Sestamibi parathyroid imaging.

Since the introduction of technetium-99m (99mTc) sestamibi (hexakis-2-methoxyisobutyl isonitrile) as a parathyroid imaging agent in 1989, many investigators using several different imaging protocols have reported uniformly excellent results for localization of parathyroid adenomas. Exact localization of hyperplastic parathyroid glands has not met with as much success. However, the results of multiple comparative studies suggest that the diagnostic utility of sestamibi protocols equals or exceeds other noninvasive, nonscintigraphic imaging strategies, including high-resolution ultrasound, computed tomography, and magnetic resonance imaging. Two different, but not necessarily mutually exclusive imaging strategies have been used: subtraction imaging using iodine-123 (123I) or 99mTc sodium pertechnetate as the thyroid agent, and sestamibi dual-phase imaging, which takes advantage of differential washout of sestamibi from thyroid and parathyroid tissue. Sestamibi subtraction imaging has been shown to have greater sensitivity for abnormal parathyroid glands compared with thallium-201 subtraction imaging using pooled data, 87% versus 71%, respectively. Dual-phase sestamibi imaging protocols are much more variable in their conduct and have a much greater variability in sensitivity, 43% to 91%, but with a pooled sensitivity of 73%. Data suggest that dual phase techniques are at least as sensitive, and in optimized protocols, superior to, thallium-201 subtraction techniques. This superiority is attributed to the favorable washout kinetics of sestamibi and the superior imaging characteristics of the 99mTc label. Specificity and positive predictive value for both sestamibi techniques are very high, typically greater than 90% and at least equal to thallium-subtraction protocols, although specificity may be slightly lower for sestamibi subtraction techniques. Therefore, sestamibi protocols are the scintigraphic procedure of choice for parathyroid imaging. Dual-phase sestamibi protocols are more robust and lend themselves to single photon emission computer tomography (SPECT) imaging, and may be followed sequentially by subtraction techniques if results are inconclusive. Despite the excellent results of sestamibi parathyroid imaging, it is unclear whether this accuracy can compete with the even better success of an experienced surgeon in initial surgeries for hyperparathyroidism, and routine preoperative imaging before initial surgery is still controversial. However, sestamibi parathyroid imaging is an excellent addition to a correlative imaging approach in reoperations for persistent and recurrent hyperparathyroidism.

Performance and metabolic effects of benzodiazepine during submaximal exercise.

The present study examined whether benzodiazepine (BZ) intake alters performance and selected hormonal and metabolic variables during submaximal exercise. Seven triathletes completed two cycling trials at 85% maximum O2 uptake starting 3 h after an ingestion of either a placebo (PLA) of gelatin or BZ (1.5 mg lorazepam) and continuing until exhaustion, according to a double-blind randomized protocol. Blood samples were collected at rest; 5, 10, and 15 min; and exhaustion for dopamine (DA), norepinephrine (NE), epinephrine (Epi), adrenocorticotropic hormone (ACTH), cortisol (CORT), insulin (INS), free fatty acid, blood glucose, and lactate (La) determinations. Time of cycling was not significantly changed after BZ or PLA administration (22.9 +/- 2.5 vs. 23.5 +/- 3.8 min, respectively). A decrease in CORT and an increase in INS (P < 0.05) were observed with BZ before cycling. In comparison with rest, exercise resulted in a decrease in INS and an increase in all the other variables investigated (P < 0.001), but DA, NE, Epi, ACTH, CORT, La, and free fatty acid were significantly less elevated under BZ (P < 0.05). No change was found in glucose and INS levels between the two treatments at the end of the test. There was a strong correlation under both PLA and BZ conditions between DA, NE, Epi, and ACTH and also between Epi and La levels. From these data, BZ intake did appear to alter metabolism but did not influence performance during intense submaximal exercise.

Determination and identification of amiloride in human urine by high-performance liquid chromatography and gas chromatography-mass spectrometry.

A simple and sensitive high-performance liquid chromatographic method was developed to screen and determine amiloride (I) in human urine. The detection limit of the method is 0.12 micrograms/ml and the recovery of amiloride from urine was 80.4-85.5% at different concentrations. The coefficients of variation were less than 2.8 and 4.4% for intra- and inter-assays, respectively. Total urinary excretion of I in 24 h after oral administration of 5 mg or 15 mg of I ranged from 22.0 to 33.3% of the total dose for three different subjects. I could be detected in urine up to at least 44 h after a 5-mg dose and 72 h after a 15-mg dose. A gas chromatographic-mass spectrometric (GC-MS) confirmatory method was established based on the methanolysis of I to methyl 3,5-diamino-6-chloropyrazine-carboxylate (II). The di-N-trimethylsilyl derivative of II showed very good GC-MS properties and provided reliable structure information for confirmation analysis of I. This is the first time that a reliable GC-MS method has been reported for the detection of urinary I.

Effects of cysteine derivatives of styrene on the transport of p-aminohippurate ion in renal plasma membrane vesicles.

The effects of cysteine conjugates of styrene, e.g. S-1/2-(phenyl-hydroxyethyl) cysteine (PEC) and its N-acetyl derivative (NAPEC) on the transport of p-amino-hippurate (PAH) ion in plasma membranes were studied in vitro using isolated rat renal brush-border membrane (BBM) and basolateral membrane (BLM) vesicles. The uptake of PAH was significantly inhibited by both PEC and NAPEC in both the membrane vesicles, as verified by decrease of the membrane/medium concentration ratio of PAH as the concentration of either PEC or NAPEC in the medium increased. These results show that both PEC and NAPEC are capable of interfering with the accumulation of PAH (a model organic anion for renal tubular transport system) by both energy-independent and energy-dependent carrier-mediated transport processes. The inhibition of PAH uptake in BBM vesicles due to 10 mM PEC or NAPEC was found to be nearly competitive, almost similar to probenecid, whereas in BLM vesicles such inhibition was found to be partially noncompetitive, as verified by the double reciprocal plots. Both PEC and NAPEC showed dose-dependent inhibition of the specific activity of the marker enzyme in each membrane, e.g. gamma-glutamyl transferase in BBM and Na(+)-K(+)-ATPase in BLM vesicles. However, no such inhibition was noticed with probenecid. The in vitro pretreatment with probenecid prevented the inhibition of gamma-glutamyl transferase activity in BBM due to PEC or NAPEC, but such was not the case for the Na(+)-K(+)-ATPase activity in BLM. In conclusion, the data suggest that the transport of cysteine or N-acetylcysteine conjugates of styrene by renal proximal tubular cells across both the membrane vesicles accompanied by the inhibition of the membrane-specific enzymes may lead to cellular dysfunction and consequently to the initial development of their nephrotoxicity.

Effect of S-(2-chloroethyl)-DL-cysteine on the transport of p-aminohippurate ion in renal plasma membrane vesicles.

The effects of S-(2-chloroethyl)-DL-cysteine (CEC) (a potent nephrotoxin) on the transport of p-aminohippurate ion (PAH) in renal plasma membrane vesicles isolated from rat renal cortex were studied in vitro. The uptake of PAH was significantly reduced in a dose-dependent manner in both the brush border membrane (BBM) and basolateral membrane (BLM) vesicles. These results demonstrate that CEC is capable of interfering with the accumulation of PAH (a model organic anion for renal tubular transport system) by both energy-independent and energy-dependent carrier-mediated transport processes. Probenecid, a typical inhibitor of the organic anion transport system, showed the highest inhibition of PAH uptake in both the membranes vesicles. These data indirectly suggest that transport by renal tubular cells may result in the accumulation of CEC in renal cellular organelles eventually in toxic concentrations. Thus, CEC showed both dose- and time-dependent inhibition of the activities of gamma-glutamyl transferase (a BBM marker enzyme) and Na+, K(+)-ATPase (a BLM marker enzyme), while no such inhibition was noticed with probenecid. Pretreatment with probenecid prevented the inhibition of the gamma-glutamyl transferase activity due to CEC in BBM, but failed to do so for the Na+,K(+)-ATPase activity in BLM vesicles. Thus, the data suggest that the inhibition of the activities of these membrane-specific enzymes by CEC could lead to the initial development of its nephrotoxicity.

Effect of cimetidine on hepatic biochemical changes, liver toxicity and major urinary metabolite excretion of trichloroethylene in rats.

The effects of cimetidine (CIM) (an inhibitor of the hepatic microsomal monooxygenase system) on the metabolism and hepatotoxicity of trichloroethylene (TRI) were studied in male Sprague-Dawley rats. Rats were given three doses of 120 mg/kg i.p. (low-dose regimen) of CIM at 0, 6 and 11 h for 1 day, or ten doses of 200 mg/kg (high-dose regimen) at 8, 11, 14 and 17 h for 2 days and 8 and 11 h on 3rd day. Trichloroethylene (0.5 or 0.65 ml/kg) was administered i.p. 1 h after 2nd dose (low-dose regimen) or 9th dose (high-dose regimen) of CIM. In the low-dose regimen study, the activity of hepatic microsomal aminopyrine N-demethylase was decreased 1 and 5 h after the second dose and 7 h after the third dose of CIM, but became normal 20 h after the last dose. The cytochrome P-450 content and the activities of aniline hydroxylase and epoxide hydratase remained unchanged. Trichloroethylene at both dose levels produced liver toxicity, as verified by increase in activities of SDH and SGPT as well as by liver histology. Cimetidine alone had no such effect. An apparent reduction in TRI toxicity by CIM (at both dose regimens) could be observed histologically. The biochemical tests (SDH and SGPT) corroborated the histological changes only when TRI was given at a dose of 0.5 ml/kg combined with a high-dose regimen of CIM. Cimetidine at both dose regimens had a tendency to decrease the in vivo metabolism of TRI.(ABSTRACT TRUNCATED AT 250 WORDS)

Application of linear integration in the morphometric study of mild and severe pulmonary alveolar injury.

In this study we applied linear integration morphometry to characterize the pulmonary alveolar reaction to toxic injury and to study possible relationships between the major tissue and cell compartments of alveolar tissue, normal and injured. Acute alveolar injury of mild and severe intensity was induced in Swiss-Webster mice by the ip administration of the chemicals diquat (4 mg/kg) and butylated hydroxytoluene (BHT; 400 mg/kg). Animals were sacrificed at Days 1 and 2 after diquat treatment and at Days 1, 3, and 5 after BHT treatment. Sampling and analysis of alveolar tissue were conducted at both levels of light and electron microscopy. Thickness distributions of arithmetic and reciprocal intercepts, as well as the arithmetic (tau) and harmonic (tau h) mean thicknesses, were established for the following alveolar compartments: septum, alveolo-capillary barrier (ACB), type I and total epithelia, capillary endothelium, and interstitium. A relative measure of the pulmonary diffusion capacity and the capillary load of alveolar septa were also determined. The parameters calculated from these thickness distributions, such as their slopes, percentages of thin intercepts, and tau/tau h ratios, proved very sensitive and useful in the detection and characterization of morphological alterations in the type I epithelial and capillary endothelial cells following either mild or severe alveolar injury. The epithelial, endothelial, and interstitial layers of pulmonary septa were all characterized by their own pattern of structural changes, so that it proved impossible to relate them in a simple way to the tissue reaction, which can be easily studied at the light microscopic level. Linear integration morphometry thus proved very useful as a morphometric approach to the study of pulmonary alveolar injury and repair.

Acute sensitivity of BHT-induced alveolar toxicity to a diquat challenge in murine lungs.

In this study we investigated the effects of a mild toxic challenge at selected points in time on the nonspecific cellular events that occurred in acutely damaged pulmonary alveoli. Swiss-Webster mice were treated with butylated hydroxytoluene (BHT, 400 mg/kg ip) and sacrificed at Days 1, 3, and 5 thereafter; either 24 or 48 hr prior to each sacrifice, the herbicide diquat was administered (4 mg/kg ip) as a challenge to the ongoing cellular events in the pulmonary alveoli. Standard morphometric techniques were used at both the levels of light and electron microscopy to evaluate the alveolar response to BHT and diquat treatments. Following BHT, early type I epithelial and endothelial damage triggered inflammatory changes in alveolar septa. Proliferation and differentiation of type II pneumocytes, aiming at the regeneration of the respiratory epithelium, ensued and peaked at Day 3. Treatment with diquat alone caused mild inflammatory changes and hypertrophy of type II pneumocytes, in the absence of necrosis of any alveolar cell type. The pinpoint administration of diquat in the early days following treatment with BHT significantly disorganized the temporal pattern of alveolar reaction. Diquat enhanced epithelial and endothelial damage only if administered before the onset of BHT-induced injury. Afterwards, the alveolar response to the combined effects of BHT and diquat could not be predicted from their known individual effects. Treatment with diquat modified either proliferation or differentiation of type II pneumocytes, depending upon time along the BHT schedule. Inflammatory and interstitial reactions were lowered when diquat was given at Days 1 and 3 post-BHT, but potentiated when given at Day 4. The results document time-related changes in the sensitivity of damaged and regenerating alveolar cells to a mild exogenous chemical challenge. They may further indicate that low levels of urban and industrial toxicants might influence pulmonary alveolar events in individuals made more susceptible by acute or chronic respiratory diseases.

Chloroform interaction with chlordecone and mirex: correlation between biochemical and histological indices of toxicity and quantitative tissue levels.

The purpose of this study was to investigate whether the tissue distribution of chlordecone (CD) and mirex (M) might explain the difference in the potentiation of CHCl3 liver injury. Male Sprague-Dawley rats received either a single oral dose of CD or M (1, 2.5, 5, 10, 25, or 50 mg/kg) or three single daily doses of CD or M (0.5, 2, or 10 mg/kg). Eighteen hours following the last treatment, the animals were divided into two groups. The first group was killed and residues of CD or M in plasma, kidney, liver, and adipose tissue were measured by gas-liquid chromatography. The other group received CHCl3 (0.5 ml/kg, po) and was killed 24 hr later. Biochemical and histological indices of liver injury were evaluated. CD administered either singly or repetitively is more effective than M in potentiating the CHCl3-induced liver injury. This was exhibited by a higher increase in the plasma activities of the enzymes alanine aminotransferase and ornithine carbamoyl transferase and a greater alteration of the morphological pattern. There was a very good correlation between biochemical and histological indices. However, the severity of the liver injury did not parallel tissue concentrations. With M, a relatively poor potentiation of the liver damage was observed although adequate hepatic concentrations were present.

Pulmonary toxicity of the insecticide fenitrothion in the rat following a single field exposure.

The pulmonary toxicity of the organophosphorus insecticide fenitrothion was evaluated following a single exposure of rats to the field formulation, at the site of an aerial spraying. Four groups of 40 Sprague-Dawley rats (including a control), set in wood enclosures, were placed under the aerial lines of the spraying aircraft. The degree of exposure was monitored at the ground level by air sampling and visual evidence of droplet activity deposition. Plasma pseudocholinesterase activity and pulmonary alveoli ultrastructure were used as indices to the fenitrothion exposure. Rat lungs were examined under light and electron microscopy at days 3, 7, 21, 60 and 180 after the exposure. Although a few signs of toxic lung injury were observed at days 3 and 7 there was no cholinergic crisis nor an effect on the pseudocholinesterase activity within 12 h in the exposed animals, when compared with controls. The alveolar toxic reaction was limited to small and discrete foci, and was entirely reversible within a period of 2 months. On a morphological basis it is thus concluded that a single field exposure to fenitrothion did not induce any permanent change in the alveolar area of the rat lung.

Biphasic mode of epithelial regeneration in murine pulmonary alveoli.

After administration to mice of butylated hydroxytoluene, the pulmonary alveolar epithelium adopts a biphasic pattern of regenerative proliferation. This hitherto-unnoticed pattern of epithelial repair in the lung was revealed by the investigation of stereologic parameters. The earliest evidence of epithelial injury involved the type I pneumocytes, whose necrosis and disappearance from the septal surface was shown by a lowered surface density (SV). Proliferation of the type II pneumocytes ensued: the volume density (VV) rose above normal soon after the onset of necrosis, only to decrease as the cells slowly differentiated into intermediate and then type I pneumocytes. A second peak of type II pneumocytes appeared as the denuding of septa persisted. This twofold proliferation was also shown by the numerical density count (NV). Differentiation into an intermediate pneumocyte was itself documented by the raised VV and SV values. These observations of a biphasic mode of proliferation of type II pneumocytes raise the question of an unsuspected, persistent action of the toxic agent within pulmonary alveoli and serve to document the homeostasis of epithelial regeneration.

Histomorphometric study of the pulmonary response of guinea pigs to chronic cotton dust inhalation.

In this study we describe, through stereological methods, the lung morphology following inhalation exposure of guinea pigs to 21 mg/m3 cotton dust (CD) for 1 year. Various stereological parameters were determined on semithin histological sections, through a multistage sampling approach, to study the reaction of the whole lung, alveolar parenchyma, and bronchioles to CD inhalation. After 1 year of exposure, the lung volume was increased. Two distinct patterns of lung response were identified among the exposed animals. In type I responders, most of the morphometric parameters measured to describe the alveolar parenchymal reaction were within control value limits (means +/- 2 SD). In type II responders, the volume density (Vv) of the parenchymal zone was decreased, while the Vv, mean thickness, and absolute volume of the alveolar septa were increased. These changes caused the surface density (Sv) of alveolar epithelium to decrease, and an estimate of the percentage of alveolar septa remaining functional for gas exchange was also significantly lowered in these animals. In both types of responders, fifth to ninth orders of bronchioles had a raised wall to lumen ratio; the Vv and mean thickness of the bronchiolar epithelium were markedly increased, denoting hyperplastic changes. Thus, chronic exposure to cotton dust induced definite morphological changes on the peripheral conducting airways in most of the exposed animals, and induced pronounced changes at the alveolar level in 8 of 17 CD-exposed guinea pigs.

Genotoxicity of dimethylnitrosamine in the presence of chrysotile asbestos UICC B and xonotlite.

Interactions of particulates with chemical genotoxic agents may play an important role in the induction of carcinogenesis. With respect to bronchogenic cancer, the synergism associated with combined exposure to asbestos and tobacco smoke is a well-documented phenomenon. The present work focused on chrysotile asbestos and xonotlite. The latter is a fibrous calcium silicate which is increasingly being used to replace asbestos in various industrial applications. The study was aimed at testing the possible interaction of these materials with dimethylnitrosamine (DMN), a genotoxic component of tobacco smoke. The capacity of fibers to interfere with the genotoxic response elicited by DMN in the UDS/hepatocyte assay system specifically designed for sensitive detection of short-patch DNA repair, was looked for. The properties of the selected fibers with respect to binding affinity towards DMN were also examined.

Toxicity of peptides of Amanita virosa mushrooms in mice.

A study was performed on the hepatic reaction of mice to acute intoxication with virotoxins (alaviroidin, viroisin, deoxoviroisin, viroidin, deoxoviroidin) and phalloidin, cyclic peptides isolated from Amanita virosa mushrooms. Purified fractions were administered intraperitoneally at various dosages to determine the LD50 which ranged from 1.0 to 5.3 mg/kg, with viroidin, phalloidin, and viroisin being the most potent. The virotoxins and phalloidin induced hemorrhagic necrosis of the liver. The development of hepatic lesions was followed by enhanced serum alanine aminotransferase (ALT) activity as well as by light and electron microscopic changes. In additional groups, bile ducts were cannulated and bile was collected for 2 hr after injection of the peptides (1 mg/kg) to determine their cholestatic potential. The earliest changes in hepatocytes were plasma membrane invagination and cytoplasmic vacuole formation. At later time periods, erythrocyte accumulation was evident in vacuoles and in the cytoplasm. The severity of hepatic damage, as judged by morphologic analysis, was correlated with serum ALT activity. Two of the peptides tested (viroisin and phalloidin) decreased bile flow by more than 50% over control values. Mild ultrastructural alterations in the bile canalicular pole of hepatocytes were observed during the development of cholestasis. Since virotoxins, like phalloidin, are bound to actin, it is possible that their affinity to cellular actin may be responsible for their hepatotoxicity.

Results of a 90-day toxicity study on 1,2,3- and 1,1,2-trichloropropane administered via the drinking water.

Trichloropropanes have been identified as environmental contaminants in sediments of the Great Lakes region of North America. Since these chemicals had the potential to find their way into drinking water, a 90-day feeding study was carried out in order to determine their subchronic toxicity. Groups of 10 male and 10 female weanling Sprague-Dawley rats were supplied drinking water ad libitum, containing 1,2,3- or 1,1,2-trichloropropane at concentrations of 1, 10, 100 or 1000 mg/L for 13 weeks. Emulphor (0.5%) was used to solubilize the chemicals. At the end of the study, the animals were killed and examined for gross and microscopic changes. Heart, liver, brain, kidney and spleen were excised and weighed. Blood was collected and subjected to a comprehensive hematological analysis. Serum was collected and profiled for changes in 12 biochemical parameters and a portion of liver was used to determined mixed function oxidase activity. Although three animals died during the study, their deaths could not be related to treatment. Decreased growth rate was observed in both sexes of the group receiving 1000 mg/L 1,2,3-trichloropropane. There was an increase in liver, kidney and brain weights (relative to body weight) in rats of both sexes fed 1000 mg/L 1,2,3-trichloropropane. Fatty livers were observed in some of the treated animals but a clear dose-relationship was not evident. An elevation in serum cholesterol was observed in female rats fed the highest dose of 1,2,3-trichloropropane.(ABSTRACT TRUNCATED AT 250 WORDS)

Mitochondrial injury of pulmonary alveolar epithelial cells in acute paraquat intoxication.

The primary ultrastructural changes in pulmonary alveolar epithelial cells are described in paraquat-injected rats. Within 6-12 hr a single intravenous injection of 40 mg/kg paraquat dichloride caused selective mitochondrial swelling and loss of intramitochondrial granules within 24 hr in alveolar Type II cells. As the mitochondrial injury advanced, microvilli disappeared from apical plasma membrane followed by a cell destruction and detachment from basement membrane. This was accompanied by secondary damage to Type II cells and interstitial cells. These results indicate that paraquat may affect primarily the Type II cells and the first lesion produced occurs in mitochondria.

Ultrastructural study of mineral fiber uptake by hepatocytes in vitro.

Cellular interactions of a series of fibrous materials were examined by the use of a well established in vitro system. Primary cultures of hepatocytes were exposed to natural attapulgite, synthetic xonotlite and natural sepiolite. Ultrastructural analyses revealed that hepatocytes can engage in the phagocytosis of all 3 types of fibers over an exposure period of 20 h. Attapulgite fibers were found in plasma membrane invaginations, and deeper in the cytoplasm, in vesicles exhibiting various shapes. Xonotlite was also incorporated in plasma membrane invaginations; furthermore, these fibers were present in large vacuoles where they were circumscribed by membranes and appeared somewhat isolated from the cytoplasm. Sepiolite fibers were also taken up by the cells and could likewise be identified in the previously described structures. These observations point to the relevance of the hepatocyte model for investigating the effects of fibrous materials at the cellular level.

Temporal analysis of rat liver injury following potentiation of carbon tetrachloride hepatotoxicity with ketonic or ketogenic compounds.

The administration of some ketonic or ketogenic compounds prior to a challenging dose of CCl4 potentiates the hepatic damage induced by this haloalkane. However, nothing is known about the recovery from the liver injury in these cases of chemically induced potentiation. To investigate this problem, we performed a temporal analysis of the hepatotoxic response of male Sprague-Dawley rats to CCl4 following a single pretreatment (p.o.) with: n-hexane, 2-hexanone, 2,5-hexanedione (15 mmol/kg in corn oil), isopropanol, acetone (33 and 34 mmol/kg in water, respectively); or the vehicle alone (10 ml/kg). They received, 18 h later, an i.p. injection of CCl4 (0.1, 0.75 or 1.0 ml/kg) and were killed 24-120 h later. Liver damage was assessed biochemically (ALT, OCT) and morphologically. A good correlation between biochemical and morphological results was observed. The ketonic or ketogenic compounds studied potentiated the liver injury produced by 0.1 ml/kg CCl4. Relative ranking orders regarding severity of maximal hepatic damage induced and time needed for complete recovery of liver injury were established; time of recovery was dependent on the maximal severity of the lesion, regardless of the potentiation. The results show that the temporal evolution of CCl4-induced liver injury is not markedly influenced by the administration of ketonic or ketogenic compounds as pretreatments, but rather depends on the severity of the maximal damage induced by the overall treatment.