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Biomedical subjects

M A Bender

Publications and source records attributed to M A Bender.

At least 37 records · Page 2Linked to original sources
PubMed1998

Herpes virus-mediated preproenkephalin gene transfer to the amygdala is antinociceptive.

To evaluate the role of the amygdala in pain modulation and opioid-mediated antinociception, a recombinant, replication-defective herpes virus carrying the human preproenkephalin cDNA was injected bilaterally into the rat amygdala. Four days after gene delivery nociceptive behavior was assessed by the formalin test. Rats infected with the virus expressing preproenkephalin showed a selective, naloxone-reversible abolition of phase 2 flinching behavior compared to rats infected with a control virus. The results implicate the amygdala in the control of pain and in opioid analgesia and demonstrate the use of recombinant herpes viruses as tools for studying gene function in specific neural pathways of the central nervous system.

Amygdala↗
PubMed1998

The beta-globin LCR is not necessary for an open chromatin structure or developmentally regulated transcription of the native mouse beta-globin locus.

The murine beta-globin locus control region (LCR) was deleted from its native chromosomal location. The approximately 25 kb deletion eliminates all sequences and structures homologous to those defined as the human LCR. In differentiated ES cells and erythroleukemia cells containing the LCR-deleted chromosome, DNasel sensitivity of the beta-globin domain is established and maintained, developmental regulation of the locus is intact, and beta-like globin RNA levels are reduced 5%-25% of normal. Thus, in the native murine beta-globin locus, the LCR is necessary for normal levels of transcription, but other elements are sufficient to establish the open chromatin structure, transcription, and developmental specificity of the locus. These findings suggest a contributory rather than dominant function for the LCR in its native location.

Animals↗
PubMed1997

Issues in cytogenetic biological dosimetry: emphasis on radiation environments in space.

Issues central to the reliability of cytogenetic biodosimetry are presented. Although it now appears that cytogenetic biodosimetry can be used reliably to reconstruct radiation dose after acute, uniform whole-body exposure (albeit within certain dose ranges), additional data are required to fully validate cytogenetic biodosimetry for the protracted and complex exposure conditions in space. Approaches are presented that could be used to obtain the data necessary for validation. It also appears that the use of dicentric aberrations for biodosimetry on missions lasting several months or more may not be reliable because of the large variability observed among individuals in the rate of loss of cells with dicentrics, making back-extrapolations uncertain. This may be testable, however, by comparing the results for dicentrics and translocations obtained by biodosimetry with the radiation dosimetry obtained on board the spacecraft. In addition to these and several other issues, estimates are provided of the current limitations of detection of dicentrics and reciprocal translocations.

Aerospace Medicine↗
PubMed1996

Analysis of mice containing a targeted deletion of beta-globin locus control region 5' hypersensitive site 3.

To examine the function of murine beta-globin locus region (LCR) 5' hypersensitive site 3 (HS3) in its native chromosomal context, we deleted this site from the mouse germ line by using homologous recombination techniques. Previous experiments with human 5' HS3 in transgenic models suggested that this site independently contains at least 50% of total LCR activity and that it interacts preferentially with the human gamma-globin genes in embryonic erythroid cells. However, in this study, we demonstrate that deletion of murine 5' HS3 reduces expression of the linked embryonic epsilon y- and beta H 1-globin genes only minimally in yolk sac-derived erythroid cells and reduces output of the linked adult beta (beta major plus beta minor) globin genes by approximately 30% in adult erythrocytes. When the selectable marker PGK-neo cassette was left within the HS3 region of the LCR, a much more severe phenotype was observed at all developmental stages, suggesting that PGK-neo interferes with LCR activity when it is retained within the LCR. Collectively, these results suggest that murine 5' HS3 is not required for globin gene switching; importantly, however, it is required for approximately 30% of the total LCR activity associated with adult beta-globin gene expression in adult erythrocytes.

Animals↗
PubMed1996

In vivo transgene activation from an HSV-based gene therapy vector by GAL4:vp16.

Herpes simplex virus type 1 (HSV-1) has many attributes which make it attractive as a base for the development of vectors for the delivery of transgenes to the nervous system. In this report we describe the adaptation of the bipartite GAL4:VP16 transactivation system to replication-deficient HSV vectors. We demonstrate that the recombinant transactivator GAL4:VP16 produced from a replication-deficient HSV vector is capable of activating transcription of a reporter gene using a synthetic promoter consisting of GAL4 binding sites and the TATA box of the adenovirus E1b gene. Activation by vector produced GAL:VP16 was demonstrated with the recombinant promoter/reporter gene cassette in the infected cell chromosome, in the genome of a second virus infecting the same cells and with a single vector engineered to produce both GAL4:VP16 transactivator and to contain a recombinant promoter/reporter gene cassette. Furthermore, the double recombinant virus also produced the reporter gene product in neurons after direct intracranial inoculation into rat hippocampus. This system may be used to extend and improve promoter function in HSV gene transfer vectors in vivo.

Animals↗
PubMed1995

HSV as a gene transfer vector for the nervous system.

Gene therapy for diseases of the nervous system requires vectors capable of delivering the therapeutic gene into postmitotic cells in vivo. Herpes simplex virus type 1 is a neurotropic virus that naturally establishes latency in neurons of the peripheral nervous system. Replication defective HSV vectors have been developed; these are deleted for at least one essential immediate early regulatory gene, rendering the virus less cytotoxic, incapable of reactivation, but still capable of establishing latency. Foreign genes can be vigorously expressed from an HSV-based vector in a transient manner in brain and other tissues. Long-term but weak foreign gene expression may be achieved in the nervous system by exploiting the transcriptional control mechanisms of the natural viral latency active promoter. To meet the needs of specific applications, either highly active long-term or regulatable transgene expression will be needed, requiring further studies in order to design the appropriate latency-based promoter systems.

Gene Transfer Techniques↗
PubMed1995

Cytogenetics research in radiation biology.

Radiation cytogenetics goes back approximately six decades and not only contributed to the earliest development of radiobiology, but continues to contribute today. Contributions on three levels are outlined here. Early contributions to radiobiological theory include the nature of dose-effect curves, dose-rate and fractionation effects, and linear energy transfer (LET) effects. Understanding of the roles of aberrations in endpoints such as cell killing, mutation and carcinogenesis have more recently contributed to unraveling mechanisms in these important radiobiological effects. Finally, the study of various details of classical radiation cytogenetics, such as half chromatid exchange or sister chromatid union, has contributed to our current understanding of cytogenetic phenomena on the molecular level.

Animals↗
PubMed1993

Time sequence of events leading to chromosomal aberration formation.

Investigations have been carried out which have measured the influence of the repair polymerases on the yield of different types of chromosomal aberrations. The studies were mainly concerned with the effect of inhibiting the polymerases on the yield of aberrations. The polymerases fill in single strand regions, and the fact that their inhibition affects the yield of aberrations suggests that single strand lesions are influential in aberration formation. The results indicate that-- 1. There are two actions of polymerases in clastogenesis. One is in their involvement in a G2 repair system, in which the pair of chromatids is concerned, and which does not yield aberrations unless the inhibition is still operating when the cells enter mitosis. The second also operates in G1 and S, and is such that when repair is inhibited, further damage accrues. 2. The second action is affected by inhibiting polymerase but operates even when the repair enzymes are active. 3. The production of chromosomal exchanges involves a series of reactions, some of which are reversible. 4. The time span over which the reactions occur is much longer than has been envisaged previously (e.g., most of a cell cycle).

Animals↗
PubMed1993

Chromosomal aberration types in cells at the second division after irradiation in G1 or G2.

Cultures of JU-56 cells were irradiated in either G1 or G2 and examined either in their first post-irradiation metaphase (in diploids) or in their second post-irradiation metaphase (in colcemid-induced tetraploids). The timing of fixation, together with tritiated thymidine pulse labelling, allowed selection for scoring only metaphases of cells that were in the G1 or G2 phase of the cell cycle during irradiation. With G1 irradiation it was found that many of the aberrations observed at the first division were not present (as derivatives) at the second division, and also that new aberrations were found at the second division, which were not derived from aberrations at the first division. Clonogenic survival was also measured in populations of cells irradiated in G1. It was found that cells containing chromosomal aberrations at the first division were not numerous enough to explain lack of survival. When frequencies of aberrations following G2 irradiation scored at the second division were compared with those scored at the first, there was a significant increase in dicentrics as compared with their progenitor asymmetrical chromatid interchanges, and of mirror-image dicentrics as compared with their progenitor sister unions. A substantial number of sister unions were also observed at the second division. We conclude that some aberrations are lost during the interphase between the first and the second post-irradiation metaphase and that new chromosomal aberrations arise during the second post-irradiation interphase.

Animals↗
PubMed1990

Radiosensitivity of skin fibroblasts from atomic bomb survivors with and without breast cancer.

Fibroblasts were established in vitro from skin biopsies obtained from 55 women and 1 man with or without breast cancer and with or without exposure to radiation from the atomic bomb explosion in Hiroshima. The radiosensitivity of these cells was evaluated by clonogenic assays after exposure to X-rays or to fission neutrons from a 252Cf source. Data were fitted to a multitarget model, S/S0 = A [1 - (1 - ekD)N], for both X-ray and neutron dose-survival curves. A single hit model, S/S0 = AekD, fits the neutron dose-survival responses as well. There were no differences in the means or variances of radiosensitivity between exposed and nonexposed groups or between patients with or without breast cancer. Hence, although the sample is not large, it provides no support for the hypothesis that atomic bomb radiation preferentially induces breast cancer in women whose cells in vitro are sensitive to cell killing by radiation.

Adolescent↗
PubMed1990

DNA polymerase alpha does not mediate G0-G1 increase in yield of X-ray-induced exchange aberrations in human peripheral blood lymphocytes.

We report experiments to test the hypothesis that the increased yield of dicentric chromosomes observed in human peripheral blood lymphocytes treated with X-rays during the G1 phase of their first cell cycle, as compared with the yield when the cells are treated in their G0 phase prior to phytohemagglutinin stimulation, is a manifestation of the recently-reported conversion of an inactive form of DNA polymerase alpha to its active form as the PHA-stimulated cells pass from G0 into G1 (Sylvia et al., 1988). The specific polymerase alpha inhibitor butylphenyl deoxyguanosine was used as an X-ray post-treatment. The results show that polymerase alpha is not involved.

Cell Cycle↗
PubMed1989

Long-term expression of the human beta-globin gene after retroviral transfer into pluripotent hematopoietic stem cells of the mouse.

We have studied the regulation of the human beta-globin gene after retroviral transfer into a variety of transformed and normal hematopoietic cells. After transfer into murine erythroleukemia cells (MEL) expression from the human beta-globin gene responds to inducers of erythroid maturation in parallel to the endogenous murine globin genes. After infection of human BFU-E, RNA expression from the virally-transferred beta-globin gene was measured at 2.5%-5% of the endogenous beta-globin level. The most improved globin vectors can transfer the human beta-globin gene into pluripotent hematopoietic stem cells in mouse bone marrow. Mice reconstituted with infected marrow show human beta-globin RNA and protein expression in peripheral blood cells for over 4 months. In these animals, both myeloid and lymphoid cells carry the integrated provirus at a level of about 1 copy per cell. In serial transplantation experiments, bone marrow from these animals is capable of repopulating secondary and tertiary recipient animals which go on to show long-term human beta-globin expression. Retroviral vectors thus provide a practical way to refine models of globin gene regulation through in vivo tests and to evaluate the feasibility of protocols for gene addition therapy.

Animals↗
PubMed1989

Chromosomal aberration and sister-chromatid exchange frequencies in peripheral blood lymphocytes of a large human population sample. II. Extension of age range.

We have previously reported on a cytogenetic-epidemiological study of chromosomal aberration and sister-chromatid exchange (SCE) frequencies in peripheral blood lymphocytes (PBL) of a cohort of 353 healthy employees of the Brookhaven National Laboratory (Bender et al., 1988). This sample has now been increased in order to extend the age range represented and, incidentally, the representation of non-white subjects. In total, the data now include chromosomal aberration information from 108,950 cells and SCE information from 25,397 cells from 613 samples from 493 subjects. Neither the mean frequencies of any of the chromosomal aberration types nor the mean frequency of SCE have changed notably through the addition of the new subjects and samples. The mean age at sampling of the population is now 43.1 years with a range of from 1.1 to 83.7 years. However, we still find no significant relationship of the frequency of any conventional aberration category to age with the single exception of the dicentric chromosome, which now shows a positive regression (p = 0.001). The raw mean SCE frequencies show a statistically significant increase with subject age, but when cigarette smoking status is taken into account, no significant age relationship is found. As with the earlier samples, neither aberration nor SCE frequencies was influenced by race. Mean SCE frequencies, measured in non-smokers, were about 5% higher in females than males. Only one aberration category, "supernumerary acentric fragment", was significantly related to sex. This "aberration", known to constitute early centromere separation of an X chromosome, is much more common in females than in males and, in the females, increases significantly with increasing subject age.

Adolescent↗