A laser-based system to heat nuclear fuel pellets at high temperature

Annealing tests are of utmost importance in nuclear fuel research, particularly to study the thermophysical properties of the material, microstructure evolution, or the released gas as a function of temperature. As an alternative to conventional furnace or induction annealing, we report on a laser-heating experiment allowing one to heat a nuclear fuel pellet made of uranium dioxide, UO2, or potentially other nuclear fuel pellets in an isothermal and controlled manner. For that purpose, we propose to use an indirect heating method based on a two compartment tungsten crucible, one containing the sample and the other acting as a laser susceptor for efficient and homogeneous heating of the assembly. With this concept, we demonstrate the heating of UO2 samples up to 1500 °C at a maximum heating rate of 30 °C/s with the use of two 500 W lasers. The system is, however, scalable to higher heating rates or higher temperatures by increasing the laser power up to few kW. The experiment has been designed to heat a pressurized water reactor fuel pellet, but the concept could be easily applied to other sample geometries or materials.

A robust and efficient automatic method to segment maize FASGA stained stem cross section images to accurately quantify histological profile

BACKGROUND

Grasses internodes are made of distinct tissues such as vascular bundles, epidermis, rind and pith. The histology of grasses stem was largely revisited recently taking advantage of the development of microscopy combined with the development of computer-automated image analysis workflows. However, the diversity and complexity of the histological profile complicates quantification. Accurate and automated analysis of histological images thus remains challenging.

RESULTS

Herein, we present a workflow that automatically segments maize internode cross section images into 40 distinct tissues: two tissues in the epidermis, 19 tissues in the rind, 14 tissues in the pith and 5 tissues in the bundles. This level of segmentation is achieved by combining the Hue, Saturation and Value properties of each pixel and the location of each pixel in FASGA stained cross sectiona. This workflow is likewise able to highlight significant and subtle histological genotypic variations between maize internodes. The grain of precision provided by the workflow also makes it possible to demonstrate different levels of sensitivity to digestion by enzymatic cocktails of the tissues in the pith. The precision and strength of the workflow is all the more impressive because it is preserved on cross section images of other grasses such as miscanthus or sorghum.

CONCLUSIONS

The fidelity of this tool and its capacity to automatically identify variations of a large number of histological profiles among different genotypes pave the way for its use to identify genotypes of interest and to study the underlying genetic bases of variations in histological profiles in maize or other species.

High throughput accurate method for estimating in vitro dry matter digestibility of maize silage

BACKGROUND

Since the introduction of studies on maize silage digestibility at the end of the nineteenth century, protocols to estimate dry matter digestibility have not stopped evolving. Since the early 1980s, the protocol developed by Aufrère became a benchmark in many laboratories to estimate in vitro dry matter digestibility. In order to increase its throughput, to facilitate its execution and to decipher the impact of the different parameters of the protocol we decided to test the combination of 7 parameters in 21 different protocols.

RESULTS

We thus tested the impact of (1) the presence or absence of pepsin in HCl solution, (2) the temperature of incubation during enzymatic hydrolysis, (3) the presence or absence of a gelatinization step, (4) washing/rinsing versus neutralization step, (5) the presence or absence of α-amyloglucosidase in enzymatic solution, (6) the duration of cellulase incubation, and (7) the concentration of the cellulase solution. The major result of our work highlighted that it was essential to carry out a gelatinization step to correctly estimate the in vitro dry matter digestibility of maize silage.

CONCLUSIONS

The proposed protocol in this paper is innovative, reliable, highthroughput and easy to implement in many laboratories to accurately quantity in vitro dry matter digestibility.

Early Transmural Response Assessed Using Magnetic Resonance Imaging Could Predict Sustained Clinical Remission and Prevent Bowel Damage in Patients with Crohn's Disease Treated with Anti-Tumour Necrosis Factor Therapy

BACKGROUND

Magnetic resonance imaging [MRI] is a promising tool to evaluate therapeutic efficacy in ileocolonic Crohn's disease [CD].

AIMS

We aimed to assess the feasibility of early MRI evaluation (week 12 [W12]) to predict corticosteroid-free remission [CFREM] at W52 and prevent long-term bowel damage.

METHODS

All patients with active CD needing anti-tumour necrosis factor [anti-TNF] therapy were consecutively enrolled in this multicentre prospective study. MRI was performed before starting therapy, at W12 and W52. CFREM was defined as Crohn's Disease Activity Index < 150, C-reactive protein < 5 mg/L and faecal calprotectin < 250 µg/g, with no switch of anti-TNF agents, no bowel resection and no therapeutic intensification between W12 and W52.

RESULTS

Among 46 patients, 22 [47.8%] achieved CFREM at W52. Anti-TNF agents were able to heal almost all CD lesions as soon as W12 [p < 0.05]. Early transmural response defined as a 25% decrease of either Clermont score (odds ratio [OR] = 7.7 [1.7-34.0], p < 0.001) or Magnetic Resonance Index of Activity (OR = 4.2 [1.3-13.3], p = 0.015) was predictive of CFREM at W52. Achieving at least two items on W12-MRI among ulceration healing, disappearance of enlarged lymph nodes or sclerolipomatosis, ΔADC [apparent diffusion coefficient] > +10% or ΔRCE [relative contrast enhancement] > -30% was associated with a likelihood of CFREM at W52 of 84.6% vs 37.5% in patients without transmural response [p < 0.001]. Early transmural response could prevent bowel damage progression over time using Clermont score (hazard ratio = 0.21 [0.0-0.9]; p = 0.037).

CONCLUSION

Evaluation of early transmural response by MRI is feasible and is a promising end point to monitor therapeutic efficacy in patients with CD.

Tissue Lignification, Cell Wall p-Coumaroylation and Degradability of Maize Stems Depend on Water Status

Water supply and valorization are two urgent issues in the utilization of maize biomass in the context of climate change and replacement of fossil resources. Maximizing maize biomass valorization is of interest to make biofuel conversion competitive, and to increase forage energetic value for animal fodder. One way to estimate biomass valorization is to quantify cell wall degradability. In this study, we evaluated the impact of water supply on cell wall degradability, cell wall contents and structure, and distribution of lignified cell types in maize internodes using dedicated high-throughput tools to effectively phenotype maize internodes from 11 inbred lines under two contrasting irrigation scenarios in field trials over three years. Overall, our results clearly showed that water deficit induced significant changes in lignin content and distribution along with a reduction in lignin p-coumaroylation, thereby impacting cell wall degradability. Additionally, we also observed that responses to a water deficit varied between the lines examined, underscoring biochemical and histological target traits for plant breeding.

Changing molecular epidemiology of methicillin-resistant Staphylococcus aureus in a small geographic area over an eight-year period

The epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) at an international level shows that most MRSA strains belong to a few pandemic clones. At the local level, a predominance of one or two clones was generally reported. However, the situation is evolving and new clones are emerging worldwide, some of them with specific biological characteristics, such as the presence of Panton-Valentine leucocidin (PVL). Understanding these changes at the local and international levels is of great importance. Our objective was to analyze the evolution of MRSA epidemiology at multiple sites on a local level (Western Switzerland) over a period of 8 years. Data were based on MRSA reports from seven sentinel laboratories and infection control programs covering different areas. Pulsed-field gel electrophoresis was used to type MRSA isolates. From 1997 to 2004, a total of 2,256 patients with MRSA were reported. Results showed the presence of four predominant clones (accounting for 86% of patients), which could be related to known international clones (Berlin, New York/Japan, Southern Germany, and Iberian clones). Within the small geographic region, the 8-year follow-up period in the different areas showed spacio-temporal differences in the relative proportions of the four clones. Other international MRSA clones, as well as clones showing genetic characteristics identical to those of community-acquired MRSA (SCCmec type IV and the presence of PVL genes), were also identified but presumably did not disseminate. Despite the worldwide predominance of a few MRSA clones, our data showed that at a local level, the epidemiology of MRSA might be different from one hospital to another. Moreover, MRSA clones were replaced by other emerging clones, suggesting a rapid change.

The elongation rate at the base of a maize leaf shows an invariant pattern during both the steady-state elongation and the establishment of the elongation zone

Spatial and temporal analyses of elongation and cell length of monocotyledon leaves have most often been performed during the period when leaves are visible and elongate at a constant rate (steady-state). In the present study, the focus was on the earlier stages, during the establishment of the elongation zone. Regardless of leaf development stage, the segment located between 0 and 35 mm from the leaf insertion point had a relative elongation rate that increased with distance from insertion point ('accelerating zone') while the segment located further than 35 mm had a relative elongation rate that decreased ('decelerating zone'). This stable pattern held for both young, non-emerged leaves, where it was restricted to the portion corresponding to the length of the blade, and for leaves during steady-state elongation. In the same way, the profile of cell length was essentially the same during early development and during steady-state elongation. The results of a temporal analysis of whole-leaf elongation rate, carried out in the field and in the greenhouse at different light intensities were consistent with a time-invariant pattern of elongation. Whole-leaf relative elongation rate increased with time until the leaf reached 30-40 mm length (although at different leaf ages depending on conditions), and declined afterwards. These results suggest that the patterns governing the elongation rate of a sector of a maize leaf are independent of the leaf developmental stage but depend on sector position only.

How to prevent port-site metastases in laparoscopic colorectal surgery

Various reports concerning port-site metastasis after laparoscopic surgery for colorectal cancer have created a new concern regarding the use of this technique for the treatment of this malignancy. The real incidence is not yet known; neither are its prognostic implications. Numerous experimental studies, both in vitro and in vivo, have been published since 1994. These studies have analyzed the possible role of pneumoperitoneum and carbon dioxide (CO(2)) and pathophysiology, as well as the influence of minimally invasive techniques on tumor response and immunity. There are no definitive results yet, but there is enough evidence to presume that the etiology of this new complication might derive from surgical technique. We present our 8-year experience with laparoscopic surgery for colorectal cancer. We also review our technique for preventing port-site implants. At this writing, we have had no port metastasis in our series of 320 colorectal cancer cases with a mean follow-up period of 54 months. The steps we follow as a routine in all cases of laparoscopic colorectal cancer are (a) fixation of trocars to the abdominal wall, (b) avoidance of touching the tumor, (c) high vascular ligation, (d) intraoperative colonoscopy and intraluminal irrigation with 5% iodine povidone, (e) specimen isolation before extraction from the abdominal cavity, and (f) intraperitoneal and trocar-site irrigation with a tumoricide solution.

Spatial distributions of expansion rate, cell division rate and cell size in maize leaves: a synthesis of the effects of soil water status, evaporative demand and temperature

The spatial distributions of leaf expansion rate, cell division rate and cell size was examined under contrasting soil water conditions, evaporative demands and temperatures in a series of experiments carried out in either constant or naturally fluctuating conditions. They were examined in the epidermis and all leaf tissues. (1) Meristem temperature affected relative elongation rate by a constant ratio at all positions in the leaf. If expressed per unit thermal time, the distribution of relative expansion rate was independent of temperature and was similar in all experiments with low evaporative demand and no water deficit. This provides a reference distribution, characteristic of the studied genotype, to which any distribution in stressed plants can be compared. (2) Evaporative demand and soil water deficit affected independently the distribution of relative elongation rate and had near-additive effects. For a given stress, a nearly constant difference was observed, at all positions of the leaf, between the relative elongation rates of stressed plants and those of control plants. This caused a reduction in the length of the zone with tissue elongation. (3) Methods for calculating cell division rate in the epidermis and in all leaf tissues are proposed and discussed. In control plants, the zone with cell division was 30 mm and 60 mm long in the epidermis and in whole tissues, respectively. Both this length and relative division rate were reduced by soil water deficit. The size of epidermal and of mesophyll cells was nearly unaffected in the leaf zone with both cell division and tissue expansion, suggesting that water deficit affects tissue expansion rate and cell division rate to the same extent. Conversely, cell size of epidermis and mesophyll were reduced by water deficit in mature parts of the leaf.

Exon 14-skipping of the adenomatous polyposis coli gene in purified epithelial cells of colonic mucosa and tumors

Adenomatous polyposis coli (APC) exon 14-skipped transcripts encode putative APC proteins of low molecular weight. To prove that exon 14-skipped mRNA variants do not simply represent tissue culture artifacts, expression of these APC transcript variants was demonstrated in native colorectal epithelium. Fresh surgical specimens of human colon were processed and epithelial cells were affinity-purified with the dynabead-immobilized monoclonal antibody Ber-EP4. Epithelium derived cDNA was PCR-amplified in the range of linear accumulation. RT-PCR products with and without APC exon 14 were evaluated by densitometry. Analyses of normal mucosa (n = 8) and matching mucosa--tumor samples (n = 4) revealed a consistent 4 to 1 ratio of APC exon 14-positive to exon 14-negative mRNA levels. We conclude, a) that APC exon 14-skipped transcripts are physiologically expressed in native human colon mucosa, and b) that ratios of exon 14-negative to exon 14-positive isoforms were not altered when colorectal tumor cells were compared with matching normal mucosa (p = 0.80).

Chemical shift as a probe of molecular interfaces: NMR studies of DNA binding by the three amino-terminal zinc finger domains from transcription factor IIIA

We report the NMR resonance assignments for a macromolecular protein/DNA complex containing the three amino-terminal zinc fingers (92 amino acid residues) of Xenopus laevis TFIIIA (termed zf1-3) bound to the physiological DNA target (15 base pairs), and for the free DNA. Comparisons are made of the chemical shifts of protein backbone 1HN, 15N, 13C alpha and 13C beta and DNA base and sugar protons of the free and bound species. Chemical shift changes are analyzed in the context of the structures of the zf1-3/DNA complex to assess the utility of chemical shift change as a probe of molecular interfaces. Chemical shift perturbations that occur upon binding in the zf1-3/DNA complex do not correspond directly to the structural interface, but rather arise from a number of direct and indirect structural and dynamic effects.

Infected abdominal aortic aneurysm associated with a psoas abscess, aorto-duodenal and sigmoid fistulas. Case report and review of the literature

A case of atherosclerotic abdominal aortic aneurysm, complicated by aortoenteric fistulizations and infected by Escherichia coli, is presented. Chronic contained rupture resulted in the formation of a huge left psoas abscess which was responsible for the symptoms. No similar case has been reported in the literature. Resection and extra-anatomic vascular reconstruction were curative.

[The 60 hour week in surgery: possible or impossible?]

The number of hours of work per week by doctors is the subject of great controversy in many countries. This has led to restrictive legislation in several states or countries (New York and Great Britain, for example) which is both cumbersome and restrictive. We have polled the Swiss surgeons (both trained and in training) in teaching hospitals on this subject with a questionnaire which also covered some other aspects of training. A majority wishes that the working week be limited (to 60 h/week). However a real limit of 60 h per 7 day week (including call duty) is not reasonable. Furthermore the other problems are considered to be more important by 84% of respondents. Thus the overall opinion is that there are too many surgeons training in a poorly structured system, both on a personal and institutional basis.

[Arolla index. A study of 88 cases of frostbite during a high-mountain race]

A sudden change in meteorological conditions provoked frostbite in 88 competitors in a high mountain race, 31 lesions being of 1st degree, 38 of superficial 2nd degree, 12 of deep 2nd degree and 7 of 3rd degree severity. Etiology, localization, treatment and outcome of the lesions are discussed. The precise knowledge of weather conditions and position of patrols over the length of the course enabled intensity of cold exposure to be related to onset of frostbite: an index termed "Arolla" is proposed which in contrast to the windchill index allows for exposure time. Distribution of patrols using standardized equipment allowed determination of importance of individual factors: the latter is considerable. Medical care in high mountain situations is commented upon.

Effects of hyper- and hypoprolactinemia on gonadotropin secretion, rat testicular luteinizing hormone/human chorionic gonadotropin receptors and testosterone production by isolated Leydig cells

The effect of prolactin (Prl) on gonadotropin secretion, testicular luteinizing hormone (LH)/human chorionic gonadotropin (hCG) receptors, and testosterone (T) production by isolated Leydig cells has been studied in 60-day-old rats treated for 4 days, 4 and 8 weeks with sulpiride (SLP), a dopaminergic antagonist, or for 4 days and 4 weeks with bromocriptine (CB), a dopaminergic agonist. Plasma Prl concentrations were significantly greater in the SLP groups (204 +/- 6 ng/ml) and lower in the CB groups (3.0 +/- 0.2 ng/ml) than those measured in the control groups (54 +/- 6 ng/ml). The plasma concentrations of gonadotropin were not affected by a 4-day treatment with SLP or CB, nor were they after a 4-week treatment with CB. However, the hyperprolactinemia induced by an 8-week treatment with SLP was associated with a reduced secretion of gonadotropin (LH, 16 +/- 4 vs. 35 +/- 6 ng/ml; FSH, 166 +/- 12 vs. 307 +/- 14 ng/ml). In SLP-induced hyperprolactinemia, a 30% increase in the density of the LH/hCG testicular binding sites was observed (178 +/- 12 fmol/mg protein), whereas a 60% decrease was measured in hypoprolactinemia (55 +/- 5 vs. control 133 +/- 5 fmol/mg protein). Plasma T levels were increased in 4-day and 4-week hyperprolactinemic animals (4.3 +/- 0.4 and 3.9 +/- 0.4 ng/ml, respectively), but returned to normal levels in the 8-week group (3.0 +/- 0.5 vs. C: 2.3 +/- 0.2 ng/ml). No T modifications were observed in hypoprolactinemic animals. Two distinct populations of Leydig cells (I and II) were obtained by centrifugation of dispersed testicular cells on a 0-45% continuous Metrizamide gradient. Both possess LH/hCG binding sites. However, the T production from Leydig cells of population II increased in the presence of hCG, whereas that of cell population I which also contain immature germinal cells did not respond. The basal and stimulated T secretions from cell populations I and II obtained from CB-treated animals were similar to controls, whereas from 4 days to 8 weeks of hyperprolactinemia, basal and hCG induced T productions from cell population II decreased progressively. These data show that hyperprolactinemia causes, in a time-dependent manner, a trophic effect on the density of LH/hCG testicular receptors; reduces basal and hCG-stimulated T production from isolated Leydig cells type II; and results in an elevated plasma T concentration which decreases with time. The latter suggests a slower T catabolism and/or an impaired peripheral conversion of T into 5 alpha-dihydrotestosterone (DHT). Although hypoprolactinemia is associated with a marked reduction in testicular LH receptors, it does not affect T production.

Maturation of the hypothalamo-pituitary-ovarian axis in adolescent girls

The first menstrual cycles after menarche are irregular and anovulatory. To determine whether these cycles reflect immature pituitary responsiveness to gonadotropin-releasing hormone (GnRH) in relationship to ovarian steroid secretion, we measured basal plasma estradiol (E2), progesterone (P), and gonadotropins as well as LH and FSH responses to GnRH in 90 healthy girls during the first 5 yr after menarche. During the first year postmenarche, sex steroids, basal gonadotropins, and responses to GnRH had not yet reached adult values. During the second year, the increase in E2 was accompanied by a higher secretion of gonadotropins, both basally and in response to GnRH, which was similar to that observed in control adult women during both phases of the menstrual cycle, although P remained low. From the third to the fifth postmenarchal years, there was a progressive increase in the luteal LH and FSH responses to GnRH, resulting in significantly higher responses than in adult controls. Despite the progressive increase in sex steroids there was still a low percentage of ovulatory cycles over the 5 postmenarchal yr (0-63%). When the data were classified according to luteal P levels, it was found that anovulatory cycles (P less than 0.9 ng/ml) with normal E2 levels (100 pg/ml) resulted in exaggerated responses to GnRH, while in ovulatory cycles with P levels greater than 10 ng/ml and normal E2 concentrations, a lower response was observed, suggesting that high concentrations of P exerted a negative feedback on LH and FSH secretion. In contrast, the association of lower E2 (less than 100 ng/ml) and P (less than 5 ng/ml) levels resulted in a synergistic positive action on gonadotropin secretion. These data extend to endogenous sex steroids the dose-dependent positive and negative actions on gonadotropin secretion previously demonstrated with exogenously administered steroids in women.

Pituitary responsiveness to LHRH and TRH in adolescent girls

Puberty is characterized by a progressive maturation of the hypothalamus-pituitary gonadal axis which, in girls results in menarche. The first menstrual cycles are usually irregular and anovulatory, and the subtle positive and negative regulation of sex steroids on the hypothalamus-pituitary axis has probably not reached adult maturity. An investigation has been carried out in 99 normal adolescent girls, divided into 3 groups: 1-2, 3-4 and 5 years after menarche, by measuring basal hormonal values as well as the responses to LHRH and TRH during the follicular and luteal phases. Basal FSH and LH values reached adult levels after the second year of menarche, while FSH and LH responses to 50microgram LHRH showed a regular and progressive increase from 1 to 5 years post-menarche, resulting, in the 5-year group and in spite of the half dose received, in definitely higher FSH and LH responses than those observed in the adult women after 100 microgram LHRH. This enhanced pituitary responsiveness to LHRH is due to still progressively increasing estradiol and progesterone secretions, the latter hormone remaining still lower than in the adults. Basal prolactin levels were significantly higher than those found in adult women with a slightly increased prolactin response to TRH and an exaggerated one of TSH, with normal T3 and T4 levels. These data show that from the onset of menarche to the complex and subtle adult menstrual cycle regulation, there is a continuing maturation of the hypothalamus-pituitary axis of the gonads which lasts approximately 5 years. It is characterized by increasing E2 secretion, low progesterone secretion and slightly increased prolactin levels, with a frequently impaired luteal phase. The enhanced pituitary sensitivity to releasing hormones is due to the positive feedback mechanism of E2 which is not yet associated with adequate progesterone secretion for a negative feedback, as in adult women. Thus, adolescence is still a maturation period, the onset of ovulation being the final step in this development.

Effects of oestrogens on prolactin and thyrotrophin responses to TRH in women during the menstrual cycle and under oral contraceptive treatment

The effects of physiological and pharmacological variations of oestrogens on prolactin and thyrotrophin (TSH) secretion have been studied during the menstrual cycle and under oral contraceptive treatment. Ten women were tested for prolactin and TSH responses to 200 mug TRH in the early follicular (days 4-6), periovulatory (days 14-15) and luteal phases (days 22-26) of the same menstrual cycle. Circulating plasma prolactin levels did not significantly vary in the three phases, but TSH basal levels were lower in the luteal than in the follicular and periovulatory periods. The prolactin response to TRH was significantly enhanced in the periovulatory phase, while the TSH response was slightly decreased. Seven women on sequential contraceptives exhibited increased basal and TRH-induced prolactin secretion during the oestrogen treatment, with an unaltered TSH secretion throughout therapy. Treatment with combined contraceptives did not alter either basal or TRH-induced prolactin secretion in eight women, but basal TSH secretion and its response to TRH were both reduced. These data show that oestrogens may produce different regulatory effects on prolactin and TSH secretion, particularly in the pituitary sensitivity to TRH stimulation. Physiological variations of oestrogen secretion such as those observed during the menstrual cycle can likewise modify prolactin levels. These results could provide some support for a regulatory role for prolactin in the menstrual cycle.

[Effect of the steroid sex hormones on the LH and FSH responses to LHRH in the normal subject]

In man both basal gonadotrophin levels and the pituitary responses to LHRH remained relatively constant throughout life. In women the pituitary sensitivity varied in the menstrual cycle due to the typical cyclic variation of oestradiol and progesterone. The max delta LH increase to 100 mug LHRH was observed in the periovulatory period (183 +/- 41 mU/ml); it was also significantly higher in the luteal (49 +/- 7 mu/ml) than in the early follicular phase (18 +/- 3 mU/ml). The effect of exogenous sex steroid hormones taken as contraceptive drugs was then studied in 15 women. Significantly lower LH and FSH basal values as well as responses to LHRH were observed in 8 normal women under oral combined contraceptives. Conversely, in 7 women under oral sequential contraceptives, basal LH and FSH remained in the normal range. The LH-FSH responses were increased and delayed when these tests were performed during the period of estrogen treatment. Thus, with combined oral contraceptives, constant and high levels of estrogens and progesterone not only inhibit the LH peak, but also decrease the basal LH-FSH levels and responses to releasing hormone. Conversely, with sequential oral contraceptives, the low level of estradiol does not inhibit these responses and even enhances them. In menopausal women both basal and gonadotrophin responses to LHRH were increased indicating an important pituitary reserve. In menstruating women a significant estradiol increase is observed 2 and 4 hours after a 100 mug LHRH injection, both during the follicular and the luteal phases whereas progesterone increases only in the luteal phase. In men, testosterone was found to increase 4 hours after a 100 mug LHRH injection. These studies show that in normal subjects, sex steroid hormones are important regulators of the sensitivity of the pituitary responsiveness to releasing hormone.