Biomedical subjects

D C McCarthy

Publications and source records attributed to D C McCarthy.

7 recordsLinked to original sources

PubMed2001

Insulin-like growth factor-1 improves somatosensory function and reduces the extent of cortical infarction and ongoing neuronal loss after hypoxia-ischemia in rats.

Treatment with insulin-like growth factor-1 has been demonstrated to reduce the extent of cortical infarction 5 days after hypoxic-ischemic brain injury. As neuronal death can be progressive and long lasting after initial injury, the present study examined the long-term effects of insulin-like growth factor-1 on late neuronal loss 20 days after hypoxic-ischemic injury, together with evaluating neurobehavioral outcome as assumed by somatosensory function. Unilateral brain injury was induced in adult rats by carotid artery ligation followed by 10 min of hypoxia (6% O2). A single dose of insulin-like growth factor-1 (50 microg) was administered intracerebroventricularly via a stereotaxically pre-fixed cannula 2 h after injury. A bilateral tactile stimulation test was used to examine the degree of somatosensory function at 3, 5, 10 and 20 days after the hypoxia in both insulin-like growth factor-1- (n=12) and its vehicle- (n=12) treated rats, along with sham-operated rats (n=9). Cortical infarction and percentage of selective neuronal loss in the cerebral cortex were examined 20 days after the hypoxic-ischemic injury in both treatment groups. Hypoxic-ischemic injury resulted in a significant delay in the time taken to contact the patch over the period examined (left/right ratio 5.1+/-0.79), particularly at 3 days (7.0+/-2.8) after the hypoxia, compared to sham-operated rats (1.1+/-0.9, P<0.05). The overall effect of insulin-like growth factor-1 in reducing the time taken to contact the patch was significant (P=0.03, 2.6+/-0.79) compared to the vehicle group. There was a trend towards a reduction of cortical infarction after insulin-like growth factor-1 treatment (P=0.058), however insulin-like growth factor-1 significantly reduced the percentage of selective neuronal loss (P=0.027) 20 days following the hypoxia. From these data we suggest that insulin-like growth factor-1 improves somatosensory function by reducing both the extent of cortical infarction and ongoing progressive neuronal death during brain recovery from hypoxic-ischemic injury.

Animals↗

PubMed1998

Upper gastrointestinal endoscopy: are preparatory interventions effective?

BACKGROUND: This study was designed to examine the effects of preparatory cognitive and behavioral information on self-confidence, anxiety, and negative affect elicited by an impending upper gastrointestinal endoscopy. METHODS: Forty-eight male and female out-patients, between 18 and 65 years of age, scheduled for a first-time, non-emergency, endoscopic examination were randomly assigned to receive one of four experimental interventions: cognitive, behavioral, combination, or attention-control. Measures of self-reported anxiety and self-reported self-confidence were obtained. RESULTS: Cognitive and combination intervention subjects were statistically younger than behavioral and attention-control subjects. A credibility assessment revealed that subjects who were taught visualization used it during their procedure. Results indicated that subjects in the cognitive and combination interventions experienced significant reduction in anxiety and increase in self-confidence from pre- to post-intervention. Self-confidence did not increase for subjects receiving the behavioral-only or the attention-control interventions. CONCLUSION: The results of this study show that preparatory information in general is effective in reducing anxiety and in increasing self-confidence before an upper gastrointestinal endoscopy. Results suggest that teaching subjects visualization before a procedure increases their use of visualization during a procedure.

Adaptation, Psychological↗

PubMed1993

Effects of cadmium on potassium currents in activated B lymphocytes.

We have applied the patch clamp technique in the whole-cell configuration to study whole-cell currents in B lymphocytes under three conditions: (i) resting; (ii) interleukin-4 (IL-4)-treated; and (iii) IL-4 plus cadmium-treated murine B lymphocytes. Through these experiments we have: (i) confirmed our earlier findings and the observation of others that resting B cells express only outward currents; (ii) confirmed the presence of an inwardly rectifying K+ current elicited by treatment with the lymphokine IL-4 that was revealed in our previous study on single channel currents; (iii) demonstrated that both inward and outward rectifying K+ currents in IL-4-treated B cells are dramatically reduced by exposure to 20 microM cadmium; and (iv) determined that the activation curve of the IL-4-induced inward rectifier is shifted to more negative voltages by cadmium. We propose that one of the mechanisms by which cadmium can mediate toxicity in activated B lymphocytes is through the suppression and modulation of potassium currents, effects that may alter the timing of entry into the cell cycle.

Animals↗

PubMed1991

Interleukin-4 activates ion channels in B lymphocytes.

The lymphokine interleukin-4 (IL-4) has been shown to induce dramatic changes in the physiology of resting B cells. We have applied the patch clamp technique in the cell attached and inside/out configurations to resting and IL-4-treated B cells to determine whether specific ion conductances result as a consequence of IL-4 action. We report here that two distinct ion channel events occur in B lymphocytes after treatment with IL-4, (i) induction of an inward rectifying K+ channel that is not observed in untreated cells, and (ii) activation of a large conductance anion channel that is normally silent in non-treated cells in the cell attached patch configuration. These data present the first evidence of a direct effect by IL-4 on ion channels and we suggest roles for these two ionic conductances in IL-4-induced B cell activation.

Animals↗

PubMed1991

The interaction between stimulus and reinforcer control on remembering.

In a symbolic matching-to-sample task, 6 pigeons obtained food by pecking a red side key when the brighter of two white lights had been presented on the center key and by pecking a green side key when the dimmer of two white lights had been presented on the center key. Across Part 1 and Parts 6 to 10, the delay between sample-stimulus presentation and the availability of the choice keys was varied between 0 s and 25 s. Across Parts 1 to 5, the delay between the emission of a correct choice and the delivery of a reinforcer was varied between 0 s and 30 s. Although increasing both types of delay decreased stimulus discriminability, lengthening the stimulus-choice delay produced a greater decrement in choice accuracy than did lengthening the choice-reinforcer delay. Additionally, the relative reinforcer rate for correct choice was varied across both types of delay. The sensitivity of behavior to the distribution of reinforcers decreased as discriminability decreased under both procedures. These data are consistent with the view, based on the generalized matching law, that sample stimuli and reinforcers interact in their control over remembering.

Animals↗

PubMed1990

Patch-clamp profile of ion channels in resting murine B lymphocytes.

Patch-clamp studies of single ion channel currents in freshly isolated murine B lymphocytes are characterized here according to their respective unitary conductances, ion selectivities, regulatory factors, distributions and kinetic behavior. The most prevalent ion channel in murine B lymphocytes is a large conductance (348 pS) nonselective anion channel. This report characterizes additional conductances including: two chloride channels (40 and 128 pS), a calcium-activated potassium channel (93 pS), and an outwardly rectifying potassium channel which displays two distinct conductances (18 and 30 pS). Like the anion channel, both chloride channels exhibit little activity in the cell-attached patch configuration. The kinetic behavior of all of these channels is complex, with variable periods of bursting and flickering activity interspersed between prolonged closed/open intervals (dwell times). It is likely that some of these channels play an important role in the signal transduction of B cell activation.

Animals↗

PubMed1989

Characterization of a large conductance non-selective anion channel in B lymphocytes.

Studies on ion channel currents in freshly isolated murine B lymphocytes with the patch clamp technique revealed the presence of a non-selective anion channel of large conductance in inside-out (i/o) patches. This channel is characterized here according to its unitary conductance, ion selectivity, regulatory factors, distribution and kinetic behaviour. With a unitary conductance of 348 +/- 4.4 pS in a normal physiological ion gradient, it exhibited an indiscriminate selectivity to cations (Na+ and K+). Selectivity to chloride over sodium was established by substitution of high concentrations of NaCl (450 mM) in the bath (i/o patches), resulting in a selectivity ratio (PCl/PNa) of 33. Selectivity to chloride over potassium was confirmed in a similar manner by substitution of TEA-Cl for KCl, yielding a selectivity ratio (PCl/Pk) greater than 80. Conductance of aspartate through the channel demonstrated the non-selective nature of this anion channel. Voltage proved to be a regulatory factor but other influences on channel activity were also present, including the configuration of the patch (channel is inactive in cell attached patches), and the enhancement of activity at negative membrane voltages by previous pulsing. Intracellular levels of calcium (i/o patches) did not appear to control channel conductances or regulate kinetic activity. Kinetic behaviour of this channel was complex, with periods of bursting and flickering activity interspersed with prolonged closed/open intervals. Multiple subconductance states were also present. The complex properties and behaviour of this channel suggest a possible role in signal transduction in B cell activation.

Animals↗