A power-efficient neural tissue stimulator with energy recovery.

This paper presents a power-efficient neural stimulator integrated circuit, designed to take advantage of our understanding of iridium-oxide electrode impedance. It efficiently creates a programmable set of voltage supplies directly from a secondary power telemetry coil, then switches the target electrode sequentially through the voltage steps. This sequence of voltages mimics the voltage of the electrode under the constant current drive, resulting in approximately constant current without the voltage drop of the more commonly used linear current source. This method sacrifices some precision, but drastically reduces the series losses seen in traditional current sources and attains power savings of 53%-66% compared to these designs. The proof-of-concept circuit consumes 125 µW per electrode and was fabricated in a 1.5-µm CMOS process, in a die area of 4.76 mm(2).

Are some subjects better taught in block rotation? A geriatric experience.

BACKGROUND AND OBJECTIVES: This study characterizes the progress in and effectiveness of learning geriatric medicine during longitudinal and block phases of a family practice residency program. METHODS: A structured second-year geriatric block rotation was added to a residency longitudinal curriculum. To assess learning, a Geriatric Assessment Instrument (GAI) consisting of 50 multiple choice questions was administered to three classes offamily practice residents (n=33)five times during training: entry into the program, beginning of the second year, pre- andpost-geriatric block rotation, and at graduation. Improvement between individual residentfirst- and third-year in-training exam scores in geriatrics of the intervention classes were compared with the four classes that preceded the introduction of the block rotation (n=38). RESULTS: Scores on the GAI improved significantly before and after the rotation but not during any other interval of training during the residency. In-training exam scores improved significantlyfor the classes taught with the block rotation over those without it. CONCLUSIONS: Most of the geriatric learning occurred during the 1-month geriatric block rotation during the residency. In-training geriatric exam scores improved significantly with a geriatric block rotation. The use of structured repetitive learning experiences during the rotation to emphasize the common clinical issues and the skewed exposure to geriatric patients in the random nature of residency clinic and inpatient encounters accountfor this result.

The electrical conductivity of human cerebrospinal fluid at body temperature.

The electrical conductivity of human cerebrospinal fluid (CSF) from seven patients was measured at both room temperature (25 degrees C) and body temperature (37 degrees C). Across the frequency range of 10 Hz-10 kHz, room temperature conductivity was 1.45 S/m, but body temperature conductivity was 1.79 S/m, approximately 23% higher. Modelers of electrical sources in the human brain have underestimated human CSF conductivity by as much as 44% for nearly two decades, and this should be corrected to increase the accuracy of source localization models.

A comparative study of the effects of insulin/glucagon infusions, parenteral amino acids and high dose corticosteroids on survival in a rabbit model of acute fulminant hepatitis.

Acute fulminant hepatitis was induced in 55 healthy adult male rabbits with the potent hepatotoxin galactosamine hydrochloride (3.75 mmoles per kg i.v.). Control rabbits (n = 27) were divided into three groups: Group I (n = 10) underwent sham surgery for placement of an indwelling central venous catheter; Group II (n = 9) received 5% dextrose and water via an indwelling central venous catheter, and Group III (n = 8) received daily intramuscular injections of 0.9% sodium chloride. Treated rabbits (n = 28) also consisted of three groups: Group IV (n = 9) received 12-hr intravenous infusions of insulin (0.029 units per kg per hr) and glucagon (2.86 micrograms per kg per hr) daily; Group V (n = 10) received a continuous infusion of parenteral amino acids (Travasol), and Group VI (n = 9) received daily intramuscular methylprednisolone (0.69 mg per kg). In each case, treatment was initiated 16 hr following galactosamine injection. Serum aminotransferase activity was determined on Days 0, 1, 4 and 10 of the 10-day study. Liver histology was obtained immediately after death and graded under code on a scale of 1 to 4 for severity of hepatitis. Rabbits surviving 10 days were sacrificed on Day 10 for histologic examination. The extent of galactosamine-induced hepatic injury was similar in all six groups as manifest by peak mean SGPT (range: 2,662 to 3,568 IU per liter), SGOT (range: 4,435 to 5,625 IU per liter) levels and hepatic histologic findings. The overall survival rate in controls was 6/27 (22%); in insulin/glucagon-treated animals 2/9 (22%), and in the amino acid-treated group 2/10 (20%).(ABSTRACT TRUNCATED AT 250 WORDS)