Smoking of crack cocaine as a risk factor for HIV infection among people who use injection drugs

Background

Little is known about the possible role that smoking crack cocaine has on the incidence of HIV infection. Given the increasing use of crack cocaine, we sought to examine whether use of this illicit drug has become a risk factor for HIV infection.

Methods

We included data from people participating in the Vancouver Injection Drug Users Study who reported injecting illicit drugs at least once in the month before enrolment, lived in the greater Vancouver area, were HIV-negative at enrolment and completed at least 1 follow-up study visit. To determine whether the risk of HIV seroconversion among daily smokers of crack cocaine changed over time, we used Cox proportional hazards regression and divided the study into 3 periods: May 1, 1996–Nov. 30, 1999 (period 1), Dec. 1, 1999–Nov. 30, 2002 (period 2), and Dec. 1, 2002–Dec. 30, 2005 (period 3).

Results

Overall, 1048 eligible injection drug users were included in our study. Of these, 137 acquired HIV infection during follow-up. The mean proportion of participants who reported daily smoking of crack cocaine increased from 11.6% in period 1 to 39.7% in period 3. After adjusting for potential confounders, we found that the risk of HIV seroconversion among participants who were daily smokers of crack cocaine increased over time (period 1: hazard ratio [HR] 1.03, 95% confidence interval [CI] 0.57–1.85; period 2: HR 1.68, 95% CI 1.01–2.80; and period 3: HR 2.74, 95% CI 1.06–7.11).

Interpretation

Smoking of crack cocaine was found to be an independent risk factor for HIV seroconversion among people who were injection drug users. This finding points to the urgent need for evidence-based public health initiatives targeted at people who smoke crack cocaine.People who inject illegal drugs are known to be at heightened risk of HIV infection and other blood-borne diseases. In 2007, more than 20% of all new cases of HIV infection recorded in Canada were attributed to injection drug use.¹ Behaviours associated with the use of particular injection drugs (e.g., cocaine and heroin) have been identified as key factors driving HIV transmission among drug users in various settings.² However, over the last decade, significant changes in the popularity of specific illegal drugs have been observed.^3,4 In recent years, cities across Canada have experienced an explosive increase in the use of crack cocaine, whereas some drugs, including heroin, appear to be less commonly used.^5–7 The proportion of drug users who smoke crack cocaine and are homeless or have marginal housing has recently been reported to be as high as 86.6% in Vancouver, 66.7% in Edmonton and 62.4% in Toronto.⁸In the United States, a seminal cross-sectional study involving inner-city young adults showed that smoking of crack cocaine was associated with HIV infection.⁹ However, in Canada, despite the documentation of changing patterns of drug use in many communities,⁸ little is known about the impact that increased smoking of crack cocaine has had on the HIV epidemic. This is problematic because public health programs for people who smoke crack cocaine have been highly controversial in Canada.⁶ We conducted a longitudinal study to evaluate whether smoking of crack cocaine has emerged as a risk factor for HIV infection among people who inject drugs.     

Structural and functional analysis of phosphothreonine-dependent FHA domain interactions

FHA domains are well established as phospho-dependent binding modules mediating signal transduction in Ser/Thr kinase signaling networks in both eukaryotic and prokaryotic species. Although they are unique in binding exclusively to phosphothreonine, the basis for this discrimination over phosphoserine has remained elusive. Here, we attempt to dissect overall binding specificity at the molecular level. We first determined the optimal peptide sequence for Rv0020c FHA domain binding by oriented peptide library screening. This served as a basis for systematic mutagenic and binding analyses, allowing us to derive relative thermodynamic contributions of conserved protein and peptide residues to binding and specificity. Structures of phosphopeptide-bound and uncomplexed Rv0020c FHA domain then directed molecular dynamics simulations which show how the extraordinary discrimination in favor of phosphothreonine occurs through formation of additional hydrogen-bonding networks that are ultimately stabilized by van der Waals interactions of the phosphothreonine γ-methyl group with a conserved pocket on the FHA domain surface.     

Young patients with colorectal cancer have poor survival in the first twenty months after operation and predictable survival in the medium and long-term: Analysis of survival and prognostic markers

Introduction

Male breast cancer (MBC) is a rare, yet potentially aggressive disease. Although literature regarding female breast cancer (FBC) is extensive, little is known about the etiopathogenesis of male breast cancer. Studies from our laboratory show that MBCs have a distinct immunophenotypic profile, suggesting that the etiopathogenesis of MBC is different from FBCs. The aim of this study was to evaluate and correlate the immunohistochemical expression of cell cycle proteins in male breast carcinoma to significant clinico-biological endpoints.

Methods

75 cases of MBC were identified using the records of the Saskatchewan Cancer Agency over 26 years (1970-1996). Cases were reviewed and analyzed for the immunohistochemical expression of PCNA, Ki67, p27, p16, p57, p21, cyclin-D1 and c-myc and correlated to clinico-biological endpoints of tumor size, node status, stage of the disease, and disease free survival (DFS).

Results

Decreased DFS was observed in the majority of tumors that overexpressed PCNA (98%, p = 0.004). The overexpression of PCNA was inversely correlated to the expression of Ki67 which was predominantly negative (78.3%). Cyclin D1 was overexpressed in 83.7% of cases. Cyclin D1 positive tumors were smaller than 2 cm (55.6%, p = 0.005), had a low incidence of lymph node metastasis (38.2%, p = 0.04) and were associated with increased DFS of >150 months (p = 0.04). Overexpression of c-myc (90%) was linked with a higher incidence of node negativity (58.3%, p = 0.006) and increased DFS (p = 0.04). p27 over expression was associated with decreased lymph node metastasis (p = 0.04). P21 and p57 positive tumors were related to decreased DFS (p = 0.04). Though p16 was overexpressed in 76.6%, this did not reach statistical significance with DFS (p = 0.06) or nodal status (p = 0.07).

Conclusion

Aberrant cell cycle protein expression supports our view that these are important pathways involved in the etiopathogenesis of MBC. Tumors with overexpression of Cyclin D1 and c-myc had better outcomes, in contrast to tumors with overexpression of p21, p57, and PCNA with significantly worse outcomes. P27 appears to be a predictive marker for lymph nodal status. Such observation strongly suggests that dysregulation of cell cycle proteins may play a unique role in the initiation and progression of disease in male breast cancer. Such findings open up new avenues for the treatment of MBC as a suitable candidate for novel CDK-based anticancer therapies in the future.     

Expression of Stretch-Activated Two-Pore Potassium Channels in Human Myometrium in Pregnancy and Labor

Background

We tested the hypothesis that the stretch-activated, four-transmembrane domain, two pore potassium channels (K2P), TREK-1 and TRAAK are gestationally-regulated in human myometrium and contribute to uterine relaxation during pregnancy until labor.

Methodology

We determined the gene and protein expression of K2P channels in non-pregnant, pregnant term and preterm laboring myometrium. We employed both molecular biological and functional studies of K2P channels in myometrial samples taken from women undergoing cesarean delivery of a fetus.

Principal Findings

TREK-1, but not TREK-2, channels are expressed in human myometrium and significantly up-regulated during pregnancy. Down-regulation of TREK-1 message was seen by Q-PCR in laboring tissues consistent with a role for TREK-1 in maintaining uterine quiescence prior to labor. The TRAAK channel was unregulated in the same women. Blockade of stretch-activated channels with a channel non-specific tarantula toxin (GsMTx-4) or the more specific TREK-1 antagonist L-methionine ethyl ester altered contractile frequency in a dose-dependent manner in pregnant myometrium. Arachidonic acid treatment lowered contractile tension an effect blocked by fluphenazine. Functional studies are consistent with a role for TREK-1 in uterine quiescence.

Conclusions

We provide evidence supporting a role for TREK-1 in contributing to uterine quiescence during gestation and hypothesize that dysregulation of this mechanism may underlie certain cases of spontaneous pre-term birth.     

Exercise elicits phase shifts and acute alterations of melatonin that vary with circadian phase

To examine the immediate phase-shifting effects of high-intensity exercise of a practical duration (1 h) on human circadian phase, five groups of healthy men 20-30 yr of age participated in studies involving no exercise or exposure to morning, afternoon, evening, or nocturnal exercise. Except during scheduled sleep/dark and exercise periods, subjects remained under modified constant routine conditions allowing a sleep period and including constant posture, knowledge of clock time, and exposure to dim light intensities averaging (+/-SD) 42 +/- 19 lx. The nocturnal onset of plasma melatonin secretion was used as a marker of circadian phase. A phase response curve was used to summarize the phase-shifting effects of exercise as a function of the timing of exercise. A significant effect of time of day on circadian phase shifts was observed (P < 0.004). Over the interval from the melatonin onset before exercise to the first onset after exercise, circadian phase was significantly advanced in the evening exercise group by 30 +/- 15 min (SE) compared with the phase delays observed in the no-exercise group (-25 +/- 14 min, P < 0.05). Phase shifts in response to evening exercise exposure were attenuated on the second day after exercise exposure and no longer significantly different from phase shifts observed in the absence of exercise. Unanticipated transient elevations of melatonin levels were observed in response to nocturnal exercise and in some evening exercise subjects. Taken together with the results from previous studies in humans and diurnal rodents, the current results suggest that 1) a longer duration of exercise exposure and/or repeated daily exposure to exercise may be necessary for reliable phase-shifting of the human circadian system and that 2) early evening exercise of high intensity may induce phase advances relevant for nonphotic entrainment of the human circadian system.     

Communication between the maternal testa and the embryo and/or endosperm affect testa attributes in tomato

Two tomato (Lycopersicon esculentum) mutants with dark testae displaying poor germination rate and percentage on both water and 100 microM gibberellin(4 + 7) were recovered. The mutants were allelic (black seed1-1; bks1-1 and bks1-2), inherited in Mendelian fashion as a recessive gene residing on chromosome 11. They are not allelic to bs (brown seed) -1, -2, or -4, which impair seed germination and possess dark testae. The bks/bs mutants accumulated dark pigment in the cell layers of the testa above the endothelium, which itself accumulated proanthocyanidins similar to wild type. The poor germination performance of bks mutant seeds was because of impediment of the mutant testae to radicle egress. Imbibition on gibberellin(4 + 7) did not ameliorate germination percentage or rate. The toughening of the bks testa and associated poor germination were partially overcome when seeds were not dried before germination or were dried under N(2). The seeds of the bks mutant have elevated activity of at least one enzyme responsible for the detoxification of reactive oxygen species. The bks mutant is epistatic to 12 anthocyaninless mutants of tomato. Bio- and physicochemical analysis of the bks testa determined that it accumulated a melanic substance. Inheritance of bks/bs mutations contrasts with that of the anthocyaninless mutants, which are inherited according to the genotype of the maternally derived testa. This suggests that the testa manufactures components before its demise that can maximize testa strength, whereas the endosperm/embryo produces factors that are conveyed to the testa, mitigating this process.     

Secondary structure prediction with support vector machines

MOTIVATION: A new method that uses support vector machines (SVMs) to predict protein secondary structure is described and evaluated. The study is designed to develop a reliable prediction method using an alternative technique and to investigate the applicability of SVMs to this type of bioinformatics problem. METHODS: Binary SVMs are trained to discriminate between two structural classes. The binary classifiers are combined in several ways to predict multi-class secondary structure. RESULTS: The average three-state prediction accuracy per protein (Q(3)) is estimated by cross-validation to be 77.07 +/- 0.26% with a segment overlap (Sov) score of 73.32 +/- 0.39%. The SVM performs similarly to the 'state-of-the-art' PSIPRED prediction method on a non-homologous test set of 121 proteins despite being trained on substantially fewer examples. A simple consensus of the SVM, PSIPRED and PROFsec achieves significantly higher prediction accuracy than the individual methods.     

Position-independent expression of a human nerve growth factor-luciferase reporter gene cloned on a yeast artificial chromosome vector.

Two yeast artificial chromosomes containing the entire human nerve growth factor gene were isolated and mapped. By homologous recombination a luciferase gene was precisely engineered into the coding portion of the NGF gene and a neomycin selection marker was placed adjacent to one of the YAC telomeres. Expression of the YAC-based NGF reporter gene and a plasmid-based NGF reporter gene were compared with the regulation of endogenous mouse NGF protein in mouse L929 fibroblasts. In contrast to the plasmid-based reporter gene, expression and regulation of the YAC-based reporter gene was independent of the site of integration of the transgene. Basic fibroblast growth factor and okadaic acid stimulated expression of the YAC transgene, whereas transforming growth factor-beta and dexamethasone inhibited it. Although cyclic AMP strongly stimulated production of the endogenous mouse NGF, no effect was seen on the human NGF reporter genes. Downregulation of the secretion of endogenous mouse NGF already occurred at an EC50 of 1-2 nM dexamethasone, but downregulation of the expression of NGF reporter genes occurred only at EC50 of 10 nM. This higher concentration was also required for upregulation of luciferase genes driven by the dexamethasone-inducible promoter of the mouse mammary tumor virus in L929 fibroblasts.