A human class II MHC-derived peptide antagonizes phosphatidylinositol 3-kinase to block IL-2 signaling.

MHC molecules bind antigenic peptides and present them to T cells. There is a growing body of evidence that MHC molecules also serve other functions. We and others have described synthetic peptides derived from regions of MHC molecules that inhibit T-cell proliferation or cytotoxicity in an allele-nonspecific manner that is independent of interaction with the T-cell receptor. In this report, we describe the mechanism of action of a synthetic MHC class II-derived peptide that blocks T-cell activation induced by IL-2. Both this peptide, corresponding to residues 65-79 of DQA*03011 (DQ 65-79), and rapamycin inhibit p70 S6 kinase activity, but only DQ 65-79 blocks Akt kinase activity, placing the effects of DQ 65-79 upstream of mTOR, a PI kinase family member. DQ 65-79, but not rapamycin, inhibits phosphatidylinositol 3-kinase (PI 3-kinase) activity in vitro. The peptide is taken up by cells, as demonstrated by confocal microscopy. These findings indicate that DQ 65-79 acts as an antagonist with PI 3-kinase, repressing downstream signaling events and inhibiting proliferation. Understanding the mechanism of action of immunomodulatory peptides may provide new insights into T-cell activation and allow the development of novel immunosuppressive agents.

Responses of striatal neurons in the behaving monkey. 3. Effects of iontophoretically applied dopamine on normal responsiveness.

In order to analyse the functions of dopamine, the effects of the iontophoretic application of dopamine on the responsiveness of striatal neurons to their normal inputs were investigated in the behaving monkey. It was shown that many neurons in the putamen had responses related to movements, of for example the mouth. Iontophoretically applied dopamine decreased the spontaneous firing rates of 178 of 267 neurons (67%) tested in the putamen, caudate nucleus, and the adjacent prefrontal cortex which also receives a dopaminergic projection. Trifluoperazine, applied iontophoretically to block dopamine receptors, increased the spontaneous firing rates of some of the neurons in the prefrontal cortex, suggesting that under normal conditions in the behaving animal the release of dopamine holds the firing rates of these neurons at a low level. The median was 9 spikes/s in the present sample of striatal neurons. Application of dopamine decreased the magnitude of the movement-related responses of the striatal neurons; this decrease in the responses was of approximately the same magnitude in spikes per second as the decrease in the spontaneous firing rate of the neurons produced by the same current of dopamine. It is suggested that this type of effect of dopamine could influence the signal to noise ratio of processing within the striatum, and that changes in this signal to noise ratio produced by disturbances of dopaminergic function could contribute to the behavioral disorders produced by dysfunctions of the dopaminergic systems.

Enhanced survival of rat neonatal cerebral cortical neurons at subatmospheric oxygen tensions in vitro.

In vitro tissue culture experiments are routinely performed at atmospheric oxygen tension (21%), although most cells experience lower oxygen tensions in vivo. The optimal oxygen tension for the survival of neurons and synthesis of neurofilament (NF) was determined using dissociated neonatal rat cerebral cortex and monoclonal antibodies to the 68 kDa and 200 kDa subunits of NF. Maximum production of each subunit determined by Enzyme-Linked Immunosorbant Assay occurred at 9% O2. Neuronal survival determined by immunohistochemistry was also maximal at 9% O2. CNS neurons are highly sensitive to oxygen tension and grow best at levels approximating capillary rather than atmospheric pO2.

Metabolic influence of the hippocampus on hypothalamus, preoptic and basal forebrain is exerted through amygdalofugal pathways.

The spread of ventral hippocampal afterdischarge activity to nuclei of the basal diencephalon was studied in rats with fornix lesions and combined lesions of the fornix and stria terminalis. The results indicate that a major hippocampal influence on specific hypothalamic, preoptic and basal forebrain structures is conveyed by way of the amygdala's stria terminalis. An additional hippocampal influence on certain basal forebrain nuclei is consistent with projections via the ventral amygdalofugal pathway.

Does pimozide block the reinforcing effect of brain stimulation?

The neuroleptic pimozide produces an extinction-like decline in the runway and Skinner box performance of rats rewarded with electrical stimulation of the medial forebrain bundle (MFB) in the lateral and posterior hypothalamus. The required dose is an order of magnitude less than the dose that incapacitates. The extinction-like decline is seen even when the drug treated rats run and receive brain stimulation in a running wheel prior to runway testing. The decline is also task-specific: after extinguishing in the Skinner box, rats readily perform in the runway, but soon show extinction in this task, too. The characteristics of pimozide's effects on rewarded behavior imply that the drug, whatever other effects it may have, does block the reinforcing effect of the brain stimulation reward.

Syndesmotic ankle sprains.

In this study we reviewed ankle sprains in a professional football team over a 6 year period. Fifteen players who sustained syndesmotic ankle sprains were compared with 28 players who sustained significant lateral ankle sprains. Players with syndesmotic sprains missed significantly more games and practices and they received substantially more treatments than players with lateral ankle sprains. Physical examination findings, results of radiographic evaluations, and etiologic factors are discussed. The external rotation stress test, a clinical method for diagnosis of this type of sprain at the time of injury, is described. Results of this study clearly demonstrate a prolonged recovery time for syndesmotic ankle sprains. Physicians and trainers who are aware of this injury can differentially diagnose these two types of sprains in the early postinjury period by the method described.

Anesthetic management of the asthmatic patient: a perioperative approach.

The patient with asthma presents an anesthetic challenge to the anesthetist. A thorough preoperative assessment, careful anesthetic planning, smooth induction, maintenance and emergence of anesthesia, and an uneventful postanesthesia recovery are essential to prevent the untoward effects of acute asthma exacerbation during the perioperative experience. Careful planning, continuous observation, and accurate diagnostic decision making are the essential components in lowering anesthetic and operative risk for patients with asthma.

Pharmacologic rationale for anesthetic agents in ambulatory practice.

Patients undergoing surgery in the ambulatory setting require anesthetic agents that expedite postoperative recovery, minimize adverse side effects, and contribute to patient satisfaction. The newer anesthetic agents that are currently used in today's practice offer the flexibility needed to provide anesthesia care for a wide variety of diagnostic and therapeutic procedures performed on an outpatient basis. It is important for the perianesthesia nurse to be familiar with the anesthetic agents used in the operating room to fully understand the influence of these drugs on the patient's recovery process. The role of the perianesthesia nurse is vital in assessing the residual effects of the anesthetic agents and instituting proper nursing interventions during the patient's postanesthesia experience. This article focuses on the rationale for the use of a variety of anesthetic and related agents necessary for the provision of ambulatory anesthesia. The commonly used agents used in ambulatory anesthesia care and their influences on the continuum of care is reviewed.

Neonatal fractures in myelomeningocele patients.

Neonatal fractures in all neonatal patients entering a spina bifida clinic over a 4-year period were reviewed retrospectively. Of six patients with fractures, all had thoracic or upper lumbar neurologic levels and all had significant contractures. The risk of fracture for patients with these two characteristics was 17%. Awareness of the risk of neonatal fracture and care in the handling of these children is stressed.

Arthroscopic posteromedial visualization of the knee.

Arthroscopic visualization of the posteromedial compartment of the knee via an anterolateral portal is not commonly practiced, yet it is relatively simple, has low morbidity, and is of diagnostic and therapeutic value. This prospective study evaluates posteromedial visualization of the knee joint in a series of 117 consecutive patients who underwent arthroscopy for diagnosis or treatment, or both, of 209 pathologic conditions. The technique was deemed simple to perform in 78% of patients. It was found to be more difficult in knees with degenerative joint disease. Posteromedial visualization was found to be essential for diagnosis or treatment in 4% of the diagnosed conditions, and helpful in an additional 13%. The technique was most useful for tears of the posterior horn of the medial meniscus, some of which were not detected by visualization from the anteromedial compartment alone. Visualization of the posteromedial compartment was deemed adequate in 89% of the patients, and there was no morbidity.

Inhibition of cell cycle progression by a synthetic peptide corresponding to residues 65-79 of an HLA class II sequence: functional similarities but mechanistic differences with the immunosuppressive drug rapamycin.

A synthetic peptide corresponding to a region of the alpha1 alpha-helix of DQA03011 (DQ 65-79) inhibits the proliferation of human PBL and T cells in an allele-nonspecific manner. It blocks proliferation stimulated by anti-CD3 mAb, PHA-P, and alloantigen, but not by PMA and ionomycin. Substitution of each amino acid with serine shows that residues 66, 68, 69, 71-73, and 75-79 are critical for function. Inhibition of proliferation is long lasting and is not reversible with exogenous IL-2. The peptide can be added 24 to 48 h after stimulation and still block proliferation. The DQ 65-79 peptide does not affect expression of IL-2 or IL-2R; however, IL-2-stimulated proliferation is inhibited. Cell cycle progression is blocked at the G1/S transition, and the activity of cdk2 (cyclin-dependent kinase 2) kinase is impaired by the continued presence of p27. Although these results suggest a mechanism similar to that of rapamycin, the peptide inhibition is not reversed with FK-506, which indicates a distinct mechanism.

Proliferating cell nuclear antigen as the cell cycle sensor for an HLA-derived peptide blocking T cell proliferation.

Synthetic peptides corresponding to structural regions of HLA molecules are novel immunosuppressive agents. A peptide corresponding to residues 65-79 of the alpha-chain of HLA-DQA03011 (DQ65-79) blocks cell cycle progression from early G1 to the G1 restriction point, which inhibits cyclin-dependent kinase-2 activity and phosphorylation of the retinoblastoma protein. A yeast two-hybrid screen identified proliferating cell nuclear Ag (PCNA) as a cellular ligand for this peptide, whose interaction with PCNA was further confirmed by in vitro biochemistry. Electron microscopy demonstrates that the DQ65-79 peptide enters the cell and colocalizes with PCNA in the T cell nucleus in vivo. Binding of the DQ65-79 peptide to PCNA did not block polymerase delta (pol delta)-dependent DNA replication in vitro. These findings support a key role for PCNA as a sensor of cell cycle progression and reveal an unanticipated function for conserved regions of HLA molecules.