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Biomedical subjects

B Weaver

Publications and source records attributed to B Weaver.

At least 37 records · Page 2Linked to original sources
PubMed1997

Object-based facilitation and inhibition from visual orienting in the human split-brain.

Object-based attention was examined in 2 split-brain patients. A precued object could move within a visual field or cross the midline to the opposite field. Normal individuals show an inhibition in detecting signals in the cued object whether it moves within or between fields. Both patients showed this effect when the cued object moved within a visual field. When it crossed the midline into the opposite visual field, however, detection was faster in the cued box. These results reveal both facilitatory and inhibitory effects on attention that are object based and may last for several hundred milliseconds. However, the inhibition requires an intact corpus callosum for interhemispheric transfer, whereas the facilitation is transferred subcortically.

Adult↗
PubMed1996

Prostatic acid phosphatase levels (enzymatic method) from completely sectioned, clinically benign, whole prostates.

Clinically benign, whole untrimmed prostates were obtained from 104 patients at autopsy, completely sectioned, and examined microscopically. The histological and gross findings of the prostate were correlated with premortem prostatic acid phosphatase levels (PAP, enzymatic method, ACA, Dupont Co.) to determine how often carcinoma of the prostate (CAP) affected PAP levels and to identify other findings within the prostate associated with elevated PAP levels. Sixty (58%) prostates did not have CAP, 34 (33%) had CAP smaller than 1 ml in volume, and 10 (10%) had CAP larger than 1 ml in volume. PAP levels were elevated (greater than 1 U/L) in 8 of 60 (13%) prostates without CAP, in 2 of the 34 (6%) prostates with CAP smaller than 1 ml, and in 1 of the 10 (10%) prostates with CAP larger than 1 ml. These differences were not statistically significant. Likewise, a statistically significant correlation between PAP levels and patient age, patient race, severe inflammation, of high grade prostatic intraepithelial neoplasia (PIN) was not found. However, there was a statistically significant correlation between PAP levels and prostate weight (p < 0.0001). This study suggest that PAP cannot distinguish between patients with clinically undetected CAP and patients without CAP. Furthermore, elevated PAP levels are often not due to metastatic CAP and additional evidence should be present, even in patients with known CAP, before an elevated PAP level is considered to be conclusive evidence of metastatic CAP.

Acid Phosphatase↗
PubMed1996

Inhibition of return to successively cued spatial locations: commentary on Pratt and Abrams (1995).

J. Pratt and R.A. Abrams (1995) reported that the inhibition of return of attention is found only for the most recently attended of 2 cued locations. This study does not dispute their findings, but suggests that a more ecologically valid experiment would have more than 2 possible target locations. Twelve male students participated in an experiment in which the target may occur in 1 of 4 possible locations, after 3 of those locations have been cued exogenously in sequence. Inhibition of return was found for each of the cued locations. This result suggests that inhibition may be an important mechanism for aiding visual search in complex environments.

Adult↗
PubMed1994

Characteristics of prostatic infarcts and their effect on serum prostate-specific antigen and prostatic acid phosphatase.

OBJECTIVES: To determine how prostatic infarcts affect serum prostate-specific antigen (PSA) and prostatic acid phosphatase (PAP) levels. METHODS: Two hundred eighteen clinically benign, whole prostates were obtained at autopsy, completely sectioned, and examined histologically. PSA and PAP levels were determined from premortem serum. RESULTS: Six of the 218 (2.8%) prostates had infarcts. The infarcts were usually multiple and usually located in the central and/or middle concentric zones of the middle third of the prostate without a preference for a particular lobe. Serum PSA by immunoradiometric assay were elevated in all 6 cases. Serum PAP by both enzymatic assay (ACA), and immunoradiometric assay were available for 5 cases and were elevated by both methods in 2 cases, approached elevated levels by both methods in 1 case, and were normal by both methods in 2 cases. The PSA and PAP levels appeared to be affected more by the age than by the size of the infarct. CONCLUSIONS: Prostatic infarcts elevate PSA levels more frequently than PAP levels, and prostatic infarcts may be responsible for some unexplained elevations of serum PSA and PAP levels.

Acid Phosphatase↗
PubMed1994

Falls on a neurorehabilitation unit: reassessment of a prevention program.

We conducted a retrospective case-control study of falls over a four year period on a 30 bed neurorehabilitation unit at the Burke Rehabilitation Hospital to characterize the nature of falls and identify factors associated with falling. The most common diagnoses treated on the unit were traumatic spinal cord injury, brain injury, and multiple sclerosis; stroke patients are treated on another service. Falls represented 72 percent of all incident reports made to the Nursing Office during the study period. One hundred seventeen (117) falls occurred in 82 patients during a time when the unit census was 28,622 patient days, yielding a rate of 1,439 falls per 1,000 patient years. One hundred fourteen (114) patients admitted with no history of falling during the same period were selected randomly for comparison. Most falls were associated with no injury (n = 96) or minor injury (n = 18). The most significant injuries occurred in three cases with lacerations requiring sutures. Falls occurred with greatest frequency during the first and fourth quartiles of the hospital stay, during the evening and while bed transfers were being performed. No association between falling and patient age, sex, diagnosis, number of medications, use of sedating medications, presence of motor, visual or cognitive impairment or orthostatic hypotension was evident. An increased risk of falling was associated with physician orders for Posey restraints. The implication of these findings for falls prevention programs is discussed.

Accidental Falls↗
PubMed1994

Object-based and environment-based inhibition of return of visual attention.

Efficient search for an object often requires that attention be prevented from returning to recently examined environmental loci. M. I. Posner and Y. A. Cohen (1984) proposed that inhibition of return (IOR) of visual attention is a search mechanism that prevents such attentional perservation. The internal representations upon which IOR functions were examined and the following conclusions were drawn: First, IOR mechanisms have access to both object- and environment-based representations. Second, environment-based inhibition can be associated with a featureless environmental location, whereas the object-based mechanism requires that attention be oriented to a visible object. These findings are discussed in terms of physiological pathways that may mediate location- and object-based effects.

Attention↗
PubMed1993

The acquisition of lysophosphatidylcholine by African trypanosomes.

Bloodstream forms of the African trypanosome, Trypanosoma brucei, can acquire substantial amounts of exogenous lysophospholipid. Lysophosphatidylcholine uptake is through a pathway consisting of three enzymes, phospholipase A1, acyl-CoA ligase, and lysophosphatidylcholine:acyl-CoA acyltransferase. The pathway enables the organism to acquire fatty acids and phospholipid head groups such as choline. Radiolabeling and 13C NMR studies show that two molecules of lysophosphatidylcholine are used to generate one molecule of cellular phosphatidylcholine. The three enzymes are associated with the trypanosomal plasma membrane and are accessible to exogenous substrates. The first enzyme, phospholipase A1, generates free fatty acid from exogenous lysophospholipid, which the second enzyme, a ligase, uses to form acyl-CoA. The fatty acyl-CoA formed by this route is in a separate pool from that derived from exogenous free fatty acid and is used by the third enzyme, acyltransferase, to acylate a second molecule of exogenous lysophospholipid. Acyltransferase is accessible to exogenous and endogenous acyl-CoA. The high activity of this pathway in bloodstream forms, compared with procyclic culture form trypanosomes, suggests that it may play a role in the acquisition of fatty acids for synthesis of the membrane form of the variant surface glycoprotein. Extracellular myristoyllysophosphatidylcholine can be used by trypanosomes as a source of myristate in remodeling the lipid anchor of the variant surface glycoprotein.

Acyltransferases↗
PubMed1992

Effect of zinc sulfate and acetylcysteine on experimental gastric ulcer: in vitro study.

A small ulcer produced in vitro by monopolar electrocoagulation on endoscopically obtained human antral biopsies and incubated in Trowel T-8 medium at 37 degrees C for 8 h has many histologic features of chronic gastric ulcer in man. Zinc sulfate and acetylcysteine in low concentrations had a significant healing effect in this ulcer model. Since the beneficial effect of zinc sulfate and acetylcysteine was counteracted by N-ethylmaleimide, a known blocker of sulfhydryl compounds, the beneficial effect of these two compounds probably was mediated through sulfhydryl compounds. Using special stain, N-(4-aminophenyl)maleimide, the sulfhydryl groups were localized in the epithelial cells of the surface layer and gastric glands.

Acetylcysteine↗
PubMed1991

Inhibitory mechanisms of attention in identification and localization tasks: time course and disruption.

It has been proposed that 1 component of the mechanism of visual selective attention is active inhibition of distracting information. A series of studies examines the time course of inhibition and the possible interfering effects of other task demands. Results demonstrate that inhibition can last at least 7 s after selection processes and that it is unaffected by predictable, unrelated intervening events. However, intervening events that are less predictable, or are the same as the inhibited stimulus, disrupt inhibition. Such results motivate a reconsideration of the previous view of distractor inhibition as a transient, fragile phenomenon.

Adolescent↗
PubMed1991

Object-centred inhibition of return of visual attention.

Our response to visual events can be delayed at positions we have recently examined attentively. Such inhibition could organize visual search through static scenes by suppressing those loci already searched, but this mechanism would fail in moving scenes as objects' locations then change during search. We cued attention to a moving object and found subsequent inhibition at the locus the object later occupied. This implies that previously examined objects are suppressed. Such object-centred inhibition would be highly adaptive, but would require a sophisticated neural implementation for a mechanism held to be sub-cortical.

Adult↗
PubMed1991

Inhibitory mechanisms of attention: locus, stability, and relationship with distractor interference effects.

This paper examines three properties of attentional inhibition mechanisms. First, previous research has suggested that the inhibitory mechanism of selective attention has a central locus between perception and action. We attempt to confirm the locus of this inhibition. Second, the processing of an unattended stimulus has been observed via the effects of the stimulus on a concurrent target (interference), and on a subsequent target (negative priming). The former effect demonstrates that distractors interfere with the processing of the target, and the latter negative priming effect implies that distractors are inhibited during selection. We demonstrate that these two measures of unattended processing can be dissociated. Third, we reveal that inhibition appears to be a stable mechanism of selection, in that effects do not decline after a large number of experimental trials.

Attention↗
PubMed1983

Inexpensive double-antibody fluoroimmunoassay for aminoglycoside antibiotics, phenytoin, and theophylline in serum.

We describe simple, clinically useful double-antibody fluoroimmunoassays for amikacin, gentamicin, tobramycin, theophylline, and phenytoin. The fluorescent tracers were prepared by conjugation to fluorescein isothiocyanate; the antisera were raised in rabbits. A simple filter fluorometer and disposable culture tubes are used. The tracer, sample, and first and second antibodies are combined and incubated at room temperature for 30 min. A precipitation-acceleration buffer is added, the samples are centrifuged, and the fluorescence of the supernate is measured directly in the assay tube without decantation. Interferences, usually negligible, can be corrected for by use of a sample blank. Results compare favorably in performance with various commercially available RIA and enzyme immunoassays.

Aminoglycosides↗