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Biomedical subjects

R M Kurtz

Publications and source records attributed to R M Kurtz.

36 records · Page 2Linked to original sources
PubMed1992

Prospective time estimation and hypnotizability in a simulator design.

The present study of prospective time estimation examined the effects of hypnosis on short time intervals using a real-simulator design. The major hypothesis predicted a 2-way interaction between group (high hypnotizable, low hypnotizable, and simulator) and condition (waking and hypnotic) across all 4 time intervals (30, 60, 120, and 240 seconds). It was further hypothesized that on a "suggested" task (a measure of hypnotic depth), high hypnotizable Ss and simulators would not differ from each other but would differ from low hypnotizable Ss. 42 undergraduates were screened on both the Creative Imagination Scale (Wilson & Barber, 1977) and the Stanford Hypnotic Clinical Scale for Adults (Morgan & J. R. Hilgard, 1975, 1979) and assigned to 1 of 3 groups (high hypnotizable, low hypnotizable, simulator) based on combined hypnotizability scores. Ss verbally estimated time intervals of 30, 60, 120, and 240 seconds, 3 times each, both while in a waking and a hypnotic condition. Hypnotic depth was assessed once following each time interval. Partial support was found for the first hypothesis where, for both the 60- and 120-second intervals, high hypnotizable Ss increased their overestimation in the hypnotic condition. Low hypnotizable and simulator Ss showed no such increase. The second hypothesis, that high hypnotizable and simulator Ss would differ from low hypnotizables on the "suggested" task, was confirmed. The partial replication of previous research was examined in the context of choice of hypnotizability measure and reliability of time estimation.

Adult↗
PubMed1991

Durability of "posthypnotic suggestions" as a function of type of suggestion and trance depth.

3 types of "posthypnotic suggestion," based upon factor analytic studies, were administered to high hypnotizable Ss (reals) and to low hypnotizable Ss instructed to simulate hypnosis (simulators) (N = 12 high and 6 low hypnotizable Ss per suggestion). The "posthypnotic suggestions" consisted of instructions given to Ss following a hypnotic induction that, when the posthypnotic cue was later given, they would re-enter the hypnotic state and perform a certain task at that time. Ss were then tested 6 times for durability of "posthypnotic response" during an 8-week period. Responses to the "suggestions" were rated by research assistants (objective scores) and by Ss themselves (subjective scores). There was a significant Trials x Type of "Suggestion" interaction for both types of scores for the reals but not for the simulators, indicating different rates of decline with time for the different "suggestions" for the hypnotic Ss. Depth of reported hypnotic trance during the assessment sessions was found to be strongly related to performance of the "posthypnotic suggestion" for both real and simulating Ss.

Adolescent↗
PubMed1990

Hypnotic susceptibility and experimental pain reduction.

We exposed 24 subjects high in hypnotic susceptibility and 24 subjects low in hypnotic susceptibility to a cold-pressor pain stimulus under either hypnotic or waking conditions, using each of two pain-reduction strategies (analgesia and distraction) separately. Trance depth level was held constant for hypnotized subjects. We used pain-tolerance levels as measures of pain, and we analyzed them by survival analysis. High susceptibles reported significantly lower pain ratings and kept their hands immersed longer in the cold water than low-susceptible subjects. There were no significant differences between hypnotic and waking condition subjects or between the different strategies. We have discussed the results in terms of a relationship in the literature between choice of experimental design (between-subjects or within-subjects) and the effectiveness of a hypnotic induction for suggested pain reduction.

Arousal↗
PubMed1989

The effects of hypnotic suggestion on pain report.

Forty-five highly susceptible volunteers rated a series of shocks using 32 pain descriptors. Descriptors were given numerical values using magnitude estimation procedures. We assigned the subjects to one of three conditions, analgesia suggestion, relaxation suggestion, or no suggestion. All subjects were administered the shocks and the suggestion appropriate to the group, in both the waking and hypnotic state. The results support the existence of two dimensions of pain which are differentially responsive to suggestion. Hypnotic-analgesia suggestion altered subjects' perceptions of the intensity without changing their perceptions of the unpleasantness of the shocks. Hypnotic-relaxation suggestion reduced the unpleasantness but not the perceived intensity of the stimuli. These findings imply that research into hypnotic pain relief is more easily interpreted if pain is viewed as multidimensional in nature.

Analgesia↗
PubMed1989

Changes in body attitude as a function of posthypnotic suggestions.

This study hypothesized that highly hypnotizable Ss who remained amnesic for posthypnotic suggestions to improve body attitude would show greater changes than Ss who were not amnesic. Ss given simulating instructions were used as a comparison group to assess experimental demands. 48 females were screened with the Harvard Group Scale of Hypnotic Susceptibility, Form A (Shor & E. Orne, 1962) and assigned to one of 4 conditions: (a) high hypnotizable with amnesia suggestions, (b) high hypnotizable without suggested amnesia, (c) low hypnotizable simulators with amnesia, and (d) low hypnotizable simulators without suggested amnesia. A fifth group was formed of those high hypnotizable Ss who remembered the suggestion despite instructions to the contrary. The Body Attitude Scale (Kurtz, 1966) was administered prior to and 3 days after the experimental suggestions. Results generally demonstrated that high hypnotizable amnesic Ss manifested the greatest attitudinal and phenomenological changes as a result of the posthypnotic suggestion, although conclusions were tempered by performance of simulating Ss. The implications for hypnosis research and clinical practice are discussed.

Adolescent↗
PubMed1989

Eicosanoid production and glucocorticoid regulatory mechanisms in cultured human trabecular meshwork cells.

The techniques we developed to propagate HTM cells in serial cell culture have provided an opportunity to investigate the spectrum of endogenous PGs and other eicosanoids that are produced by these cells. PGE2 and PGF2 alpha were the major cyclooxygenase products detected by both radioimmunoassay and thin-layer chromatography. A small amount of 6-keto PGF1 alpha was also detected, indicating that these cells are able to produce prostacyclin. The observation of a substantial increase in the proportion of PGF2 alpha relative to PGE2 at later time periods after a media change suggests a metabolic conversion of PGE2 to PGF2 alpha by these cells. Bradykinin, thrombin, platelet activating factor, and serum were found to be effective stimulators of PG production by HTM cells, whereas calcium ionophore produced only a minor effect. Using high pressure liquid chromatography, elution profiles of radiolabeled metabolites of AA suggested the presence of certain lipoxygenase products, including LTB4, 12-HETE, 15-HETE, and a small amount of 5-HETE in HTM cells. The formation of these products was inhibited by both DEX and BW 755c, reinforcing the view that metabolic conversions of AA through the lipoxygenase pathway were possible in the trabecular meshwork. We also examined the effects of glucocorticoids on specific protein synthesis in the HTM cells, using 35S-methionine labeling and SDS-PAGE techniques. Short-term (1 day) DEX treatment revealed a major induction of a protein band at approximately 30 kDa. Longer treatments (1 to 3 weeks) resulted in major inductions at approximately 55 kDa inside the cells, with the presence of secreted forms (probably glycoproteins) between 55 and 72 kDa. The short-term DEX effect on protein synthesis a phospholipase inhibitor regulating eicosanoid production within the HTM. The longer-term induction may, on the other hand, be related more directly to the development of steroid glaucoma, based on our findings that the inductions of these proteins correlate with the observed time course and dose-dependence topical glucocorticoid effects on IOP. Continued in vitro and in vivo evaluations of the eicosanoid pathways in cultured HTM cells obtained from normal and glaucomatous human eyes may help to delineate their relationship to IOP regulation and the pathogenesis and treatment of glaucoma. Glucocorticoid-induced proteins may be key participants in the regulation of phospholipase activity and hence may represent a major control mechanism of the AA cascade.(ABSTRACT TRUNCATED AT 400 WORDS)

Cells, Cultured↗
PubMed1984

Hypnosis and its effects on left and right hemisphere activity.

Recent research suggests a relationship between hypnosis and the right cerebral hemisphere in man. With several major modifications in the 1978 study of Frumkin, Ripley, and Cox, the following hypothesis was investigated: Hypnosis creates a shift towards relatively greater left ear accuracy, suggesting greater participation of the right hemisphere during a trance. Two studies were undertaken with 36 right-handed male volunteers in each; 12 of low susceptibility to hypnosis, 12 of medium susceptibility, and 12 of high susceptibility. Study 1 investigated the affect hypnosis had on the processing of musical stimuli while Study 2 investigated its affects on verbal stimuli. Study 1 found that the more susceptible an individual was to hypnosis the greater the shift towards the left ear. Study 2 found no such relationship. Possible differences in stimulus characteristics which might have caused these different results were discussed.

Adolescent↗
PubMedDate not supplied

Finite element analysis applied to cornea reshaping.

A 2-D finite element model of the cornea is developed to simulate corneal reshaping and the resulting deformation induced by refractive surgery. In the numerical simulations, linear and nonlinear elastic models are applied when stiffness inhomogeneities varying with depth are considered. Multiple simulations are created that employ different geometric configurations for the removal of the corneal tissue. Side-by-side comparisons of the different constitutive laws are also performed. To facilitate the comparison, the material property constants are identified from the same experimental data, which are obtained from mechanical tests on corneal strips and membrane inflation experiments. We then validate the resulting models by comparing computed refractive power changes with clinical results. Tissue deformations created by simulated corneal tissue removal using finite elements are consistent with clinically observed postsurgical results. The model developed provides a much more predictable refractive outcome when the stiffness inhomogeneities of the cornea and nonlinearities of the deformations are included in the simulations. Finite element analysis is a useful tool for modeling surgical effects on the cornea and developing a better understanding of the biomechanics of the cornea. The creation of patient-specific simulations would allow surgical outcomes to be predicted based on individualized finite element models.

Computer Simulation↗
PubMedDate not supplied

Photodisruption in the human cornea as a function of laser pulse width.

BACKGROUND: We investigated the role of laser pulse width in determining fluence thresholds and efficiency for corneal photodisruption. METHODS: A laser system that delivers a wide range of pulse energies and pulse widths was used to produce ablations at pulse widths from 100 femtoseconds (fs) to 7 nanoseconds (ns). The laser-induced breakdown fluence threshold at each pulse width was determined by monitoring individual plasma emissions. Using multiple shots, the photodisruption threshold and cutting depth at each pulse width were determined histologically. RESULTS: Corneal breakdown thresholds decreased at a faster rate from 7 ns to approximately 10 picoseconds (ps), compared to further reductions in pulse width below 10 ps, where little variation was seen. Breakdown for pulse widths below 10 ps showed little intershot variability, resulting in highly reproducible fluence thresholds. Corneal tissue examined histologically showed similar fluence dependency. CONCLUSIONS: Corneal tissue photodisruption thresholds demonstrate pulse width dependence. At pulse widths less than 10 ps and with fluences near the breakdown threshold, ablations are maximally precise and efficient. These findings suggest optimal laser parameters for corneal surgery.

Cornea↗
PubMedDate not supplied

Lamellar refractive surgery with scanned intrastromal picosecond and femtosecond laser pulses in animal eyes.

PURPOSE: To evaluate the use of scanned intrastromal picosecond and femtosecond laser pulses in lamellar refractive surgical procedures. METHODS: Intrastromal corneal photodisruption was performed in fresh porcine and primate cadaver eyes with a solid-state femtosecond laser. Laser pulses were focused 150 to 200 microns below the epithelial surface and scanned in a spiral pattern to create a plane. A flap was made by scanning an arc pattern from the plane of the spiral to the surface of the cornea. Tissue plane separation was graded using a standard scale, while internal surfaces were analyzed by scanning electron microscopy. Comparison was made to a picosecond laser system using the same delivery system device. Creation of a stromal lenticule for in situ keratomileusis was also demonstrated and compared with both laser systems. RESULTS: For femtosecond pulses, tissue separation was achieved best with pulse energies from 4 to 8 microJ and spot separations from 10-15 microns. Picosecond pulses accomplished less complete separations with pulse energies of 25 microJ and spot separations from 10 to 20 microns. Surface quality corresponded to dissection results, with high-grade dissections resulting in a smooth surface appearance, versus a more irregular surface for low-grade dissections. Although high-grade dissections could be created with picosecond pulses (with optimal parameters) in ex vivo porcine eyes, only femtosecond parameters produced similar results in ex vivo primate eyes. CONCLUSION: In contrast to previous attempts using picosecond lasers which require additional mechanical dissection, high precision lamellar refractive surgery may be practical with femtosecond laser pulses.

Animals↗
PubMedDate not supplied

An in vivo model of femtosecond laser intrastromal refractive surgery.

BACKGROUND AND OBJECTIVE: To develop an animal model for evaluation of femtosecond laser intrastromal refractive surgery. METHODS: Intrastromal photodisruption was performed in New Zealand Albino rabbits using a femtosecond laser system. This surgical pattern consisted of a 100 microm-tick pyramid of laser pulses starting 180 microm below the corneal surface. Animals underwent serial slit lamp examinations and corneal thickness measurements at 1,3,7,14, and 28 days, then monthly up to 1 year. RESULTS: Approximately 70 microm of central corneal thinning were seen at 1 week, remaining stable up to 7 months. CONCLUSIONS: Intrastromal photodisruption with femtosecond lasers produced consistent changes in corneal thickness without loss of corneal transparency. These changes were more stable than those produced with excimer laser procedures in a similar animal model.

Animals↗