Modeling lottery incentives for daily adherence.

Many health issues require adherence to recommended daily activities, such as taking medication to manage a chronic condition, walking a certain distance to promote weight loss, or measuring weights to assess fluid balance in heart failure. The cost of nonadherence can be high, with respect to both individual health outcomes and the healthcare system. Incentivizing adherence to daily activities can promote better health in patients and populations and potentially provide long-term cost savings. Multiple incentive structures are possible. We focus here on a daily lottery incentive in which payment occurs when both the participant's lottery number matches the number drawn and the participant adheres to the targeted daily behavior. Our objective is to model the lottery's effect on participants' probability to complete the targeted task, particularly over the short term. We combine two procedures for analyzing such binary time series: a parameter-driven regression model with an autocorrelated latent process and a comparative interrupted time series. We use the output of the regression model as the control generator for the comparative time series in order to create a quasi-experimental design.

Alterations in synaptic strength preceding axon withdrawal.

Permanent removal of axonal input to postsynaptic cells helps shape the pattern of neuronal connections in response to experience, but the process is poorly understood. Intracellular recording from newborn and adult mouse muscle fibers temporarily innervated by two axons showed an increasing disparity in the synaptic strengths of the two inputs before one was eliminated. The connection that survived gained strength by increasing the amount of neurotransmitter released (quantal content), whereas the input that was subsequently removed became progressively weaker, because of a reduction in quantal content and a reduction in quantal efficacy associated with reduced postsynaptic receptor density. Once the synaptic strengths of two inputs began to diverge, complete axonal withdrawal of the weaker input occurred within 1 to 2 days. These experiments provide a link between experience-driven changes in synaptic strength and long-term changes in connectivity in the mammalian nervous system.

In vivo imaging shows loss of synaptic sites from neuromuscular junctions in a model of myasthenia gravis.

We examined the pre- and postsynaptic elements of the neuromuscular junction during immune attack on the postsynaptic acetylcholine receptors (AChRs) in a model of myasthenia gravis (MG). We followed, in the sternomastoid muscle of living mice, the staining of nerve terminals and postsynaptic AChRs at individual neuromuscular junctions in situ for up to 16 days after exposure to a monoclonal anti-AChR antibody. Several exposures to this antibody over 6 days led to spotty loss of AChR staining 1 to 3 days later within individual neuromuscular junctions. In addition, we observed loss of motor nerve terminal staining at presynaptic sites opposed to postsynaptic regions that had lost AChRs. Sites that lost pre- and postsynaptic staining were often immediately adjacent to other junctional regions that maintained a high density of AChRs and still stained presynaptically. Ultimately, the loss of synaptic sites resulted in neuromuscular junctions that appeared to be abnormally fragmented. To determine whether junctions recovered from the immune attack, we followed some antibody-treated muscle fibers for an additional 8 days without further exposure to antibody. Signs of recovery were evident because some of the synaptic regions that had previously lost AChRs subsequently regained them. But these junctions still remained fragmented both pre- and postsynaptically. These findings suggest that the postsynaptic membrane is affected in a highly local way by the immune attack on AChRs occurring in MG. One consequence of this attack is a long-term loss of not only postsynaptic components but also the overlying nerve terminals.

An orally administered opiate blocker, naltrexone, attenuates self-injurious behavior.

Several recent reports have indicated that opioid blockers are effective in attenuating self-injurious behavior (SIB). In the present study, four patients with SIB were challenged with four fixed doses (0, 25, 50, 100 mg) of naltrexone. In a double-blind procedure, all patients received each dose on a different week as determined by latin square design. Naltrexone was given on Monday and Wednesday of each week, and patients were videotaped daily for 10 minutes in the morning and afternoon. The tapes were scored for incidents of SIB, stereotypy, and activity, with interrater reliability of 0.93. The Conners Teacher Rating Scale was administered by staff in the morning and afternoon each day. The Vineland was completed each week (Thursday). All patients had decreased SIB when treated with naltrexone. Three patients decreased their SIB as dose of naltrexone increased. There were no consistent effects of naltrexone on stereotypy, activity, or performance on the Conners or the Vineland. These results suggest that endogenous opioids are implicated in SIB and that naltrexone is a powerful tool for examination of this treatment-resistant behavior.

Changing patient needs and their impact on clinical education.

Dental records of 1,800 clinic patients were examined in nine U.S. dental schools. The objective of the study was to identify what changes, if any, occurred over the five-year period between 1978 and 1982 in dental clinic patient treatment needs. Patients were found to be older at the time of entry into the clinical system and they required less operative treatment, fewer opposing full dentures, and less fixed bridgework. Increases in single full dentures and partial dentures were recorded. No changes were observed in endodontics, periodontics, or oral surgery treatment needs. These findings present a potentially serious problem in affected areas that may lead to a decline in the availability of sufficient experiences for the clinical training of dentists.

Resolved: that a fifth year of dental education be a requirement. Remarks for the negative.

Those representing the affirmative side of the issue have failed to provide convincing evidence supporting the necessity of a required fifth year of dental education. The mechanism is already in place for additional education and experience through expanding general practice residency programs for students desiring additional experience. A required fifth year would increase the cost of dental education for all students at a time of diminishing resources and would undoubtedly result in greater health care costs for the public. The overcrowded curriculum can be addressed successfully and far more economically by restructuring the present predental/dental curriculum continuum instead of adding a required fifth year. In conclusion, the negative side asserts that there are more practical, less expensive, and more feasible ways to address the issues confronting dental education today than by adding a mandatory year to the education process.

Epigenetic regulation of CD133/PROM1 expression in glioma stem cells by Sp1/myc and promoter methylation.

Tumor stem cells, postulated to be the source cells for malignancies, have been identified in several cancers using cell-surface expression of markers including CD133, a pentaspan membrane protein. CD133+ve cells form neurospheres, exhibit self-renewal and differentiation, and are tumorigenic. However, despite its association with stem cells, a causal relationship of CD133 to tumorigenesis remains to be defined. Hypothesizing that specific epigenetic and transcription factors implicated in driving the stem cell state may concurrently regulate CD133 expression in stem cells, we analyzed the structure and regulation of CD133 promoter in glioma stem cells and glioma cell lines. Initially, a minimal promoter region was identified by analyzing the activity of CD133 promoter-driven luciferase-expressing 5'-and 3'-deletion-constructs upstream of the transcription start site. This region contained a CpG island that was hypermethylated in CD133-ve glioma stem cells (GSC) and glioma cells but unmethylated in CD133+ve ones. Of several predicted TF-binding sites in this region, the role of tandem Sp1 (-242 and -221) and two Myc (-541 and -25)-binding sites were examined. Overexpression of Sp1 or Myc increased CD133 minimal promoter-driven luciferase activity and CD133 levels in GSC and in glioma cell line. Mithramycin, a Sp1 inhibitor, decreased minimal promoter activity and downregulated CD133 levels in GSC. Gel-shift assays demonstrated direct binding of Sp1 to their predicted sites that was competitively inhibited by oligonucleotide-binding-site sequences and supershifted by anti-Sp1 confirming the interaction. Sp1 and Myc-antibody chromatin immunoprecipitation (ChIP) analysis in GSC showed enrichment of regions with Sp1 and Myc-binding sites. In CD133-ve cells, ChIP analysis showed binding of the methyl-DNA-binding proteins, MBD1, MBD2 and MeCP2 to the methylated CpG island and repression of transcription. These results demonstrate that Sp1 and Myc regulate CD133 transcription in GSC and that promoter methylation and methyl-DNA-binding proteins cause repression of CD133 by excluding transcription-factor binding.

Tie2-mediated multidrug resistance in malignant gliomas is associated with upregulation of ABC transporters.

Resistance and relapse are still primary causes that result in poor effectiveness of chemotherapy in malignant gliomas. Therefore, development of new therapeutic strategies requires the identification of key molecular pathways regulating chemoresistance. We previously found that abnormal high expression of the Tie2 receptor in gliomas was associated with tumor malignancy. Here, we studied the role of Tie2 activation in drug resistance by testing the cytotoxicity of several chemotherapeutic drugs in a panel of human glioma cell lines and brain tumor stem cells and found that Tie2 activation was significantly related to chemoresistance. The essential role of Tie2 in this phenotype was illustrated by silencing Tie2 using specific siRNA, and the subsequent abrogation of the angiopoietin 1 (Ang1)-mediated chemoresistance. Using quantitative real-time PCR and functional drug efflux studies, we observed that Tie2 activation resulted in increased expression of ATP-binding cassette (ABC) transporters. Consistent with these results, downmodulation of ABCG2 or ABCC2 resulted in the inability of Tie2 activation to induce a chemoresistant phenotype. Our results indicate that Tie2 activation may be important in modifying the evolution of gliomas during conventional chemotherapy regimens, and open new avenues for the search of more effective therapies to avoid the inevitable brain tumor recurrence.

Phase II study of carboplatin and erlotinib (Tarceva, OSI-774) in patients with recurrent glioblastoma.

Targeting the epidermal growth factor receptor (EGFR) may be effective in a subset of glioblastoma patients. This phase II study assessed the clinical activity of erlotinib plus carboplatin and to determine molecular predictors of response. The primary endpoint was progression free survival (PFS). Patients with recurrent glioblastoma with no more than two prior relapses received carboplatin intravenously on day 1 of every 28-day cycle (target AUC of 6 mg x ml/min). Daily erlotinib at 150 mg/day was dose escalated to 200 mg/day, as tolerated. Clinical and MRI assessments were made every 4 and 8 weeks, respectively. Tumor tissue was evaluated for EGFR, AKT and phosphatase and tensin homolog (PTEN) status. One partial response (PR) was observed out of 43 assessable patients. Twenty patients (47%) had stable disease (SD) for an average of 12 weeks. Median PFS was 9 weeks. The 6-month PFS rate was 14%. Median overall survival (OS) was 30 weeks. This regimen was well tolerated with grade 3/4 toxicities of fatigue, leukopenia, thrombocytopenia and rash requiring dose reductions. A recursive partitioning analysis (RPA) predicted that patients with KPS >or=90 treated with more than 1 prior regimen had the highest OS. No correlation was observed between EGFR, Akt or PTEN expression and either PFS or OS. Carboplatin plus erlotinib is well tolerated but has modest activity in unselected patients. Future trials should be stratified based on optimal molecular or clinical characteristics.

Interactions between nerve and muscle: synapse elimination at the developing neuromuscular junction.

Studies of synaptogenesis at the developing neuromuscular junction have provided a wealth of information regarding the various mechanisms that are involved in the formation of synaptic connections. In addition to synapse formation, however, the mature pattern of innervation at the neuromuscular junction (and elsewhere in the nervous system) depends on a significant loss of synaptic connections during development. The molecular mechanisms involved in the process of synapse elimination are not understood. Recent work at the neuromuscular junction suggests that changes in the postsynaptic cell may be necessary in order for nerve terminals to be eliminated. Thus, in contrast to synapse formation in which an axon terminal initiates a cascade of changes leading to the formation of pre- and postsynaptic specializations, synapse elimination may be initiated by local changes in the postsynaptic cell that disassemble the postsynaptic apparatus and ultimately remove the overlying terminal. In this review, we wish to examine the potential role that some of the factors involved in synapse formation might play in the less-well-understood phenomenon of synapse elimination.

Binocular competition in the control of geniculate cell size depends upon visual cortical N-methyl-D-aspartate receptor activation.

The lateral geniculate nucleus relays visual information from the retina to cortex. One well-known anatomical consequence of monocular deprivation during early postnatal development is a shrinkage of neurons in the lamina of the lateral geniculate nucleus that receive input from the deprived eye. This is thought to reflect the competition of afferents subserving the two eyes, possibly at the level of the visual cortex. We find that blockade of N-methyl-D-aspartate receptors in kitten visual cortex disrupts this process of binocular competition. These data provide direct evidence that postsynaptic activation of cortical neurons is required for competitive changes in lateral geniculate cell size and suggest a role for N-methyl-D-aspartate receptors in anatomical as well as physiological plasticity in the mammalian visual system.

Synaptic competition during the reformation of a neuromuscular map.

We have been studying the mechanisms whereby pools of motor neurons establish a rostrocaudal bias in the position of their synapses in some skeletal muscles. The serratus anterior (SA) muscle of the rat displays a rostrocaudal topographic map before birth, and the topography is re-established after denervation. In this report, we explore the potential role of synaptic competition between innervating axons as a means of generating topographic specificity. We followed the progress of the reformation of this map in neonatal animals under conditions that enhanced the likelihood of observing synaptic competition. This was accomplished by forcing caudal axons to regenerate ahead of rostral axons onto a surgically reduced SA muscle. In this way, caudal (C7) motor neurons had unopposed access to vacated synaptic sites on the remaining rostral half of the SA before the return of the rostral (C6) axons. Intracellular recording revealed that 2 d after the second denervation, most of the reinnervated end plates contained only axons from the C7 branch; the remaining reinnervated end plates received input from C6 only or were multiply innervated by C6 and C7 axons. After 6 d, the pattern was reversed, with most end plates innervated exclusively by C6. After 17 d, axons from C6 were the sole input to reinnervated end plates. During the transition from C7- to C6-dominated input, at end plates coinnervated by C6 and C7 axons, the average quantal content from C6 was the same as that from C7; after 7 d, the quantal content of C6 was greater than that of C7. We have thus developed an experimental situation in which the outcome of synaptic competition is predictable and can be influenced by the positional labels associated with axons from different levels in the spinal cord.