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Selected AbstractsAdd-on Phenytoin Fails to Prevent Early Seizures after Surgery for Supratentorial Brain Tumors: A Randomized Controlled StudyEPILEPSIA, Issue 2 2002Antonio De Santis Summary: ,Purpose: To determine the potential effectiveness of phenytoin (PHT) in preventing early postoperative seizures in patients undergoing craniotomy for supratentorial brain tumors. Methods: Two hundred patients requiring elective craniotomy for supratentorial brain tumors were randomized to two groups of equal size, with a prospective, open-label, controlled design. One group received PHT (18 mg/kg as an intravenous intraoperative load, followed by additional daily doses aimed at maintaining serum PHT concentrations within the 10- to 20-ęg/ml range) for 7 consecutive days. In the other group, PHT was not administered. More than 90% of patients in both groups continued to take preexisting anticonvulsant medication (AEDs) with carbamazepine or phenobarbital throughout the study. The primary efficacy end point was the number of patients remaining free from seizures during the 7-day period after the operation. Results: Of 100 patients allocated to PHT, 13 experienced seizures during the 7-day observation period, compared with 11 of 100 patients in the placebo group (p > 0.05). Most seizures occurred in the first day after surgery in both groups. There were no differences between groups in the proportion of patients experiencing more than one seizure, but there was a trend for generalized seizures to be more common in PHT-treated patients than in controls (11 vs. five patients, respectively). Status epilepticus occurred in one patient in the PHT group and in two patients in the control group. Of the 13 PHT-treated seizure patients, 11 had serum PHT concentrations within the target range, and only two had concentrations below range on the days their seizures occurred. Conclusions: PHT, given at dosages producing serum concentrations within the target range, failed to prevent early postoperative seizures in patients treated with concomitant AEDs. Prophylactic administration of PHT cannot be recommended in these patients. [source] Adolescent stress and neural plasticity in hamsters: a vasopressin-serotonin model of inappropriate aggressive behaviourEXPERIMENTAL PHYSIOLOGY, Issue 2000Craig F. Ferris Animal studies show that arginine vasopressin facilitates aggression, while serotonin (5-HT) inhibits aggression by blocking the activity of the vasopressin system. Clinical studies report that subjects with a history of ,fighting and assault' show a significant positive correlation between cerebrospinal fluid concentrations of vasopressin and aggression in the presence of a hyporeactive 5-HT system. Thus, in animals and humans, a hyporeactive 5-HT system may result in enhanced vasopressin activity and increased aggression. Can the stress of emotional and physical insult, i.e. threat and attack, during adolescence affect the development of the vasopressin and 5-HT systems and alter normal aggressive behaviour in early adulthood? Adolescent male golden hamsters were weaned at postnatal day 25, and stressed for 2 weeks by daily 1 h bouts of threat and attack by adult hamsters. Male littermates were run in a parallel stress study using daily 1 h trials of isolation in a novel environment. During early adulthood, on postnatal day 45, 3 days after the cessation of stress trials, animals were tested for aggression in a resident: intruder model. The results show a context-dependent change in aggression. Animals with a history of abuse show exaggerated attack behaviour toward smaller males compared to littermates with a history of isolation stress. Conversely, when confronted by males of equal size, animals with a history of abuse show diminished aggression and increased submission compared to controls. It was determined that the density of vasopressin fibres and neurones in the hypothalamus is lower in abused animals compared to controls. In contrast, the number of 5-HT terminals within the hypothalamus is higher in abused animals compared to controls. These results provide evidence in an animal model that stress in the form of threat and attack during adolescence can alter the balance between vasopressin and 5-HT in the brain, resulting in inappropriate aggressive behaviour in early adulthood. [source] Effects of Gender and Size on Feed Acquisition in the Pacific White Shrimp Litopenaeus vannameiJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 2 2006Dustin R. Moss Pacific white shrimp, Litopenaeus vannamei, are sexually dimorphic for growth, where subadult and adult females typically are larger than males of the same age. This character may be attributed to physiological and/or behavioral differences between the sexes. To determine if growth differences are the result of a more aggressive feeding behavior by females, four concurrent feeding trials were conducted to study the effects of gender and size on feed acquisition time. Feeding trials consisted of tanks (three replicate tanks per trial) stocked with (1) all females with small- and large-size groups, (2) all males with small- and large-size groups, (3) a random selection of males and females (resulting in larger females than males), and (4) males and females of equal size. Depending on the trial, tanks were stocked with either an equal number of males and females or small and large shrimp. Shrimp were fed a limited ration of squid, and the total feeding time (TFT) of shrimp between groups within a tank was compared. Results show that both gender and size are important factors in TFT as large shrimp out-competed small shrimp in both all-female and all-male feeding trials. Gender is more important than size as males out-competed females for feed even when they were smaller than competing females. These results suggest that sexual growth dimorphism is not the result of more aggressive feeding by females. In fact, males have a competitive advantage over females in acquiring feed. These results are counterintuitive because females typically are larger than males. Additional research is needed to investigate the physiological basis for sexual growth dimorphism in this commercially important shrimp. [source] Host selection by Anopheles arabiensis and An. quadriannulatus feeding on cattle in ZimbabweMEDICAL AND VETERINARY ENTOMOLOGY, Issue 2 2002A. Prior Abstract In the Zambezi valley, mosquito females of the Anopheles gambiae Giles complex (Diptera: Culicidae) were collected from a hut containing pairs of cattle distinguishable by known DNA markers. DNA was extracted from the blood-fed mosquito abdomens and primer sets for ungulate and mosquito DNA loci were used to identify the mosquito sibling species and individual host source(s) of their bloodmeals. The 67 mosquitoes comprised a mixture of An. arabiensis Patton (31%) and An. quadriannulatus Theobald (69%). DNA from one or both of the cattle present in the hut was detected in 91% of samples. When the hut contained an adult and a calf, the percentage of bloodmeals from the adult, the calf and adult + calf were 58%, 27% and 15%, respectively; the trend towards meals from the adult host was consistent but not always significant. When the pair of cattle comprised two adults of roughly equal size and age, then mosquitoes generally showed no significant bias towards feeding from one individual. There was no significant difference in the pattern of host selection made by An. arabiensis and An. quadriannulatus but the former had a significantly higher percentage (20%) of mixed meals than An. quadriannulatus (9%). These two members of the An. gambiae complex appear to be less selective in their choice of cattle hosts compared to day-active Diptera such as tsetse and Stomoxys, possibly because the hosts are generally asleep when Anopheles are active and there is therefore less selective pressure to adapt to host defensive behaviour. The slight bias of Anopheles towards older and/or larger cattle may be related to the host's larger surface area. [source] G protein ,3 subunit 825T genotype is not associated with differing outcome in pediatric renal transplant recipientsPEDIATRIC TRANSPLANTATION, Issue 2 2002Berthold Hocher Recent studies have identified a novel polymorphism (C825T) of the gene encoding the ,3 subunit of heterotrimeric G proteins (GNB3), associated with enhanced activation of G proteins, which appears to be more common in hypertensive patients. The donor GNB3 825TT genotype was associated with reduced kidney allograft survival in adults. We examined (in 100 Caucasian pediatric renal transplant recipients) whether the GNB3 (C825T) polymorphism was associated with disease progression and outcome after renal transplantation. The slope of 1/creatinine was determined by linear regression analysis of a median of 12 points before and after renal transplantation, and the population was divided into two groups of equal size, before and after transplantation, according to the slope. The observed frequencies were 57 for the CC, 33 for the CT, and 10 for the TT haplotype. For comparison, 738 consecutive newborn babies with the same ethnic background were typed in the same hospital. Allele frequencies were statistically not significantly different (chi-square test, p =,0.1327). When dividing the pediatric renal transplant recipients into two groups with regard to the slope of 1/creatinine, both before and after renal transplantation, the observed proportions were CC 26, CT 17, and TT 7 in the group with the poorer slope and CC 31, CT 16, and TT 3 in the group with the better slope before renal transplantation (not significant [NS], chi-square test, p =,0.1777). The observed proportions after renal transplantation were CC 26, CT 16, and TT 8 in the group with the poorer slope and CC 31, CT 15, and TT 4 in the group with the better slope, respectively (NS, chi-square test, p =,0.167). Allograft survival was not associated with the T allele. In conclusion, in a sizeable number of pediatric renal transplant recipients the GNB3 C825T polymorphism was found not to be a genetic risk factor for end-stage kidney disease. In addition, kidney graft function and survival was also found not to be associated with a recipient GNB3 C825T polymorphism. [source] A spectral heuristic for bisecting random graphs,RANDOM STRUCTURES AND ALGORITHMS, Issue 3 2006Amin Coja-OghlanArticle first published online: 27 DEC 200 The minimum bisection problem is to partition the vertices of a graph into two classes of equal size so as to minimize the number of crossing edges. Computing a minimum bisection is NP-hard in the worst case. In this paper we study a spectral heuristic for bisecting random graphs Gn(p,p,) with a planted bisection obtained as follows: partition n vertices into two classes of equal size randomly, and then insert edges inside the two classes with probability p, and edges crossing the partition with probability p independently. If , where c0 is a suitable constant, then with probability 1 , o(1) the heuristic finds a minimum bisection of Gn(p,p,) along with a certificate of optimality. Furthermore, we show that the structure of the set of all minimum bisections of Gn(p,p,) undergoes a phase transition as . The spectral heuristic solves instances in the subcritical, the critical, and the supercritical phases of the phase transition optimally with probability 1 , o(1). These results extend previous work of Boppana Proc. 28th FOCS (1987) 280,285. © 2005 Wiley Periodicals, Inc. Random Struct. Alg., 2006 [source] A unified framework for obtaining improved approximation algorithms for maximum graph bisection problems,RANDOM STRUCTURES AND ALGORITHMS, Issue 3 2002Eran Halperin We obtain improved semidefinite programming based approximation algorithms for all the natural maximum bisection problems of graphs. Among the problems considered are: MAX -BISECTION,partition the vertices of the graph into two sets of equal size such that the total weight of edges connecting vertices from different sides is maximized; MAX -VERTEX-COVER,find a set containing half of the vertices such that the total weight of edges touching this set is maximized; MAX -DENSE-SUBGRAPH,find a set containing half of the vertices such that the total weight of edges connecting two vertices from this set is maximized; and MAXUNCUT,partition the vertices into two sets of equal size such that the total weight of edges that do not cross the cut is maximized. We also consider the directed versions of these problems, such as MAX -DIRECTED-BISECTION and MAX -DIRECTED-UNCUT. These results can be used to obtain improved approximation algorithms for the unbalanced versions of the partition problems mentioned above, where we want to partition the graph into two sets of size and , where is not necessarily . Our results improve, extend and unify results of Frieze and Jerrum, Feige and Langberg, Ye, and others. All these results may be viewed as extensions of the MAX CUT algorithm of Goemans and Williamson, and the MAX 2-SAT and MAX DI-CUT algorithms of Feige and Goemans. © 2002 Wiley Periodicals, Inc. Random Struct. Alg., 20:382,402, 2002 [source] Transplant Center Volume and Outcomes After Liver RetransplantationAMERICAN JOURNAL OF TRANSPLANTATION, Issue 2 2009P. P. Reese Liver retransplantation surgery has a high rate of allograft failure due to patient comorbidities and technical demands of the procedure. Success of liver retransplantation could depend on surgeon experience and processes of care that relate to center volume. We performed a retrospective cohort study of adult liver retransplantation procedures performed from January 1, 1996 through December 31, 2005 using registry data from the Organ Procurement Transplantation Network. The primary outcome was 1-year allograft failure. Liver transplant centers were categorized as small, intermediate or high volume by dividing overall liver transplants into three tertiles of approximately equal size. Mean annual volume of overall liver transplants was <50 for low-volume centers, 50,88 for intermediate-volume centers and >88 for high-volume centers. The primary analysis consisted of 3977 liver retransplantation patients. The unadjusted risk of 1-year allograft failure was 37.8%. In multivariable logistic regression, the risk of 1-year allograft failure was not significantly different between low- (reference), intermediate- (OR 0.86, CI 0.72,1.03, p = 0.11) and high-volume centers (OR 0.88, CI 0.74,1.04, p = 0.14). Results were similar when the analysis was limited to retransplantation performed >160 days after initial transplantation. Center volume is an imprecise surrogate measure for 1-year outcomes after liver retransplantation. [source] Graph-set and packing analysis of hydrogen-bonded networks in polyamide structures in the Cambridge Structural DatabaseACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2000W. D. Samuel Motherwell The hydrogen-bond networks and crystal packing of 81 unique secondary di- and polyamides in the Cambridge Structural Database are investigated. Graph-set analysis, as implemented in the RPluto program, is used to classify network motifs. These have been rationalized in terms of the relative dispositions of the amide groups. Peptide and retropeptides exhibit significant conformational flexibility, which permits alternative hydrogen-bonding patterns. In peptides, dihedral angles of ,,,,, 105° allow an antiparallel ladder arrangement, containing rings of either the same or alternating sizes. For retropeptides, and diamides with an odd number of CH2 spacers, this conformation leads to a parallel ladder with rings of equal size. If , approaches ,60° and , 180°, ladders adopt a helical twist, and if the conformation is distorted further, a three-dimensional network is usually adopted. Diamides with aromatic or an even number of CH2 spacers generally form either antiparallel ladders or sheets, although some exhibit both polymorphs. Symmetry relationships within and between hydrogen-bonded chains, ladders and sheets in the crystal packing have also been analysed. Polyamides form considerably more complex networks, although many of the structural motifs present in the diamides occur as components of these networks. [source] | |||||||||||||