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Biomedical subjects

S E Greenwald

Publications and source records attributed to S E Greenwald.

At least 19 recordsLinked to original sources
PubMed1995

Desmin expression in rhabdomyosarcoma: influence of the desmin clone and immunohistochemical method.

AIM: To determine which, if any, of five commercially available desmin clones is most reliable at labelling desmin filaments and whether the enhanced polymer one step (EPOS) method of labelling is of any advantage in the routine diagnostic laboratory. METHODS: Thirty four rhabdomyosarcomas from the files at The Hospital for Sick Children, Great Ormond Street, London, were studied. Four different desmin clones, DE-R-11, D33, DE-U-10, and PDE, were applied to each using the conventional extravidin biotin peroxidase method. The D33 clone was also applied using the EPOS method. RESULTS: The EPOS method incorporating D33 persistently scored more cells as desmin positive and was positive in four cases which were negative on staining with the other clones. CONCLUSIONS: The D33 desmin clone used with the EPOS method is more reliable for identifying desmin filaments in tumours than other desmin antibodies tested. Different desmin clones using a routine technique label different rhabdomyosarcoma cells and therefore it is justifiable to use more than one clone.

Desmin↗
PubMed1992

Morbid anatomy in neonates with Ebstein's anomaly of the tricuspid valve: pathophysiologic and clinical implications.

The hearts of six neonates with Ebstein's anomaly of the tricuspid valve who died in the 1st month of life were compared with hearts of six age- and size-matched control neonates. All six hearts had morphologically severe disease with gross right atrial dilation and marked apical displacement of the tricuspid valve. All had a secundum atrial septal defect and four had additional cardiac lesions (pulmonary atresia in two, ventricular septal defect in two). There was significant thinning of the right ventricular free wall distal to the tricuspid valve (3 +/- 0.2 mm vs. control 4.2 +/- 0.2, p less than 0.01) and right ventricular fiber diameter was reduced (7.2 +/- 0.3 microns vs. control 11.4 +/- 0.6, p less than 0.001). The fibrous tissue content of both right and left ventricular free walls was increased (right, 29.3 +/- 2.6% vs. control 8.7 +/- 1.1, p less than 0.001; left, 23.2 +/- 1.5% vs. control 8.5 +/- 0.7%, p less than 0.001). Although the right ventricular abnormalities might be explained by hemodynamic stress in utero, abnormalities of the left ventricular free wall suggest that either genetic or nonhemodynamic environmental factors are involved in the morphogenesis of this condition. Increased right and left ventricular fibrosis may contribute to the poor early outcome in this group and may predispose to late complications, such as subnormal exercise performance, hemodynamic deterioration or late sudden death that may occur in patients with Ebstein's anomaly who survive the neonatal period.

Ebstein Anomaly↗
PubMed1992

A general method of determining the frequency-dependent propagation coefficient and characteristic impedance of an artery in the presence of reflections.

An iterative method of calculating propagation parameters at harmonics of heart rate for a uniform vascular segment from a combination of four arterial waveform measurements is presented. Measurements of blood pressure, vascular diameter, and blood flow-rate may be combined arbitrarily provided only that at least one measurement of pressure and one of flow-rate be included; the requirement of four measurements implies at least two measurement sites along the vessel. The analysis is thus a generalization of those associated with previous methods of determining propagation parameters, allowing for instance relaxation of the requirement of equal spacing in the three-point method. Results are presented for the propagation of an impulse along a rubber tube when the measurements are pressure at two sites, flow-rate and diameter.

Arteries↗
PubMed1992

The development of an in-vitro perfusion system for studies on cultured cells.

The design and use of a perfusion system, using a modified flow chamber for studies on cultured animal cells, is described. Rat thoracic aorta smooth muscle cells were isolated by an explant method and grown on Thermanox coverslips. These were introduced into the flow chamber. A flow rate of 25ml/min and a shear stress of 14.6 dynes/cm2 (12 dyne = 10 microN) (both within physiological limits) were maintained. Cells remained attached to the coverslips after 8h of perfusion with culture medium. The effect of exposing rat smooth muscle cells to the cardiovascular toxin, allylamine, is also described. The components of the system are routinely available, simple to clean, easy to assemble and sterilize. The incorporation of an in-line sensor that monitors pH, PO2, PCO2 and temperature ensures that the perfusion conditions remain within physiological limits. Automation means that minimal supervision is required. This system provides a potential mechanism in which cultured vascular cells may be perfused under controlled haemodynamic conditions, and their response to a cytotoxin may be evaluated.

Allylamine↗
PubMed1990

Effect of age on the in vitro reflection coefficient of the aortoiliac bifurcation in humans.

The local reflection coefficient (r) at the aortoiliac junction was estimated in vessels removed at autopsy from 15 females and 31 males aged 2 months to 88 years by calculating the characteristic impedance (Zc) of the abdominal aorta and the two common iliac arteries. Zc was evaluated for each vessel by measuring cross-sectional area from radiographs and propagation velocity of an isolated pressure impulse generated by a solenoid-driven piston connected to the distal end of the abdominal aorta, and detected at several sites a known distance from the junction. Attenuation coefficients in the aorta were estimated from the peak amplitude of the impulse at these several sites. We observed significant decreases with age in abdominal aortic attenuation coefficient (gamma = 0.053-5 x 10(-4) age [yr], r = -0.42, p less than 0.005), and the area ratio (AR) of the junction (sum of the iliac cross-sectional areas/aortic cross-sectional area) (AR = 0.93-0.002 x age [yr], r = -0.31, p less than 0.05). Bifurcation angle (Angle) and aortic propagation velocity (caorta) increased significantly (angle = 40.2 + 0.26 x age [yr], r = 0.41, p less than 0.01; caorta (ms-1) = 7.59 + 0.175 x age [yr], r = 0.69, p less than 0.0001). No significant association between age and iliac propagation velocity was found. On the basis of area measurements alone, it has been argued that the observed decrease in area ratio with age causes r to become more positive. The lack of age-related changes in iliac propagation velocity (and hence stiffness), an observation confirmed by most of the few reports in the literature, and the large increase in abdominal aortic stiffness, however, greatly outweighed the area ratio changes and caused a significant decline in reflection coefficient from +0.3 in early life to -0.3 in old age. (Reflection coefficient = 0.30-0.0065 x age [yr], r = -0.68, p less than 0.0001). Between the ages of 30 and 60 years, its absolute value was less than 0.1, confirming in vivo work on subjects within this age range. In children, a significant positive reflection at the distal end of the aorta will amplify the pulse wave in this region. As this vessel becomes stiffer with increasing age, amplification will increase, whereas the increasingly negative value of r will partially offset this rise, reducing pulse pressure on either side of the junction.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1986

High frequency characteristics of the arterial system.

Pressure, flow and diameter were measured in the abdominal aorta of five anesthetized dogs during normal heart beats and heart beats with a superimposed impulse (generated by rapidly injecting a small volume of saline into the system). From Fourier analysis it was found that the impulse enhanced the amplitudes of the higher harmonics so that frequencies up to 80 Hz could be studied. Both the input impedance and apparent phase velocity above 20 Hz were independent of frequency and their average values were designated as characteristic impedance and true phase velocity. Average characteristic impedance for all five animals was 2.0 +/- 0.1 X 10(8) Nsm-5 and average phase velocity was 8.3 +/- 0.6 ms-1. Phase velocities calculated from characteristic impedance (1.76-2.39 X 10(8) Nsm-5) and from the slope of the pressure-diameter relation (0.102-0.25 X 10(-8) Nm-3) were similar to the true phase velocity as defined above (6.79-9.85 ms-1). It may be concluded that the input impedance converges to characteristic impedance and apparent phase velocity converges to phase velocity for high frequencies.

Animals↗
PubMed1985

Pulmonary vascular input impedance in the newborn and infant pig.

The input impedance of the main pulmonary artery in 26 pigs aged from 1 h to 2 weeks has been calculated from measurements of pressure and flow. From these data we have derived estimates of the hydraulic power output of the right heart. The impedance spectra were similar in form to those in many other studies and were consistent with the presence of a single reflection site within the lung. The frequency of the (single) minimum decreased steadily with increasing age as did the corresponding zero crossing point on the phase curve. From estimates of propagation velocity the position of this "reflection site" was found to coincide with the position of the lung periphery in each age group. An overall fall in characteristic impedance with increasing age was found to be due to the increasing diameter of the pulmonary artery rather than to changes in its elasticity. The total power output/body weight of the right heart fell from 10.4 to 4.8 mW X kg-1 from birth to 4 weeks of age. During this period the ratio of pulsatile to steady power fell from 0.5 to 0.31. We conclude that this fall is related to a reduction in the effective reflection of pressure and flow waves within the lung due to increasing attenuation and possibly to a reduction in the magnitude of the lumped reflection coefficient itself.

Aging↗
PubMed1985

The static elastic properties and chemical composition of the rat aorta in spontaneously occurring and experimentally induced hypertension: the effect of an anti-hypertensive drug.

The static elasticity and scleroprotein content of the aorta have been measured in 24 Okamoto spontaneously hypertensive rats aged 22-25 weeks, and 24 Wistars of the same age in which hypertension had been induced by nephrectomy and treated with a steroid. From the age of 4 weeks half the animals in each group were treated with a diuretic drug. By the age of 15 weeks caudal artery systolic blood pressure was significantly lower than control values in both drug-treated groups and remained so until death. Both types of hypertension were associated with larger diameter, thicker-walled and heavier aortas than those in the drug-treated animals. Vessels from Okamoto animals contained more collagen than those from the Wistars, although the collagen content was unchanged by drug treatment. Neither drug nor strain had any clear-cut affect on elastin content. In spite of these differences in wall thickness and chemical composition, values of the functional stiffness of the aorta measured over a wide range of pressure were similar in all four groups of animals. Using a simple model of the aorta in which elastin and collagen bear stress in parallel we find that the relationship between vessel composition and static incremental elastic modulus (structural stiffness) is similar in both models of hypertension and is not changed by drug treatment in spite of the consequent reduction in blood pressure.

Aging↗
PubMed1984

Actions of cysteinyl leukotrienes in coronary, femoral and carotid vessels of the pig.

Coronary, femoral and carotid vascular beds of anaesthetised pigs were perfused with heparinised arterial blood using an extracorporeal perfusion system. Blood flow was measured in each vascular bed. Leukotriene (LT) D4 caused a dose-related reduction in flow in the left anterior descending (LAD) artery. LTs C4 and D4, angiotensin and noradrenaline caused dose-related reductions in flow in femoral and carotid vascular beds. High doses of LTD4 caused total cessation of blood flow in the LAD and femoral beds. In the femoral and carotid beds LTC4 but not LTD4 caused an initial increase followed by a prolonged reduction in flow. Indomethacin (1.4 X 10(-5) mol kg-1, i.v.) did not affect the vasoconstrictor action of LTs.

Angiotensin II↗
PubMed1983

Effects of intra-coronary administration of leukotriene D4 in the anaesthetized dog.

The left anterior descending coronary artery in anaesthetized greyhounds was perfused at constant pressure with blood pumped from the carotid artery. Phasic and mean coronary flow, left ventricular pressure, dP/dt, cardiac output, ECG, heart rate and systemic pressure were measured. Leukotriene (LT) D4 was administered into the left anterior descending coronary artery as a bolus injection. LTD4 caused dose-related reductions in coronary flow. Other parameters showed little immediate change although a gradual decrease in left ventricular pressure, dP/dt, cardiac output and systemic pressure occurred after administration of LTD4. Following intracoronary administration of LTD4 small surface haemorrhages were observed over the area perfused. The reduction in coronary flow was not inhibited by indomethacin.

Animals↗
PubMed1982

Changes in the distensibility of the intrapulmonary arteries in the normal newborn and growing pig.

The static elastic properties and structure of the intra-pulmonary arteries have been studied in pigs from fetal life to 4 months old, by radiographic and histological methods. During this period the average radius of the vessels examined varied from approximately equal to 0.9 mm at birth to 3.3 mm at the age of 4 months. The form of the pressure radius curves was similar to that observed in the systemic circulation and was characteristic of the gradual recruitment of collagen fibres with increasing pressure. In vessels near the hilum, wall thickness decreased from approximately equal to 180 microns to 100 microns during the first 2 weeks and thereafter increased to approximately equal to 250 microns. Throughout the lung and in all age groups there was a linear relationship between the logarithm of pressure strain elastic modulus (used as a measure of functional stiffness) and pressure. In contrast to the systemic arteries there was little change in functional stiffness towards the periphery, although the incremental elastic modulus (structural stiffness) did increase at sites further removed from the heart. During the first two weeks of life there was little change in functional stiffness (Ep approximately equal to 1.1 X 10(4) Nm2) although by 4 months Ep had increased by a factor of three. During this period despite fluctuations with age, an overall increase in structural stiffness was also observed (EINC approximately equal to 1 X 10(5) at 4 to 6 h to 2 X 10(5) Nm-2 at 4 months). The observations suggest that the changes in elasticity observed in early life are a consequence of the adaptation of the circulation to the lower pulmonary arterial pressure of extra-uterine life.

Aging↗
PubMed1982

Effect of smooth muscle activity on the static and dynamic elastic properties of the rabbit carotid artery.

The variation of radius with pressure was measured in vitro in the carotid artery of ten rabbits. Experiments were performed without prior conditioning of the vessel, over an inflation-deflation cycle at pressures in the range 0 to 24 kPa during treatment with, and in the absence of noradrenaline (referred to as active and passive conditions). The effect of a step change in pressure (2.7 kPa) on the radius of the vessel was investigated on a further three specimens. Under passive conditions, the variation of the static and the real part of the dynamic incremental elastic modulus with pressure and stress was similar during both inflation and deflation. Under active conditions a large degree of pressure-radius hysteresis was observed. At physiological pressures smooth muscle activity was associated with a decrease in elastic modulus when compared to passive values at the same pressure or stress. At a stress above 2 x 10(5) N.m-2 yield of the constricted vessels was observed and on further inflation and subsequent deflation the pressure radius curve was identical to that obtained under passive conditions. We suggest that conditioning a vessel, by means of repeated inflation to a high pressure and deflation to zero pressure, before measuring its elastic properties may give misleading results when applied to the vessels of living animals.

Animals↗