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Biomedical subjects

L L Thompson

Publications and source records attributed to L L Thompson.

34 records · Page 2Linked to original sources
PubMed1990

Time-temperature analysis of cell killing of BHK cells heated at temperatures in the range of 43.5 degrees C to 57.0 degrees C.

Baby hamster kidney (BHK) cells were heated at temperatures in the range of 43.5 degrees C to 57.0 degrees C to determine the time-temperature relationship of cell killing. The cells were grown on 0.025 mm thick pieces of mylar to minimize warm-up times. After heating, the cells were plated for the colony formation assay. The endpoints of 1%, 10%, or 90% isosurvival, or the D0 values of the survival curves were used to construct plots of the logarithm of the reciprocol of the exposure time versus the reciprocol of the absolute temperature. The data for each endpoint resulted in a straight line plot, indicating that the time-temperature relationship for cell killing remained constant from 43.5 degrees C to 57.0 degrees C; namely, a 1.8-fold increase in exposure time was required for a 1 degree C decrease in temperature in order to obtain isosurvival. Heated BHK cells were also examined using electron microscopy. The threshold level of altered morphology was the dissociation of polyribosomal structure and the formation of electron-dense granules within the mitochondria. The time-temperature relationship for the induction of this altered morphology was identical to that for the 90% isosurvival endpoint. Hence, the appearance of altered morphology appears to be related to cell killing.

Animals↗
PubMed1989

The development and evaluation of a clinical test of surgical resident proficiency.

The two purposes of this study were to develop a clinical test of surgical resident proficiency and to compare this clinical test with currently applied methods of resident evaluation. Appendicitis is a common surgical disease, and its accurate diagnosis depends largely on clinical acumen. Ten third-year surgical residents prospectively evaluated 107 patients admitted because of suspected appendicitis. After taking a history, performing a physical examination, and reviewing laboratory data, these residents were asked to state, as a percentage, the likelihood that each patient had appendicitis. Sixty-three patients had appendicitis documented by pathologic inspection after appendectomy. Forty-four patients did not have appendicitis, as was determined by operation (17) or by in-house observation and resolution of abdominal pain (27). These outcomes were used to calculate a diagnostic ability score (DAS) for each resident. Residents were evaluated by standard methods including in-service examinations and monthly evaluations by the attending staff. Residents were also evaluated by nonstandard, but potentially useful, neuropsychologic and psychologic tests, including the trail making test, the Ravens progressive matrices test, the paced auditory serial addition test (PASAT), the grooved pegboard test of manual dexterity, and the profile of mood states (POMS) psychologic questionnaire. Cumulative scores were calculated and compared by multiple regression with coefficient variance analysis. The correlation (R2) of DAS with standard evaluation techniques was as follows: In-service (0.055), faculty (0.508), trails (-0.293), Ravens (0.028), PASAT (0.251), dexterity (0.432), POMS (0.381). We found that (1) the DAS is a discriminating clinical test; (2) the DAS correlates with subjective faculty evaluation; and (3) the DAS does not correlate with in-service examination scores. We conclude that faculty evaluation remains the best currently applied test of surgical resident clinical proficiency as measured by the DAS.

Adult↗
PubMed1989

A comparison of the WAIS and WAIS-R using T-score conversions that correct for age, education, and sex.

A newly developed T score conversion system that corrects Wechsler Adult Intelligence Scale (WAIS) and Wechsler Adult Intelligence Scale-Revised (WAIS-R) subtest and IQ scores for appropriate demographic variables was used to compare subjects' performance on the two versions of the instrument. Using 428 pairs of subjects matched on age, education, and sex, with one person in each pair having taken the WAIS and the other the WAIS-R, we found no significant differences in level or pattern of performance when analyses were performed on the T scores. This was in contrast to highly significant differences when uncorrected scaled scores and IQ values were compared. Therefore, the T score system appears to provide a tool which may help clinicians make more direct comparisons between the results obtained on the WAIS and WAIS-R.

Adult↗
PubMed1989

The use of the Halstead-Reitan test battery with older adults.

As with younger individuals, neuropsychological evaluation of the older patient with suspected cognitive decline should be reasonably comprehensive. Only through careful analysis of the overall pattern as well as level of performance across various measures can both the likelihood and nature of cerebral dysfunction be ascertained. A neuropsychological battery such as an expanded HRB appears to be well suited for the comprehensive evaluation of the older individual who may be mildly to moderately impaired, whereas briefer test batteries may be sufficient and more practical in some cases. The HRB is widely used in clinical and research settings, yet only a few published studies have provided reference data with respect to large groups of adults over the age of 60. Preliminary data suggest that the HRB has adequate reliability and validity in older as well as younger age groups. However, information regarding the level and pattern of performance of normal individuals over the age of 75 is lacking for the HRB as well as for virtually all other popular neuropsychological measures. Studies consistently have shown that many of the component HRB measures are quite sensitive to the effects of age (as well as education), and therefore, traditional normative cutoff scores produce an unacceptably high rate of false positive diagnostic predictions in older populations. Until more appropriate older age norms are available, great caution must be used in the interpretation of results.

Adolescent↗
PubMed1989

Mechanism of killing Chinese hamster ovary cells heated in G1: effects on DNA synthesis and blocking in G2.

To determine where in the cell cycle Chinese hamster ovary cells die following heating in G1, a mild hyperthermia treatment, i.e., 10 or 11.5 min at 45.5 degrees C, resulting in 40-50% cell kill was used. After a 7-14-h delay in G1, the cells heated in G1 eventually entered S phase and replicated all their DNA. Both an autoradiographic analysis with tritiated thymidine and a bromodeoxyuridine-propidium iodide bivariate analysis by flow cytometry revealed that both clonogenic and nonclonogenic cells were delayed in progression through S phase for at least 4 h. Then they completed replication of all their DNA and entered G2. Alkaline sucrose gradient sedimentation analysis revealed that these heated cells could complete replicon elongation into cluster-sized molecules of 120-160 S which persisted for 2-12 h after heating. However, further replicon elongation into multicluster-sized molecules greater than 160 S required an additional 12 h in heated cells compared to the 4 h needed in unheated control cells. Our results when compared with the literature suggest that when G1 cells are heated to a survival level of about 50%, the nonclonogenic cells recover from a long delay in G1, traverse S at a reduced rate, and then die either in G2 or as multinucleated cells after an aberrant division.

Animals↗
PubMed1988

Recovery from effects of heat on DNA synthesis in Chinese hamster ovary cells.

The hyperthermic inhibition of cellular DNA synthesis, i.e., reduction in replicon initiation and delay in DNA chain elongation, was previously postulated to be involved in the induction of chromosomal aberrations believed to be largely responsible for killing S-phase cells. Utilizing asynchronous Chinese hamster ovary cells heated for 15 min at 45.5 degrees C, an increase in single-stranded regions in replicating DNA (as measured by BND-cellulose chromatography) persisted in heated cells for as long as replicon initiation was affected. Alkaline sucrose gradient analyses of cells pulse-labeled immediately after heating with [3H]thymidine and subsequently chased at 37 degrees C revealed that these S-phase cells can eventually complete elongation of the replicons in operation at the time of heating, but required about six times as long relative to control cells which completed replicon elongation within 4 h. DNA chain elongation into multicluster-sized molecules was prevented for up to 18 h in these heated cells, resulting in a buildup of cluster-sized molecules (approximately 120-160 S) mainly because of the long-term heat damage to the replicon initiation process. Utilizing bromodeoxyuridine (BrdU)-propidium iodide bivariate analysis on a flow cytometer to measure cell progression, control cells pulsed with BrdU and chased in unlabeled medium progressed through S and G2M with cell division starting after 2 h of chase time. In contrast, the majority of the heated S-phase cells progressed slowly and remained blocked in S phase for about 18 h before cell division was observed after 24 h postheat. Our findings suggest that possible sites for where the chromosomal aberrations may be occurring in heated S-phase cells are either (1) at the persistent single-stranded DNA regions or (2) at the regions between clusters of replicons, because this long-term heat damage to the DNA replication process might lead to many opportunities for abnormal DNA and/or protein exchanges to occur at these two sites.

Animals↗
PubMed1987

Downward comparison, prejudice, and evaluations of others: effects of self-esteem and threat.

In two studies, we explored the effects of trait self-esteem and threats to the self-concept on evaluations of others. In Study 1, subjects high, moderate, and low in self-esteem received either success, failure, or no feedback on a test and later evaluated three pairs of targets: in-groups and out-groups based on a minimal intergroup manipulation, those who scored above average and those who scored below average on the test, and themselves and the average college student. Study 2 explored the effects of self-esteem and threat on in-group favoritism in a real-world setting, campus sororities. Together, the results of these studies indicate that individuals high in self-esteem, but not those low in self-esteem, respond to threats to the self-concept by derogating out-groups relative to the in-group when the group boundaries have evaluative implications.

Achievement↗
PubMed1986

Hyperthermic radiosensitization of thermotolerant Chinese hamster ovary cells.

Synchronous G1 cells were given a priming dose of heat (45.5 degrees C for 15 min) and then heated and irradiated 6-120 h later. Compared to heat radiosensitization for cells irradiated 10 min after the priming heat dose (thermal enhancement ratio, TER of 2.6 for a 10-fold reduction in survival), heat radiosensitization 18-24 h after the priming heat dose was less (i.e., TER of 1.6 for radiation at 24 h compared with heat-radiation at 24 h). A thermotolerance ratio (TTR) at 24 h was calculated to be 2.6/1.6 = 1.6. TERs at 100-fold or 1000-fold reduction in survival and ratios of slopes of radiation survival curves also showed that the cells developed a similar amount of thermotolerance for heat radiosensitization at 18-24 h. Furthermore, since the TER for heat radiosensitization increased with heat killing either from the priming heat dose or the second heat dose in a similar manner for single or fractionated doses, the TER for nonthermotolerant and thermotolerant cells was the same when related to the heat damage (i.e., amount of killing from heat alone). When the radiation response of cells heated and irradiated 6-120 h after the priming heat dose was compared with the response of cells receiving radiation only, changes in TER as a function of time after the initial priming heat dose were shown to involve: recovery of heat damage interacting with the subsequent radiation dose, thermotolerance for heat radiosensitization, and redistribution of cells surviving the first heat dose into radioresistant phases of the cell cycle. In fact, redistribution resulted in a minimal TER at 72 h for heat-radiation compared with radiation alone, instead of at 24 h where maximal thermotolerance for heat killing was observed [P. K. Holahan and W. C. Dewey, Radiat. Res. 106, 111 (1986)]. These observations are discussed relative to clinical considerations and similar results reported from in vivo experiments.

Animals↗
PubMed1985

Contribution of the TPT to adult neuropsychological assessment: a review.

The Tactual Performance Test (TPT) is reviewed because of its widespread use in neuropsychology. The review indicates that: (1) each of the three TPT scores (Time, Memory, Location), while having considerable overlap in what is measured, contributes something unique; (2) test-retest reliability is adequate, although TPT Memory and Location are generally less reliable than TPT Time; (3) TPT Time has proven to be a sensitive and valid measure of dysfunction in heterogeneous populations of brain-damaged subjects; (4) subject variables of importance to TPT performance are age, IQ, sex, and, to a much less extent, education; (5) there are indications that TPT Time is somewhat more sensitive to right-hemisphere dysfunction, at least in acutely brain-damaged subjects; (6) in more chronic cases, the TPT may be more sensitive to extent of damage than locus of lesion; (7) in obtaining lateralizing information, TPT Time scores for each hand are most helpful; and, (8) additional information may be obtained through examining individual trial scores, pattern across three trials, and observing the subject's strategy in completing the task. Modifications and implications for rehabilitation are discussed.

Adult↗
PubMed1983

Empirical evaluation of diagnostic rules for evaluation of Luria-Nebraska Neuropsychological Battery profiles of chronic schizophrenic, schizoaffective, and brain-damaged patients.

Various decision rules have been advanced for evaluation of brain dysfunction with the Luria-Nebraska Neuropsychological Battery in a chronic schizophrenic or schizoaffective disorder psychotic population. The rules of Golden (1981a) produced the highest hit rate of 96% for identification of schizophrenics who had normal neurological examination findings as not brain damaged. Most of the psychotic profile decision rules, however, produced high false negative hit rates with known brain damaged cases. The critical level decision rules (Golden, Moses, Graber, & Berg, 1981) had the highest hit rate (76.7%) with the known brain-damaged sample. Optimal classification of diagnostic groups appeared to be facilitated by use of decision rules that were especially designed for the psychotic and brain-damaged groups, respectively.

Adult↗
PubMedDate not supplied

Evidence that the feeder effect in mammalian cells is mediated by a diffusible substance.

Chinese hamster ovary (CHO), baby hamster kidney (BHK), and NG108-15 neuroblastoma cells were heated and then plated for the colony-formation assay either with or without feeder cells present. Besides these cell lines, four other cell types were used as feeders. All cell lines functioned equally well as feeders for each of the heated cell lines. In some experiments the heated and feeder cells were separated by semipermeable membranes. This separation had no effect on the feeder effect, indicating that cell-to-cell contact was not requisite. The feeder effect appears to be mediated by a low molecular weight, diffusible substance produced by the feeder cells.

Animals↗