Lymphocyte-mediated cytotoxicity: effects of ageing, adult thymectomy and thymic factor.

Adult thymectomy, as well as ageing, depressed splenic lymphocyte-mediated cytotoxicity (LMC) in the mouse. Ageing depressed significantly LMC as early as 19 weeks of age, independently of the number of cells used for immunization. Thymectomy affected LMC only when supoptimal numbers of immunizing allogeneic cells were used. This effect peaked at 6 to 12 weeks after thymectomy. No difference between thymectomized and normal mice was observed when LMC was tested 16 to 20 weeks after thymectomy, at an age when normal control mice themselves already showed a lowered LMC due to ageing. The effect of in vivo treatment with a circulating thymic factor (TF), which was shown to disappear with ageing as well as after adult thymectomy, has been tested in adult thymectomized mice and normal young and ageing mice. TF treatment prevented LMC depression in adult thymectomized mice, whereas it depressed paradoxically splenic LMC in normal young and old mice. The possible mechanisms of the effects of adult thymectomy, ageing, and thymic factor on the different T cell subsets involved in allogeneic killer cell generation are discussed.     

6,9-deepoxy-6,9,-(phenylimino)-delta 6,8-prostaglandin I1, (U-60,257), a new inhibitor of leukotriene C and D synthesis: in vitro studies

Addition of the calcium inophore, A 23187, and cysteine to isolated mononuclear cells from rat peritoneal washings causes a marked increase in the formation of thromboxane B2 (TxB2) along with the formation of leukotrienes C and D (LT's). The formation of LT's in this system was inhibited by 6,9-deepoxy-6,9-(phenylimino)-delta 6,8-prostaglandin I1, U-60,257, or its methyl ester, U-56,467, (ID50 4.6 and 0.31 microM, respectively). There was no inhibition of TxB2 formation. By contrast, two structurally-related compounds, PGI2 and its stable analog, 6-beta-PGI1, did not affect the formation of either LT's or TxB2. The inhibition of LT formation by U-60,257 was rapidly reversed after removal of this compound from the cells. U-60,257 did not inhibit the cyclooxygenase of human polymorphonuclear leukocytes. Nor did it inhibit formation of 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) in human platelets. On the other hand, U-60,257 inhibited glutathione S-transferase activity of rat basophil leukemia cells (ID50, 37 microM), suggesting that this compound may inhibit the last step in LTC biosynthesis. In addition to inhibiting LT synthesis, U-60,257 also appears to be a competitive inhibitor of the action of LT on the guinea pig ileum, although this inhibition requires a higher drug concentration than those ordinarily encountered during assay for LT's in U-60,257-treated incubations.     

Pituitary response of prepuberal lambs to oestradiol-17 beta.

In two experiments 48 prepuberal Merino ewe lambs were injected with oestradiol-17 beta (E2) or saline to study the effect of E2 on their plasma LH levels and on oestrus and ovulation. In the three groups which received 30 (experiment I), 50 and 30 (experiment II) microgram E2 respectively, 27 out of 28 lambs showed an LH response, the corresponding mean LH peaks being 64.3 +/0 22.5, 153.6 +/-33.4 and 91.7 +/- 16.9 ng/ml at mean intervals of 11.1, 11.2 and 10.5 h, respectively, after injection. None of the 20 lambs in the control groups had an LH level higher than 18 ng/ml 12 h after injection. In the three E2 groups, 41.7, 62.5 and 37.5% of animals showed oestrus within 26 h of injection while in the control groups only one animal showed oestrus. Of 13 animals showing oestrus in the E2 groups, 11 failed to ovulate. The mean pre-injection plasma FSH level in experiment I was 102.7 ng/ml, and in four 5--7-month-old lambs over several weeks uas 155.3 ng/ml. Despite these high pre-injection levels of FSH, it appears that the follicles were unable to respond to the LH peak which followed the E2 injection.     

Protein-lipid interaction. Biophysical studies of (Ca2+ + Mg2+)-ATPase reconstituted systems

Differential scanning calorimetry, fluorescence spectroscopy and freeze-fracture electron microscopy have been applied to a study of the reconstituted Ca2+-ATPase proteins from sarcoplasmic reticulum when they are incorporated into pure lipid/water systems. The results obtained with these techniques have been used to examine the effects of this intrinsic protein upon the surrounding lipid at temperatures above and below the main lipid solid-fluid phase transition temperature (Tc). 1. Above this Tc value, the freeze-fracture data show that the proteins are randomly distributed within the plane of the bilayer. The fluorescence data show that as the protein content in the bilayer increases, so does the 'microviscosity'. 2. Below Tc the proteins occur in high protein to lipid patches, separate from the remaining crystalline lipid. The fluorescence data indicate that at these temperatures the presence of the protein causes a decrease in microviscosity, whilst the calorimetric data indicate a decrease in enthalpy of the main lipid transition. 3. A premelting of the high protein to lipid patches formed by phase separation within the lipid bilayers is indicated by the calorimetric and fluorescence data. This observation is used to rationalise the 'anomalous' properties of the dipalmitoyl phosphatidylcholine-ATPase of exhibiting activity at temperatures well below the lipid phase transition at 41 degrees C.     

Identification of a component of rat mononuclear cell SRS as leukotriene D

Slow reacting substance (SRS), produced by rat peritoneal mononuclear cells after stimulation with ionophore A23187, consists of two main components (Bach, M.K. et al. (1979) J. Immunol. 122, 160–165). One of these components was recently identified as leukotriene C-1. The other component has now been identified as leukotriene D.     

The multiple conformations of a cyclic disaccharide: DI-β-d-glucopyranose 1,6′:1′,6-dianhydride hexaacetate

The conformational behaviour of a cyclic disaccharide, di-β-d-glucopyranose 1,6′:1′,6-dianhydride hexaacetate, has been investigated. Because this molecule can exist only with the glucose rings in the unusual flexible forms, such conformational parameters as pseudorotation phase-angles have been used. Within a given number of approximations, the conformational space available for the whole system can be explored by considering only one two-dimensional map. Detailed investigations have shown that three stable conformations may be proposed. Among these, two correspond to minima found in the solid state. In one form, the six-membered rings adopt a boat conformation, whereas a skew conformation is found for the other form. However, these two conformations cannot be considered to be unique models of the conformation in solution; they both produce sets of proton-proton coupling-constants inconsistent with observed n.m.r.-spectroscopic results. At least the third form, having the six-membered rings in skew conformations, has to be taken into account. Deviations from coupling constants-molecular conformation relationships are thought to originate from ring strain.     

Respective influence of extrinsic and intrinsic factors on the age-related decrease of thymic secretion.

The serum level of a circulating thymic factor (FTS) described in our laboratory diminishes in mice after adult thymectomy and with age. However, thymuses from old mice, when grafted into young adult thymectomized recipients lacking circulating FTS, can still partially restore the circulating FTS level of the recipients, whereas newborn thymuses are less efficient in restoring the serum level of FTS in old recipients than in young adult thymectomized recipients. Taken together, our results suggests that in addition to an intrinsic deficiency of the thymic secretion, "environmental" factors play a role in the disappearance of circulating FTS with age, the more so since we observed in old mouse sera factors inhibiting the in vitro biologic activity of FTS, factors that are absent from young mouse sera.     

Lyt phenotypes of responding cells in secondary alloantigen responses.

Lymphocytes responding in a "secondary" MLC-CML system, after in vitro sensitization, apparently fall into two classes with regard to their Lyt phenotype. First, are the cells that form the majority of the proliferating cells after restimulation with either I or K + I differences, which are Lyt 1-2, and second, are Tc that are Lyt 1-2+. The Lyt 1-2- proliferating cells are not cytotoxic and are lysed by treatment with anti-Thy 1.2 serum in the presence of C.