ISSN:0005-9021    

DOI:10.1002/bbpc.19890930302

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractIt becomes increasingly evident that pulsed laser methods will contribute greatly to understanding fundamental processes in biological systems. It is now possible to perform many types of electronic and vibrational spectroscopy on the femtosecond timescale. Such measurements provide new knowledge of molecular and protein motion, transient structures and of primary photoprocesses. —Research on understanding dynamical and structural properties involved in reactions of heme proteins with ligands will be reviewed with emphasis on the interplay between advances in laser methods and the gradual refinement of our picture of the operation of these protein

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930304

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractHigh UV photon densities can be used in a wide range of applications in life sciences. Below the threshold for photodamage, time resolved fluorescence spectroscopy and UV resonance Raman Spectroscopy with proteins and nucleic acids can be performed. 1 GW/cm2is significantly above the ablation threshold of tissue and can now be transported conveniently through tapered quartz fibres. 100 GW/cm2in the tunable wavelength region 265 to 685 nm are generated by coupling nearly diffraction limited dye laser pulses into a microscope. This allows a detailed wavelength study on the interaction of high photon densities with human red blood cells, which may serve as a model for biological tissue. Using the same equipment, biological cells can be fused with each other in a very selective way. Furthermore, human chromosomes can be microdissected into fine slices and DNA for diagnosis of human disease can be isolated from these localized regions of the human genome.

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930305

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractThe high three dimensional and temporal resolution of a pulsed UV‐laser microbeam is used to manipulate subcellular structures in pollen tubes without destroying cell viability. A single pulse of about 1 μm diameter, focussed into the depth of the tube, stops immediately cytoplasmic streaming in a region of 50 μm around the irradiated spot. Calcium is released from intracellular stores within the irradiated area, as monitored by the fluorescence of the calcium sensitive dye quin‐2. The observed effects can be explained by a disruption of calcium storing organelles. The released calcium ions can depolymerize microfilaments and thus stop organelle movement. Furthermore, organelle zonation can be disturbed with a few laser pulses near the tip region. This may be due to the disturbance of the electric field, that is thought to maintain tube organiz

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930306

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractA number of methods have become available to introduce genes into animal cells. In plants the rigid cell wall has presented a substantial barrier to similar efforts. Using protoplasts represents one way to overcome the obstacles to gene transfer. In many species these wall‐less cells, however, are sensitive to manipulations and do not regenerate to plants. Furthermore, direct gene transfer into organelles is even further complicated by the fact that DNA has to pass through two membrane systems. —Recently a method has been developed to deliver DNA randomly to cells with a particle gun [1]. It is very desirable, however, to introduce DNA into specifically selected cells or their organelles. —A laser beam focussed to its diffraction limits and coupled into a microscope provides a tool to cut openings of less than 1 μm into cell walls or membranes. Under visual control cells can be selected for gene transfer or for surgical manipulation [2]. Direct transformation with cloned DNA was achieved in mammalian cells [3,4], —Now this tool was used on oilseed rape (Brassica napus). With a laser microbeam DNA was introduced into cells and microspores of Brassica napus [5,6]. Individual cells were placed in the light path of the microscope and a single laser pulse was released at the cell wall and membrane. At the site of the laser focus wall and membrane were opened. At the time of the experiment the cells were incubated in a hypotonic buffer containing DNA. The nucleic acid was taken up into the cells. The opening in the membrane was only temporary and closed within less than 5 s after the laser pulse. The cells or microspores developed into colonies or embryos respectively with a frequency of 30–50% of the untreated controls. —Using the same technique DNA was also integrated into isolated chloroplasts [7]. Furthermore DNA can be incorporated into chloroplasts inside of a cell, large quantities of DNA were first brought into the cytoplasma. Then the laser beam was focussed on each chloroplast inside of the cell and a single laser pulse was released at each organelle. Again a small opening was cut into the membrane allowing the DNA to enter the organelle [6]. This opening closed again within 1.2 s as could be demonstrated by computer enhanced image analysis. —Laser microbeams provide a new powerful tool for introducing DNA into plant cells and their organelles as well as for analyzi

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930307

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractIt is possible to make optical traps for small biological particles using the forces of radiation pressure from a single highly focused laser beam. Laser traps are localized to a few cubic μm and are capable of trapping particles from 10's of nm up to 10's of μm. With infrared laser beams of 1.06 μm wavelength, such traps are capable of confining and freely manipulating single living cells without optical damage. The trap was introduced into the viewing plane of a standard high resolution optical microscope with a high numerical aperture objective for combined trapping and viewing of cells and particles. The reproduction of E. coli bacteria and yeast cells was observed within the infra‐red trap, thus demonstrating damage free operation at power levels capable of moving cells at velocities of 100's of μm/ s in water. Manipulation of organelles within the interior of living plant and animal cells was also demonstrated. Separation of single cells from a collection of cells was accomplished. In addition to E. coli and yeast cells, the technique has been applied to red blood cells, protozoa, tobacco mosaic viruses, many varieties of motile bacteria, and plant cells. The ability to trap cells and organelles within cells having a wide variety of shapes and sizes under damage free conditions enhances the prospects for use of optical trapping techniques in the biological sci

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930308

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractThe interactions of laser radiation with animal tissue have become a vast field of study. The detailed chemical behavior of the photons with the tissue, while scientifically a fascinating topic for investigation, is difficult to study experimentally. We have used synthetic polymers and small molecules in the condensed phase as models for the study of non‐linear photochemistry of all organic systems. While such extrapolations should always be used with caution, they have been helpful in suggesting new strategies for tissue ablation which may be adaptable to experiments in vivo. —In etching and ablation by pulsed ultraviolet lasers, the power density at the surface of the polymer or tissue is critical in determining the threshold for ablation and the etch depth per pulse at photon fluxes greater than the threshold. This has been explained by a mechanism in which a single chromophore is excited to high electronic levels by the successive absorption of two or more photons. Recent experiments have been directed towards the use of pairs of laser pulses with a preset time interval separating them in order to couple the multi‐photon excitation process to the excited states of the chromophores in the solid in an optimum fashion. The initial results suggest that a certain amount of “tuning” of the laser pulse to suit the ablation kinetics of the substrate is not only possible but may be useful in practical applications of UV laser: tissue int

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930309

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractBetween 1965 and 1980 basic research into the medical use of lasers led to the discovery of new applications. Today we differentiate between three classes of principle interactions. Firstly there are the photochemical effects whereby laser energy is used to trigger off photochemical reactions on biomolecules by absorption of either natural or artificial dyes, or chromophoric groups. This is one of the basic principles of nature, e.g. photosynthesis and the vision process. —A further effect is based on the fact that the absorption of light at a suitable wavelength and intensity is converted into heat which accordingly leads to a heating effect of the irradiated tissue. It is a thermal effect whereby the result is dependent on the degree of absorption and the amount of radiation absorbed. In this way photocoagulation and tissue cutting is possible. —The third effect can be summarized under the term “non‐linear effects”, as they cannot be explained by the linear absorption of photons, i.e. radiation, and therefore are classified according to the effects that they produce. It is possible by these non‐linear effects to remove material fragments from the surface by light without heating the surrounding area. —Between the above mentioned thermal effects, there are the so‐called “photoacoustic effects”. Thermal absorption and time behaviour of the light radiation leads to changes in the acoustic and thermal density which results in the destruction of material. —The laser may contribute in future to solving the following problems: Recanalisation of arterial blood vessels; Destruction or fragmentation of stones in the kidneys, bladder, efferent urinary tracts as well as in the bilary tract; photochemical reactions by choosing the applicable laser wavelength, e.g. polymerisation of biocompatib

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930310

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractThe following paper describes the rationale for Excimer Laser Angioplasty, and discusses the development of a special designed Excimer Laser and catheter system for Laser Angioplasty in femoral and coronary arteries.Methods:A long pulsed (150 ns) Excimer Laser, operating at 308 nm, was evaluated in combination with a special designed silica based catheter system. We used 600 μm single and 6 × 200/6 × 700 μm multiple fiber catheter system to recanalize obstructed canine femoral arteries. The catheter systems were also tested in porcine anormal coronaries. Finally, Excimer Laser Angioplasty was performed in human femoral and popliteal arteries.Results:Using a long pulsed Excimer Laser at 308 nm fiberoptical transmission was excellent, without fiber breakdown. In addition, the catheter systems, especially the multiple fiber system proved to be flexible enough, even for percutaneous intracoronary application. No vessel wall perforation occurred.In 16/18 patients femoro‐popliteal occlusions were successfully recanalized in combination with subsequent balloon angioplasty.Conclusions:Excimer Laser Angioplasty is feasible in man. It increases the number of successful non operative treatments in vascular diseases and might even be an additional surgical tool. Long pulse Excimer Lasers allow easy fiberoptical transmission, and therefore might be favo

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930311

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractIn the wide field of laser applications in medicine, the photodynamic therapy is a very fascinating method for cancer diagnosis and therapy. The essential part of this treatment is the photosensitizer used, its selectivity, toxicity and phototoxicity. The first photosensitizer has been haematoporphyrinderivative (HPD); meanwhile a lot of potential dyes have been tested and the run for the “ideal” sensitizer is still going on. Also the reaction mechanisms are probably different, and depend on the dye. The last step in the reaction is the creation of the reactive oxygen molecule, which destroys the tumor cell. The selectivity of this reaction, the higher concentration of the dye in the tumor (cells and the vascular system) compared to the normal tissue, considerably depends on the type of the tumor. Beside this, the parameters of laser irradiation for a successful treatment are very critical. Laser‐tissue interactions limit the applications up to now to special tumor types and tumor stages. Nevertheless, photodynamic therapy will become increasingly important in the future, also in combination with conventional techn

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930312

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY