A pulsar in a binary with a compact object in the mass gap between neutron stars and black holes.

Some compact objects observed in gravitational wave events have masses in the gap between known neutron stars (NSs) and black holes (BHs). The nature of these mass gap objects is unknown, as is the formation of their host binary systems. We report pulsar timing observations made with the Karoo Array Telescope (MeerKAT) of PSR J0514-4002E, an eccentric binary millisecond pulsar in the globular cluster NGC 1851. We found a total binary mass of 3.887 ± 0.004 solar masses (M⊙), and multiwavelength observations show that the pulsar's binary companion is also a compact object. The companion's mass (2.09 to 2.71 M⊙, 95% confidence interval) is in the mass gap, indicating either a very massive NS or a low-mass BH. We propose that the companion formed in a merger between two earlier NSs.

Review of the role of the endogenous opioid and melanocortin systems in the restless legs syndrome.

Restless legs syndrome (RLS) is responsive to opioid, dopaminergic and iron-based treatments. Receptor blocker studies in RLS patients suggest that the therapeutic efficacy of opioids is specific to the opioid receptor and mediated indirectly through the dopaminergic system. An RLS autopsy study reveals decreases in endogenous opioids, ß-endorphin and perhaps Met-enkephalin in the thalamus of RLS patients. A total opioid receptor knock-out (mu, delta and kappa) and a mu-opioid receptor knock-out mouse model of RLS show circadian motor changes akin to RLS and, although both models show sensory changes, the mu-opioid receptor knock mouse shows circadian sensory changes closest to those seen in idiopathic RLS. Both models show changes in striatal dopamine, anaemia and low serum iron. However, only in the total receptor knock-out mouse do we see the decreases in serum ferritin that are normally found in RLS. There are also decreases in serum iron when wild-type mice are administered a mu-opioid receptor blocker. In addition, the mu-opioid receptor knock-out mouse also shows increases in striatal zinc paralleling similar changes in RLS. Adrenocorticotropic hormone and α-melanocyte stimulating hormone are derived from pro-opiomelanocortin as is ß-endorphin. However, they cause RLS-like symptoms and periodic limb movements when injected intraventricularly into rats. These results collectively suggest that an endogenous opioid deficiency is pathogenetic to RLS and that an altered melanocortin system may be causal to RLS as well.

Exploring the role of the endogenous opiate system in the pathogenesis of anemia in an opiate receptor knock-out model of Restless Legs Syndrome.

Restless Legs Syndrome (RLS) is characterized by bothersome leg discomfort accompanied by an urge to move to obtain relief and symptoms are worse at night and on lying down. There is at least partial and temporary relief with activity. It is also an opioid responsive disorder, often accompanied by iron deficiency with or without anemia, and inflammation may be a precipitating factor in some cases. We created two in-vivo opiate receptor knock out mouse models of RLS - a triple opiate receptor knock-out mouse and a mu opiate receptor knock-out mouse. Both sets of animals were restless during the sleep period as is also true of RLS. Both of our knockout models showed statistically significantly decreased Hemoglobin and Hematocrit indicating anemia and both models showed statistically significant decreases in serum iron suggestive of either iron deficiency anemia or inflammatory anemia. The rest of the hematologic studies were not consistent enough to determine which of these two types of anemia was present in either model. An additional experiment in normal wild type mice showed a statistically significant decrease in serum iron when an opiate receptor blocker was used. To our knowledge this is the first demonstration that deficiency of endogenous opioids might play a role in the production of anemia. Our hypothesis is that an intact endogenous opiate system is necessary for red cell homeostasis. The presence of opioid receptors both on red blood cells and on various immunologically based white blood cells suggest mechanisms by which deficiency in the endogenous opiate system could cause anemia of either the iron deficiency or inflammatory types. The administration of opioid agonists or antagonists to iron deficient cultures of red blood cell precursors is a next step in determining the role of the endogenous opiate system in the maintenance of red cell homeostasis and in the possible prevention of iron deficiency or inflammatory anemia where iron dysregulation is key.

Lithospheric conductors reveal source regions of convergent margin mineral systems.

The clean energy transition will require a vast increase in metal supply, yet new mineral deposit discoveries are declining, due in part to challenges associated with exploring under sedimentary and volcanic cover. Recently, several case studies have demonstrated links between lithospheric electrical conductors imaged using magnetotelluric (MT) data and mineral deposits, notably Iron Oxide Copper Gold (IOCG). Adoption of MT methods for exploration is therefore growing but the general applicability and relationship with many other deposit types remains untested. Here, we compile a global inventory of MT resistivity models from Australia, North and South America, and China and undertake the first quantitative assessment of the spatial association between conductors and three mineral deposit types commonly formed in convergent margin settings. We find that deposits formed early in an orogenic cycle such as volcanic hosted massive sulfide (VHMS) and copper porphyry deposits show weak to moderate correlations with conductors in the upper mantle. In contrast, deposits formed later in an orogenic cycle, such as orogenic gold, show strong correlations with mid-crustal conductors. These variations in resistivity response likely reflect mineralogical differences in the metal source regions of these mineral systems and suggest a metamorphic-fluid source for orogenic gold is significant. Our results indicate the resistivity structure of mineralized convergent margins strongly reflects late-stage processes and can be preserved for hundreds of millions of years. Discerning use of MT is therefore a powerful tool for mineral exploration.

Oxygen isotopes trace the origins of Earth's earliest continental crust.

Much of the current volume of Earth's continental crust had formed by the end of the Archaean eon1 (2.5 billion years ago), through melting of hydrated basaltic rocks at depths of approximately 25-50 kilometres, forming sodic granites of the tonalite-trondhjemite-granodiorite (TTG) suite2-6. However, the geodynamic setting and processes involved are debated, with fundamental questions arising, such as how and from where the required water was added to deep-crustal TTG source regions7,8. In addition, there have been no reports of voluminous, homogeneous, basaltic sequences in preserved Archaean crust that are enriched enough in incompatible trace elements to be viable TTG sources5,9. Here we use variations in the oxygen isotope composition of zircon, coupled with whole-rock geochemistry, to identify two distinct groups of TTG. Strongly sodic TTGs represent the most-primitive magmas and contain zircon with oxygen isotope compositions that reflect source rocks that had been hydrated by primordial mantle-derived water. These primitive TTGs do not require a source highly enriched in incompatible trace elements, as 'average' TTG does. By contrast, less sodic 'evolved' TTGs require a source that is enriched in both water derived from the hydrosphere and also incompatible trace elements, which are linked to the introduction of hydrated magmas (sanukitoids) formed by melting of metasomatized mantle lithosphere. By concentrating on data from the Palaeoarchaean crust of the Pilbara Craton, we can discount a subduction setting6,10-13, and instead propose that hydrated and enriched near-surface basaltic rocks were introduced into the mantle through density-driven convective overturn of the crust. These results remove many of the paradoxical impediments to understanding early continental crust formation. Our work suggests that sufficient primordial water was already present in Earth's early mafic crust to produce the primitive nuclei of the continents, with additional hydrated sources created through dynamic processes that are unique to the early Earth.

Familial and Genetic Influences on the Common Pediatric Primary Pain Disorders: A Twin Family Study.

The primary pain disorders of childhood are highly prevalent but have infrequently been studied collectively. Genetic influences have been suggested to be causally implicated. Surveys were sent to 3909 Australian twin families, assessing the lifetime prevalence of growing pains, migraine, headache, recurrent abdominal pain, low back pain, and persistent pain (not otherwise specified) in pediatric twins and their immediate family members. Comparisons between monozygous (MZ) and dizygous (DZ) twin pair correlations, concordances and odds ratios were performed to assess the contribution of additive genetic influences. Random-effects logistic regression modelling was used to evaluate relationships between twin individuals and their co-twins, mothers, fathers and oldest siblings with the subject conditions. Twin analyses of responses from 1016 families revealed significant influence of additive genetic effects on the presence of growing pains, migraine, and recurrent abdominal pain. The analyses for headache, low back pain, and persistent pain overall did not conclusively demonstrate that genetic influences were implicated more than shared environmental factors. Regression analyses demonstrated varying levels of significance in relationships between family members and twin individuals for the tested conditions, with strongest support for genetic influences in growing pains and migraine. These data, together with previously published association analyses, suggest common causal influences including genes.

Somatosensory Testing in Pediatric Patients with Chronic Pain: An Exploration of Clinical Utility.

We aimed to evaluate the utility of clinical somatosensory testing (SST), an office adaptation of laboratory quantitative sensory testing, in a biopsychosocial assessment of a pediatric chronic somatic pain sample (N = 98, 65 females, 7-18 years). Stimulus-response tests were applied at pain regions and intra-subject control sites to cutaneous stimuli (simple and dynamic touch, punctate pressure and cool) and deep pressure stimuli (using a handheld pressure algometer, and, in a subset, manually inflated cuff). Validated psychological, pain-related and functional measures were administered. Cutaneous allodynia, usually regional, was elicited by at least one stimulus in 81% of cases, most frequently by punctate pressure. Central sensitization, using a composite measure of deep pressure pain threshold and temporal summation of pain, was implied in the majority (59.2%) and associated with worse sleep impairment and psychological functioning. In regression analyses, depressive symptoms were the only significant predictor of pain intensity. Functional interference was statistically predicted by deep pressure pain threshold and depressive symptoms. Manually inflated cuff algometry had comparable sensitivity to handheld pressure algometry for deep pressure pain threshold but not temporal summation of pain. SST complemented standard biopsychosocial assessment of pediatric chronic pain; use of SST may facilitate the understanding of disordered neurobiology.

Contrasting painless and painful phenotypes of pediatric restless legs syndrome: a twin family study.

OBJECTIVE: This study was designed to investigate painless and painful subsets of pediatric restless legs syndrome (RLS) for genetic influence and for associations with iron deficiency and common pediatric pain disorders. METHODS: In a twin family study, twins (3-18 years) and their oldest siblings, mothers and fathers completed questionnaires, assessing lifetime prevalence of RLS using current criteria, as well as history of iron deficiency and pediatric pain disorders. Subsets were categorized as RLS-Painless or RLS-Painful. Within twin pair analyses were conducted to assess familial and potential genetic effects for the defined subsets. Penalized maximum likelihood logistic regression was used to test familial associations. Random-effects logistic regression modeling was used in the total pediatric sample to investigate univariate and multivariate associations with the subsets. RESULTS: Data were available for 2033 twin individuals (1007 monozygous (MZ), 1026 dizygous (DZ); 51.7% female), 688 siblings, 1013 mothers and 921 fathers. Odds ratios, correlations and casewise concordance were significantly higher in MZ than in DZ twins only for RLS-Painful. RLS-Painless, though familial (co-twin and mother), was not genetically influenced, but was independently associated with female sex (OR 0.52, p = 0.003), iron deficiency (OR 4.20, p < 0.001) and with persistent pain disorders (OR 2.28, p = 0.02). RLS-Painful was familial and was probably genetically influenced; was independently associated with non-migraine headaches (OR 2.70, p = 0.02) and recurrent abdominal pain (OR 2.07, p = 0.04). CONCLUSIONS: Pediatric RLS was heterogeneous and was categorized into contrasting painless and painful phenotypes. RLS-Painless was associated with iron deficiency while RLS-Painful accounted for the heritability of RLS.

No evidence for high-pressure melting of Earth's crust in the Archean.

Much of the present-day volume of Earth's continental crust had formed by the end of the Archean Eon, 2.5 billion years ago, through the conversion of basaltic (mafic) crust into sodic granite of tonalite, trondhjemite and granodiorite (TTG) composition. Distinctive chemical signatures in a small proportion of these rocks, the so-called high-pressure TTG, are interpreted to indicate partial melting of hydrated crust at pressures above 1.5 GPa (>50 km depth), pressures typically not reached in post-Archean continental crust. These interpretations significantly influence views on early crustal evolution and the onset of plate tectonics. Here we show that high-pressure TTG did not form through melting of crust, but through fractionation of melts derived from metasomatically enriched lithospheric mantle. Although the remaining, and dominant, group of Archean TTG did form through melting of hydrated mafic crust, there is no evidence that this occurred at depths significantly greater than the ~40 km average thickness of modern continental crust.

Chronic Widespread Pain and Fibromyalgia Syndrome: Life-Course Risk Markers in Young People.

Although the life-course concept of risk markers as potential etiological influences is well established in epidemiology, it has not featured in academic publications or clinical practice in the context of chronic widespread pain (CWP) and fibromyalgia syndrome (FMS). Studies of risk markers are required considerations for evaluation of patients and for research because there is no single cause, pathological feature, laboratory finding, or biomarker for CWP or FMS. The early-life risk markers identified by extensive literature review with best evidence for potential causal influence on the development and progression of CWP and FMS include genetic factors, premature birth, female sex, early childhood adversity, cognitive and psychosocial influences, impaired sleep, primary pain disorders, multiregional pain, physical trauma, infectious illness, obesity and inactivity, hypermobility of joints, iron deficiency, and small-fiber polyneuropathy. The case history illustrates the potential etiological influence of multiple risk markers offset by personal resilience.

Are serum ferritin and transferrin saturation risk markers for restless legs syndrome in young adults? Longitudinal and cross-sectional data from the Western Australian Pregnancy Cohort (Raine) Study.

Restless legs syndrome has been associated with serum iron deficiency in clinical studies. However, studies investigating this relationship have had inconsistent results and there are no studies in young adults. Therefore, we investigated the relationship between serum measures of iron stores and restless legs syndrome in young adults in the community. Participants in the Western Australian Pregnancy Cohort (Raine) Study answered questions on restless legs syndrome (n = 1,100, 54% female) at age 22 years, and provided serum measures of iron stores (ferritin and transferrin saturation) at ages 17 and 22 years. Restless legs syndrome was diagnosed when four International RLS Study Group criteria were met (urge to move, dysaesthesia, relief by movement, worsening during evening/night) and these symptoms occurred ≥5 times per month. Logistic regression was used to assess associations between serum iron stores and restless legs syndrome, adjusting for potential confounders. The prevalence of restless legs syndrome at age 22 years was 3.0% (n = 33, 70% female). Among those who provided restless legs syndrome and iron data at age 22 years (n = 865), the median (interquartile range) ferritin was not different between the restless legs syndrome (55 [29.5-103.5] µg L-1 ) and the non-restless legs syndrome group (65.0 [35.0-103.3] µg L-1 , p = 0.2), nor were there differences in iron deficiency prevalence (p = 0.36). There was no association between restless legs syndrome (22 years) and iron stores (17, 22 years) before or after adjustment for potential confounders. There was no association between restless legs syndrome at 22 years and iron stores at 17 or 22 years in this cohort. Serum iron stores may not be a useful indicator of restless legs syndrome risk in young adults in the community.

Common Pediatric Pain Disorders and Their Clinical Associations.

BACKGROUND: Common childhood pain conditions (nonmigraine headache, migraine, recurrent abdominal pain, growing pains, low back pain) and persistent pains are often associated with each other and have significant implications in later life. Emerging evidence suggests additional associations between these pain conditions and restless legs syndrome, iron deficiency, anxiety, and depression. The aim of this cross-sectional study in pediatric twin individuals and their siblings was to investigate these associations. MATERIALS AND METHODS: Surveys were sent to Australian twin families via the Australian Twin Registry, yielding responses from 2530 pediatric individuals. The lifetime prevalence of the common pain disorders of childhood and of other persistent pains, restless legs syndrome and iron deficiency, and anxious/depressed score were determined by questionnaires. Random-effects logistic regression modeling was used to investigate univariate and multivariate associations between conditions. RESULTS: Univariate associations were found between each of the pain conditions and persistent pain, and between the pain conditions with restless legs syndrome, iron deficiency, and anxious/depressed score. Derivative multivariate analyses retained statistically significant associations between each of the pain disorders included in the respective models (odds ratios [OR], 1.69-7.04) with the exception of growing pains with persistent pain. Of the nonpain conditions included in the multivariate analyses, restless legs syndrome remained associated with growing pains (OR, 8.50) and persistent pain (OR, 2.01). Iron deficiency remained significantly associated with migraine (OR, 2.38), persistent pain (OR, 3.70), and restless legs syndrome (OR, 5.10). CONCLUSIONS: In light of their extensive associations, the common pain conditions, persistent pain, restless legs syndrome, iron deficiency, anxiety and depression, are likely to involve common etiological mechanisms that warrant further investigation.

Somatosensory Test Responses and Physical and Psychological Functioning of Children and Adolescents with Chronic Non-neuropathic Pain: An Exploratory Study.

OBJECTIVES: This study was designed to establish preliminary feasibility testing of a set of inherently benign somatosensory stimulus-response tests (to cutaneous and deep stimuli) for bedside or office evaluation of pain disorders in children and adolescents. Associations between, and the relative influence of, cutaneous somatosensory testing (SST) responses, deep SST responses, and psychological factors (depression, pain-related catastrophizing) on pain outcomes (worst pain intensity, pain-related disability) were considered. METHODS: Sixty participants (6 to 18 y) were recruited from the pediatric chronic pain clinic. SST responses were assessed at the pain site (PS) and control sites to diverse stimuli (static/dynamic touch, punctate pressure, vibration, cool, deep pressure) using Colored Analogue Scales (CAS) with modified anchors. Validated measures of depression, pain-related catastrophizing, and pain-related functional interference were administered. RESULTS: Responses at the PS were more frequently hypersensitive than hyposensitive for all SST measures except vibration. Deep pressure responses were the only statistically significant predictor of worst pain intensity. Depression and pain-related catastrophizing accounted for a statistically significant amount of variance of pain-related disability, over and above that which was accounted for by SST responses. DISCUSSION: Preliminary feasibility of a set of somatosensory stimulus-response tests for bedside or office evaluation of pain disorders in children and adolescents was established. Deep pressure responses contributed unique information in predicting worst pain intensity but not functional interference. Although cutaneous SST responses at the PSs were frequently abnormal, cutaneous SST responses were not confirmed in this study to have clinical utility, but rather might be centrally mediated epiphenomena.

Musculoskeletal pain is associated with restless legs syndrome in young adults.

BACKGROUND: In recent years, there is considerable evidence of a relationship between the sensorimotor disorder restless legs syndrome (RLS) and pain disorders, including migraine and fibromyalgia. An association between multi-site pain and RLS has been reported in adult women. In the current study, we explored the association between musculoskeletal (MSK) pain and RLS in a large cohort of young adults. METHODS: Twenty two year olds (n = 1072), followed since birth of part of the Western Australian Pregnancy Cohort (Raine) Study, provided data on MSK pain (duration, severity, frequency, number of pain sites). RLS was considered present when 4 diagnostic criteria recommended by the International Restless Legs Syndrome Study Group were met (urge to move, dysaesthesia, relief by movement, worsening symptoms during the evening/night) and participants had these symptoms at least 5 times per month. Associations between MSK pain and RLS were analyzed by multivariable logistic regression with bias-corrected bootstrapped confidence intervals, with final models adjusted for sex, psychological distress and sleep quality. RESULTS: The prevalence of RLS was 3.0 % and MSK pain was reported by 37.4 % of the participants. In multivariable logistic regression models, strong associations were found between RLS-diagnosis and long duration (three months or more) of MSK pain (odds ratio 3.6, 95 % confidence interval 1.4-9.2) and reporting three or more pain sites (4.9, 1.6-14.6). CONCLUSIONS: Different dimensions of MSK pain were associated with RLS in young adults, suggestive of shared pathophysiological mechanisms. Overlap between these conditions requires more clinical and research attention.

In search of risk factors for chronic pain in adolescents: a case-control study of childhood and parental associations.

OBJECTIVES: This study was designed to investigate whether an individual and parental history of functional pain syndromes (FPS) is found more often in adolescents suffering from chronic pain than in their pain-free peers. METHODS: Our case-control study involved 101 adolescents aged 10-18 years. Cases were 45 patients of the Chronic Pain Clinic at Sydney Children's Hospital with diverse chronic pain disorders. Controls consisted of 56 adolescent volunteers who did not have chronic pain. Adolescents and their parents filled out questionnaires assessing demographic data as well as known and potential risk factors for chronic pain. A history of FPS was assessed by questionnaire, including restless legs syndrome (RLS). Chi-squared tests and t-tests were used to investigate univariate associations between chronic pain in adolescents and lifetime prevalence of FPS. Logistic regression was used to test multivariate associations, while controlling for possible confounders. RESULTS: Migraine, non-migraine headaches, recurrent abdominal pain (RAP), and RLS were reported significantly more frequently in cases than controls (P-values of 0.01, <0.001, 0.01, and 0.03, respectively). Parental migraine, RAP, and RLS were also significantly associated with adolescent chronic pain in the multivariate analyses. Individual history of migraine, non-migraine headaches, and RAP, along with parental history of RAP and depression significantly accounted for 36%-49% of variance in chronic pain. Other associations with chronic pain were generally in accordance with previous reports. DISCUSSION: It may be helpful when assessing a child who has chronic pain or is at risk of chronic pain, to enquire about these associations. Based on the current findings, an individual history of migraine, non-migraine headaches, and RAP, as well as parental migraine, RAP, and RLS are symptoms that are of particular relevance to assess.

Growing pains and periodic limb movements of sleep in children.

AIM: To investigate whether there was any association between growing pains (GP) and periodic limb movements of sleep (PLMS) in children referred for polysomnography (PSG), in light of the possible shared genetic determinants between GP and restless legs syndrome. METHODS: Records of all 903 children who underwent PSG at a paediatric hospital between January 2009 and May 2010 were retrospectively reviewed. Children aged 3-16 years, without neuromuscular or neurological/developmental disorders who were seen by a single sleep physician were included in the analysis. Data extracted included: current GP, PLMS index, mixed obstructive apnoea/hypopnoea index and patient demographics. GP was diagnosed in the pre-PSG consultation. RESULTS: GP was recorded in 43 of the eligible 230 children referred for PSG of whom 25.6% had a PLMS index ≥ 5/h, significantly higher than in the children without GP (10.2%) (odds ratio 3.04, χ(2) = 6.0, P = 0.014). The adjusted odds ratio for the association between GP and PLMS remained significant at 2.53 (95% CI 1.1-6.1, P < 0.05). A PLMS index ≥ 5/h was recorded in 30 of the 230 participants. GP and PLMS were also significantly multivariately associated with restlessness as the indication for PSG. CONCLUSIONS: Children with GP were three times more likely to have a PLMS index ≥ 5/h than children without GP on PSG. These results suggest that GP may be associated with PLMS, giving greater support for the hypothesis that GP might lie on the phenotypic spectrum of restless legs syndrome.

A common sleep disorder in pregnancy: restless legs syndrome and its predictors.

Restless legs syndrome (RLS) is common in the third trimester of pregnancy. In this case-control study, 22.5% of 211 women had RLS. The RLS cases had a history of growing pains (GP) more frequently than controls (P=0.042). A family history of GP (P=0.025) and RLS (P=0.018) was more frequent among cases than controls. RLS in pregnancy is predicted by family history of RLS and GP, and by childhood history of GP.

Somatosensory test responses in children with growing pains.

PURPOSE: To further the understanding of growing pains (GP), in particular, the nature of this pain disorder. METHODS: This study included 33 children aged 5-12 years who met criteria for GP (cases) and 29 children without GP of similar age and sex (controls). Nineteen controls were siblings of cases. GP was diagnosed by standard consensus questionnaires. A questionnaire addressed characteristics of the pain and family history of GP. Evidence for peripheral neuropathic disorder was tested by somatosensory testing and provocation tests of peripheral nerves. Somatosensory testing by a blinded researcher involved threshold determination and/or response magnitude to nonpainful stimuli including touch, dynamic brush, cold, vibration, and deep pressure applied to limb and abdominal sites. RESULTS: Distributional, temporal, and quality characteristics of the pain were in accordance with published descriptions. There was no indication of primary musculoskeletal disorder. No evidence was found that GP is a peripheral neuropathic pain syndrome. There were minor but statistically significantly increased responses to cutaneous cold, vibration, and to deep pressure stimuli in cases compared to controls, evident in a wider distribution than the symptomatic lower limbs. CONCLUSION: GP is a regional pain syndrome with evidence in this study of mild widespread disorder of somatosensory processing.

A radio pulsar/x-ray binary link.

Radio pulsars with millisecond spin periods are thought to have been spun up by the transfer of matter and angular momentum from a low-mass companion star during an x-ray-emitting phase. The spin periods of the neutron stars in several such low-mass x-ray binary (LMXB) systems have been shown to be in the millisecond regime, but no radio pulsations have been detected. Here we report on detection and follow-up observations of a nearby radio millisecond pulsar (MSP) in a circular binary orbit with an optically identified companion star. Optical observations indicate that an accretion disk was present in this system within the past decade. Our optical data show no evidence that one exists today, suggesting that the radio MSP has turned on after a recent LMXB phase.

An eccentric binary millisecond pulsar in the galactic plane.

Binary pulsar systems are superb probes of stellar and binary evolution and the physics of extreme environments. In a survey with the Arecibo telescope, we have found PSR J1903+0327, a radio pulsar with a rotational period of 2.15 milliseconds in a highly eccentric (e = 0.44) 95-day orbit around a solar mass (M(middle dot in circle)) companion. Infrared observations identify a possible main-sequence companion star. Conventional binary stellar evolution models predict neither large orbital eccentricities nor main-sequence companions around millisecond pulsars. Alternative formation scenarios involve recycling a neutron star in a globular cluster, then ejecting it into the Galactic disk, or membership in a hierarchical triple system. A relativistic analysis of timing observations of the pulsar finds its mass to be 1.74 +/- 0.04 M solar symbol, an unusually high value.