Transition dipole orientations in the early photolysis intermediates of rhodopsin.

The linear dichroism spectrum of rhodopsin in sonicated bovine disk membranes was measured 30, 60, 170, and 600 ns after room temperature photolysis with a linearly polarized, 7-ns laser pulse (lambda = 355 or 477 nm). A global exponential fitting procedure based on singular value decomposition was used to fit the linear dichroism data to two exponential processes which differed spectrally from one another and whose lifetimes were 42 +/- 7 ns and 225 +/- 40 ns. These results are interpreted in terms of a sequential model where bathorhodopsin (BATHO, lambda max = 543 nm) decays toward equilibrium with a blue shifted intermediate (BSI, lambda max = 478 nm). BSI then decays to lumirhodopsin (LUMI, lambda max = 492 nm). It has been suggested that two bathorhodopsins decay in parallel to their products. However, a Monte Carlo simulation of partial photolysis of solid-state visual pigment samples shows that one mechanism which creates populations of BATHO having different photolysis rates at 77 K may not be responsible for the two decay rates reported here at room temperature. The angle between the cis band and 498-nm band transition dipoles of rhodopsin is determined to be 38 degrees. The angles between both these transition dipoles and those of the long-wave-length bands of BATHO, BSI, and LUMI are also determined. It is shown that when BATHO is formed its transition dipole moves away from the original cis band transition dipole direction. The transition dipole then moves roughly twice as much towards the original cis band direction when BSI appears. Production of LUMI is associated with return of the transition dipole almost to the original orientation relative to the cis band, but with some displacement normal to the plane which contains the previous motions. The correlation between the lambda max of an intermediate and its transition dipole direction is discussed.

Cost of treatment of bleeding esophageal varices.

We examined the cost of four methods of treatment of bleeding esophageal varices--medical treatment, sclerotherapy, variceal ligation operations, and portal systemic shunts--in 49 consecutive patients from 1977 to 1979, and correlated the two-year outcome with cost. We found that, despite bias imposed by selection, the cost per patient and cost per survivor at two years was lowest in patients who received sclerotherapy, even though they were more seriously ill than patients who received other treatments. Patients treated with sclerotherapy also had the lowest mortality during primary hospitalization and the lowest readmission rate during a two-year period.

Opioid and non-opioid stress analgesia: assessment of tolerance and cross-tolerance with morphine.

Opioid and non-opioid mechanisms of analgesia elicited by two kinds of footshock stress that differ only in temporal characteristics previously have been inferred on the basis of susceptibility to naloxone blockade. The present study sought further evidence on this point by comparing these two kinds of footshock analgesia for possible tolerance development and cross-tolerance with morphine. It was found that, with repeated exposure to stress, tolerance developed to naloxone-sensitive, but not naloxone-insensitive, stress analgesia. Furthermore, morphine-tolerant rats displayed cross-tolerance to only the naloxone-sensitive form of footshock analgesia. Although prior exposure to both footshock paradigms potentiated morphine analgesia, less potentiation occurred in rats tolerant to the naloxone-sensitive footshock stress. Thus, cross-tolerance between morphine and this type of stress analgesia appears to occur in both directions. These findings are consistent with those using naloxone antagonism as a criterion for opioid mediation and support the conclusion that separate opioid and non-opioid mechanisms of stress analgesia exist.

Computer interface for data acquisition and control of an SMA 12/60.

We present an approach to the computer enhancement of the "SMA 12/60" (Technicon Instruments Corp.). Practical and theoretical considerations led to a plug-compatible system, which did not require changes in the hydraulics or methodology of the SMA. Results obtained from eight channels of the SMA using the system as described show that a sample analysis rate of 120 per hour is feasible. A desirable consequence of the increased analysis rate is a 60% decrease in the required sample volume. Before the system can be used in a clinical environment, further development will be necessary, including detection algorithms for hydraulic malfunction.