Serpinins: role in granule biogenesis, inhibition of cell death and cardiac function.

Serpinins are a family of peptides derived from proteolytic cleavage of the penultimate and the last pair of basic residues at the C-terminus of Chromogranin A. Three forms of naturally occurring serpinin have been found in AtT-20 pituitary cells and rat heart. They are serpinin, pyrogutaminated (pGlu) -serpinin and a C-terminally extended form, serpinin-RRG. In addition pGlu-serpinin has been found in brain, primarily in neurites and nerve terminals and shown to have protective effects against oxidative stress on neurons and pituitary cells. Serpinin has also been demonstrated to regulate granule biogenesis in endocrine cells by up-regulating the protease inhibitor, protease nexin-1 transcription via a cAMP-PKA-sp1 pathway. This leads to inhibition of granule protein degradation in the Golgi complex which in turn promotes granule formation. More recently, pGlu-serpinin has been demonstrated to enhance both myocardial contractility (inotropy) and relaxation (lusitropy). In the Langendorff perfused rat heart, pGlu-serpinin showed a concentration-dependent positive inotropic effect exerted through a cAMP-PKA dependent pathway. In conclusion, the serpinin peptides have profound effects at many levels that affect the endocrine and nervous systems and cardiac function.

Roles of amino acid residues near the chromophore of photoactive yellow protein.

To investigate the roles of amino acid residues around the chromophore in photoactive yellow protein (PYP), new mutants, Y42A, E46A, and T50A were prepared. Their spectroscopic properties were compared with those of wild-type, Y42F, E46Q, T50V, R52Q, and E46Q/T50V, which were previously prepared and specified. The absorption maxima of Y42A, E46A, and T50A were observed at 438, 469, and 454 nm, respectively. The results of pH titration for the chromophore demonstrated that the chromophore of PYP mutant, like the wild-type, was protonated and bleached under acidic conditions. The red-shifts of the absorption maxima in mutants tended toward a pK(a) increase. Mutation at Glu46 induced remarkable shifts in the absorption maxima and pK(a). The extinction coefficients were increased in proportion to the absorption maxima, whereas the oscillator strengths were constant. PYP mutants that conserved Tyr42 were in the pH-dependent equilibrium between two states (yellow and colorless forms). However, Y42A and Y42F were in the pH-independent equilibrium between additional intermediate state(s) at around neutral pH, in which yellow form was dominant in Y42F whereas the other was dominant in Y42A. These findings suggest that Tyr42 acts as the hinge of the protein, and the bulk as well as the hydroxyl group of Tyr42 controls the protein conformation. In all mutants, absorbance at 450 nm was decreased upon flash irradiation and afterwards recovered on a millisecond time scale. However, absorbance at 340--370 nm was increased vice versa, indicating that the long-lived near-UV intermediates are formed from mutants, as in the case of wild-type. The lifetime changes with mutation suggest the regulation of proton movement through a hydrogen-bonding network.

Thermal responses from repeated exposures to severe cold with intermittent warmer temperatures.

This study was conducted to evaluate physiological reaction and manual performance during exposure to warm (30 degrees C) and cool (10 degrees C) environments after exposure to very low temperatures (-25 degrees C). Furthermore, this experiment was conducted to study whether it is desirable to remove cold-protective jackets in warmer rooms after severe cold exposure. Eight male students remained in an extremely cold room for 20 min, after which they transferred into either the warm room or the cool room for 20 min. This pattern was repeated three times, and the total cold exposure time was 60 min. In the warm and cool rooms, the subjects either removed their cold-protective jackets (Condition A), or wore them continuously (Condition B). Rectal temperature, skin temperatures, manual performance, blood pressure, thermal, comfort and pain sensations were measured during the experiment. The effects of severe cold on almost all measurements in the cool (10 degrees C) environment were greater than those in the warm (30 degrees C) environment under both clothing conditions. The effects of severe cold on all measurements under Condition A except rectal temperature and toe skin temperature were significantly greater than those under Condition B in the cool environment but, not at all differences between Condition A and Condition B in the warm environments were significant. It was recognized that to remove cold-protective jackets in the cool room (10 degrees C) after severe cold exposure promoted the effects of severe cold. When rewarming in the warm resting room (30 degrees C), the physiological and psychological responses and manual performance were not influenced by the presence or absence of cold-protective clothing. These results suggest that it is necessary for workers to make sure to rewarm in the warm room outside of the cold storage and continue to wear cold-protective clothing in the cool room.

[Excitatory responses of superior salivatory nucleus neurons to stimulation of orbital gyrus in the cat].

The responses of superior salivatory nucleus (SSN) neurons to electrical stimulation of ipsilateral orbital gyrus were investigated in ketamine anesthetized cats. A total of 52 SSN neurons were identified by the antidromic spike responses to stimulation of the right chorda tympani nerve. Thirty-three (63%) neurons responded with spikes to stimulation of the orbital gyrus. These neurons were also activated by stimulation of ipsilateral lingual nerve. Eleven (21%) neurons received the inputs from only the lingual nerve. Remaining 8 (16%) neurons failed to respond to stimulation of neither orbital gyrus nor lingual nerve. The latency of orbital cortically evoked responses was 16.5-42.0 msec (mean +/- S.D. = 28.6 +/- 6.9 msec, n = 33), and that to stimulation of lingual nerve was 6.5-15.5 msec (9.9 +/- 2.4 msec, n = 46), respectively. In this study, convergence of excitatory inputs from orbital gyrus and sensory nerve was found in 63% of SSN neurons. These inputs would play an important role in submandibular and sublingual salivation.