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p -Phenylenediamine and its dihydrate: two-dimensional isomorphism and mechanism of the dehydration process, and N,H...N and N,H..., interactions

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2010
Agnieszka Czapik
p -Phenylenediamine can be obtained as the dihydrate, C6H8N2·2H2O, (I), and in its anhydrous form, C6H8N2, (II). The asymmetric unit of (I) contains one half of the p -phenylenediamine molecule lying about an inversion centre and two halves of water molecules, one lying on a mirror plane and the other lying across a mirror plane. In (II), the asymmetric unit consists of one molecule in a general position and two half molecules located around inversion centres. In both structures, the p -phenylenediamine molecules are arranged in layers stabilized by N,H..., interactions. The diamine layers in (I) are isostructural with half of the layers in (II). On dehydration, crystals of (I) transform to (II). Comparison of their crystal structures suggests the most plausible mechanism of the transformation process which requires, in addition to translational motion of the diamine molecules, in-plane rotation of every fourth p -phenylenediamine molecule by ca 60°. A search of the Cambridge Structural Database shows that the formation of hydrates by aromatic amines should be considered exceptional. [source]

Percutaneous Mitral Valve Repair for Mitral Regurgitation

JOURNAL OF INTERVENTIONAL CARDIOLOGY, Issue 1 2003
PETER C. BLOCK M.D.
Mitral regurgitation (MR) associated with, ischemic, and degenerative (prolapse) disease, contributes to left ventricular (LV) dysfunction due to remodeling, and LV dilation, resulting in worsening of MR. Mitral valve (MV) surgical repair has provided improvement in survival, LV function and symptoms, especially when performed early. Surgical repair is complex, due to diverse etiologies and has significant complications. The Society for Thoracic Surgery database shows that operative mortality for a 1st repair is 2% and for re-do repair is 4 times that. Cardiopulmonary bypass and cardiac arrest are required. The attendant morbidity prolongs hospitalization and recovery. Alfieri simplified mitral repair using an edge-to-edge technique which subsequently has been shown to be effective for multiple etiologies of MR. The MV leaflers are typically brought together by a central suture producing a double orifice MV without stenosis. Umana reported that MR decreased from grade 3.6 +/,0.5 to0.8 +/,0.4 (P < 0.0001)and LV ejection fraction increased from 33 +/,13% to 45 +/,11%(P = 0.0156). In 121 patients, Maisano reported freedom from re-operation of 95 +/,4.8% with up to 6 year follow-up. Oz developed a MV "grasper" that is directly placed via a left ventriculotomy and coapts both leaflets which are then fastened by a graduated spiral screw. An in-vitro model using explanted human valves showed significant reduction in MR and in canine studies, animals followed by serial echo had persistent MV coaptation. At 12 weeks the device was endothelialized. These promising results have paved the way for a percutaneous or minimally invasive off pump mitral repair. Evalve has developed catheter-based technology, which, by apposing the edges of a regurgitant MV, results in edge-to-edge repair. Release of the device is done after echo and fluoroscopic evaluation under normal loading conditions. If the desired effect is not produced the device can be repositioned or retrieved. Animal studies show excellent healing, with incorporation of the device into the leaflets at 6,10 weeks with persistent coaptation. Another percutaneous approach has been to utilize the proximity of the coronary sinus (CS) to the mitral annulus (MA). Placement of a self-compressing device in the CS along the region of the posterior MA has, in canine models, reduced MR and addresses the issues of MA dilation and its contribution to MR. Ongoing studies are underway for both techniques. (J Interven Cardiol 2003;16:93,96) [source]

Intraspecific competition drives multiple species resource polymorphism in fish communities

OIKOS, Issue 1 2008
Richard Svanbäck
It has been hypothesized that inter-specific competition will reduce species niche utilization and drive morphological evolution in character displacement. In the absence of a competitor, intra-specific competition may favor an expansion of the species niche and drive morphological evolution in character release. Despite of this theoretical framework, we sometimes find potential competitor species using the same niche range without any partitioning in niche. We used a database on test fishing in Sweden to evaluate the factors (inter- and intraspecific competition, predation, and abiotic factors) that could influence habitat choice of two competitor species. The pattern from the database shows that the occurrence of perch and roach occupying both littoral and pelagic habitats of lakes in Sweden is a general phenomenon. Furthermore, the results from the database suggest that this pattern is due to intra-specific competition rather than inter-specific competition or predation. In a field study, we estimated the morphological variation in perch and roach and found that, individuals of both species caught in the littoral zone were more deeper bodied compared to individuals caught in the pelagic zone. Pelagic perch fed more on zooplankton compared to littoral perch, independent of size, whereas the littoral perch had more macroinvertebrates and fish in their diet. Pelagic roach fed more on zooplankton compared to littoral roach, whereas littoral individuals fed more on plant material. Furthermore, we sampled littoral and pelagic fish from another lake to evaluate the generality of our first results and found the same habitat associated morphology in both perch and roach. The results show a consistent multi-species morphological separation in the littoral and pelagic habitats. This study suggests that intra-specific competition is possibly more important than inter-specific competition for the morphological pattern in the perch-roach system. [source]

Latest news and product developments

PRESCRIBER, Issue 23-24 2007
Article first published online: 8 JAN 200
Cervical cancer risk falls after COC use ends Combined oral contraceptives (COCs) are associated with a slight increase in the risk of cervical cancer but this diminishes with time after use ends, an international study has shown (Lancet 2007;370:1609,21). Analysis of data for 16 573 women with and 35 509 women without cervical cancer confirmed that using a COC for 10 years between the ages of 20 and 30 increases the incidence of invasive cervical cancer from 3.8 to 4.5 per 1000 by age 50. However, the excess risk disappears 10 years after cessation of use. , A new analysis of the US Nurses' Health Study suggests that protection against ovarian cancer does not persist beyond 20 years after cessation of COC use. This study also showed that tubal ligation is associated with reduced risk of ovarian cancer (Am J Epidemiol 2007; 166;894,901). Pharmaceutical services fund moves to PCTs The ,global sum' that provides central funding for NHS pharmaceutical services is being shifted to PCTs. The Government has included legislation for the change in the recent Health and Social Care Bill. The fund pays the fees and allowances for pharmacy contractors and appliance contractors. The Government says this is a ,natural progression and in keeping with moves to devolve NHS funds to the frontline' that will enable PCTs to manage pharmacy services better by ,encouraging best prescribing practice'. Fewer fluoroquinolones in the community Restricting prescribing of fluoroquinolone antibacterials does not increase hospital admissions for infection among older people, say Canadian researchers (Am J Med 2007;120:893,900). Their analysis of an Ontario medical database shows that, in a community where fluoroquinolones were the most widely prescribed antibacterials, a one-third reduction in prescribing was not followed by an increase in hospital admissions for infectious episodes in the over,65s. On the contrary, there was a 32 per cent reduction in admissions for gastrointestinal conditions. FDA reports increased TB risk with infliximab The US Food and Drug Administration has published an analysis of cases of TB associated with infliximab (Remicade) detected via its spontaneous adverse event reporting scheme (Ann Intern Med 2007;147: 699,702). In 2001 the FDA placed a warning about the risk of TB on product labelling for infliximab and advised testing for TB before initiating treatment. This analysis of 130 cases of TB since reported in patients treated with infliximab found that 45 per cent had developed extra-pulmonary disease; risk factors included use of immunosuppressants (including methotrexate), a history of TB and time spent in an endemic area. Of 67 cases in which treatment was initiated after the warning was issued, 34 with a negative tuberculin skin test developed TB after receiving infliximab. MHRA announces anticounterfeit strategy The UK is a transit point, distribution hub and end-user of counterfeit medicines, says the MHRA in its first anti-counterfeiting strategy (www.mhra.gov.uk). Counterfeits have been detected in the legitimate supply chain with increasing frequency since 2004, resulting in nine batch recalls and a further five incidents detected at wholesale level. The MHRA's proposed approach includes: communication to raise awareness of the risk and facilitate reporting, collaboration with the WHO, the industry and law enforcement agencies, and targeted surveillance, prosecution and regulation. Evidence lacking for choosing DMARD There is insufficient evidence to choose one DMARD or biological agent over another in patients with RA, US investigators say (www.annals.org/cgi/content/abstract/0000605,20080115000192v1). Their systematic review of meta-analyses and intervention and observational trials found no evidence of differences among DMARDs or anti-TNF agents. Mono-therapy with an anti-TNF agent was associated with superior radiographic but not clinical outcomes; methotrexate plus an anti-TNF agent was superior in clinical and functional terms to either drug given alone. Be alert to psychiatric ADRs with rimonabant Clinicians should remain alert for the development of anxiety, depression and an increased risk of suicide with rimonabant (Acomplia), say Danish investigators (Lancet 2007;370:1706,13). Their meta-analysis of four randomised trials involving a total of 4105 patients showed that rimonabant was associated with an increased risk of serious adverse events (odds ratio 1.4; number needed to harm, NNH, 59), including a 2.5,fold increased risk of depression (NNH 49) and a threefold increased risk of anxiety (NNH 166). Following a warning from the FDA of an increased risk of suicide with rimonabant, the authors say their findings indicate a need for ,increased alertness by physicians to these potentially severe psychiatric adverse reactions'. New strategy for NHS medicines information The UK Medicines Information Service (www.ukmi.nhs.uk) has published its new management strategy setting out how it will respond to recent developments in the NHS. Developments include greater access to information for patients, support for nontraditional prescribers and new commissioning arrangements. New antiretroviral Maraviroc (Celsentri) is the first CCR5 antagonist to be introduced for the treatment of HIV infection. CCR5 is one of two co-receptors to which the HIV virus must attach to achieve cell entry. Maraviroc is licensed for use by treatment-experienced patients in whom only CCR5-tropic HIV-1 is detectable. The recommended dose ranges from 150 to 600mg twice daily depending on interactions with concurrent medication. Dimeticone superior Dimeticone 4 per cent lotion (Hedrin) is superior to malathion 0.5 per cent in the eradication of head lice, a UK study in 58 children and 15 adults has shown (PLoS ONE 2007;2: e1127. doi:10.1371/journal.pone. 0001127). Two applications of dimeticone lotion one week apart cleared active infestation in 70 per cent of participants compared with 33 per cent in those who used a single application of malathion. Copyright © 2007 Wiley Interface Ltd. [source]