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Biomedical subjects

J Lyons

Publications and source records attributed to J Lyons.

At least 109 records · Page 6Linked to original sources
PubMed1975

Spin label evidence for the role of lysoglycerophosphatides in cellular membranes of hibernating mammals.

The phospholipid composition of ground squirrel heart muscle changes during hibernation: more lysoglycerophosphatides are found in the hibernating state than in the active state. Phase transitions inferred from spin label motion occur in the usual manner typical of mammalian mitochondria for the mitochondria and mitochondrial lipids from active squirrels. However, a conspicuous absence of a spin label-detectable phase transition is observed in equivalent preparations from hibernating animals. The addition of lysolecithin to preparations from active squirrels removes the break and induces a straight line in the Arrhenius plot. The lack of a spin label-detectable phase transition in hibernating animals, therefore, is attributed to an increased content of lysoglycerophosphatides present in the phospholipids during hibernation.

Adaptation, Physiological↗
PubMed1969

Stimulus generalization as a function of discrimination learning with and without errors.

After discrimination learning with and without errors, three groups of pigeons were tested for generalization to the angularity (negative stimulus) dimension. For half the subjects from each group, each angle was superimposed on a light of 555-nanometer wavelength, the positive stimulus during training; for the other half, the angles were on a black background. When tested to the angularity alone, the group which had made errors (pecked at the negative stimulus) during discrimination training showed a typical incremental (inverted) gradient of responding to the negative stimulus dimension. The control group and the one learning the discrimination without errors showed no differential control by the negative stimulus dimension. When each angle was superimposed on the positive stimulus during testing, a decremental gradient with maximum response strength to the negative stimulus was evidenced by the group learning with and the one group learning without errors.

Animals↗
PubMed1968

Further evidence of a sensory-tonic interaction in pigeons.

The five pigeons in Group 1 were given successive intradimensional discrimination training in which responses to a line of 49 degrees were reinforced on a variable-interval schedule and responses to a line of 33 degrees were not reinforced. Subsequent generalization testing with other line orientations revealed a peak shift from the positive stimulus in the direction away from the negative stimulus in all subjects. The four pigeons in Group 2 received successive discrimination training with the 49 degrees value on the key during both stimuli. During the negative stimulus, however, the floor was tilted 16 degrees counterclockwise. When tested (with the floor flat) these subjects showed peak shifts similar to those observed with Group 1. A third group of three pigeons, given successive interdimensional discrimination training with the 49 degrees line as the positive stimulus and the absence of the line as the negative, showed no peak shift in a subsequent generalization test. It was concluded that tilting the floor on which the pigeon stood systematically distorted the bird's visual perception of the orientation of the line in a manner consistent with the results of other studies in this laboratory.

Animals↗
PubMed1967

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Ink Blot Tests↗
PubMed1966

Investigations of a mirror-image transfer effect in pigeons.

In two separate experiments, pigeons trained binocularly to peck a key on which an oblique line (e.g., 60 degrees counter-clockwise rotation from horizontal) was projected yielded bi-modal angularity generalization gradients in extinction, with peaks of responding at both the training stimulus and its mirror image (in this case 120 degrees ). This mirror-image transfer effect may be analogous to an "octave effect" in auditory generalization, but Mello's finding of a mirror-image reversal transfer effect following monocular training in pigeons suggests an alternative interpretation.

Animals↗
PubMedDate not supplied

Significance of P53 in human thyroid tumors.

Mutational changes in the p53 tumor suppressor gene are the most frequent genetic alterations in human malignant tumors. Studies have shown a correlation of p53 expression in breast cancer with tumor prognosis. In contrast to mutational activation of ras and GSP in thyroid tumors, little is known about the role of p53 in thyroid tumor development. Therefore thyroid tumors and thyroid tumor cell lines were studied for the presence of p53 mutations. Snap-frozen tissues from 57 differentiated thyroid carcinomas (DTCs) and 5 goiters were studied by immunohistochemical methods. A panel of six antibodies (pAb 240, 421, 1620, 1801, DO7, and CM1) was employed by using the ABC technique. Five cell lines from DTCs (FTC133, 236, 238, PTC337, MTC164) were examined by the same technique. Additionally, genomic DNA from the cells was amplified by the polymerase chain reaction (PCR) and the PCR product studied for p53 mutations (R273H) by mutation-specific oligonucleotide hybridization (MOH) and temperature gradient gel electrophoresis (TGGE) for the p53 exon 8. None of the benign thyroid tumors and 7 of 57 (12%) DTCs strongly express p53 with a heterogeneous distribution in the tumor tissue. All seven patients have metastatic disease or dedifferentiated tumors G3 (three of seven). CM1 was positive in two cell lines (FTC-133, PTC-337), questionable in FTC-238, and negative in FTC-236 and MTC-164. All three follicular cell lines, however, and the original tumor tissue showed the same p53 mutation (R273H) in MOH analysis and TGGE. P53 mutations are rare in thyroid tumors, but the presence of p53 mutations indicates a poor prognosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMedDate not supplied

Mutational activation of RAS and GSP oncogenes in differentiated thyroid cancer and their biological implications.

Activating mutations of ras-genes (Kirsten-ras, Harvey-ras, N-ras) and genes encoding for the alpha subunit of G-proteins (Gs, Gi2, Gi3, Go, Gz) were assessed in 32 differentiated thyroid cancer (DTC) tissues from German (n = 22) and American (n = 10) patients. Gs-protein (GSP) and/or ras mutations were found in 69% of all tissues with a heterogeneous distribution pattern. An increased prevalence could be demonstrated in metastatic (8 of 9 mutation positive) when compared to localized disease (13 of 23 mutation positive) (p less than 0.001) and in patients greater than 50 years of age (16 of 18 mutation positive), when compared to younger patients (6 of 14 mutation positive) (p less than 0.001). No activating mutations were found on H-ras and K-ras genes nor on genes encoding for the alpha subunits of Gi2, Gi3, Go, and Gz. Differentiated thyroid cancer tissue from German patients revealed a higher prevalence for GSP mutations (73%) than did DTC from American patients (20%) (p less than 0.001). We demonstrated a high frequency of ras and GSP mutations in DTC and suggest that these mutations may contribute to our basic understanding of this disease and might initiate a new search for more rational and individualized therapeutic approaches in patients with DTC.

Base Sequence↗