Mechanisms of apoptosis induced by purine nucleosides in astrocytes

Astrocytes release adenine-based and guanine-based purines under physiological and, particularly, pathological conditions. Thus, the aim of this study was to determine if adenosine induced apoptosis in cultured rat astrocytes. Further, if guanosine, which increases the extracellular concentration of adenosine, also induced apoptosis determined using the TUNEL and Annexin V assays. Adenosine induced apoptosis in a concentration-dependent manner up to 100 microM. Inosine, hypoxanthine, guanine, and guanosine did not. Guanosine or adenosine (100 microM) added to the culture medium was metabolized, with 35% or 15%, respectively, remaining after 2-3 h. Guanosine evoked the extracellular accumulation of adenosine, and particularly of adenine-based nucleotides. Cotreatment with EHNA and guanosine increased the extracellular accumulation of adenosine and induced apoptosis. Inhibition of the nucleoside transporters using NBTI (100 microM) or propentophylline (100 microM) significantly decreased but did not abolish the apoptosis induced by guanosine + EHNA or adenosine + EHNA, respectively. Apoptosis produced by either guanosine + EHNA or adenosine + EHNA was unaffected by A(1) or A(2) adenosine receptor antagonists, but was significantly reduced by MRS 1523, a selective A(3) adenosine receptor antagonist. Adenosine + EHNA, not guanosine + EHNA, significantly increased the intracellular concentration of S-adenosyl-L-homocysteine (SAH) and greatly reduced the ratio of S-adenosyl-L-methioine to SAH, which is associated with apoptosis. These data demonstrate that adenosine mediates apoptosis of astrocytes both, via activation of A(3) adenosine receptors and by modulating SAH hydrolase activity. Guanosine induces apoptosis by accumulating extracellular adenosine, which then acts solely via A(3) adenosine receptors.     

Immediate ambulation following diagnostic coronary angiography procedures utilizing a vascular closure device (The Closer)

OBJECTIVE: We investigated the safety and efficacy of The Closer, a suture-mediated vascular closure device, to facilitate immediate ambulation after diagnostic coronary angiography. METHODS AND RESULTS: We identified 487 non-consecutive patients who were eligible for an immediate ambulation protocol following vascular closure after diagnostic coronary angiography. A total of 434 patients (89%) were allowed immediate ambulation (mean time, 6.3 +/- 2.4 minutes) and 34 patients (7%) were treated with intermediate duration bed rest (mean time, 105.2 +/- 55.3 minutes). Of the 34 patients treated with intermediate duration bed rest, ten had minor bleeding from the arterial access tract requiring 2 5 minutes of light compression and 24 were delayed secondary to physician preference. Nineteen patients (4%) failed to achieve hemostasis with The Closer. Outpatients were followed up at 24 hours, and inpatients were followed up the next morning. Four patients (0.8%) suffered recurrent femoral artery bleeds after initially successful vascular closure. Three recurrent bleeds occurred during the observation period in-hospital and one occurred 6 days after device deployment. At follow-up, no patients developed the following: hematoma > 4 cm, ipsilateral retroperitoneal bleed, arterio-venous fistula, pseudoaneurysm, access site infection or loss of distal pulses. No patients had lower extremity ischemia or required blood transfusion. CONCLUSION: Use of The Closer after diagnostic angiography with subsequent immediate ambulation is safe and effective for most patients. Overall, hemostasis was achieved in 96% of patients, with 89% of our patients able to ambulate immediately and 7% able to ambulate after intermediate duration bed rest.     

Field evaluation of energy expenditure in women using Tritrac accelerometers

PURPOSE: To investigate the use of Tritrac accelerometers to measure energy expenditure (EE) of various activities for women in the field setting, as compared with portable indirect calorimetry. METHODS: Twenty women (age 20-29) performed a choreographed routine of six activities (walking, jogging, stair climbing, walking on an incline, stationary cycling, and arm ergometry) while wearing a Tritrac-R3D accelerometer (Hemokinetics Inc., Madison WI) and the Cosmed K4b(2) portable metabolic cart (Cosmed, Rome, Italy). RESULTS: Comparing the mean error scores (K4b(2) - Tritrac), the Tritrac overestimated the EE (kcal x min(-1)) of walking (-1.45) and jogging (-1.75), whereas underestimating the EE of stair climbing (2.76), stationary cycling (2.75), and arm ergometry (1.20). Walking on an incline showed the lowest mean error score (-0.11). Intraclass correlations were moderate for walking (r = 0.568, < 0.05), jogging (r = 0.666, < 0.05), and stairs (r = 0.503, < 0.05) but for the other activities ranged from r = 0.290 ( > 0.05) to r = 0.480 ( < 0.05). The raw data from the Tritrac was applied to a previously developed nonlinear model to adjust the Tritrac scores to the standard of whole-room indirect calorimetry. This resulted in statistically significant improvements in the agreement between the adjusted Tritrac value and the K4b for walking, jogging, and walking on an incline ( < 0.05). CONCLUSION: When compared with portable indirect calorimetry, the Tritrac overestimates the EE of walking and jogging, whereas underestimating that of stair climbing, stationary cycling, and arm ergometry. This limits the use of such a technique to measure EE in the field. The main issues appear to be the type and intensity of the activity and the need for movement in order for the Tritrac to register EE. Activity specific linear regression equations are proposed as a tool to improve the measurement of EE using the Tritrac in the field.     

Impact of a medically supervised safer injecting facility on drug dealing and other drug-related crime

North America's first medically supervised safer injecting facility (SIF) recently opened in Vancouver, Canada. One of the concerns prior to the SIF's opening was that the facility might lead to a migration of drug activity and an increase in drug-related crime. Therefore, we examined crime rates in the neighborhood where the SIF is located in the year before versus the year after the SIF opened. No increases were seen with respect to drug trafficking (124 vs. 116) or assaults/robbery (174 vs. 180), although a decline in vehicle break-ins/vehicle theft was observed (302 vs. 227). The SIF was not associated with increased drug trafficking or crimes commonly linked to drug use.     

HIV seroprevalence among participants at a Supervised Injection Facility in Vancouver, Canada: implications for prevention, care and treatment

North America's first government sanctioned medically supervised injection facility (SIF) was opened during September 2003 in Vancouver, Canada. This was in response to a large open public drug scene, high rates of HIV and hepatitis C transmission, fatal drug overdoses, and poor health outcomes among the city's injection drug users. Between December 2003 and April 2005, a representative sample of 1,035 SIF participants were enrolled in a prospective cohort that required completing an interviewer-administered questionnaire and providing a blood sample for HIV testing. HIV infection was detected in 170/1007 (17%) participants and was associated with Aboriginal ethnicity (adjusted Odds Ratio [aOR], 2.70, 95% Confidence Interval [95% CI], 1.84–3.97), a history of borrowing used needles/syringes (aOR, 2.0, 95% CI, 1.37–2.93), previous incarceration (aOR, 1.87, 95% CI, 1.11–3.14), and daily injection cocaine use (aOR, 1.42, 95% CI, 1.00–2.03). The SIF has attracted a large number of marginalized injection drug users and presents an excellent opportunity to enhance HIV prevention through education, the provision of sterile injecting equipment, and a supervised environment to self-inject. In addition, the SIF is an important point of contact for HIV positive individuals who may not be participating in HIV care and treatment.     

曲安奈德辅助玻璃体切割术的应用

目的研究曲安奈德（TA）辅助玻璃体切割手术在临床的应用价值。方法28例（29只眼）于2004年1月～2004年12月行玻璃体切割术，术中注入已过滤的TA悬浮液0．1ml（40mg／m1），以帮助辨认玻璃体后皮质、视网膜前增殖膜、黄斑前膜、内界膜，9例硅油填充，7例C3FR（15％）填充。手术后17例随访6个月以上，11例随访3至4个月。结果所有的病例，经TA注入后，可明显的改善玻璃体后皮质、视网膜前膜、内界膜的辨认情况。糖尿病视网膜病变术后视力提高占61．5％，伴PVR的视网膜脱离术后视力提高占61．3％，黄斑裂孔4例中3例术后视力提高，4例黄斑前膜术后视力均有提高。所有28例均没有出现高眼压。8例伴PVR的视网膜脱离中6例（占75％）视网膜复位，4例黄斑裂孔均关闭，2例糖尿病黄斑水肿手术后明显减轻。结论经过滤的TA可作为玻璃体切割手术中较好的辅助工具，TA悬浮液是呈白色胶样，可粘附于玻璃体皮质、视网膜前膜或内界膜，帮助分辨玻璃体后皮质、视网膜前膜、内界膜，提高手术效率。没有发现与TA有关的副作用。     

High prevalence of HIV infection among homeless and street-involved Aboriginal youth in a Canadian setting

Aboriginal people experience a disproportionate burden of HIV infection among the adult population in Canada; however, less is known regarding the prevalence and characteristics of HIV positivity among drug-using and street-involved Aboriginal youth. We examined HIV seroprevalence and risk factors among a cohort of 529 street-involved youth in Vancouver, Canada. At baseline, 15 (2.8%) were HIV positive, of whom 7 (46.7%) were Aboriginal. Aboriginal ethnicity was a significant correlate of HIV infection (odds ratio = 2.87, 95%CI: 1.02 – 8.09). Of the HIV positive participants, 2 (28.6%) Aboriginals and 6 (75.0%) non-Aboriginals reported injection drug use; furthermore, hepatitis C co-infection was significantly less common among Aboriginal participants (p = 0.041). These findings suggest that factors other than injection drug use may promote HIV transmission among street-involved Aboriginal youth, and provide further evidence that culturally appropriate and evidence-based interventions for HIV prevention among Aboriginal young people are urgently required.     

Evidence for endogenous formation of tobacco-specific nitrosamines in rats treated with tobacco alkaloids and sodium nitrite

Carcinogenic tobacco-specific nitrosamines are present in tobacco products and are believed to play a significant role in human cancers associated with tobacco use. Additional amounts of tobacco-specific nitrosamines could be formed endogenously. We tested this hypothesis by treating rats with nicotine and sodium nitrite and analyzing their urine. Initially, we treated groups of rats with (S)-nicotine (60 micromol/kg) and NaNO2 (180 micromol/kg), (S)-nicotine alone, NaNO2 alone or 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK, 12 nmol/kg) by gavage twice daily for 4 days. We collected urine and analyzed for two metabolites of NNK; 4-(methylnitrosamino)-1-(3- pyridyl)-1-butanol and its glucuronide. We did not detect these metabolites in the urine of rats treated with nicotine alone or nicotine plus NaNO2, indicating that endogenous conversion of nicotine to NNK did not occur. However, the urine did contain N'- nitrosonornicotine (NNN), N'-nitrosoanabasine (NAB) and N'- nitrosoanatabine (NAT). Analysis of the (S)-nicotine used in this experiment demonstrated that it contained trace amounts of nornicotine, anabasine and anatabine. In a second experiment, we used an identical protocol to compare the endogenous nitrosation of this (S)-nicotine with that of synthetic (R,S)-nicotine, which did not contain detectable amounts of nornicotine, anabasine or anatabine. NNN (0.53 x 10(-3)% of nicotine dose), NAB (0.68%) and NAT (2.1%) were detected in the urine of the rats treated with the (S)-nicotine and NaNO2. NNN (0.47 x 10(- 3)% of dose), but not NAB or NAT, was present in the urine of the rats treated with synthetic (R,S)-nicotine and NaNO2. NNN probably formed via nitrosation of metabolically formed nornicotine. These results demonstrate for the first time that endogenous formation of tobacco- specific nitrosamines occurs in rats treated with tobacco alkaloids and NaNO2. The potential significance of the results with respect to nitrosamine formation in people who use tobacco products or nicotine replacement therapy is discussed.