Accessible magnetic resonance imaging

The cost of magnetic resonance imaging (MRI) is driven by magnetic field strength. Misperceptions as to the impact of field strength on performance have led to systems that are more expensive than they need to be. Careful analysis of all the factors that affect diagnostic quality lead to the conclusion that field strength per se is not a strong determinant of system performance. Freed from the constraints imposed by high-field operation, it is possible to exploit a varied set of opportunities afforded by low-field operation. In addition to lower costs and easier siting, we can take advantage of shortened T1 times, higher contrast, reduced sensitivity to motion, and reduced radiofrequency power deposition. These conceptual advantages can be made to coalesce onto practical imaging systems. We describe a low-cost MRI system that utilizes a permanent magnet of open design. Careful optimization of receiving antennas and acquisition sequences permit performance levels consistent with those needed for an effective diagnostic unit. Ancillary advantages include easy access to the patient, reduced claustrophobia, quiet and comfortable operation, and absence of a missile effect. The system can be sited in 350 sq ft and consumes a modest amount of electricity. MRI equipment of this kind can widen the population base than can access this powerful and beneficial diagnostic modality.

Clinical and experimental studies on paediatric pneumonia treated by lung easing tablets

197 cases of paediatric pneumonia from 2 hospitals were treated by Ning Fei Pian (NFP, the Lung Easing Tablets), a proprietary Chinese medicine for antipyresis, detoxication, blood invigoration, resolution of cough and phlegm; the control group was treated by penicillin, and the therapeutic results were comparable. Examinations of microcirculation and hemorrheology in the nailbed revealed improvements by NFP, which were conducive to the recovery of pneumonia. Electron-microscopically, the tablets also produced improvements in microcirculation, relief of lung edema, and the ratio of ventilation and blood flow.

Atrial natriuretic peptide in a rat model of cardiac failure. Atrial and ventricular mRNA, atrial content, plasma levels, and effect of volume loading

This study examined the relation between synthesis, atrial storage, and plasma levels of atrial natriuretic peptide (ANP), and it examined plasma ANP levels and hemodynamic output in response to volume expansion in a rat model of myocardial infarction and failure. Arterial ANP concentrations did not correlate linearly with infarct size, but they did show an abrupt increase when infarct size exceeded 30% of the left ventricle, similar to the abrupt increase of left ventricular end-diastolic pressure with infarct size greater than 30%. Consequently, a close relation was found between plasma ANP levels and left ventricular end-diastolic pressure (n = 23, r = 0.89, p less than 0.001). Atrial ANP content per gram of tissue but not ANP content per pair of atria was reduced in rats with large infarcts (greater than 40%, p less than 0.05 vs. control animals). ANP mRNA level per pair of atria (related to total atrial RNA), determined by liquid hybridization (controlled by northern blot analysis), was increased by 38% in infarcted rats (p less than 0.05 vs. controls), but the ratio of atrial ANP mRNA relative to atrial beta-actin mRNA levels was not increased. Right and left ventricular ANP mRNA level increased by 90% and 380%, respectively, far exceeding the concomitant increase in beta-actin mRNA (+26% in the left ventricle). Plasma ANP increased with volume loading in controls and rats with moderate infarcts but not in rats with large infarcts despite a similar increase in right atrial pressure (compared with control animals); thus, the relation of delta ANP/delta right atrial pressure exerted by volume loading decreased in rats with large infarcts. Similarly, the response of cardiac output and renal blood flow (determined by radioactive microspheres) to volume loading was attenuated in rats with large infarcts. Thus, in this model of chronic cardiac failure, the activation of the ANP system is closely coupled with the increase in intracardiac pressures without correlating linearly to the extent of myocardial loss. Second, in severe cardiac failure, additional stimulation such as volume loading may elicit only an attenuated ANP secretion response, for example, due to saturation of the ANP receptor sensing system or to a limited transformation rate of pro-ANP. Third, the increase in atrial ANP synthesis and the increase in atrial ANP gene expression seems limited; however, substantial specific ANP gene expression occurs in the ventricles, which, in turn, may contribute to increased plasma ANP levels in chronic heart failure.

Frequency domain compensation for inhomogeneous layers in ultrasound holography

A frequency-domain compensation method is presented that is based on the ultrasound holography B-scan (UHB) imaging principle. In an acoustic imaging system, the wavefront-angle-dependent distortions caused by any kind of known inhomogeneous reason can be compensated by this method. It is applied here in the frequency domain using the so-called rear-ranging operation for the longitudinal distortion and the multiplication of phase factors for the lateral distortion. The method is especially suitable for compensating different velocity layers in acoustic imaging systems. The results of both computer simulations and water-tank experiments are promising.

Pharmacokinetic and pharmacodynamic studies of piretanide in rabbits. IV. Effect of piretanide on the proximal tubules and the loop of Henle under a hydrated condition

In order to evaluate the effect of piretanide on the renal transport of water and osmotic substances, a clearance study was carried out in well hydrated rabbits. After intravenous bolus administration of piretanide, glomerular filtration rate, proximal tubular clearance and urine flow rate, as well as the pharmacokinetics of piretanide, were determined. A pharmacokinetic and pharmacodynamic link model which was developed in the previous paper was applied to the present experimental results. The results indicated that the effect of piretanide on the renal transport of water and osmotic substances in the hydrated rabbits was reasonably described by the model. The model analysis suggested that the diuretic response to piretanide was attributable to the inhibition of reabsorption of electrolytes in the proximal tubule, as well as in the loop of Henle.

Regeneration of tepals, stamens and ovules in explants from perianth of Hyacinthus orientalis L. importance of explant age and exogenous hormones

Regeneration of tepals, stamens and ovules from perianth explants of Hyacinthus orientalis L. in different developmental stages could be controlled by means of exogenous hormones. Perianth explants in a relatively early stage of development were competent for differentiation of tepals on Murashige and Skoog (MS) medium supplemented with 2 mg·1(-1) N(6)-benzylaminopurine (BAP) or zeatin and 0.1 mg·1(-1) 2,4-dichlorophenoxyacetic acid (2,4-D). Perianth explants in a later stage of development regenerated stamens and ovules, and marked difference was observed in the activity of BAP and zeatin in this regard. Zeatin stimulated more strongly stamen formation, while BAP enhanced ovule formation. Thus, stamens were formed when the explants were cultured for four months on medium with 2 mg·1(-1) BAP and 0.1 mg·1(-1) 2,4-D and then transferred to medium with 0.2 mg·1(-1) zeatin and 0.005 mg·1(-1) 1-naphthaleneacetic acid. On the other hand, differentiation of ovules occured in explants cultured for two weeks on the former medium and then transferred to medium with 0.1 mg·1(-1) BAP and 0.01 mg·1(-1) 2,4-D. Although ovule formation could also be obtained with 2 mg·1(-1) BAP alone, it was substantially enhanced by the presence of 0.1 mg·1(-1) 2,4-D in the medium in the early stages of culture. The results demonstrate the importance of both the developmental stage of the source organ from which explants are excised and of the hormone composition of the medium for the regeneration of different floral organs by perianth explants of Hyacinthus.

Prostaglandins involved in contractions by angiotensin II and bradykinin of isolated dog sphincter pupillae

1. The dog isolated sphincter pupillae contracted in response to acetylcholine, angiotensin II (AII), bradykinin, prostaglandins F2 alpha, D2, E2 and I2, and thionate thromboxane A2 (sTXA2) in a concentration-dependent manner. 2. AII-induced contractions were suppressed by treatment with saralasin, indomethacin, aspirin and diphloretin phosphate (DPP), a prostaglandin receptor antagonist. Contractions induced by bradykinin were also attenuated by indomethacin, aspirin and DPP. The amount of prostaglandin F2 alpha (PGF2 alpha) in the bathing media was increased approximately 41% following stimulation of the preparations by bradykinin. 3. The potency of contractile responses was in the order of PGF2 alpha greater than PGD2 = sTXA2 greater than PGE2 greater than arachidonic acid greater than PGI2. Contractions induced by PGF2 alpha were not significantly affected by treatment with indomethacin and ONO3708, an antagonist of the vasoconstrictor effect of prostaglandins, but appreciably attenuated by DPP. Arachidonic acid-induced contractions were inhibited by indomethacin. 4. Contractions of dog iris sphincter muscle in response to AII and bradykinin may be mediated via substances synthesized by cyclo-oxygenase from arachidonic acid. The distribution and nature of the prostaglandin receptors appear to differ markedly in iris sphincter and vascular smooth muscles.

Pharmacokinetic and pharmacodynamic studies of piretanide in rabbits. III. Sodium and potassium excretion under different hydrated conditions

The diuretic effect of piretanide, one of the loop diuretics, was investigated in three different hydrated conditions, namely well hydrated condition (treatment I), progressive hydropenic condition (treatment II) and complete hydropenic condition (treatment III) in rabbits. Each rabbit received intravenous administration of 1.5 or 15 mg/kg of piretanide and the urine flow rate, the excretion rates of Na and K, plasma concentrations of Na and K, urine osmolarity, plasma concentration of piretanide and urinary excretion of piretanide were determined after administration. The pharmacokinetics of piretanide was not influenced by the hydration state of the body, even in treatment III. The diuretic effect of piretanide evaluated by both urine flow rate (EH2O) and Na+K excretion rate (ENa+K), was significantly affected by the hydration state of the body. The more the hydropenic state was developed, less amounts of urine or electrolytes were excreted. A pharmacokinetic-pharmacodynamic link model which was proposed in the previous paper was applied to the present experimental results. The result indicated that the diuretic effect, even in the complete hydropenic condition (treatment III), was reasonably described by the model, with minor modifications. The time course of the excretion rate of K (EK) was not always in parallel with ENa+K, but was dependent on treatments. We found that the K-fraction, which was known as an indicator of the Na-K exchange reaction in the distal tubule, was quantitatively related to ENa+K, using a simple equation. Accordingly, the time course of EK was also calculated. The result also indicated that time courses of EK were described reasonably well by the model, regardless of treatments and doses.

Pharmacokinetic and pharmacodynamic studies of piretanide in rabbits. II: Effects on the proximal tubules and the loop of Henle

In order to clarify the effect of piretanide in the nephrons, pharmacokinetics and pharmacodynamics of piretanide were studied under a hydropenic condition in the rabbit. The hydropenic condition was developed by a simultaneous infusion of an antidiuretic hormone and hyperosmotic saline. Lithium was used as the indicator of the proximal sodium reabsorption. Plasma concentrations and urinary excretion rates of piretanide were not influenced by the hydration state of the body. The glomerular filtration rate (GFR) showed a long lasting decrease after piretanide administration; however, the urinary excretion rates of salts and water were increased prominently just after administration. The lithium clearance ratio, which was obtained by dividing the lithium renal clearance by GFR, indicated that piretanide inhibited the proximal reabsorption of sodium. The urine osmolarity after piretanide administration showed a significant decrease, and this indicated that the osmolarity of the renal medulla was also influenced by piretanide. From these observations, a model describing the transport of water and osmotic substances in the nephrons was constructed to calculate the effect of piretanide. The results indicated that the diuretic effect of piretanide in the hydropenic rabbit was reasonably described by the model. The model parameters obtained suggested that the site of action of piretanide in the proximal tubules might be in the peritubular side rather than inside the lumen, whereas the site of action in the loop of Henle might be inside the lumen.

Pharmacokinetic and pharmacodynamic studies of piretanide in rabbits. I. Effect of different hydrated conditions

The pharmacokinetics and pharmacodynamics of piretanide in rabbits were investigated. After intravenous administration, the plasma concentrations and the urinary excretion rates of piretanide, as well as the pharmacologic effects, were measured under two different hydrated conditions. In one experiment, the amount of the body fluid which was lost during diuresis was replaced by infusing Ringer's solution at exactly the same rate with the urine flow rate (treatment I). In another experiment, no compensatory infusion was made (treatment II). There was no appreciable difference between treatment I and II, as far as the plasma concentrations and urinary excretion rate were concerned. In spite of the similarities in the pharmacokinetic properties, the pharmacologic effects of piretanide were influenced considerably by the hydrated conditions of the body. The diuretic effect expressed as the excretion rate of the sum of urinary sodium and potassium was plotted against the corresponding urinary excretion rate of unchanged piretanide. The shape of the each graph showed a similar sigmoid like curve; however, the curve in treatment I was significantly shifted to the right compared to that in treatment II. This fact indicated that the pharmacologic effect of piretanide seemed to be modified by the contents of water and electrolytes in the body. The plasma concentrations and urinary excretion of piretanide were reasonably described by a linear three compartment open model.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminoterminal procollagen III peptide elevation in alcoholics who are selenium and vitamin E deficient

Serum aminoterminal procollagen III peptide (PIIIP) was measured in 36 alcoholic subjects. There was a significant elevation of PIIIP in subjects with proven liver disease (median 17.5 ng/ml, n = 24) compared to those without liver disease (median 4.7 ng/ml, n = 12). Those subjects with raised serum transaminase values (AST) had elevated PIIIP values (median 13.7 ng/ml, n = 22) compared to those with normal transaminase values (median 3.7 ng/ml, n = 14). In those alcoholic subjects who were deficient in both selenium and vitamin E there was a significant elevation (p less than 0.01) of PIIIP values (median 26.4 ng/ml, n = 7) compared to subjects with normal levels (median 7 ng/ml, n = 11). Subjects deficient in selenium alone had PIIIP values in an intermediate range. Selenium and vitamin E, as important free radical scavengers, may protect the liver in alcoholic subjects from oxidative damage leading to hepatic fibrosis.

Mutagenicity of benzidine and related compounds employed in the detection of hemoglobin

Seven compounds commonly used as chromagens for the detection of hemoglobin and its derivatives have been assayed for mutagenicity employing the Salmonella/mammalian microsome test. Three of these compounds, benzidine, o-dianisidine, and o-tolidine, were shown to be mutagenic. Since benzidine and o-tolidine are already known to be carcinogens, there is a high probability that o-dianisidine will also prove to be a carcinogen. Four compounds tested with this system, o-anisidine, diphenylamine, guaicol, and o-toluidine, were not mutagenic.