Commentary on the published position statement regarding the pathogenesis of fetal basal ganglia- thalamic hypoxic-ischaemic injury

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MR imaging in the presence of ballistic debris of unknown composition: a review of the literature and practical approach

Due to a combination of increasing indications for MR imaging, increased MRI accessibility, and extensive global armed conflict over the last few decades, an increasing number of patients now and in the future will present with retained metallic ballistic debris of unknown composition. To date, there are no guidelines on how to safely image these patients which may result in patients who would benefit from MRI not receiving it. In this article, we review the current literature pertaining to the MRI safety of retained ballistic materials and present the process we use to safely image these patients.

Psychiatry heal thyself: a lifestyle intervention targeting mental health staff to enhance uptake of lifestyle interventions for people prescribed antipsychotic medication

Introduction

People experiencing severe mental illness (SMI) face a shortened life expectancy of up to 20 years, primarily due to preventable cardiovascular (CV) diseases. Lifestyle interventions are effective in reducing CV risk, yet examples of service-wide interventions are lacking. Staff culture remains a barrier to the successful implementation of lifestyle interventions. The Keeping the Body in Mind (KBIM) program, established by SESLHD (Australia), aims to close the gap in life expectancy through multidisciplinary teams, including clinical nurse consultants, dieticians, exercise physiologists, and peer support workers. Prior to the KBIM rollout, an individualized lifestyle intervention called Keeping Our Staff In Mind (KoSiM) was offered to all district mental health staff.

Objective

KoSiM examined the effectiveness of a staff intervention to improve physical health, confidence, knowledge and attitudes of mental health staff.

Methods

Mental health staffs were invited to participate in an online survey and a 4-week individualized intervention including personalised health screening and lifestyle advice, with a 16-week follow-up. Outcomes assessed included: attitudes, confidence and knowledge regarding metabolic health, weight, waist circumference (WC), blood pressure, sleep, diet, physical activity and exercise capacity.

Results

Of a total of 702 staff, 204 completed the survey (29%). Among those completing the survey, 154 staff (75%) participated in the intervention. A mean decrease in waist circumference of 2 ± 2.7 cm, (P < 0.001) was achieved. Among staffs that were overweight or obese at baseline, 75% achieved a decrease in WC.

Conclusion

Improving staff culture regarding physical health interventions is an important step in integrating lifestyle interventions into routine care.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Abstract P2-06-14: The role of SLC7A5 (LAT1) in endocrine therapy-resistant breast cancer

Endocrine therapies are commonly used to treat estrogen receptor-positive (ER+) breast cancers, which comprise 70% of all new breast cancer cases. Unfortunately, emergence of resistance to these therapies presents a major clinical challenge. Cancer cells can adapt to the dysregulation of cellular metabolism induced by endocrine therapy in order to evade cell death.Central to this adaptation is the scavenging of free-formed amino acids from the tumor microenvironment. For example, we found 109 solute carrier (SLC) mRNAs to be differentially expressed between endocrine-sensitive and resistant cells. We began our mechanistic studies of these genes with SLC family 7 member 5 (SLC7A5 or LAT1). SLC7A5 is a key component of a transmembrane transporter, which can complex with CD98 and increase the uptake of large, neutral amino acids (such as leucine or tyrosine).

We used a panel of endocrine therapy-resistant (LCC9) and sensitive (MCF7; LCC1) breast cancer cells. SLC7A5 expression was upregulated by estrogen in MCF7 and LCC1 cells; this induction was blocked by fulvestrant treatment. Basal expression of the SLC7A5 protein in the absence of estrogen was 2.75-fold higher in LCC9 cells compared with MCF7 cells; SLC7A5 mRNA expression was 71-fold higher. Fulvestrant treatment did not significantly alter SLC7A5 mRNA or protein expression in LCC9 cells. Inhibiting SLC7A5 function using either a pharmacological inhibitor (JPH203), or depleting expression using siRNA, led to significant suppression of LCC9 cell growth. Cell cycle analysis revealed that SLC7A5 depletion caused cells to accumulate in the G1-phase, with a concurrent reduction of cells in S-phase. In four publicly available datasets of ER+, tamoxifen treated breast cancer patients, high expression of SLC7A5 was significantly associated with poor relapse-free survival.

This study uncovers a novel adaptive mechanism in endocrine therapy-resistant breast cancer cells that is facilitated by increased expression of SLC7A5, which enables them to supplement their increased metabolic needs and promoting cell growth. Blocking the functions of SLC7A5, perhaps in conjunction with inhibition of autophagy, may therefore offer a new avenue of potential therapeutic intervention against endocrine therapy-resistant breast cancers.

Citation Format: Sevigny CM, Sengupta S, Luo Z, Jin L, Pearce D, Clarke R. The role of SLC7A5 (LAT1) in endocrine therapy-resistant breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-06-14.

Abstract P5-04-17: Local network topology differences between early and late recurrence in ER+ breast cancers

Background: Late recurrence is characteristic of ER+ breast cancers. Despite an apparently effective adjuvant endocrine therapy, many breast cancers recur years after their initial endocrine treatment. Why some tumors recur early (&lt;3 years) and some recur later (&gt;5 years) is poorly understood. If systemic endocrine therapies killed all cells, recurrence would reflect only the appearance of new disease. Thus, we hypothesized that cells that survive and lie dormant may be driven, in part, by altered wiring of their cell death signaling. We, therefore, studied how cell death signaling is differentially wired in primary tumors that will recur early versus those that will recur later.

Method: Genes involved in apoptosis, autophagy, ferroptosis, necrosis, and pyroptosis were identified from KEGG to initiate network feature analysis of gene expression data from public and our first in-house gene expression dataset. Data were collected from ER+ breast cancer pre-endocrine treatment samples with up to 20 years follow-up. Publicly available datasets used were GSE6532, GSE2034, GSE7390, GSE17705, GSE12093, and TCGA. We applied our Knowledge-fused Differential Dependency Network (KDDN) analysis tool to the public datasets; KDDN has provided powerful new insights into signaling in breast and other cancers. Common gene-gene interactions (edges) predicted in at least two different datasets were extracted from all KDDN analyses results. To strengthen the relevance of these features, predicted network edges that represent known protein-protein interactions (PPI) were identified from the STRING database, and these edges were noted in the signaling graphs. Final network graphs were constructed using the common edges from all overlaid networks. We conducted IPA analysis on all nodes in the final network and selected those incorporating network hubs. We took a similar approach to our second in-house dataset, which we used for independent testing. Here, patients were included if their tumor exhibited an initial reduction in volume of at least 40% by four months in response to neo-adjuvant Letrozole. Patients were then classified into two groups during follow-up of up to 3.7 years: i) initial tumor size reduction followed by continued response (expected to recur late); ii) initial reduction followed by tumor regrowth (expected to recur early). KDDN analysis was performed on pretreatment samples from these two groups and a network created annotated with PPI information.

Results: MAPK8 and CYCS (Molecular Mechanisms of Cancer, p=1.58E-52), TNFRSF1A Neuroinflammation Signaling Pathway, p=1.26E-54), RELA, and NFKB1 (Colorectal Cancer Metastasis Signaling, p=7.94E-35), were identified as hubs. Hubs may be critical signaling components driving the differences between tumors that will become dormant and recur late. Connections between SLC25A6 and SQSTM1 (p = 0.008), BIRC2 and GABARAP (p = 0.021) in the early group, and AKT3 and IRS2 (p = 0.014) in the late group, were shared between the two final networks. With longer follow-up time on the second in-house dataset, we will better define the two groups and identify additional common phenotype specific gene-gene interactions.

Citation Format: Clarke R, Dixon M, Jin L, Pearce D, Turnbull A, Selli C, Hu R, Zwart A, Wang Y, Xuan J, Sengupta S, Sims A, Liu MC. Local network topology differences between early and late recurrence in ER+ breast cancers [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-04-17.

Abstract P5-04-03: Molecular characterisation of ER+ breast cancer dormancy and acquired resistance using a clinical model: Potential involvement of epigenetic regulation

Background: The risk of recurrence for oestrogen receptor positive (ER+) breast cancer patients treated with 5 years of adjuvant endocrine therapy persists for many years or even decades following surgery and apparently successful adjuvant therapy. This period of dormancy and acquired resistance is inherently difficult to investigate. Therefore, previous efforts have been limited to in vitro or in vivo approaches. In this study sequential tumour samples from patients receiving extended neoadjuvant endocrine treatment were characterised as a novel clinical model of ER+ breast cancer dormancy and acquired resistance.

Methods: Consecutive tumour samples from 62 patients undergoing extended (4-45 months) neoadjuvant letrozole therapy were subjected to transcriptomic and proteomic analysis, representing pre- (before treatment), early-on (13-120 days) and long-term (&gt;120 days) neoadjuvant letrozole treatment. Patients with at least a 40% initial reduction in tumour size by 4 months of treatment were included. Of these, 42 patients with no subsequent progression were classified as “dormant”, and the remaining 20 patients as “acquired resistant”. Expression analysis was performed by using Illumina BeadChips. R and BioConductor packages were used for analysis. Differentially expressed genes were determined by using paired Rank Products (FDR, 5%).

Results: Multidimensional scaling using most variant 500 genes demonstrated that long-term treated dormant samples clustered separately from their matched pre- and early-on samples whereas long-term treated resistant samples were indistinguishable from their pre-treatment counterparts. Therapy-induced changes in resistant tumours were common features of treatment, rather than being specific to resistant phenotype. Comparative analysis of long-term treated dormant and resistant tumours highlighted changes in epigenetics pathways including DNA methylation and histone acetylation. DNA methylation marks 5-methylcytosine and 5-hydroxymethylcytosine were significantly reduced in resistant tumours compared to dormant tissues after extended letrozole treatment. Decrease in 5-hydroxymethylcytosine were significant early-on.

Conclusions: This is the first patient-matched gene expression study investigating long-term aromatase inhibitor-induced dormancy and acquired resistance in breast cancer. Dormant tumors exhibit distinct molecular changes under extended treatment whereas acquired resistant tumors are more similar to matched diagnostic samples supporting the molecular concordance between primary tumors and metastases. Global loss of DNA methylation was observed in resistant tumours under extended treatment which can be predicted within first 4 months of therapy. Epigenetic alterations may lead to escape from dormancy and drive acquired resistance in a subset of patients supporting a potential role for therapy targeted at these epigenetic alterations in the management of endocrine resistant breast cancer.

Funding: This work was supported by Marie Skłodowska-Curie Individual Fellowship [H2020-MSCA-IF, 658170] and Welcome Trust Institutional Fund (ISSF3) to CS and AHS, Breast Cancer Now to AHS.

Citation Format: Selli C, Turnbull AK, Pearce D, Fernando A, Renshaw L, Thomas JS, Dixon MJ, Sims AH. Molecular characterisation of ER+ breast cancer dormancy and acquired resistance using a clinical model: Potential involvement of epigenetic regulation [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-04-03.

Imaging of the Postoperative Condition of Posterolateral Corner Injuries

Posterolateral corner (PLC) injuries of the knee are often sustained in combination with anterior or posterior cruciate ligament injuries. A variety of surgical techniques including acute repair, nonanatomical reconstructions, and anatomical reconstructions have been used to treat grade III PLC injuries. Scant literature is available on postoperative imaging of the PLC. This article reviews the more commonly used surgical techniques and the postoperative imaging assessment of the PLC of the knee.

Bone mineral density predicts fractures in chronic kidney disease

Fractures are common in chronic kidney disease (CKD). The optimal methods by which to assess fracture risk are unknown, in part, due to a lack of prospective studies. We determined if bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA), and/or high-resolution peripheral quantitative computed tomography (HRpQCT) could predict fractures in men and women ≥18 years old with stages 3 to 5 CKD. BMD was measured by DXA (at the total hip, lumbar spine, ultradistal, and 1/3 radius) and by HRpQCT (at the radius), and subjects were followed for 2 years for incident morphometric spine fractures and low-trauma clinical fractures. The mean age of the subjects was 62 years with equal numbers having stages 3, 4, and 5 CKD. Over 2 years there were 51 fractures in 35 subjects. BMD by DXA at baseline was significantly lower at all sites among those with incident fractures versus those without. For example, the mean BMD at the total hip in those with incident fractures was 0.77 g/cm2 (95% confidence interval [CI], 0.73 to 0.80) and in those without fracture was 0.95 g/cm2 (95% CI, 0.92 to 0.98). Almost all baseline HRpQCT measures were lower in those with incident fracture versus those without. For example, volumetric BMD in those with incident fractures was 232 mg HA/cm3 (95% CI, 213 to 251) and in those without fracture was 317.6 mg HA/cm3 (95% CI, 306 to 329.1). Bone loss occurred in all subjects, but was significantly greater among those with incident fractures. Our data demonstrate that low BMD (by DXA and HRpQCT) and a greater annualized percent decrease in BMD are risk factors for subsequent fracture in men and women with predialysis CKD.

The radiographic quantification of scapular malalignment after malunion of displaced clavicular shaft fractures

BACKGROUND

Malunion after displaced fractures of the clavicle can result in varying degrees of scapular malalignment and potentially scapular winging. The purpose of our study was to quantify the scapular malalignment in patients with midshaft clavicle malunions showing scapular winging.

METHODS

Eighteen patients with symptomatic midshaft clavicle malunions showing scapular winging were identified and underwent standardized computed tomography scanning of the thorax. Specific bony landmarks on the clavicle and scapula were digitized, allowing generation of 3-dimensional points. These points were acquired bilaterally so that relative translations comparing the malunited side with the contralateral side could be obtained. Statistical analysis using a paired t test was performed.

RESULTS

The mean time from fracture to examination was 42.9 months. There were 15 men and 3 women with a mean age of 41.6 years. The mean clavicular shortening was 21.1 mm (P = .0000004). The acromion of the affected scapula on average translated 24.3 mm. The components of this translation were medial, 11.9 mm (P = .00008); inferior, 20.7 mm (P = .0009); and anterior, 4.6 mm (P = .02). Posterior bony landmarks on the scapula including the superior and inferior angles of the scapula translated a total of 9.9 mm and 5.9 mm, respectively.

CONCLUSION

This is the first study to document the degree of scapular malalignment in patients with symptomatic clavicle malunions showing scapular winging. The acromion closely follows the distal clavicular fragment and translates medially, inferiorly, and anteriorly. The translations of the superior and inferior angles of the scapula are quite variable in magnitude and direction, and on average, these angles translate substantially less than the acromion.

Computer navigation in the reduction and fixation of femoral shaft fractures: a randomized control study

OBJECTIVES

We investigated the accuracy of reduction of intramedullary nailed femoral shaft fractures in human cadavers, comparing conventional and computer navigation techniques.

METHODS

Twenty femoral shaft fractures were created in human cadavers, with segmental defects ranging from 9 to 53 mm in length (Winquist 3-4, AO 32C2). All fractures were fixed with antegrade 9 mm diameter femoral nails on a radiolucent operating table. Five fractures ("Fluoro" group) were fixed with conventional techniques and fifteen fractures ("Nav 1" and "Nav 2" groups) with computer navigation, using fluoroscopic images of the normal femur to correct for length and rotation. Postoperative CT scans compared femoral length and rotation with the normal leg.

RESULTS

Mean leg length discrepancy in the computer navigation groups was smaller, namely, 3.6 mm for Nav 1 (95% CI: 1.072 to 6.128) and 4.2 mm for Nav 2 (95% CI: 0.63 to 7.75) vs. 9.8 mm for Fluoro (95% CI: 6.225 to 13.37) (p<0.023). Mean rotational discrepancies were 8.7° for Nav 1 (95% CI: 4.282 to 13.12) and 5.6° for Nav 2 (95% CI: -0.65 to 11.85) vs. 9.0° for Fluoro (95% CI: 2.752 to 15.25) (p=0.650).

CONCLUSIONS

Computer navigation significantly improves the accuracy of femoral shaft fracture fixation with regard to leg length, but not rotational deformity.

The Glucocorticoid-induced leucine zipper (GILZ) Is essential for spermatogonial survival and spermatogenesis

Spermatogenesis relies on the precise regulation of the self-renewal and differentiation of spermatogonia to provide a continuous supply of differentiating germ cells. The understanding of the cellular pathways regulating this equilibrium remains unfortunately incomplete. This investigation aimed to elucidate the testicular and ovarian functions of the glucocorticoid-induced leucine zipper protein (GILZ) encoded by the X-linked Tsc22d3 (Gilz) gene. We found that GILZ is specifically expressed in the cytoplasm of proliferating spermatogonia and preleptotene spermatocytes. While Gilz mutant female mice were fully fertile, constitutive or male germ cell-specific ablation of Gilz led to sterility due to a complete absence of post-meiotic germ cells and mature spermatozoa. Alterations were observed as early as postnatal day 5 during the first spermatogenic wave and included extensive apoptosis at the spermatogonial level and meiotic arrest in the mid-late zygotene stage. Overall, these data emphasize the essential role played by GILZ in mediating spermatogonial survival and spermatogenesis.

Control of Mycobacterium tuberculosis growth by activated natural killer cells

We characterized the underlying mechanisms by which glutathione (GSH)-enhanced natural killer (NK) cells inhibit the growth of Mycobacterium tuberculosis (M. tb) inside human monocytes. We observed that in healthy individuals, treatment of NK cells with N-acetyl cysteine (NAC), a GSH prodrug in conjunction with cytokines such as interleukin (IL)-2 + IL-12, resulted in enhanced expression of NK cytotoxic ligands (FasL and CD40L) with concomitant stasis in the intracellular growth of M. tb. Neutralization of FasL and CD40L in IL-2 + IL-12 + NAC-treated NK cells resulted in abrogation in the growth inhibition of M. tb inside monocytes. Importantly, we observed that the levels of GSH are decreased significantly in NK cells derived from individuals with HIV infection compared to healthy subjects, and this decrease correlated with a several-fold increase in the growth of M. tb inside monocytes. This study describes a novel innate defence mechanism adopted by NK cells to control M. tb infection.

Akt2/PKBbeta-sensitive regulation of renal phosphate transport

AIM

The protein kinase B (PKB)/Akt is known to stimulate the cellular uptake of glucose and amino acids. The kinase is expressed in proximal renal tubules. The present study explored the influence of Akt/PKB on renal tubular phosphate transport.

METHODS

The renal phosphate transporter NaPi-IIa was expressed in Xenopus oocytes with or without PKB/Akt and Na(+) phosphate cotransport determined using dual electrode voltage clamp. Renal phosphate excretion was determined in Akt2/PKBbeta knockout mice (akt2(-/-)) and corresponding wild-type mice (akt2(+/+)). Transporter protein abundance was determined using Western blotting and phosphate transport by (32)P uptake into brush border membrane vesicles.

RESULTS

The phosphate-induced current in NaPi-IIa-expressing Xenopus oocytes was significantly increased by the coexpression of Akt/PKB. Phosphate excretion [micromol per 24 h per g BW] was higher by 91% in akt2(-/-) than in akt2(+/+) mice. The phosphaturia of akt2(-/-) mice occurred despite normal transport activity and expression of the renal phosphate transporters NaPi-IIa, NaPi-IIc and Pit2 in the brush border membrane, a significantly decreased plasma PTH concentration (by 46%) and a significantly enhanced plasma 1,25-dihydroxyvitamin D(3) concentration (by 46%). Moreover, fractional renal Ca(2+) excretion was significantly enhanced (by 53%) and bone density significantly reduced (by 11%) in akt2(-/-) mice.

CONCLUSIONS

Akt2/PKBbeta plays a role in the acute regulation of renal phosphate transport and thus contributes to the maintenance of phosphate balance and adequate mineralization of bone.

Injury patterns to the posteromedial corner of the knee in high-grade multiligament knee injuries: a MRI study

Injury patterns to the posteromedial corner of the knee have not been previously studied in the context of multiligament knee injuries. We performed a retrospective magnetic resonance imaging and clinical review of a consecutive series of 27 dislocatable knees presenting to a single level-one trauma center from 2005 to 2008. Post-injury magnetic resonance imaging studies were reviewed by two fellowship-trained musculoskeletal radiologists to assess injury patterns to the posteromedial corner. In our series, injury to at least one structure within the posteromedial corner was observed in 81% (22/27) of cases while injury to the superficial medial collateral ligament alone was seen in 63% (17/27) of cases. Furthermore, injuries to the posterior horn of the medial meniscus were associated with a tear of the meniscotibial ligaments in all cases and with a tear of the posterior oblique ligament in 67% of cases. All patients with grade III laxity (>10 mm medial opening) under an examination under anesthesia had a complete tear of the posterior oblique ligament and meniscotibial ligament in addition to a medial collateral ligament injury. Injury to the semimembranosus attachment alone was not associated with clinically significant laxity under an examination under anesthesia. Our findings demonstrate that injuries to the posteromedial corner are common in the setting of traumatic knee dislocations. Interestingly, high-grade medial instability during an examination under anesthesia and injury to the posterior horn of the medial meniscus may be important indicators for further posteromedial corner injury.

Gibberellins: a phytohormonal basis for heterosis in maize

Four commercially important maize parental inbreds and their 12 F(1) hybrids were studied to investigate the role of the phytohormone gibberellin (GA) in the regulation of heterosis (hybrid vigor). All hybrids grew faster than any inbred. In contrast, all inbreds showed a greater promotion of shoot growth after the exogenous application of GA(3). Concentrations of endogenous GA(1), the biological effector for shoot growth in maize, and GA(19), a precursor of GA(1), were measured in apical meristematic shoot cylinders for three of the inbreds and their hybrids by gas chromatography-mass spectrometry with selected ion monitoring; deuterated GAs were used as quantitative internal standards. In 34 of 36 comparisons, hybrids contained higher concentrations of endogenous GAs than their parental inbreds. Preferential growth acceleration of the inbreds by exogenous GA(3) indicates that a deficiency of endogenous GA limits the growth of the inbreds and is thus a cause of inbreeding depression. Conversely, the increased endogenous concentration of GA in the hybrids could provide a phytohormonal basis for heterosis for shoot growth.

Weightbearing CT scan of severe flexible pes planus deformities

BACKGROUND

The three-dimensional relationships of the bones in the foot in a flatfoot deformity are difficult to assess with standard radiographs. CT scans demonstrate these relationships but are typically made in a nonweightbearing mode. Our objective was to assess the use of a weightbearing CT apparatus to image the feet in patients with severe flexible pes planus deformities and to better define the anatomical changes that occur.

MATERIALS AND METHODS

A specialized device was designed and constructed to simulate weightbearing to the feet during CT examination. Eighteen normal feet and 30 painful severe and flexible pes planus feet were imaged in both the non weightbearing and weightbearing states, set at 50% of body weight. Several measurements of intertarsal relationships were made of the pes planus and normal feet. Navicular floor to skin distance, forefoot arch angle, and subtalar joint subluxation were measured in the coronal plane in both the weightbearing and nonweightbearing states. T-tests were used to analyze measurements of navicular floor to skin distance and forefoot arch angle.

RESULTS

The weightbearing device had a significant effect on foot configuration for both normal and pes planus feet (p = 0.0008) and (p < 0.0001) respectively for both floor to skin distance and forefoot arch angle. There was a significant difference between normal feet and pes planus feet with regard to the forefoot arch angle in the nonweightbearing (p = 0.02) and weightbearing states (p = 0.01). Four of the pes planus patients had evidence of subtalar joint subluxation which was more pronounced in the weightbearing state. There was no significant difference between the navicular floor to skin distance in the normal versus pes planus feet in either the non weightbearing (p = 0.05) or the weightbearing states (p = 0.07).

CONCLUSION

A device was designed and constructed to apply a weightbearing load equal to that of 50% body weight with minimal to no patient discomfort. The resultant effects on foot configuration were significant, and are useful for assessment of degree of flexible flat foot deformity, thus guiding clinical management. The measure which most significantly differed between pes planus patients and normal volunteers was the forefoot arch angle. Forefoot arch angle may therefore be the most useful measure for the imaging diagnosis of flexible pes planus, and the degree of planus deformity.

Prevalence of vertebral fractures in adults with cystic fibrosis and their relationship to bone mineral density

STUDY OBJECTIVES

The objectives of this study were to determine the prevalence of morphometric vertebral fractures in a large cohort of adult cystic fibrosis (CF) patients, and to examine the association between fractures and bone mineral density (BMD).

DESIGN

Cross-sectional retrospective study.

SETTING

A tertiary care academic hospital.

PATIENTS

Adult CF patients who had undergone BMD testing and chest radiography within 1 month of each other.

MEASUREMENTS AND RESULTS

BMD was measured by dual-energy x-ray absorptiometry (DXA) at the lumbar spine (LS) and femoral neck (FN). Vertebral fractures were diagnosed using lateral chest radiographs. Several clinical and biochemical variables were assessed as correlates. Sixty subjects (36%) had z scores between -1.0 and -2.5, and 15 subjects (9%) had z scores of < -2.5. Twelve patients (7.2%) had 19 morphometric fractures. The mean BMD at the LS was 1.266 g/cm(2) in the fracture group and 1.112 g/cm(2) in the nonfracture group (p = 0.0002). The mean BMD at the FN was 1.129 g/cm(2) in the fracture group and 0.987 g/cm(2) in the nonfracture group (p = 0.0006). Both FEV(1) and body mass index were significantly associated with BMD at both the LS and the FN.

CONCLUSION

Seven percent of adult patients with CF had vertebral fractures as determined by morphometry. Subjects in the fracture group had both clinically and statistically higher BMD as measured by DXA. Our findings raise the intriguing possibility that BMD may not be useful in identifying CF patients with fractures.

Steroid receptor coactivator-1 splice variants differentially affect corticosteroid receptor signaling

The mechanisms of receptor- and cell-specific effects of the adrenal corticosteroid hormones via mineralo- (MRs) and glucocorticoid receptors (GRs) are still poorly understood. Because the expression levels of two splice variants of the steroid receptor coactivator-1 (SRC-1) 1a and 1e, can differ significantly in certain cell populations, we tested the hypothesis that their relative abundance could determine cell- and receptor-specific effects of corticosteroid receptor-mediated transcription. In transient transfections, we demonstrate three novel types of SRC-1a- and SRC-1e-specific effects for corticosteroid receptors. One is promoter dependence: SRC-1e much more potently coactivated transcription from several multiple response element-containing promoters. Mammalian 1-hydrid studies indicated that this likely does not involve promoter-specific coactivator recruitment. Endogenous phenylethanolamine-N-methyltransferase mRNA induction via GRs was also differentially affected by the splice variants. Another type is receptor specificity: responses mediated by the N-terminal part of the MR, but not the GR, were augmented by SRC-1e at synergizing response elements. SRC fragment SRC(988-1240) by the MR but not the GR N-terminal fragment in a 1-hybrid assay. The last type, for GRs, is ligand dependence. Due to effects on partial agonism of RU486-activated GRs, different ratios of SRC-1a and 1e can lead to large differences in the extent of antagonism of RU486 on GR-mediated transcription. Furthermore, we show that SRC-1e but not SRC-1a mRNA expression was regulated in the pituitary by corticosterone. We conclude that the cellular differences in SRC-1a to SRC-1e ratio demonstrated in vivo might be involved in cell-specific responses to corticosteroids in a promoter- and ligand-dependent way.

The Indications for and the Prognostic Significance of Amputation as the Primary Surgical Procedure for Localized Soft Tissue Sarcoma of the Extremity

BACKGROUND

The indications for primary amputation of a localized soft tissue sarcoma (STS) of the extremity are not well defined in the literature. However, it has been suggested that patients who require an amputation to treat an STS are at increased risk for developing metastases. We categorized the main indications for primary amputation in our patient population and compared their oncological outcome with the outcome of patients who underwent limb-sparing surgery.

METHODS

413 consecutive patients treated surgically at a single center for primary, nonmetastatic, deep, intermediate-, or high-grade STS of the extremity were reviewed. Indications for primary amputation were identified. Demographics and outcomes were compared between the amputation and limb-salvage groups. Multivariate Cox model analysis was used to identify independent risk factors for systemic relapse.

RESULTS

Twenty-five (6%) of 413 patients with STS underwent primary amputation: they were older (P = .05), had larger tumors (P = .001), and had a significantly greater risk of developing metastatic disease than patients who underwent limb-sparing procedures (P = .008). However, multivariate analysis demonstrated that the only independent predictors of systemic relapse were tumor size (P = .0001) and tumor grade (P = .0001). Primary amputation was not an independent risk factor for metastatic disease.

CONCLUSIONS

The decision to perform a primary amputation for an STS of the extremity is based on the location and local extent of the tumor, and the expected function of the extremity after tumor resection. The higher risk of metastases for patients who require primary amputation is accounted for by independent risk factors associated with their tumors--predominantly large tumor size.

Distinguishing transient osteoporosis of the hip from avascular necrosis

INTRODUCTION

To review the circumstances surrounding the misdiagnosis of transient osteoporosis of the hip (TOH) as avascular necrosis (AVN) and to increase physician awareness of the prevalence and diagnosis of this condition in young men, we reviewed a series of cases seen in the orthopedic unit at St. Michael's Hospital, University of Toronto.

METHODS

We studied the charts of patients with TOH referred between 1998 and 2001 with a diagnosis of AVN for demographic data, risk factors, imaging results and outcomes.

RESULTS

Twelve hips in 10 young men (mean age 41 yr, range from 32-55 yr) were identified. Nine men underwent magnetic resonance imaging (MRI) before referral, which showed characteristic changes of TOH. All 10 patients were referred for surgical intervention for a diagnosis of AVN. The correct diagnosis was made after reviewing patients' charts and the scans and was confirmed by spontaneous resolution of both symptoms and MRI findings an average of 5.5 months and 7.5 months, respectively, after consultation.

CONCLUSIONS

Despite recent publications, the prevalence of TOH among young men is still overlooked and the distinctive MRI appearance still misinterpreted. Symptoms may be severe but resolve over time with reduced weight bearing. The absence of focal changes on MRI is highly suggestive of a transient lesion. A greater level of awareness of this condition is needed to differentiate TOH from AVN, avoiding unnecessary surgery and ensuring appropriate treatment.

The serine/threonine kinases SGK2 and SGK3 are potent stimulators of the epithelial Na+ channel alpha,beta,gamma-ENaC

The serum- and glucocorticoid-inducible kinase 1 (SGK1) has been identified as a signalling molecule up-regulated by aldosterone, which stimulates the renal epithelial Na(+) channel ENaC. It is therefore thought to participate in the antinatriuretic action of this hormone. More recently, two isoforms, SGK2 and SGK3, have been cloned. The present study was performed to establish whether SGK2 and SGK3 influence ENaC activity similarly to SGK1. Dual-electrode voltage-clamp experiments in Xenopus laevis oocytes expressing alpha,ss,gamma-ENaC with or without SGK1, SGK2 or SGK3 revealed a stimulatory effect of all three kinases on the amiloride-sensitive current (I(Na)). To establish whether the SGK isoforms exert their effects through direct phosphorylation, we replaced the serine at the SGK consensus site of alphaENaC (alpha(S622A)ENaC) by site-directed mutagenesis. alpha(S622A),beta,gamma-ENaC was up-regulated similar to wild-type ENaC, suggesting that SGK isoforms do not act via direct phosphorylation of the transport proteins. In conclusion, SGK2 and SGK3 mimic the function of SGK1 and are likely to participate in the regulation of ENaC activity.

The sizes and characteristics of the minority ethnic populations of Great Britain--latest estimates

This article presents estimates of the minority ethnic populations of Great Britain in 2000 and describes the regional distributions of the different groups. It also discusses changes in the sizes of the different minority ethnic populations during the 1990s. The paper provides information on some key demographic features of these populations at the end of the 1990s--age and sex structures, proportions born in the United Kingdom and whether children lived with their natural parents.

The demographic situation in the European Union

This article draws selected material from the annual Yearbook on Demography (2000 edition) published by Eurostat, the Statistical Office of the European Communities. Some key comparisons with other regions of the world are included, together with a broad picture of the demographic situation in the European Union. Topic coverage is selective.

The role of SGK1 in hormone-regulated sodium transport

Ion transport in epithelia is regulated by a variety of hormonal and nonhormonal factors, including mineralocorticoids, insulin, shear stress and osmotic pressure. In mammals, the mineralocorticoid aldosterone is the principal regulator of sodium homeostasis and hence is central to the control of extracellular fluid volume and blood pressure. Aldosterone acts through a member of the nuclear receptor superfamily, the mineralocorticoid receptor (MR), to control the transcriptional activity of specific target genes. Recently, a serine/threonine kinase, SGK1 (serum and glucocorticoid-regulated kinase isoform 1) was identified as a candidate mediator of aldosterone action in the colon and distal nephron. The aldosterone-activated MR increases SGK1 gene transcription and SGK1, in turn, strongly stimulates the activity of the epithelial sodium channel (ENaC). Interestingly, other factors appear to regulate SGK1 gene expression and kinase activity. Insulin, for example, stimulates SGK1 activity (but not gene transcription) through its effects on phosphatidylinositol-3-kinase and osmotic shock appears to stimulate both SGK1 activity and gene transcription. Hence, SGK1 might integrate the effects of multiple hormonal and nonhormonal regulators of Na(+) transport in tight epithelia and thereby play a key role in volume homeostasis. It is interesting to speculate that SGK1 might be implicated in medical conditions, such as the insulin resistance syndrome, hypertension and congestive heart failure.

Aldosterone induces rapid apical translocation of ENaC in early portion of renal collecting system: possible role of SGK

Aldosterone controls sodium reabsorption and potassium secretion in the aldosterone-sensitive distal nephron (ASDN). Although clearance measurements have shown that aldosterone induces these transports within 30--60 min, no early effects have been demonstrated in vivo at the level of the apical epithelial sodium channel (ENaC), the main effector of this regulation. Here we show by real-time RT-PCR and immunofluorescence that an aldosterone injection in adrenalectomized rats induces alpha-ENaC subunit expression along the entire ASDN within 2 h, whereas beta- and gamma-ENaC are constitutively expressed. In the proximal ASDN portions only, ENaC is shifted toward the apical cellular pole and the apical plasma membrane within 2 and 4 h, respectively. To address the question of whether the early aldosterone-induced serum and glucocorticoid-regulated kinase (SGK) might mediate this apical shift of ENaC, we analyzed SGK induction in vivo. Two hours after aldosterone, SGK was highly induced in all segment-specific cells of the ASDN, and its level decreased thereafter. In Xenopus laevis oocytes, SGK induced ENaC activation and surface expression by a kinase activity-dependent mechanism. In conclusion, the rapid in vivo accumulation of SGK and alpha-ENaC after aldosterone injection takes place along the entire ASDN, whereas the translocation of alpha,beta,gamma-ENaC to the apical plasma membrane is restricted to its proximal portions. Results from oocyte experiments suggest the hypothesis that a localized activation of SGK may play a role in the mediation of ENaC translocation.

The serum- and glucocorticoid-induced kinase is a physiological mediator of aldosterone action

Aldosterone plays a major role in regulating sodium and potassium flux in epithelial tissues such as kidney and colon. Recent evidence suggests that serum- and glucocorticoid-regulated kinase (SGK) is induced by aldosterone and acts as a key mediator of aldosterone action in epithelial tissues. Induction of SGK messenger RNA (mRNA) has previously been shown within 30 min of addition of supraphysiological doses of aldosterone to Xenopus A6 cells and within 4 h in rat kidney in vivo. In this study we determined the time course of SGK induction, at doses of aldosterone in the physiological range, in rat kidney and colon, using Northern and Western blot analyses and in situ hybridization and determined concurrent changes in urinary sodium and potassium excretion by Kagawa bioassay. On Northern blot analysis, SGK mRNA levels were significantly elevated in both kidney and colon 60 min after the injection of aldosterone. SGK protein in late distal colon was significantly elevated 2 and 4 h after aldosterone treatment. In situ hybridization showed SGK mRNA to be induced in renal collecting ducts and distal tubular elements in both cortex and medulla by doses of aldosterone of 0.1 microg/100 g BW or more within 30 min of steroid treatment. Significant changes in urinary composition were similarly seen with an aldosterone dose of 0.1 microg/100 g BW from 90 min after aldosterone injection. The early onset of SGK induction in kidney and colon and the correlation with urinary changes in terms of both time course and dose response suggest that SGK plays an important role in mediating the effects of aldosterone on sodium homeostasis in vivo.

SGK integrates insulin and mineralocorticoid regulation of epithelial sodium transport

The epithelial Na+ channel (ENaC) constitutes the rate-limiting step for Na+ transport across tight epithelia and is the principal target of hormonal regulation, particularly by insulin and mineralocorticoids. Recently, the serine-threonine kinase (SGK) was identified as a rapidly mineralocorticoid-responsive gene, the product of which stimulates ENaC-mediated Na+ transport. Like its close relative, protein kinase B (also called Akt), SGK's kinase activity is dependent on phosphatidylinositol 3-kinase (PI3K), a key mediator of insulin signaling. In our study we show that PI3K is required for SGK-dependent stimulation of ENaC-mediated Na+ transport as well as for the production of the phosphorylated form of SGK. In A6 kidney cells, mineralocorticoid induction of the phosphorylated form of SGK preceded the increase in Na+ transport, and specific inhibition of PI3K inhibited both phosphorylation of SGK and mineralocorticoid-induced Na+ transport. Insulin both augmented SGK phosphorylation and synergized with mineralocorticoids in stimulating Na+ transport. In a Xenopus laevis oocyte coexpression assay, SGK-stimulated ENaC activity was also markedly reduced by PI3K inhibition. Finally, in vitro-translated SGK specifically interacted with the ENaC subunits expressed in Escherichia coli as glutathione S-transferase fusion proteins. These data suggest that SGK is a PI3K-dependent integrator of insulin and mineralocorticoid actions that interacts with ENaC subunits to control Na+ entry into kidney collecting duct cells.

Safety of oral versus intravenous hydration during induction therapy with intravenous foscarnet in AIDS patients with cytomegalovirus infections

We undertook a study to compare the safety of intravenous (i.v.) versus oral hydration to prevent nephrotoxicity associated with the use of foscarnet for induction therapy of cytomegalovirus (CMV) infection in HIV-infected persons. Patients, given foscarnet at a dose of 90 mg/kg every 12 h, were randomized to receive either i.v. or oral hydration. Thirty-seven patients were given i.v. hydration and 44 were given oral hydration. Median duration of therapy for both groups was 17 days. There was no difference between the 2 groups in either serious adverse events or rise of creatinine to > or = 2.0 mg/dl. However, serum creatinine, while generally remained within normal limits, increased more in patients who received oral hydration after 10 days of therapy (significant only by slope analysis, P < 0.05). Although i.v. hydration provided better protection against nephrotoxicity, oral hydration was relatively safe and convenient provided that creatinine clearance (CrCl) is monitored closely.

Human immunodeficiency virus type 1 Vpr contains two leucine-rich helices that mediate glucocorticoid receptor coactivation independently of its effects on G(2) cell cycle arrest

Human immunodeficiency virus type 1 (HIV-1) Vpr participates in nuclear targeting of the viral preintegration complex in nondividing cells and induces G(2) cell cycle arrest in proliferating cells, which creates an intracellular milieu favorable for viral replication. Vpr also activates the transcription of several promoters and enhancers by a poorly understood mechanism. Vpr enhances glucocorticoid receptor (GR) signaling and may mediate the effects of steroids on HIV replication. More specifically, recombinant Vpr can potentiate virion production from U937 cells, downregulate NF-kappaB induction, and enhance programmed cell death, all effects also mediated by glucocorticoids. Vpr has been proposed to act as a GR coactivator, although other studies suggest that these enhancing effects are merely a consequence of G(2) cell cycle arrest. We now demonstrate that Vpr functions as a GR coactivator and that this activity is independent of cell cycle arrest. In addition, we show that the Vpr-induced coactivation requires an intact glucocorticoid response element, that it is dependent on the presence of hormone and the corresponding receptor, and that it is mediated by the two highly conserved leucine-rich domains within Vpr that resemble the GR coactivator signature motif.

A common motif within the negative regulatory regions of multiple factors inhibits their transcriptional synergy

DNA regulatory elements frequently harbor multiple recognition sites for several transcriptional activators. The response mounted from such compound response elements is often more pronounced than the simple sum of effects observed at single binding sites. The determinants of such transcriptional synergy and its control, however, are poorly understood. Through a genetic approach, we have uncovered a novel protein motif that limits the transcriptional synergy of multiple DNA-binding regulators. Disruption of these conserved synergy control motifs (SC motifs) selectively increases activity at compound, but not single, response elements. Although isolated SC motifs do not regulate transcription when tethered to DNA, their transfer to an activator lacking them is sufficient to impose limits on synergy. Mechanistic analysis of the two SC motifs found in the glucocorticoid receptor N-terminal region reveals that they function irrespective of the arrangement of the receptor binding sites or their distance from the transcription start site. Proper function, however, requires the receptor's ligand-binding domain and an engaged dimer interface. Notably, the motifs are not functional in yeast and do not alter the effect of p160 coactivators, suggesting that they require other nonconserved components to operate. Many activators across multiple classes harbor seemingly unrelated negative regulatory regions. The presence of SC motifs within them, however, suggests a common function and identifies SC motifs as critical elements of a general mechanism to modulate higher-order interactions among transcriptional regulators.

Plasma membrane calcium pump isoform 1 gene expression is repressed by corticosterone and stress in rat hippocampus

Glucocorticoids (GCs) are critical to learning and memory, in large part because of their actions in the hippocampus. Chronic high levels of GCs have profound effects on hippocampal structure and function and can even result in irreversible neurodegeneration. Hippocampal GC actions are mediated by intracellular receptors that modulate the transcription of specific target genes. In a screen for genes repressed by GCs in rat hippocampus, we identified plasma membrane calcium pump isoform 1 (PMCA1), a plasma membrane calcium ATPase. In Northern blots, PMCA1 was repressed approximately 33% after a high, but not a low dose of the GC, corticosterone (B), suggesting glucocorticoid (but not mineralocorticoid) receptor-mediated repression. Furthermore, in situ hybridization demonstrated that B significantly downregulated PMCA1 mRNA in all brain regions examined. Repression of PMCA1 was also observed in cultured hippocampal neurons, but only when the cells were in the differentiated state. Stress also repressed PMCA1 expression in hippocampus of adrenal-intact animals, and a clear inverse correlation between B level and PMCA1 mRNA could be discerned. However, other non-B-dependent factors appeared to be involved in the response of PMCA1 to stress because, unlike exogenous B, cold stress did not repress PMCA1 in brain regions other than hippocampus. Moreover, in the presence of constant B (B-replaced, adrenalectomized animals), cold stress led to increased hippocampal PMCA1 expression. These observations suggest that repression of PMCA1 represents one molecular mechanism by which corticosteroids regulate Ca(2+) homeostasis and hence influence neuronal activity. Moreover, other stress-related neurohumoral factors appear to counter the repressive effects of B. Defects in the balance between GC-mediated and non-GC-mediated effects on PMCA1 expression may have adverse effects on neuronal function and ultimately result in irreversible neuronal damage.

Pleiotropic action of aldosterone in epithelia mediated by transcription and post-transcription mechanisms

The aldosterone-induced increase in sodium reabsorption across tight epithelia can be divided schematically into two functional phases: an early regulatory phase starting after a lag period of 20 to 60 minutes, during which the pre-existing transport machinery is activated, and a late phase (>2.5 h), which can be viewed as an anabolic action leading to a further amplification/differentiation of the Na+ transport machinery. At the transcriptional level, both early and late responses are initiated during the lag period, but the functional impact of newly synthesized regulatory proteins is faster than that of the structural ones. K-Ras2 and SGK were identified as the first early aldosterone-induced regulatory proteins in A6 epithelia. Their mRNAs also were shown to be regulated in vivo by aldosterone, and their expression (constitutively active K-Ras2 and wild-type SGK) was shown to increase the function of ENaC coexpressed in Xenopus oocytes. Recently, aldosterone was also shown to act on transcription factors in A6 epithelia: It down-regulates the mRNAs of the proliferation-promoting c-Myc, c-Jun, and c-Fos by a post-transcriptional mechanism, whereas it up-regulates that of Fra-2 (c-Fos antagonist) at the transcriptional level. Together, these new data illustrate the complexity of the regulatory network controlled by aldosterone and support the view that its early action is mediated by the induction of key regulatory proteins such as K-Ras2 and SGK. These early induced proteins are sites of convergence for different regulatory inputs, and thus, their aldosterone-regulated expression level tunes the impact of other regulatory cascades on sodium transport. This suggests mechanisms for the escape from aldosterone action.

Role of SGK in mineralocorticoid-regulated sodium transport

Mineralocorticoids stimulate electrogenic Na+ transport in tight epithelia by altering the transcription of specific genes. Although the earliest mineralocorticoid effect is to increase the activity of the epithelial sodium channel (ENaC), ENaC mRNA and protein levels do not change. Instead, physiologic observations suggest that a mineralocorticoid target gene(s) encodes an ENaC regulator(s). To begin to identify and characterize mineralocorticoid-regulated target genes, we used suppression-subtractive hybridization to generate a cDNA library from A6 cells, a stable cell line of Xenopus laevis of distal nephron origin. A serine-threonine kinase, SGK, was identified from this screen. Sequence comparison revealed that frog, rat, and human SGK are 92% identical and 96% similar at the amino acid level. SGK mRNA was confirmed by Northern blot to be strongly and rapidly corticosteroid stimulated in A6 cells. In situ hybridization revealed that SGK was strongly stimulated by aldosterone in rat collecting duct but not proximal tubule cells. Low levels of SGK were present in rat glomeruli, but SGK was unregulated in this structure. Finally, SGK stimulated ENaC activity approximately sevenfold when coexpressed in Xenopus laevis oocytes. These data suggest that SGK is an important mediator of aldosterone effects on Na+ transport in tight epithelia. In view of the existence of SGK homologues in invertebrates, it is interesting to speculate that SGK is an ancient kinase that was adapted to the control of epithelial Na+ transport by early vertebrates as they made the transition from a marine to a freshwater environment.

Transcriptional repression of the 5-HT1A receptor promoter by corticosterone via mineralocorticoid receptors depends on the cellular context

The diverse effects of the corticosteroid hormones are mediated in large measure by the mineralocorticoid and glucocorticoid receptors, two closely related members of the nuclear receptor superfamily. In the brain, corticosteroids regulate neuronal excitability and responses to neurotransmitters in a cell type-specific manner. The 5-HT1A receptor, for example, is highly expressed in the hippocampus and raphe but transcription is repressed by corticosterone (the principal glucocorticoid in rodents) only in hippocampus. We have used transient transfection of cultured cells to study the transcriptional regulation of the 5-HT1A receptor promoter by activators and repression by glucocorticoids. We find that transcription factors Sp1 and NF-kB subunit p65, both of which are coexpressed in hippocampus with the 5-HT1A receptor in vivo, synergistically activate a reporter driven by receptor 5'-flanking region. Primer extension data suggest that the multiple transcription initiation sites used in reporter gene transcription correlate with those used in transcription of the endogenous gene which has a TATA-less promoter. Repression of transcription by corticosteroids was found to be mediated by both mineralocorticoid and glucocorticoid receptors, but not identically. While glucocorticoid receptors potently inhibited both p65- and p65/Sp1-stimulated transcription, repression via mineralocorticoid receptors (MR) depended on the transcriptional activators that were present: p65-stimulated reporter activity was not repressed via MR, whereas a similar level of transcription resulting from synergistic activation by p65/Sp1-stimulation was repressed via MR. The context-dependence of these MR-mediated effects provides a model for the cell-type and state-dependent actions of corticosterone in the brain.

Regulation of the rat serotonin-1A receptor gene by corticosteroids

Dysregulation of the serotonergic system and abnormalities of the hypothalamic-pituitary-adrenal axis function have been implicated to be involved in neuropsychiatric disorders. Serotonin-1A receptors have been shown to be suppressed by corticosteroid hormones in a variety of animal studies. This effect may play a central role in the pathophysiology of depression. However, little is known about the molecular mechanism underlying this suppressive effect of corticosteroids. Here, we show by functional analysis of the promoter region of the rat serotonin-1A receptor gene that two NF-kappaB elements in the promoter contribute to induced transcription of the rat serotonin-1A receptor gene. Furthermore, we show that corticosteroids repress this NF-kappaB-mediated induction of transcription. Remarkably, we observed that only the glucocorticoid receptor and not the mineralocorticoid receptor was able to mediate this repressive effect of corticosteroids. We argue that negative cross-talk between the glucocorticoid receptor and NF-kappaB may provide a basis for the molecular mechanism underlying the negative action of corticosteroids on serotonin signaling in the brain.

25 years of Population Trends

This article monitors some of the more significant demographic changes over the last twenty-five years, depicted in various issues of Population Trends. It is, of necessity, selective in coverage in terms of quotes, figures and topics. Other articles in this issue go into more depth on specific topics, such as families, ethnic minority groups, marriage and divorce, health inequalities and fertility and family planning. Consequently, there is some overlap and the articles could usefully be cross-referenced. Some coverage is also given to the development of sources, international events and selected partnerships outside the Office. Relevant legislation enacted over the period is also mentioned.

In vitro expression of N-acetyl aspartate by oligodendrocytes: implications for proton magnetic resonance spectroscopy signal in vivo

Magnetic resonance spectroscopy (MRS) provides a noninvasive means of assessing in vivo tissue biochemistry. N-Acetyl aspartate (NAA) is a major brain metabolite, and its presence is used increasingly in clinical and experimental MRS studies as a putative neuronal marker. A reduction in NAA levels as assessed by in vivo 1H MRS has been suggested to be indicative of neuronal viability. However, temporal observations of brain pathologies such as multiple sclerosis, mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS), and hypothyroidism have shown reversibility in NAA levels, possibly reflecting recovery of neuronal function. A knowledge of the cellular localisation of NAA is critical in interpreting these findings. The assumption that NAA is specific to neurones is based on previous immunohistochemical studies on whole brain using NAA-specific antibodies. The neuronal localisation was further substantiated by cell culture experiments in which its presence in the oligodendrocyte-type 2 astrocyte progenitors and immature oligodendrocytes, but not in the mature oligodendrocytes, was observed. More recently, studies on oligodendrocyte biology have revealed the requirement for trophic factors to promote the generation, maturation, and survival of oligodendrocytes in vitro. Here, we have used this new information to implement a more pertinent cell cultivation procedure and demonstrate that mature oligodendrocytes can express NAA in vitro. This observation brings into question whether the NAA changes observed in clinical in vivo 1H MRS studies reflect neuronal function alone. The data presented here support the hypothesis that oligodendrocytes may express NAA in vivo and contribute to the NAA signal observed by 1H MRS.

Distinct glucocorticoid receptor transcriptional regulatory surfaces mediate the cytotoxic and cytostatic effects of glucocorticoids

Glucocorticoids act through the glucocorticoid receptor (GR), which can function as a transcriptional activator or repressor, to elicit cytostatic and cytotoxic effects in a variety of cells. The molecular mechanisms regulating these events and the target genes affected by the activated receptor remain largely undefined. Using cultured human osteosarcoma cells as a model for the GR antiproliferative effect, we demonstrate that in U20S cells, GR activation leads to irreversible growth inhibition, apoptosis, and repression of Bcl2. This cytotoxic effect is mediated by GR's transcriptional repression function, since transactivation-deficient mutants and ligands still bring about apoptosis and Bcl2 down-regulation. In contrast, the antiproliferative effect of GR in SAOS2 cells is reversible, does not result in apoptosis or repression of Bcl2, and is a function of the receptor's ability to stimulate transcription. Thus, the cytotoxic versus cytostatic outcome of glucocorticoid treatment is cell context dependent. Interestingly, the cytostatic effect of glucocorticoids in SAOS2 cells involves multiple GR activation surfaces. GR mutants and ligands that disrupt individual transcriptional activation functions (activation function 1 [AF-1] and AF-2) or receptor dimerization fail to fully inhibit cellular proliferation and, remarkably, discriminate between the targets of GR's cytostatic action, the cyclin-dependent kinase inhibitors p21(Cip1) and p27(Kip1). Induction of p21(Cip1) is agonist dependent and requires AF-2 but not AF-1 or GR dimerization. In contrast, induction of p27(Kip1) is agonist independent, does not require AF-2 or AF-1, but depends on GR dimerization. Our findings indicate that multiple GR transcriptional regulatory mechanisms that employ distinct receptor surfaces are used to evoke either the cytostatic or cytotoxic response to glucocorticoids.