ESTIMATION OF PATIENT RADIATION DOSES FROM MULTI-DETECTOR COMPUTED TOMOGRAPHY ANGIOGRAPHY PROCEDURES IN TANZANIA

The aim of the present study was to estimate the volume CT dose index (CTDIvol), dose length product (DLP) and effective dose (ED) to patients from five multi-detector computed tomography angiography (MDCTA) procedures: brain, carotid, coronary, entire aorta and lower limb from four medical institutions in Tanzania; to compare these doses to those reported in the literature, and to compare the data obtained with ICRP 103 and Monte Carlo software. The radiation doses for 217 patients were estimated using patient demographics, patient-related exposure parameters, the geometry of examination and CT-Expo V 2.4 Monte Carlo-based software. The median values of the CTDIvol, DLP and ED for MDCTA procedures of the brain and carotids were 36.8 mGy, 1481.0 mGy∙cm and 5.2 mSv, and 15.9 mGy, 1224.0 mGy∙cm and 7.8 mSv, respectively; while for the coronary, entire aortic, and lower limbs were 49.4 mGy, 1493.0 mGy∙cm and 30.6 mSv; 16.2 mGy, 2287.0 mGy∙cm and 41.1 mSv; and 6.4 mGy, 1406.0 mGy∙cm and 10.5 mSv, respectively. The ratio of the maximum to minimum ED values to individual patients across the four medical centers were 41.4, 11.1, 4.6, 9.5 and 37.4, respectively, for the brain, carotid, coronary, entire aortic and lower limb CT angiography procedures. The mean values of CTDIvol, DLP and ED in the present study were typically higher than the values reported from Kenya, Korea and Saudi Arabia. The 75th percentile values of the DLP were above the preliminary diagnostic references levels proposed by Kenya, Switzerland and Korea. The observed wide range of examination scanning protocols and patient doses for similar MDCTA procedures within and across hospitals; and the observed relatively high patient doses compared to those reported in the literature, call for the need to standardize scanning protocols and optimise patient dose from MDCTA procedures.

High-resolution, time-resolved MRA provides superior definition of lower-extremity arterial segments compared to 2D time-of-flight imaging

PURPOSE

To evaluate a novel time-resolved contrast-enhanced (CE) projection reconstruction (PR) magnetic resonance angiography (MRA) method for identifying potential bypass graft target vessels in patients with Class II-IV peripheral vascular disease.

MATERIALS AND METHODS

Twenty patients (M:F = 15:5, mean age = 58 years, range = 48-83 years), were recruited from routine MRA referrals. All imaging was performed on a 1.5 T MRI system with fast gradients (Signa LX; GE Healthcare, Waukesha, WI). Images were acquired with a novel technique that combined undersampled PR with a time-resolved acquisition to yield an MRA method with high temporal and spatial resolution. The method is called PR hyper time-resolved imaging of contrast kinetics (PR-hyperTRICKS). Quantitative and qualitative analyses were used to compare two-dimensional (2D) time-of-flight (TOF) and PR-hyperTRICKS in 13 arterial segments per lower extremity. Statistical analysis was performed with the Wilcoxon signed-rank test.

RESULTS

Fifteen percent (77/517) of the vessels were scored as missing or nondiagnostic with 2D TOF, but were scored as diagnostic with PR-hyperTRICKS. Image quality was superior with PR-hyperTRICKS vs. 2D TOF (on a four-point scale, mean rank = 3.3 +/- 1.2 vs. 2.9 +/- 1.2, P < 0.0001). PR-hyperTRICKS produced images with high contrast-to-noise ratios (CNR) and high spatial and temporal resolution. 2D TOF images were of inferior quality due to moderate spatial resolution, inferior CNR, greater flow-related artifacts, and absence of temporal resolution.

CONCLUSION

PR-hyperTRICKS provides superior preoperative assessment of lower limb ischemia compared to 2D TOF.

Lipid peroxidation and human sperm motility: protective role of vitamin E

Asthenospermia is the main factor of male infertility among patients consulting the Asir Infertility Center in Abha, Saudi Arabia. Lipid peroxidation occurring in both the seminal plasma and spermatozoa was estimated by malondialdehyde (MDA) concentration. Spermatozoal MDA concentration was higher in men with decreased sperm motility. The MDA concentration in the seminal plasma exhibited no relationship with sperm concentration, sperm motility, the number of immotile spermatozoa, or even the absence of spermatozoa. The MDA concentration in sperm pellet suspensions of asthenospermic and oligoasthenospermic patients was almost twice that of the normospermic males. The MDA concentration in the sperm pellet suspension from normospermic or oligospermic patients was about 10% that in the seminal plasma. However, the MDA concentration in the sperm pellet suspension of asthenospermic or oligoasthenospermic patients was about 15% that in the seminal plasma. Treatment of asthenospermic patients with oral Vitamin E significantly decreased the MDA concentration in spermatozoa and improved sperm motility. Eleven out of the 52 treated patients (21%) impregnated their spouses; nine of the spouses successfully ended with normal term deliveries, whereas the other two aborted in the first trimester. No pregnancies were reported in the spouses of the placebo-treated patients.

Urinary hydroxyproline and serum alkaline phosphatase in sickle cell disease

Serum alkaline phosphatase, alkaline phosphatase isoenzymes, and urinary hydroxyproline excretion were studied in 20 young adult sickle cell patients and 58 matching normal controls. Total alkaline phosphatase was significantly higher in the sickle cell patients than in controls. Heat inactivation test and isoenzyme electrophoresis indicated that bone is the predominant isoenzyme in patients. Hydroxyproline excretion was significantly higher in the sickle cell patients than in controls. Serum total alkaline phosphatase correlated well with urinary hydroxyproline excretion in sickle cell patients (r = 0.73). Both alkaline phosphatase and hydroxyproline increased with age in the sickle cell patients. This study suggests that delayed growth and/or bone destruction may contribute to the elevated levels of alkaline phosphatase and urinary hydroxyproline.

Purification of xanthine dehydrogenase from rat liver: a rapid procedure with high enzyme yields

Xanthine dehydrogenase (EC 1.2.1.37) was purified approximately 1000-fold from liver homogenates of adult male Sprague-Dawley rats. Enzyme recovery was good (greater than 20% of the starting activity was obtained), and the homogeneously pure enzyme had a molecular mass of approximately 300,000 Da. The purified protein exhibited a specific activity of 2470 units/mg protein and spectral properties identical to those of the best preparations of this enzyme reported by other investigators. Routine preparations of this enzyme also possess higher dehydrogenase:oxidase ratios (typically between 5 and 6) than do other xanthine dehydrogenase preparations so far reported in the literature. Maximum dehydrogenase:oxidase ratios, greater than 10, could be obtained from this procedure if only peak dehydrogenase fractions from the chromatography columns were saved. The present small-scale purification method, which can be completed in 48-60 h, utilizes ammonium sulfate fractionation, Sephadex G-200 column chromatography, Blue Dextran-Sepharose column chromatography, and preparative gel electrophoresis.

The effect of oxygen tension on rat hepatocytes in short-term culture

Cell viability, cytochrome P-450 content, cell respiration, and lipid peroxidation were all investigated as a function of oxygen tension in adult rat hepatocytes in short-term culture (less than 9 h). The various oxygen tensions used in this study were obtained by equilibrating culture medium with air, air + nitrogen, or air + oxygen. Cell viability, as assessed by trypan blue exclusion, was significantly greater at all time points tested when hepatocytes were cultured in Ham's F12 medium containing 132 microM O2, as compared to medium equilibrated with air (220 microM O2) or air + oxygen (298 microM O2). Cells cultured in 220 microM O2 (air) also exhibited a gradual loss of cytochrome P-450, so that by 9 h of incubation less than 60% of the active material remained. This loss of P-450 was minimized when cells were cultured in 163 microM O2 and abolished when cells were cultured in 132 microM O2. The 132 microM O2 exposure conditions also maintained cell respiration at the 1 h incubation values, whereas there was a continuous loss in cell respiration over time when the cells were cultured in either 220 microM O2 (air) or 298 microM O2 (air:O2). These cytotoxicity findings may be related to oxidative cell damage inasmuch as it was additionally demonstrated that lipid peroxidation (as measured by malondieldehyde equivalents) was consistantly lower in hepatocytes cultured in air:N2 as compared to air or air:O2. These results suggest that hepatocyte culture in low oxygen tension improves not only cell viability but also maintains other functional characteristics of the cell.

Petroleum hydrocarbon toxicity in vitro: effect of n-alkanes, benzene and toluene on pulmonary alveolar macrophages and lysosomal enzymes of the lung

The in vitro effects of straight chain alkanes (nC6-nC10), benzene and toluene on pulmonary alveolar macrophages (PAM) of rats and rabbits was studied. The concentrations used ranged from 0.02 to 1.0 mM. All hydrocarbons used in the study were cytotoxic to isolated cultured PAM cells in a dose-dependent manner. The LC50 for these hydrocarbons towards rat PAM cells was estimated to be 1.0 mM for nC8, 2 mM for nC7, 5 mM for nC9 and 10 mM for nC6, nC10, benzene and toluene. Rabbit PAM cells were more sensitive to the hydrocarbons, resulting in and LC50 half that for rat PAM cells. Hydrocarbons also caused extracellular release of the lysosomal enzymes cathepsin D (EC 3.4.23.5) and cathepsin B (EC 3.4.22.1) in a manner corresponding with cell damage. There was more cathepsin D activity released from cells than cathepsin B. In addition, hydrocarbons also caused the release of cathepsin B and D from isolated lysosomes, and there was 10-15% more enzyme activity released in the culture medium of lysosomes exposed to concentrations of 0.5 and 1.0 mM compared to PAM cell cultures of either rats or rabbits. Hydrocarbons also caused loss of cell respiration and stimulated a dose-dependent and a time-dependent increase in lipid peroxidation. The two alkanes nC7 and nC8 caused the greatest increase in lipid peroxidation and the greatest loss of cell respiration. The results indicate that there is a relationship between chain length of alkanes and their cytotoxicity to PAM cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Bipyridylium herbicide toxicity: effects of paraquat and diquat on isolated rat hepatocytes

Paraquat (1,1'-dimethyl-4,4'-bipyridylium) and diquat (1,1'-ethylene-2,2'-bipyridylium) are the two most widely used bipyridylium herbicides today. Both compounds, however, have also been found to cause liver damage in animals and man. In this study, isolated rat hepatocytes were used to assess the cytotoxicity of these two compounds. Five indices of cell damage were used to quantitate cytotoxicity: dye (trypan blue) uptake, loss of cell respiration, the extracellular release of lysosomal enzymes, the formation of thiobarbiturate (TBA)-reacting substances, and the oxidation of cellular NADH and NADPH. Diquat was shown to be more toxic than paraquat toward these cells in the first three assay systems. The acute LC50 for diquat was determined to be 80 mM, whereas the acute LC50 for paraquat was estimated to be greater than 1 M. This difference in cell sensitivity could be explained, at least in part, by the observed differences in herbicide uptake rates for these two compounds. Diquat uptake was calculated to be 9.0 +/- 1.1 nmoles/hour/10(6) cells, whereas paraquat uptake was only 5.5 +/- 0.5 nmoles/hour/10(6) cells. The dose-response curves for enzyme release and loss of cell respiration superimposed the lethality curves for both compounds. An oxidative mechanism of cytotoxicity was suggested for diquat by: the establishment of both a concentration-dependent and a time-dependent increase in lipid peroxidation (formation of TBA-reacting substances); complete oxidation of both NADPH and NADH at herbicide levels less than the LC50; and the finding that diquat stimulated glucose oxidation at subtoxic doses.

Metabolism of deoxyuridine in rabbit brain

The metabolism of [3H]deoxyuridine by rabbit brain was investigated in vitro and in vivo. In vitro, brain slices from various regions of brain and from all age groups accumulated [3H]deoxyuridine from artificial CSF. Within the slices, a portion of the accumulated [3H]deoxyuridine was metabolized to [3H]deoxyuridine phosphate, with subsequent conversion to [3H]thymidine phosphate, and ultimately [3H]DNA. The percentage of the [3H]deoxyuridine phosphorylated and subsequently converted into [3H]DNA was highest at birth and declined to adult levels in 3-month-old rabbits. Thymidine, when added to the incubation medium with the [3H]deoxyuridine, was approximately 10 times as potent as unlabeled deoxyuridine in inhibiting the intracellular phosphorylation and conversion of [3H]deoxyuridine to [3H]thymidine phosphate in brain slices. In vivo, 2.5 h after intraventricular injection of [3H]deoxyuridine, over 90% of the [3H]deoxyuridine was cleared from the central nervous system at all ages. However, in both newborn and 3-month-old rabbits, approximately 40 and 12%, respectively, of the 3H remaining in brain was phosphorylated and converted to [3H]thymidine phosphates; and 11 and 4%, respectively, of the 3H remaining in brain was converted to [3H]DNA. These results show that both immature and mature rabbit brain is able to incorporate deoxyuridine into DNA. Thus, all the enzymes involved in this conversion, including thymidylate synthetase (EC 2.1.1.45), are present and active in brain throughout life.

Effect of altered thyroid status on lysosomal enzymes and thymidylate synthetase activity in tumors and livers of host animals

The purpose of this study was to determine whether or not alternations in tumor growth induced by changes in thyroid status were mediated through changes in key enzymes, whose activity is known to be influenced by thyroid hormones. The activities of three lysosomal enzymes (cathepsin B1, cathepsin D, and acid phosphatase) and thymidylate synthetase were measured in implanted mammary tumors as well as in the livers of host animals that were either euthyroid, hypothyroid, or hyperthyroid. Hypothyroidism produced no significant change in enzyme activity in the tumors. Hyperthyroidism, on the other hand, did cause a significant increase in the activity of all lysosomal enzymes in the tumors, but did not affect thymidylate synthetase levels. In the livers of the host animals, hypothyroidism produced a significant decrease in cathepsin B1 and a significant increase in acid phosphatase but did not change cathepsin D or thymidylate synthetase levels. Hyperthyroidism produced a significant increase in all enzymes measured in the livers of the host animals. The significant decrease in tumor weight with hypothyroidism did not correlate with the insignificant changes in the enzymes tested. Similarly, there was no correlation between the significant increase in the enzymes levels found with hyperthyroidism and the insignificant change in tumor weight.

Identification, development, and regional distribution of thymidylate synthetase in adult rabbit brain

The development and regional distribution of thymidylate synthetase (TS) (EC 2.1.1.45) in rabbit brain were determined. After optimization of the assay for brain, TS activity in brain was measured by a nonspecific (3H2O release) and specific method. The specific method involved the conversion of [6-3H]deoxyuridine monophosphate (dUMP) to [3H]thymidine phosphate and the subsequent identification of [3H]thymidine.l The specific activity of the enzyme in whole brain of newborn rabbits declined from 10.35 +/- 1.17 units/mg protein to 0.71 +/- 0.09 units/mg protein at 10-12 weeks of age. Two=year-old rabbits had 0.81 +/- 0.04 units/mg protein. The decline in specific activity with age was not due to an inhibitor of TS activity or a change in the Km for dUMP. The Km for dUMP of the unpurified enzyme in the brains of both 19-day-old and young adult rabbits was 0.8 microM. In young adult rabbits (3 months) the specific activity of TS was similar in the various regions of the brain tested except for the cerebellum, which had 40% higher specific activity than the whole brain. The results show that TS is widely distributed in adult rabbit brain, and, although the activity declines with age, it stabilizes at adult levels at 3 months of age.

Partial purification and characterization of a folate-binding protein from human choroid plexus

A folate-binding protein (binder) from human choroid plexus was solubilized with Triton X-100 and partially purified in three steps: (1) affinity chromatography, (2) Sephadex G-200 column chromatography, and (3) polyacrylamide gel electrophoresis. When the partially purified binder was subjected to sodium dodecyl sulfate--polyacrylamide gel electrophoresis, the binding activity was located in the region of the gel with a molecular weight between 45,000 and 60,000. The specific activity of the binder after the three purification steps was 1.2 mu g folic acid/mg protein, a 316-fold purification. Binding activity of the partially purified binder decreased below pH 6.0 and above pH 8.0, was unaffected by treatment with ribonuclease or deoxyribonuclease, but was abolished with trypsin, chymotrypsin, or protease (Streptomyces griesus). The binding of folic acid to the human binder was inhibited by folate Greater Than H4-folate Greater Than methyl-H4-folate approximately dihydrofolate approximately pteroic acid Greater Than methotrexate approximately aminopterin.

Development and regional distribution of methionine synthetase in rabbit brain

The development and regional distribution of methionine synthetase (EC 2.1.1.13) in rabbit brain was determined. In adult rabbits, the specific activity (units per milligram protein) of methionine synthetase in cortex, cerebellum, brain stem, and corpus striatum was comparable to the specific activity in whole brain (0.5 units/mg). In the first few weeks of life, the specific activity of methionine synthetase in whole rabbit brain declined from a value of 1.1 units/mg at 1 day of age to 0.5 units/mg at 6-10 weeks. Two-year-old rabbits had 0.6 units/mg in whole brain. These results show that: (a) methionine synthetase is distributed widely in mammalian brain and (b) methionine synthetase activity in brain declines relatively little with development.

Changes in lysosomal cathepsins during liver regeneration

The effect of 2/3 hepatectomy in the adult rat on the specific and total activities of two lysosomal endopeptidases, cathepsins B1 and D, has been examined. The specific activity of both enzymes fell rapidly following hepatectomy when compared to paired, sham-operated controls. When changes in total protein were compared to changes in cathepsins B1 and D, all three decreased in a parallel fashion for the first 18 h. At 24 h, total liver protein increased rapidly while cathepsins B1 and D continued to decrease. Cathepsin B1 fell to a level of 12% of non-operated control levels at 36 h, while total protein was already back to 40% of control levels. In contrast to the decreases in the activities of the cathepsins, there was an increase in the activities of lactate dehydrogenase and malate dehydrogenase during the first two days of regeneration. The clear lag in replacement of the cathepsins relative to other liver proteins following partial hepatectomy suggests that cathepsin activity is selectively controlled and that lowering the levels of cathepsins B1 and D may play an important role in the decreased degradation of protein seen during the early phases of liver regeneration.

Hormonal effects on the biosynthesis of lactate dehydrogenase in rat hepatocytes

Rat hepatocytes have been studied in suspension culture for 10-h periods. Levels of extractable lactate dehydrogenase (LDH) have been measured in these hepatocytes at hourly intervals in order to note the balance between biosynthesis and degradation of this enzyme. Newly synthesized LDH has been measured by following the rate of incorporation of [3H]leucine into radiochemically pure LDH of high specific catalytic activity as isolated by a rapid affinity chromatographic procedure. The effects of the addition of physiological concentrations of the following hormones at the beginning of 10-h culture periods immediately following preparation of the hepatocytes by the collagen perfusion procedure have been recorded. The hormones triiodothyronine (T3), insulin, glucagon, and dexamethasone have been added singly or in combination. The culture medium has supplied variable amounts of these hormones in the 10% of fetal calf (or other) serum added, and the hepatocytes themselves have provided intracellular amounts of hormones. In addition to the added hormones, N6,O2'-dibutyryl cyclic AMP (Bt2cAMP) has also been studied. Control suspensions of hepatocytes show reproducible initial levels of extractable LDH which are maintained or slightly increased during 10 h. Such control systems also incorporate [3H]leucine into total protein and into highly purified LDH at reproducible rates during 10 h of incubation. The effects of added hormones on LDH lavels are as follows: (a) T3 causes about a 2-fold increase in LDH at 7 to 8 h in hepatocytes from young adult animals, an effect which is lowered in either younger or older animals or in thyroidectomized animals. (b) Insulin leads to a similar increase in LDH at 5 to 6 h and a falling off at 8 to 10 h. (c) Glucagon also causes an approximate doubling of the amount of extractable LDH during a 10-doubling of the amount of extractable LDH during a 10-h period. (d) Dexamethasone does not produce an increase. (e) Bt2-cAMP produces an effect indistinguishable from that of glucagon. Paired combinations of these hormones fail to produce an additive response in any case. The combinations of T3 plus dexamethaseon and insulin plus dexamethasone lead to significant reductions in levels of extractable LDH when compared to the single hormone effects cited above. With respect to rates of synthesis of total protein as measured by [3H]leucine incorporation, only glucagon, glucagon plus Bt2-cAMP, glucagon plus insulin, T3 plus Bt2cAMP, and T3 plus insulin produce significant increases during a 10-h period. However, when [3H]leucine incorporation into highly purified LDH is measured as an index of LDH biosynthesis, T3, insulin, and glucagon consistently increase the biosynthetic rates during a 10-h period. Bt2cAMP produces a smaller increase. Dexamethasone fails to produce any significant change when compared to controls. Paired combinations of hormones again do not produce any additive effect on LDH biosynthesis when the hormone producing the higher level is taken as the reference...