Variations in the locations of the recurrent laryngeal nerve in relation to the ligament of berry

Injury to the recurrent laryngeal nerve (RLN) is one of the most common iatrogenic complications of thyroid surgery. The anatomical course of the nerve also increases its susceptibility to injury and many variations have been documented in the literature. The topographical relationship of the RLN to the ligament of Berry has been extensively studied over the past decades. The consensus in the literature is divided with several authors reporting the nerve to be embedded within the ligament and others reporting a constant finding of the nerve being posterolateral to the ligament. A new operative concept has been recently introduced as a possible resolution for the conflicting reports among authors. Further investigations are needed, however, to assess its reliability and overall effects on clinical outcomes.     

Xenobiotic transporters: ascribing function from gene knockout and mutation studies.

Transporter-mediated absorption, secretion, and reabsorption of chemicals are increasingly recognized as important determinants in the biological activities of many xenobiotics. In recent years, the rapid progress in generating and characterizing mice with targeted deletion of transporters has greatly increased our knowledge of the functions of transporters in the pharmacokinetics/toxicokinetics of xenobiotics. In this introduction, we focus on functions of transporters learned from experiments on knockout mice as well as humans and rodents with natural mutations of these transporters. We limit our discussion to transporters that either directly transport xenobiotics or are important in biliary excretion or cellular defenses, namely multidrug resistance, multidrug resistance-associated proteins, breast cancer resistance protein, organic anion transporting polypeptides, organic anion transporters, organic cation transporters, nucleoside transporters, peptide transporters, bile acid transporters, cholesterol transporters, and phospholipid transporters, as well as metal transporters. Efflux transporters in intestine, liver, kidney, brain, testes, and placenta can efflux xenobiotics out of cells and serve as barriers against the entrance of xenobiotics into cells, whereas many xenobiotics enter the biological system via uptake transporters. The functional importance of a given transporter in each tissue depends on its substrate specificity, expression level, and the presence/absence of other transporters with overlapping substrate preferences. Nevertheless, a transporter may affect a tissue independent of its local expression by altering systemic metabolism. Further studies on the gene regulation and function of transporters, as well as the interrelationship between transporters and phase I/II xenobiotic-metabolizing enzymes, will provide a complete framework for developing novel strategies to protect us from xenobiotic insults.     

Tissue- and gender-specific mRNA expression of UDP-glucuronosyltransferases (UGTs) in mice.

UDP-glucuronosyltransferases (UGTs) catalyze phase II biotransformation reactions in which lipophilic substrates are conjugated with glucuronic acid to increase water solubility and enhance excretion. Currently, little information regarding tissue- or gender-specific expression of mouse UGTs is available. Mice are increasingly popular models in biomedical research, and therefore, thorough characterization of murine drug metabolism is desired. The purpose of the present study was to determine both tissue- and gender-specific UGT gene expression profiles in mice. RNA from 14 tissues was isolated from male and female C57BL/6 mice and UGT expression was determined by the branched DNA signal amplification assay. UGTs highly expressed in mouse liver include Ugt1a1, Ugt1a5, Ugt1a6, Ugt1a9, Ugt2a3, Ugt2b1, Ugt2b5/37/38, Ugt2b34, Ugt2b35, and Ugt2b36. Several isoforms were expressed in the gastrointestinal (GI) tract, including Ugt1a6, Ugt1a7c, Ugt2a3, Ugt2b34, and Ugt2b35. In kidney, Ugt1a2, Ugt1a7c, Ugt2b5/37/38, Ugt2b35, and Ugt3a1/2 were expressed. UGT expression was also observed in other tissues: lung (Ugt1a6), brain (Ugt2b35), testis and ovary (Ugt1a6 and Ugt2b35), and nasal epithelia (Ugt2a1/2). Male-predominant expression was observed for Ugt2b1 in liver, Ugt2b5/37/38 in kidney, and Ugt1a6 in lung. Female-predominant expression was observed for Ugt1a1 and Ugt1a5 in liver, Ugt1a2 in kidney, Ugt2b35 in brain, and Ugt2a1/2 in nasal epithelia. UDP-glucose pyrophosphorylase was highly expressed in liver, kidney, and GI tract, whereas UDP-glucose dehydrogenase was highly expressed in the GI tract. In conclusion, marked differences in tissue- and gender-specific expression patterns of UGTs exist in mice, potentially influencing drug metabolism and pharmacokinetics.     

Understanding gastrointestinal perfusion in critical care: so near, and yet so far

An association between abnormal gastrointestinal perfusion and critical illness has been suggested for a number of years. Much of the data to support this idea comes from studies using gastric tonometry. Although an attractive technology, the interpretation of tonometry data is complex. Furthermore, current understanding of the physiology of gastrointestinal perfusion in health and disease is incomplete. This review considers critically the striking clinical data and basic physiological investigations that support a key role for gastrointestinal hypoperfusion in initiating and/or perpetuating critical disease.     

Autonomic innervation of the nasal mucosa

The nasal passages play a crucial role in the protection and functioning of the lower airways. Consequently the nerve supply of the nasal mucosa is extensive, which is related to an immediate and adequate reaction upon a variety of external and internal stimuli. A brief review of the present knowledge on nasal autonomic innervation and pharmacology will be given. There is special attention to more advanced methods, such as radioligand receptor binding techniques, which might augment our insight in the significance of the nervous system in nasal (patho)physiology. Furthermore data on the secretory activity of the nasal glands in the rat and its neural regulation will be accentuated.     

Testicular toxicity of di-(2-ethylhexyl)phthalate in young Sprague-Dawley rats

Di-(2-ethylhexyl)phthalate (DEHP), used widely in the manufacture of plastics, is a well-known reproductive toxicant. It causes apoptosis and loss of spermatogenic cells, resulting in testicular atrophy. Reports are scarce in the literature on the progression of apoptosis following repeated doses of phthalates. DEHP's mechanism of inducing testicular atrophy has been associated with depletion of zinc in the testis. ZnT-1 is a zinc transporter that is highly expressed in the testis. Thus, DEHP might exert its toxic effects on the testis by altering the expression of ZnT-1. In this regard, 25-day old Sprague-Dawley rats were given vehicle (5 ml corn-oil/kg, po) for 2, 7 and 14 days, or DEHP (2 g/5 ml corn-oil/kg, po) daily, for 1, 2, 3, 5, 7, 10 and 14 days. Zinc content in testes was determined by atomic absorption spectrophotometry, and ZnT-1 mRNA was quantified by the branched DNA signal amplification method. Body weight gain and testicular weight (absolute and relative) were significantly lower in DEHP-treated rats. DEHP produced morphological changes in the testis, including apoptosis, necrosis, and loss of spermatogenic cells, which resulted in testicular atrophy. Apoptotic index (AI: the percentage of apoptotic cells in seminiferous tubules), determined using the TUNEL technique, was markedly increased after 1 day (AI: 2.9%, control AI: 0.1-0.3%) followed by a peak at 3 days (AI: 11.5%) and a gradual decrease till 10-14 days (AI: 7-9%). Zinc content in testis was not changed 1 day after DEHP administration, but decreased significantly at later time points. No difference was found in ZnT-1 mRNA expression between control and DEHP-treated animals until day 14. Our results suggest that apoptosis, along with necrosis, plays an important role in the mechanism of testicular atrophy by DEHP. In addition, ZnT-1 mRNA expression was not altered by DEHP and therefore, it appears that ZnT-1 cannot account for the decrease in testicular Zn content. Pathological lesions and apoptosis occurred prior to the loss of zinc in testis, suggesting that zinc depletion might be a secondary effect of DEHP-induced testicular toxicity, rather than the cause.     

Protective effect of parvalbumin on excitotoxic motor neuron death

The mechanism responsible for the selective vulnerability of motor neurons in amyotrophic lateral sclerosis (ALS) is poorly understood. Several lines of evidence indicate that susceptibility of motor neurons to Ca(2+) overload induced by excitotoxic stimuli is involved. In this study, we investigated whether the high density of Ca(2+)-permeable AMPA receptors on motor neurons gives rise to higher Ca(2+) transients in motor neurons compared to dorsal horn neurons. Dorsal horn neurons were chosen as controls as these cells do not degenerate in ALS. In cultured spinal motor neurons, the rise of the cytosolic Ca(2+) concentration induced by kainic acid (KA) and mediated by the AMPA receptor was almost twice as high as in spinal neurons from the dorsal horn. Furthermore, we investigated whether increasing the motor neuron's cytosolic Ca(2+)-buffering capacity protects them from excitotoxic death. To obtain motor neurons with increased Ca(2+) buffering capacity, we generated transgenic mice overexpressing parvalbumin (PV). These mice have no apparent phenotype. PV overexpression was present in the central nervous system, kidney, thymus, and spleen. Motor neurons from these transgenic mice expressed PV in culture and were partially protected from KA-induced death as compared to those isolated from nontransgenic littermates. PV overexpression also attenuated KA-induced Ca(2+) transients, but not those induced by depolarization. We conclude that the high density of Ca(2+)-permeable AMPA receptors on the motor neuron's surface results in high Ca(2+) transients upon stimulation and that the low cytosolic Ca(2+)-buffering capacity of motor neurons may contribute to the selective vulnerability of these cells in ALS. Overexpression of a high-affinity Ca(2+) buffer such as PV protects the motor neuron from excitotoxicity and this protective effect depends upon the mode of Ca(2+) entry into the cell.     

Toxicokinetics of acrylamide in humans after ingestion of a defined dose in a test meal to improve risk assessment for acrylamide carcinogenicity.

High amounts of acrylamide in some foods result in an estimated daily mean intake of 50 microg for a western style diet. Animal studies have shown the carcinogenicity of acrylamide upon oral exposure. However, only sparse human toxicokinetic data is available for acrylamide, which is needed for the extrapolation of human cancer risk from animal data. We evaluated the toxicokinetics of acrylamide in six young healthy volunteers after the consumption of a meal containing 0.94 mg of acrylamide. Urine was collected up to 72 hours thereafter. Unchanged acrylamide, its mercapturic acid metabolite N-acetyl-S-(2-carbamoylethyl)cysteine (AAMA), its epoxy derivative glycidamide, and the respective metabolite of glycidamide, N-acetyl-S-(2-hydroxy-2-carbamoylethyl)cysteine (GAMA), were quantified in the urine by liquid chromatography-mass spectrometry. Toxicokinetic variables were obtained by noncompartmental methods. Overall, 60.3 +/- 11.2% of the dose was recovered in the urine. Although no glycidamide was found, unchanged acrylamide, AAMA, and GAMA accounted for urinary excretion of (mean +/- SD) 4.4 +/- 1.5%, 50.0 +/- 9.4%, and 5.9 +/- 1.2% of the dose, respectively. Apparent terminal elimination half-lives for the substances were 2.4 +/- 0.4, 17.4 +/- 3.9, and 25.1 +/- 6.4 hours. The ratio of GAMA/AAMA amounts excreted was 0.12 +/- 0.02. In conclusion, most of the acrylamide ingested with food is absorbed in humans. Conjugation with glutathione exceeds the formation of the reactive metabolite glycidamide. The data suggests an at least 2-fold and 4-fold lower relative internal exposure for glycidamide from dietary acrylamide in humans compared with rats or mice, respectively. This should be considered for quantitative cancer risk assessment.