刺激脑内渗透压感受器对大鼠浅表肾单位功能的影响

我们先前已在麻醉大鼠中用锂清除率方法从全肾水平证实,脑室内注射高张盐水(icv.HS)引起的利尿和利尿钠反应是由于肾小球滤过率增加和近球小管重吸收能力降低。本实验用肾小管微穿刺方法从肾单位水平进一步观察icv.HS对浅表肾单位的单个肾单位肾小球滤过率以及近曲小管和髓袢的重吸收的影响。实验在麻醉大鼠中进行。icv.HS后,单个肾单位肾小球滤过率从39.6±1.9nl/min增加至48.8±2.0nl/min(P<0.001);近曲小管末段小管液流量从20.5±1.4nl/min增加至28.4±2.0nl/min(P<0.001);小管液菊糖浓度与血浆菊糖浓度的比值从1.98±0.98降低至1.69±0.05(P<0.01)。根据上述数据计算得到的近曲小管重吸收分数从49.2±2.2％下降至41.7±1.8％(P<0.001),而近曲小管的绝对重吸收无明显改变。这些结果与用锂清除率方法获得的结果相符合。icv.HS后,髓袢的绝对重吸收升高,而重吸收分数下降。上述结果表明刺激脑内渗透压感受器可增加浅表肾单位的肾小球滤过率,并降低近曲小管的重吸收能力,从而增加髓袢的负荷,使髓袢的绝对重吸收增加。本实验结果不能排除icv.HS对髓袢的重吸收过程具有直接影响的可能性。     

应用苯酚法测定植物组织中的碳水化合物

为了还原糖和多糖的比色测定,曾经报道过许多的比色法。目前,常用的蒽酮比色法有许多缺点:蒽酮试剂较贵;而且蒽酮在硫酸中是不稳定的;也不可用于甲基化的糖和戊糖的测定。苯酚法可用于糖、甲基化的糖和多糖的比色测定,方法简捷、便宜、灵敏度高;实验时基本上不受蛋白质存在的影响,因而简化了糖的提取程序。依据Kochert方法,作了条件试验,取得了     

甜叶菊中Stevioside的测定

在硅胶G薄层板上用氯仿:甲醇:水(38:12:2)分离出Stevioside。用蒽酮—硫酸试剂显色,然后用上海72型—分光光度计在620nm波长比色,测出甜叶菊中Stevioside的含量。本法回收率为96.50±0.539％。     

刺激脑内渗透压感受器能降低大鼠管球反馈的敏感性

在麻醉大鼠肾脏近曲小管和远曲小管分别进行微穿刺,采集小管液。测定单个肾单位肾小球滤过率(SNGFR)。由于微穿刺部位对管球反馈造成的影响,在同一肾单位,采集近曲小管末段小管液测出的SNGFR值(SNGFR_p)比在远曲小管起始段测出的SNGFR值(SNG-FR_d)高,故可将在这两个部位测得的SNGFR值的差(SNGFR_(p-d))用作衡量管球反馈(TGF)敏感性的间接指标。脑室内注射高张盐水(icv.HS)后,SNGFR_(p-d)减小,表明脑内渗透压感受器受刺激可使TGF的敏感性降低。静脉注射速尿后,icv.HS不再引起肾血浆流量和肾小球滤过率的增加,但仍能引起尿钠排出增多。上述结果表明,刺激脑内渗透压感受器可通过减弱TGF导致肾脏血流动力学的改变,而其增加尿钠排出的效应则是通过抑制肾小管的重吸收实现的。     

固相抗体放射免疫分析法测尿中微量白蛋白

将抗人白蛋白抗体(或第二抗体)与纤维素偶联,建立了固相放免法。其剂量反应曲线在20—540ng/ml范围内呈一直线,灵敏度为20ng/ml。20例正常人尿中微量白蛋白测定值为5.71±1.39 mg/24 h尿,与液相放免法的7.17±3.70mg/24 h尿的结果相接近。固相一抗放免法和液相或固相二抗放免法均有很好相关。     

木质纤维素固体基质发酵物中半纤维素、纤维素和木素的定量分析程序

拟定了木质纤维素固体基质发酵物中半纤维素、纤维素和木素的定量分析程序。本程序是将中性洗涤剂法、2M盐酸水解法、72%硫酸水解法、地衣酚比色定糖法和蒽酮比色定糖法加以综合应用而成,在具有一般化学分析条件的实验室都可使用。本程序可以同时进行多个试样的分析。因此,对于进行对比性探讨发酵物中半纤维素、纤维素和木素的含量及其转化动力学的研究,本程序尤其实用。     

脑室内注射高张盐水抑制近曲小管对水和钠的重吸收

实验在麻醉大鼠上进行。用锂清除率为指标观察脑室内注射高张盐水对近曲小管重吸收水和钠的影响。在切断单侧肾神经的动物中,脑室内注射高张盐水后的锂清除率与肾小球滤过率比值在去神经侧肾脏从0.37±0.04增加至0.51±0.05(P<0.01);神经完好侧肾脏则从0.26±0.03增加至0.31±0.04(P<0.05);双侧肾脏的肾小球滤过率、尿量、尿钠和尿钾量均增加,且去肾神经肾脏的增加幅度高于肾神经完好肾脏。在肾小管微穿刺实验中,脑室内注射高张盐水后,近曲小管末段小管液流量从24.42±1.84nl/min增加至31.86±3.09nl/min(P<0.01),小管液的渗透压无显著变化。以上实验结果表明,脑室内注射高张盐水引起的利尿、尿钠增多反应与肾小球滤过率增加和近曲小管对水、钠重吸收减少有关,体液因素在该反应中可能起主要作用。     

蒽酮分光光度法测定海藻多糖总糖含量

本文报道了在室温下用蒽酮分光光度法测定海藻多糖总糖的含量,本法总糖测定的回收率９７．５％－１０３％,标准偏差０．３。本法设备简便,迅速、准确。     

人血清中游离氨基酸的萤光微量测定法

本文介绍用邻苯二甲醛与氨基酸产生萤光微量测定人血清中游离氨基酸含量的方法。灵敏度可测到1至0.1×10~(-9)克分子氨基酸。每次测定的血清用量为5至10微升。本法具有简单、快速、灵敏的优点。血清中其他含氨物质如脲、尿酸、肌酐和氨对测定无干扰。我国正常人血清的游离氨基酸含量,从52个人测得的平均值为2.83±0.45(S.D)毫克分子/升。此法适用于临床检验和科研。     

人血清中游离氨基酸的萤光微量测定法

本文介绍用邻苯二甲醛与氨基酸产生萤光微量测定人血清中游离氨基酸含量的方法。灵敏度可测到1至0.1×10~(-9)克分子氨基酸。每次测定的血清用量为5至10微升。本法具有简单、快速、灵敏的优点。血清中其他含氮物质如脲、尿酸、肌酐和氨对测定无干扰。我国正常人血清的游离氨基酸含量,从52个人测得的平均值为2.83±0.45(S.D)毫克分子/升。此法适用于临床检验和科研。     

Head-down tilt and restraint on renal function and glomerular dynamics in the rat

A model utilizing 25 degree head-down tilt (HDT) and incorporated with chronic catheterization and renal micropuncture techniques in rats was employed to study alterations in renal function induced by HDT. Renal function and extracellular volume measurements were performed after 24 h, 4 days, and 7 days of HDT in conscious rats and compared with their own control measurements and to nontilted but similarly restrained rats. After 24 h HDT, glomerular filtration rate (GFR) increased 19 +/- 8% and renal plasma flow (RPF) increased 18 +/- 8% with increases in urine flow rate, Na+, and K+ excretion in conscious rats. These increases after 24 h were associated with an increase in extracellular volume of 16 +/- 3% (P less than 0.01). In the nontilted controls, there was a decrease in extracellular volume after 24 h of suspension. After 7 days of HDT, GFR was decreased by 7 +/- 1% (P less than 0.01), but RPF and extracellular fluid volume were not different from control values. However, RPF and GFR increased in the nontilted rats after 7 days. After 7 days of HDT renal micropuncture studies demonstrated that single-nephron filtration rate was also decreased from 43 +/- 2 to 31 +/- 3 nl/min (P less than 0.05) due solely to reductions in the glomerular ultrafiltration coefficient (0.11 +/- 0.01 to 0.07 +/- 0.01 nl.s-1 X mmHg-1, P less than 0.05). There was a dissociation between GFR and water and Na+ excretion at days 4 and 7 of HDT not observed in the nontilt restraint controls.     

Kallidin effect on renal tubular function in meclofenamate- and vehicle-pretreated rats

The effect of kallidin (lysyl-bradykinin) on the urinary recovery of sodium-22 was examined in anesthetized, volume-expanded rats. Sodium-22 was microinfused into the lumen of late proximal convoluted tubules with and without kallidin (100 pg/ml). Kallidin enhanced mean sodium-22 recovery from a control of 2.24 +/- 0.29% to 6.22 +/- 1.30% (delta = 3.98 +/- 1.31%, P less than 0.005). The urinary recovery of simultaneously microinfused inulin, mean blood pressure, urine flow, and the rate of tubular infusion were similar during control and kallidin microinfusions. Pretreatment of rats with meclofenamate (3.0 mg/kg) to inhibit renal prostaglandin synthesis blunted, but did not abolish, the effect of kallidin to promote sodium-22 recovery. The changes in sodium recovery induced by kallidin represent a 175 +/- 47% and a 58 +/- 11% increase from control values in vehicle- and meclofenamate-pretreated rats, respectively. The results indicate that kallidin, microinfused in high doses into the lumen of late proximal tubules, may lower sodium efflux in that nephron. Inhibition of prostaglandin synthesis reduced the tubular effect of kallidin, suggesting that enhanced prostaglandin synthesis may contribute to the natriuretic effects of kallidin. Alternatively, meclofenamate may directly oppose the tubular effect of kallidin.     

A micropuncture study of several indices of renal function in rats during development]

The function of single superficial nephrons has been studied by means of several micropuncture methods in 22-, 30- and 42-day rats. It was shown that intratubular hydrostatic pressure, transit time of tubular fluid through a proximal tubule and Henle's loop, as well as local reabsorption in the proximal tubules measured by Gertz's split oil droplet method increase between the 22nd and the 30th days. The ration of tubular fluid and plasma (TF/P) inulin concentrations in late proximal and in early distal tubules increases with age. The values of TF/P for Na in early distal tubules are higher in 22- and 30-day rats than in older ones. TF/P for K does not change simultaneously with that for Na. These data are consistent with the assumption that the sodium load in the distal part of the nephron is higher in young rats than in adult ones.     

Flash photolysis of caged nitric oxide inhibits proximal tubular fluid reabsorption in free-flow nephron

A nonobstructing optical method was developed to measure proximal tubular fluid reabsorption in rat nephron at 0.25 Hz. The effects of uncaging luminal nitric oxide (NO) on proximal tubular reabsorption were investigated with this method. Proximal fluid reabsorption rate was calculated as the difference of tubular flow measured simultaneously at two locations (0.8-1.8 mm apart) along a convoluted proximal tubule. Tubular flow was estimated on the basis of the propagating velocity of fluorescent dextran pulses in the lumen. Changes in local tubular flow induced by intratubular perfusion were detected simultaneously along the proximal tubule, indicating that local tubular flow can be monitored in multiple sites along a tubule. The estimated tubular reabsorption rate was 5.52 +/- 0.38 nl.min(-1).mm(-1) (n = 20). Flash photolysis of luminal caged NO (potassium nitrosylpentachlororuthenate) was induced with a 30-Hz UV nitrogen-pulsed laser. Release of NO from caged NO into the proximal tubule was confirmed by monitoring intracellular NO concentration using a cell-permeant NO-sensitive fluorescent dye (DAF-FM). Emission of DAF-FM was proportional to the number of laser pulses used for uncaging. Photolysis of luminal caged NO induced a dose-dependent inhibition of proximal tubular reabsorption without activating tubuloglomerular feedback, whereas uncaging of intracellular cGMP in the proximal tubule decreased tubular flow. Coupling of this novel method to measure reabsorption with photolysis of caged signaling molecules provides a new paradigm to study tubular reabsorption with ambient tubular flow.     

Possible role of extracellular matrix vesicles in initial calcification of healing rachitic cartilage.

Fluid (20-30 nl) was aspirated by a modified renal micropuncture technique from vitamin D-, phosphate-deficient rats. The fluid revealed a mineral forming agent which could be sedimented at 140,000 X g for 8 hours, was resistant to acid demineralization, but was destroyed by heating, freezing and thawing as well as sonication, and blocked by phospholipase A at 10-5 M but not at 10-7 M. Electron microscopic study of the fluid sediment revealed images consistent with matrix vesicles. These data are consonant with the view that matrix vesicles, their remnants, or closely associated structures comprised the mineral forming agent.     

Glomerular function in spontaneously diabetic rats.

This study was undertaken to determine whether hyperfiltration exists at the single nephron level and whether albumin excretion is increased early in the course of diabetes in Biobreeding rats. Diabetic rats were studied at 8-12 weeks after the onset of diabetes. Control animals were age-matched, diabetes-resistant rats. Urinary and tubular fluid albumin concentrations were measured by polyacrylamide gel electrophoresis. Clearance and micropuncture techniques were used to determine whole kidney and single nephron glomerular filtration rate, renal blood flow, and glomerular capillary pressure. The urinary albumin excretion rate (1.3 +/- 0.1 mg/24 hr) and the tubular fluid albumin concentration (4.7 +/- 0.7 mg/dl) in the diabetic group were significantly elevated when compared with urinary albumin excretion (0.9 +/- 0.1 mg/24 hr) and tubular fluid albumin concentration (2.5 +/- 0.5 mg/dl) in the control group. There were no significant differences in glomerular hemodynamics (whole kidney or single nephron glomerular filtration rate or glomerular capillary pressure) between diabetic and control rats. The kidney weight and kidney weight to body weight ratio were significantly higher in diabetic rats when compared with control rats. Early diabetes in Biobreeding rats is characterized by mild albuminuria and increased kidney size, but not glomerular hyperfiltration.     

Apical and basolateral endocytosis in Madin-Darby canine kidney (MDCK) cells grown on nitrocellulose filters.

Madin-Darby canine kidney (MDCK) cells (strain I) grown on 0.45 micron pore size nitrocellulose filters formed monolayers which were highly polarized and had high transepithelial electrical resistance (greater than 3000 ohm X cm2). Morphometric analysis showed that the area of the basolateral surface domain was 7.6 times larger than that of the apical. The uptake of fluid-phase markers [3H]inulin and horseradish peroxidase (HRP) was studied from the apical and the basal side of the monolayer. Uptake of [3H]inulin was biphasic and the rate during the first 40 min corresponded to a fluid phase uptake of 20.5 X 10(-8) nl/min per cell from the basolateral side, and 1.0 X 10(-8) nl/min per cell from the apical side. Electron micrographs of the monolayers after HRP uptake showed that the marker was rapidly delivered into endosome-like vesicles and into multivesicular bodies. No labelling of the Golgi complex could be observed during 2 h of uptake. Evidence was obtained for the transport of fluid phase markers across the cell. HRP and fluorescein isothiocyanate-dextran crossed the monolayers in either direction at a rate corresponding to approximately 3 X 10(-8) nl of fluid/min/cell. Adding the transcytosis rate to the rate of fluid accumulation into the cell yielded a total basolateral endocytic rate which was 6-fold greater than the apical rate. When the uptake rates were normalized for membrane area the apical and basolateral endocytic rates were about equal per unit cell surface area.     

Elevated interstitial fluid volume in rat soleus muscles by hindlimb unweighting.

Hindlimb unweighting is a commonly used model to study skeletal muscle atrophy associated with disuse and exposure to microgravity. However, a discrepancy in findings between single fibers and whole muscle has been observed. In unweighted solei, specific tension deficits are greater in whole muscle than in single fibers. Also, metabolic enzyme activity when normalized per gram of mass is depressed in whole muscle but not in single fibers. These observations suggest that soleus muscle interstitial fluid volume may be elevated with atrophy caused by unweighting in rats. The purpose of this study was to determine if soleus muscle atrophy induced by unweighting is accompanied by alterations in muscle interstitial fluid volume and to calculate the effect of any such alterations on the muscle specific tension (N/cm2 muscle cross-sectional area). Nine female Wistar rats (200 g) were hindlimb unweighted (HU) by tail suspension. Soleus muscles were studied after 28 days and compared with those from five age-matched control (C) rats. Interstitial fluid volume ([3H]inulin space) and maximum tetanic tension (Po) were measured in vitro at 25 degrees C. Soleus muscles atrophied 58% because of unweighting (C = 147.8 +/- 2.3 mg; HU = 62.3 +/- 3.6 mg, P less than 0.001). Relative muscle interstitial fluid volume increased 107% in HU rats (35.5 +/- 2.8 microliters/100 mg wet mass) compared with the control value of 17.2 +/- 0.5 microliters/100 mg (P less than 0.001); however, absolute interstitial fluid volume (microliters) was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)