Eph family receptors and ligands in vascular cell targeting and assembly

Members of the Eph family of receptor tyrosine kinases determine neural cell aggregation and targeting behavior, functions that are also critical in vascular assembly and remodeling. Among this class of diverse receptors, EphA2 (Eck) and EphB1 (ELK) represent prototypes for two receptor subfamilies distinguished by high-affinity interaction with either glycerophosphatidylinositol (GPI)-linked or transmembrane ligands, respectively. EphA2 participates in angiogenic responses to tumor necrosis factor (TNF) through an autocrine loop affecting endothelial cell migration. EphB1 and its ligand Ephrin-B1 (LERK-2) are important determinants of assembly of endothelial cells from the microvasculature of the kidney, where both are expressed in endothelial progenitors and in glomerular microvascular endothelial cells. Ephrin-B1 activation of EphB1 promotes assembly of these cells into capillary-like structures. Interaction trap approaches have identified downstream signaling proteins that complex with ligand-activated EphA2 or EphB1, including nonreceptor tyrosine kinases and SH2 domain-containing adapter proteins. The Grb 10 adapter is one of a subset that binds activated EphB1, but not EphA2, defining distinct signaling mechanisms for these related endothelial receptors. On the basis of observations in vascular endothelial cells and recent results defining Eph receptor and ligand roles in neural cell targeting, we propose that these receptors direct cell-cell recognition events that are critical in vasculogenesis and angiogenesis. (Trends Cardiovasc Med 1997;7:329-334). © 1997, Elsevier Science Inc.

Bone structure and turnover in type 2 diabetes mellitus

SUMMARY

We compared skeletal parameters in type 2 diabetic (T2DM) and non-diabetic postmenopausal women. Bone structure by dual energy x-ray absorptiometry (DXA) and HR-pQCT was not different, although procollagen type 1 amino-terminal propeptide (P1NP) and osteocalcin levels were lower in T2DM.

INTRODUCTION

T2DM is associated with increased fracture risk, but, paradoxically, with higher cross-sectional bone density (BMD) as measured by DXA. We sought explanations to this puzzle by investigating detailed structural and biochemical skeletal parameters in T2DM.

METHODS

Cross-sectional comparison of 25 postmenopausal T2DM women and 25 matched controls using DXA, high-resolution peripheral quantitative computed tomography (HR-pQCT) and biochemical bone turnover markers.

RESULTS

BMD by DXA did not differ between T2DM and controls. HR-pQCT assessment also did not differ, with the exception of cortical area at the tibia, which tended to be lower in the diabetics (difference of 12 ± 6 [mean ± SD] mm, p = 0.06). P1NP and osteocalcin levels were lower in T2DM as compared to controls (P1NP, 34.3 ± 16 vs. 57.3 ± 28 ng/ml; p = 0.005; osteocalcin, 4.5 ± 2 vs. 6.2 ± 2 nmol/L; p = 0.001).

CONCLUSIONS

Postmenopausal women with T2DM had lower levels of bone formation markers as compared to controls. Aside from a possible decrease in cortical bone area at a weight-bearing site, bone structure was not altered in T2DM. Lower bone turnover may be a skeletal parameter that is present in T2DM.

Decoupling neuronal oscillations during subthalamic nucleus stimulation in the parkinsonian primate

Subthalamic nucleus (STN) stimulation is a popular treatment for Parkinson's disease; however, its effect on neuronal activity is unclear. We performed simultaneous multi-electrode recordings in the STN and its targets, the globus pallidus internus (GPi) and externus (GPe) in the parkinsonian non-human primate during high frequency STN macro-stimulation. Our results indicate that in the parkinsonian state the abnormal neuronal oscillatory activity in the 10-15 Hz range is coherent within and between nuclei. We further show that STN macro-stimulation results in a reduction of oscillatory activity in the globus pallidus. In addition, a functional decoupling of the STN from its pallidal targets is evidenced by the reduced STN-GPi coherence, that effectively removes the STN synchronous oscillatory drive of basal ganglia output. This decoupling results in reduced coherence between neurons within the GPi which resume an independent neuronal activity pattern. This decorrelation of the basal ganglia output may result in a reduction of the fluctuations of the basal ganglia inhibitory control over thalamic neurons which may potentially contribute to the beneficial effects of deep brain high-frequency stimulation.

Amphetamine-type stimulant use and HIV/STI risk behaviour among young female sex workers in Phnom Penh, Cambodia

BACKGROUND

Use of amphetamine-type substances (ATS) has been linked to increased risk of HIV and other sexually transmitted infections (STI) worldwide. In Cambodia, recent ATS use is independently associated with incident STI infection among young female sex workers (FSWs).

METHODS

We conducted 33 in-depth interviews with women (15-29 years old) engaged in sex work to explore ATS use and vulnerability to HIV/STI.

RESULTS

Participants reported that ATS, primarily methamphetamine in pill and crystalline forms (yama), were cheap, widely available and commonly used. Yama was described as a "power drug" (thnam kamlang) which enabled women to work long hours and serve more customers. Use of ATS by clients was also common, with some providing drugs for women and/or encouraging their use, often resulting in prolonged sexual activity. Requests for unprotected sex were also more common among alternatives intoxicated clients and strategies typically employed to negotiate condom use were less effective.

CONCLUSION

ATS use was highly functional for young women engaged in sex work, facilitating a sense of power and agency and highlighting the occupational significance and normalization of ATS in this setting. This highly gendered dynamic supports the limited but emerging literature on women's use of ATS, which to date has been heavily focused on men. Results indicate an urgent need to increase awareness of the risks associated with ATS use, to provide women with sustainable alternatives for income generation, to better regulate the conditions of sex work, and to work with FSWs and their clients to develop and promote culturally appropriate harm reduction interventions.

[Targeted methods for measuring patient satisfaction in a radiological center]

PURPOSE

To investigate two event-oriented methods for evaluating patient satisfaction with radiological services like outpatient computed tomography (CT) examinations.

MATERIALS AND METHODS

159 patients (55% men, 45% women) were asked to complete a questionnaire to provide information about their satisfaction with their examination. At first, patients were asked to spontaneously recall notably positive and negative aspects (so-called "critical incidents", critical incident technique = CIT) of the examination. Subsequently a flow chart containing all single steps of the examination procedure was shown to all patients. They were asked to point out the positive and negative aspects they perceived at each step (so-called sequential incident technique = SIT).

RESULTS

The CIT-based part of the questionnaire yielded 356 comments (183 positive and 173 negative), which were assigned to one of four categories: interaction of staff with patient, procedure and organization, CT examination, and overall setting of the examination. Significantly more detailed comments regarding individual aspects of the CT examination were elicited in the second part of the survey, which was based on the SIT. There were 1413 statements with a significantly higher number of positive comments (n = 939, 66%) versus negative comments (n = 474, 34%; p < 0.001).

CONCLUSION

The critical and sequential incident techniques are suitable to measure the subjective satisfaction with the delivery of radiological services such as CT examinations. Positive comments confirm the adequacy of the existing procedures, while negative comments provide direct information about how service quality can be improved.

[Isolated ileal perforation after blunt abdominal trauma]

Perforating injuries to the small bowel due to a blunt abdominal trauma are rare. Especially in the case of an isolated injury where diagnostic investigations have failed, it may result in delayed therapy and a prolonged clinical course. Here, we report on an isolated ileal perforation caused by a blunt abdominal trauma in setting of a domestic accident.

Chemosensitivity Testing of Circulating Epithelial Cells (CETC) in Breast Cancer Patients and Correlation to Clinical Outcome

In spite of ample prognostic markers available in breast cancer, still a considerable proportion of patients with good prognostic markers suffers relapse whereas patients with poor prognostic markers may remain disease free. It would, therefore, be desirable to control, at the individual patient level, whether the applied therapy is effective. Our previous work indicates, that in cancer patients most of the epithelial cells circulating in peripheral blood (CETC) are part of the tumor and that the response of these cells reflects the response of the tumor to the applied therapies.Therefore, these cells were used to assay chemosensitivity in short time cultures analyzing the percent of cell killing during short time incubation and monitoring the decrease or increase in numbers of these cells during treatment with the respective agents providing a unique tool for therapy surveillance. Patients were prospectively analysed for the number of CETC before each new combination of chemotherapy. 1ml of blood was drawn into EDTA vials, red blood cells lysed and the white blood cell pellet stained with FITC-labelled anti-Epcam. Green fluorescent cells were detected by image analysis and dead cells excluded due to red PI fluorescence. Activity of individual compounds was determined using three different concentrations of each compound at 3h, 6h and 12hs and displayed as % cell killing. The in vitro results were then compared to in vivo reduction of CETCs and to the reduction of a marker lesion.215 patients have been investigated so far. Cell killing was dose and time dependent. The highest killing rates were observed with Epirubicin and Taxanes, agents which are known for their high activity in breast cancer. Less than 20% killing activity was termed marginal activity. In vitro sensitivitity was highly significantly predictive of in vivo CETC reduction. In some cases an increasing resistance could be shown to develop during repeated cycles of the same combination therapy. CETC reduction was correlated with a prolonged progression free survival.Thus this approach can in the future be used to test in advance the sensitivity of the circulating tumor cells to chemotherapy and at the same time monitor the current response of the cells to therapy in vivo in order to optimize and individualize therapy.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2044.

Long-term efficacy and safety of cerivastatin 0.8 mg in patients with primary hypercholesterolemia

BACKGROUND

Statins are the agents of choice in reducing elevated plasma low-density lipoprotein cholesterol (LDL-C).

HYPOTHESIS

Cerivastatin 0.8 mg has greater long-term efficacy in reducing LDL-C than pravastatin 40 mg in primary hypercholesterolemia.

METHODS

In this double-blind, parallel-group, 52-week study, patients (n = 1,170) were randomized (4:1:1) to cerivastatin 0.8 mg, cerivastatin 0.4 mg, or placebo daily. After 8 weeks, placebo was switched to pravastatin 40 mg. Patients with insufficient LDL-C lowering after 24 weeks were allowed open-labeled resin therapy.

RESULTS

Cerivastatin 0.8 mg reduced LDL-C versus cerivastatin 0.4 mg (40.8 vs. 33.6%, p <0.0001) or pravastatin 40 mg (31.5%, p<0.0001), and brought 81.8% of all patients, and 54.1% of patients with atherosclerotic disease, to National Cholesterol Education Program (NCEP) goals. Cerivastatin 0.8 mg improved mean total C (-29.0%), triglycerides (-18.3%), and high-density lipoprotein cholesterol (HDL-C) (+9.7%) (all p < or = 0.013 vs. pravastatin 40 mg). Higher baseline triglycerides were associated with greater reductions in triglycerides and elevations in HDL-C with cerivastatin. Cerivastatin was well tolerated; the most commonly reported adverse events were arthralgia, headache, pharyngitis, and rhinitis. Symptomatic creatine kinase > 10x the upper limit of normal (ULN) occurred in 1, 1.5, and 0% of patients receiving cerivastatin 0.8 mg, cerivastatin 0.4 mg, and pravastatin 40 mg, respectively. Repeat hepatic transaminases >3 x ULN occurred in 0.3-0.5, 0.5, and 0% of patients, respectively.

CONCLUSION

In long-term use, cerivastatin 0.8 mg effectively and safely brings the majority of patients to NCEP goal.

Phosphodiesterase 11A expression in the adrenal cortex, primary pigmented nodular adrenocortical disease, and other corticotropin-independent lesions

A variety of adrenal tumors and bilateral adrenocortical hyperplasias (BAH) leading to Cushing syndrome (CS) may be caused by aberrant cAMP signaling. We recently identified patients with a micronodular form of BAH that we have called "isolated micronodular adrenocortical disease" (iMAD) in whom CS was associated with inactivating mutations in phosphodiesterase (PDE) 11A ( PDE11A). In the present study, we examined PDE11A expression in normal adrenocortical tissue, sporadic tumors, and hyperplasias without PDE11A mutations, and primary pigmented nodular adrenocortical disease (PPNAD) and adenomas from patients with PRKAR1A and a single tumor with a GNAS mutation. The total number of the tumor samples that we studied was 22. Normal human tissues showed consistent PDE11A expression. There was variable expression of PDE11A in sporadic adrenocortical hyperplasia or adenomas; PPNAD tissues from patients with PRKAR1A mutations expressed consistently high levels of PDE11A in contrast to adenomas caused by GNAS mutations. Phosphorylated CREB was the highest in tissues from patients with iMAD compared to all other forms of BAH and normal adrenal tissue. We conclude that PDE11A is expressed widely in adrenal cortex. Its expression appears to be increased in PPNAD but varies widely among other adrenocortical tumors. PRKAR1A expression appears to be higher in tissues with PDE11A defects. Finally, sequencing defects in PDE11A are associated with a high state of CREB phosphorylation, just like PRKAR1A mutations. These preliminary data suggest that these two molecules are perhaps regulated in a reverse manner in their control of cAMP signaling in adrenocortical tissues.

Hepatitis B virus infection and immunization status in a new generation of injection drug users in San Francisco

Hepatitis B virus (HBV) infection is common among injection drug users (IDU). Younger IDU, however, may be less susceptible to infection due to the implementation of public health interventions, such as universal immunization programs and syringe exchange programs. To investigate the current epidemiology of HBV infection and control among a new generation of drug users in the United States, we conducted interviews and examined HBV serologic markers in a cross-section of street-recruited IDU under age 30 in San Francisco, CA. Of the 831 persons studied, 21% showed serologic evidence of current or past infection; 22% had isolated antibodies to hepatitis B surface antigen consistent with vaccine-mediated immunity; and 56% had no HBV markers. In multivariate analyses, HBV infection was associated with drug use behaviour in heterosexual males; sexual behaviour in males who have sex with males; and both drug use and sexual behaviour in females. Vaccine-mediated immunity was independently associated with female sex and younger age. In conclusion, HBV transmission persists among young IDU in San Francisco. Few young injectors show evidence of successful immunization and the majority remains susceptible to disease. Until the broad effects of universal vaccination are seen, targeted and innovative approaches to immunizing young IDU in the US are needed to prevent a substantial number of new HBV infections.

Apo B versus cholesterol in estimating cardiovascular risk and in guiding therapy: report of the thirty-person/ten-country panel

There is abundant evidence that the risk of atherosclerotic vascular disease is directly related to plasma cholesterol levels. Accordingly, all of the national and transnational screening and therapeutic guidelines are based on total or LDL cholesterol. This presumes that cholesterol is the most important lipoprotein-related proatherogenic risk variable. On the contrary, risk appears to be more directly related to the number of circulating atherogenic particles that contact and enter the arterial wall than to the measured concentration of cholesterol in these lipoprotein fractions. Each of the atherogenic lipoprotein particles contains a single molecule of apolipoprotein (apo) B and therefore the concentration of apo B provides a direct measure of the number of circulating atherogenic lipoproteins. Evidence from fundamental, epidemiological and clinical trial studies indicates that apo B is superior to any of the cholesterol indices to recognize those at increased risk of vascular disease and to judge the adequacy of lipid-lowering therapy. On the basis of this evidence, we believe that apo B should be included in all guidelines as an indicator of cardiovascular risk. In addition, the present target adopted by the Canadian guideline groups of an apo B <90 mg dL(-1) in high-risk patients should be reassessed in the light of the new clinical trial results and a new ultra-low target of <80 mg dL(-1) be considered. The evidence also indicates that the apo B/apo A-I ratio is superior to any of the conventional cholesterol ratios in patients without symptomatic vascular disease or diabetes to evaluate the lipoprotein-related risk of vascular disease.

Plexin-A3 mediates semaphorin signaling and regulates the development of hippocampal axonal projections

Plexins are receptors implicated in mediating signaling by semaphorins, a family of axonal chemorepellents. The role of specific plexins in mediating semaphorin function in vivo has not, however, yet been examined in vertebrates. Here, we show that plexin-A3 is the most ubiquitously expressed plexin family member within regions of the developing mammalian nervous system known to contain semaphorin-responsive neurons. Using a chimeric receptor construct, we provide evidence that plexin-A3 can transduce a repulsive signal in growth cones in vitro. Analysis of plexin-A3 knockout mice shows that plexin-A3 contributes to Sema3F and Sema3A signaling and that plexin-A3 regulates the development of hippocampal axonal projections in vivo.

Binding of DCC by netrin-1 to mediate axon guidance independent of adenosine A2B receptor activation

Netrins stimulate and orient axon growth through a mechanism requiring receptors of the DCC family. It has been unclear, however, whether DCC proteins are involved directly in signaling or are mere accessory proteins in a receptor complex. Further, although netrins bind cells expressing DCC, direct binding to DCC has not been demonstrated. Here we show that netrin-1 binds DCC and that the DCC cytoplasmic domain fused to a heterologous receptor ectodomain can mediate guidance through a mechanism involving derepression of cytoplasmic domain multimerization. Activation of the adenosine A2B receptor, proposed to contribute to netrin effects on axons, is not required for rat commissural axon outgrowth or Xenopus spinal axon attraction to netrin-1. Thus, DCC plays a central role in netrin signaling of axon growth and guidance independent of A2B receptor activation.

RETRACTED: Hierarchical organization of guidance receptors: silencing of netrin attraction by slit through a Robo/DCC receptor complex

Axonal growth cones that cross the nervous system midline change their responsiveness to midline guidance cues: They become repelled by the repellent Slit and simultaneously lose responsiveness to the attractant netrin. These mutually reinforcing changes help to expel growth cones from the midline by making a once-attractive environment appear repulsive. Here, we provide evidence that these two changes are causally linked: In the growth cones of embryonic Xenopus spinal axons, activation of the Slit receptor Roundabout (Robo) silences the attractive effect of netrin-1, but not its growth-stimulatory effect, through direct binding of the cytoplasmic domain of Robo to that of the netrin receptor DCC. Biologically, this hierarchical silencing mechanism helps to prevent a tug-of-war between attractive and repulsive signals in the growth cone that might cause confusion. Molecularly, silencing is enabled by a modular and interlocking design of the cytoplasmic domains of these potentially antagonistic receptors that predetermines the outcome of their simultaneous activation.