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1.
Interdiscip Perspect Infect Dis ; 2023: 9224815, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37554129

RESUMO

Coronavirus disease (COVID-19), a highly contagious and rapidly spreading disease with significant fatality in the elderly population, has swept across the world since 2019. Since its first appearance, the causative agent, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has undergone multiple mutations, with Omicron as the predominant circulating variant of concern at the moment. The gold standard for diagnosis of COVID-19 by real-time polymerase chain reaction (RT-PCR) to detect the virus is laborious and requires well-trained personnel to perform sophisticated procedures. Also, the genetic variants of SARS-CoV-2 that arise regularly could result in false-negative detection. Meanwhile, the current COVID-19 treatments such as conventional medicine, complementary and alternative medicine, passive antibody therapy, and respiratory therapy are associated with adverse effects. Thus, there is an urgent need to discover novel diagnostic and therapeutic approaches against SARS-CoV-2 and its variants. Over the past 30 years, nucleic acid-based aptamers have gained increasing attention and serve as a promising alternative to the antibodies in the diagnostic and therapeutic fields with their uniqueness of being small, nonimmunogenicity, and thermally stable. Aptamer targeting the SARS-CoV-2 structural proteins or the host receptor proteins represent a powerful tool to control COVID-19 infection. In this review, challenges faced by currently available diagnostic and therapeutic tools for COVID-19 are underscored, along with how aptamers can shed a light on the current COVID-19 pandemic, focusing on the critical factors affecting the discovery of high-affinity aptamers and their potential applications to control COVID-19 infection.

2.
J Neurosci Methods ; 397: 109948, 2023 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-37572883

RESUMO

BACKGROUND: Accurate targeting of brain structures for in-vivo electrophysiological recordings is essential for basic as well as clinical neuroscience research. Although methodologies for precise targeting and recording from the cortical surface are abundant, such protocols are scarce for deep brain structures. NEW METHOD: We have incorporated stable fiducial markers within a custom cranial cap for improved image-guided neuronavigation targeting of subcortical structures in macaque monkeys. Anchor bolt chambers allowed for a minimally invasive entrance into the brain for chronic recordings. A 3D-printed microdrive allowed for semi-chronic applications. RESULTS: We achieved an average Euclidean targeting error of 1.6 mm and a radial error of 1.2 mm over three implantations in two animals. Chronic and semi-chronic implantations allowed for recording of extracellular neuronal activity, with single-neuron activity examples shown from one macaque monkey. COMPARISON WITH EXISTING METHOD(S): Traditional stereotactic methods ignore individual anatomical variability. Our targeting approach allows for a flexible, subject-specific surgical plan with targeting errors lower than what is reported in humans, and equal to or lower than animal models using similar methods. Utilizing an anchor bolt as a chamber reduced the craniotomy size needed for electrode implantation, compared to conventional large access chambers which are prone to infection. Installation of an in-house, 3D-printed, screw-to-mount mechanical microdrive is in contrast to existing semi-chronic methods requiring fabrication, assembly, and installation of complex parts. CONCLUSIONS: Leveraging commercially available tools for implantation, our protocol decreases the risk of infection from open craniotomies, and improves the accuracy of chronic electrode implantations targeting deep brain structures in large animal models.


Assuntos
Encéfalo , Neuronavegação , Humanos , Animais , Neuronavegação/métodos , Microeletrodos , Técnicas Estereotáxicas , Craniotomia , Eletrodos Implantados
3.
Environ Monit Assess ; 195(8): 923, 2023 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-37410180

RESUMO

Anthropogenic eutrophication is a global environmental problem threatening the ecological functions of many inland freshwaters and diminishing their abilities to meet their designated uses. Water authorities worldwide are being pressed to improve their abilities to monitor, predict, and manage the incidence of harmful algal blooms (HABs). While most water quality management decisions are still based on conventional monitoring programs that lack the needed spatio-temporal resolution for effective lake/reservoir management, recent advances in remote sensing are providing new opportunities towards better understanding water quality variability in these important freshwater systems. This study assessed the potential of using the Sentinel 2 Multispectral Instrument to predict and assess the spatio-temporal variability in the water quality of the Qaraoun Reservoir, a poorly monitored Mediterranean hypereutrophic monomictic reservoir that is subject to extensive periods of HABs. The work first evaluated the ability to transfer and recalibrate previously developed reservoir-specific Landsat 7 and 8 water quality models when used with Sentinel 2 data. The results showed poor transferability between Landsat and Sentinel 2, with most models experiencing a significant drop in their predictive skill even after recalibration. Sentinel 2 models were then developed for the reservoir based on 153 water quality samples collected over 2 years. The models explored different functional forms, including multiple linear regressions (MLR), multivariate adaptive regression splines (MARS), random forests (RF), and support vector regressions (SVR). The results showed that the RF models outperformed their MLR, MARS, and SVR counterparts with regard to predicting chlorophyll-a, total suspended solids, Secchi disk depth, and phycocyanin. The coefficient of determination (R2) for the RF models varied between 85% for TSS up to 95% for SDD. Moreover, the study explored the potential of quantifying cyanotoxin concentrations indirectly from the Sentinel 2 MSI imagery by benefiting from the strong relationship between cyanotoxin levels and chlorophyll-a concentrations.


Assuntos
Monitoramento Ambiental , Qualidade da Água , Monitoramento Ambiental/métodos , Clorofila/análise , Clorofila A/análise , Lagos , Eutrofização , Proliferação Nociva de Algas , Toxinas de Cianobactérias
4.
Environ Sci Pollut Res Int ; 30(13): 37607-37621, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-36572773

RESUMO

Excessive point and non-point nutrient loadings accompanied with elevated temperatures have increased the prevalence of harmful algal bloom (HAB). HABs pose significant environmental and public health concerns, particularly for inland freshwater systems. In this study, the eutrophication and HAB dynamics in the Qaraoun Reservoir, a hypereutrophic deep monomictic reservoir suffering from poor water quality, were assessed. The reservoir was mostly phosphorus limited, and large algal particulates dominated light attenuation in the water column. During bloom events, surface chlorophyll-a concentrations increased up to 961.3 µg/L, while surface concentrations of ammonia and ortho-phosphate were rapidly depleted; surface dissolved oxygen reached supersaturation levels and surface pH levels were up to 3 units higher than those measured in the hypolimnion. Meanwhile, measured Microcystin-LR toxin concentrations in the reservoir exceeded the World Health Organization 1 µg/L provisional guideline 45% of the times. Yet, the results showed that most of the toxins were intra-cellular, suggesting that they decayed rapidly when released into the reservoir. Results from a random forests ensemble model indicated that tracking the changes in surface dissolved oxygen levels, ammonium, ortho-phosphate, and pH can be an effective program towards predicting the reservoir's trophic state and algae blooms.


Assuntos
Eutrofização , Proliferação Nociva de Algas , Qualidade da Água , Clorofila A , Água Doce , Fosfatos , Fósforo/análise
5.
Ann Med Surg (Lond) ; 80: 104058, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-36045850

RESUMO

Introduction and importance: Echinococcus infection affects the liver and lungs. However, in unusual cases it may take location in the heart. Furthermore, the settling of the cysts in the interventricular septum are especially rare. Case presentation: We report a case of a 17-years old male presented with dyspnea and productive cough. Ultrasound showed an incidental finding of a cyst in the distal part of the interventricular septum and the apex of left ventricle. He was treated with a course of antibiotics with albendazole 800 mg then was referred to the cardiac surgery department. The cyst with all its layers was resected. Clinical discussion: Cardiac hydatid cyst is extremely rare. Especially the involvement of the interventricular septum as it is responsible for only 4% of cardiac cases. Its symptoms maybe nonspecific and the diagnoses is based on echography and computed tomography. The surgical treatment under cardiopulmonary by-bass with complementary course of albendazole 800 mg seems to have a good prognostic outcome. Conclusion: Cardiac echinococcus should be kept in mind in endemic regions. The diagnosis should be made in the early and uncomplicated stages since it may be fatal. Echocardiography is sensitive and useful for the diagnosis.

6.
Nature ; 606(7914): 565-569, 2022 06.
Artigo em Inglês | MEDLINE | ID: mdl-35650430

RESUMO

Flowering plants (angiosperms) can grow at extreme altitudes, and have been observed growing as high as 6,400 metres above sea level1,2; however, the molecular mechanisms that enable plant adaptation specifically to altitude are unknown. One distinguishing feature of increasing altitude is a reduction in the partial pressure of oxygen (pO2). Here we investigated the relationship between altitude and oxygen sensing in relation to chlorophyll biosynthesis-which requires molecular oxygen3-and hypoxia-related gene expression. We show that in etiolated seedlings of angiosperm species, steady-state levels of the phototoxic chlorophyll precursor protochlorophyllide are influenced by sensing of atmospheric oxygen concentration. In Arabidopsis thaliana, this is mediated by the PLANT CYSTEINE OXIDASE (PCO) N-degron pathway substrates GROUP VII ETHYLENE RESPONSE FACTOR transcription factors (ERFVIIs). ERFVIIs positively regulate expression of FLUORESCENT IN BLUE LIGHT (FLU), which represses the first committed step of chlorophyll biosynthesis, forming an inactivation complex with tetrapyrrole synthesis enzymes that are negatively regulated by ERFVIIs, thereby suppressing protochlorophyllide. In natural populations representing diverse angiosperm clades, we find oxygen-dependent altitudinal clines for steady-state levels of protochlorophyllide, expression of inactivation complex components and hypoxia-related genes. Finally, A. thaliana accessions from contrasting altitudes display altitude-dependent ERFVII activity and accumulation. We thus identify a mechanism for genetic adaptation to absolute altitude through alteration of the sensitivity of the oxygen-sensing system.


Assuntos
Aclimatação , Altitude , Arabidopsis , Oxigênio , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Clorofila/metabolismo , Regulação da Expressão Gênica de Plantas , Oxigênio/metabolismo , Pressão Parcial , Protoclorifilida/metabolismo
7.
J Am Chem Soc ; 144(2): 733-739, 2022 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-35000393

RESUMO

Here, we quantify the effect of an external magnetic field (ß) on the oxygen evolution reaction (OER) for a cobalt oxide|fluorine-doped tin oxide coated glass (CoOx|FTO) anode. A bespoke apparatus enables us to precisely determine the relationship between magnetic flux density (ß) and OER activity at the surface of a CoOx|FTO anode. The apparatus includes a strong NdFeB magnet (ßmax = 450 ± 1 mT) capable of producing a magnetic field of 371 ± 1 mT at the surface of the anode. The distance between the magnet and the anode surface is controlled by a linear actuator, enabling submillimeter distance positioning of the magnet relative to the anode surface. We couple this apparatus with a finite element analysis magnetic model that was validated by Hall probe measurements to determine the value of ß at the anode surface. At the largest tested magnetic field strength of ß = 371 ± 1 mT, a 4.7% increase in current at 1.5 V vs the normal hydrogen electrode (NHE) and a change in the Tafel slope of 14.5 mV/dec were observed. We demonstrate through a series of OER measurements at sequential values of ß that the enhancement consists of two distinct regions. The possible use of this effect to improve the energy efficiency of commercial water electrolyzers is discussed, and major challenges pertaining to the accurate measurement of the phenomenon are demonstrated.

8.
Ann Med Surg (Lond) ; 72: 103074, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34815867

RESUMO

The complications of covid-19 may include pneumonia, acute respiratory distress syndrome (ARDS), multi-organ failure, septic shock, and death. Subcutaneous emphysema with as a complication of covid-19 has been documented in a few cases in the medical literature as case reports. A 36-year-old patient with covid-19 complained of symptoms of fever and dyspnea with no history of trauma or smoking. After computed tomography scan and x-ray, it was found that there was Subcutaneous emphysema and spontaneous pneumomediastinum. The medical treatment of corticosteroids and intravenous anticoagulant was immediately performed to improve the patient's condition significantly. The patient was discharged with nearly full recovery. We did the following-up for the patient and the results were good. The combination of these two complication is a reality for Covid-19 patients, so a quick and accurate diagnosis and continuous follow-up should be taken into account to avoid the danger to the patient's life as a result of the formed dyspnea.

9.
Obes Surg ; 31(5): 1921-1928, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33417101

RESUMO

AIMS: This study aimed at comparing the pre-, intra-, and early postoperative outcomes, between patients who underwent PVB vs general anesthesia (GA) during LSG. Follow-up of weight loss at least 1 year postoperatively was also evaluated. METHODS: A cohort study was conducted by selecting all patients who underwent LSG under PVB and GA at Makassed General Hospital between 2010 and 2016. Demographic, social, pre-op health status, body mass index (BMI), operative time, postoperative pain and pain medication consumption, postoperative complications and length of hospital stay, all were studied. Follow-up weight loss was collected up to 5 years postoperatively. Data entry, management, and descriptive and inferential statistics were performed using SPSS. RESULTS: A total of 210 participants were included in this study of which 48 constituted the PVB group and 162 patients composed the GA group. Both groups were similar in baseline demographic factors, with patients in PVB suffering from higher number and advanced stage of comorbidities than the GA group. Mean operative time was similar in between the two groups with 80 ± 20 min for PVB and 82 ± 18 min for GA group. Intraoperative complications were scarce among both study groups. GA group requested a second dose of analgesia earlier than PVB group. After at least 1 year postoperatively, the mean percentage of excess weight loss was 81.35 ± 15.5% and 77.89 ± 14.3% for the PVB and GA groups, respectively, P value 0.45. CONCLUSION: Outcomes of LSG under both types of anesthesia (PVB alone and GA alone) were found to be comparable. However, the need for analgesia was significantly less in the PVB group compared to GA group.


Assuntos
Laparoscopia , Obesidade Mórbida , Anestesia Geral , Estudos de Coortes , Gastrectomia , Humanos , Obesidade Mórbida/cirurgia , Resultado do Tratamento , Vigília
10.
J Integr Plant Biol ; 62(1): 70-89, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31638740

RESUMO

The amino-terminal residue of a protein (or amino-terminus of a peptide following protease cleavage) can be an important determinant of its stability, through the Ubiquitin Proteasome System associated N-degron pathways. Plants contain a unique combination of N-degron pathways (previously called the N-end rule pathways) E3 ligases, PROTEOLYSIS (PRT)6 and PRT1, recognizing non-overlapping sets of amino-terminal residues, and others remain to be identified. Although only very few substrates of PRT1 or PRT6 have been identified, substrates of the oxygen and nitric oxide sensing branch of the PRT6 N-degron pathway include key nuclear-located transcription factors (ETHYLENE RESPONSE FACTOR VIIs and LITTLE ZIPPER 2) and the histone-modifying Polycomb Repressive Complex 2 component VERNALIZATION 2. In response to reduced oxygen or nitric oxide levels (and other mechanisms that reduce pathway activity) these stabilized substrates regulate diverse aspects of growth and development, including response to flooding, salinity, vernalization (cold-induced flowering) and shoot apical meristem function. The N-degron pathways show great promise for use in the improvement of crop performance and for biotechnological applications. Upstream proteases, components of the different pathways and associated substrates still remain to be identified and characterized to fully appreciate how regulation of protein stability through the amino-terminal residue impacts plant biology.


Assuntos
Proteínas de Plantas/metabolismo , Plantas/metabolismo , Proteólise , Ubiquitina/metabolismo , Melhoramento Vegetal , Especificidade por Substrato
11.
Open Access Maced J Med Sci ; 7(21): 3514-3520, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-32010368

RESUMO

BACKGROUND: Diffuse astrocytomas constitute the largest group of primary malignant human intracranial tumours. They are classified by the World Health Organization (WHO) into three histological malignancy grades: diffuse astrocytomas (grade II), anaplastic astrocytomas (grade III) and glioblastoma (grade IV) based on histopathological features such as cellular atypia, mitotic activity, necrosis and microvascular proliferation. Epidermal growth factor receptor (EGFR) is a 170-kDa transmembrane tyrosine kinase receptor expressed in a variety of normal and malignant cells regulating critical cellular processes. When activated, epidermal growth factor receptor (EGFR) triggers several signalling cascades leading to increased proliferation and angiogenesis and decreased apoptosis and hence associated with aggressive progression of the tumour. Epidermal growth factor receptor (EGFR) level is known to be a strong indicator associated with the aggressive behaviour of the tumour and acts as a prognostic factor for evaluating the survival rate. AIM: To evaluate the expression of epidermal growth factor receptor (EGFR) in different grades of astrocytoma. MATERIAL AND METHODS: formalin-fixed paraffin-embedded astrocytic tumours of 44 patients were collected from the archival material of pathology department of Ghazi Al Hariri Teaching Hospital during the period from June to December 2018. Hematoxylin and eosin-stained sections were used to characterise the tumours histologically based on cellularity, nuclear hyperchromasia, polymorphism, mitotic activity, vascular proliferation and necrosis with or without pseudopallisading of tumour cells. Diagnosis and grading of astrocytic tumours in this study were made according to WHO criteria (2016). Using a monoclonal antibody to the epidermal growth factor receptor (EGFR) and immunohistochemical analysis, the expression and distribution of epidermal growth factor receptor in astrocytic tumours were examined. RESULTS: The study included 1 case pilocytic astrocytoma (grade I), 20 cases diffuse astrocytoma (grade II), 5 cases anaplastic astrocytoma (grade III) and 18 cases of glioblastoma (grade IV). Expression of EGFR was found in 38.88% of the glioblastoma samples (grade IV). However, none of the astrocytomas of WHO grades I, II and III showed immunoreactivity for EGFR protein. Different patterns of immunoreactive cells and significant intratumor heterogeneity of EGFR expression were observed in glioblastomas. CONCLUSION: The immunohistochemical expression of Epidermal growth factor receptor (EGFR) was restricted only to high-grade astrocytic tumours, namely glioblastoma, thus may use to predict glioblastoma.

12.
Proc Natl Acad Sci U S A ; 115(26): 6864-6869, 2018 06 26.
Artigo em Inglês | MEDLINE | ID: mdl-29899148

RESUMO

Asymmetric auxin distribution is instrumental for the differential growth that causes organ bending on tropic stimuli and curvatures during plant development. Local differences in auxin concentrations are achieved mainly by polarized cellular distribution of PIN auxin transporters, but whether other mechanisms involving auxin homeostasis are also relevant for the formation of auxin gradients is not clear. Here we show that auxin methylation is required for asymmetric auxin distribution across the hypocotyl, particularly during its response to gravity. We found that loss-of-function mutants in Arabidopsis IAA CARBOXYL METHYLTRANSFERASE1 (IAMT1) prematurely unfold the apical hook, and that their hypocotyls are impaired in gravitropic reorientation. This defect is linked to an auxin-dependent increase in PIN gene expression, leading to an increased polar auxin transport and lack of asymmetric distribution of PIN3 in the iamt1 mutant. Gravitropic reorientation in the iamt1 mutant could be restored with either endodermis-specific expression of IAMT1 or partial inhibition of polar auxin transport, which also results in normal PIN gene expression levels. We propose that IAA methylation is necessary in gravity-sensing cells to restrict polar auxin transport within the range of auxin levels that allow for differential responses.


Assuntos
Proteínas de Arabidopsis/biossíntese , Proteínas de Arabidopsis/metabolismo , Arabidopsis/crescimento & desenvolvimento , Regulação da Expressão Gênica de Plantas/fisiologia , Hipocótilo/crescimento & desenvolvimento , Ácidos Indolacéticos/metabolismo , Metiltransferases/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Hipocótilo/genética , Metilação , Metiltransferases/genética , Mutação
13.
Plant Biotechnol J ; 16(1): 272-279, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-28574629

RESUMO

High temperature is a general stress factor that causes a decrease in crop yield. It has been shown that auxin application reduces the male sterility caused by exposure to higher temperatures. However, widespread application of a hormone with vast effects on plant physiology may be discouraged in many cases. Therefore, the generation of new plant varieties that locally enhance auxin in reproductive organs may represent an alternative strategy. We have explored the possibility of increasing indole-3-acetic acid (IAA) in ovaries by reducing IAA methyltransferase1 (IAMT1) activity in Arabidopsis thaliana. The iamt1 mutant showed increased auxin signalling in funiculi, which correlated with a higher growth rate of wild-type pollen in contact with mutant ovaries and premature ovule fertilization. While the production of seeds per fruit was similar in the wild type and the mutant at 20 °C, exposure to 29 °C caused a more severe decrease in fertility in the wild type than in the mutant. Loss of IAMT1 activity was also associated with the production of more nodes after flowering and higher tolerance of the shoot apical meristem to higher temperatures. As a consequence, the productivity of the iamt1 mutant under higher temperatures was more than double of that of the wild type, with almost no apparent trade-off.


Assuntos
Arabidopsis/metabolismo , Ácidos Indolacéticos/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Regulação da Expressão Gênica de Plantas/genética , Regulação da Expressão Gênica de Plantas/fisiologia , Metiltransferases/genética , Metiltransferases/metabolismo , Infertilidade das Plantas/genética , Infertilidade das Plantas/fisiologia , Pólen/genética , Pólen/metabolismo , Temperatura
14.
Curr Biol ; 26(22): 3026-3032, 2016 11 21.
Artigo em Inglês | MEDLINE | ID: mdl-27773568

RESUMO

Plants adjust their growth according to gravity. Gravitropism involves gravity perception, signal transduction, and asymmetric growth response, with organ bending as a consequence [1]. Asymmetric growth results from the asymmetric distribution of the plant-specific signaling molecule auxin [2] that is generated by lateral transport, mediated in the hypocotyl predominantly by the auxin transporter PIN-FORMED3 (PIN3) [3-5]. Gravity stimulation polarizes PIN3 to the bottom sides of endodermal cells, correlating with increased auxin accumulation in adjacent tissues at the lower side of the stimulated organ, where auxin induces cell elongation and, hence, organ bending. A curvature response allows the hypocotyl to resume straight growth at a defined angle [6], implying that at some point auxin symmetry is restored to prevent overbending. Here, we present initial insights into cellular and molecular mechanisms that lead to the termination of the tropic response. We identified an auxin feedback on PIN3 polarization as underlying mechanism that restores symmetry of the PIN3-dependent auxin flow. Thus, two mechanistically distinct PIN3 polarization events redirect auxin fluxes at different time points of the gravity response: first, gravity-mediated redirection of PIN3-mediated auxin flow toward the lower hypocotyl side, where auxin gradually accumulates and promotes growth, and later PIN3 polarization to the opposite cell side, depleting this auxin maximum to end the bending. Accordingly, genetic or pharmacological interference with the late PIN3 polarization prevents termination of the response and leads to hypocotyl overbending. This observation reveals a role of auxin feedback on PIN polarity in the termination of the tropic response.


Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/fisiologia , Gravitropismo , Sensação Gravitacional , Ácidos Indolacéticos/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Proteínas de Arabidopsis/metabolismo , Retroalimentação Fisiológica , Brotos de Planta/crescimento & desenvolvimento
15.
Curr Biol ; 25(11): 1483-8, 2015 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-25981794

RESUMO

Successful emergence from the soil is essential for plant establishment in natural and farmed systems. It has been assumed that the absence of light in the soil is the preeminent signal perceived during early seedling development, leading to a distinct morphogenic plan (skotomorphogenesis) [1], characterized by traits providing an adaptive advantage until emergence and photomorphogenesis. These traits include suppressed chlorophyll synthesis, promotion of hypocotyl elongation, and formation of a closed apical hook that protects the stem cell niche from damage [2, 3]. However, absence of light by itself is not a sufficient environmental signal for early seedling development [4, 5]. Reduced oxygen levels (hypoxia) can occur in water-logged soils [6-8]. We therefore hypothesized that below-ground hypoxia may be an important, but thus far undiscovered, ecological component regulating seedling development. Here, we show that survival and establishment of seedlings following darkness depend on their ability to sense hypoxia, through enhanced stability of group VII Ethylene Response Factor (ERFVII) transcription factors. Hypoxia is perceived as a positive environmental component in diverse taxa of flowering plants, promoting maintenance of skotomorphogenic traits. Hypoxia greatly enhances survival once light is perceived, while oxygen is necessary for the subsequent effective completion of photomorphogenesis. Together with light perception, oxygen sensing therefore allows an integrated response to the complex and changing physical microenvironment encountered during early seedling growth. We propose that plants monitor the soil's gaseous environment after germination, using hypoxia as a key external cue to protect the stem cell niche, thus ensuring successful rapid establishment upon emergence above ground.


Assuntos
Magnoliopsida/crescimento & desenvolvimento , Oxigênio/fisiologia , Plântula/crescimento & desenvolvimento , Luz , Morfogênese
16.
Front Plant Sci ; 4: 441, 2013 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-24204373

RESUMO

The apical hook is a developmentally regulated structure that appears in dicotyledonous seedlings when seeds germinate buried in the soil. It protects the shoot apical meristem and cotyledons from damage while the seedling is pushing upwards seeking for light, and it is formed by differential cell expansion between both sides of the upper part of the hypocotyl. Its apparent simplicity and the fact that it is dispensable when seedlings are grown in vitro have converted the apical hook in one of the favorite experimental models to study the regulation of differential growth. The involvement of hormones -especially auxin-in this process was manifested already in the early studies. Remarkably, a gradient of this hormone across the hook curvature is instrumental to complete its development, similar to what has been proposed for other processes involving the bending of an organ, such as tropic responses. In agreement with this, other hormones-mainly gibberellins and ethylene-and the light, regulate in a timely and interconnected manner the auxin gradient to promote hook development and its opening, respectively. Here, we review the latest findings obtained mainly with the apical hook of Arabidopsis thaliana, paying special attention to the molecular mechanisms for the cross-regulation between the different hormone signaling pathways that underlie this developmental process.

17.
Proc Natl Acad Sci U S A ; 109(33): 13446-51, 2012 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-22847438

RESUMO

Plant development is modulated by the convergence of multiple environmental and endogenous signals, and the mechanisms that allow the integration of different signaling pathways is currently being unveiled. A paradigmatic case is the concurrence of brassinosteroid (BR) and gibberellin (GA) signaling in the control of cell expansion during photomorphogenesis, which is supported by physiological observations in several plants but for which no molecular mechanism has been proposed. In this work, we show that the integration of these two signaling pathways occurs through the physical interaction between the DELLA protein GAI, which is a major negative regulator of the GA pathway, and BRASSINAZOLE RESISTANT1 (BZR1), a transcription factor that broadly regulates gene expression in response to BRs. We provide biochemical evidence, both in vitro and in vivo, indicating that GAI inactivates the transcriptional regulatory activity of BZR1 upon their interaction by inhibiting the ability of BZR1 to bind to target promoters. The physiological relevance of this interaction was confirmed by the observation that the dominant gai-1 allele interferes with BR-regulated gene expression, whereas the bzr1-1D allele displays enhanced resistance to DELLA accumulation during hypocotyl elongation. Because DELLA proteins mediate the response to multiple environmental signals, our results provide an initial molecular framework for the integration with BRs of additional pathways that control plant development.


Assuntos
Arabidopsis/metabolismo , Brassinosteroides/metabolismo , Giberelinas/metabolismo , Transdução de Sinais , Arabidopsis/citologia , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Escuridão , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Giberelinas/farmacologia , Hipocótilo/efeitos dos fármacos , Hipocótilo/crescimento & desenvolvimento , Hipocótilo/metabolismo , Regiões Promotoras Genéticas/genética , Ligação Proteica/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos
18.
J Egypt Soc Parasitol ; 38(3): 813-22, 2008 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19209764

RESUMO

Sixty hamsters weighing 100-120 g were randomly assigned to 2 equal groups. GI was injected intramuscularly with saline, half an hour preoperatively as control, and GII was injected with 50 mg/kg Cefepime HCI & 7.5 mg/kg Metronidazole. After a midline lapparotomy, abdominal adhesions were induced in GI & GII. Post-operration, animals in GI was divided according to the numbers of intramuscular saline injections into 2 subgroups. GIa (15) in which animals were injected every 12 hours for 2 doses and GIb (15) where animals were injected every 12 hours for 5 days. Similarly, the antibiotic group was subdivided into GIIa (15) and GIIb (15). On the 14th day, the hamsters were sacrificed and the adhesion score was determined. The 5 day antibiotics course revealed significant reduction in incidence (P < 0.01), extent (P < 0.001) and severity (P < 0.01) of the postoperative peritoneal adhesions, while the short course failed.


Assuntos
Antibacterianos/farmacologia , Cefalosporinas/farmacologia , Metronidazol/farmacologia , Complicações Pós-Operatórias/prevenção & controle , Aderências Teciduais/prevenção & controle , Animais , Cefepima , Cricetinae , Modelos Animais de Doenças , Injeções Intramusculares , Laparotomia/efeitos adversos , Laparotomia/métodos , Mesocricetus , Complicações Pós-Operatórias/epidemiologia , Distribuição Aleatória , Fatores de Tempo , Aderências Teciduais/epidemiologia , Resultado do Tratamento
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