Femoral neck shaft angle in men with fragility fractures

Introduction. Femoral neck shaft angle (NSA) has been reported to be an independent predictor of hip fracture risk in men. We aimed to assess the role of NSA in UK men. Methods. The NSA was measured manually from the DXA scan printout in men with hip (62, 31 femoral neck and 31 trochanteric), symptomatic vertebral (91), and distal forearm (67) fractures and 389 age-matched control subjects. Age, height, weight, and BMD (g/cm(2): lumbar spine, femoral neck, and total femur) measurements were performed. Results. There was no significant difference in mean NSA between men with femoral neck and trochanteric hip fractures, so all further analyses of hip fractures utilised the combined data. There was no difference in NSA between those with hip fractures and those without (either using the combined data or analysing trochanteric and femoral neck shaft fractures separately), nor between fracture subjects as a whole and controls. Mean NSA was smaller in those with vertebral fractures (129.2° versus 131°: P = 0.001), but larger in those with distal forearm fractures (129.8° versus 128.5°: P = 0.01). Conclusions. The conflicting results suggest that femoral NSA is not an important determinant of hip fracture risk in UK men.

Doses to critical organs following radiotherapy and concomitant imaging of the larynx and breast

The development of conformal radiotherapy carries with it the implication of an increased number of imaging procedures at various stages throughout the overall treatment, principally for verification at some, or all, of the treatment fractions. This raises the issue of the balance between the benefit of these additional imaging exposures and the associated risk of radiocarcinogenesis arising from them. As such, it is necessary to appreciate the doses to critical organs for which individual carcinogenic risks have been estimated. In this study, doses to these organs have been measured with lithium fluoride thermoluminescence dosimetry loaded in anthropomorphic phantoms and subjected to realistic radiotherapy treatments of the larynx and breast, including concomitant CT and electronic portal imaging exposures associated with localization and verification of these treatments. Even for large numbers of concomitant images of either modality, arising from imaging at every fraction, the leakage and scatter from the radiotherapy itself is shown to dominate the overall organ dose, with imaging procedures generally contributing 5-20% of the total organ dose.

Organ doses from prostate radiotherapy and associated concomitant exposures

In addition to the therapeutic exposure, a course of radiotherapy will involve the additional (concomitant) irradiation of the patient using CT, simulator or portal imaging systems, for localization of the target volume and subsequent verification of treatment delivery. The number of concomitant exposures is likely to increase as the developing technical capabilities for conformal, image-guided radiotherapy make target and critical organ definition an increasingly important aspect of radiotherapy. Estimation of doses and risks to critical organs in the body from all sources is thus necessary to provide the basis for adequate justification of the exposures as required by ICRP. In this paper, doses to selected organs and tissues for which ICRP have identified fatal cancer probabilities have been measured using a realistic anthropomorphic phantom loaded with thermoluminescent dosemeters and irradiated using a treatment protocol for radical radiotherapy of the prostate. Independently, doses to the same organs and tissues have been measured from concomitant CT and portal imaging exposures given for localization and verification purposes. Although negligible in comparison with the target dose, realistic numbers of concomitant exposures give a small but significant contribution to the total dose to most organs and tissues outside the target volume. Generally, this is in the range 5-10% of the total organ dose, but can be as high as 20% for bone surfaces. These data may be used to estimate concomitant doses from any combination of CT and portal imaging and may help in the justification process, especially when additional verification exposures may be required during treatment.

Differences in bone mineral density and geometry in men and women: the Newcastle Thousand Families Study at 50 years old

In 1947 Sir James Spence initiated the Newcastle Thousand Families study, which recruited all 1142 children born in the city between May and June that year. At the age of 50 years, 832 survivors were traced and invited to attend for measurement of bone mineral density (BMD) by dual energy X-ray absorptiometry (DXA). The aim was to compare BMD measurements of men and women in this cohort, before and after adjustment for skeletal size. The femoral neck shaft angles (NSA) were also measured manually from the DXA scan printouts. A total of 171 men and 218 women agreed to participate. As expected men had greater bone mineral content and bone area at all sites (p<0.0001) and were taller and heavier (p<0.0001) than women. Men also had significantly higher BMD than women at all regions (p<0.0002), except at the femoral neck or lumbar spine. After correction for skeletal size and body weight, men had statistically significantly lower volumetric BMD at all sites. The measurement of NSA had good intra/interobserver errors and precision (coefficient of variations 0.79%, 1.2% and 1.2%). Men had significantly larger NSAs (mean 130 degrees , range 121-138 degrees ) than women (mean 128 degrees , range 119-137 degrees ). We conclude that there are gender differences in BMD, skeletal size and geometry in middle aged men and women, which together with the subsequent rate of bone loss, may influence fracture risk in later life.

A randomized controlled trial of calcium with vitamin D, alone or in combination with intravenous pamidronate, for the treatment of low bone mineral density associated with Crohn's disease

BACKGROUND

Osteoporosis is a common complication of Crohn's disease.

AIM

To study the effect on the bone mineral density of a bisphosphonate (pamidronate) given intravenously, in combination with oral calcium and vitamin D supplements, compared with oral calcium and vitamin D supplements alone.

METHODS

Seventy-four patients with Crohn's disease and low bone mineral density at the lumbar spine and/or hip were randomized to receive either a daily dose of 500 mg of calcium with 400 IU of vitamin D alone or in combination with four three-monthly infusions of 30 mg of intravenous pamidronate over the course of 12 months. The main outcome measure was the change in bone mineral density at the lumbar spine and hip, measured by dual X-ray absorptiometry, at baseline and 12 months.

RESULTS

Both groups gained bone mineral density at the lumbar spine and hip after 12 months. There were significant (P < 0.05) changes in the pamidronate group, with gains of + 2.6%[95% confidence interval (CI), 1.4-3.0] at the spine and + 1.6% (95% CI, 0.6-2.5) at the hip, compared with gains of + 1.6% (95% CI, - 0.1-3.2) and + 0.9% (95% CI, - 0.4-2.1) at the spine and hip, respectively, in the group taking vitamin D and calcium supplements alone.

CONCLUSIONS

In patients with Crohn's disease and low bone mineral density, intravenous pamidronate significantly increases the bone mineral density at the lumbar spine and hip.

PKCbeta modulates antigen receptor signaling via regulation of Btk membrane localization

Mutations in Bruton's tyrosine kinase (Btk) result in X-linked agammaglobulinemia (XLA) in humans and X-linked immunodeficiency (xid) in mice. While targeted disruption of the protein kinase C-beta (PKCbeta) gene in mice results in an immunodeficiency similar to xid, the overall tyrosine phosphorylation of Btk is significantly enhanced in PKCbeta-deficient B cells. We provide direct evidence that PKCbeta acts as a feedback loop inhibitor of Btk activation. Inhibition of PKCbeta results in a dramatic increase in B-cell receptor (BCR)-mediated Ca2+ signaling. We identified a highly conserved PKCbeta serine phosphorylation site in a short linker within the Tec homology domain of Btk. Mutation of this phosphorylation site led to enhanced tyrosine phosphorylation and membrane association of Btk, and augmented BCR and FcepsilonRI-mediated signaling in B and mast cells, respectively. These findings provide a novel mechanism whereby reversible translocation of Btk/Tec kinases regulates the threshold for immunoreceptor signaling and thereby modulates lymphocyte activation.

TCL1 oncogene expression in B cell subsets from lymphoid hyperplasia and distinct classes of B cell lymphoma

Activation of the TCL1 oncogene has been implicated in T cell leukemias/lymphomas and recently was associated with AIDS diffuse large B cell lymphomas (AIDS-DLBCL). Also, in nonmalignant lymphoid tissues, antibody staining has shown that mantle zone B cells expressed abundant Tcl1 protein, whereas germinal center (GC; centrocytes and centroblasts) B cells showed markedly reduced expression. Here, we analyze isolated B cell subsets from hyperplastic tonsil to determine a more precise pattern of Tcl1 expression with development. We also examine multiple B cell lines and B lymphoma patient samples to determine whether different tumor classes retain or alter the developmental pattern of expression. We show that TCL1 expression is not affected by Epstein-Barr virus (EBV) infection and is high in naïve B cells, reduced in GC B cells, and absent in memory B cells and plasma cells. Human herpesvirus-8 infected primary effusion lymphomas (PEL) and multiple myelomas are uniformly TCL1 negative, whereas all other transformed B cell lines tested express moderate to abundant TCL1. This observation supports the hypothesis that PEL, like myeloma, usually arise from post-GC stages of B cell development. Tcl1 protein is also detected in most naïve/GC-derived B lymphoma patient samples (23 of 27 [85%] positive), whereas most post-GC-derived B lymphomas lack expression (10 of 41 [24%] positive). These data indicate that the pattern of Tcl1 expression is distinct between naïve/GC and post-GC-derived B lymphomas (P < 0.001) and that the developmental pattern of expression is largely retained. However, post-GC-derived AIDS-DLBCL express TCL1 at a frequency equivalent to naïve/GC-derived B lymphomas in immune-competent individuals (7 of 9 [78%] positive), suggesting that TCL1 down-regulation is adversely affected by severe immune system dysfunction. These findings demonstrate that TCL1 expression in B cell lymphoma usually reflects the stage of B cell development from which they derive, except in AIDS-related lymphomas.

Unrelated umbilical cord stem cell transplantation for X-linked immunodeficiencies

Banked unrelated umbilical cord blood matched at 5 of 6 human leukocyte antigen loci was used to reconstitute the immune system in 2 brothers with X-linked lymphoproliferative syndrome and 1 boy with X-linked hyperimmunoglobulin-M syndrome. Pretransplant cytoreduction and posttransplant graft-versus-host prophylaxis were given. Hematopoietic engraftment and correction of the genetic defects were documented by molecular techniques. Two years after transplantation, all 3 patients have normal immune systems. These reports support the wider use of banked partially matched cord blood for transplantation in primary immunodeficiencies.

Primary angiitis of the central nervous system in children: 5 cases

We describe 5 children who meet criteria for primary angiitis of the central nervous system (PACNS). All patients presented with headache and/or focal neurologic deficits and exhibited clinical and/or radiographic evidence of disease progression. Two patients had disease progression prior to combined treatment with cyclophosphamide and corticosteroids; one progressed while receiving intravenous cyclophosphamide and stabilized after a change to daily oral dosing; one progressed after discontinuing therapy after less than 12 months and improved after retreatment; and one progressed on steroid therapy alone but was lost to followup. Children who have frequent or severe headaches or focal neurologic deficits should be carefully evaluated and those meeting criteria for PACNS should be treated aggressively.

The use of dynamic phantoms in interventional radiology

The authors have constructed a 2D motor-controlled test object phantom holder to simulate clinical situations in which patient movement could be a cause of image degradation. The PAtient MOvement SImulation Test Object (PAMOSITO) has been constructed with modular parts to use different mobile test objects and static structures. The system allows the programming of different cycles of movement along two axes. PAMOSITO has been used in X ray equipment dedicated to interventional radiology. Those systems usually allow for different values for frame rate, pulse width or weighted frame averaging methods. The influence of selecting different values of the parameters, patient movement and its relation to patient dose and image quality has been studied. Image blurring due to motion has been evaluated with Leeds test objects TO.10 and 18FG. Spatial resolution limits and the threshold contrast detail detectability performance have been studied.

Redundant and opposing functions of two tyrosine kinases, Btk and Lyn, in mast cell activation

Protein-tyrosine kinases play crucial roles in mast cell activation through the high-affinity IgE receptor (FcepsilonRI). In this study, we have made the following observations on growth properties and FcepsilonRI-mediated signal transduction of primary cultured mast cells from Btk-, Lyn-, and Btk/Lyn-deficient mice. First, Lyn deficiency partially reversed the survival effect of Btk deficiency. Second, FcepsilonRI-induced degranulation and leukotriene release were almost abrogated in Btk/Lyn doubly deficient mast cells while singly deficient cells exhibited normal responses. Tyrosine phosphorylation of cellular proteins including phospholipases C-gamma1 and C-gamma2 was reduced in Btk/Lyn-deficient mast cells. Accordingly, FcepsilonRI-induced elevation of intracellular Ca2+ concentrations and activation of protein kinase Cs were blunted in the doubly deficient cells. Third, in contrast, Btk and Lyn demonstrated opposing roles in cytokine secretion and mitogen-activated protein kinase activation. Lyn-deficient cells exhibited enhanced secretion of TNF-alpha and IL-2 apparently through the prolonged activation of extracellular signal-related kinases and c-Jun N-terminal kinase. Potentially accounting for this phenomenon and robust degranulation in Lyn-deficient cells, the activities of protein kinase Calpha and protein kinase CbetaII, low at basal levels, were enhanced in these cells. Fourth, cytokine secretion was severely reduced and c-Jun N-terminal kinase activation was completely abrogated in Btk/Lyn-deficient mast cells. The data together demonstrate that Btk and Lyn are involved in mast cell signaling pathways in distinctly different ways, emphasizing that multiple signal outcomes must be evaluated to fully understand the functional interactions of individual signaling components.

Engagement of the human pre-B cell receptor generates a lipid raft-dependent calcium signaling complex

Pre-B cell receptor (pre-BCR) expression is critical for B lineage development. The signaling events initiated by the pre-BCR, however, remain poorly defined. We demonstrate that lipid rafts are the major functional compartment for human pre-B cell activation. A fraction of pre-BCR was constitutively raft associated, and receptor engagement enhanced this association. These events promoted Lyn activation and Igbeta phosphorylation and led to the generation of a raft-associated signaling module composed of tyrosine phosphorylated Lyn, Syk, BLNK, PI3K, Btk, VAV, and PLCgamma2. Formation of this module was essential for pre-BCR calcium signaling. Together, these observations directly link the previously identified genetic requirement for the components of this module in B lineage development with theirfunctional role(s) in human preBCR signaling.

Hydroxychloroquine inhibits calcium signals in T cells: a new mechanism to explain its immunomodulatory properties

Hydroxychloroquine (HCQ), a lysosomotropic amine, is an immunosuppressive agent presently being evaluated in bone marrow transplant patients to treat graft-versus-host disease. While its immunosuppressive properties have been attributed primarily to its ability to interfere with antigen processing, recent reports demonstrate HCQ also blocks T-cell activation in vitro. To more precisely define the T-cell inhibitory effects of HCQ, the authors evaluated T-cell antigen receptor (TCR) signaling events in a T-cell line pretreated with HCQ. In a concentration-dependent manner, HCQ inhibited anti-TCR-induced up-regulation of CD69 expression, a distal TCR signaling event. Proximal TCR signals, including inductive protein tyrosine phosphorylation, tyrosine phosphorylation of phospholipase C gamma1, and total inositol phosphate production, were unaffected by HCQ. Strikingly, anti-TCR-crosslinking-induced calcium mobilization was significantly inhibited by HCQ, particularly at the highest concentrations tested (100 micromol/L) in both T-cell lines and primary T cells. HCQ, in a dose-dependent fashion, also reduced a B-cell antigen receptor calcium signal, indicating this effect may be a general property of HCQ. Inhibition of the calcium signal correlated directly with a reduction in the size of thapsigargin-sensitive intracellular calcium stores in HCQ-treated cells. Together, these findings suggest that disruption of TCR-crosslinking-dependent calcium signaling provides an additional mechanism to explain the immunomodulatory properties of HCQ.

Aberrant B cell receptor signaling from B29 (Igbeta, CD79b) gene mutations of chronic lymphocytic leukemia B cells

Chronic lymphocytic leukemia (CLL) B cells characteristically exhibit low or undetectable surface B cell receptor (BCR) and diminished responses to BCR-mediated signaling. These features suggest that CLL cells may have sustained mutations affecting one or more of the BCR proteins required for receptor surface assembly and signal transduction. Loss of expression and mutations in the critical BCR protein B29 (Igbeta, CD79b), are prevalent in CLL and could produce the hallmark features of these leukemic B cells. Because patient CLL cells are intractable to manipulation, we developed a model system to analyze B29 mutations. Jurkat T cells stably expressing micro, kappa, and mb1 efficiently assembled a functional BCR when infected with recombinant vaccinia virus bearing wild-type B29. In contrast, a B29 CLL mutant protein truncated in the transmembrane domain did not associate with mu or mb1 at the cell surface. Another B29 CLL mutant lacking the C-terminal immunoreceptor tyrosine activation motif tyrosine and distal residues brought the receptor to the surface as well as wild-type B29 but showed significant impairment in anti-IgM-stimulated signaling events including mitogen-activated protein kinase activation. These findings demonstrate that B29 mutations previously identified in CLL patients can affect BCR-dependent signaling and may contribute to the unresponsive B cell phenotype in CLL. Finally, the features of the B29 mutations in CLL predict that they may be generated by somatic hypermutation.

Bruton's tyrosine kinase controls a sustained calcium signal essential for B lineage development and function

Genetic data support a role for Btk during the B lineage development transitions regulated by signaling through both the pre-B and the B cell antigen receptors. Dysregulated signaling at each of these transitions can result in failure of these cell populations to proliferate and subsequent cell death. Btk-dependent IP3 production is crucial for maintaining the sustained calcium signal in response to BCR engagement and is likely to regulate a subset of transcriptional events essential for B lineage growth or survival. Identification of these Btk-dependent signals will be important in understanding B cell activation, differentiation, and cell death. This information may lead to therapies specifically targeting these events in B cell autoimmunity or malignancy and provide a fuller understanding of the appropriate target populations and potential negative consequences of Btk gene therapy in XLA. Identification of Btk/Tec family kinases in an increasing number of vertebrate and invertebrate cell lineages suggests that the link between Btk and the PLC gamma/IP3/calcium signaling pathways may be broadly conserved.

Body composition of preterm infants during infancy

AIMS

To examine body composition in preterm infants.

METHODS

Body composition was measured by dual energy x-ray absorptiometry (DEXA) at hospital discharge, term, 12 weeks, and at 6 and 12 months corrected age in 125 infants (birthweight < or = 1750 g, gestational age < or = 34 weeks).

RESULTS

Body weight derived by DEXA accurately predicted that determined by conventional scales. In both sexes lean mass (LM), fat mass (FM), %FM, bone area (BA), bone mineral mass (BMM), and bone mineral density (BMD) increased rapidly during the study; significant changes were detectable between discharge and term. At 12 months, LM, BA, and BMM, but not FM, %FM, or BMD were greater in boys than in girls. Corrected for age, LM was less than those of the reference term infant; FM and %FM were similar; BMM was greater. Corrected for weight, LM was similar to those of the reference infant, while the FM and %FM of study infants were slightly greater.

CONCLUSIONS

DEXA accurately measures body mass. Body composition in preterm boys and girls differs. Interpretation of DEXA values may depend on whether age or body weight are regarded as the appropriate reference.

In situ detection of activated Bruton's tyrosine kinase in the Ig signaling complex by phosphopeptide-specific monoclonal antibodies

Bruton's tyrosine kinase (Btk) is a critical transducer of signals originating from the B cell antigen receptor (BCR). Dosage, sequential phosphorylation, and protein interactions are interdependent mechanisms influencing Btk function. Phosphopeptide-specific mAbs recognizing two distinct phosphotyrosine modifications were used to quantify Btk activation by immunofluorescent techniques during B cell stimulation. In a population of cultured B cells stimulated by BCR crosslinking and analyzed by flow cytometry, transient phosphorylation of the regulatory Btk tyrosine residues (551Y and 223Y) was detected. The kinetics of phosphorylation of the residues were temporally distinct. Tyrosine 551, a transactivating substrate site for Src-family kinases, was maximally phosphorylated within approximately 30 seconds of stimulation as monitored by flow cytometry. Tyrosine 223, an autophosphorylation site within the SH3 domain, was maximally phosphorylated at approximately 5 minutes. Btk returned to a low tyrosine phosphorylation level within 30 minutes, despite persistent elevation of global tyrosine phosphorylation. Colocalization of activated Btk molecules with the crosslinked BCR signaling complex was observed to coincide with the period of maximal Btk tyrosine phosphorylation when stimulated B cells were analyzed with confocal microscopy. The results of these in situ temporal and spatial analyses imply that Btk signaling occurs in the region of the Ig receptor signaling complex, suggesting a similar location for downstream targets of its activity.

Case-control study of the pathogenesis and sequelae of symptomatic vertebral fractures in men

To investigate the pathogenesis and sequelae of symptomatic vertebral fractures (VF) in men, we have performed a case-control study, comparing 91 men with VF (median age 64 years, range 27-79 years) with 91 age-matched control subjects. Medical history, clinical examination and investigations were performed in all patients and control subjects, to identify potential causes of secondary osteoporosis, together with bone mineral density (BMD) measurements. BMD was lower at the lumbar spine and all sites in the hip in patients with VF than in control subjects (p < 0.001). Potential underlying causes of secondary osteoporosis were found in 41% of men with VF, compared with 9% of control subjects (OR 7.1; 95% CI 3.1-16.4). Oral corticosteroid and anti-convulsant treatment were both associated with a significantly increased risk of VF (OR 6.1; 95% CI 1.3-28.4). Although hypogonadism was not associated with an increased risk of fracture, the level of sex hormone binding globulin was higher (p < 0.001) and the free androgen index lower (p < 0.001) in men with VF than control subjects. Other factors associated with a significantly increased risk of VF were family history of bone disease (OR 6.1; 95% CI 1.3-28.4), current smoking (OR 2.8; 95% CI 1.2-6.7) and alcohol consumption of more than 250 g/week (OR 3.8; 95% CI 1.7-8.7). Men with VF were more likely to complain of back pain (p < 0.001) and greater loss of height (p < 0.001) than control subjects, and had poorer (p < 0.001) scores for the energy, pain, emotion, sleep and physical mobility domains of the Nottingham Health Profile. We conclude that symptomatic VF in men are associated with reduced BMD, underlying causes of secondary osteoporosis such as corticosteroid and anti-convulsant treatment, family history of bone disease, current smoking and high alcohol consumption, and that they impair the perceived health of the individual.

In vitro reconstitution of human B-cell ontogeny: from CD34(+) multipotent progenitors to Ig-secreting cells

We describe a long-term, in vitro culture system initiated with CD34(+) or CD34(+)CD38(-) umbilical cord blood hematopoietic progenitors that supports normal human B-lineage development, including the production of mature Ig-secreting B cells. In the first stage (human B-progenitor long-term culture [HB-LTC]), CD34(+) hematopoietic progenitors are cultured on the murine stromal cell line, S17, leading to the sustained production of large numbers of CD10(+), CD19(+) early B progenitors. Reverse transcriptase-polymerase chain reaction (RT-PCR) and three-parameter flow cytometry for VpreB (surrogate light chain), cytoplasmic mu chain, and surface IgM expression were used to characterize the CD19(+) B progenitors present within these cultures. This analysis showed distinct B-lineage subpopulations, including pro-B cells, cycling pre-B cells, and IgM+, IgD-/+ immature B cells. The limited expansion of IgM+ B cells and the immature surface phenotype of this population (IgM+, IgD+, CD10(+), CD38(+)) suggested that HB-LTC conditions were unable to provide appropriate signals for further differentiation. A second culture stage was used to determine if these immature B cells were functionally competent. Purified CD19(+) cells were transferred onto fibroblasts expressing human CD40-ligand in the presence of IL-10 and IL-4. This lead to cell proliferation, modulation of the IgM+ cell surface phenotype to one consistent with an activated mature B cell, secretion of Ig, and isotype switching. Notably, IgM and IgG producing B cells were also generated using two-stage cultures established with highly purified multipotent CD34(+)CD38(-) hematopoietic stem cell progenitors. This culture model should permit detailed in vitro analysis and genetic manipulation of the major transition points in human B ontogeny, beginning with commitment to the B lineage and leading to development and activation of mature B cells.

Comparison of ultrasound measurements at the heel between adults with mental retardation and control subjects

Little is known about the prevalence of metabolic bone disease among adults with mental retardation (now known as learning disability), although they may be at increased risk of fractures. Broadband-ultrasound attenuation (BUA) and velocity-of-sound (VOS) measurements were performed on the left heel of 170 patients in a large hospital for adults with mental retardation. For 108 of these patients, age- and gender-matched control subjects were recruited from the local community, who also underwent BUA and VOS measurements. The mean age of matched pairs of patients and control subjects was 54 (range 32-83) years for men and 53 (range 27-82) years for women. Mean +/- SEM BUA for male patients was 52 +/- 4 dB/MHz and 89 +/- 2 for control subjects, whereas for female patients it was 34 +/- 3 dB/MHz and 68 +/- 2 for control subjects. VOS was 1603 +/- 7 m/sec for male patients and 1649 +/- 5 for control subjects, and 1573 +/- 7 m/sec for female patients and 1623 +/- 5 for control subjects. All differences between patients and control subjects were significant (p < 0.005). Dual-energy X-ray absorptiometry bone mineral density (BMD) measurements were also performed in seven patients with BUA less than 50 dB/MHz, four of whom were found to have a lumbar spine or femoral neck BMD more than 2.5 SD below the mean value for young adults. This study shows that patients with mental retardation have a marked reduction in BUA and VOS measurements at the heel, compared with age-matched control subjects. There is a need to identify the major causes of low bone mass in this group, as there may be potentially avoidable risk factors for osteoporosis, such as vitamin D deficiency and hypogonadism.

Btk/Tec kinases regulate sustained increases in intracellular Ca2+ following B-cell receptor activation

Bruton's tyrosine kinase (Btk) is essential for B-lineage development and represents an emerging family of non-receptor tyrosine kinases implicated in signal transduction events initiated by a range of cell surface receptors. Increased dosage of Btk in normal B cells resulted in a striking enhancement of extracellular calcium influx following B-cell antigen receptor (BCR) cross-linking. Ectopic expression of Btk, or related Btk/Tec family kinases, restored deficient extracellular Ca2+ influx in a series of novel Btk-deficient human B-cell lines. Btk and phospholipase Cgamma (PLCgamma) co-expression resulted in tyrosine phosphorylation of PLCgamma and required the same Btk domains as those for Btk-dependent calcium influx. Receptor-dependent Btk activation led to enhanced peak inositol trisphosphate (IP3) generation and depletion of thapsigargin (Tg)-sensitive intracellular calcium stores. These results suggest that Btk maintains increased intracellular calcium levels by controlling a Tg-sensitive, IP3-gated calcium store(s) that regulates store-operated calcium entry. Overexpression of dominant-negative Syk dramatically reduced the initial phase calcium response, demonstrating that Btk/Tec and Syk family kinases may exert distinct effects on calcium signaling. Finally, co-cross-linking of the BCR and the inhibitory receptor, FcgammaRIIb1, completely abrogated Btk-dependent IP3 production and calcium store depletion. Together, these data demonstrate that Btk functions at a critical crossroads in the events controlling calcium signaling by regulating peak IP3 levels and calcium store depletion.

Phosphatidylinositol-3,4,5-trisphosphate (PtdIns-3,4,5-P3)/Tec kinase-dependent calcium signaling pathway: a target for SHIP-mediated inhibitory signals

Tec family non-receptor tyrosine kinases have been implicated in signal transduction events initiated by cell surface receptors from a broad range of cell types, including an essential role in B-cell development. A unique feature of several Tec members among known tyrosine kinases is the presence of an N-terminal pleckstrin homology (PH) domain. We directly demonstrate that phosphatidylinositol-3,4,5-trisphosphate (PtdIns-3,4,5-P3) interacting with the PH domain acts as an upstream activation signal for Tec kinases, resulting in Tec kinase-dependent phospholipase Cgamma (PLCgamma) tyrosine phosphorylation and inositol trisphosphate production. In addition, we show that this pathway is blocked when an SH2-containing inositol phosphatase (SHIP)-dependent inhibitory receptor is engaged. Together, our results suggest a general mechanism whereby PtdIns-3,4,5-P3 regulates receptor-dependent calcium signals through the function of Tec kinases.

Preliminary evidence for cyclosporin A as an alternative in the treatment of recalcitrant juvenile rheumatoid arthritis and juvenile dermatomyositis

OBJECTIVE

To evaluate the safety and efficacy of cyclosporin A (CyA) with and without methotrexate (MTX) in refractory juvenile rheumatoid arthritis (JRA) and juvenile dermatomyositis (JDMS).

METHODS

Twenty-two patients (17 with JRA, 5 with JDMS) with refractory disease were studied retrospectively. All received CyA at a mean dose of 3.2 mg/kg/day over a mean period of 16 mo (range 6-42). All other medications except nonsteroidal antiinflammatory drugs, prednisone, and hydroxychloroquine were discontinued. In addition, 16/22 patients received concomitant MTX.

RESULTS

Improvements in laboratory variables, joint counts, joint swelling, and morning stiffness were observed in most of the children with JRA. Muscle strength increased and muscle enzyme levels decreased in the patients with JDMS. CyA treatment permitted prednisone to be discontinued in 5/20 and reduced by greater than 50% in 10/20 patients. There was no evidence of hepatic or bone marrow toxicity or lymphoproliferative disease. Serum creatinine increased in 13/22 patients, but the actual values all remained within normal limits.

CONCLUSION

CyA may be an effective agent in the treatment of refractory JRA and JDMS and concomitant MTX seems to be well tolerated. These preliminary data also suggest that combined CyA/MTX therapy may be associated with further improvement in clinical outcome.

Phosphorylation of two regulatory tyrosine residues in the activation of Bruton's tyrosine kinase via alternative receptors

Mutation of Bruton's tyrosine kinase (Btk) impairs B cell maturation and function and results in a clinical phenotype of X-linked agammaglobulinemia. Activation of Btk correlates with an increase in the phosphorylation of two regulatory Btk tyrosine residues. Y551 (site 1) within the Src homology type 1 (SH1) domain is transphosphorylated by the Src family tyrosine kinases. Y223 (site 2) is an autophosphorylation site within the Btk SH3 domain. Polyclonal, phosphopeptide-specific antibodies were developed to evaluate the phosphorylation of Btk sites 1 and 2. Crosslinking of the B cell antigen receptor (BCR) or the mast cell Fcepsilon receptor, or interleukin 5 receptor stimulation each induced rapid phosphorylation at Btk sites 1 and 2 in a tightly coupled manner. Btk molecules were singly and doubly tyrosine-phosphorylated. Phosphorylated Btk comprised only a small fraction (</=5%) of the total pool of Btk molecules in the BCR-activated B cells. Increased dosage of Lyn in B cells augmented BCR-induced phosphorylation at both sites. Kinetic analysis supports a sequential activation mechanism in which individual Btk molecules undergo serial transphosphorylation (site 1) then autophosphorylation (site 2), followed by successive dephosphorylation of site 1 then site 2. The phosphorylation of conserved tyrosine residues within structurally related Tec family kinases is likely to regulate their activation.

Constitutive membrane association potentiates activation of Bruton tyrosine kinase

Mutations in the nonreceptor tyrosine kinase Btk result in the B cell immunodeficiencies X-linked agammaglobulinemia (XLA) in humans and X-linked immunodeficiency (xid) in mice. Genetic and biochemical evidence implicates Btk as a key component of several B cell signaling pathways. Activation of Btk by a point mutation (E41K) within the PH domain (Btk*) results in fibroblast transformation and is correlated with increased membrane localization of Btk. When wild type Btk is activated by coexpression with Lyn, the tyrosine phosphorylated pool of Btk is highly enriched in the membrane fraction. To determine whether membrane association is sufficient to activate Btk, we targeted Btk to the plasma membrane using a series of fusion proteins including GagBtk, CD16Btk and CD4Btk. Constitutive membrane association greatly enhanced the ability of Btk to transform Rat2 fibroblasts in the presence of high levels of Src activity. All membrane targeted forms of Btk were highly tyrosine phosphorylated. Transformation required membrane localization, Btk kinase activity, transphosphorylation by Src family kinases, and an intact SH2 domain but not the PH or SH3 domains. These data suggest that membrane localization is a critical early step in Btk activation.

Effect of intermittent cyclical disodium etidronate therapy on bone mineral density in men with vertebral fractures

OBJECTIVES

to investigate the effects of oral intermittent cyclical etidronate therapy on bone mineral density (BMD) in men with idiopathic vertebral osteoporosis.

DESIGN

consecutive case series.

SETTING

regional specialist clinic for metabolic bone disease.

SUBJECTS

42 men aged 35-81 (median 60.5) with established vertebral crush fractures and back pain, in whom secondary causes of osteoporosis had been excluded.

INTERVENTION

repeated cycles of treatment with oral disodium etidronate 400 mg daily for 14 days followed by oral calcium 500 mg as citrate daily for 76 days.

OUTCOME MEASURES

BMD measurement of the lumbar spine and femoral neck by dual energy x-ray absorptiometry at 6-12-month intervals; bone biochemistry (serum calcium, phosphate, alkaline phosphatase and urine calcium/creatinine and hydroxyproline/creatinine ratios) at 6-month intervals.

RESULTS

all 42 men have been treated for more than 18 months, and 35 of them for more than 24 months. Median follow-up for the group as a whole is 31 months (range 18-45). The treatment was well tolerated. BMD at the lumbar spine increased by a mean of 0.024 g/cm2 per year of follow-up (95% confidence interval 0.017-0.032 g/cm2). This is equivalent to an average annual rate of change of 3.2% of baseline values. There was a small, non-significant rise in mean BMD at the hip equivalent to 0.7% of baseline values per year. Serum alkaline phosphatase tended to fall in the first 6 months of treatment, returning to baseline values at 2 years. Serum calcium and phosphate were unchanged and no decrease in urinary calcium/creatinine ratio or hydroxyproline/creatinine ratio was seen.

CONCLUSIONS

intermittent cyclical etidronate therapy increased lumbar spine BMD over a 2-year period in an unselected group of men with osteoporotic vertebral fractures. This treatment warrants further evaluation in a randomized controlled trial.

Differentiation of human CD34+CD38- cord blood stem cells into B cell progenitors in vitro

Umbilical cord blood CD34+CD38- cells are a rare, quiescent, primitive progenitor subpopulation lacking expression of lymphoid and myeloid lineage specific antigens. Although myeloid, erythroid, and megakaryocytic differentiation from these cells has been described, B lineage differentiation has not been demonstrated previously. We report here that highly enriched human B cell progenitors can be consistently generated from CD34+CD38- cord blood cells using long-term culture on the murine stromal line, S17, in the absence of added cytokines. After 6-8 weeks, cell numbers increased up to 160-fold, and cultures contained > 80-90% CD10+CD19+ B progenitors. Consistent with previous reports describing delayed myeloid cell differentiation from CD34+CD38- cells, production of B cell progenitors from CD34+CD38- cord blood cells was delayed 2-4 weeks relative to cultures initiated with either CD34+CD38bright or CD34+CD38dim progenitors. Addition of Flt3 ligand to long-term cultures resulted in a 2-3-fold greater increase in the number of CD19+ cells generated after 4-8 weeks. The selective outgrowth of B cell progenitors using this culture model will be useful for a range of in vitro studies using primitive hematopoietic progenitors.

Assessment of effective dose to staff in brachytherapy

The aim of this paper is to investigate the problem of monitoring effective dose to hospital staff who are involved in the treatment of tumors using sealed sources placed inside the body (brachytherapy). In addition, the use of an unsealed source to treat the thyroid was also considered. Radiation distributions produced by both sealed sources commonly used in brachytherapy (192I, 137Cs, 226Ra) and an unsealed source used in the treatment of the thyroid (131I) were used to irradiate a Rando phantom. The brachytherapy treatments of esophageal and gynecological carcinoma were simulated. The Rando phantom was loaded with lithium fluoride thermoluminescent dosimeters at positions corresponding to a number of radiosensitive organs. Film badges and electronic personal dosimeters were attached to the Rando phantom at various anatomical sites. The Rando phantom was positioned adjacent to the patient at an angle of 90 degrees to the longitudinal axis of the patient. Irradiations were performed with and without a portable lead screen used on the radiotherapy wards. Effective dose was estimated for each simulated radiotherapy treatment and compared with the personal monitor readings. The data were used as a basis for the provision of advice on the wearing of the film badge dosimeters and the design of portable lead screens. The data also permitted a comparison between the two types of dosimeter when used for personal monitoring in brachytherapy.

Regulation of Btk by Src family tyrosine kinases

Loss of function of Bruton's tyrosine kinase (Btk) results in X-linked immunodeficiencies characterized by a broad spectrum of signaling defects, including those dependent on Src family kinase-linked cell surface receptors. A gain-of-function mutant, Btk*, induces the growth of fibroblasts in soft agar and relieves the interleukin-5 dependence of a pre-B-cell line. To genetically define Btk signaling pathways, we used a strategy to either activate or inactivate Src family kinases in fibroblasts that express Btk*. The transformation potential of Btk* was dramatically increased by coexpression with a partly activated c-Src mutant (E-378 --> G). This synergy was further potentiated by deletion of the Btk Src homology 3 domain. Downregulation of Src family kinases by the C-terminal Src kinase (Csk) suppressed Btk* activation and biological potency. In contrast, kinase-inactive Csk (K-222 --> R), which functioned as a dominant negative molecule, synergized with Btk* in biological transformation. Activation of Btk* correlated with increased phosphotyrosine on transphosphorylation and autophosphorylation sites. These findings suggest that the Src and Btk kinase families form specific signaling units in tissues in which both are expressed.

Regulation of Btk function by a major autophosphorylation site within the SH3 domain

Bruton's tyrosine kinase (Btk) plays a crucial role in B cell development. Overexpression of Btk with a Src family kinase increases tyrosine phosphorylation and catalytic activity of Btk. This occurs by transphosphorylation at Y551 in the Btk catalytic domain and the enhancement of Btk autophosphorylation at a second site. A gain-of-function mutant called Btk* containing E41 to K change within the pleckstrin homology domain induces fibroblast transformation. Btk* enhances the transphosphorylation of Y551 by endogenous Src family tyrosine kinases and autophosphorylation at the second site. We mapped the major Btk autophosphorylation site to Y223 within the SH3 domain. Mutation of Y223 to F blocks Btk autophosphorylation and dramatically potentiates the transforming activity of Btk* in fibroblasts. The location of Y223 in a potential ligand-binding pocket suggests that autophosphorylation regulates SH3-mediated signaling by Btk.

Uncertainties in dosemeter intercomparison techniques

The results of 180 intercomparisons of field dosemeters with an NPL secondary-standard exposure meter (type 2560, with a type 2561 chamber) have been analyzed in order to study variations in readings when ionization chambers are interchanged during the comparison process. It is suggested that the percentage standard error of the mean of the combined series of chamber intercomparisons be used to set a target uncertainty (0.3%), action level (0.5%) and limit of acceptability (1.0%). The target uncertainty is consistent with IAEA estimates of uncertainty for this part of the calibration chain. It is shown that if the calibration procedure is repeated, the percentage difference between the geometric means calculated from each calibration (i.e. a single interchange of chambers) may be as high as +/- 1%. This reinforces the need for at least one repetition of the intercomparison procedure.

Activation of BTK by a phosphorylation mechanism initiated by SRC family kinases

Bruton's tyrosine kinase (BTK) is pivotal in B cell activation and development through its participation in the signaling pathways of multiple hematopoietic receptors. The mechanisms controlling BTK activation were studied here by examination of the biochemical consequences of an interaction between BTK and SRC family kinases. This interaction of BTK with SRC kinases transphosphorylated BTK on tyrosine at residue 551, which led to BTK activation. BTK then autophosphorylated at a second site. The same two sites were phosphorylated upon B cell antigen receptor cross-linking. The activated BTK was predominantly membrane-associated, which suggests that BTK integrates distinct receptor signals resulting in SRC kinase activation and BTK membrane targeting.

Impaired expansion of mouse B cell progenitors lacking Btk

Mutations in the gene encoding the protein tyrosine kinase Btk are associated with the human B cell immunodeficiency X-linked agammaglobulinemia (XLA). In the mouse, a point mutation in the Btk pleckstrin homology domain segregates with a milder X-linked immunodeficiency (xid). To assess the importance of Btk function in murine lymphopoiesis, we generated multiple embryonic stem cell clones bearing a targeted disruption of the btk gene and examined their potential to produce lymphocytes in both C57BL/6 and RAG2-/- host chimeric animals. These mice provide a complementary set of in vivo competition assays that formally establish the genetic basis for the xid phenotype. Although the null mutation yields a phenotype quite similar to that of xid, it also compromises expansion of B cell precursors. Our results suggest that the murine and human consequences of Btk deficiency differ only quantitatively, and represent the same disease process.

The Btk subfamily of cytoplasmic tyrosine kinases: structure, regulation and function

The genetic defect associated with two closely related primary immunodeficiencies was recently identified as a deficiency of function of a new cytoplasmic tyrosine kinase, Bruton's tyrosine kinase (Btk). Btk and related genes expressed primarily in hematopoietic cells (Itk, Tec, Drsrc28C and Txk) comprise a new subfamily of cytoplasmic tyrosine kinases. These proteins share significant structural and sequence homology including an amino-terminal pleckstrin homology (PH) domain not present in other cytoplasmic tyrosine kinase subfamilies. This domain plays an essential role in regulation and function of the Btk subfamily proteins. Genetic evidence supports a critical role for Btk in B-lineage development. Additional studies demonstrate activation of these proteins in multiple hematopoietic signaling pathways including the B cell antigen receptor, several cytokine receptors, and a potential novel role in heterotrimeric G protein associated receptor signaling.

Long-term culture system for selective growth of human B-cell progenitors

We describe a simple reproducible system for enrichment and long-term culture of human B-cell progenitors. Enriched CD34+ cord blood mononuclear cells are seeded onto a murine stromal cell line to establish a biphasic culture system. These cultures are characterized by transient growth of myeloid cells followed by outgrowth of cells highly enriched for early B-cell progenitors. Cultures consisting of > 90% early B-lineage cells [expressing CD10, CD19, CD38, and CD45 but lacking CD20, CD22, CD23, and surface IgM] are maintained for > 12 weeks without growth factor addition. Cells remain predominantly germ line at the immunoglobulin locus and express only low levels of cytoplasmic mu chain, terminal deoxynucleotidyltransferase, and recombination-activating gene 1 product. They are unresponsive to the pre-B-cell growth factors interleukin 7 or stem cell factor, or both, suggesting that growth support is provided by a cross-reactive murine stromal cell factor. Cultured B-cell progenitors are generated in large numbers ( > 10(8) cells from a typical cord blood specimen) suitable for use in biochemical analysis and gene-transfer studies. This system should be useful for study of normal and abnormal early human B-lymphopoiesis.

A novel glucose-6-phosphate dehydrogenase in Plasmodium falciparum: cDNA and primary protein structure

The structure of the parasite-encoded G6PD (PfG6PD) may provide clues about the relative protection against malaria in humans with glucose-6-phosphate dehydrogenase (G6PD) deficiency. We have cloned Pfg6pd cDNA encoding a predicted 856 amino acid residues polypeptide with a calculated molecular mass of > 94 kDa. The predicted amino acid sequence is highly homologous to G6PD from other organisms. Pfg6pd maps as a single or low copy number gene to chromosome 14. The unusually large N-terminus and the distance between the NADP-binding site and G6PD-binding site is novel for the parasite G6PD. The differences between parasite and human G6PD proteins could potentially be exploited for designing new chemotherapeutic agents.

Deletion within the Src homology domain 3 of Bruton's tyrosine kinase resulting in X-linked agammaglobulinemia (XLA)

The gene responsible for X-linked agammaglobulinemia (XLA) has been recently identified to code for a cytoplasmic tyrosine kinase (Bruton's agammaglobulinemia tyrosine kinase, BTK), required for normal B cell development. BTK, like many other cytoplasmic tyrosine kinases, contains Src homology domains (SH2 and SH3), and catalytic kinase domain. SH3 domains are important for the targeting of signaling molecules to specific subcellular locations. We have identified a family with XLA whose affected members have a point mutation (g-->a) at the 5' splice site of intron 8, resulting in the skipping of coding exon 8 and loss of 21 amino acids forming the COOH-terminal portion of the BTK SH3 domain. The study of three generations within this kinship, using restriction fragment length polymorphism and DNA analysis, allowed identification of the mutant X chromosome responsible for XLA and the carrier status in this family. BTK mRNA was present in normal amounts in Epstein-Barr virus-induced B lymphoblastoid cell lines established from affected family members. Although the SH3 deletion did not alter BTK protein stability and kinase activity of the truncated BTK protein was normal, the affected patients nevertheless have a severe B cell defect characteristic for XLA. The mutant protein was modeled using the normal BTK SH3 domain. The deletion results in loss of two COOH-terminal beta strands containing several residues critical for the formation of the putative SH3 ligand-binding pocket. We predict that, as a result, one or more crucial SH3 binding proteins fail to interact with BTK, interrupting the cytoplasmic signal transduction process required for B cell differentiation.

Role of Bruton's tyrosine kinase in immunodeficiency

The genetic defect associated with human X-linked agammaglobulinemia and murine X-linked immunodeficiency was recently shown to result from lack of function of a new cytoplasmic tyrosine kinase, called Bruton's tyrosine kinase (Btk). The phenotypes associated with these immunodeficiencies indicate that Btk plays a critical role in B-lymphocyte development. The distinctive protein structure of Btk and preliminary functional studies suggest that Btk may act in a novel manner in a variety of signaling pathways.

Prolonged course of illness in a child with malignant lymphoma mimicking sarcoidosis

We describe a case of malignant lymphoma mimicking the rheumatic presentation of sarcoidosis in an adolescent with a 3-year history of febrile illness. Final diagnosis was established by tissue biopsy after multiple studies failed to provide histological evidence of granulomas consistent with sarcoidosis. We discuss the limited diagnostic specificity of serum angiotensin converting enzyme in sarcoidosis and emphasize the need for aggressive diagnostic evaluation of a patient whose clinical presentation is not fully explained by a known rheumatologic illness.

Mutation of unique region of Bruton's tyrosine kinase in immunodeficient XID mice

The cytoplasmic tyrosine kinase, Bruton's tyrosine kinase (Btk, formerly bpk or atk), is crucial for B cell development. Loss of kinase activity results in the human immunodeficiency, X-linked agammaglobulinemia, characterized by a failure to produce B cells. In the murine X-linked immunodeficiency (XID), B cells are present but respond abnormally to activating signals. The Btk gene, btk, was mapped to the xid region of the mouse X chromosome by interspecific backcross analysis. A single conserved residue within the amino terminal unique region of Btk was mutated in XID mice. This change in xid probably interferes with normal B cell signaling mediated by Btk protein interactions.

Acquired tracheoesophageal fistula in a premature infant

A fatality from an acquired tracheoesophageal fistula (TEF) in a very low birthweight premature infant is presented. Neonatal tracheal and esophageal injuries related to endotracheal (ET) intubation are discussed. The infant had important risk factors for the development of subglottic stenosis: birthweight less than 1000 gm, prolonged positive pressure ventilation, and repeated ET intubation. The pathologic examination was consistent with acquired fistula formation resulting from a combination of preexisting subglottic stenosis and prolonged and repeated ET intubation. The recognition of clinical signs of an acquired TEF, as observed in our patient, followed by expeditious diagnostic testing may be lifesaving.

Deficient expression of a B cell cytoplasmic tyrosine kinase in human X-linked agammaglobulinemia

We describe a novel cytoplasmic tyrosine kinase, termed BPK (B cell progenitor kinase), which is expressed in all stages of the B lineage and in myeloid cells. BPK has classic SH1, SH2, and SH3 domains, but lacks myristylation signals and a regulatory phosphorylation site corresponding to tyrosine 527 of c-src. BPK has a long, basic amino-terminal region upstream of the SH3 domain. BPK was evaluated as a candidate for human X-linked agammaglobulinemia (XLA), an inherited immunodeficiency characterized by a severe deficit of B and plasma cells and profound hypogammaglobulinemia. BPK mapped to within 100 kb of a probe defining the polymorphism most closely linked to XLA at DXS178. Reduction in or the absence of BPK mRNA, protein expression, and kinase activity was observed in XLA pre-B and B cell lines. BPK is likely the XLA gene and functions in pathways critical to B cell expansion.

Alpha-tubulin II is a male-specific protein in Plasmodium falciparum

The tubulin gene family in Plasmodium falciparum consists of one beta-tubulin and two alpha-tubulin genes (alpha-tubulin I and II). We present here data indicating that alpha-tubulin II is expressed only in male sexual stage parasites. An IgM mAb, 5E7, specifically reacted with stage III (day 4-5) through mature (day 10-11) male gametocytes and with emerging, exflagellating, or freely moving male gametes. No reactivity was detected in female gametocytes, female gametes, sporozoites, or asexual parasites. mAb 5E7 also specifically recognized male gametes of the avian parasite, Plasmodium gallinaceum, and immunoblotted a 50 kDa protein in extracts of male gametes from both species. This 50 kDa antigen was localized by immunoelectron microscopy to axonemes of male gametes in a pattern similar to that obtained with anti-alpha- and anti-beta-tubulin antibodies. Furthermore, mAb 5E7 specifically reacted with recombinant alpha-tubulin II protein obtained using the PCR-amplified alpha-tubulin II gene from a gametocyte-specific cDNA library. The sex-specific expression of alpha-tubulin II and its localization to axoneme of the male parasite suggest a role for this molecule in the morphologic changes that occur during exflagellation and in the motility of the parasite. alpha-Tubulin II and mAb 5E7 may prove useful tools in studies of the biology of sexual stage differentiation and development in P. falciparum in addition to the general understanding of post-translational modifications of tubulin isoforms.