incorporation into the various oxygens of the vitamin K epoxide product. We found that 0.95 mol atoms of oxygen were incorporated into the epoxide oxygen, 0.05 mol atoms of oxygen were incorporated into the quinone oxygen of vitamin K epoxide, and the remaining ca. 1.0 mol atoms of oxygen were incorporated into H2O. No incorporation of oxygen into vitamin K epoxide from 50% H2(18)O was observed. Thus, the carboxylase operates as a dioxygenase 5% of the time during carboxylation/oxygenation. The relevance of these findings with respect to the nonenzymic "basicity enhancement" model proposed by Ham and Dowd [(1990) J. Am. Chem. Soc. 112, 1660-1661] is discussed.

Analysis of prostaglandins in aqueous solutions by supercritical fluid extraction and chromatography.

Trace amounts of prostaglandins (PGs) were selectively analysed without derivatization using supercritical fluid extraction (SFE) and open tubular column supercritical fluid chromatography (SFC). The specific compounds studied were prostaglandin F2 alpha (PGF2 alpha), esters of PGF2 alpha, prostaglandin F1 alpha) and prostaglandin E2 (PGE2). An open tubular column was used with carbon dioxide as the mobile phase and with universal flame ionization detection. Samples were introduced into the column by direct injection using a 1-microliter sample loop or by SFE with solute focusing. The 11 standard compounds were effectively separated within 35 min using a density program at constant temperature. The minimum detectable quantity (signal-to-noise ratio = 3) using the direct injection method was 9 ng for 15-propionate PGF2 alpha isopropyl ester. Using the extraction method, the sample size in the extraction cell was increased to 100 microliters, which made it possible to analyse compounds that were present in low concentrations. Aqueous PG samples were extracted from adsorbents onto which the samples had been loaded.

Immunoglobulin production induced in vitro by glucocorticoid hormones: T cell-dependent stimulation of immunoglobulin production without B cell proliferation in cultures of human peripheral blood lymphocytes.

The direct effects of steroid hormones on the production of immunoglobulins and DNA synthesis by human T and B lymphocytes was evaluated in cultures of peripheral blood mononuclear cells. As detected by a reverse hemolytic plaque assay, the addition of 0.1 mM to 10 nM hydrocortisone to lymphocytes in culture in the absence of other stimulants or mitogens, resulted in the dramatic induction of immunoglobulin production with responses comparable to those seen in similar cultures stimulated with pokeweed mitogen. Steroid-stimulated immunoglobulin production was first seen after 48 h and peaked at 8-10 d of culture. The production of IgG, IgA, and IgM was induced following incubation with steroid. Glucocorticoids, but not estrogens or androgens, were capable of mediating this effect, and only compounds with affinity for the glucocorticoid receptor were active. The induction of immunoglobulin production was dependent on both T cells and monocytes; cultures depleted of either cell type did not produce immunoglobulin when stimulated with glucocorticoid hormones. Proliferation of B cells or T cells could not be detected by [3H]thymidine incorporation or total cell recovery from steroid-stimulated cultures, even though such cultures demonstrated marked increases in immunoglobulin production. The mechanism responsible for this functional maturation of B cells to become high rate immunoglobulin producing cells is as yet undefined, although it appears to involve more than merely steroid mediated inactivation of suppressor T cells.

Ontogeny of humoral immune function in normal chickens: a comparison of immunoglobulin-secreting cells in bone marrow, spleen, lungs and intestine.

A reverse haemolytic plaque was employed to study the ontogeny of immunoglobulin (Ig) secreting cells of either IgG, IgA, or IgM class in normal chickens. After hatching, IgM-secreting cells were detectable in the spleen by 3 days of age whereas IgG- and IgA-secreting cells were first noted at 6 days. Adult levels of Ig-secreting cells of all three classes were attained by 31 days of age in bone marrow and two separate lymphoid populations (lamina propria and intraepithelial lymphocytes). By contrast, adult levels of Ig-secreting cells were not obtained in either the spleen or the lungs until after 50 days of age. In the case of the spleen, the delay in attainment of adult levels of total Ig-secreting cells reflected the smaller spleen size in immature birds, whereas the percentages of cells secreting Ig of each class were in the adult range by 31 days. By contrast, the numbers of cells recovered from the lungs of 50-day-old chickens were near the adult range, while the percentages of cells secreting either IgG, IgA, or IgM were much fewer than those seen in the lungs of adult chickens. These data indicate that the lungs of normal chickens are populated more slowly with Ig-secreting cells than either the bone marrow, spleen, or intestine. At all ages studied, greater numbers of Ig-secreting cells, particularly of the IgG and IgM classes, were recovered from the bone marrow and spleen as compared to the lungs and intestine. Since only a portion of the total bone marrow population was studied, these data include that the bone marrow may be a major site of Ig-secreting cells in chickens beginning shortly after hatching.

B cell differentiation and immunoregulatory T cell function in human cord blood lymphocytes.

The functional maturity of T and B lymphocyte populations from human newborns was evaluated using a reverse hemolytic plaque assay to detect immunoglobulin-secreting cells generated in in vitro cultures stimulated with pokeweed mitogen (PWM), a T cell-dependent polyclonal activator, and the Epstein-Barr virus (EBV), a T cell-independent B cell activator. Cord blood lymphocytes failed to produce immunoglobulin in response to PWM, but did respond with immunoglobulin synthesis to stimulation with EBV. Co-culture experiments demonstrated that cord blood T cells would inhibit immunoglobulin production by adult cells stimulated with PWM, but not with EBV. Cord blood T cells did suppress immunoglobulin production by cord blood B cells when stimulated with a mixture of EBV and PWM, indicating that cord blood, in contrast to adult blood, contains a population of suppressor T cell precursors that are easily activated by PWM. Irradiation of the cord blood T cells with 2,000 rad eliminated the suppressor activity and revealed normal helper function for immunoglobulin (Ig) G, A, and M when these T cells were co-cultured with adult B cells. Cord blood B cells co-cultured with adult T cells or irradiated cord blood T cells did produce immunoglobulin in response to PWM, but the response was significantly lower than that of adult B cells, and only IgM was produced in these cultures. These studies demonstrate that both the T and B cells of the human newborn have significant functional differences compared with the functions of T and B lymphocyte populations in adults.

Activation of suppressor T cells during Epstein-Barr-virus-induced infectious mononucleosis.

Infectious mononucleosis is caused by the Epstein-Barr virus (EBV), an unusual human pathogen because it preferentially infects B lymphocytes and consequently activates them to produce immunoglobulins. When cultures of lymphocytes from patients with infectious mononucleosis were stimulated with polyclonal activators, unseparated cells failed to produce immunoglobulins, whereas purified B cells responded normally. Cocultures demonstrated profound suppressor T-cell activity in blood from patients with infectious mononucleosis. Early in this disease, circulating immunoglobulin-secreting cells were elevated, but during the second week their number was strikingly depressed. These data indicate that during infectious mononucleosis, EBV causes polyclonal activation of B cells, reflected by hypergammaglobulinemia and increased circulating immunoglobulin-secreting cells. Next, suppressor T cells become activated and inhibit further B-cell activation. Thus, activation of suppressor T cells in infectious mononucleosis provides a unique additional mechanism of host defense because these T cells inhibit the activation and proliferation of an important target of the causative virus.

Tissue distribution of immunoglobulin-secreting cells in normal and IgA-deficient chickens.

A reverse hemolytic plaque assay was employed to enumerate lymphoid cells actively secreting either immunoglobulin (Ig)G, IgA, or IgM in the small intestine, lungs, and lymphoid organs of normal and IgA-deficient chickens. In normal birds, intestinal lamina propria lymphocytes were proportionately richest in cells secreting IgG and IgA whereas the bone marrow was richest in IgM-secreting cells. The highest ratio of IgA to IgG secreting cells was also found in the lamina propria lymphocytes of the intestine (0.9), followed by the IgA to IgG ratios in the intestinal epithelium (0.31), and the lungs (0.19). The IgA to IgG ratios in the bone marrow (0.08) and the spleen (0.02) were considerably lower. Thus, both the intestine and the lungs were relatively enriched in cells actively secreting IgA. These IgA-secreting cells are the likely source of the IgA found in such quantities in intestinal and respiratory secretions. The tissue distribution of Ig-secreting cells was also studied in two generations of birds with experimentally induced IgA deficiency. There was a striking diminution of IgA-secreting cells in all tissues, including the intestine and lungs, whereas cells secreting IgG and IgM were normal or increased. The lack of IgA-secreting cells in these birds represents the effects of donor suppressor T cells having specificity for IgA.

A receptor for IgA on human T lymphocytes.

Receptors for IgA antibody-antigen complexes were demonstrated on 2 to 18% (mean 6.7%) of human peripheral blood T cells. The proportion of cells bearing detectable IgA receptors was low in freshly prepared T cells and increased in number after 18 to 24 hr of culture similar to the time course of appearance of the Tmu receptor. These T receptors were shown to be distinctly different from Fc-IgM and Fc-IgG receptors on T cells by blocking studies with purified IgA, IgG, and IgM.

Artifactual plaque formation in vitro and in vivo to passive transfer of specific antibody.

The localized hemolysis in gel (LHG) assay for antibody-secreting cells was used to evaluate antibody production in heterologous erythrocyte-immunized cultures of human peripheral blood lymphocytes supplemented with 10% human plasma. Antigen-specific plaques were detected in such cultures and the number of plaques varied with different lymphocyte donors and were inhibited by heat killing the cultures before assay. However, plaque number varied directly with the number of immunizing erythrocytes added to the cultures and inversely with the number of lymphocytes added. Maximum plaque production occurred within 10 min of initiation of the cultures and occurred in the absence of any lymphoid cells. Absorption of the plasma used as culture supplement with the immunizing erythrocyte resulted in complete abrogation of subsequent specific plaque formation. Mice previously passively immunized with high titered anti-erythrocyte antibody had large numbers of plaques detected 30 min after i.v. immunization with the appropriate erythrocyte. These plaques detected by LHG are the result of carry-over of aggregates of antibody-coated erythrocytes and subsequent release of this antibody in the LHG assay and are not the result of active antibody synthesis. This "pseudoplaque" production may lead to the false interpretation of plaque formation as indicating active synthesis of antibody in vivo and in vitro where such experiments are carried out in immune animals or with antibody containing serum culture supplements.

Infectious agammaglobulinemia: transmission of immunodeficiency with grafts of agammaglobulinemic cells.

Agammaglobulinemia induced in chickens by surgical bursectomy and irradiation at hatching is transmissible at 4 mo of age to sublethally irradiated normal chickens by bone marrow transplantation. The immunodeficiency which develops in the recipients persists for life and is characterized by inability to produce antibody and by progressive loss of detectable serum IgM and IgG.