Validation of a revised slow-stop flow recirculation method

Slow flow/stop flow methods have replaced the three needle technique as methods of choice for measuring recirculation. However, the time delay after reducing blood flow may affect the BUN in the systemic (slow flow/stop flow arterial line) sample and therefore limit the accuracy of this methodology. It has been observed that recirculation does not occur in a properly cannulated access unless the access blood flow rate is less than the dialyzer blood flow rate (BFR). This suggests that the systemic sample could be obtained at a higher than usual blood pump rate. We studied 50 patients and compared a revised slow-stop flow (S/SF) recirculation technique in which the systemic sample was drawn after the blood pump rate was reduced to 120 ml/min for 10 seconds and then stopped, to a non-urea based method that utilized indicator velocity dilution (IVDM). Seven patients were found to have recirculation by IVDM; all had recirculation by S/SF of more than 10% (minimum 16.7%) and an access BFR that was less than the dialyzer BFR. In the 43 patients without recirculation by IVDM, the mean recirculation by S/SF was 1.9 +/- 3.2% (mean +/- SD). Five patients without recirculation by IVDM had more than 5% recirculation by S/SF (range, 5.9 to 8.3%). Although there was a small systematic tendency to overestimate recirculation, this modified urea based method was still able to detect recirculation with good reliability. Single values above 10% are highly likely to indicate the presence of true recirculation. Repeated values over 5%, are also likely to be significant, indicating the presence of true recirculation and its clinical correlate, marginal access blood flow.     

Cardiovascular response to sudden strenuous exercise: an exercise echocardiographic study

We studied the response in left ventricular (LV) internal dimensions and posterior wall thickness during the performance of sudden strenuous exercise without warm-up (SSE) and sudden strenuous exercise with warm-up (SSEw) in 15 healthy, untrained college-aged males (26 +/- 5.0 yr). Measurements of left ventricular end-diastolic dimension (LVEDD), left ventricular end-systolic dimension (LVESD), stroke dimension (SD = LVEDD-LVESD), fractional shortening (FS = SD/EDD) and posterior wall thickness (PWT) were obtained from continuous 2-D targeted on M-mode echocardiography. Continuous EKG and blood pressure were obtained at rest and during the final 10 s of SSE (30 s of upright leg cycle ergometry of 400 W at 80 rpm). SSEw was preceded by warm-up exercise (6 min of graded leg cycle exercise of 2-min stages initial load 30 W, increasing in 30-W increments at 60 rpm, followed immediately by SSE). Our findings revealed that there were no significant differences in the LV internal dimensions (LVEDD, LVESD, FS, PWT), HR max, RPP max, ECG, and MAP max between SSE and SSEw. Sudden strenuous exercise without warm-up is not associated with a reduced LV function. The results of this study are contradictory to previous findings that have suggested that SSE is associated with transient global left ventricular (LV) dysfunction.     

Prediction of gas‐liquid two‐phase mixture flow in a vertical pipe with a sudden expansion in diameter

The principle of gas‐lift pumps is applied to vacuum‐decarburization with the RH (Ruhrstahl Heraeus) process to circulate molten steel. Gas‐lift pumps are also applicable to the transportation of molten iron/steel between different refining processes. This paper treats theoretical analysis of steady‐state flow characteristics of gas‐liquid two‐phase mixtures rising in a vertical pipe with an abrupt expansion of its diameter. The system of governing equations is based upon a one‐dimensional multi‐fluid model. Flow pattern transitions are taken into consideration. A new numerical procedure to predict the flow characteristics at the sudden expansion has been proposed. Experiments have also been performed for several conditions to confirm the applicability as well as the validity of the present numerical model. It has been found that the predictions agree reasonably well with the experimental data. Next, the effect of the sudden expansion of pipe diameter on the pump performance was investigated numerically. As a result, it has been confirmed that the sudden expansion of pipe diameter contributes to improve the pump efficiency.     

Vascular endothelium in the regulation of immune response

Endothelial cells cover the entire system of arteries, veins, and lymphatics of the human body. Once viewed as a passive coat, we now know that they represent by themselves a large immunologically active system. In this work, we briefly review endothelial cell models and heterogenicity before interrelating endothelial cells with the immune system. In the latter context, we focus on the role of cytokines and that of the five families of cell adhesions molecules.     

Treatment response to maxillary expansion and protraction

A prospective clinical trial was conducted to determine the skeletal and dental contributions to the correction of overjet and overbite in Class III patients. Thirty patients (12 males and 18 females with a mean age of 8.4 +/- 1.7 years) were treated consecutively with protraction headgear and fixed maxillary expansion appliances. For each patient, a lateral cephalogram was taken 6 months before treatment (T0); immediately before treatment (T1); and 6 months after treatment (T2). The time period (T1-T0) represented changes due to 6 months of growth without treatment; (T2-T1) represented 6 months of growth and treatment. Each patient served as his/her own control. Cephalometric analysis described by Bj?rk (1947) and Pancherz (1982a,b) was used. Sagittal and vertical measurements were made along the occlusal plane (OLs) and the occlusal plane perpendicular (OLp), and superimposed on the mid-sagittal cranial structure. The results revealed the following: with 6 months of treatment, all subjects were treated to Class I or overcorrected to Class I or Class II dental arch relationships. Overjet and sagittal molar relationships improved by an average of 6.2 and 4.5 mm, respectively. This was a result of 1.8 mm of forward maxillary growth, a 2.5-mm of backward movement of the mandible, a 1.7-mm of labial movement of maxillary incisors, a 0.2-mm of lingual movement of mandibular incisors, and a 0.2-mm of greater mesial movement of maxillary than mandibular molars. The mean overbite reduction was 2.6 mm. Maxillary and mandibular molars were erupted occlusally by 0.9 and 1.4 mm, respectively. The mandibular plane angle was increased by 1.5 degrees and the lower facial height by 2.9 mm. Individual variations in response to maxillary protraction was large for most of the parameters tested. Significant differences in treatment changes between male and female subjects were found only in the vertical eruption of mandibular incisors and maxillary and mandibular molars. These results demonstrate that significant overjet and overbite corrections can be obtained with 6 months of maxillary protraction in combination with a fixed expansion appliance.     

Homogeneous nucleation of liquid from the vapor phase in an expansion cloud chamber

A Wilson expansion cloud chamber has been used to measure the homogeneous vapor-to-liquid nucleation of several materials over the past decade. These data, representing nucleation rate as a function of temperature and supersaturation ratio for toluene, nonane, and water measured in our center, have been re-examined and are presented both in graphical form and as a table of selected data points. The latter is included for ease of comparison with theory. Measurements of the binary homogeneous nucleation of ethanol-water (E-W) mixtures are also presented. The expansion chamber experimental technique and data reduction technique are discussed. This paper is based on a presentation made in the “G. Marshall Pound Memorial Symposium on the Kinetics of Phase Transformations” presented as part of the 1990 fall meeting of TMS, October 8–12, 1990, in Detroit, MI, under the auspices of the ASM/MSD Phase Transformations Committee.     

Characterization of a tobacco epoxide hydrolase gene induced during the resistance response to TMV

CD4 is the primary receptor for the human immunodeficiency virus (HIV). Nef is an accessory protein of HIV that decreases the expression of CD4 on the surface of infected cells. In this study, we identified the Nef binding protein 1 (NBP1), which interacts specifically with Nef in vitro and in vivo. Since it shares sequence similarity with the catalytic subunit of the vacuolar ATPase (V-ATPase) and complements the loss of this VMA13 gene in yeast, NBP1 is the human homolog of Vma13p. Direct interactions between Nef and NBP1 were correlated with the ability of Nef to internalize CD4. The expression of the antisense NBP1 abrogated these effects. We conclude that NBP1 helps to connect Nef with the endocytic pathway.     

Role of gender and vascular endothelium in rat aorta response to 17 beta-estradiol

Estrogen supplementation in postmenopausal women offers significant cardiovascular protection. The mechanism for this benefit is unclear but may be due to an interaction of estrogen with the blood vessel wall (vascular smooth muscle and endothelium). We examined the response of weight-matched female and male endothelium-intact and -denuded aortae to 17 beta-estradiol, its interaction with noradrenaline, and the effect of N-nitro-L-arginine. Estradiol produced relaxation responses that were significantly greater in female endothelium-intact preparations. This response was sensitive to N-nitro-L-arginine, while the response to 17 beta-estradiol in male endothelum-intact and both female and male endothelum-denuded preparations was resistant. Estradiol also inhibited contractions to noradrenaline, which was more pronounced in the female endothelium-intact aortic rings. These data imply that estradiol interacts preferentially with the female vascular endothelium, but there exists an endothelium-independent process that can also be activated in the male aorta. Further studies are warranted to elucidate these differential mechanisms.     

Characterization of the rat myometrial contractile response to neuropeptide Y

The in vitro contractile effect of neuropeptide Y (NPY) on rat myometrial strips was for the first time demonstrated and characterised, and the EC50 value estimated to be 267 +/- 87 nM. This effect is presumably mediated by the NPY1 receptor being responsible for postsynaptic effects throughout the peripherial nervous system, thus indicating a direct uterotonic effect of NPY. Further, the effect was demonstrated to the dependent on extracellular Ca2+. Short-term exposures to NPY markedly desensitized the tissue affecting subsequent responses to NPY as well as to oxytocin (OT). This desensitization was time and concentration-dependent, but lasted less than three hours. However, long-term infusions of NPY for 5 days increased to response to both NPY and OT. Long-term infusions of OT caused a marked decrease of the NPY response, and it is concluded that common pathways for up and down regulation of the myometrial responsiveness to several peptide hormones may exist.     

前混合磨料水射流除鳞喷嘴混合腔内部流场

基于计算流体动力学多相流混合物模型,应用FLUENT软件对前混合磨料水射流除鳞喷嘴高压水与磨料混合腔内部流场进行数值模拟.比较了不同进料方式对流场均匀性的影响.分析了两侧为高压水入口条件下,磨料入口直径、高压水入口直径、高压水入口位置和角度以及收缩段锥角对流场混合均匀性的影响,得到了影响混合腔内部流场混合均匀性的合理结构参数.数值计算结果表明：入口速度一定的条件下,磨料中进式喷嘴混合腔的混合均匀性优于磨料侧进式喷嘴混合腔.随磨料入口和高压水入口直径增加,混合腔出口的射流速度均增加,但随高压水入口直径增加导致出口磨料浓度呈先增后减的趋势,磨料入口与高压水入口合理的质量流量比值约为3∶4,两侧高压水入口位置对流场混合均匀性影响较小,高压水入口角度和收缩段锥角均为30°时流场性能更佳.     

The response of human tumour blood flow to a fractionated course of thermoradiotherapy

The response of human tumour blood flow to a fractionated course of thermoradiotherapy was documented in four superficial but bulky tumours (three adenocarcinomas, one melanoma). Blood flow was measured 15, 30, 45, and 60 min after the onset of heating. These measurements were made at the same intra-tumour point during each heat fraction by use of a modified thermal clearance technique in which a correction was made for the heat dissipated by thermal conduction. This point was at least 2 cm beneath the surface in the central portion of the tumour. Extracellular pH was measured within 1 cm of this point prior to the first heat fraction and 2-3 weeks later. Hyperthermia was administered for 60 min, twice a week for 4 weeks by use of a 16-channel 915 MHz microwave applicator. Each patient also received a radiation dose of 40 Gy fractionated at 2 Gy/fx, five times a week (adenocarcinomas) or 4 Gy/fx, twice a week (melanoma). Blood flow remained relatively constant during heating after steady state conditions were attained. However, an overall decrease in tumour blood flow was observed in each patient over the course of thermoradiotherapy. In each case, a relatively small decrease in blood flow occurred between most heat fractions which resulted in an overall decrease which ranged from 50-100%. However, there was a tendency for blood flow to increase following the initial heat fraction at points where the steady state temperature was approximately 41 degrees C or less. Extracellular pH increased in two of three patients and decreased in the other.     

Characterization of the aging response of a melt-spun Al-Be-Li alloy ribbon

A rapidly solidified Al-10 wt pct Be-3 wt pet Li alloy has been produced by a melt-spinning technique. The aging behavior of the melt-spun ribbon has been characterized by a number of techniques, including differential scanning calorimetry, hardness measurements, and transmission electron microscopy. The results have shown that the aging responses of the ternary Al-Be-Li alloy are very similar to those of Al-Li binary alloys. Specifically, δ′ precipitates are formed at temperatures near 180 °C and they transform to δ at temperatures around 300 °C. Microstructural examination indicates that, in the Al-Be-Li alloy, α-Be particles are present in the matrix as independent dispersoids and, apparently, have little effect on the aging behavior of the Al-Li matrix; no new phases are present in the matrix of specimens heat treated up to 400 °C. The α-Be particles coarsen, however, above a temperature of approximately 300 °C. The growth of α-Be particles follows the classical Ostwald coarsening type of mechanism.     

Loss of endothelium mediated vascular relaxation as a response to various clamping pressures. Part II. Direct measurements of clamping pressures and scanning electron microscope study

BACKGROUND: Accurate prognosis in chronic heart failure has become increasingly important in assessing the efficacy of treatment and in appropriately allocating scarce resources for transplantation. Previous studies of severe heart failure have been limited by short follow-up periods and few deaths. OBJECTIVE: To establish clinical, hemodynamic, and cardiopulmonary exercise test determinants of survival in patients with heart failure. DESIGN: Retrospective study. SETTING: Hospital-based outpatient heart failure clinic. PARTICIPANTS: 644 patients referred for evaluation of heart failure over 10 years. MEASUREMENTS: Age, cause of heart failure, body surface area, cardiac index, ejection fraction, pulmonary capillary wedge pressure, left ventricular dimensions, watts achieved during exercise, heart rate, maximum systolic blood pressure, and oxygen uptake (VO2) at the ventilatory threshold and at peak exercise were measured at baseline. Univariate and multivariate analyses were done for clinical, hemodynamic, and exercise test predictors of death. A Cox hazards model was developed for time of death. RESULTS: During a mean follow-up period of 4 years, 187 patients (29%) died and 101 underwent transplantation. Actuarial 1-year and 5-year survival rates were 90.5% and 73.4%, respectively. Resting systolic blood pressure, watts achieved, peak VO2, VO2 at the ventilatory threshold, and peak heart rate were greater among survivors than among nonsurvivors. Cause of heart failure (coronary artery disease or cardiomyopathy) was a strong determinant of death (relative risk for coronary artery disease, 1.73; P< 0.01). By multivariate analysis, only peak VO2 was a significant predictor of death. Stratification of peak VO2 above and below 12, 14, and 16 mL/kg per minute demonstrated significant differences in risk for death, but each cut-point predicted risk to a similar degree. CONCLUSIONS: Peak VO2 outperforms clinical variables, right-heart catheterization data, exercise time, and other exercise test variables in predicting outcome in severe chronic heart failure. Direct measurement of VO2 should be included when clinical or surgical decisions are being made in patients referred for evaluation of heart failure or those considered for transplantation.     

Forearm blood flow in response to stress.

Examined the relationship between stress, forearm blood flow, and subjective anxiety. In 26 normal male Ss, electric shocks applied to the opposite forearm led to a rapid rise in anxiety and forearm blood flow. With repeated regular shocks, habituation of the vasomotor response occurred and anxiety became less intense. Changes appeared to be related to S's ability to predict accurately the intensity and frequency of the stimulus. Mental arithmetic under harassment produced a more gradual but greater rise in blood flow without an equal rise in anxiety. 23 alcoholic Ss who were judged to have limited motivation and ego strength showed a significantly lower vasomotor response during mental arithmetic. It is concluded that changes in forearm blood flow observed during stress cannot be related only to an increase in anxiety. This response seems to depend also on the significance of the stimulus to S, his psychiatric status, and his level of motivation. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of the foot withdrawal response to noxious radiant heat in the rat

The rat foot withdrawal response to noxious radiant heat has been used as a model of nociception that is particularly useful for measurements of unilateral changes in nociceptive responses. The purpose of these studies was to characterize the foot withdrawal response to graded rates of noxious skin heating. Response latencies and both surface and subsurface temperatures produced by 6 different intensities of radiant heat were measured to determine whether response latency is an appropriate measure of nociceptive threshold. With constant intensity heating, the temperature of the skin surface increased as logarithmic function of time, while subsurface temperature increased linearly with time. In contrast, a heating function that linearly increased the temperature at the skin surface increased the subsurface temperature as an exponential function of time. These results and published reports of nociceptive afferent recordings which used similar skin heating parameters, indicate that nociceptive foot withdrawal responses occur at about the same skin temperature as the activation of nociceptors. These results also indicate that since constant intensity heating produces linear increases in the subsurface temperature, then response latency can be used as an accurate measure of changes in nociceptive threshold produced by drug treatments. These observations lead to the conclusion that the foot withdrawal response latency is a valid and useful measure of nociceptive threshold in rodents.     

Characterization and optimization of the flow pattern inside a diaphragm blood pump based on flow visualization techniques

We applied two different flow visualization techniques to obtain detailed information on the inside flow of the diaphragm blood pump of our electrohydraulic total artificial heart system to determine the optimum washout effect that would result in better antithrombogenicity. Major orifice directions of the inflow and outflow Bjork-Shiley valves of the left blood pump were independently changed to create 17 varied patterns. The character and velocity of the main flow at the diaphragm-housing junction were acquired using a laser light sheet method with polyethylene tracers. Wall shear flow, a major factor governing washout in the blood pump, was estimated by a newly developed paint erosion method. In this method, quantitative evaluation for an index of washout effect was made by calculating the residual ratio of the paint on the blood pump inner surface at 30 sec of pumping. When a single circular flow was consistently observed by the laser light sheet method, the paint residual ratio become low, indicating washout was relatively good. At the lowest paint residual ratio, the center of the circular flow observed by the laser light sheet method was located at the geometric center of the blood chamber. In conclusion, the flow pattern inside the blood pump could be characterized by combined use of these two flow visualization techniques, and the significant role of circular flow in better washout was clarified.     

Corneal endothelium in patients with diabetes after extracapsular cataract extraction with intraocular lens implantation in the posterior chamber

We have examined endothelial cell density before and 3, 6, 12 months after extracapsular cataract extraction with intraocular lens implantation (posterior chamber) in diabetic patients and in non-diabetics. We have not found statistically significant differences between the mean loss of endothelial cells due to surgery in diabetic and non-diabetic patients.     

Application of a multiwire proportional chamber to the detection of axoplasmic transport

The distribution of residues of DDT and its metabolites (DDD and DDE) in tissues of Triaenophorus nodulosus and its host was studied. It has been noted that cestodes can accumulate chlororganic substances in great quantity. The ability of Bothriocephalus gowkongensis has been established to dechlorate pp-DDT and to excrete pp-, op- and mp-DDD from the organism. Pp-DDT decreases the glycogene content and causes the rise of amylolytic activity in the above cestodes in acute tests. The effect of pp-DDT on the locomotor activity of cestodes is of two-phase character. The first one is associated with the muscular influence, the second one-- with neurotrophic effect. A high toxicity of mp-DDD )0.1 mg/l) for the locomotor activity of cestodes as compared with the effect of pp- and op-DDD was revealed.