Ligand interactions with the acetylcholine receptor from Torpedo californica. Extensions of the allosteric model for cooperativity to half-of-site activity

The solubilized acetylcholine receptor from Torpedo californica showed positive cooperativity in acetylcholine binding with a dissociation constant of 1.2 X 10(-8) M. Blockade of acetylcholine binding by nicotine was competitive; blockade by d-tubocurarine appeared to result from an allosteric interaction that altered half of the acetylcholine binding sites to a lower affinity form; decamethonium blockade displayed properties of competitive and allosteric inhibition suggesting less specificity for decamethonium binding than seen with either nicotine or d-tubocurarine. The d-tubocurarine inhibition data were evaluated by several possible models involving either differential competitive inhibition or allosteric inhibiton. The data were best described by the allosteric model.     

Abnormal rapid-sequence imaging in a patient with subdural empyema: case report

Static brain images in a patient with subdural empyema showed findings similar to those of a subdural hematoma. The rapid-sequence study, however, showed increased peripheral activity on the affected side. Since this finding suggested an inflammatory process, further neuroradiologic evaluation and immediate surgical treatment were undertaken. The significance of the rapid-sequence study in subdural empyema has not been reported previously.     

The clinical course of diabetic nephropathy

A retrospective record analysis of 112 juvenile-onset diabetics with nephropathy was conducted in order to determine their clinical course. The mean duration of diabetes at the onset of proteinuria was 17.3+/-6.0 years. Early renal failure appeared two years after the onset of protein-uria, and severe renal failure (mean serum creatinine level, 8.5+/-3.9 mg/100 ml) four years after the onset of proteinuria. The mean duration of life after the onset of severe renal failure was six months. The mortality was 53%, with 59% of the deaths attributable to renal failure and 36% to cardiovascular disease. All patients experienced progressive deterioration of renal function as well as the other complications of diabetes, the rate of progression being accelerated toward the end of the course. Juvenile onset diabetics should be considered for renal transplantation before the serum creatinine level reaches 8.5 mg/100 ml.     

Bulling among yearling feedlot steers

The effect of ingestion of 250 ml X-ray contrast medium on resting gastrooesophageal sphincter pressure was studied in 10 normal human subjects. Twenty minutes after initiated intake of the contrast medium, a significant fall in sphincter pressure was recorded. In the light of studies on the neurogenic and hormonal regulation of the sphincter pressure it is attempted to account for this effect, and it is concluded that it must be a manifestation of a reflectory relaxation of the sphincter region. From a clinical point of view the consequence must be a demand for standardized conditions with regard to composition and pH of the contrast medium, time schedule and degree of abdominal compression in those cases in which radiological evaluation of the resistance against reflux is called for.     

Diazepam-ketamine anaesthesia for open heart surgery "micro-mini" drip administration technique

Two hundred open heart cases anaesthetized with a combination of diazepam-ketamine using "Micro-Mini" drip administration technique were presented. The results were eminently desirable, and in the opinion of the authors are a notable improvement over other methods for all types of cardiovascular surgery including most advanced heart diseases. The advantages of this anaesthetic method for cardiovascular surgery are as follows: 1. Effects on cardiovascular system are minimal.--2. Respiratory depression is negligible.--3. There is no increase in salivation or muscle tone.--4. Induction and maintenance of anaesthesia are simple and smooth.--5. Anaesthesia can be maintained, using a high concentration of oxygen alone, by a slight increase in rate of ketamine administration whenever necessary.--6. Post-anaesthetic psychotomimetic effects are negligible.--7. Nearly 100% of patients have excellent amnesia.--8. It has a wide margin of safety.--9. This technique has proved highly acceptable to patients and surgeons. We feel ketamine should be used in small dosages continuously administered with either "Micro-Mini" drip infusion or infusion pump. Ketamine given in this fashion should be regarded as an analgesic.     

赛买提大蒜中大蒜素的稳定性研究

文章研究了不同因素对大蒜素稳定性的影响,结果表明:大蒜素在pH为3~5时较稳定,在pH为8~11时稳定性比较差;大蒜素对热不稳定,尤其当温度高于100℃时;有机溶剂和调和油对大蒜素有稳定作用;糖类对大蒜素有一定的保护作用,尤以β-环糊精和可溶性淀粉的保护作用最佳;添加0.5%~1.0%的VC对大蒜素有保护作用,而当添加量大于1.5%时,大蒜素含量下降迅速。     

Surface Analytical Study of Synroc Subjected to Hydrothermal Attack

Specimens of the ceramic Synroc, both with (Synroc C) and without the addition of a simulated nuclear waste (Synroc B), were subjected to hydrothermal attack. The near-surface regions, both before and after attack, were characterized using X-ray photoelectron spectroscopy, Auger electron spectroscopy, and scanning electron microscopy. Ion-beam erosion was used in conjunction with these surface analysis techniques to obtain information from below the original surface. It was found that hydrothermal attack led to the formation of a modified layer extending to a maximum depth of ∼200 nm after 25 days at 350°C. Within this modified layer, the abundances and chemical states of the elements were different from those in the unattacked Synroc. The changes which were observed can be explained qualitatively by postulating that selective dissolution (e.g., for Ca and Ba), hydration (e.g., for Al and Fe), recrystallization (e.g., for Ti and Zr), and reaction with Co₂ dissolved in the liquid phase (e.g., to form CaCO₃) are all taking place.