Genotoxic effects of extremely low frequency (ELF) magnetic fields (MF) evaluated by the Tradescantia-micronucleus assay

Extremely low frequency (ELF) electric fields (EF) and magnetic fields (MF) are generated during the production, transmission, and use of electrical energy. Although epidemiology studies suggest that there is a cancer risk associated with exposure to ELF-MF, short-term genotoxicity assays with bacteria and mammalian cells have produced inconsistent results. In the present study, we investigated the possible genotoxicity of ELF-MF by using the Tradescantia-micronucleus (Trad-MN) assay, a sensitive, reproducible, well-standardized assay for genotoxicity testing. A 50 Hz ELF-MF was generated by a laboratory exposure system consisting of a pair of parallel coils in a Helmholtz configuration. Exposure of Tradescantia (clone # 4430) inflorescences to the ELF-MF, at a flux density (B) corresponding to 1 mT, for 1, 6, and 24 h resulted in a time-dependent increase in MN frequency. The results indicate that a 50 Hz MF of 1 mT field strength is genotoxic in the Trad-MN bioassay and suggest that this assay may be suitable as a biomonitor for detecting the genotoxicity of ELF-MF in the field.     

Circadian variations in the monoamine levels and monoamine oxidase activity in different regions of the rat brain as a function of age

Time-related changes in the levels of norepinephrine (NE), dopamine (DA), 5-hydroxytryptamine (5-HT) and monoamine oxidase (EC 1.4.3.4, MAO) activity have been studied in the cerebral cortex, cerebellum, medulla oblongata, hypothalamus, striatum and midbrain of 21 day, 3, 6, 12 and 24 month old rats maintained at 12 hours of light and 12 hours of dark condition. Maximum NE level was seen during the dark phase in all the regions of 3, 6, 12 and 24 month old rats, whereas in 21 day old, the maximum NE level occurred during the light phase. In the cerebral cortex and in the cerebellum of 21 day old rat DA was absent at all times. In all the other age groups, the maximum DA level was seen during the dark phase, while for 5-HT higher level was during the light phase in all the age groups. MAO activity of 3, 6, 12 and 24 month old rats showed the peak activity at the beginning of the light phase (06:00 hours), whereas cerebral cortex, cerebellum and medulla oblongata of 21 day old rat had its peak MAO activity at 14:00 hours and at 22:00 hours in other regions.     

Effect of thymoxamine on the human pupil

The specificity of thymoxamine, an alpha-adrenoceptor antagonist was determined from in vitro organ bath studies using isolated preparations of canine saphenous and portal mesenteric veins. It was found that thymoxamine interacts mainly with postjunctional alpha-adrenoceptors. The miotic effects of topical thymoxamine hydrochloride were measured in normal human eyes using infrared pupillography. The effects of five different concentrations of thymoxamine were measured over time. Time-response and concentration-response relationships were calculated. The maximal pupillary response occurs at 60 min after instillation of the drug and has a half-life of 10 hr. The minimum effective concentration of thymoxamine is 0.01%, and the maximum effective concentration is 1.3%. Thymoxamine's properties could make it a clinically useful drug to diagnose angle-closure glaucoma, and also to reverse drug-induced mydriasis.     

Administration of L-3,4-dihydroxyphenylalanine to rats after complete hepatectomy-II. Excretion of metabolites

The excretion of metabolites of l-[3-¹⁴C]dihydroxyphenylalanine (l-[3-¹⁴C]DOPA) was studied after its injection into rats with complete hepatectomies and into control rats. Approximately 60 per cent of the dose (11 mg/kg; 20 μCi) of injected [¹⁴C]DOPA was excreted in urine in 24 hr by the control rats, and 11 per cent in bile. Although a similar percentage of the dose (69.4 per cent) was excreted by the hepatectomized rats into urine, excretion was at a slower rate. Decarboxylation of injected [¹⁴C]DOPA within 24 hr appeared to be as great in the hepatectomized rats as in the controls, but metabolism of 3,4-dihydroxyphenylethylamine (dopamine, DA) to norepinephrine was less. In the operated animals most of the DA was metabolized to 3,4-dihydroxyphenylacetic acid or to homovanillic acid. Little radioactivity was present in tissues at 24 hr after injection of l-DOPA into control rats or into hepatectomized rats; however, some radioactivity appeared to be bound to protein in some tissues in both groups of rats.     

Combined techniques for double valve replacement in the infant

A 6-month-old female infant was seen with heart failure secondary to severe aortic and mitral regurgitation. As a neonate the infant had undergone an aortic valvotomy for congenital aortic stenosis. Subsequently the infant had aortic and mitral regurgitation with an infarcted papillary muscle. Double valve replacement was carried out with the St. Jude valve. The first approach was by the Manouguian procedure with extension of the aortotomy out between the left coronary cusp and the noncoronary cusp. The posterior mitral apparatus was resected, and a 19-mm St. Jude aortic valve was sewn into the mitral position. Because the enlarged aortic valve annulus was still inadequate to accommodate a 19-mm St. Jude valve, a Konno procedure was carried out to enlarge the aortic ring anteriorly. Atrial, septal, and aortic repair and right ventricular outflow tract reconstruction were carried out with bovine pericardium. Bypass was carried out with standard techniques of hypothermia, aortic cross-clamping, and cardioplegia. Postoperative anticoagulation therapy was initially with aspirin and dipyridamole (Persantine); however, clotting of the mitral prosthesis necessitated treatment with urokinase and heparin, which completely resolved the clot. Sodium warfarin (Coumadin) therapy was then begun. One year postoperatively, the child is developing normally.     

Chest wall reconstruction

The use of the End-to-End Anastomosis (EEA) circumferential stapler for reconstruction following resection of the esophagus and stomach for carcinoma of the cardia is reported here in 9 consecutive patients with fifteen anastomoses performed with this unit. The technical aspects of the EEA stapler are emphasized. Two frequent problems associated with this type of operation, namely, stenosis or leak at the suture line, are completely avoided by the use of this stapler unit. Its use is recommended.     

Surgical treatment of calcinosis cutis in the upper extremity

Recent surgical experience with 11 cases of calcinosis cutis has given the authors an opportunity to define the role of surgery in the management of this condition. In scleroderma associated with dermatomyositis, when complications or disability arise from one or more areas of calcinosis, surgery may give significant palliation. Wound healing, although a potential problem, does not constitute a contraindication to operative treatment. Damage to deep structures usually is avoidable, but in some instances is a reasonable trade-off for the benefits obtained. Follow-up has confirmed that surgery is beneficial to patient comfort and function, even in the few patients in whom some calcinosis recurred.     

Impaired parathyroid response to induced hypocalcemia in thalassemia major.

Ethylene diamine tetra-acetic acid-induced hypocalcemia was used as provocative test of parathyroid reserve in eight normocalcemic patients with thalassemia major (age 8 to 26 years) and five young adult control subjects (age 22 to 35). In response to an intravenous infusion of disodium EDTA (50 mg/kg), serum immunoreactive parathyroid hormone rose by 1.97 +/- 1.93 (SD) microliterEq/ml in the patients, controls showing a rise of 10.6 +/- 3.6 microliterEq/ml (t = 5.46, P less than 0.001). There was no relationship between parathyroid response and total iron burden as measured by serum ferritin- or desferrioxamine-induced urinary iron excretion. Impairment of parathyroid reserve is common in transfused patients with thalassemia major and may serve as a marker of significant iron overload.