Analysis of a TH1----TH2 helper cell circuit

In the present study, the T15 idiotype-recognizing T helper cell circuit was dissected with respect to its homeostasis, interactive specificity, stability over time, and effects on B cell expression. Analysis of the TH1 cells by adoptive transfer experiments indicates their short-lived state of activity, during which TH2 cells are stimulated. TH1 cell activity was also directly monitored by the use of TNP-anti-T15 hybridoma antigens. It was found that TH1 cells are detected 1 wk after priming with PC-Hy, whereas TH2 cells become activated after 4 wk of priming. Comparative analysis of TH1 cells by using two different TNP-anti-T15 hybridoma antigens indicates a TH1 specificity for a shared idiotope. The stability over time of the TH1----TH2 circuit was demonstrated by comparing TH2 frequencies in young and old mice. Finally, we addressed the question of the function of the idiotype-recognizing T helper cells and showed that stimulation of T15-idiotype-specific TH2 cells can be correlated with a significant increase in the percentage of T15 idiotype in an anti-PC response. Collectively, these data describe an idiotype-specific T helper circuit as part of the network homeostasis of the immune system.

Magnetic resonance imaging in hypertrophic cardiomyopathy

Gated magnetic resonance imaging (MRI) was performed using a 0.35-Tesla cryogenic system in 14 patients with hypertrophic cardiomyopathy (HC) in order to define the site and extent of abnormal wall thickness. These studies were compared with 2-dimensional (2-D) echocardiograms. Gated magnetic resonance imaging studies in 12 normal volunteers were used for comparison. In normal subjects and in patients with HC, the sharp demarcation of the myocardial wall permitted measurement of wall thickness. The thickness of the septal and posterolateral walls in normal subjects was 10.2 +/- 0.4 mm (+/- standard deviation) and 10.8 +/- 0.5 mm, respectively, whereas septal thickness in all but 1 patient with HC was 15.0 mm or greater. In patients with HC, septal and posterolateral wall thickness were 2.2 +/- 0.8 cm and 1.3 +/- 0.17 cm, respectively, by MRI. The 2-D echocardiographic measurements for septal and posterolateral walls were 2.4 +/- 0.6 cm and 1.4 +/- 0.7 cm, respectively. The severity and distribution of abnormal wall thickness were comparable on 2-D echo and MRI. Gated MRI is an effective and completely noninvasive technique for demonstrating the presence, site and extent of abnormal wall thickness in HC. The large field of view, ability to image directly in multiple planes, and discrete blood-endocardial interfaces are advantages for cardiovascular imaging.

The ontogeny of hypothalamic pituitary function in the pig. I. Pituitary LH and FSH in the fetus and neonate

Pituitaries were collected from fetal and postnatal pigs from day 55 p.c. until 6 weeks after birth at closely spaced intervals. LH and FSH in individual pituitaries were quantified by both homologous RIA and homologous RRA. No significant difference was found between results obtained by RIA and RRA. Both LH and FSH are first detected by RIA and RRA in the porcine fetal pituitary at 75 days p.c. Thereafter both LH and FSH pituitary content rises until term. LH pituitary concentration in both male and female fetuses and FSH pituitary concentration in males exhibit a peak just before birth. FSH pituitary concentration in females rises until birth and thereafter remains elevated. A statistically significant sex difference was found postnatally with regard to FSH content and concentration but not for LH.

Gated MRI of cardiac and paracardiac masses: initial experience

Ten cardiac and paracardiac masses were studied with magnetic resonance imaging (MRI) to evaluate the utility of this new method for determining the nature, location, and extent of such masses. The masses were intramural lesions (two cases), left atrial thrombus (one case), pericardial cysts (three cases), and mediastinal masses deforming and displacing the left atrium (two cases). ECG-gated images were obtained in all patients. In each of nine cases, MRI determined the location of the mass as intracavitary, intramural, or paracardiac, without the need for exogenous contrast material. It excluded the clinical diagnosis of cardiac tumor in one case. A combination of multislice transaxial, coronal, and sagittal images established the extent of the masses and the degree of impingement on cardiac structures. This initial experience suggests that MRI can provide as much information as echocardiography, computed tomography, and angiography combined in the evaluation of cardiac and paracardiac masses.

T-cell helper circuits

T helper cells specific for trinitrophenylated PC-binding myeloma and hybridoma antibodies are induced by priming with PC antigen, idiotype or anti-idiotypic antibody. These T helper cells are specific for a shared idiotope present on T15 and M167. Priming with the isolated heavy chains of T15 or M167, or the light chain of anti-T15 hybridoma antibody is equally effective in generating T helper cells. Evidently, the idiotope that is recognized by T cells is not dependent upon the conformation of the 7s Ig molecule. Collectively, these and other findings indicate the existence of a TH1-TH2-B cellular circuit which is based on the recognition of idiotopic determinants on T cell receptors. The implications of these findings in terms of network theory are explored.

Multiplane magnetic resonance imaging of the heart and major vessels: studies in normal volunteers

The feasibility of magnetic resonance imaging for defining anatomy of internal cardiac structures and major blood vessels was assessed in 14 normal subjects. Both electrocardiogram-gated and standard spin-echo images were obtained. The R-R interval determined the pulse repetition times in gated sequences. Gated images provided better visualization of internal cardiac morphology and of upper mediastinal vessels than did nongated images. Trabecular detail and components of the mitral valve could be resolved. All segments of the left ventricular wall could be evaluated by combining axial, coronal, and sagittal images. Gated acquisition of magnetic resonance images did not increase imaging time; five transverse slices of the left ventricle were obtained in 6.0-8.5 min. The good image quality, ease of gated acquisition, large field of view, capability of direct imaging in multiple planes, and noninvasiveness of the technique suggest that it will be an important imaging method in cardiovascular disease.

Regulatory idiotopes. Induction of idiotype-recognizing helper T cells by free light and heavy chains

Previously, we have demonstrated the induction of T helper cells that recognize idiotype by antigen (19), idiotype (20), and antiidiotype (12). The T cell population has been characterized and found to recognize both the T15 and M167 myeloma proteins, which share PC binding specificity but differ in idiotypic specificities. In the present work, we used isolated heavy and light chains of T15 and M167 to generate T helper cells, and examined the response to trinitrophenyl (TNP)-T15 and TNP-M167. We found that the heavy chains induced a dose-dependent response to TNP-T15 and TNP-M167, while the light chain priming was ineffective. When isolated chains of a monoclonal anti-T15 antibody (F6-3) were used to induce idiotype-recognizing T cells, only the F6-3 light chains generated T cell help for TNP-T15 and TNP-M167. Evidently, the idiotypic determinant that is recognized by the T cells is not dependent upon the conformation of combined heavy and light chains. These data show that the Th2 helper cells for the T15/M167 idiotopes are induced by free heavy chains of T15 and M167; the Th1 T cells that interact with the Th2 population, of T15 and M167; the Th1 T cells that interact with the Th2 population, however, can be triggered by free light chains of an antiidiotypic hybridoma antibody. These provocative findings suggest a new model for the T helper cell network.

The effects of hydrogen peroxide on lens proteins: a possible model for nuclear cataract

Soluble proteins from the human lens nucleus were incubated for 12 weeks with 0, 10, 100 and 1000 microM-H2O2. Treatments were monitored for alterations in cysteine (sulphydryl), methionine, tryptophan and other amino acids; protein size, solubility and conformation; polypeptide sizes; and non-tryptophan fluorescence. Progressive changes were observed in several of these parameters. Cysteine (up to 100%) and methionine (up to 45%) were rapidly oxidized but no significant alterations were found in any other amino acids. No new chromophores were generated but the non-tryptophan fluorescence was enhanced three-fold. The gradually increasing solvent accessibility of tryptophan residues indicated that the proteins were undergoing conformational alterations. This was accompanied by the insolubilization of protein (up to 75%). The insoluble proteins consisted largely of covalently cross-linked polymers of the lens polypeptides. Disulphide bonds and dityrosine were shown not to be involved in the cross-linking. The modifications observed, as well as their order and extent, are very similar to those found in the cataractous lens. Our observations suggest that low concentrations of H2O2 may be responsible for the oxidative modification of lens proteins during the development of senile nuclear cataracts.

Idiotype-specific T-helper cells

In the present study we investigated the induction and fine specificity of T-helper cells that recognize idiotypes. The data presented show that both low-dose priming with anti-T15 antiserum and priming with PC-Hy are effective in stimulating T15-specific T help. Phosphorylcholine-hemocyanin priming can generate these T cells in either PC-responding or nonresponding strains of mice. Furthermore, the PC-primed T-helper cells can also recognize another anti-PC myeloma, M167, that is idiotypically different from T15. The fine specificity of the anti-PC-idiotype recognizing T-helper cells was examined by studying the effect of in vitro inhibitors on the T-cell help. Both PC and PC-BSA as well as T15 and M167 had an inhibitory effect on the T help. Free T15 and M167 heavy chains also blocked the helper activity for T15; T15 and M167 light chains had no effect, however. Viewed collectively, these results show that PC-Hy priming induces T-helper cells that recognize idiotypic determinants common to both T15 and M167, and that the proteins' H chain is the major structural component of the determinant. Finally, the generation of these idiotype-recognizing T cells was found to occur by way of a T-T interaction loop, based on the finding that T-helper cells are induced by PC-Hy priming in animals that lack PC-responding B cells.

Idiotype-recognizing T helper cells that are not idiotype specific

In this study T helper cells that recognize idiotypes as carriers for a hapten-specific B cell response were analyzed under limiting dilution conditions. T helper cells, induced by phosphorylcholine-hemocyanin (PC-Hy) priming, recognize trinitrophenylated TEPC-15 and MOPC-167 (TNP-T15, TNP-167) equally well. Limiting dilution analysis indicates identical frequencies of helper cells for TNP-T15 and TNP-167. Double immunization protocols using TNP-T15 and TNP-167 fail to demonstrate additive effects. Inhibition of carrier recognition in vitro using free hapten, PC, and unconjugated T15 or M167 indicates identical specificities of helper cells for T15 and M167. Collectively, these results provide strong evidence that PC-Hy priming induces only one population of idiotype-recognizing helper cells that are unable to distinguish between the T15 and the M167 idiotopes. The helper cell induction circuit was further analyzed. PC-Hy priming induces T15/167-specific helper T cells in X-linked immune defect-expressing F1 mice. This indicates that a B cell response to PC is not required to induce idiotype-recognizing T cells. Adoptive cotransfer of B cells from PC-Hy-primed mice together with normal T cells fails to induce idiotype-recognizing T cells. These results indicate the existence of a T helper1-T helper2 induction loop. In this scheme, the T helper1 cell carries T15-like receptors and the T helper2 cells, anti-T15-like receptors. Monoclonal antiidiotypic antibodies specific for T15 also induce a T15/167-recognizing T helper cell population. This finding demonstrates that idiotope-specific priming induces non-idiotype-specific T cells. Evidently, the idiotypic T cell network is based on a different selection of idiotope determinants than the selection of the B cell idiotype network.

Particle-mediated membrane uptake of chemical carcinogens studied by fluorescence spectroscopy

The fluorescence emissions of chrysene, N-ethylcarbazole, and 1,6-diphenylhexatriene undergo large spectral shifts or changes in quantum yield, or both, upon their uptake from particulates by phospholipid vesicles. This membrane uptake of carcinogen and carcinogen-like molecules by model membranes does not result in any disruption of the lipid bilayers. The fluorescence emission of chrysene, when bound to silica, was found to be sensitive to the surface density of chrysene on the silica. These observations demonstrate the feasibility of using fluorescence spectroscopy to measure the rates of exchange of carcinogens from particulate matter to cell membranes and to characterize the surface distribution of chemical carcinogens on particulate matter. Comparison of the uptake rate of chrysene from the unperturbed crystal state, sonicated crystals, and the silica-adsorbed state demonstrated that the last condition results in the most rapid transport of chrysene into model membranes. This information should prove valuable in understanding the cocarcinogenic effects of particulates and polynuclear aromatic hydrocarbons.