Tài liệu miễn phí Sinh học
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Transcription factors from the MADS-box family play a relevant role in cell differentiation and development and include the animal SRF (serum response factor) and MEF2 (myocyte enhancer factor 2) proteins. The social amoeba Dictyostelium discoideum contains four genes coding for MADS-box transcription factors, two of these genes code for proteins that are more similar to SRF, and the other two code for proteins that are more similar to MEF2 animal factors.
12/29/2020 6:23:51 PM +00:00
Our current knowledge on tooth development derives primarily from studies in mice. Very little is known about gene expression and function during human odontogenesis. Sonic Hedgehog (SHH) signaling has been demonstrated to play crucial roles in the development of multiple organs in mice, including the tooth.
12/29/2020 6:23:42 PM +00:00
Tenm4 is a mouse homolog of the Drosophila gene Tenascin-m (Ten-m (Odd oz)), which functions in motor neuron routing. Recently, a genome-wide association analysis for bipolar disorder identified a new susceptibility locus at TENM4 increasing the importance of understanding Tenm4.
12/29/2020 6:23:32 PM +00:00
The freshwater planarian Schmidtea mediterranea has emerged as a powerful model for studies of regenerative, stem cell, and germ cell biology. Whole-mount in situ hybridization (WISH) and whole-mount fluorescent in situ hybridization (FISH) are critical methods for determining gene expression patterns in planarians.
12/29/2020 6:23:22 PM +00:00
In the male germ line of Drosophila chromatin remains decondensed and highly transcribed during meiotic prophase until it is rapidly compacted. A large proportion of the cell cycle-regulated histone H3.1 is replaced by H3.3, a histone variant encoded outside the histone repeat cluster and not subject to cell cycle controlled expression.
12/29/2020 6:23:13 PM +00:00
Thyroid hormones regulate growth and development. However, the molecular mechanisms by which thyroid hormone regulates cell structural development are not fully understood.
12/29/2020 6:23:04 PM +00:00
Individual skeletal elements of the vertebrate limbs arise through a segmentation process introducing joints in specific locations. However, the molecular pathways controlling joint formation and subsequent joint maintenance are largely unknown.
12/29/2020 6:22:56 PM +00:00
Insulin and its plasma membrane receptor constitute an ancient response system critical to cell growth and differentiation. Studies using intact Rana pipiens oocytes have shown that insulin can act at receptors on the oocyte surface to initiate resumption of the first meiotic division.
12/29/2020 6:22:49 PM +00:00
Group B Sox domain transcription factors play important roles in metazoan central nervous system development. They are, however, difficult to study as mutations often have pleiotropic effects and other Sox family members can mask phenotypes due to functional compensation.
12/29/2020 6:22:41 PM +00:00
Members of the family Syngnathidae share a unique reproductive mode termed male pregnancy. Males carry eggs in specialised brooding structures for several weeks and release free-swimming offspring.
12/29/2020 6:22:33 PM +00:00
Magnetic resonance imaging is a noninvasive method of evaluating embryonic development. Diffusion tensor imaging (DTI), based on the directional diffusivity of water molecules, is an established method of evaluating tissue structure. Yet embryonic motion degrades the in vivo acquisition of long-duration DTI.
12/29/2020 6:22:26 PM +00:00
Genetic studies in mouse have demonstrated the crucial function of PAX4 in pancreatic cell differentiation. This transcription factor specifies β- and δ-cell fate at the expense of α-cell identity by repressing Arx gene expression and ectopic expression of PAX4 in α-cells is sufficient to convert them into β-cells.
12/29/2020 6:22:11 PM +00:00
In mammals, R-spondin (Rspo), an activator of the Wnt/β-catenin signaling pathway, has been shown to be involved in ovarian differentiation. However, the role of the Rspo/Wnt/β-catenin signaling pathway in fish gonads is still unknown.
12/29/2020 6:22:03 PM +00:00
The contribution of cell proliferation to regeneration varies greatly between different metazoan models. Planarians rely on pluripotent neoblasts and amphibian limb regeneration depends upon formation of a proliferative blastema, while regeneration in Hydra can occur in the absence of cell proliferation.
12/29/2020 6:21:54 PM +00:00
The first distinct differentiation event in mammals occurs at the blastocyst stage when totipotent blastomeres differentiate into either pluripotent inner cell mass (ICM) or multipotent trophectoderm (TE). Here we determined, for the first time, global gene expression patterns in the ICM and TE isolated from bovine blastocysts.
12/29/2020 6:21:47 PM +00:00
Temperature affects virtually all cellular processes. A quick increase in temperature challenges the cells to undergo a heat shock response to maintain cellular homeostasis. Heat shock factor-1 (HSF-1) functions as a major player in this response as it activates the transcription of genes coding for molecular chaperones (also called heat shock proteins) that maintain structural integrity of proteins.
12/29/2020 6:21:40 PM +00:00
Oxygen sensing is a near universal signaling modality that, in eukaryotes ranging from protists such as Dictyostelium and Toxoplasma to humans, involves a cytoplasmic prolyl 4-hydroxylase that utilizes oxygen and α-ketoglutarate as potentially rate-limiting substrates.
12/29/2020 6:21:33 PM +00:00
Hox proteins are transcription factors involved in crucial processes during animal development. Their mode of action remains scantily documented. While other families of transcription factors, like Smad or Stat, are known cell signaling transducers, such a function has never been squarely addressed for Hox proteins.
12/29/2020 6:21:24 PM +00:00
FGF signaling plays numerous roles during organogenesis of the embryonic gut tube. Mouse explant studies suggest that different thresholds of FGF signaling from the cardiogenic mesoderm induce lung, liver, and pancreas lineages from the ventral foregut progenitor cells.
12/29/2020 6:21:14 PM +00:00
Secreted frizzled-related proteins (SFRPs) are a family of proteins that block the Wnt signaling pathway and loss of SFRP1 expression is found in breast cancer along with a multitude of other human cancers. Activated Wnt signaling leads to inappropriate mammary gland development and mammary tumorigenesis in mice.
12/29/2020 6:21:07 PM +00:00
Zebrafish has emerged as a powerful model organism to study the process of regeneration. This teleost fish has the ability to regenerate various tissues and organs like the heart, spinal cord, retina and fins.
12/29/2020 6:21:01 PM +00:00
Mouse limb bud is a prime model to study the regulatory interactions that control vertebrate organogenesis. Major aspects of limb bud development are controlled by feedback loops that define a self-regulatory signalling system.
12/29/2020 6:20:51 PM +00:00
Valvulogenesis and septation in the developing heart depend on the formation and remodeling of endocardial cushions in the atrioventricular canal (AVC) and outflow tract (OFT). These cushions are invaded by a subpopulation of endocardial cells that undergo an epithelial-mesenchymal transition in response to paracrine and autocrine transforming growth factor β (TGFβ) signals.
12/29/2020 6:20:45 PM +00:00
The WNT/β-CATENIN signaling cascade is crucial for the patterning of the early lung morphogenesis in mice, but its role in the developing human lung remains to be determined.
12/29/2020 6:20:37 PM +00:00
Calpains are calcium regulated intracellular cysteine proteases implicated in a variety of physiological functions and pathological conditions. The Drosophila melanogaster genome contains only two genes, CalpA and CalpB coding for canonical, active calpain enzymes.
12/29/2020 6:20:30 PM +00:00
The peptidylarginine deiminases (PADIs) convert positively charged arginine residues to neutrally charged citrulline on protein substrates in a process that is known as citrullination or deimination.
12/29/2020 6:20:23 PM +00:00
Among the four major bilaterian clades, Deuterostomia, Acoelomorpha, Ecdysozoa, and Lophotrochozoa, the latter shows an astonishing diversity of bodyplans. While the largest lophotrochozoan assemblage, the Spiralia, which at least comprises Annelida, Mollusca, Entoprocta, Platyhelminthes, and Nemertea, show a spiral cleavage pattern, Ectoprocta, Brachiopoda and Phoronida (the Lophophorata) cleave radially.
12/29/2020 6:20:13 PM +00:00
During early stages of brain development, secreted molecules, components of intracellular signaling pathways and transcriptional regulators act in positive and negative feed-back or feed-forward loops at the midhindbrain boundary.
12/29/2020 6:20:06 PM +00:00
Viêm họng cấp là bệnh nhiễm trùng hô hấp phổ biến, tùy thuộc tác nhân gây bệnh và sức đề kháng của cơ thể bệnh có thể chuyển biến nặng hơn. Nghiên cứu nhằm phân lập, định danh phân tử, khảo sát đặc tính kháng kháng sinh của một số chủng vi khuẩn Streptococcus gây viêm họng cấp ở người.
12/29/2020 6:07:03 PM +00:00
Khoa văn học so sánh ra đời ở phương Tây từ cuối thế kỷ XIX, đã và đang phát triển trên thế giới, được coi như một hướng đi đầy triển vọng, giàu hiệu quả trong khoa học nghiên cứu văn học. Đề tài Bộ ba tiểu thuyết Gia đình - Thoát ly - Thừa tự của Khái Hưng và tiểu thuyết Ba thế hệ của Yeom Sang Seop qua cách nhìn của khoa văn học so sánh được trình bày sơ lược ở đây chính là nhằm góp phần thể hiện mối quan hệ văn hóa giữa hai dân tộc.
12/29/2020 5:57:50 PM +00:00