Rat RT1.B-transfected fibroblast lines process and present myelin antigens and activate T cells to induce experimental autoimmune encephalomyelitis

The genes encoding the Lewis rat RT1.B molecule (MHC Class II I-A equivalent) were transfected and expressed in mouse DAP.3 fibroblast cells together with the gene encoding the mouse ICAM-1 molecule. Both molecules were stably expressed on the cell surface of DAP.3 cells under longterm culture conditions. The RT1.B/mICAM-1 transfectants presented antigen in a specific manner to a RT1. B-restricted rat T cell hybridoma specific for the 69-89 peptide of myelin basic protein (BP). In addition, the transfectants were able to present antigen to a BP69-89-specific rat T cell line. Presentation to a RT1.D (MHC Class II I-E equivalent)-restricted BP87-99-specific T cell line was minimal. Production of the Th1 cytokine IFN-gamma by BP69-89-specific T cells when stimulated by RT1.B/mICAM-1 transfectants correlated very well with proliferation to specific antigen. Moreover, RT1.B-transfected DAP.3 cells sufficiently stimulated BP69-89-specific T cells such that they were able to transfer experimental autoimmune encephalomyelitis (EAE) to Lewis rat recipients. Thus, the RT1.B molecule is functionally expressed on the surface of transfected Dap.3 fibroblasts and is capable of MHC Class II-restricted, antigen-specific presentation to rat T cells.

Apoptosis and the cell cycle in Xenopus laevis: PHA and PMA exposure of splenocytes

T cell receptor (TCR) ligation and protein kinase C (PKC) activation stimulate proliferation and modulate apoptosis in both mammalian and amphibian lymphocytes. The potential relationship between apoptosis and the cell cycle in mature Xenopus laevis splenic lymphocytes is addressed by monitoring apoptosis and DNA synthesis over time, using incorporation of propidium iodide (PI) and flow cytometry. Aliquots of the same populations of cells are followed after exposure in vitro to phytohemagglutinin (PHA) or phorbol 12-myristate 13-acetate (PMA). Significant increases in apoptosis preceed those in DNA synthesis by 12 to 16 h following exposure to both reagents. Since apoptosis preceeds DNA synthesis, these dying cells clearly do not need to enter the S phase of the cell cycle before becoming apoptotic, in contrast to mammalian T cells. Another striking difference is that the reagent with weaker mitogenic properties in this species, PHA, is significantly a more potent apoptogen, than the strong mitogen, PMA. The two phenomena then appear to be inversely related in Xenopus cells. Data on DNA synthesis suggest independence of the two phenomena, as DNA synthesis is stimulated in direct proportion to the strength of each reagent as a mitogen. Mature mammalian T-cells undergo apoptosis only when previously activated. The Xenopus lymphocytes examined were not deliberately activated by exposure to antigen or lectin. PMA, a cancer promoter in mammals, usually 'rescues' mammalian cells from apoptosis, but stimulates apoptotic increases in Xenopus cells. Thus, mature Xenopus lymphocytes may be more readily stimulated to die by cancer inducing agents than mammalian lymphocytes. This could make them less susceptible to transformation into immortalized cancer cells. This characteristic may considerably contribute to the observed resistance to spontaneous and chemically-induced neoplasia in wild type, non-isogeneic or non-inbred Xenopus.

Expression of a Fas-like proapoptotic molecule on the lymphocytes of Xenopus laevis

Ligation of the externally expressed Fas (APO1/CD95) molecule will initiate programmed cell death (apoptosis), in many mammalian developing and adult cells. Fas-induced apoptosis has not been demonstrated with the cells of any non-mammalian vertebrate. We immunostained suspensions of splenocytes from adult Xenopus laevis, the South African clawed toad, with a polyclonal rabbit anti-human Fas antibody raised against the amino acid residues 321-335 of human Fas. The binding was specific, as it was dramatically reduced by preincubation of the antibody with the Fas peptide used to make it, but not with a Fas-ligand (FasL) peptide. The binding was enhanced after in vitro exposure of the splenocytes to phytahemagglutinin (PHA), a T cell mitogen and apoptogen in this species. Sections of developing Xenopus larval tissue were also immunostained with the polyclonal rabbit anti-human Fas antibody. Consistent binding of thymocytes and splenocytes was not observed until early metamorphosis in these immunological sites. A monoclonal mouse anti-human Fas antibody, previously used to stimulate apoptosis in mammalian cells, induced significant levels of apoptosis in adult Xenopus splenocytes and additionally, bound specifically to a splenocyte extract, as assayed by ELISA. Thus, a molecule on Xenopus splenocytes shares both structural and functional homologies with human Fas, indicating the evolutionary conservation within vertebrates of this means of initiating apoptosis.

A re-examination of the role of basal forebrain cholinergic neurons in spatial working memory

The basal forebrain cholinergic system, which innervates widespread cortical and limbic structures, has traditionally been considered important for learning and memory. The use of an immunotoxin, 192 IgG-saporin, has brought this functional designation into question; selective immunolesions of basal forebrain cholinergic neurons have failed to reproduce a number of behavioral deficits that were observed with less selective lesion methods. Recent reports, however, have indicated that a mild impairment is observed in rats on a spatial working memory task after 192 IgG-saporin lesions of the rostral groups of cholinergic neurons located in the medial septal area (MSA). Those studies used a lesion protocol in which a single large volume injection of the immunotoxin was made into the MSA. In the current study, multiple small injections were made at the locations of cholinergic neurons in the MSA, producing a cholinergic depletion comparable to that reported in the earlier studies where deficits were observed. In the current study, however, rats with cholinergic lesions had no impairment in the spatial working memory task, even when delays ranging from 60 s to 8 h were imposed within a trial. The current report indicates that selective removal of cholinergic neurons in the basal forebrain may not be sufficient to produce a deficit in spatial working memory.

Spatial learning and memory at defined points of the estrous cycle: effects on performance of a hippocampal-dependent task

Learning based on hippocampal-dependent spatial navigation in female rats was assessed at identified points in the estrous cycle corresponding to low (estrus) and high (proestrus) circulating estrogen. With background training in water-maze procedures, rats learned the location of an escape platform in the maze in a single session of 8 training trials. A strong spatial bias for the escape platform was also evident in a probe trial used to assess retention of learning 30 min after the training session. This entire protocol was completed in less than an hour. The performance of the estrus and proestrus rats was indistinguishable on all behavioral measures, irrespective of the stage of estrous cycle during the task. These results indicate that rapid learning and retention for spatial information over a relatively short interval may be preserved despite morphological alterations in hippocampal dendritic spine density in the normally cycling female rat.

Spatial learning and memory at defined points of the estrous cycle: effects on performance of a hippocampal-dependent task

Learning based on hippocampal-dependent spatial navigation in female rats was assessed at identified points in the estrous cycle corresponding to low (estrus) and high (proestrus) circulating estrogen. With background training in water-maze procedures, rats learned the location of an escape platform in the maze in a single session of 8 training trials. A strong spatial bias for the escape platform was also evident in a probe trial used to assess retention of learning 30 min after the training session. This entire protocol was completed in less than an hour. The performance of the estrus and proestrus rats was indistinguishable on all behavioral measures, irrespective of the stage of estrous cycle during the task. These results indicate that rapid learning and retention for spatial information over a relatively short interval may be preserved despite morphological alterations in hippocampal dendritic spine density in the normally cycling female rat.

Prospective comparative trial of short course (four day) and continuous tobramycin in combination with cefoperazone or mezlocillin in febrile, granulocytopenic patients

In a prospective, randomized trial of 195 febrile episodes in granulocytopenic patients short course aminoglycoside treatment (initial tobramycin and cefoperazone followed by tobramycin discontinuation at day four of therapy) was compared with two regimens (tobramycin plus cefoperazone and tobramycin plus mezlocillin) in which both drugs were continued for up to 26 days. All regimens were successful as empirical therapy with comparable response rates of just over seventy per cent. Fifty-three per cent of the initial episodes of fever were related to documented infections which responded less well (P = 0.007) than unexplained fever. Patients with bacteraemia, pneumonia or Gram-positive aerobic or Pseudomonas aeruginosa infections responded poorly to all regimens. The recovery from granulocytopenia was the most important determinant of successful response. Aminoglycoside discontinuation followed by cefoperazone monotherapy after day four was statistically as effective as the combination regimens. Short course tobramycin therapy eliminated the nephrotoxicity seen in the combination limbs. The use of cefoperazone was not associated with an increased incidence of hypoprothrombinemia; however, the only three bleeding episodes occurred in patients given cefoperazone but not vitamin K. Short course aminoglycoside therapy will reduce cost and nephrotoxicity when compared with prolonged combination therapy and should be further explored in this setting, with use of different agents and comparison with monotherapy.

Sequential hemibody and local irradiation with combination chemotherapy for small cell lung carcinoma: a preliminary analysis

Sequential hemibody irradiation (SHB) was integrated with combination chemotherapy and local irradiation (LRT) in the induction and consolidation phases of a therapeutic protocol for small cell lung carcinoma (SCLC). Forty-one previously untreated patients were entered into this program. Among 38 evaluable patients (20 with limited disease [LD] and 18 with extensive disease [ED], the overall response rate was 63% (90% in LD and 33% in ED patients). The estimated overall survival is 8.1 months. The major toxicity has been myelosuppression--especially thrombocytopenia. The frequency of previously described "acute radiation syndromes" and radiation pneumonitis associated with hemibody irradiation have been substantially decreased at the current dosage with premedication and shielding techniques. The integration of SHB as a systemic therapy with combination chemotherapy and LRT is a feasible program for sequential administration of non-cross-resistant agents in SCLC and may be beneficial in patients with limited disease.