Clinical but not histological factors predict long-term prognosis in patients with histologically advanced non-decompensated alcoholic liver disease

BACKGROUND

Alcoholic liver disease (ALD) is a significant threat to public health and a leading cause of death. Despite this, the long-term clinical course and predictive factors of survival in histologically advanced ALD are not well described.

AIMS

The aim of this study was to identify clinical and histological factors that predict long-term (15-year) survival in outpatients with histologically advanced non-decompensated ALD.

METHODS

Patients (n = 134) with biopsy-proven histologically advanced (stage III or IV) ALD were followed up for 15 years or until death or orthotopic liver transplantation. At baseline, clinical and laboratory data were collected. On biopsy, the degree of fibrosis as well as other histological features (fat type and severity, lymphocyte and neutrophil infiltration) were scored semiquantitatively.

RESULTS

Most patients were male (72%) with a median age 51 (46-57). Overall, the 5-, 10- and 15-year survival was 63, 36 and 24% respectively. In multivariate analysis, persistent drinking (P = 0.01), smoking (P = 0.03), age (P = 0.01) and serum albumin at baseline (P = 0.001) were associated with significantly increased risk of death. Persistent drinking was associated with the highest risk. No histological features, including whether the stage of ALD was bridging fibrosis or cirrhosis, correlated with prognosis.

CONCLUSION

In outpatients with biopsy-proven histologically advanced non-decompensated ALD, clinical but not histological factors determine prognosis. Persistent alcohol intake is the strongest predictor and smoking habit, age and serum albumin are also independently prognostic. Abstinence from alcohol and smoking cessation should be the priorities in the long-term management of ALD.

White cell count and platelet count associate with histological alcoholic hepatitis in jaundiced harmful drinkers

Background

Patients with suspected alcoholic hepatitis and a Discriminant Function ≥32 underwent liver biopsy to confirm the diagnosis. Of these (n = 58), 43 had histological features of alcoholic hepatitis and 15 (25%) did not.

We aimed to determine the laboratory features that differentiated those patients with a histological diagnosis of alcoholic hepatitis from those without, and assess potential clinical utility.

Methods

Laboratory investigations at presentation for each of the histologically confirmed cases of alcoholic hepatitis (n = 43) were compared to those without (n = 15) to determine whether there were differences between the two groups. Univariate analysis was by Mann Whitney U Test and Multivariate analysis was by a stepwise approach.

Results

White cell count (16.2 ± 10.5 v 6.9 ± 3.5 (× 10⁹/L); p = 0.0001) and platelet count (178 ± 81 v 98.4 ± 43 (× 10⁹/L); p = 0.0005) were higher in the patients with histological features of alcoholic hepatitis than in those without. The area under the ROC curve for AH diagnosis was estimated to be 0.83 (0.73, 0.94) and 0.81 (0.69, 0.93) for white cell count and platelet count respectively.

Conclusions

Clinicians cannot accurately differentiate patients with or without alcoholic hepatitis without liver biopsy. This is critically important when deciding on specific therapies such as corticosteroids or when interpreting data from future trials in which biopsy is not mandated. In situations where liver biopsy is unsuitable or unavailable the white cell and platelet counts can be used to determine the likelihood of histological alcoholic hepatitis and guide treatment.

Perspectives on telemedicine to improve stroke treatment

Stroke is the number three cause of death and the most common cause of adult disability in the United States. Few patients receive the only established effective therapy, intravenous tissue plasminogen activator. Failure to treat may occur due to several reasons, a crucial one being the lack of acute neurologic coverage, particularly in rural settings. In this article we review the difficulties encountered by patients needing immediate care to access stroke specialists. To overcome this delay in patient care, telemedicine technology for acute stroke care is recommended. We track the emergence and evolution of "telestroke" from initial telephone consultation, to point-to-point, hub-and-spoke networks, to web-based site-independent telestroke systems. We detail the emerging evidence for the safety and efficacy of these remote telestroke systems through observational studies (TEMPiS and REACH). Lastly, we discuss areas where telestroke could potentially expand to provide more complete stroke care beyond the acute thrombolysis phase, as well as its potential to improve clinical research and the need for cost-effective research. We conclude that telestroke is currently the most practical solution to any setback faced by stroke specialists with respect to low thrombolytic rates.

Simple non-invasive fibrosis scoring systems can reliably exclude advanced fibrosis in patients with non-alcoholic fatty liver disease

BACKGROUND

Accurate evaluation of liver fibrosis in patients with non-alcoholic fatty liver disease (NAFLD) is important to identify patients who may develop complications. The aim of this study was to compare the diagnostic performance of simple non-invasive tests in identifying advanced fibrosis among patients with biopsy-proven NAFLD.

METHODS

Consecutive patients with biopsy proven NAFLD were recruited from the Newcastle Hospitals Fatty Liver Clinic from 2003 to 2009. The AST/ALT ratio, AST to platelet ratio index, BARD (weighted sum of BMI>28=1 point, AST/ALT ratio>0.8=2 points, diabetes=1 point), FIB-4 (agexAST (IU/l)/platelet count (x10(9)/litre)x radicalALT (IU/l)) and NAFLD fibrosis scores were calculated from blood tests taken at time of biopsy.

RESULTS

145 patients (82 male (61%), mean age 51+ or -12 years) were included. The mean body mass index was 35+ or -5 kg/m(2). 73 subjects (50%) had diabetes. 93 patients (64%) had non-alcoholic steatohepatitis. 27 (19%) had advanced fibrosis (Kleiner stage 3-4). The FIB-4 score had the best diagnostic accuracy for advanced fibrosis (area under receiver operator characteristic curve (AUROC) 0.86), followed by AST/ALT ratio (AUROC 0.83), NAFLD fibrosis score (AUROC 0.81), BARD (AUROC 0.77) and AST to platelet ratio index (AUROC 0.67). The AST/ALT ratio, BARD score, FIB-4 and NAFLD fibrosis scores had negative predictive values greater than 90% (93%, 95%, 95% and 92% respectively). Positive predictive values were modest. In order to exclude advanced fibrosis liver biopsy could potentially be avoided in 69% with AST/ALT ratio, 62% with FIB-4, 52% with NAFLD fibrosis score and 38% with BARD.

CONCLUSIONS

The ALT/AST ratio, FIB-4 and NAFLD fibrosis scores can reliably exclude advanced fibrosis in a high proportion of patients with NAFLD, allowing liver biopsy to be used in a more directed manner.

Oxidative stress as a trigger for cellular immune responses in patients with alcoholic liver disease

Serum antibodies reactive with neo-antigens generated during ethanol metabolism have been identified in patients with alcoholic liver disease (ALD), although their role in the pathogenesis of disease remains unclear. In this study, we characterized peripheral blood mononuclear cell (PBMC) T-cell and antibody responses to human serum albumin (HAS) adducted with acetaldehyde under reducing conditions (AcA-HSA) or with malondialdehyde (MDA-HSA) in patients with advanced ALD (AALD, n = 28), heavy drinkers with no liver disease (NALD, n = 14), and mild/moderate drinking controls (n = 22). Peak proliferative responses of PBMC were assessed in vitro by tritiated thymidine incorporation after the addition of optimized concentrations of antigen or OKT3. Antibody titers were determined by enzyme-linked immunosorbent assay (ELISA). MDA-HSA induced PBMC T-cell proliferation was significantly higher in ALD than in NALD or control patients. Moreover, 10 of 28 (36%) of ALD patients had significant T-cell proliferative responses to MDA-HSA compared to 0 of 14 (0%, P =.02) of the NALD group and 2 of 22 (9%, P <.05) of controls. No significant difference in PBMC T-cell response to Aca-HSA was seen between subject groups. Patients with positive cellular responses to MDA had higher serum anti-MDA antibody titers than those not exhibiting a positive cellular response (P <.005). In conclusion, the pattern of cellular and humoral responses to MDA adducts suggests that the development of these responses may be a susceptibility factor for the development of advanced alcoholic liver disease. The apparent importance of T-cell responses to MDA adducts suggests that oxidative stress may represent an important stimulus for the development of cellular immune responses associated with advanced ALD.

Genetic and epigenetic factors in autoimmune reactions toward cytochrome P4502E1 in alcoholic liver disease

Autoimmune reactions are often associated with alcoholic liver disease; however, the mechanisms responsible are largely unknown. This study investigates the potential role of the immune response against hydroxyethyl free radical (HER)-derived antigens and of polymorphisms in immunoregulatory genes in the development of anti-cytochrome P4502E1 (CYP2E1) autoantibodies in alcohol abusers. Immunoglobulin G (IgG) recognizing human CYP2E1 and HER-derived epitopes were measured by microplate immunosorbent assay in the sera of 90 patients with alcoholic fibrosis/cirrhosis (ALD), 37 heavy drinkers without liver disease or steatosis only (HD), and 59 healthy subjects. Single nucleotide polymorphisms in the interleukin 10 (IL-10) promoter and in exon 1 of the cytotoxic T-lymphocyte antigen-4 (CTLA-4) gene were genotyped by polymerase chain reaction-restriction fragment length polymorphism analysis. The titers and frequency of anti-CYP2E1 autoantibodies were significantly higher in ALD than in HD subjects or controls. ALD patients with anti-HER IgG had higher titers and a 4-fold increased risk (OR: 4.4 [1.8-10.9]) of developing anti-CYP2E1 autoantibodies than subjects without anti-HER antibodies. The mutant CTLA-4 G allele, but not the IL-10 polymorphism, was associated with an enhanced risk of developing anti-CYP2E1 IgG (OR: 3.8 [1.4-10.3]). CTLA-4 polymorphism did not influence antibody formation toward HER-antigens. ALD patients with concomitant anti-HER IgG and the CTLA-4 G allele had a 22-fold higher (OR: 22.9 [4.2-125.6]) risk of developing anti-CYP2E1 autoreactivity than subjects negative for these factors. In conclusion, antigenic stimulation by HER-modified CYP2E1 combined with an impaired control of T-cell proliferation by CTLA-4 mutation promotes the development of anti-CYP2E1 autoantibodies that might contribute to alcohol-induced liver injury.

Valine-alanine manganese superoxide dismutase polymorphism is not associated with alcohol-induced oxidative stress or liver fibrosis

The role of genetic factors in the pathogenesis of alcohol-induced liver disease (ALD) is receiving increasing attention. Recently, it has been reported that homozygosity for a valine to alanine substitution in the mitochondrial targeting sequence of manganese superoxide dismutase (Mn-SOD) represents a risk factor for severe ALD. Because this mutation is postulated to modify enzyme transport into mitochondria, we have sought confirmatory evidence of this association in a larger group of patients and investigated whether this polymorphism might influence alcohol-induced oxidative stress. Genotyping for the valine-alanine (Val-Ala) polymorphism of the Mn-SOD gene in 281 patients with advanced ALD (cirrhosis/fibrosis) and 218 drinkers without liver disease showed no differences in either the heterozygote (55% vs. 50%) or the homozygote (19% vs. 23%) frequency for the alanine allele. By measuring the titers of circulating antibodies against oxidized cardiolipin (OX-CL) and malondialdehyde (MDA) or hydroxy-ethyl radical (HER) adducts as markers of oxidative stress, we found a significant increase in ALD patients compared with healthy controls. However, the carriers of the alanine Mn-SOD allele had titers of anti-MDA, anti-HER, and anti-OX-CL IgG comparable with heterozygotes and patients homozygous for the valine allele. Similarly, the frequency of subjects with antibody titers above the 95th percentile of controls was not increased among homozygotes for the alanine Mn-SOD allele. In conclusion, in our population Val-Ala polymorphism in Mn-SOD influences neither susceptibility to alcohol-induced liver fibrosis nor alcohol-induced oxidative stress.

Lipid peroxidation contributes to immune reactions associated with alcoholic liver disease

Increasing evidence indicates the involvement of immune reactions in the pathogenesis of alcoholic liver disease. We have investigated whether ethanol-induced oxidative stress might contribute to immune response in alcoholics. Antibodies against human serum albumin modified by reaction with malondialdehyde (MDA), 4-hydroxynonenal (HNE), 2-hexenal, acrolein, methylglyoxal, and oxidized arachidonic and linoleic acids were measured by ELISA in 78 patients with alcoholic cirrhosis and/or hepatitis, 50 patients with nonalcoholic cirrhosis, 23 heavy drinkers with fatty liver, and 80 controls. Titers of IgG-recognizing epitopes derived from MDA, HNE, and oxidized fatty acids were significantly higher in alcoholic as compared to nonalcoholic cirrhotics or healthy controls. No differences were instead observed in the titers of IgG-recognizing acrolein-, 2-hexenal-, and methylglyoxal-modified albumin. Alcoholics showing high IgG titers to one adduct tended to have high titers to all the others. However, competition experiments showed that the antigens recognized were structurally unrelated. Anti-MDA and anti-HNE antibodies were significantly higher in cirrhotics with more severe disease as well as in heavy drinkers with cirrhosis or extensive fibrosis than in those with fatty liver only. We conclude that antigens derived from lipid peroxidation contribute to the development of immune responses associated with alcoholic liver disease.

Effects of transducer, velocity, Doppler angle, and instrument settings on the accuracy of color Doppler ultrasound

The accuracy of a commercial color Doppler ultrasound (US) system was assessed in vitro using a rotating torus phantom. The phantom consisted of a thin rubber tube filled with a blood-mimicking fluid, joined at the ends to form a torus. The torus was mounted on a disk suspended in water, and rotated at constant speeds by a motor. The torus fluid was shown in a previous study to rotate as a solid body, so that the actual fluid velocity was dependent only on the motor speed and sample volume radius. The fluid velocity could, thus, be easily compared to the color Doppler-derived velocity. The effects of instrument settings, velocity and the Doppler angle was assessed in four transducers: a 2.0-MHz phased-array transducer designed for cardiac use, a 4.0-MHz curved-array transducer designed for general thoracic use, and two linear transducers designed for vascular use (one 4.0 MHz and one 6.0 MHz). The color Doppler accuracy was found to be significantly dependent on the transducer used, the pulse-repetition frequency and wall-filter frequency, the actual fluid velocity and the Doppler angle (p < 0.001 by analysis of variance). In particular, the phased array and curved array were observed to be significantly more accurate than the two linear arrays. The torus phantom was found to provide a sensitive measure of color Doppler accuracy. Clinicians need to be aware of these effects when performing color Doppler US exams.

Mycophenolate mofetil monotherapy in liver transplantation

Chronic renal failure is a major cause of morbidity and mortality after orthotopic liver transplantation. We did a randomised controlled trial of mycophenolate mofetil monotherapy in liver transplant patients who developed renal failure associated with calcineurin-inhibitor (ciclosporin or tacrolimus) immunosuppressive therapy. Although renal failure improved when the calcineurin-inhibitor dose was reduced and ultimately stopped, the trial was stopped when three of five patients on monotherapy developed organ rejection requiring a second transplantation.

A rotating torus phantom for assessing color Doppler accuracy

A rotating torus phantom was designed to assess the accuracy of color Doppler ultrasound. A thin rubber tube was filled with blood analog fluid and joined at the ends to form a torus, then mounted on a disk submerged in water and rotated at constant speeds by a motor. Flow visualization experiments and finite element analyses demonstrated that the fluid accelerates quickly to the speed of the torus and spins as a solid body. The actual fluid velocity was found to be dependent only on the motor speed and location of the sample volume. The phantom was used to assess the accuracy of Doppler-derived velocities during two-dimensional (2-D) color imaging using a commercial ultrasound system. The Doppler-derived velocities averaged 0.81 +/- 0.11 of the imposed velocity, with the variations significantly dependent on velocity, pulse-repetition frequency and wall filter frequency (p < 0.001). The torus phantom was found to have certain advantages over currently available Doppler accuracy phantoms: 1. It has a high maximum velocity; 2. it has low velocity gradients, simplifying the calibration of 2-D color Doppler; and 3. it uses a real moving fluid that gives a realistic backscatter signal.

Aliasing-tolerant color Doppler quantification of regurgitant jets

Conservation of momentum transfer in regurgitant cardiac jets can be used to calculate the flow rate from color Doppler velocities. In this study, turbulent jets were simulated by finite elements; pseudocolor Doppler images were interpolated from the computations, with aliasing introduced artificially. Jets were also imaged by color Doppler in an in vitro flow system. To suppress aliasing errors, jet velocities were fitted iteratively to a fluid mechanical model constrained to match the orifice velocity (measured without aliasing by continuous-wave Doppler). At each iteration, the model was used to detect aliased velocities, which were excluded during the next iteration. Iteration continued until the flow rate calculated by the model and number of calculated nonaliased pixels were unchanged. The good correlations between measured and calculated flow rates in the experimental (R2 = 0.933) and computational studies (R2 = 0.990) suggest that this may be a clinically useful approach even in aliased images. Published by Elsevier Science Inc.

Hyperbaric dye solution distribution characteristics after pencil-point needle injection in a spinal cord model

BACKGROUND

The flow-rate limiting and directional characteristics of caudally directed microcatheters, which lead to intrathecal maldistribution of hyperbaric 5% lidocaine, are believed to have contributed to at least 11 cases of cauda equina syndrome. The authors investigated the distribution characteristics of hyperbaric dye solutions via caudally directed side port needles at various rates of injection in a spinal cord model to determine the potential for maldistribution.

METHODS

Using a digital video image processing technique, we injected a hyperbaric solution of phthalocyanine blue dye through caudally directed side-port needles into a supinely oriented transparent spinal canal model filled with simulated cerebrospinal fluid. Injections via commonly used spinal needles (24-gauge and 25-gauge Sprotte, and 25-gauge and 27-gauge Whitacre) were recorded using five injection rates (2, 4, 6, 8, and 16 ml/min).

RESULTS

For all needles tested, injection rate had a significant effect on the peak dye concentration (P < 0.0001). Injection rates > or = 6 ml/min (2 ml/20 s) resulted in peak dye concentrations of less than 168 mg/1 (extrapolated concentration of 1% lidocaine). Injection via the 24-gauge Sprotte needle, which has a larger orifice area and internal diameter, resulted in significantly lower peak dye concentrations than via the smaller Whitacre needles tested (P < 0.05).

CONCLUSIONS

Sacral maldistribution could be minimized by using injection rates > or = 6 ml/min (2 ml/20 s), for all of the side-port spinal needles used in this model study. When very slow injection rates (2 ml/min) are used, peak dye concentrations varied inversely and significantly with needle internal diameter and orifice area.

Transient neurologic deficit after spinal anesthesia: local anesthetic maldistribution with pencil point needles?

Recent reports of transient neurologic deficits have raised concern about the potential toxicity of single-dose spinal 5% lidocaine in 7.5% dextrose. Two cases of volunteers who experienced minor local sensory deficits after slow (60 s) injections of 2 mL 5% lidocaine via Whitacre needles are described. One case was a result of a double injection because of a "failed" block. It seemed possible that the neurologic deficit in these cases resulted from neurotoxicity associated with maldistribution of local anesthetic. Using an in vitro spinal model, we investigated drug distribution resulting from injections through side-port spinal needles to determine whether the use of these needles could result in high local concentrations of hyperbaric solutions. A spinal canal model was fabricated using human magnetic resonance measurements. The model was placed in a surgical supine position and filled with lactated Ringer's solution to simulate the specific gravity of cerebral spinal fluid at 22 degrees C. A hyperbaric solution of phthalocyanine blue dye and dextrose (SG 1.042), simulating the anesthetic, was injected through three different needles (27-gauge 4 11/16-in. Whitacre, 25-gauge 3 1/2-in. Whitacre, 25-gauge 3 1/2-in. Quincke). Triplicate injections were done at rapid (2 mL/10 s) and slow (2 mL/60 s) rates, with needle side ports oriented in a sacral and cephalad direction. At slow rates of injection, using 27- or 25-gauge sacrally directed Whitacre needles, injections showed evidence of maldistribution with extrapolated peak sacral lidocaine concentrations reaching 2.0%. In contrast, distribution after slow injection through sacrally directed Quincke needles was uniform.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro modeling of spinal anesthesia. A digital video image processing technique and its application to catheter characterization

BACKGROUND

Maldistribution of intrathecal local anesthetic has recently been implicated as a contributor to neurotoxic injury. In vitro modeling can be used to understand the distribution of anesthetic agents within the subarachnoid space. We describe an in vitro modeling technique that uses digital video image processing and its application to catheter injection of local anesthetic.

METHODS

A clear plastic model of the subarachnoid space, including a simulated spinal cord and cauda equina, was filled with lactated Ringer's solution. Phthalocyanine blue dye of known concentration was injected into the model through small-bore (28-G) and large-bore (18-G) catheters. Injections were performed at a variety of controlled rates and sacral catheter positions, and the propagation of dye throughout the model was recorded on videotape, digitized by computer, and converted to a two-dimensional image of dye concentration. A subset of data was compared with results obtained from spectrophotometric analysis.

RESULTS

There was a strong correlation (r = 0.98) between data obtained with analysis by digital video image processing and those obtained spectrophotometrically. Catheter size, catheter angle, and injection rate significantly influenced the distribution and peak concentration of simulated anesthetic. No major differences in distribution or peak concentration were observed with the two types of 28-G catheters.

CONCLUSIONS

The digital video image processing technique can be used to quantify anesthetic distribution rapidly within a model of the subarachnoid space without disturbing the distribution. The current results demonstrate a strong dependence of anesthetic distribution on catheter angle, catheter size, and injection rate. Comparisons between 28-G catheters suggest that the difference in reported incidence of cauda equina syndrome associated with different 28-G catheters cannot be explained on the basis of differences in anesthetic distribution.

Selective regulation of human neutrophil functions by the cell activation inhibitor CI-959

The cell activation inhibitor CI-959 [5-methoxy-3-(1-methylethoxy)-N-1H-tetrazol-5-ylbenzo[ b]thiophene-2- carboxamide, monosodium salt] was evaluated for its effects on human neutrophil functions. CI-959 inhibited spontaneous migration and chemotaxis toward N-formyl-methionyl-L-leucyl-L-phenylalanine (fMLP) with 50% inhibition (IC50) values of 3.6 and 3.1 microM, respectively. CI-959 also inhibited superoxide anion generation in response to C5a, fMLP, serum-opsonized zymosan (SOZ), concanavalin A (Con A), and calcium ionophore A23187 with IC50 values of 2.5, 4.7, 14.5, 5.4, and 14.8 microM, respectively. In comparison, CI-959 inhibited myeloperoxidase microM, respectively. In comparison, CI-959 inhibited myeloperoxidase release in response to C5a, fMLP, SOZ, and Con A with IC50 values of 11.6, 16.1, 7.5, and < 1.0 microM, respectively, while inhibiting the response to A23187 by only 5.5% at 100 microM. At concentrations up to 100 microM, CI-959 had no effect on the respiratory burst or degranulation in response to L-alpha-1,2-dioctanoylglycerol (DiC8) or phorbol 12-myristate 13-acetate (PMA). In addition, the compound inhibited leukotriene B4 release stimulated by fMLP and SOZ (IC50 values 4.0 and 2.5 microM, respectively), while having less activity against the A23187-stimulated response (IC50 > 100 microM). These results demonstrate that CI-959 inhibits cellular responses to stimuli that mobilize intracellular calcium. For cellular responses to inophore-mediated calcium influx, only oxygen radical production was inhibited by CI-959. CI-959 was further evaluated for its effects on neutrophil stimulus-response coupling. At 100 microM, CI-959 had no effect on human neutrophil phospholipase C or protein kinase C. CI-959 inhibited fMLP-stimulated intracellular calcium mobilization and calcium influx with IC50 values of 16.7 and 3.1 microM, respectively, and exhibited less potent calmodulin antagonist activity (IC50 = 90.5 microM). These results indicate that CI-959 may exert its stimulus- and response-specific inhibitory effects on neutrophil functions, in part, through inhibition of calcium-regulated signalling mechanisms.

Quantification of asymmetric valvular regurgitant jets by color Doppler ultrasound in vitro

Accurate quantification of regurgitant jets in natural and prosthetic heart valves has been a goal of health care workers and researchers for many years. One promising new method applies the law of conservation of momentum transfer to velocities measured by color Doppler ultrasound to calculate the flow rate in the jet. One complicating factor is that regurgitant jets from real heart valves may be highly asymmetric. The purpose of this investigation was to determine whether the accurate calculation of the flow rate in asymmetric jets imaged by color Doppler requires an asymmetric formulation of the conservation of momentum transfer, combined with a method for imaging the jet in three dimensions. Asymmetric jets issuing from narrow slits were imaged in an in vitro, steady flow system. The ultrasound transducer was rotated around the jet axis to image the jet in three dimensions. The three-dimensional imaging confirmed that jets from slits are indeed asymmetric, but become relatively axisymmetric far from the orifice. Images were analyzed by computer and the calculated flows compared to measured flows. The accuracy of an asymmetric formulation of the conservation of momentum transfer method was compared to a simpler, axisymmetric formulation. If axisymmetry was assumed in asymmetric jets, significant errors in the calculated flow rates occurred. In these cases, the calculated flow also varied widely with distance from the orifice. When asymmetry was taken into account, the errors were considerably reduced. The results suggest that, in asymmetric jets, the momentum transfer is convected around the jet axis.

Effects of a vascular graft/natural artery compliance mismatch on pulsatile flow

Attempts have been made to correlate small-diameter vascular graft patency with compliance matching between the graft and the host artery. Without knowledge about the mechanisms of failure by compliance mismatch, however, such correlations remain empirical. We have developed a flow system which mimics the flow in peripheral arteries and techniques to model a compliance mismatch in a straight elastic tube, as might occur with vascular repair. Our goal was to investigate one proposed mechanism of graft failure by compliance mismatch, that of a blood flow disturbance. Flow visualization experiments showed that, under pulsatile flow, a compliance mismatch caused trapping of 40 microns microspheres at the wall near the distal or downstream anastomosis. This suggests that the presence of a microscopic flow separation or stagnant zone in vivo may contribute to the intimal hyperplasia and thrombosis seen in failed grafts.

A comprehensive cardiovascular waveform analysis program for IBM-compatible personal computers

Computerized cardiovascular waveform processing has become a necessary and fundamental tool in the analysis of physiologic data. The availability of numerous commercial data-analysis programs has significantly enhanced the efficiency of waveform analysis. Many such programs come with their own programming language, which enables the researcher to create an application program suited to a specific series of calculations. Once written, an application program can significantly increase the efficiency with which data from a specific experiment can be analyzed. However, creating or modifying a program for each new experimental protocol can be time-consuming, especially in the error-detection and verification stages. Single-purpose programs also prove somewhat inflexible to unexpected changes in experimental formats. These problems suggested the need for a more flexible program, but one that is nevertheless specifically suited to the analysis of cardiovascular signals. This need led to the development of a program designed in collaboration with surgeons and physiologists. This program addresses some important analysis problems in cardiovascular research, and allows the user to survey and manipulate cardiovascular waveforms in an intuitive and spontaneous manner.

Errors in pressure gradient measurement by continuous wave Doppler ultrasound: type, size and age effects in bioprosthetic aortic valves

The accuracy of continuous wave Doppler ultrasound in deriving pressure gradients across bioprosthetic heart valves was evaluated in an in vitro pulse duplicator. Simultaneous pressure transducer and Doppler measurements were made in new and explanted aortic bioprosthetic valves of several sizes and four types: Carpentier-Edwards, Ionescu-Shiley, Hancock standard and Hancock modified. The mean and peak gradients calculated by the modified Bernoulli equation from Doppler velocity measurements were always greater than those measured manometrically, despite corrections for location dependence of the manometric gradient (or pressure recovery). The relation between manometric and ultrasonically determined gradient was found to be statistically dependent on the valve type (mean gradient p less than 0.0001; peak gradient p = 0.0003) and size (mean gradient p = 0.0089; peak gradient p = 0.0107). Effects of implantation were observed, but were not shown to be significant. It is concluded that the continuous wave Doppler velocity data overestimated prosthetic valve pressure gradient in all cases, even when pressure recovery was taken into account. Clinicians should be wary of Doppler data when making major diagnostic or therapeutic decisions.

In vitro quantification of regurgitant jet flow by color Doppler ultrasound and conservation of momentum

Prosthetic valve regurgitant jets can be imaged with color Doppler ultrasound (CDU), but clinical quantitation remains elusive. An equation based on an integrated conservation of momentum analysis was implemented for CDU quantitation of regurgitation. This was compared with a simple, non-CDU momentum balance analysis recently reported that requires only a pulsed Doppler ultrasound (PDU) reading within the jet and a continuous wave Doppler (CWD) reading of the orifice velocity. For in vitro steady flows, the simple, non-CDU method was accurate only with PDU readings taken 5 cm from the orifice; flows were underestimated when readings 1 and 3 cm from the orifice were used. The CDU method was accurate, even when flows calculated from readings between 0.5 and 6.0 cm from the orifice were averaged together.

Inhibition of human neutrophil activation by the allergic mediator release inhibitor, CI-949

The allergic mediator release inhibitor Cl-949 [5-methoxy-3-(1-methylethoxy)-1-phenyl-N-1H-tetrazol-5-yl-1H -indole-2-carboxamide, L-arginine salt] was evaluated for its effects on human neutrophil functions. Cl-949 (100 microM) inhibited spontaneous migration and chemotaxis toward f-met-leu-phe (FMLP) by 49.1% and 45.8%, respectively. At the same concentration, Cl-949 inhibited the phagocytosis of serum-opsonized zymosan (SOZ) by 39.0%. Cl-949 inhibited leukotriene B4 and thromboxane B2 release in response to SOZ with IC50s of 2.0 microM and 3.3 microM, while inhibiting the response to FMLP with IC50s of 1.7 and 2.0 microM. Cl-949 also inhibited myeloperoxidase release from primary lysosomal granules in response to the following stimuli with the respective IC50s (microM): C5a (40.3); FMLP (34.4): SOZ (21.4); concanavalin A (Con A) 3.9); and calcium ionophore A23187 (91.2). In contrast, Cl-949 inhibited lysozyme release from secondary granules in response to SOZ and Con A with IC50s of 99.3 and 56.1 microM, while inhibiting the response to C5a, FMLP, and A23187 by 41.2%, 52.4%, and 10.0%, respectively, at 100 microM. Cl-949 (100 microM) had no inhibitory effect against lysozyme release in response to L-alpha-1,2 dioctanoylglycerol (DiC8), or phorbol 12-myristate 13-acetate (PMA). Cl-949 inhibited superoxide anion generation stimulated by FMLP and Con A with IC50s of 33.9 and 25.8 microM, while inhibiting the response to C5a, SOZ, and A23187 by 36.6%, 24.8%, and 14.1% and having no effect on the response to DiC8 or PMA at 100 microM. These results demonstrate preferential inhibition of arachidonic acid metabolism and degranulation of primary lysosomal granules by Cl-949 with selectivity for stimuli which promote intracellular calcium mobilization or calcium influx.

In vitro ultrasound characterization of a polyurethane trileaflet valve

Polyurethane synthetic trileaflet valves were compared with commercial prostheses in vitro, in a pulse duplicator using ultrasound to characterize the flow velocities and patterns. Flow-pressure drop behavior was in the middle range of other prosthetic valves. Diastolic regurgitant jets were located by color Doppler ultrasound, and there appeared to be some leakage through the leaflet fold at the commissure. Nevertheless, the closing volumes and closed valve leakage volumes were, on average, lower than other prosthetic valves. Systolic 20 Hz spectral oscillations detected with pulsed Doppler and continuous wave Doppler were attributed to leaflet flutter in the open valve.

Predicting the compliance of small diameter vascular grafts from uniaxial tensile tests

The compliance hypothesis states that the compliance of vascular grafts should match that of the host artery for optimal patency. Although this has not been proven, the literature shows that much effort has gone into measuring compliance. Uniaxial circumferential tensile tests are simpler than compliance tests, but do not give the compliance (a multiaxial property) directly. Therefore, we have used mechanical models to correlate the two. Simple models suffer from inappropriate simplifying assumptions. In a clinically useful range, a Laplace law model and an incremental elasticity model do not predict the compliance from the rigidity as well as does a model derived from finite elasticity. This latter model has helped locate sources of errors. Variations in graft thickness, diameter, and anisotropy may be responsible for scatter in the experimental correlations between compliance and uniaxial rigidity.

Solid state line scan cameras for measuring strain in soft tissues and implants

The line scan camera, or LSC, is an inexpensive and easily applied technique for optical strain measurement of soft biomaterials. The LSC is based on a linear array of photodiodes; in gauging applications, where measurements between dark/light interfaces are important, the digital nature of the array can be exploited. Advantages of the LSC include low cost, high frequency response, applicability to front- or back-lighted samples, insensitivity to stray and nonuniform lighting as well as to accidental overexposure, ease and linearity of calibration, and lack of temperature sensitivity. With the 1024 element arrays used herein, the relative resolution is theoretically limited to 1 part in 1024, or 0.1%; in practice, the relative resolution is somewhat poorer. LSCs have been successfully used in mechanical tests to measure the diameter of arteries and compliant vascular grafts, the longitudinal strain of vascular grafts, and the dynamic diameter of elastic tube models of graft/artery systems in pulsatile flow visualization experiments.

CI-943, a potential antipsychotic agent. II. Neurochemical effects

The effects of CI-943 (a novel 8-ethyl-7,8-dihydro-1,3,5-trimethyl-1H-imidazo[1,2-c]pyrazolo[3,4- e]pyrimidine compound exhibiting a favorable antipsychotic profile in animal tests) on neurochemical parameters related to biogenic amine neurons have been studied in rat brain. CI-943 (1-40 mg/kg p.o. and 20 mg/kg i.p.) accelerated the turnover of dopamine (DA) in rat brain as demonstrated by the enhancement of levels of the DA metabolites homovanillic acid, 3,4-dihydroxyphenylacetic acid or 3-methoxytyramine and by the enhancement rate of DA synthesis in either striatum or mesolimbic regions. These increases in DA turnover induced by CI-943 are not due to DA receptor blockade as CI-943, unlike known antipsychotics, did not exhibit affinity for DA receptors either in vitro or in vivo and did not affect rat serum basal prolactin levels. Amfonelic acid enhanced the action of haloperidol in increasing striatal homovanillic acid with no effect on that of CI-943 and clozapine, suggesting that CI-943, like clozapine, would be predicted to have a low risk of extrapyramidal side effects as compared to haloperidol. Chronic administration of CI-943 (40 mg/kg i.p.) to rats for 28 days did not affect the affinity or number of striatal DA receptors; in comparison haloperidol (0.5 mg/kg i.p.) caused an increase in number of DA receptors with no change in affinity. Measures of serotonergic function were increased; noradrenergic function was not affected by CI-943, nor did it exhibit affinity for a number of central nervous system receptors in vitro. The molecular mechanism by which CI-943 increases brain DA turnover is not known at this time but appears to be unique in comparison to known antipsychotic agents.

A computerized physiologic pulse duplicator for in-vitro hydrodynamic and ultrasonic studies of prosthetic heart valves

A physiologic pulse duplicator for the simultaneous in-vitro hydrodynamic and ultrasonic evaluation of aortic prosthetic heart valves is described. The system is interfaced to a personal computer, which provides greater efficiency over manual techniques in system calibration, data acquisition, and analysis. The data analysis program aids selection of start and end systole and calculates pressure difference across the valve, the closing and regurgitant volumes, flow rates, and the Gabbay and Swanson performance indices. The pulse duplicator is designed to accommodate the ultrasonic measurement of fluid velocities, including pressure difference via the Bernoulli equation, and color-flow imaging. In tests of 19-mm, 23-mm, and 27-mm Bjork-Shiley spherical occluder valves, continuous-wave Doppler ultrasound was found to overestimate by about 50% the pressure difference measured directly by pressure transducers, a finding that is clinically important.

Finite elasticity modeling of the biaxial and uniaxial properties of compliant vascular grafts

Compliant vascular grafts were modeled by finite elasticity theory. A linear, biaxial model satisfactorily described the stress-strain behavior in inflation tests, where the sample length was fixed longitudinally and inflated. The model was then used to predict the behavior in a longitudinal test (where the longitudinal stretch was varied while keeping the pressure zero), and in a uniaxial test of a circumferential strip. The model satisfactorily predicted the longitudinal Young's modulus measured in the longitudinal test. The model was less successful in predicting the circumferential Young's modulus measured in the uniaxial test, possibly because the state of stress was not purely uniaxial.

CI-922--a novel, potent antiallergic compound--I. Inhibition of mediator release in vitro

CI-922 (3,7-dimethoxy-4-phenyl-N-1H-tetrazol-5-yl-4H-furo[3,2-b]-indole- 2-carboxamide, L-arginine salt) is a novel antiallergy compound which inhibits the release of the inflammatory mediators histamine and leukotriene (LT) from stimulated cells. CI-922 showed potent, effective inhibition of antigen-induced mediator release from human basophils and isolated guinea pig lung. The drug inhibited ragweed or housedust-induced histamine release from basophils of allergic human donors (IC50 = 8.6 microM). The antiallergy agents proxicromil (IC50 = 80 microM) and cromolyn (100 microM) were less potent than CI-922 or inactive, respectively. In fragmented lung from actively sensitized guinea pigs, CI-922 (IC50 = 1.5 microM), blocked the antigen-induced production of LT and was a more potent inhibitor of histamine release (IC50 = 13.4 microM) than proxicromil (IC50 = 72.9 microM), or cromolyn (inactive at 1 mM). CI-922 (IC50 = 0.9 microM) completely inhibited repeated contractions of guinea pig lung strips that were induced by low antigen concentration in the presence of antihistamine (H1). Nordihydroguaiaretic acid (NDGA) (IC50 = 2.8 microM), proxicromil (IC50 = 6.2 microM) and the LT antagonist FPL-55712 (IC50 = 3.3 microM) also were fully effective, but cromolyn (300 microM) was inactive. In other experiments, CI-922 (IC50 = 7.0 microM) inhibited a strong, nonrepeatable lung contraction induced with high antigen concentration (histamine responses blocked), and was six times more potent than FPL-55712. Other investigations in isolated tissue preparations showed CI-922 to be a weak inhibitor of LT or histamine-induced effects with no anticholinergic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Increase of rat serum prolactin by adenosine analogs and their blockade by the methylxanthine aminophylline

The administration of the stable adenosine analogs N6-[(R)-methyl-2-phenylethyl]adenosine (R-PIA; 0.01-1.0 mg/kg i.p.) and 1-(6-amino-9H-purin-9-yl)-1-deoxy-N-ethyl-beta-D-ribofuronamide (NECA; 0.01-1.0 mg/kg i.p.) caused a dose-related (NECA) or biphasic (R-PIA) increases in rat serum prolactin. The S-isomer of PIA was inactive up to 4 mg/kg i.p. The methylxanthine aminophylline (10 and 30 mg/kg i.p.) antagonized the R-PIA- and NECA-induced elevation of prolactin suggesting an adenosine receptor-mediated effect. The dopaminergic agents L-dopa and bromocriptine antagonized the R-PIA and NECA-induced increase in serum prolactin. Haloperidol (a dopamine antagonist) and alpha-methyl-p-tyrosine (a catecholamine synthesis inhibitor) potentiated the R-PIA-induced effects. R-PIA and NECA did not displace 3H-haloperidol from rat striatal membranes nor effect in vitro prolactin release from rat anterior pituitary cells grown in culture. Based upon these findings it is postulated that R-PIA and NECA may be increasing prolactin secretion in part by inhibiting central dopamine release, although other mechanisms may also be operating.

Wheelchair cushion effect on skin temperature, heat flux, and relative humidity

For patients subject to decubitus ulcers, wheelchair cushions should be prescribed with knowledge of the cushion's effect on the thermal as well as mechanical environment of the skin. To define thermal effects that may be encountered during routine use, tests werr made on 24 commercially available cushions. Skin temperature, heat flux and relative humidity were measured under the ischial tuberosities of a normal 24-year-old man during a 1-hour period of sitting on each cushion. After 1 hour, skin temperatures increased by means of 3.4 C and 2.8 C on foams and viscoelastic foams and there were slight decreases in heat flux as compared with control values in air. On gels, skin temperatures remained constant and heat flux increased, while water "floatation" pads caused a mean skin temperature decreased of 2.7 C along with a marked increase in heat flux. Relative humidity at the skin cushion interface increased by 10.4%, 22.8% and 19.8% on foams, gels and water floatation pads, as compared with room air values. Representative cushions from each of the general types (foam, viscoelastic foam, gel and water floatation) also were subjected to 2-hour tests which indicated the measured parameters continued to change asymptotically.

Changes in pituitary hormone secretions and corpora lutea following PGF2alpha administration to PMS/hCG-stimulated rats

Pseudopregnancy was induced in 26 day old female rats by giving 30 IU of PMS followed 56 hours later with 5 IU of hCG. Day 1 of pseudopregnancy was considered established 72 hours after PMS administration. Pseudopregnancy lasted 14 to 15 days. Ovarian weights increased for 4 to 8 times due to treatment. Histological examiniation of the corpora lutea (CL) of pseudopregnancy suggested luteolysis began on day 6 and extended to day 8. A "new" crop of CL appeared on day 9 suggesting the duration of pseudopregnancy was supported by more than one generation of CL or by CL maturing at different rates. Twice daily administration of 1 mg PGF2alpha on days 5 to 8 prevented the appearance of the "new" CL on day 9, and increased signs of luteolysis in the initially formed CL. Lower doses (0.01 and 0.1 mg, b.i.d., X 4 days) delayed the appearance of "new" CL until day 10. Blood samples withdrawn between 0930 and 1100 hours were analysed for FSH, LH and prolactin. Animals treated with 0.01 and 0.1 mg of PGF2alpha, b.i.d., X 4 days had increased LH values on day 8, thus the PG appeared luteotrophic. Rats treated with 1 mg of PGF2alpha, b.i.d., X 4 days had decreased LH values on day 7 and the CL showed subsequent luteolysis. FSH levels were relatively constant during pseudopregnancy. However, all doses of PGF2alpha reduced FSH levels on day 7. An associated decrease in uterine weight occurred, possibly due to reduced follicular development. Prolactin levels fell in response to PGF2alpha treatment which undoubtedly contributed to the observed luteolysis. The signs of early cessation of pseudopregnancy were: increased serum FSH on days 9 and 10; increasing uterine weight; and the reappearance of follicular growth. These data suggest that PGF2alpha reduced the duration of pseudopregnancy primarily by inhibiting the secretion of FSH, LH and prolactin.