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Biomedical subjects

J Gleason

Publications and source records attributed to J Gleason.

9 recordsLinked to original sources
PubMed1990

Selective nonconjugate binocular adaptation of vertical saccades and pursuits.

Hering's law describes the equal and symmetrical rotation of the two eyes. It is possible to calibrate the binocular yoking of the two eyes in response to disparate size and/or motion of the two ocular images. It is unclear if the ratio of movements by the two eyes is modified by selective adaptation of each versional system (i.e. saccades and pursuits) or if there is an apparent adaptation of Hering's law that results from a single underlying process. The latter could be accomplished by vergence (prism) adaptation, which could interact with all versional systems. In this investigation, binocularly stimulated saccades and pursuits were adapted separately for 2 hr to unequal vertical target displacements. Three adaptation paradigms were used; each included a 10% binocular gradient disparity. The adapting stimulus for the pursuit system was 0.25 Hz vertical triangular motion of 20 deg, peak to peak. Two saccade adaptation paradigms included one which emphasized correcting vertical disparity during the pulse component of the saccade, the other minimized the influence of disparity prior to, during and immediately after saccades (vergence paradigm). Yoking ratios (YRs) for vertical pursuits and saccades were compared before and after adaptation. The pursuit paradigm produced marked adaptation of the pursuit YRs while it had negligible effect on saccade YRs. The pulse saccade paradigm adapted the saccade YRs twice as much as the pursuit YRs whereas the vergence paradigm resulted in little adaptation of YRs for either saccades or pursuits. Pursuits adapted to the first paradigm in 15-30 min whereas saccades adapted to the second paradigm in 1.5-2 hr. These results indicate that there is not a single common nonconjugate adaptation mechanism for vertical pursuits and saccades. Results of the vergence paradigm demonstrate that feedback during or immediately after eye movements is necessary in order to stimulate the binocular versional adaptation mechanism. Versional adaptation may be considered as a calibration of Hering's law.

Adaptation, Ocular↗
PubMed1989

Lower limb ischemia related to use of the intraaortic balloon pump.

In this prospective study we sought to establish the incidence and nature of lower limb ischemia in patients undergoing treatment with intraaortic balloon pump (IABP) counterpulsation and to determine risk factors for its development. The sample was composed of all 258 balloon catheter insertions or attempted insertions for IABP therapy in 249 patients during a 16-month period. Assessment of the lower limbs, hemodynamic status, and pertinent medications were recorded daily throughout the patient's hospitalization. Lower limb ischemia was present in 47%, with 14% having major ischemic complications. Multivariate logistic regression, which was based on variables found to be significant in univariate analysis, revealed that preexisting peripheral vascular disease, female sex, and diabetes mellitus were related to the development of the whole range of lower limb ischemic problems. Diabetes mellitus, cardiogenic shock, and a history of smoking were associated with major ischemia. Evaluation of risks and benefits before treatment with IABP counterpulsation and careful lower limb assessment before, during, and after counterpulsation may help reduce the complications associated with this lifesaving device.

Adolescent↗
PubMed1988

Topically applied vidarabine sodium phosphate in genital herpes infection.

One hundred and thirty-four patients with recurrences of genital herpes were randomized in a double-blind trial to receive self-applied topical therapy with either vidarabine sodium phosphate in an aqueous gel or placebo gel. No significant differences were noted between the two groups in the duration of viral shedding, in the time to healing of the treated recurrence, in the interval between recurrences, or in the number of recurrences.

Administration, Topical↗
PubMed1986

Structural requirements for chemotactic activity of leukotriene B4 (LTB4).

LTB4 (5s, 12R dihdroxy-6, 14-CIS-8, 10-trans-eicosatetraenoic acid) formed in activated neutrophils by lipoxygenation of arachidonic acid is an extremely potent chemotaxin. We examined structural requirements for chemotactic and aggregatory activity of the ligand using synthetic LTB4 and several of its isomers. Additionally we examined the potency of two analogs, nor- and homo-LTB4. Dose response curves for neutrophil chemotaxis to these compounds were obtained using a modified Boyden chamber. The mean distance cells moved into the filter was determined after 30 minutes. Peak chemotactic activity of LTB4 was at 10(-7)M. At higher concentrations, chemotactic activity was decreased. The shape of the dose response curve was similar to that of FMLP except that maximum chemotaxis to LTB4 was consistently greater than chemotaxis to FMLP. A mixture of the two epimers at c-5 and c-12 shifted the response curve to the right but did not lower maximum activity. Increasing or decreasing the chain by one carbon between the first hydroxyl group and the carboxyl group also shifted the response curve to the right without lowering maximal activity. Changing the 6 double bond from cis to trans has a greater effect. Activity was only detectable at high concentrations and maximum activity achieved was less than 50% that of LTB4. Thus the chain length between the carboxyl and C-5 hydroxyl groups, the c-5 and c-12 absolute stereochemistry and the stereochemistry of the delta6 double bond are all important structural features for chemotactic activity with delta6 stereochemistry apparently having the greatest contribution. The relative potencies of these compounds in inducing aggregation were comparable to their chemotactic potencies.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Aggregation↗
PubMed1985

Reproducibility of nucleolar measurements in human intraocular melanoma cells on standard histologic microslides.

The standard deviation of nucleolar area (SDNA), as determined by semiautomated measurement of routinely prepared histologic sections, has been shown to be an effective predictor of mortality for human intraocular melanoma. One hundred cases of this tumor underwent two independent determinations of SDNA by each of two technicians using the same device. One technician performed the two measurements within two months, the other within three weeks. Analysis of these 400 values revealed the following: the more experienced of the two technicians achieved an acceptable level of reproducibility in determining SDNA; the less-experienced technician achieved a lower level of reproducibility; a systematic bias was found upon comparing SDNA values of the two technicians; and this bias can be partially corrected by applying a linear transform. These findings support the value of SDNA as a practical clinical measure of malignant potential for intraocular melanoma but also suggest that experience can enhance the reproducibility of a technician's measurements.

Cell Nucleolus↗