PubMed Health⌕ Search

Biomedical subjects

J A Stern

Publications and source records attributed to J A Stern.

13 recordsLinked to original sources
PubMed1992

Effect of task difficulty and interstimulus interval on blink parameters.

The effects of task difficulty and interstimulus interval (ISI) on blink rate, blink latency and blink duration, were studied in a modified Sternberg memory task in which either two or six characters were to be memorized. Stimuli were presented in ISI blocks at either 5.3 or 9.3 s (SOAs of 6 or 10 s). While blink rate and blink duration declined prior to each stimulus, the difficulty of the expected task (the length of the memory set) did not affect the rate of decline or the final prestimulus level. Concerning ISI, blink rate declined more rapidly during shorter ISIs but the final prestimulus level, as was the case with task difficulty, was unaffected by the ISI duration. Presentation of the 6-character memory set produced a marked immediate inhibition of blinking. The data suggest that the encoding of visual stimuli is more akin to processes invoked in preparation for input than to ensuing processing stages since both encoding as well as preparation are accompanied by inhibition of blinking.

Adolescent↗
PubMed1991

Distribution and metabolism of doxorubicin in rats undergoing testicular circulatory isolation.

Several hundred thousand men receive chemotherapy each year; many are sterilized by this treatment. Temporary testicular circulatory isolation (TCI), a regional drug delivery approach to circumvent this, decreases doxorubicin-induced testicular injury in the rat and provides partial protection from doxorubicin-related infertility. We evaluated the distribution of doxorubicin and its metabolites (doxorubicinol and doxorubicin aglycone) in rats treated with TCI. In each of 56 male Sprague-Dawley rats, the left spermatic cord and gubernaculum were mechanically clamped for 45 minutes. Immediately after clamp application, these rats received doxorubicin (6 mg/kg, intravenous bolus) and were killed at seven time points after doxorubicin administration, ranging from 30 minutes to 48 hours. Twenty-one control rats were treated identically but did not receive TCI. Doxorubicin and its metabolites were extracted from tissue (left testis, right testis, left kidney, heart, left lung, liver) and serum and analyzed by high-performance liquid chromatography. In the TCI group, the distribution of the parent drug and doxorubicinol in tissue and serum closely approximated levels from doxorubicin-treated controls not receiving TCI in all organs except left testis. No anthracycline was detected at any time point in the left testis of the TCI group. These results indicate that TCI completely protects the testis from doxorubicin exposure in this model and that TCI does not affect distribution of doxorubicin in other organs.

Animals↗
PubMed1991

Limitations of electroencephalographic monitoring in the detection of cerebral ischemia accompanying carotid endarterectomy.

An analysis was undertaken of 458 consecutive carotid endarterectomies performed over 6 years with the patient under general anesthesia and with electroencephalographic monitoring. Seventy patients (15%) had electroencephalographic changes suggestive of ischemia with carotid clamping and had shunts placed. Ischemic encephalographic changes occurred in 26% of patients with an occluded contralateral carotid artery, 21% of patients with a prior stroke history, and 12% of patients with no stroke history and a patent contralateral carotid artery. Nineteen strokes (4.1%), nine transient deficits (2.0%), and one death (0.2%) occurred in the 458 endarterectomies in this experience. Ten of the 19 strokes and five of nine transient deficits were immediately apparent when patients awoke from anesthesia. Five of 10 patients with immediate strokes and all five patients with immediate transient deficits had no ischemic electroencephalographic changes during the procedure. Two other patients with immediate strokes initially had ischemic electroencephalographic changes after carotid clamping that reversed with increased blood pressure or shunting. Therefore 7 of 10 patients with immediate strokes and all 5 patients with immediate transient deficits had electroencephalographs unchanged from baseline at completion of the procedure, and thus deficits not manifest by operative electroencephalographic changes developed. Our data do not support the tenet that electroencephalographic monitoring will always predict neurologic deficits accompanying carotid endarterectomy.

Aged↗
PubMed1976

Attention and distractibility during reading in hyperactive boys.

Nonhyperactive and clinically defined hyperactive boys were administered reading tasks under "quiet" and "distracting" conditions. Hyperactive boys were less attentive to task relevant stimuli and more attentive to task irrelevant stimuli than their controls. Our results demonstrate that the previous findings of inattentiveness among hyperactive boys on laboratory tasks can be generalized to more typical school activities such as reading.

Attention↗
PubMed1976

Electrodermal response configuration as a function of rated psychopathology in children.

Electrodermally labile children of schizophrenic, manic-depressive, and normal parents were identified as either uniphasic or biphasic responders, in each of three phases of a psychophysiological experiment. Psychological disturbance ratings, based upon test protocols, were determined independently. Analysis of the relationship between electrodermal response configuration and rated psychological pathology showed that biphasic responders were evaluated as more disturbed than uniphasic responders. The results were interpreted within a framework provided by Edelberg's work on the information content of the electrodermal recovery limb, and were seen as relevant to notions regarding schizophrenic information processing. It was hypothesized that in this situation, uniphasic responding reflected an adaptive defense against stimuli perceived as potentially threatening, whereas biphasic responding indicated overprocessing and inappropriate goal orientation.

Age Factors↗
PubMedDate not supplied

Blinks as an index of cognitive activity during reading.

Horizontal and vertical EOG recordings of eye movements were analyzed to determine the spatial and temporal distribution of blinks and the patterns of eye movements (saccades and fixation pauses) exhibited by six subjects during the reading of stories presented in two formats (on paper and on a VDT). The frequency and placement of blinks was not affected by the presentation condition. Blinks were determined to be non-randomly distributed during reading. Significantly more blinks (36%) occurred in conjunction with saccades than the proportion of time consumed by saccades (12%) would predict. Significantly more blinks (36%) occurred in the vicinity of line change saccades, which accounts for 15% of reading time, and with fixation pauses associated with regressions (42%), which accounts for 26% of reading time, than with fixation pauses during normal reading (22%), which accounts for 60% of reading time. The results of the study suggest that blink behavior during reading is under perceptual and cognitive control.

Adult↗
PubMedDate not supplied

Long-term outcome following testicular ischemia in the rat.

Male germ cells are quite sensitive to interruption in blood flow. Eight weeks after subjection to 45 minutes of testicular ischemia, the spermatogenic epithelium of the rat remains significantly damaged, though other cell types are well preserved. The authors evaluated the testicular recovery of the rats at 8 and 72 weeks after the 45-minute period of warm ischemia. Twenty-eight rats were studied: 14 underwent 45 minutes of total left testicular ischemia; 14 received no treatment. Four rats from each group were necropsied at 8 weeks to document the ischemic injury. At 72 weeks, the 18 surviving rats were necropsied to evaluate the long-term outcome of the treatment. At 8 weeks, significant left testicular injury was documented. However, at 72 weeks there was no difference in testicular weight or sperm head count between the groups: in all 36 testicles, the repopulation index was 1.00, the epididymal index was 3+, the modified Johnsen index was 14, and the spermatic cord score was 7 (all are maximum obtainable scores). Neither contralateral orchiopathy nor injury to spermatic cord structures was observed. Our work shows that ischemia-induced testicular injury is fully reversible with time in this model.

Animals↗