Relative biological effectiveness for organically bound tritium.
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Humans↗
Biomedical subjects
A Trivedi
Publications and source records attributed to A Trivedi.
GRIP1, a novel mouse protein that serves as a transcriptional coactivator in yeast for the hormone binding domains of steroid receptors.
The yeast two-hybrid system was used to isolate a clone from a 17-day-old mouse embryo cDNA library that codes for a novel 812-aa long protein fragment, glucocorticoid receptor-interacting protein 1 (GRIP1), that can interact with the hormone binding domain (HBD) of the glucocorticoid receptor. In the yeast two-hybrid system and in vitro, GRIP1 interacted with the HBDs of the glucocorticoid, estrogen, and androgen receptors in a hormone-regulated manner. When fused to the DNA binding domain of a heterologous protein, the GRIP1 fragment activated a reporter gene containing a suitable enhancer site in yeast cells and in mammalian cells, indicating that GRIP1 contains a transcriptional activation domain. Overexpression of the GRIP1 fragment in mammalian cells interfered with hormone-regulated expression of mouse mammary tumor virus-chloramphenicol acetyltransferase gene and constitutive expression of cytomegalovirus-beta-galactosidase reporter gene, but not constitutive expression from a tRNA gene promoter. This selective squelching activity suggests that GRIM can interact with an essential component of the RNA polymerase II transcription machinery. Finally, while a steroid receptor HBD fused with a GAL4 DNA binding domain did not, by itself, activate transcription of a reporter gene in yeast, coexpression of this fusion protein with GRIP1 strongly activated the reporter gene. Thus, in yeast, GRIP1 can serve as a coactivator, potentiating the transactivation functions in steroid receptor HBDs, possibly by acting as a bridge between HBDs of the receptors and the basal transcription machinery.
Amino Acid Sequence↗
Occupational levels of radiation exposure induce surface expression of interleukin-2 receptors in stimulated human peripheral blood lymphocytes.
Interleukin-2 (IL-2) is a cytokine responsible for a variety of immune and non-immune stimulatory and regulatory functions, including the activation and stimulation of cytotoxic cells able to recognize and kill human tumour cells and T-cell proliferation and differentiation. We show that low doses of radiation, in the range commonly received by atomic radiation workers or as a result of minor medical diagnostic procedures (0.25 to 10 mGy), stimulate the expression of IL-2 receptors (IL-2R) on the surface of peripheral blood lymphocytes (PBL) taken from normal human donors. This stimulated surface expression after in vitro irradiation is an indirect effect, resulting from the secretion into the medium of a soluble factor from the irradiated cells. This factor can also stimulate IL-2R surface expression in unirradiated cells. Consequently, radiation stimulation of IL-2R expression in a large population of PBL shows a triggered-type response rather than being proportional to dose. These results demonstrate that normal human cells can respond to doses of radiation in the range of common occupational or medical exposures. The data also demonstrate a possible defence mechanism against environmental stress by which a radiation-exposed cell can use an indirect signalling mechanism to communicate with and influence the biological processes in an unexposed cell.
Biological Factors↗
Inhibitory effects of naltrexone on the induction of parental behavior in juvenile rats.
Juvenile rats are rapidly responsive to pups soon after weaning, displaying maternal-like behaviors such as licking, retrieving, grouping, and crouching over pups. As juveniles reach 30 days of age, they become less responsive to pups and show increased latencies to display the same parental behaviors. In light of previous data implicating opiates in the display of ongoing maternal behavior, we administered naltrexone, a long-acting opiate antagonist, beginning 5 and 9 days prior to and continuing throughout the period of behavioral testing, which started at 26 or 30 days of age. Male and female juveniles treated with 10 mg/kg of naltrexone SC for 9 days (days 21 to 29 of age) prior to and during behavioral testing (days 30 to 37) showed longer latencies to retrieve, group, and crouch over pups than did the vehicle-injected controls. These results suggest that opioids may have a stimulatory role in parental behavior during this prepubertal period.
Aging↗
TATA-binding protein is limiting for both TATA-containing and TATA-lacking RNA polymerase III promoters in Drosophila cells.
We have investigated the role of the TATA-binding protein (TBP) in modulating RNA polymerase (Pol) III gene activity. Epitope-tagged TBP (e-TBP) was both transiently and stably transfected in Drosophila Schneider S-2 cells to increase the total cellular level of TBP. Analysis of the transcripts synthesized from cotransfected tRNA and U6 RNA genes revealed that both types of RNA Pol III promoters were substantially stimulated by an increase in e-TBP in a dose-dependent manner. Furthermore, a TBP-dependent increase in the levels of endogenous tRNA transcripts was produced in the stable line induced to express the e-TBP. We further determined whether the ability of increased TBP to induce RNA Pol III gene expression was due to a direct effect of increased TBP complexes on RNA Pol III gene promoters or an indirect consequence of enhanced expression of RNA Pol II genes. A TBP expression plasmid (e-TBP332), containing a mutation within the highly conserved carboxy-terminal domain, was both transiently and stably transfected into S-2 cells. e-TBP332 augmented the transcription from two RNA Pol II gene promoters indistinguishably from that observed when e-TBP was expressed. In contrast, e-TBP332 was completely defective in its ability to stimulate either the tRNA or U6 RNA gene promoters. In addition, increasing levels of a truncated TBP protein containing only the carboxy-terminal region failed to induce either the tRNA or U6 RNA gene promoter, whereas it retained its ability to stimulate an RNA Pol II promoter. Thus, the TBP-dependent increase in RNA Pol II gene activity is not sufficient for enhanced RNA Pol III gene transcription; rather, a direct effect on RNA Pol III promoters is required. Furthermore, these results provide the first direct evidence that the amino-terminal region of TBP is important for the formation or function of TBP-containing complexes utilized by TATA-less and TATA-containing RNA Pol III promoters. Together, these studies demonstrate that TBP is limiting for the expression of both classes of RNA Pol III promoters in Drosophila cells and implicate an important role for TBP in regulating RNA Pol III gene expression.
Animals↗
In vitro replication of plasmids containing human c-myc DNA.
A chromosomal replication initiation zone was previously mapped in cell cultures to the 5' flanking DNA of the human c-myc gene. We have used an in vitro system to examine the replication of a plasmid, pNeo.Myc-2.4, containing 2.4 kb of the c-myc initiation zone. In vitro, pNeo.Myc-2.4 generated high levels of DpnI-resistant DNA above background incorporation into control plasmids. pNeo.Myc-2.4 replicated semiconservatively to produce supercoiled and relaxed plasmid monomers, and replicative intermediates. [32P]dCMP incorporated into pNeo.Myc-2.4 appeared in Okazaki fragments and low molecular weight strands which matured to full length plasmid DNA, whereas [32P]dCMP incorporated into control plasmids appeared as continuous smears on denaturing gels. Other assays also distinguished the processive replication of pNeo.Myc-2.4 from the dispersive labeling of control plasmids. A pNeo.Myc-2.4 replication time course showed a clear preference for initiation within a restriction fragment containing the c-myc DNA. Two-dimensional electrophoresis revealed that a restriction fragment bearing the c-myc origin zone generated an arc characteristic of replicative intermediates containing a central replication bubble, while vector fragments in the plasmid generated arcs of forked intermediates. Replication bubbles visualized by electron microscopy were centered within the replication initiation zone, approximately 1.4 kb upstream of c-myc promoter P1. Okazaki fragments radiolabeled during in vitro replication showed a switch in the asymmetry of template preference within the initiation zone identified by electron microscopy, two-dimensional electrophoresis and early labeling. These data show that bidirectional, semiconservative replication can originate preferentially in vitro in the 5' flanking DNA of the c-myc gene, and that replicative intermediates present at low levels can be distinguished from molecules generated by competing, repair-type processes.
Cell-Free System↗
Percutaneous absorption of tritium-gas-contaminated pump oil.
One of the radiological problems encountered in tritium handling facilities is the hazards associated with tritium's ability to label and degrade organic materials. Experiments in which male hairless rats have been contaminated with tritium-gas-contaminated pump oil have demonstrated that tritium deposited on the skin provides an input of organically bound tritium and tritiated water in the body. The accumulation of organically bound tritium at the point of contact in the skin and in various tissues influenced tritium excretion in urine and feces. The retention of tritium in the body showed that tritium was mainly metabolized and assimilated as organically bound tritium. The distribution of tritiated water was rapid and uniform in the whole-body. Analyses of tritium excreted in animal urine and feces showed that a significant level of organically bound tritium was excreted shortly after exposure. The highest concentration of tritium activity was measured in the exposed area of the skin. An increased level of tritium accumulation in the liver and kidneys was seen. Dose calculations showed that the exposed skin had the highest dose, and the skin dose was primarily due to the retention of organically bound tritium at the point of contact. The interpretation of these data has indicated that the retention of short-term organically bound tritium in the skin may be a dominant factor for dosimetry purposes.
Absorption↗
Biological and biophysical techniques to assess radiation exposure: a perspective.
Biological dosimeters measure biologically relevant effects of radiation exposure that are in some sense an estimate of effective dose, whereas biophysical indicators serve as surrogates of absorbed dose in a manner analogous to conventional thermoluminescent dosimeters (TLD). The biological and biophysical dosimeters have the potential to play an important role in assessing unanticipated or occupational radiation exposures. For example, where the exposure is large and uncertain (i.e. radiation accidents), accurate dose information can help in deciding the most appropriate therapy and medical treatment. Another useful area is that of lifetime accumulated dose determination, and the ability to distinguish between and integrate the exposures from natural and anthropogenic (medical X-rays, indoor radon, natural background radiation, occupational and non-occupational exposures). Also, the possibility to monitor individual response and differences in inherent or induced radiation sensitivity may have important implications for radiation protection. More commonly, this type of dosimetry could be used for routine monitoring to detect and quantify unsuspected exposure, for regulatory purposes or for epidemiological studies of the long-term effects of radiation exposure (e.g. in Japanese A-bomb survivors or in the population surrounding Chernobyl). This review is a comparative study of the existing techniques and their future prospects. It summarizes the sensitivity, reproducibility, limiting dose, dose-rate, energy, LET response, sources of variability and uncertainty, and other practical aspects of each bio-indicator. The strengths and weaknesses of each approach are evaluated on the basis of common criteria for particular applications, and are summarized for each assay both in the text and in tabular form, for convenience. It is clear that no single indicator qualifies to reliably measure occupational exposures at the current levels of sensitivity conventional dosimetry services provide. Most of the bio-techniques are applicable to the detection of relatively high radiation exposures at relatively short times after exposure. Some of the bio-indicators have been identified that are, or offer future prospects for becoming, appropriate bio-indicators for dosimetry needs. However, all methods are subject to biological and other variables that are presently uncontrolled, and represent a major source of uncertainty. These include variations in background signals not directly associated with radiation exposure, inter- and intra-individual variability of radiation response, and genetic and environmental effects. Although these factors contribute to the lack of confidence in biological dosimetry, promising bio-indicators may be applied to large populations to establish the inherent variability and confounding factors that limit quantitative data collection and analysis, and reduce reliability and reproducibility.
Biological Assay↗
Iron-deficiency anaemia and physical performance in adolescent girls from different ethnic backgrounds.
One hundred and fourteen 11-14-year-old schoolgirls from Wembley, Middlesex, were assessed for Fe status (haemoglobin (Hb), packed cell volume and mean corpuscular Hb concentration, height, weight, eating habits, and ethnic origin, and undertook a step test to assess physical performance. Overall, 20% of girls had Hb less than 120 g/l, ranging from 11% in White girls to 22-25% in girls of Asian origin. Prevalence of low Hb was 20% in vegetarians, higher in White vegetarians compared with non-vegetarians (23 v. 4%), but lower in the Indian vegetarians compared with non-vegetarians (17 v. 32%). Low Hb was present in 25% of girls who had tried to lose weight in the previous year, and was more common in girls from manual social class backgrounds than non-manual (24 v. 10%). At the start of the step test the twenty-three girls with low Hb had heart rates similar to those with normal Hb, but heart rates in the low Hb group were significantly elevated immediately after the step test, and still significantly elevated 1 min later. The present results confirm the findings of a previous study in White girls, and suggest that physical performance may be compromised at mild levels of anaemia.
Adolescent↗
Skin-contact exposure to tritium-gas-contaminated stainless-steel surfaces.
One of the radiation protection problems potentially encountered in tritium-handling facilities is contamination of metal surfaces. Experiments with hairless rats have demonstrated that when intact skin is brought into contact with tritium-gas-contaminated stainless-steel surfaces, tritium can be fixed as organically bound tritium (OBT) and as tritiated oxide (HTO) in the skin. The radiological hazard associated with this route of tritium uptake is determined by the retention and distribution of tritium in the skin and other organs. The experimental data suggest that the OBT in the skin serves as an input source to the rest of the body. The urinary excretion of tritium shows a biphasic excretion for OBT and a single-phase clearance for HTO from the body. The results indicate that the exposure from this mode of contamination results in long retention of tritium in the skin as well as in non-uniform distribution of tritium in organs and macromolecules. This information is useful in evaluating the possible dosimetric concerns from this mode of exposure.
Animals↗
Chronic exposure to ionizing radiation as a tumor promoter in mouse skin.
We have tested chronic exposure to 90Y beta radiation for its action as a complete tumor promoter, a stage I tumor promoter, or a stage II tumor promoter in SENCAR mouse skin. In skin initiated with a single application of 7,12,dimethylbenz[a]anthracene (DMBA, 10 nmol), chronic exposure to beta radiation as a complete promoter (0.5 Gy, twice/week, 13 weeks) produced no tumors and, when added to a complete chemical promoter (TPA), reduced tumor frequency about 30%. A similar result was observed when beta radiation was tested as a stage II promoter. DMBA-initiated mice that received chemical (12-O-tetradecanoylphorbol-13-acetate, TPA) stage I promotion followed by 13 weeks of beta-radiation exposure (0.5 Gy, twice/week) as stage II promotion produced essentially no tumors, and combining the same chronic beta-radiation exposure with chemical (mezerein) stage II promotion reduced tumor frequency about 20% when compared to a similar group that was not irradiated. Chronic beta-radiation exposure was tested two ways as a stage I tumor promoter in initiated skin that was subsequently treated with mezerein as a stage II promoter. Stage I promotion was shown to proceed with the passage of time, indicating this process occurs naturally in the absence of chemical or physical stimulation. Hyperthermia, previously shown to be a potent inhibitor of chemically stimulated stage I promotion, had no effect on the natural process, indicating at least some differences in mechanism between the two processes. The natural process was, in fact, inhibited by chemical tumor promoters, but not by radiation. In addition to the increase resulting from this natural process, tumor frequency was further increased slightly but significantly (12-15%, P less than or equal to 0.05) when chronic radiation exposure was given as a stage I promoter (0.5 Gy, twice/week, 13 weeks) subsequent to initiation, in spite of the expected 20% reduction resulting from this dose. Exposure of initiated animals to radiation (0.5 or 1.0 Gy, twice/week, 2 weeks) in addition to TPA as stage I promotion produced a similar increase in tumor frequency (P less than 0.02). At higher radiation doses, however, tumor frequency was reduced compared to unirradiated controls. In a third test as a stage I promoter, beta radiation (0.5 Gy twice/week, 4 weeks) was given prior to initiation with N-methyl-N'-nitro-N-nitrosoguanidine in animals subsequently promoted by TPA (twice/week, 13 weeks), and again the radiation slightly but significantly (P less than 0.03) increased tumor frequency compared to the unirradiated control group.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Hemostatic technique for internal mammary artery anastomotic bleeding.
When internal mammary artery is used for myocardial revascularization, a not uncommon occurrence is intraoperative bleeding from the internal mammary artery to coronary artery anastomosis. The conventional method of hemostasis of placing additional sutures across the suture line may produce anastomotic stenosis or may aggravate the bleeding by producing tears, especially as these additional sutures are placed on a beating heart. We describe a simple technique by which hemostasis can be achieved without the risk of anastomotic stenosis or aggravation of the bleeding, as it avoids placing sutures over the anastomotic suture line.
Hemostasis, Surgical↗
The involvement of topoisomerases and DNA polymerase I in the mechanism of induced thermal and radiation resistance in yeast.
Either an ionizing radiation exposure or a heat shock is capable of inducing both thermal tolerance and radiation resistance in yeast. Yeast mutants, deficient in topoisomerase I, in topoisomerase II, or in DNA polymerase I, were used to investigate the mechanism of these inducible resistances. The absence of either or both topoisomerase activities did not prevent induction of either heat or radiation resistance. However, if both topoisomerase I and II activities were absent, the sensitivity of yeast to become thermally tolerant (in response to a heat stress) was markedly increased. The absence of only topoisomerase I activity (top1) resulted in the constitutive expression of increased radiation resistance equivalent to that induced by a heat shock in wild-type cells, and the topoisomerase I-deficient cells were not further inducible by heat. This heat-inducible component of radiation resistance (or its equivalent constitutive expression in top1 cells) was, in turn, only a portion of the full response inducible by radiation. The absence of polymerase I activity had no detectable effect on either response. Our results indicate that the actual systems that confer resistance to heat or radiation are independent of either topoisomerase activity or DNA polymerase function, but suggest that topoisomerases may have a regulatory role during the signaling of these mechanisms. The results of our experiments imply that maintenance of correct DNA topology prevents induction of the heat-shock response, and that heat-shock induction of a component of the full radiation resistance in yeast may be the consequence of topoisomerase I inactivation.
Adaptation, Physiological↗
Prevention of myocardial ischemia during coronary angioplasty: a simple new method for distal antegrade arterial blood perfusion.
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Angioplasty, Balloon↗
Coronary angioplasty of septal perforator.
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Adult↗
Changes in cyclic nucleotide profiles in proliferating multi-cell spheroids.
The intracellular concentration of cyclic adenosine 3':5'-mono-phosphate (cAMP) has been shown to be related to each developmental phase of the cell cycle. Highest levels of this nucleotide are evident during the S-phase (the DNA synthetic phase) which has also been shown to be radiation-sensitive. The relationship between the levels of cyclic nucleotides, cAMP and guanosine 3':5'-monophosphate (cGMP), and the proliferation of cells in a tumor model system was investigated using V79-171b Chinese hamster lung cells grown both as monolayer and as three dimensional cell clusters (spheroids). The spheroid which is more radiation-resistant than its monolayer counterpart, has been used by many radiobiologists as an in vitro tumor model. Our results indicate that the yin-yang hypothesis of a opposing regulatory relation between the two different classes of cyclic nucleotides only held true for monolayer cultures (both exponential and plateau phase) but could not be demonstrated in the tumor model where the levels of both nucleotides increased directly with the diameter of the growing spheroid mass.
Animals↗
Role of phospholipid fatty acids on the kinetics of high and low affinity sites of cytochrome c oxidase.
The nature of the interactions between cytochrome c oxidase and the phospholipids in mitochondrial membranes has been investigated by varying the nature of the fatty acyl components of Saccharomyces cerevisiae. A double fatty acid yeast mutant, FAI-4C, grown in combinations of unsaturated (oleic, linoleic, linolenic, and eicosenoic) and saturated (lauric and palmitic) fatty acids, was employed to modify mitochondrial membranes. The supplemented fatty acids constituted a unique combination of different acyl chain lengths with varying degrees of unsaturation which were subsequently incorporated into mitochondrial phospholipids. Phosphatidylethanolamine and cardiolipin, the predominant phospholipids of the inner mitochondrial membrane, were characterized by their high levels of supplemented unsaturated fatty acids. Increasing the chain length or the degree of unsaturation of mitochondrial membrane phospholipids had no effect on altering the nature of the phospholipid polar head group but did result in a profound change on the specific activity of cytochrome c oxidase. When studied under conditions of different ionic strengths and pHs the enzyme's activity, as documented by Eadie-Hofstee plots, showed biphasic kinetics. The kinetic parameters for the low affinity reaction were greatly influenced by the changes in the membrane fatty acids and only marginal effects were noted at the high affinity reaction site. The discontinuities in the steady-state fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene, monitored at increasing temperatures, suggested that changes in membrane fluidity were conditioned by alterations in mitochondrial membrane fatty acid constituents. These results indicate that the lipid changes affecting the low affinity binding site of cytochrome c oxidase may be the result of lipid-protein interactions which lead to enzyme conformational changes or may be due to gross changes in membrane fluidity. It may, therefore, follow that this enzyme site may be embedded in or be juxtaposed to the outer surface of the inner mitochondrial membrane bilayer in contrast to the high affinity site which has been shown to be significantly above the membrane plane.
Electron Transport Complex IV↗
Phospholipid enrichment of Saccharomyces cerevisiae and its effect on polyene sensitivity.
Sensitivity to polyene antibiotics, e.g., nystatin, amphotericin B, and filipin, was determined in phosphatidylcholine (PC) or phosphatidylethanolamine (PE) or phosphatidylserine (PS) enriched Saccharomyces cerevisiae cells, using glutamic acid, phenylalanine, glycine, and lysine transport as an index of polyene antibiotic action. As compared with normal cells, phospholipid-enriched cells acquired resistance towards different polyenes. However, the sensitivity of glutamic acid transport towards nystatin remained unaffected in PC-, PE-, or PS-enriched cells. In contrast to nystatin, the other two polyenes were more effective in checking the influx of amino acids. Results demonstrated that the specific enrichment of PC, PE, or PS could selectively protect S. cerevisiae cells from polyene antibiotic action.
Amino Acids↗