Strategies to improve electrode positioning and safety in cochlear implants

An injection-molded internal supporting rib has been produced to control the flexibility of silicone rubber encapsulated electrodes designed to electrically stimulate the auditory nerve in human subjects with severe to profound hearing loss. The rib molding dies, and molds for silicone rubber encapsulation of the electrode, were designed and machined using AutoCad and MasterCam software packages in a PC environment. After molding, the prototype plastic ribs were iteratively modified based on observations of the performance of the rib/silicone composite insert in a clear plastic model of the human scala tympani cavity. The rib-based electrodes were reliably inserted farther into these models, required less insertion force and were positioned closer to the target auditory neural elements than currently available cochlear implant electrodes. With further design improvements the injection-molded rib may also function to accurately support metal stimulating contacts and wire leads during assembly to significantly increase the manufacturing efficiency of these devices. This method to reliably control the mechanical properties of miniature implantable devices with multiple electrical leads may be valuable in other areas of biomedical device design.     

Chronic hypersensitivity lung disease with recurrent episodes of hypersensitivity pneumonitis due to a contaminated central humidifer

A child with a 4-year history of acute and chronic respiratory symptoms of unknown aetiology was investigated for hypersensitivity pneumonitis. Lung disease due to inhalation of material from a contaminated central humidifier was suggested by the clinical history, the presence of precipitating antibodies in the serum against the humidifier water, a pulmonary response to challenge with the humidifier water, and marked improvement after removal of the humidifier. No fungi were cultured from the humidifier nor were antibodies against a number of fungal antigens identified by radioimmunoassay inhibition techniques. Antigenic material was found in the humidifier water and the household water prior to its reaching the humidifier. This antigenic material was not found in laboratory tap water supplied from the same general source (Lake Michigan) but from a different pumping station. Three of the child's siblings gave histories suggestive of a single concurrent episode of acute hypersensitivity pneumonitis and one sibling had a history suggestive of chronic hypersensitivity lung disease. No association could be found between HLA-haplotypy and disease in the patient and the siblings.     

Meningiomas of the temporal bone

Meningiomas should be considered in the differential diagnosis of otologic tumors arising from the middle ear and mastoid. It is generally recognized that meningiomas may invade the temporal bone via direct extension from the intracranial space (secondary). It is not generally recognized that meningiomas can develop initially in the middle ear cleft (primary). Representative cases of primary and secondary meningiomas of the temporal bone are described and clinical aspects of diagnosis surgical management are discussed. In order to assess the pathogenesis of meningiomas of the temporal bone, histological studies were done on 200 temporal bone specimens. In certain specimens, ectopic arachnoid granulations, from which primary meningiomas may originate, were identified and described, according to location. One specimen was most unusual in that it contained ectopic glial as well as arachnoidal tissue.     

Malignant tumors of the pleura in the post-pneumothoracic cavities

The single nephron glomerular filtration rate (SNGFR) was determined in superficial (S) and juxtamedullary (JM) nephrons of 10 anesthetized rabbits by the 14C ferrocyanide infusion technique. The length of the proximal tubules and the volume of the glomeruli were also determined for the same nephrons. SNGFR was higher in JM than in S: 28.6 +/- 3.4 versus 22.6 +/- 3.0 nl/min, P less than 0.001. In JM nephrons, glomeruli were larger than in S: 1.3 +/- 0.1 versus 0.9 +/- 0.1 nl, P less than 0.001, whereas there was no difference between proximal tubule length in either category (s, 8.7 +/- 0.3 and JM, 8.9 +/- 0.5 mm). In 6 out of 8 animals, SNGFR was significantly correlated to glomerular volume. Lack of correlation was observed between SNGFR and length of proximal tubule in all animals but one. These results show that the rabbit, as well as small rodents and the dog, has a higher SNGFR in juxtamedullary than superficial glomeruli. Although this functional difference is not related to the length of the proximal tubule in each individual animal, the ratio between the mean SNGFR value and the mean length of the proximal tubule in superficial rabbit nephrons is similar to the ratio found in other species.     

Isolation of Vibrio parahaemolyticus from fecal specimens on mannitol salt agar

Kittens of 25 and 50 days of age were tested on a passive avoidance task in a 2-compartment black-white shuttle box. Latency to enter the dark side of the box was the same for both groups on Day 1, but the latency to enter the dark side on Day 2 was much shorter for the younger kittens. Other kittens were trained in a step-up active avoidance task also at 25 and 50 days of age. No differences were found in active avoidance performance between the younger and older animals, indicating that active and passive avoidance tasks may possibly reflect separate developmental processes that mature at different rates in the cat.     

Effects of doxycycline in actively purging cholera patients: a double-blind clinical trial

In 51 actively purging cholera patients the efficacy of doxycycline, a long-acting tetracycline, was compared with a placebo and tetracycline hydrochloride. Seventeen patients who were given doxycycline at the recommended dose of 2 mg/kg at the beginning of the study, at 12 h, and at the repeated dose once daily purged a mean volume of 5.1 liters of stool and received an average of 5.7 liters of intravenous fluid. Nineteen patients receiving the placebo purged 10.1 liters of stool and received 9.7 liters of fluid. Fifteen patients given tetracycline hydrochloride at 6-h intervals passed 4.8 liters of stool and received 5.5 liters of fluid. The durations of diarrhea calculated in 8-h periods were 3.5, 8.0, and 4.1 h in the respective groups receiving doxycycline, placebo, and tetracycline. The differences between the doxycycline and placebo treatments and the tetracycline and placebo treatments were statistically significant. Those receiving doxycycline became vibrio-free in about 3 days as compared with 2 days for those receiving tetracycline; the group given the placebo were vibrio positive for the duration of their hospitalization. The results show that in the treatment of cholera the administration of doxycycline once daily has effects equal to those when tetracycline is administered at 6-h intervals. This is a distinct advantage because it decreases the demand on nursing personnel in epidemics. Also, doxycycline may be safely administered in cases of suspected renal failure from prolonged shock in cholera.     

Treatment of antral and duodenal bleeding ulcers by Guevara's catheter

The catheter is based on the principle of compression and tamponage, assuring and guaranteeing hemostasis at the base of the ulcer. This method is suitable for permanently controlling an acute hemorrhage in the event medical treatment fails and surgery is contraindicated. Emergency surgery is changed to elective surgery with all its advantages.     

Oxygen intake and walking speed before and after total hip replacement

The objective of the study was to evaluate the walking ability and the energy cost of walking in patients before and after total hip replacement. The oxygen intake and the maximum walking speed were measured immediately before and 6 months after operation in 25 patients. Although the oxygen intake did not change significantly in most patients it was decreased in those patients who before surgery had had the worst walking capacity. The average maximum walking speed almost doubled in the 25 patients.