Implications of the Collar Sign in Incompletely Occluded Aneurysms after Pipeline Embolization Device Implantation: A Follow-Up Study

BACKGROUND AND PURPOSE

The angiographic collar sign has been recently described in patients with incompletely occluded aneurysms after Pipeline Embolization Device implantation. The long-term implications of this sign are unknown. We report angiographic outcomes of patients with the collar sign with follow-up of up to 45 months and the implications of this angiographic finding.

MATERIALS AND METHODS

We performed a retrospective review of a prospectively maintained data base of patients who underwent Pipeline Embolization Device implantation for an intracranial aneurysm at our institution between January 2014 and December 2016. We included patients with a collar sign at the initial follow-up angiogram after Pipeline Embolization Device implantation.

RESULTS

A total of 198 patients with 285 aneurysms were screened for the collar sign on initial and subsequent follow-up angiograms. There were 226 aneurysms (79.3%) with complete occlusion at the first follow-up. Of 59 incompletely occluded aneurysms, 19 (32.2%) aneurysms in 17 patients were found to have a collar sign on the first angiographic follow-up (median, 6 months; range, 4.2-7.2). Ten (52.6%) aneurysms underwent retreatment with a second Pipeline Embolization Device, which resulted in aneurysm occlusion in 1 (10%) patient. There were only 3 (15.8%) aneurysms with complete occlusion at the last follow-up, 2 (10.5%) of which had a single Pipeline Embolization Device implantation and another single (5.3%) aneurysm with a second Pipeline Embolization Device implantation.

CONCLUSIONS

A collar sign on the initial angiogram after Pipeline Embolization Device placement is a predictor of poor aneurysm occlusion. Because the occlusion rates remain equally low regardless of retreatment in patients with a collar sign, radiologic follow-up may be more appropriate than retreatment.

The geology and geophysics of Kuiper Belt object (486958) Arrokoth

The Cold Classical Kuiper Belt, a class of small bodies in undisturbed orbits beyond Neptune, is composed of primitive objects preserving information about Solar System formation. In January 2019, the New Horizons spacecraft flew past one of these objects, the 36-kilometer-long contact binary (486958) Arrokoth (provisional designation 2014 MU₆₉). Images from the flyby show that Arrokoth has no detectable rings, and no satellites (larger than 180 meters in diameter) within a radius of 8000 kilometers. Arrokoth has a lightly cratered, smooth surface with complex geological features, unlike those on previously visited Solar System bodies. The density of impact craters indicates the surface dates from the formation of the Solar System. The two lobes of the contact binary have closely aligned poles and equators, constraining their accretion mechanism.

Color, composition, and thermal environment of Kuiper Belt object (486958) Arrokoth

The outer Solar System object (486958) Arrokoth (provisional designation 2014 MU₆₉) has been largely undisturbed since its formation. We studied its surface composition using data collected by the New Horizons spacecraft. Methanol ice is present along with organic material, which may have formed through irradiation of simple molecules. Water ice was not detected. This composition indicates hydrogenation of carbon monoxide-rich ice and/or energetic processing of methane condensed on water ice grains in the cold, outer edge of the early Solar System. There are only small regional variations in color and spectra across the surface, which suggests that Arrokoth formed from a homogeneous or well-mixed reservoir of solids. Microwave thermal emission from the winter night side is consistent with a mean brightness temperature of 29 ± 5 kelvin.

The solar nebula origin of (486958) Arrokoth, a primordial contact binary in the Kuiper Belt

The New Horizons spacecraft's encounter with the cold classical Kuiper Belt object (486958) Arrokoth (provisional designation 2014 MU₆₉) revealed a contact-binary planetesimal. We investigated how Arrokoth formed and found that it is the product of a gentle, low-speed merger in the early Solar System. Its two lenticular lobes suggest low-velocity accumulation of numerous smaller planetesimals within a gravitationally collapsing cloud of solid particles. The geometric alignment of the lobes indicates that they were a co-orbiting binary that experienced angular momentum loss and subsequent merger, possibly because of dynamical friction and collisions within the cloud or later gas drag. Arrokoth's contact-binary shape was preserved by the benign dynamical and collisional environment of the cold classical Kuiper Belt and therefore informs the accretion processes that operated in the early Solar System.

Initial results from the New Horizons exploration of 2014 MU69, a small Kuiper Belt object

The Kuiper Belt is a distant region of the outer Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU₆₉, a cold classical Kuiper Belt object approximately 30 kilometers in diameter. Such objects have never been substantially heated by the Sun and are therefore well preserved since their formation. We describe initial results from these encounter observations. MU₆₉ is a bilobed contact binary with a flattened shape, discrete geological units, and noticeable albedo heterogeneity. However, there is little surface color or compositional heterogeneity. No evidence for satellites, rings or other dust structures, a gas coma, or solar wind interactions was detected. MU₆₉'s origin appears consistent with pebble cloud collapse followed by a low-velocity merger of its two lobes.

On Flow Diversion: The Changing Landscape of Intracerebral Aneurysm Management

Uptake of flow-diverting technology is rapidly outpacing the availability of clinical evidence. Most current usage is off-label, and the endovascular community is nearer the beginning than the end of the learning curve, given the number of devices in development. A comprehensive overview of technical specifications alongside key outcome data is essential both for clinical decision-making and to direct further investigations. Most-studied has been the Pipeline Embolization Device, which has undergone a transition to the Pipeline Flex for which outcome data are sparse or heterogeneous. Alternative endoluminal devices do not appear to be outperforming the Pipeline Embolization Device to date, though prospective studies and long-term data mostly are lacking, and between-study comparisons must be treated with caution. Nominal technical specifications may be unrelated to in situ performance, emphasizing the importance of correct radiologic sizing and device placement. Devices designed specifically for bifurcation aneurysms also lack long-term outcome data or have only recently become available for clinical use. There are no major studies directly comparing a flow-diverting device with standard coiling or microsurgical clipping. Data on flow-diverting stents are too limited in terms of long-term outcomes to reliably inform clinical decision-making. The best available evidence supports using a single endoluminal device for most indications. Recommendations on the suitability and choice of a device for bifurcation or ruptured aneurysms or for anatomically complex lesions cannot be made on the basis of current evidence. The appropriateness of flow-diverting treatment must be decided on a case-by-case basis, considering experience and the relative risks against standard approaches or observation.

Impact craters on Pluto and Charon indicate a deficit of small Kuiper belt objects

The flyby of Pluto and Charon by the New Horizons spacecraft provided high-resolution images of cratered surfaces embedded in the Kuiper belt, an extensive region of bodies orbiting beyond Neptune. Impact craters on Pluto and Charon were formed by collisions with other Kuiper belt objects (KBOs) with diameters from ~40 kilometers to ~300 meters, smaller than most KBOs observed directly by telescopes. We find a relative paucity of small craters ≲13 kilometers in diameter, which cannot be explained solely by geological resurfacing. This implies a deficit of small KBOs (≲1 to 2 kilometers in diameter). Some surfaces on Pluto and Charon are likely ≳4 billion years old, thus their crater records provide information on the size-frequency distribution of KBOs in the early Solar System.

Endothelialization following Flow Diversion for Intracranial Aneurysms: A Systematic Review

BACKGROUND

The underlying mechanism of action of flow diverters is believed to be the induction of aneurysm thrombosis and simultaneous endothelial cell growth along the device struts, thereby facilitating aneurysm exclusion from the circulation. Although extensive attention has been paid to the role of altered cerebrovascular hemodynamics using computational fluid dynamics analyses, relatively less emphasis has been placed on the role of the vascular endothelium in promoting aneurysm healing.

PURPOSE

Our aim was to systematically review all available literature investigating the mechanism of action of flow diverters in both human patients and preclinical models.

DATA SOURCES

A systematic search of PubMed, Cochrane Central Register of Controlled Trials MEDLINE, EMBASE, and the Web of Science electronic data bases was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

STUDY SELECTION

We selected articles assessing the role of endothelialization in flow-diverter treatment of cerebral aneurysms, including both preclinical and clinical studies.

DATA ANALYSIS

Ten articles were eligible for inclusion in this review. Two assessed endothelialization in human patients, while the other 8 used preclinical models (either rabbits or pigs).

DATA SYNTHESIS

Methods used to assess endothelialization included optical coherence tomography and scanning electron microscopy.

LIMITATIONS

A limitation was the heterogeneity of studies.

CONCLUSIONS

Current data regarding the temporal relationship to flow-diverter placement has largely been derived from work in preclinical animal models. Whether these cells along the device struts originate from adjacent endothelial cells or are the result of homing of circulating endothelial progenitor cells is equivocal.

Predictors of Incomplete Occlusion following Pipeline Embolization of Intracranial Aneurysms: Is It Less Effective in Older Patients?

BACKGROUND AND PURPOSE

Flow diversion with the Pipeline Embolization Device (PED) for the treatment of intracranial aneurysms is associated with a high rate of aneurysm occlusion. However, clinical and radiographic predictors of incomplete aneurysm occlusion are poorly defined. In this study, predictors of incomplete occlusion at last angiographic follow-up after PED treatment were assessed.

MATERIALS AND METHODS

A retrospective analysis of consecutive aneurysms treated with the PED between 2009 and 2016, at 3 academic institutions in the United States, was performed. Cases with angiographic follow-up were selected to evaluate factors predictive of incomplete aneurysm occlusion at last follow-up.

RESULTS

We identified 465 aneurysms treated with the PED; 380 (81.7%) aneurysms (329 procedures; median age, 58 years; female/male ratio, 4.8:1) had angiographic follow-up, and were included. Complete occlusion (100%) was achieved in 78.2% of aneurysms. Near-complete (90%-99%) and partial (<90%) occlusion were collectively achieved in 21.8% of aneurysms and defined as incomplete occlusion. Of aneurysms followed for at least 12 months (211 of 380), complete occlusion was achieved in 83.9%. Older age (older than 70 years), nonsmoking status, aneurysm location within the posterior communicating artery or posterior circulation, greater aneurysm maximal diameter (≥21 mm), and shorter follow-up time (<12 months) were significantly associated with incomplete aneurysm occlusion at last angiographic follow-up on univariable analysis. However, on multivariable logistic regression, only age, smoking status, and duration of follow-up were independently associated with occlusion status.

CONCLUSIONS

Complete occlusion following PED treatment of intracranial aneurysms can be influenced by several factors related to the patient, aneurysm, and treatment. Of these factors, older age (older than 70 years) and nonsmoking status were independent predictors of incomplete occlusion. While the physiologic explanation for these findings remains unknown, identification of factors predictive of incomplete aneurysm occlusion following PED placement can assist in patient selection and counseling and might provide insight into the biologic factors affecting endothelialization.

Treatment of Tandem Internal Carotid Artery Aneurysms Using a Single Pipeline Embolization Device: Evaluation of Safety and Efficacy

BACKGROUND AND PURPOSE

Tandem aneurysms are defined as multiple aneurysms located in close proximity on the same parent vessel. Endovascular treatment of these aneurysms has rarely been reported. Our aim was to evaluate the safety and efficacy of a single Pipeline Embolization Device for the treatment of tandem aneurysms of the internal carotid artery.

MATERIALS AND METHODS

A retrospective analysis of consecutive aneurysms treated with the Pipeline Embolization Device between 2009 and 2016 at 3 institutions in the United States was performed. Cases included aneurysms of the ICA treated with a single Pipeline Embolization Device, and they were divided into tandem versus solitary. Angiographic and clinical outcomes were compared.

RESULTS

The solitary group (median age, 58 years) underwent 184 Pipeline Embolization Device procedures for 184 aneurysms. The tandem group (median age, 50.5 years) underwent 34 procedures for 78 aneurysms. Aneurysms were primarily located along the paraophthalmic segment of the ICA in both the single and tandem groups (72.3% versus 78.2%, respectively, P = .53). The median maximal diameters in the solitary and tandem groups were 6.2 and 6.7 mm, respectively. Complete occlusion on the last angiographic follow-up was achieved in 75.1% of aneurysms in the single compared with 88.6%% in the tandem group (P = .06). Symptomatic thromboembolic complications were encountered in 2.7% and 8.8% of procedures in the single and tandem groups, respectively (P = .08).

CONCLUSIONS

Tandem aneurysms of the ICA can be treated with a single Pipeline Embolization Device with high rates of complete occlusion. While there appeared to be a trend toward higher thromboembolic complication rates, this did not reach statistical significance.

The rapid formation of Sputnik Planitia early in Pluto's history

Pluto's Sputnik Planitia is a bright, roughly circular feature that resembles a polar ice cap. It is approximately 1,000 kilometres across and is centred on a latitude of 25 degrees north and a longitude of 175 degrees, almost directly opposite the side of Pluto that always faces Charon as a result of tidal locking. One explanation for its location includes the formation of a basin in a giant impact, with subsequent upwelling of a dense interior ocean. Once the basin was established, ice would naturally have accumulated there. Then, provided that the basin was a positive gravity anomaly (with or without the ocean), true polar wander could have moved the feature towards the Pluto-Charon tidal axis, on the far side of Pluto from Charon. Here we report modelling that shows that ice quickly accumulates on Pluto near latitudes of 30 degrees north and south, even in the absence of a basin, because, averaged over its orbital period, those are Pluto's coldest regions. Within a million years of Charon's formation, ice deposits on Pluto concentrate into a single cap centred near a latitude of 30 degrees, owing to the runaway albedo effect. This accumulation of ice causes a positive gravity signature that locks, as Pluto's rotation slows, to a longitude directly opposite Charon. Once locked, Charon raises a permanent tidal bulge on Pluto, which greatly enhances the gravity signature of the ice cap. Meanwhile, the weight of the ice in Sputnik Planitia causes the crust under it to slump, creating its own basin (as has happened on Earth in Greenland). Even if the feature is now a modest negative gravity anomaly, it remains locked in place because of the permanent tidal bulge raised by Charon. Any movement of the feature away from 30 degrees latitude is countered by the preferential recondensation of ices near the coldest extremities of the cap. Therefore, our modelling suggests that Sputnik Planitia formed shortly after Charon did and has been stable, albeit gradually losing volume, over the age of the Solar System.

The small satellites of Pluto as observed by New Horizons

The New Horizons mission has provided resolved measurements of Pluto's moons Styx, Nix, Kerberos, and Hydra. All four are small, with equivalent spherical diameters of ~40 kilometers for Nix and Hydra and ~10 kilometers for Styx and Kerberos. They are also highly elongated, with maximum to minimum axis ratios of ~2. All four moons have high albedos (~50 to 90%) suggestive of a water-ice surface composition. Crater densities on Nix and Hydra imply surface ages of at least 4 billion years. The small moons rotate much faster than synchronous, with rotational poles clustered nearly orthogonal to the common pole directions of Pluto and Charon. These results reinforce the hypothesis that the small moons formed in the aftermath of a collision that produced the Pluto-Charon binary.

Identification of key residues involved in adrenomedullin binding to the AM1 receptor

BACKGROUND AND PURPOSE

Adrenomedullin (AM) is a peptide hormone whose receptors are members of the class B GPCR family. They comprise a heteromer between the GPCR, the calcitonin receptor-like receptor and one of the receptor activity-modifying proteins 1-3. AM plays a significant role in angiogenesis and its antagonist fragment AM22-52 can inhibit blood vessel and tumour growth. The mechanism by which AM interacts with its receptors is unknown.

EXPERIMENTAL APPROACH

We determined the AM22-52 binding epitope for the AM1 receptor extracellular domain using biophysical techniques, heteronuclear magnetic resonance spectroscopy and alanine scanning.

KEY RESULTS

Chemical shift perturbation experiments located the main binding epitope for AM22-52 at the AM1 receptor to the C-terminal 8 amino acids. Isothermal titration calorimetry of AM22-52 alanine-substituted peptides indicated that Y52, G51 and I47 are essential for AM1 receptor binding and that K46 and P49 and R44 have a smaller role to play. Characterization of these peptides at the full-length AM receptors was assessed in Cos7 cells by cAMP assay. This confirmed the essential role of Y52, G51 and I47 in binding to the AM1 receptor, with their substitution resulting in ≥100-fold reduction in antagonist potency compared with AM22-52 . R44A, K46A, S48A and P49A AM22-52 decreased antagonist potency by approximately 10-fold.

CONCLUSIONS AND IMPLICATIONS

This study localizes the main binding epitope of AM22-52 to its C-terminal amino acids and distinguishes essential residues involved in this binding. This will inform the development of improved AM receptor antagonists.

Science potential from a Europa lander

The prospect of a future soft landing on the surface of Europa is enticing, as it would create science opportunities that could not be achieved through flyby or orbital remote sensing, with direct relevance to Europa's potential habitability. Here, we summarize the science of a Europa lander concept, as developed by our NASA-commissioned Science Definition Team. The science concept concentrates on observations that can best be achieved by in situ examination of Europa from its surface. We discuss the suggested science objectives and investigations for a Europa lander mission, along with a model planning payload of instruments that could address these objectives. The highest priority is active sampling of Europa's non-ice material from at least two different depths (0.5-2 cm and 5-10 cm) to understand its detailed composition and chemistry and the specific nature of salts, any organic materials, and other contaminants. A secondary focus is geophysical prospecting of Europa, through seismology and magnetometry, to probe the satellite's ice shell and ocean. Finally, the surface geology can be characterized in situ at a human scale. A Europa lander could take advantage of the complex radiation environment of the satellite, landing where modeling suggests that radiation is about an order of magnitude less intense than in other regions. However, to choose a landing site that is safe and would yield the maximum science return, thorough reconnaissance of Europa would be required prior to selecting a scientifically optimized landing site.

Gross chromosomal rearrangement mediated by DNA replication in stressed cells: evidence from Escherichia coli

Gross chromosomal rearrangements (GCRs), or changes in chromosome structure, play central roles in evolution and are central to cancer formation and progression. GCRs underlie copy number variation (CNV), and therefore genomic disorders that stem from CNV. We study amplification in Escherichia coli as a model system to understand mechanisms and circumstances of GCR formation. Here, we summarize observations that led us to postulate that GCR occurs by a replicative mechanism as part of activated stress responses. We report that we do not find RecA to be downregulated by stress on a population basis and that constitutive expression of RecA does not inhibit amplification, as would be expected if downregulation of RecA made cells permissive for nonhomologous recombination. Strains deleted for the genes for three proteins that inhibit RecA activity, psiB, dinI, and recX, all show unaltered amplification, suggesting that if they do downregulate RecA indirectly, this activity does not promote amplification.

Plasmodium chabaudi AS induces pregnancy loss in association with systemic pro-inflammatory immune responses in A/J and C57BL/6 mice

The molecular mechanisms that underlie poor birth outcomes in malaria during pregnancy remain poorly defined. To assess the role of host immune responses, mice known to respond differentially to Plasmodium chabaudi AS infection were studied. Following infection at day 0 of pregnancy, A/J mice developed significantly higher parasitemia than C57BL/6 (B6) mice and succumbed to infection. Both strains had evidence of parasite accumulation in the placenta at mid-gestation and aborted, with significantly higher embryo loss in infected A/J mice on day 9. While infection-induced systemic tumour necrosis factor (TNF) and interleukin (IL)-1β in the latter were significantly higher at day 11, day 10 IL-10 levels were higher in B6 mice. No differences in the levels of splenic lymphocyte subsets, neutrophils or monocytes between infected pregnant A/J and B6 mice were observed, with most cell types expanding in response to infection regardless of pregnancy. Antibody ablation of TNF exacerbated infection in A/J mice and did not ameliorate pregnancy outcome. Thus, malaria induces poor pregnancy outcome in both the mouse strains in the context of quantitatively different systemic inflammatory responses. Further evaluation of the roles of soluble and cellular immune components, particularly at the uteroplacental level, will be required to define the most critical pregnancy-compromising mechanisms.

Io volcanism seen by new horizons: a major eruption of the Tvashtar volcano

Jupiter's moon Io is known to host active volcanoes. In February and March 2007, the New Horizons spacecraft obtained a global snapshot of Io's volcanism. A 350-kilometer-high volcanic plume was seen to emanate from the Tvashtar volcano (62 degrees N, 122 degrees W), and its motion was observed. The plume's morphology and dynamics support nonballistic models of large Io plumes and also suggest that most visible plume particles condensed within the plume rather than being ejected from the source. In images taken in Jupiter eclipse, nonthermal visible-wavelength emission was seen from individual volcanoes near Io's sub-Jupiter and anti-Jupiter points. Near-infrared emission from the brightest volcanoes indicates minimum magma temperatures in the 1150- to 1335-kelvin range, consistent with basaltic composition.

New horizons mapping of Europa and Ganymede

The New Horizons spacecraft observed Jupiter's icy satellites Europa and Ganymede during its flyby in February and March 2007 at visible and infrared wavelengths. Infrared spectral images map H2O ice absorption and hydrated contaminants, bolstering the case for an exogenous source of Europa's "non-ice" surface material and filling large gaps in compositional maps of Ganymede's Jupiter-facing hemisphere. Visual wavelength images of Europa extend knowledge of its global pattern of arcuate troughs and show that its surface scatters light more isotropically than other icy satellites.

Pyroclastic activity at Home Plate in Gusev Crater, Mars

Home Plate is a layered plateau in Gusev crater on Mars. It is composed of clastic rocks of moderately altered alkali basalt composition, enriched in some highly volatile elements. A coarsegrained lower unit lies under a finer-grained upper unit. Textural observations indicate that the lower strata were emplaced in an explosive event, and geochemical considerations favor an explosive volcanic origin over an impact origin. The lower unit likely represents accumulation of pyroclastic materials, whereas the upper unit may represent eolian reworking of the same pyroclastic materials.

Are birth-preparedness programmes effective? Results from a field trial in Siraha district, Nepal

The birth-preparedness package (BPP) promotes active preparation and decision-making for births, including pregnancy/postpartum periods, by pregnant women and their families. This paper describes a district-wide field trial of the BPP implemented through the government health system in Siraha, Nepal, during 2003-2004. The aim of the field trial was to determine the effectiveness of the BPP to positively influence planning for births, household-level behaviours that affect the health of pregnant and postpartum women and their newborns, and their use of selected health services for maternal and newborn care. Community health workers promoted desired behaviours through inter-personal counselling with individuals and groups. Content of messages included maternal and newborn-danger signs and encouraged the use of healthcare services and preparation for emergencies. Thirty-cluster baseline and endline household surveys of mothers of infants aged less than one year were used for estimating the change in key outcome indicators. Fifty-four percent of respondents (n=162) were directly exposed to BPP materials while pregnant. A composite index of seven indicators that measure knowledge of respondents, use of health services, and preparation for emergencies increased from 33% at baseline to 54% at endline (p=0.001). Five key newborn practices increased by 19 to 29 percentage points from baseline to endline (p values ranged from 0.000 to 0.06). Certain key maternal health indicators, such as skilled birth attendance and use of emergency obstetric care, did not change. The BPP can positively influence knowledge and intermediate health outcomes, such as household practices and use of some health services. The BPP can be implemented by government health services with minimal outside assistance but should be comprehensively integrated into the safe motherhood programme rather than implemented as a separate intervention.

Planetary science: bedrock formation at Meridiani Planum

The Mars Exploration Rover Opportunity discovered sulphate-rich sedimentary rocks at Meridiani Planum on Mars, which are interpreted by McCollom and Hynek as altered volcanic rocks. However, their conclusions are derived from an incorrect representation of our depositional model, which is upheld by more recent Rover data. We contend that all the available data still support an aeolian and aqueous sedimentary origin for Meridiani bedrock.

Plasmodium falciparum-infected Red Blood Cells Selected for Binding to Cultured Syncytiotrophoblast Bind to Chondroitin Sulfate A and Induce Tyrosine Phosphorylation in the Syncytiotrophoblast

An important pathogenic complication of malaria during human pregnancy is sequestration of Plasmodium-infected red blood cells (iRBCs) in the placental intervillous spaces. This sequestration is thought to be mediated in part by binding of the iRBCs to receptors expressed on the syncytiotrophoblast (ST) membrane. We report here the use of a dynamic system to study the consequences of this cytoadherence on ST function using human syncytiotrophoblast and the choriocarcinoma cell line, BeWo. Laboratory isolates of Plasmodium falciparum were selected for their ability to bind to ST and used to investigate binding-induced cellular changes in the ST. Treatment of the ST cells with chondroitinase ABC suggested that the selected parasites bind predominantly to chondroitin sulfate A, but other receptors for parasite binding may be involved. Intracellular signaling in the ST induced by iRBCs binding was investigated by assessing tyrosine phosphorylation of ST proteins following iRBC binding. We demonstrate for the first time that iRBC cytoadherence to syncytiotrophoblast enhances tyrosine phosphorylation of a series of proteins in these cells. This approach will be useful in further studies of ST function in the malaria-infected placenta, the dynamics of selection of syncytiotrophoblast-binding parasites, and the identification of new receptors for parasite cytoadherence in the placenta.

Duration selective neurons in the inferior colliculus of the rat: topographic distribution and relation of duration sensitivity to other response properties

Many animals use duration to help them identify the source and meaning of a sound. Duration-sensitive neurons have been found in the auditory midbrain of mammals and amphibians, where their selectivity seems to correspond to the lengths of species-specific vocalizations. In this study, single neurons in the rat inferior colliculus (IC) were tested for sensitivity to sound duration. About one-half (54%) of the units sampled showed some form of duration selectivity. The majority of these (76%) were long-pass neurons that responded to sounds exceeding some duration threshold (range: 5-60 ms). Band-pass neurons, which only responded to a restricted range of durations, made up 13% of duration-sensitive neurons (best durations: 15-120 ms). Other units displayed short-pass (2%) or mixed (9%) response patterns. The majority of duration-sensitive neurons were localized outside the central nucleus of the IC, especially in the dorsal cortex, where more than one-half of the neurons sampled had long-pass selectivity for duration. Band-pass duration tuned neurons were only found outside the central nucleus. Characteristics of duration-sensitive neurons in the rat support the idea that this filtering arises through an interaction of excitatory and inhibitory inputs that converge in the IC. Band-pass neurons typically responded at sound offset, suggesting that their tuning is created through the same mechanisms that have been described in echolocating bats. The finding that the first-spike latencies of all long-pass neurons were longer than the shortest duration to which they responded supports the idea that they receive transient inhibition before, or simultaneously with, a sustained excitatory input. The ranges of selectivity in rat IC neurons are within the range of durations of rat vocalizations. These data suggest that a population of neurons in the rat IC have evolved to transmit information about behaviorally relevant sound durations using mechanisms that are common to all mammals, with an emphasis on long-pass tuning characteristics.

Immunodeficient mice as hosts for hemoparasitic infections

Thiruchandurai Rajan, Julie Moore and Leonard Shultz here review the evolution of technology in murine xeno-lymphohemopoietic chimeras, produced by engraftment with xenogeneic (fetal or adult) progenitor cells or mature lymphohemopoietic tissues into immunodeficient mice, and their use as hosts for hemoprotozoan parasites. Particular attention is paid to the development of chimeras that house xenogeneic peripheral red blood cells (xeno-RBC). These chimeras are potentially invaluable models for hemoprotozoan parasites, such as Babesia and Plasmodium. There are, however, daunting limitations that have to be overcome before these models can become universally acceptable systems for the study of these parasitic agents.

Comparative flow cytometric analysis of term placental intervillous and peripheral blood from immediate postpartum women in Western kenya

Understanding maternal immune responses in the placenta is critical for management of pregnancy failures and haematogenous infections during pregnancy. However, it is unknown whether maternal placental intervillous blood (IVB) mononuclear cell populations are distinct from those found in maternal peripheral blood (PB). In this study, cell populations in the IVB and PB from immediate postpartum women were compared by flow cytometry. While levels of B and CD4+ and CD8+ T lymphocytes were similar, IVB contained significantly higher levels of monocytes (10.9+/-5.9 versus 5.5+/-2.5 per cent, respectively) and natural killer cells (14.3+/-9.6 versus 5.9+/-3.2 per cent, respectively) than the PB. Expression of the early activation marker CD69 was increased on T cells in the IVB, whereas levels of HLA-DR, a late activation marker, were similar between IVB and PB. These results suggest that maternal cells that circulate through the intervillous compartment may be subject to local influences that affect their distribution, phenotype and function. Further comparative study of these blood compartments will be necessary to elucidate the mechanisms by which the local placental milieu influences the IVB.

LAF1, a MYB transcription activator for phytochrome A signaling

The photoreceptor phytochrome (phy) A has a well-defined role in regulating gene expression in response to specific light signals. Here, we describe a new Arabidopsis mutant, laf1 (long after far-red light 1) that has an elongated hypocotyl specifically under far-red light. Gene expression studies showed that laf1 has reduced responsiveness to continuous far-red light but retains wild-type responses to other light wavelengths. As far-red light is only perceived by phyA, our results suggest that LAF1 is specifically involved in phyA signal transduction. Further analyses revealed that laf1 is affected in a subset of phyA-dependent responses and the phenotype is more severe at low far-red fluence rates. LAF1 encodes a nuclear protein with strong homology with the R2R3-MYB family of DNA-binding proteins. Experiments using yeast cells identified a transactivation domain in the C-terminal portion of the protein. LAF1 is constitutively targeted to the nucleus by signals in its N-terminal portion, and the full-length protein accumulates in distinct nuclear speckles. This accumulation in speckles is abolished by a point mutation in a lysine residue (K258R), which might serve as a modification site by a small ubiquitin-like protein (SUMO).

CTCF-binding sites flank CTG/CAG repeats and form a methylation-sensitive insulator at the DM1 locus

An expansion of a CTG repeat at the DM1 locus causes myotonic dystrophy (DM) by altering the expression of the two adjacent genes, DMPK and SIX5, and through a toxic effect of the repeat-containing RNA. Here we identify two CTCF-binding sites that flank the CTG repeat and form an insulator element between DMPK and SIX5. Methylation of these sites prevents binding of CTCF, indicating that the DM1 locus methylation in congenital DM would disrupt insulator function. Furthermore, CTCF-binding sites are associated with CTG/CAG repeats at several other loci. We suggest a general role for CTG/CAG repeats as components of insulator elements at multiple sites in the human genome.

Improved functional outcome and more rapid return to normal activity following laparoscopic hernia repair

BACKGROUND

The laparoscopic repair of inguinal hernias remains a controversial subject. Advantages in terms of reduced postoperative pain and improved functional status have been demonstrated in some studies and refuted in others. We performed a prospective study of a group of young healthy patients to measure pain levels and time to return to normal activity following totally extraperitoneal laparoscopic (TEP) hernia repair and compared these outcomes to those seen following conventional anterior repair.

METHODS

A total of 151 patients were entered into a prospective nonrandomized study. Forty-eight patients underwent anterior repair; 103 underwent TEP repair. Patients were followed at 2 and 6 weeks to assess their level of function on a five-point scale. Their use of pain medication was also assessed, and total days away from work and days until return to full activity were documented.

RESULTS

The open group returned to work at 11.5 days and to full activity at 26.7 days. The TEP group returned to work at 6.4 days and to full activity at 14.2 days (p < 0.001 for both data). There was no statistically significant difference in the use of pain medication. The TEP group reported better functional status at 2 weeks than the open group. At 6 weeks, this difference was no longer statistically significant.

CONCLUSION

As compared to conventional open repair, TEP hernia repair offers advantages in postoperative function and an earlier return to full activity.

Flooding of Ganymede's bright terrains by low-viscosity water-ice lavas

Large regions of the jovian moon Ganymede have been resurfaced, but the means has been unclear. Suggestions have ranged from volcanic eruptions of liquid water or solid ice to tectonic deformation, but definitive high-resolution morphological evidence has been lacking. Here we report digital elevation models of parts of the surface of Ganymede, derived from stereo pairs combining data from the Voyager and Galileo spacecraft, which reveal bright, smooth terrains that lie at roughly constant elevations 100 to 1,000 metres below the surrounding rougher terrains. These topographic data, together with new images that show fine-scale embayment and burial of older features, indicate that the smooth terrains were formed by flooding of shallow structural troughs by low-viscosity water-ice lavas. The oldest and most deformed areas (the 'reticulate' terrains) in general have the highest relative elevations, whereas units of the most common resurfaced type--the grooved terrain--lie at elevations between those of the smooth and reticulate terrains. Bright terrain, which accounts for some two-thirds of the surface, probably results from a continuum of processes, including crustal rifting, shallow flooding and groove formation. Volcanism plays an integral role in these processes, and is consistent with partial melting of Ganymede's interior.

Angiotensin II increases neuronal delayed rectifier K(+) current: role of 12-lipoxygenase metabolites of arachidonic acid

Angiotensin II (Ang II) elicits an Ang II type 2 (AT(2)) receptor-mediated increase in voltage-dependent delayed rectifier K(+) current (I(KV)) in neurons cultured from newborn rat hypothalamus and brain stem. In previous studies, we have determined that this effect of Ang II is mediated via a Gi protein, activation of phospholipase A(2) (PLA(2)), and generation of arachidonic acid (AA). AA is rapidly metabolized within cells via lipoxygenases (LO), cyclooxygenase (COX) or p450 monooxygenase enzymes, and the metabolic products are known regulators of K(+) currents and channels. Thus in the present study, we have investigated whether the AT(2) receptor-mediated effects of Ang II on neuronal I(KV) require AA metabolism and if so, which metabolic pathways are involved. The data presented here indicate that the stimulatory actions of Ang II and AA on neuronal I(KV) are attenuated by selective blockade of 12-LO enzymes. However, the effects of Ang II are not altered by blockade of 5-LO or p450 monooxygenase enzymes. Furthermore, the actions of Ang II are mimicked by a 12-LO metabolite of AA, but 5-LO metabolites such as leukotriene B(4) and C(4) do not alter neuronal I(KV). These data indicate that the AT(2) receptor-mediated stimulation of neuronal I(KV) is partially mediated through 12-LO metabolites of AA.

Immunity to placental malaria. II. Placental antigen-specific cytokine responses are impaired in human immunodeficiency virus-infected women

An association was demonstrated recently between elevated in vitro production of interferon (IFN)-gamma by intervillous blood mononuclear cells (IVBMCs) and protection against placental malaria (PM). Because human immunodeficiency virus (HIV)-infected pregnant women have increased susceptibility to PM, loss of the IFN-gamma response in these women may impair their ability to control PM. Measurement of cytokines in culture supernatants by ELISA revealed that IFN-gamma responses by HIV-positive IVBMCs were impaired, especially after malarial antigen stimulation. Interleukin (IL)-4 and IL-10 responses also were reduced in HIV-positive persons, the latter more so in HIV-positive, PM-positive persons. In contrast, tumor necrosis factor-alpha production generally was enhanced in PM-positive and HIV-positive persons. Overall, cytokine production was reduced in HIV-positive persons with CD4 T cell counts <500/microL, particularly in response to malarial antigen. Thus, HIV-mediated cytokine dysregulation and impairment of the protective IFN-gamma response may contribute to the increased susceptibility of HIV-positive pregnant women to malaria.

A Severe Outbreak of Tobacco mosaic virus in Georgia's Flue-Cured Tobacco

During the 2000 growing season, tobacco plants showing blotching of the leaves with light and dark green areas suggestive of Tobacco mosaic virus (TMV) infection were observed in several counties in Georgia. Symptomatic plants appeared in the field within 4 weeks after transplanting. The incidence in individual fields was as high as 100%. A survey was conducted in several tobacco-growing counties, and the presence of TMV was verified by enzyme-linked immunosorbent assay (ELISA). Symptomatic plants were collected from the following 20 counties: Appling, Bacon, Berrien, Coffee, Colquitt, Cook, Echols, Evans, Grady, Irwin, Jeff Davis, Lanier, Lowndes, Montgomery, Pierce, Tattnall, Tift, Toombs, Ware, and Wayne. Of the 79 samples tested by ELISA, TMV was found to be present in 76 samples. This high degree of incidence of TMV in Georgia's tobacco has not been observed in the past. Although the specific reasons are not clear, all severe cases of TMV were observed in two varieties, NC71 and NC72, or plants of other varieties out of beds or plant houses that held these two varieties and were clipped with the same mower. While TMV and Potato virus Y (PVY) were found most prevalent in Georgia's flue-cured tobacco in 1999 (2), none of the plants tested were positive for PVY in 2000. Cucumber mosaic virus was reported to be more common in Florida during the last 3 years (1). The severe outbreak of TMV highlights the importance of preventive measures such as observing sound sanitation practices. References: (1) T. A. Kucharek et al. Plant Dis. 82:1172, 1998; (2) H. R. Pappu et al. Plant Dis. 84:201, 2000.

NMR techniques for characterization of ligand binding: utility for lead generation and optimization in drug discovery

Over the last ten years, nmr spectroscopy has evolved into an important discipline in drug discovery. Initially, nmr was most useful as a technique to provide structural information regarding protein drug targets and target-ligand interactions. More recently, it has been shown that nmr may be used as an alternative method for identification of small molecule ligands that bind to protein drug targets. High throughput implementation of these experiments to screen small molecule libraries may lead to identification of potent and novel lead compounds. In this review, we will use examples from our own research to illustrate how nmr experiments to characterize ligand binding may be used to both screen for novel compounds during the process of lead generation, as well as provide structural information useful for lead optimization during the latter stages of a discovery program.

Galileo at Io: results from high-resolution imaging

During late 1999/early 2000, the solid state imaging experiment on the Galileo spacecraft returned more than 100 high-resolution (5 to 500 meters per pixel) images of volcanically active Io. We observed an active lava lake, an active curtain of lava, active lava flows, calderas, mountains, plateaus, and plains. Several of the sulfur dioxide-rich plumes are erupting from distal flows, rather than from the source of silicate lava (caldera or fissure, often with red pyroclastic deposits). Most of the active flows in equatorial regions are being emplaced slowly beneath insulated crust, but rapidly emplaced channelized flows are also found at all latitudes. There is no evidence for high-viscosity lava, but some bright flows may consist of sulfur rather than mafic silicates. The mountains, plateaus, and calderas are strongly influenced by tectonics and gravitational collapse. Sapping channels and scarps suggest that many portions of the upper approximately 1 kilometer are rich in volatiles.

Hydraulic high-pressure nebulization of solutions and dispersions for respiratory drug delivery

The purpose of this investigation was to assess hydraulic high-pressure nebulization as a means for respiratory drug delivery. A hydraulic high-pressure nebulizer was designed and constructed. In a design study, the output efficiency and the aerosol particle size were determined for the nebulizer as a function of nozzle diameter (5, 10, and 20 microns), gas flow rate (2 and 8 l/min), applied hydraulic pressure (2200 and 4000 psig), and distance between the nozzle orifice and impaction surface (0.25-4 cm) with an aqueous solution of fluorescein. The output efficiency was also measured with an ethanol solution and an aqueous phospholipid dispersion of liposomes. For the design study, each factor had an effect. The efficiency tended to increase with a decrease in the nozzle diameter, although the differences between the 5- and 10-micron nozzle were more sensitive to the air flow rate and nozzle-to-impaction-surface distance. Greater efficiencies were always obtained at the higher ancillary air flow rates. Operating the nebulizer at different pressures caused a change in the functional relationship between the efficiency and the nozzle-to-impaction-surface distance. For the 5-micron nozzle at high pressure, efficiency fell with increasing nozzle-to-impaction-surface distance, whereas for the data obtained with the 20-micron nozzle, the efficiency increased with nozzle-to-impaction-surface distance, with lower efficiencies obtained at the higher pressures. For the remaining observations made with the 5- and 10-micron nozzles, the efficiency as a function of nozzle-to-impaction-surface distance appeared to be variable. For the 5- and 10-micron size nozzle, there was no significant effect of the air flow rate, pressure, or nozzle-to-impaction-surface distance on the mass median aerodynamic diameter and geometric standard deviation. For the 20-micron size nozzle, the particles were not completely dried. Ethanol solutions gave somewhat higher efficiencies, whereas the phospholipid dispersion gave efficiencies comparable to the aqueous solutions nebulized under similar conditions. The efficiency of the hydraulic high-pressure nebulizer appears to be correlated with the calculated properties of the liquid jet. For respiratory drug delivery, the hydraulic high-pressure nebulizer provides reasonably high outputs of respirable particles independent of time from a single pass of liquid through the nebulizer.

Immunologic memory in the placenta: a lymphocyte recirculation hypothesis

The placenta is an immunologically unique organ where a balance between maternal immunity and fetoplacental well-being must be maintained for successful pregnancy to occur. The intervillous blood is important in this context, yet little is known about local immunologic processes, particularly how placenta-specific memory immune responses are maintained. Using malaria as an illustrative case, we describe an hypothetical model in which recirculation of memory T lymphocytes from the intervillous blood to local lymphoid tissue facilitates maintenance of local memory immunity. This explains how memory cells might be retained when the placenta is expelled at parturition and thus remain available for rapid recall from the local lymphoid tissue to the intervillous space when exposure to the same antigenic stimulus occurs in subsequent pregnancies. Study of cell-mediated immunity to infections like malaria in the intervillous blood and the use of animal models will be necessary to provide proof for this hypothesis.

Kinetics and thermodynamics of dimer formation and dissociation for a recombinant humanized monoclonal antibody to vascular endothelial growth factor

The recombinant humanized antibody (rhuMAb) VEGF has a high affinity for vascular endothelial growth factor and is currently being evaluated in clinical trials as a cancer therapeutic. Under acidic pH and low ionic strength conditions, the antibody was predominantly present as monomer. Under physiological conditions, the appearance of significant amounts of a noncovalent, reversible dimer were observed by size-exclusion chromatography. The kinetics and thermodynamics of the reversible self-association for rhuMAb VEGF monomer were investigated as a function of pH, temperature, and ionic strength by size-exclusion chromatography using the concentration jump method. The rate constant for dimer formation ranged 23-112 M(-)(1) min(-)(1) under the conditions studied, values that are significantly lower than those reported in the literature for other proteins that self-associate. The rate constant for dissociation ranged 0.0039-0.021 min(-)(1). Gibbs' free energies, enthalpies, entropies, and activation energies were determined and revealed that dimer formation is optimal at pH 7.5-8.0, which may be reflective of charge shielding occurring near the pI of the protein. There was a negative change in entropy for dissociation (values from -18.1 to -12.8 cal/mol K). In the presence of D(2)O or 1 M NaCl, dimerization was enhanced. The results of the kinetic and thermodynamic analysis of this study indicate that rhuMAb VEGF dimerization occurs primarily through hydrophobic interactions.

The SHAPES strategy: an NMR-based approach for lead generation in drug discovery

BACKGROUND

Recently, it has been shown that nuclear magnetic resonance (NMR) may be used to identify ligands that bind to low molecular weight protein drug targets. Recognizing the utility of NMR as a very sensitive method for detecting binding, we have focused on developing alternative approaches that are applicable to larger molecular weight drug targets and do not require isotopic labeling.

RESULTS

A new method for lead generation (SHAPES) is described that uses NMR to detect binding of a limited but diverse library of small molecules to a potential drug target. The compound scaffolds are derived from shapes most commonly found in known therapeutic agents. NMR detection of low (microM-mM) affinity binding is achieved using either differential line broadening or transferred NOE (nuclear Overhauser effect) NMR techniques.

CONCLUSIONS

The SHAPES method for lead generation by NMR is useful for identifying potential lead classes of drugs early in a drug design program, and is easily integrated with other discovery tools such as virtual screening, high-throughput screening and combinatorial chemistry.

Negative transcriptional regulation mediated by thyroid hormone response element 144 requires binding of the multivalent factor CTCF to a novel target DNA sequence

DNA target sites for a "multivalent" 11-zinc-finger CCTC-binding factor (CTCF) are unusually long ( approximately 50 base pairs) and remarkably different. In conjunction with the thyroid receptor (TR), CTCF binding to the lysozyme gene transcriptional silencer mediates the thyroid hormone response element (TRE)-dependent transcriptional repression. We tested whether other TREs, which in addition to the presence of a TR binding site require neighboring sequences for transcriptional function, might also contain a previously unrecognized binding site(s) for CTCF. One such candidate DNA region, previously isolated by Bigler and Eisenman (Bigler, J., and Eisenman, R. N. (1995) EMBO J. 14, 5710-5723), is the TRE-containing genomic element 144. We have identified a new CTCF target sequence that is adjacent to the TR binding site within the 144 fragment. Comparison of CTCF recognition nucleotides in the lysozyme silencer and in the 144 sequences revealed both similarities and differences. Several C-terminal CTCF zinc fingers contribute differently to binding each of these sequences. Mutations that eliminate CTCF binding impair 144-mediated negative transcriptional regulation. Thus, the 144 element provides an additional example of a functionally significant composite "TRE plus CTCF binding site" regulatory element suggesting an important role for CTCF in cooperation with the steroid/thyroid superfamily of nuclear receptors to mediate TRE-dependent transcriptional repression.

Immunity to placental malaria. I. Elevated production of interferon-gamma by placental blood mononuclear cells is associated with protection in an area with high transmission of malaria

In areas in which malaria is holoendemic, primigravidae and secundigravidae, compared with multigravidae, are highly susceptible to placental malaria (PM). The nature of gravidity-dependent immune protection against PM was investigated by measuring in vitro production of cytokines by placental intervillous blood mononuclear cells (IVBMC). The results demonstrated that interferon (IFN)-gamma may be a critical factor in protection against PM: production of this cytokine by PM-negative multigravid IVBMC was elevated compared with PM-negative primigravid and secundigravid and PM-positive multigravid cells. Low IFN-gamma responsiveness to malarial antigen stimulation, most evident in the latter group, was balanced by increased interleukin (IL)-4 production, suggesting that counter-regulation of these two cytokines may be a crucial determinant in susceptibility to PM. A counter-regulatory relationship between IL-10 and tumor necrosis factor-alpha was also observed in response to malarial antigen stimulation. These data suggest that elevated production of IFN-gamma, as part of a carefully regulated cytokine network, is important in the control of PM.

Long-term fetal microchimerism in peripheral blood mononuclear cell subsets in healthy women and women with scleroderma

Fetal CD34(+) CD38(+) cells have recently been found to persist in maternal peripheral blood for many years after pregnancy. CD34(+) CD38(+) cells are progenitor cells that can differentiate into mature immune-competent cells. We asked whether long-term fetal microchimerism occurs in T lymphocyte, B lymphocyte, monocyte, and natural-killer cell populations of previously pregnant women. We targeted women with sons and used polymerase chain reaction for a Y-chromosome-specific sequence to test DNA extracted from peripheral blood mononuclear cells (PBMC) and from CD3, CD19, CD14, and CD56/16 sorted subsets. We also asked whether persistent microchimerism might contribute to subsequent autoimmune disease in the mother and included women with the autoimmune disease scleroderma. Scleroderma has a peak incidence in women after childbearing years and has clinical similarities to chronic graft-versus-host disease that occurs after allogeneic hematopoietic stem-cell transplantation, known to involve chimerism. Sixty-eight parous women were studied for male DNA in PBMC and 20 for PBMC subsets. Microchimerism was found in PBMC from 33% (16 of 48) of healthy women and 60% (12 of 20) women with scleroderma, P =.046. Microchimerism was found in some women in CD3, CD19, CD14, and CD56/16 subsets including up to 38 years after pregnancy. Microchimerism in PBMC subsets was not appreciably more frequent in scleroderma patients than in healthy controls. Overall, microchimerism was found in CD3, CD19, and CD14 subsets in approximately one third of women and in CD56/16 in one half of women. HLA typing of mothers and sons indicated that HLA compatibility was not a requirement for persistent microchimerism in PBMC subsets. Fetal microchimerism in the face of HLA disparity implies that specific maternal immunoregulatory pathways exist that permit persistence but prevent effector function of these cells in normal women. Although microchimerism in PBMC was more frequent in women with scleroderma than healthy controls additional studies will be necessary to determine whether microchimerism plays a role in the pathogenesis of this or other autoimmune diseases.

Comparison of three solutions of ropivacaine/fentanyl for postoperative patient-controlled epidural analgesia

BACKGROUND

Ropivacaine, 0.2%, is a new local anesthetic approved for epidural analgesia. The addition of 4 microg/ml fentanyl improves analgesia from epidural ropivacaine. Use of a lower concentration of ropivacaine-fentanyl may further improve analgesia or decrease side effects.

METHODS

Thirty patients undergoing lower abdominal surgery were randomized in a double-blinded manner to receive one of three solutions: 0.2% ropivacaine-4 microg fentanyl 0.1% ropivacaine-2 microg fentanyl, or 0.05% ropivacaine-1 microg fentanyl for patient-controlled epidural analgesia after standardized combined epidural and general anesthesia. Patient-controlled epidural analgesia settings and adjustments for the three solutions were standardized to deliver equivalent drug doses. Pain scores (rest, cough, and ambulation), side effects (nausea, pruritus, sedation, motor block, hypotension, and orthostasis), and patient-controlled epidural analgesia consumption were measured for 48 h.

RESULTS

All three solutions produced equivalent analgesia. Motor block was significantly more common (30 vs. 0%) and more intense with the 0.2% ropivacaine-4 microg fentanyl solution. Other side effects were equivalent between solutions and mild in severity. A significantly smaller volume of 0.2% ropivacaine-4 microg fentanyl solution was used, whereas the 0.1% ropivacaine-2 microg fentanyl group used a significantly greater amount of ropivacaine and fentanyl.

CONCLUSIONS

Lesser concentrations of ropivacaine and fentanyl provide comparable analgesia with less motor block despite the use of similar amounts of ropivacaine and fentanyl. This finding suggests that concentration of local anesthetic solution at low doses is a primary determinant of motor block with patient-controlled epidural analgesia after lower abdominal surgery.

Dose-response effects of spinal neostigmine added to bupivacaine spinal anesthesia in volunteers

BACKGROUND

Intrathecal adjuncts often are used to enhance small-dose spinal bupivacaine for ambulatory anesthesia. Neostigmine is a novel spinal analgesic that could be a useful adjunct, but no data exist to assess the effects of neostigmine on small-dose bupivacaine spinal anesthesia.

METHODS

Eighteen volunteers received two bupivacaine spinal anesthetics (7.5 mg) in a randomized, double-blinded, crossover design. Dextrose, 5% (1 ml), was added to one spinal infusion and 6.25, 12.5, or 50 microg neostigmine in dextrose, 5%, was added to the other spinal. Sensory block was assessed with pinprick; by the duration of tolerance to electric stimulation equivalent to surgical incision at the pubis, knee, and ankle; and by the duration of tolerance to thigh tourniquet. Motor block at the quadriceps was assessed with surface electromyography. Side effects (nausea, vomiting, pruritus, and sedation) were noted. Hemodynamic and respiratory parameters were recorded every 5 min. Dose-response relations were assessed with analysis of variance, paired t tests, or Spearman rank correlation.

RESULTS

The addition of 50 microg neostigmine significantly increased the duration of sensory and motor block and the time until discharge criteria were achieved. The addition of neostigmine produced dose-dependent nausea (33-67%) and vomiting (17-50%). Neostigmine at these doses had no effect on hemodynamic or respiratory parameters.

CONCLUSIONS

The addition of 50 microg neostigmine prolonged the duration of sensory and motor block. However, high incidences of side effects and delayed recovery from anesthesia with the addition of 6.25 to 50 microg neostigmine may limit the clinical use of these doses for outpatient spinal anesthesia.

Angiotensin II type 1 receptor-mediated inhibition of K+ channel subunit kv2.2 in brain stem and hypothalamic neurons

Angiotensin II (Ang II) has powerful modulatory actions on cardiovascular function that are mediated by specific receptors located on neurons within the hypothalamus and brain stem. Incubation of neuronal cocultures of rat hypothalamus and brain stem with Ang II elicits an Ang II type 1 (AT1) receptor-mediated inhibition of total outward K+ current that contributes to an increase in neuronal firing rate. However, the exact K+ conductance(s) that is inhibited by Ang II are not established. Pharmacological manipulation of total neuronal outward K+ current revealed a component of K+ current sensitive to quinine, tetraethylammonium, and 4-aminopyridine, with IC50 values of 21.7 micromol/L, 1.49 mmol/L, and 890 micromol/L, respectively, and insensitive to alpha-dendrotoxin (100 to 500 nmol/L), charybdotoxin (100 to 500 nmol/L), and mast cell degranulating peptide (1 micromol/L). Collectively, these data suggest the presence of Kv2.2 and Kv3.1b. Biophysical examination of the quinine-sensitive neuronal K+ current demonstrated a macroscopic conductance with similar biophysical properties to those of Kv2.2 and Kv3.1b. Ang II (100 nmol/L), in the presence of the AT2 receptor blocker PD123,319, elicited an inhibition of neuronal K+ current that was abolished by quinine (50 micromol/L). Reverse transcriptase-polymerase chain reaction analysis confirmed the presence of Kv2.2 and Kv3.1b mRNA in these neurons. However, Western blot analyses demonstrated that only Kv2.2 protein was present. Coexpression of Kv2.2 and the AT1 receptor in Xenopus oocytes demonstrated an Ang II-induced inhibition of Kv2.2 current. Therefore, these data suggest that inhibition of Kv2.2 contributes to the AT1 receptor-mediated reduction of neuronal K+ current and subsequently to the modulation of cardiovascular function.

Chronic prenatal cocaine treatment down-regulates mu-opioid receptor mRNA expression in the brain of fetal Rhesus Macaque

Ribonuclease protection assays (RPA) were performed to quantify mu-opioid receptor mRNA expression in specific brain regions of day 70 Rhesus Macaque fetuses that were exposed to cocaine (3 mg/kg) or saline from days 22-70 of gestation. The content of mu-receptor mRNA was high in the diencephalon and moderate in the mesencephalon. In contrast, mu-receptor mRNA was lightly expressed in areas such as the frontal cortex, striatum and the temporal lobe. The content of mu-opioid receptor mRNA was significantly higher in the diencephalon than in other brain regions (P < 0.001; n = 4). Cocaine exposure significantly decreased the expression of mu-receptor mRNA in the fetal diencephalon (P < 0.05; n = 4 in each group). Our data would indicate that prolonged gestational cocaine exposure causes mu-opioid receptor mRNA down-regulation in specific brain regions of the fetus.

NMR screening in drug discovery

NMR methods in drug discovery have traditionally been used to obtain structural information for drug targets or target-ligand complexes. Recently, it has been shown that NMR may be used as an alternative approach for identification of ligands that bind to protein drug targets, shifting the emphasis of many NMR laboratories towards screening and design of potential drug molecules, rather than structural characterization.

Evaluation: methods and strategy for evaluation--Oregon

The authors describe the development of comprehensive mechanisms for the evaluation of Oregon's newly funded tobacco control efforts through building on established surveillance systems.

Designing an effective statewide tobacco control program--Oregon

In this report, the author documents the first stages in the development and implementation of Oregon's tobacco control program. She briefly reviews the history of tobacco control coalitions in Oregon prior to the passage of Ballot Measure 44 and attributes much of the success to earlier coalition-building efforts.