Local Laser Irradiation Research Articles

Automated tracking and laser micromanipulation of motile cells

Control over neuronal growth is a prerequisite for the creation of defined in vitro neuronal networks as assays for the elucidation of interneuronal communication. Neuronal growth has been directed by focusing a near-infrared laser beam at a nerve cell’s leading edge [A. Ehrlicher, T. Betz, B. Stuhrmann, D. Koch, V. Milner, M. G. Raizen, and J. Käs, Proc. Natl. Acad. Sci. U.S.A. 99, 16024 (2002)]. The setup reported by Ehrlicher et al. was limited to local laser irradiation and relied on a great deal of subjective interaction since the laser beam could only be steered manually. To overcome the drawbacks of the reported setup, we developed and here present a fully automated low-contrast edge detection software package, which responds to detected cell morphological changes by rapidly actuating laser steering devices, such as acousto-optical deflectors or moving mirrors, thus enabling experiments with minimum human interference. The resulting radiation patterns can be arbitrary functions of space, time, and cell morphology, and are calculated by experiment specific feedback routines. Data processing is repeated on the order of 1s allowing rapid reactions to morphological changes. The strengths of our program are the combination of real-time low contrast shape detection with complex feedback mechanisms, as well as easy adaptability due to a modular programming concept. In this article we demonstrate automated optical guidance; however, the software is easily adaptable to other problems requiring automated rapid responses of equipment to changes in the morphology of low contrast objects.

Creation of Bioactive Glass Coating on Titanium by Local Laser Irradiation; Part 2: Effect of the Irradiation on the Bioactivity of the Glass

Creation of Bioactive Glass Coating on Titanium by Local Laser Irradiation; Part 2: Effect of the Irradiation on the Bioactivity of the Glass

Creation of Bioactive Glass Coating on Titanium by Local Laser Irradiation; Part 1: Optimization of the Processing Parameters

Creation of Bioactive Glass Coating on Titanium by Local Laser Irradiation; Part 1: Optimization of the Processing Parameters

Microtubule-dependent migration of the cell nucleus toward a future leading edge in amoebae ofPhysarum polycephalum

In several cell types, an intriguing correlation exists between the position of the centrosome and the direction of cell locomotion. The centrosome is positioned between the leading edge pseudopod and the nucleus. This suggests that the polarized distribution of organelles in the cytoplasm is coupled spatially with structural and functional polarity in the cell cortex. To study cellular polarization with special interest in the roles of microtubules, we have analyzed the effects of microtubule-disrupting reagents and local laser irradiation on behaviors of both the nucleus and the centrosome in living amoebae ofPhysarum polycephalum. Physarum cells often have 2–3 pseudopods. One of the pseudopods keeps extending to become a stable leading edge while the rest retracts, a crucial step that reorients cells during locomotion. The nucleus, together with the centrosome, moves specifically toward the pseudopod that will become the leading edge. Disruption of microtubules with nocodazole randomizes positions of the nucleus, indicating the involvement of microtubules in the directional migration of the nucleus toward a specific pseudopod. The migration direction of the nucleus is reversed immediately after the UV laser is irradiated at regions between the nucleus and the future leading pseudopod. In contrast, irradiation at regions between the future tail and the nucleus does not affect nuclear migration. By immunofluorescence, we confirmed fragmentation of microtubules specifically in the irradiated region. These results suggest that the nucleus is pulled together with the centrosome toward the future leading-edge pseudopod in a microtubule-dependent manner. Microtubules seem to exert the pulling force generated in the cell cortex on the centrosome. They may serve as a mediator of shape changes initiated in the cell cortex to the organelle geometry in the endoplasm.

Long‐term tumor resistance induced by laser photo‐immunotherapy

An ideal treatment modality for metastasizing tumors should eradicate the primary tumor and elicit a systemic, tumor-selective response leading to elimination of metastases and long-term tumor resistance. Also, it should be induced by local treatment at the primary site, to limit adverse systemic effects. A new method for treating metastatic tumors which utilizes a combination of a near-infrared laser, a photosensitizer and an immunoadjuvant has been developed. It involves intra-tumor injection of the sensitizer/adjuvant solution, followed by local non-invasive laser irradiation. It has produced regression and total eradication of treated primary tumors and untreated metastases at remote sites against mammary tumors in rats. Successfully treated tumor-bearing rats showed total tumor resistance to subsequent tumor rechallenge. Our histochemical results showed that sera from cured tumor-bearing rats contained antibodies that bound strongly to the plasma membrane of both living and preserved tumor cells. Western blot analysis of tumor cell proteins using sera from successfully treated rats as the source of primary antibodies also showed distinct bands, indicating induction of tumor-selective antibodies. Our findings indicate that a systemic, long-term effect on metastatic tumors can be induced by local application of laser photo-immunotherapy. Int. J. Cancer 81:808–812, 1999. © 1999 Wiley-Liss, Inc.

Long-term tumor resistance induced by laser photo-immunotherapy.

An ideal treatment modality for metastasizing tumors should eradicate the primary tumor and elicit a systemic, tumor-selective response leading to elimination of metastases and long-term tumor resistance. Also, it should be induced by local treatment at the primary site, to limit adverse systemic effects. A new method for treating metastatic tumors which utilizes a combination of a near-infrared laser, a photosensitizer and an immunoadjuvant has been developed. It involves intra-tumor injection of the sensitizer/adjuvant solution, followed by local non-invasive laser irradiation. It has produced regression and total eradication of treated primary tumors and untreated metastases at remote sites against mammary tumors in rats. Successfully treated tumor-bearing rats showed total tumor resistance to subsequent tumor rechallenge. Our histochemical results showed that sera from cured tumor-bearing rats contained antibodies that bound strongly to the plasma membrane of both living and preserved tumor cells. Western blot analysis of tumor cell proteins using sera from successfully treated rats as the source of primary antibodies also showed distinct bands, indicating induction of tumor-selective antibodies. Our findings indicate that a systemic, long-term effect on metastatic tumors can be induced by local application of laser photo-immunotherapy.

Threshold effect of local pulsed laser irradiation on the surface state of oxide layers deposited on real germanium surfaces

Threshold effect of local pulsed laser irradiation on the surface state of oxide layers deposited on real germanium surfaces

Treatment of trigeminal neuralgia (TN) with local laser irradiation and laserpuncture: B. PopovStomatologia Bulgaria 1986: 68: 25–9

Treatment of trigeminal neuralgia (TN) with local laser irradiation and laserpuncture: B. PopovStomatologia Bulgaria 1986: 68: 25–9

Laser-induced spreading arrest of Mytilus gill cilia.

Using a "slit camera" recording technique, we have examined the effects of local laser irradiation of cilia of the gill epithelium of Mytilus edulis. The laser produces a lesion which interrupts epithelial integrity. In artificial sea water that contains high K+ or is effectively Ca++ free, metachronism of the lateral cilia continues to either side of the lesion with only minor perturbations in frequency synchronization and wave velocity, such as would be expected if metachronal wave coordination is mechanical. However, in normal sea water and other appropriate ionic conditions (i.e., where Ca++ concentration is elevated), in addition to local damage, the laser induces distinct arrest responses of the lateral cilia. Arrest is not mechanically coordinated, since cilia stop in sequence depending on stroke position as well as distance from the lesion. The velocity of arrest under standard conditions is about 3 mm/s, several orders of magnitude faster than spreading velocities associated with diffusion of materials from the injured region. Two responses can be distinguished on the basis of the kinetics of recovery of the arrested regions. These are (a) a nondecremental response that resembles spontaneous ciliary stoppage in the gills, and (b) a decremental response, where arrest nearer the stimulus point is much longer lasting. The slower recovery is often periodic, with a step size approximating lateral cell length. Arrest responses with altered kinetics also occur in laterofrontal cilia. The responses of Mytilus lateral cilia resemble the spreading ciliary arrest seen in Elliptio and arrest induced by electrical and other stimuli, and the decremental response may depend upon electrotonic spread of potential change produced at the stimulus site. If this were coupled to transient changes in Ca++ permeability of the cell membrane, a local rise in Ca++ concentration might inhibit ciliary beat at a sensitive point in the stroke cycle to produce the observed arrest.