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Medical Sciences	40%

Selected Abstracts

How to keep V(D)J recombination under control

IMMUNOLOGICAL REVIEWS, Issue 1 2004
Marjorie A. Oettinger
Summary:, Breaking apart chromosomes is not a matter to be taken lightly. The possible negative outcomes are obvious: loss of information, unstable chromosomes, chromosomal translocations, tumorigenesis, or cell death. Utilizing DNA rearrangement to generate the desired diversity in the antigen receptor loci is a risky business, and it must be carefully controlled. In general, the regulation is so precise that the negative consequences are minimal or not apparent. They are visible only when the process of V(D)J recombination goes awry, as for example in some chromosomal translocations associated with lymphoid tumors. Regulation is imposed not only to prevent the generation of random breaks in the DNA, but also to direct rearrangement to the appropriate locus or subregion of a locus in the appropriate cell at the appropriate time. Antigen receptor rearrangement is regulated essentially at four different levels: expression of the RAG1/2 recombinase, intrinsic biochemical properties of the recombinase and the cleavage reaction, the post-cleavage /DNA repair stage of the process, and accessibility of the substrate to the recombinase. Within each of these broad categories, multiple mechanisms are used to achieve the desired aims. The major focus of this review is on accessibility control and the role of chromatin and nuclear architecture in achieving this regulation, although other issues are touched upon. [source]

The Effect of Seed Vernalization and Irradiation on Growth and Photosynthesis of Field Bean Plants (Vicia faba L. minor) and on Nitrogenase Activity of Root Nodules

JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 4 2000
W. Filek
The effect of seed vernalization (2,3°C; 36 days) and irradiation intensity during vegetation of field bean upon growth and maximum leaf photosynthesis (Pmax) as well as specific (SNA) and total nitrogenase activity (TNA) of root nodules was investigated. The measurements were performed at the initial stage of pod development of varieties with undetermined (cv. Nadwi,a,ski) and determined (cv. Tibo) growth habit. In comparison with plants in shading, those which grew in full irradiation produced larger leaf area and more dry weight, achieving higher Pmax values. Stimulation of leaf area enlargement and dry weight increase, especially in respect to the dry weight of underground parts had a positive and significant effect upon TNA value. Accumulation of dry weight was higher in vernalized than non-vernalized plants, but only in the case of cv. Nadwi,la,ski, in full irradiation conditions. In the case of plants grown in poorer irradiation conditions TNA values were about 68 % (cv. Nadwi,la,ski) and 54 % (cv. Tibo) lower, due to significant limitation of root nodules. TNA value of vernalized cv. Nadwi,la,ski plants was 66 % higher in comparison with non-vernalized plants. However, the effect was visible only in full irradiation conditions, due to simultaneous greater intensity of root nodules production and higher SNA value. A positive effect of vernalization could also be observed in the decrease of a negative correlation between dry weight of root nodules and SNA in both varieties. Zusammenfassung Der Einfluss der Samenvernalisation (3,3°C; 36 Tage) und der Strahlungsintensität während der Vegetation von Fababohnen hinsichtlich des Wachstums und der maximalen Blattfotosynthese (Pmax) sowie der spezifischen (SNA) und Gesamtnitrogenaseaktivität (TNA) der Wurzelknöllchen wurde untersucht. Die Messungen wurden im ersten Stadium der Hülsenentwicklung an Sorten mit undeterminierten (cv. Nadwi,la,ski) und determinierten (cv. Tibo) Wachstumsstrukturen durchgeführt. Ein Vergleich von Pflanzen unter Beschattung mit Pflanzen unter voller Strahlung zeigte, dass beschattete Pflanzen eine gröiere Blattfläche und höheres Trockengewicht produzierten und damit höhere Pmax -Werte erreichten. Stimulation der Blattflächenvergröierung und der Trockenge wichtszunahme, insbesondere im Hinblick auf die Trockengewichte der unterirdischen Pflanzenteile hatte eine positive und signifikante Auswirkung auf den DNA-Wert. Die Akkumulation von Trockenmasse war in vernalisierten Pflanzen höher als in nicht vernalisierten; dies gilt nur für Sorte Nadwi,la,ski unter dem Einfluss voller Strahlung. Im Fall der Pflanzen, die unter geringer Strahlung wuchsen, waren die TNA-Werte ca. 68 % (cv.Nadwi,la,ski) und 54 % (cv. Tibo) geringer als Folge einer signifikanten Begrenzung des Wurzelknöllchenwachstums. TNA-Werte vernalisierter cv. Nadwi,la,ski-Pflanzen waren um 66 % höher im Vergleich mit nicht vernalisierten Pflanzen. Allerdings zeigte sich diese Wirkung nur unter voller Strahlung als Folge einer vergleichsweise gröieren Intensität der Wurzelknöllchenproduktion und höherer SNA-Werte. Der positive Effekt der Vernalisation konnte ebenfalls beobachtet werden bei einer Abnahme der negativen Korrelation zwischen dem Trockengewicht der Wurzelknöllchen und SNA in beiden Sorten. [source]

The polar ring galaxy AM1934,563 revisited,

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007
Noah Brosch
ABSTRACT We report long-slit spectroscopic observations of the dust-lane polar ring galaxy AM1934,563 obtained with the Southern African Large Telescope (SALT) during its performance verification phase. The observations target the spectral region of the H,, [N ii] and [S ii] emission lines, but also show deep Na i absorption lines, that we interpret as being produced by stars in the galaxy. We derive rotation curves along the major axis of the galaxy that extend out to about 8 kpc from the centre for both the gaseous and the stellar components, using the emission and absorption lines. We derive similar rotation curves along the major axis of the polar ring and point out differences between these and the ones of the main galaxy. We identify a small diffuse object visible only in H, emission and with a low velocity dispersion as a dwarf H ii galaxy and argue that it is probably metal poor. Its velocity indicates that it is a fourth member of the galaxy group in which AM1934,563 belongs. We discuss the observations in the context of the proposal that the object is the result of tidal mater transfer from a major neighbour galaxy and point out some observational discrepancies from this explanation. We argue that an alternative scenario that could better fit the observations may be the slow accretion of cold intergalactic gas, focused by a dense filament of galaxies in which this object is embedded. Given the pattern of rotation we found, with the asymptotic rotation of the gas in the ring being slower than that in the disc while both components have approximately the same extent, we point out that AM1934,563 may be a galaxy in which a dark matter halo is flattened along the galactic disc and the first object in which this predicted behaviour of polar ring galaxies in dark matter haloes is fulfilled. [source]

The frequency of significant pathology in women attending a general gynaecological service for postcoital bleeding

BJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 1 2001
Adam N. Rosenthal
Objectives To document the frequency of pathology in women who complain of postcoital bleeding. To determine whether negative cervical cytology excludes serious pathology in women with postcoital bleeding. To determine whether postcoital bleeding increases the risk of serious pathology in women with an abnormal smear. Design A retrospective study. Setting A university teaching hospital. Population 314 women with postcoital bleeding seen in the gynaecology service from first January 1988 to 31 December 1994. Methods Women were identified from the computerised records of the colposcopy service and copies of correspondence, which was routinely retained on computer. The latter was searched for the text strings coital and intercourse. Main outcome measure Histopathological diagnosis. Results Twelve women (4%) had invasive cancer: 10 were cervical or vaginal cancers and two endometrial cancers. Eight of the 10 cervical or vaginal cancers were clinically apparent. Four women of these 10 had had a normal smear before being referred for further investigation of postcoital bleeding. Two of these cancers were visible only with the aid of the colposcope. Thus, 0.6% of women attending a gynaecology service with postcoital bleeding, a normal looking cervix and a normal smear had invasive cancer of the cervix. Cervical intraepithelial neoplasia were found in 54 women (17.%) and 15 women (5%) had cervical polyps. Nineteen of the 63 women (30%) with significant pathology had a normal or inflammatory cervical smear. No explanation for the postcoital bleeding was found in 155 women (49 %). Conclusions Although invasive cancer is rare in women with postcoital bleeding, it is much commoner than in the general population. It seems likely that cervical intraepithelial neoplasia is also associated with postcoital bleeding, perhaps because the fragile cervical epithelium becomes detached during intercourse. Postcoital bleeding should continue to be regarded as an indication of high risk for invasive cervical cancer and for cervical intraepithelial neoplasia. Prompt referral to a colposcopy clinic is indicated, but most women with postcoital bleeding will have no serious abnormality. [source]

Mirror Self-Recognition Beyond the Face

CHILD DEVELOPMENT, Issue 1 2006
Mark Nielsen
Three studies (N=144) investigated how toddlers aged 18 and 24 months pass the surprise-mark test of self-recognition. In Study 1, toddlers were surreptitiously marked in successive conditions on their legs and faces with stickers visible only in a mirror. Rates of sticker touching did not differ significantly between conditions. In Study 2, toddlers failed to touch a sticker on their legs that had been disguised before being marked. In Study 3, having been given 30-s exposure to their disguised legs before testing, toddlers touched the stickers on their legs and faces at equivalent levels. These results suggest that toddlers pass the mark test based on expectations about what they look like, expectations that are not restricted to the face. [source]