Speechless after bone marrow transplantation: a rare complication of parainfluenza virus related group in an adult

Upper respiratory tract (URT) viral infections may cause severe consequences during myeloablative bone marrow transplantation (BMT). We present a patient with parainfluenza virus (PIV) infection during the course of BMT. He remained relatively asymptomatic during the course of cytopenia, but presented with complete loss of voice and severe laryngitis a few days after engraftment, which is not usual for adult PIV infections. Seroconversion to PIV and marked increase in antibody titres was demonstrated, with complete lymphoid engraftment. Our case illustrated that the virulence of some URT viral infections depend on host immune factors, and may remain latent until graft versus host responses can be mounted.

Translation and validation of the Functional Assessment of Cancer Therapy-Bone Marrow Transplant (FACT-BMT) Version 4 quality of life instrument into traditional Chinese

The need for a culturally sensitive instrument to assess quality of life (QOL) of patients in international oncology clinical trials has been well documented. This study was designed to evaluate the psychometric properties of the traditional Chinese translation (TCHI) of the Functional Assessment of Cancer Therapy-Bone Marrow Transplant (FACT-BMT) Version 4. The FACT-BMT consists of the FACT-General and treatment-specific concerns of bone marrow transplantation. The Chinese translation follows the standard Functional Assessment of Chronic Illness Therapy (FACIT) translation methodology. Bilingual teams from the United States and Hong Kong reviewed the translation to develop a provisional TCHI FACT-BMT, which was then pre-tested by interviewing 20 native Chinese-speaking BMT patients in Hong Kong. The pre-test results indicated good content coverage and overall comprehensibility. A refined translation, taking into account patient comments, was validated by 134 BMT patients in Hong Kong. The results indicated the high internal consistency of the TCHI FACT-BMT scales, with Cronbach's alpha coefficients ranging from 0.71 (emotional well-being) to 0.92 (FACT-BMT total). The FACT-BMT also demonstrated good construct validity when correlated with SF-36 Health Survey scales. The QOL of Chinese BMT patients can now be evaluated using a well-validated international QOL instrument in their own language.

Aggressive hepatocellular carcinoma complicating pregnancy after autologous bone marrow transplantation for non-Hodgkin's lymphoma

In the Asia-Pacific region, autologous and allogeneic bone marrow transplantation (BMT) in patients infected with the hepatitis B virus (HBV) may be complicated by fatal hepatic failure due to viral reactivation. Survivors may suffer from accelerated hepatitis and cirrhosis. We report the first case of hepatocellular carcinoma (HCC) after autologous BMT for mediastinal B cell lymphoma. The tumor developed rampantly during a planned pregnancy 5 years after BMT. Less than 40 cases of HCC complicating pregnancy have been reported, and outcome is invariably poor. Immunosuppression and HBV reactivation after autologous BMT, as well as immune tolerance and hormonal changes associated with pregnancy may contribute to the rapid tumor growth. Biochemical and radiological surveillance for HCC should be strengthened in HBV carriers after BMT, especially in patients with the histology of chronic liver disease, or biochemical/ virological evidence of increased HBV activity.

A limit on spin-charge separation in high-Tc superconductors from the absence of a vortex-memory effect

There is a long-standing debate about whether spin-charge separation is the root cause of the peculiar normal-state properties and high superconducting transition temperatures of the high-Tc materials. In the proposed state of matter, the elementary excitations are not electron-like, as in conventional metals, but rather the electron 'fractionalizes' to give excitations that are chargeless spin-1/2 fermions (spinons) and charge +e bosons (chargons). Although spin-charge separation has been well established in one dimension, the theoretical situation for two dimensions is controversial and experimental evidence for it in the high-Tc materials is indirect. A model with sharp experimental tests for a particular type of separation in two dimensions has recently been proposed. Here we report the results of those experimental tests, placing a conservative upper limit of 190 K on the energy of the proposed topological defects known as visons. There is still debate about the extent to which this experiment can settle the issue of spin-charge separation in the high-Tc copper oxides, because some forms of the separation are able to avoid the need for visons. But at least one class of theories that all predict a vortex-memory effect now are unlikely models for the copper oxides.

Association of the HLA A2-B46-DR9 haplotype with autoimmune thyroid dysfunction after bone marrow transplantation in Chinese patients

Autoimmune thyroid disease (AITD) may occur in patients after bone marrow transplantation (BMT). At a median follow-up of 4 years, among 194 allografts and 28 autografts, four patients (three allografts, one autograft) developed AITD. All carried the human leucocyte antigen (HLA) A2-B46-DR9 haplotype, strongly associated with AITD in the Chinese population. No significant thyroid disorder was detected in 190 patients without this haplotype. The frequency of AITD in BMT patients with the HLA A2-B46-DR9 haplotype was 12.5%, with a relative risk of 7.8 times that of non-carriers (P < 0.001). The risk of AITD should be recognized in recipients with high-risk HLA haplotypes, and regular screening might be warranted.

Limits on spin-charge separation from h/2e fluxoids in very underdoped YBa2Cu3O(6+x)

Magnetic flux in superconductors is usually quantized in units of h/2e. Here we report scanning SQUID and scanning Hall probe studies of single fluxoids in high purity YBa2Cu3O6.35 crystals (T(c) less, similar 13 K), extending flux quantization studies to a region of the cuprate phase diagram where the superfluid density is sufficiently low that novel behavior has been predicted. Some scenarios in which superconductivity results from spin-charge separation predict h/e fluxoids in materials with low superfluid density. Our observations of only h/2e fluxoids set limits on these theories.

Risk of haematological malignancies in HLA-B27 carriers

Human leucocyte antigen (HLA)-B27 carriers are predisposed to inflammatory and autoimmune diseases. Among 1137 patients with haematological diseases, 59 HLA-B27 carriers were identified. Compared with 18 774 volunteers, the incidence of HLA-B27 was increased in patients with acute leukaemia (relative risk RR = 1.67, P = 0.002), for both acute myeloid leukaemia (AML) (RR) = 1.67, P = 0.007) and acute lymphoblastic leukaemia (ALL) (RR = 1.68, P = 0.094). Of all the HLA-B27 carriers, four patients had ankylosing spondylitis (AS), all with lymphoid malignancies (three ALL, one Hodgkin's disease), whereas no HLA-B27 carriers with myeloid leukaemia had AS symptoms (P = 0.006). This suggests that HLA-B27 carriers may have an increased risk of acute leukaemia and those with concomitant AS may be predisposed to lymphoid malignancies.

Genetic polymorphism in exon 4 of cytochrome P450 CYP2C9 may be associated with warfarin sensitivity in Chinese patients

CYP2C9 polymorphisms reported in Caucasians (Arg144Cys in exon 3 and Ile359Leu in exon 7) are extremely uncommon in Chinese persons. The genotype of CYP2C9 in this population was characterized to investigate its relation with the interindividual variation in warfarin dosages. Eighty-nine Chinese patients receiving warfarin were recruited. Target sequences in CYP2C9 in exons 1, 4, and 5 were amplified by polymerase chain reaction, followed by direct sequencing. Polymorphisms at 4 positions were demonstrated in exon 4. Heterozygosities for 608TTG>GTG (Leu208Val), 561CAG>CCG (Gln192Pro), 537CAT>CCT (His184Pro), and 527ATT>CTT (Ile181Leu) existed at frequencies 0.75, 0.20, 0.10, and 0.09, respectively. Seventeen patients (frequency, 0.19) were homozygous for Val208. The common genotypic combinations at these loci are Ile181/His184/Gln192/Leu208Val (n = 50), Ile181/His184/Gln192/Val208 (n = 15), Ile181/His184/Gln192/Leu208 (n = 4), Ile181/His184/Gln192Pro/Leu208Val (n = 6), Ile181/His184Pro/Gln192Pro/Leu208Val (n = 4), and Ile181Leu/His184/Gln192Pro/ Leu208Val (n = 4). At codon 208, heterozygous Leu208Val and homozygous Val208 appeared to have a lower warfarin dose requirement than the homozygous Leu208. Patients who are heterozygous for Ile181Leu had a higher warfarin dose requirement than the homozygous Ile181. Amplified sequences in exons 1 and 5 did not exhibit polymorphism. In conclusion, Chinese patients showed genetic polymorphisms of CYP2C9 in exon 4 and at codon 208; most were heterozygous Leu208Val and homozygous Val208. Homozygous Leu208, a common allele in Caucasians, is uncommon in this cohort. The significance of these CYP2C9 polymorphic alleles remains to be determined.

Determination of optical constants of thin films and multilayer stacks by use of concurrent reflectance, transmittance, and ellipsometric measurements

Using measurements of reflectance, transmittance, and the ellipsometric parameter D, we have determined the thickness, refractive index, and the absorption coefficient of various thin films and thin-film stacks. (D, the relative phase between the p- and s-polarized components, is measured for both reflected and transmitted light.) These optical measurements are performed with a specially designed system at the fixed wavelength of lambda = 633 nm over the 10 degrees -75 degrees range of angles of incidence. The examined samples, prepared by means of sputtering on fused-silica substrates, consist of monolayers and trilayers of various materials of differing thickness and optical constants. These samples, which are representative of the media of rewritable phase-change optical disks, include a dielectric mixture of ZnS and SiO(2), an amorphous film of the Ge(2)Sb(2.3)Te(5) alloy, and an aluminum chromium alloy film. To avoid complications arising from reflection and transmission losses at the air-substrate interface, the samples are immersed in an index-matching fluid that eliminates the contributions of the substrate to reflected and transmitted light. A computer program estimates the unknown parameters of the film(s) by matching the experimental data to theoretically calculated values. Although our system can be used for measurements over a broad range of wavelengths, we describe only the results obtained at lambda = 633 nm.

Blocking tumor growth, invasion, and metastasis by maspin in a syngeneic breast cancer model

Maspin is a unique serine protease inhibitor of which the down-regulation is associated with the development of breast cancers. In vitro, recombinant maspin inhibits tumor cell migration and invasion. Overexpression of maspin in transgenic mice is protective against tumor progression. Additionally, maspin acts as an angiogenesis inhibitor in rat cornea model and in a xenograft tumor model. To additionally prove that maspin is directly involved in the suppression of tumor growth and metastasis, we tested maspin in a new syngeneic mammary tumor model, TM40D. This model involves the implantation of TM40D mammary tumor cells orthotopically to the mammary gland; tumors grew within the gland and then become invasive and metastatic to other organs. Here we demonstrate that TM40D cells in implanted mammary glands are highly invasive. Overall, a 75% rate of invasion and metastasis was observed in this model. However, both primary tumor growth and metastasis were significantly blocked in TM40D cells that overexpress maspin as a consequence of plasmid or retrovirus infection. Maspin-transfected tumors tended to have tumor encapsulation and less necrosis, which were associated with better prognosis and lower invasiveness. Thus, maspin can block primary tumor growth as well as invasion and metastasis. These data support the concept that maspin has a strong protective role against tumor progression.

[Clinical application of ultrasonographic indexes for assessment of amniotic fluid volume]

OBJECTIVE

To find the favorable interval of assessment of amniotic fluid volume and the optimal standard for oligohydramnios.

METHODS

To determine actual amniotic fluid volume (AAFV) by collecting amniotic fluid during cesarean section and compare it with maximum vertical pocket (MVP) and amniotic fluid index (AFI) in different interval between cesarean section and measurement and test the sensitivity and specificity of MVP and AFI of different standard.

RESULTS

The ultrasonographic results were divided into three groups according to the interval between measurement and delivery: within 24 hours group, 24-96 hours group and longer than 96 over hours group. The results of the within 24 hours and 24-96 hours groups were positively correlated with AAFV, while the results of the group longer than 96 hours were not statistically significant. The correlation coefficients were 0.840 and 0.869 for MVP, 0.789 and 0.874 for AFI respectively. The receiver-operator characteristic curve showed that MVP < 4 cm and AFI < 10 cm were superior to any other standards to scan oligohydramnios. The sensitivity of these standards was 0.76 and 0.61, and the specificity was 0.83 and 0.91.

CONCLUSION

It is highly recommended to estimate the amniotic fluid of high risk pregnant women, women with MVP < 4 cm or AFI < 10 cm and with a pregnancy week > 40 weeks should be monitered by ultrasonography every four days.

Hepatitis B virus (HBV) reactivation after cytotoxic or immunosuppressive therapy--pathogenesis and management

In an endemic area for chronic hepatitis B infection, reactivation of this virus is a serious cause of morbidity and mortality in patients undergoing cytotoxic or immunosuppressive therapy. Careful prospective serological testing has shown that hepatitis B virus reactivation is a two-staged process. The initial stage occurs during intense cytotoxic or immunosuppressive therapy and is characterised by enhanced viral replication, as reflected by increases in the serum levels of hepatitis B virus DNA, hepatitis B e antigen, hepatitis B virus DNA polymerase and infection of naïve hepatocytes with hepatitis B virus. The second stage is related to restoration of immune function following withdrawal of cytotoxic or immunosuppressive therapy, which causes rapid immune-mediated destruction of infected hepatocytes. Clinically, this can lead to hepatitis, hepatic failure and even death. The occurrence and severity of hepatitis B virus reactivation after various cytotoxic or immunosuppressive therapy is unpredictable and treatment has been disappointing, largely due to the late administration of therapy. Recently, pre-emptive treatment of chronic hepatitis B patients undergoing cytotoxic or immunosuppressive therapy, with potent nucleoside analogues has shown some promising results. Further controlled studies are needed to define the incidence and risk factors of hepatitis B reactivation so that pre-emptive treatment with nucleoside analogues could be administered to those patients at high risk of disease.

Plasma nitric oxide is associated with the occurrence of moderate to severe acute graft-versus-host disease in haemopoietic stem cell transplant recipients

BACKGROUND AND OBJECTIVES

Nitric oxide (NO) has been implicated as one of the mediators of acute graft-versus-host disease (GVHD) but reports on its measurement during haemopoietic stem cell transplantation (HSCT) in human are scarce. The present study was conducted to measure the plasma NO in HSCT recipients in order to delineate its relationships with acute GVHD.

DESIGN AND METHODS

Thirty-nine randomly selected patients undergoing HSCT were recruited. Thirty-one patients received allogeneic transplants (ALLO) from HLA-identical siblings (n=20), haploidentical parent (n=1) and matched unrelated donors (n=10). Eight patients received autologous (AUTO) HSCT. Plasma levels of nitrite/nitrate (NO(2)(-)/NO(3)(-)), the end-product of NO, were measured by chemiluminescence and the results were correlated with the occurrence and severity of acute GVHD.

RESULTS

Baseline NO(2)(-)/NO(3)(-) levels before HSCT were similar in the ALLO and AUTO patients (17.4 vs 21.1 microL, p>0.05). Significant increases in plasma NO(2)(-)/NO(3)(-) (> 2 times the baseline level) were found in all 13 patients with acute GVHD > or = grade 2, in 15 out of 18 patients with acute GVHD grade < or = 1 and 3 out of 8 patients receiving autologous HSCT. The increase in NO(2)(-)/NO(3)(-) among the three groups of patients was significantly different (135.5 vs 56.3 vs 36.6 micromol/L, p < 0.001). The average NO production, calculated as the area under the curve, was also significantly differently among the three groups of patients (44.5 vs 30.0 vs 23.8 micromol/L, p < 0.001).

INTERPRETATION AND CONCLUSIONS

Plasma NO in HSCT recipients is quantitatively associated with the occurrence of acute GVHD and its role remains to be determined.

Primary extramedullary plasmacytoma of the lacrimal gland

Primary extramedullary plasmacytoma (EMP) of the lacrimal gland is rare. Here we describe the histopathologic and imaging findings in a 77-year-old patient with primary extramedullary plasmacytoma of the lacrimal gland. The usefulness of CD79a in the diagnosis of plasmacytoma and the good response of the tumor to combined surgery and radiotherapy are illustrated. Plamacytoma should be included in the differential diagnosis of lacrimal tumors.

Late onset post-transplantation lymphoproliferative disease of recipient origin following cytogenetic relapse and occult autologous haematopoietic regeneration after allogeneic bone marrow transplantation for acute myeloid leukaemia

A post-transplantation lymphoproliferative disease (PTLD) of recipient origin was identified in one of 376 consecutive cases of allogeneic bone marrow transplantation (BMT). This occurred in a 36-year-old woman who received an allogeneic BMT for acute myeloid leukaemia in relapse. At 15 months after BMT, recipient haematopietic and leukaemic cells were found in the bone marrow, which disappeared on withdrawal of immunosuppression. However, severe graft-versus-host disease (GVHD) necessitated the continuation of immunosuppression, leading to the occurrence of PTLD in the liver and lung 12 months afterwards. Fluorescence in situ hybridisation showed that the neoplastic cells were of recipient origin. Although the PTLD also responded completely to withdrawal of immunosuppression, the patient finally died from the complications of GVHD. This case of late onset PTLD post-BMT showed features similar to those in solid organ transplantation, in that the tumour was of recipient origin and responded well to the withdrawal of immunosuppression. Of further interest is that recipient lymphoid regeneration had accompanied autologous haematopoietic regeneration and become a target for subsequent neoplastic transformation.

Philadelphia (Ph) chromosome-positive chronic myeloid leukaemia relapsing as Ph-negative leukaemia after allogeneic bone marrow transplantation

Two patients with Philadelphia chromosome-positive (Ph(+)) chronic myeloid leukaemia (CML) relapsed 1.5 and 5 years after allogeneic bone marrow transplantation (BMT). Although the leukaemias were of recipient origin, t(9;22) could no longer be detected using conventional cytogenetics/fluorescence in situ hybridization or molecularly. Both patients responded to immunotherapy with donor lymphocytes/peripheral blood stem cells, although one patient ultimately relapsed again. These patients were similar to the occurrence of Ph(-) leukaemias previously described in Ph(+) CML after treatment with interferon or autologous BMT, and might be relevant in the pathogenesis and monitoring of treatment after BMT in CML.

Clinicopathologic and prognostic features of chronic idiopathic thrombocytopenic purpura in adult Chinese patients: an analysis of 220 cases

To determine the clinicopathologic and prognostic features of chronic idiopathic thrombocytopenic purpura (ITP) in adult Chinese patients, we conducted a retrospective analysis of 220 patients seen at a single center over a 40-year period. The female-to-male ratio was 4:1, with a mean age of 42.1 +/- 1.3 years, a mean platelet count of 33.7 +/- 2.3x10(9)/l, and a mean follow-up of 116 +/- 7 months. Initial steroid treatment was required in 142 patients, 67 of whom (47.2%) achieved complete remission (CR). At 470 months, 46% patients remained in CR. Splenectomy was performed in 37 patients: in 23 patients due to primary steroid refractoriness and in 7 patients due to disease relapse following initial CR with steroids. In seven patients, data on response to steroids prior to splenectomy were not available. Splenectomy for steroid nonresponders resulted in an inferior CR rate (13 of 23, 56%) as compared with that for relapses after steroid treatment (7 of 7, 100%) (P<0.05). Compared with patients with negative antinuclear antibody (ANA), those who were ANA positive had similar responses to steroids, but significantly shorter remission after splenectomy (P<0.01). In conclusion, Chinese patients with ITP could maintain long-term remission after steroid therapy and splenectomy. In addition, primary steroid refractoriness and positive ANA were bad prognostic factors of the subsequent response to splenectomy.

[Identification of Amomum villosum, Amomum villosum var. xanthioides and Amomum longiligulare on ITS-1 sequence]

OBJECTIVE

To identify Amomum villosum Lour. and some their adulterants on molecular biology.

METHOD

The DNA of Amomum villosum Lour. and some their adulterants were extracted, and amplified using ITS-1 primer. The amplificed DNA were purified and then sequenced by direct PCR sequencing method.

RESULT

The ITS-sequence of all of the samples are 248 bp in size. But there are 7 bases in Amomum villosum Lour var. xanthioides (Wall.ex Bak) T.L. Wu et Senjen and 12 hases in Amomum longiligulare T.L. Wu. differing from Amomum villosum Lour.

CONCLUSION

The ITS-1 sequence can be used to identify effectively Amomum villosum Lour. and their adulterants.

Methylation of p15 and p16 genes in adult acute leukemia: lack of prognostic significance

BACKGROUND

Gene-promoter methylation is an epigenetic mechanism of transcription inactivation. In this study, the authors investigated the frequency and prognostic significance of p15 and p16 gene methylation in adult acute leukemia.

METHOD

The methylation-specific polymerase chain reaction (MS-PCR) was used to analyze p15 and p16 gene methylation in 49 cases of acute lymphoblastic leukemia (ALL) and 29 cases of acute myelogenous leukemia (AML).

RESULTS

At presentation, 93 % of cases of AML (8 of 8 M1, 10 of 11 M2, 2 of 2 M4, 5 of 6 M5, and 2 of 2 M6; French-American-British classification system) showed p15 methylation, but none showed p16 methylation. In ALL, 57% (5 of 8 T-ALL, 16 of 30 common-ALL, 6 of 7 pre-B ALL, and 1 of 4 early B-precursor ALL) showed p15 methylation. Only 6% showed p16 methylation, all of whom had concomitant p15 methylation. One patient acquired p16 methylation during relapse. In 23 ALL karyotyped cases, p15 methylation was found in 6 of 9 cases with normal karyotype, 3 of 7 cases with the Philadelphia chromosome, 3 of 5 cases with complex, 1 with hyperdiploidy, and 1 with trisomy 21. Three more cases with unsuccessful karyotyping but bcr/abl fusion showed p15 methylation as well. Five ALL patients were tested serially for minimal residual disease (MRD) with MS-PCR that has a sensitivity of 10(-4) to 10(-5). All showed continuous positive MS-PCR that heralded hematologic relapse. The prognostic significance of p15 methylation was tested in ALL patients, showing no impact on complete remission, 5-year overall survival, or 5-year disease-free survival.

CONCLUSION

Gene methylation of p15, but not p16, is frequent in adult acute leukemias. Methylation of p15 at diagnosis was of no prognostic significance in ALL but may be useful for monitoring MRD.

Respiratory ciliary function in bone marrow recipients

Bone marrow transplantation (BMT) recipients, particularly those with chronic graft-versus-host disease (GVHD), suffer from respiratory tract problems, including bronchiolitis obliterans (BO) and recurrent lower respiratory tract infections. Minute cilia beat continuously on the surface of respiratory mucosa, and this beating maintains the sterility of the lower respiratory tract. Dysfunction of respiratory cilia could lead to development of recurrent respiratory tract infections, which are also features of BMT recipients, although ciliary function has not been systematically studied among these subjects. We have, therefore, investigated the ciliary beat frequency (CBF) of 36 Chinese patients who had undergone allogeneic BMT. The CBF was significantly lower in the BMT group compared to controls (P < 0.001). The reduction in CBF was more severe in patients with cGVHD and BO compared with their counterparts (P = 0.048 and P = 0.077, respectively). There was a correlation between CBF with forced expiratory flow rate FEF (P = 0.024) and forced expiratory volume FEV (P = 0.044). We conclude that abnormal ciliary clearance is a common feature after allogeneic BMT, particularly among patients with BO and cGVHD. Further studies are indicated to evaluate this important phenomenon, which could be an important cause of the susceptibility for BMT recipients to respiratory infections.

Helper T-lymphocyte precursor frequency predicts the occurrence of graft-versus-host disease and disease relapse after allogeneic bone marrow transplantation from HLA-identical siblings

BACKGROUND AND OBJECTIVES

Donor helper T-lymphocytes may be involved in graft-versus-host disease (GVHD) and a graft-versus-leukemia effect after bone marrow transplantation (BMT). We assayed donor helper T-lymphocyte precursor frequencies (HTLP(f)) to see whether they could predict the severity of GVHD and disease relapse after transplantation, thereby facilitating donor selection, pre-transplant counselling and modification of GVHD prophylaxis after BMT.

DESIGN AND METHODS

Thirty-six consecutive adult BMT recipients and their HLA-identical sibling donors were recruited. HTLP((f)) was measured as a function of interleukin-2 secretion by alloreactive donor T-cells using a limiting dilution assay. Patients were followed prospectively to assess the severity of GVHD and the status of the primary disease after BMT.

RESULTS

Eight donors had HTLP((f)) less than or equal to 10(-6); no recipients of these grafts developed severe GVHD after transplantation. Twenty-eight donors had HTLP(f) greater than 10(-6) and 18 recipients of these grafts developed severe GVHD (> or = grade 2) (chi(2) test, p<0.01). Seven donors had HTLP(f) greater than 10(-5) and no recipient had disease relapse. Twenty-nine donors had HTLP(f) less than or equal to 10(-5), 11 recipients of these grafts developed disease relapse (chi(2) test, p=0.08).

INTERPRETATION AND CONCLUSIONS

BMT recipients from HLA-identical sibling donors with low (<10(-6)) and high (>10(-5)) HTLP(f) may have a low risk of acute GVHD and disease relapse after transplantation.

Anomalous weak magnetism in superconducting YBa2Cu3O6+x

For some time now, there has been considerable experimental and theoretical effort to understand the role of the normal-state "pseudogap" phase in underdoped high-temperature cuprate superconductors. Recent debate has centered on the question of whether the pseudogap is independent of superconductivity. We provide evidence from zero-field muon spin relaxation measurements in YBa2Cu3O6+x for the presence of small spontaneous static magnetic fields of electronic origin intimately related to the pseudogap transition. Our most significant finding is that, for optimal doping, these weak static magnetic fields appear well below the superconducting transition temperature. The two compositions measured suggest the existence of a quantum critical point somewhat above optimal doping.