Will peripherally restricted kappa-opioid receptor agonists (pKORAs) relieve pain with less opioid adverse effects and abuse potential?

WHAT IS KNOWN AND OBJECTIVE: Optimal utilization of opioid analgesics is significantly limited by the central nervous system adverse effects and misuse/abuse potential of currently available drugs. It has been postulated that opioid-associated adverse effects and abuse potential would be greatly reduced if opioids could be excluded from reaching the brain. We review the basic science and clinical evidence of one such approach - peripherally restricted kappa-opioid receptor (KOR) agonists (pKORAs). METHODS: Published and unpublished literature, websites and other sources were searched for basic science and clinical information related to the potential benefits and development of peripherally restricted kappa-opioid receptor agonists. Each source was summarized, reviewed and assessed. RESULTS: The historical development of pKORAs can be traced from the design of increasingly KOR-selective agonists, elucidation of the pharmacologic attributes of such compounds and strategies to restrict passage across the blood-brain barrier. Novel compounds are under development and have progressed to clinical trials. WHAT IS NEW AND CONCLUSIONS: The results from recent clinical trials suggest that peripherally restricted opioids can be successfully designed and that they can retain analgesic efficacy with a more favourable adverse effect profile.

Hand pattern indicates prostate cancer risk.

BACKGROUND: The ratio of digit lengths is fixed in utero, and may be a proxy indicator for prenatal testosterone levels. METHODS: We analysed the right-hand pattern and prostate cancer risk in 1524 prostate cancer cases and 3044 population-based controls. RESULTS: Compared with index finger shorter than ring finger (low 2D : 4D), men with index finger longer than ring finger (high 2D : 4D) showed a negative association, suggesting a protective effect with a 33% risk reduction (odds ratio (OR) 0.67, 95% confidence interval (CI) 0.57-0.80). Risk reduction was even greater (87%) in age group <60 (OR 0.13, 95% CI 0.09-0.21). CONCLUSION: Pattern of finger lengths may be a simple marker of prostate cancer risk, with length of 2D greater than 4D suggestive of lower risk.

Prostate cancer in BRCA2 germline mutation carriers is associated with poorer prognosis.

BACKGROUND: The germline BRCA2 mutation is associated with increased prostate cancer (PrCa) risk. We have assessed survival in young PrCa cases with a germline mutation in BRCA2 and investigated loss of heterozygosity at BRCA2 in their tumours. METHODS: Two cohorts were compared: one was a group with young-onset PrCa, tested for germline BRCA2 mutations (6 of 263 cases had a germline BRAC2 mutation), and the second was a validation set consisting of a clinical set from Manchester of known BRCA2 mutuation carriers (15 cases) with PrCa. Survival data were compared with a control series of patients in a single clinic as determined by Kaplan-Meier estimates. Loss of heterozygosity was tested for in the DNA of tumour tissue of the young-onset group by typing four microsatellite markers that flanked the BRCA2 gene, followed by sequencing. RESULTS: Median survival of all PrCa cases with a germline BRCA2 mutation was shorter at 4.8 years than was survival in controls at 8.5 years (P=0.002). Loss of heterozygosity was found in the majority of tumours of BRCA2 mutation carriers. Multivariate analysis confirmed that the poorer survival of PrCa in BRCA2 mutation carriers is associated with the germline BRCA2 mutation per se. CONCLUSION: BRCA2 germline mutation is an independent prognostic factor for survival in PrCa. Such patients should not be managed with active surveillance as they have more aggressive disease.

Identification of actin nucleation activity and polymerization inhibitor in ameboid cells: their regulation by chemotactic stimulation.

Actin polymerization occurs in amebae of Dictyostelium discoideum after chemotactic stimulation (Hall, A. L., A. Schlein, and J. Condeelis. 1988. J. Cell. Biochem. 37:285-299). When cells are lysed with Triton X-100 during stimulation, an actin nucleation activity is detected in lysates by measuring the rate of pyrene-labeled actin polymerization. This stimulated nucleation activity is closely correlated with actin polymerization observed in vivo in its kinetics, developmental regulation, and cytochalasin D sensitivity. Actin polymerization is coordinate with pseudopod extension in synchronized populations of cells and is correlated with the accumulation of F actin in pseudopods. The stimulated actin nucleation activity is present in low-speed pellets from Triton lysates (cytoskeletons) within 3 s of stimulation and is stable compared with the nucleation activity of whole cell lysates. Low-speed supernatants contain a reversible inhibitor of the actin nucleation activity that is itself regulated by chemotactic stimulation. Neither activity requires Ca2+ and both are fully expressed in 10 mM EGTA. Fractions containing the inhibitor do not sever actin filaments but do inhibit actin polymerization that is seeded by fragments of purified F actin. These results indicate that chemotactic stimulation of Dictyostelium discoideum generates both an actin-nucleating activity and an actin-polymerization inhibitor, and suggest that the parallel regulation of these two activities leads to the transient phases of actin polymerization observed in vivo. The different compartmentation of these two activities may account for polarized pseudopod extension in gradients of chemoattractant.

cAMP-mediated inhibition of intracellular particle movement and actin reorganization in Dictyostelium.

Before addition of cAMP, Dictyostelum amoebae rapidly translocating in buffer are elongate, exhibit expansion zones primarily at the anterior end and filamentous actin (F-actin) localization primarily in the anterior pseudopodia. Intracellular particle movement is primarily in the anterior direction, and the average rate of particle movement is roughly five times the rate of cellular translocation. Within seconds after the addition of 10(-6)M cAMP, there is a dramatic suppression of cellular translocation, an inhibition of pseudopod formation, a freeze in cellular morphology, a dramatic depression in intracellular particle movement, loss of F-actin localization in pseudopodia concomitant with relocalization of F-actin in the general cytoplasmic cortex under the plasma membrane, and a doubling of F-actin content. After 10 s, expansion zones are again visible at the cell perimeter, but they no longer are localized in the original anterior portion of the cell. There is a slight rebound in particle movement after 10 s, but particles with persistent tracks now show no directionality towards the original anterior portion of the cell, as they did before cAMP addition. Finally, in parallel with the resumption of peripheral expansion and the small rebound in particle movement, there is a decrease in total cellular F-actin to the untreated level. The pattern of microtubule organization is unaffected by the addition of cAMP.

The cyclic nucleotide phosphodiesterase gene of Dictyostelium discoideum contains three promoters specific for growth, aggregation, and late development.

The cyclic nucleotide phosphodiesterase (phosphodiesterase) plays essential roles throughout the development of Dictyostelium discoideum. It is crucial to cellular aggregation and to postaggregation morphogenesis. The phosphodiesterase gene is transcribed into three mRNAs, containing the same coding sequence connected to different 5' untranslated sequences, that accumulate at different times during the life cycle. A 1.9-kilobase (kb) mRNA is specific for growth, a 2.4-kb mRNA is specific for aggregation, and a 2.2-kb mRNA is specific for late development and is only expressed in prestalk cells. Hybridization of RNA isolated from cells at various stages of development with different upstream regions of the gene indicated separate promoters for each of the three mRNAs. The existence of specific promoters was confirmed by fusing the three putative promoter regions to the chloramphenicol acetyltransferase reporter gene, and the analysis of transformants containing these constructs. The three promoters are scattered within a 4.1-kilobase pair (kbp) region upstream of the initiation codon. The late promoter is proximal to the coding sequence, the growth-specific promoter has an initiation site that is 1.9 kbp upstream of the ATG codon, and the aggregation-specific promoter has an initiation site 3 kbp upstream.

Relationship of ligand-receptor dynamics to actin polymerization in RBL-2H3 cells transfected with the human formyl peptide receptor.

The human formyl peptide receptor (FPR) expressed in RBL-2H3 transfectants (RBL[FPR]) behaves qualitatively like the FPR expressed by neutrophils except that it causes sustained F-actin accumulation and cell shape change responses on formyl peptide stimulation. These sustained responses were not accounted for by changes in the transfected receptor's ability to interact with ligand or by receptor density. Signal transduction pathways of transfected and neutrophil FPRs are apparently similar. In transfected cells, dissociation of ligand is sensitive to guanine nucleotide, the G protein is pertussis toxin-sensitive, FPR and G protein appear to be precoupled, the F-actin response is stimulated with the same dose-response profile as in neutrophils, and the F-actin accumulation response is directly regulated by the FPR, even long after initial stimulation. Potentially significant differences between neutrophil and transfected FPR were found when receptor processing was measured. In neutrophils, practically 100% of the FPR is converted to forms that dissociate slowly from ligand and are inactive in signal transduction within 2 min of ligand stimulation. By contrast, 20% or more of transfected FPR remains rapidly dissociating even 5 min after stimulation. Although 80% of neutrophil FPR is internalized by 5 min after stimulation, transfected FPR appears to plateau at 50-60% internalized. Because actin responses in neutrophils are regulated by a small number of active receptors, the inefficiency of receptor inactivation in RBL(FPR) transfectants may account for the prolonged F-actin accumulation response.

The utility and generality of Mini-Mental State Examination scores in Alzheimer's disease.

The present study sought to evaluate the validity and generality of the Mini-Mental State Examination (MMSE) and its subsection scores. We gave the MMSE and other neuropsychological tests to 51 patients with probable Alzheimer's disease. On the basis of correlational and factor analyses, overall performance on the MMSE proved to have good concurrent validity with other comprehensive neuropsychological assessment instruments. However, the MMSE subsections should not be viewed as highly specific measures of cognition or memory.

The technical characteristics of matched filtering in digital subtraction angiography.

The technical characteristics of a new digital fluorographic image processing method called matched filtering are presented. This technique, a type of extensive temporal integration, takes a weighted sum of images acquired during passage of a contrast bolus through some area of interest. The weight of each image is governed by the magnitude of the contrast bolus in that image. An essential requirement of the matched filter is that its integral be zero. It is shown for equal exposure rates and typical bolus characteristics that matched filtering provides a factor of two higher signal-to-noise ratio (SNR) than conventional methods for bolus transit times of 10 s or higher. Equilvalently, matched filtering can yield images with quality comparable to conventional digital subtraction angiography (DSA) at a factor of four less patient exposure. The SNR obtained with matched filtering is shown to be within 30% of an ideal bound. Comparisons of matched filtering to standard recursive methods and simple integration are made. Experimental canine studies are presented which compare matched filtering with conventional DSA.

Generalized image combinations in dual KVP digital radiography.

Dual energy basis decomposition techniques apply to single projection radiographic imaging. The high and low energy images are non-linearly transformed to generate two energy-independent images characterizing the integrated Compton/photoelectric attenuation components. Characteristic linear combinations of these two basis images identify unknown materials, cancel known materials, and generate synthesized monoenergetic images. The problems of intervening materials and material displacement are solved in general for a wide class of clinical imaging tasks. The basis projection angle identifies one from a family of energy selective imaging tasks, and such performance measures as the contrast enhancement factor (CEF) and signal to noise ratio (SNR) are expressed as functions of this angle. Algorithms for the decomposition of high and low energy measurements are compared and experimental images are included.

What is repeated in a repetition? Effects of practice conditions on motor skill acquisition.

The nature of repetition and its contribution to the acquisition of motor skills in neurologically healthy subjects are examined in this article. We argue that cognitive processing is a key component of practice, which is undermined by repetitive performances. The effects on motor learning of contextual interference, knowledge-of-results delivery schedules, and observation of models are examined, with particular reference to the nature of practice. The role of repetition in learning with respect to physical therapy is also discussed.

cis-hydroxyproline stimulates the growth of rat mammary carcinoma cells.

With the ever-increasing evidence that the extracellular matrix (ECM) can stimulate tumor growth, it follows that inhibiting the synthesis of tumor-derived stroma may be a potential therapeutic target of cancer progression. The proline analog cis-hydroxyproline (CHP), an inhibitor of collagen deposition, was examined for its effects on the growth of clonal tumor cells that differentially produce type IV collagen and laminin. Two separate clones derived from rat mammary carcinoma cells that produce high and low amounts of type IV collagen and laminin were injected into the flanks of nude mice. Tumors in animals receiving CHP treatment grew faster than tumors in control animals receiving saline, although statistically not significant. Furthermore, upon administration of CHP to these clones in culture, increased proliferation rates of both cell types were observed. These results show that CHP is not useful in preventing stromal development and growth of rat mammary tumor xenografts.

Biomechanical variables related to walking performance 6-months following post-stroke rehabilitation.

BACKGROUND: Body-weight supported treadmill training has been shown to be effective in improving walking speed in post-stroke hemiparetic subjects, and those that have shown improvements generally maintain them after the completion of rehabilitation. However, currently no biomechanical variables are known to be related to those who will either continue to improve or regress in their self-selected walking speed during the 6-month period following rehabilitation. The objective of this study was to identify those biomechanical variables that are associated with subjects who continue (or did not continue) to improve their self-selected walking speed following the completion of rehabilitation. METHODS: Experimental kinematic and kinetic data were recorded from 18 hemiparetic subjects who participated in a 6-month follow-up study after completing a 12-week locomotor training program that included stepping on a treadmill with partial body weight support and manual assistance. Pearson correlation coefficients were used to determine which biomechanical variables evaluated during the post-training session were related to changes in self-selected walking speed from post-training to a 6-month follow-up session. FINDINGS: Following the completion of rehabilitation, the majority of subjects increased or retained (i.e., did not change) their self-selected walking speed from post-training to the follow-up session. Post-training step length symmetry and daily step activity were positively related to walking speed improvements. INTERPRETATION: Motor control deficits that lead to persistent step length asymmetry and low daily step activity at the end of rehabilitation are associated with poorer outcomes six months after completion of the program.

Relationships between muscle contributions to walking subtasks and functional walking status in persons with post-stroke hemiparesis.

BACKGROUND: Persons with post-stroke hemiparesis usually walk slowly and asymmetrically. Stroke severity and functional walking status are commonly predicted by post-stroke walking speed. The mechanisms that limit walking speed, and by extension functional walking status, need to be understood to improve post-stroke rehabilitation methods. METHODS: Three-dimensional forward dynamics walking simulations of hemiparetic subjects (and speed-matched controls) with different levels of functional walking status were developed to investigate the relationships between muscle contributions to walking subtasks and functional walking status. Muscle contributions to forward propulsion, swing initiation and power generation were analyzed during the pre-swing phase of the gait cycle and compared between groups. FINDINGS: Contributions from the paretic leg muscles (i.e., soleus, gastrocnemius and gluteus medius) to forward propulsion increased with improved functional walking status, with the non-paretic leg muscles (i.e., rectus femoris and vastii) compensating for reduced paretic leg propulsion in the limited community walker. Contributions to swing initiation from both paretic (i.e., gastrocnemius, iliacus and psoas) and non-paretic leg muscles (i.e., hamstrings) also increased as functional walking status improved. Power generation was also an important indicator of functional walking status, with reduced paretic leg power generation limiting the paretic leg contribution to forward propulsion and leg swing initiation. INTERPRETATION: These results suggest that deficits in muscle contributions to the walking subtasks of forward propulsion, swing initiation and power generation are directly related to functional walking status and that improving output in these muscle groups may be an effective rehabilitation strategy for improving post-stroke hemiparetic walking.

Transduction of the chemotactic signal to the actin cytoskeleton of Dictyostelium discoideum.

Dictyostelium discoideum amebae chemotax toward folate during vegetative growth and toward extracellular cAMP during the aggregation phase that follows starvation. Stimulation of starving amebae with extracellular cAMP leads to both actin polymerization and pseudopod extension (Hall et al., 1988, J. Cell. Biochem. 37, 285-299). We have identified an actin nucleation activity (NA) from starving amebae that is regulated by cAMP receptors and controls actin polymerization (Hall et al., 1989, J. Cell Biol., in press). We show here that NA from vegetative cells is also regulated by chemotactic receptors for folate. Our studies indicate that NA is an essential effector in control of the actin cytoskeleton by chemotactic receptors. Guided by a recently proposed model for signal transduction from the cAMP receptor (Snaar-Jagalska et al., 1988, Dev. Genet. 9, 215-225), we investigated which of three signaling pathways activates the NA effector. Treatment of whole cells with a commercial pertussis toxin preparation (PT) inhibited cAMP-stimulated NA. However, endotoxin contamination of the PT appears to account for this effect. The synag7 mutation and caffeine treatment do not inhibit activation of NA by cAMP. Thus, neither activation of adenylate cyclase nor a G protein sensitive to PT treatment of whole cells is necessary for the NA response. Actin nucleation activity stimulated with folate is normal in vegetative fgdA cells. However, cAMP suppresses rather than activates NA in starving fgdA cells. This indicates that the components of the actin nucleation effector are present and that a pathway regulating the inhibitor(s) of nucleation remains functional in starving fgdA cells. The locus of the fgdA defect, a G protein implicated in phospholipase C activation, is directly or indirectly responsible for transduction of the stimulatory chemotactic signal from cAMP receptors to the nucleation effector in Dictyostelium.

Changes in the association of actin-binding proteins with the actin cytoskeleton during chemotactic stimulation of Dictyostelium discoideum.

Triton-insoluble cytoskeletons were isolated from Dictyostelium discoideum AX3 cells prior to and following stimulation with 2'deoxy cyclic adenosine monophosphate (cAMP). Temporal changes in the content of actin and a 120,000 dalton actin-binding protein (ABP-120) in cytoskeletons following stimulation were monitored. Both actin and ABP-120 were incorporated into the cytoskeleton at 30-40 seconds following stimulation, which is cotemporal with the onset of pseudopod extension during stimulation of amoebae with chemoattractants. Changes in the content of total cytoskeletal protein and cytoskeletal myosin were determined under the same experimental conditions as controls. These proteins exhibited different kinetics from those of cytoskeletal ABP-120 and actin following the addition of 2'deoxy cAMP. The authors concluded that the association of ABP-120 with the cytoskeleton is regulated during cAMP signalling. Furthermore, these results indicate that ABP-120 is involved in cross-linking newly assembled actin filaments into the cytoskeleton during chemoattractant-stimulated pseudopod extension.

Relationship of pseudopod extension to chemotactic hormone-induced actin polymerization in amoeboid cells.

Aggregation-competent amoeboid cells of Dictyostelium discoideum are chemotactic toward cAMP. Video microscopy and scanning electron microscopy were used to quantitate changes in cell morphology and locomotion during uniform upshifts in the concentration of cAMP. These studies demonstrate that morphological and motile responses to cAMP are sufficiently synchronous within a cell population to allow relevant biochemical analyses to be performed on large numbers of cells. Changes in cell behavior were correlated with F-actin content by using an NBD-phallacidin binding assay. These studies demonstrate that actin polymerization occurs in two stages in response to stimulation of cells with extracellular cAMP and involves the addition of monomers to the cytochalasin D-sensitive (barbed) ends of actin filaments. The second stage of actin assembly, which peaks at 60 sec following an upshift in cAMP concentration, is temporally correlated with the growth of new pseudopods. The F-actin assembled by 60 sec is localized in these new pseudopods. These results indicate that actin polymerization may constitute one of the driving forces for pseudopod extension in amoeboid cells and that nucleation sites regulating polymerization are under the control of chemotaxis receptors.

Purification and characterization of aginactin, a newly identified agonist-regulated actin-capping protein from Dictyostelium amoebae.

Amoeboid chemotaxis involves a regulated increase in actin nucleation activity that is correlated with an increase in actin polymerization occurring seconds after chemotactic stimulation (Carson, M., Weber, A., and Zigmond, S. H. (1986) J. Cell Biol. 103, 2707-2714; Hall, A. L., Warren, V., Dharmawardhane, S., and Condeelis, J. (1989) J. Cell Biol. 109, 2207-2213). We report the isolation and characterization of an agonist-regulated capping protein, aginactin, from Dictyostelium that may regulate these changes in actin nucleation activity. Aginactin is isolated from low speed supernatants of starved amoebae by sequential anion exchange, hydrophobic interaction, fast protein liquid chromatography anion exchange, and hydroxyapatite chromatography. Aginactin migrates with an apparent molecular weight of 70,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels and gel filtration columns, suggesting that it is a globular monomer. Aginactin is a barbed-end capping protein by several criteria. It inhibits the rate and final extent of actin polymerization and increases the apparent critical concentration at substoichiometric ratios to actin. It also inhibits depolymerization of F-actin and inhibits polymerization at the barbed end of Limulus acrosomal bundles. Aginactin is unaffected by micromolar Ca2+, and it neither severs F-actin nor nucleates actin polymerization in either the presence or absence of Ca2+. Aginactin binds to and cosediments with F-actin and has an apparent Kd for capping F-actin of 2.7 nM.