Studies on the mechanism of retinoid-induced pattern duplications in the early chick limb bud: temporal and spatial aspects.

All-trans-retinoic acid causes striking digit pattern changes when it is continuously released from a bead implanted in the anterior margin of an early chick wing bud. In addition to the normal set of digits (234), extra digits form in a mirror-symmetrical arrangement, creating digit patterns such as a 432234. These retinoic acid-induced pattern duplications closely mimic those found after grafts of polarizing region cells to the same positions with regard to dose-response, timing, and positional effects. To elucidate the mechanism by which retinoic acid induces these pattern duplications, we have studied the temporal and spatial distribution of all-trans-retinoic acid and its potent analogue TTNPB in these limb buds. We find that the induction process is biphasic: there is an 8-h lag phase followed by a 6-h duplication phase, during which additional digits are irreversibly specified in the sequence digit 2, digit 3, digit 4. On average, formation of each digit seems to require between 1 and 2 h. The tissue concentrations, metabolic pattern, and spatial distribution of all-trans-retinoic acid and TTNPB in the limb rapidly reach a steady state, in which the continuous release of the retinoid is balanced by loss from metabolism and blood circulation. Pulse-chase experiments reveal that the half-time of clearance from the bud is 20 min for all-trans-retinoic acid and 80 min for TTNPB. Manipulations that change the experimentally induced steep concentration gradient of TTNPB suggest that a graded distribution of retinoid concentrations across the limb is required during the duplication phase to induce changes in the digit pattern. The extensive similarities between results obtained with retinoids and with polarizing region grafts raise the possibility that retinoic acid serves as a natural "morphogen" in the limb

Risk Factors of Diabetes Mellitus in Rural Puducherry

Purpose: Prevalence of type 2 diabetes is increasing in India. Rural area constitutes 80% of India. Hence it is essential to understand the epidemiology for appropriate interventions. Objectives: to identify risk factors of type 2 diabetes mellitus in rural Puducherry. Methodology: Cross sectional study in two villages of Puducherry, India. 1403 subjects above 25 years from 2 villages. Study measured demographic variables, Body Mass Index (BMI), physical activity, family history of Diabetes Mellitus, smoking and alcohol consumption. Fasting blood glucose was measured for study subjects. Further, those with >126 mg/dl were subjected for Oral Glucose Tolerance Test. Univariate and multivariate analysis was done. Receiver Operating characteristic Curve was plotted to find out cut off for Diabetic Risk Score. Findings: The prevalence of type 2 Diabetes Mellitus (DM) was 5.8%. The response rate was (88%). In univariate analysis age, occupation, Socio Economic Status, BMI, physical activity, family history were significant for DM. In multivariate analysis age, BMI, family history of diabetes and occupation were significant for type 2 DM. The ‘diabetes risk score’ generated by the study using age, BMI and family history of DM, had specificity, sensitivity and accuracy of 54%, 77% and 76.2% respectively. The area under curve for scoring system was 0.784 (<0.05). Conclusions: Identified risk factors are useful for early diagnosis by using ‘diabetes risk score’ – thus uncovering the iceberg of disease

Principles and effects of microRNA-mediated post-transcriptional gene regulation

MicroRNAs (miRNAs) are abundant regulatory RNAs involved in the regulation of many key biological processes. Recent advances in understanding the mechanism of RNA interference and miRNA-mediated mechanisms shed light on major principals of the formation of the regulatory complex and provide models to explain how these small regulatory RNA species interfere with gene expression and how they influence the translational status of the transcriptome. © 2006 Nature Publishing Group. All rights reserved

Reconciling a significant hierarchical assembly of massive early-type galaxies at z<~1 with mass downsizing

Hierarchical models predict that massive early-type galaxies (mETGs) are the latest systems to be in place into the cosmic scenario (at z<~0.5), conflicting with the observational phenomenon of galaxy mass downsizing, which poses that the most massive galaxies have been in place earlier that their lower-mass counterparts (since z~0.7). We have developed a semi-analytical model to test the feasibility of the major-merger origin hypothesis for mETGs, just accounting for the effects on galaxy evolution of the major mergers strictly reported by observations. The most striking model prediction is that very few present-day mETGs have been really in place since z~1, because ~90% of the mETGs existing at z~1 are going to be involved in a major merger between z~1 and the present. Accounting for this, the model derives an assembly redshift for mETGs in good agreement with hierarchical expectations, reproducing observational mass downsizing trends at the same time.Comment: 2 pages, 1 figure, Proceedings of Symposium 2 of JENAM 2010, "Environment and the Formation of Galaxies: 30 years later", ed. I. Ferreras and A. Pasquali, Astrophysics & Space Science Proceedings, Springe

Body mass estimates of an exceptionally complete Stegosaurus (Ornithischia: Thyreophora): comparing volumetric and linear bivariate mass estimation methods

© 2015 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited. The file attached is the published version of the article

Population Synthesis and the Diagnostics of High-redshift Galaxies

The effect of redshift on the observation of distant galaxies is briefly discussed emphasizing the possible sources of bias in the interpretation of high-z data. A general energetic criterion to assess physical self-consistency of evolutionary population synthesis models is also proposed, for a more appropriate use of this important tool to investigate distinctive properties of primeval galaxies.Comment: 8 pages and 6 color figures. Invited talk at the conference "New Quests in Stellar Astrophysics: The link between Stars and Cosmology", 26-30 March, 2001, Puerto Vallarta, Mexico, eds. M. Chavez et al., to be published by Kluwe

Uncertainties in the Two-Stage Reception Plate Method for Source Characterisation and Prediction of Structure-Borne Sound Power

To obtain the transmitted structure-borne power from a vibrating machine into a supporting/connected structure, three quantities are required in some form: source activity (either the free velocity or the blocked force), source mobility and receiver mobility. The three quantities can be measured directly, or indirectly using a reception plate method. Whilst direct measurements can be precise, they require extensive data acquisition and processing. The reception plate method is simpler and less precise and therefore yields an engineering grade of accuracy. This paper reports on a collaborative investigation, towards developing an industrial standard for source characterization using the reception plate method. The method yields data as frequency band-averaged values and also as equivalent single values. These simplifications result in uncertainties when obtaining the source quantities and therefore in predictions of the structure-borne sound power in installed conditions. The causes of these uncertainties are considered

The Miena cider gum, Eucalyptus gunnii subsp. divaricata (Myrtaceae): a taxon in rapid decline

The new combination Eucalyptus gunnii subsp. divaricata (McAulay & Brett) B.M.Potts comb. & stat. nov. is introduced for the Miena form of the Tasmanian cider gum Eucalyptus gunnii Hook.f., once described as a separate species, E. divaricata McAulay & Brett. This subspecies occurs on the Central Plateau of Tasmania, where it intergrades clinally with E. gunnii subsp. gunnii and E. archeri. Core populations of this subspecies are among the most frost-resistant of E. gunnii sens. lat., have juvenile foliage of interest for floriculture and have been exploited historically for their sweet sap. However, high mortality of trees in the last decade, coupled with only rare seedling recruitment and poor seed crops, is threatening the long-term survival of this taxon in the wild. E. gunnii subsp. divaricata qualifies as Endangered under Commonwealth and Tasmanian legislation