Biomedical subjects

J A Galbraith

Publications and source records attributed to J A Galbraith.

3 recordsLinked to original sources

PubMed1991

A linearized DC lamp controller.

The design of a simple and inexpensive battery powered lamp controller for microscope lamps commonly used in patch clamp and other biophysical studies is described. The circuit linearizes the normally exponential voltage-intensity curve of standard 12-V lamps by using an operational amplifier to provide feedback to the drain of a power MOSFET. When the unit is turned off, a charging circuit recharges the battery at a constant potential until the battery voltage reaches a preset level. The charging voltage is then reduced to balance the self-discharge rate of the battery.

Amplifiers, Electronic↗

PubMed1991

Subperineurial demyelination associated with reduced nerve blood flow and oxygen tension after epineurial vascular stripping.

Using laser Doppler measurements of nerve blood flow and electron microscopy, we determined that removal of the vasa nervorum from the surface of rat peripheral nerve results in an immediate 58.4% +/- (SD) 12.6% reduction in nerve blood flow (p less than 0.017) and subsequent subperineurial demyelination. To further assess the role of ischemia in demyelination, a second group of Sprague-Dawley rats (250 to 300 gm) was anesthetized and oxygen tensions were recorded with platinum microelectrodes in the tibial epineurial and endoneurial spaces before and 30 minutes after epineurial devascularization. Normal epineurial oxygen tension was 40.4 +/- (SD) 6.5 mm Hg before devascularization and 26.3 +/- 12.3 mm Hg after (p less than 0.012). Normal endoneurial oxygen tension was 22.9 +/- 6.0 mm Hg before devascularization and 14.3 +/- 5.4 mm Hg after (p less than 0.003). The topography of nerve fiber injury in this experimental model is identical with the changes induced in the sciatic nerve by circumferential compression at 30 mm Hg which is also thought to impede epineurial circulation. This subperineurial pattern of demyelination and axonal degeneration is associated with experimental interference with the epineurial circulation and may be contrasted with the central fascicular degeneration caused by microsphere embolization of the vasa nervorum via the common iliac artery. The data suggest that ischemia is the mechanism for subperineurial fiber injury after epineurial devascularization and highlight the importance of the transperineurial vessels which connect the epineurial anastomotic circulation and endoneurial capillary network.

Animals↗

PubMed1985

Quaternary naltrexone reverses morphine-induced behaviors.

This study explored the relative role of the peripheral and central nervous systems (CNS) in the production of morphine-induced behavioral changes. Toward this end we used a quaternary derivative of an opiate antagonist (naltrexone methobromide, NM) that presumably does not cross the blood-brain barrier. Naltrexone methobromide (20, 40 and 80 mg/kg, IP) was used to challenge the stereotypic locomotion, analgesia and elevated "Straub" tail response observed in C57BL/6J mice after a 30-mg/kg (IP) injection of morphine. The quaternary derivative of naltrexone reversed the locomotor hyperactivity, "Straub" tail and analgesia normally observed in the opiate-treated C57BL/6J mouse. The data reported here, if taken at face value, suggest an important role for peripheral opiate receptors in morphine-induced behavioral changes. However, these conclusions are contingent on further research to more fully evaluate NM's capacity to cross the blood-brain barrier of the C57BL/6J mouse.

Animals↗