Bonding corneal tissue: applications of photoactivated diazopyruvoyl cross-linking agent.

Photoactivated bis-diazopyruvamide-N,N'-bis(3-diazopyruvoyl)-2,2'-(ethylenedioxy)bis-(ethylamine), (DPD)-was previously shown to bond materials containing type I collagen. However, tensile strength of bonded collagenous tissue ( approximately 78% water) was low compared with that of dehydrated collagenous gelatin ( approximately 14% water). Here we investigated the role of water in corneal tissue bond strength and in bonding corneal tissue to glass. Bonding corneal tissue to glass may be of value in surgically anchoring keratoprostheses to corneas to alleviate problems with extrusion. Bovine corneal samples were lyophilized for various times resulting in tissue hydrations of zero (no water content) to approximately 3.7 (normal water content). The lyophilized corneal tissue was bonded to solid gelatin sheets, to other corneal samples and to glass using 0.3M DPD in chloroform. Control runs used chloroform only. Samples were irradiated with 100 or 200 J of 320-500 nm light. Strong bonds formed with all three materials when corneal tissue hydration was 1. No bonding occurred with chloroform alone. Formation of strong bonds only occurs with hydration levels

Effect of a 50 Hz electric field on plasma ACTH, glucose, lactate, and pyruvate levels in stressed rats.

The effect of extremely low frequency electric field (EF) on stress induced changes of plasma ACTH, glucose, lactate, and pyruvate levels was examined in ovariectomized rats. The rats were exposed to 50 Hz EF (17500 V/m) for 60 min and were restrained for the latter half (30 min) of the EF exposure period. The restraint stress significantly increased the plasma ACTH and glucose levels (P <.05: Student's t test). Restraint induced increase of plasma ACTH and glucose levels tended to be suppressed by exposure to the EF. Meanwhile, the EF exposure also affected plasma lactate level. Thus, the EF exposure significantly decreases plasma lactate levels in the stressed rats (P <.05: Student's t test). Although the precise mechanisms in the restraint dependent alteration in plasma ACTH, glucose, lactate, and pyruvate levels are not fully understood, our results demonstrate that the 50 Hz EF alter both stress responses and energy metabolism in stressed rats.

Substrate irradiation stimulation of the in vitro lactate-pyruvate interconversion reactions mediated by lactic dehydrogenase.

Experimental studies of the Comorosan effect are presented for the LDH-mediated interconversions of lactate and pyruvate. Consistent with the findings of the Comorosan group, the rate of the lactate/LDH reaction was found increased for crystalline lithium lactate irradiated with green light for times t comprising the manifold t = 15+30n sec, n = 0,1,2... However, no upper limit to the number of activating times was encountered although the Comorosan group has always obtained only six such activations. The pyruvate/LDH reaction rate was found enhanced for crystalline sodium pyruvate irradiated t = 5+30n sec. Sharpness of activations for 5-sec and 65-sec irradiated samples was investigated and found to occur only within approximately +/- 0.5 sec of 5.0 and 65.0 sec, slightly broader than the +/- 0.15-sec peak reported by Comorosan for the 5-sec signal. The data contribute to the credibility of the phenomenon but reveal sensitivity of some properties to individual laboratory or procedural factors. The first support is provided for the "discriminating function" component of Comorosan's metabolic control hypothesis.