The renin-angiotensin system and the effect of propranolol upon the cerebral cortical and hypothalamic circulation in hypoxia

The regulatory mechanisms of the cerebral blood flow have preoccupied the physiology department of Cluj since the end of the 4th decade. These studies continued over the last years. The researches progressed from the studies of regulation by blood pressure changes to the nervous regulation and to the metabolic one. This paper's subject is the renin-angiotensin and adrenalin system influence on the changes of cerebral blood flow during the general hypoxic hypoxia and cephalic ischemia. Experiments were performed in 10 dogs anaesthetised with a mixture of chloralose, urethan and morphine. Hypoxic hypoxia was obtained by breathing a mixture of 11% oxygen in nitrogen, in a closed system and cerebral ischemic hypoxia by partial compression of the carotid arteries, after the ligation of the vertebral and thyroid arteries. The arterial blood pressure and the cerebral and hypothalamic blood flow, measured with the heated thermoelement, were registered. The plasma renin activity was tested radioimmunologically before, at 1.5 min, 5, 10 and 15 min, after the beginning of hypoxia. In ischemic hypoxia the experiment was repeated after venous perfusion with propranolol (0.6 mg/kg/h). The systemic blood pressure increased in both forms of hypoxia. The cortical and hypothalamic blood flow increased with the systemic arterial blood pressure. The hypothalamic blood flow remained stable or diminished a little. Propranolol increased the cerebral blood flow during ischemic hypoxia up to 300%. The i.v. administration of angiotensin (1-5 mg/kg) increased the cortical flow, while the hypothalamic flow remained self-regulated. Plasma renin activity increased more in general hypoxic hypoxia, than in cephalic ischemic hypoxia. After propranolol the increase was higher in this hypoxia. Propranolol produced a major activation of the renin-angiotensin system and of the cortical blood flow in ischemic cephalic hypoxia, the renin-angiotensin system being located in the cerebral structure. As well high doses of angiotensin produced cerebral vasodilatation in small cerebral vessels. This effect was found in our experiments in the cortical blood flow too. Our results indicate a beneficial propranolol effect on cortical circulation in ischemic hypoxia.     

Towards Dissecting the Mechanism of Protein Phosphatase-1 Inhibition by Its C-Terminal Phosphorylation

Phosphoprotein phosphatase-1 (PP1) is a key player in the regulation of phospho-serine (pSer) and phospho-threonine (pThr) dephosphorylation and is involved in a large fraction of cellular signaling pathways. Aberrant activity of PP1 has been linked to many diseases, including cancer and heart failure. Besides a well-established activity control by regulatory proteins, an inhibitory function for phosphorylation (p) of a Thr residue in the C-terminal intrinsically disordered tail of PP1 has been demonstrated. The associated phenotype of cell-cycle arrest was repeatedly proposed to be due to autoinhibition of PP1 through either conformational changes or substrate competition. Here, we use PP1 variants created by mutations and protein semisynthesis to differentiate between these hypotheses. Our data support the hypothesis that pThr exerts its inhibitory function by mediating protein complex formation rather than by a direct mechanism of structural changes or substrate competition.     

Improved versatile gigahertz pulse generator

The high-speed pulse circuit investigated, which mainly consists of a broadband magic T with two step-recovery diodes shunted to opposite ports, is shown to generate versatile pulse trains at gigahertz frequencies (upper limit at about 5GHz). Owing to the availability of two output signals, simple pulse patterns can be produced.     

Differential pulse regenerator driven by 1 Gbit/s p.c.m.-type signals from an avalanche photodiode

A hybrid-integrated pulse regenerator circuit, essentially employing an ultrabroadband 180° hybrid, step-recovery diodes and bipolar-transistor emitter followers, was operated by 1 Gibt/s signals delivered from an avalanche photodiode. A voltage gain of 20 dB could be measured on a single regenerator stage. RZ output pulses of halfwidths down to 100 ps were obtained, with the pulse shape being independent of the shape of the input pulses.     

Mode switching of Fabry-Perot laser diodes

Mode switching of a Fabry-Perot laser diode with low spontaneous input is analyzed. To understand the transients, an additional mode competition is required. This enhanced mode competition is analyzed. Its model is based on standing waves of longitudinal laser modes burning in a spatial carrier corrugation which modulates the gain. Internal reflections by the gain corrugations always fulfil the resonance condition at the wavelength of the mirror resonances. In this way, each laser mode decreases its own losses slightly with increased photon density. As a result the total gain (inclusive of all losses) of the dominant laser mode is increased to a value >0 during nearly the entire switching process. Therefore, the photon density can increase exponentially with a risetime of about 1 ns     

16 Gbit/s multiplexer experiment

A multiplexer experiment was performed that provided an n.r.z.-format serial-output pulse stream of 16 Gbit/s bit rate and 2 V across a load of 50 ?. The bit rate of the input tributaries was 1.12 Gbit/s. The multiplexer circuit essentially employed ultrabroadband hybrid tees, fast step-recovery diodes, and fast GaAs Schottky-barrier diodes.     

Methyl acetate–methanol mixture separation by extractive distillation: Economic aspects

Methyl acetate is considered low toxicity volatile solvent produced either as a by-product during methanol carbonylation or via acetic acid esterification with methanol. In both cases, pure methyl acetate has to be isolated from the reaction mixture. Simulation of methyl acetate separation from its mixture with methanol by extraction distillation was carried out in ASPEN + software. In total three case studies were assumed using two different extraction solvents and two solvent regeneration strategies. In case A, novel extraction solvent 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid, was considered. Raw material separation was achieved in an extraction distillation column while the solvent regeneration was accomplished in a second distillation column in this case. In case study B, the same extraction solvent was used; however, its regeneration was carried out in a single-effect evaporator. Dimethyl sulfoxide was the second extraction solvent selected. Its use in methyl acetate-methanol separation is presented in case study C. As high purity of dimethyl sulfoxide was required for the methyl acetate-methanol azeotrope breaking, its regeneration was carried out in the second distillation column only. To simulate the ternary methyl acetate–methanol–extraction solvent mixtures separation, vapor–liquid equilibrium was predicted based on the NRTL equation. Further, unknown properties of the considered ionic liquid and variation of these properties with temperature were predicted and introduced into the ASPEN + components properties database. Based on these data, optimum operation parameters of the respective separation equipment were established. In all case studies, the same condition had to be fulfilled, namely minimum methyl acetate content in the distillate from the extraction distillation column of 99.5mol-%. Results of simulations using the respective optimum operation parameters were employed in the economic evaluation of the three separation unit designs studied. It was found that the least energy-demanding design corresponds to the case study B in terms of both capital as well as operation expenses.

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Opportunities for Live Cell FT-Infrared Imaging: Macromolecule Identification with 2D and 3D Localization

Infrared (IR) spectromicroscopy, or chemical imaging, is an evolving technique that is poised to make significant contributions in the fields of biology and medicine. Recent developments in sources, detectors, measurement techniques and speciman holders have now made diffraction-limited Fourier transform infrared (FTIR) imaging of cellular chemistry in living cells a reality. The availability of bright, broadband IR sources and large area, pixelated detectors facilitate live cell imaging, which requires rapid measurements using non-destructive probes. In this work, we review advances in the field of FTIR spectromicroscopy that have contributed to live-cell two and three-dimensional IR imaging, and discuss several key examples that highlight the utility of this technique for studying the structure and chemistry of living cells.     

Groove-cell analysis of distributed feedback lasers

The propagation of waves in a groove cell is analyzed. This propagation is a function of transfer matrix, which contains the gain, together with the phase constant, the length of a groove cell, and the groove reflection coefficient. When the transfer matrix is cascaded the transmission of an optical field and the reflection coefficient of a distributed feedback structure can be determined even with unequal grooves and any groove number. With the help of an eigenvalue equation the threshold gain and phase constant of the resonator modes are determined for a symmetrical laser. The increase of threshold gain is demonstrated for an inhomogeneous laser with changed mean value of effective refractive index along the laser length. Bloch waves exist in a long grating (or a closed loop) of periodic grooves