Medullary carcinoma of the thyroid in the multiple mucosal neuromas syndrome

The clinical features of the multiple mucosal neuromas (MMN) syndrome permit the recognition of these patients and their potential development of the associated medullary thyroid carcinoma (MTC). The distinctive physical appearance caused by the mucosal neuromas, the Marfanoid habitus and, occasionally, the positive family history aid in establishing the diagnosis. Neurogangliomas are frequently present in the gastrointestinal tract of these patients who may have megacolon, constipation and diarrhea. The third instance of the MMN syndrome is reported in the newborn as intestinal obstruction. It is suggested that the syndrome be considered in the differential diagnosis of Hirschsprung's disease and bowel obstruction in the neonate. Serum calcitonin measurements following stimulation by calcium or pentagastrin infusion reliably detect incipient MTC and may be used to select those MMN patients requiring thyroid surgery. Recognition of patients with the MMN syndrome and subsequent calcitonin screening and early surgical intervention will significantly reduce the chance of their developing terminal MTC. All MMN patients with mucosal neuromas or intestinal neurogangliomas should have such evaluations at least yearly. Relatives who are at risk for inheriting this dominant disease should be similarly evaluated, regardless of their normal appearance.     

EFFECT OF NITROGLYCERNE-INDUCED HYPOTENSION ON CANINE SPINAL CORD BLOOD FLOW

Twenty-four mongrel dogs were anaesthetized with pentobarbitoneand morphine sulphate. Neuromuscular blockade was achieved usingpancuronium. Spinal cord blood flow was measured using the radionuclidemicrosphere and hydrogen washout methods before, during, andfollowing nitroglycerine-induced hypotension. Heart rate, meanarterial pressure, cardiac output, pulmonary capillary wedgepressure, and acid-base balance were determined with each measurement.Mean arterial pressure was reduced by 50%. Spinal cord bloodflow, as measured by the microsphere method, increased duringthe period of hypotension, whereas values obtained using thehydrogen washout method were not significantly different fromthose at normotension. No significant change in spinal cordblood flow was detected by either method after the applicationof spinal distraction. Nitroglycerine acts predominantly onvenous capacitance vessels and it is postulated that perfusionpressure, and therefore flow, is maintained despite a reductionin arterial pressure. Presented in part at the Anual Meeting of the American Societyof Anesthesiologists, October 1985, San Francisco, California. ^*Shackleton Department of Anaesthetics, Southampton GeneralHospital, Shirley, Southampton, Hants SO9 4XY. Section of Orthopedic Surgery, Madison, Wisconsin.     

The Effects of Magnetic Resonance Imaging on Implantable Pulse Generators

The effects of magnetic resonance imaging were assessed on four dual chamber and two single chamber pulse generators. The tests were performed with a resistive, water-cooled magnet operating at 0.15 T. The 6.4-MHz radiofrequency (RF) field was operated at a maximum power of 1,000 watts with a period adjusted from 130 to 500 ms. Reed switch closure occurred in all six pulse generators tested when placed near the entrance of the magnetic resonance imaging scanner, and the generators reverted to asynchronous operation unless programmed to the "magnet off" mode. None of the pulse generators exhibited any alterations in programmed parameters or in the ability to be reprogrammed after RF pulsing. When the RF field was turned on, there was no change in the asynchronous paced cycle length in four pulse generators; however, during RF scanning there was rapid cardiac stimulation at the RF pulse period in one single chamber and one dual chamber pulse generator.     

An ethological analysis of the effects of chlordiazepoxide and bretazenil (Ro 16-6028) in the murine elevated plus-maze

The effects of chlordiazepoxide (2.5-15.0mg/kg), a full benzodiazepine receptor agonist, and bretazenil (5.0-30.0mg/kg), a partial benzodiazepine receptor agonist, were examined in the murine elevated plus-maze paradigm. Behaviours recorded comprised the traditional indices of anxiety as well as a number of ethologically derived measures. Results show that chlordiazepoxide (10-15mg/kg) and bretazenil (5-30mg/kg) not only decreased traditional indices of anxiety but also reduced risk assessment behaviours such as head-dipping and stretch attend postures from secure areas of the maze. Both compounds produced these effects without adversely affecting general activity levels. While traditional indices of anxiety did not clearly discriminate between the two compounds, some differences were apparent on the ethological measures. The dose-response curves for bretazenil were generally shallower than those for chlordiazepoxide, confirming its partial agonist profile. Together, these data support the view that benzodiazepine receptor partial agonists may have utility in the management of human anxiety disorders.     

Perceptions of practice problems encountered by family physicians, pediatricians, and orthopedic surgeons

Information about physicians' practice problems was solicited through a structured questionnaire mailed to a group of family physicians, pediatricians, and orthopedic surgeons. Overall, a lack of personal time was the major concern across the three groups of physicians. Comparisons among the three types of physicians revealed two patterns: Family physicians reported more concerns in the "interpersonal" dimension, whereas orthopedic surgeons had more concerns in the "legal-economic" dimension. These patterns of differences persisted with two variables controlled: gender and time period in which they completed their residency program. These findings indicate that physicians' concerns in their practice vary among the specialties, and they imply that the changed economy and reimbursement system might have more impact on one than the other. Thus the effectiveness of residency training and continuing education might be improved by emphasizing the specialty-related problems in practice.     

Developmental Neurotoxicity: Evaluation of Testing Procedures with Methylazoxymethanol and Methylmercury

Testing procedures for identification of potential developmentalneurotoxicants were evaluated using two prototypical developmentalneurotoxicants, methylazoxymethanol (MAM) and methylmercury(MeHg). Evaluation of offspring of LongEvans rats incorporatedassessments of developmental toxicity, neurochemistry, histology,and behavior, with most testing being completed near weaning.A number of endpoints in the testing strategy were sensitiveto the effects of prenatal exposure to MAM [30 mg/kg on GestationDay (GD) 15]: (1) MAM caused reduced neonatal body weights butdid not effect viability or postnatal survivorship; (2) measurementof total and regional brain weight and histological analysisshowed that a number of regions, the cortex and hippocampusin particular, were affected by MAM exposure; (3) an assay forglial fibrillary acidic protein (GFAP) showed that the concentrationof this protein was significantly increased in the cortex andhippocampus of treated offspring; (4) a T-maze delayed-alternationprocedure indicated that MAM-treated pups were slower in theacquisition phase of the task relative to control pups; (5)motor activity testing revealed hyperactivity in treated offspringthat persisted into adulthood; and (6) acoustic startle proceduresrevealed reduced startle amplitudes in preweanlings. Few endpointswere significantly affected by prenatal MeHg exposure (1, 2,or 4 mg/kg on GD 6–15). High fetal and neonatal mortalityand lower neonatal body weights were detected at the highestdose of MeHg. Although minimal effects of MeHg may reflect arelative insensitivity of the test species and/or the test methods,the combined results from both chemicals suggest that some proceduresnot currently required in the developmental neurotoxicity guidelinemay be useful in hazard identification, and further evaluationwith other chemicals, species, strains, and/or exposure paradigmsmay be warranted.     

Influence of spatial and temporal manipulations on the anxiolytic efficacy of chlordiazepoxide in mice previously exposed to the elevated plus-maze

It has been widely reported that the anxiolytic efficacy of benzodiazepines in the elevated plus-maze test is abolished in subjects (rats or mice) that have been given a single prior undrugged experience of the test apparatus. The present series of experiments was designed to further characterise the key experiential determinants of this intriguing phenomenon in Swiss Webster mice. Using a standard 5 min test duration for both trials, Experiment 1 confirmed the anxiolytic efficacy of chlordiazepoxide (CDP; 5-20 mg/kg) in mice naive to the plus-maze, but a virtual elimination of drug effects in animals that had been pre-exposed to the maze 24 h earlier. Experiments 2 and 3 demonstrated that, while extending the duration of initial exposure to 10 min did not prevent the loss of CDP (10 mg/kg) efficacy in a standard-duration second trial, increasing the duration of both trials reinstated an anxiolytic profile for the compound. Finally, although trial 1 confinement to an open arm did not compromise CDP efficacy when animals were subsequently allowed to freely explore the maze (Experiment 4), closed arm confinement during initial exposure abolished the drug's anxiolytic action upon retest (Experiment 5). In contrast to previous findings in rats, these data suggest that the experientially induced loss of benzodiazepine efficacy in the mouse plus-maze depends rather critically upon prior discovery and exploration of relatively safe areas of the maze (i.e. closed arms). Results are discussed in relation to the hypothesis that the absence of an anxiolytic response to benzodiazepines in plus-maze-experienced subjects reflects the acquisition of an open arm phobia during trial 1.