Reproductive efficiency and shade avoidance plasticity under simulated competition

Plant strategy and life‐history theories make different predictions about reproductive efficiency under competition. While strategy theory suggests under intense competition iteroparous perennial plants delay reproduction and semelparous annuals reproduce quickly, life‐history theory predicts both annual and perennial plants increase resource allocation to reproduction under intense competition. We tested (1) how simulated competition influences reproductive efficiency and competitive ability (CA) of different plant life histories and growth forms; (2) whether life history or growth form is associated with CA; (3) whether shade avoidance plasticity is connected to reproductive efficiency under simulated competition. We examined plastic responses of 11 herbaceous species representing different life histories and growth forms to simulated competition (spectral shade). We found that both annual and perennial plants invested more to reproduction under simulated competition in accordance with life‐history theory predictions. There was no significant difference between competitive abilities of different life histories, but across growth forms, erect species expressed greater CA (in terms of leaf number) than other growth forms. We also found that shade avoidance plasticity can increase the reproductive efficiency by capitalizing on the early life resource acquisition and conversion of these resources into reproduction. Therefore, we suggest that a reassessment of the interpretation of shade avoidance plasticity is necessary by revealing its role in reproduction, not only in competition of plants.     

An Efficient and Versatile System for Visualization and Genetic Modification of Dopaminergic Neurons in Transgenic Mice

Background & Aims

The brain dopaminergic (DA) system is involved in fine tuning many behaviors and several human diseases are associated with pathological alterations of the DA system such as Parkinson’s disease (PD) and drug addiction. Because of its complex network integration, detailed analyses of physiological and pathophysiological conditions are only possible in a whole organism with a sophisticated tool box for visualization and functional modification.

Methods & Results

Here, we have generated transgenic mice expressing the tetracycline-regulated transactivator (tTA) or the reverse tetracycline-regulated transactivator (rtTA) under control of the tyrosine hydroxylase (TH) promoter, TH-tTA (tet-OFF) and TH-rtTA (tet-ON) mice, to visualize and genetically modify DA neurons. We show their tight regulation and efficient use to overexpress proteins under the control of tet-responsive elements or to delete genes of interest with tet-responsive Cre. In combination with mice encoding tet-responsive luciferase, we visualized the DA system in living mice progressively over time.

Conclusion

These experiments establish TH-tTA and TH-rtTA mice as a powerful tool to generate and monitor mouse models for DA system diseases.     

The zebrafish mutant bumper shows a hyperproliferation of lens epithelial cells and fibre cell degeneration leading to functional blindness

The development of the eye lens is one of the classical paradigms of induction during embryonic development in vertebrates. But while there have been numerous studies aimed at discovering the genetic networks controlling early lens development, comparatively little is known about later stages, including the differentiation of secondary lens fibre cells. The analysis of mutant zebrafish isolated in forward genetic screens is an important way to investigate the roles of genes in embryogenesis. In this study we describe the zebrafish mutant bumper (bum), which shows a transient, tumour-like hyperproliferation of the lens epithelium as well as a progressively stronger defect in secondary fibre cell differentiation, which results in a significantly reduced lens size and ectopic location of the lens within the neural retina. Interestingly, the initial hyperproliferation of the lens epithelium in bum spontaneously regresses, suggesting this mutant as a valuable model to study the molecular control of tumour progression/suppression. Behavioural analyses demonstrate that, despite a morphologically normal retina, larval and adult bum^?/? zebrafish are functionally blind. We further show that these fish have defects in their craniofacial skeleton with normal but delayed formation of the scleral ossicles within the eye, several reduced craniofacial bones resulting in an abnormal skull shape, and asymmetric ectopic bone formation within the mandible. Genetic mapping located the mutation in bum to a 4 cM interval on chromosome 7 with the closest markers located at 0.2 and 0 cM, respectively.     

Diaphragmatic stimulation: a case of atrial lead dislodgement and right atrium perforation

We report a 48 year old male who presented with diaphragmatic stimulation. The biventricular implantable cardioverter and defibrillator (CRT-D) was implanted two weeks before admission and active fixation lead caused perforation of the right atrial wall. Echocardiography did not demonstrate pericardial effusion but Chest X-ray and computed tomography (CT) visualized the atrial screw helix outside the right atrial wall, penetrating through the right lung middle lobe. There was no atrial capture. After changing the pace mode DDDR to VVIR, diaphragmatic stimulation was disappeared. The atrial lead was repositioned and fixed again. During the hospital admission and after that the patient was well and free of any symptoms.     

The investigation of allele and genotype frequencies of <Emphasis Type="Italic">CYP3A5 (1*/3*)</Emphasis> and <Emphasis Type="Italic">P2Y12</Emphasis> (T744C) in Iran

Research on the frequency of the highly functional mutations of genes coding required for metabolizing enzymes has shown significant ethnic variations. However, few studies, if any, have examined the frequency distribution of major allelic variations in the context of Iran. In this regard, the present study focused on the genotype profile of Southern Iranians in order to compare allele frequencies of their CYP3A5 and P2Y12 (T744C) which have been shown to have roles in metabolizing clopidogrel, with those of other populations. Therefore, genotyping was carried out on 112 unrelated individuals by PCR–RFLP. The CYP3A5*3 allele was found in 185 persons with allelic frequency 0.82, which is the most common allele among Caucasians (90–95%). The frequency of 82% is different from other Caucasians (90–94%), Indians (67%), Vietnam (67%) and Africans (15%). but lower than frequency in Chinese populations (74%) and Korean (76%). The allele frequency of the −744T (4%) is different from frequencies of Caucasian, American, Chinese, Korean, and Subsahara population. This study confirmed significant inter-ethnic differences in CYP3A5 and P2Y12 frequencies between Iranians and other ethnic groups. The results of this study will be useful for clinical pharmacokinetic investigations and drug dosage recommendations especially antiplatelet drugs such as Clopidogrel, for Iranians.