Adsorption of thymine and uracil on 1:1 clay mineral surfaces: comprehensive ab initio study on influence of sodium cation and water.

This computational study performed using the density functional theory shows that hydrated and non-hydrated tetrahedral and octahedral kaolinite mineral surfaces in the presence of a cation adsorb the nucleic acid bases thymine and uracil well. Differences in the structure and chemistry of specific clay mineral surfaces led to a variety of DNA bases adsorption mechanisms. The energetically most predisposed positions for an adsorbate molecule on the mineral surface were revealed. The target molecule binding with the surface can be characterized as physisorption, which occurs mainly due to a cation-molecular oxygen interaction, with hydrogen bonds providing an additional stabilization. The adsorption strength is proportional to the number of intermolecular interactions formed between the target molecule and the surface. From the Atoms in Molecules analysis and comparison of binding energy values of studied systems it is concluded that the sorption activity of kaolinite minerals for thymine and uracil depends on various factors, among which are the structure and accessibility of the organic compounds. The adsorption is governed mostly by the surface type, its properties and presence of cation, which cause a selective binding of the nucleobase. Adsorbate stabilization on the mineral surface increases only slightly with explicit addition of water. Comparison of activity of different studied kaolinite mineral models reveals the following order for stabilization: octahedral-Na-water > octahedral-Na > tetrahedral-Na > tetrahedral-Na-water. Further investigation of the electrostatic potentials helps understanding of the adsorption process and confirmation of the active sites on the kaolinite mineral surfaces. Based on the conclusions that clay mineral affinity for DNA and RNA bases can vary due to different structural and chemical properties of the surface, a hypothesis on possible role of clays in the origin of life was made.

Genetic Diversity of Prunus necrotic ringspot virus Isolates Within a Cherry Orchard in New York.

A survey for Prunus necrotic ringspot virus (PNRSV) in an orchard of Prunus cerasus cv. Montmorency and Prunus avium cv. Hedelfingen in New York by enzyme-linked immunosorbent assay indicated an eightfold higher infection rate in sour cherry (33%, 32 of 96) than in sweet cherry (4%, 6 of 136) trees. The presence of PNRSV was confirmed by reverse transcription-polymerase chain reaction and amplification of the coat protein (CP) gene in total RNA from infected leaf tissue. Latent infection was prevalent in the majority of trees infected (87%, 33 of 38), while a few of them exhibited shock symptoms or had severely reduced growth (13%, 5 of 38). Asymptomatic PNRSV-infected trees clustered in spatial proximity to symptomatic trees. Sequence analysis of the CP gene (675 bp) indicated a population structure consisting of one predominant molecular variant for 10 isolates and six minor molecular variants for seven isolates. A high sequence identity was found between the CP gene of PNRSV isolates from cherry trees and other isolates from diverse hosts and various geographic origins at the nucleotide and amino acid levels (88 to 100%). Phylogenetic analyses showed a clustering of PNRSV isolates from cherry trees in New York in the predominant group PV-96.

Hydrographics and the timing of infectious salmon anemia outbreaks among Atlantic salmon (Salmo salar L.) farms in the Quoddy region of Maine, USA and New Brunswick, Canada.

Infectious salmon anemia (ISA) has caused severe morbidity and mortality in farmed Atlantic salmon in North America, Norway, Scotland and the Faroe Islands. The Quoddy region of Maine, United States of America (USA), and New Brunswick (NB), Canada is characterized by extensive tidal mixing and close proximity between farms. This region is also prone to recurrent appearances of ISA, though control measures limit disease spread and severity on infected farms. We conducted a retrospective longitudinal analysis of the apparent impact of hydrographics on the incidence and timing of ISA outbreaks on Atlantic salmon (Salmo salar L.) farms in the Quoddy region from May 2002 to August 2004. A time-series cross-sectional regression of 32 farms over 28 months demonstrated a limited, but statistically significant, spatio-temporal clustering of ISA outbreaks linked hydrographically. New outbreaks correlated temporally with those occurring on-site 1 and 3 months prior, and those occurring within one tidal-excursion upstream the same month. Other risk factors included holdover of previous year-class fish, wharf sharing, and possibly harvests of cages infected in previous months. Conclusions suggest that tidal dispersion does play a role in ISAV transmission in the Quoddy region. Dispersal of free virus and/or tidal distribution of lice or other hydrographically influenced vectors or fomites could all contribute to the spatio-temporal patterns described.

Validation of candidate bovine reference genes for use with real-time PCR.

Accurate quantification with real-time PCR requires the use of stable endogenous controls. Recently, there has been much debate concerning the stability of commonly used reference or housekeeping genes. To address this concern, a number of statistical approaches have been designed to analyse data and assist in determining the most appropriate reference genes for experimental comparisons. In this study, three programs, BestKeeper, Norm Finder, and geNorm were used to assess four candidate reference genes: 18S rRNA, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), acidic ribosomal protein large (RPLP0) and beta-actin, for use in expression profiling of individuals from divergent cattle genotypes subject to parasitic challenge with the cattle tick Boophilus microplus. Results demonstrated beta-actin and GAPDH were the most suitable reference genes in blood and could be used either individually or combined as an index to normalise data. RPLP0 was identified as the least stable gene, while 18S rRNA was omitted as being too highly expressed. As the recommendations on the most suitable reference genes varied between the programs, it is recommended that more than one should be utilised, to ensure the most robust experimental tools are selected.

Resistance of Geneva and Other Apple Rootstocks to Erwinia amylovora.

When vigorously growing shoots of 49 different apple rootstocks grown in a greenhouse were inoculated with different strains of Erwinia amylovora, Budagovsky 9 (B.9), Ottawa 3, Malling 9, and Malling 26 were the most fire blight susceptible rootstocks and Geneva 11, Geneva 65, Geneva 16, Geneva 30, Pillnitzer Au51-11, Malling 7, and several breeding selections were the most resistant. Significant strain-rootstock interactions were observed in the amount of fire blight that resulted from inoculation. Field-grown fruiting 'Royal Gala' trees on Geneva 16 and Geneva 30 rootstocks were highly resistant to rootstock infection (no tree mortality) when trees sustained severe blossom infection with E. amylovora, compared with Malling 9 and Malling 26 rootstock clones, which were highly susceptible to infection (36 to 100% tree mortality). In contrast to potted own-rooted B.9 plants inoculated in a greenhouse, B.9 rootstocks of orchard trees appeared resistant to rootstock infection (0% tree mortality). Orchard trees on Geneva 11 were moderately resistant to rootstock infection (25% tree mortality). There was general agreement in the evaluation of resistance under orchard conditions when rootstock resistance was evaluated in relation to controlled blossom inoculation or to natural blossom infection.

Bone gains and losses follow seasonal training and detraining in gymnasts.

The response of the human skeleton to high magnitude loading and unloading is poorly understood. Our aim was to evaluate changes in bone mineral density (BMD) in a group of intercollegiate gymnasts (n = 8, age = 18.6+/-0.8 years) over 24 months that included two 8-month competitive seasons and two 4-month offseasons. BMD of the hip, spine, and whole body was evaluated by DXA (Hologic QDR-1000/W) at baseline, 8, 12, 20, and 24 months. Results indicated significant seasonal trends in BMD of the femoral neck, trochanter, total hip, lumbar spine, and whole body. Specifically, there was a strikingly consistent pattern of bone density increases over the training seasons followed by clear declines in the offseasons. Increases at the spine were 3.5% and 3.7% followed by declines of 1.5% and 1.3% in the offseasons. Total hip BMD increased 2.3% and 1.9% during the competitive seasons followed by decreases of 1.5% and 1.2% in the offseasons. We observed a significant 24-month increase of 4.3% in spine BMD but no significant overall change at the hip. In conclusion, the human skeleton demonstrated a measurable response to high magnitude loading and unloading that was consistent across bone sites over 24 months of observation.

SHIRPA, a protocol for behavioral assessment: validation for longitudinal study of neurological dysfunction in mice.

Mouse models of neurological abnormalities are only valuable if accurately assessed. The three-stage SHIRPA procedure is used for the standardised assessment of mouse phenotype and has been reported in a high throughput experiment in which different mutants were ascertained at one age point using stage 1 of the protocol. In this study we have validated SHIRPA using a large cohort with one single mutation, 'legs at odd angles that causes neurological dysfunction. The cohort aged from 1 to 16 months during this study and this is the first longitudinal SHIRPA analysis.

Serum IGF-I is higher in gymnasts than runners and predicts bone and lean mass.

INTRODUCTION: We examined the relationships between insulin-like growth factor I (IGF-I), its binding protein (IGFBP-3), body composition, and bone mineral density (BMD) in collegiate runners (N = 13), gymnasts (N = 10), and noncompetitive women (N = 10). METHODS: Subjects were evaluated by dual-energy x-ray absorptiometry for body composition and BMD of the spine, hip, and whole body, fasting serum levels of IGF-I and IGFBP-3, and dietary intake. The ratio IGF-I/IGFBP-3 was calculated as a marker of IGF-I bioavailability. RESULTS: In ANOVA, IGF-I and IGF-I/IGFBP-3 in athletes with oligomenorrhea and amenorrhea did not differ from eumenorrheic athletes; thus, values were pooled. Lean/height2 and bone mass at the hip and spine were higher in gymnasts than runners and controls. Total caloric intake was similar between groups. IGF-I and IGF-I/IGFBP-3 differed between groups with gymnasts having higher IGF-I values than runners (397+/-58 vs 288+/-73 ng x mL(-1), P < 0.001) and higher IGF-I/IGFBP-3 than controls and runners (0.065+/-0.009 vs 0.056+/-0.008 vs 0.045+/-0.009, P = 0.0001). In simple regression, IGF-I and IGF-/IGFBP-3 were related to lean/height2 and BMD of the lumbar spine and hip (P < 0.01-0.0001). IGF-I and IGF-I/IGFBP-3 were multicollinear; thus, the ratio was used in subsequent stepwise regression. Lean mass, corrected for body surface area (height2), independently predicted spine and trochanteric BMD (R2 = 0.26, 0.28, respectively), whereas IGF-I/IGFBP-3 and lean/height2 together contributed to 48% of the variance in femoral neck BMD. CONCLUSION: We conclude that, in this group of young adult women, lower BMD in runners may be due, in part, to lower levels of IGF-I and the ratio of IGF-I-to-IGFBP-3 and that IGF-I may mediate the relationship between bone and lean mass.

Gastrointestinal stromal tumors may originate from a subset of CD34-positive interstitial cells of Cajal.

Most gastrointestinal stromal tumors (GISTs), a subgroup of mesenchymal neoplasms of the gut wall, express both Kit (CD117) and CD34 proteins. It has been suggested that GISTs originate from or differentiate into interstitial cells of Cajal (ICC), after several reports indicated that ICC are likely the only cells in the gut which express both Kit and CD34. ICC are among the few cell types resident in the gut which express Kit, together with mast cells. However, the question whether or not ICC express CD34 is currently disputed. Using single-cell reverse transcriptase-polymerase chain reaction (RT-PCR) on cultured murine intestinal cells, single ICC were selected by morphology and tested for the expression of c-kit and CD34 mRNA. Most ICC were only c-kit-positive, however a subset (7 out of 43) were double positive for both c-kit and CD34. In the human small intestine, sequential immunohistochemical staining for Kit and CD34 proteins on the same 3-microm sections showed that some of the ICC surrounding Auerbach's plexus and ICC within the circular muscle layer of the small intestine were positive for both Kit and CD34. In addition, CD34(+)Kit(-) cells were seen adjacent to ICC. These data from two different techniques indicate that ICC can be double positive for Kit and CD34. Thus, GISTs with the Kit(+)CD34(+) phenotype may arise from a subpopulation of CD34(+) Kit(+) ICC.

The search for the origin of rhythmicity in intestinal contraction; from tissue to single cells.

More than a century ago, rhythmic propulsive contractile activity was observed in the intestine after blockade of nerve conduction, thus demonstrating a form of peristalsis that appeared to be under myogenic control. During this century, light and electron microscopic investigations provided the hypothesis that interstitial cells of Cajal (ICC) could be the cells of origin for this rhythmicity. In recent years, physiological studies demonstrated a link between the presence of electrical slow wave activity and the presence of ICC. The recognition that the ICC cell membrane harbours the Kit protein sparked rapid advancement in ICC research, and has been essential in the identification of ICC in tissue and in culture through Kit immunohistochemistry and kit mRNA reverse transcriptase polymerase chain reaction (RT-PCR). With these techniques, electrophysiology was carried out on positively identified single ICC in culture. These methods revealed that single ICC generate spontaneous rhythmic inward currents and slow waves in membrane potential, thus providing strong evidence that ICC generate the electrical pacemaker activity for the gut musculature.

Use of SHIRPA and discriminant analysis to characterise marked differences in the behavioural phenotype of six inbred mouse strains.

Detailed characterisation of six inbred strains of mice commonly used in transgenic and knockout research was carried out using a battery of behavioural tests (SHIRPA) followed by discriminant analysis of the data. In the primary observation screen, DBA/2 mice were relatively irritable and vocalised during handling. C57BL/6 were hyperactive as measured by transfer arousal, arena activity and touch-escape tests. By contrast, C3H were markedly hypoactive, had significantly enhanced grip strength and were also significantly impaired on the visual placing task. In the elevated plus-maze, BALB/c mice showed the highest level of open arm entries and time spent in the open arms, indicating the lowest level of anxiety. There was a clear dissociation of strains on exploratory activity, as measured in the holeboard test and spontaneous locomotor activity (LMA). DBA/2 mice were hyperactive in LMA but demonstrated relatively low levels of holeboard exploration. None of the six strains learnt the water maze spatial learning task particularly well. C57BL/6 and 129/Sv demonstrated most ability and C3H showed no evidence of having acquired the task. The SHIRPA screening battery and discriminant analysis of the data have enabled us to determine the relevant contribution of a number of behavioural measurements to the marked differences in phenotype of mouse strains. These data confirm the importance of carrying out a comprehensive profile in order to accurately characterise the phenotype of gene-targeted and transgenic mice.

Interstitial cells of Cajal generate a rhythmic pacemaker current.

Networks of interstitial cells of Cajal embedded in the musculature of the gastrointestinal tract are involved in the generation of electrical pacemaker activity for gastrointestinal motility. This pacemaker activity manifests itself as rhythmic slow waves in membrane potential, and controls the frequency and propagation characteristics of gut contractile activity. Mice that lack a functional Kit receptor fail to develop the network of interstitial cells of Cajal associated with Auerbach's plexus in the mouse small intestine and do not generate slow wave activity. These cells could provide an essential component of slow wave activity (for example, a biochemical trigger that would be transferred to smooth muscle cells), or provide an actual pacemaker current that could initiate slow waves. Here we provide direct evidence that a single cell, identified as an interstitial cell of Cajal by light microscopy, electron microscopy and expression of Kit mRNA, generates spontaneous contractions and a rhythmic inward current that is insensitive to L-type calcium channel blockers. Identification of the pacemaker of gut motility will aid in the elucidation of the pathophysiology of intestinal motor disorders, and provide a target cell for pharmacological treatment.

Sex differences in health attitudes and choice of health behaviors.

College students (82 men, 166 women) were assessed on a variety of physical fitness measures and completed questionnaires regarding health behaviors and attitudes. The men's health behaviors focused on physical activity while women's focused on dietary changes for better health.

High-impact exercise promotes bone gain in well-trained female athletes.

Maximizing peak bone mass, as well as reducing its loss after menopause, is important for the prevention of osteoporosis. One mode of activity, gymnastics training, invokes high impact loading strains on the skeleton which may have powerful osteogenic effects. To examine the role of athletic activity, specifically gymnastics, on bone mineral density (BMD) accretion, we monitored longitudinal changes in regional and whole body BMD in collegiate women gymnasts and competitive athletes whose skeletons are exposed to differential loading patterns: runners and swimmers. Two cohorts were studied. Cohort I = 26 gymnasts (19.7 +/- 1.2 years), 36 runners (21.1 +/- 2.7 years) and 14 nonathletic women (19.3 +/- 1.7 years) followed over an 8-month period. Cohort II = 8 gymnasts (18.9 +/- 1.1 years), 11 swimmers (20.0 +/- 2.3 years) and 11 nonathletic women (19.0 +/- 1.2 years) followed over a 12-month period. Lumbar spine (L2-4), femoral neck, and whole body BMD (g/cm2) were assessed by dual-energy X-ray absorptiometry. For cohort I, the percent change in lumbar spine BMD after 8 months was significantly greater (p = 0.0001) in the gymnasts (2.8 +/- 2.4%) than in the runners (-0.2 +/- 2.0%) or controls (0.7 +/- 1.3%). An increase in femoral neck BMD of 1.6 +/- 3.6% in gymnasts was also greater (p < 0.05) than runners (-1.2 +/- 3.0%) and approached significance compared with controls (-0.9 +/- 2.2%, p = 0.06). For cohort II, gymnasts gained 2.3 +/- 1.6% at the lumbar spine which differed significantly (p < 0.01) from changes in swimmers (-0.3 +/- 1.5%) and controls (-0.4 +/- 1.7%). Similarly, the change at the femoral neck was greater (p < 0.001) in gymnasts (5.0 +/- 3.4%) than swimmers (-0.6 +/- 2.8%) or controls (2.0 +/- 2.3%). The percent change in BMD at any site did not differ between eumenorrheic and irregularly menstruating athletes. These results indicate that bone mineral at clinically relevant sites, the lumbar spine and femoral neck, can respond dramatically to mechanical loading characteristic of gymnastics training in college-aged women. This occurred despite high initial BMD values and was independent of reproductive hormone status. The results provide evidence to support the view that high impact loading, rather than selection bias, underlies high BMD values characteristic of women gymnasts. Because all athletes underwent resistance training throughout the year of study, muscle strengthening activity did not appear to be a significant factor in the skeletal response observed in gymnasts. We conclude that activities resulting in high skeletal impacts may be particularly osteotropic for young women.

Anxiety responses to maximal exercise testing.

The influence of maximal exercise testing on state anxiety was examined in three separate studies. Highly trained male distance runners (Study 1, n = 12) as well as college students with average (Study 2, n = 16) and below average (Study 3, n = 32) physical fitness levels completed graded maximal exercise tests. This last group was also randomly assigned to either a control or an 8 week training programme in order to determine the effect of increased fitness on the psychological responses to maximal exercise testing. Physical fitness was determined by the measurement of maximal oxygen uptake. State anxiety (State-Trait Anxiety Inventory) was assessed before and from 2-15 min following exercise. It was found that the state anxiety responses to maximal exercise testing were not influenced by re-testing or by 8 weeks of endurance training. Across the three study groups, the anxiety response was variable during the first 5 min following exercise testing; increases, decreases and no changes in anxiety were observed when compared to pre-exercise levels. The anxiety response to maximal exercise appeared to be dependent on the pre-exercise anxiety levels as well as the timing of the post-exercise assessments. It is concluded that maximal exercise testing can be associated with negative mood shifts during the first 5 min after exercise; however, this response is transitory and followed by positive mood shifts 10-15 min following such tests.

Differential effects of swimming versus weight-bearing activity on bone mineral status of eumenorrheic athletes.

To examine the role of skeletal loading patterns on bone mineral density (BMD), we compared eumenorrheic athletes who chronically trained by opposite forms of skeletal loading, intensive weight-bearing activity (gymnastics, n = 13), and nonweightbearing activity (swimming, n = 26) and 19 nonathletic controls. BMD (g/cm2) of the lumbar spine, femoral neck, trochanter, and whole body was assessed by dual energy X-ray absorptiometry (DXA). Subregion analysis of the whole body scan permitted BMD evaluation of diverse regions. Swimmers were taller (p = 0.0001), heavier (p < 0.005), and had a greater bone-free lean mass (p < 0.001) than gymnasts and nonathletic controls. When adjusted for body surface area, there was no difference in lean mass between swimmers and gymnasts, and both were higher than controls (p < 0.01). Gymnasts had a lower (p < 0.005) fat mass than swimmers and controls. There were no group differences for spine or whole body BMD, but gymnasts had higher spine BMD corrected for body mass than either swimmers or controls. Gymnasts (1.117 +/- 0.110) had higher femoral neck BMD than controls (0.974 +/- 0.105), who were higher than swimmers (0.875 +/- 0.105) (p = 0.0001). This result still applied when BMD was normalized for body weight and bone size. Trochanter BMD of gymnasts (0.898 +/- 0.130) was also higher than controls (0.784 +/- 0.097) and swimmers (0.748 +/- 0.085) (p = 0.0002), and remained higher when corrected for body mass.(ABSTRACT TRUNCATED AT 250 WORDS)

Gymnasts exhibit higher bone mass than runners despite similar prevalence of amenorrhea and oligomenorrhea.

Female athletes exhibit a higher prevalence of exercise-associated amenorrhea and oligomenorrhea compared with nonathletic women, and both conditions are related to reduced bone mineral density (BMD), particularly at the spine. This study investigated bone mass and oligomenorrhea and amenorrhea in two groups of competitive female athletes with different skeletal loading patterns: gymnasts and runners. Bone mineral density (g/cm2) of the femoral neck, lumbar spine (L2-4), and whole body was assessed by dual energy X-ray absorptiometry (QDR-1000/W, Hologic Inc., Waltham, MA) in collegiate gymnasts (n = 21) and runners (n = 20), and nonathletic college women (n = 19). The runners and gymnasts had similar values for percent body fat (14.7 +/- 2.2% and 15.6 +/- 2.9%, respectively), which were lower (p < 0.001) than controls (22.3 +/- 3.0%). Lean body mass (LBM) did not differ among the groups, but when adjusted for body surface area, gymnasts had a higher LBM/height2 (p = 0.0001) compared with runners and controls. Muscle strength was significantly greater (p < 0.05) in gymnasts for quadriceps, biceps, and hip adductor force, compared with runners and controls. Gymnasts had a significantly later menarche age (16.2 +/- 1.7 years) compared with runners (14.4 +/- 1.7 years) and controls (13.0 +/- 1.2 years). The prevalence of oligo- and amenorrhea was 47% for gymnasts (6 amenorrheic, 4 oligomenorrheic), 30% for runners (3 amenorrheic, 3 oligomenorrheic), and 0% for controls. Furthermore, athletic groups had similar menstrual histories given the higher proportion of gymnasts who had experienced primary amenorrhea. When evaluated since menarche, however, runners had somewhat longer histories due to an earlier age at menarche and slightly older ages. Dietary calcium intake did not differ among groups, although mean values were below the RDA of 1200 mg/day. By athletic group, BMD at any site did not differ among women with amenorrhea versus oligomenorrhea versus eumenorrhea, although there was a trend for the regularly menstruating athletes in both groups to have slightly higher values. Lumbar spine BMD was lower (p = 0.0001) in runners (0.98 +/- 0.11 g/cm2) compared with both gymnasts and controls (1.17 +/- 0.13 and 1.11 +/- 0.11 g/cm2, respectively). Femoral neck BMD differed among all groups (p = 0.0001): gymnasts = 1.09 +/- 0.12 g/cm2 > controls = 0.97 +/- 0.10 g/cm2 > runners = 0.88 +/- 0.11 g/cm2. Whole body BMD was lower (p < 0.01) in runners (1.04 +/- 0.06 g/cm2) compared with gymnasts and controls (1.11 +/- 0.08 and 1.09 +/- 0.06 g/cm2, respectively).(ABSTRACT TRUNCATED AT 400 WORDS)