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E Pimentel

Publications and source records attributed to E Pimentel.

At least 19 recordsLinked to original sources
PubMed2006

Charon's size and an upper limit on its atmosphere from a stellar occultation.

Pluto and its satellite, Charon (discovered in 1978; ref. 1), appear to form a double planet, rather than a hierarchical planet/satellite couple. Charon is about half Pluto's size and about one-eighth its mass. The precise radii of Pluto and Charon have remained uncertain, leading to large uncertainties on their densities. Although stellar occultations by Charon are in principle a powerful way of measuring its size, they are rare, as the satellite subtends less than 0.3 microradians (0.06 arcsec) on the sky. One occultation (in 1980) yielded a lower limit of 600 km for the satellite's radius, which was later refined to 601.5 km (ref. 4). Here we report observations from a multi-station stellar occultation by Charon, which we use to derive a radius, R(C) = 603.6 +/- 1.4 km (1sigma), and a density of rho = 1.71 +/- 0.08 g cm(-3). This occultation also provides upper limits of 110 and 15 (3sigma) nanobar for an atmosphere around Charon, assuming respectively a pure nitrogen or pure methane atmosphere.

Journal Article↗
PubMed2004

Ten-year viability study on natural populations of Drosophila sibling species from Laguna Verde, Veracruz, México.

The generation of electricity in nuclear power plants produces an increase in background radiation that could possibly have some impact on the organisms that live in that area. In order to identify and quantify any such possible effect, the natural populations of two sibling species, D. melanogaster and D. simulans, that live in the immediate vicinity of the first Mexican Nuclear Power Plant were analyzed for a period of 10 years. Collections of flies were made at two sites, one close to and one farther from the power plant, during the pre and operational stages of the reactor, and their egg-to-adult viability was analyzed. The data obtained indicate that in both sites, the egg-to-adult viability was generally higher in D. melanogaster than in D. simulans. Further, a relationship was found between egg-to-adult viability and the season of the year (warm-wet or cool-dry season). Some differences were found between the two sites. It may be concluded that there is no negative impact on the Drosophila populations studied.

Air Pollution, Radioactive↗
PubMed2003

Evidence suggesting that chlorophyllin (CHLN) may act as an inhibitor or a promoter of genetic damage induced by chromium(VI) oxide (CrO3) in somatic cells of Drosophila.

In Drosophila, 48h-old larvae were pretreated for 24h with chlorophyllin (CHLN) or sucrose and then treated with chromium(VI) oxide (CrO(3)) immediately following completion of the pretreatment period (0-day delay) or delayed 1, 2 or 3 days. The effects were scored in the wing spot test. After delays of 0 and 1 day, clear evidence of a protective effect of CHLN was found. Contrarily, after delays of 2 and 3 days, the results showed a reversal, i.e. CHLN-related events appeared more frequently than those in the sucrose control suggesting a promoting effect. It would appear prudent that CHLN be tested in a variety of situations in any given organism before decisions are reached regarding its inhibitor/promoter effects.

Animals↗
PubMed2000

Evidence that chlorophyllin (CHLN) may behave as an inhibitor or a promoter of radiation-induced genetic damage in somatic cells of drosophila.

Irradiation of 96h old Drosophila following a 24h pretreatment with 5% chlorophyllin (CHLN) was delayed 0-4 days. The antimutagenic effect of CHLN in somatic cells monitored by the wing spot test persisted for 3 days after completion of the pretreatment and appeared to terminate at a time corresponding to the cessation of mitotic divisions of wing anlagen cells. Within the same population of cells, CHLN demonstrated both an inhibitory effect as measured in mwh single spot classes, and contrarily, a promoting effect in the class of mwh/flr twin spots and to an extent in the class of large flr spots. The reason for the contrasting effects of CHLN remains to be determined.

Animals↗
PubMed2000

Effects of betulinic acid alone and in combination with irradiation in human melanoma cells.

Recently, betulinic acid was identified as a highly selective inhibitor of human melanoma growth and was reported to induce apoptosis in these cells. We have investigated the growth-inhibitory properties of this compound alone and in combination with ionizing radiation in a panel of established human melanoma cell lines as well as in normal human melanocytes. Betulinic acid strongly and consistently suppressed the growth and colony-forming ability of all human melanoma cell lines investigated. In combination with ionizing radiation the effect of betulinic acid on growth inhibition was additive in colony-forming assays. Betulinic acid also induced apoptosis in human melanoma cells as demonstrated by Annexin V binding and by the emergence of cells with apoptotic morphology. The growth-inhibitory action of betulinic acid was more pronounced in human melanoma cell lines than in normal human melanocytes. Notably, despite the induction of apoptosis, analysis of the expression of Bcl-2 family members in betulinic-acid-treated cells revealed that expression of the anti-apoptotic protein Mcl-1 was induced. Furthermore, the antiproliferative action of betulinic acid seemed to be independent of the p53 status. The properties of betulinic acid make it an interesting candidate, not only as a single agent but also in combination with radiotherapy. We conclude that the strictly additive mode of growth inhibition in combination with irradiation suggests that the two treatment modalities may function by inducing different cell death pathways or by affecting different target cell populations.

Antineoplastic Agents, Phytogenic↗
PubMed1999

On the persistence of the radioprotective effect of chlorophyllin (CHLN) in somatic cells of Drosophila.

By delaying the time of gamma irradiation of 72 h larvae, pretreated at 48 h with 5% chlorophyllin (CHLN), it was established that the overall inhibiting effect of CHLN in somatic cells of Drosophila, as measured in the wing spot test, persists for about 4 days or until the time of cessation of the proliferation of wing anlagen. In the same population of cells, some spot classes gave evidence of an inhibitory effect whereas others did not arguing against the suggestion that the radioprotective effect of CHLN is a consequence of an induced delay in development, shrinking of the potential radiation target and lowering the probability of induced events. Other observations of interest are described.

Animals↗
PubMed1998

Lysine-rich gamma-zeins are secreted in transgenic Arabidopsis plants.

We have previously shown that the maize (Zea mays L.) storage prolamine gamma-zein, accumulates in endoplasmic reticulum-derived protein bodies in transgenic plants of Arabidopsis thaliana (L.) ecotype R + P. The retention of gamma-zein in the endoplasmic reticulum was found to be mediated by structural features contained in the polypeptide, an N-terminal proline-rich and a C-terminal cysteine-rich domain which were necessary for the correct retention and assembly of gamma-zein within protein bodies (M.I. Geli et al., 1994, Plant Cell 6: 1911-1922). In the present work we incorporated in the gamma-zein gene lysine-rich coding sequences which were positioned after the N-terminal proline-rich domain and at five amino-acid residues from the C-terminus. The targeting of lysine-rich gamma-zeins was analyzed by expression of chimeric genes regulated by the cauliflower mosaic virus (CaMV) 35S promoter in transgenic Arabidopsis plants. The lysine-rich gamma-zeins were detected by immunoblotting and we found that these proteins were modified posttranslationally to reach their mature form. Subcellular fractionation and immunocytochemical studies demonstrated that glycosylated lysine-rich gamma-zeins were secreted to the cell wall of transgenic Arabidopsis leaf cells.

Arabidopsis↗
PubMed1997

On the recovery of single spots with the flr phenotype in the wing spot test in Drosophila.

Graf et al. (U. Graf, F.E. Würgler, A.J. Katz, H. Frei, H. Juon, C.B. Hall, P.G. Kale, Somatic mutation and recombination test in Drosophila, Environment Mutagen. 6 (1984) 153-188.) described the overall results of assays of a series of compounds in the Drosophila wing spot test as indicating that single mwh spots appeared most frequently, followed by less frequent twin spots with both mwh and flr cells and lastly the 'quite rare' single flr spots. Data are presented below demonstrating that some compounds behave in a manner consistent with the above description, whereas others do not in that the frequency of single flr spots is equal to or exceeds that of twin spots and cannot be described as occurring 'rarely'. It is suggested that (large) flr singles be used as a measure of mutations/deletions directly from treated transheterozygotes. An argument is presented questioning the use of treated mwh +/+ TM3 individuals as an assay of mutations/deletions at the mwh+ locus.

Animals↗
PubMed1996

Evidence for an effect of exposure to low levels of alpha particle irradiation in larval cells of Drosophila as measured in the wing-spot test.

Larvae of Drosophila were exposed to a range of concentrations of alpha particles from 3 to 318 mRad, and genetic effects measured in the wing-spot test. The results were positive, and evidence of a linear relationship between exposure and response observed. The induction of chromosome breakage is suggested by the significantly higher frequency of twin spots in the treated series compared with controls.

Alpha Particles↗
PubMed1996

The use of vaginal ultrasound to identify copper T IUDs at high risk of expulsion.

A total of 235 women who had a TCu 380A IUD inserted had a vaginal ultrasound scan performed to identify if the IUDs were correctly placed in the uterine fundus. Women identified as having a misplaced IUD had it removed. The remaining women were compared to 201 women who had an IUD inserted and had no ultrasound evaluation, matched by age and parity. Women were followed-up for one year. Gross cumulative discontinuation rates and continuation rates were calculated by life table analysis. Comparison between groups was done by the Gehan test. The study group had 34 IUDs removed because they were misplaced according to the established criteria. The expulsion rate was significantly higher in the control group, also influencing the continuation rate which was lower in the same group. Of the 34 women who had their IUD removed because it was not correctly placed, only 22 requested and had another IUD inserted. The removal of IUD determined by an ultrasound to be incorrectly placed significantly decreased expulsion rates. However, many IUDs may have been removed unnecessarily, probably resulting in many women not returning to the clinic or deciding to use another contraceptive method.

Adult↗
PubMed1994

Identification of main risk factors for tubal infertility.

OBJECTIVE: To determine the relationship between some reproductive variables and infertility caused by tubal obstruction. DESIGN: A retrospective, case-control study. SETTING: A tertiary care university hospital that is a referral center for infertility patients. PARTICIPANTS: Subjects were interviewed between March 1990 and December 1991. Cases were 215 consecutively recruited infertile women with either evidence of tubal obstruction found at laparoscopy or hydrosalpinx diagnosed by hysterosalpingography. Women with a history of surgical sterilization were excluded. Controls, selected in the same hospital, were women in the puerperium who had no history of infertility. Two controls were matched by age at the time of tubal obstruction diagnosis to each case. RESULTS: History of pelvic surgery and use of alcohol were significantly associated with the risk of infertility caused by tubal obstruction. The use of barrier, oral, and medroxyprogesterone acetate (MPA) contraceptives was associated with a protective effect. When only women with secondary infertility were analyzed, history of pelvic surgery and number of lifetime sexual partners were significant risk factors, and the previous use of oral contraceptives was the only protective factor. CONCLUSIONS: History of pelvic surgery was the most important risk factor for tubal infertility. All precautions must be taken to avoid infection and adhesion formation when pelvic surgery is performed. In addition, women can be protected from tubal infertility by using barrier, oral, or MPA contraceptive methods.

Adult↗
PubMed1993

High rate of infection with the human T-cell leukemia retrovirus type II in four Indian populations of Argentina.

Sera from 215 non-drug-injecting Toba and Mataco-Mataguayo pure Indians belonging to four communities in northern Argentina were examined using assays that allow differentiation between reactivities due to type-specific antigens of the human T-cell leukemia/lymphoma virus (HTLV). Three of these populations have very little contact with non-Indian groups and reside in remote, isolated areas. HTLV-II type-specific seroreactivity was present in 24 (13.7%) of the 175 Indians older than 13 years of age and in none of the 40 who were of younger ages. None of the Indians had antibodies reacting with HTLV-I type-specific antigen. Seroreactivity was more prevalent and appeared at younger ages in females than in males. The majority of the HTLV-II-seropositive Indians belonged to the more isolated communities. The seroprevalences among the Tobas and Mataco-Mataguayo Indians were comparable. With the exception of a Toba who was positive in a test for Treponema pallidum, no serological evidence of sexually transmitted infections with this spirochete, hepatitis B virus, hepatitis C virus, and human immunodeficiency virus was found among the Indians tested. None of the 55 non-Indian people tested in the region showed HTLV-II type-specific seroreactivity. PCR analysis of DNA isolated from peripheral blood lymphocytes of seropositive Indians confirmed that the virus present in these populations is HTLV-II. Sequence analysis of PCR-amplified genomic segments showed that the virus belongs to the HTLV-II subtype which has been found to be endemic in other Paleo-American Indians.

Adolescent↗