Memory enhancement by intrahippocampal, intraamygdala, or intraentorhinal infusion of platelet-activating factor measured in an inhibitory avoidance task.

Platelet-activating factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine), which is thought to be a retrograde messenger in long-term potentiation (LTP), enhances glutamate release and LTP through an action on presynaptic nerve endings. The PAF antagonist BN 52021 blocks CA1 LTP in hippocampal slices, and, when infused into rat dorsal hippocampus pre- or posttraining, blocks retention of inhibitory avoidance. Here we report that memory is affected by pre- or posttraining infusion of the PAF analog 1-O-hexadecyl-2-N-methylcarbamoyl-sn-glycerol-3-phosphocholine (mc-PAF) into either rat dorsal hippocampus, amygdala, or entorhinal cortex. Male Wistar rats were implanted bilaterally with cannulae in these brain regions. After recovery from surgery, the animals were trained in step-down inhibitory avoidance or in a spatial habituation task and tested for retention 24 h later. mc-PAF (1.0 microgram per side) enhanced retention test performance of the two tasks when infused into the hippocampus before training without altering training session performance. In addition, mc-PAF enhanced retention test performance of the avoidance task when infused into (i) the hippocampus 0 but not 60 min after training; (ii) the amygdala immediately after training; and (iii) the entorhinal cortex 100 but not 0 or 300 min after training. In confirmation of previous findings, BN 52021 (0.5 microgram per side) was found to be amnestic for the avoidance task when infused into the hippocampus or the amygdala immediately but not 30 or more minutes after training or into the entorhinal cortex 100 but not 0 or 300 min after training. These findings support the hypothesis that memory involves PAF-regulated events, possibly LTP, generated at the time of training in hippocampus and amygdala and 100 min later in the entorhinal cortex.

Overexpression of the c-Myc oncoprotein blocks the growth-inhibitory response but is required for the mitogenic effects of transforming growth factor beta 1.

One of the more intriguing aspects of transforming growth factor beta 1 (TGF beta 1) is its ability to function as both a mitogenic factor for certain mesenchymal cells and a potent growth inhibitor of lymphoid, endothelial, and epithelial cells. Data are presented indicating that c-myc may play a pivotal role in both the mitogenic and antiproliferative actions of TGF beta 1. In agreement with previous studies using C3H/10T1/2 fibroblasts constitutively expressing an exogenous c-myc cDNA, we show that AKR-2B fibroblasts expressing a chimeric estrogen-inducible form of c-myc (mycER) are able to form colonies in soft agar in the presence of TGF beta 1 only when c-myc is activated by hormone. Whereas these findings support a synergistic role for c-myc in mitogenic responses to TGF beta 1, we also find that c-myc can antagonize the growth-inhibitory response to TGF beta 1. Mouse keratinocytes (BALB/MK), which are normally growth-arrested by TGF beta 1, are rendered insensitive to the growth-inhibitory effects of TGF beta 1 upon mycER activation. This ability of mycER activation to block TGF beta 1-induced growth arrest was found to occur only when the fusion protein was induced with hormone in the early part of G1. Addition of estradiol late in G1 had no suppressive effect on TGF beta 1-induced growth inhibition.

Inhibitory effect of 9-(2-phosphonylmethoxyethyl)adenine on visna virus infection in lambs: a model for in vivo testing of candidate anti-human immunodeficiency virus drugs.

The acyclic nucleoside phosphonate analog 9-(2-phosphonylmethoxyethyl)adenine (PMEA) was recently found to be effective as an inhibitor of visna virus replication and cytopathic effect in sheep choroid plexus cultures. To study whether PMEA also affects visna virus infection in sheep, two groups of four lambs each were inoculated intracerebrally with 10(6.3) TCID50 of visna virus strain KV1772 and treated subcutaneously three times a week with PMEA at 10 and 25 mg/kg, respectively. The treatment was begun on the day of virus inoculation and continued for 6 weeks. A group of four lambs were infected in the same way but were not treated. The lambs were bled weekly or biweekly and the leukocytes were tested for virus. At 7 weeks after infection, the animals were sacrificed, and cerebrospinal fluid (CSF) and samples of tissue from various areas of the brain and from lungs, spleen, and lymph nodes were collected for isolation of virus and for histopathologic examination. The PMEA treatment had a striking effect on visna virus infection, which was similar for both doses of the drug. Thus, the frequency of virus isolations was much lower in PMEA-treated than in untreated lambs. The difference was particularly pronounced in the blood, CSF, and brain tissue. Furthermore, CSF cell counts were much lower and inflammatory lesions in the brain were much less severe in the treated lambs than in the untreated controls. The results indicate that PMEA inhibits the propagation and spread of visna virus in infected lambs and prevents brain lesions, at least during early infection. The drug caused no noticeable side effects during the 6 weeks of treatment.

Coexpression of two functionally independent p58 inhibitory receptors in human natural killer cell clones results in the inability to kill all normal allogeneic target cells.

In the present study, we define a group of natural killer (NK) clones (group 0) that fails to lyse all of the normal allogeneic target cells analyzed. Their specificity for HLA class I molecules was suggested by their ability to lyse class I-negative target cells and by the fact that they could lyse resistant target cells in the presence of selected anti-class I monoclonal antibodies. The use of appropriate target cells represented by either HLA-homozygous cell lines or cell transfectants revealed that these clones recognized all the HLA-C alleles. By the use of monoclonal antibodies directed to either GL183 or EB6 molecules, we showed that the EB6 molecules were responsible for the recognition of Cw4 and related alleles, while the GL183 molecules recognized Cw3 (and related C alleles). These data suggest that the GL183 and the EB6 molecules can function, in individual NK clones, as independent receptors for two different groups of HLA-C alleles, (which include all known alleles for locus C), thus resulting in their inability to lyse all normal HLA-C+ target cells. Indirect immunofluorescence and fluorescence-activated cell sorting analysis revealed that the presently defined GL183+EB6+ group 0 NK clones brightly express EB6 molecules (EB6bright) while the GL183+EB6+ group 2 clones (unable to recognize Cw4) express an EB6dull phenotype. These data also imply that the density of EB6 receptors may be critical for the generation of an optimal negative signal upon interaction with appropriate HLA-C alleles.

The Menkes/Wilson disease gene homologue in yeast provides copper to a ceruloplasmin-like oxidase required for iron uptake.

The CCC2 gene of the yeast Saccharomyces cerevisiae is homologous to the human genes defective in Wilson disease and Menkes disease. A biochemical hallmark of these diseases is a deficiency of copper in ceruloplasmin and other copper proteins found in extracytosolic compartments. Here we demonstrate that disruption of the yeast CCC2 gene results in defects in respiration and iron uptake. These defects could be reversed by supplementing cells with copper, suggesting that CCC2 mutant cells were copper deficient. However, cytosolic copper levels and copper uptake were normal. Instead, CCC2 mutant cells lacked a copper-dependent oxidase activity associated with the extracytosolic domain of the FET3-encoded protein, a ceruloplasmin homologue previously shown to be necessary for high-affinity iron uptake in yeast. Copper restored oxidase activity both in vitro and in vivo, paralleling the ability of copper to restore respiration and iron uptake. These results suggest that the CCC2-encoded protein is required for the export of copper from the cytosol into an extracytosolic compartment, supporting the proposal that intracellular copper transport is impaired in Wilson disease and Menkes disease.