Determinants of magnitude of pseudohyperkalemia in thrombocytosis

The release of potassium from platelets is a well-known cause of pseudohyperkalemia in thrombocytosis. In predicting the magnitude of pseudohyperkalemia associated with thrombocytosis, previous investigations considered only the amount of potassium released from platelets during blood clotting, although the increment in serum potassium during blood clotting depends on the quantity of potassium released from platelets as well as the volume of distribution of the released potassium, which is inversely proportionate to the hematocrit. The present study proposes a new mathematical formula to predict the magnitude of increase in serum potassium during blood clotting, and accuracy of this formula has been tested in a patient with thrombocytosis.

Determination of nitrite in cured meats by ion-exclusion chromatography with electrochemical detection

A rapid liquid chromatographic (LC) method was developed for a sensitive determination of nitrite in cured meats, using ion-exclusion chromatographic separation and electrochemical detection (IEC-EC). The current AOAC colorimetric method requires 2 h shaking in a steam bath to eliminate interference from reducing compounds such as ascorbic acid. In the present method, nitrite was analyzed in the presence of ascorbic acid without interference, and the extraction time was reduced to 1 min. The extracted nitrite was determined by ion chromatography using anion-exclusion/HS column and amperometric detector equipped with platinum or glassy carbon electrode operating at +1.0 V vs Ag/AgCl reference electrode. The detection limit was 1 ppb as NO2-. The recoveries of 50 ppm nitrite added to frankfurter and meat stick were 103 and 99.6%, respectively, with relative standard deviations less than 4%. The high speed, sensitivity, and selectivity make the new method a useful alternative to the AOAC colorimetric method.

Effect of dietary fat on the induction of hepatic microsomal cytochrome P450 isozymes by phenobarbital

Dietary polyunsaturated fatty acid is needed for optimal induction of cytochrome P450. In this study we quantitated cytochrome P450 hemoproteins in male Sprague-Dawley rats that were starved for 36 hr and then refed a fat-free diet (FF) or a diet containing 20% corn oil for 4 days. Some received phenobarbital (Pb) sodium (80 mg/kg, i.p., daily) for 3 days prior to decapitation. Microsomal cytochrome P450 levels were measured by carbon monoxide binding spectra, and the P450 isozymes separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis were quantitated by gel scanner. Cytochrome P450 PB-B was quantitated by a Western blot technique. Rats fed FF diet and administered Pb had only 21% more microsomal P450 than non-induced controls, whereas rats fed 20% corn oil diet had 59% more P450 and Pb-treated rats fed 20% corn oil diet had 181% more P450 than FF controls. Analysis of gels showed 32, 59 and 124% more P450 protein, respectively, in FF Pb, corn oil control or corn oil Pb groups than in FF controls. Cytochrome P450 PB-B was not detected in non-induced groups, but quantitation by Western blot yielded 0.32 and 0.70 nmol/mg protein, respectively, in FF Pb and corn oil Pb groups. Our findings suggest that deprivation of dietary fat reduces the total amount of cytochrome P450 hemoprotein and its inducibility by Pb through decreased P450 hemoprotein synthesis. The limiting factor(s) restricting synthesis of new cytochrome P450 hemoproteins in rats refed a diet devoid of fat may be the inability to respond to the inducer (Pb) or the paucity of utilizable fatty acids needed for synthesis of the phospholipid matrix of the endoplasmic reticulum necessary for the support and proper juxtapositioning of these protein molecules.

Determination of sulfite in foods and beverages by ion exclusion chromatography with electrochemical detection: collaborative study

A liquid chromatographic (LC) method for determination of total sulfite in foods and beverages by alkali extraction followed by ion exclusion chromatographic separation and electrochemical detection (IEC-EC) was collaboratively studied by 9 laboratories. Blind duplicate samples of starch, diluted lemon juice, wine cooler, dehydrated seafood, and instant mashed potatoes were analyzed without spiking and with added sulfite at 2 levels. The initial sulfite levels varied from 0 to 384 ppm SO2, and the levels added varied from 10 to 400 ppm. The initial sulfite levels determined by the IEC-EC method and the Monier-Williams method were in good agreement. Recovery of added sulfite by the IEC-EC method was generally higher than that by the Monier-Williams method. Within-laboratory repeatability (RSDr) for the IEC-EC method varied from 4.4 to 26.0%, and overall reproducibility (RSDR) varied from 8.5 to 39.3%. The collaborators found the method to be fast, sensitive, and easy to use, which makes it a useful alternative to the Monier-Williams method. The method has been adopted official first action.

In vitro mutagenesis studies at the arginine residues of adenylate kinase. A revised binding site for AMP in the X-ray-deduced model

Although X-ray crystallographic and NMR studies have been made on the adenylate kinases, the substrate-binding sites are not unequivocally established. In an attempt to shed light on the binding sites for MgATP2- and for AMP2- in human cytosolic adenylate kinase (EC 2.7.4.3, hAK1), we have investigated the enzymic effects of replacement of the arginine residues (R44, R132, R138, and R149), which had been assumed by Pai et al. [Pai, E. F., Sachsenheimer, W., Schirmer, R. H., & Schulz, G. E. (1977) J. Mol. Biol. 114, 37-45] to interact with the phosphoryl groups of AMP2- and MgATP2-. With use of the site-directed mutagenesis method, point mutations were made in the artificial gene for hAK1 [Kim, H. J., Nishikawa, S., Tanaka, T., Uesugi, S., Takenaka, H., Hamada, M., & Kuby, S. A. (1989) Protein Eng. 2, 379-386] to replace these arginine residues with alanyl residues and yield the mutants R44A hAK1, R132A hAK1, R138A hAK1, and R149A hAK1. The resulting large increases in the Km,app values for AMP2- of the mutant enzymes, the relatively small increases in the Km,app values for MgATP2-, and the fact that the R132A, R138A, and R149A mutant enzymes proved to be very poor catalysts are consistent with the idea that the assigned substrate binding sites of Pai et al. (1977) have been reversed and that their ATP-binding site may be assigned as the AMP site.

Theoretical investigation of the estimation of relative regional neuroreceptor concentration from a single SPECT or PET image

The validity of estimating changes in regional neuroreceptor concentration based upon a single ECT (emission computed tomography) image is examined to determine whether an image can be acquired at a time when changes in the observed regional radioactivity are much more sensitive to changes in receptor concentration than to changes in radioligand delivery. These sensitivities are defined as the normalized partial derivatives of the regional radioactivity signal (S) with respect to the total receptor (R(t)) and with respect to radioligand delivery (k(1)). Using computer simulations, it is found that ( partial differentials/ partial differentialR(t))/( S/R(t)) can be less than unity (receptor hyposensitivity), approximately equal to unity, or significantly greater than unity (receptor hypersensitivity). It is possible to find classes of parameter sets under which the receptor sensitivity is close to unity and the delivery sensitivity is of much lower magnitude. The results indicate that if the parameters for a given radioligand-neuroreceptor system can be established as belonging to one of these classes, then changes in regional neuroreceptor concentration can be estimated based upon a single ECT image.

Effect of oral dosing vehicles on the acute hepatotoxicity of carbon tetrachloride in rats

Although carbon tetrachloride (CCl4) is of concern as a drinking water contaminant, it has been necessary in most oral toxicity studies to give CCl4 in an oil vehicle due to its limited water solubility. The primary objective of our study was to assess the influence of dosing vehicles on the acute hepatotoxicity of CCl4. Fasted 200- to 230-g rats were generally found to be more susceptible to CCl4 hepatotoxicity than fasted 300- to 330-g rats. A time-course study revealed that corn oil did not delay the onset or time of maximal liver injury by an oral 100 mg/kg dose of CCl4, but did reduce the extent of injury relative to that when the chemical was given undiluted or as an aqueous emulsion. Fasted 200- to 230-g male Sprague-Dawley rats were given 0, 10, 25, 50, 100, 250, 500, or 1000 mg CCl4/kg body wt by gavage: in corn oil; as an aqueous emulsion; as the undiluted chemical; and in the 10 and 25 mg/kg doses only, in water. Blood and liver samples were taken 24 hr after dosing for measurement of serum and microsomal enzymes. Pathological examination of liver samples was also conducted. Dose-dependent increases in serum enzyme levels and pathological changes and dose-dependent decreases in microsomal P450 and glucose-6-phosphatase activity were observed in each vehicle group. Both the 10 and 25 mg/kg oral doses of CCl4 in water caused significant elevations in serum enzymes and hepatic centrolobular vacuolation. The study revealed that acute hepatotoxicity was less pronounced at each dosage level in rats given CCl4 in corn oil than in other vehicle groups. These findings demonstrate that dosing vehicles can significantly influence the acute hepatotoxicity of CCl4 in rats and are a cause for additional consideration and review of the practice of routinely using vegetable oils as a diluent in studies of volatile organic compound (VOC) toxicity. The use of aqueous Emulphor emulsions appears more appropriate in acute toxicity studies of VOC drinking water contaminants such as CCl4, in that the emulsion did not substantially alter the toxicity of CCl4 from that of undiluted CCl4 or CCl4 ingested in water.

Effect of dosing vehicles on the pharmacokinetics of orally administered carbon tetrachloride in rats

The primary objectives of this investigation were to determine whether oil and aqueous dosage vehicles alter the pharmacokinetics of orally administered carbon tetrachloride (CCl4) in rats, and to relate vehicle effects on CCl4 absorption and bioavailability to alterations of the acute hepatotoxicity of CCl4 seen in a companion study (H.J. Kim, S. Odend'hal, and J. V. Bruckner, 1990, Toxicol. Appl. Pharmacol. 102, 34-49). Fasted 200- to 230-g male Sprague-Dawley rats with indwelling arterial cannulas received 25 mg CCl4/kg body wt by gavage: in corn oil; as an Emulphor aqueous emulsion; in water; and as pure undiluted chemical. The 25 mg/kg dose was also given iv in PEG 400 through an indwelling jugular cannula. Serial blood samples were taken from the iv and gavage animals and analyzed for CCl4 content to obtain blood concentration-versus-time profiles. CCl4 was absorbed very rapidly from the GI tract, as peak concentrations of CCl4 in the blood were reached within 3-6 min of dosing in the aqueous emulsion and water groups. These peak levels were higher than those in the undiluted CCl4 group and substantially higher than those in the corn oil group. Corn oil markedly delayed the absorption of CCl4 from the GI tract and produced secondary peaks in the blood concentration-versus-time profiles. Elimination of CCl4 from the bloodstream of the iv group followed a triexponential pattern. CCl4 was eliminated from the blood at approximately the same rate in the iv and po groups, as reflected by similar elimination rate constant and half-life values. There was a high degree of correlation of both Cmax and AUC0(120) with hepatotoxicity. CCl4 was apparently less acutely hepatotoxic in corn oil due to delay and prolongation of CCl4 absorption, resulting in a marked decrease in the concentration of the chemical in the arterial blood. These findings suggest that corn oil has sufficient effect on the pharmacokinetics of orally administered CCl4 to require an appraisal of its use in studies of the acute oral toxicity of CCl4 and other volatile organic chemicals (VOCs). The use of aqueous Emulphor emulsions appears appropriate in studies of VOC contaminants of drinking water, in that the emulsion did not substantially alter the pharmacokinetics or hepatotoxicity of CCl4 from that ingested in water.

Effect of indomethacin pretreatment on acute mortality in experimental brain injury

The effect of indomethacin administration on the mortality rate of brain-injured rats was studied in four groups of animals subjected to a level of injury with a fluid-percussion apparatus predetermined to cause 50% mortality (50% lethal dose, or LD50). There were 24 animals in each of the following groups: 1) a control group, on which the LD50 was evaluated; 2) an ethanol-treated group with a mean blood serum level of 0.32 +/- 0.03 gm% (+/- standard error of the mean); 3) an indomethacin-treated group at a dose level of 3 mg/kg body weight administered intraperitoneally 10 to 15 minutes before injury; and 4) an indomethacin/ethanol-treated group. Significant differences in mortality rates were found in these experimental groups; namely, 50%, 58%, 8.3% (p less than 0.005), and 25% (p less than 0.05), respectively. The predetermined LD50 level of a 2.5- to 2.6-atm peak pressure pulse produced immediate apnea in all animals, which was either sustained (Type III), followed by temporary respiratory recovery (Type II), or followed by permanent resumption of breathing (Type I). The most important effect of indomethacin on respiratory function was manifested by a much higher percentage of Type I respiratory responses and a much lower percentage of Type II and III responses (hence a lower mortality rate). There was also a more rapid return to normal breathing in the postapneic period of recovery. Suppression of prostaglandin synthesis and of superoxide anion production at the of trauma may explain, at least in part, these favorable effects of indomethacin.

Determination of nitrite in drinking water and environmental samples by ion exclusion chromatography with electrochemical detection

An extremely sensitive determination of nitrite in drinking water (tap water and underground water) and environmental samples (rain, lake water, and soil) was achieved by ion exclusion chromatography (IEC) with electrochemical (EC) detection. Potential interferences in the determination of nitrite by the standard spectrophotometric method or by the ion exchange chromatographic method with either conductivity detection or UV detection were eliminated. The detection limit was 0.1 ppb without preconcentration. No nitrite was observed from tap water or underground drinking water. The recoveries of nitrite added to tap water at 0.02, 0.1, and 1 ppm levels were between 96 and 104.5%. The average coefficient of variation was 4.7%. The recovery results were in good agreement with those obtained by the standard spectrophotometric method. Nitrite concentrations between 0.068 and 0.19 ppm were observed in rain within a week period. A greater variation, between 0.015 and 0.26 ppm, was observed in lake water. Amounts of 19.1 ppm and 0.50 ppm nitrite were observed from fertilized and unfertilized soil, respectively.

Determination of total vitamin C by ion exclusion chromatography with electrochemical detection

A rapid and sensitive liquid chromatographic method for determination of total vitamin C in foods and beverages is described. Ascorbic acid and dehydroascorbic acid are extracted with sulfuric acid solution, and the dehydroascorbic acid in the extract is reduced to ascorbic acid by dithiothreitol at pH 7. The reduction is complete in 2 min at room temperature. The resulting total ascorbic acid is separated on an anion exclusion/high speed column with 20 mM sulfuric acid as eluant and detected amperometrically with a platinum electrode operating at +0.6-0.8 V vs Ag/AgCl reference electrode. Dithiothreitol (retention time, 3.2 min) does not interfere with the separation and detection of ascorbic acid (retention time, 1.3 min). The dehydroascorbic acid content can be estimated as the difference in ascorbic acid content measured with and without reduction by dithiothreitol. The completeness of the reduction was demonstrated by purposely allowing the oxidation of ascorbic acid in the food extract and determining the total vitamin C after reduction. The determinations of vitamin C content in selected foods and beverages were in good agreement with the expected values. Total analysis time for vitamin C is 10 min and the detection limit is 0.1 ng. The method is specific for vitamin C, and interference by other food constituents is minimal.

Oral toxicity of 1,2-dichloropropane: acute, short-term, and long-term studies in rats

The objective of this investigation was to characterize the acute and short- and long-term toxic potency of orally administered 1,2-dichloropropane (DCP). In the acute and short-term studies, male rats of 250-300 g were gavaged with 0, 100, 250, 500, or 1000 mg DCP/kg in corn oil once daily for up to 10 consecutive days. Although ingestion of DCP caused body weight loss and CNS depression, few other toxic effects were manifest 24 hr after a single dose of the chemical. Morphological changes were limited to liver centrilobular cells in 500 and 1000 mg/kg rats. Similarly, elevated activity of some serum enzymes occurred only at these two highest dose levels. Hepatic nonprotein sulfhydryl (NPS) levels were decreased and renal NPS levels increased at 24 hr. In the short-term study resistance developed to DCP hepatotoxicity over the 10 consecutive days of exposure, as reflected by progressively lower serum enzyme levels and by decreases in the severity and incidence of toxic hepatitis and periportal vacuolization. Nucleolar enlargement in hepatocytes, however, was observed at all dosage levels at 5 and 10 days. There were a number of manifestations of hemolytic anemia, including erythrophagocytosis in the liver, splenic hemosiderosis and hyperplasia of erythropoietic elements of the red pulp, renal tubular cell hemosiderosis, and hyperbilirubinemia. Urinalyses and histopathology revealed no evidence of nephrotoxicity. In the long-term study, male rats initially weighing 180-200 g were gavaged five times weekly for up to 13 weeks with 0, 100, 250, 500, or 750 mg DCP/kg. As over one-half the 750 mg/kg group died within 10 days, the survivors were sacrificed. Histopathological changes in the 750 mg/kg animals included mild hepatitis and splenic hemosiderosis, as well as adrenal medullary vacuolization and cortical lipidosis, testicular degeneration and a reduction in sperm, and increased number of degenerate spermatogonia in the epididymis in some members of the group. Similar testicular and epididymal degenerative change also were observed in some 500 mg/kg animals after 13 weeks of dosing. There was a progressive increase in the number of deaths in the 500 mg/kg group, such that more than 50% were dead by 13 weeks. No deaths occurred in the 100 or 250 mg/kg groups. The DCP dosage regimen also produced a dose-dependent decrease in body weight gain. DCP exhibited very limited hepatotoxic potential and no apparent nephrotoxic potential in the long-term study. Slight elevations in serum ornithine-carbamyltransferase activity, periportal vacuolization, and active fibroplasia in the liver were seen in the 500 mg/kg animals.

CT findings of clonorchiasis

Clonorchiasis is a snail-transmitted trematodiasis caused by Chinese liver fluke, Clonorchis sinensis. Forty-two patients with the disease were examined with CT. Seventeen patients had clonorchiasis alone, and 25 patients had clonorchiasis with hepatobiliary malignancies (20 cholangiocarcinomas, four hepatocellular carcinomas, one carcinoma of the ampulla of Vater). In three of the 17 patients with clonorchiasis alone, the CT scans were normal. In 14 patients (82%), CT showed diffuse, minimal, or mild dilatation of the intrahepatic bile ducts. None of the patients had marked dilatation. The extrahepatic biliary tree was normal in all 17 patients. All 25 patients with clonorchiasis and hepatobiliary malignancies had diffuse dilatation of the intrahepatic bile ducts on CT, including 18 patients with minimal or mild dilatation and seven patients with marked dilatation. All seven patients with marked dilatation had extrahepatic biliary malignancies. Clonorchis sinensis per se or thickening of the bile duct wall could not be recognized on CT scans. Additional abnormalities evident on CT included pyogenic liver abscesses in two patients and gallstones in five patients. The diagnosis of clonorchiasis can be suspected when CT shows diffuse, uniform, and minimal or mild dilatation of the intrahepatic bile ducts, particularly in the periphery of the liver, without evidence of extrahepatic biliary dilatation.

Synthetic genes for human muscle-type adenylate kinase in Escherichia coli

An artificial gene coding for the human muscle-type cytosolic adenylate kinase (hAK1) was chemically synthesized and directly expressed in Escherichia coli under the control of trp promoter. The DNA duplex of 596 bp was designed and constructed from 40 oligonucleotide fragments of typically 30 nucleotides in length. Twelve unique restriction sites were fairly evenly spaced in the synthetic gene to facilitate site-specific mutagenesis at any part of this recombinant protein. The genes for mutant hAK1 (Tyr 95----Phe 95, Y95F hAK1; Arg 97----Ala 97, R97A hAK1) were constructed by cassette mutagenesis and utilized restriction sites incorporated in the hAK1 gene. The recombinant hAK1 was purified to homogeneity by a two-step chromatographic procedure with a good yield, and showed the same adenylate kinase activity as that of authentic hAK1. Preliminary kinetic studies show that the enzymatic activity (Vmax app,cor/Et) of Y95F hAK1 was slightly greater than that of recombinant hAK1, whereas R97A hAK1 still possessed approximately 4% of recombinant hAK1 activity. These results suggest that the Arg-97 residue is important but not essential for catalytic activity, and that Tyr-95 can be replaced by phenylalanine without substantial effects on the enzymatic activity. Moreover, preliminary estimates of the apparent kinetic parameters suggest that these residues are not required for MgATP binding, and therefore they do not appear to be part of the MgATP binding site.

Liposarcoma arising in a giant lipomatous polyp of the esophagus

A case of liposarcoma in a giant pedunculated lipoma of the esophagus in a 49-year-old Korean woman who presented intermittent swallowing difficulty for 3 years is reported. Endoscopy and esophagography revealed that a giant smooth longitudinal tumor mass almost entirely occupied the esophageal lumen. A total esohagectomy was done. The tumor was 20 cm in length and 7 cm in average diameter with an obvious stalk measuring 3 cm in length and 1 cm in diameter. Microscopic examination disclosed a lipoma with focal ulceration and liposarcomatous change infiltrating into interstitial fibrous tissue at its distal end.

Acute cerebral infarction and changes of regional cerebral blow flow (rCBF) following experimental middle cerebral artery (MCA) occlusion

An unanaesthetized cat model of acute focal cerebral ischaemia has been established by the technique of transorbital snare ligature for middle cerebral artery (MCA) occlusion. The model was used to investigate the patterns of changes of regional cerebral blood flow (rCBF) for up to 16 h following MCA occlusion by the hydrogen clearance technique and to explore the correlation among changes of rCBF, neurological deficits, and pathological changes. The animals were divided into 2 groups according to the size of infarct which was identified by 2% triphenyl tetrazolium chloride (TTC) solution stain. Infarct larger than 10% of coronal section surface of ipsilateral hemisphere was found in 18 cats (Group A), and a smaller infarct was found in the remaining 7 cats (Group B). Between these 2 groups, there was a statistically significant difference in the average rCBF value of the ipsilateral MCA territory. The increasing grade of contralateral paralysis correlated well with the decreasing rCBF in the ipsilateral MCA territory, and the increasing grade of cerebral hemispheric swelling was directly proportional to the increasing grade of paralysis. Three patterns of changes of rCBF were observed: persistent severe ischaemia (15 cats, Group A); persistent mild to moderate ischaemia (7 cats, Group B); and immediate severe ischaemia followed by early post-ischaemic hyperaemia and death (3 cats, Group A). During the initial stage of ischaemia, a significant decrease in rCBF of the contralateral hemisphere was observed in both groups, however, in Group A rCBF gradually increased to preocclusion level, while Group B presented a further decrease in rCBF suggesting the occurrence of interhemispheric diaschisis. Thus, Group B appeared to take advantage of diaschisis during the late phase of infarct development, as well as the substantial collateral flow from the surrounding anterior and posterior cerebral artery territories.