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Biomedical subjects

P Kurtz

Publications and source records attributed to P Kurtz.

8 recordsLinked to original sources

Skepticism about the paranormal: legitimate and illegitimate.

With the growth of belief in the paranormal, skepticism can play a vital role in the scientific appraisal of claims. There are two forms: the first, hardly legitimate, is negative or total skepticism. It is nihilistic and dogmatic, and essentially self-defeating and self-contradictory. The second, a legitimate form, is selective skepticism. Here skepticism operates as a methodological principle of inquiry, testing hypotheses and theories in the light of evidence, but always open to new departures in thought. Skepticism has been applied historically to epistemology, metaphysics, religion, and ethics. The paranormal field has been full of fraud. Here the skeptic insists upon replicable experiments by neutral or skeptical observers before he will accept a claim as confirmed.

Attitude

Effects of reserpine on retention of escape reversal in mice: absence of state-dependent learning.

A discriminated escape training paradigm was used to study the effects of reserpine on learning and memory in mice. Intraperitoneal injection of reserpine before reversal training had no effect on acquisition but did produced a time-and dose-dependent impairment of retention test performance 10 days later. These results suggested that reserpine may have interfered with some aspect of memory storage. Retention impairments observed when a 2.0 mg/kg reserpine injection was given 2 hr before reversal training were not attenuated by readministering the drug before testing, a finding that provides no support for a state-dependency interpretation. Furthermore, animals treated with reserpine exhibited inferior retention of previous training, regardless of the pharmacological state present during that learning. This was interpreted as a drug-induced impairment of memory retrieval. In addition, performance during the initial discriminated escape training session suggested that reserpine may also impair acquisition under some conditions. In the last experiment, it was found that when the catecholamine precursor L-dihydroxyphenylalamine (100 mg/kg) and the indole amine precursor D,L-5-hydroxytryptophan (125 mg/kg) were both given after reserpine treatment, subsequent retention performance was not significantly impaired. The results are discussed in terms of the possible roles of biogenic amines in arousal, learning, and memory.

5-Hydroxytryptophan

Dose-related effects of metrazol on retention and EEG.

The effects of various dose levels of Metrazol on retention and electrocorticogram (ECoG) were investigated. Mice given a subconvulsive 30 mg/kg or a convulsive 50 mg/kg dose of Metrazol 15 min before reversal training in a discriminated escape learning task showed retention impairment of reversal training retention. Lower dose levels (5 or 10 mg/kg) had no effect. The 30 mg/kg dose produced asymmetrical dissociation. The convulsive dose (50 mg/kg), previously reported to result in symmetrical dissociation, produced ECoG changes that were still evident 15 min following the injection, i.e. at the time when training or testing usually took place. With lower doses (10 or 30 mg/kg), no apparent ECoG effects were observed at this interval. The implications of the findings were discussed with respect to the state-dependent hypothesis.

Animals

Anaerobic threshold and maximal aerobic power for three modes of exercise.

Alterations in selected respiratory gas exchange parameters have been proposed as sensitive, noninvasive indices of the onset of metabolic acidosis (anaerobic threshold (AT) during incremental exercise. Our purposes were to investigate the validity and feasibility of AT detection using routine laboratory measures of gas exchange, i.e., nonlinear increases in VE and VCO2 and abrupt increases in FEO2. Additionally, we examined the comparability of the AT and VO2 max among three modes of exercise (arm cranking, leg cycling, and treadmill walk-running) with double determinations obtained from 30 college-age, male volunteer subjects. The AT's for arm cranking, leg cycling, and treadmill walk-running occurred at 46.5 +/- 8.9 (means +/- SD), 63.8 +/- 9.0, and 58.6 +/- 5.8% of VO2 max, respectively. No significant difference was found between the leg exercise modes (cycling and walk-running) for the AT while all pairwise arm versus leg comparisons were significantly different. Using nine additional subjects performing leg cycling tests, a significant correlation of r = 0.95 was found between gas exchange AT measurements (expressed as % VO2 max) and venous blood lactate AT measurements (% VO2 max). We conclude that the gas exchange AT is a valid and valuable indirect method for the detection of the development of lactic acidosis during incremental exercise.

Adult

Assessing interaction patterns of students.

Teaching nursing students how to interact therapeutically with patients is a concern of all nursing faculty members. The verbatim process recording is one available method of analyzing student interactions. An analysis of 86 reported interactions of student nurses with postpartal maternity patients identified patterns of interaction that were related to patient concerns and showed deficits in student communication skills.

Clinical Competence

A controlled field trial of physiological responses to organophosphate residues in farm workers.

Blood acetylcholinesterase (ACHE) and pseudocholinesterase (PCHE) activity and urinary dialkyl phosphate (DAP) excretion were measured in a group of 15 male agriculture field workers during a five-day thinning operation in a Northern California peach orchard. Eight men were randomly assigned to work in a Guthion-treated plot, and seven men to work in an adjoining plot free from organophosphate residues. Foliage samples were taken to measure dislodgeable and total Guthion residues. The daily mean percent change in the ACHE and in the PCHE activity was less than -10.0 percent of baseline values for each group of men. Mean ACHE activity of workers in the Guthion treated plot was different from that of workers in the control plot on the fifth exposure day. The mean PCHE activity of workers in the Guthion treated plot was not different from that of workers in the control plot. Daily group-mean urinary metabolite excretion levels for workers exposed to Guthion residues were highly correlated with their daily group-mean percent change in ACHE activity. No urinary metabolites were detected in workers in the control plot. Decay in Guthion residues was markedly slower in this trial than in a comparable study conducted one year previously, emphasizing the difficulty in setting re-entry intervals based on time elapsed from pesticide application. Suggestions were made to extend the time interval of future studies on the human health effects of organophosphate residue exposure, and to further refine urinary metabolite surveillance methods toward the goal of establishing a threshold level of metabolites which would correspond to meaningful exposure to these pesticides residues.

Acetylcholinesterase