Interet diagnostique d’une injection intracaverneuse de 20 μg de Prostaglandine E1 dans l’impuissance

Intracavernous injection of 20 μg of prostaglandin E1 (PGE1) was carried out in 130 impotent patients. The erectile response was compared to the results of arteriological investigations including nocturnal penile tumescence and rigidity monitoring (NPTR) in 59 patients. The response of 60 patients positively categorized as exclusively psychogenic or vasculogenic was also compared to the pattern of the response to 80 mg of papaverine observed in a previous study by the same authors. The PGE1 test may not discriminate psychogenic from wholly organic patients since its results are not correlated to those of NPTR. It helps for the screening of vasculogenic impotence. Lack of response or a partly rigid response is consistent with this actiology but is not specific for it. A fully response makes it unlikely. Compared to papaverine, PGE1 induces less non rigid responses in psychogenic patients (15% versus 35% with papaverine) and more fully rigid responses in vasculogenic patients (respectively 12% and 5 %). Consequently the specificity of the PGE1 test is higher but its sensitivity lower than that of papaverine so that there is no clear difference in the effectiveness of the tests. Nevertheless the PGE1 test should be preferred, because it is safer. Prolonged erections occured in only 5 patients, and all ceased spontaneously. However 4 presented severely painful erections.     

A modular treatment of molecular traffic through the active site of cholinesterase

We present a model for the molecular traffic of ligands, substrates, and products through the active site of cholinesterases (ChEs). First, we describe a common treatment of the diffusion to a buried active site of cationic and neutral species. We then explain the specificity of ChEs for cationic ligands and substrates by introducing two additional components to this common treatment. The first module is a surface trap for cationic species at the entrance to the active-site gorge that operates through local, short-range electrostatic interactions and is independent of ionic strength. The second module is an ionic-strength-dependent steering mechanism generated by long-range electrostatic interactions arising from the overall distribution of charges in ChEs. Our calculations show that diffusion of charged ligands relative to neutral isosteric analogs is enhanced approximately 10-fold by the surface trap, while electrostatic steering contributes only a 1.5- to 2-fold rate enhancement at physiological salt concentration. We model clearance of cationic products from the active-site gorge as analogous to the escape of a particle from a one-dimensional well in the presence of a linear electrostatic potential. We evaluate the potential inside the gorge and provide evidence that while contributing to the steering of cationic species toward the active site, it does not appreciably retard their clearance. This optimal fine-tuning of global and local electrostatic interactions endows ChEs with maximum catalytic efficiency and specificity for a positively charged substrate, while at the same time not hindering clearance of the positively charged products.     

siRNA against presenilin 1 (PS1) down regulates amyloid β42 production in IMR-32 cells

Background  

One of the pathological hallmarks of Alzheimer's disease (AD) is the deposition of the ~4 kDa amyloid β protein (Aβ) within lesions known as senile plaques. Aβ is also deposited in the walls of cerebral blood vessels in many cases of AD. A substantial proportion of the Aβ that accumulates in the AD brain is deposited as Amyloid, which is highly insoluble, proteinaceous material with a β-pleated-sheet conformation and deposited extracellularly in the form of 5-10 nm wide straight fibrils. As γ-secretase catalyzes the final cleavage that releases the Aβ42 or 40 from amyloid β -protein precursor (APP), therefore, it is a potential therapeutic target for the treatment of AD. γ-Secretase cleavage is performed by a high molecular weight protein complex containing presenilins (PSs), nicastrin, Aph-1 and Pen-2. Previous studies have demonstrated that the presenilins (PS1 and PS2) are critical components of a large enzyme complex that performs γ-secretase cleavage.     

Embryo growth and dormancy in seeds of six Hosta species native to Korea

Although it has been speculated that Hosta seeds have an underdeveloped embryo and morphological (MD) or morphophysiological dormancy (MPD), no detailed studies have been carried out to definitively confirm this suggestion. Our first purpose was to determine if embryos of six Korean species of Hosta (H. capitata, H. clausa, H. jonesii, H. minor, H. venusta and H. yingeri) grew inside the seeds prior to germination (i.e., were underdeveloped) or did not do so (i.e., were fully developed). Our second purpose was to identify the class of dormancy found in these seeds by examining germination during incubation at 15 and/or 25°C. The initial embryo : seed ratio in seeds of the six Hosta species was between 0.78 and 0.85, and embryos elongated by 9.6 to 17.5% prior to germination. Seeds of H. capitata, H. clausa, H. venusta and H. yingeri germinated to ≥65% in light and darkness at 15 and 25°C within 30 days, those of H. minor germinated to ≥80% in light and darkness at 25°C and to 24% in light and 50% in darkness at 15°C, and those of H. jonesii germinated to 100% in light at 25°C. We conclude that embryos in seeds of these six Hosta species are underdeveloped at maturity. Because high percentages of H. capitata, H. clausa, H. venusta and H. yingeri seeds germinated at cold and warm temperatures within 30 days, they have MD. On the other hand, seeds of H. minor germinated to high and low percentages at warm and cold temperatures, respectively. Thus, some seeds have MD and others may have MPD.     

哈尔滨西郊赤狐冬季巢区的初步研究

本文利用雪地跟踪方法对哈尔滨西郊5只赤狐在1985-1986年冬季的巢区做了观察。结果表明,5只狐对巢区内各部分使用的强度是不等的,对巢区中部的某些地块使用强度要高于对外围的使用,并具有明显的方向性。5个巢区的平均活动半径为320±68米至557±82米,面积为1.44-4.O9平方公里,线性指数为1.079至2。5只狐相邻距离约1000米。