1. If cardiac force-velocity (PV) relationships are determined in a rhythmically beating isolated preparation by progressively changing afterloads, the PV curves obtained exhibit a characteristic nonhyperbolic shape with an upward convexity in the force domain close to P0. It was suggested by others that this might be due to contractile element (CE) shortening against series elastic component (SEC) and/or the early decay of the active state at isometric peak tension. 2. The present investigation performed in isolated cat papillary muscles demonstrates that neither CE shortening against SEC nor the variation of the intensity of the active state can fully account for the nonhyperbolic shape of cardiac PV curves. 3. On the other hand large parts of the remaining deviation could be eliminated if the "progressive loading sequence" (PLS) was replaced for an "interpolated loading sequence" (ILS). Here, the muscle contracts under steady state conditions either isometrically or isotonically (zero load). Single afterloaded test contractions are interpolated after every 10th beat. 4. It is concluded that the nonhyperbolic shape of cardiac PV curves, determined by progressively changing afterloads, is the expression of at least four factors: (i) the existence of displacement dependent variation of excitation-contraction coupling (including the contraction-excitation-contraction recoupling loop), (ii) CE shortening against non CE bound SEC, (iii) a variable active state and (iiii) a fourth unknown mechanism.

Animals↗

PubMedDate not supplied

[Fluorescence spectroscopy in selective percutaneous nucleotomy using the excimer laser--experimental studies].

Our intention was to test fluorescence spectroscopy as a possibility for selective laser ablation. In an experimental setup a XeCl excimer laser (308 nm) with pulse energies between 5 and 50 mJ was used for fluorescence excitation in 20 human and 100 pig vertebral segments. Tissue fluorescence was detected via a quartz fiber bundle and analyzed by a polychromator and optical multichannel analyzer. Both low and high energy levels led to a broad band fluorescence of nucleus pulposus, intervertebral muscle, spinal cord and vertebral end plate and a typical fluorescence of anulus fibrosus with peak maxima at 385 and 435 nm. Tissue fluorescence was independent of surrounding medium (with air and normal saline used) and excitation energy. Borderlines between different tissues could be clearly indicated in all cases. Using intensity rations at 350, 385 and 435 nm (I1 = I350/I385, I2 = I385/I435) tissue discrimination was possible in all cases. This results demonstrate, that discrimination between intervertebral disc and surrounding tissue is possible and could be used for selective percutaneous laser nucleotomy in the near future.

Animals↗

PubMedDate not supplied

Measuring comfort in caregivers and patients during late end-of-life care.

The purpose of this study was to test several formats of end-of-life comfort instruments for patients and closely involved caregivers. Kolcaba's Comfort Theory was the theoretical framework utilized. Different response formats for two end-of-life (EOL) comfort questionnaires (for patients and caregivers, respectively), and horizontal and vertical visual analog scales for total comfort (TC) lines were compared in two phases. Evaluable data were collected from both members of 38 patient-caregiver dyads in each phase. Suitable dyads were recruited from two hospice agencies in northeastern Ohio. Cronbach's alpha for the EOL comfort questionnaire (six response Likert-type format) tested during phase I for patients was .98 and for caregivers was .97. Test-retest reliability for the vertical TC line tested during phase I for patients was .64 and for caregivers was .79. The implications of this study for nursing practice and research are derived from the American Nursing Association (ANA) position statement about EOL care, which states that comfort is the goal of nursing for this population. These instruments will be useful for assessing comfort in actively dying patients and comfort of their caregivers as well as for developing evidence-based practice for this population.

Attitude to Health↗

PubMedDate not supplied

Corneal morphology in vitro after superficial keratectomy with q-switched Er:YSGG and free-running Er:YAG lasers.

PURPOSE: Examination of morphology in corneal ablation induced by a q-switched Er:YSGG (2.79 microm) laser and a free-running Er:YAG laser (2.94 microm). METHODS: Defined ablation of 6-mm diameter and 15, 30, 55, 90, and 120-microm depth was performed on freshly enucleated swine eyes. Er:YSGG laser parameters: fluence 1.6 J/cm2, frequency 6 Hz, spot-size 465 microm FWHM, scanning-mode, pulse number 1520 to 6210. Er:YAG laser parameters: fluence 3 J/cm2, frequency 1.5 Hz, spotsize 6 mm, wide area ablation, pulse number 2 to 13. Corneal morphology was analyzed by gross photography, histology, scanning electron microscopy, and scanning nearfield acoustic microscopy. RESULTS: Histology showed thermal damage of 5 to 15 microm in depth caused by the Er:YSGG laser in comparison with 10 to 20 microm by the Er:YAG laser. Average roughness of the ablated surface measured with scanning nearfield acoustic microscopy was 20 to 40 microm for the Er:YSGG laser and 5 to 15 microm for the Er:YAG laser. These data confirm the subjective impression of images created by scanning electron microscopy and gross photography. CONCLUSIONS: Although the Er:YAG laser system appeared to demonstrate a smoother corneal surface than the q-switched Er:YSGG laser, the thermal damage in either case poses a potential limitation for clinical use in lamellar refractive surgery.

Animals↗

PubMedDate not supplied

Argon laser laparoscopy: an effective technique for conservative treatment of unruptured ectopic pregnancy.

Between October 1987 and January 1990, 60 patients with unruptured ectopic pregnancy in the ampullary portion of the tube were treated with linear salpingotomy, using the argon laser laparoscopically. In all cases, salpingotomy was performed by the "bare-fiber" technique, with a power of 3-6 watts. The same fiber was used for incision and coagulation either with a contact or a non-contact technique. There were no instrument-related intra- or postoperative complications. Twenty-four patients were evaluated by second-look laparoscopy or hysterosalpingography for tube patency and possible formation of adhesions. In all of these patients the tubes were patent. In one patient, the tube failed to close, resulting in a fistula. Four patients had filmy adhesions, covering the tube near the incision site. There were no adhesions covering the distal part of the tube.

Argon↗

PubMedDate not supplied

Human sperm motility--enhancement and inhibition measured by laser Doppler spectroscopy.

Laser Doppler spectroscopy is an excellent instrument to measure motility parameters of human spermatozoa. Experiments have been performed by the aid of a now commercially available instrumental setup called LAZYMOT to study enhancement and inhibition as well as influences of different physical treatments on the motility of human spermatozoa. The motility enhancing influence of Kallikrein (up to 40% with 4 KU/ml) and prostaglandin E2 could be proven, thereby verifying some sort of mechanism of action within the Kallikrein-Kinin system. Furthermore tested substances in this context were bradykinin (no effect), caffeine (enhancement), salicylic acid (slight decrease), and other prostaglandins (no effect). The influence of washing, centrifugation, resuspension liquid, and temperature has been examined. It turned out that the lowest motility degradation is to be achieved by washing twice at a pH value of 7.4 at forces of 200 g for 10 min each time. The optimal temperature during this process and the measurements thereafter was found to be 36 degrees C. Unsaturated fatty acids like arachidonic acid have been found to be very strong motility inhibiting substances, which can totally block any movement of spermatozoa.

Bucladesine↗

PubMedDate not supplied

Nuclear magnetic resonance. Its clinical application.

Explore the source record for details and available documents.

Brain Diseases↗

PubMedDate not supplied

Thermal and non-thermal laser dissection.

Conventional cw-(continuous wave) laser systems such as the CO2- and Nd:YAG-laser are well established in medical therapy for tumour resection, tissue cutting, vaporisation and coagulation. The argon-ion laser is also a "classic" laser type with applications in ophthalmology, dermatology and for micro-surgery. New lasers in the IR-range of the optical spectrum appear on the market as pulsed lasers for tissue ablation searching for their specific fields of application. There is some confusion about laser applications at the moment until the new techniques and methods have proven to be really superior to other techniques. But knowing more about the laser tissue interactions one can estimate the potential of a new laser source. This article gives a short overview over the actual laser systems and the reaction processes with soft and hard tissue.

Dissection↗