Tensilely Strained Germanium Nanomembranes as Infrared Optical Gain Media

The use of tensilely strained Ge nanomembranes as mid‐infrared optical gain media is investigated. Biaxial tensile strain in Ge has the effect of lowering the direct energy bandgap relative to the fundamental indirect one, thereby increasing the internal quantum efficiency for light emission and allowing for the formation of population inversion, until at a strain of about 1.9% Ge is even converted into a direct‐bandgap material. Gain calculations are presented showing that, already at strain levels of about 1.4% and above, Ge films can provide optical gain in the technologically important 2.1–2.5 μm spectral region, with transparency carrier densities that can be readily achieved under realistic pumping conditions. Mechanically stressed Ge nanomembranes capable of accommodating the required strain levels are developed and used to demonstrate strong strain‐enhanced photoluminescence. A detailed analysis of the high‐strain emission spectra also demonstrates that the nanomembranes can be pumped above transparency, and confirms the prediction that biaxial‐strain levels in excess of only 1.4% are required to obtain significant population inversion.     

Acidic urine pH is associated with elevated levels of free urinary benzidine and N-acetylbenzidine and urothelial cell DNA adducts in exposed workers

We evaluated the influence of urine pH on the proportion of urinary benzidine (BZ) and N-acetylbenzidine present in the free, unconjugated state and on exfoliated urothelial cell DNA adduct levels in 32 workers exposed to BZ in India. Postworkshift urine pH was inversely correlated with the proportions of BZ (r = -0.78; P < 0.0001) and N-acetylbenzidine (r = -0.67; P < 0.0001) present as free compounds. Furthermore, the average of each subject's pre- and postworkshift urine pH was negatively associated with the predominant urothelial DNA adduct (P = 0.0037, adjusted for urinary BZ and metabolites), which has been shown to cochromatograph with a N-(3'-phosphodeoxyguanosin-8-yl)-N'-acetylbenzidine adduct standard. Controlling for internal dose, individuals with urine pH < 6 had 10-fold higher DNA adduct levels compared to subjects with urine pH > or = 7. As reported previously, polymorphisms in NAT1, NAT2, and GSTM1 had no impact on DNA adduct levels. This is the first study to demonstrate that urine pH has a strong influence on the presence of free urinary aromatic amine compounds and on urothelial cell DNA adduct levels in exposed humans. Because there is evidence that acidic urine has a similar influence on aromatic amines derived from cigarette smoke, urine pH, which is influenced by diet, may be an important susceptibility factor for bladder cancer caused by tobacco in the general population.     

A study on expression of the heat shock suppressed gene in distal organs of rats after scalding

In order to address the question whether stress in intact higher animals may induce cellular heat shock response in distal organs, the inhibition of normal gene expression was studied on the basis of our previous findings about the induction of heat shock proteins in liver and brain of rats after scalding. Male SD rats were scalded on the back, 10-240 min thereafter decapitated, and the heat shock suppressed gene-1 was quantitated by dot blotting. The results showed that gene-1 decreased rapidly after scalding in both the organs, and did not recover to control levels even 240 min after scalding. The decrease of gene-1 went parallell with the severity of scalding. Thus it may be concluded that stress may induce heat shock response of distant organs in intact animals. Possible pathological significance of these findings was discussed.     

Pulmonary pathology of patients treated with partial liquid ventilation

Adsorption and size exclusion in starch and cross-linked dextran were phenomena discovered in Uppsala in the 1950s [Porath (1979), Biochem. Soc. Trans. 7, 1197; Porath (1981), Current Content 19, 21; Porath (1981), J. Chromatogr. 218, 241; Janson (1987), Chromatographia 23, 361; Laurent (1993), J. Chromatogr. 633, 1]. These discoveries were the background to the development of a variety of affinity chromatographic methods. At present attempts are being made to combine size exclusion chromatography (SEC) with adsorption into a single operation that we call adsorptive SEC (AdSEC).     

Angiotensin-converting enzyme inhibition and angiotensin II subtype-1 receptor blockade during the progression of left ventricular dysfunction: differential effects on myocyte contractile processes

Inhibition of the angiotensin-converting enzyme (ACE) in the setting of chronic left ventricular (LV) dysfunction has been demonstrated to have beneficial effects on survival and symptoms. However, whether ACE inhibition has direct effects on myocyte contractile processes and if these effects are mediated primarily through the AT1 angiotensin-II receptor subtype remains unclear. The present project examined the relationship between changes in LV and myocyte function and beta adrenergic receptor transduction in four groups of six dogs each: (1) Rapid Pace: LV failure induced by chronic rapid pacing (4 weeks; 216 +/- 2 bpm); (2) Rapid Pace/ACEI: concomitant ACE inhibition (ACEI: fosinopril 30 mg/kg b.i.d.) with chronic pacing; (3) Rapid Pace/AT1 Block: concomitant AT1 Ang-II receptor blockade [Irbesartan: SR 47436(BMS-186295) 30 mg/kg b.i.d.] with chronic pacing; and (4) Control: sham controls. With Rapid Pace, the LV end-diastolic volume increased by 62% and the ejection fraction decreased by 53% from control. With Rapid Pace/ACEI, the LV end-diastolic volume was reduced by 24% and the ejection fraction increased by 26% from Rapid Pace only values. Rapid Pace/AT1 Block did not improve LV geometry or function from Rapid Pace values. Myocyte contractile function decreased by 40% with Rapid Pace and increased from this value by 32% with Rapid Pace/ACEI. Rapid Pace/AT1 Block had no effect on myocyte function when compared with Rapid Pace values. With Rapid Pace/ACEI, beta receptor density and cyclic AMP production were normalized and associated with an improvement in myocyte beta adrenergic response compared with Rapid Pace only. Although Rapid Pace/AT1 also normalized beta receptor density, cyclic AMP production was unchanged and myocyte beta adrenergic response was reduced by 15% compared with Rapid Pace only. ACE inhibition with chronic rapid pacing improved LV and myocyte geometry and function, and normalized beta receptor density and cyclic AMP production. However, AT1 Ang-II receptor blockade with chronic rapid pacing failed to provide similar protective effects on LV and myocyte geometry and function. These unique findings suggest that the effects of ACE inhibition on LV geometry and myocyte contractile processes in the setting of developing LV failure are not primarily caused by modulation of AT1 Ang-II receptor activation.     

Pharmacological inhibition of protein kinases in intact cells: antagonism of beta adrenergic receptor ligand binding by H-89 reveals limitations of usefulness

The use of pharmacological inhibitors of protein kinases represents a potentially powerful tool in dissecting the regulatory features of intracellular signaling pathways. However, although the in vitro potency, selectivity, and efficacy of numerous kinase inhibitors have been characterized, little is known regarding the usefulness of these compounds as inhibitors in intact cells. In attempting to characterize the role of protein kinase A (PKA) in regulating the beta-2 adrenergic receptor (AR) in human airway cells, we observed a seemingly profound capacity of the isoquinoline H-89, a potent and widely used PKA inhibitor, to attenuate agonist-mediated desensitization of the beta-2 AR. Although additional experiments identified H-89 as an effective inhibitor of intracellular PKA, extended analysis of the compound determined the principal effect of H-89 was via its action as a beta-2 AR antagonist. Pretreatment with or the acute addition of H-89 significantly attenuated isoproterenol-stimulated cAMP accumulation. In cells pretreated with H-89 and then washed extensively, the subsequent dose-dependent response to isoproterenol suggested beta-2 AR antagonism by retained H-89. Competition binding of [125I]iodopindolol established Ki values of approximately 180 nM and 350 nM for H-89 antagonism of beta-2 AR and beta-1 AR, respectively. Additional receptor binding studies suggest selectivity of H-89 for the beta-2 AR and beta-1 AR, although a weak antagonism (Ki values of approximately 10 microM or greater) of other G protein-coupled receptors was observed. Results from additional pharmacological and biochemical analyses of various protein kinase inhibitors further established the need for careful characterization of pharmacological inhibitors when used in intact cell models.