Zinc potentiation of the glycine receptor chloride channel is mediated by allosteric pathways

Molecular mechanisms of zinc potentiation were investigated in recombinant human alpha 1 glycine receptors (GlyRs) by whole-cell patch-clamp recording and [H-3]strychnine binding assays. In the wild-type (WT) GlyR, 1 mu M zinc enhanced the apparent binding affinity of the agonists glycine and taurine and reduced their concentrations required for half-maximal activation. Thus, in the WT GlyR, zinc potentiation apparently occurs by enhancing agonist binding. However, analysis of GlyRs incorporating mutations in the membrane-spanning domain M1-M2 and M2-M3 loops, which are both components of the agonist gating mechanism, indicates that most mutations uncoupled zinc potentiation from glycine-gated currents but preserved zinc potentiation of taurine-gated currents. One such mutation in the M2-M3 loop, L274A, abolished the ability of zinc to potentiate taurine binding but did not inhibit zinc potentiation of taurine-gated currents. In this same mutant where taurine acts as a partial agonist, zinc potentiated taurine-gated currents but did not potentiate taurine antagonism of glycine-gated currents, suggesting that zinc interacts selectively with the agonist transduction pathway. The intracellular M246A mutation, which is unlikely to bind zinc, also disrupted zinc potentiation of glycine currents. Thus, zinc potentiation of the GlyR is mediated via allosteric mechanisms that are independent of its effects on agonist binding.

Factors affecting biosynthesis by Xanthomonas albilineans of albicidin antibiotics and phytotoxins

Albicidins are important factors in systemic pathogenesis by Xanthomonas albilineans, which causes the devastating leaf scald disease of sugar cane. They ale also of substantial interest as antibiotics that selectively block prokaryote DNA replication. Albicidin biosynthesis is highly sensitive to medium composition. An optimized, chemically defined medium (SMG3) yielded 30-fold more albicidin from half the accumulated biomass, relative to sucrose peptone (SP) medium. Phosphate starvation stimulated albicidin production in SMG3 and SP media. Addition of other amino acids, ammonium ions or peptones to the defined medium increased the growth rate of X albilineans XA3, but differentially inhibited albicidin biosynthesis. Knowledge of these factors indicates new approaches to understanding mechanisms of pathogenesis and resistance to sugar cane leaf scald disease, and to strain improvement for production of albicidin antibiotics.

Characteristics of long-term cannabis users in Sydney, Australia

Two hundred long-term cannabis users (58% male) were interviewed on their characteristics and experience of use. Respondents had been regularly using cannabis for an average of 11 years and more than half used daily (56%). The most common route of administration was in a waterpipe, and nearly all (93%) smoked the flowering heads ot the plant. One in 5 (21%) had a cannabis-related conviction. The benefits of use were perceived to be its relaxing, mood-enhancing effects, and its ability to alter consciousness. The most commonly cited negative aspects of use were cost, negative psychological effects and legal status. Polydrug use was common, with alcohol and tobacco almost universally used on a regular basis. More than half the drinkers in the sample were consuming alcohol at hazardous or harmful levels.

Activation of beta(2)-adrenergic receptors hastens relaxation and mediates phosphorylation of phospholamban, troponin I, and C-protein in ventricular myocardium from patients with terminal heart failure

Background-Catecholamines hasten cardiac relaxation through beta-adrenergic receptors, presumably by phosphorylation of several proteins, but it is unknown which receptor subtypes are involved in human ventricle. We assessed the role of beta(1)- and beta(2)-adrenergic receptors in phosphorylating proteins implicated in ventricular relaxation. Methods and Results-Right ventricular trabeculae, obtained from freshly explanted hearts of patients with dilated cardiomyopathy (n=5) or ischemic cardiomyopathy (n=5), were paced at 60 bpm. After measurement of the contractile and relaxant effects of epinephrine (10 mu mol/L) or zinterol (10 mu mol/L), mediated through beta(2)-adrenergic receptors, and of norepinephrine (10 mu mol/L), mediated through beta(1)-adrenergic receptors, tissues were freeze clamped. We assessed phosphorylation of phospholamban, troponin I, and C-protein, as well as specific phosphorylation of phospholamban at serine 16 and threonine 17, Data did not differ between the 2 disease groups and were therefore pooled. Epinephrine, zinterol, and norepinephrine increased contractile force to approximately the same extent, hastened the onset of relaxation by 15+/-3%, 5+/-2%, and 20+/-3%, respectively, and reduced the time to half-relaxation by 26+/-3%, 21+/-3%, and 37+/-3%. These effects of epinephrine, zinterol, and norepinephrine were associated with phosphorylation (pmol phosphate/mg protein) of phospholamban 14+/-3, 12+/-4, and 12+/-3, troponin I 40+/-7, 33+/-7, and 31+/-6; and C-protein 7.2+/-1.9, 9.3 +/- 1.4, and 7.5 +/- 2.0. Phosphorylation of phospholamban occurred at both Ser16 and Thr17 residues through both beta(1)- and beta(2)-adrenergic receptors. Conclusions-Norepinephrine and epinephrine hasten human ventricular relaxation and promote phosphorylation of implicated proteins through both beta(1)- and beta(2)-adrenergic receptors, thereby potentially improving diastolic function.

Changes in cigarette smoking among adults in 35 populations in the mid-1980s

Objective-To examine changes in the prevalence of cigarette smoking in 35 study populations of the World Health Organisation's MONICA Project. Design-Data from two independent, community-based surveys conducted, on average, five years apart. Setting-Geographically defined populations in 21 countries mainly in eastern and western Europe. Subjects-Randomly selected men and women aged 25-64 years. Numbers of participants in each study population ranged from 586 to 2817 in each survey. Main outcome measures-Changes in proportions of current smokers, ex-smokers, and never-smokers by age and sex using data collected by standardised methods. Results-Among men, smoking prevalence decreased in most populations, by three to four percentage points over five years. In Beijing, however, it increased in all age groups-overall by 11 percentage points. Among women there were increases in smoking in about half the populations. The increases were mainly in the age group 35-54 years and often in those populations where smoking prevalence among women has been relatively low. Conclusions-Smoking initiation by middle-aged women in parts of southern and eastern Europe and among men of all ages in Beijing is a matter of concern. The various public health measures that have helped to reduce smoking among men in developed countries should be vigorously extended to these other groups now at growing risk of smoking-related disease.

Predictors of local recurrence after treatment of ductal carcinoma in situ - A meta-analysis

lBACKGROUND. Management of patients with ductal carcinoma in situ (DCIS) is a dilemma, as mastectomy provides nearly a 100% cure rate but at the expense of physical and psychologic morbidity. It would be helpful if we could predict which patients with DCIS are at sufficiently high risk of local recurrence after conservative surgery (CS) alone to warrant postoperative radiotherapy (RT) and which patients are at sufficient risk of local recurrence after CS + RT to warrant mastectomy. The authors reviewed the published studies and identified the factors that may be predictive of local recurrence after management by mastectomy, CS alone, or CS + RT. METHODS. The authors examined patient, tumor, and treatment factors as potential predictors for local recurrence and estimated the risks of recurrence based on a review of published studies. They examined the effects of patient factors (age at diagnosis and family history), tumor factors (sub-type of DCIS, grade, tumor size, necrosis, and margins), and treatment (mastectomy, CS alone, and CS + RT). The 95% confidence intervals (CI) of the recurrence rates for each of the studies were calculated for subtype, grade, and necrosis, using the exact binomial; the summary recurrence rate and 95% CI for each treatment category were calculated by quantitative meta-analysis using the fixed and random effects models applied to proportions. RESULTS, Meta-analysis yielded a summary recurrence rate of 22.5% (95% CI = 16.9-28.2) for studies employing CS alone, 8.9% (95% CI = 6.8-11.0) for CS + RT, and 1.4% (95% CI = 0.7-2.1) for studies involving mastectomy alone. These summary figures indicate a clear and statistically significant separation, and therefore outcome, between the recurrence rates of each treatment category, despite the likelihood that the patients who underwent CS alone were likely to have had smaller, possibly low grade lesions with clear margins. The patients with risk factors of presence of necrosis, high grade cytologic features, or comedo subtype were found to derive the greatest improvement in local control with the addition of RT to CS. Local recurrence among patients treated by CS alone is approximately 20%, and one-half of the recurrences are invasive cancers. For most patients, RT reduces the risk of recurrence after CS alone by at least 50%. The differences in local recurrence between CS alone and CS + RT are most apparent for those patients with high grade tumors or DCIS with necrosis, or of the comedo subtype, or DCIS with close or positive surgical margins. CONCLUSIONS, The authors recommend that radiation be added to CS if patients with DCIS who also have the risk factors for local recurrence choose breast conservation over mastectomy. The patients who may be suitable for CS alone outside of a clinical trial may be those who have low grade lesions with little or no necrosis, and with clear surgical margins. Use of the summary statistics when discussing outcomes with patients may help the patient make treatment decisions. Cancer 1999;85:616-28. (C) 1999 American Cancer Society.

Red Parkes quasars: Evidence for soft X-ray absorption

The Parkes Half-Jansky Flat-Spectrum Sample contains a large number of sources with unusually red optical-to-near-infrared (NIR) continua. If this is to be interpreted as extinction by dust in the line of sight, then associated material might also give rise to absorption in the soft X-ray regime. This hypothesis is tested using broadband (0.1-2.4 keV) data from the ROSAT All-Sky Survey. Significant (>3 sigma confidence level) correlations between the optical (and NIR)-to-soft X-ray continuum slope and optical extinction are found in the data, consistent with absorption by material with metallicity and a range in the gas-to-dust ratio as observed in the local ISM. Under this simple model, the soft X-rays are absorbed at a level consistent with the range of extinctions (0 < A(V) < 6 mag) implied by the observed optical reddening. Excess X-ray absorption by warm (ionized) gas, (i.e., a warm absorber) is not required by the data.

Site-directed mutants of RTP of Bacillus subtilis and the mechanism of replication fork arrest

DNA replication fork arrest during the termination phase of chromosome replication in Bacillus subtilis is brought about by the replication terminator protein (RTP) bound to specific DNA terminator sequences (Tev sites) distributed throughout the terminus region. An attractive suggestion by others was that crucial to the functioning of the RTP-Ter complex is a specific interaction between RTP positioned on the DNA and the helicase associated with the approaching replication fork. Ln support of this was the behaviour of two site-directed mutants of RTP. They appeared to bind Ter DNA normally but were ineffective in fork arrest as ascertained by in vitro Escherichia coli DnaB helicase and replication assays. We describe here a system for assessing the fork-arrest behaviour of RTP mutants in a bona fide in vivo assay in B. subtilis. One of the previously studied mutants, RTP.Y33N, was non-functional in fork arrest in vivo, as predicted. But through extensive analyses, this RTP mutant was shown to be severely defective in binding to Ter DNA, contrary to expectation. Taken in conjunction with recent findings on the other mutant (RTP.E30K), it is concluded that there is as yet no substantive evidence from the behaviour of RTP mutants to support the Rm-helicase interaction model for fork arrest. In an extension of the present work on RTP.Y33N, we determined the dissociation rates of complexes formed by wild-type (wt) RTP and another RTP mutant with various terminator sequences. The functional wtRTP-TerI complex was quite stable (half-life of 182 minutes), reminiscent of the great stability of the E. coli Tus-Ter complex. More significant were the exceptional stabilities of complexes comprising wtRTP and an RTP double-mutant (E39K.R42Q) bound to some particular terminator sequences. From the measurement of in vivo fork-arrest activities of the various complexes, it is concluded that the stability (half-life) of the whole RTP-Ter complex is not the overriding determinant of arrest, and that the RTP-Ter complex must be actively disrupted, or RTP removed, by the action of the approaching replication fork. (C) 1999 Academic Press.

Jurisdictional trends in opioid overdose deaths, 1988-96

This report analysed data on opioid overdose mortality between 1988 and 1996 to: examine differences between jurisdictions in the rate of fatal opioid overdose and the rate of increase in overdose; and estimate the proportion of all deaths which were attributed to opioid overdose. Australian Bureau of Statistics (ABS) data were obtained on the number of deaths attributed to opioid dependence (ICD 9 codes 304.0, 304.7) and accidental opioid poisoning (ICD 9 codes E850.0, E850.1). The highest rate of fatal overdose occurred in NSW, followed by Victoria. The standardised mortality rate among other jurisdictions fluctuated quite markedly. While the rate of opioid overdose has increased throughout Australia, the rate of increase has been greater in some of the less-populous states and territories than it has in NSW or Victoria. In 1996, approximately 6.5% of all deaths among people aged 15-24 years and approximately 10% of all deaths among those aged 25-34 were due to opioid overdose. During the interval from 1988 to 1996, the proportion of deaths attributed to opioid overdose increased. From 1988 to 1996, the proportion of deaths attributed to opioid overdose among individuals aged 25-34 years was approximately one-third that attributed to suicide, but this proportion had increased to approximately one-half by 1996. The rate of increase in the proportion of deaths attributed to opioid overdose was higher than the rate of increase in the proportion of deaths attributed to suicide.

Leaking urine in Australian women: Prevalence and associated conditions

The paper aims to (1) assess the prevalence of leaking urine and to (2) explore associations between leaking urine and a variety of other symptoms, conditions, surgical procedures and life events in three large cohorts of Australian women, who are participants in the Australian Longitudinal Study on Women's Health. Young women aged 18-23 (N = 14,000), mid-age women, 45-50 (N 13,738) and older women, 70-75 (N = 12,417), were recruited randomly from the national HIC/Medicare database. Leaking urine was reported by approximately one in eight young women [estimated prevalence 12.8% (95% CI: 12.2-13.3)] and one in three mid-age women [36.1% (CI: 35.2-37.0)] and older women [35.0% (CI: 34.1-35.9)]. Leaking urine was significantly associated with parity, conditions which increase the pressure on the pelvic floor such as constipation and obesity, past gynecological surgery and conditions which can impact on bladder control. The study showed that fewer than half the women had sought help for the problem and that younger women were less likely to be satisfied with the help available for this problem. Strategies for continence promotion, including opportunistic raising of the issue at the time of cervical screening and pregnancy care are suggested, so that the health and social outcomes of untreated chronic incontinence in women might be improved.

Ca2+ sensitivity of phospholipid scrambling in human red cell ghosts

The phospholipids in plasma membranes of erythrocytes, as well as platelets, lymphocytes and other cells are asymmetrically distributed, with sphingomyelin and phosphatidylcholine residing predominantly in the outer leaflet of the bilayer, and phosphatidylserine and phosphatidylethanolamine in the inner leaflet. It is known that Ca2+ can disrupt the phospholipid asymmetry by activation of a protein known as phospholipid scramblase, which affects bidirectional phospholipid movement in a largely non-selective manner. As Ca2+ also inhibits aminophospholipid translocase, whose Mg2+-ATPase activity is responsible for active translocation of aminophospholipids from the outer to the inner leaflet, it is important to accurately determine the sensitivity of scramblase to intracellular free Ca2+. In the present study we have utilized the favourable K-d, of Mag-fura-2 for calcium in the high micromolar range to determine free Ca2+ levels associated with lipid scrambling in resealed human red cell ghosts. The Ca2+ sensitivity was measured in parallel to the translocation of a fluorescent-labelled lipid incorporated into the ghost bilayer. The phospholipid scrambling was found to be half-maximally activated at 63-88 mu M free intracellular Ca2+. The wider applicability of the method and the physiological implications of the calcium sensitivity determined is discussed.

Effect of smoke-free policies on the behaviour of social smokers

Objective-To test the hypothesis that proposed amendments to the Occupational Safety and Health Act making all enclosed workplaces in Western Australia smoke free would result in a decrease in cigarette consumption by patrons at nightclubs, pubs, and restaurants without adversely affecting attendance. Design-Cross sectional structured interview survey. Participants and setting-Patrons of several inner city pubs and nightclubs in Perth were interviewed while queuing for admission to these venues. Outcome measures-Current social habits, smoking habits, and how these might be affected by the proposed regulations. Persons who did not smoke daily were classified as social smokers. Results-Half (50%) of the 374 patrons interviewed were male, 51% currently did not smoke at all, 34.3% smoked every day, and the remaining 15.7% smoked, brat not every day. A clear majority (62.5%) of all 374 respondents anticipated no change to the frequency of their patronage of hospitality venues if smoke-free policies became mandatory One in five (19.3%) indicated that they would,ao out more often, and 18.2% said they would go out less often. Half (52%) of daily smokers anticipated no change to their cigarette consumption, while 44.5% of daily smokers anticipated a reduction in consumption. A majority of social smokers (54%) predicted a reduction in their cigarette consumption, with 42% of these anticipating quitting. Conclusions-One in nine (11.5%) of smokers say that adoption of smoke-Pi ee policies would prompt them to quit smoking entirely without a significant decrease in attendance at pubs and nightclubs. There can be few other initiatives as simple, cheap, and popular that would achieve so much for public health.

Thylakoid membrane architecture

Confocal scanning laser microscopic observations were made on live chloroplasts in intact cells and on mechanically isolated, intact chloroplasts. Chlorophyll fluorescence was imaged to observe thylakoid membrane architecture. C-3 plant species studied included Spinacia oleracea L., Spathiphyllum sp. Schott, cv. 'Mauna Loa', and Pisum sativum L. C-4 plants were also investigated: Saccharum officinarum L., Sorghum bicolor L. Moench, Zea mays L. and Panicum miliaceum L. Some Spinacia chloroplasts were treated with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) to enhance or sodium dithionite (SD) to reduce the photosystem II fluorescence signal. Confocal microscopy images of C-3 chloroplasts differed from electron microscopy pictures because they showed discrete spots of bright fluorescence with black regions between them. There was no evidence of fluorescence from stroma thylakoids. The thylakoid membrane system at times appeared to be string-like, with brightly fluorescing grana lined up like beads. C-4 bundle sheath chloroplasts were imaged from three different types of C-4 plants. Saccharum and Sorghum bundle sheath chloroplasts showed homogeneous fluorescence and were much dimmer than mesophyll chloroplasts. Zea had rudimentary grana, and dim, homogeneous intergrana fluorescence was visualised. Panicum contained thylakoids similar in appearance and string-like arrangement to mesophyll chloroplasts. Isolated Pisum chloroplasts, treated with a drop of 5 mM MgCl2 showed a thylakoid membrane system which appeared to be unravelling. Spongy mesophyll chloroplasts of Spinacia treated with 5 mM sodium dithionite showed a granal thylakoid system with distinct regions of no fluorescence. A time-series experiment provided evidence of dynamic membrane rearrangements over a period of half an hour.

Detection of dimethyl sulfone in the human brain by in vivo proton magnetic resonance spectroscopy

We wish to report the detection of dimethyl sulfone (methylsulfonylmethane, C2H6O2S) in the brain of a normal 62-year-old male using in vivo proton magnetic resonance spectroscopy. The presence of this exogenous metabolite resulted from ingestion of a dietary supplement containing dimethyl sulfone. The concentration of this compound in the brain was measured to be 2.4 mmol, with a washout half life of approximately 7.5 days. The in vivo T-1 and T-2 relaxation times of dimethyl sulfone were measured to be 2180 ms and 385 ms, respectively. The concentration of major brain metabolites, namely N-acetylaspartate, total Creatine and Choline, and myo-Inositol were within normal limits. (C) 2000 Elsevier Science Inc. All rights reserved.

The politics and ethics of relocated art

At the end of Word War II, Soviet occupation forces removed countless art objects from German soil. Some of them were returned during the 1950s, but most either disappeared for good or were stored away secretly in cellars of Soviet museums. The Cold War then covered the issue with silence. After the collapse of the Soviet Union, museums in St Petersburg and Moscow started to exhibit some of the relocated art for the first time in half a century. The unusual quality of the paintings-mostly impressionist masterpieces-not only attracted the attention of the international art community, but also triggered a diplomatic row between Russia and Germany. Both governments advanced moral and legal claims to ownership. To make things even more complicated, many of the paintings once belonged to private collectors, some of whom were Jews. Their descendants also entered the dispute. The basic premise of this article is that the political and ethical dimensions of relocated art can be understood most adequately by eschewing a single authorial standpoint. Various positions, sometimes incommensurable ones, are thus explored in an attempt to outline possibilities for an ethics of representation and a dialogical solution to the international problem that relocated art has become.