Search PubMed⌕ Search

Biomedical subjects

M J Ackerman

Publications and source records attributed to M J Ackerman.

17 recordsLinked to original sources
PubMed1994

Hypotonicity activates a native chloride current in Xenopus oocytes.

Xenopus oocytes are frequently utilized for in vivo expression of cellular proteins, especially ion channel proteins. A thorough understanding of the endogenous conductances and their regulation is paramount for proper characterization of expressed channel proteins. Here we detail a novel chloride current (ICl.swell) responsive to hypotonicity in Xenopus oocytes using the two-electrode voltage clamp technique. Reducing the extracellular osmolarity by 50% elicited a calcium-independent chloride current having an anion conductivity sequence identical with swelling-induced chloride currents observed in epithelial cells. The hypotonicity-activated current was blocked by chloride channel blockers, trivalent lanthanides, and nucleotides. G-protein, cAMP-PKA, and arachidonic acid signaling cascades were not involved in ICl.swell activation. ICl.swell is distinct from both stretch-activated nonselective cation channels and the calcium-activated chloride current in oocytes and may play a critical role in volume regulation in Xenopus oocytes.

Animals↗
PubMed1994

Characterization of a native swelling-induced chloride current, ICl.swell, and its regulatory protein, pICln, in Xenopus oocytes.

The ability to precisely regulate cell volume is a fundamental property of most cells. Although the phenomenon of regulatory volume decrease (RVD), whereby a swollen cell loses salt and water to restore its original volume, has been appreciated for decades, the molecular identities of the proteins responsible for the volume control machinery and their regulation are essentially unknown. It appears that the rate-determining step in gaining volume control involves the activation of potassium and chloride conductance pathways. We have identified a native chloride current (ICl.swell) responsive to cell swelling in Xenopus oocytes [Ackerman et al. (1994) J Gen Physiol 103: 153-179]. Moreover, we have demonstrated that a cloned protein, pICln, endogenous to oocytes is critical for the activation of this volume-sensitive chloride conductance pathway [Krapivinsky et al. (1994) Cell 76: 439-448]. The identification of an endogenous protein participating in the regulation of an endogenous current may help understand the physiological activities of swelling-induced chloride channels.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1994

An evaluation of the quality of nursing care rendered to patients with intravenous infusions in the Windhoek Hospital Complex.

Patients on intravenous infusions are commonly seen in the Windhoek Hospital Complex. There was concern regarding the type of nursing care these patients received which led to a survey on the quality of care rendered to these patients. The findings showed that care delivered ranged from very poor to good. Some startling information became evident in that legal aspects were often ignored and that basic things such as calculating and charting the daily intake and output, were omitted. Most of these problems can be rectified through in-service education.

Female↗
PubMed1992

Optical technology: making the simulator portable.

Optical disc technology can be either analog or digital. Analog (videodiscs) simulation programs are available for the allied health professions educator to incorporate into the curriculum. Digital optical discs, currently available in three formats, follow standards that have been adopted by the International Standards Organization. The formats differ in the amount of information they can accommodate and their practical use in the health professions curriculum.

Computer Simulation↗
PubMed1991

Two novel cardiac atrial K+ channels, IK.AA and IK.PC.

Two K(+)-selective channels in neonatal rat atrial cells activated by lipophilic compounds have been characterized in detail. The arachidonic acid-stimulated channel (IK.AA) had a slope conductance of 124 +/- 17 pS at +30 mV in symmetrical 140 mM potassium and a mean open time of approximately 1 ms, and was relatively voltage independent. IK.AA activity was reversibly increased by lowering pH to 6.0. Arachidonic acid was most effective in activating this channel, although a number of lipophilic compounds resulted in activation. Surprisingly, choline, a polar molecule, also activated the channel. A second K+ channel was activated by 10 microM phosphatidylcholine applied to the intracellular surface of inside-out atrial patches. This channel (IK.PC) had a slope conductance of 60 +/- 6 pS at +40 mV and a mean open time of approximately 0.6 ms, and was also relatively voltage independent. Fatty acids are probably monomeric in the membrane under the conditions of our recording; thus detergent effects are unlikely. Since a number of compounds including fatty acids and prostaglandins activated these two channels, an indirect, channel-specific mechanism may account for activation of these two cardiac K+ channels.

Animals↗
PubMed1989

New media in medical education.

In 1984 the American Association of Medical Colleges' Panel on the General Professional Education of the Physician challenged the medical community to take a leadership position in the effective application of information science and computer technology to medical education. The medical education community has risen to that challenge through the use of microcomputer technology and optical disc media including the recently developed fully integrated Hypermedia environment to enhance the learning environment.

Audiovisual Aids↗
PubMed1984

Antagonism by taurine of pressure-induced tremor in the guinea pig.

The tremorogenic effect of high pressure was antagonized in guinea pigs by intravenous treatment with taurine in doses of 250 and 500 mg/kg. Also pretreatment with 250 mg/kg taurine suppressed tremor development as evidenced by increased threshold and decreased amplitude. It is hypothesized that antagonism of pressure-induced tremor by taurine may be related to changes in membrane calcium transport.

Animals↗
PubMed1982

Shared-resource computing for small research labs.

A real time laboratory computer network is described. This network is composed of four real-time laboratory minicomputers located in each of four division laboratories and a larger minicomputer in a centrally located computer room. Off the shelf hardware and software were used with no customization. The network is configured for resource sharing using DECnet communications software and the RSX-11-M multi-user real-time operating system. The cost effectiveness of the shared resource network and multiple real-time processing using priority scheduling is discussed. Examples of utilization within a medical research department are given.

Computers↗
PubMed1975

Calculation of the relative speed of sound in a gas mixture.

Since the frequency spectrum of a voice signal is directly dependent on the velocity of sound, studies of speech spectra include the problem of calculating the speed of sound in the gas mixture being used. A computer program written in BASIC has been developed to calculate the speed of sound relative to air in various diving gas mixtures. In addition, a set of tables available as a separate technical report has been generated using this program. These tables are designed to provide a standard reference for reporting spectral shifts in speech due to different gas mixtures under normal diving conditions.

Computers↗