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Exponential Increase (exponential + increase)
Selected AbstractsChanges in the activities of protein phosphatase type 1 and type 2A in sea urchin embryos during early developmentDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 4 2000Manabu Kawamoto In the eggs and embryos of sea urchins, the activity of protein phosphatase type 2A (PP2A) increased during the developmental period between fertilization and the morula stage, decreased after the prehatching blastula stage and increased again after hatching. The PP2A activity changed keeping pace with alteration to the activities of cAMP-dependent protein kinase (A kinase), Ca2+/calmodulin-dependent protein kinase (CaM kinase) and casein kinase. Probably, PP2A contributes to the quick turning off of cellular signals because of protein phosphorylation. The activity of protein phosphatase type 1 (PP1) was not detectable up to the morula stage and appreciably increased thereafter. In the isolated nucleus fraction, specific activities of PP1 and PP2A were higher than in whole embryos at all stages in early development. Exponential increase in the number of nuclei because of egg cleavage probably makes PP1 activity detectable in whole embryos after the morula stage. In isolated nuclei, the activities of PP1 and PP2A appreciably decreased after hatching, whereas the activities of A kinase, Ca2+/phospholipid-dependent protein kinase (C kinase) and CaM kinase, as well as casein kinase, became higher. In nuclei, cellular signals caused by protein phosphorylation after hatching do not seem to be turned off by these protein kinases so quickly as before hatching. The PP1 and PP2A in nuclei also seem to contribute to the elimination of signal noise. [source] Assessing the impact of riparian processes on streambank stability,ECOHYDROLOGY, Issue 3 2009Eddy J. Langendoen Abstract The series of biennial United States (US) National Water Quality Inventory surveys shows no reduction in the percentage of degraded miles of streams since the early 1990s despite an exponential increase in river restoration projects to improve water quality, enhance in-stream habitat and manage the riparian zone. This may suggest that many river restoration projects fail to achieve their objectives. This is partly due to a lack of understanding of the dynamics of the degraded riverine system and its interaction with the riparian zone. These projects could, therefore, benefit from using proven models of stream and riparian processes to guide restoration design and to evaluate indicators of ecological integrity. The US Department of Agriculture has developed two such models: the channel evolution computer model CONCEPTS and the riparian ecosystem model REMM. These models have been integrated to evaluate the impact of edge-of-field and riparian conservation measures on stream morphology and water quality. Vegetative riparian conservation measures are commonly used to stabilize failing streambanks. The shear strength of bank soils is greatly affected by the degree of saturation of the soils and root reinforcement provided by riparian vegetation. The integrated model was used to study the effectiveness of woody and herbaceous riparian buffers in controlling streambank erosion of an incised stream in northern Mississippi. Comparison of model results with observations showed that pore-water pressures are accurately predicted in the upper part of the streambank, away from the groundwater table. Simulated pore-water pressures deviate from those observed lower in the streambank near the phreatic surface. These discrepancies are mainly caused by differences in the simulated location of the phreatic surface and simulated evapotranspiration in case of the woody buffer. The modelling exercise further showed that a coarse rooting system, e.g. as provided by trees, significantly reduced bank erosion rates for this deeply incised stream. Published in 2009 by John Wiley & Sons, Ltd. [source] Application of a constant blood withdrawal method in equine exercise physiology studiesEQUINE VETERINARY JOURNAL, Issue 6 2001P. BARAGLI Summary The aim of the present study was to test a constant blood withdrawal method (CBWM) to collect blood samples from horses during treadmill exercise. CBWM was performed in 4 Standardbreds and 5 Haflinger horses. A peristaltic pump was used to control blood aspiration from an i.v. catheter via an extension line. Blood was collected using an automatic fractions collector, with a constant delay time between the drawing of blood and sample collection. Blood withdrawal using CBWM was made during a treadmill standardised exercise test (SET). A blood flow of 12 ml/min was used and samples collected every 60 s during the entire period of exercise. The volume of blood collected in each sample tube was 12.1 ± 0.2 ml, with a delay time of mean ± s.d. 25.3 ± 0.8 s. Plasma lactate kinetics based on measurement of lactate in each fraction showed an exponential increase during the first 13 min of exercise (10.5 min of SET and 2.5 min recovery). The peak plasma lactate concentration was observed between 2.5 and 5.5 min after the end of SET. CBWM permits the kinetics of lactate and other blood-borne variables to be studied over time. This method could be a valuable aid for use in studying equine exercise physiology. [source] Vaccines, coming of age after 200 yearsFEMS MICROBIOLOGY REVIEWS, Issue 1 2000P.Helena Mäkelä Abstract An overview on the short, only 200 years, past history and future expectations in the field of vaccines is presented. The focus is on development trends and potential rather than individual vaccines. While the first vaccines were a result of keen observation, the further development has been tightly dependent on the development of microbiology to provide both the knowledge basis and the technology for new vaccines for new purposes. The post-genomic era just starting therefore promises an exponential increase of vaccine research and new vaccines, both improved vaccines with a greater efficacy and less adverse effects to replace old ones and vaccines for prevention of diseases for which no vaccines exist. Furthermore, fully new applications to prevention or treatment of chronic diseases not traditionally associated with infections are expected. [source] Stream macroinvertebrate occurrence along gradients in organic pollution and eutrophicationFRESHWATER BIOLOGY, Issue 7 2010NIKOLAI FRIBERG Summary 1.,We analysed a large number of concurrent samples of macroinvertebrate communities and chemical indicators of eutrophication and organic pollution [total-P, total-N, NH4,N, biological oxygen demand (BOD5)] from 594 Danish stream sites. Samples were taken over an 11-year time span as part of the Danish monitoring programme on the aquatic environment. Macroinvertebrate communities were sampled in spring using a standardised kick-sampling procedure whereas chemical variables were sampled six to 24 times per year per site. Habitat variables were assessed once when macroinvertebrates were sampled. 2.,The plecopteran Leuctra showed a significant negative exponential relationship (r2 = 0.90) with BOD5 and occurred at only 16% of the sites with BOD5 above 1.6 mg L,1. Sharp declines with increasing BOD5 levels were found for the trichopteran families Sericostomatidae and Glossosomatidae although they appeared to be slightly less sensitive than Leuctra. Other plecopterans such as Isoperla showed a similar type of response curve to Leuctra (negative exponential) but occurred at sites with relatively high concentrations of BOD5 up to 3,4 mg L,1. In contrast, the response curve of the isopod Asellus aquaticus followed a saturation function reaching a plateau above 3,4 mg L,1 BOD5 and the dipteran Chironomus showed an exponential increase in occurrence with increasing BOD5 concentration. 3.,Macroinvertebrate occurrence appeared to be related primarily to concentrations of BOD5, NH4,N and total-P whereas there were almost no relationships to total-N. Occurrence of a number of taxa showed a stronger relationship to habitat conditions (width and substrate) than chemical variables. 4.,Important macroinvertebrate taxa are reduced at concentrations of BOD5 that are normally perceived as indicating unimpacted stream site conditions. Our results confirmed sensitivity/tolerance patterns used by existing bioassessment systems only to some degree. [source] Differences in temperature, organic carbon and oxygen consumption among lowland streamsFRESHWATER BIOLOGY, Issue 12 2005KAJ SAND-JENSEN Summary 1. Temperature, organic carbon and oxygen consumption were measured over a year at 13 sites in four lowlands streams within the same region in North Zealand, Denmark with the objectives of determining: (i) spatial and seasonal differences between open streams, forest streams and streams with or without lakes, (ii) factors influencing the temperature dependence of oxygen consumption rate, (iii) consequences of higher temperature and organic content in lake outlets on oxygen consumption rate, and (iv) possible consequences of forecasted global warming on degradation of organic matter. 2. High concentrations of easily degradable dissolved (DOC) and particulate organic carbon (POC) were found in open streams downstream of plankton-rich lakes, while high concentrations of recalcitrant DOC were found in a forest brook draining a forest swamp. Concentrations of predominantly recalcitrant POC and DOC were low in a groundwater-fed forest spring. Overall, DOC concentration was two to 18 times higher than POC concentrations. 3. Oxygen consumption rate at 20 °C was higher during summer than winter, higher in open than shaded streams and higher in lake outlets than inlets. Rate was closely related to concentrations of chlorophyll and POC but not to DOC. The ratio of oxygen consumption rate to total organic concentrations (DOC + POC), serving as a measure of organic degradability, was highest downstream of lakes, intermediate in open streams and lowest in forest streams. 4. Temperature coefficients describing the exponential increase of oxygen consumption rate between 4 and 20 °C averaged 0.121 °C,1 (Q10 of 3.35) in 70 measurements and showed no significant variations between seasons and stream sites or correlations with ambient temperature and organic content. 5. Oxygen consumption rate was enhanced downstream of lakes during summer because of higher temperature and, more significantly, greater concentrations of degradable organic carbon. Oxygen consumption rates were up to seven times higher in the stream with three impoundments than in a neighbouring unshaded stream and 21 times higher than in the groundwater-fed forest spring. 6. A regional climate model has calculated a dramatic 4,5 °C rise in air temperature over Denmark by 2070,2100. If this is realised, unshaded streams are estimated to become 2,3 °C warmer in summer and winter and 5,7 °C warmer in spring and, thereby, increase oxygen consumption rates at ambient temperature by 30,40% and 80,130%, respectively. Faster consumption of organic matter and dissolved oxygen downstream of point sources should increase the likelihood of oxygen stress of the stream biota and lead to the export of less organic matter but more mineralised nutrients to the coastal waters. [source] Effects of different rates and timing of application of nitrogen as slurry and mineral fertilizer on yield of herbage and nitrate-leaching potential of a maize/Italian ryegrass cropping system in north-west PortugalGRASS & FORAGE SCIENCE, Issue 1 2009H. Trindade Abstract Efficient use of cattle-slurry to avoid nitrogen (N) leaching and other losses is important in designing intensive dairy systems to minimize pollution of air and water. The response in dry-matter (DM) yield of herbage and nitrate-leaching potential to different rates and timing of application of N as cattle slurry and/or mineral fertilizer in a double-cropping system producing maize (Zea mays L.) silage and Italian ryegrass (Lolium multiflorum Lam.) was investigated in north-west Portugal. Nine treatments with different rates and combinations of cattle slurry, and with or without mineral-N fertilizer, applied at sowing and as a top-dressing to both crops, were tested and measurements were made of DM yield of herbage, N concentration of herbage, uptake of N by herbage and amounts of residual soil nitrate-N to a depth of 1 m, in a 3-year experiment. Regression analysis showed that the application of 150 and 100 kg of available N ha,1 to maize and Italian ryegrass, respectively, resulted in 0·95 of maximum DM yields of herbage and 0·90 of maximum N uptake by herbage. Residual amounts of nitrate-N in soil after maize ranged from 48 to 278 kg N ha,1 with an exponential increase in response to the amount of N applied; there were higher values of nitrate-leaching potential when mineral-N fertilizer was applied. The results suggest that it is possible in highly productive maize/Italian ryegrass systems to obtain high DM yields of herbage for maize silage and Italian ryegrass herbage with minimal leaching losses by using slurry exclusively at annual rates of up to 250 kg available N ha,1 (equivalent to 480 kg total N ha,1) in three applications. [source] Natural killer cells: integrating diversity with functionIMMUNOLOGY, Issue 4 2009Kuldeep Cheent Summary The key role of natural killer cells in many aspects of the immune response is now being recognized. The last decade has seen an exponential increase in our understanding of the workings of these cells. Receptor diversity is crucial in allowing natural killer cells to respond effectively to a variety of different pathogens. This article reviews aspects of natural killer cell diversity that combine to generate populations of functional natural killer cells that exist within both the individual and throughout the population at large. [source] A hybrid density functional theory study of the low-temperature dimethyl ether combustion pathways.ISRAEL JOURNAL OF CHEMISTRY, Issue 2-3 2002I: Chain-propagation Dimethyl ether (DME) has been proposed to be a promising alternative to conventional diesel fuel because of its favorable compression ignition property (high cetane number) and its soot-free combustion. A radical chain mechanism for hydrocarbon autoignition has been proposed for DME at low temperatures. In this mechanism, the chain initiation step consists of DME undergoing hydrogen abstraction by a highly reactive species (typically ·OH). The CH3O·H2 created in the initiation step then combines with O2; the subsequent CH3OCH2OO· radical is involved in a Lindemann-type mechanism, which can lead to the production of formaldehyde (CH2 = O) and ·OH. This concludes the chain-propagating step: the one ·OH produced then sustains the chain-reaction by creating another CH3O·H2. A relatively stable intermediate (·CH2OCH2OOH), formed via isomerization of CH3OCH2OO· in the chain-propagation step, can combine with a second O2 to produce a radical (·OOCH2OCH2OOH) that can potentially decompose into two ·OH radical (and other products). This path leads to chain-branching and an exponential increase in the rate of DME oxidation. We have used spin-polarized density functional theory with the Becke-3-parameter Lee,Parr,Yang exchange-correlation functional to calculate the structures and energies of key reactants, intermediates, and products involved in (and competing with) the chain-propagating and chain-branching steps of low-temperature DME oxidation. In this article, Part I, we consider only the chain-propagation mechanism and its competing mechanisms for DME combustion. Here, we show that only certain conformers can undergo the isomerization to ·CH2OCH2OOH. A new transition state has been discovered for the disproportionation reaction ·CH2OCH2OOH , 2CH2O + ·OH in the chain-propagating step of DME autoignition that is much lower than previous barriers. The key to making this decomposition pathway facile is initial cleavage of the O,O rather than the C,O bond. This renders all transition states along the chain-propagation potential energy surface below the CH3O·H2 + O2 reactants. In contrast with the more well-studied CH3·H2 (ethyl radical) + O2 system, the H-transfer isomerization of CH3OCH2OO· to ·CH2OCH2OOH in low-temperature DME oxidation has a much lower activation energy. This is most likely due to the larger ring strain of the analogous transition state in ethane oxidation, which is a five-membered ring opposed to a six-membered ring in dimethyl ether oxidation. Thus low-temperature ethane oxidation is much less likely to form the ·ROOH (where R is a generic group) radicals necessary for chain-branching, which leads to autoignition. Three competing reactions are considered: CH3O·H2 , CH2O + ·CH3; ·CH2OCH2OOH , 1,3-dioxetane + ·OH; and ·CH2OCH2OOH , ethylene oxide + HOO·. The reaction barriers of all these competing paths are much higher in energy (7,10 kcal/mol) than the reactants CH3O·H2 + O2 and, therefore, are unlikely low-temperature paths. Interestingly, an analysis of the highest occupied molecular orbital along the CH3O·H2 decomposition path shows that electronically excited (1A2 or 3A2) CH2O can form; this can also be shown for ·CH2OCH2OOH, which forms two formaldehyde molecules. This may explain the luminosity of DME's low-temperature flames. [source] Incidence of Hip and Other Osteoporotic Fractures in Elderly Men and Women: Dubbo Osteoporosis Epidemiology Study,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2004Kevin P Chang Abstract In this prospective 12-year study in men and women 60 years of age and older, there was a 4,6% per year reduction in the incidence rate of overall osteoporotic fractures, but the study was unable to exclude any change in the hip fracture incidence rate. Approximately one-half of hip fractures occurred before 80 years in men and two-thirds before 85 years in women. The age distribution of hip fractures underlines the need for earlier intervention in osteoporosis. Introduction: Although hip fracture is the major osteoporotic fracture in terms of health outcomes, quality of life, and costs, there is a paucity of long-term data on secular changes in men and women within a defined community. This long-term prospective population-based study over 12 years from 1989 to 2000 specifically examined the age distribution and secular changes in the incidence rates of hip and other osteoporotic fractures in men and women 60 years of age and older in a predominantly white population in Dubbo, Australia. Materials and Methods: Hip and all other clinical fractures were ascertained by reviewing all radiography reports from the two area radiology services, ensuring complete ascertainment of all clinical osteoporotic fractures. Results and Conclusion: Among the 1055 symptomatic atraumatic fractures (after excluding pathological fractures), there was a significant reduction in the overall fracture incidence rate in women (4% per year; p = 0.0003) and men (6% per year; p = 0.0004) over the 12 years. There were 229 hip fractures (175 in women and 54 in men) within 39,357 person-years of observation. The overall rate ± SE of hip fracture was 759 ± 57 per 100,000 person-years in women and 329 ± 45 per 100,000 person-years in men, with an exponential increase with age. With advancing age, the incidence rate of hip fractures in men approached that in women; the female:male ratio fell from 4.5 (95% CI: 1.3,15.7) to 1.5 (0.9,2.5) and 1.9 (1.2,2.8) in the 60,69, 70,79, and 80+ year age groups, respectively. In women, the absolute number of fractures and incidence rate continuously increased with age; however, in men, the absolute number of hip fractures peaked at 80,84 years of age and then decreased. Most importantly, despite the continuing increase with age, almost one-half (48%) of the hip fractures occurred before the age of 80 years in men, and 66% of hip fractures occurred before the age of 85 years in women. The overall hip fracture incidence is comparable with other white (except Sweden) and Asian groups as well as two other Australian studies. This study could not exclude a change in hip fracture incidence rate, even in those 80 years of age and over among whom the incidence of hip fractures was the highest. The incidence data highlight the fact that a large proportion of hip fractures occurs in those under 80 years of age, particularly in men. This age distribution underlines the need for earlier intervention in osteoporosis in women and particularly in men to achieve the most cost-effective outcomes. [source] Sulfanilic Acid: A Novel Consolidation Agent for Al2O3 in Aqueous MediaJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2006Jingxian Zhang A new solidifying agent, 4-aminobenzene sulfonic acid (sulfanilic acid), is reported in this paper. The consolidation process and mechanism were followed using on viscoelastic, FTIR, SEM, and Hg porosimetry measurements. It was shown that the Al2O3 slurries with PAA-Na as dispersant exhibited a high degree of particle stabilization. After the addition of sulfanilic acid, we observed an exponential increase in the storage modulus (G,) as a function of consolidation time. Correspondingly, Al2O3 slurries exhibited a transition from a viscous to an elastic state (in 62 min). FTIR analysis indicated that the consolidation process might follow two steps: first, the adsorption of sulfanilic acid on the Al2O3 particle surface; second, the acid,base interaction between the adsorbed PAA-Na molecules and the sulfanilic acid molecules. This interaction could possibly induce the formation of three-dimensional networks through a bridging or charge neutralization mechanism. The as-consolidated Al2O3 green samples were homogeneous, with the relative green density being 54.69%. Results showed that it was feasible to introduce sulfanilic acid for the consolidation of Al2O3 slurries in aqueous media. [source] Evolution of liver transplantation in Europe: Report of the European Liver Transplant RegistryLIVER TRANSPLANTATION, Issue 12 2003René Adam MD The European Liver Transplant Registry (ELTR) currently allows for the analysis of 44,286 liver transplantations (LTs) performed on 39,196 patients in a 13-year period. After an exponential increase, the number of LTs is plateauing due to a lack of organs. To cope with this, alternatives to cadaveric LT, such as split LT, domino LT, or living-related LT (LRLT) are being used increasingly. They now account for 11% of all procedures. One of the most important findings in the evolution of LT is the considerable improvement of results along time with, for the mean time, a one-year survival of 83%, all indications confounded. The improvement is particularly significant for cancers. This improvement is mainly represented by hepatocellular carcinoma, with a gain of 17% for 5-year survival rate from 1990 to 2000. Increasingly, older donors are used to augment the donor pool and older recipients are transplanted due to improved results and a better selection of patients. More than two thirds of deaths and three quarters of retransplantations occurred within the first year of transplantation. Retransplantation is associated with much less optimal results than first LT. One of the prominent features of recent years is the development of LRLT. LRLT is now performed by almost half of the European centers. As with split LT or domino LT, LRLT aims to provide more patients to be transplanted. Special attention is paid to reducing the risk for the donor, which is now estimated to be 0.5% mortality and 21% postoperative morbidity. [source] Microwave-Assisted Polymer Synthesis: State-of-the-Art and Future PerspectivesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2004Frank Wiesbrock Abstract Summary: Monomodal microwaves have overcome the safety uncertainties associated with the precedent domestic microwave ovens. After fast acceptance in inorganic and organic syntheses, polymer chemists have also recently discovered this new kind of microwave reactor. An almost exponential increase of the number of publications in this field reflects the steadily growing interest in the use of microwave irradiation for polymerizations. This review introduces the microwave systems and their applications in polymer syntheses, covering step-growth and ring-opening, as well as radical polymerization processes, in order to summarize the hitherto realized polymerizations. Special attention is paid to the differences between microwave-assisted and conventional heating as well as the "microwave effects". Results of search on number of publications on microwave-assisted polymerizations, sorted by year. [source] On the back of a motorbike: Middle-class mobility in Ho Chi Minh City, VietnamAMERICAN ETHNOLOGIST, Issue 1 2008ALLISON TRUITT ABSTRACT "Mobility" is a key concept in understanding processes of globalization and class formation. In this article, I examine motorbike mobility in Ho Chi Minh City and its role in reordering social stratification in urban Vietnam. In the years following trade liberalization, motorbikes emerged as exemplary symbols of purchasing power, displaying both monetized and motorized power. In response to the exponential increase in the number of motorbikes, Vietnamese state agencies inscribed streets with divisions to separate different classes of vehicles and regulate the flow of traffic. Motorbikes, I argue, elude attempts to regulate their movement precisely because they embody the very mobility promised by economic reforms. [Vietnam, traffic, commodity, circulation, public space, mobility] [source] Electrical properties of bulk n-ZnO single crystals under hydrostatic pressurePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2009I. K. Kamilov Abstract Pressure dependences of Hall coefficient RH(P) and resistivity , (P) have been measured for n-ZnO bulk crystals with impurity concentration Ni = 1017,1018 cm,3 and concentration of free electrons ,1017 cm,3 at T = 300 K at hydrostatic pressures up to P = 25 GPa. It has been found that the exponential increase of RH(P) and , (P), observed in the vicinity of the polymorphous transition PPH = 9 GPa, is caused by the increase of ionization energy of shallow donors. At P > PPH, a step-like decrease of the resistivity has been observed, indicating a phase transition from diamond structure to NaCl-type structure. In accordance with formulas derived from the ,heterophase structure , effective medium' model, phase volume fractions in the critical region of the polymorphous transformation have been calculated and the threshold values of normalized effective resistivity have been determined. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] ORIGINAL RESEARCH,ERECTILE DYSFUNCTION: Journey into the Realm of Requests for Help Presented to Sexual Medicine Specialists: Introducing Male Sexual DistressTHE JOURNAL OF SEXUAL MEDICINE, Issue 3 2007Edoardo S. Pescatori MD ABSTRACT Introduction., The recent availability of noninvasive pharmacological remedies for male sexual function triggered an exponential increase in the number of men requesting help in the sexuality area. Aim., The Italian Society of Andrology explored requests for help, not included in formerly established clinical categories of sexual medicine. Methods., A central board of 67 andrologists identified new areas of requests for help, instrumental for a web-based questionnaire, forwarded to 912 members of the Italian Society of Andrology. Results were submitted to an independent consensus development panel. Main Outcome Measures., A questionnaire response rate of 30.8% was considered acceptable according to standard response rates of medical specialist samples. Results., The Central Board interaction identified two new domains of requests for help: sexual distress and unconventional requests for pro-erectile medications. Web-based questionnaire results suggested that such domains account for 29% and 9% respectively of all requests for help already presented by male patients at sexual medicine clinics. The Independent Consensus Development Panel issued a final consensus document; herewith, the statement defining male sexual distress: A non-transitory condition and/or feeling of inadequacy such as to impair "sexual health" (WHO working definition). Inadequacy can originate both from physiological modifications of male sexual functions, and from diseases, dysfunctions, dysfunctional symptoms and dysmorphisms, both of andrological and non-andrological origin, which do not relate to "erectile dysfunction" (NIH Consensus Development Panel definition), but that might also induce erectile dysfunction. Sexual Distress can lead to a request for help which needs to be acknowledged. Conclusion., The Italian Society of Andrology identified two new areas of requests for help concerning male sexual issues: sexual distress and unconventional requests for pro-erectile medications. These domains, which do not represent new diseases, nonetheless induce the sufferers to seek help and, accordingly, need to be acknowledged. Pescatori ES, Giammusso B, Piubello G, Gentile V, and Pirozzi Farina F. Journey into the realm of requests for help presented to sexual medicine specialists: Introducing male sexual distress. J Sex Med 2007;4:762,770. [source] Chain-length specificities of maize starch synthase I enzyme: studies of glucan affinity and catalytic propertiesTHE PLANT JOURNAL, Issue 5 2001Padmavathi D. Commuri Summary It is widely known that some of the starch synthases and starch-branching enzymes are trapped inside the starch granule matrix during the course of starch deposition in amyloplasts. The objective of this study was to use maize SSI to further our understanding of the protein domains involved in starch granule entrapment and identify the chain-length specificities of the enzyme. Using affinity gel electrophoresis, we measured the dissociation constants of maize SSI and its truncated forms using various glucans. The enzyme has a high degree of specificity in terms of its substrate,enzyme dissociation constant, but has a greatly elevated affinity for increasing chain lengths of ,-1, 4 glucans. Deletion of the N-terminal arm of SSI did not affect the Kd value. Further small deletions of either N- or C-terminal domains resulted in a complete loss of any measurable affinity for its substrate, suggesting that the starch-affinity domain of SSI is not discrete from the catalytic domain. Greater affinity was displayed for the amylopectin fraction of starch as compared to amylose, whereas glycogen revealed the lowest affinity. However, when the outer chain lengths (OCL) of glycogen were extended using the phosphorylase enzyme, we found an increase in affinity for SSI between an average OCL of 7 and 14, and then an apparently exponential increase to an average OCL of 21. On the other hand, the catalytic ability of SSI was reduced several-fold using these glucans with extended chain lengths as substrates, and most of the label from [14C]ADPG was incorporated into shorter chains of dp < 10. We conclude that the rate of catalysis of SSI enzyme decreases with the OCL of its glucan substrate, and it has a very high affinity for the longer glucan chains of dp ,20, rendering the enzyme catalytically incapable at longer chain lengths. Based on the observations in this study, we propose that during amylopectin synthesis shorter A and B1 chains are extended by SSI up to a critical chain length that soon becomes unsuitable for catalysis by SSI and hence cannot be elongated further by this enzyme. Instead, SSI is likely to become entrapped as a relatively inactive protein within the starch granule. Further glucan extension for continuation of amylopectin synthesis must require a handover to other SS enzymes which can extend the glucan chains further or for branching by branching enzymes. If this is correct, this proposal provides a biochemical basis to explain how the specificities of various SS enzymes determine and set the limitations on the length of A, B, C chains in the starch granule. [source] Dementia incidence continues to increase with age in the oldest old: The 90+ studyANNALS OF NEUROLOGY, Issue 1 2010María M. Corrada ScD Objective The oldest old are the fastest growing segment of the US population, and accurate estimates of dementia incidence in this group are crucial for healthcare planning. Although dementia incidence doubles every 5 years from ages 65 to 90 years, it is unknown if this exponential increase continues past age 90 years. Here, we estimate age- and sex-specific incidence rates of all-cause dementia in people aged 90 years and older, including estimates for centenarians. Methods Participants are from The 90+ Study, a population-based longitudinal study of aging and dementia. Three hundred thirty nondemented participants aged 90 years and older at baseline were followed between January 2003 and December 2007. Age- and sex-specific incidence rates of all-cause dementia were estimated by person-years analysis. Results The overall incidence rate of all-cause dementia was 18.2% (95% confidence interval [CI], 15.3,21.5) per year and was similar for men and women (risk ratio, 0.94; 95% CI, 0.65,1.37). Rates increased exponentially with age from 12.7% per year in the 90,94-year age group, to 21.2% per year in the 95,99-year age group, to 40.7% per year in the 100+-year age group. The doubling time based on a Poisson regression was 5.5 years. Interpretation Incidence of all-cause dementia is very high in people aged 90 years and older and continues to increase exponentially with age in both men and women. Projections of the number of people with dementia should incorporate this continuing increase of dementia incidence after age 90 years. Our results foretell the growing public health burden of dementia in an increasingly aging population. ANN NEUROL 2010;67:114,121 [source] A sigmoidal transcriptional response: cooperativity, synergy and dosage effectsBIOLOGICAL REVIEWS, Issue 1 2003REINER A. VEITIA ABSTRACT A sigmoidal transcriptional response (STR) is thought to act as amolecular switch to control gene expression. This nonlinear behaviour arises as a result of the cooperative recognition of a promoter/enhancer by transcription factors (TFs) and/or their synergy to attract the basal transcriptional machinery (BTM). Although this cooperation between TFs is additive in terms of energy, it leads to an exponential increase in affinity between the BTM and the pre-initiation complexes. This exponential increase in the strength of interactions is the principle that governs synergistic systems. Here, I propose a minimalist quasi-equilibrium model to explore qualitatively the STR taking into account cooperative recognition of the promoter/enhancer and synergy. Although the focus is on the effect of activators, a similar treatment can be applied to inhibitors. One of the main insights obtained from the model is that generation of a sigmoidal threshold is possible even in the absence of cooperative DNA binding provided the TFs synergistically interact with the BTM. On the contrary, when there is cooperative binding, the impact of synergy diminishes. It will also be shown that a sigmoidal response to a morphogenetic gradient can be used to generate a nested gradient of another morphogen. Previously, I had proposed that halving the amounts of TFs involved in sigmoidal transcriptional switches could account for the abnormal dominant phenotypes associated with some of these genes. This phenomenon, called haploinsufficiency (HI), has been recognised as the basis of many human diseases. Although a formal proof linking HI and a sigmoidal response is lacking, it is tempting to explore the model from the perspective of dosage effects. [source] Characteristics of Immobilized Lipase on Hydrophobic Superparamagnetic Microspheres To Catalyze EsterificationBIOTECHNOLOGY PROGRESS, Issue 2 2004Zheng Guo A novel immobilized lipase (from Candida rugosa) on hydrophobic and superparamagnetic microspheres was prepared and used as a biocatalyst to catalyze esterification reactions in diverse solvents and reaction systems. The results showed that the immobilized lipase had over 2-fold higher activities in higher log P value solvents. An exponential increase of lipase activity against log P of two miscible solvent mixtures was observed for the first time. Both free and immobilized lipase achieved its maximum activity at the range of water activity ( aw) 0.5,0.8 or higher. At aw 0.6, the immobilized lipase exhibited markedly higher activities in heptane and a solvent-free system than did the native lipase. In multicompetitive reactions, the alcohol specificity of the lipase showed a strong chain-length dependency, and the immobilized enzyme exhibited more preference for a longer-chain alcohol, which is different from previous reports. The immobilized lipase showed higher specificities for butyric acid and the medium-chain-length fatty acids (C8,C12). Then, the immobilized lipase was extended to solvent-free synthesis of glycerides from glycerol and fatty acids. Recovered by magnetic separation, the immobilized lipase exhibited good reusability in repeated batch reaction, indicating its promising feature for biotechnology application. [source] The increasing prevalence of allergy: a challenge for the physicianCLINICAL & EXPERIMENTAL ALLERGY REVIEWS, Issue 1 2002R. Mösges Summary The prevalence of allergic disorders has increased markedly throughout the world during the past three decades. There has been considerable controversy about the extent to which the increase is real, or attributable to increased awareness or better diagnosis. It seems probable that the increased prevalence is real because longitudinal studies have shown a rapid exponential increase in allergic disorders such as asthma. Since there is a marked difference in the occurrence of allergic disorders between Western and less developed countries, as well as between rural and urban areas, it is likely that environmental (,lifestyle') factors are aetiologically involved. It also seems probable that contact with microbial antigens, in the form of childhood infections, vaccinations and contact with farm animals, can exert some protection against the later development of allergies. Studies are in progress to determine whether reduction in risk factors or intervention with anti-allergic therapies can modify the long-term outcome in populations at high risk. [source] An audit of genetic testing in diagnosis of inherited retinal disorders: a prerequisite for gene-specific interventionCLINICAL & EXPERIMENTAL OPHTHALMOLOGY, Issue 7 2009Monika Pradhan MS MRCOphth Abstract Background:, There has been an exponential increase in the number of genes implicated in inherited retinal disease over the last decade, but the genetic and phenotypic heterogeneity limited mutation detection. The high cost of sequencing and long turn around times meant that gene testing was not a viable option, particularly in New Zealand. Recently, advancements including development of micro-array-based mutation analysis and non-for-profit laboratories have resulted in affordable and time-efficient testing. This has enabled genetic diagnostics to become an integral component of the work-up for inherited retinal disease. Methods:, Genetic testing for inherited retinal disorders was initiated via the Ocular Genetic Clinic in Auckland 2 years ago. A retrospective audit of genetic testing over this period was carried out. The results of these tests and outcomes are discussed. Results:, Thirty-five probands have undergone genetic testing for retinal disorders. This has included X-Linked Retinoschisis, Leber Congenital Amaurosis, Retinitis Pigmentosa, Albinism, Achromatopsia, Usher syndrome, Stargardt disease and Mitochondrial disease. Of these, 54% of tests (19/35) showed a rare variant or pathogenic mutation. Three couples have proceeded to investigate the options of prenatal diagnosis and/or pre-implantation genetic diagnosis. Conclusion:, The introduction of genetic testing, largely via disease arrays, has been highly successful at clarifying disease genotype in our cohort. It is now a timely and cost-effective investigation that should be elemental to the assessment of inherited retinal disease. Genetic testing in an opportune fashion permits genetic counselling, enables families to make reproductive choices and might allow the possibility of gene therapy interventions. [source] Sexual orientation and substance use trajectories in emerging adulthoodADDICTION, Issue 7 2010Amelia E. Talley ABSTRACT Aims The current study examined developmental changes in substance use behaviors (SUBS) based upon sexual orientation. The analyses also attempted to address a number of methodological limitations in the extant longitudinal literature (i.e. distinct operationalizations of sexual orientation, timing of sexual orientation assessment with respect to reports of SUBs, non-linear growth). Participants Data were drawn from a longitudinal study of incoming first-time college students at a large public university (n = 3720). Design After a paper-and-pencil assessment just prior to matriculation, participants completed a web-based survey every fall and spring for 4 years (sub-sample n = 2854). Findings Latent growth models revealed that sexual minorities demonstrated significant heterogeneity with regard to substance use trajectories. Initial levels and trajectories of the frequency of substance use for sexual minority individuals were distinct, generally, from their exclusively heterosexual peers. Methodologically, the timing of the assessment of sexual orientation influenced the results, and modeling non-linear components indicated that sexual minorities are at risk for exponential increases in their frequency of certain SUBs over time (i.e. drunkenness; cannabis use). Conclusions Sexual minority and majority individuals exhibited differences in SUBs during emerging adulthood, especially when using self-identification to define sexual orientation. Individuals who endorsed a sexual minority self-identification at the onset of emerging adulthood, as opposed to 4 years later, evidenced exponential increases in rates of drunkenness and cannabis use. These results support that the timing of assessment is important and that some trajectories of sexual minority SUBs are non-linear during this developmental period. [source] | ||||||||||||||||||||||