Antitumor activity of the aqueous-alcoholic extracts from unripe cotton ball of Gossypium indicum

The present study investigated the antitumor activity of the aqueous-alcoholic extracts from unripe cotton balls of Gossypium indicum. An Exposure of murine B16 melanoma and L1210 lymphoma cells to the extracts resulted in their severe deaths in time- and concentration-dependent manners. Of the extracts, hydrophilic fractions were most efficacious for the antitumor activity and found to contain certain amounts of catechin and its derivatives. The hydrophilic extract fraction C36B2-8 had approximately 10 times more cytotoxic effects on B12 and L1210 cells than on isolated murine thymocytes. High concentrations (> 150 micrograms/ml) of C 36B3-8 mainly induced necrotic cell death. At low concentrations (< 100 micrograms/ml), however, C 36B3-8 induced not only necrosis but also apoptosis of the two tumor cell lines, which was proved by the TUNEL staining and DNA fragmentation techniques. The data indicate that certain ingredients of the cotton ball extract of G. indicum have an antitumor activity.

Purification and characterization of adenosine diphosphate ribose pyrophosphatase from human erythrocytes

Free ADP-ribose is a turnover product of NAD+, protein-bound polymeric and monomeric ADP-ribose, and cyclic ADP-ribose. But little is known about the specific cellular roles or metabolism of free ADP-ribose. ADP-ribose pyrophosphatase (EC 3.6.1.13), which hydrolyzes ADP-ribose into AMP and ribose-5'-phosphate, was purified from human erythrocytes. Purification was achieved to homogeneity by successive chromatographic steps, resulting in a final purification of 75,790-fold from the hemolysate. The purified enzyme showed a single band with the molecular weight of 34 kDa on SDS-PAGE both in the presence and absence of 2-mercaptoethanol. The molecular weight of the native enzyme calculated by gel filtration was 68 kDa, indicating that the active enzyme is a dimer of identical subunits. The enzyme requiring Mg2+ showed highest activity toward ADP-ribose, and about 40-70% activities with IDP-ribose, ADP-mannose and GDP-mannose. The enzyme showed a Km of 169 +/- 11 microM for ADP-ribose, broad pH optimum around pH 9.5, and pI of 5.1. ADP was a potent noncompetitive inhibitor with a Ki of 16 +/- 1.2 microM. These results suggest that our enzyme is unique, and different from the other ADP-ribose pyrophosphatases reported. ADP-ribose pyrophosphatase may play an important role in the regulation of intracellular steady-state of free ADP-ribose.

Intrinsic transcriptional activation-inhibition domains of the polyomavirus enhancer binding protein 2/core binding factor alpha subunit revealed in the presence of the beta subunit

A member of the polyomavirus enhancer binding protein 2/core binding factor (PEBP2/CBF) is composed of PEBP2 alphaB1/AML1 (as the alpha subunit) and a beta subunit. It plays an essential role in definitive hematopoiesis and is frequently involved in the chromosomal abnormalities associated with leukemia. In the present study, we report functionally separable modular structures in PEBP2 alphaB1 for DNA binding and for transcriptional activation. DNA binding through the Runt domain of PEBP2 alphaB1 was hindered by the adjacent carboxy-terminal region, and this inhibition was relieved by interaction with the beta subunit. Utilizing a reporter assay system in which both the alpha and beta subunits are required to achieve strong transactivation, we uncovered the presence of transcriptional activation and inhibitory domains in PEBP2 alphaB1 that were only apparent in the presence of the beta subunit. The inhibitory domain keeps the full transactivation potential of full-length PEBP2 alphaB1 below its maximum potential. Fusion of the transactivation domain of PEBP2 alphaB1 to the yeast GAL4 DNA-binding domain conferred transactivation potential, but further addition of the inhibitory domain diminished the activity. These results suggest that the activity of the alpha subunit as a transcriptional activator is regulated intramolecularly as well as by the beta subunit. PEBP2 alphaB1 and the beta subunit were targeted to the nuclear matrix via signals distinct from the nuclear localization signal. Moreover, the transactivation domain by itself was capable of associating with the nuclear matrix, which implies the existence of a relationship between transactivation and nuclear matrix attachment.

Negative regulation of granulocytic differentiation in the myeloid precursor cell line 32Dcl3 by ear-2, a mammalian homolog of Drosophila seven-up, and a chimeric leukemogenic gene, AML1/ETO

The polyomavirus enhancer binding protein 2alphaB (AML1/PEBP2alphaB/Cbfa2) plays a pivotal role in granulocyte colony-stimulating factor (G-CSF)-mediated differentiation of a myeloid progenitor cell line, 32Dc13. In this article, we report the identification of a PEBP2alphaB interacting protein, Ear-2, an orphan member of the nuclear hormone receptor superfamily that directly binds to and can inhibit the function of PEBP2alphaB. Ear-2 is expressed in proliferating 32Dc13 cells in presence of interleukin 3 but is down-regulated during differentiation induced by G-CSF. Interestingly, AML1/ETO(MTG8), a leukemogenic chimeric protein can block the differentiation of 32Dc13 cells, which is accompanied by the sustained expression of ear-2. Overexpression of Ear-2 can prevent G-CSF-induced differentiation, strongly suggesting that ear-2 is a key negative regulator of granulocytic differentiation. Our results indicate that a dynamic balance existing between PEBP2alphaB and Ear-2 appears to determine the choice between growth or differentiation for myeloid cells.

New semiautomated Doppler method for quantification of volumetric flow: intraoperative validation with multiplane transesophageal color Doppler imaging

We have validated a new semiautomated method for quantification of volumetric flow applied to multiplane transesophageal color Doppler mapping. This Doppler technique assumes only the incompressibility of the fluid and includes variations of flow area. By computing velocity vectors across a surface normal to the point of scanning, volumetric flow can be measured independently of the angle of incidence between the ultrasonic beam and the direction of blood flow. Mitral valvular flow rate was measured during surgery by transesophageal color Doppler echocardiography in 27 patients undergoing coronary artery bypass grafting at 45 sets of observations. The results were compared with those obtained by the thermodilution technique. The mean of the differences between the thermodilution technique and color Doppler echocardiography was 0.06 +/- 0.866 L/min for the mitral valvular flows (mean of differences [thermodilution-color Doppler] &/- 2 SDs of differences). Thus mitral valvular volumetric flow measured by this color Doppler method showed a close agreement to the thermodilution technique during surgery.

Purification and characterization of an antifungal PR-5 protein from pumpkin leaves

A 28-kDa antifungal PR-5 protein (PLTP) was purified from pumpkin leaves to homogeneity by using ammonium sulfate fractionation, a regenerated chitin column, and reversed-phase column chromatographies on butyl-Toyopearl and HPLC C18 columns. Analysis of 14 N-terminal amino acid sequences of PLTP shows 100% sequence identity to those of two PR-5 proteins, NP24 from tomatoes and AP24 from tobacco. The identical sequence also exhibited high amino acid sequence homology to that of an osmotin-like protein (OLP; 71%) from tobacco cells and thaumatin (64%), a sweet-tasting protein of Thaumatococcus danielli Bench. When the PLTP was immuno-blotted with antiserum raised against the tobacco OLP, the OLP antibody specifically cross-reacted with the PLTP, suggesting that they share several common epitopes in their tertiary structure of the proteins. The purified PLTP rapidly lyzed hyphal tips of Neurospora crassa at a concentration greater than 200 nM and significantly inhibited the fungal growth of Fusarium oxysporum in an agar-disc plate at a concentration greater than 2 microM. It also shows a synergistic effect with nikkomycin, a chitin synthase inhibitor, for the growth inhibition of Candida albicans.

The presence of a Sar1 gene family in Brassica campestris that suppresses a yeast vesicular transport mutation Sec12-1

Two new members (Bsar1a and Bsar1b) of the Sar1 gene family have been identified from a flower bud cDNA library of Brassica campestris and their functional characteristics were analyzed. The two clones differ from each other at 14 positions of the 193 amino acid residues deduced from their coding region. The amino acid sequences of Bsar1a and Bsar1b are most closely related to the Sar1 family, genes that function early in the process of vesicle budding from the endoplasmic reticulum (ER). The sequences contain all the conserved motifs of the Ras superfamily (G1-G4 motifs) as well as the distinctive structural feature near the C-terminus that is Sar1 specific. Our phylogenetic analysis confirmed that these two clones can indeed be considered members of the Sar1 family and that they have a close relationship to the ARF family. The Bsar1 proteins, expressed in Escherichia coli, cross-reacted with a polyclonal antibody prepared against Saccharomyces cerevisiae Sar1 protein. It also exhibited GTP-binding activity. Genomic Southern blot analysis, using the 3'-gene-specific regions of the Bsar1 cDNAs as probes, revealed that the two cDNA clones are members of a B. campestris Sar1 family that consists of 2 to 3 genes. RNA blot analysis, using the same gene-specific probes, showed that both genes are expressed with similar patterns in most tissues of the plant, including leaf, stem, root, and flower buds. Furthermore, when we placed the two Bsar1 genes under the control of the yeast pGK1 promoter into the temperature-sensitive mutant yeast strain S. cerevisiae Sec12-1, they suppressed the mutation which consists of a defect in vesicle transport. The amino acid sequence similarity, the GTP-binding activity, and the functional suppression of the yeast mutation suggest that the Bsar1 proteins are functional homologues of the Sar1 protein in S. cerevisiae and that they may perform similar biological functions.

Neoaloesin A: a new C-glucofuranosyl chromone from Aloe barbadensis

The first C-glucofuranosyl compound, named as neoaloesin A, was isolated from the leaves of Aloe barbadensis. Its structure was determined to be 8-alpha-D-glucofuranosyl-7-hydroxy-5-methyl-2-(2-oxopropyl)-4 H-1-benzopyran-4-one on the basis of chemical and spectral evidence.

Isolation of an additional soybean cDNA encoding Ypt/Rab-related small GTP-binding protein and its functional comparison to Sypt using a yeast ypt1-1 mutant

We have previously reported the isolation of a gene from a soybean cDNA library encoding a Ypt/Rab-related small GTP-binding protein, Sypt. Here, we report the isolation of a second Ypt/Rab-related gene, designated Srab2, from the same soybean cDNA library. And we compare the in vivo function of the two soybean genes utilizing a yeast ypt1-1 mutant. The Srab2 gene encodes 211 amino acid residues with a molecular mass of 23 169 Da. The deduced amino acid sequence of the Srab2 is closely related to the rat (76%) and human (75%) Rab2 proteins, but it shares relatively little homology to Sypt (46%) and Saccharomyces cerevisiae ypt proteins (41%). Genomic Southern blot analysis using the cDNA insert of Srab2 revealed that it belongs to a multigene family in the soybean genome. The protein encoded by Srab2 gene, when expressed in Escherichia coli, disclosed a GTP-binding activity. The expression pattern of the Srab2 gene is quite different from that of the Sypt gene. The Srab2 gene is predominantly expressed in the plumule region, while expression was very low in the other areas in soybean seedlings. On the other hand, the Sypt mRNA is not detectable in any tissues of soybean seedlings grown in the dark. However, light significantly suppressed the Srab2 gene expression, but enhanced the transcript levels of the Sypt gene in leaf and, at even higher levels, in root tissues. When the Srab2 and Sypt genes are introduced separately into a S cerevisiae defective in vesicular transport function, the Srab2 gene cannot complement the temperature-sensitive yeast ypt1-1 mutation at all, in contrast to the Sypt gene. In conclusion, the difference of functional complementation of the yeast mutation together with differential expression of the two genes suggest that the in vivo roles of the Srab2 and Sypt genes may be different in soybean cells.

Measurement of volumetric flow with no angle correction using multiplanar pulsed Doppler ultrasound

In this paper we show that by scanning at points on the surface of a sphere that the normal angle correction used in pulsed Doppler flow measurements is no longer necessary. Thus, it is possible to measure three-dimensional (3-D) flow using multiplanar ultrasound even though we only get one-dimensional (1-D) velocity information from pulsed Doppler ultrasound. The technique handles the three basic problems in flow measurements using ultrasound Doppler: The variations of the cross-sectional area, the time dependent changes in the velocity field, and the dependency of the angle of insonation. The technique is tested in a flow phantom using different angles of insonation to validate the angle independence of this new technique. Using six different angles of insonation in the range 0 degree to 69 degrees with flowrates in the range of 0-170 ml/s a linear dependence was found to be: measured (color Doppler) = 0.98 real flow (reference) + 1.36 ml/s, with a 95% confidence interval of +/- 13.9 ml/s.

A new Doppler method for quantification of volumetric flow: in vivo validation using color Doppler

OBJECTIVES

This study was designed to assess the accuracy of a new Doppler method for quantification of volumetric flow in vivo.

BACKGROUND

Noninvasive assessment of volumetric flow through heart valves and the great vessels remains a clinical goal. We present a new method for quantification of volumetric flow based on color Doppler mapping that computes velocity vectors over a surface normal to the point of scanning. This Doppler technique assumes only the incompressibility of the fluid. The method is basically independent of the angle of incidence between the ultrasound beam and the direction of blood flow and includes variations of flow area.

METHODS

The color Doppler method was tested in seven anesthetized pigs by measuring pulmonary volumetric flows using multiplane Doppler echocardiography. The results were compared with those obtained by the thermodilution technique. In addition, volumetric flows across the mitral valve were determined in 10 normal volunteers by transthoracic Doppler echocardiography and compared with flows obtained with velocity-encoded magnetic resonance imaging (MRI).

RESULTS

The mean value of the differences between the thermodilution technique and color Doppler were -0.16 +/- 0.94 liter/min for pulmonary volumetric flows (mean value of differences for [Thermodilution-Color Doppler] +/- 2 SD of differences). The mean value of the differences between MRI and color Doppler were 0.21 +/- 0.83 liter/min for mitral valvular volumetric flows (mean value of differences for [MRI-Color Doppler] +/- 2 SD of differences).

CONCLUSIONS

The method showed close agreement with thermodilution and MRI for assessment of volumetric flow in vivo. It is therefore a noninvasive method with potential applications for cardiac output measurement and for quantification of volumetric flow of valvular insufficiency and restrictive lesions.

MARIAN: an analysis tool for the assessment of left ventricular function measured by velocity encoding MRI

Velocity encoding MRI is a new non-invasive technique for measuring cardiac blood flow velocities. Flow in the three directions of space can be measured during the entire heart cycle. However, the analysis of large amount of data obtained from this technique requires specialized computational software packages to provide physicians with efficient analysis tools. A data visualization software package named Magnetic Resonance Imaging Analyzer (MARIAN) was developed. This software package uses visualization, animation, analysis, and computational tools adapted to time series of cardiac MRI data files, all accessible through a sophisticated graphics user interface. MARIAN was used as a tool for the analysis of the left heart blood flow patterns in two groups of human subjects: ten volunteers and eight patients. The patients were diagnosed with incapacitating angina pectoris and previous left ventricular myocardial infarction. Vector plot animations of the left atrial flow were realized for all volunteer examinations. The temporal flow velocity profiles were sampled at the tips of the mitral leaflets and in the lumen of the right upper pulmonary vein, when possible. The isovolumic relaxation time (IVRT) was estimated. The following flow parameters were obtained from the velocity profiles: at the mitral valve, the early diastolic E-wave, the late diastolic A-wave, the time of occurrence of the E- and A- waves; at the right upper pulmonary vein, the systolic S-wave, the early diastolic D-wave and the reverse late diastolic R-wave. The results obtained were consistent with previous studies using similar MRI techniques. Compared to the control group, the patient group exhibited higher isovolumic relaxation time, a lower peak E-wave, and a lower D-wave. MARIAN thus provided a fast, efficient and accurate data visualization tool for the analysis of human data.

Genotype distribution and comparison of the putative envelope region of hepatitis C virus from Korean patients

Comparative nucleotide sequence studies of the genomes of hepatitis C virus (HCV) revealed that there are at least 6 different genotypes of HCV. The prevalence of HCV genotypes among the patients with liver diseases in Korea was investigated using the polymerase chain reaction (PCR) for the NS5 region. In the 75 HCV RNA positive samples, two genotypes, type 1b and type 2a, were the major causative agents which accounted for 60% and 33% of infections respectively, while 7% could not be assigned a genotype by the methods used. The nucleotide sequences of cDNAs encoding the putative envelope proteins from 10 type 1b and 5 type 2a genotype samples were analyzed. Approximately 31-42% of the nucleotide sequences of type 1b samples examined differed from those of different genotypes. In the case of type 2a samples, 36-42% of the nucleotide sequences differed from those of different genotypes. The diversities of the amino acid sequences were the same or greater than those of the nucleotide sequences. Two hypervariable regions (HVR1 and HVR2) were recognized in both HCV genomes of genotypes 1b and 2a. However, the sequence divergence within the HVR2 region of genotype 2a was less than that of genotype 1b.

In vivo analysis and three-dimensional visualisation of blood flow patterns at vascular end-to-side anastomoses

OBJECTIVES

The aim of this study was to describe the velocity fields at distal vascular end-to-side anastomoses with different anastomosis angles in vivo.

MATERIALS AND METHODS

The abdominal aorta of ten 90 kg pigs was exposed from the superior mesenteric artery to the trifurcation. A segment of the aorta was bypassed using a polyurethane graft. Three anastomosis angles: 90 degrees (n = 3), 45 degrees (n = 3) and 15 degrees (n = 4) were studied. The bypass length, the anatomical position and the geometry of the anastomoses were standardised. During measurements, the proximal outflow segment was occluded and the flow rate was controlled by reversible iliac artery cross-clamping. Using a colour Doppler system the velocity fields were measured at various positions in the anastomosis. The colour Doppler velocity data were transferred to a computer for dynamic three-dimensional visualisation of the velocity profiles.

RESULTS

The angulation was reproduced within 10%. During the experiment, the flow rate was kept constant with Reynold's numbers typical for peripheral arteries. In the 90 degrees anastomoses very disturbed flow fields were seen. The 45 degrees anastomoses were characterised by: (1) low antegrade and retrograde velocities at the heel and (2) a zone of reverse and oscillating velocities at the toe and at one diameter downstream of the toe (1DDD) during deceleration. In the 15 degrees anastomoses no flow disturbances were seen either at the toe or at 1DDD. The velocity profiles were close to parabolic at peak flow at both positions.

CONCLUSIONS

It is concluded that the 15 degrees anastomosis is preferable from a haemodynamic point of view.

Left ventricular blood flow patterns in normal subjects: a quantitative analysis by three-dimensional magnetic resonance velocity mapping

OBJECTIVES

Magnetic resonance velocity mapping was used to investigate the hypothesis of a vortex motion within the left ventricle interacting with mitral valve motion and inflow velocity.

BACKGROUND

In vitro flow visualization studies have suggested the presence of a large anterior vortex inside the left ventricle during mitral inflow. However, to our knowledge the occurrence of this phenomenon has not been demonstrated in the human left ventricle.

METHODS

Magnetic resonance velocity mapping was performed in 26 healthy volunteers using a flow-adjusted gradient sequence for three-dimensional flow velocity acquisition in the long-axis plane of the left ventricle. By computer processing, the flow vectors in the left ventricle were visualized and animated dynamically.

RESULTS

The early diastolic mitral inflow was apically directed, and a large counterclockwise anterior vortex was created within the left ventricle shortly after the onset of the mid-diastolic semiclosure of the anterior mitral leaflet. During mid-diastolic diastasis, mitral inflow ceased until the flow accelerated again at atrial systole. The final closure of the mitral valve was preceded by a smaller vortex seen at the tips of the mitral leaflets. At systolic ejection, all flow vectors were directed toward the left ventricular outflow tract. The anterior vortex had a radius of 1.62 +/- 0.24 cm (mean +/- SD), and the average angular velocity (i.e., the rotation of an element about the center of the vortex within the central core) was 30.08 +/- 9.98 radians/s. The maximal kinetic energy of the anterior vortex was 4.3 x 10(-4) +/- 7.1 x 10(-5) J.

CONCLUSIONS

The hypothesis of a diastolic vortex formation in the human left ventricle was confirmed, and its close temporal relation to the motion of the anterior mitral leaflet was demonstrated.

Interleukin-6: a candidate mediator of human prostate cancer morbidity

OBJECTIVES

Interleukin-6 (IL-6) is evaluated as a candidate mediator of morbidity in patients with metastatic adenocarcinoma of the prostate.

METHODS

IL-6 concentration is measured by enzyme-linked immunoadsorbent assay (ELISA) in the ejaculate plasma of healthy men, in primary culture of prostate epithelial cells, in human prostate cancer cell line cultures and SCID mouse xenografts, and in the plasma of 73 men with metastatic adenocarcinoma of the prostate.

RESULTS

High levels of IL-6 secretion are found in the normal human ejaculate, in prostate epithelial primary culture, and in three of four anaplastic, androgen-independent human prostate cancer cell lines tested. In contrast, the hormone-responsive and PSA-secreting cell lines and the hormone-independent line PPC-1 do not secrete detectable levels of IL-6 by ELISA: The acquisition of a p53 mutation in LNCaP-GW and PPC-1 is not sufficient to confer the phenotype of high IL-6 secretion. Seventy-three men with well-characterized, advanced, hormone refractory prostate cancer prior to suramin therapy are tested for incidence of abnormal circulating levels of IL-6. Plasma IL-6 levels have a bimodal distribution, with the upper quartile of patients having abnormal levels from 9 to 61 pg/mL. A direct comparison of the high and low serum IL-6 groups show that elevated IL-6 levels are strongly correlated with objective measures of morbidity: decreased hematocrit, hemoglobin, and serum cholesterol, and increased white blood cell count and serum lactate dehydrogenase levels all in the absence of clinical infection.

CONCLUSIONS

These data show that IL-6 is a prostate exocrine gene product, a candidate mediator of prostate cancer morbidity, and a candidate marker of disease activity for prospective clinical testing.

Three-dimensional visualization of velocity profiles in the human main pulmonary artery with magnetic resonance phase-velocity mapping

Detailed data on blood velocity fields in the normal human main pulmonary artery are an essential platform for discriminating physiologic from pathologic pulmonary flow patterns. Over the years, many studies have revealed quite inconsistent data mainly because of lack of suitable measuring techniques. By using combined cardiac- and respiratory-triggered magnetic resonance phase velocity mapping, very consistent data were obtained in 12 volunteers. In all subjects the location of the highest axial velocities was shifted from the inferior-right toward the superior-left part of the vessel area during the right ventricular contraction, with rapidly decreasing velocities to the inferior right evolving into retrograde flow in the deceleration phase. The mean temporal velocity profile was consistently skewed with a low flow region also toward the inferior-right vessel wall. The magnetic resonance phase shift method used in this study provided remarkably consistent high-quality data about human pulmonary artery velocity fields. This is most likely because of the use of combined cardiac and respiratory triggering.

Two-dimensional mitral flow velocity profiles in pig models using epicardial Doppler echocardiography

OBJECTIVES

This study investigated the velocity distribution across the natural mitral valve.

BACKGROUND

Information about the blood velocity distribution across the mitral valve is of interest in basic fluid dynamic studies of the natural mitral valve and is needed for precise cardiac output estimates by Doppler echocardiography.

METHODS

The velocity distribution across the mitral valve was measured by epicardial Doppler echocardiography in ten 90-kg anesthetized pigs. By rotating the ultrasound transducer in 30 degrees intervals from the apical position, we constructed two-dimensional velocity profiles across the left ventricular inflow tract from diameters from each rotation arranged around a reference point. The time-averaged mitral velocity profile was calculated to estimate the error in cardiac output calculations that may occur with pulsed Doppler ultrasound when a single sample volume is used to record the mean velocity across the mitral orifice.

RESULTS

The time-averaged diastolic cross-sectional mitral velocity profiles at the level of the mitral annulus and leaflet tips were variably skewed because of the development of a large anterior vortex in the left ventricle during the deceleration of early diastolic inflow and atrial systole. The ratio of the time-velocity integral of the center sample volume to the spatially averaged time-velocity integral was 1.13 +/- 0.15 (mean +/- SD) (range 0.80 to 1.32). Using regression analysis, we found a correlation between the degree of nonuniformity of the cross-sectional velocity distribution and the peak velocity of the anterior vortex (r = 0.65, p < 0.01).

CONCLUSIONS

The assumption of a flat mean velocity profile across the mitral valve can introduce errors of +13 +/- 15% (mean +/- SD) in cardiac output measured with pulsed Doppler ultrasound when one is interrogating a single center sample volume.

What force can the myocardium generate on a prosthetic mitral valve ring? An animal experimental study

Data on the magnitude of forces which can be generated by the myocardium on a prosthetic heart valve ring are not available from the literature. Therefore, we implanted strain gauge mounted 29 mm original specification Edwards-Duromedics mitral valve prostheses in 13 pigs. The valves were implanted in both anatomic and anti-anatomic orientation. In order to estimate the forces on the valve ring, acute in vivo measurements of the dynamic deformation of the valve ring were performed and correlated with the stiffness of the same valves measured in vitro. In the post cardioplegic heart of the anesthetized pigs there was a maximum force developed by the myocardium of 6-8 N on the valve ring with a resulting maximum deformation of 40 microns with valves mounted in the anatomic position. These findings have implications for design of future mechanical mitral valves and for mitral rings used for mitral valvuloplasty. These data can also be used as reference for evaluation of safety limits in existing valves in terms of their physical properties. Based on the direction of the maximum myocardial force acting on the mitral valve ring and the difference in compliance of the valve ring along the pivotal or orthogonal axis, it is indicated from that these acute porcine studies that bileaflet valves in the mitral position are subjected to less deformation when implanted 60 degrees counter-clockwise to the native mitral intercommisural line.

Studies by pulsed Doppler ultrasonography of velocity fields downstream of graded stenoses on the abdominal aorta in pigs

PURPOSE

To investigate local hemodynamics downstream of arterial stenoses, a perivascular five-element Doppler ultrasound transducer was used for registration of one-dimensional velocity profiles and estimation of Reynolds (turbulent) normal stresses downstream of smooth, graded stenoses on the abdominal aorta in six 90 kg pigs.

METHODS

Blood velocities were registered by a 10 MHz pulsed Doppler velocimeter that used a modified zero-crossing detector with an upper -3 dB cutoff frequency of 200 Hz. Signal analysis included ensemble averaging, turbulence analysis, and dimensional visualization of velocity profiles.

RESULTS

Velocity profiles downstream of minor (< or = 40%) and moderate (40% to 65%) stenoses were skewed with the highest systolic velocities toward the anterior vessel wall and diastolic flow reversal occasionally present at the posterior vessel wall. Immediately downstream of severe (> or = 65%) stenoses a prominent poststenotic jet and systolic recirculation zones were present. Further downstream, vortices and eddies dominated the flow field. Reynolds normal stresses were highest at locations in the velocity field with high-velocity gradients corresponding to the parajet zone.

CONCLUSIONS

The present study demonstrated that pulsed Doppler ultrasonography can provide detailed and quantitative information of flow phenomena such as jetlike flow, vortices, and recirculation zones in a poststenotic flow field in the abdominal aorta.