Differential bronchodilatory effects of terbutaline, diltiazem, and aminophylline in canine intraparenchymal airways.

OBJECTIVES: Intraparenchymal airways are involved in air flow regulation. Relaxation of intraparenchymal airways to volatile anesthetics varied by topographic location. This study was conducted to determine whether other bronchodilators (terbutaline, diltiazem, and aminophylline) relax bronchiolus to a greater degree than bronchus, as seen with volatile anesthetics. DESIGN: In vitro, controlled, randomized study. SETTING: Animal research laboratory. SUBJECTS: Adult dogs (n = 9). INTERVENTIONS: Proximal (outer diameter, 4-6 mm) and distal (outer diameter, 0.8-1.5 mm) airway rings of dogs were contracted in tissue baths with the effective concentration of acetylcholine that produces half the maximum response. Airway relaxant dose-response curves were constructed to measure isometric tension after administration of terbutaline (concentration range, 10(-8) to 10(-4) M), diltiazem (concentration range, 3 x 10(-7) to 1 x 10(-4) M), and aminophylline (concentration range, 10(-7) to 10(-4) M). MEASUREMENTS AND MAIN RESULTS: All three bronchodilators caused relaxation of the proximal and distal airways. At the maximum dose, diltiazem (maximum relaxation, 95%+/-2% [proximal], 94%+/-6% [distal]; p > .05) was the most efficacious, followed by terbutaline (maximum relaxation, 72%+/-13% [proximal], 55%+/-9% [distal]; p < .05) and aminophylline (maximum relaxation, 32%+/-10% [proximal], 35%+/-18% [distal]; p > .05. At the concentrations tested, they were equally efficacious. No significant differences in relaxation between proximal and distal airways were noted with diltiazem or aminophylline in the entire dose range. However, terbutaline relaxed the distal airway more than the proximal airway in the entire dose range. CONCLUSIONS: The results demonstrate that only terbutaline showed a differential airway relaxant effect between proximal and distal airways, as seen with volatile anesthetics.     

EZ-IO in the ED: an observational,prospective study comparing flow rates with proximal and distal tibia intraosseous access in adults

Introduction

Intraosseous (IO) access is an important alternative to conventional intravenous access when intravenous access is difficult.

Methods

A nonrandomized, prospective, observational study comparing flow rates with distal and proximal tibia IO access in adults using the EZ-IO–powered drill device. The proximal tibia was the first site of insertion, and a second IO was inserted in the distal tibia if clinically indicated. Intravenous saline infusion was started for all patients, initially without, then with a pressure bag device applied.

Results

From September 19, 2008 to November 3, 2010, 22 patients were recruited, with 20 proximal tibial and 22 distal tibia insertions. Two patients had only distal tibia IO insertions. Five distal tibia and 3 proximal tibia insertions had no flow when initiating normal saline infusion without pressure. Upon comparing the mean flow rates without pressure bag, it is significantly faster in the proximal tibia, 4.96 mL/min, compared with distal tibia, 2.07 ml/min, difference of 2.89 ml/min (95% CI 1.20-4.58). Flow rates with pressure bags also revealed a similar result. Flow rates in the proximal tibia were significantly faster, 7.70 ml/min to that of distal tibia, 3.80 ml/min, difference of 3.89 ml/min (95% CI 1.68-6.10). In both proximal and distal tibia groups, the flow rates are also significantly faster with pressure bags compared with without.

Conclusion

Flow rates are significantly faster in the proximal tibia compared with the distal tibia. In addition, flow rates with pressure bags are significantly faster than without pressure bags in both groups.     

Greater activation of smooth muscle alpha-2 adrenoceptors by epinephrine in distal than in proximal segments of rat tail artery

The effects of selective blockade of alpha-1 and alpha-2 adrenoceptors on the vasoconstrictor responses to epinephrine (EPI) and norepinephrine (NOR) were compared in perfused/superfused proximal and distal segments of rat tail artery. The influence of neuronal uptake and of activation of beta adrenoceptors was also investigated. EPI was more potent in distal than in proximal segments. The antagonistic effect of idazoxan (100 nM) against EPI was greater in distal than in proximal segments, whereas the opposite result was obtained with prazosin (0.1-10 nM). No such difference were observed when NOR was used as agonist. Reducing the calcium ion concentration had a greater inhibitory effect on EPI in distal than in proximal segments. Cocaine (4 microM) increased responses to EPI and NOR to a greater extent in proximal than in distal segments. In the presence of cocaine, in proximal segments, antagonism of EPI by prazosin was reduced, whereas in distal segments, antagonism by idazoxan and the inhibitory effect of a reduction in calcium ion concentration were reduced. Propranolol (1 microM) increased responses to EPI and NOR to a greater extent in proximal than in distal segments. In the presence of propranolol, antagonism of EPI by both prazosin and idazoxan was reduced in proximal segments, and the inhibitory effect of a reduction in calcium ion concentration was lost. Forskolin (1 microM) inhibited responses to EPI and prevented the antagonistic effect of idazoxan, but not that of prazosin. From the results obtained it is suggested that smooth muscle alpha-2 adrenoceptors are distributed differently in the proximal and distal ends of the rat tail artery.(ABSTRACT TRUNCATED AT 250 WORDS)     

Analysis of proximal and distal muscle activity during handwriting tasks.

OBJECTIVE: In this study we sought to describe upper-extremity proximal and distal muscle activity in typically developing children during a handwriting task and to explore the relationship between muscle activity and speed and quality of writing. METHOD: We evaluated 35 third- and fourth-grade Israeli children using the Alef-Alef Ktav Yad Hebrew Handwriting Test. Simultaneously, we recorded the participants' upper trapezius and thumb muscle activity by surface electromyography. Using the coefficient of variation (standard deviation divided by mean amplitude) as a measure of variability within each muscle, we analyzed differences in muscle activity variability within and between muscles. RESULTS: The proximal muscle displayed significantly less variability than the distal muscles. Decreased variability in proximal muscle activity was associated with decreased variability in distal muscle activity, and decreased variability in the distal muscles was significantly associated with faster speed of writing. CONCLUSION: The lower amount of variability exhibited in the proximal muscle compared with the distal muscles seems to indicate that the proximal muscle functions as a stabilizer during a handwriting task. In addition, decreased variability in both proximal and distal muscle activity appears to be more economical and is related to faster writing speed. Knowledge of the type of proximal and distal muscle activity used during handwriting can help occupational therapists plan treatment for children with handwriting disabilities.     

Urapidil,but not dihydropyridine calcium channel inhibitors,preserves the hypoxic pulmonary vasoconstriction: an experimental study in pig arteries

Hypoxic pulmonary vasoconstriction (HPV) is a protective mechanism maintaining blood oxygenation by redirecting blood flow from poorly ventilated to well‐ventilated areas in the lung. Such a beneficial effect is blunted by antihypertensive treatment with dihydropyridine calcium channel inhibitors. The aim of the present study was to evaluate the effect of urapidil, an antihypertensive agent acting as an α₁ adrenergic antagonist and a partial 5‐HT_1A agonist, on HPV in porcine proximal and distal pulmonary artery rings, and to characterize underlying mechanisms. Rings from proximal and distal porcine pulmonary artery were suspended in organ chambers and aerated with a 95% O₂ + 5% CO₂ gas mixture. HPV was induced by changing the gas to a 95% N₂ + 5% CO₂ mixture following a low level of pre‐contraction with U46619. Hypoxia induced a contractile response in both proximal and distal pulmonary artery rings. This effect is observed in the presence of a functional endothelium and is inhibited by a soluble guanylyl cyclase inhibitor (ODQ), a NO scavenger (carboxy‐PTIO), and by catalase in proximal pulmonary artery rings. The endothelium‐dependent HPV is prevented by nicardipine and clevidipine but remained unaffected by urapidil in both proximal and distal pulmonary artery rings. These findings indicate that urapidil, in contrast to nicardipine and clevidipine, preserves the hypoxia‐triggered vasoconstriction in isolated pulmonary arteries. They further indicate the involvement of the NO‐guanylyl cyclase pathway and H₂O₂ in HPV. Further research is warranted to determine the potential clinical relevance of the preserved hypoxia‐induced pulmonary vasoconstriction by urapidil.     

Segmental nephron function in rats treated with aprotinin, an inhibitor of kallikrein

The effects on kidney function of aprotinin, an inhibitor of kallikrein and other serine proteinases, were investigated in rats made diuretic by infusion of 0.9% saline. Late proximal, early distal and late distal tubular fluid samples were collected before and after aprotinin administration (20,000 kallikrein I.U./kg b.wt. i.v.). Glomerular filtration rate and urinary excretion of solute and water were assessed simultaneously. Aprotinin did not alter blood pressure or glomerular filtration rate, but reduced urine flow from 23.8 +/- 4.5 to 16.4 +/- 3.4 microliter min-1 100 g-1 (P less than .05) and urinary kinin excretion from 23.5 +/- 3.2 to 10.8 +/- 1.9 pg min-1 100 g-1 (P less than .01). Aprotinin increased the tubular fluid to plasma inulin concentration ratio at late distal tubule puncture site, but not at late proximal or early distal tubule collection sites. Estimates of fluid reabsorption in the distal convoluted tubule, expressed as a percentage of glomerular filtration rate, as a percentage of delivery to this nephron segment or as net volume transported, increased after the administration of aprotinin by 22, 24 and 23% (P less than .05), respectively. In contrast, aprotinin did not alter the estimates of fluid reabsorption in the proximal convoluted tubule, the loop of Henle or the collecting tubule. We conclude that the antidiuretic effect of aprotinin in saline-expanded rats is related to selective augmentation of fluid reabsorption in the distal convoluted tubule. This effect of aprotinin may be the expression of reduced renal kinin levels, inhibition of serine proteases other than kallikrein or other unrecognized properties of the agent.     

基于“心肌桥-冠状动脉”模拟装置的切应力研究

背景：在动脉粥样硬化的研究领域,由于人体血液动力学环境的复杂性,动脉粥样硬化与血流动力学壁面切应力的相关性难以作出确切定论。 目的：模拟心肌桥-冠状动脉装置,分析壁冠状动脉血液动力学参数的变化特征与动脉粥样硬化间的关系。 方法：采用心肌桥-冠状动脉模拟装置进行体外模拟实验,保持系统温度、平均流量和心率等相关参数不变,调节心肌桥对壁冠状动脉的压迫程度,观察并记录壁冠状动脉近端和远端切应力平均值和震荡值的变化情况。 结果与结论：0%压迫时,壁冠状动脉近端和远端的切应力平均值和震荡值差异均不显著;50%压迫时,近端切应力震荡值明显大于远端;80%压迫时,远端切应力平均值大于近端,近端切应力震荡值大于远端。随压迫程度的增加,切应力的平均值远端高于近端,而震荡值近端高于远端。提示壁冠状动脉近端切应力震荡值的升高是导致其动脉粥样硬化发生的重要因素。     

Differential permeability of the proximal and distal rabbit small bowel

The permeability of the proximal and distal rabbit intestine for two to six carbon polyhydric alcohols was compared. Intestinal segments were mounted in chambers that permitted the measurement of the unidirectional flux across the brush border membrane. For both proximal and distal intestine, the permeability for a series of polyhydric alcohols decreased with increasing size. The proximal intestine was more permeable for four, five, and six carbon polyhydric alcohols than distal intestine. This regional permeability difference can be attributed to variations in the permeability characteristics of the brush border specifically. The uptake of alcohols was nonsaturable and was not inhibited by phlorizine or n-ethylmaleimide. The results are compatible with the concept that the brush border membrane has properties similar to artificial porous membranes and that the equivalent radius of the pores of the proximal intestine exceeds that of the distal gut.     

Functional correlates of compensatory renal hypertrophy

The functional correlates of compensatory renal hypertrophy were studied by micropuncture techniques in rats after the removal of one kidney. The glomerular filtration rate increased to roughly the same extent in the whole kidney and in individual surface nephrons, resulting in a greater amount of sodium delivered to the tubules for reabsorption. The fraction of the glomerular filtrate absorbed [determined from the tubular fluid-to-plasma ratio (TF/P) for inulin] remained unchanged in both proximal and distal portions of the nephron. The way in which the tubules adjusted to nephrectomy, however, differed in proximal and distal convolutions. After nephrectomy, the reabsorptive half-time, indicated by the rate of shrinkage of a droplet of saline in a tubule blocked with oil, was unchanged in the proximal tubule but significantly shortened in the distal convoluted tubule. Nevertheless, steady-state concentrations of sodium in an isolated raffinose droplet in the distal as well as the proximal tubule were the same in hypertrophied kidneys as in control animals. Possible reasons for this paradox are discussed.Transit time through the proximal tubules was unchanged by compensatory hypertrophy, but transit time to the distal tubules was prolonged.Changes in renal structure resulting from compensatory hypertrophy were also found to differ in the proximal and the distal protions of the nephron. Although tubular volume increased in both protions, the volume increase was twice as great in the proximal tubule as in the distal. In order, therefore, for net reabsorption to increase in the distal tubule, where the changes in tubular volume are not so marked, an increase in reabsorptive capacity per unit length of tubule is required. This increase is reflected in the shortening of reabsorptive half-time in the oil-blocked distal tubule that was actually observed.     

Contribution of individual superficial nephron segments to ammonium handling in chronic metabolic acidosis in the rat. Evidence for ammonia disequilibrium in the renal cortex.

Ammonia entry along surface nephron segments of rats was studied with micropuncture techniques under control and chronic metabolic acidosis conditions. Tubule fluid was collected successively from sites at the end and beginning of the distal tubule and at the end of the proximal tubule of the same nephron. During chronic metabolic acidosis, ammonium excretion doubled. As anticipated, the ammonium concentration (TFNH+4) was significantly higher in proximal tubule fluid during acidosis, and ammonium delivery to end proximal sites increased from 19.4 +/- 2.3 to 34.0 +/- 3.2 pmol/min (P less than 0.001). Although chronic acidosis did not affect TFNH+4 at the beginning of the distal tubule, ammonium delivery to the end of the distal tubule increased from 5.72 +/- 0.97 to 9.88 +/- 0.97 pmol/min. In both control and acidotic groups ammonium delivery was lower (P less than 0.001) to end distal sites than to end proximal sites, indicating net loss in the intervening segment. This loss was greater during chronic metabolic acidosis (23.9 +/- 3.3 vs. 13.6 +/- 2.0 pmol/min in controls, P less than 0.025). In both groups net entry of ammonia, in similar amounts, occurred along the distal tubule (P less than 0.05). In situ pH averaged 6.80 +/- 0.05 at end proximal tubule sites and fell to 6.54 +/- 0.08 at the beginning of the distal tubule (P less than 0.005). Chronic metabolic acidosis did not affect these measurements. The calculated free ammonia at the end of the proximal tubule rose from 9.3 +/- 2.2 to 21 +/- 9 microM (P less than 0.005) during chronic metabolic acidosis, and was also higher at beginning distal sites during acidosis (8.8 +/- 2.4 vs. 2.7 +/- 0.7 microM in controls, P less than 0.05). In both groups ammonia values for the beginning distal tubule fluid were lower than for end proximal tubule fluid. Thus, loss of ammonium in the loop segment is enhanced by chronic metabolic acidosis. Distal entry of ammonia is markedly less than along the proximal tubule and does not change in chronic metabolic acidosis, and ammonia permeabilities for the proximal and distal segments of surface nephrons seem different.     

Distal tubular feedback in the autoregulation of single nephron glomerular filtration rate

Renal clearance and recollection micro-puncture experiments were conducted to evaluate the possible role of a distal tubular feedback mechanism in the phenomenon of renal autoregulation in dogs. Single nephron glomerular filtration rate (SNGFR) was measured from collection sites in both the proximal (proximal SNGFR) and distal tubules (distal SNGFR). Single nephron autoregulatory behavior was assessed by evaluating the response of SNGFR to a reduction in renal arterial pressure imposed by means of an aortic constrictor. Whole kidney function was evaluated by parallel measurements of renal blood flow and inulin clearance. Whole kidney autoregulation was observed when renal arterial pressure was decreased from 141 +/- 3 (SE) mm Hg to 101 +/- 2 mm Hg; renal blood flow and GFR were not significantly altered from control values of 3.76 +/- 0.2 ml/min.g and 0.69 +/- 0.04 ml/min.g kidney weight, respectively. In 11 autoregulating preparations, proximal transit time was likewise unchanged from the control value of 26 +/- 2 s, indirectly suggesting that the superficial nephrons also participated in the autoregulatory response. However, proximal SNGFR decreased significantly from 88 +/- 7 nl/min to 66 +/- 6 nl/min, a reduction which was proportional to the decrease in arterial pressure. In 14 dogs in which both proximal SNGFR and distal SNGFR were measured at control blood pressure (136 +/- 5 mm Hg), distal SNGFR was 47 +/- 4 nl/min, a value significantly lower than that for proximal SNGFR (79 +/- 6 nl/min). In contrast to the results based upon proximal collections, distal SNGFR was not significantly altered following aortic constriction (44 +/- 5 nl/min vs. 47 +/- 5 nl/min) therefore exhibiting autoregulation in association with that observed for the whole kidney. These experiments indicate that though superficial nephrons do possess autoregulatory capability, interruption of distal delivery due to complete collection from the proximal tubule interferes with that nephron's ability to manifest an autoregulatory response. They support the concept that a feedback mechanism, related to some function of distal delivery, is of significance in the intrinsic regulation of SNGFR. The data further suggest that quantitative estimates of SNGFR based on complete proximal collections may not be representative of those throughout the superficial cortex of the dog, at least in certain experimental circumstances.     

Calcium uptake by intestinal brush border membrane vesicles. Comparison with in vivo calcium transport.

In prior studies, we examined kinetics of steady state in vivo transepithelial calcium transport in rat and hamster. The present studies related calcium uptake by the brush border to in vivo transport. We measured calcium uptake by brush border membrane vesicles from the two species. In the rat, our prior in vivo studies had shown that (a) calcium transport was mediated, (b) no nonmediated component was detectable, and (c) Vmax was 2.5 times greater in proximal than distal small intestine. In brush border membrane vesicles from the rat, Vmax for the saturable component of calcium uptake was again 2.5 times greater in proximal than distal intestine. Contrasting with in vivo studies, a major nonsaturable component was present in vesicles from proximal and distal small intestine. In the hamster, our previous in vivo studies had shown (1) both mediated and nonmediated components of calcium transport, (2) greater nonmediated transport in proximal than distal small intestines, and (3) Vmax for calcium transport twice as great in distal as in proximal small intestine. In the present study with brush border membrane vesicles from hamster, Vmax for saturable calcium transport was again twice as great in distal as in proximal small intestine. However, nonsaturable calcium transport rates relative to saturable rates were much greater with vesicles than in in vivo studies, and were greater in vesicles from distal than proximal small intestine. Since rates of saturable calcium uptake by brush border membrane vesicles parallel corresponding in vivo mediated transport rates, we conclude that the segmental rates of calcium transport in rat and hamster could be determined by brush border function.     

Dose dependence of proximal and distal tubular effects of furosemide in conscious rats

The dose-response relationship for the diuretic effect of furosemide, given as i.v. bolus injections (0.1-480 mg/kg) was investigated by clearance technique in conscious rats. By measuring the renal Li clearance, the effects on proximal and distal nephron segments were separated, and peak responses were correlated to the maximal excretion rate of furosemide in the urine. At the highest dose of furosemide, fractional Na excretion was increased from 1 to 19%, due to inhibition of fractional proximal Na reabsorption from 65 to 40% and fractional distal Na reabsorption from 97 to 57%. Furosemide inhibition of fractional proximal Na reabsorption showed a maximum at intermediate doses (7.5 mg/kg), whereas there was no maximum for the inhibition of distal fractional Na reabsorption. The natriuretic response was shorter than expected from the decline in furosemide excretion due to an abrupt fall in glomerular filtration rate and a rapid normalization of proximal fractional Na reabsorption. It is suggested that the maintenance of a normal delivery of tubular fluid to the distal nephron during furosemide-induced volume contraction may be due to inhibition of proximal tubular reabsorption.     

冠状动脉搭桥术前后内乳动脉桥及左前降支远段血流动力学改变的超声研究

目的应用常规超声结合冠脉血流显像技术观察分析冠状动脉搭桥术前后内乳动脉桥及远段左前降支血流动力学改变.方法行冠状动脉搭桥术患者46例,于手术前后超声检查左内乳动脉,其中38例患者检查左前降支远段.结果术后内乳动脉桥起始段显示率95.65%, 由术前收缩期优势型转变为术后舒张期优势型频谱.左前降支远段血流信号表现为流速及流速时间积分增加.结论常规超声结合冠脉血流显像技术可为冠状动脉搭桥术后随访提供一种无创的方法.     

Nonuniformity of AH Intervals During Stimulation at Different Left Atrial Sites

Studies in humans have found left atrial stimulation via the coronary sinus (CS) to elicit significantly shorter atrium-His (AH) intervals as compared to right atrial stimulation, but whether pacing at dijferent left atrial sites (anterior vs posterior left atrium, i.e., far distal vs proximal CSJ affects the AH interval has not been studied. Hence, in 22 patients, we compared the effects of stimulation from various atriai sites, including anterior high right atrium (HRA), distal CS, mid-CS, and proximal CS, on; stimulus-atrium (SA), AH, and stimuIus-His intervals on the His bundle electrogram. Paced cycle length differed for each patient (range 900–350 msec, mean 532 ± 140 msec), but conduction intervals from different atrial sites were compared using identical cycle length in each patient. The mean SA intervals were 34 ± 10 msec, 57 ± 10 msec, 44 ± 11 msec, and 32 ± 8 msec with stimulation, respectively, from HRA, distal CS, mid-CS. and proximal CS (each significantly different except for HRA vs proximal CSJ. The mean AH intervals were 123 ± 23 msec, 104 ± 28 msec, 95 ± 15 msec, and 90 ± 18 msec with stimulation, respectively, from HRA, distal CS, mid-CS, and proximal CS (each significantly different except for mid-CS vs proximal CSJ. In 13 patients, the discrepancy in AH intervals during distal versus proximal CS stimulation was > 15 msec; in 9 patients this difference was only < 10 msec, considered within the range of measurement error. Thus, in a significant portion of patients, discrepant AH intervals were demonstrated during stimulation from the distal versus proximal CS. These previously undescribed observations suggest that electrophysiological studies on atrioventricular nodal conduction that involve left atrial stimulation must take into account actual location of the stimulation site (anterior or posterior) in order to properly interpret the findings.     

An Illusion of Proximal Radiation of Pain Due to Distally Directed Inhibition

The perceived site of pain can frequently radiate from the site of tissue injury. However, the mechanisms supporting spatial aspects of cutaneous pain radiation remain poorly understood. Such mismatches between the actual location and the perceived location of stimuli are also found across other somatosensory modalities. During simultaneous innocuous stimulation at multiple sites, proximal stimuli are perceived as more intense than distal stimuli. To determine if pain radiates in a predominantly proximal direction, 20 subjects rated pain intensity from simultaneously applied pairs of noxious (49°C) thermal stimuli. Proximal and distal stimuli were each rated separately. As the distance between probes was decreased, pain from the proximal site increased relative to that arising from the distal site. Comparisons between paired stimuli and single control (49°C) stimuli revealed that pain arising from the distal stimulus site was inhibited. This distally directed inhibition produced an illusion that pain radiates in a proximal direction. The proximal radiation/distal inhibition of pain observed in the present investigation may represent a perceptual “copy” of neural information used to modulate withdrawal responses. Thus, supraspinally mediated responses to pain can be coordinated with spinally mediated withdrawal reflexes.PerspectiveRadiation of pain is a perplexing clinical problem. The present findings indicate that the perceived location of pain may be shaped by inhibitory as well as facilitatory processes.     

Carbonic anhydrase IV expression in rat and human gastrointestinal tract regional, cellular, and subcellular localization.

Carbonic anhydrase IV (CA IV) is a glycosylphosphatidylinositol-linked isozyme previously identified on the surface of renal tubular epithelium and certain populations of vascular endothelium. This report identifies the regional, cellular, and subcellular localization of CA IV in the rat gut. Northern blot and RT-PCR analyses demonstrated little CA IV expression in stomach or proximal small intestine, but abundant expression in distal small and large intestine. In contrast, CA II mRNA was abundant in stomach, decreased in proximal small intestine, low in distal small intestine, and abundant in large intestine. CA I mRNA was detected only in large intestine. The regional distribution of CA IV activity correlated with distribution of CA IV mRNA. Immunohistochemistry localized CA IV to the apical plasma membrane of the mucosal epithelium in distal small intestine and large intestine. Signal intensity was greatest in colon. CA IV was additionally found in submucosal capillary endothelium of all gastrointestinal regions. Immunohistochemical findings in human stomach and colon paralleled those in the rat. These studies demonstrate pre-translational isozyme-specific regulation of CA expression along the cranial-caudal axis of the gastrointestinal tract. The regional, cellular, and subcellular localizations are consistent with participation of CA IV in the extensive ion and fluid transport in the distal small and large intestine.     

D-dimer levels in VTE patients with distal and proximal clots

Objectives

There is growing evidence that venous thromboembolism (VTE) patients with distal clots (distal calf deep vein thrombosis [DVT] and sub-segmental pulmonary embolism [PE]) may not routinely benefit from anticoagulation. We compared the D-dimer levels in VTE patients with distal and proximal clots.

Some failings of pulsatility index and damping factor

Pulsatility index (PI) is a commonly used method of objective assessment of the Doppler waveform. PI falls with increasing proximal stenosis and is raised by increasing peripheral resistance. Damping factor (DF) for an arterial segment is calculated by dividing the proximal by the distal PI. DF rises with increasing severity of disease of the arterial segment. DF is not, however, sufficiently accurate to be used alone but is usually combined with transit time measurements to provide information of diagnostic use. Both PI and DF have been examined in a canine model of combined segment disease. With increasing stenosis, distal PI falls as expected but so also does proximal PI. Such a stenosis is, in effect, a flow-throttling resistance so that although the characteristics of blood flow are altered by its presence, similar changes are observed both above and below the stenosis. The reduction of PI by a stenosis distal to the insonation site may result in the false interpretation of a low PI as indicating disease proximal to the insonation site. The observed similarity between PI proximal and distal to a stenosis reduces the usefulness of pulsatility index damping factor, particularly in the assessment of the femoro-popliteal segment in combined segment disease.     

Repair of the duodenal mucosa following acid damage. A protective mechanism as an approach to new therapeutic principles?

Epithelial repair after luminal acid exposure was studied in the rabbit duodenum in vivo, HCl (200 mM for 30 min) caused uniform damage of the mucosa confined to the villi, 50% of the total villus height was affected by the acid-induced lesion in the proximal, and 70% in the distal duodenum. After demarcation and detachment of the necrotic tissue the defect was bridged by the remaining viable epithelial cells underneath a layer of mucus and necrotic debris (= necrotic layer). Mucosal repair resulted in a reduction of villus height by 62% in the proximal, and 77% in the distal duodenum. This process of mucosal repair progressed continuously, so that 9 hours after acid damage only 33% of villi in the proximal, and 41% in the distal duodenum were not yet fully restored, irrespective of luminal pH(pHL = 7 or pHL = 3). The difference between proximal and distal duodenum is due to the higher acid susceptibility of the distal duodenum. Rapid epithelial repair of the duodenal mucosa in vivo provides an important protective mechanism against the aggression from luminal acid.