Medecins & medical devices Regulations in UK

Here, you can find a quite useful article in pdf format from the MHRA website about :

What is the MHRA?
How does licensing and authorisation work?
How does the MHRA monitor the safety and quality standards?
Influencing policy

Detection of collagen fibers using Second harmonic generation (SHG) imaging

One remarkable ability of multiphoton microscopy is to provide images with micrometer 3 -dimensional (3D) resolution from within intact biological tissues. An emerging application is the observation of unstained live tissue, based on endogenous sources of nonlinear signals. Imaging intrinsic signals with molecular or structural specificity can be achieved by combining twophoton-excited fluorescence (2PEF) microscopy, second harmonic generation (SHG) microscopy, and spectrally selective detection. Endogenous sources of signal for tissue 2PEF imaging are the same as those excited by conventional one-photon absorption with near-UV or blue excitation: NAD(P)H, flavoproteins, elastin fibers, etc.However, two-photon excitation provides superior imaging depth compared with confocal/conventional microscopy[1].

In a recent study, we tried to image arterial collagen found in the media using SHG. However, it seems that there is a technical problem. Most of collagen found in the media layer of arterial wall is consisted of type IV collagen which is not detectable with SHG.however, the fibrillar collagen in adventitia (mostly type I and III) is detectable. (looking at the figure shown from ref. 1 ,in green is the collagen in adventitia and in red one find the elastin laminas in media of the vessel wall.) Here is my question: Has anyone of you ever tried to image the collagen in media in an unstained tissue using SHG?

[1] T. Boulesteix et al. , " Micrometer scale Ex Vivo multiphoton imaging of unstained arterial wall structure" Cytometry Part A, 69A(1), pp. 20-26.

more suggested readings:

High resolution imaging of collagen organisation and synthesis using a versatile collagen specific probe

Upcoming conferences ,September 2007

Online registrations open:

BMES annual fall meeting 2007 , Los Angeles, 26-29 September

Registration Open, Deadline:Auguste 29, 2007

Swiss Society of Biomedical Engineering(SSBE) 2007 Meeting: CSEM Neuchâtel ,13-14 September 2007

Registration Open, deadline: Auguste 14, 2007

Single Molecule Manipulations in Biophysics 2

Torque Measurements on single DNA Molecules

The physical properties of the DNA double helix are unlike those of any other natural or synthetic polymer. The molecule’s characteristic base stacking and braided architecture lend it unusual stiffness: It takes about 50 times more energy to bend a double-stranded DNA molecule into a circle than to perform the same operation on single-stranded DNA. Moreover, the phosphates in DNA’s backbone make it one of the most highly charged polymers known.

To perform dynamic torque measurements on single DNA molecules, molecular constructs were made.This kind of experiments have been performed in the Prof. Bustamante's laboratory at Berkeley University.

The use of three distinct chemical modifications of DNA allows for oriented tethering of the ends of the molecule and the subsequent attachment of a rotor to a third, internal position (shown on the figure). A site-specific nick in the duplex DNA is engineered adjacent to the rotor attachment point; this design allows covalent bonds in the intact strand to serve as free swivels, preventing torque from accumulating in the "lower" DNA segment. Thus, torque stored in the "upper" segment can drive the rotation of a submicron object on a low-friction molecular bearing. At low Reynolds numbers, the magnitude of the torque can be measured by multiplying the observed angular velocity by the rotational drag of the rotor.

To be continued

reference: Bustamante, C.Of torques, forces, and protein machines(2004) Protein Science, 13 (11), pp. 3061-3065.doi: 10.1110/ps.041064504

What is Biomedical Engineering?

Biomedical engineering integrates physical, chemical, mathematical, and computational sciences and engineering principles to study biology, medicine, behavior, and health.

It advances fundamental concepts; creates knowledge from the molecular to the organ systems level; and develops innovative biologics, materials, processes, implants, devices and informatics approaches for the prevention, diagnosis, and treatment of disease, for patient rehabilitation, and for improving health.

NIH working definition of bioengineering – July 24, 1997

Single Molecules Manipulations in Biophysics

Until very recently, chemists and biochemists have had to rely on bulk methods to investigate the properties of molecules and their reactions. These methods did not make it possible to directly investigate the nature, strength, and direction of intermolecular forces and torques.

During the last few years, however, the advent of novel methods of single-molecule manipulation have begun to offer researchers, for the first time, the opportunity to measure directly the forces holding molecular structures together, to measure the stresses and strains generated in the course of chemical and biochemical reactions, to exert external forces to alter the fate of these reactions, and to reveal the rules that govern the interconversion of mechanical and chemical energy in these reactions. This area of research can be rightly called mechanochemistry.

Biochemical processes as diverse as protein folding, DNA elasticity, the protein-induced bending of DNA, the stress-induced catalysis of enzymes, the mechanical properties of protein motors, and even the ubiquitous process of induced-fit molecular recognition of proteins for their ligands, are all examples in which stresses and strains develop in molecules as they move along a reaction coordinate.

to be continued

reference: Bustamante, C.Of torques, forces, and protein machines(2004) Protein Science, 13 (11), pp. 3061-3065.doi: 10.1110/ps.041064504