Effects of a nitric oxide synthesis inhibitor on renal sodium handling and diluting capacity in humans

BACKGROUND: Inhibition of nitric oxide (NO) synthesis has antinatriuretic and antidiuretic effects. Limited information is available on the role of NO in tubular sodium transport in the human kidney. METHODS: We studied nine healthy, sodium-replete males with clearance techniques during maximal diuresis. NG-monomethyl-L-arginine (L-NMMA, 3 mg/kg priming dose plus 3 mg/kg/h) was infused for 3 h, to achieve steady-state inhibition of NO synthesis. Data were compared with a time control study. RESULTS: The effects of L-NMMA were quickly established and persisted through the entire infusion period. Mean arterial pressure increased slightly from 85+/-3 to 91+/-3 mmHg (P<0.05). Renal plasma flow decreased substantially, and glomerular filtration rate slightly. Large decreases in absolute sodium excretion, from 79+/-10 to 34+/-5 micromol/min (P<0.01), and fractional sodium excretion, from 0.5+/-0.0 to 0.3+/-0.0% (P<0.01), were associated with significant reductions in fractional lithium excretion (P<0.05) and maximum urine flow (P<0.01). Minimal urine sodium concentration decreased from 5.8+/-0.04 to 3.9+/-0.4 mmol/l (P<0.01) whereas minimal urine osmolality increased (P<0.05). Plasma renin activity, aldosterone and atrial natriuretic peptide levels did not change, whereas urinary excretions of guanosine 3'5'-cyclic monophosphate and of nitrite plus nitrate decreased slightly. CONCLUSIONS: Inhibition of endogenous NO synthesis in humans to an extent that raises blood pressure only mildly causes antinatriuresis, that can be attributed to increases in sodium reabsorption both at proximal and distal nephron sites. In addition, renal diluting capacity decreases. The effects in the diluting segment have not been reported before, and may be due to medullary vasoconstriction, similar to that described for angiotensin II.     

TiO2硅藻土复合光催化剂研制及光催化氧化水中亚甲基蓝的研究

本文以Ti(SO4)2和硅藻土为原料,采用浸渍法制备TiO2硅藻土复合光催化剂,该催化剂既有良好的吸附性,也有较高的紫外光催化活性。在160W的紫外光照射、光催化剂投加量为1g/l、反应时间为30分钟的条件下,利用该催化剂处理浓度为20mg／l的亚甲基蓝水溶液,脱色率96％。     

A two-year experience of an acute pain service in Singapore

The first anaesthesia-based acute pain service in Singapore is described. The benefits, risks and resource implications of such a service during its first two years are reviewed. One thousand two hundred and sixty-eight (1,268) post-operative patients were treated with either patient-controlled analgesia (310 patients) or epidural opioid analgesia (958 patients). Retrospective analysis of the data revealed good patient satisfaction with a low incidence of potentially life threatening side-effects: more than 79% of patients reported satisfaction with pain control while only 0.2% of patients receiving epidural opioid analgesia experienced clinically significant respiratory depression. There were no reports of respiratory depression in the patient-controlled analgesia group. The authors conclude that the provision of an acute pain service in the local context was safe and resulted in excellent post-operative patient satisfaction.     

Collagen metabolism in obesity: the effect of weight loss

OBJECTIVE: To investigate the impact of obesity, fat distribution and weight loss on collagen turnover using serum concentrations of the carboxyterminal propeptide of type I procollagen (S-PICP) and the aminoterminal propeptide of type III pro-collagen (S-PIIINP) as markers for collagen turnover. DESIGN: Blood samples were obtained once at baseline, and after 8 and 16 weeks of dietary treatment (5.0 MJ/day diet). SETTING: Outpatient clinic of Hvidovre University Hospital. MAIN OUTCOME MEASURES: S-PICP, S-PIIINP, fat distribution and weight loss. RESULTS: S-PIIINP was associated with body weight (r = 0.37; P = 0.004), height (r = 0.27; P = 0.04), waist circumference (r = 0.35; P = 0.007), as well as with WHR (r = 0.33; P = 0.01) and was inversely correlated to age (r = -0.40; P = 0.002). Compared with randomly selected controls from a large pool of healthy volunteers, the obese patients had elevated S-PIIINP values before as well as during weight loss, whereas S-PICP levels were within the normal range and did not correlate with any anthropometric measures. The average weight loss after 16 weeks dietary treatment was 8.1 kg (s.d. = 0.8). S-PIIINP decreased during the 16 weeks of energy restriction (P < 0.05) and changes in S-PIIINP was correlated to body weight loss (r = 0.32; P < 0.05) and to changes in waist circumference (r = 0.34; P < 0.05) as well as changes in WHR (r = 0.30; P < 0.05). CONCLUSION: S-PIIINP is elevated in obesity and associated with body fat distribution, suggesting an increased turnover of type III collagen related to obesity in general and to abdominal obesity in particular. S-PIIINP levels decreases during weight loss in obese subjects, whereas S-PICP levels seems un-related to obesity and weight loss.     

Uniform low defect density molecular beam epitaxial HgCdTe

This paper describes recent advances in MBE HgCdTe technology. A new 3 inch production molecular beam epitaxy (MBE) system, Riber Model 32P, was installed at Rockwell in 1994. The growth technology developed over the years at Rockwell using the Riber 2300 R&D system was transferred to the 32P system in less than six months. This short period of technology transfer attests to our understanding of the MBE HgCdTe growth dynamics and the key growth parameters. Device quality material is being grown routinely in this new system. Further advances have been made to achieve better growth control. One of the biggest challenges in the growth of MBE HgCdTe is the day-to-day control of the substrate surface temperature at nucleation and during growth. This paper describes techniques that have led to growth temperature reproducibility within + - 1°C, and a variation in temperature during substrate rotation within 0.5°C. The rotation of the substrate during growth has improved the uniformity of the grown layers. The measured uniformity data on composition for a typical 3 cm × 3 cm MBE HgCdTe/CdZnTe shows the average and standard deviation values of 0.229 and 0.0006, respectively. Similarly, the average and standard deviation for the layer thickness are 7.5 and 0.06 μm, respectively. P-on-n LWIR test structure photodiodes fabricated using material grown by the new system and using rotation during growth have resulted in high-performance (R₀)A, quantum efficiency) devices at 77 and 40K. In addition, 128 × 28 focal plane arrays with excellent performance and operability have been demonstrated.     

Nonpeptide cyclic cyanoguanidines as HIV-1 protease inhibitors: synthesis, structure-activity relationships, and X-ray crystal structure studies

Comparison of the high-resolution X-ray structures of the native HIV-1 protease and its complexes with the inhibitors suggested that the enzyme flaps are flexible. The movement at the tip of the flaps could be as large as 7 A. On the basis of this observation, cyclic cyanoguanidines have been designed, synthesized, and evaluated as HIV-1 protease (PR) inhibitors. Cyclic cyanoguanidines were found to be very potent inhibitors of HIV-1 protease. The choice of cyclic cyanoguanidines over cyclic guanidines was based on the reduced basicity of the former. X-ray structure studies of the HIV PR complex with cyclic cyanoguanidine demonstrated that in analogy to cyclic urea, cyclic cyanoguanidines also displace the unique structural water molecule. The structure-activity relationship of the cyclic cyanoguanidines is compared with that of the corresponding cyclic urea analogues. The differences in binding constants of the two series of compounds have been rationalized using high-resolution X-ray structure information.