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Notes: [Auszug] Proteins that bind with high affinity to specific DNA sequences often do so through hydrogen bonding and electrostatic interactions between the DNA major groove and defined protein structural elements, such as helix-turn-helix motifs, β-ribbon recognition elements and Zn-binding domains1. ...

Notes: Abstract: To investigate the regulation of norepinephrine transporter mRNA in vivo, we analyzed the effects of reserpine on its expression in the rat adrenal medulla and locus ceruleus. First, PCR was used to clone a 0.5-kb rat cDNA fragment that exhibits 87% nucleotide identity to the corresponding human norepinephrine transporter cDNA sequence. In situ, the cDNA hybridizes specifically within norepinephrine-secreting cells, but in neither dopamine nor serotonin neurons, suggesting strongly it is a partial rat norepinephrine transporter cDNA. Reserpine, 10 mg/kg administered 24 h premortem, decreased steady-state levels of norepinephrine transporter mRNA in the adrenal medulla by ∼65% and in the locus ceruleus by ∼25%, as determined by quantitative in situ hybridization. Northern analysis confirmed the results of the in situ hybridization analysis in the adrenal medulla but did not detect the smaller changes observed in the locus ceruleus. Both analyses showed that reserpine increased tyrosine hydroxylase expression in the adrenal medulla and locus ceruleus. These results suggest that noradrenergic neurons and adrenal chromaffin cells can coordinate opposing changes in systems mediating catecholamine uptake and synthesis, to compensate for catecholamine depletion.

Notes: Abstract: Aromatic l-amino acid decarboxylase (AADC) is found in both neuronal cells and nonneuronal cells, and a single gene encodes rat AADC in both neuronal and nonneuronal tissues. However, two cDNAs for this enzyme have been identified: one from the liver and the other from pheochromocytoma. Exons 1a and 1b are found in the liver cDNA and the pheochromocytoma cDNA, respectively. In the third exon (exon 2), there are two alternatively utilized splicing acceptors specific to these exons, 1a and 1b. Structural analysis of the rat AADC gene showed that both alternative promoter usage and alternative splicing are operative for the differential expression of this gene. To demonstrate whether alternative promoter usage and splicing are tissue specific and whether the exons 1a and 1b are differentially and specifically transcribed in nonneuronal and neuronal cells, respectively, in situ hybridization histochemistry for the rat brain, adrenal gland, liver, and kidney was carried out using these two exon probes. The exon 1a probe specifically identified AADC mRNA only in nonneuronal cells, including the liver and kidney, and the exon 1b probe localized AADC mRNA to monoaminergic neurons in the CNS and the adrenal medulla. Thus, both alternative promoter usage and differential splicing are in fact operative for the tissue-specific expression of the rat AADC gene.

Notes: Abstract: Excitatory amino acid (EAA) neurotransmitters may play a role in the pathophysiology of traumatic injury to the CNS. Although NMDA receptor antagonists have been reported to have therapeutic efficacy in animal models of brain injury, these compounds may have unacceptable toxicity for clinical use. One alternative approach is to inhibit the release of EAAs following traumatic injury. The present study examined the effects of administration of a novel sodium channel blocker and EAA release inhibitor, BW1003C87, or the NMDA receptor-associated ion channel blocker magnesium chloride on cerebral edema formation following experimental brain injury in the rat. Animals (n = 33) were subjected to fluid percussion brain injury of moderate severity (2.3 atm) over the left parietal cortex. Fifteen minutes after injury, the animals received a constant infusion of BW1003C87 (10 mg/kg, i.v.), magnesium chloride (300 µmol/kg, i.v.), or saline over 15 min (2.75 ml/kg/15 min). In all animals, regional tissue water content in brain was assessed at 48 h after injury, using the wet weight/dry weight technique. In saline-treated control animals, fluid percussion brain injury produced significant regional brain edema in injured left parietal cortex (p 〈 0.001), the cortical area adjacent to the site of maximal injury (p 〈 0.001), left hippocampus (p 〈 0.001), and left thalamus (p = 0.02) at 48 h after brain injury. Administration of BW1003C87 15 min postinjury significantly reduced focal brain edema in the cortical area adjacent to the site of maximal injury (p 〈 0.02) and left hippocampus (p 〈 0.01), whereas magnesium chloride attenuated edema in left hippocampus (p = 0.02). These results suggest that excitatory neurotransmission may play an important role in the pathogenesis of posttraumatic brain edema and that pre- or post-synaptic blockade of glutamate receptor systems may attenuate part of the deleterious sequelae of traumatic brain injury.

Notes: The physics of the degenerate four-wave mixing process for resonant transitions between two degenerate energy levels is investigated by direct numerical integration of the time-dependent density matrix equations. The Zeeman structure of the upper and lower energy levels is included in a multistate formulation of the density matrix equations. The inclusion of the Zeeman structure enables the investigation of the degenerate four-wave mixing process for different polarization configurations of the forward pump, backward pump, and probe beams. Saturation curves and lineshapes are calculated for different polarization configurations and for numerous low-J transitions. At low laser intensity, the results of our calculations are in excellent agreement with perturbation theory in terms of the relative intensities of the degenerate four-wave mixing signal for linear polarization configurations. As the laser intensity increases and the resonance starts to saturate, we find in general that the relative degenerate four-wave mixing reflectivity increases for the crossed polarization configurations compared to the parallel polarization configuration because the saturation intensity is higher. However, for some resonance transitions, some of the crossed polarization configurations saturate at lower laser intensities than the parallel polarization configuration, even though the reflectivity for these crossed polarization configurations is much lower than for the parallel polarization configuration in the perturbative intensity limit. This result is explained in terms of the coupling of the various Zeeman states during the degenerate four-wave mixing interaction for specific polarization configurations. The effect of saturation on the resonance line shapes for the different polarization configurations is also investigated. Finally, a limited number of calculations are performed for resonances that are Doppler broadened as well as collision broadened. The effect of saturation on the reflectivity of the crossed polarization configurations compared to the parallel polarization configuration is even more significant for resonances with comparable Doppler and collisional broadening. © 1999 American Institute of Physics.

Notes: The physics of polarization spectroscopy (PS) is investigated by direct numerical integration of the time-dependent density matrix equations. The Zeeman structure of the upper and lower energy levels is included in a multistate formulation of the density matrix equations. The numerical solution of the time-dependent density matrix equations enables us to investigate the effects of strong saturation on PS signal levels and line shapes. Bath levels not directly coupled by the laser radiation are included in the numerical modeling to investigate the effects of collisional rates and different types of collisions on signal levels and line shapes. The effects of Doppler broadening are included by solving the density matrix equations for numerous velocity groups. At low laser power we find that the homogeneously broadened PS line shape is Lorentzian-cubed, as compared to the Lorentzian predicted in several previous low-power analytical solutions. In the low laser power regime, the line-center PS signal is proportional to (collision rate)−6, obviously greatly complicating the application of unsaturated PS for quantitative concentration measurements in flames and plasmas. As the transition begins to saturate at higher laser intensities, the dependences of the signal strength on the laser intensity and on the collision rate decrease drastically, although the line-center PS signal is still approximately proportional to (collision rate)−2. The dependence of the PS signal intensity on the ratio of the population-transfer collision rate to the dephasing collision rate is minimized for saturating pump beam intensities. For resonances that are both Doppler- and collision-broadened, the low-power PS line shape is Lorentzian with a linewidth equal to the collisional width for the case where the Doppler width is much greater than the collisional width. At low pump laser intensities, the PS signal is very dependent on the ratio of Doppler broadening to collisional broadening when the Doppler width is greater than the collisional width. However, at high intensity, the line-center PS signal intensity becomes nearly independent of collision rate when the collisional linewidth is less than the Doppler linewidth. Quantitative application of polarization spectroscopy for concentration measurements in flames and plasmas will almost certainly require resolution of the PS line shape and/or accurate measurement of the saturation curve. © 1998 American Institute of Physics.

Notes: We demonstrate that picosecond time-resolved photoelectron angular distributions (PADs) provide a sensitive probe of an evolving alignment in an excited polyatomic molecule. Such an evolving alignment can be caused by pure rotational recurrences or by rotation–vibration coupling. If a molecule is chosen for which the rotational recurrence times are well-known the method provides a means of establishing the mechanism of intramolecular vibrational energy redistribution (IVR). In the case of S1 para-difluorobenzene we observe striking alignment changes as a function of pump–probe time delay which we attribute to rotationally mediated IVR. © 1999 American Institute of Physics.