Most bacterial cells have their genes arranged in a single circle of DNA. The circle of DNA plus some attached proteins is refered to as the bacterial chromosome. Up until quite recently, it was thought that the chromosome in the tiny bacteria cell resembled a tangled ball of yarn. It is now known that multiple factors cooperate to condense DNA into a highly dynamic assembly of supercoiled loops. Although there is variability in the lower levels of chromosome structure, the global arrangement of DNA within the cell is conserved, with individual loci arrayed along the long axis in the cell in line with their order on the genetic map. This order is maintained and propagated during DNA replication. Upon duplication of a given segment of the chromosome, it is immediately released from the replisome (the DNA replication machine) and it moves rapidly to its conserved position in the incipient daughter cell compartment. Partitioning of the bacterial chromosome thus takes place while DNA replication is in progress. Furthermore, it is becoming clear that the bacterial cell is highly organized, presenting new challenges and opportunities for the design of new antibiotics.
Apoptosis is a form of programmed cell death that plays important roles during animal development, immune response, elimination of damaged cells, and maintenance of tissue homeostasis. Apoptosis is executed by intracellular proteases named caspases that are activated during the onset of apoptosis by extrinsic and intrinsic pathways.
Part1 Introduction to Apoptosis
Part 2 The Intrinsic Pathway of Apoptosis
Part 3-Extrinsic Pathway of Apoptosis
When you get the flu, viruses turn your cells into tiny factories that help spread the disease. In this animation, NPR's Robert Krulwich and medical animator David Bolinsky explain how a flu virus can trick a single cell into making a million more viruses.
In the third part, I discuss how the complex shapes of cells are created by the cytoskeleton, and I compare and contrast prokaryotes (which have actin-, tubulin-, and intermediate filament -like proteins) and eukaryotes in this regard. In particular, I speculate that cytoskeletal dynamics were necessary to evolve simple bacterial shapes and cell division, but that additional layers of complexity (namely regulated nucleation and molecular motors) allowed eukaryotes to evolve more complex shapes and organize their internal components.
The second part is devoted to understanding how the polymerization of actin can produce force, which is a current area of research in our laboratory. Here, I cover theories for how polymerization might be used to produce forces, and our efforts to test these models using optical traps, atomic force microscopes, and nanofabricated devices.
This lecture covers the biochemical basis of actin-based motility (focusing on the pathogen Listeria as a model system for this process), the biophysical mechanism of polymerization-based force generation, and an evolutionary perspective of cell shape in prokaryotes and eukaryotes. The first part covers our understanding of how cells use the actin cytoskeleton to crawl. The pathogenic bacteria Listeria (which causes food poisoning) uses the actin cytoskeleton to propel itself in the cytoplasm and also invade other cells. This system has been an important model for understanding the actin cytoskeleton at the leading edge of a motile cell and for understanding host-pathogen interactions.
IBM Research scientists, in collaboration with the Center for Probing the Nanoscale at Stanford University, have demonstrated magnetic resonance imaging (MRI) with volume resolution 100 million times finer than conventional MRI. This result, published in the Proceedings of the National Academy of Sciences (PNAS), signals a significant step forward in tools for molecular biology and nanotechnology by offering the ability to study complex 3D structures at the nanoscale. By extending MRI to such fine resolution, the scientists have created a microscope that, with further development, may ultimately be powerful enough to unravel the structure and interactions of proteins, paving the way for new advances in personalized healthcare and targeted medicine. This achievement stands to impact the study of materials from proteins to integrated circuits for which a detailed understanding of atomic structure is essential.
From nano-scale diagnostic and therapeutic tools to medication designed and developed specifically for you, new research directions at Cornell are breaking ground and shaping the health care experience of the future. Two of Cornell's preeminent faculty members with research at the forefront of these areas will explain how their work may impact human health.
* Andrew G. Clark, Jacob Gould Schurman Professor of Population Genetics, Department of Molecular Biology and Genetics
* Harold G. Craighead, Charles W. Lake, Jr. Professor of Engineering; Professor of Applied and Engineering Physics; and Director, Nanobiotechnology Center
Pediatric obesity has reached epidemic proportions in the United States with 20-25% of children considered obese. That number has doubled in the last 2 decades. The increase in the number of overweight children, and the related health problems, are serious issues. Join Dr. Robert H. Lustig, the director, Weight Assessment for Teen and Child Health (WATCH) Program at UCSF for an in-depth look at this major medical problem.
Angioplasty is a technique used to dilate an area of arterial blockage with the help of a catheter that has an inflatable small sausage-shaped balloon at its tip.Since the balloon catheter is introduced through the skin of the groin, and sometimes the arm ( percutaneous = through the skin), is placed within a blood vessel (transluminal = in the channel or lumen of a blood vessel) and is applied in the treatment of coronary arteries, the technique is also called PTCA or Percutaneous Transluminal Coronary Angioplasty.