Two prototype blood-pool agents for contrast-enhanced magnetic resonance angiography of the portal vein in pigs

RATIONALE AND OBJECTIVES

Macromolecular "blood-pool" agents such as polylysine-gadopentetate dimeglumine or albumin-gadopentetate dimeglumine, which provide prolonged intravascular enhancement, were tested as magnetic resonance (MR) angiography contrast agents for the portal vein in pigs.

METHODS

Phase-contrast MR angiography of the portal veins was performed on six pigs before and after intravenous administration of polylysine-gadopentetate dimeglumine (n = 3) or albumin-gadopentetate dimeglumine (n = 3).

RESULTS

The contrast-to-noise ratio of the portal veins was improved by 74% and 52%, respectively, using polylysine-gadopentetate dimeglumine or albumin-gadopentetate dimeglumine. More branches of the intrahepatic portal veins were visualized on postcontrast images.

CONCLUSION

Blood-pool paramagnetic contrast agents improved the visualization of hepatic vasculature using phase-contrast MR angiography in our experimental model.

Workplace assaults on minority health and mental health care workers in Los Angeles

Workplace violence is becoming increasingly recognized as a serious problem in health care settings. All 628 workers' compensation assaults claimed by minority Los Angeles County health care workers from 1986 through 1990 were abstracted. Population-at-risk data from county personnel computer tapes provided denominators by age, sex, race, job classification, and type of facility. Rates varied by type of facility (rate ratio = 38 for psychiatric hospitals vs public health facilities) and varied by job, with inpatient nursing attendants having the highest rate for caregivers. Most assaults were committed by patients (86%), followed by coworkers (8%). The average cost of an assault ($4879) was relatively low but related to the costlier problem of work-related emotional illness.

Multislab three-dimensional T2-weighted fast spin-echo imaging of the hippocampus: sequence optimization

Three-dimensional (3D) fast spin-echo (FSE) imaging can produce contiguous thin sections for high-quality multiplanar reconstructions. Such reformatted images may be useful in the evaluation of three-dimensionally complex, curvilinear anatomic structures such as the hippocampus. The authors describe a 3D FSE protocol for T2-weighted imaging of the hippocampus. The protocol uses an overlapping-multiple-slab imaging strategy to decrease imaging times and a modified refocusing radio-frequency pulse train to improve the reformatted images. The authors describe their parameter optimization, discuss the benefits and limitations of the new sequence, and present representative images of healthy volunteers.

Evaluation of the portal venous system before liver transplantation: value of phase-contrast MR angiography

OBJECTIVE

The purpose of this study was to assess the accuracy of phase-contrast MR angiography with gadolinium in evaluating the patency and blood flow direction of the portal venous system; the presence, extent, and type of varices; and the patency of surgical decompressive shunts in patients before liver transplantation. This information is essential in management and care of patients with chronic liver disease and portal hypertension and those who are candidates for liver transplantation.

SUBJECTS AND METHODS

Twenty-four patients with portal venous hypertension were evaluated with phase-contrast MR angiography. Two patients had surgical splenorenal shunts and one had a mesocaval shunt. Phase-contrast angiograms were acquired as a series of two-dimensional sequential coronal sections during breath-holding and after IV administration of gadopentetate dimeglumine. Correlative findings from color flow Doppler sonography, contrast-enhanced CT scanning, and conventional angiography were available in 23, 20, and 10 patients, respectively, and were used as standards. The images from each technique were analyzed independently for patency of and flow direction in the portal vein, splenic vein, superior mesenteric vein, and surgically created shunts, and for detection, distribution, and extent of five variceal groups.

RESULTS

Findings from phase-contrast MR angiography completely agreed with those of sonography, CT scanning, and conventional angiography. The main portal vein was patent in 18 patients, stenosed in one, partially thrombosed in one, and occluded in four. Phase-contrast MR angiography correctly showed hepatofugal flow in three patients and hepatopetal flow in 17 patients. Both the splenic and superior mesenteric veins were patent in 20, partially thrombosed in one, and occluded in three cases. Phase-contrast MR angiograms showed 85% of the variceal groups, and MR rating of variceal size was not significantly different from that of CT rating. Phase-contrast MR angiography correctly showed the patency of all three surgical decompressive shunts.

CONCLUSION

Phase-contrast MR angiography is accurate for evaluating the patency and flow direction of the portal venous system, detecting and determining the distribution and extent of varices, and assessing the patency of surgically created shunts. Therefore, it is a reliable and noninvasive technique that can provide crucial information in the preoperative workup of liver transplant recipients.

Serial magnetic resonance imaging of experimental atherosclerosis detects lesion fine structure, progression and complications in vivo

A major problem in the study of lesions of atherosclerosis is the difficulty of imaging noninvasively the lesions and following their progression in vivo. To address this problem, we have developed advanced magnetic resonance techniques to noninvasively and serially image advanced lesions of atherosclerosis in the rabbit abdominal aorta. Both lumen and wall were imaged with high resolution. Progression of disease, resulting in increase in lesion mass, decrease in arterial lumen, or stenosis, and intralesion complications, can be detected. Images acquired in vivo correlate with the fine structure of the lesions of atherosclerosis, including the fibrous cap, necrotic core, and lesion fissures, as verified by gross examination, dissection microscopy, and histology. The ability to noninvasively identify the features of atherosclerotic plaques, has significant implications for determining risks and benefits associated with different therapeutic approaches.

Improved large-scale purification of transducin, and its alpha and beta gamma subunits from frozen retinas

The transducin heterotrimer and its alpha- and beta gamma-subunits have been purified from frozen bovine rod outer segments by modifying existing procedures. The methods described here are relatively simple and fast. The yield (ca. 8 mgs/100 retinas) and purity of the transducin heterotrimer and subunits from frozen retinas is equal to or larger than those previously obtained from fresh or frozen retinas.

Inhibitory effect of cocaine on calcium mobilization in cultured rat myocardial cells

Cocaine can produce both positive and negative inotropy. The mechanism of cocaine-induced negative inotropy is poorly understood. In order to evaluate the inhibitory effect of cocaine on myocardial contractility, its action on potassium chloride-induced depolarization, release of calcium from sarcoplasmic reticulum, and sarcolemmal sodium-calcium exchange were studied. At a relatively high concentration (10(-3) M), cocaine significantly blocked an elevation of cytosolic calcium during potassium chloride-induced depolarization and significantly inhibited the release of calcium from sarcoplasmic reticulum by caffeine. In contrast, a much lower concentration of cocaine (10(-7) M) significantly reduced sarcolemmal sodium-calcium exchange. Our results suggest that the negative inotropic action of cocaine may be related to a concentration-dependent effect: higher concentrations may inhibit calcium release from sarcoplasmic reticulum and block calcium influx across the sarcolemma. In contrast, lower concentrations would lead to a positive inotropic effect because of an impaired sarcolemmal sodium-calcium exchanger.

Phase-contrast MR angiography of the portal venous system: preoperative findings in liver transplant recipients

Sequential two-dimensional phase-contrast MR angiography can be used to accurately evaluate the anatomy, patency, and flow direction of the portal venous system and the presence, extent, and distribution of portosystemic collaterals. Its large field of view, insensitivity to the patient's body habitus, and graphic display format make this MR technique extremely useful for preoperative evaluation of patients with chronic liver disease and portal hypertension. This pictorial essay illustrates the spectrum of abnormalities seen on phase-contrast MR angiography of the portal venous system in patients with endstage liver diseases and portal hypertension.

Techniques for high-resolution MR imaging of atherosclerotic plaque

Atherosclerotic cardiovascular disease is the most common cause of death in the United States. Investigation of atherosclerotic plaque morphology and composition is important because the findings may be useful in predicting prognosis or response to therapy. This study presents high-resolution magnetic resonance (MR) imaging techniques developed on a 1.5-T whole-body imager with a custom-built surface coil, for characterizing the composition and morphology of plaque removed at carotid endarterectomy. The initial comparison of MR imaging and histologic results showed good correlation. In conjunction with MR angiography, these techniques could be used in in vivo imaging to define the size, location, and contents of atherosclerotic plaque at the carotid bifurcation.

Three-dimensional fast spin-echo imaging: pulse sequence and in vivo image evaluation

Three-dimensional (3D) magnetic resonance imaging allows thin-section acquisition and therefore more accurate multiplanar reconstruction than conventional two-dimensional spin-echo imaging. Unfortunately, addition of a third acquisition plane extends imaging time greatly. With gradient-echo techniques, 3D acquisitions have become clinically useful. These techniques are limited, however, by susceptibility and other field inhomogeneity artifacts and decreased signal-to-noise ratios compared with spin-echo techniques. The authors describe implementation of a true spin-echo 3D technique that, by using fast spin-echo parameters, reduces acquisition time to a clinically useful level. Potential applications of the technique are demonstrated.

Role of digitalis-like substance in the hypertension of streptozotocin-induced diabetes in reduced renal mass rats

We have previously reported that chronic hypertension develops consistently in Wistar rats with a 25% reduction in renal mass (RRM) following the induction of insulin dependent diabetes mellitus (IDDM) with streptozotocin (STZ, 65 mg/kg body weight, intravenously). In this study, we examined the role of the endogenous digitalis-like substance in the development of hypertension. Four groups of rats were studied: 1) 25% RRM rats with STZ-induced IDDM (25-DM), 2) normal rats with STZ-induced IDDM (2K-DM), 3) 25% RRM rats with vehicle treatment (25-V), and 4) normal rats with vehicle treatment (2K-V). In 25-DM rats, blood pressure progressively increased during the 3 weeks after STZ treatment and was associated with microalbuminuria, low plasma renin activity, and extracellular volume expansion. In contrast, the 2K-DM, 25-V, and 2K-V rats remained normotensive. Furthermore, the plasma and urine levels of digoxin-like immunoreactive factor (DIF), determined by digoxin radioimmunoassay (Baxter), were significantly higher in hypertensive 25-DM rats than in their controls. The same was the case for plasma digitalis-like substance (DLS), determined by exposing canine Na+,K(+)-ATPase to plasma fractions and observing the percent inhibition. Increased DIF and DLS in hypertensive 25-DM rats was associated with a significant decrease in Na+,K(+)-ATPase activity of microsomes prepared from the left and right ventricles, when compared with microsomes from normotensive 2K-DM animals. Microsomal 5'-nucleotidase, a plasma membrane marker, was unchanged. The DIF and DLS correlated significantly with each other and with myocardial Na+,K(+)-ATPase activity and mean blood pressure. These results suggest that increased endogenous digitalis-like substance, which inhibits cardiovascular muscle cell Na(+)-K(+)-pump activity, may be involved in the mechanism of hypertension associated with IDDM in 25% RRM rats.

Adenosine-5'-carboxaldehyde: a potent inhibitor of S-adenosyl-L-homocysteine hydrolase

Adenosine-5'-carboxaldehyde (3) and its 4'-epimer (4) were synthesized and shown to be potent type I mechanism-based inhibitors of recombinant rat liver AdoHcy hydrolase with k2/KI values of 16.7 x 10(-3) and 5.5 x 10(-3) nM-1 min-1, respectively. The observation that 3 and 4 are potent inhibitors of AdoHcy hydrolase supports the hypothesis that they function as key intermediates in the mechanism by which the (Z)- and (E)-4',5'-didehydro-5'-deoxy-5'-fluoroadenosines 1 and 2 inactivate this enzyme.

Reversal of inhibition of reactive oxygen species on respiratory burst of macrophages by polysaccharide from Coriolus versicolor

Using a luminol-dependent, chemiluminescence assay we found tert-butylhydroperoxide to be a strong inhibitor of the respiratory burst of mouse peritoneal macrophages. However, the inhibition of respiratory burst induced by tert-butylhydroperoxide could be prevented after the interperitoneal injection of polysaccharide from Coriolus versicolor (PSK). Further investigation showed that glutathione peroxidase activity was markedly elevated in PSK-treated macrophages. After incubation with tert-butylhydroperoxide, higher activity of glutathione peroxidase was maintained in PSK-treated macrophages. These results suggest that the immunological function of macrophages is related to the activity of glutathione peroxidase. The non-specific immunopolysaccharide might protect macrophages from the damage induced by reactive oxygen species by enhancing antioxidative capacity.

Role of ouabain-like factors in hypertension: effects of ouabain and certain endogenous ouabain-like factors in hypertension

Several reports suggest the presence of sodium-potassium pump inhibitor in plasma and various tissues, particularly during volume-expanded state and low-renin hypertension. It has been hypothesized that by inhibiting the cardiovascular muscle-cell Na(+)-K+ pump, this inhibitor can constrict blood vessels, enhance vasoconstriction, and increase cardiac contractility, thereby raising blood pressure. Only two such endogenous inhibitors have been chemically characterized: the bufodienolide derivative, resibufogenin, obtained from toad skin and plasma; and a factor with the same structure (based on mass spectral analysis) as ouabain, from human plasma. However, unlike bufalin (aglycone), which is almost structurally identical to resibufogenin, neither ouabain nor ouabagenin (aglycone of ouabain) caused a sustained increase in blood pressure when infused in equimolar doses during a 30-min period in rats. Because the rat is 10(4)-fold less sensitive to ouabain than the human is, we wondered whether the absence of a response to ouabain was due to the short infusion time. Therefore, in new experiments ouabain was administered chronically during a 6- to 7-week period to two-kidney normal rats and rats with 70, 60, and 25% reduced renal mass. Reduced renal mass rats were used because these rats have decreased sodium excretion capacity, and thus we hoped the action of exogenous ouabain would be potentiated in these volume-expanded rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal lymphatic obstruction in diabetic rats induces systemic hypotension

We obstructed renal lymph drainage from a single kidney in diabetic rats who had received 65 mg/kg streptozotocin 6 months prior to the study. Lymphatic obstruction led to a progressive fall in systematic blood pressure from a mean arterial pressure of 101 +/- 5 (SEM) mm Hg (n = 7) to 62 +/- 4 mm Hg (n = 5) (p < .02) after 1.5 h. No change was seen in a sham-operated animal. Despite the decline in systemic blood pressure there was no significant change in the GFR of either kidney. Sodium excretion increased significantly in the experimental kidney. There was no change in the urinary excretion of cyclic GMP from either kidney, and plasma levels of atrial natriuretic peptide (ANP) did not change (55 +/- 21 pg/mL pre- to 64 +/- 18 postobstruction). The results are consistent with a systemic vasodilatation after lymphatic obstruction. The mechanism of this response is still under investigation, but apparently it does not involve ANP.

Role of digitalis-like substance in experimental insulin-dependent diabetes mellitus hypertension

Hypertension is frequently associated with insulin-dependent diabetes mellitus, but the mechanism of the hypertension is unknown. An animal model of insulin-dependent diabetes mellitus hypertension could be helpful in determining the mechanism, but experimental insulin-dependent diabetes mellitus has been infrequently and irregularly associated with hypertension. In an attempt to develop a dependable model of insulin-dependent diabetes mellitus hypertension, we studied seven series of rats receiving either streptozotocin, surgical reduction of renal mass, or both. We found that superimposing streptozotocin 65 mg/kg body weight on 25% reduced renal mass regularly produced insulin-dependent diabetes mellitus and low-renin volume-expanded hypertension and that the animals remained healthy and hypertensive for as long as followed (13 weeks). Microalbuminuria correlated temporally with blood pressure. We used this dependable model to examine the role of endogenous digitalis-like substance in the development of hypertension in insulin-dependent diabetes mellitus. Plasma levels of digoxin-like immunoreactive factor (DIF), determined with a digoxin radioimmunoassay, were significantly higher in these hypertensive rats than in normotensive control rats (two-kidney diabetic rats, 25% reduced renal mass rats receiving vehicle for streptozotocin). This increase in plasma DIF was associated with a decrease in Na+, K(+)-ATPase activity in microsomes prepared from left or right ventricle. Microsomal 5'-nucleotidase, a plasma membrane marker, was unchanged. The plasma DIF level correlated inversely with myocardial Na+, K(+)-ATPase activity and positively with systolic blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

A consistent model of insulin-dependent diabetes mellitus hypertension

Hypertension is frequently seen in insulin-dependent diabetes mellitus (IDDM), but the mechanism of the hypertension is unknown. An animal model of IDDM hypertension could be helpful in determining the mechanism, but experimental IDDM has been infrequently and irregularly associated with hypertension. In an attempt to develop a consistent model of IDDM hypertension, we superimposed streptozotocin (STZ)-induced IDDM on surgical reduction of renal mass (RRM) in Wistar rats. Seven groups of rats were studied: 1) 60% RRM receiving 65 mg/kg body weight (BW) STZ; 2) 60% RRM receiving 40 mg/kg BW STZ; 3) 25% RRM receiving 65 mg/kg BW STZ; 4) two kidney normal rats receiving 65 mg/kg BW STZ; 5) 60% RRM receiving vehicle (control for group 1); 6) 60% RRM receiving vehicle (control for group 2); and 7) 25% RRM receiving vehicle. STZ produced diabetes and hypertension within 1 to 2 weeks in all three groups of RRM rats but blood pressure was unaffected by 60% or 25% RRM alone. STZ alone had no effect on blood pressure until the 5th week when the blood pressure increased slightly. Progressive weight loss resulted from 65 mg/kg BW STZ combined with 60% RRM; the animals had to be terminated after 5 weeks. In only 60% of animals with 40 mg/kg BW STZ plus 60% RRM was IDDM produced. On the other hand, 65 mg/kg BW STZ in rats with 25% RRM regularly produced IDDM and hypertension without excessive loss of body weight. In these rats, albuminuria developed in 2 weeks. Extracellular fluid volume was elevated and plasma renin activity was depressed. The animals were healthy and hypertensive when killed at the 13th week. We suggest that the 25% RRM rat receiving 65 mg/kg BW STZ is a consistent model of IDDM hypertension, which may be useful in probing the mechanism of this type of hypertension.

[Analysis of factors influencing on the surgical results of arterial embolism in the lower extremities]

130 patients with arterial embolism in the lower extremities underwent surgical treatment. The curative rate was 66.9%, amputation rate-19.2% and the mortality rate-13.8%. Statistical study showed that sex, age and recurrent embolism had few effects on the surgical results (P < 0.05). One of the influencing factors was the ischemic time of the lower extremities. The mortality rate was 33.3% in the distal abdomen with aortic embolism and 8.7% in the lower extremities (P < 0.005). The mortality rate and amputation rate were significantly higher in embolic patients with atherosclerotic stenosis and occlusion (9% and 17%). The mortality rate and amputation rate were 2.3% and 3.4% in patients with good blood flow and were 42.1% and 57.9% in patients without good blood flow uspectively. Reembolectomies showed no satisfactory effect. The results indicated that embolectomy combined with other necessary operations did not increase the mortality rate and amputation rate (P < 0.05). Postoperative anticoagulation therapy is extremely important.

[Chemical constituents of the roots of Ostericum grosseserratum (Maxim.) Kitag]

This paper reports the isolation of eleven compounds from the roots of Ostericum grosseserratum, of which nine compounds were elucidated as myristic acid, palmitic acid, stearic acid, octacosanoic acid, succinic acid, beta-sitosterol, sitosterol-beta-D-glucoside, isoscopletin and sucrose. The results are helpful in the study of plant taxonomy.

[Hepatic segmentectomy using microwave tissue coagulator]

Hepatic segmentectomy using a microwave tissue coagulator guided by intraoperative ultrasonography is a new operative procedure, which our research unit was the first to start using from 1990. Up to now we have performed this kind of operation with success in 26 cases. Our results suggested that the new procedure simplified the original operation and greatly reduced the risk of hemorrhage and iatrogenic spread of the cancer cells during operation. Besides, this operation as a kind of definite anatomic hepatectomy can minimally resect the tumor bearing tissue in a radical fashion, while maximally preserve the tumor-free tissue of the liver.

[Discussion on criteria for appraising the endanger threatening rare medicinal plants]

This paper deals with the criteria for appraising the endanger threatening rare medicinal plants. A preliminary evaluating method is presented.

[Determination of aucubin in Plantago asiatica L., P. major L. and P. depressa Willd. by HPLC]

A HPLC method for the determination of aucubin in P. asiatica, P. major and P. depressa was established. The mobile phase is MeOH-H2O (17:83). Good in producibility and high in rate of recovery, this method provides an effective way for the study of Plantago.

[Determination of glaucocalyxin A in the leaves of Plectranthus japonicus (Burm.) Koidz. var. glaucocalyx (Maxim.) Koidz. by HPLC]

This paper reports the quantitative analysis of glaucocalyxin A in the leaves of Plectranthus japonicus var. glaucocalyx by HPLC. The chromatographic conditions were as follows: column: Shim-pack CLC-ODS; mobile phase: methanol-water (70:30). The average content of glaucocalyxin A in the leaves is 1.30%.

[Experimental anti-arrhythmic effects of zhigancao (prepared licorice) injection]

Zhigancao injection can antagonise the arrhythmia induced by chloroform, adrenaline, aconitine, strophanthine K and barium chloride, slow the heart rate, prolong P-R and Q-T intervals and antagonise the positive chronotropic response induced by isoprenaline. The LD50 of zhigancao injection is 41.2g/kg in nice by intraperitoneal.

[Determination of myristicin and safrol in the volatile oil of semen Myristicae and its processed products by TLC-scanning]

This paper reports the determination of myristicin and safrol in the volatile oil of Semen Myristicae and its processed products by TLC-Scanning. The results showed that in the processed products myristicin decreased markedly and safrol decreased slightly. The quantity of myristicin roasted with paste less than with wheat bran less than with talcum powder less than the unprocessed one. The toxicity of Semen Myristicae is related to the quantities of myristicin.

Sympathoadrenal excitation and inhibition by lower brainstem stimulation in cats

Effects of stimulation of brainstem sites on hemodynamics and plasma catecholamine levels were assessed in cats under chloralose-urethane anesthesia. Pressor areas of the dorsal medulla (DM) and ventrolateral medulla (VLM) and the depressor area of the paramedian reticular nucleus (PRN) were stimulated electrically using a monopolar electrode, or chemically using sodium glutamate microinjection. Plasma levels of norepinephrine (NE) and epinephrine (EPI) were measured in caval blood above the adrenal veins. Electrical stimulation of the DM and VLM produced increases in blood pressure and in plasma NE and EPI levels that were enhanced after acute vagotomies. The NE and EPI responses were attenuated after acute, bilateral adrenalectomies, confirming augmented adrenomedullary secretion, whereas the pressor responses were intact. Injection of sodium glutamate into the same pressor regions of the DM or VLM also produced pressor responses and elevated plasma catecholamine levels, indicating that the responses resulted from activation of neuronal perikarya. Stimulation of the PRN attenuated pressor and catecholamine responses during stimulation of the DM and VLM. The results indicate that pressor responses during stimulation of the DM and VLM are due at least partly to activation of perikarya in these regions, are associated with but not dependent on adrenomedullary activation, and are enhanced after vagotomy; and that neurons of the PRN exert inhibitory modulation of the pressor and adrenomedullary responses during stimulation of VLM and DM.

Effect of region-of-interest in computerized densitometric analysis of radiographs

The region-of-interest (ROI) in computer-assisted densitometric image analysis (CADIA) is defined by its size and location. This study evaluated the effects of these variables on two quantitative parameters, the change in density and the area with change in density. Pairs of radiographs for these analyses were obtained from sites with "no change" or "known loss" in Cynomolgus monkeys during a study of ligature-induced periodontitis. The size and location of the ROI had clear effects on the two CADIA parameters. To reduce these effects, a corrective procedure hypothesizing a linear relationship between the ROI size and the area with change in density was tested. While this procedure was sufficient to correct for ROI size-dependent differences among "no change" images, it was not effective in images with "known loss". In such images, additional adjustments by increasing threshold levels for the registered change in density were found to reduce but not to eliminate differences between ROIs of different size and location. When densitometric radiographic analysis is used for quantitative comparison of different sites, it is primarily recommended to select ROIs of similar size and location. Application of corrective procedures should follow only after careful evaluation of their effects on sensitivity and specificity.

Role of selenium-dependent glutathione peroxidase in protecting against t-butyl hydroperoxide-induced damage in hepatocytes

The role of the selenoenzyme glutathione peroxidase (Se-GSHPx) in protecting against oxidative injury was studied in hepatocytes isolated from rats fed either a low-selenium (Se-) or a selenium-adequate (Se+, control) diet. In rats fed Se- diet for eight weeks the selenium content of plasma and liver was lowered to 15 and 8%, respectively. No Se-GSHPx and only 5% of total GSHPx activity was detected in Se- hepatocytes. However, the Se- hepatocytes were as resistant as the Se+ cells to oxidative injury by 0.8 mM tert-butyl hydroperoxide (t-BuOOH), or 0.2 mM t-BuOOH plus 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), an inhibitor of oxidized glutathione (GSSG) reductase. Only at 1.5 mM t-BuOOH or at 0.5 mM t-BuOOH with BCNU were cell damage and lipid peroxidation more evident in Se- cells. At all t-BuOOH concentrations used the depletion of cellular glutathione (GSH) was similar in magnitude in Se- and Se+ cells, but Se+ cells released more glutathione (mainly GSSG), obviously due to their higher Se-GSHPx activity. These results suggest that hepatocytes devoid of Se-GSHPx activity maintain a high capacity to resist peroxidative attack, either via residual (non-Se)GSHPx activity or other compensatory GSH-associated detoxication mechanisms.

MR angiography by multiple thin slab 3D acquisition

Multiple overlapping thin 3D slab acquisition is presented as a magnitude contrast (time of flight) technique which combines advantages from multiple thin slice 2D and direct 3D volume acquisitions to obtain high-resolution cross-sectional images of vessel detail. Details of implementation and example images are presented.

Normal venous anatomy of the brain: demonstration with gadopentetate dimeglumine in enhanced 3-D MR angiography

This investigation evaluates whether gadopentetate dimeglumine enhancement of three-dimensional (3-D) acquisition MR angiography can generate clinically useful images of the normal venous anatomy of the brain. 3-D MR angiography of normal cerebral arterial anatomy has made rapid progress, although demonstration of detailed venous anatomy with similar techniques has been much less revealing. To overcome the limitation of slow venous flow, IV gadopentetate dimeglumine contrast enhancement was used to alter the relaxation times of blood, thus augmenting the venous signal. Several groups of patients were evaluated: we studied eight patients both with and without contrast enhancement, 20 patients and volunteers with multiple techniques to determine optimal technical parameters, and seven patients in whom enhanced MR studies were compared with standard selective biplane cut-film arterial angiograms. Only the large dural sinuses (such as the transverse sinus) could be seen on unenhanced studies owing to the saturation of slowly flowing venous spins. With contrast enhancement, many of the important small and large cerebral venous structures were routinely seen with reasonable scanning times (7 min). The venous anatomy was well seen for approximately one-half hour after injection and correlated well with angiograms. There are several important limitations to this technique, including a limited field of view, variable visibility of specific veins owing to technical and physiologic factors, confusion of enhancing non-flow-related structures, and lack of detailed physiologic information. Single excitation 3-D MR angiograms are insensitive in the evaluation of cerebral venous structures. Enhancement with gadopentetate dimeglumine affords rapid scanning and excellent visualization of the pertinent venous anatomy. The best image quality was obtained with a sequence of 50/7/30 degrees (TR/TE/flip angle).