Laser scalpel for solid organ surgery

Hemostasis remains a major technical problem in surgery of the liver and spleen. A high power neodymium-doped yttrium aluminum garnet (Nd:YAG) laser has been coupled with a fiberoptic delivery system and quartz blade designed to yield maximal hemostasis and minimal tissue injury. In a series of experiments we were unable to demonstrate a significant advantage of its use in partial hepatic lobectomy.

The use of the argon laser-assisted quartz scalpel for burn wound excision to fascia

We have developed a new method for coupling the hemostatic capabilities of argon laser light with the mechanical advantages of a sharpened quartz blade using fiberoptics. Using the new laser-assisted scalpel, a series of symmetrical skin excisions was done in 20- to 30-kg pigs on one side and with electrosurgery on the other. The laser scalpel was superior in its hemostatic properties (p less than 0.01) with no statistically significant difference in surgical speed. Take of split-thickness skin grafts was 90% in beds excised with either the laser or the electrosurgical device. Histologic sections showed less tissue damage with the laser-assisted scalpel than with electrocautery.

Inhibition of monocyte esterase activity by organophosphate insecticides

Organophosphate insecticides, such as Vapona, Naled, and Rabon, are highly potent inhibitors of an enzyme found in human monocytes. The enzyme, a specific monocyte esterase, could be inhibited by Vapona in blood samples via airborne contamination at levels easily achieved from commercial slow-release insecticide strips. Fifty percent inhibition (I50)--as measured on the Hemalog D (Technicon Corp.)--occurred at solution concentrations of 0.22, 1.5, and 2.6 X 10(-6) g/liter for Vapona, Rabon, and Naled, respectively. Parathion (a thiophosphate) and Baygon (a carbamate) were less potent, with I50 values of 3.7 X 10(-5) and 1.5 X 10(-4) g/liter, respectively. Dursban (another thiophosphate) and Carbaryl (a carbamate) showed only marginal inhibition. Eserine, malathion, nicotine and pyrethrum had no inhibitory effect up to 0.5 g/liter. The occurrence of this effect in vivo has not yet been shown, nor is it clear what the implications of such an effect would be. The inhibition of this enzyme by airborne contaminants, however, may interfere with the proper functioning of the Hemalog D.

Reciprocal cooperative effects of multiple ligand binding to pyruvate kinase

The formation of multiple ligand complexes with muscle pyruvate kinase was measured in terms of dissociation constants and the standard free energies of formation were calculated. The binding of Mn2+ to the enzyme (KA = 55 +/- 5 X 10(-6) M; deltaF degrees = -5.75 +/- 0.05 kcal/mol) and to the enzyme saturated with phosphoenolpyruvate (conditional free energy) KA' = 0.8 +/- 0.4 X 10(-6) M; deltaF degrees = -8.22 +/- 0.34 kcal/mol) has been measured under identical conditions giving a free energy of coupling, delta(deltaF degrees) = -2.47 +/- 0.34 kcal/mol. Such a large negative free energy of coupling is diagnostic of a strong positively cooperative effect in ligand binding. The binding of the substrate phosphoenolpyruvate to free enzyme and the enzyme-Mn2+ complex was, by necessity, measured by different methods. The free energy of phosphoenolpyruvate binding to free enzyme (KS = 1.58 +/- 0.10 X 10(-4)M; deltaF degrees = -5.13 +/- 0.04 kcal/mol) and to the enzyme-Mn2+ complex (K3 = 0.75 +/- 0.10 X 10(-6)M; deltaF degrees = -8.26 +/- 0.07 kcal/mol) also gives a large negative free energy of coupling, delta(deltaF degrees) = -3.16 +/- 0.08 kcal/mol. Such a large negative value confirms reciprocal binding effects between the divalent cation and the substrate phosphoenolpyruvate. The binding of Mn2+ to the enzyme-ADP complex was also investigated and a free energy of coupling, delta(deltaF degrees) = -0.08 +/- 0.08 kcal/mol, was measured, indicative of little or no cooperativity in binding. The free energy of coupling with Mn2+ and pyruvate was measured as -1.52 +/- 0.14 kcal/mol, showing a significant amount of cooperativity in ligand binding but a substantially smaller effect than that observed for phosphoenolpyruvate binding. The magnitude of the coupling free energy may be related to the role of the divalent cation in the formation of the enzyme-substrate complexes. In the absence of the activating monovalent cation, the coupling free energies for phosphoenolpyruvate and pyruvate binding decrease by 40-60% and 25%, respectively, substantiating a role for the monovalent cation in the formation of enzyme-substrate complexes with phosphoenolpyruvate and with pyruvate.

Effect of calcium and magnesium on deoxyribonucleic acid synthesis in rat parathyroid glands in vitro

DNA synthesis in rat parathyroid glands in organ culture is significantly affected by the calcium concentration of the medium. 3-H-thymidine incorporation over a 46-hour period was more than 100 per cent greater at 1.3 mM calcium than at 3.0 mM calcium. Thymidine incorporation was greatest at 0.9 to 1.3 mM, and fell off sharply between 1.3 and 1.8 mM calcium. Variation of magnesium concentration between 0.3 and 1.5 mM had no appreciable effect on DNA synthesis at either 1.3 or 1.8 mM calcium. No effect on DNA synthesis in rat liver explants or mouse L cells was observed over these ranges of calcium concentration, but in cultured rat kidney fragments, an opposite effect of calcium was observed, i.e., DNA synthesis was more active at 3.0 mM calcium than at 1.3 mM calcium. Time course experiments showed that a significant difference between DNA synthesis rates in high and low calcium media was observable in parathyroid glands during the first 3 hours in culture, and persisted for at least 108 hours. The calcium effect on DNA synthesis was not mediated by any direct effect on the rate of thymidine uptake by the tissue. These results suggest that a small drop in ambient calcium concentration in vivo could significantly increase the rate of DNA synthesis in the parathyroid glands, and thus provide experimental support for the concept that parathyroid hyperplasia in chronic renal insufficiency is caused by lowered serum calcium levels.

Precision alignment using a system of large rectangular fresnel lenses

A system of large rectangular Fresnel lenses has been used in the laser alignment system for the SLAC two-mile accelerator. The alignment system consists of a He-Ne laser light source, a photoelectric detector, and the lenses, one of which is located at each of 297 points which are to be aligned. Each lens has the proper focal length to focus the laser to a point image at the detector. When the alignment at a certain point is to be checked, the image from that lens is scanned by the detector. The image is found to be displaced from its normal position by an amount equal to the product of the position error and the magnification of the lens. The alignment sensitivity is +/-0.0025 mm. The targets are enclosed in a 60-cm diam evacuated light pipe to avoid atmospheric disturbances.