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Biomedical subjects

E Gordon

Publications and source records attributed to E Gordon.

At least 109 records · Page 6Linked to original sources
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↗
PubMed1993

Developmental changes in cytochrome oxidase histochemistry in the main and accessory olfactory bulbs of embryonic and neonatal garter snakes (Thamnophis sirtalis spp.).

Developmental studies examining the changes in oxidative metabolic activity are useful for understanding how and if the vomeronasal and olfactory systems respond to stimulation during embryogenesis. Garter snakes are good candidates for examining the potential functionality of the vomeronasal system in utero. In adult garter snakes, the vomeronasal system mediates many behaviors. Neonatal garter snakes exhibit these same behaviors, and the vomeronasal system has been shown to mediate feeding behavior in neonates. Using cytochrome oxidase histochemistry, we examined changes in the oxidative metabolic activity of main and accessory olfactory bulbs of embryonic and neonatal garter snakes (Thamnophis sirtalis sirtalis and T. s. parietalis). Cytochrome oxidase staining is greater in the accessory olfactory bulb than in the main olfactory bulb of embryonic garter snakes. However, neonates show no differences in the staining of the accessory and main olfactory bulbs, suggesting a change in the stimulation of the main olfactory bulb after birth. This is the first report of cytochrome oxidase histochemistry in reptiles and in the vomeronasal system of embryonic vertebrates.

Aging↗
PubMed1993

Elicitation and habituation of the electrodermal orienting response in a short interstimulus interval paradigm.

The present experiment was carried out to investigate elicitation and habituation of the electrodermal Orienting Response with stimulus trains utilising a short interstimulus interval (ISI) of 1.1 s. We sought evidence for within-train response decrement to repeated stimulus presentation, response recovery to a change stimulus and dishabituation following the change stimulus--the three properties necessary to unequivocally identify a decremental process as habituation. No autonomic study could be found using such a short ISI. Autonomic studies on this time scale are necessary if these measures are to be integrated with central event-related potential (ERP) measures of electrical brain function. Overcoming this paradigm gap required the development of novel measurement procedures to estimate the small electrodermal responses obtained, usually occurring on the recovery slope of the response to the previous stimulus in the train. With our novel measurement procedures, evidence was found indicating that electrodermal activity in such a paradigm exhibited the three classic criteria of habituation.

Acoustic Stimulation↗
PubMed1993

Pharmacokinetics and effects of mannitol on hemodynamics, blood and cerebrospinal fluid electrolytes, and osmolality during intracranial surgery.

Fifteen patients who underwent surgery for intracranial tumors under general anesthesia were given mannitol (1 g/kg of body weight) over 30 min. Measurements of mannitol concentration, osmolality, and electrolytes were determined in blood and cerebrospinal fluid (CSF) samples collected over an 8-h period. Seven sets of hemodynamic observations and four sets of intracranial pressure (ICP) measurements were also made. Mannitol disappeared from plasma in a biexponential manner. The mean maximal plasma concentration was 5.91 mg/ml at the end of mannitol infusion and decreased to 0.58 mg/ml after 8 h. The plasma half-life for the distribution phase was 0.16 h and for the elimination phase was 2.44 h. The distribution volume was 17.0 L and total plasma clearance 87.4 ml/min. There were marked interindividual variations of mannitol concentration in the CSF. The mean CSF concentration at 8 h was 97.1 micrograms/ml, started to decline earlier in 10 of 12 patients, and never exceeded 12% of that in plasma. Osmolality in serum increased with a maximum at the end of mannitol infusion (from 292 +/- 7 mOsmol/kg to 310 +/- 14 mOsmol/kg; p < 0.01), whereas CSF osmolality was unchanged, thus giving rise to a positive blood-CSF osmotic gradient of at least 10 mOsmol/kg for about 30 min. At the end of the mannitol infusion, cardiac output and pulmonary capillary wedge pressure increased significantly, whereas the hematocrit decreased. ICP was observed in five patients for 45 min, and mannitol induced a mean reduction from 11 +/- 4 to 4 +/- 2 mm Hg (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Regional cerebral blood flow during memory recognition and neuropsychological performance in patients referred for investigation of dementia.

Regional cerebral blood flow was studied at rest and during a memory recognition activation task in a preliminary investigation carried out in patients with mild to moderate dementia of Alzheimer type and in 2 control groups of subjects. There were differences in the sites of activation-increased blood flows between the normal controls and the controls with major depression, while the Alzheimer's disease subjects showed more variable patterns of flow response, which differed overall from those present in the 2 control groups.

Alzheimer Disease↗
PubMed1992

Does the N100 evoked potential really habituate? Evidence from a paradigm appropriate to a clinical setting.

This study examined the N100 component of the event related potential in a habituation paradigm with short interstimulus intervals. The paradigm was designed to be relatively brief in duration (approx. 4 min for each of two conditions), so that it could be used for clinical populations with cognitive dysfunction, in which compliance may be a problem with long paradigms. Two conditions - Ignore and Attend - were employed with normal subjects. In each condition, 15 stimulus trains, each consisting of 10 innocuous tones, were presented. The eighth tone was a change stimulus. There was a fixed interstimulus interval of 1.1 s and an inter-train interval of 5 s. From the perspective of traditional Orienting Response theory, evidence was sought for within-train habituation in terms of diminished N100 amplitude to repeated stimuli, response recovery to the change stimulus, and dishabituation of the response to the following standard stimuli. Habituation was suggested by significant decreases of approx. 50% with stimulus repetition, and response recovery to the change stimulus in both conditions. However, there was no evidence of dishabituation following the change stimulus. These results confirm that N100 fails to meet the formal requirements of response habituation, suggesting instead that it may index an earlier process than the Orienting Response.

Acoustic Stimulation↗
PubMed1992

Mosquito and arbovirus ecology in southeastern California, 1986-1990.

Mosquito abundance and western equine encephalomyelitis (WEE) and St. Louis encephalitis (SLE) virus activity were monitored in five valleys in southeastern California from June 1986 through April 1990 to study virus overwintering and possible dissemination from south to north along geographically defined corridors. Culex tarsalis Coquillett predominated in CO2 trap collections and was the only species repeatedly infected with WEE and SLE viruses. Abundance peaked during April-May and August-October. WEE virus infections in Cx. tarsalis generally were detected after the spring peak and were followed approximately 1 mo later by seroconversions in sentinel chickens. SLE virus infections occurred later in the summer but before the fall peak in Cx. tarsalis abundance. Peak Cx. tarsalis abundance occurred when monthly temperatures averaged 25 degrees C, whereas virus infections generally were detected most frequently when temperatures exceeded 29 degrees C. Although the spring increase in Cx. tarsalis abundance occurred earlier in southern valleys, the onset of virus activity was variable among valleys and did not follow a south to north progression.

Animals↗
PubMed1991

Measurement of maximum variability within event related potentials in schizophrenia.

One limitation of averaging individual late component event related potential (ERP) responses is that a single average ERP cannot reflect the variability of responses from epoch to epoch. In this article, we describe a method to quantify this variability and determine if any part of the overall ERP reflects a maximum variance through the use of response variance curves. We then apply this method to one disorder, schizophrenia, in which variability of information processing is hypothesized to underlie aspects of the symptomatology. Response variance curves in a group of unmedicated schizophrenic patients reveal systematic differences, maximal between 190 and 250 ms, compared with those in a group of medicated schizophrenic patients and normal control subjects.

Adult↗
PubMed1991

The effects of age on auditory event-related potentials.

The effects of age on event-related potentials (ERPs) elicited during a two-tone discrimination ("oddball") task were examined in 97 normal subjects aged from 17-80 years. Strong relationships were found between age and the latencies of the later ERP components N200 and P300. Furthermore the correlation between age and N200 latency at Pz was marginally higher than that of age and P300 latency. For the entire sample, the increase in P300 latency as a function of age was best described at Cz and Pz by linear regression equations. However, a segmented line model better described the P300/age relationship at Fz--the increase in P300 latency with age in subjects over 61 was five times that of subjects younger than 61 years. In this study the task required button-press identification of the targets--the significance of increased age and a delay in N200 latency is discussed with reference to the possibility of N200 latency indexing the speed of cognitive processing.

Adolescent↗
PubMed1991

Regional cerebral blood flow and recognition memory in elderly normals: potential application to Alzheimer's disease.

Regional cerebral blood flow, a physiological measure of brain function, has been used for the assessment of cognitive dysfunction in Alzheimer's disease. A number of studies have found diminished temporo-parietal regional cerebral blood flow (RCBF) in Alzheimer's disease patients at rest and have differentiated these patients from normal subjects with a high degree of sensitivity. However the majority of the Alzheimer's disease patients have been in the moderate to severe stages of the disorder. Few studies have assessed RCBF in the early stages of Alzheimer's disease. With increasing emphasis now being placed on the early detection of such patients we chose to examine RCBF during a task which made demands on those cognitive processes which are impaired in the early stages of the disease, viz. a recognition--memory task. Using a 32-channel RCBF system, we examined 20 normal control subjects over the age of 60 years and 10 patients with early to moderate Alzheimer's disease. RCBF was examined during a task of recognition--memory, and also at rest. Normal subjects showed a global increase in RCBF, with marked left frontal activation, as compared with when at rest. Resting perfusion was decreased in the Alzheimer's subject, and there appeared to be a greater degree of intersubject variability in flow during activation.

Aged↗
PubMed1990

Normal latency of the P300 event-related potential in mild-to-moderate Alzheimer's disease and depression.

A two-tone-discrimination task was used to elicit the P300 component of event-related (brain) potentials (ERPs) from patients with presumed Alzheimer's dementia of mild or moderate severity, depressed patients of older age, and cognitively normal individuals. Although the average P300 latency of the Alzheimer patients was greater than that of the depressed patients, which in turn was greater than that of older aged normals, none of the group differences in latency were statistically significant. Moreover, when latency was examined on an individual basis, less than one-quarter of the Alzheimer patients had an abnormally delayed P300 for their age. Reaction times and the percentage of correct behavioral responses to the tones did distinguish the Alzheimer from the normal group; on both measures the patients' scores were significantly worse. It was concluded that the performance of a simple tone discrimination task requiring a button-press response does not sufficiently tax those cognitive functions impaired in the earlier stages of Alzheimer's dementia to result in abnormally slowed cognitive processing of the kind reflected in P300 latency.

Aged↗
PubMed1990

Augmentation of auditory evoked potentials in somatization disorder.

Sensory input regulation was examined in terms of augmenting/reducing of auditory evoked potentials in 10 patients with somatization disorder (8 males and 2 females) and 10 age- and sex-matched normal controls. The slope of P1-N1 amplitude change as a function of stimulus intensity was greater in patients compared with controls, suggesting an enhanced central nervous system response to sensory input. Taken together with previous findings of a failure to habituate to incoming stimuli in a similar group of patients, and evidence obtained in somatizers of both over-responding to background stimuli in a simple tone-discrimination task and enhanced parietal activation during selective attention, this finding suggests disturbances in the processes of attention and in the regulation of afferent stimuli in somatization disorder, and may help explain the multiple and chronic complaints characteristic of patients with the disorder.

Acoustic Stimulation↗
PubMed1990

Smooth pursuit eye tracking dysfunction and negative symptoms in schizophrenia.

This study examined the hypothesis that negative symptoms are associated with abnormalities of smooth pursuit in schizophrenic patients. The pursuit eye movements of 25 subjects with schizophrenia and 25 matched normal control subjects were recorded using an infrared eye tracking system and quantified using the log of signal-to-noise ratio (1n S/N). The severity of negative symptoms within the schizophrenic group was rated using the Scale for the Assessment of Negative Symptoms. Previous findings of pursuit abnormalities among schizophrenic patients as a group were replicated. There was, however, no significant association between the eye tracking dysfunction and the severity of negative symptoms.

Adolescent↗