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Biomedical subjects

J Tucker

Publications and source records attributed to J Tucker.

At least 91 records · Page 5Linked to original sources
PubMed1989

Minimal neuropsychological sequelae following prophylactic treatment of the central nervous system in adult leukaemia and lymphoma.

The potential long-term toxicity of central nervous system prophylaxis (CNS-P) in adult acute lymphoblastic leukaemia (ALL, n = 17) and non-Hodgkin's lymphoma (NHL, n = 7) was investigated in a multidisciplinary study. At least 4 years had elapsed from CNS-P (mean 11.5 years) for all patients. Neurological history and physical examination were unremarkable; minor signs were commoner in older patients (P less than 0.02). Psychometry yielded normal results, but individual verbal IQ generally exceeded performance IQ, with a trend to more marked differences in younger adults (P = 0.06). EEG was scored and differed significantly from that of controls, with a tendency to more marked (but still minor) abnormalities in younger patients (P = 0.06). Brainstem auditory evoked potentials demonstrated significant but generally minor abnormality in 24% of patients. CT brain scan revealed widening of cerebral hemisphere sulci to greater than 3 mm in 38% of patients; cerebral atrophy was commoner in the older group (P less than 0.02) and those with neurological signs (P less than 0.02). MRI brain scans were normal in all patients tested. Thus, following standard CNS-P for ALL at this hospital, there is a 5% primary CNS relapse rate, and only minimal, mainly subclinical, long-term neuropsychological toxicity.

Adult↗
PubMed1989

Human ret proto-oncogene mapped to chromosome 10q11.2.

Using cosmid clones derived from human ret protooncogene as probes, we determined its chromosome localization by fluorescence in situ hybridization. Two overlapping clones, cret-1 and -2, which were cloned using the most 5' part of human ret proto-oncogene cDNA, hybridized to chromosome 10q11.2. Sixty-three and 52% of the grains obtained by cret-1 and -2, respectively, were localized to the same site. No other specific hybridization site was observed. From these data, we assigned the site of ret proto-oncogene to chromosome 10q11.2, where the possible locus responsible for multiple endocrine neoplasia type 2A (MEN2A) was mapped by linkage analysis using interstitial retinol binding protein cDNA and D10S5. These findings suggest that ret proto-oncogene might be a suitable probe for approaching the MEN2A locus.

Chromosome Mapping↗
PubMed1988

Alloreactive immune responses of transgenic mice expressing a foreign transplantation antigen in a soluble form.

Transfection of cells with the H-2Kk gene lacking the transmembrane and cytoplasmic segments resulted in secretion of the H-2Kk protein, as determined by immunoprecipitation with monoclonal anti-H-2Kk antibodies. Transgenic (H-2b X H-2d)F1 mice were established carrying integrated copies of the modified H-2Kk gene. Expression of the soluble H-2Kk antigen in the transgenic mice was demonstrated in cell supernatants of biosynthetically labeled splenic and thymic Con A blasts as well as bone marrow-derived macrophages. Soluble H-2Kk molecules were also present in the sera of the transgenic animals. No cell-surface expression of the H-2Kk antigen could be observed. In spite of the presence of the soluble H-2Kk molecules in the transgenic mice, the animals were able to generate H-2Kk-specific cytolytic T cells as well as antibody responses when stimulated with cell-surface-bound H-2Kk antigens. These responses were indistinguishable from those of the nontransgenic littermates. Possible explanations for the observed lack of tolerance are discussed.

Animals↗
PubMed1988

Minimum audible movement angle as a function of signal frequency and the velocity of the source.

Thresholds for the detection of the direction of travel of a moving sound source were determined in a single-interval, forced-choice paradigm. Both the rate at which the sound source is displaced (8 degrees-128 degrees/s) and the frequency of the signal to be localized (500-3700 Hz) affect dynamic spatial resolution. There is an inverse relationship between spatial resolution and the rate of travel, a finding that replicates an earlier observation on performance with sources displaced at high velocities [Perrott and Musicant, J. Acoust. Soc. Am. 62, 1463-1466 (1977)]. However, the magnitude of this effect depends on the actual velocities employed. Relatively small changes in spatial resolution are apparent for velocities below approximately 32 degrees/s. The significant frequency effect can be summarized as follows: Dynamic spatial resolution is better for signals below 1000 Hz than for signals above this value (within the range tested). Particularly poor resolution is evident for signals between 1300-2000 Hz. The present results indicate that signal frequency affects dynamic spatial resolution in a fashion similar to that which has been observed in the more common "static" localization test situation. There is no indication of an interaction between these two variables. These results provide additional support for the hypothesis that both static and dynamic spatial discrimination functions are dependent upon the same underlying mechanisms. The effects of velocity upon the spatial resolution problem, a unique aspect of the dynamic paradigm, can probably be explained without the necessity of additional hypothetical mechanisms in the auditory system (e.g., a specialized motion detector).

Adult↗
PubMed1988

Short-term therapy for acute myelogenous leukemia.

Since 1978, 187 patients (age range, 15 to 59, median 44 years) have received short-term chemotherapy as part of three sequential open studies (B-IX, X, Xb) or a randomized clinical trial (B-XI). An intended six cycles of Adriamycin (ADR) (doxorubicin; Adria Laboratories, Columbus, OH), cytarabine (ara-C), and thioguanine (TG) were administered with as short an intercycle time as possible. No further therapy was administered. Complete remission (CR) was achieved in 118 of 187 patients (63%). On univariate and multivariate analyses achievement of CR correlated adversely with a low serum albumin at presentation and an antecedent marrow disorder. Forty-five patients continue in first remission between 15 months and 8 1/2 years, no relapses being seen after 3 1/2 years (median follow-up, 3 1/2 years). The median duration of remission was 1 year. M3 morphology, a blast count less than 100 x 10(9)/L, and absence of hepatosplenomegaly correlated favorably with remission duration. There was no difference in duration of remission between patients receiving 3, 4, 5, or 6 cycles. The best results overall were achieved in patients under the age of 40, with 43% projected to remain free of disease at 5 years. Fifty patients remain alive between 17 months and 9 years, the predicted actuarial survival being 25% at 5 years.

Actuarial Analysis↗
PubMed1987

The morbidity and mortality of vermiculite miners and millers exposed to tremolite-actinolite: Part I. Exposure estimates.

The vermiculite ore and concentrate of a mine and mill near Libby, Montana, was found to be contaminated with fibrous tremolite-actinolite. Of 599 fibers (length greater than 5 microns and width greater than 0.45 micron) counted in eight airborne membrane filter samples, 96% had an aspect ratio greater than 10 and 16% had an aspect ratio greater than 50. Additionally, 73% of the fibers were longer than 10 microns, 36% were longer than 20 microns, and 10% were longer than 40 microns. Estimates of exposure before 1964 in the dry mill were 168 fibers/cc for working areas, 182 fibers/cc for sweepers, 88 fibers/cc for skipping, and 13 fibers/cc for the quality control laboratory. In 1964-1971, exposure estimates for these areas were 33, 36, 17, and 3 fibers/cc, respectively. Estimates of exposures in the mine before 1971 ranged from 9-23 fibers/cc for drillers and were less than 2 fibers/cc for nondrilling jobs. All 8-hr TWA job exposure estimates decreased from 1972-1976, and from 1977-1982 were less than 1 fiber/cc.

Air Pollutants, Occupational↗
PubMed1987

Duplication of one of the products of the t(8;21) translocation in a patient with refractory anemia with excess blasts in transformation.

A 34-year-old man with refractory anemia with excess blasts in transformation is reported, having a t(8;21) translocation and a duplication of one of the products, der(21). The duplicated product had not been observed at presentation in malignant disease, as far as we are aware; thus, the findings are discussed with regard to this case and other possible smoldering leukemias. The diagnostic use of cytogenetics is also considered.

Adult↗
PubMed1987

Subtle abnormalities in the short arm of chromosome 11 in acute myeloid leukemia.

A series of four patients with small deletions of the short arm of chromosome #11 is presented. In two of these patients, deletion of 11p was the sole karyotypic abnormality. When compared with similar reported cases an association with FAB type M4 is apparent. Such cases may often be undocumented, because the deletions can be subtle. One patient with erythroleukemia shows an inversion of chromosome #11 involving band 11p15. Because the patients' fetal hemoglobin (HbF) became raised during the course of the disease, it is postulated that the hemoglobin beta chain gene at 11p15 may have been disrupted.

Adolescent↗
PubMed1987

Effect of target content at higher spatial frequencies on the accuracy of the accommodation response.

The accommodation responses to sinusoidal and square-wave gratings at the same vergence (-5.0 dioptres) are compared as a function of the modulation of the fundamental of both waveforms. At low spatial frequencies (less than or equal to 2 c deg-1), responses to square-wave gratings are found to be more accurate than those to sine-waves. At higher frequencies the responses become very similar. An explanation is offered in terms of the contribution of higher harmonics to the square-wave response.

Accommodation, Ocular↗
PubMed1987

Changes in head position as a measure of auditory localization performance: auditory psychomotor coordination under monaural and binaural listening conditions.

Two experiments examined the capacity of listeners to turn and face an active sound source. Tests were conducted with sources located in the subject's forward field (an arc extending from 60 degrees to the subject's right to 60 degrees to the left). Localization performance was determined under both monaural and binaural listening conditions, using both brief pulses and sustained pulse trains as target signals. Not unexpectedly, the ability to orient the face to a hidden sound source was very poor under monaural conditions if the listener received only a brief (100-ms) tonal pulse. When continuous pulse trains were employed, localization, even under monaural conditions, became quite accurate. Across conditions, this complex motor response produced results in agreement with those that have been obtained when subjects were only required to report their spatial impressions. In particular, performance with binaural pulse trains was observed to vary as a function of the frequency of the target signals employed. Descriptions of the head movement response, along with a discussion of some of the implications of ear-head coordination, are presented.

Auditory Perception↗
PubMed1986

Alterations in rat alveolar surfactant phospholipids and proteins induced by administration of chlorphentermine.

Chlorphentermine is a cationic amphiphilic drug which produces a phospholipid storage disorder in rat lungs. Experiments were carried out to characterize changes in the composition of acellular alveolar lavage materials and to study possible mechanisms by which pulmonary surfactant phospholipidosis is produced by administration of the drug. Following ten daily injections of chlorphentermine (25 mg/kg body weight), there are 12.2- and 13.6-fold increases of pulmonary lavage total phospholipids and disaturated phosphatidylcholines (disaturated PC), respectively. In addition, there is a 2.8-fold increase in total protein and a 12.7-fold increase in the surfactant apoprotein group with molecular weights from 28,000 to 32,000. We measured incorporation of labeled palmitate, choline and glycerol into disaturated PC in type II cells and alveolar macrophages isolated from control and chlorphentermine-treated animals. The drug does not affect the incorporation of labeled substrates into disaturated PC in either cell type. However, in alveolar macrophages there is a decrease in the rate of intracellular degradation of recently synthesized disaturated PC in chlorphentermine-treated animals. The drug also inhibits the phospholipase-induced catabolism of rat surfactant disaturated PC which occurs during incubation of alveolar lavage fluid in vitro at 37 degrees C. When the lavage fluid is divided into subfractions by differential centrifugation, a larger percentage of the phospholipid is distributed in the less sedimentable subfractions in chlorphentermine-treated animals relative to controls, suggesting the accumulation of older surfactant materials. These results suggest that chlorphentermine-induced phospholipidosis of pulmonary surfactant materials is due to decreased rates of phospholipid degradation.

Animals↗
PubMed1986

31P-NMR spectra of the Ha-ras p21.nucleotide complexes.

Phosphorus nuclear magnetic resonance spectra of the Ha-ras oncogene product p21 and its nucleotide complexes have been obtained. It is shown that the 31P nuclear magnetic resonance spectra of a number of nucleotide-enzyme complexes show some common features. In particular, the chemical shift values of the beta-phosphorus resonance of enzyme-bound NTP and NDP (N = A, G) of hydrolases exhibit a downfield shift virtually identical for myosin, elongation factor Tu, and the Ha-ras oncogene product p21. This suggests that the stereochemistry around the beta-phosphorus might be similar in these compounds.

Guanosine Diphosphate↗
PubMed1986

Expression of p21 proteins in Escherichia coli and stereochemistry of the nucleotide-binding site.

v-Ha-ras encoded p21 protein (p21V), the cellular c-Ha-ras encoded protein (p21C) and its T24 mutant form p21T were produced in Escherichia coli under the control of the tac promoter. Large amounts of the authentic proteins in a soluble form can be extracted and purified without the use of denaturants or detergents. All three proteins are highly active in GDP binding, GTPase and, for p21V, autokinase activity. Inhibition of [3H]GDP binding to p21C by regio- and stereospecific phosphorothioate analogs of GDP and GTP was investigated to obtain a measure of the relative affinities of the three diphosphate and five triphosphate analogs of guanosine. p21 has a preference for the Sp isomers of GDP alpha S and GTP alpha S. It has low specificity for the Sp isomer of GTP beta S. Together with the data for GDP beta S and GTP gamma S these results are compared with those obtained for elongation factor (EF)Tu and transducin. This has enabled us to probe the structural relatedness of these proteins. We conclude that p21 seems to be more closely related to EF-Tu than to transducin.

Cell Line↗