Small bowel enteropathy: role of intraepithelial lymphocytes and of cytokines (IL-12, IFN-gamma, TNF) in the induction of epithelial cell death and renewal.

The small bowel mucosa contains within its villus epithelium a large number of intraepithelial lymphocytes (IEL) which upon activation are cytotoxic and release large quantities of IFN-gamma and TNF; these activities are increased by in vitro exposure to IL-12. Mice injected with IL-12 develop severe damage of the villus epithelial cells, in form of apoptosis, necrosis and a third distinct form of cell death, characterized ultrastructurally by progressive cell shrinkage. These lesions are accompanied by a compensatory acceleration of the epithelial renewal, a hallmark of epithelial injury. Use of a variety of mutant mice showed that these lesions require the presence of IEL (all populations being involved, thymus-dependent as well as natural killer-T cell IEL) and the release of IFN-gamma. The critical role of IFN-gamma may result in part from its capacity to induce on epithelial cells the expression of target molecules involved in the different cytotoxic pathways used by IEL. However, injection of IFN-gamma into mutant mice lacking IEL showed that IFN-gamma can directly induce villus epithelial damage as well. On the other hand, injection of TNF induces fulminant apoptosis of villus epithelial cells, starting at the top of the villi; however TNF is not required for IL-12-induced enteropathy, which is unmodified in mutant mice lacking TNF. We propose that, when activated by their cognate ligands and/or IL-12 produced by cells in the lamina propria, IEL eliminate infected and senescent epithelial cells through a combination of cytotoxicity and of IFN-gamma and TNF release. This insures the rapid epithelial renewal of the villi, which in turn helps maintain the functional integrity of the barrier.

A new laser scalpel--a brief report.

One may consider the clad silica fibre cutting probe as a cheap alternative of the popular sapphire probe, sharing some of its properties. Made of silica, the scalpels have a fair heat tolerance and may be used without cooling by liquids or gas as is necessary with sapphire blades. The laser scalpel described here is driven (powered) with a 10 W cw Nd:YAG laser energy source (1064 nm) and possesses good cutting and haemostatic properties. It may also be used with lasers emitting other wavelengths. One may assume that a diode laser emitting in the near infrared (800-810 nm) may have very similar, although no analogous cutting properties when used with the described scalpel.

Oculoplastic surgery with a contact Nd:YAG laser silica scalpel. A case report.

Baso-cellular carcinomas involving the medial canthal regions of both eyes were resected using a 10 W cw-Nd: YAG laser scalpel. The wound bed was repaired one side by a free, split-thickness graft and on the other by a frontal pedicle flap. Surgery was, for the most part, virtually bloodless. Since laser radiation immediately seals both capillaries and lymphatics, the incidence of postoperative hemorrhage and edema was significantly less than after cold scalpel surgery. Healing was uneventful. The advantages of laser-assisted surgery are worthy of consideration: not only is the operation time markedly curtailed, but the wound healing response is excellent, with only a minimal inflammatory reaction.

[The current status of sclerostomy procedures in treatment of open angle glaucoma]. / Der gegenwärtige Stand der Sklerostomieverfahren bei der Behandlung des Offenwinkelglaukoms.

METHODS: A number of ab interno and ab externo sclerostomy procedures have been described in recent years. CONCLUSION: At the present time, there is no clear indication that such interventions are superior to the classical fistulizing glaucoma operations, such as trabeculectomy.

[Surgery with the laser scalpel. Physical principles and clinical effectiveness]. / Chirurgie mit dem Laserskalpell. Physikalische Grundlagen und klinische Wirksamkeit.

BACKGROUND: The conventional surgical method for cutting vascularized tissue with scalpel and scissors may now be improved by use of the laser scalpel. In particular, the frequent interruption necessitated and the poor visibility caused by bleeding may be mitigated owing to the haemostatic properties of laser light. This instrument may be of particular value for tasks involving extrabulbar structures, such as extraocular muscles and lacrimal tissue, as well as for facial surgery. MATERIALS AND METHODS: The mode of action and physical properties of a new laser scalpel are described and its characteristics compared with those of other instruments on the market. The probe consists of a clad, sculptured silica fibre with a core diameter of 0.6 mm and a conical 0.15 mm-diameter cutting tip. Radiation generated by a low cw-Nd:YAG laser module is fed into the probe, at the exit point of which a maximal power density of 57 kW/cm2 is attained. Radiated laser energy penetrates the tissue as an incision is made, thereby inducing an efficient blood flow stasis which is amplified by thermal energy diffusing from the immediate surroundings of the scalpel tip. RESULTS: In this report, the laser scalpel is implemented for the excision of a vascularized, amelanotic, facial naevus. Both the cutting and haemostatic effects were found to be excellent, occurrence of the latter phenomenon being supported by ultrastructural findings. The healing response was comparable to that observed after conventional surgery. CONCLUSION: The new laser scalpel represents an inexpensive and effective cutting and haemostatic tool powered by a standard cw Nd:YAG laser module, with a wide spectrum of potential applications.

Versatility of the cw-Nd:YAG and diode lasers in ocular surgery.

The effectiveness of cw-Nd:YAG and diode laser light in performing transscleral chorioretinal coagulation is demonstrated in cadaver porcine eyes using a new contact probe that facilitates irradiation of these layers. Both radiation sources also may be viable alternatives to argon laser light in effecting chorioretinal and cycloendocoagulation.

Optical principles related to optimizing sclerostomy procedures.

A simple probe, consisting of a 200-micrometer uncladded silica optical fiber, advanced from a protecting 22-gauge hypodermic needle, was used to create sclerostomy fistulas both ab interno and ab externo by means of a combined radiation/mechanical effect. Perforation was achieved by exerting gentle forward pressure on the fiber in synchrony with the delivery of radiation pulses. An irradiation protocol suitable for producing such canals in cadaver porcine eyes was delineated using Ho:YAG, Nd:YAG, and diode laser energy sources. Despite significant differences in the pulse energy required for perforation (0.25, 7, and 8 J for the Ho:YAG, diode, and Nd:YAG lasers, respectively), the extent of collateral damage was comparable for each type of laser. The physical mechanisms underlying these findings are discussed.