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J R Phillips

Publications and source records attributed to J R Phillips.

At least 73 records · Page 4Linked to original sources
PubMed1988

Spatial pattern representation and transformation in monkey somatosensory cortex.

Embossed letters, used previously in pattern recognition experiments in humans, were used to study the spatial patterns of neural activity evoked in peripheral fibers and cortical neurons in areas 3b and 1 of the primary somatosensory cortex of alert rhesus (Macaca mulatta) monkeys. The object was to investigate the representation and transformation of spatial information during the early stages of peripheral and cortical neural processing. Our method consisted of sweeping each letter of the alphabet across the skin repeatedly and constructing a two-dimensional plot (called a spatial event plot) of the action potentials evoked in afferent fibers and cortical neurons. By using this method, slowly and rapidly adapting primary afferents were shown to transmit isomorphic neural images of the letters. Although the slowly adapting images were more spatially acute, both populations conveyed images of sufficient quality to account for human psychophysical performance. In the cortical areas studied, the slowly adapting neurons of area 3b stood out for the acuity, complexity, and variety of their responses. Some of the spatial event plots for these neurons were isomorphic and at least as acute as those obtained from any primary afferent. Others were highly structured but nonisomorphic. The quality and variety of responses in area 3b slowly adapting neurons suggest that they play an important role in the processing of information underlying tactual pattern recognition. The rapidly adapting neurons of area 3b and all types of neurons in area 1 yield much less structured and differentiated responses.

Animals↗
PubMed1986

Self-limited blastomycosis: a report of 39 cases.

We report 39 patients with pulmonary blastomycosis who were not treated with specific antifungal chemotherapy. Fourteen of these patients were recognized during an epidemic of blastomycosis in 1972 and did not have culturally proven disease. The remaining 25 patients were all proven instances of blastomycosis, 24 of whom had pulmonary disease only. Over a median observation period of 42 months (range: 12 to 168) one patient relapsed 52 months after the original diagnosis, while all of the others have remained clinically well. It is our belief that certain patients with blastomycosis limited to the lungs may safely be followed without specific antifungal chemotherapy until clearing occurs. These include patients with mild or no symptoms and those who have been more symptomatic but are already improving when the diagnosis is established. Worsening of the clinical picture, or evidence of extrapulmonary disease requires immediate antifungal chemotherapy.

Adolescent↗
PubMed1985

Neural mechanisms of scanned and stationary touch.

The neural mechanisms subserving the sense of touch set the limits for the acquisition of information regarding the spatial and temporal characteristics of stimuli impinging on the skin surface. The results of three different psychophysical experiments imply that the skin of the finger pad can resolve the elements of a stimulus separated by 0.9 mm when the stimulus is applied to the skin and held stationary. This resolution limit is only slightly improved (to about 0.7 mm) when movement between the stimulus and skin is allowed. Single-unit recordings from three classes of primary mechanoreceptive afferents in anesthetized monkeys shows that only one class, the slowly adapting afferents, resolve spatial detail of stationary stimuli near the resolution limit. In addition, slow adaptors appear to resolve moving stimuli (e.g., Braille-dot patterns) more effectively than do the other two classes. However, these observations do not explain the extraordinary capacity of the finger-pad skin for discriminating between fine textures. Neurophysiological evidence suggests that information about such textures (i.e., surfaces with spatial details below the resolution limit) may be conveyed by a code based on the relative engagement of the three receptor populations.

Adaptation, Physiological↗
PubMed1984

Faculty burnout.

Explore the source record for details and available documents.

Burnout, Professional↗
PubMed1984

Differential activity of vincristine and vinblastine against cultured cells.

Vincristine and vinblastine exhibit differential activity against tumors and normal tissues. In this work, a number of cultured cell lines were assayed for their sensitivity to the antiproliferative and cytotoxic effects of the two drugs following short-term (4 hr) or during continuous exposures. Differential activity was not seen when cells were subjected to continuous exposures. The concentrations of vincristine and vinblastine, respectively, that inhibited growth rates by 50% were: mouse leukemia L1210 cells, 4.4 and 4.0 nM; mouse lymphoma S49 cells, 5 and 3.5 nM; mouse neuroblastoma cells, 33 and 15 nM; HeLa cells, 1.4 and 2.6 nM; and human leukemia HL-60 cells, 4.1 and 5.3 nM. In contrast, differential toxicity was seen when cells were subjected to 4-hr exposures and transferred to drug-free medium: the 50% growth-inhibitory concentrations for vincristine and vinblastine, respectively, for inhibition (a) of proliferation of L1210 cells were 100 and 380 nM and of HL-60 cells were 23 and 900 nM and (b) of colony formation of L1210 cells were 6 and greater than 600 nM and of HeLa cells were 33 and 62 nM. Uptake and release of [3H]-vincristine and [3H]vinblastine were examined in L1210 cells under the conditions of growth experiments. Uptake of both drugs was dependent on the pH of culture media, and significantly greater amounts of [3H]vinblastine than of [3H]vincristine were associated with cells after 4-hr exposures to equal concentrations of either drug. When cells were transferred to drug-free medium after 4-hr exposures, vinblastine was released much more rapidly from cells than was vincristine, and by 0.5 hr after resuspension of cells, the amount of vincristine associated with the cells was greater than the amount of vinblastine and remained so for up to at least 6 hr.

Animals↗
PubMed1983

The spatial characteristics of tactile form perception.

The perceived orientation of a raised letterform indenting the skin of the finger reverses (from normal to its mirror-image) when the letter is held in contact with the finger and both are rotated through 180 degrees about the axis of the finger. Thus, though the pattern of stimulated skin receptors remains constant, the perceived orientation of the letter reverses. On the basis of this observation it is proposed that tactual perception of object form involves assignment of a spatial coordinate system within which the patterns of skin stimulation are interpreted. In experiments in which the orientations of letters and subjects are systematically varied within the environment, the occurrence or nonoccurrence of reversal in perceived orientation of letters has been used to investigate the origin of the proposed spatial coordinate system; that is, whether it is assigned with respect to the observer ( egocentrically ) or with respect to the environment ( geocentrically ). The results indicate that the assignment of coordinates is determined by both egocentric and geocentric factors. It is proposed that the reversal phenomena observed in these experiments, and in experiments of others which involve drawing characters on the skin, are consistent with Gibson's proposal that it is object form which is directly perceived, but that this involves interpretation of the patterns of skin stimulation within a framework of spatial coordinates.

Discrimination Learning↗
PubMed1983

Resistance to 9-beta-D-arabinofuranosyladenine in cultured leukemia L 1210 cells.

A cultured line of L1210 leukemia cells, designated L1210/ara-A, was selected for resistance to 9-beta-D-arabinofuranosyladenine (ara-A) by a series of 72-hr exposures to increasing concentrations of ara-A in the presence of 1 microM deoxycoformycin. Cells of the resistant line were about one-tenth as sensitive as were cells of the parent line to the effects of ara-A on proliferation, viability, and tumorigenicity. Cross-resistance, as determined by comparison of drug effects on rates of proliferation of L1210/C2 and L1210/ara-A cells, was seen with adenosine, deoxyadenosine, methylmercaptopurine ribonucleoside, tubercidin, and cordycepin but not with 1-beta-D-arabinofuranosylcytosine or with 9-beta-D-arabinofuranosyl-2-fluoroadenine. The levels of resistance to methylmercaptopurine ribonucleoside, cordycepin, and tubercidin were considerably greater than that seen with ara-A itself. L1210/C2 and L1210/ara-A cells were compared with respect to the effects of ara-A on cell size distributions, DNA distributions, labeling indices, and apparent rates of DNA synthesis, and the differences seen were consistent with inhibition of DNA synthesis and unbalanced growth as the major mechanism of ara-A cytotoxicity. The decreased sensitivity of DNA synthesis in L1210/ara-A cells treated with ara-A, relative to L1210/C2 cells, was due to reduced intracellular accumulation of ara-A phosphates in the resistant line. Phosphorylation of ara-A, adenosine, and tubercidin, but not deoxyadenosine or deoxycytidine, was greatly reduced in intact L1210/ara-A cells, relative to L1210/C2 cells, and adenosine kinase activity in extracts of L1210/ara-A cells was negligible. Resistance to ara-A, and cross-resistance to tubercidin, methylmercaptopurine ribonucleoside, and cordycepin is attributed to loss of adenosine kinase activity.

Adenosine Kinase↗