We have recently shown that hydrolysis of labeled angiotensin I in canine brainstem homogenate causes a rapid accumulation of the heptapeptide aniotensin-l-7) [Ang-(1-7)]. Although this angiotensin fragment has no vasopressor activity its consistent generation in brain homogenate led us to study its potential neirosecretory effects in the rat hypothalamo-neurohypophysial system (INS) in vitro. Ang-(1-7) or angiotensin U (Ang II) was added to HNS perifusate in concentrations of 0.04, 0.4, and 4 pLM, and release of arginire vasopressin (AVP) during each treatment was quantified as a percentage of the AVP release detected in the preceding collection period. Base-line release of AVP averaged 281' ±47 pg per 15 min (mean SEM) in HNS explants (five experiments, five explants per chamber) perifused in Krebs solution at 37C, after a 1-hr equilibration period. At 0.04 pM, Ang'II-or Ang-(1-7) did-not stimulate AVP release. Ang II increased AVP release over the control value by 172% ± 44% and 268% ± 66% at 0.4 and 4 pM, respectively; the same concentrations of Ang-(1-7) increased AVP release by 134% ± 12% and 216% ± 45%. The responses to Ang I and Ang-(1-7) at the highest concentration were both s cant (P < 0.05), and comparison by two-way analysis of variance indicated that Ang II and Ang-(1-7) were equipotent in stimulating AVP release over the range of concentrations studied. In the presence of the competitive Aug II antagonist [Sar',Thr'JAng 11 (20 pzM), the release of AVP increased '2-fold. Neither Ang U nor Ang-(1-7) (4 pAM) caused a further enhancement of AVP release in the presence of [Sarl,ThrJAng UI. These d.ata suggest that a hydrophobic residue in position 8 of the angiotensin peptide is not essential for activation of angiotensin receptors in the rat HNS. Moreover, the equipotence of Ang U and Ang-(1-7) indicates that Ang-(1-7) may participate in the control of AVP release.Angiotensin II (Ang II) plays an important role in the control ofcardiovascular function and body fluid regulation by acting on blood vessels, renal hemodynamics, and the endocrine system. There is also evidence that Ang II may function as a paracrine hormone, since a number of studies showed that this peptide may be synthesized and released by a variety of tissues, including the brain (1). In the central nervous system, Ang II may participate in the central regulation of blood pressure by augmenting sympathetic and parasympathetic efferent discharges (2,3), by the release of arginine vasopressin (AVP) (4, 5) and corticotropin releasing factor (6), and by stimulating thirst (7,8 (17). Since this heptapeptide fragment was generated even in the presence of the angiotensin-converting enzyme inhibitor MK-422, the results suggested that a direct pathway may exist for endogenous generation of Ang-(1-7) in the brain. Although Ang-(1-7) has been shown to possess minimal pressor activity when administered into the peripheral circulation (18,19) and may have no dipsogenic effects when administered intracerebroventricularly (20), the consist...

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A model of BMD was developed in the present study. Because overexpression of wt bestrophin shifted luminance response but did not alter the range of LP response amplitudes, the authors conclude that the rate-limiting step for generating LP amplitude occurs before activation of bestrophin or that bestrophin does not directly generate the LP conductance.

Novel spray reactors are described that employ immobilized biocatalyst (carbonic anhydrase), enabling concentration and solubilization of emitted CO(2) by allowing catalytic contact with water spray. The reactors were fed with simulated emission gas. The performance of the reactors was investigated with respect to operation variable: emission flow rate; gas composition in the emission stream; water flow rate; area-to-volume ratio of immobilized reactor core; and the enzyme load within the core. The reactors were also investigated for pressure drop and extractability of CO(2) from the emission with single vs. multiple reactors (of combined equal volume). The biotechnological process of solubilization and concentration of CO(2) from emission exhausts or streams occurring in the spray reactors could be coupled for further biochemical/chemical conversion of the concentrated CO(2).